Sharing of descriptor arrays.

src/mark-compact.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 1922 matching lines @@
     base_marker()->MarkObjectAndPush(reinterpret_cast<HeapObject*>(obj));
   }
 }
 
 
 template <class T>
 void Marker<T>::MarkTransitionArray(TransitionArray* transitions) {
   if (!base_marker()->MarkObjectWithoutPush(transitions)) return;
   Object** transitions_start = transitions->data_start();
 
-  DescriptorArray* descriptors = transitions->descriptors();
-  base_marker()->MarkObjectAndPush(descriptors);
-  mark_compact_collector()->RecordSlot(
-      transitions_start, transitions->GetDescriptorsSlot(), descriptors);
+  // We don't have to record the descriptors_pointer slot since the cell space
+  // is not compacted.
+  JSGlobalPropertyCell* descriptors_cell = transitions->descriptors_pointer();
+  base_marker()->MarkObjectAndPush(descriptors_cell);
 
   if (transitions->HasPrototypeTransitions()) {
     // 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.
     Object** proto_trans_slot = transitions->GetPrototypeTransitionsSlot();
     HeapObject* prototype_transitions = HeapObject::cast(*proto_trans_slot);
     base_marker()->MarkObjectWithoutPush(prototype_transitions);
     mark_compact_collector()->RecordSlot(
         transitions_start, proto_trans_slot, prototype_transitions);
@@ skipping 2185 matching lines @@
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 
 
 } }  // namespace v8::internal