1 /*
2 * Copyright (c) 2015, 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_INLINE_HPP
26 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
27
28 #include "gc/shenandoah/shenandoahForwarding.hpp"
29
30 #include "gc/shenandoah/shenandoahAsserts.hpp"
31 #include "oops/markWord.hpp"
32 #include "runtime/javaThread.hpp"
33
34 inline oop ShenandoahForwarding::get_forwardee_raw(oop obj) {
35 shenandoah_assert_in_heap_bounds(nullptr, obj);
36 return get_forwardee_raw_unchecked(obj);
37 }
38
39 inline oop ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
40 // JVMTI and JFR code use mark words for marking objects for their needs.
41 // On this path, we can encounter the "marked" object, but with null
42 // fwdptr. That object is still not forwarded, and we need to return
43 // the object itself.
44 markWord mark = obj->mark();
45 if (mark.is_marked()) {
46 HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
47 if (fwdptr != nullptr) {
48 return cast_to_oop(fwdptr);
49 }
50 }
51 return obj;
52 }
53
54 inline oop ShenandoahForwarding::get_forwardee_mutator(oop obj) {
55 // Same as above, but mutator thread cannot ever see null forwardee.
56 shenandoah_assert_correct(nullptr, obj);
57 assert(Thread::current()->is_Java_thread(), "Must be a mutator thread");
58
59 markWord mark = obj->mark();
60 if (mark.is_marked()) {
61 HeapWord* fwdptr = (HeapWord*) mark.clear_lock_bits().to_pointer();
62 assert(fwdptr != nullptr, "Forwarding pointer is never null here");
63 return cast_to_oop(fwdptr);
64 } else {
65 return obj;
66 }
67 }
68
69 inline oop ShenandoahForwarding::get_forwardee(oop obj) {
70 shenandoah_assert_correct(nullptr, obj);
71 return get_forwardee_raw_unchecked(obj);
72 }
73
74 inline bool ShenandoahForwarding::is_forwarded(oop obj) {
75 return obj->mark().is_marked();
76 }
77
78 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
79 markWord old_mark = obj->mark();
80 if (old_mark.is_marked()) {
81 return cast_to_oop(old_mark.clear_lock_bits().to_pointer());
82 }
83
84 markWord new_mark = markWord::encode_pointer_as_mark(update);
85 markWord prev_mark = obj->cas_set_mark(new_mark, old_mark, memory_order_conservative);
86 if (prev_mark == old_mark) {
87 return update;
88 } else {
89 return cast_to_oop(prev_mark.clear_lock_bits().to_pointer());
90 }
91 }
92
93 inline Klass* ShenandoahForwarding::klass(oop obj) {
94 if (UseCompactObjectHeaders) {
95 markWord mark = obj->mark();
96 if (mark.is_marked()) {
97 oop fwd = cast_to_oop(mark.clear_lock_bits().to_pointer());
98 mark = fwd->mark();
99 }
100 return mark.klass();
101 } else {
102 return obj->klass();
103 }
104 }
105
106 inline size_t ShenandoahForwarding::size(oop obj) {
107 return obj->size_given_klass(klass(obj));
108 }
109
110 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP