clang/lib/ARCMigrate/TransZeroOutPropsInDealloc.cpp

   1 //===--- TransZeroOutPropsInDealloc.cpp - Transformations to ARC mode -----===//
   2 //
   3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
   4 // See https://llvm.org/LICENSE.txt for license information.
   5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
   6 //
   7 //===----------------------------------------------------------------------===//
   8 //
   9 // removeZeroOutPropsInDealloc:
  10 //
  11 // Removes zero'ing out "strong" @synthesized properties in a -dealloc method.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "Transforms.h"
  16 #include "Internals.h"
  17 #include "clang/AST/ASTContext.h"
  18
  19 using namespace clang;
  20 using namespace arcmt;
  21 using namespace trans;
  22
  23 namespace {
  24
  25 class ZeroOutInDeallocRemover :
  26                            public RecursiveASTVisitor<ZeroOutInDeallocRemover> {
  27   typedef RecursiveASTVisitor<ZeroOutInDeallocRemover> base;
  28
  29   MigrationPass &Pass;
  30
  31   llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*> SynthesizedProperties;
  32   ImplicitParamDecl *SelfD;
  33   ExprSet Removables;
  34   Selector FinalizeSel;
  35
  36 public:
  37   ZeroOutInDeallocRemover(MigrationPass &pass) : Pass(pass), SelfD(nullptr) {
  38     FinalizeSel =
  39         Pass.Ctx.Selectors.getNullarySelector(&Pass.Ctx.Idents.get("finalize"));
  40   }
  41
  42   bool VisitObjCMessageExpr(ObjCMessageExpr *ME) {
  43     ASTContext &Ctx = Pass.Ctx;
  44     TransformActions &TA = Pass.TA;
  45
  46     if (ME->getReceiverKind() != ObjCMessageExpr::Instance)
  47       return true;
  48     Expr *receiver = ME->getInstanceReceiver();
  49     if (!receiver)
  50       return true;
  51
  52     DeclRefExpr *refE = dyn_cast<DeclRefExpr>(receiver->IgnoreParenCasts());
  53     if (!refE || refE->getDecl() != SelfD)
  54       return true;
  55
  56     bool BackedBySynthesizeSetter = false;
  57     for (llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*>::iterator
  58          P = SynthesizedProperties.begin(),
  59          E = SynthesizedProperties.end(); P != E; ++P) {
  60       ObjCPropertyDecl *PropDecl = P->first;
  61       if (PropDecl->getSetterName() == ME->getSelector()) {
  62         BackedBySynthesizeSetter = true;
  63         break;
  64       }
  65     }
  66     if (!BackedBySynthesizeSetter)
  67       return true;
  68
  69     // Remove the setter message if RHS is null
  70     Transaction Trans(TA);
  71     Expr *RHS = ME->getArg(0);
  72     bool RHSIsNull =
  73       RHS->isNullPointerConstant(Ctx,
  74                                  Expr::NPC_ValueDependentIsNull);
  75     if (RHSIsNull && isRemovable(ME))
  76       TA.removeStmt(ME);
  77
  78     return true;
  79   }
  80
  81   bool VisitPseudoObjectExpr(PseudoObjectExpr *POE) {
  82     if (isZeroingPropIvar(POE) && isRemovable(POE)) {
  83       Transaction Trans(Pass.TA);
  84       Pass.TA.removeStmt(POE);
  85     }
  86
  87     return true;
  88   }
  89
  90   bool VisitBinaryOperator(BinaryOperator *BOE) {
  91     if (isZeroingPropIvar(BOE) && isRemovable(BOE)) {
  92       Transaction Trans(Pass.TA);
  93       Pass.TA.removeStmt(BOE);
  94     }
  95
  96     return true;
  97   }
  98
  99   bool TraverseObjCMethodDecl(ObjCMethodDecl *D) {
 100     if (D->getMethodFamily() != OMF_dealloc &&
 101         !(D->isInstanceMethod() && D->getSelector() == FinalizeSel))
 102       return true;
 103     if (!D->hasBody())
 104       return true;
 105
 106     ObjCImplDecl *IMD = dyn_cast<ObjCImplDecl>(D->getDeclContext());
 107     if (!IMD)
 108       return true;
 109
 110     SelfD = D->getSelfDecl();
 111     collectRemovables(D->getBody(), Removables);
 112
 113     // For a 'dealloc' method use, find all property implementations in
 114     // this class implementation.
 115     for (auto *PID : IMD->property_impls()) {
 116       if (PID->getPropertyImplementation() ==
 117           ObjCPropertyImplDecl::Synthesize) {
 118         ObjCPropertyDecl *PD = PID->getPropertyDecl();
 119         ObjCMethodDecl *setterM = PD->getSetterMethodDecl();
 120         if (!(setterM && setterM->isDefined())) {
 121           ObjCPropertyAttribute::Kind AttrKind = PD->getPropertyAttributes();
 122           if (AttrKind & (ObjCPropertyAttribute::kind_retain |
 123                           ObjCPropertyAttribute::kind_copy |
 124                           ObjCPropertyAttribute::kind_strong))
 125             SynthesizedProperties[PD] = PID;
 126         }
 127       }
 128     }
 129
 130     // Now, remove all zeroing of ivars etc.
 131     base::TraverseObjCMethodDecl(D);
 132
 133     // clear out for next method.
 134     SynthesizedProperties.clear();
 135     SelfD = nullptr;
 136     Removables.clear();
 137     return true;
 138   }
 139
 140   bool TraverseFunctionDecl(FunctionDecl *D) { return true; }
 141   bool TraverseBlockDecl(BlockDecl *block) { return true; }
 142   bool TraverseBlockExpr(BlockExpr *block) { return true; }
 143
 144 private:
 145   bool isRemovable(Expr *E) const {
 146     return Removables.count(E);
 147   }
 148
 149   bool isZeroingPropIvar(Expr *E) {
 150     E = E->IgnoreParens();
 151     if (BinaryOperator *BO = dyn_cast<BinaryOperator>(E))
 152       return isZeroingPropIvar(BO);
 153     if (PseudoObjectExpr *PO = dyn_cast<PseudoObjectExpr>(E))
 154       return isZeroingPropIvar(PO);
 155     return false;
 156   }
 157
 158   bool isZeroingPropIvar(BinaryOperator *BOE) {
 159     if (BOE->getOpcode() == BO_Comma)
 160       return isZeroingPropIvar(BOE->getLHS()) &&
 161              isZeroingPropIvar(BOE->getRHS());
 162
 163     if (BOE->getOpcode() != BO_Assign)
 164       return false;
 165
 166     Expr *LHS = BOE->getLHS();
 167     if (ObjCIvarRefExpr *IV = dyn_cast<ObjCIvarRefExpr>(LHS)) {
 168       ObjCIvarDecl *IVDecl = IV->getDecl();
 169       if (!IVDecl->getType()->isObjCObjectPointerType())
 170         return false;
 171       bool IvarBacksPropertySynthesis = false;
 172       for (llvm::DenseMap<ObjCPropertyDecl*, ObjCPropertyImplDecl*>::iterator
 173            P = SynthesizedProperties.begin(),
 174            E = SynthesizedProperties.end(); P != E; ++P) {
 175         ObjCPropertyImplDecl *PropImpDecl = P->second;
 176         if (PropImpDecl && PropImpDecl->getPropertyIvarDecl() == IVDecl) {
 177           IvarBacksPropertySynthesis = true;
 178           break;
 179         }
 180       }
 181       if (!IvarBacksPropertySynthesis)
 182         return false;
 183     }
 184     else
 185         return false;
 186
 187     return isZero(BOE->getRHS());
 188   }
 189
 190   bool isZeroingPropIvar(PseudoObjectExpr *PO) {
 191     BinaryOperator *BO = dyn_cast<BinaryOperator>(PO->getSyntacticForm());
 192     if (!BO) return false;
 193     if (BO->getOpcode() != BO_Assign) return false;
 194
 195     ObjCPropertyRefExpr *PropRefExp =
 196       dyn_cast<ObjCPropertyRefExpr>(BO->getLHS()->IgnoreParens());
 197     if (!PropRefExp) return false;
 198
 199     // TODO: Using implicit property decl.
 200     if (PropRefExp->isImplicitProperty())
 201       return false;
 202
 203     if (ObjCPropertyDecl *PDecl = PropRefExp->getExplicitProperty()) {
 204       if (!SynthesizedProperties.count(PDecl))
 205         return false;
 206     }
 207
 208     return isZero(cast<OpaqueValueExpr>(BO->getRHS())->getSourceExpr());
 209   }
 210
 211   bool isZero(Expr *E) {
 212     if (E->isNullPointerConstant(Pass.Ctx, Expr::NPC_ValueDependentIsNull))
 213       return true;
 214
 215     return isZeroingPropIvar(E);
 216   }
 217 };
 218
 219 } // anonymous namespace
 220
 221 void trans::removeZeroOutPropsInDeallocFinalize(MigrationPass &pass) {
 222   ZeroOutInDeallocRemover trans(pass);
 223   trans.TraverseDecl(pass.Ctx.getTranslationUnitDecl());
 224 }