blob: 9b0c4b41b1f3603e93592012d8bc9600ed1e37ed [file] [log] [blame]
// 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 <ostream>
#include "src/accessors.h"
#include "src/compilation-dependencies.h"
#include "src/compiler/access-info.h"
#include "src/compiler/type-cache.h"
#include "src/field-index-inl.h"
#include "src/field-type.h"
#include "src/ic/call-optimization.h"
#include "src/objects-inl.h"
namespace v8 {
namespace internal {
namespace compiler {
namespace {
bool CanInlineElementAccess(Handle<Map> map) {
if (!map->IsJSObjectMap()) return false;
if (map->is_access_check_needed()) return false;
if (map->has_indexed_interceptor()) return false;
ElementsKind const elements_kind = map->elements_kind();
if (IsFastElementsKind(elements_kind)) return true;
if (IsFixedTypedArrayElementsKind(elements_kind)) return true;
return false;
}
bool CanInlinePropertyAccess(Handle<Map> map) {
// 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).
STATIC_ASSERT(ODDBALL_TYPE == LAST_PRIMITIVE_TYPE);
if (map->IsBooleanMap()) return true;
if (map->instance_type() < LAST_PRIMITIVE_TYPE) return true;
return map->IsJSObjectMap() && !map->is_dictionary_map() &&
!map->has_named_interceptor() &&
// TODO(verwaest): Whitelist contexts to which we have access.
!map->is_access_check_needed();
}
} // 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";
}
UNREACHABLE();
}
ElementAccessInfo::ElementAccessInfo() {}
ElementAccessInfo::ElementAccessInfo(MapHandles const& receiver_maps,
ElementsKind elements_kind)
: elements_kind_(elements_kind), receiver_maps_(receiver_maps) {}
// static
PropertyAccessInfo PropertyAccessInfo::NotFound(MapHandles const& receiver_maps,
MaybeHandle<JSObject> holder) {
return PropertyAccessInfo(holder, receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::DataConstant(
MapHandles const& receiver_maps, Handle<Object> constant,
MaybeHandle<JSObject> holder) {
return PropertyAccessInfo(kDataConstant, holder, constant, receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::DataField(
PropertyConstness constness, MapHandles const& receiver_maps,
FieldIndex field_index, MachineRepresentation field_representation,
Type* field_type, MaybeHandle<Map> field_map, MaybeHandle<JSObject> holder,
MaybeHandle<Map> transition_map) {
Kind kind = constness == kConst ? kDataConstantField : kDataField;
return PropertyAccessInfo(kind, holder, transition_map, field_index,
field_representation, field_type, field_map,
receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::AccessorConstant(
MapHandles const& receiver_maps, Handle<Object> constant,
MaybeHandle<JSObject> holder) {
return PropertyAccessInfo(kAccessorConstant, holder, constant, receiver_maps);
}
// static
PropertyAccessInfo PropertyAccessInfo::ModuleExport(
MapHandles const& receiver_maps, Handle<Cell> cell) {
return PropertyAccessInfo(kModuleExport, MaybeHandle<JSObject>(), cell,
receiver_maps);
}
PropertyAccessInfo::PropertyAccessInfo()
: kind_(kInvalid),
field_representation_(MachineRepresentation::kNone),
field_type_(Type::None()) {}
PropertyAccessInfo::PropertyAccessInfo(MaybeHandle<JSObject> holder,
MapHandles const& receiver_maps)
: kind_(kNotFound),
receiver_maps_(receiver_maps),
holder_(holder),
field_representation_(MachineRepresentation::kNone),
field_type_(Type::None()) {}
PropertyAccessInfo::PropertyAccessInfo(Kind kind, MaybeHandle<JSObject> holder,
Handle<Object> constant,
MapHandles const& receiver_maps)
: kind_(kind),
receiver_maps_(receiver_maps),
constant_(constant),
holder_(holder),
field_representation_(MachineRepresentation::kNone),
field_type_(Type::Any()) {}
PropertyAccessInfo::PropertyAccessInfo(
Kind kind, MaybeHandle<JSObject> holder, MaybeHandle<Map> transition_map,
FieldIndex field_index, MachineRepresentation field_representation,
Type* field_type, MaybeHandle<Map> field_map,
MapHandles const& receiver_maps)
: kind_(kind),
receiver_maps_(receiver_maps),
transition_map_(transition_map),
holder_(holder),
field_index_(field_index),
field_representation_(field_representation),
field_type_(field_type),
field_map_(field_map) {}
bool PropertyAccessInfo::Merge(PropertyAccessInfo const* that,
AccessMode access_mode, Zone* zone) {
if (this->kind_ != that->kind_) return false;
if (this->holder_.address() != that->holder_.address()) return false;
switch (this->kind_) {
case kInvalid:
break;
case kDataField:
case kDataConstantField: {
// 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 (this->field_index_.GetFieldAccessStubKey() ==
that->field_index_.GetFieldAccessStubKey()) {
switch (access_mode) {
case AccessMode::kLoad: {
if (this->field_representation_ != that->field_representation_) {
if (!IsAnyTagged(this->field_representation_) ||
!IsAnyTagged(that->field_representation_)) {
return false;
}
this->field_representation_ = MachineRepresentation::kTagged;
}
if (this->field_map_.address() != that->field_map_.address()) {
this->field_map_ = MaybeHandle<Map>();
}
break;
}
case AccessMode::kStore:
case AccessMode::kStoreInLiteral: {
// 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 (this->field_map_.address() != that->field_map_.address() ||
this->field_representation_ != that->field_representation_ ||
this->transition_map_.address() !=
that->transition_map_.address()) {
return false;
}
break;
}
}
// Merge the field type.
this->field_type_ =
Type::Union(this->field_type_, that->field_type_, zone);
// Merge the receiver maps.
this->receiver_maps_.insert(this->receiver_maps_.end(),
that->receiver_maps_.begin(),
that->receiver_maps_.end());
return true;
}
return false;
}
case kDataConstant:
case kAccessorConstant: {
// Check if we actually access the same constant.
if (this->constant_.address() == that->constant_.address()) {
this->receiver_maps_.insert(this->receiver_maps_.end(),
that->receiver_maps_.begin(),
that->receiver_maps_.end());
return true;
}
return false;
}
case kNotFound: {
this->receiver_maps_.insert(this->receiver_maps_.end(),
that->receiver_maps_.begin(),
that->receiver_maps_.end());
return true;
}
case kModuleExport: {
return false;
}
}
UNREACHABLE();
}
Handle<Cell> PropertyAccessInfo::export_cell() const {
DCHECK_EQ(kModuleExport, kind_);
return Handle<Cell>::cast(constant_);
}
AccessInfoFactory::AccessInfoFactory(CompilationDependencies* dependencies,
Handle<Context> native_context, Zone* zone)
: dependencies_(dependencies),
native_context_(native_context),
isolate_(native_context->GetIsolate()),
type_cache_(TypeCache::Get()),
zone_(zone) {
DCHECK(native_context->IsNativeContext());
}
bool AccessInfoFactory::ComputeElementAccessInfo(
Handle<Map> map, AccessMode access_mode, ElementAccessInfo* access_info) {
// Check if it is safe to inline element access for the {map}.
if (!CanInlineElementAccess(map)) return false;
ElementsKind const elements_kind = map->elements_kind();
*access_info = ElementAccessInfo(MapHandles{map}, elements_kind);
return true;
}
bool AccessInfoFactory::ComputeElementAccessInfos(
MapHandles const& maps, AccessMode access_mode,
ZoneVector<ElementAccessInfo>* access_infos) {
if (access_mode == AccessMode::kLoad) {
// 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.
ElementAccessInfo access_info;
if (ConsolidateElementLoad(maps, &access_info)) {
access_infos->push_back(access_info);
return true;
}
}
// Collect possible transition targets.
MapHandles possible_transition_targets;
possible_transition_targets.reserve(maps.size());
for (Handle<Map> map : maps) {
if (Map::TryUpdate(map).ToHandle(&map)) {
if (CanInlineElementAccess(map) &&
IsFastElementsKind(map->elements_kind()) &&
GetInitialFastElementsKind() != map->elements_kind()) {
possible_transition_targets.push_back(map);
}
}
}
// Separate the actual receiver maps and the possible transition sources.
MapHandles receiver_maps;
receiver_maps.reserve(maps.size());
MapTransitionList transitions(maps.size());
for (Handle<Map> map : maps) {
if (Map::TryUpdate(map).ToHandle(&map)) {
// Don't generate elements kind transitions from stable maps.
Map* transition_target = map->is_stable()
? nullptr
: map->FindElementsKindTransitionedMap(
possible_transition_targets);
if (transition_target == nullptr) {
receiver_maps.push_back(map);
} else {
transitions.push_back(std::make_pair(map, handle(transition_target)));
}
}
}
for (Handle<Map> receiver_map : receiver_maps) {
// Compute the element access information.
ElementAccessInfo access_info;
if (!ComputeElementAccessInfo(receiver_map, access_mode, &access_info)) {
return false;
}
// Collect the possible transitions for the {receiver_map}.
for (auto transition : transitions) {
if (transition.second.is_identical_to(receiver_map)) {
access_info.transitions().push_back(transition);
}
}
// Schedule the access information.
access_infos->push_back(access_info);
}
return true;
}
bool AccessInfoFactory::ComputePropertyAccessInfo(
Handle<Map> map, Handle<Name> name, AccessMode access_mode,
PropertyAccessInfo* access_info) {
// Check if it is safe to inline property access for the {map}.
if (!CanInlinePropertyAccess(map)) return false;
// Compute the receiver type.
Handle<Map> receiver_map = map;
// Property lookups require the name to be internalized.
name = isolate()->factory()->InternalizeName(name);
// We support fast inline cases for certain JSObject getters.
if (access_mode == AccessMode::kLoad &&
LookupSpecialFieldAccessor(map, name, access_info)) {
return true;
}
MaybeHandle<JSObject> holder;
do {
// Lookup the named property on the {map}.
Handle<DescriptorArray> descriptors(map->instance_descriptors(), isolate());
int const number = descriptors->SearchWithCache(isolate(), *name, *map);
if (number != DescriptorArray::kNotFound) {
PropertyDetails const details = descriptors->GetDetails(number);
if (access_mode == AccessMode::kStore ||
access_mode == AccessMode::kStoreInLiteral) {
// Don't bother optimizing stores to read-only properties.
if (details.IsReadOnly()) {
return false;
}
// Check for store to data property on a prototype.
if (details.kind() == kData && !holder.is_null()) {
// Store to property not found on the receiver but on a prototype, we
// need to transition to a new data property.
// Implemented according to ES6 section 9.1.9 [[Set]] (P, V, Receiver)
return LookupTransition(receiver_map, name, holder, access_info);
}
}
if (details.location() == kField) {
if (details.kind() == kData) {
int index = descriptors->GetFieldIndex(number);
Representation details_representation = details.representation();
FieldIndex field_index =
FieldIndex::ForPropertyIndex(*map, index, details_representation);
Type* field_type = Type::NonInternal();
MachineRepresentation field_representation =
MachineRepresentation::kTagged;
MaybeHandle<Map> field_map;
if (details_representation.IsSmi()) {
field_type = Type::SignedSmall();
field_representation = MachineRepresentation::kTaggedSigned;
} else if (details_representation.IsDouble()) {
field_type = type_cache_.kFloat64;
field_representation = MachineRepresentation::kFloat64;
} else if (details_representation.IsHeapObject()) {
// Extract the field type from the property details (make sure its
// representation is TaggedPointer to reflect the heap object case).
field_representation = MachineRepresentation::kTaggedPointer;
Handle<FieldType> descriptors_field_type(
descriptors->GetFieldType(number), isolate());
if (descriptors_field_type->IsNone()) {
// Store is not safe if the field type was cleared.
if (access_mode == AccessMode::kStore) return false;
// The field type was cleared by the GC, so we don't know anything
// about the contents now.
} else if (descriptors_field_type->IsClass()) {
// Add proper code dependencies in case of stable field map(s).
Handle<Map> field_owner_map(map->FindFieldOwner(number),
isolate());
dependencies()->AssumeFieldOwner(field_owner_map);
// Remember the field map, and try to infer a useful type.
field_type = Type::For(descriptors_field_type->AsClass());
field_map = descriptors_field_type->AsClass();
}
}
*access_info = PropertyAccessInfo::DataField(
details.constness(), MapHandles{receiver_map}, field_index,
field_representation, field_type, field_map, holder);
return true;
} else {
DCHECK_EQ(kAccessor, details.kind());
// TODO(turbofan): Add support for general accessors?
return false;
}
} else {
DCHECK_EQ(kDescriptor, details.location());
if (details.kind() == kData) {
DCHECK(!FLAG_track_constant_fields);
*access_info = PropertyAccessInfo::DataConstant(
MapHandles{receiver_map},
handle(descriptors->GetValue(number), isolate()), holder);
return true;
} else {
DCHECK_EQ(kAccessor, details.kind());
if (map->instance_type() == JS_MODULE_NAMESPACE_TYPE) {
DCHECK(map->is_prototype_map());
Handle<PrototypeInfo> proto_info =
Map::GetOrCreatePrototypeInfo(map, isolate());
DCHECK(proto_info->weak_cell()->IsWeakCell());
Handle<JSModuleNamespace> module_namespace(
JSModuleNamespace::cast(
WeakCell::cast(proto_info->weak_cell())->value()),
isolate());
Handle<Cell> cell(
Cell::cast(module_namespace->module()->exports()->Lookup(
isolate(), name, Smi::ToInt(name->GetHash()))),
isolate());
if (cell->value()->IsTheHole(isolate())) {
// This module has not been fully initialized yet.
return false;
}
*access_info = PropertyAccessInfo::ModuleExport(
MapHandles{receiver_map}, cell);
return true;
}
Handle<Object> accessors(descriptors->GetValue(number), isolate());
if (!accessors->IsAccessorPair()) return false;
Handle<Object> accessor(
access_mode == AccessMode::kLoad
? Handle<AccessorPair>::cast(accessors)->getter()
: Handle<AccessorPair>::cast(accessors)->setter(),
isolate());
if (!accessor->IsJSFunction()) {
CallOptimization optimization(accessor);
if (!optimization.is_simple_api_call()) return false;
if (optimization.IsCrossContextLazyAccessorPair(*native_context_,
*map)) {
return false;
}
CallOptimization::HolderLookup lookup;
holder =
optimization.LookupHolderOfExpectedType(receiver_map, &lookup);
if (lookup == CallOptimization::kHolderNotFound) return false;
DCHECK_IMPLIES(lookup == CallOptimization::kHolderIsReceiver,
holder.is_null());
DCHECK_IMPLIES(lookup == CallOptimization::kHolderFound,
!holder.is_null());
if (V8_UNLIKELY(FLAG_runtime_stats)) return false;
}
if (access_mode == AccessMode::kLoad) {
Handle<Name> cached_property_name;
if (FunctionTemplateInfo::TryGetCachedPropertyName(isolate(),
accessor)
.ToHandle(&cached_property_name)) {
if (ComputePropertyAccessInfo(map, cached_property_name,
access_mode, access_info)) {
return true;
}
}
}
*access_info = PropertyAccessInfo::AccessorConstant(
MapHandles{receiver_map}, accessor, holder);
return true;
}
}
UNREACHABLE();
}
// Don't search on the prototype chain for special indices in case of
// integer indexed exotic objects (see ES6 section 9.4.5).
if (map->IsJSTypedArrayMap() && name->IsString() &&
IsSpecialIndex(isolate()->unicode_cache(), String::cast(*name))) {
return false;
}
// Don't search on the prototype when storing in literals
if (access_mode == AccessMode::kStoreInLiteral) {
return LookupTransition(receiver_map, name, holder, access_info);
}
// Don't lookup private symbols on the prototype chain.
if (name->IsPrivate()) return false;
// Walk up the prototype chain.
if (!map->prototype()->IsJSObject()) {
// Perform the implicit ToObject for primitives here.
// Implemented according to ES6 section 7.3.2 GetV (V, P).
Handle<JSFunction> constructor;
if (Map::GetConstructorFunction(map, native_context())
.ToHandle(&constructor)) {
map = handle(constructor->initial_map(), isolate());
DCHECK(map->prototype()->IsJSObject());
} else if (map->prototype()->IsNull(isolate())) {
// 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, access_info);
}
// The property was not found, return undefined or throw depending
// on the language mode of the load operation.
// Implemented according to ES6 section 9.1.8 [[Get]] (P, Receiver)
*access_info =
PropertyAccessInfo::NotFound(MapHandles{receiver_map}, holder);
return true;
} else {
return false;
}
}
Handle<JSObject> map_prototype(JSObject::cast(map->prototype()), isolate());
if (map_prototype->map()->is_deprecated()) {
// Try to migrate the prototype object so we don't embed the deprecated
// map into the optimized code.
JSObject::TryMigrateInstance(map_prototype);
}
map = handle(map_prototype->map(), isolate());
holder = map_prototype;
} while (CanInlinePropertyAccess(map));
return false;
}
bool AccessInfoFactory::ComputePropertyAccessInfos(
MapHandles const& maps, Handle<Name> name, AccessMode access_mode,
ZoneVector<PropertyAccessInfo>* access_infos) {
for (Handle<Map> map : maps) {
if (Map::TryUpdate(map).ToHandle(&map)) {
PropertyAccessInfo access_info;
if (!ComputePropertyAccessInfo(map, name, access_mode, &access_info)) {
return false;
}
// Try to merge the {access_info} with an existing one.
bool merged = false;
for (PropertyAccessInfo& other_info : *access_infos) {
if (other_info.Merge(&access_info, access_mode, zone())) {
merged = true;
break;
}
}
if (!merged) access_infos->push_back(access_info);
}
}
return true;
}
namespace {
Maybe<ElementsKind> GeneralizeElementsKind(ElementsKind this_kind,
ElementsKind that_kind) {
if (IsHoleyOrDictionaryElementsKind(this_kind)) {
that_kind = GetHoleyElementsKind(that_kind);
} else if (IsHoleyOrDictionaryElementsKind(that_kind)) {
this_kind = GetHoleyElementsKind(this_kind);
}
if (this_kind == that_kind) return Just(this_kind);
if (IsDoubleElementsKind(that_kind) == IsDoubleElementsKind(this_kind)) {
if (IsMoreGeneralElementsKindTransition(that_kind, this_kind)) {
return Just(this_kind);
}
if (IsMoreGeneralElementsKindTransition(this_kind, that_kind)) {
return Just(that_kind);
}
}
return Nothing<ElementsKind>();
}
} // namespace
bool AccessInfoFactory::ConsolidateElementLoad(MapHandles const& maps,
ElementAccessInfo* access_info) {
if (maps.empty()) return false;
InstanceType instance_type = maps.front()->instance_type();
ElementsKind elements_kind = maps.front()->elements_kind();
for (Handle<Map> map : maps) {
if (!CanInlineElementAccess(map) || map->instance_type() != instance_type) {
return false;
}
if (!GeneralizeElementsKind(elements_kind, map->elements_kind())
.To(&elements_kind)) {
return false;
}
}
*access_info = ElementAccessInfo(maps, elements_kind);
return true;
}
bool AccessInfoFactory::LookupSpecialFieldAccessor(
Handle<Map> map, Handle<Name> name, PropertyAccessInfo* access_info) {
// Check for special JSObject field accessors.
