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/* -*- 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
#ifndef vm_Watchtower_h
#define vm_Watchtower_h
#include "js/TypeDecls.h"
#include "vm/NativeObject.h"
namespace js {
// [SMDOC] Watchtower
//
// Watchtower is a framework to hook into changes to certain objects. This gives
// us the ability to, for instance, invalidate caches or purge Warp code on
// object layout changes.
//
// Watchtower is only used for objects with certain ObjectFlags set on the
// Shape. This minimizes performance overhead for most objects.
//
// We currently use Watchtower for:
//
// - Invalidating the shape teleporting optimization. See the "Shape Teleporting
// Optimization" SMDOC comment in CacheIR.cpp.
//
// - Invalidating the MegamorphicCache, a property lookup cache for megamorphic
// property accesses. See the SMDOC comment in vm/Caches.h.
//
// There's also a testing mechanism that lets us write tests for Watchtower
// hooks. See setWatchtowerCallback and addWatchtowerTarget defined in
// TestingFunctions.cpp.
class Watchtower {
static bool watchPropertyAddSlow(JSContext* cx, Handle<NativeObject*> obj,
HandleId id);
static bool watchPropertyRemoveSlow(JSContext* cx, Handle<NativeObject*> obj,
HandleId id);
static bool watchPropertyChangeSlow(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, PropertyFlags flags);
template <AllowGC allowGC>
static bool watchPropertyModificationSlow(
JSContext* cx,
typename MaybeRooted<NativeObject*, allowGC>::HandleType obj,
typename MaybeRooted<PropertyKey, allowGC>::HandleType id);
static bool watchFreezeOrSealSlow(JSContext* cx, Handle<NativeObject*> obj);
static bool watchProtoChangeSlow(JSContext* cx, HandleObject obj);
static bool watchObjectSwapSlow(JSContext* cx, HandleObject a,
HandleObject b);
public:
static bool watchesPropertyAdd(NativeObject* obj) {
return obj->hasAnyFlag(
{ObjectFlag::IsUsedAsPrototype, ObjectFlag::UseWatchtowerTestingLog});
}
static bool watchesPropertyRemove(NativeObject* obj) {
return obj->hasAnyFlag(
{ObjectFlag::IsUsedAsPrototype, ObjectFlag::GenerationCountedGlobal,
ObjectFlag::UseWatchtowerTestingLog, ObjectFlag::HasFuseProperty});
}
static bool watchesPropertyChange(NativeObject* obj) {
return obj->hasAnyFlag(
{ObjectFlag::IsUsedAsPrototype, ObjectFlag::GenerationCountedGlobal,
ObjectFlag::HasFuseProperty, ObjectFlag::UseWatchtowerTestingLog});
}
static bool watchesPropertyModification(NativeObject* obj) {
return obj->hasAnyFlag(
{ObjectFlag::HasFuseProperty, ObjectFlag::UseWatchtowerTestingLog});
}
static bool watchesFreezeOrSeal(NativeObject* obj) {
return obj->hasAnyFlag({ObjectFlag::UseWatchtowerTestingLog});
}
static bool watchesProtoChange(JSObject* obj) {
return obj->hasAnyFlag(
{ObjectFlag::IsUsedAsPrototype, ObjectFlag::UseWatchtowerTestingLog});
}
static bool watchesObjectSwap(JSObject* a, JSObject* b) {
auto watches = [](JSObject* obj) {
return obj->hasAnyFlag(
{ObjectFlag::IsUsedAsPrototype, ObjectFlag::UseWatchtowerTestingLog});
};
return watches(a) || watches(b);
}
static bool watchPropertyAdd(JSContext* cx, Handle<NativeObject*> obj,
HandleId id) {
if (MOZ_LIKELY(!watchesPropertyAdd(obj))) {
return true;
}
return watchPropertyAddSlow(cx, obj, id);
}
static bool watchPropertyRemove(JSContext* cx, Handle<NativeObject*> obj,
HandleId id) {
if (MOZ_LIKELY(!watchesPropertyRemove(obj))) {
return true;
}
return watchPropertyRemoveSlow(cx, obj, id);
}
static bool watchPropertyChange(JSContext* cx, Handle<NativeObject*> obj,
HandleId id, PropertyFlags flags) {
if (MOZ_LIKELY(!watchesPropertyChange(obj))) {
return true;
}
return watchPropertyChangeSlow(cx, obj, id, flags);
}
// Note: We can only watch property modification for regular object slots
// with an id, not reserved slots.
template <AllowGC allowGC>
static bool watchPropertyModification(
JSContext* cx,
typename MaybeRooted<NativeObject*, allowGC>::HandleType obj,
typename MaybeRooted<PropertyKey, allowGC>::HandleType id) {
if (MOZ_LIKELY(!watchesPropertyModification(obj))) {
return true;
}
return watchPropertyModificationSlow<allowGC>(cx, obj, id);
}
static bool watchFreezeOrSeal(JSContext* cx, Handle<NativeObject*> obj) {
if (MOZ_LIKELY(!watchesFreezeOrSeal(obj))) {
return true;
}
return watchFreezeOrSealSlow(cx, obj);
}
static bool watchProtoChange(JSContext* cx, HandleObject obj) {
if (MOZ_LIKELY(!watchesProtoChange(obj))) {
return true;
}
return watchProtoChangeSlow(cx, obj);
}
static bool watchObjectSwap(JSContext* cx, HandleObject a, HandleObject b) {
if (MOZ_LIKELY(!watchesObjectSwap(a, b))) {
return true;
}
return watchObjectSwapSlow(cx, a, b);
}
};
} // namespace js
#endif /* vm_Watchtower_h */