A bug in AllocationSite::GetMode(from, to) meant that we didn't update

src/objects-inl.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 1317 matching lines @@
   }
 
   return DONT_TRACK_ALLOCATION_SITE;
 }
 
 
 AllocationSiteMode AllocationSite::GetMode(ElementsKind from,
                                            ElementsKind to) {
   if (FLAG_track_allocation_sites &&
       IsFastSmiElementsKind(from) &&
-      (IsFastObjectElementsKind(to) || IsFastDoubleElementsKind(to))) {
+      IsFastElementsKind(to) &&
+      from != to) {

[Toon Verwaest, 2013/07/11 09:35:08]

Use IsMoreGeneralElementsKind to ensure we never track backwards.

[mvstanton, 2013/07/11 13:01:33]

Done.

     return TRACK_ALLOCATION_SITE;
   }
 
   return DONT_TRACK_ALLOCATION_SITE;
 }
 
 
 MaybeObject* JSObject::EnsureCanContainHeapObjectElements() {
   ValidateElements();
   ElementsKind elements_kind = map()->elements_kind();
@@ skipping 4833 matching lines @@
 #undef WRITE_UINT32_FIELD
 #undef READ_SHORT_FIELD
 #undef WRITE_SHORT_FIELD
 #undef READ_BYTE_FIELD
 #undef WRITE_BYTE_FIELD
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_INL_H_