xref: /freebsd/contrib/llvm-project/clang/lib/AST/MicrosoftMangle.cpp (revision e64bea71c21eb42e97aa615188ba91f6cce0d36d)

//===--- MicrosoftMangle.cpp - Microsoft Visual C++ Name Mangling ---------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This provides C++ name mangling targeting the Microsoft Visual C++ ABI.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/ASTContext.h"
#include "clang/AST/Attr.h"
#include "clang/AST/CXXInheritance.h"
#include "clang/AST/CharUnits.h"
#include "clang/AST/Decl.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclOpenMP.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/ExprCXX.h"
#include "clang/AST/GlobalDecl.h"
#include "clang/AST/Mangle.h"
#include "clang/AST/VTableBuilder.h"
#include "clang/Basic/ABI.h"
#include "clang/Basic/DiagnosticOptions.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/Support/CRC.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/StringSaver.h"
#include "llvm/Support/xxhash.h"
#include <functional>
#include <optional>

using namespace clang;

namespace {

// Get GlobalDecl of DeclContext of local entities.
static GlobalDecl getGlobalDeclAsDeclContext(const DeclContext *DC) {
  GlobalDecl GD;
  if (auto *CD = dyn_cast<CXXConstructorDecl>(DC))
    GD = GlobalDecl(CD, Ctor_Complete);
  else if (auto *DD = dyn_cast<CXXDestructorDecl>(DC))
    GD = GlobalDecl(DD, Dtor_Complete);
  else
    GD = GlobalDecl(cast<FunctionDecl>(DC));
  return GD;
}

struct msvc_hashing_ostream : public llvm::raw_svector_ostream {
  raw_ostream &OS;
  llvm::SmallString<64> Buffer;

  msvc_hashing_ostream(raw_ostream &OS)
      : llvm::raw_svector_ostream(Buffer), OS(OS) {}
  ~msvc_hashing_ostream() override {
    StringRef MangledName = str();
    bool StartsWithEscape = MangledName.starts_with("\01");
    if (StartsWithEscape)
      MangledName = MangledName.drop_front(1);
    if (MangledName.size() < 4096) {
      OS << str();
      return;
    }

    llvm::MD5 Hasher;
    llvm::MD5::MD5Result Hash;
    Hasher.update(MangledName);
    Hasher.final(Hash);

    SmallString<32> HexString;
    llvm::MD5::stringifyResult(Hash, HexString);

    if (StartsWithEscape)
      OS << '\01';
    OS << "??@" << HexString << '@';
  }
};

static const DeclContext *
getLambdaDefaultArgumentDeclContext(const Decl *D) {
  if (const auto *RD = dyn_cast<CXXRecordDecl>(D))
    if (RD->isLambda())
      if (const auto *Parm =
              dyn_cast_or_null<ParmVarDecl>(RD->getLambdaContextDecl()))
        return Parm->getDeclContext();
  return nullptr;
}

/// Retrieve the declaration context that should be used when mangling
/// the given declaration.
static const DeclContext *getEffectiveDeclContext(const Decl *D) {
  // The ABI assumes that lambda closure types that occur within
  // default arguments live in the context of the function. However, due to
  // the way in which Clang parses and creates function declarations, this is
  // not the case: the lambda closure type ends up living in the context
  // where the function itself resides, because the function declaration itself
  // had not yet been created. Fix the context here.
  if (const auto *LDADC = getLambdaDefaultArgumentDeclContext(D))
    return LDADC;

  // Perform the same check for block literals.
  if (const BlockDecl *BD = dyn_cast<BlockDecl>(D)) {
    if (ParmVarDecl *ContextParam =
            dyn_cast_or_null<ParmVarDecl>(BD->getBlockManglingContextDecl()))
      return ContextParam->getDeclContext();
  }

  const DeclContext *DC = D->getDeclContext();
  if (isa<CapturedDecl>(DC) || isa<OMPDeclareReductionDecl>(DC) ||
      isa<OMPDeclareMapperDecl>(DC)) {
    return getEffectiveDeclContext(cast<Decl>(DC));
  }

  return DC->getRedeclContext();
}

static const DeclContext *getEffectiveParentContext(const DeclContext *DC) {
  return getEffectiveDeclContext(cast<Decl>(DC));
}

static const FunctionDecl *getStructor(const NamedDecl *ND) {
  if (const auto *FTD = dyn_cast<FunctionTemplateDecl>(ND))
    return FTD->getTemplatedDecl()->getCanonicalDecl();

  const auto *FD = cast<FunctionDecl>(ND);
  if (const auto *FTD = FD->getPrimaryTemplate())
    return FTD->getTemplatedDecl()->getCanonicalDecl();

  return FD->getCanonicalDecl();
}

/// MicrosoftMangleContextImpl - Overrides the default MangleContext for the
/// Microsoft Visual C++ ABI.
class MicrosoftMangleContextImpl : public MicrosoftMangleContext {
  typedef std::pair<const DeclContext *, IdentifierInfo *> DiscriminatorKeyTy;
  llvm::DenseMap<DiscriminatorKeyTy, unsigned> Discriminator;
  llvm::DenseMap<const NamedDecl *, unsigned> Uniquifier;
  llvm::DenseMap<const CXXRecordDecl *, unsigned> LambdaIds;
  llvm::DenseMap<GlobalDecl, unsigned> SEHFilterIds;
  llvm::DenseMap<GlobalDecl, unsigned> SEHFinallyIds;
  SmallString<16> AnonymousNamespaceHash;

public:
  MicrosoftMangleContextImpl(ASTContext &Context, DiagnosticsEngine &Diags,
                             bool IsAux = false);
  bool shouldMangleCXXName(const NamedDecl *D) override;
  bool shouldMangleStringLiteral(const StringLiteral *SL) override;
  void mangleCXXName(GlobalDecl GD, raw_ostream &Out) override;
  void mangleVirtualMemPtrThunk(const CXXMethodDecl *MD,
                                const MethodVFTableLocation &ML,
                                raw_ostream &Out) override;
  void mangleThunk(const CXXMethodDecl *MD, const ThunkInfo &Thunk,
                   bool ElideOverrideInfo, raw_ostream &) override;
  void mangleCXXDtorThunk(const CXXDestructorDecl *DD, CXXDtorType Type,
                          const ThunkInfo &Thunk, bool ElideOverrideInfo,
                          raw_ostream &) override;
  void mangleCXXVFTable(const CXXRecordDecl *Derived,
                        ArrayRef<const CXXRecordDecl *> BasePath,
                        raw_ostream &Out) override;
  void mangleCXXVBTable(const CXXRecordDecl *Derived,
                        ArrayRef<const CXXRecordDecl *> BasePath,
                        raw_ostream &Out) override;

  void mangleCXXVTable(const CXXRecordDecl *, raw_ostream &) override;
  void mangleCXXVirtualDisplacementMap(const CXXRecordDecl *SrcRD,
                                       const CXXRecordDecl *DstRD,
                                       raw_ostream &Out) override;
  void mangleCXXThrowInfo(QualType T, bool IsConst, bool IsVolatile,
                          bool IsUnaligned, uint32_t NumEntries,
                          raw_ostream &Out) override;
  void mangleCXXCatchableTypeArray(QualType T, uint32_t NumEntries,
                                   raw_ostream &Out) override;
  void mangleCXXCatchableType(QualType T, const CXXConstructorDecl *CD,
                              CXXCtorType CT, uint32_t Size, uint32_t NVOffset,
                              int32_t VBPtrOffset, uint32_t VBIndex,
                              raw_ostream &Out) override;
  void mangleCXXRTTI(QualType T, raw_ostream &Out) override;
  void mangleCXXRTTIName(QualType T, raw_ostream &Out,
                         bool NormalizeIntegers) override;
  void mangleCXXRTTIBaseClassDescriptor(const CXXRecordDecl *Derived,
                                        uint32_t NVOffset, int32_t VBPtrOffset,
                                        uint32_t VBTableOffset, uint32_t Flags,
                                        raw_ostream &Out) override;
  void mangleCXXRTTIBaseClassArray(const CXXRecordDecl *Derived,
                                   raw_ostream &Out) override;
  void mangleCXXRTTIClassHierarchyDescriptor(const CXXRecordDecl *Derived,
                                             raw_ostream &Out) override;
  void
  mangleCXXRTTICompleteObjectLocator(const CXXRecordDecl *Derived,
                                     ArrayRef<const CXXRecordDecl *> BasePath,
                                     raw_ostream &Out) override;
  void mangleCanonicalTypeName(QualType T, raw_ostream &,
                               bool NormalizeIntegers) override;
  void mangleReferenceTemporary(const VarDecl *, unsigned ManglingNumber,
                                raw_ostream &) override;
  void mangleStaticGuardVariable(const VarDecl *D, raw_ostream &Out) override;
  void mangleThreadSafeStaticGuardVariable(const VarDecl *D, unsigned GuardNum,
                                           raw_ostream &Out) override;
  void mangleDynamicInitializer(const VarDecl *D, raw_ostream &Out) override;
  void mangleDynamicAtExitDestructor(const VarDecl *D,
                                     raw_ostream &Out) override;
  void mangleSEHFilterExpression(GlobalDecl EnclosingDecl,
                                 raw_ostream &Out) override;
  void mangleSEHFinallyBlock(GlobalDecl EnclosingDecl,
                             raw_ostream &Out) override;
  void mangleStringLiteral(const StringLiteral *SL, raw_ostream &Out) override;
  bool getNextDiscriminator(const NamedDecl *ND, unsigned &disc) {
    const DeclContext *DC = getEffectiveDeclContext(ND);
    if (!DC->isFunctionOrMethod())
      return false;

    // Lambda closure types are already numbered, give out a phony number so
    // that they demangle nicely.
    if (const auto *RD = dyn_cast<CXXRecordDecl>(ND)) {
      if (RD->isLambda()) {
        disc = 1;
        return true;
      }
    }

    // Use the canonical number for externally visible decls.
    if (ND->isExternallyVisible()) {
      disc = getASTContext().getManglingNumber(ND, isAux());
      return true;
    }

    // Anonymous tags are already numbered.
    if (const TagDecl *Tag = dyn_cast<TagDecl>(ND)) {
      if (!Tag->hasNameForLinkage() &&
          !getASTContext().getDeclaratorForUnnamedTagDecl(Tag) &&
          !getASTContext().getTypedefNameForUnnamedTagDecl(Tag))
        return false;
    }

    // Make up a reasonable number for internal decls.
    unsigned &discriminator = Uniquifier[ND];
    if (!discriminator)
      discriminator = ++Discriminator[std::make_pair(DC, ND->getIdentifier())];
    disc = discriminator + 1;
    return true;
  }

  std::string getLambdaString(const CXXRecordDecl *Lambda) override {
    assert(Lambda->isLambda() && "RD must be a lambda!");
    std::string Name("<lambda_");

    Decl *LambdaContextDecl = Lambda->getLambdaContextDecl();
    unsigned LambdaManglingNumber = Lambda->getLambdaManglingNumber();
    unsigned LambdaId;
    const ParmVarDecl *Parm = dyn_cast_or_null<ParmVarDecl>(LambdaContextDecl);
    const FunctionDecl *Func =
        Parm ? dyn_cast<FunctionDecl>(Parm->getDeclContext()) : nullptr;

    if (Func) {
      unsigned DefaultArgNo =
          Func->getNumParams() - Parm->getFunctionScopeIndex();
      Name += llvm::utostr(DefaultArgNo);
      Name += "_";
    }

    if (LambdaManglingNumber)
      LambdaId = LambdaManglingNumber;
    else
      LambdaId = getLambdaIdForDebugInfo(Lambda);

    Name += llvm::utostr(LambdaId);
    Name += ">";
    return Name;
  }

  unsigned getLambdaId(const CXXRecordDecl *RD) {
    assert(RD->isLambda() && "RD must be a lambda!");
    assert(!RD->isExternallyVisible() && "RD must not be visible!");
    assert(RD->getLambdaManglingNumber() == 0 &&
           "RD must not have a mangling number!");
    std::pair<llvm::DenseMap<const CXXRecordDecl *, unsigned>::iterator, bool>
        Result = LambdaIds.insert(std::make_pair(RD, LambdaIds.size()));
    return Result.first->second;
  }

  unsigned getLambdaIdForDebugInfo(const CXXRecordDecl *RD) {
    assert(RD->isLambda() && "RD must be a lambda!");
    assert(!RD->isExternallyVisible() && "RD must not be visible!");
    assert(RD->getLambdaManglingNumber() == 0 &&
           "RD must not have a mangling number!");
    // The lambda should exist, but return 0 in case it doesn't.
    return LambdaIds.lookup(RD);
  }

  /// Return a character sequence that is (somewhat) unique to the TU suitable
  /// for mangling anonymous namespaces.
  StringRef getAnonymousNamespaceHash() const {
    return AnonymousNamespaceHash;
  }

private:
  void mangleInitFiniStub(const VarDecl *D, char CharCode, raw_ostream &Out);
};

/// MicrosoftCXXNameMangler - Manage the mangling of a single name for the
/// Microsoft Visual C++ ABI.
class MicrosoftCXXNameMangler {
  MicrosoftMangleContextImpl &Context;
  raw_ostream &Out;

  /// The "structor" is the top-level declaration being mangled, if
  /// that's not a template specialization; otherwise it's the pattern
  /// for that specialization.
  const NamedDecl *Structor;
  unsigned StructorType;

  typedef llvm::SmallVector<std::string, 10> BackRefVec;
  BackRefVec NameBackReferences;

  typedef llvm::DenseMap<const void *, unsigned> ArgBackRefMap;
  ArgBackRefMap FunArgBackReferences;
  ArgBackRefMap TemplateArgBackReferences;

  typedef llvm::DenseMap<const void *, StringRef> TemplateArgStringMap;
  TemplateArgStringMap TemplateArgStrings;
  llvm::BumpPtrAllocator TemplateArgStringStorageAlloc;
  llvm::StringSaver TemplateArgStringStorage;

  typedef std::set<std::pair<int, bool>> PassObjectSizeArgsSet;
  PassObjectSizeArgsSet PassObjectSizeArgs;

  ASTContext &getASTContext() const { return Context.getASTContext(); }

  const bool PointersAre64Bit;

  DiagnosticBuilder Error(SourceLocation, StringRef, StringRef);
  DiagnosticBuilder Error(SourceLocation, StringRef);
  DiagnosticBuilder Error(StringRef);

public:
  enum QualifierMangleMode { QMM_Drop, QMM_Mangle, QMM_Escape, QMM_Result };
  enum class TplArgKind { ClassNTTP, StructuralValue };

  MicrosoftCXXNameMangler(MicrosoftMangleContextImpl &C, raw_ostream &Out_)
      : Context(C), Out(Out_), Structor(nullptr), StructorType(-1),
        TemplateArgStringStorage(TemplateArgStringStorageAlloc),
        PointersAre64Bit(C.getASTContext().getTargetInfo().getPointerWidth(
                             LangAS::Default) == 64) {}

  MicrosoftCXXNameMangler(MicrosoftMangleContextImpl &C, raw_ostream &Out_,
                          const CXXConstructorDecl *D, CXXCtorType Type)
      : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
        TemplateArgStringStorage(TemplateArgStringStorageAlloc),
        PointersAre64Bit(C.getASTContext().getTargetInfo().getPointerWidth(
                             LangAS::Default) == 64) {}

  MicrosoftCXXNameMangler(MicrosoftMangleContextImpl &C, raw_ostream &Out_,
                          const CXXDestructorDecl *D, CXXDtorType Type)
      : Context(C), Out(Out_), Structor(getStructor(D)), StructorType(Type),
        TemplateArgStringStorage(TemplateArgStringStorageAlloc),
        PointersAre64Bit(C.getASTContext().getTargetInfo().getPointerWidth(
                             LangAS::Default) == 64) {}

  raw_ostream &getStream() const { return Out; }

  void mangle(GlobalDecl GD, StringRef Prefix = "?");
  void mangleName(GlobalDecl GD);
  void mangleFunctionEncoding(GlobalDecl GD, bool ShouldMangle);
  void mangleVariableEncoding(const VarDecl *VD);
  void mangleMemberDataPointer(const CXXRecordDecl *RD, const ValueDecl *VD,
                               const NonTypeTemplateParmDecl *PD,
                               QualType TemplateArgType,
                               StringRef Prefix = "$");
  void mangleMemberDataPointerInClassNTTP(const CXXRecordDecl *,
                                          const ValueDecl *);
  void mangleMemberFunctionPointer(const CXXRecordDecl *RD,
                                   const CXXMethodDecl *MD,
                                   const NonTypeTemplateParmDecl *PD,
                                   QualType TemplateArgType,
                                   StringRef Prefix = "$");
  void mangleFunctionPointer(const FunctionDecl *FD,
                             const NonTypeTemplateParmDecl *PD,
                             QualType TemplateArgType);
  void mangleVarDecl(const VarDecl *VD, const NonTypeTemplateParmDecl *PD,
                     QualType TemplateArgType);
  void mangleMemberFunctionPointerInClassNTTP(const CXXRecordDecl *RD,
                                              const CXXMethodDecl *MD);
  void mangleVirtualMemPtrThunk(const CXXMethodDecl *MD,
                                const MethodVFTableLocation &ML);
  void mangleNumber(int64_t Number);
  void mangleNumber(llvm::APSInt Number);
  void mangleFloat(llvm::APFloat Number);
  void mangleBits(llvm::APInt Number);
  void mangleTagTypeKind(TagTypeKind TK);
  void mangleArtificialTagType(TagTypeKind TK, StringRef UnqualifiedName,
                               ArrayRef<StringRef> NestedNames = {});
  void mangleAddressSpaceType(QualType T, Qualifiers Quals, SourceRange Range);
  void mangleType(QualType T, SourceRange Range,
                  QualifierMangleMode QMM = QMM_Mangle);
  void mangleFunctionType(const FunctionType *T,
                          const FunctionDecl *D = nullptr,
                          bool ForceThisQuals = false,
                          bool MangleExceptionSpec = true);
  void mangleSourceName(StringRef Name);
  void mangleNestedName(GlobalDecl GD);

  void mangleAutoReturnType(QualType T, QualifierMangleMode QMM);

private:
  bool isStructorDecl(const NamedDecl *ND) const {
    return ND == Structor || getStructor(ND) == Structor;
  }

  bool is64BitPointer(Qualifiers Quals) const {
    LangAS AddrSpace = Quals.getAddressSpace();
    return AddrSpace == LangAS::ptr64 ||
           (PointersAre64Bit && !(AddrSpace == LangAS::ptr32_sptr ||
                                  AddrSpace == LangAS::ptr32_uptr));
  }

  void mangleUnqualifiedName(GlobalDecl GD) {
    mangleUnqualifiedName(GD, cast<NamedDecl>(GD.getDecl())->getDeclName());
  }
  void mangleUnqualifiedName(GlobalDecl GD, DeclarationName Name);
  void mangleOperatorName(OverloadedOperatorKind OO, SourceLocation Loc);
  void mangleCXXDtorType(CXXDtorType T);
  void mangleQualifiers(Qualifiers Quals, bool IsMember);
  void mangleRefQualifier(RefQualifierKind RefQualifier);
  void manglePointerCVQualifiers(Qualifiers Quals);
  void manglePointerExtQualifiers(Qualifiers Quals, QualType PointeeType);
  void manglePointerAuthQualifier(Qualifiers Quals);

  void mangleUnscopedTemplateName(GlobalDecl GD);
  void
  mangleTemplateInstantiationName(GlobalDecl GD,
                                  const TemplateArgumentList &TemplateArgs);
  void mangleObjCMethodName(const ObjCMethodDecl *MD);

  void mangleFunctionArgumentType(QualType T, SourceRange Range);
  void manglePassObjectSizeArg(const PassObjectSizeAttr *POSA);

  bool isArtificialTagType(QualType T) const;

  // Declare manglers for every type class.
#define ABSTRACT_TYPE(CLASS, PARENT)
#define NON_CANONICAL_TYPE(CLASS, PARENT)
#define TYPE(CLASS, PARENT) void mangleType(const CLASS##Type *T, \
                                            Qualifiers Quals, \
                                            SourceRange Range);
#include "clang/AST/TypeNodes.inc"
#undef ABSTRACT_TYPE
#undef NON_CANONICAL_TYPE
#undef TYPE

  void mangleType(const TagDecl *TD);
  void mangleDecayedArrayType(const ArrayType *T);
  void mangleArrayType(const ArrayType *T);
  void mangleFunctionClass(const FunctionDecl *FD);
  void mangleCallingConvention(CallingConv CC, SourceRange Range);
  void mangleCallingConvention(const FunctionType *T, SourceRange Range);
  void mangleIntegerLiteral(const llvm::APSInt &Number,
                            const NonTypeTemplateParmDecl *PD = nullptr,
                            QualType TemplateArgType = QualType());
  void mangleExpression(const Expr *E, const NonTypeTemplateParmDecl *PD);
  void mangleThrowSpecification(const FunctionProtoType *T);

  void mangleTemplateArgs(const TemplateDecl *TD,
                          const TemplateArgumentList &TemplateArgs);
  void mangleTemplateArg(const TemplateDecl *TD, const TemplateArgument &TA,
                         const NamedDecl *Parm);
  void mangleTemplateArgValue(QualType T, const APValue &V, TplArgKind,
                              bool WithScalarType = false);

  void mangleObjCProtocol(const ObjCProtocolDecl *PD);
  void mangleObjCLifetime(const QualType T, Qualifiers Quals,
                          SourceRange Range);
  void mangleObjCKindOfType(const ObjCObjectType *T, Qualifiers Quals,
                            SourceRange Range);

  void mangleAutoReturnType(const MemberPointerType *T, Qualifiers Quals);
  void mangleAutoReturnType(const PointerType *T, Qualifiers Quals);
  void mangleAutoReturnType(const LValueReferenceType *T, Qualifiers Quals);
  void mangleAutoReturnType(const RValueReferenceType *T, Qualifiers Quals);
};
}

MicrosoftMangleContextImpl::MicrosoftMangleContextImpl(ASTContext &Context,
                                                       DiagnosticsEngine &Diags,
                                                       bool IsAux)
    : MicrosoftMangleContext(Context, Diags, IsAux) {
  // To mangle anonymous namespaces, hash the path to the main source file. The
  // path should be whatever (probably relative) path was passed on the command
  // line. The goal is for the compiler to produce the same output regardless of
  // working directory, so use the uncanonicalized relative path.
  //
  // It's important to make the mangled names unique because, when CodeView
  // debug info is in use, the debugger uses mangled type names to distinguish
  // between otherwise identically named types in anonymous namespaces.
  //
  // These symbols are always internal, so there is no need for the hash to
  // match what MSVC produces. For the same reason, clang is free to change the
  // hash at any time without breaking compatibility with old versions of clang.
  // The generated names are intended to look similar to what MSVC generates,
  // which are something like "?A0x01234567@".
  SourceManager &SM = Context.getSourceManager();
  if (OptionalFileEntryRef FE = SM.getFileEntryRefForID(SM.getMainFileID())) {
    // Truncate the hash so we get 8 characters of hexadecimal.
    uint32_t TruncatedHash = uint32_t(xxh3_64bits(FE->getName()));
    AnonymousNamespaceHash = llvm::utohexstr(TruncatedHash);
  } else {
    // If we don't have a path to the main file, we'll just use 0.
    AnonymousNamespaceHash = "0";
  }
}

bool MicrosoftMangleContextImpl::shouldMangleCXXName(const NamedDecl *D) {
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D)) {
    LanguageLinkage L = FD->getLanguageLinkage();
    // Overloadable functions need mangling.
    if (FD->hasAttr<OverloadableAttr>())
      return true;

    // The ABI expects that we would never mangle "typical" user-defined entry
    // points regardless of visibility or freestanding-ness.
    //
    // N.B. This is distinct from asking about "main".  "main" has a lot of
    // special rules associated with it in the standard while these
    // user-defined entry points are outside of the purview of the standard.
    // For example, there can be only one definition for "main" in a standards
    // compliant program; however nothing forbids the existence of wmain and
    // WinMain in the same translation unit.
    if (FD->isMSVCRTEntryPoint())
      return false;

    // C++ functions and those whose names are not a simple identifier need
    // mangling.
    if (!FD->getDeclName().isIdentifier() || L == CXXLanguageLinkage)
      return true;

    // C functions are not mangled.
    if (L == CLanguageLinkage)
      return false;
  }

  // Otherwise, no mangling is done outside C++ mode.
  if (!getASTContext().getLangOpts().CPlusPlus)
    return false;

  const VarDecl *VD = dyn_cast<VarDecl>(D);
  if (VD && !isa<DecompositionDecl>(D)) {
    // C variables are not mangled.
    if (VD->isExternC())
      return false;

    // Variables at global scope with internal linkage are not mangled.
    const DeclContext *DC = getEffectiveDeclContext(D);
    // Check for extern variable declared locally.
    if (DC->isFunctionOrMethod() && D->hasLinkage())
      while (!DC->isNamespace() && !DC->isTranslationUnit())
        DC = getEffectiveParentContext(DC);

    if (DC->isTranslationUnit() && D->getFormalLinkage() == Linkage::Internal &&
        !isa<VarTemplateSpecializationDecl>(D) && D->getIdentifier() != nullptr)
      return false;
  }

  return true;
}

bool
MicrosoftMangleContextImpl::shouldMangleStringLiteral(const StringLiteral *SL) {
  return true;
}

DiagnosticBuilder MicrosoftCXXNameMangler::Error(SourceLocation loc,
                                                 StringRef thing1,
                                                 StringRef thing2) {
  DiagnosticsEngine &Diags = Context.getDiags();
  unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                          "cannot mangle this %0 %1 yet");
  return Diags.Report(loc, DiagID) << thing1 << thing2;
}

DiagnosticBuilder MicrosoftCXXNameMangler::Error(SourceLocation loc,
                                                 StringRef thingy) {
  DiagnosticsEngine &Diags = Context.getDiags();
  unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                          "cannot mangle this %0 yet");
  return Diags.Report(loc, DiagID) << thingy;
}

DiagnosticBuilder MicrosoftCXXNameMangler::Error(StringRef thingy) {
  DiagnosticsEngine &Diags = Context.getDiags();
  // extra placeholders are ignored quietly when not used
  unsigned DiagID = Diags.getCustomDiagID(DiagnosticsEngine::Error,
                                          "cannot mangle this %0 yet");
  return Diags.Report(DiagID) << thingy;
}

void MicrosoftCXXNameMangler::mangle(GlobalDecl GD, StringRef Prefix) {
  const NamedDecl *D = cast<NamedDecl>(GD.getDecl());
  // MSVC doesn't mangle C++ names the same way it mangles extern "C" names.
  // Therefore it's really important that we don't decorate the
  // name with leading underscores or leading/trailing at signs. So, by
  // default, we emit an asm marker at the start so we get the name right.
  // Callers can override this with a custom prefix.

  // <mangled-name> ::= ? <name> <type-encoding>
  Out << Prefix;
  mangleName(GD);
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(D))
    mangleFunctionEncoding(GD, Context.shouldMangleDeclName(FD));
  else if (const VarDecl *VD = dyn_cast<VarDecl>(D))
    mangleVariableEncoding(VD);
  else if (isa<MSGuidDecl>(D))
    // MSVC appears to mangle GUIDs as if they were variables of type
    // 'const struct __s_GUID'.
    Out << "3U__s_GUID@@B";
  else if (isa<TemplateParamObjectDecl>(D)) {
    // Template parameter objects don't get a <type-encoding>; their type is
    // specified as part of their value.
  } else
    llvm_unreachable("Tried to mangle unexpected NamedDecl!");
}

void MicrosoftCXXNameMangler::mangleFunctionEncoding(GlobalDecl GD,
                                                     bool ShouldMangle) {
  const FunctionDecl *FD = cast<FunctionDecl>(GD.getDecl());
  // <type-encoding> ::= <function-class> <function-type>

  // Since MSVC operates on the type as written and not the canonical type, it
  // actually matters which decl we have here.  MSVC appears to choose the
  // first, since it is most likely to be the declaration in a header file.
  FD = FD->getFirstDecl();

  // We should never ever see a FunctionNoProtoType at this point.
  // We don't even know how to mangle their types anyway :).
  const FunctionProtoType *FT = FD->getType()->castAs<FunctionProtoType>();

  // extern "C" functions can hold entities that must be mangled.
  // As it stands, these functions still need to get expressed in the full
  // external name.  They have their class and type omitted, replaced with '9'.
  if (ShouldMangle) {
    // We would like to mangle all extern "C" functions using this additional
    // component but this would break compatibility with MSVC's behavior.
    // Instead, do this when we know that compatibility isn't important (in
    // other words, when it is an overloaded extern "C" function).
    if (FD->isExternC() && FD->hasAttr<OverloadableAttr>())
      Out << "$$J0";

    mangleFunctionClass(FD);

    mangleFunctionType(FT, FD, false, false);
  } else {
    Out << '9';
  }
}

void MicrosoftCXXNameMangler::mangleVariableEncoding(const VarDecl *VD) {
  // <type-encoding> ::= <storage-class> <variable-type>
  // <storage-class> ::= 0  # private static member
  //                 ::= 1  # protected static member
  //                 ::= 2  # public static member
  //                 ::= 3  # global
  //                 ::= 4  # static local

  // The first character in the encoding (after the name) is the storage class.
  if (VD->isStaticDataMember()) {
    // If it's a static member, it also encodes the access level.
    switch (VD->getAccess()) {
      default:
      case AS_private: Out << '0'; break;
      case AS_protected: Out << '1'; break;
      case AS_public: Out << '2'; break;
    }
  }
  else if (!VD->isStaticLocal())
    Out << '3';
  else
    Out << '4';
  // Now mangle the type.
  // <variable-type> ::= <type> <cvr-qualifiers>
  //                 ::= <type> <pointee-cvr-qualifiers> # pointers, references
  // Pointers and references are odd. The type of 'int * const foo;' gets
  // mangled as 'QAHA' instead of 'PAHB', for example.
  SourceRange SR = VD->getSourceRange();
  QualType Ty = VD->getType();
  if (Ty->isPointerType() || Ty->isReferenceType() ||
      Ty->isMemberPointerType()) {
    mangleType(Ty, SR, QMM_Drop);
    manglePointerExtQualifiers(
        Ty.getDesugaredType(getASTContext()).getLocalQualifiers(), QualType());
    if (const MemberPointerType *MPT = Ty->getAs<MemberPointerType>()) {
      mangleQualifiers(MPT->getPointeeType().getQualifiers(), true);
      // Member pointers are suffixed with a back reference to the member
      // pointer's class name.
      mangleName(MPT->getMostRecentCXXRecordDecl());
    } else
      mangleQualifiers(Ty->getPointeeType().getQualifiers(), false);
  } else if (const ArrayType *AT = getASTContext().getAsArrayType(Ty)) {
    // Global arrays are funny, too.
    mangleDecayedArrayType(AT);
    if (AT->getElementType()->isArrayType())
      Out << 'A';
    else
      mangleQualifiers(Ty.getQualifiers(), false);
  } else {
    mangleType(Ty, SR, QMM_Drop);
    mangleQualifiers(Ty.getQualifiers(), false);
  }
}

void MicrosoftCXXNameMangler::mangleMemberDataPointer(
    const CXXRecordDecl *RD, const ValueDecl *VD,
    const NonTypeTemplateParmDecl *PD, QualType TemplateArgType,
    StringRef Prefix) {
  // <member-data-pointer> ::= <integer-literal>
  //                       ::= $F <number> <number>
  //                       ::= $G <number> <number> <number>
  //
  // <auto-nttp> ::= $ M <type> <integer-literal>
  // <auto-nttp> ::= $ M <type> F <name> <number>
  // <auto-nttp> ::= $ M <type> G <name> <number> <number>

  int64_t FieldOffset;
  int64_t VBTableOffset;
  MSInheritanceModel IM = RD->getMSInheritanceModel();
  if (VD) {
    FieldOffset = getASTContext().getFieldOffset(VD);
    assert(FieldOffset % getASTContext().getCharWidth() == 0 &&
           "cannot take address of bitfield");
    FieldOffset /= getASTContext().getCharWidth();

    VBTableOffset = 0;

    if (IM == MSInheritanceModel::Virtual)
      FieldOffset -= getASTContext().getOffsetOfBaseWithVBPtr(RD).getQuantity();
  } else {
    FieldOffset = RD->nullFieldOffsetIsZero() ? 0 : -1;

    VBTableOffset = -1;
  }

  char Code = '\0';
  switch (IM) {
  case MSInheritanceModel::Single:      Code = '0'; break;
  case MSInheritanceModel::Multiple:    Code = '0'; break;
  case MSInheritanceModel::Virtual:     Code = 'F'; break;
  case MSInheritanceModel::Unspecified: Code = 'G'; break;
  }

  Out << Prefix;

  if (VD &&
      getASTContext().getLangOpts().isCompatibleWithMSVC(
          LangOptions::MSVC2019) &&
      PD && PD->getType()->getTypeClass() == Type::Auto &&
      !TemplateArgType.isNull()) {
    Out << "M";
    mangleType(TemplateArgType, SourceRange(), QMM_Drop);
  }

  Out << Code;

  mangleNumber(FieldOffset);

  // The C++ standard doesn't allow base-to-derived member pointer conversions
  // in template parameter contexts, so the vbptr offset of data member pointers
  // is always zero.
  if (inheritanceModelHasVBPtrOffsetField(IM))
    mangleNumber(0);
  if (inheritanceModelHasVBTableOffsetField(IM))
    mangleNumber(VBTableOffset);
}

void MicrosoftCXXNameMangler::mangleMemberDataPointerInClassNTTP(
    const CXXRecordDecl *RD, const ValueDecl *VD) {
  MSInheritanceModel IM = RD->getMSInheritanceModel();
  // <nttp-class-member-data-pointer> ::= <member-data-pointer>
  //                                  ::= N
  //                                  ::= 8 <postfix> @ <unqualified-name> @

  if (IM != MSInheritanceModel::Single && IM != MSInheritanceModel::Multiple)
    return mangleMemberDataPointer(RD, VD, nullptr, QualType(), "");

  if (!VD) {
    Out << 'N';
    return;
  }

  Out << '8';
  mangleNestedName(VD);
  Out << '@';
  mangleUnqualifiedName(VD);
  Out << '@';
}

void MicrosoftCXXNameMangler::mangleMemberFunctionPointer(
    const CXXRecordDecl *RD, const CXXMethodDecl *MD,
    const NonTypeTemplateParmDecl *PD, QualType TemplateArgType,
    StringRef Prefix) {
  // <member-function-pointer> ::= $1? <name>
  //                           ::= $H? <name> <number>
  //                           ::= $I? <name> <number> <number>
  //                           ::= $J? <name> <number> <number> <number>
  //
  // <auto-nttp> ::= $ M <type> 1? <name>
  // <auto-nttp> ::= $ M <type> H? <name> <number>
  // <auto-nttp> ::= $ M <type> I? <name> <number> <number>
  // <auto-nttp> ::= $ M <type> J? <name> <number> <number> <number>

  MSInheritanceModel IM = RD->getMSInheritanceModel();

  char Code = '\0';
  switch (IM) {
  case MSInheritanceModel::Single:      Code = '1'; break;
  case MSInheritanceModel::Multiple:    Code = 'H'; break;
  case MSInheritanceModel::Virtual:     Code = 'I'; break;
  case MSInheritanceModel::Unspecified: Code = 'J'; break;
  }

  // If non-virtual, mangle the name.  If virtual, mangle as a virtual memptr
  // thunk.
  uint64_t NVOffset = 0;
  uint64_t VBTableOffset = 0;
  uint64_t VBPtrOffset = 0;
  if (MD) {
    Out << Prefix;

    if (getASTContext().getLangOpts().isCompatibleWithMSVC(
            LangOptions::MSVC2019) &&
        PD && PD->getType()->getTypeClass() == Type::Auto &&
        !TemplateArgType.isNull()) {
      Out << "M";
      mangleType(TemplateArgType, SourceRange(), QMM_Drop);
    }

    Out << Code << '?';
    if (MD->isVirtual()) {
      MicrosoftVTableContext *VTContext =
          cast<MicrosoftVTableContext>(getASTContext().getVTableContext());
      MethodVFTableLocation ML =
          VTContext->getMethodVFTableLocation(GlobalDecl(MD));
      mangleVirtualMemPtrThunk(MD, ML);
      NVOffset = ML.VFPtrOffset.getQuantity();
      VBTableOffset = ML.VBTableIndex * 4;
      if (ML.VBase) {
        const ASTRecordLayout &Layout = getASTContext().getASTRecordLayout(RD);
        VBPtrOffset = Layout.getVBPtrOffset().getQuantity();
      }
    } else {
      mangleName(MD);
      mangleFunctionEncoding(MD, /*ShouldMangle=*/true);
    }

    if (VBTableOffset == 0 && IM == MSInheritanceModel::Virtual)
      NVOffset -= getASTContext().getOffsetOfBaseWithVBPtr(RD).getQuantity();
  } else {
    // Null single inheritance member functions are encoded as a simple nullptr.
    if (IM == MSInheritanceModel::Single) {
      Out << Prefix << "0A@";
      return;
    }
    if (IM == MSInheritanceModel::Unspecified)
      VBTableOffset = -1;
    Out << Prefix << Code;
  }

  if (inheritanceModelHasNVOffsetField(/*IsMemberFunction=*/true, IM))
    mangleNumber(static_cast<uint32_t>(NVOffset));
  if (inheritanceModelHasVBPtrOffsetField(IM))
    mangleNumber(VBPtrOffset);
  if (inheritanceModelHasVBTableOffsetField(IM))
    mangleNumber(VBTableOffset);
}

void MicrosoftCXXNameMangler::mangleFunctionPointer(
    const FunctionDecl *FD, const NonTypeTemplateParmDecl *PD,
    QualType TemplateArgType) {
  // <func-ptr> ::= $1? <mangled-name>
  // <func-ptr> ::= <auto-nttp>
  //
  // <auto-nttp> ::= $ M <type> 1? <mangled-name>
  Out << '$';

  if (getASTContext().getLangOpts().isCompatibleWithMSVC(
          LangOptions::MSVC2019) &&
      PD && PD->getType()->getTypeClass() == Type::Auto &&
      !TemplateArgType.isNull()) {
    Out << "M";
    mangleType(TemplateArgType, SourceRange(), QMM_Drop);
  }

  Out << "1?";
  mangleName(FD);
  mangleFunctionEncoding(FD, /*ShouldMangle=*/true);
}

void MicrosoftCXXNameMangler::mangleVarDecl(const VarDecl *VD,
                                            const NonTypeTemplateParmDecl *PD,
                                            QualType TemplateArgType) {
  // <var-ptr> ::= $1? <mangled-name>
  // <var-ptr> ::= <auto-nttp>
  //
  // <auto-nttp> ::= $ M <type> 1? <mangled-name>
  Out << '$';

  if (getASTContext().getLangOpts().isCompatibleWithMSVC(
          LangOptions::MSVC2019) &&
      PD && PD->getType()->getTypeClass() == Type::Auto &&
      !TemplateArgType.isNull()) {
    Out << "M";
    mangleType(TemplateArgType, SourceRange(), QMM_Drop);
  }

  Out << "1?";
  mangleName(VD);
  mangleVariableEncoding(VD);
}

void MicrosoftCXXNameMangler::mangleMemberFunctionPointerInClassNTTP(
    const CXXRecordDecl *RD, const CXXMethodDecl *MD) {
  // <nttp-class-member-function-pointer> ::= <member-function-pointer>
  //                           ::= N
  //                           ::= E? <virtual-mem-ptr-thunk>
  //                           ::= E? <mangled-name> <type-encoding>

  if (!MD) {
    if (RD->getMSInheritanceModel() != MSInheritanceModel::Single)
      return mangleMemberFunctionPointer(RD, MD, nullptr, QualType(), "");

    Out << 'N';
    return;
  }

  Out << "E?";
  if (MD->isVirtual()) {
    MicrosoftVTableContext *VTContext =
        cast<MicrosoftVTableContext>(getASTContext().getVTableContext());
    MethodVFTableLocation ML =
        VTContext->getMethodVFTableLocation(GlobalDecl(MD));
    mangleVirtualMemPtrThunk(MD, ML);
  } else {
    mangleName(MD);
    mangleFunctionEncoding(MD, /*ShouldMangle=*/true);
  }
}

void MicrosoftCXXNameMangler::mangleVirtualMemPtrThunk(
    const CXXMethodDecl *MD, const MethodVFTableLocation &ML) {
  // Get the vftable offset.
  CharUnits PointerWidth = getASTContext().toCharUnitsFromBits(
      getASTContext().getTargetInfo().getPointerWidth(LangAS::Default));
  uint64_t OffsetInVFTable = ML.Index * PointerWidth.getQuantity();

  Out << "?_9";
  mangleName(MD->getParent());
  Out << "$B";
  mangleNumber(OffsetInVFTable);
  Out << 'A';
  mangleCallingConvention(MD->getType()->castAs<FunctionProtoType>(),
                          MD->getSourceRange());
}

void MicrosoftCXXNameMangler::mangleName(GlobalDecl GD) {
  // <name> ::= <unscoped-name> {[<named-scope>]+ | [<nested-name>]}? @

  // Always start with the unqualified name.
  mangleUnqualifiedName(GD);

  mangleNestedName(GD);

  // Terminate the whole name with an '@'.
  Out << '@';
}

void MicrosoftCXXNameMangler::mangleNumber(int64_t Number) {
  mangleNumber(llvm::APSInt(llvm::APInt(64, Number), /*IsUnsigned*/false));
}

void MicrosoftCXXNameMangler::mangleNumber(llvm::APSInt Number) {
  // MSVC never mangles any integer wider than 64 bits. In general it appears
  // to convert every integer to signed 64 bit before mangling (including
  // unsigned 64 bit values). Do the same, but preserve bits beyond the bottom
  // 64.
  unsigned Width = std::max(Number.getBitWidth(), 64U);
  llvm::APInt Value = Number.extend(Width);

  // <non-negative integer> ::= A@              # when Number == 0
  //                        ::= <decimal digit> # when 1 <= Number <= 10
  //                        ::= <hex digit>+ @  # when Number >= 10
  //
  // <number>               ::= [?] <non-negative integer>

  if (Value.isNegative()) {
    Value = -Value;
    Out << '?';
  }
  mangleBits(Value);
}

void MicrosoftCXXNameMangler::mangleFloat(llvm::APFloat Number) {
  using llvm::APFloat;

  switch (APFloat::SemanticsToEnum(Number.getSemantics())) {
  case APFloat::S_IEEEsingle: Out << 'A'; break;
  case APFloat::S_IEEEdouble: Out << 'B'; break;

  // The following are all Clang extensions. We try to pick manglings that are
  // unlikely to conflict with MSVC's scheme.
  case APFloat::S_IEEEhalf: Out << 'V'; break;
  case APFloat::S_BFloat: Out << 'W'; break;
  case APFloat::S_x87DoubleExtended: Out << 'X'; break;
  case APFloat::S_IEEEquad: Out << 'Y'; break;
  case APFloat::S_PPCDoubleDouble: Out << 'Z'; break;
  case APFloat::S_PPCDoubleDoubleLegacy:
  case APFloat::S_Float8E5M2:
  case APFloat::S_Float8E4M3:
  case APFloat::S_Float8E4M3FN:
  case APFloat::S_Float8E5M2FNUZ:
  case APFloat::S_Float8E4M3FNUZ:
  case APFloat::S_Float8E4M3B11FNUZ:
  case APFloat::S_Float8E3M4:
  case APFloat::S_FloatTF32:
  case APFloat::S_Float8E8M0FNU:
  case APFloat::S_Float6E3M2FN:
  case APFloat::S_Float6E2M3FN:
  case APFloat::S_Float4E2M1FN:
    llvm_unreachable("Tried to mangle unexpected APFloat semantics");
  }

  mangleBits(Number.bitcastToAPInt());
}

void MicrosoftCXXNameMangler::mangleBits(llvm::APInt Value) {
  if (Value == 0)
    Out << "A@";
  else if (Value.uge(1) && Value.ule(10))
    Out << (Value - 1);
  else {
    // Numbers that are not encoded as decimal digits are represented as nibbles
    // in the range of ASCII characters 'A' to 'P'.
    // The number 0x123450 would be encoded as 'BCDEFA'
    llvm::SmallString<32> EncodedNumberBuffer;
    for (; Value != 0; Value.lshrInPlace(4))
      EncodedNumberBuffer.push_back('A' + (Value & 0xf).getZExtValue());
    std::reverse(EncodedNumberBuffer.begin(), EncodedNumberBuffer.end());
    Out.write(EncodedNumberBuffer.data(), EncodedNumberBuffer.size());
    Out << '@';
  }
}

static GlobalDecl isTemplate(GlobalDecl GD,
                             const TemplateArgumentList *&TemplateArgs) {
  const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
  // Check if we have a function template.
  if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
    if (const TemplateDecl *TD = FD->getPrimaryTemplate()) {
      TemplateArgs = FD->getTemplateSpecializationArgs();
      return GD.getWithDecl(TD);
    }
  }

  // Check if we have a class template.
  if (const ClassTemplateSpecializationDecl *Spec =
          dyn_cast<ClassTemplateSpecializationDecl>(ND)) {
    TemplateArgs = &Spec->getTemplateArgs();
    return GD.getWithDecl(Spec->getSpecializedTemplate());
  }

  // Check if we have a variable template.
  if (const VarTemplateSpecializationDecl *Spec =
          dyn_cast<VarTemplateSpecializationDecl>(ND)) {
    TemplateArgs = &Spec->getTemplateArgs();
    return GD.getWithDecl(Spec->getSpecializedTemplate());
  }

  return GlobalDecl();
}

void MicrosoftCXXNameMangler::mangleUnqualifiedName(GlobalDecl GD,
                                                    DeclarationName Name) {
  const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());
  //  <unqualified-name> ::= <operator-name>
  //                     ::= <ctor-dtor-name>
  //                     ::= <source-name>
  //                     ::= <template-name>

  // Check if we have a template.
  const TemplateArgumentList *TemplateArgs = nullptr;
  if (GlobalDecl TD = isTemplate(GD, TemplateArgs)) {
    // Function templates aren't considered for name back referencing.  This
    // makes sense since function templates aren't likely to occur multiple
    // times in a symbol.
    if (isa<FunctionTemplateDecl>(TD.getDecl())) {
      mangleTemplateInstantiationName(TD, *TemplateArgs);
      Out << '@';
      return;
    }

    // Here comes the tricky thing: if we need to mangle something like
    //   void foo(A::X<Y>, B::X<Y>),
    // the X<Y> part is aliased. However, if you need to mangle
    //   void foo(A::X<A::Y>, A::X<B::Y>),
    // the A::X<> part is not aliased.
    // That is, from the mangler's perspective we have a structure like this:
    //   namespace[s] -> type[ -> template-parameters]
    // but from the Clang perspective we have
    //   type [ -> template-parameters]
    //      \-> namespace[s]
    // What we do is we create a new mangler, mangle the same type (without
    // a namespace suffix) to a string using the extra mangler and then use
    // the mangled type name as a key to check the mangling of different types
    // for aliasing.

    // It's important to key cache reads off ND, not TD -- the same TD can
    // be used with different TemplateArgs, but ND uniquely identifies
    // TD / TemplateArg pairs.
    ArgBackRefMap::iterator Found = TemplateArgBackReferences.find(ND);
    if (Found == TemplateArgBackReferences.end()) {

      TemplateArgStringMap::iterator Found = TemplateArgStrings.find(ND);
      if (Found == TemplateArgStrings.end()) {
        // Mangle full template name into temporary buffer.
        llvm::SmallString<64> TemplateMangling;
        llvm::raw_svector_ostream Stream(TemplateMangling);
        MicrosoftCXXNameMangler Extra(Context, Stream);
        Extra.mangleTemplateInstantiationName(TD, *TemplateArgs);

        // Use the string backref vector to possibly get a back reference.
        mangleSourceName(TemplateMangling);

        // Memoize back reference for this type if one exist, else memoize
        // the mangling itself.
        BackRefVec::iterator StringFound =
            llvm::find(NameBackReferences, TemplateMangling);
        if (StringFound != NameBackReferences.end()) {
          TemplateArgBackReferences[ND] =
              StringFound - NameBackReferences.begin();
        } else {
          TemplateArgStrings[ND] =
              TemplateArgStringStorage.save(TemplateMangling.str());
        }
      } else {
        Out << Found->second << '@'; // Outputs a StringRef.
      }
    } else {
      Out << Found->second; // Outputs a back reference (an int).
    }
    return;
  }

  switch (Name.getNameKind()) {
    case DeclarationName::Identifier: {
      if (const IdentifierInfo *II = Name.getAsIdentifierInfo()) {
        bool IsDeviceStub =
            ND &&
            ((isa<FunctionDecl>(ND) && ND->hasAttr<CUDAGlobalAttr>()) ||
             (isa<FunctionTemplateDecl>(ND) &&
              cast<FunctionTemplateDecl>(ND)
                  ->getTemplatedDecl()
                  ->hasAttr<CUDAGlobalAttr>())) &&
            GD.getKernelReferenceKind() == KernelReferenceKind::Stub;
        bool IsOCLDeviceStub =
            ND && isa<FunctionDecl>(ND) &&
            DeviceKernelAttr::isOpenCLSpelling(
                ND->getAttr<DeviceKernelAttr>()) &&
            GD.getKernelReferenceKind() == KernelReferenceKind::Stub;
        if (IsDeviceStub)
          mangleSourceName(
              (llvm::Twine("__device_stub__") + II->getName()).str());
        else if (IsOCLDeviceStub)
          mangleSourceName(
              (llvm::Twine("__clang_ocl_kern_imp_") + II->getName()).str());
        else
          mangleSourceName(II->getName());
        break;
      }

      // Otherwise, an anonymous entity.  We must have a declaration.
      assert(ND && "mangling empty name without declaration");

      if (const NamespaceDecl *NS = dyn_cast<NamespaceDecl>(ND)) {
        if (NS->isAnonymousNamespace()) {
          Out << "?A0x" << Context.getAnonymousNamespaceHash() << '@';
          break;
        }
      }

      if (const DecompositionDecl *DD = dyn_cast<DecompositionDecl>(ND)) {
        // Decomposition declarations are considered anonymous, and get
        // numbered with a $S prefix.
        llvm::SmallString<64> Name("$S");
        // Get a unique id for the anonymous struct.
        Name += llvm::utostr(Context.getAnonymousStructId(DD) + 1);
        mangleSourceName(Name);
        break;
      }

      if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
        // We must have an anonymous union or struct declaration.
        const CXXRecordDecl *RD = VD->getType()->getAsCXXRecordDecl();
        assert(RD && "expected variable decl to have a record type");
        // Anonymous types with no tag or typedef get the name of their
        // declarator mangled in.  If they have no declarator, number them with
        // a $S prefix.
        llvm::SmallString<64> Name("$S");
        // Get a unique id for the anonymous struct.
        Name += llvm::utostr(Context.getAnonymousStructId(RD) + 1);
        mangleSourceName(Name.str());
        break;
      }

      if (const MSGuidDecl *GD = dyn_cast<MSGuidDecl>(ND)) {
        // Mangle a GUID object as if it were a variable with the corresponding
        // mangled name.
        SmallString<sizeof("_GUID_12345678_1234_1234_1234_1234567890ab")> GUID;
        llvm::raw_svector_ostream GUIDOS(GUID);
        Context.mangleMSGuidDecl(GD, GUIDOS);
        mangleSourceName(GUID);
        break;
      }

      if (const auto *TPO = dyn_cast<TemplateParamObjectDecl>(ND)) {
        Out << "?__N";
        mangleTemplateArgValue(TPO->getType().getUnqualifiedType(),
                               TPO->getValue(), TplArgKind::ClassNTTP);
        break;
      }

      // We must have an anonymous struct.
      const TagDecl *TD = cast<TagDecl>(ND);
      if (const TypedefNameDecl *D = TD->getTypedefNameForAnonDecl()) {
        assert(TD->getDeclContext() == D->getDeclContext() &&
               "Typedef should not be in another decl context!");
        assert(D->getDeclName().getAsIdentifierInfo() &&
               "Typedef was not named!");
        mangleSourceName(D->getDeclName().getAsIdentifierInfo()->getName());
        break;
      }

      if (const CXXRecordDecl *Record = dyn_cast<CXXRecordDecl>(TD)) {
        if (Record->isLambda()) {
          llvm::SmallString<10> Name("<lambda_");

          Decl *LambdaContextDecl = Record->getLambdaContextDecl();
          unsigned LambdaManglingNumber = Record->getLambdaManglingNumber();
          unsigned LambdaId;
          const ParmVarDecl *Parm =
              dyn_cast_or_null<ParmVarDecl>(LambdaContextDecl);
          const FunctionDecl *Func =
              Parm ? dyn_cast<FunctionDecl>(Parm->getDeclContext()) : nullptr;

          if (Func) {
            unsigned DefaultArgNo =
                Func->getNumParams() - Parm->getFunctionScopeIndex();
            Name += llvm::utostr(DefaultArgNo);
            Name += "_";
          }

          if (LambdaManglingNumber)
            LambdaId = LambdaManglingNumber;
          else
            LambdaId = Context.getLambdaId(Record);

          Name += llvm::utostr(LambdaId);
          Name += ">";

          mangleSourceName(Name);

          // If the context is a variable or a class member and not a parameter,
          // it is encoded in a qualified name.
          if (LambdaManglingNumber && LambdaContextDecl) {
            if ((isa<VarDecl>(LambdaContextDecl) ||
                 isa<FieldDecl>(LambdaContextDecl)) &&
                !isa<ParmVarDecl>(LambdaContextDecl)) {
              mangleUnqualifiedName(cast<NamedDecl>(LambdaContextDecl));
            }
          }
          break;
        }
      }

      llvm::SmallString<64> Name;
      if (DeclaratorDecl *DD =
              Context.getASTContext().getDeclaratorForUnnamedTagDecl(TD)) {
        // Anonymous types without a name for linkage purposes have their
        // declarator mangled in if they have one.
        Name += "<unnamed-type-";
        Name += DD->getName();
      } else if (TypedefNameDecl *TND =
                     Context.getASTContext().getTypedefNameForUnnamedTagDecl(
                         TD)) {
        // Anonymous types without a name for linkage purposes have their
        // associate typedef mangled in if they have one.
        Name += "<unnamed-type-";
        Name += TND->getName();
      } else if (isa<EnumDecl>(TD) &&
                 cast<EnumDecl>(TD)->enumerator_begin() !=
                     cast<EnumDecl>(TD)->enumerator_end()) {
        // Anonymous non-empty enums mangle in the first enumerator.
        auto *ED = cast<EnumDecl>(TD);
        Name += "<unnamed-enum-";
        Name += ED->enumerator_begin()->getName();
      } else {
        // Otherwise, number the types using a $S prefix.
        Name += "<unnamed-type-$S";
        Name += llvm::utostr(Context.getAnonymousStructId(TD) + 1);
      }
      Name += ">";
      mangleSourceName(Name.str());
      break;
    }

    case DeclarationName::ObjCZeroArgSelector:
    case DeclarationName::ObjCOneArgSelector:
    case DeclarationName::ObjCMultiArgSelector: {
      // This is reachable only when constructing an outlined SEH finally
      // block.  Nothing depends on this mangling and it's used only with
      // functinos with internal linkage.
      llvm::SmallString<64> Name;
      mangleSourceName(Name.str());
      break;
    }

    case DeclarationName::CXXConstructorName:
      if (isStructorDecl(ND)) {
        if (StructorType == Ctor_CopyingClosure) {
          Out << "?_O";
          return;
        }
        if (StructorType == Ctor_DefaultClosure) {
          Out << "?_F";
          return;
        }
      }
      Out << "?0";
      return;

    case DeclarationName::CXXDestructorName:
      if (isStructorDecl(ND))
        // If the named decl is the C++ destructor we're mangling,
        // use the type we were given.
        mangleCXXDtorType(static_cast<CXXDtorType>(StructorType));
      else
        // Otherwise, use the base destructor name. This is relevant if a
        // class with a destructor is declared within a destructor.
        mangleCXXDtorType(Dtor_Base);
      break;

    case DeclarationName::CXXConversionFunctionName:
      // <operator-name> ::= ?B # (cast)
      // The target type is encoded as the return type.
      Out << "?B";
      break;

    case DeclarationName::CXXOperatorName:
      mangleOperatorName(Name.getCXXOverloadedOperator(), ND->getLocation());
      break;

    case DeclarationName::CXXLiteralOperatorName: {
      Out << "?__K";
      mangleSourceName(Name.getCXXLiteralIdentifier()->getName());
      break;
    }

    case DeclarationName::CXXDeductionGuideName:
      llvm_unreachable("Can't mangle a deduction guide name!");

    case DeclarationName::CXXUsingDirective:
      llvm_unreachable("Can't mangle a using directive name!");
  }
}

// <postfix> ::= <unqualified-name> [<postfix>]
//           ::= <substitution> [<postfix>]
void MicrosoftCXXNameMangler::mangleNestedName(GlobalDecl GD) {
  const NamedDecl *ND = cast<NamedDecl>(GD.getDecl());

  if (const auto *ID = dyn_cast<IndirectFieldDecl>(ND))
    for (unsigned I = 1, IE = ID->getChainingSize(); I < IE; ++I)
      mangleSourceName("<unnamed-tag>");

  const DeclContext *DC = getEffectiveDeclContext(ND);
  while (!DC->isTranslationUnit()) {
    if (isa<TagDecl>(ND) || isa<VarDecl>(ND)) {
      unsigned Disc;
      if (Context.getNextDiscriminator(ND, Disc)) {
        Out << '?';
        mangleNumber(Disc);
        Out << '?';
      }
    }

    if (const BlockDecl *BD = dyn_cast<BlockDecl>(DC)) {
      auto Discriminate =
          [](StringRef Name, const unsigned Discriminator,
             const unsigned ParameterDiscriminator) -> std::string {
        std::string Buffer;
        llvm::raw_string_ostream Stream(Buffer);
        Stream << Name;
        if (Discriminator)
          Stream << '_' << Discriminator;
        if (ParameterDiscriminator)
          Stream << '_' << ParameterDiscriminator;
        return Buffer;
      };

      unsigned Discriminator = BD->getBlockManglingNumber();
      if (!Discriminator)
        Discriminator = Context.getBlockId(BD, /*Local=*/false);

      // Mangle the parameter position as a discriminator to deal with unnamed
      // parameters.  Rather than mangling the unqualified parameter name,
      // always use the position to give a uniform mangling.
      unsigned ParameterDiscriminator = 0;
      if (const auto *MC = BD->getBlockManglingContextDecl())
        if (const auto *P = dyn_cast<ParmVarDecl>(MC))
          if (const auto *F = dyn_cast<FunctionDecl>(P->getDeclContext()))
            ParameterDiscriminator =
                F->getNumParams() - P->getFunctionScopeIndex();

      DC = getEffectiveDeclContext(BD);

      Out << '?';
      mangleSourceName(Discriminate("_block_invoke", Discriminator,
                                    ParameterDiscriminator));
      // If we have a block mangling context, encode that now.  This allows us
      // to discriminate between named static data initializers in the same
      // scope.  This is handled differently from parameters, which use
      // positions to discriminate between multiple instances.
      if (const auto *MC = BD->getBlockManglingContextDecl())
        if (!isa<ParmVarDecl>(MC))
          if (const auto *ND = dyn_cast<NamedDecl>(MC))
            mangleUnqualifiedName(ND);
      // MS ABI and Itanium manglings are in inverted scopes.  In the case of a
      // RecordDecl, mangle the entire scope hierarchy at this point rather than
      // just the unqualified name to get the ordering correct.
      if (const auto *RD = dyn_cast<RecordDecl>(DC))
        mangleName(RD);
      else
        Out << '@';
      // void __cdecl
      Out << "YAX";
      // struct __block_literal *
      Out << 'P';
      // __ptr64
      if (PointersAre64Bit)
        Out << 'E';
      Out << 'A';
      mangleArtificialTagType(TagTypeKind::Struct,
                              Discriminate("__block_literal", Discriminator,
                                           ParameterDiscriminator));
      Out << "@Z";

