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