// Copyright 2017 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-updater.h" #include "src/execution/isolate.h" #include "src/handles/handles.h" #include "src/objects/field-type.h" #include "src/objects/objects-inl.h" #include "src/objects/objects.h" #include "src/objects/property-details.h" #include "src/objects/transitions.h" namespace v8 { namespace internal { namespace { inline bool EqualImmutableValues(Object obj1, Object obj2) { if (obj1 == obj2) return true; // Valid for both kData and kAccessor kinds. // TODO(ishell): compare AccessorPairs. return false; } } // namespace MapUpdater::MapUpdater(Isolate* isolate, Handle<Map> old_map) : isolate_(isolate), old_map_(old_map), old_descriptors_(old_map->instance_descriptors(), isolate_), old_nof_(old_map_->NumberOfOwnDescriptors()), new_elements_kind_(old_map_->elements_kind()), is_transitionable_fast_elements_kind_( IsTransitionableFastElementsKind(new_elements_kind_)) { // We shouldn't try to update remote objects. DCHECK( !old_map->FindRootMap(isolate).GetConstructor().IsFunctionTemplateInfo()); } Name MapUpdater::GetKey(InternalIndex descriptor) const { return old_descriptors_->GetKey(descriptor); } PropertyDetails MapUpdater::GetDetails(InternalIndex descriptor) const { DCHECK(descriptor.is_found()); if (descriptor == modified_descriptor_) { PropertyAttributes attributes = new_attributes_; // If the original map was sealed or frozen, let us used the old // attributes so that we follow the same transition path as before. // Note that the user could not have changed the attributes because // both seal and freeze make the properties non-configurable. if (integrity_level_ == SEALED || integrity_level_ == FROZEN) { attributes = old_descriptors_->GetDetails(descriptor).attributes(); } return PropertyDetails(new_kind_, attributes, new_location_, new_constness_, new_representation_); } return old_descriptors_->GetDetails(descriptor); } Object MapUpdater::GetValue(InternalIndex descriptor) const { DCHECK(descriptor.is_found()); if (descriptor == modified_descriptor_) { DCHECK_EQ(kDescriptor, new_location_); return *new_value_; } DCHECK_EQ(kDescriptor, GetDetails(descriptor).location()); return old_descriptors_->GetStrongValue(descriptor); } FieldType MapUpdater::GetFieldType(InternalIndex descriptor) const { DCHECK(descriptor.is_found()); if (descriptor == modified_descriptor_) { DCHECK_EQ(kField, new_location_); return *new_field_type_; } DCHECK_EQ(kField, GetDetails(descriptor).location()); return old_descriptors_->GetFieldType(descriptor); } Handle<FieldType> MapUpdater::GetOrComputeFieldType( InternalIndex descriptor, PropertyLocation location, Representation representation) const { DCHECK(descriptor.is_found()); // |location| is just a pre-fetched GetDetails(descriptor).location(). DCHECK_EQ(location, GetDetails(descriptor).location()); if (location == kField) { return handle(GetFieldType(descriptor), isolate_); } else { return GetValue(descriptor).OptimalType(isolate_, representation); } } Handle<FieldType> MapUpdater::GetOrComputeFieldType( Handle<DescriptorArray> descriptors, InternalIndex descriptor, PropertyLocation location, Representation representation) { // |location| is just a pre-fetched GetDetails(descriptor).location(). DCHECK_EQ(descriptors->GetDetails(descriptor).location(), location); if (location == kField) { return handle(descriptors->GetFieldType(descriptor), isolate_); } else { return descriptors->GetStrongValue(descriptor) .OptimalType(isolate_, representation); } } Handle<Map> MapUpdater::ReconfigureToDataField(InternalIndex descriptor, PropertyAttributes attributes, PropertyConstness constness, Representation representation, Handle<FieldType> field_type) { DCHECK_EQ(kInitialized, state_); DCHECK(descriptor.is_found()); DCHECK(!old_map_->is_dictionary_map()); modified_descriptor_ = descriptor; new_kind_ = kData; new_attributes_ = attributes; new_location_ = kField; PropertyDetails old_details = old_descriptors_->GetDetails(modified_descriptor_); // If property kind is not reconfigured merge the result with // representation/field type from the old descriptor. if (old_details.kind() == new_kind_) { new_constness_ = GeneralizeConstness(constness, old_details.constness()); Representation old_representation = old_details.representation(); new_representation_ = representation.generalize(old_representation); Handle<FieldType> old_field_type = GetOrComputeFieldType(old_descriptors_, modified_descriptor_, old_details.location(), new_representation_); new_field_type_ = Map::GeneralizeFieldType(old_representation, old_field_type, new_representation_, field_type, isolate_); } else { // We don't know if this is a first property kind reconfiguration // and we don't know which value was in this property previously // therefore we can't treat such a property as constant. new_constness_ = PropertyConstness::kMutable; new_representation_ = representation; new_field_type_ = field_type; } Map::GeneralizeIfCanHaveTransitionableFastElementsKind( isolate_, old_map_->instance_type(), &new_representation_, &new_field_type_); if (TryReconfigureToDataFieldInplace() == kEnd) return result_map_; if (FindRootMap() == kEnd) return result_map_; if (FindTargetMap() == kEnd) return result_map_; if (ConstructNewMap() == kAtIntegrityLevelSource) { ConstructNewMapWithIntegrityLevelTransition(); } DCHECK_EQ(kEnd, state_); return result_map_; } Handle<Map> MapUpdater::ReconfigureElementsKind(ElementsKind elements_kind) { DCHECK_EQ(kInitialized, state_); new_elements_kind_ = elements_kind; is_transitionable_fast_elements_kind_ = IsTransitionableFastElementsKind(new_elements_kind_); if (FindRootMap() == kEnd) return result_map_; if (FindTargetMap() == kEnd) return result_map_; if (ConstructNewMap() == kAtIntegrityLevelSource) { ConstructNewMapWithIntegrityLevelTransition(); } DCHECK_EQ(kEnd, state_); return result_map_; } Handle<Map> MapUpdater::Update() { DCHECK_EQ(kInitialized, state_); DCHECK(old_map_->is_deprecated()); if (FindRootMap() == kEnd) return result_map_; if (FindTargetMap() == kEnd) return result_map_; if (ConstructNewMap() == kAtIntegrityLevelSource) { ConstructNewMapWithIntegrityLevelTransition(); } DCHECK_EQ(kEnd, state_); if (FLAG_fast_map_update) { TransitionsAccessor(isolate_, old_map_).SetMigrationTarget(*result_map_); } return result_map_; } void MapUpdater::GeneralizeField(Handle<Map> map, InternalIndex modify_index, PropertyConstness new_constness, Representation new_representation, Handle<FieldType> new_field_type) { Map::GeneralizeField(isolate_, map, modify_index, new_constness, new_representation, new_field_type); DCHECK(*old_descriptors_ == old_map_->instance_descriptors() || *old_descriptors_ == integrity_source_map_->instance_descriptors()); } MapUpdater::State MapUpdater::Normalize(const char* reason) { result_map_ = Map::Normalize(isolate_, old_map_, new_elements_kind_, CLEAR_INOBJECT_PROPERTIES, reason); state_ = kEnd; return state_; // Done. } MapUpdater::State MapUpdater::TryReconfigureToDataFieldInplace() { // Updating deprecated maps in-place doesn't make sense. if (old_map_->is_deprecated()) return state_; if (new_representation_.IsNone()) return state_; // Not done yet. PropertyDetails old_details = old_descriptors_->GetDetails(modified_descriptor_); Representation old_representation = old_details.representation(); if (!old_representation.CanBeInPlaceChangedTo(new_representation_)) { return state_; // Not done yet. } DCHECK_EQ(new_kind_, old_details.kind()); DCHECK_EQ(new_attributes_, old_details.attributes()); DCHECK_EQ(kField, old_details.location()); if (FLAG_trace_generalization) { old_map_->PrintGeneralization( isolate_, stdout, "uninitialized