Adding upstream version 115.7.0esr.upstream/115.7.0esr

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

28 files changed, 7487 insertions, 0 deletions

diff --git a/third_party/rust/jsparagus-stencil/.cargo-checksum.json b/third_party/rust/jsparagus-stencil/.cargo-checksum.json
new file mode 100644
index 0000000000..62807be51a
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/.cargo-checksum.json
@@ -0,0 +1 @@
+{"files":{"Cargo.toml":"4e07563463b79faddd43c5a74609c1745d2ca78a37e6a2a4aff3eca48637aa86","src/bytecode_offset.rs":"2aa7ba8c3cfbbd832092e65b599ab1c5a28d784ccc65d9e351bba656421b9a69","src/copy/AsyncFunctionResolveKind.h":"3851ecbb4728257595dd6e900749d1d8e02558574c00424a7ff0e3ca007fa6ec","src/copy/BytecodeFormatFlags.h":"48b561791fb2ef7189ffd17a26bb65163c24d398637b8d1cf9a09bc3964adca7","src/copy/CheckIsObjectKind.h":"8f0e112396d966c9221a743d353f62671e04cdace7dd49a59898d94ba0f621b7","src/copy/CompletionKind.h":"a491664ee7423ce75f34af4efa3df47934b42139f1b19741b2aa95f02d9230bf","src/copy/FunctionFlags.h":"03564f057262b73bebf31ab6c8f6a99a22983a87f1b9e7f48219d30af837423f","src/copy/FunctionPrefixKind.h":"f540a5c646a519b2d61aa27e4be865e08a31438def00ad5ba4ba2982ad1f2275","src/copy/GeneratorAndAsyncKind.h":"301668ce705970a51abfa94f89fd5db29ef5f129525110860e9e9bf7586ef187","src/copy/GeneratorResumeKind.h":"9e3cd9dc9c7f50937c6c45d73ec092dbfd92c4b56818ae6d1504bcd77078d0a6","src/copy/Opcodes.h":"6d1d8058b362d7032687737a2fe61c15374309e83c0d00cba05fb9660bd24ca8","src/copy/SourceNotes.h":"46fdf5ee41a309bf12eccf2bad3cc4736bcb8f43c3471a2ef506b9f3624ec91c","src/copy/StencilEnums.h":"fa3c3ff54947e8d876a0c5da549f9fa51393e22d644b909cc7a08a201de6d5ef","src/copy/Symbol.h":"98a827d5bf68567a75686ee0b72b9fb960bde77e96771bbf03fc0a33b601be41","src/copy/ThrowMsgKind.h":"ba180dc8c5c8eb4ff24a5ceb1a4df70e2e9005440766576e5eb2dc5a18b0a9dd","src/env_coord.rs":"0be36a1bd307f5586affe0f3046d8b2ab2f5382b41b7b7bfb364b97d16a7c410","src/frame_slot.rs":"b20c81d67c572f20d06d493b211cd3eaa0432a8294541583643b82df3af2f813","src/function.rs":"5357f3dc871a981c7dc21aac7fe736f0e55302f27ef5c63ed04915a2c845fff6","src/gcthings.rs":"baadc7284c01961a4aa44d464a6f5a0d0be427b6d099c949d4411846738d9a45","src/lib.rs":"b003e085344277d2987ef492dc513048e8ec83217850a22ba7ca06ac01bc9b5c","src/opcode.rs":"804dc73a7adba17f557fa80deaebe0caba1be0aeaa549fae1a0dfcd56dc88f32","src/opcode_info.rs":"a27c6d5602f5ecdcc882a0167614bc7a7754d958124941b4c1c0cdc2b0a894f1","src/regexp.rs":"7436cf545b990bec7dcc51ff28d67deaca9d4ce894468fdad0dd44b25c571cf2","src/result.rs":"62d3a851b8a497eecc350eed3ba6155b01a4d0e8e5bcfdf8dab776333d19825c","src/scope.rs":"3d2269a06d3e55d24f697338fedde95d9c653faec02d4694d0b63c79979e7c5a","src/scope_notes.rs":"9947ba5aba3097321c76adcb5648a478e4a67e088fdc1e01511e51c4ad41a9f3","src/script.rs":"c28883d1f2535cffab2820d6d7c48ed853a6c00f9fb410ab7ee56117667452eb"},"package":null}
\ No newline at end of file
diff --git a/third_party/rust/jsparagus-stencil/Cargo.toml b/third_party/rust/jsparagus-stencil/Cargo.toml
new file mode 100644
index 0000000000..eb67d949d1
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/Cargo.toml
@@ -0,0 +1,20 @@
+# THIS FILE IS AUTOMATICALLY GENERATED BY CARGO
+#
+# When uploading crates to the registry Cargo will automatically
+# "normalize" Cargo.toml files for maximal compatibility
+# with all versions of Cargo and also rewrite `path` dependencies
+# to registry (e.g., crates.io) dependencies.
+#
+# If you are reading this file be aware that the original Cargo.toml
+# will likely look very different (and much more reasonable).
+# See Cargo.toml.orig for the original contents.
+
+[package]
+edition = "2018"
+name = "jsparagus-stencil"
+version = "0.1.0"
+authors = ["The jsparagus Project Developers"]
+license = "MIT/Apache-2.0"
+
+[dependencies.jsparagus-ast]
+path = "../ast"
diff --git a/third_party/rust/jsparagus-stencil/src/bytecode_offset.rs b/third_party/rust/jsparagus-stencil/src/bytecode_offset.rs
new file mode 100644
index 0000000000..3583ec6728
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/bytecode_offset.rs
@@ -0,0 +1,60 @@
+/// For tracking bytecode offsets in jumps
+#[derive(Clone, Copy, PartialEq, Debug)]
+#[must_use]
+pub struct BytecodeOffset {
+    pub offset: usize,
+}
+
+impl BytecodeOffset {
+    fn new(offset: usize) -> Self {
+        Self { offset }
+    }
+
+    /// diff_from is useful for finding the offset between two bytecodes. This is usually
+    /// used for jumps and jump_targets.
+    ///
+    /// For a forward jump, self will be a larger number, and start will be smaller
+    /// the output will be a positive number.  for a backward jump, the reverse
+    /// will be true, and the number will be negative. So it is important to use this api
+    /// consistently in both cases.
+    ///
+    /// Examples:
+    /// let offset_diff: BytecodeOffsetDiff = forward_jump_target_offset.diff_from(jump)
+    /// let offset_diff: BytecodeOffsetDiff = backward_jump_target_offset.diff_from(jump)
+    pub fn diff_from(self, start: BytecodeOffset) -> BytecodeOffsetDiff {
+        BytecodeOffsetDiff::new(self, start)
+    }
+}
+
+impl From<BytecodeOffset> for usize {
+    fn from(offset: BytecodeOffset) -> usize {
+        offset.offset
+    }
+}
+
+impl From<usize> for BytecodeOffset {
+    fn from(offset: usize) -> BytecodeOffset {
+        BytecodeOffset::new(offset)
+    }
+}
+
+pub struct BytecodeOffsetDiff {
+    diff: i32,
+}
+
+impl BytecodeOffsetDiff {
+    fn new(end: BytecodeOffset, start: BytecodeOffset) -> Self {
+        let diff = (end.offset as i128 - start.offset as i128) as i32;
+        Self { diff }
+    }
+
+    pub fn uninitialized() -> Self {
+        Self { diff: 0i32 }
+    }
+}
+
+impl From<BytecodeOffsetDiff> for i32 {
+    fn from(offset: BytecodeOffsetDiff) -> i32 {
+        offset.diff
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/copy/AsyncFunctionResolveKind.h b/third_party/rust/jsparagus-stencil/src/copy/AsyncFunctionResolveKind.h
new file mode 100644
index 0000000000..75adfcec3c
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/AsyncFunctionResolveKind.h
@@ -0,0 +1,18 @@
+/* -*- 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/. */
+
+#ifndef vm_AsyncFunctionResolveKind_h
+#define vm_AsyncFunctionResolveKind_h
+
+#include <stdint.h>  // uint8_t
+
+namespace js {
+
+enum class AsyncFunctionResolveKind : uint8_t { Fulfill, Reject };
+
+}  // namespace js
+
+#endif /* vm_AsyncFunctionResolveKind_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/BytecodeFormatFlags.h b/third_party/rust/jsparagus-stencil/src/copy/BytecodeFormatFlags.h
new file mode 100644
index 0000000000..0a0c0efafb
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/BytecodeFormatFlags.h
@@ -0,0 +1,60 @@
+/* -*- 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/. */
+
+#ifndef vm_BytecodeFormatFlags_h
+#define vm_BytecodeFormatFlags_h
+
+/*
+ * [SMDOC] Bytecode Format flags (JOF_*)
+ */
+enum {
+  JOF_BYTE = 0,         /* single bytecode, no immediates */
+  JOF_UINT8 = 1,        /* unspecified uint8_t argument */
+  JOF_UINT16 = 2,       /* unspecified uint16_t argument */
+  JOF_UINT24 = 3,       /* unspecified uint24_t argument */
+  JOF_UINT32 = 4,       /* unspecified uint32_t argument */
+  JOF_INT8 = 5,         /* int8_t literal */
+  JOF_INT32 = 6,        /* int32_t literal */
+  JOF_JUMP = 7,         /* int32_t jump offset */
+  JOF_TABLESWITCH = 8,  /* table switch */
+  JOF_ENVCOORD = 9,     /* embedded ScopeCoordinate immediate */
+  JOF_ARGC = 10,        /* uint16_t argument count */
+  JOF_QARG = 11,        /* function argument index */
+  JOF_LOCAL = 12,       /* var or block-local variable */
+  JOF_RESUMEINDEX = 13, /* yield or await resume index */
+  JOF_DOUBLE = 14,      /* inline DoubleValue */
+  JOF_GCTHING = 15,     /* uint32_t generic gc-thing index */
+  JOF_ATOM = 16,        /* uint32_t constant index */
+  JOF_OBJECT = 17,      /* uint32_t object index */
+  JOF_REGEXP = 18,      /* uint32_t regexp index */
+  JOF_SCOPE = 19,       /* uint32_t scope index */
+  JOF_BIGINT = 20,      /* uint32_t index for BigInt value */
+  JOF_ICINDEX = 21,     /* uint32_t IC index */
+  JOF_LOOPHEAD = 22,    /* JSOp::LoopHead, combines JOF_ICINDEX and JOF_UINT8 */
+  JOF_TWO_UINT8 = 23,   /* A pair of unspecified uint8_t arguments */
+  JOF_DEBUGCOORD = 24,  /* An embedded ScopeCoordinate immediate that may
+                           traverse DebugEnvironmentProxies*/
+  JOF_SHAPE = 25,       /* uint32_t shape index */
+  JOF_STRING = 26,      /* uint32_t constant index */
+  JOF_TYPEMASK = 0xFF,  /* mask for above immediate types */
+
+  JOF_NAME = 1 << 8,        /* name operation */
+  JOF_PROP = 2 << 8,        /* obj.prop operation */
+  JOF_ELEM = 3 << 8,        /* obj[index] operation */
+  JOF_MODEMASK = 0xFF << 8, /* mask for above addressing modes */
+
+  JOF_PROPSET = 1 << 16,     /* property/element/name set operation */
+  JOF_PROPINIT = 1 << 17,    /* property/element/name init operation */
+  JOF_CHECKSLOPPY = 1 << 18, /* op can only be generated in sloppy mode */
+  JOF_CHECKSTRICT = 1 << 19, /* op can only be generated in strict mode */
+  JOF_INVOKE = 1 << 20,      /* any call, construct, or eval instruction */
+  JOF_CONSTRUCT = 1 << 21,   /* invoke instruction using [[Construct]] entry */
+  JOF_SPREAD = 1 << 22,      /* invoke instruction using spread argument */
+  JOF_GNAME = 1 << 23,       /* predicted global name */
+  JOF_IC = 1 << 24,          /* baseline may use an IC for this op */
+};
+
+#endif /* vm_BytecodeFormatFlags_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/CheckIsObjectKind.h b/third_party/rust/jsparagus-stencil/src/copy/CheckIsObjectKind.h
new file mode 100644
index 0000000000..321870d6ed
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/CheckIsObjectKind.h
@@ -0,0 +1,24 @@
+/* -*- 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/. */
+
+#ifndef vm_CheckIsObjectKind_h
+#define vm_CheckIsObjectKind_h
+
+#include <stdint.h>  // uint8_t
+
+namespace js {
+
+enum class CheckIsObjectKind : uint8_t {
+  IteratorNext,
+  IteratorReturn,
+  IteratorThrow,
+  GetIterator,
+  GetAsyncIterator
+};
+
+}  // namespace js
+
+#endif /* vm_CheckIsObjectKind_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/CompletionKind.h b/third_party/rust/jsparagus-stencil/src/copy/CompletionKind.h
new file mode 100644
index 0000000000..0f9168ce83
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/CompletionKind.h
@@ -0,0 +1,16 @@
+/* -*- 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/. */
+
+#ifndef vm_CompletionKind_h
+#define vm_CompletionKind_h
+
+namespace js {
+
+enum class CompletionKind : uint8_t { Normal, Return, Throw };
+
+}  // namespace js
+
+#endif  // vm_CompletionKind_h
diff --git a/third_party/rust/jsparagus-stencil/src/copy/FunctionFlags.h b/third_party/rust/jsparagus-stencil/src/copy/FunctionFlags.h
new file mode 100644
index 0000000000..a757bf4ac5
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/FunctionFlags.h
@@ -0,0 +1,320 @@
+/* -*- 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/. */
+
+#ifndef vm_FunctionFlags_h
+#define vm_FunctionFlags_h
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT, MOZ_ASSERT_IF
+#include "mozilla/Attributes.h"  // MOZ_IMPLICIT
+
+#include <stdint.h>  // uint8_t, uint16_t
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+class JS_PUBLIC_API JSAtom;
+
+namespace js {
+
+class FunctionFlags {
+ public:
+  enum FunctionKind : uint8_t {
+    NormalFunction = 0,
+    Arrow,   // ES6 '(args) => body' syntax
+    Method,  // ES6 MethodDefinition
+    ClassConstructor,
+    Getter,
+    Setter,
+    AsmJS,  // An asm.js module or exported function
+    Wasm,   // An exported WebAssembly function
+    FunctionKindLimit
+  };
+
+  enum Flags : uint16_t {
+    // The general kind of a function. This is used to describe characteristics
+    // of functions that do not merit a dedicated flag bit below.
+    FUNCTION_KIND_SHIFT = 0,
+    FUNCTION_KIND_MASK = 0x0007,
+
+    // The AllocKind used was FunctionExtended and extra slots were allocated.
+    // These slots may be used by the engine or the embedding so care must be
+    // taken to avoid conflicts.
+    EXTENDED = 1 << 3,
+
+    // Set if function is a self-hosted builtin or intrinsic. An 'intrinsic'
+    // here means a native function used inside self-hosted code. In general, a
+    // self-hosted function should appear to script as though it were a native
+    // builtin.
+    SELF_HOSTED = 1 << 4,
+
+    // An interpreted function has or may-have bytecode and an environment. Only
+    // one of these flags may be used at a time. As a memory optimization, the
+    // SELFHOSTLAZY flag indicates there is no js::BaseScript at all and we must
+    // clone from the self-hosted realm in order to get bytecode.
+    BASESCRIPT = 1 << 5,
+    SELFHOSTLAZY = 1 << 6,
+
+    // Function may be called as a constructor. This corresponds in the spec as
+    // having a [[Construct]] internal method.
+    CONSTRUCTOR = 1 << 7,
+
+    // (1 << 8) is unused.
+
+    // Function comes from a FunctionExpression, ArrowFunction, or Function()
+    // call (not a FunctionDeclaration or nonstandard function-statement).
+    LAMBDA = 1 << 9,
+
+    // The WASM function has a JIT entry which emulates the
+    // js::BaseScript::jitCodeRaw mechanism.
+    WASM_JIT_ENTRY = 1 << 10,
+
+    // Function had no explicit name, but a name was set by SetFunctionName at
+    // compile time or SetFunctionName at runtime.
+    HAS_INFERRED_NAME = 1 << 11,
+
+    // Function had no explicit name, but a name was guessed for it anyway.
+    HAS_GUESSED_ATOM = 1 << 12,
+
+    // The 'length' or 'name property has been resolved. See fun_resolve.
+    RESOLVED_NAME = 1 << 13,
+    RESOLVED_LENGTH = 1 << 14,
+
+    // This function is kept only for skipping it over during delazification.
+    //
+    // This function is inside arrow function's parameter expression, and
+    // parsed twice, once before finding "=>" token, and once after finding
+    // "=>" and rewinding to the beginning of the parameters.
+    // ScriptStencil is created for both case, and the first one is kept only
+    // for delazification, to make sure delazification sees the same sequence
+    // of inner function to skip over.
+    //
+    // We call the first one "ghost".
+    // It should be kept lazy, and shouldn't be exposed to debugger.
+    GHOST_FUNCTION = 1 << 15,
+
+    // Shifted form of FunctionKinds.
+    NORMAL_KIND = NormalFunction << FUNCTION_KIND_SHIFT,
+    ASMJS_KIND = AsmJS << FUNCTION_KIND_SHIFT,
+    WASM_KIND = Wasm << FUNCTION_KIND_SHIFT,
+    ARROW_KIND = Arrow << FUNCTION_KIND_SHIFT,
+    METHOD_KIND = Method << FUNCTION_KIND_SHIFT,
+    CLASSCONSTRUCTOR_KIND = ClassConstructor << FUNCTION_KIND_SHIFT,
+    GETTER_KIND = Getter << FUNCTION_KIND_SHIFT,
+    SETTER_KIND = Setter << FUNCTION_KIND_SHIFT,
+
+    // Derived Flags combinations to use when creating functions.
+    NATIVE_FUN = NORMAL_KIND,
+    NATIVE_CTOR = CONSTRUCTOR | NORMAL_KIND,
+    ASMJS_CTOR = CONSTRUCTOR | ASMJS_KIND,
+    ASMJS_LAMBDA_CTOR = CONSTRUCTOR | LAMBDA | ASMJS_KIND,
+    WASM = WASM_KIND,
+    INTERPRETED_NORMAL = BASESCRIPT | CONSTRUCTOR | NORMAL_KIND,
+    INTERPRETED_CLASS_CTOR = BASESCRIPT | CONSTRUCTOR | CLASSCONSTRUCTOR_KIND,
+    INTERPRETED_GENERATOR_OR_ASYNC = BASESCRIPT | NORMAL_KIND,
+    INTERPRETED_LAMBDA = BASESCRIPT | LAMBDA | CONSTRUCTOR | NORMAL_KIND,
+    INTERPRETED_LAMBDA_ARROW = BASESCRIPT | LAMBDA | ARROW_KIND,
+    INTERPRETED_LAMBDA_GENERATOR_OR_ASYNC = BASESCRIPT | LAMBDA | NORMAL_KIND,
+    INTERPRETED_GETTER = BASESCRIPT | GETTER_KIND,
+    INTERPRETED_SETTER = BASESCRIPT | SETTER_KIND,
+    INTERPRETED_METHOD = BASESCRIPT | METHOD_KIND,
+
+    // Flags that XDR ignores. See also: js::BaseScript::MutableFlags.
+    MUTABLE_FLAGS = RESOLVED_NAME | RESOLVED_LENGTH,
+
+    // Flags preserved when cloning a function.
+    STABLE_ACROSS_CLONES =
+        CONSTRUCTOR | LAMBDA | SELF_HOSTED | FUNCTION_KIND_MASK | GHOST_FUNCTION
+  };
+
+  uint16_t flags_;
+
+ public:
+  FunctionFlags() : flags_() {
+    static_assert(sizeof(FunctionFlags) == sizeof(flags_),
+                  "No extra members allowed is it'll grow JSFunction");
+    static_assert(offsetof(FunctionFlags, flags_) == 0,
+                  "Required for JIT flag access");
+  }
+
+  explicit FunctionFlags(uint16_t flags) : flags_(flags) {}
+  MOZ_IMPLICIT FunctionFlags(Flags f) : flags_(f) {}
+
+  static_assert(((FunctionKindLimit - 1) << FUNCTION_KIND_SHIFT) <=
+                    FUNCTION_KIND_MASK,
+                "FunctionKind doesn't fit into flags_");
+
+  uint16_t toRaw() const { return flags_; }
+
+  uint16_t stableAcrossClones() const { return flags_ & STABLE_ACROSS_CLONES; }
+
+  // For flag combinations the type is int.
+  bool hasFlags(uint16_t flags) const { return flags_ & flags; }
+  FunctionFlags& setFlags(uint16_t flags) {
+    flags_ |= flags;
+    return *this;
+  }
+  FunctionFlags& clearFlags(uint16_t flags) {
+    flags_ &= ~flags;
+    return *this;
+  }
+  FunctionFlags& setFlags(uint16_t flags, bool set) {
+    if (set) {
+      setFlags(flags);
+    } else {
+      clearFlags(flags);
+    }
+    return *this;
+  }
+
+  FunctionKind kind() const {
+    return static_cast<FunctionKind>((flags_ & FUNCTION_KIND_MASK) >>
+                                     FUNCTION_KIND_SHIFT);
+  }
+
+  /* A function can be classified as either native (C++) or interpreted (JS): */
+  bool isInterpreted() const {
+    return hasFlags(BASESCRIPT) || hasFlags(SELFHOSTLAZY);
+  }
+  bool isNativeFun() const { return !isInterpreted(); }
+
+  bool isConstructor() const { return hasFlags(CONSTRUCTOR); }
+
+  bool isNonBuiltinConstructor() const {
+    // Note: keep this in sync with branchIfNotFunctionIsNonBuiltinCtor in
+    // MacroAssembler.cpp.
+    return hasFlags(BASESCRIPT) && hasFlags(CONSTRUCTOR) &&
+           !hasFlags(SELF_HOSTED);
+  }
+
+  /* Possible attributes of a native function: */
+  bool isAsmJSNative() const {
+    MOZ_ASSERT_IF(kind() == AsmJS, isNativeFun());
+    return kind() == AsmJS;
+  }
+  bool isWasm() const {
+    MOZ_ASSERT_IF(kind() == Wasm, isNativeFun());
+    return kind() == Wasm;
+  }
+  bool isWasmWithJitEntry() const {
+    MOZ_ASSERT_IF(hasFlags(WASM_JIT_ENTRY), isWasm());
+    return hasFlags(WASM_JIT_ENTRY);
+  }
+  bool isNativeWithoutJitEntry() const {
+    MOZ_ASSERT_IF(!hasJitEntry(), isNativeFun());
+    return !hasJitEntry();
+  }
+  bool isBuiltinNative() const {
+    return isNativeFun() && !isAsmJSNative() && !isWasm();
+  }
+  bool hasJitEntry() const {
+    return hasBaseScript() || hasSelfHostedLazyScript() || isWasmWithJitEntry();
+  }
+
+  /* Possible attributes of an interpreted function: */
+  bool hasInferredName() const { return hasFlags(HAS_INFERRED_NAME); }
+  bool hasGuessedAtom() const { return hasFlags(HAS_GUESSED_ATOM); }
+  bool isLambda() const { return hasFlags(LAMBDA); }
+
+  bool isNamedLambda(bool hasName) const {
+    return hasName && isLambda() && !hasInferredName() && !hasGuessedAtom();
+  }
+
+  // These methods determine which of the u.scripted.s union arms are active.
+  // For live JSFunctions the pointer values will always be non-null, but due
+  // to partial initialization the GC (and other features that scan the heap
+  // directly) may still return a null pointer.
+  bool hasBaseScript() const { return hasFlags(BASESCRIPT); }
+  bool hasSelfHostedLazyScript() const { return hasFlags(SELFHOSTLAZY); }
+
+  // Arrow functions store their lexical new.target in the first extended slot.
+  bool isArrow() const { return kind() == Arrow; }
+  // Every class-constructor is also a method.
+  bool isMethod() const {
+    return kind() == Method || kind() == ClassConstructor;
+  }
+  bool isClassConstructor() const { return kind() == ClassConstructor; }
+
+  bool isGetter() const { return kind() == Getter; }
+  bool isSetter() const { return kind() == Setter; }
+
+  bool allowSuperProperty() const {
+    return isMethod() || isGetter() || isSetter();
+  }
+
+  bool hasResolvedLength() const { return hasFlags(RESOLVED_LENGTH); }
+  bool hasResolvedName() const { return hasFlags(RESOLVED_NAME); }
+
+  bool isSelfHostedOrIntrinsic() const { return hasFlags(SELF_HOSTED); }
+  bool isSelfHostedBuiltin() const {
+    return isSelfHostedOrIntrinsic() && !isNativeFun();
+  }
+  bool isIntrinsic() const {
+    return isSelfHostedOrIntrinsic() && isNativeFun();
+  }
+
+  FunctionFlags& setKind(FunctionKind kind) {
+    this->flags_ &= ~FUNCTION_KIND_MASK;
+    this->flags_ |= static_cast<uint16_t>(kind) << FUNCTION_KIND_SHIFT;
+    return *this;
+  }
+
+  // Make the function constructible.
+  FunctionFlags& setIsConstructor() {
+    MOZ_ASSERT(!isConstructor());
+    MOZ_ASSERT(isSelfHostedBuiltin());
+    return setFlags(CONSTRUCTOR);
+  }
+
+  FunctionFlags& setIsSelfHostedBuiltin() {
+    MOZ_ASSERT(isInterpreted());
+    MOZ_ASSERT(!isSelfHostedBuiltin());
+    setFlags(SELF_HOSTED);
+    // Self-hosted functions should not be constructable.
+    return clearFlags(CONSTRUCTOR);
+  }
+  FunctionFlags& setIsIntrinsic() {
+    MOZ_ASSERT(isNativeFun());
+    MOZ_ASSERT(!isIntrinsic());
+    return setFlags(SELF_HOSTED);
+  }
+
+  FunctionFlags& setResolvedLength() { return setFlags(RESOLVED_LENGTH); }
+  FunctionFlags& setResolvedName() { return setFlags(RESOLVED_NAME); }
+
+  FunctionFlags& setInferredName() { return setFlags(HAS_INFERRED_NAME); }
+
+  FunctionFlags& setGuessedAtom() { return setFlags(HAS_GUESSED_ATOM); }
+
+  FunctionFlags& setSelfHostedLazy() { return setFlags(SELFHOSTLAZY); }
+  FunctionFlags& clearSelfHostedLazy() { return clearFlags(SELFHOSTLAZY); }
+  FunctionFlags& setBaseScript() { return setFlags(BASESCRIPT); }
+  FunctionFlags& clearBaseScript() { return clearFlags(BASESCRIPT); }
+
+  FunctionFlags& setWasmJitEntry() { return setFlags(WASM_JIT_ENTRY); }
+
+  bool isExtended() const { return hasFlags(EXTENDED); }
+  FunctionFlags& setIsExtended() { return setFlags(EXTENDED); }
+
+  bool isNativeConstructor() const { return hasFlags(NATIVE_CTOR); }
+
+  FunctionFlags& setIsGhost() { return setFlags(GHOST_FUNCTION); }
+  bool isGhost() const { return hasFlags(GHOST_FUNCTION); }
+
+  static uint16_t HasJitEntryFlags(bool isConstructing) {
+    uint16_t flags = BASESCRIPT | SELFHOSTLAZY;
+    if (!isConstructing) {
+      flags |= WASM_JIT_ENTRY;
+    }
+    return flags;
+  }
+
+  static FunctionFlags clearMutableflags(FunctionFlags flags) {
+    return FunctionFlags(flags.toRaw() & ~FunctionFlags::MUTABLE_FLAGS);
+  }
+};
+
+} /* namespace js */
+
+#endif /* vm_FunctionFlags_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/FunctionPrefixKind.h b/third_party/rust/jsparagus-stencil/src/copy/FunctionPrefixKind.h
new file mode 100644
index 0000000000..d015091647
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/FunctionPrefixKind.h
@@ -0,0 +1,18 @@
+/* -*- 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/. */
+
+#ifndef vm_FunctionPrefixKind_h
+#define vm_FunctionPrefixKind_h
+
+#include <stdint.h>  // uint8_t
+
+namespace js {
+
+enum class FunctionPrefixKind : uint8_t { None, Get, Set };
+
+}  // namespace js
+
+#endif /* vm_FunctionPrefixKind_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/GeneratorAndAsyncKind.h b/third_party/rust/jsparagus-stencil/src/copy/GeneratorAndAsyncKind.h
new file mode 100644
index 0000000000..c3761a9dec
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/GeneratorAndAsyncKind.h
@@ -0,0 +1,17 @@
+/* -*- 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/. */
+
+#ifndef vm_GeneratorAndAsyncKind_h
+#define vm_GeneratorAndAsyncKind_h
+
+namespace js {
+
+enum class GeneratorKind : bool { NotGenerator, Generator };
+enum class FunctionAsyncKind : bool { SyncFunction, AsyncFunction };
+
+} /* namespace js */
+
+#endif /* vm_GeneratorAndAsyncKind_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/GeneratorResumeKind.h b/third_party/rust/jsparagus-stencil/src/copy/GeneratorResumeKind.h
new file mode 100644
index 0000000000..7ff6c0a76b
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/GeneratorResumeKind.h
@@ -0,0 +1,18 @@
+/* -*- 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/. */
+
+#ifndef vm_GeneratorResumeKind_h
+#define vm_GeneratorResumeKind_h
+
+#include <stdint.h>  // uint8_t
+
+namespace js {
+
+enum class GeneratorResumeKind : uint8_t { Next, Throw, Return };
+
+}  // namespace js
+
+#endif /* vm_GeneratorResumeKind_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/Opcodes.h b/third_party/rust/jsparagus-stencil/src/copy/Opcodes.h
new file mode 100644
index 0000000000..abbcc98172
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/Opcodes.h
@@ -0,0 +1,3600 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sw=2 et tw=0 ft=c:
+ *
+ * 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 vm_Opcodes_h
+#define vm_Opcodes_h
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "js/TypeDecls.h"
+
+// clang-format off
+/*
+ * [SMDOC] Bytecode Definitions
+ *
+ * SpiderMonkey bytecode instructions.
+ *
+ * To use this header, define a macro of the form:
+ *
+ *     #define MACRO(op, op_snake, token, length, nuses, ndefs, format) ...
+ *
+ * Then `FOR_EACH_OPCODE(MACRO)` invokes `MACRO` for every opcode.
+ *
+ * Field        Description
+ * -----        -----------
+ * op           UpperCamelCase form of opcode id
+ * op_snake     snake_case form of opcode id
+ * token        Pretty-printer string, or null if ugly
+ * length       Number of bytes including any immediate operands
+ * nuses        Number of stack slots consumed by bytecode, -1 if variadic
+ * ndefs        Number of stack slots produced by bytecode
+ * format       JOF_ flags describing instruction operand layout, etc.
+ *
+ * For more about `format`, see the comments on the `JOF_` constants defined in
+ * BytecodeUtil.h.
+ *
+ *
+ * [SMDOC] Bytecode Invariants
+ *
+ * Creating scripts that do not follow the rules can lead to undefined
+ * behavior. Bytecode has many consumers, not just the interpreter: JITs,
+ * analyses, the debugger. That's why the rules below apply even to code that
+ * can't be reached in ordinary execution (such as code after an infinite loop
+ * or inside an `if (false)` block).
+ *
+ * The `code()` of a script must be a packed (not aligned) sequence of valid
+ * instructions from start to end. Each instruction has a single byte opcode
+ * followed by a number of operand bytes based on the opcode.
+ *
+ * ## Jump instructions
+ *
+ * Operands named `offset`, `forwardOffset`, or `defaultOffset` are jump
+ * offsets, the distance in bytes from the start of the current instruction to
+ * the start of another instruction in the same script. Operands named
+ * `forwardOffset` or `defaultOffset` must be positive.
+ *
+ * Forward jumps must jump to a `JSOp::JumpTarget` instruction.  Backward jumps,
+ * indicated by negative offsets, must jump to a `JSOp::LoopHead` instruction.
+ * Jump offsets can't be zero.
+ *
+ * Needless to say, scripts must not contain overlapping instruction sequences
+ * (in the sense of <https://en.wikipedia.org/wiki/Overlapping_gene>).
+ *
+ * A script's `trynotes` and `scopeNotes` impose further constraints. Each try
+ * note and each scope note marks a region of the bytecode where some invariant
+ * holds, or some cleanup behavior is needed--that there's a for-in iterator in
+ * a particular stack slot, for instance, which must be closed on error. All
+ * paths into the span must establish that invariant. In practice, this means
+ * other code never jumps into the span: the only way in is to execute the
+ * bytecode instruction that sets up the invariant (in our example,
+ * `JSOp::Iter`).
+ *
+ * If a script's `trynotes` (see "Try Notes" in JSScript.h) contain a
+ * `JSTRY_CATCH` or `JSTRY_FINALLY` span, there must be a `JSOp::Try`
+ * instruction immediately before the span and a `JSOp::JumpTarget immediately
+ * after it. Instructions must not jump to this `JSOp::JumpTarget`. (The VM puts
+ * us there on exception.) Furthermore, the instruction sequence immediately
+ * following a `JSTRY_CATCH` span must read `JumpTarget; Exception` or, in
+ * non-function scripts, `JumpTarget; Undefined; SetRval; Exception`. (These
+ * instructions run with an exception pending; other instructions aren't
+ * designed to handle that.)
+ *
+ * Unreachable instructions are allowed, but they have to follow all the rules.
+ *
+ * Control must not reach the end of a script. (Currently, the last instruction
+ * is always JSOp::RetRval.)
+ *
+ * ## Other operands
+ *
+ * Operands named `nameIndex` or `atomIndex` (which appear on instructions that
+ * have `JOF_ATOM` in the `format` field) must be valid indexes into
+ * `script->atoms()`.
+ *
+ * Operands named `argc` (`JOF_ARGC`) are argument counts for call
+ * instructions. `argc` must be small enough that the instruction's nuses is <=
+ * the current stack depth (see "Stack depth" below).
+ *
+ * Operands named `argno` (`JOF_QARG`) refer to an argument of the current
+ * function. `argno` must be in the range `0..script->function()->nargs()`.
+ * Instructions with these operands must appear only in function scripts.
+ *
+ * Operands named `localno` (`JOF_LOCAL`) refer to a local variable stored in
+ * the stack frame. `localno` must be in the range `0..script->nfixed()`.
+ *
+ * Operands named `resumeIndex` (`JOF_RESUMEINDEX`) refer to a resume point in
+ * the current script. `resumeIndex` must be a valid index into
+ * `script->resumeOffsets()`.
+ *
+ * Operands named `hops` and `slot` (`JOF_ENVCOORD`) refer a slot in an
+ * `EnvironmentObject`. At run time, they must point to a fixed slot in an
+ * object on the current environment chain. See `EnvironmentCoordinates`.
+ *
+ * Operands with the following names must be valid indexes into
+ * `script->gcthings()`, and the pointer in the vector must point to the right
+ * type of thing:
+ *
+ * -   `objectIndex` (`JOF_OBJECT`): `PlainObject*` or `ArrayObject*`
+ * -   `baseobjIndex` (`JOF_OBJECT`): `PlainObject*`
+ * -   `funcIndex` (`JOF_OBJECT`): `JSFunction*`
+ * -   `regexpIndex` (`JOF_REGEXP`): `RegExpObject*`
+ * -   `shapeIndex` (`JOF_SHAPE`): `Shape*`
+ * -   `scopeIndex` (`JOF_SCOPE`): `Scope*`
+ * -   `lexicalScopeIndex` (`JOF_SCOPE`): `LexicalScope*`
+ * -   `classBodyScopeIndex` (`JOF_SCOPE`): `ClassBodyScope*`
+ * -   `withScopeIndex` (`JOF_SCOPE`): `WithScope*`
+ * -   `bigIntIndex` (`JOF_BIGINT`): `BigInt*`
+ *
+ * Operands named `icIndex` (`JOF_ICINDEX`) must be exactly the number of
+ * preceding instructions in the script that have the JOF_IC flag.
+ * (Rationale: Each JOF_IC instruction has a unique entry in
+ * `script->jitScript()->icEntries()`.  At run time, in the bytecode
+ * interpreter, we have to find that entry. We could store the IC index as an
+ * operand to each JOF_IC instruction, but it's more memory-efficient to use a
+ * counter and reset the counter to `icIndex` after each jump.)
+ *
+ * ## Stack depth
+ *
+ * Each instruction has a compile-time stack depth, the number of values on the
+ * interpreter stack just before executing the instruction. It isn't explicitly
+ * present in the bytecode itself, but (for reachable instructions, anyway)
+ * it's a function of the bytecode.
+ *
+ * -   The first instruction has stack depth 0.
+ *
+ * -   Each successor of an instruction X has a stack depth equal to
+ *
+ *         X's stack depth - `js::StackUses(X)` + `js::StackDefs(X)`
+ *
+ *     except for `JSOp::Case` (below).
+ *
+ *     X's "successors" are: the next instruction in the script, if
+ *     `js::FlowsIntoNext(op)` is true for X's opcode; one or more
+ *     `JSOp::JumpTarget`s elsewhere, if X is a forward jump or
+ *     `JSOp::TableSwitch`; and/or a `JSOp::LoopHead` if it's a backward jump.
+ *
+ * -   `JSOp::Case` is a special case because its stack behavior is eccentric.
+ *     The formula above is correct for the next instruction. The jump target
+ *     has a stack depth that is 1 less.
+ *
+ * -   The `JSOp::JumpTarget` instruction immediately following a `JSTRY_CATCH`
+ *     or `JSTRY_FINALLY` span has the same stack depth as the `JSOp::Try`
+ *     instruction that precedes the span.
+ *
+ *     Every instruction covered by the `JSTRY_CATCH` or `JSTRY_FINALLY` span
+ *     must have a stack depth >= that value, so that error recovery is
+ *     guaranteed to find enough values on the stack to resume there.
+ *
+ * -   `script->nslots() - script->nfixed()` must be >= the maximum stack
+ *     depth of any instruction in `script`.  (The stack frame must be big
+ *     enough to run the code.)
+ *
+ * `BytecodeParser::parse()` computes stack depths for every reachable
+ * instruction in a script.
+ *
+ * ## Scopes and environments
+ *
+ * As with stack depth, each instruction has a static scope, which is a
+ * compile-time characterization of the eventual run-time environment chain
+ * when that instruction executes. Just as every instruction has a stack budget
+ * (nuses/ndefs), every instruction either pushes a scope, pops a scope, or
+ * neither. The same successor relation applies as above.
+ *
+ * Every scope used in a script is stored in the `JSScript::gcthings()` vector.
+ * They can be accessed using `getScope(index)` if you know what `index` to
+ * pass.
+ *
+ * The scope of every instruction (that's reachable via the successor relation)
+ * is given in two independent ways: by the bytecode itself and by the scope
+ * notes. The two sources must agree.
+ *
+ * ## Further rules
+ *
+ * All reachable instructions must be reachable without taking any backward
+ * edges.
+ *
+ * Instructions with the `JOF_CHECKSLOPPY` flag must not be used in strict mode
+ * code. `JOF_CHECKSTRICT` instructions must not be used in nonstrict code.
+ *
+ * Many instructions have their own additional rules. These are documented on
+ * the various opcodes below (look for the word "must").
+ */
+// clang-format on
+
+// clang-format off
+/*
+ * SpiderMonkey bytecode categorization (as used in generated documentation):
+ *
+ * [Index]
+ *   [Constants]
+ *   [Compound primitives]
+ *     Record literals
+ *     Tuple literals
+ *   [Expressions]
+ *     Unary operators
+ *     Binary operators
+ *     Conversions
+ *     Other expressions
+ *   [Objects]
+ *     Creating objects
+ *     Defining properties
+ *     Accessing properties
+ *     Super
+ *     Enumeration
+ *     Iteration
+ *     SetPrototype
+ *     Array literals
+ *     RegExp literals
+ *     Built-in objects
+ *   [Functions]
+ *     Creating functions
+ *     Creating constructors
+ *     Calls
+ *     Generators and async functions
+ *   [Control flow]
+ *     Jump targets
+ *     Jumps
+ *     Return
+ *     Exceptions
+ *   [Variables and scopes]
+ *     Initialization
+ *     Looking up bindings
+ *     Getting binding values
+ *     Setting binding values
+ *     Entering and leaving environments
+ *     Creating and deleting bindings
+ *     Function environment setup
+ *   [Stack operations]
+ *   [Other]
+ */
+// clang-format on
+
+// clang-format off
+#define FOR_EACH_OPCODE(MACRO) \
+    /*
+     * Push `undefined`.
+     *
+     *   Category: Constants
+     *   Operands:
+     *   Stack: => undefined
+     */ \
+    MACRO(Undefined, undefined, "", 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push `null`.
+     *
+     *   Category: Constants
+     *   Operands:
+     *   Stack: => null
+     */ \
+    MACRO(Null, null, "null", 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push a boolean constant.
+     *
+     *   Category: Constants
+     *   Operands:
+     *   Stack: => true/false
+     */ \
+    MACRO(False, false_, "false", 1, 0, 1, JOF_BYTE) \
+    MACRO(True, true_, "true", 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push the `int32_t` immediate operand as an `Int32Value`.
+     *
+     * `JSOp::Zero`, `JSOp::One`, `JSOp::Int8`, `JSOp::Uint16`, and `JSOp::Uint24`
+     * are all compact encodings for `JSOp::Int32`.
+     *
+     *   Category: Constants
+     *   Operands: int32_t val
+     *   Stack: => val
+     */ \
+    MACRO(Int32, int32, NULL, 5, 0, 1, JOF_INT32) \
+    /*
+     * Push the number `0`.
+     *
+     *   Category: Constants
+     *   Operands:
+     *   Stack: => 0
+     */ \
+    MACRO(Zero, zero, "0", 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push the number `1`.
+     *
+     *   Category: Constants
+     *   Operands:
+     *   Stack: => 1
+     */ \
+    MACRO(One, one, "1", 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push the `int8_t` immediate operand as an `Int32Value`.
+     *
+     *   Category: Constants
+     *   Operands: int8_t val
+     *   Stack: => val
+     */ \
+    MACRO(Int8, int8, NULL, 2, 0, 1, JOF_INT8) \
+    /*
+     * Push the `uint16_t` immediate operand as an `Int32Value`.
+     *
+     *   Category: Constants
+     *   Operands: uint16_t val
+     *   Stack: => val
+     */ \
+    MACRO(Uint16, uint16, NULL, 3, 0, 1, JOF_UINT16) \
+    /*
+     * Push the `uint24_t` immediate operand as an `Int32Value`.
+     *
+     *   Category: Constants
+     *   Operands: uint24_t val
+     *   Stack: => val
+     */ \
+    MACRO(Uint24, uint24, NULL, 4, 0, 1, JOF_UINT24) \
+    /*
+     * Push the 64-bit floating-point immediate operand as a `DoubleValue`.
+     *
+     * If the operand is a NaN, it must be the canonical NaN (see
+     * `JS::detail::CanonicalizeNaN`).
+     *
+     *   Category: Constants
+     *   Operands: double val
+     *   Stack: => val
+     */ \
+    MACRO(Double, double_, NULL, 9, 0, 1, JOF_DOUBLE) \
+    /*
+     * Push the BigInt constant `script->getBigInt(bigIntIndex)`.
+     *
+     *   Category: Constants
+     *   Operands: uint32_t bigIntIndex
+     *   Stack: => bigint
+     */ \
+    MACRO(BigInt, big_int, NULL, 5, 0, 1, JOF_BIGINT) \
+    /*
+     * Push the string constant `script->getAtom(atomIndex)`.
+     *
+     *   Category: Constants
+     *   Operands: uint32_t atomIndex
+     *   Stack: => string
+     */ \
+    MACRO(String, string, NULL, 5, 0, 1, JOF_STRING) \
+    /*
+     * Push a well-known symbol.
+     *
+     * `symbol` must be in range for `JS::SymbolCode`.
+     *
+     *   Category: Constants
+     *   Operands: uint8_t symbol (the JS::SymbolCode of the symbol to use)
+     *   Stack: => symbol
+     */ \
+    MACRO(Symbol, symbol, NULL, 2, 0, 1, JOF_UINT8) \
+    /*
+     * Pop the top value on the stack, discard it, and push `undefined`.
+     *
+     * Implements: [The `void` operator][1], step 3.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-void-operator
+     *
+     *   Category: Expressions
+     *   Type: Unary operators
+     *   Operands:
+     *   Stack: val => undefined
+     */ \
+    MACRO(Void, void_, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * [The `typeof` operator][1].
+     *
+     * Infallible. The result is always a string that depends on the [type][2]
+     * of `val`.
+     *
+     * `JSOp::Typeof` and `JSOp::TypeofExpr` are the same except
+     * that--amazingly--`JSOp::Typeof` affects the behavior of an immediately
+     * *preceding* `JSOp::GetName` or `JSOp::GetGName` instruction! This is how
+     * we implement [`typeof`][1] step 2, making `typeof nonExistingVariable`
+     * return `"undefined"` instead of throwing a ReferenceError.
+     *
+     * In a global scope:
+     *
+     * -   `typeof x` compiles to `GetGName "x"; Typeof`.
+     * -   `typeof (0, x)` compiles to `GetGName "x"; TypeofExpr`.
+     *
+     * Emitting the same bytecode for these two expressions would be a bug.
+     * Per spec, the latter throws a ReferenceError if `x` doesn't exist.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-typeof-operator
+     * [2]: https://tc39.es/ecma262/#sec-ecmascript-language-types
+     *
+     *   Category: Expressions
+     *   Type: Unary operators
+     *   Operands:
+     *   Stack: val => (typeof val)
+     */ \
+    MACRO(Typeof, typeof_, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    MACRO(TypeofExpr, typeof_expr, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The unary `+` operator][1].
+     *
+     * `+val` doesn't do any actual math. It just calls [ToNumber][2](val).
+     *
+     * The conversion can call `.toString()`/`.valueOf()` methods and can
+     * throw. The result on success is always a Number. (Per spec, unary `-`
+     * supports BigInts, but unary `+` does not.)
+     *
+     * [1]: https://tc39.es/ecma262/#sec-unary-plus-operator
+     * [2]: https://tc39.es/ecma262/#sec-tonumber
+     *
+     *   Category: Expressions
+     *   Type: Unary operators
+     *   Operands:
+     *   Stack: val => (+val)
+     */ \
+    MACRO(Pos, pos, "+ ", 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The unary `-` operator][1].
+     *
+     * Convert `val` to a numeric value, then push `-val`. The conversion can
+     * call `.toString()`/`.valueOf()` methods and can throw. The result on
+     * success is always numeric.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-unary-minus-operator
+     *
+     *   Category: Expressions
+     *   Type: Unary operators
+     *   Operands:
+     *   Stack: val => (-val)
+     */ \
+    MACRO(Neg, neg, "- ", 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The bitwise NOT operator][1] (`~`).
+     *
+     * `val` is converted to an integer, then bitwise negated. The conversion
+     * can call `.toString()`/`.valueOf()` methods and can throw. The result on
+     * success is always an Int32 or BigInt value.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-bitwise-not-operator
+     *
+     *   Category: Expressions
+     *   Type: Unary operators
+     *   Operands:
+     *   Stack: val => (~val)
+     */ \
+    MACRO(BitNot, bit_not, "~", 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The logical NOT operator][1] (`!`).
+     *
+     * `val` is first converted with [ToBoolean][2], then logically
+     * negated. The result is always a boolean value. This does not call
+     * user-defined methods and can't throw.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-logical-not-operator
+     * [2]: https://tc39.es/ecma262/#sec-toboolean
+     *
+     *   Category: Expressions
+     *   Type: Unary operators
+     *   Operands:
+     *   Stack: val => (!val)
+     */ \
+    MACRO(Not, not_, "!", 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [Binary bitwise operations][1] (`|`, `^`, `&`).
+     *
+     * The arguments are converted to integers first. The conversion can call
+     * `.toString()`/`.valueOf()` methods and can throw. The result on success
+     * is always an Int32 or BigInt Value.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-binary-bitwise-operators
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval OP rval)
+     */ \
+    MACRO(BitOr, bit_or, "|",  1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(BitXor, bit_xor, "^", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(BitAnd, bit_and, "&", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Loose equality operators (`==` and `!=`).
+     *
+     * Pop two values, compare them, and push the boolean result. The
+     * comparison may perform conversions that call `.toString()`/`.valueOf()`
+     * methods and can throw.
+     *
+     * Implements: [Abstract Equality Comparison][1].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-abstract-equality-comparison
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval OP rval)
+     */ \
+    MACRO(Eq, eq, "==", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Ne, ne, "!=", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Strict equality operators (`===` and `!==`).
+     *
+     * Pop two values, check whether they're equal, and push the boolean
+     * result. This does not call user-defined methods and can't throw
+     * (except possibly due to OOM while flattening a string).
+     *
+     * Implements: [Strict Equality Comparison][1].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-strict-equality-comparison
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval OP rval)
+     */ \
+    MACRO(StrictEq, strict_eq, "===", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(StrictNe, strict_ne, "!==", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Relative operators (`<`, `>`, `<=`, `>=`).
+     *
+     * Pop two values, compare them, and push the boolean result. The
+     * comparison may perform conversions that call `.toString()`/`.valueOf()`
+     * methods and can throw.
+     *
+     * Implements: [Relational Operators: Evaluation][1].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-relational-operators-runtime-semantics-evaluation
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval OP rval)
+     */ \
+    MACRO(Lt, lt, "<",  1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Gt, gt, ">",  1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Le, le, "<=", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Ge, ge, ">=", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The `instanceof` operator][1].
+     *
+     * This throws a `TypeError` if `target` is not an object. It calls
+     * `target[Symbol.hasInstance](value)` if the method exists. On success,
+     * the result is always a boolean value.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-instanceofoperator
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: value, target => (value instanceof target)
+     */ \
+    MACRO(Instanceof, instanceof, "instanceof", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The `in` operator][1].
+     *
+     * Push `true` if `obj` has a property with the key `id`. Otherwise push `false`.
+     *
+     * This throws a `TypeError` if `obj` is not an object. This can fire
+     * proxy hooks and can throw. On success, the result is always a boolean
+     * value.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-relational-operators-runtime-semantics-evaluation
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: id, obj => (id in obj)
+     */ \
+    MACRO(In, in_, "in", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [Bitwise shift operators][1] (`<<`, `>>`, `>>>`).
+     *
+     * Pop two values, convert them to integers, perform a bitwise shift, and
+     * push the result.
+     *
+     * Conversion can call `.toString()`/`.valueOf()` methods and can throw.
+     * The result on success is always an Int32 or BigInt Value.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-bitwise-shift-operators
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval OP rval)
+     */ \
+    MACRO(Lsh, lsh, "<<", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Rsh, rsh, ">>", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Ursh, ursh, ">>>", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The binary `+` operator][1].
+     *
+     * Pop two values, convert them to primitive values, add them, and push the
+     * result. If both values are numeric, add them; if either is a
+     * string, do string concatenation instead.
+     *
+     * The conversion can call `.toString()`/`.valueOf()` methods and can throw.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-addition-operator-plus-runtime-semantics-evaluation
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval + rval)
+     */ \
+    MACRO(Add, add, "+", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The binary `-` operator][1].
+     *
+     * Pop two values, convert them to numeric values, subtract the top value
+     * from the other one, and push the result.
+     *
+     * The conversion can call `.toString()`/`.valueOf()` methods and can
+     * throw. On success, the result is always numeric.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-subtraction-operator-minus-runtime-semantics-evaluation
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval - rval)
+     */ \
+    MACRO(Sub, sub, "-", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Add or subtract 1.
+     *
+     * `val` must already be a numeric value, such as the result of
+     * `JSOp::ToNumeric`.
+     *
+     * Implements: [The `++` and `--` operators][1], step 3 of each algorithm.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-postfix-increment-operator
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: val => (val +/- 1)
+     */ \
+    MACRO(Inc, inc, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Dec, dec, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The multiplicative operators][1] (`*`, `/`, `%`).
+     *
+     * Pop two values, convert them to numeric values, do math, and push the
+     * result.
+     *
+     * The conversion can call `.toString()`/`.valueOf()` methods and can
+     * throw. On success, the result is always numeric.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-multiplicative-operators-runtime-semantics-evaluation
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval OP rval)
+     */ \
+    MACRO(Mul, mul, "*", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Div, div, "/", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    MACRO(Mod, mod, "%", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * [The exponentiation operator][1] (`**`).
+     *
+     * Pop two values, convert them to numeric values, do exponentiation, and
+     * push the result. The top value is the exponent.
+     *
+     * The conversion can call `.toString()`/`.valueOf()` methods and can
+     * throw. This throws a RangeError if both values are BigInts and the
+     * exponent is negative.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-exp-operator
+     *
+     *   Category: Expressions
+     *   Type: Binary operators
+     *   Operands:
+     *   Stack: lval, rval => (lval ** rval)
+     */ \
+    MACRO(Pow, pow, "**", 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Convert a value to a property key.
+     *
+     * Implements: [ToPropertyKey][1], except that if the result would be the
+     * string representation of some integer in the range 0..2^31, we push the
+     * corresponding Int32 value instead. This is because the spec insists that
+     * array indices are strings, whereas for us they are integers.
+     *
+     * This is used for code like `++obj[index]`, which must do both a
+     * `JSOp::GetElem` and a `JSOp::SetElem` with the same property key. Both
+     * instructions would convert `index` to a property key for us, but the
+     * spec says to convert it only once.
+     *
+     * The conversion can call `.toString()`/`.valueOf()` methods and can
+     * throw.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-topropertykey
+     *
+     *   Category: Expressions
+     *   Type: Conversions
+     *   Operands:
+     *   Stack: propertyNameValue => propertyKey
+     */ \
+    MACRO(ToPropertyKey, to_property_key, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Convert a value to a numeric value (a Number or BigInt).
+     *
+     * Implements: [ToNumeric][1](val).
+     *
+     * Note: This is used to implement [`++` and `--`][2]. Surprisingly, it's
+     * not possible to get the right behavior using `JSOp::Add` and `JSOp::Sub`
+     * alone. For one thing, `JSOp::Add` sometimes does string concatenation,
+     * while `++` always does numeric addition. More fundamentally, the result
+     * of evaluating `x--` is ToNumeric(old value of `x`), a value that the
+     * sequence `GetLocal "x"; One; Sub; SetLocal "x"` does not give us.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-tonumeric
+     * [2]: https://tc39.es/ecma262/#sec-postfix-increment-operator
+     *
+     *   Category: Expressions
+     *   Type: Conversions
+     *   Operands:
+     *   Stack: val => ToNumeric(val)
+     */ \
+    MACRO(ToNumeric, to_numeric, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Convert a value to a string.
+     *
+     * Implements: [ToString][1](val).
+     *
+     * Note: This is used in code for template literals, like `${x}${y}`. Each
+     * substituted value must be converted using ToString. `JSOp::Add` by itself
+     * would do a slightly wrong kind of conversion (hint="number" rather than
+     * hint="string").
+     *
+     * [1]: https://tc39.es/ecma262/#sec-tostring
+     *
+     *   Category: Expressions
+     *   Type: Conversions
+     *   Stack: val => ToString(val)
+     */ \
+    MACRO(ToString, to_string, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Test whether the value on top of the stack is `NullValue` or
+     * `UndefinedValue` and push the boolean result.
+     *
+     *   Category: Expressions
+     *   Type: Other expressions
+     *   Operands:
+     *   Stack: val => val, IsNullOrUndefined(val)
+     */ \
+    MACRO(IsNullOrUndefined, is_null_or_undefined, NULL, 1, 1, 2, JOF_BYTE) \
+    /*
+     * Push the global `this` value. Not to be confused with the `globalThis`
+     * property on the global.
+     *
+     * This must be used only in scopes where `this` refers to the global
+     * `this`.
+     *
+     *   Category: Expressions
+     *   Type: Other expressions
+     *   Operands:
+     *   Stack: => this
+     */ \
+    MACRO(GlobalThis, global_this, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push the global `this` value for non-syntactic scope. Not to be confused
+     * with the `globalThis` property on the global.
+     *
+     * This must be used only in scopes where `this` refers to the global
+     * `this`.
+     *
+     *   Category: Expressions
+     *   Type: Other expressions
+     *   Operands:
+     *   Stack: => this
+     */ \
+    MACRO(NonSyntacticGlobalThis, non_syntactic_global_this, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Push the value of `new.target`.
+     *
+     * The result is a constructor or `undefined`.
+     *
+     * This must be used only in non-arrow function scripts.
+     *
+     * Implements: [GetNewTarget][1].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getnewtarget
+     *
+     *   Category: Expressions
+     *   Type: Other expressions
+     *   Operands:
+     *   Stack: => new.target
+     */ \
+    MACRO(NewTarget, new_target, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Dynamic import of the module specified by the string value on the top of
+     * the stack.
+     *
+     * Implements: [Import Calls][1].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-import-calls
+     *
+     *   Category: Expressions
+     *   Type: Other expressions
+     *   Operands:
+     *   Stack: moduleId, options => promise
+     */ \
+    MACRO(DynamicImport, dynamic_import, NULL, 1, 2, 1, JOF_BYTE) \
+    /*
+     * Push the `import.meta` object.
+     *
+     * This must be used only in module code.
+     *
+     *   Category: Expressions
+     *   Type: Other expressions
+     *   Operands:
+     *   Stack: => import.meta
+     */ \
+    MACRO(ImportMeta, import_meta, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Create and push a new object with no properties.
+     *
+     *   Category: Objects
+     *   Type: Creating objects
+     *   Operands:
+     *   Stack: => obj
+     */ \
+    MACRO(NewInit, new_init, NULL, 1, 0, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Create and push a new object of a predetermined shape.
+     *
+     * The new object has the shape `script->getShape(shapeIndex)`.
+     * Subsequent `InitProp` instructions must fill in all slots of the new
+     * object before it is used in any other way.
+     *
+     *   Category: Objects
+     *   Type: Creating objects
+     *   Operands: uint32_t shapeIndex
+     *   Stack: => obj
+     */ \
+    MACRO(NewObject, new_object, NULL, 5, 0, 1, JOF_SHAPE|JOF_IC) \
+    /*
+     * Push a preconstructed object.
+     *
+     * Going one step further than `JSOp::NewObject`, this instruction doesn't
+     * just reuse the shape--it actually pushes the preconstructed object
+     * `script->getObject(objectIndex)` right onto the stack. The object must
+     * be a singleton `PlainObject` or `ArrayObject`.
+     *
+     * The spec requires that an *ObjectLiteral* or *ArrayLiteral* creates a
+     * new object every time it's evaluated, so this instruction must not be
+     * used anywhere it might be executed more than once.
+     *
+     * This may only be used in non-function run-once scripts. Care also must
+     * be taken to not emit in loops or other constructs where it could run
+     * more than once.
+     *
+     *   Category: Objects
+     *   Type: Creating objects
+     *   Operands: uint32_t objectIndex
+     *   Stack: => obj
+     */ \
+    MACRO(Object, object, NULL, 5, 0, 1, JOF_OBJECT) \
+    /*
+     * Create and push a new ordinary object with the provided [[Prototype]].
+     *
+     * This is used to create the `.prototype` object for derived classes.
+     *
+     *   Category: Objects
+     *   Type: Creating objects
+     *   Operands:
+     *   Stack: proto => obj
+     */ \
+    MACRO(ObjWithProto, obj_with_proto, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Define a data property on an object.
+     *
+     * `obj` must be an object.
+     *
+     * Implements: [CreateDataPropertyOrThrow][1] as used in
+     * [PropertyDefinitionEvaluation][2] of regular and shorthand
+     * *PropertyDefinition*s.
+     *
+     *    [1]: https://tc39.es/ecma262/#sec-createdatapropertyorthrow
+     *    [2]: https://tc39.es/ecma262/#sec-object-initializer-runtime-semantics-propertydefinitionevaluation
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, val => obj
+     */ \
+    MACRO(InitProp, init_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT|JOF_IC) \
+    /*
+     * Like `JSOp::InitProp`, but define a non-enumerable property.
+     *
+     * This is used to define class methods.
+     *
+     * Implements: [PropertyDefinitionEvaluation][1] for methods, steps 3 and
+     * 4, when *enumerable* is false.
+     *
+     *    [1]: https://tc39.es/ecma262/#sec-method-definitions-runtime-semantics-propertydefinitionevaluation
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, val => obj
+     */ \
+    MACRO(InitHiddenProp, init_hidden_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT|JOF_IC) \
+    /*
+     * Like `JSOp::InitProp`, but define a non-enumerable, non-writable,
+     * non-configurable property.
+     *
+     * This is used to define the `.prototype` property on classes.
+     *
+     * Implements: [MakeConstructor][1], step 8, when *writablePrototype* is
+     * false.
+     *
+     *    [1]: https://tc39.es/ecma262/#sec-makeconstructor
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, val => obj
+     */ \
+    MACRO(InitLockedProp, init_locked_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT|JOF_IC) \
+    /*
+     * Define a data property on `obj` with property key `id` and value `val`.
+     *
+     * `obj` must be an object.
+     *
+     * Implements: [CreateDataPropertyOrThrow][1]. This instruction is used for
+     * object literals like `{0: val}` and `{[id]: val}`, and methods like
+     * `*[Symbol.iterator]() {}`.
+     *
+     * `JSOp::InitHiddenElem` is the same but defines a non-enumerable property,
+     * for class methods.
+     * `JSOp::InitLockedElem` is the same but defines a non-enumerable, non-writable, non-configurable property,
+     * for private class methods.
+     *
+     *    [1]: https://tc39.es/ecma262/#sec-createdatapropertyorthrow
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands:
+     *   Stack: obj, id, val => obj
+     */ \
+    MACRO(InitElem, init_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC) \
+    MACRO(InitHiddenElem, init_hidden_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC) \
+    MACRO(InitLockedElem, init_locked_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC) \
+    /*
+     * Define an accessor property on `obj` with the given `getter`.
+     * `nameIndex` gives the property name.
+     *
+     * `obj` must be an object and `getter` must be a function.
+     *
+     * `JSOp::InitHiddenPropGetter` is the same but defines a non-enumerable
+     * property, for getters in classes.
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, getter => obj
+     */ \
+    MACRO(InitPropGetter, init_prop_getter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT) \
+    MACRO(InitHiddenPropGetter, init_hidden_prop_getter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT) \
+    /*
+     * Define an accessor property on `obj` with property key `id` and the given `getter`.
+     *
+     * This is used to implement getters like `get [id]() {}` or `get 0() {}`.
+     *
+     * `obj` must be an object and `getter` must be a function.
+     *
+     * `JSOp::InitHiddenElemGetter` is the same but defines a non-enumerable
+     * property, for getters in classes.
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands:
+     *   Stack: obj, id, getter => obj
+     */ \
+    MACRO(InitElemGetter, init_elem_getter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT) \
+    MACRO(InitHiddenElemGetter, init_hidden_elem_getter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT) \
+    /*
+     * Define an accessor property on `obj` with the given `setter`.
+     *
+     * This is used to implement ordinary setters like `set foo(v) {}`.
+     *
+     * `obj` must be an object and `setter` must be a function.
+     *
+     * `JSOp::InitHiddenPropSetter` is the same but defines a non-enumerable
+     * property, for setters in classes.
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, setter => obj
+     */ \
+    MACRO(InitPropSetter, init_prop_setter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT) \
+    MACRO(InitHiddenPropSetter, init_hidden_prop_setter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT) \
+    /*
+     * Define an accesssor property on `obj` with property key `id` and the
+     * given `setter`.
+     *
+     * This is used to implement setters with computed property keys or numeric
+     * keys.
+     *
+     * `JSOp::InitHiddenElemSetter` is the same but defines a non-enumerable
+     * property, for setters in classes.
+     *
+     *   Category: Objects
+     *   Type: Defining properties
+     *   Operands:
+     *   Stack: obj, id, setter => obj
+     */ \
+    MACRO(InitElemSetter, init_elem_setter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT) \
+    MACRO(InitHiddenElemSetter, init_hidden_elem_setter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT) \
+    /*
+     * Get the value of the property `obj.name`. This can call getters and
+     * proxy traps.
+     *
+     * Implements: [GetV][1], [GetValue][2] step 5.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getv
+     * [2]: https://tc39.es/ecma262/#sec-getvalue
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj => obj[name]
+     */ \
+    MACRO(GetProp, get_prop, NULL, 5, 1, 1, JOF_ATOM|JOF_PROP|JOF_IC) \
+    /*
+     * Get the value of the property `obj[key]`.
+     *
+     * Implements: [GetV][1], [GetValue][2] step 5.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getv
+     * [2]: https://tc39.es/ecma262/#sec-getvalue
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands:
+     *   Stack: obj, key => obj[key]
+     */ \
+    MACRO(GetElem, get_elem, NULL, 1, 2, 1, JOF_BYTE|JOF_ELEM|JOF_IC) \
+    /*
+     * Non-strict assignment to a property, `obj.name = val`.
+     *
+     * This throws a TypeError if `obj` is null or undefined. If it's a
+     * primitive value, the property is set on ToObject(`obj`), typically with
+     * no effect.
+     *
+     * Implements: [PutValue][1] step 6 for non-strict code.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-putvalue
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, val => val
+     */ \
+    MACRO(SetProp, set_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSLOPPY|JOF_IC) \
+    /*
+     * Like `JSOp::SetProp`, but for strict mode code. Throw a TypeError if
+     * `obj[key]` exists but is non-writable, if it's an accessor property with
+     * no setter, or if `obj` is a primitive value.
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj, val => val
+     */ \
+    MACRO(StrictSetProp, strict_set_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Non-strict assignment to a property, `obj[key] = val`.
+     *
+     * Implements: [PutValue][1] step 6 for non-strict code.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-putvalue
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands:
+     *   Stack: obj, key, val => val
+     */ \
+    MACRO(SetElem, set_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSLOPPY|JOF_IC) \
+    /*
+     * Like `JSOp::SetElem`, but for strict mode code. Throw a TypeError if
+     * `obj[key]` exists but is non-writable, if it's an accessor property with
+     * no setter, or if `obj` is a primitive value.
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands:
+     *   Stack: obj, key, val => val
+     */ \
+    MACRO(StrictSetElem, strict_set_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Delete a property from `obj`. Push true on success, false if the
+     * property existed but could not be deleted. This implements `delete
+     * obj.name` in non-strict code.
+     *
+     * Throws if `obj` is null or undefined. Can call proxy traps.
+     *
+     * Implements: [`delete obj.propname`][1] step 5 in non-strict code.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-delete-operator-runtime-semantics-evaluation
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj => succeeded
+     */ \
+    MACRO(DelProp, del_prop, NULL, 5, 1, 1, JOF_ATOM|JOF_PROP|JOF_CHECKSLOPPY) \
+    /*
+     * Like `JSOp::DelProp`, but for strict mode code. Push `true` on success,
+     * else throw a TypeError.
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: obj => succeeded
+     */ \
+    MACRO(StrictDelProp, strict_del_prop, NULL, 5, 1, 1, JOF_ATOM|JOF_PROP|JOF_CHECKSTRICT) \
+    /*
+     * Delete the property `obj[key]` and push `true` on success, `false`
+     * if the property existed but could not be deleted.
+     *
+     * This throws if `obj` is null or undefined. Can call proxy traps.
+     *
+     * Implements: [`delete obj[key]`][1] step 5 in non-strict code.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-delete-operator-runtime-semantics-evaluation
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands:
+     *   Stack: obj, key => succeeded
+     */ \
+    MACRO(DelElem, del_elem, NULL, 1, 2, 1, JOF_BYTE|JOF_ELEM|JOF_CHECKSLOPPY) \
+    /*
+     * Like `JSOp::DelElem, but for strict mode code. Push `true` on success,
+     * else throw a TypeError.
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands:
+     *   Stack: obj, key => succeeded
+     */ \
+    MACRO(StrictDelElem, strict_del_elem, NULL, 1, 2, 1, JOF_BYTE|JOF_ELEM|JOF_CHECKSTRICT) \
+    /*
+     * Push true if `obj` has an own property `id`.
+     *
+     * Note that `obj` is the top value, like `JSOp::In`.
+     *
+     * This opcode is not used for normal JS. Self-hosted code uses it by
+     * calling the intrinsic `hasOwn(id, obj)`. For example,
+     * `Object.prototype.hasOwnProperty` is implemented this way (see
+     * js/src/builtin/Object.js).
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands:
+     *   Stack: id, obj => (obj.hasOwnProperty(id))
+     */ \
+    MACRO(HasOwn, has_own, NULL, 1, 2, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Push a bool representing the presence of private field id on obj.
+     * May throw, depending on the ThrowCondition.
+     *
+     * Two arguments:
+     *   - throwCondition: One of the ThrowConditions defined in
+     *     ThrowMsgKind.h. Determines why (or if) this op will throw.
+     *   - msgKind: One of the ThrowMsgKinds defined in ThrowMsgKind.h, which
+     *     maps to one of the messages in js.msg. Note: It's not possible to
+     *     pass arguments to the message at the moment.
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: ThrowCondition throwCondition, ThrowMsgKind msgKind
+     *   Stack: obj, key => obj, key, (obj.hasOwnProperty(id))
+     */ \
+    MACRO(CheckPrivateField, check_private_field, NULL, 3, 2, 3, JOF_TWO_UINT8|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Push a new private name.
+     *
+     *   Category: Objects
+     *   Type: Accessing properties
+     *   Operands: uint32_t nameIndex
+     *   Stack: => private_name
+     */ \
+    MACRO(NewPrivateName, new_private_name, NULL, 5, 0, 1, JOF_ATOM) \
+    /*
+     * Push the SuperBase of the method `callee`. The SuperBase is
+     * `callee.[[HomeObject]].[[GetPrototypeOf]]()`, the object where `super`
+     * property lookups should begin.
+     *
+     * `callee` must be a function that has a HomeObject that's an object,
+     * typically produced by `JSOp::Callee` or `JSOp::EnvCallee`.
+     *
+     * Implements: [GetSuperBase][1], except that instead of the environment,
+     * the argument supplies the callee.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getsuperbase
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands:
+     *   Stack: callee => superBase
+     */ \
+    MACRO(SuperBase, super_base, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Get the value of `receiver.name`, starting the property search at `obj`.
+     * In spec terms, `obj.[[Get]](name, receiver)`.
+     *
+     * Implements: [GetValue][1] for references created by [`super.name`][2].
+     * The `receiver` is `this` and `obj` is the SuperBase of the enclosing
+     * method.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getvalue
+     * [2]: https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands: uint32_t nameIndex
+     *   Stack: receiver, obj => super.name
+     */ \
+    MACRO(GetPropSuper, get_prop_super, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_IC) \
+    /*
+     * Get the value of `receiver[key]`, starting the property search at `obj`.
+     * In spec terms, `obj.[[Get]](key, receiver)`.
+     *
+     * Implements: [GetValue][1] for references created by [`super[key]`][2]
+     * (where the `receiver` is `this` and `obj` is the SuperBase of the enclosing
+     * method); [`Reflect.get(obj, key, receiver)`][3].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getvalue
+     * [2]: https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
+     * [3]: https://tc39.es/ecma262/#sec-reflect.get
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands:
+     *   Stack: receiver, key, obj => super[key]
+     */ \
+    MACRO(GetElemSuper, get_elem_super, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_IC) \
+    /*
+     * Assign `val` to `receiver.name`, starting the search for an existing
+     * property at `obj`. In spec terms, `obj.[[Set]](name, val, receiver)`.
+     *
+     * Implements: [PutValue][1] for references created by [`super.name`][2] in
+     * non-strict code. The `receiver` is `this` and `obj` is the SuperBase of
+     * the enclosing method.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-putvalue
+     * [2]: https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands: uint32_t nameIndex
+     *   Stack: receiver, obj, val => val
+     */ \
+    MACRO(SetPropSuper, set_prop_super, NULL, 5, 3, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSLOPPY) \
+    /*
+     * Like `JSOp::SetPropSuper`, but for strict mode code.
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands: uint32_t nameIndex
+     *   Stack: receiver, obj, val => val
+     */ \
+    MACRO(StrictSetPropSuper, strict_set_prop_super, NULL, 5, 3, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSTRICT) \
+    /*
+     * Assign `val` to `receiver[key]`, strating the search for an existing
+     * property at `obj`. In spec terms, `obj.[[Set]](key, val, receiver)`.
+     *
+     * Implements: [PutValue][1] for references created by [`super[key]`][2] in
+     * non-strict code. The `receiver` is `this` and `obj` is the SuperBase of
+     * the enclosing method.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-putvalue
+     * [2]: https://tc39.es/ecma262/#sec-super-keyword-runtime-semantics-evaluation
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands:
+     *   Stack: receiver, key, obj, val => val
+     */ \
+    MACRO(SetElemSuper, set_elem_super, NULL, 1, 4, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSLOPPY) \
+    /*
+     * Like `JSOp::SetElemSuper`, but for strict mode code.
+     *
+     *   Category: Objects
+     *   Type: Super
+     *   Operands:
+     *   Stack: receiver, key, obj, val => val
+     */ \
+    MACRO(StrictSetElemSuper, strict_set_elem_super, NULL, 1, 4, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSTRICT) \
+    /*
+     * Set up a for-in loop by pushing a `PropertyIteratorObject` over the
+     * enumerable properties of `val`.
+     *
+     * Implements: [ForIn/OfHeadEvaluation][1] step 6,
+     * [EnumerateObjectProperties][1]. (The spec refers to an "Iterator object"
+     * with a `next` method, but notes that it "is never directly accessible"
+     * to scripts. The object we use for this has no public methods.)
+     *
+     * If `val` is null or undefined, this pushes an empty iterator.
+     *
+     * The `iter` object pushed by this instruction must not be used or removed
+     * from the stack except by `JSOp::MoreIter` and `JSOp::EndIter`, or by error
+     * handling.
+     *
+     * The script's `JSScript::trynotes()` must mark the body of the `for-in`
+     * loop, i.e. exactly those instructions that begin executing with `iter`
+     * on the stack, starting with the next instruction (always
+     * `JSOp::LoopHead`). Code must not jump into or out of this region: control
+     * can enter only by executing `JSOp::Iter` and can exit only by executing a
+     * `JSOp::EndIter` or by exception unwinding. (A `JSOp::EndIter` is always
+     * emitted at the end of the loop, and extra copies are emitted on "exit
+     * slides", where a `break`, `continue`, or `return` statement exits the
+     * loop.)
+     *
+     * Typically a single try note entry marks the contiguous chunk of bytecode
+     * from the instruction after `JSOp::Iter` to `JSOp::EndIter` (inclusive);
+     * but if that range contains any instructions on exit slides, after a
+     * `JSOp::EndIter`, then those must be correctly noted as *outside* the
+     * loop.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-runtime-semantics-forin-div-ofheadevaluation-tdznames-expr-iterationkind
+     * [2]: https://tc39.es/ecma262/#sec-enumerate-object-properties
+     *
+     *   Category: Objects
+     *   Type: Enumeration
+     *   Operands:
+     *   Stack: val => iter
+     */ \
+    MACRO(Iter, iter, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Get the next property name for a for-in loop.
+     *
+     * `iter` must be a `PropertyIteratorObject` produced by `JSOp::Iter`.  This
+     * pushes the property name for the next loop iteration, or
+     * `MagicValue(JS_NO_ITER_VALUE)` if there are no more enumerable
+     * properties to iterate over. The magic value must be used only by
+     * `JSOp::IsNoIter` and `JSOp::EndIter`.
+     *
+     *   Category: Objects
+     *   Type: Enumeration
+     *   Operands:
+     *   Stack: iter => iter, name
+     */ \
+    MACRO(MoreIter, more_iter, NULL, 1, 1, 2, JOF_BYTE) \
+    /*
+     * Test whether the value on top of the stack is
+     * `MagicValue(JS_NO_ITER_VALUE)` and push the boolean result.
+     *
+     *   Category: Objects
+     *   Type: Enumeration
+     *   Operands:
+     *   Stack: val => val, done
+     */ \
+    MACRO(IsNoIter, is_no_iter, NULL, 1, 1, 2, JOF_BYTE) \
+    /*
+     * Exit a for-in loop, closing the iterator.
+     *
+     * `iter` must be a `PropertyIteratorObject` pushed by `JSOp::Iter`.
+     *
+     *   Category: Objects
+     *   Type: Enumeration
+     *   Operands:
+     *   Stack: iter, iterval =>
+     */ \
+    MACRO(EndIter, end_iter, NULL, 1, 2, 0, JOF_BYTE) \
+    /*
+     * If the iterator object on top of the stack has a `return` method,
+     * call that method. If the method exists but does not return an object,
+     * and `kind` is not `CompletionKind::Throw`, throw a TypeError. (If
+     * `kind` is `Throw`, the error we are already throwing takes precedence.)
+     *
+     * `iter` must be an object conforming to the [Iterator][1] interface.
+     *
+     * Implements: [IteratorClose][2]
+     *
+     * [1]: https://tc39.es/ecma262/#sec-iterator-interface
+     * [2]: https://tc39.es/ecma262/#sec-iteratorclose
+     *   Category: Objects
+     *   Type: Iteration
+     *   Operands: CompletionKind kind
+     *   Stack: iter =>
+     */ \
+    MACRO(CloseIter, close_iter, NULL, 2, 1, 0, JOF_UINT8|JOF_IC) \
+    /*
+     * Check that the top value on the stack is an object, and throw a
+     * TypeError if not. `kind` is used only to generate an appropriate error
+     * message.
+     *
+     * Implements: [GetIterator][1] step 5, [IteratorNext][2] step 3. Both
+     * operations call a JS method which scripts can define however they want,
+     * so they check afterwards that the method returned an object.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getiterator
+     * [2]: https://tc39.es/ecma262/#sec-iteratornext
+     *
+     *   Category: Objects
+     *   Type: Iteration
+     *   Operands: CheckIsObjectKind kind
+     *   Stack: result => result
+     */ \
+    MACRO(CheckIsObj, check_is_obj, NULL, 2, 1, 1, JOF_UINT8) \
+    /*
+     * Throw a TypeError if `val` is `null` or `undefined`.
+     *
+     * Implements: [RequireObjectCoercible][1]. But most instructions that
+     * require an object will perform this check for us, so of the dozens of
+     * calls to RequireObjectCoercible in the spec, we need this instruction
+     * only for [destructuring assignment][2] and [initialization][3].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-requireobjectcoercible
+     * [2]: https://tc39.es/ecma262/#sec-runtime-semantics-destructuringassignmentevaluation
+     * [3]: https://tc39.es/ecma262/#sec-destructuring-binding-patterns-runtime-semantics-bindinginitialization
+     *
+     *   Category: Objects
+     *   Type: Iteration
+     *   Operands:
+     *   Stack: val => val
+     */ \
+    MACRO(CheckObjCoercible, check_obj_coercible, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Create and push an async iterator wrapping the sync iterator `iter`.
+     * `next` should be `iter`'s `.next` method.
+     *
+     * Implements: [CreateAsyncToSyncIterator][1]. The spec says this operation
+     * takes one argument, but that argument is a Record with two relevant
+     * fields, `[[Iterator]]` and `[[NextMethod]]`.
+     *
+     * Used for `for await` loops.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-createasyncfromsynciterator
+     *
+     *   Category: Objects
+     *   Type: Iteration
+     *   Operands:
+     *   Stack: iter, next => asynciter
+     */ \
+    MACRO(ToAsyncIter, to_async_iter, NULL, 1, 2, 1, JOF_BYTE) \
+    /*
+     * Set the prototype of `obj`.
+     *
+     * `obj` must be an object.
+     *
+     * Implements: [B.3.1 __proto__ Property Names in Object Initializers][1], step 7.a.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-__proto__-property-names-in-object-initializers
+     *
+     *   Category: Objects
+     *   Type: SetPrototype
+     *   Operands:
+     *   Stack: obj, protoVal => obj
+     */ \
+    MACRO(MutateProto, mutate_proto, NULL, 1, 2, 1, JOF_BYTE) \
+    /*
+     * Create and push a new Array object with the given `length`,
+     * preallocating enough memory to hold that many elements.
+     *
+     *   Category: Objects
+     *   Type: Array literals
+     *   Operands: uint32_t length
+     *   Stack: => array
+     */ \
+    MACRO(NewArray, new_array, NULL, 5, 0, 1, JOF_UINT32|JOF_IC) \
+    /*
+     * Initialize an array element `array[index]` with value `val`.
+     *
+     * `val` may be `MagicValue(JS_ELEMENTS_HOLE)` pushed by `JSOp::Hole`.
+     *
+     * This never calls setters or proxy traps.
+     *
+     * `array` must be an Array object created by `JSOp::NewArray` with length >
+     * `index`, and never used except by `JSOp::InitElemArray`.
+     *
+     * Implements: [ArrayAccumulation][1], the third algorithm, step 4, in the
+     * common case where *nextIndex* is known.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-runtime-semantics-arrayaccumulation
+     *
+     *   Category: Objects
+     *   Type: Array literals
+     *   Operands: uint32_t index
+     *   Stack: array, val => array
+     */ \
+    MACRO(InitElemArray, init_elem_array, NULL, 5, 2, 1, JOF_UINT32|JOF_ELEM|JOF_PROPINIT) \
+    /*
+     * Initialize an array element `array[index++]` with value `val`.
+     *
+     * `val` may be `MagicValue(JS_ELEMENTS_HOLE)` pushed by `JSOp::Hole`. If it
+     * is, no element is defined, but the array length and the stack value
+     * `index` are still incremented.
+     *
+     * This never calls setters or proxy traps.
+     *
+     * `array` must be an Array object created by `JSOp::NewArray` and never used
+     * except by `JSOp::InitElemArray` and `JSOp::InitElemInc`.
+     *
+     * `index` must be an integer, `0 <= index <= INT32_MAX`. If `index` is
+     * `INT32_MAX`, this throws a RangeError. Unlike `InitElemArray`, it is not
+     * necessary that the `array` length > `index`.
+     *
+     * This instruction is used when an array literal contains a
+     * *SpreadElement*. In `[a, ...b, c]`, `InitElemArray 0` is used to put
+     * `a` into the array, but `InitElemInc` is used for the elements of `b`
+     * and for `c`.
+     *
+     * Implements: Several steps in [ArrayAccumulation][1] that call
+     * CreateDataProperty, set the array length, and/or increment *nextIndex*.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-runtime-semantics-arrayaccumulation
+     *
+     *   Category: Objects
+     *   Type: Array literals
+     *   Operands:
+     *   Stack: array, index, val => array, (index + 1)
+     */ \
+    MACRO(InitElemInc, init_elem_inc, NULL, 1, 3, 2, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC) \
+    /*
+     * Push `MagicValue(JS_ELEMENTS_HOLE)`, representing an *Elision* in an
+     * array literal (like the missing property 0 in the array `[, 1]`).
+     *
+     * This magic value must be used only by `JSOp::InitElemArray` or
+     * `JSOp::InitElemInc`.
+     *
+     *   Category: Objects
+     *   Type: Array literals
+     *   Operands:
+     *   Stack: => hole
+     */ \
+    MACRO(Hole, hole, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Clone and push a new RegExp object.
+     *
+     * Implements: [Evaluation for *RegularExpressionLiteral*][1].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-regular-expression-literals-runtime-semantics-evaluation
+     *
+     *   Category: Objects
+     *   Type: RegExp literals
+     *   Operands: uint32_t regexpIndex
+     *   Stack: => regexp
+     */ \
+    MACRO(RegExp, reg_exp, NULL, 5, 0, 1, JOF_REGEXP) \
+    /*
+     * Initialize a new record, preallocating `length` memory slots. `length` can still grow
+     * if needed, for example when using the spread operator.
+     *
+     * Implements: [RecordLiteral Evaluation][1] step 1.
+     *
+     * [1]: https://tc39.es/proposal-record-tuple/#sec-record-initializer-runtime-semantics-evaluation
+     *
+     *   Category: Compound primitives
+     *   Type: Record literals
+     *   Operands: uint32_t length
+     *   Stack: => rval
+     */ \
+    IF_RECORD_TUPLE(MACRO(InitRecord, init_record, NULL, 5, 0, 1, JOF_UINT32)) \
+    /*
+     * Add the last element in the stack to the preceding tuple.
+     *
+     * Implements: [AddPropertyIntoRecordEntriesList][1].
+     *
+     * [1]: https://tc39.es/proposal-record-tuple/#sec-addpropertyintorecordentrieslist
+     *
+     *   Category: Compound primitives
+     *   Type: Record literals
+     *   Operands:
+     *   Stack: record, key, value => record
+     */ \
+    IF_RECORD_TUPLE(MACRO(AddRecordProperty, add_record_property, NULL, 1, 3, 1, JOF_BYTE)) \
+    /*
+     * Add the last element in the stack to the preceding tuple.
+     *
+     * Implements: [RecordPropertyDefinitionEvaluation][1] for
+     *   RecordPropertyDefinition : ... AssignmentExpression
+     *
+     * [1]: https://tc39.es/proposal-record-tuple/#sec-addpropertyintorecordentrieslist
+     *
+     *   Category: Compound primitives
+     *   Type: Record literals
+     *   Operands:
+     *   Stack: record, value => record
+     */ \
+    IF_RECORD_TUPLE(MACRO(AddRecordSpread, add_record_spread, NULL, 1, 2, 1, JOF_BYTE)) \
+    /*
+     * Mark a record as "initialized", going from "write-only" mode to
+     * "read-only" mode.
+     *
+     *   Category: Compound primitives
+     *   Type: Record literals
+     *   Operands:
+     *   Stack: record => record
+     */ \
+    IF_RECORD_TUPLE(MACRO(FinishRecord, finish_record, NULL, 1, 1, 1, JOF_BYTE)) \
+    /*
+     * Initialize a new tuple, preallocating `length` memory slots. `length` can still grow
+     * if needed, for example when using the spread operator.
+     *
+     * Implements: [TupleLiteral Evaluation][1] step 1.
+     *
+     * [1]: https://tc39.es/proposal-record-tuple/#sec-tuple-initializer-runtime-semantics-evaluation
+     *
+     *   Category: Compound primitives
+     *   Type: Tuple literals
+     *   Operands: uint32_t length
+     *   Stack: => rval
+     */ \
+    IF_RECORD_TUPLE(MACRO(InitTuple, init_tuple, NULL, 5, 0, 1, JOF_UINT32)) \
+    /*
+     * Add the last element in the stack to the preceding tuple.
+     *
+     * Implements: [AddValueToTupleSequenceList][1].
+     *
+     * [1]: https://tc39.es/proposal-record-tuple/#sec-addvaluetotuplesequencelist
+     *
+     *   Category: Compound primitives
+     *   Type: Tuple literals
+     *   Operands:
+     *   Stack: tuple, element => tuple
+     */ \
+    IF_RECORD_TUPLE(MACRO(AddTupleElement, add_tuple_element, NULL, 1, 2, 1, JOF_BYTE)) \
+    /*
+     * Mark a tuple as "initialized", going from "write-only" mode to
+     * "read-only" mode.
+     *
+     *   Category: Compound primitives
+     *   Type: Tuple literals
+     *   Operands:
+     *   Stack: tuple => tuple
+     */ \
+    IF_RECORD_TUPLE(MACRO(FinishTuple, finish_tuple, NULL, 1, 1, 1, JOF_BYTE)) \
+    /*
+     * Push a new function object.
+     *
+     * The new function inherits the current environment chain.
+     *
+     * Used to create most JS functions. Notable exceptions are derived or
+     * default class constructors.
+     *
+     * Implements: [InstantiateFunctionObject][1], [Evaluation for
+     * *FunctionExpression*][2], and so on.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-function-definitions-runtime-semantics-instantiatefunctionobject
+     * [2]: https://tc39.es/ecma262/#sec-function-definitions-runtime-semantics-evaluation
+     *
+     *   Category: Functions
+     *   Type: Creating functions
+     *   Operands: uint32_t funcIndex
+     *   Stack: => fn
+     */ \
+    MACRO(Lambda, lambda, NULL, 5, 0, 1, JOF_OBJECT) \
+    /*
+     * Set the name of a function.
+     *
+     * `fun` must be a function object. `name` must be a string, Int32 value,
+     * or symbol (like the result of `JSOp::ToId`).
+     *
+     * Implements: [SetFunctionName][1], used e.g. to name methods with
+     * computed property names.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-setfunctionname
+     *
+     *   Category: Functions
+     *   Type: Creating functions
+     *   Operands: FunctionPrefixKind prefixKind
+     *   Stack: fun, name => fun
+     */ \
+    MACRO(SetFunName, set_fun_name, NULL, 2, 2, 1, JOF_UINT8) \
+    /*
+     * Initialize the home object for functions with super bindings.
+     *
+     * `fun` must be a method, getter, or setter, so that it has a
+     * [[HomeObject]] slot. `homeObject` must be a plain object or (for static
+     * methods) a constructor.
+     *
+     *   Category: Functions
+     *   Type: Creating functions
+     *   Operands:
+     *   Stack: fun, homeObject => fun
+     */ \
+    MACRO(InitHomeObject, init_home_object, NULL, 1, 2, 1, JOF_BYTE) \
+    /*
+     * Throw a TypeError if `baseClass` isn't either `null` or a constructor.
+     *
+     * Implements: [ClassDefinitionEvaluation][1] step 6.f.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-runtime-semantics-classdefinitionevaluation
+     *
+     *   Category: Functions
+     *   Type: Creating constructors
+     *   Operands:
+     *   Stack: baseClass => baseClass
+     */ \
+    MACRO(CheckClassHeritage, check_class_heritage, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Like `JSOp::Lambda`, but using `proto` as the new function's
+     * `[[Prototype]]` (or `%FunctionPrototype%` if `proto` is `null`).
+     *
+     * `proto` must be either a constructor or `null`. We use
+     * `JSOp::CheckClassHeritage` to check.
+     *
+     * This is used to create the constructor for a derived class.
+     *
+     * Implements: [ClassDefinitionEvaluation][1] steps 6.e.ii, 6.g.iii, and
+     * 12 for derived classes.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-runtime-semantics-classdefinitionevaluation
+     *
+     *   Category: Functions
+     *   Type: Creating constructors
+     *   Operands: uint32_t funcIndex
+     *   Stack: proto => obj
+     */ \
+    MACRO(FunWithProto, fun_with_proto, NULL, 5, 1, 1, JOF_OBJECT) \
+    /*
+     * Pushes the current global's %BuiltinObject%.
+     *
+     * `kind` must be a valid `BuiltinObjectKind` (and must not be
+     * `BuiltinObjectKind::None`).
+     *
+     *   Category: Objects
+     *   Type: Built-in objects
+     *   Operands: uint8_t kind
+     *   Stack: => %BuiltinObject%
+     */ \
+    MACRO(BuiltinObject, builtin_object, NULL, 2, 0, 1, JOF_UINT8) \
+    /*
+     * Invoke `callee` with `this` and `args`, and push the return value. Throw
+     * a TypeError if `callee` isn't a function.
+     *
+     * `JSOp::CallContent` is for `callContentFunction` in self-hosted JS, and
+     * this is for handling it differently in debugger's `onNativeCall` hook.
+     * `onNativeCall` hook disables all JITs, and `JSOp::CallContent` is
+     * treated exactly the same as `JSOP::Call` in JIT.
+     *
+     * `JSOp::CallIter` is used for implicit calls to @@iterator methods, to
+     * ensure error messages are formatted with `JSMSG_NOT_ITERABLE` ("x is not
+     * iterable") rather than `JSMSG_NOT_FUNCTION` ("x[Symbol.iterator] is not
+     * a function"). The `argc` operand must be 0 for this variation.
+     *
+     * `JSOp::CallContentIter` is `JSOp::CallContent` variant of
+     * `JSOp::CallIter`.
+     *
+     * `JSOp::CallIgnoresRv` hints to the VM that the return value is ignored.
+     * This allows alternate faster implementations to be used that avoid
+     * unnecesary allocations.
+     *
+     * Implements: [EvaluateCall][1] steps 4, 5, and 7.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-evaluatecall
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands: uint16_t argc
+     *   Stack: callee, this, args[0], ..., args[argc-1] => rval
+     */ \
+    MACRO(Call, call, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC) \
+    MACRO(CallContent, call_content, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC) \
+    MACRO(CallIter, call_iter, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC) \
+    MACRO(CallContentIter, call_content_iter, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC) \
+    MACRO(CallIgnoresRv, call_ignores_rv, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC) \
+    /*
+     * Like `JSOp::Call`, but the arguments are provided in an array rather than
+     * a span of stack slots. Used to implement spread-call syntax:
+     * `f(...args)`.
+     *
+     * `args` must be an Array object containing the actual arguments. The
+     * array must be packed (dense and free of holes; see IsPackedArray).
+     * This can be ensured by creating the array with `JSOp::NewArray` and
+     * populating it using `JSOp::InitElemArray`.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: callee, this, args => rval
+     */ \
+    MACRO(SpreadCall, spread_call, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE|JOF_SPREAD|JOF_IC) \
+    /*
+     * Push an array object that can be passed directly as the `args` argument
+     * to `JSOp::SpreadCall`. If the operation can't be optimized, push
+     * `undefined` instead.
+     *
+     * This instruction and the branch around the iterator loop are emitted
+     * only when `iterable` is the sole argument in a call, as in `f(...arr)`.
+     *
+     * See `js::OptimizeSpreadCall`.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: iterable => array_or_undefined
+     */ \
+    MACRO(OptimizeSpreadCall, optimize_spread_call, NULL, 1, 1, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Perform a direct eval in the current environment if `callee` is the
+     * builtin `eval` function, otherwise follow same behaviour as `JSOp::Call`.
+     *
+     * All direct evals use one of the JSOp::*Eval instructions here and these
+     * opcodes are only used when the syntactic conditions for a direct eval
+     * are met. If the builtin `eval` function is called though other means, it
+     * becomes an indirect eval.
+     *
+     * Direct eval causes all bindings in *enclosing* non-global scopes to be
+     * marked "aliased". The optimization that puts bindings in stack slots has
+     * to prove that the bindings won't need to be captured by closures or
+     * accessed using `JSOp::{Get,Bind,Set,Del}Name` instructions. Direct eval
+     * makes that analysis impossible.
+     *
+     * The instruction immediately following any `JSOp::*Eval` instruction must
+     * be `JSOp::Lineno`.
+     *
+     * Implements: [Function Call Evaluation][1], steps 5-7 and 9, when the
+     * syntactic critera for direct eval in step 6 are all met.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-function-calls-runtime-semantics-evaluation
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands: uint16_t argc
+     *   Stack: callee, this, args[0], ..., args[argc-1] => rval
+     */ \
+    MACRO(Eval, eval, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CHECKSLOPPY|JOF_IC) \
+    /*
+     * Spread-call variant of `JSOp::Eval`.
+     *
+     * See `JSOp::SpreadCall` for restrictions on `args`.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: callee, this, args => rval
+     */ \
+    MACRO(SpreadEval, spread_eval, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE|JOF_SPREAD|JOF_CHECKSLOPPY|JOF_IC) \
+    /*
+     * Like `JSOp::Eval`, but for strict mode code.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands: uint16_t argc
+     *   Stack: evalFn, this, args[0], ..., args[argc-1] => rval
+     */ \
+    MACRO(StrictEval, strict_eval, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Spread-call variant of `JSOp::StrictEval`.
+     *
+     * See `JSOp::SpreadCall` for restrictions on `args`.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: callee, this, args => rval
+     */ \
+    MACRO(StrictSpreadEval, strict_spread_eval, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE|JOF_SPREAD|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Push the implicit `this` value for an unqualified function call, like
+     * `foo()`. `nameIndex` gives the name of the function we're calling.
+     *
+     * The result is always `undefined` except when the name refers to a `with`
+     * binding.  For example, in `with (date) { getFullYear(); }`, the
+     * implicit `this` passed to `getFullYear` is `date`, not `undefined`.
+     *
+     * This walks the run-time environment chain looking for the environment
+     * record that contains the function. If the function call definitely
+     * refers to a local binding, use `JSOp::Undefined`.
+     *
+     * Implements: [EvaluateCall][1] step 1.b. But not entirely correctly.
+     * See [bug 1166408][2].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-evaluatecall
+     * [2]: https://bugzilla.mozilla.org/show_bug.cgi?id=1166408
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands: uint32_t nameIndex
+     *   Stack: => this
+     */ \
+    MACRO(ImplicitThis, implicit_this, "", 5, 0, 1, JOF_ATOM) \
+    /*
+     * Push the call site object for a tagged template call.
+     *
+     * `script->getObject(objectIndex)` is the call site object.
+     *
+     * The call site object will already have the `.raw` property defined on it
+     * and will be frozen.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands: uint32_t objectIndex
+     *   Stack: => callSiteObj
+     */ \
+    MACRO(CallSiteObj, call_site_obj, NULL, 5, 0, 1, JOF_OBJECT) \
+    /*
+     * Push `MagicValue(JS_IS_CONSTRUCTING)`.
+     *
+     * This magic value is a required argument to the `JSOp::New` and
+     * `JSOp::SuperCall` instructions and must not be used any other way.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: => JS_IS_CONSTRUCTING
+     */ \
+    MACRO(IsConstructing, is_constructing, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Invoke `callee` as a constructor with `args` and `newTarget`, and push
+     * the return value. Throw a TypeError if `callee` isn't a constructor.
+     *
+     * `isConstructing` must be the value pushed by `JSOp::IsConstructing`.
+     *
+     * `JSOp::SuperCall` behaves exactly like `JSOp::New`, but is used for
+     * *SuperCall* expressions, to allow JITs to distinguish them from `new`
+     * expressions.
+     *
+     * `JSOp::NewContent` is for `constructContentFunction` in self-hosted JS.
+     * See the comment for `JSOp::CallContent` for more details.
+     *
+     * Implements: [EvaluateConstruct][1] steps 7 and 8.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-evaluatenew
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands: uint16_t argc
+     *   Stack: callee, isConstructing, args[0], ..., args[argc-1], newTarget => rval
+     */ \
+    MACRO(New, new_, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CONSTRUCT|JOF_IC) \
+    MACRO(NewContent, new_content, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CONSTRUCT|JOF_IC) \
+    MACRO(SuperCall, super_call, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CONSTRUCT|JOF_IC) \
+    /*
+     * Spread-call variant of `JSOp::New`.
+     *
+     * Invokes `callee` as a constructor with `args` and `newTarget`, and
+     * pushes the return value onto the stack.
+     *
+     * `isConstructing` must be the value pushed by `JSOp::IsConstructing`.
+     * See `JSOp::SpreadCall` for restrictions on `args`.
+     *
+     * `JSOp::SpreadSuperCall` behaves exactly like `JSOp::SpreadNew`, but is
+     * used for *SuperCall* expressions.
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: callee, isConstructing, args, newTarget => rval
+     */ \
+    MACRO(SpreadNew, spread_new, NULL, 1, 4, 1, JOF_BYTE|JOF_INVOKE|JOF_CONSTRUCT|JOF_SPREAD|JOF_IC) \
+    MACRO(SpreadSuperCall, spread_super_call, NULL, 1, 4, 1, JOF_BYTE|JOF_INVOKE|JOF_CONSTRUCT|JOF_SPREAD|JOF_IC) \
+    /*
+     * Push the prototype of `callee` in preparation for calling `super()`.
+     *
+     * `callee` must be a derived class constructor.
+     *
+     * Implements: [GetSuperConstructor][1], steps 4-7.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getsuperconstructor
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: callee => superFun
+     */ \
+    MACRO(SuperFun, super_fun, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Throw a ReferenceError if `thisval` is not
+     * `MagicValue(JS_UNINITIALIZED_LEXICAL)`. Used in derived class
+     * constructors to prohibit calling `super` more than once.
+     *
+     * Implements: [BindThisValue][1], step 3.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-bindthisvalue
+     *
+     *   Category: Functions
+     *   Type: Calls
+     *   Operands:
+     *   Stack: thisval => thisval
+     */ \
+    MACRO(CheckThisReinit, check_this_reinit, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Create and push a generator object for the current frame.
+     *
+     * This instruction must appear only in scripts for generators, async
+     * functions, and async generators. There must not already be a generator
+     * object for the current frame (that is, this instruction must execute at
+     * most once per generator or async call).
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: => gen
+     */ \
+    MACRO(Generator, generator, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Suspend the current generator and return to the caller.
+     *
+     * When a generator is called, its script starts running, like any other JS
+     * function, because [FunctionDeclarationInstantation][1] and other
+     * [generator object setup][2] are implemented mostly in bytecode. However,
+     * the *FunctionBody* of the generator is not supposed to start running
+     * until the first `.next()` call, so after setup the script suspends
+     * itself: the "initial yield".
+     *
+     * Later, when resuming execution, `rval`, `gen` and `resumeKind` will
+     * receive the values passed in by `JSOp::Resume`. `resumeKind` is the
+     * `GeneratorResumeKind` stored as an Int32 value.
+     *
+     * This instruction must appear only in scripts for generators and async
+     * generators. `gen` must be the generator object for the current frame. It
+     * must not have been previously suspended. The resume point indicated by
+     * `resumeIndex` must be the next instruction in the script, which must be
+     * `AfterYield`.
+     *
+     * Implements: [GeneratorStart][3], steps 4-7.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
+     * [2]: https://tc39.es/ecma262/#sec-generator-function-definitions-runtime-semantics-evaluatebody
+     * [3]: https://tc39.es/ecma262/#sec-generatorstart
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands: uint24_t resumeIndex
+     *   Stack: gen => rval, gen, resumeKind
+     */ \
+    MACRO(InitialYield, initial_yield, NULL, 4, 1, 3, JOF_RESUMEINDEX) \
+    /*
+     * Bytecode emitted after `yield` expressions. This is useful for the
+     * Debugger and `AbstractGeneratorObject::isAfterYieldOrAwait`. It's
+     * treated as jump target op so that the Baseline Interpreter can
+     * efficiently restore the frame's interpreterICEntry when resuming a
+     * generator.
+     *
+     * The preceding instruction in the script must be `Yield`, `InitialYield`,
+     * or `Await`.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands: uint32_t icIndex
+     *   Stack: =>
+     */ \
+    MACRO(AfterYield, after_yield, NULL, 5, 0, 0, JOF_ICINDEX) \
+    /*
+     * Suspend and close the current generator, async function, or async
+     * generator.
+     *
+     * `gen` must be the generator object for the current frame.
+     *
+     * If the current function is a non-async generator, then the value in the
+     * frame's return value slot is returned to the caller. It should be an
+     * object of the form `{value: returnValue, done: true}`.
+     *
+     * If the current function is an async function or async generator, the
+     * frame's return value slot must contain the current frame's result
+     * promise, which must already be resolved or rejected.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: gen =>
+     */ \
+    MACRO(FinalYieldRval, final_yield_rval, NULL, 1, 1, 0, JOF_BYTE) \
+    /*
+     * Suspend execution of the current generator or async generator, returning
+     * `rval1`.
+     *
+     * For non-async generators, `rval1` should be an object of the form
+     * `{value: valueToYield, done: true}`. For async generators, `rval1`
+     * should be the value to yield, and the caller is responsible for creating
+     * the iterator result object (under `js::AsyncGeneratorYield`).
+     *
+     * This instruction must appear only in scripts for generators and async
+     * generators. `gen` must be the generator object for the current stack
+     * frame. The resume point indicated by `resumeIndex` must be the next
+     * instruction in the script, which must be `AfterYield`.
+     *
+     * When resuming execution, `rval2`, `gen` and `resumeKind` receive the
+     * values passed in by `JSOp::Resume`.
+     *
+     * Implements: [GeneratorYield][1] and [AsyncGeneratorYield][2].
+     *
+     * [1]: https://tc39.es/ecma262/#sec-generatoryield
+     * [2]: https://tc39.es/ecma262/#sec-asyncgeneratoryield
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands: uint24_t resumeIndex
+     *   Stack: rval1, gen => rval2, gen, resumeKind
+     */ \
+    MACRO(Yield, yield, NULL, 4, 2, 3, JOF_RESUMEINDEX) \
+    /*
+     * Pushes a boolean indicating whether the top of the stack is
+     * `MagicValue(JS_GENERATOR_CLOSING)`.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: val => val, res
+     */ \
+    MACRO(IsGenClosing, is_gen_closing, NULL, 1, 1, 2, JOF_BYTE) \
+    /*
+     * Arrange for this async function to resume asynchronously when `value`
+     * becomes resolved.
+     *
+     * This is the last thing an async function does before suspending for an
+     * `await` expression. It coerces the awaited `value` to a promise and
+     * effectively calls `.then()` on it, passing handler functions that will
+     * resume this async function call later. See `js::AsyncFunctionAwait`.
+     *
+     * This instruction must appear only in non-generator async function
+     * scripts. `gen` must be the internal generator object for the current
+     * frame. After this instruction, the script should suspend itself with
+     * `Await` (rather than exiting any other way).
+     *
+     * The result `promise` is the async function's result promise,
+     * `gen->as<AsyncFunctionGeneratorObject>().promise()`.
+     *
+     * Implements: [Await][1], steps 2-9.
+     *
+     * [1]: https://tc39.github.io/ecma262/#await
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: value, gen => promise
+     */ \
+    MACRO(AsyncAwait, async_await, NULL, 1, 2, 1, JOF_BYTE) \
+    /*
+     * Resolve or reject the current async function's result promise with
+     * 'valueOrReason'.
+     *
+     * This instruction must appear only in non-generator async function
+     * scripts. `gen` must be the internal generator object for the current
+     * frame. This instruction must run at most once per async function call,
+     * as resolving/rejecting an already resolved/rejected promise is not
+     * permitted.
+     *
+     * The result `promise` is the async function's result promise,
+     * `gen->as<AsyncFunctionGeneratorObject>().promise()`.
+     *
+     * Implements: [AsyncFunctionStart][1], step 4.d.i. and 4.e.i.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-async-functions-abstract-operations-async-function-start
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands: AsyncFunctionResolveKind fulfillOrReject
+     *   Stack: valueOrReason, gen => promise
+     */ \
+    MACRO(AsyncResolve, async_resolve, NULL, 2, 2, 1, JOF_UINT8) \
+    /*
+     * Suspend the current frame for an `await` expression.
+     *
+     * This instruction must appear only in scripts for async functions and
+     * async generators. `gen` must be the internal generator object for the
+     * current frame.
+     *
+     * This returns `promise` to the caller. Later, when this async call is
+     * resumed, `resolved`, `gen` and `resumeKind` receive the values passed in
+     * by `JSOp::Resume`, and execution continues at the next instruction,
+     * which must be `AfterYield`.
+     *
+     * This instruction is used in two subtly different ways.
+     *
+     * 1.  In async functions:
+     *
+     *         ...                          # valueToAwait
+     *         GetAliasedVar ".generator"   # valueToAwait gen
+     *         AsyncAwait                   # resultPromise
+     *         GetAliasedVar ".generator"   # resultPromise gen
+     *         Await                        # resolved gen resumeKind
+     *         AfterYield
+     *
+     *     `AsyncAwait` arranges for this frame to be resumed later and pushes
+     *     its result promise. `Await` then suspends the frame and removes it
+     *     from the stack, returning the result promise to the caller. (If this
+     *     async call hasn't awaited before, the caller may be user code.
+     *     Otherwise, the caller is self-hosted code using `resumeGenerator`.)
+     *
+     * 2.  In async generators:
+     *
+     *         ...                          # valueToAwait
+     *         GetAliasedVar ".generator"   # valueToAwait gen
+     *         Await                        # resolved gen resumeKind
+     *         AfterYield
+     *
+     *     `AsyncAwait` is not used, so (1) the value returned to the caller by
+     *     `Await` is `valueToAwait`, not `resultPromise`; and (2) the caller
+     *     is responsible for doing the async-generator equivalent of
+     *     `AsyncAwait` (namely, `js::AsyncGeneratorAwait`, called from
+     *     `js::AsyncGeneratorResume` after `js::CallSelfHostedFunction`
+     *     returns).
+     *
+     * Implements: [Await][1], steps 10-12.
+     *
+     * [1]: https://tc39.es/ecma262/#await
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands: uint24_t resumeIndex
+     *   Stack: promise, gen => resolved, gen, resumeKind
+     */ \
+    MACRO(Await, await, NULL, 4, 2, 3, JOF_RESUMEINDEX) \
+    /*
+     * Test if the re-entry to the microtask loop may be skipped.
+     *
+     * This is part of an optimization for `await` expressions. Programs very
+     * often await values that aren't promises, or promises that are already
+     * resolved. We can then sometimes skip suspending the current frame and
+     * returning to the microtask loop. If the circumstances permit the
+     * optimization, `CanSkipAwait` pushes true if the optimization is allowed,
+     * and false otherwise.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: value => value, can_skip
+     */ \
+    MACRO(CanSkipAwait, can_skip_await, NULL, 1, 1, 2, JOF_BYTE) \
+    /*
+     * Potentially extract an awaited value, if the await is skippable
+     *
+     * If re-entering the microtask loop is skippable (as checked by CanSkipAwait)
+     * if can_skip is true,  `MaybeExtractAwaitValue` replaces `value` with the result of the
+     * `await` expression (unwrapping the resolved promise, if any). Otherwise, value remains
+     * as is.
+     *
+     * In both cases, can_skip remains the same.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: value, can_skip => value_or_resolved, can_skip
+     */ \
+    MACRO(MaybeExtractAwaitValue, maybe_extract_await_value, NULL, 1, 2, 2, JOF_BYTE) \
+    /*
+     * Pushes one of the GeneratorResumeKind values as Int32Value.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands: GeneratorResumeKind resumeKind (encoded as uint8_t)
+     *   Stack: => resumeKind
+     */ \
+    MACRO(ResumeKind, resume_kind, NULL, 2, 0, 1, JOF_UINT8) \
+    /*
+     * Handle Throw and Return resumption.
+     *
+     * `gen` must be the generator object for the current frame. `resumeKind`
+     * must be a `GeneratorResumeKind` stored as an `Int32` value. If it is
+     * `Next`, continue to the next instruction. If `resumeKind` is `Throw` or
+     * `Return`, these completions are handled by throwing an exception. See
+     * `GeneratorThrowOrReturn`.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: rval, gen, resumeKind => rval
+     */ \
+    MACRO(CheckResumeKind, check_resume_kind, NULL, 1, 3, 1, JOF_BYTE) \
+    /*
+     * Resume execution of a generator, async function, or async generator.
+     *
+     * This behaves something like a call instruction. It pushes a stack frame
+     * (the one saved when `gen` was suspended, rather than a fresh one) and
+     * runs instructions in it. Once `gen` returns or yields, its return value
+     * is pushed to this frame's stack and execution continues in this script.
+     *
+     * This instruction is emitted only for the `resumeGenerator` self-hosting
+     * intrinsic. It is used in the implementation of
+     * `%GeneratorPrototype%.next`, `.throw`, and `.return`.
+     *
+     * `gen` must be a suspended generator object. `resumeKind` must be in
+     * range for `GeneratorResumeKind`.
+     *
+     *   Category: Functions
+     *   Type: Generators and async functions
+     *   Operands:
+     *   Stack: gen, val, resumeKind => rval
+     */ \
+    MACRO(Resume, resume, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE) \
+    /*
+     * No-op instruction marking the target of a jump instruction.
+     *
+     * This instruction and a few others (see `js::BytecodeIsJumpTarget`) are
+     * jump target instructions. The Baseline Interpreter uses these
+     * instructions to sync the frame's `interpreterICEntry` after a jump. Ion
+     * uses them to find block boundaries when translating bytecode to MIR.
+     *
+     *   Category: Control flow
+     *   Type: Jump targets
+     *   Operands: uint32_t icIndex
+     *   Stack: =>
+     */ \
+    MACRO(JumpTarget, jump_target, NULL, 5, 0, 0, JOF_ICINDEX) \
+    /*
+     * Marks the target of the backwards jump for some loop.
+     *
+     * This is a jump target instruction (see `JSOp::JumpTarget`). Additionally,
+     * it checks for interrupts and handles JIT tiering.
+     *
+     * The `depthHint` operand is a loop depth hint for Ion. It starts at 1 and
+     * deeply nested loops all have the same value.
+     *
+     * For the convenience of the JITs, scripts must not start with this
+     * instruction. See bug 1602390.
+     *
+     *   Category: Control flow
+     *   Type: Jump targets
+     *   Operands: uint32_t icIndex, uint8_t depthHint
+     *   Stack: =>
+     */ \
+    MACRO(LoopHead, loop_head, NULL, 6, 0, 0, JOF_LOOPHEAD) \
+    /*
+     * Jump to a 32-bit offset from the current bytecode.
+     *
+     * See "Jump instructions" above for details.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t offset
+     *   Stack: =>
+     */ \
+    MACRO(Goto, goto_, NULL, 5, 0, 0, JOF_JUMP) \
+    /*
+     * If ToBoolean(`cond`) is false, jumps to a 32-bit offset from the current
+     * instruction.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t forwardOffset
+     *   Stack: cond =>
+     */ \
+    MACRO(JumpIfFalse, jump_if_false, NULL, 5, 1, 0, JOF_JUMP|JOF_IC) \
+    /*
+     * If ToBoolean(`cond`) is true, jump to a 32-bit offset from the current
+     * instruction.
+     *
+     * `offset` may be positive or negative. This is the instruction used at the
+     * end of a do-while loop to jump back to the top.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t offset
+     *   Stack: cond =>
+     */ \
+    MACRO(JumpIfTrue, jump_if_true, NULL, 5, 1, 0, JOF_JUMP|JOF_IC) \
+    /*
+     * Short-circuit for logical AND.
+     *
+     * If ToBoolean(`cond`) is false, jump to a 32-bit offset from the current
+     * instruction. The value remains on the stack.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t forwardOffset
+     *   Stack: cond => cond
+     */ \
+    MACRO(And, and_, NULL, 5, 1, 1, JOF_JUMP|JOF_IC) \
+    /*
+     * Short-circuit for logical OR.
+     *
+     * If ToBoolean(`cond`) is true, jump to a 32-bit offset from the current
+     * instruction. The value remains on the stack.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t forwardOffset
+     *   Stack: cond => cond
+     */ \
+    MACRO(Or, or_, NULL, 5, 1, 1, JOF_JUMP|JOF_IC) \
+    /*
+     * Short-circuiting for nullish coalescing.
+     *
+     * If `val` is not null or undefined, jump to a 32-bit offset from the
+     * current instruction.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t forwardOffset
+     *   Stack: val => val
+     */ \
+    MACRO(Coalesce, coalesce, NULL, 5, 1, 1, JOF_JUMP) \
+     /*
+     * Like `JSOp::JumpIfTrue`, but if the branch is taken, pop and discard an
+     * additional stack value.
+     *
+     * This is used to implement `switch` statements when the
+     * `JSOp::TableSwitch` optimization is not possible. The switch statement
+     *
+     *     switch (expr) {
+     *         case A: stmt1;
+     *         case B: stmt2;
+     *     }
+     *
+     * compiles to this bytecode:
+     *
+     *         # dispatch code - evaluate expr, check it against each `case`,
+     *         # jump to the right place in the body or to the end.
+     *         <expr>
+     *         Dup; <A>; StrictEq; Case L1; JumpTarget
+     *         Dup; <B>; StrictEq; Case L2; JumpTarget
+     *         Default LE
+     *
+     *         # body code
+     *     L1: JumpTarget; <stmt1>
+     *     L2: JumpTarget; <stmt2>
+     *     LE: JumpTarget
+     *
+     * This opcode is weird: it's the only one whose ndefs varies depending on
+     * which way a conditional branch goes. We could implement switch
+     * statements using `JSOp::JumpIfTrue` and `JSOp::Pop`, but that would also
+     * be awkward--putting the `JSOp::Pop` inside the `switch` body would
+     * complicate fallthrough.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t forwardOffset
+     *   Stack: val, cond => val (if !cond)
+     */ \
+    MACRO(Case, case_, NULL, 5, 2, 1, JOF_JUMP) \
+    /*
+     * Like `JSOp::Goto`, but pop and discard an additional stack value.
+     *
+     * This appears after all cases for a non-optimized `switch` statement. If
+     * there's a `default:` label, it jumps to that point in the body;
+     * otherwise it jumps to the next statement.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t forwardOffset
+     *   Stack: lval =>
+     */ \
+    MACRO(Default, default_, NULL, 5, 1, 0, JOF_JUMP) \
+    /*
+     * Optimized switch-statement dispatch, used when all `case` labels are
+     * small integer constants.
+     *
+     * If `low <= i <= high`, jump to the instruction at the offset given by
+     * `script->resumeOffsets()[firstResumeIndex + i - low]`, in bytes from the
+     * start of the current script's bytecode. Otherwise, jump to the
+     * instruction at `defaultOffset` from the current instruction. All of
+     * these offsets must be in range for the current script and must point to
+     * `JSOp::JumpTarget` instructions.
+     *
+     * The following inequalities must hold: `low <= high` and
+     * `firstResumeIndex + high - low < resumeOffsets().size()`.
+     *
+     *   Category: Control flow
+     *   Type: Jumps
+     *   Operands: int32_t defaultOffset, int32_t low, int32_t high,
+     *             uint24_t firstResumeIndex
+     *   Stack: i =>
+     */ \
+    MACRO(TableSwitch, table_switch, NULL, 16, 1, 0, JOF_TABLESWITCH) \
+    /*
+     * Return `rval`.
+     *
+     * This must not be used in derived class constructors. Instead use
+     * `JSOp::SetRval`, `JSOp::CheckReturn`, and `JSOp::RetRval`.
+     *
+     *   Category: Control flow
+     *   Type: Return
+     *   Operands:
+     *   Stack: rval =>
+     */ \
+    MACRO(Return, return_, NULL, 1, 1, 0, JOF_BYTE) \
+    /*
+     * Push the current stack frame's `returnValue`. If no `JSOp::SetRval`
+     * instruction has been executed in this stack frame, this is `undefined`.
+     *
+     * Every stack frame has a `returnValue` slot, used by top-level scripts,
+     * generators, async functions, and derived class constructors. Plain
+     * functions usually use `JSOp::Return` instead.
+     *
+     *   Category: Control flow
+     *   Type: Return
+     *   Operands:
+     *   Stack: => rval
+     */ \
+    MACRO(GetRval, get_rval, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Store `rval` in the current stack frame's `returnValue` slot.
+     *
+     * This instruction must not be used in a toplevel script compiled with the
+     * `noScriptRval` option.
+     *
+     *   Category: Control flow
+     *   Type: Return
+     *   Operands:
+     *   Stack: rval =>
+     */ \
+    MACRO(SetRval, set_rval, NULL, 1, 1, 0, JOF_BYTE) \
+    /*
+     * Stop execution and return the current stack frame's `returnValue`. If no
+     * `JSOp::SetRval` instruction has been executed in this stack frame, this
+     * is `undefined`.
+     *
+     * Also emitted at end of every script so consumers don't need to worry
+     * about running off the end.
+     *
+     * If the current script is a derived class constructor, `returnValue` must
+     * be an object. The script can use `JSOp::CheckReturn` to ensure this.
+     *
+     *   Category: Control flow
+     *   Type: Return
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(RetRval, ret_rval, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * Check the return value in a derived class constructor.
+     *
+     * -   If the current stack frame's `returnValue` is an object, push
+     *     `returnValue` onto the stack.
+     *
+     * -   Otherwise, if the `returnValue` is undefined and `thisval` is an
+     *     object, push `thisval` onto the stack.
+     *
+     * -   Otherwise, throw a TypeError.
+     *
+     * This is exactly what has to happen when a derived class constructor
+     * returns. `thisval` should be the current value of `this`, or
+     * `MagicValue(JS_UNINITIALIZED_LEXICAL)` if `this` is uninitialized.
+     *
+     * Implements: [The [[Construct]] internal method of JS functions][1],
+     * steps 13 and 15.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-ecmascript-function-objects-construct-argumentslist-newtarget
+     *
+     *   Category: Control flow
+     *   Type: Return
+     *   Operands:
+     *   Stack: thisval => rval
+     */ \
+    MACRO(CheckReturn, check_return, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Throw `exc`. (ノಠ益ಠ)ノ彡┴──┴
+     *
+     * This sets the pending exception to `exc` and jumps to error-handling
+     * code. If we're in a `try` block, error handling adjusts the stack and
+     * environment chain and resumes execution at the top of the `catch` or
+     * `finally` block. Otherwise it starts unwinding the stack.
+     *
+     * Implements: [*ThrowStatement* Evaluation][1], step 3.
+     *
+     * This is also used in for-of loops. If the body of the loop throws an
+     * exception, we catch it, close the iterator, then use `JSOp::Throw` to
+     * rethrow.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-throw-statement-runtime-semantics-evaluation
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands:
+     *   Stack: exc =>
+     */ \
+    MACRO(Throw, throw_, NULL, 1, 1, 0, JOF_BYTE) \
+    /*
+     * Create and throw an Error object.
+     *
+     * Sometimes we know at emit time that an operation always throws. For
+     * example, `delete super.prop;` is allowed in methods, but always throws a
+     * ReferenceError.
+     *
+     * `msgNumber` determines the `.message` and [[Prototype]] of the new Error
+     * object.  It must be an error number in js/public/friend/ErrorNumbers.msg.
+     * The number of arguments in the error message must be 0.
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands: ThrowMsgKind msgNumber
+     *   Stack: =>
+     */ \
+    MACRO(ThrowMsg, throw_msg, NULL, 2, 0, 0, JOF_UINT8) \
+    /*
+     * Throws a runtime TypeError for invalid assignment to a `const` binding.
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands: uint32_t nameIndex
+     *   Stack:
+     */ \
+    MACRO(ThrowSetConst, throw_set_const, NULL, 5, 0, 0, JOF_ATOM|JOF_NAME) \
+    /*
+     * No-op instruction that marks the top of the bytecode for a
+     * *TryStatement*.
+     *
+     * Location information for catch/finally blocks is stored in a side table,
+     * `script->trynotes()`.
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(Try, try_, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * No-op instruction used by the exception unwinder to determine the
+     * correct environment to unwind to when performing IteratorClose due to
+     * destructuring.
+     *
+     * This instruction must appear immediately before each
+     * `JSTRY_DESTRUCTURING` span in a script's try notes.
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(TryDestructuring, try_destructuring, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * Push and clear the pending exception. ┬──┬◡ﾉ(° -°ﾉ)
+     *
+     * This must be used only in the fixed sequence of instructions following a
+     * `JSTRY_CATCH` span (see "Bytecode Invariants" above), as that's the only
+     * way instructions would run with an exception pending.
+     *
+     * Used to implement catch-blocks, including the implicit ones generated as
+     * part of for-of iteration.
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands:
+     *   Stack: => exception
+     */ \
+    MACRO(Exception, exception, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * No-op instruction that marks the start of a `finally` block.
+     *
+     *   Category: Control flow
+     *   Type: Exceptions
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(Finally, finally, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * Push `MagicValue(JS_UNINITIALIZED_LEXICAL)`, a magic value used to mark
+     * a binding as uninitialized.
+     *
+     * This magic value must be used only by `JSOp::InitLexical`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands:
+     *   Stack: => uninitialized
+     */ \
+    MACRO(Uninitialized, uninitialized, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Initialize an optimized local lexical binding; or mark it as
+     * uninitialized.
+     *
+     * This stores the value `v` in the fixed slot `localno` in the current
+     * stack frame. If `v` is the magic value produced by `JSOp::Uninitialized`,
+     * this marks the binding as uninitialized. Otherwise this initializes the
+     * binding with value `v`.
+     *
+     * Implements: [CreateMutableBinding][1] step 3, substep "record that it is
+     * uninitialized", and [InitializeBinding][2], for optimized locals. (Note:
+     * this is how `const` bindings are initialized.)
+     *
+     * [1]: https://tc39.es/ecma262/#sec-declarative-environment-records-createmutablebinding-n-d
+     * [2]: https://tc39.es/ecma262/#sec-declarative-environment-records-initializebinding-n-v
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands: uint24_t localno
+     *   Stack: v => v
+     */ \
+    MACRO(InitLexical, init_lexical, NULL, 4, 1, 1, JOF_LOCAL|JOF_NAME) \
+    /*
+     * Initialize a global lexical binding.
+     *
+     * The binding must already have been created by
+     * `GlobalOrEvalDeclInstantiation` and must be uninitialized.
+     *
+     * Like `JSOp::InitLexical` but for global lexicals. Unlike `InitLexical`
+     * this can't be used to mark a binding as uninitialized.
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands: uint32_t nameIndex
+     *   Stack: val => val
+     */ \
+    MACRO(InitGLexical, init_g_lexical, NULL, 5, 1, 1, JOF_ATOM|JOF_NAME|JOF_PROPINIT|JOF_GNAME|JOF_IC) \
+    /*
+     * Initialize an aliased lexical binding; or mark it as uninitialized.
+     *
+     * Like `JSOp::InitLexical` but for aliased bindings.
+     *
+     * Note: There is no even-less-optimized `InitName` instruction because JS
+     * doesn't need it. We always know statically which binding we're
+     * initializing.
+     *
+     * `hops` is usually 0, but in `function f(a=eval("var b;")) { }`, the
+     * argument `a` is initialized from inside a nested scope, so `hops == 1`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands: uint8_t hops, uint24_t slot
+     *   Stack: v => v
+     */ \
+    MACRO(InitAliasedLexical, init_aliased_lexical, NULL, 5, 1, 1, JOF_ENVCOORD|JOF_NAME|JOF_PROPINIT) \
+    /*
+     * Throw a ReferenceError if the value on top of the stack is uninitialized.
+     *
+     * Typically used after `JSOp::GetLocal` with the same `localno`.
+     *
+     * Implements: [GetBindingValue][1] step 3 and [SetMutableBinding][2] step
+     * 4 for declarative Environment Records.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-declarative-environment-records-getbindingvalue-n-s
+     * [2]: https://tc39.es/ecma262/#sec-declarative-environment-records-setmutablebinding-n-v-s
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands: uint24_t localno
+     *   Stack: v => v
+     */ \
+    MACRO(CheckLexical, check_lexical, NULL, 4, 1, 1, JOF_LOCAL|JOF_NAME) \
+    /*
+     * Like `JSOp::CheckLexical` but for aliased bindings.
+     *
+     * Typically used after `JSOp::GetAliasedVar` with the same hops/slot.
+     *
+     * Note: There are no `CheckName` or `CheckGName` instructions because
+     * they're unnecessary. `JSOp::{Get,Set}{Name,GName}` all check for
+     * uninitialized lexicals and throw if needed.
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands: uint8_t hops, uint24_t slot
+     *   Stack: v => v
+     */ \
+    MACRO(CheckAliasedLexical, check_aliased_lexical, NULL, 5, 1, 1, JOF_ENVCOORD|JOF_NAME) \
+    /*
+     * Throw a ReferenceError if the value on top of the stack is
+     * `MagicValue(JS_UNINITIALIZED_LEXICAL)`. Used in derived class
+     * constructors to check `this` (which needs to be initialized before use,
+     * by calling `super()`).
+     *
+     * Implements: [GetThisBinding][1] step 3.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-function-environment-records-getthisbinding
+     *
+     *   Category: Variables and scopes
+     *   Type: Initialization
+     *   Operands:
+     *   Stack: this => this
+     */ \
+    MACRO(CheckThis, check_this, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Look up a name on the global lexical environment's chain and push the
+     * environment which contains a binding for that name. If no such binding
+     * exists, push the global lexical environment.
+     *
+     *   Category: Variables and scopes
+     *   Type: Looking up bindings
+     *   Operands: uint32_t nameIndex
+     *   Stack: => global
+     */ \
+    MACRO(BindGName, bind_g_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_GNAME|JOF_IC) \
+    /*
+     * Look up a name on the environment chain and push the environment which
+     * contains a binding for that name. If no such binding exists, push the
+     * global lexical environment.
+     *
+     *   Category: Variables and scopes
+     *   Type: Looking up bindings
+     *   Operands: uint32_t nameIndex
+     *   Stack: => env
+     */ \
+    MACRO(BindName, bind_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_IC) \
+    /*
+     * Find a binding on the environment chain and push its value.
+     *
+     * If the binding is an uninitialized lexical, throw a ReferenceError. If
+     * no such binding exists, throw a ReferenceError unless the next
+     * instruction is `JSOp::Typeof`, in which case push `undefined`.
+     *
+     * Implements: [ResolveBinding][1] followed by [GetValue][2]
+     * (adjusted hackily for `typeof`).
+     *
+     * This is the fallback `Get` instruction that handles all unoptimized
+     * cases. Optimized instructions follow.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-resolvebinding
+     * [2]: https://tc39.es/ecma262/#sec-getvalue
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: => val
+     */ \
+    MACRO(GetName, get_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_IC) \
+    /*
+     * Find a global binding and push its value.
+     *
+     * This searches the global lexical environment and, failing that, the
+     * global object. (Unlike most declarative environments, the global lexical
+     * environment can gain more bindings after compilation, possibly shadowing
+     * global object properties.)
+     *
+     * This is an optimized version of `JSOp::GetName` that skips all local
+     * scopes, for use when the name doesn't refer to any local binding.
+     * `NonSyntacticVariablesObject`s break this optimization, so if the
+     * current script has a non-syntactic global scope, use `JSOp::GetName`
+     * instead.
+     *
+     * Like `JSOp::GetName`, this throws a ReferenceError if no such binding is
+     * found (unless the next instruction is `JSOp::Typeof`) or if the binding
+     * is an uninitialized lexical.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: => val
+     */ \
+    MACRO(GetGName, get_g_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_GNAME|JOF_IC) \
+    /*
+     * Push the value of an argument that is stored in the stack frame
+     * or in an `ArgumentsObject`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint16_t argno
+     *   Stack: => arguments[argno]
+     */ \
+    MACRO(GetArg, get_arg, NULL, 3, 0, 1, JOF_QARG|JOF_NAME) \
+    /*
+     * Push the value of an optimized local variable.
+     *
+     * If the variable is an uninitialized lexical, push
+     * `MagicValue(JS_UNINIITALIZED_LEXICAL)`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint24_t localno
+     *   Stack: => val
+     */ \
+    MACRO(GetLocal, get_local, NULL, 4, 0, 1, JOF_LOCAL|JOF_NAME) \
+    /*
+     * Push the value of an aliased binding.
+     *
+     * Local bindings that aren't closed over or dynamically accessed are
+     * stored in stack slots. Global and `with` bindings are object properties.
+     * All other bindings are called "aliased" and stored in
+     * `EnvironmentObject`s.
+     *
+     * Where possible, `Aliased` instructions are used to access aliased
+     * bindings.  (There's no difference in meaning between `AliasedVar` and
+     * `AliasedLexical`.) Each of these instructions has operands `hops` and
+     * `slot` that encode an [`EnvironmentCoordinate`][1], directions to the
+     * binding from the current environment object.
+     *
+     * `Aliased` instructions can't be used when there's a dynamic scope (due
+     * to non-strict `eval` or `with`) that might shadow the aliased binding.
+     *
+     * [1]: https://searchfox.org/mozilla-central/search?q=symbol:T_js%3A%3AEnvironmentCoordinate
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint8_t hops, uint24_t slot
+     *   Stack: => aliasedVar
+     */ \
+    MACRO(GetAliasedVar, get_aliased_var, NULL, 5, 0, 1, JOF_ENVCOORD|JOF_NAME) \
+    /*
+     * Push the value of an aliased binding, which may have to bypass a DebugEnvironmentProxy
+     * on the environment chain.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint8_t hops, uint24_t slot
+     *   Stack: => aliasedVar
+     */ \
+    MACRO(GetAliasedDebugVar, get_aliased_debug_var, NULL, 5, 0, 1, JOF_DEBUGCOORD|JOF_NAME) \
+    /*
+     * Get the value of a module import by name and pushes it onto the stack.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: => val
+     */ \
+    MACRO(GetImport, get_import, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME) \
+    /*
+     * Get the value of a binding from the environment `env`. If the name is
+     * not bound in `env`, throw a ReferenceError.
+     *
+     * `env` must be an environment currently on the environment chain, pushed
+     * by `JSOp::BindName` or `JSOp::BindVar`.
+     *
+     * Note: `JSOp::BindName` and `JSOp::GetBoundName` are the two halves of the
+     * `JSOp::GetName` operation: finding and reading a variable. This
+     * decomposed version is needed to implement the compound assignment and
+     * increment/decrement operators, which get and then set a variable. The
+     * spec says the variable lookup is done only once. If we did the lookup
+     * twice, there would be observable bugs, thanks to dynamic scoping. We
+     * could set the wrong variable or call proxy traps incorrectly.
+     *
+     * Implements: [GetValue][1] steps 4 and 6.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-getvalue
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: env => v
+     */ \
+    MACRO(GetBoundName, get_bound_name, NULL, 5, 1, 1, JOF_ATOM|JOF_NAME|JOF_IC) \
+    /*
+     * Push the value of an intrinsic onto the stack.
+     *
+     * Non-standard. Intrinsics are slots in the intrinsics holder object (see
+     * `GlobalObject::getIntrinsicsHolder`), which is used in lieu of global
+     * bindings in self-hosting code.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: => intrinsic[name]
+     */ \
+    MACRO(GetIntrinsic, get_intrinsic, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_IC) \
+    /*
+     * Pushes the currently executing function onto the stack.
+     *
+     * The current script must be a function script.
+     *
+     * Used to implement `super`. This is also used sometimes as a minor
+     * optimization when a named function expression refers to itself by name:
+     *
+     *     f = function fac(n) {  ... fac(n - 1) ... };
+     *
+     * This lets us optimize away a lexical environment that contains only the
+     * binding for `fac`, unless it's otherwise observable (via `with`, `eval`,
+     * or a nested closure).
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands:
+     *   Stack: => callee
+     */ \
+    MACRO(Callee, callee, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Load the callee stored in a CallObject on the environment chain. The
+     * `numHops` operand is the number of environment objects to skip on the
+     * environment chain. The environment chain element indicated by `numHops`
+     * must be a CallObject.
+     *
+     *   Category: Variables and scopes
+     *   Type: Getting binding values
+     *   Operands: uint8_t numHops
+     *   Stack: => callee
+     */ \
+    MACRO(EnvCallee, env_callee, NULL, 2, 0, 1, JOF_UINT8) \
+    /*
+     * Assign `val` to the binding in `env` with the name given by `nameIndex`.
+     * Throw a ReferenceError if the binding is an uninitialized lexical.
+     * This can call setters and/or proxy traps.
+     *
+     * `env` must be an environment currently on the environment chain,
+     * pushed by `JSOp::BindName` or `JSOp::BindVar`.
+     *
+     * This is the fallback `Set` instruction that handles all unoptimized
+     * cases. Optimized instructions follow.
+     *
+     * Implements: [PutValue][1] steps 5 and 7 for unoptimized bindings.
+     *
+     * Note: `JSOp::BindName` and `JSOp::SetName` are the two halves of simple
+     * assignment: finding and setting a variable. They are two separate
+     * instructions because, per spec, the "finding" part happens before
+     * evaluating the right-hand side of the assignment, and the "setting" part
+     * after. Optimized cases don't need a `Bind` instruction because the
+     * "finding" is done statically.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-putvalue
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: env, val => val
+     */ \
+    MACRO(SetName, set_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_CHECKSLOPPY|JOF_IC) \
+    /*
+     * Like `JSOp::SetName`, but throw a TypeError if there is no binding for
+     * the specified name in `env`, or if the binding is immutable (a `const`
+     * or read-only property).
+     *
+     * Implements: [PutValue][1] steps 5 and 7 for strict mode code.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-putvalue
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: env, val => val
+     */ \
+    MACRO(StrictSetName, strict_set_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Like `JSOp::SetName`, but for assigning to globals. `env` must be an
+     * environment pushed by `JSOp::BindGName`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: env, val => val
+     */ \
+    MACRO(SetGName, set_g_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_GNAME|JOF_CHECKSLOPPY|JOF_IC) \
+    /*
+     * Like `JSOp::StrictSetGName`, but for assigning to globals. `env` must be
+     * an environment pushed by `JSOp::BindGName`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: env, val => val
+     */ \
+    MACRO(StrictSetGName, strict_set_g_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_GNAME|JOF_CHECKSTRICT|JOF_IC) \
+    /*
+     * Assign `val` to an argument binding that's stored in the stack frame or
+     * in an `ArgumentsObject`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint16_t argno
+     *   Stack: val => val
+     */ \
+    MACRO(SetArg, set_arg, NULL, 3, 1, 1, JOF_QARG|JOF_NAME) \
+    /*
+     * Assign to an optimized local binding.
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint24_t localno
+     *   Stack: v => v
+     */ \
+    MACRO(SetLocal, set_local, NULL, 4, 1, 1, JOF_LOCAL|JOF_NAME) \
+    /*
+     * Assign to an aliased binding.
+     *
+     * Implements: [SetMutableBinding for declarative Environment Records][1],
+     * in certain cases where it's known that the binding exists, is mutable,
+     * and has been initialized.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-declarative-environment-records-setmutablebinding-n-v-s
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint8_t hops, uint24_t slot
+     *   Stack: val => val
+     */ \
+    MACRO(SetAliasedVar, set_aliased_var, NULL, 5, 1, 1, JOF_ENVCOORD|JOF_NAME|JOF_PROPSET) \
+    /*
+     * Assign to an intrinsic.
+     *
+     * Nonstandard. Intrinsics are used in lieu of global bindings in self-
+     * hosted code. The value is actually stored in the intrinsics holder
+     * object, `GlobalObject::getIntrinsicsHolder`. (Self-hosted code doesn't
+     * have many global `var`s, but it has many `function`s.)
+     *
+     *   Category: Variables and scopes
+     *   Type: Setting binding values
+     *   Operands: uint32_t nameIndex
+     *   Stack: val => val
+     */ \
+    MACRO(SetIntrinsic, set_intrinsic, NULL, 5, 1, 1, JOF_ATOM|JOF_NAME) \
+    /*
+     * Push a lexical environment onto the environment chain.
+     *
+     * The `LexicalScope` indicated by `lexicalScopeIndex` determines the shape
+     * of the new `BlockLexicalEnvironmentObject`. All bindings in the new
+     * environment are marked as uninitialized.
+     *
+     * Implements: [Evaluation of *Block*][1], steps 1-4.
+     *
+     * #### Fine print for environment chain instructions
+     *
+     * The following rules for `JSOp::{Push,Pop}LexicalEnv` also apply to
+     * `JSOp::PushClassBodyEnv`, `JSOp::PushVarEnv`, and
+     * `JSOp::{Enter,Leave}With`.
+     *
+     * Each `JSOp::PopLexicalEnv` instruction matches a particular
+     * `JSOp::PushLexicalEnv` instruction in the same script and must have the
+     * same scope and stack depth as the instruction immediately after that
+     * `PushLexicalEnv`.
+     *
+     * `JSOp::PushLexicalEnv` enters a scope that extends to some set of
+     * instructions in the script. Code must not jump into or out of this
+     * region: control can enter only by executing `PushLexicalEnv` and can
+     * exit only by executing a `PopLexicalEnv` or by exception unwinding. (A
+     * `JSOp::PopLexicalEnv` is always emitted at the end of the block, and
+     * extra copies are emitted on "exit slides", where a `break`, `continue`,
+     * or `return` statement exits the scope.)
+     *
+     * The script's `JSScript::scopeNotes()` must identify exactly which
+     * instructions begin executing in this scope. Typically this means a
+     * single entry marking the contiguous chunk of bytecode from the
+     * instruction after `JSOp::PushLexicalEnv` to `JSOp::PopLexicalEnv`
+     * (inclusive); but if that range contains any instructions on exit slides,
+     * after a `JSOp::PopLexicalEnv`, then those must be correctly noted as
+     * *outside* the scope.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-block-runtime-semantics-evaluation
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands: uint32_t lexicalScopeIndex
+     *   Stack: =>
+     */ \
+    MACRO(PushLexicalEnv, push_lexical_env, NULL, 5, 0, 0, JOF_SCOPE) \
+    /*
+     * Pop a lexical or class-body environment from the environment chain.
+     *
+     * See `JSOp::PushLexicalEnv` for the fine print.
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(PopLexicalEnv, pop_lexical_env, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * No-op instruction that indicates leaving an optimized lexical scope.
+     *
+     * If all bindings in a lexical scope are optimized into stack slots, then
+     * the runtime environment objects for that scope are optimized away. No
+     * `JSOp::{Push,Pop}LexicalEnv` instructions are emitted. However, the
+     * debugger still needs to be notified when control exits a scope; that's
+     * what this instruction does.
+     *
+     * The last instruction in a lexical or class-body scope, as indicated by
+     * scope notes, must be either this instruction (if the scope is optimized)
+     * or `JSOp::PopLexicalEnv` (if not).
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(DebugLeaveLexicalEnv, debug_leave_lexical_env, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * Replace the current block on the environment chain with a fresh block
+     * with uninitialized bindings. This implements the behavior of inducing a
+     * fresh lexical environment for every iteration of a for-in/of loop whose
+     * loop-head declares lexical variables that may be captured.
+     *
+     * The current environment must be a BlockLexicalEnvironmentObject.
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands: uint32_t lexicalScopeIndex
+     *   Stack: =>
+     */ \
+    MACRO(RecreateLexicalEnv, recreate_lexical_env, NULL, 5, 0, 0, JOF_SCOPE) \
+    /*
+     * Like `JSOp::RecreateLexicalEnv`, but the values of all the bindings are
+     * copied from the old block to the new one. This is used for C-style
+     * `for(let ...; ...; ...)` loops.
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands: uint32_t lexicalScopeIndex
+     *   Stack: =>
+     */ \
+    MACRO(FreshenLexicalEnv, freshen_lexical_env, NULL, 5, 0, 0, JOF_SCOPE) \
+    /*
+     * Push a ClassBody environment onto the environment chain.
+     *
+     * Like `JSOp::PushLexicalEnv`, but pushes a `ClassBodyEnvironmentObject`
+     * rather than a `BlockLexicalEnvironmentObject`.  `JSOp::PopLexicalEnv` is
+     * used to pop class-body environments as well as lexical environments.
+     *
+     * See `JSOp::PushLexicalEnv` for the fine print.
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands: uint32_t lexicalScopeIndex
+     *   Stack: =>
+     */ \
+    MACRO(PushClassBodyEnv, push_class_body_env, NULL, 5, 0, 0, JOF_SCOPE) \
+    /*
+     * Push a var environment onto the environment chain.
+     *
+     * Like `JSOp::PushLexicalEnv`, but pushes a `VarEnvironmentObject` rather
+     * than a `BlockLexicalEnvironmentObject`. The difference is that
+     * non-strict direct `eval` can add bindings to a var environment; see
+     * `VarScope` in Scope.h.
+     *
+     * See `JSOp::PushLexicalEnv` for the fine print.
+     *
+     * There is no corresponding `JSOp::PopVarEnv` operation, because a
+     * `VarEnvironmentObject` is never popped from the environment chain.
+     *
+     * Implements: Places in the spec where the VariableEnvironment is set:
+     *
+     * -   The bit in [PerformEval][1] where, in strict direct eval, the new
+     *     eval scope is taken as *varEnv* and becomes "*runningContext*'s
+     *     VariableEnvironment".
+     *
+     * -   The weird scoping rules for functions with default parameter
+     *     expressions, as specified in [FunctionDeclarationInstantiation][2]
+     *     step 28 ("NOTE: A separate Environment Record is needed...").
+     *
+     * Note: The spec also pushes a new VariableEnvironment on entry to every
+     * function, but the VM takes care of that as part of pushing the stack
+     * frame, before the function script starts to run, so `JSOp::PushVarEnv` is
+     * not needed.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-performeval
+     * [2]: https://tc39.es/ecma262/#sec-functiondeclarationinstantiation
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands: uint32_t scopeIndex
+     *   Stack: =>
+     */ \
+    MACRO(PushVarEnv, push_var_env, NULL, 5, 0, 0, JOF_SCOPE) \
+    /*
+     * Push a `WithEnvironmentObject` wrapping ToObject(`val`) to the
+     * environment chain.
+     *
+     * Implements: [Evaluation of `with` statements][1], steps 2-6.
+     *
+     * Operations that may need to consult a WithEnvironment can't be correctly
+     * implemented using optimized instructions like `JSOp::GetLocal`. A script
+     * must use the deoptimized `JSOp::GetName`, `BindName`, `SetName`, and
+     * `DelName` instead. Since those instructions don't work correctly with
+     * optimized locals and arguments, all bindings in scopes enclosing a
+     * `with` statement are marked as "aliased" and deoptimized too.
+     *
+     * See `JSOp::PushLexicalEnv` for the fine print.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-with-statement-runtime-semantics-evaluation
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands: uint32_t staticWithIndex
+     *   Stack: val =>
+     */ \
+    MACRO(EnterWith, enter_with, NULL, 5, 1, 0, JOF_SCOPE) \
+    /*
+     * Pop a `WithEnvironmentObject` from the environment chain.
+     *
+     * See `JSOp::PushLexicalEnv` for the fine print.
+     *
+     * Implements: [Evaluation of `with` statements][1], step 8.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-with-statement-runtime-semantics-evaluation
+     *
+     *   Category: Variables and scopes
+     *   Type: Entering and leaving environments
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(LeaveWith, leave_with, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * Push the current VariableEnvironment (the environment on the environment
+     * chain designated to receive new variables).
+     *
+     * Implements: [Annex B.3.3.1, changes to FunctionDeclarationInstantiation
+     * for block-level functions][1], step 1.a.ii.3.a, and similar steps in
+     * other Annex B.3.3 algorithms, when setting the function's second binding
+     * can't be optimized.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-web-compat-functiondeclarationinstantiation
+     *
+     *   Category: Variables and scopes
+     *   Type: Creating and deleting bindings
+     *   Operands:
+     *   Stack: => env
+     */ \
+    MACRO(BindVar, bind_var, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Check for conflicting bindings and then initialize them in global or
+     * sloppy eval scripts. This is required for global scripts with any
+     * top-level bindings, or any sloppy-eval scripts with any non-lexical
+     * top-level bindings.
+     *
+     * Implements: [GlobalDeclarationInstantiation][1] and
+     *             [EvalDeclarationInstantiation][2] (except step 12).
+     *
+     * The `lastFun` argument is a GCThingIndex of the last hoisted top-level
+     * function that is part of top-level script initialization. The gcthings
+     * from index `0` thru `lastFun` contain only scopes and hoisted functions.
+     *
+     * [1]: https://tc39.es/ecma262/#sec-globaldeclarationinstantiation
+     * [2]: https://tc39.es/ecma262/#sec-evaldeclarationinstantiation
+     *
+     *   Category: Variables and scopes
+     *   Type: Creating and deleting bindings
+     *   Operands: uint32_t lastFun
+     *   Stack: =>
+     */ \
+    MACRO(GlobalOrEvalDeclInstantiation, global_or_eval_decl_instantiation, NULL, 5, 0, 0, JOF_GCTHING) \
+    /*
+     * Look up a variable on the environment chain and delete it. Push `true`
+     * on success (if a binding was deleted, or if no such binding existed in
+     * the first place), `false` otherwise (most kinds of bindings can't be
+     * deleted).
+     *
+     * Implements: [`delete` *Identifier*][1], which [is a SyntaxError][2] in
+     * strict mode code.
+     *
+     *    [1]: https://tc39.es/ecma262/#sec-delete-operator-runtime-semantics-evaluation
+     *    [2]: https://tc39.es/ecma262/#sec-delete-operator-static-semantics-early-errors
+     *
+     *   Category: Variables and scopes
+     *   Type: Creating and deleting bindings
+     *   Operands: uint32_t nameIndex
+     *   Stack: => succeeded
+     */ \
+    MACRO(DelName, del_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_CHECKSLOPPY) \
+    /*
+     * Create and push the `arguments` object for the current function activation.
+     *
+     * When it exists, `arguments` is stored in an ordinary local variable.
+     * `JSOp::Arguments` is used in function preludes, to populate that variable
+     * before the function body runs, *not* each time `arguments` appears in a
+     * function.
+     *
+     * If a function clearly doesn't use `arguments`, we optimize it away when
+     * emitting bytecode. The function's script won't use `JSOp::Arguments` at
+     * all.
+     *
+     * The current script must be a function script. This instruction must
+     * execute at most once per function activation.
+     *
+     *   Category: Variables and scopes
+     *   Type: Function environment setup
+     *   Operands:
+     *   Stack: => arguments
+     */ \
+    MACRO(Arguments, arguments, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Create and push the rest parameter array for current function call.
+     *
+     * This must appear only in a script for a function that has a rest
+     * parameter.
+     *
+     *   Category: Variables and scopes
+     *   Type: Function environment setup
+     *   Operands:
+     *   Stack: => rest
+     */ \
+    MACRO(Rest, rest, NULL, 1, 0, 1, JOF_BYTE|JOF_IC) \
+    /*
+     * Determines the `this` value for current function frame and pushes it
+     * onto the stack.
+     *
+     * In functions, `this` is stored in a local variable. This instruction is
+     * used in the function prologue to get the value to initialize that
+     * variable.  (This doesn't apply to arrow functions, becauses they don't
+     * have a `this` binding; also, `this` is optimized away if it's unused.)
+     *
+     * Functions that have a `this` binding have a local variable named
+     * `".this"`, which is initialized using this instruction in the function
+     * prologue.
+     *
+     * In non-strict functions, `this` is always an object. Undefined/null
+     * `this` is converted into the global `this` value. Other primitive values
+     * are boxed. See `js::BoxNonStrictThis`.
+     *
+     *   Category: Variables and scopes
+     *   Type: Function environment setup
+     *   Operands:
+     *   Stack: => this
+     */ \
+    MACRO(FunctionThis, function_this, NULL, 1, 0, 1, JOF_BYTE) \
+    /*
+     * Pop the top value from the stack and discard it.
+     *
+     *   Category: Stack operations
+     *   Operands:
+     *   Stack: v =>
+     */ \
+    MACRO(Pop, pop, NULL, 1, 1, 0, JOF_BYTE) \
+    /*
+     * Pop the top `n` values from the stack. `n` must be <= the current stack
+     * depth.
+     *
+     *   Category: Stack operations
+     *   Operands: uint16_t n
+     *   Stack: v[n-1], ..., v[1], v[0] =>
+     */ \
+    MACRO(PopN, pop_n, NULL, 3, -1, 0, JOF_UINT16) \
+    /*
+     * Push a copy of the top value on the stack.
+     *
+     *   Category: Stack operations
+     *   Operands:
+     *   Stack: v => v, v
+     */ \
+    MACRO(Dup, dup, NULL, 1, 1, 2, JOF_BYTE) \
+    /*
+     * Duplicate the top two values on the stack.
+     *
+     *   Category: Stack operations
+     *   Operands:
+     *   Stack: v1, v2 => v1, v2, v1, v2
+     */ \
+    MACRO(Dup2, dup2, NULL, 1, 2, 4, JOF_BYTE) \
+    /*
+     * Push a copy of the nth value from the top of the stack.
+     *
+     * `n` must be less than the current stack depth.
+     *
+     *   Category: Stack operations
+     *   Operands: uint24_t n
+     *   Stack: v[n], v[n-1], ..., v[1], v[0] =>
+     *          v[n], v[n-1], ..., v[1], v[0], v[n]
+     */ \
+    MACRO(DupAt, dup_at, NULL, 4, 0, 1, JOF_UINT24) \
+    /*
+     * Swap the top two values on the stack.
+     *
+     *   Category: Stack operations
+     *   Operands:
+     *   Stack: v1, v2 => v2, v1
+     */ \
+    MACRO(Swap, swap, NULL, 1, 2, 2, JOF_BYTE) \
+    /*
+     * Pick the nth element from the stack and move it to the top of the stack.
+     *
+     *   Category: Stack operations
+     *   Operands: uint8_t n
+     *   Stack: v[n], v[n-1], ..., v[1], v[0] => v[n-1], ..., v[1], v[0], v[n]
+     */ \
+    MACRO(Pick, pick, NULL, 2, 0, 0, JOF_UINT8) \
+    /*
+     * Move the top of the stack value under the `n`th element of the stack.
+     * `n` must not be 0.
+     *
+     *   Category: Stack operations
+     *   Operands: uint8_t n
+     *   Stack: v[n], v[n-1], ..., v[1], v[0] => v[0], v[n], v[n-1], ..., v[1]
+     */ \
+    MACRO(Unpick, unpick, NULL, 2, 0, 0, JOF_UINT8) \
+    /*
+     * Do nothing. This is used when we need distinct bytecode locations for
+     * various mechanisms.
+     *
+     *   Category: Other
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(Nop, nop, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * No-op instruction emitted immediately after `JSOp::*Eval` so that direct
+     * eval does not have to do slow pc-to-line mapping.
+     *
+     * The `lineno` operand should agree with this script's source notes about
+     * the line number of the preceding `*Eval` instruction.
+     *
+     *   Category: Other
+     *   Operands: uint32_t lineno
+     *   Stack: =>
+     */ \
+    MACRO(Lineno, lineno, NULL, 5, 0, 0, JOF_UINT32) \
+    /*
+     * No-op instruction to hint that the top stack value is uninteresting.
+     *
+     * This affects only debug output and some error messages.
+     * In array destructuring, we emit bytecode that is roughly equivalent to
+     * `result.done ? undefined : result.value`.
+     * `NopDestructuring` is emitted after the `undefined`, so that the
+     * expression decompiler and disassembler know to casually ignore the
+     * possibility of `undefined`, and render the result of the conditional
+     * expression simply as "`result.value`".
+     *
+     *   Category: Other
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(NopDestructuring, nop_destructuring, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * No-op instruction only emitted in some self-hosted functions. Not
+     * handled by the JITs or Baseline Interpreter so the script always runs in
+     * the C++ interpreter.
+     *
+     *   Category: Other
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(ForceInterpreter, force_interpreter, NULL, 1, 0, 0, JOF_BYTE) \
+    /*
+     * Examine the top stack value, asserting that it's either a self-hosted
+     * function or a self-hosted intrinsic. This does nothing in a non-debug
+     * build.
+     *
+     *   Category: Other
+     *   Operands:
+     *   Stack: checkVal => checkVal
+     */ \
+    MACRO(DebugCheckSelfHosted, debug_check_self_hosted, NULL, 1, 1, 1, JOF_BYTE) \
+    /*
+     * Break in the debugger, if one is attached. Otherwise this is a no-op.
+     *
+     * The [`Debugger` API][1] offers a way to hook into this instruction.
+     *
+     * Implements: [Evaluation for *DebuggerStatement*][2].
+     *
+     * [1]: https://developer.mozilla.org/en-US/docs/Tools/Debugger-API/Debugger
+     * [2]: https://tc39.es/ecma262/#sec-debugger-statement-runtime-semantics-evaluation
+     *
+     *   Category: Other
+     *   Operands:
+     *   Stack: =>
+     */ \
+    MACRO(Debugger, debugger, NULL, 1, 0, 0, JOF_BYTE)
+
+// clang-format on
+
+/*
+ * In certain circumstances it may be useful to "pad out" the opcode space to
+ * a power of two.  Use this macro to do so.
+ */
+#define FOR_EACH_TRAILING_UNUSED_OPCODE(MACRO) \
+  IF_RECORD_TUPLE(/* empty */, MACRO(227))     \
+  IF_RECORD_TUPLE(/* empty */, MACRO(228))     \
+  IF_RECORD_TUPLE(/* empty */, MACRO(229))     \
+  IF_RECORD_TUPLE(/* empty */, MACRO(230))     \
+  IF_RECORD_TUPLE(/* empty */, MACRO(231))     \
+  IF_RECORD_TUPLE(/* empty */, MACRO(232))     \
+  IF_RECORD_TUPLE(/* empty */, MACRO(233))     \
+  MACRO(234)                                   \
+  MACRO(235)                                   \
+  MACRO(236)                                   \
+  MACRO(237)                                   \
+  MACRO(238)                                   \
+  MACRO(239)                                   \
+  MACRO(240)                                   \
+  MACRO(241)                                   \
+  MACRO(242)                                   \
+  MACRO(243)                                   \
+  MACRO(244)                                   \
+  MACRO(245)                                   \
+  MACRO(246)                                   \
+  MACRO(247)                                   \
+  MACRO(248)                                   \
+  MACRO(249)                                   \
+  MACRO(250)                                   \
+  MACRO(251)                                   \
+  MACRO(252)                                   \
+  MACRO(253)                                   \
+  MACRO(254)                                   \
+  MACRO(255)
+
+namespace js {
+
+// Sanity check that opcode values and trailing unused opcodes completely cover
+// the [0, 256) range.  Avert your eyes!  You don't want to know how the
+// sausage gets made.
+
+// clang-format off
+#define PLUS_ONE(...) \
+    + 1
+constexpr int JSOP_LIMIT = 0 FOR_EACH_OPCODE(PLUS_ONE);
+#undef PLUS_ONE
+
+#define TRAILING_VALUE_AND_VALUE_PLUS_ONE(val) \
+    val) && (val + 1 ==
+static_assert((JSOP_LIMIT ==
+               FOR_EACH_TRAILING_UNUSED_OPCODE(TRAILING_VALUE_AND_VALUE_PLUS_ONE)
+               256),
+              "trailing unused opcode values monotonically increase "
+              "from JSOP_LIMIT to 255");
+#undef TRAILING_VALUE_AND_VALUE_PLUS_ONE
+// clang-format on
+
+// Define JSOpLength_* constants for all ops.
+#define DEFINE_LENGTH_CONSTANT(op, op_snake, image, len, ...) \
+  constexpr size_t JSOpLength_##op = len;
+FOR_EACH_OPCODE(DEFINE_LENGTH_CONSTANT)
+#undef DEFINE_LENGTH_CONSTANT
+
+}  // namespace js
+
+/*
+ * JS operation bytecodes.
+ */
+enum class JSOp : uint8_t {
+#define ENUMERATE_OPCODE(op, ...) op,
+  FOR_EACH_OPCODE(ENUMERATE_OPCODE)
+#undef ENUMERATE_OPCODE
+};
+
+#endif  // vm_Opcodes_h
diff --git a/third_party/rust/jsparagus-stencil/src/copy/SourceNotes.h b/third_party/rust/jsparagus-stencil/src/copy/SourceNotes.h
new file mode 100644
index 0000000000..dd382bc7dc
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/SourceNotes.h
@@ -0,0 +1,428 @@
+/* -*- 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/. */
+
+#ifndef frontend_SourceNotes_h
+#define frontend_SourceNotes_h
+
+#include "mozilla/Assertions.h"  // MOZ_ASSERT
+
+#include <algorithm>  // std::min
+#include <stddef.h>   // ptrdiff_t, size_t
+#include <stdint.h>   // int8_t, uint8_t, uint32_t
+
+#include "jstypes.h"  // js::{Bit, BitMask}
+
+namespace js {
+
+/*
+ * Source notes generated along with bytecode for decompiling and debugging.
+ * A source note is a uint8_t with 4 bits of type and 4 of offset from the pc
+ * of the previous note. If 4 bits of offset aren't enough, extended delta
+ * notes (XDelta) consisting of 1 set high order bit followed by 7 offset
+ * bits are emitted before the next note. Some notes have operand offsets
+ * encoded immediately after them, in note bytes or byte-triples.
+ *
+ *                 Source Note               Extended Delta
+ *              +7-6-5-4+3-2-1-0+           +7+6-5-4-3-2-1-0+
+ *              | type  | delta |           |1| ext-delta   |
+ *              +-------+-------+           +-+-------------+
+ *
+ * At most one "gettable" note (i.e., a note of type other than NewLine,
+ * ColSpan, SetLine, and XDelta) applies to a given bytecode.
+ *
+ * NB: the js::SrcNote::specs_ array is indexed by this enum, so its
+ * initializers need to match the order here.
+ */
+
+#define FOR_EACH_SRC_NOTE_TYPE(M)                                            \
+  /* Terminates a note vector. */                                            \
+  M(Null, "null", 0)                                                         \
+  /* += or another assign-op follows. */                                     \
+  M(AssignOp, "assignop", 0)                                                 \
+  /* All notes above here are "gettable".  See SrcNote::isGettable below. */ \
+  M(ColSpan, "colspan", int8_t(SrcNote::ColSpan::Operands::Count))           \
+  /* Bytecode follows a source newline. */                                   \
+  M(NewLine, "newline", 0)                                                   \
+  M(SetLine, "setline", int8_t(SrcNote::SetLine::Operands::Count))           \
+  /* Bytecode is a recommended breakpoint. */                                \
+  M(Breakpoint, "breakpoint", 0)                                             \
+  /* Bytecode is the first in a new steppable area. */                       \
+  M(StepSep, "step-sep", 0)                                                  \
+  M(Unused7, "unused", 0)                                                    \
+  /* 8-15 (0b1xxx) are for extended delta notes. */                          \
+  M(XDelta, "xdelta", 0)
+
+// Note: need to add a new source note? If there's no Unused* note left,
+// consider bumping SrcNoteType::XDelta to 12-15 and change
+// SrcNote::XDeltaBits from 7 to 6.
+
+enum class SrcNoteType : uint8_t {
+#define DEFINE_SRC_NOTE_TYPE(sym, name, arity) sym,
+  FOR_EACH_SRC_NOTE_TYPE(DEFINE_SRC_NOTE_TYPE)
+#undef DEFINE_SRC_NOTE_TYPE
+
+      Last,
+  LastGettable = AssignOp
+};
+
+static_assert(uint8_t(SrcNoteType::XDelta) == 8, "XDelta should be 8");
+
+class SrcNote {
+  struct Spec {
+    const char* name_;
+    int8_t arity_;
+  };
+
+  static const Spec specs_[];
+
+  static constexpr unsigned TypeBits = 4;
+  static constexpr unsigned DeltaBits = 4;
+  static constexpr unsigned XDeltaBits = 7;
+
+  static constexpr uint8_t TypeMask = js::BitMask(TypeBits) << DeltaBits;
+  static constexpr ptrdiff_t DeltaMask = js::BitMask(DeltaBits);
+  static constexpr ptrdiff_t XDeltaMask = js::BitMask(XDeltaBits);
+
+  static constexpr ptrdiff_t DeltaLimit = js::Bit(DeltaBits);
+  static constexpr ptrdiff_t XDeltaLimit = js::Bit(XDeltaBits);
+
+  static constexpr inline uint8_t toShiftedTypeBits(SrcNoteType type) {
+    return (uint8_t(type) << DeltaBits);
+  }
+
+  static inline uint8_t noteValue(SrcNoteType type, ptrdiff_t delta) {
+    MOZ_ASSERT((delta & DeltaMask) == delta);
+    return noteValueUnchecked(type, delta);
+  }
+
+  static constexpr inline uint8_t noteValueUnchecked(SrcNoteType type,
+                                                     ptrdiff_t delta) {
+    return toShiftedTypeBits(type) | (delta & DeltaMask);
+  }
+
+  static inline uint8_t xDeltaValue(ptrdiff_t delta) {
+    return toShiftedTypeBits(SrcNoteType::XDelta) | (delta & XDeltaMask);
+  }
+
+  uint8_t value_;
+
+  constexpr explicit SrcNote(uint8_t value) : value_(value) {}
+
+ public:
+  constexpr SrcNote() : value_(noteValueUnchecked(SrcNoteType::Null, 0)){};
+
+  SrcNote(const SrcNote& other) = default;
+  SrcNote& operator=(const SrcNote& other) = default;
+
+  SrcNote(SrcNote&& other) = default;
+  SrcNote& operator=(SrcNote&& other) = default;
+
+  static constexpr SrcNote terminator() { return SrcNote(); }
+
+ private:
+  inline uint8_t typeBits() const { return (value_ >> DeltaBits); }
+
+  inline bool isXDelta() const {
+    return typeBits() >= uint8_t(SrcNoteType::XDelta);
+  }
+
+  inline bool isFourBytesOperand() const {
+    return value_ & FourBytesOperandFlag;
+  }
+
+  // number of operands
+  inline unsigned arity() const {
+    MOZ_ASSERT(uint8_t(type()) < uint8_t(SrcNoteType::Last));
+    return specs_[uint8_t(type())].arity_;
+  }
+
+ public:
+  inline SrcNoteType type() const {
+    if (isXDelta()) {
+      return SrcNoteType::XDelta;
+    }
+    return SrcNoteType(typeBits());
+  }
+
+  // name for disassembly/debugging output
+  const char* name() const {
+    MOZ_ASSERT(uint8_t(type()) < uint8_t(SrcNoteType::Last));
+    return specs_[uint8_t(type())].name_;
+  }
+
+  inline bool isGettable() const {
+    return uint8_t(type()) <= uint8_t(SrcNoteType::LastGettable);
+  }
+
+  inline bool isTerminator() const {
+    return value_ == uint8_t(SrcNoteType::Null);
+  }
+
+  inline ptrdiff_t delta() const {
+    if (isXDelta()) {
+      return value_ & XDeltaMask;
+    }
+    return value_ & DeltaMask;
+  }
+
+ private:
+  /*
+   * Operand fields follow certain notes and are frequency-encoded: an operand
+   * in [0,0x7f] consumes one byte, an operand in [0x80,0x7fffffff] takes four,
+   * and the high bit of the first byte is set.
+   */
+  static constexpr unsigned FourBytesOperandFlag = 0x80;
+  static constexpr unsigned FourBytesOperandMask = 0x7f;
+
+  static constexpr unsigned OperandBits = 31;
+
+ public:
+  static constexpr size_t MaxOperand = (size_t(1) << OperandBits) - 1;
+
+  static inline bool isRepresentableOperand(ptrdiff_t operand) {
+    return 0 <= operand && size_t(operand) <= MaxOperand;
+  }
+
+  class ColSpan {
+   public:
+    enum class Operands {
+      // The column span (the diff between the column corresponds to the
+      // current op and last known column).
+      Span,
+      Count
+    };
+
+   private:
+    /*
+     * SrcNoteType::ColSpan values represent changes to the column number.
+     * Colspans are signed: negative changes arise in describing constructs like
+     * for(;;) loops, that generate code in non-source order. (Negative colspans
+     * also have a history of indicating bugs in updating ParseNodes' source
+     * locations.)
+     *
+     * We store colspans in operands. However, unlike normal operands, colspans
+     * are signed, so we truncate colspans (toOperand) for storage as
+     * operands, and sign-extend operands into colspans when we read them
+     * (fromOperand).
+     */
+    static constexpr ptrdiff_t ColSpanSignBit = 1 << (OperandBits - 1);
+
+    static inline ptrdiff_t fromOperand(ptrdiff_t operand) {
+      // There should be no bits set outside the field we're going to
+      // sign-extend.
+      MOZ_ASSERT(!(operand & ~((1U << OperandBits) - 1)));
+
+      // Sign-extend the least significant OperandBits bits.
+      return (operand ^ ColSpanSignBit) - ColSpanSignBit;
+    }
+
+   public:
+    static constexpr ptrdiff_t MinColSpan = -ColSpanSignBit;
+    static constexpr ptrdiff_t MaxColSpan = ColSpanSignBit - 1;
+
+    static inline ptrdiff_t toOperand(ptrdiff_t colspan) {
+      // Truncate the two's complement colspan, for storage as an operand.
+      ptrdiff_t operand = colspan & ((1U << OperandBits) - 1);
+
+      // When we read this back, we'd better get the value we stored.
+      MOZ_ASSERT(fromOperand(operand) == colspan);
+      return operand;
+    }
+
+    static inline ptrdiff_t getSpan(const SrcNote* sn);
+  };
+
+  class SetLine {
+   public:
+    enum class Operands {
+      // The file-absolute source line number of the current op.
+      Line,
+      Count
+    };
+
+   private:
+    static inline size_t fromOperand(ptrdiff_t operand) {
+      return size_t(operand);
+    }
+
+   public:
+    static inline unsigned lengthFor(unsigned line, size_t initialLine) {
+      unsigned operandSize = toOperand(line, initialLine) >
+                                     ptrdiff_t(SrcNote::FourBytesOperandMask)
+                                 ? 4
+                                 : 1;
+      return 1 /* SetLine */ + operandSize;
+    }
+
+    static inline ptrdiff_t toOperand(size_t line, size_t initialLine) {
+      MOZ_ASSERT(line >= initialLine);
+      return ptrdiff_t(line - initialLine);
+    }
+
+    static inline size_t getLine(const SrcNote* sn, size_t initialLine);
+  };
+
+  friend class SrcNoteWriter;
+  friend class SrcNoteReader;
+  friend class SrcNoteIterator;
+};
+
+class SrcNoteWriter {
+ public:
+  // Write a source note with given `type`, and `delta` from the last source
+  // note. This writes the source note itself, and `XDelta`s if necessary.
+  //
+  // This doesn't write or allocate space for operands.
+  // If the source note is not nullary, the caller is responsible for calling
+  // `writeOperand` immediately after this.
+  //
+  // `allocator` is called with the number of bytes required to store the notes.
+  // `allocator` can be called multiple times for each source note.
+  // The last call corresponds to the source note for `type`.
+  template <typename T>
+  static bool writeNote(SrcNoteType type, ptrdiff_t delta, T allocator) {
+    while (delta >= SrcNote::DeltaLimit) {
+      ptrdiff_t xdelta = std::min(delta, SrcNote::XDeltaMask);
+      SrcNote* sn = allocator(1);
+      if (!sn) {
+        return false;
+      }
+      sn->value_ = SrcNote::xDeltaValue(xdelta);
+      delta -= xdelta;
+    }
+
+    SrcNote* sn = allocator(1);
+    if (!sn) {
+      return false;
+    }
+    sn->value_ = SrcNote::noteValue(type, delta);
+    return true;
+  }
+
+  // Write source note operand.
+  //
+  // `allocator` is called with the number of bytes required to store the
+  // operand.  `allocator` is called only once.
+  template <typename T>
+  static bool writeOperand(ptrdiff_t operand, T allocator) {
+    if (operand > ptrdiff_t(SrcNote::FourBytesOperandMask)) {
+      SrcNote* sn = allocator(4);
+      if (!sn) {
+        return false;
+      }
+
+      sn[0].value_ = (SrcNote::FourBytesOperandFlag | (operand >> 24));
+      sn[1].value_ = operand >> 16;
+      sn[2].value_ = operand >> 8;
+      sn[3].value_ = operand;
+    } else {
+      SrcNote* sn = allocator(1);
+      if (!sn) {
+        return false;
+      }
+
+      sn[0].value_ = operand;
+    }
+
+    return true;
+  }
+};
+
+class SrcNoteReader {
+  template <typename T>
+  static T getOperandHead(T sn, unsigned which) {
+    MOZ_ASSERT(sn->type() != SrcNoteType::XDelta);
+    MOZ_ASSERT(uint8_t(which) < sn->arity());
+
+    T curr = sn + 1;
+    for (; which; which--) {
+      if (curr->isFourBytesOperand()) {
+        curr += 4;
+      } else {
+        curr++;
+      }
+    }
+    return curr;
+  }
+
+ public:
+  // Return the operand of source note `sn`, specified by `which`.
+  static ptrdiff_t getOperand(const SrcNote* sn, unsigned which) {
+    const SrcNote* head = getOperandHead(sn, which);
+
+    if (head->isFourBytesOperand()) {
+      return ptrdiff_t(
+          (uint32_t(head[0].value_ & SrcNote::FourBytesOperandMask) << 24) |
+          (uint32_t(head[1].value_) << 16) | (uint32_t(head[2].value_) << 8) |
+          uint32_t(head[3].value_));
+    }
+
+    return ptrdiff_t(head[0].value_);
+  }
+};
+
+/* static */
+inline ptrdiff_t SrcNote::ColSpan::getSpan(const SrcNote* sn) {
+  return fromOperand(SrcNoteReader::getOperand(sn, unsigned(Operands::Span)));
+}
+
+/* static */
+inline size_t SrcNote::SetLine::getLine(const SrcNote* sn, size_t initialLine) {
+  return initialLine +
+         fromOperand(SrcNoteReader::getOperand(sn, unsigned(Operands::Line)));
+}
+
+// Iterate over SrcNote array, until it hits terminator.
+//
+// Usage:
+//   for (SrcNoteIterator iter(notes); !iter.atEnd(); ++iter) {
+//     auto sn = *iter; // `sn` is `const SrcNote*` typed.
+//     ...
+//   }
+class SrcNoteIterator {
+  const SrcNote* current_;
+
+  void next() {
+    unsigned arity = current_->arity();
+    current_++;
+
+    for (; arity; arity--) {
+      if (current_->isFourBytesOperand()) {
+        current_ += 4;
+      } else {
+        current_++;
+      }
+    }
+  }
+
+ public:
+  SrcNoteIterator() = delete;
+
+  SrcNoteIterator(const SrcNoteIterator& other) = delete;
+  SrcNoteIterator& operator=(const SrcNoteIterator& other) = delete;
+
+  SrcNoteIterator(SrcNoteIterator&& other) = default;
+  SrcNoteIterator& operator=(SrcNoteIterator&& other) = default;
+
+  explicit SrcNoteIterator(const SrcNote* sn) : current_(sn) {}
+
+  bool atEnd() const { return current_->isTerminator(); }
+
+  const SrcNote* operator*() const { return current_; }
+
+  // Pre-increment
+  SrcNoteIterator& operator++() {
+    next();
+    return *this;
+  }
+
+  // Post-increment
+  SrcNoteIterator operator++(int) = delete;
+};
+
+}  // namespace js
+
+#endif /* frontend_SourceNotes_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/StencilEnums.h b/third_party/rust/jsparagus-stencil/src/copy/StencilEnums.h
new file mode 100644
index 0000000000..e752df815f
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/StencilEnums.h
@@ -0,0 +1,340 @@
+/* -*- 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/. */
+
+#ifndef vm_StencilEnums_h
+#define vm_StencilEnums_h
+
+#include <stdint.h>  // uint8_t
+
+//
+// Enum definitions shared between frontend, stencil, and the VM.
+//
+
+namespace js {
+
+// [SMDOC] Try Notes
+//
+// Trynotes are attached to regions that are involved with
+// exception unwinding. They can be broken up into four categories:
+//
+// 1. Catch and Finally: Basic exception handling. A Catch trynote
+//    covers the range of the associated try. A Finally trynote covers
+//    the try and the catch.
+//
+// 2. ForIn and Destructuring: These operations create an iterator
+//    which must be cleaned up (by calling IteratorClose) during
+//    exception unwinding.
+//
+// 3. ForOf and ForOfIterclose: For-of loops handle unwinding using
+//    catch blocks. These trynotes are used for for-of breaks/returns,
+//    which create regions that are lexically within a for-of block,
+//    but logically outside of it. See TryNoteIter::settle for more
+//    details.
+//
+// 4. Loop: This represents normal for/while/do-while loops. It is
+//    unnecessary for exception unwinding, but storing the boundaries
+//    of loops here is helpful for heuristics that need to know
+//    whether a given op is inside a loop.
+enum class TryNoteKind : uint8_t {
+  Catch,
+  Finally,
+  ForIn,
+  Destructuring,
+  ForOf,
+  ForOfIterClose,
+  Loop
+};
+
+// [SMDOC] Script Flags
+//
+// Interpreted scripts represented by the BaseScript type use two flag words to
+// encode an assortment of conditions and attributes about the script.
+//
+// The "immutable" flags are a combination of input flags describing aspects of
+// the execution context that affect parsing (such as if we are an ES module or
+// normal script), and flags derived from source text. These flags are preserved
+// during cloning and serializing. As well, they should never change after the
+// BaseScript is created (although there are currently a few exceptions for
+// de-/re-lazification that remain).
+//
+// The "mutable" flags are temporary flags that are used by subsystems in the
+// engine such as the debugger or JITs. These flags are not preserved through
+// serialization or cloning since the attributes are generally associated with
+// one specific instance of a BaseScript.
+
+enum class ImmutableScriptFlagsEnum : uint32_t {
+  // Input Flags
+  //
+  // These flags are from CompileOptions or the Parser entry point. They
+  // generally cannot be derived from the source text alone.
+  // ----
+
+  // A script may have one of the following kinds: Global, Eval, Module,
+  // Function. At most one flag can be set, with a default of Global.
+  IsForEval = 1 << 0,
+  IsModule = 1 << 1,
+  IsFunction = 1 << 2,
+
+  // The script is compiled as engine-internal self-hosted JavaScript. This mode
+  // is used to implement certain library functions and has special parse,
+  // bytecode, and runtime behaviour that differs from normal script.
+  SelfHosted = 1 << 3,
+
+  // The script was compiled with the default mode set to strict mode. Note that
+  // this tracks the default value, while the actual mode used (after processing
+  // source and its directives) is the `Strict` flag below.
+  ForceStrict = 1 << 4,
+
+  // The script has a non-syntactic scope on its environment chain. That is,
+  // there may be objects about which we know nothing between the outermost
+  // syntactic scope and the global.
+  HasNonSyntacticScope = 1 << 5,
+
+  // The script return value will not be used and simplified code will be
+  // generated. This can only be applied to top-level scripts. The value this
+  // script returns will be UndefinedValue instead of what the spec normally
+  // prescribes.
+  NoScriptRval = 1 << 6,
+
+  // TreatAsRunOnce roughly indicates that a script is expected to be run no
+  // more than once. This affects optimizations and heuristics.
+  //
+  // On top-level global/eval/module scripts, this is set when the embedding
+  // ensures this script will not be re-used. In this case, parser literals may
+  // be exposed directly instead of being cloned.
+  TreatAsRunOnce = 1 << 7,
+  // ----
+
+  // Parser Flags
+  //
+  // Flags computed by the Parser from the source text and input flags.
+  // ----
+
+  // Generated code will execute in strict mode. This is due to either the
+  // ForceStrict flag being specified above, or due to source text itself (such
+  // as "use strict" directives).
+  Strict = 1 << 8,
+
+  // Script is parsed with a top-level goal of Module. This may be a top-level
+  // or an inner-function script.
+  HasModuleGoal = 1 << 9,
+
+  // Script contains inner functions.
+  //
+  // Note: This prevents relazification since inner function close-over the
+  // current scripts scopes.
+  HasInnerFunctions = 1 << 10,
+
+  // There is a direct eval statement in this script OR in any of its inner
+  // functions.
+  //
+  // Note: This prevents relazification since it can introduce inner functions.
+  HasDirectEval = 1 << 11,
+
+  // The (static) bindings of this script must support dynamic name access for
+  // read/write. The environment chain is used to do these dynamic lookups and
+  // optimizations to avoid allocating environments are suppressed.
+  //
+  // This includes direct-eval, `with`, and `delete` in this script OR in any of
+  // its inner functions.
+  //
+  // Note: Access through the arguments object is not considered dynamic binding
+  // access since it does not go through the normal name lookup mechanism.
+  BindingsAccessedDynamically = 1 << 12,
+
+  // A tagged template exists in the body (which will use JSOp::CallSiteObj in
+  // bytecode).
+  //
+  // Note: This prevents relazification since the template's object is
+  // observable to the user and cannot be recreated.
+  HasCallSiteObj = 1 << 13,
+
+  // Parser Flags for Functions
+  // ----
+
+  // This function's initial prototype is one of Function, GeneratorFunction,
+  // AsyncFunction, or AsyncGeneratorFunction as indicated by these flags.
+  //
+  // If either of these flags is set, the script may suspend and resume as it
+  // executes. Stack frames for this script also have a generator object.
+  IsAsync = 1 << 14,
+  IsGenerator = 1 << 15,
+
+  // This function's body serves as the `var` environment for a non-strict
+  // direct eval. This matters because it's the only way bindings can be
+  // dynamically added to a local environment, possibly shadowing other
+  // variables.
+  FunHasExtensibleScope = 1 << 16,
+
+  // This function has an internal .this binding and we need to emit
+  // JSOp::FunctionThis in the prologue to initialize it. This binding may be
+  // used directly for "this", or indirectly (such as class constructors).
+  FunctionHasThisBinding = 1 << 17,
+
+  // This function is a class method that must uses an internal [[HomeObject]]
+  // slot. This slot is initialized when the class definition is executed in the
+  // enclosing function.
+  NeedsHomeObject = 1 << 18,
+
+  // This function is a constructor for a derived class. This is a class that
+  // uses the `extends` syntax.
+  IsDerivedClassConstructor = 1 << 19,
+
+  // This function is synthesized by the Parser. This is used for field
+  // initializer lambdas and missing constructors for classes. These functions
+  // have unusual source coordinates and may be hidden from things like
+  // Reflect.parse.
+  IsSyntheticFunction = 1 << 20,
+
+  // This function is a class constructor that has MemberInitializer data
+  // associated with it.
+  UseMemberInitializers = 1 << 21,
+
+  // This function has a rest (`...`) parameter.
+  HasRest = 1 << 22,
+
+  // This function needs a call object or named lambda environment to be created
+  // in order to execute the function. This is done in the Stack or JIT frame
+  // setup code _before_ the bytecode prologue starts.
+  NeedsFunctionEnvironmentObjects = 1 << 23,
+
+  // An extra VarScope is used as the body scope instead of the normal
+  // FunctionScope. This is needed when parameter expressions are used AND the
+  // function has var bindings or a sloppy-direct-eval. For example,
+  //    `function(x = eval("")) { var y; }`
+  FunctionHasExtraBodyVarScope = 1 << 24,
+
+  // This function must define the implicit `arguments` binding on the function
+  // scope. If there are no free uses or an appropriate explicit binding exists,
+  // then this flag is unset.
+  //
+  // Note: Parameter expressions will not see an explicit `var arguments;`
+  // binding in the body and an implicit binding on the function-scope must
+  // still be used in that case.
+  ShouldDeclareArguments = 1 << 25,
+
+  // This function has a local (implicit or explicit) `arguments` binding. This
+  // binding is initialized by the JSOp::Arguments bytecode.
+  //
+  // Technically, every function has a binding named `arguments`. Internally,
+  // this binding is only added when `arguments` is mentioned by the function
+  // body.
+  //
+  // Examples:
+  //   ```
+  //    // Explicit definition
+  //    function f() { var arguments; return arguments; }
+  //
+  //    // Implicit use
+  //    function f() { return arguments; }
+  //
+  //    // Implicit use in arrow function
+  //    function f() { return () => arguments; }
+  //
+  //    // Implicit use in parameter expression
+  //    function f(a = arguments) { return a; }
+  //   ```
+  NeedsArgsObj = 1 << 26,
+
+  // This function must use the "mapped" form of an arguments object. This flag
+  // is set independently of whether we actually use an `arguments` binding. The
+  // conditions are specified in the ECMAScript spec.
+  HasMappedArgsObj = 1 << 27,
+
+  // Large self-hosted methods that should be inlined anyway by the JIT for
+  // performance reasons can be marked with this flag.
+  IsInlinableLargeFunction = 1 << 28,
+
+  // This function has an internal .newTarget binding and we need to emit
+  // JSOp::NewTarget in the prologue to initialize it. This binding may be
+  // used directly for "new.target", or indirectly (e.g. in super() calls).
+  FunctionHasNewTargetBinding = 1 << 29,
+};
+
+enum class MutableScriptFlagsEnum : uint32_t {
+  // Number of times the |warmUpCount| was forcibly discarded. The counter is
+  // reset when a script is successfully jit-compiled.
+  WarmupResets_MASK = 0xFF,
+
+  // If treatAsRunOnce, whether script has executed.
+  HasRunOnce = 1 << 8,
+
+  // Script has been reused for a clone.
+  HasBeenCloned = 1 << 9,
+
+  // Script has an entry in Realm::scriptCountsMap.
+  HasScriptCounts = 1 << 10,
+
+  // Script has an entry in Realm::debugScriptMap.
+  HasDebugScript = 1 << 11,
+
+  // (1 << 12) is unused.
+  // (1 << 13) is unused.
+
+  // Script supports relazification where it releases bytecode and gcthings to
+  // save memory. This process is opt-in since various complexities may disallow
+  // this for some scripts.
+  // NOTE: Must check for isRelazifiable() before setting this flag.
+  AllowRelazify = 1 << 14,
+
+  // Set if the script has opted into spew.
+  SpewEnabled = 1 << 15,
+
+  // Set if we care about a script's final warmup count.
+  NeedsFinalWarmUpCount = 1 << 16,
+
+  //
+  // IonMonkey compilation hints.
+  //
+
+  // Whether Baseline or Ion compilation has been disabled for this script.
+  // IonDisabled is equivalent to |jitScript->canIonCompile() == false| but
+  // JitScript can be discarded on GC and we don't want this to affect
+  // observable behavior (see ArgumentsGetterImpl comment).
+  BaselineDisabled = 1 << 17,
+  IonDisabled = 1 << 18,
+
+  // This script should not be inlined into others. This happens after inlining
+  // has failed.
+  Uninlineable = 1 << 19,
+
+  // (1 << 20) is unused.
+
+  // *****************************************************************
+  // The flags below are set when we bail out and invalidate a script.
+  // When we recompile, we will be more conservative.
+  // *****************************************************************
+
+  // A hoisted bounds check bailed out.
+  FailedBoundsCheck = 1 << 21,
+
+  // An instruction hoisted by LICM bailed out.
+  HadLICMInvalidation = 1 << 22,
+
+  // An instruction hoisted by InstructionReordering bailed out.
+  HadReorderingBailout = 1 << 23,
+
+  // An instruction inserted or truncated by Range Analysis bailed out.
+  HadEagerTruncationBailout = 1 << 24,
+
+  // A lexical check bailed out.
+  FailedLexicalCheck = 1 << 25,
+
+  // A guard inserted by phi specialization bailed out.
+  HadSpeculativePhiBailout = 1 << 26,
+
+  // An unbox folded with a load bailed out.
+  HadUnboxFoldingBailout = 1 << 27,
+};
+
+// Retrievable source can be retrieved using the source hook (and therefore
+// need not be XDR'd, can be discarded if desired because it can always be
+// reconstituted later, etc.).
+enum class SourceRetrievable { No = 0, Yes };
+
+}  // namespace js
+
+#endif /* vm_StencilEnums_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/Symbol.h b/third_party/rust/jsparagus-stencil/src/copy/Symbol.h
new file mode 100644
index 0000000000..1e16552b36
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/Symbol.h
@@ -0,0 +1,110 @@
+/* -*- Mode: C++; tab-width: 8; 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/. */
+
+/* Symbols. */
+
+#ifndef js_Symbol_h
+#define js_Symbol_h
+
+#include "js/shadow/Symbol.h"  // JS::shadow::Symbol::WellKnownAPILimit
+
+#include <stddef.h>  // size_t
+#include <stdint.h>  // uintptr_t, uint32_t
+
+#include "jstypes.h"  // JS_PUBLIC_API
+
+#include "js/TypeDecls.h"
+
+namespace JS {
+
+class JS_PUBLIC_API Symbol;
+
+/**
+ * Create a new Symbol with the given description. This function never returns
+ * a Symbol that is in the Runtime-wide symbol registry.
+ *
+ * If description is null, the new Symbol's [[Description]] attribute is
+ * undefined.
+ */
+extern JS_PUBLIC_API Symbol* NewSymbol(JSContext* cx,
+                                       Handle<JSString*> description);
+
+/**
+ * Symbol.for as specified in ES6.
+ *
+ * Get a Symbol with the description 'key' from the Runtime-wide symbol
+ * registry. If there is not already a Symbol with that description in the
+ * registry, a new Symbol is created and registered. 'key' must not be null.
+ */
+extern JS_PUBLIC_API Symbol* GetSymbolFor(JSContext* cx, Handle<JSString*> key);
+
+/**
+ * Get the [[Description]] attribute of the given symbol.
+ *
+ * This function is infallible. If it returns null, that means the symbol's
+ * [[Description]] is undefined.
+ */
+extern JS_PUBLIC_API JSString* GetSymbolDescription(Handle<Symbol*> symbol);
+
+/* Well-known symbols. */
+#define JS_FOR_EACH_WELL_KNOWN_SYMBOL(MACRO) \
+  MACRO(isConcatSpreadable)                  \
+  MACRO(iterator)                            \
+  MACRO(match)                               \
+  MACRO(replace)                             \
+  MACRO(search)                              \
+  MACRO(species)                             \
+  MACRO(hasInstance)                         \
+  MACRO(split)                               \
+  MACRO(toPrimitive)                         \
+  MACRO(toStringTag)                         \
+  MACRO(unscopables)                         \
+  MACRO(asyncIterator)                       \
+  MACRO(matchAll)
+
+enum class SymbolCode : uint32_t {
+// There is one SymbolCode for each well-known symbol.
+#define JS_DEFINE_SYMBOL_ENUM(name) name,
+  JS_FOR_EACH_WELL_KNOWN_SYMBOL(
+      JS_DEFINE_SYMBOL_ENUM)  // SymbolCode::iterator, etc.
+#undef JS_DEFINE_SYMBOL_ENUM
+  Limit,
+  WellKnownAPILimit = JS::shadow::Symbol::WellKnownAPILimit,
+  PrivateNameSymbol = 0xfffffffd,  // created by the #PrivateName syntax.
+  InSymbolRegistry =
+      0xfffffffe,            // created by Symbol.for() or JS::GetSymbolFor()
+  UniqueSymbol = 0xffffffff  // created by Symbol() or JS::NewSymbol()
+};
+
+/* For use in loops that iterate over the well-known symbols. */
+const size_t WellKnownSymbolLimit = size_t(SymbolCode::Limit);
+
+/**
+ * Return the SymbolCode telling what sort of symbol `symbol` is.
+ *
+ * A symbol's SymbolCode never changes once it is created.
+ */
+extern JS_PUBLIC_API SymbolCode GetSymbolCode(Handle<Symbol*> symbol);
+
+/**
+ * Get one of the well-known symbols defined by ES6. A single set of well-known
+ * symbols is shared by all compartments in a JSRuntime.
+ *
+ * `which` must be in the range [0, WellKnownSymbolLimit).
+ */
+extern JS_PUBLIC_API Symbol* GetWellKnownSymbol(JSContext* cx,
+                                                SymbolCode which);
+
+/**
+ * Return true if the given JSPropertySpec::name or JSFunctionSpec::name value
+ * is actually a symbol code and not a string. See JS_SYM_FN.
+ */
+inline bool PropertySpecNameIsSymbol(uintptr_t name) {
+  return name != 0 && name - 1 < WellKnownSymbolLimit;
+}
+
+}  // namespace JS
+
+#endif /* js_Symbol_h */
diff --git a/third_party/rust/jsparagus-stencil/src/copy/ThrowMsgKind.h b/third_party/rust/jsparagus-stencil/src/copy/ThrowMsgKind.h
new file mode 100644
index 0000000000..2631ed011a
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/copy/ThrowMsgKind.h
@@ -0,0 +1,37 @@
+/* -*- 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/. */
+
+#ifndef vm_ThrowMsgKind_h
+#define vm_ThrowMsgKind_h
+
+#include <stdint.h>  // uint8_t
+
+#include "js/friend/ErrorMessages.h"  // JSErrNum
+
+namespace js {
+
+enum class ThrowMsgKind : uint8_t {
+  AssignToCall,
+  IteratorNoThrow,
+  CantDeleteSuper,
+  // Private Fields:
+  PrivateDoubleInit,
+  PrivateBrandDoubleInit,
+  MissingPrivateOnGet,
+  MissingPrivateOnSet,
+  AssignToPrivateMethod,
+  // Decorators:
+  DecoratorInvalidReturnType,
+};
+
+JSErrNum ThrowMsgKindToErrNum(ThrowMsgKind kind);
+
+// Used for CheckPrivateField
+enum class ThrowCondition : uint8_t { ThrowHas, ThrowHasNot, OnlyCheckRhs };
+
+}  // namespace js
+
+#endif /* vm_ThrowMsgKind_h */
diff --git a/third_party/rust/jsparagus-stencil/src/env_coord.rs b/third_party/rust/jsparagus-stencil/src/env_coord.rs
new file mode 100644
index 0000000000..257afbeb39
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/env_coord.rs
@@ -0,0 +1,50 @@
+//! (EnvironmentSlot,EnvironmentHops) pair represent the reference to a slot in
+//! an environment object in the environment chain.
+//!
+//! See the SMDOC comment in m-c/js/src/vm/EnvironmentObject.h for the details
+//! about environment object and environment chain.
+
+/// Slot in the environmentslot object.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Ord, PartialOrd)]
+pub struct EnvironmentSlot {
+    slot: u32,
+}
+
+impl EnvironmentSlot {
+    pub fn new(slot: u32) -> Self {
+        Self { slot }
+    }
+
+    pub fn next(&mut self) {
+        self.slot += 1;
+    }
+}
+
+impl From<EnvironmentSlot> for u32 {
+    fn from(slot: EnvironmentSlot) -> u32 {
+        slot.slot
+    }
+}
+
+/// The number of environment objects to skip (hop) on the environment chain in
+/// order to find the associated environment object.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Ord, PartialOrd)]
+pub struct EnvironmentHops {
+    hops: u8,
+}
+
+impl EnvironmentHops {
+    pub fn new(hops: u8) -> Self {
+        Self { hops }
+    }
+
+    pub fn next(&mut self) {
+        self.hops += 1;
+    }
+}
+
+impl From<EnvironmentHops> for u8 {
+    fn from(hops: EnvironmentHops) -> u8 {
+        hops.hops
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/frame_slot.rs b/third_party/rust/jsparagus-stencil/src/frame_slot.rs
new file mode 100644
index 0000000000..84ae4e4c02
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/frame_slot.rs
@@ -0,0 +1,21 @@
+/// Slot in the stack frame.
+#[derive(Clone, Copy, Debug, PartialEq, Eq, Ord, PartialOrd)]
+pub struct FrameSlot {
+    slot: u32,
+}
+
+impl FrameSlot {
+    pub fn new(slot: u32) -> Self {
+        Self { slot }
+    }
+
+    pub fn next(&mut self) {
+        self.slot += 1;
+    }
+}
+
+impl From<FrameSlot> for u32 {
+    fn from(slot: FrameSlot) -> u32 {
+        slot.slot
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/function.rs b/third_party/rust/jsparagus-stencil/src/function.rs
new file mode 100644
index 0000000000..212491e610
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/function.rs
@@ -0,0 +1,222 @@
+#[derive(Debug)]
+pub struct FunctionFlags {
+    flags: u16,
+}
+
+// WARNING
+// The following section is generated by update_stencil.py.
+// Do mot modify manually.
+//
+// @@@@ BEGIN TYPES @@@@
+#[derive(Debug, Clone, Copy)]
+pub enum FunctionKind {
+    NormalFunction = 0,
+    Arrow = 1,
+    Method = 2,
+    ClassConstructor = 3,
+    Getter = 4,
+    Setter = 5,
+    AsmJS = 6,
+    Wasm = 7,
+    FunctionKindLimit = 8,
+}
+
+#[allow(dead_code)]
+const FUNCTION_KIND_SHIFT: u16 = 0;
+#[allow(dead_code)]
+const FUNCTION_KIND_MASK: u16 = 0x0007;
+#[allow(dead_code)]
+const EXTENDED: u16 = 1 << 3;
+#[allow(dead_code)]
+const SELF_HOSTED: u16 = 1 << 4;
+#[allow(dead_code)]
+const BASESCRIPT: u16 = 1 << 5;
+#[allow(dead_code)]
+const SELFHOSTLAZY: u16 = 1 << 6;
+#[allow(dead_code)]
+const CONSTRUCTOR: u16 = 1 << 7;
+#[allow(dead_code)]
+const LAMBDA: u16 = 1 << 9;
+#[allow(dead_code)]
+const WASM_JIT_ENTRY: u16 = 1 << 10;
+#[allow(dead_code)]
+const HAS_INFERRED_NAME: u16 = 1 << 11;
+#[allow(dead_code)]
+const HAS_GUESSED_ATOM: u16 = 1 << 12;
+#[allow(dead_code)]
+const RESOLVED_NAME: u16 = 1 << 13;
+#[allow(dead_code)]
+const RESOLVED_LENGTH: u16 = 1 << 14;
+#[allow(dead_code)]
+const GHOST_FUNCTION: u16 = 1 << 15;
+#[allow(dead_code)]
+const NORMAL_KIND: u16 = (FunctionKind::NormalFunction as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const ASMJS_KIND: u16 = (FunctionKind::AsmJS as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const WASM_KIND: u16 = (FunctionKind::Wasm as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const ARROW_KIND: u16 = (FunctionKind::Arrow as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const METHOD_KIND: u16 = (FunctionKind::Method as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const CLASSCONSTRUCTOR_KIND: u16 = (FunctionKind::ClassConstructor as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const GETTER_KIND: u16 = (FunctionKind::Getter as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const SETTER_KIND: u16 = (FunctionKind::Setter as u16) << FUNCTION_KIND_SHIFT;
+#[allow(dead_code)]
+const NATIVE_FUN: u16 = NORMAL_KIND;
+#[allow(dead_code)]
+const NATIVE_CTOR: u16 = CONSTRUCTOR | NORMAL_KIND;
+#[allow(dead_code)]
+const ASMJS_CTOR: u16 = CONSTRUCTOR | ASMJS_KIND;
+#[allow(dead_code)]
+const ASMJS_LAMBDA_CTOR: u16 = CONSTRUCTOR | LAMBDA | ASMJS_KIND;
+#[allow(dead_code)]
+const WASM: u16 = WASM_KIND;
+#[allow(dead_code)]
+const INTERPRETED_NORMAL: u16 = BASESCRIPT | CONSTRUCTOR | NORMAL_KIND;
+#[allow(dead_code)]
+const INTERPRETED_CLASS_CTOR: u16 = BASESCRIPT | CONSTRUCTOR | CLASSCONSTRUCTOR_KIND;
+#[allow(dead_code)]
+const INTERPRETED_GENERATOR_OR_ASYNC: u16 = BASESCRIPT | NORMAL_KIND;
+#[allow(dead_code)]
+const INTERPRETED_LAMBDA: u16 = BASESCRIPT | LAMBDA | CONSTRUCTOR | NORMAL_KIND;
+#[allow(dead_code)]
+const INTERPRETED_LAMBDA_ARROW: u16 = BASESCRIPT | LAMBDA | ARROW_KIND;
+#[allow(dead_code)]
+const INTERPRETED_LAMBDA_GENERATOR_OR_ASYNC: u16 = BASESCRIPT | LAMBDA | NORMAL_KIND;
+#[allow(dead_code)]
+const INTERPRETED_GETTER: u16 = BASESCRIPT | GETTER_KIND;
+#[allow(dead_code)]
+const INTERPRETED_SETTER: u16 = BASESCRIPT | SETTER_KIND;
+#[allow(dead_code)]
+const INTERPRETED_METHOD: u16 = BASESCRIPT | METHOD_KIND;
+#[allow(dead_code)]
+const MUTABLE_FLAGS: u16 = RESOLVED_NAME | RESOLVED_LENGTH;
+#[allow(dead_code)]
+const STABLE_ACROSS_CLONES: u16 =
+    CONSTRUCTOR | LAMBDA | SELF_HOSTED | FUNCTION_KIND_MASK | GHOST_FUNCTION;
+// @@@@ END TYPES @@@@
+
+#[derive(Debug)]
+pub struct FunctionSyntaxKind {
+    kind: FunctionKind,
+    is_lambda: bool,
+    is_generator: bool,
+    is_async: bool,
+}
+
+impl FunctionSyntaxKind {
+    pub fn function_declaration(is_generator: bool, is_async: bool) -> Self {
+        Self {
+            kind: FunctionKind::NormalFunction,
+            is_lambda: false,
+            is_generator,
+            is_async,
+        }
+    }
+
+    pub fn function_expression(is_generator: bool, is_async: bool) -> Self {
+        Self {
+            kind: FunctionKind::NormalFunction,
+            is_lambda: true,
+            is_generator,
+            is_async,
+        }
+    }
+
+    pub fn method(is_generator: bool, is_async: bool) -> Self {
+        Self {
+            kind: FunctionKind::Method,
+            is_lambda: false,
+            is_generator,
+            is_async,
+        }
+    }
+
+    pub fn getter() -> Self {
+        FunctionSyntaxKind {
+            kind: FunctionKind::Getter,
+            is_lambda: false,
+            is_generator: false,
+            is_async: false,
+        }
+    }
+
+    pub fn setter() -> Self {
+        FunctionSyntaxKind {
+            kind: FunctionKind::Setter,
+            is_lambda: false,
+            is_generator: false,
+            is_async: false,
+        }
+    }
+
+    pub fn arrow(is_async: bool) -> Self {
+        Self {
+            kind: FunctionKind::Arrow,
+            is_lambda: true,
+            is_generator: false,
+            is_async,
+        }
+    }
+
+    pub fn is_generator(&self) -> bool {
+        self.is_generator
+    }
+
+    pub fn is_async(&self) -> bool {
+        self.is_async
+    }
+}
+
+impl FunctionFlags {
+    fn new(flags: u16) -> Self {
+        debug_assert!(
+            (((FunctionKind::FunctionKindLimit as u16) - 1) << FUNCTION_KIND_SHIFT)
+                <= FUNCTION_KIND_MASK
+        );
+
+        Self { flags }
+    }
+
+    /// Returns empty flag that is used for top level script
+    pub fn empty() -> Self {
+        Self { flags: 0 }
+    }
+
+    pub fn interpreted(syntax_kind: FunctionSyntaxKind) -> Self {
+        let kind_flag = (syntax_kind.kind as u16) << FUNCTION_KIND_SHIFT;
+        let mut flags = BASESCRIPT | kind_flag;
+        match syntax_kind.kind {
+            FunctionKind::NormalFunction => {
+                if !syntax_kind.is_generator && !syntax_kind.is_async {
+                    flags |= CONSTRUCTOR;
+                }
+                if syntax_kind.is_lambda {
+                    flags |= LAMBDA;
+                }
+            }
+            FunctionKind::ClassConstructor => {
+                debug_assert!(!syntax_kind.is_generator);
+                debug_assert!(!syntax_kind.is_async);
+                flags |= CONSTRUCTOR;
+            }
+            _ => {}
+        }
+        Self::new(flags)
+    }
+
+    pub fn is_arrow(&self) -> bool {
+        let kind_num = (self.flags >> FUNCTION_KIND_SHIFT) & FUNCTION_KIND_MASK;
+        kind_num == FunctionKind::Arrow as u16
+    }
+}
+
+impl From<FunctionFlags> for u16 {
+    fn from(flags: FunctionFlags) -> u16 {
+        flags.flags
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/gcthings.rs b/third_party/rust/jsparagus-stencil/src/gcthings.rs
new file mode 100644
index 0000000000..bbe18fd20f
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/gcthings.rs
@@ -0,0 +1,77 @@
+use crate::regexp::RegExpIndex;
+use crate::scope::ScopeIndex;
+use crate::script::ScriptStencilIndex;
+use ast::source_atom_set::SourceAtomSetIndex;
+
+/// Corresponds to js::frontend::GCThingList::ListType
+/// in m-c/js/src/frontend/BytecodeSection.h.
+#[derive(Debug)]
+pub enum GCThing {
+    Null,
+    Atom(SourceAtomSetIndex),
+    Function(ScriptStencilIndex),
+    RegExp(RegExpIndex),
+    Scope(ScopeIndex),
+}
+
+/// Index into GCThingList.things.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct GCThingIndex {
+    index: usize,
+}
+
+impl GCThingIndex {
+    fn new(index: usize) -> Self {
+        Self { index }
+    }
+}
+
+impl From<GCThingIndex> for usize {
+    fn from(index: GCThingIndex) -> usize {
+        index.index
+    }
+}
+
+/// List of GC things.
+///
+/// Maps to JSScript::gcthings() in js/src/vm/JSScript.h.
+#[derive(Debug)]
+pub struct GCThingList {
+    things: Vec<GCThing>,
+}
+
+impl GCThingList {
+    pub fn new() -> Self {
+        Self { things: Vec::new() }
+    }
+
+    pub fn push_atom(&mut self, atom_index: SourceAtomSetIndex) -> GCThingIndex {
+        let index = self.things.len();
+        self.things.push(GCThing::Atom(atom_index));
+        GCThingIndex::new(index)
+    }
+
+    pub fn push_function(&mut self, fun_index: ScriptStencilIndex) -> GCThingIndex {
+        let index = self.things.len();
+        self.things.push(GCThing::Function(fun_index));
+        GCThingIndex::new(index)
+    }
+
+    pub fn push_regexp(&mut self, regexp_index: RegExpIndex) -> GCThingIndex {
+        let index = self.things.len();
+        self.things.push(GCThing::RegExp(regexp_index));
+        GCThingIndex::new(index)
+    }
+
+    pub fn push_scope(&mut self, scope_index: ScopeIndex) -> GCThingIndex {
+        let index = self.things.len();
+        self.things.push(GCThing::Scope(scope_index));
+        GCThingIndex::new(index)
+    }
+}
+
+impl From<GCThingList> for Vec<GCThing> {
+    fn from(list: GCThingList) -> Vec<GCThing> {
+        list.things
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/lib.rs b/third_party/rust/jsparagus-stencil/src/lib.rs
new file mode 100644
index 0000000000..e20a4305f6
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/lib.rs
@@ -0,0 +1,14 @@
+pub mod bytecode_offset;
+pub mod env_coord;
+pub mod frame_slot;
+pub mod function;
+pub mod gcthings;
+pub mod opcode;
+pub mod opcode_info;
+pub mod regexp;
+pub mod result;
+pub mod scope;
+pub mod scope_notes;
+pub mod script;
+
+extern crate jsparagus_ast as ast;
diff --git a/third_party/rust/jsparagus-stencil/src/opcode.rs b/third_party/rust/jsparagus-stencil/src/opcode.rs
new file mode 100644
index 0000000000..9331f9f5b8
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/opcode.rs
@@ -0,0 +1,586 @@
+use std::convert::TryFrom;
+
+macro_rules! using_opcode_database {
+    ( $macro:ident ! ( ) ) => {
+        $macro! {
+            [
+                // WARNING
+                // The following section is generated by update_stencil.py.
+                // Do mot modify manually.
+                //
+                // @@@@ BEGIN OPCODES @@@@
+                (Undefined, undefined, "", 1, 0, 1, JOF_BYTE),
+                (Null, null, "null", 1, 0, 1, JOF_BYTE),
+                (False, false_, "false", 1, 0, 1, JOF_BYTE),
+                (True, true_, "true", 1, 0, 1, JOF_BYTE),
+                (Int32, int32, NULL, 5, 0, 1, JOF_INT32),
+                (Zero, zero, "0", 1, 0, 1, JOF_BYTE),
+                (One, one, "1", 1, 0, 1, JOF_BYTE),
+                (Int8, int8, NULL, 2, 0, 1, JOF_INT8),
+                (Uint16, uint16, NULL, 3, 0, 1, JOF_UINT16),
+                (Uint24, uint24, NULL, 4, 0, 1, JOF_UINT24),
+                (Double, double_, NULL, 9, 0, 1, JOF_DOUBLE),
+                (BigInt, big_int, NULL, 5, 0, 1, JOF_BIGINT),
+                (String, string, NULL, 5, 0, 1, JOF_STRING),
+                (Symbol, symbol, NULL, 2, 0, 1, JOF_UINT8),
+                (Void, void_, NULL, 1, 1, 1, JOF_BYTE),
+                (Typeof, typeof_, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (TypeofExpr, typeof_expr, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (Pos, pos, "+ ", 1, 1, 1, JOF_BYTE|JOF_IC),
+                (Neg, neg, "- ", 1, 1, 1, JOF_BYTE|JOF_IC),
+                (BitNot, bit_not, "~", 1, 1, 1, JOF_BYTE|JOF_IC),
+                (Not, not_, "!", 1, 1, 1, JOF_BYTE|JOF_IC),
+                (BitOr, bit_or, "|",  1, 2, 1, JOF_BYTE|JOF_IC),
+                (BitXor, bit_xor, "^", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (BitAnd, bit_and, "&", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Eq, eq, "==", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Ne, ne, "!=", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (StrictEq, strict_eq, "===", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (StrictNe, strict_ne, "!==", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Lt, lt, "<",  1, 2, 1, JOF_BYTE|JOF_IC),
+                (Gt, gt, ">",  1, 2, 1, JOF_BYTE|JOF_IC),
+                (Le, le, "<=", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Ge, ge, ">=", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Instanceof, instanceof, "instanceof", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (In, in_, "in", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Lsh, lsh, "<<", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Rsh, rsh, ">>", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Ursh, ursh, ">>>", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Add, add, "+", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Sub, sub, "-", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Inc, inc, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (Dec, dec, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (Mul, mul, "*", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Div, div, "/", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Mod, mod, "%", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (Pow, pow, "**", 1, 2, 1, JOF_BYTE|JOF_IC),
+                (ToPropertyKey, to_property_key, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (ToNumeric, to_numeric, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (ToString, to_string, NULL, 1, 1, 1, JOF_BYTE),
+                (IsNullOrUndefined, is_null_or_undefined, NULL, 1, 1, 2, JOF_BYTE),
+                (GlobalThis, global_this, NULL, 1, 0, 1, JOF_BYTE),
+                (NonSyntacticGlobalThis, non_syntactic_global_this, NULL, 1, 0, 1, JOF_BYTE),
+                (NewTarget, new_target, NULL, 1, 0, 1, JOF_BYTE),
+                (DynamicImport, dynamic_import, NULL, 1, 2, 1, JOF_BYTE),
+                (ImportMeta, import_meta, NULL, 1, 0, 1, JOF_BYTE),
+                (NewInit, new_init, NULL, 1, 0, 1, JOF_BYTE|JOF_IC),
+                (NewObject, new_object, NULL, 5, 0, 1, JOF_SHAPE|JOF_IC),
+                (Object, object, NULL, 5, 0, 1, JOF_OBJECT),
+                (ObjWithProto, obj_with_proto, NULL, 1, 1, 1, JOF_BYTE),
+                (InitProp, init_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT|JOF_IC),
+                (InitHiddenProp, init_hidden_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT|JOF_IC),
+                (InitLockedProp, init_locked_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT|JOF_IC),
+                (InitElem, init_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC),
+                (InitHiddenElem, init_hidden_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC),
+                (InitLockedElem, init_locked_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC),
+                (InitPropGetter, init_prop_getter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT),
+                (InitHiddenPropGetter, init_hidden_prop_getter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT),
+                (InitElemGetter, init_elem_getter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT),
+                (InitHiddenElemGetter, init_hidden_elem_getter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT),
+                (InitPropSetter, init_prop_setter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT),
+                (InitHiddenPropSetter, init_hidden_prop_setter, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPINIT),
+                (InitElemSetter, init_elem_setter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT),
+                (InitHiddenElemSetter, init_hidden_elem_setter, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPINIT),
+                (GetProp, get_prop, NULL, 5, 1, 1, JOF_ATOM|JOF_PROP|JOF_IC),
+                (GetElem, get_elem, NULL, 1, 2, 1, JOF_BYTE|JOF_ELEM|JOF_IC),
+                (SetProp, set_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSLOPPY|JOF_IC),
+                (StrictSetProp, strict_set_prop, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSTRICT|JOF_IC),
+                (SetElem, set_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSLOPPY|JOF_IC),
+                (StrictSetElem, strict_set_elem, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSTRICT|JOF_IC),
+                (DelProp, del_prop, NULL, 5, 1, 1, JOF_ATOM|JOF_PROP|JOF_CHECKSLOPPY),
+                (StrictDelProp, strict_del_prop, NULL, 5, 1, 1, JOF_ATOM|JOF_PROP|JOF_CHECKSTRICT),
+                (DelElem, del_elem, NULL, 1, 2, 1, JOF_BYTE|JOF_ELEM|JOF_CHECKSLOPPY),
+                (StrictDelElem, strict_del_elem, NULL, 1, 2, 1, JOF_BYTE|JOF_ELEM|JOF_CHECKSTRICT),
+                (HasOwn, has_own, NULL, 1, 2, 1, JOF_BYTE|JOF_IC),
+                (CheckPrivateField, check_private_field, NULL, 3, 2, 3, JOF_TWO_UINT8|JOF_CHECKSTRICT|JOF_IC),
+                (NewPrivateName, new_private_name, NULL, 5, 0, 1, JOF_ATOM),
+                (SuperBase, super_base, NULL, 1, 1, 1, JOF_BYTE),
+                (GetPropSuper, get_prop_super, NULL, 5, 2, 1, JOF_ATOM|JOF_PROP|JOF_IC),
+                (GetElemSuper, get_elem_super, NULL, 1, 3, 1, JOF_BYTE|JOF_ELEM|JOF_IC),
+                (SetPropSuper, set_prop_super, NULL, 5, 3, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSLOPPY),
+                (StrictSetPropSuper, strict_set_prop_super, NULL, 5, 3, 1, JOF_ATOM|JOF_PROP|JOF_PROPSET|JOF_CHECKSTRICT),
+                (SetElemSuper, set_elem_super, NULL, 1, 4, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSLOPPY),
+                (StrictSetElemSuper, strict_set_elem_super, NULL, 1, 4, 1, JOF_BYTE|JOF_ELEM|JOF_PROPSET|JOF_CHECKSTRICT),
+                (Iter, iter, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (MoreIter, more_iter, NULL, 1, 1, 2, JOF_BYTE),
+                (IsNoIter, is_no_iter, NULL, 1, 1, 2, JOF_BYTE),
+                (EndIter, end_iter, NULL, 1, 2, 0, JOF_BYTE),
+                (CloseIter, close_iter, NULL, 2, 1, 0, JOF_UINT8|JOF_IC),
+                (CheckIsObj, check_is_obj, NULL, 2, 1, 1, JOF_UINT8),
+                (CheckObjCoercible, check_obj_coercible, NULL, 1, 1, 1, JOF_BYTE),
+                (ToAsyncIter, to_async_iter, NULL, 1, 2, 1, JOF_BYTE),
+                (MutateProto, mutate_proto, NULL, 1, 2, 1, JOF_BYTE),
+                (NewArray, new_array, NULL, 5, 0, 1, JOF_UINT32|JOF_IC),
+                (InitElemArray, init_elem_array, NULL, 5, 2, 1, JOF_UINT32|JOF_ELEM|JOF_PROPINIT),
+                (InitElemInc, init_elem_inc, NULL, 1, 3, 2, JOF_BYTE|JOF_ELEM|JOF_PROPINIT|JOF_IC),
+                (Hole, hole, NULL, 1, 0, 1, JOF_BYTE),
+                (RegExp, reg_exp, NULL, 5, 0, 1, JOF_REGEXP),
+                (Lambda, lambda, NULL, 5, 0, 1, JOF_OBJECT),
+                (SetFunName, set_fun_name, NULL, 2, 2, 1, JOF_UINT8),
+                (InitHomeObject, init_home_object, NULL, 1, 2, 1, JOF_BYTE),
+                (CheckClassHeritage, check_class_heritage, NULL, 1, 1, 1, JOF_BYTE),
+                (FunWithProto, fun_with_proto, NULL, 5, 1, 1, JOF_OBJECT),
+                (BuiltinObject, builtin_object, NULL, 2, 0, 1, JOF_UINT8),
+                (Call, call, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC),
+                (CallContent, call_content, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC),
+                (CallIter, call_iter, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC),
+                (CallContentIter, call_content_iter, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC),
+                (CallIgnoresRv, call_ignores_rv, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_IC),
+                (SpreadCall, spread_call, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE|JOF_SPREAD|JOF_IC),
+                (OptimizeSpreadCall, optimize_spread_call, NULL, 1, 1, 1, JOF_BYTE|JOF_IC),
+                (Eval, eval, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CHECKSLOPPY|JOF_IC),
+                (SpreadEval, spread_eval, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE|JOF_SPREAD|JOF_CHECKSLOPPY|JOF_IC),
+                (StrictEval, strict_eval, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CHECKSTRICT|JOF_IC),
+                (StrictSpreadEval, strict_spread_eval, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE|JOF_SPREAD|JOF_CHECKSTRICT|JOF_IC),
+                (ImplicitThis, implicit_this, "", 5, 0, 1, JOF_ATOM),
+                (CallSiteObj, call_site_obj, NULL, 5, 0, 1, JOF_OBJECT),
+                (IsConstructing, is_constructing, NULL, 1, 0, 1, JOF_BYTE),
+                (New, new_, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CONSTRUCT|JOF_IC),
+                (NewContent, new_content, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CONSTRUCT|JOF_IC),
+                (SuperCall, super_call, NULL, 3, -1, 1, JOF_ARGC|JOF_INVOKE|JOF_CONSTRUCT|JOF_IC),
+                (SpreadNew, spread_new, NULL, 1, 4, 1, JOF_BYTE|JOF_INVOKE|JOF_CONSTRUCT|JOF_SPREAD|JOF_IC),
+                (SpreadSuperCall, spread_super_call, NULL, 1, 4, 1, JOF_BYTE|JOF_INVOKE|JOF_CONSTRUCT|JOF_SPREAD|JOF_IC),
+                (SuperFun, super_fun, NULL, 1, 1, 1, JOF_BYTE),
+                (CheckThisReinit, check_this_reinit, NULL, 1, 1, 1, JOF_BYTE),
+                (Generator, generator, NULL, 1, 0, 1, JOF_BYTE),
+                (InitialYield, initial_yield, NULL, 4, 1, 3, JOF_RESUMEINDEX),
+                (AfterYield, after_yield, NULL, 5, 0, 0, JOF_ICINDEX),
+                (FinalYieldRval, final_yield_rval, NULL, 1, 1, 0, JOF_BYTE),
+                (Yield, yield, NULL, 4, 2, 3, JOF_RESUMEINDEX),
+                (IsGenClosing, is_gen_closing, NULL, 1, 1, 2, JOF_BYTE),
+                (AsyncAwait, async_await, NULL, 1, 2, 1, JOF_BYTE),
+                (AsyncResolve, async_resolve, NULL, 2, 2, 1, JOF_UINT8),
+                (Await, await, NULL, 4, 2, 3, JOF_RESUMEINDEX),
+                (CanSkipAwait, can_skip_await, NULL, 1, 1, 2, JOF_BYTE),
+                (MaybeExtractAwaitValue, maybe_extract_await_value, NULL, 1, 2, 2, JOF_BYTE),
+                (ResumeKind, resume_kind, NULL, 2, 0, 1, JOF_UINT8),
+                (CheckResumeKind, check_resume_kind, NULL, 1, 3, 1, JOF_BYTE),
+                (Resume, resume, NULL, 1, 3, 1, JOF_BYTE|JOF_INVOKE),
+                (JumpTarget, jump_target, NULL, 5, 0, 0, JOF_ICINDEX),
+                (LoopHead, loop_head, NULL, 6, 0, 0, JOF_LOOPHEAD),
+                (Goto, goto_, NULL, 5, 0, 0, JOF_JUMP),
+                (JumpIfFalse, jump_if_false, NULL, 5, 1, 0, JOF_JUMP|JOF_IC),
+                (JumpIfTrue, jump_if_true, NULL, 5, 1, 0, JOF_JUMP|JOF_IC),
+                (And, and_, NULL, 5, 1, 1, JOF_JUMP|JOF_IC),
+                (Or, or_, NULL, 5, 1, 1, JOF_JUMP|JOF_IC),
+                (Coalesce, coalesce, NULL, 5, 1, 1, JOF_JUMP),
+                (Case, case_, NULL, 5, 2, 1, JOF_JUMP),
+                (Default, default_, NULL, 5, 1, 0, JOF_JUMP),
+                (TableSwitch, table_switch, NULL, 16, 1, 0, JOF_TABLESWITCH),
+                (Return, return_, NULL, 1, 1, 0, JOF_BYTE),
+                (GetRval, get_rval, NULL, 1, 0, 1, JOF_BYTE),
+                (SetRval, set_rval, NULL, 1, 1, 0, JOF_BYTE),
+                (RetRval, ret_rval, NULL, 1, 0, 0, JOF_BYTE),
+                (CheckReturn, check_return, NULL, 1, 1, 1, JOF_BYTE),
+                (Throw, throw_, NULL, 1, 1, 0, JOF_BYTE),
+                (ThrowMsg, throw_msg, NULL, 2, 0, 0, JOF_UINT8),
+                (ThrowSetConst, throw_set_const, NULL, 5, 0, 0, JOF_ATOM|JOF_NAME),
+                (Try, try_, NULL, 1, 0, 0, JOF_BYTE),
+                (TryDestructuring, try_destructuring, NULL, 1, 0, 0, JOF_BYTE),
+                (Exception, exception, NULL, 1, 0, 1, JOF_BYTE),
+                (Finally, finally, NULL, 1, 0, 0, JOF_BYTE),
+                (Uninitialized, uninitialized, NULL, 1, 0, 1, JOF_BYTE),
+                (InitLexical, init_lexical, NULL, 4, 1, 1, JOF_LOCAL|JOF_NAME),
+                (InitGLexical, init_g_lexical, NULL, 5, 1, 1, JOF_ATOM|JOF_NAME|JOF_PROPINIT|JOF_GNAME|JOF_IC),
+                (InitAliasedLexical, init_aliased_lexical, NULL, 5, 1, 1, JOF_ENVCOORD|JOF_NAME|JOF_PROPINIT),
+                (CheckLexical, check_lexical, NULL, 4, 1, 1, JOF_LOCAL|JOF_NAME),
+                (CheckAliasedLexical, check_aliased_lexical, NULL, 5, 1, 1, JOF_ENVCOORD|JOF_NAME),
+                (CheckThis, check_this, NULL, 1, 1, 1, JOF_BYTE),
+                (BindGName, bind_g_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_GNAME|JOF_IC),
+                (BindName, bind_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_IC),
+                (GetName, get_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_IC),
+                (GetGName, get_g_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_GNAME|JOF_IC),
+                (GetArg, get_arg, NULL, 3, 0, 1, JOF_QARG|JOF_NAME),
+                (GetLocal, get_local, NULL, 4, 0, 1, JOF_LOCAL|JOF_NAME),
+                (GetAliasedVar, get_aliased_var, NULL, 5, 0, 1, JOF_ENVCOORD|JOF_NAME),
+                (GetAliasedDebugVar, get_aliased_debug_var, NULL, 5, 0, 1, JOF_DEBUGCOORD|JOF_NAME),
+                (GetImport, get_import, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME),
+                (GetBoundName, get_bound_name, NULL, 5, 1, 1, JOF_ATOM|JOF_NAME|JOF_IC),
+                (GetIntrinsic, get_intrinsic, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_IC),
+                (Callee, callee, NULL, 1, 0, 1, JOF_BYTE),
+                (EnvCallee, env_callee, NULL, 2, 0, 1, JOF_UINT8),
+                (SetName, set_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_CHECKSLOPPY|JOF_IC),
+                (StrictSetName, strict_set_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_CHECKSTRICT|JOF_IC),
+                (SetGName, set_g_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_GNAME|JOF_CHECKSLOPPY|JOF_IC),
+                (StrictSetGName, strict_set_g_name, NULL, 5, 2, 1, JOF_ATOM|JOF_NAME|JOF_PROPSET|JOF_GNAME|JOF_CHECKSTRICT|JOF_IC),
+                (SetArg, set_arg, NULL, 3, 1, 1, JOF_QARG|JOF_NAME),
+                (SetLocal, set_local, NULL, 4, 1, 1, JOF_LOCAL|JOF_NAME),
+                (SetAliasedVar, set_aliased_var, NULL, 5, 1, 1, JOF_ENVCOORD|JOF_NAME|JOF_PROPSET),
+                (SetIntrinsic, set_intrinsic, NULL, 5, 1, 1, JOF_ATOM|JOF_NAME),
+                (PushLexicalEnv, push_lexical_env, NULL, 5, 0, 0, JOF_SCOPE),
+                (PopLexicalEnv, pop_lexical_env, NULL, 1, 0, 0, JOF_BYTE),
+                (DebugLeaveLexicalEnv, debug_leave_lexical_env, NULL, 1, 0, 0, JOF_BYTE),
+                (RecreateLexicalEnv, recreate_lexical_env, NULL, 5, 0, 0, JOF_SCOPE),
+                (FreshenLexicalEnv, freshen_lexical_env, NULL, 5, 0, 0, JOF_SCOPE),
+                (PushClassBodyEnv, push_class_body_env, NULL, 5, 0, 0, JOF_SCOPE),
+                (PushVarEnv, push_var_env, NULL, 5, 0, 0, JOF_SCOPE),
+                (EnterWith, enter_with, NULL, 5, 1, 0, JOF_SCOPE),
+                (LeaveWith, leave_with, NULL, 1, 0, 0, JOF_BYTE),
+                (BindVar, bind_var, NULL, 1, 0, 1, JOF_BYTE),
+                (GlobalOrEvalDeclInstantiation, global_or_eval_decl_instantiation, NULL, 5, 0, 0, JOF_GCTHING),
+                (DelName, del_name, NULL, 5, 0, 1, JOF_ATOM|JOF_NAME|JOF_CHECKSLOPPY),
+                (Arguments, arguments, NULL, 1, 0, 1, JOF_BYTE),
+                (Rest, rest, NULL, 1, 0, 1, JOF_BYTE|JOF_IC),
+                (FunctionThis, function_this, NULL, 1, 0, 1, JOF_BYTE),
+                (Pop, pop, NULL, 1, 1, 0, JOF_BYTE),
+                (PopN, pop_n, NULL, 3, -1, 0, JOF_UINT16),
+                (Dup, dup, NULL, 1, 1, 2, JOF_BYTE),
+                (Dup2, dup2, NULL, 1, 2, 4, JOF_BYTE),
+                (DupAt, dup_at, NULL, 4, 0, 1, JOF_UINT24),
+                (Swap, swap, NULL, 1, 2, 2, JOF_BYTE),
+                (Pick, pick, NULL, 2, 0, 0, JOF_UINT8),
+                (Unpick, unpick, NULL, 2, 0, 0, JOF_UINT8),
+                (Nop, nop, NULL, 1, 0, 0, JOF_BYTE),
+                (Lineno, lineno, NULL, 5, 0, 0, JOF_UINT32),
+                (NopDestructuring, nop_destructuring, NULL, 1, 0, 0, JOF_BYTE),
+                (ForceInterpreter, force_interpreter, NULL, 1, 0, 0, JOF_BYTE),
+                (DebugCheckSelfHosted, debug_check_self_hosted, NULL, 1, 1, 1, JOF_BYTE),
+                (Debugger, debugger, NULL, 1, 0, 0, JOF_BYTE),
+                // @@@@ END OPCODES @@@@
+            ]
+        }
+    }
+}
+
+macro_rules! define_opcode_enum {
+    ( [ $( ( $op:ident , $( $_etc:tt )* ), )* ] ) => {
+        #[derive(Copy, Clone, Debug, Eq, PartialEq)]
+        #[repr(u8)]
+        pub enum Opcode {
+            $( $op, )*
+        }
+    }
+}
+
+using_opcode_database!(define_opcode_enum!());
+
+macro_rules! count_rows {
+    ( [ $( $ignored_row:tt , )* ] ) => {
+        0 $( + count_rows!(one for $ignored_row) )*
+    };
+
+    ( one for $ignored_row:tt ) => {
+        1
+    }
+}
+
+const JSOP_LIMIT: usize = using_opcode_database!(count_rows!());
+
+// WARNING
+// The following section is generated by update_stencil.py.
+// Do mot modify manually.
+//
+// @@@@ BEGIN FLAGS @@@@
+/// single bytecode, no immediates
+const JOF_BYTE: u32 = 0;
+
+/// unspecified uint8_t argument
+const JOF_UINT8: u32 = 1;
+
+/// unspecified uint16_t argument
+const JOF_UINT16: u32 = 2;
+
+/// unspecified uint24_t argument
+const JOF_UINT24: u32 = 3;
+
+/// unspecified uint32_t argument
+const JOF_UINT32: u32 = 4;
+
+/// int8_t literal
+const JOF_INT8: u32 = 5;
+
+/// int32_t literal
+const JOF_INT32: u32 = 6;
+
+/// int32_t jump offset
+const JOF_JUMP: u32 = 7;
+
+/// table switch
+const JOF_TABLESWITCH: u32 = 8;
+
+/// embedded ScopeCoordinate immediate
+const JOF_ENVCOORD: u32 = 9;
+
+/// uint16_t argument count
+const JOF_ARGC: u32 = 10;
+
+/// function argument index
+const JOF_QARG: u32 = 11;
+
+/// var or block-local variable
+const JOF_LOCAL: u32 = 12;
+
+/// yield or await resume index
+const JOF_RESUMEINDEX: u32 = 13;
+
+/// inline DoubleValue
+const JOF_DOUBLE: u32 = 14;
+
+/// uint32_t generic gc-thing index
+const JOF_GCTHING: u32 = 15;
+
+/// uint32_t constant index
+const JOF_ATOM: u32 = 16;
+
+/// uint32_t object index
+const JOF_OBJECT: u32 = 17;
+
+/// uint32_t regexp index
+const JOF_REGEXP: u32 = 18;
+
+/// uint32_t scope index
+const JOF_SCOPE: u32 = 19;
+
+/// uint32_t index for BigInt value
+const JOF_BIGINT: u32 = 20;
+
+/// uint32_t IC index
+const JOF_ICINDEX: u32 = 21;
+
+/// JSOp::LoopHead, combines JOF_ICINDEX and JOF_UINT8
+const JOF_LOOPHEAD: u32 = 22;
+
+/// A pair of unspecified uint8_t arguments
+const JOF_TWO_UINT8: u32 = 23;
+
+/// An embedded ScopeCoordinate immediate that may traverse DebugEnvironmentProxies
+const JOF_DEBUGCOORD: u32 = 24;
+
+/// uint32_t shape index
+const JOF_SHAPE: u32 = 25;
+
+/// uint32_t constant index
+const JOF_STRING: u32 = 26;
+
+/// mask for above immediate types
+const JOF_TYPEMASK: u32 = 0xFF;
+
+/// name operation
+const JOF_NAME: u32 = 1 << 8;
+
+/// obj.prop operation
+const JOF_PROP: u32 = 2 << 8;
+
+/// obj[index] operation
+const JOF_ELEM: u32 = 3 << 8;
+
+/// property/element/name set operation
+const JOF_PROPSET: u32 = 1 << 16;
+
+/// property/element/name init operation
+const JOF_PROPINIT: u32 = 1 << 17;
+
+/// op can only be generated in sloppy mode
+const JOF_CHECKSLOPPY: u32 = 1 << 18;
+
+/// op can only be generated in strict mode
+const JOF_CHECKSTRICT: u32 = 1 << 19;
+
+/// any call, construct, or eval instruction
+const JOF_INVOKE: u32 = 1 << 20;
+
+/// invoke instruction using [[Construct]] entry
+const JOF_CONSTRUCT: u32 = 1 << 21;
+
+/// invoke instruction using spread argument
+const JOF_SPREAD: u32 = 1 << 22;
+
+/// predicted global name
+const JOF_GNAME: u32 = 1 << 23;
+
+/// baseline may use an IC for this op
+const JOF_IC: u32 = 1 << 24;
+
+// @@@@ END FLAGS @@@@
+
+impl Opcode {
+    /// Return the numeric bytecode value for this opcode, as understood by the
+    /// SpiderMonkey interpreter and the rest of the VM.
+    pub fn to_byte(&self) -> u8 {
+        *self as u8
+    }
+
+    /// True if this opcode takes no operands (is a one-byte opcode) and
+    /// implements a unary operator that operates on one stack value.
+    ///
+    /// The operators `typeof` and `delete` have different bytecode patterns
+    /// and thus are not considered "simple"; `new` is considered a special
+    /// kind of function call, not a unary operator.
+    pub fn is_simple_unary_operator(self) -> bool {
+        self == Opcode::Pos
+            || self == Opcode::Neg
+            || self == Opcode::Not
+            || self == Opcode::BitNot
+            || self == Opcode::Void
+    }
+
+    /// True if this opcode takes no operands (is a one-byte opcode) and
+    /// implements a binary operator that operates on two stack values.
+    ///
+    /// The operators `||`, `&&`, and `,` have different bytecode patterns
+    /// and thus are not considered "simple".
+    pub fn is_simple_binary_operator(self) -> bool {
+        self == Opcode::BitOr
+            || self == Opcode::BitXor
+            || self == Opcode::BitAnd
+            || self == Opcode::Eq
+            || self == Opcode::Ne
+            || self == Opcode::StrictEq
+            || self == Opcode::StrictNe
+            || self == Opcode::Lt
+            || self == Opcode::Gt
+            || self == Opcode::Le
+            || self == Opcode::Ge
+            || self == Opcode::Instanceof
+            || self == Opcode::In
+            || self == Opcode::Lsh
+            || self == Opcode::Rsh
+            || self == Opcode::Ursh
+            || self == Opcode::Add
+            || self == Opcode::Sub
+            || self == Opcode::Mul
+            || self == Opcode::Div
+            || self == Opcode::Mod
+            || self == Opcode::Pow
+    }
+
+    pub fn is_jump_target(self) -> bool {
+        self == Opcode::JumpTarget || self == Opcode::LoopHead || self == Opcode::AfterYield
+    }
+
+    pub fn is_jump(self) -> bool {
+        self == Opcode::Goto
+            || self == Opcode::JumpIfFalse
+            || self == Opcode::JumpIfTrue
+            || self == Opcode::Or
+            || self == Opcode::And
+            || self == Opcode::Coalesce
+    }
+}
+
+impl TryFrom<u8> for Opcode {
+    type Error = ();
+
+    fn try_from(value: u8) -> Result<Opcode, ()> {
+        if (value as usize) < JSOP_LIMIT {
+            Ok(TABLE[value as usize])
+        } else {
+            Err(())
+        }
+    }
+}
+
+macro_rules! define_table {
+    ( [ $(
+        (
+            $op:ident , $op_snake:ident , $str:expr ,
+            $length:expr , $nuses:expr , $ndefs:expr , $format:expr
+        ) ,
+    )* ] ) => {
+        pub static TABLE: [Opcode; JSOP_LIMIT] = [
+            $( Opcode::$op , )*
+        ];
+    }
+}
+
+using_opcode_database!(define_table!());
+
+impl Opcode {
+    /// Length of this instruction, in bytes.
+    pub fn instruction_length(self) -> usize {
+        macro_rules! select_length {
+            ( [ $(
+                (
+                    $op:ident , $op_snake:ident , $str:expr ,
+                    $length:expr , $nuses:expr , $ndefs:expr , $format:expr
+                ) ,
+            )* ] ) => {
+                match self {
+                    $( Opcode::$op => $length , )*
+                }
+            }
+        }
+
+        using_opcode_database!(select_length!())
+    }
+
+    /// Number of stack slots consumed by this instruction, or -1 for variadic
+    /// instructions.
+    pub fn nuses(self) -> isize {
+        macro_rules! select_nuses {
+            ( [ $(
+                (
+                    $op:ident , $op_snake:ident , $str:expr ,
+                    $length:expr , $nuses:expr , $ndefs:expr , $format:expr
+                ) ,
+            )* ] ) => {
+                match self {
+                    $( Opcode::$op => $nuses , )*
+                }
+            }
+        }
+
+        using_opcode_database!(select_nuses!())
+    }
+
+    pub fn ndefs(self) -> usize {
+        macro_rules! select_ndefs {
+            ( [ $(
+                (
+                    $op:ident , $op_snake:ident , $str:expr ,
+                    $length:expr , $nuses:expr , $ndefs:expr , $format:expr
+                ) ,
+            )* ] ) => {
+                match self {
+                    $( Opcode::$op => $ndefs , )*
+                }
+            }
+        }
+
+        using_opcode_database!(select_ndefs!())
+    }
+
+    fn format_bits(self) -> u32 {
+        macro_rules! select_format {
+            ( [ $(
+                (
+                    $op:ident , $op_snake:ident , $str:expr ,
+                    $length:expr , $nuses:expr , $ndefs:expr , $format:expr
+                ) ,
+            )* ] ) => {
+                match self {
+                    $( Opcode::$op => $format , )*
+                }
+            }
+        }
+
+        using_opcode_database!(select_format!())
+    }
+
+    pub fn has_ic_entry(self) -> bool {
+        self.format_bits() & JOF_IC != 0
+    }
+
+    pub fn has_ic_index(self) -> bool {
+        match self.format_bits() & JOF_TYPEMASK {
+            JOF_LOOPHEAD | JOF_ICINDEX => true,
+            _ => false,
+        }
+    }
+
+    pub fn has_argc(self) -> bool {
+        self.format_bits() & JOF_TYPEMASK == JOF_ARGC
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn table_matches() {
+        for (i, t) in TABLE.iter().enumerate() {
+            assert_eq!(i, t.to_byte() as usize);
+        }
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/opcode_info.rs b/third_party/rust/jsparagus-stencil/src/opcode_info.rs
new file mode 100644
index 0000000000..a841cc0774
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/opcode_info.rs
@@ -0,0 +1,47 @@
+pub fn get_async_function_resolve_kind() -> &'static str {
+    include_str!("copy/AsyncFunctionResolveKind.h")
+}
+
+pub fn get_bytecode_format_flags() -> &'static str {
+    include_str!("copy/BytecodeFormatFlags.h")
+}
+
+pub fn get_check_is_object_kind() -> &'static str {
+    include_str!("copy/CheckIsObjectKind.h")
+}
+
+pub fn get_function_flags() -> &'static str {
+    include_str!("copy/FunctionFlags.h")
+}
+
+pub fn get_generator_and_async_kind() -> &'static str {
+    include_str!("copy/GeneratorAndAsyncKind.h")
+}
+
+pub fn get_function_prefix_kind() -> &'static str {
+    include_str!("copy/FunctionPrefixKind.h")
+}
+
+pub fn get_generator_resume_kind() -> &'static str {
+    include_str!("copy/GeneratorResumeKind.h")
+}
+
+pub fn get_opcodes_source() -> &'static str {
+    include_str!("copy/Opcodes.h")
+}
+
+pub fn get_source_notes() -> &'static str {
+    include_str!("copy/SourceNotes.h")
+}
+
+pub fn get_stencil_enums() -> &'static str {
+    include_str!("copy/StencilEnums.h")
+}
+
+pub fn get_symbol() -> &'static str {
+    include_str!("copy/Symbol.h")
+}
+
+pub fn get_throw_msg_kind() -> &'static str {
+    include_str!("copy/ThrowMsgKind.h")
+}
diff --git a/third_party/rust/jsparagus-stencil/src/regexp.rs b/third_party/rust/jsparagus-stencil/src/regexp.rs
new file mode 100644
index 0000000000..47356b1fd3
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/regexp.rs
@@ -0,0 +1,54 @@
+use ast::source_slice_list::SourceSliceIndex;
+
+#[derive(Debug)]
+pub struct RegExpItem {
+    pub pattern: SourceSliceIndex,
+    pub global: bool,
+    pub ignore_case: bool,
+    pub multi_line: bool,
+    pub dot_all: bool,
+    pub sticky: bool,
+    pub unicode: bool,
+}
+
+/// Index into RegExpList.atoms.
+#[derive(Debug, Clone, Copy)]
+pub struct RegExpIndex {
+    index: usize,
+}
+
+impl RegExpIndex {
+    fn new(index: usize) -> Self {
+        Self { index }
+    }
+}
+
+impl From<RegExpIndex> for usize {
+    fn from(index: RegExpIndex) -> usize {
+        index.index
+    }
+}
+
+/// List of RegExp.
+#[derive(Debug)]
+pub struct RegExpList {
+    items: Vec<RegExpItem>,
+}
+
+impl RegExpList {
+    pub fn new() -> Self {
+        Self { items: Vec::new() }
+    }
+
+    pub fn push(&mut self, item: RegExpItem) -> RegExpIndex {
+        let index = self.items.len();
+        self.items.push(item);
+        RegExpIndex::new(index)
+    }
+}
+
+impl From<RegExpList> for Vec<RegExpItem> {
+    fn from(list: RegExpList) -> Vec<RegExpItem> {
+        list.items
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/result.rs b/third_party/rust/jsparagus-stencil/src/result.rs
new file mode 100644
index 0000000000..6cb2fb7716
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/result.rs
@@ -0,0 +1,35 @@
+use crate::regexp::RegExpItem;
+use crate::scope::ScopeData;
+use crate::script::{ImmutableScriptData, ScriptStencil};
+
+/// The result of emitter.
+#[derive(Debug)]
+pub struct EmitResult<'alloc> {
+    pub atoms: Vec<&'alloc str>,
+    pub slices: Vec<&'alloc str>,
+    pub scopes: Vec<ScopeData>,
+    pub regexps: Vec<RegExpItem>,
+
+    pub scripts: Vec<ScriptStencil>,
+    pub script_data_list: Vec<ImmutableScriptData>,
+}
+
+impl<'alloc> EmitResult<'alloc> {
+    pub fn new(
+        atoms: Vec<&'alloc str>,
+        slices: Vec<&'alloc str>,
+        scopes: Vec<ScopeData>,
+        regexps: Vec<RegExpItem>,
+        scripts: Vec<ScriptStencil>,
+        script_data_list: Vec<ImmutableScriptData>,
+    ) -> Self {
+        Self {
+            atoms,
+            slices,
+            scopes,
+            regexps,
+            scripts,
+            script_data_list,
+        }
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/scope.rs b/third_party/rust/jsparagus-stencil/src/scope.rs
new file mode 100644
index 0000000000..9b4fa3a94b
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/scope.rs
@@ -0,0 +1,639 @@
+//! Types for the output of scope analysis.
+//!
+//! The top-level output of this analysis is the `ScopeDataMap`, which holds
+//! the following:
+//!   * `LexicalScopeData` for each lexial scope in the AST
+//!   * `GlobalScopeData` for the global scope
+//!   * `VarScopeData` for extra body var scope in function
+//!   * `FunctionScopeData` for the function scope
+//!
+//! Each scope contains a list of bindings (`BindingName`).
+
+use crate::frame_slot::FrameSlot;
+use crate::script::ScriptStencilIndex;
+use ast::associated_data::AssociatedData;
+use ast::source_atom_set::SourceAtomSetIndex;
+use ast::source_location_accessor::SourceLocationAccessor;
+use ast::type_id::NodeTypeIdAccessor;
+
+/// Corresponds to js::BindingKind in m-c/js/src/vm/Scope.h.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub enum BindingKind {
+    Var,
+    Let,
+    Const,
+}
+
+/// Information about a single binding in a JS script.
+///
+/// Corresponds to `js::BindingName` in m-c/js/src/vm/Scope.h.
+#[derive(Debug)]
+pub struct BindingName {
+    pub name: SourceAtomSetIndex,
+    pub is_closed_over: bool,
+    pub is_top_level_function: bool,
+}
+
+impl BindingName {
+    pub fn new(name: SourceAtomSetIndex, is_closed_over: bool) -> Self {
+        Self {
+            name,
+            is_closed_over,
+            is_top_level_function: false,
+        }
+    }
+
+    pub fn new_top_level_function(name: SourceAtomSetIndex, is_closed_over: bool) -> Self {
+        Self {
+            name,
+            is_closed_over,
+            is_top_level_function: true,
+        }
+    }
+}
+
+/// Corresponds to the accessor part of `js::BindingIter` in
+/// m-c/js/src/vm/Scope.h.
+pub struct BindingIterItem<'a> {
+    name: &'a BindingName,
+    kind: BindingKind,
+}
+
+impl<'a> BindingIterItem<'a> {
+    fn new(name: &'a BindingName, kind: BindingKind) -> Self {
+        Self { name, kind }
+    }
+
+    pub fn name(&self) -> SourceAtomSetIndex {
+        self.name.name
+    }
+
+    pub fn is_top_level_function(&self) -> bool {
+        self.name.is_top_level_function
+    }
+
+    pub fn is_closed_over(&self) -> bool {
+        self.name.is_closed_over
+    }
+
+    pub fn kind(&self) -> BindingKind {
+        self.kind
+    }
+}
+
+/// Accessor for both BindingName/Option<BindingName>.
+pub trait MaybeBindingName {
+    fn is_closed_over(&self) -> bool;
+}
+impl MaybeBindingName for BindingName {
+    fn is_closed_over(&self) -> bool {
+        self.is_closed_over
+    }
+}
+impl MaybeBindingName for Option<BindingName> {
+    fn is_closed_over(&self) -> bool {
+        match self {
+            Some(b) => b.is_closed_over,
+            None => false,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub struct BaseScopeData<BindingItemT>
+where
+    BindingItemT: MaybeBindingName,
+{
+    /// Corresponds to `*Scope::Data.{length, trailingNames}.`
+    /// The layout is defined by *ScopeData structs below, that has
+    /// this struct.
+    pub bindings: Vec<BindingItemT>,
+    pub has_eval: bool,
+    pub has_with: bool,
+}
+
+impl<BindingItemT> BaseScopeData<BindingItemT>
+where
+    BindingItemT: MaybeBindingName,
+{
+    pub fn new(bindings_count: usize) -> Self {
+        Self {
+            bindings: Vec::with_capacity(bindings_count),
+            has_eval: false,
+            has_with: false,
+        }
+    }
+
+    pub fn is_all_bindings_closed_over(&self) -> bool {
+        // `with` and direct `eval` can dynamically access any binding in this
+        // scope.
+        self.has_eval || self.has_with
+    }
+
+    /// Returns true if this scope needs to be allocated on heap as
+    /// EnvironmentObject.
+    pub fn needs_environment_object(&self) -> bool {
+        // `with` and direct `eval` can dynamically access bindings in this
+        // scope.
+        if self.is_all_bindings_closed_over() {
+            return true;
+        }
+
+        // If a binding in this scope is closed over by inner function,
+        // it can be accessed when this frame isn't on the stack.
+        for binding in &self.bindings {
+            if binding.is_closed_over() {
+                return true;
+            }
+        }
+
+        false
+    }
+}
+
+/// Bindings created in global environment.
+///
+/// Maps to js::GlobalScope::Data in m-c/js/src/vm/Scope.h.
+#[derive(Debug)]
+pub struct GlobalScopeData {
+    /// Bindings are sorted by kind:
+    ///
+    /// * `base.bindings[0..let_start]` - `var`s
+    /// * `base.bindings[let_start..const_start]` - `let`s
+    /// * `base.bindings[const_start..]` - `const`s
+    pub base: BaseScopeData<BindingName>,
+
+    pub let_start: usize,
+    pub const_start: usize,
+
+    /// The global functions in this script.
+    pub functions: Vec<ScriptStencilIndex>,
+}
+
+impl GlobalScopeData {
+    pub fn new(
+        var_count: usize,
+        let_count: usize,
+        const_count: usize,
+        functions: Vec<ScriptStencilIndex>,
+    ) -> Self {
+        let capacity = var_count + let_count + const_count;
+
+        Self {
+            base: BaseScopeData::new(capacity),
+            let_start: var_count,
+            const_start: var_count + let_count,
+            functions,
+        }
+    }
+
+    pub fn iter<'a>(&'a self) -> GlobalBindingIter<'a> {
+        GlobalBindingIter::new(self)
+    }
+}
+
+/// Corresponds to the iteration part of js::BindingIter
+/// in m-c/js/src/vm/Scope.h.
+pub struct GlobalBindingIter<'a> {
+    data: &'a GlobalScopeData,
+    i: usize,
+}
+
+impl<'a> GlobalBindingIter<'a> {
+    fn new(data: &'a GlobalScopeData) -> Self {
+        Self { data, i: 0 }
+    }
+}
+
+impl<'a> Iterator for GlobalBindingIter<'a> {
+    type Item = BindingIterItem<'a>;
+
+    fn next(&mut self) -> Option<BindingIterItem<'a>> {
+        if self.i == self.data.base.bindings.len() {
+            return None;
+        }
+
+        let kind = if self.i < self.data.let_start {
+            BindingKind::Var
+        } else if self.i < self.data.const_start {
+            BindingKind::Let
+        } else {
+            BindingKind::Const
+        };
+
+        let name = &self.data.base.bindings[self.i];
+
+        self.i += 1;
+
+        Some(BindingIterItem::new(name, kind))
+    }
+}
+
+/// Bindings created in var environment.
+///
+/// Maps to js::VarScope::Data in m-c/js/src/vm/Scope.h,
+/// and the parameter for js::frontend::ScopeCreationData::create
+/// in m-c/js/src/frontend/Stencil.h
+#[derive(Debug)]
+pub struct VarScopeData {
+    /// All bindings are `var`.
+    pub base: BaseScopeData<BindingName>,
+
+    /// The first frame slot of this scope.
+    ///
+    /// Unlike VarScope::Data, this struct holds the first frame slot,
+    /// instead of the next frame slot.
+    ///
+    /// This is because ScopeCreationData::create receives the first frame slot
+    /// and VarScope::Data.nextFrameSlot is calculated there.
+    pub first_frame_slot: FrameSlot,
+
+    pub function_has_extensible_scope: bool,
+
+    /// ScopeIndex of the enclosing scope.
+    ///
+    /// A parameter for ScopeCreationData::create.
+    pub enclosing: ScopeIndex,
+}
+
+impl VarScopeData {
+    pub fn new(
+        var_count: usize,
+        function_has_extensible_scope: bool,
+        enclosing: ScopeIndex,
+    ) -> Self {
+        let capacity = var_count;
+
+        Self {
+            base: BaseScopeData::new(capacity),
+            // Set to the correct value in EmitterScopeStack::enter_lexical.
+            first_frame_slot: FrameSlot::new(0),
+            function_has_extensible_scope,
+            enclosing,
+        }
+    }
+}
+
+/// Bindings created in lexical environment.
+///
+/// Maps to js::LexicalScope::Data in m-c/js/src/vm/Scope.h,
+/// and the parameter for js::frontend::ScopeCreationData::create
+/// in m-c/js/src/frontend/Stencil.h
+#[derive(Debug)]
+pub struct LexicalScopeData {
+    /// Bindings are sorted by kind:
+    ///
+    /// * `base.bindings[0..const_start]` - `let`s
+    /// * `base.bindings[const_start..]` - `const`s
+    pub base: BaseScopeData<BindingName>,
+
+    pub const_start: usize,
+
+    /// The first frame slot of this scope.
+    ///
+    /// Unlike LexicalScope::Data, this struct holds the first frame slot,
+    /// instead of the next frame slot.
+    ///
+    /// This is because ScopeCreationData::create receives the first frame slot
+    /// and LexicalScope::Data.nextFrameSlot is calculated there.
+    pub first_frame_slot: FrameSlot,
+
+    /// ScopeIndex of the enclosing scope.
+    ///
+    /// A parameter for ScopeCreationData::create.
+    pub enclosing: ScopeIndex,
+
+    /// Functions in this scope.
+    pub functions: Vec<ScriptStencilIndex>,
+}
+
+impl LexicalScopeData {
+    fn new(
+        let_count: usize,
+        const_count: usize,
+        enclosing: ScopeIndex,
+        functions: Vec<ScriptStencilIndex>,
+    ) -> Self {
+        let capacity = let_count + const_count;
+
+        Self {
+            base: BaseScopeData::new(capacity),
+            const_start: let_count,
+            // Set to the correct value in EmitterScopeStack::enter_lexical.
+            first_frame_slot: FrameSlot::new(0),
+            enclosing,
+            functions,
+        }
+    }
+
+    pub fn new_block(
+        let_count: usize,
+        const_count: usize,
+        enclosing: ScopeIndex,
+        functions: Vec<ScriptStencilIndex>,
+    ) -> Self {
+        Self::new(let_count, const_count, enclosing, functions)
+    }
+
+    pub fn new_named_lambda(enclosing: ScopeIndex) -> Self {
+        Self::new(0, 1, enclosing, Vec::new())
+    }
+
+    pub fn new_function_lexical(
+        let_count: usize,
+        const_count: usize,
+        enclosing: ScopeIndex,
+    ) -> Self {
+        Self::new(let_count, const_count, enclosing, Vec::new())
+    }
+
+    pub fn iter<'a>(&'a self) -> LexicalBindingIter<'a> {
+        LexicalBindingIter::new(self)
+    }
+}
+
+/// Corresponds to the iteration part of js::BindingIter
+/// in m-c/js/src/vm/Scope.h.
+pub struct LexicalBindingIter<'a> {
+    data: &'a LexicalScopeData,
+    i: usize,
+}
+
+impl<'a> LexicalBindingIter<'a> {
+    fn new(data: &'a LexicalScopeData) -> Self {
+        Self { data, i: 0 }
+    }
+}
+
+impl<'a> Iterator for LexicalBindingIter<'a> {
+    type Item = BindingIterItem<'a>;
+
+    fn next(&mut self) -> Option<BindingIterItem<'a>> {
+        if self.i == self.data.base.bindings.len() {
+            return None;
+        }
+
+        let kind = if self.i < self.data.const_start {
+            BindingKind::Let
+        } else {
+            BindingKind::Const
+        };
+
+        let name = &self.data.base.bindings[self.i];
+
+        self.i += 1;
+
+        Some(BindingIterItem::new(name, kind))
+    }
+}
+
+/// Bindings created in function environment.
+///
+/// Maps to js::FunctionScope::Data in m-c/js/src/vm/Scope.h,
+/// and the parameter for js::frontend::ScopeCreationData::create
+/// in m-c/js/src/frontend/Stencil.h
+#[derive(Debug)]
+pub struct FunctionScopeData {
+    /// Bindings are sorted by kind:
+    ///
+    /// * `base.bindings[0..non_positional_formal_start]` -
+    ///    positional foparameters:
+    ///      - single binding parameter with/without default
+    ///      - single binding rest parameter
+    /// * `base.bindings[non_positional_formal_start..var_start]` -
+    ///    non positional parameters:
+    ///      - destructuring parameter
+    ///      - destructuring rest parameter
+    /// * `base.bindings[var_start..]` - `var`s
+    ///
+    /// Given positional parameters range can have null slot for destructuring,
+    /// use Vec of Option<BindingName>, instead of BindingName like others.
+    pub base: BaseScopeData<Option<BindingName>>,
+
+    pub has_parameter_exprs: bool,
+
+    pub non_positional_formal_start: usize,
+    pub var_start: usize,
+
+    /// The first frame slot of this scope.
+    ///
+    /// Unlike FunctionScope::Data, this struct holds the first frame slot,
+    /// instead of the next frame slot.
+    ///
+    /// This is because ScopeCreationData::create receives the first frame slot
+    /// and FunctionScope::Data.nextFrameSlot is calculated there.
+    pub first_frame_slot: FrameSlot,
+
+    /// ScopeIndex of the enclosing scope.
+    ///
+    /// A parameter for ScopeCreationData::create.
+    pub enclosing: ScopeIndex,
+
+    pub function_index: ScriptStencilIndex,
+
+    /// True if the function is an arrow function.
+    pub is_arrow: bool,
+}
+
+impl FunctionScopeData {
+    pub fn new(
+        has_parameter_exprs: bool,
+        positional_parameter_count: usize,
+        non_positional_formal_start: usize,
+        max_var_count: usize,
+        enclosing: ScopeIndex,
+        function_index: ScriptStencilIndex,
+        is_arrow: bool,
+    ) -> Self {
+        let capacity = positional_parameter_count + non_positional_formal_start + max_var_count;
+
+        Self {
+            base: BaseScopeData::new(capacity),
+            has_parameter_exprs,
+            non_positional_formal_start: positional_parameter_count,
+            var_start: positional_parameter_count + non_positional_formal_start,
+            // Set to the correct value in EmitterScopeStack::enter_function.
+            first_frame_slot: FrameSlot::new(0),
+            enclosing,
+            function_index,
+            is_arrow,
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum ScopeData {
+    /// No scope should be generated, but this scope becomes an alias to
+    /// enclosing scope. This is used, for example, when we see a function,
+    /// and set aside a ScopeData for its lexical bindings, but upon
+    /// reaching the end of the function body, we find that there were no
+    /// lexical bindings and the spec actually says not to generate a Lexical
+    /// Environment when this function is called.
+    ///
+    /// In other places, the spec does say to create a Lexical Environment, but
+    /// it turns out it doesn't have any bindings in it and we can optimize it
+    /// away.
+    ///
+    /// NOTE: Alias can be chained.
+    Alias(ScopeIndex),
+
+    Global(GlobalScopeData),
+    Var(VarScopeData),
+    Lexical(LexicalScopeData),
+    Function(FunctionScopeData),
+}
+
+/// Index into ScopeDataList.scopes.
+#[derive(Debug, Clone, Copy, PartialEq)]
+pub struct ScopeIndex {
+    index: usize,
+}
+impl ScopeIndex {
+    fn new(index: usize) -> Self {
+        Self { index }
+    }
+
+    pub fn next(&self) -> Self {
+        Self {
+            index: self.index + 1,
+        }
+    }
+}
+
+impl From<ScopeIndex> for usize {
+    fn from(index: ScopeIndex) -> usize {
+        index.index
+    }
+}
+
+/// A vector of scopes, incrementally populated during analysis.
+/// The goal is to build a `Vec<ScopeData>`.
+#[derive(Debug)]
+pub struct ScopeDataList {
+    /// Uses Option to allow `allocate()` and `populate()` to be called
+    /// separately.
+    scopes: Vec<Option<ScopeData>>,
+}
+
+impl ScopeDataList {
+    pub fn new() -> Self {
+        Self { scopes: Vec::new() }
+    }
+
+    pub fn push(&mut self, scope: ScopeData) -> ScopeIndex {
+        let index = self.scopes.len();
+        self.scopes.push(Some(scope));
+        ScopeIndex::new(index)
+    }
+
+    pub fn allocate(&mut self) -> ScopeIndex {
+        let index = self.scopes.len();
+        self.scopes.push(None);
+        ScopeIndex::new(index)
+    }
+
+    pub fn populate(&mut self, index: ScopeIndex, scope: ScopeData) {
+        self.scopes[usize::from(index)].replace(scope);
+    }
+
+    fn get(&self, index: ScopeIndex) -> &ScopeData {
+        self.scopes[usize::from(index)]
+            .as_ref()
+            .expect("Should be populated")
+    }
+
+    pub fn get_mut(&mut self, index: ScopeIndex) -> &mut ScopeData {
+        self.scopes[usize::from(index)]
+            .as_mut()
+            .expect("Should be populated")
+    }
+}
+
+impl From<ScopeDataList> for Vec<ScopeData> {
+    fn from(list: ScopeDataList) -> Vec<ScopeData> {
+        list.scopes
+            .into_iter()
+            .map(|g| g.expect("Should be populated"))
+            .collect()
+    }
+}
+
+/// The collection of all scope data associated with bindings and scopes in the
+/// AST.
+#[derive(Debug)]
+pub struct ScopeDataMap {
+    scopes: ScopeDataList,
+    global: ScopeIndex,
+
+    /// Associates every AST node that's a scope with an index into `scopes`.
+    non_global: AssociatedData<ScopeIndex>,
+}
+
+impl ScopeDataMap {
+    pub fn new(
+        scopes: ScopeDataList,
+        global: ScopeIndex,
+        non_global: AssociatedData<ScopeIndex>,
+    ) -> Self {
+        Self {
+            scopes,
+            global,
+            non_global,
+        }
+    }
+
+    pub fn get_global_index(&self) -> ScopeIndex {
+        self.global
+    }
+
+    pub fn get_global_at(&self, index: ScopeIndex) -> &GlobalScopeData {
+        match self.scopes.get(index) {
+            ScopeData::Global(scope) => scope,
+            _ => panic!("Unexpected scope data for global"),
+        }
+    }
+
+    pub fn get_index<NodeT>(&self, node: &NodeT) -> ScopeIndex
+    where
+        NodeT: SourceLocationAccessor + NodeTypeIdAccessor,
+    {
+        self.non_global
+            .get(node)
+            .expect("There should be a scope data associated")
+            .clone()
+    }
+
+    pub fn get_lexical_at(&self, index: ScopeIndex) -> &LexicalScopeData {
+        match self.scopes.get(index) {
+            ScopeData::Lexical(scope) => scope,
+            _ => panic!("Unexpected scope data for lexical"),
+        }
+    }
+
+    pub fn get_lexical_at_mut(&mut self, index: ScopeIndex) -> &mut LexicalScopeData {
+        match self.scopes.get_mut(index) {
+            ScopeData::Lexical(scope) => scope,
+            _ => panic!("Unexpected scope data for lexical"),
+        }
+    }
+
+    pub fn get_function_at_mut(&mut self, index: ScopeIndex) -> &mut FunctionScopeData {
+        match self.scopes.get_mut(index) {
+            ScopeData::Function(scope) => scope,
+            _ => panic!("Unexpected scope data for function"),
+        }
+    }
+
+    pub fn is_alias(&mut self, index: ScopeIndex) -> bool {
+        match self.scopes.get(index) {
+            ScopeData::Alias(_) => true,
+            _ => false,
+        }
+    }
+}
+
+impl From<ScopeDataMap> for Vec<ScopeData> {
+    fn from(map: ScopeDataMap) -> Vec<ScopeData> {
+        map.scopes.into()
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/scope_notes.rs b/third_party/rust/jsparagus-stencil/src/scope_notes.rs
new file mode 100644
index 0000000000..fb9a494775
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/scope_notes.rs
@@ -0,0 +1,81 @@
+use crate::bytecode_offset::BytecodeOffset;
+use crate::gcthings::GCThingIndex;
+
+/// Maps to js::ScopeNote in m-c/js/src/vm//JSScript.h.
+#[derive(Debug)]
+pub struct ScopeNote {
+    pub index: GCThingIndex,
+    pub start: BytecodeOffset,
+    pub end: BytecodeOffset,
+    pub parent: Option<ScopeNoteIndex>,
+}
+
+impl ScopeNote {
+    fn new(index: GCThingIndex, start: BytecodeOffset, parent: Option<ScopeNoteIndex>) -> Self {
+        Self {
+            index,
+            start: start.clone(),
+            end: start,
+            parent,
+        }
+    }
+}
+
+/// Index into ScopeNoteList.notes.
+#[derive(Debug, Clone, Copy)]
+pub struct ScopeNoteIndex {
+    index: usize,
+}
+
+impl ScopeNoteIndex {
+    fn new(index: usize) -> Self {
+        Self { index }
+    }
+}
+
+impl From<ScopeNoteIndex> for usize {
+    fn from(index: ScopeNoteIndex) -> usize {
+        index.index
+    }
+}
+
+/// List of scope notes.
+///
+/// Maps to JSScript::scopeNotes() in js/src/vm/JSScript.h.
+pub struct ScopeNoteList {
+    notes: Vec<ScopeNote>,
+}
+
+impl ScopeNoteList {
+    pub fn new() -> Self {
+        Self { notes: Vec::new() }
+    }
+
+    pub fn enter_scope(
+        &mut self,
+        index: GCThingIndex,
+        offset: BytecodeOffset,
+        parent: Option<ScopeNoteIndex>,
+    ) -> ScopeNoteIndex {
+        let note_index = self.notes.len();
+        self.notes.push(ScopeNote::new(index, offset, parent));
+        ScopeNoteIndex::new(note_index)
+    }
+
+    pub fn get_scope_hole_gcthing_index(&self, scope_note_index: &ScopeNoteIndex) -> GCThingIndex {
+        self.notes
+            .get(scope_note_index.index)
+            .expect("Scope note should exist")
+            .index
+    }
+
+    pub fn leave_scope(&mut self, index: ScopeNoteIndex, offset: BytecodeOffset) {
+        self.notes[usize::from(index)].end = offset;
+    }
+}
+
+impl From<ScopeNoteList> for Vec<ScopeNote> {
+    fn from(list: ScopeNoteList) -> Vec<ScopeNote> {
+        list.notes
+    }
+}
diff --git a/third_party/rust/jsparagus-stencil/src/script.rs b/third_party/rust/jsparagus-stencil/src/script.rs
new file mode 100644
index 0000000000..ab97b88177
--- /dev/null
+++ b/third_party/rust/jsparagus-stencil/src/script.rs
@@ -0,0 +1,574 @@
+//! The result of emitter
+
+use crate::frame_slot::FrameSlot;
+use crate::function::FunctionFlags;
+use crate::gcthings::GCThing;
+use crate::scope::ScopeIndex;
+use crate::scope_notes::ScopeNote;
+use ast::source_atom_set::SourceAtomSetIndex;
+
+// WARNING
+// The following section is generated by update_stencil.py.
+// Do mot modify manually.
+//
+// @@@@ BEGIN TYPES @@@@
+#[derive(Debug, Clone, Copy)]
+pub enum ImmutableScriptFlagsEnum {
+    #[allow(dead_code)]
+    IsForEval = 1 << 0,
+    #[allow(dead_code)]
+    IsModule = 1 << 1,
+    #[allow(dead_code)]
+    IsFunction = 1 << 2,
+    #[allow(dead_code)]
+    SelfHosted = 1 << 3,
+    #[allow(dead_code)]
+    ForceStrict = 1 << 4,
+    #[allow(dead_code)]
+    HasNonSyntacticScope = 1 << 5,
+    #[allow(dead_code)]
+    NoScriptRval = 1 << 6,
+    #[allow(dead_code)]
+    TreatAsRunOnce = 1 << 7,
+    #[allow(dead_code)]
+    Strict = 1 << 8,
+    #[allow(dead_code)]
+    HasModuleGoal = 1 << 9,
+    #[allow(dead_code)]
+    HasInnerFunctions = 1 << 10,
+    #[allow(dead_code)]
+    HasDirectEval = 1 << 11,
+    #[allow(dead_code)]
+    BindingsAccessedDynamically = 1 << 12,
+    #[allow(dead_code)]
+    HasCallSiteObj = 1 << 13,
+    #[allow(dead_code)]
+    IsAsync = 1 << 14,
+    #[allow(dead_code)]
+    IsGenerator = 1 << 15,
+    #[allow(dead_code)]
+    FunHasExtensibleScope = 1 << 16,
+    #[allow(dead_code)]
+    FunctionHasThisBinding = 1 << 17,
+    #[allow(dead_code)]
+    NeedsHomeObject = 1 << 18,
+    #[allow(dead_code)]
+    IsDerivedClassConstructor = 1 << 19,
+    #[allow(dead_code)]
+    IsSyntheticFunction = 1 << 20,
+    #[allow(dead_code)]
+    UseMemberInitializers = 1 << 21,
+    #[allow(dead_code)]
+    HasRest = 1 << 22,
+    #[allow(dead_code)]
+    NeedsFunctionEnvironmentObjects = 1 << 23,
+    #[allow(dead_code)]
+    FunctionHasExtraBodyVarScope = 1 << 24,
+    #[allow(dead_code)]
+    ShouldDeclareArguments = 1 << 25,
+    #[allow(dead_code)]
+    NeedsArgsObj = 1 << 26,
+    #[allow(dead_code)]
+    HasMappedArgsObj = 1 << 27,
+    #[allow(dead_code)]
+    IsInlinableLargeFunction = 1 << 28,
+    #[allow(dead_code)]
+    FunctionHasNewTargetBinding = 1 << 29,
+}
+
+#[derive(Debug, Clone, Copy)]
+pub enum MutableScriptFlagsEnum {
+    #[allow(dead_code)]
+    HasRunOnce = 1 << 8,
+    #[allow(dead_code)]
+    HasBeenCloned = 1 << 9,
+    #[allow(dead_code)]
+    HasScriptCounts = 1 << 10,
+    #[allow(dead_code)]
+    HasDebugScript = 1 << 11,
+    #[allow(dead_code)]
+    AllowRelazify = 1 << 14,
+    #[allow(dead_code)]
+    SpewEnabled = 1 << 15,
+    #[allow(dead_code)]
+    NeedsFinalWarmUpCount = 1 << 16,
+    #[allow(dead_code)]
+    BaselineDisabled = 1 << 17,
+    #[allow(dead_code)]
+    IonDisabled = 1 << 18,
+    #[allow(dead_code)]
+    Uninlineable = 1 << 19,
+    #[allow(dead_code)]
+    FailedBoundsCheck = 1 << 21,
+    #[allow(dead_code)]
+    HadLICMInvalidation = 1 << 22,
+    #[allow(dead_code)]
+    HadReorderingBailout = 1 << 23,
+    #[allow(dead_code)]
+    HadEagerTruncationBailout = 1 << 24,
+    #[allow(dead_code)]
+    FailedLexicalCheck = 1 << 25,
+    #[allow(dead_code)]
+    HadSpeculativePhiBailout = 1 << 26,
+    #[allow(dead_code)]
+    HadUnboxFoldingBailout = 1 << 27,
+}
+
+// @@@@ END TYPES @@@@
+
+#[derive(Debug)]
+pub struct ImmutableScriptFlags {
+    value: u32,
+}
+
+impl ImmutableScriptFlags {
+    pub fn new() -> Self {
+        Self { value: 0 }
+    }
+
+    pub fn from_raw(bits: u32) -> Self {
+        Self { value: bits }
+    }
+
+    pub fn set(&mut self, bit: ImmutableScriptFlagsEnum) {
+        self.value |= bit as u32;
+    }
+
+    pub fn has(&self, bit: ImmutableScriptFlagsEnum) -> bool {
+        (self.value & bit as u32) != 0
+    }
+
+    pub fn reset(&mut self, bit: ImmutableScriptFlagsEnum) {
+        self.value &= !(bit as u32)
+    }
+}
+
+impl From<ImmutableScriptFlags> for u32 {
+    fn from(flags: ImmutableScriptFlags) -> u32 {
+        flags.value
+    }
+}
+
+/// Maps to js::ImmutableScriptData in m-c/js/src/vm/SharedStencil.h.
+#[derive(Debug)]
+pub struct ImmutableScriptData {
+    pub main_offset: u32,
+    pub nfixed: FrameSlot,
+    pub nslots: u32,
+    pub body_scope_index: u32,
+    pub num_ic_entries: u32,
+    pub fun_length: u16,
+    pub bytecode: Vec<u8>,
+    pub scope_notes: Vec<ScopeNote>,
+    // TODO: Add resume_offsets and try_notes.
+}
+
+/// Index into ImmutableScriptDataList.scripts.
+#[derive(Debug, Clone, Copy)]
+pub struct ImmutableScriptDataIndex {
+    index: usize,
+}
+
+impl ImmutableScriptDataIndex {
+    fn new(index: usize) -> Self {
+        Self { index }
+    }
+}
+
+impl From<ImmutableScriptDataIndex> for usize {
+    fn from(index: ImmutableScriptDataIndex) -> usize {
+        index.index
+    }
+}
+
+/// List of ImmutableScriptData.
+#[derive(Debug)]
+pub struct ImmutableScriptDataList {
+    /// Uses Option to allow `allocate()` and `populate()` to be called
+    /// separately.
+    items: Vec<Option<ImmutableScriptData>>,
+}
+
+impl ImmutableScriptDataList {
+    pub fn new() -> Self {
+        Self { items: Vec::new() }
+    }
+
+    pub fn push(&mut self, script: ImmutableScriptData) -> ImmutableScriptDataIndex {
+        let index = self.items.len();
+        self.items.push(Some(script));
+        ImmutableScriptDataIndex::new(index)
+    }
+
+    pub fn allocate(&mut self) -> ImmutableScriptDataIndex {
+        let index = self.items.len();
+        self.items.push(None);
+        ImmutableScriptDataIndex::new(index)
+    }
+
+    pub fn populate(&mut self, index: ImmutableScriptDataIndex, script: ImmutableScriptData) {
+        self.items[usize::from(index)].replace(script);
+    }
+}
+
+impl From<ImmutableScriptDataList> for Vec<ImmutableScriptData> {
+    fn from(list: ImmutableScriptDataList) -> Vec<ImmutableScriptData> {
+        list.items
+            .into_iter()
+            .map(|g| g.expect("Should be populated"))
+            .collect()
+    }
+}
+
+#[derive(Debug, Clone)]
+pub struct SourceExtent {
+    pub source_start: u32,
+    pub source_end: u32,
+    pub to_string_start: u32,
+    pub to_string_end: u32,
+
+    pub lineno: u32,
+    pub column: u32,
+}
+
+impl SourceExtent {
+    fn new() -> Self {
+        Self {
+            source_start: 0,
+            source_end: 0,
+            to_string_start: 0,
+            to_string_end: 0,
+
+            lineno: 0,
+            column: 0,
+        }
+    }
+
+    pub fn top_level_script(length: u32, lineno: u32, column: u32) -> Self {
+        Self {
+            source_start: 0,
+            source_end: length,
+            to_string_start: 0,
+            to_string_end: length,
+
+            lineno,
+            column,
+        }
+    }
+}
+
+/// Maps to js::frontend::ScriptStencil in m-c/js/src/frontend/Stencil.h.
+#[derive(Debug)]
+pub struct ScriptStencil {
+    // Fields for BaseScript.
+    // Used by:
+    //   * Global script
+    //   * Eval
+    //   * Module
+    //   * non-lazy Function (except asm.js module)
+    //   * lazy Function (cannot be asm.js module)
+    /// See `BaseScript::immutableFlags_`.
+    pub immutable_flags: ImmutableScriptFlags,
+
+    /// For top level script and non-lazy function script,
+    /// this is a list of GC things referred by bytecode and scope.
+    ///
+    /// For lazy function script, this contains the list of inner functions,
+    /// followed by the list of names defined and closed over by inner script.
+    /// The list of names are delimited by GCThing::Null for each scope.
+    ///
+    /// The order of scopes are depth-first post-order, and names inside each
+    /// scope is in not defined.
+    ///
+    /// Trailing scopes without any names are omitted for space efficiency.
+    pub gcthings: Vec<GCThing>,
+
+    /// See `BaseScript::sharedData_`.
+    pub immutable_script_data: Option<ImmutableScriptDataIndex>,
+
+    /// The location of this script in the source.
+    pub extent: SourceExtent,
+
+    // Fields for JSFunction.
+    // Used by:
+    //   * non-lazy Function
+    //   * lazy Function
+    //   * asm.js module
+    /// The explicit or implicit name of the function. The FunctionFlags
+    /// indicate the kind of name.
+    pub fun_name: Option<SourceAtomSetIndex>,
+
+    /// See `JSFunction::nargs_`.
+    pub fun_nargs: u16,
+
+    /// See: `FunctionFlags`.
+    pub fun_flags: FunctionFlags,
+
+    /// If this ScriptStencil refers to a lazy child of the function being
+    /// compiled, this field holds the child's immediately enclosing scope's
+    /// index. Once compilation succeeds, we will store the scope pointed by
+    /// this in the child's BaseScript.  (Debugger may become confused if lazy
+    /// scripts refer to partially initialized enclosing scopes, so we must
+    /// avoid storing the scope in the BaseScript until compilation has
+    /// completed successfully.)
+    pub lazy_function_enclosing_scope_index: Option<ScopeIndex>,
+
+    /// This function is a standalone function that is not syntactically part of
+    /// another script. Eg. Created by `new Function("")`.
+    pub is_standalone_function: bool,
+
+    /// This is set by the emitter of the enclosing script when a
+    /// reference to this function is generated.
+    pub was_function_emitted: bool,
+
+    /// This function should be marked as a singleton. It is expected to be
+    /// defined at most once. This is a heuristic only and does not affect
+    /// correctness.
+    pub is_singleton_function: bool,
+}
+
+impl ScriptStencil {
+    fn empty_top_level_script() -> Self {
+        Self {
+            immutable_flags: ImmutableScriptFlags::new(),
+            gcthings: Vec::new(),
+            immutable_script_data: None,
+            extent: SourceExtent::new(),
+            fun_name: None,
+            fun_nargs: 0,
+            fun_flags: FunctionFlags::empty(),
+            lazy_function_enclosing_scope_index: None,
+            is_standalone_function: false,
+            was_function_emitted: false,
+            is_singleton_function: false,
+        }
+    }
+
+    pub fn top_level_script(
+        gcthings: Vec<GCThing>,
+        immutable_script_data: ImmutableScriptDataIndex,
+        extent: SourceExtent,
+    ) -> Self {
+        Self {
+            immutable_flags: ImmutableScriptFlags::new(),
+            gcthings,
+            immutable_script_data: Some(immutable_script_data),
+            extent,
+            fun_name: None,
+            fun_nargs: 0,
+            fun_flags: FunctionFlags::empty(),
+            lazy_function_enclosing_scope_index: None,
+            is_standalone_function: false,
+            was_function_emitted: false,
+            is_singleton_function: false,
+        }
+    }
+
+    pub fn lazy_function(
+        extent: SourceExtent,
+        fun_name: Option<SourceAtomSetIndex>,
+        is_generator: bool,
+        is_async: bool,
+        fun_flags: FunctionFlags,
+        lazy_function_enclosing_scope_index: Option<ScopeIndex>,
+    ) -> Self {
+        let mut flags = ImmutableScriptFlagsEnum::IsFunction as u32;
+        if is_generator {
+            flags |= ImmutableScriptFlagsEnum::IsGenerator as u32;
+        }
+        if is_async {
+            flags |= ImmutableScriptFlagsEnum::IsAsync as u32;
+        }
+
+        Self {
+            immutable_flags: ImmutableScriptFlags::from_raw(flags),
+            gcthings: Vec::new(),
+            immutable_script_data: None,
+            extent,
+            fun_name,
+            fun_nargs: 0,
+            fun_flags,
+            lazy_function_enclosing_scope_index,
+            is_standalone_function: false,
+            was_function_emitted: false,
+            is_singleton_function: false,
+        }
+    }
+
+    pub fn is_function(&self) -> bool {
+        self.immutable_flags
+            .has(ImmutableScriptFlagsEnum::IsFunction)
+    }
+
+    pub fn is_non_lazy_function(&self) -> bool {
+        self.is_function() && self.immutable_script_data.is_some()
+    }
+
+    pub fn is_lazy_function(&self) -> bool {
+        self.is_function() && self.immutable_script_data.is_none()
+    }
+
+    pub fn set_function_has_this_binding(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::FunctionHasThisBinding);
+    }
+
+    pub fn set_has_rest(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags.set(ImmutableScriptFlagsEnum::HasRest);
+    }
+
+    pub fn set_needs_function_environment_objects(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::NeedsFunctionEnvironmentObjects);
+    }
+
+    pub fn set_function_has_extra_body_var_scope(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::FunctionHasExtraBodyVarScope);
+    }
+
+    pub fn set_should_declare_arguments(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::ShouldDeclareArguments);
+    }
+
+    pub fn set_needs_args_obj(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::NeedsArgsObj);
+    }
+
+    pub fn set_has_mapped_args_obj(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::HasMappedArgsObj);
+    }
+
+    pub fn set_function_has_new_target_binding(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::FunctionHasNewTargetBinding);
+    }
+
+    pub fn is_arrow_function(&self) -> bool {
+        self.is_function() && self.fun_flags.is_arrow()
+    }
+
+    pub fn set_fun_name(&mut self, name: SourceAtomSetIndex) {
+        debug_assert!(self.is_function());
+        self.fun_name = Some(name);
+    }
+
+    pub fn fun_name<'a>(&'a self) -> &'a Option<SourceAtomSetIndex> {
+        debug_assert!(self.is_function());
+        &self.fun_name
+    }
+
+    pub fn add_fun_nargs(&mut self) {
+        debug_assert!(self.is_function());
+        self.fun_nargs += 1;
+    }
+
+    /// source_start should point the start of parameter for functions.
+    pub fn set_source_starts(&mut self, source_start: usize) {
+        self.extent.source_start = source_start as u32;
+    }
+
+    /// to_string_end should point the end of function body for function,
+    /// and the end of class for constructor.
+    pub fn set_to_string_end(&mut self, to_string_end: usize) {
+        self.extent.to_string_end = to_string_end as u32;
+    }
+
+    /// source_end should point the end of function body.
+    pub fn set_source_end(&mut self, source_end: usize) {
+        self.extent.source_end = source_end as u32;
+    }
+
+    pub fn set_function_emitted(&mut self) {
+        self.was_function_emitted = true;
+    }
+
+    pub fn push_inner_function(&mut self, fun: ScriptStencilIndex) {
+        self.immutable_flags
+            .set(ImmutableScriptFlagsEnum::HasInnerFunctions);
+        self.gcthings.push(GCThing::Function(fun));
+    }
+
+    pub fn push_closed_over_bindings(&mut self, name: SourceAtomSetIndex) {
+        debug_assert!(self.is_lazy_function());
+        self.gcthings.push(GCThing::Atom(name));
+    }
+
+    pub fn push_closed_over_bindings_delimiter(&mut self) {
+        debug_assert!(self.is_lazy_function());
+        self.gcthings.push(GCThing::Null);
+    }
+}
+
+/// Index into ScriptStencilList.scripts.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+pub struct ScriptStencilIndex {
+    index: usize,
+}
+
+impl ScriptStencilIndex {
+    fn new(index: usize) -> Self {
+        Self { index }
+    }
+}
+
+impl From<ScriptStencilIndex> for usize {
+    fn from(index: ScriptStencilIndex) -> usize {
+        index.index
+    }
+}
+
+/// List of stencil scripts.
+#[derive(Debug)]
+pub struct ScriptStencilList {
+    scripts: Vec<ScriptStencil>,
+}
+
+impl ScriptStencilList {
+    pub fn new() -> Self {
+        Self {
+            scripts: Vec::new(),
+        }
+    }
+
+    pub fn new_with_empty_top_level() -> Self {
+        Self {
+            scripts: vec![ScriptStencil::empty_top_level_script()],
+        }
+    }
+
+    pub fn push(&mut self, script: ScriptStencil) -> ScriptStencilIndex {
+        let index = self.scripts.len();
+        self.scripts.push(script);
+        ScriptStencilIndex::new(index)
+    }
+
+    pub fn get<'a>(&'a self, index: ScriptStencilIndex) -> &'a ScriptStencil {
+        &self.scripts[usize::from(index)]
+    }
+
+    pub fn get_mut<'a>(&'a mut self, index: ScriptStencilIndex) -> &'a mut ScriptStencil {
+        &mut self.scripts[usize::from(index)]
+    }
+
+    pub fn set_top_level(&mut self, top_level: ScriptStencil) {
+        self.scripts[0] = top_level;
+    }
+}
+
+impl From<ScriptStencilList> for Vec<ScriptStencil> {
+    fn from(list: ScriptStencilList) -> Vec<ScriptStencil> {
+        list.scripts.into_iter().collect()
+    }
+}