CGException.cpp revision 09faeabf39a6fab2e2beb6bf03da970c17d2049a
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/Support/CallSite.h" 18 19#include "CodeGenFunction.h" 20#include "CGException.h" 21 22using namespace clang; 23using namespace CodeGen; 24 25/// Push an entry of the given size onto this protected-scope stack. 26char *EHScopeStack::allocate(size_t Size) { 27 if (!StartOfBuffer) { 28 unsigned Capacity = 1024; 29 while (Capacity < Size) Capacity *= 2; 30 StartOfBuffer = new char[Capacity]; 31 StartOfData = EndOfBuffer = StartOfBuffer + Capacity; 32 } else if (static_cast<size_t>(StartOfData - StartOfBuffer) < Size) { 33 unsigned CurrentCapacity = EndOfBuffer - StartOfBuffer; 34 unsigned UsedCapacity = CurrentCapacity - (StartOfData - StartOfBuffer); 35 36 unsigned NewCapacity = CurrentCapacity; 37 do { 38 NewCapacity *= 2; 39 } while (NewCapacity < UsedCapacity + Size); 40 41 char *NewStartOfBuffer = new char[NewCapacity]; 42 char *NewEndOfBuffer = NewStartOfBuffer + NewCapacity; 43 char *NewStartOfData = NewEndOfBuffer - UsedCapacity; 44 memcpy(NewStartOfData, StartOfData, UsedCapacity); 45 delete [] StartOfBuffer; 46 StartOfBuffer = NewStartOfBuffer; 47 EndOfBuffer = NewEndOfBuffer; 48 StartOfData = NewStartOfData; 49 } 50 51 assert(StartOfBuffer + Size <= StartOfData); 52 StartOfData -= Size; 53 return StartOfData; 54} 55 56EHScopeStack::stable_iterator 57EHScopeStack::getEnclosingEHCleanup(iterator it) const { 58 assert(it != end()); 59 do { 60 if (isa<EHCleanupScope>(*it)) { 61 if (cast<EHCleanupScope>(*it).isEHCleanup()) 62 return stabilize(it); 63 return cast<EHCleanupScope>(*it).getEnclosingEHCleanup(); 64 } 65 if (isa<EHLazyCleanupScope>(*it)) { 66 if (cast<EHLazyCleanupScope>(*it).isEHCleanup()) 67 return stabilize(it); 68 return cast<EHLazyCleanupScope>(*it).getEnclosingEHCleanup(); 69 } 70 ++it; 71 } while (it != end()); 72 return stable_end(); 73} 74 75 76void *EHScopeStack::pushLazyCleanup(CleanupKind Kind, size_t Size) { 77 assert(((Size % sizeof(void*)) == 0) && "cleanup type is misaligned"); 78 char *Buffer = allocate(EHLazyCleanupScope::getSizeForCleanupSize(Size)); 79 bool IsNormalCleanup = Kind != EHCleanup; 80 bool IsEHCleanup = Kind != NormalCleanup; 81 EHLazyCleanupScope *Scope = 82 new (Buffer) EHLazyCleanupScope(IsNormalCleanup, 83 IsEHCleanup, 84 Size, 85 BranchFixups.size(), 86 InnermostNormalCleanup, 87 InnermostEHCleanup); 88 if (IsNormalCleanup) 89 InnermostNormalCleanup = stable_begin(); 90 if (IsEHCleanup) 91 InnermostEHCleanup = stable_begin(); 92 93 return Scope->getCleanupBuffer(); 94} 95 96void EHScopeStack::pushCleanup(llvm::BasicBlock *NormalEntry, 97 llvm::BasicBlock *NormalExit, 98 llvm::BasicBlock *EHEntry, 99 llvm::BasicBlock *EHExit) { 100 char *Buffer = allocate(EHCleanupScope::getSize()); 101 new (Buffer) EHCleanupScope(BranchFixups.size(), 102 InnermostNormalCleanup, 103 InnermostEHCleanup, 104 NormalEntry, NormalExit, EHEntry, EHExit); 105 if (NormalEntry) 106 InnermostNormalCleanup = stable_begin(); 107 if (EHEntry) 108 InnermostEHCleanup = stable_begin(); 109} 110 111void EHScopeStack::popCleanup() { 112 assert(!empty() && "popping exception stack when not empty"); 113 114 if (isa<EHLazyCleanupScope>(*begin())) { 115 EHLazyCleanupScope &Cleanup = cast<EHLazyCleanupScope>(*begin()); 116 InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup(); 117 InnermostEHCleanup = Cleanup.getEnclosingEHCleanup(); 118 StartOfData += Cleanup.getAllocatedSize(); 119 } else { 120 assert(isa<EHCleanupScope>(*begin())); 121 EHCleanupScope &Cleanup = cast<EHCleanupScope>(*begin()); 122 InnermostNormalCleanup = Cleanup.getEnclosingNormalCleanup(); 123 InnermostEHCleanup = Cleanup.getEnclosingEHCleanup(); 124 StartOfData += EHCleanupScope::getSize(); 125 } 126 127 // Check whether we can shrink the branch-fixups stack. 128 if (!BranchFixups.empty()) { 129 // If we no longer have any normal cleanups, all the fixups are 130 // complete. 131 if (!hasNormalCleanups()) 132 BranchFixups.clear(); 133 134 // Otherwise we can still trim out unnecessary nulls. 135 else 136 popNullFixups(); 137 } 138} 139 140EHFilterScope *EHScopeStack::pushFilter(unsigned NumFilters) { 141 char *Buffer = allocate(EHFilterScope::getSizeForNumFilters(NumFilters)); 142 CatchDepth++; 143 return new (Buffer) EHFilterScope(NumFilters); 144} 145 146void EHScopeStack::popFilter() { 147 assert(!empty() && "popping exception stack when not empty"); 148 149 EHFilterScope &Filter = cast<EHFilterScope>(*begin()); 150 StartOfData += EHFilterScope::getSizeForNumFilters(Filter.getNumFilters()); 151 152 assert(CatchDepth > 0 && "mismatched filter push/pop"); 153 CatchDepth--; 154} 155 156EHCatchScope *EHScopeStack::pushCatch(unsigned NumHandlers) { 157 char *Buffer = allocate(EHCatchScope::getSizeForNumHandlers(NumHandlers)); 158 CatchDepth++; 159 return new (Buffer) EHCatchScope(NumHandlers); 160} 161 162void EHScopeStack::pushTerminate() { 163 char *Buffer = allocate(EHTerminateScope::getSize()); 164 CatchDepth++; 165 new (Buffer) EHTerminateScope(); 166} 167 168/// Remove any 'null' fixups on the stack. However, we can't pop more 169/// fixups than the fixup depth on the innermost normal cleanup, or 170/// else fixups that we try to add to that cleanup will end up in the 171/// wrong place. We *could* try to shrink fixup depths, but that's 172/// actually a lot of work for little benefit. 173void EHScopeStack::popNullFixups() { 174 // We expect this to only be called when there's still an innermost 175 // normal cleanup; otherwise there really shouldn't be any fixups. 176 assert(hasNormalCleanups()); 177 178 EHScopeStack::iterator it = find(InnermostNormalCleanup); 179 unsigned MinSize; 180 if (isa<EHCleanupScope>(*it)) 181 MinSize = cast<EHCleanupScope>(*it).getFixupDepth(); 182 else 183 MinSize = cast<EHLazyCleanupScope>(*it).getFixupDepth(); 184 assert(BranchFixups.size() >= MinSize && "fixup stack out of order"); 185 186 while (BranchFixups.size() > MinSize && 187 BranchFixups.back().Destination == 0) 188 BranchFixups.pop_back(); 189} 190 191void EHScopeStack::resolveBranchFixups(llvm::BasicBlock *Dest) { 192 assert(Dest && "null block passed to resolveBranchFixups"); 193 194 if (BranchFixups.empty()) return; 195 assert(hasNormalCleanups() && 196 "branch fixups exist with no normal cleanups on stack"); 197 198 for (unsigned I = 0, E = BranchFixups.size(); I != E; ++I) 199 if (BranchFixups[I].Destination == Dest) 200 BranchFixups[I].Destination = 0; 201 202 popNullFixups(); 203} 204 205static llvm::Constant *getAllocateExceptionFn(CodeGenFunction &CGF) { 206 // void *__cxa_allocate_exception(size_t thrown_size); 207 const llvm::Type *SizeTy = CGF.ConvertType(CGF.getContext().getSizeType()); 208 std::vector<const llvm::Type*> Args(1, SizeTy); 209 210 const llvm::FunctionType *FTy = 211 llvm::FunctionType::get(llvm::Type::getInt8PtrTy(CGF.getLLVMContext()), 212 Args, false); 213 214 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception"); 215} 216 217static llvm::Constant *getFreeExceptionFn(CodeGenFunction &CGF) { 218 // void __cxa_free_exception(void *thrown_exception); 219 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); 220 std::vector<const llvm::Type*> Args(1, Int8PtrTy); 221 222 const llvm::FunctionType *FTy = 223 llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), 224 Args, false); 225 226 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception"); 227} 228 229static llvm::Constant *getThrowFn(CodeGenFunction &CGF) { 230 // void __cxa_throw(void *thrown_exception, std::type_info *tinfo, 231 // void (*dest) (void *)); 232 233 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); 234 std::vector<const llvm::Type*> Args(3, Int8PtrTy); 235 236 const llvm::FunctionType *FTy = 237 llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), 238 Args, false); 239 240 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_throw"); 241} 242 243static llvm::Constant *getReThrowFn(CodeGenFunction &CGF) { 244 // void __cxa_rethrow(); 245 246 const llvm::FunctionType *FTy = 247 llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false); 248 249 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow"); 250} 251 252static llvm::Constant *getGetExceptionPtrFn(CodeGenFunction &CGF) { 253 // void *__cxa_get_exception_ptr(void*); 254 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); 255 std::vector<const llvm::Type*> Args(1, Int8PtrTy); 256 257 const llvm::FunctionType *FTy = 258 llvm::FunctionType::get(Int8PtrTy, Args, false); 259 260 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr"); 261} 262 263static llvm::Constant *getBeginCatchFn(CodeGenFunction &CGF) { 264 // void *__cxa_begin_catch(void*); 265 266 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); 267 std::vector<const llvm::Type*> Args(1, Int8PtrTy); 268 269 const llvm::FunctionType *FTy = 270 llvm::FunctionType::get(Int8PtrTy, Args, false); 271 272 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch"); 273} 274 275static llvm::Constant *getEndCatchFn(CodeGenFunction &CGF) { 276 // void __cxa_end_catch(); 277 278 const llvm::FunctionType *FTy = 279 llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false); 280 281 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch"); 282} 283 284static llvm::Constant *getUnexpectedFn(CodeGenFunction &CGF) { 285 // void __cxa_call_unexepcted(void *thrown_exception); 286 287 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(CGF.getLLVMContext()); 288 std::vector<const llvm::Type*> Args(1, Int8PtrTy); 289 290 const llvm::FunctionType *FTy = 291 llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), 292 Args, false); 293 294 return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); 295} 296 297llvm::Constant *CodeGenFunction::getUnwindResumeOrRethrowFn() { 298 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(getLLVMContext()); 299 std::vector<const llvm::Type*> Args(1, Int8PtrTy); 300 301 const llvm::FunctionType *FTy = 302 llvm::FunctionType::get(llvm::Type::getVoidTy(getLLVMContext()), Args, 303 false); 304 305 if (CGM.getLangOptions().SjLjExceptions) 306 return CGM.CreateRuntimeFunction(FTy, "_Unwind_SjLj_Resume"); 307 return CGM.CreateRuntimeFunction(FTy, "_Unwind_Resume_or_Rethrow"); 308} 309 310static llvm::Constant *getTerminateFn(CodeGenFunction &CGF) { 311 // void __terminate(); 312 313 const llvm::FunctionType *FTy = 314 llvm::FunctionType::get(llvm::Type::getVoidTy(CGF.getLLVMContext()), false); 315 316 return CGF.CGM.CreateRuntimeFunction(FTy, 317 CGF.CGM.getLangOptions().CPlusPlus ? "_ZSt9terminatev" : "abort"); 318} 319 320static const char *getCPersonalityFn(CodeGenFunction &CGF) { 321 return "__gcc_personality_v0"; 322} 323 324static const char *getObjCPersonalityFn(CodeGenFunction &CGF) { 325 if (CGF.CGM.getLangOptions().NeXTRuntime) { 326 if (CGF.CGM.getLangOptions().ObjCNonFragileABI) 327 return "__objc_personality_v0"; 328 else 329 return getCPersonalityFn(CGF); 330 } else { 331 return "__gnu_objc_personality_v0"; 332 } 333} 334 335static const char *getCXXPersonalityFn(CodeGenFunction &CGF) { 336 if (CGF.CGM.getLangOptions().SjLjExceptions) 337 return "__gxx_personality_sj0"; 338 else 339 return "__gxx_personality_v0"; 340} 341 342/// Determines the personality function to use when both C++ 343/// and Objective-C exceptions are being caught. 344static const char *getObjCXXPersonalityFn(CodeGenFunction &CGF) { 345 // The ObjC personality defers to the C++ personality for non-ObjC 346 // handlers. Unlike the C++ case, we use the same personality 347 // function on targets using (backend-driven) SJLJ EH. 348 if (CGF.CGM.getLangOptions().NeXTRuntime) { 349 if (CGF.CGM.getLangOptions().ObjCNonFragileABI) 350 return "__objc_personality_v0"; 351 352 // In the fragile ABI, just use C++ exception handling and hope 353 // they're not doing crazy exception mixing. 354 else 355 return getCXXPersonalityFn(CGF); 356 } 357 358 // I'm pretty sure the GNU runtime doesn't support mixed EH. 359 // TODO: we don't necessarily need mixed EH here; remember what 360 // kind of exceptions we actually try to catch in this function. 361 CGF.CGM.ErrorUnsupported(CGF.CurCodeDecl, 362 "the GNU Objective C runtime does not support " 363 "catching C++ and Objective C exceptions in the " 364 "same function"); 365 // Use the C++ personality just to avoid returning null. 366 return getCXXPersonalityFn(CGF); 367} 368 369static llvm::Constant *getPersonalityFn(CodeGenFunction &CGF) { 370 const char *Name; 371 const LangOptions &Opts = CGF.CGM.getLangOptions(); 372 if (Opts.CPlusPlus && Opts.ObjC1) 373 Name = getObjCXXPersonalityFn(CGF); 374 else if (Opts.CPlusPlus) 375 Name = getCXXPersonalityFn(CGF); 376 else if (Opts.ObjC1) 377 Name = getObjCPersonalityFn(CGF); 378 else 379 Name = getCPersonalityFn(CGF); 380 381 llvm::Constant *Personality = 382 CGF.CGM.CreateRuntimeFunction(llvm::FunctionType::get( 383 llvm::Type::getInt32Ty( 384 CGF.CGM.getLLVMContext()), 385 true), 386 Name); 387 return llvm::ConstantExpr::getBitCast(Personality, CGF.CGM.PtrToInt8Ty); 388} 389 390/// Returns the value to inject into a selector to indicate the 391/// presence of a catch-all. 392static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) { 393 // Possibly we should use @llvm.eh.catch.all.value here. 394 return llvm::ConstantPointerNull::get(CGF.CGM.PtrToInt8Ty); 395} 396 397/// Returns the value to inject into a selector to indicate the 398/// presence of a cleanup. 399static llvm::Constant *getCleanupValue(CodeGenFunction &CGF) { 400 return llvm::ConstantInt::get(CGF.Builder.getInt32Ty(), 0); 401} 402 403namespace { 404 /// A cleanup to free the exception object if its initialization 405 /// throws. 406 struct FreeExceptionCleanup : EHScopeStack::LazyCleanup { 407 FreeExceptionCleanup(llvm::Value *ShouldFreeVar, 408 llvm::Value *ExnLocVar) 409 : ShouldFreeVar(ShouldFreeVar), ExnLocVar(ExnLocVar) {} 410 411 llvm::Value *ShouldFreeVar; 412 llvm::Value *ExnLocVar; 413 414 void Emit(CodeGenFunction &CGF, bool IsForEH) { 415 llvm::BasicBlock *FreeBB = CGF.createBasicBlock("free-exnobj"); 416 llvm::BasicBlock *DoneBB = CGF.createBasicBlock("free-exnobj.done"); 417 418 llvm::Value *ShouldFree = CGF.Builder.CreateLoad(ShouldFreeVar, 419 "should-free-exnobj"); 420 CGF.Builder.CreateCondBr(ShouldFree, FreeBB, DoneBB); 421 CGF.EmitBlock(FreeBB); 422 llvm::Value *ExnLocLocal = CGF.Builder.CreateLoad(ExnLocVar, "exnobj"); 423 CGF.Builder.CreateCall(getFreeExceptionFn(CGF), ExnLocLocal) 424 ->setDoesNotThrow(); 425 CGF.EmitBlock(DoneBB); 426 } 427 }; 428} 429 430// Emits an exception expression into the given location. This 431// differs from EmitAnyExprToMem only in that, if a final copy-ctor 432// call is required, an exception within that copy ctor causes 433// std::terminate to be invoked. 434static void EmitAnyExprToExn(CodeGenFunction &CGF, const Expr *E, 435 llvm::Value *ExnLoc) { 436 // We want to release the allocated exception object if this 437 // expression throws. We do this by pushing an EH-only cleanup 438 // block which, furthermore, deactivates itself after the expression 439 // is complete. 440 llvm::AllocaInst *ShouldFreeVar = 441 CGF.CreateTempAlloca(llvm::Type::getInt1Ty(CGF.getLLVMContext()), 442 "should-free-exnobj.var"); 443 CGF.InitTempAlloca(ShouldFreeVar, 444 llvm::ConstantInt::getFalse(CGF.getLLVMContext())); 445 446 // A variable holding the exception pointer. This is necessary 447 // because the throw expression does not necessarily dominate the 448 // cleanup, for example if it appears in a conditional expression. 449 llvm::AllocaInst *ExnLocVar = 450 CGF.CreateTempAlloca(ExnLoc->getType(), "exnobj.var"); 451 452 // Make sure the exception object is cleaned up if there's an 453 // exception during initialization. 454 // FIXME: stmt expressions might require this to be a normal 455 // cleanup, too. 456 CGF.EHStack.pushLazyCleanup<FreeExceptionCleanup>(EHCleanup, 457 ShouldFreeVar, 458 ExnLocVar); 459 EHScopeStack::stable_iterator Cleanup = CGF.EHStack.stable_begin(); 460 461 CGF.Builder.CreateStore(ExnLoc, ExnLocVar); 462 CGF.Builder.CreateStore(llvm::ConstantInt::getTrue(CGF.getLLVMContext()), 463 ShouldFreeVar); 464 465 // __cxa_allocate_exception returns a void*; we need to cast this 466 // to the appropriate type for the object. 467 const llvm::Type *Ty = CGF.ConvertType(E->getType())->getPointerTo(); 468 llvm::Value *TypedExnLoc = CGF.Builder.CreateBitCast(ExnLoc, Ty); 469 470 // FIXME: this isn't quite right! If there's a final unelided call 471 // to a copy constructor, then according to [except.terminate]p1 we 472 // must call std::terminate() if that constructor throws, because 473 // technically that copy occurs after the exception expression is 474 // evaluated but before the exception is caught. But the best way 475 // to handle that is to teach EmitAggExpr to do the final copy 476 // differently if it can't be elided. 477 CGF.EmitAnyExprToMem(E, TypedExnLoc, /*Volatile*/ false); 478 479 CGF.Builder.CreateStore(llvm::ConstantInt::getFalse(CGF.getLLVMContext()), 480 ShouldFreeVar); 481 482 // Technically, the exception object is like a temporary; it has to 483 // be cleaned up when its full-expression is complete. 484 // Unfortunately, the AST represents full-expressions by creating a 485 // CXXExprWithTemporaries, which it only does when there are actually 486 // temporaries. 487 // 488 // If any cleanups have been added since we pushed ours, they must 489 // be from temporaries; this will get popped at the same time. 490 // Otherwise we need to pop ours off. FIXME: this is very brittle. 491 if (Cleanup == CGF.EHStack.stable_begin()) 492 CGF.PopCleanupBlock(); 493} 494 495llvm::Value *CodeGenFunction::getExceptionSlot() { 496 if (!ExceptionSlot) { 497 const llvm::Type *i8p = llvm::Type::getInt8PtrTy(getLLVMContext()); 498 ExceptionSlot = CreateTempAlloca(i8p, "exn.slot"); 499 } 500 return ExceptionSlot; 501} 502 503void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E) { 504 if (!E->getSubExpr()) { 505 if (getInvokeDest()) { 506 Builder.CreateInvoke(getReThrowFn(*this), 507 getUnreachableBlock(), 508 getInvokeDest()) 509 ->setDoesNotReturn(); 510 } else { 511 Builder.CreateCall(getReThrowFn(*this))->setDoesNotReturn(); 512 Builder.CreateUnreachable(); 513 } 514 515 // Clear the insertion point to indicate we are in unreachable code. 516 Builder.ClearInsertionPoint(); 517 return; 518 } 519 520 QualType ThrowType = E->getSubExpr()->getType(); 521 522 // Now allocate the exception object. 523 const llvm::Type *SizeTy = ConvertType(getContext().getSizeType()); 524 uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity(); 525 526 llvm::Constant *AllocExceptionFn = getAllocateExceptionFn(*this); 527 llvm::CallInst *ExceptionPtr = 528 Builder.CreateCall(AllocExceptionFn, 529 llvm::ConstantInt::get(SizeTy, TypeSize), 530 "exception"); 531 ExceptionPtr->setDoesNotThrow(); 532 533 EmitAnyExprToExn(*this, E->getSubExpr(), ExceptionPtr); 534 535 // Now throw the exception. 536 const llvm::Type *Int8PtrTy = llvm::Type::getInt8PtrTy(getLLVMContext()); 537 llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType, true); 538 539 // The address of the destructor. If the exception type has a 540 // trivial destructor (or isn't a record), we just pass null. 541 llvm::Constant *Dtor = 0; 542 if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) { 543 CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl()); 544 if (!Record->hasTrivialDestructor()) { 545 CXXDestructorDecl *DtorD = Record->getDestructor(); 546 Dtor = CGM.GetAddrOfCXXDestructor(DtorD, Dtor_Complete); 547 Dtor = llvm::ConstantExpr::getBitCast(Dtor, Int8PtrTy); 548 } 549 } 550 if (!Dtor) Dtor = llvm::Constant::getNullValue(Int8PtrTy); 551 552 if (getInvokeDest()) { 553 llvm::InvokeInst *ThrowCall = 554 Builder.CreateInvoke3(getThrowFn(*this), 555 getUnreachableBlock(), getInvokeDest(), 556 ExceptionPtr, TypeInfo, Dtor); 557 ThrowCall->setDoesNotReturn(); 558 } else { 559 llvm::CallInst *ThrowCall = 560 Builder.CreateCall3(getThrowFn(*this), ExceptionPtr, TypeInfo, Dtor); 561 ThrowCall->setDoesNotReturn(); 562 Builder.CreateUnreachable(); 563 } 564 565 // Clear the insertion point to indicate we are in unreachable code. 566 Builder.ClearInsertionPoint(); 567 568 // FIXME: For now, emit a dummy basic block because expr emitters in generally 569 // are not ready to handle emitting expressions at unreachable points. 570 EnsureInsertPoint(); 571} 572 573void CodeGenFunction::EmitStartEHSpec(const Decl *D) { 574 if (!Exceptions) 575 return; 576 577 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 578 if (FD == 0) 579 return; 580 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 581 if (Proto == 0) 582 return; 583 584 assert(!Proto->hasAnyExceptionSpec() && "function with parameter pack"); 585 586 if (!Proto->hasExceptionSpec()) 587 return; 588 589 unsigned NumExceptions = Proto->getNumExceptions(); 590 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions); 591 592 for (unsigned I = 0; I != NumExceptions; ++I) { 593 QualType Ty = Proto->getExceptionType(I); 594 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType(); 595 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType, true); 596 Filter->setFilter(I, EHType); 597 } 598} 599 600void CodeGenFunction::EmitEndEHSpec(const Decl *D) { 601 if (!Exceptions) 602 return; 603 604 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 605 if (FD == 0) 606 return; 607 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 608 if (Proto == 0) 609 return; 610 611 if (!Proto->hasExceptionSpec()) 612 return; 613 614 EHStack.popFilter(); 615} 616 617void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) { 618 EnterCXXTryStmt(S); 619 EmitStmt(S.getTryBlock()); 620 ExitCXXTryStmt(S); 621} 622 623void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 624 unsigned NumHandlers = S.getNumHandlers(); 625 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers); 626 627 for (unsigned I = 0; I != NumHandlers; ++I) { 628 const CXXCatchStmt *C = S.getHandler(I); 629 630 llvm::BasicBlock *Handler = createBasicBlock("catch"); 631 if (C->getExceptionDecl()) { 632 // FIXME: Dropping the reference type on the type into makes it 633 // impossible to correctly implement catch-by-reference 634 // semantics for pointers. Unfortunately, this is what all 635 // existing compilers do, and it's not clear that the standard 636 // personality routine is capable of doing this right. See C++ DR 388: 637 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388 638 QualType CaughtType = C->getCaughtType(); 639 CaughtType = CaughtType.getNonReferenceType().getUnqualifiedType(); 640 llvm::Value *TypeInfo = CGM.GetAddrOfRTTIDescriptor(CaughtType, true); 641 CatchScope->setHandler(I, TypeInfo, Handler); 642 } else { 643 // No exception decl indicates '...', a catch-all. 644 CatchScope->setCatchAllHandler(I, Handler); 645 } 646 } 647} 648 649/// Check whether this is a non-EH scope, i.e. a scope which doesn't 650/// affect exception handling. Currently, the only non-EH scopes are 651/// normal-only cleanup scopes. 652static bool isNonEHScope(const EHScope &S) { 653 switch (S.getKind()) { 654 case EHScope::Cleanup: 655 return !cast<EHCleanupScope>(S).isEHCleanup(); 656 case EHScope::LazyCleanup: 657 return !cast<EHLazyCleanupScope>(S).isEHCleanup(); 658 case EHScope::Filter: 659 case EHScope::Catch: 660 case EHScope::Terminate: 661 return false; 662 } 663 664 // Suppress warning. 665 return false; 666} 667 668llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() { 669 assert(EHStack.requiresLandingPad()); 670 assert(!EHStack.empty()); 671 672 if (!Exceptions) 673 return 0; 674 675 // Check the innermost scope for a cached landing pad. If this is 676 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad. 677 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad(); 678 if (LP) return LP; 679 680 // Build the landing pad for this scope. 681 LP = EmitLandingPad(); 682 assert(LP); 683 684 // Cache the landing pad on the innermost scope. If this is a 685 // non-EH scope, cache the landing pad on the enclosing scope, too. 686 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) { 687 ir->setCachedLandingPad(LP); 688 if (!isNonEHScope(*ir)) break; 689 } 690 691 return LP; 692} 693 694llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { 695 assert(EHStack.requiresLandingPad()); 696 697 // This function contains a hack to work around a design flaw in 698 // LLVM's EH IR which breaks semantics after inlining. This same 699 // hack is implemented in llvm-gcc. 700 // 701 // The LLVM EH abstraction is basically a thin veneer over the 702 // traditional GCC zero-cost design: for each range of instructions 703 // in the function, there is (at most) one "landing pad" with an 704 // associated chain of EH actions. A language-specific personality 705 // function interprets this chain of actions and (1) decides whether 706 // or not to resume execution at the landing pad and (2) if so, 707 // provides an integer indicating why it's stopping. In LLVM IR, 708 // the association of a landing pad with a range of instructions is 709 // achieved via an invoke instruction, the chain of actions becomes 710 // the arguments to the @llvm.eh.selector call, and the selector 711 // call returns the integer indicator. Other than the required 712 // presence of two intrinsic function calls in the landing pad, 713 // the IR exactly describes the layout of the output code. 714 // 715 // A principal advantage of this design is that it is completely 716 // language-agnostic; in theory, the LLVM optimizers can treat 717 // landing pads neutrally, and targets need only know how to lower 718 // the intrinsics to have a functioning exceptions system (assuming 719 // that platform exceptions follow something approximately like the 720 // GCC design). Unfortunately, landing pads cannot be combined in a 721 // language-agnostic way: given selectors A and B, there is no way 722 // to make a single landing pad which faithfully represents the 723 // semantics of propagating an exception first through A, then 724 // through B, without knowing how the personality will interpret the 725 // (lowered form of the) selectors. This means that inlining has no 726 // choice but to crudely chain invokes (i.e., to ignore invokes in 727 // the inlined function, but to turn all unwindable calls into 728 // invokes), which is only semantically valid if every unwind stops 729 // at every landing pad. 730 // 731 // Therefore, the invoke-inline hack is to guarantee that every 732 // landing pad has a catch-all. 733 const bool UseInvokeInlineHack = true; 734 735 for (EHScopeStack::iterator ir = EHStack.begin(); ; ) { 736 assert(ir != EHStack.end() && 737 "stack requiring landing pad is nothing but non-EH scopes?"); 738 739 // If this is a terminate scope, just use the singleton terminate 740 // landing pad. 741 if (isa<EHTerminateScope>(*ir)) 742 return getTerminateLandingPad(); 743 744 // If this isn't an EH scope, iterate; otherwise break out. 745 if (!isNonEHScope(*ir)) break; 746 ++ir; 747 748 // We haven't checked this scope for a cached landing pad yet. 749 if (llvm::BasicBlock *LP = ir->getCachedLandingPad()) 750 return LP; 751 } 752 753 // Save the current IR generation state. 754 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 755 756 // Create and configure the landing pad. 757 llvm::BasicBlock *LP = createBasicBlock("lpad"); 758 EmitBlock(LP); 759 760 // Save the exception pointer. It's safe to use a single exception 761 // pointer per function because EH cleanups can never have nested 762 // try/catches. 763 llvm::CallInst *Exn = 764 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_exception), "exn"); 765 Exn->setDoesNotThrow(); 766 Builder.CreateStore(Exn, getExceptionSlot()); 767 768 // Build the selector arguments. 769 llvm::SmallVector<llvm::Value*, 8> EHSelector; 770 EHSelector.push_back(Exn); 771 EHSelector.push_back(getPersonalityFn(*this)); 772 773 // Accumulate all the handlers in scope. 774 llvm::DenseMap<llvm::Value*, JumpDest> EHHandlers; 775 JumpDest CatchAll; 776 bool HasEHCleanup = false; 777 bool HasEHFilter = false; 778 llvm::SmallVector<llvm::Value*, 8> EHFilters; 779 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); 780 I != E; ++I) { 781 782 switch (I->getKind()) { 783 case EHScope::LazyCleanup: 784 if (!HasEHCleanup) 785 HasEHCleanup = cast<EHLazyCleanupScope>(*I).isEHCleanup(); 786 // We otherwise don't care about cleanups. 787 continue; 788 789 case EHScope::Cleanup: 790 if (!HasEHCleanup) 791 HasEHCleanup = cast<EHCleanupScope>(*I).isEHCleanup(); 792 // We otherwise don't care about cleanups. 793 continue; 794 795 case EHScope::Filter: { 796 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack"); 797 assert(!CatchAll.Block && "EH filter reached after catch-all"); 798 799 // Filter scopes get added to the selector in wierd ways. 800 EHFilterScope &Filter = cast<EHFilterScope>(*I); 801 HasEHFilter = true; 802 803 // Add all the filter values which we aren't already explicitly 804 // catching. 805 for (unsigned I = 0, E = Filter.getNumFilters(); I != E; ++I) { 806 llvm::Value *FV = Filter.getFilter(I); 807 if (!EHHandlers.count(FV)) 808 EHFilters.push_back(FV); 809 } 810 goto done; 811 } 812 813 case EHScope::Terminate: 814 // Terminate scopes are basically catch-alls. 815 assert(!CatchAll.Block); 816 CatchAll.Block = getTerminateHandler(); 817 CatchAll.ScopeDepth = EHStack.getEnclosingEHCleanup(I); 818 goto done; 819 820 case EHScope::Catch: 821 break; 822 } 823 824 EHCatchScope &Catch = cast<EHCatchScope>(*I); 825 for (unsigned HI = 0, HE = Catch.getNumHandlers(); HI != HE; ++HI) { 826 EHCatchScope::Handler Handler = Catch.getHandler(HI); 827 828 // Catch-all. We should only have one of these per catch. 829 if (!Handler.Type) { 830 assert(!CatchAll.Block); 831 CatchAll.Block = Handler.Block; 832 CatchAll.ScopeDepth = EHStack.getEnclosingEHCleanup(I); 833 continue; 834 } 835 836 // Check whether we already have a handler for this type. 837 JumpDest &Dest = EHHandlers[Handler.Type]; 838 if (Dest.Block) continue; 839 840 EHSelector.push_back(Handler.Type); 841 Dest.Block = Handler.Block; 842 Dest.ScopeDepth = EHStack.getEnclosingEHCleanup(I); 843 } 844 845 // Stop if we found a catch-all. 846 if (CatchAll.Block) break; 847 } 848 849 done: 850 unsigned LastToEmitInLoop = EHSelector.size(); 851 852 // If we have a catch-all, add null to the selector. 853 if (CatchAll.Block) { 854 EHSelector.push_back(getCatchAllValue(CGF)); 855 856 // If we have an EH filter, we need to add those handlers in the 857 // right place in the selector, which is to say, at the end. 858 } else if (HasEHFilter) { 859 // Create a filter expression: an integer constant saying how many 860 // filters there are (+1 to avoid ambiguity with 0 for cleanup), 861 // followed by the filter types. The personality routine only 862 // lands here if the filter doesn't match. 863 EHSelector.push_back(llvm::ConstantInt::get(Builder.getInt32Ty(), 864 EHFilters.size() + 1)); 865 EHSelector.append(EHFilters.begin(), EHFilters.end()); 866 867 // Also check whether we need a cleanup. 868 if (UseInvokeInlineHack || HasEHCleanup) 869 EHSelector.push_back(UseInvokeInlineHack 870 ? getCatchAllValue(CGF) 871 : getCleanupValue(CGF)); 872 873 // Otherwise, signal that we at least have cleanups. 874 } else if (UseInvokeInlineHack || HasEHCleanup) { 875 EHSelector.push_back(UseInvokeInlineHack 876 ? getCatchAllValue(CGF) 877 : getCleanupValue(CGF)); 878 } else { 879 assert(LastToEmitInLoop > 2); 880 LastToEmitInLoop--; 881 } 882 883 assert(EHSelector.size() >= 3 && "selector call has only two arguments!"); 884 885 // Tell the backend how to generate the landing pad. 886 llvm::CallInst *Selection = 887 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector), 888 EHSelector.begin(), EHSelector.end(), "eh.selector"); 889 Selection->setDoesNotThrow(); 890 891 // Select the right handler. 892 llvm::Value *llvm_eh_typeid_for = 893 CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); 894 895 // The results of llvm_eh_typeid_for aren't reliable --- at least 896 // not locally --- so we basically have to do this as an 'if' chain. 897 // We walk through the first N-1 catch clauses, testing and chaining, 898 // and then fall into the final clause (which is either a cleanup, a 899 // filter (possibly with a cleanup), a catch-all, or another catch). 900 for (unsigned I = 2; I != LastToEmitInLoop; ++I) { 901 llvm::Value *Type = EHSelector[I]; 902 JumpDest Dest = EHHandlers[Type]; 903 assert(Dest.Block && "no handler entry for value in selector?"); 904 905 // Figure out where to branch on a match. As a debug code-size 906 // optimization, if the scope depth matches the innermost cleanup, 907 // we branch directly to the catch handler. 908 llvm::BasicBlock *Match = Dest.Block; 909 bool MatchNeedsCleanup = Dest.ScopeDepth != EHStack.getInnermostEHCleanup(); 910 if (MatchNeedsCleanup) 911 Match = createBasicBlock("eh.match"); 912 913 llvm::BasicBlock *Next = createBasicBlock("eh.next"); 914 915 // Check whether the exception matches. 916 llvm::CallInst *Id 917 = Builder.CreateCall(llvm_eh_typeid_for, 918 Builder.CreateBitCast(Type, CGM.PtrToInt8Ty)); 919 Id->setDoesNotThrow(); 920 Builder.CreateCondBr(Builder.CreateICmpEQ(Selection, Id), 921 Match, Next); 922 923 // Emit match code if necessary. 924 if (MatchNeedsCleanup) { 925 EmitBlock(Match); 926 EmitBranchThroughEHCleanup(Dest); 927 } 928 929 // Continue to the next match. 930 EmitBlock(Next); 931 } 932 933 // Emit the final case in the selector. 934 // This might be a catch-all.... 935 if (CatchAll.Block) { 936 assert(isa<llvm::ConstantPointerNull>(EHSelector.back())); 937 EmitBranchThroughEHCleanup(CatchAll); 938 939 // ...or an EH filter... 940 } else if (HasEHFilter) { 941 llvm::Value *SavedSelection = Selection; 942 943 // First, unwind out to the outermost scope if necessary. 944 if (EHStack.hasEHCleanups()) { 945 // The end here might not dominate the beginning, so we might need to 946 // save the selector if we need it. 947 llvm::AllocaInst *SelectorVar = 0; 948 if (HasEHCleanup) { 949 SelectorVar = CreateTempAlloca(Builder.getInt32Ty(), "selector.var"); 950 Builder.CreateStore(Selection, SelectorVar); 951 } 952 953 llvm::BasicBlock *CleanupContBB = createBasicBlock("ehspec.cleanup.cont"); 954 EmitBranchThroughEHCleanup(JumpDest(CleanupContBB, EHStack.stable_end())); 955 EmitBlock(CleanupContBB); 956 957 if (HasEHCleanup) 958 SavedSelection = Builder.CreateLoad(SelectorVar, "ehspec.saved-selector"); 959 } 960 961 // If there was a cleanup, we'll need to actually check whether we 962 // landed here because the filter triggered. 963 if (UseInvokeInlineHack || HasEHCleanup) { 964 llvm::BasicBlock *RethrowBB = createBasicBlock("cleanup"); 965 llvm::BasicBlock *UnexpectedBB = createBasicBlock("ehspec.unexpected"); 966 967 llvm::Constant *Zero = llvm::ConstantInt::get(Builder.getInt32Ty(), 0); 968 llvm::Value *FailsFilter = 969 Builder.CreateICmpSLT(SavedSelection, Zero, "ehspec.fails"); 970 Builder.CreateCondBr(FailsFilter, UnexpectedBB, RethrowBB); 971 972 // The rethrow block is where we land if this was a cleanup. 973 // TODO: can this be _Unwind_Resume if the InvokeInlineHack is off? 974 EmitBlock(RethrowBB); 975 Builder.CreateCall(getUnwindResumeOrRethrowFn(), 976 Builder.CreateLoad(getExceptionSlot())) 977 ->setDoesNotReturn(); 978 Builder.CreateUnreachable(); 979 980 EmitBlock(UnexpectedBB); 981 } 982 983 // Call __cxa_call_unexpected. This doesn't need to be an invoke 984 // because __cxa_call_unexpected magically filters exceptions 985 // according to the last landing pad the exception was thrown 986 // into. Seriously. 987 Builder.CreateCall(getUnexpectedFn(*this), 988 Builder.CreateLoad(getExceptionSlot())) 989 ->setDoesNotReturn(); 990 Builder.CreateUnreachable(); 991 992 // ...or a normal catch handler... 993 } else if (!UseInvokeInlineHack && !HasEHCleanup) { 994 llvm::Value *Type = EHSelector.back(); 995 EmitBranchThroughEHCleanup(EHHandlers[Type]); 996 997 // ...or a cleanup. 998 } else { 999 // We emit a jump to a notional label at the outermost unwind state. 1000 llvm::BasicBlock *Unwind = createBasicBlock("eh.resume"); 1001 JumpDest Dest(Unwind, EHStack.stable_end()); 1002 EmitBranchThroughEHCleanup(Dest); 1003 1004 // The unwind block. We have to reload the exception here because 1005 // we might have unwound through arbitrary blocks, so the landing 1006 // pad might not dominate. 1007 EmitBlock(Unwind); 1008 1009 // This can always be a call because we necessarily didn't find 1010 // anything on the EH stack which needs our help. 1011 Builder.CreateCall(getUnwindResumeOrRethrowFn(), 1012 Builder.CreateLoad(getExceptionSlot())) 1013 ->setDoesNotReturn(); 1014 Builder.CreateUnreachable(); 1015 } 1016 1017 // Restore the old IR generation state. 1018 Builder.restoreIP(SavedIP); 1019 1020 return LP; 1021} 1022 1023/// Emits a call to __cxa_begin_catch and enters a cleanup to call 1024/// __cxa_end_catch. 1025static llvm::Value *CallBeginCatch(CodeGenFunction &CGF, llvm::Value *Exn) { 1026 llvm::CallInst *Call = CGF.Builder.CreateCall(getBeginCatchFn(CGF), Exn); 1027 Call->setDoesNotThrow(); 1028 1029 { 1030 CodeGenFunction::CleanupBlock EndCatchCleanup(CGF, NormalAndEHCleanup); 1031 1032 // __cxa_end_catch never throws, so this can just be a call. 1033 CGF.Builder.CreateCall(getEndCatchFn(CGF))->setDoesNotThrow(); 1034 } 1035 1036 return Call; 1037} 1038 1039/// A "special initializer" callback for initializing a catch 1040/// parameter during catch initialization. 1041static void InitCatchParam(CodeGenFunction &CGF, 1042 const VarDecl &CatchParam, 1043 llvm::Value *ParamAddr) { 1044 // Load the exception from where the landing pad saved it. 1045 llvm::Value *Exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot(), "exn"); 1046 1047 CanQualType CatchType = 1048 CGF.CGM.getContext().getCanonicalType(CatchParam.getType()); 1049 const llvm::Type *LLVMCatchTy = CGF.ConvertTypeForMem(CatchType); 1050 1051 // If we're catching by reference, we can just cast the object 1052 // pointer to the appropriate pointer. 1053 if (isa<ReferenceType>(CatchType)) { 1054 // __cxa_begin_catch returns the adjusted object pointer. 1055 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn); 1056 llvm::Value *ExnCast = 1057 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.byref"); 1058 CGF.Builder.CreateStore(ExnCast, ParamAddr); 1059 return; 1060 } 1061 1062 // Non-aggregates (plus complexes). 1063 bool IsComplex = false; 1064 if (!CGF.hasAggregateLLVMType(CatchType) || 1065 (IsComplex = CatchType->isAnyComplexType())) { 1066 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn); 1067 1068 // If the catch type is a pointer type, __cxa_begin_catch returns 1069 // the pointer by value. 1070 if (CatchType->hasPointerRepresentation()) { 1071 llvm::Value *CastExn = 1072 CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted"); 1073 CGF.Builder.CreateStore(CastExn, ParamAddr); 1074 return; 1075 } 1076 1077 // Otherwise, it returns a pointer into the exception object. 1078 1079 const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1080 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 1081 1082 if (IsComplex) { 1083 CGF.StoreComplexToAddr(CGF.LoadComplexFromAddr(Cast, /*volatile*/ false), 1084 ParamAddr, /*volatile*/ false); 1085 } else { 1086 llvm::Value *ExnLoad = CGF.Builder.CreateLoad(Cast, "exn.scalar"); 1087 CGF.EmitStoreOfScalar(ExnLoad, ParamAddr, /*volatile*/ false, CatchType); 1088 } 1089 return; 1090 } 1091 1092 // FIXME: this *really* needs to be done via a proper, Sema-emitted 1093 // initializer expression. 1094 1095 CXXRecordDecl *RD = CatchType.getTypePtr()->getAsCXXRecordDecl(); 1096 assert(RD && "aggregate catch type was not a record!"); 1097 1098 const llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok 1099 1100 if (RD->hasTrivialCopyConstructor()) { 1101 llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn); 1102 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 1103 CGF.EmitAggregateCopy(ParamAddr, Cast, CatchType); 1104 return; 1105 } 1106 1107 // We have to call __cxa_get_exception_ptr to get the adjusted 1108 // pointer before copying. 1109 llvm::CallInst *AdjustedExn = 1110 CGF.Builder.CreateCall(getGetExceptionPtrFn(CGF), Exn); 1111 AdjustedExn->setDoesNotThrow(); 1112 llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy); 1113 1114 CXXConstructorDecl *CD = RD->getCopyConstructor(CGF.getContext(), 0); 1115 assert(CD && "record has no copy constructor!"); 1116 llvm::Value *CopyCtor = CGF.CGM.GetAddrOfCXXConstructor(CD, Ctor_Complete); 1117 1118 CallArgList CallArgs; 1119 CallArgs.push_back(std::make_pair(RValue::get(ParamAddr), 1120 CD->getThisType(CGF.getContext()))); 1121 CallArgs.push_back(std::make_pair(RValue::get(Cast), 1122 CD->getParamDecl(0)->getType())); 1123 1124 const FunctionProtoType *FPT 1125 = CD->getType()->getAs<FunctionProtoType>(); 1126 1127 // Call the copy ctor in a terminate scope. 1128 CGF.EHStack.pushTerminate(); 1129 CGF.EmitCall(CGF.CGM.getTypes().getFunctionInfo(CallArgs, FPT), 1130 CopyCtor, ReturnValueSlot(), CallArgs, CD); 1131 CGF.EHStack.popTerminate(); 1132 1133 // Finally we can call __cxa_begin_catch. 1134 CallBeginCatch(CGF, Exn); 1135} 1136 1137/// Begins a catch statement by initializing the catch variable and 1138/// calling __cxa_begin_catch. 1139static void BeginCatch(CodeGenFunction &CGF, 1140 const CXXCatchStmt *S) { 1141 // We have to be very careful with the ordering of cleanups here: 1142 // C++ [except.throw]p4: 1143 // The destruction [of the exception temporary] occurs 1144 // immediately after the destruction of the object declared in 1145 // the exception-declaration in the handler. 1146 // 1147 // So the precise ordering is: 1148 // 1. Construct catch variable. 1149 // 2. __cxa_begin_catch 1150 // 3. Enter __cxa_end_catch cleanup 1151 // 4. Enter dtor cleanup 1152 // 1153 // We do this by initializing the exception variable with a 1154 // "special initializer", InitCatchParam. Delegation sequence: 1155 // - ExitCXXTryStmt opens a RunCleanupsScope 1156 // - EmitLocalBlockVarDecl creates the variable and debug info 1157 // - InitCatchParam initializes the variable from the exception 1158 // - CallBeginCatch calls __cxa_begin_catch 1159 // - CallBeginCatch enters the __cxa_end_catch cleanup 1160 // - EmitLocalBlockVarDecl enters the variable destructor cleanup 1161 // - EmitCXXTryStmt emits the code for the catch body 1162 // - EmitCXXTryStmt close the RunCleanupsScope 1163 1164 VarDecl *CatchParam = S->getExceptionDecl(); 1165 if (!CatchParam) { 1166 llvm::Value *Exn = CGF.Builder.CreateLoad(CGF.getExceptionSlot(), "exn"); 1167 CallBeginCatch(CGF, Exn); 1168 return; 1169 } 1170 1171 // Emit the local. 1172 CGF.EmitLocalBlockVarDecl(*CatchParam, &InitCatchParam); 1173} 1174 1175void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 1176 unsigned NumHandlers = S.getNumHandlers(); 1177 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin()); 1178 assert(CatchScope.getNumHandlers() == NumHandlers); 1179 1180 // Copy the handler blocks off before we pop the EH stack. Emitting 1181 // the handlers might scribble on this memory. 1182 llvm::SmallVector<EHCatchScope::Handler, 8> Handlers(NumHandlers); 1183 memcpy(Handlers.data(), CatchScope.begin(), 1184 NumHandlers * sizeof(EHCatchScope::Handler)); 1185 EHStack.popCatch(); 1186 1187 // The fall-through block. 1188 llvm::BasicBlock *ContBB = createBasicBlock("try.cont"); 1189 1190 // We just emitted the body of the try; jump to the continue block. 1191 if (HaveInsertPoint()) 1192 Builder.CreateBr(ContBB); 1193 1194 // Determine if we need an implicit rethrow for all these catch handlers. 1195 bool ImplicitRethrow = false; 1196 if (IsFnTryBlock) 1197 ImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) || 1198 isa<CXXConstructorDecl>(CurCodeDecl); 1199 1200 for (unsigned I = 0; I != NumHandlers; ++I) { 1201 llvm::BasicBlock *CatchBlock = Handlers[I].Block; 1202 EmitBlock(CatchBlock); 1203 1204 // Catch the exception if this isn't a catch-all. 1205 const CXXCatchStmt *C = S.getHandler(I); 1206 1207 // Enter a cleanup scope, including the catch variable and the 1208 // end-catch. 1209 RunCleanupsScope CatchScope(*this); 1210 1211 // Initialize the catch variable and set up the cleanups. 1212 BeginCatch(*this, C); 1213 1214 // If there's an implicit rethrow, push a normal "cleanup" to call 1215 // _cxa_rethrow. This needs to happen before _cxa_end_catch is 1216 // called. 1217 if (ImplicitRethrow) { 1218 CleanupBlock Rethrow(*this, NormalCleanup); 1219 EmitCallOrInvoke(getReThrowFn(*this), 0, 0); 1220 } 1221 1222 // Perform the body of the catch. 1223 EmitStmt(C->getHandlerBlock()); 1224 1225 // Fall out through the catch cleanups. 1226 CatchScope.ForceCleanup(); 1227 1228 // Branch out of the try. 1229 if (HaveInsertPoint()) 1230 Builder.CreateBr(ContBB); 1231 } 1232 1233 EmitBlock(ContBB); 1234} 1235 1236/// Enters a finally block for an implementation using zero-cost 1237/// exceptions. This is mostly general, but hard-codes some 1238/// language/ABI-specific behavior in the catch-all sections. 1239CodeGenFunction::FinallyInfo 1240CodeGenFunction::EnterFinallyBlock(const Stmt *Body, 1241 llvm::Constant *BeginCatchFn, 1242 llvm::Constant *EndCatchFn, 1243 llvm::Constant *RethrowFn) { 1244 assert((BeginCatchFn != 0) == (EndCatchFn != 0) && 1245 "begin/end catch functions not paired"); 1246 assert(RethrowFn && "rethrow function is required"); 1247 1248 // The rethrow function has one of the following two types: 1249 // void (*)() 1250 // void (*)(void*) 1251 // In the latter case we need to pass it the exception object. 1252 // But we can't use the exception slot because the @finally might 1253 // have a landing pad (which would overwrite the exception slot). 1254 const llvm::FunctionType *RethrowFnTy = 1255 cast<llvm::FunctionType>( 1256 cast<llvm::PointerType>(RethrowFn->getType()) 1257 ->getElementType()); 1258 llvm::Value *SavedExnVar = 0; 1259 if (RethrowFnTy->getNumParams()) 1260 SavedExnVar = CreateTempAlloca(Builder.getInt8PtrTy(), "finally.exn"); 1261 1262 // A finally block is a statement which must be executed on any edge 1263 // out of a given scope. Unlike a cleanup, the finally block may 1264 // contain arbitrary control flow leading out of itself. In 1265 // addition, finally blocks should always be executed, even if there 1266 // are no catch handlers higher on the stack. Therefore, we 1267 // surround the protected scope with a combination of a normal 1268 // cleanup (to catch attempts to break out of the block via normal 1269 // control flow) and an EH catch-all (semantically "outside" any try 1270 // statement to which the finally block might have been attached). 1271 // The finally block itself is generated in the context of a cleanup 1272 // which conditionally leaves the catch-all. 1273 1274 FinallyInfo Info; 1275 1276 // Jump destination for performing the finally block on an exception 1277 // edge. We'll never actually reach this block, so unreachable is 1278 // fine. 1279 JumpDest RethrowDest = getJumpDestInCurrentScope(getUnreachableBlock()); 1280 1281 // Whether the finally block is being executed for EH purposes. 1282 llvm::AllocaInst *ForEHVar = CreateTempAlloca(CGF.Builder.getInt1Ty(), 1283 "finally.for-eh"); 1284 InitTempAlloca(ForEHVar, llvm::ConstantInt::getFalse(getLLVMContext())); 1285 1286 // Enter a normal cleanup which will perform the @finally block. 1287 { 1288 CodeGenFunction::CleanupBlock Cleanup(*this, NormalCleanup); 1289 1290 // Enter a cleanup to call the end-catch function if one was provided. 1291 if (EndCatchFn) { 1292 CodeGenFunction::CleanupBlock FinallyExitCleanup(CGF, NormalAndEHCleanup); 1293 1294 llvm::BasicBlock *EndCatchBB = createBasicBlock("finally.endcatch"); 1295 llvm::BasicBlock *CleanupContBB = createBasicBlock("finally.cleanup.cont"); 1296 1297 llvm::Value *ShouldEndCatch = 1298 Builder.CreateLoad(ForEHVar, "finally.endcatch"); 1299 Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB); 1300 EmitBlock(EndCatchBB); 1301 Builder.CreateCall(EndCatchFn)->setDoesNotThrow(); 1302 EmitBlock(CleanupContBB); 1303 } 1304 1305 // Emit the finally block. 