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//===--- TransBlockObjCVariable.cpp - Tranformations to ARC mode ----------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// rewriteBlockObjCVariable:
//
// Adding __block to an obj-c variable could be either because the the variable
// is used for output storage or the user wanted to break a retain cycle.
// This transformation checks whether a reference of the variable for the block
// is actually needed (it is assigned to or its address is taken) or not.
// If the reference is not needed it will assume __block was added to break a
// cycle so it will remove '__block' and add __weak/__unsafe_unretained.
// e.g
//
// __block Foo *x;
// bar(^ { [x cake]; });
// ---->
// __weak Foo *x;
// bar(^ { [x cake]; });
//
//===----------------------------------------------------------------------===//
#include "Transforms.h"
#include "Internals.h"
#include "clang/Basic/SourceManager.h"
using namespace clang;
using namespace arcmt;
using namespace trans;
namespace {
class RootBlockObjCVarRewriter :
public RecursiveASTVisitor<RootBlockObjCVarRewriter> {
MigrationPass &Pass;
llvm::DenseSet<VarDecl *> CheckedVars;
class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> {
VarDecl *Var;
typedef RecursiveASTVisitor<BlockVarChecker> base;
public:
BlockVarChecker(VarDecl *var) : Var(var) { }
bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) {
if (BlockDeclRefExpr *
ref = dyn_cast<BlockDeclRefExpr>(castE->getSubExpr())) {
if (ref->getDecl() == Var) {
if (castE->getCastKind() == CK_LValueToRValue)
return true; // Using the value of the variable.
if (castE->getCastKind() == CK_NoOp && castE->isLValue() &&
Var->getASTContext().getLangOptions().CPlusPlus)
return true; // Binding to const C++ reference.
}
}
return base::TraverseImplicitCastExpr(castE);
}
bool VisitBlockDeclRefExpr(BlockDeclRefExpr *E) {
if (E->getDecl() == Var)
return false; // The reference of the variable, and not just its value,
// is needed.
return true;
}
};
public:
RootBlockObjCVarRewriter(MigrationPass &pass) : Pass(pass) { }
bool VisitBlockDecl(BlockDecl *block) {
SmallVector<VarDecl *, 4> BlockVars;
for (BlockDecl::capture_iterator
I = block->capture_begin(), E = block->capture_end(); I != E; ++I) {
VarDecl *var = I->getVariable();
if (I->isByRef() &&
!isAlreadyChecked(var) &&
var->getType()->isObjCObjectPointerType() &&
isImplicitStrong(var->getType())) {
BlockVars.push_back(var);
}
}
for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) {
VarDecl *var = BlockVars[i];
CheckedVars.insert(var);
BlockVarChecker checker(var);
bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody());
if (onlyValueOfVarIsNeeded) {
BlocksAttr *attr = var->getAttr<BlocksAttr>();
if(!attr)
continue;
bool useWeak = canApplyWeak(Pass.Ctx, var->getType());
SourceManager &SM = Pass.Ctx.getSourceManager();
Transaction Trans(Pass.TA);
Pass.TA.replaceText(SM.getInstantiationLoc(attr->getLocation()),
"__block",
useWeak ? "__weak" : "__unsafe_unretained");
}
}
return true;
}
private:
bool isAlreadyChecked(VarDecl *VD) {
return CheckedVars.count(VD);
}
bool isImplicitStrong(QualType ty) {
if (isa<AttributedType>(ty.getTypePtr()))
return false;
return ty.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong;
}
};
class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> {
MigrationPass &Pass;
public:
BlockObjCVarRewriter(MigrationPass &pass) : Pass(pass) { }
bool TraverseBlockDecl(BlockDecl *block) {
RootBlockObjCVarRewriter(Pass).TraverseDecl(block);
return true;
}
};
} // anonymous namespace
void trans::rewriteBlockObjCVariable(MigrationPass &pass) {
BlockObjCVarRewriter trans(pass);
trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
}
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