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

@@ -238,19 +238,20 @@
    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 {
+     if (obj->is_forwarded()) {
        assert(obj->forwardee() != obj, "must not be self-forwarded");
+       // 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 {
+       cl->do_object(obj);
+       p += obj->size();
      }
- #endif
-     p += cast_to_oop(p)->size();
    }
  }
  
  void MutableSpace::print_short() const { print_short_on(tty); }
  void MutableSpace::print_short_on( outputStream* st) const {