Track representations of fields

src/transitions.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 117 matching lines @@
     result->SetPrototypeTransitions(GetPrototypeTransitions());
   }
 
   if (insertion_index != kNotFound) {
     for (int i = 0; i < number_of_transitions; ++i) {
       if (i != insertion_index) {
         result->NoIncrementalWriteBarrierCopyFrom(this, i, i);
       }
     }
     result->NoIncrementalWriteBarrierSet(insertion_index, name, target);
+    result->set_back_pointer_storage(back_pointer_storage());
     return result;
   }
 
   insertion_index = 0;
   for (; insertion_index < number_of_transitions; ++insertion_index) {
     if (InsertionPointFound(GetKey(insertion_index), name)) break;
     result->NoIncrementalWriteBarrierCopyFrom(
         this, insertion_index, insertion_index);
   }
 
   result->NoIncrementalWriteBarrierSet(insertion_index, name, target);
 
   for (; insertion_index < number_of_transitions; ++insertion_index) {
     result->NoIncrementalWriteBarrierCopyFrom(
         this, insertion_index, insertion_index + 1);
   }
 
   result->set_back_pointer_storage(back_pointer_storage());
   return result;
 }
 
 
 } }  // namespace v8::internal