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//===--- TransBlockObjCVariable.cpp - Transformations to ARC mode ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// rewriteBlockObjCVariable:
//
// Adding __block to an obj-c variable could be either because 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/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/Basic/SourceManager.h"
using namespace clang;
using namespace arcmt;
using namespace trans;
namespace {
class RootBlockObjCVarRewriter :
public RecursiveASTVisitor<RootBlockObjCVarRewriter> {
llvm::DenseSet<VarDecl *> &VarsToChange;
class BlockVarChecker : public RecursiveASTVisitor<BlockVarChecker> {
VarDecl *Var;
typedef RecursiveASTVisitor<BlockVarChecker> base;
public:
BlockVarChecker(VarDecl *var) : Var(var) { }
bool TraverseImplicitCastExpr(ImplicitCastExpr *castE) {
if (DeclRefExpr *
ref = dyn_cast<DeclRefExpr>(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().getLangOpts().CPlusPlus)
return true; // Binding to const C++ reference.
}
}
return base::TraverseImplicitCastExpr(castE);
}
bool VisitDeclRefExpr(DeclRefExpr *E) {
if (E->getDecl() == Var)
return false; // The reference of the variable, and not just its value,
// is needed.
return true;
}
};
public:
RootBlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange)
: VarsToChange(VarsToChange) { }
bool VisitBlockDecl(BlockDecl *block) {
SmallVector<VarDecl *, 4> BlockVars;
for (const auto &I : block->captures()) {
VarDecl *var = I.getVariable();
if (I.isByRef() &&
var->getType()->isObjCObjectPointerType() &&
isImplicitStrong(var->getType())) {
BlockVars.push_back(var);
}
}
for (unsigned i = 0, e = BlockVars.size(); i != e; ++i) {
VarDecl *var = BlockVars[i];
BlockVarChecker checker(var);
bool onlyValueOfVarIsNeeded = checker.TraverseStmt(block->getBody());
if (onlyValueOfVarIsNeeded)
VarsToChange.insert(var);
else
VarsToChange.erase(var);
}
return true;
}
private:
bool isImplicitStrong(QualType ty) {
if (isa<AttributedType>(ty.getTypePtr()))
return false;
return ty.getLocalQualifiers().getObjCLifetime() == Qualifiers::OCL_Strong;
}
};
class BlockObjCVarRewriter : public RecursiveASTVisitor<BlockObjCVarRewriter> {
llvm::DenseSet<VarDecl *> &VarsToChange;
public:
BlockObjCVarRewriter(llvm::DenseSet<VarDecl *> &VarsToChange)
: VarsToChange(VarsToChange) { }
bool TraverseBlockDecl(BlockDecl *block) {
RootBlockObjCVarRewriter(VarsToChange).TraverseDecl(block);
return true;
}
};
} // anonymous namespace
void BlockObjCVariableTraverser::traverseBody(BodyContext &BodyCtx) {
MigrationPass &Pass = BodyCtx.getMigrationContext().Pass;
llvm::DenseSet<VarDecl *> VarsToChange;
BlockObjCVarRewriter trans(VarsToChange);
trans.TraverseStmt(BodyCtx.getTopStmt());
for (llvm::DenseSet<VarDecl *>::iterator
I = VarsToChange.begin(), E = VarsToChange.end(); I != E; ++I) {
VarDecl *var = *I;
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.getExpansionLoc(attr->getLocation()),
"__block",
useWeak ? "__weak" : "__unsafe_unretained");
}
}
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