//===--- CGException.cpp - Emit LLVM Code for C++ exceptions ----*- C++ -*-===// // // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. // See https://llvm.org/LICENSE.txt for license information. // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception // //===----------------------------------------------------------------------===// // // This contains code dealing with C++ exception related code generation. // //===----------------------------------------------------------------------===// #include "CGCXXABI.h" #include "CGCleanup.h" #include "CGObjCRuntime.h" #include "CodeGenFunction.h" #include "ConstantEmitter.h" #include "TargetInfo.h" #include "clang/AST/Mangle.h" #include "clang/AST/StmtCXX.h" #include "clang/AST/StmtObjC.h" #include "clang/AST/StmtVisitor.h" #include "clang/Basic/DiagnosticSema.h" #include "clang/Basic/TargetBuiltins.h" #include "llvm/IR/IntrinsicInst.h" #include "llvm/IR/Intrinsics.h" #include "llvm/IR/IntrinsicsWebAssembly.h" #include "llvm/Support/SaveAndRestore.h" using namespace clang; using namespace CodeGen; static llvm::FunctionCallee getFreeExceptionFn(CodeGenModule &CGM) { // void __cxa_free_exception(void *thrown_exception); llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception"); } static llvm::FunctionCallee getSehTryBeginFn(CodeGenModule &CGM) { llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "llvm.seh.try.begin"); } static llvm::FunctionCallee getSehTryEndFn(CodeGenModule &CGM) { llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "llvm.seh.try.end"); } static llvm::FunctionCallee getUnexpectedFn(CodeGenModule &CGM) { // void __cxa_call_unexpected(void *thrown_exception); llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected"); } llvm::FunctionCallee CodeGenModule::getTerminateFn() { // void __terminate(); llvm::FunctionType *FTy = llvm::FunctionType::get(VoidTy, /*isVarArg=*/false); StringRef name; // In C++, use std::terminate(). if (getLangOpts().CPlusPlus && getTarget().getCXXABI().isItaniumFamily()) { name = "_ZSt9terminatev"; } else if (getLangOpts().CPlusPlus && getTarget().getCXXABI().isMicrosoft()) { if (getLangOpts().isCompatibleWithMSVC(LangOptions::MSVC2015)) name = "__std_terminate"; else name = "?terminate@@YAXXZ"; } else if (getLangOpts().ObjC && getLangOpts().ObjCRuntime.hasTerminate()) name = "objc_terminate"; else name = "abort"; return CreateRuntimeFunction(FTy, name); } static llvm::FunctionCallee getCatchallRethrowFn(CodeGenModule &CGM, StringRef Name) { llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false); return CGM.CreateRuntimeFunction(FTy, Name); } const EHPersonality EHPersonality::GNU_C = { "__gcc_personality_v0", nullptr }; const EHPersonality EHPersonality::GNU_C_SJLJ = { "__gcc_personality_sj0", nullptr }; const EHPersonality EHPersonality::GNU_C_SEH = { "__gcc_personality_seh0", nullptr }; const EHPersonality EHPersonality::NeXT_ObjC = { "__objc_personality_v0", nullptr }; const EHPersonality EHPersonality::GNU_CPlusPlus = { "__gxx_personality_v0", nullptr }; const EHPersonality EHPersonality::GNU_CPlusPlus_SJLJ = { "__gxx_personality_sj0", nullptr }; const EHPersonality EHPersonality::GNU_CPlusPlus_SEH = { "__gxx_personality_seh0", nullptr }; const EHPersonality EHPersonality::GNU_ObjC = {"__gnu_objc_personality_v0", "objc_exception_throw"}; const EHPersonality EHPersonality::GNU_ObjC_SJLJ = {"__gnu_objc_personality_sj0", "objc_exception_throw"}; const EHPersonality EHPersonality::GNU_ObjC_SEH = {"__gnu_objc_personality_seh0", "objc_exception_throw"}; const EHPersonality EHPersonality::GNU_ObjCXX = { "__gnustep_objcxx_personality_v0", nullptr }; const EHPersonality EHPersonality::GNUstep_ObjC = { "__gnustep_objc_personality_v0", nullptr }; const EHPersonality EHPersonality::MSVC_except_handler = { "_except_handler3", nullptr }; const EHPersonality EHPersonality::MSVC_C_specific_handler = { "__C_specific_handler", nullptr }; const EHPersonality EHPersonality::MSVC_CxxFrameHandler3 = { "__CxxFrameHandler3", nullptr }; const EHPersonality EHPersonality::GNU_Wasm_CPlusPlus = { "__gxx_wasm_personality_v0", nullptr }; const EHPersonality EHPersonality::XL_CPlusPlus = {"__xlcxx_personality_v1", nullptr}; const EHPersonality EHPersonality::ZOS_CPlusPlus = {"__zos_cxx_personality_v2", nullptr}; static const EHPersonality &getCPersonality(const TargetInfo &Target, const LangOptions &L) { const llvm::Triple &T = Target.getTriple(); if (T.isWindowsMSVCEnvironment()) return EHPersonality::MSVC_CxxFrameHandler3; if (L.hasSjLjExceptions()) return EHPersonality::GNU_C_SJLJ; if (L.hasDWARFExceptions()) return EHPersonality::GNU_C; if (L.hasSEHExceptions()) return EHPersonality::GNU_C_SEH; return EHPersonality::GNU_C; } static const EHPersonality &getObjCPersonality(const TargetInfo &Target, const LangOptions &L) { const llvm::Triple &T = Target.getTriple(); if (T.isWindowsMSVCEnvironment()) return EHPersonality::MSVC_CxxFrameHandler3; switch (L.ObjCRuntime.getKind()) { case ObjCRuntime::FragileMacOSX: return getCPersonality(Target, L); case ObjCRuntime::MacOSX: case ObjCRuntime::iOS: case ObjCRuntime::WatchOS: return EHPersonality::NeXT_ObjC; case ObjCRuntime::GNUstep: if (T.isOSCygMing()) return EHPersonality::GNU_CPlusPlus_SEH; else if (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7)) return EHPersonality::GNUstep_ObjC; [[fallthrough]]; case ObjCRuntime::GCC: case ObjCRuntime::ObjFW: if (L.hasSjLjExceptions()) return EHPersonality::GNU_ObjC_SJLJ; if (L.hasSEHExceptions()) return EHPersonality::GNU_ObjC_SEH; return EHPersonality::GNU_ObjC; } llvm_unreachable("bad runtime kind"); } static const EHPersonality &getCXXPersonality(const TargetInfo &Target, const LangOptions &L) { const llvm::Triple &T = Target.getTriple(); if (T.isWindowsMSVCEnvironment()) return EHPersonality::MSVC_CxxFrameHandler3; if (T.isOSAIX()) return EHPersonality::XL_CPlusPlus; if (L.hasSjLjExceptions()) return EHPersonality::GNU_CPlusPlus_SJLJ; if (L.hasDWARFExceptions()) return EHPersonality::GNU_CPlusPlus; if (L.hasSEHExceptions()) return EHPersonality::GNU_CPlusPlus_SEH; if (L.hasWasmExceptions()) return EHPersonality::GNU_Wasm_CPlusPlus; if (T.isOSzOS()) return EHPersonality::ZOS_CPlusPlus; return EHPersonality::GNU_CPlusPlus; } /// Determines the personality function to use when both C++ /// and Objective-C exceptions are being caught. static const EHPersonality &getObjCXXPersonality(const TargetInfo &Target, const LangOptions &L) { if (Target.getTriple().isWindowsMSVCEnvironment()) return EHPersonality::MSVC_CxxFrameHandler3; switch (L.ObjCRuntime.getKind()) { // In the fragile ABI, just use C++ exception handling and hope // they're not doing crazy exception mixing. case ObjCRuntime::FragileMacOSX: return getCXXPersonality(Target, L); // The ObjC personality defers to the C++ personality for non-ObjC // handlers. Unlike the C++ case, we use the same personality // function on targets using (backend-driven) SJLJ EH. case ObjCRuntime::MacOSX: case ObjCRuntime::iOS: case ObjCRuntime::WatchOS: return getObjCPersonality(Target, L); case ObjCRuntime::GNUstep: return Target.getTriple().isOSCygMing() ? EHPersonality::GNU_CPlusPlus_SEH : EHPersonality::GNU_ObjCXX; // The GCC runtime's personality function inherently doesn't support // mixed EH. Use the ObjC personality just to avoid returning null. case ObjCRuntime::GCC: case ObjCRuntime::ObjFW: return getObjCPersonality(Target, L); } llvm_unreachable("bad runtime kind"); } static const EHPersonality &getSEHPersonalityMSVC(const llvm::Triple &T) { if (T.getArch() == llvm::Triple::x86) return EHPersonality::MSVC_except_handler; return EHPersonality::MSVC_C_specific_handler; } const EHPersonality &EHPersonality::get(CodeGenModule &CGM, const FunctionDecl *FD) { const llvm::Triple &T = CGM.getTarget().getTriple(); const LangOptions &L = CGM.getLangOpts(); const TargetInfo &Target = CGM.getTarget(); // Functions using SEH get an SEH personality. if (FD && FD->usesSEHTry()) return getSEHPersonalityMSVC(T); if (L.ObjC) return L.CPlusPlus ? getObjCXXPersonality(Target, L) : getObjCPersonality(Target, L); return L.CPlusPlus ? getCXXPersonality(Target, L) : getCPersonality(Target, L); } const EHPersonality &EHPersonality::get(CodeGenFunction &CGF) { const auto *FD = CGF.CurCodeDecl; // For outlined finallys and filters, use the SEH personality in case they // contain more SEH. This mostly only affects finallys. Filters could // hypothetically use gnu statement expressions to sneak in nested SEH. FD = FD ? FD : CGF.CurSEHParent.getDecl(); return get(CGF.CGM, dyn_cast_or_null(FD)); } static llvm::FunctionCallee getPersonalityFn(CodeGenModule &CGM, const EHPersonality &Personality) { return CGM.CreateRuntimeFunction(llvm::FunctionType::get(CGM.Int32Ty, true), Personality.PersonalityFn, llvm::AttributeList(), /*Local=*/true); } static llvm::Constant *getOpaquePersonalityFn(CodeGenModule &CGM, const EHPersonality &Personality) { llvm::FunctionCallee Fn = getPersonalityFn(CGM, Personality); return cast(Fn.getCallee()); } /// Check whether a landingpad instruction only uses C++ features. static bool LandingPadHasOnlyCXXUses(llvm::LandingPadInst *LPI) { for (unsigned I = 0, E = LPI->getNumClauses(); I != E; ++I) { // Look for something that would've been returned by the ObjC // runtime's GetEHType() method. llvm::Value *Val = LPI->getClause(I)->stripPointerCasts(); if (LPI->isCatch(I)) { // Check if the catch value has the ObjC prefix. if (llvm::GlobalVariable *GV = dyn_cast(Val)) // ObjC EH selector entries are always global variables with // names starting like this. if (GV->getName().starts_with("OBJC_EHTYPE")) return false; } else { // Check if any of the filter values have the ObjC prefix. llvm::Constant *CVal = cast(Val); for (llvm::User::op_iterator II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) { if (llvm::GlobalVariable *GV = cast((*II)->stripPointerCasts())) // ObjC EH selector entries are always global variables with // names starting like this. if (GV->getName().starts_with("OBJC_EHTYPE")) return false; } } } return true; } /// Check whether a personality function could reasonably be swapped /// for a C++ personality function. static bool PersonalityHasOnlyCXXUses(llvm::Constant *Fn) { for (llvm::User *U : Fn->users()) { // Conditionally white-list bitcasts. if (llvm::ConstantExpr *CE = dyn_cast(U)) { if (CE->getOpcode() != llvm::Instruction::BitCast) return false; if (!PersonalityHasOnlyCXXUses(CE)) return false; continue; } // Otherwise it must be a function. llvm::Function *F = dyn_cast(U); if (!F) return false; for (auto BB = F->begin(), E = F->end(); BB != E; ++BB) { if (BB->isLandingPad()) if (!LandingPadHasOnlyCXXUses(BB->getLandingPadInst())) return false; } } return true; } /// Try to use the C++ personality function in ObjC++. Not doing this /// can cause some incompatibilities with gcc, which is more /// aggressive about only using the ObjC++ personality in a function /// when it really needs it. void CodeGenModule::SimplifyPersonality() { // If we're not in ObjC++ -fexceptions, there's nothing to do. if (!LangOpts.CPlusPlus || !LangOpts.ObjC || !LangOpts.Exceptions) return; // Both the problem this endeavors to fix and the way the logic // above works is specific to the NeXT runtime. if (!LangOpts.ObjCRuntime.isNeXTFamily()) return; const EHPersonality &ObjCXX = EHPersonality::get(*this, /*FD=*/nullptr); const EHPersonality &CXX = getCXXPersonality(getTarget(), LangOpts); if (&ObjCXX == &CXX) return; assert(std::strcmp(ObjCXX.PersonalityFn, CXX.PersonalityFn) != 0 && "Different EHPersonalities using the same personality function."); llvm::Function *Fn = getModule().getFunction(ObjCXX.PersonalityFn); // Nothing to do if it's unused. if (!Fn || Fn->use_empty()) return; // Can't do the optimization if it has non-C++ uses. if (!PersonalityHasOnlyCXXUses(Fn)) return; // Create the C++ personality function and kill off the old // function. llvm::FunctionCallee CXXFn = getPersonalityFn(*this, CXX); // This can happen if the user is screwing with us. if (Fn->getType() != CXXFn.getCallee()->getType()) return; Fn->replaceAllUsesWith(CXXFn.getCallee()); Fn->eraseFromParent(); } /// Returns the value to inject into a selector to indicate the /// presence of a catch-all. static llvm::Constant *getCatchAllValue(CodeGenFunction &CGF) { // Possibly we should use @llvm.eh.catch.all.value here. return llvm::ConstantPointerNull::get(CGF.Int8PtrTy); } namespace { /// A cleanup to free the exception object if its initialization /// throws. struct FreeException final : EHScopeStack::Cleanup { llvm::Value *exn; FreeException(llvm::Value *exn) : exn(exn) {} void Emit(CodeGenFunction &CGF, Flags flags) override { CGF.EmitNounwindRuntimeCall(getFreeExceptionFn(CGF.CGM), exn); } }; } // end anonymous namespace // Emits an exception expression into the given location. This // differs from EmitAnyExprToMem only in that, if a final copy-ctor // call is required, an exception within that copy ctor causes // std::terminate to be invoked. void CodeGenFunction::EmitAnyExprToExn(const Expr *e, Address addr) { // Make sure the exception object is cleaned up if there's an // exception during initialization. pushFullExprCleanup(EHCleanup, addr.getPointer()); EHScopeStack::stable_iterator cleanup = EHStack.stable_begin(); // __cxa_allocate_exception returns a void*; we need to cast this // to the appropriate type for the object. llvm::Type *ty = ConvertTypeForMem(e->getType()); Address typedAddr = addr.withElementType(ty); // FIXME: this isn't quite right! If there's a final unelided call // to a copy constructor, then according to [except.terminate]p1 we // must call std::terminate() if that constructor throws, because // technically that copy occurs after the exception expression is // evaluated but before the exception is caught. But the best way // to handle that is to teach EmitAggExpr to do the final copy // differently if it can't be elided. EmitAnyExprToMem(e, typedAddr, e->getType().getQualifiers(), /*IsInit*/ true); // Deactivate the cleanup block. DeactivateCleanupBlock(cleanup, cast(typedAddr.getPointer())); } Address CodeGenFunction::getExceptionSlot() { if (!ExceptionSlot) ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot"); return Address(ExceptionSlot, Int8PtrTy, getPointerAlign()); } Address CodeGenFunction::getEHSelectorSlot() { if (!EHSelectorSlot) EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot"); return Address(EHSelectorSlot, Int32Ty, CharUnits::fromQuantity(4)); } llvm::Value *CodeGenFunction::getExceptionFromSlot() { return Builder.CreateLoad(getExceptionSlot(), "exn"); } llvm::Value *CodeGenFunction::getSelectorFromSlot() { return Builder.CreateLoad(getEHSelectorSlot(), "sel"); } void CodeGenFunction::EmitCXXThrowExpr(const CXXThrowExpr *E, bool KeepInsertionPoint) { // If the exception is being emitted in an OpenMP target region, // and the target is a GPU, we do not support exception handling. // Therefore, we emit a trap which will abort the program, and // prompt a warning indicating that a trap will be emitted. const llvm::Triple &T = Target.getTriple(); if (CGM.getLangOpts().OpenMPIsTargetDevice && (T.isNVPTX() || T.isAMDGCN())) { EmitTrapCall(llvm::Intrinsic::trap); return; } if (const Expr *SubExpr = E->getSubExpr()) { QualType ThrowType = SubExpr->getType(); if (ThrowType->isObjCObjectPointerType()) { const Stmt *ThrowStmt = E->getSubExpr(); const ObjCAtThrowStmt S(E->getExprLoc(), const_cast(ThrowStmt)); CGM.getObjCRuntime().EmitThrowStmt(*this, S, false); } else { CGM.getCXXABI().emitThrow(*this, E); } } else { CGM.getCXXABI().emitRethrow(*this, /*isNoReturn=*/true); } // throw is an expression, and the expression emitters expect us // to leave ourselves at a valid insertion point. if (KeepInsertionPoint) EmitBlock(createBasicBlock("throw.cont")); } void CodeGenFunction::EmitStartEHSpec(const Decl *D) { if (!CGM.getLangOpts().CXXExceptions) return; const FunctionDecl* FD = dyn_cast_or_null(D); if (!FD) { // Check if CapturedDecl is nothrow and create terminate scope for it. if (const CapturedDecl* CD = dyn_cast_or_null(D)) { if (CD->isNothrow()) EHStack.pushTerminate(); } return; } const FunctionProtoType *Proto = FD->getType()->getAs(); if (!Proto) return; ExceptionSpecificationType EST = Proto->getExceptionSpecType(); // In C++17 and later, 'throw()' aka EST_DynamicNone is treated the same way // as noexcept. In earlier standards, it is handled in this block, along with // 'throw(X...)'. if (EST == EST_Dynamic || (EST == EST_DynamicNone && !getLangOpts().CPlusPlus17)) { // TODO: Revisit exception specifications for the MS ABI. There is a way to // encode these in an object file but MSVC doesn't do anything with it. if (getTarget().getCXXABI().isMicrosoft()) return; // In Wasm EH we currently treat 'throw()' in the same way as 'noexcept'. In // case of throw with types, we ignore it and print a warning for now. // TODO Correctly handle exception specification in Wasm EH if (CGM.getLangOpts().hasWasmExceptions()) { if (EST == EST_DynamicNone) EHStack.pushTerminate(); else CGM.getDiags().Report(D->getLocation(), diag::warn_wasm_dynamic_exception_spec_ignored) << FD->getExceptionSpecSourceRange(); return; } // Currently Emscripten EH only handles 'throw()' but not 'throw' with // types. 'throw()' handling will be done in JS glue code so we don't need // to do anything in that case. Just print a warning message in case of // throw with types. // TODO Correctly handle exception specification in Emscripten EH if (getTarget().getCXXABI() == TargetCXXABI::WebAssembly && CGM.getLangOpts().getExceptionHandling() == LangOptions::ExceptionHandlingKind::None && EST == EST_Dynamic) CGM.getDiags().Report(D->getLocation(), diag::warn_wasm_dynamic_exception_spec_ignored) << FD->getExceptionSpecSourceRange(); unsigned NumExceptions = Proto->getNumExceptions(); EHFilterScope *Filter = EHStack.pushFilter(NumExceptions); for (unsigned I = 0; I != NumExceptions; ++I) { QualType Ty = Proto->getExceptionType(I); QualType ExceptType = Ty.getNonReferenceType().getUnqualifiedType(); llvm::Value *EHType = CGM.GetAddrOfRTTIDescriptor(ExceptType, /*ForEH=*/true); Filter->setFilter(I, EHType); } } else if (Proto->canThrow() == CT_Cannot) { // noexcept functions are simple terminate scopes. if (!getLangOpts().EHAsynch) // -EHa: HW exception still can occur EHStack.pushTerminate(); } } /// Emit the dispatch block for a filter scope if necessary. static void emitFilterDispatchBlock(CodeGenFunction &CGF, EHFilterScope &filterScope) { llvm::BasicBlock *dispatchBlock = filterScope.getCachedEHDispatchBlock(); if (!dispatchBlock) return; if (dispatchBlock->use_empty()) { delete dispatchBlock; return; } CGF.EmitBlockAfterUses(dispatchBlock); // If this isn't a catch-all filter, we need to check whether we got // here because the filter triggered. if (filterScope.getNumFilters()) { // Load the selector value. llvm::Value *selector = CGF.getSelectorFromSlot(); llvm::BasicBlock *unexpectedBB = CGF.createBasicBlock("ehspec.unexpected"); llvm::Value *zero = CGF.Builder.getInt32(0); llvm::Value *failsFilter = CGF.Builder.CreateICmpSLT(selector, zero, "ehspec.fails"); CGF.Builder.CreateCondBr(failsFilter, unexpectedBB, CGF.getEHResumeBlock(false)); CGF.EmitBlock(unexpectedBB); } // Call __cxa_call_unexpected. This doesn't need to be an invoke // because __cxa_call_unexpected magically filters exceptions // according to the last landing pad the exception was thrown // into. Seriously. llvm::Value *exn = CGF.getExceptionFromSlot(); CGF.EmitRuntimeCall(getUnexpectedFn(CGF.CGM), exn) ->setDoesNotReturn(); CGF.Builder.CreateUnreachable(); } void CodeGenFunction::EmitEndEHSpec(const Decl *D) { if (!CGM.getLangOpts().CXXExceptions) return; const FunctionDecl* FD = dyn_cast_or_null(D); if (!FD) { // Check if CapturedDecl is nothrow and pop terminate scope for it. if (const CapturedDecl* CD = dyn_cast_or_null(D)) { if (CD->isNothrow() && !EHStack.empty()) EHStack.popTerminate(); } return; } const FunctionProtoType *Proto = FD->getType()->getAs(); if (!Proto) return; ExceptionSpecificationType EST = Proto->getExceptionSpecType(); if (EST == EST_Dynamic || (EST == EST_DynamicNone && !getLangOpts().CPlusPlus17)) { // TODO: Revisit exception specifications for the MS ABI. There is a way to // encode these in an object file but MSVC doesn't do anything with it. if (getTarget().getCXXABI().isMicrosoft()) return; // In wasm we currently treat 'throw()' in the same way as 'noexcept'. In // case of throw with types, we ignore it and print a warning for now. // TODO Correctly handle exception specification in wasm if (CGM.getLangOpts().hasWasmExceptions()) { if (EST == EST_DynamicNone) EHStack.popTerminate(); return; } EHFilterScope &filterScope = cast(*EHStack.begin()); emitFilterDispatchBlock(*this, filterScope); EHStack.popFilter(); } else if (Proto->canThrow() == CT_Cannot && /* possible empty when under async exceptions */ !EHStack.empty()) { EHStack.popTerminate(); } } void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) { const llvm::Triple &T = Target.getTriple(); // If we encounter a try statement on in an OpenMP target region offloaded to // a GPU, we treat it as a basic block. const bool IsTargetDevice = (CGM.getLangOpts().OpenMPIsTargetDevice && (T.isNVPTX() || T.isAMDGCN())); if (!IsTargetDevice) EnterCXXTryStmt(S); EmitStmt(S.getTryBlock()); if (!IsTargetDevice) ExitCXXTryStmt(S); } void CodeGenFunction::EnterCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { unsigned NumHandlers = S.getNumHandlers(); EHCatchScope *CatchScope = EHStack.pushCatch(NumHandlers); for (unsigned I = 0; I != NumHandlers; ++I) { const CXXCatchStmt *C = S.getHandler(I); llvm::BasicBlock *Handler = createBasicBlock("catch"); if (C->getExceptionDecl()) { // FIXME: Dropping the reference type on the type into makes it // impossible to correctly implement catch-by-reference // semantics for pointers. Unfortunately, this is what all // existing compilers do, and it's not clear that the standard // personality routine is capable of doing this right. See C++ DR 388: // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#388 Qualifiers CaughtTypeQuals; QualType CaughtType = CGM.getContext().getUnqualifiedArrayType( C->getCaughtType().getNonReferenceType(), CaughtTypeQuals); CatchTypeInfo TypeInfo{nullptr, 0}; if (CaughtType->isObjCObjectPointerType()) TypeInfo.RTTI = CGM.getObjCRuntime().GetEHType(CaughtType); else TypeInfo = CGM.getCXXABI().getAddrOfCXXCatchHandlerType( CaughtType, C->getCaughtType()); CatchScope->setHandler(I, TypeInfo, Handler); } else { // No exception decl indicates '...', a catch-all. CatchScope->setHandler(I, CGM.getCXXABI().getCatchAllTypeInfo(), Handler); // Under async exceptions, catch(...) need to catch HW exception too // Mark scope with SehTryBegin as a SEH __try scope if (getLangOpts().EHAsynch) EmitSehTryScopeBegin(); } } } llvm::BasicBlock * CodeGenFunction::getEHDispatchBlock(EHScopeStack::stable_iterator si) { if (EHPersonality::get(*this).usesFuncletPads()) return getFuncletEHDispatchBlock(si); // The dispatch block for the end of the scope chain is a block that // just resumes unwinding. if (si == EHStack.stable_end()) return getEHResumeBlock(true); // Otherwise, we should look at the actual scope. EHScope &scope = *EHStack.find(si); llvm::BasicBlock *dispatchBlock = scope.getCachedEHDispatchBlock(); if (!dispatchBlock) { switch (scope.getKind()) { case EHScope::Catch: { // Apply a special case to a single catch-all. EHCatchScope &catchScope = cast(scope); if (catchScope.getNumHandlers() == 1 && catchScope.getHandler(0).isCatchAll()) { dispatchBlock = catchScope.getHandler(0).Block; // Otherwise, make a dispatch block. } else { dispatchBlock = createBasicBlock("catch.dispatch"); } break; } case EHScope::Cleanup: dispatchBlock = createBasicBlock("ehcleanup"); break; case EHScope::Filter: dispatchBlock = createBasicBlock("filter.dispatch"); break; case EHScope::Terminate: dispatchBlock = getTerminateHandler(); break; } scope.setCachedEHDispatchBlock(dispatchBlock); } return dispatchBlock; } llvm::BasicBlock * CodeGenFunction::getFuncletEHDispatchBlock(EHScopeStack::stable_iterator SI) { // Returning nullptr indicates that the previous dispatch block should unwind // to caller. if (SI == EHStack.stable_end()) return nullptr; // Otherwise, we should look at the actual scope. EHScope &EHS = *EHStack.find(SI); llvm::BasicBlock *DispatchBlock = EHS.getCachedEHDispatchBlock(); if (DispatchBlock) return DispatchBlock; if (EHS.getKind() == EHScope::Terminate) DispatchBlock = getTerminateFunclet(); else DispatchBlock = createBasicBlock(); CGBuilderTy Builder(*this, DispatchBlock); switch (EHS.getKind()) { case EHScope::Catch: DispatchBlock->setName("catch.dispatch"); break; case EHScope::Cleanup: DispatchBlock->setName("ehcleanup"); break; case EHScope::Filter: llvm_unreachable("exception specifications not handled yet!"); case EHScope::Terminate: DispatchBlock->setName("terminate"); break; } EHS.setCachedEHDispatchBlock(DispatchBlock); return DispatchBlock; } /// Check whether this is a non-EH scope, i.e. a scope which doesn't /// affect exception handling. Currently, the only non-EH scopes are /// normal-only cleanup scopes. static bool isNonEHScope(const EHScope &S) { switch (S.getKind()) { case EHScope::Cleanup: return !cast(S).isEHCleanup(); case EHScope::Filter: case EHScope::Catch: case EHScope::Terminate: return false; } llvm_unreachable("Invalid EHScope Kind!"); } llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() { assert(EHStack.requiresLandingPad()); assert(!EHStack.empty()); // If exceptions are disabled/ignored and SEH is not in use, then there is no // invoke destination. SEH "works" even if exceptions are off. In practice, // this means that C++ destructors and other EH cleanups don't run, which is // consistent with MSVC's behavior, except in the presence of -EHa const LangOptions &LO = CGM.getLangOpts(); if (!LO.Exceptions || LO.IgnoreExceptions) { if (!LO.Borland && !LO.MicrosoftExt) return nullptr; if (!currentFunctionUsesSEHTry()) return nullptr; } // CUDA device code doesn't have exceptions. if (LO.CUDA && LO.CUDAIsDevice) return nullptr; // Check the innermost scope for a cached landing pad. If this is // a non-EH cleanup, we'll check enclosing scopes in EmitLandingPad. llvm::BasicBlock *LP = EHStack.begin()->getCachedLandingPad(); if (LP) return LP; const EHPersonality &Personality = EHPersonality::get(*this); if (!CurFn->hasPersonalityFn()) CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality)); if (Personality.usesFuncletPads()) { // We don't need separate landing pads in the funclet model. LP = getEHDispatchBlock(EHStack.getInnermostEHScope()); } else { // Build the landing pad for this scope. LP = EmitLandingPad(); } assert(LP); // Cache the landing pad on the innermost scope. If this is a // non-EH scope, cache the landing pad on the enclosing scope, too. for (EHScopeStack::iterator ir = EHStack.begin(); true; ++ir) { ir->setCachedLandingPad(LP); if (!isNonEHScope(*ir)) break; } return LP; } llvm::BasicBlock *CodeGenFunction::EmitLandingPad() { assert(EHStack.requiresLandingPad()); assert(!CGM.getLangOpts().IgnoreExceptions && "LandingPad should not be emitted when -fignore-exceptions are in " "effect."); EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope()); switch (innermostEHScope.getKind()) { case EHScope::Terminate: return getTerminateLandingPad(); case EHScope::Catch: case EHScope::Cleanup: case EHScope::Filter: if (llvm::BasicBlock *lpad = innermostEHScope.getCachedLandingPad()) return lpad; } // Save the current IR generation state. CGBuilderTy::InsertPoint savedIP = Builder.saveAndClearIP(); auto DL = ApplyDebugLocation::CreateDefaultArtificial(*this, CurEHLocation); // Create and configure the landing pad. llvm::BasicBlock *lpad = createBasicBlock("lpad"); EmitBlock(lpad); llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty), 0); llvm::Value *LPadExn = Builder.CreateExtractValue(LPadInst, 0); Builder.CreateStore(LPadExn, getExceptionSlot()); llvm::Value *LPadSel = Builder.CreateExtractValue(LPadInst, 1); Builder.CreateStore(LPadSel, getEHSelectorSlot()); // Save the exception pointer. It's safe to use a single exception // pointer per function because EH cleanups can never have nested // try/catches. // Build the landingpad instruction. // Accumulate all the handlers in scope. bool hasCatchAll = false; bool hasCleanup = false; bool hasFilter = false; SmallVector filterTypes; llvm::SmallPtrSet catchTypes; for (EHScopeStack::iterator I = EHStack.begin(), E = EHStack.end(); I != E; ++I) { switch (I->getKind()) { case EHScope::Cleanup: // If we have a cleanup, remember that. hasCleanup = (hasCleanup || cast(*I).isEHCleanup()); continue; case EHScope::Filter: { assert(I.next() == EHStack.end() && "EH filter is not end of EH stack"); assert(!hasCatchAll && "EH filter reached after catch-all"); // Filter scopes get added to the landingpad in weird ways. EHFilterScope &filter = cast(*I); hasFilter = true; // Add all the filter values. for (unsigned i = 0, e = filter.getNumFilters(); i != e; ++i) filterTypes.push_back(filter.getFilter(i)); goto done; } case EHScope::Terminate: // Terminate scopes are basically catch-alls. assert(!hasCatchAll); hasCatchAll = true; goto done; case EHScope::Catch: break; } EHCatchScope &catchScope = cast(*I); for (unsigned hi = 0, he = catchScope.getNumHandlers(); hi != he; ++hi) { EHCatchScope::Handler handler = catchScope.getHandler(hi); assert(handler.Type.Flags == 0 && "landingpads do not support catch handler flags"); // If this is a catch-all, register that and abort. if (!handler.Type.RTTI) { assert(!hasCatchAll); hasCatchAll = true; goto done; } // Check whether we already have a handler for this type. if (catchTypes.insert(handler.Type.RTTI).second) // If not, add it directly to the landingpad. LPadInst->addClause(handler.Type.RTTI); } } done: // If we have a catch-all, add null to the landingpad. assert(!(hasCatchAll && hasFilter)); if (hasCatchAll) { LPadInst->addClause(getCatchAllValue(*this)); // If we have an EH filter, we need to add those handlers in the // right place in the landingpad, which is to say, at the end. } else if (hasFilter) { // Create a filter expression: a constant array indicating which filter // types there are. The personality routine only lands here if the filter // doesn't match. SmallVector Filters; llvm::ArrayType *AType = llvm::ArrayType::get(!filterTypes.empty() ? filterTypes[0]->getType() : Int8PtrTy, filterTypes.size()); for (unsigned i = 0, e = filterTypes.size(); i != e; ++i) Filters.push_back(cast(filterTypes[i])); llvm::Constant *FilterArray = llvm::ConstantArray::get(AType, Filters); LPadInst->addClause(FilterArray); // Also check whether we need a cleanup. if (hasCleanup) LPadInst->setCleanup(true); // Otherwise, signal that we at least have cleanups. } else if (hasCleanup) { LPadInst->setCleanup(true); } assert((LPadInst->getNumClauses() > 0 || LPadInst->isCleanup()) && "landingpad instruction has no clauses!"); // Tell the backend how to generate the landing pad. Builder.CreateBr(getEHDispatchBlock(EHStack.getInnermostEHScope())); // Restore the old IR generation state. Builder.restoreIP(savedIP); return lpad; } static void emitCatchPadBlock(CodeGenFunction &CGF, EHCatchScope &CatchScope) { llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock(); assert(DispatchBlock); CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP(); CGF.EmitBlockAfterUses(DispatchBlock); llvm::Value *ParentPad = CGF.CurrentFuncletPad; if (!ParentPad) ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext()); llvm::BasicBlock *UnwindBB = CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope()); unsigned NumHandlers = CatchScope.getNumHandlers(); llvm::CatchSwitchInst *CatchSwitch = CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers); // Test against each of the exception types we claim to catch. for (unsigned I = 0; I < NumHandlers; ++I) { const EHCatchScope::Handler &Handler = CatchScope.getHandler(I); CatchTypeInfo TypeInfo = Handler.Type; if (!TypeInfo.RTTI) TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy); CGF.Builder.SetInsertPoint(Handler.Block); if (EHPersonality::get(CGF).isMSVCXXPersonality()) { CGF.Builder.CreateCatchPad( CatchSwitch, {TypeInfo.RTTI, CGF.Builder.getInt32(TypeInfo.Flags), llvm::Constant::getNullValue(CGF.VoidPtrTy)}); } else { CGF.Builder.CreateCatchPad(CatchSwitch, {TypeInfo.RTTI}); } CatchSwitch->addHandler(Handler.Block); } CGF.Builder.restoreIP(SavedIP); } // Wasm uses Windows-style EH instructions, but it merges all catch clauses into // one big catchpad, within which we use Itanium's landingpad-style selector // comparison instructions. static void emitWasmCatchPadBlock(CodeGenFunction &CGF, EHCatchScope &CatchScope) { llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock(); assert(DispatchBlock); CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveIP(); CGF.EmitBlockAfterUses(DispatchBlock); llvm::Value *ParentPad = CGF.CurrentFuncletPad; if (!ParentPad) ParentPad = llvm::ConstantTokenNone::get(CGF.getLLVMContext()); llvm::BasicBlock *UnwindBB = CGF.getEHDispatchBlock(CatchScope.getEnclosingEHScope()); unsigned NumHandlers = CatchScope.getNumHandlers(); llvm::CatchSwitchInst *CatchSwitch = CGF.Builder.CreateCatchSwitch(ParentPad, UnwindBB, NumHandlers); // We don't use a landingpad instruction, so generate intrinsic calls to // provide exception and selector values. llvm::BasicBlock *WasmCatchStartBlock = CGF.createBasicBlock("catch.start"); CatchSwitch->addHandler(WasmCatchStartBlock); CGF.EmitBlockAfterUses(WasmCatchStartBlock); // Create a catchpad instruction. SmallVector CatchTypes; for (unsigned I = 0, E = NumHandlers; I < E; ++I) { const EHCatchScope::Handler &Handler = CatchScope.getHandler(I); CatchTypeInfo TypeInfo = Handler.Type; if (!TypeInfo.RTTI) TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy); CatchTypes.push_back(TypeInfo.RTTI); } auto *CPI = CGF.Builder.CreateCatchPad(CatchSwitch, CatchTypes); // Create calls to wasm.get.exception and wasm.get.ehselector intrinsics. // Before they are lowered appropriately later, they provide values for the // exception and selector. llvm::Function *GetExnFn = CGF.CGM.getIntrinsic(llvm::Intrinsic::wasm_get_exception); llvm::Function *GetSelectorFn = CGF.CGM.getIntrinsic(llvm::Intrinsic::wasm_get_ehselector); llvm::CallInst *Exn = CGF.Builder.CreateCall(GetExnFn, CPI); CGF.Builder.CreateStore(Exn, CGF.getExceptionSlot()); llvm::CallInst *Selector = CGF.Builder.CreateCall(GetSelectorFn, CPI); llvm::Function *TypeIDFn = CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); // If there's only a single catch-all, branch directly to its handler. if (CatchScope.getNumHandlers() == 1 && CatchScope.getHandler(0).isCatchAll()) { CGF.Builder.CreateBr(CatchScope.getHandler(0).Block); CGF.Builder.restoreIP(SavedIP); return; } // Test against each of the exception types we claim to catch. for (unsigned I = 0, E = NumHandlers;; ++I) { assert(I < E && "ran off end of handlers!"); const EHCatchScope::Handler &Handler = CatchScope.getHandler(I); CatchTypeInfo TypeInfo = Handler.Type; if (!TypeInfo.RTTI) TypeInfo.RTTI = llvm::Constant::getNullValue(CGF.VoidPtrTy); // Figure out the next block. llvm::BasicBlock *NextBlock; bool EmitNextBlock = false, NextIsEnd = false; // If this is the last handler, we're at the end, and the next block is a // block that contains a call to the rethrow function, so we can unwind to // the enclosing EH scope. The call itself will be generated later. if (I + 1 == E) { NextBlock = CGF.createBasicBlock("rethrow"); EmitNextBlock = true; NextIsEnd = true; // If the next handler is a catch-all, we're at the end, and the // next block is that handler. } else if (CatchScope.getHandler(I + 1).isCatchAll()) { NextBlock = CatchScope.getHandler(I + 1).Block; NextIsEnd = true; // Otherwise, we're not at the end and we need a new block. } else { NextBlock = CGF.createBasicBlock("catch.fallthrough"); EmitNextBlock = true; } // Figure out the catch type's index in the LSDA's type table. llvm::CallInst *TypeIndex = CGF.Builder.CreateCall(TypeIDFn, TypeInfo.RTTI); TypeIndex->setDoesNotThrow(); llvm::Value *MatchesTypeIndex = CGF.Builder.CreateICmpEQ(Selector, TypeIndex, "matches"); CGF.Builder.CreateCondBr(MatchesTypeIndex, Handler.Block, NextBlock); if (EmitNextBlock) CGF.EmitBlock(NextBlock); if (NextIsEnd) break; } CGF.Builder.restoreIP(SavedIP); } /// Emit the structure of the dispatch block for the given catch scope. /// It is an invariant that the dispatch block already exists. static void emitCatchDispatchBlock(CodeGenFunction &CGF, EHCatchScope &catchScope) { if (EHPersonality::get(CGF).isWasmPersonality()) return emitWasmCatchPadBlock(CGF, catchScope); if (EHPersonality::get(CGF).usesFuncletPads()) return emitCatchPadBlock(CGF, catchScope); llvm::BasicBlock *dispatchBlock = catchScope.getCachedEHDispatchBlock(); assert(dispatchBlock); // If there's only a single catch-all, getEHDispatchBlock returned // that catch-all as the dispatch block. if (catchScope.getNumHandlers() == 1 && catchScope.getHandler(0).isCatchAll()) { assert(dispatchBlock == catchScope.getHandler(0).Block); return; } CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveIP(); CGF.EmitBlockAfterUses(dispatchBlock); // Select the right handler. llvm::Function *llvm_eh_typeid_for = CGF.CGM.getIntrinsic(llvm::Intrinsic::eh_typeid_for); llvm::Type *argTy = llvm_eh_typeid_for->getArg(0)->getType(); LangAS globAS = CGF.CGM.GetGlobalVarAddressSpace(nullptr); // Load the selector value. llvm::Value *selector = CGF.getSelectorFromSlot(); // Test against each of the exception types we claim to catch. for (unsigned i = 0, e = catchScope.getNumHandlers(); ; ++i) { assert(i < e && "ran off end of handlers!"); const EHCatchScope::Handler &handler = catchScope.getHandler(i); llvm::Value *typeValue = handler.Type.RTTI; assert(handler.Type.Flags == 0 && "landingpads do not support catch handler flags"); assert(typeValue && "fell into catch-all case!"); // With opaque ptrs, only the address space can be a mismatch. if (typeValue->getType() != argTy) typeValue = CGF.getTargetHooks().performAddrSpaceCast(CGF, typeValue, globAS, LangAS::Default, argTy); // Figure out the next block. bool nextIsEnd; llvm::BasicBlock *nextBlock; // If this is the last handler, we're at the end, and the next // block is the block for the enclosing EH scope. if (i + 1 == e) { nextBlock = CGF.getEHDispatchBlock(catchScope.getEnclosingEHScope()); nextIsEnd = true; // If the next handler is a catch-all, we're at the end, and the // next block is that handler. } else if (catchScope.getHandler(i+1).isCatchAll()) { nextBlock = catchScope.getHandler(i+1).Block; nextIsEnd = true; // Otherwise, we're not at the end and we need a new block. } else { nextBlock = CGF.createBasicBlock("catch.fallthrough"); nextIsEnd = false; } // Figure out the catch type's index in the LSDA's type table. llvm::CallInst *typeIndex = CGF.Builder.CreateCall(llvm_eh_typeid_for, typeValue); typeIndex->setDoesNotThrow(); llvm::Value *matchesTypeIndex = CGF.Builder.CreateICmpEQ(selector, typeIndex, "matches"); CGF.Builder.CreateCondBr(matchesTypeIndex, handler.Block, nextBlock); // If the next handler is a catch-all, we're completely done. if (nextIsEnd) { CGF.Builder.restoreIP(savedIP); return; } // Otherwise we need to emit and continue at that block. CGF.EmitBlock(nextBlock); } } void CodeGenFunction::popCatchScope() { EHCatchScope &catchScope = cast(*EHStack.begin()); if (catchScope.hasEHBranches()) emitCatchDispatchBlock(*this, catchScope); EHStack.popCatch(); } void CodeGenFunction::ExitCXXTryStmt(const CXXTryStmt &S, bool IsFnTryBlock) { unsigned NumHandlers = S.getNumHandlers(); EHCatchScope &CatchScope = cast(*EHStack.begin()); assert(CatchScope.getNumHandlers() == NumHandlers); llvm::BasicBlock *DispatchBlock = CatchScope.getCachedEHDispatchBlock(); // If the catch was not required, bail out now. if (!CatchScope.hasEHBranches()) { CatchScope.clearHandlerBlocks(); EHStack.popCatch(); return; } // Emit the structure of the EH dispatch for this catch. emitCatchDispatchBlock(*this, CatchScope); // Copy the handler blocks off before we pop the EH stack. Emitting // the handlers might scribble on this memory. SmallVector Handlers( CatchScope.begin(), CatchScope.begin() + NumHandlers); EHStack.popCatch(); // The fall-through block. llvm::BasicBlock *ContBB = createBasicBlock("try.cont"); // We just emitted the body of the try; jump to the continue block. if (HaveInsertPoint()) Builder.CreateBr(ContBB); // Determine if we need an implicit rethrow for all these catch handlers; // see the comment below. bool doImplicitRethrow = false; if (IsFnTryBlock) doImplicitRethrow = isa(CurCodeDecl) || isa(CurCodeDecl); // Wasm uses Windows-style EH instructions, but merges all catch clauses into // one big catchpad. So we save the old funclet pad here before we traverse // each catch handler. SaveAndRestore RestoreCurrentFuncletPad(CurrentFuncletPad); llvm::BasicBlock *WasmCatchStartBlock = nullptr; if (EHPersonality::get(*this).isWasmPersonality()) { auto *CatchSwitch = cast(DispatchBlock->getFirstNonPHI()); WasmCatchStartBlock = CatchSwitch->hasUnwindDest() ? CatchSwitch->getSuccessor(1) : CatchSwitch->getSuccessor(0); auto *CPI = cast(WasmCatchStartBlock->getFirstNonPHI()); CurrentFuncletPad = CPI; } // Perversely, we emit the handlers backwards precisely because we // want them to appear in source order. In all of these cases, the // catch block will have exactly one predecessor, which will be a // particular block in the catch dispatch. However, in the case of // a catch-all, one of the dispatch blocks will branch to two // different handlers, and EmitBlockAfterUses will cause the second // handler to be moved before the first. bool HasCatchAll = false; for (unsigned I = NumHandlers; I != 0; --I) { HasCatchAll |= Handlers[I - 1].isCatchAll(); llvm::BasicBlock *CatchBlock = Handlers[I-1].Block; EmitBlockAfterUses(CatchBlock); // Catch the exception if this isn't a catch-all. const CXXCatchStmt *C = S.getHandler(I-1); // Enter a cleanup scope, including the catch variable and the // end-catch. RunCleanupsScope CatchScope(*this); // Initialize the catch variable and set up the cleanups. SaveAndRestore RestoreCurrentFuncletPad(CurrentFuncletPad); CGM.getCXXABI().emitBeginCatch(*this, C); // Emit the PGO counter increment. incrementProfileCounter(C); // Perform the body of the catch. EmitStmt(C->getHandlerBlock()); // [except.handle]p11: // The currently handled exception is rethrown if control // reaches the end of a handler of the function-try-block of a // constructor or destructor. // It is important that we only do this on fallthrough and not on // return. Note that it's illegal to put a return in a // constructor function-try-block's catch handler (p14), so this // really only applies to destructors. if (doImplicitRethrow && HaveInsertPoint()) { CGM.getCXXABI().emitRethrow(*this, /*isNoReturn*/false); Builder.CreateUnreachable(); Builder.ClearInsertionPoint(); } // Fall out through the catch cleanups. CatchScope.ForceCleanup(); // Branch out of the try. if (HaveInsertPoint()) Builder.CreateBr(ContBB); } // Because in wasm we merge all catch clauses into one big catchpad, in case // none of the types in catch handlers matches after we test against each of // them, we should unwind to the next EH enclosing scope. We generate a call // to rethrow function here to do that. if (EHPersonality::get(*this).isWasmPersonality() && !HasCatchAll) { assert(WasmCatchStartBlock); // Navigate for the "rethrow" block we created in emitWasmCatchPadBlock(). // Wasm uses landingpad-style conditional branches to compare selectors, so // we follow the false destination for each of the cond branches to reach // the rethrow block. llvm::BasicBlock *RethrowBlock = WasmCatchStartBlock; while (llvm::Instruction *TI = RethrowBlock->getTerminator()) { auto *BI = cast(TI); assert(BI->isConditional()); RethrowBlock = BI->getSuccessor(1); } assert(RethrowBlock != WasmCatchStartBlock && RethrowBlock->empty()); Builder.SetInsertPoint(RethrowBlock); llvm::Function *RethrowInCatchFn = CGM.getIntrinsic(llvm::Intrinsic::wasm_rethrow); EmitNoreturnRuntimeCallOrInvoke(RethrowInCatchFn, {}); } EmitBlock(ContBB); incrementProfileCounter(&S); } namespace { struct CallEndCatchForFinally final : EHScopeStack::Cleanup { llvm::Value *ForEHVar; llvm::FunctionCallee EndCatchFn; CallEndCatchForFinally(llvm::Value *ForEHVar, llvm::FunctionCallee EndCatchFn) : ForEHVar(ForEHVar), EndCatchFn(EndCatchFn) {} void Emit(CodeGenFunction &CGF, Flags flags) override { llvm::BasicBlock *EndCatchBB = CGF.createBasicBlock("finally.endcatch"); llvm::BasicBlock *CleanupContBB = CGF.createBasicBlock("finally.cleanup.cont"); llvm::Value *ShouldEndCatch = CGF.Builder.CreateFlagLoad(ForEHVar, "finally.endcatch"); CGF.Builder.CreateCondBr(ShouldEndCatch, EndCatchBB, CleanupContBB); CGF.EmitBlock(EndCatchBB); CGF.EmitRuntimeCallOrInvoke(EndCatchFn); // catch-all, so might throw CGF.EmitBlock(CleanupContBB); } }; struct PerformFinally final : EHScopeStack::Cleanup { const Stmt *Body; llvm::Value *ForEHVar; llvm::FunctionCallee EndCatchFn; llvm::FunctionCallee RethrowFn; llvm::Value *SavedExnVar; PerformFinally(const Stmt *Body, llvm::Value *ForEHVar, llvm::FunctionCallee EndCatchFn, llvm::FunctionCallee RethrowFn, llvm::Value *SavedExnVar) : Body(Body), ForEHVar(ForEHVar), EndCatchFn(EndCatchFn), RethrowFn(RethrowFn), SavedExnVar(SavedExnVar) {} void Emit(CodeGenFunction &CGF, Flags flags) override { // Enter a cleanup to call the end-catch function if one was provided. if (EndCatchFn) CGF.EHStack.pushCleanup(NormalAndEHCleanup, ForEHVar, EndCatchFn); // Save the current cleanup destination in case there are // cleanups in the finally block. llvm::Value *SavedCleanupDest = CGF.Builder.CreateLoad(CGF.getNormalCleanupDestSlot(), "cleanup.dest.saved"); // Emit the finally block. CGF.EmitStmt(Body); // If the end of the finally is reachable, check whether this was // for EH. If so, rethrow. if (CGF.HaveInsertPoint()) { llvm::BasicBlock *RethrowBB = CGF.createBasicBlock("finally.rethrow"); llvm::BasicBlock *ContBB = CGF.createBasicBlock("finally.cont"); llvm::Value *ShouldRethrow = CGF.Builder.CreateFlagLoad(ForEHVar, "finally.shouldthrow"); CGF.Builder.CreateCondBr(ShouldRethrow, RethrowBB, ContBB); CGF.EmitBlock(RethrowBB); if (SavedExnVar) { CGF.EmitRuntimeCallOrInvoke(RethrowFn, CGF.Builder.CreateAlignedLoad(CGF.Int8PtrTy, SavedExnVar, CGF.getPointerAlign())); } else { CGF.EmitRuntimeCallOrInvoke(RethrowFn); } CGF.Builder.CreateUnreachable(); CGF.EmitBlock(ContBB); // Restore the cleanup destination. CGF.Builder.CreateStore(SavedCleanupDest, CGF.getNormalCleanupDestSlot()); } // Leave the end-catch cleanup. As an optimization, pretend that // the fallthrough path was inaccessible; we've dynamically proven // that we're not in the EH case along that path. if (EndCatchFn) { CGBuilderTy::InsertPoint SavedIP = CGF.Builder.saveAndClearIP(); CGF.PopCleanupBlock(); CGF.Builder.restoreIP(SavedIP); } // Now make sure we actually have an insertion point or the // cleanup gods will hate us. CGF.EnsureInsertPoint(); } }; } // end anonymous namespace /// Enters a finally block for an implementation using zero-cost /// exceptions. This is mostly general, but hard-codes some /// language/ABI-specific behavior in the catch-all sections. void CodeGenFunction::FinallyInfo::enter(CodeGenFunction &CGF, const Stmt *body, llvm::FunctionCallee beginCatchFn, llvm::FunctionCallee endCatchFn, llvm::FunctionCallee rethrowFn) { assert((!!beginCatchFn) == (!!endCatchFn) && "begin/end catch functions not paired"); assert(rethrowFn && "rethrow function is required"); BeginCatchFn = beginCatchFn; // The rethrow function has one of the following two types: // void (*)() // void (*)(void*) // In the latter case we need to pass it the exception object. // But we can't use the exception slot because the @finally might // have a landing pad (which would overwrite the exception slot). llvm::FunctionType *rethrowFnTy = rethrowFn.getFunctionType(); SavedExnVar = nullptr; if (rethrowFnTy->getNumParams()) SavedExnVar = CGF.CreateTempAlloca(CGF.Int8PtrTy, "finally.exn"); // A finally block is a statement which must be executed on any edge // out of a given scope. Unlike a cleanup, the finally block may // contain arbitrary control flow leading out of itself. In // addition, finally blocks should always be executed, even if there // are no catch handlers higher on the stack. Therefore, we // surround the protected scope with a combination of a normal // cleanup (to catch attempts to break out of the block via normal // control flow) and an EH catch-all (semantically "outside" any try // statement to which the finally block might have been attached). // The finally block itself is generated in the context of a cleanup // which conditionally leaves the catch-all. // Jump destination for performing the finally block on an exception // edge. We'll never actually reach this block, so unreachable is // fine. RethrowDest = CGF.getJumpDestInCurrentScope(CGF.getUnreachableBlock()); // Whether the finally block is being executed for EH purposes. ForEHVar = CGF.CreateTempAlloca(CGF.Builder.getInt1Ty(), "finally.for-eh"); CGF.Builder.CreateFlagStore(false, ForEHVar); // Enter a normal cleanup which will perform the @finally block. CGF.EHStack.pushCleanup(NormalCleanup, body, ForEHVar, endCatchFn, rethrowFn, SavedExnVar); // Enter a catch-all scope. llvm::BasicBlock *catchBB = CGF.createBasicBlock("finally.catchall"); EHCatchScope *catchScope = CGF.EHStack.pushCatch(1); catchScope->setCatchAllHandler(0, catchBB); } void CodeGenFunction::FinallyInfo::exit(CodeGenFunction &CGF) { // Leave the finally catch-all. EHCatchScope &catchScope = cast(*CGF.EHStack.begin()); llvm::BasicBlock *catchBB = catchScope.getHandler(0).Block; CGF.popCatchScope(); // If there are any references to the catch-all block, emit it. if (catchBB->use_empty()) { delete catchBB; } else { CGBuilderTy::InsertPoint savedIP = CGF.Builder.saveAndClearIP(); CGF.EmitBlock(catchBB); llvm::Value *exn = nullptr; // If there's a begin-catch function, call it. if (BeginCatchFn) { exn = CGF.getExceptionFromSlot(); CGF.EmitNounwindRuntimeCall(BeginCatchFn, exn); } // If we need to remember the exception pointer to rethrow later, do so. if (SavedExnVar) { if (!exn) exn = CGF.getExceptionFromSlot(); CGF.Builder.CreateAlignedStore(exn, SavedExnVar, CGF.getPointerAlign()); } // Tell the cleanups in the finally block that we're do this for EH. CGF.Builder.CreateFlagStore(true, ForEHVar); // Thread a jump through the finally cleanup. CGF.EmitBranchThroughCleanup(RethrowDest); CGF.Builder.restoreIP(savedIP); } // Finally, leave the @finally cleanup. CGF.PopCleanupBlock(); } llvm::BasicBlock *CodeGenFunction::getTerminateLandingPad() { if (TerminateLandingPad) return TerminateLandingPad; CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); // This will get inserted at the end of the function. TerminateLandingPad = createBasicBlock("terminate.lpad"); Builder.SetInsertPoint(TerminateLandingPad); // Tell the backend that this is a landing pad. const EHPersonality &Personality = EHPersonality::get(*this); if (!CurFn->hasPersonalityFn()) CurFn->setPersonalityFn(getOpaquePersonalityFn(CGM, Personality)); llvm::LandingPadInst *LPadInst = Builder.CreateLandingPad(llvm::StructType::get(Int8PtrTy, Int32Ty), 0); LPadInst->addClause(getCatchAllValue(*this)); llvm::Value *Exn = nullptr; if (getLangOpts().CPlusPlus) Exn = Builder.CreateExtractValue(LPadInst, 0); llvm::CallInst *terminateCall = CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn); terminateCall->setDoesNotReturn(); Builder.CreateUnreachable(); // Restore the saved insertion state. Builder.restoreIP(SavedIP); return TerminateLandingPad; } llvm::BasicBlock *CodeGenFunction::getTerminateHandler() { if (TerminateHandler) return TerminateHandler; // Set up the terminate handler. This block is inserted at the very // end of the function by FinishFunction. TerminateHandler = createBasicBlock("terminate.handler"); CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); Builder.SetInsertPoint(TerminateHandler); llvm::Value *Exn = nullptr; if (getLangOpts().CPlusPlus) Exn = getExceptionFromSlot(); llvm::CallInst *terminateCall = CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn); terminateCall->setDoesNotReturn(); Builder.CreateUnreachable(); // Restore the saved insertion state. Builder.restoreIP(SavedIP); return TerminateHandler; } llvm::BasicBlock *CodeGenFunction::getTerminateFunclet() { assert(EHPersonality::get(*this).usesFuncletPads() && "use getTerminateLandingPad for non-funclet EH"); llvm::BasicBlock *&TerminateFunclet = TerminateFunclets[CurrentFuncletPad]; if (TerminateFunclet) return TerminateFunclet; CGBuilderTy::InsertPoint SavedIP = Builder.saveAndClearIP(); // Set up the terminate handler. This block is inserted at the very // end of the function by FinishFunction. TerminateFunclet = createBasicBlock("terminate.handler"); Builder.SetInsertPoint(TerminateFunclet); // Create the cleanuppad using the current parent pad as its token. Use 'none' // if this is a top-level terminate scope, which is the common case. SaveAndRestore RestoreCurrentFuncletPad(CurrentFuncletPad); llvm::Value *ParentPad = CurrentFuncletPad; if (!ParentPad) ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext()); CurrentFuncletPad = Builder.CreateCleanupPad(ParentPad); // Emit the __std_terminate call. llvm::CallInst *terminateCall = CGM.getCXXABI().emitTerminateForUnexpectedException(*this, nullptr); terminateCall->setDoesNotReturn(); Builder.CreateUnreachable(); // Restore the saved insertion state. Builder.restoreIP(SavedIP); return TerminateFunclet; } llvm::BasicBlock *CodeGenFunction::getEHResumeBlock(bool isCleanup) { if (EHResumeBlock) return EHResumeBlock; CGBuilderTy::InsertPoint SavedIP = Builder.saveIP(); // We emit a jump to a notional label at the outermost unwind state. EHResumeBlock = createBasicBlock("eh.resume"); Builder.SetInsertPoint(EHResumeBlock); const EHPersonality &Personality = EHPersonality::get(*this); // This can always be a call because we necessarily didn't find // anything on the EH stack which needs our help. const char *RethrowName = Personality.CatchallRethrowFn; if (RethrowName != nullptr && !isCleanup) { EmitRuntimeCall(getCatchallRethrowFn(CGM, RethrowName), getExceptionFromSlot())->setDoesNotReturn(); Builder.CreateUnreachable(); Builder.restoreIP(SavedIP); return EHResumeBlock; } // Recreate the landingpad's return value for the 'resume' instruction. llvm::Value *Exn = getExceptionFromSlot(); llvm::Value *Sel = getSelectorFromSlot(); llvm::Type *LPadType = llvm::StructType::get(Exn->getType(), Sel->getType()); llvm::Value *LPadVal = llvm::PoisonValue::get(LPadType); LPadVal = Builder.CreateInsertValue(LPadVal, Exn, 0, "lpad.val"); LPadVal = Builder.CreateInsertValue(LPadVal, Sel, 1, "lpad.val"); Builder.CreateResume(LPadVal); Builder.restoreIP(SavedIP); return EHResumeBlock; } void CodeGenFunction::EmitSEHTryStmt(const SEHTryStmt &S) { EnterSEHTryStmt(S); { JumpDest TryExit = getJumpDestInCurrentScope("__try.__leave"); SEHTryEpilogueStack.push_back(&TryExit); llvm::BasicBlock *TryBB = nullptr; // IsEHa: emit an invoke to _seh_try_begin() runtime for -EHa if (getLangOpts().EHAsynch) { EmitRuntimeCallOrInvoke(getSehTryBeginFn(CGM)); if (SEHTryEpilogueStack.size() == 1) // outermost only TryBB = Builder.GetInsertBlock(); } EmitStmt(S.getTryBlock()); // Volatilize all blocks in Try, till current insert point if (TryBB) { llvm::SmallPtrSet Visited; VolatilizeTryBlocks(TryBB, Visited); } SEHTryEpilogueStack.pop_back(); if (!TryExit.getBlock()->use_empty()) EmitBlock(TryExit.getBlock(), /*IsFinished=*/true); else delete TryExit.getBlock(); } ExitSEHTryStmt(S); } // Recursively walk through blocks in a _try // and make all memory instructions volatile void CodeGenFunction::VolatilizeTryBlocks( llvm::BasicBlock *BB, llvm::SmallPtrSet &V) { if (BB == SEHTryEpilogueStack.back()->getBlock() /* end of Try */ || !V.insert(BB).second /* already visited */ || !BB->getParent() /* not emitted */ || BB->empty()) return; if (!BB->isEHPad()) { for (llvm::BasicBlock::iterator J = BB->begin(), JE = BB->end(); J != JE; ++J) { if (auto LI = dyn_cast(J)) { LI->setVolatile(true); } else if (auto SI = dyn_cast(J)) { SI->setVolatile(true); } else if (auto* MCI = dyn_cast(J)) { MCI->setVolatile(llvm::ConstantInt::get(Builder.getInt1Ty(), 1)); } } } const llvm::Instruction *TI = BB->getTerminator(); if (TI) { unsigned N = TI->getNumSuccessors(); for (unsigned I = 0; I < N; I++) VolatilizeTryBlocks(TI->getSuccessor(I), V); } } namespace { struct PerformSEHFinally final : EHScopeStack::Cleanup { llvm::Function *OutlinedFinally; PerformSEHFinally(llvm::Function *OutlinedFinally) : OutlinedFinally(OutlinedFinally) {} void Emit(CodeGenFunction &CGF, Flags F) override { ASTContext &Context = CGF.getContext(); CodeGenModule &CGM = CGF.CGM; CallArgList Args; // Compute the two argument values. QualType ArgTys[2] = {Context.UnsignedCharTy, Context.VoidPtrTy}; llvm::Value *FP = nullptr; // If CFG.IsOutlinedSEHHelper is true, then we are within a finally block. if (CGF.IsOutlinedSEHHelper) { FP = &CGF.CurFn->arg_begin()[1]; } else { llvm::Function *LocalAddrFn = CGM.getIntrinsic(llvm::Intrinsic::localaddress); FP = CGF.Builder.CreateCall(LocalAddrFn); } llvm::Value *IsForEH = llvm::ConstantInt::get(CGF.ConvertType(ArgTys[0]), F.isForEHCleanup()); // Except _leave and fall-through at the end, all other exits in a _try // (return/goto/continue/break) are considered as abnormal terminations // since _leave/fall-through is always Indexed 0, // just use NormalCleanupDestSlot (>= 1 for goto/return/..), // as 1st Arg to indicate abnormal termination if (!F.isForEHCleanup() && F.hasExitSwitch()) { Address Addr = CGF.getNormalCleanupDestSlot(); llvm::Value *Load = CGF.Builder.CreateLoad(Addr, "cleanup.dest"); llvm::Value *Zero = llvm::Constant::getNullValue(CGM.Int32Ty); IsForEH = CGF.Builder.CreateICmpNE(Load, Zero); } Args.add(RValue::get(IsForEH), ArgTys[0]); Args.add(RValue::get(FP), ArgTys[1]); // Arrange a two-arg function info and type. const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeBuiltinFunctionCall(Context.VoidTy, Args); auto Callee = CGCallee::forDirect(OutlinedFinally); CGF.EmitCall(FnInfo, Callee, ReturnValueSlot(), Args); } }; } // end anonymous namespace namespace { /// Find all local variable captures in the statement. struct CaptureFinder : ConstStmtVisitor { CodeGenFunction &ParentCGF; const VarDecl *ParentThis; llvm::SmallSetVector Captures; Address SEHCodeSlot = Address::invalid(); CaptureFinder(CodeGenFunction &ParentCGF, const VarDecl *ParentThis) : ParentCGF(ParentCGF), ParentThis(ParentThis) {} // Return true if we need to do any capturing work. bool foundCaptures() { return !Captures.empty() || SEHCodeSlot.isValid(); } void Visit(const Stmt *S) { // See if this is a capture, then recurse. ConstStmtVisitor::Visit(S); for (const Stmt *Child : S->children()) if (Child) Visit(Child); } void VisitDeclRefExpr(const DeclRefExpr *E) { // If this is already a capture, just make sure we capture 'this'. if (E->refersToEnclosingVariableOrCapture()) Captures.insert(ParentThis); const auto *D = dyn_cast(E->getDecl()); if (D && D->isLocalVarDeclOrParm() && D->hasLocalStorage()) Captures.insert(D); } void VisitCXXThisExpr(const CXXThisExpr *E) { Captures.insert(ParentThis); } void VisitCallExpr(const CallExpr *E) { // We only need to add parent frame allocations for these builtins in x86. if (ParentCGF.getTarget().getTriple().getArch() != llvm::Triple::x86) return; unsigned ID = E->getBuiltinCallee(); switch (ID) { case Builtin::BI__exception_code: case Builtin::BI_exception_code: // This is the simple case where we are the outermost finally. All we // have to do here is make sure we escape this and recover it in the // outlined handler. if (!SEHCodeSlot.isValid()) SEHCodeSlot = ParentCGF.SEHCodeSlotStack.back(); break; } } }; } // end anonymous namespace Address CodeGenFunction::recoverAddrOfEscapedLocal(CodeGenFunction &ParentCGF, Address ParentVar, llvm::Value *ParentFP) { llvm::CallInst *RecoverCall = nullptr; CGBuilderTy Builder(*this, AllocaInsertPt); if (auto *ParentAlloca = dyn_cast(ParentVar.getPointer())) { // Mark the variable escaped if nobody else referenced it and compute the // localescape index. auto InsertPair = ParentCGF.EscapedLocals.insert( std::make_pair(ParentAlloca, ParentCGF.EscapedLocals.size())); int FrameEscapeIdx = InsertPair.first->second; // call ptr @llvm.localrecover(ptr @parentFn, ptr %fp, i32 N) llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration( &CGM.getModule(), llvm::Intrinsic::localrecover); RecoverCall = Builder.CreateCall( FrameRecoverFn, {ParentCGF.CurFn, ParentFP, llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)}); } else { // If the parent didn't have an alloca, we're doing some nested outlining. // Just clone the existing localrecover call, but tweak the FP argument to // use our FP value. All other arguments are constants. auto *ParentRecover = cast(ParentVar.getPointer()->stripPointerCasts()); assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover && "expected alloca or localrecover in parent LocalDeclMap"); RecoverCall = cast(ParentRecover->clone()); RecoverCall->setArgOperand(1, ParentFP); RecoverCall->insertBefore(AllocaInsertPt); } // Bitcast the variable, rename it, and insert it in the local decl map. llvm::Value *ChildVar = Builder.CreateBitCast(RecoverCall, ParentVar.getType()); ChildVar->setName(ParentVar.getName()); return ParentVar.withPointer(ChildVar, KnownNonNull); } void CodeGenFunction::EmitCapturedLocals(CodeGenFunction &ParentCGF, const Stmt *OutlinedStmt, bool IsFilter) { // Find all captures in the Stmt. CaptureFinder Finder(ParentCGF, ParentCGF.CXXABIThisDecl); Finder.Visit(OutlinedStmt); // We can exit early on x86_64 when there are no captures. We just have to // save the exception code in filters so that __exception_code() works. if (!Finder.foundCaptures() && CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) { if (IsFilter) EmitSEHExceptionCodeSave(ParentCGF, nullptr, nullptr); return; } llvm::Value *EntryFP = nullptr; CGBuilderTy Builder(CGM, AllocaInsertPt); if (IsFilter && CGM.getTarget().getTriple().getArch() == llvm::Triple::x86) { // 32-bit SEH filters need to be careful about FP recovery. The end of the // EH registration is passed in as the EBP physical register. We can // recover that with llvm.frameaddress(1). EntryFP = Builder.CreateCall( CGM.getIntrinsic(llvm::Intrinsic::frameaddress, AllocaInt8PtrTy), {Builder.getInt32(1)}); } else { // Otherwise, for x64 and 32-bit finally functions, the parent FP is the // second parameter. auto AI = CurFn->arg_begin(); ++AI; EntryFP = &*AI; } llvm::Value *ParentFP = EntryFP; if (IsFilter) { // Given whatever FP the runtime provided us in EntryFP, recover the true // frame pointer of the parent function. We only need to do this in filters, // since finally funclets recover the parent FP for us. llvm::Function *RecoverFPIntrin = CGM.getIntrinsic(llvm::Intrinsic::eh_recoverfp); ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentCGF.CurFn, EntryFP}); // if the parent is a _finally, the passed-in ParentFP is the FP // of parent _finally, not Establisher's FP (FP of outermost function). // Establkisher FP is 2nd paramenter passed into parent _finally. // Fortunately, it's always saved in parent's frame. The following // code retrieves it, and escapes it so that spill instruction won't be // optimized away. if (ParentCGF.ParentCGF != nullptr) { // Locate and escape Parent's frame_pointer.addr alloca // Depending on target, should be 1st/2nd one in LocalDeclMap. // Let's just scan for ImplicitParamDecl with VoidPtrTy. llvm::AllocaInst *FramePtrAddrAlloca = nullptr; for (auto &I : ParentCGF.LocalDeclMap) { const VarDecl *D = cast(I.first); if (isa(D) && D->getType() == getContext().VoidPtrTy) { assert(D->getName().starts_with("frame_pointer")); FramePtrAddrAlloca = cast(I.second.getPointer()); break; } } assert(FramePtrAddrAlloca); auto InsertPair = ParentCGF.EscapedLocals.insert( std::make_pair(FramePtrAddrAlloca, ParentCGF.EscapedLocals.size())); int FrameEscapeIdx = InsertPair.first->second; // an example of a filter's prolog:: // %0 = call ptr @llvm.eh.recoverfp(@"?fin$0@0@main@@",..) // %1 = call ptr @llvm.localrecover(@"?fin$0@0@main@@",..) // %2 = load ptr, ptr %1, align 8 // ==> %2 is the frame-pointer of outermost host function llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration( &CGM.getModule(), llvm::Intrinsic::localrecover); ParentFP = Builder.CreateCall( FrameRecoverFn, {ParentCGF.CurFn, ParentFP, llvm::ConstantInt::get(Int32Ty, FrameEscapeIdx)}); ParentFP = Builder.CreateLoad( Address(ParentFP, CGM.VoidPtrTy, getPointerAlign())); } } // Create llvm.localrecover calls for all captures. for (const VarDecl *VD : Finder.Captures) { if (VD->getType()->isVariablyModifiedType()) { CGM.ErrorUnsupported(VD, "VLA captured by SEH"); continue; } assert((isa(VD) || VD->isLocalVarDeclOrParm()) && "captured non-local variable"); auto L = ParentCGF.LambdaCaptureFields.find(VD); if (L != ParentCGF.LambdaCaptureFields.end()) { LambdaCaptureFields[VD] = L->second; continue; } // If this decl hasn't been declared yet, it will be declared in the // OutlinedStmt. auto I = ParentCGF.LocalDeclMap.find(VD); if (I == ParentCGF.LocalDeclMap.end()) continue; Address ParentVar = I->second; Address Recovered = recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP); setAddrOfLocalVar(VD, Recovered); if (isa(VD)) { CXXABIThisAlignment = ParentCGF.CXXABIThisAlignment; CXXThisAlignment = ParentCGF.CXXThisAlignment; CXXABIThisValue = Builder.CreateLoad(Recovered, "this"); if (ParentCGF.LambdaThisCaptureField) { LambdaThisCaptureField = ParentCGF.LambdaThisCaptureField; // We are in a lambda function where "this" is captured so the // CXXThisValue need to be loaded from the lambda capture LValue ThisFieldLValue = EmitLValueForLambdaField(LambdaThisCaptureField); if (!LambdaThisCaptureField->getType()->isPointerType()) { CXXThisValue = ThisFieldLValue.getAddress(*this).getPointer(); } else { CXXThisValue = EmitLoadOfLValue(ThisFieldLValue, SourceLocation()) .getScalarVal(); } } else { CXXThisValue = CXXABIThisValue; } } } if (Finder.SEHCodeSlot.isValid()) { SEHCodeSlotStack.push_back( recoverAddrOfEscapedLocal(ParentCGF, Finder.SEHCodeSlot, ParentFP)); } if (IsFilter) EmitSEHExceptionCodeSave(ParentCGF, ParentFP, EntryFP); } /// Arrange a function prototype that can be called by Windows exception /// handling personalities. On Win64, the prototype looks like: /// RetTy func(void *EHPtrs, void *ParentFP); void CodeGenFunction::startOutlinedSEHHelper(CodeGenFunction &ParentCGF, bool IsFilter, const Stmt *OutlinedStmt) { SourceLocation StartLoc = OutlinedStmt->getBeginLoc(); // Get the mangled function name. SmallString<128> Name; { llvm::raw_svector_ostream OS(Name); GlobalDecl ParentSEHFn = ParentCGF.CurSEHParent; assert(ParentSEHFn && "No CurSEHParent!"); MangleContext &Mangler = CGM.getCXXABI().getMangleContext(); if (IsFilter) Mangler.mangleSEHFilterExpression(ParentSEHFn, OS); else Mangler.mangleSEHFinallyBlock(ParentSEHFn, OS); } FunctionArgList Args; if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 || !IsFilter) { // All SEH finally functions take two parameters. Win64 filters take two // parameters. Win32 filters take no parameters. if (IsFilter) { Args.push_back(ImplicitParamDecl::Create( getContext(), /*DC=*/nullptr, StartLoc, &getContext().Idents.get("exception_pointers"), getContext().VoidPtrTy, ImplicitParamKind::Other)); } else { Args.push_back(ImplicitParamDecl::Create( getContext(), /*DC=*/nullptr, StartLoc, &getContext().Idents.get("abnormal_termination"), getContext().UnsignedCharTy, ImplicitParamKind::Other)); } Args.push_back(ImplicitParamDecl::Create( getContext(), /*DC=*/nullptr, StartLoc, &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy, ImplicitParamKind::Other)); } QualType RetTy = IsFilter ? getContext().LongTy : getContext().VoidTy; const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeBuiltinFunctionDeclaration(RetTy, Args); llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FnInfo); llvm::Function *Fn = llvm::Function::Create( FnTy, llvm::GlobalValue::InternalLinkage, Name.str(), &CGM.getModule()); IsOutlinedSEHHelper = true; StartFunction(GlobalDecl(), RetTy, Fn, FnInfo, Args, OutlinedStmt->getBeginLoc(), OutlinedStmt->getBeginLoc()); CurSEHParent = ParentCGF.CurSEHParent; CGM.SetInternalFunctionAttributes(GlobalDecl(), CurFn, FnInfo); EmitCapturedLocals(ParentCGF, OutlinedStmt, IsFilter); } /// Create a stub filter function that will ultimately hold the code of the /// filter expression. The EH preparation passes in LLVM will outline the code /// from the main function body into this stub. llvm::Function * CodeGenFunction::GenerateSEHFilterFunction(CodeGenFunction &ParentCGF, const SEHExceptStmt &Except) { const Expr *FilterExpr = Except.getFilterExpr(); startOutlinedSEHHelper(ParentCGF, true, FilterExpr); // Emit the original filter expression, convert to i32, and return. llvm::Value *R = EmitScalarExpr(FilterExpr); R = Builder.CreateIntCast(R, ConvertType(getContext().LongTy), FilterExpr->getType()->isSignedIntegerType()); Builder.CreateStore(R, ReturnValue); FinishFunction(FilterExpr->getEndLoc()); return CurFn; } llvm::Function * CodeGenFunction::GenerateSEHFinallyFunction(CodeGenFunction &ParentCGF, const SEHFinallyStmt &Finally) { const Stmt *FinallyBlock = Finally.getBlock(); startOutlinedSEHHelper(ParentCGF, false, FinallyBlock); // Emit the original filter expression, convert to i32, and return. EmitStmt(FinallyBlock); FinishFunction(FinallyBlock->getEndLoc()); return CurFn; } void CodeGenFunction::EmitSEHExceptionCodeSave(CodeGenFunction &ParentCGF, llvm::Value *ParentFP, llvm::Value *EntryFP) { // Get the pointer to the EXCEPTION_POINTERS struct. This is returned by the // __exception_info intrinsic. if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) { // On Win64, the info is passed as the first parameter to the filter. SEHInfo = &*CurFn->arg_begin(); SEHCodeSlotStack.push_back( CreateMemTemp(getContext().IntTy, "__exception_code")); } else { // On Win32, the EBP on entry to the filter points to the end of an // exception registration object. It contains 6 32-bit fields, and the info // pointer is stored in the second field. So, GEP 20 bytes backwards and // load the pointer. SEHInfo = Builder.CreateConstInBoundsGEP1_32(Int8Ty, EntryFP, -20); SEHInfo = Builder.CreateAlignedLoad(Int8PtrTy, SEHInfo, getPointerAlign()); SEHCodeSlotStack.push_back(recoverAddrOfEscapedLocal( ParentCGF, ParentCGF.SEHCodeSlotStack.back(), ParentFP)); } // Save the exception code in the exception slot to unify exception access in // the filter function and the landing pad. // struct EXCEPTION_POINTERS { // EXCEPTION_RECORD *ExceptionRecord; // CONTEXT *ContextRecord; // }; // int exceptioncode = exception_pointers->ExceptionRecord->ExceptionCode; llvm::Type *RecordTy = llvm::PointerType::getUnqual(getLLVMContext()); llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy); llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, SEHInfo, 0); Rec = Builder.CreateAlignedLoad(RecordTy, Rec, getPointerAlign()); llvm::Value *Code = Builder.CreateAlignedLoad(Int32Ty, Rec, getIntAlign()); assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except"); Builder.CreateStore(Code, SEHCodeSlotStack.back()); } llvm::Value *CodeGenFunction::EmitSEHExceptionInfo() { // Sema should diagnose calling this builtin outside of a filter context, but // don't crash if we screw up. if (!SEHInfo) return llvm::UndefValue::get(Int8PtrTy); assert(SEHInfo->getType() == Int8PtrTy); return SEHInfo; } llvm::Value *CodeGenFunction::EmitSEHExceptionCode() { assert(!SEHCodeSlotStack.empty() && "emitting EH code outside of __except"); return Builder.CreateLoad(SEHCodeSlotStack.back()); } llvm::Value *CodeGenFunction::EmitSEHAbnormalTermination() { // Abnormal termination is just the first parameter to the outlined finally // helper. auto AI = CurFn->arg_begin(); return Builder.CreateZExt(&*AI, Int32Ty); } void CodeGenFunction::pushSEHCleanup(CleanupKind Kind, llvm::Function *FinallyFunc) { EHStack.pushCleanup(Kind, FinallyFunc); } void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) { CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true); HelperCGF.ParentCGF = this; if (const SEHFinallyStmt *Finally = S.getFinallyHandler()) { // Outline the finally block. llvm::Function *FinallyFunc = HelperCGF.GenerateSEHFinallyFunction(*this, *Finally); // Push a cleanup for __finally blocks. EHStack.pushCleanup(NormalAndEHCleanup, FinallyFunc); return; } // Otherwise, we must have an __except block. const SEHExceptStmt *Except = S.getExceptHandler(); assert(Except); EHCatchScope *CatchScope = EHStack.pushCatch(1); SEHCodeSlotStack.push_back( CreateMemTemp(getContext().IntTy, "__exception_code")); // If the filter is known to evaluate to 1, then we can use the clause // "catch i8* null". We can't do this on x86 because the filter has to save // the exception code. llvm::Constant *C = ConstantEmitter(*this).tryEmitAbstract(Except->getFilterExpr(), getContext().IntTy); if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86 && C && C->isOneValue()) { CatchScope->setCatchAllHandler(0, createBasicBlock("__except")); return; } // In general, we have to emit an outlined filter function. Use the function // in place of the RTTI typeinfo global that C++ EH uses. llvm::Function *FilterFunc = HelperCGF.GenerateSEHFilterFunction(*this, *Except); CatchScope->setHandler(0, FilterFunc, createBasicBlock("__except.ret")); } void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) { // Just pop the cleanup if it's a __finally block. if (S.getFinallyHandler()) { PopCleanupBlock(); return; } // IsEHa: emit an invoke _seh_try_end() to mark end of FT flow if (getLangOpts().EHAsynch && Builder.GetInsertBlock()) { llvm::FunctionCallee SehTryEnd = getSehTryEndFn(CGM); EmitRuntimeCallOrInvoke(SehTryEnd); } // Otherwise, we must have an __except block. const SEHExceptStmt *Except = S.getExceptHandler(); assert(Except && "__try must have __finally xor __except"); EHCatchScope &CatchScope = cast(*EHStack.begin()); // Don't emit the __except block if the __try block lacked invokes. // TODO: Model unwind edges from instructions, either with iload / istore or // a try body function. if (!CatchScope.hasEHBranches()) { CatchScope.clearHandlerBlocks(); EHStack.popCatch(); SEHCodeSlotStack.pop_back(); return; } // The fall-through block. llvm::BasicBlock *ContBB = createBasicBlock("__try.cont"); // We just emitted the body of the __try; jump to the continue block. if (HaveInsertPoint()) Builder.CreateBr(ContBB); // Check if our filter function returned true. emitCatchDispatchBlock(*this, CatchScope); // Grab the block before we pop the handler. llvm::BasicBlock *CatchPadBB = CatchScope.getHandler(0).Block; EHStack.popCatch(); EmitBlockAfterUses(CatchPadBB); // __except blocks don't get outlined into funclets, so immediately do a // catchret. llvm::CatchPadInst *CPI = cast(CatchPadBB->getFirstNonPHI()); llvm::BasicBlock *ExceptBB = createBasicBlock("__except"); Builder.CreateCatchRet(CPI, ExceptBB); EmitBlock(ExceptBB); // On Win64, the exception code is returned in EAX. Copy it into the slot. if (CGM.getTarget().getTriple().getArch() != llvm::Triple::x86) { llvm::Function *SEHCodeIntrin = CGM.getIntrinsic(llvm::Intrinsic::eh_exceptioncode); llvm::Value *Code = Builder.CreateCall(SEHCodeIntrin, {CPI}); Builder.CreateStore(Code, SEHCodeSlotStack.back()); } // Emit the __except body. EmitStmt(Except->getBlock()); // End the lifetime of the exception code. SEHCodeSlotStack.pop_back(); if (HaveInsertPoint()) Builder.CreateBr(ContBB); EmitBlock(ContBB); } void CodeGenFunction::EmitSEHLeaveStmt(const SEHLeaveStmt &S) { // If this code is reachable then emit a stop point (if generating // debug info). We have to do this ourselves because we are on the // "simple" statement path. if (HaveInsertPoint()) EmitStopPoint(&S); // This must be a __leave from a __finally block, which we warn on and is UB. // Just emit unreachable. if (!isSEHTryScope()) { Builder.CreateUnreachable(); Builder.ClearInsertionPoint(); return; } EmitBranchThroughCleanup(*SEHTryEpilogueStack.back()); }