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

rev 55608 : Rename ShenandoahBrooksPointer to ShenandoahForwarding
rev 55609 : Eliminate extra forwarding pointer per object

@@ -24,42 +24,47 @@
 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
 
 #include "gc/shenandoah/shenandoahAsserts.hpp"
 #include "gc/shenandoah/shenandoahForwarding.hpp"
+#include "oops/markOop.inline.hpp"
 #include "runtime/atomic.hpp"
 
-inline HeapWord** ShenandoahForwarding::forward_ptr_addr(oop obj) {
-  return (HeapWord**)((HeapWord*) obj + word_offset());
-}
-
-inline void ShenandoahForwarding::initialize(oop obj) {
-  shenandoah_assert_in_heap(NULL, obj);
-  *forward_ptr_addr(obj) = (HeapWord*) obj;
-}
-
-inline void ShenandoahForwarding::set_forwardee_raw(oop obj, HeapWord* update) {
-  shenandoah_assert_in_heap(NULL, obj);
-  *forward_ptr_addr(obj) = update;
-}
-
 inline HeapWord* ShenandoahForwarding::get_forwardee_raw(oop obj) {
   shenandoah_assert_in_heap(NULL, obj);
-  return *forward_ptr_addr(obj);
+  return get_forwardee_raw_unchecked(obj);
 }
 
 inline HeapWord* ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
-  return *forward_ptr_addr(obj);
+  markOop mark = obj->mark_raw();
+  if (mark->is_marked()) {
+    return (HeapWord*) mark->clear_lock_bits();
+  } else {
+    return (HeapWord*) obj;
+  }
 }
 
 inline oop ShenandoahForwarding::get_forwardee(oop obj) {
   shenandoah_assert_correct(NULL, obj);
-  return oop(*forward_ptr_addr(obj));
+  return oop(get_forwardee_raw_unchecked(obj));
+}
+
+inline bool ShenandoahForwarding::is_forwarded(oop obj) {
+  return obj->mark_raw()->is_marked();
 }
 
 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
-  oop result = (oop) Atomic::cmpxchg(update, (oop*)forward_ptr_addr(obj), obj);
-  shenandoah_assert_correct_except(NULL, obj, !oopDesc::equals_raw(result, obj));
-  return result;
+  markOop old_mark = obj->mark_raw();
+  if (old_mark->is_marked()) {
+    return (oop) old_mark->clear_lock_bits();
+  }
+
+  markOop new_mark = markOopDesc::encode_pointer_as_mark(update);
+  markOop prev_mark = obj->cas_set_mark_raw(new_mark, old_mark);
+  if (prev_mark == old_mark) {
+    return obj;
+  } else {
+    return (oop) prev_mark->clear_lock_bits();
+  }
 }
 
 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP