Clear next map word when folding allocations into js arrays.

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 1294 matching lines @@
 #if DEBUG
   if (FLAG_enable_slow_asserts) {
     ElementsAccessor* accessor = GetElementsAccessor();
     accessor->Validate(this);
   }
 #endif
 }
 
 
 bool JSObject::ShouldTrackAllocationInfo() {
-  if (map()->CanTrackAllocationSite()) {
+  if (AllocationSite::CanTrack(map()->instance_type())) {
     if (!IsJSArray()) {
       return true;
     }
 
     return AllocationSite::GetMode(GetElementsKind()) ==
         TRACK_ALLOCATION_SITE;
   }
   return false;
 }
 
@@ skipping 16 matching lines @@
   if (FLAG_track_allocation_sites &&
       IsFastSmiElementsKind(from) &&
       IsMoreGeneralElementsKindTransition(from, to)) {
     return TRACK_ALLOCATION_SITE;
   }
 
   return DONT_TRACK_ALLOCATION_SITE;
 }
 
 
+inline bool AllocationSite::CanTrack(InstanceType type) {
+  return type == JS_ARRAY_TYPE;
+}
+
+
 MaybeObject* JSObject::EnsureCanContainHeapObjectElements() {
   ValidateElements();
   ElementsKind elements_kind = map()->elements_kind();
   if (!IsFastObjectElementsKind(elements_kind)) {
     if (IsFastHoleyElementsKind(elements_kind)) {
       return TransitionElementsKind(FAST_HOLEY_ELEMENTS);
     } else {
       return TransitionElementsKind(FAST_ELEMENTS);
     }
   }
@@ skipping 2224 matching lines @@
 bool Map::is_dictionary_map() {
   return DictionaryMap::decode(bit_field3());
 }
 
 
 Code::Flags Code::flags() {
   return static_cast<Flags>(READ_INT_FIELD(this, kFlagsOffset));
 }
 
 
-inline bool Map::CanTrackAllocationSite() {
-  return instance_type() == JS_ARRAY_TYPE;
-}
-
-
 void Map::set_owns_descriptors(bool is_shared) {
   set_bit_field3(OwnsDescriptors::update(bit_field3(), is_shared));
 }
 
 
 bool Map::owns_descriptors() {
   return OwnsDescriptors::decode(bit_field3());
 }
 
 
@@ skipping 2681 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_