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 "llvm/Intrinsics.h" 20#include "llvm/Support/CallSite.h" 21 22using namespace clang; 23using namespace CodeGen; 24 25static llvm::Constant *getAllocateExceptionFn(CodeGenFunction &CGF) { 26 // void *__cxa_allocate_exception(size_t thrown_size); 27 28 llvm::FunctionType *FTy = 29 llvm::FunctionType::get(CGF.Int8PtrTy, CGF.SizeTy, /*IsVarArgs=*/false); 30 31 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception"); 32} 33 34static llvm::Constant *getFreeExceptionFn(CodeGenFunction &CGF) { 35 // void __cxa_free_exception(void *thrown_exception); 36 37 llvm::FunctionType *FTy = 38 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 39 40 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception"); 41} 42 43static llvm::Constant *getThrowFn(CodeGenFunction &CGF) { 44 // void __cxa_throw(void *thrown_exception, std::type_info *tinfo, 45 // void (*dest) (void *)); 46 47 llvm::Type *Args[3] = { CGF.Int8PtrTy, CGF.Int8PtrTy, CGF.Int8PtrTy }; 48 llvm::FunctionType *FTy = 49 llvm::FunctionType::get(CGF.VoidTy, Args, /*IsVarArgs=*/false); 50 51 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_throw"); 52} 53 54static llvm::Constant *getReThrowFn(CodeGenFunction &CGF) { 55 // void __cxa_rethrow(); 56 57 llvm::FunctionType *FTy = 58 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false); 59 60 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow"); 61} 62 63static llvm::Constant *getGetExceptionPtrFn(CodeGenFunction &CGF) { 64 // void *__cxa_get_exception_ptr(void*); 65 66 llvm::FunctionType *FTy = 67 llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 68 69 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr"); 70} 71 72static llvm::Constant *getBeginCatchFn(CodeGenFunction &CGF) { 73 // void *__cxa_begin_catch(void*); 74 75 llvm::FunctionType *FTy = 76 llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 77 78 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch"); 79} 80 81static llvm::Constant *getEndCatchFn(CodeGenFunction &CGF) { 82 // void __cxa_end_catch(); 83 84 llvm::FunctionType *FTy = 85 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false); 86 87 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch"); 88} 89 90static llvm::Constant *getUnexpectedFn(CodeGenFunction &CGF) { 91 // void __cxa_call_unexepcted(void *thrown_exception); 92 93 llvm::FunctionType *FTy = 94 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 95 96 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); 97} 98 99llvm::Constant *CodeGenFunction::getUnwindResumeFn() { 100 llvm::FunctionType *FTy = 101 llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); 102 103 if (CGM.getLangOpts().SjLjExceptions) 104 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume"); 105 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume"); 106} 107 108llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() { 109 llvm::FunctionType *FTy = 110 llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); 111 112 if (CGM.getLangOpts().SjLjExceptions) 113 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume_or_Rethrow"); 114 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume_or_Rethrow"); 115} 116 117static llvm::Constant *getTerminateFn(CodeGenFunction &CGF) { 118 // void __terminate(); 119 120 llvm::FunctionType *FTy = 121 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false); 122 123 StringRef name; 124 125 // In C++, use std::terminate(). 126 if (CGF.getLangOpts().CPlusPlus) 127 name = "_ZSt9terminatev"; // FIXME: mangling! 128 else if (CGF.getLangOpts().ObjC1 && 129 CGF.getLangOpts().ObjCRuntime.hasTerminate()) 130 name = "objc_terminate"; 131 else 132 name = "abort"; 133 return CGF.CGM.CreateRuntimeFunction(FTy, name); 134} 135 136static llvm::Constant *getCatchallRethrowFn(CodeGenFunction &CGF, 137 StringRef Name) { 138 llvm::FunctionType *FTy = 139 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 140 141 return CGF.CGM.CreateRuntimeFunction(FTy, Name); 142} 143 144namespace { 145 /// The exceptions personality for a function. 146 struct EHPersonality { 147 const char *PersonalityFn; 148 149 // If this is non-null, this personality requires a non-standard 150 // function for rethrowing an exception after a catchall cleanup. 151 // This function must have prototype void(void*). 152 const char *CatchallRethrowFn; 153 154 static const EHPersonality &get(const LangOptions &Lang); 155 static const EHPersonality GNU_C; 156 static const EHPersonality GNU_C_SJLJ; 157 static const EHPersonality GNU_ObjC; 158 static const EHPersonality GNU_ObjCXX; 159 static const EHPersonality NeXT_ObjC; 160 static const EHPersonality GNU_CPlusPlus; 161 static const EHPersonality GNU_CPlusPlus_SJLJ; 162 }; 163} 164 165const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", 0 }; 166const EHPersonality EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", 0 }; 167const EHPersonality EHPersonality::NeXT_ObjC = { "__objc_personality_v0", 0 }; 168const EHPersonality EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", 0}; 169const EHPersonality 170EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", 0 }; 171const EHPersonality 172EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"}; 173const EHPersonality 174EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", 0 }; 175 176static const EHPersonality &getCPersonality(const LangOptions &L) { 177 if (L.SjLjExceptions) 178 return EHPersonality::GNU_C_SJLJ; 179 return EHPersonality::GNU_C; 180} 181 182static const EHPersonality &getObjCPersonality(const LangOptions &L) { 183 switch (L.ObjCRuntime.getKind()) { 184 case ObjCRuntime::FragileMacOSX: 185 return getCPersonality(L); 186 case ObjCRuntime::MacOSX: 187 case ObjCRuntime::iOS: 188 return EHPersonality::NeXT_ObjC; 189 case ObjCRuntime::GNUstep: 190 case ObjCRuntime::GCC: 191 case ObjCRuntime::ObjFW: 192 return EHPersonality::GNU_ObjC; 193 } 194 llvm_unreachable("bad runtime kind"); 195} 196 197static const EHPersonality &getCXXPersonality(const LangOptions &L) { 198 if (L.SjLjExceptions) 199 return EHPersonality::GNU_CPlusPlus_SJLJ; 200 else 201 return EHPersonality::GNU_CPlusPlus; 202} 203 204/// Determines the personality function to use when both C++ 205/// and Objective-C exceptions are being caught. 206static const EHPersonality &getObjCXXPersonality(const LangOptions &L) { 207 switch (L.ObjCRuntime.getKind()) { 208 // The ObjC personality defers to the C++ personality for non-ObjC 209 // handlers. Unlike the C++ case, we use the same personality 210 // function on targets using (backend-driven) SJLJ EH. 211 case ObjCRuntime::MacOSX: 212 case ObjCRuntime::iOS: 213 return EHPersonality::NeXT_ObjC; 214 215 // In the fragile ABI, just use C++ exception handling and hope 216 // they're not doing crazy exception mixing. 217 case ObjCRuntime::FragileMacOSX: 218 return getCXXPersonality(L); 219 220 // The GCC runtime's personality function inherently doesn't support 221 // mixed EH. Use the C++ personality just to avoid returning null. 222 case ObjCRuntime::GCC: 223 case ObjCRuntime::ObjFW: // XXX: this will change soon 224 return EHPersonality::GNU_ObjC; 225 case ObjCRuntime::GNUstep: 226 return EHPersonality::GNU_ObjCXX; 227 } 228 llvm_unreachable("bad runtime kind"); 229} 230 231const EHPersonality &EHPersonality::get(const LangOptions &L) { 232 if (L.CPlusPlus && L.ObjC1) 233 return getObjCXXPersonality(L); 234 else if (L.CPlusPlus) 235 return getCXXPersonality(L); 236 else if (L.ObjC1) 237 return getObjCPersonality(L); 238 else 239 return getCPersonality(L); 240} 241 242static llvm::Constant *getPersonalityFn(CodeGenModule &CGM, 243 const EHPersonality &Personality) { 244 llvm::Constant *Fn = 245 CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true), 246 Personality.PersonalityFn); 247 return Fn; 248} 249 250static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM, 251 const EHPersonality &Personality) { 252 llvm::Constant *Fn = getPersonalityFn(CGM, Personality); 253 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy); 254} 255 256/// Check whether a personality function could reasonably be swapped 257/// for a C++ personality function. 258static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) { 259 for (llvm::Constant::use_iterator 260 I = Fn->use_begin(), E = Fn->use_end(); I != E; ++I) { 261 llvm::User *User = *I; 262 263 // Conditionally white-list bitcasts. 264 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(User)) { 265 if (CE->getOpcode() != llvm::Instruction::BitCast) return false; 266 if (!PersonalityHasOnlyCXXUses(CE)) 267 return false; 268 continue; 269 } 270 271 // Otherwise, it has to be a landingpad instruction. 272 llvm::LandingPadInst *LPI = dyn_cast<llvm::LandingPadInst>(User); 273 if (!LPI) return false; 274 275 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) { 276 // Look for something that would've been returned by the ObjC 277 // runtime's GetEHType() method. 278 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts(); 279 if (LPI->isCatch(I)) { 280 // Check if the catch value has the ObjC prefix. 281 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val)) 282 // ObjC EH selector entries are always global variables with 283 // names starting like this. 284 if (GV->getName().startswith("OBJC_EHTYPE")) 285 return false; 286 } else { 287 // Check if any of the filter values have the ObjC prefix. 288 llvm::Constant *CVal = cast<llvm::Constant>(Val); 289 for (llvm::User::op_iterator 290 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) { 291 if (llvm::GlobalVariable *GV = 292 cast<llvm::GlobalVariable>((*II)->stripPointerCasts())) 293 // ObjC EH selector entries are always global variables with 294 // names starting like this. 295 if (GV->getName().startswith("OBJC_EHTYPE")) 296 return false; 297 } 298 } 299 } 300 } 301 302 return true; 303} 304 305/// Try to use the C++ personality function in ObjC++. Not doing this 306/// can cause some incompatibilities with gcc, which is more 307/// aggressive about only using the ObjC++ personality in a function 308/// when it really needs it. 309void CodeGenModule::SimplifyPersonality() { 310 // For now, this is really a Darwin-specific operation. 