// Copyright 2019 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "src/objects/map.h"
#include "src/execution/frames.h"
#include "src/execution/isolate.h"
#include "src/handles/handles-inl.h"
#include "src/handles/maybe-handles.h"
#include "src/heap/heap-write-barrier-inl.h"
#include "src/init/bootstrapper.h"
#include "src/logging/counters-inl.h"
#include "src/logging/log.h"
#include "src/objects/arguments-inl.h"
#include "src/objects/descriptor-array.h"
#include "src/objects/elements-kind.h"
#include "src/objects/field-type.h"
#include "src/objects/js-objects.h"
#include "src/objects/map-updater.h"
#include "src/objects/maybe-object.h"
#include "src/objects/oddball.h"
#include "src/objects/property.h"
#include "src/objects/transitions-inl.h"
#include "src/roots/roots.h"
#include "src/utils/ostreams.h"
#include "src/zone/zone-containers.h"
#include "torque-generated/field-offsets.h"
namespace v8 {
namespace internal {
Map Map::GetPrototypeChainRootMap(Isolate* isolate) const {
DisallowGarbageCollection no_alloc;
if (IsJSReceiverMap()) {
return *this;
}
int constructor_function_index = GetConstructorFunctionIndex();
if (constructor_function_index != Map::kNoConstructorFunctionIndex) {
Context native_context = isolate->context().native_context();
JSFunction constructor_function =
JSFunction::cast(native_context.get(constructor_function_index));
return constructor_function.initial_map();
}
return ReadOnlyRoots(isolate).null_value().map();
}
// static
MaybeHandle<JSFunction> Map::GetConstructorFunction(
Handle<Map> map, Handle<Context> native_context) {
if (map->IsPrimitiveMap()) {
int const constructor_function_index = map->GetConstructorFunctionIndex();
if (constructor_function_index != kNoConstructorFunctionIndex) {
return handle(
JSFunction::cast(native_context->get(constructor_function_index)),
native_context->GetIsolate());
}
}
return MaybeHandle<JSFunction>();
}
void Map::PrintReconfiguration(Isolate* isolate, FILE* file,
InternalIndex modify_index, PropertyKind kind,
PropertyAttributes attributes) {
OFStream os(file);
os << "[reconfiguring]";
Name name = instance_descriptors(isolate).GetKey(modify_index);
if (name.IsString()) {
String::cast(name).PrintOn(file);
} else {
os << "{symbol " << reinterpret_cast<void*>(name.ptr()) << "}";
}
os << ": " << (kind == kData ? "kData" : "ACCESSORS") << ", attrs: ";
os << attributes << " [";
JavaScriptFrame::PrintTop(isolate, file, false, true);
os << "]\n";
}
Map Map::GetInstanceTypeMap(ReadOnlyRoots roots, InstanceType type) {
Map map;
switch (type) {
#define MAKE_CASE(TYPE, Name, name) \
case TYPE: \
map = roots.name##_map(); \
break;
STRUCT_LIST(MAKE_CASE)
#undef MAKE_CASE
#define MAKE_CASE(TYPE, Name, name) \
case TYPE: \
map = roots.name##_map(); \
break;
TORQUE_DEFINED_INSTANCE_TYPE_LIST(MAKE_CASE)
#undef MAKE_CASE
default:
UNREACHABLE();
}
return map;
}
VisitorId Map::GetVisitorId(Map map) {
STATIC_ASSERT(kVisitorIdCount <= 256);
const int instance_type = map.instance_type();
if (instance_type < FIRST_NONSTRING_TYPE) {
switch (instance_type & kStringRepresentationMask) {
case kSeqStringTag:
if ((instance_type & kStringEncodingMask) == kOneByteStringTag) {
return kVisitSeqOneByteString;
} else {
return kVisitSeqTwoByteString;
}
case kConsStringTag:
if (IsShortcutCandidate(instance_type)) {
return kVisitShortcutCandidate;
} else {
return kVisitConsString;
}
case kSlicedStringTag:
return kVisitSlicedString;
case kExternalStringTag:
return kVisitDataObject;
case kThinStringTag:
return kVisitThinString;
}
UNREACHABLE();
}
switch (instance_type) {
case BYTE_ARRAY_TYPE:
return kVisitByteArray;
case BYTECODE_ARRAY_TYPE:
return kVisitBytecodeArray;
case FREE_SPACE_TYPE:
return kVisitFreeSpace;
case EMBEDDER_DATA_ARRAY_TYPE:
return kVisitEmbedderDataArray;
case OBJECT_BOILERPLATE_DESCRIPTION_TYPE:
case CLOSURE_FEEDBACK_CELL_ARRAY_TYPE:
case HASH_TABLE_TYPE:
case ORDERED_HASH_MAP_TYPE:
case ORDERED_HASH_SET_TYPE:
case ORDERED_NAME_DICTIONARY_TYPE:
case NAME_DICTIONARY_TYPE:
case GLOBAL_DICTIONARY_TYPE:
case NUMBER_DICTIONARY_TYPE:
case SIMPLE_NUMBER_DICTIONARY_TYPE:
case SCRIPT_CONTEXT_TABLE_TYPE:
return kVisitFixedArray;
case AWAIT_CONTEXT_TYPE:
case BLOCK_CONTEXT_TYPE:
case CATCH_CONTEXT_TYPE:
case DEBUG_EVALUATE_CONTEXT_TYPE:
case EVAL_CONTEXT_TYPE:
case FUNCTION_CONTEXT_TYPE:
case MODULE_CONTEXT_TYPE:
case SCRIPT_CONTEXT_TYPE:
case WITH_CONTEXT_TYPE:
return kVisitContext;
case NATIVE_CONTEXT_TYPE:
return kVisitNativeContext;
case EPHEMERON_HASH_TABLE_TYPE:
return kVisitEphemeronHashTable;
case FIXED_DOUBLE_ARRAY_TYPE:
return kVisitFixedDoubleArray;
case PROPERTY_ARRAY_TYPE:
return kVisitPropertyArray;
case FEEDBACK_CELL_TYPE:
return kVisitFeedbackCell;
case FEEDBACK_METADATA_TYPE:
return kVisitFeedbackMetadata;
case MAP_TYPE:
return kVisitMap;
case CODE_TYPE:
return kVisitCode;
case CELL_TYPE:
return kVisitCell;
case PROPERTY_CELL_TYPE:
return kVisitPropertyCell;
case TRANSITION_ARRAY_TYPE:
return kVisitTransitionArray;
case JS_WEAK_MAP_TYPE:
case JS_WEAK_SET_TYPE:
return kVisitJSWeakCollection;
case CALL_HANDLER_INFO_TYPE:
return kVisitStruct;
case JS_PROXY_TYPE:
return kVisitStruct;
case SYMBOL_TYPE:
return kVisitSymbol;
case JS_ARRAY_BUFFER_TYPE:
return kVisitJSArrayBuffer;
case JS_DATA_VIEW_TYPE:
return kVisitJSDataView;
case JS_FUNCTION_TYPE:
case JS_PROMISE_CONSTRUCTOR_TYPE:
case JS_REG_EXP_CONSTRUCTOR_TYPE:
case JS_ARRAY_CONSTRUCTOR_TYPE:
#define TYPED_ARRAY_CONSTRUCTORS_SWITCH(Type, type, TYPE, Ctype) \
case TYPE##_TYPED_ARRAY_CONSTRUCTOR_TYPE:
TYPED_ARRAYS(TYPED_ARRAY_CONSTRUCTORS_SWITCH)
#undef TYPED_ARRAY_CONSTRUCTORS_SWITCH
return kVisitJSFunction;
case JS_TYPED_ARRAY_TYPE:
return kVisitJSTypedArray;
case SMALL_ORDERED_HASH_MAP_TYPE:
return kVisitSmallOrderedHashMap;
case SMALL_ORDERED_HASH_SET_TYPE:
return kVisitSmallOrderedHashSet;
case SMALL_ORDERED_NAME_DICTIONARY_TYPE:
return kVisitSmallOrderedNameDictionary;
case SWISS_NAME_DICTIONARY_TYPE:
return kVisitSwissNameDictionary;
case CODE_DATA_CONTAINER_TYPE:
return kVisitCodeDataContainer;
case PREPARSE_DATA_TYPE:
return kVisitPreparseData;
case COVERAGE_INFO_TYPE:
return kVisitCoverageInfo;
case JS_ARGUMENTS_OBJECT_TYPE:
case JS_ARRAY_ITERATOR_PROTOTYPE_TYPE:
case JS_ARRAY_ITERATOR_TYPE:
case JS_ARRAY_TYPE:
case JS_ASYNC_FROM_SYNC_ITERATOR_TYPE:
case JS_ASYNC_FUNCTION_OBJECT_TYPE:
case JS_ASYNC_GENERATOR_OBJECT_TYPE:
case JS_CONTEXT_EXTENSION_OBJECT_TYPE:
case JS_DATE_TYPE:
case JS_ERROR_TYPE:
case JS_FINALIZATION_REGISTRY_TYPE:
case JS_GENERATOR_OBJECT_TYPE:
case JS_ITERATOR_PROTOTYPE_TYPE:
case JS_MAP_ITERATOR_PROTOTYPE_TYPE:
case JS_MAP_KEY_ITERATOR_TYPE:
case JS_MAP_KEY_VALUE_ITERATOR_TYPE:
case JS_MAP_TYPE:
case JS_MAP_VALUE_ITERATOR_TYPE:
case JS_MESSAGE_OBJECT_TYPE:
case JS_MODULE_NAMESPACE_TYPE:
case JS_OBJECT_PROTOTYPE_TYPE:
case JS_OBJECT_TYPE:
case JS_PRIMITIVE_WRAPPER_TYPE:
case JS_PROMISE_PROTOTYPE_TYPE:
case JS_PROMISE_TYPE:
case JS_REG_EXP_PROTOTYPE_TYPE:
case JS_REG_EXP_STRING_ITERATOR_TYPE:
case JS_REG_EXP_TYPE:
case JS_SET_ITERATOR_PROTOTYPE_TYPE:
case JS_SET_KEY_VALUE_ITERATOR_TYPE:
case JS_SET_PROTOTYPE_TYPE:
case JS_SET_TYPE:
case JS_SET_VALUE_ITERATOR_TYPE:
case JS_STRING_ITERATOR_PROTOTYPE_TYPE:
case JS_STRING_ITERATOR_TYPE:
case JS_TYPED_ARRAY_PROTOTYPE_TYPE:
#ifdef V8_INTL_SUPPORT
case JS_V8_BREAK_ITERATOR_TYPE:
case JS_COLLATOR_TYPE:
case JS_DATE_TIME_FORMAT_TYPE:
case JS_DISPLAY_NAMES_TYPE:
case JS_LIST_FORMAT_TYPE:
case JS_LOCALE_TYPE:
case JS_NUMBER_FORMAT_TYPE:
case JS_PLURAL_RULES_TYPE:
case JS_RELATIVE_TIME_FORMAT_TYPE:
case JS_SEGMENT_ITERATOR_TYPE:
case JS_SEGMENTER_TYPE:
case JS_SEGMENTS_TYPE:
#endif // V8_INTL_SUPPORT
#if V8_ENABLE_WEBASSEMBLY
case WASM_EXCEPTION_OBJECT_TYPE:
case WASM_GLOBAL_OBJECT_TYPE:
case WASM_MEMORY_OBJECT_TYPE:
case WASM_MODULE_OBJECT_TYPE:
case WASM_TABLE_OBJECT_TYPE:
case WASM_VALUE_OBJECT_TYPE:
#endif // V8_ENABLE_WEBASSEMBLY
case JS_BOUND_FUNCTION_TYPE: {
const bool has_raw_data_fields =
COMPRESS_POINTERS_BOOL && JSObject::GetEmbedderFieldCount(map) > 0;
return has_raw_data_fields ? kVisitJSObject : kVisitJSObjectFast;
}
case JS_API_OBJECT_TYPE:
case JS_GLOBAL_PROXY_TYPE:
case JS_GLOBAL_OBJECT_TYPE:
case JS_SPECIAL_API_OBJECT_TYPE:
return kVisitJSApiObject;
case JS_WEAK_REF_TYPE:
return kVisitJSWeakRef;
case WEAK_CELL_TYPE:
return kVisitWeakCell;
case FILLER_TYPE:
case FOREIGN_TYPE:
case HEAP_NUMBER_TYPE:
return kVisitDataObject;
case BIGINT_TYPE:
return kVisitBigInt;
case ALLOCATION_SITE_TYPE:
return kVisitAllocationSite;
#define MAKE_STRUCT_CASE(TYPE, Name, name) case TYPE:
STRUCT_LIST(MAKE_STRUCT_CASE)
#undef MAKE_STRUCT_CASE
if (instance_type == PROTOTYPE_INFO_TYPE) {
return kVisitPrototypeInfo;
}
#if V8_ENABLE_WEBASSEMBLY
if (instance_type == WASM_CAPI_FUNCTION_DATA_TYPE) {
return kVisitWasmCapiFunctionData;
}
if (instance_type == WASM_INDIRECT_FUNCTION_TABLE_TYPE) {
return kVisitWasmIndirectFunctionTable;
}
#endif // V8_ENABLE_WEBASSEMBLY
return kVisitStruct;
case LOAD_HANDLER_TYPE:
case STORE_HANDLER_TYPE:
return kVisitDataHandler;
case SOURCE_TEXT_MODULE_TYPE:
return kVisitSourceTextModule;
case SYNTHETIC_MODULE_TYPE:
return kVisitSyntheticModule;
#if V8_ENABLE_WEBASSEMBLY
case WASM_INSTANCE_OBJECT_TYPE:
return kVisitWasmInstanceObject;
case WASM_ARRAY_TYPE:
return kVisitWasmArray;
case WASM_STRUCT_TYPE:
return kVisitWasmStruct;
case WASM_TYPE_INFO_TYPE:
return kVisitWasmTypeInfo;
#endif // V8_ENABLE_WEBASSEMBLY
#define MAKE_TQ_CASE(TYPE, Name) \
case TYPE: \
return kVisit##Name;
TORQUE_INSTANCE_TYPE_TO_BODY_DESCRIPTOR_LIST(MAKE_TQ_CASE)
#undef MAKE_TQ_CASE
default:
UNREACHABLE();
}
}
void Map::PrintGeneralization(
Isolate* isolate, FILE* file, const char* reason,
InternalIndex modify_index, int split, int descriptors,
bool descriptor_to_field, Representation old_representation,
Representation new_representation, PropertyConstness old_constness,
PropertyConstness new_constness, MaybeHandle<FieldType> old_field_type,
MaybeHandle<Object> old_value, MaybeHandle<FieldType> new_field_type,
MaybeHandle<Object> new_value) {
OFStream os(file);
os << "[generalizing]";
Name name = instance_descriptors(isolate).GetKey(modify_index);
if (name.IsString()) {
String::cast(name).PrintOn(file);
} else {
os << "{symbol " << reinterpret_cast<void*>(name.ptr()) << "}";
}
os << ":";
if (descriptor_to_field) {
os << "c";
} else {
os << old_representation.Mnemonic() << "{";
if (old_field_type.is_null()) {
os << Brief(*(old_value.ToHandleChecked()));
} else {
old_field_type.ToHandleChecked()->PrintTo(os);
}
os << ";" << old_constness << "}";
}
os << "->" << new_representation.Mnemonic() << "{";
if (new_field_type.is_null()) {
os << Brief(*(new_value.ToHandleChecked()));
} else {
new_field_type.ToHandleChecked()->PrintTo(os);
}
os << ";" << new_constness << "} (";
if (strlen(reason) > 0) {
os << reason;
} else {
os << "+" << (descriptors - split) << " maps";
}
os << ") [";
JavaScriptFrame::PrintTop(isolate, file, false, true);
os << "]\n";
}
// static
MaybeObjectHandle Map::WrapFieldType(Isolate* isolate, Handle<FieldType> type) {
if (type->IsClass()) {
return MaybeObjectHandle::Weak(type->AsClass(), isolate);
}
return MaybeObjectHandle(type);
}
// static
FieldType Map::UnwrapFieldType(MaybeObject wrapped_type) {
if (wrapped_type->IsCleared()) {
return FieldType::None();
}
HeapObject heap_object;
if (wrapped_type->GetHeapObjectIfWeak(&heap_object)) {
return FieldType::cast(heap_object);
}
return wrapped_type->cast<FieldType>();
}
MaybeHandle<Map> Map::CopyWithField(Isolate* isolate, Handle<Map> map,
Handle<Name> name, Handle<FieldType> type,
PropertyAttributes attributes,
PropertyConstness constness,
Representation representation,
TransitionFlag flag) {
DCHECK(map->instance_descriptors(isolate)
.Search(*name, map->NumberOfOwnDescriptors())
.is_not_found());
// Ensure the descriptor array does not get too big.
if (map->NumberOfOwnDescriptors() >= kMaxNumberOfDescriptors) {
return MaybeHandle<Map>();
}
// Compute the new index for new field.
int index = map->NextFreePropertyIndex();
if (map->instance_type() == JS_CONTEXT_EXTENSION_OBJECT_TYPE) {
constness = PropertyConstness::kMutable;
representation = Representation::Tagged();
type = FieldType::Any(isolate);
} else {
Map::GeneralizeIfCanHaveTransitionableFastElementsKind(
isolate, map->instance_type(), &representation, &type);
}
MaybeObjectHandle wrapped_type = WrapFieldType(isolate, type);
Descriptor d = Descriptor::DataField(name, index, attributes, constness,
representation, wrapped_type);
Handle<Map> new_map = Map::CopyAddDescriptor(isolate, map, &d, flag);
new_map->AccountAddedPropertyField();
return new_map;
}
MaybeHandle<Map> Map::CopyWithConstant(Isolate* isolate, Handle<Map> map,
Handle<Name> name,
Handle<Object> constant,
PropertyAttributes attributes,
TransitionFlag flag) {
// Ensure the descriptor array does not get too big.
if (map->NumberOfOwnDescriptors() >= kMaxNumberOfDescriptors) {
return MaybeHandle<Map>();
}
Representation representation = constant->OptimalRepresentation(isolate);
Handle<FieldType> type = constant->OptimalType(isolate, representation);
return CopyWithField(isolate, map, name, type, attributes,
PropertyConstness::kConst, representation, flag);
}
bool Map::InstancesNeedRewriting(Map target) const {
int target_number_of_fields = target.NumberOfFields();
int target_inobject = target.GetInObjectProperties();
int target_unused = target.UnusedPropertyFields();
int old_number_of_fields;
return InstancesNeedRewriting(target, target_number_of_fields,
target_inobject, target_unused,
&old_number_of_fields);
}
bool Map::InstancesNeedRewriting(Map target, int target_number_of_fields,
int target_inobject, int target_unused,
int* old_number_of_fields) const {
// If fields were added (or removed), rewrite the instance.
*old_number_of_fields = NumberOfFields();
DCHECK(target_number_of_fields >= *old_number_of_fields);
if (target_number_of_fields != *old_number_of_fields) return true;
// If smi descriptors were replaced by double descriptors, rewrite.
DescriptorArray old_desc = instance_descriptors();
DescriptorArray new_desc = target.instance_descriptors();
for (InternalIndex i : IterateOwnDescriptors()) {
if (new_desc.GetDetails(i).representation().IsDouble() !=
old_desc.GetDetails(i).representation().IsDouble()) {
return true;
}
}
// If no fields were added, and no inobject properties were removed, setting
// the map is sufficient.
if (target_inobject == GetInObjectProperties()) return false;
// In-object slack tracking may have reduced the object size of the new map.
// In that case, succeed if all existing fields were inobject, and they still
// fit within the new inobject size.
DCHECK(target_inobject < GetInObjectProperties());
if (target_number_of_fields <= target_inobject) {
DCHECK(target_number_of_fields + target_unused == target_inobject);
return false;
}
// Otherwise, properties will need to be moved to the backing store.
return true;
}
int Map::NumberOfFields() const {
DescriptorArray descriptors = instance_descriptors();
int result = 0;
for (InternalIndex i : IterateOwnDescriptors()) {
if (descriptors.GetDetails(i).location() == kField) result++;
}
return result;
}
Map::FieldCounts Map::GetFieldCounts() const {
DescriptorArray descriptors = instance_descriptors();
int mutable_count = 0;
int const_count = 0;
for (InternalIndex i : IterateOwnDescriptors()) {
PropertyDetails details = descriptors.GetDetails(i);
if (details.location() == kField) {
switch (details.constness()) {
case PropertyConstness::kMutable:
mutable_count++;
break;
case PropertyConstness::kConst:
const_count++;
break;
}
}
}
return FieldCounts(mutable_count, const_count);
}
bool Map::HasOutOfObjectProperties() const {
return GetInObjectProperties() < NumberOfFields();
}
void Map::DeprecateTransitionTree(Isolate* isolate) {
if (is_deprecated()) return;
DisallowGarbageCollection no_gc;
TransitionsAccessor transitions(isolate, *this, &no_gc);
int num_transitions = transitions.NumberOfTransitions();
for (int i = 0; i < num_transitions; ++i) {
transitions.GetTarget(i).DeprecateTransitionTree(isolate);
}
DCHECK(!constructor_or_back_pointer().IsFunctionTemplateInfo());
DCHECK(CanBeDeprecated());
set_is_deprecated(true);
if (FLAG_log_maps) {
LOG(isolate, MapEvent("Deprecate", handle(*this, isolate), Handle<Map>()));
}
dependent_code().DeoptimizeDependentCodeGroup(
DependentCode::kTransitionGroup);
NotifyLeafMapLayoutChange(isolate);
}
// Installs |new_descriptors| over the current instance_descriptors to ensure
// proper sharing of descriptor arrays.
void Map::ReplaceDescriptors(Isolate* isolate,
DescriptorArray new_descriptors) {
// Don't overwrite the empty descriptor array or initial map's descriptors.
if (NumberOfOwnDescriptors() == 0 ||
GetBackPointer(isolate).IsUndefined(isolate)) {
return;
}
DescriptorArray to_replace = instance_descriptors(isolate);
// Replace descriptors by new_descriptors in all maps that share it. The old
// descriptors will not be trimmed in the mark-compactor, we need to mark
// all its elements.
Map current = *this;
#ifndef V8_DISABLE_WRITE_BARRIERS
WriteBarrier::Marking(to_replace, to_replace.number_of_descriptors());
#endif
while (current.instance_descriptors(isolate) == to_replace) {
Object next = current.GetBackPointer(isolate);
if (next.IsUndefined(isolate)) break; // Stop overwriting at initial map.
current.SetEnumLength(kInvalidEnumCacheSentinel);
current.UpdateDescriptors(isolate, new_descriptors,
current.NumberOfOwnDescriptors());
current = Map::cast(next);
}
set_owns_descriptors(false);
}
Map Map::FindRootMap(Isolate* isolate) const {
DisallowGarbageCollection no_gc;
Map result = *this;
while (true) {
Object back = result.GetBackPointer(isolate);
if (back.IsUndefined(isolate)) {
// Initial map must not contain descriptors in the descriptors array
// that do not belong to the map.
DCHECK_LE(result.NumberOfOwnDescriptors(),
result.instance_descriptors(isolate, kRelaxedLoad)
.number_of_descriptors());
return result;
}
result = Map::cast(back);
}
}
Map Map::FindFieldOwner(Isolate* isolate, InternalIndex descriptor) const {
DisallowGarbageCollection no_gc;
DCHECK_EQ(kField, instance_descriptors(isolate, kRelaxedLoad)
.GetDetails(descriptor)
.location());
Map result = *this;
while (true) {
Object back = result.GetBackPointer(isolate);
if (back.IsUndefined(isolate)) break;
const Map parent = Map::cast(back);
if (parent.NumberOfOwnDescriptors() <= descriptor.as_int()) break;
result = parent;
}
return result;
}
void Map::UpdateFieldType(Isolate* isolate, InternalIndex descriptor,
Handle<Name> name, PropertyConstness new_constness,
Representation new_representation,
const MaybeObjectHandle& new_wrapped_type) {
DCHECK(new_wrapped_type->IsSmi() || new_wrapped_type->IsWeak());
// We store raw pointers in the queue, so no allocations are allowed.
DisallowGarbageCollection no_gc;
PropertyDetails details =
instance_descriptors(isolate).GetDetails(descriptor);
if (details.location() != kField) return;
DCHECK_EQ(kData, details.kind());
if (new_constness != details.constness() && is_prototype_map()) {
JSObject::InvalidatePrototypeChains(*this);
}
Zone zone(isolate->allocator(), ZONE_NAME);
ZoneQueue<Map> backlog(&zone);
backlog.push(*this);
while (!backlog.empty()) {
Map current = backlog.front();
backlog.pop();
TransitionsAccessor transitions(isolate, current, &no_gc);
int num_transitions = transitions.NumberOfTransitions();
for (int i = 0; i < num_transitions; ++i) {
Map target = transitions.GetTarget(i);
backlog.push(target);
}
DescriptorArray descriptors = current.instance_descriptors(isolate);
PropertyDetails details = descriptors.GetDetails(descriptor);
// It is allowed to change representation here only from None
// to something or from Smi or HeapObject to Tagged.
DCHECK(details.representation().Equals(new_representation) ||
details.representation().CanBeInPlaceChangedTo(new_representation));
// Skip if already updated the shared descriptor.
if (new_constness != details.constness() ||
!new_representation.Equals(details.representation()) ||
descriptors.GetFieldType(descriptor) != *new_wrapped_type.object()) {
Descriptor d = Descriptor::DataField(
name, descriptors.GetFieldIndex(descriptor), details.attributes(),
new_constness, new_representation, new_wrapped_type);
descriptors.Replace(descriptor, &d);
}
}
}
bool FieldTypeIsCleared(Representation rep, FieldType type) {
return type.IsNone() && rep.IsHeapObject();
}
// static
Handle<FieldType> Map::GeneralizeFieldType(Representation rep1,
Handle<FieldType> type1,
Representation rep2,
Handle<FieldType> type2,
Isolate* isolate) {
// Cleared field types need special treatment. They represent lost knowledge,
// so we must be conservative, so their generalization with any other type
// is "Any".
if (FieldTypeIsCleared(rep1, *type1) || FieldTypeIsCleared(rep2, *type2)) {
return FieldType::Any(isolate);
}
if (type1->NowIs(type2)) return type2;
if (type2->NowIs(type1)) return type1;
return FieldType::Any(isolate);
}
// static
void Map::GeneralizeField(Isolate* isolate, Handle<Map> map,
InternalIndex modify_index,
PropertyConstness new_constness,
Representation new_representation,
Handle<FieldType> new_field_type) {
// Check if we actually need to generalize the field type at all.
Handle<DescriptorArray> old_descriptors(map->instance_descriptors(isolate),
isolate);
PropertyDetails old_details = old_descriptors->GetDetails(modify_index);
PropertyConstness old_constness = old_details.constness();
Representation old_representation = old_details.representation();
Handle<FieldType> old_field_type(old_descriptors->GetFieldType(modify_index),
isolate);
// Return if the current map is general enough to hold requested constness and
// representation/field type.
if (IsGeneralizableTo(new_constness, old_constness) &&
old_representation.Equals(new_representation) &&
!FieldTypeIsCleared(new_representation, *new_field_type) &&
// Checking old_field_type for being cleared is not necessary because
// the NowIs check below would fail anyway in that case.
new_field_type->NowIs(old_field_type)) {
DCHECK(GeneralizeFieldType(old_representation, old_field_type,
new_representation, new_field_type, isolate)
->NowIs(old_field_type));
return;
}
// Determine the field owner.
Handle<Map> field_owner(map->FindFieldOwner(isolate, modify_index), isolate);
Handle<DescriptorArray> descriptors(
field_owner->instance_descriptors(isolate), isolate);
DCHECK_EQ(*old_field_type, descriptors->GetFieldType(modify_index));
new_field_type =
Map::GeneralizeFieldType(old_representation, old_field_type,
new_representation, new_field_type, isolate);
new_constness = GeneralizeConstness(old_constness, new_constness);
PropertyDetails details = descriptors->GetDetails(modify_index);
Handle<Name> name(descriptors->GetKey(modify_index), isolate);
MaybeObjectHandle wrapped_type(WrapFieldType(isolate, new_field_type));
field_owner->UpdateFieldType(isolate, modify_index, name, new_constness,
new_representation, wrapped_type);
if (new_constness != old_constness) {
field_owner->dependent_code().DeoptimizeDependentCodeGroup(
DependentCode::kFieldConstGroup);
}
if (!new_field_type->Equals(*old_field_type)) {
field_owner->dependent_code().DeoptimizeDependentCodeGroup(
DependentCode::kFieldTypeGroup);
}
if (!new_representation.Equals(old_representation)) {
field_owner->dependent_code().DeoptimizeDependentCodeGroup(
DependentCode::kFieldRepresentationGroup);
}
if (FLAG_trace_generalization) {
map->PrintGeneralization(
isolate, stdout, "field type generalization", modify_index,
map->NumberOfOwnDescriptors(), map->NumberOfOwnDescriptors(), false,
details.representation(),
descriptors->GetDetails(modify_index).representation(), old_constness,
new_constness, old_field_type, MaybeHandle<Object>(), new_field_type,
MaybeHandle<Object>());
}
}
namespace {
Map SearchMigrationTarget(Isolate* isolate, Map old_map) {
DisallowGarbageCollection no_gc;
DisallowDeoptimization no_deoptimization(isolate);
Map target = old_map;
do {
target = TransitionsAccessor(isolate, target, &no_gc).GetMigrationTarget();
} while (!target.is_null() && target.is_deprecated());
if (target.is_null()) return Map();
// TODO(ishell): if this validation ever become a bottleneck consider adding a
// bit to the Map telling whether it contains fields whose field types may be
// cleared.
// TODO(ishell): revisit handling of cleared field types in
// TryReplayPropertyTransitions() and consider checking the target map's field
// types instead of old_map's types.
// Go to slow map updating if the old_map has fast properties with cleared
// field types.
DescriptorArray old_descriptors = old_map.instance_descriptors(isolate);
for (InternalIndex i : old_map.IterateOwnDescriptors()) {
PropertyDetails old_details = old_descriptors.GetDetails(i);
if (old_details.location() == kField && old_details.kind() == kData) {
FieldType old_type = old_descriptors.GetFieldType(i);
if (FieldTypeIsCleared(old_details.representation(), old_type)) {
return Map();
}
}
}
SLOW_DCHECK(Map::TryUpdateSlow(isolate, old_map) == target);
return target;
}
} // namespace
// TODO(ishell): Move TryUpdate() and friends to MapUpdater
// static
MaybeHandle<Map> Map::TryUpdate(Isolate* isolate, Handle<Map> old_map) {
DisallowGarbageCollection no_gc;
DisallowDeoptimization no_deoptimization(isolate);
if (!old_map->is_deprecated()) return old_map;
if (FLAG_fast_map_update) {
Map target_map = SearchMigrationTarget(isolate, *old_map);
if (!target_map.is_null()) {
return handle(target_map, isolate);
}
}
Map new_map = TryUpdateSlow(isolate, *old_map);
if (new_map.is_null()) return MaybeHandle<Map>();
if (FLAG_fast_map_update) {
TransitionsAccessor(isolate, *old_map, &no_gc).SetMigrationTarget(new_map);
}
return handle(new_map, isolate);
}
namespace {
struct IntegrityLevelTransitionInfo {
explicit IntegrityLevelTransitionInfo(Map map)
: integrity_level_source_map(map) {}
bool has_integrity_level_transition = false;
PropertyAttributes integrity_level = NONE;
Map integrity_level_source_map;
Symbol integrity_level_symbol;
};
IntegrityLevelTransitionInfo DetectIntegrityLevelTransitions(
Map map, Isolate* isolate, DisallowGarbageCollection* no_gc) {
IntegrityLevelTransitionInfo info(map);
// Figure out the most restrictive integrity level transition (it should
// be the last one in the transition tree).
DCHECK(!map.is_extensible());
Map previous = Map::cast(map.GetBackPointer(isolate));
TransitionsAccessor last_transitions(isolate, previous, no_gc);
if (!last_transitions.HasIntegrityLevelTransitionTo(
map, &(info.integrity_level_symbol), &(info.integrity_level))) {
// The last transition was not integrity level transition - just bail out.
// This can happen in the following cases:
// - there are private symbol transitions following the integrity level
// transitions (see crbug.com/v8/8854).
// - there is a getter added in addition to an existing setter (or a setter
// in addition to an existing getter).
return info;
}
Map source_map = previous;
// Now walk up the back pointer chain and skip all integrity level
// transitions. If we encounter any non-integrity level transition interleaved
// with integrity level transitions, just bail out.
while (!source_map.is_extensible()) {
previous = Map::cast(source_map.GetBackPointer(isolate));
TransitionsAccessor transitions(isolate, previous, no_gc);
if (!transitions.HasIntegrityLevelTransitionTo(source_map)) {
return info;
}
source_map = previous;
}
// Integrity-level transitions never change number of descriptors.
CHECK_EQ(map.NumberOfOwnDescriptors(), source_map.NumberOfOwnDescriptors());
info.has_integrity_level_transition = true;
info.integrity_level_source_map = source_map;
return info;
}
} // namespace
Map Map::TryUpdateSlow(Isolate* isolate, Map old_map) {
DisallowGarbageCollection no_gc;
DisallowDeoptimization no_deoptimization(isolate);
// Check the state of the root map.
Map root_map = old_map.FindRootMap(isolate);
if (root_map.is_deprecated()) {
JSFunction constructor = JSFunction::cast(root_map.GetConstructor());
DCHECK(constructor.has_initial_map());
DCHECK(constructor.initial_map().is_dictionary_map());
if (constructor.initial_map().elements_kind() != old_map.elements_kind()) {
return Map();
}
return constructor.initial_map();
}
if (!old_map.EquivalentToForTransition(root_map)) return Map();
ElementsKind from_kind = root_map.elements_kind();
ElementsKind to_kind = old_map.elements_kind();
IntegrityLevelTransitionInfo info(old_map);
if (root_map.is_extensible() != old_map.is_extensible()) {
DCHECK(!old_map.is_extensible());
DCHECK(root_map.is_extensible());
info = DetectIntegrityLevelTransitions(old_map, isolate, &no_gc);
// Bail out if there were some private symbol transitions mixed up
// with the integrity level transitions.
if (!info.has_integrity_level_transition) return Map();
// Make sure to replay the original elements kind transitions, before
// the integrity level transition sets the elements to dictionary mode.
DCHECK(to_kind == DICTIONARY_ELEMENTS ||
to_kind == SLOW_STRING_WRAPPER_ELEMENTS ||
IsTypedArrayElementsKind(to_kind) ||
IsAnyHoleyNonextensibleElementsKind(to_kind));
to_kind = info.integrity_level_source_map.elements_kind();
}
if (from_kind != to_kind) {
// Try to follow existing elements kind transitions.
root_map = root_map.LookupElementsTransitionMap(isolate, to_kind);
if (root_map.is_null()) return Map();
// From here on, use the map with correct elements kind as root map.
}
// Replay the transitions as they were before the integrity level transition.
Map result = root_map.TryReplayPropertyTransitions(
isolate, info.integrity_level_source_map);
if (result.is_null()) return Map();
if (info.has_integrity_level_transition) {
// Now replay the integrity level transition.
result = TransitionsAccessor(isolate, result, &no_gc)
.SearchSpecial(info.integrity_level_symbol);
}
DCHECK_IMPLIES(!result.is_null(),
old_map.elements_kind() == result.elements_kind());
DCHECK_IMPLIES(!result.is_null(),
old_map.instance_type() == result.instance_type());
return result;
}
Map Map::TryReplayPropertyTransitions(Isolate* isolate, Map old_map) {
DisallowGarbageCollection no_gc;
DisallowDeoptimization no_deoptimization(isolate);
int root_nof = NumberOfOwnDescriptors();
int old_nof = old_map.NumberOfOwnDescriptors();
DescriptorArray old_descriptors = old_map.instance_descriptors(isolate);
Map new_map = *this;
for (InternalIndex i : InternalIndex::Range(root_nof, old_nof)) {
PropertyDetails old_details = old_descriptors.GetDetails(i);
Map transition =
TransitionsAccessor(isolate, new_map, &no_gc)
.SearchTransition(old_descriptors.GetKey(i), old_details.kind(),
old_details.attributes());
if (transition.is_null()) return Map();
new_map = transition;
DescriptorArray new_descriptors = new_map.instance_descriptors(isolate);
PropertyDetails new_details = new_descriptors.GetDetails(i);
DCHECK_EQ(old_details.kind(), new_details.kind());
DCHECK_EQ(old_details.attributes(), new_details.attributes());
if (!IsGeneralizableTo(old_details.constness(), new_details.constness())) {
return Map();
}
DCHECK(IsGeneralizableTo(old_details.location(), new_details.location()));
if (!old_details.representation().fits_into(new_details.representation())) {
return Map();
}
if (new_details.location() == kField) {
if (new_details.kind() == kData) {
FieldType new_type = new_descriptors.GetFieldType(i);
// Cleared field types need special treatment. They represent lost
// knowledge, so we must first generalize the new_type to "Any".
if (FieldTypeIsCleared(new_details.representation(), new_type)) {
return Map();
}
DCHECK_EQ(kData, old_details.kind());
DCHECK_EQ(kField, old_details.location());
FieldType old_type = old_descriptors.GetFieldType(i);
if (FieldTypeIsCleared(old_details.representation(), old_type) ||
!old_type.NowIs(new_type)) {
return Map();
}
} else {
DCHECK_EQ(kAccessor, new_details.kind());
#ifdef DEBUG
FieldType new_type = new_descriptors.GetFieldType(i);
DCHECK(new_type.IsAny());
#endif
UNREACHABLE();
}
} else {
DCHECK_EQ(kDescriptor, new_details.location());
if (old_details.location() == kField ||
old_descriptors.GetStrongValue(i) !=
new_descriptors.GetStrongValue(i)) {
return Map();
}
}
}
if (new_map.NumberOfOwnDescriptors() != old_nof) return Map();
return new_map;
}
// static
Handle<Map> Map::Update(Isolate* isolate, Handle<Map> map) {
if (!map->is_deprecated()) return map;
if (FLAG_fast_map_update) {
Map target_map = SearchMigrationTarget(isolate, *map);
if (!target_map.is_null()) {
return handle(target_map, isolate);
}
}
MapUpdater mu(isolate, map);
return mu.Update();
}
void Map::EnsureDescriptorSlack(Isolate* isolate, Handle<Map> map, int slack) {
// Only supports adding slack to owned descriptors.
DCHECK(map->owns_descriptors());
Handle<DescriptorArray> descriptors(map->instance_descriptors(isolate),
isolate);
int old_size = map->NumberOfOwnDescriptors();
if (slack <= descriptors->number_of_slack_descriptors()) return;
Handle<DescriptorArray> new_descriptors =
DescriptorArray::CopyUpTo(isolate, descriptors, old_size, slack);
DisallowGarbageCollection no_gc;
if (old_size == 0) {
map->UpdateDescriptors(isolate, *new_descriptors,
map->NumberOfOwnDescriptors());
return;
}
// If the source descriptors had an enum cache we copy it. This ensures
// that the maps to which we push the new descriptor array back can rely
// on a cache always being available once it is set. If the map has more
// enumerated descriptors than available in the original cache, the cache
// will be lazily replaced by the extended cache when needed.
new_descriptors->CopyEnumCacheFrom(*descriptors);
// Replace descriptors by new_descriptors in all maps that share it. The old
// descriptors will not be trimmed in the mark-compactor, we need to mark
// all its elements.
#ifndef V8_DISABLE_WRITE_BARRIERS
WriteBarrier::Marking(*descriptors, descriptors->number_of_descriptors());
#endif
// Update the descriptors from {map} (inclusive) until the initial map
// (exclusive). In the case that {map} is the initial map, update it.
map->UpdateDescriptors(isolate, *new_descriptors,
map->NumberOfOwnDescriptors());
Object next = map->GetBackPointer();
if (next.IsUndefined(isolate)) return;
Map current = Map::cast(next);
while (current.instance_descriptors(isolate) == *descriptors) {
next = current.GetBackPointer();
if (next.IsUndefined(isolate)) break;
current.UpdateDescriptors(isolate, *new_descriptors,
current.NumberOfOwnDescriptors());
current = Map::cast(next);
}
}
// static
Handle<Map> Map::GetObjectCreateMap(Isolate* isolate,
Handle<HeapObject> prototype) {
Handle<Map> map(isolate->native_context()->object_function().initial_map(),
isolate);
if (map->prototype() == *prototype) return map;
if (prototype->IsNull(isolate)) {
return isolate->slow_object_with_null_prototype_map();
}
if (prototype->IsJSObject()) {
Handle<JSObject> js_prototype = Handle<JSObject>::cast(prototype);
if (!js_prototype->map().is_prototype_map()) {
JSObject::OptimizeAsPrototype(js_prototype);
}
Handle<PrototypeInfo> info =
Map::GetOrCreatePrototypeInfo(js_prototype, isolate);
// TODO(verwaest): Use inobject slack tracking for this map.
if (info->HasObjectCreateMap()) {
map = handle(info->ObjectCreateMap(), isolate);
} else {
map = Map::CopyInitialMap(isolate, map);
Map::SetPrototype(isolate, map, prototype);
PrototypeInfo::SetObjectCreateMap(info, map);
}
return map;
}
return Map::TransitionToPrototype(isolate, map, prototype);
}
// static
MaybeHandle<Map> Map::TryGetObjectCreateMap(Isolate* isolate,
Handle<HeapObject> prototype) {
Handle<Map> map(isolate->native_context()->object_function().initial_map(),
isolate);
if (map->prototype() == *prototype) return map;
if (prototype->IsNull(isolate)) {
return isolate->slow_object_with_null_prototype_map();
}
if (!prototype->IsJSObject()) return MaybeHandle<Map>();
Handle<JSObject> js_prototype = Handle<JSObject>::cast(prototype);
if (!js_prototype->map().is_prototype_map()) return MaybeHandle<Map>();
Handle<PrototypeInfo> info =
Map::GetOrCreatePrototypeInfo(js_prototype, isolate);
if (!info->HasObjectCreateMap()) return MaybeHandle<Map>();
return handle(info->ObjectCreateMap(), isolate);
}
static bool ContainsMap(MapHandles const& maps, Map map) {
DCHECK(!map.is_null());
for (Handle<Map> current : maps) {
if (!current.is_null() && *current == map) return true;
}
return false;
}
static bool HasElementsKind(MapHandles const& maps,
ElementsKind elements_kind) {
for (Handle<Map> current : maps) {
if (!current.is_null() && current->elements_kind() == elements_kind)
return true;
}
return false;
}
Map Map::FindElementsKindTransitionedMap(Isolate* isolate,
MapHandles const& candidates) {
DisallowGarbageCollection no_gc;
DisallowDeoptimization no_deoptimization(isolate);
if (IsDetached(isolate)) return Map();
ElementsKind kind = elements_kind();
bool packed = IsFastPackedElementsKind(kind);
Map transition;
if (IsTransitionableFastElementsKind(kind)) {
// Check the state of the root map.
Map root_map = FindRootMap(isolate);
if (!EquivalentToForElementsKindTransition(root_map)) return Map();
root_map = root_map.LookupElementsTransitionMap(isolate, kind);
DCHECK(!root_map.is_null());
// Starting from the next existing elements kind transition try to
// replay the property transitions that does not involve instance rewriting
// (ElementsTransitionAndStoreStub does not support that).
for (root_map = root_map.ElementsTransitionMap(isolate);
!root_map.is_null() && root_map.has_fast_elements();
root_map = root_map.ElementsTransitionMap(isolate)) {
// If root_map's elements kind doesn't match any of the elements kind in
// the candidates there is no need to do any additional work.
if (!HasElementsKind(candidates, root_map.elements_kind())) continue;
Map current = root_map.TryReplayPropertyTransitions(isolate, *this);
if (current.is_null()) continue;
if (InstancesNeedRewriting(current)) continue;
if (ContainsMap(candidates, current) &&
(packed || !IsFastPackedElementsKind(current.elements_kind()))) {
transition = current;
packed = packed && IsFastPackedElementsKind(current.elements_kind());
}
}
}
return transition;
}
static Map FindClosestElementsTransition(Isolate* isolate, Map map,
ElementsKind to_kind) {
// Ensure we are requested to search elements kind transition "near the root".
DCHECK_EQ(map.FindRootMap(isolate).NumberOfOwnDescriptors(),
map.NumberOfOwnDescriptors());
Map current_map = map;
ElementsKind kind = map.elements_kind();
while (kind != to_kind) {
Map next_map = current_map.ElementsTransitionMap(isolate);
if (next_map.is_null()) return current_map;
kind = next_map.elements_kind();
current_map = next_map;
}
DCHECK_EQ(to_kind, current_map.elements_kind());
return current_map;
}
Map Map::LookupElementsTransitionMap(Isolate* isolate, ElementsKind to_kind) {
Map to_map = FindClosestElementsTransition(isolate, *this, to_kind);
if (to_map.elements_kind() == to_kind) return to_map;
return Map();
}
bool Map::IsMapInArrayPrototypeChain(Isolate* isolate) const {
if (isolate->initial_array_prototype()->map() == *this) {
return true;
}
if (isolate->initial_object_prototype()->map() == *this) {
return true;
}
return false;
}
Handle<Map> Map::TransitionElementsTo(Isolate* isolate, Handle<Map> map,
ElementsKind to_kind) {
ElementsKind from_kind = map->elements_kind();
if (from_kind == to_kind) return map;
Context native_context = isolate->context().native_context();
if (from_kind == FAST_SLOPPY_ARGUMENTS_ELEMENTS) {
if (*map == native_context.fast_aliased_arguments_map()) {
DCHECK_EQ(SLOW_SLOPPY_ARGUMENTS_ELEMENTS, to_kind);
return handle(native_context.slow_aliased_arguments_map(), isolate);
}
} else if (from_kind == SLOW_SLOPPY_ARGUMENTS_ELEMENTS) {
if (*map == native_context.slow_aliased_arguments_map()) {
DCHECK_EQ(FAST_SLOPPY_ARGUMENTS_ELEMENTS, to_kind);
return handle(native_context.fast_aliased_arguments_map(), isolate);
}
} else if (IsFastElementsKind(from_kind) && IsFastElementsKind(to_kind)) {
// Reuse map transitions for JSArrays.
DisallowGarbageCollection no_gc;
if (native_context.GetInitialJSArrayMap(from_kind) == *map) {
Object maybe_transitioned_map =
native_context.get(Context::ArrayMapIndex(to_kind));
if (maybe_transitioned_map.IsMap()) {
return handle(Map::cast(maybe_transitioned_map), isolate);
}
}
}
DCHECK(!map->IsUndefined(isolate));
// Check if we can go back in the elements kind transition chain.
if (IsHoleyElementsKind(from_kind) &&
to_kind == GetPackedElementsKind(from_kind) &&
map->GetBackPointer().IsMap() &&
Map::cast(map->GetBackPointer()).elements_kind() == to_kind) {
return handle(Map::cast(map->GetBackPointer()), isolate);
}
bool allow_store_transition = IsTransitionElementsKind(from_kind);
// Only store fast element maps in ascending generality.
if (IsFastElementsKind(to_kind)) {
allow_store_transition =
allow_store_transition && IsTransitionableFastElementsKind(from_kind) &&
IsMoreGeneralElementsKindTransition(from_kind, to_kind);
}
if (!allow_store_transition) {
return Map::CopyAsElementsKind(isolate, map, to_kind, OMIT_TRANSITION);
}
return MapUpdater{isolate, map}.ReconfigureElementsKind(to_kind);
}
static Handle<Map> AddMissingElementsTransitions(Isolate* isolate,
Handle<Map> map,
ElementsKind to_kind) {
DCHECK(IsTransitionElementsKind(map->elements_kind()));
Handle<Map> current_map = map;
ElementsKind kind = map->elements_kind();
TransitionFlag flag;
if (map->IsDetached(isolate)) {
flag = OMIT_TRANSITION;
} else {
flag = INSERT_TRANSITION;
if (IsFastElementsKind(kind)) {
while (kind != to_kind && !IsTerminalElementsKind(kind)) {
kind = GetNextTransitionElementsKind(kind);
current_map = Map::CopyAsElementsKind(isolate, current_map, kind, flag);
}
}
}
// In case we are exiting the fast elements kind system, just add the map in
// the end.
if (kind != to_kind) {
current_map = Map::CopyAsElementsKind(isolate, current_map, to_kind, flag);
}
DCHECK(current_map->elements_kind() == to_kind);
return current_map;
}
// static
Handle<Map> Map::AsElementsKind(Isolate* isolate, Handle<Map> map,
ElementsKind kind) {
Handle<Map> closest_map(FindClosestElementsTransition(isolate, *map, kind),
isolate);
if (closest_map->elements_kind() == kind) {
return closest_map;
}
return AddMissingElementsTransitions(isolate, closest_map, kind);
}
int Map::NumberOfEnumerableProperties() const {
int result = 0;
DescriptorArray descs = instance_descriptors(kRelaxedLoad);
for (InternalIndex i : IterateOwnDescriptors()) {
if ((descs.GetDetails(i).attributes() & ONLY_ENUMERABLE) == 0 &&
!descs.GetKey(i).FilterKey(ENUMERABLE_STRINGS)) {
result++;
}
}
return result;
}
int Map::NextFreePropertyIndex() const {
int number_of_own_descriptors = NumberOfOwnDescriptors();
DescriptorArray descs = instance_descriptors();
// Search properties backwards to find the last field.
for (int i = number_of_own_descriptors - 1; i >= 0; --i) {
PropertyDetails details = descs.GetDetails(InternalIndex(i));
if (details.location() == kField) {
return details.field_index() + details.field_width_in_words();
}
}
return 0;
}
bool Map::OnlyHasSimpleProperties() const {
// Wrapped string elements aren't explicitly stored in the elements backing
// store, but are loaded indirectly from the underlying string.
return !IsStringWrapperElementsKind(elements_kind()) &&
!IsSpecialReceiverMap() && !is_dictionary_map();
}
bool Map::MayHaveReadOnlyElementsInPrototypeChain(Isolate* isolate) {
for (PrototypeIterator iter(isolate, *this); !iter.IsAtEnd();
iter.Advance()) {
// Be conservative, don't look into any JSReceivers that may have custom
// elements. For example, into JSProxies, String wrappers (which have have
// non-configurable, non-writable elements), API objects, etc.
if (iter.GetCurrent().map().IsCustomElementsReceiverMap()) return true;
JSObject current = iter.GetCurrent<JSObject>();
ElementsKind elements_kind = current.GetElementsKind(isolate);
if (IsFrozenElementsKind(elements_kind)) return true;
if (IsDictionaryElementsKind(elements_kind) &&
current.element_dictionary(isolate).requires_slow_elements()) {
return true;
}
if (IsSlowArgumentsElementsKind(elements_kind)) {
SloppyArgumentsElements elements =
SloppyArgumentsElements::cast(current.elements(isolate));
Object arguments = elements.arguments();
if (NumberDictionary::cast(arguments).requires_slow_elements()) {
return true;
}
}
}
return false;
}
Handle<Map> Map::RawCopy(Isolate* isolate, Handle<Map> map, int instance_size,
int inobject_properties) {
Handle<Map> result = isolate->factory()->NewMap(
map->instance_type(), instance_size, TERMINAL_FAST_ELEMENTS_KIND,
inobject_properties);
Handle<HeapObject> prototype(map->prototype(), isolate);
Map::SetPrototype(isolate, result, prototype);
result->set_constructor_or_back_pointer(map->GetConstructor());
// TODO(solanes, v8:7790, v8:11353): set_relaxed_bit_field could be an atomic
// set if TSAN could see the transitions happening in StoreIC.
result->set_relaxed_bit_field(map->bit_field());
result->set_bit_field2(map->bit_field2());
int new_bit_field3 = map->bit_field3();
new_bit_field3 = Bits3::OwnsDescriptorsBit::update(new_bit_field3, true);
new_bit_field3 = Bits3::NumberOfOwnDescriptorsBits::update(new_bit_field3, 0);
new_bit_field3 =
Bits3::EnumLengthBits::update(new_bit_field3, kInvalidEnumCacheSentinel);
new_bit_field3 = Bits3::IsDeprecatedBit::update(new_bit_field3, false);
new_bit_field3 = Bits3::IsInRetainedMapListBit::update(new_bit_field3, false);
if (!map->is_dictionary_map()) {
new_bit_field3 = Bits3::IsUnstableBit::update(new_bit_field3, false);
}
result->set_bit_field3(new_bit_field3);
result->clear_padding();
return result;
}
Handle<Map> Map::Normalize(Isolate* isolate, Handle<Map> fast_map,
ElementsKind new_elements_kind,
PropertyNormalizationMode mode, const char* reason) {
DCHECK(!fast_map->is_dictionary_map());
Handle<Object> maybe_cache(isolate->native_context()->normalized_map_cache(),
isolate);
bool use_cache =
!fast_map->is_prototype_map() && !maybe_cache->IsUndefined(isolate);
Handle<NormalizedMapCache> cache;
if (use_cache) cache = Handle<NormalizedMapCache>::cast(maybe_cache);
Handle<Map> new_map;
if (use_cache &&
cache->Get(fast_map, new_elements_kind, mode).ToHandle(&new_map)) {
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) new_map->DictionaryMapVerify(isolate);
#endif
#ifdef ENABLE_SLOW_DCHECKS
if (FLAG_enable_slow_asserts) {
// The cached map should match newly created normalized map bit-by-bit,
// except for the code cache, which can contain some ICs which can be
// applied to the shared map, dependent code and weak cell cache.
Handle<Map> fresh = Map::CopyNormalized(isolate, fast_map, mode);
fresh->set_elements_kind(new_elements_kind);
STATIC_ASSERT(Map::kPrototypeValidityCellOffset ==
Map::kDependentCodeOffset + kTaggedSize);
DCHECK_EQ(0, memcmp(reinterpret_cast<void*>(fresh->address()),
reinterpret_cast<void*>(new_map->address()),
Map::kBitField3Offset));
// The IsInRetainedMapListBit might be different if the {new_map}
// that we got from the {cache} was already embedded into optimized
// code somewhere.
// The IsMigrationTargetBit might be different if the {new_map} from
// {cache} has already been marked as a migration target.
constexpr int ignored_bit_field3_bits =
Bits3::IsInRetainedMapListBit::kMask |
Bits3::IsMigrationTargetBit::kMask;
DCHECK_EQ(fresh->bit_field3() & ~ignored_bit_field3_bits,
new_map->bit_field3() & ~ignored_bit_field3_bits);
int offset = Map::kBitField3Offset + kInt32Size;
DCHECK_EQ(0, memcmp(reinterpret_cast<void*>(fresh->address() + offset),
reinterpret_cast<void*>(new_map->address() + offset),
Map::kDependentCodeOffset - offset));
offset = Map::kPrototypeValidityCellOffset + kTaggedSize;
if (new_map->is_prototype_map()) {
// For prototype maps, the PrototypeInfo is not copied.
STATIC_ASSERT(Map::kTransitionsOrPrototypeInfoOffset ==
Map::kPrototypeValidityCellOffset + kTaggedSize);
offset = kTransitionsOrPrototypeInfoOffset + kTaggedSize;
DCHECK_EQ(fresh->raw_transitions(),
MaybeObject::FromObject(Smi::zero()));
}
DCHECK_EQ(0, memcmp(reinterpret_cast<void*>(fresh->address() + offset),
reinterpret_cast<void*>(new_map->address() + offset),
Map::kSize - offset));
}
#endif
if (FLAG_log_maps) {
LOG(isolate, MapEvent("NormalizeCached", fast_map, new_map, reason));
}
} else {
new_map = Map::CopyNormalized(isolate, fast_map, mode);
new_map->set_elements_kind(new_elements_kind);
if (use_cache) {
cache->Set(fast_map, new_map);
isolate->counters()->maps_normalized()->Increment();
}
if (FLAG_log_maps) {
LOG(isolate, MapEvent("Normalize", fast_map, new_map, reason));
}
}
fast_map->NotifyLeafMapLayoutChange(isolate);
return new_map;
}
Handle<Map> Map::CopyNormalized(Isolate* isolate, Handle<Map> map,
PropertyNormalizationMode mode) {
int new_instance_size = map->instance_size();
if (mode == CLEAR_INOBJECT_PROPERTIES) {
new_instance_size -= map->GetInObjectProperties() * kTaggedSize;
}
Handle<Map> result = RawCopy(
isolate, map, new_instance_size,
mode == CLEAR_INOBJECT_PROPERTIES ? 0 : map->GetInObjectProperties());
// Clear the unused_property_fields explicitly as this field should not
// be accessed for normalized maps.
result->SetInObjectUnusedPropertyFields(0);
result->set_is_dictionary_map(true);
result->set_is_migration_target(false);
result->set_may_have_interesting_symbols(true);
result->set_construction_counter(kNoSlackTracking);
#ifdef VERIFY_HEAP
if (FLAG_verify_heap) result->DictionaryMapVerify(isolate);
#endif
return result;
}
// Return an immutable prototype exotic object version of the input map.
// Never even try to cache it in the transition tree, as it is intended
// for the global object and its prototype chain, and excluding it saves
// memory on the map transition tree.
// static
Handle<Map> Map::TransitionToImmutableProto(Isolate* isolate, Handle<Map> map) {
Handle<Map> new_map = Map::Copy(isolate, map, "ImmutablePrototype");
new_map->set_is_immutable_proto(true);
return new_map;
}
namespace {
void EnsureInitialMap(Isolate* isolate, Handle<Map> map) {
#ifdef DEBUG
Object maybe_constructor = map->GetConstructor();
DCHECK((maybe_constructor.IsJSFunction() &&
*map == JSFunction::cast(maybe_constructor).initial_map()) ||
// Below are the exceptions to the check above.
// Strict function maps have Function as a constructor but the
// Function's initial map is a sloppy function map.
*map == *isolate->strict_function_map() ||
*map == *isolate->strict_function_with_name_map() ||
// Same holds for GeneratorFunction and its initial map.
*map == *isolate->generator_function_map() ||
*map == *isolate->generator_function_with_name_map() ||
// AsyncFunction has Null as a constructor.
*map == *isolate->async_function_map() ||
*map == *isolate->async_function_with_name_map());
#endif
// Initial maps must not contain descriptors in the descriptors array
// that do not belong to the map.
DCHECK_EQ(map->NumberOfOwnDescriptors(),
map->instance_descriptors(isolate).number_of_descriptors());
}
} // namespace
// static
Handle<Map> Map::CopyInitialMapNormalized(Isolate* isolate, Handle<Map> map,
PropertyNormalizationMode mode) {
EnsureInitialMap(isolate, map);
return CopyNormalized(isolate, map, mode);
}
// static
Handle<Map> Map::CopyInitialMap(Isolate* isolate, Handle<Map> map,
int instance_size, int inobject_properties,
int unused_property_fields) {
EnsureInitialMap(isolate, map);
Handle<Map> result =
RawCopy(isolate, map, instance_size, inobject_properties);
// Please note instance_type and instance_size are set when allocated.
result->SetInObjectUnusedPropertyFields(unused_property_fields);
int number_of_own_descriptors = map->NumberOfOwnDescriptors();
if (number_of_own_descriptors > 0) {
// The copy will use the same descriptors array without ownership.
DescriptorArray descriptors = map->instance_descriptors(isolate);
result->set_owns_descriptors(false);
result->UpdateDescriptors(isolate, descriptors, number_of_own_descriptors);
DCHECK_EQ(result->NumberOfFields(),
result->GetInObjectProperties() - result->UnusedPropertyFields());
}
return result;
}
Handle<Map> Map::CopyDropDescriptors(Isolate* isolate, Handle<Map> map) {
Handle<Map> result =
RawCopy(isolate, map, map->instance_size(),
map->IsJSObjectMap() ? map->GetInObjectProperties() : 0);
// Please note instance_type and instance_size are set when allocated.
if (map->IsJSObjectMap()) {
result->CopyUnusedPropertyFields(*map);
}
map->NotifyLeafMapLayoutChange(isolate);
return result;
}
Handle<Map> Map::ShareDescriptor(Isolate* isolate, Handle<Map> map,
Handle<DescriptorArray> descriptors,
Descriptor* descriptor) {
// Sanity check. This path is only to be taken if the map owns its descriptor
// array, implying that its NumberOfOwnDescriptors equals the number of
// descriptors in the descriptor array.
DCHECK_EQ(map->NumberOfOwnDescriptors(),
map->instance_descriptors(isolate).number_of_descriptors());
Handle<Map> result = CopyDropDescriptors(isolate, map);
Handle<Name> name = descriptor->GetKey();
// Properly mark the {result} if the {name} is an "interesting symbol".
if (name->IsInterestingSymbol()) {
result->set_may_have_interesting_symbols(true);
}
// Ensure there's space for the new descriptor in the shared descriptor array.
if (descriptors->number_of_slack_descriptors() == 0) {
int old_size = descriptors->number_of_descriptors();
if (old_size == 0) {
descriptors = DescriptorArray::Allocate(isolate, 0, 1);
} else {
int slack = SlackForArraySize(old_size, kMaxNumberOfDescriptors);
EnsureDescriptorSlack(isolate, map, slack);
descriptors = handle(map->instance_descriptors(isolate), isolate);
}
}
{
DisallowGarbageCollection no_gc;
descriptors->Append(descriptor);
result->InitializeDescriptors(isolate, *descriptors);
}
DCHECK(result->NumberOfOwnDescriptors() == map->NumberOfOwnDescriptors() + 1);
ConnectTransition(isolate, map, result, name, SIMPLE_PROPERTY_TRANSITION);
return result;
}
void Map::ConnectTransition(Isolate* isolate, Handle<Map> parent,
Handle<Map> child, Handle<Name> name,
SimpleTransitionFlag flag) {
DCHECK_IMPLIES(name->IsInterestingSymbol(),
child->may_have_interesting_symbols());
DCHECK_IMPLIES(parent->may_have_interesting_symbols(),
child->may_have_interesting_symbols());
if (!parent->GetBackPointer().IsUndefined(isolate)) {
parent->set_owns_descriptors(false);
} else if (!parent->IsDetached(isolate)) {
// |parent| is initial map and it must not contain descriptors in the
// descriptors array that do not belong to the map.
DCHECK_EQ(parent->NumberOfOwnDescriptors(),
parent->instance_descriptors(isolate).number_of_descriptors());
}
if (parent->IsDetached(isolate)) {
DCHECK(child->IsDetached(isolate));
if (FLAG_log_maps) {
LOG(isolate, MapEvent("Transition", parent, child, "prototype", name));
}
} else {
TransitionsAccessor(isolate, parent).Insert(name, child, flag);
if (FLAG_log_maps) {
LOG(isolate, MapEvent("Transition", parent, child, "", name));
}
}
}
Handle<Map> Map::CopyReplaceDescriptors(Isolate* isolate, Handle<Map> map,
Handle<DescriptorArray> descriptors,
TransitionFlag flag,
MaybeHandle<Name> maybe_name,
const char* reason,
SimpleTransitionFlag simple_flag) {
DCHECK(descriptors->IsSortedNoDuplicates());
Handle<Map> result = CopyDropDescriptors(isolate, map);
bool is_connected = false;
// Properly mark the {result} if the {name} is an "interesting symbol".
Handle<Name> name;
if (maybe_name.ToHandle(&name) && name->IsInterestingSymbol()) {
result->set_may_have_interesting_symbols(true);
}
if (map->is_prototype_map()) {
result->InitializeDescriptors(isolate, *descriptors);
} else {
if (flag == INSERT_TRANSITION &&
TransitionsAccessor(isolate, map).CanHaveMoreTransitions()) {
result->InitializeDescriptors(isolate, *descriptors);
DCHECK(!maybe_name.is_null());
ConnectTransition(isolate, map, result, name, simple_flag);
is_connected = true;
} else {
descriptors->GeneralizeAllFields();
result->InitializeDescriptors(isolate, *descriptors);
}
}
if (FLAG_log_maps && !is_connected) {
LOG(isolate, MapEvent("ReplaceDescriptors", map, result, reason,
maybe_name.is_null() ? Handle<HeapObject>() : name));
}
return result;
}
// Creates transition tree starting from |split_map| and adding all descriptors
// starting from descriptor with index |split_map|.NumberOfOwnDescriptors().
// The way how it is done is tricky because of GC and special descriptors
// marking logic.
Handle<Map> Map::AddMissingTransitions(Isolate* isolate, Handle<Map> split_map,
Handle<DescriptorArray> descriptors) {
DCHECK(descriptors->IsSortedNoDuplicates());
int split_nof = split_map->NumberOfOwnDescriptors();
int nof_descriptors = descriptors->number_of_descriptors();
DCHECK_LT(split_nof, nof_descriptors);
// Start with creating last map which will own full descriptors array.
// This is necessary to guarantee that GC will mark the whole descriptor
// array if any of the allocations happening below fail.
// Number of unused properties is temporarily incorrect and the layout
// descriptor could unnecessarily be in slow mode but we will fix after
// all the other intermediate maps are created.
// Also the last map might have interesting symbols, we temporarily set
// the flag and clear it right before the descriptors are installed. This
// makes heap verification happy and ensures the flag ends up accurate.
Handle<Map> last_map = CopyDropDescriptors(isolate, split_map);
last_map->InitializeDescriptors(isolate, *descriptors);
last_map->SetInObjectUnusedPropertyFields(0);
last_map->set_may_have_interesting_symbols(true);
// During creation of intermediate maps we violate descriptors sharing
// invariant since the last map is not yet connected to the transition tree
// we create here. But it is safe because GC never trims map's descriptors
// if there are no dead transitions from that map and this is exactly the
// case for all the intermediate maps we create here.
Handle<Map> map = split_map;
for (InternalIndex i : InternalIndex::Range(split_nof, nof_descriptors - 1)) {
Handle<Map> new_map = CopyDropDescriptors(isolate, map);
InstallDescriptors(isolate, map, new_map, i, descriptors);
map = new_map;
}
map->NotifyLeafMapLayoutChange(isolate);
last_map->set_may_have_interesting_symbols(false);
InstallDescriptors(isolate, map, last_map, InternalIndex(nof_descriptors - 1),
descriptors);
return last_map;
}
// Since this method is used to rewrite an existing transition tree, it can
// always insert transitions without checking.
void Map::InstallDescriptors(Isolate* isolate, Handle<Map> parent,
Handle<Map> child, InternalIndex new_descriptor,
Handle<DescriptorArray> descriptors) {
DCHECK(descriptors->IsSortedNoDuplicates());
child->SetInstanceDescriptors(isolate, *descriptors,
new_descriptor.as_int() + 1);
child->CopyUnusedPropertyFields(*parent);
PropertyDetails details = descriptors->GetDetails(new_descriptor);
if (details.location() == kField) {
child->AccountAddedPropertyField();
}
Handle<Name> name = handle(descriptors->GetKey(new_descriptor), isolate);
if (parent->may_have_interesting_symbols() || name->IsInterestingSymbol()) {
child->set_may_have_interesting_symbols(true);
}
ConnectTransition(isolate, parent, child, name, SIMPLE_PROPERTY_TRANSITION);
}
Handle<Map> Map::CopyAsElementsKind(Isolate* isolate, Handle<Map> map,
ElementsKind kind, TransitionFlag flag) {
// Only certain objects are allowed to have non-terminal fast transitional
// elements kinds.
DCHECK(map->IsJSObjectMap());
DCHECK_IMPLIES(
!map->CanHaveFastTransitionableElementsKind(),
IsDictionaryElementsKind(kind) || IsTerminalElementsKind(kind));
Map maybe_elements_transition_map;
if (flag == INSERT_TRANSITION) {
// Ensure we are requested to add elements kind transition "near the root".
DCHECK_EQ(map->FindRootMap(isolate).NumberOfOwnDescriptors(),
map->NumberOfOwnDescriptors());
maybe_elements_transition_map = map->ElementsTransitionMap(isolate);
DCHECK(
maybe_elements_transition_map.is_null() ||
(maybe_elements_transition_map.elements_kind() == DICTIONARY_ELEMENTS &&
kind == DICTIONARY_ELEMENTS));
DCHECK(!IsFastElementsKind(kind) ||
IsMoreGeneralElementsKindTransition(map->elements_kind(), kind));
DCHECK(kind != map->elements_kind());
}
bool insert_transition =
flag == INSERT_TRANSITION &&
TransitionsAccessor(isolate, map).CanHaveMoreTransitions() &&
maybe_elements_transition_map.is_null();
if (insert_transition) {
Handle<Map> new_map = CopyForElementsTransition(isolate, map);
new_map->set_elements_kind(kind);
Handle<Name> name = isolate->factory()->elements_transition_symbol();
ConnectTransition(isolate, map, new_map, name, SPECIAL_TRANSITION);
return new_map;
}
// Create a new free-floating map only if we are not allowed to store it.
Handle<Map> new_map = Copy(isolate, map, "CopyAsElementsKind");
new_map->set_elements_kind(kind);
return new_map;
}
Handle<Map> Map::AsLanguageMode(Isolate* isolate, Handle<Map> initial_map,
Handle<SharedFunctionInfo> shared_info) {
DCHECK(InstanceTypeChecker::IsJSFunction(initial_map->instance_type()));
// Initial map for sloppy mode function is stored in the function
// constructor. Initial maps for strict mode are cached as special transitions
// using |strict_function_transition_symbol| as a key.
if (is_sloppy(shared_info->language_mode())) return initial_map;
Handle<Map> function_map(Map::cast(isolate->native_context()->get(
shared_info->function_map_index())),
isolate);
STATIC_ASSERT(LanguageModeSize == 2);
DCHECK_EQ(LanguageMode::kStrict, shared_info->language_mode());
Handle<Symbol> transition_symbol =
isolate->factory()->strict_function_transition_symbol();
Map maybe_transition = TransitionsAccessor(isolate, initial_map)
.SearchSpecial(*transition_symbol);
if (!maybe_transition.is_null()) {
return handle(maybe_transition, isolate);
}
initial_map->NotifyLeafMapLayoutChange(isolate);
// Create new map taking descriptors from the |function_map| and all
// the other details from the |initial_map|.
Handle<Map> map =
Map::CopyInitialMap(isolate, function_map, initial_map->instance_size(),
initial_map->GetInObjectProperties(),
initial_map->UnusedPropertyFields());
map->SetConstructor(initial_map->GetConstructor());
map->set_prototype(initial_map->prototype());
map->set_construction_counter(initial_map->construction_counter());
if (TransitionsAccessor(isolate, initial_map).CanHaveMoreTransitions()) {
Map::ConnectTransition(isolate, initial_map, map, transition_symbol,
SPECIAL_TRANSITION);
}
return map;
}
Handle<Map> Map::CopyForElementsTransition(Isolate* isolate, Handle<Map> map) {
DCHECK(!map->IsDetached(isolate));
Handle<Map> new_map = CopyDropDescriptors(isolate, map);
if (map->owns_descriptors()) {
// In case the map owned its own descriptors, share the descriptors and
// transfer ownership to the new map.
// The properties did not change, so reuse descriptors.
map->set_owns_descriptors(false);
new_map->InitializeDescriptors(isolate, map->instance_descriptors(isolate));
} else {
// In case the map did not own its own descriptors, a split is forced by
// copying the map; creating a new descriptor array cell.
Handle<DescriptorArray> descriptors(map->instance_descriptors(isolate),
isolate);
int number_of_own_descriptors = map->NumberOfOwnDescriptors();
Handle<DescriptorArray> new_descriptors = DescriptorArray::CopyUpTo(
isolate, descriptors, number_of_own_descriptors);
new_map->InitializeDescriptors(isolate, *new_descriptors);
}
return new_map;
}
Handle<Map> Map::Copy(Isolate* isolate, Handle<Map> map, const char* reason) {
Handle<DescriptorArray> descriptors(map->instance_descriptors(isolate),
isolate);
int number_of_own_descriptors = map->NumberOfOwnDescriptors();
Handle<DescriptorArray> new_descriptors = DescriptorArray::CopyUpTo(
isolate, descriptors, number_of_own_descriptors);
return CopyReplaceDescriptors(isolate, map, new_descriptors, OMIT_TRANSITION,
MaybeHandle<Name>(), reason,
SPECIAL_TRANSITION);
}
Handle<Map> Map::Create(Isolate* isolate, int inobject_properties) {
Handle<Map> copy =
Copy(isolate, handle(isolate->object_function()->initial_map(), isolate),
"MapCreate");
// Check that we do not overflow the instance size when adding the extra
// inobject properties. If the instance size overflows, we allocate as many
// properties as we can as inobject properties.
if (inobject_properties > JSObject::kMaxInObjectProperties) {
inobject_properties = JSObject::kMaxInObjectProperties;
}
int new_instance_size =
JSObject::kHeaderSize + kTaggedSize * inobject_properties;
// Adjust the map with the extra inobject properties.
copy->set_instance_size(new_instance_size);
copy->SetInObjectPropertiesStartInWords(JSObject::kHeaderSize / kTaggedSize);
DCHECK_EQ(copy->GetInObjectProperties(), inobject_properties);
copy->SetInObjectUnusedPropertyFields(inobject_properties);
copy->set_visitor_id(Map::GetVisitorId(*copy));
return copy;
}
Handle<Map> Map::CopyForPreventExtensions(
Isolate* isolate, Handle<Map> map, PropertyAttributes attrs_to_add,
Handle<Symbol> transition_marker, const char* reason,
bool old_map_is_dictionary_elements_kind) {
int num_descriptors = map->NumberOfOwnDescriptors();
Handle<DescriptorArray> new_desc = DescriptorArray::CopyUpToAddAttributes(
isolate, handle(map->instance_descriptors(isolate), isolate),
num_descriptors, attrs_to_add);
// Do not track transitions during bootstrapping.
TransitionFlag flag =
isolate->bootstrapper()->IsActive() ? OMIT_TRANSITION : INSERT_TRANSITION;
Handle<Map> new_map =
CopyReplaceDescriptors(isolate, map, new_desc, flag, transition_marker,
reason, SPECIAL_TRANSITION);
new_map->set_is_extensible(false);
if (!IsTypedArrayElementsKind(map->elements_kind())) {
ElementsKind new_kind = IsStringWrapperElementsKind(map->elements_kind())
? SLOW_STRING_WRAPPER_ELEMENTS
: DICTIONARY_ELEMENTS;
if (FLAG_enable_sealed_frozen_elements_kind &&
!old_map_is_dictionary_elements_kind) {
switch (map->elements_kind()) {
case PACKED_ELEMENTS:
if (attrs_to_add == SEALED) {
new_kind = PACKED_SEALED_ELEMENTS;
} else if (attrs_to_add == FROZEN) {
new_kind = PACKED_FROZEN_ELEMENTS;
} else {
new_kind = PACKED_NONEXTENSIBLE_ELEMENTS;
}
break;
case PACKED_NONEXTENSIBLE_ELEMENTS:
if (attrs_to_add == SEALED) {
new_kind = PACKED_SEALED_ELEMENTS;
} else if (attrs_to_add == FROZEN) {
new_kind = PACKED_FROZEN_ELEMENTS;
}
break;
case PACKED_SEALED_ELEMENTS:
if (attrs_to_add == FROZEN) {
new_kind = PACKED_FROZEN_ELEMENTS;
}
break;
case HOLEY_ELEMENTS:
if (attrs_to_add == SEALED) {
new_kind = HOLEY_SEALED_ELEMENTS;
} else if (attrs_to_add == FROZEN) {
new_kind = HOLEY_FROZEN_ELEMENTS;
} else {
new_kind = HOLEY_NONEXTENSIBLE_ELEMENTS;
}
break;
case HOLEY_NONEXTENSIBLE_ELEMENTS:
if (attrs_to_add == SEALED) {
new_kind = HOLEY_SEALED_ELEMENTS;
} else if (attrs_to_add == FROZEN) {
new_kind = HOLEY_FROZEN_ELEMENTS;
}
break;
case HOLEY_SEALED_ELEMENTS:
if (attrs_to_add == FROZEN) {
new_kind = HOLEY_FROZEN_ELEMENTS;
}
break;
default:
break;
}
}
new_map->set_elements_kind(new_kind);
}
return new_map;
}
namespace {
bool CanHoldValue(DescriptorArray descriptors, InternalIndex descriptor,
PropertyConstness constness, Object value) {
PropertyDetails details = descriptors.GetDetails(descriptor);
if (details.location() == kField) {
if (details.kind() == kData) {
return IsGeneralizableTo(constness, details.constness()) &&
value.FitsRepresentation(details.representation()) &&
descriptors.GetFieldType(descriptor).NowContains(value);
} else {
DCHECK_EQ(kAccessor, details.kind());
return false;
}
} else {
DCHECK_EQ(kDescriptor, details.location());
DCHECK_EQ(PropertyConstness::kConst, details.constness());
DCHECK_EQ(kAccessor, details.kind());
return false;
}
UNREACHABLE();
}
Handle<Map> UpdateDescriptorForValue(Isolate* isolate, Handle<Map> map,
InternalIndex descriptor,
PropertyConstness constness,
Handle<Object> value) {
if (CanHoldValue(map->instance_descriptors(isolate), descriptor, constness,
*value)) {
return map;
}
PropertyAttributes attributes =
map->instance_descriptors(isolate).GetDetails(descriptor).attributes();
Representation representation = value->OptimalRepresentation(isolate);
Handle<FieldType> type = value->OptimalType(isolate, representation);
MapUpdater mu(isolate, map);
return mu.ReconfigureToDataField(descriptor, attributes, constness,
representation, type);
}
} // namespace
// static
Handle<Map> Map::PrepareForDataProperty(Isolate* isolate, Handle<Map> map,
InternalIndex descriptor,
PropertyConstness constness,
Handle<Object> value) {
// Update to the newest map before storing the property.
map = Update(isolate, map);
// Dictionaries can store any property value.
DCHECK(!map->is_dictionary_map());
return UpdateDescriptorForValue(isolate, map, descriptor, constness, value);
}
Handle<Map> Map::TransitionToDataProperty(Isolate* isolate, Handle<Map> map,
Handle<Name> name,
Handle<Object> value,
PropertyAttributes attributes,
PropertyConstness constness,
StoreOrigin store_origin) {
RuntimeCallTimerScope stats_scope(
isolate,
map->IsDetached(isolate)
? RuntimeCallCounterId::kPrototypeMap_TransitionToDataProperty
: RuntimeCallCounterId::kMap_TransitionToDataProperty);
DCHECK(name->IsUniqueName());
DCHECK(!map->is_dictionary_map());
// Migrate to the newest map before storing the property.
map = Update(isolate, map);
Map maybe_transition = TransitionsAccessor(isolate, map)
.SearchTransition(*name, kData, attributes);
if (!maybe_transition.is_null()) {
Handle<Map> transition(maybe_transition, isolate);
InternalIndex descriptor = transition->LastAdded();
DCHECK_EQ(attributes, transition->instance_descriptors(isolate)
.GetDetails(descriptor)
.attributes());
return UpdateDescriptorForValue(isolate, transition, descriptor, constness,
value);
}
// Do not track transitions during bootstrapping.
TransitionFlag flag =
isolate->bootstrapper()->IsActive() ? OMIT_TRANSITION : INSERT_TRANSITION;
MaybeHandle<Map> maybe_map;
if (!map->TooManyFastProperties(store_origin)) {
Representation representation = value->OptimalRepresentation(isolate);
Handle<FieldType> type = value->OptimalType(isolate, representation);
maybe_map = Map::CopyWithField(isolate, map, name, type, attributes,
constness, representation, flag);
}
Handle<Map> result;
if (!maybe_map.ToHandle(&result)) {
const char* reason = "TooManyFastProperties";
#if V8_TRACE_MAPS
std::unique_ptr<ScopedVector<char>> buffer;
if (FLAG_log_maps) {
ScopedVector<char> name_buffer(100);
name->NameShortPrint(name_buffer);
buffer.reset(new ScopedVector<char>(128));
SNPrintF(*buffer, "TooManyFastProperties %s", name_buffer.begin());
reason = buffer->begin();
}
#endif
Handle<Object> maybe_constructor(map->GetConstructor(), isolate);
if (FLAG_feedback_normalization && map->new_target_is_base() &&
maybe_constructor->IsJSFunction() &&
!JSFunction::cast(*maybe_constructor).shared().native()) {
Handle<JSFunction> constructor =
Handle<JSFunction>::cast(maybe_constructor);
DCHECK_NE(*constructor,
constructor->context().native_context().object_function());
Handle<Map> initial_map(constructor->initial_map(), isolate);
result = Map::Normalize(isolate, initial_map, CLEAR_INOBJECT_PROPERTIES,
reason);
initial_map->DeprecateTransitionTree(isolate);
Handle<HeapObject> prototype(result->prototype(), isolate);
JSFunction::SetInitialMap(isolate, constructor, result, prototype);
// Deoptimize all code that embeds the previous initial map.
initial_map->dependent_code().DeoptimizeDependentCodeGroup(
DependentCode::kInitialMapChangedGroup);
if (!result->EquivalentToForNormalization(*map,
CLEAR_INOBJECT_PROPERTIES)) {
result =
Map::Normalize(isolate, map, CLEAR_INOBJECT_PROPERTIES, reason);
}
} else {
result = Map::Normalize(isolate, map, CLEAR_INOBJECT_PROPERTIES, reason);
}
}
return result;
}
Handle<Map> Map::ReconfigureExistingProperty(Isolate* isolate, Handle<Map> map,
InternalIndex descriptor,
PropertyKind kind,
PropertyAttributes attributes,
PropertyConstness constness) {
// Dictionaries have to be reconfigured in-place.
DCHECK(!map->is_dictionary_map());
if (!map->GetBackPointer().IsMap()) {
// There is no benefit from reconstructing transition tree for maps without
// back pointers, normalize and try to hit the map cache instead.
return Map::Normalize(isolate, map, CLEAR_INOBJECT_PROPERTIES,
"Normalize_AttributesMismatchProtoMap");
}
if (FLAG_trace_generalization) {
map->PrintReconfiguration(isolate, stdout, descriptor, kind, attributes);
}
MapUpdater mu(isolate, map);
DCHECK_EQ(kData, kind); // Only kData case is supported so far.
Handle<Map> new_map = mu.ReconfigureToDataField(
descriptor, attributes, constness, Representation::None(),
FieldType::None(isolate));
return new_map;
}
Handle<Map> Map::TransitionToAccessorProperty(Isolate* isolate, Handle<Map> map,
Handle<Name> name,
InternalIndex descriptor,
Handle<Object> getter,
Handle<Object> setter,
PropertyAttributes attributes) {
RuntimeCallTimerScope stats_scope(
isolate,
map->IsDetached(isolate)
? RuntimeCallCounterId::kPrototypeMap_TransitionToAccessorProperty
: RuntimeCallCounterId::kMap_TransitionToAccessorProperty);
// At least one of the accessors needs to be a new value.
DCHECK(!getter->IsNull(isolate) || !setter->IsNull(isolate));
DCHECK(name->IsUniqueName());
// Migrate to the newest map before transitioning to the new property.
map = Update(isolate, map);
// Dictionary maps can always have additional data properties.
if (map->is_dictionary_map()) return map;
PropertyNormalizationMode mode = map->is_prototype_map()
? KEEP_INOBJECT_PROPERTIES
: CLEAR_INOBJECT_PROPERTIES;
Map maybe_transition = TransitionsAccessor(isolate, map)
.SearchTransition(*name, kAccessor, attributes);
if (!maybe_transition.is_null()) {
Handle<Map> transition(maybe_transition, isolate);
DescriptorArray descriptors = transition->instance_descriptors(isolate);
InternalIndex descriptor = transition->LastAdded();
DCHECK(descriptors.GetKey(descriptor).Equals(*name));
DCHECK_EQ(kAccessor, descriptors.GetDetails(descriptor).kind());
DCHECK_EQ(attributes, descriptors.GetDetails(descriptor).attributes());
Handle<Object> maybe_pair(descriptors.GetStrongValue(descriptor), isolate);
if (!maybe_pair->IsAccessorPair()) {
return Map::Normalize(isolate, map, mode,
"TransitionToAccessorFromNonPair");
}
Handle<AccessorPair> pair = Handle<AccessorPair>::cast(maybe_pair);
if (!pair->Equals(*getter, *setter)) {
return Map::Normalize(isolate, map, mode,
"TransitionToDifferentAccessor");
}
return transition;
}
Handle<AccessorPair> pair;
DescriptorArray old_descriptors = map->instance_descriptors(isolate);
if (descriptor.is_found()) {
if (descriptor != map->LastAdded()) {
return Map::Normalize(isolate, map, mode, "AccessorsOverwritingNonLast");
}
PropertyDetails old_details = old_descriptors.GetDetails(descriptor);
if (old_details.kind() != kAccessor) {
return Map::Normalize(isolate, map, mode,
"AccessorsOverwritingNonAccessors");
}
if (old_details.attributes() != attributes) {
return Map::Normalize(isolate, map, mode, "AccessorsWithAttributes");
}
Handle<Object> maybe_pair(old_descriptors.GetStrongValue(descriptor),
isolate);
if (!maybe_pair->IsAccessorPair()) {
return Map::Normalize(isolate, map, mode, "AccessorsOverwritingNonPair");
}
Handle<AccessorPair> current_pair = Handle<AccessorPair>::cast(maybe_pair);
if (current_pair->Equals(*getter, *setter)) return map;
bool overwriting_accessor = false;
if (!getter->IsNull(isolate) &&
!current_pair->get(ACCESSOR_GETTER).IsNull(isolate) &&
current_pair->get(ACCESSOR_GETTER) != *getter) {
overwriting_accessor = true;
}
if (!setter->IsNull(isolate) &&
!current_pair->get(ACCESSOR_SETTER).IsNull(isolate) &&
current_pair->get(ACCESSOR_SETTER) != *setter) {
overwriting_accessor = true;
}
if (overwriting_accessor) {
return Map::Normalize(isolate, map, mode,
"AccessorsOverwritingAccessors");
}
pair = AccessorPair::Copy(isolate, Handle<AccessorPair>::cast(maybe_pair));
} else if (map->NumberOfOwnDescriptors() >= kMaxNumberOfDescriptors ||
map->TooManyFastProperties(StoreOrigin::kNamed)) {
return Map::Normalize(isolate, map, CLEAR_INOBJECT_PROPERTIES,
"TooManyAccessors");
} else {
pair = isolate->factory()->NewAccessorPair();
}
pair->SetComponents(*getter, *setter);
// Do not track transitions during bootstrapping.
TransitionFlag flag =
isolate->bootstrapper()->IsActive() ? OMIT_TRANSITION : INSERT_TRANSITION;
Descriptor d = Descriptor::AccessorConstant(name, pair, attributes);
return Map::CopyInsertDescriptor(isolate, map, &d, flag);
}
Handle<Map> Map::CopyAddDescriptor(Isolate* isolate, Handle<Map> map,
Descriptor* descriptor,
TransitionFlag flag) {
Handle<DescriptorArray> descriptors(map->instance_descriptors(isolate),
isolate);
// Share descriptors only if map owns descriptors and it not an initial map.
if (flag == INSERT_TRANSITION && map->owns_descriptors() &&
!map->GetBackPointer().IsUndefined(isolate) &&
TransitionsAccessor(isolate, map).CanHaveMoreTransitions()) {
return ShareDescriptor(isolate, map, descriptors, descriptor);
}
int nof = map->NumberOfOwnDescriptors();
Handle<DescriptorArray> new_descriptors =
DescriptorArray::CopyUpTo(isolate, descriptors, nof, 1);
new_descriptors->Append(descriptor);
return CopyReplaceDescriptors(isolate, map, new_descriptors, flag,
descriptor->GetKey(), "CopyAddDescriptor",
SIMPLE_PROPERTY_TRANSITION);
}
Handle<Map> Map::CopyInsertDescriptor(Isolate* isolate, Handle<Map> map,
Descriptor* descriptor,
TransitionFlag flag) {
Handle<DescriptorArray> old_descriptors(map->instance_descriptors(isolate),
isolate);
// We replace the key if it is already present.
InternalIndex index =
old_descriptors->SearchWithCache(isolate, *descriptor->GetKey(), *map);
if (index.is_found()) {
return CopyReplaceDescriptor(isolate, map, old_descriptors, descriptor,
index, flag);
}
return CopyAddDescriptor(isolate, map, descriptor, flag);
}
Handle<Map> Map::CopyReplaceDescriptor(Isolate* isolate, Handle<Map> map,
Handle<DescriptorArray> descriptors,
Descriptor* descriptor,
InternalIndex insertion_index,
TransitionFlag flag) {
Handle<Name> key = descriptor->GetKey();
DCHECK_EQ(*key, descriptors->GetKey(insertion_index));
// This function does not support replacing property fields as
// that would break property field counters.
DCHECK_NE(kField, descriptor->GetDetails().location());
DCHECK_NE(kField, descriptors->GetDetails(insertion_index).location());
Handle<DescriptorArray> new_descriptors = DescriptorArray::CopyUpTo(
isolate, descriptors, map->NumberOfOwnDescriptors());
new_descriptors->Replace(insertion_index, descriptor);
SimpleTransitionFlag simple_flag =
(insertion_index.as_int() == descriptors->number_of_descriptors() - 1)
? SIMPLE_PROPERTY_TRANSITION
: PROPERTY_TRANSITION;
return CopyReplaceDescriptors(isolate, map, new_descriptors, flag, key,
"CopyReplaceDescriptor", simple_flag);
}
int Map::Hash() {
// For performance reasons we only hash the 2 most variable fields of a map:
// prototype map and bit_field2. For predictability reasons we use objects'
// offsets in respective pages for hashing instead of raw addresses. We use
// the map of the prototype because the prototype itself could be compacted,
// whereas the map will not be moved.
// NOTE: If we want to compact maps, this hash function won't work as intended
// anymore.
// Shift away the tag.
int hash = ObjectAddressForHashing(prototype().map().ptr()) >> 2;
return hash ^ bit_field2();
}
namespace {
bool CheckEquivalent(const Map first, const Map second) {
return first.GetConstructor() == second.GetConstructor() &&
first.prototype() == second.prototype() &&
first.instance_type() == second.instance_type() &&
first.bit_field() == second.bit_field() &&
first.is_extensible() == second.is_extensible() &&
first.new_target_is_base() == second.new_target_is_base();
}
} // namespace
bool Map::EquivalentToForTransition(const Map other) const {
CHECK_EQ(GetConstructor(), other.GetConstructor());
CHECK_EQ(instance_type(), other.instance_type());
if (bit_field() != other.bit_field()) return false;
if (new_target_is_base() != other.new_target_is_base()) return false;
if (prototype() != other.prototype()) return false;
if (InstanceTypeChecker::IsJSFunction(instance_type())) {
// JSFunctions require more checks to ensure that sloppy function is
// not equivalent to strict function.
int nof =
std::min(NumberOfOwnDescriptors(), other.NumberOfOwnDescriptors());
return instance_descriptors().IsEqualUpTo(other.instance_descriptors(),
nof);
}
return true;
}
bool Map::EquivalentToForElementsKindTransition(const Map other) const {
if (!EquivalentToForTransition(other)) return false;
#ifdef DEBUG
// Ensure that we don't try to generate elements kind transitions from maps
// with fields that may be generalized in-place. This must already be handled
// during addition of a new field.
DescriptorArray descriptors = instance_descriptors();
for (InternalIndex i : IterateOwnDescriptors()) {
PropertyDetails details = descriptors.GetDetails(i);
if (details.location() == kField) {
DCHECK(IsMostGeneralFieldType(details.representation(),
descriptors.GetFieldType(i)));
}
}
#endif
return true;
}
bool Map::EquivalentToForNormalization(const Map other,
ElementsKind elements_kind,
PropertyNormalizationMode mode) const {
int properties =
mode == CLEAR_INOBJECT_PROPERTIES ? 0 : other.GetInObjectProperties();
// Make sure the elements_kind bits are in bit_field2.
DCHECK_EQ(this->elements_kind(),
Map::Bits2::ElementsKindBits::decode(bit_field2()));
int adjusted_other_bit_field2 =
Map::Bits2::ElementsKindBits::update(other.bit_field2(), elements_kind);
return CheckEquivalent(*this, other) &&
bit_field2() == adjusted_other_bit_field2 &&
GetInObjectProperties() == properties &&
JSObject::GetEmbedderFieldCount(*this) ==
JSObject::GetEmbedderFieldCount(other);
}
static void GetMinInobjectSlack(Map map, void* data) {
int slack = map.UnusedPropertyFields();
if (*reinterpret_cast<int*>(data) > slack) {
*reinterpret_cast<int*>(data) = slack;
}
}
int Map::ComputeMinObjectSlack(Isolate* isolate) {
DisallowGarbageCollection no_gc;
// Has to be an initial map.
DCHECK(GetBackPointer().IsUndefined(isolate));
int slack = UnusedPropertyFields();
TransitionsAccessor transitions(isolate, *this, &no_gc);
transitions.TraverseTransitionTree(&GetMinInobjectSlack, &slack);
return slack;
}
static void ShrinkInstanceSize(Map map, void* data) {
int slack = *reinterpret_cast<int*>(data);
DCHECK_GE(slack, 0);
#ifdef DEBUG
int old_visitor_id = Map::GetVisitorId(map);
int new_unused = map.UnusedPropertyFields() - slack;
#endif
map.set_instance_size(map.InstanceSizeFromSlack(slack));
map.set_construction_counter(Map::kNoSlackTracking);
DCHECK_EQ(old_visitor_id, Map::GetVisitorId(map));
DCHECK_EQ(new_unused, map.UnusedPropertyFields());
}
static void StopSlackTracking(Map map, void* data) {
map.set_construction_counter(Map::kNoSlackTracking);
}
void Map::CompleteInobjectSlackTracking(Isolate* isolate) {
DisallowGarbageCollection no_gc;
// Has to be an initial map.
DCHECK(GetBackPointer().IsUndefined(isolate));
int slack = ComputeMinObjectSlack(isolate);
TransitionsAccessor transitions(isolate, *this, &no_gc);
if (slack != 0) {
// Resize the initial map and all maps in its transition tree.
transitions.TraverseTransitionTree(&ShrinkInstanceSize, &slack);
} else {
transitions.TraverseTransitionTree(&StopSlackTracking, nullptr);
}
}
void Map::SetInstanceDescriptors(Isolate* isolate, DescriptorArray descriptors,
int number_of_own_descriptors) {
set_instance_descriptors(descriptors, kReleaseStore);
SetNumberOfOwnDescriptors(number_of_own_descriptors);
#ifndef V8_DISABLE_WRITE_BARRIERS
WriteBarrier::Marking(descriptors, number_of_own_descriptors);
#endif
}
// static
Handle<PrototypeInfo> Map::GetOrCreatePrototypeInfo(Handle<JSObject> prototype,
Isolate* isolate) {
Object maybe_proto_info = prototype->map().prototype_info();
if (maybe_proto_info.IsPrototypeInfo()) {
return handle(PrototypeInfo::cast(maybe_proto_info), isolate);
}
Handle<PrototypeInfo> proto_info = isolate->factory()->NewPrototypeInfo();
prototype->map().set_prototype_info(*proto_info);
return proto_info;
}
// static
Handle<PrototypeInfo> Map::GetOrCreatePrototypeInfo(Handle<Map> prototype_map,
Isolate* isolate) {
Object maybe_proto_info = prototype_map->prototype_info();
if (maybe_proto_info.IsPrototypeInfo()) {
return handle(PrototypeInfo::cast(maybe_proto_info), isolate);
}
Handle<PrototypeInfo> proto_info = isolate->factory()->NewPrototypeInfo();
prototype_map->set_prototype_info(*proto_info);
return proto_info;
}
// static
void Map::SetShouldBeFastPrototypeMap(Handle<Map> map, bool value,
Isolate* isolate) {
if (value == false && !map->prototype_info().IsPrototypeInfo()) {
// "False" is the implicit default value, so there's nothing to do.
return;
}
GetOrCreatePrototypeInfo(map, isolate)->set_should_be_fast_map(value);
}
// static
Handle<Object> Map::GetOrCreatePrototypeChainValidityCell(Handle<Map> map,
Isolate* isolate) {
Handle<Object> maybe_prototype;
if (map->IsJSGlobalObjectMap()) {
DCHECK(map->is_prototype_map());
// Global object is prototype of a global proxy and therefore we can
// use its validity cell for guarding global object's prototype change.
maybe_prototype = isolate->global_object();
} else {
maybe_prototype =
handle(map->GetPrototypeChainRootMap(isolate).prototype(), isolate);
}
if (!maybe_prototype->IsJSObject()) {
return handle(Smi::FromInt(Map::kPrototypeChainValid), isolate);
}
Handle<JSObject> prototype = Handle<JSObject>::cast(maybe_prototype);
// Ensure the prototype is registered with its own prototypes so its cell
// will be invalidated when necessary.
JSObject::LazyRegisterPrototypeUser(handle(prototype->map(), isolate),
isolate);
Object maybe_cell = prototype->map().prototype_validity_cell();
// Return existing cell if it's still valid.
if (maybe_cell.IsCell()) {
Handle<Cell> cell(Cell::cast(maybe_cell), isolate);
if (cell->value() == Smi::FromInt(Map::kPrototypeChainValid)) {
return cell;
}
}
// Otherwise create a new cell.
Handle<Cell> cell = isolate->factory()->NewCell(
handle(Smi::FromInt(Map::kPrototypeChainValid), isolate));
prototype->map().set_prototype_validity_cell(*cell);
return cell;
}
// static
bool Map::IsPrototypeChainInvalidated(Map map) {
DCHECK(map.is_prototype_map());
Object maybe_cell = map.prototype_validity_cell();
if (maybe_cell.IsCell()) {
Cell cell = Cell::cast(maybe_cell);
return cell.value() != Smi::FromInt(Map::kPrototypeChainValid);
}
return true;
}
// static
void Map::SetPrototype(Isolate* isolate, Handle<Map> map,
Handle<HeapObject> prototype,
bool enable_prototype_setup_mode) {
RuntimeCallTimerScope stats_scope(isolate,
RuntimeCallCounterId::kMap_SetPrototype);
if (prototype->IsJSObject()) {
Handle<JSObject> prototype_jsobj = Handle<JSObject>::cast(prototype);
JSObject::OptimizeAsPrototype(prototype_jsobj, enable_prototype_setup_mode);
} else {
DCHECK(prototype->IsNull(isolate) || prototype->IsJSProxy());
}
WriteBarrierMode wb_mode =
prototype->IsNull(isolate) ? SKIP_WRITE_BARRIER : UPDATE_WRITE_BARRIER;
map->set_prototype(*prototype, wb_mode);
}
void Map::StartInobjectSlackTracking() {
DCHECK(!IsInobjectSlackTrackingInProgress());
if (UnusedPropertyFields() == 0) return;
set_construction_counter(Map::kSlackTrackingCounterStart);
}
Handle<Map> Map::TransitionToPrototype(Isolate* isolate, Handle<Map> map,
Handle<HeapObject> prototype) {
Handle<Map> new_map =
TransitionsAccessor(isolate, map).GetPrototypeTransition(prototype);
if (new_map.is_null()) {
new_map = Copy(isolate, map, "TransitionToPrototype");
TransitionsAccessor(isolate, map)
.PutPrototypeTransition(prototype, new_map);
Map::SetPrototype(isolate, new_map, prototype);
}
return new_map;
}
Handle<NormalizedMapCache> NormalizedMapCache::New(Isolate* isolate) {
Handle<WeakFixedArray> array(
isolate->factory()->NewWeakFixedArray(kEntries, AllocationType::kOld));
return Handle<NormalizedMapCache>::cast(array);
}
MaybeHandle<Map> NormalizedMapCache::Get(Handle<Map> fast_map,
ElementsKind elements_kind,
PropertyNormalizationMode mode) {
DisallowGarbageCollection no_gc;
MaybeObject value = WeakFixedArray::Get(GetIndex(fast_map));
HeapObject heap_object;
if (!value->GetHeapObjectIfWeak(&heap_object)) {
return MaybeHandle<Map>();
}
Map normalized_map = Map::cast(heap_object);
if (!normalized_map.EquivalentToForNormalization(*fast_map, elements_kind,
mode)) {
return MaybeHandle<Map>();
}
return handle(normalized_map, GetIsolate());
}
void NormalizedMapCache::Set(Handle<Map> fast_map, Handle<Map> normalized_map) {
DisallowGarbageCollection no_gc;
DCHECK(normalized_map->is_dictionary_map());
WeakFixedArray::Set(GetIndex(fast_map),
HeapObjectReference::Weak(*normalized_map));
}
} // namespace internal
} // namespace v8