1 //===--- TransBlockObjCVariable.cpp - Transformations to ARC mode ---------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // rewriteBlockObjCVariable:
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.
21 // bar(^ { [x cake]; });
24 // bar(^ { [x cake]; });
26 //===----------------------------------------------------------------------===//
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"
34 using namespace clang;
35 using namespace arcmt;
36 using namespace trans;
40 class RootBlockObjCVarRewriter :
41 public RecursiveASTVisitor<RootBlockObjCVarRewriter> {
42 llvm::DenseSet<VarDecl *> &VarsToChange;
44 class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> {
47 typedef RecursiveASTVisitor<BlockVarChecker> base;
49 BlockVarChecker(VarDecl *var) : Var(var) { }
51 bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) {
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.
63 return base::TraverseImplicitCastExpr(castE);
66 bool VisitDeclRefExpr(DeclRefExpr *E) {
67 if (E->getDecl() == Var)
68 return false; // The reference of the variable, and not just its value,
75 RootBlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange)
76 : VarsToChange(VarsToChange) { }
78 bool VisitBlockDecl(BlockDecl *block) {
79 SmallVector<VarDecl *, 4> BlockVars;
81 for (const auto &I : block->captures()) {
82 VarDecl *var = I.getVariable();
84 var->getType()->isObjCObjectPointerType() &&
85 isImplicitStrong(var->getType())) {
86 BlockVars.push_back(var);
90 for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) {
91 VarDecl *var = BlockVars[i];
93 BlockVarChecker checker(var);
94 bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody());
95 if (onlyValueOfVarIsNeeded)
96 VarsToChange.insert(var);
98 VarsToChange.erase(var);
105 bool isImplicitStrong(QualType ty) {
106 if (isa<AttributedType>(ty.getTypePtr()))
108 return ty.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong;
112 class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> {
113 llvm::DenseSet<VarDecl *> &VarsToChange;
116 BlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange)
117 : VarsToChange(VarsToChange) { }
119 bool TraverseBlockDecl(BlockDecl *block) {
120 RootBlockObjCVarRewriter(VarsToChange).TraverseDecl(block);
125 } // anonymous namespace
127 void BlockObjCVariableTraverser::traverseBody(BodyContext &BodyCtx) {
128 MigrationPass &Pass = BodyCtx.getMigrationContext().Pass;
129 llvm::DenseSet<VarDecl *> VarsToChange;
131 BlockObjCVarRewriter trans(VarsToChange);
132 trans.TraverseStmt(BodyCtx.getTopStmt());
134 for (llvm::DenseSet<VarDecl *>::iterator
135 I = VarsToChange.begin(), E = VarsToChange.end(); I != E; ++I) {
137 BlocksAttr *attr = var->getAttr<BlocksAttr>();
140 bool useWeak = canApplyWeak(Pass.Ctx, var->getType());
141 SourceManager &SM = Pass.Ctx.getSourceManager();
142 Transaction Trans(Pass.TA);
143 Pass.TA.replaceText(SM.getExpansionLoc(attr->getLocation()),
145 useWeak ? "__weak" : "__unsafe_unretained");