clang/lib/CodeGen/CGObjCRuntime.cpp

   1 //==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==//
   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 // This abstract class defines the interface for Objective-C runtime-specific
  10 // code generation.  It provides some concrete helper methods for functionality
  11 // shared between all (or most) of the Objective-C runtimes supported by clang.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "CGObjCRuntime.h"
  16 #include "CGCXXABI.h"
  17 #include "CGCleanup.h"
  18 #include "CGRecordLayout.h"
  19 #include "CodeGenFunction.h"
  20 #include "CodeGenModule.h"
  21 #include "clang/AST/RecordLayout.h"
  22 #include "clang/AST/StmtObjC.h"
  23 #include "clang/CodeGen/CGFunctionInfo.h"
  24 #include "clang/CodeGen/CodeGenABITypes.h"
  25 #include "llvm/IR/Instruction.h"
  26 #include "llvm/Support/SaveAndRestore.h"
  27
  28 using namespace clang;
  29 using namespace CodeGen;
  30
  31 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
  32                                               const ObjCInterfaceDecl *OID,
  33                                               const ObjCIvarDecl *Ivar) {
  34   return CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar) /
  35          CGM.getContext().getCharWidth();
  36 }
  37
  38 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
  39                                               const ObjCImplementationDecl *OID,
  40                                               const ObjCIvarDecl *Ivar) {
  41   return CGM.getContext().lookupFieldBitOffset(OID->getClassInterface(), OID,
  42                                                Ivar) /
  43          CGM.getContext().getCharWidth();
  44 }
  45
  46 unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
  47     CodeGen::CodeGenModule &CGM,
  48     const ObjCInterfaceDecl *ID,
  49     const ObjCIvarDecl *Ivar) {
  50   return CGM.getContext().lookupFieldBitOffset(ID, ID->getImplementation(),
  51                                                Ivar);
  52 }
  53
  54 LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
  55                                                const ObjCInterfaceDecl *OID,
  56                                                llvm::Value *BaseValue,
  57                                                const ObjCIvarDecl *Ivar,
  58                                                unsigned CVRQualifiers,
  59                                                llvm::Value *Offset) {
  60   // Compute (type*) ( (char *) BaseValue + Offset)
  61   QualType InterfaceTy{OID->getTypeForDecl(), 0};
  62   QualType ObjectPtrTy =
  63       CGF.CGM.getContext().getObjCObjectPointerType(InterfaceTy);
  64   QualType IvarTy =
  65       Ivar->getUsageType(ObjectPtrTy).withCVRQualifiers(CVRQualifiers);
  66   llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy);
  67   llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy);
  68   V = CGF.Builder.CreateInBoundsGEP(CGF.Int8Ty, V, Offset, "add.ptr");
  69
  70   if (!Ivar->isBitField()) {
  71     V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy));
  72     LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy);
  73     return LV;
  74   }
  75
  76   // We need to compute an access strategy for this bit-field. We are given the
  77   // offset to the first byte in the bit-field, the sub-byte offset is taken
  78   // from the original layout. We reuse the normal bit-field access strategy by
  79   // treating this as an access to a struct where the bit-field is in byte 0,
  80   // and adjust the containing type size as appropriate.
  81   //
  82   // FIXME: Note that currently we make a very conservative estimate of the
  83   // alignment of the bit-field, because (a) it is not clear what guarantees the
  84   // runtime makes us, and (b) we don't have a way to specify that the struct is
  85   // at an alignment plus offset.
  86   //
  87   // Note, there is a subtle invariant here: we can only call this routine on
  88   // non-synthesized ivars but we may be called for synthesized ivars.  However,
  89   // a synthesized ivar can never be a bit-field, so this is safe.
  90   uint64_t FieldBitOffset =
  91       CGF.CGM.getContext().lookupFieldBitOffset(OID, nullptr, Ivar);
  92   uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth();
  93   uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign();
  94   uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext());
  95   CharUnits StorageSize = CGF.CGM.getContext().toCharUnitsFromBits(
  96       llvm::alignTo(BitOffset + BitFieldSize, AlignmentBits));
  97   CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits);
  98
  99   // Allocate a new CGBitFieldInfo object to describe this access.
 100   //
 101   // FIXME: This is incredibly wasteful, these should be uniqued or part of some
 102   // layout object. However, this is blocked on other cleanups to the
 103   // Objective-C code, so for now we just live with allocating a bunch of these
 104   // objects.
 105   CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo(
 106     CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize,
 107                              CGF.CGM.getContext().toBits(StorageSize),
 108                              CharUnits::fromQuantity(0)));
 109
 110   Address Addr = Address(V, CGF.Int8Ty, Alignment);
 111   Addr = CGF.Builder.CreateElementBitCast(Addr,
 112                                    llvm::Type::getIntNTy(CGF.getLLVMContext(),
 113                                                          Info->StorageSize));
 114   return LValue::MakeBitfield(Addr, *Info, IvarTy,
 115                               LValueBaseInfo(AlignmentSource::Decl),
 116                               TBAAAccessInfo());
 117 }
 118
 119 namespace {
 120   struct CatchHandler {
 121     const VarDecl *Variable;
 122     const Stmt *Body;
 123     llvm::BasicBlock *Block;
 124     llvm::Constant *TypeInfo;
 125     /// Flags used to differentiate cleanups and catchalls in Windows SEH
 126     unsigned Flags;
 127   };
 128
 129   struct CallObjCEndCatch final : EHScopeStack::Cleanup {
 130     CallObjCEndCatch(bool MightThrow, llvm::FunctionCallee Fn)
 131         : MightThrow(MightThrow), Fn(Fn) {}
 132     bool MightThrow;
 133     llvm::FunctionCallee Fn;
 134
 135     void Emit(CodeGenFunction &CGF, Flags flags) override {
 136       if (MightThrow)
 137         CGF.EmitRuntimeCallOrInvoke(Fn);
 138       else
 139         CGF.EmitNounwindRuntimeCall(Fn);
 140     }
 141   };
 142 }
 143
 144 void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF,
 145                                      const ObjCAtTryStmt &S,
 146                                      llvm::FunctionCallee beginCatchFn,
 147                                      llvm::FunctionCallee endCatchFn,
 148                                      llvm::FunctionCallee exceptionRethrowFn) {
 149   // Jump destination for falling out of catch bodies.
 150   CodeGenFunction::JumpDest Cont;
 151   if (S.getNumCatchStmts())
 152     Cont = CGF.getJumpDestInCurrentScope("eh.cont");
 153
 154   bool useFunclets = EHPersonality::get(CGF).usesFuncletPads();
 155
 156   CodeGenFunction::FinallyInfo FinallyInfo;
 157   if (!useFunclets)
 158     if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt())
 159       FinallyInfo.enter(CGF, Finally->getFinallyBody(),
 160                         beginCatchFn, endCatchFn, exceptionRethrowFn);
 161
 162   SmallVector<CatchHandler, 8> Handlers;
 163
 164
 165   // Enter the catch, if there is one.
 166   if (S.getNumCatchStmts()) {
 167     for (const ObjCAtCatchStmt *CatchStmt : S.catch_stmts()) {
 168       const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl();
 169
 170       Handlers.push_back(CatchHandler());
 171       CatchHandler &Handler = Handlers.back();
 172       Handler.Variable = CatchDecl;
 173       Handler.Body = CatchStmt->getCatchBody();
 174       Handler.Block = CGF.createBasicBlock("catch");
 175       Handler.Flags = 0;
 176
 177       // @catch(...) always matches.
 178       if (!CatchDecl) {
 179         auto catchAll = getCatchAllTypeInfo();
 180         Handler.TypeInfo = catchAll.RTTI;
 181         Handler.Flags = catchAll.Flags;
 182         // Don't consider any other catches.
 183         break;
 184       }
 185
 186       Handler.TypeInfo = GetEHType(CatchDecl->getType());
 187     }
 188
 189     EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size());
 190     for (unsigned I = 0, E = Handlers.size(); I != E; ++I)
 191       Catch->setHandler(I, { Handlers[I].TypeInfo, Handlers[I].Flags }, Handlers[I].Block);
 192   }
 193
 194   if (useFunclets)
 195     if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) {
 196         CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
 197         if (!CGF.CurSEHParent)
 198             CGF.CurSEHParent = cast<NamedDecl>(CGF.CurFuncDecl);
 199         // Outline the finally block.
 200         const Stmt *FinallyBlock = Finally->getFinallyBody();
 201         HelperCGF.startOutlinedSEHHelper(CGF, /*isFilter*/false, FinallyBlock);
 202
 203         // Emit the original filter expression, convert to i32, and return.
 204         HelperCGF.EmitStmt(FinallyBlock);
 205
 206         HelperCGF.FinishFunction(FinallyBlock->getEndLoc());
 207
 208         llvm::Function *FinallyFunc = HelperCGF.CurFn;
 209
 210
 211         // Push a cleanup for __finally blocks.
 212         CGF.pushSEHCleanup(NormalAndEHCleanup, FinallyFunc);
 213     }
 214
 215
 216   // Emit the try body.
 217   CGF.EmitStmt(S.getTryBody());
 218
 219   // Leave the try.
 220   if (S.getNumCatchStmts())
 221     CGF.popCatchScope();
 222
 223   // Remember where we were.
 224   CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP();
 225
 226   // Emit the handlers.
 227   for (unsigned I = 0, E = Handlers.size(); I != E; ++I) {
 228     CatchHandler &Handler = Handlers[I];
 229
 230     CGF.EmitBlock(Handler.Block);
 231
 232     CodeGenFunction::LexicalScope Cleanups(CGF, Handler.Body->getSourceRange());
 233     SaveAndRestore RevertAfterScope(CGF.CurrentFuncletPad);
 234     if (useFunclets) {
 235       llvm::Instruction *CPICandidate = Handler.Block->getFirstNonPHI();
 236       if (auto *CPI = dyn_cast_or_null<llvm::CatchPadInst>(CPICandidate)) {
 237         CGF.CurrentFuncletPad = CPI;
 238         CPI->setOperand(2, CGF.getExceptionSlot().getPointer());
 239         CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
 240       }
 241     }
 242
 243     llvm::Value *RawExn = CGF.getExceptionFromSlot();
 244
 245     // Enter the catch.
 246     llvm::Value *Exn = RawExn;
 247     if (beginCatchFn)
 248       Exn = CGF.EmitNounwindRuntimeCall(beginCatchFn, RawExn, "exn.adjusted");
 249
 250     if (endCatchFn) {
 251       // Add a cleanup to leave the catch.
 252       bool EndCatchMightThrow = (Handler.Variable == nullptr);
 253
 254       CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup,
 255                                                 EndCatchMightThrow,
 256                                                 endCatchFn);
 257     }
 258
 259     // Bind the catch parameter if it exists.
 260     if (const VarDecl *CatchParam = Handler.Variable) {
 261       llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType());
 262       llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType);
 263
 264       CGF.EmitAutoVarDecl(*CatchParam);
 265       EmitInitOfCatchParam(CGF, CastExn, CatchParam);
 266     }
 267
 268     CGF.ObjCEHValueStack.push_back(Exn);
 269     CGF.EmitStmt(Handler.Body);
 270     CGF.ObjCEHValueStack.pop_back();
 271
 272     // Leave any cleanups associated with the catch.
 273     Cleanups.ForceCleanup();
 274
 275     CGF.EmitBranchThroughCleanup(Cont);
 276   }
 277
 278   // Go back to the try-statement fallthrough.
 279   CGF.Builder.restoreIP(SavedIP);
 280
 281   // Pop out of the finally.
 282   if (!useFunclets && S.getFinallyStmt())
 283     FinallyInfo.exit(CGF);
 284
 285   if (Cont.isValid())
 286     CGF.EmitBlock(Cont.getBlock());
 287 }
 288
 289 void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF,
 290                                          llvm::Value *exn,
 291                                          const VarDecl *paramDecl) {
 292
 293   Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl);
 294
 295   switch (paramDecl->getType().getQualifiers().getObjCLifetime()) {
 296   case Qualifiers::OCL_Strong:
 297     exn = CGF.EmitARCRetainNonBlock(exn);
 298     [[fallthrough]];
 299
 300   case Qualifiers::OCL_None:
 301   case Qualifiers::OCL_ExplicitNone:
 302   case Qualifiers::OCL_Autoreleasing:
 303     CGF.Builder.CreateStore(exn, paramAddr);
 304     return;
 305
 306   case Qualifiers::OCL_Weak:
 307     CGF.EmitARCInitWeak(paramAddr, exn);
 308     return;
 309   }
 310   llvm_unreachable("invalid ownership qualifier");
 311 }
 312
 313 namespace {
 314   struct CallSyncExit final : EHScopeStack::Cleanup {
 315     llvm::FunctionCallee SyncExitFn;
 316     llvm::Value *SyncArg;
 317     CallSyncExit(llvm::FunctionCallee SyncExitFn, llvm::Value *SyncArg)
 318         : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {}
 319
 320     void Emit(CodeGenFunction &CGF, Flags flags) override {
 321       CGF.EmitNounwindRuntimeCall(SyncExitFn, SyncArg);
 322     }
 323   };
 324 }
 325
 326 void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF,
 327                                            const ObjCAtSynchronizedStmt &S,
 328                                            llvm::FunctionCallee syncEnterFn,
 329                                            llvm::FunctionCallee syncExitFn) {
 330   CodeGenFunction::RunCleanupsScope cleanups(CGF);
 331
 332   // Evaluate the lock operand.  This is guaranteed to dominate the
 333   // ARC release and lock-release cleanups.
 334   const Expr *lockExpr = S.getSynchExpr();
 335   llvm::Value *lock;
 336   if (CGF.getLangOpts().ObjCAutoRefCount) {
 337     lock = CGF.EmitARCRetainScalarExpr(lockExpr);
 338     lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock);
 339   } else {
 340     lock = CGF.EmitScalarExpr(lockExpr);
 341   }
 342   lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy);
 343
 344   // Acquire the lock.
 345   CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow();
 346
 347   // Register an all-paths cleanup to release the lock.
 348   CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock);
 349
 350   // Emit the body of the statement.
 351   CGF.EmitStmt(S.getSynchBody());
 352 }
 353
 354 /// Compute the pointer-to-function type to which a message send
 355 /// should be casted in order to correctly call the given method
 356 /// with the given arguments.
 357 ///
 358 /// \param method - may be null
 359 /// \param resultType - the result type to use if there's no method
 360 /// \param callArgs - the actual arguments, including implicit ones
 361 CGObjCRuntime::MessageSendInfo
 362 CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
 363                                   QualType resultType,
 364                                   CallArgList &callArgs) {
 365   unsigned ProgramAS = CGM.getDataLayout().getProgramAddressSpace();
 366
 367   // If there's a method, use information from that.
 368   if (method) {
 369     const CGFunctionInfo &signature =
 370       CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty);
 371
 372     llvm::PointerType *signatureType =
 373       CGM.getTypes().GetFunctionType(signature)->getPointerTo(ProgramAS);
 374
 375     const CGFunctionInfo &signatureForCall =
 376       CGM.getTypes().arrangeCall(signature, callArgs);
 377
 378     return MessageSendInfo(signatureForCall, signatureType);
 379   }
 380
 381   // There's no method;  just use a default CC.
 382   const CGFunctionInfo &argsInfo =
 383     CGM.getTypes().arrangeUnprototypedObjCMessageSend(resultType, callArgs);
 384
 385   // Derive the signature to call from that.
 386   llvm::PointerType *signatureType =
 387     CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo(ProgramAS);
 388   return MessageSendInfo(argsInfo, signatureType);
 389 }
 390
 391 bool CGObjCRuntime::canMessageReceiverBeNull(CodeGenFunction &CGF,
 392                                              const ObjCMethodDecl *method,
 393                                              bool isSuper,
 394                                        const ObjCInterfaceDecl *classReceiver,
 395                                              llvm::Value *receiver) {
 396   // Super dispatch assumes that self is non-null; even the messenger
 397   // doesn't have a null check internally.
 398   if (isSuper)
 399     return false;
 400
 401   // If this is a direct dispatch of a class method, check whether the class,
 402   // or anything in its hierarchy, was weak-linked.
 403   if (classReceiver && method && method->isClassMethod())
 404     return isWeakLinkedClass(classReceiver);
 405
 406   // If we're emitting a method, and self is const (meaning just ARC, for now),
 407   // and the receiver is a load of self, then self is a valid object.
 408   if (auto curMethod =
 409                dyn_cast_or_null<ObjCMethodDecl>(CGF.CurCodeDecl)) {
 410     auto self = curMethod->getSelfDecl();
 411     if (self->getType().isConstQualified()) {
 412       if (auto LI = dyn_cast<llvm::LoadInst>(receiver->stripPointerCasts())) {
 413         llvm::Value *selfAddr = CGF.GetAddrOfLocalVar(self).getPointer();
 414         if (selfAddr == LI->getPointerOperand()) {
 415           return false;
 416         }
 417       }
 418     }
 419   }
 420
 421   // Otherwise, assume it can be null.
 422   return true;
 423 }
 424
 425 bool CGObjCRuntime::isWeakLinkedClass(const ObjCInterfaceDecl *ID) {
 426   do {
 427     if (ID->isWeakImported())
 428       return true;
 429   } while ((ID = ID->getSuperClass()));
 430
 431   return false;
 432 }
 433
 434 void CGObjCRuntime::destroyCalleeDestroyedArguments(CodeGenFunction &CGF,
 435                                               const ObjCMethodDecl *method,
 436                                               const CallArgList &callArgs) {
 437   CallArgList::const_iterator I = callArgs.begin();
 438   for (auto i = method->param_begin(), e = method->param_end();
 439          i != e; ++i, ++I) {
 440     const ParmVarDecl *param = (*i);
 441     if (param->hasAttr<NSConsumedAttr>()) {
 442       RValue RV = I->getRValue(CGF);
 443       assert(RV.isScalar() &&
 444              "NullReturnState::complete - arg not on object");
 445       CGF.EmitARCRelease(RV.getScalarVal(), ARCImpreciseLifetime);
 446     } else {
 447       QualType QT = param->getType();
 448       auto *RT = QT->getAs<RecordType>();
 449       if (RT && RT->getDecl()->isParamDestroyedInCallee()) {
 450         RValue RV = I->getRValue(CGF);
 451         QualType::DestructionKind DtorKind = QT.isDestructedType();
 452         switch (DtorKind) {
 453         case QualType::DK_cxx_destructor:
 454           CGF.destroyCXXObject(CGF, RV.getAggregateAddress(), QT);
 455           break;
 456         case QualType::DK_nontrivial_c_struct:
 457           CGF.destroyNonTrivialCStruct(CGF, RV.getAggregateAddress(), QT);
 458           break;
 459         default:
 460           llvm_unreachable("unexpected dtor kind");
 461           break;
 462         }
 463       }
 464     }
 465   }
 466 }
 467
 468 llvm::Constant *
 469 clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
 470                                        const ObjCProtocolDecl *protocol) {
 471   return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);
 472 }
 473
 474 std::string CGObjCRuntime::getSymbolNameForMethod(const ObjCMethodDecl *OMD,
 475                                                   bool includeCategoryName) {
 476   std::string buffer;
 477   llvm::raw_string_ostream out(buffer);
 478   CGM.getCXXABI().getMangleContext().mangleObjCMethodName(OMD, out,
 479                                        /*includePrefixByte=*/true,
 480                                        includeCategoryName);
 481   return buffer;
 482 }