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annotate graal/GraalCompiler/src/com/sun/c1x/opt/PhiSimplifier.java @ 2509:16b9a8b5ad39

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Renamings Runtime=>GraalRuntime and Compiler=>GraalCompiler
author Thomas Wuerthinger <thomas@wuerthinger.net>
date Wed, 27 Apr 2011 11:50:44 +0200
parents graal/Compiler/src/com/sun/c1x/opt/PhiSimplifier.java@9ec15d6914ca
children
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2507
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1 /*
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2 * Copyright (c) 2009, 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.opt;
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24
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25 import com.sun.c1x.graph.IR;
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26 import com.sun.c1x.ir.*;
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27 import com.sun.c1x.value.*;
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28
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29 /**
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30 * The {@code PhiSimplifier} class is a helper class that can reduce phi instructions.
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31 *
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32 * @author Ben L. Titzer
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33 */
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34 public final class PhiSimplifier implements BlockClosure {
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35
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36 final IR ir;
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37 final InstructionSubstituter subst;
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38
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39 public PhiSimplifier(IR ir) {
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40 this.ir = ir;
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41 this.subst = new InstructionSubstituter(ir);
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42 ir.startBlock.iterateAnyOrder(this, false);
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43 subst.finish();
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44 }
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45
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46 /**
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47 * This method is called for each block and processes any phi statements in the block.
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48 * @param block the block to apply the simplification to
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49 */
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50 public void apply(BlockBegin block) {
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51 FrameState state = block.stateBefore();
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52 for (int i = 0; i < state.stackSize(); i++) {
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53 simplify(state.stackAt(i));
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54 }
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55 for (int i = 0; i < state.localsSize(); i++) {
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56 simplify(state.localAt(i));
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57 }
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58 }
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59
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60 Value simplify(Value x) {
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61 if (x == null || !(x instanceof Phi)) {
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62 return x;
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63 }
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64 Phi phi = (Phi) x;
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65 if (phi.hasSubst()) {
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66 // already substituted, but the subst could be a phi itself, so simplify
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67 return simplify(subst.getSubst(phi));
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68 } else if (phi.checkFlag(Value.Flag.PhiCannotSimplify)) {
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69 // already tried, cannot simplify this phi
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70 return phi;
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71 } else if (phi.checkFlag(Value.Flag.PhiVisited)) {
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72 // break cycles in phis
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73 return phi;
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74 } else if (phi.isIllegal()) {
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75 // don't bother with illegals
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76 return phi;
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77 } else {
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78 // attempt to simplify the phi by recursively simplifying its operands
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79 phi.setFlag(Value.Flag.PhiVisited);
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80 Value phiSubst = null;
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81 int max = phi.inputCount();
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82 boolean cannotSimplify = false;
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83 for (int i = 0; i < max; i++) {
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84 Value oldInstr = phi.inputAt(i);
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85
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86 if (oldInstr == null || oldInstr.isIllegal() || oldInstr.isDeadPhi()) {
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87 // if one operand is illegal, make the entire phi illegal
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88 phi.makeDead();
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89 phi.clearFlag(Value.Flag.PhiVisited);
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90 return phi;
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91 }
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92
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93 Value newInstr = simplify(oldInstr);
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94
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95 if (newInstr == null || newInstr.isIllegal() || newInstr.isDeadPhi()) {
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96 // if the subst instruction is illegal, make the entire phi illegal
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97 phi.makeDead();
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98 phi.clearFlag(Value.Flag.PhiVisited);
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99 return phi;
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100 }
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101
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102 // attempt to simplify this operand
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103 if (!cannotSimplify) {
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104
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105 if (newInstr != phi && newInstr != phiSubst) {
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106 if (phiSubst == null) {
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107 phiSubst = newInstr;
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108 continue;
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109 }
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110 // this phi cannot be simplified
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111 cannotSimplify = true;
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112 }
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113 }
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114 }
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115 if (cannotSimplify) {
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116 phi.setFlag(Value.Flag.PhiCannotSimplify);
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117 phi.clearFlag(Value.Flag.PhiVisited);
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118 return phi;
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119 }
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120
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121 // successfully simplified the phi
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122 assert phiSubst != null : "illegal phi function";
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123 phi.clearFlag(Value.Flag.PhiVisited);
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124 subst.setSubst(phi, phiSubst);
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125 return phiSubst;
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126 }
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127 }
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128 }