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ObjectGroup.cpp
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ObjectGroup.cpp
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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
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
#include "vm/ObjectGroup.h"
#include "mozilla/Maybe.h"
#include "mozilla/Unused.h"
#include "jsexn.h"
#include "builtin/DataViewObject.h"
#include "gc/FreeOp.h"
#include "gc/HashUtil.h"
#include "gc/Policy.h"
#include "gc/StoreBuffer.h"
#include "js/CharacterEncoding.h"
#include "js/UniquePtr.h"
#include "vm/ArrayObject.h"
#include "vm/GlobalObject.h"
#include "vm/JSObject.h"
#include "vm/RegExpObject.h"
#include "vm/Shape.h"
#include "vm/TaggedProto.h"
#include "gc/Marking-inl.h"
#include "gc/ObjectKind-inl.h"
#include "vm/JSObject-inl.h"
#include "vm/NativeObject-inl.h"
#include "vm/TypeInference-inl.h"
using namespace js;
/////////////////////////////////////////////////////////////////////
// ObjectGroup
/////////////////////////////////////////////////////////////////////
ObjectGroup::ObjectGroup(const Class* clasp, TaggedProto proto,
JS::Realm* realm, ObjectGroupFlags initialFlags)
: clasp_(clasp), proto_(proto), realm_(realm), flags_(initialFlags) {
/* Windows may not appear on prototype chains. */
MOZ_ASSERT_IF(proto.isObject(), !IsWindow(proto.toObject()));
MOZ_ASSERT(JS::StringIsASCII(clasp->name));
setGeneration(zone()->types.generation);
}
void ObjectGroup::finalize(FreeOp* fop) {
if (auto newScript = newScriptDontCheckGeneration()) {
newScript->clear();
fop->delete_(this, newScript, newScript->gcMallocBytes(),
MemoryUse::ObjectGroupAddendum);
}
if (maybePreliminaryObjectsDontCheckGeneration()) {
maybePreliminaryObjectsDontCheckGeneration()->clear();
}
fop->delete_(this, maybePreliminaryObjectsDontCheckGeneration(),
MemoryUse::ObjectGroupAddendum);
}
void ObjectGroup::setProtoUnchecked(TaggedProto proto) {
proto_ = proto;
MOZ_ASSERT_IF(proto_.isObject() && proto_.toObject()->isNative(),
proto_.toObject()->isDelegate());
}
void ObjectGroup::setProto(TaggedProto proto) {
MOZ_ASSERT(singleton());
setProtoUnchecked(proto);
}
size_t ObjectGroup::sizeOfExcludingThis(
mozilla::MallocSizeOf mallocSizeOf) const {
size_t n = 0;
if (TypeNewScript* newScript = newScriptDontCheckGeneration()) {
n += newScript->sizeOfIncludingThis(mallocSizeOf);
}
return n;
}
static inline size_t AddendumAllocSize(ObjectGroup::AddendumKind kind,
void* addendum) {
if (kind == ObjectGroup::Addendum_NewScript) {
auto newScript = static_cast<TypeNewScript*>(addendum);
return newScript->gcMallocBytes();
}
if (kind == ObjectGroup::Addendum_PreliminaryObjects) {
return sizeof(PreliminaryObjectArrayWithTemplate);
}
// Other addendum kinds point to GC memory tracked elsewhere.
return 0;
}
void ObjectGroup::setAddendum(AddendumKind kind, void* addendum,
bool writeBarrier /* = true */) {
MOZ_ASSERT(!needsSweep());
MOZ_ASSERT(kind <= (OBJECT_FLAG_ADDENDUM_MASK >> OBJECT_FLAG_ADDENDUM_SHIFT));
RemoveCellMemory(this, AddendumAllocSize(addendumKind(), addendum_),
MemoryUse::ObjectGroupAddendum);
if (writeBarrier) {
// Manually trigger barriers if we are clearing new script or
// preliminary object information. Other addendums are immutable.
AutoSweepObjectGroup sweep(this);
switch (addendumKind()) {
case Addendum_PreliminaryObjects:
PreliminaryObjectArrayWithTemplate::writeBarrierPre(
maybePreliminaryObjects(sweep));
break;
case Addendum_NewScript:
TypeNewScript::writeBarrierPre(newScript(sweep));
break;
case Addendum_None:
break;
default:
MOZ_ASSERT(addendumKind() == kind);
}
}
flags_ &= ~OBJECT_FLAG_ADDENDUM_MASK;
flags_ |= kind << OBJECT_FLAG_ADDENDUM_SHIFT;
addendum_ = addendum;
AddCellMemory(this, AddendumAllocSize(kind, addendum),
MemoryUse::ObjectGroupAddendum);
}
/* static */
bool ObjectGroup::useSingletonForClone(JSFunction* fun) {
if (!fun->isInterpreted()) {
return false;
}
if (fun->isArrow()) {
return false;
}
if (fun->isSingleton()) {
return false;
}
/*
* When a function is being used as a wrapper for another function, it
* improves precision greatly to distinguish between different instances of
* the wrapper; otherwise we will conflate much of the information about
* the wrapped functions.
*
* An important example is the Class.create function at the core of the
* Prototype.js library, which looks like:
*
* var Class = {
* create: function() {
* return function() {
* this.initialize.apply(this, arguments);
* }
* }
* };
*
* Each instance of the innermost function will have a different wrapped
* initialize method. We capture this, along with similar cases, by looking
* for short scripts which use both .apply and arguments. For such scripts,
* whenever creating a new instance of the function we both give that
* instance a singleton type and clone the underlying script.
*/
uint32_t begin, end;
if (fun->hasScript()) {
if (!fun->nonLazyScript()->isLikelyConstructorWrapper()) {
return false;
}
begin = fun->nonLazyScript()->sourceStart();
end = fun->nonLazyScript()->sourceEnd();
} else {
if (!fun->lazyScript()->isLikelyConstructorWrapper()) {
return false;
}
begin = fun->lazyScript()->sourceStart();
end = fun->lazyScript()->sourceEnd();
}
return end - begin <= 100;
}
/* static */
bool ObjectGroup::useSingletonForNewObject(JSContext* cx, JSScript* script,
jsbytecode* pc) {
/*
* Make a heuristic guess at a use of JSOP_NEW that the constructed object
* should have a fresh group. We do this when the NEW is immediately
* followed by a simple assignment to an object's .prototype field.
* This is designed to catch common patterns for subclassing in JS:
*
* function Super() { ... }
* function Sub1() { ... }
* function Sub2() { ... }
*
* Sub1.prototype = new Super();
* Sub2.prototype = new Super();
*
* Using distinct groups for the particular prototypes of Sub1 and
* Sub2 lets us continue to distinguish the two subclasses and any extra
* properties added to those prototype objects.
*/
if (script->isGenerator() || script->isAsync()) {
return false;
}
if (JSOp(*pc) != JSOP_NEW) {
return false;
}
pc += JSOP_NEW_LENGTH;
if (JSOp(*pc) == JSOP_SETPROP) {
if (script->getName(pc) == cx->names().prototype) {
return true;
}
}
return false;
}
/* static */
bool ObjectGroup::useSingletonForAllocationSite(JSScript* script,
jsbytecode* pc,
JSProtoKey key) {
/*
* Objects created outside loops in global and eval scripts should have
* singleton types. For now this is only done for plain objects, but not
* typed arrays or normal arrays.
*/
if (script->functionNonDelazifying() && !script->treatAsRunOnce()) {
return false;
}
if (key != JSProto_Object) {
return false;
}
// All loops in the script will have a try note indicating their boundary.
if (!script->hasTrynotes()) {
return true;
}
uint32_t offset = script->pcToOffset(pc);
for (const JSTryNote& tn : script->trynotes()) {
if (tn.kind != JSTRY_FOR_IN && tn.kind != JSTRY_FOR_OF &&
tn.kind != JSTRY_LOOP) {
continue;
}
if (tn.start <= offset && offset < tn.start + tn.length) {
return false;
}
}
return true;
}
/////////////////////////////////////////////////////////////////////
// JSObject
/////////////////////////////////////////////////////////////////////
bool GlobalObject::shouldSplicePrototype() {
// During bootstrapping, we need to make sure not to splice a new prototype in
// for the global object if its __proto__ had previously been set to non-null,
// as this will change the prototype for all other objects with the same type.
return staticPrototype() == nullptr;
}
/* static */
bool JSObject::splicePrototype(JSContext* cx, HandleObject obj,
Handle<TaggedProto> proto) {
MOZ_ASSERT(cx->compartment() == obj->compartment());
/*
* For singleton groups representing only a single JSObject, the proto
* can be rearranged as needed without destroying type information for
* the old or new types.
*/
MOZ_ASSERT(obj->isSingleton());
// Windows may not appear on prototype chains.
MOZ_ASSERT_IF(proto.isObject(), !IsWindow(proto.toObject()));
#ifdef DEBUG
const Class* oldClass = obj->getClass();
#endif
if (proto.isObject()) {
RootedObject protoObj(cx, proto.toObject());
if (!JSObject::setDelegate(cx, protoObj)) {
return false;
}
}
// Force type instantiation when splicing lazy group.
RootedObjectGroup group(cx, JSObject::getGroup(cx, obj));
if (!group) {
return false;
}
RootedObjectGroup protoGroup(cx, nullptr);
if (proto.isObject()) {
RootedObject protoObj(cx, proto.toObject());
protoGroup = JSObject::getGroup(cx, protoObj);
if (!protoGroup) {
return false;
}
}
MOZ_ASSERT(group->clasp() == oldClass,
"splicing a prototype doesn't change a group's class");
group->setProto(proto);
return true;
}
/* static */
ObjectGroup* JSObject::makeLazyGroup(JSContext* cx, HandleObject obj) {
MOZ_ASSERT(obj->hasLazyGroup());
MOZ_ASSERT(cx->compartment() == obj->compartment());
// Find flags which need to be specified immediately on the object.
// Don't track whether singletons are packed.
ObjectGroupFlags initialFlags =
OBJECT_FLAG_SINGLETON | OBJECT_FLAG_NON_PACKED;
if (obj->isIteratedSingleton()) {
initialFlags |= OBJECT_FLAG_ITERATED;
}
if (obj->isNative() && obj->as<NativeObject>().isIndexed()) {
initialFlags |= OBJECT_FLAG_SPARSE_INDEXES;
}
if (obj->is<ArrayObject>() && obj->as<ArrayObject>().length() > INT32_MAX) {
initialFlags |= OBJECT_FLAG_LENGTH_OVERFLOW;
}
Rooted<TaggedProto> proto(cx, obj->taggedProto());
ObjectGroup* group = ObjectGroupRealm::makeGroup(
cx, obj->nonCCWRealm(), obj->getClass(), proto, initialFlags);
if (!group) {
return nullptr;
}
AutoEnterAnalysis enter(cx);
/* Fill in the type according to the state of this object. */
if (obj->is<JSFunction>() && obj->as<JSFunction>().isInterpreted()) {
group->setInterpretedFunction(&obj->as<JSFunction>());
}
obj->group_ = group;
return group;
}
/* static */
bool JSObject::setNewGroupUnknown(JSContext* cx, ObjectGroupRealm& realm,
const js::Class* clasp,
JS::HandleObject obj) {
ObjectGroup::setDefaultNewGroupUnknown(cx, realm, clasp, obj);
return JSObject::setFlags(cx, obj, BaseShape::NEW_GROUP_UNKNOWN);
}
/////////////////////////////////////////////////////////////////////
// ObjectGroupRealm NewTable
/////////////////////////////////////////////////////////////////////
/*
* Entries for the per-realm set of groups which are the default
* types to use for some prototype. An optional associated object is used which
* allows multiple groups to be created with the same prototype. The
* associated object may be a function (for types constructed with 'new') or a
* type descriptor (for typed objects). These entries are also used for the set
* of lazy groups in the realm, which use a null associated object
* (though there are only a few of these per realm).
*/
struct ObjectGroupRealm::NewEntry {
WeakHeapPtrObjectGroup group;
// Note: This pointer is only used for equality and does not need a read
// barrier.
