1 /* 2 * Copyright (c) 2015, 2015, 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.core.common.alloc; 24 25 import java.util.ArrayList; 26 import java.util.BitSet; 27 import java.util.List; 28 import java.util.PriorityQueue; 29 30 import org.graalvm.compiler.core.common.alloc.TraceBuilderResult.TrivialTracePredicate; 31 import org.graalvm.compiler.core.common.cfg.AbstractBlockBase; 32 import org.graalvm.compiler.debug.Debug; 33 import org.graalvm.compiler.debug.Indent; 34 35 /** 36 * Computes traces by starting at a trace head and keep adding predecessors as long as possible. 37 */ 38 public final class UniDirectionalTraceBuilder { 39 40 public static TraceBuilderResult computeTraces(AbstractBlockBase<?> startBlock, AbstractBlockBase<?>[] blocks, TrivialTracePredicate pred) { 41 return new UniDirectionalTraceBuilder(blocks).build(startBlock, blocks, pred); 42 } 43 44 private final PriorityQueue<AbstractBlockBase<?>> worklist; 45 private final BitSet processed; 46 /** 47 * Contains the number of unprocessed predecessors for every {@link AbstractBlockBase#getId() 48 * block}. 49 */ 50 private final int[] blocked; 51 private final Trace[] blockToTrace; 52 53 private UniDirectionalTraceBuilder(AbstractBlockBase<?>[] blocks) { 54 processed = new BitSet(blocks.length); 55 worklist = new PriorityQueue<>(UniDirectionalTraceBuilder::compare); 56 assert (worklist != null); 57 58 blocked = new int[blocks.length]; 59 blockToTrace = new Trace[blocks.length]; 60 for (AbstractBlockBase<?> block : blocks) { 61 blocked[block.getId()] = block.getPredecessorCount(); 62 } 63 } 64 65 private static int compare(AbstractBlockBase<?> a, AbstractBlockBase<?> b) { 66 return Double.compare(b.probability(), a.probability()); 67 } 68 69 private boolean processed(AbstractBlockBase<?> b) { 70 return processed.get(b.getId()); 71 } 72 73 @SuppressWarnings("try") 74 private TraceBuilderResult build(AbstractBlockBase<?> startBlock, AbstractBlockBase<?>[] blocks, TrivialTracePredicate pred) { 75 try (Indent indent = Debug.logAndIndent("UniDirectionalTraceBuilder: start trace building: %s", startBlock)) { 76 ArrayList<Trace> traces = buildTraces(startBlock); 77 return TraceBuilderResult.create(blocks, traces, blockToTrace, pred); 78 } 79 } 80 81 protected ArrayList<Trace> buildTraces(AbstractBlockBase<?> startBlock) { 82 ArrayList<Trace> traces = new ArrayList<>(); 83 // add start block 84 worklist.add(startBlock); 85 // process worklist 86 while (!worklist.isEmpty()) { 87 AbstractBlockBase<?> block = worklist.poll(); 88 assert block != null; 89 if (!processed(block)) { 90 Trace trace = new Trace(startTrace(block)); 91 for (AbstractBlockBase<?> traceBlock : trace.getBlocks()) { 92 blockToTrace[traceBlock.getId()] = trace; 93 } 94 trace.setId(traces.size()); 95 traces.add(trace); 96 } 97 } 98 return traces; 99 } 100 101 /** 102 * Build a new trace starting at {@code block}. 103 */ 104 @SuppressWarnings("try") 105 private List<AbstractBlockBase<?>> startTrace(AbstractBlockBase<?> block) { 106 assert checkPredecessorsProcessed(block); 107 ArrayList<AbstractBlockBase<?>> trace = new ArrayList<>(); 108 int blockNumber = 0; 109 try (Indent i = Debug.logAndIndent("StartTrace: %s", block)) { 110 for (AbstractBlockBase<?> currentBlock = block; currentBlock != null; currentBlock = selectNext(currentBlock)) { 111 Debug.log("add %s (prob: %f)", currentBlock, currentBlock.probability()); 112 processed.set(currentBlock.getId()); 113 trace.add(currentBlock); 114 unblock(currentBlock); 115 currentBlock.setLinearScanNumber(blockNumber++); 116 } 117 } 118 return trace; 119 } 120 121 private boolean checkPredecessorsProcessed(AbstractBlockBase<?> block) { 122 for (AbstractBlockBase<?> pred : block.getPredecessors()) { 123 if (!processed(pred)) { 124 assert false : "Predecessor unscheduled: " + pred; 125 return false; 126 } 127 128 } 129 return true; 130 } 131 132 /** 133 * Decrease the {@link #blocked} count for all predecessors and add them to the worklist once 134 * the count reaches 0. 135 */ 136 private void unblock(AbstractBlockBase<?> currentBlock) { 137 for (AbstractBlockBase<?> successor : currentBlock.getSuccessors()) { 138 if (!processed(successor)) { 139 int blockCount = --blocked[successor.getId()]; 140 assert blockCount >= 0; 141 if (blockCount == 0) { 142 worklist.add(successor); 143 } 144 } 145 } 146 } 147 148 /** 149 * @return The unprocessed predecessor with the highest probability, or {@code null}. 150 */ 151 private AbstractBlockBase<?> selectNext(AbstractBlockBase<?> currentBlock) { 152 AbstractBlockBase<?> next = null; 153 for (AbstractBlockBase<?> succ : currentBlock.getSuccessors()) { 154 if (!processed(succ) && (next == null || succ.probability() > next.probability())) { 155 next = succ; 156 } 157 } 158 return next; 159 } 160 }