1 /*
   2  * Copyright (c) 2011, 2012, 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 package jdk.vm.ci.meta;
  24 
  25 import java.util.IdentityHashMap;
  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 IdentityHashMap}s with {@link LocationIdentity} values as keys.
  36  */
  37 public 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     public static final LocationIdentity ANY_LOCATION = new AnyLocationIdentity();
  52 
  53     public static LocationIdentity any() {
  54         return ANY_LOCATION;
  55     }
  56 
  57     /**
  58      * Denotes a location is unchanging in all cases. Not that this is different than the Java
  59      * notion of final which only requires definite assignment.
  60      */
  61     public abstract boolean isImmutable();
  62 
  63     public final boolean isMutable() {
  64         return !isImmutable();
  65     }
  66 
  67     public final boolean isAny() {
  68         return this == ANY_LOCATION;
  69     }
  70 
  71     public final boolean isSingle() {
  72         return this != ANY_LOCATION;
  73     }
  74 
  75     public final boolean overlaps(LocationIdentity other) {
  76         return isAny() || other.isAny() || this.equals(other);
  77     }
  78 }