1 /*
2 * Copyright (c) 2009, 2018, 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.nodes.calc;
26
27 import org.graalvm.compiler.core.common.type.AbstractPointerStamp;
28 import org.graalvm.compiler.core.common.type.ObjectStamp;
29 import org.graalvm.compiler.core.common.type.Stamp;
30 import org.graalvm.compiler.graph.NodeClass;
31 import org.graalvm.compiler.graph.spi.CanonicalizerTool;
32 import org.graalvm.compiler.nodeinfo.NodeCycles;
33 import org.graalvm.compiler.nodeinfo.NodeInfo;
34 import org.graalvm.compiler.nodes.CompressionNode;
35 import org.graalvm.compiler.nodes.LogicConstantNode;
36 import org.graalvm.compiler.nodes.LogicNode;
37 import org.graalvm.compiler.nodes.NodeView;
38 import org.graalvm.compiler.nodes.UnaryOpLogicNode;
39 import org.graalvm.compiler.nodes.ValueNode;
40 import org.graalvm.compiler.nodes.spi.LIRLowerable;
41 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
42 import org.graalvm.compiler.nodes.spi.Virtualizable;
43 import org.graalvm.compiler.nodes.spi.VirtualizerTool;
44 import org.graalvm.compiler.nodes.type.StampTool;
45
46 import jdk.vm.ci.meta.JavaConstant;
47 import jdk.vm.ci.meta.TriState;
48
49 /**
50 * An IsNullNode will be true if the supplied value is null, and false if it is non-null.
51 */
52 @NodeInfo(cycles = NodeCycles.CYCLES_2)
53 public final class IsNullNode extends UnaryOpLogicNode implements LIRLowerable, Virtualizable {
54
55 public static final NodeClass<IsNullNode> TYPE = NodeClass.create(IsNullNode.class);
56
57 /*
58 * When linear pointer compression is enabled, compressed and uncompressed nulls differ.
59 */
60 private final JavaConstant nullConstant;
61
62 private IsNullNode(ValueNode object, JavaConstant nullConstant) {
63 super(TYPE, object);
64 this.nullConstant = nullConstant;
65 assert object != null;
66 }
67
68 public IsNullNode(ValueNode object) {
69 this(object, JavaConstant.NULL_POINTER);
70 }
71
72 public JavaConstant nullConstant() {
73 return nullConstant;
74 }
75
76 public static LogicNode create(ValueNode forValue) {
77 return canonicalized(null, forValue, JavaConstant.NULL_POINTER);
78 }
79
80 @Override
81 public void generate(NodeLIRBuilderTool gen) {
82 // Nothing to do.
83 }
84
85 @Override
86 public boolean verify() {
87 assertTrue(getValue() != null, "is null input must not be null");
88 assertTrue(getValue().stamp(NodeView.DEFAULT) instanceof AbstractPointerStamp, "input must be a pointer not %s", getValue().stamp(NodeView.DEFAULT));
89 return super.verify();
90 }
91
92 @Override
93 public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {
94 return canonicalized(this, forValue, nullConstant);
95 }
96
97 private static LogicNode canonicalized(IsNullNode node, ValueNode forValue, JavaConstant forNullConstant) {
98 JavaConstant nullConstant = forNullConstant;
99 ValueNode value = forValue;
100 while (true) {
101 if (StampTool.isPointerAlwaysNull(value)) {
102 return LogicConstantNode.tautology();
103 } else if (StampTool.isPointerNonNull(value)) {
104 return LogicConstantNode.contradiction();
105 }
106
107 if (value instanceof ConvertNode) {
108 ConvertNode convertNode = (ConvertNode) value;
109 if (convertNode.mayNullCheckSkipConversion()) {
110 value = convertNode.getValue();
111 continue;
112 }
113 /*
114 * CompressionNode.mayNullCheckSkipConversion returns false when linear pointer
115 * compression is enabled.
116 */
117 if (value instanceof CompressionNode) {
118 CompressionNode compressionNode = (CompressionNode) value;
119 nullConstant = compressionNode.nullConstant();
120 value = compressionNode.getValue();
121 continue;
122 }
123 }
124 /*
125 * If we are at original node, just return it. Otherwise create a new node.
126 */
127 return (node != null && value == forValue) ? node : new IsNullNode(value, nullConstant);
128 }
129 }
130
131 @Override
132 public void virtualize(VirtualizerTool tool) {
133 ValueNode alias = tool.getAlias(getValue());
134 TriState fold = tryFold(alias.stamp(NodeView.DEFAULT));
135 if (fold != TriState.UNKNOWN) {
136 tool.replaceWithValue(LogicConstantNode.forBoolean(fold.isTrue(), graph()));
137 }
138 }
139
140 @Override
141 public Stamp getSucceedingStampForValue(boolean negated) {
142 // Ignore any more precise input stamp since canonicalization will skip through PiNodes
143 AbstractPointerStamp pointerStamp = (AbstractPointerStamp) getValue().stamp(NodeView.DEFAULT).unrestricted();
144 return negated ? pointerStamp.asNonNull() : pointerStamp.asAlwaysNull();
145 }
146
147 @Override
148 public TriState tryFold(Stamp valueStamp) {
149 if (valueStamp instanceof ObjectStamp) {
150 ObjectStamp objectStamp = (ObjectStamp) valueStamp;
151 if (objectStamp.alwaysNull()) {
152 return TriState.TRUE;
153 } else if (objectStamp.nonNull()) {
154 return TriState.FALSE;
155 }
156 }
157 return TriState.UNKNOWN;
158 }
159 }