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/klass.hpp"
32 #include "oops/markWord.hpp"
33 #include "runtime/javaThread.hpp"
34
35 inline oop ShenandoahForwarding::get_forwardee_raw(oop obj) {
36 shenandoah_assert_in_heap_bounds(nullptr, obj);
37 return get_forwardee_raw_unchecked(obj);
38 }
39
40 static HeapWord* to_forwardee(markWord mark) {
41 return reinterpret_cast<HeapWord*>(mark.value() & ~(markWord::lock_mask_in_place | markWord::self_fwd_mask_in_place));
42 }
43 inline oop ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
44 // JVMTI and JFR code use mark words for marking objects for their needs.
45 // On this path, we can encounter the "marked" object, but with null
46 // fwdptr. That object is still not forwarded, and we need to return
47 // the object itself.
48 markWord mark = obj->mark();
49 if (mark.is_marked()) {
50 HeapWord* fwdptr = to_forwardee(mark);
51 if (fwdptr != nullptr) {
52 return cast_to_oop(fwdptr);
53 }
54 }
55 return obj;
56 }
57
58 inline oop ShenandoahForwarding::get_forwardee_mutator(oop obj) {
59 // Same as above, but mutator thread cannot ever see null forwardee.
60 shenandoah_assert_correct(nullptr, obj);
61 assert(Thread::current()->is_Java_thread(), "Must be a mutator thread");
62
63 markWord mark = obj->mark();
64 if (mark.is_marked()) {
65 HeapWord* fwdptr = to_forwardee(mark);
66 assert(fwdptr != nullptr, "Forwarding pointer is never null here");
67 return cast_to_oop(fwdptr);
68 } else {
69 return obj;
70 }
71 }
72
73 inline oop ShenandoahForwarding::get_forwardee(oop obj) {
74 shenandoah_assert_correct(nullptr, obj);
75 return get_forwardee_raw_unchecked(obj);
76 }
77
78 inline bool ShenandoahForwarding::is_forwarded(markWord m) {
79 return (m.value() & (markWord::lock_mask_in_place | markWord::self_fwd_mask_in_place)) > markWord::monitor_value;
80 }
81
82 inline bool ShenandoahForwarding::is_forwarded(oop obj) {
83 return is_forwarded(obj->mark());
84 }
85
86 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
87 markWord old_mark = obj->mark();
88 if (is_forwarded(old_mark)) {
89 return cast_to_oop(to_forwardee(old_mark));
90 }
91
92 markWord new_mark = markWord::encode_pointer_as_mark(update);
93 if (UseCompactObjectHeaders && old_mark.is_hashed_not_expanded()) {
94 new_mark = markWord(new_mark.value() | FWDED_HASH_TRANSITION);
95 }
96 markWord prev_mark = obj->cas_set_mark(new_mark, old_mark, memory_order_conservative);
97 if (prev_mark == old_mark) {
98 return update;
99 } else {
100 return cast_to_oop(to_forwardee(prev_mark));
101 }
102 }
103
104 inline Klass* ShenandoahForwarding::klass(oop obj) {
105 if (UseCompactObjectHeaders) {
106 markWord mark = obj->mark();
107 if (mark.is_marked()) {
108 oop fwd = cast_to_oop(to_forwardee(mark));
109 mark = fwd->mark();
110 }
111 return mark.klass();
112 } else {
113 return obj->klass();
114 }
115 }
116
117 inline size_t ShenandoahForwarding::size(oop obj) {
118 markWord mark = obj->mark();
119 if (is_forwarded(mark)) {
120 oop fwd = cast_to_oop(to_forwardee(mark));
121 markWord fwd_mark = fwd->mark();
122 Klass* klass = UseCompactObjectHeaders ? fwd_mark.klass() : fwd->klass();
123 size_t size = fwd->base_size_given_klass(fwd_mark, klass);
124 if (UseCompactObjectHeaders) {
125 if ((mark.value() & FWDED_HASH_TRANSITION) != FWDED_HASH_TRANSITION) {
126 if (fwd_mark.is_expanded() && klass->expand_for_hash(fwd)) {
127 size = align_object_size(size + 1);
128 }
129 }
130 }
131 return size;
132 } else {
133 Klass* klass = UseCompactObjectHeaders ? mark.klass() : obj->klass();
134 return obj->size_given_mark_and_klass(mark, klass);
135 }
136 }
137
138 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP