1 //===--- CGException.cpp - Emit LLVM Code for C++ exceptions --------------===// 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 contains code dealing with C++ exception related code generation. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "CodeGenFunction.h" 15 #include "CGCleanup.h" 16 #include "CGObjCRuntime.h" 17 #include "TargetInfo.h" 18 #include "clang/AST/StmtCXX.h" 19 #include "clang/AST/StmtObjC.h" 20 #include "llvm/IR/Intrinsics.h" 21 #include "llvm/Support/CallSite.h" 22 23 using namespace clang; 24 using namespace CodeGen; 25 26 static llvm::Constant *getAllocateExceptionFn(CodeGenModule &CGM) { 27 // void *__cxa_allocate_exception(size_t thrown_size); 28 29 llvm::FunctionType *FTy = 30 llvm::FunctionType::get(CGM.Int8PtrTy, CGM.SizeTy, /*IsVarArgs=*/false); 31 32 return CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception"); 33 } 34 35 static llvm::Constant *getFreeExceptionFn(CodeGenModule &CGM) { 36 // void __cxa_free_exception(void *thrown_exception); 37 38 llvm::FunctionType *FTy = 39 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 40 41 return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception"); 42 } 43 44 static llvm::Constant *getThrowFn(CodeGenModule &CGM) { 45 // void __cxa_throw(void *thrown_exception, std::type_info *tinfo, 46 // void (*dest) (void *)); 47 48 llvm::Type *Args[3] = { CGM.Int8PtrTy, CGM.Int8PtrTy, CGM.Int8PtrTy }; 49 llvm::FunctionType *FTy = 50 llvm::FunctionType::get(CGM.VoidTy, Args, /*IsVarArgs=*/false); 51 52 return CGM.CreateRuntimeFunction(FTy, "__cxa_throw"); 53 } 54 55 static llvm::Constant *getReThrowFn(CodeGenModule &CGM) { 56 // void __cxa_rethrow(); 57 58 llvm::FunctionType *FTy = 59 llvm::FunctionType::get(CGM.VoidTy, /*IsVarArgs=*/false); 60 61 return CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow"); 62 } 63 64 static llvm::Constant *getGetExceptionPtrFn(CodeGenModule &CGM) { 65 // void *__cxa_get_exception_ptr(void*); 66 67 llvm::FunctionType *FTy = 68 llvm::FunctionType::get(CGM.Int8PtrTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 69 70 return CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr"); 71 } 72 73 static llvm::Constant *getBeginCatchFn(CodeGenModule &CGM) { 74 // void *__cxa_begin_catch(void*); 75 76 llvm::FunctionType *FTy = 77 llvm::FunctionType::get(CGM.Int8PtrTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 78 79 return CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch"); 80 } 81 82 static llvm::Constant *getEndCatchFn(CodeGenModule &CGM) { 83 // void __cxa_end_catch(); 84 85 llvm::FunctionType *FTy = 86 llvm::FunctionType::get(CGM.VoidTy, /*IsVarArgs=*/false); 87 88 return CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch"); 89 } 90 91 static llvm::Constant *getUnexpectedFn(CodeGenModule &CGM) { 92 // void __cxa_call_unexepcted(void *thrown_exception); 93 94 llvm::FunctionType *FTy = 95 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 96 97 return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); 98 } 99 100 llvm::Constant *CodeGenFunction::getUnwindResumeFn() { 101 llvm::FunctionType *FTy = 102 llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); 103 104 if (CGM.getLangOpts().SjLjExceptions) 105 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume"); 106 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume"); 107 } 108 109 llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() { 110 llvm::FunctionType *FTy = 111 llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); 112 113 if (CGM.getLangOpts().SjLjExceptions) 114 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume_or_Rethrow"); 115 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume_or_Rethrow"); 116 } 117 118 static llvm::Constant *getTerminateFn(CodeGenModule &CGM) { 119 // void __terminate(); 120 121 llvm::FunctionType *FTy = 122 llvm::FunctionType::get(CGM.VoidTy, /*IsVarArgs=*/false); 123 124 StringRef name; 125 126 // In C++, use std::terminate(). 127 if (CGM.getLangOpts().CPlusPlus) 128 name = "_ZSt9terminatev"; // FIXME: mangling! 129 else if (CGM.getLangOpts().ObjC1 && 130 CGM.getLangOpts().ObjCRuntime.hasTerminate()) 131 name = "objc_terminate"; 132 else 133 name = "abort"; 134 return CGM.CreateRuntimeFunction(FTy, name); 135 } 136 137 static llvm::Constant *getCatchallRethrowFn(CodeGenModule &CGM, 138 StringRef Name) { 139 llvm::FunctionType *FTy = 140 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 141 142 return CGM.CreateRuntimeFunction(FTy, Name); 143 } 144 145 namespace { 146 /// The exceptions personality for a function. 147 struct EHPersonality { 148 const char *PersonalityFn; 149 150 // If this is non-null, this personality requires a non-standard 151 // function for rethrowing an exception after a catchall cleanup. 152 // This function must have prototype void(void*). 153 const char *CatchallRethrowFn; 154 155 static const EHPersonality &get(const LangOptions &Lang); 156 static const EHPersonality GNU_C; 157 static const EHPersonality GNU_C_SJLJ; 158 static const EHPersonality GNU_ObjC; 159 static const EHPersonality GNUstep_ObjC; 160 static const EHPersonality GNU_ObjCXX; 161 static const EHPersonality NeXT_ObjC; 162 static const EHPersonality GNU_CPlusPlus; 163 static const EHPersonality GNU_CPlusPlus_SJLJ; 164 }; 165 } 166 167 const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", 0 }; 168 const EHPersonality EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", 0 }; 169 const EHPersonality EHPersonality::NeXT_ObjC = { "__objc_personality_v0", 0 }; 170 const EHPersonality EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", 0}; 171 const EHPersonality 172 EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", 0 }; 173 const EHPersonality 174 EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"}; 175 const EHPersonality 176 EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", 0 }; 177 const EHPersonality 178 EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", 0 }; 179 180 static const EHPersonality &getCPersonality(const LangOptions &L) { 181 if (L.SjLjExceptions) 182 return EHPersonality::GNU_C_SJLJ; 183 return EHPersonality::GNU_C; 184 } 185 186 static const EHPersonality &getObjCPersonality(const LangOptions &L) { 187 switch (L.ObjCRuntime.getKind()) { 188 case ObjCRuntime::FragileMacOSX: 189 return getCPersonality(L); 190 case ObjCRuntime::MacOSX: 191 case ObjCRuntime::iOS: 192 return EHPersonality::NeXT_ObjC; 193 case ObjCRuntime::GNUstep: 194 if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7)) 195 return EHPersonality::GNUstep_ObjC; 196 // fallthrough 197 case ObjCRuntime::GCC: 198 case ObjCRuntime::ObjFW: 199 return EHPersonality::GNU_ObjC; 200 } 201 llvm_unreachable("bad runtime kind"); 202 } 203 204 static const EHPersonality &getCXXPersonality(const LangOptions &L) { 205 if (L.SjLjExceptions) 206 return EHPersonality::GNU_CPlusPlus_SJLJ; 207 else 208 return EHPersonality::GNU_CPlusPlus; 209 } 210 211 /// Determines the personality function to use when both C++ 212 /// and Objective-C exceptions are being caught. 213 static const EHPersonality &getObjCXXPersonality(const LangOptions &L) { 214 switch (L.ObjCRuntime.getKind()) { 215 // The ObjC personality defers to the C++ personality for non-ObjC 216 // handlers. Unlike the C++ case, we use the same personality 217 // function on targets using (backend-driven) SJLJ EH. 218 case ObjCRuntime::MacOSX: 219 case ObjCRuntime::iOS: 220 return EHPersonality::NeXT_ObjC; 221 222 // In the fragile ABI, just use C++ exception handling and hope 223 // they're not doing crazy exception mixing. 224 case ObjCRuntime::FragileMacOSX: 225 return getCXXPersonality(L); 226 227 // The GCC runtime's personality function inherently doesn't support 228 // mixed EH. Use the C++ personality just to avoid returning null. 229 case ObjCRuntime::GCC: 230 case ObjCRuntime::ObjFW: // XXX: this will change soon 231 return EHPersonality::GNU_ObjC; 232 case ObjCRuntime::GNUstep: 233 return EHPersonality::GNU_ObjCXX; 234 } 235 llvm_unreachable("bad runtime kind"); 236 } 237 238 const EHPersonality &EHPersonality::get(const LangOptions &L) { 239 if (L.CPlusPlus && L.ObjC1) 240 return getObjCXXPersonality(L); 241 else if (L.CPlusPlus) 242 return getCXXPersonality(L); 243 else if (L.ObjC1) 244 return getObjCPersonality(L); 245 else 246 return getCPersonality(L); 247 } 248 249 static llvm::Constant *getPersonalityFn(CodeGenModule &CGM, 250 const EHPersonality &Personality) { 251 llvm::Constant *Fn = 252 CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true), 253 Personality.PersonalityFn); 254 return Fn; 255 } 256 257 static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM, 258 const EHPersonality &Personality) { 259 llvm::Constant *Fn = getPersonalityFn(CGM, Personality); 260 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy); 261 } 262 263 /// Check whether a personality function could reasonably be swapped 264 /// for a C++ personality function. 265 static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) { 266 for (llvm::Constant::use_iterator 267 I = Fn->use_begin(), E = Fn->use_end(); I != E; ++I) { 268 llvm::User *User = *I; 269 270 // Conditionally white-list bitcasts. 271 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(User)) { 272 if (CE->getOpcode() != llvm::Instruction::BitCast) return false; 273 if (!PersonalityHasOnlyCXXUses(CE)) 274 return false; 275 continue; 276 } 277 278 // Otherwise, it has to be a landingpad instruction. 279 llvm::LandingPadInst *LPI = dyn_cast<llvm::LandingPadInst>(User); 280 if (!LPI) return false; 281 282 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) { 283 // Look for something that would've been returned by the ObjC 284 // runtime's GetEHType() method. 285 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts(); 286 if (LPI->isCatch(I)) { 287 // Check if the catch value has the ObjC prefix. 288 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val)) 289 // ObjC EH selector entries are always global variables with 290 // names starting like this. 291 if (GV->getName().startswith("OBJC_EHTYPE")) 292 return false; 293 } else { 294 // Check if any of the filter values have the ObjC prefix. 295 llvm::Constant *CVal = cast<llvm::Constant>(Val); 296 for (llvm::User::op_iterator 297 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) { 298 if (llvm::GlobalVariable *GV = 299 cast<llvm::GlobalVariable>((*II)->stripPointerCasts())) 300 // ObjC EH selector entries are always global variables with 301 // names starting like this. 302 if (GV->getName().startswith("OBJC_EHTYPE")) 303 return false; 304 } 305 } 306 } 307 } 308 309 return true; 310 } 311 312 /// Try to use the C++ personality function in ObjC++. Not doing this 313 /// can cause some incompatibilities with gcc, which is more 314 /// aggressive about only using the ObjC++ personality in a function 315 /// when it really needs it. 316 void CodeGenModule::SimplifyPersonality() { 317 // If we're not in ObjC++ -fexceptions, there's nothing to do. 318 if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions) 319 return; 320 321 // Both the problem this endeavors to fix and the way the logic 322 // above works is specific to the NeXT runtime. 323 if (!LangOpts.ObjCRuntime.isNeXTFamily()) 324 return; 325 326 const EHPersonality &ObjCXX = EHPersonality::get(LangOpts); 327 const EHPersonality &CXX = getCXXPersonality(LangOpts); 328 if (&ObjCXX == &CXX) 329 return; 330 331 assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 && 332 "Different EHPersonalities using the same personality function."); 333 334 llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn); 335 336 // Nothing to do if it's unused. 337 if (!Fn || Fn->use_empty()) return; 338 339 // Can't do the optimization if it has non-C++ uses. 340 if (!PersonalityHasOnlyCXXUses(Fn)) return; 341 342 // Create the C++ personality function and kill off the old 343 // function. 344 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX); 345 346 // This can happen if the user is screwing with us. 347 if (Fn->getType() != CXXFn->getType()) return; 348 349 Fn->replaceAllUsesWith(CXXFn); 350 Fn->eraseFromParent(); 351 } 352 353 /// Returns the value to inject into a selector to indicate the 354 /// presence of a catch-all. 355 static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) { 356 // Possibly we should use @llvm.eh.catch.all.value here. 357 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy); 358 } 359 360 namespace { 361 /// A cleanup to free the exception object if its initialization 362 /// throws. 363 struct FreeException : EHScopeStack::Cleanup { 364 llvm::Value *exn; 365 FreeException(llvm::Value *exn) : exn(exn) {} 366 void Emit(CodeGenFunction &CGF, Flags flags) { 367 CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn); 368 } 369 }; 370 } 371 372 // Emits an exception expression into the given location. This 373 // differs from EmitAnyExprToMem only in that, if a final copy-ctor 374 // call is required, an exception within that copy ctor causes 375 // std::terminate to be invoked. 376 static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *e, 377 llvm::Value *addr) { 378 // Make sure the exception object is cleaned up if there's an 379 // exception during initialization. 380 CGF.pushFullExprCleanup<FreeException>(EHCleanup, addr); 381 EHScopeStack::stable_iterator cleanup = CGF.EHStack.stable_begin(); 382 383 // __cxa_allocate_exception returns a void*; we need to cast this 384 // to the appropriate type for the object. 385 llvm::Type *ty = CGF.ConvertTypeForMem(e->getType())->getPointerTo(); 386 llvm::Value *typedAddr = CGF.Builder.CreateBitCast(addr, ty); 387 388 // FIXME: this isn't quite right! If there's a final unelided call 389 // to a copy constructor, then according to [except.terminate]p1 we 390 // must call std::terminate() if that constructor throws, because 391 // technically that copy occurs after the exception expression is 392 // evaluated but before the exception is caught. But the best way 393 // to handle that is to teach EmitAggExpr to do the final copy 394 // differently if it can't be elided. 395 CGF.EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(), 396 /*IsInit*/ true); 397 398 // Deactivate the cleanup block. 399 CGF.DeactivateCleanupBlock(cleanup, cast<llvm::Instruction>(typedAddr)); 400 } 401 402 llvm::Value *CodeGenFunction::getExceptionSlot() { 403 if (!ExceptionSlot) 404 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot"); 405 return ExceptionSlot; 406 } 407 408 llvm::Value *CodeGenFunction::getEHSelectorSlot() { 409 if (!EHSelectorSlot) 410 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot"); 411 return EHSelectorSlot; 412 } 413 414 llvm::Value *CodeGenFunction::getExceptionFromSlot() { 415 return Builder.CreateLoad(getExceptionSlot(), "exn"); 416 } 417 418 llvm::Value *CodeGenFunction::getSelectorFromSlot() { 419 return Builder.CreateLoad(getEHSelectorSlot(), "sel"); 420 } 421 422 void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) { 423 if (!E->getSubExpr()) { 424 EmitNoreturnRuntimeCallOrInvoke(getReThrowFn(CGM), 425 ArrayRef<llvm::Value*>()); 426 427 // throw is an expression, and the expression emitters expect us 428 // to leave ourselves at a valid insertion point. 429 EmitBlock(createBasicBlock("throw.cont")); 430 431 return; 432 } 433 434 QualType ThrowType = E->getSubExpr()->getType(); 435 436 if (ThrowType->isObjCObjectPointerType()) { 437 const Stmt *ThrowStmt = E->getSubExpr(); 438 const ObjCAtThrowStmt S(E->getExprLoc(), 439 const_cast<Stmt *>(ThrowStmt)); 440 CGM.getObjCRuntime().EmitThrowStmt(*this, S, false); 441 // This will clear insertion point which was not cleared in 442 // call to EmitThrowStmt. 443 EmitBlock(createBasicBlock("throw.cont")); 444 return; 445 } 446 447 // Now allocate the exception object. 448 llvm::Type *SizeTy = ConvertType(getContext().getSizeType()); 449 uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity(); 450 451 llvm::Constant *AllocExceptionFn = getAllocateExceptionFn(CGM); 452 llvm::CallInst *ExceptionPtr = 453 EmitNounwindRuntimeCall(AllocExceptionFn, 454 llvm::ConstantInt::get(SizeTy, TypeSize), 455 "exception"); 456 457 EmitAnyExprToExn(*this, E->getSubExpr(), ExceptionPtr); 458 459 // Now throw the exception. 460 llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType, 461 /*ForEH=*/true); 462 463 // The address of the destructor. If the exception type has a 464 // trivial destructor (or isn't a record), we just pass null. 465 llvm::Constant *Dtor = 0; 466 if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) { 467 CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl()); 468 if (!Record->hasTrivialDestructor()) { 469 CXXDestructorDecl *DtorD = Record->getDestructor(); 470 Dtor = CGM.GetAddrOfCXXDestructor(DtorD, Dtor_Complete); 471 Dtor = llvm::ConstantExpr::getBitCast(Dtor, Int8PtrTy); 472 } 473 } 474 if (!Dtor) Dtor = llvm::Constant::getNullValue(Int8PtrTy); 475 476 llvm::Value *args[] = { ExceptionPtr, TypeInfo, Dtor }; 477 EmitNoreturnRuntimeCallOrInvoke(getThrowFn(CGM), args); 478 479 // throw is an expression, and the expression emitters expect us 480 // to leave ourselves at a valid insertion point. 481 EmitBlock(createBasicBlock("throw.cont")); 482 } 483 484 void CodeGenFunction::EmitStartEHSpec(const Decl *D) { 485 if (!CGM.getLangOpts().CXXExceptions) 486 return; 487 488 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 489 if (FD == 0) 490 return; 491 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 492 if (Proto == 0) 493 return; 494 495 ExceptionSpecificationType EST = Proto->getExceptionSpecType(); 496 if (isNoexceptExceptionSpec(EST)) { 497 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) { 498 // noexcept functions are simple terminate scopes. 499 EHStack.pushTerminate(); 500 } 501 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) { 502 unsigned NumExceptions = Proto->getNumExceptions(); 503 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions); 504 505 for (unsigned I = 0; I != NumExceptions; ++I) { 506 QualType Ty = Proto->getExceptionType(I); 507 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType(); 508 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType, 509 /*ForEH=*/true); 510 Filter->setFilter(I, EHType); 511 } 512 } 513 } 514 515 /// Emit the dispatch block for a filter scope if necessary. 516 static void emitFilterDispatchBlock(CodeGenFunction &CGF, 517 EHFilterScope &filterScope) { 518 llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock(); 519 if (!dispatchBlock) return; 520 if (dispatchBlock->use_empty()) { 521 delete dispatchBlock; 522 return; 523 } 524 525 CGF.EmitBlockAfterUses(dispatchBlock); 526 527 // If this isn't a catch-all filter, we need to check whether we got 528 // here because the filter triggered. 529 if (filterScope.getNumFilters()) { 530 // Load the selector value. 531 llvm::Value *selector = CGF.getSelectorFromSlot(); 532 llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected"); 533 534 llvm::Value *zero = CGF.Builder.getInt32(0); 535 llvm::Value *failsFilter = 536 CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails"); 537 CGF.Builder.CreateCondBr(failsFilter, unexpectedBB, CGF.getEHResumeBlock(false)); 538 539 CGF.EmitBlock(unexpectedBB); 540 } 541 542 // Call __cxa_call_unexpected. This doesn't need to be an invoke 543 // because __cxa_call_unexpected magically filters exceptions 544 // according to the last landing pad the exception was thrown 545 // into. Seriously. 546 llvm::Value *exn = CGF.getExceptionFromSlot(); 547 CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn) 548 ->setDoesNotReturn(); 549 CGF.Builder.CreateUnreachable(); 550 } 551 552 void CodeGenFunction::EmitEndEHSpec(const Decl *D) { 553 if (!CGM.getLangOpts().CXXExceptions) 554 return; 555 556 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 557 if (FD == 0) 558 return; 559 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 560 if (Proto == 0) 561 return; 562 563 ExceptionSpecificationType EST = Proto->getExceptionSpecType(); 564 if (isNoexceptExceptionSpec(EST)) { 565 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) { 566 EHStack.popTerminate(); 567 } 568 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) { 569 EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin()); 570 emitFilterDispatchBlock(*this, filterScope); 571 EHStack.popFilter(); 572 } 573 } 574 575 void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) { 576 EnterCXXTryStmt(S); 577 EmitStmt(S.getTryBlock()); 578 ExitCXXTryStmt(S); 579 } 580 581 void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 582 unsigned NumHandlers = S.getNumHandlers(); 583 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers); 584 585 for (unsigned I = 0; I != NumHandlers; ++I) { 586 const CXXCatchStmt *C = S.getHandler(I); 587 588 llvm::BasicBlock *Handler = createBasicBlock("catch"); 589 if (C->getExceptionDecl()) { 590 // FIXME: Dropping the reference type on the type into makes it 591 // impossible to correctly implement catch-by-reference 592 // semantics for pointers. Unfortunately, this is what all 593 // existing compilers do, and it's not clear that the standard 594 // personality routine is capable of doing this right. See C++ DR 388: 595 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388 596 QualType CaughtType = C->getCaughtType(); 597 CaughtType = CaughtType.getNonReferenceType().getUnqualifiedType(); 598 599 llvm::Value *TypeInfo = 0; 600 if (CaughtType->isObjCObjectPointerType()) 601 TypeInfo = CGM.getObjCRuntime().GetEHType(CaughtType); 602 else 603 TypeInfo = CGM.GetAddrOfRTTIDescriptor(CaughtType, /*ForEH=*/true); 604 CatchScope->setHandler(I, TypeInfo, Handler); 605 } else { 606 // No exception decl indicates '...', a catch-all. 607 CatchScope->setCatchAllHandler(I, Handler); 608 } 609 } 610 } 611 612 llvm::BasicBlock * 613 CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) { 614 // The dispatch block for the end of the scope chain is a block that 615 // just resumes unwinding. 616 if (si == EHStack.stable_end()) 617 return getEHResumeBlock(true); 618 619 // Otherwise, we should look at the actual scope. 620 EHScope &scope = *EHStack.find(si); 621 622 llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock(); 623 if (!dispatchBlock) { 624 switch (scope.getKind()) { 625 case EHScope::Catch: { 626 // Apply a special case to a single catch-all. 627 EHCatchScope &catchScope = cast<EHCatchScope>(scope); 628 if (catchScope.getNumHandlers() == 1 && 629 catchScope.getHandler(0).isCatchAll()) { 630 dispatchBlock = catchScope.getHandler(0).Block; 631 632 // Otherwise, make a dispatch block. 633 } else { 634 dispatchBlock = createBasicBlock("catch.dispatch"); 635 } 636 break; 637 } 638 639 case EHScope::Cleanup: 640 dispatchBlock = createBasicBlock("ehcleanup"); 641 break; 642 643 case EHScope::Filter: 644 dispatchBlock = createBasicBlock("filter.dispatch"); 645 break; 646 647 case EHScope::Terminate: 648 dispatchBlock = getTerminateHandler(); 649 break; 650 } 651 scope.setCachedEHDispatchBlock(dispatchBlock); 652 } 653 return dispatchBlock; 654 } 655 656 /// Check whether this is a non-EH scope, i.e. a scope which doesn't 657 /// affect exception handling. Currently, the only non-EH scopes are 658 /// normal-only cleanup scopes. 