[es6] Better support for built-ins subclassing.

src/objects-inl.h

 // Copyright 2012 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.
 //
 // Review notes:
 //
 // - The use of macros in these inline functions may seem superfluous
 // but it is absolutely needed to make sure gcc generates optimal
 // code. gcc is not happy when attempting to inline too deep.
 //
@@ skipping 2114 matching lines @@
 
 
 void WeakCell::clear_next(Heap* heap) {
   set_next(heap->the_hole_value(), SKIP_WRITE_BARRIER);
 }
 
 
 bool WeakCell::next_cleared() { return next()->IsTheHole(); }
 
 
-int JSObject::GetHeaderSize() {
-  InstanceType type = map()->instance_type();
+int JSObject::GetHeaderSize() { return GetHeaderSize(map()->instance_type()); }
+
+
+int JSObject::GetHeaderSize(InstanceType type) {
   // Check for the most common kind of JavaScript object before
   // falling into the generic switch. This speeds up the internal
   // field operations considerably on average.
   if (type == JS_OBJECT_TYPE) return JSObject::kHeaderSize;
   switch (type) {
     case JS_GENERATOR_OBJECT_TYPE:
       return JSGeneratorObject::kSize;
     case JS_MODULE_TYPE:
       return JSModule::kSize;
     case JS_GLOBAL_PROXY_TYPE:
@@ skipping 36 matching lines @@
       return JSObject::kHeaderSize;
     case JS_MESSAGE_OBJECT_TYPE:
       return JSMessageObject::kSize;
     default:
       UNREACHABLE();
       return 0;
   }
 }
 
 
-int JSObject::GetInternalFieldCount() {
-  DCHECK(1 << kPointerSizeLog2 == kPointerSize);
-  // Make sure to adjust for the number of in-object properties. These
-  // properties do contribute to the size, but are not internal fields.
-  return ((Size() - GetHeaderSize()) >> kPointerSizeLog2) -
-         map()->GetInObjectProperties();
+int JSObject::GetInternalFieldCount(Map* map) {
+  int instance_size = map->instance_size();
+  if (instance_size == kVariableSizeSentinel) return 0;
+  InstanceType instance_type = map->instance_type();
+  return ((instance_size - GetHeaderSize(instance_type)) >> kPointerSizeLog2) -
+         map->GetInObjectProperties();
 }
 
 
+int JSObject::GetInternalFieldCount() { return GetInternalFieldCount(map()); }
+
+
 int JSObject::GetInternalFieldOffset(int index) {
   DCHECK(index < GetInternalFieldCount() && index >= 0);
   return GetHeaderSize() + (kPointerSize * index);
 }
 
 
 Object* JSObject::GetInternalField(int index) {
   DCHECK(index < GetInternalFieldCount() && index >= 0);
   // Internal objects do follow immediately after the header, whereas in-object
   // properties are at the end of the object. Therefore there is no need
@@ skipping 3403 matching lines @@
 }
 
 
 void Map::SetConstructor(Object* constructor, WriteBarrierMode mode) {
   // Never overwrite a back pointer with a constructor.
   DCHECK(!constructor_or_backpointer()->IsMap());
   set_constructor_or_backpointer(constructor, mode);
 }
 
 
+Handle<Map> Map::CopyInitialMap(Handle<Map> map) {
+  return CopyInitialMap(map, map->instance_size(), map->GetInObjectProperties(),
+                        map->unused_property_fields());
+}
+
+
 ACCESSORS(JSFunction, shared, SharedFunctionInfo, kSharedFunctionInfoOffset)
 ACCESSORS(JSFunction, literals_or_bindings, FixedArray, kLiteralsOffset)
 ACCESSORS(JSFunction, next_function_link, Object, kNextFunctionLinkOffset)
 
 ACCESSORS(GlobalObject, builtins, JSBuiltinsObject, kBuiltinsOffset)
 ACCESSORS(GlobalObject, native_context, Context, kNativeContextOffset)
 ACCESSORS(GlobalObject, global_proxy, JSObject, kGlobalProxyOffset)
 
 ACCESSORS(JSGlobalProxy, native_context, Object, kNativeContextOffset)
 ACCESSORS(JSGlobalProxy, hash, Object, kHashOffset)
@@ skipping 2497 matching lines @@
 #undef WRITE_INT64_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 #undef NOBARRIER_READ_BYTE_FIELD
 #undef NOBARRIER_WRITE_BYTE_FIELD
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_OBJECTS_INL_H_