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//===--- TransZeroOutPropsInDealloc.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
//
//===----------------------------------------------------------------------===//
//
// removeZeroOutPropsInDealloc:
//
// Removes zero'ing out "strong" @synthesized properties in a -dealloc method.
//
//===----------------------------------------------------------------------===//
#include "Transforms.h"
#include "Internals.h"
#include "clang/AST/ASTContext.h"
using namespace clang;
using namespace arcmt;
using namespace trans;
namespace {
class ZeroOutInDeallocRemover :
public RecursiveASTVisitor<ZeroOutInDeallocRemover> {
typedef RecursiveASTVisitor<ZeroOutInDeallocRemover> base;
MigrationPass &Pass;
llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*> SynthesizedProperties;
ImplicitParamDecl *SelfD;
ExprSet Removables;
Selector FinalizeSel;
public:
ZeroOutInDeallocRemover(MigrationPass &pass) : Pass(pass), SelfD(nullptr) {
FinalizeSel =
Pass.Ctx.Selectors.getNullarySelector(&Pass.Ctx.Idents.get("finalize"));
}
bool VisitObjCMessageExpr(ObjCMessageExpr *ME) {
ASTContext &Ctx = Pass.Ctx;
TransformActions &TA = Pass.TA;
if (ME->getReceiverKind() != ObjCMessageExpr::Instance)
return true;
Expr *receiver = ME->getInstanceReceiver();
if (!receiver)
return true;
DeclRefExpr *refE = dyn_cast<DeclRefExpr>(receiver->IgnoreParenCasts());
if (!refE || refE->getDecl() != SelfD)
return true;
bool BackedBySynthesizeSetter = false;
for (llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*>::iterator
P = SynthesizedProperties.begin(),
E = SynthesizedProperties.end(); P != E; ++P) {
ObjCPropertyDecl *PropDecl = P->first;
if (PropDecl->getSetterName() == ME->getSelector()) {
BackedBySynthesizeSetter = true;
break;
}
}
if (!BackedBySynthesizeSetter)
return true;
// Remove the setter message if RHS is null
Transaction Trans(TA);
Expr *RHS = ME->getArg(0);
bool RHSIsNull =
RHS->isNullPointerConstant(Ctx,
Expr::NPC_ValueDependentIsNull);
if (RHSIsNull && isRemovable(ME))
TA.removeStmt(ME);
return true;
}
bool VisitPseudoObjectExpr(PseudoObjectExpr *POE) {
if (isZeroingPropIvar(POE) && isRemovable(POE)) {
Transaction Trans(Pass.TA);
Pass.TA.removeStmt(POE);
}
return true;
}
bool VisitBinaryOperator(BinaryOperator *BOE) {
if (isZeroingPropIvar(BOE) && isRemovable(BOE)) {
Transaction Trans(Pass.TA);
Pass.TA.removeStmt(BOE);
}
return true;
}
bool TraverseObjCMethodDecl(ObjCMethodDecl *D) {
if (D->getMethodFamily() != OMF_dealloc &&
!(D->isInstanceMethod() && D->getSelector() == FinalizeSel))
return true;
if (!D->hasBody())
return true;
ObjCImplDecl *IMD = dyn_cast<ObjCImplDecl>(D->getDeclContext());
if (!IMD)
return true;
SelfD = D->getSelfDecl();
collectRemovables(D->getBody(), Removables);
// For a 'dealloc' method use, find all property implementations in
// this class implementation.
for (auto *PID : IMD->property_impls()) {
if (PID->getPropertyImplementation() ==
ObjCPropertyImplDecl::Synthesize) {
ObjCPropertyDecl *PD = PID->getPropertyDecl();
ObjCMethodDecl *setterM = PD->getSetterMethodDecl();
if (!(setterM && setterM->isDefined())) {
ObjCPropertyDecl::PropertyAttributeKind AttrKind =
PD->getPropertyAttributes();
if (AttrKind &
(ObjCPropertyDecl::OBJC_PR_retain |
ObjCPropertyDecl::OBJC_PR_copy |
ObjCPropertyDecl::OBJC_PR_strong))
SynthesizedProperties[PD] = PID;
}
}
}
// Now, remove all zeroing of ivars etc.
base::TraverseObjCMethodDecl(D);
// clear out for next method.
SynthesizedProperties.clear();
SelfD = nullptr;
Removables.clear();
return true;
}
bool TraverseFunctionDecl(FunctionDecl *D) { return true; }
bool TraverseBlockDecl(BlockDecl *block) { return true; }
bool TraverseBlockExpr(BlockExpr *block) { return true; }
private:
bool isRemovable(Expr *E) const {
return Removables.count(E);
}
bool isZeroingPropIvar(Expr *E) {
E = E->IgnoreParens();
if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E))
return isZeroingPropIvar(BO);
if (PseudoObjectExpr *PO = dyn_cast<PseudoObjectExpr>(E))
return isZeroingPropIvar(PO);
return false;
}
bool isZeroingPropIvar(BinaryOperator *BOE) {
if (BOE->getOpcode() == BO_Comma)
return isZeroingPropIvar(BOE->getLHS()) &&
isZeroingPropIvar(BOE->getRHS());
if (BOE->getOpcode() != BO_Assign)
return false;
Expr *LHS = BOE->getLHS();
if (ObjCIvarRefExpr *IV = dyn_cast<ObjCIvarRefExpr>(LHS)) {
ObjCIvarDecl *IVDecl = IV->getDecl();
if (!IVDecl->getType()->isObjCObjectPointerType())
return false;
bool IvarBacksPropertySynthesis = false;
for (llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*>::iterator
P = SynthesizedProperties.begin(),
E = SynthesizedProperties.end(); P != E; ++P) {
ObjCPropertyImplDecl *PropImpDecl = P->second;
if (PropImpDecl && PropImpDecl->getPropertyIvarDecl() == IVDecl) {
IvarBacksPropertySynthesis = true;
break;
}
}
if (!IvarBacksPropertySynthesis)
return false;
}
else
return false;
return isZero(BOE->getRHS());
}
bool isZeroingPropIvar(PseudoObjectExpr *PO) {
BinaryOperator *BO = dyn_cast<BinaryOperator>(PO->getSyntacticForm());
if (!BO) return false;
if (BO->getOpcode() != BO_Assign) return false;
ObjCPropertyRefExpr *PropRefExp =
dyn_cast<ObjCPropertyRefExpr>(BO->getLHS()->IgnoreParens());
if (!PropRefExp) return false;
// TODO: Using implicit property decl.
if (PropRefExp->isImplicitProperty())
return false;
if (ObjCPropertyDecl *PDecl = PropRefExp->getExplicitProperty()) {
if (!SynthesizedProperties.count(PDecl))
return false;
}
return isZero(cast<OpaqueValueExpr>(BO->getRHS())->getSourceExpr());
}
bool isZero(Expr *E) {
if (E->isNullPointerConstant(Pass.Ctx, Expr::NPC_ValueDependentIsNull))
return true;
return isZeroingPropIvar(E);
}
};
} // anonymous namespace
void trans::removeZeroOutPropsInDeallocFinalize(MigrationPass &pass) {
ZeroOutInDeallocRemover trans(pass);
trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
}
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