Adding upstream version 115.7.0esr.upstream/115.7.0esrupstream

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

1 files changed, 875 insertions, 0 deletions

diff --git a/js/src/vm/JSFunction.h b/js/src/vm/JSFunction.h
new file mode 100644
index 0000000000..7f44f601c5
--- /dev/null
+++ b/js/src/vm/JSFunction.h
@@ -0,0 +1,875 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
+ * vim: set ts=8 sts=2 et sw=2 tw=80:
+ * This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef vm_JSFunction_h
+#define vm_JSFunction_h
+
+/*
+ * JS function definitions.
+ */
+
+#include <string_view>
+
+#include "jstypes.h"
+
+#include "gc/Policy.h"
+#include "js/shadow/Function.h"        // JS::shadow::Function
+#include "vm/FunctionFlags.h"          // FunctionFlags
+#include "vm/FunctionPrefixKind.h"     // FunctionPrefixKind
+#include "vm/GeneratorAndAsyncKind.h"  // GeneratorKind, FunctionAsyncKind
+#include "vm/JSAtom.h"
+#include "vm/JSObject.h"
+#include "vm/JSScript.h"
+
+class JSJitInfo;
+
+namespace js {
+
+class FunctionExtended;
+struct SelfHostedLazyScript;
+
+using Native = JSNative;
+
+static constexpr std::string_view FunctionConstructorMedialSigils = ") {\n";
+static constexpr std::string_view FunctionConstructorFinalBrace = "\n}";
+
+// JSFunctions can have one of two classes:
+extern const JSClass FunctionClass;
+extern const JSClass ExtendedFunctionClass;
+
+namespace wasm {
+
+class Instance;
+
+}  // namespace wasm
+}  // namespace js
+
+class JSFunction : public js::NativeObject {
+ public:
+  static_assert(sizeof(js::FunctionFlags) == sizeof(uint16_t));
+  static constexpr size_t ArgCountShift = 16;
+  static constexpr size_t FlagsMask = js::BitMask(ArgCountShift);
+  static constexpr size_t ArgCountMask = js::BitMask(16) << ArgCountShift;
+
+  enum {
+    /*
+     * Bitfield composed of FunctionFlags and argument count, stored as a
+     * PrivateUint32Value.
+     *
+     * If any of these flags needs to be accessed in off-thread JIT compilation,
+     * copy it to js::jit::WrappedFunction.
+     */
+    FlagsAndArgCountSlot,
+
+    /*
+     * For native functions, the native method pointer stored as a private
+     * value, or undefined.
+     *
+     * For interpreted functions, the environment object for new activations or
+     * null.
+     */
+    NativeFuncOrInterpretedEnvSlot,
+
+    /*
+     * For native functions this is one of:
+     *
+     *  - JSJitInfo* to be used by the JIT, only used if isBuiltinNative() for
+     *    builtin natives
+     *
+     *  - wasm function index for wasm/asm.js without a jit entry. Always has
+     *    the low bit set to ensure it's never identical to a BaseScript*
+     *    pointer
+     *
+     *  - a wasm JIT entry
+     *
+     * The JIT depends on none of the above being a valid BaseScript pointer.
+     *
+     * For interpreted functions this is either a BaseScript or the
+     * SelfHostedLazyScript pointer.
+     *
+     * These are all stored as private values, because the JIT assumes that it
+     * can access the SelfHostedLazyScript and BaseScript pointer in the same
+     * way.
+     */
+    NativeJitInfoOrInterpretedScriptSlot,
+
+    // The `atom_` field can have different meanings depending on the function
+    // type and flags. It is used for diagnostics, decompiling, and
+    //
+    //   a. If HAS_GUESSED_ATOM is not set, to store the initial value of the
+    //      "name" property of functions. But also see RESOLVED_NAME.
+    //   b. If HAS_GUESSED_ATOM is set, `atom_` is only used for diagnostics,
+    //      but must not be used for the "name" property.
+    //   c. If HAS_INFERRED_NAME is set, the function wasn't given an explicit
+    //      name in the source text, e.g. `function fn(){}`, but instead it
+    //      was inferred based on how the function was defined in the source
+    //      text. The exact name inference rules are defined in the ECMAScript
+    //      specification.
+    //      Name inference can happen at compile-time, for example in
+    //      `var fn = function(){}`, or it can happen at runtime, for example
+    //      in `var o = {[Symbol.iterator]: function(){}}`. When it happens at
+    //      compile-time, the HAS_INFERRED_NAME is set directly in the
+    //      bytecode emitter, when it happens at runtime, the flag is set when
+    //      evaluating the JSOp::SetFunName bytecode.
+    //   d. HAS_GUESSED_ATOM and HAS_INFERRED_NAME cannot both be set.
+    //   e. `atom_` can be null if neither an explicit, nor inferred, nor a
+    //      guessed name was set.
+    //
+    // Self-hosted functions have two names. For example, Array.prototype.sort
+    // has the standard name "sort", but the implementation in Array.js is named
+    // "ArraySort".
+    //
+    // -   In the self-hosting realm, these functions have `_atom` set to the
+    //     implementation name.
+    //
+    // -   When we clone these functions into normal realms, we set `_atom` to
+    //     the standard name. (The self-hosted name is also stored on the clone,
+    //     in another slot; see GetClonedSelfHostedFunctionName().)
+    AtomSlot,
+
+    SlotCount
+  };
+
+ private:
+  using FunctionFlags = js::FunctionFlags;
+
+ public:
+  static inline JSFunction* create(JSContext* cx, js::gc::AllocKind kind,
+                                   js::gc::Heap heap,
+                                   js::Handle<js::SharedShape*> shape);
+
+  /* Call objects must be created for each invocation of this function. */
+  bool needsCallObject() const;
+
+  bool needsExtraBodyVarEnvironment() const;
+  bool needsNamedLambdaEnvironment() const;
+
+  bool needsFunctionEnvironmentObjects() const {
+    bool res = nonLazyScript()->needsFunctionEnvironmentObjects();
+    MOZ_ASSERT(res == (needsCallObject() || needsNamedLambdaEnvironment()));
+    return res;
+  }
+
+  bool needsSomeEnvironmentObject() const {
+    return needsFunctionEnvironmentObjects() || needsExtraBodyVarEnvironment();
+  }
+
+  uint32_t flagsAndArgCountRaw() const {
+    return getFixedSlot(FlagsAndArgCountSlot).toPrivateUint32();
+  }
+
+  void initFlagsAndArgCount() {
+    initFixedSlot(FlagsAndArgCountSlot, JS::PrivateUint32Value(0));
+  }
+
+  size_t nargs() const { return flagsAndArgCountRaw() >> ArgCountShift; }
+
+  FunctionFlags flags() const {
+    return FunctionFlags(uint16_t(flagsAndArgCountRaw() & FlagsMask));
+  }
+
+  FunctionFlags::FunctionKind kind() const { return flags().kind(); }
+
+  /* A function can be classified as either native (C++) or interpreted (JS): */
+  bool isInterpreted() const { return flags().isInterpreted(); }
+  bool isNativeFun() const { return flags().isNativeFun(); }
+
+  bool isConstructor() const { return flags().isConstructor(); }
+
+  bool isNonBuiltinConstructor() const {
+    return flags().isNonBuiltinConstructor();
+  }
+
+  /* Possible attributes of a native function: */
+  bool isAsmJSNative() const { return flags().isAsmJSNative(); }
+
+  bool isWasm() const { return flags().isWasm(); }
+  bool isWasmWithJitEntry() const { return flags().isWasmWithJitEntry(); }
+  bool isNativeWithoutJitEntry() const {
+    return flags().isNativeWithoutJitEntry();
+  }
+  bool isBuiltinNative() const { return flags().isBuiltinNative(); }
+
+  bool hasJitEntry() const { return flags().hasJitEntry(); }
+
+  /* Possible attributes of an interpreted function: */
+  bool hasInferredName() const { return flags().hasInferredName(); }
+  bool hasGuessedAtom() const { return flags().hasGuessedAtom(); }
+
+  bool isLambda() const { return flags().isLambda(); }
+
+  // These methods determine which kind of script we hold.
+  //
+  // For live JSFunctions the pointer values will always be non-null, but due to
+  // partial initialization the GC (and other features that scan the heap
+  // directly) may still return a null pointer.
+  bool hasSelfHostedLazyScript() const {
+    return flags().hasSelfHostedLazyScript();
+  }
+  bool hasBaseScript() const { return flags().hasBaseScript(); }
+
+  bool hasBytecode() const {
+    MOZ_ASSERT(!isIncomplete());
+    return hasBaseScript() && baseScript()->hasBytecode();
+  }
+
+  bool isGhost() const { return flags().isGhost(); }
+
+  // Arrow functions store their lexical new.target in the first extended slot.
+  bool isArrow() const { return flags().isArrow(); }
+  // Every class-constructor is also a method.
+  bool isMethod() const { return flags().isMethod(); }
+  bool isClassConstructor() const { return flags().isClassConstructor(); }
+
+  bool isGetter() const { return flags().isGetter(); }
+  bool isSetter() const { return flags().isSetter(); }
+
+  bool allowSuperProperty() const { return flags().allowSuperProperty(); }
+
+  bool hasResolvedLength() const { return flags().hasResolvedLength(); }
+  bool hasResolvedName() const { return flags().hasResolvedName(); }
+
+  bool isSelfHostedOrIntrinsic() const {
+    return flags().isSelfHostedOrIntrinsic();
+  }
+  bool isSelfHostedBuiltin() const { return flags().isSelfHostedBuiltin(); }
+
+  bool isIntrinsic() const { return flags().isIntrinsic(); }
+
+  bool hasJitScript() const {
+    if (!hasBaseScript()) {
+      return false;
+    }
+
+    return baseScript()->hasJitScript();
+  }
+
+  /* Compound attributes: */
+  bool isBuiltin() const { return isBuiltinNative() || isSelfHostedBuiltin(); }
+
+  bool isNamedLambda() const {
+    return flags().isNamedLambda(displayAtom() != nullptr);
+  }
+
+  bool hasLexicalThis() const { return isArrow(); }
+
+  bool isBuiltinFunctionConstructor();
+  bool needsPrototypeProperty();
+
+  // Returns true if this function must have a non-configurable .prototype data
+  // property. This is used to ensure looking up .prototype elsewhere will have
+  // no side-effects.
+  bool hasNonConfigurablePrototypeDataProperty();
+
+  // Returns true if |new Fun()| should not allocate a new object caller-side
+  // but pass the uninitialized-lexical MagicValue and rely on the callee to
+  // construct its own |this| object.
+  bool constructorNeedsUninitializedThis() const {
+    MOZ_ASSERT(isConstructor());
+    MOZ_ASSERT(isInterpreted());
+    return isDerivedClassConstructor();
+  }
+
+  /* Returns the strictness of this function, which must be interpreted. */
+  bool strict() const { return baseScript()->strict(); }
+
+  void setFlags(FunctionFlags flags) { setFlags(flags.toRaw()); }
+  void setFlags(uint16_t flags) {
+    uint32_t flagsAndArgCount = flagsAndArgCountRaw();
+    flagsAndArgCount &= ~FlagsMask;
+    flagsAndArgCount |= flags;
+    js::HeapSlot& slot = getFixedSlotRef(FlagsAndArgCountSlot);
+    slot.unbarrieredSet(JS::PrivateUint32Value(flagsAndArgCount));
+  }
+
+  // Make the function constructible.
+  void setIsConstructor() { setFlags(flags().setIsConstructor()); }
+
+  // Can be called multiple times by the parser.
+  void setArgCount(uint16_t nargs) {
+    uint32_t flagsAndArgCount = flagsAndArgCountRaw();
+    flagsAndArgCount &= ~ArgCountMask;
+    flagsAndArgCount |= nargs << ArgCountShift;
+    js::HeapSlot& slot = getFixedSlotRef(FlagsAndArgCountSlot);
+    slot.unbarrieredSet(JS::PrivateUint32Value(flagsAndArgCount));
+  }
+
+  void setIsSelfHostedBuiltin() { setFlags(flags().setIsSelfHostedBuiltin()); }
+  void setIsIntrinsic() { setFlags(flags().setIsIntrinsic()); }
+
+  void setResolvedLength() { setFlags(flags().setResolvedLength()); }
+  void setResolvedName() { setFlags(flags().setResolvedName()); }
+
+  static inline bool getUnresolvedLength(JSContext* cx, js::HandleFunction fun,
+                                         uint16_t* length);
+
+  inline JSAtom* infallibleGetUnresolvedName(JSContext* cx);
+
+  JSAtom* explicitName() const {
+    return (hasInferredName() || hasGuessedAtom()) ? nullptr : rawAtom();
+  }
+
+  JSAtom* explicitOrInferredName() const {
+    return hasGuessedAtom() ? nullptr : rawAtom();
+  }
+
+  void initAtom(JSAtom* atom) {
+    MOZ_ASSERT_IF(atom, js::AtomIsMarked(zone(), atom));
+    MOZ_ASSERT(getFixedSlot(AtomSlot).isUndefined());
+    if (atom) {
+      initFixedSlot(AtomSlot, JS::StringValue(atom));
+    }
+  }
+
+  void setAtom(JSAtom* atom) {
+    MOZ_ASSERT_IF(atom, js::AtomIsMarked(zone(), atom));
+    setFixedSlot(AtomSlot, atom ? JS::StringValue(atom) : JS::UndefinedValue());
+  }
+
+  JSAtom* displayAtom() const { return rawAtom(); }
+
+  JSAtom* rawAtom() const {
+    JS::Value value = getFixedSlot(AtomSlot);
+    return value.isUndefined() ? nullptr : &value.toString()->asAtom();
+  }
+
+  void setInferredName(JSAtom* atom) {
+    MOZ_ASSERT(!rawAtom());
+    MOZ_ASSERT(atom);
+    MOZ_ASSERT(!hasGuessedAtom());
+    setAtom(atom);
+    setFlags(flags().setInferredName());
+  }
+  JSAtom* inferredName() const {
+    MOZ_ASSERT(hasInferredName());
+    MOZ_ASSERT(rawAtom());
+    return rawAtom();
+  }
+
+  void setGuessedAtom(JSAtom* atom) {
+    MOZ_ASSERT(!rawAtom());
+    MOZ_ASSERT(atom);
+    MOZ_ASSERT(!hasInferredName());
+    MOZ_ASSERT(!hasGuessedAtom());
+    setAtom(atom);
+    setFlags(flags().setGuessedAtom());
+  }
+
+  /* uint16_t representation bounds number of call object dynamic slots. */
+  enum { MAX_ARGS_AND_VARS = 2 * ((1U << 16) - 1) };
+
+  /*
+   * For an interpreted function, accessors for the initial scope object of
+   * activations (stack frames) of the function.
+   */
+  JSObject* environment() const {
+    MOZ_ASSERT(isInterpreted());
+    return getFixedSlot(NativeFuncOrInterpretedEnvSlot).toObjectOrNull();
+  }
+
+  void initEnvironment(JSObject* obj) {
+    MOZ_ASSERT(isInterpreted());
+    initFixedSlot(NativeFuncOrInterpretedEnvSlot, JS::ObjectOrNullValue(obj));
+  }
+
+ public:
+  static constexpr size_t offsetOfFlagsAndArgCount() {
+    return getFixedSlotOffset(FlagsAndArgCountSlot);
+  }
+  static size_t offsetOfEnvironment() { return offsetOfNativeOrEnv(); }
+  static size_t offsetOfAtom() { return getFixedSlotOffset(AtomSlot); }
+
+  static bool delazifyLazilyInterpretedFunction(JSContext* cx,
+                                                js::HandleFunction fun);
+  static bool delazifySelfHostedLazyFunction(JSContext* cx,
+                                             js::HandleFunction fun);
+  void maybeRelazify(JSRuntime* rt);
+
+  // Function Scripts
+  //
+  // Interpreted functions have either a BaseScript or a SelfHostedLazyScript. A
+  // BaseScript may either be lazy or non-lazy (hasBytecode()). Methods may
+  // return a JSScript* if underlying BaseScript is known to have bytecode.
+  //
+  // There are several methods to get the script of an interpreted function:
+  //
+  // - For all interpreted functions, getOrCreateScript() will get the
+  //   JSScript, delazifying the function if necessary. This is the safest to
+  //   use, but has extra checks, requires a cx and may trigger a GC.
+  //
+  // - For functions known to have a JSScript, nonLazyScript() will get it.
+
+  static JSScript* getOrCreateScript(JSContext* cx, js::HandleFunction fun) {
+    MOZ_ASSERT(fun->isInterpreted());
+    MOZ_ASSERT(cx);
+
+    if (fun->hasSelfHostedLazyScript()) {
+      if (!delazifySelfHostedLazyFunction(cx, fun)) {
+        return nullptr;
+      }
+      return fun->nonLazyScript();
+    }
+
+    MOZ_ASSERT(fun->hasBaseScript());
+
+    if (!fun->baseScript()->hasBytecode()) {
+      if (!delazifyLazilyInterpretedFunction(cx, fun)) {
+        return nullptr;
+      }
+    }
+    return fun->nonLazyScript();
+  }
+
+  // If this is a scripted function, returns its canonical function (the
+  // original function allocated by the frontend). Note that lazy self-hosted
+  // builtins don't have a lazy script so in that case we also return nullptr.
+  JSFunction* maybeCanonicalFunction() const {
+    if (hasBaseScript()) {
+      return baseScript()->function();
+    }
+    return nullptr;
+  }
+
+ private:
+  void* nativeJitInfoOrInterpretedScript() const {
+    return getFixedSlot(NativeJitInfoOrInterpretedScriptSlot).toPrivate();
+  }
+  void setNativeJitInfoOrInterpretedScript(void* ptr) {
+    // This always stores a PrivateValue and so doesn't require a barrier.
+    js::HeapSlot& slot = getFixedSlotRef(NativeJitInfoOrInterpretedScriptSlot);
+    slot.unbarrieredSet(JS::PrivateValue(ptr));
+  }
+
+ public:
+  // The default state of a JSFunction that is not ready for execution. If
+  // observed outside initialization, this is the result of failure during
+  // bytecode compilation.
+  //
+  // A BaseScript is fully initialized before u.script.s.script_ is initialized
+  // with a reference to it.
+  bool isIncomplete() const {
+    return isInterpreted() && !nativeJitInfoOrInterpretedScript();
+  }
+
+  JSScript* nonLazyScript() const {
+    MOZ_ASSERT(hasBytecode());
+    return static_cast<JSScript*>(baseScript());
+  }
+
+  js::SelfHostedLazyScript* selfHostedLazyScript() const {
+    MOZ_ASSERT(hasSelfHostedLazyScript());
+    return static_cast<js::SelfHostedLazyScript*>(
+        nativeJitInfoOrInterpretedScript());
+  }
+
+  // Access fields defined on both lazy and non-lazy scripts.
+  js::BaseScript* baseScript() const {
+    MOZ_ASSERT(hasBaseScript());
+    return static_cast<JSScript*>(nativeJitInfoOrInterpretedScript());
+  }
+
+  static inline bool getLength(JSContext* cx, js::HandleFunction fun,
+                               uint16_t* length);
+
+  js::Scope* enclosingScope() const { return baseScript()->enclosingScope(); }
+
+  void setEnclosingLazyScript(js::BaseScript* enclosingScript) {
+    baseScript()->setEnclosingScript(enclosingScript);
+  }
+
+  js::GeneratorKind generatorKind() const {
+    if (hasBaseScript()) {
+      return baseScript()->generatorKind();
+    }
+    if (hasSelfHostedLazyScript()) {
+      return clonedSelfHostedGeneratorKind();
+    }
+    return js::GeneratorKind::NotGenerator;
+  }
+
+  js::GeneratorKind clonedSelfHostedGeneratorKind() const;
+
+  bool isGenerator() const {
+    return generatorKind() == js::GeneratorKind::Generator;
+  }
+
+  js::FunctionAsyncKind asyncKind() const {
+    if (hasBaseScript()) {
+      return baseScript()->asyncKind();
+    }
+    return js::FunctionAsyncKind::SyncFunction;
+  }
+
+  bool isAsync() const {
+    return asyncKind() == js::FunctionAsyncKind::AsyncFunction;
+  }
+
+  bool isGeneratorOrAsync() const { return isGenerator() || isAsync(); }
+
+  void initScript(js::BaseScript* script) {
+    MOZ_ASSERT_IF(script, realm() == script->realm());
+    MOZ_ASSERT(isInterpreted());
+    MOZ_ASSERT_IF(hasBaseScript(),
+                  !baseScript());  // No write barrier required.
+    setNativeJitInfoOrInterpretedScript(script);
+  }
+
+  void initSelfHostedLazyScript(js::SelfHostedLazyScript* lazy) {
+    MOZ_ASSERT(isSelfHostedBuiltin());
+    MOZ_ASSERT(isInterpreted());
+    if (hasBaseScript()) {
+      js::gc::PreWriteBarrier(baseScript());
+    }
+    FunctionFlags f = flags();
+    f.clearBaseScript();
+    f.setSelfHostedLazy();
+    setFlags(f);
+    setNativeJitInfoOrInterpretedScript(lazy);
+    MOZ_ASSERT(hasSelfHostedLazyScript());
+  }
+
+  void clearSelfHostedLazyScript() {
+    MOZ_ASSERT(isSelfHostedBuiltin());
+    MOZ_ASSERT(isInterpreted());
+    MOZ_ASSERT(!hasBaseScript());  // No write barrier required.
+    FunctionFlags f = flags();
+    f.clearSelfHostedLazy();
+    f.setBaseScript();
+    setFlags(f);
+    setNativeJitInfoOrInterpretedScript(nullptr);
+    MOZ_ASSERT(isIncomplete());
+  }
+
+  JSNative native() const {
+    MOZ_ASSERT(isNativeFun());
+    return nativeUnchecked();
+  }
+  JSNative nativeUnchecked() const {
+    // Can be called by Ion off-main thread.
+    JS::Value value = getFixedSlot(NativeFuncOrInterpretedEnvSlot);
+    return reinterpret_cast<JSNative>(value.toPrivate());
+  }
+
+  JSNative maybeNative() const { return isInterpreted() ? nullptr : native(); }
+
+  void initNative(js::Native native, const JSJitInfo* jitInfo) {
+    MOZ_ASSERT(isNativeFun());
+    MOZ_ASSERT_IF(jitInfo, isBuiltinNative());
+    MOZ_ASSERT(native);
+    initFixedSlot(NativeFuncOrInterpretedEnvSlot,
+                  JS::PrivateValue(reinterpret_cast<void*>(native)));
+    setNativeJitInfoOrInterpretedScript(const_cast<JSJitInfo*>(jitInfo));
+  }
+  bool hasJitInfo() const { return isBuiltinNative() && jitInfoUnchecked(); }
+  const JSJitInfo* jitInfo() const {
+    MOZ_ASSERT(hasJitInfo());
+    return jitInfoUnchecked();
+  }
+  const JSJitInfo* jitInfoUnchecked() const {
+    // Can be called by Ion off-main thread.
+    return static_cast<const JSJitInfo*>(nativeJitInfoOrInterpretedScript());
+  }
+  void setJitInfo(const JSJitInfo* data) {
+    MOZ_ASSERT(isBuiltinNative());
+    MOZ_ASSERT(data);
+    setNativeJitInfoOrInterpretedScript(const_cast<JSJitInfo*>(data));
+  }
+
+  // wasm functions are always natives and either:
+  //  - store a function-index in u.n.extra and can only be called through the
+  //    fun->native() entry point from C++.
+  //  - store a jit-entry code pointer in u.n.extra and can be called by jit
+  //    code directly. C++ callers can still use the fun->native() entry point
+  //    (computing the function index from the jit-entry point).
+  void setWasmFuncIndex(uint32_t funcIndex) {
+    MOZ_ASSERT(isWasm() || isAsmJSNative());
+    MOZ_ASSERT(!isWasmWithJitEntry());
+    MOZ_ASSERT(!nativeJitInfoOrInterpretedScript());
+    // See wasmFuncIndex_ comment for why we set the low bit.
+    uintptr_t tagged = (uintptr_t(funcIndex) << 1) | 1;
+    setNativeJitInfoOrInterpretedScript(reinterpret_cast<void*>(tagged));
+  }
+  uint32_t wasmFuncIndex() const {
+    MOZ_ASSERT(isWasm() || isAsmJSNative());
+    MOZ_ASSERT(!isWasmWithJitEntry());
+    uintptr_t tagged = uintptr_t(nativeJitInfoOrInterpretedScript());
+    MOZ_ASSERT(tagged & 1);
+    return tagged >> 1;
+  }
+  void setWasmJitEntry(void** entry) {
+    MOZ_ASSERT(*entry);
+    MOZ_ASSERT(isWasm());
+    MOZ_ASSERT(!isWasmWithJitEntry());
+    setFlags(flags().setWasmJitEntry());
+    setNativeJitInfoOrInterpretedScript(entry);
+    MOZ_ASSERT(isWasmWithJitEntry());
+  }
+  void** wasmJitEntry() const {
+    MOZ_ASSERT(isWasmWithJitEntry());
+    return static_cast<void**>(nativeJitInfoOrInterpretedScript());
+  }
+  inline js::wasm::Instance& wasmInstance() const;
+
+  bool isDerivedClassConstructor() const;
+  bool isSyntheticFunction() const;
+
+  static unsigned offsetOfNativeOrEnv() {
+    return getFixedSlotOffset(NativeFuncOrInterpretedEnvSlot);
+  }
+  static unsigned offsetOfJitInfoOrScript() {
+    return getFixedSlotOffset(NativeJitInfoOrInterpretedScriptSlot);
+  }
+
+  inline void trace(JSTracer* trc);
+
+ public:
+  inline bool isExtended() const {
+    bool extended = flags().isExtended();
+    MOZ_ASSERT_IF(isTenured(),
+                  extended == (asTenured().getAllocKind() ==
+                               js::gc::AllocKind::FUNCTION_EXTENDED));
+    return extended;
+  }
+
+  /*
+   * Accessors for data stored in extended functions. Use setExtendedSlot if the
+   * function has already been initialized. Otherwise use initExtendedSlot.
+   */
+  inline void initExtendedSlot(uint32_t slot, const js::Value& val);
+  inline void setExtendedSlot(uint32_t slot, const js::Value& val);
+  inline const js::Value& getExtendedSlot(uint32_t slot) const;
+
+  /* GC support. */
+  js::gc::AllocKind getAllocKind() const {
+    static_assert(
+        js::gc::AllocKind::FUNCTION != js::gc::AllocKind::FUNCTION_EXTENDED,
+        "extended/non-extended AllocKinds have to be different "
+        "for getAllocKind() to have a reason to exist");
+
+    js::gc::AllocKind kind = js::gc::AllocKind::FUNCTION;
+    if (isExtended()) {
+      kind = js::gc::AllocKind::FUNCTION_EXTENDED;
+    }
+    MOZ_ASSERT_IF(isTenured(), kind == asTenured().getAllocKind());
+    return kind;
+  }
+
+  // If we're constructing with this function, choose an appropriate
+  // allocKind.
+  static bool getAllocKindForThis(JSContext* cx, js::HandleFunction func,
+                                  js::gc::AllocKind& allocKind);
+};
+
+static_assert(sizeof(JSFunction) == sizeof(JS::shadow::Function),
+              "shadow interface must match actual interface");
+
+static_assert(unsigned(JSFunction::FlagsAndArgCountSlot) ==
+              unsigned(JS::shadow::Function::FlagsAndArgCountSlot));
+static_assert(unsigned(JSFunction::NativeFuncOrInterpretedEnvSlot) ==
+              unsigned(JS::shadow::Function::NativeFuncOrInterpretedEnvSlot));
+static_assert(
+    unsigned(JSFunction::NativeJitInfoOrInterpretedScriptSlot) ==
+    unsigned(JS::shadow::Function::NativeJitInfoOrInterpretedScriptSlot));
+static_assert(unsigned(JSFunction::AtomSlot) ==
+              unsigned(JS::shadow::Function::AtomSlot));
+
+extern JSString* fun_toStringHelper(JSContext* cx, js::HandleObject obj,
+                                    bool isToSource);
+
+namespace js {
+
+extern bool Function(JSContext* cx, unsigned argc, Value* vp);
+
+extern bool Generator(JSContext* cx, unsigned argc, Value* vp);
+
+extern bool AsyncFunctionConstructor(JSContext* cx, unsigned argc, Value* vp);
+
+extern bool AsyncGeneratorConstructor(JSContext* cx, unsigned argc, Value* vp);
+
+// If enclosingEnv is null, the function will have a null environment()
+// (yes, null, not the global lexical environment).  In all cases, the global
+// will be used as the terminating environment.
+
+extern JSFunction* NewFunctionWithProto(
+    JSContext* cx, JSNative native, unsigned nargs, FunctionFlags flags,
+    HandleObject enclosingEnv, Handle<JSAtom*> atom, HandleObject proto,
+    gc::AllocKind allocKind = gc::AllocKind::FUNCTION,
+    NewObjectKind newKind = GenericObject);
+
+// Allocate a new function backed by a JSNative.  Note that by default this
+// creates a tenured object.
+inline JSFunction* NewNativeFunction(
+    JSContext* cx, JSNative native, unsigned nargs, Handle<JSAtom*> atom,
+    gc::AllocKind allocKind = gc::AllocKind::FUNCTION,
+    NewObjectKind newKind = TenuredObject,
+    FunctionFlags flags = FunctionFlags::NATIVE_FUN) {
+  MOZ_ASSERT(native);
+  return NewFunctionWithProto(cx, native, nargs, flags, nullptr, atom, nullptr,
+                              allocKind, newKind);
+}
+
+// Allocate a new constructor backed by a JSNative.  Note that by default this
+// creates a tenured object.
+inline JSFunction* NewNativeConstructor(
+    JSContext* cx, JSNative native, unsigned nargs, Handle<JSAtom*> atom,
+    gc::AllocKind allocKind = gc::AllocKind::FUNCTION,
+    NewObjectKind newKind = TenuredObject,
+    FunctionFlags flags = FunctionFlags::NATIVE_CTOR) {
+  MOZ_ASSERT(native);
+  MOZ_ASSERT(flags.isNativeConstructor());
+  return NewFunctionWithProto(cx, native, nargs, flags, nullptr, atom, nullptr,
+                              allocKind, newKind);
+}
+
+// Determine which [[Prototype]] to use when creating a new function using the
+// requested generator and async kind.
+//
+// This sets `proto` to `nullptr` for non-generator, synchronous functions to
+// mean "the builtin %FunctionPrototype% in the current realm", the common case.
+//
+// We could set it to `cx->global()->getOrCreateFunctionPrototype()`, but
+// nullptr gets a fast path in e.g. js::NewObjectWithClassProtoCommon.
+extern bool GetFunctionPrototype(JSContext* cx, js::GeneratorKind generatorKind,
+                                 js::FunctionAsyncKind asyncKind,
+                                 js::MutableHandleObject proto);
+
+extern JSAtom* IdToFunctionName(
+    JSContext* cx, HandleId id,
+    FunctionPrefixKind prefixKind = FunctionPrefixKind::None);
+
+extern bool SetFunctionName(JSContext* cx, HandleFunction fun, HandleValue name,
+                            FunctionPrefixKind prefixKind);
+
+extern JSFunction* DefineFunction(
+    JSContext* cx, HandleObject obj, HandleId id, JSNative native,
+    unsigned nargs, unsigned flags,
+    gc::AllocKind allocKind = gc::AllocKind::FUNCTION);
+
+extern bool fun_toString(JSContext* cx, unsigned argc, Value* vp);
+
+extern void ThrowTypeErrorBehavior(JSContext* cx);
+
+/*
+ * Function extended with reserved slots for use by various kinds of functions.
+ * Most functions do not have these extensions, but enough do that efficient
+ * storage is required (no malloc'ed reserved slots).
+ */
+class FunctionExtended : public JSFunction {
+ public:
+  enum {
+    FirstExtendedSlot = JSFunction::SlotCount,
+    SecondExtendedSlot,
+
+    SlotCount
+  };
+
+  static const uint32_t NUM_EXTENDED_SLOTS = 2;
+
+  static const uint32_t METHOD_HOMEOBJECT_SLOT = 0;
+
+  // wasm/asm.js exported functions store a code pointer to their direct entry
+  // point (see CodeRange::funcUncheckedCallEntry()) to support the call_ref
+  // instruction.
+  static const uint32_t WASM_FUNC_UNCHECKED_ENTRY_SLOT = 0;
+
+  // wasm/asm.js exported functions store the wasm::Instance pointer of their
+  // instance.
+  static const uint32_t WASM_INSTANCE_SLOT = 1;
+
+  // asm.js module functions store their WasmModuleObject in the first slot.
+  static const uint32_t ASMJS_MODULE_SLOT = 0;
+
+  // Async module callback handlers store their ModuleObject in the first slot.
+  static const uint32_t MODULE_SLOT = 0;
+
+  static inline size_t offsetOfExtendedSlot(uint32_t which) {
+    MOZ_ASSERT(which < NUM_EXTENDED_SLOTS);
+    return getFixedSlotOffset(FirstExtendedSlot + which);
+  }
+  static inline size_t offsetOfMethodHomeObjectSlot() {
+    return offsetOfExtendedSlot(METHOD_HOMEOBJECT_SLOT);
+  }
+
+ private:
+  friend class JSFunction;
+};
+
+extern JSFunction* CloneFunctionReuseScript(JSContext* cx, HandleFunction fun,
+                                            HandleObject enclosingEnv,
+                                            HandleObject proto);
+
+extern JSFunction* CloneAsmJSModuleFunction(JSContext* cx, HandleFunction fun);
+
+}  // namespace js
+
+template <>
+inline bool JSObject::is<JSFunction>() const {
+  return getClass()->isJSFunction();
+}
+
+inline void JSFunction::initExtendedSlot(uint32_t which, const js::Value& val) {
+  MOZ_ASSERT(isExtended());
+  MOZ_ASSERT(which < js::FunctionExtended::NUM_EXTENDED_SLOTS);
+  MOZ_ASSERT(js::IsObjectValueInCompartment(val, compartment()));
+  initFixedSlot(js::FunctionExtended::FirstExtendedSlot + which, val);
+}
+
+inline void JSFunction::setExtendedSlot(uint32_t which, const js::Value& val) {
+  MOZ_ASSERT(isExtended());
+  MOZ_ASSERT(which < js::FunctionExtended::NUM_EXTENDED_SLOTS);
+  MOZ_ASSERT(js::IsObjectValueInCompartment(val, compartment()));
+  setFixedSlot(js::FunctionExtended::FirstExtendedSlot + which, val);
+}
+
+inline const js::Value& JSFunction::getExtendedSlot(uint32_t which) const {
+  MOZ_ASSERT(isExtended());
+  MOZ_ASSERT(which < js::FunctionExtended::NUM_EXTENDED_SLOTS);
+  return getFixedSlot(js::FunctionExtended::FirstExtendedSlot + which);
+}
+
+inline js::wasm::Instance& JSFunction::wasmInstance() const {
+  MOZ_ASSERT(isWasm() || isAsmJSNative());
+  MOZ_ASSERT(
+      !getExtendedSlot(js::FunctionExtended::WASM_INSTANCE_SLOT).isUndefined());
+  return *static_cast<js::wasm::Instance*>(
+      getExtendedSlot(js::FunctionExtended::WASM_INSTANCE_SLOT).toPrivate());
+}
+
+namespace js {
+
+JSString* FunctionToString(JSContext* cx, HandleFunction fun, bool isToSource);
+
+/*
+ * Report an error that call.thisv is not compatible with the specified class,
+ * assuming that the method (clasp->name).prototype.<name of callee function>
+ * is what was called.
+ */
+extern void ReportIncompatibleMethod(JSContext* cx, const CallArgs& args,
+                                     const JSClass* clasp);
+
+/*
+ * Report an error that call.thisv is not an acceptable this for the callee
+ * function.
+ */
+extern void ReportIncompatible(JSContext* cx, const CallArgs& args);
+
+extern bool fun_apply(JSContext* cx, unsigned argc, Value* vp);
+
+extern bool fun_call(JSContext* cx, unsigned argc, Value* vp);
+
+} /* namespace js */
+
+#ifdef DEBUG
+namespace JS {
+namespace detail {
+
+JS_PUBLIC_API void CheckIsValidConstructible(const Value& calleev);
+
+}  // namespace detail
+}  // namespace JS
+#endif
+
+#endif /* vm_JSFunction_h */