1/* 2 * Copyright (c) 2011, 2016, 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. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25package org.graalvm.word; 26 27// JaCoCo Exclude 28 29/** 30 * Marker interface for location identities. A different location identity of two memory accesses 31 * guarantees that the two accesses do not interfere. 32 * 33 * Clients of {@link LocationIdentity} must use {@link #equals(Object)}, not {@code ==}, when 34 * comparing two {@link LocationIdentity} values for equality. Likewise, they must not use 35 * {@link java.util.IdentityHashMap}s with {@link LocationIdentity} values as keys. 36 */ 37public abstract class LocationIdentity { 38 39 private static final class AnyLocationIdentity extends LocationIdentity { 40 @Override 41 public boolean isImmutable() { 42 return false; 43 } 44 45 @Override 46 public String toString() { 47 return "ANY_LOCATION"; 48 } 49 } 50 51 private static final class InitLocationIdentity extends LocationIdentity { 52 @Override 53 public boolean isImmutable() { 54 return true; 55 } 56 57 @Override 58 public String toString() { 59 return "INIT_LOCATION"; 60 } 61 } 62 63 public static final LocationIdentity ANY_LOCATION = new AnyLocationIdentity(); 64 public static final LocationIdentity INIT_LOCATION = new InitLocationIdentity(); 65 66 /** 67 * Indicates that the given location is the union of all possible mutable locations. A write to 68 * such a location kill all reads from mutable locations and a read from this location is killed 69 * by any write (except for initialization writes). 70 */ 71 public static LocationIdentity any() { 72 return ANY_LOCATION; 73 } 74 75 /** 76 * Location only allowed to be used for writes. Indicates that a completely new memory location 77 * is written. Kills no read. The previous value at the given location must be either 78 * uninitialized or null. Writes to this location do not need a GC pre-barrier. 79 */ 80 public static LocationIdentity init() { 81 return INIT_LOCATION; 82 } 83 84 /** 85 * Denotes a location is unchanging in all cases. Not that this is different than the Java 86 * notion of final which only requires definite assignment. 87 */ 88 public abstract boolean isImmutable(); 89 90 public final boolean isMutable() { 91 return !isImmutable(); 92 } 93 94 public final boolean isAny() { 95 return this == ANY_LOCATION; 96 } 97 98 public final boolean isInit() { 99 return this == INIT_LOCATION; 100 } 101 102 public final boolean isSingle() { 103 return this != ANY_LOCATION; 104 } 105 106 public final boolean overlaps(LocationIdentity other) { 107 return isAny() || other.isAny() || this.equals(other); 108 } 109} 110