text: //===--- 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 "CodeGenFunction.h"
  #include "CGCXXABI.h"
  #include "CGCleanup.h"
  #include "CGObjCRuntime.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/TargetBuiltins.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/IntrinsicInst.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, /*IsVarArgs=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_free_exception");
  }
  
  static llvm::FunctionCallee getUnexpectedFn(CodeGenModule &CGM) {
    // void __cxa_call_unexpected(void *thrown_exception);
  
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*IsVarArgs=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_call_unexpected");
  }
  
  llvm::FunctionCallee CodeGenModule::getTerminateFn() {
    // void __terminate();
  
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(VoidTy, /*IsVarArgs=*/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, /*IsVarArgs=*/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 };
  
  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.SjLjExceptions)
      return EHPersonality::GNU_C_SJLJ;
    if (L.DWARFExceptions)
      return EHPersonality::GNU_C;
    if (L.SEHExceptions)
      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 (L.ObjCRuntime.getVersion() >= VersionTuple(1, 7))
        return EHPersonality::GNUstep_ObjC;
      LLVM_FALLTHROUGH;
    case ObjCRuntime::GCC:
    case ObjCRuntime::ObjFW:
      if (L.SjLjExceptions)
        return EHPersonality::GNU_ObjC_SJLJ;
      if (L.SEHExceptions)
        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 (L.SjLjExceptions)
      return EHPersonality::GNU_CPlusPlus_SJLJ;
    if (L.DWARFExceptions)
      return EHPersonality::GNU_CPlusPlus;
    if (L.SEHExceptions)
      return EHPersonality::GNU_CPlusPlus_SEH;
    // Wasm EH is a non-MVP feature for now.
    if (Target.hasFeature("exception-handling") &&
        (T.getArch() == llvm::Triple::wasm32 ||
         T.getArch() == llvm::Triple::wasm64))
      return EHPersonality::GNU_Wasm_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 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;
    return get(CGF.CGM, dyn_cast_or_null<FunctionDecl>(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);
    llvm::PointerType* Int8PtrTy = llvm::PointerType::get(
        llvm::Type::getInt8Ty(CGM.getLLVMContext()),
        CGM.getDataLayout().getProgramAddressSpace());
  
    return llvm::ConstantExpr::getBitCast(cast<llvm::Constant>(Fn.getCallee()),
                                          Int8PtrTy);
  }
  
  /// 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<llvm::GlobalVariable>(Val))
          // ObjC EH selector entries are always global variables with
          // names starting like this.
          if (GV->getName().startswith("OBJC_EHTYPE"))
            return false;
      } else {
        // Check if any of the filter values have the ObjC prefix.
        llvm::Constant *CVal = cast<llvm::Constant>(Val);
        for (llvm::User::op_iterator
                II = CVal->op_begin(), IE = CVal->op_end(); II != IE; ++II) {
          if (llvm::GlobalVariable *GV =
              cast<llvm::GlobalVariable>((*II)->stripPointerCasts()))
            // ObjC EH selector entries are always global variables with
            // names starting like this.
            if (GV->getName().startswith("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<llvm::ConstantExpr>(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<llvm::Function>(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<FreeException>(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())->getPointerTo();
    Address typedAddr = Builder.CreateBitCast(addr, 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<llvm::Instruction>(typedAddr.getPointer()));
  }
  
  Address CodeGenFunction::getExceptionSlot() {
    if (!ExceptionSlot)
      ExceptionSlot = CreateTempAlloca(Int8PtrTy, "exn.slot");
    return Address(ExceptionSlot, getPointerAlign());
  }
  
  Address CodeGenFunction::getEHSelectorSlot() {
    if (!EHSelectorSlot)
      EHSelectorSlot = CreateTempAlloca(Int32Ty, "ehselector.slot");
    return Address(EHSelectorSlot, 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 (const Expr *SubExpr = E->getSubExpr()) {
      QualType ThrowType = SubExpr->getType();
      if (ThrowType->isObjCObjectPointerType()) {
        const Stmt *ThrowStmt = E->getSubExpr();
        const ObjCAtThrowStmt S(E->getExprLoc(), const_cast<Stmt *>(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<FunctionDecl>(D);
    if (!FD) {
      // Check if CapturedDecl is nothrow and create terminate scope for it.
      if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
        if (CD->isNothrow())
          EHStack.pushTerminate();
      }
      return;
    }
    const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
    if (!Proto)
      return;
  
    ExceptionSpecificationType EST = Proto->getExceptionSpecType();
    if (isNoexceptExceptionSpec(EST) && Proto->canThrow() == CT_Cannot) {
      // noexcept functions are simple terminate scopes.
      EHStack.pushTerminate();
    } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
      // 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;
      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);
      }
    }
  }
  
  /// 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<FunctionDecl>(D);
    if (!FD) {
      // Check if CapturedDecl is nothrow and pop terminate scope for it.
      if (const CapturedDecl* CD = dyn_cast_or_null<CapturedDecl>(D)) {
        if (CD->isNothrow())
          EHStack.popTerminate();
      }
      return;
    }
    const FunctionProtoType *Proto = FD->getType()->getAs<FunctionProtoType>();
    if (!Proto)
      return;
  
    ExceptionSpecificationType EST = Proto->getExceptionSpecType();
    if (isNoexceptExceptionSpec(EST) && Proto->canThrow() == CT_Cannot) {
      EHStack.popTerminate();
    } else if (EST == EST_Dynamic || EST == EST_DynamicNone) {
      // 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;
      EHFilterScope &filterScope = cast<EHFilterScope>(*EHStack.begin());
      emitFilterDispatchBlock(*this, filterScope);
      EHStack.popFilter();
    }
  }
  
  void CodeGenFunction::EmitCXXTryStmt(const CXXTryStmt &S) {
    EnterCXXTryStmt(S);
    EmitStmt(S.getTryBlock());
    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);
      }
    }
  }
  
  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<EHCatchScope>(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;
  
      case EHScope::PadEnd:
        llvm_unreachable("PadEnd unnecessary for Itanium!");
      }
      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;
  
    case EHScope::PadEnd:
      llvm_unreachable("PadEnd dispatch block missing!");
    }
    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<EHCleanupScope>(S).isEHCleanup();
    case EHScope::Filter:
    case EHScope::Catch:
    case EHScope::Terminate:
    case EHScope::PadEnd:
      return false;
    }
  
    llvm_unreachable("Invalid EHScope Kind!");
  }
  
  llvm::BasicBlock *CodeGenFunction::getInvokeDestImpl() {
    assert(EHStack.requiresLandingPad());
    assert(!EHStack.empty());
  
    // If exceptions are disabled 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.
    const LangOptions &LO = CGM.getLangOpts();
    if (!LO.Exceptions) {
      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());
  
    EHScope &innermostEHScope = *EHStack.find(EHStack.getInnermostEHScope());
    switch (innermostEHScope.getKind()) {
    case EHScope::Terminate:
      return getTerminateLandingPad();
  
    case EHScope::PadEnd:
      llvm_unreachable("PadEnd unnecessary for Itanium!");
  
    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<llvm::Value*, 4> filterTypes;
    llvm::SmallPtrSet<llvm::Value*, 4> 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<EHCleanupScope>(*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<EHFilterScope>(*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;
  
      case EHScope::PadEnd:
        llvm_unreachable("PadEnd unnecessary for Itanium!");
      }
  
      EHCatchScope &catchScope = cast<EHCatchScope>(*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<llvm::Constant*, 8> 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<llvm::Constant>(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<llvm::Value *, 4> 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);
  
    // 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!");
      typeValue = CGF.Builder.CreateBitCast(typeValue, CGF.Int8PtrTy);
  
      // 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<EHCatchScope>(*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<EHCatchScope>(*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<EHCatchScope::Handler, 8> 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<CXXDestructorDecl>(CurCodeDecl) ||
                          isa<CXXConstructorDecl>(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<llvm::Instruction *> RestoreCurrentFuncletPad(
        CurrentFuncletPad);
    llvm::BasicBlock *WasmCatchStartBlock = nullptr;
    if (EHPersonality::get(*this).isWasmPersonality()) {
      auto *CatchSwitch =
          cast<llvm::CatchSwitchInst>(DispatchBlock->getFirstNonPHI());
      WasmCatchStartBlock = CatchSwitch->hasUnwindDest()
                                ? CatchSwitch->getSuccessor(1)
                                : CatchSwitch->getSuccessor(0);
      auto *CPI = cast<llvm::CatchPadInst>(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<llvm::Instruction *> 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<llvm::BranchInst>(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_in_catch);
      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<CallEndCatchForFinally>(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(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<PerformFinally>(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<EHCatchScope>(*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<llvm::Instruction *> RestoreCurrentFuncletPad(
        CurrentFuncletPad);
    llvm::Value *ParentPad = CurrentFuncletPad;
    if (!ParentPad)
      ParentPad = llvm::ConstantTokenNone::get(CGM.getLLVMContext());
    CurrentFuncletPad = Builder.CreateCleanupPad(ParentPad);
  
    // Emit the __std_terminate call.
    llvm::Value *Exn = nullptr;
    // In case of wasm personality, we need to pass the exception value to
    // __clang_call_terminate function.
    if (getLangOpts().CPlusPlus &&
        EHPersonality::get(*this).isWasmPersonality()) {
      llvm::Function *GetExnFn =
          CGM.getIntrinsic(llvm::Intrinsic::wasm_get_exception);
      Exn = Builder.CreateCall(GetExnFn, CurrentFuncletPad);
    }
    llvm::CallInst *terminateCall =
        CGM.getCXXABI().emitTerminateForUnexpectedException(*this, Exn);
    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::UndefValue::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);
      EmitStmt(S.getTryBlock());
      SEHTryEpilogueStack.pop_back();
  
      if (!TryExit.getBlock()->use_empty())
        EmitBlock(TryExit.getBlock(), /*IsFinished=*/true);
      else
        delete TryExit.getBlock();
    }
    ExitSEHTryStmt(S);
  }
  
  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());
      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<CaptureFinder> {
    CodeGenFunction &ParentCGF;
    const VarDecl *ParentThis;
    llvm::SmallSetVector<const VarDecl *, 4> 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<CaptureFinder>::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);
        return;
      }
  
      const auto *D = dyn_cast<VarDecl>(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<llvm::AllocaInst>(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 i8* @llvm.localrecover(i8* bitcast(@parentFn), i8* %fp, i32 N)
      llvm::Function *FrameRecoverFn = llvm::Intrinsic::getDeclaration(
          &CGM.getModule(), llvm::Intrinsic::localrecover);
      llvm::Constant *ParentI8Fn =
          llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
      RecoverCall = Builder.CreateCall(
          FrameRecoverFn, {ParentI8Fn, 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<llvm::IntrinsicInst>(ParentVar.getPointer()->stripPointerCasts());
      assert(ParentRecover->getIntrinsicID() == llvm::Intrinsic::localrecover &&
             "expected alloca or localrecover in parent LocalDeclMap");
      RecoverCall = cast<llvm::CallInst>(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 Address(ChildVar, ParentVar.getAlignment());
  }
  
  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), {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);
      llvm::Constant *ParentI8Fn =
          llvm::ConstantExpr::getBitCast(ParentCGF.CurFn, Int8PtrTy);
      ParentFP = Builder.CreateCall(RecoverFPIntrin, {ParentI8Fn, EntryFP});
    }
  
    // Create llvm.localrecover calls for all captures.
    for (const VarDecl *VD : Finder.Captures) {
      if (isa<ImplicitParamDecl>(VD)) {
        CGM.ErrorUnsupported(VD, "'this' captured by SEH");
        CXXThisValue = llvm::UndefValue::get(ConvertTypeForMem(VD->getType()));
        continue;
      }
      if (VD->getType()->isVariablyModifiedType()) {
        CGM.ErrorUnsupported(VD, "VLA captured by SEH");
        continue;
      }
      assert((isa<ImplicitParamDecl>(VD) || VD->isLocalVarDeclOrParm()) &&
             "captured non-local variable");
  
      // 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;
      setAddrOfLocalVar(
          VD, recoverAddrOfEscapedLocal(ParentCGF, ParentVar, ParentFP));
    }
  
    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);
      const NamedDecl *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, ImplicitParamDecl::Other));
      } else {
        Args.push_back(ImplicitParamDecl::Create(
            getContext(), /*DC=*/nullptr, StartLoc,
            &getContext().Idents.get("abnormal_termination"),
            getContext().UnsignedCharTy, ImplicitParamDecl::Other));
      }
      Args.push_back(ImplicitParamDecl::Create(
          getContext(), /*DC=*/nullptr, StartLoc,
          &getContext().Idents.get("frame_pointer"), getContext().VoidPtrTy,
          ImplicitParamDecl::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.SetLLVMFunctionAttributes(GlobalDecl(), FnInfo, CurFn);
    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.CreateBitCast(SEHInfo, Int8PtrTy->getPointerTo());
      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 = CGM.Int32Ty->getPointerTo();
    llvm::Type *PtrsTy = llvm::StructType::get(RecordTy, CGM.VoidPtrTy);
    llvm::Value *Ptrs = Builder.CreateBitCast(SEHInfo, PtrsTy->getPointerTo());
    llvm::Value *Rec = Builder.CreateStructGEP(PtrsTy, Ptrs, 0);
    Rec = Builder.CreateAlignedLoad(Rec, getPointerAlign());
    llvm::Value *Code = Builder.CreateAlignedLoad(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<PerformSEHFinally>(Kind, FinallyFunc);
  }
  
  void CodeGenFunction::EnterSEHTryStmt(const SEHTryStmt &S) {
    CodeGenFunction HelperCGF(CGM, /*suppressNewContext=*/true);
    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<PerformSEHFinally>(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);
    llvm::Constant *OpaqueFunc =
        llvm::ConstantExpr::getBitCast(FilterFunc, Int8PtrTy);
    CatchScope->setHandler(0, OpaqueFunc, createBasicBlock("__except.ret"));
  }
  
  void CodeGenFunction::ExitSEHTryStmt(const SEHTryStmt &S) {
    // Just pop the cleanup if it's a __finally block.
    if (S.getFinallyHandler()) {
      PopCleanupBlock();
      return;
    }
  
    // Otherwise, we must have an __except block.
    const SEHExceptStmt *Except = S.getExceptHandler();
    assert(Except && "__try must have __finally xor __except");
    EHCatchScope &CatchScope = cast<EHCatchScope>(*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<llvm::CatchPadInst>(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());
  }
  