src/hotspot/share/gc/parallel/mutableSpace.cpp

@@ -203,26 +203,40 @@
    while (obj_addr < t) {
      obj_addr += cast_to_oop(obj_addr)->oop_iterate_size(cl);
    }
  }
  
- void MutableSpace::object_iterate(ObjectClosure* cl) {
+ template<bool COMPACT_HEADERS>
+ void MutableSpace::object_iterate_impl(ObjectClosure* cl) {
    HeapWord* p = bottom();
    while (p < top()) {
      oop obj = cast_to_oop(p);
      // When promotion-failure occurs during Young GC, eden/from space is not cleared,
      // so we can encounter objects with "forwarded" markword.
      // They are essentially dead, so skipping them
      if (!obj->is_forwarded()) {
        cl->do_object(obj);
-     }
- #ifdef ASSERT
-     else {
+       p += obj->size();
+     } else {
        assert(obj->forwardee() != obj, "must not be self-forwarded");
+       if (COMPACT_HEADERS) {
+         // It is safe to use the forwardee here. Parallel GC only uses
+         // header-based forwarding during promotion. Full GC doesn't
+         // use the object header for forwarding at all.
+         p += obj->forwardee()->size();
+       } else {
+         p += obj->size();
+       }
      }
- #endif
-     p += obj->size();
+   }
+ }
+ 
+ void MutableSpace::object_iterate(ObjectClosure* cl) {
+   if (UseCompactObjectHeaders) {
+     object_iterate_impl<true>(cl);
+   } else {
+     object_iterate_impl<false>(cl);
    }
  }
  
  void MutableSpace::print_short() const { print_short_on(tty); }
  void MutableSpace::print_short_on( outputStream* st) const {