001/*
002 * Copyright (c) 2013, 2015, Oracle and/or its affiliates. All rights reserved.
003 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
004 *
005 * This code is free software; you can redistribute it and/or modify it
006 * under the terms of the GNU General Public License version 2 only, as
007 * published by the Free Software Foundation.
008 *
009 * This code is distributed in the hope that it will be useful, but WITHOUT
010 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
011 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
012 * version 2 for more details (a copy is included in the LICENSE file that
013 * accompanied this code).
014 *
015 * You should have received a copy of the GNU General Public License version
016 * 2 along with this work; if not, write to the Free Software Foundation,
017 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
018 *
019 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
020 * or visit www.oracle.com if you need additional information or have any
021 * questions.
022 */
023package com.oracle.graal.word.nodes;
024
025import jdk.internal.jvmci.meta.*;
026
027import com.oracle.graal.compiler.common.type.*;
028import com.oracle.graal.graph.*;
029import com.oracle.graal.graph.spi.*;
030import com.oracle.graal.nodeinfo.*;
031import com.oracle.graal.nodes.*;
032import com.oracle.graal.nodes.spi.*;
033import com.oracle.graal.word.Word.Opcode;
034
035/**
036 * Casts between Word and Object exposed by the {@link Opcode#FROM_OBJECT} and
037 * {@link Opcode#TO_OBJECT} operations. It has an impact on the pointer maps for the GC, so it must
038 * not be scheduled or optimized away.
039 */
040@NodeInfo
041public final class WordCastNode extends FixedWithNextNode implements LIRLowerable, Canonicalizable {
042
043    public static final NodeClass<WordCastNode> TYPE = NodeClass.create(WordCastNode.class);
044    @Input ValueNode input;
045
046    public static WordCastNode wordToObject(ValueNode input, Kind wordKind) {
047        assert input.getKind() == wordKind;
048        return new WordCastNode(StampFactory.object(), input);
049    }
050
051    public static WordCastNode objectToWord(ValueNode input, Kind wordKind) {
052        assert input.stamp() instanceof ObjectStamp;
053        return new WordCastNode(StampFactory.forKind(wordKind), input);
054    }
055
056    public static WordCastNode addressToWord(ValueNode input, Kind wordKind) {
057        assert input.stamp() instanceof AbstractPointerStamp;
058        return new WordCastNode(StampFactory.forKind(wordKind), input);
059    }
060
061    public WordCastNode(Stamp stamp, ValueNode input) {
062        super(TYPE, stamp);
063        this.input = input;
064    }
065
066    public ValueNode getInput() {
067        return input;
068    }
069
070    @Override
071    public Node canonical(CanonicalizerTool tool) {
072        if (tool.allUsagesAvailable() && hasNoUsages()) {
073            /* If the cast is unused, it can be eliminated. */
074            return input;
075        }
076
077        assert !stamp().isCompatible(input.stamp());
078        if (input.isConstant()) {
079            /* Null pointers are uncritical for GC, so they can be constant folded. */
080            if (input.asJavaConstant().isNull()) {
081                return ConstantNode.forIntegerStamp(stamp(), 0);
082            } else if (input.asJavaConstant().getKind().isNumericInteger() && input.asJavaConstant().asLong() == 0) {
083                return ConstantNode.forConstant(stamp(), JavaConstant.NULL_POINTER, tool.getMetaAccess());
084            }
085        }
086
087        return this;
088    }
089
090    @Override
091    public void generate(NodeLIRBuilderTool generator) {
092        Value value = generator.operand(input);
093        LIRKind kind = generator.getLIRGeneratorTool().getLIRKind(stamp());
094        assert generator.getLIRGeneratorTool().target().getSizeInBytes(kind.getPlatformKind()) == generator.getLIRGeneratorTool().target().getSizeInBytes(value.getPlatformKind());
095
096        if (kind.isValue() && !value.getLIRKind().isValue()) {
097            // only add reference information, but never drop it
098            kind = value.getLIRKind().changeType(kind.getPlatformKind());
099        }
100
101        if (kind.equals(value.getLIRKind())) {
102            generator.setResult(this, value);
103        } else {
104            AllocatableValue result = generator.getLIRGeneratorTool().newVariable(kind);
105            generator.getLIRGeneratorTool().emitMove(result, value);
106            generator.setResult(this, result);
107        }
108    }
109}