Ensure slow properties for simple {__proto__:null} literals.

src/objects.cc

 // 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/objects.h"
 
 #include <cmath>
 #include <iomanip>
 #include <memory>
 #include <sstream>
@@ skipping 8654 matching lines @@
 // for the global object and its prototype chain, and excluding it saves
 // memory on the map transition tree.
 
 // static
 Handle<Map> Map::TransitionToImmutableProto(Handle<Map> map) {
   Handle<Map> new_map = Map::Copy(map, "ImmutablePrototype");
   new_map->set_immutable_proto(true);
   return new_map;
 }
 
-Handle<Map> Map::CopyInitialMap(Handle<Map> map, int instance_size,
-                                int in_object_properties,
-                                int unused_property_fields) {
+namespace {
+void EnsureInitialMap(Handle<Map> map) {
 #ifdef DEBUG
   Isolate* isolate = map->GetIsolate();
   // Strict function maps have Function as a constructor but the
   // Function's initial map is a sloppy function map. Same holds for
   // GeneratorFunction / AsyncFunction and its initial map.
   Object* constructor = map->GetConstructor();
   DCHECK(constructor->IsJSFunction());
   DCHECK(*map == JSFunction::cast(constructor)->initial_map() ||
          *map == *isolate->strict_function_map() ||
          *map == *isolate->generator_function_map() ||
          *map == *isolate->async_function_map());
 #endif
   // Initial maps must always own their descriptors and it's descriptor array
   // does not contain descriptors that do not belong to the map.
   DCHECK(map->owns_descriptors());
   DCHECK_EQ(map->NumberOfOwnDescriptors(),
             map->instance_descriptors()->number_of_descriptors());
+}
+}  // namespace
 
+// static
+Handle<Map> Map::CopyInitialMapNormalized(Handle<Map> map,
+                                          PropertyNormalizationMode mode) {
+  EnsureInitialMap(map);
+  return CopyNormalized(map, mode);
+}
+
+// static
+Handle<Map> Map::CopyInitialMap(Handle<Map> map, int instance_size,
+                                int in_object_properties,
+                                int unused_property_fields) {
+  EnsureInitialMap(map);
   Handle<Map> result = RawCopy(map, instance_size);
 
   // Please note instance_type and instance_size are set when allocated.
   result->SetInObjectProperties(in_object_properties);
   result->set_unused_property_fields(unused_property_fields);
 
   int number_of_own_descriptors = map->NumberOfOwnDescriptors();
   if (number_of_own_descriptors > 0) {
     // The copy will use the same descriptors array.
     result->UpdateDescriptors(map->instance_descriptors(),
@@ skipping 11581 matching lines @@
       // depend on this.
       return DICTIONARY_ELEMENTS;
     }
     DCHECK_LE(kind, LAST_ELEMENTS_KIND);
     return kind;
   }
 }
 
 }  // namespace internal
 }  // namespace v8