shenandoahForwarding.inline.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * published by the Free Software Foundation.
 *
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 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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#ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
#define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP

#include "gc/shenandoah/shenandoahForwarding.hpp"

#include "gc/shenandoah/shenandoahAsserts.hpp"
#include "oops/markWord.inline.hpp"
#include "runtime/thread.hpp"

inline oop ShenandoahForwarding::get_forwardee_raw(oop obj) {
  shenandoah_assert_in_heap(NULL, obj);
  return get_forwardee_raw_unchecked(obj);
}

inline oop ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
  // JVMTI and JFR code use mark words for marking objects for their needs.
  // On this path, we can encounter the "marked" object, but with NULL
  // fwdptr. That object is still not forwarded, and we need to return
  // the object itself.
  markWord mark = obj->mark();
  if (mark.is_marked()) {
    HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
    if (fwdptr != NULL) {
      return cast_to_oop(fwdptr);
    }
  }
  return obj;
}

inline oop ShenandoahForwarding::get_forwardee_mutator(oop obj) {
  // Same as above, but mutator thread cannot ever see NULL forwardee.
  shenandoah_assert_correct(NULL, obj);
  assert(Thread::current()->is_Java_thread(), "Must be a mutator thread");

  markWord mark = obj->mark();
  if (mark.is_marked()) {
    HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
    assert(fwdptr != NULL, "Forwarding pointer is never null here");
    return cast_to_oop(fwdptr);
  } else {
    return obj;
  }
}

inline oop ShenandoahForwarding::get_forwardee(oop obj) {
  shenandoah_assert_correct(NULL, obj);
  return get_forwardee_raw_unchecked(obj);
}

inline bool ShenandoahForwarding::is_forwarded(oop obj) {
  return obj->mark().is_marked();
}

inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
  markWord old_mark = obj->mark();
  if (old_mark.is_marked()) {
    return cast_to_oop(old_mark.clear_lock_bits().to_pointer());
  }

  markWord new_mark = markWord::encode_pointer_as_mark(update);
  markWord prev_mark = obj->cas_set_mark(new_mark, old_mark, memory_order_conservative);
  if (prev_mark == old_mark) {
    return update;
  } else {
    return cast_to_oop(prev_mark.clear_lock_bits().to_pointer());
  }
}

#endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP