Promoting elements transitions to their own field.

src/runtime.cc

 // Copyright 2012 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 1218 matching lines @@
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DisableAccessChecks) {
   ASSERT(args.length() == 1);
   CONVERT_ARG_CHECKED(HeapObject, object, 0);
   Map* old_map = object->map();
   bool needs_access_checks = old_map->is_access_check_needed();
   if (needs_access_checks) {
     // Copy map so it won't interfere constructor's initial map.
     Object* new_map;
-    { MaybeObject* maybe_new_map = old_map->CopyDropTransitions();
+    { MaybeObject* maybe_new_map =
+          old_map->CopyDropTransitions(DescriptorArray::MAY_BE_SHARED);
       if (!maybe_new_map->ToObject(&new_map)) return maybe_new_map;
     }
 
     Map::cast(new_map)->set_is_access_check_needed(false);
     object->set_map(Map::cast(new_map));
   }
   return isolate->heap()->ToBoolean(needs_access_checks);
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_EnableAccessChecks) {
   ASSERT(args.length() == 1);
   CONVERT_ARG_CHECKED(HeapObject, object, 0);
   Map* old_map = object->map();
   if (!old_map->is_access_check_needed()) {
     // Copy map so it won't interfere constructor's initial map.
     Object* new_map;
-    { MaybeObject* maybe_new_map = old_map->CopyDropTransitions();
+    { MaybeObject* maybe_new_map =
+          old_map->CopyDropTransitions(DescriptorArray::MAY_BE_SHARED);
       if (!maybe_new_map->ToObject(&new_map)) return maybe_new_map;
     }
 
     Map::cast(new_map)->set_is_access_check_needed(true);
     object->set_map(Map::cast(new_map));
   }
   return isolate->heap()->undefined_value();
 }
 
 
@@ skipping 8964 matching lines @@
           }
           return maybe_value;
         }
         return value;
       } else {
         return heap->undefined_value();
       }
     }
     case INTERCEPTOR:
     case MAP_TRANSITION:
-    case ELEMENTS_TRANSITION:
     case CONSTANT_TRANSITION:
     case NULL_DESCRIPTOR:
       return heap->undefined_value();
     case HANDLER:
       UNREACHABLE();
       return heap->undefined_value();
   }
   UNREACHABLE();  // keep the compiler happy
   return heap->undefined_value();
 }
@@ skipping 3292 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal