Add m-esr52 at 52.6.0

1 files changed, 2077 insertions, 0 deletions

diff --git a/js/src/vm/Stack.h b/js/src/vm/Stack.h
new file mode 100644
index 000000000..552738d89
--- /dev/null
+++ b/js/src/vm/Stack.h
@@ -0,0 +1,2077 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
+ * vim: set ts=8 sts=4 et sw=4 tw=99:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef vm_Stack_h
+#define vm_Stack_h
+
+#include "mozilla/Atomics.h"
+#include "mozilla/Maybe.h"
+#include "mozilla/MemoryReporting.h"
+#include "mozilla/Variant.h"
+
+#include "jsfun.h"
+#include "jsscript.h"
+#include "jsutil.h"
+
+#include "gc/Rooting.h"
+#include "jit/JitFrameIterator.h"
+#ifdef CHECK_OSIPOINT_REGISTERS
+#include "jit/Registers.h" // for RegisterDump
+#endif
+#include "js/RootingAPI.h"
+#include "vm/ArgumentsObject.h"
+#include "vm/SavedFrame.h"
+#include "wasm/WasmFrameIterator.h"
+
+struct JSCompartment;
+
+namespace JS {
+namespace dbg {
+#ifdef JS_BROKEN_GCC_ATTRIBUTE_WARNING
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wattributes"
+#endif // JS_BROKEN_GCC_ATTRIBUTE_WARNING
+
+class JS_PUBLIC_API(AutoEntryMonitor);
+
+#ifdef JS_BROKEN_GCC_ATTRIBUTE_WARNING
+#pragma GCC diagnostic pop
+#endif // JS_BROKEN_GCC_ATTRIBUTE_WARNING
+} // namespace dbg
+} // namespace JS
+
+namespace js {
+
+class InterpreterRegs;
+class CallObject;
+class FrameIter;
+class EnvironmentObject;
+class ScriptFrameIter;
+class SPSProfiler;
+class InterpreterFrame;
+class LexicalEnvironmentObject;
+class EnvironmentIter;
+class EnvironmentCoordinate;
+
+class SavedFrame;
+
+namespace jit {
+class CommonFrameLayout;
+}
+namespace wasm {
+class Instance;
+}
+
+// VM stack layout
+//
+// A JSRuntime's stack consists of a linked list of activations. Every activation
+// contains a number of scripted frames that are either running in the interpreter
+// (InterpreterActivation) or JIT code (JitActivation). The frames inside a single
+// activation are contiguous: whenever C++ calls back into JS, a new activation is
+// pushed.
+//
+// Every activation is tied to a single JSContext and JSCompartment. This means we
+// can reconstruct a given context's stack by skipping activations belonging to other
+// contexts. This happens whenever an embedding enters the JS engine on cx1 and
+// then, from a native called by the JS engine, reenters the VM on cx2.
+
+// Interpreter frames (InterpreterFrame)
+//
+// Each interpreter script activation (global or function code) is given a
+// fixed-size header (js::InterpreterFrame). The frame contains bookkeeping
+// information about the activation and links to the previous frame.
+//
+// The values after an InterpreterFrame in memory are its locals followed by its
+// expression stack. InterpreterFrame::argv_ points to the frame's arguments.
+// Missing formal arguments are padded with |undefined|, so the number of
+// arguments is always >= the number of formals.
+//
+// The top of an activation's current frame's expression stack is pointed to by
+// the activation's "current regs", which contains the stack pointer 'sp'. In
+// the interpreter, sp is adjusted as individual values are pushed and popped
+// from the stack and the InterpreterRegs struct (pointed to by the
+// InterpreterActivation) is a local var of js::Interpret.
+
+enum MaybeCheckAliasing { CHECK_ALIASING = true, DONT_CHECK_ALIASING = false };
+enum MaybeCheckTDZ { CheckTDZ = true, DontCheckTDZ = false };
+
+/*****************************************************************************/
+
+namespace jit {
+    class BaselineFrame;
+    class RematerializedFrame;
+} // namespace jit
+
+/*
+ * Pointer to either a ScriptFrameIter::Data, an InterpreterFrame, or a Baseline
+ * JIT frame.
+ *
+ * The Debugger may cache ScriptFrameIter::Data as a bookmark to reconstruct a
+ * ScriptFrameIter without doing a full stack walk.
+ *
+ * There is no way to directly create such an AbstractFramePtr. To do so, the
+ * user must call ScriptFrameIter::copyDataAsAbstractFramePtr().
+ *
+ * ScriptFrameIter::abstractFramePtr() will never return an AbstractFramePtr
+ * that is in fact a ScriptFrameIter::Data.
+ *
+ * To recover a ScriptFrameIter settled at the location pointed to by an
+ * AbstractFramePtr, use the THIS_FRAME_ITER macro in Debugger.cpp. As an
+ * aside, no asScriptFrameIterData() is provided because C++ is stupid and
+ * cannot forward declare inner classes.
+ */
+
+class AbstractFramePtr
+{
+    friend class FrameIter;
+
+    uintptr_t ptr_;
+
+    enum {
+        Tag_ScriptFrameIterData = 0x0,
+        Tag_InterpreterFrame = 0x1,
+        Tag_BaselineFrame = 0x2,
+        Tag_RematerializedFrame = 0x3,
+        TagMask = 0x3
+    };
+
+  public:
+    AbstractFramePtr()
+      : ptr_(0)
+    {}
+
+    MOZ_IMPLICIT AbstractFramePtr(InterpreterFrame* fp)
+      : ptr_(fp ? uintptr_t(fp) | Tag_InterpreterFrame : 0)
+    {
+        MOZ_ASSERT_IF(fp, asInterpreterFrame() == fp);
+    }
+
+    MOZ_IMPLICIT AbstractFramePtr(jit::BaselineFrame* fp)
+      : ptr_(fp ? uintptr_t(fp) | Tag_BaselineFrame : 0)
+    {
+        MOZ_ASSERT_IF(fp, asBaselineFrame() == fp);
+    }
+
+    MOZ_IMPLICIT AbstractFramePtr(jit::RematerializedFrame* fp)
+      : ptr_(fp ? uintptr_t(fp) | Tag_RematerializedFrame : 0)
+    {
+        MOZ_ASSERT_IF(fp, asRematerializedFrame() == fp);
+    }
+
+    static AbstractFramePtr FromRaw(void* raw) {
+        AbstractFramePtr frame;
+        frame.ptr_ = uintptr_t(raw);
+        return frame;
+    }
+
+    bool isScriptFrameIterData() const {
+        return !!ptr_ && (ptr_ & TagMask) == Tag_ScriptFrameIterData;
+    }
+    bool isInterpreterFrame() const {
+        return (ptr_ & TagMask) == Tag_InterpreterFrame;
+    }
+    InterpreterFrame* asInterpreterFrame() const {
+        MOZ_ASSERT(isInterpreterFrame());
+        InterpreterFrame* res = (InterpreterFrame*)(ptr_ & ~TagMask);
+        MOZ_ASSERT(res);
+        return res;
+    }
+    bool isBaselineFrame() const {
+        return (ptr_ & TagMask) == Tag_BaselineFrame;
+    }
+    jit::BaselineFrame* asBaselineFrame() const {
+        MOZ_ASSERT(isBaselineFrame());
+        jit::BaselineFrame* res = (jit::BaselineFrame*)(ptr_ & ~TagMask);
+        MOZ_ASSERT(res);
+        return res;
+    }
+    bool isRematerializedFrame() const {
+        return (ptr_ & TagMask) == Tag_RematerializedFrame;
+    }
+    jit::RematerializedFrame* asRematerializedFrame() const {
+        MOZ_ASSERT(isRematerializedFrame());
+        jit::RematerializedFrame* res = (jit::RematerializedFrame*)(ptr_ & ~TagMask);
+        MOZ_ASSERT(res);
+        return res;
+    }
+
+    void* raw() const { return reinterpret_cast<void*>(ptr_); }
+
+    bool operator ==(const AbstractFramePtr& other) const { return ptr_ == other.ptr_; }
+    bool operator !=(const AbstractFramePtr& other) const { return ptr_ != other.ptr_; }
+
+    explicit operator bool() const { return !!ptr_; }
+
+    inline JSObject* environmentChain() const;
+    inline CallObject& callObj() const;
+    inline bool initFunctionEnvironmentObjects(JSContext* cx);
+    inline bool pushVarEnvironment(JSContext* cx, HandleScope scope);
+    template <typename SpecificEnvironment>
+    inline void pushOnEnvironmentChain(SpecificEnvironment& env);
+    template <typename SpecificEnvironment>
+    inline void popOffEnvironmentChain();
+
+    inline JSCompartment* compartment() const;
+
+    inline bool hasInitialEnvironment() const;
+    inline bool isGlobalFrame() const;
+    inline bool isModuleFrame() const;
+    inline bool isEvalFrame() const;
+    inline bool isDebuggerEvalFrame() const;
+    inline bool hasCachedSavedFrame() const;
+    inline void setHasCachedSavedFrame();
+
+    inline JSScript* script() const;
+    inline JSFunction* callee() const;
+    inline Value calleev() const;
+    inline Value& thisArgument() const;
+
+    inline Value newTarget() const;
+
+    inline bool debuggerNeedsCheckPrimitiveReturn() const;
+
+    inline bool isFunctionFrame() const;
+    inline bool isNonStrictDirectEvalFrame() const;
+    inline bool isStrictEvalFrame() const;
+
+    inline unsigned numActualArgs() const;
+    inline unsigned numFormalArgs() const;
+
+    inline Value* argv() const;
+
+    inline bool hasArgs() const;
+    inline bool hasArgsObj() const;
+    inline ArgumentsObject& argsObj() const;
+    inline void initArgsObj(ArgumentsObject& argsobj) const;
+    inline bool createSingleton() const;
+
+    inline Value& unaliasedLocal(uint32_t i);
+    inline Value& unaliasedFormal(unsigned i, MaybeCheckAliasing checkAliasing = CHECK_ALIASING);
+    inline Value& unaliasedActual(unsigned i, MaybeCheckAliasing checkAliasing = CHECK_ALIASING);
+    template <class Op> inline void unaliasedForEachActual(JSContext* cx, Op op);
+
+    inline bool prevUpToDate() const;
+    inline void setPrevUpToDate() const;
+    inline void unsetPrevUpToDate() const;
+
+    inline bool isDebuggee() const;
+    inline void setIsDebuggee();
+    inline void unsetIsDebuggee();
+
+    inline HandleValue returnValue() const;
+    inline void setReturnValue(const Value& rval) const;
+
+    friend void GDBTestInitAbstractFramePtr(AbstractFramePtr&, void*);
+    friend void GDBTestInitAbstractFramePtr(AbstractFramePtr&, InterpreterFrame*);
+    friend void GDBTestInitAbstractFramePtr(AbstractFramePtr&, jit::BaselineFrame*);
+    friend void GDBTestInitAbstractFramePtr(AbstractFramePtr&, jit::RematerializedFrame*);
+};
+
+class NullFramePtr : public AbstractFramePtr
+{
+  public:
+    NullFramePtr()
+      : AbstractFramePtr()
+    { }
+};
+
+enum MaybeConstruct { NO_CONSTRUCT = false, CONSTRUCT = true };
+
+/*****************************************************************************/
+
+class InterpreterFrame
+{
+    enum Flags : uint32_t {
+        CONSTRUCTING           =        0x1,  /* frame is for a constructor invocation */
+
+        RESUMED_GENERATOR      =        0x2,  /* frame is for a resumed generator invocation */
+
+        /* Function prologue state */
+        HAS_INITIAL_ENV        =        0x4,  /* callobj created for function or var env for eval */
+        HAS_ARGS_OBJ           =        0x8,  /* ArgumentsObject created for needsArgsObj script */
+
+        /* Lazy frame initialization */
+        HAS_RVAL               =       0x10,  /* frame has rval_ set */
+
+        /* Debugger state */
+        PREV_UP_TO_DATE        =       0x20,  /* see DebugScopes::updateLiveScopes */
+
+        /*
+         * See comment above 'isDebuggee' in jscompartment.h for explanation of
+         * invariants of debuggee compartments, scripts, and frames.
+         */
+        DEBUGGEE               =       0x40,  /* Execution is being observed by Debugger */
+
+        /* Used in tracking calls and profiling (see vm/SPSProfiler.cpp) */
+        HAS_PUSHED_SPS_FRAME   =       0x80,  /* SPS was notified of entry */
+
+        /*
+         * If set, we entered one of the JITs and ScriptFrameIter should skip
+         * this frame.
+         */
+        RUNNING_IN_JIT         =      0x100,
+
+        /* Miscellaneous state. */
+        CREATE_SINGLETON       =      0x200,  /* Constructed |this| object should be singleton. */
+
+        /*
+         * If set, this frame has been on the stack when
+         * |js::SavedStacks::saveCurrentStack| was called, and so there is a
+         * |js::SavedFrame| object cached for this frame.
+         */
+        HAS_CACHED_SAVED_FRAME =      0x400,
+    };
+
+    mutable uint32_t    flags_;         /* bits described by Flags */
+    uint32_t            nactual_;       /* number of actual arguments, for function frames */
+    JSScript*           script_;        /* the script we're executing */
+    JSObject*           envChain_;      /* current environment chain */
+    Value               rval_;          /* if HAS_RVAL, return value of the frame */
+    ArgumentsObject*    argsObj_;       /* if HAS_ARGS_OBJ, the call's arguments object */
+
+    /*
+     * Previous frame and its pc and sp. Always nullptr for
+     * InterpreterActivation's entry frame, always non-nullptr for inline
+     * frames.
+     */
+    InterpreterFrame*   prev_;
+    jsbytecode*         prevpc_;
+    Value*              prevsp_;
+
+    void*               unused;
+
+    /*
+     * For an eval-in-frame DEBUGGER_EVAL frame, the frame in whose scope
+     * we're evaluating code. Iteration treats this as our previous frame.
+     */
+    AbstractFramePtr    evalInFramePrev_;
+
+    Value*              argv_;         /* If hasArgs(), points to frame's arguments. */
+    LifoAlloc::Mark     mark_;          /* Used to release memory for this frame. */
+
+    static void staticAsserts() {
+        JS_STATIC_ASSERT(offsetof(InterpreterFrame, rval_) % sizeof(Value) == 0);
+        JS_STATIC_ASSERT(sizeof(InterpreterFrame) % sizeof(Value) == 0);
+    }
+
+    /*
+     * The utilities are private since they are not able to assert that only
+     * unaliased vars/formals are accessed. Normal code should prefer the
+     * InterpreterFrame::unaliased* members (or InterpreterRegs::stackDepth for
+     * the usual "depth is at least" assertions).
+     */
+    Value* slots() const { return (Value*)(this + 1); }
+    Value* base() const { return slots() + script()->nfixed(); }
+
+    friend class FrameIter;
+    friend class InterpreterRegs;
+    friend class InterpreterStack;
+    friend class jit::BaselineFrame;
+
+    /*
+     * Frame initialization, called by InterpreterStack operations after acquiring
+     * the raw memory for the frame:
+     */
+
+    /* Used for Invoke and Interpret. */
+    void initCallFrame(JSContext* cx, InterpreterFrame* prev, jsbytecode* prevpc, Value* prevsp,
+                       JSFunction& callee, JSScript* script, Value* argv, uint32_t nactual,
+                       MaybeConstruct constructing);
+
+    /* Used for global and eval frames. */
+    void initExecuteFrame(JSContext* cx, HandleScript script, AbstractFramePtr prev,
+                          const Value& newTargetValue, HandleObject envChain);
+
+  public:
+    /*
+     * Frame prologue/epilogue
+     *
+     * Every stack frame must have 'prologue' called before executing the
+     * first op and 'epilogue' called after executing the last op and before
+     * popping the frame (whether the exit is exceptional or not).
+     *
+     * For inline JS calls/returns, it is easy to call the prologue/epilogue
+     * exactly once. When calling JS from C++, Invoke/Execute push the stack
+     * frame but do *not* call the prologue/epilogue. That means Interpret
+     * must call the prologue/epilogue for the entry frame. This scheme
+     * simplifies jit compilation.
+     *
+     * An important corner case is what happens when an error occurs (OOM,
+     * over-recursed) after pushing the stack frame but before 'prologue' is
+     * called or completes fully. To simplify usage, 'epilogue' does not assume
+     * 'prologue' has completed and handles all the intermediate state details.
+     */
+
+    bool prologue(JSContext* cx);
+    void epilogue(JSContext* cx, jsbytecode* pc);
+
+    bool checkReturn(JSContext* cx, HandleValue thisv);
+
+    bool initFunctionEnvironmentObjects(JSContext* cx);
+
+    /*
+     * Initialize locals of newly-pushed frame to undefined.
+     */
+    void initLocals();
+
+    /*
+     * Stack frame type
+     *
+     * A stack frame may have one of four types, which determines which
+     * members of the frame may be accessed and other invariants:
+     *
+     *  global frame:   execution of global code
+     *  function frame: execution of function code
+     *  module frame:   execution of a module
+     *  eval frame:     execution of eval code
+     */
+
+    bool isGlobalFrame() const {
+        return script_->isGlobalCode();
+    }
+
+    bool isModuleFrame() const {
+        return script_->module();
+    }
+
+    bool isEvalFrame() const {
+        return script_->isForEval();
+    }
+
+    bool isFunctionFrame() const {
+        return script_->functionNonDelazifying();
+    }
+
+    inline bool isStrictEvalFrame() const {
+        return isEvalFrame() && script()->strict();
+    }
+
+    bool isNonStrictEvalFrame() const {
+        return isEvalFrame() && !script()->strict();
+    }
+
+    bool isNonGlobalEvalFrame() const;
+
+    bool isNonStrictDirectEvalFrame() const {
+        return isNonStrictEvalFrame() && isNonGlobalEvalFrame();
+    }
+
+    /*
+     * Previous frame
+     *
+     * A frame's 'prev' frame is either null or the previous frame pointed to
+     * by cx->regs->fp when this frame was pushed. Often, given two prev-linked
+     * frames, the next-frame is a function or eval that was called by the
+     * prev-frame, but not always: the prev-frame may have called a native that
+     * reentered the VM through JS_CallFunctionValue on the same context
+     * (without calling JS_SaveFrameChain) which pushed the next-frame. Thus,
+     * 'prev' has little semantic meaning and basically just tells the VM what
+     * to set cx->regs->fp to when this frame is popped.
+     */
+
+    InterpreterFrame* prev() const {
+        return prev_;
+    }
+
+    AbstractFramePtr evalInFramePrev() const {
+        MOZ_ASSERT(isEvalFrame());
+        return evalInFramePrev_;
+    }
+
+    /*
+     * (Unaliased) locals and arguments
+     *
+     * Only non-eval function frames have arguments. The arguments pushed by
+     * the caller are the 'actual' arguments. The declared arguments of the
+     * callee are the 'formal' arguments. When the caller passes less actual
+     * arguments, missing formal arguments are padded with |undefined|.
+     *
+     * When a local/formal variable is aliased (accessed by nested closures,
+     * environment operations, or 'arguments'), the canonical location for
+     * that value is the slot of an environment object.  Aliased locals don't
+     * have stack slots assigned to them.  These functions assert that
+     * accesses to stack values are unaliased.
+     */
+
+    inline Value& unaliasedLocal(uint32_t i);
+
+    bool hasArgs() const { return isFunctionFrame(); }
+    inline Value& unaliasedFormal(unsigned i, MaybeCheckAliasing = CHECK_ALIASING);
+    inline Value& unaliasedActual(unsigned i, MaybeCheckAliasing = CHECK_ALIASING);
+    template <class Op> inline void unaliasedForEachActual(Op op);
+
+    unsigned numFormalArgs() const { MOZ_ASSERT(hasArgs()); return callee().nargs(); }
+    unsigned numActualArgs() const { MOZ_ASSERT(hasArgs()); return nactual_; }
+
+    /* Watch out, this exposes a pointer to the unaliased formal arg array. */
+    Value* argv() const { MOZ_ASSERT(hasArgs()); return argv_; }
+
+    /*
+     * Arguments object
+     *
+     * If a non-eval function has script->needsArgsObj, an arguments object is
+     * created in the prologue and stored in the local variable for the
+     * 'arguments' binding (script->argumentsLocal). Since this local is
+     * mutable, the arguments object can be overwritten and we can "lose" the
+     * arguments object. Thus, InterpreterFrame keeps an explicit argsObj_ field so
+     * that the original arguments object is always available.
+     */
+
+    ArgumentsObject& argsObj() const;
+    void initArgsObj(ArgumentsObject& argsobj);
+
+    JSObject* createRestParameter(JSContext* cx);
+
+    /*
+     * Environment chain
+     *
+     * In theory, the environment chain would contain an object for every
+     * lexical scope. However, only objects that are required for dynamic
+     * lookup are actually created.
+     *
+     * Given that an InterpreterFrame corresponds roughly to a ES Execution
+     * Context (ES 10.3), InterpreterFrame::varObj corresponds to the
+     * VariableEnvironment component of a Exection Context. Intuitively, the
+     * variables object is where new bindings (variables and functions) are
+     * stored. One might expect that this is either the Call object or
+     * envChain.globalObj for function or global code, respectively, however
+     * the JSAPI allows calls of Execute to specify a variables object on the
+     * environment chain other than the call/global object. This allows
+     * embeddings to run multiple scripts under the same global, each time
+     * using a new variables object to collect and discard the script's global
+     * variables.
+     */
+
+    inline HandleObject environmentChain() const;
+
+    inline EnvironmentObject& aliasedEnvironment(EnvironmentCoordinate ec) const;
+    inline GlobalObject& global() const;
+    inline CallObject& callObj() const;
+    inline JSObject& varObj() const;
+    inline LexicalEnvironmentObject& extensibleLexicalEnvironment() const;
+
+    template <typename SpecificEnvironment>
+    inline void pushOnEnvironmentChain(SpecificEnvironment& env);
+    template <typename SpecificEnvironment>
+    inline void popOffEnvironmentChain();
+    inline void replaceInnermostEnvironment(EnvironmentObject& env);
+
+    // Push a VarEnvironmentObject for function frames of functions that have
+    // parameter expressions with closed over var bindings.
+    bool pushVarEnvironment(JSContext* cx, HandleScope scope);
+
+    /*
+     * For lexical envs with aliased locals, these interfaces push and pop
+     * entries on the environment chain.  The "freshen" operation replaces the
+     * current lexical env with a fresh copy of it, to implement semantics
+     * providing distinct bindings per iteration of a for(;;) loop whose head
+     * has a lexical declaration.  The "recreate" operation replaces the
+     * current lexical env with a copy of it containing uninitialized
+     * bindings, to implement semantics providing distinct bindings per
+     * iteration of a for-in/of loop.
+     */
+
+    bool pushLexicalEnvironment(JSContext* cx, Handle<LexicalScope*> scope);
+    bool freshenLexicalEnvironment(JSContext* cx);
+    bool recreateLexicalEnvironment(JSContext* cx);
+
+    /*
+     * Script
+     *
+     * All frames have an associated JSScript which holds the bytecode being
+     * executed for the frame.
+     */
+
+    JSScript* script() const {
+        return script_;
+    }
+
+    /* Return the previous frame's pc. */
+    jsbytecode* prevpc() {
+        MOZ_ASSERT(prev_);
+        return prevpc_;
+    }
+
+    /* Return the previous frame's sp. */
+    Value* prevsp() {
+        MOZ_ASSERT(prev_);
+        return prevsp_;
+    }
+
+    /*
+     * Return the 'this' argument passed to a non-eval function frame. This is
+     * not necessarily the frame's this-binding, for instance non-strict
+     * functions will box primitive 'this' values and thisArgument() will
+     * return the original, unboxed Value.
+     */
+    Value& thisArgument() const {
+        MOZ_ASSERT(isFunctionFrame());
+        return argv()[-1];
+    }
+
+    /*
+     * Callee
+     *
+     * Only function frames have a callee. An eval frame in a function has the
+     * same callee as its containing function frame.
+     */
+
+    JSFunction& callee() const {
+        MOZ_ASSERT(isFunctionFrame());
+        return calleev().toObject().as<JSFunction>();
+    }
+
+    const Value& calleev() const {
+        MOZ_ASSERT(isFunctionFrame());
+        return argv()[-2];
+    }
+
+    /*
+     * New Target
+     *
+     * Only function frames have a meaningful newTarget. An eval frame in a
+     * function will have a copy of the newTarget of the enclosing function
+     * frame.
+     */
+    Value newTarget() const {
+        if (isEvalFrame())
+            return ((Value*)this)[-1];
+
+        MOZ_ASSERT(isFunctionFrame());
+
+        if (callee().isArrow())
+            return callee().getExtendedSlot(FunctionExtended::ARROW_NEWTARGET_SLOT);
+
+        if (isConstructing()) {
+            unsigned pushedArgs = Max(numFormalArgs(), numActualArgs());
+            return argv()[pushedArgs];
+        }
+        return UndefinedValue();
+    }
+
+    /* Profiler flags */
+
+    bool hasPushedSPSFrame() {
+        return !!(flags_ & HAS_PUSHED_SPS_FRAME);
+    }
+
+    void setPushedSPSFrame() {
+        flags_ |= HAS_PUSHED_SPS_FRAME;
+    }
+
+    void unsetPushedSPSFrame() {
+        flags_ &= ~HAS_PUSHED_SPS_FRAME;
+    }
+
+    /* Return value */
+
+    bool hasReturnValue() const {
+        return flags_ & HAS_RVAL;
+    }
+
+    MutableHandleValue returnValue() {
+        if (!hasReturnValue())
+            rval_.setUndefined();
+        return MutableHandleValue::fromMarkedLocation(&rval_);
+    }
+
+    void markReturnValue() {
+        flags_ |= HAS_RVAL;
+    }
+
+    void setReturnValue(const Value& v) {
+        rval_ = v;
+        markReturnValue();
+    }
+
+    void clearReturnValue() {
+        rval_.setUndefined();
+        markReturnValue();
+    }
+
+    void resumeGeneratorFrame(JSObject* envChain) {
+        MOZ_ASSERT(script()->isGenerator());
+        MOZ_ASSERT(isFunctionFrame());
+        flags_ |= HAS_INITIAL_ENV;
+        envChain_ = envChain;
+    }
+
+    /*
+     * Other flags
+     */
+
+    bool isConstructing() const {
+        return !!(flags_ & CONSTRUCTING);
+    }
+
+    void setResumedGenerator() {
+        flags_ |= RESUMED_GENERATOR;
+    }
+    bool isResumedGenerator() const {
+        return !!(flags_ & RESUMED_GENERATOR);
+    }
+
+    /*
+     * These two queries should not be used in general: the presence/absence of
+     * the call/args object is determined by the static(ish) properties of the
+     * JSFunction/JSScript. These queries should only be performed when probing
+     * a stack frame that may be in the middle of the prologue (during which
+     * time the call/args object are created).
+     */
+
+    inline bool hasInitialEnvironment() const;
+
+    bool hasInitialEnvironmentUnchecked() const {
+        return flags_ & HAS_INITIAL_ENV;
+    }
+
+    bool hasArgsObj() const {
+        MOZ_ASSERT(script()->needsArgsObj());
+        return flags_ & HAS_ARGS_OBJ;
+    }
+
+    void setCreateSingleton() {
+        MOZ_ASSERT(isConstructing());
+        flags_ |= CREATE_SINGLETON;
+    }
+    bool createSingleton() const {
+        MOZ_ASSERT(isConstructing());
+        return flags_ & CREATE_SINGLETON;
+    }
+
+    /*
+     * Debugger eval frames.
+     *
+     * - If evalInFramePrev_ is non-null, frame was created for an "eval in
+     *   frame" call, which can push a successor to any live frame; so its
+     *   logical "prev" frame is not necessarily the previous frame in memory.
+     *   Iteration should treat evalInFramePrev_ as this frame's previous frame.
+     *
+     * - Don't bother to JIT it, because it's probably short-lived.
+     *
+     * - It is required to have a environment chain object outside the
+     *   js::EnvironmentObject hierarchy: either a global object, or a
+     *   DebugEnvironmentProxy.
+     */
+    bool isDebuggerEvalFrame() const {
+        return isEvalFrame() && !!evalInFramePrev_;
+    }
+
+    bool prevUpToDate() const {
+        return !!(flags_ & PREV_UP_TO_DATE);
+    }
+
+    void setPrevUpToDate() {
+        flags_ |= PREV_UP_TO_DATE;
+    }
+
+    void unsetPrevUpToDate() {
+        flags_ &= ~PREV_UP_TO_DATE;
+    }
+
+    bool isDebuggee() const {
+        return !!(flags_ & DEBUGGEE);
+    }
+
+    void setIsDebuggee() {
+        flags_ |= DEBUGGEE;
+    }
+
+    inline void unsetIsDebuggee();
+
+    bool hasCachedSavedFrame() const {
+        return flags_ & HAS_CACHED_SAVED_FRAME;
+    }
+    void setHasCachedSavedFrame() {
+        flags_ |= HAS_CACHED_SAVED_FRAME;
+    }
+
+  public:
+    void trace(JSTracer* trc, Value* sp, jsbytecode* pc);
+    void traceValues(JSTracer* trc, unsigned start, unsigned end);
+
+    // Entered Baseline/Ion from the interpreter.
+    bool runningInJit() const {
+        return !!(flags_ & RUNNING_IN_JIT);
+    }
+    void setRunningInJit() {
+        flags_ |= RUNNING_IN_JIT;
+    }
+    void clearRunningInJit() {
+        flags_ &= ~RUNNING_IN_JIT;
+    }
+};
+
+/*****************************************************************************/
+
+class InterpreterRegs
+{
+  public:
+    Value* sp;
+    jsbytecode* pc;
+  private:
+    InterpreterFrame* fp_;
+  public:
+    InterpreterFrame* fp() const { return fp_; }
+
+    unsigned stackDepth() const {
+        MOZ_ASSERT(sp >= fp_->base());
+        return sp - fp_->base();
+    }
+
+    Value* spForStackDepth(unsigned depth) const {
+        MOZ_ASSERT(fp_->script()->nfixed() + depth <= fp_->script()->nslots());
+        return fp_->base() + depth;
+    }
+
+    /* For generators. */
+    void rebaseFromTo(const InterpreterRegs& from, InterpreterFrame& to) {
+        fp_ = &to;
+        sp = to.slots() + (from.sp - from.fp_->slots());
+        pc = from.pc;
+        MOZ_ASSERT(fp_);
+    }
+
+    void popInlineFrame() {
+        pc = fp_->prevpc();
+        unsigned spForNewTarget = fp_->isResumedGenerator() ? 0 : fp_->isConstructing();
+        sp = fp_->prevsp() - fp_->numActualArgs() - 1 - spForNewTarget;
+        fp_ = fp_->prev();
+        MOZ_ASSERT(fp_);
+    }
+    void prepareToRun(InterpreterFrame& fp, JSScript* script) {
+        pc = script->code();
+        sp = fp.slots() + script->nfixed();
+        fp_ = &fp;
+    }
+
+    void setToEndOfScript();
+
+    MutableHandleValue stackHandleAt(int i) {
+        return MutableHandleValue::fromMarkedLocation(&sp[i]);
+    }
+
+    HandleValue stackHandleAt(int i) const {
+        return HandleValue::fromMarkedLocation(&sp[i]);
+    }
+
+    friend void GDBTestInitInterpreterRegs(InterpreterRegs&, js::InterpreterFrame*,
+                                           JS::Value*, uint8_t*);
+};
+
+/*****************************************************************************/
+
+class InterpreterStack
+{
+    friend class InterpreterActivation;
+
+    static const size_t DEFAULT_CHUNK_SIZE = 4 * 1024;
+    LifoAlloc allocator_;
+
+    // Number of interpreter frames on the stack, for over-recursion checks.
+    static const size_t MAX_FRAMES = 50 * 1000;
+    static const size_t MAX_FRAMES_TRUSTED = MAX_FRAMES + 1000;
+    size_t frameCount_;
+
+    inline uint8_t* allocateFrame(JSContext* cx, size_t size);
+
+    inline InterpreterFrame*
+    getCallFrame(JSContext* cx, const CallArgs& args, HandleScript script,
+                 MaybeConstruct constructing, Value** pargv);
+
+    void releaseFrame(InterpreterFrame* fp) {
+        frameCount_--;
+        allocator_.release(fp->mark_);
+    }
+
+  public:
+    InterpreterStack()
+      : allocator_(DEFAULT_CHUNK_SIZE),
+        frameCount_(0)
+    { }
+
+    ~InterpreterStack() {
+        MOZ_ASSERT(frameCount_ == 0);
+    }
+
+    // For execution of eval or global code.
+    InterpreterFrame* pushExecuteFrame(JSContext* cx, HandleScript script,
+                                       const Value& newTargetValue, HandleObject envChain,
+                                       AbstractFramePtr evalInFrame);
+
+    // Called to invoke a function.
+    InterpreterFrame* pushInvokeFrame(JSContext* cx, const CallArgs& args,
+                                      MaybeConstruct constructing);
+
+    // The interpreter can push light-weight, "inline" frames without entering a
+    // new InterpreterActivation or recursively calling Interpret.
+    bool pushInlineFrame(JSContext* cx, InterpreterRegs& regs, const CallArgs& args,
+                         HandleScript script, MaybeConstruct constructing);
+
+    void popInlineFrame(InterpreterRegs& regs);
+
+    bool resumeGeneratorCallFrame(JSContext* cx, InterpreterRegs& regs,
+                                  HandleFunction callee, HandleValue newTarget,
+                                  HandleObject envChain);
+
+    inline void purge(JSRuntime* rt);
+
+    size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const {
+        return allocator_.sizeOfExcludingThis(mallocSizeOf);
+    }
+};
+
+void MarkInterpreterActivations(JSRuntime* rt, JSTracer* trc);
+
+/*****************************************************************************/
+
+/** Base class for all function call args. */
+class AnyInvokeArgs : public JS::CallArgs
+{
+};
+
+/** Base class for all function construction args. */
+class AnyConstructArgs : public JS::CallArgs
+{
+    // Only js::Construct (or internal methods that call the qualified CallArgs
+    // versions) should do these things!
+    void setCallee(const Value& v) = delete;
+    void setThis(const Value& v) = delete;
+    MutableHandleValue newTarget() const = delete;
+    MutableHandleValue rval() const = delete;
+};
+
+namespace detail {
+
+/** Function call/construct args of statically-unknown count. */
+template <MaybeConstruct Construct>
+class GenericArgsBase
+  : public mozilla::Conditional<Construct, AnyConstructArgs, AnyInvokeArgs>::Type
+{
+  protected:
+    AutoValueVector v_;
+
+    explicit GenericArgsBase(JSContext* cx) : v_(cx) {}
+
+  public:
+    bool init(JSContext* cx, unsigned argc) {
+        if (argc > ARGS_LENGTH_MAX) {
+            JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr, JSMSG_TOO_MANY_ARGUMENTS);
+            return false;
+        }
+
+        // callee, this, arguments[, new.target iff constructing]
+        size_t len = 2 + argc + uint32_t(Construct);
+        MOZ_ASSERT(len > argc);  // no overflow
+        if (!v_.resize(len))
+            return false;
+
+        *static_cast<JS::CallArgs*>(this) = CallArgsFromVp(argc, v_.begin());
+        this->constructing_ = Construct;
+        if (Construct)
+            this->CallArgs::setThis(MagicValue(JS_IS_CONSTRUCTING));
+        return true;
+    }
+};
+
+/** Function call/construct args of statically-known count. */
+template <MaybeConstruct Construct, size_t N>
+class FixedArgsBase
+  : public mozilla::Conditional<Construct, AnyConstructArgs, AnyInvokeArgs>::Type
+{
+    static_assert(N <= ARGS_LENGTH_MAX, "o/~ too many args o/~");
+
+  protected:
+    JS::AutoValueArray<2 + N + uint32_t(Construct)> v_;
+
+    explicit FixedArgsBase(JSContext* cx) : v_(cx) {
+        *static_cast<JS::CallArgs*>(this) = CallArgsFromVp(N, v_.begin());
+        this->constructing_ = Construct;
+        if (Construct)
+            this->CallArgs::setThis(MagicValue(JS_IS_CONSTRUCTING));
+    }
+};
+
+} // namespace detail
+
+/** Function call args of statically-unknown count. */
+class InvokeArgs : public detail::GenericArgsBase<NO_CONSTRUCT>
+{
+    using Base = detail::GenericArgsBase<NO_CONSTRUCT>;
+
+  public:
+    explicit InvokeArgs(JSContext* cx) : Base(cx) {}
+};
+
+/** Function call args of statically-known count. */
+template <size_t N>
+class FixedInvokeArgs : public detail::FixedArgsBase<NO_CONSTRUCT, N>
+{
+    using Base = detail::FixedArgsBase<NO_CONSTRUCT, N>;
+
+  public:
+    explicit FixedInvokeArgs(JSContext* cx) : Base(cx) {}
+};
+
+/** Function construct args of statically-unknown count. */
+class ConstructArgs : public detail::GenericArgsBase<CONSTRUCT>
+{
+    using Base = detail::GenericArgsBase<CONSTRUCT>;
+
+  public:
+    explicit ConstructArgs(JSContext* cx) : Base(cx) {}
+};
+
+/** Function call args of statically-known count. */
+template <size_t N>
+class FixedConstructArgs : public detail::FixedArgsBase<CONSTRUCT, N>
+{
+    using Base = detail::FixedArgsBase<CONSTRUCT, N>;
+
+  public:
+    explicit FixedConstructArgs(JSContext* cx) : Base(cx) {}
+};
+
+template <class Args, class Arraylike>
+inline bool
+FillArgumentsFromArraylike(JSContext* cx, Args& args, const Arraylike& arraylike)
+{
+    uint32_t len = arraylike.length();
+    if (!args.init(cx, len))
+        return false;
+
+    for (uint32_t i = 0; i < len; i++)
+        args[i].set(arraylike[i]);
+
+    return true;
+}
+
+template <>
+struct DefaultHasher<AbstractFramePtr> {
+    typedef AbstractFramePtr Lookup;
+
+    static js::HashNumber hash(const Lookup& key) {
+        return size_t(key.raw());
+    }
+
+    static bool match(const AbstractFramePtr& k, const Lookup& l) {
+        return k == l;
+    }
+};
+
+/*****************************************************************************/
+
+// SavedFrame caching to minimize stack walking.
+//
+// SavedFrames are hash consed to minimize expensive (with regards to both space
+// and time) allocations in the face of many stack frames that tend to share the
+// same older tail frames. Despite that, in scenarios where we are frequently
+// saving the same or similar stacks, such as when the Debugger's allocation
+// site tracking is enabled, these older stack frames still get walked
+// repeatedly just to create the lookup structs to find their corresponding
+// SavedFrames in the hash table. This stack walking is slow, and we would like
+// to minimize it.
+//
+// We have reserved a bit on most of SpiderMonkey's various frame
+// representations (the exceptions being asm and inlined ion frames). As we
+// create SavedFrame objects for live stack frames in SavedStacks::insertFrames,
+// we set this bit and append the SavedFrame object to the cache. As we walk the
+// stack, if we encounter a frame that has this bit set, that indicates that we
+// have already captured a SavedFrame object for the given stack frame (but not
+// necessarily the current pc) during a previous call to insertFrames. We know
+// that the frame's parent was also captured and has its bit set as well, but
+// additionally we know the parent was captured at its current pc. For the
+// parent, rather than continuing the expensive stack walk, we do a quick and
+// cache-friendly linear search through the frame cache. Upon finishing search
+// through the frame cache, stale entries are removed.
+//
+// The frame cache maintains the invariant that its first E[0] .. E[j-1]
+// entries are live and sorted from oldest to younger frames, where 0 < j < n
+// and n = the length of the cache. When searching the cache, we require
+// that we are considering the youngest live frame whose bit is set. Every
+// cache entry E[i] where i >= j is a stale entry. Consider the following
+// scenario:
+//
+//     P  >  Q  >  R  >  S          Initial stack, bits not set.
+//     P* >  Q* >  R* >  S*         Capture a SavedFrame stack, set bits.
+//     P* >  Q* >  R*               Return from S.
+//     P* >  Q*                     Return from R.
+//     P* >  Q* >  T                Call T, its bit is not set.
+//
+// The frame cache was populated with [P, Q, R, S] when we captured a
+// SavedFrame stack, but because we returned from frames R and S, their
+// entries in the frame cache are now stale. This fact is unbeknownst to us
+// because we do not observe frame pops. Upon capturing a second stack, we
+// start stack walking at the youngest frame T, which does not have its bit
+// set and must take the hash table lookup slow path rather than the frame
+// cache short circuit. Next we proceed to Q and find that it has its bit
+// set, and it is therefore the youngest live frame with its bit set. We
+// search through the frame cache from oldest to youngest and find the cache
+// entry matching Q. We know that T is the next younger live frame from Q
+// and that T does not have an entry in the frame cache because its bit was
+// not set. Therefore, we have found entry E[j-1] and the subsequent entries
+// are stale and should be purged from the frame cache.
+//
+// We have a LiveSavedFrameCache for each activation to minimize the number of
+// entries that must be scanned through, and to avoid the headaches of
+// maintaining a cache for each compartment and invalidating stale cache entries
+// in the presence of cross-compartment calls.
+class LiveSavedFrameCache
+{
+  public:
+    using FramePtr = mozilla::Variant<AbstractFramePtr, jit::CommonFrameLayout*>;
+
+  private:
+    struct Entry
+    {
+        FramePtr             framePtr;
+        jsbytecode*          pc;
+        HeapPtr<SavedFrame*> savedFrame;
+
+        Entry(FramePtr& framePtr, jsbytecode* pc, SavedFrame* savedFrame)
+          : framePtr(framePtr)
+          , pc(pc)
+          , savedFrame(savedFrame)
+        { }
+    };
+
+    using EntryVector = Vector<Entry, 0, SystemAllocPolicy>;
+    EntryVector* frames;
+
+    LiveSavedFrameCache(const LiveSavedFrameCache&) = delete;
+    LiveSavedFrameCache& operator=(const LiveSavedFrameCache&) = delete;
+
+  public:
+    explicit LiveSavedFrameCache() : frames(nullptr) { }
+
+    LiveSavedFrameCache(LiveSavedFrameCache&& rhs)
+        : frames(rhs.frames)
+    {
+        MOZ_ASSERT(this != &rhs, "self-move disallowed");
+        rhs.frames = nullptr;
+    }
+
+    ~LiveSavedFrameCache() {
+        if (frames) {
+            js_delete(frames);
+            frames = nullptr;
+        }
+    }
+
+    bool initialized() const { return !!frames; }
+    bool init(JSContext* cx) {
+        frames = js_new<EntryVector>();
+        if (!frames) {
+            JS_ReportOutOfMemory(cx);
+            return false;
+        }
+        return true;
+    }
+
+    static mozilla::Maybe<FramePtr> getFramePtr(FrameIter& iter);
+    void trace(JSTracer* trc);
+
+    void find(JSContext* cx, FrameIter& frameIter, MutableHandleSavedFrame frame) const;
+    bool insert(JSContext* cx, FramePtr& framePtr, jsbytecode* pc, HandleSavedFrame savedFrame);
+};
+
+static_assert(sizeof(LiveSavedFrameCache) == sizeof(uintptr_t),
+              "Every js::Activation has a LiveSavedFrameCache, so we need to be pretty careful "
+              "about avoiding bloat. If you're adding members to LiveSavedFrameCache, maybe you "
+              "should consider figuring out a way to make js::Activation have a "
+              "LiveSavedFrameCache* instead of a Rooted<LiveSavedFrameCache>.");
+
+/*****************************************************************************/
+
+class InterpreterActivation;
+class WasmActivation;
+
+namespace jit {
+    class JitActivation;
+} // namespace jit
+
+// This class is separate from Activation, because it calls JSCompartment::wrap()
+// which can GC and walk the stack. It's not safe to do that within the
+// JitActivation constructor.
+class MOZ_RAII ActivationEntryMonitor
+{
+    JSContext* cx_;
+
+    // The entry point monitor that was set on cx_->runtime() when this
+    // ActivationEntryMonitor was created.
+    JS::dbg::AutoEntryMonitor* entryMonitor_;
+
+    explicit ActivationEntryMonitor(JSContext* cx);
+
+    ActivationEntryMonitor(const ActivationEntryMonitor& other) = delete;
+    void operator=(const ActivationEntryMonitor& other) = delete;
+
+    Value asyncStack(JSContext* cx);
+
+  public:
+    ActivationEntryMonitor(JSContext* cx, InterpreterFrame* entryFrame);
+    ActivationEntryMonitor(JSContext* cx, jit::CalleeToken entryToken);
+    inline ~ActivationEntryMonitor();
+};
+
+class Activation
+{
+  protected:
+    JSContext* cx_;
+    JSCompartment* compartment_;
+    Activation* prev_;
+    Activation* prevProfiling_;
+
+    // Counter incremented by JS::HideScriptedCaller and decremented by
+    // JS::UnhideScriptedCaller. If > 0 for the top activation,
+    // DescribeScriptedCaller will return null instead of querying that
+    // activation, which should prompt the caller to consult embedding-specific
+    // data structures instead.
+    size_t hideScriptedCallerCount_;
+
+    // The cache of SavedFrame objects we have already captured when walking
+    // this activation's stack.
+    Rooted<LiveSavedFrameCache> frameCache_;
+
+    // Youngest saved frame of an async stack that will be iterated during stack
+    // capture in place of the actual stack of previous activations. Note that
+    // the stack of this activation is captured entirely before this is used.
+    //
+    // Usually this is nullptr, meaning that normal stack capture will occur.
+    // When this is set, the stack of any previous activation is ignored.
+    Rooted<SavedFrame*> asyncStack_;
+
+    // Value of asyncCause to be attached to asyncStack_.
+    const char* asyncCause_;
+
+    // True if the async call was explicitly requested, e.g. via
+    // callFunctionWithAsyncStack.
