1 /*
   2  * Copyright (c) 2013, 2018, Red Hat, Inc. All rights reserved.
   3  *
   4  * This code is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU General Public License version 2 only, as
   6  * published by the Free Software Foundation.
   7  *
   8  * This code is distributed in the hope that it will be useful, but WITHOUT
   9  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  10  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  11  * version 2 for more details (a copy is included in the LICENSE file that
  12  * accompanied this code).
  13  *
  14  * You should have received a copy of the GNU General Public License version
  15  * 2 along with this work; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  17  *
  18  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  19  * or visit www.oracle.com if you need additional information or have any
  20  * questions.
  21  *
  22  */
  23 
  24 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP
  25 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP
  26 
  27 #include "oops/oop.hpp"
  28 #include "utilities/globalDefinitions.hpp"
  29 
  30 class ShenandoahForwarding {
  31 public:
  32   /* Gets forwardee from the given object.
  33    */
  34   static inline oop get_forwardee(oop obj);
  35 
  36   /* Gets forwardee from the given object. Only from mutator thread.
  37    */
  38   static inline oop get_forwardee_mutator(oop obj);
  39 
  40   /* Returns the raw value from forwardee slot.
  41    */
  42   static inline HeapWord* get_forwardee_raw(oop obj);
  43 
  44   /* Returns the raw value from forwardee slot without any checks.
  45    * Used for quick verification.
  46    */
  47   static inline HeapWord* get_forwardee_raw_unchecked(oop obj);
  48 
  49   /**
  50    * Returns true if the object is forwarded, false otherwise.
  51    */
  52   static inline bool is_forwarded(oop obj);
  53 
  54   /* Tries to atomically update forwardee in $holder object to $update.
  55    * Assumes $holder points at itself.
  56    * Asserts $holder is in from-space.
  57    * Asserts $update is in to-space.
  58    *
  59    * Returns the new object 'update' upon success, or
  60    * the new forwardee that a competing thread installed.
  61    */
  62   static inline oop try_update_forwardee(oop obj, oop update);
  63 
  64 };
  65 
  66 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP