Some tests and simplified TransitionArray copying

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 113 matching lines @@
 
   int number_of_transitions = map->transitions()->number_of_transitions();
   int new_size = number_of_transitions;
 
   int insertion_index = map->transitions()->Search(*name);
   if (insertion_index == kNotFound) ++new_size;
 
   Handle<TransitionArray> result =
       map->GetIsolate()->factory()->NewTransitionArray(new_size);
 
-  // The map's transition array may have disappeared or grown smaller during
-  // the allocation above as it was weakly traversed. Trim the result copy if
-  // needed, and recompute variables.
+  // The map's transition array may grown smaller during the allocation above as
+  // it was weakly traversed, though it is guaranteed not to disappear. Trim the
+  // result copy if needed, and recompute variables.
+  ASSERT(map->HasTransitionArray());
   DisallowHeapAllocation no_gc;
-  if (!map->HasTransitionArray()) {
-    if (flag == SIMPLE_TRANSITION) {
-      ASSERT(result->length() >= kSimpleTransitionSize);
-      result->Shrink(kSimpleTransitionSize);
-      result->set(kSimpleTransitionTarget, *target);
-    } else {
-      ASSERT(result->length() >= ToKeyIndex(1));
-      result->Shrink(ToKeyIndex(1));
-      result->set(kPrototypeTransitionsIndex, Smi::FromInt(0));
-      result->NoIncrementalWriteBarrierSet(0, *name, *target);
-    }
-    result->set_back_pointer_storage(map->GetBackPointer());
-
-    return result;
-  }
-
   TransitionArray* array = map->transitions();
   if (array->number_of_transitions() != number_of_transitions) {
     ASSERT(array->number_of_transitions() < number_of_transitions);
 
     number_of_transitions = array->number_of_transitions();
     new_size = number_of_transitions;
 
     insertion_index = array->Search(*name);
     if (insertion_index == kNotFound) ++new_size;
 
@@ skipping 28 matching lines @@
     result->NoIncrementalWriteBarrierCopyFrom(
         array, insertion_index, insertion_index + 1);
   }
 
   result->set_back_pointer_storage(array->back_pointer_storage());
   return result;
 }
 
 
 } }  // namespace v8::internal