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2867
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1 /*
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2 * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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4 *
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5 * This code is free software; you can redistribute it and/or modify it
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6 * under the terms of the GNU General Public License version 2 only, as
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7 * published by the Free Software Foundation.
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8 *
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9 * This code is distributed in the hope that it will be useful, but WITHOUT
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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12 * version 2 for more details (a copy is included in the LICENSE file that
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13 * accompanied this code).
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14 *
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15 * You should have received a copy of the GNU General Public License version
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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18 *
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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20 * or visit www.oracle.com if you need additional information or have any
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21 * questions.
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22 */
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23 package com.sun.c1x.graph;
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24
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25 import java.util.*;
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26
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27 import com.oracle.graal.graph.*;
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28 import com.oracle.max.graal.schedule.*;
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29 import com.sun.c1x.*;
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30 import com.sun.c1x.gen.*;
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31 import com.sun.c1x.ir.*;
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32
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33
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34 public class DeadCodeElimination extends Phase {
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35
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36 private NodeBitMap alive;
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37 private Queue<Node> worklist;
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38 private Graph graph;
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39
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40 public int deletedNodeCount;
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41
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42 @Override
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43 protected void run(Graph graph) {
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44 this.graph = graph;
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45 this.alive = graph.createNodeBitMap();
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46 this.worklist = new ArrayDeque<Node>();
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47
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48 addToWorklist(graph.start());
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49
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50 iterateSuccessors();
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51 disconnectCFGNodes();
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52
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53 iterateInputs();
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54 disconnectNonCFGNodes();
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55
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56 deleteCFGNodes();
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57 deleteNonCFGNodes();
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58
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59 new PhiSimplifier(graph);
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60
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61 if (C1XOptions.TraceDeadCodeElimination) {
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62 System.out.printf("dead code elimination: deleted %d nodes\n", deletedNodeCount);
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63 }
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64 }
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65
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66 private void iterateSuccessors() {
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67 Node current;
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68 while ((current = nextNode()) != null) {
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69 for (Node successor : current.successors()) {
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70 addToWorklist(successor);
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71 }
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72 }
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73 }
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74
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75 private void disconnectCFGNodes() {
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76 for (Node node : graph.getNodes()) {
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77 if (node != Node.Null && !alive.isMarked(node) && Schedule.isCFG(node)) {
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78 // iterate backwards so that the predecessor indexes in removePhiPredecessor are correct
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79 for (int i = node.successors().size() - 1; i >= 0; i--) {
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80 Node successor = node.successors().get(i);
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81 if (successor != Node.Null && alive.isMarked(successor)) {
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82 if (successor instanceof Merge) {
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83 ((Merge) successor).removePhiPredecessor(node);
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84 }
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85 }
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86 }
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87 node.successors().clearAll();
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88 node.inputs().clearAll();
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89 }
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90 }
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91 }
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92
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93 private void deleteCFGNodes() {
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94 for (Node node : graph.getNodes()) {
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95 if (node != Node.Null && !alive.isMarked(node) && Schedule.isCFG(node)) {
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96 node.delete();
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97 deletedNodeCount++;
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98 }
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99 }
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100 }
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101
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102 private void iterateInputs() {
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103 for (Node node : graph.getNodes()) {
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104 if (node != Node.Null && alive.isMarked(node)) {
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105 for (Node input : node.inputs()) {
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106 addToWorklist(input);
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107 }
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108 }
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109 }
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110 Node current;
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111 while ((current = nextNode()) != null) {
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112 for (Node input : current.inputs()) {
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113 addToWorklist(input);
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114 }
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115 }
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116 }
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117
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118 private void disconnectNonCFGNodes() {
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119 for (Node node : graph.getNodes()) {
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120 if (node != Node.Null && !alive.isMarked(node) && !Schedule.isCFG(node)) {
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121 node.inputs().clearAll();
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122 }
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123 }
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124 }
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125
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126 private void deleteNonCFGNodes() {
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127 for (Node node : graph.getNodes()) {
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128 if (node != Node.Null && !alive.isMarked(node) && !Schedule.isCFG(node)) {
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129 node.delete();
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130 deletedNodeCount++;
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131 }
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132 }
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133 }
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134
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135 private Node nextNode() {
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136 return worklist.poll();
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137 }
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138
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139 private void addToWorklist(Node node) {
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140 if (node != null && !alive.isMarked(node)) {
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141 alive.mark(node);
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142 worklist.add(node);
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143 }
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144 }
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145 }
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