1 /*
2 * Copyright (c) 2006, 2019, Oracle and/or its affiliates. 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.
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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
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23 */
24
25 #ifndef SHARE_OOPS_MARKWORD_INLINE_HPP
26 #define SHARE_OOPS_MARKWORD_INLINE_HPP
27
28 #include "oops/markWord.hpp"
29
30 #include "oops/klass.hpp"
31 #include "oops/oop.inline.hpp"
32 #include "runtime/globals.hpp"
33 #include "runtime/safepoint.hpp"
34
35 // Should this header be preserved during GC?
36 inline bool markWord::must_be_preserved(const oopDesc* obj) const {
37 if (UseBiasedLocking) {
38 if (has_bias_pattern()) {
39 // Will reset bias at end of collection
40 // Mark words of biased and currently locked objects are preserved separately
41 return false;
42 }
43 markWord prototype_header = prototype_for_klass(obj->klass());
44 if (prototype_header.has_bias_pattern()) {
45 // Individual instance which has its bias revoked; must return
46 // true for correctness
47 return true;
48 }
49 }
50 return (!is_unlocked() || !has_no_hash());
51 }
52
53 // Should this header be preserved in the case of a promotion failure during scavenge?
54 inline bool markWord::must_be_preserved_for_promotion_failure(const oopDesc* obj) const {
55 if (UseBiasedLocking) {
56 // We don't explicitly save off the mark words of biased and
57 // currently-locked objects during scavenges, so if during a
58 // promotion failure we encounter either a biased mark word or a
59 // klass which still has a biasable prototype header, we have to
60 // preserve the mark word. This results in oversaving, but promotion
61 // failures are rare, and this avoids adding more complex logic to
62 // the scavengers to call new variants of
63 // BiasedLocking::preserve_marks() / restore_marks() in the middle
64 // of a scavenge when a promotion failure has first been detected.
65 if (has_bias_pattern() || prototype_for_klass(obj->klass()).has_bias_pattern()) {
66 return true;
67 }
68 }
69 return (!is_unlocked() || !has_no_hash());
70 }
71
72 inline markWord markWord::prototype_for_klass(const Klass* klass) {
73 markWord prototype_header = klass->prototype_header();
74 assert(UseCompactObjectHeaders || prototype_header == prototype() || prototype_header.has_bias_pattern(), "corrupt prototype header");
75
76 return prototype_header;
77 }
78
79 #ifdef _LP64
80 markWord markWord::actual_mark() const {
81 assert(UseCompactObjectHeaders, "only safe when using compact headers");
82 if (has_displaced_mark_helper()) {
83 return displaced_mark_helper();
84 } else {
85 return *this;
86 }
87 }
88
89 narrowKlass markWord::narrow_klass() const {
90 assert(UseCompactObjectHeaders, "only used with compact object headers");
91 return narrowKlass(value() >> klass_shift);
92 }
93
94 Klass* markWord::klass() const {
95 assert(UseCompactObjectHeaders, "only used with compact object headers");
96 assert(!CompressedKlassPointers::is_null(narrow_klass()), "narrow klass must not be null: " INTPTR_FORMAT, value());
97 return CompressedKlassPointers::decode_not_null(narrow_klass());
98 }
99
100 Klass* markWord::klass_or_null() const {
101 assert(UseCompactObjectHeaders, "only used with compact object headers");
102 return CompressedKlassPointers::decode(narrow_klass());
103 }
104
105 markWord markWord::set_narrow_klass(const narrowKlass nklass) const {
106 assert(UseCompactObjectHeaders, "only used with compact object headers");
107 return markWord((value() & ~klass_mask_in_place) | ((uintptr_t) nklass << klass_shift));
108 }
109
110 Klass* markWord::safe_klass() const {
111 assert(UseCompactObjectHeaders, "only used with compact object headers");
112 assert(SafepointSynchronize::is_at_safepoint(), "only call at safepoint");
113 markWord m = *this;
114 if (m.has_displaced_mark_helper()) {
115 m = m.displaced_mark_helper();
116 }
117 return CompressedKlassPointers::decode_not_null(m.narrow_klass());
118 }
119
120 markWord markWord::set_klass(const Klass* klass) const {
121 assert(UseCompactObjectHeaders, "only used with compact object headers");
122 assert(UseCompressedClassPointers, "expect compressed klass pointers");
123 // TODO: Don't cast to non-const, change CKP::encode() to accept const Klass* instead.
124 narrowKlass nklass = CompressedKlassPointers::encode(const_cast<Klass*>(klass));
125 return set_narrow_klass(nklass);
126 }
127 #endif
128
129 #endif // SHARE_OOPS_MARKWORD_INLINE_HPP