Short-circuit embedded cons strings.

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 215 matching lines @@
   Code* code = Code::cast(Code::GetObjectFromEntryAddress(entry_address));
   heap->mark_compact_collector()->RecordCodeEntrySlot(entry_address, code);
   StaticVisitor::MarkObject(heap, code);
 }
 
 
 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());
   if (!FLAG_weak_embedded_maps_in_optimized_code || !FLAG_collect_maps ||
       rinfo->host()->kind() != Code::OPTIMIZED_FUNCTION ||
       !object->IsMap() || !Map::cast(object)->CanTransition()) {
-    heap->mark_compact_collector()->RecordRelocSlot(rinfo, object);
-    StaticVisitor::MarkObject(heap, object);
+    Object** target_address = rinfo->target_object_address();

[Michael Starzinger, 2013/06/20 23:25:27]

This change is missing the slot recording for the reloc slot in the code.
Frankly it surprises me that this would pass the test suite.

Also I am not sure passing a non-heap slot to the StaticVisitor here will work,
because if the target happens to be in an evacuation candidate this stack(!)
slot will be recorded in the slots buffer.

+    Object* old_target = *target_address;
+    StaticVisitor::VisitPointer(heap, target_address);
+    if (*target_address != old_target) {
+      rinfo->set_target_object(*target_address);
+    }
   }
 }
 
 
 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);
@@ skipping 564 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_