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 *

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 * published by the Free Software Foundation.

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 * This code is distributed in the hope that it will be useful, but WITHOUT

 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * version 2 for more details (a copy is included in the LICENSE file that

 * accompanied this code).

 *

 * You should have received a copy of the GNU General Public License version

 * 2 along with this work; if not, write to the Free Software Foundation,

 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.

 *

 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA

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package org.graalvm.compiler.loop;

import static org.graalvm.compiler.core.common.GraalOptions.LoopMaxUnswitch;

import static org.graalvm.compiler.core.common.GraalOptions.MaximumDesiredSize;

import static org.graalvm.compiler.core.common.GraalOptions.MinimumPeelProbability;

import java.util.List;

import org.graalvm.compiler.core.common.util.UnsignedLong;

import org.graalvm.compiler.debug.CounterKey;

import org.graalvm.compiler.debug.DebugContext;

import org.graalvm.compiler.graph.Node;

import org.graalvm.compiler.graph.NodeBitMap;

import org.graalvm.compiler.nodes.AbstractBeginNode;

import org.graalvm.compiler.nodes.ControlSplitNode;

import org.graalvm.compiler.nodes.DeoptimizeNode;

import org.graalvm.compiler.nodes.FixedNode;

import org.graalvm.compiler.nodes.FixedWithNextNode;

import org.graalvm.compiler.nodes.InvokeNode;

import org.graalvm.compiler.nodes.LoopBeginNode;

import org.graalvm.compiler.nodes.MergeNode;

import org.graalvm.compiler.nodes.StructuredGraph;

import org.graalvm.compiler.nodes.VirtualState;

import org.graalvm.compiler.nodes.VirtualState.VirtualClosure;

import org.graalvm.compiler.nodes.cfg.Block;

import org.graalvm.compiler.nodes.cfg.ControlFlowGraph;

import org.graalvm.compiler.nodes.debug.ControlFlowAnchorNode;

import org.graalvm.compiler.nodes.java.TypeSwitchNode;

import org.graalvm.compiler.options.Option;

import org.graalvm.compiler.options.OptionKey;

import org.graalvm.compiler.options.OptionType;

import org.graalvm.compiler.options.OptionValues;

import jdk.vm.ci.meta.MetaAccessProvider;

public class DefaultLoopPolicies implements LoopPolicies {

    public static class Options {

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> LoopUnswitchMaxIncrease = new OptionKey<>(500);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> LoopUnswitchTrivial = new OptionKey<>(10);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Double> LoopUnswitchFrequencyBoost = new OptionKey<>(10.0);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> FullUnrollMaxNodes = new OptionKey<>(300);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> FullUnrollMaxIterations = new OptionKey<>(600);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> ExactFullUnrollMaxNodes = new OptionKey<>(1200);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> ExactPartialUnrollMaxNodes = new OptionKey<>(200);

        @Option(help = "", type = OptionType.Expert) public static final OptionKey<Integer> UnrollMaxIterations = new OptionKey<>(16);

    }

    @Override

    public boolean shouldPeel(LoopEx loop, ControlFlowGraph cfg, MetaAccessProvider metaAccess) {

        LoopBeginNode loopBegin = loop.loopBegin();

        double entryProbability = cfg.blockFor(loopBegin.forwardEnd()).getRelativeFrequency();

        OptionValues options = cfg.graph.getOptions();

        if (entryProbability > MinimumPeelProbability.getValue(options) && loop.size() + loopBegin.graph().getNodeCount() < MaximumDesiredSize.getValue(options)) {

            // check whether we're allowed to peel this loop

            return loop.canDuplicateLoop();

        } else {

            return false;

        }

    }

    @Override

    public boolean shouldFullUnroll(LoopEx loop) {

        if (!loop.isCounted() || !loop.counted().isConstantMaxTripCount()) {

            return false;

        }

        OptionValues options = loop.entryPoint().getOptions();

        CountedLoopInfo counted = loop.counted();

        UnsignedLong maxTrips = counted.constantMaxTripCount();

        if (maxTrips.equals(0)) {

            return loop.canDuplicateLoop();

        }

        int maxNodes = (counted.isExactTripCount() && counted.isConstantExactTripCount()) ? Options.ExactFullUnrollMaxNodes.getValue(options) : Options.FullUnrollMaxNodes.getValue(options);

        maxNodes = Math.min(maxNodes, Math.max(0, MaximumDesiredSize.getValue(options) - loop.loopBegin().graph().getNodeCount()));

        int size = Math.max(1, loop.size() - 1 - loop.loopBegin().phis().count());

        /* @formatter:off

         * The check below should not throw ArithmeticException because:

         * maxTrips is guaranteed to be >= 1 by the check above

         * - maxTrips * size can not overfow because:

         *   - maxTrips <= FullUnrollMaxIterations <= Integer.MAX_VALUE

         *   - 1 <= size <= Integer.MAX_VALUE

         * @formatter:on

         */

        if (maxTrips.isLessOrEqualTo(Options.FullUnrollMaxIterations.getValue(options)) && maxTrips.minus(1).times(size).isLessOrEqualTo(maxNodes)) {

            // check whether we're allowed to unroll this loop

            return loop.canDuplicateLoop();

        } else {

            return false;

        }

    }

    @Override

    public boolean shouldPartiallyUnroll(LoopEx loop) {

        LoopBeginNode loopBegin = loop.loopBegin();

        if (!loop.isCounted()) {

            loopBegin.getDebug().log(DebugContext.VERBOSE_LEVEL, "shouldPartiallyUnroll %s isn't counted", loopBegin);

            return false;

        }

        OptionValues options = loop.entryPoint().getOptions();

        int maxNodes = Options.ExactPartialUnrollMaxNodes.getValue(options);

        maxNodes = Math.min(maxNodes, Math.max(0, MaximumDesiredSize.getValue(options) - loop.loopBegin().graph().getNodeCount()));

        int size = Math.max(1, loop.size() - 1 - loop.loopBegin().phis().count());

        int unrollFactor = loopBegin.getUnrollFactor();

        if (unrollFactor == 1) {

            double loopFrequency = loopBegin.loopFrequency();

            if (loopBegin.isSimpleLoop() && loopFrequency < 5.0) {

                loopBegin.getDebug().log(DebugContext.VERBOSE_LEVEL, "shouldPartiallyUnroll %s frequency too low %s ", loopBegin, loopFrequency);

                return false;

            }

            loopBegin.setLoopOrigFrequency(loopFrequency);

        }

        int maxUnroll = Options.UnrollMaxIterations.getValue(options);

        // Now correct size for the next unroll. UnrollMaxIterations == 1 means perform the

        // pre/main/post transformation but don't actually unroll the main loop.

        size += size;

        if (maxUnroll == 1 && loopBegin.isSimpleLoop() || size <= maxNodes && unrollFactor < maxUnroll) {

            // Will the next unroll fit?

            if ((int) loopBegin.loopOrigFrequency() < (unrollFactor * 2)) {

                return false;

            }

            // Check whether we're allowed to unroll this loop

            for (Node node : loop.inside().nodes()) {

                if (node instanceof ControlFlowAnchorNode) {

                    return false;

                }

                if (node instanceof InvokeNode) {

                    return false;

                }

            }

            return true;

        } else {

            loopBegin.getDebug().log(DebugContext.VERBOSE_LEVEL, "shouldPartiallyUnroll %s unrolled loop is too large %s ", loopBegin, size);

            return false;

        }

    }

    @Override

    public boolean shouldTryUnswitch(LoopEx loop) {

        LoopBeginNode loopBegin = loop.loopBegin();

        double loopFrequency = loopBegin.loopFrequency();

        if (loopFrequency <= 1.0) {

            return false;

        }

        OptionValues options = loop.entryPoint().getOptions();

        return loopBegin.unswitches() <= LoopMaxUnswitch.getValue(options);

    }

    private static final class CountingClosure implements VirtualClosure {

        int count;

        @Override

        public void apply(VirtualState node) {

            count++;

        }

    }

    private static class IsolatedInitialization {

        static final CounterKey UNSWITCH_SPLIT_WITH_PHIS = DebugContext.counter("UnswitchSplitWithPhis");

    }

    @Override

    public boolean shouldUnswitch(LoopEx loop, List<ControlSplitNode> controlSplits) {

        int phis = 0;

        StructuredGraph graph = loop.loopBegin().graph();

        DebugContext debug = graph.getDebug();

        NodeBitMap branchNodes = graph.createNodeBitMap();

        for (ControlSplitNode controlSplit : controlSplits) {

            for (Node successor : controlSplit.successors()) {

                AbstractBeginNode branch = (AbstractBeginNode) successor;

                // this may count twice because of fall-through in switches

                loop.nodesInLoopBranch(branchNodes, branch);

            }

            Block postDomBlock = loop.loopsData().getCFG().blockFor(controlSplit).getPostdominator();

            if (postDomBlock != null) {

                IsolatedInitialization.UNSWITCH_SPLIT_WITH_PHIS.increment(debug);

                phis += ((MergeNode) postDomBlock.getBeginNode()).phis().count();

            }

        }

        int inBranchTotal = branchNodes.count();

        CountingClosure stateNodesCount = new CountingClosure();

        double loopFrequency = loop.loopBegin().loopFrequency();

        OptionValues options = loop.loopBegin().getOptions();

        int maxDiff = Options.LoopUnswitchTrivial.getValue(options) + (int) (Options.LoopUnswitchFrequencyBoost.getValue(options) * (loopFrequency - 1.0 + phis));

        maxDiff = Math.min(maxDiff, Options.LoopUnswitchMaxIncrease.getValue(options));

        int remainingGraphSpace = MaximumDesiredSize.getValue(options) - graph.getNodeCount();

        maxDiff = Math.min(maxDiff, remainingGraphSpace);

        loop.loopBegin().stateAfter().applyToVirtual(stateNodesCount);

        int loopTotal = loop.size() - loop.loopBegin().phis().count() - stateNodesCount.count - 1;

        int actualDiff = (loopTotal - inBranchTotal);

        ControlSplitNode firstSplit = controlSplits.get(0);

        if (firstSplit instanceof TypeSwitchNode) {

            int copies = firstSplit.successors().count() - 1;

            for (Node succ : firstSplit.successors()) {

                FixedNode current = (FixedNode) succ;

                while (current instanceof FixedWithNextNode) {

                    current = ((FixedWithNextNode) current).next();

                }

                if (current instanceof DeoptimizeNode) {

                    copies--;

                }

            }

            actualDiff = actualDiff * copies;

        }

        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,

                        loopFrequency, phis, actualDiff <= maxDiff);

        if (actualDiff <= maxDiff) {

            // check whether we're allowed to unswitch this loop

            return loop.canDuplicateLoop();

        } else {

            return false;

        }

    }

}