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