1306 EmitStmt(Body); 1307 1308 // If the end of the finally is reachable, check whether this was 1309 // for EH. If so, rethrow. 1310 if (HaveInsertPoint()) { 1311 llvm::BasicBlock *RethrowBB = createBasicBlock("finally.rethrow"); 1312 llvm::BasicBlock *ContBB = createBasicBlock("finally.cont"); 1313 1314 llvm::Value *ShouldRethrow = 1315 Builder.CreateLoad(ForEHVar, "finally.shouldthrow"); 1316 Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB); 1317 1318 EmitBlock(RethrowBB); 1319 if (SavedExnVar) { 1320 llvm::Value *Args[] = { Builder.CreateLoad(SavedExnVar) }; 1321 EmitCallOrInvoke(RethrowFn, Args, Args+1); 1322 } else { 1323 EmitCallOrInvoke(RethrowFn, 0, 0); 1324 } 1325 Builder.CreateUnreachable(); 1326 1327 EmitBlock(ContBB); 1328 } 1329 1330 // Leave the end-catch cleanup. As an optimization, pretend that 1331 // the fallthrough path was inaccessible; we've dynamically proven 1332 // that we're not in the EH case along that path. 1333 if (EndCatchFn) { 1334 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1335 PopCleanupBlock(); 1336 Builder.restoreIP(SavedIP); 1337 } 1338 1339 // Now make sure we actually have an insertion point or the 1340 // cleanup gods will hate us. 1341 EnsureInsertPoint(); 1342 } 1343 1344 // Enter a catch-all scope. 1345 llvm::BasicBlock *CatchAllBB = createBasicBlock("finally.catchall"); 1346 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP(); 1347 Builder.SetInsertPoint(CatchAllBB); 1348 1349 // If there's a begin-catch function, call it. 1350 if (BeginCatchFn) { 1351 Builder.CreateCall(BeginCatchFn, Builder.CreateLoad(getExceptionSlot())) 1352 ->setDoesNotThrow(); 1353 } 1354 1355 // If we need to remember the exception pointer to rethrow later, do so. 1356 if (SavedExnVar) { 1357 llvm::Value *SavedExn = Builder.CreateLoad(getExceptionSlot()); 1358 Builder.CreateStore(SavedExn, SavedExnVar); 1359 } 1360 1361 // Tell the finally block that we're in EH. 1362 Builder.CreateStore(llvm::ConstantInt::getTrue(getLLVMContext()), ForEHVar); 1363 1364 // Thread a jump through the finally cleanup. 1365 EmitBranchThroughCleanup(RethrowDest); 1366 1367 Builder.restoreIP(SavedIP); 1368 1369 EHCatchScope *CatchScope = EHStack.pushCatch(1); 1370 CatchScope->setCatchAllHandler(0, CatchAllBB); 1371 1372 return Info; 1373} 1374 1375void CodeGenFunction::ExitFinallyBlock(FinallyInfo &Info) { 1376 // Leave the finally catch-all. 1377 EHCatchScope &Catch = cast<EHCatchScope>(*EHStack.begin()); 1378 llvm::BasicBlock *CatchAllBB = Catch.getHandler(0).Block; 1379 EHStack.popCatch(); 1380 1381 // And leave the normal cleanup. 1382 PopCleanupBlock(); 1383 1384 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1385 EmitBlock(CatchAllBB, true); 1386 1387 Builder.restoreIP(SavedIP); 1388} 1389 1390llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() { 1391 if (TerminateLandingPad) 1392 return TerminateLandingPad; 1393 1394 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1395 1396 // This will get inserted at the end of the function. 1397 TerminateLandingPad = createBasicBlock("terminate.lpad"); 1398 Builder.SetInsertPoint(TerminateLandingPad); 1399 1400 // Tell the backend that this is a landing pad. 1401 llvm::CallInst *Exn = 1402 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_exception), "exn"); 1403 Exn->setDoesNotThrow(); 1404 1405 // Tell the backend what the exception table should be: 1406 // nothing but a catch-all. 1407 llvm::Value *Args[3] = { Exn, getPersonalityFn(*this), 1408 getCatchAllValue(*this) }; 1409 Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::eh_selector), 1410 Args, Args+3, "eh.selector") 1411 ->setDoesNotThrow(); 1412 1413 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this)); 1414 TerminateCall->setDoesNotReturn(); 1415 TerminateCall->setDoesNotThrow(); 1416 CGF.Builder.CreateUnreachable(); 1417 1418 // Restore the saved insertion state. 1419 Builder.restoreIP(SavedIP); 1420 1421 return TerminateLandingPad; 1422} 1423 1424llvm::BasicBlock *CodeGenFunction::getTerminateHandler() { 1425 if (TerminateHandler) 1426 return TerminateHandler; 1427 1428 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1429 1430 // Set up the terminate handler. This block is inserted at the very 1431 // end of the function by FinishFunction. 1432 TerminateHandler = createBasicBlock("terminate.handler"); 1433 Builder.SetInsertPoint(TerminateHandler); 1434 llvm::CallInst *TerminateCall = Builder.CreateCall(getTerminateFn(*this)); 1435 TerminateCall->setDoesNotReturn(); 1436 TerminateCall->setDoesNotThrow(); 1437 Builder.CreateUnreachable(); 1438 1439 // Restore the saved insertion state. 1440 Builder.restoreIP(SavedIP); 1441 1442 return TerminateHandler; 1443} 1444 1445CodeGenFunction::CleanupBlock::CleanupBlock(CodeGenFunction &CGF, 1446 CleanupKind Kind) 1447 : CGF(CGF), SavedIP(CGF.Builder.saveIP()), NormalCleanupExitBB(0) { 1448 llvm::BasicBlock *EntryBB = CGF.createBasicBlock("cleanup"); 1449 CGF.Builder.SetInsertPoint(EntryBB); 1450 1451 switch (Kind) { 1452 case NormalAndEHCleanup: 1453 NormalCleanupEntryBB = EHCleanupEntryBB = EntryBB; 1454 break; 1455 1456 case NormalCleanup: 1457 NormalCleanupEntryBB = EntryBB; 1458 EHCleanupEntryBB = 0; 1459 break; 1460 1461 case EHCleanup: 1462 NormalCleanupEntryBB = 0; 1463 EHCleanupEntryBB = EntryBB; 1464 CGF.EHStack.pushTerminate(); 1465 break; 1466 } 1467} 1468 1469void CodeGenFunction::CleanupBlock::beginEHCleanup() { 1470 assert(EHCleanupEntryBB == 0 && "already started an EH cleanup"); 1471 NormalCleanupExitBB = CGF.Builder.GetInsertBlock(); 1472 assert(NormalCleanupExitBB && "end of normal cleanup is unreachable"); 1473 1474 EHCleanupEntryBB = CGF.createBasicBlock("eh.cleanup"); 1475 CGF.Builder.SetInsertPoint(EHCleanupEntryBB); 1476 CGF.EHStack.pushTerminate(); 1477} 1478 1479CodeGenFunction::CleanupBlock::~CleanupBlock() { 1480 llvm::BasicBlock *EHCleanupExitBB = 0; 1481 1482 // If we're currently writing the EH cleanup... 1483 if (EHCleanupEntryBB) { 1484 // Set the EH cleanup exit block. 1485 EHCleanupExitBB = CGF.Builder.GetInsertBlock(); 1486 assert(EHCleanupExitBB && "end of EH cleanup is unreachable"); 1487 1488 // If we're actually writing both at once, set the normal exit, too. 1489 if (EHCleanupEntryBB == NormalCleanupEntryBB) 1490 NormalCleanupExitBB = EHCleanupExitBB; 1491 1492 // Otherwise, we must have pushed a terminate handler. 1493 else 1494 CGF.EHStack.popTerminate(); 1495 1496 // Otherwise, just set the normal cleanup exit block. 1497 } else { 1498 NormalCleanupExitBB = CGF.Builder.GetInsertBlock(); 1499 assert(NormalCleanupExitBB && "end of normal cleanup is unreachable"); 1500 } 1501 1502 CGF.EHStack.pushCleanup(NormalCleanupEntryBB, NormalCleanupExitBB, 1503 EHCleanupEntryBB, EHCleanupExitBB); 1504 1505 CGF.Builder.restoreIP(SavedIP); 1506} 1507 1508void EHScopeStack::LazyCleanup::_anchor() {} 1509