1 /*
   2  * Copyright (c) 2014, 2015, 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 org.graalvm.compiler.core.common.type;
  24 
  25 import org.graalvm.compiler.core.common.LIRKind;
  26 import org.graalvm.compiler.core.common.spi.LIRKindTool;
  27 import org.graalvm.compiler.debug.GraalError;
  28 
  29 import jdk.vm.ci.meta.Constant;
  30 import jdk.vm.ci.meta.JavaKind;
  31 import jdk.vm.ci.meta.MemoryAccessProvider;
  32 import jdk.vm.ci.meta.MetaAccessProvider;
  33 import jdk.vm.ci.meta.ResolvedJavaType;
  34 
  35 /**
  36  * Singleton stamp representing the value of type {@code void}.
  37  */
  38 public final class VoidStamp extends Stamp {
  39 
  40     private VoidStamp() {
  41     }
  42 
  43     @Override
  44     public Stamp unrestricted() {
  45         return this;
  46     }
  47 
  48     @Override
  49     public JavaKind getStackKind() {
  50         return JavaKind.Void;
  51     }
  52 
  53     @Override
  54     public Stamp improveWith(Stamp other) {
  55         assert other instanceof VoidStamp;
  56         return this;
  57     }
  58 
  59     @Override
  60     public LIRKind getLIRKind(LIRKindTool tool) {
  61         throw GraalError.shouldNotReachHere("void stamp has no value");
  62     }
  63 
  64     @Override
  65     public ResolvedJavaType javaType(MetaAccessProvider metaAccess) {
  66         return metaAccess.lookupJavaType(Void.TYPE);
  67     }
  68 
  69     @Override
  70     public String toString() {
  71         return "void";
  72     }
  73 
  74     @Override
  75     public boolean alwaysDistinct(Stamp other) {
  76         return this != other;
  77     }
  78 
  79     @Override
  80     public Stamp meet(Stamp other) {
  81         assert other instanceof VoidStamp;
  82         return this;
  83     }
  84 
  85     @Override
  86     public Stamp join(Stamp other) {
  87         assert other instanceof VoidStamp;
  88         return this;
  89     }
  90 
  91     @Override
  92     public boolean isCompatible(Stamp stamp) {
  93         return stamp instanceof VoidStamp;
  94     }
  95 
  96     @Override
  97     public boolean isCompatible(Constant constant) {
  98         return false;
  99     }
 100 
 101     @Override
 102     public Stamp empty() {
 103         // the void stamp is always empty
 104         return this;
 105     }
 106 
 107     @Override
 108     public boolean hasValues() {
 109         return false;
 110     }
 111 
 112     @Override
 113     public Constant readConstant(MemoryAccessProvider provider, Constant base, long displacement) {
 114         throw GraalError.shouldNotReachHere("can't read values of void stamp");
 115     }
 116 
 117     @Override
 118     public Stamp constant(Constant c, MetaAccessProvider meta) {
 119         throw GraalError.shouldNotReachHere("void stamp has no value");
 120     }
 121 
 122     private static final VoidStamp instance = new VoidStamp();
 123 
 124     static VoidStamp getInstance() {
 125         return instance;
 126     }
 127 }