Adding upstream version 110.0.1.upstream/110.0.1upstream

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

45 files changed, 9767 insertions, 0 deletions

diff --git a/js/src/devtools/rootAnalysis/CFG.js b/js/src/devtools/rootAnalysis/CFG.js
new file mode 100644
index 0000000000..f8e71fc818
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/CFG.js
@@ -0,0 +1,930 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+// Utility code for traversing the JSON data structures produced by sixgill.
+
+"use strict";
+
+var TRACING = false;
+
+// Find all points (positions within the code) of the body given by the list of
+// bodies and the blockId to match (which will specify an outer function or a
+// loop within it), recursing into loops if needed.
+function findAllPoints(bodies, blockId, bits)
+{
+    var points = [];
+    var body;
+
+    for (var xbody of bodies) {
+        if (sameBlockId(xbody.BlockId, blockId)) {
+            assert(!body);
+            body = xbody;
+        }
+    }
+    assert(body);
+
+    if (!("PEdge" in body))
+        return;
+    for (var edge of body.PEdge) {
+        points.push([body, edge.Index[0], bits]);
+        if (edge.Kind == "Loop")
+            points.push(...findAllPoints(bodies, edge.BlockId, bits));
+    }
+
+    return points;
+}
+
+// Visitor of a graph of <body, ppoint> vertexes and sixgill-generated edges,
+// where the edges represent the actual computation happening.
+//
+// Uses the syntax `var Visitor = class { ... }` rather than `class Visitor`
+// to allow reloading this file with the JS debugger.
+var Visitor = class {
+    constructor(bodies) {
+        this.visited_bodies = new Map();
+        for (const body of bodies) {
+            this.visited_bodies.set(body, new Map());
+        }
+    }
+
+    // Returns whether we should keep going after seeing this <body, ppoint>
+    // pair. Also records it as visited.
+    visit(body, ppoint, info) {
+        const visited = this.visited_bodies.get(body);
+        const existing = visited.get(ppoint);
+        const action = this.next_action(existing, info);
+        const merged = this.merge_info(existing, info);
+        visited.set(ppoint, merged);
+        return [action, merged];
+    }
+
+    // Default implementation does a basic "only visit nodes once" search.
+    // (Whether this is BFS/DFS/other is determined by the caller.)
+
+    // Override if you need to revisit nodes. Valid actions are "continue",
+    // "prune", and "done". "continue" means continue with the search. "prune"
+    // means stop at this node, only continue on other edges. "done" means the
+    // whole search is complete even if unvisited nodes remain.
+    next_action(prev, current) { return prev ? "prune" : "continue"; }
+
+    // Update the info at a node. If this is the first time the node has been
+    // seen, `prev` will be undefined. `current` will be the info computed by
+    // `extend_path`. The node will be updated with the return value.
+    merge_info(prev, current) { return true; }
+
+    // Prepend `edge` to the info stored at the successor node, returning
+    // the updated info value. This should be overridden by pretty much any
+    // subclass, as a traversal's semantics are largely determined by this method.
+    extend_path(edge, body, ppoint, successor_path) { return true; }
+};
+
+function findMatchingBlock(bodies, blockId) {
+    for (const body of bodies) {
+        if (sameBlockId(body.BlockId, blockId)) {
+            return body;
+        }
+    }
+    assert(false);
+}
+
+// Perform a mostly breadth-first search through the graph of <body, ppoints>.
+// This is only mostly breadth-first because the visitor decides whether to
+// stop searching when it sees an already-visited node. It can choose to
+// re-visit a node in order to find "better" paths that include a node more
+// than once.
+//
+// The return value depends on how the search finishes. If a 'done' action
+// is returned by visitor.visit(), use the information returned by
+// that call. If the search completes without reaching the entry point of
+// the function (the "root"), return null. If the search manages to reach
+// the root, return the value of the `result_if_reached_root` parameter.
+//
+// This allows this function to be used in different ways. If the visitor
+// associates a value with each node that chains onto its successors
+// (or predecessors in the "upwards" search order), then this will return
+// a complete path through the graph. But this can also be used to test
+// whether a condition holds (eg "the exit point is reachable after
+// calling SomethingImportant()"), in which case no path is needed and the
+// visitor will cause the return value to be a simple boolean (or null
+// if it terminates the search before reaching the root.)
+//
+// The information returned by the visitor for a node is often called
+// `path` in the code below, even though it may not represent a path.
+//
+function BFS_upwards(start_body, start_ppoint, bodies, visitor,
+                     initial_successor_info={},
+                     result_if_reached_root=null)
+{
+    const work = [[start_body, start_ppoint, null, initial_successor_info]];
+    if (TRACING) {
+        printErr(`BFS start at ${blockIdentifier(start_body)}:${start_ppoint}`);
+    }
+
+    let reached_root = false;
+    while (work.length > 0) {
+        const [body, ppoint, edgeToAdd, successor_path] = work.shift();
+        if (TRACING) {
+            printErr(`prepending edge from ${ppoint} to state '${successor_path}'`);
+        }
+        let path = visitor.extend_path(edgeToAdd, body, ppoint, successor_path);
+
+        const [action,  merged_path] = visitor.visit(body, ppoint, path);
+        if (action === "done") {
+            return merged_path;
+        }
+        if (action === "prune") {
+            // Do not push anything else to the work queue, but continue processing
+            // other branches.
+            continue;
+        }
+        assert(action == "continue");
+        path = merged_path;
+
+        const predecessors = getPredecessors(body);
+        for (const edge of (predecessors[ppoint] || [])) {
+            if (edge.Kind == "Loop") {
+                // Propagate the search into the exit point of the loop body.
+                const loopBody = findMatchingBlock(bodies, edge.BlockId);
+                const loopEnd = loopBody.Index[1];
+                work.push([loopBody, loopEnd, null, path]);
+                // Don't continue to predecessors here without going through
+                // the loop. (The points in this body that enter the loop will
+                // be traversed when we reach the entry point of the loop.)
+            } else {
+                work.push([body, edge.Index[0], edge, path]);
+            }
+        }
+
+        // Check for hitting the entry point of a loop body.
+        if (ppoint == body.Index[0] && body.BlockId.Kind == "Loop") {
+            // Propagate to outer body parents that enter the loop body.
+            for (const parent of (body.BlockPPoint || [])) {
+                const parentBody = findMatchingBlock(bodies, parent.BlockId);
+                work.push([parentBody, parent.Index, null, path]);
+            }
+
+            // This point is also preceded by the *end* of this loop, for the
+            // previous iteration.
+            work.push([body, body.Index[1], null, path]);
+        }
+
+        // Check for reaching the root of the function.
+        if (body === start_body && ppoint == body.Index[0]) {
+            reached_root = true;
+        }
+    }
+
+    // The search space was exhausted without finding a 'done' state. That
+    // might be because all search paths were pruned before reaching the entry
+    // point of the function, in which case reached_root will be false. (If
+    // reached_root is true, then we may still not have visited the entire
+    // graph, if some paths were pruned but at least one made it to the root.)
+    return reached_root ? result_if_reached_root : null;
+}
+
+// Given the CFG for the constructor call of some RAII, return whether the
+// given edge is the matching destructor call.
+function isMatchingDestructor(constructor, edge)
+{
+    if (edge.Kind != "Call")
+        return false;
+    var callee = edge.Exp[0];
+    if (callee.Kind != "Var")
+        return false;
+    var variable = callee.Variable;
+    assert(variable.Kind == "Func");
+    if (variable.Name[1].charAt(0) != '~')
+        return false;
+
+    // Note that in some situations, a regular function can begin with '~', so
+    // we don't necessarily have a destructor in hand. This is probably a
+    // sixgill artifact, but in js::wasm::ModuleGenerator::~ModuleGenerator, a
+    // templatized static inline EraseIf is invoked, and it gets named ~EraseIf
+    // for some reason.
+    if (!("PEdgeCallInstance" in edge))
+        return false;
+
+    var constructExp = constructor.PEdgeCallInstance.Exp;
+    assert(constructExp.Kind == "Var");
+
+    var destructExp = edge.PEdgeCallInstance.Exp;
+    if (destructExp.Kind != "Var")
+        return false;
+
+    return sameVariable(constructExp.Variable, destructExp.Variable);
+}
+
+// Return all calls within the RAII scope of any constructor matched by
+// isConstructor(). (Note that this would be insufficient if you needed to
+// treat each instance separately, such as when different regions of a function
+// body were guarded by these constructors and you needed to do something
+// different with each.)
+function allRAIIGuardedCallPoints(typeInfo, bodies, body, isConstructor)
+{
+    if (!("PEdge" in body))
+        return [];
+
+    var points = [];
+
+    for (var edge of body.PEdge) {
+        if (edge.Kind != "Call")
+            continue;
+        var callee = edge.Exp[0];
+        if (callee.Kind != "Var")
+            continue;
+        var variable = callee.Variable;
+        assert(variable.Kind == "Func");
+        const bits = isConstructor(typeInfo, edge.Type, variable.Name);
+        if (!bits)
+            continue;
+        if (!("PEdgeCallInstance" in edge))
+            continue;
+        if (edge.PEdgeCallInstance.Exp.Kind != "Var")
+            continue;
+
+        points.push(...pointsInRAIIScope(bodies, body, edge, bits));
+    }
+
+    return points;
+}
+
+// Test whether the given edge is the constructor corresponding to the given
+// destructor edge.
+function isMatchingConstructor(destructor, edge)
+{
+    if (edge.Kind != "Call")
+        return false;
+    var callee = edge.Exp[0];
+    if (callee.Kind != "Var")
+        return false;
+    var variable = callee.Variable;
+    if (variable.Kind != "Func")
+        return false;
+    var name = readable(variable.Name[0]);
+    var destructorName = readable(destructor.Exp[0].Variable.Name[0]);
+    var match = destructorName.match(/^(.*?::)~(\w+)\(/);
+    if (!match) {
+        printErr("Unhandled destructor syntax: " + destructorName);
+        return false;
+    }
+    var constructorSubstring = match[1] + match[2];
+    if (name.indexOf(constructorSubstring) == -1)
+        return false;
+
+    var destructExp = destructor.PEdgeCallInstance.Exp;
+    if (destructExp.Kind != "Var")
+        return false;
+
+    var constructExp = edge.PEdgeCallInstance.Exp;
+    if (constructExp.Kind != "Var")
+        return false;
+
+    return sameVariable(constructExp.Variable, destructExp.Variable);
+}
+
+function findMatchingConstructor(destructorEdge, body, warnIfNotFound=true)
+{
+    var worklist = [destructorEdge];
+    var predecessors = getPredecessors(body);
+    while(worklist.length > 0) {
+        var edge = worklist.pop();
+        if (isMatchingConstructor(destructorEdge, edge))
+            return edge;
+        if (edge.Index[0] in predecessors) {
+            for (var e of predecessors[edge.Index[0]])
+                worklist.push(e);
+        }
+    }
+    if (warnIfNotFound)
+        printErr("Could not find matching constructor!");
+    return undefined;
+}
+
+function pointsInRAIIScope(bodies, body, constructorEdge, bits) {
+    var seen = {};
+    var worklist = [constructorEdge.Index[1]];
+    var points = [];
+    while (worklist.length) {
+        var point = worklist.pop();
+        if (point in seen)
+            continue;
+        seen[point] = true;
+        points.push([body, point, bits]);
+        var successors = getSuccessors(body);
+        if (!(point in successors))
+            continue;
+        for (var nedge of successors[point]) {
+            if (isMatchingDestructor(constructorEdge, nedge))
+                continue;
+            if (nedge.Kind == "Loop")
+                points.push(...findAllPoints(bodies, nedge.BlockId, bits));
+            worklist.push(nedge.Index[1]);
+        }
+    }
+
+    return points;
+}
+
+function isImmobileValue(exp) {
+    if (exp.Kind == "Int" && exp.String == "0") {
+        return true;
+    }
+    return false;
+}
+
+function expressionIsVariableAddress(exp, variable)
+{
+    while (exp.Kind == "Fld")
+        exp = exp.Exp[0];
+    return exp.Kind == "Var" && sameVariable(exp.Variable, variable);
+}
+
+function edgeTakesVariableAddress(edge, variable, body)
+{
+    if (ignoreEdgeUse(edge, variable, body))
+        return false;
+    if (ignoreEdgeAddressTaken(edge))
+        return false;
+    switch (edge.Kind) {
+    case "Assign":
+        return expressionIsVariableAddress(edge.Exp[1], variable);
+    case "Call":
+        if ("PEdgeCallArguments" in edge) {
+            for (var exp of edge.PEdgeCallArguments.Exp) {
+                if (expressionIsVariableAddress(exp, variable))
+                    return true;
+            }
+        }
+        return false;
+    default:
+        return false;
+    }
+}
+
+// Look at an invocation of a virtual method or function pointer contained in a
+// field, and return the static type of the invocant (or the containing struct,
+// for a function pointer field.)
+function getFieldCallInstanceCSU(edge, field)
+{
+    if ("FieldInstanceFunction" in field) {
+        // We have a 'this'.
+        const instanceExp = edge.PEdgeCallInstance.Exp;
+        if (instanceExp.Kind == 'Drf') {
+            // somevar->foo()
+            return edge.Type.TypeFunctionCSU.Type.Name;
+        } else if (instanceExp.Kind == 'Fld') {
+            // somevar.foo()
+            return instanceExp.Field.FieldCSU.Type.Name;
+        } else if (instanceExp.Kind == 'Index') {
+            // A strange construct.
+            // C++ code: static_cast<JS::CustomAutoRooter*>(this)->trace(trc);
+            // CFG: Call(21,30, this*[-1]{JS::CustomAutoRooter}.trace*(trc*))
+            return instanceExp.Type.Name;
+        } else if (instanceExp.Kind == 'Var') {
+            // C++: reinterpret_cast<SimpleTimeZone*>(gRawGMT)->~SimpleTimeZone();
+            // CFG:
+            //   # icu_64::SimpleTimeZone::icu_64::SimpleTimeZone.__comp_dtor
+            //   [6,7] Call gRawGMT.icu_64::SimpleTimeZone.__comp_dtor ()
+            return field.FieldCSU.Type.Name;
+        } else {
+            printErr("------------------ edge -------------------");
+            printErr(JSON.stringify(edge, null, 4));
+            printErr("------------------ field -------------------");
+            printErr(JSON.stringify(field, null, 4));
+            assert(false, `unrecognized FieldInstanceFunction Kind ${instanceExp.Kind}`);
+        }
+    } else {
+        // somefar.foo() where somevar is a field of some CSU.
+        return field.FieldCSU.Type.Name;
+    }
+}
+
+function expressionUsesVariable(exp, variable)
+{
+    if (exp.Kind == "Var" && sameVariable(exp.Variable, variable))
+        return true;
+    if (!("Exp" in exp))
+        return false;
+    for (var childExp of exp.Exp) {
+        if (expressionUsesVariable(childExp, variable))
+            return true;
+    }
+    return false;
+}
+
+function expressionUsesVariableContents(exp, variable)
+{
+    if (!("Exp" in exp))
+        return false;
+    for (var childExp of exp.Exp) {
+        if (childExp.Kind == 'Drf') {
+            if (expressionUsesVariable(childExp, variable))
+                return true;
+        } else if (expressionUsesVariableContents(childExp, variable)) {
+            return true;
+        }
+    }
+    return false;
+}
+
+// Detect simple |return nullptr;| statements.
+function isReturningImmobileValue(edge, variable)
+{
+    if (variable.Kind == "Return") {
+        if (edge.Exp[0].Kind == "Var" && sameVariable(edge.Exp[0].Variable, variable)) {
+            if (isImmobileValue(edge.Exp[1]))
+                return true;
+        }
+    }
+    return false;
+}
+
+// If the edge uses the given variable's value, return the earliest point at
+// which the use is definite. Usually, that means the source of the edge
+// (anything that reaches that source point will end up using the variable, but
+// there may be other ways to reach the destination of the edge.)
+//
+// Return values are implicitly used at the very last point in the function.
+// This makes a difference: if an RAII class GCs in its destructor, we need to
+// start looking at the final point in the function, not one point back from
+// that, since that would skip over the GCing call.
+//
+// Note that this returns true only if the variable's incoming value is used.
+// So this would return false for 'obj':
+//
+//     obj = someFunction();
+//
+// but these would return true:
+//
+//     obj = someFunction(obj);
+//     obj->foo = someFunction();
+//
+function edgeUsesVariable(edge, variable, body)
+{
+    if (ignoreEdgeUse(edge, variable, body))
+        return 0;
+
+    if (variable.Kind == "Return" && body.Index[1] == edge.Index[1] && body.BlockId.Kind == "Function") {
+        // The last point in the function body is treated as using the return
+        // value. This is the only time the destination point is returned
+        // rather than the source point.
+        return edge.Index[1];
+    }
+
+    var src = edge.Index[0];
+
+    switch (edge.Kind) {
+
+    case "Assign": {
+        // Detect `Return := nullptr`.
+        if (isReturningImmobileValue(edge, variable))
+            return 0;
+        const [lhs, rhs] = edge.Exp;
+        // Detect `lhs := ...variable...`
+        if (expressionUsesVariable(rhs, variable))
+            return src;
+        // Detect `...variable... := rhs` but not `variable := rhs`. The latter
+        // overwrites the previous value of `variable` without using it.
+        if (expressionUsesVariable(lhs, variable) && !expressionIsVariable(lhs, variable))
+            return src;
+        return 0;
+    }
+
+    case "Assume":
+        return expressionUsesVariableContents(edge.Exp[0], variable) ? src : 0;
+
+    case "Call": {
+        const callee = edge.Exp[0];
+        if (expressionUsesVariable(callee, variable))
+            return src;
+        if ("PEdgeCallInstance" in edge) {
+            if (expressionUsesVariable(edge.PEdgeCallInstance.Exp, variable)) {
+                if (edgeStartsValueLiveRange(edge, variable)) {
+                    // If the variable is being constructed, then the incoming
+                    // value is not used here; it didn't exist before
+                    // construction. (The analysis doesn't get told where
+                    // variables are defined, so must infer it from
+                    // construction. If the variable does not have a
+                    // constructor, its live range may be larger than it really
+                    // ought to be if it is defined within a loop body, but
+                    // that is conservative.)
+                } else {
+                    return src;
+                }
+            }
+        }
+        if ("PEdgeCallArguments" in edge) {
+            for (var exp of edge.PEdgeCallArguments.Exp) {
+                if (expressionUsesVariable(exp, variable))
+                    return src;
+            }
+        }
+        if (edge.Exp.length == 1)
+            return 0;
+
+        // Assigning call result to a variable.
+        const lhs = edge.Exp[1];
+        if (expressionUsesVariable(lhs, variable) && !expressionIsVariable(lhs, variable))
+            return src;
+        return 0;
+    }
+
+    case "Loop":
+        return 0;
+
+    case "Assembly":
+        return 0;
+
+    default:
+        assert(false);
+    }
+}
+
+function expressionIsVariable(exp, variable)
+{
+    return exp.Kind == "Var" && sameVariable(exp.Variable, variable);
+}
+
+function expressionIsMethodOnVariable(exp, variable)
+{
+    // This might be calling a method on a base class, in which case exp will
+    // be an unnamed field of the variable instead of the variable itself.
+    while (exp.Kind == "Fld" && exp.Field.Name[0].startsWith("field:"))
+        exp = exp.Exp[0];
+
+    return exp.Kind == "Var" && sameVariable(exp.Variable, variable);
+}
+
+// Return whether the edge starts the live range of a variable's value, by setting
+// it to some new value. Examples of starting obj's live range:
+//
+//     obj = foo;
+//     obj = foo();
+//     obj = foo(obj);         // uses previous value but then sets to new value
+//     SomeClass obj(true, 1); // constructor
+//
+function edgeStartsValueLiveRange(edge, variable)
+{
+    // Direct assignments start live range of lhs: var = value
+    if (edge.Kind == "Assign") {
+        const [lhs, rhs] = edge.Exp;
+        return (expressionIsVariable(lhs, variable) &&
+                !isReturningImmobileValue(edge, variable));
+    }
+
+    if (edge.Kind != "Call")
+        return false;
+
+    // Assignments of call results start live range: var = foo()
+    if (1 in edge.Exp) {
+        var lhs = edge.Exp[1];
+        if (expressionIsVariable(lhs, variable))
+            return true;
+    }
+
+    // Constructor calls start live range of instance: SomeClass var(...)
+    if ("PEdgeCallInstance" in edge) {
+        var instance = edge.PEdgeCallInstance.Exp;
+
+        // Kludge around incorrect dereference on some constructor calls.
+        if (instance.Kind == "Drf")
+            instance = instance.Exp[0];
+
+        if (!expressionIsVariable(instance, variable))
+            return false;
+
+        var callee = edge.Exp[0];
+        if (callee.Kind != "Var")
+            return false;
+
+        assert(callee.Variable.Kind == "Func");
+        var calleeName = readable(callee.Variable.Name[0]);
+
+        // Constructor calls include the text 'Name::Name(' or 'Name<...>::Name('.
+        var openParen = calleeName.indexOf('(');
+        if (openParen < 0)
+            return false;
+        calleeName = calleeName.substring(0, openParen);
+
+        var lastColon = calleeName.lastIndexOf('::');
+        if (lastColon < 0)
+            return false;
+        var constructorName = calleeName.substr(lastColon + 2);
+        calleeName = calleeName.substr(0, lastColon);
+
+        var lastTemplateOpen = calleeName.lastIndexOf('<');
+        if (lastTemplateOpen >= 0)
+            calleeName = calleeName.substr(0, lastTemplateOpen);
+
+        if (calleeName.endsWith(constructorName))
+            return true;
+    }
+
+    return false;
+}
+
+// Return whether an edge "clears out" a variable's value. A simple example
+// would be
+//
+//     var = nullptr;
+//
+// for analyses for which nullptr is a "safe" value (eg GC rooting hazards; you
+// can't get in trouble by holding a nullptr live across a GC.) A more complex
+// example is a Maybe<T> that gets reset:
+//
+//     Maybe<AutoCheckCannotGC> nogc;
+//     nogc.emplace(cx);
+//     nogc.reset();
+//     gc();             // <-- not a problem; nogc is invalidated by prev line
+//     nogc.emplace(cx);
+//     foo(nogc);
+//
+// Yet another example is a UniquePtr being passed by value, which means the
+// receiver takes ownership:
+//
+//     UniquePtr<JSObject*> uobj(obj);
+//     foo(uobj);
+//     gc();
+//
+function edgeEndsValueLiveRange(edge, variable, body)
+{
+    // var = nullptr;
+    if (edge.Kind == "Assign") {
+        const [lhs, rhs] = edge.Exp;
+        return expressionIsVariable(lhs, variable) && isImmobileValue(rhs);
+    }
+
+    if (edge.Kind != "Call")
+        return false;
+
+    var callee = edge.Exp[0];
+
+    if (edge.Type.Kind == 'Function' &&
+        edge.Exp[0].Kind == 'Var' &&
+        edge.Exp[0].Variable.Kind == 'Func' &&
+        edge.Exp[0].Variable.Name[1] == 'MarkVariableAsGCSafe' &&
+        edge.Exp[0].Variable.Name[0].includes("JS::detail::MarkVariableAsGCSafe") &&
+        expressionIsVariable(edge.PEdgeCallArguments.Exp[0], variable))
+    {
+        // explicit JS_HAZ_VARIABLE_IS_GC_SAFE annotation
+        return true;
+    }
+
+    if (edge.Type.Kind == 'Function' &&
+        edge.Exp[0].Kind == 'Var' &&
+        edge.Exp[0].Variable.Kind == 'Func' &&
+        edge.Exp[0].Variable.Name[1] == 'move' &&
+        edge.Exp[0].Variable.Name[0].includes('std::move(') &&
+        expressionIsVariable(edge.PEdgeCallArguments.Exp[0], variable) &&
+        edge.Exp[1].Kind == 'Var' &&
+        edge.Exp[1].Variable.Kind == 'Temp')
+    {
+        // temp = std::move(var)
+        //
+        // If var is a UniquePtr, and we pass it into something that takes
+        // ownership, then it should be considered to be invalid. Example:
+        //
+        //     consume(std::move(var));
+        //
+        // where consume takes a UniquePtr. This will compile to something like
+        //
+        //     UniquePtr* __temp_1 = &std::move(var);
+        //     UniquePtr&& __temp_2(*temp_1); // move constructor
+        //     consume(__temp_2);
+        //     ~UniquePtr(__temp_2);
+        //
+        // The line commented with "// move constructor" is a result of passing
+        // a UniquePtr as a parameter. If consume() took a UniquePtr&&
+        // directly, this would just be:
+        //
+        //     UniquePtr* __temp_1 = &std::move(var);
+        //     consume(__temp_1);
+        //
+        // which is not guaranteed to move from the reference. It might just
+        // ignore the parameter. We can't predict what consume(UniquePtr&&)
+        // will do. We do know that UniquePtr(UniquePtr&& other) moves out of
+        // `other`.
+        //
+        // The std::move() technically is irrelevant, but because we only care
+        // about bare variables, it has to be used, which is fortunate because
+        // the UniquePtr&& constructor operates on a temporary, not the
+        // variable we care about.
+
+        const lhs = edge.Exp[1].Variable;
+        if (basicBlockEatsVariable(lhs, body, edge.Index[1]))
+          return true;
+    }
+
+    if (edge.Type.Kind == 'Function' &&
+        edge.Type.TypeFunctionCSU &&
+        edge.PEdgeCallInstance &&
+        expressionIsMethodOnVariable(edge.PEdgeCallInstance.Exp, variable))
+    {
+        const typeName = edge.Type.TypeFunctionCSU.Type.Name;
+        const m = typeName.match(/^(((\w|::)+?)(\w+))</);
+        if (m) {
+            const [, type, namespace,, classname] = m;
+
+            // special-case: the initial constructor that doesn't provide a value.
+            // Useful for things like Maybe<T>.
+            const ctorName = `${namespace}${classname}<T>::${classname}()`;
+            if (callee.Kind == 'Var' &&
+                typesWithSafeConstructors.has(type) &&
+                callee.Variable.Name[0].includes(ctorName))
+            {
+                return true;
+            }
+
+            // special-case: UniquePtr::reset() and similar.
+            if (callee.Kind == 'Var' &&
+                type in resetterMethods &&
+                resetterMethods[type].has(callee.Variable.Name[1]))
+            {
+                return true;
+            }
+        }
+    }
+
+    // special-case: passing UniquePtr<T> by value.
+    if (edge.Type.Kind == 'Function' &&
+        edge.Type.TypeFunctionArgument &&
+        edge.PEdgeCallArguments)
+    {
+        for (const i in edge.Type.TypeFunctionArgument) {
+            const param = edge.Type.TypeFunctionArgument[i];
+            if (param.Type.Kind != 'CSU')
+                continue;
+            if (!param.Type.Name.startsWith("mozilla::UniquePtr<"))
+                continue;
+            const arg = edge.PEdgeCallArguments.Exp[i];
+            if (expressionIsVariable(arg, variable)) {
+                return true;
+            }
+        }
+    }
+
+    return false;
+}
+
+function edgeMovesVariable(edge, variable)
+{
+    if (edge.Kind != 'Call')
+        return false;
+    const callee = edge.Exp[0];
+    if (callee.Kind == 'Var' &&
+        callee.Variable.Kind == 'Func')
+    {
+        const { Variable: { Name: [ fullname, shortname ] } } = callee;
+        const [ mangled, unmangled ] = splitFunction(fullname);
+        // Match a UniquePtr move constructor.
+        if (unmangled.match(/::UniquePtr<[^>]*>::UniquePtr\((\w+::)*UniquePtr<[^>]*>&&/))
+            return true;
+    }
+
+    return false;
+}
+
+// Scan forward through the basic block in 'body' starting at 'startpoint',
+// looking for a call that passes 'variable' to a move constructor that
+// "consumes" it (eg UniquePtr::UniquePtr(UniquePtr&&)).
+function basicBlockEatsVariable(variable, body, startpoint)
+{
+    const successors = getSuccessors(body);
+    let point = startpoint;
+    while (point in successors) {
+        // Only handle a single basic block. If it forks, stop looking.
+        const edges = successors[point];
+        if (edges.length != 1) {
+            return false;
+        }
+        const edge = edges[0];
+
+        if (edgeMovesVariable(edge, variable)) {
+            return true;
+        }
+
+        // edgeStartsValueLiveRange will find places where 'variable' is given
+        // a new value. Never observed in practice, since this function is only
+        // called with a temporary resulting from std::move(), which is used
+        // immediately for a call. But just to be robust to future uses:
+        if (edgeStartsValueLiveRange(edge, variable)) {
+            return false;
+        }
+
+        point = edge.Index[1];
+    }
+
+    return false;
+}
+
+function edgeIsNonReleasingDtor(body, edge, calleeName, functionBodies) {
+    if (edge.Kind !== "Call") {
+        return false;
+    }
+    if (!isRefcountedDtor(calleeName)) {
+        return false;
+    }
+
+    let callee = edge.Exp[0];
+    while (callee.Kind === "Drf") {
+        callee = callee.Exp[0];
+    }
+
+    const instance = edge.PEdgeCallInstance.Exp;
+    if (instance.Kind !== "Var") {
+        // TODO: handle field destructors
+        return false;
+    }
+
+    // Test whether the dtor call is dominated by operations on the variable
+    // that mean it will not go to a zero refcount in the dtor: either because
+    // it's already dead (eg r.forget() was called) or because it can be proven
+    // to have a ref count of greater than 1. This is implemented by looking
+    // for the reverse: find a path scanning backwards from the dtor call where
+    // the variable is used in any way that does *not* ensure that it is
+    // trivially destructible.
+
+    const variable = instance.Variable;
+
+    const visitor = new class extends Visitor {
+        // Do not revisit nodes. For new nodes, relay the decision made by
+        // extend_path.
+        next_action(seen, current) { return seen ? "prune" : current; }
+
+        // We don't revisit, so always use the new.
+        merge_info(seen, current) { return current; }
+
+        // Return the action to take from this node.
+        extend_path(edge, body, ppoint, successor_path) {
+            if (!edge) {
+                // Dummy edge to join two points.
+                return "continue";
+            }
+
+            if (!edgeUsesVariable(edge, variable, body)) {
+                // Nothing of interest on this edge, keep searching.
+                return "continue";
+            }
+
+            if (edgeEndsValueLiveRange(edge, variable, body)) {
+                // This path is safe!
+                return "prune";
+            }
+
+            // Unsafe. Found a use that might set the variable to a
+            // nonzero refcount.
+            return "done";
+        }
+    }(functionBodies);
+
+    // Searching upwards from a destructor call, return the opposite of: is
+    // there a path to a use or the start of the function that does NOT hit a
+    // safe assignment like refptr.forget() first?
+    //
+    // In graph terms: return whether the destructor call is dominated by forget() calls (or similar).
+    return !BFS_upwards(
+        body, edge.Index[0], functionBodies, visitor, "start",
+        true // Return value if we reach the root without finding a non-forget() use.
+    );
+}
+
+// gcc uses something like "__dt_del " for virtual destructors that it
+// generates.
+function isSyntheticVirtualDestructor(funcName) {
+    return funcName.endsWith(" ");
+}
+
+function typedField(field)
+{
+    if ("FieldInstanceFunction" in field) {
+        // Virtual call
+        //
+        // This makes a minimal attempt at dealing with overloading, by
+        // incorporating the number of parameters. So far, that is all that has
+        // been needed. If more is needed, sixgill will need to produce a full
+        // mangled type.
+        const {Type, Name: [name]} = field;
+
+        // Virtual destructors don't need a type or argument count,
+        // and synthetic ones don't have them filled in.
+        if (isSyntheticVirtualDestructor(name)) {
+            return name;
+        }
+
+        var nargs = 0;
+        if (Type.Kind == "Function" && "TypeFunctionArguments" in Type)
+            nargs = Type.TypeFunctionArguments.Type.length;
+        return name + ":" + nargs;
+    } else {
+        // Function pointer field
+        return field.Name[0];
+    }
+}
+
+function fieldKey(csuName, field)
+{
+    return csuName + "." + typedField(field);
+}
diff --git a/js/src/devtools/rootAnalysis/Makefile.in b/js/src/devtools/rootAnalysis/Makefile.in
new file mode 100644
index 0000000000..e8bc57471a
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/Makefile.in
@@ -0,0 +1,79 @@
+# -*- Mode: makefile -*-
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This Makefile is used to kick off a static rooting analysis. This Makefile is
+# NOT intended for use as part of the standard Mozilla build. Instead, this
+# Makefile will use $PATH to subvert compiler invocations to add in the sixgill
+# plugin, and then do a regular build of whatever portion of the tree you are
+# analyzing. The plugins will dump out several xdb database files. Various
+# analysis scripts, written in JS, will run over those database files to
+# produce the final analysis output.
+
+include $(topsrcdir)/config/config.mk
+
+# Tree to build and analyze, defaulting to the current tree
+TARGET_JSOBJDIR ?= $(TOPOBJDIR)
+
+# Path to a JS binary to use to run the analysis. You really want this to be an
+# optimized build.
+JS ?= $(DIST)/bin/js
+
+# Path to an xgill checkout containing the GCC plugin, xdb-processing binaries,
+# and compiler wrapper scripts used to automatically integrate into an existing
+# build system.
+SIXGILL ?= @SIXGILL_PATH@
+
+# Path to the JS scripts that will perform the analysis, defaulting to the same
+# place as this Makefile.in, which is probably what you want.
+ANALYSIS_SCRIPT_DIR ?= $(srcdir)
+
+# Number of simultanous analyzeRoots.js scripts to run.
+JOBS ?= 6
+
+all : rootingHazards.txt allFunctions.txt
+
+CALL_JS := time env PATH=$$PATH:$(SIXGILL)/bin XDB=$(SIXGILL)/bin/xdb.so $(JS) 
+
+src_body.xdb src_comp.xdb: run_complete
+	@echo Started compilation at $$(date)
+	$(ANALYSIS_SCRIPT_DIR)/run_complete --foreground --build-root=$(TARGET_JSOBJDIR) --work-dir=work -b $(SIXGILL)/bin $(CURDIR)
+	@echo Finished compilation at $$(date)
+
+callgraph.txt: src_body.xdb src_comp.xdb computeCallgraph.js
+	@echo Started computation of $@ at $$(date)
+	$(CALL_JS) $(ANALYSIS_SCRIPT_DIR)/computeCallgraph.js > $@.tmp
+	mv $@.tmp $@
+	@echo Finished computation of $@ at $$(date)
+
+gcFunctions.txt: callgraph.txt computeGCFunctions.js annotations.js
+	@echo Started computation of $@ at $$(date)
+	$(CALL_JS) $(ANALYSIS_SCRIPT_DIR)/computeGCFunctions.js ./callgraph.txt > $@.tmp
+	mv $@.tmp $@
+	@echo Finished computation of $@ at $$(date)
+
+gcFunctions.lst: gcFunctions.txt
+	perl -lne 'print $$1 if /^GC Function: (.*)/' gcFunctions.txt > $@
+
+suppressedFunctions.lst: gcFunctions.txt
+	perl -lne 'print $$1 if /^Suppressed Function: (.*)/' gcFunctions.txt > $@
+
+gcTypes.txt: src_comp.xdb computeGCTypes.js annotations.js
+	@echo Started computation of $@ at $$(date)
+	$(CALL_JS) $(ANALYSIS_SCRIPT_DIR)/computeGCTypes.js > $@.tmp
+	mv $@.tmp $@
+	@echo Finished computation of $@ at $$(date)
+
+allFunctions.txt: src_body.xdb
+	@echo Started computation of $@ at $$(date)
+	time $(SIXGILL)/bin/xdbkeys $^ > $@.tmp
+	mv $@.tmp $@
+	@echo Finished computation of $@ at $$(date)
+
+rootingHazards.txt: gcFunctions.lst suppressedFunctions.lst gcTypes.txt analyzeRoots.js annotations.js gen-hazards.sh
+	@echo Started computation of $@ at $$(date)
+	time env JS=$(JS) ANALYZE='$(ANALYSIS_SCRIPT_DIR)/analyzeRoots.js' SIXGILL='$(SIXGILL)' '$(ANALYSIS_SCRIPT_DIR)/gen-hazards.sh' $(JOBS) > $@.tmp
+	mv $@.tmp $@
+	@echo Finished computation of $@ at $$(date)
diff --git a/js/src/devtools/rootAnalysis/README.md b/js/src/devtools/rootAnalysis/README.md
new file mode 100644
index 0000000000..08a4fcde29
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/README.md
@@ -0,0 +1,3 @@
+# Spidermonkey JSAPI rooting analysis
+
+See js/src/docs/HazardAnalysis/index.md
diff --git a/js/src/devtools/rootAnalysis/analyze.py b/js/src/devtools/rootAnalysis/analyze.py
new file mode 100755
index 0000000000..b779f4f778
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/analyze.py
@@ -0,0 +1,440 @@
+#!/usr/bin/env python3
+
+#
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+"""
+Runs the static rooting analysis
+"""
+
+import argparse
+import os
+import subprocess
+import sys
+from subprocess import Popen
+
+try:
+    from shlex import quote
+except ImportError:
+    from pipes import quote
+
+
+def execfile(thefile, globals):
+    exec(compile(open(thefile).read(), filename=thefile, mode="exec"), globals)
+
+
+# Label a string as an output.
+class Output(str):
+    pass
+
+
+# Label a string as a pattern for multiple inputs.
+class MultiInput(str):
+    pass
+
+
+def env(config):
+    e = dict(os.environ)
+    e["PATH"] = ":".join(p for p in (config.get("sixgill_bin"), e["PATH"]) if p)
+    e["XDB"] = "%(sixgill_bin)s/xdb.so" % config
+    e["SOURCE"] = config["source"]
+    return e
+
+
+def fill(command, config):
+    filled = []
+    for s in command:
+        try:
+            rep = s.format(**config)
+        except KeyError:
+            print("Substitution failed: %s" % s)
+            filled = None
+            break
+
+        if isinstance(s, Output):
+            filled.append(Output(rep))
+        elif isinstance(s, MultiInput):
+            N = int(config["jobs"])
+            for i in range(1, N + 1):
+                filled.append(rep.format(i=i, n=N))
+        else:
+            filled.append(rep)
+
+    if filled is None:
+        raise Exception("substitution failure")
+
+    return tuple(filled)
+
+
+def print_command(command, outfile=None, env=None):
+    output = " ".join(quote(s) for s in command)
+    if outfile:
+        output += " > " + outfile
+    if env:
+        changed = {}
+        e = os.environ
+        for key, value in env.items():
+            if (key not in e) or (e[key] != value):
+                changed[key] = value
+        if changed:
+            outputs = []
+            for key, value in changed.items():
+                if key in e and e[key] in value:
+                    start = value.index(e[key])
+                    end = start + len(e[key])
+                    outputs.append(
+                        '%s="%s${%s}%s"' % (key, value[:start], key, value[end:])
+                    )
+                else:
+                    outputs.append("%s='%s'" % (key, value))
+            output = " ".join(outputs) + " " + output
+
+    print(output)
+
+
+JOBS = {
+    "list-dbs": {"command": ["ls", "-l"]},
+    "rawcalls": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/computeCallgraph.js",
+            "{typeInfo}",
+            Output("rawcalls"),
+            Output("rawEdges"),
+            "{i}",
+            "{n}",
+        ],
+        "multi-output": True,
+        "outputs": ["rawcalls.{i}.of.{n}", "gcEdges.{i}.of.{n}"],
+    },
+    "mergeJSON": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/mergeJSON.js",
+            MultiInput("{rawEdges}"),
+            Output("gcEdges"),
+        ],
+        "outputs": ["gcEdges.json"],
+    },
+    "gcFunctions": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/computeGCFunctions.js",
+            MultiInput("{rawcalls}"),
+            "--outputs",
+            Output("callgraph"),
+            Output("gcFunctions"),
+            Output("gcFunctions_list"),
+            Output("limitedFunctions_list"),
+        ],
+        "outputs": [
+            "callgraph.txt",
+            "gcFunctions.txt",
+            "gcFunctions.lst",
+            "limitedFunctions.lst",
+        ],
+    },
+    "gcTypes": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/computeGCTypes.js",
+            Output("gcTypes"),
+            Output("typeInfo"),
+        ],
+        "outputs": ["gcTypes.txt", "typeInfo.txt"],
+    },
+    "allFunctions": {
+        "command": ["{sixgill_bin}/xdbkeys", "src_body.xdb"],
+        "redirect-output": "allFunctions.txt",
+    },
+    "hazards": {
+        "command": [
+            "{js}",
+            "{analysis_scriptdir}/analyzeRoots.js",
+            "{gcFunctions_list}",
+            "{gcEdges}",
+            "{limitedFunctions_list}",
+            "{gcTypes}",
+            "{typeInfo}",
+            "{i}",
+            "{n}",
+            "tmp.{i}.of.{n}",
+        ],
+        "multi-output": True,
+        "redirect-output": "rootingHazards.{i}.of.{n}",
+    },
+    "gather-hazards": {
+        "command": ["cat", MultiInput("{hazards}")],
+        "redirect-output": "rootingHazards.txt",
+    },
+    "explain": {
+        "command": [
+            sys.executable,
+            "{analysis_scriptdir}/explain.py",
+            "{gather-hazards}",
+            "{gcFunctions}",
+            Output("explained_hazards"),
+            Output("unnecessary"),
+            Output("refs"),
+        ],
+        "outputs": ["hazards.txt", "unnecessary.txt", "refs.txt"],
+    },
+    "heapwrites": {
+        "command": ["{js}", "{analysis_scriptdir}/analyzeHeapWrites.js"],
+        "redirect-output": "heapWriteHazards.txt",
+    },
+}
+
+
+# Generator of (i, j, item) tuples corresponding to outputs:
+#  - i is just the index of the yielded tuple (a la enumerate())
+#  - j is the index of the item in the command list
+#  - item is command[j]
+def out_indexes(command):
+    i = 0
+    for (j, fragment) in enumerate(command):
+        if isinstance(fragment, Output):
+            yield (i, j, fragment)
+            i += 1
+
+
+def run_job(name, config):
+    job = JOBS[name]
+    outs = job.get("outputs") or job.get("redirect-output")
+    print("Running " + name + " to generate " + str(outs))
+    if "function" in job:
+        job["function"](config, job["redirect-output"])
+        return
+
+    N = int(config["jobs"]) if job.get("multi-output") else 1
+    config["n"] = N
+    jobs = {}
+    for i in range(1, N + 1):
+        config["i"] = i
+        cmd = fill(job["command"], config)
+        info = spawn_command(cmd, job, name, config)
+        jobs[info["proc"].pid] = info
+
+    final_status = 0
+    while jobs:
+        pid, status = os.wait()
+        final_status = final_status or status
+        info = jobs[pid]
+        del jobs[pid]
+        if "redirect" in info:
+            info["redirect"].close()
+
+        # Rename the temporary files to their final names.
+        for (temp, final) in info["rename_map"].items():
+            try:
+                if config["verbose"]:
+                    print("Renaming %s -> %s" % (temp, final))
+                os.rename(temp, final)
+            except OSError:
+                print("Error renaming %s -> %s" % (temp, final))
+                raise
+
+    if final_status != 0:
+        raise Exception("job {} returned status {}".format(name, final_status))
+
+
+def spawn_command(cmdspec, job, name, config):
+    rename_map = {}
+
+    if "redirect-output" in job:
+        stdout_filename = "{}.tmp{}".format(name, config.get("i", ""))
+        final_outfile = job["redirect-output"].format(**config)
+        rename_map[stdout_filename] = final_outfile
+        command = cmdspec
+        if config["verbose"]:
+            print_command(cmdspec, outfile=final_outfile, env=env(config))
+    else:
+        outfiles = job["outputs"]
+        outfiles = fill(outfiles, config)
+        stdout_filename = None
+
+        # To print the supposedly-executed command, replace the Outputs in the
+        # command with final output file names. (The actual command will be
+        # using temporary files that get renamed at the end.)
+        if config["verbose"]:
+            pc = list(cmdspec)
+            for (i, j, name) in out_indexes(cmdspec):
+                pc[j] = outfiles[i]
+            print_command(pc, env=env(config))
+
+        # Replace the Outputs with temporary filenames, and record a mapping
+        # from those temp names to their actual final names that will be used
+        # if the command succeeds.
+        command = list(cmdspec)
+        for (i, j, name) in out_indexes(cmdspec):
+            command[j] = "{}.tmp{}".format(name, config.get("i", ""))
+            rename_map[command[j]] = outfiles[i]
+
+    sys.stdout.flush()
+    info = {"rename_map": rename_map}
+    if stdout_filename:
+        info["redirect"] = open(stdout_filename, "w")
+        info["proc"] = Popen(command, stdout=info["redirect"], env=env(config))
+    else:
+        info["proc"] = Popen(command, env=env(config))
+
+    if config["verbose"]:
+        print("Spawned process {}".format(info["proc"].pid))
+
+    return info
+
+
+# Default to conservatively assuming 4GB/job.
+def max_parallel_jobs(job_size=4 * 2 ** 30):
+    """Return the max number of parallel jobs we can run without overfilling
+    memory, assuming heavyweight jobs."""
+    from_cores = int(subprocess.check_output(["nproc", "--ignore=1"]).strip())
+    mem_bytes = os.sysconf("SC_PAGE_SIZE") * os.sysconf("SC_PHYS_PAGES")
+    from_mem = round(mem_bytes / job_size)
+    return min(from_cores, from_mem)
+
+
+config = {"analysis_scriptdir": os.path.dirname(__file__)}
+
+defaults = [
+    "%s/defaults.py" % config["analysis_scriptdir"],
+    "%s/defaults.py" % os.getcwd(),
+]
+
+parser = argparse.ArgumentParser(
+    description="Statically analyze build tree for rooting hazards."
+)
+parser.add_argument(
+    "step", metavar="STEP", type=str, nargs="?", help="run only step STEP"
+)
+parser.add_argument(
+    "--source", metavar="SOURCE", type=str, nargs="?", help="source code to analyze"
+)
+parser.add_argument(
+    "--js",
+    metavar="JSSHELL",
+    type=str,
+    nargs="?",
+    help="full path to ctypes-capable JS shell",
+)
+parser.add_argument(
+    "--first",
+    metavar="STEP",
+    type=str,
+    nargs="?",
+    help="execute all jobs starting with STEP",
+)
+parser.add_argument(
+    "--last", metavar="STEP", type=str, nargs="?", help="stop at step STEP"
+)
+parser.add_argument(
+    "--jobs",
+    "-j",
+    default=None,
+    metavar="JOBS",
+    type=int,
+    help="number of simultaneous analyzeRoots.js jobs",
+)
+parser.add_argument(
+    "--list", const=True, nargs="?", type=bool, help="display available steps"
+)
+parser.add_argument(
+    "--expect-file",
+    type=str,
+    nargs="?",
+    help="deprecated option, temporarily still present for backwards " "compatibility",
+)
+parser.add_argument(
+    "--verbose",
+    "-v",
+    action="count",
+    default=1,
+    help="Display cut & paste commands to run individual steps",
+)
+parser.add_argument("--quiet", "-q", action="count", default=0, help="Suppress output")
+
+args = parser.parse_args()
+args.verbose = max(0, args.verbose - args.quiet)
+
+for default in defaults:
+    try:
+        execfile(default, config)
+        if args.verbose:
+            print("Loaded %s" % default)
+    except Exception:
+        pass
+
+data = config.copy()
+
+for k, v in vars(args).items():
+    if v is not None:
+        data[k] = v
+
+if args.jobs is not None:
+    data["jobs"] = args.jobs
+if not data.get("jobs"):
+    data["jobs"] = max_parallel_jobs()
+
+if "GECKO_PATH" in os.environ:
+    data["source"] = os.environ["GECKO_PATH"]
+if "SOURCE" in os.environ:
+    data["source"] = os.environ["SOURCE"]
+
+steps = [
+    "gcTypes",
+    "rawcalls",
+    "gcFunctions",
+    "mergeJSON",
+    "allFunctions",
+    "hazards",
+    "gather-hazards",
+    "explain",
+    "heapwrites",
+]
+
+if args.list:
+    for step in steps:
+        job = JOBS[step]
+        outfiles = job.get("outputs") or job.get("redirect-output")
+        if outfiles:
+            print(
+                "%s\n    ->%s %s"
+                % (step, "*" if job.get("multi-output") else "", outfiles)
+            )
+        else:
+            print(step)
+    sys.exit(0)
+
+for step in steps:
+    job = JOBS[step]
+    if "redirect-output" in job:
+        data[step] = job["redirect-output"]
+    elif "outputs" in job and "command" in job:
+        outfiles = job["outputs"]
+        for (i, j, name) in out_indexes(job["command"]):
+            data[name] = outfiles[i]
+        num_outputs = len(list(out_indexes(job["command"])))
+        assert (
+            len(outfiles) == num_outputs
+        ), 'step "%s": mismatched number of output files (%d) and params (%d)' % (
+            step,
+            num_outputs,
+            len(outfiles),
+        )  # NOQA: E501
+
+if args.step:
+    if args.first or args.last:
+        raise Exception(
+            "--first and --last cannot be used when a step argument is given"
+        )
+    steps = [args.step]
+else:
+    if args.first:
+        steps = steps[steps.index(args.first) :]
+    if args.last:
+        steps = steps[: steps.index(args.last) + 1]
+
+for step in steps:
+    run_job(step, data)
diff --git a/js/src/devtools/rootAnalysis/analyzeHeapWrites.js b/js/src/devtools/rootAnalysis/analyzeHeapWrites.js
new file mode 100644
index 0000000000..fdb9eaffb8
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/analyzeHeapWrites.js
@@ -0,0 +1,1398 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('callgraph.js');
+loadRelativeToScript('dumpCFG.js');
+
+///////////////////////////////////////////////////////////////////////////////
+// Annotations
+///////////////////////////////////////////////////////////////////////////////
+
+function checkExternalFunction(entry)
+{
+    var whitelist = [
+        "__builtin_clz",
+        "__builtin_expect",
+        "isprint",
+        "ceilf",
+        "floorf",
+        /^rusturl/,
+        "memcmp",
+        "strcmp",
+        "fmod",
+        "floor",
+        "ceil",
+        "atof",
+        /memchr/,
+        "strlen",
+        /Servo_DeclarationBlock_GetCssText/,
+        "Servo_GetArcStringData",
+        "Servo_IsWorkerThread",
+        /nsIFrame::AppendOwnedAnonBoxes/,
+        // Assume that atomic accesses are threadsafe.
+        /^__atomic_/,
+    ];
+    if (entry.matches(whitelist))
+        return;
+
+    // memcpy and memset are safe if the target pointer is threadsafe.
+    const simpleWrites = [
+        "memcpy",
+        "memset",
+        "memmove",
+    ];
+
+    if (entry.isSafeArgument(1) && simpleWrites.includes(entry.name))
+        return;
+
+    dumpError(entry, null, "External function");
+}
+
+function hasThreadsafeReferenceCounts(entry, regexp)
+{
+    // regexp should match some nsISupports-operating function and produce the
+    // name of the nsISupports class via exec().
+
+    // nsISupports classes which have threadsafe reference counting.
+    var whitelist = [
+        "nsIRunnable",
+
+        // I don't know if these always have threadsafe refcounts.
+        "nsAtom",
+        "nsIPermissionManager",
+        "nsIURI",
+    ];
+
+    var match = regexp.exec(entry.name);
+    return match && nameMatchesArray(match[1], whitelist);
+}
+
+function checkOverridableVirtualCall(entry, location, callee)
+{
+    // We get here when a virtual call is made on a structure which might be
+    // overridden by script or by a binary extension. This includes almost
+    // everything under nsISupports, however, so for the most part we ignore
+    // this issue. The exception is for nsISupports AddRef/Release, which are
+    // not in general threadsafe and whose overrides will not be generated by
+    // the callgraph analysis.
+    if (callee != "nsISupports.AddRef" && callee != "nsISupports.Release")
+        return;
+
+    if (hasThreadsafeReferenceCounts(entry, /::~?nsCOMPtr\(.*?\[with T = (.*?)\]$/))
+        return;
+    if (hasThreadsafeReferenceCounts(entry, /RefPtrTraits.*?::Release.*?\[with U = (.*?)\]/))
+        return;
+    if (hasThreadsafeReferenceCounts(entry, /nsCOMPtr<T>::assign_assuming_AddRef.*?\[with T = (.*?)\]/))
+        return;
+    if (hasThreadsafeReferenceCounts(entry, /nsCOMPtr<T>::assign_with_AddRef.*?\[with T = (.*?)\]/))
+        return;
+
+    // Watch for raw addref/release.
+    var whitelist = [
+        "Gecko_AddRefAtom",
+        "Gecko_ReleaseAtom",
+        /nsPrincipal::Get/,
+        /CounterStylePtr::Reset/,
+    ];
+    if (entry.matches(whitelist))
+        return;
+
+    dumpError(entry, location, "AddRef/Release on nsISupports");
+}
+
+function checkIndirectCall(entry, location, callee)
+{
+    var name = entry.name;
+
+    // These hash table callbacks should be threadsafe.
+    if (/PLDHashTable/.test(name) && (/matchEntry/.test(callee) || /hashKey/.test(callee)))
+        return;
+    if (/PL_HashTable/.test(name) && /keyCompare/.test(callee))
+        return;
+
+    dumpError(entry, location, "Indirect call " + callee);
+}
+
+function checkVariableAssignment(entry, location, variable)
+{
+    var name = entry.name;
+
+    dumpError(entry, location, "Variable assignment " + variable);
+}
+
+// Annotations for function parameters, based on function name and parameter
+// name + type.
+function treatAsSafeArgument(entry, varName, csuName)
+{
+    var whitelist = [
+        // These iterator classes should all be thread local. They are passed
+        // in to some Servo bindings and are created on the heap by others, so
+        // just ignore writes to them.
+        [null, null, /StyleChildrenIterator/],
+        [null, null, /ExplicitChildIterator/],
+
+        // The use of BeginReading() to instantiate this class confuses the
+        // analysis.
+        [null, null, /nsReadingIterator/],
+
+        // These classes are passed to some Servo bindings to fill in.
+        [/^Gecko_/, null, "nsStyleImageLayers"],
+        [/^Gecko_/, null, /FontFamilyList/],
+
+        // Various Servo binding out parameters. This is a mess and there needs
+        // to be a way to indicate which params are out parameters, either using
+        // an attribute or a naming convention.
+        ["Gecko_CopyAnimationNames", "aDest", null],
+        ["Gecko_SetAnimationName", "aStyleAnimation", null],
+        ["Gecko_SetCounterStyleToName", "aPtr", null],
+        ["Gecko_SetCounterStyleToSymbols", "aPtr", null],
+        ["Gecko_SetCounterStyleToString", "aPtr", null],
+        ["Gecko_CopyCounterStyle", "aDst", null],
+        ["Gecko_SetMozBinding", "aDisplay", null],
+        [/ClassOrClassList/, /aClass/, null],
+        ["Gecko_GetAtomAsUTF16", "aLength", null],
+        ["Gecko_CopyMozBindingFrom", "aDest", null],
+        ["Gecko_SetNullImageValue", "aImage", null],
+        ["Gecko_SetGradientImageValue", "aImage", null],
+        ["Gecko_SetImageElement", "aImage", null],
+        ["Gecko_SetLayerImageImageValue", "aImage", null],
+        ["Gecko_CopyImageValueFrom", "aImage", null],
+        ["Gecko_SetCursorArrayLength", "aStyleUI", null],
+        ["Gecko_CopyCursorArrayFrom", "aDest", null],
+        ["Gecko_SetCursorImageValue", "aCursor", null],
+        ["Gecko_SetListStyleImageImageValue", "aList", null],
+        ["Gecko_SetListStyleImageNone", "aList", null],
+        ["Gecko_CopyListStyleImageFrom", "aList", null],
+        ["Gecko_ClearStyleContents", "aContent", null],
+        ["Gecko_CopyStyleContentsFrom", "aContent", null],
+        ["Gecko_CopyStyleGridTemplateValues", "aGridTemplate", null],
+        ["Gecko_ResetStyleCoord", null, null],
+        ["Gecko_CopyClipPathValueFrom", "aDst", null],
+        ["Gecko_DestroyClipPath", "aClip", null],
+        ["Gecko_ResetFilters", "effects", null],
+        [/Gecko_CSSValue_Set/, "aCSSValue", null],
+        ["Gecko_CSSValue_Drop", "aCSSValue", null],
+        ["Gecko_CSSFontFaceRule_GetCssText", "aResult", null],
+        ["Gecko_EnsureTArrayCapacity", "aArray", null],
+        ["Gecko_ClearPODTArray", "aArray", null],
+        ["Gecko_SetStyleGridTemplate", "aGridTemplate", null],
+        ["Gecko_ResizeTArrayForStrings", "aArray", null],
+        ["Gecko_ClearAndResizeStyleContents", "aContent", null],
+        [/Gecko_ClearAndResizeCounter/, "aContent", null],
+        [/Gecko_CopyCounter.*?From/, "aContent", null],
+        [/Gecko_SetContentDataImageValue/, "aList", null],
+        [/Gecko_SetContentData/, "aContent", null],
+        ["Gecko_SetCounterFunction", "aContent", null],
+        [/Gecko_EnsureStyle.*?ArrayLength/, "aArray", null],
+        ["Gecko_GetOrCreateKeyframeAtStart", "aKeyframes", null],
+        ["Gecko_GetOrCreateInitialKeyframe", "aKeyframes", null],
+        ["Gecko_GetOrCreateFinalKeyframe", "aKeyframes", null],
+        ["Gecko_AppendPropertyValuePair", "aProperties", null],
+        ["Gecko_SetStyleCoordCalcValue", null, null],
+        ["Gecko_StyleClipPath_SetURLValue", "aClip", null],
+        ["Gecko_nsStyleFilter_SetURLValue", "aEffects", null],
+        ["Gecko_nsStyleSVG_SetDashArrayLength", "aSvg", null],
+        ["Gecko_nsStyleSVG_CopyDashArray", "aDst", null],
+        ["Gecko_nsStyleFont_SetLang", "aFont", null],
+        ["Gecko_nsStyleFont_CopyLangFrom", "aFont", null],
+        ["Gecko_ClearWillChange", "aDisplay", null],
+        ["Gecko_AppendWillChange", "aDisplay", null],
+        ["Gecko_CopyWillChangeFrom", "aDest", null],
+        ["Gecko_InitializeImageCropRect", "aImage", null],
+        ["Gecko_CopyShapeSourceFrom", "aDst", null],
+        ["Gecko_DestroyShapeSource", "aShape", null],
+        ["Gecko_StyleShapeSource_SetURLValue", "aShape", null],
+        ["Gecko_NewBasicShape", "aShape", null],
+        ["Gecko_NewShapeImage", "aShape", null],
+        ["Gecko_nsFont_InitSystem", "aDest", null],
+        ["Gecko_nsFont_SetFontFeatureValuesLookup", "aFont", null],
+        ["Gecko_nsFont_ResetFontFeatureValuesLookup", "aFont", null],
+        ["Gecko_nsStyleFont_FixupNoneGeneric", "aFont", null],
+        ["Gecko_StyleTransition_SetUnsupportedProperty", "aTransition", null],
+        ["Gecko_AddPropertyToSet", "aPropertySet", null],
+        ["Gecko_CalcStyleDifference", "aAnyStyleChanged", null],
+        ["Gecko_CalcStyleDifference", "aOnlyResetStructsChanged", null],
+        ["Gecko_nsStyleSVG_CopyContextProperties", "aDst", null],
+        ["Gecko_nsStyleFont_PrefillDefaultForGeneric", "aFont", null],
+        ["Gecko_nsStyleSVG_SetContextPropertiesLength", "aSvg", null],
+        ["Gecko_ClearAlternateValues", "aFont", null],
+        ["Gecko_AppendAlternateValues", "aFont", null],
+        ["Gecko_CopyAlternateValuesFrom", "aDest", null],
+        ["Gecko_CounterStyle_GetName", "aResult", null],
+        ["Gecko_CounterStyle_GetSingleString", "aResult", null],
+        ["Gecko_nsTArray_FontFamilyName_AppendNamed", "aNames", null],
+        ["Gecko_nsTArray_FontFamilyName_AppendGeneric", "aNames", null],
+    ];
+    for (var [entryMatch, varMatch, csuMatch] of whitelist) {
+        assert(entryMatch || varMatch || csuMatch);
+        if (entryMatch && !nameMatches(entry.name, entryMatch))
+            continue;
+        if (varMatch && !nameMatches(varName, varMatch))
+            continue;
+        if (csuMatch && (!csuName || !nameMatches(csuName, csuMatch)))
+            continue;
+        return true;
+    }
+    return false;
+}
+
+function isSafeAssignment(entry, edge, variable)
+{
+    if (edge.Kind != 'Assign')
+        return false;
+
+    var [mangled, unmangled] = splitFunction(entry.name);
+
+    // The assignment
+    //
+    //   nsFont* font = fontTypes[eType];
+    //
+    // ends up with 'font' pointing to a member of 'this', so it should inherit
+    // the safety of 'this'.
+    if (unmangled.includes("mozilla::LangGroupFontPrefs::Initialize") &&
+        variable == 'font')
+    {
+        const [lhs, rhs] = edge.Exp;
+        const {Kind, Exp: [{Kind: indexKind, Exp: [collection, index]}]} = rhs;
+        if (Kind == 'Drf' &&
+            indexKind == 'Index' &&
+            collection.Kind == 'Var' &&
+            collection.Variable.Name[0] == 'fontTypes')
+        {
+            return entry.isSafeArgument(0); // 'this'
+        }
+    }
+
+    return false;
+}
+
+function checkFieldWrite(entry, location, fields)
+{
+    var name = entry.name;
+    for (var field of fields) {
+        // The analysis is having some trouble keeping track of whether
+        // already_AddRefed and nsCOMPtr structures are safe to access.
+        // Hopefully these will be thread local, but it would be better to
+        // improve the analysis to handle these.
+        if (/already_AddRefed.*?.mRawPtr/.test(field))
+            return;
+        if (/nsCOMPtr<.*?>.mRawPtr/.test(field))
+            return;
+
+        if (/\bThreadLocal<\b/.test(field))
+            return;
+
+        // Debugging check for string corruption.
+        if (field == "nsStringBuffer.mCanary")
+            return;
+    }
+
+    var str = "";
+    for (var field of fields)
+        str += " " + field;
+
+    dumpError(entry, location, "Field write" + str);
+}
+
+function checkDereferenceWrite(entry, location, variable)
+{
+    var name = entry.name;
+
+    // Maybe<T> uses placement new on local storage in a way we don't understand.
+    // Allow this if the Maybe<> value itself is threadsafe.
+    if (/Maybe.*?::emplace/.test(name) && entry.isSafeArgument(0))
+        return;
+
+    // UniquePtr writes through temporaries referring to its internal storage.
+    // Allow this if the UniquePtr<> is threadsafe.
+    if (/UniquePtr.*?::reset/.test(name) && entry.isSafeArgument(0))
+        return;
+
+    // Operations on nsISupports reference counts.
+    if (hasThreadsafeReferenceCounts(entry, /nsCOMPtr<T>::swap\(.*?\[with T = (.*?)\]/))
+        return;
+
+    // ConvertToLowerCase::write writes through a local pointer into the first
+    // argument.
+    if (/ConvertToLowerCase::write/.test(name) && entry.isSafeArgument(0))
+        return;
+
+    dumpError(entry, location, "Dereference write " + (variable ? variable : "<unknown>"));
+}
+
+function ignoreCallEdge(entry, callee)
+{
+    var name = entry.name;
+
+    // nsPropertyTable::GetPropertyInternal has the option of removing data
+    // from the table, but when it is called by nsPropertyTable::GetProperty
+    // this will not occur.
+    if (/nsPropertyTable::GetPropertyInternal/.test(callee) &&
+        /nsPropertyTable::GetProperty/.test(name))
+    {
+        return true;
+    }
+
+    // Document::PropertyTable calls GetExtraPropertyTable (which has side
+    // effects) if the input category is non-zero. If a literal zero was passed
+    // in for the category then we treat it as a safe argument, per
+    // isEdgeSafeArgument, so just watch for that.
+    if (/Document::GetExtraPropertyTable/.test(callee) &&
+        /Document::PropertyTable/.test(name) &&
+        entry.isSafeArgument(1))
+    {
+        return true;
+    }
+
+    // This function has an explicit test for being on the main thread if the
+    // style has non-threadsafe refcounts, but the analysis isn't smart enough
+    // to understand what the actual styles that can be involved are.
+    if (/nsStyleList::SetCounterStyle/.test(callee))
+        return true;
+
+    // CachedBorderImageData is exclusively owned by nsStyleImage, but the
+    // analysis is not smart enough to know this.
+    if (/CachedBorderImageData::PurgeCachedImages/.test(callee) &&
+        /nsStyleImage::/.test(name) &&
+        entry.isSafeArgument(0))
+    {
+        return true;
+    }
+
+    // StyleShapeSource exclusively owns its UniquePtr<nsStyleImage>.
+    if (/nsStyleImage::SetURLValue/.test(callee) &&
+        /StyleShapeSource::SetURL/.test(name) &&
+        entry.isSafeArgument(0))
+    {
+        return true;
+    }
+
+    // The AddRef through a just-assigned heap pointer here is not handled by
+    // the analysis.
+    if (/nsCSSValue::Array::AddRef/.test(callee) &&
+        /nsStyleContentData::SetCounters/.test(name) &&
+        entry.isSafeArgument(2))
+    {
+        return true;
+    }
+
+    // AllChildrenIterator asks AppendOwnedAnonBoxes to append into an nsTArray
+    // local variable.
+    if (/nsIFrame::AppendOwnedAnonBoxes/.test(callee) &&
+        /AllChildrenIterator::AppendNativeAnonymousChildren/.test(name))
+    {
+        return true;
+    }
+
+    // Runnables are created and named on one thread, then dispatched
+    // (possibly to another). Writes on the origin thread are ok.
+    if (/::SetName/.test(callee) &&
+        /::UnlabeledDispatch/.test(name))
+    {
+        return true;
+    }
+
+    // We manually lock here
+    if (name == "Gecko_nsFont_InitSystem" ||
+        name == "Gecko_GetFontMetrics" ||
+        name == "Gecko_nsStyleFont_FixupMinFontSize" ||
+        /ThreadSafeGetDefaultFontHelper/.test(name))
+    {
+        return true;
+    }
+
+    return false;
+}
+
+function ignoreContents(entry)
+{
+    var whitelist = [
+        // We don't care what happens when we're about to crash.
+        "abort",
+        /MOZ_ReportAssertionFailure/,
+        /MOZ_ReportCrash/,
+        /MOZ_Crash/,
+        /MOZ_CrashPrintf/,
+        /AnnotateMozCrashReason/,
+        /InvalidArrayIndex_CRASH/,
+        /NS_ABORT_OOM/,
+
+        // These ought to be threadsafe.
+        "NS_DebugBreak",
+        /mozalloc_handle_oom/,
+        /^NS_Log/, /log_print/, /LazyLogModule::operator/,
+        /SprintfLiteral/, "PR_smprintf", "PR_smprintf_free",
+        /NS_DispatchToMainThread/, /NS_ReleaseOnMainThread/,
+        /NS_NewRunnableFunction/, /NS_Atomize/,
+        /nsCSSValue::BufferFromString/,
+        /NS_xstrdup/,
+        /Assert_NoQueryNeeded/,
+        /AssertCurrentThreadOwnsMe/,
+        /PlatformThread::CurrentId/,
+        /imgRequestProxy::GetProgressTracker/, // Uses an AutoLock
+        /Smprintf/,
+        "malloc",
+        "calloc",
+        "free",
+        "realloc",
+        "memalign",
+        "strdup",
+        "strndup",
+        "moz_xmalloc",
+        "moz_xcalloc",
+        "moz_xrealloc",
+        "moz_xmemalign",
+        "moz_xstrdup",
+        "moz_xstrndup",
+        "jemalloc_thread_local_arena",
+
+        // These all create static strings in local storage, which is threadsafe
+        // to do but not understood by the analysis yet.
+        / EmptyString\(\)/,
+
+        // These could probably be handled by treating the scope of PSAutoLock
+        // aka BaseAutoLock<PSMutex> as threadsafe.
+        /profiler_register_thread/,
+        /profiler_unregister_thread/,
+
+        // The analysis thinks we'll write to mBits in the DoGetStyleFoo<false>
+        // call.  Maybe the template parameter confuses it?
+        /ComputedStyle::PeekStyle/,
+
+        // The analysis can't cope with the indirection used for the objects
+        // being initialized here, from nsCSSValue::Array::Create to the return
+        // value of the Item(i) getter.
+        /nsCSSValue::SetCalcValue/,
+
+        // Unable to analyze safety of linked list initialization.
+        "Gecko_NewCSSValueSharedList",
+        "Gecko_CSSValue_InitSharedList",
+
+        // Unable to trace through dataflow, but straightforward if inspected.
+        "Gecko_NewNoneTransform",
+
+        // Need main thread assertions or other fixes.
+        /EffectCompositor::GetServoAnimationRule/,
+    ];
+    if (entry.matches(whitelist))
+        return true;
+
+    if (entry.isSafeArgument(0)) {
+        var heapWhitelist = [
+            // Operations on heap structures pointed to by arrays and strings are
+            // threadsafe as long as the array/string itself is threadsafe.
+            /nsTArray_Impl.*?::AppendElement/,
+            /nsTArray_Impl.*?::RemoveElementsAt/,
+            /nsTArray_Impl.*?::ReplaceElementsAt/,
+            /nsTArray_Impl.*?::InsertElementAt/,
+            /nsTArray_Impl.*?::SetCapacity/,
+            /nsTArray_Impl.*?::SetLength/,
+            /nsTArray_base.*?::EnsureCapacity/,
+            /nsTArray_base.*?::ShiftData/,
+            /AutoTArray.*?::Init/,
+            /(nsTSubstring<T>|nsAC?String)::SetCapacity/,
+            /(nsTSubstring<T>|nsAC?String)::SetLength/,
+            /(nsTSubstring<T>|nsAC?String)::Assign/,
+            /(nsTSubstring<T>|nsAC?String)::Append/,
+            /(nsTSubstring<T>|nsAC?String)::Replace/,
+            /(nsTSubstring<T>|nsAC?String)::Trim/,
+            /(nsTSubstring<T>|nsAC?String)::Truncate/,
+            /(nsTSubstring<T>|nsAC?String)::StripTaggedASCII/,
+            /(nsTSubstring<T>|nsAC?String)::operator=/,
+            /nsTAutoStringN<T, N>::nsTAutoStringN/,
+
+            // Similar for some other data structures
+            /nsCOMArray_base::SetCapacity/,
+            /nsCOMArray_base::Clear/,
+            /nsCOMArray_base::AppendElement/,
+
+            // UniquePtr is similar.
+            /mozilla::UniquePtr/,
+
+            // The use of unique pointers when copying mCropRect here confuses
+            // the analysis.
+            /nsStyleImage::DoCopy/,
+        ];
+        if (entry.matches(heapWhitelist))
+            return true;
+    }
+
+    if (entry.isSafeArgument(1)) {
+        var firstArgWhitelist = [
+            /nsTextFormatter::snprintf/,
+            /nsTextFormatter::ssprintf/,
+            /_ASCIIToUpperInSitu/,
+
+            // Handle some writes into an array whose safety we don't have a good way
+            // of tracking currently.
+            /FillImageLayerList/,
+            /FillImageLayerPositionCoordList/,
+        ];
+        if (entry.matches(firstArgWhitelist))
+            return true;
+    }
+
+    if (entry.isSafeArgument(2)) {
+        var secondArgWhitelist = [
+            /nsStringBuffer::ToString/,
+            /AppendUTF\d+toUTF\d+/,
+            /AppendASCIItoUTF\d+/,
+        ];
+        if (entry.matches(secondArgWhitelist))
+            return true;
+    }
+
+    return false;
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Sixgill Utilities
+///////////////////////////////////////////////////////////////////////////////
+
+function variableName(variable)
+{
+    return (variable && variable.Name) ? variable.Name[0] : null;
+}
+
+function stripFields(exp)
+{
+    // Fields and index operations do not involve any dereferences. Remove them
+    // from the expression but remember any encountered fields for use by
+    // annotations later on.
+    var fields = [];
+    while (true) {
+        if (exp.Kind == "Index") {
+            exp = exp.Exp[0];
+            continue;
+        }
+        if (exp.Kind == "Fld") {
+            var csuName = exp.Field.FieldCSU.Type.Name;
+            var fieldName = exp.Field.Name[0];
+            assert(csuName && fieldName);
+            fields.push(csuName + "." + fieldName);
+            exp = exp.Exp[0];
+            continue;
+        }
+        break;
+    }
+    return [exp, fields];
+}
+
+function isLocalVariable(variable)
+{
+    switch (variable.Kind) {
+      case "Return":
+      case "Temp":
+      case "Local":
+      case "Arg":
+        return true;
+    }
+    return false;
+}
+
+function isDirectCall(edge, regexp)
+{
+    return edge.Kind == "Call"
+        && edge.Exp[0].Kind == "Var"
+        && regexp.test(variableName(edge.Exp[0].Variable));
+}
+
+function isZero(exp)
+{
+    return exp.Kind == "Int" && exp.String == "0";
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Analysis Structures
+///////////////////////////////////////////////////////////////////////////////
+
+// Safe arguments are those which may be written through (directly, not through
+// pointer fields etc.) without concerns about thread safety. This includes
+// pointers to stack data, null pointers, and other data we know is thread
+// local, such as certain arguments to the root functions.
+//
+// Entries in the worklist keep track of the pointer arguments to the function
+// which are safe using a sorted array, so that this can be propagated down the
+// stack. Zero is |this|, and arguments are indexed starting at one.
+
+function WorklistEntry(name, safeArguments, stack, parameterNames)
+{
+    this.name = name;
+    this.safeArguments = safeArguments;
+    this.stack = stack;
+    this.parameterNames = parameterNames;
+}
+
+WorklistEntry.prototype.readable = function()
+{
+    const [ mangled, readable ] = splitFunction(this.name);
+    return readable;
+}
+
+WorklistEntry.prototype.mangledName = function()
+{
+    var str = this.name;
+    for (var safe of this.safeArguments)
+        str += " SAFE " + safe;
+    return str;
+}
+
+WorklistEntry.prototype.isSafeArgument = function(index)
+{
+    for (var safe of this.safeArguments) {
+        if (index == safe)
+            return true;
+    }
+    return false;
+}
+
+WorklistEntry.prototype.setParameterName = function(index, name)
+{
+    this.parameterNames[index] = name;
+}
+
+WorklistEntry.prototype.addSafeArgument = function(index)
+{
+    if (this.isSafeArgument(index))
+        return;
+    this.safeArguments.push(index);
+
+    // Sorting isn't necessary for correctness but makes printed stack info tidier.
+    this.safeArguments.sort();
+}
+
+function safeArgumentIndex(variable)
+{
+    if (variable.Kind == "This")
+        return 0;
+    if (variable.Kind == "Arg")
+        return variable.Index + 1;
+    return -1;
+}
+
+function nameMatches(name, match)
+{
+    if (typeof match == "string") {
+        if (name == match)
+            return true;
+    } else {
+        assert(match instanceof RegExp);
+        if (match.test(name))
+            return true;
+    }
+    return false;
+}
+
+function nameMatchesArray(name, matchArray)
+{
+    for (var match of matchArray) {
+        if (nameMatches(name, match))
+            return true;
+    }
+    return false;
+}
+
+WorklistEntry.prototype.matches = function(matchArray)
+{
+    return nameMatchesArray(this.name, matchArray);
+}
+
+function CallSite(callee, safeArguments, location, parameterNames)
+{
+    this.callee = callee;
+    this.safeArguments = safeArguments;
+    this.location = location;
+    this.parameterNames = parameterNames;
+}
+
+CallSite.prototype.safeString = function()
+{
+    if (this.safeArguments.length) {
+        var str = "";
+        for (var i = 0; i < this.safeArguments.length; i++) {
+            var arg = this.safeArguments[i];
+            if (arg in this.parameterNames)
+                str += " " + this.parameterNames[arg];
+            else
+                str += " <" + ((arg == 0) ? "this" : "arg" + (arg - 1)) + ">";
+        }
+        return " ### SafeArguments:" + str;
+    }
+    return "";
+}
+
+///////////////////////////////////////////////////////////////////////////////
+// Analysis Core
+///////////////////////////////////////////////////////////////////////////////
+
+var errorCount = 0;
+var errorLimit = 100;
+
+// We want to suppress output for functions that ended up not having any
+// hazards, for brevity of the final output. So each new toplevel function will
+// initialize this to a string, which should be printed only if an error is
+// seen.
+var errorHeader;
+
+var startTime = new Date;
+function elapsedTime()
+{
+    var seconds = (new Date - startTime) / 1000;
+    return "[" + seconds.toFixed(2) + "s] ";
+}
+
+var options = parse_options([
+    {
+        name: '--strip-prefix',
+        default: os.getenv('SOURCE') || '',
+        type: 'string'
+    },
+    {
+        name: '--add-prefix',
+        default: os.getenv('URLPREFIX') || '',
+        type: 'string'
+    },
+    {
+        name: '--verbose',
+        type: 'bool'
+    },
+]);
+
+function add_trailing_slash(str) {
+    if (str == '')
+        return str;
+    return str.endsWith("/") ? str : str + "/";
+}
+
+var removePrefix = add_trailing_slash(options.strip_prefix);
+var addPrefix = add_trailing_slash(options.add_prefix);
+
+if (options.verbose) {
+    printErr(`Removing prefix ${removePrefix} from paths`);
+    printErr(`Prepending ${addPrefix} to paths`);
+}
+
+print(elapsedTime() + "Loading types...");
+if (os.getenv("TYPECACHE"))
+    loadTypesWithCache('src_comp.xdb', os.getenv("TYPECACHE"));
+else
+    loadTypes('src_comp.xdb');
+print(elapsedTime() + "Starting analysis...");
+
+var xdb = xdbLibrary();
+xdb.open("src_body.xdb");
+
+var minStream = xdb.min_data_stream();
+var maxStream = xdb.max_data_stream();
+var roots = [];
+
+var [flag, arg] = scriptArgs;
+if (flag && (flag == '-f' || flag == '--function')) {
+    roots = [arg];
+} else {
+    for (var bodyIndex = minStream; bodyIndex <= maxStream; bodyIndex++) {
+        var key = xdb.read_key(bodyIndex);
+        var name = key.readString();
+        if (/^Gecko_/.test(name)) {
+            var data = xdb.read_entry(key);
+            if (/ServoBindings.cpp/.test(data.readString()))
+                roots.push(name);
+            xdb.free_string(data);
+        }
+        xdb.free_string(key);
+    }
+}
+
+print(elapsedTime() + "Found " + roots.length + " roots.");
+for (var i = 0; i < roots.length; i++) {
+    var root = roots[i];
+    errorHeader = elapsedTime() + "#" + (i + 1) + " Analyzing " + root + " ...";
+    try {
+        processRoot(root);
+    } catch (e) {
+        if (e != "Error!")
+            throw e;
+    }
+}
+
+print(`${elapsedTime()}Completed analysis, found ${errorCount}/${errorLimit} allowed errors`);
+
+var currentBody;
+
+// All local variable assignments we have seen in either the outer or inner
+// function. This crosses loop boundaries, and currently has an unsoundness
+// where later assignments in a loop are not taken into account.
+var assignments;
+
+// All loops in the current function which are reachable off main thread.
+var reachableLoops;
+
+// Functions that are reachable from the current root.
+var reachable = {};
+
+function dumpError(entry, location, text)
+{
+    if (errorHeader) {
+        print(errorHeader);
+        errorHeader = undefined;
+    }
+
+    var stack = entry.stack;
+    print("Error: " + text);
+    print("Location: " + entry.name + (location ? " @ " + location : "") + stack[0].safeString());
+    print("Stack Trace:");
+    // Include the callers in the stack trace instead of the callees. Make sure
+    // the dummy stack entry we added for the original roots is in place.
+    assert(stack[stack.length - 1].location == null);
+    for (var i = 0; i < stack.length - 1; i++)
+        print(stack[i + 1].callee + " @ " + stack[i].location + stack[i + 1].safeString());
+    print("\n");
+
+    if (++errorCount == errorLimit) {
+        print("Maximum number of errors encountered, exiting...");
+        quit();
+    }
+
+    throw "Error!";
+}
+
+// If edge is an assignment from a local variable, return the rhs variable.
+function variableAssignRhs(edge)
+{
+    if (edge.Kind == "Assign" && edge.Exp[1].Kind == "Drf" && edge.Exp[1].Exp[0].Kind == "Var") {
+        var variable = edge.Exp[1].Exp[0].Variable;
+        if (isLocalVariable(variable))
+            return variable;
+    }
+    return null;
+}
+
+function processAssign(body, entry, location, lhs, edge)
+{
+    var fields;
+    [lhs, fields] = stripFields(lhs);
+
+    switch (lhs.Kind) {
+      case "Var":
+        var name = variableName(lhs.Variable);
+        if (isLocalVariable(lhs.Variable)) {
+            // Remember any assignments to local variables in this function.
+            // Note that we ignore any points where the variable's address is
+            // taken and indirect assignments might occur. This is an
+            // unsoundness in the analysis.
+
+            let assign = [body, edge];
+
+            // Chain assignments if the RHS has only been assigned once.
+            var rhsVariable = variableAssignRhs(edge);
+            if (rhsVariable) {
+                var rhsAssign = singleAssignment(variableName(rhsVariable));
+                if (rhsAssign)
+                    assign = rhsAssign;
+            }
+
+            if (!(name in assignments))
+                assignments[name] = [];
+            assignments[name].push(assign);
+        } else {
+            checkVariableAssignment(entry, location, name);
+        }
+        return;
+      case "Drf":
+        var variable = null;
+        if (lhs.Exp[0].Kind == "Var") {
+            variable = lhs.Exp[0].Variable;
+            if (isSafeVariable(entry, variable))
+                return;
+        } else if (lhs.Exp[0].Kind == "Fld") {
+            const {
+                Name: [ fieldName ],
+                Type: {Kind, Type: fieldType},
+                FieldCSU: {Type: {Kind: containerTypeKind,
+                                  Name: containerTypeName}}
+            } = lhs.Exp[0].Field;
+            const [containerExpr] = lhs.Exp[0].Exp;
+
+            if (containerTypeKind == 'CSU' &&
+                Kind == 'Pointer' &&
+                isEdgeSafeArgument(entry, containerExpr) &&
+                isSafeMemberPointer(containerTypeName, fieldName, fieldType))
+            {
+                return;
+            }
+        }
+        if (fields.length)
+            checkFieldWrite(entry, location, fields);
+        else
+            checkDereferenceWrite(entry, location, variableName(variable));
+        return;
+      case "Int":
+        if (isZero(lhs)) {
+            // This shows up under MOZ_ASSERT, to crash the process.
+            return;
+        }
+    }
+    dumpError(entry, location, "Unknown assignment " + JSON.stringify(lhs));
+}
+
+function get_location(rawLocation) {
+    const filename = rawLocation.CacheString.replace(removePrefix, '');
+    return addPrefix + filename + "#" + rawLocation.Line;
+}
+
+function process(entry, body, addCallee)
+{
+    if (!("PEdge" in body))
+        return;
+
+    // Add any arguments which are safe due to annotations.
+    if ("DefineVariable" in body) {
+        for (var defvar of body.DefineVariable) {
+            var index = safeArgumentIndex(defvar.Variable);
+            if (index >= 0) {
+                var varName = index ? variableName(defvar.Variable) : "this";
+                assert(varName);
+                entry.setParameterName(index, varName);
+                var csuName = null;
+                var type = defvar.Type;
+                if (type.Kind == "Pointer" && type.Type.Kind == "CSU")
+                    csuName = type.Type.Name;
+                if (treatAsSafeArgument(entry, varName, csuName))
+                    entry.addSafeArgument(index);
+            }
+        }
+    }
+
+    // Points in the body which are reachable if we are not on the main thread.
+    var nonMainThreadPoints = [];
+    nonMainThreadPoints[body.Index[0]] = true;
+
+    for (var edge of body.PEdge) {
+        // Ignore code that only executes on the main thread.
+        if (!(edge.Index[0] in nonMainThreadPoints))
+            continue;
+
+        var location = get_location(body.PPoint[edge.Index[0] - 1].Location);
+
+        var callees = getCallees(edge);
+        for (var callee of callees) {
+            switch (callee.kind) {
+            case "direct":
+                var safeArguments = getEdgeSafeArguments(entry, edge, callee.name);
+                addCallee(new CallSite(callee.name, safeArguments, location, {}));
+                break;
+              case "resolved-field":
+                break;
+              case "field":
+                var field = callee.csu + "." + callee.field;
+                if (callee.isVirtual)
+                    checkOverridableVirtualCall(entry, location, field);
+                else
+                    checkIndirectCall(entry, location, field);
+                break;
+              case "indirect":
+                checkIndirectCall(entry, location, callee.variable);
+                break;
+              default:
+                dumpError(entry, location, "Unknown call " + callee.kind);
+                break;
+            }
+        }
+
+        var fallthrough = true;
+
+        if (edge.Kind == "Assign") {
+            assert(edge.Exp.length == 2);
+            processAssign(body, entry, location, edge.Exp[0], edge);
+        } else if (edge.Kind == "Call") {
+            assert(edge.Exp.length <= 2);
+            if (edge.Exp.length == 2)
+                processAssign(body, entry, location, edge.Exp[1], edge);
+
+            // Treat assertion failures as if they don't return, so that
+            // asserting NS_IsMainThread() is sufficient to prevent the
+            // analysis from considering a block of code.
+            if (isDirectCall(edge, /MOZ_ReportAssertionFailure/))
+                fallthrough = false;
+        } else if (edge.Kind == "Loop") {
+            reachableLoops[edge.BlockId.Loop] = true;
+        } else if (edge.Kind == "Assume") {
+            if (testFailsOffMainThread(edge.Exp[0], edge.PEdgeAssumeNonZero))
+                fallthrough = false;
+        }
+
+        if (fallthrough)
+            nonMainThreadPoints[edge.Index[1]] = true;
+    }
+}
+
+function maybeProcessMissingFunction(entry, addCallee)
+{
+    // If a function is missing it might be because a destructor Foo::~Foo() is
+    // being called but GCC only gave us an implementation for
+    // Foo::~Foo(int32). See computeCallgraph.js for a little more info.
+    var name = entry.name;
+    if (name.indexOf("::~") > 0 && name.indexOf("()") > 0) {
+        var callee = name.replace("()", "(int32)");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    // Similarly, a call to a C1 constructor might invoke the C4 constructor. A
+    // mangled constructor will be something like _ZN<length><name>C1E... or in
+    // the case of a templatized constructor, _ZN<length><name>C1I...EE... so
+    // we hack it and look for "C1E" or "C1I" and replace them with their C4
+    // variants. This will have rare false matches, but so far we haven't hit
+    // any external function calls of that sort.
+    if (entry.mangledName().includes("C1E") || entry.mangledName().includes("C1I")) {
+        var callee = name.replace("C1E", "C4E").replace("C1I", "C4I");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    // Hack to manually follow some typedefs that show up on some functions.
+    // This is a bug in the sixgill GCC plugin I think, since sixgill is
+    // supposed to follow any typedefs itself.
+    if (/mozilla::dom::Element/.test(name)) {
+        var callee = name.replace("mozilla::dom::Element", "Document::Element");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    // Hack for contravariant return types. When overriding a virtual method
+    // with a method that returns a different return type (a subtype of the
+    // original return type), we are getting the right mangled name but the
+    // wrong return type in the unmangled name.
+    if (/\$nsTextFrame*/.test(name)) {
+        var callee = name.replace("nsTextFrame", "nsIFrame");
+        addCallee(new CallSite(name, entry.safeArguments, entry.stack[0].location, entry.parameterNames));
+        return true;
+    }
+
+    return false;
+}
+
+function processRoot(name)
+{
+    var safeArguments = [];
+    var parameterNames = {};
+    var worklist = [new WorklistEntry(name, safeArguments, [new CallSite(name, safeArguments, null, parameterNames)], parameterNames)];
+
+    reachable = {};
+
+    while (worklist.length > 0) {
+        var entry = worklist.pop();
+
+        // In principle we would be better off doing a meet-over-paths here to get
+        // the common subset of arguments which are safe to write through. However,
+        // analyzing functions separately for each subset if simpler, ensures that
+        // the stack traces we produce accurately characterize the stack arguments,
+        // and should be fast enough for now.
+
+        if (entry.mangledName() in reachable)
+            continue;
+        reachable[entry.mangledName()] = true;
+
+        if (ignoreContents(entry))
+            continue;
+
+        var data = xdb.read_entry(entry.name);
+        var dataString = data.readString();
+        var callees = [];
+        if (dataString.length) {
+            // Reverse the order of the bodies we process so that we visit the
+            // outer function and see its assignments before the inner loops.
+            assignments = {};
+            reachableLoops = {};
+            var bodies = JSON.parse(dataString).reverse();
+            for (var body of bodies) {
+                if (!body.BlockId.Loop || body.BlockId.Loop in reachableLoops) {
+                    currentBody = body;
+                    process(entry, body, Array.prototype.push.bind(callees));
+                }
+            }
+        } else {
+            if (!maybeProcessMissingFunction(entry, Array.prototype.push.bind(callees)))
+                checkExternalFunction(entry);
+        }
+        xdb.free_string(data);
+
+        for (var callee of callees) {
+            if (!ignoreCallEdge(entry, callee.callee)) {
+                var nstack = [callee, ...entry.stack];
+                worklist.push(new WorklistEntry(callee.callee, callee.safeArguments, nstack, callee.parameterNames));
+            }
+        }
+    }
+}
+
+function isEdgeSafeArgument(entry, exp)
+{
+    var fields;
+    [exp, fields] = stripFields(exp);
+
+    if (exp.Kind == "Var" && isLocalVariable(exp.Variable))
+        return true;
+    if (exp.Kind == "Drf" && exp.Exp[0].Kind == "Var") {
+        var variable = exp.Exp[0].Variable;
+        return isSafeVariable(entry, variable);
+    }
+    if (isZero(exp))
+        return true;
+    return false;
+}
+
+function getEdgeSafeArguments(entry, edge, callee)
+{
+    assert(edge.Kind == "Call");
+    var res = [];
+    if ("PEdgeCallInstance" in edge) {
+        if (isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            res.push(0);
+    }
+    if ("PEdgeCallArguments" in edge) {
+        var args = edge.PEdgeCallArguments.Exp;
+        for (var i = 0; i < args.length; i++) {
+            if (isEdgeSafeArgument(entry, args[i]))
+                res.push(i + 1);
+        }
+    }
+    return res;
+}
+
+function singleAssignment(name)
+{
+    if (name in assignments) {
+        var edges = assignments[name];
+        if (edges.length == 1)
+            return edges[0];
+    }
+    return null;
+}
+
+function expressionValueEdge(exp) {
+    if (!(exp.Kind == "Var" && exp.Variable.Kind == "Temp"))
+        return null;
+    const assign = singleAssignment(variableName(exp.Variable));
+    if (!assign)
+        return null;
+    const [body, edge] = assign;
+    return edge;
+}
+
+// Examples:
+//
+//   void foo(type* aSafe) {
+//     type* safeBecauseNew = new type(...);
+//     type* unsafeBecauseMultipleAssignments = new type(...);
+//     if (rand())
+//       unsafeBecauseMultipleAssignments = bar();
+//     type* safeBecauseSingleAssignmentOfSafe = aSafe;
+//   }
+//
+function isSafeVariable(entry, variable)
+{
+    var index = safeArgumentIndex(variable);
+    if (index >= 0)
+        return entry.isSafeArgument(index);
+
+    if (variable.Kind != "Temp" && variable.Kind != "Local")
+        return false;
+    var name = variableName(variable);
+
+    if (!entry.safeLocals)
+        entry.safeLocals = new Map;
+    if (entry.safeLocals.has(name))
+        return entry.safeLocals.get(name);
+
+    const safe = isSafeLocalVariable(entry, name);
+    entry.safeLocals.set(name, safe);
+    return safe;
+}
+
+function isSafeLocalVariable(entry, name)
+{
+    // If there is a single place where this variable has been assigned on
+    // edges we are considering, look at that edge.
+    var assign = singleAssignment(name);
+    if (assign) {
+        const [body, edge] = assign;
+
+        // Treat temporary pointers to DebugOnly contents as thread local.
+        if (isDirectCall(edge, /DebugOnly.*?::operator/))
+            return true;
+
+        // Treat heap allocated pointers as thread local during construction.
+        // Hopefully the construction code doesn't leak pointers to the object
+        // to places where other threads might access it.
+        if (isDirectCall(edge, /operator new/) ||
+            isDirectCall(edge, /nsCSSValue::Array::Create/))
+        {
+            return true;
+        }
+
+        if ("PEdgeCallInstance" in edge) {
+            // References to the contents of an array are threadsafe if the array
+            // itself is threadsafe.
+            if ((isDirectCall(edge, /operator\[\]/) ||
+                 isDirectCall(edge, /nsTArray.*?::InsertElementAt\b/) ||
+                 isDirectCall(edge, /nsStyleContent::ContentAt/) ||
+                 isDirectCall(edge, /nsTArray_base.*?::GetAutoArrayBuffer\b/)) &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            {
+                return true;
+            }
+
+            // Watch for the coerced result of a getter_AddRefs or getter_Copies call.
+            if (isDirectCall(edge, /operator /)) {
+                var otherEdge = expressionValueEdge(edge.PEdgeCallInstance.Exp);
+                if (otherEdge &&
+                    isDirectCall(otherEdge, /getter_(?:AddRefs|Copies)/) &&
+                    isEdgeSafeArgument(entry, otherEdge.PEdgeCallArguments.Exp[0]))
+                {
+                    return true;
+                }
+            }
+
+            // RefPtr::operator->() and operator* transmit the safety of the
+            // RefPtr to the return value.
+            if (isDirectCall(edge, /RefPtr<.*?>::operator(->|\*)\(\)/) &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            {
+                return true;
+            }
+
+            // Placement-new returns a pointer that is as safe as the pointer
+            // passed to it. Exp[0] is the size, Exp[1] is the pointer/address.
+            // Note that the invocation of the constructor is a separate call,
+            // and so need not be considered here.
+            if (isDirectCall(edge, /operator new/) &&
+                edge.PEdgeCallInstance.Exp.length == 2 &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp[1]))
+            {
+                return true;
+            }
+
+            // Coercion via AsAString preserves safety.
+            if (isDirectCall(edge, /AsAString/) &&
+                isEdgeSafeArgument(entry, edge.PEdgeCallInstance.Exp))
+            {
+                return true;
+            }
+
+            // Special case:
+            //
+            //   keyframe->mTimingFunction.emplace()
+            //   keyframe->mTimingFunction->Init()
+            //
+            // The object calling Init should be considered safe here because
+            // we just emplaced it, though in general keyframe::operator->
+            // could do something crazy.
+            if (isDirectCall(edge, /operator->/)) do {
+                const predges = getPredecessors(body)[edge.Index[0]];
+                if (!predges || predges.length != 1)
+                    break;
+                const predge = predges[0];
+                if (!isDirectCall(predge, /\bemplace\b/))
+                    break;
+                const instance = predge.PEdgeCallInstance;
+                if (JSON.stringify(instance) == JSON.stringify(edge.PEdgeCallInstance))
+                    return true;
+            } while (false);
+        }
+
+        if (isSafeAssignment(entry, edge, name))
+            return true;
+
+        // Watch out for variables which were assigned arguments.
+        var rhsVariable = variableAssignRhs(edge);
+        if (rhsVariable)
+            return isSafeVariable(entry, rhsVariable);
+    }
+
+    // When temporary stack structures are created (either to return or to call
+    // methods on without assigning them a name), the generated sixgill JSON is
+    // rather strange. The temporary has structure type and is never assigned
+    // to, but is dereferenced. GCC is probably not showing us everything it is
+    // doing to compile this code. Pattern match for this case here.
+
+    // The variable should have structure type.
+    var type = null;
+    for (var defvar of currentBody.DefineVariable) {
+        if (variableName(defvar.Variable) == name) {
+            type = defvar.Type;
+            break;
+        }
+    }
+    if (!type || type.Kind != "CSU")
+        return false;
+
+    // The variable should not have been written to anywhere up to this point.
+    // If it is initialized at this point we should have seen *some* write
+    // already, since the CFG edges are visited in reverse post order.
+    if (name in assignments)
+        return false;
+
+    return true;
+}
+
+function isSafeMemberPointer(containerType, memberName, memberType)
+{
+    // nsTArray owns its header.
+    if (containerType.includes("nsTArray_base") && memberName == "mHdr")
+        return true;
+
+    if (memberType.Kind != 'Pointer')
+        return false;
+
+    // Special-cases go here :)
+    return false;
+}
+
+// Return whether 'exp == value' holds only when execution is on the main thread.
+function testFailsOffMainThread(exp, value) {
+    switch (exp.Kind) {
+      case "Drf":
+        var edge = expressionValueEdge(exp.Exp[0]);
+        if (edge) {
+            if (isDirectCall(edge, /NS_IsMainThread/) && value)
+                return true;
+            if (isDirectCall(edge, /IsInServoTraversal/) && !value)
+                return true;
+            if (isDirectCall(edge, /IsCurrentThreadInServoTraversal/) && !value)
+                return true;
+            if (isDirectCall(edge, /__builtin_expect/))
+                return testFailsOffMainThread(edge.PEdgeCallArguments.Exp[0], value);
+            if (edge.Kind == "Assign")
+                return testFailsOffMainThread(edge.Exp[1], value);
+        }
+        break;
+      case "Unop":
+        if (exp.OpCode == "LogicalNot")
+            return testFailsOffMainThread(exp.Exp[0], !value);
+        break;
+      case "Binop":
+        if (exp.OpCode == "NotEqual" || exp.OpCode == "Equal") {
+            var cmpExp = isZero(exp.Exp[0])
+                ? exp.Exp[1]
+                : (isZero(exp.Exp[1]) ? exp.Exp[0] : null);
+            if (cmpExp)
+                return testFailsOffMainThread(cmpExp, exp.OpCode == "NotEqual" ? value : !value);
+        }
+        break;
+      case "Int":
+        if (exp.String == "0" && value)
+            return true;
+        if (exp.String == "1" && !value)
+            return true;
+        break;
+    }
+    return false;
+}
diff --git a/js/src/devtools/rootAnalysis/analyzeRoots.js b/js/src/devtools/rootAnalysis/analyzeRoots.js
new file mode 100644
index 0000000000..b66a66cec3
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/analyzeRoots.js
@@ -0,0 +1,919 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('CFG.js');
+loadRelativeToScript('dumpCFG.js');
+
+var sourceRoot = (os.getenv('SOURCE') || '') + '/';
+
+var functionName;
+var functionBodies;
+
+try {
+    var options = parse_options([
+        {
+            name: "--function",
+            type: 'string',
+        },
+        {
+            name: "-f",
+            type: "string",
+            dest: "function",
+        },
+        {
+            name: "gcFunctions",
+            default: "gcFunctions.lst"
+        },
+        {
+            name: "gcEdges",
+            default: "gcEdges.json"
+        },
+        {
+            name: "limitedFunctions",
+            default: "limitedFunctions.lst"
+        },
+        {
+            name: "gcTypes",
+            default: "gcTypes.txt"
+        },
+        {
+            name: "typeInfo",
+            default: "typeInfo.txt"
+        },
+        {
+            name: "batch",
+            type: "number",
+            default: 1
+        },
+        {
+            name: "numBatches",
+            type: "number",
+            default: 1
+        },
+        {
+            name: "tmpfile",
+            default: "tmp.txt"
+        },
+    ]);
+} catch (e) {
+    printErr(e);
+    printErr("Usage: analyzeRoots.js [-f function_name] <gcFunctions.lst> <gcEdges.txt> <limitedFunctions.lst> <gcTypes.txt> <typeInfo.txt> [start end [tmpfile]]");
+    quit(1);
+}
+var gcFunctions = {};
+var text = snarf(options.gcFunctions).split("\n");
+assert(text.pop().length == 0);
+for (const line of text)
+    gcFunctions[mangled(line)] = readable(line);
+
+var limitedFunctions = JSON.parse(snarf(options.limitedFunctions));
+text = null;
+
+var typeInfo = loadTypeInfo(options.typeInfo);
+
+var gcEdges = JSON.parse(os.file.readFile(options.gcEdges));
+
+var match;
+var gcThings = {};
+var gcPointers = {};
+
+text = snarf(options.gcTypes).split("\n");
+for (var line of text) {
+    if (match = /^GCThing: (.*)/.exec(line))
+        gcThings[match[1]] = true;
+    if (match = /^GCPointer: (.*)/.exec(line))
+        gcPointers[match[1]] = true;
+}
+text = null;
+
+function isGCType(type)
+{
+    if (type.Kind == "CSU")
+        return type.Name in gcThings;
+    else if (type.Kind == "Array")
+        return isGCType(type.Type);
+    return false;
+}
+
+function isUnrootedType(type)
+{
+    if (type.Kind == "Pointer")
+        return isGCType(type.Type);
+    else if (type.Kind == "Array") {
+        if (!type.Type) {
+            printErr("Received Array Kind with no Type");
+            printErr(JSON.stringify(type));
+            printErr(getBacktrace({args: true, locals: true}));
+        }
+        return isUnrootedType(type.Type);
+    } else if (type.Kind == "CSU")
+        return type.Name in gcPointers;
+    else
+        return false;
+}
+
+function edgeCanGC(edge)
+{
+    if (edge.Kind != "Call")
+        return false;
+
+    var callee = edge.Exp[0];
+
+    while (callee.Kind == "Drf")
+        callee = callee.Exp[0];
+
+    if (callee.Kind == "Var") {
+        var variable = callee.Variable;
+
+        if (variable.Kind == "Func") {
+            var func = mangled(variable.Name[0]);
+            if ((func in gcFunctions) || ((func + internalMarker) in gcFunctions))
+                return `'${func}$${gcFunctions[func]}'`;
+            return false;
+        }
+
+        var varName = variable.Name[0];
+        return indirectCallCannotGC(functionName, varName) ? false : "'*" + varName + "'";
+    }
+
+    assert(callee.Kind == "Fld");
+    const staticCSU = getFieldCallInstanceCSU(edge, callee.Field);
+
+    if (fieldCallCannotGC(staticCSU, callee.Field.Name[0]))
+        return false;
+
+    const fieldkey = fieldKey(staticCSU, callee.Field);
+    if (fieldkey in gcFunctions)
+        return `'${fieldkey}'`;
+    return false;
+}
+
+// Search upwards through a function's control flow graph (CFG) to find a path containing:
+//
+// - a use of a variable, preceded by
+//
+// - a function call that can GC, preceded by
+//
+// - a use of the variable that shows that the live range starts at least that
+//   far back, preceded by
+//
+// - an informative use of the variable (which might be the same use), one that
+//   assigns to it a value that might contain a GC pointer (or is the start of
+//   the function for parameters or 'this'.) This is not necessary for
+//   correctness, it just makes it easier to understand why something might be
+//   a hazard. The output of the analysis will include the whole path from the
+//   informative use to the post-GC use, to make the problem as understandable
+//   as possible.
+//
+// A canonical example might be:
+//
+//     void foo() {
+//         JS::Value* val = lookupValue(); <-- informative use
+//         if (!val.isUndefined()) {       <-- any use
+//             GC();                       <-- GC call
+//         }
+//         putValue(val);                  <-- a use after a GC
+//     }
+//
+// The search is performed on an underlying CFG that we traverse in
+// breadth-first order (to find the shortest path). We build a path starting
+// from an empty path and conditionally lengthening and improving it according
+// to the computation occurring on each incoming edge. (If that path so far
+// does not have a GC call and we traverse an edge with a GC call, then we
+// lengthen the path by that edge and record it as including a GC call.) The
+// resulting path may include a point or edge more than once! For example, in:
+//
+//     void foo(JS::Value val) {
+//         for (int i = 0; i < N; i++) {
+//             GC();
+//             val = processValue(val);
+//         }
+//     }
+//
+// the path would start at the point after processValue(), go through the GC(),
+// then back to the processValue() (for the call in the previous loop
+// iteration).
+//
+// While searching, each point is annotated with a path node corresponding to
+// the best path found to that node so far. When a later search ends up at the
+// same point, the best path node is kept. (But the path that it heads may
+// include an earlier path node for the same point, as in the case above.)
+//
+// What info we want depends on whether the variable turns out to be live
+// across a GC call. We are looking for both hazards (unrooted variables live
+// across GC calls) and unnecessary roots (rooted variables that have no GC
+// calls in their live ranges.)
+//
+// If not:
+//
+//  - 'minimumUse': the earliest point in each body that uses the variable, for
+//    reporting on unnecessary roots.
+//
+// If so:
+//
+//  - 'successor': a path from the GC call to a use of the variable after the GC
+//    call, chained through 'successor' field in the returned edge descriptor
+//
+//  - 'gcInfo': a direct pointer to the GC call edge
+//
+function findGCBeforeValueUse(start_body, start_point, suppressed_bits, variable)
+{
+    const isGCSuppressed = Boolean(suppressed_bits & ATTR_GC_SUPPRESSED);
+
+    // Scan through all edges preceding an unrooted variable use, using an
+    // explicit worklist, looking for a GC call and a preceding point where the
+    // variable is known to be live. A worklist contains an incoming edge
+    // together with a description of where it or one of its successors GC'd
+    // (if any).
+
+    class Path {
+        get ProgressProperties() { return ["informativeUse", "anyUse", "gcInfo"]; }
+
+        constructor(successor_path, body, ppoint) {
+            Object.assign(this, {body, ppoint});
+            if (successor_path !== undefined) {
+                this.successor = successor_path;
+                for (const prop of this.ProgressProperties) {
+                    if (prop in successor_path) {
+                        this[prop] = successor_path[prop];
+                    }
+                }
+            }
+        }
+
+        toString() {
+            const trail = [];
+            for (let path = this; path.ppoint; path = path.successor) {
+                trail.push(path.ppoint);
+            }
+            return trail.join();
+        }
+
+        // Return -1, 0, or 1 to indicate how complete this Path is compared
+        // to another one.
+        compare(other) {
+            for (const prop of this.ProgressProperties) {
+                const a = this.hasOwnProperty(prop);
+                const b = other.hasOwnProperty(prop);
+                if (a != b) {
+                    return a - b;
+                }
+            }
+            return 0;
+        }
+    };
+
+    // In case we never find an informative use, keep track of the best path
+    // found with any use.
+    let bestPathWithAnyUse = null;
+
+    const visitor = new class extends Visitor {
+        constructor() {
+            super(functionBodies);
+        }
+
+        // Do a BFS upwards through the CFG, starting from a use of the
+        // variable and searching for a path containing a GC followed by an
+        // initializing use of the variable (or, in forward direction, a start
+        // of the variable's live range, a GC within that live range, and then
+        // a use showing that the live range extends past the GC call.)
+        // Actually, possibly two uses: any use at all, and then if available
+        // an "informative" use that is more convincing (they may be the same).
+        //
+        // The CFG is a graph (a 'body' here is acyclic, but they can contain
+        // loop nodes that bridge to additional bodies for the loop, so the
+        // overall graph can by cyclic.) That means there may be multiple paths
+        // from point A to point B, and we want paths with a GC on them. This
+        // can be thought of as searching for a "maximal GCing" path from a use
+        // A to an initialization B.
+        //
+        // This is implemented as a BFS search that when it reaches a point
+        // that has been visited before, stops if and only if the current path
+        // being advanced is a less GC-ful path. The traversal pushes a
+        // `gcInfo` token, initially empty, up through the graph and stores the
+        // maximal one visited so far at every point.
+        //
+        // Note that this means we may traverse through the same point more
+        // than once, and so in theory this scan is superlinear -- if you visit
+        // every point twice, once for a non GC path and once for a GC path, it
+        // would be 2^n. But that is unlikely to matter, since you'd need lots
+        // of split/join pairs that GC on one side and not the other, and you'd
+        // have to visit them in an unlucky order. This could be fixed by
+        // updating the gcInfo for past points in a path when a GC is found,
+        // but it hasn't been found to matter in practice yet.
+
+        next_action(prev, current) {
+            // Continue if first visit, or the new path is more complete than the old path. This
+            // could be enhanced at some point to choose paths with 'better'
+            // examples of GC (eg a call that invokes GC through concrete functions rather than going through a function pointer that is conservatively assumed to GC.)
+
+            if (!current) {
+                // This search path has been terminated.
+                return "prune";
+            }
+
+            if (current.informativeUse) {
+                // We have a path with an informative use leading to a GC
+                // leading to the starting point.
+                assert(current.gcInfo);
+                return "done";
+            }
+
+            if (prev === undefined) {
+                // first visit
+                return "continue";
+            }
+
+            if (!prev.gcInfo && current.gcInfo) {
+                // More GC.
+                return "continue";
+            } else {
+                return "prune";
+            }
+        }
+
+        merge_info(prev, current) {
+            // Keep the most complete path.
+
+            if (!prev || !current) {
+                return prev || current;
+            }
+
+            // Tie goes to the first found, since it will be shorter when doing a BFS-like search.
+            return prev.compare(current) >= 0 ? prev : current;
+        }
+
+        extend_path(edge, body, ppoint, successor_path) {
+            // Clone the successor path node and then tack on the new point. Other values
+            // will be updated during the rest of this function, according to what is
+            // happening on the edge.
+            const path = new Path(successor_path, body, ppoint);
+            if (edge === null) {
+                // Artificial edge to connect loops to their surrounding nodes in the outer body.
+                // Does not influence "completeness" of path.
+                return path;
+            }
+
+            assert(ppoint == edge.Index[0]);
+
+            if (edgeEndsValueLiveRange(edge, variable, body)) {
+                // Terminate the search through this point.
+                return null;
+            }
+
+            const edge_starts = edgeStartsValueLiveRange(edge, variable);
+            const edge_uses = edgeUsesVariable(edge, variable, body);
+
+            if (edge_starts || edge_uses) {
+                if (!body.minimumUse || ppoint < body.minimumUse)
+                    body.minimumUse = ppoint;
+            }
+
+            if (edge_starts) {
+                // This is a beginning of the variable's live range. If we can
+                // reach a GC call from here, then we're done -- we have a path
+                // from the beginning of the live range, through the GC call, to a
+                // use after the GC call that proves its live range extends at
+                // least that far.
+                if (path.gcInfo) {
+                    path.anyUse = path.anyUse || edge;
+                    path.informativeUse = path.informativeUse || edge;
+                    return path;
+                }
+
+                // Otherwise, truncate this particular branch of the search at this
+                // edge -- there is no GC after this use, and traversing the edge
+                // would lead to a different live range.
+                return null;
+            }
+
+            // The value is live across this edge. Check whether this edge can GC (if we don't have a GC yet on this path.)
+            const had_gcInfo = Boolean(path.gcInfo);
+            if (!path.gcInfo && !(body.attrs[ppoint] & ATTR_GC_SUPPRESSED) && !isGCSuppressed) {
+                var gcName = edgeCanGC(edge, body);
+                if (gcName) {
+                    path.gcInfo = {name:gcName, body, ppoint};
+                }
+            }
+
+            // Beginning of function?
+            if (ppoint == body.Index[0] && body.BlockId.Kind != "Loop") {
+                if (path.gcInfo && (variable.Kind == "Arg" || variable.Kind == "This")) {
+                    // The scope of arguments starts at the beginning of the
+                    // function.
+                    path.anyUse = path.informativeUse = true;
+                }
+
+                if (path.anyUse) {
+                    // We know the variable was live across the GC. We may or
+                    // may not have found an "informative" explanation
+                    // beginning of the live range. (This can happen if the
+                    // live range started when a variable is used as a
+                    // retparam.)
+                    return path;
+                }
+            }
+
+            if (!path.gcInfo) {
+                // We haven't reached a GC yet, so don't start looking for uses.
+                return path;
+            }
+
+            if (!edge_uses) {
+                // We have a GC. If this edge doesn't use the value, then there
+                // is no change to the completeness of the path.
+                return path;
+            }
+
+            // The live range starts at least this far back, so we're done for
+            // the same reason as with edge_starts. The only difference is that
+            // a GC on this edge indicates a hazard, whereas if we're killing a
+            // live range in the GC call then it's not live *across* the call.
+            //
+            // However, we may want to generate a longer usage chain for the
+            // variable than is minimally necessary. For example, consider:
+            //
+            //   Value v = f();
+            //   if (v.isUndefined())
+            //     return false;
+            //   gc();
+            //   return v;
+            //
+            // The call to .isUndefined() is considered to be a use and
+            // therefore indicates that v must be live at that point. But it's
+            // more helpful to the user to continue the 'successor' path to
+            // include the ancestor where the value was generated. So we will
+            // only stop here if edge.Kind is Assign; otherwise, we'll pass a
+            // "preGCLive" value up through the worklist to remember that the
+            // variable *is* alive before the GC and so this function should be
+            // returning a true value even if we don't find an assignment.
+
+            // One special case: if the use of the variable is on the
+            // destination part of the edge (which currently only happens for
+            // the return value and a terminal edge in the body), and this edge
+            // is also GCing, then that usage happens *after* the GC and so
+            // should not be used for anyUse or informativeUse. This matters
+            // for a hazard involving a destructor GC'ing after an immobile
+            // return value has been assigned:
+            //
+            //   GCInDestructor guard(cx);
+            //   if (cond()) {
+            //     return nullptr;
+            //   }
+            //
+            // which boils down to
+            //
+            //   p1 --(construct guard)-->
+            //   p2 --(call cond)-->
+            //   p3 --(returnval := nullptr) -->
+            //   p4 --(destruct guard, possibly GCing)-->
+            //   p5
+            //
+            // The return value is considered to be live at p5. The live range
+            // of the return value would ordinarily be from p3->p4->p5, except
+            // that the nullptr assignment means it needn't be considered live
+            // back that far, and so the live range is *just* p5. The GC on the
+            // 4->5 edge happens just before that range, so the value was not
+            // live across the GC.
+            //
+            if (!had_gcInfo && edge_uses == edge.Index[1]) {
+                return path; // New GC does not cross this variable use.
+            }
+
+            path.anyUse = path.anyUse || edge;
+            bestPathWithAnyUse = bestPathWithAnyUse || path;
+            if (edge.Kind == 'Assign') {
+                path.informativeUse = edge; // Done! Setting this terminates the search.
+            }
+
+            return path;
+        };
+    };
+
+    return BFS_upwards(start_body, start_point, functionBodies, visitor, new Path()) || bestPathWithAnyUse;
+}
+
+function variableLiveAcrossGC(suppressed, variable)
+{
+    // A variable is live across a GC if (1) it is used by an edge (as in, it
+    // was at least initialized), and (2) it is used after a GC in a successor
+    // edge.
+
+    for (var body of functionBodies)
+        body.minimumUse = 0;
+
+    for (var body of functionBodies) {
+        if (!("PEdge" in body))
+            continue;
+        for (var edge of body.PEdge) {
+            // Examples:
+            //
+            //   JSObject* obj = NewObject();
+            //   cangc();
+            //   obj = NewObject();     <-- mentions 'obj' but kills previous value
+            //
+            // This is not a hazard. Contrast this with:
+            //
+            //   JSObject* obj = NewObject();
+            //   cangc();
+            //   obj = LookAt(obj);  <-- uses 'obj' and kills previous value
+            //
+            // This is a hazard; the initial value of obj is live across
+            // cangc(). And a third possibility:
+            //
+            //   JSObject* obj = NewObject();
+            //   obj = CopyObject(obj);
+            //
+            // This is not a hazard, because even though CopyObject can GC, obj
+            // is not live across it. (obj is live before CopyObject, and
+            // probably after, but not across.) There may be a hazard within
+            // CopyObject, of course.
+            //
+
+            // Ignore uses that are just invalidating the previous value.
+            if (edgeEndsValueLiveRange(edge, variable, body))
+                continue;
+
+            var usePoint = edgeUsesVariable(edge, variable, body);
+            if (usePoint) {
+                var call = findGCBeforeValueUse(body, usePoint, suppressed, variable);
+                if (!call)
+                    continue;
+
+                call.afterGCUse = usePoint;
+                return call;
+            }
+        }
+    }
+    return null;
+}
+
+// An unrooted variable has its address stored in another variable via
+// assignment, or passed into a function that can GC. If the address is
+// assigned into some other variable, we can't track it to see if it is held
+// live across a GC. If it is passed into a function that can GC, then it's
+// sort of like a Handle to an unrooted location, and the callee could GC
+// before overwriting it or rooting it.
+function unsafeVariableAddressTaken(suppressed, variable)
+{
+    for (var body of functionBodies) {
+        if (!("PEdge" in body))
+            continue;
+        for (var edge of body.PEdge) {
+            if (edgeTakesVariableAddress(edge, variable, body)) {
+                if (edge.Kind == "Assign" || (!(suppressed & ATTR_GC_SUPPRESSED) && edgeCanGC(edge)))
+                    return {body:body, ppoint:edge.Index[0]};
+            }
+        }
+    }
+    return null;
+}
+
+// Read out the brief (non-JSON, semi-human-readable) CFG description for the
+// given function and store it.
+function loadPrintedLines(functionName)
+{
+    assert(!os.system("xdbfind src_body.xdb '" + functionName + "' > " + options.tmpfile));
+    var lines = snarf(options.tmpfile).split('\n');
+
+    for (var body of functionBodies)
+        body.lines = [];
+
+    // Distribute lines of output to the block they originate from.
+    var currentBody = null;
+    for (var line of lines) {
+        if (/^block:/.test(line)) {
+            if (match = /:(loop#[\d#]+)/.exec(line)) {
+                var loop = match[1];
+                var found = false;
+                for (var body of functionBodies) {
+                    if (body.BlockId.Kind == "Loop" && body.BlockId.Loop == loop) {
+                        assert(!found);
+                        found = true;
+                        currentBody = body;
+                    }
+                }
+                assert(found);
+            } else {
+                for (var body of functionBodies) {
+                    if (body.BlockId.Kind == "Function")
+                        currentBody = body;
+                }
+            }
+        }
+        if (currentBody)
+            currentBody.lines.push(line);
+    }
+}
+
+function findLocation(body, ppoint, opts={brief: false})
+{
+    var location = body.PPoint[ppoint - 1].Location;
+    var file = location.CacheString;
+
+    if (file.indexOf(sourceRoot) == 0)
+        file = file.substring(sourceRoot.length);
+
+    if (opts.brief) {
+        var m = /.*\/(.*)/.exec(file);
+        if (m)
+            file = m[1];
+    }
+
+    return file + ":" + location.Line;
+}
+
+function locationLine(text)
+{
+    if (match = /:(\d+)$/.exec(text))
+        return match[1];
+    return 0;
+}
+
+function printEntryTrace(functionName, entry)
+{
+    var gcPoint = entry.gcInfo ? entry.gcInfo.ppoint : 0;
+
+    if (!functionBodies[0].lines)
+        loadPrintedLines(functionName);
+
+    while (entry.successor) {
+        var ppoint = entry.ppoint;
+        var lineText = findLocation(entry.body, ppoint, {"brief": true});
+
+        var edgeText = "";
+        if (entry.successor && entry.successor.body == entry.body) {
+            // If the next point in the trace is in the same block, look for an
+            // edge between them.
+            var next = entry.successor.ppoint;
+
+            if (!entry.body.edgeTable) {
+                var table = {};
+                entry.body.edgeTable = table;
+                for (var line of entry.body.lines) {
+                    if (match = /^\w+\((\d+,\d+),/.exec(line))
+                        table[match[1]] = line; // May be multiple?
+                }
+                if (entry.body.BlockId.Kind == 'Loop') {
+                    const [startPoint, endPoint] = entry.body.Index;
+                    table[`${endPoint},${startPoint}`] = '(loop to next iteration)';
+                }
+            }
+
+            edgeText = entry.body.edgeTable[ppoint + "," + next];
+            assert(edgeText);
+            if (ppoint == gcPoint)
+                edgeText += " [[GC call]]";
+        } else {
+            // Look for any outgoing edge from the chosen point.
+            for (var line of entry.body.lines) {
+                if (match = /\((\d+),/.exec(line)) {
+                    if (match[1] == ppoint) {
+                        edgeText = line;
+                        break;
+                    }
+                }
+            }
+            if (ppoint == entry.body.Index[1] && entry.body.BlockId.Kind == "Function")
+                edgeText += " [[end of function]]";
+        }
+
+        print("    " + lineText + (edgeText.length ? ": " + edgeText : ""));
+        entry = entry.successor;
+    }
+}
+
+function isRootedType(type)
+{
+    return type.Kind == "CSU" && ((type.Name in typeInfo.RootedPointers) ||
+                                  (type.Name in typeInfo.RootedGCThings));
+}
+
+function typeDesc(type)
+{
+    if (type.Kind == "CSU") {
+        return type.Name;
+    } else if ('Type' in type) {
+        var inner = typeDesc(type.Type);
+        if (type.Kind == 'Pointer')
+            return inner + '*';
+        else if (type.Kind == 'Array')
+            return inner + '[]';
+        else
+            return inner + '?';
+    } else {
+        return '???';
+    }
+}
+
+function processBodies(functionName, wholeBodyAttrs)
+{
+    if (!("DefineVariable" in functionBodies[0]))
+      return;
+    const funcInfo = limitedFunctions[mangled(functionName)] || { attributes: 0 };
+    const suppressed = funcInfo.attributes | wholeBodyAttrs;
+
+    // Look for the JS_EXPECT_HAZARDS annotation, and output a different
+    // message in that case that won't be counted as a hazard.
+    var annotations = new Set();
+    for (const variable of functionBodies[0].DefineVariable) {
+        if (variable.Variable.Kind == "Func" && variable.Variable.Name[0] == functionName) {
+            for (const { Name: [tag, value] } of (variable.Type.Annotation || [])) {
+                if (tag == 'annotate')
+                    annotations.add(value);
+            }
+        }
+    }
+
+    var missingExpectedHazard = annotations.has("Expect Hazards");
+
+    // Awful special case, hopefully temporary:
+    //
+    // The DOM bindings code generator uses "holders" to externally root
+    // variables. So for example:
+    //
+    //       StringObjectRecordOrLong arg0;
+    //       StringObjectRecordOrLongArgument arg0_holder(arg0);
+    //       arg0_holder.TrySetToStringObjectRecord(cx, args[0]);
+    //       GC();
+    //       self->PassUnion22(cx, arg0);
+    //
+    // This appears to be a rooting hazard on arg0, but it is rooted by
+    // arg0_holder if you set it to any of its union types that requires
+    // rooting.
+    //
+    // Additionally, the holder may be reported as a hazard because it's not
+    // itself a Rooted or a subclass of AutoRooter; it contains a
+    // Maybe<RecordRooter<T>> that will get emplaced if rooting is required.
+    //
+    // Hopefully these will be simplified at some point (see bug 1517829), but
+    // for now we special-case functions in the mozilla::dom namespace that
+    // contain locals with types ending in "Argument". Or
+    // Maybe<SomethingArgument>. Or Maybe<SpiderMonkeyInterfaceRooter<T>>. It's
+    // a harsh world.
+    const ignoreVars = new Set();
+    if (functionName.match(/mozilla::dom::/)) {
+        const vars = functionBodies[0].DefineVariable.filter(
+            v => v.Type.Kind == 'CSU' && v.Variable.Kind == 'Local'
+        ).map(
+            v => [ v.Variable.Name[0], v.Type.Name ]
+        );
+
+        const holders = vars.filter(
+            ([n, t]) => n.match(/^arg\d+_holder$/) &&
+                        (t.includes("Argument") || t.includes("Rooter")));
+        for (const [holder,] of holders) {
+            ignoreVars.add(holder); // Ignore the holder.
+            ignoreVars.add(holder.replace("_holder", "")); // Ignore the "managed" arg.
+        }
+    }
+
+    for (const variable of functionBodies[0].DefineVariable) {
+        var name;
+        if (variable.Variable.Kind == "This")
+            name = "this";
+        else if (variable.Variable.Kind == "Return")
+            name = "<returnvalue>";
+        else
+            name = variable.Variable.Name[0];
+
+        if (ignoreVars.has(name))
+            continue;
+
+        if (isRootedType(variable.Type)) {
+            if (!variableLiveAcrossGC(suppressed, variable.Variable)) {
+                // The earliest use of the variable should be its constructor.
+                var lineText;
+                for (var body of functionBodies) {
+                    if (body.minimumUse) {
+                        var text = findLocation(body, body.minimumUse);
+                        if (!lineText || locationLine(lineText) > locationLine(text))
+                            lineText = text;
+                    }
+                }
+                print("\nFunction '" + functionName + "'" +
+                      " has unnecessary root '" + name + "' at " + lineText);
+            }
+        } else if (isUnrootedType(variable.Type)) {
+            var result = variableLiveAcrossGC(suppressed, variable.Variable);
+            if (result) {
+                assert(result.gcInfo);
+                var lineText = findLocation(result.gcInfo.body, result.gcInfo.ppoint);
+                if (annotations.has('Expect Hazards')) {
+                    print("\nThis is expected, but '" + functionName + "'" +
+                          " has unrooted '" + name + "'" +
+                          " of type '" + typeDesc(variable.Type) + "'" +
+                          " live across GC call " + result.gcInfo.name +
+                          " at " + lineText);
+                    missingExpectedHazard = false;
+                } else {
+                    print("\nFunction '" + functionName + "'" +
+                          " has unrooted '" + name + "'" +
+                          " of type '" + typeDesc(variable.Type) + "'" +
+                          " live across GC call " + result.gcInfo.name +
+                          " at " + lineText);
+                }
+                printEntryTrace(functionName, result);
+            }
+            result = unsafeVariableAddressTaken(suppressed, variable.Variable);
+            if (result) {
+                var lineText = findLocation(result.body, result.ppoint);
+                print("\nFunction '" + functionName + "'" +
+                      " takes unsafe address of unrooted '" + name + "'" +
+                      " at " + lineText);
+                printEntryTrace(functionName, {body:result.body, ppoint:result.ppoint});
+            }
+        }
+    }
+
+    if (missingExpectedHazard) {
+        const {
+            Location: [
+                { CacheString: startfile, Line: startline },
+                { CacheString: endfile, Line: endline }
+            ]
+        } = functionBodies[0];
+
+        const loc = (startfile == endfile) ? `${startfile}:${startline}-${endline}`
+              : `${startfile}:${startline}`;
+
+        print("\nFunction '" + functionName + "' expected hazard(s) but none were found at " + loc);
+    }
+}
+
+if (options.batch == 1)
+    print("Time: " + new Date);
+
+var xdb = xdbLibrary();
+xdb.open("src_body.xdb");
+
+var minStream = xdb.min_data_stream()|0;
+var maxStream = xdb.max_data_stream()|0;
+
+var start = batchStart(options.batch, options.numBatches, minStream, maxStream);
+var end = batchLast(options.batch, options.numBatches, minStream, maxStream);
+
+function process(name, json) {
+    functionName = name;
+    functionBodies = JSON.parse(json);
+
+    // Annotate body with a table of all points within the body that may be in
+    // a limited scope (eg within the scope of a GC suppression RAII class.)
+    // body.attrs is a plain object indexed by point, with the value being a
+    // bit set stored in an integer.
+    for (var body of functionBodies)
+        body.attrs = [];
+
+    for (var body of functionBodies) {
+        for (var [pbody, id, attrs] of allRAIIGuardedCallPoints(typeInfo, functionBodies, body, isLimitConstructor))
+        {
+            if (attrs)
+                pbody.attrs[id] = attrs;
+        }
+        for (const edgeAttr of gcEdges[blockIdentifier(body)] || []) {
+            body.attrs[edgeAttr.Index[0]] |= edgeAttr.attrs;
+        }
+    }
+
+    // Special case: std::swap of two refcounted values thinks it can drop the
+    // ref count to zero. Or rather, it just calls operator=() in a context
+    // where the refcount will never drop to zero. Limit all calls within the
+    // body with LIMIT_CANNOT_GC.
+    let wholeBodyAttrs = 0;
+    if (functionName.includes("std::swap") || functionName.includes("mozilla::Swap")) {
+        wholeBodyAttrs = ATTR_GC_SUPPRESSED;
+    }
+
+    processBodies(functionName, wholeBodyAttrs);
+}
+
+if (options.function) {
+    var data = xdb.read_entry(options.function);
+    var json = data.readString();
+    debugger;
+    process(options.function, json);
+    xdb.free_string(data);
+    quit(0);
+}
+
+for (var nameIndex = start; nameIndex <= end; nameIndex++) {
+    var name = xdb.read_key(nameIndex);
+    var functionName = name.readString();
+    var data = xdb.read_entry(name);
+    xdb.free_string(name);
+    var json = data.readString();
+    try {
+        process(functionName, json);
+    } catch (e) {
+        printErr("Exception caught while handling " + functionName);
+        throw(e);
+    }
+    xdb.free_string(data);
+}
diff --git a/js/src/devtools/rootAnalysis/annotations.js b/js/src/devtools/rootAnalysis/annotations.js
new file mode 100644
index 0000000000..1e195b7ca1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/annotations.js
@@ -0,0 +1,488 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+// Ignore calls made through these function pointers
+var ignoreIndirectCalls = {
+    "mallocSizeOf" : true,
+    "aMallocSizeOf" : true,
+    "__conv" : true,
+    "__convf" : true,
+    "prerrortable.c:callback_newtable" : true,
+    "mozalloc_oom.cpp:void (* gAbortHandler)(size_t)" : true,
+};
+
+// Types that when constructed with no arguments, are "safe" values (they do
+// not contain GC pointers, or values with nontrivial destructors.)
+var typesWithSafeConstructors = new Set([
+    "mozilla::Maybe",
+    "mozilla::dom::Nullable",
+    "mozilla::dom::Optional",
+    "mozilla::UniquePtr",
+    "js::UniquePtr"
+]);
+
+var resetterMethods = {
+    'mozilla::Maybe': new Set(["reset"]),
+    'mozilla::UniquePtr': new Set(["reset"]),
+    'js::UniquePtr': new Set(["reset"]),
+    'mozilla::dom::Nullable': new Set(["SetNull"]),
+    'mozilla::dom::TypedArray_base': new Set(["Reset"]),
+    'RefPtr': new Set(["forget"]),
+    'nsCOMPtr': new Set(["forget"]),
+};
+
+function isRefcountedDtor(name) {
+    return name.includes("::~RefPtr(") || name.includes("::~nsCOMPtr(");
+}
+
+function indirectCallCannotGC(fullCaller, fullVariable)
+{
+    var caller = readable(fullCaller);
+
+    // This is usually a simple variable name, but sometimes a full name gets
+    // passed through. And sometimes that name is truncated. Examples:
+    //   _ZL13gAbortHandler$mozalloc_oom.cpp:void (* gAbortHandler)(size_t)
+    //   _ZL14pMutexUnlockFn$umutex.cpp:void (* pMutexUnlockFn)(const void*
+    var name = readable(fullVariable);
+
+    if (name in ignoreIndirectCalls)
+        return true;
+
+    if (name == "mapper" && caller == "ptio.c:pt_MapError")
+        return true;
+
+    if (name == "params" && caller == "PR_ExplodeTime")
+        return true;
+
+    // hook called during script finalization which cannot GC.
+    if (/CallDestroyScriptHook/.test(caller))
+        return true;
+
+    // Call through a 'callback' function pointer, in a place where we're going
+    // to be throwing a JS exception.
+    if (name == "callback" && caller.includes("js::ErrorToException"))
+        return true;
+
+    // The math cache only gets called with non-GC math functions.
+    if (name == "f" && caller.includes("js::MathCache::lookup"))
+        return true;
+
+    // It would probably be better to somehow rewrite PR_CallOnce(foo) into a
+    // call of foo, but for now just assume that nobody is crazy enough to use
+    // PR_CallOnce with a function that can GC.
+    if (name == "func" && caller == "PR_CallOnce")
+        return true;
+
+    return false;
+}
+
+// Ignore calls through functions pointers with these types
+var ignoreClasses = {
+    "JSStringFinalizer" : true,
+    "SprintfState" : true,
+    "SprintfStateStr" : true,
+    "JSLocaleCallbacks" : true,
+    "JSC::ExecutableAllocator" : true,
+    "PRIOMethods": true,
+    "_MD_IOVector" : true,
+    "malloc_table_t": true, // replace_malloc
+    "malloc_hook_table_t": true, // replace_malloc
+    "mozilla::MallocSizeOf": true,
+    "MozMallocSizeOf": true,
+};
+
+// Ignore calls through TYPE.FIELD, where TYPE is the class or struct name containing
+// a function pointer field named FIELD.
+var ignoreCallees = {
+    "js::Class.trace" : true,
+    "js::Class.finalize" : true,
+    "JSClassOps.trace" : true,
+    "JSClassOps.finalize" : true,
+    "JSRuntime.destroyPrincipals" : true,
+    "icu_50::UObject.__deleting_dtor" : true, // destructors in ICU code can't cause GC
+    "mozilla::CycleCollectedJSRuntime.DescribeCustomObjects" : true, // During tracing, cannot GC.
+    "mozilla::CycleCollectedJSRuntime.NoteCustomGCThingXPCOMChildren" : true, // During tracing, cannot GC.
+    "PLDHashTableOps.hashKey" : true,
+    "PLDHashTableOps.clearEntry" : true,
+    "z_stream_s.zfree" : true,
+    "z_stream_s.zalloc" : true,
+    "GrGLInterface.fCallback" : true,
+    "std::strstreambuf._M_alloc_fun" : true,
+    "std::strstreambuf._M_free_fun" : true,
+    "struct js::gc::Callback<void (*)(JSContext*, void*)>.op" : true,
+    "mozilla::ThreadSharedFloatArrayBufferList::Storage.mFree" : true,
+    "mozilla::SizeOfState.mMallocSizeOf": true,
+    "mozilla::gfx::SourceSurfaceRawData.mDeallocator": true,
+};
+
+function fieldCallCannotGC(csu, fullfield)
+{
+    if (csu in ignoreClasses)
+        return true;
+    if (fullfield in ignoreCallees)
+        return true;
+    return false;
+}
+
+function ignoreEdgeUse(edge, variable, body)
+{
+    // Horrible special case for ignoring a false positive in xptcstubs: there
+    // is a local variable 'paramBuffer' holding an array of nsXPTCMiniVariant
+    // on the stack, which appears to be live across a GC call because its
+    // constructor is called when the array is initialized, even though the
+    // constructor is a no-op. So we'll do a very narrow exclusion for the use
+    // that incorrectly started the live range, which was basically "__temp_1 =
+    // paramBuffer".
+    //
+    // By scoping it so narrowly, we can detect most hazards that would be
+    // caused by modifications in the PrepareAndDispatch code. It just barely
+    // avoids having a hazard already.
+    if (('Name' in variable) && (variable.Name[0] == 'paramBuffer')) {
+        if (body.BlockId.Kind == 'Function' && body.BlockId.Variable.Name[0] == 'PrepareAndDispatch')
+            if (edge.Kind == 'Assign' && edge.Type.Kind == 'Pointer')
+                if (edge.Exp[0].Kind == 'Var' && edge.Exp[1].Kind == 'Var')
+                    if (edge.Exp[1].Variable.Kind == 'Local' && edge.Exp[1].Variable.Name[0] == 'paramBuffer')
+                        return true;
+    }
+
+    // Functions which should not be treated as using variable.
+    if (edge.Kind == "Call") {
+        var callee = edge.Exp[0];
+        if (callee.Kind == "Var") {
+            var name = callee.Variable.Name[0];
+            if (/~DebugOnly/.test(name))
+                return true;
+            if (/~ScopedThreadSafeStringInspector/.test(name))
+                return true;
+        }
+    }
+
+    return false;
+}
+
+function ignoreEdgeAddressTaken(edge)
+{
+    // Functions which may take indirect pointers to unrooted GC things,
+    // but will copy them into rooted locations before calling anything
+    // that can GC. These parameters should usually be replaced with
+    // handles or mutable handles.
+    if (edge.Kind == "Call") {
+        var callee = edge.Exp[0];
+        if (callee.Kind == "Var") {
+            var name = callee.Variable.Name[0];
+            if (/js::Invoke\(/.test(name))
+                return true;
+        }
+    }
+
+    return false;
+}
+
+// Ignore calls of these functions (so ignore any stack containing these)
+var ignoreFunctions = {
+    "ptio.c:pt_MapError" : true,
+    "je_malloc_printf" : true,
+    "malloc_usable_size" : true,
+    "vprintf_stderr" : true,
+    "PR_ExplodeTime" : true,
+    "PR_ErrorInstallTable" : true,
+    "PR_SetThreadPrivate" : true,
+    "uint8 NS_IsMainThread()" : true,
+
+    // Has an indirect call under it by the name "__f", which seemed too
+    // generic to ignore by itself.
+    "void* std::_Locale_impl::~_Locale_impl(int32)" : true,
+
+    // Bug 1056410 - devirtualization prevents the standard nsISupports::Release heuristic from working
+    "uint32 nsXPConnect::Release()" : true,
+    "uint32 nsAtom::Release()" : true,
+
+    // Allocation API
+    "malloc": true,
+    "calloc": true,
+    "realloc": true,
+    "free": true,
+
+    // FIXME!
+    "NS_LogInit": true,
+    "NS_LogTerm": true,
+    "NS_LogAddRef": true,
+    "NS_LogRelease": true,
+    "NS_LogCtor": true,
+    "NS_LogDtor": true,
+    "NS_LogCOMPtrAddRef": true,
+    "NS_LogCOMPtrRelease": true,
+
+    // FIXME!
+    "NS_DebugBreak": true,
+
+    // Similar to heap snapshot mock classes, and GTests below. This posts a
+    // synchronous runnable when a GTest fails, and we are pretty sure that the
+    // particular runnable it posts can't even GC, but the analysis isn't
+    // currently smart enough to determine that. In either case, this is (a)
+    // only in GTests, and (b) only when the Gtest has already failed. We have
+    // static and dynamic checks for no GC in the non-test code, and in the test
+    // code we fall back to only the dynamic checks.
+    "void test::RingbufferDumper::OnTestPartResult(testing::TestPartResult*)" : true,
+
+    "float64 JS_GetCurrentEmbedderTime()" : true,
+
+    // This calls any JSObjectMovedOp for the tenured object via an indirect call.
+    "JSObject* js::TenuringTracer::moveToTenuredSlow(JSObject*)" : true,
+
+    "void js::Nursery::freeMallocedBuffers()" : true,
+
+    "void js::AutoEnterOOMUnsafeRegion::crash(uint64, int8*)" : true,
+
+    "void mozilla::dom::WorkerPrivate::AssertIsOnWorkerThread() const" : true,
+
+    // It would be cool to somehow annotate that nsTHashtable<T> will use
+    // nsTHashtable<T>::s_MatchEntry for its matchEntry function pointer, but
+    // there is no mechanism for that. So we will just annotate a particularly
+    // troublesome logging-related usage.
+    "EntryType* nsTHashtable<EntryType>::PutEntry(nsTHashtable<EntryType>::KeyType, const fallible_t&) [with EntryType = nsBaseHashtableET<nsCharPtrHashKey, nsAutoPtr<mozilla::LogModule> >; nsTHashtable<EntryType>::KeyType = const char*; nsTHashtable<EntryType>::fallible_t = mozilla::fallible_t]" : true,
+    "EntryType* nsTHashtable<EntryType>::GetEntry(nsTHashtable<EntryType>::KeyType) const [with EntryType = nsBaseHashtableET<nsCharPtrHashKey, nsAutoPtr<mozilla::LogModule> >; nsTHashtable<EntryType>::KeyType = const char*]" : true,
+    "EntryType* nsTHashtable<EntryType>::PutEntry(nsTHashtable<EntryType>::KeyType) [with EntryType = nsBaseHashtableET<nsPtrHashKey<const mozilla::BlockingResourceBase>, nsAutoPtr<mozilla::DeadlockDetector<mozilla::BlockingResourceBase>::OrderingEntry> >; nsTHashtable<EntryType>::KeyType = const mozilla::BlockingResourceBase*]" : true,
+    "EntryType* nsTHashtable<EntryType>::GetEntry(nsTHashtable<EntryType>::KeyType) const [with EntryType = nsBaseHashtableET<nsPtrHashKey<const mozilla::BlockingResourceBase>, nsAutoPtr<mozilla::DeadlockDetector<mozilla::BlockingResourceBase>::OrderingEntry> >; nsTHashtable<EntryType>::KeyType = const mozilla::BlockingResourceBase*]" : true,
+
+    // VTune internals that lazy-load a shared library and make IndirectCalls.
+    "iJIT_IsProfilingActive" : true,
+    "iJIT_NotifyEvent": true,
+
+    // The big hammers.
+    "PR_GetCurrentThread" : true,
+    "calloc" : true,
+
+    // This will happen early enough in initialization to not matter.
+    "_PR_UnixInit" : true,
+
+    "uint8 nsContentUtils::IsExpandedPrincipal(nsIPrincipal*)" : true,
+
+    "void mozilla::AutoProfilerLabel::~AutoProfilerLabel(int32)" : true,
+
+    // Stores a function pointer in an AutoProfilerLabelData struct and calls it.
+    // And it's in mozglue, which doesn't have access to the attributes yet.
+    "void mozilla::ProfilerLabelEnd(mozilla::Tuple<void*, unsigned int>*)" : true,
+
+    // This gets into PLDHashTable function pointer territory, and should get
+    // set up early enough to not do anything when it matters anyway.
+    "mozilla::LogModule* mozilla::LogModule::Get(int8*)": true,
+
+    // This annotation is correct, but the reasoning is still being hashed out
+    // in bug 1582326 comment 8 and on.
+    "nsCycleCollector.cpp:nsISupports* CanonicalizeXPCOMParticipant(nsISupports*)": true,
+
+    // PLDHashTable again
+    "void mozilla::DeadlockDetector<T>::Add(const T*) [with T = mozilla::BlockingResourceBase]": true,
+
+    // OOM handling during logging
+    "void mozilla::detail::log_print(mozilla::LogModule*, int32, int8*)": true,
+
+    // This would need to know that the nsCOMPtr refcount will not go to zero.
+    "uint8 XPCJSRuntime::DescribeCustomObjects(JSObject*, JSClass*, int8[72]*)[72]) const": true,
+
+    // As the comment says "Refcount isn't zero, so Suspect won't delete anything."
+    "uint64 nsCycleCollectingAutoRefCnt::incr(void*, nsCycleCollectionParticipant*) [with void (* suspect)(void*, nsCycleCollectionParticipant*, nsCycleCollectingAutoRefCnt*, bool*) = NS_CycleCollectorSuspect3; uintptr_t = long unsigned int]": true,
+
+    // Calls MergeSort
+    "uint8 v8::internal::RegExpDisjunction::SortConsecutiveAtoms(v8::internal::RegExpCompiler*)": true,
+
+    // nsIEventTarget.IsOnCurrentThreadInfallible does not get resolved, and
+    // this is called on non-JS threads so cannot use AutoSuppressGCAnalysis.
+    "uint8 nsAutoOwningEventTarget::IsCurrentThread() const": true,
+
+    // ~JSStreamConsumer calls 2 ~RefCnt/~nsCOMPtr destructors for its fields,
+    // but the body of the destructor is written so that all Releases
+    // are proxied, and the members will all be empty at destruction time.
+    "void mozilla::dom::JSStreamConsumer::~JSStreamConsumer() [[base_dtor]]": true,
+};
+
+function extraGCFunctions(readableNames) {
+    return ["ffi_call"].filter(f => f in readableNames);
+}
+
+function isProtobuf(name)
+{
+    return name.match(/\bgoogle::protobuf\b/) ||
+           name.match(/\bmozilla::devtools::protobuf\b/);
+}
+
+function isHeapSnapshotMockClass(name)
+{
+    return name.match(/\bMockWriter\b/) ||
+           name.match(/\bMockDeserializedNode\b/);
+}
+
+function isGTest(name)
+{
+    return name.match(/\btesting::/);
+}
+
+function isICU(name)
+{
+    return name.match(/\bicu_\d+::/) ||
+           name.match(/u(prv_malloc|prv_realloc|prv_free|case_toFullLower)_\d+/)
+}
+
+function ignoreGCFunction(mangled, readableNames)
+{
+    // Field calls will not be in readableNames
+    if (!(mangled in readableNames))
+        return false;
+
+    const fun = readableNames[mangled][0];
+
+    if (fun in ignoreFunctions)
+        return true;
+
+    // The protobuf library, and [de]serialization code generated by the
+    // protobuf compiler, uses a _ton_ of function pointers but they are all
+    // internal. The same is true for ICU. Easiest to just ignore that mess
+    // here.
+    if (isProtobuf(fun) || isICU(fun))
+        return true;
+
+    // Ignore anything that goes through heap snapshot GTests or mocked classes
+    // used in heap snapshot GTests. GTest and GMock expose a lot of virtual
+    // methods and function pointers that could potentially GC after an
+    // assertion has already failed (depending on user-provided code), but don't
+    // exhibit that behavior currently. For non-test code, we have dynamic and
+    // static checks that ensure we don't GC. However, for test code we opt out
+    // of static checks here, because of the above stated GMock/GTest issues,
+    // and rely on only the dynamic checks provided by AutoAssertCannotGC.
+    if (isHeapSnapshotMockClass(fun) || isGTest(fun))
+        return true;
+
+    // Templatized function
+    if (fun.includes("void nsCOMPtr<T>::Assert_NoQueryNeeded()"))
+        return true;
+
+    // Bug 1577915 - Sixgill is ignoring a template param that makes its CFG
+    // impossible.
+    if (fun.includes("UnwrapObjectInternal") && fun.includes("mayBeWrapper = false"))
+        return true;
+
+    // These call through an 'op' function pointer.
+    if (fun.includes("js::WeakMap<Key, Value, HashPolicy>::getDelegate("))
+        return true;
+
+    // TODO: modify refillFreeList<NoGC> to not need data flow analysis to
+    // understand it cannot GC. As of gcc 6, the same problem occurs with
+    // tryNewTenuredThing, tryNewNurseryObject, and others.
+    if (/refillFreeList|tryNew/.test(fun) && /= js::NoGC/.test(fun))
+        return true;
+
+    return false;
+}
+
+function stripUCSAndNamespace(name)
+{
+    name = name.replace(/(struct|class|union|const) /g, "");
+    name = name.replace(/(js::ctypes::|js::|JS::|mozilla::dom::|mozilla::)/g, "");
+    return name;
+}
+
+function extraRootedGCThings()
+{
+    return [ 'JSAddonId' ];
+}
+
+function extraRootedPointers()
+{
+    return [
+    ];
+}
+
+function isRootedGCPointerTypeName(name)
+{
+    name = stripUCSAndNamespace(name);
+
+    if (name.startsWith('MaybeRooted<'))
+        return /\(js::AllowGC\)1u>::RootType/.test(name);
+
+    return false;
+}
+
+function isUnsafeStorage(typeName)
+{
+    typeName = stripUCSAndNamespace(typeName);
+    return typeName.startsWith('UniquePtr<');
+}
+
+// If edgeType is a constructor type, return whatever bits it implies for its
+// scope (or zero if not matching).
+function isLimitConstructor(typeInfo, edgeType, varName)
+{
+    // Check whether this could be a constructor
+    if (edgeType.Kind != 'Function')
+        return 0;
+    if (!('TypeFunctionCSU' in edgeType))
+        return 0;
+    if (edgeType.Type.Kind != 'Void')
+        return 0;
+
+    // Check whether the type is a known suppression type.
+    var type = edgeType.TypeFunctionCSU.Type.Name;
+    let attrs = 0;
+    if (type in typeInfo.GCSuppressors)
+        attrs = attrs | ATTR_GC_SUPPRESSED;
+
+    // And now make sure this is the constructor, not some other method on a
+    // suppression type. varName[0] contains the qualified name.
+    var [ mangled, unmangled ] = splitFunction(varName[0]);
+    if (mangled.search(/C\d[EI]/) == -1)
+        return 0; // Mangled names of constructors have C<num>E or C<num>I
+    var m = unmangled.match(/([~\w]+)(?:<.*>)?\(/);
+    if (!m)
+        return 0;
+    var type_stem = type.replace(/\w+::/g, '').replace(/\<.*\>/g, '');
+    if (m[1] != type_stem)
+        return 0;
+
+    return attrs;
+}
+
+// XPIDL-generated methods may invoke JS code, depending on the IDL
+// attributes. This is not visible in the static callgraph since it
+// goes through generated asm code. We can use the JS_HAZ_CAN_RUN_SCRIPT
+// annotation to tell whether this is possible, which is set programmatically
+// by the code generator when needed (bug 1347999):
+// https://searchfox.org/mozilla-central/rev/81c52abeec336685330af5956c37b4bcf8926476/xpcom/idl-parser/xpidl/header.py#213-219
+//
+// Note that WebIDL callbacks can also invoke JS code, but our code generator
+// produces regular C++ code and so does not need any annotations. (There will
+// be a call to JS::Call() or similar.)
+function virtualCanRunJS(csu, field)
+{
+    const tags = typeInfo.OtherFieldTags;
+    const iface = tags[csu]
+    if (!iface) {
+        return false;
+    }
+    const virtual_method_tags = iface[field];
+    return virtual_method_tags && virtual_method_tags.includes("Can run script");
+}
+
+function listNonGCPointers() {
+    return [
+        // Safe only because jsids are currently only made from pinned strings.
+        'NPIdentifier',
+    ];
+}
+
+function isJSNative(mangled)
+{
+    // _Z...E = function
+    // 9JSContext = JSContext*
+    // j = uint32
+    // PN2JS5Value = JS::Value*
+    //   P = pointer
+    //   N2JS = JS::
+    //   5Value = Value
+    return mangled.endsWith("P9JSContextjPN2JS5ValueE") && mangled.startsWith("_Z");
+}
diff --git a/js/src/devtools/rootAnalysis/build.js b/js/src/devtools/rootAnalysis/build.js
new file mode 100644
index 0000000000..78ef04fea1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/build.js
@@ -0,0 +1,15 @@
+#!/bin/sh
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+
+set -e
+
+cd $SOURCE
+./mach configure
+./mach build export
+./mach build -X nsprpub mfbt memory memory/mozalloc modules/zlib mozglue js/src xpcom/glue js/xpconnect/loader js/xpconnect/wrappers js/xpconnect/src
+status=$?
+echo "[[[[ build.js complete, exit code $status ]]]]"
+exit $status
diff --git a/js/src/devtools/rootAnalysis/build/sixgill-b2g.manifest b/js/src/devtools/rootAnalysis/build/sixgill-b2g.manifest
new file mode 100644
index 0000000000..1ecb5d0665
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/build/sixgill-b2g.manifest
@@ -0,0 +1,10 @@
+[
+{
+"hg_id" : "ec7b7d2442e8",
+"algorithm" : "sha512",
+"digest" : "49627d734df52cb9e7319733da5a6be1812b9373355dc300ee5600b431122570e00d380d50c7c5b5003c462c2c2cb022494b42c4ad00f8eba01c2259cbe6e502",
+"filename" : "sixgill.tar.xz",
+"size" : 2628868,
+"unpack" : true
+}
+]
diff --git a/js/src/devtools/rootAnalysis/build/sixgill.manifest b/js/src/devtools/rootAnalysis/build/sixgill.manifest
new file mode 100644
index 0000000000..49ccdcbd3f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/build/sixgill.manifest
@@ -0,0 +1,10 @@
+[
+{
+"digest" : "2e56a3cf84764b8e63720e5f961cff7ba8ba5cf2f353dac55c69486489bcd89f53a757e09469a07700b80cd09f09666c2db4ce375b67060ac3be967714597231",
+"size" : 2629600,
+"hg_id" : "221d0d2eead9",
+"unpack" : true,
+"filename" : "sixgill.tar.xz",
+"algorithm" : "sha512"
+}
+]
diff --git a/js/src/devtools/rootAnalysis/callgraph.js b/js/src/devtools/rootAnalysis/callgraph.js
new file mode 100644
index 0000000000..34143b3ce6
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/callgraph.js
@@ -0,0 +1,189 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('CFG.js');
+
+// Map from csu => set of immediate subclasses
+var subclasses = new Map();
+
+// Map from csu => set of immediate superclasses
+var superclasses = new Map();
+
+// Map from "csu.name:nargs" => set of full method name
+var virtualDefinitions = new Map();
+
+// Every virtual method declaration, anywhere.
+//
+// Map from csu => Set of function-info.
+// function-info: {
+//   name : simple string
+//   typedfield : "name:nargs" ("mangled" field name)
+//   field: full Field datastructure
+//   annotations : Set of [annotation-name, annotation-value] 2-element arrays
+//   inherited : whether the method is inherited from a base class
+//   pureVirtual : whether the method is pure virtual on this CSU
+//   dtor : if this is a virtual destructor with a definition in this class or
+//     a superclass, then the full name of the definition as if it were defined
+//     in this class. This is weird, but it's how gcc emits it. We will add a
+//     synthetic call from this function to its immediate base classes' dtors,
+//     so even if the function does not actually exist and is inherited from a
+//     base class, we will get a path to the inherited function. (Regular
+//     virtual methods are *not* claimed to exist when they don't.)
+// }
+var virtualDeclarations = new Map();
+
+var virtualResolutionsSeen = new Set();
+
+var ID = {
+    jscode: 1,
+    anyfunc: 2,
+    nogcfunc: 3,
+    gc: 4,
+};
+
+// map is a map from names to sets of entries.
+function addToNamedSet(map, name, entry)
+{
+    if (!map.has(name))
+      map.set(name, new Set());
+    const s = map.get(name);
+    s.add(entry);
+    return s;
+}
+
+// CSU is "Class/Struct/Union"
+function processCSU(csuName, csu)
+{
+    if (!("FunctionField" in csu))
+        return;
+
+    for (const {Base} of (csu.CSUBaseClass || [])) {
+        addToNamedSet(subclasses, Base, csuName);
+        addToNamedSet(superclasses, csuName, Base);
+    }
+
+    for (const {Field, Variable} of csu.FunctionField) {
+        // Virtual method
+        const info = Field[0];
+        const name = info.Name[0];
+        const annotations = new Set();
+        const funcInfo = {
+            name,
+            typedfield: typedField(info),
+            field: info,
+            annotations,
+            inherited: (info.FieldCSU.Type.Name != csuName), // Always false for virtual dtors
+            pureVirtual: Boolean(Variable),
+            dtor: false,
+        };
+
+        if (Variable && isSyntheticVirtualDestructor(name)) {
+            // This is one of gcc's artificial dtors.
+            funcInfo.dtor = Variable.Name[0];
+            funcInfo.pureVirtual = false;
+        }
+
+        addToNamedSet(virtualDeclarations, csuName, funcInfo);
+        if ('Annotation' in info) {
+            for (const {Name: [annType, annValue]} of info.Annotation) {
+                annotations.add([annType, annValue]);
+            }
+        }
+
+        if (Variable) {
+            // Note: not dealing with overloading correctly.
+            const name = Variable.Name[0];
+            addToNamedSet(virtualDefinitions, fieldKey(csuName, Field[0]), name);
+        }
+    }
+}
+
+// Return a list of all callees that the given edge might be a call to. Each
+// one is represented by an object with a 'kind' field that is one of
+// ('direct', 'field', 'resolved-field', 'indirect', 'unknown'), though note
+// that 'resolved-field' is really a global record of virtual method
+// resolutions, indepedent of this particular edge.
+function getCallees(edge)
+{
+    if (edge.Kind != "Call")
+        return [];
+
+    const callee = edge.Exp[0];
+    if (callee.Kind == "Var") {
+        assert(callee.Variable.Kind == "Func");
+        return [{'kind': 'direct', 'name': callee.Variable.Name[0]}];
+    }
+
+    // At some point, we were intentionally invoking invalid function pointers
+    // (as in, a small integer cast to a function pointer type) to convey a
+    // small amount of information in the crash address.
+    if (callee.Kind == "Int")
+        return []; // Intentional crash
+
+    assert(callee.Kind == "Drf");
+    const called = callee.Exp[0];
+    if (called.Kind == "Var") {
+        // indirect call through a variable.
+        return [{'kind': "indirect", 'variable': callee.Exp[0].Variable.Name[0]}];
+    }
+
+    if (called.Kind != "Fld") {
+        // unknown call target.
+        return [{'kind': "unknown"}];
+    }
+
+    // Return one 'field' callee record giving the full description of what's
+    // happening here (which is either a virtual method call, or a call through
+    // a function pointer stored in a field), and then boil the call down to a
+    // synthetic function that incorporates both the name of the field and the
+    // static type of whatever you're calling the method on. Both refer to the
+    // same call; they're just different ways of describing it.
+    const callees = [];
+    const field = callee.Exp[0].Field;
+    callees.push({'kind': "field", 'csu': field.FieldCSU.Type.Name,
+                  'field': field.Name[0],
+                  'isVirtual': ("FieldInstanceFunction" in field)});
+
+    const staticCSU = getFieldCallInstanceCSU(edge, field);
+    callees.push({'kind': "direct", 'name': fieldKey(staticCSU, field)});
+
+    return callees;
+}
+
+function loadTypes(type_xdb_filename) {
+    const xdb = xdbLibrary();
+    xdb.open(type_xdb_filename);
+
+    const minStream = xdb.min_data_stream();
+    const maxStream = xdb.max_data_stream();
+
+    for (var csuIndex = minStream; csuIndex <= maxStream; csuIndex++) {
+        const csu = xdb.read_key(csuIndex);
+        const data = xdb.read_entry(csu);
+        const json = JSON.parse(data.readString());
+        processCSU(csu.readString(), json[0]);
+
+        xdb.free_string(csu);
+        xdb.free_string(data);
+    }
+}
+
+function loadTypesWithCache(type_xdb_filename, cache_filename) {
+    try {
+        const cacheAB = os.file.readFile(cache_filename, "binary");
+        const cb = serialize();
+        cb.clonebuffer = cacheAB.buffer;
+        const cacheData = deserialize(cb);
+        subclasses = cacheData.subclasses;
+        superclasses = cacheData.superclasses;
+        virtualDefinitions = cacheData.virtualDefinitions;
+    } catch (e) {
+        loadTypes(type_xdb_filename);
+        const cb = serialize({subclasses, superclasses, virtualDefinitions});
+        os.file.writeTypedArrayToFile(cache_filename,
+                                      new Uint8Array(cb.arraybuffer));
+    }
+}
diff --git a/js/src/devtools/rootAnalysis/computeCallgraph.js b/js/src/devtools/rootAnalysis/computeCallgraph.js
new file mode 100644
index 0000000000..6da79bc496
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/computeCallgraph.js
@@ -0,0 +1,430 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('callgraph.js');
+
+var options = parse_options([
+    {
+        name: '--function',
+        type: 'string'
+    },
+    {
+        name: 'typeInfo_filename',
+        type: 'string',
+        default: "typeInfo.txt"
+    },
+    {
+        name: 'callgraphOut_filename',
+        type: 'string',
+        default: "rawcalls.txt"
+    },
+    {
+        name: 'gcEdgesOut_filename',
+        type: 'string',
+        default: "gcEdges.json"
+    },
+    {
+        name: 'batch',
+        default: 1,
+        type: 'number'
+    },
+    {
+        name: 'numBatches',
+        default: 1,
+        type: 'number'
+    },
+]);
+
+var origOut = os.file.redirect(options.callgraphOut_filename);
+
+var memoized = new Map();
+
+var unmangled2id = new Set();
+
+var gcEdges = {};
+
+// Insert a string into the name table and return the ID. Do not use for
+// functions, which must be handled specially.
+function getId(name)
+{
+    let id = memoized.get(name);
+    if (id !== undefined)
+        return id;
+
+    id = memoized.size + 1;
+    memoized.set(name, id);
+    print(`#${id} ${name}`);
+
+    return id;
+}
+
+// Split a function into mangled and unmangled parts and return the ID for the
+// function.
+function functionId(name)
+{
+    const [mangled, unmangled] = splitFunction(name);
+    const id = getId(mangled);
+
+    // Only produce a mangled -> unmangled mapping once, unless there are
+    // multiple unmangled names for the same mangled name.
+    if (unmangled2id.has(unmangled))
+        return id;
+
+    print(`= ${id} ${unmangled}`);
+    unmangled2id.add(unmangled);
+    return id;
+}
+
+var lastline;
+function printOnce(line)
+{
+    if (line != lastline) {
+        print(line);
+        lastline = line;
+    }
+}
+
+// Returns a table mapping function name to lists of
+// [annotation-name, annotation-value] pairs:
+//   { function-name => [ [annotation-name, annotation-value] ] }
+//
+// Note that sixgill will only store certain attributes (annotation-names), so
+// this won't be *all* the attributes in the source, just the ones that sixgill
+// watches for.
+function getAllAttributes(body)
+{
+    var all_annotations = {};
+    for (var v of (body.DefineVariable || [])) {
+        if (v.Variable.Kind != 'Func')
+            continue;
+        var name = v.Variable.Name[0];
+        var annotations = all_annotations[name] = [];
+
+        for (var ann of (v.Type.Annotation || [])) {
+            annotations.push(ann.Name);
+        }
+    }
+
+    return all_annotations;
+}
+
+// Get just the annotations understood by the hazard analysis.
+function getAnnotations(functionName, body) {
+    var tags = new Set();
+    var attributes = getAllAttributes(body);
+    if (functionName in attributes) {
+        for (var [ annName, annValue ] of attributes[functionName]) {
+            if (annName == 'annotate')
+                tags.add(annValue);
+        }
+    }
+    return tags;
+}
+
+// Scan through a function body, pulling out all annotations and calls and
+// recording them in callgraph.txt.
+function processBody(functionName, body, functionBodies)
+{
+    if (!('PEdge' in body))
+        return;
+
+    for (var tag of getAnnotations(functionName, body).values()) {
+        const id = functionId(functionName);
+        print(`T ${id} ${tag}`);
+        if (tag == "Calls JSNatives")
+            printOnce(`D ${id} ${functionId("(js-code)")}`);
+    }
+
+    // Set of all callees that have been output so far, in order to suppress
+    // repeated callgraph edges from being recorded. This uses a Map from
+    // callees to limit sets, because we don't want a limited edge to prevent
+    // an unlimited edge from being recorded later. (So an edge will be skipped
+    // if it exists and is at least as limited as the previously seen edge.)
+    //
+    // Limit sets are implemented as integers interpreted as bitfields.
+    //
+    var seen = new Map();
+
+    lastline = null;
+    for (var edge of body.PEdge) {
+        if (edge.Kind != "Call")
+            continue;
+
+        // The attrs (eg ATTR_GC_SUPPRESSED) are determined by whatever RAII
+        // scopes might be active, which have been computed previously for all
+        // points in the body.
+        var edgeAttrs = body.attrs[edge.Index[0]] | 0;
+
+        for (var callee of getCallees(edge)) {
+            // Special-case some calls when we can derive more information about them, eg
+            // that they are a destructor that won't do anything.
+            if (callee.kind === "direct" && edgeIsNonReleasingDtor(body, edge, callee.name, functionBodies)) {
+                const block = blockIdentifier(body);
+                addToKeyedList(gcEdges, block, { Index: edge.Index, attrs: ATTR_GC_SUPPRESSED | ATTR_NONRELEASING });
+            }
+
+            // Individual callees may have additional attrs. The only such
+            // bit currently is that nsISupports.{AddRef,Release} are assumed
+            // to never GC.
+            const attrs = edgeAttrs | callee.attrs;
+            let prologue = attrs ? `/${attrs} ` : "";
+            prologue += functionId(functionName) + " ";
+            if (callee.kind == 'direct') {
+                const prev_attrs = seen.has(callee.name) ? seen.get(callee.name) : ATTRS_UNVISITED;
+                if (prev_attrs & ~attrs) {
+                    // Only output an edge if it loosens a limit.
+                    seen.set(callee.name, prev_attrs & attrs);
+                    printOnce("D " + prologue + functionId(callee.name));
+                }
+            } else if (callee.kind == 'field') {
+                var { csu, field, isVirtual } = callee;
+                const tag = isVirtual ? 'V' : 'F';
+                const fullfield = `${csu}.${field}`;
+                printOnce(`${tag} ${prologue}${getId(fullfield)} CLASS ${csu} FIELD ${field}`);
+            } else if (callee.kind == 'resolved-field') {
+                // Fully-resolved field (virtual method) call. Record the
+                // callgraph edges. Do not consider attrs, since they are local
+                // to this callsite and we are writing out a global record
+                // here.
+                //
+                // Any field call that does *not* have an R entry must be
+                // assumed to call anything.
+                var { csu, field, callees } = callee;
+                var fullFieldName = csu + "." + field;
+                if (!virtualResolutionsSeen.has(fullFieldName)) {
+                    virtualResolutionsSeen.add(fullFieldName);
+                    for (var target of callees)
+                        printOnce("R " + getId(fullFieldName) + " " + functionId(target.name));
+                }
+            } else if (callee.kind == 'indirect') {
+                printOnce("I " + prologue + "VARIABLE " + callee.variable);
+            } else if (callee.kind == 'unknown') {
+                printOnce("I " + prologue + "VARIABLE UNKNOWN");
+            } else {
+                printErr("invalid " + callee.kind + " callee");
+                debugger;
+            }
+        }
+    }
+}
+
+// Reserve IDs for special function names.
+
+// represents anything that can run JS
+assert(ID.jscode == functionId("(js-code)"));
+
+// function pointers will get an edge to this in loadCallgraph.js; only the ID
+// reservation is present in callgraph.txt
+assert(ID.anyfunc == functionId("(any-function)"));
+
+// same as above, but for fields annotated to never GC
+assert(ID.nogcfunc == functionId("(nogc-function)"));
+
+// garbage collection
+assert(ID.gc == functionId("(GC)"));
+
+var typeInfo = loadTypeInfo(options.typeInfo_filename);
+
+loadTypes("src_comp.xdb");
+
+// Arbitrary JS code must always be assumed to GC. In real code, there would
+// always be a path anyway through some arbitrary JSNative, but this route will be shorter.
+print(`D ${ID.jscode} ${ID.gc}`);
+
+// An unknown function is assumed to GC.
+print(`D ${ID.anyfunc} ${ID.gc}`);
+
+// Output call edges for all virtual methods defined anywhere, from
+// Class.methodname to what a (dynamic) instance of Class would run when
+// methodname was called (either Class::methodname() if defined, or some
+// Base::methodname() for inherited method definitions).
+for (const [fieldkey, methods] of virtualDefinitions) {
+    const caller = getId(fieldkey);
+    for (const name of methods) {
+        const callee = functionId(name);
+        printOnce(`D ${caller} ${callee}`);
+    }
+}
+
+// Output call edges from C.methodname -> S.methodname for all subclasses S of
+// class C. This is for when you are calling methodname on a pointer/ref of
+// dynamic type C, so that the callgraph contains calls to all descendant
+// subclasses' implementations.
+for (const [csu, methods] of virtualDeclarations) {
+    for (const {field, dtor} of methods) {
+        const caller = getId(fieldKey(csu, field));
+        if (virtualCanRunJS(csu, field.Name[0]))
+            printOnce(`D ${caller} ${functionId("(js-code)")}`);
+        if (dtor)
+            printOnce(`D ${caller} ${functionId(dtor)}`);
+        if (!subclasses.has(csu))
+            continue;
+        for (const sub of subclasses.get(csu)) {
+            printOnce(`D ${caller} ${getId(fieldKey(sub, field))}`);
+        }
+    }
+}
+
+var xdb = xdbLibrary();
+xdb.open("src_body.xdb");
+
+printErr("Finished loading data structures");
+
+var minStream = xdb.min_data_stream();
+var maxStream = xdb.max_data_stream();
+
+if (options.function) {
+    var index = xdb.lookup_key(options.function);
+    if (!index) {
+        printErr("Function not found");
+        quit(1);
+    }
+    minStream = maxStream = index;
+}
+
+function process(functionName, functionBodies)
+{
+    for (var body of functionBodies)
+        body.attrs = [];
+
+    for (var body of functionBodies) {
+        for (var [pbody, id, attrs] of allRAIIGuardedCallPoints(typeInfo, functionBodies, body, isLimitConstructor)) {
+            pbody.attrs[id] = attrs;
+        }
+    }
+
+    for (var body of functionBodies)
+        processBody(functionName, body, functionBodies);
+
+    // Not strictly necessary, but add an edge from the synthetic "(js-code)"
+    // to RunScript to allow better stacks than just randomly selecting a
+    // JSNative to blame things on.
+    if (functionName.includes("js::RunScript"))
+        print(`D ${functionId("(js-code)")} ${functionId(functionName)}`);
+
+    // GCC generates multiple constructors and destructors ("in-charge" and
+    // "not-in-charge") to handle virtual base classes. They are normally
+    // identical, and it appears that GCC does some magic to alias them to the
+    // same thing. But this aliasing is not visible to the analysis. So we'll
+    // add a dummy call edge from "foo" -> "foo *INTERNAL* ", since only "foo"
+    // will show up as called but only "foo *INTERNAL* " will be emitted in the
+    // case where the constructors are identical.
+    //
+    // This is slightly conservative in the case where they are *not*
+    // identical, but that should be rare enough that we don't care.
+    var markerPos = functionName.indexOf(internalMarker);
+    if (markerPos > 0) {
+        var inChargeXTor = functionName.replace(internalMarker, "");
+        printOnce("D " + functionId(inChargeXTor) + " " + functionId(functionName));
+    }
+
+    const [ mangled, unmangled ] = splitFunction(functionName);
+
+    // Further note: from https://itanium-cxx-abi.github.io/cxx-abi/abi.html the
+    // different kinds of constructors/destructors are:
+    // C1	# complete object constructor
+    // C2	# base object constructor
+    // C3	# complete object allocating constructor
+    // D0	# deleting destructor
+    // D1	# complete object destructor
+    // D2	# base object destructor
+    //
+    // In actual practice, I have observed C4 and D4 xtors generated by gcc
+    // 4.9.3 (but not 4.7.3). The gcc source code says:
+    //
+    //   /* This is the old-style "[unified]" constructor.
+    //      In some cases, we may emit this function and call
+    //      it from the clones in order to share code and save space.  */
+    //
+    // Unfortunately, that "call... from the clones" does not seem to appear in
+    // the CFG we get from GCC. So if we see a C4 constructor or D4 destructor,
+    // inject an edge to it from C1, C2, and C3 (or D1, D2, and D3). (Note that
+    // C3 isn't even used in current GCC, but add the edge anyway just in
+    // case.)
+    //
+    // from gcc/cp/mangle.c:
+    //
+    // <special-name> ::= D0 # deleting (in-charge) destructor
+    //                ::= D1 # complete object (in-charge) destructor
+    //                ::= D2 # base object (not-in-charge) destructor
+    // <special-name> ::= C1   # complete object constructor
+    //                ::= C2   # base object constructor
+    //                ::= C3   # complete object allocating constructor
+    //
+    // Currently, allocating constructors are never used.
+    //
+    if (functionName.indexOf("C4") != -1) {
+        // E terminates the method name (and precedes the method parameters).
+        // If eg "C4E" shows up in the mangled name for another reason, this
+        // will create bogus edges in the callgraph. But it will affect little
+        // and is somewhat difficult to avoid, so we will live with it.
+        //
+        // Another possibility! A templatized constructor will contain C4I...E
+        // for template arguments.
+        //
+        for (let [synthetic, variant, desc] of [
+            ['C4E', 'C1E', 'complete_ctor'],
+            ['C4E', 'C2E', 'base_ctor'],
+            ['C4E', 'C3E', 'complete_alloc_ctor'],
+            ['C4I', 'C1I', 'complete_ctor'],
+            ['C4I', 'C2I', 'base_ctor'],
+            ['C4I', 'C3I', 'complete_alloc_ctor']])
+        {
+            if (mangled.indexOf(synthetic) == -1)
+                continue;
+
+            let variant_mangled = mangled.replace(synthetic, variant);
+            let variant_full = `${variant_mangled}$${unmangled} [[${desc}]]`;
+            printOnce("D " + functionId(variant_full) + " " + functionId(functionName));
+        }
+    }
+
+    // For destructors:
+    //
+    // I've never seen D4Ev() + D4Ev(int32), only one or the other. So
+    // for a D4Ev of any sort, create:
+    //
+    //   D0() -> D1()  # deleting destructor calls complete destructor, then deletes
+    //   D1() -> D2()  # complete destructor calls base destructor, then destroys virtual bases
+    //   D2() -> D4(?) # base destructor might be aliased to unified destructor
+    //                 # use whichever one is defined, in-charge or not.
+    //                 # ('?') means either () or (int32).
+    //
+    // Note that this doesn't actually make sense -- D0 and D1 should be
+    // in-charge, but gcc doesn't seem to give them the in-charge parameter?!
+    //
+    if (functionName.indexOf("D4Ev") != -1 && functionName.indexOf("::~") != -1) {
+        const not_in_charge_dtor = functionName.replace("(int32)", "()");
+        const D0 = not_in_charge_dtor.replace("D4Ev", "D0Ev") + " [[deleting_dtor]]";
+        const D1 = not_in_charge_dtor.replace("D4Ev", "D1Ev") + " [[complete_dtor]]";
+        const D2 = not_in_charge_dtor.replace("D4Ev", "D2Ev") + " [[base_dtor]]";
+        printOnce("D " + functionId(D0) + " " + functionId(D1));
+        printOnce("D " + functionId(D1) + " " + functionId(D2));
+        printOnce("D " + functionId(D2) + " " + functionId(functionName));
+    }
+
+    if (isJSNative(mangled))
+        printOnce(`D ${functionId("(js-code)")} ${functionId(functionName)}`);
+}
+
+var start = batchStart(options.batch, options.numBatches, minStream, maxStream);
+var end = batchLast(options.batch, options.numBatches, minStream, maxStream);
+
+for (var nameIndex = start; nameIndex <= end; nameIndex++) {
+    var name = xdb.read_key(nameIndex);
+    var data = xdb.read_entry(name);
+    process(name.readString(), JSON.parse(data.readString()));
+    xdb.free_string(name);
+    xdb.free_string(data);
+}
+
+os.file.close(os.file.redirect(options.gcEdgesOut_filename));
+
+print(JSON.stringify(gcEdges, null, 4));
+
+os.file.close(os.file.redirect(origOut));
diff --git a/js/src/devtools/rootAnalysis/computeGCFunctions.js b/js/src/devtools/rootAnalysis/computeGCFunctions.js
new file mode 100644
index 0000000000..90705051c9
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/computeGCFunctions.js
@@ -0,0 +1,103 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+loadRelativeToScript('loadCallgraph.js');
+
+function usage() {
+  throw "Usage: computeGCFunctions.js <rawcalls1.txt> <rawcalls2.txt>... --outputs <out:callgraph.txt> <out:gcFunctions.txt> <out:gcFunctions.lst> <out:gcEdges.txt> <out:limitedFunctions.lst>";
+}
+
+if (typeof scriptArgs[0] != 'string')
+  usage();
+
+var start = "Time: " + new Date;
+
+try {
+  var options = parse_options([
+    {
+      name: 'inputs',
+      dest: 'rawcalls_filenames',
+      nargs: '+'
+    },
+    {
+      name: '--outputs',
+      type: 'bool'
+    },
+    {
+      name: 'callgraph',
+      type: 'string',
+      default: 'callgraph.txt'
+    },
+    {
+      name: 'gcFunctions',
+      type: 'string',
+      default: 'gcFunctions.txt'
+    },
+    {
+      name: 'gcFunctionsList',
+      type: 'string',
+      default: 'gcFunctions.lst'
+    },
+    {
+      name: 'limitedFunctions',
+      type: 'string',
+      default: 'limitedFunctions.lst'
+    },
+  ]);
+} catch {
+  printErr("Usage: computeGCFunctions.js <rawcalls1.txt> <rawcalls2.txt>... --outputs <out:callgraph.txt> <out:gcFunctions.txt> <out:gcFunctions.lst> <out:gcEdges.txt> <out:limitedFunctions.lst>");
+  quit(1);
+};
+
+var {
+  gcFunctions,
+  functions,
+  calleesOf,
+  limitedFunctions
+} = loadCallgraph(options.rawcalls_filenames);
+
+printErr("Writing " + options.gcFunctions);
+redirect(options.gcFunctions);
+
+for (var name in gcFunctions) {
+    for (let readable of (functions.readableName[name] || [name])) {
+        print("");
+        const fullname = (name == readable) ? name : name + "$" + readable;
+        print("GC Function: " + fullname);
+        let current = name;
+        do {
+            current = gcFunctions[current];
+            if (current === 'internal')
+                ; // Hit the end
+            else if (current in functions.readableName)
+                print("    " + functions.readableName[current][0]);
+            else
+                print("    " + current);
+        } while (current in gcFunctions);
+    }
+}
+
+printErr("Writing " + options.gcFunctionsList);
+redirect(options.gcFunctionsList);
+for (var name in gcFunctions) {
+    if (name in functions.readableName) {
+        for (var readable of functions.readableName[name])
+            print(name + "$" + readable);
+    } else {
+        print(name);
+    }
+}
+
+printErr("Writing " + options.limitedFunctions);
+redirect(options.limitedFunctions);
+print(JSON.stringify(limitedFunctions, null, 4));
+
+printErr("Writing " + options.callgraph);
+redirect(options.callgraph);
+saveCallgraph(functions, calleesOf);
diff --git a/js/src/devtools/rootAnalysis/computeGCTypes.js b/js/src/devtools/rootAnalysis/computeGCTypes.js
new file mode 100644
index 0000000000..9fc72f6d44
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/computeGCTypes.js
@@ -0,0 +1,517 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('annotations.js');
+
+var options = parse_options([
+    { name: "gcTypes", default: "gcTypes.txt" },
+    { name: "typeInfo", default: "typeInfo.txt" }
+]);
+
+var typeInfo = {
+    'GCPointers': [],
+    'GCThings': [],
+    'GCInvalidated': [],
+    'NonGCTypes': {}, // unused
+    'NonGCPointers': {},
+    'RootedGCThings': {},
+    'RootedPointers': {},
+    'RootedBases': {'JS::AutoGCRooter': true},
+    'InheritFromTemplateArgs': {},
+    'OtherCSUTags': {},
+    'OtherFieldTags': {},
+
+    // RAII types within which we should assume GC is suppressed, eg
+    // AutoSuppressGC.
+    'GCSuppressors': {},
+};
+
+var gDescriptors = new Map; // Map from descriptor string => Set of typeName
+
+var structureParents = {}; // Map from field => list of <parent, fieldName>
+var pointerParents = {}; // Map from field => list of <parent, fieldName>
+var baseClasses = {}; // Map from struct name => list of base class name strings
+var subClasses = {}; // Map from struct name => list of subclass  name strings
+
+var gcTypes = {}; // map from parent struct => Set of GC typed children
+var gcPointers = {}; // map from parent struct => Set of GC typed children
+var gcFields = new Map;
+
+var rootedPointers = {};
+
+// Accumulate the base GC types before propagating info through the type graph,
+// so that we can include edges from types processed later
+// (eg MOZ_INHERIT_TYPE_ANNOTATIONS_FROM_TEMPLATE_ARGS).
+var pendingGCTypes = [];
+var pendingGCPointers = [];
+
+function processCSU(csu, body)
+{
+    for (let { 'Name': [ annType, tag ] } of (body.Annotation || [])) {
+        if (annType != 'annotate')
+            continue;
+
+        if (tag == 'GC Pointer')
+            typeInfo.GCPointers.push(csu);
+        else if (tag == 'Invalidated by GC')
+            typeInfo.GCInvalidated.push(csu);
+        else if (tag == 'GC Thing')
+            typeInfo.GCThings.push(csu);
+        else if (tag == 'Suppressed GC Pointer')
+            typeInfo.NonGCPointers[csu] = true;
+        else if (tag == 'Rooted Pointer')
+            typeInfo.RootedPointers[csu] = true;
+        else if (tag == 'Rooted Base')
+            typeInfo.RootedBases[csu] = true;
+        else if (tag == 'Suppress GC')
+            typeInfo.GCSuppressors[csu] = true;
+        else if (tag == 'moz_inherit_type_annotations_from_template_args')
+            typeInfo.InheritFromTemplateArgs[csu] = true;
+        else
+            addToKeyedList(typeInfo.OtherCSUTags, csu, tag);
+    }
+
+    for (let { 'Base': base } of (body.CSUBaseClass || []))
+        addBaseClass(csu, base);
+
+    for (const field of (body.DataField || [])) {
+        var type = field.Field.Type;
+        var fieldName = field.Field.Name[0];
+        if (type.Kind == "Pointer") {
+            var target = type.Type;
+            if (target.Kind == "CSU")
+                addNestedPointer(csu, target.Name, fieldName);
+        }
+        if (type.Kind == "Array") {
+            var target = type.Type;
+            if (target.Kind == "CSU")
+                addNestedStructure(csu, target.Name, fieldName);
+        }
+        if (type.Kind == "CSU")
+            addNestedStructure(csu, type.Name, fieldName);
+
+        for (const { 'Name': [ annType, tag ] } of (field.Annotation || [])) {
+            if (!(csu in typeInfo.OtherFieldTags))
+                typeInfo.OtherFieldTags[csu] = [];
+            addToKeyedList(typeInfo.OtherFieldTags[csu], fieldName, tag);
+        }
+    }
+
+    for (const funcfield of (body.FunctionField || [])) {
+        const fields = funcfield.Field;
+        // Pure virtual functions will not have field.Variable; others will.
+        for (const field of funcfield.Field) {
+            for (const {'Name': [annType, tag]} of (field.Annotation || [])) {
+                if (!(csu in typeInfo.OtherFieldTags))
+                    typeInfo.OtherFieldTags[csu] = {};
+                addToKeyedList(typeInfo.OtherFieldTags[csu], field.Name[0], tag);
+            }
+        }
+    }
+}
+
+// csu.field is of type inner
+function addNestedStructure(csu, inner, field)
+{
+    if (!(inner in structureParents))
+        structureParents[inner] = [];
+
+    // Skip fields that are really base classes, to avoid duplicating the base
+    // fields; addBaseClass already added a "base-N" name.
+    if (field.match(/^field:\d+$/) && (csu in baseClasses) && (baseClasses[csu].indexOf(inner) != -1))
+        return;
+
+    structureParents[inner].push([ csu, field ]);
+}
+
+function addBaseClass(csu, base) {
+    if (!(csu in baseClasses))
+        baseClasses[csu] = [];
+    baseClasses[csu].push(base);
+    if (!(base in subClasses))
+        subClasses[base] = [];
+    subClasses[base].push(csu);
+    var k = baseClasses[csu].length;
+    addNestedStructure(csu, base, `<base-${k}>`);
+}
+
+function addNestedPointer(csu, inner, field)
+{
+    if (!(inner in pointerParents))
+        pointerParents[inner] = [];
+    pointerParents[inner].push([ csu, field ]);
+}
+
+var xdb = xdbLibrary();
+xdb.open("src_comp.xdb");
+
+var minStream = xdb.min_data_stream();
+var maxStream = xdb.max_data_stream();
+
+for (var csuIndex = minStream; csuIndex <= maxStream; csuIndex++) {
+    var csu = xdb.read_key(csuIndex);
+    var data = xdb.read_entry(csu);
+    var json = JSON.parse(data.readString());
+    assert(json.length == 1);
+    processCSU(csu.readString(), json[0]);
+
+    xdb.free_string(csu);
+    xdb.free_string(data);
+}
+
+for (const typename of extraRootedGCThings())
+    typeInfo.RootedGCThings[typename] = true;
+
+for (const typename of extraRootedPointers())
+    typeInfo.RootedPointers[typename] = true;
+
+// Everything that inherits from a "Rooted Base" is considered to be rooted.
+// This is for things like CustomAutoRooter and its subclasses.
+var basework = Object.keys(typeInfo.RootedBases);
+while (basework.length) {
+    const base = basework.pop();
+    typeInfo.RootedPointers[base] = true;
+    if (base in subClasses)
+        basework.push(...subClasses[base]);
+}
+
+// Now that we have the whole hierarchy set up, add all the types and propagate
+// info.
+for (const csu of typeInfo.GCThings)
+    addGCType(csu);
+for (const csu of typeInfo.GCPointers)
+    addGCPointer(csu);
+for (const csu of typeInfo.GCInvalidated)
+    addGCPointer(csu);
+
+function parseTemplateType(typeName, validate=false) {
+    // We only want templatized types. `Foo<U, T>::Member` doesn't count.
+    // Foo<U, T>::Bar<X, Y> does count. Which turns out to be a simple rule:
+    // check whether the type ends in '>'.
+    if (!typeName.endsWith(">")) {
+        return [typeName, undefined];
+    }
+
+    // "Tokenize" into angle brackets, commas, and everything else. We store
+    // match objects as tokens because we'll need the string offset after we
+    // finish grabbing the template parameters.
+    const tokens = [];
+    const tokenizer = /[<>,]|[^<>,]+/g;
+    let match;
+    while ((match = tokenizer.exec(typeName)) !== null) {
+    	tokens.push(match);
+    }
+
+    // Walk backwards through the tokens, stopping when we find the matching
+    // open bracket.
+    const args = [];
+    let depth = 0;
+    let arg;
+    let first_result;
+    for (const match of tokens.reverse()) {
+        const token = match[0];
+        if (depth == 1 && (token == ',' || token == '<')) {
+            // We've walked back to the beginning of a template parameter,
+            // where we will see either a comma or open bracket.
+            args.unshift(arg);
+            arg = '';
+        } else if (depth == 0 && token == '>') {
+            arg = ''; // We just started.
+        } else {
+            arg = token + arg;
+        }
+
+        // Maintain the depth.
+        if (token == '<') {
+            // This could be bug 1728151.
+            assert(depth > 0, `Invalid type: too many '<' signs in '${typeName}'`);
+            depth--;
+        } else if (token == '>') {
+            depth++;
+        }
+
+        if (depth == 0) {
+            // We've walked out of the template parameter list.
+            // Record the results.
+            assert(args.length > 0);
+            const templateName = typeName.substr(0, match.index);
+            const result = [templateName, args.map(arg => arg.trim())];
+            if (!validate) {
+                // Normal processing is to return the result the first time we
+                // get to the '<' that matches the terminal '>', without validating
+                // that the rest of the type name is balanced.
+                return result;
+            } else if (!first_result) {
+                // If we are validating, remember the result when we hit the
+                // first matching '<', but then keep processing the rest of
+                // the input string to count brackets.
+                first_result = result;
+            }
+        }
+    }
+
+    // This could be bug 1728151.
+    assert(depth == 0, `Invalid type: too many '>' signs in '${typeName}'`);
+    return first_result;
+}
+
+if (os.getenv("HAZARD_RUN_INTERNAL_TESTS")) {
+    function check_parse(typeName, result) {
+        assertEq(JSON.stringify(parseTemplateType(typeName)), JSON.stringify(result));
+    }
+
+    check_parse("int", ["int", undefined]);
+    check_parse("Type<int>", ["Type", ["int"]]);
+    check_parse("Container<int, double>", ["Container", ["int", "double"]]);
+    check_parse("Container<Container<void, void>, double>", ["Container", ["Container<void, void>", "double"]]);
+    check_parse("Foo<Bar<a,b>,Bar<a,b>>::Container<Container<void, void>, double>", ["Foo<Bar<a,b>,Bar<a,b>>::Container", ["Container<void, void>", "double"]]);
+    check_parse("AlignedStorage2<TypedArray<foo>>", ["AlignedStorage2", ["TypedArray<foo>"]]);
+    check_parse("mozilla::AlignedStorage2<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> >",
+        [
+            "mozilla::AlignedStorage2",
+            [
+                "mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer>"
+            ]
+        ]
+    );
+    check_parse(
+        "mozilla::ArrayIterator<const mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >&, nsTArray_Impl<mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >, nsTArrayInfallibleAllocator> >",
+        [
+            "mozilla::ArrayIterator",
+            [
+                "const mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >&",
+                "nsTArray_Impl<mozilla::dom::binding_detail::RecordEntry<nsTString<char16_t>, mozilla::dom::Nullable<mozilla::dom::TypedArray<unsigned char, JS::UnwrapArrayBufferMaybeShared, JS::GetArrayBufferMaybeSharedData, JS::GetArrayBufferMaybeSharedLengthAndData, JS::NewArrayBuffer> > >, nsTArrayInfallibleAllocator>"
+            ]
+        ]
+    );
+
+    function check_throws(f, exc) {
+        try {
+            f();
+        } catch (e) {
+            assertEq(e.message.includes(exc), true, "incorrect exception: " + e.message);
+            return;
+        }
+        assertEq(undefined, exc);
+    }
+    // Note that these need to end in '>' or the whole thing will be ignored.
+    check_throws(() => parseTemplateType("foo>", true), "too many '>' signs");
+    check_throws(() => parseTemplateType("foo<<>", true), "too many '<' signs");
+    check_throws(() => parseTemplateType("foo<a::bar<a,b>", true), "too many '<' signs");
+    check_throws(() => parseTemplateType("foo<a>*>::bar<a,b>", true), "too many '>' signs");
+}
+
+// GC Thing and GC Pointer annotations can be inherited from template args if
+// this annotation is used. Think of Maybe<T> for example: Maybe<JSObject*> has
+// the same GC rules as JSObject*.
+
+var inheritors = Object.keys(typeInfo.InheritFromTemplateArgs).sort((a, b) => a.length - b.length);
+for (const csu of inheritors) {
+    const [templateName, templateArgs] = parseTemplateType(csu);
+    for (const param of templateArgs) {
+        const pos = param.search(/\**$/);
+        const ptrdness = param.length - pos;
+        const core_type = param.substr(0, pos);
+        if (ptrdness == 0) {
+            addToKeyedList(structureParents, core_type, [csu, "template-param-" + param]);
+        } else if (ptrdness == 1) {
+            addToKeyedList(pointerParents, core_type, [csu, "template-param-" + param]);
+        }
+    }
+}
+
+// "typeName is a (pointer to a)^'typePtrLevel' GC type because it contains a field
+// named 'child' of type 'why' (or pointer to 'why' if fieldPtrLevel == 1), which is
+// itself a GCThing or GCPointer."
+function markGCType(typeName, child, why, typePtrLevel, fieldPtrLevel, indent)
+{
+    // Some types, like UniquePtr, do not mark/trace/relocate their contained
+    // pointers and so should not hold them live across a GC. UniquePtr in
+    // particular should be the only thing pointing to a structure containing a
+    // GCPointer, so nothing else can possibly trace it and it'll die when the
+    // UniquePtr goes out of scope. So we say that memory pointed to by a
+    // UniquePtr is just as unsafe as the stack for storing GC pointers.
+    if (!fieldPtrLevel && isUnsafeStorage(typeName)) {
+        // The UniquePtr itself is on the stack but when you dereference the
+        // contained pointer, you get to the unsafe memory that we are treating
+        // as if it were the stack (aka ptrLevel 0). Note that
+        // UniquePtr<UniquePtr<JSObject*>> is fine, so we don't want to just
+        // hardcode the ptrLevel.
+        fieldPtrLevel = -1;
+    }
+
+    // Example: with:
+    //    struct Pair { JSObject* foo; int bar; };
+    //    struct { Pair** info }***
+    // make a call to:
+    //    child='info' typePtrLevel=3 fieldPtrLevel=2
+    // for a final ptrLevel of 5, used to later call:
+    //    child='foo' typePtrLevel=5 fieldPtrLevel=1
+    //
+    var ptrLevel = typePtrLevel + fieldPtrLevel;
+
+    // ...except when > 2 levels of pointers away from an actual GC thing, stop
+    // searching the graph. (This would just be > 1, except that a UniquePtr
+    // field might still have a GC pointer.)
+    if (ptrLevel > 2)
+        return;
+
+    if (isRootedGCPointerTypeName(typeName) && !(typeName in typeInfo.RootedPointers))
+        printErr("FIXME: use in-source annotation for " + typeName);
+
+    if (ptrLevel == 0 && (typeName in typeInfo.RootedGCThings))
+        return;
+    if (ptrLevel == 1 && (isRootedGCPointerTypeName(typeName) || (typeName in typeInfo.RootedPointers)))
+        return;
+
+    if (ptrLevel == 0) {
+        if (typeName in typeInfo.NonGCTypes)
+            return;
+        if (!(typeName in gcTypes))
+            gcTypes[typeName] = new Set();
+        gcTypes[typeName].add(why);
+    } else if (ptrLevel == 1) {
+        if (typeName in typeInfo.NonGCPointers)
+            return;
+        if (!(typeName in gcPointers))
+            gcPointers[typeName] = new Set();
+        gcPointers[typeName].add(why);
+    }
+
+    if (ptrLevel < 2) {
+        if (!gcFields.has(typeName))
+            gcFields.set(typeName, new Map());
+        gcFields.get(typeName).set(child, [ why, fieldPtrLevel ]);
+    }
+
+    if (typeName in structureParents) {
+        for (var field of structureParents[typeName]) {
+            var [ holderType, fieldName ] = field;
+            markGCType(holderType, fieldName, typeName, ptrLevel, 0, indent + "  ");
+        }
+    }
+    if (typeName in pointerParents) {
+        for (var field of pointerParents[typeName]) {
+            var [ holderType, fieldName ] = field;
+            markGCType(holderType, fieldName, typeName, ptrLevel, 1, indent + "  ");
+        }
+    }
+}
+
+function addGCType(typeName, child, why, depth, fieldPtrLevel)
+{
+    pendingGCTypes.push([typeName, '<annotation>', '(annotation)', 0, 0]);
+}
+
+function addGCPointer(typeName)
+{
+    pendingGCPointers.push([typeName, '<pointer-annotation>', '(annotation)', 1, 0]);
+}
+
+for (const pending of pendingGCTypes) {
+    markGCType(...pending);
+}
+for (const pending of pendingGCPointers) {
+    markGCType(...pending);
+}
+
+// Call a function for a type and every type that contains the type in a field
+// or as a base class (which internally is pretty much the same thing --
+// subclasses are structs beginning with the base class and adding on their
+// local fields.)
+function foreachContainingStruct(typeName, func, seen = new Set())
+{
+    function recurse(container, typeName) {
+        if (seen.has(typeName))
+            return;
+        seen.add(typeName);
+
+        func(container, typeName);
+
+        if (typeName in subClasses) {
+            for (const sub of subClasses[typeName])
+                recurse("subclass of " + typeName, sub);
+        }
+        if (typeName in structureParents) {
+            for (const [holder, field] of structureParents[typeName])
+                recurse(field + " : " + typeName, holder);
+        }
+    }
+
+    recurse('<annotation>', typeName);
+}
+
+for (var type of listNonGCPointers())
+    typeInfo.NonGCPointers[type] = true;
+
+function explain(csu, indent, seen) {
+    if (!seen)
+        seen = new Set();
+    seen.add(csu);
+    if (!gcFields.has(csu))
+        return;
+    var fields = gcFields.get(csu);
+
+    if (fields.has('<annotation>')) {
+        print(indent + "which is annotated as a GCThing");
+        return;
+    }
+    if (fields.has('<pointer-annotation>')) {
+        print(indent + "which is annotated as a GCPointer");
+        return;
+    }
+    for (var [ field, [ child, ptrdness ] ] of fields) {
+        var msg = indent;
+        if (field[0] == '<')
+            msg += "inherits from ";
+        else {
+            if (field.startsWith("template-param-")) {
+                msg += "inherits annotations from template parameter '" + field.substr(15) + "' ";
+            } else {
+                msg += "contains field '" + field + "' ";
+            }
+            if (ptrdness == -1)
+                msg += "(with a pointer to unsafe storage) holding a ";
+            else if (ptrdness == 0)
+                msg += "of type ";
+            else
+                msg += "pointing to type ";
+        }
+        msg += child;
+        print(msg);
+        if (!seen.has(child))
+            explain(child, indent + "  ", seen);
+    }
+}
+
+var origOut = os.file.redirect(options.gcTypes);
+
+for (var csu in gcTypes) {
+    print("GCThing: " + csu);
+    explain(csu, "  ");
+}
+for (var csu in gcPointers) {
+    print("GCPointer: " + csu);
+    explain(csu, "  ");
+}
+
+// Redirect output to the typeInfo file and close the gcTypes file.
+os.file.close(os.file.redirect(options.typeInfo));
+
+// Compute the set of types that suppress GC within their RAII scopes (eg
+// AutoSuppressGC, AutoSuppressGCForAnalysis).
+var seen = new Set();
+for (let csu in typeInfo.GCSuppressors)
+    foreachContainingStruct(csu,
+                            (holder, typeName) => { typeInfo.GCSuppressors[typeName] = holder },
+                            seen);
+
+print(JSON.stringify(typeInfo, null, 4));
+
+os.file.close(os.file.redirect(origOut));
diff --git a/js/src/devtools/rootAnalysis/dumpCFG.js b/js/src/devtools/rootAnalysis/dumpCFG.js
new file mode 100644
index 0000000000..ac4897669b
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/dumpCFG.js
@@ -0,0 +1,267 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// const cfg = loadCFG(scriptArgs[0]);
+// dump_CFG(cfg);
+
+function loadCFG(filename) {
+  const data = os.file.readFile(filename);
+  return JSON.parse(data);
+}
+
+function dump_CFG(cfg) {
+  for (const body of cfg)
+    dump_body(body);
+}
+
+function dump_body(body, src, dst) {
+  const {BlockId,Command,DefineVariable,Index,Location,PEdge,PPoint,Version} = body;
+
+  const [mangled, unmangled] = splitFunction(BlockId.Variable.Name[0]);
+  print(`${unmangled} at ${Location[0].CacheString}:${Location[0].Line}`);
+
+  if (src === undefined) {
+    for (const def of DefineVariable)
+      print(str_definition(def));
+    print("");
+  }
+
+  for (const edge of PEdge) {
+    if (src === undefined || edge.Index[0] == src) {
+      if (dst == undefined || edge.Index[1] == dst)
+        print(str_edge(edge, body));
+    }
+  }
+}
+
+function str_definition(def) {
+  const {Type, Variable} = def;
+  return `define ${str_Variable(Variable)} : ${str_Type(Type)}`;
+}
+
+function badFormat(what, val) {
+  printErr("Bad format of " + what + ": " + JSON.stringify(val, null, 4));
+  printErr((new Error).stack);
+}
+
+function str_Variable(variable) {
+  if (variable.Kind == 'Return')
+    return '<returnval>';
+  else if (variable.Kind == 'This')
+    return 'this';
+
+  try {
+    return variable.Name[1];
+  } catch(e) {
+    badFormat("variable", variable);
+  }
+}
+
+function str_Type(type) {
+  try {
+    const {Kind, Type, Name, TypeFunctionArguments} = type;
+    if (Kind == 'Pointer')
+      return str_Type(Type) + "*";
+    else if (Kind == 'CSU')
+      return Name;
+    else if (Kind == 'Array')
+      return str_Type(Type) + "[]";
+
+    return Kind;
+  } catch(e) {
+    badFormat("type", type);
+  }
+}
+
+var OpCodeNames = {
+  'LessEqual': ['<=', '>'],
+  'LessThan': ['<', '>='],
+  'GreaterEqual': ['>=', '<'],
+  'Greater': ['>', '<='],
+  'Plus': '+',
+  'Minus': '-',
+};
+
+function opcode_name(opcode, invert) {
+  if (opcode in OpCodeNames) {
+    const name = OpCodeNames[opcode];
+    if (invert === undefined)
+      return name;
+    return name[invert ? 1 : 0];
+  } else {
+    if (invert === undefined)
+      return opcode;
+    return (invert ? '!' : '') + opcode;
+  }
+}
+
+function str_value(val, env, options) {
+  const {Kind, Variable, String, Exp} = val;
+  if (Kind == 'Var')
+    return str_Variable(Variable);
+  else if (Kind == 'Drf') {
+    // Suppress the vtable lookup dereference
+    if (Exp[0].Kind == 'Fld' && "FieldInstanceFunction" in Exp[0].Field)
+      return str_value(Exp[0], env);
+    const exp = str_value(Exp[0], env);
+    if (options && options.noderef)
+      return exp;
+    return "*" + exp;
+  } else if (Kind == 'Fld') {
+    const {Exp, Field} = val;
+    const name = Field.Name[0];
+    if ("FieldInstanceFunction" in Field) {
+      return Field.FieldCSU.Type.Name + "." + name;
+    }
+    const container = str_value(Exp[0]);
+    if (container.startsWith("*"))
+      return container.substring(1) + "->" + name;
+    return container + "." + name;
+  } else if (Kind == 'Empty') {
+    return '<unknown>';
+  } else if (Kind == 'Binop') {
+    const {OpCode} = val;
+    const op = opcode_name(OpCode);
+    return `${str_value(Exp[0], env)} ${op} ${str_value(Exp[1], env)}`;
+  } else if (Kind == 'Unop') {
+    const exp = str_value(Exp[0], env);
+    const {OpCode} = val;
+    if (OpCode == 'LogicalNot')
+      return `not ${exp}`;
+    return `${OpCode}(${exp})`;
+  } else if (Kind == 'Index') {
+    const index = str_value(Exp[1], env);
+    if (Exp[0].Kind == 'Drf')
+      return `${str_value(Exp[0], env, {noderef:true})}[${index}]`;
+    else
+      return `&${str_value(Exp[0], env)}[${index}]`;
+  } else if (Kind == 'NullTest') {
+    return `nullptr == ${str_value(Exp[0], env)}`;
+  } else if (Kind == "String") {
+    return '"' + String + '"';
+  } else if (String !== undefined) {
+    return String;
+  }
+  badFormat("value", val);
+}
+
+function str_thiscall_Exp(exp) {
+  return exp.Kind == 'Drf' ? str_value(exp.Exp[0]) + "->" : str_value(exp) + ".";
+}
+
+function stripcsu(s) {
+    return s.replace("class ", "").replace("struct ", "").replace("union ");
+}
+
+function str_call(prefix, edge, env) {
+  const {Exp, Type, PEdgeCallArguments, PEdgeCallInstance} = edge;
+  const {Kind, Type:cType, TypeFunctionArguments, TypeFunctionCSU} = Type;
+
+  if (Kind == 'Function') {
+    const params = PEdgeCallArguments ? PEdgeCallArguments.Exp : [];
+    const strParams = params.map(str_value);
+
+    let func;
+    let comment = "";
+    let assign_exp;
+    if (PEdgeCallInstance) {
+      const csu = TypeFunctionCSU.Type.Name;
+      const method = str_value(Exp[0], env);
+
+      // Heuristic to only display the csu for constructors
+      if (csu.includes(method)) {
+        func = stripcsu(csu) + "::" + method;
+      } else {
+        func = method;
+        comment = "# " + csu + "::" + method + "\n";
+      }
+
+      const {Exp: thisExp} = PEdgeCallInstance;
+      func = str_thiscall_Exp(thisExp) + func;
+    } else {
+      func = str_value(Exp[0]);
+    }
+    assign_exp = Exp[1];
+
+    let assign = "";
+    if (assign_exp) {
+      assign = str_value(assign_exp) + " := ";
+    }
+    return `${comment}${prefix} Call ${assign}${func}(${strParams.join(", ")})`;
+  }
+
+  print(JSON.stringify(edge, null, 4));
+  throw new Error("unhandled format error");
+}
+
+function str_assign(prefix, edge) {
+  const {Exp} = edge;
+  const [lhs, rhs] = Exp;
+  return `${prefix} Assign ${str_value(lhs)} := ${str_value(rhs)}`;
+}
+
+function str_loop(prefix, edge) {
+  const {BlockId: {Loop}} = edge;
+  return `${prefix} Loop ${Loop}`;
+}
+
+function str_assume(prefix, edge) {
+  const {Exp, PEdgeAssumeNonZero} = edge;
+  const cmp = PEdgeAssumeNonZero ? "" : "!";
+
+  const {Exp: aExp, Kind, OpCode} = Exp[0];
+  if (Kind == 'Binop') {
+    const [lhs, rhs] = aExp;
+    const op = opcode_name(OpCode, !PEdgeAssumeNonZero);
+    return `${prefix} Assume ${str_value(lhs)} ${op} ${str_value(rhs)}`;
+  } else if (Kind == 'Unop') {
+    return `${prefix} Assume ${cmp}${OpCode} ${str_value(aExp[0])}`;
+  } else if (Kind == 'NullTest') {
+    return `${prefix} Assume nullptr ${cmp}== ${str_value(aExp[0])}`;
+  } else if (Kind == 'Drf') {
+    return `${prefix} Assume ${cmp}${str_value(Exp[0])}`;
+  }
+
+  print(JSON.stringify(edge, null, 4));
+  throw new Error("unhandled format error");
+}
+
+function str_edge(edge, env) {
+  const {Index, Kind} = edge;
+  const [src, dst] = Index;
+  const prefix = `[${src},${dst}]`;
+
+  if (Kind == "Call")
+    return str_call(prefix, edge, env);
+  if (Kind == 'Assign')
+    return str_assign(prefix, edge);
+  if (Kind == 'Assume')
+    return str_assume(prefix, edge);
+  if (Kind == 'Loop')
+    return str_loop(prefix, edge);
+
+  print(JSON.stringify(edge, null, 4));
+  throw "unhandled edge type";
+}
+
+function str(unknown) {
+  if ("Name" in unknown) {
+    return str_Variable(unknown);
+  } else if ("Index" in unknown) {
+    // Note: Variable also has .Index, with a different meaning.
+    return str_edge(unknown);
+  } else if ("Kind" in unknown) {
+    if ("BlockId" in unknown)
+      return str_Variable(unknown);
+    return str_value(unknown);
+  } else if ("Type" in unknown) {
+    return str_Type(unknown);
+  }
+  return "unknown";
+}
+
+function jdump(x) {
+  print(JSON.stringify(x, null, 4));
+  quit(0);
+}
diff --git a/js/src/devtools/rootAnalysis/expect.b2g.json b/js/src/devtools/rootAnalysis/expect.b2g.json
new file mode 100644
index 0000000000..06f2beb36f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/expect.b2g.json
@@ -0,0 +1,3 @@
+{
+  "expect-hazards": 0
+}
diff --git a/js/src/devtools/rootAnalysis/expect.browser.json b/js/src/devtools/rootAnalysis/expect.browser.json
new file mode 100644
index 0000000000..06f2beb36f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/expect.browser.json
@@ -0,0 +1,3 @@
+{
+  "expect-hazards": 0
+}
diff --git a/js/src/devtools/rootAnalysis/expect.shell.json b/js/src/devtools/rootAnalysis/expect.shell.json
new file mode 100644
index 0000000000..06f2beb36f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/expect.shell.json
@@ -0,0 +1,3 @@
+{
+  "expect-hazards": 0
+}
diff --git a/js/src/devtools/rootAnalysis/explain.py b/js/src/devtools/rootAnalysis/explain.py
new file mode 100755
index 0000000000..becfcf17a0
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/explain.py
@@ -0,0 +1,158 @@
+#!/usr/bin/python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this file,
+# You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import argparse
+import re
+from collections import defaultdict
+
+parser = argparse.ArgumentParser(description="Process some integers.")
+parser.add_argument("rootingHazards", nargs="?", default="rootingHazards.txt")
+parser.add_argument("gcFunctions", nargs="?", default="gcFunctions.txt")
+parser.add_argument("hazards", nargs="?", default="hazards.txt")
+parser.add_argument("extra", nargs="?", default="unnecessary.txt")
+parser.add_argument("refs", nargs="?", default="refs.txt")
+args = parser.parse_args()
+
+
+# Imitate splitFunction from utility.js.
+def splitfunc(full):
+    idx = full.find("$")
+    if idx == -1:
+        return (full, full)
+    return (full[0:idx], full[idx + 1 :])
+
+
+num_hazards = 0
+num_refs = 0
+num_missing = 0
+
+try:
+    with open(args.rootingHazards) as rootingHazards, open(
+        args.hazards, "w"
+    ) as hazards, open(args.extra, "w") as extra, open(args.refs, "w") as refs:
+        current_gcFunction = None
+
+        # Map from a GC function name to the list of hazards resulting from
+        # that GC function
+        hazardousGCFunctions = defaultdict(list)
+
+        # List of tuples (gcFunction, index of hazard) used to maintain the
+        # ordering of the hazards
+        hazardOrder = []
+
+        # Map from a hazardous GC function to the filename containing it.
+        fileOfFunction = {}
+
+        for line in rootingHazards:
+            m = re.match(r"^Time: (.*)", line)
+            mm = re.match(r"^Run on:", line)
+            if m or mm:
+                print(line, file=hazards)
+                print(line, file=extra)
+                print(line, file=refs)
+                continue
+
+            m = re.match(r"^Function.*has unnecessary root", line)
+            if m:
+                print(line, file=extra)
+                continue
+
+            m = re.match(r"^Function.*takes unsafe address of unrooted", line)
+            if m:
+                num_refs += 1
+                print(line, file=refs)
+                continue
+
+            m = re.match(
+                r"^Function.*has unrooted.*of type.*live across GC call '(.*?)' at (\S+):\d+$",
+                line,
+            )  # NOQA: E501
+            if m:
+                # Replace mangled$unmangled with just the unmangled part in the output.
+                current_gcFunction = m.group(1)
+                _, readable = splitfunc(current_gcFunction)
+                hazardousGCFunctions[current_gcFunction].append(
+                    line.replace(current_gcFunction, readable)
+                )
+                hazardOrder.append(
+                    (
+                        current_gcFunction,
+                        len(hazardousGCFunctions[current_gcFunction]) - 1,
+                    )
+                )
+                num_hazards += 1
+                fileOfFunction[current_gcFunction] = m.group(2)
+                continue
+
+            m = re.match(r"Function.*expected hazard.*but none were found", line)
+            if m:
+                num_missing += 1
+                print(line + "\n", file=hazards)
+                continue
+
+            if current_gcFunction:
+                if not line.strip():
+                    # Blank line => end of this hazard
+                    current_gcFunction = None
+                else:
+                    hazardousGCFunctions[current_gcFunction][-1] += line
+
+        mangled2full = {}
+        with open(args.gcFunctions) as gcFunctions:
+            gcExplanations = {}  # gcFunction => stack showing why it can GC
+
+            current_func = None
+            explanation = None
+            for line in gcFunctions:
+                m = re.match(r"^GC Function: (.*)", line)
+                if m:
+                    if current_func:
+                        gcExplanations[current_func] = explanation
+                    current_func = m.group(1)
+                    mangled, _ = splitfunc(current_func)
+                    mangled2full[mangled] = current_func
+                    explanation = line
+                elif current_func:
+                    explanation += line
+            if current_func:
+                gcExplanations[current_func] = explanation
+
+        for gcFunction, index in hazardOrder:
+            gcHazards = hazardousGCFunctions[gcFunction]
+
+            if gcFunction in gcExplanations:
+                key = gcFunction
+            else:
+                # Mangled constructor/destructor names can map to multiple
+                # unmangled names. We have both here, and the unmangled name
+                # seen here in the caller may not match the unmangled name in
+                # the callee, so if we don't find the full function then key
+                # off of the mangled name instead.
+                #
+                # Normally the analysis tries to use the mangled name for
+                # identity comparison, but here we're processing human-readable
+                # output. Perhaps a better solution might be to treat the
+                # rootingHazards.txt input here as internal and only list
+                # mangled names, expanding them to unmangled names when
+                # producing hazards.txt and the other output files.
+                mangled, _ = splitfunc(gcFunction)
+                key = mangled2full[mangled]
+
+            if key in gcExplanations:
+                print(gcHazards[index] + gcExplanations[key], file=hazards)
+            else:
+                print(gcHazards[index], file=hazards)
+
+except IOError as e:
+    print("Failed: %s" % str(e))
+
+print("Wrote %s" % args.hazards)
+print("Wrote %s" % args.extra)
+print("Wrote %s" % args.refs)
+print(
+    "Found %d hazards %d unsafe references %d missing"
+    % (num_hazards, num_refs, num_missing)
+)
diff --git a/js/src/devtools/rootAnalysis/gen-hazards.sh b/js/src/devtools/rootAnalysis/gen-hazards.sh
new file mode 100755
index 0000000000..7007969a14
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/gen-hazards.sh
@@ -0,0 +1,15 @@
+#!/bin/sh
+
+set -e
+
+JOBS="$1"
+
+for j in $(seq $JOBS); do
+    env PATH=$PATH:$SIXGILL/bin XDB=$SIXGILL/bin/xdb.so $JS $ANALYZE gcFunctions.lst suppressedFunctions.lst gcTypes.txt $j $JOBS tmp.$j > rootingHazards.$j &
+done
+
+wait
+
+for j in $(seq $JOBS); do
+    cat rootingHazards.$j
+done
diff --git a/js/src/devtools/rootAnalysis/loadCallgraph.js b/js/src/devtools/rootAnalysis/loadCallgraph.js
new file mode 100644
index 0000000000..eef76c24b3
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/loadCallgraph.js
@@ -0,0 +1,586 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('utility.js');
+loadRelativeToScript('callgraph.js');
+
+// Functions come out of sixgill in the form "mangled$readable". The mangled
+// name is Truth. One mangled name might correspond to multiple readable names,
+// for multiple reasons, including (1) sixgill/gcc doesn't always qualify types
+// the same way or de-typedef the same amount; (2) sixgill's output treats
+// references and pointers the same, and so doesn't distinguish them, but C++
+// treats them as separate for overloading and linking; (3) (identical)
+// destructors sometimes have an int32 parameter, sometimes not.
+//
+// The readable names are useful because they're far more meaningful to the
+// user, and are what should show up in reports and questions to mrgiggles. At
+// least in most cases, it's fine to have the extra mangled name tacked onto
+// the beginning for these.
+//
+// The strategy used is to separate out the pieces whenever they are read in,
+// create a table mapping mangled names to all readable names, and use the
+// mangled names in all computation -- except for limited circumstances when
+// the readable name is used in annotations.
+//
+// Note that callgraph.txt uses a compressed representation -- each name is
+// mapped to an integer, and those integers are what is recorded in the edges.
+// But the integers depend on the full name, whereas the true edge should only
+// consider the mangled name. And some of the names encoded in callgraph.txt
+// are FieldCalls, not just function names.
+
+var gcEdges = {};
+
+// Returns whether the function was added. (It will be refused if it was
+// already there, or if attrs or annotations say it shouldn't be added.)
+function addGCFunction(caller, reason, gcFunctions, functionAttrs, functions)
+{
+    if (functionAttrs[caller] && functionAttrs[caller][1] & ATTR_GC_SUPPRESSED)
+        return false;
+
+    if (ignoreGCFunction(functions.name[caller], functions.readableName))
+        return false;
+
+    if (!(caller in gcFunctions)) {
+        gcFunctions[caller] = reason;
+        return true;
+    }
+
+    return false;
+}
+
+// Every caller->callee callsite is associated with attrs saying what is
+// allowed at that callsite (eg if it's in a GC suppression zone, it would have
+// ATTR_GC_SUPPRESSED set.) A given caller might call the same callee multiple
+// times, with different attributes. Associate the <caller,callee> edge with
+// the intersection (AND) and disjunction (OR) of all of the callsites' attrs.
+// The AND ('all') says what attributes are present for all callers; the OR
+// ('any') says what attributes are present on any caller. Preserve the
+// original order.
+//
+// During the same scan, build callersOf from calleesOf.
+function generate_callgraph(rawCallees) {
+    const callersOf = new Map();
+    const calleesOf = new Map();
+
+    for (const [caller, callee_attrs] of rawCallees) {
+        const ordered_callees = [];
+
+        // callee_attrs is a list of {callee,any,all} objects.
+        const callee2any = new Map();
+        const callee2all = new Map();
+        for (const {callee, any, all} of callee_attrs) {
+            const prev_any = callee2any.get(callee);
+            if (prev_any === undefined) {
+                assert(!callee2all.has(callee));
+                callee2any.set(callee, any);
+                callee2all.set(callee, all);
+                ordered_callees.push(callee);
+            } else {
+                const prev_all = callee2all.get(callee);
+                callee2any.set(callee, prev_any | any);
+                callee2all.set(callee, prev_all & all);
+            }
+        }
+
+        // Update the contents of callee_attrs to contain a single entry for
+        // each callee, with its attrs set to the AND of the attrs observed at
+        // all callsites within this caller function.
+        callee_attrs.length = 0;
+        for (const callee of ordered_callees) {
+            const any = callee2any.get(callee);
+            const all = callee2all.get(callee);
+            if (!calleesOf.has(caller))
+                calleesOf.set(caller, new Map());
+            calleesOf.get(caller).set(callee, {any, all});
+            if (!callersOf.has(callee))
+                callersOf.set(callee, new Map());
+            callersOf.get(callee).set(caller, {any, all});
+        }
+    }
+
+    return {callersOf, calleesOf};
+}
+
+// Returns object mapping mangled => reason for GCing
+function loadRawCallgraphFile(file)
+{
+    const functions = {
+        // "Map" from identifier to mangled name, or sometimes to a Class.Field name.
+        name: [""],
+
+        // map from mangled name => list of readable names
+        readableName: {},
+
+        mangledToId: {}
+    };
+
+    const fieldCallAttrs = {};
+    const fieldCallCSU = new Map(); // map from full field name id => csu name
+
+    // set of mangled names (map from mangled name => [any,all])
+    var functionAttrs = {};
+
+    const gcCalls = [];
+    const indirectCalls = [];
+
+    // map from mangled => list of tuples of {'callee':mangled, 'any':intset, 'all':intset}
+    const rawCallees = new Map();
+
+    for (let line of readFileLines_gen(file)) {
+        line = line.replace(/\n/, "");
+
+        let match;
+        if (match = line.charAt(0) == "#" && /^\#(\d+) (.*)/.exec(line)) {
+            const [ _, id, mangled ] = match;
+            assert(functions.name.length == id);
+            functions.name.push(mangled);
+            functions.mangledToId[mangled] = id|0;
+            continue;
+        }
+        if (match = line.charAt(0) == "=" && /^= (\d+) (.*)/.exec(line)) {
+            const [ _, id, readable ] = match;
+            const mangled = functions.name[id];
+            if (mangled in functions.readableName)
+                functions.readableName[mangled].push(readable);
+            else
+                functions.readableName[mangled] = [ readable ];
+            continue;
+        }
+
+        let attrs = 0;
+        // Example line: D /17 6 7
+        //
+        // This means a direct call from 6 -> 7, but within a scope that
+        // applies attrs 0x1 and 0x10 to the callee.
+        //
+        // Look for a bit specifier and remove it from the line if found.
+        if (line.indexOf("/") != -1) {
+            match = /^(..)\/(\d+) (.*)/.exec(line);
+            line = match[1] + match[3];
+            attrs = match[2]|0;
+        }
+        const tag = line.charAt(0);
+        if (match = tag == 'I' && /^I (\d+) VARIABLE ([^\,]*)/.exec(line)) {
+            const caller = match[1]|0;
+            const name = match[2];
+            if (indirectCallCannotGC(functions.name[caller], name))
+                attrs |= ATTR_GC_SUPPRESSED;
+            indirectCalls.push([caller, "IndirectCall: " + name, attrs]);
+        } else if (match = tag == 'F' && /^F (\d+) (\d+) CLASS (.*?) FIELD (.*)/.exec(line)) {
+            const caller = match[1]|0;
+            const fullfield = match[2]|0;
+            const csu = match[3];
+            const fullfield_str = csu + "." + match[4];
+            assert(functions.name[fullfield] == fullfield_str);
+            if (attrs)
+                fieldCallAttrs[fullfield] = attrs;
+            addToMappedList(rawCallees, caller, {callee:fullfield, any:attrs, all:attrs});
+            fieldCallCSU.set(fullfield, csu);
+
+            if (fieldCallCannotGC(csu, fullfield_str))
+                addToMappedList(rawCallees, fullfield, {callee:ID.nogcfunc, any:0, all:0});
+            else
+                addToMappedList(rawCallees, fullfield, {callee:ID.anyfunc, any:0, all:0});
+        } else if (match = tag == 'V' && /^V (\d+) (\d+) CLASS (.*?) FIELD (.*)/.exec(line)) {
+            // V tag is no longer used, but we are still emitting it becasue it
+            // can be helpful to understand what's going on.
+        } else if (match = tag == 'D' && /^D (\d+) (\d+)/.exec(line)) {
+            const caller = match[1]|0;
+            const callee = match[2]|0;
+            addToMappedList(rawCallees, caller, {callee, any:attrs, all:attrs});
+        } else if (match = tag == 'R' && /^R (\d+) (\d+)/.exec(line)) {
+            assert(false, "R tag is no longer used");
+        } else if (match = tag == 'T' && /^T (\d+) (.*)/.exec(line)) {
+            const id = match[1]|0;
+            let tag = match[2];
+            if (tag == 'GC Call')
+                gcCalls.push(id);
+        } else {
+            assert(false, "Invalid format in callgraph line: " + line);
+        }
+    }
+
+    printErr("Loaded " + file);
+
+    return {
+        fieldCallAttrs,
+        fieldCallCSU,
+        gcCalls,
+        indirectCalls,
+        rawCallees,
+        functions
+    };
+}
+
+// Take a set of rawcalls filenames (as in, the raw callgraph data output by
+// computeCallgraph.js) and combine them into a global callgraph, renumbering
+// the IDs as needed.
+function mergeRawCallgraphs(filenames) {
+    let d;
+    for (const filename of filenames) {
+        const raw = loadRawCallgraphFile(filename);
+        if (!d) {
+            d = raw;
+            continue;
+        }
+
+        const {
+            fieldCallAttrs,
+            fieldCallCSU,
+            gcCalls,
+            indirectCalls,
+            rawCallees,
+            functions
+        } = raw;
+
+        // Compute the ID mapping. Incoming functions that already have an ID
+        // will be mapped to that ID; new ones will allocate a fresh ID.
+        const remap = new Array(functions.name.length);
+        for (let i = 1; i < functions.name.length; i++) {
+            const mangled = functions.name[i];
+            const old_id = d.functions.mangledToId[mangled]
+            if (old_id) {
+                remap[i] = old_id;
+            } else {
+                const newid = d.functions.name.length;
+                d.functions.mangledToId[mangled] = newid;
+                d.functions.name.push(mangled);
+                remap[i] = newid;
+                assert(!(mangled in d.functions.readableName), mangled + " readable name is already found");
+                const readables = functions.readableName[mangled];
+                if (readables !== undefined)
+                    d.functions.readableName[mangled] = readables;
+            }
+        }
+
+        for (const [fullfield, attrs] of Object.entries(fieldCallAttrs))
+            d.fieldCallAttrs[remap[fullfield]] = attrs;
+        for (const [fullfield, csu] of fieldCallCSU.entries())
+            d.fieldCallCSU.set(remap[fullfield], csu);
+        for (const call of gcCalls)
+            d.gcCalls.push(remap[call]);
+        for (const [caller, name, attrs] of indirectCalls)
+            d.indirectCalls.push([remap[caller], name, attrs]);
+        for (const [caller, callees] of rawCallees) {
+            for (const {callee, any, all} of callees) {
+                addToMappedList(d.rawCallees, remap[caller]|0, {callee:remap[callee], any, all});
+            }
+        }
+    }
+
+    return d;
+}
+
+function loadCallgraph(files)
+{
+    const {
+        fieldCallAttrs,
+        fieldCallCSU,
+        gcCalls,
+        indirectCalls,
+        rawCallees,
+        functions
+    } = mergeRawCallgraphs(files);
+
+    assert(ID.jscode == functions.mangledToId["(js-code)"]);
+    assert(ID.anyfunc == functions.mangledToId["(any-function)"]);
+    assert(ID.nogcfunc == functions.mangledToId["(nogc-function)"]);
+    assert(ID.gc == functions.mangledToId["(GC)"]);
+
+    addToMappedList(rawCallees, functions.mangledToId["(any-function)"], {callee:ID.gc, any:0, all:0});
+
+    // Compute functionAttrs: it should contain the set of functions that
+    // are *always* called within some sort of limited context (eg GC
+    // suppression).
+
+    // set of mangled names (map from mangled name => [any,all])
+    const functionAttrs = {};
+
+    // Initialize to field calls with attrs set.
+    for (var [name, attrs] of Object.entries(fieldCallAttrs))
+        functionAttrs[name] = [attrs, attrs];
+
+    // map from ID => reason
+    const gcFunctions = { [ID.gc]: 'internal' };
+
+    // Add in any extra functions at the end. (If we did this early, it would
+    // mess up the id <-> name correspondence. Also, we need to know if the
+    // functions even exist in the first place.)
+    for (var func of extraGCFunctions(functions.readableName)) {
+        addGCFunction(functions.mangledToId[func], "annotation", gcFunctions, functionAttrs, functions);
+    }
+
+    for (const func of gcCalls)
+        addToMappedList(rawCallees, func, {callee:ID.gc, any:0, all:0});
+
+    for (const [caller, indirect, attrs] of indirectCalls) {
+        const id = functions.name.length;
+        functions.name.push(indirect);
+        functions.mangledToId[indirect] = id;
+        addToMappedList(rawCallees, caller, {callee:id, any:attrs, all:attrs});
+        addToMappedList(rawCallees, id, {callee:ID.anyfunc, any:0, all:0});
+    }
+
+    // Callers have a list of callees, with duplicates (if the same function is
+    // called more than once.) Merge the repeated calls, only keeping attrs
+    // that are in force for *every* callsite of that callee. Also, generate
+    // the callersOf table at the same time.
+    //
+    // calleesOf : map from mangled => {mangled callee => {'any':intset, 'all':intset}}
+    // callersOf : map from mangled => {mangled caller => {'any':intset, 'all':intset}}
+    const {callersOf, calleesOf} = generate_callgraph(rawCallees);
+
+    // Compute functionAttrs: it should contain the set of functions that
+    // are *always* called within some sort of limited context (eg GC
+    // suppression).
+
+    // Initialize to field calls with attrs set.
+    for (var [name, attrs] of Object.entries(fieldCallAttrs))
+        functionAttrs[name] = [attrs, attrs];
+
+    // Initialize functionAttrs to the set of all functions, where each one is
+    // maximally attributed, and return a worklist containing all simple roots
+    // (nodes with no callers).
+    const simple_roots = gather_simple_roots(functionAttrs, calleesOf, callersOf);
+
+    // Traverse the graph, spreading the attrs down from the roots.
+    propagate_attrs(simple_roots, functionAttrs, calleesOf);
+
+    // There are a surprising number of "recursive roots", where there is a
+    // cycle of functions calling each other but not called by anything else,
+    // and these roots may also have descendants. Now that the above traversal
+    // has eliminated everything reachable from simple roots, traverse the
+    // remaining graph to gather up a representative function from each root
+    // cycle.
+    //
+    // Simple example: in the JS shell build, moz_xstrdup calls itself, but
+    // there are no calls to it from within js/src.
+    const recursive_roots = gather_recursive_roots(functionAttrs, calleesOf, callersOf, functions);
+
+    // And do a final traversal starting with the recursive roots.
+    propagate_attrs(recursive_roots, functionAttrs, calleesOf);
+
+    for (const [f, [any, all]] of Object.entries(functionAttrs)) {
+        // Throw out all functions with no attrs set, to reduce the size of the
+        // output. From now on, "not in functionAttrs" means [any=0, all=0].
+        if (any == 0 && all == 0)
+            delete functionAttrs[f];
+
+        // Remove GC-suppressed functions from the set of functions known to GC.
+        if (all & ATTR_GC_SUPPRESSED)
+            delete gcFunctions[name];
+    }
+
+    // functionAttrs now contains all functions that are ever called in an
+    // attributed context, based on the known callgraph (i.e., calls through
+    // function pointers are not taken into consideration.)
+
+    // Sanity check to make sure the callgraph has some functions annotated as
+    // GC Calls. This is mostly a check to be sure the earlier processing
+    // succeeded (as opposed to, say, running on empty xdb files because you
+    // didn't actually compile anything interesting.)
+    assert(gcCalls.length > 0, "No GC functions found!");
+
+    // Initialize the worklist to all known gcFunctions.
+    const worklist = [ID.gc];
+
+    // Include all field calls (but not virtual method calls).
+    for (const [name, csuName] of fieldCallCSU) {
+        const fullFieldName = functions.name[name];
+        if (!fieldCallCannotGC(csuName, fullFieldName)) {
+            gcFunctions[name] = 'arbitrary function pointer ' + fullFieldName;
+            worklist.push(name);
+        }
+    }
+
+    // Recursively find all callers not always called in a GC suppression
+    // context, and add them to the set of gcFunctions.
+    while (worklist.length) {
+        name = worklist.shift();
+        assert(name in gcFunctions, "gcFunctions does not contain " + name);
+        if (!callersOf.has(name))
+            continue;
+        for (const [caller, {any, all}] of callersOf.get(name)) {
+            if (!(all & ATTR_GC_SUPPRESSED)) {
+                if (addGCFunction(caller, name, gcFunctions, functionAttrs, functions))
+                    worklist.push(caller);
+            }
+        }
+    }
+
+    // Convert functionAttrs to limitedFunctions (using mangled names instead
+    // of ids.)
+
+    // set of mangled names (map from mangled name => {any,all,recursive_root:bool}
+    var limitedFunctions = {};
+
+    for (const [id, [any, all]] of Object.entries(functionAttrs)) {
+        if (all) {
+            limitedFunctions[functions.name[id]] = { attributes: all };
+        }
+    }
+
+    for (const [id, limits, label] of recursive_roots) {
+        const name = functions.name[id];
+        const s = limitedFunctions[name] || (limitedFunctions[name] = {});
+        s.recursive_root = true;
+    }
+
+    // Remap ids to mangled names.
+    const namedGCFunctions = {};
+    for (const [caller, reason] of Object.entries(gcFunctions)) {
+        namedGCFunctions[functions.name[caller]] = functions.name[reason] || reason;
+    }
+
+    return {
+        gcFunctions: namedGCFunctions,
+        functions,
+        calleesOf,
+        callersOf,
+        limitedFunctions
+    };
+}
+
+function saveCallgraph(functions, calleesOf) {
+    // Write out all the ids and their readable names.
+    let id = -1;
+    for (const name of functions.name) {
+        id += 1;
+        if (id == 0) continue;
+        print(`#${id} ${name}`);
+        for (const readable of (functions.readableName[name] || [])) {
+            if (readable != name)
+                print(`= ${id} ${readable}`);
+        }
+    }
+
+    // Omit field calls for now; let them appear as if they were functions.
+
+    const attrstring = range => range.any || range.all ? `${range.all}:${range.any} ` : '';
+    for (const [caller, callees] of calleesOf) {
+        for (const [callee, attrs] of callees) {
+            print(`D ${attrstring(attrs)}${caller} ${callee}`);
+        }
+    }
+
+    // Omit tags for now. This really should preserve all tags. The "GC Call"
+    // tag will already be represented in the graph by having an edge to the
+    // "(GC)" node.
+}
+
+// Return a worklist of functions with no callers, and also initialize
+// functionAttrs to the set of all functions, each mapped to
+// [ATTRS_NONE, ATTRS_UNVISITED].
+function gather_simple_roots(functionAttrs, calleesOf, callersOf) {
+    const roots = [];
+    for (const callee of callersOf.keys())
+        functionAttrs[callee] = [ATTRS_NONE, ATTRS_UNVISITED];
+    for (const caller of calleesOf.keys()) {
+        functionAttrs[caller] = [ATTRS_NONE, ATTRS_UNVISITED];
+        if (!callersOf.has(caller))
+            roots.push([caller, ATTRS_NONE, 'root']);
+    }
+
+    return roots;
+}
+
+// Recursively traverse the callgraph from the roots. Recurse through every
+// edge that weakens the attrs. (Attrs that entirely disappear, ie go to a zero
+// intset, will be removed from functionAttrs.)
+function propagate_attrs(roots, functionAttrs, calleesOf) {
+    const worklist = Array.from(roots);
+    let top = worklist.length;
+    while (top > 0) {
+        // Consider caller where (graph) -> caller -> (0 or more callees)
+        // 'callercaller' is for debugging.
+        const [caller, edge_attrs, callercaller] = worklist[--top];
+        assert(caller in functionAttrs);
+        const [prev_any, prev_all] = functionAttrs[caller];
+        assert(prev_any !== undefined);
+        assert(prev_all !== undefined);
+        const [new_any, new_all] = [prev_any | edge_attrs, prev_all & edge_attrs];
+        if (prev_any != new_any || prev_all != new_all) {
+            // Update function attrs, then recurse to the children if anything
+            // was updated.
+            functionAttrs[caller] = [new_any, new_all];
+            for (const [callee, {any, all}] of (calleesOf.get(caller) || new Map))
+                worklist[top++] = [callee, all | edge_attrs, caller];
+        }
+    }
+}
+
+// Mutually-recursive roots and their descendants will not have been visited,
+// and will still be set to [0, ATTRS_UNVISITED]. Scan through and gather them.
+function gather_recursive_roots(functionAttrs, calleesOf, callersOf, functions) {
+    const roots = [];
+
+    // Pick any node. Mark everything reachable by adding to a 'seen' set. At
+    // the end, if there are any incoming edges to that node from an unmarked
+    // node, then it is not a root. Otherwise, mark the node as a root. (There
+    // will be at least one back edge coming into the node from a marked node
+    // in this case, since otherwise it would have already been considered to
+    // be a root.)
+    //
+    // Repeat with remaining unmarked nodes until all nodes are marked.
+    const seen = new Set();
+    for (let [func, [any, all]] of Object.entries(functionAttrs)) {
+        func = func|0;
+        if (all != ATTRS_UNVISITED)
+            continue;
+
+        // We should only be looking at nodes with callers, since otherwise
+        // they would have been handled in the previous pass!
+        assert(callersOf.has(func));
+        assert(callersOf.get(func).size > 0);
+
+        if (seen.has(func))
+            continue;
+
+        const work = [func];
+        while (work.length > 0) {
+            const f = work.pop();
+            if (!calleesOf.has(f)) continue;
+            for (const callee of calleesOf.get(f).keys()) {
+                if (!seen.has(callee) &&
+                    callee != func &&
+                    functionAttrs[callee][1] == ATTRS_UNVISITED)
+                {
+                    work.push(callee);
+                    seen.add(callee);
+                }
+            }
+        }
+
+        assert(!seen.has(func));
+        seen.add(func);
+        if ([...callersOf.get(func).keys()].findIndex(f => !seen.has(f)) == -1) {
+            // No unmarked incoming edges, including self-edges, so this is a
+            // (recursive) root.
+            roots.push([func, ATTRS_NONE, 'recursive-root']);
+        }
+    }
+
+    return roots;
+
+    tmp = calleesOf;
+    calleesOf = {};
+    for (const [callerId, callees] of Object.entries(calleesOf)) {
+        const caller = functionNames[callerId];
+        for (const {calleeId, limits} of callees)
+            calleesOf[caller][functionNames[calleeId]] = limits;
+    }
+
+    tmp = callersOf;
+    callersOf = {};
+    for (const [calleeId, callers] of Object.entries(callersOf)) {
+        const callee = functionNames[calleeId];
+        callersOf[callee] = {};
+        for (const {callerId, limits} of callers)
+            callersOf[callee][functionNames[caller]] = limits;
+    }
+}
diff --git a/js/src/devtools/rootAnalysis/mach_commands.py b/js/src/devtools/rootAnalysis/mach_commands.py
new file mode 100644
index 0000000000..9404614807
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mach_commands.py
@@ -0,0 +1,453 @@
+# -*- coding: utf-8 -*-
+
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+
+import argparse
+import json
+import os
+import textwrap
+
+# Command files like this are listed in build/mach_initialize.py in alphabetical
+# order, but we need to access commands earlier in the sorted order to grab
+# their arguments. Force them to load now.
+import mozbuild.artifact_commands  # NOQA: F401
+import mozbuild.build_commands  # NOQA: F401
+from mach.base import FailedCommandError, MachError
+from mach.decorators import Command, CommandArgument, SubCommand
+from mach.registrar import Registrar
+from mozbuild.mozconfig import MozconfigLoader
+
+
+# Use a decorator to copy command arguments off of the named command. Instead
+# of a decorator, this could be straight code that edits eg
+# MachCommands.build_shell._mach_command.arguments, but that looked uglier.
+def inherit_command_args(command, subcommand=None):
+    """Decorator for inheriting all command-line arguments from `mach build`.
+
+    This should come earlier in the source file than @Command or @SubCommand,
+    because it relies on that decorator having run first."""
+
+    def inherited(func):
+        handler = Registrar.command_handlers.get(command)
+        if handler is not None and subcommand is not None:
+            handler = handler.subcommand_handlers.get(subcommand)
+        if handler is None:
+            raise MachError(
+                "{} command unknown or not yet loaded".format(
+                    command if subcommand is None else command + " " + subcommand
+                )
+            )
+        func._mach_command.arguments.extend(handler.arguments)
+        return func
+
+    return inherited
+
+
+def state_dir():
+    return os.environ.get("MOZBUILD_STATE_PATH", os.path.expanduser("~/.mozbuild"))
+
+
+def tools_dir():
+    if os.environ.get("MOZ_FETCHES_DIR"):
+        # In automation, tools are provided by toolchain dependencies.
+        return os.path.join(os.environ["HOME"], os.environ["MOZ_FETCHES_DIR"])
+
+    # In development, `mach hazard bootstrap` installs the tools separately
+    # to avoid colliding with the "main" compiler versions, which can
+    # change separately (and the precompiled sixgill and compiler version
+    # must match exactly).
+    return os.path.join(state_dir(), "hazard-tools")
+
+
+def sixgill_dir():
+    return os.path.join(tools_dir(), "sixgill")
+
+
+def gcc_dir():
+    return os.path.join(tools_dir(), "gcc")
+
+
+def script_dir(command_context):
+    return os.path.join(command_context.topsrcdir, "js/src/devtools/rootAnalysis")
+
+
+def get_work_dir(command_context, application, given):
+    if given is not None:
+        return given
+    return os.path.join(command_context.topsrcdir, "haz-" + application)
+
+
+def ensure_dir_exists(dir):
+    os.makedirs(dir, exist_ok=True)
+    return dir
+
+
+# Force the use of hazard-compatible installs of tools.
+def setup_env_for_tools(env):
+    gccbin = os.path.join(gcc_dir(), "bin")
+    env["CC"] = os.path.join(gccbin, "gcc")
+    env["CXX"] = os.path.join(gccbin, "g++")
+    env["PATH"] = "{sixgill_dir}/usr/bin:{gccbin}:{PATH}".format(
+        sixgill_dir=sixgill_dir(), gccbin=gccbin, PATH=env["PATH"]
+    )
+
+
+def setup_env_for_shell(env, shell):
+    """Add JS shell directory to dynamic lib search path"""
+    for var in ("LD_LIBRARY_PATH", "DYLD_LIBRARY_PATH"):
+        env[var] = ":".join(p for p in (env.get(var), os.path.dirname(shell)) if p)
+
+
+@Command(
+    "hazards",
+    category="build",
+    order="declaration",
+    description="Commands for running the static analysis for GC rooting hazards",
+)
+def hazards(command_context):
+    """Commands related to performing the GC rooting hazard analysis"""
+    print("See `mach hazards --help` for a list of subcommands")
+
+
+@inherit_command_args("artifact", "toolchain")
+@SubCommand(
+    "hazards",
+    "bootstrap",
+    description="Install prerequisites for the hazard analysis",
+)
+def bootstrap(command_context, **kwargs):
+    orig_dir = os.getcwd()
+    os.chdir(ensure_dir_exists(tools_dir()))
+    try:
+        kwargs["from_build"] = ("linux64-gcc-sixgill", "linux64-gcc-9")
+        command_context._mach_context.commands.dispatch(
+            "artifact", command_context._mach_context, subcommand="toolchain", **kwargs
+        )
+    finally:
+        os.chdir(orig_dir)
+
+
+@inherit_command_args("build")
+@SubCommand(
+    "hazards", "build-shell", description="Build a shell for the hazard analysis"
+)
+@CommandArgument(
+    "--mozconfig",
+    default=None,
+    metavar="FILENAME",
+    help="Build with the given mozconfig.",
+)
+def build_shell(command_context, **kwargs):
+    """Build a JS shell to use to run the rooting hazard analysis."""
+    # The JS shell requires some specific configuration settings to execute
+    # the hazard analysis code, and configuration is done via mozconfig.
+    # Subprocesses find MOZCONFIG in the environment, so we can't just
+    # modify the settings in this process's loaded version. Pass it through
+    # the environment.
+
+    default_mozconfig = "js/src/devtools/rootAnalysis/mozconfig.haz_shell"
+    mozconfig_path = (
+        kwargs.pop("mozconfig", None)
+        or os.environ.get("MOZCONFIG")
+        or default_mozconfig
+    )
+    mozconfig_path = os.path.join(command_context.topsrcdir, mozconfig_path)
+    loader = MozconfigLoader(command_context.topsrcdir)
+    mozconfig = loader.read_mozconfig(mozconfig_path)
+
+    # Validate the mozconfig settings in case the user overrode the default.
+    configure_args = mozconfig["configure_args"]
+    if "--enable-ctypes" not in configure_args:
+        raise FailedCommandError(
+            "ctypes required in hazard JS shell, mozconfig=" + mozconfig_path
+        )
+
+    # Transmit the mozconfig location to build subprocesses.
+    os.environ["MOZCONFIG"] = mozconfig_path
+
+    setup_env_for_tools(os.environ)
+
+    # Set a default objdir for the shell, for developer builds.
+    os.environ.setdefault(
+        "MOZ_OBJDIR", os.path.join(command_context.topsrcdir, "obj-haz-shell")
+    )
+
+    return command_context._mach_context.commands.dispatch(
+        "build", command_context._mach_context, **kwargs
+    )
+
+
+def read_json_file(filename):
+    with open(filename) as fh:
+        return json.load(fh)
+
+
+def ensure_shell(command_context, objdir):
+    if objdir is None:
+        objdir = os.path.join(command_context.topsrcdir, "obj-haz-shell")
+
+    try:
+        binaries = read_json_file(os.path.join(objdir, "binaries.json"))
+        info = [b for b in binaries["programs"] if b["program"] == "js"][0]
+        return os.path.join(objdir, info["install_target"], "js")
+    except (OSError, KeyError):
+        raise FailedCommandError(
+            """\
+no shell found in %s -- must build the JS shell with `mach hazards build-shell` first"""
+            % objdir
+        )
+
+
+@inherit_command_args("build")
+@SubCommand(
+    "hazards",
+    "gather",
+    description="Gather analysis data by compiling the given application",
+)
+@CommandArgument(
+    "--application", default="browser", help="Build the given application."
+)
+@CommandArgument(
+    "--haz-objdir", default=None, help="Write object files to this directory."
+)
+@CommandArgument(
+    "--work-dir", default=None, help="Directory for output and working files."
+)
+def gather_hazard_data(command_context, **kwargs):
+    """Gather analysis information by compiling the tree"""
+    application = kwargs["application"]
+    objdir = kwargs["haz_objdir"]
+    if objdir is None:
+        objdir = os.environ.get("HAZ_OBJDIR")
+    if objdir is None:
+        objdir = os.path.join(command_context.topsrcdir, "obj-analyzed-" + application)
+
+    work_dir = get_work_dir(command_context, application, kwargs["work_dir"])
+    ensure_dir_exists(work_dir)
+    with open(os.path.join(work_dir, "defaults.py"), "wt") as fh:
+        data = textwrap.dedent(
+            """\
+            analysis_scriptdir = "{script_dir}"
+            objdir = "{objdir}"
+            source = "{srcdir}"
+            sixgill = "{sixgill_dir}/usr/libexec/sixgill"
+            sixgill_bin = "{sixgill_dir}/usr/bin"
+        """
+        ).format(
+            script_dir=script_dir(command_context),
+            objdir=objdir,
+            srcdir=command_context.topsrcdir,
+            sixgill_dir=sixgill_dir(),
+            gcc_dir=gcc_dir(),
+        )
+        fh.write(data)
+
+    buildscript = " ".join(
+        [
+            command_context.topsrcdir + "/mach hazards compile",
+            "--job-size=3.0",  # Conservatively estimate 3GB/process
+            "--application=" + application,
+            "--haz-objdir=" + objdir,
+        ]
+    )
+    args = [
+        os.path.join(script_dir(command_context), "run_complete"),
+        "--foreground",
+        "--no-logs",
+        "--build-root=" + objdir,
+        "--wrap-dir=" + sixgill_dir() + "/usr/libexec/sixgill/scripts/wrap_gcc",
+        "--work-dir=work",
+        "-b",
+        sixgill_dir() + "/usr/bin",
+        "--buildcommand=" + buildscript,
+        ".",
+    ]
+
+    return command_context.run_process(args=args, cwd=work_dir, pass_thru=True)
+
+
+@inherit_command_args("build")
+@SubCommand("hazards", "compile", description=argparse.SUPPRESS)
+@CommandArgument(
+    "--mozconfig",
+    default=None,
+    metavar="FILENAME",
+    help="Build with the given mozconfig.",
+)
+@CommandArgument(
+    "--application", default="browser", help="Build the given application."
+)
+@CommandArgument(
+    "--haz-objdir",
+    default=os.environ.get("HAZ_OBJDIR"),
+    help="Write object files to this directory.",
+)
+def inner_compile(command_context, **kwargs):
+    """Build a source tree and gather analysis information while running
+    under the influence of the analysis collection server."""
+
+    env = os.environ
+
+    # Check whether we are running underneath the manager (and therefore
+    # have a server to talk to).
+    if "XGILL_CONFIG" not in env:
+        raise Exception(
+            "no sixgill manager detected. `mach hazards compile` "
+            + "should only be run from `mach hazards gather`"
+        )
+
+    app = kwargs.pop("application")
+    default_mozconfig = "js/src/devtools/rootAnalysis/mozconfig.%s" % app
+    mozconfig_path = (
+        kwargs.pop("mozconfig", None) or env.get("MOZCONFIG") or default_mozconfig
+    )
+    mozconfig_path = os.path.join(command_context.topsrcdir, mozconfig_path)
+
+    # Validate the mozconfig.
+
+    # Require an explicit --enable-project/application=APP (even if you just
+    # want to build the default browser application.)
+    loader = MozconfigLoader(command_context.topsrcdir)
+    mozconfig = loader.read_mozconfig(mozconfig_path)
+    configure_args = mozconfig["configure_args"]
+    if (
+        "--enable-project=%s" % app not in configure_args
+        and "--enable-application=%s" % app not in configure_args
+    ):
+        raise Exception("mozconfig %s builds wrong project" % mozconfig_path)
+    if not any("--with-compiler-wrapper" in a for a in configure_args):
+        raise Exception("mozconfig must wrap compiles")
+
+    # Communicate mozconfig to build subprocesses.
+    env["MOZCONFIG"] = os.path.join(command_context.topsrcdir, mozconfig_path)
+
+    # hazard mozconfigs need to find binaries in .mozbuild
+    env["MOZBUILD_STATE_PATH"] = state_dir()
+
+    # Suppress the gathering of sources, to save disk space and memory.
+    env["XGILL_NO_SOURCE"] = "1"
+
+    setup_env_for_tools(env)
+
+    if "haz_objdir" in kwargs:
+        env["MOZ_OBJDIR"] = kwargs.pop("haz_objdir")
+
+    return command_context._mach_context.commands.dispatch(
+        "build", command_context._mach_context, **kwargs
+    )
+
+
+@SubCommand(
+    "hazards", "analyze", description="Analyzed gathered data for rooting hazards"
+)
+@CommandArgument(
+    "--application",
+    default="browser",
+    help="Analyze the output for the given application.",
+)
+@CommandArgument(
+    "--shell-objdir",
+    default=None,
+    help="objdir containing the optimized JS shell for running the analysis.",
+)
+@CommandArgument(
+    "--work-dir", default=None, help="Directory for output and working files."
+)
+@CommandArgument(
+    "--jobs", "-j", default=None, type=int, help="Number of parallel analyzers."
+)
+@CommandArgument(
+    "--verbose",
+    "-v",
+    default=False,
+    action="store_true",
+    help="Display executed commands.",
+)
+@CommandArgument(
+    "--from-stage",
+    default=None,
+    help="Stage to begin running at ('list' to see all).",
+)
+@CommandArgument(
+    "extra",
+    nargs=argparse.REMAINDER,
+    default=(),
+    help="Remaining non-optional arguments to analyze.py script",
+)
+def analyze(
+    command_context,
+    application,
+    shell_objdir,
+    work_dir,
+    jobs,
+    verbose,
+    from_stage,
+    extra,
+):
+    """Analyzed gathered data for rooting hazards"""
+
+    shell = ensure_shell(command_context, shell_objdir)
+    args = [
+        os.path.join(script_dir(command_context), "analyze.py"),
+        "--js",
+        shell,
+        *extra,
+    ]
+
+    if from_stage is None:
+        pass
+    elif from_stage == "list":
+        args.append("--list")
+    else:
+        args.extend(["--first", from_stage])
+
+    if jobs is not None:
+        args.extend(["-j", jobs])
+
+    if verbose:
+        args.append("-v")
+
+    setup_env_for_tools(os.environ)
+    setup_env_for_shell(os.environ, shell)
+
+    work_dir = get_work_dir(command_context, application, work_dir)
+    return command_context.run_process(args=args, cwd=work_dir, pass_thru=True)
+
+
+@SubCommand(
+    "hazards",
+    "self-test",
+    description="Run a self-test to verify hazards are detected",
+)
+@CommandArgument(
+    "--shell-objdir",
+    default=None,
+    help="objdir containing the optimized JS shell for running the analysis.",
+)
+@CommandArgument(
+    "extra",
+    nargs=argparse.REMAINDER,
+    help="Remaining non-optional arguments to pass to run-test.py",
+)
+def self_test(command_context, shell_objdir, extra):
+    """Analyzed gathered data for rooting hazards"""
+    shell = ensure_shell(command_context, shell_objdir)
+    args = [
+        os.path.join(script_dir(command_context), "run-test.py"),
+        "-v",
+        "--js",
+        shell,
+        "--sixgill",
+        os.path.join(tools_dir(), "sixgill"),
+        "--gccdir",
+        gcc_dir(),
+    ]
+    args.extend(extra)
+
+    setup_env_for_tools(os.environ)
+    setup_env_for_shell(os.environ, shell)
+
+    return command_context.run_process(args=args, pass_thru=True)
diff --git a/js/src/devtools/rootAnalysis/mergeJSON.js b/js/src/devtools/rootAnalysis/mergeJSON.js
new file mode 100644
index 0000000000..56fb3a2ab1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mergeJSON.js
@@ -0,0 +1,18 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+var infiles = [...scriptArgs];
+var outfile = infiles.pop();
+
+const output = {};
+for (const filename of infiles) {
+    const data = JSON.parse(os.file.readFile(filename));
+    Object.assign(output, data);
+}
+
+var origOut = os.file.redirect(outfile);
+print(JSON.stringify(output, null, 4));
+os.file.close(os.file.redirect(origOut));
diff --git a/js/src/devtools/rootAnalysis/mozconfig.browser b/js/src/devtools/rootAnalysis/mozconfig.browser
new file mode 100644
index 0000000000..3dd50bae8e
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.browser
@@ -0,0 +1,15 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This mozconfig is used when analyzing the source code of the Firefox browser
+# for GC rooting hazards. See
+# <https://wiki.mozilla.org/Javascript:SpiderMonkey:ExactStackRooting>.
+
+ac_add_options --enable-project=browser
+ac_add_options --enable-js-shell
+
+# the sixgill wrapper is not compatible with building wasm objects with clang.
+export WASM_SANDBOXED_LIBRARIES=
+
+. $topsrcdir/js/src/devtools/rootAnalysis/mozconfig.common
diff --git a/js/src/devtools/rootAnalysis/mozconfig.common b/js/src/devtools/rootAnalysis/mozconfig.common
new file mode 100644
index 0000000000..c68fb6a26c
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.common
@@ -0,0 +1,37 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Configuration shared between browser and shell builds.
+
+# The configuration options are chosen to compile the most code
+# (--enable-debug, --enable-tests) in the trickiest way possible
+# (--enable-optimize) to maximize the chance of seeing tricky static orderings.
+ac_add_options --enable-debug
+ac_add_options --enable-tests
+ac_add_options --enable-optimize
+
+# Wrap all compiler invocations in order to enable the plugin and send
+# information to a common database.
+if [ -z "$AUTOMATION" ]; then
+    # Developer build: `mach hazards bootstrap` puts tools here:
+    TOOLS_DIR="$MOZBUILD_STATE_PATH/hazard-tools"
+else
+    # Automation build: tools are downloaded from upstream tasks.
+    TOOLS_DIR="$MOZ_FETCHES_DIR"
+fi
+ac_add_options --with-compiler-wrapper="${TOOLS_DIR}"/sixgill/usr/libexec/sixgill/scripts/wrap_gcc/basecc
+
+# Stuff that gets in the way.
+ac_add_options --without-ccache
+ac_add_options --disable-replace-malloc
+
+# -Wattributes is very verbose due to attributes being ignored on template
+# instantiations.
+#
+# -Wignored-attributes is very verbose due to attributes being
+# ignored on template parameters.
+ANALYSIS_EXTRA_CFLAGS="-Wno-attributes -Wno-ignored-attributes"
+CFLAGS="$CFLAGS $ANALYSIS_EXTRA_CFLAGS"
+CPPFLAGS="$CPPFLAGS $ANALYSIS_EXTRA_CFLAGS"
+CXXFLAGS="$CXXFLAGS $ANALYSIS_EXTRA_CFLAGS"
diff --git a/js/src/devtools/rootAnalysis/mozconfig.haz_shell b/js/src/devtools/rootAnalysis/mozconfig.haz_shell
new file mode 100644
index 0000000000..68741f0454
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.haz_shell
@@ -0,0 +1,18 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This mozconfig is for compiling the JS shell that runs the static rooting
+# hazard analysis. See
+# <https://wiki.mozilla.org/Javascript:SpiderMonkey:ExactStackRooting>.
+
+ac_add_options --enable-ctypes
+ac_add_options --enable-optimize
+ac_add_options --disable-debug
+ac_add_options --enable-project=js
+ac_add_options --enable-nspr-build
+ac_add_options --disable-jemalloc
+
+if [ -n "$AUTOMATION" ]; then
+  mk_add_options MOZ_OBJDIR="${HAZARD_SHELL_OBJDIR}"
+fi
diff --git a/js/src/devtools/rootAnalysis/mozconfig.js b/js/src/devtools/rootAnalysis/mozconfig.js
new file mode 100644
index 0000000000..07e584c210
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/mozconfig.js
@@ -0,0 +1,16 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This mozconfig is used when analyzing the source code of the js/src tree for
+# GC rooting hazards. See
+# <https://wiki.mozilla.org/Javascript:SpiderMonkey:ExactStackRooting>.
+
+ac_add_options --enable-project=js
+
+# Also compile NSPR to see through its part of the control flow graph (not
+# currently needed, but also helps with weird problems finding the right
+# headers.)
+ac_add_options --enable-nspr-build
+
+. $topsrcdir/js/src/devtools/rootAnalysis/mozconfig.common
diff --git a/js/src/devtools/rootAnalysis/run-analysis.sh b/js/src/devtools/rootAnalysis/run-analysis.sh
new file mode 100755
index 0000000000..157821cc92
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/run-analysis.sh
@@ -0,0 +1,4 @@
+#!/bin/sh
+
+SRCDIR=$(cd $(dirname $0)/../../../..; pwd)
+GECKO_PATH=$SRCDIR $SRCDIR/taskcluster/scripts/builder/build-haz-linux.sh $(pwd) "$@"
diff --git a/js/src/devtools/rootAnalysis/run-test.py b/js/src/devtools/rootAnalysis/run-test.py
new file mode 100755
index 0000000000..2768f3be1b
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/run-test.py
@@ -0,0 +1,140 @@
+#!/usr/bin/env python3
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import argparse
+import os
+import site
+import subprocess
+from glob import glob
+
+scriptdir = os.path.abspath(os.path.dirname(__file__))
+testdir = os.path.join(scriptdir, "t")
+
+site.addsitedir(testdir)
+from testlib import Test, equal
+
+parser = argparse.ArgumentParser(description="run hazard analysis tests")
+parser.add_argument(
+    "--js", default=os.environ.get("JS"), help="JS binary to run the tests with"
+)
+parser.add_argument(
+    "--sixgill",
+    default=os.environ.get("SIXGILL", os.path.join(testdir, "sixgill")),
+    help="Path to root of sixgill installation",
+)
+parser.add_argument(
+    "--sixgill-bin",
+    default=os.environ.get("SIXGILL_BIN"),
+    help="Path to sixgill binary dir",
+)
+parser.add_argument(
+    "--sixgill-plugin",
+    default=os.environ.get("SIXGILL_PLUGIN"),
+    help="Full path to sixgill gcc plugin",
+)
+parser.add_argument(
+    "--gccdir", default=os.environ.get("GCCDIR"), help="Path to GCC installation dir"
+)
+parser.add_argument("--cc", default=os.environ.get("CC"), help="Path to gcc")
+parser.add_argument("--cxx", default=os.environ.get("CXX"), help="Path to g++")
+parser.add_argument(
+    "--verbose",
+    "-v",
+    action="store_true",
+    help="Display verbose output, including commands executed",
+)
+parser.add_argument(
+    "tests",
+    nargs="*",
+    default=[
+        "sixgill-tree",
+        "suppression",
+        "hazards",
+        "exceptions",
+        "virtual",
+        "graph",
+    ],
+    help="tests to run",
+)
+
+cfg = parser.parse_args()
+
+if not cfg.js:
+    exit("Must specify JS binary through environment variable or --js option")
+if not cfg.cc:
+    if cfg.gccdir:
+        cfg.cc = os.path.join(cfg.gccdir, "bin", "gcc")
+    else:
+        cfg.cc = "gcc"
+if not cfg.cxx:
+    if cfg.gccdir:
+        cfg.cxx = os.path.join(cfg.gccdir, "bin", "g++")
+    else:
+        cfg.cxx = "g++"
+if not cfg.sixgill_bin:
+    cfg.sixgill_bin = os.path.join(cfg.sixgill, "usr", "bin")
+if not cfg.sixgill_plugin:
+    cfg.sixgill_plugin = os.path.join(
+        cfg.sixgill, "usr", "libexec", "sixgill", "gcc", "xgill.so"
+    )
+
+subprocess.check_call(
+    [cfg.js, "-e", 'if (!getBuildConfiguration()["has-ctypes"]) quit(1)']
+)
+
+
+def binpath(prog):
+    return os.path.join(cfg.sixgill_bin, prog)
+
+
+def make_dir(dirname, exist_ok=True):
+    try:
+        os.mkdir(dirname)
+    except OSError as e:
+        if exist_ok and e.strerror == "File exists":
+            pass
+        else:
+            raise
+
+
+outroot = os.path.join(testdir, "out")
+make_dir(outroot)
+
+os.environ["HAZARD_RUN_INTERNAL_TESTS"] = "1"
+
+failed = set()
+passed = set()
+for name in cfg.tests:
+    name = os.path.basename(name)
+    indir = os.path.join(testdir, name)
+    outdir = os.path.join(outroot, name)
+    make_dir(outdir)
+
+    test = Test(indir, outdir, cfg, verbose=cfg.verbose)
+
+    os.chdir(outdir)
+    for xdb in glob("*.xdb"):
+        os.unlink(xdb)
+    print("START TEST {}".format(name), flush=True)
+    testpath = os.path.join(indir, "test.py")
+    testscript = open(testpath).read()
+    testcode = compile(testscript, testpath, "exec")
+    try:
+        exec(testcode, {"test": test, "equal": equal})
+    except subprocess.CalledProcessError:
+        print("TEST-FAILED: %s" % name)
+        failed.add(name)
+    except AssertionError:
+        print("TEST-FAILED: %s" % name)
+        failed.add(name)
+        raise
+    else:
+        print("TEST-PASSED: %s" % name)
+        passed.add(name)
+
+if failed:
+    raise Exception("Failed tests: " + " ".join(failed))
+
+print(f"All {len(passed)} tests passed.")
diff --git a/js/src/devtools/rootAnalysis/run_complete b/js/src/devtools/rootAnalysis/run_complete
new file mode 100755
index 0000000000..c9355267db
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/run_complete
@@ -0,0 +1,384 @@
+#!/usr/bin/perl
+
+# Sixgill: Static assertion checker for C/C++ programs.
+# Copyright (C) 2009-2010  Stanford University
+# Author: Brian Hackett
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# do a complete run of the system from raw source to reports. this requires
+# various run_monitor processes to be running in the background (maybe on other
+# machines) and watching a shared poll_file for jobs. if the output directory
+# for this script already exists then an incremental analysis will be performed
+# and the reports will only reflect the changes since the earlier run.
+
+use strict;
+use warnings;
+use IO::Handle;
+use File::Basename qw(basename dirname);
+use Getopt::Long;
+use Cwd;
+
+#################################
+# environment specific settings #
+#################################
+
+my $WORKDIR;
+my $SIXGILL_BIN;
+
+# poll file shared with the run_monitor script.
+my $poll_file;
+
+# root directory of the project.
+my $build_dir;
+
+# directory containing gcc wrapper scripts.
+my $wrap_dir;
+
+# optional file with annotations from the web interface.
+my $ann_file = "";
+
+# optional output directory to do a diff against.
+my $old_dir = "";
+
+# run in the foreground
+my $foreground;
+
+my $builder = "make -j4";
+
+my $suppress_logs;
+GetOptions("build-root|b=s" => \$build_dir,
+           "poll-file=s" => \$poll_file,
+           "no-logs!" => \$suppress_logs,
+           "work-dir=s" => \$WORKDIR,
+           "sixgill-binaries|binaries|b=s" => \$SIXGILL_BIN,
+           "wrap-dir=s" => \$wrap_dir,
+           "annotations-file|annotations|a=s" => \$ann_file,
+           "old-dir|old=s" => \$old_dir,
+           "foreground!" => \$foreground,
+           "buildcommand=s" => \$builder,
+           )
+    or die;
+
+if (not -d $build_dir) {
+    mkdir($build_dir);
+}
+if ($old_dir ne "" && not -d $old_dir) {
+    die "Old directory '$old_dir' does not exist\n";
+}
+
+$WORKDIR ||= "sixgill-work";
+mkdir($WORKDIR, 0755) if ! -d $WORKDIR;
+$poll_file ||= "$WORKDIR/poll.file";
+$build_dir ||= "$WORKDIR/js-inbound-xgill";
+
+if (!defined $SIXGILL_BIN) {
+    chomp(my $path = `which xmanager`);
+    if ($path) {
+        use File::Basename qw(dirname);
+        $SIXGILL_BIN = dirname($path);
+    } else {
+        die "Cannot find sixgill binaries. Use the -b option.";
+    }
+}
+
+$wrap_dir ||= "$WORKDIR/xgill-inbound/wrap_gcc";
+$wrap_dir = "$SIXGILL_BIN/../scripts/wrap_gcc" if not (-e "$wrap_dir/basecc");
+die "Bad wrapper directory: $wrap_dir" if not (-e "$wrap_dir/basecc");
+
+# code to clean the project from $build_dir.
+sub clean_project {
+    system("make clean");
+}
+
+# code to build the project from $build_dir.
+sub build_project {
+    return system($builder) >> 8;
+}
+
+our %kill_on_exit;
+END {
+    for my $pid (keys %kill_on_exit) {
+        kill($pid);
+    }
+}
+
+# commands to start the various xgill binaries. timeouts can be specified
+# for the backend analyses here, and a memory limit can be specified for
+# xmanager if desired (and USE_COUNT_ALLOCATOR is defined in util/alloc.h).
+my $xmanager = "$SIXGILL_BIN/xmanager";
+my $xsource = "$SIXGILL_BIN/xsource";
+my $xmemlocal = "$SIXGILL_BIN/xmemlocal -timeout=20";
+my $xinfer = "$SIXGILL_BIN/xinfer -timeout=60";
+my $xcheck = "$SIXGILL_BIN/xcheck -timeout=30";
+
+# prefix directory to strip off source files.
+my $prefix_dir = $build_dir;
+
+##########################
+# general purpose script #
+##########################
+
+# Prevent ccache from being used. I don't think this does any good. The problem
+# I'm struggling with is that if autoconf.mk still has 'ccache gcc' in it, the
+# builds fail in a mysterious way.
+$ENV{CCACHE_COMPILERCHECK} = 'date +%s.%N';
+delete $ENV{CCACHE_PREFIX};
+
+my $usage = "USAGE: run_complete result-dir\n";
+my $result_dir = shift or die $usage;
+
+if (not $foreground) {
+    my $pid = fork();
+    if ($pid != 0) {
+        print "Forked, exiting...\n";
+        exit(0);
+    }
+}
+
+# if the result directory does not already exist, mark for a clean build.
+my $do_clean = 0;
+if (not (-d $result_dir)) {
+    $do_clean = 1;
+    mkdir $result_dir;
+}
+
+if (!$suppress_logs) {
+    my $log_file = "$result_dir/complete.log";
+    open(OUT, ">>", $log_file) or die "append to $log_file: $!";
+    OUT->autoflush(1);  # don't buffer writes to the main log.
+
+    # redirect stdout and stderr to the log.
+    STDOUT->fdopen(\*OUT, "w");
+    STDERR->fdopen(\*OUT, "w");
+}
+
+# pids to wait on before exiting. these are collating worker output.
+my @waitpids;
+
+chdir $result_dir;
+
+# to do a partial run, comment out the commands here you don't want to do.
+
+my $status = run_build();
+
+# end of run commands.
+
+for my $pid (@waitpids) {
+    waitpid($pid, 0);
+    $status ||= $? >> 8;
+}
+
+print "Exiting run_complete with status $status\n";
+exit $status;
+
+# get the IP address which a freshly created manager is listening on.
+sub get_manager_address
+{
+    my $log_file = shift or die;
+
+    # give the manager one second to start, any longer and something's broken.
+    sleep(1);
+
+    my $log_data = `cat $log_file`;
+    my ($port) = $log_data =~ /Listening on ([\.\:0-9]*)/
+      or die "no manager found";
+    print OUT "Connecting to manager on port $port\n" unless $suppress_logs;
+    print "Connecting to manager on port $port.\n";
+    return $1;
+}
+
+sub logging_suffix {
+    my ($show_logs, $log_file) = @_;
+    return $show_logs ? "2>&1 | tee $log_file"
+                      : "> $log_file 2>&1";
+}
+
+sub run_build
+{
+    print "build started: ";
+    print scalar(localtime());
+    print "\n";
+
+    # fork off a process to run the build.
+    defined(my $pid = fork) or die;
+
+    # log file for the manager.
+    my $manager_log_file = "$result_dir/build_manager.log";
+
+    if (!$pid) {
+        # this is the child process, fork another process to run a manager.
+        defined(my $pid = fork) or die;
+        my $logging = logging_suffix($suppress_logs, $manager_log_file);
+        exec("$xmanager -terminate-on-assert $logging") if (!$pid);
+        $kill_on_exit{$pid} = 1;
+
+        if (!$suppress_logs) {
+            # open new streams to redirect stdout and stderr.
+            open(LOGOUT, "> $result_dir/build.log");
+            open(LOGERR, "> $result_dir/build_err.log");
+            STDOUT->fdopen(\*LOGOUT, "w");
+            STDERR->fdopen(\*LOGERR, "w");
+        }
+
+        my $address = get_manager_address($manager_log_file);
+
+        # write the configuration file for the wrapper script.
+        my $config_file = "$WORKDIR/xgill.config";
+        open(CONFIG, ">", $config_file) or die "create $config_file: $!";
+        print CONFIG "$prefix_dir\n";
+        print CONFIG Cwd::abs_path("$result_dir/build_xgill.log")."\n";
+        print CONFIG "$address\n";
+        my @extra = ("-fplugin-arg-xgill-mangle=1");
+        push(@extra, "-fplugin-arg-xgill-annfile=$ann_file")
+            if ($ann_file ne "" && -e $ann_file);
+        print CONFIG join(" ", @extra) . "\n";
+        close(CONFIG);
+
+	# Tell the wrapper where to find the config
+	$ENV{"XGILL_CONFIG"} = Cwd::abs_path($config_file);
+
+        # If overriding $CC, use GCCDIR to tell the wrapper scripts where the
+        # real compiler is. If $CC is not set, then the wrapper script will
+        # search $PATH anyway.
+        if (exists $ENV{CC}) {
+            $ENV{GCCDIR} = dirname($ENV{CC});
+        }
+
+        # Force the wrapper scripts to be run in place of the compiler during
+        # whatever build process we use.
+        $ENV{CC} = "$wrap_dir/" . basename($ENV{CC} // "gcc");
+        $ENV{CXX} = "$wrap_dir/" . basename($ENV{CXX} // "g++");
+
+        # do the build, cleaning if necessary.
+        chdir $build_dir;
+        clean_project() if ($do_clean);
+        my $exit_status = build_project();
+
+        # signal the manager that it's over.
+        system("$xsource -remote=$address -end-manager");
+
+        # wait for the manager to clean up and terminate.
+        print "Waiting for manager to finish (build status $exit_status)...\n";
+        waitpid($pid, 0);
+        my $manager_status = $?;
+        delete $kill_on_exit{$pid};
+
+        # build is finished, the complete run can resume.
+        # return value only useful if --foreground
+        print "Exiting with status " . ($manager_status || $exit_status) . "\n";
+        exit($manager_status || $exit_status);
+    }
+
+    # this is the complete process, wait for the build to finish.
+    waitpid($pid, 0);
+    my $status = $? >> 8;
+    print "build finished (status $status): ";
+    print scalar(localtime());
+    print "\n";
+
+    return $status;
+}
+
+sub run_pass
+{
+    my ($name, $command) = @_;
+    my $log_file = "$result_dir/manager.$name.log";
+
+    # extra commands to pass to the manager.
+    my $manager_extra = "";
+    $manager_extra .= "-modset-wait=10" if ($name eq "xmemlocal");
+
+    # fork off a manager process for the analysis.
+    defined(my $pid = fork) or die;
+    my $logging = logging_suffix($suppress_logs, $log_file);
+    exec("$xmanager $manager_extra $logging") if (!$pid);
+
+    my $address = get_manager_address($log_file);
+
+    # write the poll file for this pass.
+    if (! -d dirname($poll_file)) {
+        system("mkdir", "-p", dirname($poll_file));
+    }
+    open(POLL, "> $poll_file");
+    print POLL "$command\n";
+    print POLL "$result_dir/$name\n";
+    print POLL "$address\n";
+    close(POLL);
+
+    print "$name started: ";
+    print scalar(localtime());
+    print "\n";
+
+    waitpid($pid, 0);
+    unlink($poll_file);
+
+    print "$name finished: ";
+    print scalar(localtime());
+    print "\n";
+
+    # collate the worker's output into a single file. make this asynchronous
+    # so we can wait a bit and make sure we get all worker output.
+    defined($pid = fork) or die;
+
+    if (!$pid) {
+        sleep(20);
+        exec("cat $name.*.log > $name.log");
+    }
+
+    push(@waitpids, $pid);
+}
+
+# the names of all directories containing reports to archive.
+my $indexes;
+
+sub run_index
+{
+    my ($name, $kind) = @_;
+
+    return if (not (-e "report_$kind.xdb"));
+
+    print "$name started: ";
+    print scalar(localtime());
+    print "\n";
+
+    # make an index for the report diff if applicable.
+    if ($old_dir ne "") {
+        system("make_index $kind $old_dir > $name.diff.log");
+        system("mv $kind diff_$kind");
+        $indexes .= " diff_$kind";
+    }
+
+    # make an index for the full set of reports.
+    system("make_index $kind > $name.log");
+    $indexes .= " $kind";
+
+    print "$name finished: ";
+    print scalar(localtime());
+    print "\n";
+}
+
+sub archive_indexes
+{
+    print "archive started: ";
+    print scalar(localtime());
+    print "\n";
+
+    system("tar -czf reports.tgz $indexes");
+    system("rm -rf $indexes");
+
+    print "archive finished: ";
+    print scalar(localtime());
+    print "\n";
+}
diff --git a/js/src/devtools/rootAnalysis/t/exceptions/source.cpp b/js/src/devtools/rootAnalysis/t/exceptions/source.cpp
new file mode 100644
index 0000000000..8d38a790a1
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/exceptions/source.cpp
@@ -0,0 +1,57 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+// Simply including <exception> was enough to crash sixgill at one point.
+#include <exception>
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+class RAII_GC {
+ public:
+  RAII_GC() {}
+  ~RAII_GC() { GC(); }
+};
+
+// ~AutoSomething calls GC because of the RAII_GC field. The constructor,
+// though, should *not* GC -- unless it throws an exception. Which is not
+// possible when compiled with -fno-exceptions. This test will try it both
+// ways.
+class AutoSomething {
+  RAII_GC gc;
+
+ public:
+  AutoSomething() : gc() {
+    asm("");  // Ooh, scary, this might throw an exception
+  }
+  ~AutoSomething() { asm(""); }
+};
+
+extern Cell* getcell();
+
+extern void usevar(Cell* cell);
+
+void f() {
+  Cell* thing = getcell();  // Live range starts here
+
+  // When compiling with -fexceptions, there should be a hazard below. With
+  // -fno-exceptions, there should not be one. We will check both.
+  {
+    AutoSomething smth;  // Constructor can GC only if exceptions are enabled
+    usevar(thing);       // Live range ends here
+  }  // In particular, 'thing' is dead at the destructor, so no hazard
+}
diff --git a/js/src/devtools/rootAnalysis/t/exceptions/test.py b/js/src/devtools/rootAnalysis/t/exceptions/test.py
new file mode 100644
index 0000000000..a40753d87a
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/exceptions/test.py
@@ -0,0 +1,21 @@
+# flake8: noqa: F821
+
+test.compile("source.cpp", "-fno-exceptions")
+test.run_analysis_script("gcTypes")
+
+hazards = test.load_hazards()
+assert len(hazards) == 0
+
+# If we compile with exceptions, then there *should* be a hazard because
+# AutoSomething::AutoSomething might throw an exception, which would cause the
+# partially-constructed value to be torn down, which will call ~RAII_GC.
+
+test.compile("source.cpp", "-fexceptions")
+test.run_analysis_script("gcTypes")
+
+hazards = test.load_hazards()
+assert len(hazards) == 1
+hazard = hazards[0]
+assert hazard.function == "void f()"
+assert hazard.variable == "thing"
+assert "AutoSomething::AutoSomething" in hazard.GCFunction
diff --git a/js/src/devtools/rootAnalysis/t/graph/source.cpp b/js/src/devtools/rootAnalysis/t/graph/source.cpp
new file mode 100644
index 0000000000..0adff8d532
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/graph/source.cpp
@@ -0,0 +1,90 @@
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+extern void g(int x);
+extern void h(int x);
+
+void f(int x) {
+  if (x % 3) {
+    GC();
+    g(x);
+  }
+  h(x);
+}
+
+void g(int x) {
+  if (x % 2) f(x);
+  h(x);
+}
+
+void h(int x) {
+  if (x) {
+    f(x - 1);
+    g(x - 1);
+  }
+}
+
+void leaf() { asm(""); }
+
+void nonrecursive_root() {
+  leaf();
+  leaf();
+  GC();
+}
+
+void self_recursive(int x) {
+  if (x) self_recursive(x - 1);
+}
+
+// Set up the graph
+//
+//   n1 <--> n2          n4 <--> n5
+//           \                  /
+//            --> n3 <---------
+//                 \
+//                  ---> n6 --> n7 <---> n8 --> n9
+//
+// So recursive roots are one of (n1, n2) plus one of (n4, n5).
+extern void n1(int x);
+extern void n2(int x);
+extern void n3(int x);
+extern void n4(int x);
+extern void n5(int x);
+extern void n6(int x);
+extern void n7(int x);
+extern void n8(int x);
+extern void n9(int x);
+
+void n1(int x) { n2(x); }
+
+void n2(int x) {
+  if (x) n1(x - 1);
+  n3(x);
+}
+
+void n4(int x) { n5(x); }
+
+void n5(int x) {
+  if (x) n4(x - 1);
+  n3(x);
+}
+
+void n3(int x) { n6(x); }
+
+void n6(int x) { n7(x); }
+
+void n7(int x) { n8(x); }
+
+void n8(int x) {
+  if (x) n7(x - 1);
+  n9(x);
+}
+
+void n9(int x) { asm(""); }
diff --git a/js/src/devtools/rootAnalysis/t/graph/test.py b/js/src/devtools/rootAnalysis/t/graph/test.py
new file mode 100644
index 0000000000..f78500f200
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/graph/test.py
@@ -0,0 +1,54 @@
+# 'test' is provided by the calling script.
+# flake8: noqa: F821
+
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes")
+
+info = test.load_typeInfo()
+
+gcFunctions = test.load_gcFunctions()
+
+f = "void f(int32)"
+g = "void g(int32)"
+h = "void h(int32)"
+
+assert f in gcFunctions
+assert g in gcFunctions
+assert h in gcFunctions
+assert "void leaf()" not in gcFunctions
+assert "void nonrecursive_root()" in gcFunctions
+
+callgraph = test.load_callgraph()
+assert callgraph.calleeGraph[f][g]
+assert callgraph.calleeGraph[f][h]
+assert callgraph.calleeGraph[g][f]
+assert callgraph.calleeGraph[g][h]
+
+node = ["void n{}(int32)".format(i) for i in range(10)]
+mnode = [callgraph.unmangledToMangled.get(f) for f in node]
+for src, dst in [
+    (1, 2),
+    (2, 1),
+    (4, 5),
+    (5, 4),
+    (2, 3),
+    (5, 3),
+    (3, 6),
+    (6, 7),
+    (7, 8),
+    (8, 7),
+    (8, 9),
+]:
+    assert callgraph.calleeGraph[node[src]][node[dst]]
+
+funcInfo = test.load_funcInfo()
+rroots = set(
+    [
+        callgraph.mangledToUnmangled[f]
+        for f in funcInfo
+        if funcInfo[f].get("recursive_root")
+    ]
+)
+assert len(set([node[1], node[2]]) & rroots) == 1
+assert len(set([node[4], node[5]]) & rroots) == 1
+assert len(rroots) == 4, "rroots = {}".format(rroots)  # n1, n4, f, self_recursive
diff --git a/js/src/devtools/rootAnalysis/t/hazards/source.cpp b/js/src/devtools/rootAnalysis/t/hazards/source.cpp
new file mode 100644
index 0000000000..979591ef6b
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/hazards/source.cpp
@@ -0,0 +1,459 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include <utility>
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+// MarkVariableAsGCSafe is a magic function name used as an
+// explicit annotation.
+
+namespace JS {
+namespace detail {
+template <typename T>
+static void MarkVariableAsGCSafe(T&) {
+  asm("");
+}
+}  // namespace detail
+}  // namespace JS
+
+#define JS_HAZ_VARIABLE_IS_GC_SAFE(var) JS::detail::MarkVariableAsGCSafe(var)
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+template <typename T, typename U>
+struct UntypedContainer {
+  char data[sizeof(T) + sizeof(U)];
+} ANNOTATE("moz_inherit_type_annotations_from_template_args");
+
+struct RootedCell {
+  RootedCell(Cell*) {}
+} ANNOTATE("Rooted Pointer");
+
+class AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Base() {}
+  ~AutoSuppressGC_Base() {}
+} ANNOTATE("Suppress GC");
+
+class AutoSuppressGC_Child : public AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Child() : AutoSuppressGC_Base() {}
+};
+
+class AutoSuppressGC {
+  AutoSuppressGC_Child helpImBeingSuppressed;
+
+ public:
+  AutoSuppressGC() {}
+};
+
+extern void GC() ANNOTATE("GC Call");
+extern void invisible();
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+  invisible();
+}
+
+extern void usecell(Cell*);
+
+void suppressedFunction() {
+  GC();  // Calls GC, but is always called within AutoSuppressGC
+}
+
+void halfSuppressedFunction() {
+  GC();  // Calls GC, but is sometimes called within AutoSuppressGC
+}
+
+void unsuppressedFunction() {
+  GC();  // Calls GC, never within AutoSuppressGC
+}
+
+class IDL_Interface {
+ public:
+  ANNOTATE("Can run script") virtual void canScriptThis() {}
+  virtual void cannotScriptThis() {}
+  ANNOTATE("Can run script") virtual void overridden_canScriptThis() = 0;
+  virtual void overridden_cannotScriptThis() = 0;
+};
+
+class IDL_Subclass : public IDL_Interface {
+  ANNOTATE("Can run script") void overridden_canScriptThis() override {}
+  void overridden_cannotScriptThis() override {}
+};
+
+volatile static int x = 3;
+volatile static int* xp = &x;
+struct GCInDestructor {
+  ~GCInDestructor() {
+    invisible();
+    asm("");
+    *xp = 4;
+    GC();
+  }
+};
+
+template <typename T>
+void usecontainer(T* value) {
+  if (value) asm("");
+}
+
+Cell* cell() {
+  static Cell c;
+  return &c;
+}
+
+Cell* f() {
+  GCInDestructor kaboom;
+
+  Cell* cell1 = cell();
+  Cell* cell2 = cell();
+  Cell* cell3 = cell();
+  Cell* cell4 = cell();
+  {
+    AutoSuppressGC nogc;
+    suppressedFunction();
+    halfSuppressedFunction();
+  }
+  usecell(cell1);
+  halfSuppressedFunction();
+  usecell(cell2);
+  unsuppressedFunction();
+  {
+    // Old bug: it would look from the first AutoSuppressGC constructor it
+    // found to the last destructor. This statement *should* have no effect.
+    AutoSuppressGC nogc;
+  }
+  usecell(cell3);
+  Cell* cell5 = cell();
+  usecell(cell5);
+
+  {
+    // Templatized container that inherits attributes from Cell*, should
+    // report a hazard.
+    UntypedContainer<int, Cell*> container1;
+    usecontainer(&container1);
+    GC();
+    usecontainer(&container1);
+  }
+
+  {
+    // As above, but with a non-GC type.
+    UntypedContainer<int, double> container2;
+    usecontainer(&container2);
+    GC();
+    usecontainer(&container2);
+  }
+
+  // Hazard in return value due to ~GCInDestructor
+  Cell* cell6 = cell();
+  return cell6;
+}
+
+Cell* copy_and_gc(Cell* src) {
+  GC();
+  return reinterpret_cast<Cell*>(88);
+}
+
+void use(Cell* cell) {
+  static int x = 0;
+  if (cell) x++;
+}
+
+struct CellContainer {
+  Cell* cell;
+  CellContainer() { asm(""); }
+};
+
+void loopy() {
+  Cell cell;
+
+  // No hazard: haz1 is not live during call to copy_and_gc.
+  Cell* haz1;
+  for (int i = 0; i < 10; i++) {
+    haz1 = copy_and_gc(haz1);
+  }
+
+  // No hazard: haz2 is live up to just before the GC, and starting at the
+  // next statement after it, but not across the GC.
+  Cell* haz2 = &cell;
+  for (int j = 0; j < 10; j++) {
+    use(haz2);
+    GC();
+    haz2 = &cell;
+  }
+
+  // Hazard: haz3 is live from the final statement in one iteration, across
+  // the GC in the next, to the use in the 2nd statement.
+  Cell* haz3;
+  for (int k = 0; k < 10; k++) {
+    GC();
+    use(haz3);
+    haz3 = &cell;
+  }
+
+  // Hazard: haz4 is live across a GC hidden in a loop.
+  Cell* haz4 = &cell;
+  for (int i2 = 0; i2 < 10; i2++) {
+    GC();
+  }
+  use(haz4);
+
+  // Hazard: haz5 is live from within a loop across a GC.
+  Cell* haz5;
+  for (int i3 = 0; i3 < 10; i3++) {
+    haz5 = &cell;
+  }
+  GC();
+  use(haz5);
+
+  // No hazard: similar to the haz3 case, but verifying that we do not get
+  // into an infinite loop.
+  Cell* haz6;
+  for (int i4 = 0; i4 < 10; i4++) {
+    GC();
+    haz6 = &cell;
+  }
+
+  // No hazard: haz7 is constructed within the body, so it can't make a
+  // hazard across iterations. Note that this requires CellContainer to have
+  // a constructor, because otherwise the analysis doesn't see where
+  // variables are declared. (With the constructor, it knows that
+  // construction of haz7 obliterates any previous value it might have had.
+  // Not that that's possible given its scope, but the analysis doesn't get
+  // that information.)
+  for (int i5 = 0; i5 < 10; i5++) {
+    GC();
+    CellContainer haz7;
+    use(haz7.cell);
+    haz7.cell = &cell;
+  }
+
+  // Hazard: make sure we *can* see hazards across iterations involving
+  // CellContainer;
+  CellContainer haz8;
+  for (int i6 = 0; i6 < 10; i6++) {
+    GC();
+    use(haz8.cell);
+    haz8.cell = &cell;
+  }
+}
+
+namespace mozilla {
+template <typename T>
+class UniquePtr {
+  T* val;
+
+ public:
+  UniquePtr() : val(nullptr) { asm(""); }
+  UniquePtr(T* p) : val(p) {}
+  UniquePtr(UniquePtr<T>&& u) : val(u.val) { u.val = nullptr; }
+  ~UniquePtr() { use(val); }
+  T* get() { return val; }
+  void reset() { val = nullptr; }
+} ANNOTATE("moz_inherit_type_annotations_from_template_args");
+}  // namespace mozilla
+
+extern void consume(mozilla::UniquePtr<Cell> uptr);
+
+void safevals() {
+  Cell cell;
+
+  // Simple hazard.
+  Cell* unsafe1 = &cell;
+  GC();
+  use(unsafe1);
+
+  // Safe because it's known to be nullptr.
+  Cell* safe2 = &cell;
+  safe2 = nullptr;
+  GC();
+  use(safe2);
+
+  // Unsafe because it may not be nullptr.
+  Cell* unsafe3 = &cell;
+  if (reinterpret_cast<long>(&cell) & 0x100) {
+    unsafe3 = nullptr;
+  }
+  GC();
+  use(unsafe3);
+
+  // Unsafe because it's not nullptr anymore.
+  Cell* unsafe3b = &cell;
+  unsafe3b = nullptr;
+  unsafe3b = &cell;
+  GC();
+  use(unsafe3b);
+
+  // Hazard involving UniquePtr.
+  {
+    mozilla::UniquePtr<Cell> unsafe4(&cell);
+    GC();
+    // Destructor uses unsafe4.
+  }
+
+  // reset() to safe value before the GC.
+  {
+    mozilla::UniquePtr<Cell> safe5(&cell);
+    safe5.reset();
+    GC();
+  }
+
+  // reset() to safe value after the GC.
+  {
+    mozilla::UniquePtr<Cell> safe6(&cell);
+    GC();
+    safe6.reset();
+  }
+
+  // reset() to safe value after the GC -- but we've already used it, so it's
+  // too late.
+  {
+    mozilla::UniquePtr<Cell> unsafe7(&cell);
+    GC();
+    use(unsafe7.get());
+    unsafe7.reset();
+  }
+
+  // initialized to safe value.
+  {
+    mozilla::UniquePtr<Cell> safe8;
+    GC();
+  }
+
+  // passed to a function that takes ownership before GC.
+  {
+    mozilla::UniquePtr<Cell> safe9(&cell);
+    consume(std::move(safe9));
+    GC();
+  }
+
+  // passed to a function that takes ownership after GC.
+  {
+    mozilla::UniquePtr<Cell> unsafe10(&cell);
+    GC();
+    consume(std::move(unsafe10));
+  }
+
+  // annotated to be safe before the GC. (This doesn't make
+  // a lot of sense here; the annotation is for when some
+  // type is known to only contain safe values, eg it is
+  // initialized as empty, or it is a union and we know
+  // that the GC pointer variants are not in use.)
+  {
+    mozilla::UniquePtr<Cell> safe11(&cell);
+    JS_HAZ_VARIABLE_IS_GC_SAFE(safe11);
+    GC();
+  }
+
+  // annotate as safe value after the GC -- since nothing else
+  // has touched the variable, that means it was already safe
+  // during the GC.
+  {
+    mozilla::UniquePtr<Cell> safe12(&cell);
+    GC();
+    JS_HAZ_VARIABLE_IS_GC_SAFE(safe12);
+  }
+
+  // annotate as safe after the GC -- but we've already used it, so it's
+  // too late.
+  {
+    mozilla::UniquePtr<Cell> unsafe13(&cell);
+    GC();
+    use(unsafe13.get());
+    JS_HAZ_VARIABLE_IS_GC_SAFE(unsafe13);
+  }
+
+  // Check JS_HAZ_CAN_RUN_SCRIPT annotation handling.
+  IDL_Subclass sub;
+  IDL_Subclass* subp = &sub;
+  IDL_Interface* base = &sub;
+  {
+    Cell* unsafe14 = &cell;
+    base->canScriptThis();
+    use(unsafe14);
+  }
+  {
+    Cell* unsafe15 = &cell;
+    subp->canScriptThis();
+    use(unsafe15);
+  }
+  {
+    // Almost the same as the last one, except call using the actual object, not
+    // a pointer. The type is known, so there is no danger of the actual type
+    // being a subclass that has overridden the method with an implementation
+    // that calls script.
+    Cell* safe16 = &cell;
+    sub.canScriptThis();
+    use(safe16);
+  }
+  {
+    Cell* safe17 = &cell;
+    base->cannotScriptThis();
+    use(safe17);
+  }
+  {
+    Cell* safe18 = &cell;
+    subp->cannotScriptThis();
+    use(safe18);
+  }
+}
+
+// Make sure `this` is live at the beginning of a function.
+class Subcell : public Cell {
+  int method() {
+    GC();
+    return f;  // this->f
+  }
+};
+
+template <typename T>
+struct RefPtr {
+  ~RefPtr() { GC(); }
+  void forget() {}
+};
+
+Cell* refptr_test1() {
+  static Cell cell;
+  RefPtr<float> v1;
+  Cell* ref_unsafe1 = &cell;
+  return ref_unsafe1;
+}
+
+Cell* refptr_test2() {
+  static Cell cell;
+  RefPtr<float> v2;
+  Cell* ref_safe2 = &cell;
+  v2.forget();
+  return ref_safe2;
+}
+
+Cell* refptr_test3() {
+  static Cell cell;
+  RefPtr<float> v3;
+  Cell* ref_unsafe3 = &cell;
+  if (x) {
+    v3.forget();
+  }
+  return ref_unsafe3;
+}
+
+Cell* refptr_test4() {
+  static Cell cell;
+  RefPtr<int> r;
+  return &cell;  // hazard in return value
+}
+
+Cell* refptr_test5() {
+  static Cell cell;
+  RefPtr<int> r;
+  return nullptr;  // returning immobile value, so no hazard
+}
diff --git a/js/src/devtools/rootAnalysis/t/hazards/test.py b/js/src/devtools/rootAnalysis/t/hazards/test.py
new file mode 100644
index 0000000000..75b8811c0f
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/hazards/test.py
@@ -0,0 +1,101 @@
+# flake8: noqa: F821
+
+from collections import defaultdict
+
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes")
+
+# gcFunctions should be the inverse, but we get to rely on unmangled names here.
+gcFunctions = test.load_gcFunctions()
+assert "void GC()" in gcFunctions
+assert "void suppressedFunction()" not in gcFunctions
+assert "void halfSuppressedFunction()" in gcFunctions
+assert "void unsuppressedFunction()" in gcFunctions
+assert "int32 Subcell::method()" in gcFunctions
+assert "Cell* f()" in gcFunctions
+
+hazards = test.load_hazards()
+hazmap = {haz.variable: haz for haz in hazards}
+assert "cell1" not in hazmap
+assert "cell2" in hazmap
+assert "cell3" in hazmap
+assert "cell4" not in hazmap
+assert "cell5" not in hazmap
+assert "cell6" not in hazmap
+assert "<returnvalue>" in hazmap
+assert "this" in hazmap
+
+# All hazards should be in f(), loopy(), safevals(), method(), and refptr_test{1,3,4}()
+assert hazmap["cell2"].function == "Cell* f()"
+haz_functions = set(haz.function for haz in hazards)
+print(haz_functions)
+assert len(haz_functions) == 7
+
+# Check that the correct GC call is reported for each hazard. (cell3 has a
+# hazard from two different GC calls; it doesn't really matter which is
+# reported.)
+assert hazmap["cell2"].GCFunction == "void halfSuppressedFunction()"
+assert hazmap["cell3"].GCFunction in (
+    "void halfSuppressedFunction()",
+    "void unsuppressedFunction()",
+)
+returnval_hazards = set(
+    haz.function for haz in hazards if haz.variable == "<returnvalue>"
+)
+assert returnval_hazards == set(
+    [
+        "Cell* f()",
+        "Cell* refptr_test1()",
+        "Cell* refptr_test3()",
+        "Cell* refptr_test4()",
+    ]
+)
+
+assert "container1" in hazmap
+assert "container2" not in hazmap
+
+# Type names are handy to have in the report.
+assert hazmap["cell2"].type == "Cell*"
+assert hazmap["<returnvalue>"].type == "Cell*"
+assert hazmap["this"].type == "Subcell*"
+
+# loopy hazards. See comments in source.
+assert "haz1" not in hazmap
+assert "haz2" not in hazmap
+assert "haz3" in hazmap
+assert "haz4" in hazmap
+assert "haz5" in hazmap
+assert "haz6" not in hazmap
+assert "haz7" not in hazmap
+assert "haz8" in hazmap
+
+# safevals hazards. See comments in source.
+assert "unsafe1" in hazmap
+assert "safe2" not in hazmap
+assert "unsafe3" in hazmap
+assert "unsafe3b" in hazmap
+assert "unsafe4" in hazmap
+assert "safe5" not in hazmap
+assert "safe6" not in hazmap
+assert "unsafe7" in hazmap
+assert "safe8" not in hazmap
+assert "safe9" not in hazmap
+assert "safe10" not in hazmap
+assert "safe11" not in hazmap
+assert "safe12" not in hazmap
+assert "unsafe13" in hazmap
+assert "unsafe14" in hazmap
+assert "unsafe15" in hazmap
+assert "safe16" not in hazmap
+assert "safe17" not in hazmap
+assert "safe18" not in hazmap
+
+# method hazard.
+
+byfunc = defaultdict(lambda: defaultdict(dict))
+for haz in hazards:
+    byfunc[haz.function][haz.variable] = haz
+
+methhaz = byfunc["int32 Subcell::method()"]
+assert "this" in methhaz
+assert methhaz["this"].type == "Subcell*"
diff --git a/js/src/devtools/rootAnalysis/t/sixgill-tree/source.cpp b/js/src/devtools/rootAnalysis/t/sixgill-tree/source.cpp
new file mode 100644
index 0000000000..149d77b03a
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/sixgill-tree/source.cpp
@@ -0,0 +1,76 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+namespace js {
+namespace gc {
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+}  // namespace gc
+}  // namespace js
+
+struct Bogon {};
+
+struct JustACell : public js::gc::Cell {
+  bool iHaveNoDataMembers() { return true; }
+};
+
+struct JSObject : public js::gc::Cell, public Bogon {
+  int g;
+};
+
+struct SpecialObject : public JSObject {
+  int z;
+};
+
+struct ErrorResult {
+  bool hasObj;
+  JSObject* obj;
+  void trace() {}
+} ANNOTATE("Suppressed GC Pointer");
+
+struct OkContainer {
+  ErrorResult res;
+  bool happy;
+};
+
+struct UnrootedPointer {
+  JSObject* obj;
+};
+
+template <typename T>
+class Rooted {
+  T data;
+} ANNOTATE("Rooted Pointer");
+
+extern void js_GC() ANNOTATE("GC Call") ANNOTATE("Slow");
+
+void js_GC() {}
+
+void root_arg(JSObject* obj, JSObject* random) {
+  // Use all these types so they get included in the output.
+  SpecialObject so;
+  UnrootedPointer up;
+  Bogon b;
+  OkContainer okc;
+  Rooted<JSObject*> ro;
+  Rooted<SpecialObject*> rso;
+
+  obj = random;
+
+  JSObject* other1 = obj;
+  js_GC();
+
+  float MARKER1 = 0;
+  JSObject* other2 = obj;
+  other1->f = 1;
+  other2->f = -1;
+
+  unsigned int u1 = 1;
+  unsigned int u2 = -1;
+}
diff --git a/js/src/devtools/rootAnalysis/t/sixgill-tree/test.py b/js/src/devtools/rootAnalysis/t/sixgill-tree/test.py
new file mode 100644
index 0000000000..5e99fff908
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/sixgill-tree/test.py
@@ -0,0 +1,63 @@
+# flake8: noqa: F821
+import re
+
+test.compile("source.cpp")
+test.computeGCTypes()
+body = test.process_body(test.load_db_entry("src_body", re.compile(r"root_arg"))[0])
+
+# Rendering positive and negative integers
+marker1 = body.assignment_line("MARKER1")
+equal(body.edge_from_line(marker1 + 2)["Exp"][1]["String"], "1")
+equal(body.edge_from_line(marker1 + 3)["Exp"][1]["String"], "-1")
+
+equal(body.edge_from_point(body.assignment_point("u1"))["Exp"][1]["String"], "1")
+equal(
+    body.edge_from_point(body.assignment_point("u2"))["Exp"][1]["String"], "4294967295"
+)
+
+assert "obj" in body["Variables"]
+assert "random" in body["Variables"]
+assert "other1" in body["Variables"]
+assert "other2" in body["Variables"]
+
+# Test function annotations
+js_GC = test.process_body(test.load_db_entry("src_body", re.compile(r"js_GC"))[0])
+annotations = js_GC["Variables"]["void js_GC()"]["Annotation"]
+assert annotations
+found_call_annotate = False
+for annotation in annotations:
+    (annType, value) = annotation["Name"]
+    if annType == "annotate" and value == "GC Call":
+        found_call_annotate = True
+assert found_call_annotate
+
+# Test type annotations
+
+# js::gc::Cell first
+cell = test.load_db_entry("src_comp", "js::gc::Cell")[0]
+assert cell["Kind"] == "Struct"
+annotations = cell["Annotation"]
+assert len(annotations) == 1
+(tag, value) = annotations[0]["Name"]
+assert tag == "annotate"
+assert value == "GC Thing"
+
+# Check JSObject inheritance.
+JSObject = test.load_db_entry("src_comp", "JSObject")[0]
+bases = [b["Base"] for b in JSObject["CSUBaseClass"]]
+assert "js::gc::Cell" in bases
+assert "Bogon" in bases
+assert len(bases) == 2
+
+# Check type analysis
+gctypes = test.load_gcTypes()
+assert "js::gc::Cell" in gctypes["GCThings"]
+assert "JustACell" in gctypes["GCThings"]
+assert "JSObject" in gctypes["GCThings"]
+assert "SpecialObject" in gctypes["GCThings"]
+assert "UnrootedPointer" in gctypes["GCPointers"]
+assert "Bogon" not in gctypes["GCThings"]
+assert "Bogon" not in gctypes["GCPointers"]
+assert "ErrorResult" not in gctypes["GCPointers"]
+assert "OkContainer" not in gctypes["GCPointers"]
+assert "class Rooted<JSObject*>" not in gctypes["GCPointers"]
diff --git a/js/src/devtools/rootAnalysis/t/sixgill.py b/js/src/devtools/rootAnalysis/t/sixgill.py
new file mode 100644
index 0000000000..0b8c2c7073
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/sixgill.py
@@ -0,0 +1,70 @@
+#!/usr/bin/env python
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+from collections import defaultdict
+
+# Simplified version of the body info.
+
+
+class Body(dict):
+    def __init__(self, body):
+        self["BlockIdKind"] = body["BlockId"]["Kind"]
+        if "Variable" in body["BlockId"]:
+            self["BlockName"] = body["BlockId"]["Variable"]["Name"][0].split("$")[-1]
+        loc = body["Location"]
+        self["LineRange"] = (loc[0]["Line"], loc[1]["Line"])
+        self["Filename"] = loc[0]["CacheString"]
+        self["Edges"] = body.get("PEdge", [])
+        self["Points"] = {
+            i: p["Location"]["Line"] for i, p in enumerate(body["PPoint"], 1)
+        }
+        self["Index"] = body["Index"]
+        self["Variables"] = {
+            x["Variable"]["Name"][0].split("$")[-1]: x["Type"]
+            for x in body["DefineVariable"]
+        }
+
+        # Indexes
+        self["Line2Points"] = defaultdict(list)
+        for point, line in self["Points"].items():
+            self["Line2Points"][line].append(point)
+        self["SrcPoint2Edges"] = defaultdict(list)
+        for edge in self["Edges"]:
+            src, dst = edge["Index"]
+            self["SrcPoint2Edges"][src].append(edge)
+        self["Line2Edges"] = defaultdict(list)
+        for (src, edges) in self["SrcPoint2Edges"].items():
+            line = self["Points"][src]
+            self["Line2Edges"][line].extend(edges)
+
+    def edges_from_line(self, line):
+        return self["Line2Edges"][line]
+
+    def edge_from_line(self, line):
+        edges = self.edges_from_line(line)
+        assert len(edges) == 1
+        return edges[0]
+
+    def edges_from_point(self, point):
+        return self["SrcPoint2Edges"][point]
+
+    def edge_from_point(self, point):
+        edges = self.edges_from_point(point)
+        assert len(edges) == 1
+        return edges[0]
+
+    def assignment_point(self, varname):
+        for edge in self["Edges"]:
+            if edge["Kind"] != "Assign":
+                continue
+            dst = edge["Exp"][0]
+            if dst["Kind"] != "Var":
+                continue
+            if dst["Variable"]["Name"][0] == varname:
+                return edge["Index"][0]
+        raise Exception("assignment to variable %s not found" % varname)
+
+    def assignment_line(self, varname):
+        return self["Points"][self.assignment_point(varname)]
diff --git a/js/src/devtools/rootAnalysis/t/suppression/source.cpp b/js/src/devtools/rootAnalysis/t/suppression/source.cpp
new file mode 100644
index 0000000000..56e458bdaa
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/suppression/source.cpp
@@ -0,0 +1,72 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+class AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Base() {}
+  ~AutoSuppressGC_Base() {}
+} ANNOTATE("Suppress GC");
+
+class AutoSuppressGC_Child : public AutoSuppressGC_Base {
+ public:
+  AutoSuppressGC_Child() : AutoSuppressGC_Base() {}
+};
+
+class AutoSuppressGC {
+  AutoSuppressGC_Child helpImBeingSuppressed;
+
+ public:
+  AutoSuppressGC() {}
+};
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+extern void foo(Cell*);
+
+void suppressedFunction() {
+  GC();  // Calls GC, but is always called within AutoSuppressGC
+}
+
+void halfSuppressedFunction() {
+  GC();  // Calls GC, but is sometimes called within AutoSuppressGC
+}
+
+void unsuppressedFunction() {
+  GC();  // Calls GC, never within AutoSuppressGC
+}
+
+void f() {
+  Cell* cell1 = nullptr;
+  Cell* cell2 = nullptr;
+  Cell* cell3 = nullptr;
+  {
+    AutoSuppressGC nogc;
+    suppressedFunction();
+    halfSuppressedFunction();
+  }
+  foo(cell1);
+  halfSuppressedFunction();
+  foo(cell2);
+  unsuppressedFunction();
+  {
+    // Old bug: it would look from the first AutoSuppressGC constructor it
+    // found to the last destructor. This statement *should* have no effect.
+    AutoSuppressGC nogc;
+  }
+  foo(cell3);
+}
diff --git a/js/src/devtools/rootAnalysis/t/suppression/test.py b/js/src/devtools/rootAnalysis/t/suppression/test.py
new file mode 100644
index 0000000000..118ae422ab
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/suppression/test.py
@@ -0,0 +1,21 @@
+# flake8: noqa: F821
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes", upto="gcFunctions")
+
+# The suppressions file uses mangled names.
+info = test.load_funcInfo()
+suppressed = [f for f, v in info.items() if v.get("limits", 0) | 1]
+
+# Only one of these is fully suppressed (ie, *always* called within the scope
+# of an AutoSuppressGC).
+assert len(list(filter(lambda f: "suppressedFunction" in f, suppressed))) == 1
+assert len(list(filter(lambda f: "halfSuppressedFunction" in f, suppressed))) == 0
+assert len(list(filter(lambda f: "unsuppressedFunction" in f, suppressed))) == 0
+
+# gcFunctions should be the inverse, but we get to rely on unmangled names here.
+gcFunctions = test.load_gcFunctions()
+assert "void GC()" in gcFunctions
+assert "void suppressedFunction()" not in gcFunctions
+assert "void halfSuppressedFunction()" in gcFunctions
+assert "void unsuppressedFunction()" in gcFunctions
+assert "void f()" in gcFunctions
diff --git a/js/src/devtools/rootAnalysis/t/testlib.py b/js/src/devtools/rootAnalysis/t/testlib.py
new file mode 100644
index 0000000000..a29e640ba4
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/testlib.py
@@ -0,0 +1,230 @@
+import json
+import os
+import re
+import subprocess
+import sys
+from collections import defaultdict, namedtuple
+
+from sixgill import Body
+
+scriptdir = os.path.abspath(os.path.join(os.path.dirname(__file__), ".."))
+
+HazardSummary = namedtuple(
+    "HazardSummary", ["function", "variable", "type", "GCFunction", "location"]
+)
+
+Callgraph = namedtuple(
+    "Callgraph",
+    [
+        "functionNames",
+        "nameToId",
+        "mangledToUnmangled",
+        "unmangledToMangled",
+        "calleesOf",
+        "callersOf",
+        "tags",
+        "calleeGraph",
+        "callerGraph",
+    ],
+)
+
+
+def equal(got, expected):
+    if got != expected:
+        print("Got '%s', expected '%s'" % (got, expected))
+
+
+def extract_unmangled(func):
+    return func.split("$")[-1]
+
+
+class Test(object):
+    def __init__(self, indir, outdir, cfg, verbose=0):
+        self.indir = indir
+        self.outdir = outdir
+        self.cfg = cfg
+        self.verbose = verbose
+
+    def infile(self, path):
+        return os.path.join(self.indir, path)
+
+    def binpath(self, prog):
+        return os.path.join(self.cfg.sixgill_bin, prog)
+
+    def compile(self, source, options=""):
+        env = os.environ
+        env["CCACHE_DISABLE"] = "1"
+        cmd = "{CXX} -c {source} -O3 -std=c++11 -fplugin={sixgill} -fplugin-arg-xgill-mangle=1 {options}".format(  # NOQA: E501
+            source=self.infile(source),
+            CXX=self.cfg.cxx,
+            sixgill=self.cfg.sixgill_plugin,
+            options=options,
+        )
+        if self.cfg.verbose:
+            print("Running %s" % cmd)
+        subprocess.check_call(["sh", "-c", cmd])
+
+    def load_db_entry(self, dbname, pattern):
+        """Look up an entry from an XDB database file, 'pattern' may be an exact
+        matching string, or an re pattern object matching a single entry."""
+
+        if hasattr(pattern, "match"):
+            output = subprocess.check_output(
+                [self.binpath("xdbkeys"), dbname + ".xdb"], universal_newlines=True
+            )
+            matches = list(filter(lambda _: re.search(pattern, _), output.splitlines()))
+            if len(matches) == 0:
+                raise Exception("entry not found")
+            if len(matches) > 1:
+                raise Exception("multiple entries found")
+            pattern = matches[0]
+
+        output = subprocess.check_output(
+            [self.binpath("xdbfind"), "-json", dbname + ".xdb", pattern],
+            universal_newlines=True,
+        )
+        return json.loads(output)
+
+    def run_analysis_script(self, startPhase, upto=None):
+        open("defaults.py", "w").write(
+            """\
+analysis_scriptdir = '{scriptdir}'
+sixgill_bin = '{bindir}'
+""".format(
+                scriptdir=scriptdir, bindir=self.cfg.sixgill_bin
+            )
+        )
+        cmd = [
+            sys.executable,
+            os.path.join(scriptdir, "analyze.py"),
+            "-v" if self.verbose else "-q",
+        ]
+        cmd += ["--first", startPhase]
+        if upto:
+            cmd += ["--last", upto]
+        cmd.append("--source=%s" % self.indir)
+        cmd.append("--js=%s" % self.cfg.js)
+        if self.cfg.verbose:
+            cmd.append("--verbose")
+            print("Running " + " ".join(cmd))
+        subprocess.check_call(cmd)
+
+    def computeGCTypes(self):
+        self.run_analysis_script("gcTypes", upto="gcTypes")
+
+    def computeHazards(self):
+        self.run_analysis_script("gcTypes")
+
+    def load_text_file(self, filename, extract=lambda l: l):
+        fullpath = os.path.join(self.outdir, filename)
+        values = (extract(line.strip()) for line in open(fullpath, "r"))
+        return list(filter(lambda _: _ is not None, values))
+
+    def load_json_file(self, filename, reviver=None):
+        fullpath = os.path.join(self.outdir, filename)
+        with open(fullpath) as fh:
+            return json.load(fh, object_hook=reviver)
+
+    def load_gcTypes(self):
+        def grab_type(line):
+            m = re.match(r"^(GC\w+): (.*)", line)
+            if m:
+                return (m.group(1) + "s", m.group(2))
+            return None
+
+        gctypes = defaultdict(list)
+        for collection, typename in self.load_text_file(
+            "gcTypes.txt", extract=grab_type
+        ):
+            gctypes[collection].append(typename)
+        return gctypes
+
+    def load_typeInfo(self, filename="typeInfo.txt"):
+        return self.load_json_file(filename)
+
+    def load_funcInfo(self, filename="limitedFunctions.lst"):
+        return self.load_json_file(filename)
+
+    def load_gcFunctions(self):
+        return self.load_text_file("gcFunctions.lst", extract=extract_unmangled)
+
+    def load_callgraph(self):
+        data = Callgraph(
+            functionNames=["dummy"],
+            nameToId={},
+            mangledToUnmangled={},
+            unmangledToMangled={},
+            calleesOf=defaultdict(list),
+            callersOf=defaultdict(list),
+            tags=defaultdict(set),
+            calleeGraph=defaultdict(dict),
+            callerGraph=defaultdict(dict),
+        )
+
+        def lookup(id):
+            mangled = data.functionNames[int(id)]
+            return data.mangledToUnmangled.get(mangled, mangled)
+
+        def add_call(caller, callee, limit):
+            data.calleesOf[caller].append(callee)
+            data.callersOf[callee].append(caller)
+            data.calleeGraph[caller][callee] = True
+            data.callerGraph[callee][caller] = True
+
+        def process(line):
+            if line.startswith("#"):
+                name = line.split(" ", 1)[1]
+                data.nameToId[name] = len(data.functionNames)
+                data.functionNames.append(name)
+                return
+
+            if line.startswith("="):
+                m = re.match(r"^= (\d+) (.*)", line)
+                mangled = data.functionNames[int(m.group(1))]
+                unmangled = m.group(2)
+                data.nameToId[unmangled] = id
+                data.mangledToUnmangled[mangled] = unmangled
+                data.unmangledToMangled[unmangled] = mangled
+                return
+
+            limit = 0
+            m = re.match(r"^\w (?:/(\d+))? ", line)
+            if m:
+                limit = int(m[1])
+
+            tokens = line.split(" ")
+            if tokens[0] in ("D", "R"):
+                _, caller, callee = tokens
+                add_call(lookup(caller), lookup(callee), limit)
+            elif tokens[0] == "T":
+                data.tags[tokens[1]].add(line.split(" ", 2)[2])
+            elif tokens[0] in ("F", "V"):
+                pass
+
+            elif tokens[0] == "I":
+                m = re.match(r"^I (\d+) VARIABLE ([^\,]*)", line)
+                pass
+
+        self.load_text_file("callgraph.txt", extract=process)
+        return data
+
+    def load_hazards(self):
+        def grab_hazard(line):
+            m = re.match(
+                r"Function '(.*?)' has unrooted '(.*?)' of type '(.*?)' live across GC call '(.*?)' at (.*)",  # NOQA: E501
+                line,
+            )
+            if m:
+                info = list(m.groups())
+                info[0] = info[0].split("$")[-1]
+                info[3] = info[3].split("$")[-1]
+                return HazardSummary(*info)
+            return None
+
+        return self.load_text_file("rootingHazards.txt", extract=grab_hazard)
+
+    def process_body(self, body):
+        return Body(body)
+
+    def process_bodies(self, bodies):
+        return [self.process_body(b) for b in bodies]
diff --git a/js/src/devtools/rootAnalysis/t/virtual/source.cpp b/js/src/devtools/rootAnalysis/t/virtual/source.cpp
new file mode 100644
index 0000000000..83633a3436
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/virtual/source.cpp
@@ -0,0 +1,292 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#define ANNOTATE(property) __attribute__((annotate(property)))
+
+extern void GC() ANNOTATE("GC Call");
+
+void GC() {
+  // If the implementation is too trivial, the function body won't be emitted at
+  // all.
+  asm("");
+}
+
+// Special-cased function -- code that can run JS has an artificial edge to
+// js::RunScript.
+namespace js {
+void RunScript() { GC(); }
+}  // namespace js
+
+struct Cell {
+  int f;
+} ANNOTATE("GC Thing");
+
+extern void foo();
+
+void bar() { GC(); }
+
+typedef void (*func_t)();
+
+class Base {
+ public:
+  int ANNOTATE("field annotation") dummy;
+  virtual void someGC() ANNOTATE("Base pure virtual method") = 0;
+  virtual void someGC(int) ANNOTATE("overloaded Base pure virtual method") = 0;
+  virtual void sibGC() = 0;
+  virtual void onBase() { bar(); }
+  func_t functionField;
+
+  // For now, this is just to verify that the plugin doesn't crash. The
+  // analysis code does not yet look at this annotation or output it anywhere
+  // (though it *is* being recorded.)
+  static float testAnnotations() ANNOTATE("static func");
+
+  // Similar, though sixgill currently completely ignores parameter annotations.
+  static double testParamAnnotations(Cell& ANNOTATE("param annotation")
+                                         ANNOTATE("second param annot") cell)
+      ANNOTATE("static func") ANNOTATE("second func");
+};
+
+float Base::testAnnotations() {
+  asm("");
+  return 1.1;
+}
+
+double Base::testParamAnnotations(Cell& cell) {
+  asm("");
+  return 1.2;
+}
+
+class Super : public Base {
+ public:
+  virtual void ANNOTATE("Super pure virtual") noneGC() = 0;
+  virtual void allGC() = 0;
+  virtual void onSuper() { asm(""); }
+  void nonVirtualFunc() { asm(""); }
+};
+
+class Sub1 : public Super {
+ public:
+  void noneGC() override { foo(); }
+  void someGC() override ANNOTATE("Sub1 override") ANNOTATE("second attr") {
+    foo();
+  }
+  void someGC(int) override ANNOTATE("Sub1 override for int overload") {
+    foo();
+  }
+  void allGC() override {
+    foo();
+    bar();
+  }
+  void sibGC() override { foo(); }
+  void onBase() override { foo(); }
+} ANNOTATE("CSU1") ANNOTATE("CSU2");
+
+class Sub2 : public Super {
+ public:
+  void noneGC() override { foo(); }
+  void someGC() override {
+    foo();
+    bar();
+  }
+  void someGC(int) override {
+    foo();
+    bar();
+  }
+  void allGC() override {
+    foo();
+    bar();
+  }
+  void sibGC() override { foo(); }
+};
+
+class Sibling : public Base {
+ public:
+  virtual void noneGC() { foo(); }
+  void someGC() override {
+    foo();
+    bar();
+  }
+  void someGC(int) override {
+    foo();
+    bar();
+  }
+  virtual void allGC() {
+    foo();
+    bar();
+  }
+  void sibGC() override { bar(); }
+};
+
+class AutoSuppressGC {
+ public:
+  AutoSuppressGC() {}
+  ~AutoSuppressGC() {}
+} ANNOTATE("Suppress GC");
+
+void use(Cell*) { asm(""); }
+
+class nsISupports {
+ public:
+  virtual ANNOTATE("Can run script") void danger() { asm(""); }
+
+  virtual ~nsISupports() = 0;
+};
+
+class nsIPrincipal : public nsISupports {
+ public:
+  ~nsIPrincipal() override{};
+};
+
+struct JSPrincipals {
+  int debugToken;
+  JSPrincipals() = default;
+  virtual ~JSPrincipals() { GC(); }
+};
+
+class nsJSPrincipals : public nsIPrincipal, public JSPrincipals {
+ public:
+  void Release() { delete this; }
+};
+
+class SafePrincipals : public nsIPrincipal {
+ public:
+  ~SafePrincipals() { foo(); }
+};
+
+void f() {
+  Sub1 s1;
+  Sub2 s2;
+
+  static Cell cell;
+  {
+    Cell* c1 = &cell;
+    s1.noneGC();
+    use(c1);
+  }
+  {
+    Cell* c2 = &cell;
+    s2.someGC();
+    use(c2);
+  }
+  {
+    Cell* c3 = &cell;
+    s1.allGC();
+    use(c3);
+  }
+  {
+    Cell* c4 = &cell;
+    s2.noneGC();
+    use(c4);
+  }
+  {
+    Cell* c5 = &cell;
+    s2.someGC();
+    use(c5);
+  }
+  {
+    Cell* c6 = &cell;
+    s2.allGC();
+    use(c6);
+  }
+
+  Super* super = &s2;
+  {
+    Cell* c7 = &cell;
+    super->noneGC();
+    use(c7);
+  }
+  {
+    Cell* c8 = &cell;
+    super->someGC();
+    use(c8);
+  }
+  {
+    Cell* c9 = &cell;
+    super->allGC();
+    use(c9);
+  }
+
+  {
+    Cell* c10 = &cell;
+    s1.functionField();
+    use(c10);
+  }
+  {
+    Cell* c11 = &cell;
+    super->functionField();
+    use(c11);
+  }
+  {
+    Cell* c12 = &cell;
+    super->sibGC();
+    use(c12);
+  }
+
+  Base* base = &s2;
+  {
+    Cell* c13 = &cell;
+    base->sibGC();
+    use(c13);
+  }
+
+  nsJSPrincipals pals;
+  {
+    Cell* c14 = &cell;
+    nsISupports* p = &pals;
+    p->danger();
+    use(c14);
+  }
+
+  // Base defines, Sub1 overrides, static Super can call either.
+  {
+    Cell* c15 = &cell;
+    super->onBase();
+    use(c15);
+  }
+
+  {
+    Cell* c16 = &cell;
+    s2.someGC(7);
+    use(c16);
+  }
+
+  {
+    Cell* c17 = &cell;
+    super->someGC(7);
+    use(c17);
+  }
+
+  {
+    nsJSPrincipals* princ = new nsJSPrincipals();
+    Cell* c18 = &cell;
+    delete princ;  // Can GC
+    use(c18);
+  }
+
+  {
+    nsJSPrincipals* princ = new nsJSPrincipals();
+    nsISupports* supp = static_cast<nsISupports*>(princ);
+    Cell* c19 = &cell;
+    delete supp;  // Can GC
+    use(c19);
+  }
+
+  {
+    auto* safe = new SafePrincipals();
+    Cell* c20 = &cell;
+    delete safe;  // Cannot GC
+    use(c20);
+  }
+
+  {
+    auto* safe = new SafePrincipals();
+    nsISupports* supp = static_cast<nsISupports*>(safe);
+    Cell* c21 = &cell;
+    delete supp;  // Compiler thinks destructor can GC.
+    use(c21);
+  }
+}
diff --git a/js/src/devtools/rootAnalysis/t/virtual/test.py b/js/src/devtools/rootAnalysis/t/virtual/test.py
new file mode 100644
index 0000000000..e8474ae28b
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/t/virtual/test.py
@@ -0,0 +1,91 @@
+# 'test' is provided by the calling script.
+# flake8: noqa: F821
+
+test.compile("source.cpp")
+test.run_analysis_script("gcTypes")
+
+info = test.load_typeInfo()
+
+assert "Sub1" in info["OtherCSUTags"]
+assert ["CSU1", "CSU2"] == sorted(info["OtherCSUTags"]["Sub1"])
+assert "Base" in info["OtherFieldTags"]
+assert "someGC" in info["OtherFieldTags"]["Base"]
+assert "Sub1" in info["OtherFieldTags"]
+assert "someGC" in info["OtherFieldTags"]["Sub1"]
+
+# For now, fields with the same name (eg overloaded virtual methods) just
+# accumulate attributes.
+assert ["Sub1 override", "Sub1 override for int overload", "second attr"] == sorted(
+    info["OtherFieldTags"]["Sub1"]["someGC"]
+)
+
+gcFunctions = test.load_gcFunctions()
+
+assert "void Sub1::noneGC()" not in gcFunctions
+assert "void Sub1::someGC()" not in gcFunctions
+assert "void Sub1::someGC(int32)" not in gcFunctions
+assert "void Sub1::allGC()" in gcFunctions
+assert "void Sub2::noneGC()" not in gcFunctions
+assert "void Sub2::someGC()" in gcFunctions
+assert "void Sub2::someGC(int32)" in gcFunctions
+assert "void Sub2::allGC()" in gcFunctions
+
+callgraph = test.load_callgraph()
+
+assert callgraph.calleeGraph["void f()"]["Super.noneGC:0"]
+assert callgraph.calleeGraph["Super.noneGC:0"]["Sub1.noneGC:0"]
+assert callgraph.calleeGraph["Super.noneGC:0"]["Sub2.noneGC:0"]
+assert callgraph.calleeGraph["Sub1.noneGC:0"]["void Sub1::noneGC()"]
+assert callgraph.calleeGraph["Sub2.noneGC:0"]["void Sub2::noneGC()"]
+assert "void Sibling::noneGC()" not in callgraph.calleeGraph["Super.noneGC:0"]
+assert callgraph.calleeGraph["Super.onBase:0"]["Sub1.onBase:0"]
+assert callgraph.calleeGraph["Sub1.onBase:0"]["void Sub1::onBase()"]
+assert callgraph.calleeGraph["Super.onBase:0"]["void Base::onBase()"]
+assert "void Sibling::onBase()" not in callgraph.calleeGraph["Super.onBase:0"]
+
+hazards = test.load_hazards()
+hazmap = {haz.variable: haz for haz in hazards}
+
+assert "c1" not in hazmap
+assert "c2" in hazmap
+assert "c3" in hazmap
+assert "c4" not in hazmap
+assert "c5" in hazmap
+assert "c6" in hazmap
+assert "c7" not in hazmap
+assert "c8" in hazmap
+assert "c9" in hazmap
+assert "c10" in hazmap
+assert "c11" in hazmap
+
+# Virtual resolution should take the static type into account: the only method
+# implementations considered should be those of descendants, even if the
+# virtual method is inherited and not overridden in the static class. (Base
+# defines sibGC() as pure virtual, Super inherits it without overriding,
+# Sibling and Sub2 both implement it.)
+
+# Call Base.sibGC on a Super pointer: can only call Sub2.sibGC(), which does not GC.
+# In particular, PEdgeCallInstance.Exp.Field.FieldCSU.Type = {Kind: "CSU", Name="Super"}
+assert "c12" not in hazmap
+# Call Base.sibGC on a Base pointer; can call Sibling.sibGC(), which GCs.
+assert "c13" in hazmap
+
+# Call nsISupports.danger() which is annotated to be overridable and hence can GC.
+assert "c14" in hazmap
+
+# someGC(int) overload
+assert "c16" in hazmap
+assert "c17" in hazmap
+
+# Super.onBase() could call the GC'ing Base::onBase().
+assert "c15" in hazmap
+
+# virtual ~nsJSPrincipals calls ~JSPrincipals calls GC.
+assert "c18" in hazmap
+assert "c19" in hazmap
+
+# ~SafePrincipals does not GC.
+assert "c20" not in hazmap
+
+# ...but when cast to a nsISupports*, the compiler can't tell that it won't.
+assert "c21" in hazmap
diff --git a/js/src/devtools/rootAnalysis/utility.js b/js/src/devtools/rootAnalysis/utility.js
new file mode 100644
index 0000000000..b91128f280
--- /dev/null
+++ b/js/src/devtools/rootAnalysis/utility.js
@@ -0,0 +1,419 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this file,
+ * You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+/* -*- indent-tabs-mode: nil; js-indent-level: 4 -*- */
+
+"use strict";
+
+loadRelativeToScript('dumpCFG.js');
+
+// Attribute bits - each call edge may carry a set of 'attrs' bits, saying eg
+// that the edge takes place within a scope where GC is suppressed, for
+// example.
+var ATTR_GC_SUPPRESSED     = 1;
+var ATTR_CANSCRIPT_BOUNDED = 2; // Unimplemented
+var ATTR_DOM_ITERATING     = 4; // Unimplemented
+var ATTR_NONRELEASING      = 8; // ~RefPtr of value whose refcount will not go to zero
+
+var ATTRS_NONE             = 0;
+var ATTRS_ALL              = 7; // All possible bits set
+
+// The traversal algorithms we run will recurse into children if you change any
+// attrs bit to zero. Use all bits set to maximally attributed, including
+// additional bits that all just mean "unvisited", so that the first time we
+// see a node with this attrs, we're guaranteed to turn at least one bit off
+// and thereby keep going.
+var ATTRS_UNVISITED = 0xffff;
+
+// gcc appends this to mangled function names for "not in charge"
+// constructors/destructors.
+var internalMarker = " *INTERNAL* ";
+
+if (! Set.prototype.hasOwnProperty("update")) {
+    Object.defineProperty(Set.prototype, "update", {
+        value: function (collection) {
+            for (let elt of collection)
+                this.add(elt);
+        }
+    });
+}
+
+function assert(x, msg)
+{
+    if (x)
+        return;
+    debugger;
+    if (msg)
+        throw new Error("assertion failed: " + msg + "\n");
+    else
+        throw new Error("assertion failed");
+}
+
+function defined(x) {
+    return x !== undefined;
+}
+
+function xprint(x, padding)
+{
+    if (!padding)
+        padding = "";
+    if (x instanceof Array) {
+        print(padding + "[");
+        for (var elem of x)
+            xprint(elem, padding + " ");
+        print(padding + "]");
+    } else if (x instanceof Object) {
+        print(padding + "{");
+        for (var prop in x) {
+            print(padding + " " + prop + ":");
+            xprint(x[prop], padding + "  ");
+        }
+        print(padding + "}");
+    } else {
+        print(padding + x);
+    }
+}
+
+// Command-line argument parser.
+//
+// `parameters` is a dict of parameters specs, each of which is a dict with keys:
+//
+//   - name: name of option, prefixed with "--" if it is named (otherwise, it
+//     is interpreted as a positional parameter.)
+//   - dest: key to store the result in, defaulting to the parameter name without
+//     any leading "--"" and with dashes replaced with underscores.
+//   - default: value of option if no value is given. Positional parameters with
+//     a default value are optional. If no default is given, the parameter's name
+//     is not included in the return value.
+//   - type: `bool` if it takes no argument, otherwise an argument is required.
+//     Named arguments default to 'bool', positional arguments to 'string'.
+//   - nargs: the only supported value is `+`, which means to grab all following
+//     arguments, up to the next named option, and store them as a list.
+//
+// The command line is parsed for `--foo=value` and `--bar` arguments.
+//
+// Return value is a dict of parameter values, keyed off of `dest` as determined
+// above. An extra option named "rest" will be set to the list of all remaining
+// arguments passed in.
+//
+function parse_options(parameters, inArgs = scriptArgs) {
+    const options = {};
+
+    const named = {};
+    const positional = [];
+    for (const param of parameters) {
+        if (param.name.startsWith("-")) {
+            named[param.name] = param;
+            if (!param.dest) {
+                if (!param.name.startsWith("--")) {
+                    throw new Error(`parameter '${param.name}' requires param.dest to be set`);
+                }
+                param.dest = param.name.substring(2).replace("-", "_");
+            }
+        } else {
+            if (!('default' in param) && positional.length > 0 && ('default' in positional.at(-1))) {
+                throw new Error(`required parameter '${param.name}' follows optional parameter`);
+            }
+            param.positional = true;
+            positional.push(param);
+            param.dest = param.dest || param.name.replace("-", "_");
+        }
+
+        if (!param.type) {
+            if (param.nargs === "+") {
+                param.type = "list";
+            } else if (param.positional) {
+                param.type = "string";
+            } else {
+                param.type = "bool";
+            }
+        }
+
+        if ('default' in param) {
+            options[param.dest] = param.default;
+        }
+    }
+
+    options.rest = [];
+    const args = [...inArgs];
+    let grabbing_into = undefined;
+    while (args.length > 0) {
+        let arg = args.shift();
+        let param;
+        if (arg.startsWith("-") && arg in named) {
+            param = named[arg];
+            if (param.type !== 'bool') {
+                if (args.length == 0) {
+                    throw(new Error(`${param.name} requires an argument`));
+                }
+                arg = args.shift();
+            }
+        } else {
+            const pos = arg.indexOf("=");
+            if (pos != -1) {
+                const name = arg.substring(0, pos);
+                param = named[name];
+                if (!param) {
+                    throw(new Error(`Unknown option '${name}'`));
+                } else if (param.type === 'bool') {
+                    throw(new Error(`--${param.name} does not take an argument`));
+                }
+                arg = arg.substring(pos + 1);
+            }
+        }
+
+        // If this isn't a --named param, and we're not accumulating into a nargs="+" param, then
+        // use the next positional.
+        if (!param && !grabbing_into && positional.length > 0) {
+            param = positional.shift();
+        }
+
+        // If a parameter was identified, then any old accumulator is done and we might start a new one.
+        if (param) {
+            if (param.type === 'list') {
+                grabbing_into = options[param.dest] = options[param.dest] || [];
+            } else {
+                grabbing_into = undefined;
+            }
+        }
+
+        if (grabbing_into) {
+            grabbing_into.push(arg);
+        } else if (param) {
+            if (param.type === 'bool') {
+                options[param.dest] = true;
+            } else {
+                options[param.dest] = arg;
+            }
+        } else {
+            options.rest.push(arg);
+        }
+    }
+
+    for (const param of positional) {
+        if (!('default' in param)) {
+            throw(new Error(`'${param.name}' option is required`));
+        }
+    }
+
+    for (const param of parameters) {
+        if (param.nargs === '+' && options[param.dest].length == 0) {
+            throw(new Error(`at least one value required for option '${param.name}'`));
+        }
+    }
+
+    return options;
+}
+
+function sameBlockId(id0, id1)
+{
+    if (id0.Kind != id1.Kind)
+        return false;
+    if (!sameVariable(id0.Variable, id1.Variable))
+        return false;
+    if (id0.Kind == "Loop" && id0.Loop != id1.Loop)
+        return false;
+    return true;
+}
+
+function sameVariable(var0, var1)
+{
+    assert("Name" in var0 || var0.Kind == "This" || var0.Kind == "Return");
+    assert("Name" in var1 || var1.Kind == "This" || var1.Kind == "Return");
+    if ("Name" in var0)
+        return "Name" in var1 && var0.Name[0] == var1.Name[0];
+    return var0.Kind == var1.Kind;
+}
+
+function blockIdentifier(body)
+{
+    if (body.BlockId.Kind == "Loop")
+        return body.BlockId.Loop;
+    assert(body.BlockId.Kind == "Function", "body.Kind should be Function, not " + body.BlockId.Kind);
+    return body.BlockId.Variable.Name[0];
+}
+
+function collectBodyEdges(body)
+{
+    body.predecessors = [];
+    body.successors = [];
+    if (!("PEdge" in body))
+        return;
+
+    for (var edge of body.PEdge) {
+        var [ source, target ] = edge.Index;
+        if (!(target in body.predecessors))
+            body.predecessors[target] = [];
+        body.predecessors[target].push(edge);
+        if (!(source in body.successors))
+            body.successors[source] = [];
+        body.successors[source].push(edge);
+    }
+}
+
+function getPredecessors(body)
+{
+    if (!('predecessors' in body))
+        collectBodyEdges(body);
+    return body.predecessors;
+}
+
+function getSuccessors(body)
+{
+    if (!('successors' in body))
+        collectBodyEdges(body);
+    return body.successors;
+}
+
+// Split apart a function from sixgill into its mangled and unmangled name. If
+// no mangled name was given, use the unmangled name as its mangled name
+function splitFunction(func)
+{
+    var split = func.indexOf("$");
+    if (split != -1)
+        return [ func.substr(0, split), func.substr(split+1) ];
+    split = func.indexOf("|");
+    if (split != -1)
+        return [ func.substr(0, split), func.substr(split+1) ];
+    return [ func, func ];
+}
+
+function mangled(fullname)
+{
+    var [ mangled, unmangled ] = splitFunction(fullname);
+    return mangled;
+}
+
+function readable(fullname)
+{
+    var [ mangled, unmangled ] = splitFunction(fullname);
+    return unmangled;
+}
+
+function xdbLibrary()
+{
+    var lib = ctypes.open(os.getenv('XDB'));
+    var api = {
+        open: lib.declare("xdb_open", ctypes.default_abi, ctypes.void_t, ctypes.char.ptr),
+        min_data_stream: lib.declare("xdb_min_data_stream", ctypes.default_abi, ctypes.int),
+        max_data_stream: lib.declare("xdb_max_data_stream", ctypes.default_abi, ctypes.int),
+        read_key: lib.declare("xdb_read_key", ctypes.default_abi, ctypes.char.ptr, ctypes.int),
+        read_entry: lib.declare("xdb_read_entry", ctypes.default_abi, ctypes.char.ptr, ctypes.char.ptr),
+        free_string: lib.declare("xdb_free", ctypes.default_abi, ctypes.void_t, ctypes.char.ptr)
+    };
+    try {
+        api.lookup_key = lib.declare("xdb_lookup_key", ctypes.default_abi, ctypes.int, ctypes.char.ptr);
+    } catch (e) {
+        // lookup_key is for development use only and is not strictly necessary.
+    }
+    return api;
+}
+
+function openLibrary(names) {
+    for (const name of names) {
+        try {
+            return ctypes.open(name);
+        } catch(e) {
+        }
+    }
+    return undefined;
+}
+
+function cLibrary()
+{
+    const lib = openLibrary(['libc.so.6', 'libc.so', 'libc.dylib']);
+    if (!lib) {
+        throw new Error("Unable to open libc");
+    }
+
+    if (getBuildConfiguration()["moz-memory"]) {
+        throw new Error("cannot use libc functions with --enable-jemalloc, since they will be routed " +
+                        "through jemalloc, but calling libc.free() directly will bypass it and the " +
+                        "malloc/free will be mismatched");
+    }
+
+    return {
+        fopen: lib.declare("fopen", ctypes.default_abi, ctypes.void_t.ptr, ctypes.char.ptr, ctypes.char.ptr),
+        getline: lib.declare("getline", ctypes.default_abi, ctypes.ssize_t, ctypes.char.ptr.ptr, ctypes.size_t.ptr, ctypes.void_t.ptr),
+        fclose: lib.declare("fclose", ctypes.default_abi, ctypes.int, ctypes.void_t.ptr),
+        free: lib.declare("free", ctypes.default_abi, ctypes.void_t, ctypes.void_t.ptr),
+    };
+}
+
+function* readFileLines_gen(filename)
+{
+    var libc = cLibrary();
+    var linebuf = ctypes.char.ptr();
+    var bufsize = ctypes.size_t(0);
+    var fp = libc.fopen(filename, "r");
+    if (fp.isNull())
+        throw new Error("Unable to open '" + filename + "'");
+
+    while (libc.getline(linebuf.address(), bufsize.address(), fp) > 0)
+        yield linebuf.readString();
+    libc.fclose(fp);
+    libc.free(ctypes.void_t.ptr(linebuf));
+}
+
+function addToKeyedList(collection, key, entry)
+{
+    if (!(key in collection))
+        collection[key] = [];
+    collection[key].push(entry);
+    return collection[key];
+}
+
+function addToMappedList(map, key, entry)
+{
+    if (!map.has(key))
+        map.set(key, []);
+    map.get(key).push(entry);
+    return map.get(key);
+}
+
+function loadTypeInfo(filename)
+{
+    return JSON.parse(os.file.readFile(filename));
+}
+
+// Given the range `first` .. `last`, break it down into `count` batches and
+// return the start of the (1-based) `num` batch.
+function batchStart(num, count, first, last) {
+  const N = (last - first) + 1;
+  return Math.floor((num - 1) / count * N) + first;
+}
+
+// As above, but return the last value in the (1-based) `num` batch.
+function batchLast(num, count, first, last) {
+  const N = (last - first) + 1;
+  return Math.floor(num / count * N) + first - 1;
+}
+
+// Debugging tool. See usage below.
+function PropertyTracer(traced_prop, check) {
+    return {
+        matches(prop, value) {
+            if (prop != traced_prop)
+                return false;
+            if ('value' in check)
+                return value == check.value;
+            return true;
+        },
+
+        // Also called when defining a property.
+        set(obj, prop, value) {
+            if (this.matches(prop, value))
+                debugger;
+            return Reflect.set(...arguments);
+        },
+    };
+}
+
+// Usage: var myobj = traced({}, 'name', {value: 'Bob'})
+//
+// This will execute a `debugger;` statement when myobj['name'] is defined or
+// set to 'Bob'.
+function traced(obj, traced_prop, check) {
+  return new Proxy(obj, PropertyTracer(traced_prop, check));
+}