Don't create new maps in CurrentMapForDeprecated.

src/objects.cc

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2519 matching lines @@
 
   if (old_representation.IsNone()) {
     UNREACHABLE();
     old_descriptors->SetRepresentation(modify_index, new_representation);
     return this;
   }
 
   int descriptors = old_map->NumberOfOwnDescriptors();
   Map* root_map = old_map->FindRootMap();
 
+  // Check the state of the root map.
   if (!old_map->EquivalentToForTransition(root_map)) {
     return CopyGeneralizeAllRepresentations();
   }
 
   int verbatim = root_map->NumberOfOwnDescriptors();
 
   Map* updated = root_map->FindUpdatedMap(
       verbatim, descriptors, old_descriptors);
   if (updated == NULL) return CopyGeneralizeAllRepresentations();
 
-  // Check the state of the root map.
   DescriptorArray* updated_descriptors = updated->instance_descriptors();
 
   int valid = updated->NumberOfOwnDescriptors();
   if (updated_descriptors->IsMoreGeneralThan(
           verbatim, valid, descriptors, old_descriptors)) {
     Representation updated_representation =
         updated_descriptors->GetDetails(modify_index).representation();
     if (new_representation.fits_into(updated_representation)) {
       if (FLAG_trace_generalization &&
           !(modify_index == 0 && new_representation.IsSmi())) {
@@ skipping 56 matching lines @@
       Handle<Map>(new_map);
       return maybe_map;
     }
   }
 
   new_map->set_owns_descriptors(true);
   return new_map;
 }
 
 
+Map* Map::CurrentMapForDeprecated() {
+  AssertNoAllocation no_allocation;
+  if (!is_deprecated()) return this;
+
+  DescriptorArray* old_descriptors = instance_descriptors();
+
+  int descriptors = NumberOfOwnDescriptors();
+  Map* root_map = FindRootMap();
+
+  // Check the state of the root map.
+  if (!EquivalentToForTransition(root_map)) return NULL;
+  int verbatim = root_map->NumberOfOwnDescriptors();
+
+  Map* updated = root_map->FindUpdatedMap(
+      verbatim, descriptors, old_descriptors);
+  if (updated == NULL) return NULL;
+
+  DescriptorArray* updated_descriptors = updated->instance_descriptors();
+  int valid = updated->NumberOfOwnDescriptors();
+  if (!updated_descriptors->IsMoreGeneralThan(
+          verbatim, valid, descriptors, old_descriptors)) {
+    return NULL;
+  }
+
+  return updated;
+}
+
+
 MaybeObject* JSObject::SetPropertyWithInterceptor(
     Name* name,
     Object* value,
     PropertyAttributes attributes,
     StrictModeFlag strict_mode) {
   // TODO(rossberg): Support symbols in the API.
   if (name->IsSymbol()) return value;
   Isolate* isolate = GetIsolate();
   HandleScope scope(isolate);
   Handle<JSObject> this_handle(this);
@@ skipping 12793 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal