Moving prototype transitions into the header of the transition array.

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 27 matching lines @@
 MaybeObject* TransitionArray::Allocate(int number_of_transitions) {
   Heap* heap = Isolate::Current()->heap();
   // Use FixedArray to not use DescriptorArray::cast on incomplete object.
   FixedArray* array;
   { MaybeObject* maybe_array =
         heap->AllocateFixedArray(ToKeyIndex(number_of_transitions));
     if (!maybe_array->To(&array)) return maybe_array;
   }
 
   array->set(kElementsTransitionIndex, Smi::FromInt(0));
+  array->set(kPrototypeTransitionsIndex, Smi::FromInt(0));
   return array;
 }
 
 
 void TransitionArray::CopyFrom(TransitionArray* origin,
                                int origin_transition,
                                int target_transition,
                                const WhitenessWitness& witness) {
   this->Set(target_transition,
             origin->GetKey(origin_transition),
@@ skipping 33 matching lines @@
 
   { MaybeObject* maybe_array;
     maybe_array = TransitionArray::Allocate(new_size);
     if (!maybe_array->To(&result)) return maybe_array;
   }
 
   if (HasElementsTransition()) {
     result->set_elements_transition(elements_transition());
   }
 
+  if (HasPrototypeTransitions()) {
+    result->SetPrototypeTransitions(GetPrototypeTransitions());
+  }
+
   FixedArray::WhitenessWitness witness(result);
 
   if (insertion_index != kNotFound) {
     for (int i = 0; i < number_of_transitions; ++i) {
       if (i != insertion_index) result->CopyFrom(this, i, i, witness);
     }
     result->Set(insertion_index, name, value, witness);
     return result;
   }
 
   insertion_index = 0;
   for (; insertion_index < number_of_transitions; ++insertion_index) {
     if (InsertionPointFound(GetKey(insertion_index), name)) break;
     result->CopyFrom(this, insertion_index, insertion_index, witness);
   }
 
   result->Set(insertion_index, name, value, witness);
 
   for (; insertion_index < number_of_transitions; ++insertion_index) {
     result->CopyFrom(this, insertion_index, insertion_index + 1, witness);
   }
 
   return result;
 }
 
 
 } }  // namespace v8::internal