Adding upstream version 115.7.0esr.upstream/115.7.0esr

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

129 files changed, 16598 insertions, 0 deletions

diff --git a/js/src/devtools/Instruments.cpp b/js/src/devtools/Instruments.cpp
new file mode 100644
index 0000000000..39fbe882b8
--- /dev/null
+++ b/js/src/devtools/Instruments.cpp
@@ -0,0 +1,223 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "Instruments.h"
+#include "mozilla/Attributes.h"
+
+#ifdef __APPLE__
+
+#  include <dlfcn.h>
+#  include <CoreFoundation/CoreFoundation.h>
+#  include <unistd.h>
+
+// There are now 2 paths to the DTPerformanceSession framework. We try to load
+// the one contained in /Applications/Xcode.app first, falling back to the one
+// contained in /Library/Developer/4.0/Instruments.
+#  define DTPerformanceLibraryPath                                   \
+    "/Applications/Xcode.app/Contents/Developer/Library/Frameworks/" \
+    "DTPerformanceSession.framework/Versions/Current/DTPerformanceSession"
+#  define OldDTPerformanceLibraryPath                \
+    "/Library/Developer/4.0/Instruments/Frameworks/" \
+    "DTPerformanceSession.framework/Versions/Current/DTPerformanceSession"
+
+extern "C" {
+
+typedef CFTypeRef DTPerformanceSessionRef;
+
+#  define DTPerformanceSession_TimeProfiler \
+    "com.apple.instruments.dtps.timeprofiler"
+// DTPerformanceSession_Option_SamplingInterval is measured in microseconds
+#  define DTPerformanceSession_Option_SamplingInterval \
+    "com.apple.instruments.dtps.option.samplinginterval"
+
+typedef void (*dtps_errorcallback_t)(CFStringRef, CFErrorRef);
+typedef DTPerformanceSessionRef (*DTPerformanceSessionCreateFunction)(
+    CFStringRef, CFStringRef, CFDictionaryRef, CFErrorRef*);
+typedef bool (*DTPerformanceSessionAddInstrumentFunction)(
+    DTPerformanceSessionRef, CFStringRef, CFDictionaryRef, dtps_errorcallback_t,
+    CFErrorRef*);
+typedef bool (*DTPerformanceSessionIsRecordingFunction)(
+    DTPerformanceSessionRef);
+typedef bool (*DTPerformanceSessionStartFunction)(DTPerformanceSessionRef,
+                                                  CFArrayRef, CFErrorRef*);
+typedef bool (*DTPerformanceSessionStopFunction)(DTPerformanceSessionRef,
+                                                 CFArrayRef, CFErrorRef*);
+typedef bool (*DTPerformanceSessionSaveFunction)(DTPerformanceSessionRef,
+                                                 CFStringRef, CFErrorRef*);
+
+}  // extern "C"
+
+namespace Instruments {
+
+static const int kSamplingInterval = 20;  // microseconds
+
+template <typename T>
+class AutoReleased {
+ public:
+  MOZ_IMPLICIT AutoReleased(T aTypeRef) : mTypeRef(aTypeRef) {}
+  ~AutoReleased() {
+    if (mTypeRef) {
+      CFRelease(mTypeRef);
+    }
+  }
+
+  operator T() { return mTypeRef; }
+
+ private:
+  T mTypeRef;
+};
+
+#  define DTPERFORMANCE_SYMBOLS               \
+    SYMBOL(DTPerformanceSessionCreate)        \
+    SYMBOL(DTPerformanceSessionAddInstrument) \
+    SYMBOL(DTPerformanceSessionIsRecording)   \
+    SYMBOL(DTPerformanceSessionStart)         \
+    SYMBOL(DTPerformanceSessionStop)          \
+    SYMBOL(DTPerformanceSessionSave)
+
+#  define SYMBOL(_sym) _sym##Function _sym = nullptr;
+
+DTPERFORMANCE_SYMBOLS
+
+#  undef SYMBOL
+
+void* LoadDTPerformanceLibraries(bool dontLoad) {
+  int flags = RTLD_LAZY | RTLD_LOCAL | RTLD_NODELETE;
+  if (dontLoad) {
+    flags |= RTLD_NOLOAD;
+  }
+
+  void* DTPerformanceLibrary = dlopen(DTPerformanceLibraryPath, flags);
+  if (!DTPerformanceLibrary) {
+    DTPerformanceLibrary = dlopen(OldDTPerformanceLibraryPath, flags);
+  }
+  return DTPerformanceLibrary;
+}
+
+bool LoadDTPerformanceLibrary() {
+  void* DTPerformanceLibrary = LoadDTPerformanceLibraries(true);
+  if (!DTPerformanceLibrary) {
+    DTPerformanceLibrary = LoadDTPerformanceLibraries(false);
+    if (!DTPerformanceLibrary) {
+      return false;
+    }
+  }
+
+#  define SYMBOL(_sym)                                                        \
+    _sym =                                                                    \
+        reinterpret_cast<_sym##Function>(dlsym(DTPerformanceLibrary, #_sym)); \
+    if (!_sym) {                                                              \
+      dlclose(DTPerformanceLibrary);                                          \
+      DTPerformanceLibrary = nullptr;                                         \
+      return false;                                                           \
+    }
+
+  DTPERFORMANCE_SYMBOLS
+
+#  undef SYMBOL
+
+  dlclose(DTPerformanceLibrary);
+
+  return true;
+}
+
+static DTPerformanceSessionRef gSession;
+
+bool Error(CFErrorRef error) {
+  if (gSession) {
+    CFErrorRef unused = nullptr;
+    DTPerformanceSessionStop(gSession, nullptr, &unused);
+    CFRelease(gSession);
+    gSession = nullptr;
+  }
+#  ifdef DEBUG
+  AutoReleased<CFDataRef> data = CFStringCreateExternalRepresentation(
+      nullptr, CFErrorCopyDescription(error), kCFStringEncodingUTF8, '?');
+  if (data != nullptr) {
+    printf("%.*s\n\n", (int)CFDataGetLength(data), CFDataGetBytePtr(data));
+  }
+#  endif
+  return false;
+}
+
+bool Start(pid_t pid) {
+  if (gSession) {
+    return false;
+  }
+
+  if (!LoadDTPerformanceLibrary()) {
+    return false;
+  }
+
+  AutoReleased<CFStringRef> process =
+      CFStringCreateWithFormat(kCFAllocatorDefault, nullptr, CFSTR("%d"), pid);
+  if (!process) {
+    return false;
+  }
+  CFErrorRef error = nullptr;
+  gSession = DTPerformanceSessionCreate(nullptr, process, nullptr, &error);
+  if (!gSession) {
+    return Error(error);
+  }
+
+  AutoReleased<CFNumberRef> interval =
+      CFNumberCreate(0, kCFNumberIntType, &kSamplingInterval);
+  if (!interval) {
+    return false;
+  }
+  CFStringRef keys[1] = {CFSTR(DTPerformanceSession_Option_SamplingInterval)};
+  CFNumberRef values[1] = {interval};
+  AutoReleased<CFDictionaryRef> options = CFDictionaryCreate(
+      kCFAllocatorDefault, (const void**)keys, (const void**)values, 1,
+      &kCFTypeDictionaryKeyCallBacks, &kCFTypeDictionaryValueCallBacks);
+  if (!options) {
+    return false;
+  }
+
+  if (!DTPerformanceSessionAddInstrument(
+          gSession, CFSTR(DTPerformanceSession_TimeProfiler), options, nullptr,
+          &error)) {
+    return Error(error);
+  }
+
+  return Resume();
+}
+
+void Pause() {
+  if (gSession && DTPerformanceSessionIsRecording(gSession)) {
+    CFErrorRef error = nullptr;
+    if (!DTPerformanceSessionStop(gSession, nullptr, &error)) {
+      Error(error);
+    }
+  }
+}
+
+bool Resume() {
+  if (!gSession) {
+    return false;
+  }
+
+  CFErrorRef error = nullptr;
+  return DTPerformanceSessionStart(gSession, nullptr, &error) || Error(error);
+}
+
+void Stop(const char* profileName) {
+  Pause();
+
+  CFErrorRef error = nullptr;
+  AutoReleased<CFStringRef> name =
+      CFStringCreateWithFormat(kCFAllocatorDefault, nullptr, CFSTR("%s%s"),
+                               "/tmp/", profileName ? profileName : "mozilla");
+  if (!DTPerformanceSessionSave(gSession, name, &error)) {
+    Error(error);
+    return;
+  }
+
+  CFRelease(gSession);
+  gSession = nullptr;
+}
+
+}  // namespace Instruments
+
+#endif /* __APPLE__ */
diff --git a/js/src/devtools/Instruments.h b/js/src/devtools/Instruments.h
new file mode 100644
index 0000000000..9e8f197755
--- /dev/null
+++ b/js/src/devtools/Instruments.h
@@ -0,0 +1,23 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef devtools_Instruments_h
+#define devtools_Instruments_h
+
+#ifdef __APPLE__
+
+#  include <unistd.h>
+
+namespace Instruments {
+
+bool Start(pid_t pid);
+void Pause();
+bool Resume();
+void Stop(const char* profileName);
+
+}  // namespace Instruments
+
+#endif /* __APPLE__ */
+
+#endif /* devtools_Instruments_h */
diff --git a/js/src/devtools/automation/README b/js/src/devtools/automation/README
new file mode 100644
index 0000000000..70f56fd230
--- /dev/null
+++ b/js/src/devtools/automation/README
@@ -0,0 +1,39 @@
+autospider.py is intended both as the harness for running automation builds, as
+well as a way to easily reproduce automation builds on a developer workstation.
+Some brave souls also use it as the basis for doing their normal local builds.
+
+Basic usage:
+
+  ./js/src/devtools/automation/autospider.py plain
+
+The script may be run from any directory. This will configure and build the
+source, then run a series of tests. See the --help message for many different
+ways of suppressing various actions or changing the output.
+
+The different possible build+test configurations are controlled mostly by JSON
+files in a variants/ directory (eg there is a .../variants/plain file for the
+above command).
+
+In automation, the test jobs will run with a dynamically loaded library that
+catches crashes and generates minidumps, so that autospider.py can produce a
+readable stack trace at the end of the run. Currently this library is only
+available on linux64, and is built via the following procedure:
+
+    % git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
+    % export PATH=$PATH:$(pwd)/depot_tools
+    % mkdir breakpad
+    % cd breakpad
+    # python must be python2.7
+    % fetch breakpad
+    % cd src
+    % git fetch https://github.com/hotsphink/breakpad injector
+    % git checkout FETCH_HEAD
+    % cd ..
+    % mkdir obj
+    % cd obj
+    # Possibly set $PATH to include a recent gcc
+    % ../src/configure --enable-static
+    % mkdir ../root
+    % make install DESTDIR=$(pwd)/../root
+
+The shared library will now be in root/usr/local/lib64/libbreakpadinjector.so
diff --git a/js/src/devtools/automation/arm64-jittests-timeouts.txt b/js/src/devtools/automation/arm64-jittests-timeouts.txt
new file mode 100644
index 0000000000..2c23ca3535
--- /dev/null
+++ b/js/src/devtools/automation/arm64-jittests-timeouts.txt
@@ -0,0 +1,2 @@
+basic/bug1610192.js
+ion/pow-base-power-of-two.js
diff --git a/js/src/devtools/automation/arm64-jstests-slow.txt b/js/src/devtools/automation/arm64-jstests-slow.txt
new file mode 100644
index 0000000000..c4c09ac79b
--- /dev/null
+++ b/js/src/devtools/automation/arm64-jstests-slow.txt
@@ -0,0 +1,52 @@
+non262/object/15.2.3.6-dictionary-redefinition-01-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-02-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-03-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-04-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-05-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-06-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-07-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-08-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-09-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-10-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-11-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-12-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-13-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-14-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-15-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-16-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-17-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-18-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-19-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-20-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-21-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-22-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-23-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-24-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-25-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-26-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-27-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-30-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-31-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-32-of-32.js
+non262/object/15.2.3.6-middle-redefinition-1-of-8.js
+non262/object/15.2.3.6-middle-redefinition-2-of-8.js
+non262/object/15.2.3.6-middle-redefinition-3-of-8.js
+non262/object/15.2.3.6-middle-redefinition-4-of-8.js
+non262/object/15.2.3.6-middle-redefinition-5-of-8.js
+non262/object/15.2.3.6-middle-redefinition-6-of-8.js
+non262/object/15.2.3.6-middle-redefinition-7-of-8.js
+non262/object/15.2.3.6-middle-redefinition-8-of-8.js
+non262/object/15.2.3.6-redefinition-1-of-4.js
+non262/object/15.2.3.6-redefinition-2-of-4.js
+non262/object/15.2.3.6-redefinition-3-of-4.js
+non262/object/15.2.3.6-redefinition-4-of-4.js
+non262/extensions/clone-complex-object.js
+non262/reflect-parse/classes.js
+non262/reflect-parse/destructuring-variable-declarations.js
+test262/built-ins/RegExp/CharacterClassEscapes/character-class-non-whitespace-class-escape-flags-u.js
+test262/built-ins/RegExp/CharacterClassEscapes/character-class-non-digit-class-escape-flags-u.js
+test262/built-ins/RegExp/CharacterClassEscapes/character-class-non-word-class-escape-flags-u.js
+test262/built-ins/RegExp/property-escapes/generated/
+test262/built-ins/RegExp/property-escapes/generated/General_Category_-_Letter.js
+test262/built-ins/RegExp/property-escapes/generated/General_Category_-_Other.js
+test262/built-ins/RegExp/property-escapes/generated/General_Category_-_Unassigned.js
diff --git a/js/src/devtools/automation/autospider.py b/js/src/devtools/automation/autospider.py
new file mode 100755
index 0000000000..66e25e2078
--- /dev/null
+++ b/js/src/devtools/automation/autospider.py
@@ -0,0 +1,701 @@
+#!/usr/bin/env python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import argparse
+import json
+import logging
+import multiprocessing
+import os
+import platform
+import shlex
+import shutil
+import subprocess
+import sys
+from collections import Counter, namedtuple
+from logging import info
+from os import environ as env
+from pathlib import Path
+from subprocess import Popen
+from threading import Timer
+
+Dirs = namedtuple("Dirs", ["scripts", "js_src", "source", "fetches"])
+
+
+def directories(pathmodule, cwd, fixup=lambda s: s):
+    scripts = pathmodule.join(fixup(cwd), fixup(pathmodule.dirname(__file__)))
+    js_src = pathmodule.abspath(pathmodule.join(scripts, "..", ".."))
+    source = pathmodule.abspath(pathmodule.join(js_src, "..", ".."))
+    mozbuild = pathmodule.abspath(
+        # os.path.expanduser does not work on Windows.
+        env.get("MOZBUILD_STATE_PATH")
+        or pathmodule.join(Path.home(), ".mozbuild")
+    )
+    fetches = pathmodule.abspath(env.get("MOZ_FETCHES_DIR", mozbuild))
+    return Dirs(scripts, js_src, source, fetches)
+
+
+def quote(s):
+    # shlex quotes for the purpose of passing to the native shell, which is cmd
+    # on Windows, and therefore will not replace backslashed paths with forward
+    # slashes. When such a path is passed to sh, the backslashes will be
+    # interpreted as escape sequences.
+    return shlex.quote(s).replace("\\", "/")
+
+
+# Some scripts will be called with sh, which cannot use backslashed
+# paths. So for direct subprocess.* invocation, use normal paths from
+# DIR, but when running under the shell, use POSIX style paths.
+DIR = directories(os.path, os.getcwd())
+
+AUTOMATION = env.get("AUTOMATION", False)
+
+parser = argparse.ArgumentParser(description="Run a spidermonkey shell build job")
+parser.add_argument(
+    "--verbose",
+    action="store_true",
+    default=AUTOMATION,
+    help="display additional logging info",
+)
+parser.add_argument(
+    "--dep", action="store_true", help="do not clobber the objdir before building"
+)
+parser.add_argument(
+    "--keep",
+    action="store_true",
+    help="do not delete the sanitizer output directory (for testing)",
+)
+parser.add_argument(
+    "--platform",
+    "-p",
+    type=str,
+    metavar="PLATFORM",
+    default="",
+    help='build platform, including a suffix ("-debug" or "") used '
+    'by buildbot to override the variant\'s "debug" setting. The platform can be '
+    "used to specify 32 vs 64 bits.",
+)
+parser.add_argument(
+    "--timeout",
+    "-t",
+    type=int,
+    metavar="TIMEOUT",
+    default=12600,
+    help="kill job after TIMEOUT seconds",
+)
+parser.add_argument(
+    "--objdir",
+    type=str,
+    metavar="DIR",
+    # The real default must be set later so that OBJDIR can be
+    # relative to the srcdir.
+    default=env.get("OBJDIR"),
+    help="object directory",
+)
+group = parser.add_mutually_exclusive_group()
+group.add_argument(
+    "--optimize",
+    action="store_true",
+    help="generate an optimized build. Overrides variant setting.",
+)
+group.add_argument(
+    "--no-optimize",
+    action="store_false",
+    dest="optimize",
+    help="generate a non-optimized build. Overrides variant setting.",
+)
+group.set_defaults(optimize=None)
+group = parser.add_mutually_exclusive_group()
+group.add_argument(
+    "--debug",
+    action="store_true",
+    help="generate a debug build. Overrides variant setting.",
+)
+group.add_argument(
+    "--no-debug",
+    action="store_false",
+    dest="debug",
+    help="generate a non-debug build. Overrides variant setting.",
+)
+group.set_defaults(debug=None)
+group = parser.add_mutually_exclusive_group()
+group.add_argument(
+    "--jemalloc",
+    action="store_true",
+    dest="jemalloc",
+    help="use mozilla's jemalloc instead of the default allocator",
+)
+group.add_argument(
+    "--no-jemalloc",
+    action="store_false",
+    dest="jemalloc",
+    help="use the default allocator instead of mozilla's jemalloc",
+)
+group.set_defaults(jemalloc=None)
+parser.add_argument(
+    "--run-tests",
+    "--tests",
+    type=str,
+    metavar="TESTSUITE",
+    default="",
+    help="comma-separated set of test suites to add to the variant's default set",
+)
+parser.add_argument(
+    "--skip-tests",
+    "--skip",
+    type=str,
+    metavar="TESTSUITE",
+    default="",
+    help="comma-separated set of test suites to remove from the variant's default "
+    "set",
+)
+parser.add_argument(
+    "--build-only",
+    "--build",
+    dest="skip_tests",
+    action="store_const",
+    const="all",
+    help="only do a build, do not run any tests",
+)
+parser.add_argument(
+    "--nobuild",
+    action="store_true",
+    help="Do not do a build. Rerun tests on existing build.",
+)
+parser.add_argument(
+    "variant", type=str, help="type of job requested, see variants/ subdir"
+)
+args = parser.parse_args()
+
+logging.basicConfig(level=logging.INFO, format="%(message)s")
+
+env["CPP_UNIT_TESTS_DIR_JS_SRC"] = DIR.js_src
+if AUTOMATION and platform.system() == "Windows":
+    # build/win{32,64}/mozconfig.vs-latest uses TOOLTOOL_DIR to set VSPATH.
+    env["TOOLTOOL_DIR"] = DIR.fetches
+
+OBJDIR = args.objdir or os.path.join(DIR.source, "obj-spider")
+OBJDIR = os.path.abspath(OBJDIR)
+OUTDIR = os.path.join(OBJDIR, "out")
+MAKE = env.get("MAKE", "make")
+PYTHON = sys.executable
+
+for d in DIR._fields:
+    info("DIR.{name} = {dir}".format(name=d, dir=getattr(DIR, d)))
+
+
+def ensure_dir_exists(
+    name, clobber=True, creation_marker_filename="CREATED-BY-AUTOSPIDER"
+):
+    if creation_marker_filename is None:
+        marker = None
+    else:
+        marker = os.path.join(name, creation_marker_filename)
+    if clobber:
+        if (
+            not AUTOMATION
+            and marker
+            and os.path.exists(name)
+            and not os.path.exists(marker)
+        ):
+            raise Exception(
+                "Refusing to delete objdir %s because it was not created by autospider"
+                % name
+            )
+        shutil.rmtree(name, ignore_errors=True)
+    try:
+        os.mkdir(name)
+        if marker:
+            open(marker, "a").close()
+    except OSError:
+        if clobber:
+            raise
+
+
+with open(os.path.join(DIR.scripts, "variants", args.variant)) as fh:
+    variant = json.load(fh)
+
+if args.variant == "nonunified":
+    # Rewrite js/src/**/moz.build to replace UNIFIED_SOURCES to SOURCES.
+    # Note that this modifies the current checkout.
+    for dirpath, dirnames, filenames in os.walk(DIR.js_src):
+        if "moz.build" in filenames:
+            in_place = ["-i"]
+            if platform.system() == "Darwin":
+                in_place.append("")
+            subprocess.check_call(
+                ["sed"]
+                + in_place
+                + ["s/UNIFIED_SOURCES/SOURCES/", os.path.join(dirpath, "moz.build")]
+            )
+
+CONFIGURE_ARGS = variant["configure-args"]
+
+compiler = variant.get("compiler")
+if compiler != "gcc" and "clang-plugin" not in CONFIGURE_ARGS:
+    CONFIGURE_ARGS += " --enable-clang-plugin"
+
+if compiler == "gcc":
+    if AUTOMATION:
+        fetches = env["MOZ_FETCHES_DIR"]
+        env["CC"] = os.path.join(fetches, "gcc", "bin", "gcc")
+        env["CXX"] = os.path.join(fetches, "gcc", "bin", "g++")
+    else:
+        env["CC"] = "gcc"
+        env["CXX"] = "g++"
+
+opt = args.optimize
+if opt is None:
+    opt = variant.get("optimize")
+if opt is not None:
+    CONFIGURE_ARGS += " --enable-optimize" if opt else " --disable-optimize"
+
+opt = args.debug
+if opt is None:
+    opt = variant.get("debug")
+if opt is not None:
+    CONFIGURE_ARGS += " --enable-debug" if opt else " --disable-debug"
+
+opt = args.jemalloc
+if opt is not None:
+    CONFIGURE_ARGS += " --enable-jemalloc" if opt else " --disable-jemalloc"
+
+# By default, we build with NSPR, even if not specified. But we actively allow
+# builds to disable NSPR.
+opt = variant.get("nspr")
+if opt is None or opt:
+    CONFIGURE_ARGS += " --enable-nspr-build"
+
+# Some of the variants request a particular word size (eg ARM simulators).
+word_bits = variant.get("bits")
+
+# On Linux and Windows, we build 32- and 64-bit versions on a 64 bit
+# host, so the caller has to specify what is desired.
+if word_bits is None and args.platform:
+    platform_arch = args.platform.split("-")[0]
+    if platform_arch in ("win32", "linux"):
+        word_bits = 32
+    elif platform_arch in ("win64", "linux64"):
+        word_bits = 64
+
+# Fall back to the word size of the host.
+if word_bits is None:
+    word_bits = 64 if platform.architecture()[0] == "64bit" else 32
+
+# Need a platform name to use as a key in variant files.
+if args.platform:
+    variant_platform = args.platform.split("-")[0]
+elif platform.system() == "Windows":
+    variant_platform = "win64" if word_bits == 64 else "win32"
+elif platform.system() == "Linux":
+    variant_platform = "linux64" if word_bits == 64 else "linux"
+elif platform.system() == "Darwin":
+    variant_platform = "macosx64"
+else:
+    variant_platform = "other"
+
+env["LD_LIBRARY_PATH"] = ":".join(
+    d
+    for d in [
+        # for libnspr etc.
+        os.path.join(OBJDIR, "dist", "bin"),
+        # existing search path, if any
+        env.get("LD_LIBRARY_PATH"),
+    ]
+    if d is not None
+)
+
+os.environ["SOURCE"] = DIR.source
+if platform.system() == "Windows":
+    MAKE = env.get("MAKE", "mozmake")
+
+# Configure flags, based on word length and cross-compilation
+if word_bits == 32:
+    if platform.system() == "Windows":
+        CONFIGURE_ARGS += " --target=i686-pc-windows-msvc"
+    elif platform.system() == "Linux":
+        if not platform.machine().startswith("arm"):
+            CONFIGURE_ARGS += " --target=i686-pc-linux"
+
+    # Add SSE2 support for x86/x64 architectures.
+    if not platform.machine().startswith("arm"):
+        if platform.system() == "Windows":
+            sse_flags = "-arch:SSE2"
+        else:
+            sse_flags = "-msse -msse2 -mfpmath=sse"
+        env["CCFLAGS"] = "{0} {1}".format(env.get("CCFLAGS", ""), sse_flags)
+        env["CXXFLAGS"] = "{0} {1}".format(env.get("CXXFLAGS", ""), sse_flags)
+else:
+    if platform.system() == "Windows":
+        CONFIGURE_ARGS += " --target=x86_64-pc-windows-msvc"
+
+if platform.system() == "Linux" and AUTOMATION:
+    CONFIGURE_ARGS = "--enable-stdcxx-compat " + CONFIGURE_ARGS
+
+# Timeouts.
+ACTIVE_PROCESSES = set()
+
+
+def killall():
+    for proc in ACTIVE_PROCESSES:
+        proc.kill()
+    ACTIVE_PROCESSES.clear()
+
+
+timer = Timer(args.timeout, killall)
+timer.daemon = True
+timer.start()
+
+ensure_dir_exists(OBJDIR, clobber=not args.dep and not args.nobuild)
+ensure_dir_exists(OUTDIR, clobber=not args.keep)
+
+# Any jobs that wish to produce additional output can save them into the upload
+# directory if there is such a thing, falling back to OBJDIR.
+env.setdefault("MOZ_UPLOAD_DIR", OBJDIR)
+ensure_dir_exists(env["MOZ_UPLOAD_DIR"], clobber=False, creation_marker_filename=None)
+info("MOZ_UPLOAD_DIR = {}".format(env["MOZ_UPLOAD_DIR"]))
+
+
+def run_command(command, check=False, **kwargs):
+    kwargs.setdefault("cwd", OBJDIR)
+    info("in directory {}, running {}".format(kwargs["cwd"], command))
+    if platform.system() == "Windows":
+        # Windows will use cmd for the shell, which causes all sorts of
+        # problems. Use sh instead, quoting appropriately. (Use sh in all
+        # cases, not just when shell=True, because we want to be able to use
+        # paths that sh understands and cmd does not.)
+        if not isinstance(command, list):
+            if kwargs.get("shell"):
+                command = shlex.split(command)
+            else:
+                command = [command]
+
+        command = " ".join(quote(c) for c in command)
+        command = ["sh", "-c", command]
+        kwargs["shell"] = False
+    proc = Popen(command, **kwargs)
+    ACTIVE_PROCESSES.add(proc)
+    stdout, stderr = None, None
+    try:
+        stdout, stderr = proc.communicate()
+    finally:
+        ACTIVE_PROCESSES.discard(proc)
+    status = proc.wait()
+    if check and status != 0:
+        raise subprocess.CalledProcessError(status, command, output=stderr)
+    return stdout, stderr, status
+
+
+# Replacement strings in environment variables.
+REPLACEMENTS = {
+    "DIR": DIR.scripts,
+    "MOZ_FETCHES_DIR": DIR.fetches,
+    "MOZ_UPLOAD_DIR": env["MOZ_UPLOAD_DIR"],
+    "OUTDIR": OUTDIR,
+}
+
+# Add in environment variable settings for this variant. Normally used to
+# modify the flags passed to the shell or to set the GC zeal mode.
+for k, v in variant.get("env", {}).items():
+    env[k] = v.format(**REPLACEMENTS)
+
+if AUTOMATION:
+    # Currently only supported on linux64.
+    if platform.system() == "Linux" and word_bits == 64:
+        use_minidump = variant.get("use_minidump", True)
+    else:
+        use_minidump = False
+else:
+    use_minidump = False
+
+
+def resolve_path(dirs, *components):
+    if None in components:
+        return None
+    for dir in dirs:
+        path = os.path.join(dir, *components)
+        if os.path.exists(path):
+            return path
+
+
+if use_minidump:
+    env.setdefault("MINIDUMP_SAVE_PATH", env["MOZ_UPLOAD_DIR"])
+
+    injector_basename = {
+        "Linux": "libbreakpadinjector.so",
+        "Darwin": "breakpadinjector.dylib",
+    }.get(platform.system())
+
+    injector_lib = resolve_path((DIR.fetches,), "injector", injector_basename)
+    stackwalk = resolve_path((DIR.fetches,), "minidump-stackwalk", "minidump-stackwalk")
+    if stackwalk is not None:
+        env.setdefault("MINIDUMP_STACKWALK", stackwalk)
+    dump_syms = resolve_path((DIR.fetches,), "dump_syms", "dump_syms")
+    if dump_syms is not None:
+        env.setdefault("DUMP_SYMS", dump_syms)
+
+    if injector_lib is None:
+        use_minidump = False
+
+    info("use_minidump is {}".format(use_minidump))
+    info("  MINIDUMP_SAVE_PATH={}".format(env["MINIDUMP_SAVE_PATH"]))
+    info("  injector lib is {}".format(injector_lib))
+    info("  MINIDUMP_STACKWALK={}".format(env.get("MINIDUMP_STACKWALK")))
+
+
+mozconfig = os.path.join(DIR.source, "mozconfig.autospider")
+CONFIGURE_ARGS += " --prefix={OBJDIR}/dist".format(OBJDIR=quote(OBJDIR))
+
+# Generate a mozconfig.
+with open(mozconfig, "wt") as fh:
+    if AUTOMATION and platform.system() == "Windows":
+        fh.write('. "$topsrcdir/build/%s/mozconfig.vs-latest"\n' % variant_platform)
+    fh.write("ac_add_options --enable-project=js\n")
+    fh.write("ac_add_options " + CONFIGURE_ARGS + "\n")
+    fh.write("mk_add_options MOZ_OBJDIR=" + quote(OBJDIR) + "\n")
+
+env["MOZCONFIG"] = mozconfig
+
+mach = os.path.join(DIR.source, "mach")
+
+if not args.nobuild:
+    # Do the build
+    run_command([sys.executable, mach, "build"], check=True)
+
+    if use_minidump:
+        # Convert symbols to breakpad format.
+        cmd_env = env.copy()
+        cmd_env["MOZ_SOURCE_REPO"] = "file://" + DIR.source
+        cmd_env["RUSTC_COMMIT"] = "0"
+        cmd_env["MOZ_CRASHREPORTER"] = "1"
+        cmd_env["MOZ_AUTOMATION_BUILD_SYMBOLS"] = "1"
+        run_command(
+            [
+                sys.executable,
+                mach,
+                "build",
+                "recurse_syms",
+            ],
+            check=True,
+            env=cmd_env,
+        )
+
+COMMAND_PREFIX = []
+# On Linux, disable ASLR to make shell builds a bit more reproducible.
+# Bug 1795718 - Disable in automation for now as call to setarch requires extra
+# docker privileges.
+if not AUTOMATION and subprocess.call("type setarch >/dev/null 2>&1", shell=True) == 0:
+    COMMAND_PREFIX.extend(["setarch", platform.machine(), "-R"])
+
+
+def run_test_command(command, **kwargs):
+    _, _, status = run_command(COMMAND_PREFIX + command, check=False, **kwargs)
+    return status
+
+
+def run_jsapitests(args):
+    jsapi_test_binary = os.path.join(OBJDIR, "dist", "bin", "jsapi-tests")
+    test_env = env.copy()
+    test_env["TOPSRCDIR"] = DIR.source
+    if use_minidump and platform.system() == "Linux":
+        test_env["LD_PRELOAD"] = injector_lib
+    st = run_test_command([jsapi_test_binary] + args, env=test_env)
+    if st < 0:
+        print(
+            "PROCESS-CRASH | {} | application crashed".format(
+                " ".join(["jsapi-tests"] + args)
+            )
+        )
+        print("Return code: {}".format(st))
+    return st
+
+
+default_test_suites = frozenset(["jstests", "jittest", "jsapitests", "checks"])
+nondefault_test_suites = frozenset(["gdb"])
+all_test_suites = default_test_suites | nondefault_test_suites
+
+test_suites = set(default_test_suites)
+
+
+def normalize_tests(tests):
+    if "all" in tests:
+        return default_test_suites
+    return tests
+
+
+# Override environment variant settings conditionally.
+for k, v in variant.get("conditional-env", {}).get(variant_platform, {}).items():
+    env[k] = v.format(**REPLACEMENTS)
+
+# Skip any tests that are not run on this platform (or the 'all' platform).
+test_suites -= set(
+    normalize_tests(variant.get("skip-tests", {}).get(variant_platform, []))
+)
+test_suites -= set(normalize_tests(variant.get("skip-tests", {}).get("all", [])))
+
+# Add in additional tests for this platform (or the 'all' platform).
+test_suites |= set(
+    normalize_tests(variant.get("extra-tests", {}).get(variant_platform, []))
+)
+test_suites |= set(normalize_tests(variant.get("extra-tests", {}).get("all", [])))
+
+# Now adjust the variant's default test list with command-line arguments.
+test_suites |= set(normalize_tests(args.run_tests.split(",")))
+test_suites -= set(normalize_tests(args.skip_tests.split(",")))
+if "all" in args.skip_tests.split(","):
+    test_suites = []
+
+# Bug 1557130 - Atomics tests can create many additional threads which can
+# lead to resource exhaustion, resulting in intermittent failures. This was
+# only seen on beefy machines (> 32 cores), so limit the number of parallel
+# workers for now.
+#
+# Bug 1391877 - Windows test runs are getting mysterious timeouts when run
+# through taskcluster, but only when running many jit-test jobs in parallel.
+# Even at 16, some tests can overflow the paging file.
+worker_max = multiprocessing.cpu_count()
+jstest_workers = worker_max
+jittest_workers = worker_max
+if platform.system() == "Windows":
+    jstest_workers = min(worker_max, 16)
+    env["JSTESTS_EXTRA_ARGS"] = "-j{} ".format(jstest_workers) + env.get(
+        "JSTESTS_EXTRA_ARGS", ""
+    )
+    jittest_workers = min(worker_max, 8)
+    env["JITTEST_EXTRA_ARGS"] = "-j{} ".format(jittest_workers) + env.get(
+        "JITTEST_EXTRA_ARGS", ""
+    )
+print(
+    f"using {jstest_workers}/{worker_max} workers for jstests, "
+    f"{jittest_workers}/{worker_max} for jittest"
+)
+
+if use_minidump:
+    # Set up later js invocations to run with the breakpad injector loaded.
+    # Originally, I intended for this to be used with LD_PRELOAD, but when
+    # cross-compiling from 64- to 32-bit, that will fail and produce stderr
+    # output when running any 64-bit commands, which breaks eg mozconfig
+    # processing. So use the --dll command line mechanism universally.
+    for v in ("JSTESTS_EXTRA_ARGS", "JITTEST_EXTRA_ARGS"):
+        env[v] = "--args='--dll %s' %s" % (injector_lib, env.get(v, ""))
+
+# Always run all enabled tests, even if earlier ones failed. But return the
+# first failed status.
+results = [("(make-nonempty)", 0)]
+
+if "checks" in test_suites:
+    results.append(("make check", run_test_command([MAKE, "check"])))
+
+if "jittest" in test_suites:
+    results.append(("make check-jit-test", run_test_command([MAKE, "check-jit-test"])))
+if "jsapitests" in test_suites:
+    st = run_jsapitests([])
+    if st == 0:
+        st = run_jsapitests(["--frontend-only"])
+    results.append(("jsapi-tests", st))
+if "jstests" in test_suites:
+    results.append(("jstests", run_test_command([MAKE, "check-jstests"])))
+if "gdb" in test_suites:
+    test_script = os.path.join(DIR.js_src, "gdb", "run-tests.py")
+    auto_args = ["-s", "-o", "--no-progress"] if AUTOMATION else []
+    extra_args = env.get("GDBTEST_EXTRA_ARGS", "").split(" ")
+    results.append(
+        (
+            "gdb",
+            run_test_command([PYTHON, test_script, *auto_args, *extra_args, OBJDIR]),
+        )
+    )
+
+# FIXME bug 1291449: This would be unnecessary if we could run msan with -mllvm
+# -msan-keep-going, but in clang 3.8 it causes a hang during compilation.
+if variant.get("ignore-test-failures"):
+    logging.warning("Ignoring test results %s" % (results,))
+    results = [("ignored", 0)]
+
+if args.variant == "msan":
+    files = filter(lambda f: f.startswith("sanitize_log."), os.listdir(OUTDIR))
+    fullfiles = [os.path.join(OUTDIR, f) for f in files]
+
+    # Summarize results
+    sites = Counter()
+    errors = Counter()
+    for filename in fullfiles:
+        with open(os.path.join(OUTDIR, filename), "rb") as fh:
+            for line in fh:
+                m = re.match(
+                    r"^SUMMARY: \w+Sanitizer: (?:data race|use-of-uninitialized-value) (.*)",  # NOQA: E501
+                    line.strip(),
+                )
+                if m:
+                    # Some reports include file:line:column, some just
+                    # file:line. Just in case it's nondeterministic, we will
+                    # canonicalize to just the line number.
+                    site = re.sub(r"^(\S+?:\d+)(:\d+)* ", r"\1 ", m.group(1))
+                    sites[site] += 1
+
+    # Write a summary file and display it to stdout.
+    summary_filename = os.path.join(
+        env["MOZ_UPLOAD_DIR"], "%s_summary.txt" % args.variant
+    )
+    with open(summary_filename, "wb") as outfh:
+        for location, count in sites.most_common():
+            print >> outfh, "%d %s" % (count, location)
+    print(open(summary_filename, "rb").read())
+
+    if "max-errors" in variant:
+        max_allowed = variant["max-errors"]
+        print("Found %d errors out of %d allowed" % (len(sites), max_allowed))
+        if len(sites) > max_allowed:
+            results.append(("too many msan errors", 1))
+
+    # Gather individual results into a tarball. Note that these are
+    # distinguished only by pid of the JS process running within each test, so
+    # given the 16-bit limitation of pids, it's totally possible that some of
+    # these files will be lost due to being overwritten.
+    command = [
+        "tar",
+        "-C",
+        OUTDIR,
+        "-zcf",
+        os.path.join(env["MOZ_UPLOAD_DIR"], "%s.tar.gz" % args.variant),
+    ]
+    command += files
+    subprocess.call(command)
+
+# Upload dist/bin/js as js.wasm for the WASI build.
+if args.variant == "wasi":
+    command = [
+        "cp",
+        os.path.join(OBJDIR, "dist/bin/js"),
+        os.path.join(env["MOZ_UPLOAD_DIR"], "js.wasm"),
+    ]
+    subprocess.call(command)
+
+# Generate stacks from minidumps.
+if use_minidump:
+    venv_python = os.path.join(OBJDIR, "_virtualenvs", "build", "bin", "python3")
+    run_command(
+        [
+            venv_python,
+            os.path.join(DIR.source, "testing/mozbase/mozcrash/mozcrash/mozcrash.py"),
+            os.getenv("TMPDIR", "/tmp"),
+            os.path.join(OBJDIR, "dist/crashreporter-symbols"),
+        ]
+    )
+
+for name, st in results:
+    print("exit status %d for '%s'" % (st, name))
+
+# Pick the "worst" exit status. SIGSEGV might give a status of -11, so use the
+# maximum absolute value instead of just the maximum.
+exit_status = max((st for _, st in results), key=abs)
+
+# The exit status on Windows can be something like 2147483651 (0x80000003),
+# which will be converted to status zero in the caller. Mask off the high bits,
+# but if the result is zero then fall back to returning 1.
+if exit_status & 0xFF:
+    sys.exit(exit_status & 0xFF)
+else:
+    sys.exit(1 if exit_status else 0)
diff --git a/js/src/devtools/automation/cgc-jittest-timeouts.txt b/js/src/devtools/automation/cgc-jittest-timeouts.txt
new file mode 100644
index 0000000000..cde72dfd2c
--- /dev/null
+++ b/js/src/devtools/automation/cgc-jittest-timeouts.txt
@@ -0,0 +1,55 @@
+asm.js/testBug1117235.js
+asm.js/testParallelCompile.js
+auto-regress/bug653395.js
+auto-regress/bug654392.js
+auto-regress/bug675251.js
+auto-regress/bug729797.js
+baseline/bug847446.js
+baseline/bug852175.js
+basic/bug1610192.js
+basic/bug632964-regexp.js
+basic/bug656261.js
+basic/bug677957-2.js
+basic/bug753283.js
+basic/bug867946.js
+basic/destructuring-iterator.js
+basic/offThreadCompileToStencil-01.js
+basic/testAtomize.js
+basic/testBug614653.js
+basic/testBug686274.js
+basic/testManyVars.js
+basic/testTypedArrayInit.js
+debug/DebuggeeWouldRun-01.js
+debug/DebuggeeWouldRun-02.js
+gc/bug-1014972.js
+gc/bug-1246593.js
+gc/bug-906236.js
+gc/bug-906241.js
+ion/bug1197769.js
+ion/bug779245.js
+ion/bug787921.js
+ion/bug977966.js
+ion/close-iterators-1.js
+parallel/alloc-many-objs.js
+parallel/alloc-too-many-objs.js
+parser/bug-1263881-1.js
+parser/bug-1263881-2.js
+parser/bug-1263881-3.js
+parser/bug-1355046.js
+parser/modifier-yield-without-operand-2.js
+saved-stacks/bug-1006876-too-much-recursion.js
+self-test/assertDeepEq.js
+sunspider/check-string-unpack-code.js
+TypedObject/jit-read-u16-from-struct-array-in-struct.js
+TypedObject/jit-read-u32-from-struct-array-in-struct.js
+v8-v5/check-earley-boyer.js
+v8-v5/check-raytrace.js
+v8-v5/check-regexp.js
+v8-v5/check-splay.js
+wasm/spec/br_table.wast.js
+wasm/spec/f32.wast.js
+wasm/spec/f32_cmp.wast.js
+wasm/spec/f64.wast.js
+wasm/spec/f64_cmp.wast.js
+wasm/spec/float_exprs.wast.js
+xdr/decode-off-thread.js
diff --git a/js/src/devtools/automation/cgc-jstests-slow.txt b/js/src/devtools/automation/cgc-jstests-slow.txt
new file mode 100644
index 0000000000..16290cb047
--- /dev/null
+++ b/js/src/devtools/automation/cgc-jstests-slow.txt
@@ -0,0 +1,65 @@
+non262/object/15.2.3.6-dictionary-redefinition-01-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-02-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-03-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-04-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-05-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-06-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-07-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-08-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-09-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-10-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-11-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-12-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-13-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-14-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-15-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-16-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-17-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-18-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-19-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-20-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-21-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-22-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-23-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-24-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-25-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-26-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-27-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-28-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-29-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-30-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-31-of-32.js
+non262/object/15.2.3.6-dictionary-redefinition-32-of-32.js
+non262/object/15.2.3.6-middle-redefinition-1-of-8.js
+non262/object/15.2.3.6-middle-redefinition-2-of-8.js
+non262/object/15.2.3.6-middle-redefinition-3-of-8.js
+non262/object/15.2.3.6-middle-redefinition-4-of-8.js
+non262/object/15.2.3.6-middle-redefinition-5-of-8.js
+non262/object/15.2.3.6-middle-redefinition-6-of-8.js
+non262/object/15.2.3.6-middle-redefinition-7-of-8.js
+non262/object/15.2.3.6-middle-redefinition-8-of-8.js
+non262/object/15.2.3.6-redefinition-1-of-4.js
+non262/object/15.2.3.6-redefinition-2-of-4.js
+non262/object/15.2.3.6-redefinition-3-of-4.js
+non262/object/15.2.3.6-redefinition-4-of-4.js
+non262/extensions/array-isArray-proxy-recursion.js
+non262/String/normalize-generateddata-part0.js
+non262/String/normalize-generateddata-part1-not-listed.js
+non262/String/normalize-generateddata-part1.js
+non262/String/normalize-generateddata-part2.js
+non262/String/normalize-generateddata-part3.js
+non262/GC/regress-203278-2.js
+non262/GC/regress-203278-3.js
+non262/GC/regress-278725.js
+non262/regress/regress-312588.js
+non262/regress/regress-321971.js
+non262/regress/regress-360969-01.js
+non262/regress/regress-360969-02.js
+non262/regress/regress-360969-03.js
+non262/regress/regress-360969-04.js
+non262/regress/regress-360969-05.js
+non262/regress/regress-360969-06.js
+non262/extensions/regress-477187.js
+non262/regress/regress-452498-052-a.js
+non262/extensions/clone-complex-object.js
+non262/extensions/clone-object-deep.js
diff --git a/js/src/devtools/automation/smoosh-jittest-known-failure.txt b/js/src/devtools/automation/smoosh-jittest-known-failure.txt
new file mode 100644
index 0000000000..8d32545934
--- /dev/null
+++ b/js/src/devtools/automation/smoosh-jittest-known-failure.txt
@@ -0,0 +1,4 @@
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/641
+class/class-static-01.js
+class/class-static-02.js
+class/class-static-03.js
diff --git a/js/src/devtools/automation/smoosh-jstests-known-failure-and-slow.txt b/js/src/devtools/automation/smoosh-jstests-known-failure-and-slow.txt
new file mode 100644
index 0000000000..7d905ca6c7
--- /dev/null
+++ b/js/src/devtools/automation/smoosh-jstests-known-failure-and-slow.txt
@@ -0,0 +1,81 @@
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/635
+test262/language/expressions/assignmenttargettype/parenthesized-primaryexpression-objectliteral.js
+
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/641
+test262/language/expressions/function/static-init-await-binding.js
+test262/language/expressions/generators/static-init-await-binding.js
+test262/language/expressions/object/ident-name-prop-name-literal-await-static-init.js
+test262/language/expressions/object/identifier-shorthand-static-init-await-valid.js
+test262/language/expressions/object/method-definition/static-init-await-binding-accessor.js
+test262/language/expressions/object/method-definition/static-init-await-binding-generator.js
+test262/language/expressions/object/method-definition/static-init-await-binding-normal.js
+test262/language/statements/class/static-init-abrupt.js
+test262/language/statements/class/static-init-arguments-functions.js
+test262/language/statements/class/static-init-arguments-methods.js
+test262/language/statements/class/static-init-await-binding-valid.js
+test262/language/statements/class/static-init-expr-new-target.js
+test262/language/statements/class/static-init-expr-this.js
+test262/language/statements/class/static-init-scope-lex-close.js
+test262/language/statements/class/static-init-scope-var-close.js
+test262/language/statements/class/static-init-scope-var-derived.js
+test262/language/statements/class/static-init-scope-var-open.js
+test262/language/statements/class/static-init-statement-list-optional.js
+test262/language/statements/class/static-init-super-property.js
+test262/language/statements/const/static-init-await-binding-valid.js
+test262/language/statements/function/static-init-await-binding-valid.js
+test262/language/statements/let/static-init-await-binding-valid.js
+test262/language/statements/try/static-init-await-binding-valid.js
+test262/language/statements/variable/dstr/ary-ptrn-elem-id-static-init-await-valid.js
+test262/language/statements/variable/dstr/obj-ptrn-elem-id-static-init-await-valid.js
+test262/language/statements/variable/static-init-await-binding-valid.js
+
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/650
+test262/language/expressions/dynamic-import/2nd-param-assert-enumeration-abrupt.js
+test262/language/expressions/dynamic-import/2nd-param-assert-enumeration.js
+test262/language/expressions/dynamic-import/2nd-param-assert-non-object.js
+test262/language/expressions/dynamic-import/2nd-param-assert-undefined.js
+test262/language/expressions/dynamic-import/2nd-param-assert-value-abrupt.js
+test262/language/expressions/dynamic-import/2nd-param-assert-value-non-string.js
+test262/language/expressions/dynamic-import/2nd-param-evaluation-abrupt-return.js
+test262/language/expressions/dynamic-import/2nd-param-evaluation-abrupt-throw.js
+test262/language/expressions/dynamic-import/2nd-param-evaluation-sequence.js
+test262/language/expressions/dynamic-import/2nd-param-get-assert-error.js
+test262/language/expressions/dynamic-import/2nd-param-in.js
+test262/language/expressions/dynamic-import/2nd-param-non-object.js
+test262/language/expressions/dynamic-import/2nd-param-trailing-comma-fulfill.js
+test262/language/expressions/dynamic-import/2nd-param-trailing-comma-reject.js
+test262/language/expressions/dynamic-import/2nd-param-yield-expr.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-labeled-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-labeled-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-do-while-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-do-while-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-braceless-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-braceless-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-return-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-return-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-braceless-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-braceless-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-expression-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-expression-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/top-level-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/top-level-trailing-comma-second.js
+test262/language/expressions/dynamic-import/trailing-comma-fulfill.js
+test262/language/expressions/dynamic-import/trailing-comma-reject.js
+
+# slow
+non262/String/normalize-generateddata-part0.js
+non262/String/normalize-generateddata-part1-not-listed.js
+non262/String/normalize-generateddata-part1.js
+non262/String/normalize-generateddata-part2.js
+non262/String/normalize-generateddata-part3.js
+non262/regress/regress-155081-2.js
diff --git a/js/src/devtools/automation/smoosh-jstests-known-failure.txt b/js/src/devtools/automation/smoosh-jstests-known-failure.txt
new file mode 100644
index 0000000000..7a3be5c211
--- /dev/null
+++ b/js/src/devtools/automation/smoosh-jstests-known-failure.txt
@@ -0,0 +1,73 @@
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/635
+test262/language/expressions/assignmenttargettype/parenthesized-primaryexpression-objectliteral.js
+
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/641
+test262/language/expressions/function/static-init-await-binding.js
+test262/language/expressions/generators/static-init-await-binding.js
+test262/language/expressions/object/ident-name-prop-name-literal-await-static-init.js
+test262/language/expressions/object/identifier-shorthand-static-init-await-valid.js
+test262/language/expressions/object/method-definition/static-init-await-binding-accessor.js
+test262/language/expressions/object/method-definition/static-init-await-binding-generator.js
+test262/language/expressions/object/method-definition/static-init-await-binding-normal.js
+test262/language/statements/class/static-init-abrupt.js
+test262/language/statements/class/static-init-arguments-functions.js
+test262/language/statements/class/static-init-arguments-methods.js
+test262/language/statements/class/static-init-await-binding-valid.js
+test262/language/statements/class/static-init-expr-new-target.js
+test262/language/statements/class/static-init-expr-this.js
+test262/language/statements/class/static-init-scope-lex-close.js
+test262/language/statements/class/static-init-scope-var-close.js
+test262/language/statements/class/static-init-scope-var-derived.js
+test262/language/statements/class/static-init-scope-var-open.js
+test262/language/statements/class/static-init-statement-list-optional.js
+test262/language/statements/class/static-init-super-property.js
+test262/language/statements/const/static-init-await-binding-valid.js
+test262/language/statements/function/static-init-await-binding-valid.js
+test262/language/statements/let/static-init-await-binding-valid.js
+test262/language/statements/try/static-init-await-binding-valid.js
+test262/language/statements/variable/dstr/ary-ptrn-elem-id-static-init-await-valid.js
+test262/language/statements/variable/dstr/obj-ptrn-elem-id-static-init-await-valid.js
+test262/language/statements/variable/static-init-await-binding-valid.js
+
+# https://github.com/mozilla-spidermonkey/jsparagus/issues/650
+test262/language/expressions/dynamic-import/2nd-param-assert-enumeration-abrupt.js
+test262/language/expressions/dynamic-import/2nd-param-assert-enumeration.js
+test262/language/expressions/dynamic-import/2nd-param-assert-non-object.js
+test262/language/expressions/dynamic-import/2nd-param-assert-undefined.js
+test262/language/expressions/dynamic-import/2nd-param-assert-value-abrupt.js
+test262/language/expressions/dynamic-import/2nd-param-assert-value-non-string.js
+test262/language/expressions/dynamic-import/2nd-param-evaluation-abrupt-return.js
+test262/language/expressions/dynamic-import/2nd-param-evaluation-abrupt-throw.js
+test262/language/expressions/dynamic-import/2nd-param-evaluation-sequence.js
+test262/language/expressions/dynamic-import/2nd-param-get-assert-error.js
+test262/language/expressions/dynamic-import/2nd-param-in.js
+test262/language/expressions/dynamic-import/2nd-param-non-object.js
+test262/language/expressions/dynamic-import/2nd-param-trailing-comma-fulfill.js
+test262/language/expressions/dynamic-import/2nd-param-trailing-comma-reject.js
+test262/language/expressions/dynamic-import/2nd-param-yield-expr.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-labeled-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-labeled-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-block-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-do-while-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-do-while-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-braceless-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-braceless-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-else-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-return-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-return-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-function-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-braceless-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-braceless-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-if-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-expression-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-expression-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/nested-with-trailing-comma-second.js
+test262/language/expressions/dynamic-import/syntax/valid/top-level-trailing-comma-first.js
+test262/language/expressions/dynamic-import/syntax/valid/top-level-trailing-comma-second.js
+test262/language/expressions/dynamic-import/trailing-comma-fulfill.js
+test262/language/expressions/dynamic-import/trailing-comma-reject.js
diff --git a/js/src/devtools/automation/smoosh-jstests-slow.txt b/js/src/devtools/automation/smoosh-jstests-slow.txt
new file mode 100644
index 0000000000..e69de29bb2
--- /dev/null
+++ b/js/src/devtools/automation/smoosh-jstests-slow.txt
diff --git a/js/src/devtools/automation/tsan-slow.txt b/js/src/devtools/automation/tsan-slow.txt
new file mode 100644
index 0000000000..06dc763c08
--- /dev/null
+++ b/js/src/devtools/automation/tsan-slow.txt
@@ -0,0 +1,23 @@
+# Skip tests that run too slowly under tsan.
+basic/spread-call-maxarg.js
+basic/spread-call-near-maxarg.js
+arrays/too-long-array-splice.js
+bug-1698543.js
+# Skip tests that use too much memory under tsan - see bug 1519263.
+bug1355573.js
+max-string-length.js
+expr-decompiler-bug1475953.js
+regress-303213.js
+f32.wast.js
+f64.wast.js
+f32_cmp.wast.js
+f64_cmp.wast.js
+bug1470732.js
+bug1238815.js
+bug1315943.js
+bug-1382431.js
+float_exprs.wast.js
+bug858586.js
+bug1296667.js
+bug-1465695.js
+integer.js
diff --git a/js/src/devtools/automation/variants/arm-sim b/js/src/devtools/automation/variants/arm-sim
new file mode 100644
index 0000000000..80ca937e01
--- /dev/null
+++ b/js/src/devtools/automation/variants/arm-sim
@@ -0,0 +1,7 @@
+{
+    "__comment1": "Bug 1700372: --disable-clang-plugin is needed to avoid a warning (that we treat as an error) for comparing a number to itself to test for NaN",
+    "configure-args": "--enable-simulator=arm --target=i686-pc-linux --enable-rust-simd --disable-clang-plugin",
+    "optimize": true,
+    "debug": true,
+    "bits": 32
+}
diff --git a/js/src/devtools/automation/variants/arm-sim-osx b/js/src/devtools/automation/variants/arm-sim-osx
new file mode 100644
index 0000000000..4e03dadd9f
--- /dev/null
+++ b/js/src/devtools/automation/variants/arm-sim-osx
@@ -0,0 +1,6 @@
+{
+    "configure-args": "--enable-simulator=arm --target=i686-apple-darwin10.0.0 --enable-rust-simd",
+    "optimize": true,
+    "debug": true,
+    "bits": 32
+}
diff --git a/js/src/devtools/automation/variants/arm64-sim b/js/src/devtools/automation/variants/arm64-sim
new file mode 100644
index 0000000000..bbaec58fac
--- /dev/null
+++ b/js/src/devtools/automation/variants/arm64-sim
@@ -0,0 +1,10 @@
+{
+    "configure-args": "--enable-simulator=arm64 --enable-rust-simd",
+    "optimize": true,
+    "debug": true,
+    "env": {
+        "JSTESTS_EXTRA_ARGS": "--exclude-file={DIR}/arm64-jstests-slow.txt",
+        "JITTEST_EXTRA_ARGS": "--ignore-timeouts={DIR}/arm64-jittests-timeouts.txt --jitflags=none --args=--baseline-eager -x ion/ -x asm.js/"
+    },
+    "bits": 64
+}
diff --git a/js/src/devtools/automation/variants/asan b/js/src/devtools/automation/variants/asan
new file mode 100644
index 0000000000..62091639f6
--- /dev/null
+++ b/js/src/devtools/automation/variants/asan
@@ -0,0 +1,10 @@
+{
+    "configure-args": "--enable-debug-symbols='-gline-tables-only' --enable-gczeal --disable-jemalloc --enable-address-sanitizer --enable-rust-simd",
+    "optimize": true,
+    "debug": false,
+    "compiler": "clang",
+    "env": {
+        "LLVM_SYMBOLIZER": "{MOZ_FETCHES_DIR}/llvm-symbolizer/bin/llvm-symbolizer"
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/compacting b/js/src/devtools/automation/variants/compacting
new file mode 100644
index 0000000000..68d22bd72e
--- /dev/null
+++ b/js/src/devtools/automation/variants/compacting
@@ -0,0 +1,14 @@
+{
+    "configure-args": "--enable-ctypes --enable-rust-simd",
+    "optimize": true,
+    "debug": true,
+    "env": {
+        "JS_GC_ZEAL": "IncrementalMultipleSlices",
+        "JITTEST_EXTRA_ARGS": "--args=--enable-parallel-marking --jitflags=debug --ignore-timeouts={DIR}/cgc-jittest-timeouts.txt",
+        "JSTESTS_EXTRA_ARGS": "--args=--enable-parallel-marking --exclude-file={DIR}/cgc-jstests-slow.txt"
+    },
+    "skip-tests": {
+        "win32": ["jstests"],
+        "win64": ["jstests"]
+    }
+}
diff --git a/js/src/devtools/automation/variants/dtrace b/js/src/devtools/automation/variants/dtrace
new file mode 100644
index 0000000000..0678819225
--- /dev/null
+++ b/js/src/devtools/automation/variants/dtrace
@@ -0,0 +1,5 @@
+{
+    "configure-args": "--enable-dtrace --enable-debug-symbols --enable-rust-simd",
+    "optimize": true,
+    "debug": true,
+}
diff --git a/js/src/devtools/automation/variants/fuzzilli b/js/src/devtools/automation/variants/fuzzilli
new file mode 100644
index 0000000000..61605e3a96
--- /dev/null
+++ b/js/src/devtools/automation/variants/fuzzilli
@@ -0,0 +1,14 @@
+{
+    "configure-args": "--enable-js-fuzzilli --enable-fuzzing --enable-gczeal --disable-shared-js",
+    "optimize": true,
+    "debug": true,
+    "nspr": false,
+    "compiler": "clang",
+    "env": {
+        "JITTEST_EXTRA_ARGS": "--jitflags=ion"
+    },
+    "skip-tests": {
+        "all": ["jstests"]
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/fuzzing b/js/src/devtools/automation/variants/fuzzing
new file mode 100644
index 0000000000..146b89e355
--- /dev/null
+++ b/js/src/devtools/automation/variants/fuzzing
@@ -0,0 +1,13 @@
+{
+    "configure-args": "--enable-fuzzing --enable-gczeal --enable-debug-symbols='-gline-tables-only -gdwarf-2' --disable-jemalloc --disable-stdcxx-compat --enable-address-sanitizer --enable-ctypes --enable-nspr-build --enable-rust-simd",
+    "optimize": true,
+    "debug": false,
+    "compiler": "clang",
+    "env": {
+        "JITTEST_EXTRA_ARGS": "--jitflags=none",
+        "JSTESTS_EXTRA_ARGS": "--jitflags=none",
+        "LLVM_SYMBOLIZER": "{MOZ_FETCHES_DIR}/llvm-symbolizer/bin/llvm-symbolizer",
+        "ASAN_SYMBOLIZER_PATH": "{MOZ_FETCHES_DIR}/llvm-symbolizer/bin/llvm-symbolizer"
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/gdb b/js/src/devtools/automation/variants/gdb
new file mode 100644
index 0000000000..d86d265680
--- /dev/null
+++ b/js/src/devtools/automation/variants/gdb
@@ -0,0 +1,16 @@
+{
+    "configure-args": "--enable-rust-simd",
+    "debug": true,
+    "optimize": false,
+    "compiler": "gcc",
+    "skip-tests": {
+        "all": ["jstests", "jittest", "jsapitests"]
+    },
+    "extra-tests": {
+        "all": ["gdb"]
+    },
+    "env": {
+        "GDBTEST_EXTRA_ARGS": "--exclude=unwind"
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/msan b/js/src/devtools/automation/variants/msan
new file mode 100644
index 0000000000..e85e67dfb5
--- /dev/null
+++ b/js/src/devtools/automation/variants/msan
@@ -0,0 +1,14 @@
+{
+    "configure-args": "--enable-debug-symbols='-gline-tables-only' --disable-jemalloc --enable-memory-sanitizer --without-system-zlib --enable-rust-simd",
+    "optimize": true,
+    "debug": false,
+    "compiler": "clang",
+    "env": {
+        "JITTEST_EXTRA_ARGS": "--jitflags=interp --ignore-timeouts={DIR}/cgc-jittest-timeouts.txt",
+        "JSTESTS_EXTRA_ARGS": "--jitflags=interp --exclude-file={DIR}/cgc-jstests-slow.txt",
+        "MSAN_OPTIONS": "external_symbolizer_path={MOZ_FETCHES_DIR}/llvm-symbolizer/bin/llvm-symbolizer:log_path={OUTDIR}/sanitize_log"
+    },
+    "ignore-test-failures": "true",
+    "max-errors": 7,
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/nojit b/js/src/devtools/automation/variants/nojit
new file mode 100644
index 0000000000..9cebcfcd16
--- /dev/null
+++ b/js/src/devtools/automation/variants/nojit
@@ -0,0 +1,4 @@
+{
+    "configure-args": "--disable-jit --enable-warnings-as-errors --enable-rust-simd",
+    "optimize": true
+}
diff --git a/js/src/devtools/automation/variants/nojit-debug b/js/src/devtools/automation/variants/nojit-debug
new file mode 100644
index 0000000000..c067d617b1
--- /dev/null
+++ b/js/src/devtools/automation/variants/nojit-debug
@@ -0,0 +1,4 @@
+{
+    "configure-args": "--disable-jit --enable-warnings-as-errors --enable-rust-simd",
+    "optimize": false
+}
diff --git a/js/src/devtools/automation/variants/nonunified b/js/src/devtools/automation/variants/nonunified
new file mode 100644
index 0000000000..9e6c40430f
--- /dev/null
+++ b/js/src/devtools/automation/variants/nonunified
@@ -0,0 +1,10 @@
+{
+    "configure-args": "--enable-warnings-as-errors --enable-rust-simd",
+    "debug": true,
+    "env": {
+        "JS_SMOOSH_DISABLE_OPCODE_CHECK": "1"
+    },
+    "skip-tests": {
+        "all": ["jstests", "jittest", "checks"]
+    }
+}
diff --git a/js/src/devtools/automation/variants/plain b/js/src/devtools/automation/variants/plain
new file mode 100644
index 0000000000..0c97a5d535
--- /dev/null
+++ b/js/src/devtools/automation/variants/plain
@@ -0,0 +1,8 @@
+{
+    "configure-args": "--enable-rust-simd",
+    "optimize": true,
+    "compiler": "gcc",
+    "env": {
+        "JSTESTS_EXTRA_ARGS": "--jitflags=jstests"
+    }
+}
diff --git a/js/src/devtools/automation/variants/plaindebug b/js/src/devtools/automation/variants/plaindebug
new file mode 100644
index 0000000000..c03419f8f9
--- /dev/null
+++ b/js/src/devtools/automation/variants/plaindebug
@@ -0,0 +1,7 @@
+{
+    "configure-args": "--enable-rust-simd",
+    "debug": true,
+    "env": {
+        "JSTESTS_EXTRA_ARGS": "--jitflags=debug"
+    }
+}
diff --git a/js/src/devtools/automation/variants/rootanalysis b/js/src/devtools/automation/variants/rootanalysis
new file mode 100644
index 0000000000..7c0fb5242b
--- /dev/null
+++ b/js/src/devtools/automation/variants/rootanalysis
@@ -0,0 +1,9 @@
+{
+    "configure-args": "--enable-ctypes --enable-rust-simd",
+    "optimize": true,
+    "debug": true,
+    "env": {
+        "JS_GC_ZEAL": "GenerationalGC",
+        "JSTESTS_EXTRA_ARGS": "--jitflags=debug"
+    }
+}
diff --git a/js/src/devtools/automation/variants/rtdebug b/js/src/devtools/automation/variants/rtdebug
new file mode 100644
index 0000000000..d3450261ff
--- /dev/null
+++ b/js/src/devtools/automation/variants/rtdebug
@@ -0,0 +1,8 @@
+{
+    "debug": true,
+    "optimize": true,
+    "configure-args": "--enable-record-tuple",
+    "skip-tests": {
+        "all": ["jittest", "jsapitests", "checks"]
+    }
+}
diff --git a/js/src/devtools/automation/variants/smoosh b/js/src/devtools/automation/variants/smoosh
new file mode 100644
index 0000000000..148c2f8c21
--- /dev/null
+++ b/js/src/devtools/automation/variants/smoosh
@@ -0,0 +1,8 @@
+{
+    "configure-args": "--enable-rust-simd --enable-smoosh",
+    "optimize": true,
+    "env": {
+        "JSTESTS_EXTRA_ARGS": "--args='--smoosh' --jitflags=jstests --exclude-file={DIR}/smoosh-jstests-known-failure.txt",
+        "JITTEST_EXTRA_ARGS": "--args='--smoosh' --exclude-file={DIR}/smoosh-jittest-known-failure.txt"
+    }
+}
diff --git a/js/src/devtools/automation/variants/smooshdebug b/js/src/devtools/automation/variants/smooshdebug
new file mode 100644
index 0000000000..07b50cf917
--- /dev/null
+++ b/js/src/devtools/automation/variants/smooshdebug
@@ -0,0 +1,8 @@
+{
+    "configure-args": "--enable-rust-simd --enable-smoosh",
+    "debug": true,
+    "env": {
+        "JSTESTS_EXTRA_ARGS": "--args='--smoosh' --jitflags=debug --exclude-file={DIR}/smoosh-jstests-known-failure-and-slow.txt",
+        "JITTEST_EXTRA_ARGS": "--args='--smoosh' --exclude-file={DIR}/smoosh-jittest-known-failure.txt"
+    }
+}
diff --git a/js/src/devtools/automation/variants/tsan b/js/src/devtools/automation/variants/tsan
new file mode 100644
index 0000000000..76629bd576
--- /dev/null
+++ b/js/src/devtools/automation/variants/tsan
@@ -0,0 +1,12 @@
+{
+    "configure-args": "--enable-debug-symbols='-gline-tables-only' --disable-jemalloc --enable-thread-sanitizer --enable-rust-simd",
+    "optimize": true,
+    "debug": false,
+    "compiler": "clang",
+    "env": {
+        "LLVM_SYMBOLIZER": "{MOZ_FETCHES_DIR}/llvm-symbolizer/bin/llvm-symbolizer",
+        "JITTEST_EXTRA_ARGS": "--args=--enable-parallel-marking --jitflags=tsan --ignore-timeouts={DIR}/cgc-jittest-timeouts.txt --unusable-error-status --exclude-from={DIR}/tsan-slow.txt",
+        "JSTESTS_EXTRA_ARGS": "--args=--enable-parallel-marking --exclude-file={DIR}/cgc-jstests-slow.txt"
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/warnaserr b/js/src/devtools/automation/variants/warnaserr
new file mode 100644
index 0000000000..98d5e96fe1
--- /dev/null
+++ b/js/src/devtools/automation/variants/warnaserr
@@ -0,0 +1,4 @@
+{
+    "configure-args": "--enable-warnings-as-errors --enable-rust-simd",
+    "optimize": true
+}
diff --git a/js/src/devtools/automation/variants/warnaserrdebug b/js/src/devtools/automation/variants/warnaserrdebug
new file mode 100644
index 0000000000..ca1f14fef1
--- /dev/null
+++ b/js/src/devtools/automation/variants/warnaserrdebug
@@ -0,0 +1,4 @@
+{
+    "configure-args": "--enable-warnings-as-errors",
+    "debug": true
+}
diff --git a/js/src/devtools/automation/variants/wasi b/js/src/devtools/automation/variants/wasi
new file mode 100644
index 0000000000..18fb91ba4e
--- /dev/null
+++ b/js/src/devtools/automation/variants/wasi
@@ -0,0 +1,14 @@
+{
+    "configure-args": "--enable-project=js --target=wasm32-unknown-wasi --disable-stdcxx-compat --without-system-zlib --without-intl-api --disable-jit --disable-shared-js --disable-shared-memory --disable-tests --disable-clang-plugin --disable-debug-symbols --enable-jitspew",
+    "optimize": true,
+    "debug": false,
+    "nspr": false,
+    "compiler": "clang",
+    "env": {
+        "JITTEST_EXTRA_ARGS": "--jitflags=none"
+    },
+    "skip-tests": {
+        "all": ["jstests", "jittest", "jsapitests"]
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/wasi-intl b/js/src/devtools/automation/variants/wasi-intl
new file mode 100644
index 0000000000..dbaaffff66
--- /dev/null
+++ b/js/src/devtools/automation/variants/wasi-intl
@@ -0,0 +1,14 @@
+{
+    "configure-args": "--enable-project=js --target=wasm32-unknown-wasi --disable-stdcxx-compat --without-system-zlib --disable-jit --disable-shared-js --disable-shared-memory --disable-tests --disable-clang-plugin --disable-debug-symbols --enable-jitspew",
+    "optimize": true,
+    "debug": false,
+    "nspr": false,
+    "compiler": "clang",
+    "env": {
+        "JITTEST_EXTRA_ARGS": "--jitflags=none"
+    },
+    "skip-tests": {
+        "all": ["jstests", "jittest", "jsapitests"]
+    },
+    "use_minidump": false
+}
diff --git a/js/src/devtools/automation/variants/wasm-noexperimental b/js/src/devtools/automation/variants/wasm-noexperimental
new file mode 100644
index 0000000000..2d1fcb4e58
--- /dev/null
+++ b/js/src/devtools/automation/variants/wasm-noexperimental
@@ -0,0 +1,7 @@
+{
+    "configure-args": "--wasm-no-experimental",
+    "debug": true,
+    "skip-tests": {
+        "all": ["jstests", "jsapitests"]
+    }
+}
diff --git a/js/src/devtools/gc-ubench/argparse.js b/js/src/devtools/gc-ubench/argparse.js
new file mode 100644
index 0000000000..454b53fb71
--- /dev/null
+++ b/js/src/devtools/gc-ubench/argparse.js
@@ -0,0 +1,127 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Command-line argument parser, modeled after but not identical to Python's
+// argparse.
+
+var ArgParser = class {
+  constructor(desc) {
+    this._params = [];
+    this._doc = desc;
+
+    this.add_argument("--help", {
+      help: "display this help message",
+    });
+  }
+
+  // name is '--foo', '-f', or an array of aliases.
+  //
+  // spec is an options object with keys:
+  //   dest: key name to store the result in (optional for long options)
+  //   default: value to use if not passed on command line (optional)
+  //   help: description of the option to show in --help
+  //   options: array of valid choices
+  //
+  // Prefixes of long option names are allowed. If a prefix is ambiguous, it
+  // will match the first parameter added to the ArgParser.
+  add_argument(name, spec) {
+    const names = Array.isArray(name) ? name : [name];
+
+    spec = Object.assign({}, spec);
+    spec.aliases = names;
+    for (const name of names) {
+      if (!name.startsWith("-")) {
+        throw new Error(`unhandled argument syntax '${name}'`);
+      }
+      if (name.startsWith("--")) {
+        spec.dest = spec.dest || name.substr(2);
+      }
+      this._params.push({ name, spec });
+    }
+  }
+
+  parse_args(args) {
+    const opts = {};
+    const rest = [];
+
+    for (const { spec } of this._params) {
+      if (spec.default !== undefined) {
+        opts[spec.dest] = spec.default;
+      }
+    }
+
+    const seen = new Set();
+    for (let i = 0; i < args.length; i++) {
+      const arg = args[i];
+      if (!arg.startsWith("-")) {
+        rest.push(arg);
+        continue;
+      } else if (arg === "--") {
+        rest.push(args.slice(i+1));
+        break;
+      }
+
+      if (arg == "--help" || arg == "-h") {
+        this.help();
+      }
+
+      let parameter;
+      let [passed, value] = arg.split("=");
+      for (const { name, spec } of this._params) {
+        if (passed.startsWith("--")) {
+          if (name.startsWith(passed)) {
+            parameter = spec;
+          }
+        } else if (passed.startsWith("-") && passed === name) {
+          parameter = spec;
+        }
+        if (parameter) {
+          if (value === undefined) {
+            value = args[++i];
+          }
+          opts[parameter.dest] = value;
+          break;
+        }
+      }
+
+      if (parameter) {
+        if (seen.has(parameter)) {
+          throw new Error(`${parameter.aliases[0]} given multiple times`);
+        }
+        seen.add(parameter);
+      } else {
+        throw new Error(`invalid command-line argument '${arg}'`);
+      }
+    }
+
+    for (const { name, spec } of this._params) {
+      if (spec.options && !spec.options.includes(opts[spec.dest])) {
+        throw new Error(`invalid ${name} value '${opts[spec.dest]}'`);
+        opts[spec.dest] = spec.default;
+      }
+    }
+
+    return { opts, rest };
+  }
+
+  help() {
+    print(`Usage: ${this._doc}`);
+    const specs = new Set(this._params.map(p => p.spec));
+    const optstrs = [...specs].map(p => p.aliases.join(", "));
+    let maxlen = Math.max(...optstrs.map(s => s.length));
+    for (const spec of specs) {
+      const name = spec.aliases[0];
+      let helptext = spec.help ?? "undocumented";
+      if ("options" in spec) {
+        helptext += ` (one of ${spec.options.map(x => `'${x}'`).join(", ")})`;
+      }
+      if ("default" in spec) {
+        helptext += ` (default '${spec.default}')`;
+      }
+      const optstr = spec.aliases.join(", ");
+      print(`  ${optstr.padEnd(maxlen)}  ${helptext}`);
+    }
+    quit(0);
+  }
+};
diff --git a/js/src/devtools/gc-ubench/benchmarks/bigTextNodes.js b/js/src/devtools/gc-ubench/benchmarks/bigTextNodes.js
new file mode 100644
index 0000000000..0a66be03d3
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/bigTextNodes.js
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "bigTextNodes",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [ textNode, textNode, ... ]",
+
+      enabled: "document" in globalThis,
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePerFrame: "8",
+      defaultGarbagePiles: "8",
+
+      makeGarbage: N => {
+        var a = [];
+        var s = "x";
+        for (var i = 0; i < 16; i++) {
+          s = s + s;
+        }
+        for (var i = 0; i < N; i++) {
+          a.push(document.createTextNode(s));
+        }
+        garbage[garbageIndex++] = a;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/deepWeakMap.js b/js/src/devtools/gc-ubench/benchmarks/deepWeakMap.js
new file mode 100644
index 0000000000..bf46d1d97b
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/deepWeakMap.js
@@ -0,0 +1,40 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "deepWeakMap",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "o={wm,k}; w.mk[k]=o2={wm2,k2}; wm2[k2]=....",
+
+      defaultGarbagePerFrame: "1K",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      makeGarbage: M => {
+        var initial = {};
+        var prev = initial;
+        for (var i = 0; i < M; i++) {
+          var obj = [new WeakMap(), Object.create(null)];
+          obj[0].set(obj[1], prev);
+          prev = obj;
+        }
+        garbage[garbageIndex++] = initial;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/events.js b/js/src/devtools/gc-ubench/benchmarks/events.js
new file mode 100644
index 0000000000..0fe91b7596
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/events.js
@@ -0,0 +1,40 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "events",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [ textNode, textNode, ... ]",
+
+      enabled: "document" in globalThis,
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePerFrame: "100K",
+      defaultGarbagePiles: "8",
+
+      makeGarbage: N => {
+        var a = [];
+        for (var i = 0; i < N; i++) {
+          var e = document.createEvent("Events");
+          e.initEvent("TestEvent", true, true);
+          a.push(e);
+        }
+        garbage[garbageIndex++] = a;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/expandoEvents.js b/js/src/devtools/gc-ubench/benchmarks/expandoEvents.js
new file mode 100644
index 0000000000..4c6a53c8fe
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/expandoEvents.js
@@ -0,0 +1,41 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "expandoEvents",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [ textNode, textNode, ... ]",
+
+      enabled: "document" in globalThis,
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePerFrame: "100K",
+      defaultGarbagePiles: "8",
+
+      makeGarbage: N => {
+        var a = [];
+        for (var i = 0; i < N; i++) {
+          var e = document.createEvent("Events");
+          e.initEvent("TestEvent", true, true);
+          e.color = ["tuna"];
+          a.push(e);
+        }
+        garbage[garbageIndex++] = a;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayArrayLiteral.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayArrayLiteral.js
new file mode 100644
index 0000000000..a9003d8be6
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayArrayLiteral.js
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayArrayLiteral",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [[], ....]",
+      defaultGarbagePerFrame: "1M",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+      makeGarbage: N => {
+        for (var i = 0; i < N; i++) {
+          garbage[garbageIndex++] = ["foo", "bar", "baz", "baa"];
+          if (garbageIndex == garbage.length) {
+            garbageIndex = 0;
+          }
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayBuffer.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayBuffer.js
new file mode 100644
index 0000000000..06bf73eea8
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayBuffer.js
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayBuffer",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = ArrayBuffer(N); # (large malloc data)",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePerFrame: "4M",
+      defaultGarbagePiles: "8K",
+
+      makeGarbage: N => {
+        var ab = new ArrayBuffer(N);
+        var view = new Uint8Array(ab);
+        view[0] = 1;
+        view[N - 1] = 2;
+        garbage[garbageIndex++] = ab;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayFgFinalized.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayFgFinalized.js
new file mode 100644
index 0000000000..d61d56b81c
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayFgFinalized.js
@@ -0,0 +1,37 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayFgFinalized",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description:
+        "var foo = [ new Map, new Map, ... ]; # (foreground finalized)",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePiles: "8K",
+      defaultGarbagePerFrame: "48K",
+
+      makeGarbage: N => {
+        var arr = [];
+        for (var i = 0; i < N; i++) {
+          arr.push(new Map());
+        }
+        garbage[garbageIndex++] = arr;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayLargeArray.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayLargeArray.js
new file mode 100644
index 0000000000..38e4f2a85b
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayLargeArray.js
@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayLargeArray",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [[...], ....]",
+      defaultGarbagePerFrame: "3M",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+      makeGarbage: N => {
+        var a = new Array(N);
+        for (var i = 0; i < N; i++) {
+          a[i] = N - i;
+        }
+        garbage[garbageIndex++] = a;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayLargeObject.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayLargeObject.js
new file mode 100644
index 0000000000..ed1c38b271
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayLargeObject.js
@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayLargeObject",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = { LARGE }; # (large slots)",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePiles: "8K",
+      defaultGarbagePerFrame: "64K",
+
+      makeGarbage: N => {
+        var obj = {};
+        for (var i = 0; i < N; i++) {
+          obj["key" + i] = i;
+        }
+        garbage[garbageIndex++] = obj;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayNewObject.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayNewObject.js
new file mode 100644
index 0000000000..04487aac20
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayNewObject.js
@@ -0,0 +1,33 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayNewObject",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [new Object(), ....]",
+      defaultGarbagePerFrame: "128K",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      makeGarbage: N => {
+        for (var i = 0; i < N; i++) {
+          garbage[garbageIndex++] = new Object();
+          if (garbageIndex == garbage.length) {
+            garbageIndex = 0;
+          }
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayObjectLiteral.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayObjectLiteral.js
new file mode 100644
index 0000000000..a31e76bdc6
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayObjectLiteral.js
@@ -0,0 +1,32 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayObjectLiteral",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [{}, ....]",
+      defaultGarbagePerFrame: "384K",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+      makeGarbage: N => {
+        for (var i = 0; i < N; i++) {
+          garbage[garbageIndex++] = { a: "foo", b: "bar", 0: "foo", 1: "bar" };
+          if (garbageIndex == garbage.length) {
+            garbageIndex = 0;
+          }
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/globalArrayReallocArray.js b/js/src/devtools/gc-ubench/benchmarks/globalArrayReallocArray.js
new file mode 100644
index 0000000000..54316736e1
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/globalArrayReallocArray.js
@@ -0,0 +1,34 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "globalArrayReallocArray",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [[,,,], ....]",
+      defaultGarbagePerFrame: "2M",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+      makeGarbage: N => {
+        var a = [];
+        for (var i = 0; i < N; i++) {
+          a[i] = N - i;
+        }
+        garbage[garbageIndex++] = a;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/largeArrayPropertyAndElements.js b/js/src/devtools/gc-ubench/benchmarks/largeArrayPropertyAndElements.js
new file mode 100644
index 0000000000..0202f56e40
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/largeArrayPropertyAndElements.js
@@ -0,0 +1,40 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "largeArrayPropertyAndElements",
+  (function() {
+    var garbage;
+    var index;
+
+    return {
+      description: "Large array with both properties and elements",
+
+      load: n => {
+        garbage = new Array(n);
+        garbage.fill(null);
+        index = 0;
+      },
+
+      unload: () => {
+        garbage = null;
+        index = 0;
+      },
+
+      defaultGarbagePiles: "100K",
+      defaultGarbagePerFrame: "48K",
+
+      makeGarbage: n => {
+        for (var i = 0; i < n; i++) {
+          index++;
+          index %= garbage.length;
+
+          var obj = {};
+          garbage[index] = obj;
+          garbage["key-" + index] = obj;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/noAllocation.js b/js/src/devtools/gc-ubench/benchmarks/noAllocation.js
new file mode 100644
index 0000000000..8e6ba53943
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/noAllocation.js
@@ -0,0 +1,10 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set("noAllocation", {
+  description: "Do not generate any garbage.",
+  load: N => {},
+  unload: () => {},
+  makeGarbage: N => {},
+});
diff --git a/js/src/devtools/gc-ubench/benchmarks/pairCyclicWeakMap.js b/js/src/devtools/gc-ubench/benchmarks/pairCyclicWeakMap.js
new file mode 100644
index 0000000000..ac43325b6f
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/pairCyclicWeakMap.js
@@ -0,0 +1,46 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "pairCyclicWeakMap",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "wm1[k1] = k2; wm2[k2] = k3; wm1[k3] = k4; wm2[k4] = ...",
+
+      defaultGarbagePerFrame: "10K",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      makeGarbage: M => {
+        var wm1 = new WeakMap();
+        var wm2 = new WeakMap();
+        var initialKey = {};
+        var key = initialKey;
+        var value = {};
+        for (var i = 0; i < M / 2; i++) {
+          wm1.set(key, value);
+          key = value;
+          value = {};
+          wm2.set(key, value);
+          key = value;
+          value = {};
+        }
+        garbage[garbageIndex++] = [initialKey, wm1, wm2];
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/propertyTreeSplitting.js b/js/src/devtools/gc-ubench/benchmarks/propertyTreeSplitting.js
new file mode 100644
index 0000000000..9fc62b29e2
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/propertyTreeSplitting.js
@@ -0,0 +1,24 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "propertyTreeSplitting",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    var obj = {};
+    return {
+      description: "use delete to generate Shape garbage (piles are unused)",
+      load: N => {},
+      unload: () => {},
+      makeGarbage: N => {
+        for (var a = 0; a < N; ++a) {
+          obj.x = 1;
+          obj.y = 2;
+          delete obj.x;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/selfCyclicWeakMap.js b/js/src/devtools/gc-ubench/benchmarks/selfCyclicWeakMap.js
new file mode 100644
index 0000000000..c7736c72b9
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/selfCyclicWeakMap.js
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "selfCyclicWeakMap",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var wm = new WeakMap(); wm[k1] = k2; wm[k2] = k3; ...",
+
+      defaultGarbagePerFrame: "10K",
+      defaultGarbagePiles: "1K",
+
+      load: N => {
+        garbage = new Array(N);
+      },
+
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      makeGarbage: M => {
+        var wm = new WeakMap();
+        var initialKey = {};
+        var key = initialKey;
+        var value = {};
+        for (var i = 0; i < M; i++) {
+          wm.set(key, value);
+          key = value;
+          value = {};
+        }
+        garbage[garbageIndex++] = [initialKey, wm];
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/benchmarks/textNodes.js b/js/src/devtools/gc-ubench/benchmarks/textNodes.js
new file mode 100644
index 0000000000..07fd07e7b7
--- /dev/null
+++ b/js/src/devtools/gc-ubench/benchmarks/textNodes.js
@@ -0,0 +1,38 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+tests.set(
+  "textNodes",
+  (function() {
+    var garbage = [];
+    var garbageIndex = 0;
+    return {
+      description: "var foo = [ textNode, textNode, ... ]",
+
+      enabled: "document" in globalThis,
+
+      load: N => {
+        garbage = new Array(N);
+      },
+      unload: () => {
+        garbage = [];
+        garbageIndex = 0;
+      },
+
+      defaultGarbagePerFrame: "100K",
+      defaultGarbagePiles: "8",
+
+      makeGarbage: N => {
+        var a = [];
+        for (var i = 0; i < N; i++) {
+          a.push(document.createTextNode("t" + i));
+        }
+        garbage[garbageIndex++] = a;
+        if (garbageIndex == garbage.length) {
+          garbageIndex = 0;
+        }
+      },
+    };
+  })()
+);
diff --git a/js/src/devtools/gc-ubench/harness.js b/js/src/devtools/gc-ubench/harness.js
new file mode 100644
index 0000000000..db7fa06d63
--- /dev/null
+++ b/js/src/devtools/gc-ubench/harness.js
@@ -0,0 +1,328 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Global defaults
+
+// Allocate this much "garbage" per frame. This might correspond exactly to a
+// number of objects/values, or it might be some set of objects, depending on
+// the mutator in question.
+var gDefaultGarbagePerFrame = "8K";
+
+// In order to avoid a performance cliff between when the per-frame garbage
+// fits in the nursery and when it doesn't, most mutators will collect multiple
+// "piles" of garbage and round-robin through them, so that the per-frame
+// garbage stays alive for some number of frames. There will still be some
+// internal temporary allocations that don't end up in the piles; presumably,
+// the nursery will take care of those.
+//
+// If the per-frame garbage is K and the number of piles is P, then some of the
+// garbage will start getting tenured as long as P*K > size(nursery).
+var gDefaultGarbagePiles = "8";
+
+var gDefaultTestDuration = 8.0;
+
+// The Host interface that provides functionality needed by the test harnesses
+// (web + various shells). Subclasses should override with the appropriate
+// functionality. The methods that throw an error must be implemented. The ones
+// that return undefined are optional.
+//
+// Note that currently the web UI doesn't really use the scheduling pieces of
+// this.
+var Host = class {
+  constructor() {}
+  start_turn() {
+    throw new Error("unimplemented");
+  }
+  end_turn() {
+    throw new Error("unimplemented");
+  }
+  suspend(duration) {
+    throw new Error("unimplemented");
+  } // Shell driver only
+  now() {
+    return performance.now();
+  }
+
+  minorGCCount() {
+    return undefined;
+  }
+  majorGCCount() {
+    return undefined;
+  }
+  GCSliceCount() {
+    return undefined;
+  }
+
+  features = {
+    haveMemorySizes: false,
+    haveGCCounts: false,
+  };
+};
+
+function percent(x) {
+  return `${(x*100).toFixed(2)}%`;
+}
+
+function parse_units(v) {
+  if (!v.length) {
+    return NaN;
+  }
+  var lastChar = v[v.length - 1].toLowerCase();
+  if (!isNaN(parseFloat(lastChar))) {
+    return parseFloat(v);
+  }
+  var units = parseFloat(v.substr(0, v.length - 1));
+  if (lastChar == "k") {
+    return units * 1e3;
+  }
+  if (lastChar == "m") {
+    return units * 1e6;
+  }
+  if (lastChar == "g") {
+    return units * 1e9;
+  }
+  return NaN;
+}
+
+var AllocationLoad = class {
+  constructor(info, name) {
+    this.load = info;
+    this.load.name = this.load.name ?? name;
+
+    this._garbagePerFrame =
+      info.garbagePerFrame ||
+      parse_units(info.defaultGarbagePerFrame || gDefaultGarbagePerFrame);
+    this._garbagePiles =
+      info.garbagePiles ||
+      parse_units(info.defaultGarbagePiles || gDefaultGarbagePiles);
+  }
+
+  get name() {
+    return this.load.name;
+  }
+  get description() {
+    return this.load.description;
+  }
+  get garbagePerFrame() {
+    return this._garbagePerFrame;
+  }
+  set garbagePerFrame(amount) {
+    this._garbagePerFrame = amount;
+  }
+  get garbagePiles() {
+    return this._garbagePiles;
+  }
+  set garbagePiles(amount) {
+    this._garbagePiles = amount;
+  }
+
+  start() {
+    this.load.load(this._garbagePiles);
+  }
+
+  stop() {
+    this.load.unload();
+  }
+
+  reload() {
+    this.stop();
+    this.start();
+  }
+
+  tick() {
+    this.load.makeGarbage(this._garbagePerFrame);
+  }
+
+  is_dummy_load() {
+    return this.load.name == "noAllocation";
+  }
+};
+
+var AllocationLoadManager = class {
+  constructor(tests) {
+    this._loads = new Map();
+    for (const [name, info] of tests.entries()) {
+      this._loads.set(name, new AllocationLoad(info, name));
+    }
+    this._active = undefined;
+    this._paused = false;
+
+    // Public API
+    this.sequencer = null;
+    this.testDurationMS = gDefaultTestDuration * 1000;
+  }
+
+  getByName(name) {
+    const mutator = this._loads.get(name);
+    if (!mutator) {
+      throw new Error(`invalid mutator '${name}'`);
+    }
+    return mutator;
+  }
+
+  activeLoad() {
+    return this._active;
+  }
+
+  setActiveLoad(mutator) {
+    if (this._active) {
+      this._active.stop();
+    }
+    this._active = mutator;
+    this._active.start();
+  }
+
+  deactivateLoad() {
+    this._active.stop();
+    this._active = undefined;
+  }
+
+  get paused() {
+    return this._paused;
+  }
+  set paused(pause) {
+    this._paused = pause;
+  }
+
+  load_running() {
+    return this._active;
+  }
+
+  change_garbagePiles(amount) {
+    if (this._active) {
+      this._active.garbagePiles = amount;
+      this._active.reload();
+    }
+  }
+
+  change_garbagePerFrame(amount) {
+    if (this._active) {
+      this._active.garbagePerFrame = amount;
+    }
+  }
+
+  tick(now = gHost.now()) {
+    this.lastActive = this._active;
+    let completed = false;
+
+    if (this.sequencer) {
+      if (this.sequencer.tick(now)) {
+        completed = true;
+        if (this.sequencer.current) {
+          this.setActiveLoad(this.sequencer.current);
+        } else {
+          this.deactivateLoad();
+        }
+        if (this.sequencer.done()) {
+          this.sequencer = null;
+        }
+      }
+    }
+
+    if (this._active && !this._paused) {
+      this._active.tick();
+    }
+
+    return completed;
+  }
+
+  startSequencer(sequencer, now = gHost.now()) {
+    this.sequencer = sequencer;
+    this.sequencer.start(now);
+    this.setActiveLoad(this.sequencer.current);
+  }
+
+  stopped() {
+    return !this.sequencer || this.sequencer.done();
+  }
+
+  currentLoadRemaining(now = gHost.now()) {
+    if (this.stopped()) {
+      return 0;
+    }
+
+    // TODO: The web UI displays a countdown to the end of the current mutator.
+    // This won't work for potential future things like "run until 3 major GCs
+    // have been seen", so the API will need to be modified to provide
+    // information in that case.
+    return this.testDurationMS - this.sequencer.currentLoadElapsed(now);
+  }
+};
+
+// Current test state.
+var gLoadMgr = undefined;
+
+function format_with_units(n, label, shortlabel, kbase) {
+  if (n < kbase * 4) {
+    return `${n} ${label}`;
+  } else if (n < kbase ** 2 * 4) {
+    return `${(n / kbase).toFixed(2)}K${shortlabel}`;
+  } else if (n < kbase ** 3 * 4) {
+    return `${(n / kbase ** 2).toFixed(2)}M${shortlabel}`;
+  }
+  return `${(n / kbase ** 3).toFixed(2)}G${shortlabel}`;
+}
+
+function format_bytes(bytes) {
+  return format_with_units(bytes, "bytes", "B", 1024);
+}
+
+function format_num(n) {
+  return format_with_units(n, "", "", 1000);
+}
+
+function update_histogram(histogram, delay) {
+  // Round to a whole number of 10us intervals to provide enough resolution to
+  // capture a 16ms target with adequate accuracy.
+  delay = Math.round(delay * 100) / 100;
+  var current = histogram.has(delay) ? histogram.get(delay) : 0;
+  histogram.set(delay, ++current);
+}
+
+// Compute a score based on the total ms we missed frames by per second.
+function compute_test_score(histogram) {
+  var score = 0;
+  for (let [delay, count] of histogram) {
+    score += Math.abs((delay - 1000 / 60) * count);
+  }
+  score = score / (gLoadMgr.testDurationMS / 1000);
+  return Math.round(score * 1000) / 1000;
+}
+
+// Build a spark-lines histogram for the test results to show with the aggregate score.
+function compute_spark_histogram_percents(histogram) {
+  var ranges = [
+    [-99999999, 16.6],
+    [16.6, 16.8],
+    [16.8, 25],
+    [25, 33.4],
+    [33.4, 60],
+    [60, 100],
+    [100, 300],
+    [300, 99999999],
+  ];
+  var rescaled = new Map();
+  for (let [delay] of histogram) {
+    for (var i = 0; i < ranges.length; ++i) {
+      var low = ranges[i][0];
+      var high = ranges[i][1];
+      if (low <= delay && delay < high) {
+        update_histogram(rescaled, i);
+        break;
+      }
+    }
+  }
+  var total = 0;
+  for (const [, count] of rescaled) {
+    total += count;
+  }
+
+  var spark = [];
+  for (let i = 0; i < ranges.length; ++i) {
+    const amt = rescaled.has(i) ? rescaled.get(i) : 0;
+    spark.push(amt / total);
+  }
+
+  return spark;
+}
diff --git a/js/src/devtools/gc-ubench/index.html b/js/src/devtools/gc-ubench/index.html
new file mode 100644
index 0000000000..4abce385f2
--- /dev/null
+++ b/js/src/devtools/gc-ubench/index.html
@@ -0,0 +1,90 @@
+<!-- This Source Code Form is subject to the terms of the Mozilla Public
+   - License, v. 2.0. If a copy of the MPL was not distributed with this file,
+   - You can obtain one at http://mozilla.org/MPL/2.0/. -->
+
+<html>
+<head>
+  <title>GC uBench</title>
+  <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
+
+  <!-- Benchmark harness and UI -->
+  <script src="harness.js"></script>
+  <script src="perf.js"></script>
+  <script src="sequencer.js"></script>
+  <script src="ui.js"></script>
+
+  <!-- List of garbage-creating test loads -->
+  <script src="test_list.js"></script>
+
+  <!-- Collect all test loads into a `tests` Map -->
+  <script>
+    var tests = new Map();
+    foreach_test_file(path => import("./" + path));
+  </script>
+
+</head>
+
+<body onload="onload()" onunload="onunload()">
+
+<canvas id="graph" width="1080" height="400" style="padding-left:10px"></canvas>
+<canvas id="memgraph" width="1080" height="400" style="padding-left:10px"></canvas>
+<div id="memgraph-disabled" style="display: none"><i>No performance.mozMemory object available. If running Firefox, set dom.enable_memory_stats to True to see heap size info.</i></div>
+
+<hr>
+
+<div id='track-sizes-div'>
+  Show heap size graph: <input id='track-sizes' type='checkbox' onclick="trackHeapSizes(this.checked)">
+</div>
+
+<div>
+  Update display:
+  <input type="checkbox" id="do-graph" onchange="onUpdateDisplayChanged()" checked></input>
+</div>
+
+<div>
+  Run allocation load
+  <input type="checkbox" id="do-load" onchange="onDoLoadChange()" checked></input>
+</div>
+
+<div>
+    Allocation load:
+    <select id="test-selection" required onchange="onLoadChange()"></select>
+    <span id="load-running">(init)</span>
+</div>
+
+<div>
+    &nbsp;&nbsp;&nbsp;&nbsp;Garbage items per frame:
+    <input type="text" id="garbage-per-frame" size="5" value="8K"
+           onchange="garbage_per_frame_changed()"></input>
+</div>
+<div>
+    &nbsp;&nbsp;&nbsp;&nbsp;Garbage piles:
+    <input type="text" id="garbage-piles" size="5" value="8"
+           onchange="garbage_piles_changed()"></input>
+</div>
+
+<hr>
+
+<div>
+    Duration: <input type="text" id="test-duration" size="3" value="8" onchange="duration_changed()"></input>s
+    <input type="button" id="test-one" value="Run Test" onclick="run_one_test()"></input>
+    <input type="button" id="test-all" value="Run All Tests" onclick="run_all_tests()"></input>
+</div>
+
+<div>
+    &nbsp;&nbsp;&nbsp;&nbsp;Time remaining: <span id="test-progress">(not running)</span>
+</div
+
+<div>
+    &nbsp;&nbsp;&nbsp;&nbsp;60 fps: <span id="pct60">n/a</span>
+    &nbsp;&nbsp;&nbsp;&nbsp;45 fps: <span id="pct45">n/a</span>
+    &nbsp;&nbsp;&nbsp;&nbsp;30 fps: <span id="pct30">n/a</span>
+</div
+
+<div id="results-Area">
+    Test Results:
+    <div id="results-display" style="padding-left: 10px; border: 1px solid black;"></div>
+</div>
+
+</body>
+</html>
diff --git a/js/src/devtools/gc-ubench/perf.js b/js/src/devtools/gc-ubench/perf.js
new file mode 100644
index 0000000000..dc370ee0da
--- /dev/null
+++ b/js/src/devtools/gc-ubench/perf.js
@@ -0,0 +1,217 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Performance monitoring and calculation.
+
+function round_up(val, interval) {
+  return val + (interval - (val % interval));
+}
+
+// Class for inter-frame timing, which handles being paused and resumed.
+var FrameTimer = class {
+  constructor() {
+    // Start time of the current active test, adjusted for any time spent
+    // stopped (so `now - this.start` is how long the current active test
+    // has run for.)
+    this.start = undefined;
+
+    // Timestamp of callback following the previous frame.
+    this.prev = undefined;
+
+    // Timestamp when drawing was paused, or zero if drawing is active.
+    this.stopped = 0;
+  }
+
+  is_stopped() {
+    return this.stopped != 0;
+  }
+
+  start_recording(now = gHost.now()) {
+    this.start = this.prev = now;
+  }
+
+  on_frame_finished(now = gHost.now()) {
+    const delay = now - this.prev;
+    this.prev = now;
+    return delay;
+  }
+
+  pause(now = gHost.now()) {
+    this.stopped = now;
+    // Abuse this.prev to store the time elapsed since the previous frame.
+    // This will be used to adjust this.prev when we resume.
+    this.prev = now - this.prev;
+  }
+
+  resume(now = gHost.now()) {
+    this.prev = now - this.prev;
+    const stop_duration = now - this.stopped;
+    this.start += stop_duration;
+    this.stopped = 0;
+  }
+};
+
+// Per-frame time sampling infra.
+var sampleTime = 16.666667; // ms
+var sampleIndex = 0;
+
+// Class for maintaining a rolling window of per-frame GC-related counters:
+// inter-frame delay, minor/major/slice GC counts, cumulative bytes, etc.
+var FrameHistory = class {
+  constructor(numSamples) {
+    // Private
+    this._frameTimer = new FrameTimer();
+    this._numSamples = numSamples;
+
+    // Public API
+    this.delays = new Array(numSamples);
+    this.gcBytes = new Array(numSamples);
+    this.mallocBytes = new Array(numSamples);
+    this.gcs = new Array(numSamples);
+    this.minorGCs = new Array(numSamples);
+    this.majorGCs = new Array(numSamples);
+    this.slices = new Array(numSamples);
+
+    sampleIndex = 0;
+    this.reset();
+  }
+
+  start(now = gHost.now()) {
+    this._frameTimer.start_recording(now);
+  }
+
+  reset() {
+    this.delays.fill(0);
+    this.gcBytes.fill(0);
+    this.mallocBytes.fill(0);
+    this.gcs.fill(this.gcs[sampleIndex]);
+    this.minorGCs.fill(this.minorGCs[sampleIndex]);
+    this.majorGCs.fill(this.majorGCs[sampleIndex]);
+    this.slices.fill(this.slices[sampleIndex]);
+
+    sampleIndex = 0;
+  }
+
+  get numSamples() {
+    return this._numSamples;
+  }
+
+  findMax(collection) {
+    // Depends on having at least one non-negative entry, and unfilled
+    // entries being <= max.
+    var maxIndex = 0;
+    for (let i = 0; i < this._numSamples; i++) {
+      if (collection[i] >= collection[maxIndex]) {
+        maxIndex = i;
+      }
+    }
+    return maxIndex;
+  }
+
+  findMaxDelay() {
+    return this.findMax(this.delays);
+  }
+
+  on_frame(now = gHost.now()) {
+    const delay = this._frameTimer.on_frame_finished(now);
+
+    // Total time elapsed while the active test has been running.
+    var t = now - this._frameTimer.start;
+    var newIndex = Math.round(t / sampleTime);
+    while (sampleIndex < newIndex) {
+      sampleIndex++;
+      var idx = sampleIndex % this._numSamples;
+      this.delays[idx] = delay;
+      if (gHost.features.haveMemorySizes) {
+        this.gcBytes[idx] = gHost.gcBytes;
+        this.mallocBytes[idx] = gHost.mallocBytes;
+      }
+      if (gHost.features.haveGCCounts) {
+        this.minorGCs[idx] = gHost.minorGCCount;
+        this.majorGCs[idx] = gHost.majorGCCount;
+        this.slices[idx] = gHost.GCSliceCount;
+      }
+    }
+
+    return delay;
+  }
+
+  pause() {
+    this._frameTimer.pause();
+  }
+
+  resume() {
+    this._frameTimer.resume();
+  }
+
+  is_stopped() {
+    return this._frameTimer.is_stopped();
+  }
+};
+
+var PerfTracker = class {
+  constructor() {
+    // Private
+    this._currentLoadStart = undefined;
+    this._frameCount = undefined;
+    this._mutating_ms = undefined;
+    this._suspend_sec = undefined;
+    this._minorGCs = undefined;
+    this._majorGCs = undefined;
+
+    // Public
+    this.results = [];
+  }
+
+  on_load_start(load, now = gHost.now()) {
+    this._currentLoadStart = now;
+    this._frameCount = 0;
+    this._mutating_ms = 0;
+    this._suspend_sec = 0;
+    this._majorGCs = gHost.majorGCCount;
+    this._minorGCs = gHost.minorGCCount;
+  }
+
+  on_load_end(load, now = gHost.now()) {
+    const elapsed_time = (now - this._currentLoadStart) / 1000;
+    const full_time = round_up(elapsed_time, 1 / 60);
+    const frame_60fps_limit = Math.round(full_time * 60);
+    const dropped_60fps_frames = frame_60fps_limit - this._frameCount;
+    const dropped_60fps_fraction = dropped_60fps_frames / frame_60fps_limit;
+
+    const mutating_and_gc_fraction = this._mutating_ms / (full_time * 1000);
+
+    const result = {
+      load,
+      elapsed_time,
+      mutating: this._mutating_ms / 1000,
+      mutating_and_gc_fraction,
+      suspended: this._suspend_sec,
+      full_time,
+      frames: this._frameCount,
+      dropped_60fps_frames,
+      dropped_60fps_fraction,
+      majorGCs: gHost.majorGCCount - this._majorGCs,
+      minorGCs: gHost.minorGCCount - this._minorGCs,
+    };
+    this.results.push(result);
+
+    this._currentLoadStart = undefined;
+    this._frameCount = 0;
+
+    return result;
+  }
+
+  after_suspend(wait_sec) {
+    this._suspend_sec += wait_sec;
+  }
+
+  before_mutator(now = gHost.now()) {
+    this._frameCount++;
+  }
+
+  after_mutator(start_time, end_time = gHost.now()) {
+    this._mutating_ms += end_time - start_time;
+  }
+};
diff --git a/js/src/devtools/gc-ubench/scheduler.js b/js/src/devtools/gc-ubench/scheduler.js
new file mode 100644
index 0000000000..8f4a483b33
--- /dev/null
+++ b/js/src/devtools/gc-ubench/scheduler.js
@@ -0,0 +1,64 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Frame schedulers: executing a frame's worth of mutation, and possibly
+// waiting for a later frame. (These schedulers will halt the main thread,
+// allowing background threads to continue working.)
+
+var Scheduler = class {
+  constructor(perfMonitor) {
+    this._perfMonitor = perfMonitor;
+  }
+
+  start(loadMgr, timestamp) {
+    return loadMgr.start(timestamp);
+  }
+  tick(loadMgr, timestamp) {}
+  wait_for_next_frame(t0, tick_start, tick_end) {}
+};
+
+// "Sync to vsync" scheduler: after the mutator is done for a frame, wait until
+// the beginning of the next 60fps frame.
+var VsyncScheduler = class extends Scheduler {
+  tick(loadMgr, timestamp) {
+    this._perfMonitor.before_mutator(timestamp);
+    gHost.start_turn();
+    const completed = loadMgr.tick(timestamp);
+    gHost.end_turn();
+    this._perfMonitor.after_mutator(timestamp);
+    return completed;
+  }
+
+  wait_for_next_frame(t0, tick_start, tick_end) {
+    // Compute how long until the next 60fps vsync event, and wait that long.
+    const elapsed = (tick_end - t0) / 1000;
+    const period = 1 / FPS;
+    const used = elapsed % period;
+    const delay = period - used;
+    gHost.suspend(delay);
+    this._perfMonitor.after_suspend(delay);
+  }
+};
+
+// Try to maintain 60fps, but if we overrun a frame, do more processing
+// immediately to make the next frame come up as soon as possible.
+var OptimizeForFrameRate = class extends Scheduler {
+  tick(loadMgr, timestamp) {
+    this._perfMonitor.before_mutator(timestamp);
+    gHost.start_turn();
+    const completed = loadMgr.tick(timestamp);
+    gHost.end_turn();
+    this._perfMonitor.after_mutator(timestamp);
+    return completed;
+  }
+
+  wait_for_next_frame(t0, tick_start, tick_end) {
+    const next_frame_ms = round_up(tick_start, 1000 / FPS);
+    if (tick_end < next_frame_ms) {
+      const delay = (next_frame_ms - tick_end) / 1000;
+      gHost.suspend(delay);
+      this._perfMonitor.after_suspend(delay);
+    }
+  }
+};
diff --git a/js/src/devtools/gc-ubench/sequencer.js b/js/src/devtools/gc-ubench/sequencer.js
new file mode 100644
index 0000000000..0271140c04
--- /dev/null
+++ b/js/src/devtools/gc-ubench/sequencer.js
@@ -0,0 +1,298 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// A Sequencer handles transitioning between different mutators. Typically, it
+// will base the decision to transition on things like elapsed time, number of
+// GCs observed, or similar. However, they might also implement a search for
+// some result value by running for some time while measuring, tweaking
+// parameters, and re-running until an in-range result is found.
+
+var Sequencer = class {
+  // Return the current mutator (of class AllocationLoad).
+  get current() {
+    throw new Error("unimplemented");
+  }
+
+  start(now = gHost.now()) {
+    this.started = now;
+  }
+
+  // Called by user to handle advancing time. Subclasses will normally override
+  // do_tick() instead. Returns the results of a trial if complete (the mutator
+  // reached its allotted time or otherwise determined that its timing data
+  // should be valid), and falsy otherwise.
+  tick(now = gHost.now()) {
+    if (this.done()) {
+      throw new Error("tick() called on completed sequencer");
+    }
+
+    return this.do_tick(now);
+  }
+
+  // Implement in subclass to handle time advancing. Must return trial's result
+  // if complete. Called by tick(), above.
+  do_tick(now = gHost.now()) {
+    throw new Error("unimplemented");
+  }
+
+  // Returns whether this sequencer is done running trials.
+  done() {
+    throw new Error("unimplemented");
+  }
+
+  restart(now = gHost.now()) {
+    this.reset();
+    this.start(now);
+  }
+
+  // Returns how long the current load has been running.
+  currentLoadElapsed(now = gHost.now()) {
+    return now - this.started;
+  }
+};
+
+// Run a single trial of a mutator and be done.
+var SingleMutatorSequencer = class extends Sequencer {
+  constructor(mutator, perf, duration_sec) {
+    super();
+    this.mutator = mutator;
+    this.perf = perf;
+    if (!(duration_sec > 0)) {
+      throw new Error(`invalid duration '${duration_sec}'`);
+    }
+    this.duration = duration_sec * 1000;
+    this.state = 'init'; // init -> running -> done
+    this.lastResult = undefined;
+  }
+
+  get current() {
+    return this.state === 'done' ? undefined : this.mutator;
+  }
+
+  reset() {
+    this.state = 'init';
+  }
+
+  start(now = gHost.now()) {
+    if (this.state !== 'init') {
+      throw new Error("cannot restart a single-mutator sequencer");
+    }
+    super.start(now);
+    this.state = 'running';
+    this.perf.on_load_start(this.current, now);
+  }
+
+  do_tick(now) {
+    if (this.currentLoadElapsed(now) < this.duration) {
+      return false;
+    }
+
+    const load = this.current;
+    this.state = 'done';
+    return this.perf.on_load_end(load, now);
+  }
+
+  done() {
+    return this.state === 'done';
+  }
+};
+
+// For each of series of sequencers, run until done.
+var ChainSequencer = class extends Sequencer {
+  constructor(sequencers) {
+    super();
+    this.sequencers = sequencers;
+    this.idx = -1;
+    this.state = sequencers.length ? 'init' : 'done'; // init -> running -> done
+  }
+
+  get current() {
+    return this.idx >= 0 ? this.sequencers[this.idx].current : undefined;
+  }
+
+  reset() {
+    this.state = 'init';
+    this.idx = -1;
+  }
+
+  start(now = gHost.now()) {
+    super.start(now);
+    if (this.sequencers.length === 0) {
+      this.state = 'done';
+      return;
+    }
+
+    this.idx = 0;
+    this.sequencers[0].start(now);
+    this.state = 'running';
+  }
+
+  do_tick(now) {
+    const sequencer = this.sequencers[this.idx];
+    const trial_result = sequencer.do_tick(now);
+    if (!trial_result) {
+      return false; // Trial is still going.
+    }
+
+    if (!sequencer.done()) {
+      // A single trial has completed, but the sequencer is not yet done.
+      return trial_result;
+    }
+
+    this.idx++;
+    if (this.idx < this.sequencers.length) {
+      this.sequencers[this.idx].start();
+    } else {
+      this.idx = -1;
+      this.state = 'done';
+    }
+
+    return trial_result;
+  }
+
+  done() {
+    return this.state === 'done';
+  }
+};
+
+var RunUntilSequencer = class extends Sequencer {
+  constructor(sequencer, loadMgr) {
+    super();
+    this.loadMgr = loadMgr;
+    this.sequencer = sequencer;
+
+    // init -> running -> done
+    this.state = sequencer.done() ? 'done' : 'init';
+  }
+
+  get current() {
+    return this.sequencer?.current;
+  }
+
+  reset() {
+    this.sequencer.reset();
+    this.state = 'init';
+  }
+
+  start(now) {
+    super.start(now);
+    this.sequencer.start(now);
+    this.initSearch(now);
+    this.state = 'running';
+  }
+
+  initSearch(now) {}
+
+  done() {
+    return this.state === 'done';
+  }
+
+  do_tick(now) {
+    const trial_result = this.sequencer.do_tick(now);
+    if (trial_result) {
+      if (this.searchComplete(trial_result)) {
+        this.state = 'done';
+      } else {
+        this.sequencer.restart(now);
+      }
+    }
+    return trial_result;
+  }
+
+  // Take the result of the last mutator run into account (only notified after
+  // a mutator is complete, so cannot be used to decide when to end the
+  // mutator.)
+  searchComplete(result) {
+    throw new Error("must implement in subclass");
+  }
+};
+
+// Run trials, adjusting garbagePerFrame, until 50% of the frames are dropped.
+var Find50Sequencer = class extends RunUntilSequencer {
+  constructor(sequencer, loadMgr, goal=0.5, low_range=0.45, high_range=0.55) {
+    super(sequencer, loadMgr);
+
+    // Run trials with varying garbagePerFrame, looking for a setting that
+    // drops 50% of the frames, until we have been searching in the range for
+    // `persistence` times.
+    this.low_range = low_range;
+    this.goal = goal;
+    this.high_range = high_range;
+    this.persistence = 3;
+
+    this.clear();
+  }
+
+  reset() {
+    super.reset();
+    this.clear();
+  }
+
+  clear() {
+    this.garbagePerFrame = undefined;
+
+    this.good = undefined;
+    this.goodAt = undefined;
+    this.bad = undefined;
+    this.badAt = undefined;
+
+    this.numInRange = 0;
+  }
+
+  start(now) {
+    super.start(now);
+    if (!this.done()) {
+      this.garbagePerFrame = this.sequencer.current.garbagePerFrame;
+    }
+  }
+
+  searchComplete(result) {
+    print(
+      `Saw ${percent(result.dropped_60fps_fraction)} with garbagePerFrame=${this.garbagePerFrame}`
+    );
+
+    // This is brittle with respect to noise. It might be better to do a linear
+    // regression and stop at an error threshold.
+    if (result.dropped_60fps_fraction < this.goal) {
+      if (this.goodAt === undefined || this.goodAt < this.garbagePerFrame) {
+        this.goodAt = this.garbagePerFrame;
+        this.good = result.dropped_60fps_fraction;
+      }
+      if (this.badAt !== undefined) {
+        this.garbagePerFrame = Math.trunc(
+          (this.garbagePerFrame + this.badAt) / 2
+        );
+      } else {
+        this.garbagePerFrame *= 2;
+      }
+    } else {
+      if (this.badAt === undefined || this.badAt > this.garbagePerFrame) {
+        this.badAt = this.garbagePerFrame;
+        this.bad = result.dropped_60fps_fraction;
+      }
+      if (this.goodAt !== undefined) {
+        this.garbagePerFrame = Math.trunc(
+          (this.garbagePerFrame + this.goodAt) / 2
+        );
+      } else {
+        this.garbagePerFrame = Math.trunc(this.garbagePerFrame / 2);
+      }
+    }
+
+    if (
+      this.low_range < result.dropped_60fps_fraction &&
+      result.dropped_60fps_fraction < this.high_range
+    ) {
+      this.numInRange++;
+      if (this.numInRange >= this.persistence) {
+        return true;
+      }
+    }
+
+    print(`next run with ${this.garbagePerFrame}`);
+    this.loadMgr.change_garbagePerFrame(this.garbagePerFrame);
+
+    return false;
+  }
+};
diff --git a/js/src/devtools/gc-ubench/shell-bench.js b/js/src/devtools/gc-ubench/shell-bench.js
new file mode 100644
index 0000000000..9640cddce9
--- /dev/null
+++ b/js/src/devtools/gc-ubench/shell-bench.js
@@ -0,0 +1,147 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+var FPS = 60;
+var gNumSamples = 500;
+
+// This requires a gHost to have been created that provides host-specific
+// facilities. See eg spidermonkey.js.
+
+loadRelativeToScript("argparse.js");
+loadRelativeToScript("harness.js");
+loadRelativeToScript("sequencer.js");
+loadRelativeToScript("scheduler.js");
+loadRelativeToScript("perf.js");
+loadRelativeToScript("test_list.js");
+
+var gPerf = new PerfTracker();
+
+var tests = new Map();
+foreach_test_file(f => loadRelativeToScript(f));
+for (const [name, info] of tests.entries()) {
+  if ("enabled" in info && !info.enabled) {
+    tests.delete(name);
+  }
+}
+
+function tick(loadMgr, timestamp) {
+  gPerf.before_mutator(timestamp);
+  gHost.start_turn();
+  const events = loadMgr.tick(timestamp);
+  gHost.end_turn();
+  gPerf.after_mutator(timestamp);
+  return events;
+}
+
+function run(opts, loads) {
+  const sequence = [];
+  for (const mut of loads) {
+    if (tests.has(mut)) {
+      sequence.push(mut);
+    } else if (mut === "all") {
+      sequence.push(...tests.keys());
+    } else {
+      sequence.push(...[...tests.keys()].filter(t => t.includes(mut)));
+    }
+  }
+  if (loads.length === 0) {
+    sequence.push(...tests.keys());
+  }
+
+  const loadMgr = new AllocationLoadManager(tests);
+  const perf = new FrameHistory(gNumSamples);
+
+  const mutators = sequence.map(name => new SingleMutatorSequencer(loadMgr.getByName(name), gPerf, opts.duration));
+  let sequencer;
+  if (opts.sequencer == 'cycle') {
+    sequencer = new ChainSequencer(mutators);
+  } else if (opts.sequencer == 'find50') {
+    const seekers = mutators.map(s => new Find50Sequencer(s, loadMgr));
+    sequencer = new ChainSequencer(seekers);
+  }
+
+  const schedulerCtors = {
+    keepup: OptimizeForFrameRate,
+    vsync: VsyncScheduler,
+  };
+  const scheduler = new schedulerCtors[opts.sched](gPerf);
+
+  perf.start();
+
+  const t0 = gHost.now();
+
+  let possible = 0;
+  let frames = 0;
+  loadMgr.startSequencer(sequencer);
+  print(`${loadMgr.activeLoad().name} starting`);
+  while (loadMgr.load_running()) {
+    const timestamp = gHost.now();
+    const completed = scheduler.tick(loadMgr, timestamp);
+    const after_tick = gHost.now();
+
+    perf.on_frame(timestamp);
+
+    if (completed) {
+      print(`${loadMgr.lastActive.name} ended`);
+      if (loadMgr.load_running()) {
+        print(`${loadMgr.activeLoad().name} starting`);
+      }
+    }
+
+    frames++;
+    if (completed) {
+      possible += (loadMgr.testDurationMS / 1000) * FPS;
+      const elapsed = ((after_tick - t0) / 1000).toFixed(2);
+      print(`  observed ${frames} / ${possible} frames in ${elapsed} seconds`);
+    }
+
+    scheduler.wait_for_next_frame(t0, timestamp, after_tick);
+  }
+}
+
+function report_results() {
+  for (const result of gPerf.results) {
+    const {
+      load,
+      elapsed_time,
+      mutating,
+      mutating_and_gc_fraction,
+      suspended,
+      full_time,
+      frames,
+      dropped_60fps_frames,
+      dropped_60fps_fraction,
+      minorGCs,
+      majorGCs,
+    } = result;
+
+    const drop_pct = percent(dropped_60fps_fraction);
+    const mut_pct = percent(mutating_and_gc_fraction);
+    const mut_sec = mutating.toFixed(2);
+    const full_sec = full_time.toFixed(2);
+    const susp_sec = suspended.toFixed(2);
+    print(`${load.name}:
+  ${frames} (60fps) frames seen out of expected ${Math.floor(full_time * 60)}
+  ${dropped_60fps_frames} = ${drop_pct} 60fps frames dropped
+  ${mut_pct} of run spent mutating and GCing (${mut_sec}sec out of ${full_sec}sec vs ${susp_sec} sec waiting)
+  ${minorGCs} minor GCs, ${majorGCs} major GCs
+`);
+  }
+}
+
+var argparse = new ArgParser("JS shell microbenchmark runner");
+argparse.add_argument(["--duration", "-d"], {
+  default: gDefaultTestDuration,
+  help: "how long to run mutators for (in seconds)"
+});
+argparse.add_argument("--sched", {
+  default: "keepup",
+  options: ["keepup", "vsync"],
+  help: "frame scheduler"
+});
+argparse.add_argument("--sequencer", {
+  default: "cycle",
+  options: ["cycle", "find50"],
+  help: "mutator sequencer"
+});
diff --git a/js/src/devtools/gc-ubench/spidermonkey.js b/js/src/devtools/gc-ubench/spidermonkey.js
new file mode 100644
index 0000000000..0ad0aa9771
--- /dev/null
+++ b/js/src/devtools/gc-ubench/spidermonkey.js
@@ -0,0 +1,57 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// SpiderMonkey JS shell benchmark script
+//
+// Usage: run $JS spidermonkey.js --help
+
+loadRelativeToScript("shell-bench.js");
+
+var SpiderMonkey = class extends Host {
+  start_turn() {}
+
+  end_turn() {
+    clearKeptObjects();
+    maybegc();
+    drainJobQueue();
+  }
+
+  suspend(duration) {
+    sleep(duration);
+  }
+
+  get minorGCCount() {
+    return performance.mozMemory.gc.minorGCCount;
+  }
+  get majorGCCount() {
+    return performance.mozMemory.gc.majorGCCount;
+  }
+  get GCSliceCount() {
+    return performance.mozMemory.gc.sliceCount;
+  }
+  get gcBytes() {
+    return performance.mozMemory.gc.zone.gcBytes;
+  }
+  get gcAllocTrigger() {
+    return performance.mozMemory.gc.zone.gcAllocTrigger;
+  }
+
+  features = {
+    haveMemorySizes: true,
+    haveGCCounts: true,
+  };
+};
+
+var gHost = new SpiderMonkey();
+var { opts, rest: mutators } = argparse.parse_args(scriptArgs);
+run(opts, mutators);
+
+print("\nTest results:\n");
+report_results();
+
+var outfile = "spidermonkey-results.json";
+var origOut = redirect(outfile);
+print(JSON.stringify(gPerf.results));
+redirect(origOut);
+print(`Wrote detailed results to ${outfile}`);
diff --git a/js/src/devtools/gc-ubench/test_list.js b/js/src/devtools/gc-ubench/test_list.js
new file mode 100644
index 0000000000..03ed30cf9e
--- /dev/null
+++ b/js/src/devtools/gc-ubench/test_list.js
@@ -0,0 +1,20 @@
+function foreach_test_file(callback) {
+  callback("benchmarks/noAllocation.js");
+  callback("benchmarks/globalArrayNewObject.js");
+  callback("benchmarks/globalArrayArrayLiteral.js");
+  callback("benchmarks/globalArrayLargeArray.js");
+  callback("benchmarks/globalArrayLargeObject.js");
+  callback("benchmarks/globalArrayObjectLiteral.js");
+  callback("benchmarks/globalArrayReallocArray.js");
+  callback("benchmarks/globalArrayBuffer.js");
+  callback("benchmarks/globalArrayFgFinalized.js");
+  callback("benchmarks/largeArrayPropertyAndElements.js");
+  callback("benchmarks/selfCyclicWeakMap.js");
+  callback("benchmarks/pairCyclicWeakMap.js");
+  callback("benchmarks/deepWeakMap.js");
+  callback("benchmarks/textNodes.js");
+  callback("benchmarks/bigTextNodes.js");
+  callback("benchmarks/events.js");
+  callback("benchmarks/expandoEvents.js");
+  callback("benchmarks/propertyTreeSplitting.js");
+}
diff --git a/js/src/devtools/gc-ubench/ui.js b/js/src/devtools/gc-ubench/ui.js
new file mode 100644
index 0000000000..4905f97904
--- /dev/null
+++ b/js/src/devtools/gc-ubench/ui.js
@@ -0,0 +1,700 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+var stroke = {
+  gcslice: "rgb(255,100,0)",
+  minor: "rgb(0,255,100)",
+  initialMajor: "rgb(180,60,255)",
+};
+
+var numSamples = 500;
+
+var gHistogram = new Map(); // {ms: count}
+var gHistory = new FrameHistory(numSamples);
+var gPerf = new PerfTracker();
+
+var latencyGraph;
+var memoryGraph;
+var ctx;
+var memoryCtx;
+
+var loadState = "(init)"; // One of '(active)', '(inactive)', '(N/A)'
+var testState = "idle"; // One of 'idle' or 'running'.
+var enabled = { trackingSizes: false };
+
+var gMemory = performance.mozMemory?.gc || performance.mozMemory || {};
+
+var Firefox = class extends Host {
+  start_turn() {
+    // Handled by Gecko.
+  }
+
+  end_turn() {
+    // Handled by Gecko.
+  }
+
+  suspend(duration) {
+    // Not used; requestAnimationFrame takes its place.
+    throw new Error("unimplemented");
+  }
+
+  get minorGCCount() {
+    return gMemory.minorGCCount;
+  }
+  get majorGCCount() {
+    return gMemory.majorGCCount;
+  }
+  get GCSliceCount() {
+    return gMemory.sliceCount;
+  }
+  get gcBytes() {
+    return gMemory.zone.gcBytes;
+  }
+  get gcAllocTrigger() {
+    return gMemory.zone.gcAllocTrigger;
+  }
+
+  features = {
+    haveMemorySizes: 'gcBytes' in gMemory,
+    haveGCCounts: 'majorGCCount' in gMemory,
+  };
+};
+
+var gHost = new Firefox();
+
+function parse_units(v) {
+  if (!v.length) {
+    return NaN;
+  }
+  var lastChar = v[v.length - 1].toLowerCase();
+  if (!isNaN(parseFloat(lastChar))) {
+    return parseFloat(v);
+  }
+  var units = parseFloat(v.substr(0, v.length - 1));
+  if (lastChar == "k") {
+    return units * 1e3;
+  }
+  if (lastChar == "m") {
+    return units * 1e6;
+  }
+  if (lastChar == "g") {
+    return units * 1e9;
+  }
+  return NaN;
+}
+
+var Graph = class {
+  constructor(ctx) {
+    this.ctx = ctx;
+
+    var { height } = ctx.canvas;
+    this.layout = {
+      xAxisLabel_Y: height - 20,
+    };
+  }
+
+  xpos(index) {
+    return index * 2;
+  }
+
+  clear() {
+    const { width, height } = this.ctx.canvas;
+    this.ctx.clearRect(0, 0, width, height);
+  }
+
+  drawScale(delay) {
+    this.drawHBar(delay, `${delay}ms`, "rgb(150,150,150)");
+  }
+
+  draw60fps() {
+    this.drawHBar(1000 / 60, "60fps", "#00cf61", 25);
+  }
+
+  draw30fps() {
+    this.drawHBar(1000 / 30, "30fps", "#cf0061", 25);
+  }
+
+  drawAxisLabels(x_label, y_label) {
+    const ctx = this.ctx;
+    const { width, height } = ctx.canvas;
+
+    ctx.fillText(x_label, width / 2, this.layout.xAxisLabel_Y);
+
+    ctx.save();
+    ctx.rotate(Math.PI / 2);
+    var start = height / 2 - ctx.measureText(y_label).width / 2;
+    ctx.fillText(y_label, start, -width + 20);
+    ctx.restore();
+  }
+
+  drawFrame() {
+    const ctx = this.ctx;
+    const { width, height } = ctx.canvas;
+
+    // Draw frame to show size
+    ctx.strokeStyle = "rgb(0,0,0)";
+    ctx.fillStyle = "rgb(0,0,0)";
+    ctx.beginPath();
+    ctx.moveTo(0, 0);
+    ctx.lineTo(width, 0);
+    ctx.lineTo(width, height);
+    ctx.lineTo(0, height);
+    ctx.closePath();
+    ctx.stroke();
+  }
+};
+
+var LatencyGraph = class extends Graph {
+  constructor(ctx) {
+    super(ctx);
+    console.log(this.ctx);
+  }
+
+  ypos(delay) {
+    const { height } = this.ctx.canvas;
+
+    const r = height + 100 - Math.log(delay) * 64;
+    if (r < 5) {
+      return 5;
+    }
+    return r;
+  }
+
+  drawHBar(delay, label, color = "rgb(0,0,0)", label_offset = 0) {
+    const ctx = this.ctx;
+
+    ctx.fillStyle = color;
+    ctx.strokeStyle = color;
+    ctx.fillText(
+      label,
+      this.xpos(numSamples) + 4 + label_offset,
+      this.ypos(delay) + 3
+    );
+
+    ctx.beginPath();
+    ctx.moveTo(this.xpos(0), this.ypos(delay));
+    ctx.lineTo(this.xpos(numSamples) + label_offset, this.ypos(delay));
+    ctx.stroke();
+    ctx.strokeStyle = "rgb(0,0,0)";
+    ctx.fillStyle = "rgb(0,0,0)";
+  }
+
+  draw() {
+    const ctx = this.ctx;
+
+    this.clear();
+    this.drawFrame();
+
+    for (var delay of [10, 20, 30, 50, 100, 200, 400, 800]) {
+      this.drawScale(delay);
+    }
+    this.draw60fps();
+    this.draw30fps();
+
+    var worst = 0,
+      worstpos = 0;
+    ctx.beginPath();
+    for (let i = 0; i < numSamples; i++) {
+      ctx.lineTo(this.xpos(i), this.ypos(gHistory.delays[i]));
+      if (gHistory.delays[i] >= worst) {
+        worst = gHistory.delays[i];
+        worstpos = i;
+      }
+    }
+    ctx.stroke();
+
+    // Draw vertical lines marking minor and major GCs
+    if (gHost.features.haveGCCounts) {
+      ctx.strokeStyle = stroke.gcslice;
+      let idx = sampleIndex % numSamples;
+      const count = {
+        major: gHistory.majorGCs[idx],
+        minor: 0,
+        slice: gHistory.slices[idx],
+      };
+      for (let i = 0; i < numSamples; i++) {
+        idx = (sampleIndex + i) % numSamples;
+        const isMajorStart = count.major < gHistory.majorGCs[idx];
+        if (count.slice < gHistory.slices[idx]) {
+          if (isMajorStart) {
+            ctx.strokeStyle = stroke.initialMajor;
+          }
+          ctx.beginPath();
+          ctx.moveTo(this.xpos(idx), 0);
+          ctx.lineTo(this.xpos(idx), this.layout.xAxisLabel_Y);
+          ctx.stroke();
+          if (isMajorStart) {
+            ctx.strokeStyle = stroke.gcslice;
+          }
+        }
+        count.major = gHistory.majorGCs[idx];
+        count.slice = gHistory.slices[idx];
+      }
+
+      ctx.strokeStyle = stroke.minor;
+      idx = sampleIndex % numSamples;
+      count.minor = gHistory.minorGCs[idx];
+      for (let i = 0; i < numSamples; i++) {
+        idx = (sampleIndex + i) % numSamples;
+        if (count.minor < gHistory.minorGCs[idx]) {
+          ctx.beginPath();
+          ctx.moveTo(this.xpos(idx), 0);
+          ctx.lineTo(this.xpos(idx), 20);
+          ctx.stroke();
+        }
+        count.minor = gHistory.minorGCs[idx];
+      }
+    }
+
+    ctx.fillStyle = "rgb(255,0,0)";
+    if (worst) {
+      ctx.fillText(
+        `${worst.toFixed(2)}ms`,
+        this.xpos(worstpos) - 10,
+        this.ypos(worst) - 14
+      );
+    }
+
+    // Mark and label the slowest frame
+    ctx.beginPath();
+    var where = sampleIndex % numSamples;
+    ctx.arc(
+      this.xpos(where),
+      this.ypos(gHistory.delays[where]),
+      5,
+      0,
+      Math.PI * 2,
+      true
+    );
+    ctx.fill();
+    ctx.fillStyle = "rgb(0,0,0)";
+
+    this.drawAxisLabels("Time", "Pause between frames (log scale)");
+  }
+};
+
+var MemoryGraph = class extends Graph {
+  constructor(ctx) {
+    super(ctx);
+    this.worstEver = this.bestEver = gHost.gcBytes;
+    this.limit = Math.max(this.worstEver, gHost.gcAllocTrigger);
+  }
+
+  ypos(size) {
+    const { height } = this.ctx.canvas;
+
+    const range = this.limit - this.bestEver;
+    const percent = (size - this.bestEver) / range;
+
+    return (1 - percent) * height * 0.9 + 20;
+  }
+
+  drawHBar(size, label, color = "rgb(150,150,150)") {
+    const ctx = this.ctx;
+
+    const y = this.ypos(size);
+
+    ctx.fillStyle = color;
+    ctx.strokeStyle = color;
+    ctx.fillText(label, this.xpos(numSamples) + 4, y + 3);
+
+    ctx.beginPath();
+    ctx.moveTo(this.xpos(0), y);
+    ctx.lineTo(this.xpos(numSamples), y);
+    ctx.stroke();
+    ctx.strokeStyle = "rgb(0,0,0)";
+    ctx.fillStyle = "rgb(0,0,0)";
+  }
+
+  draw() {
+    const ctx = this.ctx;
+
+    this.clear();
+    this.drawFrame();
+
+    var worst = 0,
+      worstpos = 0;
+    for (let i = 0; i < numSamples; i++) {
+      if (gHistory.gcBytes[i] >= worst) {
+        worst = gHistory.gcBytes[i];
+        worstpos = i;
+      }
+      if (gHistory.gcBytes[i] < this.bestEver) {
+        this.bestEver = gHistory.gcBytes[i];
+      }
+    }
+
+    if (this.worstEver < worst) {
+      this.worstEver = worst;
+      this.limit = Math.max(this.worstEver, gHost.gcAllocTrigger);
+    }
+
+    this.drawHBar(
+      this.bestEver,
+      `${format_bytes(this.bestEver)} min`,
+      "#00cf61"
+    );
+    this.drawHBar(
+      this.worstEver,
+      `${format_bytes(this.worstEver)} max`,
+      "#cc1111"
+    );
+    this.drawHBar(
+      gHost.gcAllocTrigger,
+      `${format_bytes(gHost.gcAllocTrigger)} trigger`,
+      "#cc11cc"
+    );
+
+    ctx.fillStyle = "rgb(255,0,0)";
+    if (worst) {
+      ctx.fillText(
+        format_bytes(worst),
+        this.xpos(worstpos) - 10,
+        this.ypos(worst) - 14
+      );
+    }
+
+    ctx.beginPath();
+    var where = sampleIndex % numSamples;
+    ctx.arc(
+      this.xpos(where),
+      this.ypos(gHistory.gcBytes[where]),
+      5,
+      0,
+      Math.PI * 2,
+      true
+    );
+    ctx.fill();
+
+    ctx.beginPath();
+    for (let i = 0; i < numSamples; i++) {
+      if (i == (sampleIndex + 1) % numSamples) {
+        ctx.moveTo(this.xpos(i), this.ypos(gHistory.gcBytes[i]));
+      } else {
+        ctx.lineTo(this.xpos(i), this.ypos(gHistory.gcBytes[i]));
+      }
+      if (i == where) {
+        ctx.stroke();
+      }
+    }
+    ctx.stroke();
+
+    this.drawAxisLabels("Time", "Heap Memory Usage");
+  }
+};
+
+function onUpdateDisplayChanged() {
+  const do_graph = document.getElementById("do-graph");
+  if (do_graph.checked) {
+    window.requestAnimationFrame(handler);
+    gHistory.resume();
+  } else {
+    gHistory.pause();
+  }
+  update_load_state_indicator();
+}
+
+function onDoLoadChange() {
+  const do_load = document.getElementById("do-load");
+  gLoadMgr.paused = !do_load.checked;
+  console.log(`load paused: ${gLoadMgr.paused}`);
+  update_load_state_indicator();
+}
+
+var previous = 0;
+function handler(timestamp) {
+  if (gHistory.is_stopped()) {
+    return;
+  }
+
+  const completed = gLoadMgr.tick(timestamp);
+  if (completed) {
+    end_test(timestamp, gLoadMgr.lastActive);
+    if (!gLoadMgr.stopped()) {
+      start_test();
+    }
+    update_load_display();
+  }
+
+  if (testState == "running") {
+    document.getElementById("test-progress").textContent =
+      (gLoadMgr.currentLoadRemaining(timestamp) / 1000).toFixed(1) + " sec";
+  }
+
+  const delay = gHistory.on_frame(timestamp);
+
+  update_histogram(gHistogram, delay);
+
+  latencyGraph.draw();
+  if (memoryGraph) {
+    memoryGraph.draw();
+  }
+  window.requestAnimationFrame(handler);
+}
+
+// For interactive debugging.
+//
+// ['a', 'b', 'b', 'b', 'c', 'c'] => ['a', 'b x 3', 'c x 2']
+function summarize(arr) {
+  if (!arr.length) {
+    return [];
+  }
+
+  var result = [];
+  var run_start = 0;
+  var prev = arr[0];
+  for (let i = 1; i <= arr.length; i++) {
+    if (i == arr.length || arr[i] != prev) {
+      if (i == run_start + 1) {
+        result.push(arr[i]);
+      } else {
+        result.push(prev + " x " + (i - run_start));
+      }
+      run_start = i;
+    }
+    if (i != arr.length) {
+      prev = arr[i];
+    }
+  }
+
+  return result;
+}
+
+function reset_draw_state() {
+  gHistory.reset();
+}
+
+function onunload() {
+  gLoadMgr.deactivateLoad();
+}
+
+function onload() {
+  // The order of `tests` is currently based on their asynchronous load
+  // order, rather than the listed order. Rearrange by extracting the test
+  // names from their filenames, which is kind of gross.
+  _tests = tests;
+  tests = new Map();
+  foreach_test_file(fn => {
+    // "benchmarks/foo.js" => "foo"
+    const name = fn.split(/\//)[1].split(/\./)[0];
+    tests.set(name, _tests.get(name));
+  });
+  _tests = undefined;
+
+  gLoadMgr = new AllocationLoadManager(tests);
+
+  // Load initial test duration.
+  duration_changed();
+
+  // Load initial garbage size.
+  garbage_piles_changed();
+  garbage_per_frame_changed();
+
+  // Populate the test selection dropdown.
+  var select = document.getElementById("test-selection");
+  for (var [name, test] of tests) {
+    test.name = name;
+    var option = document.createElement("option");
+    option.id = name;
+    option.text = name;
+    option.title = test.description;
+    select.add(option);
+  }
+
+  // Load the initial test.
+  gLoadMgr.setActiveLoad(gLoadMgr.getByName("noAllocation"));
+  update_load_display();
+  document.getElementById("test-selection").value = "noAllocation";
+
+  // Polyfill rAF.
+  var requestAnimationFrame =
+    window.requestAnimationFrame ||
+    window.mozRequestAnimationFrame ||
+    window.webkitRequestAnimationFrame ||
+    window.msRequestAnimationFrame;
+  window.requestAnimationFrame = requestAnimationFrame;
+
+  // Acquire our canvas.
+  var canvas = document.getElementById("graph");
+  latencyGraph = new LatencyGraph(canvas.getContext("2d"));
+
+  if (!gHost.features.haveMemorySizes) {
+    document.getElementById("memgraph-disabled").style.display = "block";
+    document.getElementById("track-sizes-div").style.display = "none";
+  }
+
+  trackHeapSizes(document.getElementById("track-sizes").checked);
+
+  update_load_state_indicator();
+  gHistory.start();
+
+  // Start drawing.
+  reset_draw_state();
+  window.requestAnimationFrame(handler);
+}
+
+function run_one_test() {
+  start_test_cycle([gLoadMgr.activeLoad().name]);
+}
+
+function run_all_tests() {
+  start_test_cycle([...tests.keys()]);
+}
+
+function start_test_cycle(tests_to_run) {
+  // Convert from an iterable to an array for pop.
+  const duration = gLoadMgr.testDurationMS / 1000;
+  const mutators = tests_to_run.map(name => new SingleMutatorSequencer(gLoadMgr.getByName(name), gPerf, duration));
+  const sequencer = new ChainSequencer(mutators);
+  gLoadMgr.startSequencer(sequencer);
+  testState = "running";
+  gHistogram.clear();
+  reset_draw_state();
+}
+
+function update_load_state_indicator() {
+  if (
+    !gLoadMgr.load_running() ||
+    gLoadMgr.activeLoad().name == "noAllocation"
+  ) {
+    loadState = "(none)";
+  } else if (gHistory.is_stopped() || gLoadMgr.paused) {
+    loadState = "(inactive)";
+  } else {
+    loadState = "(active)";
+  }
+  document.getElementById("load-running").textContent = loadState;
+}
+
+function start_test() {
+  console.log(`Running test: ${gLoadMgr.activeLoad().name}`);
+  document.getElementById("test-selection").value = gLoadMgr.activeLoad().name;
+  update_load_state_indicator();
+}
+
+function end_test(timestamp, load) {
+  document.getElementById("test-progress").textContent = "(not running)";
+  report_test_result(load, gHistogram);
+  gHistogram.clear();
+  console.log(`Ending test ${load.name}`);
+  if (gLoadMgr.stopped()) {
+    testState = "idle";
+  }
+  update_load_state_indicator();
+  reset_draw_state();
+}
+
+function compute_test_spark_histogram(histogram) {
+  const percents = compute_spark_histogram_percents(histogram);
+
+  var sparks = "▁▂▃▄▅▆▇█";
+  var colors = [
+    "#aaaa00",
+    "#007700",
+    "#dd0000",
+    "#ff0000",
+    "#ff0000",
+    "#ff0000",
+    "#ff0000",
+    "#ff0000",
+  ];
+  var line = "";
+  for (let i = 0; i < percents.length; ++i) {
+    var spark = sparks.charAt(parseInt(percents[i] * sparks.length));
+    line += `<span style="color:${colors[i]}">${spark}</span>`;
+  }
+  return line;
+}
+
+function report_test_result(load, histogram) {
+  var resultList = document.getElementById("results-display");
+  var resultElem = document.createElement("div");
+  var score = compute_test_score(histogram);
+  var sparks = compute_test_spark_histogram(histogram);
+  var params = `(${format_num(load.garbagePerFrame)},${format_num(
+    load.garbagePiles
+  )})`;
+  resultElem.innerHTML = `${score.toFixed(3)} ms/s : ${sparks} : ${
+    load.name
+  }${params} - ${load.description}`;
+  resultList.appendChild(resultElem);
+}
+
+function update_load_display() {
+  const garbage = gLoadMgr.activeLoad()
+    ? gLoadMgr.activeLoad().garbagePerFrame
+    : parse_units(gDefaultGarbagePerFrame);
+  document.getElementById("garbage-per-frame").value = format_num(garbage);
+  const piles = gLoadMgr.activeLoad()
+    ? gLoadMgr.activeLoad().garbagePiles
+    : parse_units(gDefaultGarbagePiles);
+  document.getElementById("garbage-piles").value = format_num(piles);
+  update_load_state_indicator();
+}
+
+function duration_changed() {
+  var durationInput = document.getElementById("test-duration");
+  gLoadMgr.testDurationMS = parseInt(durationInput.value) * 1000;
+  console.log(
+    `Updated test duration to: ${gLoadMgr.testDurationMS / 1000} seconds`
+  );
+}
+
+function onLoadChange() {
+  var select = document.getElementById("test-selection");
+  console.log(`Switching to test: ${select.value}`);
+  gLoadMgr.setActiveLoad(gLoadMgr.getByName(select.value));
+  update_load_display();
+  gHistogram.clear();
+  reset_draw_state();
+}
+
+function garbage_piles_changed() {
+  const input = document.getElementById("garbage-piles");
+  const value = parse_units(input.value);
+  if (isNaN(value)) {
+    update_load_display();
+    return;
+  }
+
+  if (gLoadMgr.load_running()) {
+    gLoadMgr.change_garbagePiles(value);
+    console.log(
+      `Updated garbage-piles to ${gLoadMgr.activeLoad().garbagePiles} items`
+    );
+  }
+  gHistogram.clear();
+  reset_draw_state();
+}
+
+function garbage_per_frame_changed() {
+  const input = document.getElementById("garbage-per-frame");
+  var value = parse_units(input.value);
+  if (isNaN(value)) {
+    update_load_display();
+    return;
+  }
+  if (gLoadMgr.load_running()) {
+    gLoadMgr.change_garbagePerFrame = value;
+    console.log(
+      `Updated garbage-per-frame to ${
+        gLoadMgr.activeLoad().garbagePerFrame
+      } items`
+    );
+  }
+}
+
+function trackHeapSizes(track) {
+  enabled.trackingSizes = track && gHost.features.haveMemorySizes;
+
+  var canvas = document.getElementById("memgraph");
+
+  if (enabled.trackingSizes) {
+    canvas.style.display = "block";
+    memoryGraph = new MemoryGraph(canvas.getContext("2d"));
+  } else {
+    canvas.style.display = "none";
+    memoryGraph = null;
+  }
+}
diff --git a/js/src/devtools/gc-ubench/v8.js b/js/src/devtools/gc-ubench/v8.js
new file mode 100644
index 0000000000..0c46c2b4c4
--- /dev/null
+++ b/js/src/devtools/gc-ubench/v8.js
@@ -0,0 +1,42 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// V8 JS shell benchmark script
+//
+// Usage: run d8 v8.js -- --help
+
+globalThis.loadRelativeToScript = load;
+
+load("shell-bench.js");
+
+var V8 = class extends Host {
+  constructor() {
+    super();
+    this.waitTA = new Int32Array(new SharedArrayBuffer(4));
+  }
+
+  start_turn() {}
+
+  end_turn() {}
+
+  suspend(duration) {
+    const response = Atomics.wait(this.waitTA, 0, 0, duration * 1000);
+    if (response !== 'timed-out') {
+      throw new Exception(`unexpected response from Atomics.wait: ${response}`);
+    }
+  }
+
+  features = {
+    haveMemorySizes: false,
+    haveGCCounts: false
+  };
+};
+
+var gHost = new V8();
+
+var { opts, rest: mutators } = argparse.parse_args(arguments);
+run(opts, mutators);
+
+print("\nTest results:\n");
+report_results();
diff --git a/js/src/devtools/gc/README.txt b/js/src/devtools/gc/README.txt
new file mode 100644
index 0000000000..f4f37efbaa
--- /dev/null
+++ b/js/src/devtools/gc/README.txt
@@ -0,0 +1,6 @@
+Usage:
+
+Requirements:
+1) The shell has to be compiled with --enable-gctimer
+
+Tested with python2.6
diff --git a/js/src/devtools/gc/gc-test.py b/js/src/devtools/gc/gc-test.py
new file mode 100644
index 0000000000..9b8fbc25b1
--- /dev/null
+++ b/js/src/devtools/gc/gc-test.py
@@ -0,0 +1,191 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Works with python2.6
+
+import json
+import math
+import os
+import sys
+from operator import itemgetter
+from subprocess import PIPE, Popen
+
+
+class Test:
+    def __init__(self, path, name):
+        self.path = path
+        self.name = name
+
+    @classmethod
+    def from_file(cls, path, name, options):
+        return cls(path, name)
+
+
+def find_tests(dir, substring=None):
+    ans = []
+    for dirpath, dirnames, filenames in os.walk(dir):
+        if dirpath == ".":
+            continue
+        for filename in filenames:
+            if not filename.endswith(".js"):
+                continue
+            test = os.path.join(dirpath, filename)
+            if substring is None or substring in os.path.relpath(test, dir):
+                ans.append([test, filename])
+    return ans
+
+
+def get_test_cmd(path):
+    return [JS, "-f", path]
+
+
+def avg(seq):
+    return sum(seq) / len(seq)
+
+
+def stddev(seq, mean):
+    diffs = ((float(item) - mean) ** 2 for item in seq)
+    return math.sqrt(sum(diffs) / len(seq))
+
+
+def run_test(test):
+    env = os.environ.copy()
+    env["MOZ_GCTIMER"] = "stderr"
+    cmd = get_test_cmd(test.path)
+    total = []
+    mark = []
+    sweep = []
+    close_fds = sys.platform != "win32"
+    p = Popen(cmd, stdin=PIPE, stdout=PIPE, stderr=PIPE, close_fds=close_fds, env=env)
+    out, err = p.communicate()
+    out, err = out.decode(), err.decode()
+
+    float_array = [float(_) for _ in err.split()]
+
+    if len(float_array) == 0:
+        print("Error: No data from application. Configured with --enable-gctimer?")
+        sys.exit(1)
+
+    for i, currItem in enumerate(float_array):
+        if i % 3 == 0:
+            total.append(currItem)
+        else:
+            if i % 3 == 1:
+                mark.append(currItem)
+            else:
+                sweep.append(currItem)
+
+    return max(total), avg(total), max(mark), avg(mark), max(sweep), avg(sweep)
+
+
+def run_tests(tests, test_dir):
+    bench_map = {}
+
+    try:
+        for i, test in enumerate(tests):
+            filename_str = '"%s"' % test.name
+            TMax, TAvg, MMax, MAvg, SMax, SAvg = run_test(test)
+            bench_map[test.name] = [TMax, TAvg, MMax, MAvg, SMax, SAvg]
+            fmt = '%20s: {"TMax": %4.1f, "TAvg": %4.1f, "MMax": %4.1f, "MAvg": %4.1f, "SMax": %4.1f, "SAvg": %4.1f}'  # NOQA: E501
+            if i != len(tests) - 1:
+                fmt += ","
+            print(fmt % (filename_str, TMax, TAvg, MMax, MAvg, SMax, MAvg))
+    except KeyboardInterrupt:
+        print("fail")
+
+    return dict(
+        (
+            filename,
+            dict(TMax=TMax, TAvg=TAvg, MMax=MMax, MAvg=MAvg, SMax=SMax, SAvg=SAvg),
+        )
+        for filename, (TMax, TAvg, MMax, MAvg, SMax, SAvg) in bench_map.iteritems()
+    )
+
+
+def compare(current, baseline):
+    percent_speedups = []
+    for key, current_result in current.iteritems():
+        try:
+            baseline_result = baseline[key]
+        except KeyError:
+            print(key, "missing from baseline")
+            continue
+
+        val_getter = itemgetter("TMax", "TAvg", "MMax", "MAvg", "SMax", "SAvg")
+        BTMax, BTAvg, BMMax, BMAvg, BSMax, BSAvg = val_getter(baseline_result)
+        CTMax, CTAvg, CMMax, CMAvg, CSMax, CSAvg = val_getter(current_result)
+
+        if CTAvg <= BTAvg:
+            speedup = (CTAvg / BTAvg - 1) * 100
+            result = "faster: %6.2f < baseline %6.2f (%+6.2f%%)" % (
+                CTAvg,
+                BTAvg,
+                speedup,
+            )
+            percent_speedups.append(speedup)
+        else:
+            slowdown = (CTAvg / BTAvg - 1) * 100
+            result = "SLOWER: %6.2f > baseline %6.2f (%+6.2f%%) " % (
+                CTAvg,
+                BTAvg,
+                slowdown,
+            )
+            percent_speedups.append(slowdown)
+        print("%30s: %s" % (key, result))
+    if percent_speedups:
+        print("Average speedup: %.2f%%" % avg(percent_speedups))
+
+
+if __name__ == "__main__":
+    script_path = os.path.abspath(__file__)
+    script_dir = os.path.dirname(script_path)
+    test_dir = os.path.join(script_dir, "tests")
+
+    from optparse import OptionParser
+
+    op = OptionParser(usage="%prog [options] JS_SHELL [TESTS]")
+
+    op.add_option(
+        "-b",
+        "--baseline",
+        metavar="JSON_PATH",
+        dest="baseline_path",
+        help="json file with baseline values to " "compare against",
+    )
+
+    (OPTIONS, args) = op.parse_args()
+    if len(args) < 1:
+        op.error("missing JS_SHELL argument")
+    # We need to make sure we are using backslashes on Windows.
+    JS, test_args = os.path.normpath(args[0]), args[1:]
+
+    test_list = []
+    bench_map = {}
+
+    test_list = find_tests(test_dir)
+
+    if not test_list:
+        print >>sys.stderr, "No tests found matching command line arguments."
+        sys.exit(0)
+
+    test_list = [Test.from_file(tst, name, OPTIONS) for tst, name in test_list]
+
+    try:
+        print("{")
+        bench_map = run_tests(test_list, test_dir)
+        print("}")
+
+    except OSError:
+        if not os.path.exists(JS):
+            print >>sys.stderr, "JS shell argument: file does not exist: '%s'" % JS
+            sys.exit(1)
+        else:
+            raise
+
+    if OPTIONS.baseline_path:
+        baseline_map = []
+        fh = open(OPTIONS.baseline_path, "r")
+        baseline_map = json.load(fh)
+        fh.close()
+        compare(current=bench_map, baseline=baseline_map)
diff --git a/js/src/devtools/gc/tests/clock.js b/js/src/devtools/gc/tests/clock.js
new file mode 100644
index 0000000000..fd2fb985f1
--- /dev/null
+++ b/js/src/devtools/gc/tests/clock.js
@@ -0,0 +1,35 @@
+//Shell version of Clock Benchmark: https://bug548388.bugzilla.mozilla.org/attachment.cgi?id=434576
+
+var t0;
+var tl;
+
+function alloc(dt) {
+    if (dt > 100)
+        dt = 100;
+    for (var i = 0; i < dt * 1000; ++i) {
+        var o = new String("aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa");
+    }
+}
+
+function cycle() {
+    if (!running)
+        return;
+
+    var t1 = new Date;
+    if (t0 == undefined) t0 = t1;
+
+    if (tl != undefined) {
+        var dt = t1 - tl;
+        alloc(dt);
+    }
+
+    tl = t1;
+
+    if(t1 - t0 > (5 * 1000))
+        running = false;
+}
+
+var running = true;
+while(running)
+    cycle();
+
diff --git a/js/src/devtools/gc/tests/dslots.js b/js/src/devtools/gc/tests/dslots.js
new file mode 100644
index 0000000000..8fcb6e8aa3
--- /dev/null
+++ b/js/src/devtools/gc/tests/dslots.js
@@ -0,0 +1,26 @@
+//Benchmark to measure overhead of dslots allocation and deallocation
+
+function Object0() {};
+function Object1() { this.a=1; };
+function Object2() { this.a=1; this.b=1; };
+function Object3() { this.a=1; this.b=1; this.c=1; };
+function Object4() { this.a=1; this.b=1; this.c=1; this.d=1; };
+function Object5() { this.a=1; this.b=1; this.c=1; this.d=1; this.e=1; };
+
+function test() {
+    var N = 1e5;
+    gc();
+
+    for(var i = 0; i<=5; i++)
+    {
+        var tmp = i==0 ? Object0 : i==1 ? Object1 : i==2 ? Object2 : i==3 ? Object3 : i==4 ? Object4 : Object5;
+        for (var j = 0; j != N; j++) {
+            var a = new tmp();
+        }
+        gc();
+    }
+}
+
+for(var i = 0; i<=5; i++) {
+    test();
+}
diff --git a/js/src/devtools/gc/tests/loops.js b/js/src/devtools/gc/tests/loops.js
new file mode 100644
index 0000000000..a99961a3ef
--- /dev/null
+++ b/js/src/devtools/gc/tests/loops.js
@@ -0,0 +1,55 @@
+//Measure plain GC.
+
+var t = [];
+var N = 500000
+
+for(var i = 0; i < N; i++)
+    t[i] = {};
+
+gc()
+
+t = [];
+
+gc();
+
+for(var i = 0; i < N; i++)
+    t[i] = ({});
+
+gc();
+
+t = [];
+
+gc();
+
+
+for(var i = 0; i < N; i++)
+    t[i] = "asdf";
+    
+gc();
+
+t = [];
+
+gc();
+
+
+for(var i = 0; i < N; i++)
+    t[i] = 1.12345;
+    
+gc();
+
+t=[];
+
+gc();
+
+for(var i = 0; i < N; i++) {
+    t[i] = ({});
+    if (i != 0)
+        t[i].a = t[i-1];
+}
+    
+gc();
+
+t = [];
+
+gc();
+
diff --git a/js/src/devtools/gc/tests/objGraph.js b/js/src/devtools/gc/tests/objGraph.js
new file mode 100644
index 0000000000..607633173b
--- /dev/null
+++ b/js/src/devtools/gc/tests/objGraph.js
@@ -0,0 +1,37 @@
+test();
+
+function test()
+{
+  function generate_big_object_graph()
+  {
+    var root = {};
+    f(root, 17);
+    return root;
+    function f(parent, depth) {
+      if (depth == 0) 
+          return;
+      --depth;
+
+      f(parent.a = {}, depth);
+      f(parent.b = {}, depth);
+    }
+  }
+
+  function f(obj) {
+    with (obj)
+      return arguments;
+  }
+
+  for(var i = 0; i != 10; ++i) 
+  {
+    gc();
+    var x = null;
+    x = f(generate_big_object_graph());
+
+    gc(); //all used
+
+    x = null;
+
+    gc(); //all free
+  }
+}
diff --git a/js/src/devtools/gnuplot/gcTimer.gnu b/js/src/devtools/gnuplot/gcTimer.gnu
new file mode 100644
index 0000000000..b8b3ac9d85
--- /dev/null
+++ b/js/src/devtools/gnuplot/gcTimer.gnu
@@ -0,0 +1,24 @@
+# gnuplot script to visualize GCMETER results.
+# usage: "gnuplot gcTimer.gnu >outputfile.png"
+
+set terminal png
+# set Title
+set title "Title goes here!"
+set datafile missing "-"
+set noxtics
+#set ytics nomirror
+set ylabel "msec"
+set key below
+set style data linespoints
+
+#set data file
+plot 'gcTimer.dat' using 2 title columnheader(2), \
+'' u 3 title columnheader(3) with points, \
+'' u 4 title columnheader(4), \
+'' u 5 title columnheader(5), \
+'' u 6 title columnheader(6) with points, \
+'' u 7 title columnheader(7) with points, \
+'' u 8 title columnheader(8) with points, \
+'' u 9 title columnheader(9) with points, \
+'' u 10 title columnheader(10) with points, \
+'' u 11 title columnheader(11) with points
diff --git a/js/src/devtools/javascript-trace.d b/js/src/devtools/javascript-trace.d
new file mode 100644
index 0000000000..db759291c9
--- /dev/null
+++ b/js/src/devtools/javascript-trace.d
@@ -0,0 +1,34 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/*
+ * javascript provider probes
+ *
+ * function-entry       (filename, classname, funcname)
+ * function-return      (filename, classname, funcname)
+ * object-create        (classname, *object)
+ * object-finalize      (NULL, classname, *object)
+ * execute-start        (filename, lineno)
+ * execute-done         (filename, lineno)
+ */
+
+provider javascript {
+ probe function__entry(const char *, const char *, const char *);
+ probe function__return(const char *, const char *, const char *);
+ /* XXX must use unsigned longs here instead of uintptr_t for OS X
+    (Apple radar: 5194316 & 5565198) */
+ probe object__create(const char *, unsigned long);
+ probe object__finalize(const char *, const char *, unsigned long);
+ probe execute__start(const char *, int);
+ probe execute__done(const char *, int);
+};
+
+/*
+#pragma D attributes Unstable/Unstable/Common provider mozilla provider
+#pragma D attributes Private/Private/Unknown provider mozilla module
+#pragma D attributes Private/Private/Unknown provider mozilla function
+#pragma D attributes Unstable/Unstable/Common provider mozilla name
+*/
+
diff --git a/js/src/devtools/octane-csv.sh b/js/src/devtools/octane-csv.sh
new file mode 100755
index 0000000000..1049a2b47e
--- /dev/null
+++ b/js/src/devtools/octane-csv.sh
@@ -0,0 +1,76 @@
+#!/usr/bin/env bash
+
+set -e -o pipefail
+
+function echo_to_stderr {
+    echo "$1" 1>&2
+}
+
+function usage_and_exit {
+    echo_to_stderr "Usage:"
+    echo_to_stderr "    $0 <path-to-js> <number-of-iterations>"
+    echo_to_stderr
+    echo_to_stderr "Run octane <number-of-iterations> times, and aggregate the results"
+    echo_to_stderr "into one CSV file, which is written to stdout."
+    echo_to_stderr
+    echo_to_stderr "See the js/src/devtools/plot-octane.R script for plotting the"
+    echo_to_stderr "results."
+    echo_to_stderr
+    echo_to_stderr "Complete example usage with plotting:"
+    echo_to_stderr
+    echo_to_stderr "    \$ ./js/src/devtools/octane-csv.sh path/to/js 20 > control.csv"
+    echo_to_stderr
+    echo_to_stderr "    Next, apply some patch you'd like to test."
+    echo_to_stderr
+    echo_to_stderr "    \$ ./js/src/devtools/octane-csv.sh path/to/js 20 > variable.csv"
+    echo_to_stderr "    \$ ./js/src/devtools/plot-octane.R control.csv variable.csv"
+    echo_to_stderr
+    echo_to_stderr "    Open Rplots.pdf to view the results."
+    exit 1
+}
+
+if [[ "$#" != "2" ]]; then
+    usage_and_exit
+fi
+
+# Get the absolute, normalized $JS path, and ensure its an executable.
+
+JS_DIR=$(dirname $1)
+if [[ ! -d "$JS_DIR" ]]; then
+    echo_to_stderr "error: no such directory $JS_DIR"
+    echo_to_stderr
+    usage_and_exit
+fi
+
+JS=$(basename $1)
+cd "$JS_DIR" > /dev/null
+JS="$(pwd)/$JS"
+if [[ ! -e "$JS" ]]; then
+    echo_to_stderr "error: '$JS' is not executable"
+    echo_to_stderr
+    usage_and_exit
+fi
+cd - > /dev/null
+
+# Go to the js/src/octane directory.
+
+cd $(dirname $0)/../octane > /dev/null
+
+# Run octane and transform the results into CSV.
+#
+# Run once as a warm up, and to grab the column headers. Then run the benchmark
+# $ITERS times, grabbing just the data rows.
+
+echo_to_stderr "Warm up"
+"$JS" ./run.js | grep -v -- "----" | cut -f 1 -d ':' | tr '\n' ','
+echo
+
+ITERS=$2
+while [[ "$ITERS" -ge "1" ]]; do
+    echo_to_stderr "Iterations left: $ITERS"
+    "$JS" ./run.js | grep -v -- "----" | cut -f 2 -d ':' | tr '\n' ','
+    echo
+    ITERS=$((ITERS - 1))
+done
+
+echo_to_stderr "All done :)"
diff --git a/js/src/devtools/plot-octane.R b/js/src/devtools/plot-octane.R
new file mode 100755
index 0000000000..cd7ac7303a
--- /dev/null
+++ b/js/src/devtools/plot-octane.R
@@ -0,0 +1,38 @@
+#!/usr/bin/env Rscript
+
+# Usage:
+#
+#     octane.R control.csv variable.csv
+#
+# Output will be placed in Rplots.pdf
+#
+# Remember: on Octane, higher is better!
+
+library(ggplot2)
+
+args <- commandArgs(trailingOnly = TRUE)
+
+# Reading in data.
+control <- read.table(args[1], sep=",", header=TRUE)
+variable <- read.table(args[2], sep=",", header=TRUE)
+
+# Pulling out columns that we want to plot.
+# Not totally necessary.
+ctrl <- control$Score..version.9.
+var <- variable$Score..version.9.
+
+# Concatenating the values we want to plot.
+score <- c(ctrl, var)
+# Creating a vector of labels for the data points.
+label <- c(rep("control", length(ctrl)), rep("variable", length(var)))
+
+# Creating a data frame of the score and label.
+data <- data.frame(label, score)
+
+# Now plotting!
+ggplot(data, aes(label, score, color=label, pch=label)) +
+  # Adding boxplot without the outliers.
+  geom_boxplot(outlier.shape=NA) +
+  # Adding jitter plot on top of the boxplot. If you want to spread the points
+  # more, increase jitter.
+  geom_jitter(position=position_jitter(width=0.05)) 
diff --git a/js/src/devtools/release/release-notes b/js/src/devtools/release/release-notes
new file mode 100644
index 0000000000..48cc53ac9e
--- /dev/null
+++ b/js/src/devtools/release/release-notes
@@ -0,0 +1,195 @@
+#!/usr/bin/perl
+
+# How to use:
+#
+# Step 1: run release-notes diff old-jsapi.h new-jsapi.h > diff.txt
+#
+# Step 2: edit diff.txt
+#  - when a function has been renamed, get the - and + lines adjacent and mark the - line with [renamed] at the end
+#  - when a function has been replaced, do the same (replacements behave differently)
+#  - for anything that isn't a simple addition, deletion, rename, or replace, tag with [other]
+#    (things tagged [other] will be put in a separate section for manual fixup)
+#
+# Step 3: run release-notes < diff.txt > changes.txt
+#  - this will group changes into sections and annotate them with bug numbers
+#  - the bugs chosen are just the bug that last touched each line, and are unlikely to be entirely accurate
+#
+# Step 4: run release-notes mdn < changes.txt > final.txt
+#  - this will add an MDN link to every list item, first checking whether such a link is valid
+#
+# Step 5: paste into the MDN page, eg https://developer.mozilla.org/en-US/docs/Mozilla/Projects/SpiderMonkey/Releases/45
+
+# Upcoming: basing everything off of jsapi.h is probably not going to work for
+# much longer, given that more stuff is moving into js/public. Scan
+# js/public/*.h too and record where everything comes from (to automate header
+# changes in the notes)?
+#
+# This is only looking at C style APIs. Dump out all methods too?
+#
+# The enbuggification should be split out into a separate phase because it is
+# wrong a fair amount of the time (whitespace changes, parameter changes,
+# etc.), and should have a way of running repeatedly so you can incrementally
+# fix stuff up.
+#
+# It would be very nice to have an example program that links against mozjs,
+# tested in CI, so we can diff that for release notes.
+
+use strict;
+use warnings;
+
+if (@ARGV && $ARGV[0] eq 'diff') {
+    my ($orig_file, $new_file) = @ARGV[1..2];
+    my $orig_api = grab_api($orig_file);
+    my $new_api = grab_api($new_file);
+    diff_apis($orig_api, $new_api);
+    exit 0;
+}
+
+my $path = "/en-US/docs/Mozilla/Projects/SpiderMonkey/JSAPI_Reference";
+my $url_prefix = "https://developer.mozilla.org$path";
+
+if (@ARGV && $ARGV[0] eq 'mdn') {
+    shift(@ARGV);
+    while(<>) {
+        if (/<li>([\w:]+)/) {
+            print STDERR "Checking $1...\n";
+            system("wget", "-q", "$url_prefix/$1");
+            if ($? == 0) {
+                s!<li>([\w:]+)!<li><a href="$path/$1">$1</a>!;
+            }
+        }
+        print;
+    }
+    exit 0;
+}
+
+sub grab_api {
+    my ($file) = @_;
+    open(my $fh, "<", $file) or die "open $file: $!";
+    my $grabbing;
+    my @api;
+    while(<$fh>) {
+        if ($grabbing && /^(\w+)/) {
+            push @api, $1;
+        }
+        $grabbing = /JS_PUBLIC_API/;
+    }
+    return \@api;
+}
+
+sub diff_apis {
+    my ($old, $new) = @_;
+    my %old;
+    @old{@$old} = ();
+    my %new;
+    @new{@$new} = ();
+
+    open(my $ofh, ">", "/tmp/r-c.diff.1");
+    print $ofh "$_\n" foreach (@$old);
+    close $ofh;
+    open(my $nfh, ">", "/tmp/r-c.diff.2");
+    print $nfh "$_\n" foreach (@$new);
+    close $nfh;
+    open(my $diff, "diff -u /tmp/r-c.diff.1 /tmp/r-c.diff.2 |");
+    while(<$diff>) {
+        if (/^-(\w+)/) {
+            next if exists $new{$1}; # Still exists, so skip it
+        } elsif (/^\+(\w+)/) {
+            next if exists $old{$1}; # It was already there, skip it
+        }
+        print;
+    }
+}
+
+my @added;
+my @renamed;
+my @replaced;
+my @deleted;
+my @other;
+
+my %N;
+
+my $renaming;
+my $replacing;
+while (<>) {
+    my $name;
+    if (/^[ +-](\w+)/) {
+        $name = $1;
+        $N{$name} = $name =~ /^JS_/ ? $name : "JS::$name";
+    }
+
+    if (/^-/) {
+        die if ! $name;
+        if (/\[rename\]/) {
+            $renaming = $name;
+        } elsif (/\[replace\]/) {
+            $replacing = $name;
+        } elsif (/\[other\]/) {
+            push @other, $name;
+        } else {
+            push @deleted, $name;
+        }
+    } elsif (/^\+/) {
+        die if ! $name;
+        if ($renaming) {
+            push @renamed, [ $renaming, $name ];
+            undef $renaming;
+        } elsif ($replacing) {
+            push @replaced, [ $replacing, $name ];
+            undef $replacing;
+        } elsif (/\[other\]/) {
+            push @other, $name;
+        } else {
+            push @added, $name;
+        }
+    }
+}
+
+open(my $fh, "<", "jsapi.blame") or die "open jsapi.blame: $!";
+my $grabbing;
+my %changerev;
+my %revs;
+while(<$fh>) {
+    if ($grabbing && /^\s*(\d+): (\w+)/ ) {
+        $changerev{$2} = $1;
+        $revs{$1} = 1;
+    }
+    $grabbing = /JS_PUBLIC_API/;
+}
+
+my %bug;
+for my $rev (keys %revs) {
+    open(my $fh, "hg log -r $rev -T '{desc}' |");
+    while(<$fh>) {
+        if (/[bB]ug (\d+)/) {
+            $bug{$rev} = $1;
+        }
+    }
+}
+
+sub get_bug_suffix {
+    my ($api) = @_;
+    $DB::single = 1 if ! $changerev{$api};
+    my $bug = $bug{$changerev{$api}};
+    return $bug ? " {{{bug($bug)}}}" : "";
+}
+
+print "(new apis)\n";
+print "<ul>\n";
+print "  <li>$N{$_}" . get_bug_suffix($_) . "</li>\n" foreach @added;
+print "  <li>$N{$_->[0]} renamed to $N{$_->[1]}" . get_bug_suffix($_->[1]) . "</li>\n" foreach @renamed;
+print "  <li>$N{$_->[0]} replaced with $N{$_->[1]}" . get_bug_suffix($_->[1]) . "</li>\n" foreach @replaced;
+print "</ul>\n";
+print "\n";
+
+print qq(<h2 id="Deleted_APIs">Deleted APIs</h2>\n);
+print "<ul>\n";
+print "  <li>$N{$_}</li>\n" foreach @deleted;
+print "</ul>\n";
+print "\n";
+
+print qq(<h2 id="Changed_APIs">Changed APIs</h2>\n);
+print "<ul>\n";
+print "  <li>$N{$_}" . get_bug_suffix($_) . "</li>\n" foreach @other;
+print "</ul>\n";
+print "\n";
diff --git a/js/src/devtools/rootAnalysis/CFG.js b/js/src/devtools/rootAnalysis/CFG.js
new file mode 100644
index 0000000000..1b6f714279
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/CFG.js
@@ -0,0 +1,1178 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+// Utility code for traversing the JSON data structures produced by sixgill.
+
+"use strict";
+
+var TRACING = false;
+
+// When edge.Kind == "Pointer", these are the meanings of the edge.Reference field.
+var PTR_POINTER = 0;
+var PTR_REFERENCE = 1;
+var PTR_RVALUE_REF = 2;
+
+// Find all points (positions within the code) of the body given by the list of
+// bodies and the blockId to match (which will specify an outer function or a
+// loop within it), recursing into loops if needed.
+function findAllPoints(bodies, blockId, bits)
+{
+    var points = [];
+    var body;
+
+    for (var xbody of bodies) {
+        if (sameBlockId(xbody.BlockId, blockId)) {
+            assert(!body);
+            body = xbody;
+        }
+    }
+    assert(body);
+
+    if (!("PEdge" in body))
+        return;
+    for (var edge of body.PEdge) {
+        points.push([body, edge.Index[0], bits]);
+        if (edge.Kind == "Loop")
+            points.push(...findAllPoints(bodies, edge.BlockId, bits));
+    }
+
+    return points;
+}
+
+// Visitor of a graph of <body, ppoint> vertexes and sixgill-generated edges,
+// where the edges represent the actual computation happening.
+//
+// Uses the syntax `var Visitor = class { ... }` rather than `class Visitor`
+// to allow reloading this file with the JS debugger.
+var Visitor = class {
+    constructor(bodies) {
+        this.visited_bodies = new Map();
+        for (const body of bodies) {
+            this.visited_bodies.set(body, new Map());
+        }
+    }
+
+    // Prepend `edge` to the info stored at the successor node, returning
+    // the updated info value. This should be overridden by pretty much any
+    // subclass, as a traversal's semantics are largely determined by this method.
+    extend_path(edge, body, ppoint, successor_value) { return true; }
+
+    // Default implementation does a basic "only visit nodes once" search.
+    // (Whether this is BFS/DFS/other is determined by the caller.)
+
+    // Override if you need to revisit nodes. Valid actions are "continue",
+    // "prune", and "done". "continue" means continue with the search. "prune"
+    // means do not continue to predecessors of this node, only continue with
+    // the remaining entries in the work queue. "done" means the
+    // whole search is complete even if unvisited nodes remain.
+    next_action(prev, current) { return prev ? "prune" : "continue"; }
+
+    // Update the info at a node. If this is the first time the node has been
+    // seen, `prev` will be undefined. `current` will be the info computed by
+    // `extend_path`. The node will be updated with the return value.
+    merge_info(prev, current) { return true; }
+
+    // Default visit() implementation. Subclasses will usually leave this alone
+    // and use the other methods as extension points.
+    //
+    // Take a body, a point within that body, and the info computed by
+    // extend_path() for that point when traversing an edge. Return whether the
+    // search should continue ("continue"), the search should be pruned and
+    // other paths followed ("prune"), or that the whole search is complete and
+    // it is time to return a value ("done", and the value returned by
+    // merge_info() will be returned by the overall search).
+    //
+    // Persistently record the value computed so far at each point, and call
+    // (overridable) next_action() and merge_info() methods with the previous
+    // and freshly-computed value for each point.
+    //
+    // Often, extend_path() will decide how/whether to continue the search and
+    // will return the search action to take, and next_action() will blindly
+    // return it if the point has not yet been visited. (And if it has, it will
+    // prune this branch of the search so that no point is visited multiple
+    // times.)
+    visit(body, ppoint, info) {
+        const visited_value_table = this.visited_bodies.get(body);
+        const existing_value_if_visited = visited_value_table.get(ppoint);
+        const action = this.next_action(existing_value_if_visited, info);
+        const merged = this.merge_info(existing_value_if_visited, info);
+        visited_value_table.set(ppoint, merged);
+        return [action, merged];
+    }
+};
+
+function findMatchingBlock(bodies, blockId) {
+    for (const body of bodies) {
+        if (sameBlockId(body.BlockId, blockId)) {
+            return body;
+        }
+    }
+    assert(false);
+}
+
+// For a given function containing a set of bodies, each containing a set of
+// ppoints, perform a mostly breadth-first traversal through the complete graph
+// of all <body, ppoint> nodes throughout all the bodies of the function.
+//
+// When traversing, every <body, ppoint> node is associated with a value that
+// is assigned or updated whenever it is visited. The overall traversal
+// terminates when a given condition is reached, and an arbitrary custom value
+// is returned. If the search completes without the termination condition
+// being reached, it will return the value associated with the entrypoint
+// node, which is initialized to `entrypoint_fallback_value` (and thus serves as
+// the fallback return value if all search paths are pruned before reaching
+// the entrypoint.)
+//
+// The traversal is only *mostly* breadth-first because the visitor decides
+// whether to stop searching when it sees a node. If a node is visited for a
+// second time, the visitor can choose to continue (and thus revisit the node)
+// in order to find "better" paths that may include a node more than once.
+// The search is done in the "upwards" direction -- as in, it starts at the
+// exit point and searches through predecessors.
+//
+// Override visitor.visit() to return an action and a value. The action
+// determines whether the overall search should terminate ('done'), or
+// continues looking through the predecessors of the current node ('continue'),
+// or whether it should just continue processing the work queue without
+// looking at predecessors ('prune').
+//
+// This allows this function to be used in different ways. If the visitor
+// associates a value with each node that chains onto its forward-flow successors
+// (predecessors in the "upwards" search order), then a complete path through
+// the graph will be returned.
+//
+// Alternatively, BFS_upwards() can be used to test whether a condition holds
+// (eg "the exit point is reachable only after calling SomethingImportant()"),
+// in which case no path is needed and the visitor can compute a simple boolean
+// every time it encounters a point. Note that `entrypoint_fallback_value` will
+// still be returned if the search terminates without ever reaching the
+// entrypoint, which is useful for dominator analyses.
+//
+// See the Visitor base class's implementation of visit(), above, for the
+// most commonly used visit logic.
+function BFS_upwards(start_body, start_ppoint, bodies, visitor,
+                     initial_successor_value = {},
+                     entrypoint_fallback_value=null)
+{
+    let entrypoint_value = entrypoint_fallback_value;
+
+    const work = [[start_body, start_ppoint, null, initial_successor_value]];
+    if (TRACING) {
+        printErr(`BFS start at ${blockIdentifier(start_body)}:${start_ppoint}`);
+    }
+
+    while (work.length > 0) {
+        const [body, ppoint, edgeToAdd, successor_value] = work.shift();
+        if (TRACING) {
+            const s = edgeToAdd ? " : " + str(edgeToAdd) : "";
+            printErr(`prepending edge from ${ppoint} to state '${successor_value}'${s}`);
+        }
+        let value = visitor.extend_path(edgeToAdd, body, ppoint, successor_value);
+
+        const [action,  merged_value] = visitor.visit(body, ppoint, value);
+        if (action === "done") {
+            return merged_value;
+        }
+        if (action === "prune") {
+            // Do not push anything else to the work queue, but continue processing
+            // other branches.
+            continue;
+        }
+        assert(action == "continue");
+        value = merged_value;
+
+        const predecessors = getPredecessors(body);
+        for (const edge of (predecessors[ppoint] || [])) {
+            if (edge.Kind == "Loop") {
+                // Propagate the search into the exit point of the loop body.
+                const loopBody = findMatchingBlock(bodies, edge.BlockId);
+                const loopEnd = loopBody.Index[1];
+                work.push([loopBody, loopEnd, null, value]);
+                // Don't continue to predecessors here without going through
+                // the loop. (The points in this body that enter the loop will
+                // be traversed when we reach the entry point of the loop.)
+            }
+            work.push([body, edge.Index[0], edge, value]);
+        }
+
+        // Check for hitting the entry point of a loop body.
+        if (ppoint == body.Index[0] && body.BlockId.Kind == "Loop") {
+            // Propagate to outer body parents that enter the loop body.
+            for (const parent of (body.BlockPPoint || [])) {
+                const parentBody = findMatchingBlock(bodies, parent.BlockId);
+                work.push([parentBody, parent.Index, null, value]);
+            }
+
+            // This point is also preceded by the *end* of this loop, for the
+            // previous iteration.
+            work.push([body, body.Index[1], null, value]);
+        }
+
+        // Check for reaching the entrypoint of the function.
+        if (body === start_body && ppoint == body.Index[0]) {
+            entrypoint_value = value;
+        }
+    }
+
+    // The search space was exhausted without finding a 'done' state. That
+    // might be because all search paths were pruned before reaching the entry
+    // point of the function, in which case entrypoint_value will still be its initial
+    // value. (If entrypoint_value has been set, then we may still not have visited the
+    // entire graph, if some paths were pruned but at least one made it to the entrypoint.)
+    return entrypoint_value;
+}
+
+// Given the CFG for the constructor call of some RAII, return whether the
+// given edge is the matching destructor call.
+function isMatchingDestructor(constructor, edge)
+{
+    if (edge.Kind != "Call")
+        return false;
+    var callee = edge.Exp[0];
+    if (callee.Kind != "Var")
+        return false;
+    var variable = callee.Variable;
+    assert(variable.Kind == "Func");
+    if (variable.Name[1].charAt(0) != '~')
+        return false;
+
+    // Note that in some situations, a regular function can begin with '~', so
+    // we don't necessarily have a destructor in hand. This is probably a
+    // sixgill artifact, but in js::wasm::ModuleGenerator::~ModuleGenerator, a
+    // templatized static inline EraseIf is invoked, and it gets named ~EraseIf
+    // for some reason.
+    if (!("PEdgeCallInstance" in edge))
+        return false;
+
+    var constructExp = constructor.PEdgeCallInstance.Exp;
+    assert(constructExp.Kind == "Var");
+
+    var destructExp = edge.PEdgeCallInstance.Exp;
+    if (destructExp.Kind != "Var")
+        return false;
+
+    return sameVariable(constructExp.Variable, destructExp.Variable);
+}
+
+// Return all calls within the RAII scope of any constructor matched by
+// isConstructor(). (Note that this would be insufficient if you needed to
+// treat each instance separately, such as when different regions of a function
+// body were guarded by these constructors and you needed to do something
+// different with each.)
+function allRAIIGuardedCallPoints(typeInfo, bodies, body, isConstructor)
+{
+    if (!("PEdge" in body))
+        return [];
+
+    var points = [];
+
+    for (var edge of body.PEdge) {
+        if (edge.Kind != "Call")
+            continue;
+        var callee = edge.Exp[0];
+        if (callee.Kind != "Var")
+            continue;
+        var variable = callee.Variable;
+        assert(variable.Kind == "Func");
+        const bits = isConstructor(typeInfo, edge.Type, variable.Name);
+        if (!bits)
+            continue;
+        if (!("PEdgeCallInstance" in edge))
+            continue;
+        if (edge.PEdgeCallInstance.Exp.Kind != "Var")
+            continue;
+
+        points.push(...pointsInRAIIScope(bodies, body, edge, bits));
+    }
+
+    return points;
+}
+
+// Test whether the given edge is the constructor corresponding to the given
+// destructor edge.
+function isMatchingConstructor(destructor, edge)
+{
+    if (edge.Kind != "Call")
+        return false;
+    var callee = edge.Exp[0];
+    if (callee.Kind != "Var")
+        return false;
+    var variable = callee.Variable;
+    if (variable.Kind != "Func")
+        return false;
+    var name = readable(variable.Name[0]);
+    var destructorName = readable(destructor.Exp[0].Variable.Name[0]);
+    var match = destructorName.match(/^(.*?::)~(\w+)\(/);
+    if (!match) {
+        printErr("Unhandled destructor syntax: " + destructorName);
+        return false;
+    }
+    var constructorSubstring = match[1] + match[2];
+    if (name.indexOf(constructorSubstring) == -1)
+        return false;
+
+    var destructExp = destructor.PEdgeCallInstance.Exp;
+    if (destructExp.Kind != "Var")
+        return false;
+
+    var constructExp = edge.PEdgeCallInstance.Exp;
+    if (constructExp.Kind != "Var")
+        return false;
+
+    return sameVariable(constructExp.Variable, destructExp.Variable);
+}
+
+function findMatchingConstructor(destructorEdge, body, warnIfNotFound=true)
+{
+    var worklist = [destructorEdge];
+    var predecessors = getPredecessors(body);
+    while(worklist.length > 0) {
+        var edge = worklist.pop();
+        if (isMatchingConstructor(destructorEdge, edge))
+            return edge;
+        if (edge.Index[0] in predecessors) {
+            for (var e of predecessors[edge.Index[0]])
+                worklist.push(e);
+        }
+    }
+    if (warnIfNotFound)
+        printErr("Could not find matching constructor!");
+    return undefined;
+}
+
+function pointsInRAIIScope(bodies, body, constructorEdge, bits) {
+    var seen = {};
+    var worklist = [constructorEdge.Index[1]];
+    var points = [];
+    while (worklist.length) {
+        var point = worklist.pop();
+        if (point in seen)
+            continue;
+        seen[point] = true;
+        points.push([body, point, bits]);
+        var successors = getSuccessors(body);
+        if (!(point in successors))
+            continue;
+        for (var nedge of successors[point]) {
+            if (isMatchingDestructor(constructorEdge, nedge))
+                continue;
+            if (nedge.Kind == "Loop")
+                points.push(...findAllPoints(bodies, nedge.BlockId, bits));
+            worklist.push(nedge.Index[1]);
+        }
+    }
+
+    return points;
+}
+
+function isImmobileValue(exp) {
+    if (exp.Kind == "Int" && exp.String == "0") {
+        return true;
+    }
+    return false;
+}
+
+// Returns whether decl is a body.DefineVariable[] entry for a non-temporary reference.
+function isReferenceDecl(decl) {
+    return decl.Type.Kind == "Pointer" && decl.Type.Reference != PTR_POINTER && decl.Variable.Kind != "Temp";
+}
+
+function expressionIsVariableAddress(exp, variable)
+{
+    while (exp.Kind == "Fld")
+        exp = exp.Exp[0];
+    return exp.Kind == "Var" && sameVariable(exp.Variable, variable);
+}
+
+function edgeTakesVariableAddress(edge, variable, body)
+{
+    if (ignoreEdgeUse(edge, variable, body))
+        return false;
+    if (ignoreEdgeAddressTaken(edge))
+        return false;
+    switch (edge.Kind) {
+    case "Assign":
+        return expressionIsVariableAddress(edge.Exp[1], variable);
+    case "Call":
+        if ("PEdgeCallArguments" in edge) {
+            for (var exp of edge.PEdgeCallArguments.Exp) {
+                if (expressionIsVariableAddress(exp, variable))
+                    return true;
+            }
+        }
+        return false;
+    default:
+        return false;
+    }
+}
+
+// Look at an invocation of a virtual method or function pointer contained in a
+// field, and return the static type of the invocant (or the containing struct,
+// for a function pointer field.)
+function getFieldCallInstanceCSU(edge, field)
+{
+    if ("FieldInstanceFunction" in field) {
+        // We have a 'this'.
+        const instanceExp = edge.PEdgeCallInstance.Exp;
+        if (instanceExp.Kind == 'Drf') {
+            // somevar->foo()
+            return edge.Type.TypeFunctionCSU.Type.Name;
+        } else if (instanceExp.Kind == 'Fld') {
+            // somevar.foo()
+            return instanceExp.Field.FieldCSU.Type.Name;
+        } else if (instanceExp.Kind == 'Index') {
+            // A strange construct.
+            // C++ code: static_cast<JS::CustomAutoRooter*>(this)->trace(trc);
+            // CFG: Call(21,30, this*[-1]{JS::CustomAutoRooter}.trace*(trc*))
+            return instanceExp.Type.Name;
+        } else if (instanceExp.Kind == 'Var') {
+            // C++: reinterpret_cast<SimpleTimeZone*>(gRawGMT)->~SimpleTimeZone();
+            // CFG:
+            //   # icu_64::SimpleTimeZone::icu_64::SimpleTimeZone.__comp_dtor
+            //   [6,7] Call gRawGMT.icu_64::SimpleTimeZone.__comp_dtor ()
+            return field.FieldCSU.Type.Name;
+        } else {
+            printErr("------------------ edge -------------------");
+            printErr(JSON.stringify(edge, null, 4));
+            printErr("------------------ field -------------------");
+            printErr(JSON.stringify(field, null, 4));
+            assert(false, `unrecognized FieldInstanceFunction Kind ${instanceExp.Kind}`);
+        }
+    } else {
+        // somefar.foo() where somevar is a field of some CSU.
+        return field.FieldCSU.Type.Name;
+    }
+}
+
+function expressionUsesVariable(exp, variable)
+{
+    if (exp.Kind == "Var" && sameVariable(exp.Variable, variable))
+        return true;
+    if (!("Exp" in exp))
+        return false;
+    for (var childExp of exp.Exp) {
+        if (expressionUsesVariable(childExp, variable))
+            return true;
+    }
+    return false;
+}
+
+function expressionUsesVariableContents(exp, variable)
+{
+    if (!("Exp" in exp))
+        return false;
+    for (var childExp of exp.Exp) {
+        if (childExp.Kind == 'Drf') {
+            if (expressionUsesVariable(childExp, variable))
+                return true;
+        } else if (expressionUsesVariableContents(childExp, variable)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+// Detect simple |return nullptr;| statements.
+function isReturningImmobileValue(edge, variable)
+{
+    if (variable.Kind == "Return") {
+        if (edge.Exp[0].Kind == "Var" && sameVariable(edge.Exp[0].Variable, variable)) {
+            if (isImmobileValue(edge.Exp[1]))
+                return true;
+        }
+    }
+    return false;
+}
+
+// If the edge uses the given variable's value, return the earliest point at
+// which the use is definite. Usually, that means the source of the edge
+// (anything that reaches that source point will end up using the variable, but
+// there may be other ways to reach the destination of the edge.)
+//
+// Return values are implicitly used at the very last point in the function.
+// This makes a difference: if an RAII class GCs in its destructor, we need to
+// start looking at the final point in the function, not one point back from
+// that, since that would skip over the GCing call.
+//
+// Certain references may be annotated to be live to the end of the function
+// as well (eg AutoCheckCannotGC&& parameters).
+//
+// Note that this returns a nonzero value only if the variable's incoming value is used.
+// So this would return 0 for 'obj':
+//
+//     obj = someFunction();
+//
+// but these would return a positive value:
+//
+//     obj = someFunction(obj);
+//     obj->foo = someFunction();
+//
+function edgeUsesVariable(edge, variable, body, liveToEnd=false)
+{
+    if (ignoreEdgeUse(edge, variable, body))
+        return 0;
+
+    if (variable.Kind == "Return") {
+        liveToEnd = true;
+    }
+
+    if (liveToEnd && body.Index[1] == edge.Index[1] && body.BlockId.Kind == "Function") {
+        // The last point in the function body is treated as using the return
+        // value. This is the only time the destination point is returned
+        // rather than the source point.
+        return edge.Index[1];
+    }
+
+    var src = edge.Index[0];
+
+    switch (edge.Kind) {
+
+    case "Assign": {
+        // Detect `Return := nullptr`.
+        if (isReturningImmobileValue(edge, variable))
+            return 0;
+        const [lhs, rhs] = edge.Exp;
+        // Detect `lhs := ...variable...`
+        if (expressionUsesVariable(rhs, variable))
+            return src;
+        // Detect `...variable... := rhs` but not `variable := rhs`. The latter
+        // overwrites the previous value of `variable` without using it.
+        if (expressionUsesVariable(lhs, variable) && !expressionIsVariable(lhs, variable))
+            return src;
+        return 0;
+    }
+
+    case "Assume":
+        return expressionUsesVariableContents(edge.Exp[0], variable) ? src : 0;
+
+    case "Call": {
+        const callee = edge.Exp[0];
+        if (expressionUsesVariable(callee, variable))
+            return src;
+        if ("PEdgeCallInstance" in edge) {
+            if (expressionUsesVariable(edge.PEdgeCallInstance.Exp, variable)) {
+                if (edgeStartsValueLiveRange(edge, variable)) {
+                    // If the variable is being constructed, then the incoming
+                    // value is not used here; it didn't exist before
+                    // construction. (The analysis doesn't get told where
+                    // variables are defined, so must infer it from
+                    // construction. If the variable does not have a
+                    // constructor, its live range may be larger than it really
+                    // ought to be if it is defined within a loop body, but
+                    // that is conservative.)
+                } else {
+                    return src;
+                }
+            }
+        }
+        if ("PEdgeCallArguments" in edge) {
+            for (var exp of edge.PEdgeCallArguments.Exp) {
+                if (expressionUsesVariable(exp, variable))
+                    return src;
+            }
+        }
+        if (edge.Exp.length == 1)
+            return 0;
+
+        // Assigning call result to a variable.
+        const lhs = edge.Exp[1];
+        if (expressionUsesVariable(lhs, variable) && !expressionIsVariable(lhs, variable))
+            return src;
+        return 0;
+    }
+
+    case "Loop":
+        return 0;
+
+    case "Assembly":
+        return 0;
+
+    default:
+        assert(false);
+    }
+}
+
+// If `decl` is the body.DefineVariable[] declaration of a reference type, then
+// return the expression without the outer dereference. Otherwise, return the
+// original expression.
+function maybeDereference(exp, decl) {
+    if (exp.Kind == "Drf" && exp.Exp[0].Kind == "Var") {
+        if (isReferenceDecl(decl)) {
+            return exp.Exp[0];
+        }
+    }
+    return exp;
+}
+
+function expressionIsVariable(exp, variable)
+{
+    return exp.Kind == "Var" && sameVariable(exp.Variable, variable);
+}
+
+// Similar to the above, except treat uses of a reference as if they were uses
+// of the dereferenced contents. This requires knowing the type of the
+// variable, and so takes its declaration rather than the variable itself.
+function expressionIsDeclaredVariable(exp, decl)
+{
+    exp = maybeDereference(exp, decl);
+    return expressionIsVariable(exp, decl.Variable);
+}
+
+function expressionIsMethodOnVariableDecl(exp, decl)
+{
+    // This might be calling a method on a base class, in which case exp will
+    // be an unnamed field of the variable instead of the variable itself.
+    while (exp.Kind == "Fld" && exp.Field.Name[0].startsWith("field:"))
+        exp = exp.Exp[0];
+    return expressionIsDeclaredVariable(exp, decl);
+}
+
+// Return whether the edge starts the live range of a variable's value, by setting
+// it to some new value. Examples of starting obj's live range:
+//
+//     obj = foo;
+//     obj = foo();
+//     obj = foo(obj);         // uses previous value but then sets to new value
+//     SomeClass obj(true, 1); // constructor
+//
+function edgeStartsValueLiveRange(edge, variable)
+{
+    // Direct assignments start live range of lhs: var = value
+    if (edge.Kind == "Assign") {
+        const [lhs, rhs] = edge.Exp;
+        return (expressionIsVariable(lhs, variable) &&
+                !isReturningImmobileValue(edge, variable));
+    }
+
+    if (edge.Kind != "Call")
+        return false;
+
+    // Assignments of call results start live range: var = foo()
+    if (1 in edge.Exp) {
+        var lhs = edge.Exp[1];
+        if (expressionIsVariable(lhs, variable))
+            return true;
+    }
+
+    // Constructor calls start live range of instance: SomeClass var(...)
+    if ("PEdgeCallInstance" in edge) {
+        var instance = edge.PEdgeCallInstance.Exp;
+
+        // Kludge around incorrect dereference on some constructor calls.
+        if (instance.Kind == "Drf")
+            instance = instance.Exp[0];
+
+        if (!expressionIsVariable(instance, variable))
+            return false;
+
+        var callee = edge.Exp[0];
+        if (callee.Kind != "Var")
+            return false;
+
+        assert(callee.Variable.Kind == "Func");
+        var calleeName = readable(callee.Variable.Name[0]);
+
+        // Constructor calls include the text 'Name::Name(' or 'Name<...>::Name('.
+        var openParen = calleeName.indexOf('(');
+        if (openParen < 0)
+            return false;
+        calleeName = calleeName.substring(0, openParen);
+
+        var lastColon = calleeName.lastIndexOf('::');
+        if (lastColon < 0)
+            return false;
+        var constructorName = calleeName.substr(lastColon + 2);
+        calleeName = calleeName.substr(0, lastColon);
+
+        var lastTemplateOpen = calleeName.lastIndexOf('<');
+        if (lastTemplateOpen >= 0)
+            calleeName = calleeName.substr(0, lastTemplateOpen);
+
+        if (calleeName.endsWith(constructorName))
+            return true;
+    }
+
+    return false;
+}
+
+// Return the result of a `matcher` callback on the call found in the given
+// `edge`, if the edge is a direct call to a named function (if not, return false).
+// `matcher` is given the name of the callee (actually, a tuple
+// [fully qualified name, base name]), an array of expressions containing the
+// arguments, and if the result of the call is assigned to a variable,
+// the expression representing that variable(the lhs).
+//
+// https://firefox-source-docs.mozilla.org/js/HazardAnalysis/CFG.html for
+// documentation of the data structure used here.
+function matchEdgeCall(edge, matcher) {
+    if (edge.Kind != "Call") {
+        return false;
+    }
+
+    const callee = edge.Exp[0];
+
+    if (edge.Type.Kind == 'Function' &&
+        edge.Exp[0].Kind == 'Var' &&
+        edge.Exp[0].Variable.Kind == 'Func') {
+        const calleeName = edge.Exp[0].Variable.Name;
+        const args = edge.PEdgeCallArguments;
+        const argExprs = args ? args.Exp : [];
+        const lhs = edge.Exp[1]; // May be undefined
+        return matcher(calleeName, argExprs, lhs);
+    }
+
+    return false;
+}
+
+function edgeMarksVariableGCSafe(edge, variable) {
+    return matchEdgeCall(edge, (calleeName, argExprs, _lhs) => {
+        // explicit JS_HAZ_VARIABLE_IS_GC_SAFE annotation
+        return (calleeName[1] == 'MarkVariableAsGCSafe' &&
+            calleeName[0].includes("JS::detail::MarkVariableAsGCSafe") &&
+            argExprs.length == 1 &&
+            expressionIsVariable(argExprs[0], variable));
+    });
+}
+
+// Match an optional <namespace>:: followed by the class name,
+// and then an optional template parameter marker.
+//
+// Example: mozilla::dom::UniquePtr<...
+//
+function parseTypeName(typeName) {
+    const m = typeName.match(/^(((?:\w|::)+::)?(\w+))\b(\<)?/);
+    if (!m) {
+        return undefined;
+    }
+    const [, type, raw_namespace, classname, is_specialized] = m;
+    const namespace = raw_namespace === null ? "" : raw_namespace;
+    return { type, namespace, classname, is_specialized }
+}
+
+// Return whether an edge "clears out" a variable's value. A simple example
+// would be
+//
+//     var = nullptr;
+//
+// for analyses for which nullptr is a "safe" value (eg GC rooting hazards; you
+// can't get in trouble by holding a nullptr live across a GC.) A more complex
+// example is a Maybe<T> that gets reset:
+//
+//     Maybe<AutoCheckCannotGC> nogc;
+//     nogc.emplace(cx);
+//     nogc.reset();
+//     gc();             // <-- not a problem; nogc is invalidated by prev line
+//     nogc.emplace(cx);
+//     foo(nogc);
+//
+// Yet another example is a UniquePtr being passed by value, which means the
+// receiver takes ownership:
+//
+//     UniquePtr<JSObject*> uobj(obj);
+//     foo(uobj);
+//     gc();
+//
+function edgeEndsValueLiveRange(edge, variable, body)
+{
+    // var = nullptr;
+    if (edge.Kind == "Assign") {
+        const [lhs, rhs] = edge.Exp;
+        return expressionIsVariable(lhs, variable) && isImmobileValue(rhs);
+    }
+
+    if (edge.Kind != "Call")
+        return false;
+
+    if (edgeMarksVariableGCSafe(edge, variable)) {
+        // explicit JS_HAZ_VARIABLE_IS_GC_SAFE annotation
+        return true;
+    }
+
+    const decl = lookupVariable(body, variable);
+
+    if (matchEdgeCall(edge, (calleeName, argExprs, lhs) => {
+        return calleeName[1] == 'move' && calleeName[0].includes('std::move(') &&
+            expressionIsDeclaredVariable(argExprs[0], decl) &&
+            lhs &&
+            lhs.Kind == 'Var' &&
+            lhs.Variable.Kind == 'Temp';
+    })) {
+        // temp = std::move(var)
+        //
+        // If var is a UniquePtr, and we pass it into something that takes
+        // ownership, then it should be considered to be invalid. Example:
+        //
+        //     consume(std::move(var));
+        //
+        // where consume takes a UniquePtr. This will compile to something like
+        //
+        //     UniquePtr* __temp_1 = &std::move(var);
+        //     UniquePtr&& __temp_2(*temp_1); // move constructor
+        //     consume(__temp_2);
+        //     ~UniquePtr(__temp_2);
+        //
+        // The line commented with "// move constructor" is a result of passing
+        // a UniquePtr as a parameter. If consume() took a UniquePtr&&
+        // directly, this would just be:
+        //
+        //     UniquePtr* __temp_1 = &std::move(var);
+        //     consume(__temp_1);
+        //
+        // which is not guaranteed to move from the reference. It might just
+        // ignore the parameter. We can't predict what consume(UniquePtr&&)
+        // will do. We do know that UniquePtr(UniquePtr&& other) moves out of
+        // `other`.
+        //
+        // The std::move() technically is irrelevant, but because we only care
+        // about bare variables, it has to be used, which is fortunate because
+        // the UniquePtr&& constructor operates on a temporary, not the
+        // variable we care about.
+
+        const lhs = edge.Exp[1].Variable;
+        if (basicBlockEatsVariable(lhs, body, edge.Index[1]))
+          return true;
+    }
+
+    const callee = edge.Exp[0];
+
+    if (edge.Type.Kind == 'Function' &&
+        edge.Type.TypeFunctionCSU &&
+        edge.PEdgeCallInstance &&
+        expressionIsMethodOnVariableDecl(edge.PEdgeCallInstance.Exp, decl))
+    {
+        const typeName = edge.Type.TypeFunctionCSU.Type.Name;
+
+        // Synthesize a zero-arg constructor name like
+        // mozilla::dom::UniquePtr<T>::UniquePtr(). Note that the `<T>` is
+        // literal -- the pretty name from sixgill will render the actual
+        // constructor name as something like
+        //
+        //   UniquePtr<T>::UniquePtr() [where T = int]
+        //
+        const parsed = parseTypeName(typeName);
+        if (parsed) {
+            const { type, namespace, classname, is_specialized } = parsed;
+
+            // special-case: the initial constructor that doesn't provide a value.
+            // Useful for things like Maybe<T>.
+            const template = is_specialized ? '<T>' : '';
+            const ctorName = `${namespace}${classname}${template}::${classname}()`;
+            if (callee.Kind == 'Var' &&
+                typesWithSafeConstructors.has(type) &&
+                callee.Variable.Name[0].includes(ctorName))
+            {
+                return true;
+            }
+
+            // special-case: UniquePtr::reset() and similar.
+            if (callee.Kind == 'Var' &&
+                type in resetterMethods &&
+                resetterMethods[type].has(callee.Variable.Name[1]))
+            {
+                return true;
+            }
+        }
+    }
+
+    // special-case: passing UniquePtr<T> by value.
+    if (edge.Type.Kind == 'Function' &&
+        edge.Type.TypeFunctionArgument &&
+        edge.PEdgeCallArguments)
+    {
+        for (const i in edge.Type.TypeFunctionArgument) {
+            const param = edge.Type.TypeFunctionArgument[i];
+            if (param.Type.Kind != 'CSU')
+                continue;
+            if (!param.Type.Name.startsWith("mozilla::UniquePtr<"))
+                continue;
+            const arg = edge.PEdgeCallArguments.Exp[i];
+            if (expressionIsVariable(arg, variable)) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+// Look up a variable in the list of declarations for this body.
+function lookupVariable(body, variable) {
+    for (const decl of (body.DefineVariable || [])) {
+        if (sameVariable(decl.Variable, variable)) {
+            return decl;
+        }
+    }
+    return undefined;
+}
+
+function edgeMovesVariable(edge, variable, body)
+{
+    if (edge.Kind != 'Call')
+        return false;
+    const callee = edge.Exp[0];
+    if (callee.Kind == 'Var' &&
+        callee.Variable.Kind == 'Func')
+    {
+        const { Variable: { Name: [ fullname, shortname ] } } = callee;
+
+        // Match an rvalue parameter.
+
+        if (!edge || !edge.PEdgeCallArguments || !edge.PEdgeCallArguments.Exp) {
+            return false;
+        }
+
+        for (const arg of edge.PEdgeCallArguments.Exp) {
+            if (arg.Kind != 'Drf') continue;
+            const val = arg.Exp[0];
+            if (val.Kind == 'Var' && sameVariable(val.Variable, variable)) {
+                // This argument is the variable we're looking for. Return true
+                // if it is passed as an rvalue reference.
+                const type = lookupVariable(body, variable).Type;
+                if (type.Kind == "Pointer" && type.Reference == PTR_RVALUE_REF) {
+                    return true;
+                }
+            }
+        }
+    }
+
+    return false;
+}
+
+// Scan forward through the basic block in 'body' starting at 'startpoint',
+// looking for a call that passes 'variable' to a move constructor that
+// "consumes" it (eg UniquePtr::UniquePtr(UniquePtr&&)).
+function basicBlockEatsVariable(variable, body, startpoint)
+{
+    const successors = getSuccessors(body);
+    let point = startpoint;
+    while (point in successors) {
+        // Only handle a single basic block. If it forks, stop looking.
+        const edges = successors[point];
+        if (edges.length != 1) {
+            return false;
+        }
+        const edge = edges[0];
+
+        if (edgeMovesVariable(edge, variable, body)) {
+            return true;
+        }
+
+        // edgeStartsValueLiveRange will find places where 'variable' is given
+        // a new value. Never observed in practice, since this function is only
+        // called with a temporary resulting from std::move(), which is used
+        // immediately for a call. But just to be robust to future uses:
+        if (edgeStartsValueLiveRange(edge, variable)) {
+            return false;
+        }
+
+        point = edge.Index[1];
+    }
+
+    return false;
+}
+
+var PROP_REFCNT          = 1 << 0;
+var PROP_SHARED_PTR_DTOR = 1 << 1;
+
+function getCalleeProperties(calleeName) {
+    let props = 0;
+
+    if (isRefcountedDtor(calleeName)) {
+        props |= PROP_REFCNT;
+    }
+    if (calleeName.includes("~shared_ptr()")) {
+        props |= PROP_SHARED_PTR_DTOR;
+    }
+    return props;
+}
+
+// Basic C++ ABI mangling: prefix an identifier with its length, in decimal.
+function mangle(name) {
+    return name.length + name;
+}
+
+var TriviallyDestructibleTypes = new Set([
+    // Single-token types from
+    // https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-builtin
+    "void", "wchar_t", "bool", "char", "short", "int", "long", "float", "double",
+    "__int64", "__int128", "__float128", "char32_t", "char16_t", "char8_t",
+    // Remaining observed cases. These are types T in shared_ptr<T> that have
+    // been observed, where the types themselves have trivial destructors, and
+    // the custom deleter doesn't do anything nontrivial that we might care about.
+    "_IO_FILE"
+]);
+function synthesizeDestructorName(className) {
+    if (className.includes("<") || className.includes(" ") || className.includes("{")) {
+        return;
+    }
+    if (TriviallyDestructibleTypes.has(className)) {
+        return;
+    }
+    const parts = className.split("::");
+    const mangled_dtor = "_ZN" + parts.map(p => mangle(p)).join("") + "D2Ev";
+    const pretty_dtor = `void ${className}::~${parts.at(-1)}()`;
+    // Note that there will be a later check to verify that the function name
+    // synthesized here is an actual function, and assert if not (see
+    // assertFunctionExists() in computeCallgraph.js.)
+    return mangled_dtor + "$" + pretty_dtor;
+}
+
+function getCallEdgeProperties(body, edge, calleeName, functionBodies) {
+    let attrs = 0;
+    let extraCalls = [];
+
+    if (edge.Kind !== "Call") {
+        return { attrs, extraCalls };
+    }
+
+    const props = getCalleeProperties(calleeName);
+    if (props & PROP_REFCNT) {
+        // std::swap of two refcounted values thinks it can drop the
+        // ref count to zero. Or rather, it just calls operator=() in a context
+        // where the refcount will never drop to zero.
+        const blockId = blockIdentifier(body);
+        if (blockId.includes("std::swap") || blockId.includes("mozilla::Swap")) {
+            // Replace the refcnt release call with nothing. It's not going to happen.
+            attrs |= ATTR_REPLACED;
+        }
+    }
+
+    if (props & PROP_SHARED_PTR_DTOR) {
+        // Replace shared_ptr<T>::~shared_ptr() calls to T::~T() calls.
+        // Note that this will only apply to simple cases.
+        // Any templatized type, in particular, will be ignored and the original
+        // call tree will be left alone. If this triggers a hazard, then we can
+        // consider extending the mangling support.
+        //
+        // If the call to ~shared_ptr is not replaced, then it might end up calling
+        // an unknown function pointer. This does not always happen-- in some cases,
+        // the call tree below ~shared_ptr will invoke the correct destructor without
+        // going through function pointers.
+        const m = calleeName.match(/shared_ptr<(.*?)>::~shared_ptr\(\)(?: \[with T = ([\w:]+))?/);
+        assert(m);
+        let className = m[1] == "T" ? m[2] : m[1];
+        assert(className != "");
+        // cv qualification does not apply to destructors.
+        className = className.replace("const ", "");
+        className = className.replace("volatile ", "");
+        const dtor = synthesizeDestructorName(className);
+        if (dtor) {
+            attrs |= ATTR_REPLACED;
+            extraCalls.push({
+                attrs: ATTR_SYNTHETIC,
+                name: dtor,
+            });
+        }
+    }
+
+    if ((props & PROP_REFCNT) == 0) {
+        return { attrs, extraCalls };
+    }
+
+    let callee = edge.Exp[0];
+    while (callee.Kind === "Drf") {
+        callee = callee.Exp[0];
+    }
+
+    const instance = edge.PEdgeCallInstance.Exp;
+    if (instance.Kind !== "Var") {
+        // TODO: handle field destructors
+        return { attrs, extraCalls };
+    }
+
+    // Test whether the dtor call is dominated by operations on the variable
+    // that mean it will not go to a zero refcount in the dtor: either because
+    // it's already dead (eg r.forget() was called) or because it can be proven
+    // to have a ref count of greater than 1. This is implemented by looking
+    // for the reverse: find a path scanning backwards from the dtor call where
+    // the variable is used in any way that does *not* ensure that it is
+    // trivially destructible.
+
+    const variable = instance.Variable;
+
+    const visitor = new class DominatorVisitor extends Visitor {
+        // Do not revisit nodes. For new nodes, relay the decision made by
+        // extend_path.
+        next_action(seen, current) { return seen ? "prune" : current; }
+
+        // We don't revisit, so always use the new.
+        merge_info(seen, current) { return current; }
+
+        // Return the action to take from this node.
+        extend_path(edge, body, ppoint, successor_value) {
+            if (!edge) {
+                // Dummy edge to join two points.
+                return "continue";
+            }
+
+            if (!edgeUsesVariable(edge, variable, body)) {
+                // Nothing of interest on this edge, keep searching.
+                return "continue";
+            }
+
+            if (edgeEndsValueLiveRange(edge, variable, body)) {
+                // This path is safe!
+                return "prune";
+            }
+
+            // Unsafe. Found a use that might set the variable to a
+            // nonzero refcount.
+            return "done";
+        }
+    }(functionBodies);
+
+    // Searching upwards from a destructor call, return the opposite of: is
+    // there a path to a use or the start of the function that does NOT hit a
+    // safe assignment like refptr.forget() first?
+    //
+    // In graph terms: return whether the destructor call is dominated by forget() calls (or similar).
+    const edgeIsNonReleasingDtor = !BFS_upwards(
+        body, edge.Index[0], functionBodies, visitor, "start",
+        false // Return value if we do not reach the root without finding a non-forget() use.
+    );
+    if (edgeIsNonReleasingDtor) {
+        attrs |= ATTR_GC_SUPPRESSED | ATTR_NONRELEASING;
+    }
+    return { attrs, extraCalls };
+}
+
+// gcc uses something like "__dt_del " for virtual destructors that it
+// generates.
+function isSyntheticVirtualDestructor(funcName) {
+    return funcName.endsWith(" ");
+}
+
+function typedField(field)
+{
+    if ("FieldInstanceFunction" in field) {
+        // Virtual call
+        //
+        // This makes a minimal attempt at dealing with overloading, by
+        // incorporating the number of parameters. So far, that is all that has
+        // been needed. If more is needed, sixgill will need to produce a full
+        // mangled type.
+        const {Type, Name: [name]} = field;
+
+        // Virtual destructors don't need a type or argument count,
+        // and synthetic ones don't have them filled in.
+        if (isSyntheticVirtualDestructor(name)) {
+            return name;
+        }
+
+        var nargs = 0;
+        if (Type.Kind == "Function" && "TypeFunctionArguments" in Type)
+            nargs = Type.TypeFunctionArguments.Type.length;
+        return name + ":" + nargs;
+    } else {
+        // Function pointer field
+        return field.Name[0];
+    }
+}
+
+function fieldKey(csuName, field)
+{
+    return csuName + "." + typedField(field);
+}
diff --git a/js/src/devtools/rootAnalysis/README.md b/js/src/devtools/rootAnalysis/README.md
new file mode 100644
index 0000000000..08a4fcde29
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/README.md
@@ -0,0 +1,3 @@
+# Spidermonkey JSAPI rooting analysis
+
+See js/src/docs/HazardAnalysis/index.md
diff --git a/js/src/devtools/rootAnalysis/analyze.py b/js/src/devtools/rootAnalysis/analyze.py
new file mode 100755
index 0000000000..ab1d04c2a8
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/analyze.py
@@ -0,0 +1,462 @@
+#!/usr/bin/env python3
+
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Runs the static rooting analysis
+"""
+
+import argparse
+import os
+import subprocess
+import sys
+from subprocess import Popen
+
+try:
+    from shlex import quote
+except ImportError:
+    from pipes import quote
+
+
+def execfile(thefile, globals):
+    exec(compile(open(thefile).read(), filename=thefile, mode="exec"), globals)
+
+
+# Label a string as an output.
+class Output(str):
+    pass
+
+
+# Label a string as a pattern for multiple inputs.
+class MultiInput(str):
+    pass
+
+
+# Construct a new environment by merging in some settings needed for running the individual scripts.
+def env(config):
+    # Add config['sixgill_bin'] to $PATH if not already there.
+    path = os.environ["PATH"].split(":")
+    if dir := config.get("sixgill_bin"):
+        if dir not in path:
+            path.insert(0, dir)
+
+    return dict(
+        os.environ,
+        PATH=":".join(path),
+        XDB=f"{config['sixgill_bin']}/xdb.so",
+        SOURCE=config["source"],
+    )
+
+
+def fill(command, config):
+    filled = []
+    for s in command:
+        try:
+            rep = s.format(**config)
+        except KeyError:
+            print("Substitution failed: %s" % s)
+            filled = None
+            break
+
+        if isinstance(s, Output):
+            filled.append(Output(rep))
+        elif isinstance(s, MultiInput):
+            N = int(config["jobs"])
+            for i in range(1, N + 1):
+                filled.append(rep.format(i=i, n=N))
+        else:
+            filled.append(rep)
+
+    if filled is None:
+        raise Exception("substitution failure")
+
+    return tuple(filled)
+
+
+def print_command(job, config, env=None):
+    # Display a command to run that has roughly the same effect as what was
+    # actually run. The actual command uses temporary files that get renamed at
+    # the end, and run some commands in parallel chunks. The printed command
+    # will substitute in the actual output and run in a single chunk, so that
+    # it is easier to cut & paste and add a --function flag for debugging.
+    cfg = dict(config, n=1, i=1, jobs=1)
+    cmd = job_command_with_final_output_names(job)
+    cmd = fill(cmd, cfg)
+
+    cmd = [quote(s) for s in cmd]
+    if outfile := job.get("redirect-output"):
+        cmd.extend([">", quote(outfile.format(**cfg))])
+    if HOME := os.environ.get("HOME"):
+        cmd = [s.replace(HOME, "~") for s in cmd]
+
+    if env:
+        # Try to keep the command as short as possible by only displaying
+        # modified environment variable settings.
+        e = os.environ
+        changed = {key: value for key, value in env.items() if value != e.get(key)}
+        if changed:
+            settings = []
+            for key, value in changed.items():
+                if key in e and e[key] in value:
+                    # Display modifications as V=prefix${V}suffix when
+                    # possible. This can make a huge different for $PATH.
+                    start = value.index(e[key])
+                    end = start + len(e[key])
+                    setting = '%s="%s${%s}%s"' % (key, value[:start], key, value[end:])
+                else:
+                    setting = '%s="%s"' % (key, value)
+                if HOME:
+                    setting = setting.replace(HOME, "$HOME")
+                settings.append(setting)
+
+            cmd = settings + cmd
+
+    print("  " + " ".join(cmd))
+
+
+JOBS = {
+    "list-dbs": {"command": ["ls", "-l"]},
+    "rawcalls": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/computeCallgraph.js",
+            "{typeInfo}",
+            Output("{rawcalls}"),
+            "{i}",
+            "{n}",
+        ],
+        "multi-output": True,
+        "outputs": ["rawcalls.{i}.of.{n}"],
+    },
+    "gcFunctions": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/computeGCFunctions.js",
+            MultiInput("{rawcalls}"),
+            "--outputs",
+            Output("{callgraph}"),
+            Output("{gcFunctions}"),
+            Output("{gcFunctions_list}"),
+            Output("{limitedFunctions_list}"),
+        ],
+        "outputs": [
+            "callgraph.txt",
+            "gcFunctions.txt",
+            "gcFunctions.lst",
+            "limitedFunctions.lst",
+        ],
+    },
+    "gcTypes": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/computeGCTypes.js",
+            Output("{gcTypes}"),
+            Output("{typeInfo}"),
+        ],
+        "outputs": ["gcTypes.txt", "typeInfo.txt"],
+    },
+    "allFunctions": {
+        "command": ["{sixgill_bin}/xdbkeys", "src_body.xdb"],
+        "redirect-output": "allFunctions.txt",
+    },
+    "hazards": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/analyzeRoots.js",
+            "{gcFunctions_list}",
+            "{limitedFunctions_list}",
+            "{gcTypes}",
+            "{typeInfo}",
+            "{i}",
+            "{n}",
+            "tmp.{i}.of.{n}",
+        ],
+        "multi-output": True,
+        "redirect-output": "rootingHazards.{i}.of.{n}",
+    },
+    "gather-hazards": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/mergeJSON.js",
+            MultiInput("{hazards}"),
+            Output("{all_hazards}"),
+        ],
+        "outputs": ["rootingHazards.json"],
+    },
+    "explain": {
+        "command": [
+            sys.executable,
+            "{analysis_scriptdir}/explain.py",
+            "{all_hazards}",
+            "{gcFunctions}",
+            Output("{explained_hazards}"),
+            Output("{unnecessary}"),
+            Output("{refs}"),
+            Output("{html}"),
+        ],
+        "outputs": ["hazards.txt", "unnecessary.txt", "refs.txt", "hazards.html"],
+    },
+    "heapwrites": {
+        "command": ["{js}", "{analysis_scriptdir}/analyzeHeapWrites.js"],
+        "redirect-output": "heapWriteHazards.txt",
+    },
+}
+
+
+# Generator of (i, j, item) tuples corresponding to outputs:
+#  - i is just the index of the yielded tuple (a la enumerate())
+#  - j is the index of the item in the command list
+#  - item is command[j]
+def out_indexes(command):
+    i = 0
+    for (j, fragment) in enumerate(command):
+        if isinstance(fragment, Output):
+            yield (i, j, fragment)
+            i += 1
+
+
+def job_command_with_final_output_names(job):
+    outfiles = job.get("outputs", [])
+    command = list(job["command"])
+    for (i, j, name) in out_indexes(job["command"]):
+        command[j] = outfiles[i]
+    return command
+
+
+def run_job(name, config):
+    job = JOBS[name]
+    outs = job.get("outputs") or job.get("redirect-output")
+    print("Running " + name + " to generate " + str(outs))
+    if "function" in job:
+        job["function"](config, job["redirect-output"])
+        return
+
+    N = int(config["jobs"]) if job.get("multi-output") else 1
+    config["n"] = N
+    jobs = {}
+    for i in range(1, N + 1):
+        config["i"] = i
+        cmd = fill(job["command"], config)
+        info = spawn_command(cmd, job, name, config)
+        jobs[info["proc"].pid] = info
+
+    if config["verbose"] > 0:
+        print_command(job, config, env=env(config))
+
+    final_status = 0
+    while jobs:
+        pid, status = os.wait()
+        final_status = final_status or status
+        info = jobs[pid]
+        del jobs[pid]
+        if "redirect" in info:
+            info["redirect"].close()
+
+        # Rename the temporary files to their final names.
+        for (temp, final) in info["rename_map"].items():
+            try:
+                if config["verbose"] > 1:
+                    print("Renaming %s -> %s" % (temp, final))
+                os.rename(temp, final)
+            except OSError:
+                print("Error renaming %s -> %s" % (temp, final))
+                raise
+
+    if final_status != 0:
+        raise Exception("job {} returned status {}".format(name, final_status))
+
+
+def spawn_command(cmdspec, job, name, config):
+    rename_map = {}
+
+    if "redirect-output" in job:
+        stdout_filename = "{}.tmp{}".format(name, config.get("i", ""))
+        final_outfile = job["redirect-output"].format(**config)
+        rename_map[stdout_filename] = final_outfile
+        command = cmdspec
+    else:
+        outfiles = fill(job["outputs"], config)
+        stdout_filename = None
+
+        # Replace the Outputs with temporary filenames, and record a mapping
+        # from those temp names to their actual final names that will be used
+        # if the command succeeds.
+        command = list(cmdspec)
+        for (i, j, raw_name) in out_indexes(cmdspec):
+            [name] = fill([raw_name], config)
+            command[j] = "{}.tmp{}".format(name, config.get("i", ""))
+            rename_map[command[j]] = outfiles[i]
+
+    sys.stdout.flush()
+    info = {"rename_map": rename_map}
+    if stdout_filename:
+        info["redirect"] = open(stdout_filename, "w")
+        info["proc"] = Popen(command, stdout=info["redirect"], env=env(config))
+    else:
+        info["proc"] = Popen(command, env=env(config))
+
+    if config["verbose"] > 1:
+        print("Spawned process {}".format(info["proc"].pid))
+
+    return info
+
+
+# Default to conservatively assuming 4GB/job.
+def max_parallel_jobs(job_size=4 * 2 ** 30):
+    """Return the max number of parallel jobs we can run without overfilling
+    memory, assuming heavyweight jobs."""
+    from_cores = int(subprocess.check_output(["nproc", "--ignore=1"]).strip())
+    mem_bytes = os.sysconf("SC_PAGE_SIZE") * os.sysconf("SC_PHYS_PAGES")
+    from_mem = round(mem_bytes / job_size)
+    return min(from_cores, from_mem)
+
+
+config = {"analysis_scriptdir": os.path.dirname(__file__)}
+
+defaults = [
+    "%s/defaults.py" % config["analysis_scriptdir"],
+    "%s/defaults.py" % os.getcwd(),
+]
+
+parser = argparse.ArgumentParser(
+    description="Statically analyze build tree for rooting hazards."
+)
+parser.add_argument(
+    "step", metavar="STEP", type=str, nargs="?", help="run only step STEP"
+)
+parser.add_argument(
+    "--source", metavar="SOURCE", type=str, nargs="?", help="source code to analyze"
+)
+parser.add_argument(
+    "--js",
+    metavar="JSSHELL",
+    type=str,
+    nargs="?",
+    help="full path to ctypes-capable JS shell",
+)
+parser.add_argument(
+    "--first",
+    metavar="STEP",
+    type=str,
+    nargs="?",
+    help="execute all jobs starting with STEP",
+)
+parser.add_argument(
+    "--last", metavar="STEP", type=str, nargs="?", help="stop at step STEP"
+)
+parser.add_argument(
+    "--jobs",
+    "-j",
+    default=None,
+    metavar="JOBS",
+    type=int,
+    help="number of simultaneous analyzeRoots.js jobs",
+)
+parser.add_argument(
+    "--list", const=True, nargs="?", type=bool, help="display available steps"
+)
+parser.add_argument(
+    "--expect-file",
+    type=str,
+    nargs="?",
+    help="deprecated option, temporarily still present for backwards " "compatibility",
+)
+parser.add_argument(
+    "--verbose",
+    "-v",
+    action="count",
+    default=1,
+    help="Display cut & paste commands to run individual steps (give twice for more output)",
+)
+parser.add_argument("--quiet", "-q", action="count", default=0, help="Suppress output")
+
+args = parser.parse_args()
+args.verbose = max(0, args.verbose - args.quiet)
+
+for default in defaults:
+    try:
+        execfile(default, config)
+        if args.verbose > 1:
+            print("Loaded %s" % default)
+    except Exception:
+        pass
+
+# execfile() used config as the globals for running the
+# defaults.py script, and will have set a __builtins__ key as a side effect.
+del config["__builtins__"]
+data = config.copy()
+
+for k, v in vars(args).items():
+    if v is not None:
+        data[k] = v
+
+if args.jobs is not None:
+    data["jobs"] = args.jobs
+if not data.get("jobs"):
+    data["jobs"] = max_parallel_jobs()
+
+if "GECKO_PATH" in os.environ:
+    data["source"] = os.environ["GECKO_PATH"]
+if "SOURCE" in os.environ:
+    data["source"] = os.environ["SOURCE"]
+
+steps = [
+    "gcTypes",
+    "rawcalls",
+    "gcFunctions",
+    "allFunctions",
+    "hazards",
+    "gather-hazards",
+    "explain",
+    "heapwrites",
+]
+
+if args.list:
+    for step in steps:
+        job = JOBS[step]
+        outfiles = job.get("outputs") or job.get("redirect-output")
+        if outfiles:
+            print(
+                "%s\n    ->%s %s"
+                % (step, "*" if job.get("multi-output") else "", outfiles)
+            )
+        else:
+            print(step)
+    sys.exit(0)
+
+for step in steps:
+    job = JOBS[step]
+    if "redirect-output" in job:
+        data[step] = job["redirect-output"]
+    elif "outputs" in job and "command" in job:
+        outfiles = job["outputs"]
+        num_outputs = 0
+        for (i, j, name) in out_indexes(job["command"]):
+            # Trim the {curly brackets} off of the output keys.
+            data[name[1:-1]] = outfiles[i]
+            num_outputs += 1
+        assert (
+            len(outfiles) == num_outputs
+        ), 'step "%s": mismatched number of output files (%d) and params (%d)' % (
+            step,
+            num_outputs,
+            len(outfiles),
+        )  # NOQA: E501
+
+if args.step:
+    if args.first or args.last:
+        raise Exception(
+            "--first and --last cannot be used when a step argument is given"
+        )
+    steps = [args.step]
+else:
+    if args.first:
+        steps = steps[steps.index(args.first) :]
+    if args.last:
+        steps = steps[: steps.index(args.last) + 1]
+
+for step in steps:
+    run_job(step, data)
diff --git a/js/src/devtools/rootAnalysis/analyzeHeapWrites.js b/js/src/devtools/rootAnalysis/analyzeHeapWrites.js
new file mode 100644
index 0000000000..fdb9eaffb8
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/analyzeHeapWrites.js
@@ -0,0 +1,1398 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('callgraph.js');
+loadRelativeToScript('dumpCFG.js');
+
+///////////////////////////////////////////////////////////////////////////////
+// Annotations
+///////////////////////////////////////////////////////////////////////////////
+
+function checkExternalFunction(entry)
+{
+    var whitelist = [
+        "__builtin_clz",
+        "__builtin_expect",
+        "isprint",
+        "ceilf",
+        "floorf",
+        /^rusturl/,
+        "memcmp",
+        "strcmp",
+        "fmod",
+        "floor",
+        "ceil",
+        "atof",
+        /memchr/,
+        "strlen",
+        /Servo_DeclarationBlock_GetCssText/,
+        "Servo_GetArcStringData",
+        "Servo_IsWorkerThread",
+        /nsIFrame::AppendOwnedAnonBoxes/,
+        // Assume that atomic accesses are threadsafe.
+        /^__atomic_/,
+    ];
+    if (entry.matches(whitelist))
+        return;
+
+    // memcpy and memset are safe if the target pointer is threadsafe.
+    const simpleWrites = [
+        "memcpy",
+        "memset",
+        "memmove",
+    ];
+
+    if (entry.isSafeArgument(1) && simpleWrites.includes(entry.name))
+        return;
+
+    dumpError(entry, null, "External function");
+}
+
+function hasThreadsafeReferenceCounts(entry, regexp)
+{
+    // regexp should match some nsISupports-operating function and produce the
+    // name of the nsISupports class via exec().
+
+    // nsISupports classes which have threadsafe reference counting.
+    var whitelist = [
+        "nsIRunnable",
+
+        // I don't know if these always have threadsafe refcounts.
+        "nsAtom",
+        "nsIPermissionManager",
+        "nsIURI",
+    ];
+
+    var match = regexp.exec(entry.name);
+    return match && nameMatchesArray(match[1], whitelist);
+}
+
+function checkOverridableVirtualCall(entry, location, callee)
+{
+    // We get here when a virtual call is made on a structure which might be
+    // overridden by script or by a binary extension. This includes almost
+    // everything under nsISupports, however, so for the most part we ignore
+    // this issue. The exception is for nsISupports AddRef/Release, which are
+    // not in general threadsafe and whose overrides will not be generated by
+    // the callgraph analysis.
+    if (callee != "nsISupports.AddRef" && callee != "nsISupports.Release")
+        return;
+
+    if (hasThreadsafeReferenceCounts(entry, /::~?nsCOMPtr\(.*?\[with T = (.*?)\]$/))
+        return;
+    if (hasThreadsafeReferenceCounts(entry, /RefPtrTraits.*?::Release.*?\[with U = (.*?)\]/))
+        return;
+    if (hasThreadsafeReferenceCounts(entry, /nsCOMPtr<T>::assign_assuming_AddRef.*?\[with T = (.*?)\]/))
+        return;
+    if (hasThreadsafeReferenceCounts(entry, /nsCOMPtr<T>::assign_with_AddRef.*?\[with T = (.*?)\]/))
+        return;
+
+    // Watch for raw addref/release.
+    var whitelist = [
+        "Gecko_AddRefAtom",
+        "Gecko_ReleaseAtom",
+        /nsPrincipal::Get/,
+        /CounterStylePtr::Reset/,
+    ];
+    if (entry.matches(whitelist))
+        return;
+
+    dumpError(entry, location, "AddRef/Release on nsISupports");
+}
+
+function checkIndirectCall(entry, location, callee)
+{
+    var name = entry.name;
+
+    // These hash table callbacks should be threadsafe.
+    if (/PLDHashTable/.test(name) && (/matchEntry/.test(callee) || /hashKey/.test(callee)))
+        return;
+    if (/PL_HashTable/.test(name) && /keyCompare/.test(callee))
+        return;
+
+    dumpError(entry, location, "Indirect call " + callee);
+}
+
+function checkVariableAssignment(entry, location, variable)
+{
+    var name = entry.name;
+
+    dumpError(entry, location, "Variable assignment " + variable);
+}
+
+// Annotations for function parameters, based on function name and parameter
+// name + type.
+function treatAsSafeArgument(entry, varName, csuName)
+{
+    var whitelist = [
+        // These iterator classes should all be thread local. They are passed
+        // in to some Servo bindings and are created on the heap by others, so
+        // just ignore writes to them.
+        [null, null, /StyleChildrenIterator/],
+        [null, null, /ExplicitChildIterator/],
+
+        // The use of BeginReading() to instantiate this class confuses the
+        // analysis.
+        [null, null, /nsReadingIterator/],
+
+        // These classes are passed to some Servo bindings to fill in.
+        [/^Gecko_/, null, "nsStyleImageLayers"],
+        [/^Gecko_/, null, /FontFamilyList/],
+
+        // Various Servo binding out parameters. This is a mess and there needs
+        // to be a way to indicate which params are out parameters, either using
+        // an attribute or a naming convention.
+        ["Gecko_CopyAnimationNames", "aDest", null],
+        ["Gecko_SetAnimationName", "aStyleAnimation", null],
+        ["Gecko_SetCounterStyleToName", "aPtr", null],
+        ["Gecko_SetCounterStyleToSymbols", "aPtr", null],
+        ["Gecko_SetCounterStyleToString", "aPtr", null],
+        ["Gecko_CopyCounterStyle", "aDst", null],
+        ["Gecko_SetMozBinding", "aDisplay", null],
+        [/ClassOrClassList/, /aClass/, null],
+        ["Gecko_GetAtomAsUTF16", "aLength", null],
+        ["Gecko_CopyMozBindingFrom", "aDest", null],
+        ["Gecko_SetNullImageValue", "aImage", null],
+        ["Gecko_SetGradientImageValue", "aImage", null],
+        ["Gecko_SetImageElement", "aImage", null],
+        ["Gecko_SetLayerImageImageValue", "aImage", null],
+        ["Gecko_CopyImageValueFrom", "aImage", null],
+        ["Gecko_SetCursorArrayLength", "aStyleUI", null],
+        ["Gecko_CopyCursorArrayFrom", "aDest", null],
+        ["Gecko_SetCursorImageValue", "aCursor", null],
+        ["Gecko_SetListStyleImageImageValue", "aList", null],
+        ["Gecko_SetListStyleImageNone", "aList", null],
+        ["Gecko_CopyListStyleImageFrom", "aList", null],
+        ["Gecko_ClearStyleContents", "aContent", null],
+        ["Gecko_CopyStyleContentsFrom", "aContent", null],
+        ["Gecko_CopyStyleGridTemplateValues", "aGridTemplate", null],
+        ["Gecko_ResetStyleCoord", null, null],
+        ["Gecko_CopyClipPathValueFrom", "aDst", null],
+        ["Gecko_DestroyClipPath", "aClip", null],
+        ["Gecko_ResetFilters", "effects", null],
+        [/Gecko_CSSValue_Set/, "aCSSValue", null],
+        ["Gecko_CSSValue_Drop", "aCSSValue", null],
+        ["Gecko_CSSFontFaceRule_GetCssText", "aResult", null],
+        ["Gecko_EnsureTArrayCapacity", "aArray", null],
+        ["Gecko_ClearPODTArray", "aArray", null],
+        ["Gecko_SetStyleGridTemplate", "aGridTemplate", null],
+        ["Gecko_ResizeTArrayForStrings", "aArray", null],
+        ["Gecko_ClearAndResizeStyleContents", "aContent", null],
+        [/Gecko_ClearAndResizeCounter/, "aContent", null],
+        [/Gecko_CopyCounter.*?From/, "aContent", null],
+        [/Gecko_SetContentDataImageValue/, "aList", null],
+        [/Gecko_SetContentData/, "aContent", null],
+        ["Gecko_SetCounterFunction", "aContent", null],
+        [/Gecko_EnsureStyle.*?ArrayLength/, "aArray", null],
+        ["Gecko_GetOrCreateKeyframeAtStart", "aKeyframes", null],
+        ["Gecko_GetOrCreateInitialKeyframe", "aKeyframes", null],
+        ["Gecko_GetOrCreateFinalKeyframe", "aKeyframes", null],
+        ["Gecko_AppendPropertyValuePair", "aProperties", null],
+        ["Gecko_SetStyleCoordCalcValue", null, null],
+        ["Gecko_StyleClipPath_SetURLValue", "aClip", null],
+        ["Gecko_nsStyleFilter_SetURLValue", "aEffects", null],
+        ["Gecko_nsStyleSVG_SetDashArrayLength", "aSvg", null],
+        ["Gecko_nsStyleSVG_CopyDashArray", "aDst", null],
+        ["Gecko_nsStyleFont_SetLang", "aFont", null],
+        ["Gecko_nsStyleFont_CopyLangFrom", "aFont", null],
+        ["Gecko_ClearWillChange", "aDisplay", null],
+        ["Gecko_AppendWillChange", "aDisplay", null],
+        ["Gecko_CopyWillChangeFrom", "aDest", null],
+        ["Gecko_InitializeImageCropRect", "aImage", null],
+        ["Gecko_CopyShapeSourceFrom", "aDst", null],
+        ["Gecko_DestroyShapeSource", "aShape", null],
+        ["Gecko_StyleShapeSource_SetURLValue", "aShape", null],
+        ["Gecko_NewBasicShape", "aShape", null],
+        ["Gecko_NewShapeImage", "aShape", null],
+        ["Gecko_nsFont_InitSystem", "aDest", null],
+        ["Gecko_nsFont_SetFontFeatureValuesLookup", "aFont", null],
+        ["Gecko_nsFont_ResetFontFeatureValuesLookup", "aFont", null],
+        ["Gecko_nsStyleFont_FixupNoneGeneric", "aFont", null],
+        ["Gecko_StyleTransition_SetUnsupportedProperty", "aTransition", null],
+        ["Gecko_AddPropertyToSet", "aPropertySet", null],
+        ["Gecko_CalcStyleDifference", "aAnyStyleChanged", null],
+        ["Gecko_CalcStyleDifference", "aOnlyResetStructsChanged", null],
+        ["Gecko_nsStyleSVG_CopyContextProperties", "aDst", null],
+        ["Gecko_nsStyleFont_PrefillDefaultForGeneric", "aFont", null],
+        ["Gecko_nsStyleSVG_SetContextPropertiesLength", "aSvg", null],
+        ["Gecko_ClearAlternateValues", "aFont", null],
+        ["Gecko_AppendAlternateValues", "aFont", null],
+        ["Gecko_CopyAlternateValuesFrom", "aDest", null],
+        ["Gecko_CounterStyle_GetName", "aResult", null],
+        ["Gecko_CounterStyle_GetSingleString", "aResult", null],
+        ["Gecko_nsTArray_FontFamilyName_AppendNamed", "aNames", null],
+        ["Gecko_nsTArray_FontFamilyName_AppendGeneric", "aNames", null],
+    ];
+    for (var [entryMatch, varMatch, csuMatch] of whitelist) {
+        assert(entryMatch || varMatch || csuMatch);
+        if (entryMatch && !nameMatches(entry.name, entryMatch))
+            continue;
+        if (varMatch && !nameMatches(varName, varMatch))
+            continue;
+        if (csuMatch && (!csuName || !nameMatches(csuName, csuMatch)))
+            continue;
+        return true;
+    }
+    return false;
+}
+
+function isSafeAssignment(entry, edge, variable)
+{
+    if (edge.Kind != 'Assign')
+        return false;
+
+    var [mangled, unmangled] = splitFunction(entry.name);
+
+    // The assignment
+    //
+    //   nsFont* font = fontTypes[eType];
+    //
+    // ends up with 'font' pointing to a member of 'this', so it should inherit
+    // the safety of 'this'.
+    if (unmangled.includes("mozilla::LangGroupFontPrefs::Initialize") &&
+        variable == 'font')
+    {
+        const [lhs, rhs] = edge.Exp;
+        const {Kind, Exp: [{Kind: indexKind, Exp: [collection, index]}]} = rhs;
+        if (Kind == 'Drf' &&
+            indexKind == 'Index' &&
+            collection.Kind == 'Var' &&
+            collection.Variable.Name[0] == 'fontTypes')
+        {
+            return entry.isSafeArgument(0); // 'this'
+        }
+    }
+
+    return false;
+}
+
+function checkFieldWrite(entry, location, fields)
+{
+    var name = entry.name;
+    for (var field of fields) {
+        // The analysis is having some trouble keeping track of whether
+        // already_AddRefed and nsCOMPtr structures are safe to access.
+        // Hopefully these will be thread local, but it would be better to
+        // improve the analysis to handle these.
+        if (/already_AddRefed.*?.mRawPtr/.test(field))
+            return;
+        if (/nsCOMPtr<.*?>.mRawPtr/.test(field))
+            return;
+
+        if (/\bThreadLocal<\b/.test(field))
+            return;
+
+        // Debugging check for string corruption.
+        if (field == "nsStringBuffer.mCanary")
+            return;
+    }
+
+    var str = "";
+    for (var field of fields)
+        str += " " + field;
+
+    dumpError(entry, location, "Field write" + str);
+}
+
+function checkDereferenceWrite(entry, location, variable)
+{
+    var name = entry.name;
+
+    // Maybe<T> uses placement new on local storage in a way we don't understand.
+    // Allow this if the Maybe<> value itself is threadsafe.
+    if (/Maybe.*?::emplace/.test(name) && entry.isSafeArgument(0))
+        return;
+
+    // UniquePtr writes through temporaries referring to its internal storage.
+    // Allow this if the UniquePtr<> is threadsafe.
+    if (/UniquePtr.*?::reset/.test(name) && entry.isSafeArgument(0))
+        return;
+
+    // Operations on nsISupports reference counts.
+    if (hasThreadsafeReferenceCounts(entry, /nsCOMPtr<T>::swap\(.*?\[with T = (.*?)\]/))
+        return;
+
+    // ConvertToLowerCase::write writes through a local pointer into the first
+    // argument.
+    if (/ConvertToLowerCase::write/.test(name) && entry.isSafeArgument(0))
+        return;
+
+    dumpError(entry, location, "Dereference write " + (variable ? variable : "<unknown>"));
+}
+
+function ignoreCallEdge(entry, callee)
+{
+    var name = entry.name;
+
+    // nsPropertyTable::GetPropertyInternal has the option of removing data
+    // from the table, but when it is called by nsPropertyTable::GetProperty
+    // this will not occur.
+    if (/nsPropertyTable::GetPropertyInternal/.test(callee) &&
+        /nsPropertyTable::GetProperty/.test(name))
+    {
+        return true;
+    }
+
+    // Document::PropertyTable calls GetExtraPropertyTable (which has side
+    // effects) if the input category is non-zero. If a literal zero was passed
+    // in for the category then we treat it as a safe argument, per
+    // isEdgeSafeArgument, so just watch for that.
+    if (/Document::GetExtraPropertyTable/.test(callee) &&
+        /Document::PropertyTable/.test(name) &&
+        entry.isSafeArgument(1))
+    {
+        return true;
+    }
+
+    // This function has an explicit test for being on the main thread if the
+    // style has non-threadsafe refcounts, but the analysis isn't smart enough
+    // to understand what the actual styles that can be involved are.
+    if (/nsStyleList::SetCounterStyle/.test(callee))
+        return true;
+
+    // CachedBorderImageData is exclusively owned by nsStyleImage, but the
+    // analysis is not smart enough to know this.
+    if (/CachedBorderImageData::PurgeCachedImages/.test(callee) &&
+        /nsStyleImage::/.test(name) &&
+        entry.isSafeArgument(0))
+    {
+        return true;
+    }
+
+    // StyleShapeSource exclusively owns its UniquePtr<nsStyleImage>.
+    if (/nsStyleImage::SetURLValue/.test(callee) &&
+        /StyleShapeSource::SetURL/.test(name) &&
+        entry.isSafeArgument(0))
+    {
+        return true;
+    }
+
+    // The AddRef through a just-assigned heap pointer here is not handled by
+    // the analysis.
+    if (/nsCSSValue::Array::AddRef/.test(callee) &&
+        /nsStyleContentData::SetCounters/.test(name) &&
+        entry.isSafeArgument(2))
+    {
+        return true;
+    }
+
+    // AllChildrenIterator asks AppendOwnedAnonBoxes to append into an nsTArray
+    // local variable.
+    if (/nsIFrame::AppendOwnedAnonBoxes/.test(callee) &&
+        /AllChildrenIterator::AppendNativeAnonymousChildren/.test(name))
+    {
+        return true;
+    }
+
+    // Runnables are created and named on one thread, then dispatched
+    // (possibly to another). Writes on the origin thread are ok.
+    if (/::SetName/.test(callee) &&
+        /::UnlabeledDispatch/.test(name))
+    {
+        return true;
+    }
+
+    // We manually lock here
+    if (name == "Gecko_nsFont_InitSystem" ||
+        name == "Gecko_GetFontMetrics" ||
+        name == "Gecko_nsStyleFont_FixupMinFontSize" ||
+        /ThreadSafeGetDefaultFontHelper/.test(name))
+    {
+        return true;
+    }
+
+    return false;
+}
+
+function ignoreContents(entry)
+{
+    var whitelist = [
+        // We don't care what happens when we're about to crash.
+        "abort",
+        /MOZ_ReportAssertionFailure/,
+        /MOZ_ReportCrash/,
+        /MOZ_Crash/,
+        /MOZ_CrashPrintf/,
+        /AnnotateMozCrashReason/,
+        /InvalidArrayIndex_CRASH/,
+        /NS_ABORT_OOM/,
+
+        // These ought to be threadsafe.
+        "NS_DebugBreak",
+        /mozalloc_handle_oom/,
+        /^NS_Log/, /log_print/, /LazyLogModule::operator/,
+        /SprintfLiteral/, "PR_smprintf", "PR_smprintf_free",
+        /NS_DispatchToMainThread/, /NS_ReleaseOnMainThread/,
+        /NS_NewRunnableFunction/, /NS_Atomize/,
+        /nsCSSValue::BufferFromString/,
+        /NS_xstrdup/,
+        /Assert_NoQueryNeeded/,
+        /AssertCurrentThreadOwnsMe/,
+        /PlatformThread::CurrentId/,
+        /imgRequestProxy::GetProgressTracker/, // Uses an AutoLock
+        /Smprintf/,
+        "malloc",
+        "calloc",
+        "free",
+        "realloc",
+        "memalign",
+        "strdup",
+        "strndup",
+        "moz_xmalloc",
+        "moz_xcalloc",
+        "moz_xrealloc",
+        "moz_xmemalign",
+        "moz_xstrdup",
+        "moz_xstrndup",
+        "jemalloc_thread_local_arena",
+
+        // These all create static strings in local storage, which is threadsafe
+        // to do but not understood by the analysis yet.
+        / EmptyString\(\)/,
+
+        // These could probably be handled by treating the scope of PSAutoLock
+        // aka BaseAutoLock<PSMutex> as threadsafe.
+        /profiler_register_thread/,
+        /profiler_unregister_thread/,
+
+        // The analysis thinks we'll write to mBits in the DoGetStyleFoo<false>
+        // call.  Maybe the template parameter confuses it?
+        /ComputedStyle::PeekStyle/,
+
+        // The analysis can't cope with the indirection used for the objects
+        // being initialized here, from nsCSSValue::Array::Create to the return
+        // value of the Item(i) getter.
+        /nsCSSValue::SetCalcValue/,
+
+        // Unable to analyze safety of linked list initialization.
+        "Gecko_NewCSSValueSharedList",
+        "Gecko_CSSValue_InitSharedList",
+
+        // Unable to trace through dataflow, but straightforward if inspected.
+        "Gecko_NewNoneTransform",
+
+        // Need main thread assertions or other fixes.
+        /EffectCompositor::GetServoAnimationRule/,
+    ];
+    if (entry.matches(whitelist))
+        return true;
+
+    if (entry.isSafeArgument(0)) {
+        var heapWhitelist = [
+            // Operations on heap structures pointed to by arrays and strings are
+            // threadsafe as long as the array/string itself is threadsafe.
+            /nsTArray_Impl.*?::AppendElement/,
+            /nsTArray_Impl.*?::RemoveElementsAt/,
+            /nsTArray_Impl.*?::ReplaceElementsAt/,
+            /nsTArray_Impl.*?::InsertElementAt/,
+            /nsTArray_Impl.*?::SetCapacity/,
+            /nsTArray_Impl.*?::SetLength/,
+            /nsTArray_base.*?::EnsureCapacity/,
+            /nsTArray_base.*?::ShiftData/,
+            /AutoTArray.*?::Init/,
+            /(nsTSubstring<T>|nsAC?String)::SetCapacity/,
+            /(nsTSubstring<T>|nsAC?String)::SetLength/,
+            /(nsTSubstring<T>|nsAC?String)::Assign/,
+            /(nsTSubstring<T>|nsAC?String)::Append/,
+            /(nsTSubstring<T>|nsAC?String)::Replace/,
+            /(nsTSubstring<T>|nsAC?String)::Trim/,
+            /(nsTSubstring<T>|nsAC?String)::Truncate/,
+            /(nsTSubstring<T>|nsAC?String)::StripTaggedASCII/,
+            /(nsTSubstring<T>|nsAC?String)::operator=/,
+            /nsTAutoStringN<T, N>::nsTAutoStringN/,
+
+            // Similar for some other data structures
+            /nsCOMArray_base::SetCapacity/,
+            /nsCOMArray_base::Clear/,
+            /nsCOMArray_base::AppendElement/,
+
+            // UniquePtr is similar.
+            /mozilla::UniquePtr/,
+
+            // The use of unique pointers when copying mCropRect here confuses
+            // the analysis.
+            /nsStyleImage::DoCopy/,
+        ];
+        if (entry.matches(heapWhitelist))
+            return true;
+    }
+
+    if (entry.isSafeArgument(1)) {
+        var firstArgWhitelist = [
+            /nsTextFormatter::snprintf/,
+            /nsTextFormatter::ssprintf/,
+            /_ASCIIToUpperInSitu/,
+
+            // Handle some writes into an array whose safety we don't have a good way
+            // of tracking currently.
+            /FillImageLayerList/,
+            /FillImageLayerPositionCoordList/,
+        ];
+        if (entry.matches(firstArgWhitelist))
+            return true;
+    }
+
+    if (entry.isSafeArgument(2)) {
+        var secondArgWhitelist = [
+            /nsStringBuffer::ToString/,
+            /AppendUTF\d+toUTF\d+/,
+            /AppendASCIItoUTF\d+/,
+        ];
+        if (entry.matches(secondArgWhitelist))
+            return true;
+    }
+
+    return false;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Sixgill Utilities
+///////////////////////////////////////////////////////////////////////////////
+
+function variableName(variable)
+{
+    return (variable && variable.Name) ? variable.Name[0] : null;
+}
+
+function stripFields(exp)
+{
+    // Fields and index operations do not involve any dereferences. Remove them
+    // from the expression but remember any encountered fields for use by
+    // annotations later on.
+    var fields = [];
+    while (true) {
+        if (exp.Kind == "Index") {
+            exp = exp.Exp[0];
+            continue;
+        }
+        if (exp.Kind == "Fld") {
+            var csuName = exp.Field.FieldCSU.Type.Name;
+            var fieldName = exp.Field.Name[0];
+            assert(csuName && fieldName);
+            fields.push(csuName + "." + fieldName);
+            exp = exp.Exp[0];
+            continue;
+        }
+        break;
+    }
+    return [exp, fields];
+}
+
+function isLocalVariable(variable)
+{
+    switch (variable.Kind) {
+      case "Return":
+      case "Temp":
+      case "Local":
+      case "Arg":
+        return true;
+    }
+    return false;
+}
+
+function isDirectCall(edge, regexp)
+{
+    return edge.Kind == "Call"
+        && edge.Exp[0].Kind == "Var"
+        && regexp.test(variableName(edge.Exp[0].Variable));
+}
+
+function isZero(exp)
+{
+    return exp.Kind == "Int" && exp.String == "0";
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Analysis Structures
+///////////////////////////////////////////////////////////////////////////////
+
+// Safe arguments are those which may be written through (directly, not through
+// pointer fields etc.) without concerns about thread safety. This includes
+// pointers to stack data, null pointers, and other data we know is thread
+// local, such as certain arguments to the root functions.
+//
+// Entries in the worklist keep track of the pointer arguments to the function
+// which are safe using a sorted array, so that this can be propagated down the
+// stack. Zero is |this|, and arguments are indexed starting at one.
+
+function WorklistEntry(name, safeArguments, stack, parameterNames)
+{
+    this.name = name;
+    this.safeArguments = safeArguments;
+    this.stack = stack;
+    this.parameterNames = parameterNames;
+}
+
+WorklistEntry.prototype.readable = function()
+{
+    const [ mangled, readable ] = splitFunction(this.name);
+    return readable;
+}
+
+WorklistEntry.prototype.mangledName = function()
+{
+    var str = this.name;
+    for (var safe of this.safeArguments)
+        str += " SAFE " + safe;
+    return str;
+}
+
+WorklistEntry.prototype.isSafeArgument = function(index)
+{
+    for (var safe of this.safeArguments) {
+        if (index == safe)
+            return true;
+    }
+    return false;
+}
+
+WorklistEntry.prototype.setParameterName = function(index, name)
+{
+    this.parameterNames[index] = name;
+}
+
+WorklistEntry.prototype.addSafeArgument = function(index)
+{
+    if (this.isSafeArgument(index))
+        return;
+    this.safeArguments.push(index);
+
+    // Sorting isn't necessary for correctness but makes printed stack info tidier.
+    this.safeArguments.sort();
+}
+
+function safeArgumentIndex(variable)
+{
+    if (variable.Kind == "This")
+        return 0;
+    if (variable.Kind == "Arg")
+        return variable.Index + 1;
+    return -1;
+}
+
+function nameMatches(name, match)
+{
+    if (typeof match == "string") {
+        if (name == match)
+            return true;
+    } else {
+        assert(match instanceof RegExp);
+        if (match.test(name))
+            return true;
+    }
+    return false;
+}
+
+function nameMatchesArray(name, matchArray)
+{
+    for (var match of matchArray) {
+        if (nameMatches(name, match))
+            return true;
+    }
+    return false;
+}
+
+WorklistEntry.prototype.matches = function(matchArray)
+{
+    return nameMatchesArray(this.name, matchArray);
+}
+
+function CallSite(callee, safeArguments, location, parameterNames)
+{
+    this.callee = callee;
+    this.safeArguments = safeArguments;
+    this.location = location;
+    this.parameterNames = parameterNames;
+}
+
+CallSite.prototype.safeString = function()
+{
+    if (this.safeArguments.length) {
+        var str = "";
+        for (var i = 0; i < this.safeArguments.length; i++) {
+            var arg = this.safeArguments[i];
+            if (arg in this.parameterNames)
+                str += " " + this.parameterNames[arg];
+            else
+                str += " <" + ((arg == 0) ? "this" : "arg" + (arg - 1)) + ">";
+        }
+        return " ### SafeArguments:" + str;
+    }
+    return "";
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Analysis Core
+///////////////////////////////////////////////////////////////////////////////
+
+var errorCount = 0;
+var errorLimit = 100;
+
+// We want to suppress output for functions that ended up not having any
+// hazards, for brevity of the final output. So each new toplevel function will
+// initialize this to a string, which should be printed only if an error is
+// seen.
+var errorHeader;
+
+var startTime = new Date;
+function elapsedTime()
+{
+    var seconds = (new Date - startTime) / 1000;
+    return "[" + seconds.toFixed(2) + "s] ";
+}
+
+var options = parse_options([
+    {
+        name: '--strip-prefix',
+        default: os.getenv('SOURCE') || '',
+        type: 'string'
+    },
+    {
+        name: '--add-prefix',
+        default: os.getenv('URLPREFIX') || '',
+        type: 'string'
+    },
+    {
+        name: '--verbose',
+        type: 'bool'
+    },
+]);
+
+function add_trailing_slash(str) {
+    if (str == '')
+        return str;
+    return str.endsWith("/") ? str : str + "/";
+}
+
+var removePrefix = add_trailing_slash(options.strip_prefix);
+var addPrefix = add_trailing_slash(options.add_prefix);
+
+if (options.verbose) {
+    printErr(`Removing prefix ${removePrefix} from paths`);
+    printErr(`Prepending ${addPrefix} to paths`);
+}
+
+print(elapsedTime() + "Loading types...");
+if (os.getenv("TYPECACHE"))
+    loadTypesWithCache('src_comp.xdb', os.getenv("TYPECACHE"));
+else
+    loadTypes('src_comp.xdb');
+print(elapsedTime() + "Starting analysis...");
+
+var xdb = xdbLibrary();
+xdb.open("src_body.xdb");
+
+var minStream = xdb.min_data_stream();
+var maxStream = xdb.max_data_stream();
+var roots = [];
+
+var [flag, arg] = scriptArgs;
+if (flag && (flag == '-f' || flag == '--function')) {
+    roots = [arg];
+} else {
+    for (var bodyIndex = minStream; bodyIndex <= maxStream; bodyIndex++) {
+        var key = xdb.read_key(bodyIndex);
+        var name = key.readString();
+        if (/^Gecko_/.test(name)) {
+            var data = xdb.read_entry(key);
+            if (/ServoBindings.cpp/.test(data.readString()))
+                roots.push(name);
+            xdb.free_string(data);
+        }
+        xdb.free_string(key);
+    }
+}
+
+print(elapsedTime() + "Found " + roots.length + " roots.");
+for (var i = 0; i < roots.length; i++) {
+    var root = roots[i];
+    errorHeader = elapsedTime() + "#" + (i + 1) + " Analyzing " + root + " ...";
+    try {
+        processRoot(root);
+    } catch (e) {
+        if (e != "Error!")
+            throw e;
+    }
+}
+
+print(`${elapsedTime()}Completed analysis, found ${errorCount}/${errorLimit} allowed errors`);
+
+var currentBody;
+
+// All local variable assignments we have seen in either the outer or inner
+// function. This crosses loop boundaries, and currently has an unsoundness
+// where later assignments in a loop are not taken into account.
+var assignments;
+
+// All loops in the current function which are reachable off main thread.
+var reachableLoops;
+
+// Functions that are reachable from the current root.
+var reachable = {};
+
+function dumpError(entry, location, text)
+{
+    if (errorHeader) {
+        print(errorHeader);
+        errorHeader = undefined;
+    }
+
+    var stack = entry.stack;
+    print("Error: " + text);
+    print("Location: " + entry.name + (location ? " @ " + location : "") + stack[0].safeString());
+    print("Stack Trace:");
+    // Include the callers in the stack trace instead of the callees. Make sure
+    // the dummy stack entry we added for the original roots is in place.
+    assert(stack[stack.length - 1].location == null);
+    for (var i = 0; i < stack.length - 1; i++)
+        print(stack[i + 1].callee + " @ " + stack[i].location + stack[i + 1].safeString());
+    print("\n");
+
+    if (++errorCount == errorLimit) {
+        print("Maximum number of errors encountered, exiting...");
+        quit();
+    }
+
+    throw "Error!";
+}
+
+// If edge is an assignment from a local variable, return the rhs variable.
+function variableAssignRhs(edge)
+{
+    if (edge.Kind == "Assign" && edge.Exp[1].Kind == "Drf" && edge.Exp[1].Exp[0].Kind == "Var") {
+        var variable = edge.Exp[1].Exp[0].Variable;
+        if (isLocalVariable(variable))
+            return variable;
+    }
+    return null;
+}
+
+function processAssign(body, entry, location, lhs, edge)
+{
+    var fields;
+    [lhs, fields] = stripFields(lhs);
+
+    switch (lhs.Kind) {
+      case "Var":
+        var name = variableName(lhs.Variable);
+        if (isLocalVariable(lhs.Variable)) {
+            // Remember any assignments to local variables in this function.
+            // Note that we ignore any points where the variable's address is
+            // taken and indirect assignments might occur. This is an
+            // unsoundness in the analysis.
+
+            let assign = [body, edge];
+
+            // Chain assignments if the RHS has only been assigned once.
+            var rhsVariable = variableAssignRhs(edge);
+            if (rhsVariable) {
+                var rhsAssign = singleAssignment(variableName(rhsVariable));
+                if (rhsAssign)
+                    assign = rhsAssign;
+            }
+
+            if (!(name in assignments))
+                assignments[name] = [];
+            assignments[name].push(assign);
+        } else {
+            checkVariableAssignment(entry, location, name);
+        }
+        return;
+      case "Drf":
+        var variable = null;
+        if (lhs.Exp[0].Kind == "Var") {
+            variable = lhs.Exp[0].Variable;
+            if (isSafeVariable(entry, variable))
+                return;
+        } else if (lhs.Exp[0].Kind == "Fld") {
+            const {
+                Name: [ fieldName ],
+                Type: {Kind, Type: fieldType},
+                FieldCSU: {Type: {Kind: containerTypeKind,
+                                  Name: containerTypeName}}
+            } = lhs.Exp[0].Field;
+            const [containerExpr] = lhs.Exp[0].Exp;
+
+            if (containerTypeKind == 'CSU' &&
+                Kind == 'Pointer' &&
+                isEdgeSafeArgument(entry, containerExpr) &&
+                isSafeMemberPointer(containerTypeName, fieldName, fieldType))
+            {
+                return;
+            }
+        }
+        if (fields.length)
+            checkFieldWrite(entry, location, fields);
+        else
+            checkDereferenceWrite(entry, location, variableName(variable));
+        return;
+      case "Int":
+        if (isZero(lhs)) {
+            // This shows up under MOZ_ASSERT, to crash the process.
+            return;
+        }
+    }
+    dumpError(entry, location, "Unknown assignment " + JSON.stringify(lhs));
+}
+
+function get_location(rawLocation) {
+    const filename = rawLocation.CacheString.replace(removePrefix, '');
+    return addPrefix + filename + "#" + rawLocation.Line;
+}
+
+function process(entry, body, addCallee)
+{
+    if (!("PEdge" in body))
+        return;
+
+    // Add any arguments which are safe due to annotations.
+    if ("DefineVariable" in body) {
+        for (var defvar of body.DefineVariable) {
+            var index = safeArgumentIndex(defvar.Variable);
+            if (index >= 0) {
+                var varName = index ? variableName(defvar.Variable) : "this";
+                assert(varName);
+                entry.setParameterName(index, varName);
+                var csuName = null;
+                var type = defvar.Type;
+                if (type.Kind == "Pointer" && type.Type.Kind == "CSU")
+                    csuName = type.Type.Name;
+                if (treatAsSafeArgument(entry, varName, csuName))
+                    entry.addSafeArgument(index);
+            }
+        }
+    }
+
+    // Points in the body which are reachable if we are not on the main thread.
+    var nonMainThreadPoints = [];
+    nonMainThreadPoints[body.Index[0]] = true;
+
+    for (var edge of body.PEdge) {
+        // Ignore code that only executes on the main thread.
+        if (!(edge.Index[0] in nonMainThreadPoints))
+            continue;
+
+        var location = get_location(body.PPoint[edge.Index[0] - 1].Location);
+
+        var callees = getCallees(edge);
+        for (var callee of callees) {
+            switch (callee.kind) {
+            case "direct":
+                var safeArguments = getEdgeSafeArguments(entry, edge, callee.name);
+                addCallee(new CallSite(callee.name, safeArguments, location, {}));
+                break;
+              case "resolved-field":
+                break;
+              case "field":
+                var field = callee.csu + "." + callee.field;
+                if (callee.isVirtual)
+                    checkOverridableVirtualCall(entry, location, field);
+                else
+                    checkIndirectCall(entry, location, field);
+                break;
+              case "indirect":
+                checkIndirectCall(entry, location, callee.variable);
+                break;
+              default:
+                dumpError(entry, location, "Unknown call " + callee.kind);
+                break;
+            }
+        }
+
+        var fallthrough = true;
+
+        if (edge.Kind == "Assign") {
+            assert(edge.Exp.length == 2);
+            processAssign(body, entry, location, edge.Exp[0], edge);
+        } else if (edge.Kind == "Call") {
+            assert(edge.Exp.length <= 2);
+            if (edge.Exp.length == 2)
+                processAssign(body, entry, location, edge.Exp[1], edge);
+
+            // Treat assertion failures as if they don't return, so that
+            // asserting NS_IsMainThread() is sufficient to prevent the
+            // analysis from considering a block of code.
+            if (isDirectCall(edge, /MOZ_ReportAssertionFailure/))
+                fallthrough = false;
+        } else if (edge.Kind == "Loop") {
+            reachableLoops[edge.BlockId.Loop] = true;
+        } else if (edge.Kind == "Assume") {
+            if (testFailsOffMainThread(edge.Exp[0], edge.PEdgeAssumeNonZero))
+                fallthrough = false;
+        }
+
+        if (fallthrough)
+            nonMainThreadPoints[edge.Index[1]] = true;
+    }
+}
+
+function maybeProcessMissingFunction(entry, addCallee)
+{
+    // If a function is missing it might be because a destructor Foo::~Foo() is
+    // being called but GCC only gave us an implementation for
+    // Foo::~Foo(int32). See computeCallgraph.js for a little more info.
+    var name = entry.name;
+    if (name.indexOf("::~") > 0 && name.indexOf("()") > 0) {
+        var callee = name.replace("()", "(int32)");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    // Similarly, a call to a C1 constructor might invoke the C4 constructor. A
+    // mangled constructor will be something like _ZN<length><name>C1E... or in
+    // the case of a templatized constructor, _ZN<length><name>C1I...EE... so
+    // we hack it and look for "C1E" or "C1I" and replace them with their C4
+    // variants. This will have rare false matches, but so far we haven't hit
+    // any external function calls of that sort.
+    if (entry.mangledName().includes("C1E") || entry.mangledName().includes("C1I")) {
+        var callee = name.replace("C1E", "C4E").replace("C1I", "C4I");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    // Hack to manually follow some typedefs that show up on some functions.
+    // This is a bug in the sixgill GCC plugin I think, since sixgill is
+    // supposed to follow any typedefs itself.
+    if (/mozilla::dom::Element/.test(name)) {
+        var callee = name.replace("mozilla::dom::Element", "Document::Element");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    // Hack for contravariant return types. When overriding a virtual method
+    // with a method that returns a different return type (a subtype of the
+    // original return type), we are getting the right mangled name but the
+    // wrong return type in the unmangled name.
+    if (/\$nsTextFrame*/.test(name)) {
+        var callee = name.replace("nsTextFrame", "nsIFrame");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    return false;
+}
+
+function processRoot(name)
+{
+    var safeArguments = [];
+    var parameterNames = {};
+    var worklist = [new WorklistEntry(name, safeArguments, [new CallSite(name, safeArguments, null, parameterNames)], parameterNames)];
+
+    reachable = {};
+
+    while (worklist.length > 0) {
+        var entry = worklist.pop();
+
+        // In principle we would be better off doing a meet-over-paths here to get
+        // the common subset of arguments which are safe to write through. However,
+        // analyzing functions separately for each subset if simpler, ensures that
+        // the stack traces we produce accurately characterize the stack arguments,
+        // and should be fast enough for now.
+
+        if (entry.mangledName() in reachable)
+            continue;
+        reachable[entry.mangledName()] = true;
+
+        if (ignoreContents(entry))
+            continue;
+
+        var data = xdb.read_entry(entry.name);
+        var dataString = data.readString();
+        var callees = [];
+        if (dataString.length) {
+            // Reverse the order of the bodies we process so that we visit the
+            // outer function and see its assignments before the inner loops.
+            assignments = {};
+            reachableLoops = {};
+            var bodies = JSON.parse(dataString).reverse();
+            for (var body of bodies) {
+                if (!body.BlockId.Loop || body.BlockId.Loop in reachableLoops) {
+                    currentBody = body;
+                    process(entry, body, Array.prototype.push.bind(callees));
+                }
+            }
+        } else {
+            if (!maybeProcessMissingFunction(entry, Array.prototype.push.bind(callees)))
+                checkExternalFunction(entry);
+        }
+        xdb.free_string(data);
+
+        for (var callee of callees) {
+            if (!ignoreCallEdge(entry, callee.callee)) {
+                var nstack = [callee, ...entry.stack];
+                worklist.push(new WorklistEntry(callee.callee, callee.safeArguments, nstack, callee.parameterNames));
+            }
+        }
+    }
+}
+
+function isEdgeSafeArgument(entry, exp)
+{
+    var fields;
+    [exp, fields] = stripFields(exp);
+
+    if (exp.Kind == "Var" && isLocalVariable(exp.Variable))
+        return true;
+    if (exp.Kind == "Drf" && exp.Exp[0].Kind == "Var") {
+        var variable = exp.Exp[0].Variable;
+        return isSafeVariable(entry, variable);
+    }
+    if (isZero(exp))
+        return true;
+    return false;
+}
+
+function getEdgeSafeArguments(entry, edge, callee)
+{
+    assert(edge.Kind == "Call");
+    var res = [];
+    if ("PEdgeCallInstance" in edge) {
+        if (isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            res.push(0);
+    }
+    if ("PEdgeCallArguments" in edge) {
+        var args = edge.PEdgeCallArguments.Exp;
+        for (var i = 0; i < args.length; i++) {
+            if (isEdgeSafeArgument(entry, args[i]))
+                res.push(i + 1);
+        }
+    }
+    return res;
+}
+
+function singleAssignment(name)
+{
+    if (name in assignments) {
+        var edges = assignments[name];
+        if (edges.length == 1)
+            return edges[0];
+    }
+    return null;
+}
+
+function expressionValueEdge(exp) {
+    if (!(exp.Kind == "Var" && exp.Variable.Kind == "Temp"))
+        return null;
+    const assign = singleAssignment(variableName(exp.Variable));
+    if (!assign)
+        return null;
+    const [body, edge] = assign;
+    return edge;
+}
+
+// Examples:
+//
+//   void foo(type* aSafe) {
+//     type* safeBecauseNew = new type(...);
+//     type* unsafeBecauseMultipleAssignments = new type(...);
+//     if (rand())
+//       unsafeBecauseMultipleAssignments = bar();
+//     type* safeBecauseSingleAssignmentOfSafe = aSafe;
+//   }
+//
+function isSafeVariable(entry, variable)
+{
+    var index = safeArgumentIndex(variable);
+    if (index >= 0)
+        return entry.isSafeArgument(index);
+
+    if (variable.Kind != "Temp" && variable.Kind != "Local")
+        return false;
+    var name = variableName(variable);
+
+    if (!entry.safeLocals)
+        entry.safeLocals = new Map;
+    if (entry.safeLocals.has(name))
+        return entry.safeLocals.get(name);
+
+    const safe = isSafeLocalVariable(entry, name);
+    entry.safeLocals.set(name, safe);
+    return safe;
+}
+
+function isSafeLocalVariable(entry, name)
+{
+    // If there is a single place where this variable has been assigned on
+    // edges we are considering, look at that edge.
+    var assign = singleAssignment(name);
+    if (assign) {
+        const [body, edge] = assign;
+
+        // Treat temporary pointers to DebugOnly contents as thread local.
+        if (isDirectCall(edge, /DebugOnly.*?::operator/))
+            return true;
+
+        // Treat heap allocated pointers as thread local during construction.
+        // Hopefully the construction code doesn't leak pointers to the object
+        // to places where other threads might access it.
+        if (isDirectCall(edge, /operator new/) ||
+            isDirectCall(edge, /nsCSSValue::Array::Create/))
+        {
+            return true;
+        }
+
+        if ("PEdgeCallInstance" in edge) {
+            // References to the contents of an array are threadsafe if the array
+            // itself is threadsafe.
+            if ((isDirectCall(edge, /operator\[\]/) ||
+                 isDirectCall(edge, /nsTArray.*?::InsertElementAt\b/) ||
+                 isDirectCall(edge, /nsStyleContent::ContentAt/) ||
+                 isDirectCall(edge, /nsTArray_base.*?::GetAutoArrayBuffer\b/)) &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            {
+                return true;
+            }
+
+            // Watch for the coerced result of a getter_AddRefs or getter_Copies call.
+            if (isDirectCall(edge, /operator /)) {
+                var otherEdge = expressionValueEdge(edge.PEdgeCallInstance.Exp);
+                if (otherEdge &&
+                    isDirectCall(otherEdge, /getter_(?:AddRefs|Copies)/) &&
+                    isEdgeSafeArgument(entry, otherEdge.PEdgeCallArguments.Exp[0]))
+                {
+                    return true;
+                }
+            }
+
+            // RefPtr::operator->() and operator* transmit the safety of the
+            // RefPtr to the return value.
+            if (isDirectCall(edge, /RefPtr<.*?>::operator(->|\*)\(\)/) &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            {
+                return true;
+            }
+
+            // Placement-new returns a pointer that is as safe as the pointer
+            // passed to it. Exp[0] is the size, Exp[1] is the pointer/address.
+            // Note that the invocation of the constructor is a separate call,
+            // and so need not be considered here.
+            if (isDirectCall(edge, /operator new/) &&
+                edge.PEdgeCallInstance.Exp.length == 2 &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp[1]))
+            {
+                return true;
+            }
+
+            // Coercion via AsAString preserves safety.
+            if (isDirectCall(edge, /AsAString/) &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            {
+                return true;
+            }
+
+            // Special case:
+            //
+            //   keyframe->mTimingFunction.emplace()
+            //   keyframe->mTimingFunction->Init()
+            //
+            // The object calling Init should be considered safe here because
+            // we just emplaced it, though in general keyframe::operator->
+            // could do something crazy.
+            if (isDirectCall(edge, /operator->/)) do {
+                const predges = getPredecessors(body)[edge.Index[0]];
+                if (!predges || predges.length != 1)
+                    break;
+                const predge = predges[0];
+                if (!isDirectCall(predge, /\bemplace\b/))
+                    break;
+                const instance = predge.PEdgeCallInstance;
+                if (JSON.stringify(instance) == JSON.stringify(edge.PEdgeCallInstance))
+                    return true;
+            } while (false);
+        }
+
+        if (isSafeAssignment(entry, edge, name))
+            return true;
+
+        // Watch out for variables which were assigned arguments.
+        var rhsVariable = variableAssignRhs(edge);
+        if (rhsVariable)
+            return isSafeVariable(entry, rhsVariable);
+    }
+
+    // When temporary stack structures are created (either to return or to call
+    // methods on without assigning them a name), the generated sixgill JSON is
+    // rather strange. The temporary has structure type and is never assigned
+    // to, but is dereferenced. GCC is probably not showing us everything it is
+    // doing to compile this code. Pattern match for this case here.
+
+    // The variable should have structure type.
+    var type = null;
+    for (var defvar of currentBody.DefineVariable) {
+        if (variableName(defvar.Variable) == name) {
+            type = defvar.Type;
+            break;
+        }
+    }
+    if (!type || type.Kind != "CSU")
+        return false;
+
+    // The variable should not have been written to anywhere up to this point.
+    // If it is initialized at this point we should have seen *some* write
+    // already, since the CFG edges are visited in reverse post order.
+    if (name in assignments)
+        return false;
+
+    return true;
+}
+
+function isSafeMemberPointer(containerType, memberName, memberType)
+{
+    // nsTArray owns its header.
+    if (containerType.includes("nsTArray_base") && memberName == "mHdr")
+        return true;
+
+    if (memberType.Kind != 'Pointer')
+        return false;
+
+    // Special-cases go here :)
+    return false;
+}
+
+// Return whether 'exp == value' holds only when execution is on the main thread.
+function testFailsOffMainThread(exp, value) {
+    switch (exp.Kind) {
+      case "Drf":
+        var edge = expressionValueEdge(exp.Exp[0]);
+        if (edge) {
+            if (isDirectCall(edge, /NS_IsMainThread/) && value)
+                return true;
+            if (isDirectCall(edge, /IsInServoTraversal/) && !value)
+                return true;
+            if (isDirectCall(edge, /IsCurrentThreadInServoTraversal/) && !value)
+                return true;
+            if (isDirectCall(edge, /__builtin_expect/))
+                return testFailsOffMainThread(edge.PEdgeCallArguments.Exp[0], value);
+            if (edge.Kind == "Assign")
+                return testFailsOffMainThread(edge.Exp[1], value);
+        }
+        break;
+      case "Unop":
+        if (exp.OpCode == "LogicalNot")
+            return testFailsOffMainThread(exp.Exp[0], !value);
+        break;
+      case "Binop":
+        if (exp.OpCode == "NotEqual" || exp.OpCode == "Equal") {
+            var cmpExp = isZero(exp.Exp[0])
+                ? exp.Exp[1]
+                : (isZero(exp.Exp[1]) ? exp.Exp[0] : null);
+            if (cmpExp)
+                return testFailsOffMainThread(cmpExp, exp.OpCode == "NotEqual" ? value : !value);
+        }
+        break;
+      case "Int":
+        if (exp.String == "0" && value)
+            return true;
+        if (exp.String == "1" && !value)
+            return true;
+        break;
+    }
+    return false;
+}
diff --git a/js/src/devtools/rootAnalysis/analyzeRoots.js b/js/src/devtools/rootAnalysis/analyzeRoots.js
new file mode 100644
index 0000000000..46bc7ea1fb
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/analyzeRoots.js
@@ -0,0 +1,963 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('callgraph.js');
+loadRelativeToScript('CFG.js');
+loadRelativeToScript('dumpCFG.js');
+
+var sourceRoot = (os.getenv('SOURCE') || '') + '/';
+
+var functionName;
+var functionBodies;
+
+try {
+    var options = parse_options([
+        {
+            name: "--function",
+            type: 'string',
+        },
+        {
+            name: "-f",
+            type: "string",
+            dest: "function",
+        },
+        {
+            name: "gcFunctions",
+            default: "gcFunctions.lst"
+        },
+        {
+            name: "limitedFunctions",
+            default: "limitedFunctions.lst"
+        },
+        {
+            name: "gcTypes",
+            default: "gcTypes.txt"
+        },
+        {
+            name: "typeInfo",
+            default: "typeInfo.txt"
+        },
+        {
+            name: "batch",
+            type: "number",
+            default: 1
+        },
+        {
+            name: "numBatches",
+            type: "number",
+            default: 1
+        },
+        {
+            name: "tmpfile",
+            default: "tmp.txt"
+        },
+    ]);
+} catch (e) {
+    printErr(e);
+    printErr("Usage: analyzeRoots.js [-f function_name] <gcFunctions.lst> <limitedFunctions.lst> <gcTypes.txt> <typeInfo.txt> [start end [tmpfile]]");
+    quit(1);
+}
+var gcFunctions = {};
+var text = snarf(options.gcFunctions).split("\n");
+assert(text.pop().length == 0);
+for (const line of text)
+    gcFunctions[mangled(line)] = readable(line);
+
+var limitedFunctions = JSON.parse(snarf(options.limitedFunctions));
+text = null;
+
+var typeInfo = loadTypeInfo(options.typeInfo);
+
+var match;
+var gcThings = new Set();
+var gcPointers = new Set();
+var gcRefs = new Set(typeInfo.GCRefs);
+
+text = snarf(options.gcTypes).split("\n");
+for (var line of text) {
+    if (match = /^GCThing: (.*)/.exec(line))
+        gcThings.add(match[1]);
+    if (match = /^GCPointer: (.*)/.exec(line))
+        gcPointers.add(match[1]);
+}
+text = null;
+
+function isGCRef(type)
+{
+    if (type.Kind == "CSU")
+        return gcRefs.has(type.Name);
+    return false;
+}
+
+function isGCType(type)
+{
+    if (type.Kind == "CSU")
+        return gcThings.has(type.Name);
+    else if (type.Kind == "Array")
+        return isGCType(type.Type);
+    return false;
+}
+
+function isUnrootedPointerDeclType(decl)
+{
+    // Treat non-temporary T& references as if they were the underlying type T.
+    // For now, restrict this to only the types specifically annotated with JS_HAZ_GC_REF
+    // to avoid lots of false positives with other types.
+    let type = isReferenceDecl(decl) && isGCRef(decl.Type.Type) ? decl.Type.Type : decl.Type;
+
+    while (type.Kind == "Array") {
+        type = type.Type;
+    }
+
+    if (type.Kind == "Pointer") {
+        return isGCType(type.Type);
+    } else if (type.Kind == "CSU") {
+        return gcPointers.has(type.Name);
+    } else {
+        return false;
+    }
+}
+
+function edgeCanGC(functionName, body, edge, scopeAttrs, functionBodies)
+{
+    if (edge.Kind != "Call") {
+        return false;
+    }
+
+    for (const { callee, attrs } of getCallees(body, edge, scopeAttrs, functionBodies)) {
+        if (attrs & (ATTR_GC_SUPPRESSED | ATTR_REPLACED)) {
+            continue;
+        }
+
+        if (callee.kind == "direct") {
+            const func = mangled(callee.name);
+            if ((func in gcFunctions) || ((func + internalMarker) in gcFunctions))
+                return `'${func}$${gcFunctions[func]}'`;
+            return false;
+        } else if (callee.kind == "indirect") {
+            if (!indirectCallCannotGC(functionName, callee.variable)) {
+                return "'*" + callee.variable + "'";
+            }
+        } else if (callee.kind == "field") {
+            if (fieldCallCannotGC(callee.staticCSU, callee.field)) {
+                continue;
+            }
+            const fieldkey = callee.fieldKey;
+            if (fieldkey in gcFunctions) {
+                return `'${fieldkey}'`;
+            }
+        } else {
+            return "<unknown>";
+        }
+    }
+
+    return false;
+}
+
+// Search upwards through a function's control flow graph (CFG) to find a path containing:
+//
+// - a use of a variable, preceded by
+//
+// - a function call that can GC, preceded by
+//
+// - a use of the variable that shows that the live range starts at least that
+//   far back, preceded by
+//
+// - an informative use of the variable (which might be the same use), one that
+//   assigns to it a value that might contain a GC pointer (or is the start of
+//   the function for parameters or 'this'.) This is not necessary for
+//   correctness, it just makes it easier to understand why something might be
+//   a hazard. The output of the analysis will include the whole path from the
+//   informative use to the post-GC use, to make the problem as understandable
+//   as possible.
+//
+// A canonical example might be:
+//
+//     void foo() {
+//         JS::Value* val = lookupValue(); <-- informative use
+//         if (!val.isUndefined()) {       <-- any use
+//             GC();                       <-- GC call
+//         }
+//         putValue(val);                  <-- a use after a GC
+//     }
+//
+// The search is performed on an underlying CFG that we traverse in
+// breadth-first order (to find the shortest path). We build a path starting
+// from an empty path and conditionally lengthening and improving it according
+// to the computation occurring on each incoming edge. (If that path so far
+// does not have a GC call and we traverse an edge with a GC call, then we
+// lengthen the path by that edge and record it as including a GC call.) The
+// resulting path may include a point or edge more than once! For example, in:
+//
+//     void foo(JS::Value val) {
+//         for (int i = 0; i < N; i++) {
+//             GC();
+//             val = processValue(val);
+//         }
+//     }
+//
+// the path would start at the point after processValue(), go through the GC(),
+// then back to the processValue() (for the call in the previous loop
+// iteration).
+//
+// While searching, each point is annotated with a path node corresponding to
+// the best path found to that node so far. When a later search ends up at the
+// same point, the best path node is kept. (But the path that it heads may
+// include an earlier path node for the same point, as in the case above.)
+//
+// What info we want depends on whether the variable turns out to be live
+// across a GC call. We are looking for both hazards (unrooted variables live
+// across GC calls) and unnecessary roots (rooted variables that have no GC
+// calls in their live ranges.)
+//
+// If not:
+//
+//  - 'minimumUse': the earliest point in each body that uses the variable, for
+//    reporting on unnecessary roots.
+//
+// If so:
+//
+//  - 'successor': a path from the GC call to a use of the variable after the GC
+//    call, chained through 'successor' field in the returned edge descriptor
+//
+//  - 'gcInfo': a direct pointer to the GC call edge
+//
+function findGCBeforeValueUse(start_body, start_point, funcAttrs, variable)
+{
+    // Scan through all edges preceding an unrooted variable use, using an
+    // explicit worklist, looking for a GC call and a preceding point where the
+    // variable is known to be live. A worklist contains an incoming edge
+    // together with a description of where it or one of its successors GC'd
+    // (if any).
+
+    class Path {
+        get ProgressProperties() { return ["informativeUse", "anyUse", "gcInfo"]; }
+
+        constructor(successor_path, body, ppoint) {
+            Object.assign(this, {body, ppoint});
+            if (successor_path !== undefined) {
+                this.successor = successor_path;
+                for (const prop of this.ProgressProperties) {
+                    if (prop in successor_path) {
+                        this[prop] = successor_path[prop];
+                    }
+                }
+            }
+        }
+
+        toString() {
+            const trail = [];
+            for (let path = this; path.ppoint; path = path.successor) {
+                trail.push(path.ppoint);
+            }
+            return trail.join();
+        }
+
+        // Return -1, 0, or 1 to indicate how complete this Path is compared
+        // to another one.
+        compare(other) {
+            for (const prop of this.ProgressProperties) {
+                const a = this.hasOwnProperty(prop);
+                const b = other.hasOwnProperty(prop);
+                if (a != b) {
+                    return a - b;
+                }
+            }
+            return 0;
+        }
+    };
+
+    // In case we never find an informative use, keep track of the best path
+    // found with any use.
+    let bestPathWithAnyUse = null;
+
+    const visitor = new class extends Visitor {
+        constructor() {
+            super(functionBodies);
+        }
+
+        // Do a BFS upwards through the CFG, starting from a use of the
+        // variable and searching for a path containing a GC followed by an
+        // initializing use of the variable (or, in forward direction, a start
+        // of the variable's live range, a GC within that live range, and then
+        // a use showing that the live range extends past the GC call.)
+        // Actually, possibly two uses: any use at all, and then if available
+        // an "informative" use that is more convincing (they may be the same).
+        //
+        // The CFG is a graph (a 'body' here is acyclic, but they can contain
+        // loop nodes that bridge to additional bodies for the loop, so the
+        // overall graph can by cyclic.) That means there may be multiple paths
+        // from point A to point B, and we want paths with a GC on them. This
+        // can be thought of as searching for a "maximal GCing" path from a use
+        // A to an initialization B.
+        //
+        // This is implemented as a BFS search that when it reaches a point
+        // that has been visited before, stops if and only if the current path
+        // being advanced is a less GC-ful path. The traversal pushes a
+        // `gcInfo` token, initially empty, up through the graph and stores the
+        // maximal one visited so far at every point.
+        //
+        // Note that this means we may traverse through the same point more
+        // than once, and so in theory this scan is superlinear -- if you visit
+        // every point twice, once for a non GC path and once for a GC path, it
+        // would be 2^n. But that is unlikely to matter, since you'd need lots
+        // of split/join pairs that GC on one side and not the other, and you'd
+        // have to visit them in an unlucky order. This could be fixed by
+        // updating the gcInfo for past points in a path when a GC is found,
+        // but it hasn't been found to matter in practice yet.
+
+        next_action(prev, current) {
+            // Continue if first visit, or the new path is more complete than the old path. This
+            // could be enhanced at some point to choose paths with 'better'
+            // examples of GC (eg a call that invokes GC through concrete functions rather than going through a function pointer that is conservatively assumed to GC.)
+
+            if (!current) {
+                // This search path has been terminated.
+                return "prune";
+            }
+
+            if (current.informativeUse) {
+                // We have a path with an informative use leading to a GC
+                // leading to the starting point.
+                assert(current.gcInfo);
+                return "done";
+            }
+
+            if (prev === undefined) {
+                // first visit
+                return "continue";
+            }
+
+            if (!prev.gcInfo && current.gcInfo) {
+                // More GC.
+                return "continue";
+            } else {
+                return "prune";
+            }
+        }
+
+        merge_info(prev, current) {
+            // Keep the most complete path.
+
+            if (!prev || !current) {
+                return prev || current;
+            }
+
+            // Tie goes to the first found, since it will be shorter when doing a BFS-like search.
+            return prev.compare(current) >= 0 ? prev : current;
+        }
+
+        extend_path(edge, body, ppoint, successor_path) {
+            // Clone the successor path node and then tack on the new point. Other values
+            // will be updated during the rest of this function, according to what is
+            // happening on the edge.
+            const path = new Path(successor_path, body, ppoint);
+            if (edge === null) {
+                // Artificial edge to connect loops to their surrounding nodes in the outer body.
+                // Does not influence "completeness" of path.
+                return path;
+            }
+
+            assert(ppoint == edge.Index[0]);
+
+            if (edgeEndsValueLiveRange(edge, variable, body)) {
+                // Terminate the search through this point.
+                return null;
+            }
+
+            const edge_starts = edgeStartsValueLiveRange(edge, variable);
+            const edge_uses = edgeUsesVariable(edge, variable, body);
+
+            if (edge_starts || edge_uses) {
+                if (!body.minimumUse || ppoint < body.minimumUse)
+                    body.minimumUse = ppoint;
+            }
+
+            if (edge_starts) {
+                // This is a beginning of the variable's live range. If we can
+                // reach a GC call from here, then we're done -- we have a path
+                // from the beginning of the live range, through the GC call, to a
+                // use after the GC call that proves its live range extends at
+                // least that far.
+                if (path.gcInfo) {
+                    path.anyUse = path.anyUse || edge;
+                    path.informativeUse = path.informativeUse || edge;
+                    return path;
+                }
+
+                // Otherwise, truncate this particular branch of the search at this
+                // edge -- there is no GC after this use, and traversing the edge
+                // would lead to a different live range.
+                return null;
+            }
+
+            // The value is live across this edge. Check whether this edge can
+            // GC (if we don't have a GC yet on this path.)
+            const had_gcInfo = Boolean(path.gcInfo);
+            const edgeAttrs = body.attrs[ppoint] | funcAttrs;
+            if (!path.gcInfo && !(edgeAttrs & (ATTR_GC_SUPPRESSED | ATTR_REPLACED))) {
+                var gcName = edgeCanGC(functionName, body, edge, edgeAttrs, functionBodies);
+                if (gcName) {
+                    path.gcInfo = {name:gcName, body, ppoint, edge: edge.Index};
+                }
+            }
+
+            // Beginning of function?
+            if (ppoint == body.Index[0] && body.BlockId.Kind != "Loop") {
+                if (path.gcInfo && (variable.Kind == "Arg" || variable.Kind == "This")) {
+                    // The scope of arguments starts at the beginning of the
+                    // function.
+                    path.anyUse = path.informativeUse = true;
+                }
+
+                if (path.anyUse) {
+                    // We know the variable was live across the GC. We may or
+                    // may not have found an "informative" explanation
+                    // beginning of the live range. (This can happen if the
+                    // live range started when a variable is used as a
+                    // retparam.)
+                    return path;
+                }
+            }
+
+            if (!path.gcInfo) {
+                // We haven't reached a GC yet, so don't start looking for uses.
+                return path;
+            }
+
+            if (!edge_uses) {
+                // We have a GC. If this edge doesn't use the value, then there
+                // is no change to the completeness of the path.
+                return path;
+            }
+
+            // The live range starts at least this far back, so we're done for
+            // the same reason as with edge_starts. The only difference is that
+            // a GC on this edge indicates a hazard, whereas if we're killing a
+            // live range in the GC call then it's not live *across* the call.
+            //
+            // However, we may want to generate a longer usage chain for the
+            // variable than is minimally necessary. For example, consider:
+            //
+            //   Value v = f();
+            //   if (v.isUndefined())
+            //     return false;
+            //   gc();
+            //   return v;
+            //
+            // The call to .isUndefined() is considered to be a use and
+            // therefore indicates that v must be live at that point. But it's
+            // more helpful to the user to continue the 'successor' path to
+            // include the ancestor where the value was generated. So we will
+            // only stop here if edge.Kind is Assign; otherwise, we'll pass a
+            // "preGCLive" value up through the worklist to remember that the
+            // variable *is* alive before the GC and so this function should be
+            // returning a true value even if we don't find an assignment.
+
+            // One special case: if the use of the variable is on the
+            // destination part of the edge (which currently only happens for
+            // the return value and a terminal edge in the body), and this edge
+            // is also GCing, then that usage happens *after* the GC and so
+            // should not be used for anyUse or informativeUse. This matters
+            // for a hazard involving a destructor GC'ing after an immobile
+            // return value has been assigned:
+            //
+            //   GCInDestructor guard(cx);
+            //   if (cond()) {
+            //     return nullptr;
+            //   }
+            //
+            // which boils down to
+            //
+            //   p1 --(construct guard)-->
+            //   p2 --(call cond)-->
+            //   p3 --(returnval := nullptr) -->
+            //   p4 --(destruct guard, possibly GCing)-->
+            //   p5
+            //
+            // The return value is considered to be live at p5. The live range
+            // of the return value would ordinarily be from p3->p4->p5, except
+            // that the nullptr assignment means it needn't be considered live
+            // back that far, and so the live range is *just* p5. The GC on the
+            // 4->5 edge happens just before that range, so the value was not
+            // live across the GC.
+            //
+            if (!had_gcInfo && edge_uses == edge.Index[1]) {
+                return path; // New GC does not cross this variable use.
+            }
+
+            path.anyUse = path.anyUse || edge;
+            bestPathWithAnyUse = bestPathWithAnyUse || path;
+            if (edge.Kind == 'Assign') {
+                path.informativeUse = edge; // Done! Setting this terminates the search.
+            }
+
+            return path;
+        };
+    };
+
+    const result = BFS_upwards(start_body, start_point, functionBodies, visitor, new Path());
+    if (result && result.gcInfo && result.anyUse) {
+        return result;
+    } else {
+        return bestPathWithAnyUse;
+    }
+}
+
+function variableLiveAcrossGC(funcAttrs, variable, liveToEnd=false)
+{
+    // A variable is live across a GC if (1) it is used by an edge (as in, it
+    // was at least initialized), and (2) it is used after a GC in a successor
+    // edge.
+
+    for (var body of functionBodies)
+        body.minimumUse = 0;
+
+    for (var body of functionBodies) {
+        if (!("PEdge" in body))
+            continue;
+        for (var edge of body.PEdge) {
+            // Examples:
+            //
+            //   JSObject* obj = NewObject();
+            //   cangc();
+            //   obj = NewObject();     <-- mentions 'obj' but kills previous value
+            //
+            // This is not a hazard. Contrast this with:
+            //
+            //   JSObject* obj = NewObject();
+            //   cangc();
+            //   obj = LookAt(obj);  <-- uses 'obj' and kills previous value
+            //
+            // This is a hazard; the initial value of obj is live across
+            // cangc(). And a third possibility:
+            //
+            //   JSObject* obj = NewObject();
+            //   obj = CopyObject(obj);
+            //
+            // This is not a hazard, because even though CopyObject can GC, obj
+            // is not live across it. (obj is live before CopyObject, and
+            // probably after, but not across.) There may be a hazard within
+            // CopyObject, of course.
+            //
+
+            // Ignore uses that are just invalidating the previous value.
+            if (edgeEndsValueLiveRange(edge, variable, body))
+                continue;
+
+            var usePoint = edgeUsesVariable(edge, variable, body, liveToEnd);
+            if (usePoint) {
+                var call = findGCBeforeValueUse(body, usePoint, funcAttrs, variable);
+                if (!call)
+                    continue;
+
+                call.afterGCUse = usePoint;
+                return call;
+            }
+        }
+    }
+    return null;
+}
+
+// An unrooted variable has its address stored in another variable via
+// assignment, or passed into a function that can GC. If the address is
+// assigned into some other variable, we can't track it to see if it is held
+// live across a GC. If it is passed into a function that can GC, then it's
+// sort of like a Handle to an unrooted location, and the callee could GC
+// before overwriting it or rooting it.
+function unsafeVariableAddressTaken(funcAttrs, variable)
+{
+    for (var body of functionBodies) {
+        if (!("PEdge" in body))
+            continue;
+        for (var edge of body.PEdge) {
+            if (edgeTakesVariableAddress(edge, variable, body)) {
+                if (funcAttrs & (ATTR_GC_SUPPRESSED | ATTR_REPLACED)) {
+                    continue;
+                }
+                if (edge.Kind == "Assign" || edgeCanGC(functionName, body, edge, funcAttrs, functionBodies)) {
+                    return {body:body, ppoint:edge.Index[0]};
+                }
+            }
+        }
+    }
+    return null;
+}
+
+// Read out the brief (non-JSON, semi-human-readable) CFG description for the
+// given function and store it.
+function loadPrintedLines(functionName)
+{
+    assert(!os.system("xdbfind src_body.xdb '" + functionName + "' > " + options.tmpfile));
+    var lines = snarf(options.tmpfile).split('\n');
+
+    for (var body of functionBodies)
+        body.lines = [];
+
+    // Distribute lines of output to the block they originate from.
+    var currentBody = null;
+    for (var line of lines) {
+        if (/^block:/.test(line)) {
+            if (match = /:(loop#[\d#]+)/.exec(line)) {
+                var loop = match[1];
+                var found = false;
+                for (var body of functionBodies) {
+                    if (body.BlockId.Kind == "Loop" && body.BlockId.Loop == loop) {
+                        assert(!found);
+                        found = true;
+                        currentBody = body;
+                    }
+                }
+                assert(found);
+            } else {
+                for (var body of functionBodies) {
+                    if (body.BlockId.Kind == "Function")
+                        currentBody = body;
+                }
+            }
+        }
+        if (currentBody)
+            currentBody.lines.push(line);
+    }
+}
+
+function findLocation(body, ppoint, opts={brief: false})
+{
+    var location = body.PPoint[ppoint ? ppoint - 1 : 0].Location;
+    var file = location.CacheString;
+
+    if (file.indexOf(sourceRoot) == 0)
+        file = file.substring(sourceRoot.length);
+
+    if (opts.brief) {
+        var m = /.*\/(.*)/.exec(file);
+        if (m)
+            file = m[1];
+    }
+
+    return file + ":" + location.Line;
+}
+
+function locationLine(text)
+{
+    if (match = /:(\d+)$/.exec(text))
+        return match[1];
+    return 0;
+}
+
+function getEntryTrace(functionName, entry)
+{
+    const trace = [];
+
+    var gcPoint = entry.gcInfo ? entry.gcInfo.ppoint : 0;
+
+    if (!functionBodies[0].lines)
+        loadPrintedLines(functionName);
+
+    while (entry.successor) {
+        var ppoint = entry.ppoint;
+        var lineText = findLocation(entry.body, ppoint, {"brief": true});
+
+        var edgeText = "";
+        if (entry.successor && entry.successor.body == entry.body) {
+            // If the next point in the trace is in the same block, look for an
+            // edge between them.
+            var next = entry.successor.ppoint;
+
+            if (!entry.body.edgeTable) {
+                var table = {};
+                entry.body.edgeTable = table;
+                for (var line of entry.body.lines) {
+                    if (match = /^\w+\((\d+,\d+),/.exec(line))
+                        table[match[1]] = line; // May be multiple?
+                }
+                if (entry.body.BlockId.Kind == 'Loop') {
+                    const [startPoint, endPoint] = entry.body.Index;
+                    table[`${endPoint},${startPoint}`] = '(loop to next iteration)';
+                }
+            }
+
+            edgeText = entry.body.edgeTable[ppoint + "," + next];
+            assert(edgeText);
+            if (ppoint == gcPoint)
+                edgeText += " [[GC call]]";
+        } else {
+            // Look for any outgoing edge from the chosen point.
+            for (var line of entry.body.lines) {
+                if (match = /\((\d+),/.exec(line)) {
+                    if (match[1] == ppoint) {
+                        edgeText = line;
+                        break;
+                    }
+                }
+            }
+            if (ppoint == entry.body.Index[1] && entry.body.BlockId.Kind == "Function")
+                edgeText += " [[end of function]]";
+        }
+
+        // TODO: Store this in a more structured form for better markup, and perhaps
+        // linking to line numbers.
+        trace.push({lineText, edgeText});
+        entry = entry.successor;
+    }
+
+    return trace;
+}
+
+function isRootedDeclType(decl)
+{
+    // Treat non-temporary T& references as if they were the underlying type T.
+    const type = isReferenceDecl(decl) ? decl.Type.Type : decl.Type;
+    return type.Kind == "CSU" && ((type.Name in typeInfo.RootedPointers) ||
+                                  (type.Name in typeInfo.RootedGCThings));
+}
+
+function printRecord(record) {
+    print(JSON.stringify(record));
+}
+
+function processBodies(functionName, wholeBodyAttrs)
+{
+    if (!("DefineVariable" in functionBodies[0]))
+      return;
+    const funcInfo = limitedFunctions[mangled(functionName)] || { attributes: 0 };
+    const funcAttrs = funcInfo.attributes | wholeBodyAttrs;
+
+    // Look for the JS_EXPECT_HAZARDS annotation, so as to output a different
+    // message in that case that won't be counted as a hazard.
+    var annotations = new Set();
+    for (const variable of functionBodies[0].DefineVariable) {
+        if (variable.Variable.Kind == "Func" && variable.Variable.Name[0] == functionName) {
+            for (const { Name: [tag, value] } of (variable.Type.Annotation || [])) {
+                if (tag == 'annotate')
+                    annotations.add(value);
+            }
+        }
+    }
+
+    let missingExpectedHazard = annotations.has("Expect Hazards");
+
+    // Awful special case, hopefully temporary:
+    //
+    // The DOM bindings code generator uses "holders" to externally root
+    // variables. So for example:
+    //
+    //       StringObjectRecordOrLong arg0;
+    //       StringObjectRecordOrLongArgument arg0_holder(arg0);
+    //       arg0_holder.TrySetToStringObjectRecord(cx, args[0]);
+    //       GC();
+    //       self->PassUnion22(cx, arg0);
+    //
+    // This appears to be a rooting hazard on arg0, but it is rooted by
+    // arg0_holder if you set it to any of its union types that requires
+    // rooting.
+    //
+    // Additionally, the holder may be reported as a hazard because it's not
+    // itself a Rooted or a subclass of AutoRooter; it contains a
+    // Maybe<RecordRooter<T>> that will get emplaced if rooting is required.
+    //
+    // Hopefully these will be simplified at some point (see bug 1517829), but
+    // for now we special-case functions in the mozilla::dom namespace that
+    // contain locals with types ending in "Argument". Or
+    // Maybe<SomethingArgument>. Or Maybe<SpiderMonkeyInterfaceRooter<T>>. It's
+    // a harsh world.
+    const ignoreVars = new Set();
+    if (functionName.match(/mozilla::dom::/)) {
+        const vars = functionBodies[0].DefineVariable.filter(
+            v => v.Type.Kind == 'CSU' && v.Variable.Kind == 'Local'
+        ).map(
+            v => [ v.Variable.Name[0], v.Type.Name ]
+        );
+
+        const holders = vars.filter(
+            ([n, t]) => n.match(/^arg\d+_holder$/) &&
+                        (t.includes("Argument") || t.includes("Rooter")));
+        for (const [holder,] of holders) {
+            ignoreVars.add(holder); // Ignore the holder.
+            ignoreVars.add(holder.replace("_holder", "")); // Ignore the "managed" arg.
+        }
+    }
+
+    const [mangledSymbol, readable] = splitFunction(functionName);
+
+    for (let decl of functionBodies[0].DefineVariable) {
+        var name;
+        if (decl.Variable.Kind == "This")
+            name = "this";
+        else if (decl.Variable.Kind == "Return")
+            name = "<returnvalue>";
+        else
+            name = decl.Variable.Name[0];
+
+        if (ignoreVars.has(name))
+            continue;
+
+        let liveToEnd = false;
+        if (decl.Variable.Kind == "Arg" && isReferenceDecl(decl) && decl.Type.Reference == 2) {
+            // References won't run destructors, so they would normally not be
+            // considered live at the end of the function. In order to handle
+            // the pattern of moving a GC-unsafe value into a function (eg an
+            // AutoCheckCannotGC&&), assume all argument rvalue references live to the
+            // end of the function unless their liveness is terminated by
+            // calling reset() or moving them into another function call.
+            liveToEnd = true;
+        }
+
+        if (isRootedDeclType(decl)) {
+            if (!variableLiveAcrossGC(funcAttrs, decl.Variable)) {
+                // The earliest use of the variable should be its constructor.
+                var lineText;
+                for (var body of functionBodies) {
+                    if (body.minimumUse) {
+                        var text = findLocation(body, body.minimumUse);
+                        if (!lineText || locationLine(lineText) > locationLine(text))
+                            lineText = text;
+                    }
+                }
+                const record = {
+                    record: "unnecessary",
+                    functionName,
+                    mangled: mangledSymbol,
+                    readable,
+                    variable: name,
+                    type: str_Type(decl.Type),
+                    loc: lineText || "???",
+                }
+                print(",");
+                printRecord(record);
+            }
+        } else if (isUnrootedPointerDeclType(decl)) {
+            var result = variableLiveAcrossGC(funcAttrs, decl.Variable, liveToEnd);
+            if (result) {
+                assert(result.gcInfo);
+                const edge = result.gcInfo.edge;
+                const body = result.gcInfo.body;
+                const lineText = findLocation(body, result.gcInfo.ppoint);
+                const makeLoc = l => [l.Location.CacheString, l.Location.Line];
+                const range = [makeLoc(body.PPoint[edge[0] - 1]), makeLoc(body.PPoint[edge[1] - 1])];
+                const record = {
+                    record: "unrooted",
+                    expected: annotations.has("Expect Hazards"),
+                    functionName,
+                    mangled: mangledSymbol,
+                    readable,
+                    variable: name,
+                    type: str_Type(decl.Type),
+                    gccall: result.gcInfo.name.replaceAll("'", ""),
+                    gcrange: range,
+                    loc: lineText,
+                    trace: getEntryTrace(functionName, result),
+                };
+                missingExpectedHazard = false;
+                print(",");
+                printRecord(record);
+            }
+            result = unsafeVariableAddressTaken(funcAttrs, decl.Variable);
+            if (result) {
+                var lineText = findLocation(result.body, result.ppoint);
+                const record = {
+                    record: "address",
+                    functionName,
+                    mangled: mangledSymbol,
+                    readable,
+                    variable: name,
+                    loc: lineText,
+                    trace: getEntryTrace(functionName, {body:result.body, ppoint:result.ppoint}),
+                };
+                print(",");
+                printRecord(record);
+            }
+        }
+    }
+
+    if (missingExpectedHazard) {
+        const {
+            Location: [
+                { CacheString: startfile, Line: startline },
+                { CacheString: endfile, Line: endline }
+            ]
+        } = functionBodies[0];
+
+        const loc = (startfile == endfile) ? `${startfile}:${startline}-${endline}`
+              : `${startfile}:${startline}`;
+
+        const record = {
+            record: "missing",
+            functionName,
+            mangled: mangledSymbol,
+            readable,
+            loc,
+        }
+        print(",");
+        printRecord(record);
+    }
+}
+
+print("[\n");
+var now = new Date();
+printRecord({record: "time", iso: "" + now, t: now.getTime()});
+
+var xdb = xdbLibrary();
+xdb.open("src_body.xdb");
+
+var minStream = xdb.min_data_stream()|0;
+var maxStream = xdb.max_data_stream()|0;
+
+var start = batchStart(options.batch, options.numBatches, minStream, maxStream);
+var end = batchLast(options.batch, options.numBatches, minStream, maxStream);
+
+function process(name, json) {
+    functionName = name;
+    functionBodies = JSON.parse(json);
+
+    // Annotate body with a table of all points within the body that may be in
+    // a limited scope (eg within the scope of a GC suppression RAII class.)
+    // body.attrs is a plain object indexed by point, with the value being a
+    // bit set stored in an integer.
+    for (var body of functionBodies)
+        body.attrs = [];
+
+    for (var body of functionBodies) {
+        for (var [pbody, id, attrs] of allRAIIGuardedCallPoints(typeInfo, functionBodies, body, isLimitConstructor))
+        {
+            if (attrs)
+                pbody.attrs[id] = attrs;
+        }
+    }
+
+    processBodies(functionName);
+}
+
+if (options.function) {
+    var data = xdb.read_entry(options.function);
+    var json = data.readString();
+    debugger;
+    process(options.function, json);
+    xdb.free_string(data);
+    print("\n]\n");
+    quit(0);
+}
+
+for (var nameIndex = start; nameIndex <= end; nameIndex++) {
+    var name = xdb.read_key(nameIndex);
+    var functionName = name.readString();
+    var data = xdb.read_entry(name);
+    xdb.free_string(name);
+    var json = data.readString();
+    try {
+        process(functionName, json);
+    } catch (e) {
+        printErr("Exception caught while handling " + functionName);
+        throw(e);
+    }
+    xdb.free_string(data);
+}
+
+print("\n]\n");
diff --git a/js/src/devtools/rootAnalysis/annotations.js b/js/src/devtools/rootAnalysis/annotations.js
new file mode 100644
index 0000000000..fa859636f1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/annotations.js
@@ -0,0 +1,489 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+// Ignore calls made through these function pointers
+var ignoreIndirectCalls = {
+    "mallocSizeOf" : true,
+    "aMallocSizeOf" : true,
+    "__conv" : true,
+    "__convf" : true,
+    "prerrortable.c:callback_newtable" : true,
+    "mozalloc_oom.cpp:void (* gAbortHandler)(size_t)" : true,
+};
+
+// Types that when constructed with no arguments, are "safe" values (they do
+// not contain GC pointers, or values with nontrivial destructors.)
+var typesWithSafeConstructors = new Set([
+    "mozilla::Maybe",
+    "mozilla::dom::Nullable",
+    "mozilla::dom::Optional",
+    "mozilla::UniquePtr",
+    "js::UniquePtr"
+]);
+
+var resetterMethods = {
+    'mozilla::Maybe': new Set(["reset"]),
+    'mozilla::UniquePtr': new Set(["reset"]),
+    'js::UniquePtr': new Set(["reset"]),
+    'mozilla::dom::Nullable': new Set(["SetNull"]),
+    'mozilla::dom::TypedArray_base': new Set(["Reset"]),
+    'RefPtr': new Set(["forget"]),
+    'nsCOMPtr': new Set(["forget"]),
+    'JS::AutoAssertNoGC': new Set(["reset"]),
+};
+
+function isRefcountedDtor(name) {
+    return name.includes("::~RefPtr(") || name.includes("::~nsCOMPtr(");
+}
+
+function indirectCallCannotGC(fullCaller, fullVariable)
+{
+    var caller = readable(fullCaller);
+
+    // This is usually a simple variable name, but sometimes a full name gets
+    // passed through. And sometimes that name is truncated. Examples:
+    //   _ZL13gAbortHandler$mozalloc_oom.cpp:void (* gAbortHandler)(size_t)
+    //   _ZL14pMutexUnlockFn$umutex.cpp:void (* pMutexUnlockFn)(const void*
+    var name = readable(fullVariable);
+
+    if (name in ignoreIndirectCalls)
+        return true;
+
+    if (name == "mapper" && caller == "ptio.c:pt_MapError")
+        return true;
+
+    if (name == "params" && caller == "PR_ExplodeTime")
+        return true;
+
+    // hook called during script finalization which cannot GC.
+    if (/CallDestroyScriptHook/.test(caller))
+        return true;
+
+    // Call through a 'callback' function pointer, in a place where we're going
+    // to be throwing a JS exception.
+    if (name == "callback" && caller.includes("js::ErrorToException"))
+        return true;
+
+    // The math cache only gets called with non-GC math functions.
+    if (name == "f" && caller.includes("js::MathCache::lookup"))
+        return true;
+
+    // It would probably be better to somehow rewrite PR_CallOnce(foo) into a
+    // call of foo, but for now just assume that nobody is crazy enough to use
+    // PR_CallOnce with a function that can GC.
+    if (name == "func" && caller == "PR_CallOnce")
+        return true;
+
+    return false;
+}
+
+// Ignore calls through functions pointers with these types
+var ignoreClasses = {
+    "JSStringFinalizer" : true,
+    "SprintfState" : true,
+    "SprintfStateStr" : true,
+    "JSLocaleCallbacks" : true,
+    "JSC::ExecutableAllocator" : true,
+    "PRIOMethods": true,
+    "_MD_IOVector" : true,
+    "malloc_table_t": true, // replace_malloc
+    "malloc_hook_table_t": true, // replace_malloc
+    "mozilla::MallocSizeOf": true,
+    "MozMallocSizeOf": true,
+};
+
+// Ignore calls through TYPE.FIELD, where TYPE is the class or struct name containing
+// a function pointer field named FIELD.
+var ignoreCallees = {
+    "js::Class.trace" : true,
+    "js::Class.finalize" : true,
+    "JSClassOps.trace" : true,
+    "JSClassOps.finalize" : true,
+    "JSRuntime.destroyPrincipals" : true,
+    "icu_50::UObject.__deleting_dtor" : true, // destructors in ICU code can't cause GC
+    "mozilla::CycleCollectedJSRuntime.DescribeCustomObjects" : true, // During tracing, cannot GC.
+    "mozilla::CycleCollectedJSRuntime.NoteCustomGCThingXPCOMChildren" : true, // During tracing, cannot GC.
+    "PLDHashTableOps.hashKey" : true,
+    "PLDHashTableOps.clearEntry" : true,
+    "z_stream_s.zfree" : true,
+    "z_stream_s.zalloc" : true,
+    "GrGLInterface.fCallback" : true,
+    "std::strstreambuf._M_alloc_fun" : true,
+    "std::strstreambuf._M_free_fun" : true,
+    "struct js::gc::Callback<void (*)(JSContext*, void*)>.op" : true,
+    "mozilla::ThreadSharedFloatArrayBufferList::Storage.mFree" : true,
+    "mozilla::SizeOfState.mMallocSizeOf": true,
+    "mozilla::gfx::SourceSurfaceRawData.mDeallocator": true,
+};
+
+function fieldCallCannotGC(csu, fullfield)
+{
+    if (csu in ignoreClasses)
+        return true;
+    if (fullfield in ignoreCallees)
+        return true;
+    return false;
+}
+
+function ignoreEdgeUse(edge, variable, body)
+{
+    // Horrible special case for ignoring a false positive in xptcstubs: there
+    // is a local variable 'paramBuffer' holding an array of nsXPTCMiniVariant
+    // on the stack, which appears to be live across a GC call because its
+    // constructor is called when the array is initialized, even though the
+    // constructor is a no-op. So we'll do a very narrow exclusion for the use
+    // that incorrectly started the live range, which was basically "__temp_1 =
+    // paramBuffer".
+    //
+    // By scoping it so narrowly, we can detect most hazards that would be
+    // caused by modifications in the PrepareAndDispatch code. It just barely
+    // avoids having a hazard already.
+    if (('Name' in variable) && (variable.Name[0] == 'paramBuffer')) {
+        if (body.BlockId.Kind == 'Function' && body.BlockId.Variable.Name[0] == 'PrepareAndDispatch')
+            if (edge.Kind == 'Assign' && edge.Type.Kind == 'Pointer')
+                if (edge.Exp[0].Kind == 'Var' && edge.Exp[1].Kind == 'Var')
+                    if (edge.Exp[1].Variable.Kind == 'Local' && edge.Exp[1].Variable.Name[0] == 'paramBuffer')
+                        return true;
+    }
+
+    // Functions which should not be treated as using variable.
+    if (edge.Kind == "Call") {
+        var callee = edge.Exp[0];
+        if (callee.Kind == "Var") {
+            var name = callee.Variable.Name[0];
+            if (/~DebugOnly/.test(name))
+                return true;
+            if (/~ScopedThreadSafeStringInspector/.test(name))
+                return true;
+        }
+    }
+
+    return false;
+}
+
+function ignoreEdgeAddressTaken(edge)
+{
+    // Functions which may take indirect pointers to unrooted GC things,
+    // but will copy them into rooted locations before calling anything
+    // that can GC. These parameters should usually be replaced with
+    // handles or mutable handles.
+    if (edge.Kind == "Call") {
+        var callee = edge.Exp[0];
+        if (callee.Kind == "Var") {
+            var name = callee.Variable.Name[0];
+            if (/js::Invoke\(/.test(name))
+                return true;
+        }
+    }
+
+    return false;
+}
+
+// Ignore calls of these functions (so ignore any stack containing these)
+var ignoreFunctions = {
+    "ptio.c:pt_MapError" : true,
+    "je_malloc_printf" : true,
+    "malloc_usable_size" : true,
+    "vprintf_stderr" : true,
+    "PR_ExplodeTime" : true,
+    "PR_ErrorInstallTable" : true,
+    "PR_SetThreadPrivate" : true,
+    "uint8 NS_IsMainThread()" : true,
+
+    // Has an indirect call under it by the name "__f", which seemed too
+    // generic to ignore by itself.
+    "void* std::_Locale_impl::~_Locale_impl(int32)" : true,
+
+    // Bug 1056410 - devirtualization prevents the standard nsISupports::Release heuristic from working
+    "uint32 nsXPConnect::Release()" : true,
+    "uint32 nsAtom::Release()" : true,
+
+    // Allocation API
+    "malloc": true,
+    "calloc": true,
+    "realloc": true,
+    "free": true,
+
+    // FIXME!
+    "NS_LogInit": true,
+    "NS_LogTerm": true,
+    "NS_LogAddRef": true,
+    "NS_LogRelease": true,
+    "NS_LogCtor": true,
+    "NS_LogDtor": true,
+    "NS_LogCOMPtrAddRef": true,
+    "NS_LogCOMPtrRelease": true,
+
+    // FIXME!
+    "NS_DebugBreak": true,
+
+    // Similar to heap snapshot mock classes, and GTests below. This posts a
+    // synchronous runnable when a GTest fails, and we are pretty sure that the
+    // particular runnable it posts can't even GC, but the analysis isn't
+    // currently smart enough to determine that. In either case, this is (a)
+    // only in GTests, and (b) only when the Gtest has already failed. We have
+    // static and dynamic checks for no GC in the non-test code, and in the test
+    // code we fall back to only the dynamic checks.
+    "void test::RingbufferDumper::OnTestPartResult(testing::TestPartResult*)" : true,
+
+    "float64 JS_GetCurrentEmbedderTime()" : true,
+
+    // This calls any JSObjectMovedOp for the tenured object via an indirect call.
+    "JSObject* js::TenuringTracer::moveToTenuredSlow(JSObject*)" : true,
+
+    "void js::Nursery::freeMallocedBuffers()" : true,
+
+    "void js::AutoEnterOOMUnsafeRegion::crash(uint64, int8*)" : true,
+
+    "void mozilla::dom::WorkerPrivate::AssertIsOnWorkerThread() const" : true,
+
+    // It would be cool to somehow annotate that nsTHashtable<T> will use
+    // nsTHashtable<T>::s_MatchEntry for its matchEntry function pointer, but
+    // there is no mechanism for that. So we will just annotate a particularly
+    // troublesome logging-related usage.
+    "EntryType* nsTHashtable<EntryType>::PutEntry(nsTHashtable<EntryType>::KeyType, const fallible_t&) [with EntryType = nsBaseHashtableET<nsCharPtrHashKey, nsAutoPtr<mozilla::LogModule> >; nsTHashtable<EntryType>::KeyType = const char*; nsTHashtable<EntryType>::fallible_t = mozilla::fallible_t]" : true,
+    "EntryType* nsTHashtable<EntryType>::GetEntry(nsTHashtable<EntryType>::KeyType) const [with EntryType = nsBaseHashtableET<nsCharPtrHashKey, nsAutoPtr<mozilla::LogModule> >; nsTHashtable<EntryType>::KeyType = const char*]" : true,
+    "EntryType* nsTHashtable<EntryType>::PutEntry(nsTHashtable<EntryType>::KeyType) [with EntryType = nsBaseHashtableET<nsPtrHashKey<const mozilla::BlockingResourceBase>, nsAutoPtr<mozilla::DeadlockDetector<mozilla::BlockingResourceBase>::OrderingEntry> >; nsTHashtable<EntryType>::KeyType = const mozilla::BlockingResourceBase*]" : true,
+    "EntryType* nsTHashtable<EntryType>::GetEntry(nsTHashtable<EntryType>::KeyType) const [with EntryType = nsBaseHashtableET<nsPtrHashKey<const mozilla::BlockingResourceBase>, nsAutoPtr<mozilla::DeadlockDetector<mozilla::BlockingResourceBase>::OrderingEntry> >; nsTHashtable<EntryType>::KeyType = const mozilla::BlockingResourceBase*]" : true,
+
+    // VTune internals that lazy-load a shared library and make IndirectCalls.
+    "iJIT_IsProfilingActive" : true,
+    "iJIT_NotifyEvent": true,
+
+    // The big hammers.
+    "PR_GetCurrentThread" : true,
+    "calloc" : true,
+
+    // This will happen early enough in initialization to not matter.
+    "_PR_UnixInit" : true,
+
+    "uint8 nsContentUtils::IsExpandedPrincipal(nsIPrincipal*)" : true,
+
+    "void mozilla::AutoProfilerLabel::~AutoProfilerLabel(int32)" : true,
+
+    // Stores a function pointer in an AutoProfilerLabelData struct and calls it.
+    // And it's in mozglue, which doesn't have access to the attributes yet.
+    "void mozilla::ProfilerLabelEnd(std::tuple<void*, unsigned int>*)" : true,
+
+    // This gets into PLDHashTable function pointer territory, and should get
+    // set up early enough to not do anything when it matters anyway.
+    "mozilla::LogModule* mozilla::LogModule::Get(int8*)": true,
+
+    // This annotation is correct, but the reasoning is still being hashed out
+    // in bug 1582326 comment 8 and on.
+    "nsCycleCollector.cpp:nsISupports* CanonicalizeXPCOMParticipant(nsISupports*)": true,
+
+    // PLDHashTable again
+    "void mozilla::DeadlockDetector<T>::Add(const T*) [with T = mozilla::BlockingResourceBase]": true,
+
+    // OOM handling during logging
+    "void mozilla::detail::log_print(mozilla::LogModule*, int32, int8*)": true,
+
+    // This would need to know that the nsCOMPtr refcount will not go to zero.
+    "uint8 XPCJSRuntime::DescribeCustomObjects(JSObject*, JSClass*, int8[72]*)[72]) const": true,
+
+    // As the comment says "Refcount isn't zero, so Suspect won't delete anything."
+    "uint64 nsCycleCollectingAutoRefCnt::incr(void*, nsCycleCollectionParticipant*) [with void (* suspect)(void*, nsCycleCollectionParticipant*, nsCycleCollectingAutoRefCnt*, bool*) = NS_CycleCollectorSuspect3; uintptr_t = long unsigned int]": true,
+
+    // Calls MergeSort
+    "uint8 v8::internal::RegExpDisjunction::SortConsecutiveAtoms(v8::internal::RegExpCompiler*)": true,
+
+    // nsIEventTarget.IsOnCurrentThreadInfallible does not get resolved, and
+    // this is called on non-JS threads so cannot use AutoSuppressGCAnalysis.
+    "uint8 nsAutoOwningEventTarget::IsCurrentThread() const": true,
+
+    // ~JSStreamConsumer calls 2 ~RefCnt/~nsCOMPtr destructors for its fields,
+    // but the body of the destructor is written so that all Releases
+    // are proxied, and the members will all be empty at destruction time.
+    "void mozilla::dom::JSStreamConsumer::~JSStreamConsumer() [[base_dtor]]": true,
+};
+
+function extraGCFunctions(readableNames) {
+    return ["ffi_call"].filter(f => f in readableNames);
+}
+
+function isProtobuf(name)
+{
+    return name.match(/\bgoogle::protobuf\b/) ||
+           name.match(/\bmozilla::devtools::protobuf\b/);
+}
+
+function isHeapSnapshotMockClass(name)
+{
+    return name.match(/\bMockWriter\b/) ||
+           name.match(/\bMockDeserializedNode\b/);
+}
+
+function isGTest(name)
+{
+    return name.match(/\btesting::/);
+}
+
+function isICU(name)
+{
+    return name.match(/\bicu_\d+::/) ||
+           name.match(/u(prv_malloc|prv_realloc|prv_free|case_toFullLower)_\d+/)
+}
+
+function ignoreGCFunction(mangled, readableNames)
+{
+    // Field calls will not be in readableNames
+    if (!(mangled in readableNames))
+        return false;
+
+    const fun = readableNames[mangled][0];
+
+    if (fun in ignoreFunctions)
+        return true;
+
+    // The protobuf library, and [de]serialization code generated by the
+    // protobuf compiler, uses a _ton_ of function pointers but they are all
+    // internal. The same is true for ICU. Easiest to just ignore that mess
+    // here.
+    if (isProtobuf(fun) || isICU(fun))
+        return true;
+
+    // Ignore anything that goes through heap snapshot GTests or mocked classes
+    // used in heap snapshot GTests. GTest and GMock expose a lot of virtual
+    // methods and function pointers that could potentially GC after an
+    // assertion has already failed (depending on user-provided code), but don't
+    // exhibit that behavior currently. For non-test code, we have dynamic and
+    // static checks that ensure we don't GC. However, for test code we opt out
+    // of static checks here, because of the above stated GMock/GTest issues,
+    // and rely on only the dynamic checks provided by AutoAssertCannotGC.
+    if (isHeapSnapshotMockClass(fun) || isGTest(fun))
+        return true;
+
+    // Templatized function
+    if (fun.includes("void nsCOMPtr<T>::Assert_NoQueryNeeded()"))
+        return true;
+
+    // Bug 1577915 - Sixgill is ignoring a template param that makes its CFG
+    // impossible.
+    if (fun.includes("UnwrapObjectInternal") && fun.includes("mayBeWrapper = false"))
+        return true;
+
+    // These call through an 'op' function pointer.
+    if (fun.includes("js::WeakMap<Key, Value, HashPolicy>::getDelegate("))
+        return true;
+
+    // TODO: modify refillFreeList<NoGC> to not need data flow analysis to
+    // understand it cannot GC. As of gcc 6, the same problem occurs with
+    // tryNewTenuredThing, tryNewNurseryObject, and others.
+    if (/refillFreeList|tryNew/.test(fun) && /= js::NoGC/.test(fun))
+        return true;
+
+    return false;
+}
+
+function stripUCSAndNamespace(name)
+{
+    name = name.replace(/(struct|class|union|const) /g, "");
+    name = name.replace(/(js::ctypes::|js::|JS::|mozilla::dom::|mozilla::)/g, "");
+    return name;
+}
+
+function extraRootedGCThings()
+{
+    return [ 'JSAddonId' ];
+}
+
+function extraRootedPointers()
+{
+    return [
+    ];
+}
+
+function isRootedGCPointerTypeName(name)
+{
+    name = stripUCSAndNamespace(name);
+
+    if (name.startsWith('MaybeRooted<'))
+        return /\(js::AllowGC\)1u>::RootType/.test(name);
+
+    return false;
+}
+
+function isUnsafeStorage(typeName)
+{
+    typeName = stripUCSAndNamespace(typeName);
+    return typeName.startsWith('UniquePtr<');
+}
+
+// If edgeType is a constructor type, return whatever bits it implies for its
+// scope (or zero if not matching).
+function isLimitConstructor(typeInfo, edgeType, varName)
+{
+    // Check whether this could be a constructor
+    if (edgeType.Kind != 'Function')
+        return 0;
+    if (!('TypeFunctionCSU' in edgeType))
+        return 0;
+    if (edgeType.Type.Kind != 'Void')
+        return 0;
+
+    // Check whether the type is a known suppression type.
+    var type = edgeType.TypeFunctionCSU.Type.Name;
+    let attrs = 0;
+    if (type in typeInfo.GCSuppressors)
+        attrs = attrs | ATTR_GC_SUPPRESSED;
+
+    // And now make sure this is the constructor, not some other method on a
+    // suppression type. varName[0] contains the qualified name.
+    var [ mangled, unmangled ] = splitFunction(varName[0]);
+    if (mangled.search(/C\d[EI]/) == -1)
+        return 0; // Mangled names of constructors have C<num>E or C<num>I
+    var m = unmangled.match(/([~\w]+)(?:<.*>)?\(/);
+    if (!m)
+        return 0;
+    var type_stem = type.replace(/\w+::/g, '').replace(/\<.*\>/g, '');
+    if (m[1] != type_stem)
+        return 0;
+
+    return attrs;
+}
+
+// XPIDL-generated methods may invoke JS code, depending on the IDL
+// attributes. This is not visible in the static callgraph since it
+// goes through generated asm code. We can use the JS_HAZ_CAN_RUN_SCRIPT
+// annotation to tell whether this is possible, which is set programmatically
+// by the code generator when needed (bug 1347999):
+// https://searchfox.org/mozilla-central/rev/81c52abeec336685330af5956c37b4bcf8926476/xpcom/idl-parser/xpidl/header.py#213-219
+//
+// Note that WebIDL callbacks can also invoke JS code, but our code generator
+// produces regular C++ code and so does not need any annotations. (There will
+// be a call to JS::Call() or similar.)
+function virtualCanRunJS(csu, field)
+{
+    const tags = typeInfo.OtherFieldTags;
+    const iface = tags[csu]
+    if (!iface) {
+        return false;
+    }
+    const virtual_method_tags = iface[field];
+    return virtual_method_tags && virtual_method_tags.includes("Can run script");
+}
+
+function listNonGCPointers() {
+    return [
+        // Safe only because jsids are currently only made from pinned strings.
+        'NPIdentifier',
+    ];
+}
+
+function isJSNative(mangled)
+{
+    // _Z...E = function
+    // 9JSContext = JSContext*
+    // j = uint32
+    // PN2JS5Value = JS::Value*
+    //   P = pointer
+    //   N2JS = JS::
+    //   5Value = Value
+    return mangled.endsWith("P9JSContextjPN2JS5ValueE") && mangled.startsWith("_Z");
+}
diff --git a/js/src/devtools/rootAnalysis/build.js b/js/src/devtools/rootAnalysis/build.js
new file mode 100644
index 0000000000..78ef04fea1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/build.js
@@ -0,0 +1,15 @@
+#!/bin/sh
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+set -e
+
+cd $SOURCE
+./mach configure
+./mach build export
+./mach build -X nsprpub mfbt memory memory/mozalloc modules/zlib mozglue js/src xpcom/glue js/xpconnect/loader js/xpconnect/wrappers js/xpconnect/src
+status=$?
+echo "[[[[ build.js complete, exit code $status ]]]]"
+exit $status
diff --git a/js/src/devtools/rootAnalysis/build/sixgill-b2g.manifest b/js/src/devtools/rootAnalysis/build/sixgill-b2g.manifest
new file mode 100644
index 0000000000..1ecb5d0665
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/build/sixgill-b2g.manifest
@@ -0,0 +1,10 @@
+[
+{
+"hg_id" : "ec7b7d2442e8",
+"algorithm" : "sha512",
+"digest" : "49627d734df52cb9e7319733da5a6be1812b9373355dc300ee5600b431122570e00d380d50c7c5b5003c462c2c2cb022494b42c4ad00f8eba01c2259cbe6e502",
+"filename" : "sixgill.tar.xz",
+"size" : 2628868,
+"unpack" : true
+}
+]
diff --git a/js/src/devtools/rootAnalysis/build/sixgill.manifest b/js/src/devtools/rootAnalysis/build/sixgill.manifest
new file mode 100644
index 0000000000..49ccdcbd3f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/build/sixgill.manifest
@@ -0,0 +1,10 @@
+[
+{
+"digest" : "2e56a3cf84764b8e63720e5f961cff7ba8ba5cf2f353dac55c69486489bcd89f53a757e09469a07700b80cd09f09666c2db4ce375b67060ac3be967714597231",
+"size" : 2629600,
+"hg_id" : "221d0d2eead9",
+"unpack" : true,
+"filename" : "sixgill.tar.xz",
+"algorithm" : "sha512"
+}
+]
diff --git a/js/src/devtools/rootAnalysis/callgraph.js b/js/src/devtools/rootAnalysis/callgraph.js
new file mode 100644
index 0000000000..1dd31574fd
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/callgraph.js
@@ -0,0 +1,213 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('CFG.js');
+
+// Map from csu => set of immediate subclasses
+var subclasses = new Map();
+
+// Map from csu => set of immediate superclasses
+var superclasses = new Map();
+
+// Map from "csu.name:nargs" => set of full method name
+var virtualDefinitions = new Map();
+
+// Every virtual method declaration, anywhere.
+//
+// Map from csu => Set of function-info.
+// function-info: {
+//   name : simple string
+//   typedfield : "name:nargs" ("mangled" field name)
+//   field: full Field datastructure
+//   annotations : Set of [annotation-name, annotation-value] 2-element arrays
+//   inherited : whether the method is inherited from a base class
+//   pureVirtual : whether the method is pure virtual on this CSU
+//   dtor : if this is a virtual destructor with a definition in this class or
+//     a superclass, then the full name of the definition as if it were defined
+//     in this class. This is weird, but it's how gcc emits it. We will add a
+//     synthetic call from this function to its immediate base classes' dtors,
+//     so even if the function does not actually exist and is inherited from a
+//     base class, we will get a path to the inherited function. (Regular
+//     virtual methods are *not* claimed to exist when they don't.)
+// }
+var virtualDeclarations = new Map();
+
+var virtualResolutionsSeen = new Set();
+
+var ID = {
+    jscode: 1,
+    anyfunc: 2,
+    nogcfunc: 3,
+    gc: 4,
+};
+
+// map is a map from names to sets of entries.
+function addToNamedSet(map, name, entry)
+{
+    if (!map.has(name))
+      map.set(name, new Set());
+    const s = map.get(name);
+    s.add(entry);
+    return s;
+}
+
+// CSU is "Class/Struct/Union"
+function processCSU(csuName, csu)
+{
+    if (!("FunctionField" in csu))
+        return;
+
+    for (const {Base} of (csu.CSUBaseClass || [])) {
+        addToNamedSet(subclasses, Base, csuName);
+        addToNamedSet(superclasses, csuName, Base);
+    }
+
+    for (const {Field, Variable} of csu.FunctionField) {
+        // Virtual method
+        const info = Field[0];
+        const name = info.Name[0];
+        const annotations = new Set();
+        const funcInfo = {
+            name,
+            typedfield: typedField(info),
+            field: info,
+            annotations,
+            inherited: (info.FieldCSU.Type.Name != csuName), // Always false for virtual dtors
+            pureVirtual: Boolean(Variable),
+            dtor: false,
+        };
+
+        if (Variable && isSyntheticVirtualDestructor(name)) {
+            // This is one of gcc's artificial dtors.
+            funcInfo.dtor = Variable.Name[0];
+            funcInfo.pureVirtual = false;
+        }
+
+        addToNamedSet(virtualDeclarations, csuName, funcInfo);
+        if ('Annotation' in info) {
+            for (const {Name: [annType, annValue]} of info.Annotation) {
+                annotations.add([annType, annValue]);
+            }
+        }
+
+        if (Variable) {
+            // Note: not dealing with overloading correctly.
+            const name = Variable.Name[0];
+            addToNamedSet(virtualDefinitions, fieldKey(csuName, Field[0]), name);
+        }
+    }
+}
+
+// Return a list of all callees that the given edge might be a call to. Each
+// one is represented by an object with a 'kind' field that is one of
+// ('direct', 'field', 'resolved-field', 'indirect', 'unknown'), though note
+// that 'resolved-field' is really a global record of virtual method
+// resolutions, indepedent of this particular edge.
+function translateCallees(edge)
+{
+    if (edge.Kind != "Call")
+        return [];
+
+    const callee = edge.Exp[0];
+    if (callee.Kind == "Var") {
+        assert(callee.Variable.Kind == "Func");
+        return [{'kind': 'direct', 'name': callee.Variable.Name[0]}];
+    }
+
+    // At some point, we were intentionally invoking invalid function pointers
+    // (as in, a small integer cast to a function pointer type) to convey a
+    // small amount of information in the crash address.
+    if (callee.Kind == "Int")
+        return []; // Intentional crash
+
+    assert(callee.Kind == "Drf");
+    const called = callee.Exp[0];
+    if (called.Kind == "Var") {
+        // indirect call through a variable.
+        return [{'kind': "indirect", 'variable': callee.Exp[0].Variable.Name[0]}];
+    }
+
+    if (called.Kind != "Fld") {
+        // unknown call target.
+        return [{'kind': "unknown"}];
+    }
+
+    // Return one 'field' callee record giving the full description of what's
+    // happening here (which is either a virtual method call, or a call through
+    // a function pointer stored in a field), and then boil the call down to a
+    // synthetic function that incorporates both the name of the field and the
+    // static type of whatever you're calling the method on. Both refer to the
+    // same call; they're just different ways of describing it.
+    const callees = [];
+    const field = callee.Exp[0].Field;
+    const staticCSU = getFieldCallInstanceCSU(edge, field);
+    callees.push({'kind': "field", 'csu': field.FieldCSU.Type.Name, staticCSU,
+                  'field': field.Name[0], 'fieldKey': fieldKey(staticCSU, field),
+                  'isVirtual': ("FieldInstanceFunction" in field)});
+    callees.push({'kind': "direct", 'name': fieldKey(staticCSU, field)});
+
+    return callees;
+}
+
+function getCallees(body, edge, scopeAttrs, functionBodies) {
+    const calls = [];
+
+    // getCallEdgeProperties can set the ATTR_REPLACED attribute, which
+    // means that the call in the edge has been replaced by zero or
+    // more edges to other functions. This is used when the original
+    // edge will end up calling through a function pointer or something
+    // (eg ~shared_ptr<T> calls a function pointer that can only be
+    // T::~T()). The original call edges are left in the graph in case
+    // they are useful for other purposes.
+    for (const callee of translateCallees(edge)) {
+        if (callee.kind != "direct") {
+            calls.push({ callee, attrs: scopeAttrs });
+        } else {
+            const edgeInfo = getCallEdgeProperties(body, edge, callee.name, functionBodies);
+            for (const extra of (edgeInfo.extraCalls || [])) {
+                calls.push({ attrs: scopeAttrs | extra.attrs, callee: { name: extra.name, 'kind': "direct", } });
+            }
+            calls.push({ callee, attrs: scopeAttrs | edgeInfo.attrs});
+        }
+    }
+
+    return calls;
+}
+
+function loadTypes(type_xdb_filename) {
+    const xdb = xdbLibrary();
+    xdb.open(type_xdb_filename);
+
+    const minStream = xdb.min_data_stream();
+    const maxStream = xdb.max_data_stream();
+
+    for (var csuIndex = minStream; csuIndex <= maxStream; csuIndex++) {
+        const csu = xdb.read_key(csuIndex);
+        const data = xdb.read_entry(csu);
+        const json = JSON.parse(data.readString());
+        processCSU(csu.readString(), json[0]);
+
+        xdb.free_string(csu);
+        xdb.free_string(data);
+    }
+}
+
+function loadTypesWithCache(type_xdb_filename, cache_filename) {
+    try {
+        const cacheAB = os.file.readFile(cache_filename, "binary");
+        const cb = serialize();
+        cb.clonebuffer = cacheAB.buffer;
+        const cacheData = deserialize(cb);
+        subclasses = cacheData.subclasses;
+        superclasses = cacheData.superclasses;
+        virtualDefinitions = cacheData.virtualDefinitions;
+    } catch (e) {
+        loadTypes(type_xdb_filename);
+        const cb = serialize({subclasses, superclasses, virtualDefinitions});
+        os.file.writeTypedArrayToFile(cache_filename,
+                                      new Uint8Array(cb.arraybuffer));
+    }
+}
diff --git a/js/src/devtools/rootAnalysis/computeCallgraph.js b/js/src/devtools/rootAnalysis/computeCallgraph.js
new file mode 100644
index 0000000000..d847465678
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/computeCallgraph.js
@@ -0,0 +1,434 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('callgraph.js');
+
+var options = parse_options([
+    {
+        name: '--verbose',
+        type: 'bool'
+    },
+    {
+        name: '--function',
+        type: 'string'
+    },
+    {
+        name: 'typeInfo_filename',
+        type: 'string',
+        default: "typeInfo.txt"
+    },
+    {
+        name: 'callgraphOut_filename',
+        type: 'string',
+        default: "rawcalls.txt"
+    },
+    {
+        name: 'batch',
+        default: 1,
+        type: 'number'
+    },
+    {
+        name: 'numBatches',
+        default: 1,
+        type: 'number'
+    },
+]);
+
+var origOut = os.file.redirect(options.callgraphOut_filename);
+
+var memoized = new Map();
+
+var unmangled2id = new Set();
+
+// Insert a string into the name table and return the ID. Do not use for
+// functions, which must be handled specially.
+function getId(name)
+{
+    let id = memoized.get(name);
+    if (id !== undefined)
+        return id;
+
+    id = memoized.size + 1;
+    memoized.set(name, id);
+    print(`#${id} ${name}`);
+
+    return id;
+}
+
+// Split a function into mangled and unmangled parts and return the ID for the
+// function.
+function functionId(name)
+{
+    const [mangled, unmangled] = splitFunction(name);
+    const id = getId(mangled);
+
+    // Only produce a mangled -> unmangled mapping once, unless there are
+    // multiple unmangled names for the same mangled name.
+    if (unmangled2id.has(unmangled))
+        return id;
+
+    print(`= ${id} ${unmangled}`);
+    unmangled2id.add(unmangled);
+    return id;
+}
+
+var lastline;
+function printOnce(line)
+{
+    if (line != lastline) {
+        print(line);
+        lastline = line;
+    }
+}
+
+// Returns a table mapping function name to lists of
+// [annotation-name, annotation-value] pairs:
+//   { function-name => [ [annotation-name, annotation-value] ] }
+//
+// Note that sixgill will only store certain attributes (annotation-names), so
+// this won't be *all* the attributes in the source, just the ones that sixgill
+// watches for.
+function getAllAttributes(body)
+{
+    var all_annotations = {};
+    for (var v of (body.DefineVariable || [])) {
+        if (v.Variable.Kind != 'Func')
+            continue;
+        var name = v.Variable.Name[0];
+        var annotations = all_annotations[name] = [];
+
+        for (var ann of (v.Type.Annotation || [])) {
+            annotations.push(ann.Name);
+        }
+    }
+
+    return all_annotations;
+}
+
+// Get just the annotations understood by the hazard analysis.
+function getAnnotations(functionName, body) {
+    var tags = new Set();
+    var attributes = getAllAttributes(body);
+    if (functionName in attributes) {
+        for (var [ annName, annValue ] of attributes[functionName]) {
+            if (annName == 'annotate')
+                tags.add(annValue);
+        }
+    }
+    return tags;
+}
+
+// Scan through a function body, pulling out all annotations and calls and
+// recording them in callgraph.txt.
+function processBody(functionName, body, functionBodies)
+{
+    if (!('PEdge' in body))
+        return;
+
+    for (var tag of getAnnotations(functionName, body).values()) {
+        const id = functionId(functionName);
+        print(`T ${id} ${tag}`);
+        if (tag == "Calls JSNatives")
+            printOnce(`D ${id} ${functionId("(js-code)")}`);
+    }
+
+    // Set of all callees that have been output so far, in order to suppress
+    // repeated callgraph edges from being recorded. This uses a Map from
+    // callees to limit sets, because we don't want a limited edge to prevent
+    // an unlimited edge from being recorded later. (So an edge will be skipped
+    // if it exists and is at least as limited as the previously seen edge.)
+    //
+    // Limit sets are implemented as integers interpreted as bitfields.
+    //
+    var seen = new Map();
+
+    lastline = null;
+    for (var edge of body.PEdge) {
+        if (edge.Kind != "Call")
+            continue;
+
+        // The attrs (eg ATTR_GC_SUPPRESSED) are determined by whatever RAII
+        // scopes might be active, which have been computed previously for all
+        // points in the body.
+        const scopeAttrs = body.attrs[edge.Index[0]] | 0;
+
+        for (const { callee, attrs } of getCallees(body, edge, scopeAttrs, functionBodies)) {
+            // Some function names will be synthesized by manually constructing
+            // their names. Verify that we managed to synthesize an existing function.
+            // This cannot be done later with either the callees or callers tables,
+            // because the function may be an otherwise uncalled leaf.
+            if (attrs & ATTR_SYNTHETIC) {
+                assertFunctionExists(callee.name);
+            }
+
+            // Individual callees may have additional attrs. The only such
+            // bit currently is that nsISupports.{AddRef,Release} are assumed
+            // to never GC.
+            let prologue = attrs ? `/${attrs} ` : "";
+            prologue += functionId(functionName) + " ";
+            if (callee.kind == 'direct') {
+                const prev_attrs = seen.has(callee.name) ? seen.get(callee.name) : ATTRS_UNVISITED;
+                if (prev_attrs & ~attrs) {
+                    // Only output an edge if it loosens a limit.
+                    seen.set(callee.name, prev_attrs & attrs);
+                    printOnce("D " + prologue + functionId(callee.name));
+                }
+            } else if (callee.kind == 'field') {
+                var { csu, field, isVirtual } = callee;
+                const tag = isVirtual ? 'V' : 'F';
+                const fullfield = `${csu}.${field}`;
+                printOnce(`${tag} ${prologue}${getId(fullfield)} CLASS ${csu} FIELD ${field}`);
+            } else if (callee.kind == 'resolved-field') {
+                // Fully-resolved field (virtual method) call. Record the
+                // callgraph edges. Do not consider attrs, since they are local
+                // to this callsite and we are writing out a global record
+                // here.
+                //
+                // Any field call that does *not* have an R entry must be
+                // assumed to call anything.
+                var { csu, field, callees } = callee;
+                var fullFieldName = csu + "." + field;
+                if (!virtualResolutionsSeen.has(fullFieldName)) {
+                    virtualResolutionsSeen.add(fullFieldName);
+                    for (var target of callees)
+                        printOnce("R " + getId(fullFieldName) + " " + functionId(target.name));
+                }
+            } else if (callee.kind == 'indirect') {
+                printOnce("I " + prologue + "VARIABLE " + callee.variable);
+            } else if (callee.kind == 'unknown') {
+                printOnce("I " + prologue + "VARIABLE UNKNOWN");
+            } else {
+                printErr("invalid " + callee.kind + " callee");
+                debugger;
+            }
+        }
+    }
+}
+
+// Reserve IDs for special function names.
+
+// represents anything that can run JS
+assert(ID.jscode == functionId("(js-code)"));
+
+// function pointers will get an edge to this in loadCallgraph.js; only the ID
+// reservation is present in callgraph.txt
+assert(ID.anyfunc == functionId("(any-function)"));
+
+// same as above, but for fields annotated to never GC
+assert(ID.nogcfunc == functionId("(nogc-function)"));
+
+// garbage collection
+assert(ID.gc == functionId("(GC)"));
+
+var typeInfo = loadTypeInfo(options.typeInfo_filename);
+
+loadTypes("src_comp.xdb");
+
+// Arbitrary JS code must always be assumed to GC. In real code, there would
+// always be a path anyway through some arbitrary JSNative, but this route will be shorter.
+print(`D ${ID.jscode} ${ID.gc}`);
+
+// An unknown function is assumed to GC.
+print(`D ${ID.anyfunc} ${ID.gc}`);
+
+// Output call edges for all virtual methods defined anywhere, from
+// Class.methodname to what a (dynamic) instance of Class would run when
+// methodname was called (either Class::methodname() if defined, or some
+// Base::methodname() for inherited method definitions).
+for (const [fieldkey, methods] of virtualDefinitions) {
+    const caller = getId(fieldkey);
+    for (const name of methods) {
+        const callee = functionId(name);
+        printOnce(`D ${caller} ${callee}`);
+    }
+}
+
+// Output call edges from C.methodname -> S.methodname for all subclasses S of
+// class C. This is for when you are calling methodname on a pointer/ref of
+// dynamic type C, so that the callgraph contains calls to all descendant
+// subclasses' implementations.
+for (const [csu, methods] of virtualDeclarations) {
+    for (const {field, dtor} of methods) {
+        const caller = getId(fieldKey(csu, field));
+        if (virtualCanRunJS(csu, field.Name[0]))
+            printOnce(`D ${caller} ${functionId("(js-code)")}`);
+        if (dtor)
+            printOnce(`D ${caller} ${functionId(dtor)}`);
+        if (!subclasses.has(csu))
+            continue;
+        for (const sub of subclasses.get(csu)) {
+            printOnce(`D ${caller} ${getId(fieldKey(sub, field))}`);
+        }
+    }
+}
+
+var xdb = xdbLibrary();
+xdb.open("src_body.xdb");
+
+if (options.verbose) {
+    printErr("Finished loading data structures");
+}
+
+var minStream = xdb.min_data_stream();
+var maxStream = xdb.max_data_stream();
+
+if (options.function) {
+    var index = xdb.lookup_key(options.function);
+    if (!index) {
+        printErr("Function not found");
+        quit(1);
+    }
+    minStream = maxStream = index;
+}
+
+function assertFunctionExists(name) {
+    var data = xdb.read_entry(name);
+    assert(data.contents != 0, `synthetic function '${name}' not found!`);
+}
+
+function process(functionName, functionBodies)
+{
+    for (var body of functionBodies)
+        body.attrs = [];
+
+    for (var body of functionBodies) {
+        for (var [pbody, id, attrs] of allRAIIGuardedCallPoints(typeInfo, functionBodies, body, isLimitConstructor)) {
+            pbody.attrs[id] = attrs;
+        }
+    }
+
+    if (options.function) {
+        debugger;
+    }
+    for (var body of functionBodies) {
+        processBody(functionName, body, functionBodies);
+    }
+
+    // Not strictly necessary, but add an edge from the synthetic "(js-code)"
+    // to RunScript to allow better stacks than just randomly selecting a
+    // JSNative to blame things on.
+    if (functionName.includes("js::RunScript"))
+        print(`D ${functionId("(js-code)")} ${functionId(functionName)}`);
+
+    // GCC generates multiple constructors and destructors ("in-charge" and
+    // "not-in-charge") to handle virtual base classes. They are normally
+    // identical, and it appears that GCC does some magic to alias them to the
+    // same thing. But this aliasing is not visible to the analysis. So we'll
+    // add a dummy call edge from "foo" -> "foo *INTERNAL* ", since only "foo"
+    // will show up as called but only "foo *INTERNAL* " will be emitted in the
+    // case where the constructors are identical.
+    //
+    // This is slightly conservative in the case where they are *not*
+    // identical, but that should be rare enough that we don't care.
+    var markerPos = functionName.indexOf(internalMarker);
+    if (markerPos > 0) {
+        var inChargeXTor = functionName.replace(internalMarker, "");
+        printOnce("D " + functionId(inChargeXTor) + " " + functionId(functionName));
+    }
+
+    const [ mangled, unmangled ] = splitFunction(functionName);
+
+    // Further note: from https://itanium-cxx-abi.github.io/cxx-abi/abi.html the
+    // different kinds of constructors/destructors are:
+    // C1	# complete object constructor
+    // C2	# base object constructor
+    // C3	# complete object allocating constructor
+    // D0	# deleting destructor
+    // D1	# complete object destructor
+    // D2	# base object destructor
+    //
+    // In actual practice, I have observed C4 and D4 xtors generated by gcc
+    // 4.9.3 (but not 4.7.3). The gcc source code says:
+    //
+    //   /* This is the old-style "[unified]" constructor.
+    //      In some cases, we may emit this function and call
+    //      it from the clones in order to share code and save space.  */
+    //
+    // Unfortunately, that "call... from the clones" does not seem to appear in
+    // the CFG we get from GCC. So if we see a C4 constructor or D4 destructor,
+    // inject an edge to it from C1, C2, and C3 (or D1, D2, and D3). (Note that
+    // C3 isn't even used in current GCC, but add the edge anyway just in
+    // case.)
+    //
+    // from gcc/cp/mangle.c:
+    //
+    // <special-name> ::= D0 # deleting (in-charge) destructor
+    //                ::= D1 # complete object (in-charge) destructor
+    //                ::= D2 # base object (not-in-charge) destructor
+    // <special-name> ::= C1   # complete object constructor
+    //                ::= C2   # base object constructor
+    //                ::= C3   # complete object allocating constructor
+    //
+    // Currently, allocating constructors are never used.
+    //
+    if (functionName.indexOf("C4") != -1) {
+        // E terminates the method name (and precedes the method parameters).
+        // If eg "C4E" shows up in the mangled name for another reason, this
+        // will create bogus edges in the callgraph. But it will affect little
+        // and is somewhat difficult to avoid, so we will live with it.
+        //
+        // Another possibility! A templatized constructor will contain C4I...E
+        // for template arguments.
+        //
+        for (let [synthetic, variant, desc] of [
+            ['C4E', 'C1E', 'complete_ctor'],
+            ['C4E', 'C2E', 'base_ctor'],
+            ['C4E', 'C3E', 'complete_alloc_ctor'],
+            ['C4I', 'C1I', 'complete_ctor'],
+            ['C4I', 'C2I', 'base_ctor'],
+            ['C4I', 'C3I', 'complete_alloc_ctor']])
+        {
+            if (mangled.indexOf(synthetic) == -1)
+                continue;
+
+            let variant_mangled = mangled.replace(synthetic, variant);
+            let variant_full = `${variant_mangled}$${unmangled} [[${desc}]]`;
+            printOnce("D " + functionId(variant_full) + " " + functionId(functionName));
+        }
+    }
+
+    // For destructors:
+    //
+    // I've never seen D4Ev() + D4Ev(int32), only one or the other. So
+    // for a D4Ev of any sort, create:
+    //
+    //   D0() -> D1()  # deleting destructor calls complete destructor, then deletes
+    //   D1() -> D2()  # complete destructor calls base destructor, then destroys virtual bases
+    //   D2() -> D4(?) # base destructor might be aliased to unified destructor
+    //                 # use whichever one is defined, in-charge or not.
+    //                 # ('?') means either () or (int32).
+    //
+    // Note that this doesn't actually make sense -- D0 and D1 should be
+    // in-charge, but gcc doesn't seem to give them the in-charge parameter?!
+    //
+    if (functionName.indexOf("D4Ev") != -1 && functionName.indexOf("::~") != -1) {
+        const not_in_charge_dtor = functionName.replace("(int32)", "()");
+        const D0 = not_in_charge_dtor.replace("D4Ev", "D0Ev") + " [[deleting_dtor]]";
+        const D1 = not_in_charge_dtor.replace("D4Ev", "D1Ev") + " [[complete_dtor]]";
+        const D2 = not_in_charge_dtor.replace("D4Ev", "D2Ev") + " [[base_dtor]]";
+        printOnce("D " + functionId(D0) + " " + functionId(D1));
+        printOnce("D " + functionId(D1) + " " + functionId(D2));
+        printOnce("D " + functionId(D2) + " " + functionId(functionName));
+    }
+
+    if (isJSNative(mangled))
+        printOnce(`D ${functionId("(js-code)")} ${functionId(functionName)}`);
+}
+
+var start = batchStart(options.batch, options.numBatches, minStream, maxStream);
+var end = batchLast(options.batch, options.numBatches, minStream, maxStream);
+
+for (var nameIndex = start; nameIndex <= end; nameIndex++) {
+    var name = xdb.read_key(nameIndex);
+    var data = xdb.read_entry(name);
+    process(name.readString(), JSON.parse(data.readString()));
+    xdb.free_string(name);
+    xdb.free_string(data);
+}
+
+os.file.close(os.file.redirect(origOut));
diff --git a/js/src/devtools/rootAnalysis/computeGCFunctions.js b/js/src/devtools/rootAnalysis/computeGCFunctions.js
new file mode 100644
index 0000000000..99410efdf8
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/computeGCFunctions.js
@@ -0,0 +1,113 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('loadCallgraph.js');
+
+function usage() {
+  throw "Usage: computeGCFunctions.js <rawcalls1.txt> <rawcalls2.txt>... --outputs <out:callgraph.txt> <out:gcFunctions.txt> <out:gcFunctions.lst> <out:gcEdges.txt> <out:limitedFunctions.lst>";
+}
+
+if (typeof scriptArgs[0] != 'string')
+  usage();
+
+var start = "Time: " + new Date;
+
+try {
+  var options = parse_options([
+    {
+      name: '--verbose',
+      type: 'bool'
+    },
+    {
+      name: 'inputs',
+      dest: 'rawcalls_filenames',
+      nargs: '+'
+    },
+    {
+      name: '--outputs',
+      type: 'bool'
+    },
+    {
+      name: 'callgraph',
+      type: 'string',
+      default: 'callgraph.txt'
+    },
+    {
+      name: 'gcFunctions',
+      type: 'string',
+      default: 'gcFunctions.txt'
+    },
+    {
+      name: 'gcFunctionsList',
+      type: 'string',
+      default: 'gcFunctions.lst'
+    },
+    {
+      name: 'limitedFunctions',
+      type: 'string',
+      default: 'limitedFunctions.lst'
+    },
+  ]);
+} catch {
+  printErr("Usage: computeGCFunctions.js [--verbose] <rawcalls1.txt> <rawcalls2.txt>... --outputs <out:callgraph.txt> <out:gcFunctions.txt> <out:gcFunctions.lst> <out:gcEdges.txt> <out:limitedFunctions.lst>");
+  quit(1);
+};
+
+function info(message) {
+  if (options.verbose) {
+    printErr(message);
+  }
+}
+
+var {
+  gcFunctions,
+  functions,
+  calleesOf,
+  limitedFunctions
+} = loadCallgraph(options.rawcalls_filenames, options.verbose);
+
+info("Writing " + options.gcFunctions);
+redirect(options.gcFunctions);
+
+for (var name in gcFunctions) {
+    for (let readable of (functions.readableName[name] || [name])) {
+        print("");
+        const fullname = (name == readable) ? name : name + "$" + readable;
+        print("GC Function: " + fullname);
+        let current = name;
+        do {
+            current = gcFunctions[current];
+            if (current === 'internal')
+                ; // Hit the end
+            else if (current in functions.readableName)
+                print("    " + functions.readableName[current][0]);
+            else
+                print("    " + current);
+        } while (current in gcFunctions);
+    }
+}
+
+info("Writing " + options.gcFunctionsList);
+redirect(options.gcFunctionsList);
+for (var name in gcFunctions) {
+    if (name in functions.readableName) {
+        for (var readable of functions.readableName[name])
+            print(name + "$" + readable);
+    } else {
+        print(name);
+    }
+}
+
+info("Writing " + options.limitedFunctions);
+redirect(options.limitedFunctions);
+print(JSON.stringify(limitedFunctions, null, 4));
+
+info("Writing " + options.callgraph);
+redirect(options.callgraph);
+saveCallgraph(functions, calleesOf);
diff --git a/js/src/devtools/rootAnalysis/computeGCTypes.js b/js/src/devtools/rootAnalysis/computeGCTypes.js
new file mode 100644
index 0000000000..eb327da5d2
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/computeGCTypes.js
@@ -0,0 +1,516 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+
+var options = parse_options([
+    { name: "gcTypes", default: "gcTypes.txt" },
+    { name: "typeInfo", default: "typeInfo.txt" }
+]);
+
+var typeInfo = {
+    'GCPointers': [],
+    'GCThings': [],
+    'GCInvalidated': [],
+    'GCRefs': [],
+    'NonGCTypes': {}, // unused
+    'NonGCPointers': {},
+    'RootedGCThings': {},
+    'RootedPointers': {},
+    'RootedBases': {'JS::AutoGCRooter': true},
+    'InheritFromTemplateArgs': {},
+    'OtherCSUTags': {},
+    'OtherFieldTags': {},
+
+    // RAII types within which we should assume GC is suppressed, eg
+    // AutoSuppressGC.
+    'GCSuppressors': {},
+};
+
+var gDescriptors = new Map; // Map from descriptor string => Set of typeName
+
+var structureParents = {}; // Map from field => list of <parent, fieldName>
+var pointerParents = {}; // Map from field => list of <parent, fieldName>
+var baseClasses = {}; // Map from struct name => list of base class name strings
+var subClasses = {}; // Map from struct name => list of subclass  name strings
+
+var gcTypes = {}; // map from parent struct => Set of GC typed children
+var gcPointers = {}; // map from parent struct => Set of GC typed children
+var gcFields = new Map;
+
+var rootedPointers = {};
+
+// Accumulate the base GC types before propagating info through the type graph,
+// so that we can include edges from types processed later
+// (eg MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS).
+var pendingGCTypes = []; // array of [name, reason, ptrdness]
+
+function processCSU(csu, body)
+{
+    for (let { 'Name': [ annType, tag ] } of (body.Annotation || [])) {
+        if (annType != 'annotate')
+            continue;
+
+        if (tag == 'GC Pointer')
+            typeInfo.GCPointers.push(csu);
+        else if (tag == 'Invalidated by GC')
+            typeInfo.GCInvalidated.push(csu);
+        else if (tag == 'GC Pointer or Reference')
+            typeInfo.GCRefs.push(csu);
+        else if (tag == 'GC Thing')
+            typeInfo.GCThings.push(csu);
+        else if (tag == 'Suppressed GC Pointer')
+            typeInfo.NonGCPointers[csu] = true;
+        else if (tag == 'Rooted Pointer')
+            typeInfo.RootedPointers[csu] = true;
+        else if (tag == 'Rooted Base')
+            typeInfo.RootedBases[csu] = true;
+        else if (tag == 'Suppress GC')
+            typeInfo.GCSuppressors[csu] = true;
+        else if (tag == 'moz_inherit_type_annotations_from_template_args')
+            typeInfo.InheritFromTemplateArgs[csu] = true;
+        else
+            addToKeyedList(typeInfo.OtherCSUTags, csu, tag);
+    }
+
+    for (let { 'Base': base } of (body.CSUBaseClass || []))
+        addBaseClass(csu, base);
+
+    for (const field of (body.DataField || [])) {
+        var type = field.Field.Type;
+        var fieldName = field.Field.Name[0];
+        if (type.Kind == "Pointer") {
+            var target = type.Type;
+            if (target.Kind == "CSU")
+                addNestedPointer(csu, target.Name, fieldName);
+        }
+        if (type.Kind == "Array") {
+            var target = type.Type;
+            if (target.Kind == "CSU")
+                addNestedStructure(csu, target.Name, fieldName);
+        }
+        if (type.Kind == "CSU")
+            addNestedStructure(csu, type.Name, fieldName);
+
+        for (const { 'Name': [ annType, tag ] } of (field.Annotation || [])) {
+            if (!(csu in typeInfo.OtherFieldTags))
+                typeInfo.OtherFieldTags[csu] = [];
+            addToKeyedList(typeInfo.OtherFieldTags[csu], fieldName, tag);
+        }
+    }
+
+    for (const funcfield of (body.FunctionField || [])) {
+        const fields = funcfield.Field;
+        // Pure virtual functions will not have field.Variable; others will.
+        for (const field of funcfield.Field) {
+            for (const {'Name': [annType, tag]} of (field.Annotation || [])) {
+                if (!(csu in typeInfo.OtherFieldTags))
+                    typeInfo.OtherFieldTags[csu] = {};
+                addToKeyedList(typeInfo.OtherFieldTags[csu], field.Name[0], tag);
+            }
+        }
+    }
+}
+
+// csu.field is of type inner
+function addNestedStructure(csu, inner, field)
+{
+    if (!(inner in structureParents))
+        structureParents[inner] = [];
+
+    // Skip fields that are really base classes, to avoid duplicating the base
+    // fields; addBaseClass already added a "base-N" name.
+    if (field.match(/^field:\d+$/) && (csu in baseClasses) && (baseClasses[csu].indexOf(inner) != -1))
+        return;
+
+    structureParents[inner].push([ csu, field ]);
+}
+
+function addBaseClass(csu, base) {
+    if (!(csu in baseClasses))
+        baseClasses[csu] = [];
+    baseClasses[csu].push(base);
+    if (!(base in subClasses))
+        subClasses[base] = [];
+    subClasses[base].push(csu);
+    var k = baseClasses[csu].length;
+    addNestedStructure(csu, base, `<base-${k}>`);
+}
+
+function addNestedPointer(csu, inner, field)
+{
+    if (!(inner in pointerParents))
+        pointerParents[inner] = [];
+    pointerParents[inner].push([ csu, field ]);
+}
+
+var xdb = xdbLibrary();
+xdb.open("src_comp.xdb");
+
+var minStream = xdb.min_data_stream();
+var maxStream = xdb.max_data_stream();
+
+for (var csuIndex = minStream; csuIndex <= maxStream; csuIndex++) {
+    var csu = xdb.read_key(csuIndex);
+    var data = xdb.read_entry(csu);
+    var json = JSON.parse(data.readString());
+    assert(json.length == 1);
+    processCSU(csu.readString(), json[0]);
+
+    xdb.free_string(csu);
+    xdb.free_string(data);
+}
+
+for (const typename of extraRootedGCThings())
+    typeInfo.RootedGCThings[typename] = true;
+
+for (const typename of extraRootedPointers())
+    typeInfo.RootedPointers[typename] = true;
+
+// Everything that inherits from a "Rooted Base" is considered to be rooted.
+// This is for things like CustomAutoRooter and its subclasses.
+var basework = Object.keys(typeInfo.RootedBases);
+while (basework.length) {
+    const base = basework.pop();
+    typeInfo.RootedPointers[base] = true;
+    if (base in subClasses)
+        basework.push(...subClasses[base]);
+}
+
+// Now that we have the whole hierarchy set up, add all the types and propagate
+// info.
+for (const csu of typeInfo.GCThings)
+    addGCType(csu);
+for (const csu of typeInfo.GCPointers)
+    addGCPointer(csu);
+for (const csu of typeInfo.GCInvalidated)
+    addGCPointer(csu);
+
+function parseTemplateType(typeName, validate=false) {
+    // We only want templatized types. `Foo<U, T>::Member` doesn't count.
+    // Foo<U, T>::Bar<X, Y> does count. Which turns out to be a simple rule:
+    // check whether the type ends in '>'.
+    if (!typeName.endsWith(">")) {
+        return [typeName, undefined];
+    }
+
+    // "Tokenize" into angle brackets, commas, and everything else. We store
+    // match objects as tokens because we'll need the string offset after we
+    // finish grabbing the template parameters.
+    const tokens = [];
+    const tokenizer = /[<>,]|[^<>,]+/g;
+    let match;
+    while ((match = tokenizer.exec(typeName)) !== null) {
+    	tokens.push(match);
+    }
+
+    // Walk backwards through the tokens, stopping when we find the matching
+    // open bracket.
+    const args = [];
+    let depth = 0;
+    let arg;
+    let first_result;
+    for (const match of tokens.reverse()) {
+        const token = match[0];
+        if (depth == 1 && (token == ',' || token == '<')) {
+            // We've walked back to the beginning of a template parameter,
+            // where we will see either a comma or open bracket.
+            args.unshift(arg);
+            arg = '';
+        } else if (depth == 0 && token == '>') {
+            arg = ''; // We just started.
+        } else {
+            arg = token + arg;
+        }
+
+        // Maintain the depth.
+        if (token == '<') {
+            // This could be bug 1728151.
+            assert(depth > 0, `Invalid type: too many '<' signs in '${typeName}'`);
+            depth--;
+        } else if (token == '>') {
+            depth++;
+        }
+
+        if (depth == 0) {
+            // We've walked out of the template parameter list.
+            // Record the results.
+            assert(args.length > 0);
+            const templateName = typeName.substr(0, match.index);
+            const result = [templateName, args.map(arg => arg.trim())];
+            if (!validate) {
+                // Normal processing is to return the result the first time we
+                // get to the '<' that matches the terminal '>', without validating
+                // that the rest of the type name is balanced.
+                return result;
+            } else if (!first_result) {
+                // If we are validating, remember the result when we hit the
+                // first matching '<', but then keep processing the rest of
+                // the input string to count brackets.
+                first_result = result;
+            }
+        }
+    }
+
+    // This could be bug 1728151.
+    assert(depth == 0, `Invalid type: too many '>' signs in '${typeName}'`);
+    return first_result;
+}
+
+if (os.getenv("HAZARD_RUN_INTERNAL_TESTS")) {
+    function check_parse(typeName, result) {
+        assertEq(JSON.stringify(parseTemplateType(typeName)), JSON.stringify(result));
+    }
+
+    check_parse("int", ["int", undefined]);
+    check_parse("Type<int>", ["Type", ["int"]]);
+    check_parse("Container<int, double>", ["Container", ["int", "double"]]);
+    check_parse("Container<Container<void, void>, double>", ["Container", ["Container<void, void>", "double"]]);
+    check_parse("Foo<Bar<a,b>,Bar<a,b>>::Container<Container<void, void>, double>", ["Foo<Bar<a,b>,Bar<a,b>>::Container", ["Container<void, void>", "double"]]);
+    check_parse("AlignedStorage2<TypedArray<foo>>", ["AlignedStorage2", ["TypedArray<foo>"]]);
+    check_parse("mozilla::AlignedStorage2<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> >",
+        [
+            "mozilla::AlignedStorage2",
+            [
+                "mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer>"
+            ]
+        ]
+    );
+    check_parse(
+        "mozilla::ArrayIterator<const mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >&, nsTArray_Impl<mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >, nsTArrayInfallibleAllocator> >",
+        [
+            "mozilla::ArrayIterator",
+            [
+                "const mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >&",
+                "nsTArray_Impl<mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >, nsTArrayInfallibleAllocator>"
+            ]
+        ]
+    );
+
+    function check_throws(f, exc) {
+        try {
+            f();
+        } catch (e) {
+            assertEq(e.message.includes(exc), true, "incorrect exception: " + e.message);
+            return;
+        }
+        assertEq(undefined, exc);
+    }
+    // Note that these need to end in '>' or the whole thing will be ignored.
+    check_throws(() => parseTemplateType("foo>", true), "too many '>' signs");
+    check_throws(() => parseTemplateType("foo<<>", true), "too many '<' signs");
+    check_throws(() => parseTemplateType("foo<a::bar<a,b>", true), "too many '<' signs");
+    check_throws(() => parseTemplateType("foo<a>*>::bar<a,b>", true), "too many '>' signs");
+}
+
+// GC Thing and GC Pointer annotations can be inherited from template args if
+// this annotation is used. Think of Maybe<T> for example: Maybe<JSObject*> has
+// the same GC rules as JSObject*.
+
+var inheritors = Object.keys(typeInfo.InheritFromTemplateArgs).sort((a, b) => a.length - b.length);
+for (const csu of inheritors) {
+    const [templateName, templateArgs] = parseTemplateType(csu);
+    for (const param of templateArgs) {
+        const pos = param.search(/\**$/);
+        const ptrdness = param.length - pos;
+        const core_type = param.substr(0, pos);
+        if (ptrdness == 0) {
+            addToKeyedList(structureParents, core_type, [csu, "template-param-" + param]);
+        } else if (ptrdness == 1) {
+            addToKeyedList(pointerParents, core_type, [csu, "template-param-" + param]);
+        }
+    }
+}
+
+// "typeName is a (pointer to a)^'typePtrLevel' GC type because it contains a field
+// named 'child' of type 'why' (or pointer to 'why' if fieldPtrLevel == 1), which is
+// itself a GCThing or GCPointer."
+function markGCType(typeName, child, why, typePtrLevel, fieldPtrLevel, indent)
+{
+    // Some types, like UniquePtr, do not mark/trace/relocate their contained
+    // pointers and so should not hold them live across a GC. UniquePtr in
+    // particular should be the only thing pointing to a structure containing a
+    // GCPointer, so nothing else can possibly trace it and it'll die when the
+    // UniquePtr goes out of scope. So we say that memory pointed to by a
+    // UniquePtr is just as unsafe as the stack for storing GC pointers.
+    if (!fieldPtrLevel && isUnsafeStorage(typeName)) {
+        // The UniquePtr itself is on the stack but when you dereference the
+        // contained pointer, you get to the unsafe memory that we are treating
+        // as if it were the stack (aka ptrLevel 0). Note that
+        // UniquePtr<UniquePtr<JSObject*>> is fine, so we don't want to just
+        // hardcode the ptrLevel.
+        fieldPtrLevel = -1;
+    }
+
+    // Example: with:
+    //    struct Pair { JSObject* foo; int bar; };
+    //    struct { Pair** info }***
+    // make a call to:
+    //    child='info' typePtrLevel=3 fieldPtrLevel=2
+    // for a final ptrLevel of 5, used to later call:
+    //    child='foo' typePtrLevel=5 fieldPtrLevel=1
+    //
+    var ptrLevel = typePtrLevel + fieldPtrLevel;
+
+    // ...except when > 2 levels of pointers away from an actual GC thing, stop
+    // searching the graph. (This would just be > 1, except that a UniquePtr
+    // field might still have a GC pointer.)
+    if (ptrLevel > 2)
+        return;
+
+    if (isRootedGCPointerTypeName(typeName) && !(typeName in typeInfo.RootedPointers))
+        printErr("FIXME: use in-source annotation for " + typeName);
+
+    if (ptrLevel == 0 && (typeName in typeInfo.RootedGCThings))
+        return;
+    if (ptrLevel == 1 && (isRootedGCPointerTypeName(typeName) || (typeName in typeInfo.RootedPointers)))
+        return;
+
+    if (ptrLevel == 0) {
+        if (typeName in typeInfo.NonGCTypes)
+            return;
+        if (!(typeName in gcTypes))
+            gcTypes[typeName] = new Set();
+        gcTypes[typeName].add(why);
+    } else if (ptrLevel == 1) {
+        if (typeName in typeInfo.NonGCPointers)
+            return;
+        if (!(typeName in gcPointers))
+            gcPointers[typeName] = new Set();
+        gcPointers[typeName].add(why);
+    }
+
+    if (ptrLevel < 2) {
+        if (!gcFields.has(typeName))
+            gcFields.set(typeName, new Map());
+        gcFields.get(typeName).set(child, [ why, fieldPtrLevel ]);
+    }
+
+    if (typeName in structureParents) {
+        for (var field of structureParents[typeName]) {
+            var [ holderType, fieldName ] = field;
+            markGCType(holderType, fieldName, typeName, ptrLevel, 0, indent + "  ");
+        }
+    }
+    if (typeName in pointerParents) {
+        for (var field of pointerParents[typeName]) {
+            var [ holderType, fieldName ] = field;
+            markGCType(holderType, fieldName, typeName, ptrLevel, 1, indent + "  ");
+        }
+    }
+}
+
+function addGCType(typeName, child, why, depth, fieldPtrLevel)
+{
+    pendingGCTypes.push([typeName, '<annotation>', '(annotation)', 0, 0]);
+}
+
+function addGCPointer(typeName)
+{
+    pendingGCTypes.push([typeName, '<pointer-annotation>', '(annotation)', 1, 0]);
+}
+
+for (const pending of pendingGCTypes) {
+    markGCType(...pending);
+}
+
+// Call a function for a type and every type that contains the type in a field
+// or as a base class (which internally is pretty much the same thing --
+// subclasses are structs beginning with the base class and adding on their
+// local fields.)
+function foreachContainingStruct(typeName, func, seen = new Set())
+{
+    function recurse(container, typeName) {
+        if (seen.has(typeName))
+            return;
+        seen.add(typeName);
+
+        func(container, typeName);
+
+        if (typeName in subClasses) {
+            for (const sub of subClasses[typeName])
+                recurse("subclass of " + typeName, sub);
+        }
+        if (typeName in structureParents) {
+            for (const [holder, field] of structureParents[typeName])
+                recurse(field + " : " + typeName, holder);
+        }
+    }
+
+    recurse('<annotation>', typeName);
+}
+
+for (var type of listNonGCPointers())
+    typeInfo.NonGCPointers[type] = true;
+
+function explain(csu, indent, seen) {
+    if (!seen)
+        seen = new Set();
+    seen.add(csu);
+    if (!gcFields.has(csu))
+        return;
+    var fields = gcFields.get(csu);
+
+    if (fields.has('<annotation>')) {
+        print(indent + "which is annotated as a GCThing");
+        return;
+    }
+    if (fields.has('<pointer-annotation>')) {
+        print(indent + "which is annotated as a GCPointer");
+        return;
+    }
+    for (var [ field, [ child, ptrdness ] ] of fields) {
+        var msg = indent;
+        if (field[0] == '<')
+            msg += "inherits from ";
+        else {
+            if (field.startsWith("template-param-")) {
+                msg += "inherits annotations from template parameter '" + field.substr(15) + "' ";
+            } else {
+                msg += "contains field '" + field + "' ";
+            }
+            if (ptrdness == -1)
+                msg += "(with a pointer to unsafe storage) holding a ";
+            else if (ptrdness == 0)
+                msg += "of type ";
+            else
+                msg += "pointing to type ";
+        }
+        msg += child;
+        print(msg);
+        if (!seen.has(child))
+            explain(child, indent + "  ", seen);
+    }
+}
+
+var origOut = os.file.redirect(options.gcTypes);
+
+for (var csu in gcTypes) {
+    print("GCThing: " + csu);
+    explain(csu, "  ");
+}
+for (var csu in gcPointers) {
+    print("GCPointer: " + csu);
+    explain(csu, "  ");
+}
+
+// Redirect output to the typeInfo file and close the gcTypes file.
+os.file.close(os.file.redirect(options.typeInfo));
+
+// Compute the set of types that suppress GC within their RAII scopes (eg
+// AutoSuppressGC, AutoSuppressGCForAnalysis).
+var seen = new Set();
+for (let csu in typeInfo.GCSuppressors)
+    foreachContainingStruct(csu,
+                            (holder, typeName) => { typeInfo.GCSuppressors[typeName] = holder },
+                            seen);
+
+print(JSON.stringify(typeInfo, null, 4));
+
+os.file.close(os.file.redirect(origOut));
diff --git a/js/src/devtools/rootAnalysis/dumpCFG.js b/js/src/devtools/rootAnalysis/dumpCFG.js
new file mode 100644
index 0000000000..0ac220840c
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/dumpCFG.js
@@ -0,0 +1,273 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// const cfg = loadCFG(scriptArgs[0]);
+// dump_CFG(cfg);
+
+function loadCFG(filename) {
+  const data = os.file.readFile(filename);
+  return JSON.parse(data);
+}
+
+function dump_CFG(cfg) {
+  for (const body of cfg)
+    dump_body(body);
+}
+
+function dump_body(body, src, dst) {
+  const {BlockId,Command,DefineVariable,Index,Location,PEdge,PPoint,Version} = body;
+
+  const [mangled, unmangled] = splitFunction(BlockId.Variable.Name[0]);
+  print(`${unmangled} at ${Location[0].CacheString}:${Location[0].Line}`);
+
+  if (src === undefined) {
+    for (const def of DefineVariable)
+      print(str_definition(def));
+    print("");
+  }
+
+  for (const edge of PEdge) {
+    if (src === undefined || edge.Index[0] == src) {
+      if (dst == undefined || edge.Index[1] == dst)
+        print(str_edge(edge, body));
+    }
+  }
+}
+
+function str_definition(def) {
+  const {Type, Variable} = def;
+  return `define ${str_Variable(Variable)} : ${str_Type(Type)}`;
+}
+
+function badFormat(what, val) {
+  printErr("Bad format of " + what + ": " + JSON.stringify(val, null, 4));
+  printErr((new Error).stack);
+}
+
+function str_Variable(variable) {
+  if (variable.Kind == 'Return')
+    return '<returnval>';
+  else if (variable.Kind == 'This')
+    return 'this';
+
+  try {
+    return variable.Name[1];
+  } catch(e) {
+    badFormat("variable", variable);
+  }
+}
+
+function str_Type(type) {
+  try {
+    const {Kind, Type, Name, TypeFunctionArguments} = type;
+    if (Kind == 'Pointer')
+      return str_Type(Type) + ["*", "&", "&&"][type.Reference];
+    else if (Kind == 'CSU')
+      return Name;
+    else if (Kind == 'Array')
+      return str_Type(Type) + "[]";
+    else if (Kind == 'Function')
+      return str_Type(Type) + "()";
+
+    return Kind;
+  } catch(e) {
+    badFormat("type", type);
+  }
+}
+
+var OpCodeNames = {
+  'LessEqual': ['<=', '>'],
+  'LessThan': ['<', '>='],
+  'GreaterEqual': ['>=', '<'],
+  'Greater': ['>', '<='],
+  'Plus': '+',
+  'Minus': '-',
+};
+
+function opcode_name(opcode, invert) {
+  if (opcode in OpCodeNames) {
+    const name = OpCodeNames[opcode];
+    if (invert === undefined)
+      return name;
+    return name[invert ? 1 : 0];
+  } else {
+    if (invert === undefined)
+      return opcode;
+    return (invert ? '!' : '') + opcode;
+  }
+}
+
+function str_value(val, env, options) {
+  const {Kind, Variable, String, Exp} = val;
+  if (Kind == 'Var')
+    return str_Variable(Variable);
+  else if (Kind == 'Drf') {
+    // Suppress the vtable lookup dereference
+    if (Exp[0].Kind == 'Fld' && "FieldInstanceFunction" in Exp[0].Field)
+      return str_value(Exp[0], env);
+    const exp = str_value(Exp[0], env);
+    if (options && options.noderef)
+      return exp;
+    return "*" + exp;
+  } else if (Kind == 'Fld') {
+    const {Exp, Field} = val;
+    const name = Field.Name[0];
+    if ("FieldInstanceFunction" in Field) {
+      return Field.FieldCSU.Type.Name + "." + name;
+    }
+    const container = str_value(Exp[0]);
+    if (container.startsWith("*"))
+      return container.substring(1) + "->" + name;
+    return container + "." + name;
+  } else if (Kind == 'Empty') {
+    return '<unknown>';
+  } else if (Kind == 'Binop') {
+    const {OpCode} = val;
+    const op = opcode_name(OpCode);
+    return `${str_value(Exp[0], env)} ${op} ${str_value(Exp[1], env)}`;
+  } else if (Kind == 'Unop') {
+    const exp = str_value(Exp[0], env);
+    const {OpCode} = val;
+    if (OpCode == 'LogicalNot')
+      return `not ${exp}`;
+    return `${OpCode}(${exp})`;
+  } else if (Kind == 'Index') {
+    const index = str_value(Exp[1], env);
+    if (Exp[0].Kind == 'Drf')
+      return `${str_value(Exp[0], env, {noderef:true})}[${index}]`;
+    else
+      return `&${str_value(Exp[0], env)}[${index}]`;
+  } else if (Kind == 'NullTest') {
+    return `nullptr == ${str_value(Exp[0], env)}`;
+  } else if (Kind == "String") {
+    return '"' + String + '"';
+  } else if (String !== undefined) {
+    return String;
+  }
+  badFormat("value", val);
+}
+
+function str_thiscall_Exp(exp) {
+  return exp.Kind == 'Drf' ? str_value(exp.Exp[0]) + "->" : str_value(exp) + ".";
+}
+
+function stripcsu(s) {
+    return s.replace("class ", "").replace("struct ", "").replace("union ");
+}
+
+function str_call(prefix, edge, env) {
+  const {Exp, Type, PEdgeCallArguments, PEdgeCallInstance} = edge;
+  const {Kind, Type:cType, TypeFunctionArguments, TypeFunctionCSU} = Type;
+
+  if (Kind == 'Function') {
+    const params = PEdgeCallArguments ? PEdgeCallArguments.Exp : [];
+    const strParams = params.map(str_value);
+
+    let func;
+    let comment = "";
+    let assign_exp;
+    if (PEdgeCallInstance) {
+      const csu = TypeFunctionCSU.Type.Name;
+      const method = str_value(Exp[0], env);
+
+      // Heuristic to only display the csu for constructors
+      if (csu.includes(method)) {
+        func = stripcsu(csu) + "::" + method;
+      } else {
+        func = method;
+        comment = "# " + csu + "::" + method + "\n";
+      }
+
+      const {Exp: thisExp} = PEdgeCallInstance;
+      func = str_thiscall_Exp(thisExp) + func;
+    } else {
+      func = str_value(Exp[0]);
+    }
+    assign_exp = Exp[1];
+
+    let assign = "";
+    if (assign_exp) {
+      assign = str_value(assign_exp) + " := ";
+    }
+    return `${comment}${prefix} Call ${assign}${func}(${strParams.join(", ")})`;
+  }
+
+  print(JSON.stringify(edge, null, 4));
+  throw new Error("unhandled format error");
+}
+
+function str_assign(prefix, edge) {
+  const {Exp} = edge;
+  const [lhs, rhs] = Exp;
+  return `${prefix} Assign ${str_value(lhs)} := ${str_value(rhs)}`;
+}
+
+function str_loop(prefix, edge) {
+  const {BlockId: {Loop}} = edge;
+  return `${prefix} Loop ${Loop}`;
+}
+
+function str_assume(prefix, edge) {
+  const {Exp, PEdgeAssumeNonZero} = edge;
+  const cmp = PEdgeAssumeNonZero ? "" : "!";
+
+  const {Exp: aExp, Kind, OpCode} = Exp[0];
+  if (Kind == 'Binop') {
+    const [lhs, rhs] = aExp;
+    const op = opcode_name(OpCode, !PEdgeAssumeNonZero);
+    return `${prefix} Assume ${str_value(lhs)} ${op} ${str_value(rhs)}`;
+  } else if (Kind == 'Unop') {
+    return `${prefix} Assume ${cmp}${OpCode} ${str_value(aExp[0])}`;
+  } else if (Kind == 'NullTest') {
+    return `${prefix} Assume nullptr ${cmp}== ${str_value(aExp[0])}`;
+  } else if (Kind == 'Drf') {
+    return `${prefix} Assume ${cmp}${str_value(Exp[0])}`;
+  }
+
+  print(JSON.stringify(edge, null, 4));
+  throw new Error("unhandled format error");
+}
+
+function str_edge(edge, env) {
+  const {Index, Kind} = edge;
+  const [src, dst] = Index;
+  const prefix = `[${src},${dst}]`;
+
+  if (Kind == "Call")
+    return str_call(prefix, edge, env);
+  if (Kind == 'Assign')
+    return str_assign(prefix, edge);
+  if (Kind == 'Assume')
+    return str_assume(prefix, edge);
+  if (Kind == 'Loop')
+    return str_loop(prefix, edge);
+
+  print(JSON.stringify(edge, null, 4));
+  throw "unhandled edge type";
+}
+
+function str(unknown) {
+  if ("Name" in unknown) {
+    return str_Variable(unknown);
+  } else if ("Index" in unknown) {
+    // Note: Variable also has .Index, with a different meaning.
+    return str_edge(unknown);
+  } else if ("Type" in unknown) {
+    if ("Variable" in unknown) {
+      return str_definition(unknown);
+    } else {
+      return str_Type(unknown);
+    }
+  } else if ("Kind" in unknown) {
+    if ("BlockId" in unknown)
+      return str_Variable(unknown);
+    return str_value(unknown);
+  }
+  return "unknown";
+}
+
+function jdump(x) {
+  print(JSON.stringify(x, null, 4));
+  quit(0);
+}
diff --git a/js/src/devtools/rootAnalysis/expect.b2g.json b/js/src/devtools/rootAnalysis/expect.b2g.json
new file mode 100644
index 0000000000..06f2beb36f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/expect.b2g.json
@@ -0,0 +1,3 @@
+{
+  "expect-hazards": 0
+}
diff --git a/js/src/devtools/rootAnalysis/expect.browser.json b/js/src/devtools/rootAnalysis/expect.browser.json
new file mode 100644
index 0000000000..06f2beb36f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/expect.browser.json
@@ -0,0 +1,3 @@
+{
+  "expect-hazards": 0
+}
diff --git a/js/src/devtools/rootAnalysis/expect.shell.json b/js/src/devtools/rootAnalysis/expect.shell.json
new file mode 100644
index 0000000000..06f2beb36f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/expect.shell.json
@@ -0,0 +1,3 @@
+{
+  "expect-hazards": 0
+}
diff --git a/js/src/devtools/rootAnalysis/explain.py b/js/src/devtools/rootAnalysis/explain.py
new file mode 100755
index 0000000000..2fb45e07f9
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/explain.py
@@ -0,0 +1,345 @@
+#!/usr/bin/python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import argparse
+import json
+import pathlib
+import re
+from html import escape
+
+SRCDIR = pathlib.Path(__file__).parent.parent.parent.absolute()
+
+parser = argparse.ArgumentParser(
+    description="Convert the JSON output of the hazard analysis into various text files describing the results.",
+    formatter_class=argparse.ArgumentDefaultsHelpFormatter,
+)
+parser.add_argument("--verbose", type=bool, default=False, help="verbose output")
+
+inputs = parser.add_argument_group("Input")
+inputs.add_argument(
+    "rootingHazards",
+    nargs="?",
+    default="rootingHazards.json",
+    help="JSON input file describing the output of the hazard analysis",
+)
+
+outputs = parser.add_argument_group("Output")
+outputs.add_argument(
+    "gcFunctions",
+    nargs="?",
+    default="gcFunctions.txt",
+    help="file containing a list of functions that can GC",
+)
+outputs.add_argument(
+    "hazards",
+    nargs="?",
+    default="hazards.txt",
+    help="file containing the rooting hazards found",
+)
+outputs.add_argument(
+    "extra",
+    nargs="?",
+    default="unnecessary.txt",
+    help="file containing unnecessary roots",
+)
+outputs.add_argument(
+    "refs",
+    nargs="?",
+    default="refs.txt",
+    help="file containing a list of unsafe references to unrooted values",
+)
+outputs.add_argument(
+    "html",
+    nargs="?",
+    default="hazards.html",
+    help="HTML-formatted file with the hazards found",
+)
+
+args = parser.parse_args()
+
+
+# Imitate splitFunction from utility.js.
+def splitfunc(full):
+    idx = full.find("$")
+    if idx == -1:
+        return (full, full)
+    return (full[0:idx], full[idx + 1 :])
+
+
+def print_header(outfh):
+    print(
+        """\
+<!DOCTYPE html>
+<head>
+<meta charset="utf-8">
+<style>
+input {
+  position: absolute;
+  opacity: 0;
+  z-index: -1;
+}
+tt {
+  background: #eee;
+}
+.tab-label {
+  cursor: s-resize;
+}
+.tab-label a {
+  color: #222;
+}
+.tab-label:hover {
+  background: #eee;
+}
+.tab-label::after {
+  content: " \\25B6";
+  width: 1em;
+  height: 1em;
+  color: #75f;
+  text-align: center;
+  transition: all 0.35s;
+}
+.accorntent {
+  max-height: 0;
+  padding: 0 1em;
+  color: #2c3e50;
+  overflow: hidden;
+  background: white;
+  transition: all 0.35s;
+}
+
+input:checked + .tab-label::after {
+  transform: rotate(90deg);
+  content: " \\25BC";
+}
+input:checked + .tab-label {
+  cursor: n-resize;
+}
+input:checked ~ .accorntent {
+  max-height: 100vh;
+}
+</style>
+</head>
+<body>""",
+        file=outfh,
+    )
+
+
+def print_footer(outfh):
+    print("</ol></body>", file=outfh)
+
+
+def sourcelink(symbol=None, loc=None, range=None):
+    if symbol:
+        return f"https://searchfox.org/mozilla-central/search?q=symbol:{symbol}"
+    elif range:
+        filename, lineno = loc.split(":")
+        [f0, l0] = range[0]
+        [f1, l1] = range[1]
+        if f0 == f1 and l1 > l0:
+            return f"../{filename}?L={l0}-{l1 - 1}#{l0}"
+        else:
+            return f"../{filename}?L={l0}#{l0}"
+    elif loc:
+        filename, lineno = loc.split(":")
+        return f"../{filename}?L={lineno}#{lineno}"
+    else:
+        raise Exception("missing argument to sourcelink()")
+
+
+def quoted_dict(d):
+    return {k: escape(v) for k, v in d.items() if type(v) == str}
+
+
+num_hazards = 0
+num_refs = 0
+num_missing = 0
+
+try:
+    with open(args.rootingHazards) as rootingHazards, open(
+        args.hazards, "w"
+    ) as hazards, open(args.extra, "w") as extra, open(args.refs, "w") as refs, open(
+        args.html, "w"
+    ) as html:
+        current_gcFunction = None
+
+        hazardousGCFunctions = set()
+
+        results = json.load(rootingHazards)
+        print_header(html)
+
+        when = min((r for r in results if r["record"] == "time"), key=lambda r: r["t"])[
+            "iso"
+        ]
+        line = f"Time: {when}"
+        print(line, file=hazards)
+        print(line, file=extra)
+        print(line, file=refs)
+
+        checkboxCounter = 0
+        hazard_results = []
+        seen_time = False
+        for result in results:
+            if result["record"] == "unrooted":
+                hazard_results.append(result)
+                gccall_mangled, _ = splitfunc(result["gccall"])
+                hazardousGCFunctions.add(gccall_mangled)
+                if not result.get("expected"):
+                    num_hazards += 1
+
+            elif result["record"] == "unnecessary":
+                print(
+                    "\nFunction '{mangled}' has unnecessary root '{variable}' of type {type} at {loc}".format(
+                        **result
+                    ),
+                    file=extra,
+                )
+
+            elif result["record"] == "address":
+                print(
+                    (
+                        "\nFunction '{functionName}'"
+                        " takes unsafe address of unrooted '{variable}'"
+                        " at {loc}"
+                    ).format(**result),
+                    file=refs,
+                )
+                num_refs += 1
+
+            elif result["record"] == "missing":
+                print(
+                    "\nFunction '{functionName}' expected hazard(s) but none were found at {loc}".format(
+                        **result
+                    ),
+                    file=hazards,
+                )
+                num_missing += 1
+
+        readable2mangled = {}
+        with open(args.gcFunctions) as gcFunctions:
+            gcExplanations = {}  # gcFunction => stack showing why it can GC
+
+            current_func = None
+            explanation = []
+            for line in gcFunctions:
+                if m := re.match(r"^GC Function: (.*)", line):
+                    if current_func:
+                        gcExplanations[splitfunc(current_func)[0]] = explanation
+                    functionName = m.group(1)
+                    mangled, readable = splitfunc(functionName)
+                    if mangled not in hazardousGCFunctions:
+                        current_func = None
+                        continue
+                    current_func = functionName
+                    if readable != mangled:
+                        readable2mangled[readable] = mangled
+                    # TODO: store the mangled name here, and change
+                    # gcFunctions.txt -> gcFunctions.json and key off of the mangled name.
+                    explanation = [readable]
+                elif current_func:
+                    explanation.append(line.strip())
+            if current_func:
+                gcExplanations[splitfunc(current_func)[0]] = explanation
+
+        print(
+            "Found %d hazards, %d unsafe references, %d missing."
+            % (num_hazards, num_refs, num_missing),
+            file=html,
+        )
+        print("<ol>", file=html)
+
+        for result in hazard_results:
+            (result["gccall_mangled"], result["gccall_readable"]) = splitfunc(
+                result["gccall"]
+            )
+            # Attempt to extract out the function name. Won't handle `Foo<int, Bar<int>>::Foo()`.
+            if m := re.search(r"((?:\w|:|<[^>]*?>)+)\(", result["gccall_readable"]):
+                result["gccall_short"] = m.group(1) + "()"
+            else:
+                result["gccall_short"] = result["gccall_readable"]
+            if result.get("expected"):
+                print("\nThis is expected, but ", end="", file=hazards)
+            else:
+                print("\nFunction ", end="", file=hazards)
+            print(
+                "'{readable}' has unrooted '{variable}'"
+                " of type '{type}' live across GC call '{gccall_readable}' at {loc}".format(
+                    **result
+                ),
+                file=hazards,
+            )
+            for edge in result["trace"]:
+                print("    {lineText}: {edgeText}".format(**edge), file=hazards)
+            explanation = gcExplanations.get(result["gccall_mangled"])
+            explanation = explanation or gcExplanations.get(
+                readable2mangled.get(
+                    result["gccall_readable"], result["gccall_readable"]
+                ),
+                [],
+            )
+            if explanation:
+                print("GC Function: " + explanation[0], file=hazards)
+                for func in explanation[1:]:
+                    print("   " + func, file=hazards)
+            print(file=hazards)
+
+            if result.get("expected"):
+                continue
+
+            cfgid = f"CFG_{checkboxCounter}"
+            gcid = f"GC_{checkboxCounter}"
+            checkboxCounter += 1
+            print(
+                (
+                    "<li><ul>\n"
+                    "<li>Function <a href='{symbol_url}'>{readable}</a>\n"
+                    "<li>has unrooted <tt>{variable}</tt> of type '<tt>{type}</tt>'\n"
+                    "<li><input type='checkbox' id='{cfgid}'><label class='tab-label' for='{cfgid}'>"
+                    "live across GC call to"
+                    "</label>\n"
+                    "<div class='accorntent'>\n"
+                ).format(
+                    **quoted_dict(result),
+                    symbol_url=sourcelink(symbol=result["mangled"]),
+                    cfgid=cfgid,
+                ),
+                file=html,
+            )
+            for edge in result["trace"]:
+                print(
+                    "<pre>    {lineText}: {edgeText}</pre>".format(**quoted_dict(edge)),
+                    file=html,
+                )
+            print("</div>", file=html)
+            print(
+                "<li><input type='checkbox' id='{gcid}'><label class='tab-label' for='{gcid}'>"
+                "<a href='{loc_url}'><tt>{gccall_short}</tt></a> at {loc}"
+                "</label>\n"
+                "<div class='accorntent'>".format(
+                    **quoted_dict(result),
+                    loc_url=sourcelink(range=result["gcrange"], loc=result["loc"]),
+                    gcid=gcid,
+                ),
+                file=html,
+            )
+            for func in explanation:
+                print(f"<pre>{escape(func)}</pre>", file=html)
+            print("</div><hr></ul>", file=html)
+
+        print_footer(html)
+
+except IOError as e:
+    print("Failed: %s" % str(e))
+
+if args.verbose:
+    print("Wrote %s" % args.hazards)
+    print("Wrote %s" % args.extra)
+    print("Wrote %s" % args.refs)
+    print("Wrote %s" % args.html)
+
+print(
+    "Found %d hazards %d unsafe references %d missing"
+    % (num_hazards, num_refs, num_missing)
+)
diff --git a/js/src/devtools/rootAnalysis/gen-hazards.sh b/js/src/devtools/rootAnalysis/gen-hazards.sh
new file mode 100755
index 0000000000..7007969a14
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/gen-hazards.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+set -e
+
+JOBS="$1"
+
+for j in $(seq $JOBS); do
+    env PATH=$PATH:$SIXGILL/bin XDB=$SIXGILL/bin/xdb.so $JS $ANALYZE gcFunctions.lst suppressedFunctions.lst gcTypes.txt $j $JOBS tmp.$j > rootingHazards.$j &
+done
+
+wait
+
+for j in $(seq $JOBS); do
+    cat rootingHazards.$j
+done
diff --git a/js/src/devtools/rootAnalysis/loadCallgraph.js b/js/src/devtools/rootAnalysis/loadCallgraph.js
new file mode 100644
index 0000000000..0a388f4de1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/loadCallgraph.js
@@ -0,0 +1,590 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('callgraph.js');
+
+// Functions come out of sixgill in the form "mangled$readable". The mangled
+// name is Truth. One mangled name might correspond to multiple readable names,
+// for multiple reasons, including (1) sixgill/gcc doesn't always qualify types
+// the same way or de-typedef the same amount; (2) sixgill's output treats
+// references and pointers the same, and so doesn't distinguish them, but C++
+// treats them as separate for overloading and linking; (3) (identical)
+// destructors sometimes have an int32 parameter, sometimes not.
+//
+// The readable names are useful because they're far more meaningful to the
+// user, and are what should show up in reports and questions to mrgiggles. At
+// least in most cases, it's fine to have the extra mangled name tacked onto
+// the beginning for these.
+//
+// The strategy used is to separate out the pieces whenever they are read in,
+// create a table mapping mangled names to all readable names, and use the
+// mangled names in all computation -- except for limited circumstances when
+// the readable name is used in annotations.
+//
+// Note that callgraph.txt uses a compressed representation -- each name is
+// mapped to an integer, and those integers are what is recorded in the edges.
+// But the integers depend on the full name, whereas the true edge should only
+// consider the mangled name. And some of the names encoded in callgraph.txt
+// are FieldCalls, not just function names.
+
+var gcEdges = {};
+
+// Returns whether the function was added. (It will be refused if it was
+// already there, or if attrs or annotations say it shouldn't be added.)
+function addGCFunction(caller, reason, gcFunctions, functionAttrs, functions)
+{
+    if (functionAttrs[caller] && functionAttrs[caller][1] & ATTR_GC_SUPPRESSED)
+        return false;
+
+    if (ignoreGCFunction(functions.name[caller], functions.readableName))
+        return false;
+
+    if (!(caller in gcFunctions)) {
+        gcFunctions[caller] = reason;
+        return true;
+    }
+
+    return false;
+}
+
+// Every caller->callee callsite is associated with attrs saying what is
+// allowed at that callsite (eg if it's in a GC suppression zone, it would have
+// ATTR_GC_SUPPRESSED set.) A given caller might call the same callee multiple
+// times, with different attributes. Associate the <caller,callee> edge with
+// the intersection (AND) and disjunction (OR) of all of the callsites' attrs.
+// The AND ('all') says what attributes are present for all callers; the OR
+// ('any') says what attributes are present on any caller. Preserve the
+// original order.
+//
+// During the same scan, build callersOf from calleesOf.
+function generate_callgraph(rawCallees) {
+    const callersOf = new Map();
+    const calleesOf = new Map();
+
+    for (const [caller, callee_attrs] of rawCallees) {
+        const ordered_callees = [];
+
+        // callee_attrs is a list of {callee,any,all} objects.
+        const callee2any = new Map();
+        const callee2all = new Map();
+        for (const {callee, any, all} of callee_attrs) {
+            const prev_any = callee2any.get(callee);
+            if (prev_any === undefined) {
+                assert(!callee2all.has(callee));
+                callee2any.set(callee, any);
+                callee2all.set(callee, all);
+                ordered_callees.push(callee);
+            } else {
+                const prev_all = callee2all.get(callee);
+                callee2any.set(callee, prev_any | any);
+                callee2all.set(callee, prev_all & all);
+            }
+        }
+
+        // Update the contents of callee_attrs to contain a single entry for
+        // each callee, with its attrs set to the AND of the attrs observed at
+        // all callsites within this caller function.
+        callee_attrs.length = 0;
+        for (const callee of ordered_callees) {
+            const any = callee2any.get(callee);
+            const all = callee2all.get(callee);
+            if (!calleesOf.has(caller))
+                calleesOf.set(caller, new Map());
+            calleesOf.get(caller).set(callee, {any, all});
+            if (!callersOf.has(callee))
+                callersOf.set(callee, new Map());
+            callersOf.get(callee).set(caller, {any, all});
+        }
+    }
+
+    return {callersOf, calleesOf};
+}
+
+// Returns object mapping mangled => reason for GCing
+function loadRawCallgraphFile(file, verbose)
+{
+    const functions = {
+        // "Map" from identifier to mangled name, or sometimes to a Class.Field name.
+        name: [""],
+
+        // map from mangled name => list of readable names
+        readableName: {},
+
+        mangledToId: {}
+    };
+
+    const fieldCallAttrs = {};
+    const fieldCallCSU = new Map(); // map from full field name id => csu name
+
+    // set of mangled names (map from mangled name => [any,all])
+    var functionAttrs = {};
+
+    const gcCalls = [];
+    const indirectCalls = [];
+
+    // map from mangled => list of tuples of {'callee':mangled, 'any':intset, 'all':intset}
+    const rawCallees = new Map();
+
+    for (let line of readFileLines_gen(file)) {
+        line = line.replace(/\n/, "");
+
+        let match;
+        if (match = line.charAt(0) == "#" && /^\#(\d+) (.*)/.exec(line)) {
+            const [ _, id, mangled ] = match;
+            assert(functions.name.length == id);
+            functions.name.push(mangled);
+            functions.mangledToId[mangled] = id|0;
+            continue;
+        }
+        if (match = line.charAt(0) == "=" && /^= (\d+) (.*)/.exec(line)) {
+            const [ _, id, readable ] = match;
+            const mangled = functions.name[id];
+            if (mangled in functions.readableName)
+                functions.readableName[mangled].push(readable);
+            else
+                functions.readableName[mangled] = [ readable ];
+            continue;
+        }
+
+        let attrs = 0;
+        // Example line: D /17 6 7
+        //
+        // This means a direct call from 6 -> 7, but within a scope that
+        // applies attrs 0x1 and 0x10 to the callee.
+        //
+        // Look for a bit specifier and remove it from the line if found.
+        if (line.indexOf("/") != -1) {
+            match = /^(..)\/(\d+) (.*)/.exec(line);
+            line = match[1] + match[3];
+            attrs = match[2]|0;
+        }
+        const tag = line.charAt(0);
+        if (match = tag == 'I' && /^I (\d+) VARIABLE ([^\,]*)/.exec(line)) {
+            const caller = match[1]|0;
+            const name = match[2];
+            if (indirectCallCannotGC(functions.name[caller], name))
+                attrs |= ATTR_GC_SUPPRESSED;
+            indirectCalls.push([caller, "IndirectCall: " + name, attrs]);
+        } else if (match = tag == 'F' && /^F (\d+) (\d+) CLASS (.*?) FIELD (.*)/.exec(line)) {
+            const caller = match[1]|0;
+            const fullfield = match[2]|0;
+            const csu = match[3];
+            const fullfield_str = csu + "." + match[4];
+            assert(functions.name[fullfield] == fullfield_str);
+            if (attrs)
+                fieldCallAttrs[fullfield] = attrs;
+            addToMappedList(rawCallees, caller, {callee:fullfield, any:attrs, all:attrs});
+            fieldCallCSU.set(fullfield, csu);
+
+            if (fieldCallCannotGC(csu, fullfield_str))
+                addToMappedList(rawCallees, fullfield, {callee:ID.nogcfunc, any:0, all:0});
+            else
+                addToMappedList(rawCallees, fullfield, {callee:ID.anyfunc, any:0, all:0});
+        } else if (match = tag == 'V' && /^V (\d+) (\d+) CLASS (.*?) FIELD (.*)/.exec(line)) {
+            // V tag is no longer used, but we are still emitting it becasue it
+            // can be helpful to understand what's going on.
+        } else if (match = tag == 'D' && /^D (\d+) (\d+)/.exec(line)) {
+            const caller = match[1]|0;
+            const callee = match[2]|0;
+            addToMappedList(rawCallees, caller, {callee, any:attrs, all:attrs});
+        } else if (match = tag == 'R' && /^R (\d+) (\d+)/.exec(line)) {
+            assert(false, "R tag is no longer used");
+        } else if (match = tag == 'T' && /^T (\d+) (.*)/.exec(line)) {
+            const id = match[1]|0;
+            let tag = match[2];
+            if (tag == 'GC Call')
+                gcCalls.push(id);
+        } else {
+            assert(false, "Invalid format in callgraph line: " + line);
+        }
+    }
+
+    if (verbose) {
+        printErr("Loaded[verbose=" + verbose + "] " + file);
+    }
+
+    return {
+        fieldCallAttrs,
+        fieldCallCSU,
+        gcCalls,
+        indirectCalls,
+        rawCallees,
+        functions
+    };
+}
+
+// Take a set of rawcalls filenames (as in, the raw callgraph data output by
+// computeCallgraph.js) and combine them into a global callgraph, renumbering
+// the IDs as needed.
+function mergeRawCallgraphs(filenames, verbose) {
+    let d;
+    for (const filename of filenames) {
+        const raw = loadRawCallgraphFile(filename, verbose);
+        if (!d) {
+            d = raw;
+            continue;
+        }
+
+        const {
+            fieldCallAttrs,
+            fieldCallCSU,
+            gcCalls,
+            indirectCalls,
+            rawCallees,
+            functions
+        } = raw;
+
+        // Compute the ID mapping. Incoming functions that already have an ID
+        // will be mapped to that ID; new ones will allocate a fresh ID.
+        const remap = new Array(functions.name.length);
+        for (let i = 1; i < functions.name.length; i++) {
+            const mangled = functions.name[i];
+            const old_id = d.functions.mangledToId[mangled]
+            if (old_id) {
+                remap[i] = old_id;
+            } else {
+                const newid = d.functions.name.length;
+                d.functions.mangledToId[mangled] = newid;
+                d.functions.name.push(mangled);
+                remap[i] = newid;
+                assert(!(mangled in d.functions.readableName), mangled + " readable name is already found");
+                const readables = functions.readableName[mangled];
+                if (readables !== undefined)
+                    d.functions.readableName[mangled] = readables;
+            }
+        }
+
+        for (const [fullfield, attrs] of Object.entries(fieldCallAttrs))
+            d.fieldCallAttrs[remap[fullfield]] = attrs;
+        for (const [fullfield, csu] of fieldCallCSU.entries())
+            d.fieldCallCSU.set(remap[fullfield], csu);
+        for (const call of gcCalls)
+            d.gcCalls.push(remap[call]);
+        for (const [caller, name, attrs] of indirectCalls)
+            d.indirectCalls.push([remap[caller], name, attrs]);
+        for (const [caller, callees] of rawCallees) {
+            for (const {callee, any, all} of callees) {
+                addToMappedList(d.rawCallees, remap[caller]|0, {callee:remap[callee], any, all});
+            }
+        }
+    }
+
+    return d;
+}
+
+function loadCallgraph(files, verbose)
+{
+    const {
+        fieldCallAttrs,
+        fieldCallCSU,
+        gcCalls,
+        indirectCalls,
+        rawCallees,
+        functions
+    } = mergeRawCallgraphs(files, verbose);
+
+    assert(ID.jscode == functions.mangledToId["(js-code)"]);
+    assert(ID.anyfunc == functions.mangledToId["(any-function)"]);
+    assert(ID.nogcfunc == functions.mangledToId["(nogc-function)"]);
+    assert(ID.gc == functions.mangledToId["(GC)"]);
+
+    addToMappedList(rawCallees, functions.mangledToId["(any-function)"], {callee:ID.gc, any:0, all:0});
+
+    // Compute functionAttrs: it should contain the set of functions that
+    // are *always* called within some sort of limited context (eg GC
+    // suppression).
+
+    // set of mangled names (map from mangled name => [any,all])
+    const functionAttrs = {};
+
+    // Initialize to field calls with attrs set.
+    for (var [name, attrs] of Object.entries(fieldCallAttrs))
+        functionAttrs[name] = [attrs, attrs];
+
+    // map from ID => reason
+    const gcFunctions = { [ID.gc]: 'internal' };
+
+    // Add in any extra functions at the end. (If we did this early, it would
+    // mess up the id <-> name correspondence. Also, we need to know if the
+    // functions even exist in the first place.)
+    for (var func of extraGCFunctions(functions.readableName)) {
+        addGCFunction(functions.mangledToId[func], "annotation", gcFunctions, functionAttrs, functions);
+    }
+
+    for (const func of gcCalls)
+        addToMappedList(rawCallees, func, {callee:ID.gc, any:0, all:0});
+
+    for (const [caller, indirect, attrs] of indirectCalls) {
+        const id = functions.name.length;
+        functions.name.push(indirect);
+        functions.mangledToId[indirect] = id;
+        addToMappedList(rawCallees, caller, {callee:id, any:attrs, all:attrs});
+        addToMappedList(rawCallees, id, {callee:ID.anyfunc, any:0, all:0});
+    }
+
+    // Callers have a list of callees, with duplicates (if the same function is
+    // called more than once.) Merge the repeated calls, only keeping attrs
+    // that are in force for *every* callsite of that callee. Also, generate
+    // the callersOf table at the same time.
+    //
+    // calleesOf : map from mangled => {mangled callee => {'any':intset, 'all':intset}}
+    // callersOf : map from mangled => {mangled caller => {'any':intset, 'all':intset}}
+    const {callersOf, calleesOf} = generate_callgraph(rawCallees);
+
+    // Compute functionAttrs: it should contain the set of functions that
+    // are *always* called within some sort of limited context (eg GC
+    // suppression).
+
+    // Initialize to field calls with attrs set.
+    for (var [name, attrs] of Object.entries(fieldCallAttrs))
+        functionAttrs[name] = [attrs, attrs];
+
+    // Initialize functionAttrs to the set of all functions, where each one is
+    // maximally attributed, and return a worklist containing all simple roots
+    // (nodes with no callers).
+    const simple_roots = gather_simple_roots(functionAttrs, calleesOf, callersOf);
+
+    // Traverse the graph, spreading the attrs down from the roots.
+    propagate_attrs(simple_roots, functionAttrs, calleesOf);
+
+    // There are a surprising number of "recursive roots", where there is a
+    // cycle of functions calling each other but not called by anything else,
+    // and these roots may also have descendants. Now that the above traversal
+    // has eliminated everything reachable from simple roots, traverse the
+    // remaining graph to gather up a representative function from each root
+    // cycle.
+    //
+    // Simple example: in the JS shell build, moz_xstrdup calls itself, but
+    // there are no calls to it from within js/src.
+    const recursive_roots = gather_recursive_roots(functionAttrs, calleesOf, callersOf, functions);
+
+    // And do a final traversal starting with the recursive roots.
+    propagate_attrs(recursive_roots, functionAttrs, calleesOf);
+
+    for (const [f, [any, all]] of Object.entries(functionAttrs)) {
+        // Throw out all functions with no attrs set, to reduce the size of the
+        // output. From now on, "not in functionAttrs" means [any=0, all=0].
+        if (any == 0 && all == 0)
+            delete functionAttrs[f];
+
+        // Remove GC-suppressed functions from the set of functions known to GC.
+        // Also remove functions only reachable through calls that have been
+        // replaced.
+        if (all & (ATTR_GC_SUPPRESSED | ATTR_REPLACED))
+            delete gcFunctions[name];
+    }
+
+    // functionAttrs now contains all functions that are ever called in an
+    // attributed context, based on the known callgraph (i.e., calls through
+    // function pointers are not taken into consideration.)
+
+    // Sanity check to make sure the callgraph has some functions annotated as
+    // GC Calls. This is mostly a check to be sure the earlier processing
+    // succeeded (as opposed to, say, running on empty xdb files because you
+    // didn't actually compile anything interesting.)
+    assert(gcCalls.length > 0, "No GC functions found!");
+
+    // Initialize the worklist to all known gcFunctions.
+    const worklist = [ID.gc];
+
+    // Include all field calls (but not virtual method calls).
+    for (const [name, csuName] of fieldCallCSU) {
+        const fullFieldName = functions.name[name];
+        if (!fieldCallCannotGC(csuName, fullFieldName)) {
+            gcFunctions[name] = 'arbitrary function pointer ' + fullFieldName;
+            worklist.push(name);
+        }
+    }
+
+    // Recursively find all callers not always called in a GC suppression
+    // context, and add them to the set of gcFunctions.
+    while (worklist.length) {
+        name = worklist.shift();
+        assert(name in gcFunctions, "gcFunctions does not contain " + name);
+        if (!callersOf.has(name))
+            continue;
+        for (const [caller, {any, all}] of callersOf.get(name)) {
+            if ((all & (ATTR_GC_SUPPRESSED | ATTR_REPLACED)) == 0) {
+                if (addGCFunction(caller, name, gcFunctions, functionAttrs, functions))
+                    worklist.push(caller);
+            }
+        }
+    }
+
+    // Convert functionAttrs to limitedFunctions (using mangled names instead
+    // of ids.)
+
+    // set of mangled names (map from mangled name => {any,all,recursive_root:bool}
+    var limitedFunctions = {};
+
+    for (const [id, [any, all]] of Object.entries(functionAttrs)) {
+        if (all) {
+            limitedFunctions[functions.name[id]] = { attributes: all };
+        }
+    }
+
+    for (const [id, limits, label] of recursive_roots) {
+        const name = functions.name[id];
+        const s = limitedFunctions[name] || (limitedFunctions[name] = {});
+        s.recursive_root = true;
+    }
+
+    // Remap ids to mangled names.
+    const namedGCFunctions = {};
+    for (const [caller, reason] of Object.entries(gcFunctions)) {
+        namedGCFunctions[functions.name[caller]] = functions.name[reason] || reason;
+    }
+
+    return {
+        gcFunctions: namedGCFunctions,
+        functions,
+        calleesOf,
+        callersOf,
+        limitedFunctions
+    };
+}
+
+function saveCallgraph(functions, calleesOf) {
+    // Write out all the ids and their readable names.
+    let id = -1;
+    for (const name of functions.name) {
+        id += 1;
+        if (id == 0) continue;
+        print(`#${id} ${name}`);
+        for (const readable of (functions.readableName[name] || [])) {
+            if (readable != name)
+                print(`= ${id} ${readable}`);
+        }
+    }
+
+    // Omit field calls for now; let them appear as if they were functions.
+
+    const attrstring = range => range.any || range.all ? `${range.all}:${range.any} ` : '';
+    for (const [caller, callees] of calleesOf) {
+        for (const [callee, attrs] of callees) {
+            print(`D ${attrstring(attrs)}${caller} ${callee}`);
+        }
+    }
+
+    // Omit tags for now. This really should preserve all tags. The "GC Call"
+    // tag will already be represented in the graph by having an edge to the
+    // "(GC)" node.
+}
+
+// Return a worklist of functions with no callers, and also initialize
+// functionAttrs to the set of all functions, each mapped to
+// [ATTRS_NONE, ATTRS_UNVISITED].
+function gather_simple_roots(functionAttrs, calleesOf, callersOf) {
+    const roots = [];
+    for (const callee of callersOf.keys())
+        functionAttrs[callee] = [ATTRS_NONE, ATTRS_UNVISITED];
+    for (const caller of calleesOf.keys()) {
+        functionAttrs[caller] = [ATTRS_NONE, ATTRS_UNVISITED];
+        if (!callersOf.has(caller))
+            roots.push([caller, ATTRS_NONE, 'root']);
+    }
+
+    return roots;
+}
+
+// Recursively traverse the callgraph from the roots. Recurse through every
+// edge that weakens the attrs. (Attrs that entirely disappear, ie go to a zero
+// intset, will be removed from functionAttrs.)
+function propagate_attrs(roots, functionAttrs, calleesOf) {
+    const worklist = Array.from(roots);
+    let top = worklist.length;
+    while (top > 0) {
+        // Consider caller where (graph) -> caller -> (0 or more callees)
+        // 'callercaller' is for debugging.
+        const [caller, edge_attrs, callercaller] = worklist[--top];
+        assert(caller in functionAttrs);
+        const [prev_any, prev_all] = functionAttrs[caller];
+        assert(prev_any !== undefined);
+        assert(prev_all !== undefined);
+        const [new_any, new_all] = [prev_any | edge_attrs, prev_all & edge_attrs];
+        if (prev_any != new_any || prev_all != new_all) {
+            // Update function attrs, then recurse to the children if anything
+            // was updated.
+            functionAttrs[caller] = [new_any, new_all];
+            for (const [callee, {any, all}] of (calleesOf.get(caller) || new Map))
+                worklist[top++] = [callee, all | edge_attrs, caller];
+        }
+    }
+}
+
+// Mutually-recursive roots and their descendants will not have been visited,
+// and will still be set to [0, ATTRS_UNVISITED]. Scan through and gather them.
+function gather_recursive_roots(functionAttrs, calleesOf, callersOf, functions) {
+    const roots = [];
+
+    // Pick any node. Mark everything reachable by adding to a 'seen' set. At
+    // the end, if there are any incoming edges to that node from an unmarked
+    // node, then it is not a root. Otherwise, mark the node as a root. (There
+    // will be at least one back edge coming into the node from a marked node
+    // in this case, since otherwise it would have already been considered to
+    // be a root.)
+    //
+    // Repeat with remaining unmarked nodes until all nodes are marked.
+    const seen = new Set();
+    for (let [func, [any, all]] of Object.entries(functionAttrs)) {
+        func = func|0;
+        if (all != ATTRS_UNVISITED)
+            continue;
+
+        // We should only be looking at nodes with callers, since otherwise
+        // they would have been handled in the previous pass!
+        assert(callersOf.has(func));
+        assert(callersOf.get(func).size > 0);
+
+        if (seen.has(func))
+            continue;
+
+        const work = [func];
+        while (work.length > 0) {
+            const f = work.pop();
+            if (!calleesOf.has(f)) continue;
+            for (const callee of calleesOf.get(f).keys()) {
+                if (!seen.has(callee) &&
+                    callee != func &&
+                    functionAttrs[callee][1] == ATTRS_UNVISITED)
+                {
+                    work.push(callee);
+                    seen.add(callee);
+                }
+            }
+        }
+
+        assert(!seen.has(func));
+        seen.add(func);
+        if ([...callersOf.get(func).keys()].findIndex(f => !seen.has(f)) == -1) {
+            // No unmarked incoming edges, including self-edges, so this is a
+            // (recursive) root.
+            roots.push([func, ATTRS_NONE, 'recursive-root']);
+        }
+    }
+
+    return roots;
+
+    tmp = calleesOf;
+    calleesOf = {};
+    for (const [callerId, callees] of Object.entries(calleesOf)) {
+        const caller = functionNames[callerId];
+        for (const {calleeId, limits} of callees)
+            calleesOf[caller][functionNames[calleeId]] = limits;
+    }
+
+    tmp = callersOf;
+    callersOf = {};
+    for (const [calleeId, callers] of Object.entries(callersOf)) {
+        const callee = functionNames[calleeId];
+        callersOf[callee] = {};
+        for (const {callerId, limits} of callers)
+            callersOf[callee][functionNames[caller]] = limits;
+    }
+}
diff --git a/js/src/devtools/rootAnalysis/mach_commands.py b/js/src/devtools/rootAnalysis/mach_commands.py
new file mode 100644
index 0000000000..f21cbaf45c
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mach_commands.py
@@ -0,0 +1,689 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import argparse
+import html
+import json
+import logging
+import os
+import re
+import textwrap
+import webbrowser
+
+# Command files like this are listed in build/mach_initialize.py in alphabetical
+# order, but we need to access commands earlier in the sorted order to grab
+# their arguments. Force them to load now.
+import mozbuild.artifact_commands  # NOQA: F401
+import mozbuild.build_commands  # NOQA: F401
+import mozhttpd
+from mach.base import FailedCommandError, MachError
+from mach.decorators import Command, CommandArgument, SubCommand
+from mach.registrar import Registrar
+from mozbuild.mozconfig import MozconfigLoader
+
+
+# Use a decorator to copy command arguments off of the named command. Instead
+# of a decorator, this could be straight code that edits eg
+# MachCommands.build_shell._mach_command.arguments, but that looked uglier.
+def inherit_command_args(command, subcommand=None):
+    """Decorator for inheriting all command-line arguments from `mach build`.
+
+    This should come earlier in the source file than @Command or @SubCommand,
+    because it relies on that decorator having run first."""
+
+    def inherited(func):
+        handler = Registrar.command_handlers.get(command)
+        if handler is not None and subcommand is not None:
+            handler = handler.subcommand_handlers.get(subcommand)
+        if handler is None:
+            raise MachError(
+                "{} command unknown or not yet loaded".format(
+                    command if subcommand is None else command + " " + subcommand
+                )
+            )
+        func._mach_command.arguments.extend(handler.arguments)
+        return func
+
+    return inherited
+
+
+def state_dir():
+    return os.environ.get("MOZBUILD_STATE_PATH", os.path.expanduser("~/.mozbuild"))
+
+
+def tools_dir():
+    if os.environ.get("MOZ_FETCHES_DIR"):
+        # In automation, tools are provided by toolchain dependencies.
+        return os.path.join(os.environ["HOME"], os.environ["MOZ_FETCHES_DIR"])
+
+    # In development, `mach hazard bootstrap` installs the tools separately
+    # to avoid colliding with the "main" compiler versions, which can
+    # change separately (and the precompiled sixgill and compiler version
+    # must match exactly).
+    return os.path.join(state_dir(), "hazard-tools")
+
+
+def sixgill_dir():
+    return os.path.join(tools_dir(), "sixgill")
+
+
+def gcc_dir():
+    return os.path.join(tools_dir(), "gcc")
+
+
+def script_dir(command_context):
+    return os.path.join(command_context.topsrcdir, "js/src/devtools/rootAnalysis")
+
+
+def get_work_dir(command_context, project, given):
+    if given is not None:
+        return given
+    return os.path.join(command_context.topsrcdir, "haz-" + project)
+
+
+def get_objdir(command_context, kwargs):
+    project = kwargs["project"]
+    objdir = kwargs["haz_objdir"]
+    if objdir is None:
+        objdir = os.environ.get("HAZ_OBJDIR")
+    if objdir is None:
+        objdir = os.path.join(command_context.topsrcdir, "obj-analyzed-" + project)
+    return objdir
+
+
+def ensure_dir_exists(dir):
+    os.makedirs(dir, exist_ok=True)
+    return dir
+
+
+# Force the use of hazard-compatible installs of tools.
+def setup_env_for_tools(env):
+    gccbin = os.path.join(gcc_dir(), "bin")
+    env["CC"] = os.path.join(gccbin, "gcc")
+    env["CXX"] = os.path.join(gccbin, "g++")
+    env["PATH"] = "{sixgill_dir}/usr/bin:{gccbin}:{PATH}".format(
+        sixgill_dir=sixgill_dir(), gccbin=gccbin, PATH=env["PATH"]
+    )
+
+
+def setup_env_for_shell(env, shell):
+    """Add JS shell directory to dynamic lib search path"""
+    for var in ("LD_LIBRARY_PATH", "DYLD_LIBRARY_PATH"):
+        env[var] = ":".join(p for p in (env.get(var), os.path.dirname(shell)) if p)
+
+
+@Command(
+    "hazards",
+    category="build",
+    order="declaration",
+    description="Commands for running the static analysis for GC rooting hazards",
+)
+def hazards(command_context):
+    """Commands related to performing the GC rooting hazard analysis"""
+    print("See `mach hazards --help` for a list of subcommands")
+
+
+@inherit_command_args("artifact", "toolchain")
+@SubCommand(
+    "hazards",
+    "bootstrap",
+    description="Install prerequisites for the hazard analysis",
+)
+def bootstrap(command_context, **kwargs):
+    orig_dir = os.getcwd()
+    os.chdir(ensure_dir_exists(tools_dir()))
+    try:
+        kwargs["from_build"] = ("linux64-gcc-sixgill", "linux64-gcc-9")
+        command_context._mach_context.commands.dispatch(
+            "artifact", command_context._mach_context, subcommand="toolchain", **kwargs
+        )
+    finally:
+        os.chdir(orig_dir)
+
+
+CLOBBER_CHOICES = {"objdir", "work", "shell", "all"}
+
+
+@SubCommand("hazards", "clobber", description="Clean up hazard-related files")
+@CommandArgument("--project", default="browser", help="Build the given project.")
+@CommandArgument("--application", dest="project", help="Build the given project.")
+@CommandArgument("--haz-objdir", default=None, help="Hazard analysis objdir.")
+@CommandArgument(
+    "--work-dir", default=None, help="Directory for output and working files."
+)
+@CommandArgument(
+    "what",
+    default=["objdir", "work"],
+    nargs="*",
+    help="Target to clobber, must be one of {{{}}} (default "
+    "objdir and work).".format(", ".join(CLOBBER_CHOICES)),
+)
+def clobber(command_context, what, **kwargs):
+    from mozbuild.controller.clobber import Clobberer
+
+    what = set(what)
+    if "all" in what:
+        what.update(CLOBBER_CHOICES)
+    invalid = what - CLOBBER_CHOICES
+    if invalid:
+        print(
+            "Unknown clobber target(s): {}. Choose from {{{}}}".format(
+                ", ".join(invalid), ", ".join(CLOBBER_CHOICES)
+            )
+        )
+        return 1
+
+    try:
+        substs = command_context.substs
+    except BuildEnvironmentNotFoundException:
+        substs = {}
+
+    if "objdir" in what:
+        objdir = get_objdir(command_context, kwargs)
+        print(f"removing {objdir}")
+        Clobberer(command_context.topsrcdir, objdir, substs).remove_objdir(full=True)
+    if "work" in what:
+        project = kwargs["project"]
+        work_dir = get_work_dir(command_context, project, kwargs["work_dir"])
+        print(f"removing {work_dir}")
+        Clobberer(command_context.topsrcdir, work_dir, substs).remove_objdir(full=True)
+    if "shell" in what:
+        objdir = os.path.join(command_context.topsrcdir, "obj-haz-shell")
+        print(f"removing {objdir}")
+        Clobberer(command_context.topsrcdir, objdir, substs).remove_objdir(full=True)
+
+
+@inherit_command_args("build")
+@SubCommand(
+    "hazards", "build-shell", description="Build a shell for the hazard analysis"
+)
+@CommandArgument(
+    "--mozconfig",
+    default=None,
+    metavar="FILENAME",
+    help="Build with the given mozconfig.",
+)
+def build_shell(command_context, **kwargs):
+    """Build a JS shell to use to run the rooting hazard analysis."""
+    # The JS shell requires some specific configuration settings to execute
+    # the hazard analysis code, and configuration is done via mozconfig.
+    # Subprocesses find MOZCONFIG in the environment, so we can't just
+    # modify the settings in this process's loaded version. Pass it through
+    # the environment.
+
+    default_mozconfig = "js/src/devtools/rootAnalysis/mozconfig.haz_shell"
+    mozconfig_path = (
+        kwargs.pop("mozconfig", None)
+        or os.environ.get("MOZCONFIG")
+        or default_mozconfig
+    )
+    mozconfig_path = os.path.join(command_context.topsrcdir, mozconfig_path)
+    loader = MozconfigLoader(command_context.topsrcdir)
+    mozconfig = loader.read_mozconfig(mozconfig_path)
+
+    # Validate the mozconfig settings in case the user overrode the default.
+    configure_args = mozconfig["configure_args"]
+    if "--enable-ctypes" not in configure_args:
+        raise FailedCommandError(
+            "ctypes required in hazard JS shell, mozconfig=" + mozconfig_path
+        )
+
+    # Transmit the mozconfig location to build subprocesses.
+    os.environ["MOZCONFIG"] = mozconfig_path
+
+    setup_env_for_tools(os.environ)
+
+    # Set a default objdir for the shell, for developer builds.
+    os.environ.setdefault(
+        "MOZ_OBJDIR", os.path.join(command_context.topsrcdir, "obj-haz-shell")
+    )
+
+    return command_context._mach_context.commands.dispatch(
+        "build", command_context._mach_context, **kwargs
+    )
+
+
+def read_json_file(filename):
+    with open(filename) as fh:
+        return json.load(fh)
+
+
+def ensure_shell(command_context, objdir):
+    if objdir is None:
+        objdir = os.path.join(command_context.topsrcdir, "obj-haz-shell")
+
+    try:
+        binaries = read_json_file(os.path.join(objdir, "binaries.json"))
+        info = [b for b in binaries["programs"] if b["program"] == "js"][0]
+        return os.path.join(objdir, info["install_target"], "js")
+    except (OSError, KeyError):
+        raise FailedCommandError(
+            """\
+no shell found in %s -- must build the JS shell with `mach hazards build-shell` first"""
+            % objdir
+        )
+
+
+def validate_mozconfig(command_context, kwargs):
+    app = kwargs.pop("project")
+    default_mozconfig = "js/src/devtools/rootAnalysis/mozconfig.%s" % app
+    mozconfig_path = (
+        kwargs.pop("mozconfig", None)
+        or os.environ.get("MOZCONFIG")
+        or default_mozconfig
+    )
+    mozconfig_path = os.path.join(command_context.topsrcdir, mozconfig_path)
+
+    loader = MozconfigLoader(command_context.topsrcdir)
+    mozconfig = loader.read_mozconfig(mozconfig_path)
+    configure_args = mozconfig["configure_args"]
+
+    # Require an explicit --enable-project/application=APP (even if you just
+    # want to build the default browser project.)
+    if (
+        "--enable-project=%s" % app not in configure_args
+        and "--enable-application=%s" % app not in configure_args
+    ):
+        raise FailedCommandError(
+            textwrap.dedent(
+                f"""\
+            mozconfig {mozconfig_path} builds wrong project.
+            unset MOZCONFIG to use the default {default_mozconfig}\
+            """
+            )
+        )
+
+    if not any("--with-compiler-wrapper" in a for a in configure_args):
+        raise FailedCommandError(
+            "mozconfig must wrap compiles with --with-compiler-wrapper"
+        )
+
+    return mozconfig_path
+
+
+@inherit_command_args("build")
+@SubCommand(
+    "hazards",
+    "gather",
+    description="Gather analysis data by compiling the given project",
+)
+@CommandArgument("--project", default="browser", help="Build the given project.")
+@CommandArgument("--application", dest="project", help="Build the given project.")
+@CommandArgument(
+    "--haz-objdir", default=None, help="Write object files to this directory."
+)
+@CommandArgument(
+    "--work-dir", default=None, help="Directory for output and working files."
+)
+def gather_hazard_data(command_context, **kwargs):
+    """Gather analysis information by compiling the tree"""
+    project = kwargs["project"]
+    objdir = get_objdir(command_context, kwargs)
+
+    work_dir = get_work_dir(command_context, project, kwargs["work_dir"])
+    ensure_dir_exists(work_dir)
+    with open(os.path.join(work_dir, "defaults.py"), "wt") as fh:
+        data = textwrap.dedent(
+            """\
+            analysis_scriptdir = "{script_dir}"
+            objdir = "{objdir}"
+            source = "{srcdir}"
+            sixgill = "{sixgill_dir}/usr/libexec/sixgill"
+            sixgill_bin = "{sixgill_dir}/usr/bin"
+        """
+        ).format(
+            script_dir=script_dir(command_context),
+            objdir=objdir,
+            srcdir=command_context.topsrcdir,
+            sixgill_dir=sixgill_dir(),
+            gcc_dir=gcc_dir(),
+        )
+        fh.write(data)
+
+    buildscript = " ".join(
+        [
+            command_context.topsrcdir + "/mach hazards compile",
+            *kwargs.get("what", []),
+            "--job-size=3.0",  # Conservatively estimate 3GB/process
+            "--project=" + project,
+            "--haz-objdir=" + objdir,
+        ]
+    )
+    args = [
+        os.path.join(script_dir(command_context), "run_complete"),
+        "--foreground",
+        "--no-logs",
+        "--build-root=" + objdir,
+        "--wrap-dir=" + sixgill_dir() + "/usr/libexec/sixgill/scripts/wrap_gcc",
+        "--work-dir=work",
+        "-b",
+        sixgill_dir() + "/usr/bin",
+        "--buildcommand=" + buildscript,
+        ".",
+    ]
+
+    return command_context.run_process(args=args, cwd=work_dir, pass_thru=True)
+
+
+@inherit_command_args("build")
+@SubCommand("hazards", "compile", description=argparse.SUPPRESS)
+@CommandArgument(
+    "--mozconfig",
+    default=None,
+    metavar="FILENAME",
+    help="Build with the given mozconfig.",
+)
+@CommandArgument("--project", default="browser", help="Build the given project.")
+@CommandArgument("--application", dest="project", help="Build the given project.")
+@CommandArgument(
+    "--haz-objdir",
+    default=os.environ.get("HAZ_OBJDIR"),
+    help="Write object files to this directory.",
+)
+def inner_compile(command_context, **kwargs):
+    """Build a source tree and gather analysis information while running
+    under the influence of the analysis collection server."""
+
+    env = os.environ
+
+    # Check whether we are running underneath the manager (and therefore
+    # have a server to talk to).
+    if "XGILL_CONFIG" not in env:
+        raise FailedCommandError(
+            "no sixgill manager detected. `mach hazards compile` "
+            + "should only be run from `mach hazards gather`"
+        )
+
+    mozconfig_path = validate_mozconfig(command_context, kwargs)
+
+    # Communicate mozconfig to build subprocesses.
+    env["MOZCONFIG"] = os.path.join(command_context.topsrcdir, mozconfig_path)
+
+    # hazard mozconfigs need to find binaries in .mozbuild
+    env["MOZBUILD_STATE_PATH"] = state_dir()
+
+    # Suppress the gathering of sources, to save disk space and memory.
+    env["XGILL_NO_SOURCE"] = "1"
+
+    setup_env_for_tools(env)
+
+    if "haz_objdir" in kwargs:
+        env["MOZ_OBJDIR"] = kwargs.pop("haz_objdir")
+
+    return command_context._mach_context.commands.dispatch(
+        "build", command_context._mach_context, **kwargs
+    )
+
+
+@SubCommand(
+    "hazards", "analyze", description="Analyzed gathered data for rooting hazards"
+)
+@CommandArgument(
+    "--project",
+    default="browser",
+    help="Analyze the output for the given project.",
+)
+@CommandArgument("--application", dest="project", help="Build the given project.")
+@CommandArgument(
+    "--shell-objdir",
+    default=None,
+    help="objdir containing the optimized JS shell for running the analysis.",
+)
+@CommandArgument(
+    "--work-dir", default=None, help="Directory for output and working files."
+)
+@CommandArgument(
+    "--jobs", "-j", default=None, type=int, help="Number of parallel analyzers."
+)
+@CommandArgument(
+    "--verbose",
+    "-v",
+    default=False,
+    action="store_true",
+    help="Display executed commands.",
+)
+@CommandArgument(
+    "--from-stage",
+    default=None,
+    help="Stage to begin running at ('list' to see all).",
+)
+@CommandArgument(
+    "extra",
+    nargs=argparse.REMAINDER,
+    default=(),
+    help="Remaining non-optional arguments to analyze.py script",
+)
+def analyze(
+    command_context,
+    project,
+    shell_objdir,
+    work_dir,
+    jobs,
+    verbose,
+    from_stage,
+    extra,
+):
+    """Analyzed gathered data for rooting hazards"""
+
+    shell = ensure_shell(command_context, shell_objdir)
+    args = [
+        os.path.join(script_dir(command_context), "analyze.py"),
+        "--js",
+        shell,
+        *extra,
+    ]
+
+    if from_stage is None:
+        pass
+    elif from_stage == "list":
+        args.append("--list")
+    else:
+        args.extend(["--first", from_stage])
+
+    if jobs is not None:
+        args.extend(["-j", jobs])
+
+    if verbose:
+        args.append("-v")
+
+    setup_env_for_tools(os.environ)
+    setup_env_for_shell(os.environ, shell)
+
+    work_dir = get_work_dir(command_context, project, work_dir)
+    return command_context.run_process(args=args, cwd=work_dir, pass_thru=True)
+
+
+@SubCommand(
+    "hazards",
+    "self-test",
+    description="Run a self-test to verify hazards are detected",
+)
+@CommandArgument(
+    "--shell-objdir",
+    default=None,
+    help="objdir containing the optimized JS shell for running the analysis.",
+)
+@CommandArgument(
+    "extra",
+    nargs=argparse.REMAINDER,
+    help="Remaining non-optional arguments to pass to run-test.py",
+)
+def self_test(command_context, shell_objdir, extra):
+    """Analyzed gathered data for rooting hazards"""
+    shell = ensure_shell(command_context, shell_objdir)
+    args = [
+        os.path.join(script_dir(command_context), "run-test.py"),
+        "-v",
+        "--js",
+        shell,
+        "--sixgill",
+        os.path.join(tools_dir(), "sixgill"),
+        "--gccdir",
+        gcc_dir(),
+    ]
+    args.extend(extra)
+
+    setup_env_for_tools(os.environ)
+    setup_env_for_shell(os.environ, shell)
+
+    return command_context.run_process(args=args, pass_thru=True)
+
+
+def annotated_source(filename, query):
+    """The index page has URLs of the format <http://.../path/to/source.cpp?L=m-n#m>.
+    The `#m` part will be stripped off and used by the browser to jump to the correct line.
+    The `?L=m-n` or `?L=m` parameter will be processed here on the server to highlight
+    the given line range."""
+    linequery = query.replace("L=", "")
+    if "-" in linequery:
+        line0, line1 = linequery.split("-", 1)
+    else:
+        line0, line1 = linequery or "0", linequery or "0"
+    line0 = int(line0)
+    line1 = int(line1)
+
+    fh = open(filename, "rt")
+
+    out = "<pre>"
+    for lineno, line in enumerate(fh, 1):
+        processed = f"{lineno} <span id='{lineno}'"
+        if line0 <= lineno and lineno <= line1:
+            processed += " style='background: yellow'"
+        processed += ">" + html.escape(line.rstrip()) + "</span>\n"
+        out += processed
+
+    return out
+
+
+@SubCommand(
+    "hazards", "view", description="Display a web page describing any hazards found"
+)
+@CommandArgument(
+    "--project",
+    default="browser",
+    help="Analyze the output for the given project.",
+)
+@CommandArgument("--application", dest="project", help="Build the given project.")
+@CommandArgument(
+    "--haz-objdir", default=None, help="Write object files to this directory."
+)
+@CommandArgument(
+    "--work-dir", default=None, help="Directory for output and working files."
+)
+@CommandArgument("--port", default=6006, help="Port of the web server")
+@CommandArgument(
+    "--serve-only",
+    default=False,
+    action="store_true",
+    help="Serve only, do not navigate to page",
+)
+def view_hazards(command_context, project, haz_objdir, work_dir, port, serve_only):
+    work_dir = get_work_dir(command_context, project, work_dir)
+    haztop = os.path.basename(work_dir)
+    if haz_objdir is None:
+        haz_objdir = os.environ.get("HAZ_OBJDIR")
+    if haz_objdir is None:
+        haz_objdir = os.path.join(command_context.topsrcdir, "obj-analyzed-" + project)
+
+    httpd = None
+
+    def serve_source_file(request, path):
+        info = {"req": path}
+
+        def log(fmt, level=logging.INFO):
+            return command_context.log(level, "view-hazards", info, fmt)
+
+        if path in ("", f"{haztop}"):
+            info["dest"] = f"/{haztop}/hazards.html"
+            info["code"] = 301
+            log("serve '{req}' -> {code} {dest}")
+            return (info["code"], {"Location": info["dest"]}, "")
+
+        # Allow files to be served from the source directory or the objdir.
+        roots = (command_context.topsrcdir, haz_objdir)
+
+        try:
+            # Validate the path. Some source files have weird characters in their paths (eg "+"), but they
+            # all start with an alphanumeric or underscore.
+            command_context.log(
+                logging.DEBUG, "view-hazards", {"path": path}, "Raw path: {path}"
+            )
+            path_component = r"\w[\w\-\.\+]*"
+            if not re.match(f"({path_component}/)*{path_component}$", path):
+                raise ValueError("invalid path")
+
+            # Resolve the path to under one of the roots, and
+            # ensure that the actual file really is underneath a root directory.
+            for rootdir in roots:
+                fullpath = os.path.join(rootdir, path)
+                info["path"] = fullpath
+                fullpath = os.path.realpath(fullpath)
+                if os.path.isfile(fullpath):
+                    # symlinks between roots are ok, but not symlinks outside of the roots.
+                    tops = [
+                        d
+                        for d in roots
+                        if fullpath.startswith(os.path.realpath(d) + "/")
+                    ]
+                    if len(tops) > 0:
+                        break  # Found a file underneath a root.
+            else:
+                raise IOError("not found")
+
+            html = annotated_source(fullpath, request.query)
+            log("serve '{req}' -> 200 {path}")
+            return (
+                200,
+                {"Content-type": "text/html", "Content-length": len(html)},
+                html,
+            )
+        except (IOError, ValueError):
+            log("serve '{req}' -> 404 {path}", logging.ERROR)
+            return (
+                404,
+                {"Content-type": "text/plain"},
+                "We don't have that around here. Don't be asking for it.",
+            )
+
+    httpd = mozhttpd.MozHttpd(
+        port=port,
+        docroot=None,
+        path_mappings={"/" + haztop: work_dir},
+        urlhandlers=[
+            # Treat everything not starting with /haz-browser/ (or /haz-js/)
+            # as a source file to be processed. Everything else is served
+            # as a plain file.
+            {
+                "method": "GET",
+                "path": "/(?!haz-" + project + "/)(.*)",
+                "function": serve_source_file,
+            },
+        ],
+        log_requests=True,
+    )
+
+    # The mozhttpd request handler class eats log messages.
+    httpd.handler_class.log_message = lambda self, format, *args: command_context.log(
+        logging.INFO, "view-hazards", {}, format % args
+    )
+
+    print("Serving at %s:%s" % (httpd.host, httpd.port))
+
+    httpd.start(block=False)
+    url = httpd.get_url(f"/{haztop}/hazards.html")
+    display_url = True
+    if not serve_only:
+        try:
+            webbrowser.get().open_new_tab(url)
+            display_url = False
+        except Exception:
+            pass
+    if display_url:
+        print("Please open %s in a browser." % url)
+
+    print("Hit CTRL+c to stop server.")
+    httpd.server.join()
diff --git a/js/src/devtools/rootAnalysis/mergeJSON.js b/js/src/devtools/rootAnalysis/mergeJSON.js
new file mode 100644
index 0000000000..2ac5a983db
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mergeJSON.js
@@ -0,0 +1,26 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+var infiles = [...scriptArgs];
+var outfile = infiles.pop();
+
+let output;
+for (const filename of infiles) {
+    const data = JSON.parse(os.file.readFile(filename));
+    if (!output) {
+        output = data;
+    } else if (Array.isArray(data) != Array.isArray(output)) {
+        throw new Error('mismatched types');
+    } else if (Array.isArray(output)) {
+        output.push(...data);
+    } else {
+        Object.assign(output, data);
+    }
+}
+
+var origOut = os.file.redirect(outfile);
+print(JSON.stringify(output, null, 4));
+os.file.close(os.file.redirect(origOut));
diff --git a/js/src/devtools/rootAnalysis/mozconfig.browser b/js/src/devtools/rootAnalysis/mozconfig.browser
new file mode 100644
index 0000000000..3dd50bae8e
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.browser
@@ -0,0 +1,15 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This mozconfig is used when analyzing the source code of the Firefox browser
+# for GC rooting hazards. See
+# <https://wiki.mozilla.org/Javascript:SpiderMonkey:ExactStackRooting>.
+
+ac_add_options --enable-project=browser
+ac_add_options --enable-js-shell
+
+# the sixgill wrapper is not compatible with building wasm objects with clang.
+export WASM_SANDBOXED_LIBRARIES=
+
+. $topsrcdir/js/src/devtools/rootAnalysis/mozconfig.common
diff --git a/js/src/devtools/rootAnalysis/mozconfig.common b/js/src/devtools/rootAnalysis/mozconfig.common
new file mode 100644
index 0000000000..c68fb6a26c
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.common
@@ -0,0 +1,37 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Configuration shared between browser and shell builds.
+
+# The configuration options are chosen to compile the most code
+# (--enable-debug, --enable-tests) in the trickiest way possible
+# (--enable-optimize) to maximize the chance of seeing tricky static orderings.
+ac_add_options --enable-debug
+ac_add_options --enable-tests
+ac_add_options --enable-optimize
+
+# Wrap all compiler invocations in order to enable the plugin and send
+# information to a common database.
+if [ -z "$AUTOMATION" ]; then
+    # Developer build: `mach hazards bootstrap` puts tools here:
+    TOOLS_DIR="$MOZBUILD_STATE_PATH/hazard-tools"
+else
+    # Automation build: tools are downloaded from upstream tasks.
+    TOOLS_DIR="$MOZ_FETCHES_DIR"
+fi
+ac_add_options --with-compiler-wrapper="${TOOLS_DIR}"/sixgill/usr/libexec/sixgill/scripts/wrap_gcc/basecc
+
+# Stuff that gets in the way.
+ac_add_options --without-ccache
+ac_add_options --disable-replace-malloc
+
+# -Wattributes is very verbose due to attributes being ignored on template
+# instantiations.
+#
+# -Wignored-attributes is very verbose due to attributes being
+# ignored on template parameters.
+ANALYSIS_EXTRA_CFLAGS="-Wno-attributes -Wno-ignored-attributes"
+CFLAGS="$CFLAGS $ANALYSIS_EXTRA_CFLAGS"
+CPPFLAGS="$CPPFLAGS $ANALYSIS_EXTRA_CFLAGS"
+CXXFLAGS="$CXXFLAGS $ANALYSIS_EXTRA_CFLAGS"
diff --git a/js/src/devtools/rootAnalysis/mozconfig.haz_shell b/js/src/devtools/rootAnalysis/mozconfig.haz_shell
new file mode 100644
index 0000000000..68741f0454
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.haz_shell
@@ -0,0 +1,18 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This mozconfig is for compiling the JS shell that runs the static rooting
+# hazard analysis. See
+# <https://wiki.mozilla.org/Javascript:SpiderMonkey:ExactStackRooting>.
+
+ac_add_options --enable-ctypes
+ac_add_options --enable-optimize
+ac_add_options --disable-debug
+ac_add_options --enable-project=js
+ac_add_options --enable-nspr-build
+ac_add_options --disable-jemalloc
+
+if [ -n "$AUTOMATION" ]; then
+  mk_add_options MOZ_OBJDIR="${HAZARD_SHELL_OBJDIR}"
+fi
diff --git a/js/src/devtools/rootAnalysis/mozconfig.js b/js/src/devtools/rootAnalysis/mozconfig.js
new file mode 100644
index 0000000000..07e584c210
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.js
@@ -0,0 +1,16 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This mozconfig is used when analyzing the source code of the js/src tree for
+# GC rooting hazards. See
+# <https://wiki.mozilla.org/Javascript:SpiderMonkey:ExactStackRooting>.
+
+ac_add_options --enable-project=js
+
+# Also compile NSPR to see through its part of the control flow graph (not
+# currently needed, but also helps with weird problems finding the right
+# headers.)
+ac_add_options --enable-nspr-build
+
+. $topsrcdir/js/src/devtools/rootAnalysis/mozconfig.common
diff --git a/js/src/devtools/rootAnalysis/run-analysis.sh b/js/src/devtools/rootAnalysis/run-analysis.sh
new file mode 100755
index 0000000000..157821cc92
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/run-analysis.sh
@@ -0,0 +1,4 @@
+#!/bin/sh
+
+SRCDIR=$(cd $(dirname $0)/../../../..; pwd)
+GECKO_PATH=$SRCDIR $SRCDIR/taskcluster/scripts/builder/build-haz-linux.sh $(pwd) "$@"
diff --git a/js/src/devtools/rootAnalysis/run-test.py b/js/src/devtools/rootAnalysis/run-test.py
new file mode 100755
index 0000000000..5c698a9e77
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/run-test.py
@@ -0,0 +1,154 @@
+#!/usr/bin/env python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import argparse
+import os
+import site
+import subprocess
+import sys
+from glob import glob
+
+scriptdir = os.path.abspath(os.path.dirname(__file__))
+testdir = os.path.join(scriptdir, "t")
+
+site.addsitedir(testdir)
+from testlib import Test, equal
+
+parser = argparse.ArgumentParser(description="run hazard analysis tests")
+parser.add_argument(
+    "--js", default=os.environ.get("JS"), help="JS binary to run the tests with"
+)
+parser.add_argument(
+    "--sixgill",
+    default=os.environ.get("SIXGILL", os.path.join(testdir, "sixgill")),
+    help="Path to root of sixgill installation",
+)
+parser.add_argument(
+    "--sixgill-bin",
+    default=os.environ.get("SIXGILL_BIN"),
+    help="Path to sixgill binary dir",
+)
+parser.add_argument(
+    "--sixgill-plugin",
+    default=os.environ.get("SIXGILL_PLUGIN"),
+    help="Full path to sixgill gcc plugin",
+)
+parser.add_argument(
+    "--gccdir", default=os.environ.get("GCCDIR"), help="Path to GCC installation dir"
+)
+parser.add_argument("--cc", default=os.environ.get("CC"), help="Path to gcc")
+parser.add_argument("--cxx", default=os.environ.get("CXX"), help="Path to g++")
+parser.add_argument(
+    "--verbose",
+    "-v",
+    default=0,
+    action="count",
+    help="Display verbose output, including commands executed",
+)
+ALL_TESTS = [
+    "sixgill-tree",
+    "suppression",
+    "hazards",
+    "exceptions",
+    "virtual",
+    "graph",
+    "types",
+]
+parser.add_argument(
+    "tests",
+    nargs="*",
+    default=ALL_TESTS,
+    help="tests to run",
+)
+
+cfg = parser.parse_args()
+
+if not cfg.js:
+    sys.exit("Must specify JS binary through environment variable or --js option")
+if not cfg.cc:
+    if cfg.gccdir:
+        cfg.cc = os.path.join(cfg.gccdir, "bin", "gcc")
+    else:
+        cfg.cc = "gcc"
+if not cfg.cxx:
+    if cfg.gccdir:
+        cfg.cxx = os.path.join(cfg.gccdir, "bin", "g++")
+    else:
+        cfg.cxx = "g++"
+if not cfg.sixgill_bin:
+    cfg.sixgill_bin = os.path.join(cfg.sixgill, "usr", "bin")
+if not cfg.sixgill_plugin:
+    cfg.sixgill_plugin = os.path.join(
+        cfg.sixgill, "usr", "libexec", "sixgill", "gcc", "xgill.so"
+    )
+
+subprocess.check_call(
+    [cfg.js, "-e", 'if (!getBuildConfiguration()["has-ctypes"]) quit(1)']
+)
+
+
+def binpath(prog):
+    return os.path.join(cfg.sixgill_bin, prog)
+
+
+def make_dir(dirname, exist_ok=True):
+    try:
+        os.mkdir(dirname)
+    except OSError as e:
+        if exist_ok and e.strerror == "File exists":
+            pass
+        else:
+            raise
+
+
+outroot = os.path.join(testdir, "out")
+make_dir(outroot)
+
+os.environ["HAZARD_RUN_INTERNAL_TESTS"] = "1"
+
+exclude = []
+tests = []
+for t in cfg.tests:
+    if t.startswith("!"):
+        exclude.append(t[1:])
+    else:
+        tests.append(t)
+if len(tests) == 0:
+    tests = filter(lambda t: t not in exclude, ALL_TESTS)
+
+failed = set()
+passed = set()
+for path in tests:
+    name = os.path.basename(path)
+    indir = os.path.join(testdir, name)
+    outdir = os.path.join(outroot, name)
+    make_dir(outdir)
+
+    test = Test(indir, outdir, cfg, verbose=cfg.verbose)
+
+    os.chdir(outdir)
+    for xdb in glob("*.xdb"):
+        os.unlink(xdb)
+    print("START TEST {}".format(name), flush=True)
+    testpath = os.path.join(indir, "test.py")
+    testscript = open(testpath).read()
+    testcode = compile(testscript, testpath, "exec")
+    try:
+        exec(testcode, {"test": test, "equal": equal})
+    except subprocess.CalledProcessError:
+        print("TEST-FAILED: %s" % name)
+        failed.add(name)
+    except AssertionError:
+        print("TEST-FAILED: %s" % name)
+        failed.add(name)
+        raise
+    else:
+        print("TEST-PASSED: %s" % name)
+        passed.add(name)
+
+if failed:
+    raise Exception("Failed tests: " + " ".join(failed))
+
+print(f"All {len(passed)} tests passed.")
diff --git a/js/src/devtools/rootAnalysis/run_complete b/js/src/devtools/rootAnalysis/run_complete
new file mode 100755
index 0000000000..c9355267db
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/run_complete
@@ -0,0 +1,384 @@
+#!/usr/bin/perl
+
+# Sixgill: Static assertion checker for C/C++ programs.
+# Copyright (C) 2009-2010  Stanford University
+# Author: Brian Hackett
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# do a complete run of the system from raw source to reports. this requires
+# various run_monitor processes to be running in the background (maybe on other
+# machines) and watching a shared poll_file for jobs. if the output directory
+# for this script already exists then an incremental analysis will be performed
+# and the reports will only reflect the changes since the earlier run.
+
+use strict;
+use warnings;
+use IO::Handle;
+use File::Basename qw(basename dirname);
+use Getopt::Long;
+use Cwd;
+
+#################################
+# environment specific settings #
+#################################
+
+my $WORKDIR;
+my $SIXGILL_BIN;
+
+# poll file shared with the run_monitor script.
+my $poll_file;
+
+# root directory of the project.
+my $build_dir;
+
+# directory containing gcc wrapper scripts.
+my $wrap_dir;
+
+# optional file with annotations from the web interface.
+my $ann_file = "";
+
+# optional output directory to do a diff against.
+my $old_dir = "";
+
+# run in the foreground
+my $foreground;
+
+my $builder = "make -j4";
+
+my $suppress_logs;
+GetOptions("build-root|b=s" => \$build_dir,
+           "poll-file=s" => \$poll_file,
+           "no-logs!" => \$suppress_logs,
+           "work-dir=s" => \$WORKDIR,
+           "sixgill-binaries|binaries|b=s" => \$SIXGILL_BIN,
+           "wrap-dir=s" => \$wrap_dir,
+           "annotations-file|annotations|a=s" => \$ann_file,
+           "old-dir|old=s" => \$old_dir,
+           "foreground!" => \$foreground,
+           "buildcommand=s" => \$builder,
+           )
+    or die;
+
+if (not -d $build_dir) {
+    mkdir($build_dir);
+}
+if ($old_dir ne "" && not -d $old_dir) {
+    die "Old directory '$old_dir' does not exist\n";
+}
+
+$WORKDIR ||= "sixgill-work";
+mkdir($WORKDIR, 0755) if ! -d $WORKDIR;
+$poll_file ||= "$WORKDIR/poll.file";
+$build_dir ||= "$WORKDIR/js-inbound-xgill";
+
+if (!defined $SIXGILL_BIN) {
+    chomp(my $path = `which xmanager`);
+    if ($path) {
+        use File::Basename qw(dirname);
+        $SIXGILL_BIN = dirname($path);
+    } else {
+        die "Cannot find sixgill binaries. Use the -b option.";
+    }
+}
+
+$wrap_dir ||= "$WORKDIR/xgill-inbound/wrap_gcc";
+$wrap_dir = "$SIXGILL_BIN/../scripts/wrap_gcc" if not (-e "$wrap_dir/basecc");
+die "Bad wrapper directory: $wrap_dir" if not (-e "$wrap_dir/basecc");
+
+# code to clean the project from $build_dir.
+sub clean_project {
+    system("make clean");
+}
+
+# code to build the project from $build_dir.
+sub build_project {
+    return system($builder) >> 8;
+}
+
+our %kill_on_exit;
+END {
+    for my $pid (keys %kill_on_exit) {
+        kill($pid);
+    }
+}
+
+# commands to start the various xgill binaries. timeouts can be specified
+# for the backend analyses here, and a memory limit can be specified for
+# xmanager if desired (and USE_COUNT_ALLOCATOR is defined in util/alloc.h).
+my $xmanager = "$SIXGILL_BIN/xmanager";
+my $xsource = "$SIXGILL_BIN/xsource";
+my $xmemlocal = "$SIXGILL_BIN/xmemlocal -timeout=20";
+my $xinfer = "$SIXGILL_BIN/xinfer -timeout=60";
+my $xcheck = "$SIXGILL_BIN/xcheck -timeout=30";
+
+# prefix directory to strip off source files.
+my $prefix_dir = $build_dir;
+
+##########################
+# general purpose script #
+##########################
+
+# Prevent ccache from being used. I don't think this does any good. The problem
+# I'm struggling with is that if autoconf.mk still has 'ccache gcc' in it, the
+# builds fail in a mysterious way.
+$ENV{CCACHE_COMPILERCHECK} = 'date +%s.%N';
+delete $ENV{CCACHE_PREFIX};
+
+my $usage = "USAGE: run_complete result-dir\n";
+my $result_dir = shift or die $usage;
+
+if (not $foreground) {
+    my $pid = fork();
+    if ($pid != 0) {
+        print "Forked, exiting...\n";
+        exit(0);
+    }
+}
+
+# if the result directory does not already exist, mark for a clean build.
+my $do_clean = 0;
+if (not (-d $result_dir)) {
+    $do_clean = 1;
+    mkdir $result_dir;
+}
+
+if (!$suppress_logs) {
+    my $log_file = "$result_dir/complete.log";
+    open(OUT, ">>", $log_file) or die "append to $log_file: $!";
+    OUT->autoflush(1);  # don't buffer writes to the main log.
+
+    # redirect stdout and stderr to the log.
+    STDOUT->fdopen(\*OUT, "w");
+    STDERR->fdopen(\*OUT, "w");
+}
+
+# pids to wait on before exiting. these are collating worker output.
+my @waitpids;
+
+chdir $result_dir;
+
+# to do a partial run, comment out the commands here you don't want to do.
+
+my $status = run_build();
+
+# end of run commands.
+
+for my $pid (@waitpids) {
+    waitpid($pid, 0);
+    $status ||= $? >> 8;
+}
+
+print "Exiting run_complete with status $status\n";
+exit $status;
+
+# get the IP address which a freshly created manager is listening on.
+sub get_manager_address
+{
+    my $log_file = shift or die;
+
+    # give the manager one second to start, any longer and something's broken.
+    sleep(1);
+
+    my $log_data = `cat $log_file`;
+    my ($port) = $log_data =~ /Listening on ([\.\:0-9]*)/
+      or die "no manager found";
+    print OUT "Connecting to manager on port $port\n" unless $suppress_logs;
+    print "Connecting to manager on port $port.\n";
+    return $1;
+}
+
+sub logging_suffix {
+    my ($show_logs, $log_file) = @_;
+    return $show_logs ? "2>&1 | tee $log_file"
+                      : "> $log_file 2>&1";
+}
+
+sub run_build
+{
+    print "build started: ";
+    print scalar(localtime());
+    print "\n";
+
+    # fork off a process to run the build.
+    defined(my $pid = fork) or die;
+
+    # log file for the manager.
+    my $manager_log_file = "$result_dir/build_manager.log";
+
+    if (!$pid) {
+        # this is the child process, fork another process to run a manager.
+        defined(my $pid = fork) or die;
+        my $logging = logging_suffix($suppress_logs, $manager_log_file);
+        exec("$xmanager -terminate-on-assert $logging") if (!$pid);
+        $kill_on_exit{$pid} = 1;
+
+        if (!$suppress_logs) {
+            # open new streams to redirect stdout and stderr.
+            open(LOGOUT, "> $result_dir/build.log");
+            open(LOGERR, "> $result_dir/build_err.log");
+            STDOUT->fdopen(\*LOGOUT, "w");
+            STDERR->fdopen(\*LOGERR, "w");
+        }
+
+        my $address = get_manager_address($manager_log_file);
+
+        # write the configuration file for the wrapper script.
+        my $config_file = "$WORKDIR/xgill.config";
+        open(CONFIG, ">", $config_file) or die "create $config_file: $!";
+        print CONFIG "$prefix_dir\n";
+        print CONFIG Cwd::abs_path("$result_dir/build_xgill.log")."\n";
+        print CONFIG "$address\n";
+        my @extra = ("-fplugin-arg-xgill-mangle=1");
+        push(@extra, "-fplugin-arg-xgill-annfile=$ann_file")
+            if ($ann_file ne "" && -e $ann_file);
+        print CONFIG join(" ", @extra) . "\n";
+        close(CONFIG);
+
+	# Tell the wrapper where to find the config
+	$ENV{"XGILL_CONFIG"} = Cwd::abs_path($config_file);
+
+        # If overriding $CC, use GCCDIR to tell the wrapper scripts where the
+        # real compiler is. If $CC is not set, then the wrapper script will
+        # search $PATH anyway.
+        if (exists $ENV{CC}) {
+            $ENV{GCCDIR} = dirname($ENV{CC});
+        }
+
+        # Force the wrapper scripts to be run in place of the compiler during
+        # whatever build process we use.
+        $ENV{CC} = "$wrap_dir/" . basename($ENV{CC} // "gcc");
+        $ENV{CXX} = "$wrap_dir/" . basename($ENV{CXX} // "g++");
+
+        # do the build, cleaning if necessary.
+        chdir $build_dir;
+        clean_project() if ($do_clean);
+        my $exit_status = build_project();
+
+        # signal the manager that it's over.
+        system("$xsource -remote=$address -end-manager");
+
+        # wait for the manager to clean up and terminate.
+        print "Waiting for manager to finish (build status $exit_status)...\n";
+        waitpid($pid, 0);
+        my $manager_status = $?;
+        delete $kill_on_exit{$pid};
+
+        # build is finished, the complete run can resume.
+        # return value only useful if --foreground
+        print "Exiting with status " . ($manager_status || $exit_status) . "\n";
+        exit($manager_status || $exit_status);
+    }
+
+    # this is the complete process, wait for the build to finish.
+    waitpid($pid, 0);
+    my $status = $? >> 8;
+    print "build finished (status $status): ";
+    print scalar(localtime());
+    print "\n";
+
+    return $status;
+}
+
+sub run_pass
+{
+    my ($name, $command) = @_;
+    my $log_file = "$result_dir/manager.$name.log";
+
+    # extra commands to pass to the manager.
+    my $manager_extra = "";
+    $manager_extra .= "-modset-wait=10" if ($name eq "xmemlocal");
+
+    # fork off a manager process for the analysis.
+    defined(my $pid = fork) or die;
+    my $logging = logging_suffix($suppress_logs, $log_file);
+    exec("$xmanager $manager_extra $logging") if (!$pid);
+
+    my $address = get_manager_address($log_file);
+
+    # write the poll file for this pass.
+    if (! -d dirname($poll_file)) {
+        system("mkdir", "-p", dirname($poll_file));
+    }
+    open(POLL, "> $poll_file");
+    print POLL "$command\n";
+    print POLL "$result_dir/$name\n";
+    print POLL "$address\n";
+    close(POLL);
+
+    print "$name started: ";
+    print scalar(localtime());
+    print "\n";
+
+    waitpid($pid, 0);
+    unlink($poll_file);
+
+    print "$name finished: ";
+    print scalar(localtime());
+    print "\n";
+
+    # collate the worker's output into a single file. make this asynchronous
+    # so we can wait a bit and make sure we get all worker output.
+    defined($pid = fork) or die;
+
+    if (!$pid) {
+        sleep(20);
+        exec("cat $name.*.log > $name.log");
+    }
+
+    push(@waitpids, $pid);
+}
+
+# the names of all directories containing reports to archive.
+my $indexes;
+
+sub run_index
+{
+    my ($name, $kind) = @_;
+
+    return if (not (-e "report_$kind.xdb"));
+
+    print "$name started: ";
+    print scalar(localtime());
+    print "\n";
+
+    # make an index for the report diff if applicable.
+    if ($old_dir ne "") {
+        system("make_index $kind $old_dir > $name.diff.log");
+        system("mv $kind diff_$kind");
+        $indexes .= " diff_$kind";
+    }
+
+    # make an index for the full set of reports.
+    system("make_index $kind > $name.log");
+    $indexes .= " $kind";
+
+    print "$name finished: ";
+    print scalar(localtime());
+    print "\n";
+}
+
+sub archive_indexes
+{
+    print "archive started: ";
+    print scalar(localtime());
+    print "\n";
+
+    system("tar -czf reports.tgz $indexes");
+    system("rm -rf $indexes");
+
+    print "archive finished: ";
+    print scalar(localtime());
+    print "\n";
+}
diff --git a/js/src/devtools/rootAnalysis/t/exceptions/source.cpp b/js/src/devtools/rootAnalysis/t/exceptions/source.cpp
new file mode 100644
index 0000000000..8d38a790a1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/exceptions/source.cpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Simply including <exception> was enough to crash sixgill at one point.
+#include <exception>
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+class RAII_GC {
+ public:
+  RAII_GC() {}
+  ~RAII_GC() { GC(); }
+};
+
+// ~AutoSomething calls GC because of the RAII_GC field. The constructor,
+// though, should *not* GC -- unless it throws an exception. Which is not
+// possible when compiled with -fno-exceptions. This test will try it both
+// ways.
+class AutoSomething {
+  RAII_GC gc;
+
+ public:
+  AutoSomething() : gc() {
+    asm("");  // Ooh, scary, this might throw an exception
+  }
+  ~AutoSomething() { asm(""); }
+};
+
+extern Cell* getcell();
+
+extern void usevar(Cell* cell);
+
+void f() {
+  Cell* thing = getcell();  // Live range starts here
+
+  // When compiling with -fexceptions, there should be a hazard below. With
+  // -fno-exceptions, there should not be one. We will check both.
+  {
+    AutoSomething smth;  // Constructor can GC only if exceptions are enabled
+    usevar(thing);       // Live range ends here
+  }  // In particular, 'thing' is dead at the destructor, so no hazard
+}
diff --git a/js/src/devtools/rootAnalysis/t/exceptions/test.py b/js/src/devtools/rootAnalysis/t/exceptions/test.py
new file mode 100644
index 0000000000..a40753d87a
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/exceptions/test.py
@@ -0,0 +1,21 @@
+# flake8: noqa: F821
+
+test.compile("source.cpp", "-fno-exceptions")
+test.run_analysis_script("gcTypes")
+
+hazards = test.load_hazards()
+assert len(hazards) == 0
+
+# If we compile with exceptions, then there *should* be a hazard because
+# AutoSomething::AutoSomething might throw an exception, which would cause the
+# partially-constructed value to be torn down, which will call ~RAII_GC.
+
+test.compile("source.cpp", "-fexceptions")
+test.run_analysis_script("gcTypes")
+
+hazards = test.load_hazards()
+assert len(hazards) == 1
+hazard = hazards[0]
+assert hazard.function == "void f()"
+assert hazard.variable == "thing"
+assert "AutoSomething::AutoSomething" in hazard.GCFunction
diff --git a/js/src/devtools/rootAnalysis/t/graph/source.cpp b/js/src/devtools/rootAnalysis/t/graph/source.cpp
new file mode 100644
index 0000000000..0adff8d532
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/graph/source.cpp
@@ -0,0 +1,90 @@
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+extern void g(int x);
+extern void h(int x);
+
+void f(int x) {
+  if (x % 3) {
+    GC();
+    g(x);
+  }
+  h(x);
+}
+
+void g(int x) {
+  if (x % 2) f(x);
+  h(x);
+}
+
+void h(int x) {
+  if (x) {
+    f(x - 1);
+    g(x - 1);
+  }
+}
+
+void leaf() { asm(""); }
+
+void nonrecursive_root() {
+  leaf();
+  leaf();
+  GC();
+}
+
+void self_recursive(int x) {
+  if (x) self_recursive(x - 1);
+}
+
+// Set up the graph
+//
+//   n1 <--> n2          n4 <--> n5
+//           \                  /
+//            --> n3 <---------
+//                 \
+//                  ---> n6 --> n7 <---> n8 --> n9
+//
+// So recursive roots are one of (n1, n2) plus one of (n4, n5).
+extern void n1(int x);
+extern void n2(int x);
+extern void n3(int x);
+extern void n4(int x);
+extern void n5(int x);
+extern void n6(int x);
+extern void n7(int x);
+extern void n8(int x);
+extern void n9(int x);
+
+void n1(int x) { n2(x); }
+
+void n2(int x) {
+  if (x) n1(x - 1);
+  n3(x);
+}
+
+void n4(int x) { n5(x); }
+
+void n5(int x) {
+  if (x) n4(x - 1);
+  n3(x);
+}
+
+void n3(int x) { n6(x); }
+
+void n6(int x) { n7(x); }
+
+void n7(int x) { n8(x); }
+
+void n8(int x) {
+  if (x) n7(x - 1);
+  n9(x);
+}
+
+void n9(int x) { asm(""); }
diff --git a/js/src/devtools/rootAnalysis/t/graph/test.py b/js/src/devtools/rootAnalysis/t/graph/test.py
new file mode 100644
index 0000000000..f78500f200
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/graph/test.py
@@ -0,0 +1,54 @@
+# 'test' is provided by the calling script.
+# flake8: noqa: F821
+
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes")
+
+info = test.load_typeInfo()
+
+gcFunctions = test.load_gcFunctions()
+
+f = "void f(int32)"
+g = "void g(int32)"
+h = "void h(int32)"
+
+assert f in gcFunctions
+assert g in gcFunctions
+assert h in gcFunctions
+assert "void leaf()" not in gcFunctions
+assert "void nonrecursive_root()" in gcFunctions
+
+callgraph = test.load_callgraph()
+assert callgraph.calleeGraph[f][g]
+assert callgraph.calleeGraph[f][h]
+assert callgraph.calleeGraph[g][f]
+assert callgraph.calleeGraph[g][h]
+
+node = ["void n{}(int32)".format(i) for i in range(10)]
+mnode = [callgraph.unmangledToMangled.get(f) for f in node]
+for src, dst in [
+    (1, 2),
+    (2, 1),
+    (4, 5),
+    (5, 4),
+    (2, 3),
+    (5, 3),
+    (3, 6),
+    (6, 7),
+    (7, 8),
+    (8, 7),
+    (8, 9),
+]:
+    assert callgraph.calleeGraph[node[src]][node[dst]]
+
+funcInfo = test.load_funcInfo()
+rroots = set(
+    [
+        callgraph.mangledToUnmangled[f]
+        for f in funcInfo
+        if funcInfo[f].get("recursive_root")
+    ]
+)
+assert len(set([node[1], node[2]]) & rroots) == 1
+assert len(set([node[4], node[5]]) & rroots) == 1
+assert len(rroots) == 4, "rroots = {}".format(rroots)  # n1, n4, f, self_recursive
diff --git a/js/src/devtools/rootAnalysis/t/hazards/source.cpp b/js/src/devtools/rootAnalysis/t/hazards/source.cpp
new file mode 100644
index 0000000000..fe991653af
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/hazards/source.cpp
@@ -0,0 +1,566 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <utility>
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+// MarkVariableAsGCSafe is a magic function name used as an
+// explicit annotation.
+
+namespace JS {
+namespace detail {
+template <typename T>
+static void MarkVariableAsGCSafe(T&) {
+  asm("");
+}
+}  // namespace detail
+}  // namespace JS
+
+#define JS_HAZ_VARIABLE_IS_GC_SAFE(var) JS::detail::MarkVariableAsGCSafe(var)
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+template <typename T, typename U>
+struct UntypedContainer {
+  char data[sizeof(T) + sizeof(U)];
+} ANNOTATE("moz_inherit_type_annotations_from_template_args");
+
+struct RootedCell {
+  RootedCell(Cell*) {}
+} ANNOTATE("Rooted Pointer");
+
+class AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Base() {}
+  ~AutoSuppressGC_Base() {}
+} ANNOTATE("Suppress GC");
+
+class AutoSuppressGC_Child : public AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Child() : AutoSuppressGC_Base() {}
+};
+
+class AutoSuppressGC {
+  AutoSuppressGC_Child helpImBeingSuppressed;
+
+ public:
+  AutoSuppressGC() {}
+};
+
+class AutoCheckCannotGC {
+ public:
+  AutoCheckCannotGC() {}
+  ~AutoCheckCannotGC() { asm(""); }
+} ANNOTATE("Invalidated by GC");
+
+extern void GC() ANNOTATE("GC Call");
+extern void invisible();
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+  invisible();
+}
+
+extern void usecell(Cell*);
+
+extern bool flipcoin();
+
+void suppressedFunction() {
+  GC();  // Calls GC, but is always called within AutoSuppressGC
+}
+
+void halfSuppressedFunction() {
+  GC();  // Calls GC, but is sometimes called within AutoSuppressGC
+}
+
+void unsuppressedFunction() {
+  GC();  // Calls GC, never within AutoSuppressGC
+}
+
+class IDL_Interface {
+ public:
+  ANNOTATE("Can run script") virtual void canScriptThis() {}
+  virtual void cannotScriptThis() {}
+  ANNOTATE("Can run script") virtual void overridden_canScriptThis() = 0;
+  virtual void overridden_cannotScriptThis() = 0;
+};
+
+class IDL_Subclass : public IDL_Interface {
+  ANNOTATE("Can run script") void overridden_canScriptThis() override {}
+  void overridden_cannotScriptThis() override {}
+};
+
+volatile static int x = 3;
+volatile static int* xp = &x;
+struct GCInDestructor {
+  ~GCInDestructor() {
+    invisible();
+    asm("");
+    *xp = 4;
+    GC();
+  }
+};
+
+template <typename T>
+void usecontainer(T* value) {
+  if (value) asm("");
+}
+
+Cell* cell() {
+  static Cell c;
+  return &c;
+}
+
+Cell* f() {
+  GCInDestructor kaboom;
+
+  Cell* cell1 = cell();
+  Cell* cell2 = cell();
+  Cell* cell3 = cell();
+  Cell* cell4 = cell();
+  {
+    AutoSuppressGC nogc;
+    suppressedFunction();
+    halfSuppressedFunction();
+  }
+  usecell(cell1);
+  halfSuppressedFunction();
+  usecell(cell2);
+  unsuppressedFunction();
+  {
+    // Old bug: it would look from the first AutoSuppressGC constructor it
+    // found to the last destructor. This statement *should* have no effect.
+    AutoSuppressGC nogc;
+  }
+  usecell(cell3);
+  Cell* cell5 = cell();
+  usecell(cell5);
+
+  {
+    // Templatized container that inherits attributes from Cell*, should
+    // report a hazard.
+    UntypedContainer<int, Cell*> container1;
+    usecontainer(&container1);
+    GC();
+    usecontainer(&container1);
+  }
+
+  {
+    // As above, but with a non-GC type.
+    UntypedContainer<int, double> container2;
+    usecontainer(&container2);
+    GC();
+    usecontainer(&container2);
+  }
+
+  // Hazard in return value due to ~GCInDestructor
+  Cell* cell6 = cell();
+  return cell6;
+}
+
+Cell* copy_and_gc(Cell* src) {
+  GC();
+  return reinterpret_cast<Cell*>(88);
+}
+
+void use(Cell* cell) {
+  static int x = 0;
+  if (cell) x++;
+}
+
+struct CellContainer {
+  Cell* cell;
+  CellContainer() { asm(""); }
+};
+
+void loopy() {
+  Cell cell;
+
+  // No hazard: haz1 is not live during call to copy_and_gc.
+  Cell* haz1;
+  for (int i = 0; i < 10; i++) {
+    haz1 = copy_and_gc(haz1);
+  }
+
+  // No hazard: haz2 is live up to just before the GC, and starting at the
+  // next statement after it, but not across the GC.
+  Cell* haz2 = &cell;
+  for (int j = 0; j < 10; j++) {
+    use(haz2);
+    GC();
+    haz2 = &cell;
+  }
+
+  // Hazard: haz3 is live from the final statement in one iteration, across
+  // the GC in the next, to the use in the 2nd statement.
+  Cell* haz3;
+  for (int k = 0; k < 10; k++) {
+    GC();
+    use(haz3);
+    haz3 = &cell;
+  }
+
+  // Hazard: haz4 is live across a GC hidden in a loop.
+  Cell* haz4 = &cell;
+  for (int i2 = 0; i2 < 10; i2++) {
+    GC();
+  }
+  use(haz4);
+
+  // Hazard: haz5 is live from within a loop across a GC.
+  Cell* haz5;
+  for (int i3 = 0; i3 < 10; i3++) {
+    haz5 = &cell;
+  }
+  GC();
+  use(haz5);
+
+  // No hazard: similar to the haz3 case, but verifying that we do not get
+  // into an infinite loop.
+  Cell* haz6;
+  for (int i4 = 0; i4 < 10; i4++) {
+    GC();
+    haz6 = &cell;
+  }
+
+  // No hazard: haz7 is constructed within the body, so it can't make a
+  // hazard across iterations. Note that this requires CellContainer to have
+  // a constructor, because otherwise the analysis doesn't see where
+  // variables are declared. (With the constructor, it knows that
+  // construction of haz7 obliterates any previous value it might have had.
+  // Not that that's possible given its scope, but the analysis doesn't get
+  // that information.)
+  for (int i5 = 0; i5 < 10; i5++) {
+    GC();
+    CellContainer haz7;
+    use(haz7.cell);
+    haz7.cell = &cell;
+  }
+
+  // Hazard: make sure we *can* see hazards across iterations involving
+  // CellContainer;
+  CellContainer haz8;
+  for (int i6 = 0; i6 < 10; i6++) {
+    GC();
+    use(haz8.cell);
+    haz8.cell = &cell;
+  }
+}
+
+namespace mozilla {
+template <typename T>
+class UniquePtr {
+  T* val;
+
+ public:
+  UniquePtr() : val(nullptr) { asm(""); }
+  UniquePtr(T* p) : val(p) {}
+  UniquePtr(UniquePtr<T>&& u) : val(u.val) { u.val = nullptr; }
+  ~UniquePtr() { use(val); }
+  T* get() { return val; }
+  void reset() { val = nullptr; }
+} ANNOTATE("moz_inherit_type_annotations_from_template_args");
+}  // namespace mozilla
+
+extern void consume(mozilla::UniquePtr<Cell> uptr);
+
+void safevals() {
+  Cell cell;
+
+  // Simple hazard.
+  Cell* unsafe1 = &cell;
+  GC();
+  use(unsafe1);
+
+  // Safe because it's known to be nullptr.
+  Cell* safe2 = &cell;
+  safe2 = nullptr;
+  GC();
+  use(safe2);
+
+  // Unsafe because it may not be nullptr.
+  Cell* unsafe3 = &cell;
+  if (reinterpret_cast<long>(&cell) & 0x100) {
+    unsafe3 = nullptr;
+  }
+  GC();
+  use(unsafe3);
+
+  // Unsafe because it's not nullptr anymore.
+  Cell* unsafe3b = &cell;
+  unsafe3b = nullptr;
+  unsafe3b = &cell;
+  GC();
+  use(unsafe3b);
+
+  // Hazard involving UniquePtr.
+  {
+    mozilla::UniquePtr<Cell> unsafe4(&cell);
+    GC();
+    // Destructor uses unsafe4.
+  }
+
+  // reset() to safe value before the GC.
+  {
+    mozilla::UniquePtr<Cell> safe5(&cell);
+    safe5.reset();
+    GC();
+  }
+
+  // reset() to safe value after the GC.
+  {
+    mozilla::UniquePtr<Cell> safe6(&cell);
+    GC();
+    safe6.reset();
+  }
+
+  // reset() to safe value after the GC -- but we've already used it, so it's
+  // too late.
+  {
+    mozilla::UniquePtr<Cell> unsafe7(&cell);
+    GC();
+    use(unsafe7.get());
+    unsafe7.reset();
+  }
+
+  // initialized to safe value.
+  {
+    mozilla::UniquePtr<Cell> safe8;
+    GC();
+  }
+
+  // passed to a function that takes ownership before GC.
+  {
+    mozilla::UniquePtr<Cell> safe9(&cell);
+    consume(std::move(safe9));
+    GC();
+  }
+
+  // passed to a function that takes ownership after GC.
+  {
+    mozilla::UniquePtr<Cell> unsafe10(&cell);
+    GC();
+    consume(std::move(unsafe10));
+  }
+
+  // annotated to be safe before the GC. (This doesn't make
+  // a lot of sense here; the annotation is for when some
+  // type is known to only contain safe values, eg it is
+  // initialized as empty, or it is a union and we know
+  // that the GC pointer variants are not in use.)
+  {
+    mozilla::UniquePtr<Cell> safe11(&cell);
+    JS_HAZ_VARIABLE_IS_GC_SAFE(safe11);
+    GC();
+  }
+
+  // annotate as safe value after the GC -- since nothing else
+  // has touched the variable, that means it was already safe
+  // during the GC.
+  {
+    mozilla::UniquePtr<Cell> safe12(&cell);
+    GC();
+    JS_HAZ_VARIABLE_IS_GC_SAFE(safe12);
+  }
+
+  // annotate as safe after the GC -- but we've already used it, so it's
+  // too late.
+  {
+    mozilla::UniquePtr<Cell> unsafe13(&cell);
+    GC();
+    use(unsafe13.get());
+    JS_HAZ_VARIABLE_IS_GC_SAFE(unsafe13);
+  }
+
+  // Check JS_HAZ_CAN_RUN_SCRIPT annotation handling.
+  IDL_Subclass sub;
+  IDL_Subclass* subp = &sub;
+  IDL_Interface* base = &sub;
+  {
+    Cell* unsafe14 = &cell;
+    base->canScriptThis();
+    use(unsafe14);
+  }
+  {
+    Cell* unsafe15 = &cell;
+    subp->canScriptThis();
+    use(unsafe15);
+  }
+  {
+    // Almost the same as the last one, except call using the actual object, not
+    // a pointer. The type is known, so there is no danger of the actual type
+    // being a subclass that has overridden the method with an implementation
+    // that calls script.
+    Cell* safe16 = &cell;
+    sub.canScriptThis();
+    use(safe16);
+  }
+  {
+    Cell* safe17 = &cell;
+    base->cannotScriptThis();
+    use(safe17);
+  }
+  {
+    Cell* safe18 = &cell;
+    subp->cannotScriptThis();
+    use(safe18);
+  }
+  {
+    // A use after a GC, but not before. (This does not initialize safe19 by
+    // setting it to a value, because assignment would start its live range, and
+    // this test is to see if a variable with no known live range start requires
+    // a use before the GC or not. It should.)
+    Cell* safe19;
+    GC();
+    extern void initCellPtr(Cell**);
+    initCellPtr(&safe19);
+  }
+}
+
+// Make sure `this` is live at the beginning of a function.
+class Subcell : public Cell {
+  int method() {
+    GC();
+    return f;  // this->f
+  }
+};
+
+template <typename T>
+struct RefPtr {
+  ~RefPtr() { GC(); }
+  bool forget() { return true; }
+  bool use() { return true; }
+  void assign_with_AddRef(T* aRawPtr) { asm(""); }
+};
+
+extern bool flipcoin();
+
+Cell* refptr_test1() {
+  static Cell cell;
+  RefPtr<float> v1;
+  Cell* ref_unsafe1 = &cell;
+  return ref_unsafe1;
+}
+
+Cell* refptr_test2() {
+  static Cell cell;
+  RefPtr<float> v2;
+  Cell* ref_safe2 = &cell;
+  v2.forget();
+  return ref_safe2;
+}
+
+Cell* refptr_test3() {
+  static Cell cell;
+  RefPtr<float> v3;
+  Cell* ref_unsafe3 = &cell;
+  if (x) {
+    v3.forget();
+  }
+  return ref_unsafe3;
+}
+
+Cell* refptr_test4() {
+  static Cell cell;
+  RefPtr<int> r;
+  return &cell;  // hazard in return value
+}
+
+Cell* refptr_test5() {
+  static Cell cell;
+  RefPtr<int> r;
+  return nullptr;  // returning immobile value, so no hazard
+}
+
+float somefloat = 1.2;
+
+Cell* refptr_test6() {
+  static Cell cell;
+  RefPtr<float> v6;
+  Cell* ref_unsafe6 = &cell;
+  // v6 can be used without an intervening forget() before the end of the
+  // function, even though forget() will be called at least once.
+  v6.forget();
+  if (x) {
+    v6.forget();
+    v6.assign_with_AddRef(&somefloat);
+  }
+  return ref_unsafe6;
+}
+
+Cell* refptr_test7() {
+  static Cell cell;
+  RefPtr<float> v7;
+  Cell* ref_unsafe7 = &cell;
+  // Similar to above, but with a loop.
+  while (flipcoin()) {
+    v7.forget();
+    v7.assign_with_AddRef(&somefloat);
+  }
+  return ref_unsafe7;
+}
+
+Cell* refptr_test8() {
+  static Cell cell;
+  RefPtr<float> v8;
+  Cell* ref_unsafe8 = &cell;
+  // If the loop is traversed, forget() will be called. But that doesn't
+  // matter, because even on the last iteration v8.use() will have been called
+  // (and potentially dropped the refcount or whatever.)
+  while (v8.use()) {
+    v8.forget();
+  }
+  return ref_unsafe8;
+}
+
+Cell* refptr_test9() {
+  static Cell cell;
+  RefPtr<float> v9;
+  Cell* ref_safe9 = &cell;
+  // Even when not going through the loop, forget() will be called and so the
+  // dtor will not Release.
+  while (v9.forget()) {
+    v9.assign_with_AddRef(&somefloat);
+  }
+  return ref_safe9;
+}
+
+Cell* refptr_test10() {
+  static Cell cell;
+  RefPtr<float> v10;
+  Cell* ref_unsafe10 = &cell;
+  // The destructor has a backwards path that skips the loop body.
+  v10.assign_with_AddRef(&somefloat);
+  while (flipcoin()) {
+    v10.forget();
+  }
+  return ref_unsafe10;
+}
+
+std::pair<bool, AutoCheckCannotGC> pair_returning_function() {
+  return std::make_pair(true, AutoCheckCannotGC());
+}
+
+void aggr_init_unsafe() {
+  // nogc will be live after the call, so across the GC.
+  auto [ok, nogc] = pair_returning_function();
+  GC();
+}
+
+void aggr_init_safe() {
+  // The analysis should be able to tell that nogc is only live after the call,
+  // not before. (This is to check for a problem where the return value was
+  // getting stored into a different temporary than the local nogc variable,
+  // and so its initialization was never seen and so it was assumed to be live
+  // throughout the function.)
+  GC();
+  auto [ok, nogc] = pair_returning_function();
+}
diff --git a/js/src/devtools/rootAnalysis/t/hazards/test.py b/js/src/devtools/rootAnalysis/t/hazards/test.py
new file mode 100644
index 0000000000..c4e9549305
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/hazards/test.py
@@ -0,0 +1,121 @@
+# flake8: noqa: F821
+
+from collections import defaultdict
+
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes")
+
+# gcFunctions should be the inverse, but we get to rely on unmangled names here.
+gcFunctions = test.load_gcFunctions()
+assert "void GC()" in gcFunctions
+assert "void suppressedFunction()" not in gcFunctions
+assert "void halfSuppressedFunction()" in gcFunctions
+assert "void unsuppressedFunction()" in gcFunctions
+assert "int32 Subcell::method()" in gcFunctions
+assert "Cell* f()" in gcFunctions
+
+hazards = test.load_hazards()
+hazmap = {haz.variable: haz for haz in hazards}
+assert "cell1" not in hazmap
+assert "cell2" in hazmap
+assert "cell3" in hazmap
+assert "cell4" not in hazmap
+assert "cell5" not in hazmap
+assert "cell6" not in hazmap
+assert "<returnvalue>" in hazmap
+assert "this" in hazmap
+
+assert hazmap["cell2"].function == "Cell* f()"
+
+# Check that the correct GC call is reported for each hazard. (cell3 has a
+# hazard from two different GC calls; it doesn't really matter which is
+# reported.)
+assert hazmap["cell2"].GCFunction == "void halfSuppressedFunction()"
+assert hazmap["cell3"].GCFunction in (
+    "void halfSuppressedFunction()",
+    "void unsuppressedFunction()",
+)
+returnval_hazards = set(
+    haz.function for haz in hazards if haz.variable == "<returnvalue>"
+)
+assert "Cell* f()" in returnval_hazards
+assert "Cell* refptr_test1()" in returnval_hazards
+assert "Cell* refptr_test2()" not in returnval_hazards
+assert "Cell* refptr_test3()" in returnval_hazards
+assert "Cell* refptr_test4()" in returnval_hazards
+assert "Cell* refptr_test5()" not in returnval_hazards
+assert "Cell* refptr_test6()" in returnval_hazards
+assert "Cell* refptr_test7()" in returnval_hazards
+assert "Cell* refptr_test8()" in returnval_hazards
+assert "Cell* refptr_test9()" not in returnval_hazards
+
+assert "container1" in hazmap
+assert "container2" not in hazmap
+
+# Type names are handy to have in the report.
+assert hazmap["cell2"].type == "Cell*"
+assert hazmap["<returnvalue>"].type == "Cell*"
+assert hazmap["this"].type == "Subcell*"
+
+# loopy hazards. See comments in source.
+assert "haz1" not in hazmap
+assert "haz2" not in hazmap
+assert "haz3" in hazmap
+assert "haz4" in hazmap
+assert "haz5" in hazmap
+assert "haz6" not in hazmap
+assert "haz7" not in hazmap
+assert "haz8" in hazmap
+
+# safevals hazards. See comments in source.
+assert "unsafe1" in hazmap
+assert "safe2" not in hazmap
+assert "unsafe3" in hazmap
+assert "unsafe3b" in hazmap
+assert "unsafe4" in hazmap
+assert "safe5" not in hazmap
+assert "safe6" not in hazmap
+assert "unsafe7" in hazmap
+assert "safe8" not in hazmap
+assert "safe9" not in hazmap
+assert "safe10" not in hazmap
+assert "safe11" not in hazmap
+assert "safe12" not in hazmap
+assert "unsafe13" in hazmap
+assert "unsafe14" in hazmap
+assert "unsafe15" in hazmap
+assert "safe16" not in hazmap
+assert "safe17" not in hazmap
+assert "safe18" not in hazmap
+assert "safe19" not in hazmap
+
+# method hazard.
+
+byfunc = defaultdict(lambda: defaultdict(dict))
+for haz in hazards:
+    byfunc[haz.function][haz.variable] = haz
+
+methhaz = byfunc["int32 Subcell::method()"]
+assert "this" in methhaz
+assert methhaz["this"].type == "Subcell*"
+
+haz_functions = set(haz.function for haz in hazards)
+
+# RefPtr<T> tests.
+
+haz_functions = set(haz.function for haz in hazards)
+assert "Cell* refptr_test1()" in haz_functions
+assert "Cell* refptr_test2()" not in haz_functions
+assert "Cell* refptr_test3()" in haz_functions
+assert "Cell* refptr_test4()" in haz_functions
+assert "Cell* refptr_test5()" not in haz_functions
+assert "Cell* refptr_test6()" in haz_functions
+assert "Cell* refptr_test7()" in haz_functions
+assert "Cell* refptr_test8()" in haz_functions
+assert "Cell* refptr_test9()" not in haz_functions
+assert "Cell* refptr_test10()" in haz_functions
+
+# aggr_init tests.
+
+assert "void aggr_init_safe()" not in haz_functions
+assert "void aggr_init_unsafe()" in haz_functions
diff --git a/js/src/devtools/rootAnalysis/t/sixgill-tree/source.cpp b/js/src/devtools/rootAnalysis/t/sixgill-tree/source.cpp
new file mode 100644
index 0000000000..149d77b03a
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/sixgill-tree/source.cpp
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+namespace js {
+namespace gc {
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+}  // namespace gc
+}  // namespace js
+
+struct Bogon {};
+
+struct JustACell : public js::gc::Cell {
+  bool iHaveNoDataMembers() { return true; }
+};
+
+struct JSObject : public js::gc::Cell, public Bogon {
+  int g;
+};
+
+struct SpecialObject : public JSObject {
+  int z;
+};
+
+struct ErrorResult {
+  bool hasObj;
+  JSObject* obj;
+  void trace() {}
+} ANNOTATE("Suppressed GC Pointer");
+
+struct OkContainer {
+  ErrorResult res;
+  bool happy;
+};
+
+struct UnrootedPointer {
+  JSObject* obj;
+};
+
+template <typename T>
+class Rooted {
+  T data;
+} ANNOTATE("Rooted Pointer");
+
+extern void js_GC() ANNOTATE("GC Call") ANNOTATE("Slow");
+
+void js_GC() {}
+
+void root_arg(JSObject* obj, JSObject* random) {
+  // Use all these types so they get included in the output.
+  SpecialObject so;
+  UnrootedPointer up;
+  Bogon b;
+  OkContainer okc;
+  Rooted<JSObject*> ro;
+  Rooted<SpecialObject*> rso;
+
+  obj = random;
+
+  JSObject* other1 = obj;
+  js_GC();
+
+  float MARKER1 = 0;
+  JSObject* other2 = obj;
+  other1->f = 1;
+  other2->f = -1;
+
+  unsigned int u1 = 1;
+  unsigned int u2 = -1;
+}
diff --git a/js/src/devtools/rootAnalysis/t/sixgill-tree/test.py b/js/src/devtools/rootAnalysis/t/sixgill-tree/test.py
new file mode 100644
index 0000000000..5e99fff908
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/sixgill-tree/test.py
@@ -0,0 +1,63 @@
+# flake8: noqa: F821
+import re
+
+test.compile("source.cpp")
+test.computeGCTypes()
+body = test.process_body(test.load_db_entry("src_body", re.compile(r"root_arg"))[0])
+
+# Rendering positive and negative integers
+marker1 = body.assignment_line("MARKER1")
+equal(body.edge_from_line(marker1 + 2)["Exp"][1]["String"], "1")
+equal(body.edge_from_line(marker1 + 3)["Exp"][1]["String"], "-1")
+
+equal(body.edge_from_point(body.assignment_point("u1"))["Exp"][1]["String"], "1")
+equal(
+    body.edge_from_point(body.assignment_point("u2"))["Exp"][1]["String"], "4294967295"
+)
+
+assert "obj" in body["Variables"]
+assert "random" in body["Variables"]
+assert "other1" in body["Variables"]
+assert "other2" in body["Variables"]
+
+# Test function annotations
+js_GC = test.process_body(test.load_db_entry("src_body", re.compile(r"js_GC"))[0])
+annotations = js_GC["Variables"]["void js_GC()"]["Annotation"]
+assert annotations
+found_call_annotate = False
+for annotation in annotations:
+    (annType, value) = annotation["Name"]
+    if annType == "annotate" and value == "GC Call":
+        found_call_annotate = True
+assert found_call_annotate
+
+# Test type annotations
+
+# js::gc::Cell first
+cell = test.load_db_entry("src_comp", "js::gc::Cell")[0]
+assert cell["Kind"] == "Struct"
+annotations = cell["Annotation"]
+assert len(annotations) == 1
+(tag, value) = annotations[0]["Name"]
+assert tag == "annotate"
+assert value == "GC Thing"
+
+# Check JSObject inheritance.
+JSObject = test.load_db_entry("src_comp", "JSObject")[0]
+bases = [b["Base"] for b in JSObject["CSUBaseClass"]]
+assert "js::gc::Cell" in bases
+assert "Bogon" in bases
+assert len(bases) == 2
+
+# Check type analysis
+gctypes = test.load_gcTypes()
+assert "js::gc::Cell" in gctypes["GCThings"]
+assert "JustACell" in gctypes["GCThings"]
+assert "JSObject" in gctypes["GCThings"]
+assert "SpecialObject" in gctypes["GCThings"]
+assert "UnrootedPointer" in gctypes["GCPointers"]
+assert "Bogon" not in gctypes["GCThings"]
+assert "Bogon" not in gctypes["GCPointers"]
+assert "ErrorResult" not in gctypes["GCPointers"]
+assert "OkContainer" not in gctypes["GCPointers"]
+assert "class Rooted<JSObject*>" not in gctypes["GCPointers"]
diff --git a/js/src/devtools/rootAnalysis/t/sixgill.py b/js/src/devtools/rootAnalysis/t/sixgill.py
new file mode 100644
index 0000000000..0b8c2c7073
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/sixgill.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from collections import defaultdict
+
+# Simplified version of the body info.
+
+
+class Body(dict):
+    def __init__(self, body):
+        self["BlockIdKind"] = body["BlockId"]["Kind"]
+        if "Variable" in body["BlockId"]:
+            self["BlockName"] = body["BlockId"]["Variable"]["Name"][0].split("$")[-1]
+        loc = body["Location"]
+        self["LineRange"] = (loc[0]["Line"], loc[1]["Line"])
+        self["Filename"] = loc[0]["CacheString"]
+        self["Edges"] = body.get("PEdge", [])
+        self["Points"] = {
+            i: p["Location"]["Line"] for i, p in enumerate(body["PPoint"], 1)
+        }
+        self["Index"] = body["Index"]
+        self["Variables"] = {
+            x["Variable"]["Name"][0].split("$")[-1]: x["Type"]
+            for x in body["DefineVariable"]
+        }
+
+        # Indexes
+        self["Line2Points"] = defaultdict(list)
+        for point, line in self["Points"].items():
+            self["Line2Points"][line].append(point)
+        self["SrcPoint2Edges"] = defaultdict(list)
+        for edge in self["Edges"]:
+            src, dst = edge["Index"]
+            self["SrcPoint2Edges"][src].append(edge)
+        self["Line2Edges"] = defaultdict(list)
+        for (src, edges) in self["SrcPoint2Edges"].items():
+            line = self["Points"][src]
+            self["Line2Edges"][line].extend(edges)
+
+    def edges_from_line(self, line):
+        return self["Line2Edges"][line]
+
+    def edge_from_line(self, line):
+        edges = self.edges_from_line(line)
+        assert len(edges) == 1
+        return edges[0]
+
+    def edges_from_point(self, point):
+        return self["SrcPoint2Edges"][point]
+
+    def edge_from_point(self, point):
+        edges = self.edges_from_point(point)
+        assert len(edges) == 1
+        return edges[0]
+
+    def assignment_point(self, varname):
+        for edge in self["Edges"]:
+            if edge["Kind"] != "Assign":
+                continue
+            dst = edge["Exp"][0]
+            if dst["Kind"] != "Var":
+                continue
+            if dst["Variable"]["Name"][0] == varname:
+                return edge["Index"][0]
+        raise Exception("assignment to variable %s not found" % varname)
+
+    def assignment_line(self, varname):
+        return self["Points"][self.assignment_point(varname)]
diff --git a/js/src/devtools/rootAnalysis/t/suppression/source.cpp b/js/src/devtools/rootAnalysis/t/suppression/source.cpp
new file mode 100644
index 0000000000..56e458bdaa
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/suppression/source.cpp
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+class AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Base() {}
+  ~AutoSuppressGC_Base() {}
+} ANNOTATE("Suppress GC");
+
+class AutoSuppressGC_Child : public AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Child() : AutoSuppressGC_Base() {}
+};
+
+class AutoSuppressGC {
+  AutoSuppressGC_Child helpImBeingSuppressed;
+
+ public:
+  AutoSuppressGC() {}
+};
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+extern void foo(Cell*);
+
+void suppressedFunction() {
+  GC();  // Calls GC, but is always called within AutoSuppressGC
+}
+
+void halfSuppressedFunction() {
+  GC();  // Calls GC, but is sometimes called within AutoSuppressGC
+}
+
+void unsuppressedFunction() {
+  GC();  // Calls GC, never within AutoSuppressGC
+}
+
+void f() {
+  Cell* cell1 = nullptr;
+  Cell* cell2 = nullptr;
+  Cell* cell3 = nullptr;
+  {
+    AutoSuppressGC nogc;
+    suppressedFunction();
+    halfSuppressedFunction();
+  }
+  foo(cell1);
+  halfSuppressedFunction();
+  foo(cell2);
+  unsuppressedFunction();
+  {
+    // Old bug: it would look from the first AutoSuppressGC constructor it
+    // found to the last destructor. This statement *should* have no effect.
+    AutoSuppressGC nogc;
+  }
+  foo(cell3);
+}
diff --git a/js/src/devtools/rootAnalysis/t/suppression/test.py b/js/src/devtools/rootAnalysis/t/suppression/test.py
new file mode 100644
index 0000000000..118ae422ab
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/suppression/test.py
@@ -0,0 +1,21 @@
+# flake8: noqa: F821
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes", upto="gcFunctions")
+
+# The suppressions file uses mangled names.
+info = test.load_funcInfo()
+suppressed = [f for f, v in info.items() if v.get("limits", 0) | 1]
+
+# Only one of these is fully suppressed (ie, *always* called within the scope
+# of an AutoSuppressGC).
+assert len(list(filter(lambda f: "suppressedFunction" in f, suppressed))) == 1
+assert len(list(filter(lambda f: "halfSuppressedFunction" in f, suppressed))) == 0
+assert len(list(filter(lambda f: "unsuppressedFunction" in f, suppressed))) == 0
+
+# gcFunctions should be the inverse, but we get to rely on unmangled names here.
+gcFunctions = test.load_gcFunctions()
+assert "void GC()" in gcFunctions
+assert "void suppressedFunction()" not in gcFunctions
+assert "void halfSuppressedFunction()" in gcFunctions
+assert "void unsuppressedFunction()" in gcFunctions
+assert "void f()" in gcFunctions
diff --git a/js/src/devtools/rootAnalysis/t/testlib.py b/js/src/devtools/rootAnalysis/t/testlib.py
new file mode 100644
index 0000000000..a7187395c6
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/testlib.py
@@ -0,0 +1,231 @@
+import json
+import os
+import re
+import subprocess
+import sys
+from collections import defaultdict, namedtuple
+
+from sixgill import Body
+
+scriptdir = os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
+
+HazardSummary = namedtuple(
+    "HazardSummary", ["function", "variable", "type", "GCFunction", "location"]
+)
+
+Callgraph = namedtuple(
+    "Callgraph",
+    [
+        "functionNames",
+        "nameToId",
+        "mangledToUnmangled",
+        "unmangledToMangled",
+        "calleesOf",
+        "callersOf",
+        "tags",
+        "calleeGraph",
+        "callerGraph",
+    ],
+)
+
+
+def equal(got, expected):
+    if got != expected:
+        print("Got '%s', expected '%s'" % (got, expected))
+
+
+def extract_unmangled(func):
+    return func.split("$")[-1]
+
+
+class Test(object):
+    def __init__(self, indir, outdir, cfg, verbose=0):
+        self.indir = indir
+        self.outdir = outdir
+        self.cfg = cfg
+        self.verbose = verbose
+
+    def infile(self, path):
+        return os.path.join(self.indir, path)
+
+    def binpath(self, prog):
+        return os.path.join(self.cfg.sixgill_bin, prog)
+
+    def compile(self, source, options=""):
+        env = os.environ
+        env["CCACHE_DISABLE"] = "1"
+        if "-fexceptions" not in options and "-fno-exceptions" not in options:
+            options += " -fno-exceptions"
+        cmd = "{CXX} -c {source} -O3 -std=c++17 -fplugin={sixgill} -fplugin-arg-xgill-mangle=1 {options}".format(  # NOQA: E501
+            source=self.infile(source),
+            CXX=self.cfg.cxx,
+            sixgill=self.cfg.sixgill_plugin,
+            options=options,
+        )
+        if self.cfg.verbose > 0:
+            print("Running %s" % cmd)
+        subprocess.check_call(["sh", "-c", cmd])
+
+    def load_db_entry(self, dbname, pattern):
+        """Look up an entry from an XDB database file, 'pattern' may be an exact
+        matching string, or an re pattern object matching a single entry."""
+
+        if hasattr(pattern, "match"):
+            output = subprocess.check_output(
+                [self.binpath("xdbkeys"), dbname + ".xdb"], universal_newlines=True
+            )
+            matches = list(filter(lambda _: re.search(pattern, _), output.splitlines()))
+            if len(matches) == 0:
+                raise Exception("entry not found")
+            if len(matches) > 1:
+                raise Exception("multiple entries found")
+            pattern = matches[0]
+
+        output = subprocess.check_output(
+            [self.binpath("xdbfind"), "-json", dbname + ".xdb", pattern],
+            universal_newlines=True,
+        )
+        return json.loads(output)
+
+    def run_analysis_script(self, startPhase="gcTypes", upto=None):
+        open("defaults.py", "w").write(
+            """\
+analysis_scriptdir = '{scriptdir}'
+sixgill_bin = '{bindir}'
+""".format(
+                scriptdir=scriptdir, bindir=self.cfg.sixgill_bin
+            )
+        )
+        cmd = [
+            sys.executable,
+            os.path.join(scriptdir, "analyze.py"),
+            ["-q", "", "-v"][min(self.verbose, 2)],
+        ]
+        cmd += ["--first", startPhase]
+        if upto:
+            cmd += ["--last", upto]
+        cmd.append("--source=%s" % self.indir)
+        cmd.append("--js=%s" % self.cfg.js)
+        if self.cfg.verbose:
+            print("Running " + " ".join(cmd))
+        subprocess.check_call(cmd)
+
+    def computeGCTypes(self):
+        self.run_analysis_script("gcTypes", upto="gcTypes")
+
+    def computeHazards(self):
+        self.run_analysis_script("gcTypes")
+
+    def load_text_file(self, filename, extract=lambda l: l):
+        fullpath = os.path.join(self.outdir, filename)
+        values = (extract(line.strip()) for line in open(fullpath, "r"))
+        return list(filter(lambda _: _ is not None, values))
+
+    def load_json_file(self, filename, reviver=None):
+        fullpath = os.path.join(self.outdir, filename)
+        with open(fullpath) as fh:
+            return json.load(fh, object_hook=reviver)
+
+    def load_gcTypes(self):
+        def grab_type(line):
+            m = re.match(r"^(GC\w+): (.*)", line)
+            if m:
+                return (m.group(1) + "s", m.group(2))
+            return None
+
+        gctypes = defaultdict(list)
+        for collection, typename in self.load_text_file(
+            "gcTypes.txt", extract=grab_type
+        ):
+            gctypes[collection].append(typename)
+        return gctypes
+
+    def load_typeInfo(self, filename="typeInfo.txt"):
+        return self.load_json_file(filename)
+
+    def load_funcInfo(self, filename="limitedFunctions.lst"):
+        return self.load_json_file(filename)
+
+    def load_gcFunctions(self):
+        return self.load_text_file("gcFunctions.lst", extract=extract_unmangled)
+
+    def load_callgraph(self):
+        data = Callgraph(
+            functionNames=["dummy"],
+            nameToId={},
+            mangledToUnmangled={},
+            unmangledToMangled={},
+            calleesOf=defaultdict(list),
+            callersOf=defaultdict(list),
+            tags=defaultdict(set),
+            calleeGraph=defaultdict(dict),
+            callerGraph=defaultdict(dict),
+        )
+
+        def lookup(id):
+            mangled = data.functionNames[int(id)]
+            return data.mangledToUnmangled.get(mangled, mangled)
+
+        def add_call(caller, callee, limit):
+            data.calleesOf[caller].append(callee)
+            data.callersOf[callee].append(caller)
+            data.calleeGraph[caller][callee] = True
+            data.callerGraph[callee][caller] = True
+
+        def process(line):
+            if line.startswith("#"):
+                name = line.split(" ", 1)[1]
+                data.nameToId[name] = len(data.functionNames)
+                data.functionNames.append(name)
+                return
+
+            if line.startswith("="):
+                m = re.match(r"^= (\d+) (.*)", line)
+                mangled = data.functionNames[int(m.group(1))]
+                unmangled = m.group(2)
+                data.nameToId[unmangled] = id
+                data.mangledToUnmangled[mangled] = unmangled
+                data.unmangledToMangled[unmangled] = mangled
+                return
+
+            limit = 0
+            m = re.match(r"^\w (?:/(\d+))? ", line)
+            if m:
+                limit = int(m[1])
+
+            tokens = line.split(" ")
+            if tokens[0] in ("D", "R"):
+                _, caller, callee = tokens
+                add_call(lookup(caller), lookup(callee), limit)
+            elif tokens[0] == "T":
+                data.tags[tokens[1]].add(line.split(" ", 2)[2])
+            elif tokens[0] in ("F", "V"):
+                pass
+
+            elif tokens[0] == "I":
+                m = re.match(r"^I (\d+) VARIABLE ([^\,]*)", line)
+                pass
+
+        self.load_text_file("callgraph.txt", extract=process)
+        return data
+
+    def load_hazards(self):
+        def grab_hazard(line):
+            m = re.match(
+                r"Function '(.*?)' has unrooted '(.*?)' of type '(.*?)' live across GC call '(.*?)' at (.*)",  # NOQA: E501
+                line,
+            )
+            if m:
+                info = list(m.groups())
+                info[0] = info[0].split("$")[-1]
+                info[3] = info[3].split("$")[-1]
+                return HazardSummary(*info)
+            return None
+
+        return self.load_text_file("hazards.txt", extract=grab_hazard)
+
+    def process_body(self, body):
+        return Body(body)
+
+    def process_bodies(self, bodies):
+        return [self.process_body(b) for b in bodies]
diff --git a/js/src/devtools/rootAnalysis/t/types/source.cpp b/js/src/devtools/rootAnalysis/t/types/source.cpp
new file mode 100644
index 0000000000..e823f0339b
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/types/source.cpp
@@ -0,0 +1,120 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <memory>
+#include <utility>
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+namespace World {
+namespace NS {
+struct Unsafe {
+  int g;
+  ~Unsafe() { asm(""); }
+} ANNOTATE("Invalidated by GC") ANNOTATE("GC Pointer or Reference");
+}  // namespace NS
+}  // namespace World
+
+extern void GC() ANNOTATE("GC Call");
+extern void invisible();
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+  invisible();
+}
+
+struct GCOnDestruction {
+  ~GCOnDestruction() { GC(); }
+};
+
+struct NoGCOnDestruction {
+  ~NoGCOnDestruction() { asm(""); }
+};
+
+extern void usecell(Cell*);
+
+Cell* cell() {
+  static Cell c;
+  return &c;
+}
+
+template <typename T, typename U>
+struct SimpleTemplate {
+  int member;
+};
+
+template <typename T, typename U>
+class ANNOTATE("moz_inherit_type_annotations_from_template_args") Container {
+ public:
+  template <typename V, typename W>
+  void foo(V& v, W& w) {
+    class InnerClass {};
+    InnerClass xxx;
+    return;
+  }
+};
+
+Cell* f() {
+  Container<int, double> c1;
+  Container<SimpleTemplate<int, int>, SimpleTemplate<double, double>> c2;
+  Container<Container<int, double>, Container<void, void>> c3;
+  Container<Container<SimpleTemplate<int, int>, void>,
+            Container<void, SimpleTemplate<char, char>>>
+      c4;
+
+  return nullptr;
+};
+
+void rvalue_ref(World::NS::Unsafe&& arg1) { GC(); }
+
+void ref(const World::NS::Unsafe& arg2) {
+  GC();
+  static int use = arg2.g;
+}
+
+// A function that consumes a parameter, but only if passed by rvalue reference.
+extern void eat(World::NS::Unsafe&&);
+extern void eat(World::NS::Unsafe&);
+
+void rvalue_ref_ok() {
+  World::NS::Unsafe unsafe1;
+  eat(std::move(unsafe1));
+  GC();
+}
+
+void rvalue_ref_not_ok() {
+  World::NS::Unsafe unsafe2;
+  eat(unsafe2);
+  GC();
+}
+
+void rvalue_ref_arg_ok(World::NS::Unsafe&& unsafe3) {
+  eat(std::move(unsafe3));
+  GC();
+}
+
+void rvalue_ref_arg_not_ok(World::NS::Unsafe&& unsafe4) {
+  eat(unsafe4);
+  GC();
+}
+
+void shared_ptr_hazard() {
+  Cell* unsafe5 = f();
+  { auto p = std::make_shared<GCOnDestruction>(); }
+  usecell(unsafe5);
+}
+
+void shared_ptr_no_hazard() {
+  Cell* safe6 = f();
+  { auto p = std::make_shared<NoGCOnDestruction>(); }
+  usecell(safe6);
+}
diff --git a/js/src/devtools/rootAnalysis/t/types/test.py b/js/src/devtools/rootAnalysis/t/types/test.py
new file mode 100644
index 0000000000..4a2b985abf
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/types/test.py
@@ -0,0 +1,16 @@
+# flake8: noqa: F821
+
+from collections import defaultdict
+
+test.compile("source.cpp")
+test.run_analysis_script()
+hazards = test.load_hazards()
+hazmap = {haz.variable: haz for haz in hazards}
+assert "arg1" in hazmap
+assert "arg2" in hazmap
+assert "unsafe1" not in hazmap
+assert "unsafe2" in hazmap
+assert "unsafe3" not in hazmap
+assert "unsafe4" in hazmap
+assert "unsafe5" in hazmap
+assert "safe6" not in hazmap
diff --git a/js/src/devtools/rootAnalysis/t/virtual/source.cpp b/js/src/devtools/rootAnalysis/t/virtual/source.cpp
new file mode 100644
index 0000000000..83633a3436
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/virtual/source.cpp
@@ -0,0 +1,292 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+// Special-cased function -- code that can run JS has an artificial edge to
+// js::RunScript.
+namespace js {
+void RunScript() { GC(); }
+}  // namespace js
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+extern void foo();
+
+void bar() { GC(); }
+
+typedef void (*func_t)();
+
+class Base {
+ public:
+  int ANNOTATE("field annotation") dummy;
+  virtual void someGC() ANNOTATE("Base pure virtual method") = 0;
+  virtual void someGC(int) ANNOTATE("overloaded Base pure virtual method") = 0;
+  virtual void sibGC() = 0;
+  virtual void onBase() { bar(); }
+  func_t functionField;
+
+  // For now, this is just to verify that the plugin doesn't crash. The
+  // analysis code does not yet look at this annotation or output it anywhere
+  // (though it *is* being recorded.)
+  static float testAnnotations() ANNOTATE("static func");
+
+  // Similar, though sixgill currently completely ignores parameter annotations.
+  static double testParamAnnotations(Cell& ANNOTATE("param annotation")
+                                         ANNOTATE("second param annot") cell)
+      ANNOTATE("static func") ANNOTATE("second func");
+};
+
+float Base::testAnnotations() {
+  asm("");
+  return 1.1;
+}
+
+double Base::testParamAnnotations(Cell& cell) {
+  asm("");
+  return 1.2;
+}
+
+class Super : public Base {
+ public:
+  virtual void ANNOTATE("Super pure virtual") noneGC() = 0;
+  virtual void allGC() = 0;
+  virtual void onSuper() { asm(""); }
+  void nonVirtualFunc() { asm(""); }
+};
+
+class Sub1 : public Super {
+ public:
+  void noneGC() override { foo(); }
+  void someGC() override ANNOTATE("Sub1 override") ANNOTATE("second attr") {
+    foo();
+  }
+  void someGC(int) override ANNOTATE("Sub1 override for int overload") {
+    foo();
+  }
+  void allGC() override {
+    foo();
+    bar();
+  }
+  void sibGC() override { foo(); }
+  void onBase() override { foo(); }
+} ANNOTATE("CSU1") ANNOTATE("CSU2");
+
+class Sub2 : public Super {
+ public:
+  void noneGC() override { foo(); }
+  void someGC() override {
+    foo();
+    bar();
+  }
+  void someGC(int) override {
+    foo();
+    bar();
+  }
+  void allGC() override {
+    foo();
+    bar();
+  }
+  void sibGC() override { foo(); }
+};
+
+class Sibling : public Base {
+ public:
+  virtual void noneGC() { foo(); }
+  void someGC() override {
+    foo();
+    bar();
+  }
+  void someGC(int) override {
+    foo();
+    bar();
+  }
+  virtual void allGC() {
+    foo();
+    bar();
+  }
+  void sibGC() override { bar(); }
+};
+
+class AutoSuppressGC {
+ public:
+  AutoSuppressGC() {}
+  ~AutoSuppressGC() {}
+} ANNOTATE("Suppress GC");
+
+void use(Cell*) { asm(""); }
+
+class nsISupports {
+ public:
+  virtual ANNOTATE("Can run script") void danger() { asm(""); }
+
+  virtual ~nsISupports() = 0;
+};
+
+class nsIPrincipal : public nsISupports {
+ public:
+  ~nsIPrincipal() override{};
+};
+
+struct JSPrincipals {
+  int debugToken;
+  JSPrincipals() = default;
+  virtual ~JSPrincipals() { GC(); }
+};
+
+class nsJSPrincipals : public nsIPrincipal, public JSPrincipals {
+ public:
+  void Release() { delete this; }
+};
+
+class SafePrincipals : public nsIPrincipal {
+ public:
+  ~SafePrincipals() { foo(); }
+};
+
+void f() {
+  Sub1 s1;
+  Sub2 s2;
+
+  static Cell cell;
+  {
+    Cell* c1 = &cell;
+    s1.noneGC();
+    use(c1);
+  }
+  {
+    Cell* c2 = &cell;
+    s2.someGC();
+    use(c2);
+  }
+  {
+    Cell* c3 = &cell;
+    s1.allGC();
+    use(c3);
+  }
+  {
+    Cell* c4 = &cell;
+    s2.noneGC();
+    use(c4);
+  }
+  {
+    Cell* c5 = &cell;
+    s2.someGC();
+    use(c5);
+  }
+  {
+    Cell* c6 = &cell;
+    s2.allGC();
+    use(c6);
+  }
+
+  Super* super = &s2;
+  {
+    Cell* c7 = &cell;
+    super->noneGC();
+    use(c7);
+  }
+  {
+    Cell* c8 = &cell;
+    super->someGC();
+    use(c8);
+  }
+  {
+    Cell* c9 = &cell;
+    super->allGC();
+    use(c9);
+  }
+
+  {
+    Cell* c10 = &cell;
+    s1.functionField();
+    use(c10);
+  }
+  {
+    Cell* c11 = &cell;
+    super->functionField();
+    use(c11);
+  }
+  {
+    Cell* c12 = &cell;
+    super->sibGC();
+    use(c12);
+  }
+
+  Base* base = &s2;
+  {
+    Cell* c13 = &cell;
+    base->sibGC();
+    use(c13);
+  }
+
+  nsJSPrincipals pals;
+  {
+    Cell* c14 = &cell;
+    nsISupports* p = &pals;
+    p->danger();
+    use(c14);
+  }
+
+  // Base defines, Sub1 overrides, static Super can call either.
+  {
+    Cell* c15 = &cell;
+    super->onBase();
+    use(c15);
+  }
+
+  {
+    Cell* c16 = &cell;
+    s2.someGC(7);
+    use(c16);
+  }
+
+  {
+    Cell* c17 = &cell;
+    super->someGC(7);
+    use(c17);
+  }
+
+  {
+    nsJSPrincipals* princ = new nsJSPrincipals();
+    Cell* c18 = &cell;
+    delete princ;  // Can GC
+    use(c18);
+  }
+
+  {
+    nsJSPrincipals* princ = new nsJSPrincipals();
+    nsISupports* supp = static_cast<nsISupports*>(princ);
+    Cell* c19 = &cell;
+    delete supp;  // Can GC
+    use(c19);
+  }
+
+  {
+    auto* safe = new SafePrincipals();
+    Cell* c20 = &cell;
+    delete safe;  // Cannot GC
+    use(c20);
+  }
+
+  {
+    auto* safe = new SafePrincipals();
+    nsISupports* supp = static_cast<nsISupports*>(safe);
+    Cell* c21 = &cell;
+    delete supp;  // Compiler thinks destructor can GC.
+    use(c21);
+  }
+}
diff --git a/js/src/devtools/rootAnalysis/t/virtual/test.py b/js/src/devtools/rootAnalysis/t/virtual/test.py
new file mode 100644
index 0000000000..e8474ae28b
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/virtual/test.py
@@ -0,0 +1,91 @@
+# 'test' is provided by the calling script.
+# flake8: noqa: F821
+
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes")
+
+info = test.load_typeInfo()
+
+assert "Sub1" in info["OtherCSUTags"]
+assert ["CSU1", "CSU2"] == sorted(info["OtherCSUTags"]["Sub1"])
+assert "Base" in info["OtherFieldTags"]
+assert "someGC" in info["OtherFieldTags"]["Base"]
+assert "Sub1" in info["OtherFieldTags"]
+assert "someGC" in info["OtherFieldTags"]["Sub1"]
+
+# For now, fields with the same name (eg overloaded virtual methods) just
+# accumulate attributes.
+assert ["Sub1 override", "Sub1 override for int overload", "second attr"] == sorted(
+    info["OtherFieldTags"]["Sub1"]["someGC"]
+)
+
+gcFunctions = test.load_gcFunctions()
+
+assert "void Sub1::noneGC()" not in gcFunctions
+assert "void Sub1::someGC()" not in gcFunctions
+assert "void Sub1::someGC(int32)" not in gcFunctions
+assert "void Sub1::allGC()" in gcFunctions
+assert "void Sub2::noneGC()" not in gcFunctions
+assert "void Sub2::someGC()" in gcFunctions
+assert "void Sub2::someGC(int32)" in gcFunctions
+assert "void Sub2::allGC()" in gcFunctions
+
+callgraph = test.load_callgraph()
+
+assert callgraph.calleeGraph["void f()"]["Super.noneGC:0"]
+assert callgraph.calleeGraph["Super.noneGC:0"]["Sub1.noneGC:0"]
+assert callgraph.calleeGraph["Super.noneGC:0"]["Sub2.noneGC:0"]
+assert callgraph.calleeGraph["Sub1.noneGC:0"]["void Sub1::noneGC()"]
+assert callgraph.calleeGraph["Sub2.noneGC:0"]["void Sub2::noneGC()"]
+assert "void Sibling::noneGC()" not in callgraph.calleeGraph["Super.noneGC:0"]
+assert callgraph.calleeGraph["Super.onBase:0"]["Sub1.onBase:0"]
+assert callgraph.calleeGraph["Sub1.onBase:0"]["void Sub1::onBase()"]
+assert callgraph.calleeGraph["Super.onBase:0"]["void Base::onBase()"]
+assert "void Sibling::onBase()" not in callgraph.calleeGraph["Super.onBase:0"]
+
+hazards = test.load_hazards()
+hazmap = {haz.variable: haz for haz in hazards}
+
+assert "c1" not in hazmap
+assert "c2" in hazmap
+assert "c3" in hazmap
+assert "c4" not in hazmap
+assert "c5" in hazmap
+assert "c6" in hazmap
+assert "c7" not in hazmap
+assert "c8" in hazmap
+assert "c9" in hazmap
+assert "c10" in hazmap
+assert "c11" in hazmap
+
+# Virtual resolution should take the static type into account: the only method
+# implementations considered should be those of descendants, even if the
+# virtual method is inherited and not overridden in the static class. (Base
+# defines sibGC() as pure virtual, Super inherits it without overriding,
+# Sibling and Sub2 both implement it.)
+
+# Call Base.sibGC on a Super pointer: can only call Sub2.sibGC(), which does not GC.
+# In particular, PEdgeCallInstance.Exp.Field.FieldCSU.Type = {Kind: "CSU", Name="Super"}
+assert "c12" not in hazmap
+# Call Base.sibGC on a Base pointer; can call Sibling.sibGC(), which GCs.
+assert "c13" in hazmap
+
+# Call nsISupports.danger() which is annotated to be overridable and hence can GC.
+assert "c14" in hazmap
+
+# someGC(int) overload
+assert "c16" in hazmap
+assert "c17" in hazmap
+
+# Super.onBase() could call the GC'ing Base::onBase().
+assert "c15" in hazmap
+
+# virtual ~nsJSPrincipals calls ~JSPrincipals calls GC.
+assert "c18" in hazmap
+assert "c19" in hazmap
+
+# ~SafePrincipals does not GC.
+assert "c20" not in hazmap
+
+# ...but when cast to a nsISupports*, the compiler can't tell that it won't.
+assert "c21" in hazmap
diff --git a/js/src/devtools/rootAnalysis/utility.js b/js/src/devtools/rootAnalysis/utility.js
new file mode 100644
index 0000000000..5ec8c3e961
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/utility.js
@@ -0,0 +1,422 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('dumpCFG.js');
+
+// Attribute bits - each call edge may carry a set of 'attrs' bits, saying eg
+// that the edge takes place within a scope where GC is suppressed, for
+// example.
+var ATTR_GC_SUPPRESSED     = 1 << 0;
+var ATTR_CANSCRIPT_BOUNDED = 1 << 1; // Unimplemented
+var ATTR_DOM_ITERATING     = 1 << 2; // Unimplemented
+var ATTR_NONRELEASING      = 1 << 3; // ~RefPtr of value whose refcount will not go to zero
+var ATTR_REPLACED          = 1 << 4; // Ignore edge, it was replaced by zero or more better edges.
+var ATTR_SYNTHETIC         = 1 << 5; // Call was manufactured in some way.
+
+var ATTR_LAST              = 1 << 5;
+var ATTRS_NONE             = 0;
+var ATTRS_ALL              = (ATTR_LAST << 1) - 1; // All possible bits set
+
+// The traversal algorithms we run will recurse into children if you change any
+// attrs bit to zero. Use all bits set to maximally attributed, including
+// additional bits that all just mean "unvisited", so that the first time we
+// see a node with this attrs, we're guaranteed to turn at least one bit off
+// and thereby keep going.
+var ATTRS_UNVISITED = 0xffff;
+
+// gcc appends this to mangled function names for "not in charge"
+// constructors/destructors.
+var internalMarker = " *INTERNAL* ";
+
+if (! Set.prototype.hasOwnProperty("update")) {
+    Object.defineProperty(Set.prototype, "update", {
+        value: function (collection) {
+            for (let elt of collection)
+                this.add(elt);
+        }
+    });
+}
+
+function assert(x, msg)
+{
+    if (x)
+        return;
+    debugger;
+    if (msg)
+        throw new Error("assertion failed: " + msg + "\n");
+    else
+        throw new Error("assertion failed");
+}
+
+function defined(x) {
+    return x !== undefined;
+}
+
+function xprint(x, padding)
+{
+    if (!padding)
+        padding = "";
+    if (x instanceof Array) {
+        print(padding + "[");
+        for (var elem of x)
+            xprint(elem, padding + " ");
+        print(padding + "]");
+    } else if (x instanceof Object) {
+        print(padding + "{");
+        for (var prop in x) {
+            print(padding + " " + prop + ":");
+            xprint(x[prop], padding + "  ");
+        }
+        print(padding + "}");
+    } else {
+        print(padding + x);
+    }
+}
+
+// Command-line argument parser.
+//
+// `parameters` is a dict of parameters specs, each of which is a dict with keys:
+//
+//   - name: name of option, prefixed with "--" if it is named (otherwise, it
+//     is interpreted as a positional parameter.)
+//   - dest: key to store the result in, defaulting to the parameter name without
+//     any leading "--"" and with dashes replaced with underscores.
+//   - default: value of option if no value is given. Positional parameters with
+//     a default value are optional. If no default is given, the parameter's name
+//     is not included in the return value.
+//   - type: `bool` if it takes no argument, otherwise an argument is required.
+//     Named arguments default to 'bool', positional arguments to 'string'.
+//   - nargs: the only supported value is `+`, which means to grab all following
+//     arguments, up to the next named option, and store them as a list.
+//
+// The command line is parsed for `--foo=value` and `--bar` arguments.
+//
+// Return value is a dict of parameter values, keyed off of `dest` as determined
+// above. An extra option named "rest" will be set to the list of all remaining
+// arguments passed in.
+//
+function parse_options(parameters, inArgs = scriptArgs) {
+    const options = {};
+
+    const named = {};
+    const positional = [];
+    for (const param of parameters) {
+        if (param.name.startsWith("-")) {
+            named[param.name] = param;
+            if (!param.dest) {
+                if (!param.name.startsWith("--")) {
+                    throw new Error(`parameter '${param.name}' requires param.dest to be set`);
+                }
+                param.dest = param.name.substring(2).replace("-", "_");
+            }
+        } else {
+            if (!('default' in param) && positional.length > 0 && ('default' in positional.at(-1))) {
+                throw new Error(`required parameter '${param.name}' follows optional parameter`);
+            }
+            param.positional = true;
+            positional.push(param);
+            param.dest = param.dest || param.name.replace("-", "_");
+        }
+
+        if (!param.type) {
+            if (param.nargs === "+") {
+                param.type = "list";
+            } else if (param.positional) {
+                param.type = "string";
+            } else {
+                param.type = "bool";
+            }
+        }
+
+        if ('default' in param) {
+            options[param.dest] = param.default;
+        }
+    }
+
+    options.rest = [];
+    const args = [...inArgs];
+    let grabbing_into = undefined;
+    while (args.length > 0) {
+        let arg = args.shift();
+        let param;
+        if (arg.startsWith("-") && arg in named) {
+            param = named[arg];
+            if (param.type !== 'bool') {
+                if (args.length == 0) {
+                    throw(new Error(`${param.name} requires an argument`));
+                }
+                arg = args.shift();
+            }
+        } else {
+            const pos = arg.indexOf("=");
+            if (pos != -1) {
+                const name = arg.substring(0, pos);
+                param = named[name];
+                if (!param) {
+                    throw(new Error(`Unknown option '${name}'`));
+                } else if (param.type === 'bool') {
+                    throw(new Error(`--${param.name} does not take an argument`));
+                }
+                arg = arg.substring(pos + 1);
+            }
+        }
+
+        // If this isn't a --named param, and we're not accumulating into a nargs="+" param, then
+        // use the next positional.
+        if (!param && !grabbing_into && positional.length > 0) {
+            param = positional.shift();
+        }
+
+        // If a parameter was identified, then any old accumulator is done and we might start a new one.
+        if (param) {
+            if (param.type === 'list') {
+                grabbing_into = options[param.dest] = options[param.dest] || [];
+            } else {
+                grabbing_into = undefined;
+            }
+        }
+
+        if (grabbing_into) {
+            grabbing_into.push(arg);
+        } else if (param) {
+            if (param.type === 'bool') {
+                options[param.dest] = true;
+            } else {
+                options[param.dest] = arg;
+            }
+        } else {
+            options.rest.push(arg);
+        }
+    }
+
+    for (const param of positional) {
+        if (!('default' in param)) {
+            throw(new Error(`'${param.name}' option is required`));
+        }
+    }
+
+    for (const param of parameters) {
+        if (param.nargs === '+' && options[param.dest].length == 0) {
+            throw(new Error(`at least one value required for option '${param.name}'`));
+        }
+    }
+
+    return options;
+}
+
+function sameBlockId(id0, id1)
+{
+    if (id0.Kind != id1.Kind)
+        return false;
+    if (!sameVariable(id0.Variable, id1.Variable))
+        return false;
+    if (id0.Kind == "Loop" && id0.Loop != id1.Loop)
+        return false;
+    return true;
+}
+
+function sameVariable(var0, var1)
+{
+    assert("Name" in var0 || var0.Kind == "This" || var0.Kind == "Return");
+    assert("Name" in var1 || var1.Kind == "This" || var1.Kind == "Return");
+    if ("Name" in var0)
+        return "Name" in var1 && var0.Name[0] == var1.Name[0];
+    return var0.Kind == var1.Kind;
+}
+
+function blockIdentifier(body)
+{
+    if (body.BlockId.Kind == "Loop")
+        return body.BlockId.Loop;
+    assert(body.BlockId.Kind == "Function", "body.Kind should be Function, not " + body.BlockId.Kind);
+    return body.BlockId.Variable.Name[0];
+}
+
+function collectBodyEdges(body)
+{
+    body.predecessors = [];
+    body.successors = [];
+    if (!("PEdge" in body))
+        return;
+
+    for (var edge of body.PEdge) {
+        var [ source, target ] = edge.Index;
+        if (!(target in body.predecessors))
+            body.predecessors[target] = [];
+        body.predecessors[target].push(edge);
+        if (!(source in body.successors))
+            body.successors[source] = [];
+        body.successors[source].push(edge);
+    }
+}
+
+function getPredecessors(body)
+{
+    if (!('predecessors' in body))
+        collectBodyEdges(body);
+    return body.predecessors;
+}
+
+function getSuccessors(body)
+{
+    if (!('successors' in body))
+        collectBodyEdges(body);
+    return body.successors;
+}
+
+// Split apart a function from sixgill into its mangled and unmangled name. If
+// no mangled name was given, use the unmangled name as its mangled name
+function splitFunction(func)
+{
+    var split = func.indexOf("$");
+    if (split != -1)
+        return [ func.substr(0, split), func.substr(split+1) ];
+    split = func.indexOf("|");
+    if (split != -1)
+        return [ func.substr(0, split), func.substr(split+1) ];
+    return [ func, func ];
+}
+
+function mangled(fullname)
+{
+    var [ mangled, unmangled ] = splitFunction(fullname);
+    return mangled;
+}
+
+function readable(fullname)
+{
+    var [ mangled, unmangled ] = splitFunction(fullname);
+    return unmangled;
+}
+
+function xdbLibrary()
+{
+    var lib = ctypes.open(os.getenv('XDB'));
+    var api = {
+        open: lib.declare("xdb_open", ctypes.default_abi, ctypes.void_t, ctypes.char.ptr),
+        min_data_stream: lib.declare("xdb_min_data_stream", ctypes.default_abi, ctypes.int),
+        max_data_stream: lib.declare("xdb_max_data_stream", ctypes.default_abi, ctypes.int),
+        read_key: lib.declare("xdb_read_key", ctypes.default_abi, ctypes.char.ptr, ctypes.int),
+        read_entry: lib.declare("xdb_read_entry", ctypes.default_abi, ctypes.char.ptr, ctypes.char.ptr),
+        free_string: lib.declare("xdb_free", ctypes.default_abi, ctypes.void_t, ctypes.char.ptr)
+    };
+    try {
+        api.lookup_key = lib.declare("xdb_lookup_key", ctypes.default_abi, ctypes.int, ctypes.char.ptr);
+    } catch (e) {
+        // lookup_key is for development use only and is not strictly necessary.
+    }
+    return api;
+}
+
+function openLibrary(names) {
+    for (const name of names) {
+        try {
+            return ctypes.open(name);
+        } catch(e) {
+        }
+    }
+    return undefined;
+}
+
+function cLibrary()
+{
+    const lib = openLibrary(['libc.so.6', 'libc.so', 'libc.dylib']);
+    if (!lib) {
+        throw new Error("Unable to open libc");
+    }
+
+    if (getBuildConfiguration()["moz-memory"]) {
+        throw new Error("cannot use libc functions with --enable-jemalloc, since they will be routed " +
+                        "through jemalloc, but calling libc.free() directly will bypass it and the " +
+                        "malloc/free will be mismatched");
+    }
+
+    return {
+        fopen: lib.declare("fopen", ctypes.default_abi, ctypes.void_t.ptr, ctypes.char.ptr, ctypes.char.ptr),
+        getline: lib.declare("getline", ctypes.default_abi, ctypes.ssize_t, ctypes.char.ptr.ptr, ctypes.size_t.ptr, ctypes.void_t.ptr),
+        fclose: lib.declare("fclose", ctypes.default_abi, ctypes.int, ctypes.void_t.ptr),
+        free: lib.declare("free", ctypes.default_abi, ctypes.void_t, ctypes.void_t.ptr),
+    };
+}
+
+function* readFileLines_gen(filename)
+{
+    var libc = cLibrary();
+    var linebuf = ctypes.char.ptr();
+    var bufsize = ctypes.size_t(0);
+    var fp = libc.fopen(filename, "r");
+    if (fp.isNull())
+        throw new Error("Unable to open '" + filename + "'");
+
+    while (libc.getline(linebuf.address(), bufsize.address(), fp) > 0)
+        yield linebuf.readString();
+    libc.fclose(fp);
+    libc.free(ctypes.void_t.ptr(linebuf));
+}
+
+function addToKeyedList(collection, key, entry)
+{
+    if (!(key in collection))
+        collection[key] = [];
+    collection[key].push(entry);
+    return collection[key];
+}
+
+function addToMappedList(map, key, entry)
+{
+    if (!map.has(key))
+        map.set(key, []);
+    map.get(key).push(entry);
+    return map.get(key);
+}
+
+function loadTypeInfo(filename)
+{
+    return JSON.parse(os.file.readFile(filename));
+}
+
+// Given the range `first` .. `last`, break it down into `count` batches and
+// return the start of the (1-based) `num` batch.
+function batchStart(num, count, first, last) {
+  const N = (last - first) + 1;
+  return Math.floor((num - 1) / count * N) + first;
+}
+
+// As above, but return the last value in the (1-based) `num` batch.
+function batchLast(num, count, first, last) {
+  const N = (last - first) + 1;
+  return Math.floor(num / count * N) + first - 1;
+}
+
+// Debugging tool. See usage below.
+function PropertyTracer(traced_prop, check) {
+    return {
+        matches(prop, value) {
+            if (prop != traced_prop)
+                return false;
+            if ('value' in check)
+                return value == check.value;
+            return true;
+        },
+
+        // Also called when defining a property.
+        set(obj, prop, value) {
+            if (this.matches(prop, value))
+                debugger;
+            return Reflect.set(...arguments);
+        },
+    };
+}
+
+// Usage: var myobj = traced({}, 'name', {value: 'Bob'})
+//
+// This will execute a `debugger;` statement when myobj['name'] is defined or
+// set to 'Bob'.
+function traced(obj, traced_prop, check) {
+  return new Proxy(obj, PropertyTracer(traced_prop, check));
+}
diff --git a/js/src/devtools/vprof/manifest.mk b/js/src/devtools/vprof/manifest.mk
new file mode 100644
index 0000000000..e18a17fb5d
--- /dev/null
+++ b/js/src/devtools/vprof/manifest.mk
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+avmplus_CXXSRCS := $(avmplus_CXXSRCS) \
+  $(curdir)/vprof.cpp \
+  $(NULL)
diff --git a/js/src/devtools/vprof/readme.txt b/js/src/devtools/vprof/readme.txt
new file mode 100644
index 0000000000..f84bfc27e5
--- /dev/null
+++ b/js/src/devtools/vprof/readme.txt
@@ -0,0 +1,97 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+The two files vprof.h and vprof.cpp implement a simple value-profiling mechanism. By including these two files in avmplus (or any other project), you can value profile data as you wish (currently integers).
+
+Usage:
+#include "vprof.h"  // in the source file you want to use it
+
+_vprof (value);
+
+At the end of the execution, for each probe you'll get the data associated with the probe, such as:
+
+File                                        line    avg     [min : max] total       count
+..\..\pcre\pcre_valid_utf8.cpp  182 50222.75916 [0 :    104947] 4036955604  80381
+
+The probe is defined at line 182 of file pcre_vali_utf8.cpp. It was called 80381 times. The min value of the probe was 0 while its max was 10497 and its average was  50222.75916. The total sum of all values of the probe is 4036955604. Later, I plan to add more options on the spectrum of data among others.
+
+A few typical uses
+------------------
+
+To see how many times a given function gets executed do:
+
+void f()
+{
+    _vprof(1);
+    ...
+}
+
+void f()
+{
+        _vprof(1);
+        ...
+       if (...) {
+           _vprof(1);
+           ...
+       } else {
+           _vprof(1);
+           ...
+       }
+}
+
+Here are a few examples of using the value-profiling utility:
+
+  _vprof (e);
+    at the end of program execution, you'll get a dump of the source location of this probe,
+    its min, max, average, the total sum of all instances of e, and the total number of times this probe was called.
+
+  _vprof (x > 0);
+    shows how many times and what percentage of the cases x was > 0,
+    that is the probablitiy that x > 0.
+
+ _vprof (n % 2 == 0);
+    shows how many times n was an even number
+    as well as th probablitiy of n being an even number.
+
+ _hprof (n, 4, 1000, 5000, 5001, 10000);
+    gives you the histogram of n over the given 4 bucket boundaries:
+        # cases <  1000
+        # cases >= 1000 and < 5000
+        # cases >= 5000 and < 5001
+        # cases >= 5001 and < 10000
+        # cases >= 10000
+
+ _nvprof ("event name", value);
+    all instances with the same name are merged
+    so, you can call _vprof with the same event name at difference places
+
+ _vprof (e, myProbe);
+    value profile e and call myProbe (void* vprofID) at the profiling point.
+    inside the probe, the client has the predefined variables:
+    _VAL, _COUNT, _SUM, _MIN, _MAX, and the general purpose registers
+    _IVAR1, ..., IVAR4      general integer registrs
+    _I64VAR1, ..., I64VAR4  general integer64 registrs
+    _DVAR1, ..., _DVAR4     general double registers
+    _GENPTR a generic pointer that can be used by the client
+    the number of registers can be changed in vprof.h
+
+Named Events
+------------
+_nvprof ("event name", value);
+    all instances with the same name are merged
+    so, you can call _vprof with the same event name at difference places
+
+
+Custom Probes
+--------------
+You can call your own custom probe at the profiling point.
+_vprof (v, myProbe);
+   value profile v and call myProbe (void* vprofID) at the profiling point
+   inside the probe, the client has the predefined variables:
+   _VAL, _COUNT, _SUM, _MIN, _MAX, and the general purpose registers
+   _IVAR1, ..., IVAR4   general integer registrs
+   _I64VAR1, ..., I64VAR4 general integer64 registrs
+   _DVAR1, ..., _DVAR4  general double registers
+  the number of registers can be changed in vprof.h
+  _GENPTR a generic pointer that can be used for almost anything
diff --git a/js/src/devtools/vprof/testVprofMT.c b/js/src/devtools/vprof/testVprofMT.c
new file mode 100644
index 0000000000..da85389565
--- /dev/null
+++ b/js/src/devtools/vprof/testVprofMT.c
@@ -0,0 +1,88 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: t; tab-width: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <windows.h>
+#include <stdio.h>
+#include <time.h>
+
+#include "vprof.h"
+
+static void cProbe(void* vprofID) {
+  if (_VAL == _IVAR1) _I64VAR1++;
+  _IVAR1 = _IVAR0;
+
+  if (_VAL == _IVAR0) _I64VAR0++;
+  _IVAR0 = (int)_VAL;
+
+  _DVAR0 = ((double)_I64VAR0) / _COUNT;
+  _DVAR1 = ((double)_I64VAR1) / _COUNT;
+}
+
+//__declspec (thread) boolean cv;
+// #define if(c) cv = (c); _vprof (cv); if (cv)
+// #define if(c) cv = (c); _vprof (cv, cProbe); if (cv)
+
+#define THREADS 1
+#define COUNT 100000
+#define SLEEPTIME 0
+
+static int64_t evens = 0;
+static int64_t odds = 0;
+
+void sub(int val) {
+  int i;
+  //_vprof (1);
+  for (i = 0; i < COUNT; i++) {
+    //_nvprof ("Iteration", 1);
+    //_nvprof ("Iteration", 1);
+    _vprof(i);
+    //_vprof (i);
+    //_hprof(i, 3, (int64_t) 1000, (int64_t)2000, (int64_t)3000);
+    //_hprof(i, 3, 10000, 10001, 3000000);
+    //_nhprof("Event", i, 3, 10000, 10001, 3000000);
+    //_nhprof("Event", i, 3, 10000, 10001, 3000000);
+    // Sleep(SLEEPTIME);
+    if (i % 2 == 0) {
+      //_vprof (i);
+      ////_hprof(i, 3, 10000, 10001, 3000000);
+      //_nvprof ("Iteration", i);
+      evens++;
+    } else {
+      //_vprof (1);
+      _vprof(i, cProbe);
+      odds++;
+    }
+    //_nvprof ("Iterate", 1);
+  }
+  // printf("sub %d done.\n", val);
+}
+
+HANDLE array[THREADS];
+
+static int run(void) {
+  int i;
+
+  time_t start_time = time(0);
+
+  for (i = 0; i < THREADS; i++) {
+    array[i] = CreateThread(0, 0, (LPTHREAD_START_ROUTINE)sub, (LPVOID)i, 0, 0);
+  }
+
+  for (i = 0; i < THREADS; i++) {
+    WaitForSingleObject(array[i], INFINITE);
+  }
+
+  return 0;
+}
+
+int main() {
+  DWORD start, end;
+
+  start = GetTickCount();
+  run();
+  end = GetTickCount();
+
+  printf("\nRun took %d msecs\n\n", end - start);
+}
diff --git a/js/src/devtools/vprof/vprof.cpp b/js/src/devtools/vprof/vprof.cpp
new file mode 100644
index 0000000000..873c354b7e
--- /dev/null
+++ b/js/src/devtools/vprof/vprof.cpp
@@ -0,0 +1,359 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: t; tab-width: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "VMPI.h"
+
+// Note, this is not supported in configurations with more than one AvmCore
+// running in the same process.
+
+#ifdef WIN32
+#  include "util/WindowsWrapper.h"
+#else
+#  define __cdecl
+#  include <stdarg.h>
+#  include <string.h>
+#endif
+
+#include "vprof.h"
+
+#ifndef MIN
+#  define MIN(x, y) ((x) <= (y) ? x : y)
+#endif
+#ifndef MAX
+#  define MAX(x, y) ((x) >= (y) ? x : y)
+#endif
+
+#ifndef MAXINT
+#  define MAXINT int(unsigned(-1) >> 1)
+#endif
+
+#ifndef MAXINT64
+#  define MAXINT64 int64_t(uint64_t(-1) >> 1)
+#endif
+
+#ifndef __STDC_WANT_SECURE_LIB__
+#  define sprintf_s(b, size, fmt, ...) sprintf((b), (fmt), __VA_ARGS__)
+#endif
+
+#if THREADED
+#  define DO_LOCK(lock) \
+    Lock(lock);         \
+    {
+#  define DO_UNLOCK(lock) \
+    }                     \
+    ;                     \
+    Unlock(lock)
+#else
+#  define DO_LOCK(lock) \
+    {                   \
+      (void)(lock);
+#  define DO_UNLOCK(lock) }
+#endif
+
+#if THREAD_SAFE
+#  define LOCK(lock) DO_LOCK(lock)
+#  define UNLOCK(lock) DO_UNLOCK(lock)
+#else
+#  define LOCK(lock) \
+    {                \
+      (void)(lock);
+#  define UNLOCK(lock) }
+#endif
+
+static entry* entries = nullptr;
+static bool notInitialized = true;
+static long glock = LOCK_IS_FREE;
+
+#define Lock(lock)                                                         \
+  while (_InterlockedCompareExchange(lock, LOCK_IS_TAKEN, LOCK_IS_FREE) == \
+         LOCK_IS_TAKEN) {                                                  \
+  };
+#define Unlock(lock) \
+  _InterlockedCompareExchange(lock, LOCK_IS_FREE, LOCK_IS_TAKEN);
+
+#if defined(WIN32)
+static void vprof_printf(const char* format, ...) {
+  va_list args;
+  va_start(args, format);
+
+  char buf[1024];
+  vsnprintf(buf, sizeof(buf), format, args);
+
+  va_end(args);
+
+  printf(buf);
+  ::OutputDebugStringA(buf);
+}
+#else
+#  define vprof_printf printf
+#endif
+
+static inline entry* reverse(entry* s) {
+  entry_t e, n, p;
+
+  p = nullptr;
+  for (e = s; e; e = n) {
+    n = e->next;
+    e->next = p;
+    p = e;
+  }
+
+  return p;
+}
+
+static char* f(double d) {
+  static char s[80];
+  char* p;
+  sprintf_s(s, sizeof(s), "%lf", d);
+  p = s + VMPI_strlen(s) - 1;
+  while (*p == '0') {
+    *p = '\0';
+    p--;
+    if (p == s) break;
+  }
+  if (*p == '.') *p = '\0';
+  return s;
+}
+
+static void dumpProfile(void) {
+  entry_t e;
+
+  entries = reverse(entries);
+  vprof_printf("event avg [min : max] total count\n");
+  for (e = entries; e; e = e->next) {
+    if (e->count == 0) continue;  // ignore entries with zero count.
+    vprof_printf("%s", e->file);
+    if (e->line >= 0) {
+      vprof_printf(":%d", e->line);
+    }
+    vprof_printf(" %s [%lld : %lld] %lld %lld ",
+                 f(((double)e->sum) / ((double)e->count)),
+                 (long long int)e->min, (long long int)e->max,
+                 (long long int)e->sum, (long long int)e->count);
+    if (e->h) {
+      int j = MAXINT;
+      for (j = 0; j < e->h->nbins; j++) {
+        vprof_printf("(%lld < %lld) ", (long long int)e->h->count[j],
+                     (long long int)e->h->lb[j]);
+      }
+      vprof_printf("(%lld >= %lld) ", (long long int)e->h->count[e->h->nbins],
+                   (long long int)e->h->lb[e->h->nbins - 1]);
+    }
+    if (e->func) {
+      int j;
+      for (j = 0; j < NUM_EVARS; j++) {
+        if (e->ivar[j] != 0) {
+          vprof_printf("IVAR%d %d ", j, e->ivar[j]);
+        }
+      }
+      for (j = 0; j < NUM_EVARS; j++) {
+        if (e->i64var[j] != 0) {
+          vprof_printf("I64VAR%d %lld ", j, (long long int)e->i64var[j]);
+        }
+      }
+      for (j = 0; j < NUM_EVARS; j++) {
+        if (e->dvar[j] != 0) {
+          vprof_printf("DVAR%d %lf ", j, e->dvar[j]);
+        }
+      }
+    }
+    vprof_printf("\n");
+  }
+  entries = reverse(entries);
+}
+
+static inline entry_t findEntry(char* file, int line) {
+  for (entry_t e = entries; e; e = e->next) {
+    if ((e->line == line) && (VMPI_strcmp(e->file, file) == 0)) {
+      return e;
+    }
+  }
+  return nullptr;
+}
+
+// Initialize the location pointed to by 'id' to a new value profile entry
+// associated with 'file' and 'line', or do nothing if already initialized.
+// An optional final argument provides a user-defined probe function.
+
+int initValueProfile(void** id, char* file, int line, ...) {
+  DO_LOCK(&glock);
+  entry_t e = (entry_t)*id;
+  if (notInitialized) {
+    atexit(dumpProfile);
+    notInitialized = false;
+  }
+
+  if (e == nullptr) {
+    e = findEntry(file, line);
+    if (e) {
+      *id = e;
+    }
+  }
+
+  if (e == nullptr) {
+    va_list va;
+    e = (entry_t)malloc(sizeof(entry));
+    e->lock = LOCK_IS_FREE;
+    e->file = file;
+    e->line = line;
+    e->value = 0;
+    e->sum = 0;
+    e->count = 0;
+    e->min = 0;
+    e->max = 0;
+    // optional probe function argument
+    va_start(va, line);
+    e->func = (void(__cdecl*)(void*))va_arg(va, void*);
+    va_end(va);
+    e->h = nullptr;
+    e->genptr = nullptr;
+    VMPI_memset(&e->ivar, 0, sizeof(e->ivar));
+    VMPI_memset(&e->i64var, 0, sizeof(e->i64var));
+    VMPI_memset(&e->dvar, 0, sizeof(e->dvar));
+    e->next = entries;
+    entries = e;
+    *id = e;
+  }
+  DO_UNLOCK(&glock);
+
+  return 0;
+}
+
+// Record a value profile event.
+
+int profileValue(void* id, int64_t value) {
+  entry_t e = (entry_t)id;
+  long* lock = &(e->lock);
+  LOCK(lock);
+  e->value = value;
+  if (e->count == 0) {
+    e->sum = value;
+    e->count = 1;
+    e->min = value;
+    e->max = value;
+  } else {
+    e->sum += value;
+    e->count++;
+    e->min = MIN(e->min, value);
+    e->max = MAX(e->max, value);
+  }
+  if (e->func) e->func(e);
+  UNLOCK(lock);
+
+  return 0;
+}
+
+// Initialize the location pointed to by 'id' to a new histogram profile entry
+// associated with 'file' and 'line', or do nothing if already initialized.
+
+int initHistProfile(void** id, char* file, int line, int nbins, ...) {
+  DO_LOCK(&glock);
+  entry_t e = (entry_t)*id;
+  if (notInitialized) {
+    atexit(dumpProfile);
+    notInitialized = false;
+  }
+
+  if (e == nullptr) {
+    e = findEntry(file, line);
+    if (e) {
+      *id = e;
+    }
+  }
+
+  if (e == nullptr) {
+    va_list va;
+    hist_t h;
+    int b, n, s;
+    int64_t* lb;
+
+    e = (entry_t)malloc(sizeof(entry));
+    e->lock = LOCK_IS_FREE;
+    e->file = file;
+    e->line = line;
+    e->value = 0;
+    e->sum = 0;
+    e->count = 0;
+    e->min = 0;
+    e->max = 0;
+    e->func = nullptr;
+    e->h = h = (hist_t)malloc(sizeof(hist));
+    n = 1 + MAX(nbins, 0);
+    h->nbins = n - 1;
+    s = n * sizeof(int64_t);
+    lb = (int64_t*)malloc(s);
+    h->lb = lb;
+    VMPI_memset(h->lb, 0, s);
+    h->count = (int64_t*)malloc(s);
+    VMPI_memset(h->count, 0, s);
+
+    va_start(va, nbins);
+    for (b = 0; b < nbins; b++) {
+      // lb[b] = va_arg (va, int64_t);
+      lb[b] = va_arg(va, int);
+    }
+    lb[b] = MAXINT64;
+    va_end(va);
+
+    e->genptr = nullptr;
+    VMPI_memset(&e->ivar, 0, sizeof(e->ivar));
+    VMPI_memset(&e->i64var, 0, sizeof(e->i64var));
+    VMPI_memset(&e->dvar, 0, sizeof(e->dvar));
+    e->next = entries;
+    entries = e;
+    *id = e;
+  }
+  DO_UNLOCK(&glock);
+
+  return 0;
+}
+
+// Record a histogram profile event.
+
+int histValue(void* id, int64_t value) {
+  entry_t e = (entry_t)id;
+  long* lock = &(e->lock);
+  hist_t h = e->h;
+  int nbins = h->nbins;
+  int64_t* lb = h->lb;
+  int b;
+
+  LOCK(lock);
+  e->value = value;
+  if (e->count == 0) {
+    e->sum = value;
+    e->count = 1;
+    e->min = value;
+    e->max = value;
+  } else {
+    e->sum += value;
+    e->count++;
+    e->min = MIN(e->min, value);
+    e->max = MAX(e->max, value);
+  }
+  for (b = 0; b < nbins; b++) {
+    if (value < lb[b]) break;
+  }
+  h->count[b]++;
+  UNLOCK(lock);
+
+  return 0;
+}
+
+#if defined(_MSC_VER) && defined(_M_IX86)
+uint64_t readTimestampCounter() {
+  // read the cpu cycle counter.  1 tick = 1 cycle on IA32
+  _asm rdtsc;
+}
+#elif defined(__GNUC__) && (__i386__ || __x86_64__)
+uint64_t readTimestampCounter() {
+  uint32_t lo, hi;
+  __asm__ __volatile__("rdtsc" : "=a"(lo), "=d"(hi));
+  return (uint64_t(hi) << 32) | lo;
+}
+#else
+// add stub for platforms without it, so fat builds don't fail
+uint64_t readTimestampCounter() { return 0; }
+#endif
diff --git a/js/src/devtools/vprof/vprof.h b/js/src/devtools/vprof/vprof.h
new file mode 100644
index 0000000000..3d7b290d04
--- /dev/null
+++ b/js/src/devtools/vprof/vprof.h
@@ -0,0 +1,270 @@
+/* -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: t; tab-width: 4 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+//
+//  Here are a few examples of using the value-profiling utility:
+//
+//  _vprof (e);
+//    at the end of program execution, you'll get a dump of the source location
+//    of this probe, its min, max, average, the total sum of all instances of e,
+//    and the total number of times this probe was called.
+//
+//  _vprof (x > 0);
+//    shows how many times and what percentage of the cases x was > 0,
+//    that is the probablitiy that x > 0.
+//
+// _vprof (n % 2 == 0);
+//    shows how many times n was an even number
+//    as well as th probablitiy of n being an even number.
+//
+// _hprof (n, 4, 1000, 5000, 5001, 10000);
+//    gives you the histogram of n over the given 4 bucket boundaries:
+//        # cases <  1000
+//        # cases >= 1000 and < 5000
+//        # cases >= 5000 and < 5001
+//        # cases >= 5001 and < 10000
+//        # cases >= 10000
+//
+// _nvprof ("event name", value);
+//    all instances with the same name are merged
+//    so, you can call _vprof with the same event name at difference places
+//
+// _vprof (e, myProbe);
+//    value profile e and call myProbe (void* vprofID) at the profiling point.
+//    inside the probe, the client has the predefined variables:
+//    _VAL, _COUNT, _SUM, _MIN, _MAX, and the general purpose registers
+//    _IVAR1, ..., IVAR4      general integer registrs
+//    _I64VAR1, ..., I64VAR4  general integer64 registrs
+//    _DVAR1, ..., _DVAR4     general double registers
+//    _GENPTR a generic pointer that can be used by the client
+//    the number of registers can be changed in vprof.h
+//
+
+#ifndef devtools_vprof_vprof_h
+#define devtools_vprof_vprof_h
+//
+// If the application for which you want to use vprof is threaded, THREADED must
+// be defined as 1, otherwise define it as 0
+//
+// If your application is not threaded, define THREAD_SAFE 0,
+// otherwise, you have the option of setting THREAD_SAFE to 1 which results in
+// exact counts or to 0 which results in a much more efficient but non-exact
+// counts
+//
+#define THREADED 0
+#define THREAD_SAFE 0
+
+#include "VMPI.h"
+
+// Note, this is not supported in configurations with more than one AvmCore
+// running in the same process.
+
+// portable align macro
+#if defined(_MSC_VER)
+#  define vprof_align8(t) __declspec(align(8)) t
+#elif defined(__GNUC__)
+#  define vprof_align8(t) t __attribute__((aligned(8)))
+#elif defined(__SUNPRO_C) || defined(__SUNPRO_CC)
+#  define vprof_align8(t) t __attribute__((aligned(8)))
+#elif defined(VMCFG_SYMBIAN)
+#  define vprof_align8(t) t __attribute__((aligned(8)))
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int initValueProfile(void** id, char* file, int line, ...);
+int profileValue(void* id, int64_t value);
+int initHistProfile(void** id, char* file, int line, int nbins, ...);
+int histValue(void* id, int64_t value);
+uint64_t readTimestampCounter();
+
+#ifdef __cplusplus
+}
+#endif
+
+// #define DOPROF
+
+#ifndef DOPROF
+#  define _nvprof(e, v)
+#  ifndef VMCFG_SYMBIAN
+#    define _vprof(v, ...)
+#    define _hprof(v, n, ...)
+#    define _nhprof(e, v, n, ...)
+#    define _ntprof_begin(e)
+#    define _ntprof_end(e)
+#    define _jvprof_init(id, ...)
+#    define _jnvprof_init(id, e, ...)
+#    define _jhprof_init(id, n, ...)
+#    define _jnhprof_init(id, e, n, ...)
+#    define _jvprof(id, v)
+#    define _jhprof(id, v)
+#  endif  // ! VMCFG_SYMBIAN
+#else
+
+// Historical/compatibility note:
+// The macros below were originally written using conditional expressions, not
+// if/else.  The original author said that this was done to allow _vprof and
+// _nvprof to be used in an expression context, but the old code had already
+// wrapped the macro bodies in { }, so it is not clear how this could have
+// worked.  At present, the profiling macros must appear in a statement context
+// only.
+
+#  define _vprof(v, ...)                                                \
+    do {                                                                \
+      static void* id = 0;                                              \
+      if (id == 0)                                                      \
+        initValueProfile(&id, __FILE__, __LINE__, ##__VA_ARGS__, NULL); \
+      profileValue(id, (int64_t)(v));                                   \
+    } while (0)
+
+#  define _nvprof(e, v)                                         \
+    do {                                                        \
+      static void* id = 0;                                      \
+      if (id == 0) initValueProfile(&id, (char*)(e), -1, NULL); \
+      profileValue(id, (int64_t)(v));                           \
+    } while (0)
+
+#  define _hprof(v, n, ...)                                                \
+    do {                                                                   \
+      static void* id = 0;                                                 \
+      if (id == 0)                                                         \
+        initHistProfile(&id, __FILE__, __LINE__, (int)(n), ##__VA_ARGS__); \
+      histValue(id, (int64_t)(v));                                         \
+    } while (0)
+
+#  define _nhprof(e, v, n, ...)                                        \
+    do {                                                               \
+      static void* id = 0;                                             \
+      if (id == 0)                                                     \
+        initHistProfile(&id, (char*)(e), -1, (int)(n), ##__VA_ARGS__); \
+      histValue(id, (int64_t)(v));                                     \
+    } while (0)
+
+// Profile execution time between _ntprof_begin(e) and _ntprof_end(e).
+// The tag 'e' must match at the beginning and end of the region to
+// be timed.  Regions may be nested or overlap arbitrarily, as it is
+// the tag alone that defines the begin/end correspondence.
+
+#  define _ntprof_begin(e)                                      \
+    do {                                                        \
+      static void* id = 0;                                      \
+      if (id == 0) initValueProfile(&id, (char*)(e), -1, NULL); \
+      ((entry_t)id)->i64var[0] = readTimestampCounter();        \
+    } while (0)
+
+// Assume 2.6 Ghz CPU
+#  define TICKS_PER_USEC 2600
+
+#  define _ntprof_end(e)                                        \
+    do {                                                        \
+      static void* id = 0;                                      \
+      uint64_t stop = readTimestampCounter();                   \
+      if (id == 0) initValueProfile(&id, (char*)(e), -1, NULL); \
+      uint64_t start = ((entry_t)id)->i64var[0];                \
+      uint64_t usecs = (stop - start) / TICKS_PER_USEC;         \
+      profileValue(id, usecs);                                  \
+    } while (0)
+
+// These macros separate the creation of a profile record from its later usage.
+// They are intended for profiling JIT-generated code.  Once created, the JIT
+// can bind a pointer to the profile record into the generated code, which can
+// then record profile events during execution.
+
+#  define _jvprof_init(id, ...) \
+    if (*(id) == 0)             \
+    initValueProfile((id), __FILE__, __LINE__, ##__VA_ARGS__, NULL)
+
+#  define _jnvprof_init(id, e, ...) \
+    if (*(id) == 0) initValueProfile((id), (char*)(e), -1, ##__VA_ARGS__, NULL)
+
+#  define _jhprof_init(id, n, ...) \
+    if (*(id) == 0)                \
+    initHistProfile((id), __FILE__, __LINE__, (int)(n), ##__VA_ARGS__)
+
+#  define _jnhprof_init(id, e, n, ...) \
+    if (*(id) == 0)                    \
+    initHistProfile((id), (char*)(e), -1, (int)(n), ##__VA_ARGS__)
+
+// Calls to the _jvprof and _jhprof macros must be wrapped in a non-inline
+// function in order to be invoked from JIT-compiled code.
+
+#  define _jvprof(id, v) profileValue((id), (int64_t)(v))
+
+#  define _jhprof(id, v) histValue((id), (int64_t)(v))
+
+#endif
+
+#define NUM_EVARS 4
+
+enum { LOCK_IS_FREE = 0, LOCK_IS_TAKEN = 1 };
+
+extern
+#ifdef __cplusplus
+    "C"
+#endif
+    long
+    _InterlockedCompareExchange(long volatile* Destination, long Exchange,
+                                long Comperand);
+
+typedef struct hist hist;
+
+typedef struct hist {
+  int nbins;
+  int64_t* lb;
+  int64_t* count;
+}* hist_t;
+
+typedef struct entry entry;
+
+typedef struct entry {
+  long lock;
+  char* file;
+  int line;
+  int64_t value;
+  int64_t count;
+  int64_t sum;
+  int64_t min;
+  int64_t max;
+  void (*func)(void*);
+  hist* h;
+
+  entry* next;
+
+  // exposed to the clients
+  void* genptr;
+  int ivar[NUM_EVARS];
+  vprof_align8(int64_t) i64var[NUM_EVARS];
+  vprof_align8(double) dvar[NUM_EVARS];
+  //
+
+  char pad[128];  // avoid false sharing
+}* entry_t;
+
+#define _VAL ((entry_t)vprofID)->value
+#define _COUNT ((entry_t)vprofID)->count
+#define _SUM ((entry_t)vprofID)->sum
+#define _MIN ((entry_t)vprofID)->min
+#define _MAX ((entry_t)vprofID)->max
+
+#define _GENPTR ((entry_t)vprofID)->genptr
+
+#define _IVAR0 ((entry_t)vprofID)->ivar[0]
+#define _IVAR1 ((entry_t)vprofID)->ivar[1]
+#define _IVAR2 ((entry_t)vprofID)->ivar[2]
+#define _IVAR3 ((entry_t)vprofID)->ivar[3]
+
+#define _I64VAR0 ((entry_t)vprofID)->i64var[0]
+#define _I64VAR1 ((entry_t)vprofID)->i64var[1]
+#define _I64VAR2 ((entry_t)vprofID)->i64var[2]
+#define _I64VAR3 ((entry_t)vprofID)->i64var[3]
+
+#define _DVAR0 ((entry_t)vprofID)->dvar[0]
+#define _DVAR1 ((entry_t)vprofID)->dvar[1]
+#define _DVAR2 ((entry_t)vprofID)->dvar[2]
+#define _DVAR3 ((entry_t)vprofID)->dvar[3]
+
+#endif /* devtools_vprof_vprof_h */