Reland "In-object double fields unboxing (for 64-bit only)."

src/runtime/runtime-object.cc

 // Copyright 2014 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/v8.h"
 
 #include "src/arguments.h"
 #include "src/bootstrapper.h"
 #include "src/debug.h"
 #include "src/runtime/runtime.h"
@@ skipping 1382 matching lines @@
   RUNTIME_ASSERT((index->value() & 1) == 1);
   FieldIndex field_index =
       FieldIndex::ForLoadByFieldIndex(object->map(), index->value());
   if (field_index.is_inobject()) {
     RUNTIME_ASSERT(field_index.property_index() <
                    object->map()->inobject_properties());
   } else {
     RUNTIME_ASSERT(field_index.outobject_array_index() <
                    object->properties()->length());
   }
-  Handle<Object> raw_value(object->RawFastPropertyAt(field_index), isolate);
-  RUNTIME_ASSERT(raw_value->IsMutableHeapNumber());
-  return *Object::WrapForRead(isolate, raw_value, Representation::Double());
+  return *JSObject::FastPropertyAt(object, Representation::Double(),
+                                   field_index);
 }
 
 
 RUNTIME_FUNCTION(Runtime_TryMigrateInstance) {
   HandleScope scope(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_HANDLE_CHECKED(Object, object, 0);
   if (!object->IsJSObject()) return Smi::FromInt(0);
   Handle<JSObject> js_object = Handle<JSObject>::cast(object);
   if (!js_object->map()->is_deprecated()) return Smi::FromInt(0);
@@ skipping 164 matching lines @@
 
 RUNTIME_FUNCTION(RuntimeReference_ClassOf) {
   SealHandleScope shs(isolate);
   DCHECK(args.length() == 1);
   CONVERT_ARG_CHECKED(Object, obj, 0);
   if (!obj->IsJSReceiver()) return isolate->heap()->null_value();
   return JSReceiver::cast(obj)->class_name();
 }
 }
 }  // namespace v8::internal