Use an allocation site scratchpad to speed up allocaton site processing during gc.

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 1362 matching lines @@
       break;
     case TRANSITIONS:
       return DependentCode::kAllocationSiteTransitionChangedGroup;
       break;
   }
   UNREACHABLE();
   return DependentCode::kAllocationSiteTransitionChangedGroup;
 }
 
 
-inline void AllocationSite::IncrementMementoFoundCount() {
+inline bool AllocationSite::IncrementMementoFoundCount() {
+  if (IsZombie()) return false;
+
   int value = memento_found_count()->value();
   set_memento_found_count(Smi::FromInt(value + 1));
+  return value == 0;
 }
 
 
 inline void AllocationSite::IncrementMementoCreateCount() {
   ASSERT(FLAG_allocation_site_pretenuring);
   int value = memento_create_count()->value();
   set_memento_create_count(Smi::FromInt(value + 1));
 }
 
 
@@ skipping 5064 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_