1//===--- TransBlockObjCVariable.cpp - Transformations to ARC mode ---------===// 2// 3// The LLVM Compiler Infrastructure 4// 5// This file is distributed under the University of Illinois Open Source 6// License. See LICENSE.TXT for details. 7// 8//===----------------------------------------------------------------------===// 9// 10// rewriteBlockObjCVariable: 11// 12// Adding __block to an obj-c variable could be either because the variable 13// is used for output storage or the user wanted to break a retain cycle. 14// This transformation checks whether a reference of the variable for the block 15// is actually needed (it is assigned to or its address is taken) or not. 16// If the reference is not needed it will assume __block was added to break a 17// cycle so it will remove '__block' and add __weak/__unsafe_unretained. 18// e.g 19// 20// __block Foo *x; 21// bar(^ { [x cake]; }); 22// ----> 23// __weak Foo *x; 24// bar(^ { [x cake]; }); 25// 26//===----------------------------------------------------------------------===// 27 28#include "Transforms.h" 29#include "Internals.h" 30#include "clang/AST/ASTContext.h" 31#include "clang/AST/Attr.h" 32#include "clang/Basic/SourceManager.h" 33 34using namespace clang; 35using namespace arcmt; 36using namespace trans; 37 38namespace { 39 40class RootBlockObjCVarRewriter : 41 public RecursiveASTVisitor<RootBlockObjCVarRewriter> { 42 llvm::DenseSet<VarDecl *> &VarsToChange; 43 44 class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> { 45 VarDecl *Var; 46 47 typedef RecursiveASTVisitor<BlockVarChecker> base; 48 public: 49 BlockVarChecker(VarDecl *var) : Var(var) { } 50 51 bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) { 52 if (DeclRefExpr * 53 ref = dyn_cast<DeclRefExpr>(castE->getSubExpr())) { 54 if (ref->getDecl() == Var) { 55 if (castE->getCastKind() == CK_LValueToRValue) 56 return true; // Using the value of the variable. 57 if (castE->getCastKind() == CK_NoOp && castE->isLValue() && 58 Var->getASTContext().getLangOpts().CPlusPlus) 59 return true; // Binding to const C++ reference. 60 } 61 } 62 63 return base::TraverseImplicitCastExpr(castE); 64 } 65 66 bool VisitDeclRefExpr(DeclRefExpr *E) { 67 if (E->getDecl() == Var) 68 return false; // The reference of the variable, and not just its value, 69 // is needed. 70 return true; 71 } 72 }; 73 74public: 75 RootBlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange) 76 : VarsToChange(VarsToChange) { } 77 78 bool VisitBlockDecl(BlockDecl *block) { 79 SmallVector<VarDecl *, 4> BlockVars; 80 81 for (BlockDecl::capture_iterator 82 I = block->capture_begin(), E = block->capture_end(); I != E; ++I) { 83 VarDecl *var = I->getVariable(); 84 if (I->isByRef() && 85 var->getType()->isObjCObjectPointerType() && 86 isImplicitStrong(var->getType())) { 87 BlockVars.push_back(var); 88 } 89 } 90 91 for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) { 92 VarDecl *var = BlockVars[i]; 93 94 BlockVarChecker checker(var); 95 bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody()); 96 if (onlyValueOfVarIsNeeded) 97 VarsToChange.insert(var); 98 else 99 VarsToChange.erase(var); 100 } 101 102 return true; 103 } 104 105private: 106 bool isImplicitStrong(QualType ty) { 107 if (isa<AttributedType>(ty.getTypePtr())) 108 return false; 109 return ty.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong; 110 } 111}; 112 113class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> { 114 llvm::DenseSet<VarDecl *> &VarsToChange; 115 116public: 117 BlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange) 118 : VarsToChange(VarsToChange) { } 119 120 bool TraverseBlockDecl(BlockDecl *block) { 121 RootBlockObjCVarRewriter(VarsToChange).TraverseDecl(block); 122 return true; 123 } 124}; 125 126} // anonymous namespace 127 128void BlockObjCVariableTraverser::traverseBody(BodyContext &BodyCtx) { 129 MigrationPass &Pass = BodyCtx.getMigrationContext().Pass; 130 llvm::DenseSet<VarDecl *> VarsToChange; 131 132 BlockObjCVarRewriter trans(VarsToChange); 133 trans.TraverseStmt(BodyCtx.getTopStmt()); 134 135 for (llvm::DenseSet<VarDecl *>::iterator 136 I = VarsToChange.begin(), E = VarsToChange.end(); I != E; ++I) { 137 VarDecl *var = *I; 138 BlocksAttr *attr = var->getAttr<BlocksAttr>(); 139 if(!attr) 140 continue; 141 bool useWeak = canApplyWeak(Pass.Ctx, var->getType()); 142 SourceManager &SM = Pass.Ctx.getSourceManager(); 143 Transaction Trans(Pass.TA); 144 Pass.TA.replaceText(SM.getExpansionLoc(attr->getLocation()), 145 "__block", 146 useWeak ? "__weak" : "__unsafe_unretained"); 147 } 148} 149