1 //===--- CGException.cpp - Emit LLVM Code for C++ exceptions ----*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 // 10 // This contains code dealing with C++ exception related code generation. 11 // 12 //===----------------------------------------------------------------------===// 13 14 #include "CodeGenFunction.h" 15 #include "CGCXXABI.h" 16 #include "CGCleanup.h" 17 #include "CGObjCRuntime.h" 18 #include "TargetInfo.h" 19 #include "clang/AST/Mangle.h" 20 #include "clang/AST/StmtCXX.h" 21 #include "clang/AST/StmtObjC.h" 22 #include "clang/AST/StmtVisitor.h" 23 #include "clang/Basic/TargetBuiltins.h" 24 #include "llvm/IR/CallSite.h" 25 #include "llvm/IR/Intrinsics.h" 26 #include "llvm/IR/IntrinsicInst.h" 27 #include "llvm/Support/SaveAndRestore.h" 28 29 using namespace clang; 30 using namespace CodeGen; 31 32 static llvm::Constant *getFreeExceptionFn(CodeGenModule &CGM) { 33 // void __cxa_free_exception(void *thrown_exception); 34 35 llvm::FunctionType *FTy = 36 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 37 38 return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception"); 39 } 40 41 static llvm::Constant *getUnexpectedFn(CodeGenModule &CGM) { 42 // void __cxa_call_unexpected(void *thrown_exception); 43 44 llvm::FunctionType *FTy = 45 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 46 47 return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); 48 } 49 50 llvm::Constant *CodeGenModule::getTerminateFn() { 51 // void __terminate(); 52 53 llvm::FunctionType *FTy = 54 llvm::FunctionType::get(VoidTy, /*IsVarArgs=*/false); 55 56 StringRef name; 57 58 // In C++, use std::terminate(). 59 if (getLangOpts().CPlusPlus && 60 getTarget().getCXXABI().isItaniumFamily()) { 61 name = "_ZSt9terminatev"; 62 } else if (getLangOpts().CPlusPlus && 63 getTarget().getCXXABI().isMicrosoft()) { 64 if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015)) 65 name = "__std_terminate"; 66 else 67 name = "\01?terminate@@YAXXZ"; 68 } else if (getLangOpts().ObjC1 && 69 getLangOpts().ObjCRuntime.hasTerminate()) 70 name = "objc_terminate"; 71 else 72 name = "abort"; 73 return CreateRuntimeFunction(FTy, name); 74 } 75 76 static llvm::Constant *getCatchallRethrowFn(CodeGenModule &CGM, 77 StringRef Name) { 78 llvm::FunctionType *FTy = 79 llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false); 80 81 return CGM.CreateRuntimeFunction(FTy, Name); 82 } 83 84 const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr }; 85 const EHPersonality 86 EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr }; 87 const EHPersonality 88 EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr }; 89 const EHPersonality 90 EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr }; 91 const EHPersonality 92 EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr }; 93 const EHPersonality 94 EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr }; 95 const EHPersonality 96 EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr }; 97 const EHPersonality 98 EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"}; 99 const EHPersonality 100 EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr }; 101 const EHPersonality 102 EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr }; 103 const EHPersonality 104 EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr }; 105 const EHPersonality 106 EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr }; 107 const EHPersonality 108 EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr }; 109 110 /// On Win64, use libgcc's SEH personality function. We fall back to dwarf on 111 /// other platforms, unless the user asked for SjLj exceptions. 112 static bool useLibGCCSEHPersonality(const llvm::Triple &T) { 113 return T.isOSWindows() && T.getArch() == llvm::Triple::x86_64; 114 } 115 116 static const EHPersonality &getCPersonality(const llvm::Triple &T, 117 const LangOptions &L) { 118 if (L.SjLjExceptions) 119 return EHPersonality::GNU_C_SJLJ; 120 else if (useLibGCCSEHPersonality(T)) 121 return EHPersonality::GNU_C_SEH; 122 return EHPersonality::GNU_C; 123 } 124 125 static const EHPersonality &getObjCPersonality(const llvm::Triple &T, 126 const LangOptions &L) { 127 switch (L.ObjCRuntime.getKind()) { 128 case ObjCRuntime::FragileMacOSX: 129 return getCPersonality(T, L); 130 case ObjCRuntime::MacOSX: 131 case ObjCRuntime::iOS: 132 case ObjCRuntime::WatchOS: 133 return EHPersonality::NeXT_ObjC; 134 case ObjCRuntime::GNUstep: 135 if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7)) 136 return EHPersonality::GNUstep_ObjC; 137 // fallthrough 138 case ObjCRuntime::GCC: 139 case ObjCRuntime::ObjFW: 140 return EHPersonality::GNU_ObjC; 141 } 142 llvm_unreachable("bad runtime kind"); 143 } 144 145 static const EHPersonality &getCXXPersonality(const llvm::Triple &T, 146 const LangOptions &L) { 147 if (L.SjLjExceptions) 148 return EHPersonality::GNU_CPlusPlus_SJLJ; 149 else if (useLibGCCSEHPersonality(T)) 150 return EHPersonality::GNU_CPlusPlus_SEH; 151 return EHPersonality::GNU_CPlusPlus; 152 } 153 154 /// Determines the personality function to use when both C++ 155 /// and Objective-C exceptions are being caught. 156 static const EHPersonality &getObjCXXPersonality(const llvm::Triple &T, 157 const LangOptions &L) { 158 switch (L.ObjCRuntime.getKind()) { 159 // The ObjC personality defers to the C++ personality for non-ObjC 160 // handlers. Unlike the C++ case, we use the same personality 161 // function on targets using (backend-driven) SJLJ EH. 162 case ObjCRuntime::MacOSX: 163 case ObjCRuntime::iOS: 164 case ObjCRuntime::WatchOS: 165 return EHPersonality::NeXT_ObjC; 166 167 // In the fragile ABI, just use C++ exception handling and hope 168 // they're not doing crazy exception mixing. 169 case ObjCRuntime::FragileMacOSX: 170 return getCXXPersonality(T, L); 171 172 // The GCC runtime's personality function inherently doesn't support 173 // mixed EH. Use the C++ personality just to avoid returning null. 174 case ObjCRuntime::GCC: 175 case ObjCRuntime::ObjFW: // XXX: this will change soon 176 return EHPersonality::GNU_ObjC; 177 case ObjCRuntime::GNUstep: 178 return EHPersonality::GNU_ObjCXX; 179 } 180 llvm_unreachable("bad runtime kind"); 181 } 182 183 static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) { 184 if (T.getArch() == llvm::Triple::x86) 185 return EHPersonality::MSVC_except_handler; 186 return EHPersonality::MSVC_C_specific_handler; 187 } 188 189 const EHPersonality &EHPersonality::get(CodeGenModule &CGM, 190 const FunctionDecl *FD) { 191 const llvm::Triple &T = CGM.getTarget().getTriple(); 192 const LangOptions &L = CGM.getLangOpts(); 193 194 // Functions using SEH get an SEH personality. 195 if (FD && FD->usesSEHTry()) 196 return getSEHPersonalityMSVC(T); 197 198 // Try to pick a personality function that is compatible with MSVC if we're 199 // not compiling Obj-C. Obj-C users better have an Obj-C runtime that supports 200 // the GCC-style personality function. 201 if (T.isWindowsMSVCEnvironment() && !L.ObjC1) { 202 if (L.SjLjExceptions) 203 return EHPersonality::GNU_CPlusPlus_SJLJ; 204 else 205 return EHPersonality::MSVC_CxxFrameHandler3; 206 } 207 208 if (L.CPlusPlus && L.ObjC1) 209 return getObjCXXPersonality(T, L); 210 else if (L.CPlusPlus) 211 return getCXXPersonality(T, L); 212 else if (L.ObjC1) 213 return getObjCPersonality(T, L); 214 else 215 return getCPersonality(T, L); 216 } 217 218 const EHPersonality &EHPersonality::get(CodeGenFunction &CGF) { 219 return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(CGF.CurCodeDecl)); 220 } 221 222 static llvm::Constant *getPersonalityFn(CodeGenModule &CGM, 223 const EHPersonality &Personality) { 224 llvm::Constant *Fn = 225 CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true), 226 Personality.PersonalityFn); 227 return Fn; 228 } 229 230 static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM, 231 const EHPersonality &Personality) { 232 llvm::Constant *Fn = getPersonalityFn(CGM, Personality); 233 return llvm::ConstantExpr::getBitCast(Fn, CGM.Int8PtrTy); 234 } 235 236 /// Check whether a landingpad instruction only uses C++ features. 237 static bool LandingPadHasOnlyCXXUses(llvm::LandingPadInst *LPI) { 238 for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) { 239 // Look for something that would've been returned by the ObjC 240 // runtime's GetEHType() method. 241 llvm::Value *Val = LPI->getClause(I)->stripPointerCasts(); 242 if (LPI->isCatch(I)) { 243 // Check if the catch value has the ObjC prefix. 244 if (llvm::GlobalVariable *GV = dyn_cast<llvm::GlobalVariable>(Val)) 245 // ObjC EH selector entries are always global variables with 246 // names starting like this. 247 if (GV->getName().startswith("OBJC_EHTYPE")) 248 return false; 249 } else { 250 // Check if any of the filter values have the ObjC prefix. 251 llvm::Constant *CVal = cast<llvm::Constant>(Val); 252 for (llvm::User::op_iterator 253 II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) { 254 if (llvm::GlobalVariable *GV = 255 cast<llvm::GlobalVariable>((*II)->stripPointerCasts())) 256 // ObjC EH selector entries are always global variables with 257 // names starting like this. 258 if (GV->getName().startswith("OBJC_EHTYPE")) 259 return false; 260 } 261 } 262 } 263 return true; 264 } 265 266 /// Check whether a personality function could reasonably be swapped 267 /// for a C++ personality function. 268 static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) { 269 for (llvm::User *U : Fn->users()) { 270 // Conditionally white-list bitcasts. 271 if (llvm::ConstantExpr *CE = dyn_cast<llvm::ConstantExpr>(U)) { 272 if (CE->getOpcode() != llvm::Instruction::BitCast) return false; 273 if (!PersonalityHasOnlyCXXUses(CE)) 274 return false; 275 continue; 276 } 277 278 // Otherwise it must be a function. 279 llvm::Function *F = dyn_cast<llvm::Function>(U); 280 if (!F) return false; 281 282 for (auto BB = F->begin(), E = F->end(); BB != E; ++BB) { 283 if (BB->isLandingPad()) 284 if (!LandingPadHasOnlyCXXUses(BB->getLandingPadInst())) 285 return false; 286 } 287 } 288 289 return true; 290 } 291 292 /// Try to use the C++ personality function in ObjC++. Not doing this 293 /// can cause some incompatibilities with gcc, which is more 294 /// aggressive about only using the ObjC++ personality in a function 295 /// when it really needs it. 296 void CodeGenModule::SimplifyPersonality() { 297 // If we're not in ObjC++ -fexceptions, there's nothing to do. 298 if (!LangOpts.CPlusPlus || !LangOpts.ObjC1 || !LangOpts.Exceptions) 299 return; 300 301 // Both the problem this endeavors to fix and the way the logic 302 // above works is specific to the NeXT runtime. 303 if (!LangOpts.ObjCRuntime.isNeXTFamily()) 304 return; 305 306 const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr); 307 const EHPersonality &CXX = 308 getCXXPersonality(getTarget().getTriple(), LangOpts); 309 if (&ObjCXX == &CXX) 310 return; 311 312 assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 && 313 "Different EHPersonalities using the same personality function."); 314 315 llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn); 316 317 // Nothing to do if it's unused. 318 if (!Fn || Fn->use_empty()) return; 319 320 // Can't do the optimization if it has non-C++ uses. 321 if (!PersonalityHasOnlyCXXUses(Fn)) return; 322 323 // Create the C++ personality function and kill off the old 324 // function. 325 llvm::Constant *CXXFn = getPersonalityFn(*this, CXX); 326 327 // This can happen if the user is screwing with us. 328 if (Fn->getType() != CXXFn->getType()) return; 329 330 Fn->replaceAllUsesWith(CXXFn); 331 Fn->eraseFromParent(); 332 } 333 334 /// Returns the value to inject into a selector to indicate the 335 /// presence of a catch-all. 336 static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) { 337 // Possibly we should use @llvm.eh.catch.all.value here. 338 return llvm::ConstantPointerNull::get(CGF.Int8PtrTy); 339 } 340 341 namespace { 342 /// A cleanup to free the exception object if its initialization 343 /// throws. 344 struct FreeException final : EHScopeStack::Cleanup { 345 llvm::Value *exn; 346 FreeException(llvm::Value *exn) : exn(exn) {} 347 void Emit(CodeGenFunction &CGF, Flags flags) override { 348 CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn); 349 } 350 }; 351 } // end anonymous namespace 352 353 // Emits an exception expression into the given location. This 354 // differs from EmitAnyExprToMem only in that, if a final copy-ctor 355 // call is required, an exception within that copy ctor causes 356 // std::terminate to be invoked. 357 void CodeGenFunction::EmitAnyExprToExn(const Expr *e, Address addr) { 358 // Make sure the exception object is cleaned up if there's an 359 // exception during initialization. 360 pushFullExprCleanup<FreeException>(EHCleanup, addr.getPointer()); 361 EHScopeStack::stable_iterator cleanup = EHStack.stable_begin(); 362 363 // __cxa_allocate_exception returns a void*; we need to cast this 364 // to the appropriate type for the object. 365 llvm::Type *ty = ConvertTypeForMem(e->getType())->getPointerTo(); 366 Address typedAddr = Builder.CreateBitCast(addr, ty); 367 368 // FIXME: this isn't quite right! If there's a final unelided call 369 // to a copy constructor, then according to [except.terminate]p1 we 370 // must call std::terminate() if that constructor throws, because 371 // technically that copy occurs after the exception expression is 372 // evaluated but before the exception is caught. But the best way 373 // to handle that is to teach EmitAggExpr to do the final copy 374 // differently if it can't be elided. 375 EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(), 376 /*IsInit*/ true); 377 378 // Deactivate the cleanup block. 379 DeactivateCleanupBlock(cleanup, 380 cast<llvm::Instruction>(typedAddr.getPointer())); 381 } 382 383 Address CodeGenFunction::getExceptionSlot() { 384 if (!ExceptionSlot) 385 ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot"); 386 return Address(ExceptionSlot, getPointerAlign()); 387 } 388 389 Address CodeGenFunction::getEHSelectorSlot() { 390 if (!EHSelectorSlot) 391 EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot"); 392 return Address(EHSelectorSlot, CharUnits::fromQuantity(4)); 393 } 394 395 llvm::Value *CodeGenFunction::getExceptionFromSlot() { 396 return Builder.CreateLoad(getExceptionSlot(), "exn"); 397 } 398 399 llvm::Value *CodeGenFunction::getSelectorFromSlot() { 400 return Builder.CreateLoad(getEHSelectorSlot(), "sel"); 401 } 402 403 void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E, 404 bool KeepInsertionPoint) { 405 if (const Expr *SubExpr = E->getSubExpr()) { 406 QualType ThrowType = SubExpr->getType(); 407 if (ThrowType->isObjCObjectPointerType()) { 408 const Stmt *ThrowStmt = E->getSubExpr(); 409 const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(ThrowStmt)); 410 CGM.getObjCRuntime().EmitThrowStmt(*this, S, false); 411 } else { 412 CGM.getCXXABI().emitThrow(*this, E); 413 } 414 } else { 415 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true); 416 } 417 418 // throw is an expression, and the expression emitters expect us 419 // to leave ourselves at a valid insertion point. 420 if (KeepInsertionPoint) 421 EmitBlock(createBasicBlock("throw.cont")); 422 } 423 424 void CodeGenFunction::EmitStartEHSpec(const Decl *D) { 425 if (!CGM.getLangOpts().CXXExceptions) 426 return; 427 428 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 429 if (!FD) { 430 // Check if CapturedDecl is nothrow and create terminate scope for it. 431 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) { 432 if (CD->isNothrow()) 433 EHStack.pushTerminate(); 434 } 435 return; 436 } 437 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 438 if (!Proto) 439 return; 440 441 ExceptionSpecificationType EST = Proto->getExceptionSpecType(); 442 if (isNoexceptExceptionSpec(EST)) { 443 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) { 444 // noexcept functions are simple terminate scopes. 445 EHStack.pushTerminate(); 446 } 447 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) { 448 // TODO: Revisit exception specifications for the MS ABI. There is a way to 449 // encode these in an object file but MSVC doesn't do anything with it. 450 if (getTarget().getCXXABI().isMicrosoft()) 451 return; 452 unsigned NumExceptions = Proto->getNumExceptions(); 453 EHFilterScope *Filter = EHStack.pushFilter(NumExceptions); 454 455 for (unsigned I = 0; I != NumExceptions; ++I) { 456 QualType Ty = Proto->getExceptionType(I); 457 QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType(); 458 llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType, 459 /*ForEH=*/true); 460 Filter->setFilter(I, EHType); 461 } 462 } 463 } 464 465 /// Emit the dispatch block for a filter scope if necessary. 466 static void emitFilterDispatchBlock(CodeGenFunction &CGF, 467 EHFilterScope &filterScope) { 468 llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock(); 469 if (!dispatchBlock) return; 470 if (dispatchBlock->use_empty()) { 471 delete dispatchBlock; 472 return; 473 } 474 475 CGF.EmitBlockAfterUses(dispatchBlock); 476 477 // If this isn't a catch-all filter, we need to check whether we got 478 // here because the filter triggered. 479 if (filterScope.getNumFilters()) { 480 // Load the selector value. 481 llvm::Value *selector = CGF.getSelectorFromSlot(); 482 llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected"); 483 484 llvm::Value *zero = CGF.Builder.getInt32(0); 485 llvm::Value *failsFilter = 486 CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails"); 487 CGF.Builder.CreateCondBr(failsFilter, unexpectedBB, 488 CGF.getEHResumeBlock(false)); 489 490 CGF.EmitBlock(unexpectedBB); 491 } 492 493 // Call __cxa_call_unexpected. This doesn't need to be an invoke 494 // because __cxa_call_unexpected magically filters exceptions 495 // according to the last landing pad the exception was thrown 496 // into. Seriously. 497 llvm::Value *exn = CGF.getExceptionFromSlot(); 498 CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn) 499 ->setDoesNotReturn(); 500 CGF.Builder.CreateUnreachable(); 501 } 502 503 void CodeGenFunction::EmitEndEHSpec(const Decl *D) { 504 if (!CGM.getLangOpts().CXXExceptions) 505 return; 506 507 const FunctionDecl* FD = dyn_cast_or_null<FunctionDecl>(D); 508 if (!FD) { 509 // Check if CapturedDecl is nothrow and pop terminate scope for it. 510 if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) { 511 if (CD->isNothrow()) 512 EHStack.popTerminate(); 513 } 514 return; 515 } 516 const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>(); 517 if (!Proto) 518 return; 519 520 ExceptionSpecificationType EST = Proto->getExceptionSpecType(); 521 if (isNoexceptExceptionSpec(EST)) { 522 if (Proto->getNoexceptSpec(getContext()) == FunctionProtoType::NR_Nothrow) { 523 EHStack.popTerminate(); 524 } 525 } else if (EST == EST_Dynamic || EST == EST_DynamicNone) { 526 // TODO: Revisit exception specifications for the MS ABI. There is a way to 527 // encode these in an object file but MSVC doesn't do anything with it. 528 if (getTarget().getCXXABI().isMicrosoft()) 529 return; 530 EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin()); 531 emitFilterDispatchBlock(*this, filterScope); 532 EHStack.popFilter(); 533 } 534 } 535 536 void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) { 537 EnterCXXTryStmt(S); 538 EmitStmt(S.getTryBlock()); 539 ExitCXXTryStmt(S); 540 } 541 542 void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 543 unsigned NumHandlers = S.getNumHandlers(); 544 EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers); 545 546 for (unsigned I = 0; I != NumHandlers; ++I) { 547 const CXXCatchStmt *C = S.getHandler(I); 548 549 llvm::BasicBlock *Handler = createBasicBlock("catch"); 550 if (C->getExceptionDecl()) { 551 // FIXME: Dropping the reference type on the type into makes it 552 // impossible to correctly implement catch-by-reference 553 // semantics for pointers. Unfortunately, this is what all 554 // existing compilers do, and it's not clear that the standard 555 // personality routine is capable of doing this right. See C++ DR 388: 556 // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388 557 Qualifiers CaughtTypeQuals; 558 QualType CaughtType = CGM.getContext().getUnqualifiedArrayType( 559 C->getCaughtType().getNonReferenceType(), CaughtTypeQuals); 560 561 CatchTypeInfo TypeInfo{nullptr, 0}; 562 if (CaughtType->isObjCObjectPointerType()) 563 TypeInfo.RTTI = CGM.getObjCRuntime().GetEHType(CaughtType); 564 else 565 TypeInfo = CGM.getCXXABI().getAddrOfCXXCatchHandlerType( 566 CaughtType, C->getCaughtType()); 567 CatchScope->setHandler(I, TypeInfo, Handler); 568 } else { 569 // No exception decl indicates '...', a catch-all. 570 CatchScope->setHandler(I, CGM.getCXXABI().getCatchAllTypeInfo(), Handler); 571 } 572 } 573 } 574 575 llvm::BasicBlock * 576 CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) { 577 if (EHPersonality::get(*this).usesFuncletPads()) 578 return getMSVCDispatchBlock(si); 579 580 // The dispatch block for the end of the scope chain is a block that 581 // just resumes unwinding. 582 if (si == EHStack.stable_end()) 583 return getEHResumeBlock(true); 584 585 // Otherwise, we should look at the actual scope. 586 EHScope &scope = *EHStack.find(si); 587 588 llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock(); 589 if (!dispatchBlock) { 590 switch (scope.getKind()) { 591 case EHScope::Catch: { 592 // Apply a special case to a single catch-all. 593 EHCatchScope &catchScope = cast<EHCatchScope>(scope); 594 if (catchScope.getNumHandlers() == 1 && 595 catchScope.getHandler(0).isCatchAll()) { 596 dispatchBlock = catchScope.getHandler(0).Block; 597 598 // Otherwise, make a dispatch block. 599 } else { 600 dispatchBlock = createBasicBlock("catch.dispatch"); 601 } 602 break; 603 } 604 605 case EHScope::Cleanup: 606 dispatchBlock = createBasicBlock("ehcleanup"); 607 break; 608 609 case EHScope::Filter: 610 dispatchBlock = createBasicBlock("filter.dispatch"); 611 break; 612 613 case EHScope::Terminate: 614 dispatchBlock = getTerminateHandler(); 615 break; 616 617 case EHScope::PadEnd: 618 llvm_unreachable("PadEnd unnecessary for Itanium!"); 619 } 620 scope.setCachedEHDispatchBlock(dispatchBlock); 621 } 622 return dispatchBlock; 623 } 624 625 llvm::BasicBlock * 626 CodeGenFunction::getMSVCDispatchBlock(EHScopeStack::stable_iterator SI) { 627 // Returning nullptr indicates that the previous dispatch block should unwind 628 // to caller. 629 if (SI == EHStack.stable_end()) 630 return nullptr; 631 632 // Otherwise, we should look at the actual scope. 633 EHScope &EHS = *EHStack.find(SI); 634 635 llvm::BasicBlock *DispatchBlock = EHS.getCachedEHDispatchBlock(); 636 if (DispatchBlock) 637 return DispatchBlock; 638 639 if (EHS.getKind() == EHScope::Terminate) 640 DispatchBlock = getTerminateHandler(); 641 else 642 DispatchBlock = createBasicBlock(); 643 CGBuilderTy Builder(*this, DispatchBlock); 644 645 switch (EHS.getKind()) { 646 case EHScope::Catch: 647 DispatchBlock->setName("catch.dispatch"); 648 break; 649 650 case EHScope::Cleanup: 651 DispatchBlock->setName("ehcleanup"); 652 break; 653 654 case EHScope::Filter: 655 llvm_unreachable("exception specifications not handled yet!"); 656 657 case EHScope::Terminate: 658 DispatchBlock->setName("terminate"); 659 break; 660 661 case EHScope::PadEnd: 662 llvm_unreachable("PadEnd dispatch block missing!"); 663 } 664 EHS.setCachedEHDispatchBlock(DispatchBlock); 665 return DispatchBlock; 666 } 667 668 /// Check whether this is a non-EH scope, i.e. a scope which doesn't 669 /// affect exception handling. Currently, the only non-EH scopes are 670 /// normal-only cleanup scopes. 671 static bool isNonEHScope(const EHScope &S) { 672 switch (S.getKind()) { 673 case EHScope::Cleanup: 674 return !cast<EHCleanupScope>(S).isEHCleanup(); 675 case EHScope::Filter: 676 case EHScope::Catch: 677 case EHScope::Terminate: 678 case EHScope::PadEnd: 679 return false; 680 } 681 682 llvm_unreachable("Invalid EHScope Kind!"); 683 } 684 685 llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() { 686 assert(EHStack.requiresLandingPad()); 687 assert(!EHStack.empty()); 688 689 // If exceptions are disabled, there are usually no landingpads. However, when 690 // SEH is enabled, functions using SEH still get landingpads. 691 const LangOptions &LO = CGM.getLangOpts(); 692 if (!LO.Exceptions) { 693 if (!LO.Borland && !LO.MicrosoftExt) 694 return nullptr; 695 if (!currentFunctionUsesSEHTry()) 696 return nullptr; 697 } 698 699 // Check the innermost scope for a cached landing pad. If this is 700 // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad. 701 llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad(); 702 if (LP) return LP; 703 704 const EHPersonality &Personality = EHPersonality::get(*this); 705 706 if (!CurFn->hasPersonalityFn()) 707 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality)); 708 709 if (Personality.usesFuncletPads()) { 710 // We don't need separate landing pads in the funclet model. 711 LP = getEHDispatchBlock(EHStack.getInnermostEHScope()); 712 } else { 713 // Build the landing pad for this scope. 714 LP = EmitLandingPad(); 715 } 716 717 assert(LP); 718 719 // Cache the landing pad on the innermost scope. If this is a 720 // non-EH scope, cache the landing pad on the enclosing scope, too. 721 for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) { 722 ir->setCachedLandingPad(LP); 723 if (!isNonEHScope(*ir)) break; 724 } 725 726 return LP; 727 } 728 729 llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { 730 assert(EHStack.requiresLandingPad()); 731 732 EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope()); 733 switch (innermostEHScope.getKind()) { 734 case EHScope::Terminate: 735 return getTerminateLandingPad(); 736 737 case EHScope::PadEnd: 738 llvm_unreachable("PadEnd unnecessary for Itanium!"); 739 740 case EHScope::Catch: 741 case EHScope::Cleanup: 742 case EHScope::Filter: 743 if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad()) 744 return lpad; 745 } 746 747 // Save the current IR generation state. 748 CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP(); 749 auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation); 750 751 // Create and configure the landing pad. 752 llvm::BasicBlock *lpad = createBasicBlock("lpad"); 753 EmitBlock(lpad); 754 755 llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad( 756 llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0); 757 758 llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0); 759 Builder.CreateStore(LPadExn, getExceptionSlot()); 760 llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1); 761 Builder.CreateStore(LPadSel, getEHSelectorSlot()); 762 763 // Save the exception pointer. It's safe to use a single exception 764 // pointer per function because EH cleanups can never have nested 765 // try/catches. 766 // Build the landingpad instruction. 767 768 // Accumulate all the handlers in scope. 769 bool hasCatchAll = false; 770 bool hasCleanup = false; 771 bool hasFilter = false; 772 SmallVector<llvm::Value*, 4> filterTypes; 773 llvm::SmallPtrSet<llvm::Value*, 4> catchTypes; 774 for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E; 775 ++I) { 776 777 switch (I->getKind()) { 778 case EHScope::Cleanup: 779 // If we have a cleanup, remember that. 780 hasCleanup = (hasCleanup || cast<EHCleanupScope>(*I).isEHCleanup()); 781 continue; 782 783 case EHScope::Filter: { 784 assert(I.next() == EHStack.end() && "EH filter is not end of EH stack"); 785 assert(!hasCatchAll && "EH filter reached after catch-all"); 786 787 // Filter scopes get added to the landingpad in weird ways. 788 EHFilterScope &filter = cast<EHFilterScope>(*I); 789 hasFilter = true; 790 791 // Add all the filter values. 792 for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i) 793 filterTypes.push_back(filter.getFilter(i)); 794 goto done; 795 } 796 797 case EHScope::Terminate: 798 // Terminate scopes are basically catch-alls. 799 assert(!hasCatchAll); 800 hasCatchAll = true; 801 goto done; 802 803 case EHScope::Catch: 804 break; 805 806 case EHScope::PadEnd: 807 llvm_unreachable("PadEnd unnecessary for Itanium!"); 808 } 809 810 EHCatchScope &catchScope = cast<EHCatchScope>(*I); 811 for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) { 812 EHCatchScope::Handler handler = catchScope.getHandler(hi); 813 assert(handler.Type.Flags == 0 && 814 "landingpads do not support catch handler flags"); 815 816 // If this is a catch-all, register that and abort. 817 if (!handler.Type.RTTI) { 818 assert(!hasCatchAll); 819 hasCatchAll = true; 820 goto done; 821 } 822 823 // Check whether we already have a handler for this type. 824 if (catchTypes.insert(handler.Type.RTTI).second) 825 // If not, add it directly to the landingpad. 826 LPadInst->addClause(handler.Type.RTTI); 827 } 828 } 829 830 done: 831 // If we have a catch-all, add null to the landingpad. 832 assert(!(hasCatchAll && hasFilter)); 833 if (hasCatchAll) { 834 LPadInst->addClause(getCatchAllValue(*this)); 835 836 // If we have an EH filter, we need to add those handlers in the 837 // right place in the landingpad, which is to say, at the end. 838 } else if (hasFilter) { 839 // Create a filter expression: a constant array indicating which filter 840 // types there are. The personality routine only lands here if the filter 841 // doesn't match. 842 SmallVector<llvm::Constant*, 8> Filters; 843 llvm::ArrayType *AType = 844 llvm::ArrayType::get(!filterTypes.empty() ? 845 filterTypes[0]->getType() : Int8PtrTy, 846 filterTypes.size()); 847 848 for (unsigned i = 0, e = filterTypes.size(); i != e; ++i) 849 Filters.push_back(cast<llvm::Constant>(filterTypes[i])); 850 llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters); 851 LPadInst->addClause(FilterArray); 852 853 // Also check whether we need a cleanup. 854 if (hasCleanup) 855 LPadInst->setCleanup(true); 856 857 // Otherwise, signal that we at least have cleanups. 858 } else if (hasCleanup) { 859 LPadInst->setCleanup(true); 860 } 861 862 assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) && 863 "landingpad instruction has no clauses!"); 864 865 // Tell the backend how to generate the landing pad. 866 Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope())); 867 868 // Restore the old IR generation state. 869 Builder.restoreIP(savedIP); 870 871 return lpad; 872 } 873 874 static void emitCatchPadBlock(CodeGenFunction &CGF, EHCatchScope &CatchScope) { 875 llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock(); 876 assert(DispatchBlock); 877 878 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP(); 879 CGF.EmitBlockAfterUses(DispatchBlock); 880 881 llvm::Value *ParentPad = CGF.CurrentFuncletPad; 882 if (!ParentPad) 883 ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext()); 884 llvm::BasicBlock *UnwindBB = 885 CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope()); 886 887 unsigned NumHandlers = CatchScope.getNumHandlers(); 888 llvm::CatchSwitchInst *CatchSwitch = 889 CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers); 890 891 // Test against each of the exception types we claim to catch. 892 for (unsigned I = 0; I < NumHandlers; ++I) { 893 const EHCatchScope::Handler &Handler = CatchScope.getHandler(I); 894 895 CatchTypeInfo TypeInfo = Handler.Type; 896 if (!TypeInfo.RTTI) 897 TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy); 898 899 CGF.Builder.SetInsertPoint(Handler.Block); 900 901 if (EHPersonality::get(CGF).isMSVCXXPersonality()) { 902 CGF.Builder.CreateCatchPad( 903 CatchSwitch, {TypeInfo.RTTI, CGF.Builder.getInt32(TypeInfo.Flags), 904 llvm::Constant::getNullValue(CGF.VoidPtrTy)}); 905 } else { 906 CGF.Builder.CreateCatchPad(CatchSwitch, {TypeInfo.RTTI}); 907 } 908 909 CatchSwitch->addHandler(Handler.Block); 910 } 911 CGF.Builder.restoreIP(SavedIP); 912 } 913 914 /// Emit the structure of the dispatch block for the given catch scope. 915 /// It is an invariant that the dispatch block already exists. 916 static void emitCatchDispatchBlock(CodeGenFunction &CGF, 917 EHCatchScope &catchScope) { 918 if (EHPersonality::get(CGF).usesFuncletPads()) 919 return emitCatchPadBlock(CGF, catchScope); 920 921 llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock(); 922 assert(dispatchBlock); 923 924 // If there's only a single catch-all, getEHDispatchBlock returned 925 // that catch-all as the dispatch block. 926 if (catchScope.getNumHandlers() == 1 && 927 catchScope.getHandler(0).isCatchAll()) { 928 assert(dispatchBlock == catchScope.getHandler(0).Block); 929 return; 930 } 931 932 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP(); 933 CGF.EmitBlockAfterUses(dispatchBlock); 934 935 // Select the right handler. 936 llvm::Value *llvm_eh_typeid_for = 937 CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); 938 939 // Load the selector value. 940 llvm::Value *selector = CGF.getSelectorFromSlot(); 941 942 // Test against each of the exception types we claim to catch. 943 for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) { 944 assert(i < e && "ran off end of handlers!"); 945 const EHCatchScope::Handler &handler = catchScope.getHandler(i); 946 947 llvm::Value *typeValue = handler.Type.RTTI; 948 assert(handler.Type.Flags == 0 && 949 "landingpads do not support catch handler flags"); 950 assert(typeValue && "fell into catch-all case!"); 951 typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy); 952 953 // Figure out the next block. 954 bool nextIsEnd; 955 llvm::BasicBlock *nextBlock; 956 957 // If this is the last handler, we're at the end, and the next 958 // block is the block for the enclosing EH scope. 959 if (i + 1 == e) { 960 nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope()); 961 nextIsEnd = true; 962 963 // If the next handler is a catch-all, we're at the end, and the 964 // next block is that handler. 965 } else if (catchScope.getHandler(i+1).isCatchAll()) { 966 nextBlock = catchScope.getHandler(i+1).Block; 967 nextIsEnd = true; 968 969 // Otherwise, we're not at the end and we need a new block. 970 } else { 971 nextBlock = CGF.createBasicBlock("catch.fallthrough"); 972 nextIsEnd = false; 973 } 974 975 // Figure out the catch type's index in the LSDA's type table. 976 llvm::CallInst *typeIndex = 977 CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue); 978 typeIndex->setDoesNotThrow(); 979 980 llvm::Value *matchesTypeIndex = 981 CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches"); 982 CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock); 983 984 // If the next handler is a catch-all, we're completely done. 985 if (nextIsEnd) { 986 CGF.Builder.restoreIP(savedIP); 987 return; 988 } 989 // Otherwise we need to emit and continue at that block. 990 CGF.EmitBlock(nextBlock); 991 } 992 } 993 994 void CodeGenFunction::popCatchScope() { 995 EHCatchScope &catchScope = cast<EHCatchScope>(*EHStack.begin()); 996 if (catchScope.hasEHBranches()) 997 emitCatchDispatchBlock(*this, catchScope); 998 EHStack.popCatch(); 999 } 1000 1001 void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { 1002 unsigned NumHandlers = S.getNumHandlers(); 1003 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin()); 1004 assert(CatchScope.getNumHandlers() == NumHandlers); 1005 1006 // If the catch was not required, bail out now. 1007 if (!CatchScope.hasEHBranches()) { 1008 CatchScope.clearHandlerBlocks(); 1009 EHStack.popCatch(); 1010 return; 1011 } 1012 1013 // Emit the structure of the EH dispatch for this catch. 1014 emitCatchDispatchBlock(*this, CatchScope); 1015 1016 // Copy the handler blocks off before we pop the EH stack. Emitting 1017 // the handlers might scribble on this memory. 1018 SmallVector<EHCatchScope::Handler, 8> Handlers( 1019 CatchScope.begin(), CatchScope.begin() + NumHandlers); 1020 1021 EHStack.popCatch(); 1022 1023 // The fall-through block. 1024 llvm::BasicBlock *ContBB = createBasicBlock("try.cont"); 1025 1026 // We just emitted the body of the try; jump to the continue block. 1027 if (HaveInsertPoint()) 1028 Builder.CreateBr(ContBB); 1029 1030 // Determine if we need an implicit rethrow for all these catch handlers; 1031 // see the comment below. 1032 bool doImplicitRethrow = false; 1033 if (IsFnTryBlock) 1034 doImplicitRethrow = isa<CXXDestructorDecl>(CurCodeDecl) || 1035 isa<CXXConstructorDecl>(CurCodeDecl); 1036 1037 // Perversely, we emit the handlers backwards precisely because we 1038 // want them to appear in source order. In all of these cases, the 1039 // catch block will have exactly one predecessor, which will be a 1040 // particular block in the catch dispatch. However, in the case of 1041 // a catch-all, one of the dispatch blocks will branch to two 1042 // different handlers, and EmitBlockAfterUses will cause the second 1043 // handler to be moved before the first. 1044 for (unsigned I = NumHandlers; I != 0; --I) { 1045 llvm::BasicBlock *CatchBlock = Handlers[I-1].Block; 1046 EmitBlockAfterUses(CatchBlock); 1047 1048 // Catch the exception if this isn't a catch-all. 1049 const CXXCatchStmt *C = S.getHandler(I-1); 1050 1051 // Enter a cleanup scope, including the catch variable and the 1052 // end-catch. 1053 RunCleanupsScope CatchScope(*this); 1054 1055 // Initialize the catch variable and set up the cleanups. 1056 SaveAndRestore<llvm::Instruction *> RestoreCurrentFuncletPad( 1057 CurrentFuncletPad); 1058 CGM.getCXXABI().emitBeginCatch(*this, C); 1059 1060 // Emit the PGO counter increment. 1061 incrementProfileCounter(C); 1062 1063 // Perform the body of the catch. 1064 EmitStmt(C->getHandlerBlock()); 1065 1066 // [except.handle]p11: 1067 // The currently handled exception is rethrown if control 1068 // reaches the end of a handler of the function-try-block of a 1069 // constructor or destructor. 1070 1071 // It is important that we only do this on fallthrough and not on 1072 // return. Note that it's illegal to put a return in a 1073 // constructor function-try-block's catch handler (p14), so this 1074 // really only applies to destructors. 1075 if (doImplicitRethrow && HaveInsertPoint()) { 1076 CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false); 1077 Builder.CreateUnreachable(); 1078 Builder.ClearInsertionPoint(); 1079 } 1080 1081 // Fall out through the catch cleanups. 1082 CatchScope.ForceCleanup(); 1083 1084 // Branch out of the try. 1085 if (HaveInsertPoint()) 1086 Builder.CreateBr(ContBB); 1087 } 1088 1089 EmitBlock(ContBB); 1090 incrementProfileCounter(&S); 1091 } 1092 1093 namespace { 1094 struct CallEndCatchForFinally final : EHScopeStack::Cleanup { 1095 llvm::Value *ForEHVar; 1096 llvm::Value *EndCatchFn; 1097 CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::Value *EndCatchFn) 1098 : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {} 1099 1100 void Emit(CodeGenFunction &CGF, Flags flags) override { 1101 llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch"); 1102 llvm::BasicBlock *CleanupContBB = 1103 CGF.createBasicBlock("finally.cleanup.cont"); 1104 1105 llvm::Value *ShouldEndCatch = 1106 CGF.Builder.CreateFlagLoad(ForEHVar, "finally.endcatch"); 1107 CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB); 1108 CGF.EmitBlock(EndCatchBB); 1109 CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw 1110 CGF.EmitBlock(CleanupContBB); 1111 } 1112 }; 1113 1114 struct PerformFinally final : EHScopeStack::Cleanup { 1115 const Stmt *Body; 1116 llvm::Value *ForEHVar; 1117 llvm::Value *EndCatchFn; 1118 llvm::Value *RethrowFn; 1119 llvm::Value *SavedExnVar; 1120 1121 PerformFinally(const Stmt *Body, llvm::Value *ForEHVar, 1122 llvm::Value *EndCatchFn, 1123 llvm::Value *RethrowFn, llvm::Value *SavedExnVar) 1124 : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn), 1125 RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {} 1126 1127 void Emit(CodeGenFunction &CGF, Flags flags) override { 1128 // Enter a cleanup to call the end-catch function if one was provided. 1129 if (EndCatchFn) 1130 CGF.EHStack.pushCleanup<CallEndCatchForFinally>(NormalAndEHCleanup, 1131 ForEHVar, EndCatchFn); 1132 1133 // Save the current cleanup destination in case there are 1134 // cleanups in the finally block. 1135 llvm::Value *SavedCleanupDest = 1136 CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(), 1137 "cleanup.dest.saved"); 1138 1139 // Emit the finally block. 1140 CGF.EmitStmt(Body); 1141 1142 // If the end of the finally is reachable, check whether this was 1143 // for EH. If so, rethrow. 1144 if (CGF.HaveInsertPoint()) { 1145 llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow"); 1146 llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont"); 1147 1148 llvm::Value *ShouldRethrow = 1149 CGF.Builder.CreateFlagLoad(ForEHVar, "finally.shouldthrow"); 1150 CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB); 1151 1152 CGF.EmitBlock(RethrowBB); 1153 if (SavedExnVar) { 1154 CGF.EmitRuntimeCallOrInvoke(RethrowFn, 1155 CGF.Builder.CreateAlignedLoad(SavedExnVar, CGF.getPointerAlign())); 1156 } else { 1157 CGF.EmitRuntimeCallOrInvoke(RethrowFn); 1158 } 1159 CGF.Builder.CreateUnreachable(); 1160 1161 CGF.EmitBlock(ContBB); 1162 1163 // Restore the cleanup destination. 1164 CGF.Builder.CreateStore(SavedCleanupDest, 1165 CGF.getNormalCleanupDestSlot()); 1166 } 1167 1168 // Leave the end-catch cleanup. As an optimization, pretend that 1169 // the fallthrough path was inaccessible; we've dynamically proven 1170 // that we're not in the EH case along that path. 1171 if (EndCatchFn) { 1172 CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); 1173 CGF.PopCleanupBlock(); 1174 CGF.Builder.restoreIP(SavedIP); 1175 } 1176 1177 // Now make sure we actually have an insertion point or the 1178 // cleanup gods will hate us. 1179 CGF.EnsureInsertPoint(); 1180 } 1181 }; 1182 } // end anonymous namespace 1183 1184 /// Enters a finally block for an implementation using zero-cost 1185 /// exceptions. This is mostly general, but hard-codes some 1186 /// language/ABI-specific behavior in the catch-all sections. 1187 void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF, 1188 const Stmt *body, 1189 llvm::Constant *beginCatchFn, 1190 llvm::Constant *endCatchFn, 1191 llvm::Constant *rethrowFn) { 1192 assert((beginCatchFn != nullptr) == (endCatchFn != nullptr) && 1193 "begin/end catch functions not paired"); 1194 assert(rethrowFn && "rethrow function is required"); 1195 1196 BeginCatchFn = beginCatchFn; 1197 1198 // The rethrow function has one of the following two types: 1199 // void (*)() 1200 // void (*)(void*) 1201 // In the latter case we need to pass it the exception object. 1202 // But we can't use the exception slot because the @finally might 1203 // have a landing pad (which would overwrite the exception slot). 1204 llvm::FunctionType *rethrowFnTy = 1205 cast<llvm::FunctionType>( 1206 cast<llvm::PointerType>(rethrowFn->getType())->getElementType()); 1207 SavedExnVar = nullptr; 1208 if (rethrowFnTy->getNumParams()) 1209 SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn"); 1210 1211 // A finally block is a statement which must be executed on any edge 1212 // out of a given scope. Unlike a cleanup, the finally block may 1213 // contain arbitrary control flow leading out of itself. In 1214 // addition, finally blocks should always be executed, even if there 1215 // are no catch handlers higher on the stack. Therefore, we 1216 // surround the protected scope with a combination of a normal 1217 // cleanup (to catch attempts to break out of the block via normal 1218 // control flow) and an EH catch-all (semantically "outside" any try 1219 // statement to which the finally block might have been attached). 1220 // The finally block itself is generated in the context of a cleanup 1221 // which conditionally leaves the catch-all. 1222 1223 // Jump destination for performing the finally block on an exception 1224 // edge. We'll never actually reach this block, so unreachable is 1225 // fine. 1226 RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock()); 1227 1228 // Whether the finally block is being executed for EH purposes. 1229 ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh"); 1230 CGF.Builder.CreateFlagStore(false, ForEHVar); 1231 1232 // Enter a normal cleanup which will perform the @finally block. 1233 CGF.EHStack.pushCleanup<PerformFinally>(NormalCleanup, body, 1234 ForEHVar, endCatchFn, 1235 rethrowFn, SavedExnVar); 1236 1237 // Enter a catch-all scope. 1238 llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall"); 1239 EHCatchScope *catchScope = CGF.EHStack.pushCatch(1); 1240 catchScope->setCatchAllHandler(0, catchBB); 1241 } 1242 1243 void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) { 1244 // Leave the finally catch-all. 1245 EHCatchScope &catchScope = cast<EHCatchScope>(*CGF.EHStack.begin()); 1246 llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block; 1247 1248 CGF.popCatchScope(); 1249 1250 // If there are any references to the catch-all block, emit it. 1251 if (catchBB->use_empty()) { 1252 delete catchBB; 1253 } else { 1254 CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP(); 1255 CGF.EmitBlock(catchBB); 1256 1257 llvm::Value *exn = nullptr; 1258 1259 // If there's a begin-catch function, call it. 1260 if (BeginCatchFn) { 1261 exn = CGF.getExceptionFromSlot(); 1262 CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn); 1263 } 1264 1265 // If we need to remember the exception pointer to rethrow later, do so. 1266 if (SavedExnVar) { 1267 if (!exn) exn = CGF.getExceptionFromSlot(); 1268 CGF.Builder.CreateAlignedStore(exn, SavedExnVar, CGF.getPointerAlign()); 1269 } 1270 1271 // Tell the cleanups in the finally block that we're do this for EH. 1272 CGF.Builder.CreateFlagStore(true, ForEHVar); 1273 1274 // Thread a jump through the finally cleanup. 1275 CGF.EmitBranchThroughCleanup(RethrowDest); 1276 1277 CGF.Builder.restoreIP(savedIP); 1278 } 1279 1280 // Finally, leave the @finally cleanup. 1281 CGF.PopCleanupBlock(); 1282 } 1283 1284 llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() { 1285 if (TerminateLandingPad) 1286 return TerminateLandingPad; 1287 1288 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1289 1290 // This will get inserted at the end of the function. 1291 TerminateLandingPad = createBasicBlock("terminate.lpad"); 1292 Builder.SetInsertPoint(TerminateLandingPad); 1293 1294 // Tell the backend that this is a landing pad. 1295 const EHPersonality &Personality = EHPersonality::get(*this); 1296 1297 if (!CurFn->hasPersonalityFn()) 1298 CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality)); 1299 1300 llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad( 1301 llvm::StructType::get(Int8PtrTy, Int32Ty, nullptr), 0); 1302 LPadInst->addClause(getCatchAllValue(*this)); 1303 1304 llvm::Value *Exn = nullptr; 1305 if (getLangOpts().CPlusPlus) 1306 Exn = Builder.CreateExtractValue(LPadInst, 0); 1307 llvm::CallInst *terminateCall = 1308 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn); 1309 terminateCall->setDoesNotReturn(); 1310 Builder.CreateUnreachable(); 1311 1312 // Restore the saved insertion state. 1313 Builder.restoreIP(SavedIP); 1314 1315 return TerminateLandingPad; 1316 } 1317 1318 llvm::BasicBlock *CodeGenFunction::getTerminateHandler() { 1319 if (TerminateHandler) 1320 return TerminateHandler; 1321 1322 CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); 1323 1324 // Set up the terminate handler. This block is inserted at the very 1325 // end of the function by FinishFunction. 1326 TerminateHandler = createBasicBlock("terminate.handler"); 1327 Builder.SetInsertPoint(TerminateHandler); 1328 llvm::Value *Exn = nullptr; 1329 if (EHPersonality::get(*this).usesFuncletPads()) { 1330 llvm::Value *ParentPad = CurrentFuncletPad; 1331 if (!ParentPad) 1332 ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext()); 1333 Builder.CreateCleanupPad(ParentPad); 1334 } else { 1335 if (getLangOpts().CPlusPlus) 1336 Exn = getExceptionFromSlot(); 1337 } 1338 llvm::CallInst *terminateCall = 1339 CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn); 1340 terminateCall->setDoesNotReturn(); 1341 Builder.CreateUnreachable(); 1342 1343 // Restore the saved insertion state. 1344 Builder.restoreIP(SavedIP); 1345 1346 return TerminateHandler; 1347 } 1348 1349 llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) { 1350 if (EHResumeBlock) return EHResumeBlock; 1351 1352 CGBuilderTy::InsertPoint SavedIP = Builder.saveIP(); 1353 1354 // We emit a jump to a notional label at the outermost unwind state. 1355 EHResumeBlock = createBasicBlock("eh.resume"); 1356 Builder.SetInsertPoint(EHResumeBlock); 1357 1358 const EHPersonality &Personality = EHPersonality::get(*this); 1359 1360 // This can always be a call because we necessarily didn't find 1361 // anything on the EH stack which needs our help. 1362 const char *RethrowName = Personality.CatchallRethrowFn; 1363 if (RethrowName != nullptr && !isCleanup) { 1364 EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName), 1365 getExceptionFromSlot())->setDoesNotReturn(); 1366 Builder.CreateUnreachable(); 1367 Builder.restoreIP(SavedIP); 1368 return EHResumeBlock; 1369 } 1370 1371 // Recreate the landingpad's return value for the 'resume' instruction. 1372 llvm::Value *Exn = getExceptionFromSlot(); 1373 llvm::Value *Sel = getSelectorFromSlot(); 1374 1375 llvm::Type *LPadType = llvm::StructType::get(Exn->getType(), 1376 Sel->getType(), nullptr); 1377 llvm::Value *LPadVal = llvm::UndefValue::get(LPadType); 1378 LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val"); 1379 LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val"); 1380 1381 Builder.CreateResume(LPadVal); 1382 Builder.restoreIP(SavedIP); 1383 return EHResumeBlock; 1384 } 1385 1386 void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) { 1387 EnterSEHTryStmt(S); 1388 { 1389 JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave"); 1390 1391 SEHTryEpilogueStack.push_back(&TryExit); 1392 EmitStmt(S.getTryBlock()); 1393 SEHTryEpilogueStack.pop_back(); 1394 1395 if (!TryExit.getBlock()->use_empty()) 1396 EmitBlock(TryExit.getBlock(), /*IsFinished=*/true); 1397 else 1398 delete TryExit.getBlock(); 1399 } 1400 ExitSEHTryStmt(S); 1401 } 1402 1403 namespace { 1404 struct PerformSEHFinally final : EHScopeStack::Cleanup { 1405 llvm::Function *OutlinedFinally; 1406 PerformSEHFinally(llvm::Function *OutlinedFinally) 1407 : OutlinedFinally(OutlinedFinally) {} 1408 1409 void Emit(CodeGenFunction &CGF, Flags F) override { 1410 ASTContext &Context = CGF.getContext(); 1411 CodeGenModule &CGM = CGF.CGM; 1412 1413 CallArgList Args; 1414 1415 // Compute the two argument values. 1416 QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy}; 1417 llvm::Value *LocalAddrFn = CGM.getIntrinsic(llvm::Intrinsic::localaddress); 1418 llvm::Value *FP = CGF.Builder.CreateCall(LocalAddrFn); 1419 llvm::Value *IsForEH = 1420 llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup()); 1421 Args.add(RValue::get(IsForEH), ArgTys[0]); 1422 Args.add(RValue::get(FP), ArgTys[1]); 1423 1424 // Arrange a two-arg function info and type. 1425 FunctionProtoType::ExtProtoInfo EPI; 1426 const auto *FPT = cast<FunctionProtoType>( 1427 Context.getFunctionType(Context.VoidTy, ArgTys, EPI)); 1428 const CGFunctionInfo &FnInfo = 1429 CGM.getTypes().arrangeFreeFunctionCall(Args, FPT, 1430 /*chainCall=*/false); 1431 1432 CGF.EmitCall(FnInfo, OutlinedFinally, ReturnValueSlot(), Args); 1433 } 1434 }; 1435 } // end anonymous namespace 1436 1437 namespace { 1438 /// Find all local variable captures in the statement. 1439 struct CaptureFinder : ConstStmtVisitor<CaptureFinder> { 1440 CodeGenFunction &ParentCGF; 1441 const VarDecl *ParentThis; 1442 llvm::SmallSetVector<const VarDecl *, 4> Captures; 1443 Address SEHCodeSlot = Address::invalid(); 1444 CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis) 1445 : ParentCGF(ParentCGF), ParentThis(ParentThis) {} 1446 1447 // Return true if we need to do any capturing work. 1448 bool foundCaptures() { 1449 return !Captures.empty() || SEHCodeSlot.isValid(); 1450 } 1451 1452 void Visit(const Stmt *S) { 1453 // See if this is a capture, then recurse. 1454 ConstStmtVisitor<CaptureFinder>::Visit(S); 1455 for (const Stmt *Child : S->children()) 1456 if (Child) 1457 Visit(Child); 1458 } 1459 1460 void VisitDeclRefExpr(const DeclRefExpr *E) { 1461 // If this is already a capture, just make sure we capture 'this'. 1462 if (E->refersToEnclosingVariableOrCapture()) { 1463 Captures.insert(ParentThis); 1464 return; 1465 } 1466 1467 const auto *D = dyn_cast<VarDecl>(E->getDecl()); 1468 if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage()) 1469 Captures.insert(D); 1470 } 1471 1472 void VisitCXXThisExpr(const CXXThisExpr *E) { 1473 Captures.insert(ParentThis); 1474 } 1475 1476 void VisitCallExpr(const CallExpr *E) { 1477 // We only need to add parent frame allocations for these builtins in x86. 1478 if (ParentCGF.getTarget().getTriple().getArch() != llvm::Triple::x86) 1479 return; 1480 1481 unsigned ID = E->getBuiltinCallee(); 1482 switch (ID) { 1483 case Builtin::BI__exception_code: 1484 case Builtin::BI_exception_code: 1485 // This is the simple case where we are the outermost finally. All we 1486 // have to do here is make sure we escape this and recover it in the 1487 // outlined handler. 1488 if (!SEHCodeSlot.isValid()) 1489 SEHCodeSlot = ParentCGF.SEHCodeSlotStack.back(); 1490 break; 1491 } 1492 } 1493 }; 1494 } // end anonymous namespace 1495 1496 Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF, 1497 Address ParentVar, 1498 llvm::Value *ParentFP) { 1499 llvm::CallInst *RecoverCall = nullptr; 1500 CGBuilderTy Builder(*this, AllocaInsertPt); 1501 if (auto *ParentAlloca = dyn_cast<llvm::AllocaInst>(ParentVar.getPointer())) { 1502 // Mark the variable escaped if nobody else referenced it and compute the 1503 // localescape index. 1504 auto InsertPair = ParentCGF.EscapedLocals.insert( 1505 std::make_pair(ParentAlloca, ParentCGF.EscapedLocals.size())); 1506 int FrameEscapeIdx = InsertPair.first->second; 1507 // call i8* @llvm.localrecover(i8* bitcast(@parentFn), i8* %fp, i32 N) 1508 llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration( 1509 &CGM.getModule(), llvm::Intrinsic::localrecover); 1510 llvm::Constant *ParentI8Fn = 1511 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy); 1512 RecoverCall = Builder.CreateCall( 1513 FrameRecoverFn, {ParentI8Fn, ParentFP, 1514 llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)}); 1515 1516 } else { 1517 // If the parent didn't have an alloca, we're doing some nested outlining. 1518 // Just clone the existing localrecover call, but tweak the FP argument to 1519 // use our FP value. All other arguments are constants. 1520 auto *ParentRecover = 1521 cast<llvm::IntrinsicInst>(ParentVar.getPointer()->stripPointerCasts()); 1522 assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover && 1523 "expected alloca or localrecover in parent LocalDeclMap"); 1524 RecoverCall = cast<llvm::CallInst>(ParentRecover->clone()); 1525 RecoverCall->setArgOperand(1, ParentFP); 1526 RecoverCall->insertBefore(AllocaInsertPt); 1527 } 1528 1529 // Bitcast the variable, rename it, and insert it in the local decl map. 1530 llvm::Value *ChildVar = 1531 Builder.CreateBitCast(RecoverCall, ParentVar.getType()); 1532 ChildVar->setName(ParentVar.getName()); 1533 return Address(ChildVar, ParentVar.getAlignment()); 1534 } 1535 1536 void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF, 1537 const Stmt *OutlinedStmt, 1538 bool IsFilter) { 1539 // Find all captures in the Stmt. 1540 CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl); 1541 Finder.Visit(OutlinedStmt); 1542 1543 // We can exit early on x86_64 when there are no captures. We just have to 1544 // save the exception code in filters so that __exception_code() works. 1545 if (!Finder.foundCaptures() && 1546 CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) { 1547 if (IsFilter) 1548 EmitSEHExceptionCodeSave(ParentCGF, nullptr, nullptr); 1549 return; 1550 } 1551 1552 llvm::Value *EntryFP = nullptr; 1553 CGBuilderTy Builder(CGM, AllocaInsertPt); 1554 if (IsFilter && CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) { 1555 // 32-bit SEH filters need to be careful about FP recovery. The end of the 1556 // EH registration is passed in as the EBP physical register. We can 1557 // recover that with llvm.frameaddress(1). 1558 EntryFP = Builder.CreateCall( 1559 CGM.getIntrinsic(llvm::Intrinsic::frameaddress), {Builder.getInt32(1)}); 1560 } else { 1561 // Otherwise, for x64 and 32-bit finally functions, the parent FP is the 1562 // second parameter. 1563 auto AI = CurFn->arg_begin(); 1564 ++AI; 1565 EntryFP = &*AI; 1566 } 1567 1568 llvm::Value *ParentFP = EntryFP; 1569 if (IsFilter) { 1570 // Given whatever FP the runtime provided us in EntryFP, recover the true 1571 // frame pointer of the parent function. We only need to do this in filters, 1572 // since finally funclets recover the parent FP for us. 1573 llvm::Function *RecoverFPIntrin = 1574 CGM.getIntrinsic(llvm::Intrinsic::x86_seh_recoverfp); 1575 llvm::Constant *ParentI8Fn = 1576 llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy); 1577 ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryFP}); 1578 } 1579 1580 // Create llvm.localrecover calls for all captures. 1581 for (const VarDecl *VD : Finder.Captures) { 1582 if (isa<ImplicitParamDecl>(VD)) { 1583 CGM.ErrorUnsupported(VD, "'this' captured by SEH"); 1584 CXXThisValue = llvm::UndefValue::get(ConvertTypeForMem(VD->getType())); 1585 continue; 1586 } 1587 if (VD->getType()->isVariablyModifiedType()) { 1588 CGM.ErrorUnsupported(VD, "VLA captured by SEH"); 1589 continue; 1590 } 1591 assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) && 1592 "captured non-local variable"); 1593 1594 // If this decl hasn't been declared yet, it will be declared in the 1595 // OutlinedStmt. 1596 auto I = ParentCGF.LocalDeclMap.find(VD); 1597 if (I == ParentCGF.LocalDeclMap.end()) 1598 continue; 1599 1600 Address ParentVar = I->second; 1601 setAddrOfLocalVar( 1602 VD, recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP)); 1603 } 1604 1605 if (Finder.SEHCodeSlot.isValid()) { 1606 SEHCodeSlotStack.push_back( 1607 recoverAddrOfEscapedLocal(ParentCGF, Finder.SEHCodeSlot, ParentFP)); 1608 } 1609 1610 if (IsFilter) 1611 EmitSEHExceptionCodeSave(ParentCGF, ParentFP, EntryFP); 1612 } 1613 1614 /// Arrange a function prototype that can be called by Windows exception 1615 /// handling personalities. On Win64, the prototype looks like: 1616 /// RetTy func(void *EHPtrs, void *ParentFP); 1617 void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF, 1618 bool IsFilter, 1619 const Stmt *OutlinedStmt) { 1620 SourceLocation StartLoc = OutlinedStmt->getLocStart(); 1621 1622 // Get the mangled function name. 1623 SmallString<128> Name; 1624 { 1625 llvm::raw_svector_ostream OS(Name); 1626 const Decl *ParentCodeDecl = ParentCGF.CurCodeDecl; 1627 const NamedDecl *Parent = dyn_cast_or_null<NamedDecl>(ParentCodeDecl); 1628 assert(Parent && "FIXME: handle unnamed decls (lambdas, blocks) with SEH"); 1629 MangleContext &Mangler = CGM.getCXXABI().getMangleContext(); 1630 if (IsFilter) 1631 Mangler.mangleSEHFilterExpression(Parent, OS); 1632 else 1633 Mangler.mangleSEHFinallyBlock(Parent, OS); 1634 } 1635 1636 FunctionArgList Args; 1637 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 || !IsFilter) { 1638 // All SEH finally functions take two parameters. Win64 filters take two 1639 // parameters. Win32 filters take no parameters. 1640 if (IsFilter) { 1641 Args.push_back(ImplicitParamDecl::Create( 1642 getContext(), nullptr, StartLoc, 1643 &getContext().Idents.get("exception_pointers"), 1644 getContext().VoidPtrTy)); 1645 } else { 1646 Args.push_back(ImplicitParamDecl::Create( 1647 getContext(), nullptr, StartLoc, 1648 &getContext().Idents.get("abnormal_termination"), 1649 getContext().UnsignedCharTy)); 1650 } 1651 Args.push_back(ImplicitParamDecl::Create( 1652 getContext(), nullptr, StartLoc, 1653 &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy)); 1654 } 1655 1656 QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy; 1657 1658 llvm::Function *ParentFn = ParentCGF.CurFn; 1659 const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeFreeFunctionDeclaration( 1660 RetTy, Args, FunctionType::ExtInfo(), /*isVariadic=*/false); 1661 1662 llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo); 1663 llvm::Function *Fn = llvm::Function::Create( 1664 FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule()); 1665 // The filter is either in the same comdat as the function, or it's internal. 1666 if (llvm::Comdat *C = ParentFn->getComdat()) { 1667 Fn->setComdat(C); 1668 } else if (ParentFn->hasWeakLinkage() || ParentFn->hasLinkOnceLinkage()) { 1669 llvm::Comdat *C = CGM.getModule().getOrInsertComdat(ParentFn->getName()); 1670 ParentFn->setComdat(C); 1671 Fn->setComdat(C); 1672 } else { 1673 Fn->setLinkage(llvm::GlobalValue::InternalLinkage); 1674 } 1675 1676 IsOutlinedSEHHelper = true; 1677 1678 StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args, 1679 OutlinedStmt->getLocStart(), OutlinedStmt->getLocStart()); 1680 1681 CGM.SetLLVMFunctionAttributes(nullptr, FnInfo, CurFn); 1682 EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter); 1683 } 1684 1685 /// Create a stub filter function that will ultimately hold the code of the 1686 /// filter expression. The EH preparation passes in LLVM will outline the code 1687 /// from the main function body into this stub. 1688 llvm::Function * 1689 CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF, 1690 const SEHExceptStmt &Except) { 1691 const Expr *FilterExpr = Except.getFilterExpr(); 1692 startOutlinedSEHHelper(ParentCGF, true, FilterExpr); 1693 1694 // Emit the original filter expression, convert to i32, and return. 1695 llvm::Value *R = EmitScalarExpr(FilterExpr); 1696 R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy), 1697 FilterExpr->getType()->isSignedIntegerType()); 1698 Builder.CreateStore(R, ReturnValue); 1699 1700 FinishFunction(FilterExpr->getLocEnd()); 1701 1702 return CurFn; 1703 } 1704 1705 llvm::Function * 1706 CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF, 1707 const SEHFinallyStmt &Finally) { 1708 const Stmt *FinallyBlock = Finally.getBlock(); 1709 startOutlinedSEHHelper(ParentCGF, false, FinallyBlock); 1710 1711 // Mark finally block calls as nounwind and noinline to make LLVM's job a 1712 // little easier. 1713 // FIXME: Remove these restrictions in the future. 1714 CurFn->addFnAttr(llvm::Attribute::NoUnwind); 1715 CurFn->addFnAttr(llvm::Attribute::NoInline); 1716 1717 // Emit the original filter expression, convert to i32, and return. 1718 EmitStmt(FinallyBlock); 1719 1720 FinishFunction(FinallyBlock->getLocEnd()); 1721 1722 return CurFn; 1723 } 1724 1725 void CodeGenFunction::EmitSEHExceptionCodeSave(CodeGenFunction &ParentCGF, 1726 llvm::Value *ParentFP, 1727 llvm::Value *EntryFP) { 1728 // Get the pointer to the EXCEPTION_POINTERS struct. This is returned by the 1729 // __exception_info intrinsic. 1730 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) { 1731 // On Win64, the info is passed as the first parameter to the filter. 1732 SEHInfo = &*CurFn->arg_begin(); 1733 SEHCodeSlotStack.push_back( 1734 CreateMemTemp(getContext().IntTy, "__exception_code")); 1735 } else { 1736 // On Win32, the EBP on entry to the filter points to the end of an 1737 // exception registration object. It contains 6 32-bit fields, and the info 1738 // pointer is stored in the second field. So, GEP 20 bytes backwards and 1739 // load the pointer. 1740 SEHInfo = Builder.CreateConstInBoundsGEP1_32(Int8Ty, EntryFP, -20); 1741 SEHInfo = Builder.CreateBitCast(SEHInfo, Int8PtrTy->getPointerTo()); 1742 SEHInfo = Builder.CreateAlignedLoad(Int8PtrTy, SEHInfo, getPointerAlign()); 1743 SEHCodeSlotStack.push_back(recoverAddrOfEscapedLocal( 1744 ParentCGF, ParentCGF.SEHCodeSlotStack.back(), ParentFP)); 1745 } 1746 1747 // Save the exception code in the exception slot to unify exception access in 1748 // the filter function and the landing pad. 1749 // struct EXCEPTION_POINTERS { 1750 // EXCEPTION_RECORD *ExceptionRecord; 1751 // CONTEXT *ContextRecord; 1752 // }; 1753 // int exceptioncode = exception_pointers->ExceptionRecord->ExceptionCode; 1754 llvm::Type *RecordTy = CGM.Int32Ty->getPointerTo(); 1755 llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy, nullptr); 1756 llvm::Value *Ptrs = Builder.CreateBitCast(SEHInfo, PtrsTy->getPointerTo()); 1757 llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0); 1758 Rec = Builder.CreateAlignedLoad(Rec, getPointerAlign()); 1759 llvm::Value *Code = Builder.CreateAlignedLoad(Rec, getIntAlign()); 1760 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except"); 1761 Builder.CreateStore(Code, SEHCodeSlotStack.back()); 1762 } 1763 1764 llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() { 1765 // Sema should diagnose calling this builtin outside of a filter context, but 1766 // don't crash if we screw up. 1767 if (!SEHInfo) 1768 return llvm::UndefValue::get(Int8PtrTy); 1769 assert(SEHInfo->getType() == Int8PtrTy); 1770 return SEHInfo; 1771 } 1772 1773 llvm::Value *CodeGenFunction::EmitSEHExceptionCode() { 1774 assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except"); 1775 return Builder.CreateLoad(SEHCodeSlotStack.back()); 1776 } 1777 1778 llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() { 1779 // Abnormal termination is just the first parameter to the outlined finally 1780 // helper. 1781 auto AI = CurFn->arg_begin(); 1782 return Builder.CreateZExt(&*AI, Int32Ty); 1783 } 1784 1785 void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) { 1786 CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true); 1787 if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) { 1788 // Outline the finally block. 1789 llvm::Function *FinallyFunc = 1790 HelperCGF.GenerateSEHFinallyFunction(*this, *Finally); 1791 1792 // Push a cleanup for __finally blocks. 1793 EHStack.pushCleanup<PerformSEHFinally>(NormalAndEHCleanup, FinallyFunc); 1794 return; 1795 } 1796 1797 // Otherwise, we must have an __except block. 1798 const SEHExceptStmt *Except = S.getExceptHandler(); 1799 assert(Except); 1800 EHCatchScope *CatchScope = EHStack.pushCatch(1); 1801 SEHCodeSlotStack.push_back( 1802 CreateMemTemp(getContext().IntTy, "__exception_code")); 1803 1804 // If the filter is known to evaluate to 1, then we can use the clause 1805 // "catch i8* null". We can't do this on x86 because the filter has to save 1806 // the exception code. 1807 llvm::Constant *C = 1808 CGM.EmitConstantExpr(Except->getFilterExpr(), getContext().IntTy, this); 1809 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 && C && 1810 C->isOneValue()) { 1811 CatchScope->setCatchAllHandler(0, createBasicBlock("__except")); 1812 return; 1813 } 1814 1815 // In general, we have to emit an outlined filter function. Use the function 1816 // in place of the RTTI typeinfo global that C++ EH uses. 1817 llvm::Function *FilterFunc = 1818 HelperCGF.GenerateSEHFilterFunction(*this, *Except); 1819 llvm::Constant *OpaqueFunc = 1820 llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy); 1821 CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except.ret")); 1822 } 1823 1824 void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) { 1825 // Just pop the cleanup if it's a __finally block. 1826 if (S.getFinallyHandler()) { 1827 PopCleanupBlock(); 1828 return; 1829 } 1830 1831 // Otherwise, we must have an __except block. 1832 const SEHExceptStmt *Except = S.getExceptHandler(); 1833 assert(Except && "__try must have __finally xor __except"); 1834 EHCatchScope &CatchScope = cast<EHCatchScope>(*EHStack.begin()); 1835 1836 // Don't emit the __except block if the __try block lacked invokes. 1837 // TODO: Model unwind edges from instructions, either with iload / istore or 1838 // a try body function. 1839 if (!CatchScope.hasEHBranches()) { 1840 CatchScope.clearHandlerBlocks(); 1841 EHStack.popCatch(); 1842 SEHCodeSlotStack.pop_back(); 1843 return; 1844 } 1845 1846 // The fall-through block. 1847 llvm::BasicBlock *ContBB = createBasicBlock("__try.cont"); 1848 1849 // We just emitted the body of the __try; jump to the continue block. 1850 if (HaveInsertPoint()) 1851 Builder.CreateBr(ContBB); 1852 1853 // Check if our filter function returned true. 1854 emitCatchDispatchBlock(*this, CatchScope); 1855 1856 // Grab the block before we pop the handler. 1857 llvm::BasicBlock *CatchPadBB = CatchScope.getHandler(0).Block; 1858 EHStack.popCatch(); 1859 1860 EmitBlockAfterUses(CatchPadBB); 1861 1862 // __except blocks don't get outlined into funclets, so immediately do a 1863 // catchret. 1864 llvm::CatchPadInst *CPI = 1865 cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHI()); 1866 llvm::BasicBlock *ExceptBB = createBasicBlock("__except"); 1867 Builder.CreateCatchRet(CPI, ExceptBB); 1868 EmitBlock(ExceptBB); 1869 1870 // On Win64, the exception code is returned in EAX. Copy it into the slot. 1871 if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) { 1872 llvm::Function *SEHCodeIntrin = 1873 CGM.getIntrinsic(llvm::Intrinsic::eh_exceptioncode); 1874 llvm::Value *Code = Builder.CreateCall(SEHCodeIntrin, {CPI}); 1875 Builder.CreateStore(Code, SEHCodeSlotStack.back()); 1876 } 1877 1878 // Emit the __except body. 1879 EmitStmt(Except->getBlock()); 1880 1881 // End the lifetime of the exception code. 1882 SEHCodeSlotStack.pop_back(); 1883 1884 if (HaveInsertPoint()) 1885 Builder.CreateBr(ContBB); 1886 1887 EmitBlock(ContBB); 1888 } 1889 1890 void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) { 1891 // If this code is reachable then emit a stop point (if generating 1892 // debug info). We have to do this ourselves because we are on the 1893 // "simple" statement path. 1894 if (HaveInsertPoint()) 1895 EmitStopPoint(&S); 1896 1897 // This must be a __leave from a __finally block, which we warn on and is UB. 1898 // Just emit unreachable. 1899 if (!isSEHTryScope()) { 1900 Builder.CreateUnreachable(); 1901 Builder.ClearInsertionPoint(); 1902 return; 1903 } 1904 1905 EmitBranchThroughCleanup(*SEHTryEpilogueStack.back()); 1906 } 1907