CGException.cpp revision f394078fde147dcf27e9b6a7965517388d64dcb6
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 "clang/AST/StmtCXX.h" 15 16#include "llvm/Intrinsics.h" 17#include "llvm/IntrinsicInst.h" 18#include "llvm/Support/CallSite.h" 19 20#include "CGObjCRuntime.h" 21#include "CodeGenFunction.h" 22#include "CGException.h" 23#include "CGCleanup.h" 24#include "TargetInfo.h" 25 26using namespace clang; 27using namespace CodeGen; 28 29static llvm::Constant *getAllocateExceptionFn(CodeGenFunction &CGF) { 30 // void *__cxa_allocate_exception(size_t thrown_size); 31 32 llvm::FunctionType *FTy = 33 llvm::FunctionType::get(CGF.Int8PtrTy, CGF.SizeTy, /*IsVarArgs=*/false); 34 35 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception"); 36} 37 38static llvm::Constant *getFreeExceptionFn(CodeGenFunction &CGF) { 39 // void __cxa_free_exception(void *thrown_exception); 40 41 llvm::FunctionType *FTy = 42 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 43 44 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception"); 45} 46 47static llvm::Constant *getThrowFn(CodeGenFunction &CGF) { 48 // void __cxa_throw(void *thrown_exception, std::type_info *tinfo, 49 // void (*dest) (void *)); 50 51 llvm::Type *Args[3] = { CGF.Int8PtrTy, CGF.Int8PtrTy, CGF.Int8PtrTy }; 52 llvm::FunctionType *FTy = 53 llvm::FunctionType::get(CGF.VoidTy, Args, /*IsVarArgs=*/false); 54 55 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_throw"); 56} 57 58static llvm::Constant *getReThrowFn(CodeGenFunction &CGF) { 59 // void __cxa_rethrow(); 60 61 llvm::FunctionType *FTy = 62 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false); 63 64 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow"); 65} 66 67static llvm::Constant *getGetExceptionPtrFn(CodeGenFunction &CGF) { 68 // void *__cxa_get_exception_ptr(void*); 69 70 llvm::FunctionType *FTy = 71 llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 72 73 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr"); 74} 75 76static llvm::Constant *getBeginCatchFn(CodeGenFunction &CGF) { 77 // void *__cxa_begin_catch(void*); 78 79 llvm::FunctionType *FTy = 80 llvm::FunctionType::get(CGF.Int8PtrTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 81 82 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch"); 83} 84 85static llvm::Constant *getEndCatchFn(CodeGenFunction &CGF) { 86 // void __cxa_end_catch(); 87 88 llvm::FunctionType *FTy = 89 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false); 90 91 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch"); 92} 93 94static llvm::Constant *getUnexpectedFn(CodeGenFunction &CGF) { 95 // void __cxa_call_unexepcted(void *thrown_exception); 96 97 llvm::FunctionType *FTy = 98 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 99 100 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); 101} 102 103llvm::Constant *CodeGenFunction::getUnwindResumeFn() { 104 llvm::FunctionType *FTy = 105 llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); 106 107 if (CGM.getLangOptions().SjLjExceptions) 108 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume"); 109 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume"); 110} 111 112llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() { 113 llvm::FunctionType *FTy = 114 llvm::FunctionType::get(VoidTy, Int8PtrTy, /*IsVarArgs=*/false); 115 116 if (CGM.getLangOptions().SjLjExceptions) 117 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume_or_Rethrow"); 118 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume_or_Rethrow"); 119} 120 121static llvm::Constant *getTerminateFn(CodeGenFunction &CGF) { 122 // void __terminate(); 123 124 llvm::FunctionType *FTy = 125 llvm::FunctionType::get(CGF.VoidTy, /*IsVarArgs=*/false); 126 127 StringRef name; 128 129 // In C++, use std::terminate(). 130 if (CGF.getLangOptions().CPlusPlus) 131 name = "_ZSt9terminatev"; // FIXME: mangling! 132 else if (CGF.getLangOptions().ObjC1 && 133 CGF.CGM.getCodeGenOpts().ObjCRuntimeHasTerminate) 134 name = "objc_terminate"; 135 else 136 name = "abort"; 137 return CGF.CGM.CreateRuntimeFunction(FTy, name); 138} 139 140static llvm::Constant *getCatchallRethrowFn(CodeGenFunction &CGF, 141 StringRef Name) { 142 llvm::FunctionType *FTy = 143 llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, /*IsVarArgs=*/false); 144 145 return CGF.CGM.CreateRuntimeFunction(FTy, Name); 146} 147 148const EHPersonality EHPersonality::GNU_C("__gcc_personality_v0"); 149const EHPersonality EHPersonality::GNU_C_SJLJ("__gcc_personality_sj0"); 150const EHPersonality EHPersonality::NeXT_ObjC("__objc_personality_v0"); 151const EHPersonality EHPersonality::GNU_CPlusPlus("__gxx_personality_v0"); 152const EHPersonality EHPersonality::GNU_CPlusPlus_SJLJ("__gxx_personality_sj0"); 153const EHPersonality EHPersonality::GNU_ObjC("__gnu_objc_personality_v0", 154 "objc_exception_throw"); 155const EHPersonality EHPersonality::GNU_ObjCXX("__gnustep_objcxx_personality_v0"); 156 157static const EHPersonality &getCPersonality(const LangOptions &L) { 158 if (L.SjLjExceptions) 159 return EHPersonality::GNU_C_SJLJ; 160 return EHPersonality::GNU_C; 161} 162 163static const EHPersonality &getObjCPersonality(const LangOptions &L) { 164 if (L.NeXTRuntime) { 165 if (L.ObjCNonFragileABI) return EHPersonality::NeXT_ObjC; 166 else return getCPersonality(L); 167 } else { 168 return EHPersonality::GNU_ObjC; 169 } 170} 171 172static const EHPersonality &getCXXPersonality(const LangOptions &L) { 173 if (L.SjLjExceptions) 174 return EHPersonality::GNU_CPlusPlus_SJLJ; 175 else 176 return EHPersonality::GNU_CPlusPlus; 177} 178 179/// Determines the personality function to use when both C++ 180/// and Objective-C exceptions are being caught. 181static const EHPersonality &getObjCXXPersonality(const LangOptions &L) { 182 // The ObjC personality defers to the C++ personality for non-ObjC 183 // handlers. Unlike the C++ case, we use the same personality 184 // function on targets using (backend-driven) SJLJ EH. 185 if (L.NeXTRuntime) { 186 if (L.ObjCNonFragileABI) 187 return EHPersonality::NeXT_ObjC; 188 189 // In the fragile ABI, just use C++ exception handling and hope 190 // they're not doing crazy exception mixing. 191 else 192 return getCXXPersonality(L); 193 } 194 195 // The GNU runtime's personality function inherently doesn't support 196 // mixed EH. Use the C++ personality just to avoid returning null. 197 return EHPersonality::GNU_ObjCXX; 198} 199 200const EHPersonality &EHPersonality::get(const LangOptions &L) { 201 if (L.CPlusPlus && L.ObjC1) 202 return getObjCXXPersonality(L); 203 else if (L.CPlusPlus) 204 return getCXXPersonality(L); 205 else if (L.ObjC1) 206 return getObjCPersonality(L); 207 else 208 return getCPersonality(L); 209} 210 211static llvm::Constant *getPersonalityFn(CodeGenModule &CGM, 212 const EHPersonality &Personality) { 213 llvm::Constant *Fn = 214 CGM.CreateRuntimeFunction(llvm::FunctionType::get( 215 llvm::Type::getInt32Ty(CGM.getLLVMContext()), 216 true), 217 Personality.getPersonalityFnName()); 218 return Fn; 219} 220 221static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM, 222 const EHPersonality &Personality) { 223 llvm::Constant *Fn = getPersonalityFn(CGM, Personality); 224 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy); 225} 226 227/// Check whether a personality function could reasonably be swapped 228/// for a C++ personality function. 229static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) { 230 for (llvm::Constant::use_iterator 231 I = Fn->use_begin(), E = Fn->use_end(); I != E; ++I) { 232 llvm::User *User = *I; 233 234 // Conditionally white-list bitcasts. 235 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(User)) { 236 if (CE->getOpcode() != llvm::Instruction::BitCast) return false; 237 if (!PersonalityHasOnlyCXXUses(CE)) 238 return false; 239 continue; 240 } 241 242 // Otherwise, it has to be a landingpad instruction. 243 llvm::LandingPadInst *LPI = dyn_cast<llvm::LandingPadInst>(User); 244 if (!LPI) return false; 245 246 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) { 247 // Look for something that would've been returned by the ObjC 248 // runtime's GetEHType() method. 249 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts(); 250 if (LPI->isCatch(I)) { 251 // Check if the catch value has the ObjC prefix. 252 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val)) 253 // ObjC EH selector entries are always global variables with 254 // names starting like this. 255 if (GV->getName().startswith("OBJC_EHTYPE")) 256 return false; 257 } else { 258 // Check if any of the filter values have the ObjC prefix. 259 llvm::Constant *CVal = cast<llvm::Constant>(Val); 260 for (llvm::User::op_iterator 261 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) { 262 if (llvm::GlobalVariable *GV = 263 cast<llvm::GlobalVariable>((*II)->stripPointerCasts())) 264 // ObjC EH selector entries are always global variables with 265 // names starting like this. 266 if (GV->getName().startswith("OBJC_EHTYPE")) 267 return false; 268 } 269 } 270 } 271 } 272 273 return true; 274} 275 276/// Try to use the C++ personality function in ObjC++. Not doing this 277/// can cause some incompatibilities with gcc, which is more 278/// aggressive about only using the ObjC++ personality in a function 279/// when it really needs it. 280void CodeGenModule::SimplifyPersonality() { 281 // For now, this is really a Darwin-specific operation. 282 if (!Context.getTargetInfo().getTriple().isOSDarwin()) 283 return; 284 285 // If we're not in ObjC++ -fexceptions, there's nothing to do. 286 if (!Features.CPlusPlus || !Features.ObjC1 || !Features.Exceptions) 287 return; 288 289 const EHPersonality &ObjCXX = EHPersonality::get(Features); 290 const EHPersonality &CXX = getCXXPersonality(Features); 291 if (&ObjCXX == &CXX || 292 ObjCXX.getPersonalityFnName() == CXX.getPersonalityFnName()) 293 return; 294 295 llvm::Function *Fn = 296 getModule().getFunction(ObjCXX.getPersonalityFnName()); 297 298 // Nothing to do if it's unused. 299 if (!Fn || Fn->use_empty()) return; 300 301 // Can't do the optimization if it has non-C++ uses. 302 if (!PersonalityHasOnlyCXXUses(Fn)) return; 303 304 // Create the C++ personality function and kill off the old 305 // function. 306 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX); 307 308 // This can happen if the user is screwing with us. 309 if (Fn->getType() != CXXFn->getType()) return; 310 311 Fn->replaceAllUsesWith(CXXFn); 312 Fn->eraseFromParent(); 313} 314 315/// Returns the value to inject into a selector to indicate the 316/// presence of a catch-all. 317static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) { 318 // Possibly we should use @llvm.eh.catch.all.value here. 319 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy); 320} 321 322namespace { 323 /// A cleanup to free the exception object if its initialization 324 /// throws. 325 struct FreeException : EHScopeStack::Cleanup { 326 llvm::Value *exn; 327 FreeException(llvm::Value *exn) : exn(exn) {} 328 void Emit(CodeGenFunction &CGF, Flags flags) { 329 CGF.Builder.CreateCall(getFreeExceptionFn(CGF), exn) 330 ->setDoesNotThrow(); 331 } 332 }; 333} 334 335// Emits an exception expression into the given location. This 336// differs from EmitAnyExprToMem only in that, if a final copy-ctor 337// call is required, an exception within that copy ctor causes 338// std::terminate to be invoked. 339static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *e, 340 llvm::Value *addr) { 341 // Make sure the exception object is cleaned up if there's an 342 // exception during initialization. 343 CGF.pushFullExprCleanup<FreeException>(EHCleanup, addr); 344 EHScopeStack::stable_iterator cleanup = CGF.EHStack.stable_begin(); 345 346 // __cxa_allocate_exception returns a void*; we need to cast this 347 // to the appropriate type for the object. 348 llvm::Type *ty = CGF.ConvertTypeForMem(e->getType())->getPointerTo(); 349 llvm::Value *typedAddr = CGF.Builder.CreateBitCast(addr, ty); 350 351 // FIXME: this isn't quite right! If there's a final unelided call 352 // to a copy constructor, then according to [except.terminate]p1 we 353 // must call std::terminate() if that constructor throws, because 354 // technically that copy occurs after the exception expression is 355 // evaluated but before the exception is caught. But the best way 356 // to handle that is to teach EmitAggExpr to do the final copy 357 // differently if it can't be elided. 358 CGF.EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(), 359 /*IsInit*/ true); 360 361 // Deactivate the cleanup block. 362 CGF.DeactivateCleanupBlock(cleanup, cast<llvm::Instruction>(typedAddr)); 363} 364 365llvm::Value *CodeGenFunction::getExceptionSlot() { 366 if (!ExceptionSlot) 367 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot"); 368 return ExceptionSlot; 369} 370 371llvm::Value *CodeGenFunction::getEHSelectorSlot() { 372 if (!EHSelectorSlot) 373 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot"); 374 return EHSelectorSlot; 375} 376 377llvm::Value *CodeGenFunction::getExceptionFromSlot() { 378 return Builder.CreateLoad(getExceptionSlot(), "exn"); 379} 380 381llvm::Value *CodeGenFunction::getSelectorFromSlot() { 382 return Builder.CreateLoad(getEHSelectorSlot(), "sel"); 383} 384 385void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) { 386 if (!E->getSubExpr()) { 387 if (getInvokeDest()) { 388 Builder.CreateInvoke(getReThrowFn(*this), 389 getUnreachableBlock(), 390 getInvokeDest()) 391 ->setDoesNotReturn(); 392 } else { 393 Builder.CreateCall(getReThrowFn(*this))->setDoesNotReturn(); 394 Builder.CreateUnreachable(); 395 } 396 397 // throw is an expression, and the expression emitters expect us 398 // to leave ourselves at a valid insertion point. 399 EmitBlock(createBasicBlock("throw.cont")); 400 401 return; 402 } 403 404 QualType ThrowType = E->getSubExpr()->getType(); 405 406 // Now allocate the exception object. 407 llvm::Type *SizeTy = ConvertType(getContext().getSizeType()); 408 uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity(); 409 410 llvm::Constant *AllocExceptionFn = getAllocateExceptionFn(*this); 411 llvm::CallInst *ExceptionPtr = 412 Builder.CreateCall(AllocExceptionFn, 413 llvm::ConstantInt::get(SizeTy, TypeSize), 414 "exception"); 415 ExceptionPtr->setDoesNotThrow(); 416 417 EmitAnyExprToExn(*this, E->getSubExpr(), ExceptionPtr); 418 419 // Now throw the exception. 420 llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType, 421 /*ForEH=*/true); 422 423 // The address of the destructor. If the exception type has a 424 // trivial destructor (or isn't a record), we just pass null. 425 llvm::Constant *Dtor = 0; 426 if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) { 427 CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl()); 428 if (!Record->hasTrivialDestructor()) { 429 CXXDestructorDecl *DtorD = Record->getDestructor(); 430 Dtor = CGM.GetAddrOfCXXDestructor(DtorD, Dtor_Complete); 431 Dtor = llvm::ConstantExpr::getBitCast(Dtor, Int8PtrTy); 432 } 433 } 434 if (!Dtor) Dtor = llvm::Constant::getNullValue(Int8PtrTy); 435 436 if (getInvokeDest()) { 437 llvm::InvokeInst *ThrowCall = 438 Builder.CreateInvoke3(getThrowFn(*this), 439 getUnreachableBlock(), getInvokeDest(), 440 ExceptionPtr, TypeInfo, Dtor); 441 ThrowCall->setDoesNotReturn(); 442 } else { 443 llvm::CallInst *ThrowCall = 444 Builder.CreateCall3(getThrowFn(*this), ExceptionPtr, TypeInfo, Dtor); 445 ThrowCall->setDoesNotReturn(); 446 Builder.CreateUnreachable(); 447 } 448 449 // throw is an expression, and the expression emitters expect us 450 // to leave ourselves at a valid insertion point. 451 EmitBlock(createBasicBlock("throw.cont")); 452} 453 454void CodeGenFunction::EmitStartEHSpec(const Decl *D) { 455 if (!CGM.getLangOptions().CXXExceptions) 456 return; 457 458 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 459 if (FD == 0) 460 return; 461 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 462 if (Proto == 0) 463 return; 464 465 ExceptionSpecificationType EST = Proto->getExceptionSpecType(); 466 if (isNoexceptExceptionSpec(EST)) { 467 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) { 468 // noexcept functions are simple terminate scopes. 469 EHStack.pushTerminate(); 470 } 471 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) { 472 unsigned NumExceptions = Proto->getNumExceptions(); 473 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions); 474 475 for (unsigned I = 0; I != NumExceptions; ++I) { 476 QualType Ty = Proto->getExceptionType(I); 477 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType(); 478 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType, 479 /*ForEH=*/true); 480 Filter->setFilter(I, EHType); 481 } 482 } 483} 484 485/// Emit the dispatch block for a filter scope if necessary. 486static void emitFilterDispatchBlock(CodeGenFunction &CGF, 487 EHFilterScope &filterScope) { 488 llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock(); 489 if (!dispatchBlock) return; 490 if (dispatchBlock->use_empty()) { 491 delete dispatchBlock; 492 return; 493 } 494 495 CGF.EmitBlockAfterUses(dispatchBlock); 496 497 // If this isn't a catch-all filter, we need to check whether we got 498 // here because the filter triggered. 499 if (filterScope.getNumFilters()) { 500 // Load the selector value. 501 llvm::Value *selector = CGF.getSelectorFromSlot(); 502 llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected"); 503 504 llvm::Value *zero = CGF.Builder.getInt32(0); 505 llvm::Value *failsFilter = 506 CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails"); 507 CGF.Builder.CreateCondBr(failsFilter, unexpectedBB, CGF.getEHResumeBlock()); 508 509 CGF.EmitBlock(unexpectedBB); 510 } 511 512 // Call __cxa_call_unexpected. This doesn't need to be an invoke 513 // because __cxa_call_unexpected magically filters exceptions 514 // according to the last landing pad the exception was thrown 515 // into. Seriously. 516 llvm::Value *exn = CGF.getExceptionFromSlot(); 517 CGF.Builder.CreateCall(getUnexpectedFn(CGF), exn) 518 ->setDoesNotReturn(); 519 CGF.Builder.CreateUnreachable(); 520} 521 522void CodeGenFunction::EmitEndEHSpec(const Decl *D) { 523 if (!CGM.getLangOptions().CXXExceptions) 524 return; 525 526 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 527 if (FD == 0) 528 return; 529 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 530 if (Proto == 0) 531 return; 532 533 ExceptionSpecificationType EST = Proto->getExceptionSpecType(); 534 if (isNoexceptExceptionSpec(EST)) { 535 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) { 536 EHStack.popTerminate(); 537 } 538 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) { 539 EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin()); 540 emitFilterDispatchBlock(*this, filterScope); 541 EHStack.popFilter(); 542 } 543} 544 545void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) { 546 EnterCXXTryStmt(S); 547 EmitStmt(S.getTryBlock()); 548 ExitCXXTryStmt(S); 549} 550 551void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 552 unsigned NumHandlers = S.getNumHandlers(); 553 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers); 554 555 for (unsigned I = 0; I != NumHandlers; ++I) { 556 const CXXCatchStmt *C = S.getHandler(I); 557 558 llvm::BasicBlock *Handler = createBasicBlock("catch"); 559 if (C->getExceptionDecl()) { 560 // FIXME: Dropping the reference type on the type into makes it 561 // impossible to correctly implement catch-by-reference 562 // semantics for pointers. Unfortunately, this is what all 563 // existing compilers do, and it's not clear that the standard 564 // personality routine is capable of doing this right. See C++ DR 388: 565 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388 566 QualType CaughtType = C->getCaughtType(); 567 CaughtType = CaughtType.getNonReferenceType().getUnqualifiedType(); 568 569 llvm::Value *TypeInfo = 0; 570 if (CaughtType->isObjCObjectPointerType()) 571 TypeInfo = CGM.getObjCRuntime().GetEHType(CaughtType); 572 else 573 TypeInfo = CGM.GetAddrOfRTTIDescriptor(CaughtType, /*ForEH=*/true); 574 CatchScope->setHandler(I, TypeInfo, Handler); 575 } else { 576 // No exception decl indicates '...', a catch-all. 577 CatchScope->setCatchAllHandler(I, Handler); 578 } 579 } 580} 581 582llvm::BasicBlock * 583CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) { 584 // The dispatch block for the end of the scope chain is a block that 585 // just resumes unwinding. 586 if (si == EHStack.stable_end()) 587 return getEHResumeBlock(); 588 589 // Otherwise, we should look at the actual scope. 590 EHScope &scope = *EHStack.find(si); 591 592 llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock(); 593 if (!dispatchBlock) { 594 switch (scope.getKind()) { 595 case EHScope::Catch: { 596 // Apply a special case to a single catch-all. 597 EHCatchScope &catchScope = cast<EHCatchScope>(scope); 598 if (catchScope.getNumHandlers() == 1 && 599 catchScope.getHandler(0).isCatchAll()) { 600 dispatchBlock = catchScope.getHandler(0).Block; 601 602 // Otherwise, make a dispatch block. 603 } else { 604 dispatchBlock = createBasicBlock("catch.dispatch"); 605 } 606 break; 607 } 608 609 case EHScope::Cleanup: 610 dispatchBlock = createBasicBlock("ehcleanup"); 611 break; 612 613 case EHScope::Filter: 614 dispatchBlock = createBasicBlock("filter.dispatch"); 615 break; 616 617 case EHScope::Terminate: 618 dispatchBlock = getTerminateHandler(); 619 break; 620 } 621 scope.setCachedEHDispatchBlock(dispatchBlock); 622 } 623 return dispatchBlock; 624} 625 626/// Check whether this is a non-EH scope, i.e. a scope which doesn't 627/// affect exception handling. Currently, the only non-EH scopes are 628/// normal-only cleanup scopes. 629static bool isNonEHScope(const EHScope &S) { 630 switch (S.getKind()) { 631 case EHScope::Cleanup: 632 return !cast<EHCleanupScope>(S).isEHCleanup(); 633 case EHScope::Filter: 634 case EHScope::Catch: 635 case EHScope::Terminate: 636 return false; 637 } 638 639 // Suppress warning. 640 return false; 641} 642 643llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() { 644 assert(EHStack.requiresLandingPad()); 645 assert(!EHStack.empty()); 646 647 if (!CGM.getLangOptions().Exceptions) 648 return 0; 649 650 // Check the innermost scope for a cached landing pad. If this is 651 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad. 652 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad(); 653 if (LP) return LP; 654 655 // Build the landing pad for this scope. 656 LP = EmitLandingPad(); 657 assert(LP); 658 659 // Cache the landing pad on the innermost scope. If this is a 660 // non-EH scope, cache the landing pad on the enclosing scope, too. 661 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) { 662 ir->setCachedLandingPad(LP); 663 if (!isNonEHScope(*ir)) break; 664 } 665 666 return LP; 667} 668 669// This code contains a hack to work around a design flaw in 670// LLVM's EH IR which breaks semantics after inlining. This same 671// hack is implemented in llvm-gcc. 672// 673// The LLVM EH abstraction is basically a thin veneer over the 674// traditional GCC zero-cost design: for each range of instructions 675// in the function, there is (at most) one "landing pad" with an 676// associated chain of EH actions. A language-specific personality 677// function interprets this chain of actions and (1) decides whether 678// or not to resume execution at the landing pad and (2) if so, 679// provides an integer indicating why it's stopping. In LLVM IR, 680// the association of a landing pad with a range of instructions is 681// achieved via an invoke instruction, the chain of actions becomes 682// the arguments to the @llvm.eh.selector call, and the selector 683// call returns the integer indicator. Other than the required 684// presence of two intrinsic function calls in the landing pad, 685// the IR exactly describes the layout of the output code. 686// 687// A principal advantage of this design is that it is completely 688// language-agnostic; in theory, the LLVM optimizers can treat 689// landing pads neutrally, and targets need only know how to lower 690// the intrinsics to have a functioning exceptions system (assuming 691// that platform exceptions follow something approximately like the 692// GCC design). Unfortunately, landing pads cannot be combined in a 693// language-agnostic way: given selectors A and B, there is no way 694// to make a single landing pad which faithfully represents the 695// semantics of propagating an exception first through A, then 696// through B, without knowing how the personality will interpret the 697// (lowered form of the) selectors. This means that inlining has no 698// choice but to crudely chain invokes (i.e., to ignore invokes in 699// the inlined function, but to turn all unwindable calls into 700// invokes), which is only semantically valid if every unwind stops 701// at every landing pad. 702// 703// Therefore, the invoke-inline hack is to guarantee that every 704// landing pad has a catch-all. 705enum CleanupHackLevel_t { 706 /// A level of hack that requires that all landing pads have 707 /// catch-alls. 708 CHL_MandatoryCatchall, 709 710 /// A level of hack that requires that all landing pads handle 711 /// cleanups. 712 CHL_MandatoryCleanup, 713 714 /// No hacks at all; ideal IR generation. 715 CHL_Ideal 716}; 717const CleanupHackLevel_t CleanupHackLevel = CHL_MandatoryCleanup; 718 719llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { 720 assert(EHStack.requiresLandingPad()); 721 722 EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope()); 723 switch (innermostEHScope.getKind()) { 724 case EHScope::Terminate: 725 return getTerminateLandingPad(); 726 727 case EHScope::Catch: 728 case EHScope::Cleanup: 729 case EHScope::Filter: 730 if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad()) 731 return lpad; 732 } 733 734 // Save the current IR generation state. 735 CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP(); 736 737 const EHPersonality &personality = EHPersonality::get(getLangOptions()); 738 739 // Create and configure the landing pad. 740 llvm::BasicBlock *lpad = createBasicBlock("lpad"); 741 EmitBlock(lpad); 742 743 llvm::LandingPadInst *LPadInst = 744 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, NULL), 745 getOpaquePersonalityFn(CGM, personality), 0); 746 747 llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0); 748 Builder.CreateStore(LPadExn, getExceptionSlot()); 749 llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1); 750 Builder.CreateStore(LPadSel, getEHSelectorSlot()); 751 752 // Save the exception pointer. It's safe to use a single exception 753 // pointer per function because EH cleanups can never have nested 754 // try/catches. 755 // Build the landingpad instruction. 756 757 // Accumulate all the handlers in scope. 758 bool hasCatchAll = false; 759 bool hasCleanup = false; 760 bool hasFilter = false; 761 SmallVector<llvm::Value*, 4> filterTypes; 762 llvm::SmallPtrSet<llvm::Value*, 4> catchTypes; 763 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); 764 I != E; ++I) { 765 766 switch (I->getKind()) { 767 case EHScope::Cleanup: 768 // If we have a cleanup, remember that. 769 hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup()); 770 continue; 771 772 case EHScope::Filter: { 773 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack"); 774 assert(!hasCatchAll && "EH filter reached after catch-all"); 775 776 // Filter scopes get added to the landingpad in weird ways. 777 EHFilterScope &filter = cast<EHFilterScope>(*I); 778 hasFilter = true; 779 780 // Add all the filter values. 781 for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i) 782 filterTypes.push_back(filter.getFilter(i)); 783 goto done; 784 } 785 786 case EHScope::Terminate: 787 // Terminate scopes are basically catch-alls. 788 assert(!hasCatchAll); 789 hasCatchAll = true; 790 goto done; 791 792 case EHScope::Catch: 793 break; 794 } 795 796 EHCatchScope &catchScope = cast<EHCatchScope>(*I); 797 for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) { 798 EHCatchScope::Handler handler = catchScope.getHandler(hi); 799 800 // If this is a catch-all, register that and abort. 801 if (!handler.Type) { 802 assert(!hasCatchAll); 803 hasCatchAll = true; 804 goto done; 805 } 806 807 // Check whether we already have a handler for this type. 808 if (catchTypes.insert(handler.Type)) 809 // If not, add it directly to the landingpad. 810 LPadInst->addClause(handler.Type); 811 } 812 } 813 814 done: 815 // If we have a catch-all, add null to the landingpad. 816 assert(!(hasCatchAll && hasFilter)); 817 if (hasCatchAll) { 818 LPadInst->addClause(getCatchAllValue(*this)); 819 820 // If we have an EH filter, we need to add those handlers in the 821 // right place in the landingpad, which is to say, at the end. 822 } else if (hasFilter) { 823 // Create a filter expression: a constant array indicating which filter 824 // types there are. The personality routine only lands here if the filter 825 // doesn't match. 826 llvm::SmallVector<llvm::Constant*, 8> Filters; 827 llvm::ArrayType *AType = 828 llvm::ArrayType::get(!filterTypes.empty() ? 829 filterTypes[0]->getType() : Int8PtrTy, 830 filterTypes.size()); 831 832 for (unsigned i = 0, e = filterTypes.size(); i != e; ++i) 833 Filters.push_back(cast<llvm::Constant>(filterTypes[i])); 834 llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters); 835 LPadInst->addClause(FilterArray); 836 837 // Also check whether we need a cleanup. 838 if (hasCleanup) 839 LPadInst->setCleanup(true); 840 841 // Otherwise, signal that we at least have cleanups. 842 } else if (CleanupHackLevel == CHL_MandatoryCatchall || hasCleanup) { 843 if (CleanupHackLevel == CHL_MandatoryCatchall) 844 LPadInst->addClause(getCatchAllValue(*this)); 845 else 846 LPadInst->setCleanup(true); 847 } 848 849 assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) && 850 "landingpad instruction has no clauses!"); 851 852 // Tell the backend how to generate the landing pad. 853 Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope())); 854 855 // Restore the old IR generation state. 856 Builder.restoreIP(savedIP); 857 858 return lpad; 859} 860 861namespace { 862 /// A cleanup to call __cxa_end_catch. In many cases, the caught 863 /// exception type lets us state definitively that the thrown exception 864 /// type does not have a destructor. In particular: 865 /// - Catch-alls tell us nothing, so we have to conservatively 866 /// assume that the thrown exception might have a destructor. 867 /// - Catches by reference behave according to their base types. 868 /// - Catches of non-record types will only trigger for exceptions 869 /// of non-record types, which never have destructors. 870 /// - Catches of record types can trigger for arbitrary subclasses 871 /// of the caught type, so we have to assume the actual thrown 872 /// exception type might have a throwing destructor, even if the 873 /// caught type's destructor is trivial or nothrow. 874 struct CallEndCatch : EHScopeStack::Cleanup { 875 CallEndCatch(bool MightThrow) : MightThrow(MightThrow) {} 876 bool MightThrow; 877 878 void Emit(CodeGenFunction &CGF, Flags flags) { 879 if (!MightThrow) { 880 CGF.Builder.CreateCall(getEndCatchFn(CGF))->setDoesNotThrow(); 881 return; 882 } 883 884 CGF.EmitCallOrInvoke(getEndCatchFn(CGF)); 885 } 886 }; 887} 888 889/// Emits a call to __cxa_begin_catch and enters a cleanup to call 890/// __cxa_end_catch. 891/// 892/// \param EndMightThrow - true if __cxa_end_catch might throw 893static llvm::Value *CallBeginCatch(CodeGenFunction &CGF, 894 llvm::Value *Exn, 895 bool EndMightThrow) { 896 llvm::CallInst *Call = CGF.Builder.CreateCall(getBeginCatchFn(CGF), Exn); 897 Call->setDoesNotThrow(); 898 899 CGF.EHStack.pushCleanup<CallEndCatch>(NormalAndEHCleanup, EndMightThrow); 900 901 return Call; 902} 903 904/// A "special initializer" callback for initializing a catch 905/// parameter during catch initialization. 906static void InitCatchParam(CodeGenFunction &CGF, 907 const VarDecl &CatchParam, 908 llvm::Value *ParamAddr) { 909 // Load the exception from where the landing pad saved it. 910 llvm::Value *Exn = CGF.getExceptionFromSlot(); 911 912 CanQualType CatchType = 913 CGF.CGM.getContext().getCanonicalType(CatchParam.getType()); 914 llvm::Type *LLVMCatchTy = CGF.ConvertTypeForMem(CatchType); 915 916 // If we're catching by reference, we can just cast the object 917 // pointer to the appropriate pointer. 918 if (isa<ReferenceType>(CatchType)) { 919 QualType CaughtType = cast<ReferenceType>(CatchType)->getPointeeType(); 920 bool EndCatchMightThrow = CaughtType->isRecordType(); 921 922 // __cxa_begin_catch returns the adjusted object pointer. 923 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, EndCatchMightThrow); 924 925 // We have no way to tell the personality function that we're 926 // catching by reference, so if we're catching a pointer, 927 // __cxa_begin_catch will actually return that pointer by value. 928 if (const PointerType *PT = dyn_cast<PointerType>(CaughtType)) { 929 QualType PointeeType = PT->getPointeeType(); 930 931 // When catching by reference, generally we should just ignore 932 // this by-value pointer and use the exception object instead. 933 if (!PointeeType->isRecordType()) { 934 935 // Exn points to the struct _Unwind_Exception header, which 936 // we have to skip past in order to reach the exception data. 937 unsigned HeaderSize = 938 CGF.CGM.getTargetCodeGenInfo().getSizeOfUnwindException(); 939 AdjustedExn = CGF.Builder.CreateConstGEP1_32(Exn, HeaderSize); 940 941 // However, if we're catching a pointer-to-record type that won't 942 // work, because the personality function might have adjusted 943 // the pointer. There's actually no way for us to fully satisfy 944 // the language/ABI contract here: we can't use Exn because it 945 // might have the wrong adjustment, but we can't use the by-value 946 // pointer because it's off by a level of abstraction. 947 // 948 // The current solution is to dump the adjusted pointer into an 949 // alloca, which breaks language semantics (because changing the 950 // pointer doesn't change the exception) but at least works. 951 // The better solution would be to filter out non-exact matches 952 // and rethrow them, but this is tricky because the rethrow 953 // really needs to be catchable by other sites at this landing 954 // pad. The best solution is to fix the personality function. 955 } else { 956 // Pull the pointer for the reference type off. 957 llvm::Type *PtrTy = 958 cast<llvm::PointerType>(LLVMCatchTy)->getElementType(); 959 960 // Create the temporary and write the adjusted pointer into it. 961 llvm::Value *ExnPtrTmp = CGF.CreateTempAlloca(PtrTy, "exn.byref.tmp"); 962 llvm::Value *Casted = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 963 CGF.Builder.CreateStore(Casted, ExnPtrTmp); 964 965 // Bind the reference to the temporary. 966 AdjustedExn = ExnPtrTmp; 967 } 968 } 969 970 llvm::Value *ExnCast = 971 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.byref"); 972 CGF.Builder.CreateStore(ExnCast, ParamAddr); 973 return; 974 } 975 976 // Non-aggregates (plus complexes). 977 bool IsComplex = false; 978 if (!CGF.hasAggregateLLVMType(CatchType) || 979 (IsComplex = CatchType->isAnyComplexType())) { 980 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, false); 981 982 // If the catch type is a pointer type, __cxa_begin_catch returns 983 // the pointer by value. 984 if (CatchType->hasPointerRepresentation()) { 985 llvm::Value *CastExn = 986 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted"); 987 CGF.Builder.CreateStore(CastExn, ParamAddr); 988 return; 989 } 990 991 // Otherwise, it returns a pointer into the exception object. 992 993 llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 994 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 995 996 if (IsComplex) { 997 CGF.StoreComplexToAddr(CGF.LoadComplexFromAddr(Cast, /*volatile*/ false), 998 ParamAddr, /*volatile*/ false); 999 } else { 1000 unsigned Alignment = 1001 CGF.getContext().getDeclAlign(&CatchParam).getQuantity(); 1002 llvm::Value *ExnLoad = CGF.Builder.CreateLoad(Cast, "exn.scalar"); 1003 CGF.EmitStoreOfScalar(ExnLoad, ParamAddr, /*volatile*/ false, Alignment, 1004 CatchType); 1005 } 1006 return; 1007 } 1008 1009 assert(isa<RecordType>(CatchType) && "unexpected catch type!"); 1010 1011 llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1012 1013 // Check for a copy expression. If we don't have a copy expression, 1014 // that means a trivial copy is okay. 1015 const Expr *copyExpr = CatchParam.getInit(); 1016 if (!copyExpr) { 1017 llvm::Value *rawAdjustedExn = CallBeginCatch(CGF, Exn, true); 1018 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy); 1019 CGF.EmitAggregateCopy(ParamAddr, adjustedExn, CatchType); 1020 return; 1021 } 1022 1023 // We have to call __cxa_get_exception_ptr to get the adjusted 1024 // pointer before copying. 1025 llvm::CallInst *rawAdjustedExn = 1026 CGF.Builder.CreateCall(getGetExceptionPtrFn(CGF), Exn); 1027 rawAdjustedExn->setDoesNotThrow(); 1028 1029 // Cast that to the appropriate type. 1030 llvm::Value *adjustedExn = CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy); 1031 1032 // The copy expression is defined in terms of an OpaqueValueExpr. 1033 // Find it and map it to the adjusted expression. 1034 CodeGenFunction::OpaqueValueMapping 1035 opaque(CGF, OpaqueValueExpr::findInCopyConstruct(copyExpr), 1036 CGF.MakeAddrLValue(adjustedExn, CatchParam.getType())); 1037 1038 // Call the copy ctor in a terminate scope. 1039 CGF.EHStack.pushTerminate(); 1040 1041 // Perform the copy construction. 1042 unsigned Alignment = CGF.getContext().getDeclAlign(&CatchParam).getQuantity(); 1043 CGF.EmitAggExpr(copyExpr, 1044 AggValueSlot::forAddr(ParamAddr, Alignment, Qualifiers(), 1045 AggValueSlot::IsNotDestructed, 1046 AggValueSlot::DoesNotNeedGCBarriers, 1047 AggValueSlot::IsNotAliased)); 1048 1049 // Leave the terminate scope. 1050 CGF.EHStack.popTerminate(); 1051 1052 // Undo the opaque value mapping. 1053 opaque.pop(); 1054 1055 // Finally we can call __cxa_begin_catch. 1056 CallBeginCatch(CGF, Exn, true); 1057} 1058 1059/// Begins a catch statement by initializing the catch variable and 1060/// calling __cxa_begin_catch. 1061static void BeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *S) { 1062 // We have to be very careful with the ordering of cleanups here: 1063 // C++ [except.throw]p4: 1064 // The destruction [of the exception temporary] occurs 1065 // immediately after the destruction of the object declared in 1066 // the exception-declaration in the handler. 1067 // 1068 // So the precise ordering is: 1069 // 1. Construct catch variable. 1070 // 2. __cxa_begin_catch 1071 // 3. Enter __cxa_end_catch cleanup 1072 // 4. Enter dtor cleanup 1073 // 1074 // We do this by using a slightly abnormal initialization process. 1075 // Delegation sequence: 1076 // - ExitCXXTryStmt opens a RunCleanupsScope 1077 // - EmitAutoVarAlloca creates the variable and debug info 1078 // - InitCatchParam initializes the variable from the exception 1079 // - CallBeginCatch calls __cxa_begin_catch 1080 // - CallBeginCatch enters the __cxa_end_catch cleanup 1081 // - EmitAutoVarCleanups enters the variable destructor cleanup 1082 // - EmitCXXTryStmt emits the code for the catch body 1083 // - EmitCXXTryStmt close the RunCleanupsScope 1084 1085 VarDecl *CatchParam = S->getExceptionDecl(); 1086 if (!CatchParam) { 1087 llvm::Value *Exn = CGF.getExceptionFromSlot(); 1088 CallBeginCatch(CGF, Exn, true); 1089 return; 1090 } 1091 1092 // Emit the local. 1093 CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam); 1094 InitCatchParam(CGF, *CatchParam, var.getObjectAddress(CGF)); 1095 CGF.EmitAutoVarCleanups(var); 1096} 1097 1098namespace { 1099 struct CallRethrow : EHScopeStack::Cleanup { 1100 void Emit(CodeGenFunction &CGF, Flags flags) { 1101 CGF.EmitCallOrInvoke(getReThrowFn(CGF)); 1102 } 1103 }; 1104} 1105 1106/// Emit the structure of the dispatch block for the given catch scope. 1107/// It is an invariant that the dispatch block already exists. 1108static void emitCatchDispatchBlock(CodeGenFunction &CGF, 1109 EHCatchScope &catchScope) { 1110 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock(); 1111 assert(dispatchBlock); 1112 1113 // If there's only a single catch-all, getEHDispatchBlock returned 1114 // that catch-all as the dispatch block. 1115 if (catchScope.getNumHandlers() == 1 && 1116 catchScope.getHandler(0).isCatchAll()) { 1117 assert(dispatchBlock == catchScope.getHandler(0).Block); 1118 return; 1119 } 1120 1121 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP(); 1122 CGF.EmitBlockAfterUses(dispatchBlock); 1123 1124 // Select the right handler. 1125 llvm::Value *llvm_eh_typeid_for = 1126 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); 1127 1128 // Load the selector value. 1129 llvm::Value *selector = CGF.getSelectorFromSlot(); 1130 1131 // Test against each of the exception types we claim to catch. 1132 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) { 1133 assert(i < e && "ran off end of handlers!"); 1134 const EHCatchScope::Handler &handler = catchScope.getHandler(i); 1135 1136 llvm::Value *typeValue = handler.Type; 1137 assert(typeValue && "fell into catch-all case!"); 1138 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy); 1139 1140 // Figure out the next block. 1141 bool nextIsEnd; 1142 llvm::BasicBlock *nextBlock; 1143 1144 // If this is the last handler, we're at the end, and the next 1145 // block is the block for the enclosing EH scope. 1146 if (i + 1 == e) { 1147 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope()); 1148 nextIsEnd = true; 1149 1150 // If the next handler is a catch-all, we're at the end, and the 1151 // next block is that handler. 1152 } else if (catchScope.getHandler(i+1).isCatchAll()) { 1153 nextBlock = catchScope.getHandler(i+1).Block; 1154 nextIsEnd = true; 1155 1156 // Otherwise, we're not at the end and we need a new block. 1157 } else { 1158 nextBlock = CGF.createBasicBlock("catch.fallthrough"); 1159 nextIsEnd = false; 1160 } 1161 1162 // Figure out the catch type's index in the LSDA's type table. 1163 llvm::CallInst *typeIndex = 1164 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue); 1165 typeIndex->setDoesNotThrow(); 1166 1167 llvm::Value *matchesTypeIndex = 1168 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches"); 1169 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock); 1170 1171 // If the next handler is a catch-all, we're completely done. 1172 if (nextIsEnd) { 1173 CGF.Builder.restoreIP(savedIP); 1174 return; 1175 1176 // Otherwise we need to emit and continue at that block. 1177 } else { 1178 CGF.EmitBlock(nextBlock); 1179 } 1180 } 1181 1182 llvm_unreachable("fell out of loop!"); 1183} 1184 1185void CodeGenFunction::popCatchScope() { 1186 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin()); 1187 if (catchScope.hasEHBranches()) 1188 emitCatchDispatchBlock(*this, catchScope); 1189 EHStack.popCatch(); 1190} 1191 1192void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 1193 unsigned NumHandlers = S.getNumHandlers(); 1194 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin()); 1195 assert(CatchScope.getNumHandlers() == NumHandlers); 1196 1197 // If the catch was not required, bail out now. 1198 if (!CatchScope.hasEHBranches()) { 1199 EHStack.popCatch(); 1200 return; 1201 } 1202 1203 // Emit the structure of the EH dispatch for this catch. 1204 emitCatchDispatchBlock(*this, CatchScope); 1205 1206 // Copy the handler blocks off before we pop the EH stack. Emitting 1207 // the handlers might scribble on this memory. 1208 SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers); 1209 memcpy(Handlers.data(), CatchScope.begin(), 1210 NumHandlers * sizeof(EHCatchScope::Handler)); 1211 1212 EHStack.popCatch(); 1213 1214 // The fall-through block. 1215 llvm::BasicBlock *ContBB = createBasicBlock("try.cont"); 1216 1217 // We just emitted the body of the try; jump to the continue block. 1218 if (HaveInsertPoint()) 1219 Builder.CreateBr(ContBB); 1220 1221 // Determine if we need an implicit rethrow for all these catch handlers. 1222 bool ImplicitRethrow = false; 1223 if (IsFnTryBlock) 1224 ImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) || 1225 isa<CXXConstructorDecl>(CurCodeDecl); 1226 1227 // Perversely, we emit the handlers backwards precisely because we 1228 // want them to appear in source order. In all of these cases, the 1229 // catch block will have exactly one predecessor, which will be a 1230 // particular block in the catch dispatch. However, in the case of 1231 // a catch-all, one of the dispatch blocks will branch to two 1232 // different handlers, and EmitBlockAfterUses will cause the second 1233 // handler to be moved before the first. 1234 for (unsigned I = NumHandlers; I != 0; --I) { 1235 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block; 1236 EmitBlockAfterUses(CatchBlock); 1237 1238 // Catch the exception if this isn't a catch-all. 1239 const CXXCatchStmt *C = S.getHandler(I-1); 1240 1241 // Enter a cleanup scope, including the catch variable and the 1242 // end-catch. 1243 RunCleanupsScope CatchScope(*this); 1244 1245 // Initialize the catch variable and set up the cleanups. 1246 BeginCatch(*this, C); 1247 1248 // If there's an implicit rethrow, push a normal "cleanup" to call 1249 // _cxa_rethrow. This needs to happen before __cxa_end_catch is 1250 // called, and so it is pushed after BeginCatch. 1251 if (ImplicitRethrow) 1252 EHStack.pushCleanup<CallRethrow>(NormalCleanup); 1253 1254 // Perform the body of the catch. 1255 EmitStmt(C->getHandlerBlock()); 1256 1257 // Fall out through the catch cleanups. 1258 CatchScope.ForceCleanup(); 1259 1260 // Branch out of the try. 1261 if (HaveInsertPoint()) 1262 Builder.CreateBr(ContBB); 1263 } 1264 1265 EmitBlock(ContBB); 1266} 1267 1268namespace { 1269 struct CallEndCatchForFinally : EHScopeStack::Cleanup { 1270 llvm::Value *ForEHVar; 1271 llvm::Value *EndCatchFn; 1272 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn) 1273 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {} 1274 1275 void Emit(CodeGenFunction &CGF, Flags flags) { 1276 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch"); 1277 llvm::BasicBlock *CleanupContBB = 1278 CGF.createBasicBlock("finally.cleanup.cont"); 1279 1280 llvm::Value *ShouldEndCatch = 1281 CGF.Builder.CreateLoad(ForEHVar, "finally.endcatch"); 1282 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB); 1283 CGF.EmitBlock(EndCatchBB); 1284 CGF.EmitCallOrInvoke(EndCatchFn); // catch-all, so might throw 1285 CGF.EmitBlock(CleanupContBB); 1286 } 1287 }; 1288 1289 struct PerformFinally : EHScopeStack::Cleanup { 1290 const Stmt *Body; 1291 llvm::Value *ForEHVar; 1292 llvm::Value *EndCatchFn; 1293 llvm::Value *RethrowFn; 1294 llvm::Value *SavedExnVar; 1295 1296 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar, 1297 llvm::Value *EndCatchFn, 1298 llvm::Value *RethrowFn, llvm::Value *SavedExnVar) 1299 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn), 1300 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {} 1301 1302 void Emit(CodeGenFunction &CGF, Flags flags) { 1303 // Enter a cleanup to call the end-catch function if one was provided. 1304 if (EndCatchFn) 1305 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup, 1306 ForEHVar, EndCatchFn); 1307 1308 // Save the current cleanup destination in case there are 1309 // cleanups in the finally block. 1310 llvm::Value *SavedCleanupDest = 1311 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(), 1312 "cleanup.dest.saved"); 1313 1314 // Emit the finally block. 1315 CGF.EmitStmt(Body); 1316 1317 // If the end of the finally is reachable, check whether this was 1318 // for EH. If so, rethrow. 1319 if (CGF.HaveInsertPoint()) { 1320 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow"); 1321 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont"); 1322 1323 llvm::Value *ShouldRethrow = 1324 CGF.Builder.CreateLoad(ForEHVar, "finally.shouldthrow"); 1325 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB); 1326 1327 CGF.EmitBlock(RethrowBB); 1328 if (SavedExnVar) { 1329 CGF.EmitCallOrInvoke(RethrowFn, CGF.Builder.CreateLoad(SavedExnVar)); 1330 } else { 1331 CGF.EmitCallOrInvoke(RethrowFn); 1332 } 1333 CGF.Builder.CreateUnreachable(); 1334 1335 CGF.EmitBlock(ContBB); 1336 1337 // Restore the cleanup destination. 1338 CGF.Builder.CreateStore(SavedCleanupDest, 1339 CGF.getNormalCleanupDestSlot()); 1340 } 1341 1342 // Leave the end-catch cleanup. As an optimization, pretend that 1343 // the fallthrough path was inaccessible; we've dynamically proven 1344 // that we're not in the EH case along that path. 1345 if (EndCatchFn) { 1346 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); 1347 CGF.PopCleanupBlock(); 1348 CGF.Builder.restoreIP(SavedIP); 1349 } 1350 1351 // Now make sure we actually have an insertion point or the 1352 // cleanup gods will hate us. 1353 CGF.EnsureInsertPoint(); 1354 } 1355 }; 1356} 1357 1358/// Enters a finally block for an implementation using zero-cost 1359/// exceptions. This is mostly general, but hard-codes some 1360/// language/ABI-specific behavior in the catch-all sections. 1361void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF, 1362 const Stmt *body, 1363 llvm::Constant *beginCatchFn, 1364 llvm::Constant *endCatchFn, 1365 llvm::Constant *rethrowFn) { 1366 assert((beginCatchFn != 0) == (endCatchFn != 0) && 1367 "begin/end catch functions not paired"); 1368 assert(rethrowFn && "rethrow function is required"); 1369 1370 BeginCatchFn = beginCatchFn; 1371 1372 // The rethrow function has one of the following two types: 1373 // void (*)() 1374 // void (*)(void*) 1375 // In the latter case we need to pass it the exception object. 1376 // But we can't use the exception slot because the @finally might 1377 // have a landing pad (which would overwrite the exception slot). 1378 llvm::FunctionType *rethrowFnTy = 1379 cast<llvm::FunctionType>( 1380 cast<llvm::PointerType>(rethrowFn->getType())->getElementType()); 1381 SavedExnVar = 0; 1382 if (rethrowFnTy->getNumParams()) 1383 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn"); 1384 1385 // A finally block is a statement which must be executed on any edge 1386 // out of a given scope. Unlike a cleanup, the finally block may 1387 // contain arbitrary control flow leading out of itself. In 1388 // addition, finally blocks should always be executed, even if there 1389 // are no catch handlers higher on the stack. Therefore, we 1390 // surround the protected scope with a combination of a normal 1391 // cleanup (to catch attempts to break out of the block via normal 1392 // control flow) and an EH catch-all (semantically "outside" any try 1393 // statement to which the finally block might have been attached). 1394 // The finally block itself is generated in the context of a cleanup 1395 // which conditionally leaves the catch-all. 1396 1397 // Jump destination for performing the finally block on an exception 1398 // edge. We'll never actually reach this block, so unreachable is 1399 // fine. 1400 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock()); 1401 1402 // Whether the finally block is being executed for EH purposes. 1403 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh"); 1404 CGF.Builder.CreateStore(CGF.Builder.getFalse(), ForEHVar); 1405 1406 // Enter a normal cleanup which will perform the @finally block. 1407 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body, 1408 ForEHVar, endCatchFn, 1409 rethrowFn, SavedExnVar); 1410 1411 // Enter a catch-all scope. 1412 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall"); 1413 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1); 1414 catchScope->setCatchAllHandler(0, catchBB); 1415} 1416 1417void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) { 1418 // Leave the finally catch-all. 1419 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin()); 1420 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block; 1421 1422 CGF.popCatchScope(); 1423 1424 // If there are any references to the catch-all block, emit it. 1425 if (catchBB->use_empty()) { 1426 delete catchBB; 1427 } else { 1428 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP(); 1429 CGF.EmitBlock(catchBB); 1430 1431 llvm::Value *exn = 0; 1432 1433 // If there's a begin-catch function, call it. 1434 if (BeginCatchFn) { 1435 exn = CGF.getExceptionFromSlot(); 1436 CGF.Builder.CreateCall(BeginCatchFn, exn)->setDoesNotThrow(); 1437 } 1438 1439 // If we need to remember the exception pointer to rethrow later, do so. 1440 if (SavedExnVar) { 1441 if (!exn) exn = CGF.getExceptionFromSlot(); 1442 CGF.Builder.CreateStore(exn, SavedExnVar); 1443 } 1444 1445 // Tell the cleanups in the finally block that we're do this for EH. 1446 CGF.Builder.CreateStore(CGF.Builder.getTrue(), ForEHVar); 1447 1448 // Thread a jump through the finally cleanup. 1449 CGF.EmitBranchThroughCleanup(RethrowDest); 1450 1451 CGF.Builder.restoreIP(savedIP); 1452 } 1453 1454 // Finally, leave the @finally cleanup. 1455 CGF.PopCleanupBlock(); 1456} 1457 1458llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() { 1459 if (TerminateLandingPad) 1460 return TerminateLandingPad; 1461 1462 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1463 1464 // This will get inserted at the end of the function. 1465 TerminateLandingPad = createBasicBlock("terminate.lpad"); 1466 Builder.SetInsertPoint(TerminateLandingPad); 1467 1468 // Tell the backend that this is a landing pad. 1469 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOptions()); 1470 llvm::LandingPadInst *LPadInst = 1471 Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty, NULL), 1472 getOpaquePersonalityFn(CGM, Personality), 0); 1473 LPadInst->addClause(getCatchAllValue(*this)); 1474 1475 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this)); 1476 TerminateCall->setDoesNotReturn(); 1477 TerminateCall->setDoesNotThrow(); 1478 Builder.CreateUnreachable(); 1479 1480 // Restore the saved insertion state. 1481 Builder.restoreIP(SavedIP); 1482 1483 return TerminateLandingPad; 1484} 1485 1486llvm::BasicBlock *CodeGenFunction::getTerminateHandler() { 1487 if (TerminateHandler) 1488 return TerminateHandler; 1489 1490 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1491 1492 // Set up the terminate handler. This block is inserted at the very 1493 // end of the function by FinishFunction. 1494 TerminateHandler = createBasicBlock("terminate.handler"); 1495 Builder.SetInsertPoint(TerminateHandler); 1496 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this)); 1497 TerminateCall->setDoesNotReturn(); 1498 TerminateCall->setDoesNotThrow(); 1499 Builder.CreateUnreachable(); 1500 1501 // Restore the saved insertion state. 1502 Builder.restoreIP(SavedIP); 1503 1504 return TerminateHandler; 1505} 1506 1507llvm::BasicBlock *CodeGenFunction::getEHResumeBlock() { 1508 if (EHResumeBlock) return EHResumeBlock; 1509 1510 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP(); 1511 1512 // We emit a jump to a notional label at the outermost unwind state. 1513 EHResumeBlock = createBasicBlock("eh.resume"); 1514 Builder.SetInsertPoint(EHResumeBlock); 1515 1516 const EHPersonality &Personality = EHPersonality::get(CGM.getLangOptions()); 1517 1518 // This can always be a call because we necessarily didn't find 1519 // anything on the EH stack which needs our help. 1520 StringRef RethrowName = Personality.getCatchallRethrowFnName(); 1521 if (!RethrowName.empty()) { 1522 Builder.CreateCall(getCatchallRethrowFn(*this, RethrowName), 1523 getExceptionFromSlot()) 1524 ->setDoesNotReturn(); 1525 } else { 1526 llvm::Value *Exn = getExceptionFromSlot(); 1527 1528 switch (CleanupHackLevel) { 1529 case CHL_MandatoryCatchall: 1530 // In mandatory-catchall mode, we need to use 1531 // _Unwind_Resume_or_Rethrow, or whatever the personality's 1532 // equivalent is. 1533 Builder.CreateCall(getUnwindResumeOrRethrowFn(), Exn) 1534 ->setDoesNotReturn(); 1535 break; 1536 case CHL_MandatoryCleanup: { 1537 // In mandatory-cleanup mode, we should use 'resume'. 1538 1539 // Recreate the landingpad's return value for the 'resume' instruction. 1540 llvm::Value *Exn = getExceptionFromSlot(); 1541 llvm::Value *Sel = getSelectorFromSlot(); 1542 1543 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(), 1544 Sel->getType(), NULL); 1545 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType); 1546 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val"); 1547 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val"); 1548 1549 Builder.CreateResume(LPadVal); 1550 Builder.restoreIP(SavedIP); 1551 return EHResumeBlock; 1552 } 1553 case CHL_Ideal: 1554 // In an idealized mode where we don't have to worry about the 1555 // optimizer combining landing pads, we should just use 1556 // _Unwind_Resume (or the personality's equivalent). 1557 Builder.CreateCall(getUnwindResumeFn(), Exn) 1558 ->setDoesNotReturn(); 1559 break; 1560 } 1561 } 1562 1563 Builder.CreateUnreachable(); 1564 1565 Builder.restoreIP(SavedIP); 1566 1567 return EHResumeBlock; 1568} 1569