Add bit_field3 to Map objects

src/mark-compact.cc

 // Copyright 2011 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 1063 matching lines @@
 }
 
 
 void MarkCompactCollector::MarkMapContents(Map* map) {
   // Mark prototype transitions array but don't push it into marking stack.
   // This will make references from it weak. We will clean dead prototype
   // transitions in ClearNonLiveTransitions.
   FixedArray* prototype_transitions = map->unchecked_prototype_transitions();
   if (!prototype_transitions->IsMarked()) SetMark(prototype_transitions);
 
-  MarkDescriptorArray(reinterpret_cast<DescriptorArray*>(
-      *HeapObject::RawField(map, Map::kInstanceDescriptorsOffset)));
+  Object* raw_descriptor_array =
+      *HeapObject::RawField(map,
+                            Map::kInstanceDescriptorsOrBitField3Offset);
+  if (!raw_descriptor_array->IsSmi()) {
+    MarkDescriptorArray(
+        reinterpret_cast<DescriptorArray*>(raw_descriptor_array));
+  }
 
   // Mark the Object* fields of the Map.
   // Since the descriptor array has been marked already, it is fine
   // that one of these fields contains a pointer to it.
   Object** start_slot = HeapObject::RawField(map,
                                              Map::kPointerFieldsBeginOffset);
 
   Object** end_slot = HeapObject::RawField(map, Map::kPointerFieldsEndOffset);
 
   StaticMarkingVisitor::VisitPointers(map->heap(), start_slot, end_slot);
@@ skipping 2033 matching lines @@
 }
 
 
 void MarkCompactCollector::Initialize() {
   StaticPointersToNewGenUpdatingVisitor::Initialize();
   StaticMarkingVisitor::Initialize();
 }
 
 
 } }  // namespace v8::internal