text: //===------- ItaniumCXXABI.cpp - Emit LLVM Code from ASTs for a Module ----===//
  //
  // 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 provides C++ code generation targeting the Itanium C++ ABI.  The class
  // in this file generates structures that follow the Itanium C++ ABI, which is
  // documented at:
  //  https://itanium-cxx-abi.github.io/cxx-abi/abi.html
  //  https://itanium-cxx-abi.github.io/cxx-abi/abi-eh.html
  //
  // It also supports the closely-related ARM ABI, documented at:
  // https://developer.arm.com/documentation/ihi0041/g/
  //
  //===----------------------------------------------------------------------===//
  
  #include "CGCXXABI.h"
  #include "CGCleanup.h"
  #include "CGRecordLayout.h"
  #include "CGVTables.h"
  #include "CodeGenFunction.h"
  #include "CodeGenModule.h"
  #include "TargetInfo.h"
  #include "clang/AST/Attr.h"
  #include "clang/AST/Mangle.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/AST/Type.h"
  #include "clang/CodeGen/ConstantInitBuilder.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/GlobalPtrAuthInfo.h"
  #include "llvm/IR/GlobalValue.h"
  #include "llvm/IR/Instructions.h"
  #include "llvm/IR/Intrinsics.h"
  #include "llvm/IR/Value.h"
  #include "llvm/Support/ScopedPrinter.h"
  
  using namespace clang;
  using namespace CodeGen;
  
  namespace {
  class ItaniumCXXABI : public CodeGen::CGCXXABI {
    /// VTables - All the vtables which have been defined.
    llvm::DenseMap<const CXXRecordDecl *, llvm::GlobalVariable *> VTables;
  
    /// All the thread wrapper functions that have been used.
    llvm::SmallVector<std::pair<const VarDecl *, llvm::Function *>, 8>
        ThreadWrappers;
  
  protected:
    bool UseARMMethodPtrABI;
    bool UseARMGuardVarABI;
    bool Use32BitVTableOffsetABI;
  
    ItaniumMangleContext &getMangleContext() {
      return cast<ItaniumMangleContext>(CodeGen::CGCXXABI::getMangleContext());
    }
  
  public:
    ItaniumCXXABI(CodeGen::CodeGenModule &CGM,
                  bool UseARMMethodPtrABI = false,
                  bool UseARMGuardVarABI = false) :
      CGCXXABI(CGM), UseARMMethodPtrABI(UseARMMethodPtrABI),
      UseARMGuardVarABI(UseARMGuardVarABI),
      Use32BitVTableOffsetABI(false) { }
  
    bool classifyReturnType(CGFunctionInfo &FI) const override;
  
    RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override {
      // If C++ prohibits us from making a copy, pass by address.
      if (!RD->canPassInRegisters())
        return RAA_Indirect;
      return RAA_Default;
    }
  
    bool isThisCompleteObject(GlobalDecl GD) const override {
      // The Itanium ABI has separate complete-object vs.  base-object
      // variants of both constructors and destructors.
      if (isa<CXXDestructorDecl>(GD.getDecl())) {
        switch (GD.getDtorType()) {
        case Dtor_Complete:
        case Dtor_Deleting:
          return true;
  
        case Dtor_Base:
          return false;
  
        case Dtor_Comdat:
          llvm_unreachable("emitting dtor comdat as function?");
        }
        llvm_unreachable("bad dtor kind");
      }
      if (isa<CXXConstructorDecl>(GD.getDecl())) {
        switch (GD.getCtorType()) {
        case Ctor_Complete:
          return true;
  
        case Ctor_Base:
          return false;
  
        case Ctor_CopyingClosure:
        case Ctor_DefaultClosure:
          llvm_unreachable("closure ctors in Itanium ABI?");
  
        case Ctor_Comdat:
          llvm_unreachable("emitting ctor comdat as function?");
        }
        llvm_unreachable("bad dtor kind");
      }
  
      // No other kinds.
      return false;
    }
  
    bool isZeroInitializable(const MemberPointerType *MPT) override;
  
    llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT) override;
  
    CGCallee
      EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
                                      const Expr *E,
                                      Address This,
                                      llvm::Value *&ThisPtrForCall,
                                      llvm::Value *MemFnPtr,
                                      const MemberPointerType *MPT) override;
  
    llvm::Value *
      EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
                                   Address Base,
                                   llvm::Value *MemPtr,
                                   const MemberPointerType *MPT) override;
  
    llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
                                             const CastExpr *E,
                                             llvm::Value *Src) override;
    llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
                                                llvm::Constant *Src) override;
  
    llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT) override;
  
    llvm::Constant *EmitMemberFunctionPointer(const CXXMethodDecl *MD) override;
    llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
                                          CharUnits offset) override;
    llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT) override;
    llvm::Constant *BuildMemberPointer(const CXXMethodDecl *MD,
                                       CharUnits ThisAdjustment);
  
    llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
                                             llvm::Value *L, llvm::Value *R,
                                             const MemberPointerType *MPT,
                                             bool Inequality) override;
  
    llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
                                           llvm::Value *Addr,
                                           const MemberPointerType *MPT) override;
  
    void emitVirtualObjectDelete(CodeGenFunction &CGF, const CXXDeleteExpr *DE,
                                 Address Ptr, QualType ElementType,
                                 const CXXDestructorDecl *Dtor) override;
  
    void emitRethrow(CodeGenFunction &CGF, bool isNoReturn) override;
    void emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) override;
  
    void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) override;
  
    llvm::CallInst *
    emitTerminateForUnexpectedException(CodeGenFunction &CGF,
                                        llvm::Value *Exn) override;
  
    void EmitFundamentalRTTIDescriptors(const CXXRecordDecl *RD);
    llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) override;
    CatchTypeInfo
    getAddrOfCXXCatchHandlerType(QualType Ty,
                                 QualType CatchHandlerType) override {
      return CatchTypeInfo{getAddrOfRTTIDescriptor(Ty), 0};
    }
  
    bool shouldTypeidBeNullChecked(bool IsDeref, QualType SrcRecordTy) override;
    void EmitBadTypeidCall(CodeGenFunction &CGF) override;
    llvm::Value *EmitTypeid(CodeGenFunction &CGF, QualType SrcRecordTy,
                            Address ThisPtr,
                            llvm::Type *StdTypeInfoPtrTy) override;
  
    bool shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
                                            QualType SrcRecordTy) override;
  
    llvm::Value *EmitDynamicCastCall(CodeGenFunction &CGF, Address Value,
                                     QualType SrcRecordTy, QualType DestTy,
                                     QualType DestRecordTy,
                                     llvm::BasicBlock *CastEnd) override;
  
    llvm::Value *EmitDynamicCastToVoid(CodeGenFunction &CGF, Address Value,
                                       QualType SrcRecordTy,
                                       QualType DestTy) override;
  
    bool EmitBadCastCall(CodeGenFunction &CGF) override;
  
    llvm::Value *
      GetVirtualBaseClassOffset(CodeGenFunction &CGF, Address This,
                                const CXXRecordDecl *ClassDecl,
                                const CXXRecordDecl *BaseClassDecl) override;
  
    void EmitCXXConstructors(const CXXConstructorDecl *D) override;
  
    AddedStructorArgCounts
    buildStructorSignature(GlobalDecl GD,
                           SmallVectorImpl<CanQualType> &ArgTys) override;
  
    bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
                                CXXDtorType DT) const override {
      // Itanium does not emit any destructor variant as an inline thunk.
      // Delegating may occur as an optimization, but all variants are either
      // emitted with external linkage or as linkonce if they are inline and used.
      return false;
    }
  
    void EmitCXXDestructors(const CXXDestructorDecl *D) override;
  
    void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
                                   FunctionArgList &Params) override;
  
    void EmitInstanceFunctionProlog(CodeGenFunction &CGF) override;
  
    AddedStructorArgs getImplicitConstructorArgs(CodeGenFunction &CGF,
                                                 const CXXConstructorDecl *D,
                                                 CXXCtorType Type,
                                                 bool ForVirtualBase,
                                                 bool Delegating) override;
  
    llvm::Value *getCXXDestructorImplicitParam(CodeGenFunction &CGF,
                                               const CXXDestructorDecl *DD,
                                               CXXDtorType Type,
                                               bool ForVirtualBase,
                                               bool Delegating) override;
  
    void EmitDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *DD,
                            CXXDtorType Type, bool ForVirtualBase,
                            bool Delegating, Address This,
                            QualType ThisTy) override;
  
    void emitVTableDefinitions(CodeGenVTables &CGVT,
                               const CXXRecordDecl *RD) override;
  
    bool isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
                                             CodeGenFunction::VPtr Vptr) override;
  
    bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) override {
      return true;
    }
  
    llvm::Constant *
    getVTableAddressPoint(BaseSubobject Base,
                          const CXXRecordDecl *VTableClass) override;
  
    llvm::Value *getVTableAddressPointInStructor(
        CodeGenFunction &CGF, const CXXRecordDecl *VTableClass,
        BaseSubobject Base, const CXXRecordDecl *NearestVBase) override;
  
    llvm::Value *getVTableAddressPointInStructorWithVTT(
        CodeGenFunction &CGF, const CXXRecordDecl *VTableClass,
        BaseSubobject Base, const CXXRecordDecl *NearestVBase);
  
    llvm::Constant *
    getVTableAddressPointForConstExpr(BaseSubobject Base,
                                      const CXXRecordDecl *VTableClass) override;
  
    llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
                                          CharUnits VPtrOffset) override;
  
    CGCallee getVirtualFunctionPointer(CodeGenFunction &CGF, GlobalDecl GD,
                                       Address This, llvm::Type *Ty,
                                       SourceLocation Loc) override;
  
    llvm::Value *EmitVirtualDestructorCall(CodeGenFunction &CGF,
                                           const CXXDestructorDecl *Dtor,
                                           CXXDtorType DtorType, Address This,
                                           DeleteOrMemberCallExpr E) override;
  
    void emitVirtualInheritanceTables(const CXXRecordDecl *RD) override;
  
    bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const override;
    bool canSpeculativelyEmitVTableAsBaseClass(const CXXRecordDecl *RD) const;
  
    void setThunkLinkage(llvm::Function *Thunk, bool ForVTable, GlobalDecl GD,
                         bool ReturnAdjustment) override {
      // Allow inlining of thunks by emitting them with available_externally
      // linkage together with vtables when needed.
      if (ForVTable && !Thunk->hasLocalLinkage())
        Thunk->setLinkage(llvm::GlobalValue::AvailableExternallyLinkage);
      CGM.setGVProperties(Thunk, GD);
    }
  
    bool exportThunk() override { return true; }
  
    llvm::Value *performThisAdjustment(CodeGenFunction &CGF, Address This,
                                       const ThisAdjustment &TA) override;
  
    llvm::Value *performReturnAdjustment(CodeGenFunction &CGF, Address Ret,
                                         const ReturnAdjustment &RA) override;
  
    size_t getSrcArgforCopyCtor(const CXXConstructorDecl *,
                                FunctionArgList &Args) const override {
      assert(!Args.empty() && "expected the arglist to not be empty!");
      return Args.size() - 1;
    }
  
    StringRef GetPureVirtualCallName() override { return "__cxa_pure_virtual"; }
    StringRef GetDeletedVirtualCallName() override
      { return "__cxa_deleted_virtual"; }
  
    CharUnits getArrayCookieSizeImpl(QualType elementType) override;
    Address InitializeArrayCookie(CodeGenFunction &CGF,
                                  Address NewPtr,
                                  llvm::Value *NumElements,
                                  const CXXNewExpr *expr,
                                  QualType ElementType) override;
    llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF,
                                     Address allocPtr,
                                     CharUnits cookieSize) override;
  
    void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
                         llvm::GlobalVariable *DeclPtr,
                         bool PerformInit) override;
    void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                            llvm::FunctionCallee dtor,
                            llvm::Constant *addr) override;
  
    llvm::Function *getOrCreateThreadLocalWrapper(const VarDecl *VD,
                                                  llvm::Value *Val);
    void EmitThreadLocalInitFuncs(
        CodeGenModule &CGM,
        ArrayRef<const VarDecl *> CXXThreadLocals,
        ArrayRef<llvm::Function *> CXXThreadLocalInits,
        ArrayRef<const VarDecl *> CXXThreadLocalInitVars) override;
  
    /// Determine whether we will definitely emit this variable with a constant
    /// initializer, either because the language semantics demand it or because
    /// we know that the initializer is a constant.
    bool isEmittedWithConstantInitializer(const VarDecl *VD) const {
      VD = VD->getMostRecentDecl();
      if (VD->hasAttr<ConstInitAttr>())
        return true;
  
      // All later checks examine the initializer specified on the variable. If
      // the variable is weak, such examination would not be correct.
      if (VD->isWeak() || VD->hasAttr<SelectAnyAttr>())
        return false;
  
      const VarDecl *InitDecl = VD->getInitializingDeclaration();
      if (!InitDecl)
        return false;
  
      // If there's no initializer to run, this is constant initialization.
      if (!InitDecl->hasInit())
        return true;
  
      // If we have the only definition, we don't need a thread wrapper if we
      // will emit the value as a constant.
      if (isUniqueGVALinkage(getContext().GetGVALinkageForVariable(VD)))
        return !VD->needsDestruction(getContext()) && InitDecl->evaluateValue();
  
      // Otherwise, we need a thread wrapper unless we know that every
      // translation unit will emit the value as a constant. We rely on the
      // variable being constant-initialized in every translation unit if it's
      // constant-initialized in any translation unit, which isn't actually
      // guaranteed by the standard but is necessary for sanity.
      return InitDecl->hasConstantInitialization();
    }
  
    bool usesThreadWrapperFunction(const VarDecl *VD) const override {
      return !isEmittedWithConstantInitializer(VD) ||
             VD->needsDestruction(getContext());
    }
    LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, const VarDecl *VD,
                                        QualType LValType) override;
  
    bool NeedsVTTParameter(GlobalDecl GD) override;
  
    llvm::Constant *
    getOrCreateVirtualFunctionPointerThunk(const CXXMethodDecl *MD);
  
    /**************************** RTTI Uniqueness ******************************/
  
  protected:
    /// Returns true if the ABI requires RTTI type_info objects to be unique
    /// across a program.
    virtual bool shouldRTTIBeUnique() const { return true; }
  
  public:
    /// What sort of unique-RTTI behavior should we use?
    enum RTTIUniquenessKind {
      /// We are guaranteeing, or need to guarantee, that the RTTI string
      /// is unique.
      RUK_Unique,
  
      /// We are not guaranteeing uniqueness for the RTTI string, so we
      /// can demote to hidden visibility but must use string comparisons.
      RUK_NonUniqueHidden,
  
      /// We are not guaranteeing uniqueness for the RTTI string, so we
      /// have to use string comparisons, but we also have to emit it with
      /// non-hidden visibility.
      RUK_NonUniqueVisible
    };
  
    /// Return the required visibility status for the given type and linkage in
    /// the current ABI.
    RTTIUniquenessKind
    classifyRTTIUniqueness(QualType CanTy,
                           llvm::GlobalValue::LinkageTypes Linkage) const;
    friend class ItaniumRTTIBuilder;
  
    void emitCXXStructor(GlobalDecl GD) override;
  
    std::pair<llvm::Value *, const CXXRecordDecl *>
    LoadVTablePtr(CodeGenFunction &CGF, Address This,
                  const CXXRecordDecl *RD) override;
  
   private:
     llvm::Constant *
     getSignedVirtualMemberFunctionPointer(const CXXMethodDecl *MD);
  
     bool hasAnyUnusedVirtualInlineFunction(const CXXRecordDecl *RD) const {
       const auto &VtableLayout =
           CGM.getItaniumVTableContext().getVTableLayout(RD);
  
       for (const auto &VtableComponent : VtableLayout.vtable_components()) {
         // Skip empty slot.
         if (!VtableComponent.isUsedFunctionPointerKind())
           continue;
  
         const CXXMethodDecl *Method = VtableComponent.getFunctionDecl();
         if (!Method->getCanonicalDecl()->isInlined())
           continue;
  
         StringRef Name = CGM.getMangledName(VtableComponent.getGlobalDecl());
         auto *Entry = CGM.GetGlobalValue(Name);
         // This checks if virtual inline function has already been emitted.
         // Note that it is possible that this inline function would be emitted
         // after trying to emit vtable speculatively. Because of this we do
         // an extra pass after emitting all deferred vtables to find and emit
         // these vtables opportunistically.
         if (!Entry || Entry->isDeclaration())
           return true;
       }
       return false;
    }
  
    bool isVTableHidden(const CXXRecordDecl *RD) const {
      const auto &VtableLayout =
              CGM.getItaniumVTableContext().getVTableLayout(RD);
  
      for (const auto &VtableComponent : VtableLayout.vtable_components()) {
        if (VtableComponent.isRTTIKind()) {
          const CXXRecordDecl *RTTIDecl = VtableComponent.getRTTIDecl();
          if (RTTIDecl->getVisibility() == Visibility::HiddenVisibility)
            return true;
        } else if (VtableComponent.isUsedFunctionPointerKind()) {
          const CXXMethodDecl *Method = VtableComponent.getFunctionDecl();
          if (Method->getVisibility() == Visibility::HiddenVisibility &&
              !Method->isDefined())
            return true;
        }
      }
      return false;
    }
  };
  
  class ARMCXXABI : public ItaniumCXXABI {
  public:
    ARMCXXABI(CodeGen::CodeGenModule &CGM) :
      ItaniumCXXABI(CGM, /*UseARMMethodPtrABI=*/true,
                    /*UseARMGuardVarABI=*/true) {}
  
    bool HasThisReturn(GlobalDecl GD) const override {
      return (isa<CXXConstructorDecl>(GD.getDecl()) || (
                isa<CXXDestructorDecl>(GD.getDecl()) &&
                GD.getDtorType() != Dtor_Deleting));
    }
  
    void EmitReturnFromThunk(CodeGenFunction &CGF, RValue RV,
                             QualType ResTy) override;
  
    CharUnits getArrayCookieSizeImpl(QualType elementType) override;
    Address InitializeArrayCookie(CodeGenFunction &CGF,
                                  Address NewPtr,
                                  llvm::Value *NumElements,
                                  const CXXNewExpr *expr,
                                  QualType ElementType) override;
    llvm::Value *readArrayCookieImpl(CodeGenFunction &CGF, Address allocPtr,
                                     CharUnits cookieSize) override;
  };
  
  class AppleARM64CXXABI : public ARMCXXABI {
  public:
    AppleARM64CXXABI(CodeGen::CodeGenModule &CGM) : ARMCXXABI(CGM) {
      Use32BitVTableOffsetABI = true;
    }
  
    // ARM64 libraries are prepared for non-unique RTTI.
    bool shouldRTTIBeUnique() const override { return false; }
  };
  
  class FuchsiaCXXABI final : public ItaniumCXXABI {
  public:
    explicit FuchsiaCXXABI(CodeGen::CodeGenModule &CGM)
        : ItaniumCXXABI(CGM) {}
  
  private:
    bool HasThisReturn(GlobalDecl GD) const override {
      return isa<CXXConstructorDecl>(GD.getDecl()) ||
             (isa<CXXDestructorDecl>(GD.getDecl()) &&
              GD.getDtorType() != Dtor_Deleting);
    }
  };
  
  class WebAssemblyCXXABI final : public ItaniumCXXABI {
  public:
    explicit WebAssemblyCXXABI(CodeGen::CodeGenModule &CGM)
        : ItaniumCXXABI(CGM, /*UseARMMethodPtrABI=*/true,
                        /*UseARMGuardVarABI=*/true) {}
    void emitBeginCatch(CodeGenFunction &CGF, const CXXCatchStmt *C) override;
  
  private:
    bool HasThisReturn(GlobalDecl GD) const override {
      return isa<CXXConstructorDecl>(GD.getDecl()) ||
             (isa<CXXDestructorDecl>(GD.getDecl()) &&
              GD.getDtorType() != Dtor_Deleting);
    }
    bool canCallMismatchedFunctionType() const override { return false; }
  };
  
  class XLCXXABI final : public ItaniumCXXABI {
  public:
    explicit XLCXXABI(CodeGen::CodeGenModule &CGM)
        : ItaniumCXXABI(CGM) {}
  
    void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                            llvm::FunctionCallee dtor,
                            llvm::Constant *addr) override;
  
    bool useSinitAndSterm() const override { return true; }
  
  private:
    void emitCXXStermFinalizer(const VarDecl &D, llvm::Function *dtorStub,
                               llvm::Constant *addr);
  };
  }
  
  CodeGen::CGCXXABI *CodeGen::CreateItaniumCXXABI(CodeGenModule &CGM) {
    switch (CGM.getTarget().getCXXABI().getKind()) {
    // For IR-generation purposes, there's no significant difference
    // between the ARM and iOS ABIs.
    case TargetCXXABI::GenericARM:
    case TargetCXXABI::iOS:
    case TargetCXXABI::WatchOS:
      return new ARMCXXABI(CGM);
  
    case TargetCXXABI::AppleARM64:
      return new AppleARM64CXXABI(CGM);
  
    case TargetCXXABI::Fuchsia:
      return new FuchsiaCXXABI(CGM);
  
    // Note that AArch64 uses the generic ItaniumCXXABI class since it doesn't
    // include the other 32-bit ARM oddities: constructor/destructor return values
    // and array cookies.
    case TargetCXXABI::GenericAArch64:
      return new ItaniumCXXABI(CGM, /*UseARMMethodPtrABI=*/true,
                               /*UseARMGuardVarABI=*/true);
  
    case TargetCXXABI::GenericMIPS:
      return new ItaniumCXXABI(CGM, /*UseARMMethodPtrABI=*/true);
  
    case TargetCXXABI::WebAssembly:
      return new WebAssemblyCXXABI(CGM);
  
    case TargetCXXABI::XL:
      return new XLCXXABI(CGM);
  
    case TargetCXXABI::GenericItanium:
      if (CGM.getContext().getTargetInfo().getTriple().getArch()
          == llvm::Triple::le32) {
        // For PNaCl, use ARM-style method pointers so that PNaCl code
        // does not assume anything about the alignment of function
        // pointers.
        return new ItaniumCXXABI(CGM, /*UseARMMethodPtrABI=*/true);
      }
      return new ItaniumCXXABI(CGM);
  
    case TargetCXXABI::Microsoft:
      llvm_unreachable("Microsoft ABI is not Itanium-based");
    }
    llvm_unreachable("bad ABI kind");
  }
  
  llvm::Type *
  ItaniumCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
    if (MPT->isMemberDataPointer())
      return CGM.PtrDiffTy;
    return llvm::StructType::get(CGM.PtrDiffTy, CGM.PtrDiffTy);
  }
  
  /// In the Itanium and ARM ABIs, method pointers have the form:
  ///   struct { ptrdiff_t ptr; ptrdiff_t adj; } memptr;
  ///
  /// In the Itanium ABI:
  ///  - method pointers are virtual if (memptr.ptr & 1) is nonzero
  ///  - the this-adjustment is (memptr.adj)
  ///  - the virtual offset is (memptr.ptr - 1)
  ///
  /// In the ARM ABI:
  ///  - method pointers are virtual if (memptr.adj & 1) is nonzero
  ///  - the this-adjustment is (memptr.adj >> 1)
  ///  - the virtual offset is (memptr.ptr)
  /// ARM uses 'adj' for the virtual flag because Thumb functions
  /// may be only single-byte aligned.
  ///
  /// If the member is virtual, the adjusted 'this' pointer points
  /// to a vtable pointer from which the virtual offset is applied.
  ///
  /// If the member is non-virtual, memptr.ptr is the address of
  /// the function to call.
  CGCallee ItaniumCXXABI::EmitLoadOfMemberFunctionPointer(
      CodeGenFunction &CGF, const Expr *E, Address ThisAddr,
      llvm::Value *&ThisPtrForCall,
      llvm::Value *MemFnPtr, const MemberPointerType *MPT) {
    CGBuilderTy &Builder = CGF.Builder;
  
    const FunctionProtoType *FPT =
      MPT->getPointeeType()->getAs<FunctionProtoType>();
    auto *RD =
        cast<CXXRecordDecl>(MPT->getClass()->castAs<RecordType>()->getDecl());
  
    llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(
        CGM.getTypes().arrangeCXXMethodType(RD, FPT, /*FD=*/nullptr));
  
    llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(CGM.PtrDiffTy, 1);
  
    llvm::BasicBlock *FnVirtual = CGF.createBasicBlock("memptr.virtual");
    llvm::BasicBlock *FnNonVirtual = CGF.createBasicBlock("memptr.nonvirtual");
    llvm::BasicBlock *FnEnd = CGF.createBasicBlock("memptr.end");
  
    // Extract memptr.adj, which is in the second field.
    llvm::Value *RawAdj = Builder.CreateExtractValue(MemFnPtr, 1, "memptr.adj");
  
    // Compute the true adjustment.
    llvm::Value *Adj = RawAdj;
    if (UseARMMethodPtrABI)
      Adj = Builder.CreateAShr(Adj, ptrdiff_1, "memptr.adj.shifted");
  
    // Apply the adjustment and cast back to the original struct type
    // for consistency.
    llvm::Value *This = ThisAddr.getPointer();
    llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
    Ptr = Builder.CreateInBoundsGEP(Ptr, Adj);
    This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
    ThisPtrForCall = This;
  
    // Load the function pointer.
    llvm::Value *FnAsInt = Builder.CreateExtractValue(MemFnPtr, 0, "memptr.ptr");
  
    // If the LSB in the function pointer is 1, the function pointer points to
    // a virtual function.
    llvm::Value *IsVirtual;
    if (UseARMMethodPtrABI)
      IsVirtual = Builder.CreateAnd(RawAdj, ptrdiff_1);
    else
      IsVirtual = Builder.CreateAnd(FnAsInt, ptrdiff_1);
    IsVirtual = Builder.CreateIsNotNull(IsVirtual, "memptr.isvirtual");
    Builder.CreateCondBr(IsVirtual, FnVirtual, FnNonVirtual);
  
    // In the virtual path, the adjustment left 'This' pointing to the
    // vtable of the correct base subobject.  The "function pointer" is an
    // offset within the vtable (+1 for the virtual flag on non-ARM).
    CGF.EmitBlock(FnVirtual);
  
    // Cast the adjusted this to a pointer to vtable pointer and load.
    llvm::Type *VTableTy = Builder.getInt8PtrTy();
    CharUnits VTablePtrAlign =
      CGF.CGM.getDynamicOffsetAlignment(ThisAddr.getAlignment(), RD,
                                        CGF.getPointerAlign());
    llvm::Value *VTable =
      CGF.GetVTablePtr(Address(This, VTablePtrAlign), VTableTy, RD);
  
    // Apply the offset.
    // On ARM64, to reserve extra space in virtual member function pointers,
    // we only pay attention to the low 32 bits of the offset.
    llvm::Value *VTableOffset = FnAsInt;
    if (!UseARMMethodPtrABI)
      VTableOffset = Builder.CreateSub(VTableOffset, ptrdiff_1);
    if (Use32BitVTableOffsetABI) {
      VTableOffset = Builder.CreateTrunc(VTableOffset, CGF.Int32Ty);
      VTableOffset = Builder.CreateZExt(VTableOffset, CGM.PtrDiffTy);
    }
  
    // Check the address of the function pointer if CFI on member function
    // pointers is enabled.
    llvm::Constant *CheckSourceLocation;
    llvm::Constant *CheckTypeDesc;
    bool ShouldEmitCFICheck = CGF.SanOpts.has(SanitizerKind::CFIMFCall) &&
                              CGM.HasHiddenLTOVisibility(RD);
    bool ShouldEmitVFEInfo = CGM.getCodeGenOpts().VirtualFunctionElimination &&
                             CGM.HasHiddenLTOVisibility(RD);
    bool ShouldEmitWPDInfo =
        CGM.getCodeGenOpts().WholeProgramVTables &&
        // Don't insert type tests if we are forcing public std visibility.
        !CGM.HasLTOVisibilityPublicStd(RD);
    llvm::Value *VirtualFn = nullptr;
  
    {
      CodeGenFunction::SanitizerScope SanScope(&CGF);
      llvm::Value *TypeId = nullptr;
      llvm::Value *CheckResult = nullptr;
  
      if (ShouldEmitCFICheck || ShouldEmitVFEInfo || ShouldEmitWPDInfo) {
        // If doing CFI, VFE or WPD, we will need the metadata node to check
        // against.
        llvm::Metadata *MD =
            CGM.CreateMetadataIdentifierForVirtualMemPtrType(QualType(MPT, 0));
        TypeId = llvm::MetadataAsValue::get(CGF.getLLVMContext(), MD);
      }
  
      if (ShouldEmitVFEInfo) {
        llvm::Value *VFPAddr = Builder.CreateGEP(VTable, VTableOffset);
  
        // If doing VFE, load from the vtable with a type.checked.load intrinsic
        // call. Note that we use the GEP to calculate the address to load from
        // and pass 0 as the offset to the intrinsic. This is because every
        // vtable slot of the correct type is marked with matching metadata, and
        // we know that the load must be from one of these slots.
        llvm::Value *CheckedLoad = Builder.CreateCall(
            CGM.getIntrinsic(llvm::Intrinsic::type_checked_load),
            {VFPAddr, llvm::ConstantInt::get(CGM.Int32Ty, 0), TypeId});
        CheckResult = Builder.CreateExtractValue(CheckedLoad, 1);
        VirtualFn = Builder.CreateExtractValue(CheckedLoad, 0);
        VirtualFn = Builder.CreateBitCast(VirtualFn, FTy->getPointerTo(),
                                          "memptr.virtualfn");
      } else {
        // When not doing VFE, emit a normal load, as it allows more
        // optimisations than type.checked.load.
        if (ShouldEmitCFICheck || ShouldEmitWPDInfo) {
          llvm::Value *VFPAddr = Builder.CreateGEP(VTable, VTableOffset);
          CheckResult = Builder.CreateCall(
              CGM.getIntrinsic(llvm::Intrinsic::type_test),
              {Builder.CreateBitCast(VFPAddr, CGF.Int8PtrTy), TypeId});
        }
  
        if (CGM.getItaniumVTableContext().isRelativeLayout()) {
          VirtualFn = CGF.Builder.CreateCall(
              CGM.getIntrinsic(llvm::Intrinsic::load_relative,
                               {VTableOffset->getType()}),
              {VTable, VTableOffset});
          VirtualFn = CGF.Builder.CreateBitCast(VirtualFn, FTy->getPointerTo());
        } else {
          llvm::Value *VFPAddr = CGF.Builder.CreateGEP(VTable, VTableOffset);
          VFPAddr = CGF.Builder.CreateBitCast(
              VFPAddr, FTy->getPointerTo()->getPointerTo());
          VirtualFn = CGF.Builder.CreateAlignedLoad(
              VFPAddr, CGF.getPointerAlign(), "memptr.virtualfn");
        }
      }
      assert(VirtualFn && "Virtual fuction pointer not created!");
      assert((!ShouldEmitCFICheck || !ShouldEmitVFEInfo || !ShouldEmitWPDInfo ||
              CheckResult) &&
             "Check result required but not created!");
  
      if (ShouldEmitCFICheck) {
        // If doing CFI, emit the check.
        CheckSourceLocation = CGF.EmitCheckSourceLocation(E->getBeginLoc());
        CheckTypeDesc = CGF.EmitCheckTypeDescriptor(QualType(MPT, 0));
        llvm::Constant *StaticData[] = {
            llvm::ConstantInt::get(CGF.Int8Ty, CodeGenFunction::CFITCK_VMFCall),
            CheckSourceLocation,
            CheckTypeDesc,
        };
  
        if (CGM.getCodeGenOpts().SanitizeTrap.has(SanitizerKind::CFIMFCall)) {
          CGF.EmitTrapCheck(CheckResult, SanitizerHandler::CFICheckFail);
        } else {
          llvm::Value *AllVtables = llvm::MetadataAsValue::get(
              CGM.getLLVMContext(),
              llvm::MDString::get(CGM.getLLVMContext(), "all-vtables"));
          llvm::Value *ValidVtable = Builder.CreateCall(
              CGM.getIntrinsic(llvm::Intrinsic::type_test), {VTable, AllVtables});
          CGF.EmitCheck(std::make_pair(CheckResult, SanitizerKind::CFIMFCall),
                        SanitizerHandler::CFICheckFail, StaticData,
                        {VTable, ValidVtable});
        }
  
        FnVirtual = Builder.GetInsertBlock();
      }
    } // End of sanitizer scope
  
    CGF.EmitBranch(FnEnd);
  
    // In the non-virtual path, the function pointer is actually a
    // function pointer.
    CGF.EmitBlock(FnNonVirtual);
    llvm::Value *NonVirtualFn =
      Builder.CreateIntToPtr(FnAsInt, FTy->getPointerTo(), "memptr.nonvirtualfn");
  
    // Check the function pointer if CFI on member function pointers is enabled.
    if (ShouldEmitCFICheck) {
      CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
      if (RD->hasDefinition()) {
        CodeGenFunction::SanitizerScope SanScope(&CGF);
  
        llvm::Constant *StaticData[] = {
            llvm::ConstantInt::get(CGF.Int8Ty, CodeGenFunction::CFITCK_NVMFCall),
            CheckSourceLocation,
            CheckTypeDesc,
        };
  
        llvm::Value *Bit = Builder.getFalse();
        llvm::Value *CastedNonVirtualFn =
            Builder.CreateBitCast(NonVirtualFn, CGF.Int8PtrTy);
        for (const CXXRecordDecl *Base : CGM.getMostBaseClasses(RD)) {
          llvm::Metadata *MD = CGM.CreateMetadataIdentifierForType(
              getContext().getMemberPointerType(
                  MPT->getPointeeType(),
                  getContext().getRecordType(Base).getTypePtr()));
          llvm::Value *TypeId =
              llvm::MetadataAsValue::get(CGF.getLLVMContext(), MD);
  
          llvm::Value *TypeTest =
              Builder.CreateCall(CGM.getIntrinsic(llvm::Intrinsic::type_test),
                                 {CastedNonVirtualFn, TypeId});
          Bit = Builder.CreateOr(Bit, TypeTest);
        }
  
        CGF.EmitCheck(std::make_pair(Bit, SanitizerKind::CFIMFCall),
                      SanitizerHandler::CFICheckFail, StaticData,
                      {CastedNonVirtualFn, llvm::UndefValue::get(CGF.IntPtrTy)});
  
        FnNonVirtual = Builder.GetInsertBlock();
      }
    }
  
    // We're done.
    CGF.EmitBlock(FnEnd);
    llvm::PHINode *CalleePtr = Builder.CreatePHI(FTy->getPointerTo(), 2);
    CalleePtr->addIncoming(VirtualFn, FnVirtual);
    CalleePtr->addIncoming(NonVirtualFn, FnNonVirtual);
  
    CGPointerAuthInfo PointerAuth;
  
    if (const auto &Schema =
            CGM.getCodeGenOpts().PointerAuth.CXXMemberFunctionPointers) {
      llvm::PHINode *DiscriminatorPHI = Builder.CreatePHI(CGF.IntPtrTy, 2);
      DiscriminatorPHI->addIncoming(llvm::ConstantInt::get(CGF.IntPtrTy, 0),
                                    FnVirtual);
      const auto &AuthInfo =
          CGM.getMemberFunctionPointerAuthInfo(QualType(MPT, 0));
      assert(Schema.getKey() == AuthInfo.getKey() &&
             "Keys for virtual and non-virtual member functions must match");
      auto *NonVirtualDiscriminator = AuthInfo.getDiscriminator();
      DiscriminatorPHI->addIncoming(NonVirtualDiscriminator, FnNonVirtual);
      PointerAuth = CGPointerAuthInfo(Schema.getKey(), DiscriminatorPHI);
    }
  
    CGCallee Callee(FPT, CalleePtr, PointerAuth);
    return Callee;
  }
  
  /// Compute an l-value by applying the given pointer-to-member to a
  /// base object.
  llvm::Value *ItaniumCXXABI::EmitMemberDataPointerAddress(
      CodeGenFunction &CGF, const Expr *E, Address Base, llvm::Value *MemPtr,
      const MemberPointerType *MPT) {
    assert(MemPtr->getType() == CGM.PtrDiffTy);
  
    CGBuilderTy &Builder = CGF.Builder;
  
    // Cast to char*.
    Base = Builder.CreateElementBitCast(Base, CGF.Int8Ty);
  
    // Apply the offset, which we assume is non-null.
    llvm::Value *Addr =
      Builder.CreateInBoundsGEP(Base.getPointer(), MemPtr, "memptr.offset");
  
    // Cast the address to the appropriate pointer type, adopting the
    // address space of the base pointer.
    llvm::Type *PType = CGF.ConvertTypeForMem(MPT->getPointeeType())
                              ->getPointerTo(Base.getAddressSpace());
    return Builder.CreateBitCast(Addr, PType);
  }
  
  // See if it's possible to return a constant signed pointer.
  static llvm::Constant *pointerAuthResignConstant(
      llvm::Value *Ptr, const CGPointerAuthInfo &CurAuthInfo,
      const CGPointerAuthInfo &NewAuthInfo, CodeGenModule &CGM) {
    Optional<llvm::GlobalPtrAuthInfo> Info =
        llvm::GlobalPtrAuthInfo::analyze(Ptr);
  
    if (!Info || !isa<llvm::Constant>(NewAuthInfo.getDiscriminator()))
      return nullptr;
  
    assert(Info->getKey()->getZExtValue() == CurAuthInfo.getKey() &&
           Info->getAddrDiscriminator()->isZeroValue() &&
           Info->getDiscriminator() == CurAuthInfo.getDiscriminator() &&
           "unexpected key or discriminators");
  
    return CGM.getConstantSignedPointer(
        Info->getPointer(), NewAuthInfo.getKey(), nullptr,
        cast<llvm::Constant>(NewAuthInfo.getDiscriminator()));
  }
  
  /// Perform a bitcast, derived-to-base, or base-to-derived member pointer
  /// conversion.
  ///
  /// Bitcast conversions are always a no-op under Itanium.
  ///
  /// Obligatory offset/adjustment diagram:
  ///         <-- offset -->          <-- adjustment -->
  ///   |--------------------------|----------------------|--------------------|
  ///   ^Derived address point     ^Base address point    ^Member address point
  ///
  /// So when converting a base member pointer to a derived member pointer,
  /// we add the offset to the adjustment because the address point has
  /// decreased;  and conversely, when converting a derived MP to a base MP
  /// we subtract the offset from the adjustment because the address point
  /// has increased.
  ///
  /// The standard forbids (at compile time) conversion to and from
  /// virtual bases, which is why we don't have to consider them here.
  ///
  /// The standard forbids (at run time) casting a derived MP to a base
  /// MP when the derived MP does not point to a member of the base.
  /// This is why -1 is a reasonable choice for null data member
  /// pointers.
  llvm::Value *
  ItaniumCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
                                             const CastExpr *E,
                                             llvm::Value *src) {
    // Use constant emission if we can.
    if (isa<llvm::Constant>(src))
      return EmitMemberPointerConversion(E, cast<llvm::Constant>(src));
  
    assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
           E->getCastKind() == CK_BaseToDerivedMemberPointer ||
           E->getCastKind() == CK_ReinterpretMemberPointer);
  
    CGBuilderTy &Builder = CGF.Builder;
    QualType dstType = E->getType();
  
    if (dstType->isMemberFunctionPointerType())
      if (const auto &newAuthInfo =
              CGM.getMemberFunctionPointerAuthInfo(dstType)) {
        QualType srcType = E->getSubExpr()->getType();
        assert(srcType->isMemberFunctionPointerType());
        const auto &curAuthInfo = CGM.getMemberFunctionPointerAuthInfo(srcType);
        llvm::Value *memFnPtr = Builder.CreateExtractValue(src, 0, "memptr.ptr");
        llvm::Type *origTy = memFnPtr->getType();
  
        llvm::BasicBlock *startBB = Builder.GetInsertBlock();
        llvm::BasicBlock *resignBB = CGF.createBasicBlock("resign");
        llvm::BasicBlock *mergeBB = CGF.createBasicBlock("merge");
  
        // Check whether we have a virtual offset or a pointer to a function.
        assert(UseARMMethodPtrABI && "ARM ABI expected");
        llvm::Value *adj = Builder.CreateExtractValue(src, 1, "memptr.adj");
        llvm::Constant *ptrdiff_1 = llvm::ConstantInt::get(CGM.PtrDiffTy, 1);
        llvm::Value *andVal = Builder.CreateAnd(adj, ptrdiff_1);
        llvm::Value *isVirtualOffset =
            Builder.CreateIsNotNull(andVal, "is.virtual.offset");
        Builder.CreateCondBr(isVirtualOffset, mergeBB, resignBB);
  
        CGF.EmitBlock(resignBB);
        llvm::Type *ptrTy = llvm::PointerType::getUnqual(CGM.Int8Ty);
        memFnPtr = Builder.CreateIntToPtr(memFnPtr, ptrTy);
        memFnPtr = CGF.EmitPointerAuthResign(memFnPtr, srcType, curAuthInfo,
                                             newAuthInfo,
                                             isa<llvm::Constant>(src));
        memFnPtr = Builder.CreatePtrToInt(memFnPtr, origTy);
        llvm::Value *resignedVal = Builder.CreateInsertValue(src, memFnPtr, 0);
        resignBB = Builder.GetInsertBlock();
  
        CGF.EmitBlock(mergeBB);
        llvm::PHINode *newSrc = Builder.CreatePHI(src->getType(), 2);
        newSrc->addIncoming(src, startBB);
        newSrc->addIncoming(resignedVal, resignBB);
        src = newSrc;
      }
  
    // Under Itanium, reinterprets don't require any additional processing.
    if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
  
    llvm::Constant *adj = getMemberPointerAdjustment(E);
    if (!adj) return src;
  
    bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
  
    const MemberPointerType *destTy =
      E->getType()->castAs<MemberPointerType>();
  
    // For member data pointers, this is just a matter of adding the
    // offset if the source is non-null.
    if (destTy->isMemberDataPointer()) {
      llvm::Value *dst;
      if (isDerivedToBase)
        dst = Builder.CreateNSWSub(src, adj, "adj");
      else
        dst = Builder.CreateNSWAdd(src, adj, "adj");
  
      // Null check.
      llvm::Value *null = llvm::Constant::getAllOnesValue(src->getType());
      llvm::Value *isNull = Builder.CreateICmpEQ(src, null, "memptr.isnull");
      return Builder.CreateSelect(isNull, src, dst);
    }
  
    // The this-adjustment is left-shifted by 1 on ARM.
    if (UseARMMethodPtrABI) {
      uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
      offset <<= 1;
      adj = llvm::ConstantInt::get(adj->getType(), offset);
    }
  
    llvm::Value *srcAdj = Builder.CreateExtractValue(src, 1, "src.adj");
    llvm::Value *dstAdj;
    if (isDerivedToBase)
      dstAdj = Builder.CreateNSWSub(srcAdj, adj, "adj");
    else
      dstAdj = Builder.CreateNSWAdd(srcAdj, adj, "adj");
  
    return Builder.CreateInsertValue(src, dstAdj, 1);
  }
  
  llvm::Constant *
  ItaniumCXXABI::EmitMemberPointerConversion(const CastExpr *E,
                                             llvm::Constant *src) {
    assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
           E->getCastKind() == CK_BaseToDerivedMemberPointer ||
           E->getCastKind() == CK_ReinterpretMemberPointer);
  
    QualType dstType = E->getType();
  
    if (dstType->isMemberFunctionPointerType())
      if (const auto &newAuthInfo =
              CGM.getMemberFunctionPointerAuthInfo(dstType)) {
        assert(UseARMMethodPtrABI && "ARM ABI expected");
        QualType srcType = E->getSubExpr()->getType();
        const auto &curAuthInfo = CGM.getMemberFunctionPointerAuthInfo(srcType);
        llvm::Constant *memFnPtr = llvm::ConstantExpr::getExtractValue(src, 0);
        llvm::Constant *constPtr =
            pointerAuthResignConstant(cast<llvm::User>(memFnPtr)->getOperand(0),
                                      curAuthInfo, newAuthInfo, CGM);
        constPtr = llvm::ConstantExpr::getPtrToInt(constPtr, memFnPtr->getType());
        src = llvm::ConstantExpr::getInsertValue(src, constPtr, 0);
      }
  
    // Under Itanium, reinterprets don't require any additional processing.
    if (E->getCastKind() == CK_ReinterpretMemberPointer) return src;
  
    // If the adjustment is trivial, we don't need to do anything.
    llvm::Constant *adj = getMemberPointerAdjustment(E);
    if (!adj) return src;
  
    bool isDerivedToBase = (E->getCastKind() == CK_DerivedToBaseMemberPointer);
  
    const MemberPointerType *destTy =
      E->getType()->castAs<MemberPointerType>();
  
    // For member data pointers, this is just a matter of adding the
    // offset if the source is non-null.
    if (destTy->isMemberDataPointer()) {
      // null maps to null.
      if (src->isAllOnesValue()) return src;
  
      if (isDerivedToBase)
        return llvm::ConstantExpr::getNSWSub(src, adj);
      else
        return llvm::ConstantExpr::getNSWAdd(src, adj);
    }
  
    // The this-adjustment is left-shifted by 1 on ARM.
    if (UseARMMethodPtrABI) {
      uint64_t offset = cast<llvm::ConstantInt>(adj)->getZExtValue();
      offset <<= 1;
      adj = llvm::ConstantInt::get(adj->getType(), offset);
    }
  
    llvm::Constant *srcAdj = llvm::ConstantExpr::getExtractValue(src, 1);
    llvm::Constant *dstAdj;
    if (isDerivedToBase)
      dstAdj = llvm::ConstantExpr::getNSWSub(srcAdj, adj);
    else
      dstAdj = llvm::ConstantExpr::getNSWAdd(srcAdj, adj);
  
    return llvm::ConstantExpr::getInsertValue(src, dstAdj, 1);
  }
  
  llvm::Constant *
  ItaniumCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
    // Itanium C++ ABI 2.3:
    //   A NULL pointer is represented as -1.
    if (MPT->isMemberDataPointer())
      return llvm::ConstantInt::get(CGM.PtrDiffTy, -1ULL, /*isSigned=*/true);
  
    llvm::Constant *Zero = llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
    llvm::Constant *Values[2] = { Zero, Zero };
    return llvm::ConstantStruct::getAnon(Values);
  }
  
  llvm::Constant *
  ItaniumCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
                                       CharUnits offset) {
    // Itanium C++ ABI 2.3:
    //   A pointer to data member is an offset from the base address of
    //   the class object containing it, represented as a ptrdiff_t
    return llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity());
  }
  
  llvm::Constant *
  ItaniumCXXABI::EmitMemberFunctionPointer(const CXXMethodDecl *MD) {
    return BuildMemberPointer(MD, CharUnits::Zero());
  }
  
  llvm::Constant *ItaniumCXXABI::BuildMemberPointer(const CXXMethodDecl *MD,
                                                    CharUnits ThisAdjustment) {
    assert(MD->isInstance() && "Member function must not be static!");
  
    CodeGenTypes &Types = CGM.getTypes();
  
    // Get the function pointer (or index if this is a virtual function).
    llvm::Constant *MemPtr[2];
    if (MD->isVirtual()) {
      uint64_t Index = CGM.getItaniumVTableContext().getMethodVTableIndex(MD);
      uint64_t VTableOffset;
      if (CGM.getItaniumVTableContext().isRelativeLayout()) {
        // Multiply by 4-byte relative offsets.
        VTableOffset = Index * 4;
      } else {
        const ASTContext &Context = getContext();
        CharUnits PointerWidth = Context.toCharUnitsFromBits(
            Context.getTargetInfo().getPointerWidth(0));
        VTableOffset = Index * PointerWidth.getQuantity();
      }
  
      if (UseARMMethodPtrABI) {
        // ARM C++ ABI 3.2.1:
        //   This ABI specifies that adj contains twice the this
        //   adjustment, plus 1 if the member function is virtual. The
        //   least significant bit of adj then makes exactly the same
        //   discrimination as the least significant bit of ptr does for
        //   Itanium.
  
        // We cannot use the Itanium ABI's representation for virtual member
        // function pointers under pointer authentication because it would
        // require us to store both the virtual offset and the constant
        // discriminator in the pointer, which would be immediately vulnerable
        // to attack.  Instead we introduce a thunk that does the virtual dispatch
        // and store it as if it were a non-virtual member function.  This means
        // that virtual function pointers may not compare equal anymore, but
        // fortunately they aren't required to by the standard, and we do make
        // a best-effort attempt to re-use the thunk.
        //
        // To support interoperation with code in which pointer authentication
        // is disabled, derefencing a member function pointer must still handle
        // the virtual case, but it can use a discriminator which should never
        // be valid.
        const auto &Schema =
            CGM.getCodeGenOpts().PointerAuth.CXXMemberFunctionPointers;
        if (Schema)
          MemPtr[0] = llvm::ConstantExpr::getPtrToInt(
              getSignedVirtualMemberFunctionPointer(MD), CGM.PtrDiffTy);
        else
          MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset);
        // Don't set the LSB of adj to 1 if pointer authentication for member
        // function pointers is enabled.
        MemPtr[1] =
            llvm::ConstantInt::get(CGM.PtrDiffTy,
                                   2 * ThisAdjustment.getQuantity() + !Schema);
      } else {
        // Itanium C++ ABI 2.3:
        //   For a virtual function, [the pointer field] is 1 plus the
        //   virtual table offset (in bytes) of the function,
        //   represented as a ptrdiff_t.
        MemPtr[0] = llvm::ConstantInt::get(CGM.PtrDiffTy, VTableOffset + 1);
        MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
                                           ThisAdjustment.getQuantity());
      }
    } else {
      const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
      llvm::Type *Ty;
      // Check whether the function has a computable LLVM signature.
      if (Types.isFuncTypeConvertible(FPT)) {
        // The function has a computable LLVM signature; use the correct type.
        Ty = Types.GetFunctionType(Types.arrangeCXXMethodDeclaration(MD));
      } else {
        // Use an arbitrary non-function type to tell GetAddrOfFunction that the
        // function type is incomplete.
        Ty = CGM.PtrDiffTy;
      }
      llvm::Constant *addr = CGM.getMemberFunctionPointer(MD, Ty);
  
      MemPtr[0] = llvm::ConstantExpr::getPtrToInt(addr, CGM.PtrDiffTy);
      MemPtr[1] = llvm::ConstantInt::get(CGM.PtrDiffTy,
                                         (UseARMMethodPtrABI ? 2 : 1) *
                                         ThisAdjustment.getQuantity());
    }
  
    return llvm::ConstantStruct::getAnon(MemPtr);
  }
  
  llvm::Constant *ItaniumCXXABI::EmitMemberPointer(const APValue &MP,
                                                   QualType MPType) {
    const MemberPointerType *MPT = MPType->castAs<MemberPointerType>();
    const ValueDecl *MPD = MP.getMemberPointerDecl();
    if (!MPD)
      return EmitNullMemberPointer(MPT);
  
    CharUnits ThisAdjustment = getContext().getMemberPointerPathAdjustment(MP);
  
    if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD))
      return BuildMemberPointer(MD, ThisAdjustment);
  
    CharUnits FieldOffset =
      getContext().toCharUnitsFromBits(getContext().getFieldOffset(MPD));
    return EmitMemberDataPointer(MPT, ThisAdjustment + FieldOffset);
  }
  
  /// The comparison algorithm is pretty easy: the member pointers are
  /// the same if they're either bitwise identical *or* both null.
  ///
  /// ARM is different here only because null-ness is more complicated.
  llvm::Value *
  ItaniumCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
                                             llvm::Value *L,
                                             llvm::Value *R,
                                             const MemberPointerType *MPT,
                                             bool Inequality) {
    CGBuilderTy &Builder = CGF.Builder;
  
    llvm::ICmpInst::Predicate Eq;
    llvm::Instruction::BinaryOps And, Or;
    if (Inequality) {
      Eq = llvm::ICmpInst::ICMP_NE;
      And = llvm::Instruction::Or;
      Or = llvm::Instruction::And;
    } else {
      Eq = llvm::ICmpInst::ICMP_EQ;
      And = llvm::Instruction::And;
      Or = llvm::Instruction::Or;
    }
  
    // Member data pointers are easy because there's a unique null
    // value, so it just comes down to bitwise equality.
    if (MPT->isMemberDataPointer())
      return Builder.CreateICmp(Eq, L, R);
  
    // For member function pointers, the tautologies are more complex.
    // The Itanium tautology is:
    //   (L == R) <==> (L.ptr == R.ptr && (L.ptr == 0 || L.adj == R.adj))
    // The ARM tautology is:
    //   (L == R) <==> (L.ptr == R.ptr &&
    //                  (L.adj == R.adj ||
    //                   (L.ptr == 0 && ((L.adj|R.adj) & 1) == 0)))
    // The inequality tautologies have exactly the same structure, except
    // applying De Morgan's laws.
  
    llvm::Value *LPtr = Builder.CreateExtractValue(L, 0, "lhs.memptr.ptr");
    llvm::Value *RPtr = Builder.CreateExtractValue(R, 0, "rhs.memptr.ptr");
  
    // This condition tests whether L.ptr == R.ptr.  This must always be
    // true for equality to hold.
    llvm::Value *PtrEq = Builder.CreateICmp(Eq, LPtr, RPtr, "cmp.ptr");
  
    // This condition, together with the assumption that L.ptr == R.ptr,
    // tests whether the pointers are both null.  ARM imposes an extra
    // condition.
    llvm::Value *Zero = llvm::Constant::getNullValue(LPtr->getType());
    llvm::Value *EqZero = Builder.CreateICmp(Eq, LPtr, Zero, "cmp.ptr.null");
  
    // This condition tests whether L.adj == R.adj.  If this isn't
    // true, the pointers are unequal unless they're both null.
    llvm::Value *LAdj = Builder.CreateExtractValue(L, 1, "lhs.memptr.adj");
    llvm::Value *RAdj = Builder.CreateExtractValue(R, 1, "rhs.memptr.adj");
    llvm::Value *AdjEq = Builder.CreateICmp(Eq, LAdj, RAdj, "cmp.adj");
  
    // Null member function pointers on ARM clear the low bit of Adj,
    // so the zero condition has to check that neither low bit is set.
    if (UseARMMethodPtrABI) {
      llvm::Value *One = llvm::ConstantInt::get(LPtr->getType(), 1);
  
      // Compute (l.adj | r.adj) & 1 and test it against zero.
      llvm::Value *OrAdj = Builder.CreateOr(LAdj, RAdj, "or.adj");
      llvm::Value *OrAdjAnd1 = Builder.CreateAnd(OrAdj, One);
      llvm::Value *OrAdjAnd1EqZero = Builder.CreateICmp(Eq, OrAdjAnd1, Zero,
                                                        "cmp.or.adj");
      EqZero = Builder.CreateBinOp(And, EqZero, OrAdjAnd1EqZero);
    }
  
    // Tie together all our conditions.
    llvm::Value *Result = Builder.CreateBinOp(Or, EqZero, AdjEq);
    Result = Builder.CreateBinOp(And, PtrEq, Result,
                                 Inequality ? "memptr.ne" : "memptr.eq");
    return Result;
  }
  
  llvm::Value *
  ItaniumCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
                                            llvm::Value *MemPtr,
                                            const MemberPointerType *MPT) {
    CGBuilderTy &Builder = CGF.Builder;
  
    /// For member data pointers, this is just a check against -1.
    if (MPT->isMemberDataPointer()) {
      assert(MemPtr->getType() == CGM.PtrDiffTy);
      llvm::Value *NegativeOne =
        llvm::Constant::getAllOnesValue(MemPtr->getType());
      return Builder.CreateICmpNE(MemPtr, NegativeOne, "memptr.tobool");
    }
  
    // In Itanium, a member function pointer is not null if 'ptr' is not null.
    llvm::Value *Ptr = Builder.CreateExtractValue(MemPtr, 0, "memptr.ptr");
  
    llvm::Constant *Zero = llvm::ConstantInt::get(Ptr->getType(), 0);
    llvm::Value *Result = Builder.CreateICmpNE(Ptr, Zero, "memptr.tobool");
  
    // On ARM, a member function pointer is also non-null if the low bit of 'adj'
    // (the virtual bit) is set.
    if (UseARMMethodPtrABI) {
      llvm::Constant *One = llvm::ConstantInt::get(Ptr->getType(), 1);
      llvm::Value *Adj = Builder.CreateExtractValue(MemPtr, 1, "memptr.adj");
      llvm::Value *VirtualBit = Builder.CreateAnd(Adj, One, "memptr.virtualbit");
      llvm::Value *IsVirtual = Builder.CreateICmpNE(VirtualBit, Zero,
                                                    "memptr.isvirtual");
      Result = Builder.CreateOr(Result, IsVirtual);
    }
  
    return Result;
  }
  
  bool ItaniumCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
    const CXXRecordDecl *RD = FI.getReturnType()->getAsCXXRecordDecl();
    if (!RD)
      return false;
  
    // If C++ prohibits us from making a copy, return by address.
    if (!RD->canPassInRegisters()) {
      auto Align = CGM.getContext().getTypeAlignInChars(FI.getReturnType());
      FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
      return true;
    }
    return false;
  }
  
  /// The Itanium ABI requires non-zero initialization only for data
  /// member pointers, for which '0' is a valid offset.
  bool ItaniumCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
    return MPT->isMemberFunctionPointer();
  }
  
  /// The Itanium ABI always places an offset to the complete object
  /// at entry -2 in the vtable.
  void ItaniumCXXABI::emitVirtualObjectDelete(CodeGenFunction &CGF,
                                              const CXXDeleteExpr *DE,
                                              Address Ptr,
                                              QualType ElementType,
                                              const CXXDestructorDecl *Dtor) {
    bool UseGlobalDelete = DE->isGlobalDelete();
    if (UseGlobalDelete) {
      // Derive the complete-object pointer, which is what we need
      // to pass to the deallocation function.
  
      // Grab the vtable pointer as an intptr_t*.
      auto *ClassDecl =
          cast<CXXRecordDecl>(ElementType->castAs<RecordType>()->getDecl());
      llvm::Value *VTable =
          CGF.GetVTablePtr(Ptr, CGF.IntPtrTy->getPointerTo(), ClassDecl);
  
      // Track back to entry -2 and pull out the offset there.
      llvm::Value *OffsetPtr = CGF.Builder.CreateConstInBoundsGEP1_64(
          VTable, -2, "complete-offset.ptr");
      llvm::Value *Offset =
        CGF.Builder.CreateAlignedLoad(OffsetPtr, CGF.getPointerAlign());
  
      // Apply the offset.
      llvm::Value *CompletePtr =
        CGF.Builder.CreateBitCast(Ptr.getPointer(), CGF.Int8PtrTy);
      CompletePtr = CGF.Builder.CreateInBoundsGEP(CompletePtr, Offset);
  
      // If we're supposed to call the global delete, make sure we do so
      // even if the destructor throws.
      CGF.pushCallObjectDeleteCleanup(DE->getOperatorDelete(), CompletePtr,
                                      ElementType);
    }
  
    // FIXME: Provide a source location here even though there's no
    // CXXMemberCallExpr for dtor call.
    CXXDtorType DtorType = UseGlobalDelete ? Dtor_Complete : Dtor_Deleting;
    EmitVirtualDestructorCall(CGF, Dtor, DtorType, Ptr, DE);
  
    if (UseGlobalDelete)
      CGF.PopCleanupBlock();
  }
  
  void ItaniumCXXABI::emitRethrow(CodeGenFunction &CGF, bool isNoReturn) {
    // void __cxa_rethrow();
  
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
  
    llvm::FunctionCallee Fn = CGM.CreateRuntimeFunction(FTy, "__cxa_rethrow");
  
    if (isNoReturn)
      CGF.EmitNoreturnRuntimeCallOrInvoke(Fn, None);
    else
      CGF.EmitRuntimeCallOrInvoke(Fn);
  }
  
  static llvm::FunctionCallee getAllocateExceptionFn(CodeGenModule &CGM) {
    // void *__cxa_allocate_exception(size_t thrown_size);
  
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.Int8PtrTy, CGM.SizeTy, /*isVarArg=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_allocate_exception");
  }
  
  static llvm::FunctionCallee getThrowFn(CodeGenModule &CGM) {
    // void __cxa_throw(void *thrown_exception, std::type_info *tinfo,
    //                  void (*dest) (void *));
  
    llvm::Type *Args[3] = { CGM.Int8PtrTy, CGM.Int8PtrTy, CGM.Int8PtrTy };
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.VoidTy, Args, /*isVarArg=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_throw");
  }
  
  void ItaniumCXXABI::emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) {
    QualType ThrowType = E->getSubExpr()->getType();
    // Now allocate the exception object.
    llvm::Type *SizeTy = CGF.ConvertType(getContext().getSizeType());
    uint64_t TypeSize = getContext().getTypeSizeInChars(ThrowType).getQuantity();
  
    llvm::FunctionCallee AllocExceptionFn = getAllocateExceptionFn(CGM);
    llvm::CallInst *ExceptionPtr = CGF.EmitNounwindRuntimeCall(
        AllocExceptionFn, llvm::ConstantInt::get(SizeTy, TypeSize), "exception");
  
    CharUnits ExnAlign = CGF.getContext().getExnObjectAlignment();
    CGF.EmitAnyExprToExn(E->getSubExpr(), Address(ExceptionPtr, ExnAlign));
  
    // Now throw the exception.
    llvm::Constant *TypeInfo = CGM.GetAddrOfRTTIDescriptor(ThrowType,
                                                           /*ForEH=*/true);
  
    // The address of the destructor.  If the exception type has a
    // trivial destructor (or isn't a record), we just pass null.
    llvm::Constant *Dtor = nullptr;
    if (const RecordType *RecordTy = ThrowType->getAs<RecordType>()) {
      CXXRecordDecl *Record = cast<CXXRecordDecl>(RecordTy->getDecl());
      if (!Record->hasTrivialDestructor()) {
        CXXDestructorDecl *DtorD = Record->getDestructor();
        Dtor = CGM.getAddrOfCXXStructor(GlobalDecl(DtorD, Dtor_Complete));
        Dtor = CGM.getFunctionPointer(Dtor, DtorD->getType());
        Dtor = llvm::ConstantExpr::getBitCast(Dtor, CGM.Int8PtrTy);
      }
    }
    if (!Dtor) Dtor = llvm::Constant::getNullValue(CGM.Int8PtrTy);
  
    llvm::Value *args[] = { ExceptionPtr, TypeInfo, Dtor };
    CGF.EmitNoreturnRuntimeCallOrInvoke(getThrowFn(CGM), args);
  }
  
  static llvm::FunctionCallee getItaniumDynamicCastFn(CodeGenFunction &CGF) {
    // void *__dynamic_cast(const void *sub,
    //                      const abi::__class_type_info *src,
    //                      const abi::__class_type_info *dst,
    //                      std::ptrdiff_t src2dst_offset);
  
    llvm::Type *Int8PtrTy = CGF.Int8PtrTy;
    llvm::Type *PtrDiffTy =
      CGF.ConvertType(CGF.getContext().getPointerDiffType());
  
    llvm::Type *Args[4] = { Int8PtrTy, Int8PtrTy, Int8PtrTy, PtrDiffTy };
  
    llvm::FunctionType *FTy = llvm::FunctionType::get(Int8PtrTy, Args, false);
  
    // Mark the function as nounwind readonly.
    llvm::Attribute::AttrKind FuncAttrs[] = { llvm::Attribute::NoUnwind,
                                              llvm::Attribute::ReadOnly };
    llvm::AttributeList Attrs = llvm::AttributeList::get(
        CGF.getLLVMContext(), llvm::AttributeList::FunctionIndex, FuncAttrs);
  
    return CGF.CGM.CreateRuntimeFunction(FTy, "__dynamic_cast", Attrs);
  }
  
  static llvm::FunctionCallee getBadCastFn(CodeGenFunction &CGF) {
    // void __cxa_bad_cast();
    llvm::FunctionType *FTy = llvm::FunctionType::get(CGF.VoidTy, false);
    return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_bad_cast");
  }
  
  /// Compute the src2dst_offset hint as described in the
  /// Itanium C++ ABI [2.9.7]
  static CharUnits computeOffsetHint(ASTContext &Context,
                                     const CXXRecordDecl *Src,
                                     const CXXRecordDecl *Dst) {
    CXXBasePaths Paths(/*FindAmbiguities=*/true, /*RecordPaths=*/true,
                       /*DetectVirtual=*/false);
  
    // If Dst is not derived from Src we can skip the whole computation below and
    // return that Src is not a public base of Dst.  Record all inheritance paths.
    if (!Dst->isDerivedFrom(Src, Paths))
      return CharUnits::fromQuantity(-2ULL);
  
    unsigned NumPublicPaths = 0;
    CharUnits Offset;
  
    // Now walk all possible inheritance paths.
    for (const CXXBasePath &Path : Paths) {
      if (Path.Access != AS_public)  // Ignore non-public inheritance.
        continue;
  
      ++NumPublicPaths;
  
      for (const CXXBasePathElement &PathElement : Path) {
        // If the path contains a virtual base class we can't give any hint.
        // -1: no hint.
        if (PathElement.Base->isVirtual())
          return CharUnits::fromQuantity(-1ULL);
  
        if (NumPublicPaths > 1) // Won't use offsets, skip computation.
          continue;
  
        // Accumulate the base class offsets.
        const ASTRecordLayout &L = Context.getASTRecordLayout(PathElement.Class);
        Offset += L.getBaseClassOffset(
            PathElement.Base->getType()->getAsCXXRecordDecl());
      }
    }
  
    // -2: Src is not a public base of Dst.
    if (NumPublicPaths == 0)
      return CharUnits::fromQuantity(-2ULL);
  
    // -3: Src is a multiple public base type but never a virtual base type.
    if (NumPublicPaths > 1)
      return CharUnits::fromQuantity(-3ULL);
  
    // Otherwise, the Src type is a unique public nonvirtual base type of Dst.
    // Return the offset of Src from the origin of Dst.
    return Offset;
  }
  
  static llvm::FunctionCallee getBadTypeidFn(CodeGenFunction &CGF) {
    // void __cxa_bad_typeid();
    llvm::FunctionType *FTy = llvm::FunctionType::get(CGF.VoidTy, false);
  
    return CGF.CGM.CreateRuntimeFunction(FTy, "__cxa_bad_typeid");
  }
  
  bool ItaniumCXXABI::shouldTypeidBeNullChecked(bool IsDeref,
                                                QualType SrcRecordTy) {
    return IsDeref;
  }
  
  void ItaniumCXXABI::EmitBadTypeidCall(CodeGenFunction &CGF) {
    llvm::FunctionCallee Fn = getBadTypeidFn(CGF);
    llvm::CallBase *Call = CGF.EmitRuntimeCallOrInvoke(Fn);
    Call->setDoesNotReturn();
    CGF.Builder.CreateUnreachable();
  }
  
  llvm::Value *ItaniumCXXABI::EmitTypeid(CodeGenFunction &CGF,
                                         QualType SrcRecordTy,
                                         Address ThisPtr,
                                         llvm::Type *StdTypeInfoPtrTy) {
    auto *ClassDecl =
        cast<CXXRecordDecl>(SrcRecordTy->castAs<RecordType>()->getDecl());
    llvm::Value *Value =
        CGF.GetVTablePtr(ThisPtr, StdTypeInfoPtrTy->getPointerTo(), ClassDecl);
  
    if (CGM.getItaniumVTableContext().isRelativeLayout()) {
      // Load the type info.
      Value = CGF.Builder.CreateBitCast(Value, CGM.Int8PtrTy);
      Value = CGF.Builder.CreateCall(
          CGM.getIntrinsic(llvm::Intrinsic::load_relative, {CGM.Int32Ty}),
          {Value, llvm::ConstantInt::get(CGM.Int32Ty, -4)});
  
      // Setup to dereference again since this is a proxy we accessed.
      Value = CGF.Builder.CreateBitCast(Value, StdTypeInfoPtrTy->getPointerTo());
    } else {
      // Load the type info.
      Value = CGF.Builder.CreateConstInBoundsGEP1_64(Value, -1ULL);
    }
    return CGF.Builder.CreateAlignedLoad(Value, CGF.getPointerAlign());
  }
  
  bool ItaniumCXXABI::shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
                                                         QualType SrcRecordTy) {
    return SrcIsPtr;
  }
  
  llvm::Value *ItaniumCXXABI::EmitDynamicCastCall(
      CodeGenFunction &CGF, Address ThisAddr, QualType SrcRecordTy,
      QualType DestTy, QualType DestRecordTy, llvm::BasicBlock *CastEnd) {
    llvm::Type *PtrDiffLTy =
        CGF.ConvertType(CGF.getContext().getPointerDiffType());
    llvm::Type *DestLTy = CGF.ConvertType(DestTy);
  
    llvm::Value *SrcRTTI =
        CGF.CGM.GetAddrOfRTTIDescriptor(SrcRecordTy.getUnqualifiedType());
    llvm::Value *DestRTTI =
        CGF.CGM.GetAddrOfRTTIDescriptor(DestRecordTy.getUnqualifiedType());
  
    // Compute the offset hint.
    const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
    const CXXRecordDecl *DestDecl = DestRecordTy->getAsCXXRecordDecl();
    llvm::Value *OffsetHint = llvm::ConstantInt::get(
        PtrDiffLTy,
        computeOffsetHint(CGF.getContext(), SrcDecl, DestDecl).getQuantity());
  
    // Emit the call to __dynamic_cast.
    llvm::Value *Value = ThisAddr.getPointer();
    Value = CGF.EmitCastToVoidPtr(Value);
  
    llvm::Value *args[] = {Value, SrcRTTI, DestRTTI, OffsetHint};
    Value = CGF.EmitNounwindRuntimeCall(getItaniumDynamicCastFn(CGF), args);
    Value = CGF.Builder.CreateBitCast(Value, DestLTy);
  
    /// C++ [expr.dynamic.cast]p9:
    ///   A failed cast to reference type throws std::bad_cast
    if (DestTy->isReferenceType()) {
      llvm::BasicBlock *BadCastBlock =
          CGF.createBasicBlock("dynamic_cast.bad_cast");
  
      llvm::Value *IsNull = CGF.Builder.CreateIsNull(Value);
      CGF.Builder.CreateCondBr(IsNull, BadCastBlock, CastEnd);
  
      CGF.EmitBlock(BadCastBlock);
      EmitBadCastCall(CGF);
    }
  
    return Value;
  }
  
  llvm::Value *ItaniumCXXABI::EmitDynamicCastToVoid(CodeGenFunction &CGF,
                                                    Address ThisAddr,
                                                    QualType SrcRecordTy,
                                                    QualType DestTy) {
    llvm::Type *DestLTy = CGF.ConvertType(DestTy);
    auto *ClassDecl =
        cast<CXXRecordDecl>(SrcRecordTy->castAs<RecordType>()->getDecl());
    llvm::Value *OffsetToTop;
    if (CGM.getItaniumVTableContext().isRelativeLayout()) {
      // Get the vtable pointer.
      llvm::Value *VTable =
          CGF.GetVTablePtr(ThisAddr, CGM.Int32Ty->getPointerTo(), ClassDecl);
  
      // Get the offset-to-top from the vtable.
      OffsetToTop =
          CGF.Builder.CreateConstInBoundsGEP1_32(/*Type=*/nullptr, VTable, -2U);
      OffsetToTop = CGF.Builder.CreateAlignedLoad(
          OffsetToTop, CharUnits::fromQuantity(4), "offset.to.top");
    } else {
      llvm::Type *PtrDiffLTy =
          CGF.ConvertType(CGF.getContext().getPointerDiffType());
  
      // Get the vtable pointer.
      llvm::Value *VTable =
          CGF.GetVTablePtr(ThisAddr, PtrDiffLTy->getPointerTo(), ClassDecl);
  
      // Get the offset-to-top from the vtable.
      OffsetToTop = CGF.Builder.CreateConstInBoundsGEP1_64(VTable, -2ULL);
      OffsetToTop = CGF.Builder.CreateAlignedLoad(
          OffsetToTop, CGF.getPointerAlign(), "offset.to.top");
    }
    // Finally, add the offset to the pointer.
    llvm::Value *Value = ThisAddr.getPointer();
    Value = CGF.EmitCastToVoidPtr(Value);
    Value = CGF.Builder.CreateInBoundsGEP(Value, OffsetToTop);
    return CGF.Builder.CreateBitCast(Value, DestLTy);
  }
  
  bool ItaniumCXXABI::EmitBadCastCall(CodeGenFunction &CGF) {
    llvm::FunctionCallee Fn = getBadCastFn(CGF);
    llvm::CallBase *Call = CGF.EmitRuntimeCallOrInvoke(Fn);
    Call->setDoesNotReturn();
    CGF.Builder.CreateUnreachable();
    return true;
  }
  
  llvm::Value *
  ItaniumCXXABI::GetVirtualBaseClassOffset(CodeGenFunction &CGF,
                                           Address This,
                                           const CXXRecordDecl *ClassDecl,
                                           const CXXRecordDecl *BaseClassDecl) {
    llvm::Value *VTablePtr = CGF.GetVTablePtr(This, CGM.Int8PtrTy, ClassDecl);
    CharUnits VBaseOffsetOffset =
        CGM.getItaniumVTableContext().getVirtualBaseOffsetOffset(ClassDecl,
                                                                 BaseClassDecl);
    llvm::Value *VBaseOffsetPtr =
      CGF.Builder.CreateConstGEP1_64(VTablePtr, VBaseOffsetOffset.getQuantity(),
                                     "vbase.offset.ptr");
  
    llvm::Value *VBaseOffset;
    if (CGM.getItaniumVTableContext().isRelativeLayout()) {
      VBaseOffsetPtr =
          CGF.Builder.CreateBitCast(VBaseOffsetPtr, CGF.Int32Ty->getPointerTo());
      VBaseOffset = CGF.Builder.CreateAlignedLoad(
          VBaseOffsetPtr, CharUnits::fromQuantity(4), "vbase.offset");
    } else {
      VBaseOffsetPtr = CGF.Builder.CreateBitCast(VBaseOffsetPtr,
                                                 CGM.PtrDiffTy->getPointerTo());
      VBaseOffset = CGF.Builder.CreateAlignedLoad(
          VBaseOffsetPtr, CGF.getPointerAlign(), "vbase.offset");
    }
    return VBaseOffset;
  }
  
  void ItaniumCXXABI::EmitCXXConstructors(const CXXConstructorDecl *D) {
    // Just make sure we're in sync with TargetCXXABI.
    assert(CGM.getTarget().getCXXABI().hasConstructorVariants());
  
    // The constructor used for constructing this as a base class;
    // ignores virtual bases.
    CGM.EmitGlobal(GlobalDecl(D, Ctor_Base));
  
    // The constructor used for constructing this as a complete class;
    // constructs the virtual bases, then calls the base constructor.
    if (!D->getParent()->isAbstract()) {
      // We don't need to emit the complete ctor if the class is abstract.
      CGM.EmitGlobal(GlobalDecl(D, Ctor_Complete));
    }
  }
  
  CGCXXABI::AddedStructorArgCounts
  ItaniumCXXABI::buildStructorSignature(GlobalDecl GD,
                                        SmallVectorImpl<CanQualType> &ArgTys) {
    ASTContext &Context = getContext();
  
    // All parameters are already in place except VTT, which goes after 'this'.
    // These are Clang types, so we don't need to worry about sret yet.
  
    // Check if we need to add a VTT parameter (which has type void **).
    if ((isa<CXXConstructorDecl>(GD.getDecl()) ? GD.getCtorType() == Ctor_Base
                                               : GD.getDtorType() == Dtor_Base) &&
        cast<CXXMethodDecl>(GD.getDecl())->getParent()->getNumVBases() != 0) {
      ArgTys.insert(ArgTys.begin() + 1,
                    Context.getPointerType(Context.VoidPtrTy));
      return AddedStructorArgCounts::prefix(1);
    }
    return AddedStructorArgCounts{};
  }
  
  void ItaniumCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
    // The destructor used for destructing this as a base class; ignores
    // virtual bases.
    CGM.EmitGlobal(GlobalDecl(D, Dtor_Base));
  
    // The destructor used for destructing this as a most-derived class;
    // call the base destructor and then destructs any virtual bases.
    CGM.EmitGlobal(GlobalDecl(D, Dtor_Complete));
  
    // The destructor in a virtual table is always a 'deleting'
    // destructor, which calls the complete destructor and then uses the
    // appropriate operator delete.
    if (D->isVirtual())
      CGM.EmitGlobal(GlobalDecl(D, Dtor_Deleting));
  }
  
  void ItaniumCXXABI::addImplicitStructorParams(CodeGenFunction &CGF,
                                                QualType &ResTy,
                                                FunctionArgList &Params) {
    const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
    assert(isa<CXXConstructorDecl>(MD) || isa<CXXDestructorDecl>(MD));
  
    // Check if we need a VTT parameter as well.
    if (NeedsVTTParameter(CGF.CurGD)) {
      ASTContext &Context = getContext();
  
      // FIXME: avoid the fake decl
      QualType T = Context.getPointerType(Context.VoidPtrTy);
      auto *VTTDecl = ImplicitParamDecl::Create(
          Context, /*DC=*/nullptr, MD->getLocation(), &Context.Idents.get("vtt"),
          T, ImplicitParamDecl::CXXVTT);
      Params.insert(Params.begin() + 1, VTTDecl);
      getStructorImplicitParamDecl(CGF) = VTTDecl;
    }
  }
  
  void ItaniumCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
    // Naked functions have no prolog.
    if (CGF.CurFuncDecl && CGF.CurFuncDecl->hasAttr<NakedAttr>())
      return;
  
    /// Initialize the 'this' slot. In the Itanium C++ ABI, no prologue
    /// adjustments are required, because they are all handled by thunks.
    setCXXABIThisValue(CGF, loadIncomingCXXThis(CGF));
  
    /// Initialize the 'vtt' slot if needed.
    if (getStructorImplicitParamDecl(CGF)) {
      getStructorImplicitParamValue(CGF) = CGF.Builder.CreateLoad(
          CGF.GetAddrOfLocalVar(getStructorImplicitParamDecl(CGF)), "vtt");
    }
  
    /// If this is a function that the ABI specifies returns 'this', initialize
    /// the return slot to 'this' at the start of the function.
    ///
    /// Unlike the setting of return types, this is done within the ABI
    /// implementation instead of by clients of CGCXXABI because:
    /// 1) getThisValue is currently protected
    /// 2) in theory, an ABI could implement 'this' returns some other way;
    ///    HasThisReturn only specifies a contract, not the implementation
    if (HasThisReturn(CGF.CurGD))
      CGF.Builder.CreateStore(getThisValue(CGF), CGF.ReturnValue);
  }
  
  CGCXXABI::AddedStructorArgs ItaniumCXXABI::getImplicitConstructorArgs(
      CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
      bool ForVirtualBase, bool Delegating) {
    if (!NeedsVTTParameter(GlobalDecl(D, Type)))
      return AddedStructorArgs{};
  
    // Insert the implicit 'vtt' argument as the second argument.
    llvm::Value *VTT =
        CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase, Delegating);
    QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
    return AddedStructorArgs::prefix({{VTT, VTTTy}});
  }
  
  llvm::Value *ItaniumCXXABI::getCXXDestructorImplicitParam(
      CodeGenFunction &CGF, const CXXDestructorDecl *DD, CXXDtorType Type,
      bool ForVirtualBase, bool Delegating) {
    GlobalDecl GD(DD, Type);
    return CGF.GetVTTParameter(GD, ForVirtualBase, Delegating);
  }
  
  void ItaniumCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
                                         const CXXDestructorDecl *DD,
                                         CXXDtorType Type, bool ForVirtualBase,
                                         bool Delegating, Address This,
                                         QualType ThisTy) {
    GlobalDecl GD(DD, Type);
    llvm::Value *VTT =
        getCXXDestructorImplicitParam(CGF, DD, Type, ForVirtualBase, Delegating);
    QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
  
    CGCallee Callee;
    if (getContext().getLangOpts().AppleKext &&
        Type != Dtor_Base && DD->isVirtual())
      Callee = CGF.BuildAppleKextVirtualDestructorCall(DD, Type, DD->getParent());
    else
      Callee = CGCallee::forDirect(CGM.getAddrOfCXXStructor(GD), GD);
  
    CGF.EmitCXXDestructorCall(GD, Callee, This.getPointer(), ThisTy, VTT, VTTTy,
                              nullptr);
  }
  
  void ItaniumCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
                                            const CXXRecordDecl *RD) {
    llvm::GlobalVariable *VTable = getAddrOfVTable(RD, CharUnits());
    if (VTable->hasInitializer())
      return;
  
    ItaniumVTableContext &VTContext = CGM.getItaniumVTableContext();
    const VTableLayout &VTLayout = VTContext.getVTableLayout(RD);
    llvm::GlobalVariable::LinkageTypes Linkage = CGM.getVTableLinkage(RD);
    llvm::Constant *RTTI =
        CGM.GetAddrOfRTTIDescriptor(CGM.getContext().getTagDeclType(RD));
  
    // Create and set the initializer.
    ConstantInitBuilder builder(CGM);
    auto components = builder.beginStruct();
    CGVT.createVTableInitializer(components, VTLayout, RTTI,
                                 llvm::GlobalValue::isLocalLinkage(Linkage));
    components.finishAndSetAsInitializer(VTable);
  
    // Set the correct linkage.
    VTable->setLinkage(Linkage);
  
    if (CGM.supportsCOMDAT() && VTable->isWeakForLinker())
      VTable->setComdat(CGM.getModule().getOrInsertComdat(VTable->getName()));
  
    // Set the right visibility.
    CGM.setGVProperties(VTable, RD);
  
    // If this is the magic class __cxxabiv1::__fundamental_type_info,
    // we will emit the typeinfo for the fundamental types. This is the
    // same behaviour as GCC.
    const DeclContext *DC = RD->getDeclContext();
    if (RD->getIdentifier() &&
        RD->getIdentifier()->isStr("__fundamental_type_info") &&
        isa<NamespaceDecl>(DC) && cast<NamespaceDecl>(DC)->getIdentifier() &&
        cast<NamespaceDecl>(DC)->getIdentifier()->isStr("__cxxabiv1") &&
        DC->getParent()->isTranslationUnit())
      EmitFundamentalRTTIDescriptors(RD);
  
    if (!VTable->isDeclarationForLinker())
      CGM.EmitVTableTypeMetadata(RD, VTable, VTLayout);
  
    if (VTContext.isRelativeLayout() && !VTable->isDSOLocal())
      CGVT.GenerateRelativeVTableAlias(VTable, VTable->getName());
  }
  
  bool ItaniumCXXABI::isVirtualOffsetNeededForVTableField(
      CodeGenFunction &CGF, CodeGenFunction::VPtr Vptr) {
    if (Vptr.NearestVBase == nullptr)
      return false;
    return NeedsVTTParameter(CGF.CurGD);
  }
  
  llvm::Value *ItaniumCXXABI::getVTableAddressPointInStructor(
      CodeGenFunction &CGF, const CXXRecordDecl *VTableClass, BaseSubobject Base,
      const CXXRecordDecl *NearestVBase) {
  
    if ((Base.getBase()->getNumVBases() || NearestVBase != nullptr) &&
        NeedsVTTParameter(CGF.CurGD)) {
      return getVTableAddressPointInStructorWithVTT(CGF, VTableClass, Base,
                                                    NearestVBase);
    }
    return getVTableAddressPoint(Base, VTableClass);
  }
  
  llvm::Constant *
  ItaniumCXXABI::getVTableAddressPoint(BaseSubobject Base,
                                       const CXXRecordDecl *VTableClass) {
    llvm::GlobalValue *VTable = getAddrOfVTable(VTableClass, CharUnits());
  
    // Find the appropriate vtable within the vtable group, and the address point
    // within that vtable.
    VTableLayout::AddressPointLocation AddressPoint =
        CGM.getItaniumVTableContext()
            .getVTableLayout(VTableClass)
            .getAddressPoint(Base);
    llvm::Value *Indices[] = {
      llvm::ConstantInt::get(CGM.Int32Ty, 0),
      llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.VTableIndex),
      llvm::ConstantInt::get(CGM.Int32Ty, AddressPoint.AddressPointIndex),
    };
  
    return llvm::ConstantExpr::getGetElementPtr(VTable->getValueType(), VTable,
                                                Indices, /*InBounds=*/true,
                                                /*InRangeIndex=*/1);
  }
  
  llvm::Value *ItaniumCXXABI::getVTableAddressPointInStructorWithVTT(
      CodeGenFunction &CGF, const CXXRecordDecl *VTableClass, BaseSubobject Base,
      const CXXRecordDecl *NearestVBase) {
    assert((Base.getBase()->getNumVBases() || NearestVBase != nullptr) &&
           NeedsVTTParameter(CGF.CurGD) && "This class doesn't have VTT");
  
    // Get the secondary vpointer index.
    uint64_t VirtualPointerIndex =
        CGM.getVTables().getSecondaryVirtualPointerIndex(VTableClass, Base);
  
    /// Load the VTT.
    llvm::Value *VTT = CGF.LoadCXXVTT();
    if (VirtualPointerIndex)
      VTT = CGF.Builder.CreateConstInBoundsGEP1_64(VTT, VirtualPointerIndex);
  
    // And load the address point from the VTT.
    llvm::Value *AP = CGF.Builder.CreateAlignedLoad(VTT, CGF.getPointerAlign());
  
    if (auto &Schema = CGF.CGM.getCodeGenOpts().PointerAuth.CXXVTTVTablePointers) {
      CGPointerAuthInfo PointerAuth = CGF.EmitPointerAuthInfo(Schema, VTT,
                                                              GlobalDecl(),
                                                              QualType());
      AP = CGF.EmitPointerAuthAuth(PointerAuth, AP);
    }
  
    return AP;
  }
  
  llvm::Constant *ItaniumCXXABI::getVTableAddressPointForConstExpr(
      BaseSubobject Base, const CXXRecordDecl *VTableClass) {
    llvm::Constant *AP = getVTableAddressPoint(Base, VTableClass);
  
    if (auto &Schema = CGM.getCodeGenOpts().PointerAuth.CXXVTablePointers)
      AP = CGM.getConstantSignedPointer(AP, Schema, nullptr, GlobalDecl(),
                                        QualType());
  
    return AP;
  }
  
  llvm::GlobalVariable *ItaniumCXXABI::getAddrOfVTable(const CXXRecordDecl *RD,
                                                       CharUnits VPtrOffset) {
    assert(VPtrOffset.isZero() && "Itanium ABI only supports zero vptr offsets");
  
    llvm::GlobalVariable *&VTable = VTables[RD];
    if (VTable)
      return VTable;
  
    // Queue up this vtable for possible deferred emission.
    CGM.addDeferredVTable(RD);
  
    SmallString<256> Name;
    llvm::raw_svector_ostream Out(Name);
    getMangleContext().mangleCXXVTable(RD, Out);
  
    const VTableLayout &VTLayout =
        CGM.getItaniumVTableContext().getVTableLayout(RD);
    llvm::Type *VTableType = CGM.getVTables().getVTableType(VTLayout);
  
    // Use pointer alignment for the vtable. Otherwise we would align them based
    // on the size of the initializer which doesn't make sense as only single
    // values are read.
    unsigned PAlign = CGM.getItaniumVTableContext().isRelativeLayout()
                          ? 32
                          : CGM.getTarget().getPointerAlign(0);
  
    VTable = CGM.CreateOrReplaceCXXRuntimeVariable(
        Name, VTableType, llvm::GlobalValue::ExternalLinkage,
        getContext().toCharUnitsFromBits(PAlign).getQuantity());
    VTable->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
  
    CGM.setGVProperties(VTable, RD);
  
    return VTable;
  }
  
  CGCallee ItaniumCXXABI::getVirtualFunctionPointer(CodeGenFunction &CGF,
                                                    GlobalDecl GD,
                                                    Address This,
                                                    llvm::Type *Ty,
                                                    SourceLocation Loc) {
    auto *MethodDecl = cast<CXXMethodDecl>(GD.getDecl());
    llvm::Value *VTable = CGF.GetVTablePtr(
        This, Ty->getPointerTo()->getPointerTo(), MethodDecl->getParent());
  
    uint64_t VTableIndex = CGM.getItaniumVTableContext().getMethodVTableIndex(GD);
    llvm::Value *VFunc, *VTableSlotPtr = nullptr;
    auto &Schema = CGM.getCodeGenOpts().PointerAuth.CXXVirtualFunctionPointers;
    if (!Schema && CGF.ShouldEmitVTableTypeCheckedLoad(MethodDecl->getParent())) {
      VFunc = CGF.EmitVTableTypeCheckedLoad(
          MethodDecl->getParent(), VTable,
          VTableIndex * CGM.getContext().getTargetInfo().getPointerWidth(0) / 8);
    } else {
      CGF.EmitTypeMetadataCodeForVCall(MethodDecl->getParent(), VTable, Loc);
  
      llvm::Value *VFuncLoad;
      if (CGM.getItaniumVTableContext().isRelativeLayout()) {
        VTable = CGF.Builder.CreateBitCast(VTable, CGM.Int8PtrTy);
        llvm::Value *Load = CGF.Builder.CreateCall(
            CGM.getIntrinsic(llvm::Intrinsic::load_relative, {CGM.Int32Ty}),
            {VTable, llvm::ConstantInt::get(CGM.Int32Ty, 4 * VTableIndex)});
        VFuncLoad = CGF.Builder.CreateBitCast(Load, Ty->getPointerTo());
      } else {
        VTable =
            CGF.Builder.CreateBitCast(VTable, Ty->getPointerTo()->getPointerTo());
        VTableSlotPtr =
            CGF.Builder.CreateConstInBoundsGEP1_64(VTable, VTableIndex, "vfn");
        VFuncLoad =
            CGF.Builder.CreateAlignedLoad(VTableSlotPtr, CGF.getPointerAlign());
      }
  
      // Add !invariant.load md to virtual function load to indicate that
      // function didn't change inside vtable.
      // It's safe to add it without -fstrict-vtable-pointers, but it would not
      // help in devirtualization because it will only matter if we will have 2
      // the same virtual function loads from the same vtable load, which won't
      // happen without enabled devirtualization with -fstrict-vtable-pointers.
      if (CGM.getCodeGenOpts().OptimizationLevel > 0 &&
          CGM.getCodeGenOpts().StrictVTablePointers) {
        if (auto *VFuncLoadInstr = dyn_cast<llvm::Instruction>(VFuncLoad)) {
          VFuncLoadInstr->setMetadata(
              llvm::LLVMContext::MD_invariant_load,
              llvm::MDNode::get(CGM.getLLVMContext(),
                                llvm::ArrayRef<llvm::Metadata *>()));
        }
      }
      VFunc = VFuncLoad;
    }
  
    CGPointerAuthInfo PointerAuth;
    if (Schema) {
      assert(VTableSlotPtr && "virtual function pointer not set");
      GD = CGM.getItaniumVTableContext().findOriginalMethod(GD.getCanonicalDecl());
      PointerAuth = CGF.EmitPointerAuthInfo(Schema, VTableSlotPtr, GD, QualType());
    }
    CGCallee Callee(GD, VFunc, PointerAuth);
    return Callee;
  }
  
  llvm::Value *ItaniumCXXABI::EmitVirtualDestructorCall(
      CodeGenFunction &CGF, const CXXDestructorDecl *Dtor, CXXDtorType DtorType,
      Address This, DeleteOrMemberCallExpr E) {
    auto *CE = E.dyn_cast<const CXXMemberCallExpr *>();
    auto *D = E.dyn_cast<const CXXDeleteExpr *>();
    assert((CE != nullptr) ^ (D != nullptr));
    assert(CE == nullptr || CE->arg_begin() == CE->arg_end());
    assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
  
    GlobalDecl GD(Dtor, DtorType);
    const CGFunctionInfo *FInfo =
        &CGM.getTypes().arrangeCXXStructorDeclaration(GD);
    llvm::FunctionType *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
    CGCallee Callee = CGCallee::forVirtual(CE, GD, This, Ty);
  
    QualType ThisTy;
    if (CE) {
      ThisTy = CE->getObjectType();
    } else {
      ThisTy = D->getDestroyedType();
    }
  
    CGF.EmitCXXDestructorCall(GD, Callee, This.getPointer(), ThisTy, nullptr,
                              QualType(), nullptr);
    return nullptr;
  }
  
  void ItaniumCXXABI::emitVirtualInheritanceTables(const CXXRecordDecl *RD) {
    CodeGenVTables &VTables = CGM.getVTables();
    llvm::GlobalVariable *VTT = VTables.GetAddrOfVTT(RD);
    VTables.EmitVTTDefinition(VTT, CGM.getVTableLinkage(RD), RD);
  }
  
  bool ItaniumCXXABI::canSpeculativelyEmitVTableAsBaseClass(
      const CXXRecordDecl *RD) const {
    // We don't emit available_externally vtables if we are in -fapple-kext mode
    // because kext mode does not permit devirtualization.
    if (CGM.getLangOpts().AppleKext)
      return false;
  
    // If the vtable is hidden then it is not safe to emit an available_externally
    // copy of vtable.
    if (isVTableHidden(RD))
      return false;
  
    if (CGM.getCodeGenOpts().ForceEmitVTables)
      return true;
  
    // If we don't have any not emitted inline virtual function then we are safe
    // to emit an available_externally copy of vtable.
    // FIXME we can still emit a copy of the vtable if we
    // can emit definition of the inline functions.
    if (hasAnyUnusedVirtualInlineFunction(RD))
      return false;
  
    // For a class with virtual bases, we must also be able to speculatively
    // emit the VTT, because CodeGen doesn't have separate notions of "can emit
    // the vtable" and "can emit the VTT". For a base subobject, this means we
    // need to be able to emit non-virtual base vtables.
    if (RD->getNumVBases()) {
      for (const auto &B : RD->bases()) {
        auto *BRD = B.getType()->getAsCXXRecordDecl();
        assert(BRD && "no class for base specifier");
        if (B.isVirtual() || !BRD->isDynamicClass())
          continue;
        if (!canSpeculativelyEmitVTableAsBaseClass(BRD))
          return false;
      }
    }
  
    return true;
  }
  
  bool ItaniumCXXABI::canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const {
    if (!canSpeculativelyEmitVTableAsBaseClass(RD))
      return false;
  
    // For a complete-object vtable (or more specifically, for the VTT), we need
    // to be able to speculatively emit the vtables of all dynamic virtual bases.
    for (const auto &B : RD->vbases()) {
      auto *BRD = B.getType()->getAsCXXRecordDecl();
      assert(BRD && "no class for base specifier");
      if (!BRD->isDynamicClass())
        continue;
      if (!canSpeculativelyEmitVTableAsBaseClass(BRD))
        return false;
    }
  
    return true;
  }
  static llvm::Value *performTypeAdjustment(CodeGenFunction &CGF,
                                            Address InitialPtr,
                                            int64_t NonVirtualAdjustment,
                                            int64_t VirtualAdjustment,
                                            bool IsReturnAdjustment) {
    if (!NonVirtualAdjustment && !VirtualAdjustment)
      return InitialPtr.getPointer();
  
    Address V = CGF.Builder.CreateElementBitCast(InitialPtr, CGF.Int8Ty);
  
    // In a base-to-derived cast, the non-virtual adjustment is applied first.
    if (NonVirtualAdjustment && !IsReturnAdjustment) {
      V = CGF.Builder.CreateConstInBoundsByteGEP(V,
                                CharUnits::fromQuantity(NonVirtualAdjustment));
    }
  
    // Perform the virtual adjustment if we have one.
    llvm::Value *ResultPtr;
    if (VirtualAdjustment) {
      Address VTablePtrPtr = CGF.Builder.CreateElementBitCast(V, CGF.Int8PtrTy);
      llvm::Value *VTablePtr = CGF.Builder.CreateLoad(VTablePtrPtr);
  
      if (auto &Schema = CGF.CGM.getCodeGenOpts().PointerAuth.CXXVTablePointers) {
        CGPointerAuthInfo PointerAuth = CGF.EmitPointerAuthInfo(Schema, nullptr,
                                                                GlobalDecl(),
                                                                QualType());
        VTablePtr = CGF.EmitPointerAuthAuth(PointerAuth, VTablePtr);
      }
  
      llvm::Value *Offset;
      llvm::Value *OffsetPtr =
          CGF.Builder.CreateConstInBoundsGEP1_64(VTablePtr, VirtualAdjustment);
      if (CGF.CGM.getItaniumVTableContext().isRelativeLayout()) {
        // Load the adjustment offset from the vtable as a 32-bit int.
        OffsetPtr =
            CGF.Builder.CreateBitCast(OffsetPtr, CGF.Int32Ty->getPointerTo());
        Offset =
            CGF.Builder.CreateAlignedLoad(OffsetPtr, CharUnits::fromQuantity(4));
      } else {
        llvm::Type *PtrDiffTy =
            CGF.ConvertType(CGF.getContext().getPointerDiffType());
  
        OffsetPtr =
            CGF.Builder.CreateBitCast(OffsetPtr, PtrDiffTy->getPointerTo());
  
        // Load the adjustment offset from the vtable.
        Offset = CGF.Builder.CreateAlignedLoad(OffsetPtr, CGF.getPointerAlign());
      }
      // Adjust our pointer.
      ResultPtr = CGF.Builder.CreateInBoundsGEP(V.getPointer(), Offset);
    } else {
      ResultPtr = V.getPointer();
    }
  
    // In a derived-to-base conversion, the non-virtual adjustment is
    // applied second.
    if (NonVirtualAdjustment && IsReturnAdjustment) {
      ResultPtr = CGF.Builder.CreateConstInBoundsGEP1_64(ResultPtr,
                                                         NonVirtualAdjustment);
    }
  
    // Cast back to the original type.
    return CGF.Builder.CreateBitCast(ResultPtr, InitialPtr.getType());
  }
  
  llvm::Value *ItaniumCXXABI::performThisAdjustment(CodeGenFunction &CGF,
                                                    Address This,
                                                    const ThisAdjustment &TA) {
    return performTypeAdjustment(CGF, This, TA.NonVirtual,
                                 TA.Virtual.Itanium.VCallOffsetOffset,
                                 /*IsReturnAdjustment=*/false);
  }
  
  llvm::Value *
  ItaniumCXXABI::performReturnAdjustment(CodeGenFunction &CGF, Address Ret,
                                         const ReturnAdjustment &RA) {
    return performTypeAdjustment(CGF, Ret, RA.NonVirtual,
                                 RA.Virtual.Itanium.VBaseOffsetOffset,
                                 /*IsReturnAdjustment=*/true);
  }
  
  void ARMCXXABI::EmitReturnFromThunk(CodeGenFunction &CGF,
                                      RValue RV, QualType ResultType) {
    if (!isa<CXXDestructorDecl>(CGF.CurGD.getDecl()))
      return ItaniumCXXABI::EmitReturnFromThunk(CGF, RV, ResultType);
  
    // Destructor thunks in the ARM ABI have indeterminate results.
    llvm::Type *T = CGF.ReturnValue.getElementType();
    RValue Undef = RValue::get(llvm::UndefValue::get(T));
    return ItaniumCXXABI::EmitReturnFromThunk(CGF, Undef, ResultType);
  }
  
  /************************** Array allocation cookies **************************/
  
  CharUnits ItaniumCXXABI::getArrayCookieSizeImpl(QualType elementType) {
    // The array cookie is a size_t; pad that up to the element alignment.
    // The cookie is actually right-justified in that space.
    return std::max(CharUnits::fromQuantity(CGM.SizeSizeInBytes),
                    CGM.getContext().getPreferredTypeAlignInChars(elementType));
  }
  
  Address ItaniumCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
                                               Address NewPtr,
                                               llvm::Value *NumElements,
                                               const CXXNewExpr *expr,
                                               QualType ElementType) {
    assert(requiresArrayCookie(expr));
  
    unsigned AS = NewPtr.getAddressSpace();
  
    ASTContext &Ctx = getContext();
    CharUnits SizeSize = CGF.getSizeSize();
  
    // The size of the cookie.
    CharUnits CookieSize =
        std::max(SizeSize, Ctx.getPreferredTypeAlignInChars(ElementType));
    assert(CookieSize == getArrayCookieSizeImpl(ElementType));
  
    // Compute an offset to the cookie.
    Address CookiePtr = NewPtr;
    CharUnits CookieOffset = CookieSize - SizeSize;
    if (!CookieOffset.isZero())
      CookiePtr = CGF.Builder.CreateConstInBoundsByteGEP(CookiePtr, CookieOffset);
  
    // Write the number of elements into the appropriate slot.
    Address NumElementsPtr =
        CGF.Builder.CreateElementBitCast(CookiePtr, CGF.SizeTy);
    llvm::Instruction *SI = CGF.Builder.CreateStore(NumElements, NumElementsPtr);
  
    // Handle the array cookie specially in ASan.
    if (CGM.getLangOpts().Sanitize.has(SanitizerKind::Address) && AS == 0 &&
        (expr->getOperatorNew()->isReplaceableGlobalAllocationFunction() ||
         CGM.getCodeGenOpts().SanitizeAddressPoisonCustomArrayCookie)) {
      // The store to the CookiePtr does not need to be instrumented.
      CGM.getSanitizerMetadata()->disableSanitizerForInstruction(SI);
      llvm::FunctionType *FTy =
          llvm::FunctionType::get(CGM.VoidTy, NumElementsPtr.getType(), false);
      llvm::FunctionCallee F =
          CGM.CreateRuntimeFunction(FTy, "__asan_poison_cxx_array_cookie");
      CGF.Builder.CreateCall(F, NumElementsPtr.getPointer());
    }
  
    // Finally, compute a pointer to the actual data buffer by skipping
    // over the cookie completely.
    return CGF.Builder.CreateConstInBoundsByteGEP(NewPtr, CookieSize);
  }
  
  llvm::Value *ItaniumCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
                                                  Address allocPtr,
                                                  CharUnits cookieSize) {
    // The element size is right-justified in the cookie.
    Address numElementsPtr = allocPtr;
    CharUnits numElementsOffset = cookieSize - CGF.getSizeSize();
    if (!numElementsOffset.isZero())
      numElementsPtr =
        CGF.Builder.CreateConstInBoundsByteGEP(numElementsPtr, numElementsOffset);
  
    unsigned AS = allocPtr.getAddressSpace();
    numElementsPtr = CGF.Builder.CreateElementBitCast(numElementsPtr, CGF.SizeTy);
    if (!CGM.getLangOpts().Sanitize.has(SanitizerKind::Address) || AS != 0)
      return CGF.Builder.CreateLoad(numElementsPtr);
    // In asan mode emit a function call instead of a regular load and let the
    // run-time deal with it: if the shadow is properly poisoned return the
    // cookie, otherwise return 0 to avoid an infinite loop calling DTORs.
    // We can't simply ignore this load using nosanitize metadata because
    // the metadata may be lost.
    llvm::FunctionType *FTy =
        llvm::FunctionType::get(CGF.SizeTy, CGF.SizeTy->getPointerTo(0), false);
    llvm::FunctionCallee F =
        CGM.CreateRuntimeFunction(FTy, "__asan_load_cxx_array_cookie");
    return CGF.Builder.CreateCall(F, numElementsPtr.getPointer());
  }
  
  CharUnits ARMCXXABI::getArrayCookieSizeImpl(QualType elementType) {
    // ARM says that the cookie is always:
    //   struct array_cookie {
    //     std::size_t element_size; // element_size != 0
    //     std::size_t element_count;
    //   };
    // But the base ABI doesn't give anything an alignment greater than
    // 8, so we can dismiss this as typical ABI-author blindness to
    // actual language complexity and round up to the element alignment.
    return std::max(CharUnits::fromQuantity(2 * CGM.SizeSizeInBytes),
                    CGM.getContext().getTypeAlignInChars(elementType));
  }
  
  Address ARMCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
                                           Address newPtr,
                                           llvm::Value *numElements,
                                           const CXXNewExpr *expr,
                                           QualType elementType) {
    assert(requiresArrayCookie(expr));
  
    // The cookie is always at the start of the buffer.
    Address cookie = newPtr;
  
    // The first element is the element size.
    cookie = CGF.Builder.CreateElementBitCast(cookie, CGF.SizeTy);
    llvm::Value *elementSize = llvm::ConstantInt::get(CGF.SizeTy,
                   getContext().getTypeSizeInChars(elementType).getQuantity());
    CGF.Builder.CreateStore(elementSize, cookie);
  
    // The second element is the element count.
    cookie = CGF.Builder.CreateConstInBoundsGEP(cookie, 1);
    CGF.Builder.CreateStore(numElements, cookie);
  
    // Finally, compute a pointer to the actual data buffer by skipping
    // over the cookie completely.
    CharUnits cookieSize = ARMCXXABI::getArrayCookieSizeImpl(elementType);
    return CGF.Builder.CreateConstInBoundsByteGEP(newPtr, cookieSize);
  }
  
  llvm::Value *ARMCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
                                              Address allocPtr,
                                              CharUnits cookieSize) {
    // The number of elements is at offset sizeof(size_t) relative to
    // the allocated pointer.
    Address numElementsPtr
      = CGF.Builder.CreateConstInBoundsByteGEP(allocPtr, CGF.getSizeSize());
  
    numElementsPtr = CGF.Builder.CreateElementBitCast(numElementsPtr, CGF.SizeTy);
    return CGF.Builder.CreateLoad(numElementsPtr);
  }
  
  /*********************** Static local initialization **************************/
  
  static llvm::FunctionCallee getGuardAcquireFn(CodeGenModule &CGM,
                                                llvm::PointerType *GuardPtrTy) {
    // int __cxa_guard_acquire(__guard *guard_object);
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.getTypes().ConvertType(CGM.getContext().IntTy),
                              GuardPtrTy, /*isVarArg=*/false);
    return CGM.CreateRuntimeFunction(
        FTy, "__cxa_guard_acquire",
        llvm::AttributeList::get(CGM.getLLVMContext(),
                                 llvm::AttributeList::FunctionIndex,
                                 llvm::Attribute::NoUnwind));
  }
  
  static llvm::FunctionCallee getGuardReleaseFn(CodeGenModule &CGM,
                                                llvm::PointerType *GuardPtrTy) {
    // void __cxa_guard_release(__guard *guard_object);
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
    return CGM.CreateRuntimeFunction(
        FTy, "__cxa_guard_release",
        llvm::AttributeList::get(CGM.getLLVMContext(),
                                 llvm::AttributeList::FunctionIndex,
                                 llvm::Attribute::NoUnwind));
  }
  
  static llvm::FunctionCallee getGuardAbortFn(CodeGenModule &CGM,
                                              llvm::PointerType *GuardPtrTy) {
    // void __cxa_guard_abort(__guard *guard_object);
    llvm::FunctionType *FTy =
      llvm::FunctionType::get(CGM.VoidTy, GuardPtrTy, /*isVarArg=*/false);
    return CGM.CreateRuntimeFunction(
        FTy, "__cxa_guard_abort",
        llvm::AttributeList::get(CGM.getLLVMContext(),
                                 llvm::AttributeList::FunctionIndex,
                                 llvm::Attribute::NoUnwind));
  }
  
  namespace {
    struct CallGuardAbort final : EHScopeStack::Cleanup {
      llvm::GlobalVariable *Guard;
      CallGuardAbort(llvm::GlobalVariable *Guard) : Guard(Guard) {}
  
      void Emit(CodeGenFunction &CGF, Flags flags) override {
        CGF.EmitNounwindRuntimeCall(getGuardAbortFn(CGF.CGM, Guard->getType()),
                                    Guard);
      }
    };
  }
  
  /// The ARM code here follows the Itanium code closely enough that we
  /// just special-case it at particular places.
  void ItaniumCXXABI::EmitGuardedInit(CodeGenFunction &CGF,
                                      const VarDecl &D,
                                      llvm::GlobalVariable *var,
                                      bool shouldPerformInit) {
    CGBuilderTy &Builder = CGF.Builder;
  
