1 //===--- TransBlockObjCVariable.cpp - Tranformations 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 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/Basic/SourceManager.h"
32 using namespace clang;
33 using namespace arcmt;
34 using namespace trans;
35 using llvm::StringRef;
39 class RootBlockObjCVarRewriter :
40 public RecursiveASTVisitor<RootBlockObjCVarRewriter> {
42 llvm::DenseSet<VarDecl *> CheckedVars;
44 class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> {
47 typedef RecursiveASTVisitor<BlockVarChecker> base;
49 BlockVarChecker(VarDecl *var) : Var(var) { }
51 bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) {
52 if (BlockDeclRefExpr *
53 ref = dyn_cast<BlockDeclRefExpr>(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().getLangOptions().CPlusPlus)
59 return true; // Binding to const C++ reference.
63 return base::TraverseImplicitCastExpr(castE);
66 bool VisitBlockDeclRefExpr(BlockDeclRefExpr *E) {
67 if (E->getDecl() == Var)
68 return false; // The reference of the variable, and not just its value,
75 RootBlockObjCVarRewriter(MigrationPass &pass) : Pass(pass) { }
77 bool VisitBlockDecl(BlockDecl *block) {
78 llvm::SmallVector<VarDecl *, 4> BlockVars;
80 for (BlockDecl::capture_iterator
81 I = block->capture_begin(), E = block->capture_end(); I != E; ++I) {
82 VarDecl *var = I->getVariable();
84 !isAlreadyChecked(var) &&
85 var->getType()->isObjCObjectPointerType() &&
86 isImplicitStrong(var->getType())) {
87 BlockVars.push_back(var);
91 for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) {
92 VarDecl *var = BlockVars[i];
93 CheckedVars.insert(var);
95 BlockVarChecker checker(var);
96 bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody());
97 if (onlyValueOfVarIsNeeded) {
98 BlocksAttr *attr = var->getAttr<BlocksAttr>();
101 bool useWeak = canApplyWeak(Pass.Ctx, var->getType());
102 SourceManager &SM = Pass.Ctx.getSourceManager();
103 Transaction Trans(Pass.TA);
104 Pass.TA.replaceText(SM.getInstantiationLoc(attr->getLocation()),
106 useWeak ? "__weak" : "__unsafe_unretained");
115 bool isAlreadyChecked(VarDecl *VD) {
116 return CheckedVars.count(VD);
119 bool isImplicitStrong(QualType ty) {
120 if (isa<AttributedType>(ty.getTypePtr()))
122 return ty.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong;
126 class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> {
130 BlockObjCVarRewriter(MigrationPass &pass) : Pass(pass) { }
132 bool TraverseBlockDecl(BlockDecl *block) {
133 RootBlockObjCVarRewriter(Pass).TraverseDecl(block);
138 } // anonymous namespace
140 void trans::rewriteBlockObjCVariable(MigrationPass &pass) {
141 BlockObjCVarRewriter trans(pass);
142 trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());