001/*
002 * Copyright (c) 2011, 2012, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package jdk.internal.jvmci.meta;
024
025import java.util.*;
026
027// JaCoCo Exclude
028
029/**
030 * Marker interface for location identities. A different location identity of two memory accesses
031 * guarantees that the two accesses do not interfere.
032 *
033 * Clients of {@link LocationIdentity} must use {@link #equals(Object)}, not {@code ==}, when
034 * comparing two {@link LocationIdentity} values for equality. Likewise, they must not use
035 * {@link IdentityHashMap}s with {@link LocationIdentity} values as keys.
036 */
037public abstract class LocationIdentity {
038
039    private static final class AnyLocationIdentity extends LocationIdentity {
040        @Override
041        public boolean isImmutable() {
042            return false;
043        }
044
045        @Override
046        public String toString() {
047            return "ANY_LOCATION";
048        }
049    }
050
051    public static final LocationIdentity ANY_LOCATION = new AnyLocationIdentity();
052
053    public static LocationIdentity any() {
054        return ANY_LOCATION;
055    }
056
057    /**
058     * Denotes a location is unchanging in all cases. Not that this is different than the Java
059     * notion of final which only requires definite assignment.
060     */
061    public abstract boolean isImmutable();
062
063    public final boolean isMutable() {
064        return !isImmutable();
065    }
066
067    public final boolean isAny() {
068        return this == ANY_LOCATION;
069    }
070
071    public final boolean isSingle() {
072        return this != ANY_LOCATION;
073    }
074
075    public final boolean overlaps(LocationIdentity other) {
076        return isAny() || other.isAny() || this.equals(other);
077    }
078}