[runtime] Introduce maps for the likely cases of FromPropertyDescriptor.
This change improves performance for the common case of Object.getOwnPropertyDescriptor by up 3x-4x, where we just return a property descriptor object for a regular data or accessor property. R=yangguo@chromium.org Review URL: https://codereview.chromium.org/1607943003 Cr-Commit-Position: refs/heads/master@{#33398}
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@ -2732,6 +2732,89 @@ bool Genesis::InstallNatives(ContextType context_type) {
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InstallBuiltinFunctionIds();
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// Create a map for accessor property descriptors (a variant of JSObject
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// that predefines four properties get, set, configurable and enumerable).
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{
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// AccessorPropertyDescriptor initial map.
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Handle<Map> map =
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factory()->NewMap(JS_OBJECT_TYPE, JSAccessorPropertyDescriptor::kSize);
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// Create the descriptor array for the property descriptor object.
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Map::EnsureDescriptorSlack(map, 4);
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{ // get
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DataDescriptor d(factory()->get_string(),
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JSAccessorPropertyDescriptor::kGetIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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{ // set
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DataDescriptor d(factory()->set_string(),
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JSAccessorPropertyDescriptor::kSetIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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{ // enumerable
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DataDescriptor d(factory()->enumerable_string(),
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JSAccessorPropertyDescriptor::kEnumerableIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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{ // configurable
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DataDescriptor d(factory()->configurable_string(),
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JSAccessorPropertyDescriptor::kConfigurableIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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Map::SetPrototype(map, isolate()->initial_object_prototype());
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map->SetInObjectProperties(4);
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map->set_unused_property_fields(0);
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native_context()->set_accessor_property_descriptor_map(*map);
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}
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// Create a map for data property descriptors (a variant of JSObject
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// that predefines four properties value, writable, configurable and
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// enumerable).
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{
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// DataPropertyDescriptor initial map.
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Handle<Map> map =
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factory()->NewMap(JS_OBJECT_TYPE, JSDataPropertyDescriptor::kSize);
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// Create the descriptor array for the property descriptor object.
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Map::EnsureDescriptorSlack(map, 4);
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{ // value
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DataDescriptor d(factory()->value_string(),
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JSDataPropertyDescriptor::kValueIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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{ // writable
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DataDescriptor d(factory()->writable_string(),
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JSDataPropertyDescriptor::kWritableIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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{ // enumerable
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DataDescriptor d(factory()->enumerable_string(),
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JSDataPropertyDescriptor::kEnumerableIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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{ // configurable
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DataDescriptor d(factory()->configurable_string(),
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JSDataPropertyDescriptor::kConfigurableIndex, NONE,
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Representation::Tagged());
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map->AppendDescriptor(&d);
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}
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Map::SetPrototype(map, isolate()->initial_object_prototype());
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map->SetInObjectProperties(4);
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map->set_unused_property_fields(0);
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native_context()->set_data_property_descriptor_map(*map);
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}
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// Create a constructor for RegExp results (a variant of Array that
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// predefines the two properties index and match).
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{
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@ -155,6 +155,8 @@ enum BindingFlags {
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V(GLOBAL_PROXY_INDEX, JSObject, global_proxy_object) \
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V(EMBEDDER_DATA_INDEX, FixedArray, embedder_data) \
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/* Below is alpha-sorted */ \
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V(ACCESSOR_PROPERTY_DESCRIPTOR_MAP_INDEX, Map, \
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accessor_property_descriptor_map) \
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V(ALLOW_CODE_GEN_FROM_STRINGS_INDEX, Object, allow_code_gen_from_strings) \
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V(ARRAY_BUFFER_FUN_INDEX, JSFunction, array_buffer_fun) \
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V(ARRAY_BUFFER_MAP_INDEX, Map, array_buffer_map) \
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@ -171,6 +173,7 @@ enum BindingFlags {
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call_as_constructor_delegate) \
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V(CALL_AS_FUNCTION_DELEGATE_INDEX, JSFunction, call_as_function_delegate) \
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V(CONTEXT_EXTENSION_FUNCTION_INDEX, JSFunction, context_extension_function) \
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V(DATA_PROPERTY_DESCRIPTOR_MAP_INDEX, Map, data_property_descriptor_map) \
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V(DATA_VIEW_FUN_INDEX, JSFunction, data_view_fun) \
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V(DATE_FUNCTION_INDEX, JSFunction, date_function) \
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V(ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX, Object, \
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@ -2559,6 +2559,52 @@ class JSObject: public JSReceiver {
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};
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// JSAccessorPropertyDescriptor is just a JSObject with a specific initial
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// map. This initial map adds in-object properties for "get", "set",
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// "enumerable" and "configurable" properties, as assigned by the
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// FromPropertyDescriptor function for regular accessor properties.
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class JSAccessorPropertyDescriptor: public JSObject {
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public:
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// Offsets of object fields.
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static const int kGetOffset = JSObject::kHeaderSize;
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static const int kSetOffset = kGetOffset + kPointerSize;
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static const int kEnumerableOffset = kSetOffset + kPointerSize;
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static const int kConfigurableOffset = kEnumerableOffset + kPointerSize;
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static const int kSize = kConfigurableOffset + kPointerSize;
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// Indices of in-object properties.
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static const int kGetIndex = 0;
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static const int kSetIndex = 1;
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static const int kEnumerableIndex = 2;
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static const int kConfigurableIndex = 3;
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private:
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DISALLOW_IMPLICIT_CONSTRUCTORS(JSAccessorPropertyDescriptor);
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};
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// JSDataPropertyDescriptor is just a JSObject with a specific initial map.
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// This initial map adds in-object properties for "value", "writable",
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// "enumerable" and "configurable" properties, as assigned by the
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// FromPropertyDescriptor function for regular data properties.
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class JSDataPropertyDescriptor: public JSObject {
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public:
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// Offsets of object fields.
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static const int kValueOffset = JSObject::kHeaderSize;
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static const int kWritableOffset = kValueOffset + kPointerSize;
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static const int kEnumerableOffset = kWritableOffset + kPointerSize;
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static const int kConfigurableOffset = kEnumerableOffset + kPointerSize;
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static const int kSize = kConfigurableOffset + kPointerSize;
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// Indices of in-object properties.
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static const int kValueIndex = 0;
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static const int kWritableIndex = 1;
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static const int kEnumerableIndex = 2;
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static const int kConfigurableIndex = 3;
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private:
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DISALLOW_IMPLICIT_CONSTRUCTORS(JSDataPropertyDescriptor);
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};
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// Common superclass for FixedArrays that allow implementations to share
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// common accessors and some code paths.
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class FixedArrayBase: public HeapObject {
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@ -13,6 +13,8 @@
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namespace v8 {
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namespace internal {
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namespace {
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// Helper function for ToPropertyDescriptor. Comments describe steps for
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// "enumerable", other properties are handled the same way.
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// Returns false if an exception was thrown.
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@ -101,19 +103,51 @@ bool ToPropertyDescriptorFastPath(Isolate* isolate, Handle<Object> obj,
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}
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static void CreateDataProperty(Isolate* isolate, Handle<JSObject> object,
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Handle<String> name, Handle<Object> value) {
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void CreateDataProperty(Isolate* isolate, Handle<JSObject> object,
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Handle<String> name, Handle<Object> value) {
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LookupIterator it(object, name, LookupIterator::OWN_SKIP_INTERCEPTOR);
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Maybe<bool> result = JSObject::CreateDataProperty(&it, value);
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CHECK(result.IsJust() && result.FromJust());
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}
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} // namespace
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// ES6 6.2.4.4 "FromPropertyDescriptor"
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Handle<Object> PropertyDescriptor::ToObject(Isolate* isolate) {
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DCHECK(!(PropertyDescriptor::IsAccessorDescriptor(this) &&
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PropertyDescriptor::IsDataDescriptor(this)));
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Factory* factory = isolate->factory();
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if (IsRegularAccessorProperty()) {
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// Fast case for regular accessor properties.
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Handle<JSObject> result = factory->NewJSObjectFromMap(
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isolate->accessor_property_descriptor_map());
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result->InObjectPropertyAtPut(JSAccessorPropertyDescriptor::kGetIndex,
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*get());
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result->InObjectPropertyAtPut(JSAccessorPropertyDescriptor::kSetIndex,
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*set());
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result->InObjectPropertyAtPut(
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JSAccessorPropertyDescriptor::kEnumerableIndex,
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isolate->heap()->ToBoolean(enumerable()));
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result->InObjectPropertyAtPut(
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JSAccessorPropertyDescriptor::kConfigurableIndex,
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isolate->heap()->ToBoolean(configurable()));
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return result;
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}
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if (IsRegularDataProperty()) {
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// Fast case for regular data properties.
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Handle<JSObject> result =
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factory->NewJSObjectFromMap(isolate->data_property_descriptor_map());
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result->InObjectPropertyAtPut(JSDataPropertyDescriptor::kValueIndex,
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*value());
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result->InObjectPropertyAtPut(JSDataPropertyDescriptor::kWritableIndex,
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isolate->heap()->ToBoolean(writable()));
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result->InObjectPropertyAtPut(JSDataPropertyDescriptor::kEnumerableIndex,
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isolate->heap()->ToBoolean(enumerable()));
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result->InObjectPropertyAtPut(JSDataPropertyDescriptor::kConfigurableIndex,
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isolate->heap()->ToBoolean(configurable()));
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return result;
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}
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Handle<JSObject> result = factory->NewJSObject(isolate->object_function());
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if (has_value()) {
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CreateDataProperty(isolate, result, factory->value_string(), value());
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@ -57,6 +57,16 @@ class PropertyDescriptor {
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!has_value() && !has_get() && !has_set();
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}
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bool IsRegularAccessorProperty() const {
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return has_configurable() && has_enumerable() && !has_value() &&
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!has_writable() && has_get() && has_set();
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}
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bool IsRegularDataProperty() const {
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return has_configurable() && has_enumerable() && has_value() &&
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has_writable() && !has_get() && !has_set();
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}
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bool enumerable() const { return enumerable_; }
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void set_enumerable(bool enumerable) {
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enumerable_ = enumerable;
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