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.PiNode;
39 import org.graalvm.compiler.nodes.UnaryOpLogicNode;
40 import org.graalvm.compiler.nodes.ValueNode;
41 import org.graalvm.compiler.nodes.spi.LIRLowerable;
42 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
43 import org.graalvm.compiler.nodes.spi.Virtualizable;
44 import org.graalvm.compiler.nodes.spi.VirtualizerTool;
45 import org.graalvm.compiler.nodes.type.StampTool;
46 import org.graalvm.compiler.nodes.util.GraphUtil;
47
48 import jdk.vm.ci.meta.JavaConstant;
49 import jdk.vm.ci.meta.TriState;
50
51 /**
52 * An IsNullNode will be true if the supplied value is null, and false if it is non-null.
53 */
54 @NodeInfo(cycles = NodeCycles.CYCLES_2)
55 public final class IsNullNode extends UnaryOpLogicNode implements LIRLowerable, Virtualizable {
56
57 public static final NodeClass<IsNullNode> TYPE = NodeClass.create(IsNullNode.class);
58
59 /*
60 * When linear pointer compression is enabled, compressed and uncompressed nulls differ.
61 */
62 private final JavaConstant nullConstant;
63
64 private IsNullNode(ValueNode object, JavaConstant nullConstant) {
65 super(TYPE, object);
66 this.nullConstant = nullConstant;
67 assert object != null;
68 }
69
70 public IsNullNode(ValueNode object) {
71 this(object, JavaConstant.NULL_POINTER);
72 }
73
74 public JavaConstant nullConstant() {
75 return nullConstant;
76 }
77
78 public static LogicNode create(ValueNode forValue) {
79 return canonicalized(null, forValue, JavaConstant.NULL_POINTER);
80 }
81
82 @Override
83 public void generate(NodeLIRBuilderTool gen) {
84 // Nothing to do.
85 }
86
87 @Override
88 public boolean verify() {
89 assertTrue(getValue() != null, "is null input must not be null");
90 assertTrue(getValue().stamp(NodeView.DEFAULT) instanceof AbstractPointerStamp, "input must be a pointer not %s", getValue().stamp(NodeView.DEFAULT));
91 return super.verify();
92 }
93
94 @Override
95 public ValueNode canonical(CanonicalizerTool tool, ValueNode forValue) {
96 return canonicalized(this, forValue, nullConstant);
97 }
98
99 private static LogicNode canonicalized(IsNullNode node, ValueNode forValue, JavaConstant forNullConstant) {
100 JavaConstant nullConstant = forNullConstant;
101 ValueNode value = forValue;
102 while (true) {
103 if (StampTool.isPointerAlwaysNull(value)) {
104 return LogicConstantNode.tautology();
105 } else if (StampTool.isPointerNonNull(value)) {
106 return LogicConstantNode.contradiction();
107 }
108
109 if (value instanceof PiNode) {
110 value = GraphUtil.skipPi(value);
111 continue;
112 }
113
114 if (value instanceof ConvertNode) {
115 ConvertNode convertNode = (ConvertNode) value;
116 if (convertNode.mayNullCheckSkipConversion()) {
117 value = convertNode.getValue();
118 continue;
119 }
120 /*
121 * CompressionNode.mayNullCheckSkipConversion returns false when linear pointer
122 * compression is enabled.
123 */
124 if (value instanceof CompressionNode) {
125 CompressionNode compressionNode = (CompressionNode) value;
126 nullConstant = compressionNode.nullConstant();
127 value = compressionNode.getValue();
128 continue;
129 }
130 }
131 /*
132 * If we are at original node, just return it. Otherwise create a new node.
133 */
134 return (node != null && value == forValue) ? node : new IsNullNode(value, nullConstant);
135 }
136 }
137
138 @Override
139 public void virtualize(VirtualizerTool tool) {
140 ValueNode alias = tool.getAlias(getValue());
141 TriState fold = tryFold(alias.stamp(NodeView.DEFAULT));
142 if (fold != TriState.UNKNOWN) {
143 tool.replaceWithValue(LogicConstantNode.forBoolean(fold.isTrue(), graph()));
144 }
145 }
146
147 @Override
148 public Stamp getSucceedingStampForValue(boolean negated) {
149 // Ignore any more precise input stamp since canonicalization will skip through PiNodes
150 AbstractPointerStamp pointerStamp = (AbstractPointerStamp) getValue().stamp(NodeView.DEFAULT).unrestricted();
151 return negated ? pointerStamp.asNonNull() : pointerStamp.asAlwaysNull();
152 }
153
154 @Override
155 public TriState tryFold(Stamp valueStamp) {
156 if (valueStamp instanceof ObjectStamp) {
157 ObjectStamp objectStamp = (ObjectStamp) valueStamp;
158 if (objectStamp.alwaysNull()) {
159 return TriState.TRUE;
160 } else if (objectStamp.nonNull()) {
161 return TriState.FALSE;
162 }
163 }
164 return TriState.UNKNOWN;
165 }
166 }