1 /* 2 * Copyright (c) 2009, 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.nodes.calc; 24 25 import org.graalvm.compiler.core.common.type.AbstractPointerStamp; 26 import org.graalvm.compiler.core.common.type.ObjectStamp; 27 import org.graalvm.compiler.core.common.type.Stamp; 28 import org.graalvm.compiler.graph.NodeClass; 29 import org.graalvm.compiler.graph.spi.CanonicalizerTool; 30 import org.graalvm.compiler.nodeinfo.NodeCycles; 31 import org.graalvm.compiler.nodeinfo.NodeInfo; 32 import org.graalvm.compiler.nodes.LogicConstantNode; 33 import org.graalvm.compiler.nodes.LogicNode; 34 import org.graalvm.compiler.nodes.PiNode; 35 import org.graalvm.compiler.nodes.UnaryOpLogicNode; 36 import org.graalvm.compiler.nodes.ValueNode; 37 import org.graalvm.compiler.nodes.spi.LIRLowerable; 38 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool; 39 import org.graalvm.compiler.nodes.spi.Virtualizable; 40 import org.graalvm.compiler.nodes.spi.VirtualizerTool; 41 import org.graalvm.compiler.nodes.type.StampTool; 42 import org.graalvm.compiler.nodes.util.GraphUtil; 43 44 import jdk.vm.ci.meta.TriState; 45 46 /** 47 * An IsNullNode will be true if the supplied value is null, and false if it is non-null. 48 */ 49 @NodeInfo(cycles = NodeCycles.CYCLES_2) 50 public final class IsNullNode extends UnaryOpLogicNode implements LIRLowerable, Virtualizable { 51 52 public static final NodeClass<IsNullNode> TYPE = NodeClass.create(IsNullNode.class); 53 54 public IsNullNode(ValueNode object) { 55 super(TYPE, object); 56 assert object != null; 57 } 58 59 public static LogicNode create(ValueNode forValue) { 60 LogicNode result = tryCanonicalize(forValue); 61 return result == null ? new IsNullNode(GraphUtil.skipPi(forValue)) : result; 62 } 63 64 public static LogicNode tryCanonicalize(ValueNode forValue) { 65 if (StampTool.isPointerAlwaysNull(forValue)) { 66 return LogicConstantNode.tautology(); 67 } else if (StampTool.isPointerNonNull(forValue)) { 68 return LogicConstantNode.contradiction(); 69 } 70 return null; 71 } 72 73 @Override 74 public void generate(NodeLIRBuilderTool gen) { 75 // Nothing to do. 76 } 77 78 @Override 79 public boolean verify() { 80 assertTrue(getValue() != null, "is null input must not be null"); 81 assertTrue(getValue().stamp() instanceof AbstractPointerStamp, "input must be a pointer not %s", getValue().stamp()); 82 return super.verify(); 83 } 84 85 @Override 86 public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) { 87 88 LogicNode result = tryCanonicalize(forValue); 89 if (result != null) { 90 return result; 91 } 92 93 if (forValue instanceof PiNode) { 94 return IsNullNode.create(GraphUtil.skipPi(forValue)); 95 } 96 97 if (forValue instanceof ConvertNode) { 98 ConvertNode convertNode = (ConvertNode) forValue; 99 if (convertNode.mayNullCheckSkipConversion()) { 100 return IsNullNode.create(convertNode.getValue()); 101 } 102 } 103 104 return this; 105 } 106 107 @Override 108 public void virtualize(VirtualizerTool tool) { 109 ValueNode alias = tool.getAlias(getValue()); 110 TriState fold = tryFold(alias.stamp()); 111 if (fold != TriState.UNKNOWN) { 112 tool.replaceWithValue(LogicConstantNode.forBoolean(fold.isTrue(), graph())); 113 } 114 } 115 116 @Override 117 public Stamp getSucceedingStampForValue(boolean negated) { 118 AbstractPointerStamp pointerStamp = (AbstractPointerStamp) getValue().stamp(); 119 return negated ? pointerStamp.asNonNull() : pointerStamp.asAlwaysNull(); 120 } 121 122 @Override 123 public TriState tryFold(Stamp valueStamp) { 124 if (valueStamp instanceof ObjectStamp) { 125 ObjectStamp objectStamp = (ObjectStamp) valueStamp; 126 if (objectStamp.alwaysNull()) { 127 return TriState.TRUE; 128 } else if (objectStamp.nonNull()) { 129 return TriState.FALSE; 130 } 131 } 132 return TriState.UNKNOWN; 133 } 134 }