Make cells pointing to JSObjects weak in optimized code.

src/objects-visiting-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 243 matching lines @@
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitEmbeddedPointer(
     Heap* heap, RelocInfo* rinfo) {
   ASSERT(rinfo->rmode() == RelocInfo::EMBEDDED_OBJECT);
   ASSERT(!rinfo->target_object()->IsConsString());
   HeapObject* object = HeapObject::cast(rinfo->target_object());
   heap->mark_compact_collector()->RecordRelocSlot(rinfo, object);
+  // TODO(ulan): It could be better to record slots only for strongly embedded
+  // objects here and record slots for weakly embedded object during clearing
+  // of non-live references in mark-compact.
   if (!Code::IsWeakEmbeddedObject(rinfo->host()->kind(), object)) {
     StaticVisitor::MarkObject(heap, object);
   }
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitCell(
     Heap* heap, RelocInfo* rinfo) {
   ASSERT(rinfo->rmode() == RelocInfo::CELL);
   Cell* cell = rinfo->target_cell();
-  StaticVisitor::MarkObject(heap, cell);
+  // No need to record slots because the cell space is not compacted during GC.
+  if (!Code::IsWeakEmbeddedObject(rinfo->host()->kind(), cell)) {
+    StaticVisitor::MarkObject(heap, cell);
+  }
 }
 
 
 template<typename StaticVisitor>
 void StaticMarkingVisitor<StaticVisitor>::VisitDebugTarget(
     Heap* heap, RelocInfo* rinfo) {
   ASSERT((RelocInfo::IsJSReturn(rinfo->rmode()) &&
           rinfo->IsPatchedReturnSequence()) ||
          (RelocInfo::IsDebugBreakSlot(rinfo->rmode()) &&
           rinfo->IsPatchedDebugBreakSlotSequence()));
@@ skipping 642 matching lines @@
   RelocIterator it(this, mode_mask);
   for (; !it.done(); it.next()) {
     it.rinfo()->template Visit<StaticVisitor>(heap);
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_OBJECTS_VISITING_INL_H_