1 /*
2  * Copyright (c) 2013, 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
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22  */
23 
24 
25 package org.graalvm.compiler.word;
26 
27 import static org.graalvm.compiler.nodeinfo.NodeCycles.CYCLES_1;
28 import static org.graalvm.compiler.nodeinfo.NodeSize.SIZE_1;
29 
30 import org.graalvm.compiler.core.common.LIRKind;
31 import org.graalvm.compiler.core.common.type.AbstractPointerStamp;
32 import org.graalvm.compiler.core.common.type.IntegerStamp;
33 import org.graalvm.compiler.core.common.type.ObjectStamp;
34 import org.graalvm.compiler.core.common.type.Stamp;
35 import org.graalvm.compiler.core.common.type.StampFactory;
36 import org.graalvm.compiler.graph.Node;
37 import org.graalvm.compiler.graph.NodeClass;
38 import org.graalvm.compiler.graph.spi.Canonicalizable;
39 import org.graalvm.compiler.graph.spi.CanonicalizerTool;
40 import org.graalvm.compiler.lir.ConstantValue;
41 import org.graalvm.compiler.nodeinfo.NodeInfo;
42 import org.graalvm.compiler.nodes.ConstantNode;
43 import org.graalvm.compiler.nodes.FixedWithNextNode;
44 import org.graalvm.compiler.nodes.NodeView;
45 import org.graalvm.compiler.nodes.ValueNode;
46 import org.graalvm.compiler.nodes.spi.LIRLowerable;
47 import org.graalvm.compiler.nodes.spi.NodeLIRBuilderTool;
48 import org.graalvm.compiler.nodes.type.NarrowOopStamp;
49 
50 import jdk.vm.ci.meta.AllocatableValue;
51 import jdk.vm.ci.meta.JavaConstant;
52 import jdk.vm.ci.meta.JavaKind;
53 import jdk.vm.ci.meta.Value;
54 import jdk.vm.ci.meta.ValueKind;
55 
56 /**
57  * Casts between Word and Object exposed by the {@link Word#fromAddress},
58  * {@link Word#objectToTrackedPointer}, {@link Word#objectToUntrackedPointer} and
59  * {@link Word#toObject()} operations. It has an impact on the pointer maps for the GC, so it must
60  * not be scheduled or optimized away.
61  */
62 @NodeInfo(cycles = CYCLES_1, size = SIZE_1)
63 public final class WordCastNode extends FixedWithNextNode implements LIRLowerable, Canonicalizable {
64 
65     public static final NodeClass<WordCastNode> TYPE = NodeClass.create(WordCastNode.class);
66 
67     @Input ValueNode input;
68     private final boolean trackedPointer;
69 
wordToObject(ValueNode input, JavaKind wordKind)70     public static WordCastNode wordToObject(ValueNode input, JavaKind wordKind) {
71         assert input.getStackKind() == wordKind;
72         return new WordCastNode(objectStampFor(input), input);
73     }
74 
wordToObjectNonNull(ValueNode input, JavaKind wordKind)75     public static WordCastNode wordToObjectNonNull(ValueNode input, JavaKind wordKind) {
76         assert input.getStackKind() == wordKind;
77         return new WordCastNode(StampFactory.objectNonNull(), input);
78     }
79 
wordToNarrowObject(ValueNode input, NarrowOopStamp stamp)80     public static WordCastNode wordToNarrowObject(ValueNode input, NarrowOopStamp stamp) {
81         return new WordCastNode(stamp, input);
82     }
83 
addressToWord(ValueNode input, JavaKind wordKind)84     public static WordCastNode addressToWord(ValueNode input, JavaKind wordKind) {
85         assert input.stamp(NodeView.DEFAULT) instanceof AbstractPointerStamp;
86         return new WordCastNode(StampFactory.forKind(wordKind), input);
87     }
88 
objectToTrackedPointer(ValueNode input, JavaKind wordKind)89     public static WordCastNode objectToTrackedPointer(ValueNode input, JavaKind wordKind) {
90         assert input.stamp(NodeView.DEFAULT) instanceof ObjectStamp;
91         return new WordCastNode(StampFactory.forKind(wordKind), input);
92     }
93 
objectToUntrackedPointer(ValueNode input, JavaKind wordKind)94     public static WordCastNode objectToUntrackedPointer(ValueNode input, JavaKind wordKind) {
95         assert input.stamp(NodeView.DEFAULT) instanceof ObjectStamp;
96         return new WordCastNode(StampFactory.forKind(wordKind), input, false);
97     }
98 
narrowOopToUntrackedWord(ValueNode input, JavaKind wordKind)99     public static WordCastNode narrowOopToUntrackedWord(ValueNode input, JavaKind wordKind) {
100         assert input.stamp(NodeView.DEFAULT) instanceof NarrowOopStamp;
101         return new WordCastNode(StampFactory.forKind(wordKind), input, false);
102     }
103 
WordCastNode(Stamp stamp, ValueNode input)104     private WordCastNode(Stamp stamp, ValueNode input) {
105         this(stamp, input, true);
106     }
107 
WordCastNode(Stamp stamp, ValueNode input, boolean trackedPointer)108     protected WordCastNode(Stamp stamp, ValueNode input, boolean trackedPointer) {
109         super(TYPE, stamp);
110         this.input = input;
111         this.trackedPointer = trackedPointer;
112     }
113 
getInput()114     public ValueNode getInput() {
115         return input;
116     }
117 
isZeroConstant(ValueNode value)118     private static boolean isZeroConstant(ValueNode value) {
119         JavaConstant constant = value.asJavaConstant();
120         return constant.getJavaKind().isNumericInteger() && constant.asLong() == 0;
121     }
122 
objectStampFor(ValueNode input)123     private static Stamp objectStampFor(ValueNode input) {
124         Stamp inputStamp = input.stamp(NodeView.DEFAULT);
125         if (inputStamp instanceof AbstractPointerStamp) {
126             AbstractPointerStamp pointerStamp = (AbstractPointerStamp) inputStamp;
127             if (pointerStamp.alwaysNull()) {
128                 return StampFactory.alwaysNull();
129             } else if (pointerStamp.nonNull()) {
130                 return StampFactory.objectNonNull();
131             }
132         } else if (inputStamp instanceof IntegerStamp && !((IntegerStamp) inputStamp).contains(0)) {
133             return StampFactory.objectNonNull();
134         } else if (input.isConstant() && isZeroConstant(input)) {
135             return StampFactory.alwaysNull();
136         }
137         return StampFactory.object();
138     }
139 
140     @Override
inferStamp()141     public boolean inferStamp() {
142         if (stamp instanceof AbstractPointerStamp) {
143             AbstractPointerStamp objectStamp = (AbstractPointerStamp) stamp;
144             if (!objectStamp.alwaysNull() && !objectStamp.nonNull()) {
145                 Stamp newStamp = stamp;
146                 Stamp inputStamp = input.stamp(NodeView.DEFAULT);
147                 if (inputStamp instanceof AbstractPointerStamp) {
148                     AbstractPointerStamp pointerStamp = (AbstractPointerStamp) inputStamp;
149                     if (pointerStamp.alwaysNull()) {
150                         newStamp = objectStamp.asAlwaysNull();
151                     } else if (pointerStamp.nonNull()) {
152                         newStamp = objectStamp.asNonNull();
153                     }
154                 } else if (inputStamp instanceof IntegerStamp && !((IntegerStamp) inputStamp).contains(0)) {
155                     newStamp = objectStamp.asNonNull();
156                 } else if (input.isConstant() && isZeroConstant(input)) {
157                     newStamp = objectStamp.asAlwaysNull();
158                 }
159                 return updateStamp(newStamp);
160             }
161         }
162         return false;
163     }
164 
165     @Override
canonical(CanonicalizerTool tool)166     public Node canonical(CanonicalizerTool tool) {
167         if (tool.allUsagesAvailable() && hasNoUsages()) {
168             /* If the cast is unused, it can be eliminated. */
169             return input;
170         }
171 
172         assert !stamp.isCompatible(input.stamp(NodeView.DEFAULT));
173         if (input.isConstant()) {
174             /* Null pointers are uncritical for GC, so they can be constant folded. */
175             if (input.asJavaConstant().isNull()) {
176                 return ConstantNode.forIntegerStamp(stamp, 0);
177             } else if (isZeroConstant(input)) {
178                 return ConstantNode.forConstant(stamp, ((AbstractPointerStamp) stamp).nullConstant(), tool.getMetaAccess());
179             }
180         }
181 
182         return this;
183     }
184 
185     @Override
generate(NodeLIRBuilderTool generator)186     public void generate(NodeLIRBuilderTool generator) {
187         Value value = generator.operand(input);
188         ValueKind<?> kind = generator.getLIRGeneratorTool().getLIRKind(stamp(NodeView.DEFAULT));
189         assert kind.getPlatformKind().getSizeInBytes() == value.getPlatformKind().getSizeInBytes();
190 
191         if (trackedPointer && LIRKind.isValue(kind) && !LIRKind.isValue(value)) {
192             // just change the PlatformKind, but don't drop reference information
193             kind = value.getValueKind().changeType(kind.getPlatformKind());
194         }
195 
196         if (kind.equals(value.getValueKind()) && !(value instanceof ConstantValue)) {
197             generator.setResult(this, value);
198         } else {
199             AllocatableValue result = generator.getLIRGeneratorTool().newVariable(kind);
200             if (stamp.equals(StampFactory.object())) {
201                 generator.getLIRGeneratorTool().emitConvertZeroToNull(result, value);
202             } else if (!trackedPointer && !((AbstractPointerStamp) input.stamp(NodeView.DEFAULT)).nonNull()) {
203                 generator.getLIRGeneratorTool().emitConvertNullToZero(result, value);
204             } else {
205                 generator.getLIRGeneratorTool().emitMove(result, value);
206             }
207             generator.setResult(this, result);
208         }
209     }
210 }
211