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 */ 23 package org.graalvm.compiler.java; 24 25 import java.util.List; 26 27 import org.graalvm.compiler.nodes.AbstractBeginNode; 28 import org.graalvm.compiler.nodes.AbstractMergeNode; 29 import org.graalvm.compiler.nodes.ControlSplitNode; 30 import org.graalvm.compiler.nodes.FixedNode; 31 import org.graalvm.compiler.nodes.LoopBeginNode; 32 import org.graalvm.compiler.nodes.LoopExitNode; 33 import org.graalvm.compiler.nodes.StructuredGraph; 34 import org.graalvm.compiler.nodes.cfg.ControlFlowGraph; 35 import org.graalvm.compiler.phases.Phase; 36 import org.graalvm.compiler.phases.graph.ReentrantNodeIterator; 37 import org.graalvm.util.EconomicMap; 38 39 public final class ComputeLoopFrequenciesClosure extends ReentrantNodeIterator.NodeIteratorClosure<Double> { 40 41 private static final ComputeLoopFrequenciesClosure INSTANCE = new ComputeLoopFrequenciesClosure(); 42 43 private ComputeLoopFrequenciesClosure() { 44 // nothing to do 45 } 46 47 @Override 48 protected Double processNode(FixedNode node, Double currentState) { 49 // normal nodes never change the probability of a path 50 return currentState; 51 } 52 53 @Override 54 protected Double merge(AbstractMergeNode merge, List<Double> states) { 55 // a merge has the sum of all predecessor probabilities 56 double result = 0.0; 57 for (double d : states) { 58 result += d; 59 } 60 return result; 61 } 62 63 @Override 64 protected Double afterSplit(AbstractBeginNode node, Double oldState) { 65 // a control split splits up the probability 66 ControlSplitNode split = (ControlSplitNode) node.predecessor(); 67 return oldState * split.probability(node); 68 } 69 70 @Override 71 protected EconomicMap<LoopExitNode, Double> processLoop(LoopBeginNode loop, Double initialState) { 72 EconomicMap<LoopExitNode, Double> exitStates = ReentrantNodeIterator.processLoop(this, loop, 1D).exitStates; 73 74 double exitProbability = 0.0; 75 for (double d : exitStates.getValues()) { 76 exitProbability += d; 77 } 78 exitProbability = Math.min(1D, exitProbability); 79 if (exitProbability < ControlFlowGraph.MIN_PROBABILITY) { 80 exitProbability = ControlFlowGraph.MIN_PROBABILITY; 81 } 82 assert exitProbability <= 1D && exitProbability >= 0D; 83 double loopFrequency = 1D / exitProbability; 84 loop.setLoopFrequency(loopFrequency); 85 86 double adjustmentFactor = initialState * loopFrequency; 87 exitStates.replaceAll((exitNode, probability) -> multiplySaturate(probability, adjustmentFactor)); 88 89 return exitStates; 90 } 91 92 /** 93 * Multiplies a and b and saturates the result to {@link ControlFlowGraph#MAX_PROBABILITY}. 94 */ 95 public static double multiplySaturate(double a, double b) { 96 double r = a * b; 97 if (r > ControlFlowGraph.MAX_PROBABILITY) { 98 return ControlFlowGraph.MAX_PROBABILITY; 99 } 100 return r; 101 } 102 103 /** 104 * Computes the frequencies of all loops in the given graph. This is done by performing a 105 * reverse postorder iteration and computing the probability of all fixed nodes. The combined 106 * probability of all exits of a loop can be used to compute the loop's expected frequency. 107 */ 108 public static void compute(StructuredGraph graph) { 109 if (graph.hasLoops()) { 110 ReentrantNodeIterator.apply(INSTANCE, graph.start(), 1D); 111 } 112 } 113 114 public static class ComputeLoopFrequencyPhase extends Phase { 115 116 @Override 117 protected void run(StructuredGraph graph) { 118 compute(graph); 119 } 120 } 121 122 public static final ComputeLoopFrequencyPhase PHASE_INSTANCE = new ComputeLoopFrequencyPhase(); 123 124 }