--- a/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp	Thu Dec 18 01:27:04 2008 -0800
+++ b/src/share/vm/gc_implementation/parallelScavenge/psParallelCompact.hpp	Thu Dec 18 10:53:35 2008 -0800
@@ -1154,8 +1154,10 @@
                                 HeapWord* end_addr);
 
   // Decrement the destination count for each non-empty source region in the
-  // range [beg_region, region(region_align_up(end_addr))).
+  // range [beg_region, region(region_align_up(end_addr))).  If the destination
+  // count for a region goes to 0 and it needs to be filled, enqueue it.
   static void decrement_destination_counts(ParCompactionManager* cm,
+                                           SpaceId src_space_id,
                                            size_t beg_region,
                                            HeapWord* end_addr);
 
@@ -1230,6 +1232,8 @@
 #endif  // #ifndef PRODUCT
 
 #ifdef  ASSERT
+  // Sanity check the new location of a word in the heap.
+  static inline void check_new_location(HeapWord* old_addr, HeapWord* new_addr);
   // Verify that all the regions have been emptied.
   static void verify_complete(SpaceId space_id);
 #endif  // #ifdef ASSERT
@@ -1397,6 +1401,15 @@
   }
 }
 
+#ifdef ASSERT
+inline void
+PSParallelCompact::check_new_location(HeapWord* old_addr, HeapWord* new_addr)
+{
+  assert(old_addr >= new_addr || space_id(old_addr) != space_id(new_addr),
+         "must move left or to a different space");
+}
+#endif // ASSERT
+
 class MoveAndUpdateClosure: public ParMarkBitMapClosure {
  public:
   inline MoveAndUpdateClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm,