Fix missing slot recording in transition compaction.

src/objects.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 7426 matching lines @@
     case INTERCEPTOR:
       return false;
     case NONEXISTENT:
       break;
   }
   UNREACHABLE();
   return true;
 }
 
 
+// TODO(mstarzinger): This method should be moved into MarkCompactCollector,
+// because it cannot be called from outside the GC and we already have methods
+// depending on the transitions layout in the GC anyways.
 void Map::ClearNonLiveTransitions(Heap* heap) {
   Object* array = *RawField(this, Map::kInstanceDescriptorsOrBitField3Offset);
   // If there are no descriptors to be cleared, return.
   // TODO(verwaest) Should be an assert, otherwise back pointers are not
   // properly cleared.
   if (array->IsSmi()) return;
   DescriptorArray* d = DescriptorArray::cast(array);
 
   int descriptor_index = 0;
   // Compact all live descriptors to the left.
   for (int i = 0; i < d->number_of_descriptors(); ++i) {
     if (!ClearNonLiveTransitionsFromDescriptor(heap, d, i)) {
       if (i != descriptor_index) {
-        d->SetKeyUnchecked(heap, descriptor_index, d->GetKey(i));
+        String* key = d->GetKey(i);
+        Object* value = d->GetValue(i);
+        d->SetKeyUnchecked(heap, descriptor_index, key);
         d->SetDetailsUnchecked(descriptor_index, d->GetDetails(i).AsSmi());
-        d->SetValueUnchecked(heap, descriptor_index, d->GetValue(i));
+        d->SetValueUnchecked(heap, descriptor_index, value);
+        MarkCompactCollector* collector = heap->mark_compact_collector();
+        Object** key_slot = d->GetKeySlot(descriptor_index);
+        collector->RecordSlot(key_slot, key_slot, key);
+        if (value->IsHeapObject()) {
+          Object** value_slot = d->GetValueSlot(descriptor_index);
+          collector->RecordSlot(value_slot, value_slot, value);
+        }
       }
       descriptor_index++;
     }
   }
 
   Map* elements_transition = d->elements_transition_map();
   if (elements_transition != NULL &&
       ClearBackPointer(heap, elements_transition)) {
     elements_transition = NULL;
     d->ClearElementsTransition();
@@ skipping 5892 matching lines @@
   set_year(Smi::FromInt(year), SKIP_WRITE_BARRIER);
   set_month(Smi::FromInt(month), SKIP_WRITE_BARRIER);
   set_day(Smi::FromInt(day), SKIP_WRITE_BARRIER);
   set_weekday(Smi::FromInt(weekday), SKIP_WRITE_BARRIER);
   set_hour(Smi::FromInt(hour), SKIP_WRITE_BARRIER);
   set_min(Smi::FromInt(min), SKIP_WRITE_BARRIER);
   set_sec(Smi::FromInt(sec), SKIP_WRITE_BARRIER);
 }
 
 } }  // namespace v8::internal