1 //==- CGObjCRuntime.cpp - Interface to Shared Objective-C Runtime Features ==// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This abstract class defines the interface for Objective-C runtime-specific 11 // code generation. It provides some concrete helper methods for functionality 12 // shared between all (or most) of the Objective-C runtimes supported by clang. 13 // 14 //===----------------------------------------------------------------------===// 15 16 #include "CGObjCRuntime.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 "llvm/IR/CallSite.h" 25 26 using namespace clang; 27 using namespace CodeGen; 28 29 static uint64_t LookupFieldBitOffset(CodeGen::CodeGenModule &CGM, 30 const ObjCInterfaceDecl *OID, 31 const ObjCImplementationDecl *ID, 32 const ObjCIvarDecl *Ivar) { 33 const ObjCInterfaceDecl *Container = Ivar->getContainingInterface(); 34 35 // FIXME: We should eliminate the need to have ObjCImplementationDecl passed 36 // in here; it should never be necessary because that should be the lexical 37 // decl context for the ivar. 38 39 // If we know have an implementation (and the ivar is in it) then 40 // look up in the implementation layout. 41 const ASTRecordLayout *RL; 42 if (ID && declaresSameEntity(ID->getClassInterface(), Container)) 43 RL = &CGM.getContext().getASTObjCImplementationLayout(ID); 44 else 45 RL = &CGM.getContext().getASTObjCInterfaceLayout(Container); 46 47 // Compute field index. 48 // 49 // FIXME: The index here is closely tied to how ASTContext::getObjCLayout is 50 // implemented. This should be fixed to get the information from the layout 51 // directly. 52 unsigned Index = 0; 53 54 for (const ObjCIvarDecl *IVD = Container->all_declared_ivar_begin(); 55 IVD; IVD = IVD->getNextIvar()) { 56 if (Ivar == IVD) 57 break; 58 ++Index; 59 } 60 assert(Index < RL->getFieldCount() && "Ivar is not inside record layout!"); 61 62 return RL->getFieldOffset(Index); 63 } 64 65 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM, 66 const ObjCInterfaceDecl *OID, 67 const ObjCIvarDecl *Ivar) { 68 return LookupFieldBitOffset(CGM, OID, nullptr, Ivar) / 69 CGM.getContext().getCharWidth(); 70 } 71 72 uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM, 73 const ObjCImplementationDecl *OID, 74 const ObjCIvarDecl *Ivar) { 75 return LookupFieldBitOffset(CGM, OID->getClassInterface(), OID, Ivar) / 76 CGM.getContext().getCharWidth(); 77 } 78 79 unsigned CGObjCRuntime::ComputeBitfieldBitOffset( 80 CodeGen::CodeGenModule &CGM, 81 const ObjCInterfaceDecl *ID, 82 const ObjCIvarDecl *Ivar) { 83 return LookupFieldBitOffset(CGM, ID, ID->getImplementation(), Ivar); 84 } 85 86 LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF, 87 const ObjCInterfaceDecl *OID, 88 llvm::Value *BaseValue, 89 const ObjCIvarDecl *Ivar, 90 unsigned CVRQualifiers, 91 llvm::Value *Offset) { 92 // Compute (type*) ( (char *) BaseValue + Offset) 93 QualType IvarTy = Ivar->getType(); 94 llvm::Type *LTy = CGF.CGM.getTypes().ConvertTypeForMem(IvarTy); 95 llvm::Value *V = CGF.Builder.CreateBitCast(BaseValue, CGF.Int8PtrTy); 96 V = CGF.Builder.CreateInBoundsGEP(V, Offset, "add.ptr"); 97 98 if (!Ivar->isBitField()) { 99 V = CGF.Builder.CreateBitCast(V, llvm::PointerType::getUnqual(LTy)); 100 LValue LV = CGF.MakeNaturalAlignAddrLValue(V, IvarTy); 101 LV.getQuals().addCVRQualifiers(CVRQualifiers); 102 return LV; 103 } 104 105 // We need to compute an access strategy for this bit-field. We are given the 106 // offset to the first byte in the bit-field, the sub-byte offset is taken 107 // from the original layout. We reuse the normal bit-field access strategy by 108 // treating this as an access to a struct where the bit-field is in byte 0, 109 // and adjust the containing type size as appropriate. 110 // 111 // FIXME: Note that currently we make a very conservative estimate of the 112 // alignment of the bit-field, because (a) it is not clear what guarantees the 113 // runtime makes us, and (b) we don't have a way to specify that the struct is 114 // at an alignment plus offset. 115 // 116 // Note, there is a subtle invariant here: we can only call this routine on 117 // non-synthesized ivars but we may be called for synthesized ivars. However, 118 // a synthesized ivar can never be a bit-field, so this is safe. 119 uint64_t FieldBitOffset = LookupFieldBitOffset(CGF.CGM, OID, nullptr, Ivar); 120 uint64_t BitOffset = FieldBitOffset % CGF.CGM.getContext().getCharWidth(); 121 uint64_t AlignmentBits = CGF.CGM.getTarget().getCharAlign(); 122 uint64_t BitFieldSize = Ivar->getBitWidthValue(CGF.getContext()); 123 CharUnits StorageSize = 124 CGF.CGM.getContext().toCharUnitsFromBits( 125 llvm::RoundUpToAlignment(BitOffset + BitFieldSize, AlignmentBits)); 126 CharUnits Alignment = CGF.CGM.getContext().toCharUnitsFromBits(AlignmentBits); 127 128 // Allocate a new CGBitFieldInfo object to describe this access. 129 // 130 // FIXME: This is incredibly wasteful, these should be uniqued or part of some 131 // layout object. However, this is blocked on other cleanups to the 132 // Objective-C code, so for now we just live with allocating a bunch of these 133 // objects. 134 CGBitFieldInfo *Info = new (CGF.CGM.getContext()) CGBitFieldInfo( 135 CGBitFieldInfo::MakeInfo(CGF.CGM.getTypes(), Ivar, BitOffset, BitFieldSize, 136 CGF.CGM.getContext().toBits(StorageSize), 137 CharUnits::fromQuantity(0))); 138 139 Address Addr(V, Alignment); 140 Addr = CGF.Builder.CreateElementBitCast(Addr, 141 llvm::Type::getIntNTy(CGF.getLLVMContext(), 142 Info->StorageSize)); 143 return LValue::MakeBitfield(Addr, *Info, 144 IvarTy.withCVRQualifiers(CVRQualifiers), 145 AlignmentSource::Decl); 146 } 147 148 namespace { 149 struct CatchHandler { 150 const VarDecl *Variable; 151 const Stmt *Body; 152 llvm::BasicBlock *Block; 153 llvm::Constant *TypeInfo; 154 }; 155 156 struct CallObjCEndCatch final : EHScopeStack::Cleanup { 157 CallObjCEndCatch(bool MightThrow, llvm::Value *Fn) : 158 MightThrow(MightThrow), Fn(Fn) {} 159 bool MightThrow; 160 llvm::Value *Fn; 161 162 void Emit(CodeGenFunction &CGF, Flags flags) override { 163 if (!MightThrow) { 164 CGF.Builder.CreateCall(Fn)->setDoesNotThrow(); 165 return; 166 } 167 168 CGF.EmitRuntimeCallOrInvoke(Fn); 169 } 170 }; 171 } 172 173 174 void CGObjCRuntime::EmitTryCatchStmt(CodeGenFunction &CGF, 175 const ObjCAtTryStmt &S, 176 llvm::Constant *beginCatchFn, 177 llvm::Constant *endCatchFn, 178 llvm::Constant *exceptionRethrowFn) { 179 // Jump destination for falling out of catch bodies. 180 CodeGenFunction::JumpDest Cont; 181 if (S.getNumCatchStmts()) 182 Cont = CGF.getJumpDestInCurrentScope("eh.cont"); 183 184 CodeGenFunction::FinallyInfo FinallyInfo; 185 if (const ObjCAtFinallyStmt *Finally = S.getFinallyStmt()) 186 FinallyInfo.enter(CGF, Finally->getFinallyBody(), 187 beginCatchFn, endCatchFn, exceptionRethrowFn); 188 189 SmallVector<CatchHandler, 8> Handlers; 190 191 // Enter the catch, if there is one. 192 if (S.getNumCatchStmts()) { 193 for (unsigned I = 0, N = S.getNumCatchStmts(); I != N; ++I) { 194 const ObjCAtCatchStmt *CatchStmt = S.getCatchStmt(I); 195 const VarDecl *CatchDecl = CatchStmt->getCatchParamDecl(); 196 197 Handlers.push_back(CatchHandler()); 198 CatchHandler &Handler = Handlers.back(); 199 Handler.Variable = CatchDecl; 200 Handler.Body = CatchStmt->getCatchBody(); 201 Handler.Block = CGF.createBasicBlock("catch"); 202 203 // @catch(...) always matches. 204 if (!CatchDecl) { 205 Handler.TypeInfo = nullptr; // catch-all 206 // Don't consider any other catches. 207 break; 208 } 209 210 Handler.TypeInfo = GetEHType(CatchDecl->getType()); 211 } 212 213 EHCatchScope *Catch = CGF.EHStack.pushCatch(Handlers.size()); 214 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) 215 Catch->setHandler(I, Handlers[I].TypeInfo, Handlers[I].Block); 216 } 217 218 // Emit the try body. 219 CGF.EmitStmt(S.getTryBody()); 220 221 // Leave the try. 222 if (S.getNumCatchStmts()) 223 CGF.popCatchScope(); 224 225 // Remember where we were. 226 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); 227 228 // Emit the handlers. 229 for (unsigned I = 0, E = Handlers.size(); I != E; ++I) { 230 CatchHandler &Handler = Handlers[I]; 231 232 CGF.EmitBlock(Handler.Block); 233 llvm::Value *RawExn = CGF.getExceptionFromSlot(); 234 235 // Enter the catch. 236 llvm::Value *Exn = RawExn; 237 if (beginCatchFn) { 238 Exn = CGF.Builder.CreateCall(beginCatchFn, RawExn, "exn.adjusted"); 239 cast<llvm::CallInst>(Exn)->setDoesNotThrow(); 240 } 241 242 CodeGenFunction::LexicalScope cleanups(CGF, Handler.Body->getSourceRange()); 243 244 if (endCatchFn) { 245 // Add a cleanup to leave the catch. 246 bool EndCatchMightThrow = (Handler.Variable == nullptr); 247 248 CGF.EHStack.pushCleanup<CallObjCEndCatch>(NormalAndEHCleanup, 249 EndCatchMightThrow, 250 endCatchFn); 251 } 252 253 // Bind the catch parameter if it exists. 254 if (const VarDecl *CatchParam = Handler.Variable) { 255 llvm::Type *CatchType = CGF.ConvertType(CatchParam->getType()); 256 llvm::Value *CastExn = CGF.Builder.CreateBitCast(Exn, CatchType); 257 258 CGF.EmitAutoVarDecl(*CatchParam); 259 EmitInitOfCatchParam(CGF, CastExn, CatchParam); 260 } 261 262 CGF.ObjCEHValueStack.push_back(Exn); 263 CGF.EmitStmt(Handler.Body); 264 CGF.ObjCEHValueStack.pop_back(); 265 266 // Leave any cleanups associated with the catch. 267 cleanups.ForceCleanup(); 268 269 CGF.EmitBranchThroughCleanup(Cont); 270 } 271 272 // Go back to the try-statement fallthrough. 273 CGF.Builder.restoreIP(SavedIP); 274 275 // Pop out of the finally. 276 if (S.getFinallyStmt()) 277 FinallyInfo.exit(CGF); 278 279 if (Cont.isValid()) 280 CGF.EmitBlock(Cont.getBlock()); 281 } 282 283 void CGObjCRuntime::EmitInitOfCatchParam(CodeGenFunction &CGF, 284 llvm::Value *exn, 285 const VarDecl *paramDecl) { 286 287 Address paramAddr = CGF.GetAddrOfLocalVar(paramDecl); 288 289 switch (paramDecl->getType().getQualifiers().getObjCLifetime()) { 290 case Qualifiers::OCL_Strong: 291 exn = CGF.EmitARCRetainNonBlock(exn); 292 // fallthrough 293 294 case Qualifiers::OCL_None: 295 case Qualifiers::OCL_ExplicitNone: 296 case Qualifiers::OCL_Autoreleasing: 297 CGF.Builder.CreateStore(exn, paramAddr); 298 return; 299 300 case Qualifiers::OCL_Weak: 301 CGF.EmitARCInitWeak(paramAddr, exn); 302 return; 303 } 304 llvm_unreachable("invalid ownership qualifier"); 305 } 306 307 namespace { 308 struct CallSyncExit final : EHScopeStack::Cleanup { 309 llvm::Value *SyncExitFn; 310 llvm::Value *SyncArg; 311 CallSyncExit(llvm::Value *SyncExitFn, llvm::Value *SyncArg) 312 : SyncExitFn(SyncExitFn), SyncArg(SyncArg) {} 313 314 void Emit(CodeGenFunction &CGF, Flags flags) override { 315 CGF.Builder.CreateCall(SyncExitFn, SyncArg)->setDoesNotThrow(); 316 } 317 }; 318 } 319 320 void CGObjCRuntime::EmitAtSynchronizedStmt(CodeGenFunction &CGF, 321 const ObjCAtSynchronizedStmt &S, 322 llvm::Function *syncEnterFn, 323 llvm::Function *syncExitFn) { 324 CodeGenFunction::RunCleanupsScope cleanups(CGF); 325 326 // Evaluate the lock operand. This is guaranteed to dominate the 327 // ARC release and lock-release cleanups. 328 const Expr *lockExpr = S.getSynchExpr(); 329 llvm::Value *lock; 330 if (CGF.getLangOpts().ObjCAutoRefCount) { 331 lock = CGF.EmitARCRetainScalarExpr(lockExpr); 332 lock = CGF.EmitObjCConsumeObject(lockExpr->getType(), lock); 333 } else { 334 lock = CGF.EmitScalarExpr(lockExpr); 335 } 336 lock = CGF.Builder.CreateBitCast(lock, CGF.VoidPtrTy); 337 338 // Acquire the lock. 339 CGF.Builder.CreateCall(syncEnterFn, lock)->setDoesNotThrow(); 340 341 // Register an all-paths cleanup to release the lock. 342 CGF.EHStack.pushCleanup<CallSyncExit>(NormalAndEHCleanup, syncExitFn, lock); 343 344 // Emit the body of the statement. 345 CGF.EmitStmt(S.getSynchBody()); 346 } 347 348 /// Compute the pointer-to-function type to which a message send 349 /// should be casted in order to correctly call the given method 350 /// with the given arguments. 351 /// 352 /// \param method - may be null 353 /// \param resultType - the result type to use if there's no method 354 /// \param callArgs - the actual arguments, including implicit ones 355 CGObjCRuntime::MessageSendInfo 356 CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method, 357 QualType resultType, 358 CallArgList &callArgs) { 359 // If there's a method, use information from that. 360 if (method) { 361 const CGFunctionInfo &signature = 362 CGM.getTypes().arrangeObjCMessageSendSignature(method, callArgs[0].Ty); 363 364 llvm::PointerType *signatureType = 365 CGM.getTypes().GetFunctionType(signature)->getPointerTo(); 366 367 // If that's not variadic, there's no need to recompute the ABI 368 // arrangement. 369 if (!signature.isVariadic()) 370 return MessageSendInfo(signature, signatureType); 371 372 // Otherwise, there is. 373 FunctionType::ExtInfo einfo = signature.getExtInfo(); 374 const CGFunctionInfo &argsInfo = 375 CGM.getTypes().arrangeFreeFunctionCall(resultType, callArgs, einfo, 376 signature.getRequiredArgs()); 377 378 return MessageSendInfo(argsInfo, signatureType); 379 } 380 381 // There's no method; just use a default CC. 382 const CGFunctionInfo &argsInfo = 383 CGM.getTypes().arrangeFreeFunctionCall(resultType, callArgs, 384 FunctionType::ExtInfo(), 385 RequiredArgs::All); 386 387 // Derive the signature to call from that. 388 llvm::PointerType *signatureType = 389 CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo(); 390 return MessageSendInfo(argsInfo, signatureType); 391 } 392