659 static bool isNonEHScope(const EHScope &S) { 660 switch (S.getKind()) { 661 case EHScope::Cleanup: 662 return !cast<EHCleanupScope>(S).isEHCleanup(); 663 case EHScope::Filter: 664 case EHScope::Catch: 665 case EHScope::Terminate: 666 return false; 667 } 668 669 llvm_unreachable("Invalid EHScope Kind!"); 670 } 671 672 llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() { 673 assert(EHStack.requiresLandingPad()); 674 assert(!EHStack.empty()); 675 676 if (!CGM.getLangOpts().Exceptions) 677 return 0; 678 679 // Check the innermost scope for a cached landing pad. If this is 680 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad. 681 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad(); 682 if (LP) return LP; 683 684 // Build the landing pad for this scope. 685 LP = EmitLandingPad(); 686 assert(LP); 687 688 // Cache the landing pad on the innermost scope. If this is a 689 // non-EH scope, cache the landing pad on the enclosing scope, too. 690 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) { 691 ir->setCachedLandingPad(LP); 692 if (!isNonEHScope(*ir)) break; 693 } 694 695 return LP; 696 } 697 698 // This code contains a hack to work around a design flaw in 699 // LLVM's EH IR which breaks semantics after inlining. This same 700 // hack is implemented in llvm-gcc. 701 // 702 // The LLVM EH abstraction is basically a thin veneer over the 703 // traditional GCC zero-cost design: for each range of instructions 704 // in the function, there is (at most) one "landing pad" with an 705 // associated chain of EH actions. A language-specific personality 706 // function interprets this chain of actions and (1) decides whether 707 // or not to resume execution at the landing pad and (2) if so, 708 // provides an integer indicating why it's stopping. In LLVM IR, 709 // the association of a landing pad with a range of instructions is 710 // achieved via an invoke instruction, the chain of actions becomes 711 // the arguments to the @llvm.eh.selector call, and the selector 712 // call returns the integer indicator. Other than the required 713 // presence of two intrinsic function calls in the landing pad, 714 // the IR exactly describes the layout of the output code. 715 // 716 // A principal advantage of this design is that it is completely 717 // language-agnostic; in theory, the LLVM optimizers can treat 718 // landing pads neutrally, and targets need only know how to lower 719 // the intrinsics to have a functioning exceptions system (assuming 720 // that platform exceptions follow something approximately like the 721 // GCC design). Unfortunately, landing pads cannot be combined in a 722 // language-agnostic way: given selectors A and B, there is no way 723 // to make a single landing pad which faithfully represents the 724 // semantics of propagating an exception first through A, then 725 // through B, without knowing how the personality will interpret the 726 // (lowered form of the) selectors. This means that inlining has no 727 // choice but to crudely chain invokes (i.e., to ignore invokes in 728 // the inlined function, but to turn all unwindable calls into 729 // invokes), which is only semantically valid if every unwind stops 730 // at every landing pad. 731 // 732 // Therefore, the invoke-inline hack is to guarantee that every 733 // landing pad has a catch-all. 734 enum CleanupHackLevel_t { 735 /// A level of hack that requires that all landing pads have 736 /// catch-alls. 737 CHL_MandatoryCatchall, 738 739 /// A level of hack that requires that all landing pads handle 740 /// cleanups. 741 CHL_MandatoryCleanup, 742 743 /// No hacks at all; ideal IR generation. 744 CHL_Ideal 745 }; 746 const CleanupHackLevel_t CleanupHackLevel = CHL_MandatoryCleanup; 747 748 llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { 749 assert(EHStack.requiresLandingPad()); 750 751 EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope()); 752 switch (innermostEHScope.getKind()) { 753 case EHScope::Terminate: 754 return getTerminateLandingPad(); 755 756 case EHScope::Catch: 757 case EHScope::Cleanup: 758 case EHScope::Filter: 759 if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad()) 760 return lpad; 761 } 762 763 // Save the current IR generation state. 764 CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP(); 765 766 const EHPersonality &personality = EHPersonality::get(getLangOpts()); 767 768 // Create and configure the landing pad. 769 llvm::BasicBlock *lpad = createBasicBlock("lpad"); 770 EmitBlock(lpad); 771 772 llvm::LandingPadInst *LPadInst = 773 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, NULL), 774 getOpaquePersonalityFn(CGM, personality), 0); 775 776 llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0); 777 Builder.CreateStore(LPadExn, getExceptionSlot()); 778 llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1); 779 Builder.CreateStore(LPadSel, getEHSelectorSlot()); 780 781 // Save the exception pointer. It's safe to use a single exception 782 // pointer per function because EH cleanups can never have nested 783 // try/catches. 784 // Build the landingpad instruction. 785 786 // Accumulate all the handlers in scope. 787 bool hasCatchAll = false; 788 bool hasCleanup = false; 789 bool hasFilter = false; 790 SmallVector<llvm::Value*, 4> filterTypes; 791 llvm::SmallPtrSet<llvm::Value*, 4> catchTypes; 792 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); 793 I != E; ++I) { 794 795 switch (I->getKind()) { 796 case EHScope::Cleanup: 797 // If we have a cleanup, remember that. 798 hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup()); 799 continue; 800 801 case EHScope::Filter: { 802 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack"); 803 assert(!hasCatchAll && "EH filter reached after catch-all"); 804 805 // Filter scopes get added to the landingpad in weird ways. 806 EHFilterScope &filter = cast<EHFilterScope>(*I); 807 hasFilter = true; 808 809 // Add all the filter values. 810 for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i) 811 filterTypes.push_back(filter.getFilter(i)); 812 goto done; 813 } 814 815 case EHScope::Terminate: 816 // Terminate scopes are basically catch-alls. 817 assert(!hasCatchAll); 818 hasCatchAll = true; 819 goto done; 820 821 case EHScope::Catch: 822 break; 823 } 824 825 EHCatchScope &catchScope = cast<EHCatchScope>(*I); 826 for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) { 827 EHCatchScope::Handler handler = catchScope.getHandler(hi); 828 829 // If this is a catch-all, register that and abort. 830 if (!handler.Type) { 831 assert(!hasCatchAll); 832 hasCatchAll = true; 833 goto done; 834 } 835 836 // Check whether we already have a handler for this type. 837 if (catchTypes.insert(handler.Type)) 838 // If not, add it directly to the landingpad. 839 LPadInst->addClause(handler.Type); 840 } 841 } 842 843 done: 844 // If we have a catch-all, add null to the landingpad. 845 assert(!(hasCatchAll && hasFilter)); 846 if (hasCatchAll) { 847 LPadInst->addClause(getCatchAllValue(*this)); 848 849 // If we have an EH filter, we need to add those handlers in the 850 // right place in the landingpad, which is to say, at the end. 851 } else if (hasFilter) { 852 // Create a filter expression: a constant array indicating which filter 853 // types there are. The personality routine only lands here if the filter 854 // doesn't match. 855 SmallVector<llvm::Constant*, 8> Filters; 856 llvm::ArrayType *AType = 857 llvm::ArrayType::get(!filterTypes.empty() ? 858 filterTypes[0]->getType() : Int8PtrTy, 859 filterTypes.size()); 860 861 for (unsigned i = 0, e = filterTypes.size(); i != e; ++i) 862 Filters.push_back(cast<llvm::Constant>(filterTypes[i])); 863 llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters); 864 LPadInst->addClause(FilterArray); 865 866 // Also check whether we need a cleanup. 867 if (hasCleanup) 868 LPadInst->setCleanup(true); 869 870 // Otherwise, signal that we at least have cleanups. 871 } else if (CleanupHackLevel == CHL_MandatoryCatchall || hasCleanup) { 872 if (CleanupHackLevel == CHL_MandatoryCatchall) 873 LPadInst->addClause(getCatchAllValue(*this)); 874 else 875 LPadInst->setCleanup(true); 876 } 877 878 assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) && 879 "landingpad instruction has no clauses!"); 880 881 // Tell the backend how to generate the landing pad. 882 Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope())); 883 884 // Restore the old IR generation state. 885 Builder.restoreIP(savedIP); 886 887 return lpad; 888 } 889 890 namespace { 891 /// A cleanup to call __cxa_end_catch. In many cases, the caught 892 /// exception type lets us state definitively that the thrown exception 893 /// type does not have a destructor. In particular: 894 /// - Catch-alls tell us nothing, so we have to conservatively 895 /// assume that the thrown exception might have a destructor. 896 /// - Catches by reference behave according to their base types. 897 /// - Catches of non-record types will only trigger for exceptions 898 /// of non-record types, which never have destructors. 899 /// - Catches of record types can trigger for arbitrary subclasses 900 /// of the caught type, so we have to assume the actual thrown 901 /// exception type might have a throwing destructor, even if the 902 /// caught type's destructor is trivial or nothrow. 903 struct CallEndCatch : EHScopeStack::Cleanup { 904 CallEndCatch(bool MightThrow) : MightThrow(MightThrow) {} 905 bool MightThrow; 906 907 void Emit(CodeGenFunction &CGF, Flags flags) { 908 if (!MightThrow) { 909 CGF.EmitNounwindRuntimeCall(getEndCatchFn(CGF.CGM)); 910 return; 911 } 912 913 CGF.EmitRuntimeCallOrInvoke(getEndCatchFn(CGF.CGM)); 914 } 915 }; 916 } 917 918 /// Emits a call to __cxa_begin_catch and enters a cleanup to call 919 /// __cxa_end_catch. 920 /// 921 /// \param EndMightThrow - true if __cxa_end_catch might throw 922 static llvm::Value *CallBeginCatch(CodeGenFunction &CGF, 923 llvm::Value *Exn, 924 bool EndMightThrow) { 925 llvm::CallInst *call = 926 CGF.EmitNounwindRuntimeCall(getBeginCatchFn(CGF.CGM), Exn); 927 928 CGF.EHStack.pushCleanup<CallEndCatch>(NormalAndEHCleanup, EndMightThrow); 929 930 return call; 931 } 932 933 /// A "special initializer" callback for initializing a catch 934 /// parameter during catch initialization. 935 static void InitCatchParam(CodeGenFunction &CGF, 936 const VarDecl &CatchParam, 937 llvm::Value *ParamAddr) { 938 // Load the exception from where the landing pad saved it. 939 llvm::Value *Exn = CGF.getExceptionFromSlot(); 940 941 CanQualType CatchType = 942 CGF.CGM.getContext().getCanonicalType(CatchParam.getType()); 943 llvm::Type *LLVMCatchTy = CGF.ConvertTypeForMem(CatchType); 944 945 // If we're catching by reference, we can just cast the object 946 // pointer to the appropriate pointer. 947 if (isa<ReferenceType>(CatchType)) { 948 QualType CaughtType = cast<ReferenceType>(CatchType)->getPointeeType(); 949 bool EndCatchMightThrow = CaughtType->isRecordType(); 950 951 // __cxa_begin_catch returns the adjusted object pointer. 952 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, EndCatchMightThrow); 953 954 // We have no way to tell the personality function that we're 955 // catching by reference, so if we're catching a pointer, 956 // __cxa_begin_catch will actually return that pointer by value. 957 if (const PointerType *PT = dyn_cast<PointerType>(CaughtType)) { 958 QualType PointeeType = PT->getPointeeType(); 959 960 // When catching by reference, generally we should just ignore 961 // this by-value pointer and use the exception object instead. 962 if (!PointeeType->isRecordType()) { 963 964 // Exn points to the struct _Unwind_Exception header, which 965 // we have to skip past in order to reach the exception data. 966 unsigned HeaderSize = 967 CGF.CGM.getTargetCodeGenInfo().getSizeOfUnwindException(); 968 AdjustedExn = CGF.Builder.CreateConstGEP1_32(Exn, HeaderSize); 969 970 // However, if we're catching a pointer-to-record type that won't 971 // work, because the personality function might have adjusted 972 // the pointer. There's actually no way for us to fully satisfy 973 // the language/ABI contract here: we can't use Exn because it 974 // might have the wrong adjustment, but we can't use the by-value 975 // pointer because it's off by a level of abstraction. 976 // 977 // The current solution is to dump the adjusted pointer into an 978 // alloca, which breaks language semantics (because changing the 979 // pointer doesn't change the exception) but at least works. 980 // The better solution would be to filter out non-exact matches 981 // and rethrow them, but this is tricky because the rethrow 982 // really needs to be catchable by other sites at this landing 983 // pad. The best solution is to fix the personality function. 984 } else { 985 // Pull the pointer for the reference type off. 986 llvm::Type *PtrTy = 987 cast<llvm::PointerType>(LLVMCatchTy)->getElementType(); 988 989 // Create the temporary and write the adjusted pointer into it. 990 llvm::Value *ExnPtrTmp = CGF.CreateTempAlloca(PtrTy, "exn.byref.tmp"); 991 llvm::Value *Casted = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 992 CGF.Builder.CreateStore(Casted, ExnPtrTmp); 993 994 // Bind the reference to the temporary. 995 AdjustedExn = ExnPtrTmp; 996 } 997 } 998 999 llvm::Value *ExnCast = 1000 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.byref"); 1001 CGF.Builder.CreateStore(ExnCast, ParamAddr); 1002 return; 1003 } 1004 1005 // Scalars and complexes. 1006 TypeEvaluationKind TEK = CGF.getEvaluationKind(CatchType); 1007 if (TEK != TEK_Aggregate) { 1008 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, false); 1009 1010 // If the catch type is a pointer type, __cxa_begin_catch returns 1011 // the pointer by value. 1012 if (CatchType->hasPointerRepresentation()) { 1013 llvm::Value *CastExn = 1014 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted"); 1015 1016 switch (CatchType.getQualifiers().getObjCLifetime()) { 1017 case Qualifiers::OCL_Strong: 1018 CastExn = CGF.EmitARCRetainNonBlock(CastExn); 1019 // fallthrough 1020 1021 case Qualifiers::OCL_None: 1022 case Qualifiers::OCL_ExplicitNone: 1023 case Qualifiers::OCL_Autoreleasing: 1024 CGF.Builder.CreateStore(CastExn, ParamAddr); 1025 return; 1026 1027 case Qualifiers::OCL_Weak: 1028 CGF.EmitARCInitWeak(ParamAddr, CastExn); 1029 return; 1030 } 1031 llvm_unreachable("bad ownership qualifier!"); 1032 } 1033 1034 // Otherwise, it returns a pointer into the exception object. 1035 1036 llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1037 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 1038 1039 LValue srcLV = CGF.MakeNaturalAlignAddrLValue(Cast, CatchType); 1040 LValue destLV = CGF.MakeAddrLValue(ParamAddr, CatchType, 1041 CGF.getContext().getDeclAlign(&CatchParam)); 1042 switch (TEK) { 1043 case TEK_Complex: 1044 CGF.EmitStoreOfComplex(CGF.EmitLoadOfComplex(srcLV), destLV, 1045 /*init*/ true); 1046 return; 1047 case TEK_Scalar: { 1048 llvm::Value *ExnLoad = CGF.EmitLoadOfScalar(srcLV); 1049 CGF.EmitStoreOfScalar(ExnLoad, destLV, /*init*/ true); 1050 return; 1051 } 1052 case TEK_Aggregate: 1053 llvm_unreachable("evaluation kind filtered out!"); 1054 } 1055 llvm_unreachable("bad evaluation kind"); 1056 } 1057 1058 assert(isa<RecordType>(CatchType) && "unexpected catch type!"); 1059 1060 llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1061 1062 // Check for a copy expression. If we don't have a copy expression, 1063 // that means a trivial copy is okay. 1064 const Expr *copyExpr = CatchParam.getInit(); 1065 if (!copyExpr) { 1066 llvm::Value *rawAdjustedExn = CallBeginCatch(CGF, Exn, true); 1067 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy); 1068 CGF.EmitAggregateCopy(ParamAddr, adjustedExn, CatchType); 1069 return; 1070 } 1071 1072 // We have to call __cxa_get_exception_ptr to get the adjusted 1073 // pointer before copying. 1074 llvm::CallInst *rawAdjustedExn = 1075 CGF.EmitNounwindRuntimeCall(getGetExceptionPtrFn(CGF.CGM), Exn); 1076 1077 // Cast that to the appropriate type. 1078 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy); 1079 1080 // The copy expression is defined in terms of an OpaqueValueExpr. 1081 // Find it and map it to the adjusted expression. 1082 CodeGenFunction::OpaqueValueMapping 1083 opaque(CGF, OpaqueValueExpr::findInCopyConstruct(copyExpr), 1084 CGF.MakeAddrLValue(adjustedExn, CatchParam.getType())); 1085 1086 // Call the copy ctor in a terminate scope. 1087 CGF.EHStack.pushTerminate(); 1088 1089 // Perform the copy construction. 1090 CharUnits Alignment = CGF.getContext().getDeclAlign(&CatchParam); 1091 CGF.EmitAggExpr(copyExpr, 1092 AggValueSlot::forAddr(ParamAddr, Alignment, Qualifiers(), 1093 AggValueSlot::IsNotDestructed, 1094 AggValueSlot::DoesNotNeedGCBarriers, 1095 AggValueSlot::IsNotAliased)); 1096 1097 // Leave the terminate scope. 1098 CGF.EHStack.popTerminate(); 1099 1100 // Undo the opaque value mapping. 1101 opaque.pop(); 1102 1103 // Finally we can call __cxa_begin_catch. 1104 CallBeginCatch(CGF, Exn, true); 1105 } 1106 1107 /// Begins a catch statement by initializing the catch variable and 1108 /// calling __cxa_begin_catch. 1109 static void BeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *S) { 1110 // We have to be very careful with the ordering of cleanups here: 1111 // C++ [except.throw]p4: 1112 // The destruction [of the exception temporary] occurs 1113 // immediately after the destruction of the object declared in 1114 // the exception-declaration in the handler. 1115 // 1116 // So the precise ordering is: 1117 // 1. Construct catch variable. 1118 // 2. __cxa_begin_catch 1119 // 3. Enter __cxa_end_catch cleanup 1120 // 4. Enter dtor cleanup 1121 // 1122 // We do this by using a slightly abnormal initialization process. 1123 // Delegation sequence: 1124 // - ExitCXXTryStmt opens a RunCleanupsScope 1125 // - EmitAutoVarAlloca creates the variable and debug info 1126 // - InitCatchParam initializes the variable from the exception 1127 // - CallBeginCatch calls __cxa_begin_catch 1128 // - CallBeginCatch enters the __cxa_end_catch cleanup 1129 // - EmitAutoVarCleanups enters the variable destructor cleanup 1130 // - EmitCXXTryStmt emits the code for the catch body 1131 // - EmitCXXTryStmt close the RunCleanupsScope 1132 1133 VarDecl *CatchParam = S->getExceptionDecl(); 1134 if (!CatchParam) { 1135 llvm::Value *Exn = CGF.getExceptionFromSlot(); 1136 CallBeginCatch(CGF, Exn, true); 1137 return; 1138 } 1139 1140 // Emit the local. 1141 CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam); 1142 InitCatchParam(CGF, *CatchParam, var.getObjectAddress(CGF)); 1143 CGF.EmitAutoVarCleanups(var); 1144 } 1145 1146 /// Emit the structure of the dispatch block for the given catch scope. 1147 /// It is an invariant that the dispatch block already exists. 1148 static void emitCatchDispatchBlock(CodeGenFunction &CGF, 1149 EHCatchScope &catchScope) { 1150 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock(); 1151 assert(dispatchBlock); 1152 1153 // If there's only a single catch-all, getEHDispatchBlock returned 1154 // that catch-all as the dispatch block. 1155 if (catchScope.getNumHandlers() == 1 && 1156 catchScope.getHandler(0).isCatchAll()) { 1157 assert(dispatchBlock == catchScope.getHandler(0).Block); 1158 return; 1159 } 1160 1161 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP(); 1162 CGF.EmitBlockAfterUses(dispatchBlock); 1163 1164 // Select the right handler. 1165 llvm::Value *llvm_eh_typeid_for = 1166 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); 1167 1168 // Load the selector value. 1169 llvm::Value *selector = CGF.getSelectorFromSlot(); 1170 1171 // Test against each of the exception types we claim to catch. 1172 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) { 1173 assert(i < e && "ran off end of handlers!"); 1174 const EHCatchScope::Handler &handler = catchScope.getHandler(i); 1175 1176 llvm::Value *typeValue = handler.Type; 1177 assert(typeValue && "fell into catch-all case!"); 1178 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy); 1179 1180 // Figure out the next block. 1181 bool nextIsEnd; 1182 llvm::BasicBlock *nextBlock; 1183 1184 // If this is the last handler, we're at the end, and the next 1185 // block is the block for the enclosing EH scope. 1186 if (i + 1 == e) { 1187 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope()); 1188 nextIsEnd = true; 1189 1190 // If the next handler is a catch-all, we're at the end, and the 1191 // next block is that handler. 1192 } else if (catchScope.getHandler(i+1).isCatchAll()) { 1193 nextBlock = catchScope.getHandler(i+1).Block; 1194 nextIsEnd = true; 1195 1196 // Otherwise, we're not at the end and we need a new block. 1197 } else { 1198 nextBlock = CGF.createBasicBlock("catch.fallthrough"); 1199 nextIsEnd = false; 1200 } 1201 1202 // Figure out the catch type's index in the LSDA's type table. 1203 llvm::CallInst *typeIndex = 1204 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue); 1205 typeIndex->setDoesNotThrow(); 1206 1207 llvm::Value *matchesTypeIndex = 1208 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches"); 1209 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock); 1210 1211 // If the next handler is a catch-all, we're completely done. 1212 if (nextIsEnd) { 1213 CGF.Builder.restoreIP(savedIP); 1214 return; 1215 } 1216 // Otherwise we need to emit and continue at that block. 1217 CGF.EmitBlock(nextBlock); 1218 } 1219 } 1220 1221 void CodeGenFunction::popCatchScope() { 1222 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin()); 1223 if (catchScope.hasEHBranches()) 1224 emitCatchDispatchBlock(*this, catchScope); 1225 EHStack.popCatch(); 1226 } 1227 1228 void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 1229 unsigned NumHandlers = S.getNumHandlers(); 1230 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin()); 1231 assert(CatchScope.getNumHandlers() == NumHandlers); 1232 1233 // If the catch was not required, bail out now. 1234 if (!CatchScope.hasEHBranches()) { 1235 EHStack.popCatch(); 1236 return; 1237 } 1238 1239 // Emit the structure of the EH dispatch for this catch. 1240 emitCatchDispatchBlock(*this, CatchScope); 1241 1242 // Copy the handler blocks off before we pop the EH stack. Emitting 1243 // the handlers might scribble on this memory. 1244 SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers); 1245 memcpy(Handlers.data(), CatchScope.begin(), 1246 NumHandlers * sizeof(EHCatchScope::Handler)); 1247 1248 EHStack.popCatch(); 1249 1250 // The fall-through block. 1251 llvm::BasicBlock *ContBB = createBasicBlock("try.cont"); 1252 1253 // We just emitted the body of the try; jump to the continue block. 1254 if (HaveInsertPoint()) 1255 Builder.CreateBr(ContBB); 1256 1257 // Determine if we need an implicit rethrow for all these catch handlers; 1258 // see the comment below. 1259 bool doImplicitRethrow = false; 1260 if (IsFnTryBlock) 1261 doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) || 1262 isa<CXXConstructorDecl>(CurCodeDecl); 1263 1264 // Perversely, we emit the handlers backwards precisely because we 1265 // want them to appear in source order. In all of these cases, the 1266 // catch block will have exactly one predecessor, which will be a 1267 // particular block in the catch dispatch. However, in the case of 1268 // a catch-all, one of the dispatch blocks will branch to two 1269 // different handlers, and EmitBlockAfterUses will cause the second 1270 // handler to be moved before the first. 1271 for (unsigned I = NumHandlers; I != 0; --I) { 1272 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block; 1273 EmitBlockAfterUses(CatchBlock); 1274 1275 // Catch the exception if this isn't a catch-all. 1276 const CXXCatchStmt *C = S.getHandler(I-1); 1277 1278 // Enter a cleanup scope, including the catch variable and the 1279 // end-catch. 1280 RunCleanupsScope CatchScope(*this); 1281 1282 // Initialize the catch variable and set up the cleanups. 1283 BeginCatch(*this, C); 1284 1285 // Perform the body of the catch. 1286 EmitStmt(C->getHandlerBlock()); 1287 1288 // [except.handle]p11: 1289 // The currently handled exception is rethrown if control 1290 // reaches the end of a handler of the function-try-block of a 1291 // constructor or destructor. 1292 1293 // It is important that we only do this on fallthrough and not on 1294 // return. Note that it's illegal to put a return in a 1295 // constructor function-try-block's catch handler (p14), so this 1296 // really only applies to destructors. 1297 if (doImplicitRethrow && HaveInsertPoint()) { 1298 EmitRuntimeCallOrInvoke(getReThrowFn(CGM)); 1299 Builder.CreateUnreachable(); 1300 Builder.ClearInsertionPoint(); 1301 } 1302 1303 // Fall out through the catch cleanups. 1304 CatchScope.ForceCleanup(); 1305 1306 // Branch out of the try. 1307 if (HaveInsertPoint()) 1308 Builder.CreateBr(ContBB); 1309 } 1310 1311 EmitBlock(ContBB); 1312 } 1313 1314 namespace { 1315 struct CallEndCatchForFinally : EHScopeStack::Cleanup { 1316 llvm::Value *ForEHVar; 1317 llvm::Value *EndCatchFn; 1318 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn) 1319 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {} 1320 1321 void Emit(CodeGenFunction &CGF, Flags flags) { 1322 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch"); 1323 llvm::BasicBlock *CleanupContBB = 1324 CGF.createBasicBlock("finally.cleanup.cont"); 1325 1326 llvm::Value *ShouldEndCatch = 1327 CGF.Builder.CreateLoad(ForEHVar, "finally.endcatch"); 1328 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB); 1329 CGF.EmitBlock(EndCatchBB); 1330 CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw 1331 CGF.EmitBlock(CleanupContBB); 1332 } 1333 }; 1334 1335 struct PerformFinally : EHScopeStack::Cleanup { 1336 const Stmt *Body; 1337 llvm::Value *ForEHVar; 1338 llvm::Value *EndCatchFn; 1339 llvm::Value *RethrowFn; 1340 llvm::Value *SavedExnVar; 1341 1342 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar, 1343 llvm::Value *EndCatchFn, 1344 llvm::Value *RethrowFn, llvm::Value *SavedExnVar) 1345 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn), 1346 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {} 1347 1348 void Emit(CodeGenFunction &CGF, Flags flags) { 1349 // Enter a cleanup to call the end-catch function if one was provided. 1350 if (EndCatchFn) 1351 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup, 1352 ForEHVar, EndCatchFn); 1353 1354 // Save the current cleanup destination in case there are 1355 // cleanups in the finally block. 1356 llvm::Value *SavedCleanupDest = 1357 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(), 1358 "cleanup.dest.saved"); 1359 1360 // Emit the finally block. 1361 CGF.EmitStmt(Body); 1362 1363 // If the end of the finally is reachable, check whether this was 1364 // for EH. If so, rethrow. 1365 if (CGF.HaveInsertPoint()) { 1366 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow"); 1367 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont"); 1368 1369 llvm::Value *ShouldRethrow = 1370 CGF.Builder.CreateLoad(ForEHVar, "finally.shouldthrow"); 1371 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB); 1372 1373 CGF.EmitBlock(RethrowBB); 1374 if (SavedExnVar) { 1375 CGF.EmitRuntimeCallOrInvoke(RethrowFn, 1376 CGF.Builder.CreateLoad(SavedExnVar)); 1377 } else { 1378 CGF.EmitRuntimeCallOrInvoke(RethrowFn); 1379 } 1380 CGF.Builder.CreateUnreachable(); 1381 1382 CGF.EmitBlock(ContBB); 1383 1384 // Restore the cleanup destination. 1385 CGF.Builder.CreateStore(SavedCleanupDest, 1386 CGF.getNormalCleanupDestSlot()); 1387 } 1388 1389 // Leave the end-catch cleanup. As an optimization, pretend that 1390 // the fallthrough path was inaccessible; we've dynamically proven 1391 // that we're not in the EH case along that path. 1392 if (EndCatchFn) { 1393 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); 1394 CGF.PopCleanupBlock(); 1395 CGF.Builder.restoreIP(SavedIP); 1396 } 1397 1398 // Now make sure we actually have an insertion point or the 1399 // cleanup gods will hate us. 1400 CGF.EnsureInsertPoint(); 1401 } 1402 }; 1403 } 1404 1405 /// Enters a finally block for an implementation using zero-cost 1406 /// exceptions. This is mostly general, but hard-codes some 1407 /// language/ABI-specific behavior in the catch-all sections. 1408 void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF, 1409 const Stmt *body, 1410 llvm::Constant *beginCatchFn, 1411 llvm::Constant *endCatchFn, 1412 llvm::Constant *rethrowFn) { 1413 assert((beginCatchFn != 0) == (endCatchFn != 0) && 1414 "begin/end catch functions not paired"); 1415 assert(rethrowFn && "rethrow function is required"); 1416 1417 BeginCatchFn = beginCatchFn; 1418 1419 // The rethrow function has one of the following two types: 1420 // void (*)() 1421 // void (*)(void*) 1422 // In the latter case we need to pass it the exception object. 1423 // But we can't use the exception slot because the @finally might 1424 // have a landing pad (which would overwrite the exception slot). 1425 llvm::FunctionType *rethrowFnTy = 1426 cast<llvm::FunctionType>( 1427 cast<llvm::PointerType>(rethrowFn->getType())->getElementType()); 1428 SavedExnVar = 0; 1429 if (rethrowFnTy->getNumParams()) 1430 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn"); 1431 1432 // A finally block is a statement which must be executed on any edge 1433 // out of a given scope. Unlike a cleanup, the finally block may 1434 // contain arbitrary control flow leading out of itself. In 1435 // addition, finally blocks should always be executed, even if there 1436 // are no catch handlers higher on the stack. Therefore, we 1437 // surround the protected scope with a combination of a normal 1438 // cleanup (to catch attempts to break out of the block via normal 1439 // control flow) and an EH catch-all (semantically "outside" any try 1440 // statement to which the finally block might have been attached). 1441 // The finally block itself is generated in the context of a cleanup 1442 // which conditionally leaves the catch-all. 1443 1444 // Jump destination for performing the finally block on an exception 1445 // edge. We'll never actually reach this block, so unreachable is 1446 // fine. 1447 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock()); 1448 1449 // Whether the finally block is being executed for EH purposes. 1450 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh"); 1451 CGF.Builder.CreateStore(CGF.Builder.getFalse(), ForEHVar); 1452 1453 // Enter a normal cleanup which will perform the @finally block. 1454 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body, 1455 ForEHVar, endCatchFn, 1456 rethrowFn, SavedExnVar); 1457 1458 // Enter a catch-all scope. 1459 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall"); 1460 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1); 1461 catchScope->setCatchAllHandler(0, catchBB); 1462 } 1463 1464 void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) { 1465 // Leave the finally catch-all. 1466 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin()); 1467 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block; 1468 1469 CGF.popCatchScope(); 1470 1471 // If there are any references to the catch-all block, emit it. 1472 if (catchBB->use_empty()) { 1473 delete catchBB; 1474 } else { 1475 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP(); 1476 CGF.EmitBlock(catchBB); 1477 1478 llvm::Value *exn = 0; 1479 1480 // If there's a begin-catch function, call it. 1481 if (BeginCatchFn) { 1482 exn = CGF.getExceptionFromSlot(); 1483 CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn); 1484 } 1485 1486 // If we need to remember the exception pointer to rethrow later, do so. 1487 if (SavedExnVar) { 1488 if (!exn) exn = CGF.getExceptionFromSlot(); 1489 CGF.Builder.CreateStore(exn, SavedExnVar); 1490 } 1491 1492 // Tell the cleanups in the finally block that we're do this for EH. 1493 CGF.Builder.CreateStore(CGF.Builder.getTrue(), ForEHVar); 1494 1495 // Thread a jump through the finally cleanup. 1496 CGF.EmitBranchThroughCleanup(RethrowDest); 1497 1498 CGF.Builder.restoreIP(savedIP); 1499 } 1500 1501 // Finally, leave the @finally cleanup. 1502 CGF.PopCleanupBlock(); 1503 } 1504 1505 /// In a terminate landing pad, should we use __clang__call_terminate 1506 /// or just a naked call to std::terminate? 1507 /// 1508 /// __clang_call_terminate calls __cxa_begin_catch, which then allows 1509 /// std::terminate to usefully report something about the 1510 /// violating exception. 1511 static bool useClangCallTerminate(CodeGenModule &CGM) { 1512 // Only do this for Itanium-family ABIs in C++ mode. 1513 return (CGM.getLangOpts().CPlusPlus && 1514 CGM.getTarget().getCXXABI().isItaniumFamily()); 1515 } 1516 1517 /// Get or define the following function: 1518 /// void @__clang_call_terminate(i8* %exn) nounwind noreturn 1519 /// This code is used only in C++. 1520 static llvm::Constant *getClangCallTerminateFn(CodeGenModule &CGM) { 1521 llvm::FunctionType *fnTy = 1522 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 1523 llvm::Constant *fnRef = 1524 CGM.CreateRuntimeFunction(fnTy, "__clang_call_terminate"); 1525 1526 llvm::Function *fn = dyn_cast<llvm::Function>(fnRef); 1527 if (fn && fn->empty()) { 1528 fn->setDoesNotThrow(); 1529 fn->setDoesNotReturn(); 1530 1531 // What we really want is to massively penalize inlining without 1532 // forbidding it completely. The difference between that and 1533 // 'noinline' is negligible. 1534 fn->addFnAttr(llvm::Attribute::NoInline); 1535 1536 // Allow this function to be shared across translation units, but 1537 // we don't want it to turn into an exported symbol. 1538 fn->setLinkage(llvm::Function::LinkOnceODRLinkage); 1539 fn->setVisibility(llvm::Function::HiddenVisibility); 1540 1541 // Set up the function. 1542 llvm::BasicBlock *entry = 1543 llvm::BasicBlock::Create(CGM.getLLVMContext(), "", fn); 1544 CGBuilderTy builder(entry); 1545 1546 // Pull the exception pointer out of the parameter list. 1547 llvm::Value *exn = &*fn->arg_begin(); 1548 1549 // Call __cxa_begin_catch(exn). 1550 llvm::CallInst *catchCall = builder.CreateCall(getBeginCatchFn(CGM), exn); 1551 catchCall->setDoesNotThrow(); 1552 catchCall->setCallingConv(CGM.getRuntimeCC()); 1553 1554 // Call std::terminate(). 1555 llvm::CallInst *termCall = builder.CreateCall(getTerminateFn(CGM)); 1556 termCall->setDoesNotThrow(); 1557 termCall->setDoesNotReturn(); 1558 termCall->setCallingConv(CGM.getRuntimeCC()); 1559 1560 // std::terminate cannot return. 1561 builder.CreateUnreachable(); 1562 } 1563 1564 return fnRef; 1565 } 1566 1567 llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() { 1568 if (TerminateLandingPad) 1569 return TerminateLandingPad; 1570 1571 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1572 1573 // This will get inserted at the end of the function. 1574 TerminateLandingPad = createBasicBlock("terminate.lpad"); 1575 Builder.SetInsertPoint(TerminateLandingPad); 1576 1577 // Tell the backend that this is a landing pad. 1578 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOpts()); 1579 llvm::LandingPadInst *LPadInst = 1580 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, NULL), 1581 getOpaquePersonalityFn(CGM, Personality), 0); 1582 LPadInst->addClause(getCatchAllValue(*this)); 1583 1584 llvm::CallInst *terminateCall; 1585 if (useClangCallTerminate(CGM)) { 1586 // Extract out the exception pointer. 1587 llvm::Value *exn = Builder.CreateExtractValue(LPadInst, 0); 1588 terminateCall = EmitNounwindRuntimeCall(getClangCallTerminateFn(CGM), exn); 1589 } else { 1590 terminateCall = EmitNounwindRuntimeCall(getTerminateFn(CGM)); 1591 } 1592 terminateCall->setDoesNotReturn(); 1593 Builder.CreateUnreachable(); 1594 1595 // Restore the saved insertion state. 1596 Builder.restoreIP(SavedIP); 1597 1598 return TerminateLandingPad; 1599 } 1600 1601 llvm::BasicBlock *CodeGenFunction::getTerminateHandler() { 1602 if (TerminateHandler) 1603 return TerminateHandler; 1604 1605 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1606 1607 // Set up the terminate handler. This block is inserted at the very 1608 // end of the function by FinishFunction. 1609 TerminateHandler = createBasicBlock("terminate.handler"); 1610 Builder.SetInsertPoint(TerminateHandler); 1611 llvm::CallInst *TerminateCall = EmitNounwindRuntimeCall(getTerminateFn(CGM)); 1612 TerminateCall->setDoesNotReturn(); 1613 Builder.CreateUnreachable(); 1614 1615 // Restore the saved insertion state. 1616 Builder.restoreIP(SavedIP); 1617 1618 return TerminateHandler; 1619 } 1620 1621 llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) { 1622 if (EHResumeBlock) return EHResumeBlock; 1623 1624 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP(); 1625 1626 // We emit a jump to a notional label at the outermost unwind state. 1627 EHResumeBlock = createBasicBlock("eh.resume"); 1628 Builder.SetInsertPoint(EHResumeBlock); 1629 1630 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOpts()); 1631 1632 // This can always be a call because we necessarily didn't find 1633 // anything on the EH stack which needs our help. 1634 const char *RethrowName = Personality.CatchallRethrowFn; 1635 if (RethrowName != 0 && !isCleanup) { 1636 EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName), 1637 getExceptionFromSlot()) 1638 ->setDoesNotReturn(); 1639 } else { 1640 switch (CleanupHackLevel) { 1641 case CHL_MandatoryCatchall: 1642 // In mandatory-catchall mode, we need to use 1643 // _Unwind_Resume_or_Rethrow, or whatever the personality's 1644 // equivalent is. 1645 EmitRuntimeCall(getUnwindResumeOrRethrowFn(), 1646 getExceptionFromSlot()) 1647 ->setDoesNotReturn(); 1648 break; 1649 case CHL_MandatoryCleanup: { 1650 // In mandatory-cleanup mode, we should use 'resume'. 1651 1652 // Recreate the landingpad's return value for the 'resume' instruction. 1653 llvm::Value *Exn = getExceptionFromSlot(); 1654 llvm::Value *Sel = getSelectorFromSlot(); 1655 1656 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(), 1657 Sel->getType(), NULL); 1658 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType); 1659 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val"); 1660 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val"); 1661 1662 Builder.CreateResume(LPadVal); 1663 Builder.restoreIP(SavedIP); 1664 return EHResumeBlock; 1665 } 1666 case CHL_Ideal: 1667 // In an idealized mode where we don't have to worry about the 1668 // optimizer combining landing pads, we should just use 1669 // _Unwind_Resume (or the personality's equivalent). 1670 EmitRuntimeCall(getUnwindResumeFn(), getExceptionFromSlot()) 1671 ->setDoesNotReturn(); 1672 break; 1673 } 1674 } 1675 1676 Builder.CreateUnreachable(); 1677 1678 Builder.restoreIP(SavedIP); 1679 1680 return EHResumeBlock; 1681 } 1682