field", modified_descriptor_, old_nof_, old_nof_, false, old_representation, new_representation_, old_details.constness(), new_constness_, handle(old_descriptors_->GetFieldType(modified_descriptor_), isolate_), MaybeHandle<Object>(), new_field_type_, MaybeHandle<Object>()); } Handle<Map> field_owner( old_map_->FindFieldOwner(isolate_, modified_descriptor_), isolate_); GeneralizeField(field_owner, modified_descriptor_, new_constness_, new_representation_, new_field_type_); // Check that the descriptor array was updated. DCHECK(old_descriptors_->GetDetails(modified_descriptor_) .representation() .Equals(new_representation_)); DCHECK(old_descriptors_->GetFieldType(modified_descriptor_) .NowIs(new_field_type_)); result_map_ = old_map_; state_ = kEnd; return state_; // Done. } bool MapUpdater::TrySaveIntegrityLevelTransitions() { // Figure out the most restrictive integrity level transition (it should // be the last one in the transition tree). Handle<Map> previous = handle(Map::cast(old_map_->GetBackPointer()), isolate_); Symbol integrity_level_symbol; TransitionsAccessor last_transitions(isolate_, previous); if (!last_transitions.HasIntegrityLevelTransitionTo( *old_map_, &integrity_level_symbol, &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 false; } integrity_level_symbol_ = handle(integrity_level_symbol, isolate_); integrity_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 (!integrity_source_map_->is_extensible()) { previous = handle(Map::cast(integrity_source_map_->GetBackPointer()), isolate_); TransitionsAccessor transitions(isolate_, previous); if (!transitions.HasIntegrityLevelTransitionTo(*integrity_source_map_)) { return false; } integrity_source_map_ = previous; } // Integrity-level transitions never change number of descriptors. CHECK_EQ(old_map_->NumberOfOwnDescriptors(), integrity_source_map_->NumberOfOwnDescriptors()); has_integrity_level_transition_ = true; old_descriptors_ = handle(integrity_source_map_->instance_descriptors(), isolate_); return true; } MapUpdater::State MapUpdater::FindRootMap() { DCHECK_EQ(kInitialized, state_); // Check the state of the root map. root_map_ = handle(old_map_->FindRootMap(isolate_), isolate_); ElementsKind from_kind = root_map_->elements_kind(); ElementsKind to_kind = new_elements_kind_; if (root_map_->is_deprecated()) { state_ = kEnd; result_map_ = handle( JSFunction::cast(root_map_->GetConstructor()).initial_map(), isolate_); result_map_ = Map::AsElementsKind(isolate_, result_map_, to_kind); DCHECK(result_map_->is_dictionary_map()); return state_; } if (!old_map_->EquivalentToForTransition(*root_map_)) { return Normalize("Normalize_NotEquivalent"); } else if (old_map_->is_extensible() != root_map_->is_extensible()) { DCHECK(!old_map_->is_extensible()); DCHECK(root_map_->is_extensible()); // We have an integrity level transition in the tree, let us make a note // of that transition to be able to replay it later. if (!TrySaveIntegrityLevelTransitions()) { return Normalize("Normalize_PrivateSymbolsOnNonExtensible"); } // We want to build transitions to the original element kind (before // the seal transitions), so change {to_kind} accordingly. DCHECK(to_kind == DICTIONARY_ELEMENTS || to_kind == SLOW_STRING_WRAPPER_ELEMENTS || IsTypedArrayElementsKind(to_kind) || IsAnyNonextensibleElementsKind(to_kind)); to_kind = integrity_source_map_->elements_kind(); } // TODO(ishell): Add a test for SLOW_SLOPPY_ARGUMENTS_ELEMENTS. if (from_kind != to_kind && to_kind != DICTIONARY_ELEMENTS && to_kind != SLOW_STRING_WRAPPER_ELEMENTS && to_kind != SLOW_SLOPPY_ARGUMENTS_ELEMENTS && !(IsTransitionableFastElementsKind(from_kind) && IsMoreGeneralElementsKindTransition(from_kind, to_kind))) { return Normalize("Normalize_InvalidElementsTransition"); } int root_nof = root_map_->NumberOfOwnDescriptors(); if (modified_descriptor_.is_found() && modified_descriptor_.as_int() < root_nof) { PropertyDetails old_details = old_descriptors_->GetDetails(modified_descriptor_); if (old_details.kind() != new_kind_ || old_details.attributes() != new_attributes_) { return Normalize("Normalize_RootModification1"); } if (old_details.location() != kField) { return Normalize("Normalize_RootModification2"); } if (!new_representation_.fits_into(old_details.representation())) { return Normalize("Normalize_RootModification4"); } DCHECK_EQ(kData, old_details.kind()); DCHECK_EQ(kData, new_kind_); DCHECK_EQ(kField, new_location_); // Modify root map in-place. The GeneralizeField method is a no-op // if the {old_map_} is already general enough to hold the requested // {new_constness_} and {new_field_type_}. GeneralizeField(old_map_, modified_descriptor_, new_constness_, old_details.representation(), new_field_type_); } // From here on, use the map with correct elements kind as root map. root_map_ = Map::AsElementsKind(isolate_, root_map_, to_kind); state_ = kAtRootMap; return state_; // Not done yet. } MapUpdater::State MapUpdater::FindTargetMap() { DCHECK_EQ(kAtRootMap, state_); target_map_ = root_map_; int root_nof = root_map_->NumberOfOwnDescriptors(); for (InternalIndex i : InternalIndex::Range(root_nof, old_nof_)) { PropertyDetails old_details = GetDetails(i); Map transition = TransitionsAccessor(isolate_, target_map_) .SearchTransition(GetKey(i), old_details.kind(), old_details.attributes()); if (transition.is_null()) break; Handle<Map> tmp_map(transition, isolate_); Handle<DescriptorArray> tmp_descriptors(tmp_map->instance_descriptors(), isolate_); // Check if target map is incompatible. PropertyDetails tmp_details = tmp_descriptors->GetDetails(i); DCHECK_EQ(old_details.kind(), tmp_details.kind()); DCHECK_EQ(old_details.attributes(), tmp_details.attributes()); if (old_details.kind() == kAccessor && !EqualImmutableValues(GetValue(i), tmp_descriptors->GetStrongValue(i))) { // TODO(ishell): mutable accessors are not implemented yet. return Normalize("Normalize_Incompatible"); } if (!IsGeneralizableTo(old_details.location(), tmp_details.location())) { break; } Representation tmp_representation = tmp_details.representation(); if (!old_details.representation().fits_into(tmp_representation)) { break; } if (tmp_details.location() == kField) { Handle<FieldType> old_field_type = GetOrComputeFieldType(i, old_details.location(), tmp_representation); GeneralizeField(tmp_map, i, old_details.constness(), tmp_representation, old_field_type); } else { // kDescriptor: Check that the value matches. if (!EqualImmutableValues(GetValue(i), tmp_descriptors->GetStrongValue(i))) { break; } } DCHECK(!tmp_map->is_deprecated()); target_map_ = tmp_map; } // Directly change the map if the target map is more general. int target_nof = target_map_->NumberOfOwnDescriptors(); if (target_nof == old_nof_) { #ifdef DEBUG if (modified_descriptor_.is_found()) { DescriptorArray target_descriptors = target_map_->instance_descriptors(); PropertyDetails details = target_descriptors.GetDetails(modified_descriptor_); DCHECK_EQ(new_kind_, details.kind()); DCHECK_EQ(GetDetails(modified_descriptor_).attributes(), details.attributes()); DCHECK(IsGeneralizableTo(new_constness_, details.constness())); DCHECK_EQ(new_location_, details.location()); DCHECK(new_representation_.fits_into(details.representation())); if (new_location_ == kField) { DCHECK_EQ(kField, details.location()); DCHECK(new_field_type_->NowIs( target_descriptors.GetFieldType(modified_descriptor_))); } else { DCHECK(details.location() == kField || EqualImmutableValues( *new_value_, target_descriptors.GetStrongValue(modified_descriptor_))); } } #endif if (*target_map_ != *old_map_) { old_map_->NotifyLeafMapLayoutChange(isolate_); } if (!has_integrity_level_transition_) { result_map_ = target_map_; state_ = kEnd; return state_; // Done. } // We try to replay the integrity level transition here. Map transition = TransitionsAccessor(isolate_, target_map_) .SearchSpecial(*integrity_level_symbol_); if (!transition.is_null()) { result_map_ = handle(transition, isolate_); state_ = kEnd; return state_; // Done. } } // Find the last compatible target map in the transition tree. for (InternalIndex i : InternalIndex::Range(target_nof, old_nof_)) { PropertyDetails old_details = GetDetails(i); Map transition = TransitionsAccessor(isolate_, target_map_) .SearchTransition(GetKey(i), old_details.kind(), old_details.attributes()); if (transition.is_null()) break; Handle<Map> tmp_map(transition, isolate_); Handle<DescriptorArray> tmp_descriptors(tmp_map->instance_descriptors(), isolate_); #ifdef DEBUG // Check that target map is compatible. PropertyDetails tmp_details = tmp_descriptors->GetDetails(i); DCHECK_EQ(old_details.kind(), tmp_details.kind()); DCHECK_EQ(old_details.attributes(), tmp_details.attributes()); #endif if (old_details.kind() == kAccessor && !EqualImmutableValues(GetValue(i), tmp_descriptors->GetStrongValue(i))) { return Normalize("Normalize_Incompatible"); } DCHECK(!tmp_map->is_deprecated()); target_map_ = tmp_map; } state_ = kAtTargetMap; return state_; // Not done yet. } Handle<DescriptorArray> MapUpdater::BuildDescriptorArray() { InstanceType instance_type = old_map_->instance_type(); int target_nof = target_map_->NumberOfOwnDescriptors(); Handle<DescriptorArray> target_descriptors( target_map_->instance_descriptors(), isolate_); // Allocate a new descriptor array large enough to hold the required // descriptors, with minimally the exact same size as the old descriptor // array. int new_slack = std::max<int>(old_nof_, old_descriptors_->number_of_descriptors()) - old_nof_; Handle<DescriptorArray> new_descriptors = DescriptorArray::Allocate(isolate_, old_nof_, new_slack); DCHECK(new_descriptors->number_of_all_descriptors() > target_descriptors->number_of_all_descriptors() || new_descriptors->number_of_slack_descriptors() > 0 || new_descriptors->number_of_descriptors() == old_descriptors_->number_of_descriptors()); DCHECK(new_descriptors->number_of_descriptors() == old_nof_); int root_nof = root_map_->NumberOfOwnDescriptors(); // Given that we passed root modification check in FindRootMap() so // the root descriptors are either not modified at all or already more // general than we requested. Take |root_nof| entries as is. // 0 -> |root_nof| int current_offset = 0; for (InternalIndex i : InternalIndex::Range(root_nof)) { PropertyDetails old_details = old_descriptors_->GetDetails(i); if (old_details.location() == kField) { current_offset += old_details.field_width_in_words(); } Descriptor d(handle(GetKey(i), isolate_), MaybeObjectHandle(old_descriptors_->GetValue(i), isolate_), old_details); new_descriptors->Set(i, &d); } // Merge "updated" old_descriptor entries with target_descriptor entries. // |root_nof| -> |target_nof| for (InternalIndex i : InternalIndex::Range(root_nof, target_nof)) { Handle<Name> key(GetKey(i), isolate_); PropertyDetails old_details = GetDetails(i); PropertyDetails target_details = target_descriptors->GetDetails(i); PropertyKind next_kind = old_details.kind(); PropertyAttributes next_attributes = old_details.attributes(); DCHECK_EQ(next_kind, target_details.kind()); DCHECK_EQ(next_attributes, target_details.attributes()); PropertyConstness next_constness = GeneralizeConstness( old_details.constness(), target_details.constness()); // Note: failed values equality check does not invalidate per-object // property constness. PropertyLocation next_location = old_details.location() == kField || target_details.location() == kField || !EqualImmutableValues(target_descriptors->GetStrongValue(i), GetValue(i)) ? kField : kDescriptor; // Ensure that mutable values are stored in fields. DCHECK_IMPLIES(next_constness == PropertyConstness::kMutable, next_location == kField); Representation next_representation = old_details.representation().generalize( target_details.representation()); if (next_location == kField) { Handle<FieldType> old_field_type = GetOrComputeFieldType(i, old_details.location(), next_representation); Handle<FieldType> target_field_type = GetOrComputeFieldType(target_descriptors, i, target_details.location(), next_representation); Handle<FieldType> next_field_type = Map::GeneralizeFieldType( old_details.representation(), old_field_type, next_representation, target_field_type, isolate_); Map::GeneralizeIfCanHaveTransitionableFastElementsKind( isolate_, instance_type, &next_representation, &next_field_type); MaybeObjectHandle wrapped_type( Map::WrapFieldType(isolate_, next_field_type)); Descriptor d; if (next_kind == kData) { d = Descriptor::DataField(key, current_offset, next_attributes, next_constness, next_representation, wrapped_type); } else { // TODO(ishell): mutable accessors are not implemented yet. UNIMPLEMENTED(); } current_offset += d.GetDetails().field_width_in_words(); new_descriptors->Set(i, &d); } else { DCHECK_EQ(kDescriptor, next_location); DCHECK_EQ(PropertyConstness::kConst, next_constness); Handle<Object> value(GetValue(i), isolate_); DCHECK_EQ(kAccessor, next_kind); Descriptor d = Descriptor::AccessorConstant(key, value, next_attributes); new_descriptors->Set(i, &d); } } // Take "updated" old_descriptor entries. // |target_nof| -> |old_nof| for (InternalIndex i : InternalIndex::Range(target_nof, old_nof_)) { PropertyDetails old_details = GetDetails(i); Handle<Name> key(GetKey(i), isolate_); PropertyKind next_kind = old_details.kind(); PropertyAttributes next_attributes = old_details.attributes(); PropertyConstness next_constness = old_details.constness(); PropertyLocation next_location = old_details.location(); Representation next_representation = old_details.representation(); Descriptor d; if (next_location == kField) { Handle<FieldType> next_field_type = GetOrComputeFieldType(i, old_details.location(), next_representation); // If the |new_elements_kind_| is still transitionable then the old map's // elements kind is also transitionable and therefore the old descriptors // array must already have generalized field type. CHECK_IMPLIES( is_transitionable_fast_elements_kind_, Map::IsMostGeneralFieldType(next_representation, *next_field_type)); MaybeObjectHandle wrapped_type( Map::WrapFieldType(isolate_, next_field_type)); Descriptor d; if (next_kind == kData) { d = Descriptor::DataField(key, current_offset, next_attributes, next_constness, next_representation, wrapped_type); } else { // TODO(ishell): mutable accessors are not implemented yet. UNIMPLEMENTED(); } current_offset += d.GetDetails().field_width_in_words(); new_descriptors->Set(i, &d); } else { DCHECK_EQ(kDescriptor, next_location); DCHECK_EQ(PropertyConstness::kConst, next_constness); Handle<Object> value(GetValue(i), isolate_); if (next_kind == kData) { d = Descriptor::DataConstant(key, value, next_attributes); } else { DCHECK_EQ(kAccessor, next_kind); d = Descriptor::AccessorConstant(key, value, next_attributes); } new_descriptors->Set(i, &d); } } new_descriptors->Sort(); return new_descriptors; } Handle<Map> MapUpdater::FindSplitMap(Handle<DescriptorArray> descriptors) { DisallowHeapAllocation no_allocation; int root_nof = root_map_->NumberOfOwnDescriptors(); Map current = *root_map_; for (InternalIndex i : InternalIndex::Range(root_nof, old_nof_)) { Name name = descriptors->GetKey(i); PropertyDetails details = descriptors->GetDetails(i); Map next = TransitionsAccessor(isolate_, current, &no_allocation) .SearchTransition(name, details.kind(), details.attributes()); if (next.is_null()) break; DescriptorArray next_descriptors = next.instance_descriptors(); PropertyDetails next_details = next_descriptors.GetDetails(i); DCHECK_EQ(details.kind(), next_details.kind()); DCHECK_EQ(details.attributes(), next_details.attributes()); if (details.constness() != next_details.constness()) break; if (details.location() != next_details.location()) break; if (!details.representation().Equals(next_details.representation())) break; if (next_details.location() == kField) { FieldType next_field_type = next_descriptors.GetFieldType(i); if (!descriptors->GetFieldType(i).NowIs(next_field_type)) { break; } } else { if (!EqualImmutableValues(descriptors->GetStrongValue(i), next_descriptors.GetStrongValue(i))) { break; } } current = next; } return handle(current, isolate_); } MapUpdater::State MapUpdater::ConstructNewMap() { Handle<DescriptorArray> new_descriptors = BuildDescriptorArray(); Handle<Map> split_map = FindSplitMap(new_descriptors); int split_nof = split_map->NumberOfOwnDescriptors(); if (old_nof_ == split_nof) { CHECK(has_integrity_level_transition_); state_ = kAtIntegrityLevelSource; return state_; } InternalIndex split_index(split_nof); PropertyDetails split_details = GetDetails(split_index); TransitionsAccessor transitions(isolate_, split_map); // Invalidate a transition target at |key|. Map maybe_transition = transitions.SearchTransition( GetKey(split_index), split_details.kind(), split_details.attributes()); if (!maybe_transition.is_null()) { maybe_transition.DeprecateTransitionTree(isolate_); } // If |maybe_transition| is not nullptr then the transition array already // contains entry for given descriptor. This means that the transition // could be inserted regardless of whether transitions array is full or not. if (maybe_transition.is_null() && !transitions.CanHaveMoreTransitions()) { return Normalize("Normalize_CantHaveMoreTransitions"); } old_map_->NotifyLeafMapLayoutChange(isolate_); if (FLAG_trace_generalization && modified_descriptor_.is_found()) { PropertyDetails old_details = old_descriptors_->GetDetails(modified_descriptor_); PropertyDetails new_details = new_descriptors->GetDetails(modified_descriptor_); MaybeHandle<FieldType> old_field_type; MaybeHandle<FieldType> new_field_type; MaybeHandle<Object> old_value; MaybeHandle<Object> new_value; if (old_details.location() == kField) { old_field_type = handle( old_descriptors_->GetFieldType(modified_descriptor_), isolate_); } else { old_value = handle(old_descriptors_->GetStrongValue(modified_descriptor_), isolate_); } if (new_details.location() == kField) { new_field_type = handle(new_descriptors->GetFieldType(modified_descriptor_), isolate_); } else { new_value = handle(new_descriptors->GetStrongValue(modified_descriptor_), isolate_); } old_map_->PrintGeneralization( isolate_, stdout, "", modified_descriptor_, split_nof, old_nof_, old_details.location() == kDescriptor && new_location_ == kField, old_details.representation(), new_details.representation(), old_details.constness(), new_details.constness(), old_field_type, old_value, new_field_type, new_value); } Handle<LayoutDescriptor> new_layout_descriptor = LayoutDescriptor::New(isolate_, split_map, new_descriptors, old_nof_); Handle<Map> new_map = Map::AddMissingTransitions( isolate_, split_map, new_descriptors, new_layout_descriptor); // Deprecated part of the transition tree is no longer reachable, so replace // current instance descriptors in the "survived" part of the tree with // the new descriptors to maintain descriptors sharing invariant. split_map->ReplaceDescriptors(isolate_, *new_descriptors, *new_layout_descriptor); if (has_integrity_level_transition_) { target_map_ = new_map; state_ = kAtIntegrityLevelSource; } else { result_map_ = new_map; state_ = kEnd; } return state_; // Done. } MapUpdater::State MapUpdater::ConstructNewMapWithIntegrityLevelTransition() { DCHECK_EQ(kAtIntegrityLevelSource, state_); TransitionsAccessor transitions(isolate_, target_map_); if (!transitions.CanHaveMoreTransitions()) { return Normalize("Normalize_CantHaveMoreTransitions"); } result_map_ = Map::CopyForPreventExtensions( isolate_, target_map_, integrity_level_, integrity_level_symbol_, "CopyForPreventExtensions", old_map_->elements_kind() == DICTIONARY_ELEMENTS); DCHECK_IMPLIES(old_map_->elements_kind() == DICTIONARY_ELEMENTS, result_map_->elements_kind() == DICTIONARY_ELEMENTS); state_ = kEnd; return state_; } } // namespace internal } // namespace v8