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 
  24 
  25 package org.graalvm.compiler.core.common.type;
  26 
  27 import org.graalvm.compiler.core.common.LIRKind;
  28 import org.graalvm.compiler.core.common.spi.LIRKindTool;
  29 import org.graalvm.compiler.debug.GraalError;
  30 
  31 import jdk.vm.ci.meta.Constant;
  32 import jdk.vm.ci.meta.JavaKind;
  33 import jdk.vm.ci.meta.MemoryAccessProvider;
  34 import jdk.vm.ci.meta.MetaAccessProvider;
  35 import jdk.vm.ci.meta.ResolvedJavaType;
  36 
  37 /**
  38  * Singleton stamp representing the value of type {@code void}.
  39  */
  40 public final class VoidStamp extends Stamp {
  41 
  42     private VoidStamp() {
  43     }
  44 
  45     @Override
  46     public Stamp unrestricted() {
  47         return this;
  48     }
  49 
  50     @Override
  51     public boolean isUnrestricted() {
  52         return true;
  53     }
  54 
  55     @Override
  56     public JavaKind getStackKind() {
  57         return JavaKind.Void;
  58     }
  59 
  60     @Override
  61     public Stamp improveWith(Stamp other) {
  62         assert other instanceof VoidStamp;
  63         return this;
  64     }
  65 
  66     @Override
  67     public LIRKind getLIRKind(LIRKindTool tool) {
  68         throw GraalError.shouldNotReachHere("void stamp has no value");
  69     }
  70 
  71     @Override
  72     public ResolvedJavaType javaType(MetaAccessProvider metaAccess) {
  73         return metaAccess.lookupJavaType(Void.TYPE);
  74     }
  75 
  76     @Override
  77     public String toString() {
  78         return "void";
  79     }
  80 
  81     @Override
  82     public boolean alwaysDistinct(Stamp other) {
  83         return this != other;
  84     }
  85 
  86     @Override
  87     public Stamp meet(Stamp other) {
  88         assert other instanceof VoidStamp;
  89         return this;
  90     }
  91 
  92     @Override
  93     public Stamp join(Stamp other) {
  94         assert other instanceof VoidStamp;
  95         return this;
  96     }
  97 
  98     @Override
  99     public boolean isCompatible(Stamp stamp) {
 100         return stamp instanceof VoidStamp;
 101     }
 102 
 103     @Override
 104     public boolean isCompatible(Constant constant) {
 105         return false;
 106     }
 107 
 108     @Override
 109     public Stamp empty() {
 110         // the void stamp is always empty
 111         return this;
 112     }
 113 
 114     @Override
 115     public boolean hasValues() {
 116         return false;
 117     }
 118 
 119     @Override
 120     public Constant readConstant(MemoryAccessProvider provider, Constant base, long displacement) {
 121         throw GraalError.shouldNotReachHere("can't read values of void stamp");
 122     }
 123 
 124     @Override
 125     public Stamp constant(Constant c, MetaAccessProvider meta) {
 126         throw GraalError.shouldNotReachHere("void stamp has no value");
 127     }
 128 
 129     private static final VoidStamp instance = new VoidStamp();
 130 
 131     static VoidStamp getInstance() {
 132         return instance;
 133     }
 134 }