JSObject* associated;
NewEntry(ObjectGroup* group, JSObject* associated)
: group(group), associated(associated) {}
struct Lookup {
const Class* clasp;
TaggedProto proto;
JSObject* associated;
Lookup(const Class* clasp, TaggedProto proto, JSObject* associated)
: clasp(clasp), proto(proto), associated(associated) {
MOZ_ASSERT((associated && associated->is<JSFunction>()) == !clasp);
}
explicit Lookup(const NewEntry& entry)
: clasp(entry.group.unbarrieredGet()->clasp()),
proto(entry.group.unbarrieredGet()->proto()),
associated(entry.associated) {
if (associated && associated->is<JSFunction>()) {
clasp = nullptr;
}
}
};
bool needsSweep() {
return IsAboutToBeFinalized(&group) ||
(associated && IsAboutToBeFinalizedUnbarriered(&associated));
}
bool operator==(const NewEntry& other) const {
return group == other.group && associated == other.associated;
}
};
namespace js {
template <>
struct MovableCellHasher<ObjectGroupRealm::NewEntry> {
using Key = ObjectGroupRealm::NewEntry;
using Lookup = ObjectGroupRealm::NewEntry::Lookup;
static bool hasHash(const Lookup& l) {
return MovableCellHasher<TaggedProto>::hasHash(l.proto) &&
MovableCellHasher<JSObject*>::hasHash(l.associated);
}
static bool ensureHash(const Lookup& l) {
return MovableCellHasher<TaggedProto>::ensureHash(l.proto) &&
MovableCellHasher<JSObject*>::ensureHash(l.associated);
}
static inline HashNumber hash(const Lookup& lookup) {
HashNumber hash = MovableCellHasher<TaggedProto>::hash(lookup.proto);
hash = mozilla::AddToHash(
hash, MovableCellHasher<JSObject*>::hash(lookup.associated));
return mozilla::AddToHash(hash, mozilla::HashGeneric(lookup.clasp));
}
static inline bool match(const ObjectGroupRealm::NewEntry& key,
const Lookup& lookup) {
if (lookup.clasp && key.group.unbarrieredGet()->clasp() != lookup.clasp) {
return false;
}
TaggedProto proto = key.group.unbarrieredGet()->proto();
if (!MovableCellHasher<TaggedProto>::match(proto, lookup.proto)) {
return false;
}
return MovableCellHasher<JSObject*>::match(key.associated,
lookup.associated);
}
};
} // namespace js
class ObjectGroupRealm::NewTable
: public JS::WeakCache<js::GCHashSet<NewEntry, MovableCellHasher<NewEntry>,
SystemAllocPolicy>> {
using Table =
js::GCHashSet<NewEntry, MovableCellHasher<NewEntry>, SystemAllocPolicy>;
using Base = JS::WeakCache<Table>;
public:
explicit NewTable(Zone* zone) : Base(zone) {}
};
/* static*/ ObjectGroupRealm& ObjectGroupRealm::get(const ObjectGroup* group) {
return group->realm()->objectGroups_;
}
/* static*/ ObjectGroupRealm& ObjectGroupRealm::getForNewObject(JSContext* cx) {
return cx->realm()->objectGroups_;
}
MOZ_ALWAYS_INLINE ObjectGroup* ObjectGroupRealm::DefaultNewGroupCache::lookup(
const Class* clasp, TaggedProto proto, JSObject* associated) {
if (group_ && associated_ == associated && group_->proto() == proto &&
(!clasp || group_->clasp() == clasp)) {
return group_;
}
return nullptr;
}
/* static */
ObjectGroup* ObjectGroup::defaultNewGroup(JSContext* cx, const Class* clasp,
TaggedProto proto,
JSObject* associated) {
MOZ_ASSERT_IF(associated, proto.isObject());
MOZ_ASSERT_IF(proto.isObject(),
cx->isInsideCurrentCompartment(proto.toObject()));
// A null lookup clasp is used for 'new' groups with an associated
// function. The group starts out as a plain object but might mutate into an
// unboxed plain object.
MOZ_ASSERT_IF(!clasp, !!associated);
if (associated) {
MOZ_ASSERT_IF(!associated->is<TypeDescr>(), !clasp);
if (associated->is<JSFunction>()) {
// Canonicalize new functions to use the original one associated with its
// script.
associated = associated->as<JSFunction>().maybeCanonicalFunction();
// If we have previously cleared the 'new' script information for this
// function, don't try to construct another one. Also, for simplicity,
// don't bother optimizing cross-realm constructors.
if (associated && (associated->as<JSFunction>().wasNewScriptCleared() ||
associated->as<JSFunction>().realm() != cx->realm())) {
associated = nullptr;
}
} else if (associated->is<TypeDescr>()) {
if (!clasp) {
// This can happen when we call Reflect.construct with a TypeDescr as
// newTarget argument. We're creating a plain object in this case, so
// don't set the TypeDescr on the group.
associated = nullptr;
}
} else {
associated = nullptr;
}
if (!associated) {
clasp = &PlainObject::class_;
}
}
ObjectGroupRealm& groups = ObjectGroupRealm::getForNewObject(cx);
if (ObjectGroup* group =
groups.defaultNewGroupCache.lookup(clasp, proto, associated)) {
return group;
}
AutoEnterAnalysis enter(cx);
ObjectGroupRealm::NewTable*& table = groups.defaultNewTable;
if (!table) {
table = cx->new_<ObjectGroupRealm::NewTable>(cx->zone());
if (!table) {
return nullptr;
}
}
if (proto.isObject() && !proto.toObject()->isDelegate()) {
RootedObject protoObj(cx, proto.toObject());
if (!JSObject::setDelegate(cx, protoObj)) {
return nullptr;
}
// Objects which are prototypes of one another should be singletons, so
// that their type information can be tracked more precisely. Limit
// this group change to plain objects, to avoid issues with other types
// of singletons like typed arrays.
if (protoObj->is<PlainObject>() && !protoObj->isSingleton()) {
if (!JSObject::changeToSingleton(cx, protoObj)) {
return nullptr;
}
// |ReshapeForProtoMutation| ensures singletons will reshape when
// prototype is mutated so clear the UNCACHEABLE_PROTO flag.
if (protoObj->hasUncacheableProto()) {
HandleNativeObject nobj = protoObj.as<NativeObject>();
if (!NativeObject::clearFlag(cx, nobj, BaseShape::UNCACHEABLE_PROTO)) {
return nullptr;
}
}
}
}
ObjectGroupRealm::NewTable::AddPtr p = table->lookupForAdd(
ObjectGroupRealm::NewEntry::Lookup(clasp, proto, associated));
if (p) {
ObjectGroup* group = p->group;
MOZ_ASSERT_IF(clasp, group->clasp() == clasp);
MOZ_ASSERT_IF(!clasp, group->clasp() == &PlainObject::class_);
MOZ_ASSERT(group->proto() == proto);
groups.defaultNewGroupCache.put(group, associated);
return group;
}
ObjectGroupFlags initialFlags = 0;
if (proto.isDynamic() ||
(proto.isObject() && proto.toObject()->isNewGroupUnknown())) {
initialFlags = OBJECT_FLAG_DYNAMIC_MASK;
}
Rooted<TaggedProto> protoRoot(cx, proto);
ObjectGroup* group = ObjectGroupRealm::makeGroup(
cx, cx->realm(), clasp ? clasp : &PlainObject::class_, protoRoot,
initialFlags);
if (!group) {
return nullptr;
}
if (!table->add(p, ObjectGroupRealm::NewEntry(group, associated))) {
ReportOutOfMemory(cx);
return nullptr;
}
if (associated) {
if (associated->is<JSFunction>()) {
if (!TypeNewScript::make(cx, group, &associated->as<JSFunction>())) {
return nullptr;
}
} else {
group->setTypeDescr(&associated->as<TypeDescr>());
}
}
/*
* Some builtin objects have slotful native properties baked in at
* creation via the Shape::{insert,get}initialShape mechanism. Since
* these properties are never explicitly defined on new objects, update
* the type information for them here.
*/
const JSAtomState& names = cx->names();
if (clasp == &RegExpObject::class_) {
AddTypePropertyId(cx, group, nullptr, NameToId(names.lastIndex),
TypeSet::Int32Type());
} else if (clasp == &StringObject::class_) {
AddTypePropertyId(cx, group, nullptr, NameToId(names.length),
TypeSet::Int32Type());
} else if (ErrorObject::isErrorClass(clasp)) {
AddTypePropertyId(cx, group, nullptr, NameToId(names.fileName),
TypeSet::StringType());
AddTypePropertyId(cx, group, nullptr, NameToId(names.lineNumber),
TypeSet::Int32Type());
AddTypePropertyId(cx, group, nullptr, NameToId(names.columnNumber),
TypeSet::Int32Type());
}
groups.defaultNewGroupCache.put(group, associated);
return group;
}
/* static */
ObjectGroup* ObjectGroup::lazySingletonGroup(JSContext* cx,
ObjectGroup* oldGroup,
const Class* clasp,
TaggedProto proto) {
ObjectGroupRealm& realm = oldGroup ? ObjectGroupRealm::get(oldGroup)
: ObjectGroupRealm::getForNewObject(cx);
MOZ_ASSERT_IF(proto.isObject(),
cx->compartment() == proto.toObject()->compartment());
ObjectGroupRealm::NewTable*& table = realm.lazyTable;
if (!table) {
table = cx->new_<ObjectGroupRealm::NewTable>(cx->zone());
if (!table) {
return nullptr;
}
}
ObjectGroupRealm::NewTable::AddPtr p = table->lookupForAdd(
ObjectGroupRealm::NewEntry::Lookup(clasp, proto, nullptr));
if (p) {
ObjectGroup* group = p->group;
MOZ_ASSERT(group->lazy());
return group;
}
AutoEnterAnalysis enter(cx);
Rooted<TaggedProto> protoRoot(cx, proto);
ObjectGroup* group = ObjectGroupRealm::makeGroup(
cx, oldGroup ? oldGroup->realm() : cx->realm(), clasp, protoRoot,
OBJECT_FLAG_SINGLETON | OBJECT_FLAG_LAZY_SINGLETON);
if (!group) {
return nullptr;
}
if (!table->add(p, ObjectGroupRealm::NewEntry(group, nullptr))) {
ReportOutOfMemory(cx);
return nullptr;
}
return group;
}
/* static */
void ObjectGroup::setDefaultNewGroupUnknown(JSContext* cx,
ObjectGroupRealm& realm,
const Class* clasp,
HandleObject obj) {
// If the object already has a new group, mark that group as unknown.
ObjectGroupRealm::NewTable* table = realm.defaultNewTable;
if (table) {
Rooted<TaggedProto> taggedProto(cx, TaggedProto(obj));
auto lookup =
ObjectGroupRealm::NewEntry::Lookup(clasp, taggedProto, nullptr);
auto p = table->lookup(lookup);
if (p) {
MarkObjectGroupUnknownProperties(cx, p->group);
}
}
}
#ifdef DEBUG
/* static */
bool ObjectGroup::hasDefaultNewGroup(JSObject* proto, const Class* clasp,
ObjectGroup* group) {
ObjectGroupRealm::NewTable* table =
ObjectGroupRealm::get(group).defaultNewTable;
if (table) {
auto lookup =
ObjectGroupRealm::NewEntry::Lookup(clasp, TaggedProto(proto), nullptr);
auto p = table->lookup(lookup);
return p && p->group == group;
}
return false;
}
#endif /* DEBUG */
inline const Class* GetClassForProtoKey(JSProtoKey key) {
switch (key) {
case JSProto_Null:
case JSProto_Object:
return &PlainObject::class_;
case JSProto_Array:
return &ArrayObject::class_;
case JSProto_Int8Array:
case JSProto_Uint8Array:
case JSProto_Int16Array:
case JSProto_Uint16Array:
case JSProto_Int32Array:
case JSProto_Uint32Array:
case JSProto_Float32Array:
case JSProto_Float64Array:
case JSProto_Uint8ClampedArray:
case JSProto_BigInt64Array:
case JSProto_BigUint64Array:
return &TypedArrayObject::classes[key - JSProto_Int8Array];
default:
// We only expect to see plain objects, arrays, and typed arrays here.
MOZ_CRASH("Bad proto key");
}
}
/* static */
ObjectGroup* ObjectGroup::defaultNewGroup(JSContext* cx, JSProtoKey key) {
JSObject* proto = nullptr;
if (key != JSProto_Null) {
proto = GlobalObject::getOrCreatePrototype(cx, key);
if (!proto) {
return nullptr;
}
}
return defaultNewGroup(cx, GetClassForProtoKey(key), TaggedProto(proto));
}
/////////////////////////////////////////////////////////////////////
// ObjectGroupRealm ArrayObjectTable
/////////////////////////////////////////////////////////////////////
struct ObjectGroupRealm::ArrayObjectKey : public DefaultHasher<ArrayObjectKey> {
TypeSet::Type type;
ArrayObjectKey() : type(TypeSet::UndefinedType()) {}
explicit ArrayObjectKey(TypeSet::Type type) : type(type) {}
static inline uint32_t hash(const ArrayObjectKey& v) { return v.type.raw(); }
static inline bool match(const ArrayObjectKey& v1, const ArrayObjectKey& v2) {
return v1.type == v2.type;
}
bool operator==(const ArrayObjectKey& other) { return type == other.type; }
bool operator!=(const ArrayObjectKey& other) { return !(*this == other); }
bool needsSweep() {
MOZ_ASSERT(type.isUnknown() || !type.isSingleton());
if (!type.isUnknown() && type.isGroup()) {
ObjectGroup* group = type.groupNoBarrier();
if (IsAboutToBeFinalizedUnbarriered(&group)) {
return true;
}
if (group != type.groupNoBarrier()) {
type = TypeSet::ObjectType(group);
}
}
return false;
}
};
static inline bool NumberTypes(TypeSet::Type a, TypeSet::Type b) {
return (a.isPrimitive(ValueType::Int32) ||
a.isPrimitive(ValueType::Double)) &&
(b.isPrimitive(ValueType::Int32) || b.isPrimitive(ValueType::Double));
}
/*
* As for GetValueType, but requires object types to be non-singletons with
* their default prototype. These are the only values that should appear in
* arrays and objects whose type can be fixed.
*/
static inline TypeSet::Type GetValueTypeForTable(const Value& v) {
TypeSet::Type type = TypeSet::GetValueType(v);
MOZ_ASSERT(!type.isSingleton());
return type;
}
/* static */
ArrayObject* ObjectGroup::newArrayObject(JSContext* cx, const Value* vp,
size_t length, NewObjectKind newKind,
NewArrayKind arrayKind) {
MOZ_ASSERT(newKind != SingletonObject);
// If we are making a copy on write array, don't try to adjust the group as
// getOrFixupCopyOnWriteObject will do this before any objects are copied
// from this one.
if (arrayKind == NewArrayKind::CopyOnWrite) {
ArrayObject* obj = NewDenseCopiedArray(cx, length, vp, nullptr, newKind);
if (!obj || !ObjectElements::MakeElementsCopyOnWrite(cx, obj)) {
return nullptr;
}
return obj;
}
// Get a type which captures all the elements in the array to be created.
Rooted<TypeSet::Type> elementType(cx, TypeSet::UnknownType());
if (arrayKind != NewArrayKind::UnknownIndex && length != 0) {
elementType = GetValueTypeForTable(vp[0]);
for (unsigned i = 1; i < length; i++) {
TypeSet::Type ntype = GetValueTypeForTable(vp[i]);
if (ntype != elementType) {
if (NumberTypes(elementType, ntype)) {
elementType = TypeSet::DoubleType();
} else {
elementType = TypeSet::UnknownType();
break;
}
}
}
}
ObjectGroupRealm& realm = ObjectGroupRealm::getForNewObject(cx);
ObjectGroupRealm::ArrayObjectTable*& table = realm.arrayObjectTable;
if (!table) {
table = cx->new_<ObjectGroupRealm::ArrayObjectTable>();
if (!table) {
return nullptr;
}
}
ObjectGroupRealm::ArrayObjectKey key(elementType);
DependentAddPtr<ObjectGroupRealm::ArrayObjectTable> p(cx, *table, key);
RootedObjectGroup group(cx);
if (p) {
group = p->value();
} else {
JSObject* proto = GlobalObject::getOrCreateArrayPrototype(cx, cx->global());
if (!proto) {
return nullptr;
}
Rooted<TaggedProto> taggedProto(cx, TaggedProto(proto));
group = ObjectGroupRealm::makeGroup(cx, cx->realm(), &ArrayObject::class_,
taggedProto);
if (!group) {
return nullptr;
}
AddTypePropertyId(cx, group, nullptr, JSID_VOID, elementType);
if (!p.add(cx, *table, ObjectGroupRealm::ArrayObjectKey(elementType),
group)) {
return nullptr;
}
}
// The type of the elements being added will already be reflected in type
// information.
ShouldUpdateTypes updateTypes = ShouldUpdateTypes::DontUpdate;
return NewCopiedArrayTryUseGroup(cx, group, vp, length, newKind, updateTypes);
}
// Try to change the group of |source| to match that of |target|.
static bool GiveObjectGroup(JSContext* cx, JSObject* source, JSObject* target) {
MOZ_ASSERT(source->group() != target->group());
if (!target->is<ArrayObject>() || !source->is<ArrayObject>()) {
return true;
}
source->setGroup(target->group());
for (size_t i = 0; i < source->as<ArrayObject>().getDenseInitializedLength();
i++) {
Value v = source->as<ArrayObject>().getDenseElement(i);
AddTypePropertyId(cx, source->group(), source, JSID_VOID, v);
}
return true;
}
static bool SameGroup(JSObject* first, JSObject* second) {
return first->group() == second->group();
}
// When generating a multidimensional array of literals, such as
// [[1,2],[3,4],[5.5,6.5]], try to ensure that each element of the array has
// the same group. This is mainly important when the elements might have
// different native vs. unboxed layouts, or different unboxed layouts, and
// accessing the heterogenous layouts from JIT code will be much slower than
// if they were homogenous.
//
// To do this, with each new array element we compare it with one of the
// previous ones, and try to mutate the group of the new element to fit that
// of the old element. If this isn't possible, the groups for all old elements
// are mutated to fit that of the new element.
bool js::CombineArrayElementTypes(JSContext* cx, JSObject* newObj,
const Value* compare, size_t ncompare) {
if (!ncompare || !compare[0].isObject()) {
return true;
}
JSObject* oldObj = &compare[0].toObject();
if (SameGroup(oldObj, newObj)) {
return true;
}
if (!GiveObjectGroup(cx, newObj, oldObj)) {
return false;
}
if (SameGroup(oldObj, newObj)) {
return true;
}
if (!GiveObjectGroup(cx, oldObj, newObj)) {
return false;
}
if (SameGroup(oldObj, newObj)) {
for (size_t i = 1; i < ncompare; i++) {
if (compare[i].isObject() && !SameGroup(&compare[i].toObject(), newObj)) {
if (!GiveObjectGroup(cx, &compare[i].toObject(), newObj)) {
return false;
}
}
}
}
return true;
}
// Similarly to CombineArrayElementTypes, if we are generating an array of
// plain objects with a consistent property layout, such as
// [{p:[1,2]},{p:[3,4]},{p:[5.5,6.5]}], where those plain objects in
// turn have arrays as their own properties, try to ensure that a consistent
// group is given to each array held by the same property of the plain objects.
bool js::CombinePlainObjectPropertyTypes(JSContext* cx, JSObject* newObj,
const Value* compare,
size_t ncompare) {
if (!ncompare || !compare[0].isObject()) {
return true;
}
JSObject* oldObj = &compare[0].toObject();
if (!SameGroup(oldObj, newObj)) {
return true;
}
if (newObj->is<PlainObject>()) {
if (newObj->as<PlainObject>().lastProperty() !=
oldObj->as<PlainObject>().lastProperty()) {
return true;
}
for (size_t slot = 0; slot < newObj->as<PlainObject>().slotSpan(); slot++) {
Value newValue = newObj->as<PlainObject>().getSlot(slot);
Value oldValue = oldObj->as<PlainObject>().getSlot(slot);
if (!newValue.isObject() || !oldValue.isObject()) {
continue;
}
JSObject* newInnerObj = &newValue.toObject();
JSObject* oldInnerObj = &oldValue.toObject();
if (SameGroup(oldInnerObj, newInnerObj)) {
continue;