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1 //===-- TransEmptyStatementsAndDealloc.cpp - Transformations to ARC mode --===//
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2 //
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3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
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4 // See https://llvm.org/LICENSE.txt for license information.
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5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
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6 //
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7 //===----------------------------------------------------------------------===//
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8 //
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9 // removeEmptyStatementsAndDealloc:
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10 //
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11 // Removes empty statements that are leftovers from previous transformations.
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12 // e.g for
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13 //
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14 // [x retain];
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15 //
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16 // removeRetainReleaseDealloc will leave an empty ";" that removeEmptyStatements
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17 // will remove.
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18 //
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19 //===----------------------------------------------------------------------===//
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20
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21 #include "Transforms.h"
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22 #include "Internals.h"
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23 #include "clang/AST/ASTContext.h"
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24 #include "clang/AST/StmtVisitor.h"
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25 #include "clang/Basic/SourceManager.h"
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26
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27 using namespace clang;
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28 using namespace arcmt;
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29 using namespace trans;
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30
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31 static bool isEmptyARCMTMacroStatement(NullStmt *S,
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32 std::vector<SourceLocation> &MacroLocs,
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33 ASTContext &Ctx) {
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34 if (!S->hasLeadingEmptyMacro())
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35 return false;
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36
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37 SourceLocation SemiLoc = S->getSemiLoc();
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38 if (SemiLoc.isInvalid() || SemiLoc.isMacroID())
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39 return false;
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40
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41 if (MacroLocs.empty())
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42 return false;
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43
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44 SourceManager &SM = Ctx.getSourceManager();
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45 std::vector<SourceLocation>::iterator I = llvm::upper_bound(
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46 MacroLocs, SemiLoc, BeforeThanCompare<SourceLocation>(SM));
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47 --I;
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48 SourceLocation
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49 AfterMacroLoc = I->getLocWithOffset(getARCMTMacroName().size());
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50 assert(AfterMacroLoc.isFileID());
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51
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52 if (AfterMacroLoc == SemiLoc)
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53 return true;
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54
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55 int RelOffs = 0;
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56 if (!SM.isInSameSLocAddrSpace(AfterMacroLoc, SemiLoc, &RelOffs))
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57 return false;
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58 if (RelOffs < 0)
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59 return false;
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60
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61 // We make the reasonable assumption that a semicolon after 100 characters
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62 // means that it is not the next token after our macro. If this assumption
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63 // fails it is not critical, we will just fail to clear out, e.g., an empty
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64 // 'if'.
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65 if (RelOffs - getARCMTMacroName().size() > 100)
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66 return false;
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67
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68 SourceLocation AfterMacroSemiLoc = findSemiAfterLocation(AfterMacroLoc, Ctx);
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69 return AfterMacroSemiLoc == SemiLoc;
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70 }
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71
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72 namespace {
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73
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74 /// Returns true if the statement became empty due to previous
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75 /// transformations.
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76 class EmptyChecker : public StmtVisitor<EmptyChecker, bool> {
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77 ASTContext &Ctx;
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78 std::vector<SourceLocation> &MacroLocs;
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79
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80 public:
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81 EmptyChecker(ASTContext &ctx, std::vector<SourceLocation> ¯oLocs)
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82 : Ctx(ctx), MacroLocs(macroLocs) { }
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83
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84 bool VisitNullStmt(NullStmt *S) {
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85 return isEmptyARCMTMacroStatement(S, MacroLocs, Ctx);
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86 }
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87 bool VisitCompoundStmt(CompoundStmt *S) {
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88 if (S->body_empty())
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89 return false; // was already empty, not because of transformations.
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90 for (auto *I : S->body())
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91 if (!Visit(I))
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92 return false;
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93 return true;
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94 }
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95 bool VisitIfStmt(IfStmt *S) {
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96 if (S->getConditionVariable())
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97 return false;
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98 Expr *condE = S->getCond();
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99 if (!condE)
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100 return false;
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101 if (hasSideEffects(condE, Ctx))
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102 return false;
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103 if (!S->getThen() || !Visit(S->getThen()))
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104 return false;
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105 return !S->getElse() || Visit(S->getElse());
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106 }
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107 bool VisitWhileStmt(WhileStmt *S) {
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108 if (S->getConditionVariable())
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109 return false;
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110 Expr *condE = S->getCond();
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111 if (!condE)
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112 return false;
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113 if (hasSideEffects(condE, Ctx))
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114 return false;
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115 if (!S->getBody())
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116 return false;
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117 return Visit(S->getBody());
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118 }
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119 bool VisitDoStmt(DoStmt *S) {
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120 Expr *condE = S->getCond();
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121 if (!condE)
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122 return false;
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123 if (hasSideEffects(condE, Ctx))
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124 return false;
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125 if (!S->getBody())
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126 return false;
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127 return Visit(S->getBody());
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128 }
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129 bool VisitObjCForCollectionStmt(ObjCForCollectionStmt *S) {
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130 Expr *Exp = S->getCollection();
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131 if (!Exp)
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132 return false;
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133 if (hasSideEffects(Exp, Ctx))
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134 return false;
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135 if (!S->getBody())
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136 return false;
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137 return Visit(S->getBody());
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138 }
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139 bool VisitObjCAutoreleasePoolStmt(ObjCAutoreleasePoolStmt *S) {
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140 if (!S->getSubStmt())
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141 return false;
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142 return Visit(S->getSubStmt());
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143 }
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144 };
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145
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146 class EmptyStatementsRemover :
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147 public RecursiveASTVisitor<EmptyStatementsRemover> {
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148 MigrationPass &Pass;
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149
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150 public:
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151 EmptyStatementsRemover(MigrationPass &pass) : Pass(pass) { }
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152
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153 bool TraverseStmtExpr(StmtExpr *E) {
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154 CompoundStmt *S = E->getSubStmt();
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155 for (CompoundStmt::body_iterator
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156 I = S->body_begin(), E = S->body_end(); I != E; ++I) {
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157 if (I != E - 1)
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158 check(*I);
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159 TraverseStmt(*I);
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160 }
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161 return true;
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162 }
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163
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164 bool VisitCompoundStmt(CompoundStmt *S) {
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165 for (auto *I : S->body())
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166 check(I);
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167 return true;
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168 }
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169
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170 ASTContext &getContext() { return Pass.Ctx; }
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171
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172 private:
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173 void check(Stmt *S) {
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174 if (!S) return;
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175 if (EmptyChecker(Pass.Ctx, Pass.ARCMTMacroLocs).Visit(S)) {
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176 Transaction Trans(Pass.TA);
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177 Pass.TA.removeStmt(S);
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178 }
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179 }
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180 };
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181
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182 } // anonymous namespace
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183
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184 static bool isBodyEmpty(CompoundStmt *body, ASTContext &Ctx,
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185 std::vector<SourceLocation> &MacroLocs) {
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186 for (auto *I : body->body())
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187 if (!EmptyChecker(Ctx, MacroLocs).Visit(I))
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188 return false;
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189
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190 return true;
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191 }
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192
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193 static void cleanupDeallocOrFinalize(MigrationPass &pass) {
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194 ASTContext &Ctx = pass.Ctx;
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195 TransformActions &TA = pass.TA;
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196 DeclContext *DC = Ctx.getTranslationUnitDecl();
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197 Selector FinalizeSel =
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198 Ctx.Selectors.getNullarySelector(&pass.Ctx.Idents.get("finalize"));
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199
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200 typedef DeclContext::specific_decl_iterator<ObjCImplementationDecl>
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201 impl_iterator;
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202 for (impl_iterator I = impl_iterator(DC->decls_begin()),
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203 E = impl_iterator(DC->decls_end()); I != E; ++I) {
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204 ObjCMethodDecl *DeallocM = nullptr;
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205 ObjCMethodDecl *FinalizeM = nullptr;
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206 for (auto *MD : I->instance_methods()) {
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207 if (!MD->hasBody())
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208 continue;
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209
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210 if (MD->getMethodFamily() == OMF_dealloc) {
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211 DeallocM = MD;
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212 } else if (MD->isInstanceMethod() && MD->getSelector() == FinalizeSel) {
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213 FinalizeM = MD;
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214 }
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215 }
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216
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217 if (DeallocM) {
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218 if (isBodyEmpty(DeallocM->getCompoundBody(), Ctx, pass.ARCMTMacroLocs)) {
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219 Transaction Trans(TA);
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220 TA.remove(DeallocM->getSourceRange());
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221 }
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222
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223 if (FinalizeM) {
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224 Transaction Trans(TA);
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225 TA.remove(FinalizeM->getSourceRange());
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226 }
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227
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228 } else if (FinalizeM) {
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229 if (isBodyEmpty(FinalizeM->getCompoundBody(), Ctx, pass.ARCMTMacroLocs)) {
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230 Transaction Trans(TA);
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231 TA.remove(FinalizeM->getSourceRange());
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232 } else {
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233 Transaction Trans(TA);
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234 TA.replaceText(FinalizeM->getSelectorStartLoc(), "finalize", "dealloc");
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235 }
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236 }
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237 }
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238 }
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239
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240 void trans::removeEmptyStatementsAndDeallocFinalize(MigrationPass &pass) {
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241 EmptyStatementsRemover(pass).TraverseDecl(pass.Ctx.getTranslationUnitDecl());
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242
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243 cleanupDeallocOrFinalize(pass);
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244
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245 for (unsigned i = 0, e = pass.ARCMTMacroLocs.size(); i != e; ++i) {
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246 Transaction Trans(pass.TA);
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247 pass.TA.remove(pass.ARCMTMacroLocs[i]);
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248 }
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249 }
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