//===--- 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() != SelfD18
)

      return true;

    bool BackedBySynthesizeSetter = false;

    for (llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*>::iterator

         P = SynthesizedProperties.begin(),

         E = SynthesizedProperties.end(); P != E; 
++P9
) {

      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)21
) {

      Transaction Trans(Pass.TA);

      Pass.TA.removeStmt(POE);

    }

    return true;

  }

  bool VisitBinaryOperator(BinaryOperator *BOE) {

    if (isZeroingPropIvar(BOE) && 
isRemovable(BOE)14
) {

      Transaction Trans(Pass.TA);

      Pass.TA.removeStmt(BOE);

    }

    return true;

  }

  bool TraverseObjCMethodDecl(ObjCMethodDecl *D) {

    if (D->getMethodFamily() != OMF_dealloc &&

        
!(958
D->isInstanceMethod()958
 && 
D->getSelector() == FinalizeSel805
))

      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())) {

          ObjCPropertyAttribute::Kind AttrKind = PD->getPropertyAttributes();

          if (AttrKind & (ObjCPropertyAttribute::kind_retain |

                          ObjCPropertyAttribute::kind_copy |

                          ObjCPropertyAttribute::kind_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; 
++P28
) {

        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 false2
;

    if (BO->getOpcode() != BO_Assign) 
return false0
;

    ObjCPropertyRefExpr *PropRefExp =

      dyn_cast<ObjCPropertyRefExpr>(BO->getLHS()->IgnoreParens());

    if (!PropRefExp) 
return false0
;

    // 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());

}