001/*
002 * Copyright (c) 2011, 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.nodes;
024
025import java.util.*;
026
027import com.oracle.graal.graph.*;
028import com.oracle.graal.nodeinfo.*;
029import com.oracle.graal.nodes.spi.*;
030
031/**
032 * LoopEnd nodes represent a loop back-edge. When a LoopEnd is reached, execution continues at the
033 * {@linkplain #loopBegin() loop header}.
034 */
035@NodeInfo
036public final class LoopEndNode extends AbstractEndNode {
037
038    public static final NodeClass<LoopEndNode> TYPE = NodeClass.create(LoopEndNode.class);
039    @Input(InputType.Association) LoopBeginNode loopBegin;
040    protected boolean canSafepoint;
041    protected int endIndex;
042
043    public LoopEndNode(LoopBeginNode begin) {
044        super(TYPE);
045        int idx = begin.nextEndIndex();
046        assert idx >= 0;
047        this.endIndex = idx;
048        this.loopBegin = begin;
049        this.canSafepoint = true;
050    }
051
052    @Override
053    public AbstractMergeNode merge() {
054        return loopBegin();
055    }
056
057    public LoopBeginNode loopBegin() {
058        return loopBegin;
059    }
060
061    public void setLoopBegin(LoopBeginNode x) {
062        updateUsages(this.loopBegin, x);
063        this.loopBegin = x;
064    }
065
066    public void disableSafepoint() {
067        this.canSafepoint = false;
068    }
069
070    public boolean canSafepoint() {
071        return canSafepoint;
072    }
073
074    @Override
075    public void generate(NodeLIRBuilderTool gen) {
076        gen.visitLoopEnd(this);
077        super.generate(gen);
078    }
079
080    @Override
081    public boolean verify() {
082        assertTrue(loopBegin != null, "must have a loop begin");
083        assertTrue(hasNoUsages(), "LoopEnds can not be used");
084        return super.verify();
085    }
086
087    /**
088     * Returns the index of this loop end amongst its {@link LoopBeginNode}'s loop ends.<br>
089     *
090     * Since a LoopBeginNode also has {@linkplain LoopBeginNode#forwardEnds() forward ends}, this is
091     * <b>not</b> the index into {@link PhiNode} values at the loop begin. Use
092     * {@link LoopBeginNode#phiPredecessorIndex(AbstractEndNode)} for this purpose.
093     *
094     */
095    int endIndex() {
096        return endIndex;
097    }
098
099    void setEndIndex(int idx) {
100        this.endIndex = idx;
101    }
102
103    @Override
104    public Iterable<? extends Node> cfgSuccessors() {
105        return Collections.emptyList();
106    }
107}