311 if (!Context.getTargetInfo().getTriple().isOSDarwin()) 312 return; 313 314 // If we're not in ObjC++ -fexceptions, there's nothing to do. 315 if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions) 316 return; 317 318 const EHPersonality &ObjCXX = EHPersonality::get(LangOpts); 319 const EHPersonality &CXX = getCXXPersonality(LangOpts); 320 if (&ObjCXX == &CXX) 321 return; 322 323 assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 && 324 "Different EHPersonalities using the same personality function."); 325 326 llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn); 327 328 // Nothing to do if it's unused. 329 if (!Fn || Fn->use_empty()) return; 330 331 // Can't do the optimization if it has non-C++ uses. 332 if (!PersonalityHasOnlyCXXUses(Fn)) return; 333 334 // Create the C++ personality function and kill off the old 335 // function. 336 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX); 337 338 // This can happen if the user is screwing with us. 339 if (Fn->getType() != CXXFn->getType()) return; 340 341 Fn->replaceAllUsesWith(CXXFn); 342 Fn->eraseFromParent(); 343} 344 345/// Returns the value to inject into a selector to indicate the 346/// presence of a catch-all. 347static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) { 348 // Possibly we should use @llvm.eh.catch.all.value here. 349 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy); 350} 351 352namespace { 353 /// A cleanup to free the exception object if its initialization 354 /// throws. 355 struct FreeException : EHScopeStack::Cleanup { 356 llvm::Value *exn; 357 FreeException(llvm::Value *exn) : exn(exn) {} 358 void Emit(CodeGenFunction &CGF, Flags flags) { 359 CGF.Builder.CreateCall(getFreeExceptionFn(CGF), exn) 360 ->setDoesNotThrow(); 361 } 362 }; 363} 364 365// Emits an exception expression into the given location. This 366// differs from EmitAnyExprToMem only in that, if a final copy-ctor 367// call is required, an exception within that copy ctor causes 368// std::terminate to be invoked. 369static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *e, 370 llvm::Value *addr) { 371 // Make sure the exception object is cleaned up if there's an 372 // exception during initialization. 373 CGF.pushFullExprCleanup<FreeException>(EHCleanup, addr); 374 EHScopeStack::stable_iterator cleanup = CGF.EHStack.stable_begin(); 375 376 // __cxa_allocate_exception returns a void*; we need to cast this 377 // to the appropriate type for the object. 378 llvm::Type *ty = CGF.ConvertTypeForMem(e->getType())->getPointerTo(); 379 llvm::Value *typedAddr = CGF.Builder.CreateBitCast(addr, ty); 380 381 // FIXME: this isn't quite right! If there's a final unelided call 382 // to a copy constructor, then according to [except.terminate]p1 we 383 // must call std::terminate() if that constructor throws, because 384 // technically that copy occurs after the exception expression is 385 // evaluated but before the exception is caught. But the best way 386 // to handle that is to teach EmitAggExpr to do the final copy 387 // differently if it can't be elided. 388 CGF.EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(), 389 /*IsInit*/ true); 390 391 // Deactivate the cleanup block. 392 CGF.DeactivateCleanupBlock(cleanup, cast<llvm::Instruction>(typedAddr)); 393} 394 395llvm::Value *CodeGenFunction::getExceptionSlot() { 396 if (!ExceptionSlot) 397 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot"); 398 return ExceptionSlot; 399} 400 401llvm::Value *CodeGenFunction::getEHSelectorSlot() { 402 if (!EHSelectorSlot) 403 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot"); 404 return EHSelectorSlot; 405} 406 407llvm::Value *CodeGenFunction::getExceptionFromSlot() { 408 return Builder.CreateLoad(getExceptionSlot(), "exn"); 409} 410 411llvm::Value *CodeGenFunction::getSelectorFromSlot() { 412 return Builder.CreateLoad(getEHSelectorSlot(), "sel"); 413} 414 415void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) { 416 if (!E->getSubExpr()) { 417 if (getInvokeDest()) { 418 Builder.CreateInvoke(getReThrowFn(*this), 419 getUnreachableBlock(), 420 getInvokeDest()) 421 ->setDoesNotReturn(); 422 } else { 423 Builder.CreateCall(getReThrowFn(*this))->setDoesNotReturn(); 424 Builder.CreateUnreachable(); 425 } 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 // Now allocate the exception object. 437 llvm::Type *SizeTy = ConvertType(getContext().getSizeType()); 438 uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity(); 439 440 llvm::Constant *AllocExceptionFn = getAllocateExceptionFn(*this); 441 llvm::CallInst *ExceptionPtr = 442 Builder.CreateCall(AllocExceptionFn, 443 llvm::ConstantInt::get(SizeTy, TypeSize), 444 "exception"); 445 ExceptionPtr->setDoesNotThrow(); 446 447 EmitAnyExprToExn(*this, E->getSubExpr(), ExceptionPtr); 448 449 // Now throw the exception. 450 llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType, 451 /*ForEH=*/true); 452 453 // The address of the destructor. If the exception type has a 454 // trivial destructor (or isn't a record), we just pass null. 455 llvm::Constant *Dtor = 0; 456 if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) { 457 CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl()); 458 if (!Record->hasTrivialDestructor()) { 459 CXXDestructorDecl *DtorD = Record->getDestructor(); 460 Dtor = CGM.GetAddrOfCXXDestructor(DtorD, Dtor_Complete); 461 Dtor = llvm::ConstantExpr::getBitCast(Dtor, Int8PtrTy); 462 } 463 } 464 if (!Dtor) Dtor = llvm::Constant::getNullValue(Int8PtrTy); 465 466 if (getInvokeDest()) { 467 llvm::InvokeInst *ThrowCall = 468 Builder.CreateInvoke3(getThrowFn(*this), 469 getUnreachableBlock(), getInvokeDest(), 470 ExceptionPtr, TypeInfo, Dtor); 471 ThrowCall->setDoesNotReturn(); 472 } else { 473 llvm::CallInst *ThrowCall = 474 Builder.CreateCall3(getThrowFn(*this), ExceptionPtr, TypeInfo, Dtor); 475 ThrowCall->setDoesNotReturn(); 476 Builder.CreateUnreachable(); 477 } 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 484void 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. 516static 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()); 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.Builder.CreateCall(getUnexpectedFn(CGF), exn) 548 ->setDoesNotReturn(); 549 CGF.Builder.CreateUnreachable(); 550} 551 552void 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 575void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) { 576 EnterCXXTryStmt(S); 577 EmitStmt(S.getTryBlock()); 578 ExitCXXTryStmt(S); 579} 580 581void 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 612llvm::BasicBlock * 613CodeGenFunction::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(); 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. 659static 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 672llvm::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. 734enum 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}; 746const CleanupHackLevel_t CleanupHackLevel = CHL_MandatoryCleanup; 747 748llvm::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 llvm::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 890namespace { 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.Builder.CreateCall(getEndCatchFn(CGF))->setDoesNotThrow(); 910 return; 911 } 912 913 CGF.EmitCallOrInvoke(getEndCatchFn(CGF)); 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 922static llvm::Value *CallBeginCatch(CodeGenFunction &CGF, 923 llvm::Value *Exn, 924 bool EndMightThrow) { 925 llvm::CallInst *Call = CGF.Builder.CreateCall(getBeginCatchFn(CGF), Exn); 926 Call->setDoesNotThrow(); 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. 935static 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 // Non-aggregates (plus complexes). 1006 bool IsComplex = false; 1007 if (!CGF.hasAggregateLLVMType(CatchType) || 1008 (IsComplex = CatchType->isAnyComplexType())) { 1009 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, false); 1010 1011 // If the catch type is a pointer type, __cxa_begin_catch returns 1012 // the pointer by value. 1013 if (CatchType->hasPointerRepresentation()) { 1014 llvm::Value *CastExn = 1015 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted"); 1016 1017 switch (CatchType.getQualifiers().getObjCLifetime()) { 1018 case Qualifiers::OCL_Strong: 1019 CastExn = CGF.EmitARCRetainNonBlock(CastExn); 1020 // fallthrough 1021 1022 case Qualifiers::OCL_None: 1023 case Qualifiers::OCL_ExplicitNone: 1024 case Qualifiers::OCL_Autoreleasing: 1025 CGF.Builder.CreateStore(CastExn, ParamAddr); 1026 return; 1027 1028 case Qualifiers::OCL_Weak: 1029 CGF.EmitARCInitWeak(ParamAddr, CastExn); 1030 return; 1031 } 1032 llvm_unreachable("bad ownership qualifier!"); 1033 } 1034 1035 // Otherwise, it returns a pointer into the exception object. 1036 1037 llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1038 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 1039 1040 if (IsComplex) { 1041 CGF.StoreComplexToAddr(CGF.LoadComplexFromAddr(Cast, /*volatile*/ false), 1042 ParamAddr, /*volatile*/ false); 1043 } else { 1044 unsigned Alignment = 1045 CGF.getContext().getDeclAlign(&CatchParam).getQuantity(); 1046 llvm::Value *ExnLoad = CGF.Builder.CreateLoad(Cast, "exn.scalar"); 1047 CGF.EmitStoreOfScalar(ExnLoad, ParamAddr, /*volatile*/ false, Alignment, 1048 CatchType); 1049 } 1050 return; 1051 } 1052 1053 assert(isa<RecordType>(CatchType) && "unexpected catch type!"); 1054 1055 llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1056 1057 // Check for a copy expression. If we don't have a copy expression, 1058 // that means a trivial copy is okay. 1059 const Expr *copyExpr = CatchParam.getInit(); 1060 if (!copyExpr) { 1061 llvm::Value *rawAdjustedExn = CallBeginCatch(CGF, Exn, true); 1062 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy); 1063 CGF.EmitAggregateCopy(ParamAddr, adjustedExn, CatchType); 1064 return; 1065 } 1066 1067 // We have to call __cxa_get_exception_ptr to get the adjusted 1068 // pointer before copying. 1069 llvm::CallInst *rawAdjustedExn = 1070 CGF.Builder.CreateCall(getGetExceptionPtrFn(CGF), Exn); 1071 rawAdjustedExn->setDoesNotThrow(); 1072 1073 // Cast that to the appropriate type. 1074 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy); 1075 1076 // The copy expression is defined in terms of an OpaqueValueExpr. 1077 // Find it and map it to the adjusted expression. 1078 CodeGenFunction::OpaqueValueMapping 1079 opaque(CGF, OpaqueValueExpr::findInCopyConstruct(copyExpr), 1080 CGF.MakeAddrLValue(adjustedExn, CatchParam.getType())); 1081 1082 // Call the copy ctor in a terminate scope. 1083 CGF.EHStack.pushTerminate(); 1084 1085 // Perform the copy construction. 1086 CharUnits Alignment = CGF.getContext().getDeclAlign(&CatchParam); 1087 CGF.EmitAggExpr(copyExpr, 1088 AggValueSlot::forAddr(ParamAddr, Alignment, Qualifiers(), 1089 AggValueSlot::IsNotDestructed, 1090 AggValueSlot::DoesNotNeedGCBarriers, 1091 AggValueSlot::IsNotAliased)); 1092 1093 // Leave the terminate scope. 1094 CGF.EHStack.popTerminate(); 1095 1096 // Undo the opaque value mapping. 1097 opaque.pop(); 1098 1099 // Finally we can call __cxa_begin_catch. 1100 CallBeginCatch(CGF, Exn, true); 1101} 1102 1103/// Begins a catch statement by initializing the catch variable and 1104/// calling __cxa_begin_catch. 1105static void BeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *S) { 1106 // We have to be very careful with the ordering of cleanups here: 1107 // C++ [except.throw]p4: 1108 // The destruction [of the exception temporary] occurs 1109 // immediately after the destruction of the object declared in 1110 // the exception-declaration in the handler. 1111 // 1112 // So the precise ordering is: 1113 // 1. Construct catch variable. 1114 // 2. __cxa_begin_catch 1115 // 3. Enter __cxa_end_catch cleanup 1116 // 4. Enter dtor cleanup 1117 // 1118 // We do this by using a slightly abnormal initialization process. 1119 // Delegation sequence: 1120 // - ExitCXXTryStmt opens a RunCleanupsScope 1121 // - EmitAutoVarAlloca creates the variable and debug info 1122 // - InitCatchParam initializes the variable from the exception 1123 // - CallBeginCatch calls __cxa_begin_catch 1124 // - CallBeginCatch enters the __cxa_end_catch cleanup 1125 // - EmitAutoVarCleanups enters the variable destructor cleanup 1126 // - EmitCXXTryStmt emits the code for the catch body 1127 // - EmitCXXTryStmt close the RunCleanupsScope 1128 1129 VarDecl *CatchParam = S->getExceptionDecl(); 1130 if (!CatchParam) { 1131 llvm::Value *Exn = CGF.getExceptionFromSlot(); 1132 CallBeginCatch(CGF, Exn, true); 1133 return; 1134 } 1135 1136 // Emit the local. 1137 CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam); 1138 InitCatchParam(CGF, *CatchParam, var.getObjectAddress(CGF)); 1139 CGF.EmitAutoVarCleanups(var); 1140} 1141 1142/// Emit the structure of the dispatch block for the given catch scope. 1143/// It is an invariant that the dispatch block already exists. 1144static void emitCatchDispatchBlock(CodeGenFunction &CGF, 1145 EHCatchScope &catchScope) { 1146 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock(); 1147 assert(dispatchBlock); 1148 1149 // If there's only a single catch-all, getEHDispatchBlock returned 1150 // that catch-all as the dispatch block. 1151 if (catchScope.getNumHandlers() == 1 && 1152 catchScope.getHandler(0).isCatchAll()) { 1153 assert(dispatchBlock == catchScope.getHandler(0).Block); 1154 return; 1155 } 1156 1157 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP(); 1158 CGF.EmitBlockAfterUses(dispatchBlock); 1159 1160 // Select the right handler. 1161 llvm::Value *llvm_eh_typeid_for = 1162 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); 1163 1164 // Load the selector value. 1165 llvm::Value *selector = CGF.getSelectorFromSlot(); 1166 1167 // Test against each of the exception types we claim to catch. 1168 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) { 1169 assert(i < e && "ran off end of handlers!"); 1170 const EHCatchScope::Handler &handler = catchScope.getHandler(i); 1171 1172 llvm::Value *typeValue = handler.Type; 1173 assert(typeValue && "fell into catch-all case!"); 1174 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy); 1175 1176 // Figure out the next block. 1177 bool nextIsEnd; 1178 llvm::BasicBlock *nextBlock; 1179 1180 // If this is the last handler, we're at the end, and the next 1181 // block is the block for the enclosing EH scope. 1182 if (i + 1 == e) { 1183 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope()); 1184 nextIsEnd = true; 1185 1186 // If the next handler is a catch-all, we're at the end, and the 1187 // next block is that handler. 1188 } else if (catchScope.getHandler(i+1).isCatchAll()) { 1189 nextBlock = catchScope.getHandler(i+1).Block; 1190 nextIsEnd = true; 1191 1192 // Otherwise, we're not at the end and we need a new block. 1193 } else { 1194 nextBlock = CGF.createBasicBlock("catch.fallthrough"); 1195 nextIsEnd = false; 1196 } 1197 1198 // Figure out the catch type's index in the LSDA's type table. 1199 llvm::CallInst *typeIndex = 1200 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue); 1201 typeIndex->setDoesNotThrow(); 1202 1203 llvm::Value *matchesTypeIndex = 1204 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches"); 1205 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock); 1206 1207 // If the next handler is a catch-all, we're completely done. 1208 if (nextIsEnd) { 1209 CGF.Builder.restoreIP(savedIP); 1210 return; 1211 } 1212 // Otherwise we need to emit and continue at that block. 1213 CGF.EmitBlock(nextBlock); 1214 } 1215} 1216 1217void CodeGenFunction::popCatchScope() { 1218 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin()); 1219 if (catchScope.hasEHBranches()) 1220 emitCatchDispatchBlock(*this, catchScope); 1221 EHStack.popCatch(); 1222} 1223 1224void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 1225 unsigned NumHandlers = S.getNumHandlers(); 1226 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin()); 1227 assert(CatchScope.getNumHandlers() == NumHandlers); 1228 1229 // If the catch was not required, bail out now. 1230 if (!CatchScope.hasEHBranches()) { 1231 EHStack.popCatch(); 1232 return; 1233 } 1234 1235 // Emit the structure of the EH dispatch for this catch. 1236 emitCatchDispatchBlock(*this, CatchScope); 1237 1238 // Copy the handler blocks off before we pop the EH stack. Emitting 1239 // the handlers might scribble on this memory. 1240 SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers); 1241 memcpy(Handlers.data(), CatchScope.begin(), 1242 NumHandlers * sizeof(EHCatchScope::Handler)); 1243 1244 EHStack.popCatch(); 1245 1246 // The fall-through block. 1247 llvm::BasicBlock *ContBB = createBasicBlock("try.cont"); 1248 1249 // We just emitted the body of the try; jump to the continue block. 1250 if (HaveInsertPoint()) 1251 Builder.CreateBr(ContBB); 1252 1253 // Determine if we need an implicit rethrow for all these catch handlers; 1254 // see the comment below. 1255 bool doImplicitRethrow = false; 1256 if (IsFnTryBlock) 1257 doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) || 1258 isa<CXXConstructorDecl>(CurCodeDecl); 1259 1260 // Perversely, we emit the handlers backwards precisely because we 1261 // want them to appear in source order. In all of these cases, the 1262 // catch block will have exactly one predecessor, which will be a 1263 // particular block in the catch dispatch. However, in the case of 1264 // a catch-all, one of the dispatch blocks will branch to two 1265 // different handlers, and EmitBlockAfterUses will cause the second 1266 // handler to be moved before the first. 1267 for (unsigned I = NumHandlers; I != 0; --I) { 1268 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block; 1269 EmitBlockAfterUses(CatchBlock); 1270 1271 // Catch the exception if this isn't a catch-all. 1272 const CXXCatchStmt *C = S.getHandler(I-1); 1273 1274 // Enter a cleanup scope, including the catch variable and the 1275 // end-catch. 1276 RunCleanupsScope CatchScope(*this); 1277 1278 // Initialize the catch variable and set up the cleanups. 1279 BeginCatch(*this, C); 1280 1281 // Perform the body of the catch. 1282 EmitStmt(C->getHandlerBlock()); 1283 1284 // [except.handle]p11: 1285 // The currently handled exception is rethrown if control 1286 // reaches the end of a handler of the function-try-block of a 1287 // constructor or destructor. 1288 1289 // It is important that we only do this on fallthrough and not on 1290 // return. Note that it's illegal to put a return in a 1291 // constructor function-try-block's catch handler (p14), so this 1292 // really only applies to destructors. 1293 if (doImplicitRethrow && HaveInsertPoint()) { 1294 EmitCallOrInvoke(getReThrowFn(*this)); 1295 Builder.CreateUnreachable(); 1296 Builder.ClearInsertionPoint(); 1297 } 1298 1299 // Fall out through the catch cleanups. 1300 CatchScope.ForceCleanup(); 1301 1302 // Branch out of the try. 1303 if (HaveInsertPoint()) 1304 Builder.CreateBr(ContBB); 1305 } 1306 1307 EmitBlock(ContBB); 1308} 1309 1310namespace { 1311 struct CallEndCatchForFinally : EHScopeStack::Cleanup { 1312 llvm::Value *ForEHVar; 1313 llvm::Value *EndCatchFn; 1314 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn) 1315 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {} 1316 1317 void Emit(CodeGenFunction &CGF, Flags flags) { 1318 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch"); 1319 llvm::BasicBlock *CleanupContBB = 1320 CGF.createBasicBlock("finally.cleanup.cont"); 1321 1322 llvm::Value *ShouldEndCatch = 1323 CGF.Builder.CreateLoad(ForEHVar, "finally.endcatch"); 1324 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB); 1325 CGF.EmitBlock(EndCatchBB); 1326 CGF.EmitCallOrInvoke(EndCatchFn); // catch-all, so might throw 1327 CGF.EmitBlock(CleanupContBB); 1328 } 1329 }; 1330 1331 struct PerformFinally : EHScopeStack::Cleanup { 1332 const Stmt *Body; 1333 llvm::Value *ForEHVar; 1334 llvm::Value *EndCatchFn; 1335 llvm::Value *RethrowFn; 1336 llvm::Value *SavedExnVar; 1337 1338 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar, 1339 llvm::Value *EndCatchFn, 1340 llvm::Value *RethrowFn, llvm::Value *SavedExnVar) 1341 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn), 1342 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {} 1343 1344 void Emit(CodeGenFunction &CGF, Flags flags) { 1345 // Enter a cleanup to call the end-catch function if one was provided. 1346 if (EndCatchFn) 1347 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup, 1348 ForEHVar, EndCatchFn); 1349 1350 // Save the current cleanup destination in case there are 1351 // cleanups in the finally block. 1352 llvm::Value *SavedCleanupDest = 1353 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(), 1354 "cleanup.dest.saved"); 1355 1356 // Emit the finally block. 1357 CGF.EmitStmt(Body); 1358 1359 // If the end of the finally is reachable, check whether this was 1360 // for EH. If so, rethrow. 1361 if (CGF.HaveInsertPoint()) { 1362 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow"); 1363 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont"); 1364 1365 llvm::Value *ShouldRethrow = 1366 CGF.Builder.CreateLoad(ForEHVar, "finally.shouldthrow"); 1367 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB); 1368 1369 CGF.EmitBlock(RethrowBB); 1370 if (SavedExnVar) { 1371 CGF.EmitCallOrInvoke(RethrowFn, CGF.Builder.CreateLoad(SavedExnVar)); 1372 } else { 1373 CGF.EmitCallOrInvoke(RethrowFn); 1374 } 1375 CGF.Builder.CreateUnreachable(); 1376 1377 CGF.EmitBlock(ContBB); 1378 1379 // Restore the cleanup destination. 1380 CGF.Builder.CreateStore(SavedCleanupDest, 1381 CGF.getNormalCleanupDestSlot()); 1382 } 1383 1384 // Leave the end-catch cleanup. As an optimization, pretend that 1385 // the fallthrough path was inaccessible; we've dynamically proven 1386 // that we're not in the EH case along that path. 1387 if (EndCatchFn) { 1388 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); 1389 CGF.PopCleanupBlock(); 1390 CGF.Builder.restoreIP(SavedIP); 1391 } 1392 1393 // Now make sure we actually have an insertion point or the 1394 // cleanup gods will hate us. 1395 CGF.EnsureInsertPoint(); 1396 } 1397 }; 1398} 1399 1400/// Enters a finally block for an implementation using zero-cost 1401/// exceptions. This is mostly general, but hard-codes some 1402/// language/ABI-specific behavior in the catch-all sections. 1403void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF, 1404 const Stmt *body, 1405 llvm::Constant *beginCatchFn, 1406 llvm::Constant *endCatchFn, 1407 llvm::Constant *rethrowFn) { 1408 assert((beginCatchFn != 0) == (endCatchFn != 0) && 1409 "begin/end catch functions not paired"); 1410 assert(rethrowFn && "rethrow function is required"); 1411 1412 BeginCatchFn = beginCatchFn; 1413 1414 // The rethrow function has one of the following two types: 1415 // void (*)() 1416 // void (*)(void*) 1417 // In the latter case we need to pass it the exception object. 1418 // But we can't use the exception slot because the @finally might 1419 // have a landing pad (which would overwrite the exception slot). 1420 llvm::FunctionType *rethrowFnTy = 1421 cast<llvm::FunctionType>( 1422 cast<llvm::PointerType>(rethrowFn->getType())->getElementType()); 1423 SavedExnVar = 0; 1424 if (rethrowFnTy->getNumParams()) 1425 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn"); 1426 1427 // A finally block is a statement which must be executed on any edge 1428 // out of a given scope. Unlike a cleanup, the finally block may 1429 // contain arbitrary control flow leading out of itself. In 1430 // addition, finally blocks should always be executed, even if there 1431 // are no catch handlers higher on the stack. Therefore, we 1432 // surround the protected scope with a combination of a normal 1433 // cleanup (to catch attempts to break out of the block via normal 1434 // control flow) and an EH catch-all (semantically "outside" any try 1435 // statement to which the finally block might have been attached). 1436 // The finally block itself is generated in the context of a cleanup 1437 // which conditionally leaves the catch-all. 1438 1439 // Jump destination for performing the finally block on an exception 1440 // edge. We'll never actually reach this block, so unreachable is 1441 // fine. 1442 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock()); 1443 1444 // Whether the finally block is being executed for EH purposes. 1445 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh"); 1446 CGF.Builder.CreateStore(CGF.Builder.getFalse(), ForEHVar); 1447 1448 // Enter a normal cleanup which will perform the @finally block. 1449 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body, 1450 ForEHVar, endCatchFn, 1451 rethrowFn, SavedExnVar); 1452 1453 // Enter a catch-all scope. 1454 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall"); 1455 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1); 1456 catchScope->setCatchAllHandler(0, catchBB); 1457} 1458 1459void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) { 1460 // Leave the finally catch-all. 1461 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin()); 1462 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block; 1463 1464 CGF.popCatchScope(); 1465 1466 // If there are any references to the catch-all block, emit it. 1467 if (catchBB->use_empty()) { 1468 delete catchBB; 1469 } else { 1470 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP(); 1471 CGF.EmitBlock(catchBB); 1472 1473 llvm::Value *exn = 0; 1474 1475 // If there's a begin-catch function, call it. 1476 if (BeginCatchFn) { 1477 exn = CGF.getExceptionFromSlot(); 1478 CGF.Builder.CreateCall(BeginCatchFn, exn)->setDoesNotThrow(); 1479 } 1480 1481 // If we need to remember the exception pointer to rethrow later, do so. 1482 if (SavedExnVar) { 1483 if (!exn) exn = CGF.getExceptionFromSlot(); 1484 CGF.Builder.CreateStore(exn, SavedExnVar); 1485 } 1486 1487 // Tell the cleanups in the finally block that we're do this for EH. 1488 CGF.Builder.CreateStore(CGF.Builder.getTrue(), ForEHVar); 1489 1490 // Thread a jump through the finally cleanup. 1491 CGF.EmitBranchThroughCleanup(RethrowDest); 1492 1493 CGF.Builder.restoreIP(savedIP); 1494 } 1495 1496 // Finally, leave the @finally cleanup. 1497 CGF.PopCleanupBlock(); 1498} 1499 1500llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() { 1501 if (TerminateLandingPad) 1502 return TerminateLandingPad; 1503 1504 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1505 1506 // This will get inserted at the end of the function. 1507 TerminateLandingPad = createBasicBlock("terminate.lpad"); 1508 Builder.SetInsertPoint(TerminateLandingPad); 1509 1510 // Tell the backend that this is a landing pad. 1511 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOpts()); 1512 llvm::LandingPadInst *LPadInst = 1513 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, NULL), 1514 getOpaquePersonalityFn(CGM, Personality), 0); 1515 LPadInst->addClause(getCatchAllValue(*this)); 1516 1517 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this)); 1518 TerminateCall->setDoesNotReturn(); 1519 TerminateCall->setDoesNotThrow(); 1520 Builder.CreateUnreachable(); 1521 1522 // Restore the saved insertion state. 1523 Builder.restoreIP(SavedIP); 1524 1525 return TerminateLandingPad; 1526} 1527 1528llvm::BasicBlock *CodeGenFunction::getTerminateHandler() { 1529 if (TerminateHandler) 1530 return TerminateHandler; 1531 1532 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1533 1534 // Set up the terminate handler. This block is inserted at the very 1535 // end of the function by FinishFunction. 1536 TerminateHandler = createBasicBlock("terminate.handler"); 1537 Builder.SetInsertPoint(TerminateHandler); 1538 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this)); 1539 TerminateCall->setDoesNotReturn(); 1540 TerminateCall->setDoesNotThrow(); 1541 Builder.CreateUnreachable(); 1542 1543 // Restore the saved insertion state. 1544 Builder.restoreIP(SavedIP); 1545 1546 return TerminateHandler; 1547} 1548 1549llvm::BasicBlock *CodeGenFunction::getEHResumeBlock() { 1550 if (EHResumeBlock) return EHResumeBlock; 1551 1552 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP(); 1553 1554 // We emit a jump to a notional label at the outermost unwind state. 1555 EHResumeBlock = createBasicBlock("eh.resume"); 1556 Builder.SetInsertPoint(EHResumeBlock); 1557 1558 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOpts()); 1559 1560 // This can always be a call because we necessarily didn't find 1561 // anything on the EH stack which needs our help. 1562 const char *RethrowName = Personality.CatchallRethrowFn; 1563 if (RethrowName != 0) { 1564 Builder.CreateCall(getCatchallRethrowFn(*this, RethrowName), 1565 getExceptionFromSlot()) 1566 ->setDoesNotReturn(); 1567 } else { 1568 switch (CleanupHackLevel) { 1569 case CHL_MandatoryCatchall: 1570 // In mandatory-catchall mode, we need to use 1571 // _Unwind_Resume_or_Rethrow, or whatever the personality's 1572 // equivalent is. 1573 Builder.CreateCall(getUnwindResumeOrRethrowFn(), 1574 getExceptionFromSlot()) 1575 ->setDoesNotReturn(); 1576 break; 1577 case CHL_MandatoryCleanup: { 1578 // In mandatory-cleanup mode, we should use 'resume'. 1579 1580 // Recreate the landingpad's return value for the 'resume' instruction. 1581 llvm::Value *Exn = getExceptionFromSlot(); 1582 llvm::Value *Sel = getSelectorFromSlot(); 1583 1584 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(), 1585 Sel->getType(), NULL); 1586 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType); 1587 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val"); 1588 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val"); 1589 1590 Builder.CreateResume(LPadVal); 1591 Builder.restoreIP(SavedIP); 1592 return EHResumeBlock; 1593 } 1594 case CHL_Ideal: 1595 // In an idealized mode where we don't have to worry about the 1596 // optimizer combining landing pads, we should just use 1597 // _Unwind_Resume (or the personality's equivalent). 1598 Builder.CreateCall(getUnwindResumeFn(), getExceptionFromSlot()) 1599 ->setDoesNotReturn(); 1600 break; 1601 } 1602 } 1603 1604 Builder.CreateUnreachable(); 1605 1606 Builder.restoreIP(SavedIP); 1607 1608 return EHResumeBlock; 1609} 1610