text: //===--- MicrosoftCXXABI.cpp - Emit LLVM Code from ASTs for a Module ------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This provides C++ code generation targeting the Microsoft Visual C++ ABI.
  // The class in this file generates structures that follow the Microsoft
  // Visual C++ ABI, which is actually not very well documented at all outside
  // of Microsoft.
  //
  //===----------------------------------------------------------------------===//
  
  #include "CGCXXABI.h"
  #include "CGCleanup.h"
  #include "CGVTables.h"
  #include "CodeGenModule.h"
  #include "CodeGenTypes.h"
  #include "TargetInfo.h"
  #include "clang/AST/Decl.h"
  #include "clang/AST/DeclCXX.h"
  #include "clang/AST/StmtCXX.h"
  #include "clang/AST/VTableBuilder.h"
  #include "llvm/ADT/StringExtras.h"
  #include "llvm/ADT/StringSet.h"
  #include "llvm/IR/CallSite.h"
  #include "llvm/IR/Intrinsics.h"
  
  using namespace clang;
  using namespace CodeGen;
  
  namespace {
  
  /// Holds all the vbtable globals for a given class.
  struct VBTableGlobals {
    const VPtrInfoVector *VBTables;
    SmallVector<llvm::GlobalVariable *, 2> Globals;
  };
  
  class MicrosoftCXXABI : public CGCXXABI {
  public:
    MicrosoftCXXABI(CodeGenModule &CGM)
        : CGCXXABI(CGM), BaseClassDescriptorType(nullptr),
          ClassHierarchyDescriptorType(nullptr),
          CompleteObjectLocatorType(nullptr), CatchableTypeType(nullptr),
          ThrowInfoType(nullptr) {}
  
    bool HasThisReturn(GlobalDecl GD) const override;
    bool hasMostDerivedReturn(GlobalDecl GD) const override;
  
    bool classifyReturnType(CGFunctionInfo &FI) const override;
  
    RecordArgABI getRecordArgABI(const CXXRecordDecl *RD) const override;
  
    bool isSRetParameterAfterThis() const override { return true; }
  
    bool isThisCompleteObject(GlobalDecl GD) const override {
      // The Microsoft ABI doesn't use separate complete-object vs.
      // base-object variants of constructors, but it does of 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");
      }
  
      // No other kinds.
      return false;
    }
  
    size_t getSrcArgforCopyCtor(const CXXConstructorDecl *CD,
                                FunctionArgList &Args) const override {
      assert(Args.size() >= 2 &&
             "expected the arglist to have at least two args!");
      // The 'most_derived' parameter goes second if the ctor is variadic and
      // has v-bases.
      if (CD->getParent()->getNumVBases() > 0 &&
          CD->getType()->castAs<FunctionProtoType>()->isVariadic())
        return 2;
      return 1;
    }
  
    std::vector<CharUnits> getVBPtrOffsets(const CXXRecordDecl *RD) override {
      std::vector<CharUnits> VBPtrOffsets;
      const ASTContext &Context = getContext();
      const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
  
      const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
      for (const VPtrInfo *VBT : *VBGlobals.VBTables) {
        const ASTRecordLayout &SubobjectLayout =
            Context.getASTRecordLayout(VBT->BaseWithVPtr);
        CharUnits Offs = VBT->NonVirtualOffset;
        Offs += SubobjectLayout.getVBPtrOffset();
        if (VBT->getVBaseWithVPtr())
          Offs += Layout.getVBaseClassOffset(VBT->getVBaseWithVPtr());
        VBPtrOffsets.push_back(Offs);
      }
      llvm::array_pod_sort(VBPtrOffsets.begin(), VBPtrOffsets.end());
      return VBPtrOffsets;
    }
  
    StringRef GetPureVirtualCallName() override { return "_purecall"; }
    StringRef GetDeletedVirtualCallName() override { return "_purecall"; }
  
    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::GlobalVariable *getMSCompleteObjectLocator(const CXXRecordDecl *RD,
                                                     const VPtrInfo *Info);
  
    llvm::Constant *getAddrOfRTTIDescriptor(QualType Ty) override;
    CatchTypeInfo
    getAddrOfCXXCatchHandlerType(QualType Ty, QualType CatchHandlerType) override;
  
    /// MSVC needs an extra flag to indicate a catchall.
    CatchTypeInfo getCatchAllTypeInfo() override {
      return CatchTypeInfo{nullptr, 0x40};
    }
  
    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;
    bool canSpeculativelyEmitVTable(const CXXRecordDecl *RD) const override {
      return false;
    }
  
    llvm::Value *
    GetVirtualBaseClassOffset(CodeGenFunction &CGF, Address This,
                              const CXXRecordDecl *ClassDecl,
                              const CXXRecordDecl *BaseClassDecl) override;
  
    llvm::BasicBlock *
    EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
                                  const CXXRecordDecl *RD) override;
  
    void initializeHiddenVirtualInheritanceMembers(CodeGenFunction &CGF,
                                                const CXXRecordDecl *RD) override;
  
    void EmitCXXConstructors(const CXXConstructorDecl *D) override;
  
    // Background on MSVC destructors
    // ==============================
    //
    // Both Itanium and MSVC ABIs have destructor variants.  The variant names
    // roughly correspond in the following way:
    //   Itanium       Microsoft
    //   Base       -> no name, just ~Class
    //   Complete   -> vbase destructor
    //   Deleting   -> scalar deleting destructor
    //                 vector deleting destructor
    //
    // The base and complete destructors are the same as in Itanium, although the
    // complete destructor does not accept a VTT parameter when there are virtual
    // bases.  A separate mechanism involving vtordisps is used to ensure that
    // virtual methods of destroyed subobjects are not called.
    //
    // The deleting destructors accept an i32 bitfield as a second parameter.  Bit
    // 1 indicates if the memory should be deleted.  Bit 2 indicates if the this
    // pointer points to an array.  The scalar deleting destructor assumes that
    // bit 2 is zero, and therefore does not contain a loop.
    //
    // For virtual destructors, only one entry is reserved in the vftable, and it
    // always points to the vector deleting destructor.  The vector deleting
    // destructor is the most general, so it can be used to destroy objects in
    // place, delete single heap objects, or delete arrays.
    //
    // A TU defining a non-inline destructor is only guaranteed to emit a base
    // destructor, and all of the other variants are emitted on an as-needed basis
    // in COMDATs.  Because a non-base destructor can be emitted in a TU that
    // lacks a definition for the destructor, non-base destructors must always
    // delegate to or alias the base destructor.
  
    void buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
                                SmallVectorImpl<CanQualType> &ArgTys) override;
  
    /// Non-base dtors should be emitted as delegating thunks in this ABI.
    bool useThunkForDtorVariant(const CXXDestructorDecl *Dtor,
                                CXXDtorType DT) const override {
      return DT != Dtor_Base;
    }
  
    void EmitCXXDestructors(const CXXDestructorDecl *D) override;
  
    const CXXRecordDecl *
    getThisArgumentTypeForMethod(const CXXMethodDecl *MD) override {
      MD = MD->getCanonicalDecl();
      if (MD->isVirtual() && !isa<CXXDestructorDecl>(MD)) {
        MicrosoftVTableContext::MethodVFTableLocation ML =
            CGM.getMicrosoftVTableContext().getMethodVFTableLocation(MD);
        // The vbases might be ordered differently in the final overrider object
        // and the complete object, so the "this" argument may sometimes point to
        // memory that has no particular type (e.g. past the complete object).
        // In this case, we just use a generic pointer type.
        // FIXME: might want to have a more precise type in the non-virtual
        // multiple inheritance case.
        if (ML.VBase || !ML.VFPtrOffset.isZero())
          return nullptr;
      }
      return MD->getParent();
    }
  
    Address
    adjustThisArgumentForVirtualFunctionCall(CodeGenFunction &CGF, GlobalDecl GD,
                                             Address This,
                                             bool VirtualCall) override;
  
    void addImplicitStructorParams(CodeGenFunction &CGF, QualType &ResTy,
                                   FunctionArgList &Params) override;
  
    llvm::Value *adjustThisParameterInVirtualFunctionPrologue(
        CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) override;
  
    void EmitInstanceFunctionProlog(CodeGenFunction &CGF) override;
  
    unsigned addImplicitConstructorArgs(CodeGenFunction &CGF,
                                        const CXXConstructorDecl *D,
                                        CXXCtorType Type, bool ForVirtualBase,
                                        bool Delegating,
                                        CallArgList &Args) override;
  
    void EmitDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *DD,
                            CXXDtorType Type, bool ForVirtualBase,
                            bool Delegating, Address This) override;
  
    void emitVTableBitSetEntries(VPtrInfo *Info, const CXXRecordDecl *RD,
                                 llvm::GlobalVariable *VTable);
  
    void emitVTableDefinitions(CodeGenVTables &CGVT,
                               const CXXRecordDecl *RD) override;
  
    bool isVirtualOffsetNeededForVTableField(CodeGenFunction &CGF,
                                             CodeGenFunction::VPtr Vptr) override;
  
    /// Don't initialize vptrs if dynamic class
    /// is marked with with the 'novtable' attribute.
    bool doStructorsInitializeVPtrs(const CXXRecordDecl *VTableClass) override {
      return !VTableClass->hasAttr<MSNoVTableAttr>();
    }
  
    llvm::Constant *
    getVTableAddressPoint(BaseSubobject Base,
                          const CXXRecordDecl *VTableClass) override;
  
    llvm::Value *getVTableAddressPointInStructor(
        CodeGenFunction &CGF, const CXXRecordDecl *VTableClass,
        BaseSubobject Base, const CXXRecordDecl *NearestVBase) override;
  
    llvm::Constant *
    getVTableAddressPointForConstExpr(BaseSubobject Base,
                                      const CXXRecordDecl *VTableClass) override;
  
    llvm::GlobalVariable *getAddrOfVTable(const CXXRecordDecl *RD,
                                          CharUnits VPtrOffset) override;
  
    llvm::Value *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,
                                           const CXXMemberCallExpr *CE) override;
  
    void adjustCallArgsForDestructorThunk(CodeGenFunction &CGF, GlobalDecl GD,
                                          CallArgList &CallArgs) override {
      assert(GD.getDtorType() == Dtor_Deleting &&
             "Only deleting destructor thunks are available in this ABI");
      CallArgs.add(RValue::get(getStructorImplicitParamValue(CGF)),
                   getContext().IntTy);
    }
  
    void emitVirtualInheritanceTables(const CXXRecordDecl *RD) override;
  
    llvm::GlobalVariable *
    getAddrOfVBTable(const VPtrInfo &VBT, const CXXRecordDecl *RD,
                     llvm::GlobalVariable::LinkageTypes Linkage);
  
    llvm::GlobalVariable *
    getAddrOfVirtualDisplacementMap(const CXXRecordDecl *SrcRD,
                                    const CXXRecordDecl *DstRD) {
      SmallString<256> OutName;
      llvm::raw_svector_ostream Out(OutName);
      getMangleContext().mangleCXXVirtualDisplacementMap(SrcRD, DstRD, Out);
      StringRef MangledName = OutName.str();
  
      if (auto *VDispMap = CGM.getModule().getNamedGlobal(MangledName))
        return VDispMap;
  
      MicrosoftVTableContext &VTContext = CGM.getMicrosoftVTableContext();
      unsigned NumEntries = 1 + SrcRD->getNumVBases();
      SmallVector<llvm::Constant *, 4> Map(NumEntries,
                                           llvm::UndefValue::get(CGM.IntTy));
      Map[0] = llvm::ConstantInt::get(CGM.IntTy, 0);
      bool AnyDifferent = false;
      for (const auto &I : SrcRD->vbases()) {
        const CXXRecordDecl *VBase = I.getType()->getAsCXXRecordDecl();
        if (!DstRD->isVirtuallyDerivedFrom(VBase))
          continue;
  
        unsigned SrcVBIndex = VTContext.getVBTableIndex(SrcRD, VBase);
        unsigned DstVBIndex = VTContext.getVBTableIndex(DstRD, VBase);
        Map[SrcVBIndex] = llvm::ConstantInt::get(CGM.IntTy, DstVBIndex * 4);
        AnyDifferent |= SrcVBIndex != DstVBIndex;
      }
      // This map would be useless, don't use it.
      if (!AnyDifferent)
        return nullptr;
  
      llvm::ArrayType *VDispMapTy = llvm::ArrayType::get(CGM.IntTy, Map.size());
      llvm::Constant *Init = llvm::ConstantArray::get(VDispMapTy, Map);
      llvm::GlobalValue::LinkageTypes Linkage =
          SrcRD->isExternallyVisible() && DstRD->isExternallyVisible()
              ? llvm::GlobalValue::LinkOnceODRLinkage
              : llvm::GlobalValue::InternalLinkage;
      auto *VDispMap = new llvm::GlobalVariable(
          CGM.getModule(), VDispMapTy, /*Constant=*/true, Linkage,
          /*Initializer=*/Init, MangledName);
      return VDispMap;
    }
  
    void emitVBTableDefinition(const VPtrInfo &VBT, const CXXRecordDecl *RD,
                               llvm::GlobalVariable *GV) const;
  
    void setThunkLinkage(llvm::Function *Thunk, bool ForVTable,
                         GlobalDecl GD, bool ReturnAdjustment) override {
      // Never dllimport/dllexport thunks.
      Thunk->setDLLStorageClass(llvm::GlobalValue::DefaultStorageClass);
  
      GVALinkage Linkage =
          getContext().GetGVALinkageForFunction(cast<FunctionDecl>(GD.getDecl()));
  
      if (Linkage == GVA_Internal)
        Thunk->setLinkage(llvm::GlobalValue::InternalLinkage);
      else if (ReturnAdjustment)
        Thunk->setLinkage(llvm::GlobalValue::WeakODRLinkage);
      else
        Thunk->setLinkage(llvm::GlobalValue::LinkOnceODRLinkage);
    }
  
    llvm::Value *performThisAdjustment(CodeGenFunction &CGF, Address This,
                                       const ThisAdjustment &TA) override;
  
    llvm::Value *performReturnAdjustment(CodeGenFunction &CGF, Address Ret,
                                         const ReturnAdjustment &RA) override;
  
    void EmitThreadLocalInitFuncs(
        CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
        ArrayRef<llvm::Function *> CXXThreadLocalInits,
        ArrayRef<const VarDecl *> CXXThreadLocalInitVars) override;
  
    bool usesThreadWrapperFunction() const override { return false; }
    LValue EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF, const VarDecl *VD,
                                        QualType LValType) override;
  
    void EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
                         llvm::GlobalVariable *DeclPtr,
                         bool PerformInit) override;
    void registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                            llvm::Constant *Dtor, llvm::Constant *Addr) override;
  
    // ==== Notes on array cookies =========
    //
    // MSVC seems to only use cookies when the class has a destructor; a
    // two-argument usual array deallocation function isn't sufficient.
    //
    // For example, this code prints "100" and "1":
    //   struct A {
    //     char x;
    //     void *operator new[](size_t sz) {
    //       printf("%u\n", sz);
    //       return malloc(sz);
    //     }
    //     void operator delete[](void *p, size_t sz) {
    //       printf("%u\n", sz);
    //       free(p);
    //     }
    //   };
    //   int main() {
    //     A *p = new A[100];
    //     delete[] p;
    //   }
    // Whereas it prints "104" and "104" if you give A a destructor.
  
    bool requiresArrayCookie(const CXXDeleteExpr *expr,
                             QualType elementType) override;
    bool requiresArrayCookie(const CXXNewExpr *expr) override;
    CharUnits getArrayCookieSizeImpl(QualType type) 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;
  
    friend struct MSRTTIBuilder;
  
    bool isImageRelative() const {
      return CGM.getTarget().getPointerWidth(/*AddressSpace=*/0) == 64;
    }
  
    // 5 routines for constructing the llvm types for MS RTTI structs.
    llvm::StructType *getTypeDescriptorType(StringRef TypeInfoString) {
      llvm::SmallString<32> TDTypeName("rtti.TypeDescriptor");
      TDTypeName += llvm::utostr(TypeInfoString.size());
      llvm::StructType *&TypeDescriptorType =
          TypeDescriptorTypeMap[TypeInfoString.size()];
      if (TypeDescriptorType)
        return TypeDescriptorType;
      llvm::Type *FieldTypes[] = {
          CGM.Int8PtrPtrTy,
          CGM.Int8PtrTy,
          llvm::ArrayType::get(CGM.Int8Ty, TypeInfoString.size() + 1)};
      TypeDescriptorType =
          llvm::StructType::create(CGM.getLLVMContext(), FieldTypes, TDTypeName);
      return TypeDescriptorType;
    }
  
    llvm::Type *getImageRelativeType(llvm::Type *PtrType) {
      if (!isImageRelative())
        return PtrType;
      return CGM.IntTy;
    }
  
    llvm::StructType *getBaseClassDescriptorType() {
      if (BaseClassDescriptorType)
        return BaseClassDescriptorType;
      llvm::Type *FieldTypes[] = {
          getImageRelativeType(CGM.Int8PtrTy),
          CGM.IntTy,
          CGM.IntTy,
          CGM.IntTy,
          CGM.IntTy,
          CGM.IntTy,
          getImageRelativeType(getClassHierarchyDescriptorType()->getPointerTo()),
      };
      BaseClassDescriptorType = llvm::StructType::create(
          CGM.getLLVMContext(), FieldTypes, "rtti.BaseClassDescriptor");
      return BaseClassDescriptorType;
    }
  
    llvm::StructType *getClassHierarchyDescriptorType() {
      if (ClassHierarchyDescriptorType)
        return ClassHierarchyDescriptorType;
      // Forward-declare RTTIClassHierarchyDescriptor to break a cycle.
      ClassHierarchyDescriptorType = llvm::StructType::create(
          CGM.getLLVMContext(), "rtti.ClassHierarchyDescriptor");
      llvm::Type *FieldTypes[] = {
          CGM.IntTy,
          CGM.IntTy,
          CGM.IntTy,
          getImageRelativeType(
              getBaseClassDescriptorType()->getPointerTo()->getPointerTo()),
      };
      ClassHierarchyDescriptorType->setBody(FieldTypes);
      return ClassHierarchyDescriptorType;
    }
  
    llvm::StructType *getCompleteObjectLocatorType() {
      if (CompleteObjectLocatorType)
        return CompleteObjectLocatorType;
      CompleteObjectLocatorType = llvm::StructType::create(
          CGM.getLLVMContext(), "rtti.CompleteObjectLocator");
      llvm::Type *FieldTypes[] = {
          CGM.IntTy,
          CGM.IntTy,
          CGM.IntTy,
          getImageRelativeType(CGM.Int8PtrTy),
          getImageRelativeType(getClassHierarchyDescriptorType()->getPointerTo()),
          getImageRelativeType(CompleteObjectLocatorType),
      };
      llvm::ArrayRef<llvm::Type *> FieldTypesRef(FieldTypes);
      if (!isImageRelative())
        FieldTypesRef = FieldTypesRef.drop_back();
      CompleteObjectLocatorType->setBody(FieldTypesRef);
      return CompleteObjectLocatorType;
    }
  
    llvm::GlobalVariable *getImageBase() {
      StringRef Name = "__ImageBase";
      if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(Name))
        return GV;
  
      return new llvm::GlobalVariable(CGM.getModule(), CGM.Int8Ty,
                                      /*isConstant=*/true,
                                      llvm::GlobalValue::ExternalLinkage,
                                      /*Initializer=*/nullptr, Name);
    }
  
    llvm::Constant *getImageRelativeConstant(llvm::Constant *PtrVal) {
      if (!isImageRelative())
        return PtrVal;
  
      if (PtrVal->isNullValue())
        return llvm::Constant::getNullValue(CGM.IntTy);
  
      llvm::Constant *ImageBaseAsInt =
          llvm::ConstantExpr::getPtrToInt(getImageBase(), CGM.IntPtrTy);
      llvm::Constant *PtrValAsInt =
          llvm::ConstantExpr::getPtrToInt(PtrVal, CGM.IntPtrTy);
      llvm::Constant *Diff =
          llvm::ConstantExpr::getSub(PtrValAsInt, ImageBaseAsInt,
                                     /*HasNUW=*/true, /*HasNSW=*/true);
      return llvm::ConstantExpr::getTrunc(Diff, CGM.IntTy);
    }
  
  private:
    MicrosoftMangleContext &getMangleContext() {
      return cast<MicrosoftMangleContext>(CodeGen::CGCXXABI::getMangleContext());
    }
  
    llvm::Constant *getZeroInt() {
      return llvm::ConstantInt::get(CGM.IntTy, 0);
    }
  
    llvm::Constant *getAllOnesInt() {
      return  llvm::Constant::getAllOnesValue(CGM.IntTy);
    }
  
    CharUnits getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD);
  
    void
    GetNullMemberPointerFields(const MemberPointerType *MPT,
                               llvm::SmallVectorImpl<llvm::Constant *> &fields);
  
    /// \brief Shared code for virtual base adjustment.  Returns the offset from
    /// the vbptr to the virtual base.  Optionally returns the address of the
    /// vbptr itself.
    llvm::Value *GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
                                         Address Base,
                                         llvm::Value *VBPtrOffset,
                                         llvm::Value *VBTableOffset,
                                         llvm::Value **VBPtr = nullptr);
  
    llvm::Value *GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
                                         Address Base,
                                         int32_t VBPtrOffset,
                                         int32_t VBTableOffset,
                                         llvm::Value **VBPtr = nullptr) {
      assert(VBTableOffset % 4 == 0 && "should be byte offset into table of i32s");
      llvm::Value *VBPOffset = llvm::ConstantInt::get(CGM.IntTy, VBPtrOffset),
                  *VBTOffset = llvm::ConstantInt::get(CGM.IntTy, VBTableOffset);
      return GetVBaseOffsetFromVBPtr(CGF, Base, VBPOffset, VBTOffset, VBPtr);
    }
  
    std::pair<Address, llvm::Value *>
    performBaseAdjustment(CodeGenFunction &CGF, Address Value,
                          QualType SrcRecordTy);
  
    /// \brief Performs a full virtual base adjustment.  Used to dereference
    /// pointers to members of virtual bases.
    llvm::Value *AdjustVirtualBase(CodeGenFunction &CGF, const Expr *E,
                                   const CXXRecordDecl *RD, Address Base,
                                   llvm::Value *VirtualBaseAdjustmentOffset,
                                   llvm::Value *VBPtrOffset /* optional */);
  
    /// \brief Emits a full member pointer with the fields common to data and
    /// function member pointers.
    llvm::Constant *EmitFullMemberPointer(llvm::Constant *FirstField,
                                          bool IsMemberFunction,
                                          const CXXRecordDecl *RD,
                                          CharUnits NonVirtualBaseAdjustment,
                                          unsigned VBTableIndex);
  
    bool MemberPointerConstantIsNull(const MemberPointerType *MPT,
                                     llvm::Constant *MP);
  
    /// \brief - Initialize all vbptrs of 'this' with RD as the complete type.
    void EmitVBPtrStores(CodeGenFunction &CGF, const CXXRecordDecl *RD);
  
    /// \brief Caching wrapper around VBTableBuilder::enumerateVBTables().
    const VBTableGlobals &enumerateVBTables(const CXXRecordDecl *RD);
  
    /// \brief Generate a thunk for calling a virtual member function MD.
    llvm::Function *EmitVirtualMemPtrThunk(
        const CXXMethodDecl *MD,
        const MicrosoftVTableContext::MethodVFTableLocation &ML);
  
  public:
    llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT) override;
  
    bool isZeroInitializable(const MemberPointerType *MPT) override;
  
    bool isMemberPointerConvertible(const MemberPointerType *MPT) const override {
      const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
      return RD->hasAttr<MSInheritanceAttr>();
    }
  
    llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT) override;
  
    llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
                                          CharUnits offset) override;
    llvm::Constant *EmitMemberFunctionPointer(const CXXMethodDecl *MD) override;
    llvm::Constant *EmitMemberPointer(const APValue &MP, QualType MPT) override;
  
    llvm::Value *EmitMemberPointerComparison(CodeGenFunction &CGF,
                                             llvm::Value *L,
                                             llvm::Value *R,
                                             const MemberPointerType *MPT,
                                             bool Inequality) override;
  
    llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
                                            llvm::Value *MemPtr,
                                            const MemberPointerType *MPT) override;
  
    llvm::Value *
    EmitMemberDataPointerAddress(CodeGenFunction &CGF, const Expr *E,
                                 Address Base, llvm::Value *MemPtr,
                                 const MemberPointerType *MPT) override;
  
    llvm::Value *EmitNonNullMemberPointerConversion(
        const MemberPointerType *SrcTy, const MemberPointerType *DstTy,
        CastKind CK, CastExpr::path_const_iterator PathBegin,
        CastExpr::path_const_iterator PathEnd, llvm::Value *Src,
        CGBuilderTy &Builder);
  
    llvm::Value *EmitMemberPointerConversion(CodeGenFunction &CGF,
                                             const CastExpr *E,
                                             llvm::Value *Src) override;
  
    llvm::Constant *EmitMemberPointerConversion(const CastExpr *E,
                                                llvm::Constant *Src) override;
  
    llvm::Constant *EmitMemberPointerConversion(
        const MemberPointerType *SrcTy, const MemberPointerType *DstTy,
        CastKind CK, CastExpr::path_const_iterator PathBegin,
        CastExpr::path_const_iterator PathEnd, llvm::Constant *Src);
  
    llvm::Value *
    EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF, const Expr *E,
                                    Address This, llvm::Value *&ThisPtrForCall,
                                    llvm::Value *MemPtr,
                                    const MemberPointerType *MPT) override;
  
    void emitCXXStructor(const CXXMethodDecl *MD, StructorType Type) override;
  
    llvm::StructType *getCatchableTypeType() {
      if (CatchableTypeType)
        return CatchableTypeType;
      llvm::Type *FieldTypes[] = {
          CGM.IntTy,                           // Flags
          getImageRelativeType(CGM.Int8PtrTy), // TypeDescriptor
          CGM.IntTy,                           // NonVirtualAdjustment
          CGM.IntTy,                           // OffsetToVBPtr
          CGM.IntTy,                           // VBTableIndex
          CGM.IntTy,                           // Size
          getImageRelativeType(CGM.Int8PtrTy)  // CopyCtor
      };
      CatchableTypeType = llvm::StructType::create(
          CGM.getLLVMContext(), FieldTypes, "eh.CatchableType");
      return CatchableTypeType;
    }
  
    llvm::StructType *getCatchableTypeArrayType(uint32_t NumEntries) {
      llvm::StructType *&CatchableTypeArrayType =
          CatchableTypeArrayTypeMap[NumEntries];
      if (CatchableTypeArrayType)
        return CatchableTypeArrayType;
  
      llvm::SmallString<23> CTATypeName("eh.CatchableTypeArray.");
      CTATypeName += llvm::utostr(NumEntries);
      llvm::Type *CTType =
          getImageRelativeType(getCatchableTypeType()->getPointerTo());
      llvm::Type *FieldTypes[] = {
          CGM.IntTy,                               // NumEntries
          llvm::ArrayType::get(CTType, NumEntries) // CatchableTypes
      };
      CatchableTypeArrayType =
          llvm::StructType::create(CGM.getLLVMContext(), FieldTypes, CTATypeName);
      return CatchableTypeArrayType;
    }
  
    llvm::StructType *getThrowInfoType() {
      if (ThrowInfoType)
        return ThrowInfoType;
      llvm::Type *FieldTypes[] = {
          CGM.IntTy,                           // Flags
          getImageRelativeType(CGM.Int8PtrTy), // CleanupFn
          getImageRelativeType(CGM.Int8PtrTy), // ForwardCompat
          getImageRelativeType(CGM.Int8PtrTy)  // CatchableTypeArray
      };
      ThrowInfoType = llvm::StructType::create(CGM.getLLVMContext(), FieldTypes,
                                               "eh.ThrowInfo");
      return ThrowInfoType;
    }
  
    llvm::Constant *getThrowFn() {
      // _CxxThrowException is passed an exception object and a ThrowInfo object
      // which describes the exception.
      llvm::Type *Args[] = {CGM.Int8PtrTy, getThrowInfoType()->getPointerTo()};
      llvm::FunctionType *FTy =
          llvm::FunctionType::get(CGM.VoidTy, Args, /*IsVarArgs=*/false);
      auto *Fn = cast<llvm::Function>(
          CGM.CreateRuntimeFunction(FTy, "_CxxThrowException"));
      // _CxxThrowException is stdcall on 32-bit x86 platforms.
      if (CGM.getTarget().getTriple().getArch() == llvm::Triple::x86)
        Fn->setCallingConv(llvm::CallingConv::X86_StdCall);
      return Fn;
    }
  
    llvm::Function *getAddrOfCXXCtorClosure(const CXXConstructorDecl *CD,
                                            CXXCtorType CT);
  
    llvm::Constant *getCatchableType(QualType T,
                                     uint32_t NVOffset = 0,
                                     int32_t VBPtrOffset = -1,
                                     uint32_t VBIndex = 0);
  
    llvm::GlobalVariable *getCatchableTypeArray(QualType T);
  
    llvm::GlobalVariable *getThrowInfo(QualType T) override;
  
  private:
    typedef std::pair<const CXXRecordDecl *, CharUnits> VFTableIdTy;
    typedef llvm::DenseMap<VFTableIdTy, llvm::GlobalVariable *> VTablesMapTy;
    typedef llvm::DenseMap<VFTableIdTy, llvm::GlobalValue *> VFTablesMapTy;
    /// \brief All the vftables that have been referenced.
    VFTablesMapTy VFTablesMap;
    VTablesMapTy VTablesMap;
  
    /// \brief This set holds the record decls we've deferred vtable emission for.
    llvm::SmallPtrSet<const CXXRecordDecl *, 4> DeferredVFTables;
  
  
    /// \brief All the vbtables which have been referenced.
    llvm::DenseMap<const CXXRecordDecl *, VBTableGlobals> VBTablesMap;
  
    /// Info on the global variable used to guard initialization of static locals.
    /// The BitIndex field is only used for externally invisible declarations.
    struct GuardInfo {
      GuardInfo() : Guard(nullptr), BitIndex(0) {}
      llvm::GlobalVariable *Guard;
      unsigned BitIndex;
    };
  
    /// Map from DeclContext to the current guard variable.  We assume that the
    /// AST is visited in source code order.
    llvm::DenseMap<const DeclContext *, GuardInfo> GuardVariableMap;
    llvm::DenseMap<const DeclContext *, GuardInfo> ThreadLocalGuardVariableMap;
    llvm::DenseMap<const DeclContext *, unsigned> ThreadSafeGuardNumMap;
  
    llvm::DenseMap<size_t, llvm::StructType *> TypeDescriptorTypeMap;
    llvm::StructType *BaseClassDescriptorType;
    llvm::StructType *ClassHierarchyDescriptorType;
    llvm::StructType *CompleteObjectLocatorType;
  
    llvm::DenseMap<QualType, llvm::GlobalVariable *> CatchableTypeArrays;
  
    llvm::StructType *CatchableTypeType;
    llvm::DenseMap<uint32_t, llvm::StructType *> CatchableTypeArrayTypeMap;
    llvm::StructType *ThrowInfoType;
  };
  
  }
  
  CGCXXABI::RecordArgABI
  MicrosoftCXXABI::getRecordArgABI(const CXXRecordDecl *RD) const {
    switch (CGM.getTarget().getTriple().getArch()) {
    default:
      // FIXME: Implement for other architectures.
      return RAA_Default;
  
    case llvm::Triple::x86:
      // All record arguments are passed in memory on x86.  Decide whether to
      // construct the object directly in argument memory, or to construct the
      // argument elsewhere and copy the bytes during the call.
  
      // If C++ prohibits us from making a copy, construct the arguments directly
      // into argument memory.
      if (!canCopyArgument(RD))
        return RAA_DirectInMemory;
  
      // Otherwise, construct the argument into a temporary and copy the bytes
      // into the outgoing argument memory.
      return RAA_Default;
  
    case llvm::Triple::x86_64:
      // Win64 passes objects with non-trivial copy ctors indirectly.
      if (RD->hasNonTrivialCopyConstructor())
        return RAA_Indirect;
  
      // If an object has a destructor, we'd really like to pass it indirectly
      // because it allows us to elide copies.  Unfortunately, MSVC makes that
      // impossible for small types, which it will pass in a single register or
      // stack slot. Most objects with dtors are large-ish, so handle that early.
      // We can't call out all large objects as being indirect because there are
      // multiple x64 calling conventions and the C++ ABI code shouldn't dictate
      // how we pass large POD types.
      if (RD->hasNonTrivialDestructor() &&
          getContext().getTypeSize(RD->getTypeForDecl()) > 64)
        return RAA_Indirect;
  
      // We have a trivial copy constructor or no copy constructors, but we have
      // to make sure it isn't deleted.
      bool CopyDeleted = false;
      for (const CXXConstructorDecl *CD : RD->ctors()) {
        if (CD->isCopyConstructor()) {
          assert(CD->isTrivial());
          // We had at least one undeleted trivial copy ctor.  Return directly.
          if (!CD->isDeleted())
            return RAA_Default;
          CopyDeleted = true;
        }
      }
  
      // The trivial copy constructor was deleted.  Return indirectly.
      if (CopyDeleted)
        return RAA_Indirect;
  
      // There were no copy ctors.  Return in RAX.
      return RAA_Default;
    }
  
    llvm_unreachable("invalid enum");
  }
  
  void MicrosoftCXXABI::emitVirtualObjectDelete(CodeGenFunction &CGF,
                                                const CXXDeleteExpr *DE,
                                                Address Ptr,
                                                QualType ElementType,
                                                const CXXDestructorDecl *Dtor) {
    // FIXME: Provide a source location here even though there's no
    // CXXMemberCallExpr for dtor call.
    bool UseGlobalDelete = DE->isGlobalDelete();
    CXXDtorType DtorType = UseGlobalDelete ? Dtor_Complete : Dtor_Deleting;
    llvm::Value *MDThis =
        EmitVirtualDestructorCall(CGF, Dtor, DtorType, Ptr, /*CE=*/nullptr);
    if (UseGlobalDelete)
      CGF.EmitDeleteCall(DE->getOperatorDelete(), MDThis, ElementType);
  }
  
  void MicrosoftCXXABI::emitRethrow(CodeGenFunction &CGF, bool isNoReturn) {
    llvm::Value *Args[] = {
        llvm::ConstantPointerNull::get(CGM.Int8PtrTy),
        llvm::ConstantPointerNull::get(getThrowInfoType()->getPointerTo())};
    auto *Fn = getThrowFn();
    if (isNoReturn)
      CGF.EmitNoreturnRuntimeCallOrInvoke(Fn, Args);
    else
      CGF.EmitRuntimeCallOrInvoke(Fn, Args);
  }
  
  namespace {
  struct CatchRetScope final : EHScopeStack::Cleanup {
    llvm::CatchPadInst *CPI;
  
    CatchRetScope(llvm::CatchPadInst *CPI) : CPI(CPI) {}
  
    void Emit(CodeGenFunction &CGF, Flags flags) override {
      llvm::BasicBlock *BB = CGF.createBasicBlock("catchret.dest");
      CGF.Builder.CreateCatchRet(CPI, BB);
      CGF.EmitBlock(BB);
    }
  };
  }
  
  void MicrosoftCXXABI::emitBeginCatch(CodeGenFunction &CGF,
                                       const CXXCatchStmt *S) {
    // In the MS ABI, the runtime handles the copy, and the catch handler is
    // responsible for destruction.
    VarDecl *CatchParam = S->getExceptionDecl();
    llvm::BasicBlock *CatchPadBB = CGF.Builder.GetInsertBlock();
    llvm::CatchPadInst *CPI =
        cast<llvm::CatchPadInst>(CatchPadBB->getFirstNonPHI());
    CGF.CurrentFuncletPad = CPI;
  
    // If this is a catch-all or the catch parameter is unnamed, we don't need to
    // emit an alloca to the object.
    if (!CatchParam || !CatchParam->getDeclName()) {
      CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
      return;
    }
  
    CodeGenFunction::AutoVarEmission var = CGF.EmitAutoVarAlloca(*CatchParam);
    CPI->setArgOperand(2, var.getObjectAddress(CGF).getPointer());
    CGF.EHStack.pushCleanup<CatchRetScope>(NormalCleanup, CPI);
    CGF.EmitAutoVarCleanups(var);
  }
  
  /// We need to perform a generic polymorphic operation (like a typeid
  /// or a cast), which requires an object with a vfptr.  Adjust the
  /// address to point to an object with a vfptr.
  std::pair<Address, llvm::Value *>
  MicrosoftCXXABI::performBaseAdjustment(CodeGenFunction &CGF, Address Value,
                                         QualType SrcRecordTy) {
    Value = CGF.Builder.CreateBitCast(Value, CGF.Int8PtrTy);
    const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
    const ASTContext &Context = getContext();
  
    // If the class itself has a vfptr, great.  This check implicitly
    // covers non-virtual base subobjects: a class with its own virtual
    // functions would be a candidate to be a primary base.
    if (Context.getASTRecordLayout(SrcDecl).hasExtendableVFPtr())
      return std::make_pair(Value, llvm::ConstantInt::get(CGF.Int32Ty, 0));
  
    // Okay, one of the vbases must have a vfptr, or else this isn't
    // actually a polymorphic class.
    const CXXRecordDecl *PolymorphicBase = nullptr;
    for (auto &Base : SrcDecl->vbases()) {
      const CXXRecordDecl *BaseDecl = Base.getType()->getAsCXXRecordDecl();
      if (Context.getASTRecordLayout(BaseDecl).hasExtendableVFPtr()) {
        PolymorphicBase = BaseDecl;
        break;
      }
    }
    assert(PolymorphicBase && "polymorphic class has no apparent vfptr?");
  
    llvm::Value *Offset =
      GetVirtualBaseClassOffset(CGF, Value, SrcDecl, PolymorphicBase);
    llvm::Value *Ptr = CGF.Builder.CreateInBoundsGEP(Value.getPointer(), Offset);
    Offset = CGF.Builder.CreateTrunc(Offset, CGF.Int32Ty);
    CharUnits VBaseAlign =
      CGF.CGM.getVBaseAlignment(Value.getAlignment(), SrcDecl, PolymorphicBase);
    return std::make_pair(Address(Ptr, VBaseAlign), Offset);
  }
  
  bool MicrosoftCXXABI::shouldTypeidBeNullChecked(bool IsDeref,
                                                  QualType SrcRecordTy) {
    const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
    return IsDeref &&
           !getContext().getASTRecordLayout(SrcDecl).hasExtendableVFPtr();
  }
  
  static llvm::CallSite emitRTtypeidCall(CodeGenFunction &CGF,
                                         llvm::Value *Argument) {
    llvm::Type *ArgTypes[] = {CGF.Int8PtrTy};
    llvm::FunctionType *FTy =
        llvm::FunctionType::get(CGF.Int8PtrTy, ArgTypes, false);
    llvm::Value *Args[] = {Argument};
    llvm::Constant *Fn = CGF.CGM.CreateRuntimeFunction(FTy, "__RTtypeid");
    return CGF.EmitRuntimeCallOrInvoke(Fn, Args);
  }
  
  void MicrosoftCXXABI::EmitBadTypeidCall(CodeGenFunction &CGF) {
    llvm::CallSite Call =
        emitRTtypeidCall(CGF, llvm::Constant::getNullValue(CGM.VoidPtrTy));
    Call.setDoesNotReturn();
    CGF.Builder.CreateUnreachable();
  }
  
  llvm::Value *MicrosoftCXXABI::EmitTypeid(CodeGenFunction &CGF,
                                           QualType SrcRecordTy,
                                           Address ThisPtr,
                                           llvm::Type *StdTypeInfoPtrTy) {
    llvm::Value *Offset;
    std::tie(ThisPtr, Offset) = performBaseAdjustment(CGF, ThisPtr, SrcRecordTy);
    auto Typeid = emitRTtypeidCall(CGF, ThisPtr.getPointer()).getInstruction();
    return CGF.Builder.CreateBitCast(Typeid, StdTypeInfoPtrTy);
  }
  
  bool MicrosoftCXXABI::shouldDynamicCastCallBeNullChecked(bool SrcIsPtr,
                                                           QualType SrcRecordTy) {
    const CXXRecordDecl *SrcDecl = SrcRecordTy->getAsCXXRecordDecl();
    return SrcIsPtr &&
           !getContext().getASTRecordLayout(SrcDecl).hasExtendableVFPtr();
  }
  
  llvm::Value *MicrosoftCXXABI::EmitDynamicCastCall(
      CodeGenFunction &CGF, Address This, QualType SrcRecordTy,
      QualType DestTy, QualType DestRecordTy, llvm::BasicBlock *CastEnd) {
    llvm::Type *DestLTy = CGF.ConvertType(DestTy);
  
    llvm::Value *SrcRTTI =
        CGF.CGM.GetAddrOfRTTIDescriptor(SrcRecordTy.getUnqualifiedType());
    llvm::Value *DestRTTI =
        CGF.CGM.GetAddrOfRTTIDescriptor(DestRecordTy.getUnqualifiedType());
  
    llvm::Value *Offset;
    std::tie(This, Offset) = performBaseAdjustment(CGF, This, SrcRecordTy);
    llvm::Value *ThisPtr = This.getPointer();
  
    // PVOID __RTDynamicCast(
    //   PVOID inptr,
    //   LONG VfDelta,
    //   PVOID SrcType,
    //   PVOID TargetType,
    //   BOOL isReference)
    llvm::Type *ArgTypes[] = {CGF.Int8PtrTy, CGF.Int32Ty, CGF.Int8PtrTy,
                              CGF.Int8PtrTy, CGF.Int32Ty};
    llvm::Constant *Function = CGF.CGM.CreateRuntimeFunction(
        llvm::FunctionType::get(CGF.Int8PtrTy, ArgTypes, false),
        "__RTDynamicCast");
    llvm::Value *Args[] = {
        ThisPtr, Offset, SrcRTTI, DestRTTI,
        llvm::ConstantInt::get(CGF.Int32Ty, DestTy->isReferenceType())};
    ThisPtr = CGF.EmitRuntimeCallOrInvoke(Function, Args).getInstruction();
    return CGF.Builder.CreateBitCast(ThisPtr, DestLTy);
  }
  
  llvm::Value *
  MicrosoftCXXABI::EmitDynamicCastToVoid(CodeGenFunction &CGF, Address Value,
                                         QualType SrcRecordTy,
                                         QualType DestTy) {
    llvm::Value *Offset;
    std::tie(Value, Offset) = performBaseAdjustment(CGF, Value, SrcRecordTy);
  
    // PVOID __RTCastToVoid(
    //   PVOID inptr)
    llvm::Type *ArgTypes[] = {CGF.Int8PtrTy};
    llvm::Constant *Function = CGF.CGM.CreateRuntimeFunction(
        llvm::FunctionType::get(CGF.Int8PtrTy, ArgTypes, false),
        "__RTCastToVoid");
    llvm::Value *Args[] = {Value.getPointer()};
    return CGF.EmitRuntimeCall(Function, Args);
  }
  
  bool MicrosoftCXXABI::EmitBadCastCall(CodeGenFunction &CGF) {
    return false;
  }
  
  llvm::Value *MicrosoftCXXABI::GetVirtualBaseClassOffset(
      CodeGenFunction &CGF, Address This, const CXXRecordDecl *ClassDecl,
      const CXXRecordDecl *BaseClassDecl) {
    const ASTContext &Context = getContext();
    int64_t VBPtrChars =
        Context.getASTRecordLayout(ClassDecl).getVBPtrOffset().getQuantity();
    llvm::Value *VBPtrOffset = llvm::ConstantInt::get(CGM.PtrDiffTy, VBPtrChars);
    CharUnits IntSize = Context.getTypeSizeInChars(Context.IntTy);
    CharUnits VBTableChars =
        IntSize *
        CGM.getMicrosoftVTableContext().getVBTableIndex(ClassDecl, BaseClassDecl);
    llvm::Value *VBTableOffset =
        llvm::ConstantInt::get(CGM.IntTy, VBTableChars.getQuantity());
  
    llvm::Value *VBPtrToNewBase =
        GetVBaseOffsetFromVBPtr(CGF, This, VBPtrOffset, VBTableOffset);
    VBPtrToNewBase =
        CGF.Builder.CreateSExtOrBitCast(VBPtrToNewBase, CGM.PtrDiffTy);
    return CGF.Builder.CreateNSWAdd(VBPtrOffset, VBPtrToNewBase);
  }
  
  bool MicrosoftCXXABI::HasThisReturn(GlobalDecl GD) const {
    return isa<CXXConstructorDecl>(GD.getDecl());
  }
  
  static bool isDeletingDtor(GlobalDecl GD) {
    return isa<CXXDestructorDecl>(GD.getDecl()) &&
           GD.getDtorType() == Dtor_Deleting;
  }
  
  bool MicrosoftCXXABI::hasMostDerivedReturn(GlobalDecl GD) const {
    return isDeletingDtor(GD);
  }
  
  bool MicrosoftCXXABI::classifyReturnType(CGFunctionInfo &FI) const {
    const CXXRecordDecl *RD = FI.getReturnType()->getAsCXXRecordDecl();
    if (!RD)
      return false;
  
    CharUnits Align = CGM.getContext().getTypeAlignInChars(FI.getReturnType());
    if (FI.isInstanceMethod()) {
      // If it's an instance method, aggregates are always returned indirectly via
      // the second parameter.
      FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
      FI.getReturnInfo().setSRetAfterThis(FI.isInstanceMethod());
      return true;
    } else if (!RD->isPOD()) {
      // If it's a free function, non-POD types are returned indirectly.
      FI.getReturnInfo() = ABIArgInfo::getIndirect(Align, /*ByVal=*/false);
      return true;
    }
  
    // Otherwise, use the C ABI rules.
    return false;
  }
  
  llvm::BasicBlock *
  MicrosoftCXXABI::EmitCtorCompleteObjectHandler(CodeGenFunction &CGF,
                                                 const CXXRecordDecl *RD) {
    llvm::Value *IsMostDerivedClass = getStructorImplicitParamValue(CGF);
    assert(IsMostDerivedClass &&
           "ctor for a class with virtual bases must have an implicit parameter");
    llvm::Value *IsCompleteObject =
      CGF.Builder.CreateIsNotNull(IsMostDerivedClass, "is_complete_object");
  
    llvm::BasicBlock *CallVbaseCtorsBB = CGF.createBasicBlock("ctor.init_vbases");
    llvm::BasicBlock *SkipVbaseCtorsBB = CGF.createBasicBlock("ctor.skip_vbases");
    CGF.Builder.CreateCondBr(IsCompleteObject,
                             CallVbaseCtorsBB, SkipVbaseCtorsBB);
  
    CGF.EmitBlock(CallVbaseCtorsBB);
  
    // Fill in the vbtable pointers here.
    EmitVBPtrStores(CGF, RD);
  
    // CGF will put the base ctor calls in this basic block for us later.
  
    return SkipVbaseCtorsBB;
  }
  
  void MicrosoftCXXABI::initializeHiddenVirtualInheritanceMembers(
      CodeGenFunction &CGF, const CXXRecordDecl *RD) {
    // In most cases, an override for a vbase virtual method can adjust
    // the "this" parameter by applying a constant offset.
    // However, this is not enough while a constructor or a destructor of some
    // class X is being executed if all the following conditions are met:
    //  - X has virtual bases, (1)
    //  - X overrides a virtual method M of a vbase Y, (2)
    //  - X itself is a vbase of the most derived class.
    //
    // If (1) and (2) are true, the vtorDisp for vbase Y is a hidden member of X
    // which holds the extra amount of "this" adjustment we must do when we use
    // the X vftables (i.e. during X ctor or dtor).
    // Outside the ctors and dtors, the values of vtorDisps are zero.
  
    const ASTRecordLayout &Layout = getContext().getASTRecordLayout(RD);
    typedef ASTRecordLayout::VBaseOffsetsMapTy VBOffsets;
    const VBOffsets &VBaseMap = Layout.getVBaseOffsetsMap();
    CGBuilderTy &Builder = CGF.Builder;
  
    unsigned AS = getThisAddress(CGF).getAddressSpace();
    llvm::Value *Int8This = nullptr;  // Initialize lazily.
  
    for (VBOffsets::const_iterator I = VBaseMap.begin(), E = VBaseMap.end();
          I != E; ++I) {
      if (!I->second.hasVtorDisp())
        continue;
  
      llvm::Value *VBaseOffset =
          GetVirtualBaseClassOffset(CGF, getThisAddress(CGF), RD, I->first);
      // FIXME: it doesn't look right that we SExt in GetVirtualBaseClassOffset()
      // just to Trunc back immediately.
      VBaseOffset = Builder.CreateTruncOrBitCast(VBaseOffset, CGF.Int32Ty);
      uint64_t ConstantVBaseOffset =
          Layout.getVBaseClassOffset(I->first).getQuantity();
  
      // vtorDisp_for_vbase = vbptr[vbase_idx] - offsetof(RD, vbase).
      llvm::Value *VtorDispValue = Builder.CreateSub(
          VBaseOffset, llvm::ConstantInt::get(CGM.Int32Ty, ConstantVBaseOffset),
          "vtordisp.value");
  
      if (!Int8This)
        Int8This = Builder.CreateBitCast(getThisValue(CGF),
                                         CGF.Int8Ty->getPointerTo(AS));
      llvm::Value *VtorDispPtr = Builder.CreateInBoundsGEP(Int8This, VBaseOffset);
      // vtorDisp is always the 32-bits before the vbase in the class layout.
      VtorDispPtr = Builder.CreateConstGEP1_32(VtorDispPtr, -4);
      VtorDispPtr = Builder.CreateBitCast(
          VtorDispPtr, CGF.Int32Ty->getPointerTo(AS), "vtordisp.ptr");
  
      Builder.CreateAlignedStore(VtorDispValue, VtorDispPtr,
                                 CharUnits::fromQuantity(4));
    }
  }
  
  static bool hasDefaultCXXMethodCC(ASTContext &Context,
                                    const CXXMethodDecl *MD) {
    CallingConv ExpectedCallingConv = Context.getDefaultCallingConvention(
        /*IsVariadic=*/false, /*IsCXXMethod=*/true);
    CallingConv ActualCallingConv =
        MD->getType()->getAs<FunctionProtoType>()->getCallConv();
    return ExpectedCallingConv == ActualCallingConv;
  }
  
  void MicrosoftCXXABI::EmitCXXConstructors(const CXXConstructorDecl *D) {
    // There's only one constructor type in this ABI.
    CGM.EmitGlobal(GlobalDecl(D, Ctor_Complete));
  
    // Exported default constructors either have a simple call-site where they use
    // the typical calling convention and have a single 'this' pointer for an
    // argument -or- they get a wrapper function which appropriately thunks to the
    // real default constructor.  This thunk is the default constructor closure.
    if (D->hasAttr<DLLExportAttr>() && D->isDefaultConstructor())
      if (!hasDefaultCXXMethodCC(getContext(), D) || D->getNumParams() != 0) {
        llvm::Function *Fn = getAddrOfCXXCtorClosure(D, Ctor_DefaultClosure);
        Fn->setLinkage(llvm::GlobalValue::WeakODRLinkage);
        Fn->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
      }
  }
  
  void MicrosoftCXXABI::EmitVBPtrStores(CodeGenFunction &CGF,
                                        const CXXRecordDecl *RD) {
    Address This = getThisAddress(CGF);
    This = CGF.Builder.CreateElementBitCast(This, CGM.Int8Ty, "this.int8");
    const ASTContext &Context = getContext();
    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
  
    const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
    for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
      const VPtrInfo *VBT = (*VBGlobals.VBTables)[I];
      llvm::GlobalVariable *GV = VBGlobals.Globals[I];
      const ASTRecordLayout &SubobjectLayout =
          Context.getASTRecordLayout(VBT->BaseWithVPtr);
      CharUnits Offs = VBT->NonVirtualOffset;
      Offs += SubobjectLayout.getVBPtrOffset();
      if (VBT->getVBaseWithVPtr())
        Offs += Layout.getVBaseClassOffset(VBT->getVBaseWithVPtr());
      Address VBPtr = CGF.Builder.CreateConstInBoundsByteGEP(This, Offs);
      llvm::Value *GVPtr =
          CGF.Builder.CreateConstInBoundsGEP2_32(GV->getValueType(), GV, 0, 0);
      VBPtr = CGF.Builder.CreateElementBitCast(VBPtr, GVPtr->getType(),
                                        "vbptr." + VBT->ReusingBase->getName());
      CGF.Builder.CreateStore(GVPtr, VBPtr);
    }
  }
  
  void
  MicrosoftCXXABI::buildStructorSignature(const CXXMethodDecl *MD, StructorType T,
                                          SmallVectorImpl<CanQualType> &ArgTys) {
    // TODO: 'for base' flag
    if (T == StructorType::Deleting) {
      // The scalar deleting destructor takes an implicit int parameter.
      ArgTys.push_back(getContext().IntTy);
    }
    auto *CD = dyn_cast<CXXConstructorDecl>(MD);
    if (!CD)
      return;
  
    // All parameters are already in place except is_most_derived, which goes
    // after 'this' if it's variadic and last if it's not.
  
    const CXXRecordDecl *Class = CD->getParent();
    const FunctionProtoType *FPT = CD->getType()->castAs<FunctionProtoType>();
    if (Class->getNumVBases()) {
      if (FPT->isVariadic())
        ArgTys.insert(ArgTys.begin() + 1, getContext().IntTy);
      else
        ArgTys.push_back(getContext().IntTy);
    }
  }
  
  void MicrosoftCXXABI::EmitCXXDestructors(const CXXDestructorDecl *D) {
    // The TU defining a dtor is only guaranteed to emit a base destructor.  All
    // other destructor variants are delegating thunks.
    CGM.EmitGlobal(GlobalDecl(D, Dtor_Base));
  }
  
  CharUnits
  MicrosoftCXXABI::getVirtualFunctionPrologueThisAdjustment(GlobalDecl GD) {
    GD = GD.getCanonicalDecl();
    const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  
    GlobalDecl LookupGD = GD;
    if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
      // Complete destructors take a pointer to the complete object as a
      // parameter, thus don't need this adjustment.
      if (GD.getDtorType() == Dtor_Complete)
        return CharUnits();
  
      // There's no Dtor_Base in vftable but it shares the this adjustment with
      // the deleting one, so look it up instead.
      LookupGD = GlobalDecl(DD, Dtor_Deleting);
    }
  
    MicrosoftVTableContext::MethodVFTableLocation ML =
        CGM.getMicrosoftVTableContext().getMethodVFTableLocation(LookupGD);
    CharUnits Adjustment = ML.VFPtrOffset;
  
    // Normal virtual instance methods need to adjust from the vfptr that first
    // defined the virtual method to the virtual base subobject, but destructors
    // do not.  The vector deleting destructor thunk applies this adjustment for
    // us if necessary.
    if (isa<CXXDestructorDecl>(MD))
      Adjustment = CharUnits::Zero();
  
    if (ML.VBase) {
      const ASTRecordLayout &DerivedLayout =
          getContext().getASTRecordLayout(MD->getParent());
      Adjustment += DerivedLayout.getVBaseClassOffset(ML.VBase);
    }
  
    return Adjustment;
  }
  
  Address MicrosoftCXXABI::adjustThisArgumentForVirtualFunctionCall(
      CodeGenFunction &CGF, GlobalDecl GD, Address This,
      bool VirtualCall) {
    if (!VirtualCall) {
      // If the call of a virtual function is not virtual, we just have to
      // compensate for the adjustment the virtual function does in its prologue.
      CharUnits Adjustment = getVirtualFunctionPrologueThisAdjustment(GD);
      if (Adjustment.isZero())
        return This;
  
      This = CGF.Builder.CreateElementBitCast(This, CGF.Int8Ty);
      assert(Adjustment.isPositive());
      return CGF.Builder.CreateConstByteGEP(This, Adjustment);
    }
  
    GD = GD.getCanonicalDecl();
    const CXXMethodDecl *MD = cast<CXXMethodDecl>(GD.getDecl());
  
    GlobalDecl LookupGD = GD;
    if (const CXXDestructorDecl *DD = dyn_cast<CXXDestructorDecl>(MD)) {
      // Complete dtors take a pointer to the complete object,
      // thus don't need adjustment.
      if (GD.getDtorType() == Dtor_Complete)
        return This;
  
      // There's only Dtor_Deleting in vftable but it shares the this adjustment
      // with the base one, so look up the deleting one instead.
      LookupGD = GlobalDecl(DD, Dtor_Deleting);
    }
    MicrosoftVTableContext::MethodVFTableLocation ML =
        CGM.getMicrosoftVTableContext().getMethodVFTableLocation(LookupGD);
  
    CharUnits StaticOffset = ML.VFPtrOffset;
  
    // Base destructors expect 'this' to point to the beginning of the base
    // subobject, not the first vfptr that happens to contain the virtual dtor.
    // However, we still need to apply the virtual base adjustment.
    if (isa<CXXDestructorDecl>(MD) && GD.getDtorType() == Dtor_Base)
      StaticOffset = CharUnits::Zero();
  
    Address Result = This;
    if (ML.VBase) {
      Result = CGF.Builder.CreateElementBitCast(Result, CGF.Int8Ty);
      
      const CXXRecordDecl *Derived = MD->getParent();
      const CXXRecordDecl *VBase = ML.VBase;
      llvm::Value *VBaseOffset =
        GetVirtualBaseClassOffset(CGF, Result, Derived, VBase);
      llvm::Value *VBasePtr =
        CGF.Builder.CreateInBoundsGEP(Result.getPointer(), VBaseOffset);
      CharUnits VBaseAlign =
        CGF.CGM.getVBaseAlignment(Result.getAlignment(), Derived, VBase);
      Result = Address(VBasePtr, VBaseAlign);
    }
    if (!StaticOffset.isZero()) {
      assert(StaticOffset.isPositive());
      Result = CGF.Builder.CreateElementBitCast(Result, CGF.Int8Ty);
      if (ML.VBase) {
        // Non-virtual adjustment might result in a pointer outside the allocated
        // object, e.g. if the final overrider class is laid out after the virtual
        // base that declares a method in the most derived class.
        // FIXME: Update the code that emits this adjustment in thunks prologues.
        Result = CGF.Builder.CreateConstByteGEP(Result, StaticOffset);
      } else {
        Result = CGF.Builder.CreateConstInBoundsByteGEP(Result, StaticOffset);
      }
    }
    return Result;
  }
  
  void MicrosoftCXXABI::addImplicitStructorParams(CodeGenFunction &CGF,
                                                  QualType &ResTy,
                                                  FunctionArgList &Params) {
    ASTContext &Context = getContext();
    const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
    assert(isa<CXXConstructorDecl>(MD) || isa<CXXDestructorDecl>(MD));
    if (isa<CXXConstructorDecl>(MD) && MD->getParent()->getNumVBases()) {
      ImplicitParamDecl *IsMostDerived
        = ImplicitParamDecl::Create(Context, nullptr,
                                    CGF.CurGD.getDecl()->getLocation(),
                                    &Context.Idents.get("is_most_derived"),
                                    Context.IntTy);
      // The 'most_derived' parameter goes second if the ctor is variadic and last
      // if it's not.  Dtors can't be variadic.
      const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
      if (FPT->isVariadic())
        Params.insert(Params.begin() + 1, IsMostDerived);
      else
        Params.push_back(IsMostDerived);
      getStructorImplicitParamDecl(CGF) = IsMostDerived;
    } else if (isDeletingDtor(CGF.CurGD)) {
      ImplicitParamDecl *ShouldDelete
        = ImplicitParamDecl::Create(Context, nullptr,
                                    CGF.CurGD.getDecl()->getLocation(),
                                    &Context.Idents.get("should_call_delete"),
                                    Context.IntTy);
      Params.push_back(ShouldDelete);
      getStructorImplicitParamDecl(CGF) = ShouldDelete;
    }
  }
  
  llvm::Value *MicrosoftCXXABI::adjustThisParameterInVirtualFunctionPrologue(
      CodeGenFunction &CGF, GlobalDecl GD, llvm::Value *This) {
    // In this ABI, every virtual function takes a pointer to one of the
    // subobjects that first defines it as the 'this' parameter, rather than a
    // pointer to the final overrider subobject. Thus, we need to adjust it back
    // to the final overrider subobject before use.
    // See comments in the MicrosoftVFTableContext implementation for the details.
    CharUnits Adjustment = getVirtualFunctionPrologueThisAdjustment(GD);
    if (Adjustment.isZero())
      return This;
  
    unsigned AS = cast<llvm::PointerType>(This->getType())->getAddressSpace();
    llvm::Type *charPtrTy = CGF.Int8Ty->getPointerTo(AS),
               *thisTy = This->getType();
  
    This = CGF.Builder.CreateBitCast(This, charPtrTy);
    assert(Adjustment.isPositive());
    This = CGF.Builder.CreateConstInBoundsGEP1_32(CGF.Int8Ty, This,
                                                  -Adjustment.getQuantity());
    return CGF.Builder.CreateBitCast(This, thisTy);
  }
  
  void MicrosoftCXXABI::EmitInstanceFunctionProlog(CodeGenFunction &CGF) {
    EmitThisParam(CGF);
  
    /// 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);
    else if (hasMostDerivedReturn(CGF.CurGD))
      CGF.Builder.CreateStore(CGF.EmitCastToVoidPtr(getThisValue(CGF)),
                              CGF.ReturnValue);
  
    const CXXMethodDecl *MD = cast<CXXMethodDecl>(CGF.CurGD.getDecl());
    if (isa<CXXConstructorDecl>(MD) && MD->getParent()->getNumVBases()) {
      assert(getStructorImplicitParamDecl(CGF) &&
             "no implicit parameter for a constructor with virtual bases?");
      getStructorImplicitParamValue(CGF)
        = CGF.Builder.CreateLoad(
            CGF.GetAddrOfLocalVar(getStructorImplicitParamDecl(CGF)),
            "is_most_derived");
    }
  
    if (isDeletingDtor(CGF.CurGD)) {
      assert(getStructorImplicitParamDecl(CGF) &&
             "no implicit parameter for a deleting destructor?");
      getStructorImplicitParamValue(CGF)
        = CGF.Builder.CreateLoad(
            CGF.GetAddrOfLocalVar(getStructorImplicitParamDecl(CGF)),
            "should_call_delete");
    }
  }
  
  unsigned MicrosoftCXXABI::addImplicitConstructorArgs(
      CodeGenFunction &CGF, const CXXConstructorDecl *D, CXXCtorType Type,
      bool ForVirtualBase, bool Delegating, CallArgList &Args) {
    assert(Type == Ctor_Complete || Type == Ctor_Base);
  
    // Check if we need a 'most_derived' parameter.
    if (!D->getParent()->getNumVBases())
      return 0;
  
    // Add the 'most_derived' argument second if we are variadic or last if not.
    const FunctionProtoType *FPT = D->getType()->castAs<FunctionProtoType>();
    llvm::Value *MostDerivedArg =
        llvm::ConstantInt::get(CGM.Int32Ty, Type == Ctor_Complete);
    RValue RV = RValue::get(MostDerivedArg);
    if (MostDerivedArg) {
      if (FPT->isVariadic())
        Args.insert(Args.begin() + 1,
                    CallArg(RV, getContext().IntTy, /*needscopy=*/false));
      else
        Args.add(RV, getContext().IntTy);
    }
  
    return 1;  // Added one arg.
  }
  
  void MicrosoftCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
                                           const CXXDestructorDecl *DD,
                                           CXXDtorType Type, bool ForVirtualBase,
                                           bool Delegating, Address This) {
    llvm::Value *Callee = CGM.getAddrOfCXXStructor(DD, getFromDtorType(Type));
  
    if (DD->isVirtual()) {
      assert(Type != CXXDtorType::Dtor_Deleting &&
             "The deleting destructor should only be called via a virtual call");
      This = adjustThisArgumentForVirtualFunctionCall(CGF, GlobalDecl(DD, Type),
                                                      This, false);
    }
  
    CGF.EmitCXXStructorCall(DD, Callee, ReturnValueSlot(), This.getPointer(),
                            /*ImplicitParam=*/nullptr,
                            /*ImplicitParamTy=*/QualType(), nullptr,
                            getFromDtorType(Type));
  }
  
  void MicrosoftCXXABI::emitVTableBitSetEntries(VPtrInfo *Info,
                                                const CXXRecordDecl *RD,
                                                llvm::GlobalVariable *VTable) {
    if (!getContext().getLangOpts().Sanitize.has(SanitizerKind::CFIVCall) &&
        !getContext().getLangOpts().Sanitize.has(SanitizerKind::CFINVCall) &&
        !getContext().getLangOpts().Sanitize.has(SanitizerKind::CFIDerivedCast) &&
        !getContext().getLangOpts().Sanitize.has(SanitizerKind::CFIUnrelatedCast))
      return;
  
    llvm::NamedMDNode *BitsetsMD =
        CGM.getModule().getOrInsertNamedMetadata("llvm.bitsets");
  
    // The location of the first virtual function pointer in the virtual table,
    // aka the "address point" on Itanium. This is at offset 0 if RTTI is
    // disabled, or sizeof(void*) if RTTI is enabled.
    CharUnits AddressPoint =
        getContext().getLangOpts().RTTIData
            ? getContext().toCharUnitsFromBits(
                  getContext().getTargetInfo().getPointerWidth(0))
            : CharUnits::Zero();
  
    if (Info->PathToBaseWithVPtr.empty()) {
      if (!CGM.IsCFIBlacklistedRecord(RD))
        CGM.CreateVTableBitSetEntry(BitsetsMD, VTable, AddressPoint, RD);
      return;
    }
  
    // Add a bitset entry for the least derived base belonging to this vftable.
    if (!CGM.IsCFIBlacklistedRecord(Info->PathToBaseWithVPtr.back()))
      CGM.CreateVTableBitSetEntry(BitsetsMD, VTable, AddressPoint,
                                  Info->PathToBaseWithVPtr.back());
  
    // Add a bitset entry for each derived class that is laid out at the same
    // offset as the least derived base.
    for (unsigned I = Info->PathToBaseWithVPtr.size() - 1; I != 0; --I) {
      const CXXRecordDecl *DerivedRD = Info->PathToBaseWithVPtr[I - 1];
      const CXXRecordDecl *BaseRD = Info->PathToBaseWithVPtr[I];
  
      const ASTRecordLayout &Layout =
          getContext().getASTRecordLayout(DerivedRD);
      CharUnits Offset;
      auto VBI = Layout.getVBaseOffsetsMap().find(BaseRD);
      if (VBI == Layout.getVBaseOffsetsMap().end())
        Offset = Layout.getBaseClassOffset(BaseRD);
      else
        Offset = VBI->second.VBaseOffset;
      if (!Offset.isZero())
        return;
      if (!CGM.IsCFIBlacklistedRecord(DerivedRD))
        CGM.CreateVTableBitSetEntry(BitsetsMD, VTable, AddressPoint, DerivedRD);
    }
  
    // Finally do the same for the most derived class.
    if (Info->FullOffsetInMDC.isZero() && !CGM.IsCFIBlacklistedRecord(RD))
      CGM.CreateVTableBitSetEntry(BitsetsMD, VTable, AddressPoint, RD);
  }
  
  void MicrosoftCXXABI::emitVTableDefinitions(CodeGenVTables &CGVT,
                                              const CXXRecordDecl *RD) {
    MicrosoftVTableContext &VFTContext = CGM.getMicrosoftVTableContext();
    const VPtrInfoVector &VFPtrs = VFTContext.getVFPtrOffsets(RD);
  
    for (VPtrInfo *Info : VFPtrs) {
      llvm::GlobalVariable *VTable = getAddrOfVTable(RD, Info->FullOffsetInMDC);
      if (VTable->hasInitializer())
        continue;
  
      llvm::Constant *RTTI = getContext().getLangOpts().RTTIData
                                 ? getMSCompleteObjectLocator(RD, Info)
                                 : nullptr;
  
      const VTableLayout &VTLayout =
        VFTContext.getVFTableLayout(RD, Info->FullOffsetInMDC);
      llvm::Constant *Init = CGVT.CreateVTableInitializer(
          RD, VTLayout.vtable_component_begin(),
          VTLayout.getNumVTableComponents(), VTLayout.vtable_thunk_begin(),
          VTLayout.getNumVTableThunks(), RTTI);
  
      VTable->setInitializer(Init);
  
      emitVTableBitSetEntries(Info, RD, VTable);
    }
  }
  
  bool MicrosoftCXXABI::isVirtualOffsetNeededForVTableField(
      CodeGenFunction &CGF, CodeGenFunction::VPtr Vptr) {
    return Vptr.NearestVBase != nullptr;
  }
  
  llvm::Value *MicrosoftCXXABI::getVTableAddressPointInStructor(
      CodeGenFunction &CGF, const CXXRecordDecl *VTableClass, BaseSubobject Base,
      const CXXRecordDecl *NearestVBase) {
    llvm::Constant *VTableAddressPoint = getVTableAddressPoint(Base, VTableClass);
    if (!VTableAddressPoint) {
      assert(Base.getBase()->getNumVBases() &&
             !getContext().getASTRecordLayout(Base.getBase()).hasOwnVFPtr());
    }
    return VTableAddressPoint;
  }
  
  static void mangleVFTableName(MicrosoftMangleContext &MangleContext,
                                const CXXRecordDecl *RD, const VPtrInfo *VFPtr,
                                SmallString<256> &Name) {
    llvm::raw_svector_ostream Out(Name);
    MangleContext.mangleCXXVFTable(RD, VFPtr->MangledPath, Out);
  }
  
  llvm::Constant *
  MicrosoftCXXABI::getVTableAddressPoint(BaseSubobject Base,
                                         const CXXRecordDecl *VTableClass) {
    (void)getAddrOfVTable(VTableClass, Base.getBaseOffset());
    VFTableIdTy ID(VTableClass, Base.getBaseOffset());
    return VFTablesMap[ID];
  }
  
  llvm::Constant *MicrosoftCXXABI::getVTableAddressPointForConstExpr(
      BaseSubobject Base, const CXXRecordDecl *VTableClass) {
    llvm::Constant *VFTable = getVTableAddressPoint(Base, VTableClass);
    assert(VFTable && "Couldn't find a vftable for the given base?");
    return VFTable;
  }
  
  llvm::GlobalVariable *MicrosoftCXXABI::getAddrOfVTable(const CXXRecordDecl *RD,
                                                         CharUnits VPtrOffset) {
    // getAddrOfVTable may return 0 if asked to get an address of a vtable which
    // shouldn't be used in the given record type. We want to cache this result in
    // VFTablesMap, thus a simple zero check is not sufficient.
  
    VFTableIdTy ID(RD, VPtrOffset);
    VTablesMapTy::iterator I;
    bool Inserted;
    std::tie(I, Inserted) = VTablesMap.insert(std::make_pair(ID, nullptr));
    if (!Inserted)
      return I->second;
  
    llvm::GlobalVariable *&VTable = I->second;
  
    MicrosoftVTableContext &VTContext = CGM.getMicrosoftVTableContext();
    const VPtrInfoVector &VFPtrs = VTContext.getVFPtrOffsets(RD);
  
    if (DeferredVFTables.insert(RD).second) {
      // We haven't processed this record type before.
      // Queue up this v-table for possible deferred emission.
      CGM.addDeferredVTable(RD);
  
  #ifndef NDEBUG
      // Create all the vftables at once in order to make sure each vftable has
      // a unique mangled name.
      llvm::StringSet<> ObservedMangledNames;
      for (size_t J = 0, F = VFPtrs.size(); J != F; ++J) {
        SmallString<256> Name;
        mangleVFTableName(getMangleContext(), RD, VFPtrs[J], Name);
        if (!ObservedMangledNames.insert(Name.str()).second)
          llvm_unreachable("Already saw this mangling before?");
      }
  #endif
    }
  
    VPtrInfo *const *VFPtrI =
        std::find_if(VFPtrs.begin(), VFPtrs.end(), [&](VPtrInfo *VPI) {
          return VPI->FullOffsetInMDC == VPtrOffset;
        });
    if (VFPtrI == VFPtrs.end()) {
      VFTablesMap[ID] = nullptr;
      return nullptr;
    }
    VPtrInfo *VFPtr = *VFPtrI;
  
    SmallString<256> VFTableName;
    mangleVFTableName(getMangleContext(), RD, VFPtr, VFTableName);
  
    llvm::GlobalValue::LinkageTypes VFTableLinkage = CGM.getVTableLinkage(RD);
    bool VFTableComesFromAnotherTU =
        llvm::GlobalValue::isAvailableExternallyLinkage(VFTableLinkage) ||
        llvm::GlobalValue::isExternalLinkage(VFTableLinkage);
    bool VTableAliasIsRequred =
        !VFTableComesFromAnotherTU && getContext().getLangOpts().RTTIData;
  
    if (llvm::GlobalValue *VFTable =
            CGM.getModule().getNamedGlobal(VFTableName)) {
      VFTablesMap[ID] = VFTable;
      VTable = VTableAliasIsRequred
                   ? cast<llvm::GlobalVariable>(
                         cast<llvm::GlobalAlias>(VFTable)->getBaseObject())
                   : cast<llvm::GlobalVariable>(VFTable);
      return VTable;
    }
  
    uint64_t NumVTableSlots =
        VTContext.getVFTableLayout(RD, VFPtr->FullOffsetInMDC)
            .getNumVTableComponents();
    llvm::GlobalValue::LinkageTypes VTableLinkage =
        VTableAliasIsRequred ? llvm::GlobalValue::PrivateLinkage : VFTableLinkage;
  
    StringRef VTableName = VTableAliasIsRequred ? StringRef() : VFTableName.str();
  
    llvm::ArrayType *VTableType =
        llvm::ArrayType::get(CGM.Int8PtrTy, NumVTableSlots);
  
    // Create a backing variable for the contents of VTable.  The VTable may
    // or may not include space for a pointer to RTTI data.
    llvm::GlobalValue *VFTable;
    VTable = new llvm::GlobalVariable(CGM.getModule(), VTableType,
                                      /*isConstant=*/true, VTableLinkage,
                                      /*Initializer=*/nullptr, VTableName);
    VTable->setUnnamedAddr(true);
  
    llvm::Comdat *C = nullptr;
    if (!VFTableComesFromAnotherTU &&
        (llvm::GlobalValue::isWeakForLinker(VFTableLinkage) ||
         (llvm::GlobalValue::isLocalLinkage(VFTableLinkage) &&
          VTableAliasIsRequred)))
      C = CGM.getModule().getOrInsertComdat(VFTableName.str());
  
    // Only insert a pointer into the VFTable for RTTI data if we are not
    // importing it.  We never reference the RTTI data directly so there is no
    // need to make room for it.
    if (VTableAliasIsRequred) {
      llvm::Value *GEPIndices[] = {llvm::ConstantInt::get(CGM.IntTy, 0),
                                   llvm::ConstantInt::get(CGM.IntTy, 1)};
      // Create a GEP which points just after the first entry in the VFTable,
      // this should be the location of the first virtual method.
      llvm::Constant *VTableGEP = llvm::ConstantExpr::getInBoundsGetElementPtr(
          VTable->getValueType(), VTable, GEPIndices);
      if (llvm::GlobalValue::isWeakForLinker(VFTableLinkage)) {
        VFTableLinkage = llvm::GlobalValue::ExternalLinkage;
        if (C)
          C->setSelectionKind(llvm::Comdat::Largest);
      }
      VFTable = llvm::GlobalAlias::create(CGM.Int8PtrTy,
                                          /*AddressSpace=*/0, VFTableLinkage,
                                          VFTableName.str(), VTableGEP,
                                          &CGM.getModule());
      VFTable->setUnnamedAddr(true);
    } else {
      // We don't need a GlobalAlias to be a symbol for the VTable if we won't
      // be referencing any RTTI data.
      // The GlobalVariable will end up being an appropriate definition of the
      // VFTable.
      VFTable = VTable;
    }
    if (C)
      VTable->setComdat(C);
  
    if (RD->hasAttr<DLLImportAttr>())
      VFTable->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
    else if (RD->hasAttr<DLLExportAttr>())
      VFTable->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
  
    VFTablesMap[ID] = VFTable;
    return VTable;
  }
  
  // Compute the identity of the most derived class whose virtual table is located
  // at the given offset into RD.
  static const CXXRecordDecl *getClassAtVTableLocation(ASTContext &Ctx,
                                                       const CXXRecordDecl *RD,
                                                       CharUnits Offset) {
    if (Offset.isZero())
      return RD;
  
    const ASTRecordLayout &Layout = Ctx.getASTRecordLayout(RD);
    const CXXRecordDecl *MaxBase = nullptr;
    CharUnits MaxBaseOffset;
    for (auto &&B : RD->bases()) {
      const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
      CharUnits BaseOffset = Layout.getBaseClassOffset(Base);
      if (BaseOffset <= Offset && BaseOffset >= MaxBaseOffset) {
        MaxBase = Base;
        MaxBaseOffset = BaseOffset;
      }
    }
    for (auto &&B : RD->vbases()) {
      const CXXRecordDecl *Base = B.getType()->getAsCXXRecordDecl();
      CharUnits BaseOffset = Layout.getVBaseClassOffset(Base);
      if (BaseOffset <= Offset && BaseOffset >= MaxBaseOffset) {
        MaxBase = Base;
        MaxBaseOffset = BaseOffset;
      }
    }
    assert(MaxBase);
    return getClassAtVTableLocation(Ctx, MaxBase, Offset - MaxBaseOffset);
  }
  
  // Compute the identity of the most derived class whose virtual table is located
  // at the MethodVFTableLocation ML.
  static const CXXRecordDecl *
  getClassAtVTableLocation(ASTContext &Ctx, GlobalDecl GD,
                           MicrosoftVTableContext::MethodVFTableLocation &ML) {
    const CXXRecordDecl *RD = ML.VBase;
    if (!RD)
      RD = cast<CXXMethodDecl>(GD.getDecl())->getParent();
  
    return getClassAtVTableLocation(Ctx, RD, ML.VFPtrOffset);
  }
  
  llvm::Value *MicrosoftCXXABI::getVirtualFunctionPointer(CodeGenFunction &CGF,
                                                          GlobalDecl GD,
                                                          Address This,
                                                          llvm::Type *Ty,
                                                          SourceLocation Loc) {
    GD = GD.getCanonicalDecl();
    CGBuilderTy &Builder = CGF.Builder;
  
    Ty = Ty->getPointerTo()->getPointerTo();
    Address VPtr =
        adjustThisArgumentForVirtualFunctionCall(CGF, GD, This, true);
  
    auto *MethodDecl = cast<CXXMethodDecl>(GD.getDecl());
    llvm::Value *VTable = CGF.GetVTablePtr(VPtr, Ty, MethodDecl->getParent());
  
    MicrosoftVTableContext::MethodVFTableLocation ML =
        CGM.getMicrosoftVTableContext().getMethodVFTableLocation(GD);
    if (CGF.SanOpts.has(SanitizerKind::CFIVCall))
      CGF.EmitVTablePtrCheck(getClassAtVTableLocation(getContext(), GD, ML),
                             VTable, CodeGenFunction::CFITCK_VCall, Loc);
  
    llvm::Value *VFuncPtr =
        Builder.CreateConstInBoundsGEP1_64(VTable, ML.Index, "vfn");
    return Builder.CreateAlignedLoad(VFuncPtr, CGF.getPointerAlign());
  }
  
  llvm::Value *MicrosoftCXXABI::EmitVirtualDestructorCall(
      CodeGenFunction &CGF, const CXXDestructorDecl *Dtor, CXXDtorType DtorType,
      Address This, const CXXMemberCallExpr *CE) {
    assert(CE == nullptr || CE->arg_begin() == CE->arg_end());
    assert(DtorType == Dtor_Deleting || DtorType == Dtor_Complete);
  
    // We have only one destructor in the vftable but can get both behaviors
    // by passing an implicit int parameter.
    GlobalDecl GD(Dtor, Dtor_Deleting);
    const CGFunctionInfo *FInfo = &CGM.getTypes().arrangeCXXStructorDeclaration(
        Dtor, StructorType::Deleting);
    llvm::Type *Ty = CGF.CGM.getTypes().GetFunctionType(*FInfo);
    llvm::Value *Callee = getVirtualFunctionPointer(
        CGF, GD, This, Ty, CE ? CE->getLocStart() : SourceLocation());
  
    ASTContext &Context = getContext();
    llvm::Value *ImplicitParam = llvm::ConstantInt::get(
        llvm::IntegerType::getInt32Ty(CGF.getLLVMContext()),
        DtorType == Dtor_Deleting);
  
    This = adjustThisArgumentForVirtualFunctionCall(CGF, GD, This, true);
    RValue RV = CGF.EmitCXXStructorCall(Dtor, Callee, ReturnValueSlot(),
                                        This.getPointer(),
                                        ImplicitParam, Context.IntTy, CE,
                                        StructorType::Deleting);
    return RV.getScalarVal();
  }
  
  const VBTableGlobals &
  MicrosoftCXXABI::enumerateVBTables(const CXXRecordDecl *RD) {
    // At this layer, we can key the cache off of a single class, which is much
    // easier than caching each vbtable individually.
    llvm::DenseMap<const CXXRecordDecl*, VBTableGlobals>::iterator Entry;
    bool Added;
    std::tie(Entry, Added) =
        VBTablesMap.insert(std::make_pair(RD, VBTableGlobals()));
    VBTableGlobals &VBGlobals = Entry->second;
    if (!Added)
      return VBGlobals;
  
    MicrosoftVTableContext &Context = CGM.getMicrosoftVTableContext();
    VBGlobals.VBTables = &Context.enumerateVBTables(RD);
  
    // Cache the globals for all vbtables so we don't have to recompute the
    // mangled names.
    llvm::GlobalVariable::LinkageTypes Linkage = CGM.getVTableLinkage(RD);
    for (VPtrInfoVector::const_iterator I = VBGlobals.VBTables->begin(),
                                        E = VBGlobals.VBTables->end();
         I != E; ++I) {
      VBGlobals.Globals.push_back(getAddrOfVBTable(**I, RD, Linkage));
    }
  
    return VBGlobals;
  }
  
  llvm::Function *MicrosoftCXXABI::EmitVirtualMemPtrThunk(
      const CXXMethodDecl *MD,
      const MicrosoftVTableContext::MethodVFTableLocation &ML) {
    assert(!isa<CXXConstructorDecl>(MD) && !isa<CXXDestructorDecl>(MD) &&
           "can't form pointers to ctors or virtual dtors");
  
    // Calculate the mangled name.
    SmallString<256> ThunkName;
    llvm::raw_svector_ostream Out(ThunkName);
    getMangleContext().mangleVirtualMemPtrThunk(MD, Out);
  
    // If the thunk has been generated previously, just return it.
    if (llvm::GlobalValue *GV = CGM.getModule().getNamedValue(ThunkName))
      return cast<llvm::Function>(GV);
  
    // Create the llvm::Function.
    const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeMSMemberPointerThunk(MD);
    llvm::FunctionType *ThunkTy = CGM.getTypes().GetFunctionType(FnInfo);
    llvm::Function *ThunkFn =
        llvm::Function::Create(ThunkTy, llvm::Function::ExternalLinkage,
                               ThunkName.str(), &CGM.getModule());
    assert(ThunkFn->getName() == ThunkName && "name was uniqued!");
  
    ThunkFn->setLinkage(MD->isExternallyVisible()
                            ? llvm::GlobalValue::LinkOnceODRLinkage
                            : llvm::GlobalValue::InternalLinkage);
    if (MD->isExternallyVisible())
      ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
  
    CGM.SetLLVMFunctionAttributes(MD, FnInfo, ThunkFn);
    CGM.SetLLVMFunctionAttributesForDefinition(MD, ThunkFn);
  
    // Add the "thunk" attribute so that LLVM knows that the return type is
    // meaningless. These thunks can be used to call functions with differing
    // return types, and the caller is required to cast the prototype
    // appropriately to extract the correct value.
    ThunkFn->addFnAttr("thunk");
  
    // These thunks can be compared, so they are not unnamed.
    ThunkFn->setUnnamedAddr(false);
  
    // Start codegen.
    CodeGenFunction CGF(CGM);
    CGF.CurGD = GlobalDecl(MD);
    CGF.CurFuncIsThunk = true;
  
    // Build FunctionArgs, but only include the implicit 'this' parameter
    // declaration.
    FunctionArgList FunctionArgs;
    buildThisParam(CGF, FunctionArgs);
  
    // Start defining the function.
    CGF.StartFunction(GlobalDecl(), FnInfo.getReturnType(), ThunkFn, FnInfo,
                      FunctionArgs, MD->getLocation(), SourceLocation());
    EmitThisParam(CGF);
  
    // Load the vfptr and then callee from the vftable.  The callee should have
    // adjusted 'this' so that the vfptr is at offset zero.
    llvm::Value *VTable = CGF.GetVTablePtr(
        getThisAddress(CGF), ThunkTy->getPointerTo()->getPointerTo(), MD->getParent());
  
    llvm::Value *VFuncPtr =
        CGF.Builder.CreateConstInBoundsGEP1_64(VTable, ML.Index, "vfn");
    llvm::Value *Callee =
      CGF.Builder.CreateAlignedLoad(VFuncPtr, CGF.getPointerAlign());
  
    CGF.EmitMustTailThunk(MD, getThisValue(CGF), Callee);
  
    return ThunkFn;
  }
  
  void MicrosoftCXXABI::emitVirtualInheritanceTables(const CXXRecordDecl *RD) {
    const VBTableGlobals &VBGlobals = enumerateVBTables(RD);
    for (unsigned I = 0, E = VBGlobals.VBTables->size(); I != E; ++I) {
      const VPtrInfo *VBT = (*VBGlobals.VBTables)[I];
      llvm::GlobalVariable *GV = VBGlobals.Globals[I];
      if (GV->isDeclaration())
        emitVBTableDefinition(*VBT, RD, GV);
    }
  }
  
  llvm::GlobalVariable *
  MicrosoftCXXABI::getAddrOfVBTable(const VPtrInfo &VBT, const CXXRecordDecl *RD,
                                    llvm::GlobalVariable::LinkageTypes Linkage) {
    SmallString<256> OutName;
    llvm::raw_svector_ostream Out(OutName);
    getMangleContext().mangleCXXVBTable(RD, VBT.MangledPath, Out);
    StringRef Name = OutName.str();
  
    llvm::ArrayType *VBTableType =
        llvm::ArrayType::get(CGM.IntTy, 1 + VBT.ReusingBase->getNumVBases());
  
    assert(!CGM.getModule().getNamedGlobal(Name) &&
           "vbtable with this name already exists: mangling bug?");
    llvm::GlobalVariable *GV =
        CGM.CreateOrReplaceCXXRuntimeVariable(Name, VBTableType, Linkage);
    GV->setUnnamedAddr(true);
  
    if (RD->hasAttr<DLLImportAttr>())
      GV->setDLLStorageClass(llvm::GlobalValue::DLLImportStorageClass);
    else if (RD->hasAttr<DLLExportAttr>())
      GV->setDLLStorageClass(llvm::GlobalValue::DLLExportStorageClass);
  
    if (!GV->hasExternalLinkage())
      emitVBTableDefinition(VBT, RD, GV);
  
    return GV;
  }
  
  void MicrosoftCXXABI::emitVBTableDefinition(const VPtrInfo &VBT,
                                              const CXXRecordDecl *RD,
                                              llvm::GlobalVariable *GV) const {
    const CXXRecordDecl *ReusingBase = VBT.ReusingBase;
  
    assert(RD->getNumVBases() && ReusingBase->getNumVBases() &&
           "should only emit vbtables for classes with vbtables");
  
    const ASTRecordLayout &BaseLayout =
        getContext().getASTRecordLayout(VBT.BaseWithVPtr);
    const ASTRecordLayout &DerivedLayout = getContext().getASTRecordLayout(RD);
  
    SmallVector<llvm::Constant *, 4> Offsets(1 + ReusingBase->getNumVBases(),
                                             nullptr);
  
    // The offset from ReusingBase's vbptr to itself always leads.
    CharUnits VBPtrOffset = BaseLayout.getVBPtrOffset();
    Offsets[0] = llvm::ConstantInt::get(CGM.IntTy, -VBPtrOffset.getQuantity());
  
    MicrosoftVTableContext &Context = CGM.getMicrosoftVTableContext();
    for (const auto &I : ReusingBase->vbases()) {
      const CXXRecordDecl *VBase = I.getType()->getAsCXXRecordDecl();
      CharUnits Offset = DerivedLayout.getVBaseClassOffset(VBase);
      assert(!Offset.isNegative());
  
      // Make it relative to the subobject vbptr.
      CharUnits CompleteVBPtrOffset = VBT.NonVirtualOffset + VBPtrOffset;
      if (VBT.getVBaseWithVPtr())
        CompleteVBPtrOffset +=
            DerivedLayout.getVBaseClassOffset(VBT.getVBaseWithVPtr());
      Offset -= CompleteVBPtrOffset;
  
      unsigned VBIndex = Context.getVBTableIndex(ReusingBase, VBase);
      assert(Offsets[VBIndex] == nullptr && "The same vbindex seen twice?");
      Offsets[VBIndex] = llvm::ConstantInt::get(CGM.IntTy, Offset.getQuantity());
    }
  
    assert(Offsets.size() ==
           cast<llvm::ArrayType>(cast<llvm::PointerType>(GV->getType())
                                 ->getElementType())->getNumElements());
    llvm::ArrayType *VBTableType =
      llvm::ArrayType::get(CGM.IntTy, Offsets.size());
    llvm::Constant *Init = llvm::ConstantArray::get(VBTableType, Offsets);
    GV->setInitializer(Init);
  }
  
  llvm::Value *MicrosoftCXXABI::performThisAdjustment(CodeGenFunction &CGF,
                                                      Address This,
                                                      const ThisAdjustment &TA) {
    if (TA.isEmpty())
      return This.getPointer();
  
    This = CGF.Builder.CreateElementBitCast(This, CGF.Int8Ty);
  
    llvm::Value *V;
    if (TA.Virtual.isEmpty()) {
      V = This.getPointer();
    } else {
      assert(TA.Virtual.Microsoft.VtordispOffset < 0);
      // Adjust the this argument based on the vtordisp value.
      Address VtorDispPtr =
          CGF.Builder.CreateConstInBoundsByteGEP(This,
                   CharUnits::fromQuantity(TA.Virtual.Microsoft.VtordispOffset));
      VtorDispPtr = CGF.Builder.CreateElementBitCast(VtorDispPtr, CGF.Int32Ty);
      llvm::Value *VtorDisp = CGF.Builder.CreateLoad(VtorDispPtr, "vtordisp");
      V = CGF.Builder.CreateGEP(This.getPointer(),
                                CGF.Builder.CreateNeg(VtorDisp));
  
      // Unfortunately, having applied the vtordisp means that we no
      // longer really have a known alignment for the vbptr step.
      // We'll assume the vbptr is pointer-aligned.
  
      if (TA.Virtual.Microsoft.VBPtrOffset) {
        // If the final overrider is defined in a virtual base other than the one
        // that holds the vfptr, we have to use a vtordispex thunk which looks up
        // the vbtable of the derived class.
        assert(TA.Virtual.Microsoft.VBPtrOffset > 0);
        assert(TA.Virtual.Microsoft.VBOffsetOffset >= 0);
        llvm::Value *VBPtr;
        llvm::Value *VBaseOffset =
            GetVBaseOffsetFromVBPtr(CGF, Address(V, CGF.getPointerAlign()),
                                    -TA.Virtual.Microsoft.VBPtrOffset,
                                    TA.Virtual.Microsoft.VBOffsetOffset, &VBPtr);
        V = CGF.Builder.CreateInBoundsGEP(VBPtr, VBaseOffset);
      }
    }
  
    if (TA.NonVirtual) {
      // Non-virtual adjustment might result in a pointer outside the allocated
      // object, e.g. if the final overrider class is laid out after the virtual
      // base that declares a method in the most derived class.
      V = CGF.Builder.CreateConstGEP1_32(V, TA.NonVirtual);
    }
  
    // Don't need to bitcast back, the call CodeGen will handle this.
    return V;
  }
  
  llvm::Value *
  MicrosoftCXXABI::performReturnAdjustment(CodeGenFunction &CGF, Address Ret,
                                           const ReturnAdjustment &RA) {
    if (RA.isEmpty())
      return Ret.getPointer();
  
    auto OrigTy = Ret.getType();
    Ret = CGF.Builder.CreateElementBitCast(Ret, CGF.Int8Ty);
  
    llvm::Value *V = Ret.getPointer();
    if (RA.Virtual.Microsoft.VBIndex) {
      assert(RA.Virtual.Microsoft.VBIndex > 0);
      int32_t IntSize = CGF.getIntSize().getQuantity();
      llvm::Value *VBPtr;
      llvm::Value *VBaseOffset =
          GetVBaseOffsetFromVBPtr(CGF, Ret, RA.Virtual.Microsoft.VBPtrOffset,
                                  IntSize * RA.Virtual.Microsoft.VBIndex, &VBPtr);
      V = CGF.Builder.CreateInBoundsGEP(VBPtr, VBaseOffset);
    }
  
    if (RA.NonVirtual)
      V = CGF.Builder.CreateConstInBoundsGEP1_32(CGF.Int8Ty, V, RA.NonVirtual);
  
    // Cast back to the original type.
    return CGF.Builder.CreateBitCast(V, OrigTy);
  }
  
  bool MicrosoftCXXABI::requiresArrayCookie(const CXXDeleteExpr *expr,
                                     QualType elementType) {
    // Microsoft seems to completely ignore the possibility of a
    // two-argument usual deallocation function.
    return elementType.isDestructedType();
  }
  
  bool MicrosoftCXXABI::requiresArrayCookie(const CXXNewExpr *expr) {
    // Microsoft seems to completely ignore the possibility of a
    // two-argument usual deallocation function.
    return expr->getAllocatedType().isDestructedType();
  }
  
  CharUnits MicrosoftCXXABI::getArrayCookieSizeImpl(QualType type) {
    // The array cookie is always a size_t; we then pad that out to the
    // alignment of the element type.
    ASTContext &Ctx = getContext();
    return std::max(Ctx.getTypeSizeInChars(Ctx.getSizeType()),
                    Ctx.getTypeAlignInChars(type));
  }
  
  llvm::Value *MicrosoftCXXABI::readArrayCookieImpl(CodeGenFunction &CGF,
                                                    Address allocPtr,
                                                    CharUnits cookieSize) {
    Address numElementsPtr =
      CGF.Builder.CreateElementBitCast(allocPtr, CGF.SizeTy);
    return CGF.Builder.CreateLoad(numElementsPtr);
  }
  
  Address MicrosoftCXXABI::InitializeArrayCookie(CodeGenFunction &CGF,
                                                 Address newPtr,
                                                 llvm::Value *numElements,
                                                 const CXXNewExpr *expr,
                                                 QualType elementType) {
    assert(requiresArrayCookie(expr));
  
    // The size of the cookie.
    CharUnits cookieSize = getArrayCookieSizeImpl(elementType);
  
    // Compute an offset to the cookie.
    Address cookiePtr = newPtr;
  
    // Write the number of elements into the appropriate slot.
    Address numElementsPtr
      = CGF.Builder.CreateElementBitCast(cookiePtr, CGF.SizeTy);
    CGF.Builder.CreateStore(numElements, numElementsPtr);
  
    // Finally, compute a pointer to the actual data buffer by skipping
    // over the cookie completely.
    return CGF.Builder.CreateConstInBoundsByteGEP(newPtr, cookieSize);
  }
  
  static void emitGlobalDtorWithTLRegDtor(CodeGenFunction &CGF, const VarDecl &VD,
                                          llvm::Constant *Dtor,
                                          llvm::Constant *Addr) {
    // Create a function which calls the destructor.
    llvm::Constant *DtorStub = CGF.createAtExitStub(VD, Dtor, Addr);
  
    // extern "C" int __tlregdtor(void (*f)(void));
    llvm::FunctionType *TLRegDtorTy = llvm::FunctionType::get(
        CGF.IntTy, DtorStub->getType(), /*IsVarArg=*/false);
  
    llvm::Constant *TLRegDtor =
        CGF.CGM.CreateRuntimeFunction(TLRegDtorTy, "__tlregdtor");
    if (llvm::Function *TLRegDtorFn = dyn_cast<llvm::Function>(TLRegDtor))
      TLRegDtorFn->setDoesNotThrow();
  
    CGF.EmitNounwindRuntimeCall(TLRegDtor, DtorStub);
  }
  
  void MicrosoftCXXABI::registerGlobalDtor(CodeGenFunction &CGF, const VarDecl &D,
                                           llvm::Constant *Dtor,
                                           llvm::Constant *Addr) {
    if (D.getTLSKind())
      return emitGlobalDtorWithTLRegDtor(CGF, D, Dtor, Addr);
  
    // The default behavior is to use atexit.
    CGF.registerGlobalDtorWithAtExit(D, Dtor, Addr);
  }
  
  void MicrosoftCXXABI::EmitThreadLocalInitFuncs(
      CodeGenModule &CGM, ArrayRef<const VarDecl *> CXXThreadLocals,
      ArrayRef<llvm::Function *> CXXThreadLocalInits,
      ArrayRef<const VarDecl *> CXXThreadLocalInitVars) {
    // This will create a GV in the .CRT$XDU section.  It will point to our
    // initialization function.  The CRT will call all of these function
    // pointers at start-up time and, eventually, at thread-creation time.
    auto AddToXDU = [&CGM](llvm::Function *InitFunc) {
      llvm::GlobalVariable *InitFuncPtr = new llvm::GlobalVariable(
          CGM.getModule(), InitFunc->getType(), /*IsConstant=*/true,
          llvm::GlobalVariable::InternalLinkage, InitFunc,
          Twine(InitFunc->getName(), "$initializer$"));
      InitFuncPtr->setSection(".CRT$XDU");
      // This variable has discardable linkage, we have to add it to @llvm.used to
      // ensure it won't get discarded.
      CGM.addUsedGlobal(InitFuncPtr);
      return InitFuncPtr;
    };
  
    std::vector<llvm::Function *> NonComdatInits;
    for (size_t I = 0, E = CXXThreadLocalInitVars.size(); I != E; ++I) {
      llvm::GlobalVariable *GV = cast<llvm::GlobalVariable>(
          CGM.GetGlobalValue(CGM.getMangledName(CXXThreadLocalInitVars[I])));
      llvm::Function *F = CXXThreadLocalInits[I];
  
      // If the GV is already in a comdat group, then we have to join it.
      if (llvm::Comdat *C = GV->getComdat())
        AddToXDU(F)->setComdat(C);
      else
        NonComdatInits.push_back(F);
    }
  
    if (!NonComdatInits.empty()) {
      llvm::FunctionType *FTy =
          llvm::FunctionType::get(CGM.VoidTy, /*isVarArg=*/false);
      llvm::Function *InitFunc = CGM.CreateGlobalInitOrDestructFunction(
          FTy, "__tls_init", CGM.getTypes().arrangeNullaryFunction(),
          SourceLocation(), /*TLS=*/true);
      CodeGenFunction(CGM).GenerateCXXGlobalInitFunc(InitFunc, NonComdatInits);
  
      AddToXDU(InitFunc);
    }
  }
  
  LValue MicrosoftCXXABI::EmitThreadLocalVarDeclLValue(CodeGenFunction &CGF,
                                                       const VarDecl *VD,
                                                       QualType LValType) {
    CGF.CGM.ErrorUnsupported(VD, "thread wrappers");
    return LValue();
  }
  
  static ConstantAddress getInitThreadEpochPtr(CodeGenModule &CGM) {
    StringRef VarName("_Init_thread_epoch");
    CharUnits Align = CGM.getIntAlign();
    if (auto *GV = CGM.getModule().getNamedGlobal(VarName))
      return ConstantAddress(GV, Align);
    auto *GV = new llvm::GlobalVariable(
        CGM.getModule(), CGM.IntTy,
        /*Constant=*/false, llvm::GlobalVariable::ExternalLinkage,
        /*Initializer=*/nullptr, VarName,
        /*InsertBefore=*/nullptr, llvm::GlobalVariable::GeneralDynamicTLSModel);
    GV->setAlignment(Align.getQuantity());
    return ConstantAddress(GV, Align);
  }
  
  static llvm::Constant *getInitThreadHeaderFn(CodeGenModule &CGM) {
    llvm::FunctionType *FTy =
        llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()),
                                CGM.IntTy->getPointerTo(), /*isVarArg=*/false);
    return CGM.CreateRuntimeFunction(
        FTy, "_Init_thread_header",
        llvm::AttributeSet::get(CGM.getLLVMContext(),
                                llvm::AttributeSet::FunctionIndex,
                                llvm::Attribute::NoUnwind));
  }
  
  static llvm::Constant *getInitThreadFooterFn(CodeGenModule &CGM) {
    llvm::FunctionType *FTy =
        llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()),
                                CGM.IntTy->getPointerTo(), /*isVarArg=*/false);
    return CGM.CreateRuntimeFunction(
        FTy, "_Init_thread_footer",
        llvm::AttributeSet::get(CGM.getLLVMContext(),
                                llvm::AttributeSet::FunctionIndex,
                                llvm::Attribute::NoUnwind));
  }
  
  static llvm::Constant *getInitThreadAbortFn(CodeGenModule &CGM) {
    llvm::FunctionType *FTy =
        llvm::FunctionType::get(llvm::Type::getVoidTy(CGM.getLLVMContext()),
                                CGM.IntTy->getPointerTo(), /*isVarArg=*/false);
    return CGM.CreateRuntimeFunction(
        FTy, "_Init_thread_abort",
        llvm::AttributeSet::get(CGM.getLLVMContext(),
                                llvm::AttributeSet::FunctionIndex,
                                llvm::Attribute::NoUnwind));
  }
  
  namespace {
  struct ResetGuardBit final : EHScopeStack::Cleanup {
    Address Guard;
    unsigned GuardNum;
    ResetGuardBit(Address Guard, unsigned GuardNum)
        : Guard(Guard), GuardNum(GuardNum) {}
  
    void Emit(CodeGenFunction &CGF, Flags flags) override {
      // Reset the bit in the mask so that the static variable may be
      // reinitialized.
      CGBuilderTy &Builder = CGF.Builder;
      llvm::LoadInst *LI = Builder.CreateLoad(Guard);
      llvm::ConstantInt *Mask =
          llvm::ConstantInt::get(CGF.IntTy, ~(1U << GuardNum));
      Builder.CreateStore(Builder.CreateAnd(LI, Mask), Guard);
    }
  };
  
  struct CallInitThreadAbort final : EHScopeStack::Cleanup {
    llvm::Value *Guard;
    CallInitThreadAbort(Address Guard) : Guard(Guard.getPointer()) {}
  
    void Emit(CodeGenFunction &CGF, Flags flags) override {
      // Calling _Init_thread_abort will reset the guard's state.
      CGF.EmitNounwindRuntimeCall(getInitThreadAbortFn(CGF.CGM), Guard);
    }
  };
  }
  
  void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
                                        llvm::GlobalVariable *GV,
                                        bool PerformInit) {
    // MSVC only uses guards for static locals.
    if (!D.isStaticLocal()) {
      assert(GV->hasWeakLinkage() || GV->hasLinkOnceLinkage());
      // GlobalOpt is allowed to discard the initializer, so use linkonce_odr.
      llvm::Function *F = CGF.CurFn;
      F->setLinkage(llvm::GlobalValue::LinkOnceODRLinkage);
      F->setComdat(CGM.getModule().getOrInsertComdat(F->getName()));
      CGF.EmitCXXGlobalVarDeclInit(D, GV, PerformInit);
      return;
    }
  
    bool ThreadlocalStatic = D.getTLSKind();
    bool ThreadsafeStatic = getContext().getLangOpts().ThreadsafeStatics;
  
    // Thread-safe static variables which aren't thread-specific have a
    // per-variable guard.
    bool HasPerVariableGuard = ThreadsafeStatic && !ThreadlocalStatic;
  
    CGBuilderTy &Builder = CGF.Builder;
    llvm::IntegerType *GuardTy = CGF.Int32Ty;
    llvm::ConstantInt *Zero = llvm::ConstantInt::get(GuardTy, 0);
    CharUnits GuardAlign = CharUnits::fromQuantity(4);
  
    // Get the guard variable for this function if we have one already.
    GuardInfo *GI = nullptr;
    if (ThreadlocalStatic)
      GI = &ThreadLocalGuardVariableMap[D.getDeclContext()];
    else if (!ThreadsafeStatic)
      GI = &GuardVariableMap[D.getDeclContext()];
  
    llvm::GlobalVariable *GuardVar = GI ? GI->Guard : nullptr;
    unsigned GuardNum;
    if (D.isExternallyVisible()) {
      // Externally visible variables have to be numbered in Sema to properly
      // handle unreachable VarDecls.
      GuardNum = getContext().getStaticLocalNumber(&D);
      assert(GuardNum > 0);
      GuardNum--;
    } else if (HasPerVariableGuard) {
      GuardNum = ThreadSafeGuardNumMap[D.getDeclContext()]++;
    } else {
      // Non-externally visible variables are numbered here in CodeGen.
      GuardNum = GI->BitIndex++;
    }
  
    if (!HasPerVariableGuard && GuardNum >= 32) {
      if (D.isExternallyVisible())
        ErrorUnsupportedABI(CGF, "more than 32 guarded initializations");
      GuardNum %= 32;
      GuardVar = nullptr;
    }
  
    if (!GuardVar) {
      // Mangle the name for the guard.
      SmallString<256> GuardName;
      {
        llvm::raw_svector_ostream Out(GuardName);
        if (HasPerVariableGuard)
          getMangleContext().mangleThreadSafeStaticGuardVariable(&D, GuardNum,
                                                                 Out);
        else
          getMangleContext().mangleStaticGuardVariable(&D, Out);
      }
  
      // Create the guard variable with a zero-initializer. Just absorb linkage,
      // visibility and dll storage class from the guarded variable.
      GuardVar =
          new llvm::GlobalVariable(CGM.getModule(), GuardTy, /*isConstant=*/false,
                                   GV->getLinkage(), Zero, GuardName.str());
      GuardVar->setVisibility(GV->getVisibility());
      GuardVar->setDLLStorageClass(GV->getDLLStorageClass());
      GuardVar->setAlignment(GuardAlign.getQuantity());
      if (GuardVar->isWeakForLinker())
        GuardVar->setComdat(
            CGM.getModule().getOrInsertComdat(GuardVar->getName()));
      if (D.getTLSKind())
        GuardVar->setThreadLocal(true);
      if (GI && !HasPerVariableGuard)
        GI->Guard = GuardVar;
    }
  
    ConstantAddress GuardAddr(GuardVar, GuardAlign);
  
    assert(GuardVar->getLinkage() == GV->getLinkage() &&
           "static local from the same function had different linkage");
  
    if (!HasPerVariableGuard) {
      // Pseudo code for the test:
      // if (!(GuardVar & MyGuardBit)) {
      //   GuardVar |= MyGuardBit;
      //   ... initialize the object ...;
      // }
  
      // Test our bit from the guard variable.
      llvm::ConstantInt *Bit = llvm::ConstantInt::get(GuardTy, 1U << GuardNum);
      llvm::LoadInst *LI = Builder.CreateLoad(GuardAddr);
      llvm::Value *IsInitialized =
          Builder.CreateICmpNE(Builder.CreateAnd(LI, Bit), Zero);
      llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
      llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
      Builder.CreateCondBr(IsInitialized, EndBlock, InitBlock);
  
      // Set our bit in the guard variable and emit the initializer and add a global
      // destructor if appropriate.
      CGF.EmitBlock(InitBlock);
      Builder.CreateStore(Builder.CreateOr(LI, Bit), GuardAddr);
      CGF.EHStack.pushCleanup<ResetGuardBit>(EHCleanup, GuardAddr, GuardNum);
      CGF.EmitCXXGlobalVarDeclInit(D, GV, PerformInit);
      CGF.PopCleanupBlock();
      Builder.CreateBr(EndBlock);
  
      // Continue.
      CGF.EmitBlock(EndBlock);
    } else {
      // Pseudo code for the test:
      // if (TSS > _Init_thread_epoch) {
      //   _Init_thread_header(&TSS);
      //   if (TSS == -1) {
      //     ... initialize the object ...;
      //     _Init_thread_footer(&TSS);
      //   }
      // }
      //
      // The algorithm is almost identical to what can be found in the appendix
      // found in N2325.
  
      // This BasicBLock determines whether or not we have any work to do.
      llvm::LoadInst *FirstGuardLoad = Builder.CreateLoad(GuardAddr);
      FirstGuardLoad->setOrdering(llvm::AtomicOrdering::Unordered);
      llvm::LoadInst *InitThreadEpoch =
          Builder.CreateLoad(getInitThreadEpochPtr(CGM));
      llvm::Value *IsUninitialized =
          Builder.CreateICmpSGT(FirstGuardLoad, InitThreadEpoch);
      llvm::BasicBlock *AttemptInitBlock = CGF.createBasicBlock("init.attempt");
      llvm::BasicBlock *EndBlock = CGF.createBasicBlock("init.end");
      Builder.CreateCondBr(IsUninitialized, AttemptInitBlock, EndBlock);
  
      // This BasicBlock attempts to determine whether or not this thread is
      // responsible for doing the initialization.
      CGF.EmitBlock(AttemptInitBlock);
      CGF.EmitNounwindRuntimeCall(getInitThreadHeaderFn(CGM),
                                  GuardAddr.getPointer());
      llvm::LoadInst *SecondGuardLoad = Builder.CreateLoad(GuardAddr);
      SecondGuardLoad->setOrdering(llvm::AtomicOrdering::Unordered);
      llvm::Value *ShouldDoInit =
          Builder.CreateICmpEQ(SecondGuardLoad, getAllOnesInt());
      llvm::BasicBlock *InitBlock = CGF.createBasicBlock("init");
      Builder.CreateCondBr(ShouldDoInit, InitBlock, EndBlock);
  
      // Ok, we ended up getting selected as the initializing thread.
      CGF.EmitBlock(InitBlock);
      CGF.EHStack.pushCleanup<CallInitThreadAbort>(EHCleanup, GuardAddr);
      CGF.EmitCXXGlobalVarDeclInit(D, GV, PerformInit);
      CGF.PopCleanupBlock();
      CGF.EmitNounwindRuntimeCall(getInitThreadFooterFn(CGM),
                                  GuardAddr.getPointer());
      Builder.CreateBr(EndBlock);
  
      CGF.EmitBlock(EndBlock);
    }
  }
  
  bool MicrosoftCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
    // Null-ness for function memptrs only depends on the first field, which is
    // the function pointer.  The rest don't matter, so we can zero initialize.
    if (MPT->isMemberFunctionPointer())
      return true;
  
    // The virtual base adjustment field is always -1 for null, so if we have one
    // we can't zero initialize.  The field offset is sometimes also -1 if 0 is a
    // valid field offset.
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
    return (!MSInheritanceAttr::hasVBTableOffsetField(Inheritance) &&
            RD->nullFieldOffsetIsZero());
  }
  
  llvm::Type *
  MicrosoftCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
    llvm::SmallVector<llvm::Type *, 4> fields;
    if (MPT->isMemberFunctionPointer())
      fields.push_back(CGM.VoidPtrTy);  // FunctionPointerOrVirtualThunk
    else
      fields.push_back(CGM.IntTy);  // FieldOffset
  
    if (MSInheritanceAttr::hasNVOffsetField(MPT->isMemberFunctionPointer(),
                                            Inheritance))
      fields.push_back(CGM.IntTy);
    if (MSInheritanceAttr::hasVBPtrOffsetField(Inheritance))
      fields.push_back(CGM.IntTy);
    if (MSInheritanceAttr::hasVBTableOffsetField(Inheritance))
      fields.push_back(CGM.IntTy);  // VirtualBaseAdjustmentOffset
  
    if (fields.size() == 1)
      return fields[0];
    return llvm::StructType::get(CGM.getLLVMContext(), fields);
  }
  
  void MicrosoftCXXABI::
  GetNullMemberPointerFields(const MemberPointerType *MPT,
                             llvm::SmallVectorImpl<llvm::Constant *> &fields) {
    assert(fields.empty());
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
    if (MPT->isMemberFunctionPointer()) {
      // FunctionPointerOrVirtualThunk
      fields.push_back(llvm::Constant::getNullValue(CGM.VoidPtrTy));
    } else {
      if (RD->nullFieldOffsetIsZero())
        fields.push_back(getZeroInt());  // FieldOffset
      else
        fields.push_back(getAllOnesInt());  // FieldOffset
    }
  
    if (MSInheritanceAttr::hasNVOffsetField(MPT->isMemberFunctionPointer(),
                                            Inheritance))
      fields.push_back(getZeroInt());
    if (MSInheritanceAttr::hasVBPtrOffsetField(Inheritance))
      fields.push_back(getZeroInt());
    if (MSInheritanceAttr::hasVBTableOffsetField(Inheritance))
      fields.push_back(getAllOnesInt());
  }
  
  llvm::Constant *
  MicrosoftCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
    llvm::SmallVector<llvm::Constant *, 4> fields;
    GetNullMemberPointerFields(MPT, fields);
    if (fields.size() == 1)
      return fields[0];
    llvm::Constant *Res = llvm::ConstantStruct::getAnon(fields);
    assert(Res->getType() == ConvertMemberPointerType(MPT));
    return Res;
  }
  
  llvm::Constant *
  MicrosoftCXXABI::EmitFullMemberPointer(llvm::Constant *FirstField,
                                         bool IsMemberFunction,
                                         const CXXRecordDecl *RD,
                                         CharUnits NonVirtualBaseAdjustment,
                                         unsigned VBTableIndex) {
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
  
    // Single inheritance class member pointer are represented as scalars instead
    // of aggregates.
    if (MSInheritanceAttr::hasOnlyOneField(IsMemberFunction, Inheritance))
      return FirstField;
  
    llvm::SmallVector<llvm::Constant *, 4> fields;
    fields.push_back(FirstField);
  
    if (MSInheritanceAttr::hasNVOffsetField(IsMemberFunction, Inheritance))
      fields.push_back(llvm::ConstantInt::get(
        CGM.IntTy, NonVirtualBaseAdjustment.getQuantity()));
  
    if (MSInheritanceAttr::hasVBPtrOffsetField(Inheritance)) {
      CharUnits Offs = CharUnits::Zero();
      if (VBTableIndex)
        Offs = getContext().getASTRecordLayout(RD).getVBPtrOffset();
      fields.push_back(llvm::ConstantInt::get(CGM.IntTy, Offs.getQuantity()));
    }
  
    // The rest of the fields are adjusted by conversions to a more derived class.
    if (MSInheritanceAttr::hasVBTableOffsetField(Inheritance))
      fields.push_back(llvm::ConstantInt::get(CGM.IntTy, VBTableIndex));
  
    return llvm::ConstantStruct::getAnon(fields);
  }
  
  llvm::Constant *
  MicrosoftCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
                                         CharUnits offset) {
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    if (RD->getMSInheritanceModel() ==
        MSInheritanceAttr::Keyword_virtual_inheritance)
      offset -= getContext().getOffsetOfBaseWithVBPtr(RD);
    llvm::Constant *FirstField =
      llvm::ConstantInt::get(CGM.IntTy, offset.getQuantity());
    return EmitFullMemberPointer(FirstField, /*IsMemberFunction=*/false, RD,
                                 CharUnits::Zero(), /*VBTableIndex=*/0);
  }
  
  llvm::Constant *MicrosoftCXXABI::EmitMemberPointer(const APValue &MP,
                                                     QualType MPType) {
    const MemberPointerType *DstTy = MPType->castAs<MemberPointerType>();
    const ValueDecl *MPD = MP.getMemberPointerDecl();
    if (!MPD)
      return EmitNullMemberPointer(DstTy);
  
    ASTContext &Ctx = getContext();
    ArrayRef<const CXXRecordDecl *> MemberPointerPath = MP.getMemberPointerPath();
  
    llvm::Constant *C;
    if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(MPD)) {
      C = EmitMemberFunctionPointer(MD);
    } else {
      CharUnits FieldOffset = Ctx.toCharUnitsFromBits(Ctx.getFieldOffset(MPD));
      C = EmitMemberDataPointer(DstTy, FieldOffset);
    }
  
    if (!MemberPointerPath.empty()) {
      const CXXRecordDecl *SrcRD = cast<CXXRecordDecl>(MPD->getDeclContext());
      const Type *SrcRecTy = Ctx.getTypeDeclType(SrcRD).getTypePtr();
      const MemberPointerType *SrcTy =
          Ctx.getMemberPointerType(DstTy->getPointeeType(), SrcRecTy)
              ->castAs<MemberPointerType>();
  
      bool DerivedMember = MP.isMemberPointerToDerivedMember();
      SmallVector<const CXXBaseSpecifier *, 4> DerivedToBasePath;
      const CXXRecordDecl *PrevRD = SrcRD;
      for (const CXXRecordDecl *PathElem : MemberPointerPath) {
        const CXXRecordDecl *Base = nullptr;
        const CXXRecordDecl *Derived = nullptr;
        if (DerivedMember) {
          Base = PathElem;
          Derived = PrevRD;
        } else {
          Base = PrevRD;
          Derived = PathElem;
        }
        for (const CXXBaseSpecifier &BS : Derived->bases())
          if (BS.getType()->getAsCXXRecordDecl()->getCanonicalDecl() ==
              Base->getCanonicalDecl())
            DerivedToBasePath.push_back(&BS);
        PrevRD = PathElem;
      }
      assert(DerivedToBasePath.size() == MemberPointerPath.size());
  
      CastKind CK = DerivedMember ? CK_DerivedToBaseMemberPointer
                                  : CK_BaseToDerivedMemberPointer;
      C = EmitMemberPointerConversion(SrcTy, DstTy, CK, DerivedToBasePath.begin(),
                                      DerivedToBasePath.end(), C);
    }
    return C;
  }
  
  llvm::Constant *
  MicrosoftCXXABI::EmitMemberFunctionPointer(const CXXMethodDecl *MD) {
    assert(MD->isInstance() && "Member function must not be static!");
  
    MD = MD->getCanonicalDecl();
    CharUnits NonVirtualBaseAdjustment = CharUnits::Zero();
    const CXXRecordDecl *RD = MD->getParent()->getMostRecentDecl();
    CodeGenTypes &Types = CGM.getTypes();
  
    unsigned VBTableIndex = 0;
    llvm::Constant *FirstField;
    const FunctionProtoType *FPT = MD->getType()->castAs<FunctionProtoType>();
    if (!MD->isVirtual()) {
      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;
      }
      FirstField = CGM.GetAddrOfFunction(MD, Ty);
    } else {
      auto &VTableContext = CGM.getMicrosoftVTableContext();
      MicrosoftVTableContext::MethodVFTableLocation ML =
          VTableContext.getMethodVFTableLocation(MD);
      FirstField = EmitVirtualMemPtrThunk(MD, ML);
      // Include the vfptr adjustment if the method is in a non-primary vftable.
      NonVirtualBaseAdjustment += ML.VFPtrOffset;
      if (ML.VBase)
        VBTableIndex = VTableContext.getVBTableIndex(RD, ML.VBase) * 4;
    }
  
    if (VBTableIndex == 0 &&
        RD->getMSInheritanceModel() ==
            MSInheritanceAttr::Keyword_virtual_inheritance)
      NonVirtualBaseAdjustment -= getContext().getOffsetOfBaseWithVBPtr(RD);
  
    // The rest of the fields are common with data member pointers.
    FirstField = llvm::ConstantExpr::getBitCast(FirstField, CGM.VoidPtrTy);
    return EmitFullMemberPointer(FirstField, /*IsMemberFunction=*/true, RD,
                                 NonVirtualBaseAdjustment, VBTableIndex);
  }
  
  /// Member pointers are the same if they're either bitwise identical *or* both
  /// null.  Null-ness for function members is determined by the first field,
  /// while for data member pointers we must compare all fields.
  llvm::Value *
  MicrosoftCXXABI::EmitMemberPointerComparison(CodeGenFunction &CGF,
                                               llvm::Value *L,
                                               llvm::Value *R,
                                               const MemberPointerType *MPT,
                                               bool Inequality) {
    CGBuilderTy &Builder = CGF.Builder;
  
    // Handle != comparisons by switching the sense of all boolean operations.
    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;
    }
  
    // If this is a single field member pointer (single inheritance), this is a
    // single icmp.
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
    if (MSInheritanceAttr::hasOnlyOneField(MPT->isMemberFunctionPointer(),
                                           Inheritance))
      return Builder.CreateICmp(Eq, L, R);
  
    // Compare the first field.
    llvm::Value *L0 = Builder.CreateExtractValue(L, 0, "lhs.0");
    llvm::Value *R0 = Builder.CreateExtractValue(R, 0, "rhs.0");
    llvm::Value *Cmp0 = Builder.CreateICmp(Eq, L0, R0, "memptr.cmp.first");
  
    // Compare everything other than the first field.
    llvm::Value *Res = nullptr;
    llvm::StructType *LType = cast<llvm::StructType>(L->getType());
    for (unsigned I = 1, E = LType->getNumElements(); I != E; ++I) {
      llvm::Value *LF = Builder.CreateExtractValue(L, I);
      llvm::Value *RF = Builder.CreateExtractValue(R, I);
      llvm::Value *Cmp = Builder.CreateICmp(Eq, LF, RF, "memptr.cmp.rest");
      if (Res)
        Res = Builder.CreateBinOp(And, Res, Cmp);
      else
        Res = Cmp;
    }
  
    // Check if the first field is 0 if this is a function pointer.
    if (MPT->isMemberFunctionPointer()) {
      // (l1 == r1 && ...) || l0 == 0
      llvm::Value *Zero = llvm::Constant::getNullValue(L0->getType());
      llvm::Value *IsZero = Builder.CreateICmp(Eq, L0, Zero, "memptr.cmp.iszero");
      Res = Builder.CreateBinOp(Or, Res, IsZero);
    }
  
    // Combine the comparison of the first field, which must always be true for
    // this comparison to succeeed.
    return Builder.CreateBinOp(And, Res, Cmp0, "memptr.cmp");
  }
  
  llvm::Value *
  MicrosoftCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
                                              llvm::Value *MemPtr,
                                              const MemberPointerType *MPT) {
    CGBuilderTy &Builder = CGF.Builder;
    llvm::SmallVector<llvm::Constant *, 4> fields;
    // We only need one field for member functions.
    if (MPT->isMemberFunctionPointer())
      fields.push_back(llvm::Constant::getNullValue(CGM.VoidPtrTy));
    else
      GetNullMemberPointerFields(MPT, fields);
    assert(!fields.empty());
    llvm::Value *FirstField = MemPtr;
    if (MemPtr->getType()->isStructTy())
      FirstField = Builder.CreateExtractValue(MemPtr, 0);
    llvm::Value *Res = Builder.CreateICmpNE(FirstField, fields[0], "memptr.cmp0");
  
    // For function member pointers, we only need to test the function pointer
    // field.  The other fields if any can be garbage.
    if (MPT->isMemberFunctionPointer())
      return Res;
  
    // Otherwise, emit a series of compares and combine the results.
    for (int I = 1, E = fields.size(); I < E; ++I) {
      llvm::Value *Field = Builder.CreateExtractValue(MemPtr, I);
      llvm::Value *Next = Builder.CreateICmpNE(Field, fields[I], "memptr.cmp");
      Res = Builder.CreateOr(Res, Next, "memptr.tobool");
    }
    return Res;
  }
  
  bool MicrosoftCXXABI::MemberPointerConstantIsNull(const MemberPointerType *MPT,
                                                    llvm::Constant *Val) {
    // Function pointers are null if the pointer in the first field is null.
    if (MPT->isMemberFunctionPointer()) {
      llvm::Constant *FirstField = Val->getType()->isStructTy() ?
        Val->getAggregateElement(0U) : Val;
      return FirstField->isNullValue();
    }
  
    // If it's not a function pointer and it's zero initializable, we can easily
    // check zero.
    if (isZeroInitializable(MPT) && Val->isNullValue())
      return true;
  
    // Otherwise, break down all the fields for comparison.  Hopefully these
    // little Constants are reused, while a big null struct might not be.
    llvm::SmallVector<llvm::Constant *, 4> Fields;
    GetNullMemberPointerFields(MPT, Fields);
    if (Fields.size() == 1) {
      assert(Val->getType()->isIntegerTy());
      return Val == Fields[0];
    }
  
    unsigned I, E;
    for (I = 0, E = Fields.size(); I != E; ++I) {
      if (Val->getAggregateElement(I) != Fields[I])
        break;
    }
    return I == E;
  }
  
  llvm::Value *
  MicrosoftCXXABI::GetVBaseOffsetFromVBPtr(CodeGenFunction &CGF,
                                           Address This,
                                           llvm::Value *VBPtrOffset,
                                           llvm::Value *VBTableOffset,
                                           llvm::Value **VBPtrOut) {
    CGBuilderTy &Builder = CGF.Builder;
    // Load the vbtable pointer from the vbptr in the instance.
    This = Builder.CreateElementBitCast(This, CGM.Int8Ty);
    llvm::Value *VBPtr =
      Builder.CreateInBoundsGEP(This.getPointer(), VBPtrOffset, "vbptr");
    if (VBPtrOut) *VBPtrOut = VBPtr;
    VBPtr = Builder.CreateBitCast(VBPtr,
              CGM.Int32Ty->getPointerTo(0)->getPointerTo(This.getAddressSpace()));
  
    CharUnits VBPtrAlign;
    if (auto CI = dyn_cast<llvm::ConstantInt>(VBPtrOffset)) {
      VBPtrAlign = This.getAlignment().alignmentAtOffset(
                                     CharUnits::fromQuantity(CI->getSExtValue()));
    } else {
      VBPtrAlign = CGF.getPointerAlign();
    }
  
    llvm::Value *VBTable = Builder.CreateAlignedLoad(VBPtr, VBPtrAlign, "vbtable");
  
    // Translate from byte offset to table index. It improves analyzability.
    llvm::Value *VBTableIndex = Builder.CreateAShr(
        VBTableOffset, llvm::ConstantInt::get(VBTableOffset->getType(), 2),
        "vbtindex", /*isExact=*/true);
  
    // Load an i32 offset from the vb-table.
    llvm::Value *VBaseOffs = Builder.CreateInBoundsGEP(VBTable, VBTableIndex);
    VBaseOffs = Builder.CreateBitCast(VBaseOffs, CGM.Int32Ty->getPointerTo(0));
    return Builder.CreateAlignedLoad(VBaseOffs, CharUnits::fromQuantity(4),
                                     "vbase_offs");
  }
  
  // Returns an adjusted base cast to i8*, since we do more address arithmetic on
  // it.
  llvm::Value *MicrosoftCXXABI::AdjustVirtualBase(
      CodeGenFunction &CGF, const Expr *E, const CXXRecordDecl *RD,
      Address Base, llvm::Value *VBTableOffset, llvm::Value *VBPtrOffset) {
    CGBuilderTy &Builder = CGF.Builder;
    Base = Builder.CreateElementBitCast(Base, CGM.Int8Ty);
    llvm::BasicBlock *OriginalBB = nullptr;
    llvm::BasicBlock *SkipAdjustBB = nullptr;
    llvm::BasicBlock *VBaseAdjustBB = nullptr;
  
    // In the unspecified inheritance model, there might not be a vbtable at all,
    // in which case we need to skip the virtual base lookup.  If there is a
    // vbtable, the first entry is a no-op entry that gives back the original
    // base, so look for a virtual base adjustment offset of zero.
    if (VBPtrOffset) {
      OriginalBB = Builder.GetInsertBlock();
      VBaseAdjustBB = CGF.createBasicBlock("memptr.vadjust");
      SkipAdjustBB = CGF.createBasicBlock("memptr.skip_vadjust");
      llvm::Value *IsVirtual =
        Builder.CreateICmpNE(VBTableOffset, getZeroInt(),
                             "memptr.is_vbase");
      Builder.CreateCondBr(IsVirtual, VBaseAdjustBB, SkipAdjustBB);
      CGF.EmitBlock(VBaseAdjustBB);
    }
  
    // If we weren't given a dynamic vbptr offset, RD should be complete and we'll
    // know the vbptr offset.
    if (!VBPtrOffset) {
      CharUnits offs = CharUnits::Zero();
      if (!RD->hasDefinition()) {
        DiagnosticsEngine &Diags = CGF.CGM.getDiags();
        unsigned DiagID = Diags.getCustomDiagID(
            DiagnosticsEngine::Error,
            "member pointer representation requires a "
            "complete class type for %0 to perform this expression");
        Diags.Report(E->getExprLoc(), DiagID) << RD << E->getSourceRange();
      } else if (RD->getNumVBases())
        offs = getContext().getASTRecordLayout(RD).getVBPtrOffset();
      VBPtrOffset = llvm::ConstantInt::get(CGM.IntTy, offs.getQuantity());
    }
    llvm::Value *VBPtr = nullptr;
    llvm::Value *VBaseOffs =
      GetVBaseOffsetFromVBPtr(CGF, Base, VBPtrOffset, VBTableOffset, &VBPtr);
    llvm::Value *AdjustedBase = Builder.CreateInBoundsGEP(VBPtr, VBaseOffs);
  
    // Merge control flow with the case where we didn't have to adjust.
    if (VBaseAdjustBB) {
      Builder.CreateBr(SkipAdjustBB);
      CGF.EmitBlock(SkipAdjustBB);
      llvm::PHINode *Phi = Builder.CreatePHI(CGM.Int8PtrTy, 2, "memptr.base");
      Phi->addIncoming(Base.getPointer(), OriginalBB);
      Phi->addIncoming(AdjustedBase, VBaseAdjustBB);
      return Phi;
    }
    return AdjustedBase;
  }
  
  llvm::Value *MicrosoftCXXABI::EmitMemberDataPointerAddress(
      CodeGenFunction &CGF, const Expr *E, Address Base, llvm::Value *MemPtr,
      const MemberPointerType *MPT) {
    assert(MPT->isMemberDataPointer());
    unsigned AS = Base.getAddressSpace();
    llvm::Type *PType =
        CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
    CGBuilderTy &Builder = CGF.Builder;
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
  
    // Extract the fields we need, regardless of model.  We'll apply them if we
    // have them.
    llvm::Value *FieldOffset = MemPtr;
    llvm::Value *VirtualBaseAdjustmentOffset = nullptr;
    llvm::Value *VBPtrOffset = nullptr;
    if (MemPtr->getType()->isStructTy()) {
      // We need to extract values.
      unsigned I = 0;
      FieldOffset = Builder.CreateExtractValue(MemPtr, I++);
      if (MSInheritanceAttr::hasVBPtrOffsetField(Inheritance))
        VBPtrOffset = Builder.CreateExtractValue(MemPtr, I++);
      if (MSInheritanceAttr::hasVBTableOffsetField(Inheritance))
        VirtualBaseAdjustmentOffset = Builder.CreateExtractValue(MemPtr, I++);
    }
  
    llvm::Value *Addr;
    if (VirtualBaseAdjustmentOffset) {
      Addr = AdjustVirtualBase(CGF, E, RD, Base, VirtualBaseAdjustmentOffset,
                               VBPtrOffset);
    } else {
      Addr = Base.getPointer();
    }
  
    // Cast to char*.
    Addr = Builder.CreateBitCast(Addr, CGF.Int8Ty->getPointerTo(AS));
  
    // Apply the offset, which we assume is non-null.
    Addr = Builder.CreateInBoundsGEP(Addr, FieldOffset, "memptr.offset");
  
    // Cast the address to the appropriate pointer type, adopting the address
    // space of the base pointer.
    return Builder.CreateBitCast(Addr, PType);
  }
  
  llvm::Value *
  MicrosoftCXXABI::EmitMemberPointerConversion(CodeGenFunction &CGF,
                                               const CastExpr *E,
                                               llvm::Value *Src) {
    assert(E->getCastKind() == CK_DerivedToBaseMemberPointer ||
           E->getCastKind() == CK_BaseToDerivedMemberPointer ||
           E->getCastKind() == CK_ReinterpretMemberPointer);
  
    // Use constant emission if we can.
    if (isa<llvm::Constant>(Src))
      return EmitMemberPointerConversion(E, cast<llvm::Constant>(Src));
  
    // We may be adding or dropping fields from the member pointer, so we need
    // both types and the inheritance models of both records.
    const MemberPointerType *SrcTy =
      E->getSubExpr()->getType()->castAs<MemberPointerType>();
    const MemberPointerType *DstTy = E->getType()->castAs<MemberPointerType>();
    bool IsFunc = SrcTy->isMemberFunctionPointer();
  
    // If the classes use the same null representation, reinterpret_cast is a nop.
    bool IsReinterpret = E->getCastKind() == CK_ReinterpretMemberPointer;
    if (IsReinterpret && IsFunc)
      return Src;
  
    CXXRecordDecl *SrcRD = SrcTy->getMostRecentCXXRecordDecl();
    CXXRecordDecl *DstRD = DstTy->getMostRecentCXXRecordDecl();
    if (IsReinterpret &&
        SrcRD->nullFieldOffsetIsZero() == DstRD->nullFieldOffsetIsZero())
      return Src;
  
    CGBuilderTy &Builder = CGF.Builder;
  
    // Branch past the conversion if Src is null.
    llvm::Value *IsNotNull = EmitMemberPointerIsNotNull(CGF, Src, SrcTy);
    llvm::Constant *DstNull = EmitNullMemberPointer(DstTy);
  
    // C++ 5.2.10p9: The null member pointer value is converted to the null member
    //   pointer value of the destination type.
    if (IsReinterpret) {
      // For reinterpret casts, sema ensures that src and dst are both functions
      // or data and have the same size, which means the LLVM types should match.
      assert(Src->getType() == DstNull->getType());
      return Builder.CreateSelect(IsNotNull, Src, DstNull);
    }
  
    llvm::BasicBlock *OriginalBB = Builder.GetInsertBlock();
    llvm::BasicBlock *ConvertBB = CGF.createBasicBlock("memptr.convert");
    llvm::BasicBlock *ContinueBB = CGF.createBasicBlock("memptr.converted");
    Builder.CreateCondBr(IsNotNull, ConvertBB, ContinueBB);
    CGF.EmitBlock(ConvertBB);
  
    llvm::Value *Dst = EmitNonNullMemberPointerConversion(
        SrcTy, DstTy, E->getCastKind(), E->path_begin(), E->path_end(), Src,
        Builder);
  
    Builder.CreateBr(ContinueBB);
  
    // In the continuation, choose between DstNull and Dst.
    CGF.EmitBlock(ContinueBB);
    llvm::PHINode *Phi = Builder.CreatePHI(DstNull->getType(), 2, "memptr.converted");
    Phi->addIncoming(DstNull, OriginalBB);
    Phi->addIncoming(Dst, ConvertBB);
    return Phi;
  }
  
  llvm::Value *MicrosoftCXXABI::EmitNonNullMemberPointerConversion(
      const MemberPointerType *SrcTy, const MemberPointerType *DstTy, CastKind CK,
      CastExpr::path_const_iterator PathBegin,
      CastExpr::path_const_iterator PathEnd, llvm::Value *Src,
      CGBuilderTy &Builder) {
    const CXXRecordDecl *SrcRD = SrcTy->getMostRecentCXXRecordDecl();
    const CXXRecordDecl *DstRD = DstTy->getMostRecentCXXRecordDecl();
    MSInheritanceAttr::Spelling SrcInheritance = SrcRD->getMSInheritanceModel();
    MSInheritanceAttr::Spelling DstInheritance = DstRD->getMSInheritanceModel();
    bool IsFunc = SrcTy->isMemberFunctionPointer();
    bool IsConstant = isa<llvm::Constant>(Src);
  
    // Decompose src.
    llvm::Value *FirstField = Src;
    llvm::Value *NonVirtualBaseAdjustment = getZeroInt();
    llvm::Value *VirtualBaseAdjustmentOffset = getZeroInt();
    llvm::Value *VBPtrOffset = getZeroInt();
    if (!MSInheritanceAttr::hasOnlyOneField(IsFunc, SrcInheritance)) {
      // We need to extract values.
      unsigned I = 0;
      FirstField = Builder.CreateExtractValue(Src, I++);
      if (MSInheritanceAttr::hasNVOffsetField(IsFunc, SrcInheritance))
        NonVirtualBaseAdjustment = Builder.CreateExtractValue(Src, I++);
      if (MSInheritanceAttr::hasVBPtrOffsetField(SrcInheritance))
        VBPtrOffset = Builder.CreateExtractValue(Src, I++);
      if (MSInheritanceAttr::hasVBTableOffsetField(SrcInheritance))
        VirtualBaseAdjustmentOffset = Builder.CreateExtractValue(Src, I++);
    }
  
    bool IsDerivedToBase = (CK == CK_DerivedToBaseMemberPointer);
    const MemberPointerType *DerivedTy = IsDerivedToBase ? SrcTy : DstTy;
    const CXXRecordDecl *DerivedClass = DerivedTy->getMostRecentCXXRecordDecl();
  
    // For data pointers, we adjust the field offset directly.  For functions, we
    // have a separate field.
    llvm::Value *&NVAdjustField = IsFunc ? NonVirtualBaseAdjustment : FirstField;
  
    // The virtual inheritance model has a quirk: the virtual base table is always
    // referenced when dereferencing a member pointer even if the member pointer
    // is non-virtual.  This is accounted for by adjusting the non-virtual offset
    // to point backwards to the top of the MDC from the first VBase.  Undo this
    // adjustment to normalize the member pointer.
    llvm::Value *SrcVBIndexEqZero =
        Builder.CreateICmpEQ(VirtualBaseAdjustmentOffset, getZeroInt());
    if (SrcInheritance == MSInheritanceAttr::Keyword_virtual_inheritance) {
      if (int64_t SrcOffsetToFirstVBase =
              getContext().getOffsetOfBaseWithVBPtr(SrcRD).getQuantity()) {
        llvm::Value *UndoSrcAdjustment = Builder.CreateSelect(
            SrcVBIndexEqZero,
            llvm::ConstantInt::get(CGM.IntTy, SrcOffsetToFirstVBase),
            getZeroInt());
        NVAdjustField = Builder.CreateNSWAdd(NVAdjustField, UndoSrcAdjustment);
      }
    }
  
    // A non-zero vbindex implies that we are dealing with a source member in a
    // floating virtual base in addition to some non-virtual offset.  If the
    // vbindex is zero, we are dealing with a source that exists in a non-virtual,
    // fixed, base.  The difference between these two cases is that the vbindex +
    // nvoffset *always* point to the member regardless of what context they are
    // evaluated in so long as the vbindex is adjusted.  A member inside a fixed
    // base requires explicit nv adjustment.
    llvm::Constant *BaseClassOffset = llvm::ConstantInt::get(
        CGM.IntTy,
        CGM.computeNonVirtualBaseClassOffset(DerivedClass, PathBegin, PathEnd)
            .getQuantity());
  
    llvm::Value *NVDisp;
    if (IsDerivedToBase)
      NVDisp = Builder.CreateNSWSub(NVAdjustField, BaseClassOffset, "adj");
    else
      NVDisp = Builder.CreateNSWAdd(NVAdjustField, BaseClassOffset, "adj");
  
    NVAdjustField = Builder.CreateSelect(SrcVBIndexEqZero, NVDisp, getZeroInt());
  
    // Update the vbindex to an appropriate value in the destination because
    // SrcRD's vbtable might not be a strict prefix of the one in DstRD.
    llvm::Value *DstVBIndexEqZero = SrcVBIndexEqZero;
    if (MSInheritanceAttr::hasVBTableOffsetField(DstInheritance) &&
        MSInheritanceAttr::hasVBTableOffsetField(SrcInheritance)) {
      if (llvm::GlobalVariable *VDispMap =
              getAddrOfVirtualDisplacementMap(SrcRD, DstRD)) {
        llvm::Value *VBIndex = Builder.CreateExactUDiv(
            VirtualBaseAdjustmentOffset, llvm::ConstantInt::get(CGM.IntTy, 4));
        if (IsConstant) {
          llvm::Constant *Mapping = VDispMap->getInitializer();
          VirtualBaseAdjustmentOffset =
              Mapping->getAggregateElement(cast<llvm::Constant>(VBIndex));
        } else {
          llvm::Value *Idxs[] = {getZeroInt(), VBIndex};
          VirtualBaseAdjustmentOffset =
              Builder.CreateAlignedLoad(Builder.CreateInBoundsGEP(VDispMap, Idxs),
                                        CharUnits::fromQuantity(4));
        }
  
        DstVBIndexEqZero =
            Builder.CreateICmpEQ(VirtualBaseAdjustmentOffset, getZeroInt());
      }
    }
  
    // Set the VBPtrOffset to zero if the vbindex is zero.  Otherwise, initialize
    // it to the offset of the vbptr.
    if (MSInheritanceAttr::hasVBPtrOffsetField(DstInheritance)) {
      llvm::Value *DstVBPtrOffset = llvm::ConstantInt::get(
          CGM.IntTy,
          getContext().getASTRecordLayout(DstRD).getVBPtrOffset().getQuantity());
      VBPtrOffset =
          Builder.CreateSelect(DstVBIndexEqZero, getZeroInt(), DstVBPtrOffset);
    }
  
