Access old space marking bits from runtime only when incremental marking is in MARKING state.

src/builtins.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 250 matching lines @@
   // we still do it.
   heap->CreateFillerObjectAt(elms->address(), to_trim * entry_size);
 
   int new_start_index = to_trim * (entry_size / kPointerSize);
   former_start[new_start_index] = map;
   former_start[new_start_index + 1] = Smi::FromInt(len - to_trim);
 
   // Maintain marking consistency for HeapObjectIterator and
   // IncrementalMarking.
   int size_delta = to_trim * entry_size;
-  if (heap->marking()->TransferMark(elms->address(),
-                                    elms->address() + size_delta)) {
-    MemoryChunk::IncrementLiveBytesFromMutator(elms->address(), -size_delta);
-  }
+  heap->marking()->TransferMark(elms->address(), elms->address() + size_delta);
+  heap->AdjustLiveBytes(elms->address(), -size_delta, Heap::FROM_MUTATOR);

[Michael Starzinger, 2014/03/19 11:25:26]

Unfortunately this is not correct. The adjustment happens after the mark bits
have been transferred but still targets the old address. Hence, the mark bit is
already gone.

Also I claim that AdjustLiveBytes() should not take an "Address" but and
"Object*" as a first parameter.

 
   FixedArrayBase* new_elms = FixedArrayBase::cast(HeapObject::FromAddress(
       elms->address() + size_delta));
   HeapProfiler* profiler = heap->isolate()->heap_profiler();
   if (profiler->is_tracking_object_moves()) {
     profiler->ObjectMoveEvent(elms->address(),
                               new_elms->address(),
                               new_elms->Size());
   }
   return new_elms;
@@ skipping 1473 matching lines @@
 }
 BUILTIN_LIST_C(DEFINE_BUILTIN_ACCESSOR_C)
 BUILTIN_LIST_A(DEFINE_BUILTIN_ACCESSOR_A)
 BUILTIN_LIST_H(DEFINE_BUILTIN_ACCESSOR_H)
 BUILTIN_LIST_DEBUG_A(DEFINE_BUILTIN_ACCESSOR_A)
 #undef DEFINE_BUILTIN_ACCESSOR_C
 #undef DEFINE_BUILTIN_ACCESSOR_A
 
 
 } }  // namespace v8::internal