1 /*
2 * Copyright (c) 2015, 2020, 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_INLINE_HPP
25 #define SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
26
27 #include "gc/shenandoah/shenandoahAsserts.hpp"
28 #include "gc/shenandoah/shenandoahForwarding.hpp"
29 #include "oops/markOop.inline.hpp"
30 #include "runtime/atomic.hpp"
31
get_forwardee_raw(oop obj)32 inline HeapWord* ShenandoahForwarding::get_forwardee_raw(oop obj) {
33 shenandoah_assert_in_heap(NULL, obj);
34 return get_forwardee_raw_unchecked(obj);
35 }
36
get_forwardee_raw_unchecked(oop obj)37 inline HeapWord* ShenandoahForwarding::get_forwardee_raw_unchecked(oop obj) {
38 // JVMTI and JFR code use mark words for marking objects for their needs.
39 // On this path, we can encounter the "marked" object, but with NULL
40 // fwdptr. That object is still not forwarded, and we need to return
41 // the object itself.
42 markOop mark = obj->mark_raw();
43 if (mark->is_marked()) {
44 HeapWord* fwdptr = (HeapWord*) mark->clear_lock_bits();
45 if (fwdptr != NULL) {
46 return fwdptr;
47 }
48 }
49 return (HeapWord*)obj;
50 }
51
get_forwardee_mutator(oop obj)52 inline oop ShenandoahForwarding::get_forwardee_mutator(oop obj) {
53 // Same as above, but mutator thread cannot ever see NULL forwardee.
54 shenandoah_assert_correct(NULL, obj);
55 assert(Thread::current()->is_Java_thread(), "Must be a mutator thread");
56
57 markOop mark = obj->mark_raw();
58 if (mark->is_marked()) {
59 HeapWord* fwdptr = (HeapWord*)mark->clear_lock_bits();
60 assert(fwdptr != NULL, "Forwarding pointer is never null here");
61 return oop(fwdptr);
62 } else {
63 return obj;
64 }
65 }
66
get_forwardee(oop obj)67 inline oop ShenandoahForwarding::get_forwardee(oop obj) {
68 shenandoah_assert_correct(NULL, obj);
69 return oop(get_forwardee_raw_unchecked(obj));
70 }
71
is_forwarded(oop obj)72 inline bool ShenandoahForwarding::is_forwarded(oop obj) {
73 return obj->mark_raw()->is_marked();
74 }
75
try_update_forwardee(oop obj,oop update)76 inline oop ShenandoahForwarding::try_update_forwardee(oop obj, oop update) {
77 markOop old_mark = obj->mark_raw();
78 if (old_mark->is_marked()) {
79 return (oop) old_mark->clear_lock_bits();
80 }
81
82 markOop new_mark = markOopDesc::encode_pointer_as_mark(update);
83 markOop prev_mark = obj->cas_set_mark_raw(new_mark, old_mark);
84 if (prev_mark == old_mark) {
85 return update;
86 } else {
87 return (oop) prev_mark->clear_lock_bits();
88 }
89 }
90
91 #endif // SHARE_GC_SHENANDOAH_SHENANDOAHFORWARDING_INLINE_HPP
92