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/* -*- 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 */
#ifndef vm_ReceiverGuard_h
#define vm_ReceiverGuard_h
#include "vm/Shape.h"
namespace js {
// A ReceiverGuard encapsulates the information about an object that needs to
// be tested to determine if it has the same 'structure' as another object.
// The guard includes the shape and/or group of the object, and which of these
// is tested, as well as the meaning here of 'structure', depends on the kind
// of object being tested:
// NativeObject: The structure of a native object is determined by its shape.
// Two objects with the same shape have the same class, prototype, flags,
// and all properties except those stored in dense elements.
// ProxyObject: The structure of a proxy object is determined by its shape.
// Proxies with the same shape have the same class and prototype, but no
// other commonality is guaranteed.
// TypedObject: The structure of a typed object is determined by its group.
// All typed objects with the same group have the same class, prototype, and
// own properties.
// UnboxedPlainObject: The structure of an unboxed plain object is determined
// by its group and its expando object's shape, if there is one. All unboxed
// plain objects with the same group and expando shape have the same
// properties except those stored in the expando's dense elements.
class HeapReceiverGuard;
class RootedReceiverGuard;
class ReceiverGuard
ObjectGroup* group;
Shape* shape;
: group(nullptr), shape(nullptr)
inline MOZ_IMPLICIT ReceiverGuard(const HeapReceiverGuard& guard);
inline MOZ_IMPLICIT ReceiverGuard(const RootedReceiverGuard& guard);
explicit ReceiverGuard(JSObject* obj);
ReceiverGuard(ObjectGroup* group, Shape* shape);
bool operator ==(const ReceiverGuard& other) const {
return group == && shape == other.shape;
bool operator !=(const ReceiverGuard& other) const {
return !(*this == other);
uintptr_t hash() const {
return (uintptr_t(group) >> 3) ^ (uintptr_t(shape) >> 3);
class HeapReceiverGuard
HeapPtrObjectGroup group_;
HeapPtrShape shape_;
explicit HeapReceiverGuard(const ReceiverGuard& guard)
: group_(, shape_(guard.shape)
bool matches(const ReceiverGuard& guard) {
return group_ == && shape_ == guard.shape;
void update(const ReceiverGuard& other) {
group_ =;
shape_ = other.shape;
void init(const ReceiverGuard& other) {
void trace(JSTracer* trc);
Shape* shape() const {
return shape_;
ObjectGroup* group() const {
return group_;
static size_t offsetOfShape() {
return offsetof(HeapReceiverGuard, shape_);
static size_t offsetOfGroup() {
return offsetof(HeapReceiverGuard, group_);
// Bits to munge into Baseline IC compiler keys when that IC has a
// HeapReceiverGuard. This uses at most two bits for data.
static int32_t keyBits(JSObject* obj);
class RootedReceiverGuard
RootedObjectGroup group;
RootedShape shape;
RootedReceiverGuard(JSContext* cx, const ReceiverGuard& guard)
: group(cx,, shape(cx, guard.shape)
ReceiverGuard::ReceiverGuard(const HeapReceiverGuard& guard)
: group(, shape(guard.shape())
ReceiverGuard::ReceiverGuard(const RootedReceiverGuard& guard)
: group(, shape(guard.shape)
} // namespace js
#endif /* vm_ReceiverGuard_h */