1 /*
2 * Copyright (c) 2017, 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.
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 #ifndef SHARE_GC_Z_ZMARKSTACKENTRY_HPP
25 #define SHARE_GC_Z_ZMARKSTACKENTRY_HPP
26
27 #include "gc/z/zBitField.hpp"
28 #include "memory/allocation.hpp"
29
30 //
31 // Mark stack entry layout
32 // -----------------------
33 //
34 // Object entry
35 // ------------
36 //
37 // 6
38 // 3 3 2 1 0
39 // +--------------------------------------------------------------------+-+-+-+
40 // |11111111 11111111 11111111 11111111 11111111 11111111 11111111 11111|1|1|1|
41 // +--------------------------------------------------------------------+-+-+-+
42 // | | | |
43 // | 2-2 Follow Flag (1-bit) * | |
44 // | | |
45 // | 1-1 Partial Array Flag (1-bit) * |
46 // | |
47 // | 0-0 Final Flag (1-bit) *
48 // |
49 // * 63-3 Object Address (62-bits)
50 //
51 //
52 // Partial array entry
53 // -------------------
54 //
55 // 6 3 3
56 // 3 2 1 2 1 0
57 // +------------------------------------+---------------------------------+-+-+
58 // |11111111 11111111 11111111 11111111 |11111111 11111111 11111111 111111|1|1|
59 // +------------------------------------+---------------------------------+-+-+
60 // | | | |
61 // | | 1-1 Partial Array Flag (1-bit) * |
62 // | | |
63 // | | 0-0 Final Flag (1-bit) *
64 // | |
65 // | * 31-2 Partial Array Length (30-bits)
66 // |
67 // * 63-32 Partial Array Address Offset (32-bits)
68 //
69
70 class ZMarkStackEntry {
71 private:
72 typedef ZBitField<uint64_t, bool, 0, 1> field_finalizable;
73 typedef ZBitField<uint64_t, bool, 1, 1> field_partial_array;
74 typedef ZBitField<uint64_t, bool, 2, 1> field_follow;
75 typedef ZBitField<uint64_t, uintptr_t, 3, 61> field_object_address;
76 typedef ZBitField<uint64_t, size_t, 2, 30> field_partial_array_length;
77 typedef ZBitField<uint64_t, size_t, 32, 32> field_partial_array_offset;
78
79 uint64_t _entry;
80
81 public:
82 ZMarkStackEntry() {
83 // This constructor is intentionally left empty and does not initialize
84 // _entry to allow it to be optimized out when instantiating ZMarkStack,
85 // which has a long array of ZMarkStackEntry elements, but doesn't care
86 // what _entry is initialized to.
87 }
88
89 ZMarkStackEntry(uintptr_t object_address, bool follow, bool finalizable) :
90 _entry(field_object_address::encode(object_address) |
91 field_follow::encode(follow) |
92 field_partial_array::encode(false) |
93 field_finalizable::encode(finalizable)) {}
94
95 ZMarkStackEntry(size_t partial_array_offset, size_t partial_array_length, bool finalizable) :
96 _entry(field_partial_array_offset::encode(partial_array_offset) |
97 field_partial_array_length::encode(partial_array_length) |
98 field_partial_array::encode(true) |
99 field_finalizable::encode(finalizable)) {}
100
101 bool finalizable() const {
102 return field_finalizable::decode(_entry);
103 }
104
105 bool partial_array() const {
106 return field_partial_array::decode(_entry);
107 }
108
109 size_t partial_array_offset() const {
110 return field_partial_array_offset::decode(_entry);
111 }
112
113 size_t partial_array_length() const {
114 return field_partial_array_length::decode(_entry);
115 }
116
117 bool follow() const {
118 return field_follow::decode(_entry);
119 }
120
121 uintptr_t object_address() const {
122 return field_object_address::decode(_entry);
123 }
124 };
125
126 #endif // SHARE_GC_Z_ZMARKSTACKENTRY_HPP