FieldIndex field_index;
if (Accessors::IsJSObjectFieldAccessor(map, name, &field_index)) {
Type* field_type = Type::NonInternal();
MachineRepresentation field_representation = MachineRepresentation::kTagged;
if (map->IsStringMap()) {
DCHECK(Name::Equals(factory()->length_string(), name));
// The String::length property is always a smi in the range
// [0, String::kMaxLength].
field_type = type_cache_.kStringLengthType;
field_representation = MachineRepresentation::kTaggedSigned;
} else if (map->IsJSArrayMap()) {
DCHECK(Name::Equals(factory()->length_string(), name));
// The JSArray::length property is a smi in the range
// [0, FixedDoubleArray::kMaxLength] in case of fast double
// elements, a smi in the range [0, FixedArray::kMaxLength]
// in case of other fast elements, and [0, kMaxUInt32] in
// case of other arrays.
if (IsDoubleElementsKind(map->elements_kind())) {
field_type = type_cache_.kFixedDoubleArrayLengthType;
field_representation = MachineRepresentation::kTaggedSigned;
} else if (IsFastElementsKind(map->elements_kind())) {
field_type = type_cache_.kFixedArrayLengthType;
field_representation = MachineRepresentation::kTaggedSigned;
} else {
field_type = type_cache_.kJSArrayLengthType;
}
}
// Special fields are always mutable.
*access_info =
PropertyAccessInfo::DataField(kMutable, MapHandles{map}, field_index,
field_representation, field_type);
return true;
}
return false;
}
bool AccessInfoFactory::LookupTransition(Handle<Map> map, Handle<Name> name,
MaybeHandle<JSObject> holder,
PropertyAccessInfo* access_info) {
// Check if the {map} has a data transition with the given {name}.
Map* transition =
TransitionsAccessor(map).SearchTransition(*name, kData, NONE);
if (transition == nullptr) return false;
Handle<Map> transition_map(transition);
int const number = transition_map->LastAdded();
PropertyDetails const details =
transition_map->instance_descriptors()->GetDetails(number);
// Don't bother optimizing stores to read-only properties.
if (details.IsReadOnly()) return false;
// TODO(bmeurer): Handle transition to data constant?
if (details.location() != kField) return false;
int const index = details.field_index();
Representation details_representation = details.representation();
FieldIndex field_index = FieldIndex::ForPropertyIndex(*transition_map, index,
details_representation);
Type* field_type = Type::NonInternal();
MaybeHandle<Map> field_map;
MachineRepresentation field_representation = MachineRepresentation::kTagged;
if (details_representation.IsSmi()) {
field_type = Type::SignedSmall();
field_representation = MachineRepresentation::kTaggedSigned;
} else if (details_representation.IsDouble()) {
field_type = type_cache_.kFloat64;
field_representation = MachineRepresentation::kFloat64;
} else if (details_representation.IsHeapObject()) {
// Extract the field type from the property details (make sure its
// representation is TaggedPointer to reflect the heap object case).
field_representation = MachineRepresentation::kTaggedPointer;
Handle<FieldType> descriptors_field_type(
transition_map->instance_descriptors()->GetFieldType(number),
isolate());
if (descriptors_field_type->IsNone()) {
// Store is not safe if the field type was cleared.
return false;
} else if (descriptors_field_type->IsClass()) {
// Add proper code dependencies in case of stable field map(s).
Handle<Map> field_owner_map(transition_map->FindFieldOwner(number),
isolate());
dependencies()->AssumeFieldOwner(field_owner_map);
// Remember the field map, and try to infer a useful type.
field_type = Type::For(descriptors_field_type->AsClass());
field_map = descriptors_field_type->AsClass();
}
}
dependencies()->AssumeMapNotDeprecated(transition_map);
// Transitioning stores are never stores to constant fields.
*access_info = PropertyAccessInfo::DataField(
kMutable, MapHandles{map}, field_index, field_representation, field_type,
field_map, holder, transition_map);
return true;
}
Factory* AccessInfoFactory::factory() const { return isolate()->factory(); }
} // namespace compiler
} // namespace internal
} // namespace v8