src/hotspot/share/gc/shenandoah/shenandoahTraversalGC.inline.hpp

rev 56680 : 8232730: Shenandoah: Traversal should not CAS the roots
Reviewed-by: XXX

*** 33,48 ****
  #include "gc/shenandoah/shenandoahTaskqueue.hpp"
  #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
  #include "oops/compressedOops.inline.hpp"
  #include "oops/oop.inline.hpp"
  
! template <class T, bool STRING_DEDUP, bool DEGEN>
  void ShenandoahTraversalGC::process_oop(T* p, Thread* thread, ShenandoahObjToScanQueue* queue, ShenandoahMarkingContext* const mark_context) {
    T o = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(o)) {
      oop obj = CompressedOops::decode_not_null(o);
      if (DEGEN) {
        oop forw = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
        if (obj != forw) {
          // Update reference.
          RawAccess<IS_NOT_NULL>::oop_store(p, forw);
        }
--- 33,49 ----
  #include "gc/shenandoah/shenandoahTaskqueue.hpp"
  #include "gc/shenandoah/shenandoahTaskqueue.inline.hpp"
  #include "oops/compressedOops.inline.hpp"
  #include "oops/oop.inline.hpp"
  
! template <class T, bool STRING_DEDUP, bool DEGEN, bool ATOMIC_UPDATE>
  void ShenandoahTraversalGC::process_oop(T* p, Thread* thread, ShenandoahObjToScanQueue* queue, ShenandoahMarkingContext* const mark_context) {
    T o = RawAccess<>::oop_load(p);
    if (!CompressedOops::is_null(o)) {
      oop obj = CompressedOops::decode_not_null(o);
      if (DEGEN) {
+       assert(!ATOMIC_UPDATE, "Degen path assumes non-atomic updates");
        oop forw = ShenandoahBarrierSet::resolve_forwarded_not_null(obj);
        if (obj != forw) {
          // Update reference.
          RawAccess<IS_NOT_NULL>::oop_store(p, forw);
        }
*** 52,62 ****
--- 53,67 ----
        if (obj == forw) {
          forw = _heap->evacuate_object(obj, thread);
        }
        shenandoah_assert_forwarded_except(p, obj, _heap->cancelled_gc());
        // Update reference.
+       if (ATOMIC_UPDATE) {
          ShenandoahHeap::cas_oop(forw, p, obj);
+       } else {
+         RawAccess<IS_NOT_NULL>::oop_store(p, forw);
+       }
        obj = forw;
      }
  
      shenandoah_assert_not_forwarded(p, obj);
      shenandoah_assert_not_in_cset_except(p, obj, _heap->cancelled_gc());