+    bool asyncCallIsExplicit_;
+
+    enum Kind { Interpreter, Jit, Wasm };
+    Kind kind_;
+
+    inline Activation(JSContext* cx, Kind kind);
+    inline ~Activation();
+
+  public:
+    JSContext* cx() const {
+        return cx_;
+    }
+    JSCompartment* compartment() const {
+        return compartment_;
+    }
+    Activation* prev() const {
+        return prev_;
+    }
+    Activation* prevProfiling() const { return prevProfiling_; }
+    inline Activation* mostRecentProfiling();
+
+    bool isInterpreter() const {
+        return kind_ == Interpreter;
+    }
+    bool isJit() const {
+        return kind_ == Jit;
+    }
+    bool isWasm() const {
+        return kind_ == Wasm;
+    }
+
+    inline bool isProfiling() const;
+    void registerProfiling();
+    void unregisterProfiling();
+
+    InterpreterActivation* asInterpreter() const {
+        MOZ_ASSERT(isInterpreter());
+        return (InterpreterActivation*)this;
+    }
+    jit::JitActivation* asJit() const {
+        MOZ_ASSERT(isJit());
+        return (jit::JitActivation*)this;
+    }
+    WasmActivation* asWasm() const {
+        MOZ_ASSERT(isWasm());
+        return (WasmActivation*)this;
+    }
+
+    void hideScriptedCaller() {
+        hideScriptedCallerCount_++;
+    }
+    void unhideScriptedCaller() {
+        MOZ_ASSERT(hideScriptedCallerCount_ > 0);
+        hideScriptedCallerCount_--;
+    }
+    bool scriptedCallerIsHidden() const {
+        return hideScriptedCallerCount_ > 0;
+    }
+
+    static size_t offsetOfPrevProfiling() {
+        return offsetof(Activation, prevProfiling_);
+    }
+
+    SavedFrame* asyncStack() {
+        return asyncStack_;
+    }
+
+    const char* asyncCause() const {
+        return asyncCause_;
+    }
+
+    bool asyncCallIsExplicit() const {
+        return asyncCallIsExplicit_;
+    }
+
+    inline LiveSavedFrameCache* getLiveSavedFrameCache(JSContext* cx);
+
+  private:
+    Activation(const Activation& other) = delete;
+    void operator=(const Activation& other) = delete;
+};
+
+// This variable holds a special opcode value which is greater than all normal
+// opcodes, and is chosen such that the bitwise or of this value with any
+// opcode is this value.
+static const jsbytecode EnableInterruptsPseudoOpcode = -1;
+
+static_assert(EnableInterruptsPseudoOpcode >= JSOP_LIMIT,
+              "EnableInterruptsPseudoOpcode must be greater than any opcode");
+static_assert(EnableInterruptsPseudoOpcode == jsbytecode(-1),
+              "EnableInterruptsPseudoOpcode must be the maximum jsbytecode value");
+
+class InterpreterFrameIterator;
+class RunState;
+
+class InterpreterActivation : public Activation
+{
+    friend class js::InterpreterFrameIterator;
+
+    InterpreterRegs regs_;
+    InterpreterFrame* entryFrame_;
+    size_t opMask_; // For debugger interrupts, see js::Interpret.
+
+#ifdef DEBUG
+    size_t oldFrameCount_;
+#endif
+
+  public:
+    inline InterpreterActivation(RunState& state, JSContext* cx, InterpreterFrame* entryFrame);
+    inline ~InterpreterActivation();
+
+    inline bool pushInlineFrame(const CallArgs& args, HandleScript script,
+                                MaybeConstruct constructing);
+    inline void popInlineFrame(InterpreterFrame* frame);
+
+    inline bool resumeGeneratorFrame(HandleFunction callee, HandleValue newTarget,
+                                     HandleObject envChain);
+
+    InterpreterFrame* current() const {
+        return regs_.fp();
+    }
+    InterpreterRegs& regs() {
+        return regs_;
+    }
+    InterpreterFrame* entryFrame() const {
+        return entryFrame_;
+    }
+    size_t opMask() const {
+        return opMask_;
+    }
+
+    bool isProfiling() const {
+        return false;
+    }
+
+    // If this js::Interpret frame is running |script|, enable interrupts.
+    void enableInterruptsIfRunning(JSScript* script) {
+        if (regs_.fp()->script() == script)
+            enableInterruptsUnconditionally();
+    }
+    void enableInterruptsUnconditionally() {
+        opMask_ = EnableInterruptsPseudoOpcode;
+    }
+    void clearInterruptsMask() {
+        opMask_ = 0;
+    }
+};
+
+// Iterates over a thread's activation list. If given a runtime, iterate over
+// the runtime's main thread's activation list.
+class ActivationIterator
+{
+    uint8_t* jitTop_;
+
+  protected:
+    Activation* activation_;
+
+  private:
+    void settle();
+
+  public:
+    explicit ActivationIterator(JSRuntime* rt);
+
+    ActivationIterator& operator++();
+
+    Activation* operator->() const {
+        return activation_;
+    }
+    Activation* activation() const {
+        return activation_;
+    }
+    uint8_t* jitTop() const {
+        MOZ_ASSERT(activation_->isJit());
+        return jitTop_;
+    }
+    bool done() const {
+        return activation_ == nullptr;
+    }
+};
+
+namespace jit {
+
+class BailoutFrameInfo;
+
+// A JitActivation is used for frames running in Baseline or Ion.
+class JitActivation : public Activation
+{
+    uint8_t* prevJitTop_;
+    JitActivation* prevJitActivation_;
+    bool active_;
+
+    // Rematerialized Ion frames which has info copied out of snapshots. Maps
+    // frame pointers (i.e. jitTop) to a vector of rematerializations of all
+    // inline frames associated with that frame.
+    //
+    // This table is lazily initialized by calling getRematerializedFrame.
+    typedef GCVector<RematerializedFrame*> RematerializedFrameVector;
+    typedef HashMap<uint8_t*, RematerializedFrameVector> RematerializedFrameTable;
+    RematerializedFrameTable* rematerializedFrames_;
+
+    // This vector is used to remember the outcome of the evaluation of recover
+    // instructions.
+    //
+    // RInstructionResults are appended into this vector when Snapshot values
+    // have to be read, or when the evaluation has to run before some mutating
+    // code.  Each RInstructionResults belongs to one frame which has to bailout
+    // as soon as we get back to it.
+    typedef Vector<RInstructionResults, 1> IonRecoveryMap;
+    IonRecoveryMap ionRecovery_;
+
+    // If we are bailing out from Ion, then this field should be a non-null
+    // pointer which references the BailoutFrameInfo used to walk the inner
+    // frames. This field is used for all newly constructed JitFrameIterators to
+    // read the innermost frame information from this bailout data instead of
+    // reading it from the stack.
+    BailoutFrameInfo* bailoutData_;
+
+    // When profiling is enabled, these fields will be updated to reflect the
+    // last pushed frame for this activation, and if that frame has been
+    // left for a call, the native code site of the call.
+    mozilla::Atomic<void*, mozilla::Relaxed> lastProfilingFrame_;
+    mozilla::Atomic<void*, mozilla::Relaxed> lastProfilingCallSite_;
+    static_assert(sizeof(mozilla::Atomic<void*, mozilla::Relaxed>) == sizeof(void*),
+                  "Atomic should have same memory format as underlying type.");
+
+    void clearRematerializedFrames();
+
+#ifdef CHECK_OSIPOINT_REGISTERS
+  protected:
+    // Used to verify that live registers don't change between a VM call and
+    // the OsiPoint that follows it. Protected to silence Clang warning.
+    uint32_t checkRegs_;
+    RegisterDump regs_;
+#endif
+
+  public:
+    explicit JitActivation(JSContext* cx, bool active = true);
+    ~JitActivation();
+
+    bool isActive() const {
+        return active_;
+    }
+    void setActive(JSContext* cx, bool active = true);
+
+    bool isProfiling() const;
+
+    uint8_t* prevJitTop() const {
+        return prevJitTop_;
+    }
+    JitActivation* prevJitActivation() const {
+        return prevJitActivation_;
+    }
+    static size_t offsetOfPrevJitTop() {
+        return offsetof(JitActivation, prevJitTop_);
+    }
+    static size_t offsetOfPrevJitActivation() {
+        return offsetof(JitActivation, prevJitActivation_);
+    }
+    static size_t offsetOfActiveUint8() {
+        MOZ_ASSERT(sizeof(bool) == 1);
+        return offsetof(JitActivation, active_);
+    }
+
+#ifdef CHECK_OSIPOINT_REGISTERS
+    void setCheckRegs(bool check) {
+        checkRegs_ = check;
+    }
+    static size_t offsetOfCheckRegs() {
+        return offsetof(JitActivation, checkRegs_);
+    }
+    static size_t offsetOfRegs() {
+        return offsetof(JitActivation, regs_);
+    }
+#endif
+
+    // Look up a rematerialized frame keyed by the fp, rematerializing the
+    // frame if one doesn't already exist. A frame can only be rematerialized
+    // if an IonFrameIterator pointing to the nearest uninlined frame can be
+    // provided, as values need to be read out of snapshots.
+    //
+    // The inlineDepth must be within bounds of the frame pointed to by iter.
+    RematerializedFrame* getRematerializedFrame(JSContext* cx, const JitFrameIterator& iter,
+                                                size_t inlineDepth = 0);
+
+    // Look up a rematerialized frame by the fp. If inlineDepth is out of
+    // bounds of what has been rematerialized, nullptr is returned.
+    RematerializedFrame* lookupRematerializedFrame(uint8_t* top, size_t inlineDepth = 0);
+
+    // Remove all rematerialized frames associated with the fp top from the
+    // Debugger.
+    void removeRematerializedFramesFromDebugger(JSContext* cx, uint8_t* top);
+
+    bool hasRematerializedFrame(uint8_t* top, size_t inlineDepth = 0) {
+        return !!lookupRematerializedFrame(top, inlineDepth);
+    }
+
+    // Remove a previous rematerialization by fp.
+    void removeRematerializedFrame(uint8_t* top);
+
+    void markRematerializedFrames(JSTracer* trc);
+
+
+    // Register the results of on Ion frame recovery.
+    bool registerIonFrameRecovery(RInstructionResults&& results);
+
+    // Return the pointer to the Ion frame recovery, if it is already registered.
+    RInstructionResults* maybeIonFrameRecovery(JitFrameLayout* fp);
+
+    // If an Ion frame recovery exists for the |fp| frame exists, then remove it
+    // from the activation.
+    void removeIonFrameRecovery(JitFrameLayout* fp);
+
+    void markIonRecovery(JSTracer* trc);
+
+    // Return the bailout information if it is registered.
+    const BailoutFrameInfo* bailoutData() const { return bailoutData_; }
+
+    // Register the bailout data when it is constructed.
+    void setBailoutData(BailoutFrameInfo* bailoutData);
+
+    // Unregister the bailout data when the frame is reconstructed.
+    void cleanBailoutData();
+
+    static size_t offsetOfLastProfilingFrame() {
+        return offsetof(JitActivation, lastProfilingFrame_);
+    }
+    void* lastProfilingFrame() {
+        return lastProfilingFrame_;
+    }
+    void setLastProfilingFrame(void* ptr) {
+        lastProfilingFrame_ = ptr;
+    }
+
+    static size_t offsetOfLastProfilingCallSite() {
+        return offsetof(JitActivation, lastProfilingCallSite_);
+    }
+    void* lastProfilingCallSite() {
+        return lastProfilingCallSite_;
+    }
+    void setLastProfilingCallSite(void* ptr) {
+        lastProfilingCallSite_ = ptr;
+    }
+};
+
+// A filtering of the ActivationIterator to only stop at JitActivations.
+class JitActivationIterator : public ActivationIterator
+{
+    void settle() {
+        while (!done() && !activation_->isJit())
+            ActivationIterator::operator++();
+    }
+
+  public:
+    explicit JitActivationIterator(JSRuntime* rt)
+      : ActivationIterator(rt)
+    {
+        settle();
+    }
+
+    JitActivationIterator& operator++() {
+        ActivationIterator::operator++();
+        settle();
+        return *this;
+    }
+};
+
+} // namespace jit
+
+// Iterates over the frames of a single InterpreterActivation.
+class InterpreterFrameIterator
+{
+    InterpreterActivation* activation_;
+    InterpreterFrame* fp_;
+    jsbytecode* pc_;
+    Value* sp_;
+
+  public:
+    explicit InterpreterFrameIterator(InterpreterActivation* activation)
+      : activation_(activation),
+        fp_(nullptr),
+        pc_(nullptr),
+        sp_(nullptr)
+    {
+        if (activation) {
+            fp_ = activation->current();
+            pc_ = activation->regs().pc;
+            sp_ = activation->regs().sp;
+        }
+    }
+
+    InterpreterFrame* frame() const {
+        MOZ_ASSERT(!done());
+        return fp_;
+    }
+    jsbytecode* pc() const {
+        MOZ_ASSERT(!done());
+        return pc_;
+    }
+    Value* sp() const {
+        MOZ_ASSERT(!done());
+        return sp_;
+    }
+
+    InterpreterFrameIterator& operator++();
+
+    bool done() const {
+        return fp_ == nullptr;
+    }
+};
+
+// A WasmActivation is part of two activation linked lists:
+//  - the normal Activation list used by FrameIter
+//  - a list of only WasmActivations that is signal-safe since it is accessed
+//    from the profiler at arbitrary points
+//
+// An eventual goal is to remove WasmActivation and to run asm code in a
+// JitActivation interleaved with Ion/Baseline jit code. This would allow
+// efficient calls back and forth but requires that we can walk the stack for
+// all kinds of jit code.
+class WasmActivation : public Activation
+{
+    WasmActivation* prevWasm_;
+    void* entrySP_;
+    void* resumePC_;
+    uint8_t* fp_;
+    wasm::ExitReason exitReason_;
+
+  public:
+    explicit WasmActivation(JSContext* cx);
+    ~WasmActivation();
+
+    WasmActivation* prevWasm() const { return prevWasm_; }
+
+    bool isProfiling() const {
+        return true;
+    }
+
+    // Returns a pointer to the base of the innermost stack frame of wasm code
+    // in this activation.
+    uint8_t* fp() const { return fp_; }
+
+    // Returns the reason why wasm code called out of wasm code.
+    wasm::ExitReason exitReason() const { return exitReason_; }
+
+    // Read by JIT code:
+    static unsigned offsetOfContext() { return offsetof(WasmActivation, cx_); }
+    static unsigned offsetOfResumePC() { return offsetof(WasmActivation, resumePC_); }
+
+    // Written by JIT code:
+    static unsigned offsetOfEntrySP() { return offsetof(WasmActivation, entrySP_); }
+    static unsigned offsetOfFP() { return offsetof(WasmActivation, fp_); }
+    static unsigned offsetOfExitReason() { return offsetof(WasmActivation, exitReason_); }
+
+    // Read/written from SIGSEGV handler:
+    void setResumePC(void* pc) { resumePC_ = pc; }
+    void* resumePC() const { return resumePC_; }
+};
+
+// A FrameIter walks over the runtime's stack of JS script activations,
+// abstracting over whether the JS scripts were running in the interpreter or
+// different modes of compiled code.
+//
+// FrameIter is parameterized by what it includes in the stack iteration:
+//  - When provided, the optional JSPrincipal argument will cause FrameIter to
+//    only show frames in globals whose JSPrincipals are subsumed (via
+//    JSSecurityCallbacks::subsume) by the given JSPrincipal.
+//
+// Additionally, there are derived FrameIter types that automatically skip
+// certain frames:
+//  - ScriptFrameIter only shows frames that have an associated JSScript
+//    (currently everything other than wasm stack frames). When !hasScript(),
+//    clients must stick to the portion of the
+//    interface marked below.
+//  - NonBuiltinScriptFrameIter additionally filters out builtin (self-hosted)
+//    scripts.
+class FrameIter
+{
+  public:
+    enum DebuggerEvalOption { FOLLOW_DEBUGGER_EVAL_PREV_LINK,
+                              IGNORE_DEBUGGER_EVAL_PREV_LINK };
+    enum State { DONE, INTERP, JIT, WASM };
+
+    // Unlike ScriptFrameIter itself, ScriptFrameIter::Data can be allocated on
+    // the heap, so this structure should not contain any GC things.
+    struct Data
+    {
+        JSContext * cx_;
+        DebuggerEvalOption  debuggerEvalOption_;
+        JSPrincipals *      principals_;
+
+        State               state_;
+
+        jsbytecode *        pc_;
+
+        InterpreterFrameIterator interpFrames_;
+        ActivationIterator activations_;
+
+        jit::JitFrameIterator jitFrames_;
+        unsigned ionInlineFrameNo_;
+        wasm::FrameIterator wasmFrames_;
+
+        Data(JSContext* cx, DebuggerEvalOption debuggerEvalOption, JSPrincipals* principals);
+        Data(const Data& other);
+    };
+
+    explicit FrameIter(JSContext* cx,
+                       DebuggerEvalOption = FOLLOW_DEBUGGER_EVAL_PREV_LINK);
+    FrameIter(JSContext* cx, DebuggerEvalOption, JSPrincipals*);
+    FrameIter(const FrameIter& iter);
+    MOZ_IMPLICIT FrameIter(const Data& data);
+    MOZ_IMPLICIT FrameIter(AbstractFramePtr frame);
+
+    bool done() const { return data_.state_ == DONE; }
+
+    // -------------------------------------------------------
+    // The following functions can only be called when !done()
+    // -------------------------------------------------------
+
+    FrameIter& operator++();
+
+    JSCompartment* compartment() const;
+    Activation* activation() const { return data_.activations_.activation(); }
+
+    bool isInterp() const { MOZ_ASSERT(!done()); return data_.state_ == INTERP;  }
+    bool isJit() const { MOZ_ASSERT(!done()); return data_.state_ == JIT; }
+    bool isWasm() const { MOZ_ASSERT(!done()); return data_.state_ == WASM; }
+    inline bool isIon() const;
+    inline bool isBaseline() const;
+    inline bool isPhysicalIonFrame() const;
+
+    bool isEvalFrame() const;
+    bool isFunctionFrame() const;
+    bool hasArgs() const { return isFunctionFrame(); }
+
+    // These two methods may not be called with asm frames.
+    inline bool hasCachedSavedFrame() const;
+    inline void setHasCachedSavedFrame();
+
+    ScriptSource* scriptSource() const;
+    const char* filename() const;
+    const char16_t* displayURL() const;
+    unsigned computeLine(uint32_t* column = nullptr) const;
+    JSAtom* functionDisplayAtom() const;
+    bool mutedErrors() const;
+
+    bool hasScript() const { return !isWasm(); }
+
+    // -----------------------------------------------------------
+    // The following functions can only be called when hasScript()
+    // -----------------------------------------------------------
+
+    inline JSScript* script() const;
+
+    bool        isConstructing() const;
+    jsbytecode* pc() const { MOZ_ASSERT(!done()); return data_.pc_; }
+    void        updatePcQuadratic();
+
+    // The function |calleeTemplate()| returns either the function from which
+    // the current |callee| was cloned or the |callee| if it can be read. As
+    // long as we do not have to investigate the environment chain or build a
+    // new frame, we should prefer to use |calleeTemplate| instead of
+    // |callee|, as requesting the |callee| might cause the invalidation of
+    // the frame. (see js::Lambda)
+    JSFunction* calleeTemplate() const;
+    JSFunction* callee(JSContext* cx) const;
+
+    JSFunction* maybeCallee(JSContext* cx) const {
+        return isFunctionFrame() ? callee(cx) : nullptr;
+    }
+
+    bool        matchCallee(JSContext* cx, HandleFunction fun) const;
+
+    unsigned    numActualArgs() const;
+    unsigned    numFormalArgs() const;
+    Value       unaliasedActual(unsigned i, MaybeCheckAliasing = CHECK_ALIASING) const;
+    template <class Op> inline void unaliasedForEachActual(JSContext* cx, Op op);
+
+    JSObject*  environmentChain(JSContext* cx) const;
+    CallObject& callObj(JSContext* cx) const;
+
+    bool        hasArgsObj() const;
+    ArgumentsObject& argsObj() const;
+
+    // Get the original |this| value passed to this function. May not be the
+    // actual this-binding (for instance, derived class constructors will
+    // change their this-value later and non-strict functions will box
+    // primitives).
+    Value       thisArgument(JSContext* cx) const;
+
+    Value       newTarget() const;
+
+    Value       returnValue() const;
+    void        setReturnValue(const Value& v);
+
+    // These are only valid for the top frame.
+    size_t      numFrameSlots() const;
+    Value       frameSlotValue(size_t index) const;
+
+    // Ensures that we have rematerialized the top frame and its associated
+    // inline frames. Can only be called when isIon().
+    bool ensureHasRematerializedFrame(JSContext* cx);
+
+    // True when isInterp() or isBaseline(). True when isIon() if it
+    // has a rematerialized frame. False otherwise false otherwise.
+    bool hasUsableAbstractFramePtr() const;
+
+    // -----------------------------------------------------------
+    // The following functions can only be called when isInterp(),
+    // isBaseline(), or isIon(). Further, abstractFramePtr() can
+    // only be called when hasUsableAbstractFramePtr().
+    // -----------------------------------------------------------
+
+    AbstractFramePtr abstractFramePtr() const;
+    AbstractFramePtr copyDataAsAbstractFramePtr() const;
+    Data* copyData() const;
+
+    // This can only be called when isInterp():
+    inline InterpreterFrame* interpFrame() const;
+
+    // This can only be called when isPhysicalIonFrame():
+    inline jit::CommonFrameLayout* physicalIonFrame() const;
+
+    // This is used to provide a raw interface for debugging.
+    void* rawFramePtr() const;
+
+  private:
+    Data data_;
+    jit::InlineFrameIterator ionInlineFrames_;
+
+    void popActivation();
+    void popInterpreterFrame();
+    void nextJitFrame();
+    void popJitFrame();
+    void popWasmFrame();
+    void settleOnActivation();
+};
+
+class ScriptFrameIter : public FrameIter
+{
+    void settle() {
+        while (!done() && !hasScript())
+            FrameIter::operator++();
+    }
+
+  public:
+    explicit ScriptFrameIter(JSContext* cx,
+                             DebuggerEvalOption debuggerEvalOption = FOLLOW_DEBUGGER_EVAL_PREV_LINK)
+      : FrameIter(cx, debuggerEvalOption)
+    {
+        settle();
+    }
+
+    ScriptFrameIter(JSContext* cx,
+                    DebuggerEvalOption debuggerEvalOption,
+                    JSPrincipals* prin)
+      : FrameIter(cx, debuggerEvalOption, prin)
+    {
+        settle();
+    }
+
+    ScriptFrameIter(const ScriptFrameIter& iter) : FrameIter(iter) { settle(); }
+    explicit ScriptFrameIter(const FrameIter::Data& data) : FrameIter(data) { settle(); }
+    explicit ScriptFrameIter(AbstractFramePtr frame) : FrameIter(frame) { settle(); }
+
+    ScriptFrameIter& operator++() {
+        FrameIter::operator++();
+        settle();
+        return *this;
+    }
+};
+
+#ifdef DEBUG
+bool SelfHostedFramesVisible();
+#else
+static inline bool
+SelfHostedFramesVisible()
+{
+    return false;
+}
+#endif
+
+/* A filtering of the FrameIter to only stop at non-self-hosted scripts. */
+class NonBuiltinFrameIter : public FrameIter
+{
+    void settle();
+
+  public:
+    explicit NonBuiltinFrameIter(JSContext* cx,
+                                 FrameIter::DebuggerEvalOption debuggerEvalOption =
+                                 FrameIter::FOLLOW_DEBUGGER_EVAL_PREV_LINK)
+      : FrameIter(cx, debuggerEvalOption)
+    {
+        settle();
+    }
+
+    NonBuiltinFrameIter(JSContext* cx,
+                        FrameIter::DebuggerEvalOption debuggerEvalOption,
+                        JSPrincipals* principals)
+      : FrameIter(cx, debuggerEvalOption, principals)
+    {
+        settle();
+    }
+
+    NonBuiltinFrameIter(JSContext* cx, JSPrincipals* principals)
+      : FrameIter(cx, FrameIter::FOLLOW_DEBUGGER_EVAL_PREV_LINK, principals)
+    {
+        settle();
+    }
+
+    explicit NonBuiltinFrameIter(const FrameIter::Data& data)
+      : FrameIter(data)
+    {}
+
+    NonBuiltinFrameIter& operator++() {
+        FrameIter::operator++();
+        settle();
+        return *this;
+    }
+};
+
+/* A filtering of the ScriptFrameIter to only stop at non-self-hosted scripts. */
+class NonBuiltinScriptFrameIter : public ScriptFrameIter
+{
+    void settle();
+
+  public:
+    explicit NonBuiltinScriptFrameIter(JSContext* cx,
+                                       ScriptFrameIter::DebuggerEvalOption debuggerEvalOption =
+                                       ScriptFrameIter::FOLLOW_DEBUGGER_EVAL_PREV_LINK)
+      : ScriptFrameIter(cx, debuggerEvalOption)
+    {
+        settle();
+    }
+
+    NonBuiltinScriptFrameIter(JSContext* cx,
+                              ScriptFrameIter::DebuggerEvalOption debuggerEvalOption,
+                              JSPrincipals* principals)
+      : ScriptFrameIter(cx, debuggerEvalOption, principals)
+    {
+        settle();
+    }
+
+    explicit NonBuiltinScriptFrameIter(const ScriptFrameIter::Data& data)
+      : ScriptFrameIter(data)
+    {}
+
+    NonBuiltinScriptFrameIter& operator++() {
+        ScriptFrameIter::operator++();
+        settle();
+        return *this;
+    }
+};
+
+/*
+ * Blindly iterate over all frames in the current thread's stack. These frames
+ * can be from different contexts and compartments, so beware.
+ */
+class AllFramesIter : public FrameIter
+{
+  public:
+    explicit AllFramesIter(JSContext* cx)
+      : FrameIter(cx, ScriptFrameIter::IGNORE_DEBUGGER_EVAL_PREV_LINK)
+    {}
+};
+
+/* Iterates over all script frame in the current thread's stack.
+ * See also AllFramesIter and ScriptFrameIter.
+ */
+class AllScriptFramesIter : public ScriptFrameIter
+{
+  public:
+    explicit AllScriptFramesIter(JSContext* cx)
+      : ScriptFrameIter(cx, ScriptFrameIter::IGNORE_DEBUGGER_EVAL_PREV_LINK)
+    {}
+};
+
+/* Popular inline definitions. */
+
+inline JSScript*
+FrameIter::script() const
+{
+    MOZ_ASSERT(!done());
+    if (data_.state_ == INTERP)
+        return interpFrame()->script();
+    MOZ_ASSERT(data_.state_ == JIT);
+    if (data_.jitFrames_.isIonJS())
+        return ionInlineFrames_.script();
+    return data_.jitFrames_.script();
+}
+
+inline bool
+FrameIter::isIon() const
+{
+    return isJit() && data_.jitFrames_.isIonJS();
+}
+
+inline bool
+FrameIter::isBaseline() const
+{
+    return isJit() && data_.jitFrames_.isBaselineJS();
+}
+
+inline InterpreterFrame*
+FrameIter::interpFrame() const
+{
+    MOZ_ASSERT(data_.state_ == INTERP);
+    return data_.interpFrames_.frame();
+}
+
+inline bool
+FrameIter::isPhysicalIonFrame() const
+{
+    return isJit() &&
+           data_.jitFrames_.isIonScripted() &&
+           ionInlineFrames_.frameNo() == 0;
+}
+
+inline jit::CommonFrameLayout*
+FrameIter::physicalIonFrame() const
+{
+    MOZ_ASSERT(isPhysicalIonFrame());
+    return data_.jitFrames_.current();
+}
+
+}  /* namespace js */
+#endif /* vm_Stack_h */