Promoting elements transitions to their own field.

src/hydrogen-instructions.h

 // 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 2074 matching lines @@
 
     // Since transitioned elements maps of the initial map don't fail the map
     // check, the CheckMaps instruction doesn't need to depend on ElementsKinds.
     check_map->ClearGVNFlag(kDependsOnElementsKind);
 
     ElementsKind kind = map->elements_kind();
     bool packed = IsFastPackedElementsKind(kind);
     while (CanTransitionToMoreGeneralFastElementsKind(kind, packed)) {
       kind = GetNextMoreGeneralFastElementsKind(kind, packed);
       Map* transitioned_map =
-          map->LookupElementsTransitionMap(kind, NULL);
+          map->LookupElementsTransitionMap(kind);
       if (transitioned_map) {
         map_set->Add(Handle<Map>(transitioned_map));
       }
     };
     map_set->Sort();
     return check_map;
   }
 
   virtual Representation RequiredInputRepresentation(int index) {
     return Representation::Tagged();
@@ skipping 2951 matching lines @@
   DECLARE_CONCRETE_INSTRUCTION(LoadFieldByIndex);
 };
 
 
 #undef DECLARE_INSTRUCTION
 #undef DECLARE_CONCRETE_INSTRUCTION
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_INSTRUCTIONS_H_