1/* 2 * Copyright (c) 2011, 2014, 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. 8 * 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. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23package org.graalvm.compiler.java; 24 25import java.util.List; 26 27import org.graalvm.compiler.nodes.AbstractBeginNode; 28import org.graalvm.compiler.nodes.AbstractMergeNode; 29import org.graalvm.compiler.nodes.ControlSplitNode; 30import org.graalvm.compiler.nodes.FixedNode; 31import org.graalvm.compiler.nodes.LoopBeginNode; 32import org.graalvm.compiler.nodes.LoopExitNode; 33import org.graalvm.compiler.nodes.StructuredGraph; 34import org.graalvm.compiler.nodes.cfg.ControlFlowGraph; 35import org.graalvm.compiler.phases.Phase; 36import org.graalvm.compiler.phases.graph.ReentrantNodeIterator; 37import org.graalvm.util.EconomicMap; 38 39import static org.graalvm.compiler.nodes.cfg.ControlFlowGraph.multiplyProbabilities; 40 41public final class ComputeLoopFrequenciesClosure extends ReentrantNodeIterator.NodeIteratorClosure<Double> { 42 43 private static final ComputeLoopFrequenciesClosure INSTANCE = new ComputeLoopFrequenciesClosure(); 44 45 private ComputeLoopFrequenciesClosure() { 46 // nothing to do 47 } 48 49 @Override 50 protected Double processNode(FixedNode node, Double currentState) { 51 // normal nodes never change the probability of a path 52 return currentState; 53 } 54 55 @Override 56 protected Double merge(AbstractMergeNode merge, List<Double> states) { 57 // a merge has the sum of all predecessor probabilities 58 double result = 0.0; 59 for (double d : states) { 60 result += d; 61 } 62 return result; 63 } 64 65 @Override 66 protected Double afterSplit(AbstractBeginNode node, Double oldState) { 67 // a control split splits up the probability 68 ControlSplitNode split = (ControlSplitNode) node.predecessor(); 69 return oldState * split.probability(node); 70 } 71 72 @Override 73 protected EconomicMap<LoopExitNode, Double> processLoop(LoopBeginNode loop, Double initialState) { 74 EconomicMap<LoopExitNode, Double> exitStates = ReentrantNodeIterator.processLoop(this, loop, 1D).exitStates; 75 76 double exitProbability = 0.0; 77 for (double d : exitStates.getValues()) { 78 exitProbability += d; 79 } 80 exitProbability = Math.min(1.0, exitProbability); 81 exitProbability = Math.max(ControlFlowGraph.MIN_PROBABILITY, exitProbability); 82 double loopFrequency = 1.0 / exitProbability; 83 loop.setLoopFrequency(loopFrequency); 84 85 double adjustmentFactor = initialState * loopFrequency; 86 exitStates.replaceAll((exitNode, probability) -> multiplyProbabilities(probability, adjustmentFactor)); 87 88 return exitStates; 89 } 90 91 /** 92 * Computes the frequencies of all loops in the given graph. This is done by performing a 93 * reverse postorder iteration and computing the probability of all fixed nodes. The combined 94 * probability of all exits of a loop can be used to compute the loop's expected frequency. 95 */ 96 public static void compute(StructuredGraph graph) { 97 if (graph.hasLoops()) { 98 ReentrantNodeIterator.apply(INSTANCE, graph.start(), 1D); 99 } 100 } 101 102 public static class ComputeLoopFrequencyPhase extends Phase { 103 104 @Override 105 protected void run(StructuredGraph graph) { 106 compute(graph); 107 } 108 } 109 110 public static final ComputeLoopFrequencyPhase PHASE_INSTANCE = new ComputeLoopFrequencyPhase(); 111 112} 113