1 /*
2 * Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * The Universal Permissive License (UPL), Version 1.0
6 *
7 * Subject to the condition set forth below, permission is hereby granted to any
8 * person obtaining a copy of this software, associated documentation and/or
9 * data (collectively the "Software"), free of charge and under any and all
10 * copyright rights in the Software, and any and all patent rights owned or
11 * freely licensable by each licensor hereunder covering either (i) the
12 * unmodified Software as contributed to or provided by such licensor, or (ii)
13 * the Larger Works (as defined below), to deal in both
14 *
15 * (a) the Software, and
16 *
17 * (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
18 * one is included with the Software each a "Larger Work" to which the Software
19 * is contributed by such licensors),
20 *
21 * without restriction, including without limitation the rights to copy, create
22 * derivative works of, display, perform, and distribute the Software and make,
23 * use, sell, offer for sale, import, export, have made, and have sold the
24 * Software and the Larger Work(s), and to sublicense the foregoing rights on
25 * either these or other terms.
26 *
27 * This license is subject to the following condition:
28 *
29 * The above copyright notice and either this complete permission notice or at a
30 * minimum a reference to the UPL must be included in all copies or substantial
31 * portions of the Software.
32 *
33 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
34 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
35 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
36 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
37 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
38 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
39 * SOFTWARE.
40 */
41 package jdk.internal.vm.compiler.word;
42
43 // JaCoCo Exclude
44
45 /**
46 * Marker interface for location identities. A different location identity of two memory accesses
47 * guarantees that the two accesses do not interfere.
48 * <p>
49 * Clients of {@link LocationIdentity} must use {@link #equals(Object)}, not {@code ==}, when
50 * comparing two {@link LocationIdentity} values for equality. Likewise, they must not use
51 * {@link java.util.IdentityHashMap}s with {@link LocationIdentity} values as keys.
52 *
53 * @since 1.0
54 */
55 public abstract class LocationIdentity {
56
57 private static final class AnyLocationIdentity extends LocationIdentity {
58 @Override
59 public boolean isImmutable() {
60 return false;
61 }
62
63 @Override
64 public String toString() {
65 return "ANY_LOCATION";
66 }
67 }
68
69 private static final class InitLocationIdentity extends LocationIdentity {
70 @Override
71 public boolean isImmutable() {
72 return true;
73 }
74
75 @Override
76 public String toString() {
77 return "INIT_LOCATION";
78 }
79 }
80
81 /**
82 * Creates a new location identity. Subclasses are responsible to provide proper implementations
83 * of {@link #equals} and {@link #hashCode}.
84 *
85 * @since 1.0
86 */
87 protected LocationIdentity() {
88 }
89
90 /**
91 * Indicates that the given location is the union of all possible mutable locations. A write to
92 * such a location kill all reads from mutable locations and a read from this location is killed
93 * by any write (except for initialization writes).
94 *
95 * @since 1.0
96 */
97 public static final LocationIdentity ANY_LOCATION = new AnyLocationIdentity();
98
99 /**
100 * Location only allowed to be used for writes. Indicates that a completely new memory location
101 * is written. Kills no read. The previous value at the given location must be either
102 * uninitialized or null. Writes to this location do not need a GC pre-barrier.
103 *
104 * @since 1.0
105 */
106 public static final LocationIdentity INIT_LOCATION = new InitLocationIdentity();
107
108 /**
109 * Indicates that the given location is the union of all possible mutable locations. A write to
110 * such a location kill all reads from mutable locations and a read from this location is killed
111 * by any write (except for initialization writes).
112 *
113 * @since 1.0
114 */
115 public static LocationIdentity any() {
116 return ANY_LOCATION;
117 }
118
119 /**
120 * Location only allowed to be used for writes. Indicates that a completely new memory location
121 * is written. Kills no read. The previous value at the given location must be either
122 * uninitialized or null. Writes to this location do not need a GC pre-barrier.
123 *
124 * @since 1.0
125 */
126 public static LocationIdentity init() {
127 return INIT_LOCATION;
128 }
129
130 /**
131 * Denotes a location is unchanging in all cases. Not that this is different than the Java
132 * notion of final which only requires definite assignment.
133 *
134 * @since 1.0
135 */
136 public abstract boolean isImmutable();
137
138 /**
139 * The inversion of {@link #isImmutable}.
140 *
141 * @since 1.0
142 */
143 public final boolean isMutable() {
144 return !isImmutable();
145 }
146
147 /**
148 * Returns true if this location identity is {@link #any}.
149 *
150 * @since 1.0
151 */
152 public final boolean isAny() {
153 return this == ANY_LOCATION;
154 }
155
156 /**
157 * Returns true if this location identity is {@link #init}.
158 *
159 * @since 1.0
160 */
161 public final boolean isInit() {
162 return this == INIT_LOCATION;
163 }
164
165 /**
166 * Returns true if this location identity is not {@link #any}.
167 *
168 * @since 1.0
169 */
170 public final boolean isSingle() {
171 return this != ANY_LOCATION;
172 }
173
174 /**
175 * Returns true if the memory slice denoted by this location identity may overlap with the
176 * provided other location identity.
177 *
178 * @since 1.0
179 */
180 public final boolean overlaps(LocationIdentity other) {
181 return isAny() || other.isAny() || this.equals(other);
182 }
183 }