    // Inline variables that weren't instantiated from variable templates have
    // partially-ordered initialization within their translation unit.
    bool NonTemplateInline =
        D.isInline() &&
        !isTemplateInstantiation(D.getTemplateSpecializationKind());
  
    // We only need to use thread-safe statics for local non-TLS variables and
    // inline variables; other global initialization is always single-threaded
    // or (through lazy dynamic loading in multiple threads) unsequenced.
    bool threadsafe = getContext().getLangOpts().ThreadsafeStatics &&
                      (D.isLocalVarDecl() || NonTemplateInline) &&
                      !D.getTLSKind();
  
    // If we have a global variable with internal linkage and thread-safe statics
    // are disabled, we can just let the guard variable be of type i8.
    bool useInt8GuardVariable = !threadsafe && var->hasInternalLinkage();
  
    llvm::IntegerType *guardTy;
    CharUnits guardAlignment;
    if (useInt8GuardVariable) {
      guardTy = CGF.Int8Ty;
      guardAlignment = CharUnits::One();
    } else {
      // Guard variables are 64 bits in the generic ABI and size width on ARM
      // (i.e. 32-bit on AArch32, 64-bit on AArch64).
      if (UseARMGuardVarABI) {
        guardTy = CGF.SizeTy;
        guardAlignment = CGF.getSizeAlign();
      } else {
        guardTy = CGF.Int64Ty;
        guardAlignment = CharUnits::fromQuantity(
                               CGM.getDataLayout().getABITypeAlignment(guardTy));
      }
    }
    llvm::PointerType *guardPtrTy = guardTy->getPointerTo(
        CGF.CGM.getDataLayout().getDefaultGlobalsAddressSpace());
  
    // Create the guard variable if we don't already have it (as we
    // might if we're double-emitting this function body).
    llvm::GlobalVariable *guard = CGM.getStaticLocalDeclGuardAddress(&D);
    if (!guard) {
      // Mangle the name for the guard.
      SmallString<256> guardName;
      {
        llvm::raw_svector_ostream out(guardName);
        getMangleContext().mangleStaticGuardVariable(&D, out);
      }
  
      // Create the guard variable with a zero-initializer.
      // Just absorb linkage and visibility from the guarded variable.
      guard = new llvm::GlobalVariable(CGM.getModule(), guardTy,
                                       false, var->getLinkage(),
                                       llvm::ConstantInt::get(guardTy, 0),
                                       guardName.str());
      guard->setDSOLocal(var->isDSOLocal());
      guard->setVisibility(var->getVisibility());
      // If the variable is thread-local, so is its guard variable.
      guard->setThreadLocalMode(var->getThreadLocalMode());
      guard->setAlignment(guardAlignment.getAsAlign());
  
      // The ABI says: "It is suggested that it be emitted in the same COMDAT
      // group as the associated data object." In practice, this doesn't work for
      // non-ELF and non-Wasm object formats, so only do it for ELF and Wasm.
      llvm::Comdat *C = var->getComdat();
      if (!D.isLocalVarDecl() && C &&
          (CGM.getTarget().getTriple().isOSBinFormatELF() ||
           CGM.getTarget().getTriple().isOSBinFormatWasm())) {
        guard->setComdat(C);
        // An inline variable's guard function is run from the per-TU
        // initialization function, not via a dedicated global ctor function, so
        // we can't put it in a comdat.
        if (!NonTemplateInline)
          CGF.CurFn->setComdat(C);
      } else if (CGM.supportsCOMDAT() && guard->isWeakForLinker()) {
        guard->setComdat(CGM.getModule().getOrInsertComdat(guard->getName()));
      }
  
      CGM.setStaticLocalDeclGuardAddress(&D, guard);
    }
  
    Address guardAddr = Address(guard, guardAlignment);
  
    // Test whether the variable has completed initialization.
    //
    // Itanium C++ ABI 3.3.2:
    //   The following is pseudo-code showing how these functions can be used:
    //     if (obj_guard.first_byte == 0) {
    //       if ( __cxa_guard_acquire (&obj_guard) ) {
    //         try {
    //           ... initialize the object ...;
    //         } catch (...) {
    //            __cxa_guard_abort (&obj_guard);
    //            throw;
    //         }
    //         ... queue object destructor with __cxa_atexit() ...;
    //         __cxa_guard_release (&obj_guard);
    //       }
    //     }
  
    // Load the first byte of the guard variable.
    llvm::LoadInst *LI =
        Builder.CreateLoad(Builder.CreateElementBitCast(guardAddr, CGM.Int8Ty));
  
    // Itanium ABI:
    //   An implementation supporting thread-safety on multiprocessor
    //   systems must also guarantee that references to the initialized
    //   object do not occur before the load of the initialization flag.
    //
    // In LLVM, we do this by marking the load Acquire.
    if (threadsafe)
      LI->setAtomic(llvm::AtomicOrdering::Acquire);
  
    // For ARM, we should only check the first bit, rather than the entire byte:
    //
    // ARM C++ ABI 3.2.3.1:
    //   To support the potential use of initialization guard variables
    //   as semaphores that are the target of ARM SWP and LDREX/STREX
    //   synchronizing instructions we define a static initialization
    //   guard variable to be a 4-byte aligned, 4-byte word with the
    //   following inline access protocol.
    //     #define INITIALIZED 1
    //     if ((obj_guard & INITIALIZED) != INITIALIZED) {
    //       if (__cxa_guard_acquire(&obj_guard))
    //         ...
    //     }
    //
    // and similarly for ARM64:
    //
    // ARM64 C++ ABI 3.2.2:
    //   This ABI instead only specifies the value bit 0 of the static guard
    //   variable; all other bits are platform defined. Bit 0 shall be 0 when the
    //   variable is not initialized and 1 when it is.
    llvm::Value *V =
        (UseARMGuardVarABI && !useInt8GuardVariable)
            ? Builder.CreateAnd(LI, llvm::ConstantInt::get(CGM.Int8Ty, 1))
            : LI;
    llvm::Value *NeedsInit = Builder.CreateIsNull(V, "guard.uninitialized");
  
    llvm::BasicBlock *InitCheckBlock = CGF.createBasicBlock("init.check");
    llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
  
    // Check if the first byte of the guard variable is zero.
    CGF.EmitCXXGuardedInitBranch(NeedsInit, InitCheckBlock, EndBlock,
                                 CodeGenFunction::GuardKind::VariableGuard, &D);
  
    CGF.EmitBlock(InitCheckBlock);
  
    // Variables used when coping with thread-safe statics and exceptions.
    if (threadsafe) {
      // Call __cxa_guard_acquire.
      llvm::Value *V
        = CGF.EmitNounwindRuntimeCall(getGuardAcquireFn(CGM, guardPtrTy), guard);
  
      llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
  
      Builder.CreateCondBr(Builder.CreateIsNotNull(V, "tobool"),
                           InitBlock, EndBlock);
  
      // Call __cxa_guard_abort along the exceptional edge.
      CGF.EHStack.pushCleanup<CallGuardAbort>(EHCleanup, guard);
  
      CGF.EmitBlock(InitBlock);
    }
  
    // Emit the initializer and add a global destructor if appropriate.
    CGF.EmitCXXGlobalVarDeclInit(D, var, shouldPerformInit);
  
    if (threadsafe) {
      // Pop the guard-abort cleanup if we pushed one.
      CGF.PopCleanupBlock();
  
      // Call __cxa_guard_release.  This cannot throw.
      CGF.EmitNounwindRuntimeCall(getGuardReleaseFn(CGM, guardPtrTy),
                                  guardAddr.getPointer());
    } else {
      Builder.CreateStore(llvm::ConstantInt::get(guardTy, 1), guardAddr);
    }
  
    CGF.EmitBlock(EndBlock);
  }
  
  /// Register a global destructor using __cxa_atexit.
  static void emitGlobalDtorWithCXAAtExit(CodeGenFunction &CGF,
                                          llvm::FunctionCallee dtor,
                                          llvm::Constant *addr, bool TLS) {
    assert((TLS || CGF.getTypes().getCodeGenOpts().CXAAtExit) &&
           "__cxa_atexit is disabled");
    const char *Name = "__cxa_atexit";
    if (TLS) {
      const llvm::Triple &T = CGF.getTarget().getTriple();
      Name = T.isOSDarwin() ?  "_tlv_atexit" : "__cxa_thread_atexit";
    }
  
    // We're assuming that the destructor function is something we can
    // reasonably call with the default CC.  Go ahead and cast it to the
    // right prototype.
    llvm::Type *dtorTy =
      llvm::FunctionType::get(CGF.VoidTy, CGF.Int8PtrTy, false)->getPointerTo();
  
    // Preserve address space of addr.
    auto AddrAS = addr ? addr->getType()->getPointerAddressSpace() : 0;
    auto AddrInt8PtrTy =
        AddrAS ? CGF.Int8Ty->getPointerTo(AddrAS) : CGF.Int8PtrTy;
  
    // Create a variable that binds the atexit to this shared object.
    llvm::Constant *handle =
        CGF.CGM.CreateRuntimeVariable(CGF.Int8Ty, "__dso_handle");
    auto *GV = cast<llvm::GlobalValue>(handle->stripPointerCasts());
    GV->setVisibility(llvm::GlobalValue::HiddenVisibility);
  
    // extern "C" int __cxa_atexit(void (*f)(void *), void *p, void *d);
    llvm::Type *paramTys[] = {dtorTy, AddrInt8PtrTy, handle->getType()};
    llvm::FunctionType *atexitTy =
      llvm::FunctionType::get(CGF.IntTy, paramTys, false);
  
    // Fetch the actual function.
    llvm::FunctionCallee atexit = CGF.CGM.CreateRuntimeFunction(atexitTy, Name);
    if (llvm::Function *fn = dyn_cast<llvm::Function>(atexit.getCallee()))
      fn->setDoesNotThrow();
  
    auto &Context = CGF.CGM.getContext();
    FunctionProtoType::ExtProtoInfo EPI(Context.getDefaultCallingConvention(
        /*IsVariadic=*/false, /*IsCXXMethod=*/false));
    QualType fnType =
        Context.getFunctionType(Context.VoidTy, {Context.VoidPtrTy}, EPI);
    llvm::Constant *dtorCallee = cast<llvm::Constant>(dtor.getCallee());
    dtorCallee = CGF.CGM.getFunctionPointer(dtorCallee, fnType);
  
    if (!addr)
      // addr is null when we are trying to register a dtor annotated with
      // __attribute__((destructor)) in a constructor function. Using null here is
      // okay because this argument is just passed back to the destructor
      // function.
      addr = llvm::Constant::getNullValue(CGF.Int8PtrTy);
  
    llvm::Value *args[] = {llvm::ConstantExpr::getBitCast(dtorCallee, dtorTy),
                           llvm::ConstantExpr::getBitCast(addr, AddrInt8PtrTy),
                           handle};
    CGF.EmitNounwindRuntimeCall(atexit, args);
  }
  
  static llvm::Function *createGlobalInitOrCleanupFn(CodeGen::CodeGenModule &CGM,
                                                     StringRef FnName) {
    // Create a function that registers/unregisters destructors that have the same
    // priority.
    llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, false);
    llvm::Function *GlobalInitOrCleanupFn = CGM.CreateGlobalInitOrCleanUpFunction(
        FTy, FnName, CGM.getTypes().arrangeNullaryFunction(), SourceLocation());
  
    return GlobalInitOrCleanupFn;
  }
  
  static FunctionDecl *
  createGlobalInitOrCleanupFnDecl(CodeGen::CodeGenModule &CGM, StringRef FnName) {
    ASTContext &Ctx = CGM.getContext();
    QualType FunctionTy = Ctx.getFunctionType(Ctx.VoidTy, llvm::None, {});
    return FunctionDecl::Create(
        Ctx, Ctx.getTranslationUnitDecl(), SourceLocation(), SourceLocation(),
        &Ctx.Idents.get(FnName), FunctionTy, nullptr, SC_Static, false, false);
  }
  
  void CodeGenModule::unregisterGlobalDtorsWithUnAtExit() {
    for (const auto &I : DtorsUsingAtExit) {
      int Priority = I.first;
      std::string GlobalCleanupFnName =
          std::string("__GLOBAL_cleanup_") + llvm::to_string(Priority);
  
      llvm::Function *GlobalCleanupFn =
          createGlobalInitOrCleanupFn(*this, GlobalCleanupFnName);
  
      FunctionDecl *GlobalCleanupFD =
          createGlobalInitOrCleanupFnDecl(*this, GlobalCleanupFnName);
  
      CodeGenFunction CGF(*this);
      CGF.StartFunction(GlobalDecl(GlobalCleanupFD), getContext().VoidTy,
                        GlobalCleanupFn, getTypes().arrangeNullaryFunction(),
                        FunctionArgList(), SourceLocation(), SourceLocation());
  
      // Get the destructor function type, void(*)(void).
      llvm::FunctionType *dtorFuncTy = llvm::FunctionType::get(CGF.VoidTy, false);
      llvm::Type *dtorTy = dtorFuncTy->getPointerTo();
  
      // Destructor functions are run/unregistered in non-ascending
      // order of their priorities.
      const llvm::TinyPtrVector<llvm::Function *> &Dtors = I.second;
      auto itv = Dtors.rbegin();
      while (itv != Dtors.rend()) {
        llvm::Function *Dtor = *itv;
  
        // We're assuming that the destructor function is something we can
        // reasonably call with the correct CC.  Go ahead and cast it to the
        // right prototype.
        llvm::Constant *dtor = llvm::ConstantExpr::getBitCast(Dtor, dtorTy);
        llvm::Value *V = CGF.unregisterGlobalDtorWithUnAtExit(dtor);
        llvm::Value *NeedsDestruct =
            CGF.Builder.CreateIsNull(V, "needs_destruct");
  
        llvm::BasicBlock *DestructCallBlock =
            CGF.createBasicBlock("destruct.call");
        llvm::BasicBlock *EndBlock = CGF.createBasicBlock(
            (itv + 1) != Dtors.rend() ? "unatexit.call" : "destruct.end");
        // Check if unatexit returns a value of 0. If it does, jump to
        // DestructCallBlock, otherwise jump to EndBlock directly.
        CGF.Builder.CreateCondBr(NeedsDestruct, DestructCallBlock, EndBlock);
  
        CGF.EmitBlock(DestructCallBlock);
  
        // Emit the call to casted Dtor.
        llvm::CallInst *CI = CGF.Builder.CreateCall(dtorFuncTy, dtor);
        // Make sure the call and the callee agree on calling convention.
        CI->setCallingConv(Dtor->getCallingConv());
  
        CGF.EmitBlock(EndBlock);
  
        itv++;
      }
  
      CGF.FinishFunction();
      AddGlobalDtor(GlobalCleanupFn, Priority);
    }
  }
  
  void CodeGenModule::registerGlobalDtorsWithAtExit() {
    for (const auto &I : DtorsUsingAtExit) {
      int Priority = I.first;
      std::string GlobalInitFnName =
          std::string("__GLOBAL_init_") + llvm::to_string(Priority);
      llvm::Function *GlobalInitFn =
          createGlobalInitOrCleanupFn(*this, GlobalInitFnName);
      FunctionDecl *GlobalInitFD =
          createGlobalInitOrCleanupFnDecl(*this, GlobalInitFnName);
  
      CodeGenFunction CGF(*this);
      CGF.StartFunction(GlobalDecl(GlobalInitFD), getContext().VoidTy,
                        GlobalInitFn, getTypes().arrangeNullaryFunction(),
                        FunctionArgList(), SourceLocation(), SourceLocation());
  
      // Since constructor functions are run in non-descending order of their
      // priorities, destructors are registered in non-descending order of their
      // priorities, and since destructor functions are run in the reverse order
      // of their registration, destructor functions are run in non-ascending
      // order of their priorities.
      const llvm::TinyPtrVector<llvm::Function *> &Dtors = I.second;
      for (auto *Dtor : Dtors) {
        // Register the destructor function calling __cxa_atexit if it is
        // available. Otherwise fall back on calling atexit.
        if (getCodeGenOpts().CXAAtExit) {
          emitGlobalDtorWithCXAAtExit(CGF, Dtor, nullptr, false);
        } else {
          // Get the destructor function type, void(*)(void).
          llvm::Type *dtorTy =
              llvm::FunctionType::get(CGF.VoidTy, false)->getPointerTo();
  
          // We're assuming that the destructor function is something we can
          // reasonably call with the correct CC.  Go ahead and cast it to the
          // right prototype.
          CGF.registerGlobalDtorWithAtExit(
              llvm::ConstantExpr::getBitCast(Dtor, dtorTy));
        }
      }
  
      CGF.FinishFunction();
      AddGlobalCtor(GlobalInitFn, Priority, nullptr);
    }
  
    if (getCXXABI().useSinitAndSterm())
      unregisterGlobalDtorsWithUnAtExit();
  }
  
  /// Register a global destructor as best as we know how.
  void ItaniumCXXABI::registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                                         llvm::FunctionCallee dtor,
                                         llvm::Constant *addr) {
    if (D.isNoDestroy(CGM.getContext()))
      return;
  
    // emitGlobalDtorWithCXAAtExit will emit a call to either __cxa_thread_atexit
    // or __cxa_atexit depending on whether this VarDecl is a thread-local storage
    // or not. CXAAtExit controls only __cxa_atexit, so use it if it is enabled.
    // We can always use __cxa_thread_atexit.
    if (CGM.getCodeGenOpts().CXAAtExit || D.getTLSKind())
      return emitGlobalDtorWithCXAAtExit(CGF, dtor, addr, D.getTLSKind());
  
    // In Apple kexts, we want to add a global destructor entry.
    // FIXME: shouldn't this be guarded by some variable?
    if (CGM.getLangOpts().AppleKext) {
      // Generate a global destructor entry.
      return CGM.AddCXXDtorEntry(dtor, addr);
    }
  
    CGF.registerGlobalDtorWithAtExit(D, dtor, addr);
  }
  
  static bool isThreadWrapperReplaceable(const VarDecl *VD,
                                         CodeGen::CodeGenModule &CGM) {
    assert(!VD->isStaticLocal() && "static local VarDecls don't need wrappers!");
    // Darwin prefers to have references to thread local variables to go through
    // the thread wrapper instead of directly referencing the backing variable.
    return VD->getTLSKind() == VarDecl::TLS_Dynamic &&
           CGM.getTarget().getTriple().isOSDarwin();
  }
  
  /// Get the appropriate linkage for the wrapper function. This is essentially
  /// the weak form of the variable's linkage; every translation unit which needs
  /// the wrapper emits a copy, and we want the linker to merge them.
  static llvm::GlobalValue::LinkageTypes
  getThreadLocalWrapperLinkage(const VarDecl *VD, CodeGen::CodeGenModule &CGM) {
    llvm::GlobalValue::LinkageTypes VarLinkage =
        CGM.getLLVMLinkageVarDefinition(VD, /*IsConstant=*/false);
  
    // For internal linkage variables, we don't need an external or weak wrapper.
    if (llvm::GlobalValue::isLocalLinkage(VarLinkage))
      return VarLinkage;
  
    // If the thread wrapper is replaceable, give it appropriate linkage.
    if (isThreadWrapperReplaceable(VD, CGM))
      if (!llvm::GlobalVariable::isLinkOnceLinkage(VarLinkage) &&
          !llvm::GlobalVariable::isWeakODRLinkage(VarLinkage))
        return VarLinkage;
    return llvm::GlobalValue::WeakODRLinkage;
  }
  
  llvm::Function *
  ItaniumCXXABI::getOrCreateThreadLocalWrapper(const VarDecl *VD,
                                               llvm::Value *Val) {
    // Mangle the name for the thread_local wrapper function.
    SmallString<256> WrapperName;
    {
      llvm::raw_svector_ostream Out(WrapperName);
      getMangleContext().mangleItaniumThreadLocalWrapper(VD, Out);
    }
  
    // FIXME: If VD is a definition, we should regenerate the function attributes
    // before returning.
    if (llvm::Value *V = CGM.getModule().getNamedValue(WrapperName))
      return cast<llvm::Function>(V);
  
    QualType RetQT = VD->getType();
    if (RetQT->isReferenceType())
      RetQT = RetQT.getNonReferenceType();
  
    const CGFunctionInfo &FI = CGM.getTypes().arrangeBuiltinFunctionDeclaration(
        getContext().getPointerType(RetQT), FunctionArgList());
  
    llvm::FunctionType *FnTy = CGM.getTypes().GetFunctionType(FI);
    llvm::Function *Wrapper =
        llvm::Function::Create(FnTy, getThreadLocalWrapperLinkage(VD, CGM),
                               WrapperName.str(), &CGM.getModule());
  
    if (CGM.supportsCOMDAT() && Wrapper->isWeakForLinker())
      Wrapper->setComdat(CGM.getModule().getOrInsertComdat(Wrapper->getName()));
  
    CGM.SetLLVMFunctionAttributes(GlobalDecl(), FI, Wrapper);
  
    // Always resolve references to the wrapper at link time.
    if (!Wrapper->hasLocalLinkage())
      if (!isThreadWrapperReplaceable(VD, CGM) ||
          llvm::GlobalVariable::isLinkOnceLinkage(Wrapper->getLinkage()) ||
          llvm::GlobalVariable::isWeakODRLinkage(Wrapper->getLinkage()) ||
          VD->getVisibility() == HiddenVisibility)
        Wrapper->setVisibility(llvm::GlobalValue::HiddenVisibility);
  
    if (isThreadWrapperReplaceable(VD, CGM)) {
      Wrapper->setCallingConv(llvm::CallingConv::CXX_FAST_TLS);
      Wrapper->addFnAttr(llvm::Attribute::NoUnwind);
    }
  
    ThreadWrappers.push_back({VD, Wrapper});
    return Wrapper;
  }
  
  void ItaniumCXXABI::EmitThreadLocalInitFuncs(
      CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
      ArrayRef<llvm::Function *> CXXThreadLocalInits,
      ArrayRef<const VarDecl *> CXXThreadLocalInitVars) {
    llvm::Function *InitFunc = nullptr;
  
    // Separate initializers into those with ordered (or partially-ordered)
    // initialization and those with unordered initialization.
    llvm::SmallVector<llvm::Function *, 8> OrderedInits;
    llvm::SmallDenseMap<const VarDecl *, llvm::Function *> UnorderedInits;
    for (unsigned I = 0; I != CXXThreadLocalInits.size(); ++I) {
      if (isTemplateInstantiation(
              CXXThreadLocalInitVars[I]->getTemplateSpecializationKind()))
        UnorderedInits[CXXThreadLocalInitVars[I]->getCanonicalDecl()] =
            CXXThreadLocalInits[I];
      else
        OrderedInits.push_back(CXXThreadLocalInits[I]);
    }
  
    if (!OrderedInits.empty()) {
      // Generate a guarded initialization function.
      llvm::FunctionType *FTy =
          llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
      const CGFunctionInfo &FI = CGM.getTypes().arrangeNullaryFunction();
      InitFunc = CGM.CreateGlobalInitOrCleanUpFunction(FTy, "__tls_init", FI,
                                                       SourceLocation(),
                                                       /*TLS=*/true);
      llvm::GlobalVariable *Guard = new llvm::GlobalVariable(
          CGM.getModule(), CGM.Int8Ty, /*isConstant=*/false,
          llvm::GlobalVariable::InternalLinkage,
          llvm::ConstantInt::get(CGM.Int8Ty, 0), "__tls_guard");
      Guard->setThreadLocal(true);
      Guard->setThreadLocalMode(CGM.GetDefaultLLVMTLSModel());
  
      CharUnits GuardAlign = CharUnits::One();
      Guard->setAlignment(GuardAlign.getAsAlign());
  
      CodeGenFunction(CGM).GenerateCXXGlobalInitFunc(
          InitFunc, OrderedInits, ConstantAddress(Guard, GuardAlign));
      // On Darwin platforms, use CXX_FAST_TLS calling convention.
      if (CGM.getTarget().getTriple().isOSDarwin()) {
        InitFunc->setCallingConv(llvm::CallingConv::CXX_FAST_TLS);
        InitFunc->addFnAttr(llvm::Attribute::NoUnwind);
      }
    }
  
    // Create declarations for thread wrappers for all thread-local variables
    // with non-discardable definitions in this translation unit.
    for (const VarDecl *VD : CXXThreadLocals) {
      if (VD->hasDefinition() &&
          !isDiscardableGVALinkage(getContext().GetGVALinkageForVariable(VD))) {
        llvm::GlobalValue *GV = CGM.GetGlobalValue(CGM.getMangledName(VD));
        getOrCreateThreadLocalWrapper(VD, GV);
      }
    }
  
    // Emit all referenced thread wrappers.
    for (auto VDAndWrapper : ThreadWrappers) {
      const VarDecl *VD = VDAndWrapper.first;
      llvm::GlobalVariable *Var =
          cast<llvm::GlobalVariable>(CGM.GetGlobalValue(CGM.getMangledName(VD)));
      llvm::Function *Wrapper = VDAndWrapper.second;
  
      // Some targets require that all access to thread local variables go through
      // the thread wrapper.  This means that we cannot attempt to create a thread
      // wrapper or a thread helper.
      if (!VD->hasDefinition()) {
        if (isThreadWrapperReplaceable(VD, CGM)) {
          Wrapper->setLinkage(llvm::Function::ExternalLinkage);
          continue;
        }
  
        // If this isn't a TU in which this variable is defined, the thread
        // wrapper is discardable.
        if (Wrapper->getLinkage() == llvm::Function::WeakODRLinkage)
          Wrapper->setLinkage(llvm::Function::LinkOnceODRLinkage);
      }
  
      CGM.SetLLVMFunctionAttributesForDefinition(nullptr, Wrapper);
  
      // Mangle the name for the thread_local initialization function.
      SmallString<256> InitFnName;
      {
        llvm::raw_svector_ostream Out(InitFnName);
        getMangleContext().mangleItaniumThreadLocalInit(VD, Out);
      }
  
      llvm::FunctionType *InitFnTy = llvm::FunctionType::get(CGM.VoidTy, false);
  
      // If we have a definition for the variable, emit the initialization
      // function as an alias to the global Init function (if any). Otherwise,
      // produce a declaration of the initialization function.
      llvm::GlobalValue *Init = nullptr;
      bool InitIsInitFunc = false;
      bool HasConstantInitialization = false;
      if (!usesThreadWrapperFunction(VD)) {
        HasConstantInitialization = true;
      } else if (VD->hasDefinition()) {
        InitIsInitFunc = true;
        llvm::Function *InitFuncToUse = InitFunc;
        if (isTemplateInstantiation(VD->getTemplateSpecializationKind()))
          InitFuncToUse = UnorderedInits.lookup(VD->getCanonicalDecl());
        if (InitFuncToUse)
          Init = llvm::GlobalAlias::create(Var->getLinkage(), InitFnName.str(),
                                           InitFuncToUse);
      } else {
        // Emit a weak global function referring to the initialization function.
        // This function will not exist if the TU defining the thread_local
        // variable in question does not need any dynamic initialization for
        // its thread_local variables.
        Init = llvm::Function::Create(InitFnTy,
                                      llvm::GlobalVariable::ExternalWeakLinkage,
                                      InitFnName.str(), &CGM.getModule());
        const CGFunctionInfo &FI = CGM.getTypes().arrangeNullaryFunction();
        CGM.SetLLVMFunctionAttributes(GlobalDecl(), FI,
                                      cast<llvm::Function>(Init));
      }
  
      if (Init) {
        Init->setVisibility(Var->getVisibility());
        // Don't mark an extern_weak function DSO local on windows.
        if (!CGM.getTriple().isOSWindows() || !Init->hasExternalWeakLinkage())
          Init->setDSOLocal(Var->isDSOLocal());
      }
  
      llvm::LLVMContext &Context = CGM.getModule().getContext();
      llvm::BasicBlock *Entry = llvm::BasicBlock::Create(Context, "", Wrapper);
      CGBuilderTy Builder(CGM, Entry);
      if (HasConstantInitialization) {
        // No dynamic initialization to invoke.
      } else if (InitIsInitFunc) {
        if (Init) {
          llvm::CallInst *CallVal = Builder.CreateCall(InitFnTy, Init);
          if (isThreadWrapperReplaceable(VD, CGM)) {
            CallVal->setCallingConv(llvm::CallingConv::CXX_FAST_TLS);
            llvm::Function *Fn =
                cast<llvm::Function>(cast<llvm::GlobalAlias>(Init)->getAliasee());
            Fn->setCallingConv(llvm::CallingConv::CXX_FAST_TLS);
          }
        }
      } else {
        // Don't know whether we have an init function. Call it if it exists.
        llvm::Value *Have = Builder.CreateIsNotNull(Init);
        llvm::BasicBlock *InitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
        llvm::BasicBlock *ExitBB = llvm::BasicBlock::Create(Context, "", Wrapper);
        Builder.CreateCondBr(Have, InitBB, ExitBB);
  
        Builder.SetInsertPoint(InitBB);
        Builder.CreateCall(InitFnTy, Init);
        Builder.CreateBr(ExitBB);
  
        Builder.SetInsertPoint(ExitBB);
      }
  
      // For a reference, the result of the wrapper function is a pointer to
      // the referenced object.
      llvm::Value *Val = Var;
      if (VD->getType()->isReferenceType()) {
        CharUnits Align = CGM.getContext().getDeclAlign(VD);
        Val = Builder.CreateAlignedLoad(Val, Align);
      }
      if (Val->getType() != Wrapper->getReturnType())
        Val = Builder.CreatePointerBitCastOrAddrSpaceCast(
            Val, Wrapper->getReturnType(), "");
      Builder.CreateRet(Val);
    }
  }
  
  LValue ItaniumCXXABI::EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
                                                     const VarDecl *VD,
                                                     QualType LValType) {
    llvm::Value *Val = CGF.CGM.GetAddrOfGlobalVar(VD);
    llvm::Function *Wrapper = getOrCreateThreadLocalWrapper(VD, Val);
  
    llvm::CallInst *CallVal = CGF.Builder.CreateCall(Wrapper);
    CallVal->setCallingConv(Wrapper->getCallingConv());
  
    LValue LV;
    if (VD->getType()->isReferenceType())
      LV = CGF.MakeNaturalAlignAddrLValue(CallVal, LValType);
    else
      LV = CGF.MakeAddrLValue(CallVal, LValType,
                              CGF.getContext().getDeclAlign(VD));
    // FIXME: need setObjCGCLValueClass?
    return LV;
  }
  
  /// Return whether the given global decl needs a VTT parameter, which it does
  /// if it's a base constructor or destructor with virtual bases.
  bool ItaniumCXXABI::NeedsVTTParameter(GlobalDecl GD) {
    const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  
    // We don't have any virtual bases, just return early.
    if (!MD->getParent()->getNumVBases())
      return false;
  
    // Check if we have a base constructor.
    if (isa<CXXConstructorDecl>(MD) && GD.getCtorType() == Ctor_Base)
      return true;
  
    // Check if we have a base destructor.
    if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
      return true;
  
    return false;
  }
  
  llvm::Constant *
  ItaniumCXXABI::getOrCreateVirtualFunctionPointerThunk(const CXXMethodDecl *MD) {
    SmallString<256> MethodName;
    llvm::raw_svector_ostream Out(MethodName);
    getMangleContext().mangleCXXName(MD, Out);
    MethodName += "_vfpthunk_";
    StringRef ThunkName = MethodName.str();
    llvm::Function *ThunkFn;
    if ((ThunkFn = cast_or_null<llvm::Function>(
             CGM.getModule().getNamedValue(ThunkName))))
      return ThunkFn;
  
    const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeCXXMethodDeclaration(MD);
    llvm::FunctionType *ThunkTy = CGM.getTypes().GetFunctionType(FnInfo);
    llvm::GlobalValue::LinkageTypes Linkage =
        MD->isExternallyVisible() ? llvm::GlobalValue::LinkOnceODRLinkage
                                  : llvm::GlobalValue::InternalLinkage;
    ThunkFn =
        llvm::Function::Create(ThunkTy, Linkage, ThunkName, &CGM.getModule());
    ThunkFn->setVisibility(llvm::GlobalValue::HiddenVisibility);
    assert(ThunkFn->getName() == ThunkName && "name was uniqued!");
  
    CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn);
    CGM.SetLLVMFunctionAttributesForDefinition(MD, ThunkFn);
  
    // Start codegen.
    CodeGenFunction CGF(CGM);
    CGF.CurGD = GlobalDecl(MD);
    CGF.CurFuncIsThunk = true;
  
    // Build FunctionArgs.
    FunctionArgList FunctionArgs;
    CGF.BuildFunctionArgList(CGF.CurGD, FunctionArgs);
  
    CGF.StartFunction(GlobalDecl(), FnInfo.getReturnType(), ThunkFn, FnInfo,
                      FunctionArgs, MD->getLocation(), SourceLocation());
    llvm::Value *ThisVal = loadIncomingCXXThis(CGF);
    setCXXABIThisValue(CGF, ThisVal);
  
    CallArgList CallArgs;
    for (const VarDecl *VD : FunctionArgs)
      CGF.EmitDelegateCallArg(CallArgs, VD, SourceLocation());
  
    const FunctionProtoType *FPT = MD->getType()->getAs<FunctionProtoType>();
    RequiredArgs Required = RequiredArgs::forPrototypePlus(FPT, /*this*/ 1);
    const CGFunctionInfo &CallInfo =
        CGM.getTypes().arrangeCXXMethodCall(CallArgs, FPT, Required, 0);
    CGCallee Callee = CGCallee::forVirtual(nullptr, GlobalDecl(MD),
                                           getThisAddress(CGF), ThunkTy);
    llvm::CallBase *CallOrInvoke;
    CGF.EmitCall(CallInfo, Callee, ReturnValueSlot(), CallArgs, &CallOrInvoke,
                 SourceLocation(), true);
    auto *Call = cast<llvm::CallInst>(CallOrInvoke);
    Call->setTailCallKind(llvm::CallInst::TCK_MustTail);
    if (Call->getType()->isVoidTy())
      CGF.Builder.CreateRetVoid();
    else
      CGF.Builder.CreateRet(Call);
  
    // Finish the function to maintain CodeGenFunction invariants.
    // FIXME: Don't emit unreachable code.
    CGF.EmitBlock(CGF.createBasicBlock());
    CGF.FinishFunction();
    return ThunkFn;
  }
  
  namespace {
  class ItaniumRTTIBuilder {
    CodeGenModule &CGM;  // Per-module state.
    llvm::LLVMContext &VMContext;
    const ItaniumCXXABI &CXXABI;  // Per-module state.
  
    /// Fields - The fields of the RTTI descriptor currently being built.
    SmallVector<llvm::Constant *, 16> Fields;
  
    /// GetAddrOfTypeName - Returns the mangled type name of the given type.
    llvm::GlobalVariable *
    GetAddrOfTypeName(QualType Ty, llvm::GlobalVariable::LinkageTypes Linkage);
  
    /// GetAddrOfExternalRTTIDescriptor - Returns the constant for the RTTI
    /// descriptor of the given type.
    llvm::Constant *GetAddrOfExternalRTTIDescriptor(QualType Ty);
  
    /// BuildVTablePointer - Build the vtable pointer for the given type.
    void BuildVTablePointer(const Type *Ty);
  
    /// BuildSIClassTypeInfo - Build an abi::__si_class_type_info, used for single
    /// inheritance, according to the Itanium C++ ABI, 2.9.5p6b.
    void BuildSIClassTypeInfo(const CXXRecordDecl *RD);
  
    /// BuildVMIClassTypeInfo - Build an abi::__vmi_class_type_info, used for
    /// classes with bases that do not satisfy the abi::__si_class_type_info
    /// constraints, according ti the Itanium C++ ABI, 2.9.5p5c.
    void BuildVMIClassTypeInfo(const CXXRecordDecl *RD);
  
    /// BuildPointerTypeInfo - Build an abi::__pointer_type_info struct, used
    /// for pointer types.
    void BuildPointerTypeInfo(QualType PointeeTy);
  
    /// BuildObjCObjectTypeInfo - Build the appropriate kind of
    /// type_info for an object type.
    void BuildObjCObjectTypeInfo(const ObjCObjectType *Ty);
  
    /// BuildPointerToMemberTypeInfo - Build an abi::__pointer_to_member_type_info
    /// struct, used for member pointer types.
    void BuildPointerToMemberTypeInfo(const MemberPointerType *Ty);
  
  public:
    ItaniumRTTIBuilder(const ItaniumCXXABI &ABI)
        : CGM(ABI.CGM), VMContext(CGM.getModule().getContext()), CXXABI(ABI) {}
  
    // Pointer type info flags.
    enum {
      /// PTI_Const - Type has const qualifier.
      PTI_Const = 0x1,
  
      /// PTI_Volatile - Type has volatile qualifier.
      PTI_Volatile = 0x2,
  
      /// PTI_Restrict - Type has restrict qualifier.
      PTI_Restrict = 0x4,
  
      /// PTI_Incomplete - Type is incomplete.
      PTI_Incomplete = 0x8,
  
      /// PTI_ContainingClassIncomplete - Containing class is incomplete.
      /// (in pointer to member).
      PTI_ContainingClassIncomplete = 0x10,
  
      /// PTI_TransactionSafe - Pointee is transaction_safe function (C++ TM TS).
      //PTI_TransactionSafe = 0x20,
  
      /// PTI_Noexcept - Pointee is noexcept function (C++1z).
      PTI_Noexcept = 0x40,
    };
  
    // VMI type info flags.
    enum {
      /// VMI_NonDiamondRepeat - Class has non-diamond repeated inheritance.
      VMI_NonDiamondRepeat = 0x1,
  
      /// VMI_DiamondShaped - Class is diamond shaped.
      VMI_DiamondShaped = 0x2
    };
  
    // Base class type info flags.
    enum {
      /// BCTI_Virtual - Base class is virtual.
      BCTI_Virtual = 0x1,
  
      /// BCTI_Public - Base class is public.
      BCTI_Public = 0x2
    };
  
    /// BuildTypeInfo - Build the RTTI type info struct for the given type, or
    /// link to an existing RTTI descriptor if one already exists.
    llvm::Constant *BuildTypeInfo(QualType Ty);
  
    /// BuildTypeInfo - Build the RTTI type info struct for the given type.
    llvm::Constant *BuildTypeInfo(
        QualType Ty,
        llvm::GlobalVariable::LinkageTypes Linkage,
        llvm::GlobalValue::VisibilityTypes Visibility,
        llvm::GlobalValue::DLLStorageClassTypes DLLStorageClass);
  };
  }
  
  llvm::GlobalVariable *ItaniumRTTIBuilder::GetAddrOfTypeName(
      QualType Ty, llvm::GlobalVariable::LinkageTypes Linkage) {
    SmallString<256> Name;
    llvm::raw_svector_ostream Out(Name);
    CGM.getCXXABI().getMangleContext().mangleCXXRTTIName(Ty, Out);
  
    // We know that the mangled name of the type starts at index 4 of the
    // mangled name of the typename, so we can just index into it in order to
    // get the mangled name of the type.
    llvm::Constant *Init = llvm::ConstantDataArray::getString(VMContext,
                                                              Name.substr(4));
    auto Align = CGM.getContext().getTypeAlignInChars(CGM.getContext().CharTy);
  
    llvm::GlobalVariable *GV = CGM.CreateOrReplaceCXXRuntimeVariable(
        Name, Init->getType(), Linkage, Align.getQuantity());
  
    GV->setInitializer(Init);
  
    return GV;
  }
  
  llvm::Constant *
  ItaniumRTTIBuilder::GetAddrOfExternalRTTIDescriptor(QualType Ty) {
    // Mangle the RTTI name.
    SmallString<256> Name;
    llvm::raw_svector_ostream Out(Name);
    CGM.getCXXABI().getMangleContext().mangleCXXRTTI(Ty, Out);
  
    // Look for an existing global.
    llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(Name);
  
    if (!GV) {
      // Create a new global variable.
      // Note for the future: If we would ever like to do deferred emission of
      // RTTI, check if emitting vtables opportunistically need any adjustment.
  
      GV = new llvm::GlobalVariable(CGM.getModule(), CGM.Int8PtrTy,
                                    /*isConstant=*/true,
                                    llvm::GlobalValue::ExternalLinkage, nullptr,
                                    Name);
      const CXXRecordDecl *RD = Ty->getAsCXXRecordDecl();
      CGM.setGVProperties(GV, RD);
    }
  
    return llvm::ConstantExpr::getBitCast(GV, CGM.Int8PtrTy);
  }
  
  /// TypeInfoIsInStandardLibrary - Given a builtin type, returns whether the type
  /// info for that type is defined in the standard library.
  static bool TypeInfoIsInStandardLibrary(const BuiltinType *Ty) {
    // Itanium C++ ABI 2.9.2:
    //   Basic type information (e.g. for "int", "bool", etc.) will be kept in
    //   the run-time support library. Specifically, the run-time support
    //   library should contain type_info objects for the types X, X* and
    //   X const*, for every X in: void, std::nullptr_t, bool, wchar_t, char,
    //   unsigned char, signed char, short, unsigned short, int, unsigned int,
    //   long, unsigned long, long long, unsigned long long, float, double,
    //   long double, char16_t, char32_t, and the IEEE 754r decimal and
    //   half-precision floating point types.
    //
    // GCC also emits RTTI for __int128.
    // FIXME: We do not emit RTTI information for decimal types here.
  
    // Types added here must also be added to EmitFundamentalRTTIDescriptors.
    switch (Ty->getKind()) {
      case BuiltinType::Void:
      case BuiltinType::NullPtr:
      case BuiltinType::Bool:
      case BuiltinType::WChar_S:
      case BuiltinType::WChar_U:
      case BuiltinType::Char_U:
      case BuiltinType::Char_S:
      case BuiltinType::UChar:
      case BuiltinType::SChar:
      case BuiltinType::Short:
      case BuiltinType::UShort:
      case BuiltinType::Int:
      case BuiltinType::UInt:
      case BuiltinType::Long:
      case BuiltinType::ULong:
      case BuiltinType::LongLong:
      case BuiltinType::ULongLong:
      case BuiltinType::Half:
      case BuiltinType::Float:
      case BuiltinType::Double:
      case BuiltinType::LongDouble:
      case BuiltinType::Float16:
      case BuiltinType::Float128:
      case BuiltinType::Char8:
      case BuiltinType::Char16:
      case BuiltinType::Char32:
      case BuiltinType::Int128:
      case BuiltinType::UInt128:
        return true;
  
  #define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
      case BuiltinType::Id:
  #include "clang/Basic/OpenCLImageTypes.def"
  #define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
      case BuiltinType::Id:
  #include "clang/Basic/OpenCLExtensionTypes.def"
      case BuiltinType::OCLSampler:
      case BuiltinType::OCLEvent:
      case BuiltinType::OCLClkEvent:
      case BuiltinType::OCLQueue:
      case BuiltinType::OCLReserveID:
  #define SVE_TYPE(Name, Id, SingletonId) \
      case BuiltinType::Id:
  #include "clang/Basic/AArch64SVEACLETypes.def"
  #define PPC_VECTOR_TYPE(Name, Id, Size) \
      case BuiltinType::Id:
  #include "clang/Basic/PPCTypes.def"
      case BuiltinType::ShortAccum:
      case BuiltinType::Accum:
      case BuiltinType::LongAccum:
      case BuiltinType::UShortAccum:
      case BuiltinType::UAccum:
      case BuiltinType::ULongAccum:
      case BuiltinType::ShortFract:
      case BuiltinType::Fract:
      case BuiltinType::LongFract:
      case BuiltinType::UShortFract:
      case BuiltinType::UFract:
      case BuiltinType::ULongFract:
      case BuiltinType::SatShortAccum:
      case BuiltinType::SatAccum:
      case BuiltinType::SatLongAccum:
      case BuiltinType::SatUShortAccum:
      case BuiltinType::SatUAccum:
      case BuiltinType::SatULongAccum:
      case BuiltinType::SatShortFract:
      case BuiltinType::SatFract:
      case BuiltinType::SatLongFract:
      case BuiltinType::SatUShortFract:
      case BuiltinType::SatUFract:
      case BuiltinType::SatULongFract:
      case BuiltinType::BFloat16:
        return false;
  
      case BuiltinType::Dependent:
  #define BUILTIN_TYPE(Id, SingletonId)
  #define PLACEHOLDER_TYPE(Id, SingletonId) \
      case BuiltinType::Id:
  #include "clang/AST/BuiltinTypes.def"
        llvm_unreachable("asking for RRTI for a placeholder type!");
  
      case BuiltinType::ObjCId:
      case BuiltinType::ObjCClass:
      case BuiltinType::ObjCSel:
        llvm_unreachable("FIXME: Objective-C types are unsupported!");
    }
  
    llvm_unreachable("Invalid BuiltinType Kind!");
  }
  
  static bool TypeInfoIsInStandardLibrary(const PointerType *PointerTy) {
    QualType PointeeTy = PointerTy->getPointeeType();
    const BuiltinType *BuiltinTy = dyn_cast<BuiltinType>(PointeeTy);
    if (!BuiltinTy)
      return false;
  
    // Check the qualifiers.
    Qualifiers Quals = PointeeTy.getQualifiers();
    Quals.removeConst();
  
    if (!Quals.empty())
      return false;
  
    return TypeInfoIsInStandardLibrary(BuiltinTy);
  }
  
  /// IsStandardLibraryRTTIDescriptor - Returns whether the type
  /// information for the given type exists in the standard library.
  static bool IsStandardLibraryRTTIDescriptor(QualType Ty) {
    // Type info for builtin types is defined in the standard library.
    if (const BuiltinType *BuiltinTy = dyn_cast<BuiltinType>(Ty))
      return TypeInfoIsInStandardLibrary(BuiltinTy);
  
    // Type info for some pointer types to builtin types is defined in the
    // standard library.
    if (const PointerType *PointerTy = dyn_cast<PointerType>(Ty))
      return TypeInfoIsInStandardLibrary(PointerTy);
  
    return false;
  }
  
  /// ShouldUseExternalRTTIDescriptor - Returns whether the type information for
  /// the given type exists somewhere else, and that we should not emit the type
  /// information in this translation unit.  Assumes that it is not a
  /// standard-library type.
  static bool ShouldUseExternalRTTIDescriptor(CodeGenModule &CGM,
                                              QualType Ty) {
    ASTContext &Context = CGM.getContext();
  
    // If RTTI is disabled, assume it might be disabled in the
    // translation unit that defines any potential key function, too.
    if (!Context.getLangOpts().RTTI) return false;
  
    if (const RecordType *RecordTy = dyn_cast<RecordType>(Ty)) {
      const CXXRecordDecl *RD = cast<CXXRecordDecl>(RecordTy->getDecl());
      if (!RD->hasDefinition())
        return false;
  
      if (!RD->isDynamicClass())
        return false;
  
      // FIXME: this may need to be reconsidered if the key function
      // changes.
      // N.B. We must always emit the RTTI data ourselves if there exists a key
      // function.
      bool IsDLLImport = RD->hasAttr<DLLImportAttr>();
  
      // Don't import the RTTI but emit it locally.
      if (CGM.getTriple().isWindowsGNUEnvironment())
        return false;
  
      if (CGM.getVTables().isVTableExternal(RD))
        return IsDLLImport && !CGM.getTriple().isWindowsItaniumEnvironment()
                   ? false
                   : true;
  
      if (IsDLLImport)
        return true;
    }
  
    return false;
  }
  
  /// IsIncompleteClassType - Returns whether the given record type is incomplete.
  static bool IsIncompleteClassType(const RecordType *RecordTy) {
    return !RecordTy->getDecl()->isCompleteDefinition();
  }
  
  /// ContainsIncompleteClassType - Returns whether the given type contains an
  /// incomplete class type. This is true if
  ///
  ///   * The given type is an incomplete class type.
  ///   * The given type is a pointer type whose pointee type contains an
  ///     incomplete class type.
  ///   * The given type is a member pointer type whose class is an incomplete
  ///     class type.
  ///   * The given type is a member pointer type whoise pointee type contains an
  ///     incomplete class type.
  /// is an indirect or direct pointer to an incomplete class type.
  static bool ContainsIncompleteClassType(QualType Ty) {
    if (const RecordType *RecordTy = dyn_cast<RecordType>(Ty)) {
      if (IsIncompleteClassType(RecordTy))
        return true;
    }
  
    if (const PointerType *PointerTy = dyn_cast<PointerType>(Ty))
      return ContainsIncompleteClassType(PointerTy->getPointeeType());
  
    if (const MemberPointerType *MemberPointerTy =
        dyn_cast<MemberPointerType>(Ty)) {
      // Check if the class type is incomplete.
      const RecordType *ClassType = cast<RecordType>(MemberPointerTy->getClass());
      if (IsIncompleteClassType(ClassType))
        return true;
  
      return ContainsIncompleteClassType(MemberPointerTy->getPointeeType());
    }
  
    return false;
  }
  
  // CanUseSingleInheritance - Return whether the given record decl has a "single,
  // public, non-virtual base at offset zero (i.e. the derived class is dynamic
  // iff the base is)", according to Itanium C++ ABI, 2.95p6b.
  static bool CanUseSingleInheritance(const CXXRecordDecl *RD) {
    // Check the number of bases.
    if (RD->getNumBases() != 1)
      return false;
  
    // Get the base.
    CXXRecordDecl::base_class_const_iterator Base = RD->bases_begin();
  
    // Check that the base is not virtual.
    if (Base->isVirtual())
      return false;
  
    // Check that the base is public.
    if (Base->getAccessSpecifier() != AS_public)
      return false;
  
    // Check that the class is dynamic iff the base is.
    auto *BaseDecl =
        cast<CXXRecordDecl>(Base->getType()->castAs<RecordType>()->getDecl());
    if (!BaseDecl->isEmpty() &&
        BaseDecl->isDynamicClass() != RD->isDynamicClass())
      return false;
  
    return true;
  }
  
  void ItaniumRTTIBuilder::BuildVTablePointer(const Type *Ty) {
    // abi::__class_type_info.
    static const char * const ClassTypeInfo =
      "_ZTVN10__cxxabiv117__class_type_infoE";
    // abi::__si_class_type_info.
    static const char * const SIClassTypeInfo =
      "_ZTVN10__cxxabiv120__si_class_type_infoE";
    // abi::__vmi_class_type_info.
    static const char * const VMIClassTypeInfo =
      "_ZTVN10__cxxabiv121__vmi_class_type_infoE";
  
    const char *VTableName = nullptr;
  
    switch (Ty->getTypeClass()) {
  #define TYPE(Class, Base)
  #define ABSTRACT_TYPE(Class, Base)
  #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base) case Type::Class:
  #define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
  #define DEPENDENT_TYPE(Class, Base) case Type::Class:
  #include "clang/AST/TypeNodes.inc"
      llvm_unreachable("Non-canonical and dependent types shouldn't get here");
  
    case Type::LValueReference:
    case Type::RValueReference:
      llvm_unreachable("References shouldn't get here");
  
    case Type::Auto:
    case Type::DeducedTemplateSpecialization:
      llvm_unreachable("Undeduced type shouldn't get here");
  
    case Type::Pipe:
      llvm_unreachable("Pipe types shouldn't get here");
  
    case Type::Builtin:
    case Type::ExtInt:
    // GCC treats vector and complex types as fundamental types.
    case Type::Vector:
    case Type::ExtVector:
    case Type::ConstantMatrix:
    case Type::Complex:
    case Type::Atomic:
    // FIXME: GCC treats block pointers as fundamental types?!
    case Type::BlockPointer:
      // abi::__fundamental_type_info.
      VTableName = "_ZTVN10__cxxabiv123__fundamental_type_infoE";
      break;
  
    case Type::ConstantArray:
    case Type::IncompleteArray:
    case Type::VariableArray:
      // abi::__array_type_info.
      VTableName = "_ZTVN10__cxxabiv117__array_type_infoE";
      break;
  
    case Type::FunctionNoProto:
    case Type::FunctionProto:
      // abi::__function_type_info.
      VTableName = "_ZTVN10__cxxabiv120__function_type_infoE";
      break;
  
    case Type::Enum:
      // abi::__enum_type_info.
      VTableName = "_ZTVN10__cxxabiv116__enum_type_infoE";
      break;
  
    case Type::Record: {
      const CXXRecordDecl *RD =
        cast<CXXRecordDecl>(cast<RecordType>(Ty)->getDecl());
  
      if (!RD->hasDefinition() || !RD->getNumBases()) {
        VTableName = ClassTypeInfo;
      } else if (CanUseSingleInheritance(RD)) {
        VTableName = SIClassTypeInfo;
      } else {
        VTableName = VMIClassTypeInfo;
      }
  
      break;
    }
  
    case Type::ObjCObject:
      // Ignore protocol qualifiers.
      Ty = cast<ObjCObjectType>(Ty)->getBaseType().getTypePtr();
  
      // Handle id and Class.
      if (isa<BuiltinType>(Ty)) {
        VTableName = ClassTypeInfo;
        break;
      }
  
      assert(isa<ObjCInterfaceType>(Ty));
      LLVM_FALLTHROUGH;
  
    case Type::ObjCInterface:
      if (cast<ObjCInterfaceType>(Ty)->getDecl()->getSuperClass()) {
        VTableName = SIClassTypeInfo;
      } else {
        VTableName = ClassTypeInfo;
      }
      break;
  
    case Type::ObjCObjectPointer:
    case Type::Pointer:
      // abi::__pointer_type_info.
      VTableName = "_ZTVN10__cxxabiv119__pointer_type_infoE";
      break;
  
    case Type::MemberPointer:
      // abi::__pointer_to_member_type_info.
      VTableName = "_ZTVN10__cxxabiv129__pointer_to_member_type_infoE";
      break;
    }
  
    llvm::Constant *VTable = nullptr;
  
    // Check if the alias exists. If it doesn't, then get or create the global.
    if (CGM.getItaniumVTableContext().isRelativeLayout())
      VTable = CGM.getModule().getNamedAlias(VTableName);
    if (!VTable)
      VTable = CGM.getModule().getOrInsertGlobal(VTableName, CGM.Int8PtrTy);
  
    CGM.setDSOLocal(cast<llvm::GlobalValue>(VTable->stripPointerCasts()));
  
    llvm::Type *PtrDiffTy =
        CGM.getTypes().ConvertType(CGM.getContext().getPointerDiffType());
  
    // The vtable address point is 2.
    if (CGM.getItaniumVTableContext().isRelativeLayout()) {
      // The vtable address point is 8 bytes after its start:
      // 4 for the offset to top + 4 for the relative offset to rtti.
      llvm::Constant *Eight = llvm::ConstantInt::get(CGM.Int32Ty, 8);
      VTable = llvm::ConstantExpr::getBitCast(VTable, CGM.Int8PtrTy);
      VTable =
          llvm::ConstantExpr::getInBoundsGetElementPtr(CGM.Int8Ty, VTable, Eight);
    } else {
      llvm::Constant *Two = llvm::ConstantInt::get(PtrDiffTy, 2);
      VTable = llvm::ConstantExpr::getInBoundsGetElementPtr(CGM.Int8PtrTy, VTable,
                                                            Two);
    }
    VTable = llvm::ConstantExpr::getBitCast(VTable, CGM.Int8PtrTy);
  
    if (auto &Schema = CGM.getCodeGenOpts().PointerAuth.CXXVTablePointers)
      VTable = CGM.getConstantSignedPointer(VTable, Schema, nullptr, GlobalDecl(),
                                            QualType());
  
    Fields.push_back(VTable);
  }
  
  /// Return the linkage that the type info and type info name constants
  /// should have for the given type.
  static llvm::GlobalVariable::LinkageTypes getTypeInfoLinkage(CodeGenModule &CGM,
                                                               QualType Ty) {
    // Itanium C++ ABI 2.9.5p7:
    //   In addition, it and all of the intermediate abi::__pointer_type_info
    //   structs in the chain down to the abi::__class_type_info for the
    //   incomplete class type must be prevented from resolving to the
    //   corresponding type_info structs for the complete class type, possibly
    //   by making them local static objects. Finally, a dummy class RTTI is
    //   generated for the incomplete type that will not resolve to the final
    //   complete class RTTI (because the latter need not exist), possibly by
    //   making it a local static object.
    if (ContainsIncompleteClassType(Ty))
      return llvm::GlobalValue::InternalLinkage;
  
    switch (Ty->getLinkage()) {
    case NoLinkage:
    case InternalLinkage:
    case UniqueExternalLinkage:
      return llvm::GlobalValue::InternalLinkage;
  
    case VisibleNoLinkage:
    case ModuleInternalLinkage:
    case ModuleLinkage:
    case ExternalLinkage:
      // RTTI is not enabled, which means that this type info struct is going
      // to be used for exception handling. Give it linkonce_odr linkage.
      if (!CGM.getLangOpts().RTTI)
        return llvm::GlobalValue::LinkOnceODRLinkage;
  
      if (const RecordType *Record = dyn_cast<RecordType>(Ty)) {
        const CXXRecordDecl *RD = cast<CXXRecordDecl>(Record->getDecl());
        if (RD->hasAttr<WeakAttr>())
          return llvm::GlobalValue::WeakODRLinkage;
        if (CGM.getTriple().isWindowsItaniumEnvironment())
          if (RD->hasAttr<DLLImportAttr>() &&
              ShouldUseExternalRTTIDescriptor(CGM, Ty))
            return llvm::GlobalValue::ExternalLinkage;
        // MinGW always uses LinkOnceODRLinkage for type info.
        if (RD->isDynamicClass() &&
            !CGM.getContext()
                 .getTargetInfo()
                 .getTriple()
                 .isWindowsGNUEnvironment())
          return CGM.getVTableLinkage(RD);
      }
  
      return llvm::GlobalValue::LinkOnceODRLinkage;
    }
  
    llvm_unreachable("Invalid linkage!");
  }
  
  llvm::Constant *ItaniumRTTIBuilder::BuildTypeInfo(QualType Ty) {
    // We want to operate on the canonical type.
    Ty = Ty.getCanonicalType();
  
    // Check if we've already emitted an RTTI descriptor for this type.
    SmallString<256> Name;
    llvm::raw_svector_ostream Out(Name);
    CGM.getCXXABI().getMangleContext().mangleCXXRTTI(Ty, Out);
  
    llvm::GlobalVariable *OldGV = CGM.getModule().getNamedGlobal(Name);
    if (OldGV && !OldGV->isDeclaration()) {
      assert(!OldGV->hasAvailableExternallyLinkage() &&
             "available_externally typeinfos not yet implemented");
  
      return llvm::ConstantExpr::getBitCast(OldGV, CGM.Int8PtrTy);
    }
  
    // Check if there is already an external RTTI descriptor for this type.
    if (IsStandardLibraryRTTIDescriptor(Ty) ||
        ShouldUseExternalRTTIDescriptor(CGM, Ty))
      return GetAddrOfExternalRTTIDescriptor(Ty);
  
    // Emit the standard library with external linkage.
    llvm::GlobalVariable::LinkageTypes Linkage = getTypeInfoLinkage(CGM, Ty);
  
    // Give the type_info object and name the formal visibility of the
    // type itself.
    llvm::GlobalValue::VisibilityTypes llvmVisibility;
    if (llvm::GlobalValue::isLocalLinkage(Linkage))
      // If the linkage is local, only default visibility makes sense.
      llvmVisibility = llvm::GlobalValue::DefaultVisibility;
    else if (CXXABI.classifyRTTIUniqueness(Ty, Linkage) ==
             ItaniumCXXABI::RUK_NonUniqueHidden)
      llvmVisibility = llvm::GlobalValue::HiddenVisibility;
    else
      llvmVisibility = CodeGenModule::GetLLVMVisibility(Ty->getVisibility());
  
    llvm::GlobalValue::DLLStorageClassTypes DLLStorageClass =
        llvm::GlobalValue::DefaultStorageClass;
    if (CGM.getTriple().isWindowsItaniumEnvironment()) {
      auto RD = Ty->getAsCXXRecordDecl();
      if (RD && RD->hasAttr<DLLExportAttr>())
        DLLStorageClass = llvm::GlobalValue::DLLExportStorageClass;
    }
  
    return BuildTypeInfo(Ty, Linkage, llvmVisibility, DLLStorageClass);
  }
  
  llvm::Constant *ItaniumRTTIBuilder::BuildTypeInfo(
        QualType Ty,
        llvm::GlobalVariable::LinkageTypes Linkage,
        llvm::GlobalValue::VisibilityTypes Visibility,
        llvm::GlobalValue::DLLStorageClassTypes DLLStorageClass) {
    // Add the vtable pointer.
    BuildVTablePointer(cast<Type>(Ty));
  
    // And the name.
    llvm::GlobalVariable *TypeName = GetAddrOfTypeName(Ty, Linkage);
    llvm::Constant *TypeNameField;
  
    // If we're supposed to demote the visibility, be sure to set a flag
    // to use a string comparison for type_info comparisons.
    ItaniumCXXABI::RTTIUniquenessKind RTTIUniqueness =
        CXXABI.classifyRTTIUniqueness(Ty, Linkage);
    if (RTTIUniqueness != ItaniumCXXABI::RUK_Unique) {
      // The flag is the sign bit, which on ARM64 is defined to be clear
      // for global pointers.  This is very ARM64-specific.
      TypeNameField = llvm::ConstantExpr::getPtrToInt(TypeName, CGM.Int64Ty);
      llvm::Constant *flag =
          llvm::ConstantInt::get(CGM.Int64Ty, ((uint64_t)1) << 63);
      TypeNameField = llvm::ConstantExpr::getAdd(TypeNameField, flag);
      TypeNameField =
          llvm::ConstantExpr::getIntToPtr(TypeNameField, CGM.Int8PtrTy);
    } else {
      TypeNameField = llvm::ConstantExpr::getBitCast(TypeName, CGM.Int8PtrTy);
    }
    Fields.push_back(TypeNameField);
  
    switch (Ty->getTypeClass()) {
  #define TYPE(Class, Base)
  #define ABSTRACT_TYPE(Class, Base)
  #define NON_CANONICAL_UNLESS_DEPENDENT_TYPE(Class, Base) case Type::Class:
  #define NON_CANONICAL_TYPE(Class, Base) case Type::Class:
  #define DEPENDENT_TYPE(Class, Base) case Type::Class:
  #include "clang/AST/TypeNodes.inc"
      llvm_unreachable("Non-canonical and dependent types shouldn't get here");
  
    // GCC treats vector types as fundamental types.
    case Type::Builtin:
    case Type::Vector:
    case Type::ExtVector:
    case Type::ConstantMatrix:
    case Type::Complex:
    case Type::BlockPointer:
      // Itanium C++ ABI 2.9.5p4:
      // abi::__fundamental_type_info adds no data members to std::type_info.
      break;
  
    case Type::LValueReference:
    case Type::RValueReference:
      llvm_unreachable("References shouldn't get here");
  
    case Type::Auto:
    case Type::DeducedTemplateSpecialization:
      llvm_unreachable("Undeduced type shouldn't get here");
  
    case Type::Pipe:
      break;
  
    case Type::ExtInt:
      break;
  
    case Type::ConstantArray:
    case Type::IncompleteArray:
    case Type::VariableArray:
      // Itanium C++ ABI 2.9.5p5:
      // abi::__array_type_info adds no data members to std::type_info.
      break;
  
    case Type::FunctionNoProto:
    case Type::FunctionProto:
      // Itanium C++ ABI 2.9.5p5:
      // abi::__function_type_info adds no data members to std::type_info.
      break;
  
    case Type::Enum:
      // Itanium C++ ABI 2.9.5p5:
      // abi::__enum_type_info adds no data members to std::type_info.
      break;
  
    case Type::Record: {
      const CXXRecordDecl *RD =
        cast<CXXRecordDecl>(cast<RecordType>(Ty)->getDecl());
      if (!RD->hasDefinition() || !RD->getNumBases()) {
        // We don't need to emit any fields.
        break;
      }
  
      if (CanUseSingleInheritance(RD))
        BuildSIClassTypeInfo(RD);
      else
        BuildVMIClassTypeInfo(RD);
  
      break;
    }
  
    case Type::ObjCObject:
    case Type::ObjCInterface:
      BuildObjCObjectTypeInfo(cast<ObjCObjectType>(Ty));
      break;
  
    case Type::ObjCObjectPointer:
      BuildPointerTypeInfo(cast<ObjCObjectPointerType>(Ty)->getPointeeType());
      break;
  
    case Type::Pointer:
      BuildPointerTypeInfo(cast<PointerType>(Ty)->getPointeeType());
      break;
  
    case Type::MemberPointer:
      BuildPointerToMemberTypeInfo(cast<MemberPointerType>(Ty));
      break;
  
    case Type::Atomic:
      // No fields, at least for the moment.
      break;
    }
  
    llvm::Constant *Init = llvm::ConstantStruct::getAnon(Fields);
  
    SmallString<256> Name;
    llvm::raw_svector_ostream Out(Name);
    CGM.getCXXABI().getMangleContext().mangleCXXRTTI(Ty, Out);
    llvm::Module &M = CGM.getModule();
    llvm::GlobalVariable *OldGV = M.getNamedGlobal(Name);
    llvm::GlobalVariable *GV =
        new llvm::GlobalVariable(M, Init->getType(),
                                 /*isConstant=*/true, Linkage, Init, Name);
  
    // If there's already an old global variable, replace it with the new one.
    if (OldGV) {
      GV->takeName(OldGV);
      llvm::Constant *NewPtr =
        llvm::ConstantExpr::getBitCast(GV, OldGV->getType());
      OldGV->replaceAllUsesWith(NewPtr);
      OldGV->eraseFromParent();
    }
  
    if (CGM.supportsCOMDAT() && GV->isWeakForLinker())
      GV->setComdat(M.getOrInsertComdat(GV->getName()));
  
    CharUnits Align =
        CGM.getContext().toCharUnitsFromBits(CGM.getTarget().getPointerAlign(0));
    GV->setAlignment(Align.getAsAlign());
  
    // The Itanium ABI specifies that type_info objects must be globally
    // unique, with one exception: if the type is an incomplete class
    // type or a (possibly indirect) pointer to one.  That exception
    // affects the general case of comparing type_info objects produced
    // by the typeid operator, which is why the comparison operators on
    // std::type_info generally use the type_info name pointers instead
    // of the object addresses.  However, the language's built-in uses
    // of RTTI generally require class types to be complete, even when
    // manipulating pointers to those class types.  This allows the
    // implementation of dynamic_cast to rely on address equality tests,
    // which is much faster.
  
    // All of this is to say that it's important that both the type_info
    // object and the type_info name be uniqued when weakly emitted.
  
    TypeName->setVisibility(Visibility);
    CGM.setDSOLocal(TypeName);
  
    GV->setVisibility(Visibility);
    CGM.setDSOLocal(GV);
  
    TypeName->setDLLStorageClass(DLLStorageClass);
    GV->setDLLStorageClass(DLLStorageClass);
  
    TypeName->setPartition(CGM.getCodeGenOpts().SymbolPartition);
    GV->setPartition(CGM.getCodeGenOpts().SymbolPartition);
  
    return llvm::ConstantExpr::getBitCast(GV, CGM.Int8PtrTy);
  }
  
  /// BuildObjCObjectTypeInfo - Build the appropriate kind of type_info
  /// for the given Objective-C object type.
  void ItaniumRTTIBuilder::BuildObjCObjectTypeInfo(const ObjCObjectType *OT) {
    // Drop qualifiers.
    const Type *T = OT->getBaseType().getTypePtr();
    assert(isa<BuiltinType>(T) || isa<ObjCInterfaceType>(T));
  
    // The builtin types are abi::__class_type_infos and don't require
    // extra fields.
    if (isa<BuiltinType>(T)) return;
  
    ObjCInterfaceDecl *Class = cast<ObjCInterfaceType>(T)->getDecl();
    ObjCInterfaceDecl *Super = Class->getSuperClass();
  
    // Root classes are also __class_type_info.
    if (!Super) return;
  
    QualType SuperTy = CGM.getContext().getObjCInterfaceType(Super);
  
    // Everything else is single inheritance.
    llvm::Constant *BaseTypeInfo =
        ItaniumRTTIBuilder(CXXABI).BuildTypeInfo(SuperTy);
    Fields.push_back(BaseTypeInfo);
  }
  
  /// BuildSIClassTypeInfo - Build an abi::__si_class_type_info, used for single
  /// inheritance, according to the Itanium C++ ABI, 2.95p6b.
  void ItaniumRTTIBuilder::BuildSIClassTypeInfo(const CXXRecordDecl *RD) {
    // Itanium C++ ABI 2.9.5p6b:
    // It adds to abi::__class_type_info a single member pointing to the
    // type_info structure for the base type,
    llvm::Constant *BaseTypeInfo =
      ItaniumRTTIBuilder(CXXABI).BuildTypeInfo(RD->bases_begin()->getType());
    Fields.push_back(BaseTypeInfo);
  }
  
  namespace {
    /// SeenBases - Contains virtual and non-virtual bases seen when traversing
    /// a class hierarchy.
    struct SeenBases {
      llvm::SmallPtrSet<const CXXRecordDecl *, 16> NonVirtualBases;
      llvm::SmallPtrSet<const CXXRecordDecl *, 16> VirtualBases;
    };
  }
  
  /// ComputeVMIClassTypeInfoFlags - Compute the value of the flags member in
  /// abi::__vmi_class_type_info.
  ///
  static unsigned ComputeVMIClassTypeInfoFlags(const CXXBaseSpecifier *Base,
                                               SeenBases &Bases) {
  
    unsigned Flags = 0;
  
    auto *BaseDecl =
        cast<CXXRecordDecl>(Base->getType()->castAs<RecordType>()->getDecl());
  
    if (Base->isVirtual()) {
      // Mark the virtual base as seen.
      if (!Bases.VirtualBases.insert(BaseDecl).second) {
        // If this virtual base has been seen before, then the class is diamond
        // shaped.
        Flags |= ItaniumRTTIBuilder::VMI_DiamondShaped;
      } else {
        if (Bases.NonVirtualBases.count(BaseDecl))
          Flags |= ItaniumRTTIBuilder::VMI_NonDiamondRepeat;
      }
    } else {
      // Mark the non-virtual base as seen.
      if (!Bases.NonVirtualBases.insert(BaseDecl).second) {
        // If this non-virtual base has been seen before, then the class has non-
        // diamond shaped repeated inheritance.
        Flags |= ItaniumRTTIBuilder::VMI_NonDiamondRepeat;
      } else {
        if (Bases.VirtualBases.count(BaseDecl))
          Flags |= ItaniumRTTIBuilder::VMI_NonDiamondRepeat;
      }
    }
  
    // Walk all bases.
    for (const auto &I : BaseDecl->bases())
      Flags |= ComputeVMIClassTypeInfoFlags(&I, Bases);
  
    return Flags;
  }
  
  static unsigned ComputeVMIClassTypeInfoFlags(const CXXRecordDecl *RD) {
    unsigned Flags = 0;
    SeenBases Bases;
  
    // Walk all bases.
    for (const auto &I : RD->bases())
      Flags |= ComputeVMIClassTypeInfoFlags(&I, Bases);
  
    return Flags;
  }
  
  /// BuildVMIClassTypeInfo - Build an abi::__vmi_class_type_info, used for
  /// classes with bases that do not satisfy the abi::__si_class_type_info
  /// constraints, according ti the Itanium C++ ABI, 2.9.5p5c.
  void ItaniumRTTIBuilder::BuildVMIClassTypeInfo(const CXXRecordDecl *RD) {
    llvm::Type *UnsignedIntLTy =
      CGM.getTypes().ConvertType(CGM.getContext().UnsignedIntTy);
  
    // Itanium C++ ABI 2.9.5p6c:
    //   __flags is a word with flags describing details about the class
    //   structure, which may be referenced by using the __flags_masks
    //   enumeration. These flags refer to both direct and indirect bases.
    unsigned Flags = ComputeVMIClassTypeInfoFlags(RD);
    Fields.push_back(llvm::ConstantInt::get(UnsignedIntLTy, Flags));
  
    // Itanium C++ ABI 2.9.5p6c:
    //   __base_count is a word with the number of direct proper base class
    //   descriptions that follow.
    Fields.push_back(llvm::ConstantInt::get(UnsignedIntLTy, RD->getNumBases()));
  
    if (!RD->getNumBases())
      return;
  
    // Now add the base class descriptions.
  
    // Itanium C++ ABI 2.9.5p6c:
    //   __base_info[] is an array of base class descriptions -- one for every
    //   direct proper base. Each description is of the type:
    //
    //   struct abi::__base_class_type_info {
    //   public:
    //     const __class_type_info *__base_type;
    //     long __offset_flags;
    //
    //     enum __offset_flags_masks {
    //       __virtual_mask = 0x1,
    //       __public_mask = 0x2,
    //       __offset_shift = 8
    //     };
    //   };
  
    // If we're in mingw and 'long' isn't wide enough for a pointer, use 'long
    // long' instead of 'long' for __offset_flags. libstdc++abi uses long long on
    // LLP64 platforms.
    // FIXME: Consider updating libc++abi to match, and extend this logic to all
    // LLP64 platforms.
    QualType OffsetFlagsTy = CGM.getContext().LongTy;
    const TargetInfo &TI = CGM.getContext().getTargetInfo();
    if (TI.getTriple().isOSCygMing() && TI.getPointerWidth(0) > TI.getLongWidth())
      OffsetFlagsTy = CGM.getContext().LongLongTy;
    llvm::Type *OffsetFlagsLTy =
        CGM.getTypes().ConvertType(OffsetFlagsTy);
  
    for (const auto &Base : RD->bases()) {
      // The __base_type member points to the RTTI for the base type.
      Fields.push_back(ItaniumRTTIBuilder(CXXABI).BuildTypeInfo(Base.getType()));
  
      auto *BaseDecl =
          cast<CXXRecordDecl>(Base.getType()->castAs<RecordType>()->getDecl());
  
      int64_t OffsetFlags = 0;
  
      // All but the lower 8 bits of __offset_flags are a signed offset.
      // For a non-virtual base, this is the offset in the object of the base
      // subobject. For a virtual base, this is the offset in the virtual table of
      // the virtual base offset for the virtual base referenced (negative).
      CharUnits Offset;
      if (Base.isVirtual())
        Offset =
          CGM.getItaniumVTableContext().getVirtualBaseOffsetOffset(RD, BaseDecl);
      else {
        const ASTRecordLayout &Layout = CGM.getContext().getASTRecordLayout(RD);
        Offset = Layout.getBaseClassOffset(BaseDecl);
      };
  
      OffsetFlags = uint64_t(Offset.getQuantity()) << 8;
  
      // The low-order byte of __offset_flags contains flags, as given by the
      // masks from the enumeration __offset_flags_masks.
      if (Base.isVirtual())
        OffsetFlags |= BCTI_Virtual;
      if (Base.getAccessSpecifier() == AS_public)
        OffsetFlags |= BCTI_Public;
  
      Fields.push_back(llvm::ConstantInt::get(OffsetFlagsLTy, OffsetFlags));
    }
  }
  
  /// Compute the flags for a __pbase_type_info, and remove the corresponding
  /// pieces from \p Type.
  static unsigned extractPBaseFlags(ASTContext &Ctx, QualType &Type) {
    unsigned Flags = 0;
  
    if (Type.isConstQualified())
      Flags |= ItaniumRTTIBuilder::PTI_Const;
    if (Type.isVolatileQualified())
      Flags |= ItaniumRTTIBuilder::PTI_Volatile;
    if (Type.isRestrictQualified())
      Flags |= ItaniumRTTIBuilder::PTI_Restrict;
    Type = Type.getUnqualifiedType();
  
    // Itanium C++ ABI 2.9.5p7:
    //   When the abi::__pbase_type_info is for a direct or indirect pointer to an
    //   incomplete class type, the incomplete target type flag is set.
    if (ContainsIncompleteClassType(Type))
      Flags |= ItaniumRTTIBuilder::PTI_Incomplete;
  
    if (auto *Proto = Type->getAs<FunctionProtoType>()) {
      if (Proto->isNothrow()) {
        Flags |= ItaniumRTTIBuilder::PTI_Noexcept;
        Type = Ctx.getFunctionTypeWithExceptionSpec(Type, EST_None);
      }
    }
  
    return Flags;
  }
  
  /// BuildPointerTypeInfo - Build an abi::__pointer_type_info struct,
  /// used for pointer types.
  void ItaniumRTTIBuilder::BuildPointerTypeInfo(QualType PointeeTy) {
    // Itanium C++ ABI 2.9.5p7:
    //   __flags is a flag word describing the cv-qualification and other
    //   attributes of the type pointed to
    unsigned Flags = extractPBaseFlags(CGM.getContext(), PointeeTy);
  
    llvm::Type *UnsignedIntLTy =
      CGM.getTypes().ConvertType(CGM.getContext().UnsignedIntTy);
    Fields.push_back(llvm::ConstantInt::get(UnsignedIntLTy, Flags));
  
    // Itanium C++ ABI 2.9.5p7:
    //  __pointee is a pointer to the std::type_info derivation for the
    //  unqualified type being pointed to.
    llvm::Constant *PointeeTypeInfo =
        ItaniumRTTIBuilder(CXXABI).BuildTypeInfo(PointeeTy);
    Fields.push_back(PointeeTypeInfo);
  }
  
  /// BuildPointerToMemberTypeInfo - Build an abi::__pointer_to_member_type_info
  /// struct, used for member pointer types.
  void
  ItaniumRTTIBuilder::BuildPointerToMemberTypeInfo(const MemberPointerType *Ty) {
    QualType PointeeTy = Ty->getPointeeType();
  
    // Itanium C++ ABI 2.9.5p7:
    //   __flags is a flag word describing the cv-qualification and other
    //   attributes of the type pointed to.
    unsigned Flags = extractPBaseFlags(CGM.getContext(), PointeeTy);
  
    const RecordType *ClassType = cast<RecordType>(Ty->getClass());
    if (IsIncompleteClassType(ClassType))
      Flags |= PTI_ContainingClassIncomplete;
  
    llvm::Type *UnsignedIntLTy =
      CGM.getTypes().ConvertType(CGM.getContext().UnsignedIntTy);
    Fields.push_back(llvm::ConstantInt::get(UnsignedIntLTy, Flags));
  
    // Itanium C++ ABI 2.9.5p7:
    //   __pointee is a pointer to the std::type_info derivation for the
    //   unqualified type being pointed to.
    llvm::Constant *PointeeTypeInfo =
        ItaniumRTTIBuilder(CXXABI).BuildTypeInfo(PointeeTy);
    Fields.push_back(PointeeTypeInfo);
  
    // Itanium C++ ABI 2.9.5p9:
    //   __context is a pointer to an abi::__class_type_info corresponding to the
    //   class type containing the member pointed to
    //   (e.g., the "A" in "int A::*").
    Fields.push_back(
        ItaniumRTTIBuilder(CXXABI).BuildTypeInfo(QualType(ClassType, 0)));
  }
  
  llvm::Constant *ItaniumCXXABI::getAddrOfRTTIDescriptor(QualType Ty) {
    return ItaniumRTTIBuilder(*this).BuildTypeInfo(Ty);
  }
  
  void ItaniumCXXABI::EmitFundamentalRTTIDescriptors(const CXXRecordDecl *RD) {
    // Types added here must also be added to TypeInfoIsInStandardLibrary.
    QualType FundamentalTypes[] = {
        getContext().VoidTy,             getContext().NullPtrTy,
        getContext().BoolTy,             getContext().WCharTy,
        getContext().CharTy,             getContext().UnsignedCharTy,
        getContext().SignedCharTy,       getContext().ShortTy,
        getContext().UnsignedShortTy,    getContext().IntTy,
        getContext().UnsignedIntTy,      getContext().LongTy,
        getContext().UnsignedLongTy,     getContext().LongLongTy,
        getContext().UnsignedLongLongTy, getContext().Int128Ty,
        getContext().UnsignedInt128Ty,   getContext().HalfTy,
        getContext().FloatTy,            getContext().DoubleTy,
        getContext().LongDoubleTy,       getContext().Float128Ty,
        getContext().Char8Ty,            getContext().Char16Ty,
        getContext().Char32Ty
    };
    llvm::GlobalValue::DLLStorageClassTypes DLLStorageClass =
        RD->hasAttr<DLLExportAttr>()
        ? llvm::GlobalValue::DLLExportStorageClass
        : llvm::GlobalValue::DefaultStorageClass;
    llvm::GlobalValue::VisibilityTypes Visibility =
        CodeGenModule::GetLLVMVisibility(RD->getVisibility());
    for (const QualType &FundamentalType : FundamentalTypes) {
      QualType PointerType = getContext().getPointerType(FundamentalType);
      QualType PointerTypeConst = getContext().getPointerType(
          FundamentalType.withConst());
      for (QualType Type : {FundamentalType, PointerType, PointerTypeConst})
        ItaniumRTTIBuilder(*this).BuildTypeInfo(
            Type, llvm::GlobalValue::ExternalLinkage,
            Visibility, DLLStorageClass);
    }
  }
  
  /// What sort of uniqueness rules should we use for the RTTI for the
  /// given type?
  ItaniumCXXABI::RTTIUniquenessKind ItaniumCXXABI::classifyRTTIUniqueness(
      QualType CanTy, llvm::GlobalValue::LinkageTypes Linkage) const {
    if (shouldRTTIBeUnique())
      return RUK_Unique;
  
    // It's only necessary for linkonce_odr or weak_odr linkage.
    if (Linkage != llvm::GlobalValue::LinkOnceODRLinkage &&
        Linkage != llvm::GlobalValue::WeakODRLinkage)
      return RUK_Unique;
  
    // It's only necessary with default visibility.
    if (CanTy->getVisibility() != DefaultVisibility)
      return RUK_Unique;
  
    // If we're not required to publish this symbol, hide it.
    if (Linkage == llvm::GlobalValue::LinkOnceODRLinkage)
      return RUK_NonUniqueHidden;
  
    // If we're required to publish this symbol, as we might be under an
    // explicit instantiation, leave it with default visibility but
    // enable string-comparisons.
    assert(Linkage == llvm::GlobalValue::WeakODRLinkage);
    return RUK_NonUniqueVisible;
  }
  
  // Find out how to codegen the complete destructor and constructor
  namespace {
  enum class StructorCodegen { Emit, RAUW, Alias, COMDAT };
  }
  static StructorCodegen getCodegenToUse(CodeGenModule &CGM,
                                         const CXXMethodDecl *MD) {
    if (!CGM.getCodeGenOpts().CXXCtorDtorAliases)
      return StructorCodegen::Emit;
  
    // The complete and base structors are not equivalent if there are any virtual
    // bases, so emit separate functions.
    if (MD->getParent()->getNumVBases())
      return StructorCodegen::Emit;
  
    GlobalDecl AliasDecl;
    if (const auto *DD = dyn_cast<CXXDestructorDecl>(MD)) {
      AliasDecl = GlobalDecl(DD, Dtor_Complete);
    } else {
      const auto *CD = cast<CXXConstructorDecl>(MD);
      AliasDecl = GlobalDecl(CD, Ctor_Complete);
    }
    llvm::GlobalValue::LinkageTypes Linkage = CGM.getFunctionLinkage(AliasDecl);
  
    if (llvm::GlobalValue::isDiscardableIfUnused(Linkage))
      return StructorCodegen::RAUW;
  
    // FIXME: Should we allow available_externally aliases?
    if (!llvm::GlobalAlias::isValidLinkage(Linkage))
      return StructorCodegen::RAUW;
  
    if (llvm::GlobalValue::isWeakForLinker(Linkage)) {
      // Only ELF and wasm support COMDATs with arbitrary names (C5/D5).
      if (CGM.getTarget().getTriple().isOSBinFormatELF() ||
          CGM.getTarget().getTriple().isOSBinFormatWasm())
        return StructorCodegen::COMDAT;
      return StructorCodegen::Emit;
    }
  
    return StructorCodegen::Alias;
  }
  
  static void emitConstructorDestructorAlias(CodeGenModule &CGM,
                                             GlobalDecl AliasDecl,
                                             GlobalDecl TargetDecl) {
    llvm::GlobalValue::LinkageTypes Linkage = CGM.getFunctionLinkage(AliasDecl);
  
    StringRef MangledName = CGM.getMangledName(AliasDecl);
    llvm::GlobalValue *Entry = CGM.GetGlobalValue(MangledName);
    if (Entry && !Entry->isDeclaration())
      return;
  
    auto *Aliasee = cast<llvm::GlobalValue>(CGM.GetAddrOfGlobal(TargetDecl));
  
    // Create the alias with no name.
    auto *Alias = llvm::GlobalAlias::create(Linkage, "", Aliasee);
  
    // Constructors and destructors are always unnamed_addr.
    Alias->setUnnamedAddr(llvm::GlobalValue::UnnamedAddr::Global);
  
    // Switch any previous uses to the alias.
    if (Entry) {
      assert(Entry->getType() == Aliasee->getType() &&
             "declaration exists with different type");
      Alias->takeName(Entry);
      Entry->replaceAllUsesWith(Alias);
      Entry->eraseFromParent();
    } else {
      Alias->setName(MangledName);
    }
  
    // Finally, set up the alias with its proper name and attributes.
    CGM.SetCommonAttributes(AliasDecl, Alias);
  }
  
  void ItaniumCXXABI::emitCXXStructor(GlobalDecl GD) {
    auto *MD = cast<CXXMethodDecl>(GD.getDecl());
    auto *CD = dyn_cast<CXXConstructorDecl>(MD);
    const CXXDestructorDecl *DD = CD ? nullptr : cast<CXXDestructorDecl>(MD);
  
    StructorCodegen CGType = getCodegenToUse(CGM, MD);
  
    if (CD ? GD.getCtorType() == Ctor_Complete
           : GD.getDtorType() == Dtor_Complete) {
      GlobalDecl BaseDecl;
      if (CD)
        BaseDecl = GD.getWithCtorType(Ctor_Base);
      else
        BaseDecl = GD.getWithDtorType(Dtor_Base);
  
      if (CGType == StructorCodegen::Alias || CGType == StructorCodegen::COMDAT) {
        emitConstructorDestructorAlias(CGM, GD, BaseDecl);
        return;
      }
  
      if (CGType == StructorCodegen::RAUW) {
        StringRef MangledName = CGM.getMangledName(GD);
        auto *Aliasee = CGM.GetAddrOfGlobal(BaseDecl);
        CGM.addReplacement(MangledName, Aliasee);
        return;
      }
    }
  
    // The base destructor is equivalent to the base destructor of its
    // base class if there is exactly one non-virtual base class with a
    // non-trivial destructor, there are no fields with a non-trivial
    // destructor, and the body of the destructor is trivial.
    if (DD && GD.getDtorType() == Dtor_Base &&
        CGType != StructorCodegen::COMDAT &&
        !CGM.TryEmitBaseDestructorAsAlias(DD))
      return;
  
    // FIXME: The deleting destructor is equivalent to the selected operator
    // delete if:
    //  * either the delete is a destroying operator delete or the destructor
    //    would be trivial if it weren't virtual,
    //  * the conversion from the 'this' parameter to the first parameter of the
    //    destructor is equivalent to a bitcast,
    //  * the destructor does not have an implicit "this" return, and
    //  * the operator delete has the same calling convention and IR function type
    //    as the destructor.
    // In such cases we should try to emit the deleting dtor as an alias to the
    // selected 'operator delete'.
  
    llvm::Function *Fn = CGM.codegenCXXStructor(GD);
  
    if (CGType == StructorCodegen::COMDAT) {
      SmallString<256> Buffer;
      llvm::raw_svector_ostream Out(Buffer);
      if (DD)
        getMangleContext().mangleCXXDtorComdat(DD, Out);
      else
        getMangleContext().mangleCXXCtorComdat(CD, Out);
      llvm::Comdat *C = CGM.getModule().getOrInsertComdat(Out.str());
      Fn->setComdat(C);
    } else {
      CGM.maybeSetTrivialComdat(*MD, *Fn);
    }
  }
  
  static llvm::FunctionCallee getBeginCatchFn(CodeGenModule &CGM) {
    // void *__cxa_begin_catch(void*);
    llvm::FunctionType *FTy = llvm::FunctionType::get(
        CGM.Int8PtrTy, CGM.Int8PtrTy, /*isVarArg=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_begin_catch");
  }
  
  static llvm::FunctionCallee getEndCatchFn(CodeGenModule &CGM) {
    // void __cxa_end_catch();
    llvm::FunctionType *FTy =
        llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_end_catch");
  }
  
  static llvm::FunctionCallee getGetExceptionPtrFn(CodeGenModule &CGM) {
    // void *__cxa_get_exception_ptr(void*);
    llvm::FunctionType *FTy = llvm::FunctionType::get(
        CGM.Int8PtrTy, CGM.Int8PtrTy, /*isVarArg=*/false);
  
    return CGM.CreateRuntimeFunction(FTy, "__cxa_get_exception_ptr");
  }
  
  namespace {
    /// A cleanup to call __cxa_end_catch.  In many cases, the caught
    /// exception type lets us state definitively that the thrown exception
    /// type does not have a destructor.  In particular:
    ///   - Catch-alls tell us nothing, so we have to conservatively
    ///     assume that the thrown exception might have a destructor.
    ///   - Catches by reference behave according to their base types.
    ///   - Catches of non-record types will only trigger for exceptions
    ///     of non-record types, which never have destructors.
    ///   - Catches of record types can trigger for arbitrary subclasses
    ///     of the caught type, so we have to assume the actual thrown
    ///     exception type might have a throwing destructor, even if the
    ///     caught type's destructor is trivial or nothrow.
    struct CallEndCatch final : EHScopeStack::Cleanup {
      CallEndCatch(bool MightThrow) : MightThrow(MightThrow) {}
      bool MightThrow;
  
      void Emit(CodeGenFunction &CGF, Flags flags) override {
        if (!MightThrow) {
          CGF.EmitNounwindRuntimeCall(getEndCatchFn(CGF.CGM));
          return;
        }
  
        CGF.EmitRuntimeCallOrInvoke(getEndCatchFn(CGF.CGM));
      }
    };
  }
  
  /// Emits a call to __cxa_begin_catch and enters a cleanup to call
  /// __cxa_end_catch.
  ///
  /// \param EndMightThrow - true if __cxa_end_catch might throw
  static llvm::Value *CallBeginCatch(CodeGenFunction &CGF,
                                     llvm::Value *Exn,
                                     bool EndMightThrow) {
    llvm::CallInst *call =
      CGF.EmitNounwindRuntimeCall(getBeginCatchFn(CGF.CGM), Exn);
  
    CGF.EHStack.pushCleanup<CallEndCatch>(NormalAndEHCleanup, EndMightThrow);
  
    return call;
  }
  
  /// A "special initializer" callback for initializing a catch
  /// parameter during catch initialization.
  static void InitCatchParam(CodeGenFunction &CGF,
                             const VarDecl &CatchParam,
                             Address ParamAddr,
                             SourceLocation Loc) {
    // Load the exception from where the landing pad saved it.
    llvm::Value *Exn = CGF.getExceptionFromSlot();
  
    CanQualType CatchType =
      CGF.CGM.getContext().getCanonicalType(CatchParam.getType());
    llvm::Type *LLVMCatchTy = CGF.ConvertTypeForMem(CatchType);
  
    // If we're catching by reference, we can just cast the object
    // pointer to the appropriate pointer.
    if (isa<ReferenceType>(CatchType)) {
      QualType CaughtType = cast<ReferenceType>(CatchType)->getPointeeType();
      bool EndCatchMightThrow = CaughtType->isRecordType();
  
      // __cxa_begin_catch returns the adjusted object pointer.
      llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, EndCatchMightThrow);
  
      // We have no way to tell the personality function that we're
      // catching by reference, so if we're catching a pointer,
      // __cxa_begin_catch will actually return that pointer by value.
      if (const PointerType *PT = dyn_cast<PointerType>(CaughtType)) {
        QualType PointeeType = PT->getPointeeType();
  
        // When catching by reference, generally we should just ignore
        // this by-value pointer and use the exception object instead.
        if (!PointeeType->isRecordType()) {
  
          // Exn points to the struct _Unwind_Exception header, which
          // we have to skip past in order to reach the exception data.
          unsigned HeaderSize =
            CGF.CGM.getTargetCodeGenInfo().getSizeOfUnwindException();
          AdjustedExn = CGF.Builder.CreateConstGEP1_32(Exn, HeaderSize);
  
        // However, if we're catching a pointer-to-record type that won't
        // work, because the personality function might have adjusted
        // the pointer.  There's actually no way for us to fully satisfy
        // the language/ABI contract here:  we can't use Exn because it
        // might have the wrong adjustment, but we can't use the by-value
        // pointer because it's off by a level of abstraction.
        //
        // The current solution is to dump the adjusted pointer into an
        // alloca, which breaks language semantics (because changing the
        // pointer doesn't change the exception) but at least works.
        // The better solution would be to filter out non-exact matches
        // and rethrow them, but this is tricky because the rethrow
        // really needs to be catchable by other sites at this landing
        // pad.  The best solution is to fix the personality function.
        } else {
          // Pull the pointer for the reference type off.
          llvm::Type *PtrTy =
            cast<llvm::PointerType>(LLVMCatchTy)->getElementType();
  
          // Create the temporary and write the adjusted pointer into it.
          Address ExnPtrTmp =
            CGF.CreateTempAlloca(PtrTy, CGF.getPointerAlign(), "exn.byref.tmp");
          llvm::Value *Casted = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
          CGF.Builder.CreateStore(Casted, ExnPtrTmp);
  
          // Bind the reference to the temporary.
          AdjustedExn = ExnPtrTmp.getPointer();
        }
      }
  
      llvm::Value *ExnCast =
        CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.byref");
      CGF.Builder.CreateStore(ExnCast, ParamAddr);
      return;
    }
  
    // Scalars and complexes.
    TypeEvaluationKind TEK = CGF.getEvaluationKind(CatchType);
    if (TEK != TEK_Aggregate) {
      llvm::Value *AdjustedExn = CallBeginCatch(CGF, Exn, false);
  
      // If the catch type is a pointer type, __cxa_begin_catch returns
      // the pointer by value.
      if (CatchType->hasPointerRepresentation()) {
        llvm::Value *CastExn =
          CGF.Builder.CreateBitCast(AdjustedExn, LLVMCatchTy, "exn.casted");
  
        switch (CatchType.getQualifiers().getObjCLifetime()) {
        case Qualifiers::OCL_Strong:
          CastExn = CGF.EmitARCRetainNonBlock(CastExn);
          LLVM_FALLTHROUGH;
  
        case Qualifiers::OCL_None:
        case Qualifiers::OCL_ExplicitNone:
        case Qualifiers::OCL_Autoreleasing:
          CGF.Builder.CreateStore(CastExn, ParamAddr);
          return;
  
        case Qualifiers::OCL_Weak:
          CGF.EmitARCInitWeak(ParamAddr, CastExn);
          return;
        }
        llvm_unreachable("bad ownership qualifier!");
      }
  
      // Otherwise, it returns a pointer into the exception object.
  
      llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
      llvm::Value *Cast = CGF.Builder.CreateBitCast(AdjustedExn, PtrTy);
  
      LValue srcLV = CGF.MakeNaturalAlignAddrLValue(Cast, CatchType);
      LValue destLV = CGF.MakeAddrLValue(ParamAddr, CatchType);
      switch (TEK) {
      case TEK_Complex:
        CGF.EmitStoreOfComplex(CGF.EmitLoadOfComplex(srcLV, Loc), destLV,
                               /*init*/ true);
        return;
      case TEK_Scalar: {
        llvm::Value *ExnLoad = CGF.EmitLoadOfScalar(srcLV, Loc);
        CGF.EmitStoreOfScalar(ExnLoad, destLV, /*init*/ true);
        return;
      }
      case TEK_Aggregate:
        llvm_unreachable("evaluation kind filtered out!");
      }
      llvm_unreachable("bad evaluation kind");
    }
  
    assert(isa<RecordType>(CatchType) && "unexpected catch type!");
    auto catchRD = CatchType->getAsCXXRecordDecl();
    CharUnits caughtExnAlignment = CGF.CGM.getClassPointerAlignment(catchRD);
  
    llvm::Type *PtrTy = LLVMCatchTy->getPointerTo(0); // addrspace 0 ok
  
    // Check for a copy expression.  If we don't have a copy expression,
    // that means a trivial copy is okay.
    const Expr *copyExpr = CatchParam.getInit();
    if (!copyExpr) {
      llvm::Value *rawAdjustedExn = CallBeginCatch(CGF, Exn, true);
      Address adjustedExn(CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy),
                          caughtExnAlignment);
      LValue Dest = CGF.MakeAddrLValue(ParamAddr, CatchType);
      LValue Src = CGF.MakeAddrLValue(adjustedExn, CatchType);
      CGF.EmitAggregateCopy(Dest, Src, CatchType, AggValueSlot::DoesNotOverlap);
      return;
    }
  
    // We have to call __cxa_get_exception_ptr to get the adjusted
    // pointer before copying.
    llvm::CallInst *rawAdjustedExn =
      CGF.EmitNounwindRuntimeCall(getGetExceptionPtrFn(CGF.CGM), Exn);
  
    // Cast that to the appropriate type.
    Address adjustedExn(CGF.Builder.CreateBitCast(rawAdjustedExn, PtrTy),
                        caughtExnAlignment);
  
    // The copy expression is defined in terms of an OpaqueValueExpr.
    // Find it and map it to the adjusted expression.
    CodeGenFunction::OpaqueValueMapping
      opaque(CGF, OpaqueValueExpr::findInCopyConstruct(copyExpr),
             CGF.MakeAddrLValue(adjustedExn, CatchParam.getType()));
  
    // Call the copy ctor in a terminate scope.
    CGF.EHStack.pushTerminate();
  
    // Perform the copy construction.
    CGF.EmitAggExpr(copyExpr,
                    AggValueSlot::forAddr(ParamAddr, Qualifiers(),
                                          AggValueSlot::IsNotDestructed,
                                          AggValueSlot::DoesNotNeedGCBarriers,
                                          AggValueSlot::IsNotAliased,
                                          AggValueSlot::DoesNotOverlap));
  
    // Leave the terminate scope.
    CGF.EHStack.popTerminate();
  
    // Undo the opaque value mapping.
    opaque.pop();
  
    // Finally we can call __cxa_begin_catch.
    CallBeginCatch(CGF, Exn, true);
  }
  
  /// Begins a catch statement by initializing the catch variable and
  /// calling __cxa_begin_catch.
  void ItaniumCXXABI::emitBeginCatch(CodeGenFunction &CGF,
                                     const CXXCatchStmt *S) {
    // We have to be very careful with the ordering of cleanups here:
    //   C++ [except.throw]p4:
    //     The destruction [of the exception temporary] occurs
    //     immediately after the destruction of the object declared in
    //     the exception-declaration in the handler.
    //
    // So the precise ordering is:
    //   1.  Construct catch variable.
    //   2.  __cxa_begin_catch
    //   3.  Enter __cxa_end_catch cleanup
    //   4.  Enter dtor cleanup
    //
    // We do this by using a slightly abnormal initialization process.
    // Delegation sequence:
    //   - ExitCXXTryStmt opens a RunCleanupsScope
    //     - EmitAutoVarAlloca creates the variable and debug info
    //       - InitCatchParam initializes the variable from the exception
    //       - CallBeginCatch calls __cxa_begin_catch
    //       - CallBeginCatch enters the __cxa_end_catch cleanup
    //     - EmitAutoVarCleanups enters the variable destructor cleanup
    //   - EmitCXXTryStmt emits the code for the catch body
    //   - EmitCXXTryStmt close the RunCleanupsScope
  
    VarDecl *CatchParam = S->getExceptionDecl();
    if (!CatchParam) {
      llvm::Value *Exn = CGF.getExceptionFromSlot();
      CallBeginCatch(CGF, Exn, true);
      return;
    }
  
    // Emit the local.
    CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam);
    InitCatchParam(CGF, *CatchParam, var.getObjectAddress(CGF), S->getBeginLoc());
    CGF.EmitAutoVarCleanups(var);
  }
  
  /// Get or define the following function:
  ///   void @__clang_call_terminate(i8* %exn) nounwind noreturn
  /// This code is used only in C++.
  static llvm::FunctionCallee getClangCallTerminateFn(CodeGenModule &CGM) {
    llvm::FunctionType *fnTy =
      llvm::FunctionType::get(CGM.VoidTy, CGM.Int8PtrTy, /*isVarArg=*/false);
    llvm::FunctionCallee fnRef = CGM.CreateRuntimeFunction(
        fnTy, "__clang_call_terminate", llvm::AttributeList(), /*Local=*/true);
    llvm::Function *fn =
        cast<llvm::Function>(fnRef.getCallee()->stripPointerCasts());
    if (fn->empty()) {
      fn->setDoesNotThrow();
      fn->setDoesNotReturn();
  
      // What we really want is to massively penalize inlining without
      // forbidding it completely.  The difference between that and
      // 'noinline' is negligible.
      fn->addFnAttr(llvm::Attribute::NoInline);
  
      // Allow this function to be shared across translation units, but
      // we don't want it to turn into an exported symbol.
      fn->setLinkage(llvm::Function::LinkOnceODRLinkage);
      fn->setVisibility(llvm::Function::HiddenVisibility);
      if (CGM.supportsCOMDAT())
        fn->setComdat(CGM.getModule().getOrInsertComdat(fn->getName()));
  
      // Set up the function.
      llvm::BasicBlock *entry =
          llvm::BasicBlock::Create(CGM.getLLVMContext(), "", fn);
      CGBuilderTy builder(CGM, entry);
  
      // Pull the exception pointer out of the parameter list.
      llvm::Value *exn = &*fn->arg_begin();
  
      // Call __cxa_begin_catch(exn).
      llvm::CallInst *catchCall = builder.CreateCall(getBeginCatchFn(CGM), exn);
      catchCall->setDoesNotThrow();
      catchCall->setCallingConv(CGM.getRuntimeCC());
  
      // Call std::terminate().
      llvm::CallInst *termCall = builder.CreateCall(CGM.getTerminateFn());
      termCall->setDoesNotThrow();
      termCall->setDoesNotReturn();
      termCall->setCallingConv(CGM.getRuntimeCC());
  
      // std::terminate cannot return.
      builder.CreateUnreachable();
    }
    return fnRef;
  }
  
  llvm::CallInst *
  ItaniumCXXABI::emitTerminateForUnexpectedException(CodeGenFunction &CGF,
                                                     llvm::Value *Exn) {
    // In C++, we want to call __cxa_begin_catch() before terminating.
    if (Exn) {
      assert(CGF.CGM.getLangOpts().CPlusPlus);
      return CGF.EmitNounwindRuntimeCall(getClangCallTerminateFn(CGF.CGM), Exn);
    }
    return CGF.EmitNounwindRuntimeCall(CGF.CGM.getTerminateFn());
  }
  
  std::pair<llvm::Value *, const CXXRecordDecl *>
  ItaniumCXXABI::LoadVTablePtr(CodeGenFunction &CGF, Address This,
                               const CXXRecordDecl *RD) {
    return {CGF.GetVTablePtr(This, CGM.Int8PtrTy, RD), RD};
  }
  
  llvm::Constant *
  ItaniumCXXABI::getSignedVirtualMemberFunctionPointer(const CXXMethodDecl *MD) {
    const CXXMethodDecl *origMD =
        cast<CXXMethodDecl>(CGM.getItaniumVTableContext()
                                .findOriginalMethod(MD->getCanonicalDecl())
                                .getDecl());
    llvm::Constant *thunk = getOrCreateVirtualFunctionPointerThunk(origMD);
    QualType funcType = CGM.getContext().getMemberPointerType(
        MD->getType(), MD->getParent()->getTypeForDecl());
    return CGM.getMemberFunctionPointer(thunk, funcType, MD);
  }
  
  void WebAssemblyCXXABI::emitBeginCatch(CodeGenFunction &CGF,
                                         const CXXCatchStmt *C) {
    if (CGF.getTarget().hasFeature("exception-handling"))
      CGF.EHStack.pushCleanup<CatchRetScope>(
          NormalCleanup, cast<llvm::CatchPadInst>(CGF.CurrentFuncletPad));
    ItaniumCXXABI::emitBeginCatch(CGF, C);
  }
  
  /// Register a global destructor as best as we know how.
  void XLCXXABI::registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                                    llvm::FunctionCallee dtor,
                                    llvm::Constant *addr) {
    if (D.getTLSKind() != VarDecl::TLS_None)
      llvm::report_fatal_error("thread local storage not yet implemented on AIX");
  
    // Create __dtor function for the var decl.
    llvm::Function *dtorStub =
        cast<llvm::Function>(CGF.createAtExitStub(D, dtor, addr));
  
    // Register above __dtor with atexit().
    CGF.registerGlobalDtorWithAtExit(dtorStub);
  
    // Emit __finalize function to unregister __dtor and (as appropriate) call
    // __dtor.
    emitCXXStermFinalizer(D, dtorStub, addr);
  }
  
  void XLCXXABI::emitCXXStermFinalizer(const VarDecl &D, llvm::Function *dtorStub,
                                       llvm::Constant *addr) {
    llvm::FunctionType *FTy = llvm::FunctionType::get(CGM.VoidTy, false);
    SmallString<256> FnName;
    {
      llvm::raw_svector_ostream Out(FnName);
      getMangleContext().mangleDynamicStermFinalizer(&D, Out);
    }
  
    // Create the finalization action associated with a variable.
    const CGFunctionInfo &FI = CGM.getTypes().arrangeNullaryFunction();
    llvm::Function *StermFinalizer = CGM.CreateGlobalInitOrCleanUpFunction(
        FTy, FnName.str(), FI, D.getLocation());
  
    CodeGenFunction CGF(CGM);
  
    CGF.StartFunction(GlobalDecl(), CGM.getContext().VoidTy, StermFinalizer, FI,
                      FunctionArgList(), D.getLocation(),
                      D.getInit()->getExprLoc());
  
    // The unatexit subroutine unregisters __dtor functions that were previously
    // registered by the atexit subroutine. If the referenced function is found,
    // the unatexit returns a value of 0, meaning that the cleanup is still
    // pending (and we should call the __dtor function).
    llvm::Value *V = CGF.unregisterGlobalDtorWithUnAtExit(dtorStub);
  
    llvm::Value *NeedsDestruct = CGF.Builder.CreateIsNull(V, "needs_destruct");
  
    llvm::BasicBlock *DestructCallBlock = CGF.createBasicBlock("destruct.call");
    llvm::BasicBlock *EndBlock = CGF.createBasicBlock("destruct.end");
  
    // Check if unatexit returns a value of 0. If it does, jump to
    // DestructCallBlock, otherwise jump to EndBlock directly.
    CGF.Builder.CreateCondBr(NeedsDestruct, DestructCallBlock, EndBlock);
  
    CGF.EmitBlock(DestructCallBlock);
  
    // Emit the call to dtorStub.
    llvm::CallInst *CI = CGF.Builder.CreateCall(dtorStub);
  
    // Make sure the call and the callee agree on calling convention.
    CI->setCallingConv(dtorStub->getCallingConv());
  
    CGF.EmitBlock(EndBlock);
  
    CGF.FinishFunction();
  
    assert(!D.getAttr<InitPriorityAttr>() &&
           "Prioritized sinit and sterm functions are not yet supported.");
  
    if (isTemplateInstantiation(D.getTemplateSpecializationKind()) ||
        getContext().GetGVALinkageForVariable(&D) == GVA_DiscardableODR)
      // According to C++ [basic.start.init]p2, class template static data
      // members (i.e., implicitly or explicitly instantiated specializations)
      // have unordered initialization. As a consequence, we can put them into
      // their own llvm.global_dtors entry.
      CGM.AddCXXStermFinalizerToGlobalDtor(StermFinalizer, 65535);
    else
      CGM.AddCXXStermFinalizerEntry(StermFinalizer);
  }
  