1 /*
   2  * Copyright (c) 2013, 2019, Red Hat, Inc. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP
  26 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP
  27 
  28 #include "oops/oop.hpp"
  29 #include "utilities/globalDefinitions.hpp"
  30 
  31 class ShenandoahForwarding {
  32 public:
  33   /* Gets forwardee from the given object.
  34    */
  35   static inline oop get_forwardee(oop obj);
  36 
  37   /* Returns the raw value from forwardee slot.
  38    */
  39   static inline HeapWord* get_forwardee_raw(oop obj);
  40 
  41   /* Returns the raw value from forwardee slot without any checks.
  42    * Used for quick verification.
  43    */
  44   static inline HeapWord* get_forwardee_raw_unchecked(oop obj);
  45 
  46   /**
  47    * Returns true if the object is forwarded, false otherwise.
  48    */
  49   static inline bool is_forwarded(oop obj);
  50 
  51   /* Tries to atomically update forwardee in $holder object to $update.
  52    * Assumes $holder points at itself.
  53    * Asserts $holder is in from-space.
  54    * Asserts $update is in to-space.
  55    *
  56    * Returns the new object 'update' upon success, or
  57    * the new forwardee that a competing thread installed.
  58    */
  59   static inline oop try_update_forwardee(oop obj, oop update);
  60 
  61 };
  62 
  63 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP