DefaultLoopPolicies.java revision 13482:6d53d0ae27e5 
1/*
2 * Copyright (c) 2012, 2016, 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.
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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.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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23package org.graalvm.compiler.loop;
24
25import static org.graalvm.compiler.core.common.GraalOptions.LoopMaxUnswitch;
26import static org.graalvm.compiler.core.common.GraalOptions.MaximumDesiredSize;
27import static org.graalvm.compiler.core.common.GraalOptions.MinimumPeelProbability;
28
29import java.util.List;
30
31import org.graalvm.compiler.debug.CounterKey;
32import org.graalvm.compiler.debug.DebugContext;
33import org.graalvm.compiler.graph.Node;
34import org.graalvm.compiler.graph.NodeBitMap;
35import org.graalvm.compiler.nodes.AbstractBeginNode;
36import org.graalvm.compiler.nodes.ControlSplitNode;
37import org.graalvm.compiler.nodes.DeoptimizeNode;
38import org.graalvm.compiler.nodes.FixedNode;
39import org.graalvm.compiler.nodes.FixedWithNextNode;
40import org.graalvm.compiler.nodes.InvokeNode;
41import org.graalvm.compiler.nodes.LoopBeginNode;
42import org.graalvm.compiler.nodes.MergeNode;
43import org.graalvm.compiler.nodes.StructuredGraph;
44import org.graalvm.compiler.nodes.VirtualState;
45import org.graalvm.compiler.nodes.VirtualState.VirtualClosure;
46import org.graalvm.compiler.nodes.cfg.Block;
47import org.graalvm.compiler.nodes.cfg.ControlFlowGraph;
48import org.graalvm.compiler.nodes.debug.ControlFlowAnchorNode;
49import org.graalvm.compiler.nodes.java.TypeSwitchNode;
50import org.graalvm.compiler.options.Option;
51import org.graalvm.compiler.options.OptionKey;
52import org.graalvm.compiler.options.OptionType;
53import org.graalvm.compiler.options.OptionValues;
54
55import jdk.vm.ci.meta.MetaAccessProvider;
56
57public class DefaultLoopPolicies implements LoopPolicies {
58    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> LoopUnswitchMaxIncrease = new OptionKey<>(500);
59    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> LoopUnswitchTrivial = new OptionKey<>(10);
60    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Double> LoopUnswitchFrequencyBoost = new OptionKey<>(10.0);
61
62    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> FullUnrollMaxNodes = new OptionKey<>(300);
63    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> FullUnrollMaxIterations = new OptionKey<>(600);
64    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> ExactFullUnrollMaxNodes = new OptionKey<>(1200);
65    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> ExactPartialUnrollMaxNodes = new OptionKey<>(200);
66
67    @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> UnrollMaxIterations = new OptionKey<>(16);
68
69    @Override
70    public boolean shouldPeel(LoopEx loop, ControlFlowGraph cfg, MetaAccessProvider metaAccess) {
71        LoopBeginNode loopBegin = loop.loopBegin();
72        double entryProbability = cfg.blockFor(loopBegin.forwardEnd()).probability();
73        OptionValues options = cfg.graph.getOptions();
74        if (entryProbability > MinimumPeelProbability.getValue(options) && loop.size() + loopBegin.graph().getNodeCount() < MaximumDesiredSize.getValue(options)) {
75            // check whether we're allowed to peel this loop
76            return loop.canDuplicateLoop();
77        } else {
78            return false;
79        }
80    }
81
82    @Override
83    public boolean shouldFullUnroll(LoopEx loop) {
84        if (!loop.isCounted() || !loop.counted().isConstantMaxTripCount()) {
85            return false;
86        }
87        OptionValues options = loop.entryPoint().getOptions();
88        CountedLoopInfo counted = loop.counted();
89        long maxTrips = counted.constantMaxTripCount();
90        int maxNodes = (counted.isExactTripCount() && counted.isConstantExactTripCount()) ? ExactFullUnrollMaxNodes.getValue(options) : FullUnrollMaxNodes.getValue(options);
91        maxNodes = Math.min(maxNodes, Math.max(0, MaximumDesiredSize.getValue(options) - loop.loopBegin().graph().getNodeCount()));
92        int size = Math.max(1, loop.size() - 1 - loop.loopBegin().phis().count());
93        if (maxTrips <= FullUnrollMaxIterations.getValue(options) && size * (maxTrips - 1) <= maxNodes) {
94            // check whether we're allowed to unroll this loop
95            return loop.canDuplicateLoop();
96        } else {
97            return false;
98        }
99    }
100
101    @Override
102    public boolean shouldPartiallyUnroll(LoopEx loop) {
103        LoopBeginNode loopBegin = loop.loopBegin();
104        if (!loop.isCounted()) {
105            loopBegin.getDebug().log(DebugContext.VERBOSE_LEVEL, "shouldPartiallyUnroll %s isn't counted", loopBegin);
106            return false;
107        }
108        OptionValues options = loop.entryPoint().getOptions();
109        int maxNodes = ExactPartialUnrollMaxNodes.getValue(options);
110        maxNodes = Math.min(maxNodes, Math.max(0, MaximumDesiredSize.getValue(options) - loop.loopBegin().graph().getNodeCount()));
111        int size = Math.max(1, loop.size() - 1 - loop.loopBegin().phis().count());
112        int unrollFactor = loopBegin.getUnrollFactor();
113        if (unrollFactor == 1) {
114            double loopFrequency = loopBegin.loopFrequency();
115            if (loopBegin.isSimpleLoop() && loopFrequency < 5.0) {
116                loopBegin.getDebug().log(DebugContext.VERBOSE_LEVEL, "shouldPartiallyUnroll %s frequency too low %s ", loopBegin, loopFrequency);
117                return false;
118            }
119            loopBegin.setLoopOrigFrequency(loopFrequency);
120        }
121        int maxUnroll = UnrollMaxIterations.getValue(options);
122        // Now correct size for the next unroll. UnrollMaxIterations == 1 means perform the
123        // pre/main/post transformation but don't actually unroll the main loop.
124        size += size;
125        if (maxUnroll == 1 && loopBegin.isSimpleLoop() || size <= maxNodes && unrollFactor < maxUnroll) {
126            // Will the next unroll fit?
127            if ((int) loopBegin.loopOrigFrequency() < (unrollFactor * 2)) {
128                return false;
129            }
130            // Check whether we're allowed to unroll this loop
131            for (Node node : loop.inside().nodes()) {
132                if (node instanceof ControlFlowAnchorNode) {
133                    return false;
134                }
135                if (node instanceof InvokeNode) {
136                    return false;
137                }
138            }
139            return true;
140        } else {
141            loopBegin.getDebug().log(DebugContext.VERBOSE_LEVEL, "shouldPartiallyUnroll %s unrolled loop is too large %s ", loopBegin, size);
142            return false;
143        }
144    }
145
146    @Override
147    public boolean shouldTryUnswitch(LoopEx loop) {
148        LoopBeginNode loopBegin = loop.loopBegin();
149        double loopFrequency = loopBegin.loopFrequency();
150        if (loopFrequency <= 1.0) {
151            return false;
152        }
153        OptionValues options = loop.entryPoint().getOptions();
154        return loopBegin.unswitches() <= LoopMaxUnswitch.getValue(options);
155    }
156
157    private static final class CountingClosure implements VirtualClosure {
158        int count;
159
160        @Override
161        public void apply(VirtualState node) {
162            count++;
163        }
164    }
165
166    private static class IsolatedInitialization {
167        static final CounterKey UNSWITCH_SPLIT_WITH_PHIS = DebugContext.counter("UnswitchSplitWithPhis");
168    }
169
170    @Override
171    public boolean shouldUnswitch(LoopEx loop, List<ControlSplitNode> controlSplits) {
172        int phis = 0;
173        StructuredGraph graph = loop.loopBegin().graph();
174        DebugContext debug = graph.getDebug();
175        NodeBitMap branchNodes = graph.createNodeBitMap();
176        for (ControlSplitNode controlSplit : controlSplits) {
177            for (Node successor : controlSplit.successors()) {
178                AbstractBeginNode branch = (AbstractBeginNode) successor;
179                // this may count twice because of fall-through in switches
180                loop.nodesInLoopBranch(branchNodes, branch);
181            }
182            Block postDomBlock = loop.loopsData().getCFG().blockFor(controlSplit).getPostdominator();
183            if (postDomBlock != null) {
184                IsolatedInitialization.UNSWITCH_SPLIT_WITH_PHIS.increment(debug);
185                phis += ((MergeNode) postDomBlock.getBeginNode()).phis().count();
186            }
187        }
188        int inBranchTotal = branchNodes.count();
189
190        CountingClosure stateNodesCount = new CountingClosure();
191        double loopFrequency = loop.loopBegin().loopFrequency();
192        OptionValues options = loop.loopBegin().getOptions();
193        int maxDiff = LoopUnswitchTrivial.getValue(options) + (int) (LoopUnswitchFrequencyBoost.getValue(options) * (loopFrequency - 1.0 + phis));
194
195        maxDiff = Math.min(maxDiff, LoopUnswitchMaxIncrease.getValue(options));
196        int remainingGraphSpace = MaximumDesiredSize.getValue(options) - graph.getNodeCount();
197        maxDiff = Math.min(maxDiff, remainingGraphSpace);
198
199        loop.loopBegin().stateAfter().applyToVirtual(stateNodesCount);
200        int loopTotal = loop.size() - loop.loopBegin().phis().count() - stateNodesCount.count - 1;
201        int actualDiff = (loopTotal - inBranchTotal);
202        ControlSplitNode firstSplit = controlSplits.get(0);
203        if (firstSplit instanceof TypeSwitchNode) {
204            int copies = firstSplit.successors().count() - 1;
205            for (Node succ : firstSplit.successors()) {
206                FixedNode current = (FixedNode) succ;
207                while (current instanceof FixedWithNextNode) {
208                    current = ((FixedWithNextNode) current).next();
209                }
210                if (current instanceof DeoptimizeNode) {
211                    copies--;
212                }
213            }
214            actualDiff = actualDiff * copies;
215        }
216
217        debug.log("shouldUnswitch(%s, %s) : delta=%d (%.2f%% inside of branches), max=%d, f=%.2f, phis=%d -> %b", loop, controlSplits, actualDiff, (double) (inBranchTotal) / loopTotal * 100, maxDiff,
218                        loopFrequency, phis, actualDiff <= maxDiff);
219        if (actualDiff <= maxDiff) {
220            // check whether we're allowed to unswitch this loop
221            return loop.canDuplicateLoop();
222        } else {
223            return false;
224        }
225    }
226
227}
228