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access-info.cc
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// Copyright 2015 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/compiler/access-info.h"
#include <ostream>
#include "src/builtins/accessors.h"
#include "src/compiler/compilation-dependencies.h"
#include "src/compiler/heap-refs.h"
#include "src/compiler/js-heap-broker-inl.h"
#include "src/compiler/simplified-operator.h"
#include "src/compiler/type-cache.h"
#include "src/ic/call-optimization.h"
#include "src/objects/cell-inl.h"
#include "src/objects/field-index-inl.h"
#include "src/objects/field-type.h"
#include "src/objects/objects-inl.h"
#include "src/objects/struct-inl.h"
#include "src/objects/templates.h"
namespace v8 {
namespace internal {
namespace compiler {
namespace {
bool CanInlinePropertyAccess(MapRef map, AccessMode access_mode) {
// We can inline property access to prototypes of all primitives, except
// the special Oddball ones that have no wrapper counterparts (i.e. Null,
// Undefined and TheHole).
// We can only inline accesses to dictionary mode holders if the access is a
// load and the holder is a prototype. The latter ensures a 1:1
// relationship between the map and the object (and therefore the property
// dictionary).
static_assert(ODDBALL_TYPE == LAST_PRIMITIVE_HEAP_OBJECT_TYPE);
if (IsBooleanMap(*map.object())) return true;
if (map.instance_type() < LAST_PRIMITIVE_HEAP_OBJECT_TYPE) return true;
if (IsJSObjectMap(*map.object())) {
if (map.is_dictionary_map()) {
if (!V8_DICT_PROPERTY_CONST_TRACKING_BOOL) return false;
return access_mode == AccessMode::kLoad &&
map.object()->is_prototype_map();
}
return !map.object()->has_named_interceptor() &&
// TODO(verwaest): Allowlist contexts to which we have access.
!map.is_access_check_needed();
}
return false;
}
#ifdef DEBUG
bool HasFieldRepresentationDependenciesOnMap(
ZoneVector<CompilationDependency const*>& dependencies,
Handle<Map> const& field_owner_map) {
for (auto dep : dependencies) {
if (CompilationDependencies::IsFieldRepresentationDependencyOnMap(
dep, field_owner_map)) {
return true;
}
}
return false;
}
#endif
} // namespace
std::ostream& operator<<(std::ostream& os, AccessMode access_mode) {
switch (access_mode) {
case AccessMode::kLoad:
return os << "Load";
case AccessMode::kStore:
return os << "Store";
case AccessMode::kStoreInLiteral:
return os << "StoreInLiteral";
case AccessMode::kHas:
return os << "Has";
case AccessMode::kDefine:
return os << "Define";
}
UNREACHABLE();
}
ElementAccessInfo::ElementAccessInfo(
ZoneVector<MapRef>&& lookup_start_object_maps, ElementsKind elements_kind,
Zone* zone)
: elements_kind_(elements_kind),
lookup_start_object_maps_(lookup_start_object_maps),
transition_sources_(zone) {
CHECK(!lookup_start_object_maps.empty());
}
// static
PropertyAccessInfo PropertyAccessInfo::Invalid(Zone* zone) {
return PropertyAccessInfo(zone);
}
// static
PropertyAccessInfo PropertyAccessInfo::NotFound(Zone* zone, MapRef receiver_map,
OptionalJSObjectRef holder) {
return PropertyAccessInfo(zone, kNotFound, holder, {{receiver_map}, zone});
}
// static
PropertyAccessInfo PropertyAccessInfo::DataField(
JSHeapBroker* broker, Zone* zone, MapRef receiver_map,
ZoneVector<CompilationDependency const*>&& dependencies,
FieldIndex field_index, Representation field_representation,
Type field_type, MapRef field_owner_map, OptionalMapRef field_map,
OptionalJSObjectRef holder, OptionalMapRef transition_map) {
DCHECK(!field_representation.IsNone());
DCHECK_IMPLIES(
field_representation.IsDouble(),
HasFieldRepresentationDependenciesOnMap(
dependencies, transition_map.has_value() ? transition_map->object()
: holder.has_value() ? holder->map(broker).object()
: receiver_map.object()));
return PropertyAccessInfo(kDataField, holder, transition_map, field_index,
field_representation, field_type, field_owner_map,
field_map, {{receiver_map}, zone},
std::move(dependencies));
}
// static
PropertyAccessInfo PropertyAccessInfo::FastDataConstant(
Zone* zone, MapRef receiver_map,
ZoneVector<CompilationDependency const*>&& dependencies,
FieldIndex field_index, Representation field_representation,
Type field_type, MapRef field_owner_map, OptionalMapRef field_map,
OptionalJSObjectRef holder, OptionalMapRef transition_map) {
DCHECK(!field_representation.IsNone());
return PropertyAccessInfo(kFastDataConstant, holder, transition_map,
field_index, field_representation, field_type,
field_owner_map, field_map, {{receiver_map}, zone},
std::move(dependencies));
}
// static
PropertyAccessInfo PropertyAccessInfo::FastAccessorConstant(
Zone* zone, MapRef receiver_map, OptionalJSObjectRef holder,