    // Likewise, apply a similar adjustment so that dereferencing the member
    // pointer correctly accounts for the distance between the start of the first
    // virtual base and the top of the MDC.
    if (DstInheritance == MSInheritanceAttr::Keyword_virtual_inheritance) {
      if (int64_t DstOffsetToFirstVBase =
              getContext().getOffsetOfBaseWithVBPtr(DstRD).getQuantity()) {
        llvm::Value *DoDstAdjustment = Builder.CreateSelect(
            DstVBIndexEqZero,
            llvm::ConstantInt::get(CGM.IntTy, DstOffsetToFirstVBase),
            getZeroInt());
        NVAdjustField = Builder.CreateNSWSub(NVAdjustField, DoDstAdjustment);
      }
    }
  
    // Recompose dst from the null struct and the adjusted fields from src.
    llvm::Value *Dst;
    if (MSInheritanceAttr::hasOnlyOneField(IsFunc, DstInheritance)) {
      Dst = FirstField;
    } else {
      Dst = llvm::UndefValue::get(ConvertMemberPointerType(DstTy));
      unsigned Idx = 0;
      Dst = Builder.CreateInsertValue(Dst, FirstField, Idx++);
      if (MSInheritanceAttr::hasNVOffsetField(IsFunc, DstInheritance))
        Dst = Builder.CreateInsertValue(Dst, NonVirtualBaseAdjustment, Idx++);
      if (MSInheritanceAttr::hasVBPtrOffsetField(DstInheritance))
        Dst = Builder.CreateInsertValue(Dst, VBPtrOffset, Idx++);
      if (MSInheritanceAttr::hasVBTableOffsetField(DstInheritance))
        Dst = Builder.CreateInsertValue(Dst, VirtualBaseAdjustmentOffset, Idx++);
    }
    return Dst;
  }
  
  llvm::Constant *
  MicrosoftCXXABI::EmitMemberPointerConversion(const CastExpr *E,
                                               llvm::Constant *Src) {
    const MemberPointerType *SrcTy =
        E->getSubExpr()->getType()->castAs<MemberPointerType>();
    const MemberPointerType *DstTy = E->getType()->castAs<MemberPointerType>();
  
    CastKind CK = E->getCastKind();
  
    return EmitMemberPointerConversion(SrcTy, DstTy, CK, E->path_begin(),
                                       E->path_end(), Src);
  }
  
  llvm::Constant *MicrosoftCXXABI::EmitMemberPointerConversion(
      const MemberPointerType *SrcTy, const MemberPointerType *DstTy, CastKind CK,
      CastExpr::path_const_iterator PathBegin,
      CastExpr::path_const_iterator PathEnd, llvm::Constant *Src) {
    assert(CK == CK_DerivedToBaseMemberPointer ||
           CK == CK_BaseToDerivedMemberPointer ||
           CK == CK_ReinterpretMemberPointer);
    // If src is null, emit a new null for dst.  We can't return src because dst
    // might have a new representation.
    if (MemberPointerConstantIsNull(SrcTy, Src))
      return EmitNullMemberPointer(DstTy);
  
    // We don't need to do anything for reinterpret_casts of non-null member
    // pointers.  We should only get here when the two type representations have
    // the same size.
    if (CK == CK_ReinterpretMemberPointer)
      return Src;
  
    CGBuilderTy Builder(CGM, CGM.getLLVMContext());
    auto *Dst = cast<llvm::Constant>(EmitNonNullMemberPointerConversion(
        SrcTy, DstTy, CK, PathBegin, PathEnd, Src, Builder));
  
    return Dst;
  }
  
  llvm::Value *MicrosoftCXXABI::EmitLoadOfMemberFunctionPointer(
      CodeGenFunction &CGF, const Expr *E, Address This,
      llvm::Value *&ThisPtrForCall, llvm::Value *MemPtr,
      const MemberPointerType *MPT) {
    assert(MPT->isMemberFunctionPointer());
    const FunctionProtoType *FPT =
      MPT->getPointeeType()->castAs<FunctionProtoType>();
    const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
    llvm::FunctionType *FTy = CGM.getTypes().GetFunctionType(
        CGM.getTypes().arrangeCXXMethodType(RD, FPT, /*FD=*/nullptr));
    CGBuilderTy &Builder = CGF.Builder;
  
    MSInheritanceAttr::Spelling Inheritance = RD->getMSInheritanceModel();
  
    // Extract the fields we need, regardless of model.  We'll apply them if we
    // have them.
    llvm::Value *FunctionPointer = MemPtr;
    llvm::Value *NonVirtualBaseAdjustment = nullptr;
    llvm::Value *VirtualBaseAdjustmentOffset = nullptr;
    llvm::Value *VBPtrOffset = nullptr;
    if (MemPtr->getType()->isStructTy()) {
      // We need to extract values.
      unsigned I = 0;
      FunctionPointer = Builder.CreateExtractValue(MemPtr, I++);
      if (MSInheritanceAttr::hasNVOffsetField(MPT, Inheritance))
        NonVirtualBaseAdjustment = Builder.CreateExtractValue(MemPtr, I++);
      if (MSInheritanceAttr::hasVBPtrOffsetField(Inheritance))
        VBPtrOffset = Builder.CreateExtractValue(MemPtr, I++);
      if (MSInheritanceAttr::hasVBTableOffsetField(Inheritance))
        VirtualBaseAdjustmentOffset = Builder.CreateExtractValue(MemPtr, I++);
    }
  
    if (VirtualBaseAdjustmentOffset) {
      ThisPtrForCall = AdjustVirtualBase(CGF, E, RD, This,
                                     VirtualBaseAdjustmentOffset, VBPtrOffset);
    } else {
      ThisPtrForCall = This.getPointer();
    }
  
    if (NonVirtualBaseAdjustment) {
      // Apply the adjustment and cast back to the original struct type.
      llvm::Value *Ptr = Builder.CreateBitCast(ThisPtrForCall, CGF.Int8PtrTy);
      Ptr = Builder.CreateInBoundsGEP(Ptr, NonVirtualBaseAdjustment);
      ThisPtrForCall = Builder.CreateBitCast(Ptr, ThisPtrForCall->getType(),
                                             "this.adjusted");
    }
  
    return Builder.CreateBitCast(FunctionPointer, FTy->getPointerTo());
  }
  
  CGCXXABI *clang::CodeGen::CreateMicrosoftCXXABI(CodeGenModule &CGM) {
    return new MicrosoftCXXABI(CGM);
  }
  
  // MS RTTI Overview:
  // The run time type information emitted by cl.exe contains 5 distinct types of
  // structures.  Many of them reference each other.
  //
  // TypeInfo:  Static classes that are returned by typeid.
  //
  // CompleteObjectLocator:  Referenced by vftables.  They contain information
  //   required for dynamic casting, including OffsetFromTop.  They also contain
  //   a reference to the TypeInfo for the type and a reference to the
  //   CompleteHierarchyDescriptor for the type.
  //
  // ClassHieararchyDescriptor: Contains information about a class hierarchy.
  //   Used during dynamic_cast to walk a class hierarchy.  References a base
  //   class array and the size of said array.
  //
  // BaseClassArray: Contains a list of classes in a hierarchy.  BaseClassArray is
  //   somewhat of a misnomer because the most derived class is also in the list
  //   as well as multiple copies of virtual bases (if they occur multiple times
  //   in the hiearchy.)  The BaseClassArray contains one BaseClassDescriptor for
  //   every path in the hierarchy, in pre-order depth first order.  Note, we do
  //   not declare a specific llvm type for BaseClassArray, it's merely an array
  //   of BaseClassDescriptor pointers.
  //
  // BaseClassDescriptor: Contains information about a class in a class hierarchy.
  //   BaseClassDescriptor is also somewhat of a misnomer for the same reason that
  //   BaseClassArray is.  It contains information about a class within a
  //   hierarchy such as: is this base is ambiguous and what is its offset in the
  //   vbtable.  The names of the BaseClassDescriptors have all of their fields
  //   mangled into them so they can be aggressively deduplicated by the linker.
  
  static llvm::GlobalVariable *getTypeInfoVTable(CodeGenModule &CGM) {
    StringRef MangledName("\01??_7type_info@@6B@");
    if (auto VTable = CGM.getModule().getNamedGlobal(MangledName))
      return VTable;
    return new llvm::GlobalVariable(CGM.getModule(), CGM.Int8PtrTy,
                                    /*Constant=*/true,
                                    llvm::GlobalVariable::ExternalLinkage,
                                    /*Initializer=*/nullptr, MangledName);
  }
  
  namespace {
  
  /// \brief A Helper struct that stores information about a class in a class
  /// hierarchy.  The information stored in these structs struct is used during
  /// the generation of ClassHierarchyDescriptors and BaseClassDescriptors.
  // During RTTI creation, MSRTTIClasses are stored in a contiguous array with
  // implicit depth first pre-order tree connectivity.  getFirstChild and
  // getNextSibling allow us to walk the tree efficiently.
  struct MSRTTIClass {
    enum {
      IsPrivateOnPath = 1 | 8,
      IsAmbiguous = 2,
      IsPrivate = 4,
      IsVirtual = 16,
      HasHierarchyDescriptor = 64
    };
    MSRTTIClass(const CXXRecordDecl *RD) : RD(RD) {}
    uint32_t initialize(const MSRTTIClass *Parent,
                        const CXXBaseSpecifier *Specifier);
  
    MSRTTIClass *getFirstChild() { return this + 1; }
    static MSRTTIClass *getNextChild(MSRTTIClass *Child) {
      return Child + 1 + Child->NumBases;
    }
  
    const CXXRecordDecl *RD, *VirtualRoot;
    uint32_t Flags, NumBases, OffsetInVBase;
  };
  
  /// \brief Recursively initialize the base class array.
  uint32_t MSRTTIClass::initialize(const MSRTTIClass *Parent,
                                   const CXXBaseSpecifier *Specifier) {
    Flags = HasHierarchyDescriptor;
    if (!Parent) {
      VirtualRoot = nullptr;
      OffsetInVBase = 0;
    } else {
      if (Specifier->getAccessSpecifier() != AS_public)
        Flags |= IsPrivate | IsPrivateOnPath;
      if (Specifier->isVirtual()) {
        Flags |= IsVirtual;
        VirtualRoot = RD;
        OffsetInVBase = 0;
      } else {
        if (Parent->Flags & IsPrivateOnPath)
          Flags |= IsPrivateOnPath;
        VirtualRoot = Parent->VirtualRoot;
        OffsetInVBase = Parent->OffsetInVBase + RD->getASTContext()
            .getASTRecordLayout(Parent->RD).getBaseClassOffset(RD).getQuantity();
      }
    }
    NumBases = 0;
    MSRTTIClass *Child = getFirstChild();
    for (const CXXBaseSpecifier &Base : RD->bases()) {
      NumBases += Child->initialize(this, &Base) + 1;
      Child = getNextChild(Child);
    }
    return NumBases;
  }
  
  static llvm::GlobalValue::LinkageTypes getLinkageForRTTI(QualType Ty) {
    switch (Ty->getLinkage()) {
    case NoLinkage:
    case InternalLinkage:
    case UniqueExternalLinkage:
      return llvm::GlobalValue::InternalLinkage;
  
    case VisibleNoLinkage:
    case ExternalLinkage:
      return llvm::GlobalValue::LinkOnceODRLinkage;
    }
    llvm_unreachable("Invalid linkage!");
  }
  
  /// \brief An ephemeral helper class for building MS RTTI types.  It caches some
  /// calls to the module and information about the most derived class in a
  /// hierarchy.
  struct MSRTTIBuilder {
    enum {
      HasBranchingHierarchy = 1,
      HasVirtualBranchingHierarchy = 2,
      HasAmbiguousBases = 4
    };
  
    MSRTTIBuilder(MicrosoftCXXABI &ABI, const CXXRecordDecl *RD)
        : CGM(ABI.CGM), Context(CGM.getContext()),
          VMContext(CGM.getLLVMContext()), Module(CGM.getModule()), RD(RD),
          Linkage(getLinkageForRTTI(CGM.getContext().getTagDeclType(RD))),
          ABI(ABI) {}
  
    llvm::GlobalVariable *getBaseClassDescriptor(const MSRTTIClass &Classes);
    llvm::GlobalVariable *
    getBaseClassArray(SmallVectorImpl<MSRTTIClass> &Classes);
    llvm::GlobalVariable *getClassHierarchyDescriptor();
    llvm::GlobalVariable *getCompleteObjectLocator(const VPtrInfo *Info);
  
    CodeGenModule &CGM;
    ASTContext &Context;
    llvm::LLVMContext &VMContext;
    llvm::Module &Module;
    const CXXRecordDecl *RD;
    llvm::GlobalVariable::LinkageTypes Linkage;
    MicrosoftCXXABI &ABI;
  };
  
  } // namespace
  
  /// \brief Recursively serializes a class hierarchy in pre-order depth first
  /// order.
  static void serializeClassHierarchy(SmallVectorImpl<MSRTTIClass> &Classes,
                                      const CXXRecordDecl *RD) {
    Classes.push_back(MSRTTIClass(RD));
    for (const CXXBaseSpecifier &Base : RD->bases())
      serializeClassHierarchy(Classes, Base.getType()->getAsCXXRecordDecl());
  }
  
  /// \brief Find ambiguity among base classes.
  static void
  detectAmbiguousBases(SmallVectorImpl<MSRTTIClass> &Classes) {
    llvm::SmallPtrSet<const CXXRecordDecl *, 8> VirtualBases;
    llvm::SmallPtrSet<const CXXRecordDecl *, 8> UniqueBases;
    llvm::SmallPtrSet<const CXXRecordDecl *, 8> AmbiguousBases;
    for (MSRTTIClass *Class = &Classes.front(); Class <= &Classes.back();) {
      if ((Class->Flags & MSRTTIClass::IsVirtual) &&
          !VirtualBases.insert(Class->RD).second) {
        Class = MSRTTIClass::getNextChild(Class);
        continue;
      }
      if (!UniqueBases.insert(Class->RD).second)
        AmbiguousBases.insert(Class->RD);
      Class++;
    }
    if (AmbiguousBases.empty())
      return;
    for (MSRTTIClass &Class : Classes)
      if (AmbiguousBases.count(Class.RD))
        Class.Flags |= MSRTTIClass::IsAmbiguous;
  }
  
  llvm::GlobalVariable *MSRTTIBuilder::getClassHierarchyDescriptor() {
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      ABI.getMangleContext().mangleCXXRTTIClassHierarchyDescriptor(RD, Out);
    }
  
    // Check to see if we've already declared this ClassHierarchyDescriptor.
    if (auto CHD = Module.getNamedGlobal(MangledName))
      return CHD;
  
    // Serialize the class hierarchy and initialize the CHD Fields.
    SmallVector<MSRTTIClass, 8> Classes;
    serializeClassHierarchy(Classes, RD);
    Classes.front().initialize(/*Parent=*/nullptr, /*Specifier=*/nullptr);
    detectAmbiguousBases(Classes);
    int Flags = 0;
    for (auto Class : Classes) {
      if (Class.RD->getNumBases() > 1)
        Flags |= HasBranchingHierarchy;
      // Note: cl.exe does not calculate "HasAmbiguousBases" correctly.  We
      // believe the field isn't actually used.
      if (Class.Flags & MSRTTIClass::IsAmbiguous)
        Flags |= HasAmbiguousBases;
    }
    if ((Flags & HasBranchingHierarchy) && RD->getNumVBases() != 0)
      Flags |= HasVirtualBranchingHierarchy;
    // These gep indices are used to get the address of the first element of the
    // base class array.
    llvm::Value *GEPIndices[] = {llvm::ConstantInt::get(CGM.IntTy, 0),
                                 llvm::ConstantInt::get(CGM.IntTy, 0)};
  
    // Forward-declare the class hierarchy descriptor
    auto Type = ABI.getClassHierarchyDescriptorType();
    auto CHD = new llvm::GlobalVariable(Module, Type, /*Constant=*/true, Linkage,
                                        /*Initializer=*/nullptr,
                                        MangledName);
    if (CHD->isWeakForLinker())
      CHD->setComdat(CGM.getModule().getOrInsertComdat(CHD->getName()));
  
    auto *Bases = getBaseClassArray(Classes);
  
    // Initialize the base class ClassHierarchyDescriptor.
    llvm::Constant *Fields[] = {
        llvm::ConstantInt::get(CGM.IntTy, 0), // Unknown
        llvm::ConstantInt::get(CGM.IntTy, Flags),
        llvm::ConstantInt::get(CGM.IntTy, Classes.size()),
        ABI.getImageRelativeConstant(llvm::ConstantExpr::getInBoundsGetElementPtr(
            Bases->getValueType(), Bases,
            llvm::ArrayRef<llvm::Value *>(GEPIndices))),
    };
    CHD->setInitializer(llvm::ConstantStruct::get(Type, Fields));
    return CHD;
  }
  
  llvm::GlobalVariable *
  MSRTTIBuilder::getBaseClassArray(SmallVectorImpl<MSRTTIClass> &Classes) {
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      ABI.getMangleContext().mangleCXXRTTIBaseClassArray(RD, Out);
    }
  
    // Forward-declare the base class array.
    // cl.exe pads the base class array with 1 (in 32 bit mode) or 4 (in 64 bit
    // mode) bytes of padding.  We provide a pointer sized amount of padding by
    // adding +1 to Classes.size().  The sections have pointer alignment and are
    // marked pick-any so it shouldn't matter.
    llvm::Type *PtrType = ABI.getImageRelativeType(
        ABI.getBaseClassDescriptorType()->getPointerTo());
    auto *ArrType = llvm::ArrayType::get(PtrType, Classes.size() + 1);
    auto *BCA =
        new llvm::GlobalVariable(Module, ArrType,
                                 /*Constant=*/true, Linkage,
                                 /*Initializer=*/nullptr, MangledName);
    if (BCA->isWeakForLinker())
      BCA->setComdat(CGM.getModule().getOrInsertComdat(BCA->getName()));
  
    // Initialize the BaseClassArray.
    SmallVector<llvm::Constant *, 8> BaseClassArrayData;
    for (MSRTTIClass &Class : Classes)
      BaseClassArrayData.push_back(
          ABI.getImageRelativeConstant(getBaseClassDescriptor(Class)));
    BaseClassArrayData.push_back(llvm::Constant::getNullValue(PtrType));
    BCA->setInitializer(llvm::ConstantArray::get(ArrType, BaseClassArrayData));
    return BCA;
  }
  
  llvm::GlobalVariable *
  MSRTTIBuilder::getBaseClassDescriptor(const MSRTTIClass &Class) {
    // Compute the fields for the BaseClassDescriptor.  They are computed up front
    // because they are mangled into the name of the object.
    uint32_t OffsetInVBTable = 0;
    int32_t VBPtrOffset = -1;
    if (Class.VirtualRoot) {
      auto &VTableContext = CGM.getMicrosoftVTableContext();
      OffsetInVBTable = VTableContext.getVBTableIndex(RD, Class.VirtualRoot) * 4;
      VBPtrOffset = Context.getASTRecordLayout(RD).getVBPtrOffset().getQuantity();
    }
  
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      ABI.getMangleContext().mangleCXXRTTIBaseClassDescriptor(
          Class.RD, Class.OffsetInVBase, VBPtrOffset, OffsetInVBTable,
          Class.Flags, Out);
    }
  
    // Check to see if we've already declared this object.
    if (auto BCD = Module.getNamedGlobal(MangledName))
      return BCD;
  
    // Forward-declare the base class descriptor.
    auto Type = ABI.getBaseClassDescriptorType();
    auto BCD =
        new llvm::GlobalVariable(Module, Type, /*Constant=*/true, Linkage,
                                 /*Initializer=*/nullptr, MangledName);
    if (BCD->isWeakForLinker())
      BCD->setComdat(CGM.getModule().getOrInsertComdat(BCD->getName()));
  
    // Initialize the BaseClassDescriptor.
    llvm::Constant *Fields[] = {
        ABI.getImageRelativeConstant(
            ABI.getAddrOfRTTIDescriptor(Context.getTypeDeclType(Class.RD))),
        llvm::ConstantInt::get(CGM.IntTy, Class.NumBases),
        llvm::ConstantInt::get(CGM.IntTy, Class.OffsetInVBase),
        llvm::ConstantInt::get(CGM.IntTy, VBPtrOffset),
        llvm::ConstantInt::get(CGM.IntTy, OffsetInVBTable),
        llvm::ConstantInt::get(CGM.IntTy, Class.Flags),
        ABI.getImageRelativeConstant(
            MSRTTIBuilder(ABI, Class.RD).getClassHierarchyDescriptor()),
    };
    BCD->setInitializer(llvm::ConstantStruct::get(Type, Fields));
    return BCD;
  }
  
  llvm::GlobalVariable *
  MSRTTIBuilder::getCompleteObjectLocator(const VPtrInfo *Info) {
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      ABI.getMangleContext().mangleCXXRTTICompleteObjectLocator(RD, Info->MangledPath, Out);
    }
  
    // Check to see if we've already computed this complete object locator.
    if (auto COL = Module.getNamedGlobal(MangledName))
      return COL;
  
    // Compute the fields of the complete object locator.
    int OffsetToTop = Info->FullOffsetInMDC.getQuantity();
    int VFPtrOffset = 0;
    // The offset includes the vtordisp if one exists.
    if (const CXXRecordDecl *VBase = Info->getVBaseWithVPtr())
      if (Context.getASTRecordLayout(RD)
        .getVBaseOffsetsMap()
        .find(VBase)
        ->second.hasVtorDisp())
        VFPtrOffset = Info->NonVirtualOffset.getQuantity() + 4;
  
    // Forward-declare the complete object locator.
    llvm::StructType *Type = ABI.getCompleteObjectLocatorType();
    auto COL = new llvm::GlobalVariable(Module, Type, /*Constant=*/true, Linkage,
      /*Initializer=*/nullptr, MangledName);
  
    // Initialize the CompleteObjectLocator.
    llvm::Constant *Fields[] = {
        llvm::ConstantInt::get(CGM.IntTy, ABI.isImageRelative()),
        llvm::ConstantInt::get(CGM.IntTy, OffsetToTop),
        llvm::ConstantInt::get(CGM.IntTy, VFPtrOffset),
        ABI.getImageRelativeConstant(
            CGM.GetAddrOfRTTIDescriptor(Context.getTypeDeclType(RD))),
        ABI.getImageRelativeConstant(getClassHierarchyDescriptor()),
        ABI.getImageRelativeConstant(COL),
    };
    llvm::ArrayRef<llvm::Constant *> FieldsRef(Fields);
    if (!ABI.isImageRelative())
      FieldsRef = FieldsRef.drop_back();
    COL->setInitializer(llvm::ConstantStruct::get(Type, FieldsRef));
    if (COL->isWeakForLinker())
      COL->setComdat(CGM.getModule().getOrInsertComdat(COL->getName()));
    return COL;
  }
  
  static QualType decomposeTypeForEH(ASTContext &Context, QualType T,
                                     bool &IsConst, bool &IsVolatile) {
    T = Context.getExceptionObjectType(T);
  
    // C++14 [except.handle]p3:
    //   A handler is a match for an exception object of type E if [...]
    //     - the handler is of type cv T or const T& where T is a pointer type and
    //       E is a pointer type that can be converted to T by [...]
    //         - a qualification conversion
    IsConst = false;
    IsVolatile = false;
    QualType PointeeType = T->getPointeeType();
    if (!PointeeType.isNull()) {
      IsConst = PointeeType.isConstQualified();
      IsVolatile = PointeeType.isVolatileQualified();
    }
  
    // Member pointer types like "const int A::*" are represented by having RTTI
    // for "int A::*" and separately storing the const qualifier.
    if (const auto *MPTy = T->getAs<MemberPointerType>())
      T = Context.getMemberPointerType(PointeeType.getUnqualifiedType(),
                                       MPTy->getClass());
  
    // Pointer types like "const int * const *" are represented by having RTTI
    // for "const int **" and separately storing the const qualifier.
    if (T->isPointerType())
      T = Context.getPointerType(PointeeType.getUnqualifiedType());
  
    return T;
  }
  
  CatchTypeInfo
  MicrosoftCXXABI::getAddrOfCXXCatchHandlerType(QualType Type,
                                                QualType CatchHandlerType) {
    // TypeDescriptors for exceptions never have qualified pointer types,
    // qualifiers are stored seperately in order to support qualification
    // conversions.
    bool IsConst, IsVolatile;
    Type = decomposeTypeForEH(getContext(), Type, IsConst, IsVolatile);
  
    bool IsReference = CatchHandlerType->isReferenceType();
  
    uint32_t Flags = 0;
    if (IsConst)
      Flags |= 1;
    if (IsVolatile)
      Flags |= 2;
    if (IsReference)
      Flags |= 8;
  
    return CatchTypeInfo{getAddrOfRTTIDescriptor(Type)->stripPointerCasts(),
                         Flags};
  }
  
  /// \brief Gets a TypeDescriptor.  Returns a llvm::Constant * rather than a
  /// llvm::GlobalVariable * because different type descriptors have different
  /// types, and need to be abstracted.  They are abstracting by casting the
  /// address to an Int8PtrTy.
  llvm::Constant *MicrosoftCXXABI::getAddrOfRTTIDescriptor(QualType Type) {
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      getMangleContext().mangleCXXRTTI(Type, Out);
    }
  
    // Check to see if we've already declared this TypeDescriptor.
    if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(MangledName))
      return llvm::ConstantExpr::getBitCast(GV, CGM.Int8PtrTy);
  
    // Compute the fields for the TypeDescriptor.
    SmallString<256> TypeInfoString;
    {
      llvm::raw_svector_ostream Out(TypeInfoString);
      getMangleContext().mangleCXXRTTIName(Type, Out);
    }
  
    // Declare and initialize the TypeDescriptor.
    llvm::Constant *Fields[] = {
      getTypeInfoVTable(CGM),                        // VFPtr
      llvm::ConstantPointerNull::get(CGM.Int8PtrTy), // Runtime data
      llvm::ConstantDataArray::getString(CGM.getLLVMContext(), TypeInfoString)};
    llvm::StructType *TypeDescriptorType =
        getTypeDescriptorType(TypeInfoString);
    auto *Var = new llvm::GlobalVariable(
        CGM.getModule(), TypeDescriptorType, /*Constant=*/false,
        getLinkageForRTTI(Type),
        llvm::ConstantStruct::get(TypeDescriptorType, Fields),
        MangledName);
    if (Var->isWeakForLinker())
      Var->setComdat(CGM.getModule().getOrInsertComdat(Var->getName()));
    return llvm::ConstantExpr::getBitCast(Var, CGM.Int8PtrTy);
  }
  
  /// \brief Gets or a creates a Microsoft CompleteObjectLocator.
  llvm::GlobalVariable *
  MicrosoftCXXABI::getMSCompleteObjectLocator(const CXXRecordDecl *RD,
                                              const VPtrInfo *Info) {
    return MSRTTIBuilder(*this, RD).getCompleteObjectLocator(Info);
  }
  
  static void emitCXXConstructor(CodeGenModule &CGM,
                                 const CXXConstructorDecl *ctor,
                                 StructorType ctorType) {
    // There are no constructor variants, always emit the complete destructor.
    llvm::Function *Fn = CGM.codegenCXXStructor(ctor, StructorType::Complete);
    CGM.maybeSetTrivialComdat(*ctor, *Fn);
  }
  
  static void emitCXXDestructor(CodeGenModule &CGM, const CXXDestructorDecl *dtor,
                                StructorType dtorType) {
    // The complete destructor is equivalent to the base destructor for
    // classes with no virtual bases, so try to emit it as an alias.
    if (!dtor->getParent()->getNumVBases() &&
        (dtorType == StructorType::Complete || dtorType == StructorType::Base)) {
      bool ProducedAlias = !CGM.TryEmitDefinitionAsAlias(
          GlobalDecl(dtor, Dtor_Complete), GlobalDecl(dtor, Dtor_Base), true);
      if (ProducedAlias) {
        if (dtorType == StructorType::Complete)
          return;
        if (dtor->isVirtual())
          CGM.getVTables().EmitThunks(GlobalDecl(dtor, Dtor_Complete));
      }
    }
  
    // 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 (dtorType == StructorType::Base && !CGM.TryEmitBaseDestructorAsAlias(dtor))
      return;
  
    llvm::Function *Fn = CGM.codegenCXXStructor(dtor, dtorType);
    if (Fn->isWeakForLinker())
      Fn->setComdat(CGM.getModule().getOrInsertComdat(Fn->getName()));
  }
  
  void MicrosoftCXXABI::emitCXXStructor(const CXXMethodDecl *MD,
                                        StructorType Type) {
    if (auto *CD = dyn_cast<CXXConstructorDecl>(MD)) {
      emitCXXConstructor(CGM, CD, Type);
      return;
    }
    emitCXXDestructor(CGM, cast<CXXDestructorDecl>(MD), Type);
  }
  
  llvm::Function *
  MicrosoftCXXABI::getAddrOfCXXCtorClosure(const CXXConstructorDecl *CD,
                                           CXXCtorType CT) {
    assert(CT == Ctor_CopyingClosure || CT == Ctor_DefaultClosure);
  
    // Calculate the mangled name.
    SmallString<256> ThunkName;
    llvm::raw_svector_ostream Out(ThunkName);
    getMangleContext().mangleCXXCtor(CD, CT, Out);
  
    // If the thunk has been generated previously, just return it.
    if (llvm::GlobalValue *GV = CGM.getModule().getNamedValue(ThunkName))
      return cast<llvm::Function>(GV);
  
    // Create the llvm::Function.
    const CGFunctionInfo &FnInfo = CGM.getTypes().arrangeMSCtorClosure(CD, CT);
    llvm::FunctionType *ThunkTy = CGM.getTypes().GetFunctionType(FnInfo);
    const CXXRecordDecl *RD = CD->getParent();
    QualType RecordTy = getContext().getRecordType(RD);
    llvm::Function *ThunkFn = llvm::Function::Create(
        ThunkTy, getLinkageForRTTI(RecordTy), ThunkName.str(), &CGM.getModule());
    ThunkFn->setCallingConv(static_cast<llvm::CallingConv::ID>(
        FnInfo.getEffectiveCallingConvention()));
    if (ThunkFn->isWeakForLinker())
      ThunkFn->setComdat(CGM.getModule().getOrInsertComdat(ThunkFn->getName()));
    bool IsCopy = CT == Ctor_CopyingClosure;
  
    // Start codegen.
    CodeGenFunction CGF(CGM);
    CGF.CurGD = GlobalDecl(CD, Ctor_Complete);
  
    // Build FunctionArgs.
    FunctionArgList FunctionArgs;
  
    // A constructor always starts with a 'this' pointer as its first argument.
    buildThisParam(CGF, FunctionArgs);
  
    // Following the 'this' pointer is a reference to the source object that we
    // are copying from.
    ImplicitParamDecl SrcParam(
        getContext(), nullptr, SourceLocation(), &getContext().Idents.get("src"),
        getContext().getLValueReferenceType(RecordTy,
                                            /*SpelledAsLValue=*/true));
    if (IsCopy)
      FunctionArgs.push_back(&SrcParam);
  
    // Constructors for classes which utilize virtual bases have an additional
    // parameter which indicates whether or not it is being delegated to by a more
    // derived constructor.
    ImplicitParamDecl IsMostDerived(getContext(), nullptr, SourceLocation(),
                                    &getContext().Idents.get("is_most_derived"),
                                    getContext().IntTy);
    // Only add the parameter to the list if thie class has virtual bases.
    if (RD->getNumVBases() > 0)
      FunctionArgs.push_back(&IsMostDerived);
  
    // Start defining the function.
    CGF.StartFunction(GlobalDecl(), FnInfo.getReturnType(), ThunkFn, FnInfo,
                      FunctionArgs, CD->getLocation(), SourceLocation());
    EmitThisParam(CGF);
    llvm::Value *This = getThisValue(CGF);
  
    llvm::Value *SrcVal =
        IsCopy ? CGF.Builder.CreateLoad(CGF.GetAddrOfLocalVar(&SrcParam), "src")
               : nullptr;
  
    CallArgList Args;
  
    // Push the this ptr.
    Args.add(RValue::get(This), CD->getThisType(getContext()));
  
    // Push the src ptr.
    if (SrcVal)
      Args.add(RValue::get(SrcVal), SrcParam.getType());
  
    // Add the rest of the default arguments.
    std::vector<Stmt *> ArgVec;
    for (unsigned I = IsCopy ? 1 : 0, E = CD->getNumParams(); I != E; ++I) {
      Stmt *DefaultArg = getContext().getDefaultArgExprForConstructor(CD, I);
      assert(DefaultArg && "sema forgot to instantiate default args");
      ArgVec.push_back(DefaultArg);
    }
  
    CodeGenFunction::RunCleanupsScope Cleanups(CGF);
  
    const auto *FPT = CD->getType()->castAs<FunctionProtoType>();
    CGF.EmitCallArgs(Args, FPT, llvm::makeArrayRef(ArgVec), CD, IsCopy ? 1 : 0);
  
    // Insert any ABI-specific implicit constructor arguments.
    unsigned ExtraArgs = addImplicitConstructorArgs(CGF, CD, Ctor_Complete,
                                                    /*ForVirtualBase=*/false,
                                                    /*Delegating=*/false, Args);
  
    // Call the destructor with our arguments.
    llvm::Value *CalleeFn = CGM.getAddrOfCXXStructor(CD, StructorType::Complete);
    const CGFunctionInfo &CalleeInfo = CGM.getTypes().arrangeCXXConstructorCall(
        Args, CD, Ctor_Complete, ExtraArgs);
    CGF.EmitCall(CalleeInfo, CalleeFn, ReturnValueSlot(), Args, CD);
  
    Cleanups.ForceCleanup();
  
    // Emit the ret instruction, remove any temporary instructions created for the
    // aid of CodeGen.
    CGF.FinishFunction(SourceLocation());
  
    return ThunkFn;
  }
  
  llvm::Constant *MicrosoftCXXABI::getCatchableType(QualType T,
                                                    uint32_t NVOffset,
                                                    int32_t VBPtrOffset,
                                                    uint32_t VBIndex) {
    assert(!T->isReferenceType());
  
    CXXRecordDecl *RD = T->getAsCXXRecordDecl();
    const CXXConstructorDecl *CD =
        RD ? CGM.getContext().getCopyConstructorForExceptionObject(RD) : nullptr;
    CXXCtorType CT = Ctor_Complete;
    if (CD)
      if (!hasDefaultCXXMethodCC(getContext(), CD) || CD->getNumParams() != 1)
        CT = Ctor_CopyingClosure;
  
    uint32_t Size = getContext().getTypeSizeInChars(T).getQuantity();
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      getMangleContext().mangleCXXCatchableType(T, CD, CT, Size, NVOffset,
                                                VBPtrOffset, VBIndex, Out);
    }
    if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(MangledName))
      return getImageRelativeConstant(GV);
  
    // The TypeDescriptor is used by the runtime to determine if a catch handler
    // is appropriate for the exception object.
    llvm::Constant *TD = getImageRelativeConstant(getAddrOfRTTIDescriptor(T));
  
    // The runtime is responsible for calling the copy constructor if the
    // exception is caught by value.
    llvm::Constant *CopyCtor;
    if (CD) {
      if (CT == Ctor_CopyingClosure)
        CopyCtor = getAddrOfCXXCtorClosure(CD, Ctor_CopyingClosure);
      else
        CopyCtor = CGM.getAddrOfCXXStructor(CD, StructorType::Complete);
  
      CopyCtor = llvm::ConstantExpr::getBitCast(CopyCtor, CGM.Int8PtrTy);
    } else {
      CopyCtor = llvm::Constant::getNullValue(CGM.Int8PtrTy);
    }
    CopyCtor = getImageRelativeConstant(CopyCtor);
  
    bool IsScalar = !RD;
    bool HasVirtualBases = false;
    bool IsStdBadAlloc = false; // std::bad_alloc is special for some reason.
    QualType PointeeType = T;
    if (T->isPointerType())
      PointeeType = T->getPointeeType();
    if (const CXXRecordDecl *RD = PointeeType->getAsCXXRecordDecl()) {
      HasVirtualBases = RD->getNumVBases() > 0;
      if (IdentifierInfo *II = RD->getIdentifier())
        IsStdBadAlloc = II->isStr("bad_alloc") && RD->isInStdNamespace();
    }
  
    // Encode the relevant CatchableType properties into the Flags bitfield.
    // FIXME: Figure out how bits 2 or 8 can get set.
    uint32_t Flags = 0;
    if (IsScalar)
      Flags |= 1;
    if (HasVirtualBases)
      Flags |= 4;
    if (IsStdBadAlloc)
      Flags |= 16;
  
    llvm::Constant *Fields[] = {
        llvm::ConstantInt::get(CGM.IntTy, Flags),       // Flags
        TD,                                             // TypeDescriptor
        llvm::ConstantInt::get(CGM.IntTy, NVOffset),    // NonVirtualAdjustment
        llvm::ConstantInt::get(CGM.IntTy, VBPtrOffset), // OffsetToVBPtr
        llvm::ConstantInt::get(CGM.IntTy, VBIndex),     // VBTableIndex
        llvm::ConstantInt::get(CGM.IntTy, Size),        // Size
        CopyCtor                                        // CopyCtor
    };
    llvm::StructType *CTType = getCatchableTypeType();
    auto *GV = new llvm::GlobalVariable(
        CGM.getModule(), CTType, /*Constant=*/true, getLinkageForRTTI(T),
        llvm::ConstantStruct::get(CTType, Fields), MangledName);
    GV->setUnnamedAddr(true);
    GV->setSection(".xdata");
    if (GV->isWeakForLinker())
      GV->setComdat(CGM.getModule().getOrInsertComdat(GV->getName()));
    return getImageRelativeConstant(GV);
  }
  
  llvm::GlobalVariable *MicrosoftCXXABI::getCatchableTypeArray(QualType T) {
    assert(!T->isReferenceType());
  
    // See if we've already generated a CatchableTypeArray for this type before.
    llvm::GlobalVariable *&CTA = CatchableTypeArrays[T];
    if (CTA)
      return CTA;
  
    // Ensure that we don't have duplicate entries in our CatchableTypeArray by
    // using a SmallSetVector.  Duplicates may arise due to virtual bases
    // occurring more than once in the hierarchy.
    llvm::SmallSetVector<llvm::Constant *, 2> CatchableTypes;
  
    // C++14 [except.handle]p3:
    //   A handler is a match for an exception object of type E if [...]
    //     - the handler is of type cv T or cv T& and T is an unambiguous public
    //       base class of E, or
    //     - the handler is of type cv T or const T& where T is a pointer type and
    //       E is a pointer type that can be converted to T by [...]
    //         - a standard pointer conversion (4.10) not involving conversions to
    //           pointers to private or protected or ambiguous classes
    const CXXRecordDecl *MostDerivedClass = nullptr;
    bool IsPointer = T->isPointerType();
    if (IsPointer)
      MostDerivedClass = T->getPointeeType()->getAsCXXRecordDecl();
    else
      MostDerivedClass = T->getAsCXXRecordDecl();
  
    // Collect all the unambiguous public bases of the MostDerivedClass.
    if (MostDerivedClass) {
      const ASTContext &Context = getContext();
      const ASTRecordLayout &MostDerivedLayout =
          Context.getASTRecordLayout(MostDerivedClass);
      MicrosoftVTableContext &VTableContext = CGM.getMicrosoftVTableContext();
      SmallVector<MSRTTIClass, 8> Classes;
      serializeClassHierarchy(Classes, MostDerivedClass);
      Classes.front().initialize(/*Parent=*/nullptr, /*Specifier=*/nullptr);
      detectAmbiguousBases(Classes);
      for (const MSRTTIClass &Class : Classes) {
        // Skip any ambiguous or private bases.
        if (Class.Flags &
            (MSRTTIClass::IsPrivateOnPath | MSRTTIClass::IsAmbiguous))
          continue;
        // Write down how to convert from a derived pointer to a base pointer.
        uint32_t OffsetInVBTable = 0;
        int32_t VBPtrOffset = -1;
        if (Class.VirtualRoot) {
          OffsetInVBTable =
            VTableContext.getVBTableIndex(MostDerivedClass, Class.VirtualRoot)*4;
          VBPtrOffset = MostDerivedLayout.getVBPtrOffset().getQuantity();
        }
  
        // Turn our record back into a pointer if the exception object is a
        // pointer.
        QualType RTTITy = QualType(Class.RD->getTypeForDecl(), 0);
        if (IsPointer)
          RTTITy = Context.getPointerType(RTTITy);
        CatchableTypes.insert(getCatchableType(RTTITy, Class.OffsetInVBase,
                                               VBPtrOffset, OffsetInVBTable));
      }
    }
  
    // C++14 [except.handle]p3:
    //   A handler is a match for an exception object of type E if
    //     - The handler is of type cv T or cv T& and E and T are the same type
    //       (ignoring the top-level cv-qualifiers)
    CatchableTypes.insert(getCatchableType(T));
  
    // C++14 [except.handle]p3:
    //   A handler is a match for an exception object of type E if
    //     - the handler is of type cv T or const T& where T is a pointer type and
    //       E is a pointer type that can be converted to T by [...]
    //         - a standard pointer conversion (4.10) not involving conversions to
    //           pointers to private or protected or ambiguous classes
    //
    // C++14 [conv.ptr]p2:
    //   A prvalue of type "pointer to cv T," where T is an object type, can be
    //   converted to a prvalue of type "pointer to cv void".
    if (IsPointer && T->getPointeeType()->isObjectType())
      CatchableTypes.insert(getCatchableType(getContext().VoidPtrTy));
  
    // C++14 [except.handle]p3:
    //   A handler is a match for an exception object of type E if [...]
    //     - the handler is of type cv T or const T& where T is a pointer or
    //       pointer to member type and E is std::nullptr_t.
    //
    // We cannot possibly list all possible pointer types here, making this
    // implementation incompatible with the standard.  However, MSVC includes an
    // entry for pointer-to-void in this case.  Let's do the same.
    if (T->isNullPtrType())
      CatchableTypes.insert(getCatchableType(getContext().VoidPtrTy));
  
    uint32_t NumEntries = CatchableTypes.size();
    llvm::Type *CTType =
        getImageRelativeType(getCatchableTypeType()->getPointerTo());
    llvm::ArrayType *AT = llvm::ArrayType::get(CTType, NumEntries);
    llvm::StructType *CTAType = getCatchableTypeArrayType(NumEntries);
    llvm::Constant *Fields[] = {
        llvm::ConstantInt::get(CGM.IntTy, NumEntries),    // NumEntries
        llvm::ConstantArray::get(
            AT, llvm::makeArrayRef(CatchableTypes.begin(),
                                   CatchableTypes.end())) // CatchableTypes
    };
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      getMangleContext().mangleCXXCatchableTypeArray(T, NumEntries, Out);
    }
    CTA = new llvm::GlobalVariable(
        CGM.getModule(), CTAType, /*Constant=*/true, getLinkageForRTTI(T),
        llvm::ConstantStruct::get(CTAType, Fields), MangledName);
    CTA->setUnnamedAddr(true);
    CTA->setSection(".xdata");
    if (CTA->isWeakForLinker())
      CTA->setComdat(CGM.getModule().getOrInsertComdat(CTA->getName()));
    return CTA;
  }
  
  llvm::GlobalVariable *MicrosoftCXXABI::getThrowInfo(QualType T) {
    bool IsConst, IsVolatile;
    T = decomposeTypeForEH(getContext(), T, IsConst, IsVolatile);
  
    // The CatchableTypeArray enumerates the various (CV-unqualified) types that
    // the exception object may be caught as.
    llvm::GlobalVariable *CTA = getCatchableTypeArray(T);
    // The first field in a CatchableTypeArray is the number of CatchableTypes.
    // This is used as a component of the mangled name which means that we need to
    // know what it is in order to see if we have previously generated the
    // ThrowInfo.
    uint32_t NumEntries =
        cast<llvm::ConstantInt>(CTA->getInitializer()->getAggregateElement(0U))
            ->getLimitedValue();
  
    SmallString<256> MangledName;
    {
      llvm::raw_svector_ostream Out(MangledName);
      getMangleContext().mangleCXXThrowInfo(T, IsConst, IsVolatile, NumEntries,
                                            Out);
    }
  
    // Reuse a previously generated ThrowInfo if we have generated an appropriate
    // one before.
    if (llvm::GlobalVariable *GV = CGM.getModule().getNamedGlobal(MangledName))
      return GV;
  
    // The RTTI TypeDescriptor uses an unqualified type but catch clauses must
    // be at least as CV qualified.  Encode this requirement into the Flags
    // bitfield.
    uint32_t Flags = 0;
    if (IsConst)
      Flags |= 1;
    if (IsVolatile)
      Flags |= 2;
  
    // The cleanup-function (a destructor) must be called when the exception
    // object's lifetime ends.
    llvm::Constant *CleanupFn = llvm::Constant::getNullValue(CGM.Int8PtrTy);
    if (const CXXRecordDecl *RD = T->getAsCXXRecordDecl())
      if (CXXDestructorDecl *DtorD = RD->getDestructor())
        if (!DtorD->isTrivial())
          CleanupFn = llvm::ConstantExpr::getBitCast(
              CGM.getAddrOfCXXStructor(DtorD, StructorType::Complete),
              CGM.Int8PtrTy);
    // This is unused as far as we can tell, initialize it to null.
    llvm::Constant *ForwardCompat =
        getImageRelativeConstant(llvm::Constant::getNullValue(CGM.Int8PtrTy));
    llvm::Constant *PointerToCatchableTypes = getImageRelativeConstant(
        llvm::ConstantExpr::getBitCast(CTA, CGM.Int8PtrTy));
    llvm::StructType *TIType = getThrowInfoType();
    llvm::Constant *Fields[] = {
        llvm::ConstantInt::get(CGM.IntTy, Flags), // Flags
        getImageRelativeConstant(CleanupFn),      // CleanupFn
        ForwardCompat,                            // ForwardCompat
        PointerToCatchableTypes                   // CatchableTypeArray
    };
    auto *GV = new llvm::GlobalVariable(
        CGM.getModule(), TIType, /*Constant=*/true, getLinkageForRTTI(T),
        llvm::ConstantStruct::get(TIType, Fields), StringRef(MangledName));
    GV->setUnnamedAddr(true);
    GV->setSection(".xdata");
    if (GV->isWeakForLinker())
      GV->setComdat(CGM.getModule().getOrInsertComdat(GV->getName()));
    return GV;
  }
  
  void MicrosoftCXXABI::emitThrow(CodeGenFunction &CGF, const CXXThrowExpr *E) {
    const Expr *SubExpr = E->getSubExpr();
    QualType ThrowType = SubExpr->getType();
    // The exception object lives on the stack and it's address is passed to the
    // runtime function.
    Address AI = CGF.CreateMemTemp(ThrowType);
    CGF.EmitAnyExprToMem(SubExpr, AI, ThrowType.getQualifiers(),
                         /*IsInit=*/true);
  
    // The so-called ThrowInfo is used to describe how the exception object may be
    // caught.
    llvm::GlobalVariable *TI = getThrowInfo(ThrowType);
  
    // Call into the runtime to throw the exception.
    llvm::Value *Args[] = {
      CGF.Builder.CreateBitCast(AI.getPointer(), CGM.Int8PtrTy),
      TI
    };
    CGF.EmitNoreturnRuntimeCallOrInvoke(getThrowFn(), Args);
  }
  