Allow partial scanning of large arrays in order to avoid

src/mark-compact-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 65 matching lines @@
   ASSERT(obj->IsHeapObject());
   HeapObject* heap_object = HeapObject::cast(obj);
   return Marking::MarkBitFrom(heap_object).Get();
 }
 
 
 void MarkCompactCollector::RecordSlot(Object** anchor_slot,
                                       Object** slot,
                                       Object* object) {
   Page* object_page = Page::FromAddress(reinterpret_cast<Address>(object));
+  // Ensure the anchor slot is on the first 'page' of a large object.
+  ASSERT(Page::FromAddress(reinterpret_cast<Address>(anchor_slot))->owner() !=
+         NULL);
   if (object_page->IsEvacuationCandidate() &&
       !ShouldSkipEvacuationSlotRecording(anchor_slot)) {
     if (!SlotsBuffer::AddTo(&slots_buffer_allocator_,
                             object_page->slots_buffer_address(),
                             slot,
                             SlotsBuffer::FAIL_ON_OVERFLOW)) {
       EvictEvacuationCandidate(object_page);
     }
   }
 }
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_MARK_COMPACT_INL_H_