hotspot/src/jdk.internal.vm.compiler/share/classes/org.graalvm.compiler.loop.phases/src/org/graalvm/compiler/loop/phases/LoopUnswitchingPhase.java

/*
 * Copyright (c) 2012, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * 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.phases;

import java.util.Iterator;
import java.util.List;

import org.graalvm.compiler.debug.Debug;
import org.graalvm.compiler.debug.DebugCounter;
import org.graalvm.compiler.graph.Node;
import org.graalvm.compiler.loop.LoopEx;
import org.graalvm.compiler.loop.LoopPolicies;
import org.graalvm.compiler.loop.LoopsData;
import org.graalvm.compiler.nodes.AbstractBeginNode;
import org.graalvm.compiler.nodes.ControlSplitNode;
import org.graalvm.compiler.nodes.StructuredGraph;

public class LoopUnswitchingPhase extends ContextlessLoopPhase<LoopPolicies> {
    private static final DebugCounter UNSWITCHED = Debug.counter("Unswitched");
    private static final DebugCounter UNSWITCH_CANDIDATES = Debug.counter("UnswitchCandidates");
    private static final DebugCounter UNSWITCH_EARLY_REJECTS = Debug.counter("UnswitchEarlyRejects");

    public LoopUnswitchingPhase(LoopPolicies policies) {
        super(policies);
    }

    @Override
    protected void run(StructuredGraph graph) {
        if (graph.hasLoops()) {
            boolean unswitched;
            do {
                unswitched = false;
                final LoopsData dataUnswitch = new LoopsData(graph);
                for (LoopEx loop : dataUnswitch.outerFirst()) {
                    if (getPolicies().shouldTryUnswitch(loop)) {
                        List<ControlSplitNode> controlSplits = LoopTransformations.findUnswitchable(loop);
                        if (controlSplits != null) {
                            UNSWITCH_CANDIDATES.increment();
                            if (getPolicies().shouldUnswitch(loop, controlSplits)) {
                                if (Debug.isLogEnabled()) {
                                    logUnswitch(loop, controlSplits);
                                }
                                LoopTransformations.unswitch(loop, controlSplits);
                                Debug.dump(Debug.INFO_LOG_LEVEL, graph, "After unswitch %s", controlSplits);
                                UNSWITCHED.increment();
                                unswitched = true;
                                break;
                            }
                        }
                    } else {
                        UNSWITCH_EARLY_REJECTS.increment();
                    }
                }
            } while (unswitched);
        }
    }

    private static void logUnswitch(LoopEx loop, List<ControlSplitNode> controlSplits) {
        StringBuilder sb = new StringBuilder("Unswitching ");
        sb.append(loop).append(" at ");
        for (ControlSplitNode controlSplit : controlSplits) {
            sb.append(controlSplit).append(" [");
            Iterator<Node> it = controlSplit.successors().iterator();
            while (it.hasNext()) {
                sb.append(controlSplit.probability((AbstractBeginNode) it.next()));
                if (it.hasNext()) {
                    sb.append(", ");
                }
            }
            sb.append("]");
        }
        Debug.log("%s", sb);
    }

    @Override
    public float codeSizeIncrease() {
        return 10.0f;
    }
}