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   /* Gets forwardee from the given object. Only from mutator thread.
38    */
39   static inline oop get_forwardee_mutator(oop obj);
40 
41   /* Returns the raw value from forwardee slot.
42    */
43   static inline oop get_forwardee_raw(oop obj);
44 
45   /* Returns the raw value from forwardee slot without any checks.
46    * Used for quick verification.
47    */
48   static inline oop get_forwardee_raw_unchecked(oop obj);
49 
50   /**
51    * Returns true if the object is forwarded, false otherwise.
52    */
53   static inline bool is_forwarded(oop obj);
54 
55   /* Tries to atomically update forwardee in $holder object to $update.
56    * Assumes $holder points at itself.
57    * Asserts $holder is in from-space.
58    * Asserts $update is in to-space.
59    *
60    * Returns the new object 'update' upon success, or
61    * the new forwardee that a competing thread installed.
62    */
63   static inline oop try_update_forwardee(oop obj, oop update);
64 
65   static inline size_t size(oop obj);
66   static inline Klass* klass(oop obj);
67 };
68 
69 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_HPP