OptionalObjectRef constant, OptionalJSObjectRef api_holder) {
return PropertyAccessInfo(zone, kFastAccessorConstant, holder, constant,
api_holder, {} /* name */, {{receiver_map}, zone});
}
// static
PropertyAccessInfo PropertyAccessInfo::ModuleExport(Zone* zone,
MapRef receiver_map,
CellRef cell) {
return PropertyAccessInfo(zone, kModuleExport, {} /* holder */,
cell /* constant */, {} /* api_holder */,
{} /* name */, {{receiver_map}, zone});
}
// static
PropertyAccessInfo PropertyAccessInfo::StringLength(Zone* zone,
MapRef receiver_map) {
return PropertyAccessInfo(zone, kStringLength, {}, {{receiver_map}, zone});
}
// static
PropertyAccessInfo PropertyAccessInfo::DictionaryProtoDataConstant(
Zone* zone, MapRef receiver_map, JSObjectRef holder,
InternalIndex dictionary_index, NameRef name) {
return PropertyAccessInfo(zone, kDictionaryProtoDataConstant, holder,
{{receiver_map}, zone}, dictionary_index, name);
}
// static
PropertyAccessInfo PropertyAccessInfo::DictionaryProtoAccessorConstant(
Zone* zone, MapRef receiver_map, OptionalJSObjectRef holder,
ObjectRef constant, OptionalJSObjectRef api_holder, NameRef property_name) {
return PropertyAccessInfo(zone, kDictionaryProtoAccessorConstant, holder,
constant, api_holder, property_name,
{{receiver_map}, zone});
}
PropertyAccessInfo::PropertyAccessInfo(Zone* zone)
: kind_(kInvalid),
lookup_start_object_maps_(zone),
unrecorded_dependencies_(zone),
field_representation_(Representation::None()),
field_type_(Type::None()),
dictionary_index_(InternalIndex::NotFound()) {}
PropertyAccessInfo::PropertyAccessInfo(
Zone* zone, Kind kind, OptionalJSObjectRef holder,
ZoneVector<MapRef>&& lookup_start_object_maps)
: kind_(kind),
lookup_start_object_maps_(lookup_start_object_maps),
holder_(holder),
unrecorded_dependencies_(zone),
field_representation_(Representation::None()),
field_type_(Type::None()),
dictionary_index_(InternalIndex::NotFound()) {}
PropertyAccessInfo::PropertyAccessInfo(
Zone* zone, Kind kind, OptionalJSObjectRef holder,
OptionalObjectRef constant, OptionalJSObjectRef api_holder,
OptionalNameRef name, ZoneVector<MapRef>&& lookup_start_object_maps)
: kind_(kind),
lookup_start_object_maps_(lookup_start_object_maps),
constant_(constant),
holder_(holder),
api_holder_(api_holder),
unrecorded_dependencies_(zone),
field_representation_(Representation::None()),
field_type_(Type::Any()),
dictionary_index_(InternalIndex::NotFound()),
name_(name) {
DCHECK_IMPLIES(kind == kDictionaryProtoAccessorConstant, name.has_value());
}
PropertyAccessInfo::PropertyAccessInfo(
Kind kind, OptionalJSObjectRef holder, OptionalMapRef transition_map,
FieldIndex field_index, Representation field_representation,
Type field_type, MapRef field_owner_map, OptionalMapRef field_map,
ZoneVector<MapRef>&& lookup_start_object_maps,
ZoneVector<CompilationDependency const*>&& unrecorded_dependencies)
: kind_(kind),
lookup_start_object_maps_(lookup_start_object_maps),
holder_(holder),
unrecorded_dependencies_(std::move(unrecorded_dependencies)),
transition_map_(transition_map),
field_index_(field_index),
field_representation_(field_representation),
field_type_(field_type),
field_owner_map_(field_owner_map),
field_map_(field_map),
dictionary_index_(InternalIndex::NotFound()) {
DCHECK_IMPLIES(transition_map.has_value(),
field_owner_map.equals(transition_map.value()));
}
PropertyAccessInfo::PropertyAccessInfo(
Zone* zone, Kind kind, OptionalJSObjectRef holder,
ZoneVector<MapRef>&& lookup_start_object_maps,
InternalIndex dictionary_index, NameRef name)
: kind_(kind),
lookup_start_object_maps_(lookup_start_object_maps),
holder_(holder),
unrecorded_dependencies_(zone),
field_representation_(Representation::None()),
field_type_(Type::Any()),
dictionary_index_(dictionary_index),
name_{name} {}
namespace {
template <class RefT>
bool OptionalRefEquals(OptionalRef<RefT> lhs, OptionalRef<RefT> rhs) {
if (!lhs.has_value()) return !rhs.has_value();
if (!rhs.has_value()) return false;
return lhs->equals(rhs.value());
}
template <class T>
void AppendVector(ZoneVector<T>* dst, const ZoneVector<T>& src) {
dst->insert(dst->end(), src.begin(), src.end());
}
} // namespace
bool PropertyAccessInfo::Merge(PropertyAccessInfo const* that,
AccessMode access_mode, Zone* zone) {
if (kind_ != that->kind_) return false;
if (!OptionalRefEquals(holder_, that->holder_)) return false;
switch (kind_) {
case kInvalid:
DCHECK_EQ(that->kind_, kInvalid);
return true;
case kDataField:
case kFastDataConstant: {
// Check if we actually access the same field (we use the
// GetFieldAccessStubKey method here just like the ICs do
// since that way we only compare the relevant bits of the
// field indices).
if (field_index_.GetFieldAccessStubKey() !=
that->field_index_.GetFieldAccessStubKey()) {
return false;
}
switch (access_mode) {
case AccessMode::kHas:
case AccessMode::kLoad: {
if (!field_representation_.Equals(that->field_representation_)) {
if (field_representation_.IsDouble() ||
that->field_representation_.IsDouble()) {
return false;
}
field_representation_ = Representation::Tagged();
}
if (!OptionalRefEquals(field_map_, that->field_map_)) {
field_map_ = {};
}
break;
}
case AccessMode::kStore:
case AccessMode::kStoreInLiteral:
case AccessMode::kDefine: {
// For stores, the field map and field representation information
// must match exactly, otherwise we cannot merge the stores. We
// also need to make sure that in case of transitioning stores,
// the transition targets match.
if (!OptionalRefEquals(field_map_, that->field_map_) ||
!field_representation_.Equals(that->field_representation_) ||
!OptionalRefEquals(transition_map_, that->transition_map_)) {
return false;
}
break;
}
}
field_type_ = Type::Union(field_type_, that->field_type_, zone);
AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
AppendVector(&unrecorded_dependencies_, that->unrecorded_dependencies_);
return true;
}
case kDictionaryProtoAccessorConstant:
case kFastAccessorConstant: {
// Check if we actually access the same constant.
if (!OptionalRefEquals(constant_, that->constant_)) return false;
DCHECK(unrecorded_dependencies_.empty());
DCHECK(that->unrecorded_dependencies_.empty());
AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
return true;
}
case kDictionaryProtoDataConstant: {
DCHECK_EQ(AccessMode::kLoad, access_mode);
if (dictionary_index_ != that->dictionary_index_) return false;
AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
return true;
}
case kNotFound:
case kStringLength: {
DCHECK(unrecorded_dependencies_.empty());
DCHECK(that->unrecorded_dependencies_.empty());
AppendVector(&lookup_start_object_maps_, that->lookup_start_object_maps_);
return true;
}
case kModuleExport:
return false;
}
}
ConstFieldInfo PropertyAccessInfo::GetConstFieldInfo() const {
return IsFastDataConstant() ? ConstFieldInfo(*field_owner_map_)
: ConstFieldInfo::None();
}
AccessInfoFactory::AccessInfoFactory(JSHeapBroker* broker, Zone* zone)
: broker_(broker), type_cache_(TypeCache::Get()), zone_(zone) {}
base::Optional<ElementAccessInfo> AccessInfoFactory::ComputeElementAccessInfo(
MapRef map, AccessMode access_mode) const {
if (!map.CanInlineElementAccess()) return {};
return ElementAccessInfo({{map}, zone()}, map.elements_kind(), zone());
}
bool AccessInfoFactory::ComputeElementAccessInfos(
ElementAccessFeedback const& feedback,
ZoneVector<ElementAccessInfo>* access_infos) const {
AccessMode access_mode = feedback.keyed_mode().access_mode();
if (access_mode == AccessMode::kLoad || access_mode == AccessMode::kHas) {
// For polymorphic loads of similar elements kinds (i.e. all tagged or all
// double), always use the "worst case" code without a transition. This is
// much faster than transitioning the elements to the worst case, trading a
// TransitionElementsKind for a CheckMaps, avoiding mutation of the array.
base::Optional<ElementAccessInfo> access_info =
ConsolidateElementLoad(feedback);
if (access_info.has_value()) {
access_infos->push_back(*access_info);
return true;
}
}
for (auto const& group : feedback.transition_groups()) {
DCHECK(!group.empty());
OptionalMapRef target = group.front();
base::Optional<ElementAccessInfo> access_info =
ComputeElementAccessInfo(target.value(), access_mode);
if (!access_info.has_value()) return false;
for (size_t i = 1; i < group.size(); ++i) {
OptionalMapRef map_ref = group[i];
if (!map_ref.has_value()) continue;
access_info->AddTransitionSource(map_ref.value());
}
access_infos->push_back(*access_info);
}
return true;
}
PropertyAccessInfo AccessInfoFactory::ComputeDataFieldAccessInfo(
MapRef receiver_map, MapRef map, NameRef name, OptionalJSObjectRef holder,
InternalIndex descriptor, AccessMode access_mode) const {
DCHECK(descriptor.is_found());
// TODO(jgruber,v8:7790): Use DescriptorArrayRef instead.
Handle<DescriptorArray> descriptors =
map.instance_descriptors(broker()).object();
PropertyDetails const details = descriptors->GetDetails(descriptor);
int index = descriptors->GetFieldIndex(descriptor);
Representation details_representation = details.representation();
if (details_representation.IsNone()) {
// The ICs collect feedback in PREMONOMORPHIC state already,
// but at this point the {receiver_map} might still contain
// fields for which the representation has not yet been
// determined by the runtime. So we need to catch this case
// here and fall back to use the regular IC logic instead.
return Invalid();
}
FieldIndex field_index = FieldIndex::ForPropertyIndex(*map.object(), index,
details_representation);
// Private brands are used when loading private methods, which are stored in a
// BlockContext, an internal object.
Type field_type = name.object()->IsPrivateBrand() ? Type::OtherInternal()
: Type::NonInternal();
OptionalMapRef field_map;
ZoneVector<CompilationDependency const*> unrecorded_dependencies(zone());
Handle<FieldType> descriptors_field_type =
broker()->CanonicalPersistentHandle(
descriptors->GetFieldType(descriptor));
OptionalObjectRef descriptors_field_type_ref =
TryMakeRef<Object>(broker(), descriptors_field_type);
if (!descriptors_field_type_ref.has_value()) return Invalid();
// Note: FindFieldOwner may be called multiple times throughout one
// compilation. This is safe since its result is fixed for a given map and
// descriptor.
MapRef field_owner_map = map.FindFieldOwner(broker(), descriptor);
if (details_representation.IsSmi()) {
field_type = Type::SignedSmall();
unrecorded_dependencies.push_back(
dependencies()->FieldRepresentationDependencyOffTheRecord(
map, field_owner_map, descriptor, details_representation));
} else if (details_representation.IsDouble()) {
field_type = type_cache_->kFloat64;
unrecorded_dependencies.push_back(
dependencies()->FieldRepresentationDependencyOffTheRecord(
map, field_owner_map, descriptor, details_representation));
} else if (details_representation.IsHeapObject()) {
if (IsNone(*descriptors_field_type)) {
switch (access_mode) {
case AccessMode::kStore:
case AccessMode::kStoreInLiteral:
case AccessMode::kDefine:
// Store is not safe if the field type was cleared.
return Invalid();
case AccessMode::kLoad:
case AccessMode::kHas:
break;
}
// The field type was cleared by the GC, so we don't know anything
// about the contents now.
}
unrecorded_dependencies.push_back(
dependencies()->FieldRepresentationDependencyOffTheRecord(
map, field_owner_map, descriptor, details_representation));
if (IsClass(*descriptors_field_type)) {
// Remember the field map, and try to infer a useful type.
OptionalMapRef maybe_field_map =
TryMakeRef(broker(), FieldType::AsClass(*descriptors_field_type));
if (!maybe_field_map.has_value()) return Invalid();
field_type = Type::For(maybe_field_map.value(), broker());
field_map = maybe_field_map;
}
} else {
CHECK(details_representation.IsTagged());
}
// TODO(turbofan): We may want to do this only depending on the use
// of the access info.
unrecorded_dependencies.push_back(
dependencies()->FieldTypeDependencyOffTheRecord(
map, field_owner_map, descriptor,
descriptors_field_type_ref.value()));
PropertyConstness constness =
dependencies()->DependOnFieldConstness(map, field_owner_map, descriptor);
switch (constness) {
case PropertyConstness::kMutable:
return PropertyAccessInfo::DataField(
broker(), zone(), receiver_map, std::move(unrecorded_dependencies),
field_index, details_representation, field_type, field_owner_map,
field_map, holder, {});
case PropertyConstness::kConst:
return PropertyAccessInfo::FastDataConstant(
zone(), receiver_map, std::move(unrecorded_dependencies), field_index,
details_representation, field_type, field_owner_map, field_map,
holder, {});
}
UNREACHABLE();
}
namespace {
using AccessorsObjectGetter = std::function<Handle<Object>()>;
PropertyAccessInfo AccessorAccessInfoHelper(
Isolate* isolate, Zone* zone, JSHeapBroker* broker,
const AccessInfoFactory* ai_factory, MapRef receiver_map, NameRef name,
MapRef holder_map, OptionalJSObjectRef holder, AccessMode access_mode,
AccessorsObjectGetter get_accessors) {
if (holder_map.instance_type() == JS_MODULE_NAMESPACE_TYPE) {
DCHECK(holder_map.object()->is_prototype_map());
Handle<PrototypeInfo> proto_info = broker->CanonicalPersistentHandle(
PrototypeInfo::cast(holder_map.object()->prototype_info()));
Handle<JSModuleNamespace> module_namespace =
broker->CanonicalPersistentHandle(
JSModuleNamespace::cast(proto_info->module_namespace()));
Handle<Cell> cell = broker->CanonicalPersistentHandle(
Cell::cast(module_namespace->module()->exports()->Lookup(
isolate, name.object(),
Smi::ToInt(Object::GetHash(*name.object())))));
if (IsAnyStore(access_mode)) {
// ES#sec-module-namespace-exotic-objects-set-p-v-receiver
// ES#sec-module-namespace-exotic-objects-defineownproperty-p-desc
//
// Storing to a module namespace object is always an error or a no-op in
// JS.
return PropertyAccessInfo::Invalid(zone);
}
if (IsTheHole(cell->value(kRelaxedLoad), isolate)) {
// This module has not been fully initialized yet.
return PropertyAccessInfo::Invalid(zone);
}
OptionalCellRef cell_ref = TryMakeRef(broker, cell);
if (!cell_ref.has_value()) {
return PropertyAccessInfo::Invalid(zone);
}
return PropertyAccessInfo::ModuleExport(zone, receiver_map,
cell_ref.value());
}
if (access_mode == AccessMode::kHas) {
// kHas is not supported for dictionary mode objects.
DCHECK(!holder_map.is_dictionary_map());
// HasProperty checks don't call getter/setters, existence is sufficient.
return PropertyAccessInfo::FastAccessorConstant(zone, receiver_map, holder,
{}, {});
}
Handle<Object> maybe_accessors = get_accessors();
if (!IsAccessorPair(*maybe_accessors)) {
return PropertyAccessInfo::Invalid(zone);
}
Handle<AccessorPair> accessors = Handle<AccessorPair>::cast(maybe_accessors);
Handle<Object> accessor = broker->CanonicalPersistentHandle(
access_mode == AccessMode::kLoad ? accessors->getter(kAcquireLoad)
: accessors->setter(kAcquireLoad));
OptionalObjectRef accessor_ref = TryMakeRef(broker, accessor);
if (!accessor_ref.has_value()) return PropertyAccessInfo::Invalid(zone);
OptionalJSObjectRef api_holder_ref;
if (!IsJSFunction(*accessor)) {
CallOptimization optimization(broker->local_isolate_or_isolate(), accessor);
if (!optimization.is_simple_api_call() ||
optimization.IsCrossContextLazyAccessorPair(
*broker->target_native_context().object(), *holder_map.object())) {
return PropertyAccessInfo::Invalid(zone);
}
if (DEBUG_BOOL && holder.has_value()) {
base::Optional<Tagged<NativeContext>> holder_creation_context =
holder->object()->GetCreationContext();
CHECK(holder_creation_context.has_value());
CHECK_EQ(*broker->target_native_context().object(),
holder_creation_context.value());
}
CallOptimization::HolderLookup holder_lookup;
Handle<JSObject> api_holder = broker->CanonicalPersistentHandle(
optimization.LookupHolderOfExpectedType(
broker->local_isolate_or_isolate(), receiver_map.object(),
&holder_lookup));
if (holder_lookup == CallOptimization::kHolderNotFound) {
return PropertyAccessInfo::Invalid(zone);
}
DCHECK_IMPLIES(holder_lookup == CallOptimization::kHolderIsReceiver,
api_holder.is_null());
DCHECK_IMPLIES(holder_lookup == CallOptimization::kHolderFound,
!api_holder.is_null());
if (!api_holder.is_null()) {
api_holder_ref = TryMakeRef(broker, api_holder);
if (!api_holder_ref.has_value()) return PropertyAccessInfo::Invalid(zone);
}
}
if (access_mode == AccessMode::kLoad) {
base::Optional<Tagged<Name>> cached_property_name =
FunctionTemplateInfo::TryGetCachedPropertyName(isolate, *accessor);
if (cached_property_name.has_value()) {
OptionalNameRef cached_property_name_ref =
TryMakeRef(broker, cached_property_name.value());
if (cached_property_name_ref.has_value()) {
PropertyAccessInfo access_info = ai_factory->ComputePropertyAccessInfo(
holder_map, cached_property_name_ref.value(), access_mode);
if (!access_info.IsInvalid()) return access_info;
}
}
}
if (holder_map.is_dictionary_map()) {
CHECK(!api_holder_ref.has_value());
return PropertyAccessInfo::DictionaryProtoAccessorConstant(
zone, receiver_map, holder, accessor_ref.value(), api_holder_ref, name);
} else {
return PropertyAccessInfo::FastAccessorConstant(
zone, receiver_map, holder, accessor_ref.value(), api_holder_ref);
}
}
} // namespace
PropertyAccessInfo AccessInfoFactory::ComputeAccessorDescriptorAccessInfo(
MapRef receiver_map, NameRef name, MapRef holder_map,
OptionalJSObjectRef holder, InternalIndex descriptor,
AccessMode access_mode) const {
DCHECK(descriptor.is_found());
Handle<DescriptorArray> descriptors = broker()->CanonicalPersistentHandle(
holder_map.object()->instance_descriptors(kRelaxedLoad));
SLOW_DCHECK(descriptor ==
descriptors->Search(*name.object(), *holder_map.object(), true));
auto get_accessors = [&]() {
return broker()->CanonicalPersistentHandle(
descriptors->GetStrongValue(descriptor));
};
return AccessorAccessInfoHelper(isolate(), zone(), broker(), this,
receiver_map, name, holder_map, holder,
access_mode, get_accessors);
}
PropertyAccessInfo AccessInfoFactory::ComputeDictionaryProtoAccessInfo(
MapRef receiver_map, NameRef name, JSObjectRef holder,
InternalIndex dictionary_index, AccessMode access_mode,
PropertyDetails details) const {
CHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
DCHECK(holder.map(broker()).object()->is_prototype_map());
DCHECK_EQ(access_mode, AccessMode::kLoad);
// We can only inline accesses to constant properties.
if (details.constness() != PropertyConstness::kConst) {
return Invalid();
}
if (details.kind() == PropertyKind::kData) {
return PropertyAccessInfo::DictionaryProtoDataConstant(
zone(), receiver_map, holder, dictionary_index, name);
}
auto get_accessors = [&]() {
return JSObject::DictionaryPropertyAt(isolate(), holder.object(),
dictionary_index);
};
return AccessorAccessInfoHelper(isolate(), zone(), broker(), this,
receiver_map, name, holder.map(broker()),
holder, access_mode, get_accessors);
}
bool AccessInfoFactory::TryLoadPropertyDetails(
MapRef map, OptionalJSObjectRef maybe_holder, NameRef name,
InternalIndex* index_out, PropertyDetails* details_out) const {
if (map.is_dictionary_map()) {
DCHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
DCHECK(map.object()->is_prototype_map());
DisallowGarbageCollection no_gc;
if (!maybe_holder.has_value()) {
// TODO(v8:11457) In this situation, we have a dictionary mode prototype
// as a receiver. Consider other means of obtaining the holder in this
// situation.
// Without the holder, we can't get the property details.
return false;
}
Handle<JSObject> holder = maybe_holder->object();
if (V8_ENABLE_SWISS_NAME_DICTIONARY_BOOL) {
Tagged<SwissNameDictionary> dict = holder->property_dictionary_swiss();
*index_out = dict->FindEntry(isolate(), name.object());
if (index_out->is_found()) {
*details_out = dict->DetailsAt(*index_out);
}
} else {
Tagged<NameDictionary> dict = holder->property_dictionary();
*index_out = dict->FindEntry(isolate(), name.object());
if (index_out->is_found()) {
*details_out = dict->DetailsAt(*index_out);
}
}
} else {
Tagged<DescriptorArray> descriptors =
*map.instance_descriptors(broker()).object();
*index_out = descriptors->Search(*name.object(), *map.object(), true);
if (index_out->is_found()) {
*details_out = descriptors->GetDetails(*index_out);
}
}
return true;
}
PropertyAccessInfo AccessInfoFactory::ComputePropertyAccessInfo(
MapRef map, NameRef name, AccessMode access_mode) const {
CHECK(name.IsUniqueName());
// Dictionary property const tracking is unsupported with concurrent inlining.
CHECK(!V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
JSHeapBroker::MapUpdaterGuardIfNeeded mumd_scope(broker());
if (access_mode == AccessMode::kHas && !IsJSReceiverMap(*map.object())) {
return Invalid();
}
// Check if it is safe to inline property access for the {map}.
if (!CanInlinePropertyAccess(map, access_mode)) {
return Invalid();
}
// We support fast inline cases for certain JSObject getters.
if (access_mode == AccessMode::kLoad || access_mode == AccessMode::kHas) {
PropertyAccessInfo access_info = LookupSpecialFieldAccessor(map, name);
if (!access_info.IsInvalid()) return access_info;
}
// Only relevant if V8_DICT_PROPERTY_CONST_TRACKING enabled.
bool dictionary_prototype_on_chain = false;
bool fast_mode_prototype_on_chain = false;
// Remember the receiver map. We use {map} as loop variable.
MapRef receiver_map = map;
OptionalJSObjectRef holder;
// Perform the implicit ToObject for primitives here.
// Implemented according to ES6 section 7.3.2 GetV (V, P).
// Note: Keep sync'd with
// CompilationDependencies::DependOnStablePrototypeChains.
if (receiver_map.IsPrimitiveMap()) {
OptionalJSFunctionRef constructor =
broker()->target_native_context().GetConstructorFunction(broker(),
receiver_map);
if (!constructor.has_value()) return Invalid();
map = constructor->initial_map(broker());
DCHECK(!map.IsPrimitiveMap());
}
while (true) {
PropertyDetails details = PropertyDetails::Empty();
InternalIndex index = InternalIndex::NotFound();
if (!TryLoadPropertyDetails(map, holder, name, &index, &details)) {
return Invalid();
}
if (index.is_found()) {
if (IsAnyStore(access_mode)) {
DCHECK(!map.is_dictionary_map());
// Don't bother optimizing stores to read-only properties.
if (details.IsReadOnly()) return Invalid();
if (details.kind() == PropertyKind::kData && holder.has_value()) {
// This is a store to a property not found on the receiver but on a
// prototype. According to ES6 section 9.1.9 [[Set]], we need to
// create a new data property on the receiver. We can still optimize
// if such a transition already exists.
return LookupTransition(receiver_map, name, holder, NONE);
}
}
if (map.is_dictionary_map()) {
DCHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
if (fast_mode_prototype_on_chain) {
// TODO(v8:11248) While the work on dictionary mode prototypes is in
// progress, we may still see fast mode objects on the chain prior to
// reaching a dictionary mode prototype holding the property . Due to
// this only being an intermediate state, we don't stupport these kind
// of heterogenous prototype chains.
return Invalid();
}
// TryLoadPropertyDetails only succeeds if we know the holder.
return ComputeDictionaryProtoAccessInfo(
receiver_map, name, holder.value(), index, access_mode, details);
}
if (dictionary_prototype_on_chain) {
// If V8_DICT_PROPERTY_CONST_TRACKING_BOOL was disabled, then a
// dictionary prototype would have caused a bailout earlier.
DCHECK(V8_DICT_PROPERTY_CONST_TRACKING_BOOL);
// TODO(v8:11248) We have a fast mode holder, but there was a dictionary
// mode prototype earlier on the chain. Note that seeing a fast mode
// prototype even though V8_DICT_PROPERTY_CONST_TRACKING is enabled
// should only be possible while the implementation of dictionary mode
// prototypes is work in progress. Eventually, enabling
// V8_DICT_PROPERTY_CONST_TRACKING will guarantee that all prototypes
// are always in dictionary mode, making this case unreachable. However,
// due to the complications of checking dictionary mode prototypes for
// modification, we don't attempt to support dictionary mode prototypes
// occuring before a fast mode holder on the chain.
return Invalid();
}
if (details.location() == PropertyLocation::kField) {
if (details.kind() == PropertyKind::kData) {
return ComputeDataFieldAccessInfo(receiver_map, map, name, holder,
index, access_mode);
} else {
DCHECK_EQ(PropertyKind::kAccessor, details.kind());
// TODO(turbofan): Add support for general accessors?
return Invalid();
}
} else {
DCHECK_EQ(PropertyLocation::kDescriptor, details.location());
DCHECK_EQ(PropertyKind::kAccessor, details.kind());
return ComputeAccessorDescriptorAccessInfo(receiver_map, name, map,
holder, index, access_mode);
}
UNREACHABLE();
}
// The property wasn't found on {map}. Look on the prototype if appropriate.
DCHECK(!index.is_found());
// Don't search on the prototype chain for special indices in case of
// integer indexed exotic objects (see ES6 section 9.4.5).
if (IsJSTypedArrayMap(*map.object()) && name.IsString()) {
StringRef name_str = name.AsString();
SharedStringAccessGuardIfNeeded access_guard(
*name_str.object(), broker()->local_isolate_or_isolate());
if (IsSpecialIndex(*name_str.object(), access_guard)) return Invalid();
}
// Don't search on the prototype when storing in literals, or performing a
// Define operation
if (access_mode == AccessMode::kStoreInLiteral ||
access_mode == AccessMode::kDefine) {
PropertyAttributes attrs = NONE;
if (name.object()->IsPrivate()) {
// When PrivateNames are added to an object, they are by definition
// non-enumerable.
attrs = DONT_ENUM;
}
return LookupTransition(receiver_map, name, holder, attrs);
}
// Don't lookup private symbols on the prototype chain.
if (name.object()->IsPrivate()) {
return Invalid();
}
if (V8_DICT_PROPERTY_CONST_TRACKING_BOOL && holder.has_value()) {
// At this point, we are past the first loop iteration.
DCHECK(holder->object()->map()->is_prototype_map());
DCHECK(!holder->map(broker()).equals(receiver_map));
fast_mode_prototype_on_chain =
fast_mode_prototype_on_chain || !map.is_dictionary_map();
dictionary_prototype_on_chain =
dictionary_prototype_on_chain || map.is_dictionary_map();
}
// Walk up the prototype chain.
// Load the map's prototype's map to guarantee that every time we use it,
// we use the same Map.
HeapObjectRef prototype = map.prototype(broker());
MapRef map_prototype_map = prototype.map(broker());
if (!IsJSObjectMap(*map_prototype_map.object())) {
// Don't allow proxies on the prototype chain.
if (!prototype.IsNull()) {
DCHECK(IsJSProxy(*prototype.object()) ||
IsWasmObject(*prototype.object()));
return Invalid();
}
DCHECK(prototype.IsNull());
if (dictionary_prototype_on_chain) {
// TODO(v8:11248) See earlier comment about
// dictionary_prototype_on_chain. We don't support absent properties
// with dictionary mode prototypes on the chain, either. This is again
// just due to how we currently deal with dependencies for dictionary
// properties during finalization.
return Invalid();
}
// Store to property not found on the receiver or any prototype, we need
// to transition to a new data property.
// Implemented according to ES6 section 9.1.9 [[Set]] (P, V, Receiver)
if (access_mode == AccessMode::kStore) {
return LookupTransition(receiver_map, name, holder, NONE);
}
// The property was not found (access returns undefined or throws
// depending on the language mode of the load operation.
// Implemented according to ES6 section 9.1.8 [[Get]] (P, Receiver)
return PropertyAccessInfo::NotFound(zone(), receiver_map, holder);
}
holder = prototype.AsJSObject();
map = map_prototype_map;
if (!CanInlinePropertyAccess(map, access_mode)) {
return Invalid();
}
// Successful lookup on prototype chain needs to guarantee that all the
// prototypes up to the holder have stable maps, except for dictionary-mode
// prototypes. We currently do this by taking a
// DependOnStablePrototypeChains dependency in the caller.
//
// TODO(jgruber): This is brittle and easy to miss. Consider a refactor
// that moves the responsibility of taking the dependency into
// AccessInfoFactory.
}
UNREACHABLE();
}
PropertyAccessInfo AccessInfoFactory::FinalizePropertyAccessInfosAsOne(
ZoneVector<PropertyAccessInfo> access_infos, AccessMode access_mode) const {
ZoneVector<PropertyAccessInfo> merged_access_infos(zone());
MergePropertyAccessInfos(access_infos, access_mode, &merged_access_infos);
if (merged_access_infos.size() == 1) {
PropertyAccessInfo& result = merged_access_infos.front();
if (!result.IsInvalid()) {
result.RecordDependencies(dependencies());
return result;
}
}
return Invalid();
}
void PropertyAccessInfo::RecordDependencies(
CompilationDependencies* dependencies) {
for (CompilationDependency const* d : unrecorded_dependencies_) {
dependencies->RecordDependency(d);
}
unrecorded_dependencies_.clear();
}
bool AccessInfoFactory::FinalizePropertyAccessInfos(
ZoneVector<PropertyAccessInfo> access_infos, AccessMode access_mode,
ZoneVector<PropertyAccessInfo>* result) const {
if (access_infos.empty()) return false;
MergePropertyAccessInfos(access_infos, access_mode, result);
for (PropertyAccessInfo const& info : *result) {
if (info.IsInvalid()) return false;
}
for (PropertyAccessInfo& info : *result) {
info.RecordDependencies(dependencies());
}
return true;
}
void AccessInfoFactory::MergePropertyAccessInfos(
ZoneVector<PropertyAccessInfo> infos, AccessMode access_mode,
ZoneVector<PropertyAccessInfo>* result) const {
DCHECK(result->empty());
for (auto it = infos.begin(), end = infos.end(); it != end; ++it) {
bool merged = false;
for (auto ot = it + 1; ot != end; ++ot) {
if (ot->Merge(&(*it), access_mode, zone())) {
merged = true;
break;
}
}
if (!merged) result->push_back(*it);
}
CHECK(!result->empty());
}
CompilationDependencies* AccessInfoFactory::dependencies() const {
return broker()->dependencies();
}
Isolate* AccessInfoFactory::isolate() const { return broker()->isolate(); }
namespace {
Maybe<ElementsKind> GeneralizeElementsKind(ElementsKind this_kind,
ElementsKind that_kind) {
if (IsHoleyElementsKind(this_kind)) {
that_kind = GetHoleyElementsKind(that_kind);