      // If the effective context was a Record, we have fully mangled the
      // qualified name and do not need to continue.
      if (isa<RecordDecl>(DC))
        break;
      continue;
    } else if (const ObjCMethodDecl *Method = dyn_cast<ObjCMethodDecl>(DC)) {
      mangleObjCMethodName(Method);
    } else if (isa<NamedDecl>(DC)) {
      ND = cast<NamedDecl>(DC);
      if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
        mangle(getGlobalDeclAsDeclContext(FD), "?");
        break;
      } else {
        mangleUnqualifiedName(ND);
        // Lambdas in default arguments conceptually belong to the function the
        // parameter corresponds to.
        if (const auto *LDADC = getLambdaDefaultArgumentDeclContext(ND)) {
          DC = LDADC;
          continue;
        }
      }
    }
    DC = DC->getParent();
  }
}

void MicrosoftCXXNameMangler::mangleCXXDtorType(CXXDtorType T) {
  // Microsoft uses the names on the case labels for these dtor variants.  Clang
  // uses the Itanium terminology internally.  Everything in this ABI delegates
  // towards the base dtor.
  switch (T) {
  // <operator-name> ::= ?1  # destructor
  case Dtor_Base: Out << "?1"; return;
  // <operator-name> ::= ?_D # vbase destructor
  case Dtor_Complete: Out << "?_D"; return;
  // <operator-name> ::= ?_G # scalar deleting destructor
  case Dtor_Deleting: Out << "?_G"; return;
  // <operator-name> ::= ?_E # vector deleting destructor
  // FIXME: Add a vector deleting dtor type.  It goes in the vtable, so we need
  // it.
  case Dtor_Comdat:
    llvm_unreachable("not expecting a COMDAT");
  }
  llvm_unreachable("Unsupported dtor type?");
}

void MicrosoftCXXNameMangler::mangleOperatorName(OverloadedOperatorKind OO,
                                                 SourceLocation Loc) {
  switch (OO) {
  //                     ?0 # constructor
  //                     ?1 # destructor
  // <operator-name> ::= ?2 # new
  case OO_New: Out << "?2"; break;
  // <operator-name> ::= ?3 # delete
  case OO_Delete: Out << "?3"; break;
  // <operator-name> ::= ?4 # =
  case OO_Equal: Out << "?4"; break;
  // <operator-name> ::= ?5 # >>
  case OO_GreaterGreater: Out << "?5"; break;
  // <operator-name> ::= ?6 # <<
  case OO_LessLess: Out << "?6"; break;
  // <operator-name> ::= ?7 # !
  case OO_Exclaim: Out << "?7"; break;
  // <operator-name> ::= ?8 # ==
  case OO_EqualEqual: Out << "?8"; break;
  // <operator-name> ::= ?9 # !=
  case OO_ExclaimEqual: Out << "?9"; break;
  // <operator-name> ::= ?A # []
  case OO_Subscript: Out << "?A"; break;
  //                     ?B # conversion
  // <operator-name> ::= ?C # ->
  case OO_Arrow: Out << "?C"; break;
  // <operator-name> ::= ?D # *
  case OO_Star: Out << "?D"; break;
  // <operator-name> ::= ?E # ++
  case OO_PlusPlus: Out << "?E"; break;
  // <operator-name> ::= ?F # --
  case OO_MinusMinus: Out << "?F"; break;
  // <operator-name> ::= ?G # -
  case OO_Minus: Out << "?G"; break;
  // <operator-name> ::= ?H # +
  case OO_Plus: Out << "?H"; break;
  // <operator-name> ::= ?I # &
  case OO_Amp: Out << "?I"; break;
  // <operator-name> ::= ?J # ->*
  case OO_ArrowStar: Out << "?J"; break;
  // <operator-name> ::= ?K # /
  case OO_Slash: Out << "?K"; break;
  // <operator-name> ::= ?L # %
  case OO_Percent: Out << "?L"; break;
  // <operator-name> ::= ?M # <
  case OO_Less: Out << "?M"; break;
  // <operator-name> ::= ?N # <=
  case OO_LessEqual: Out << "?N"; break;
  // <operator-name> ::= ?O # >
  case OO_Greater: Out << "?O"; break;
  // <operator-name> ::= ?P # >=
  case OO_GreaterEqual: Out << "?P"; break;
  // <operator-name> ::= ?Q # ,
  case OO_Comma: Out << "?Q"; break;
  // <operator-name> ::= ?R # ()
  case OO_Call: Out << "?R"; break;
  // <operator-name> ::= ?S # ~
  case OO_Tilde: Out << "?S"; break;
  // <operator-name> ::= ?T # ^
  case OO_Caret: Out << "?T"; break;
  // <operator-name> ::= ?U # |
  case OO_Pipe: Out << "?U"; break;
  // <operator-name> ::= ?V # &&
  case OO_AmpAmp: Out << "?V"; break;
  // <operator-name> ::= ?W # ||
  case OO_PipePipe: Out << "?W"; break;
  // <operator-name> ::= ?X # *=
  case OO_StarEqual: Out << "?X"; break;
  // <operator-name> ::= ?Y # +=
  case OO_PlusEqual: Out << "?Y"; break;
  // <operator-name> ::= ?Z # -=
  case OO_MinusEqual: Out << "?Z"; break;
  // <operator-name> ::= ?_0 # /=
  case OO_SlashEqual: Out << "?_0"; break;
  // <operator-name> ::= ?_1 # %=
  case OO_PercentEqual: Out << "?_1"; break;
  // <operator-name> ::= ?_2 # >>=
  case OO_GreaterGreaterEqual: Out << "?_2"; break;
  // <operator-name> ::= ?_3 # <<=
  case OO_LessLessEqual: Out << "?_3"; break;
  // <operator-name> ::= ?_4 # &=
  case OO_AmpEqual: Out << "?_4"; break;
  // <operator-name> ::= ?_5 # |=
  case OO_PipeEqual: Out << "?_5"; break;
  // <operator-name> ::= ?_6 # ^=
  case OO_CaretEqual: Out << "?_6"; break;
  //                     ?_7 # vftable
  //                     ?_8 # vbtable
  //                     ?_9 # vcall
  //                     ?_A # typeof
  //                     ?_B # local static guard
  //                     ?_C # string
  //                     ?_D # vbase destructor
  //                     ?_E # vector deleting destructor
  //                     ?_F # default constructor closure
  //                     ?_G # scalar deleting destructor
  //                     ?_H # vector constructor iterator
  //                     ?_I # vector destructor iterator
  //                     ?_J # vector vbase constructor iterator
  //                     ?_K # virtual displacement map
  //                     ?_L # eh vector constructor iterator
  //                     ?_M # eh vector destructor iterator
  //                     ?_N # eh vector vbase constructor iterator
  //                     ?_O # copy constructor closure
  //                     ?_P<name> # udt returning <name>
  //                     ?_Q # <unknown>
  //                     ?_R0 # RTTI Type Descriptor
  //                     ?_R1 # RTTI Base Class Descriptor at (a,b,c,d)
  //                     ?_R2 # RTTI Base Class Array
  //                     ?_R3 # RTTI Class Hierarchy Descriptor
  //                     ?_R4 # RTTI Complete Object Locator
  //                     ?_S # local vftable
  //                     ?_T # local vftable constructor closure
  // <operator-name> ::= ?_U # new[]
  case OO_Array_New: Out << "?_U"; break;
  // <operator-name> ::= ?_V # delete[]
  case OO_Array_Delete: Out << "?_V"; break;
  // <operator-name> ::= ?__L # co_await
  case OO_Coawait: Out << "?__L"; break;
  // <operator-name> ::= ?__M # <=>
  case OO_Spaceship: Out << "?__M"; break;

  case OO_Conditional: {
    Error(Loc, "conditional operator");
    break;
  }

  case OO_None:
  case NUM_OVERLOADED_OPERATORS:
    llvm_unreachable("Not an overloaded operator");
  }
}

void MicrosoftCXXNameMangler::mangleSourceName(StringRef Name) {
  // <source name> ::= <identifier> @
  BackRefVec::iterator Found = llvm::find(NameBackReferences, Name);
  if (Found == NameBackReferences.end()) {
    if (NameBackReferences.size() < 10)
      NameBackReferences.push_back(std::string(Name));
    Out << Name << '@';
  } else {
    Out << (Found - NameBackReferences.begin());
  }
}

void MicrosoftCXXNameMangler::mangleObjCMethodName(const ObjCMethodDecl *MD) {
  Context.mangleObjCMethodNameAsSourceName(MD, Out);
}

void MicrosoftCXXNameMangler::mangleTemplateInstantiationName(
    GlobalDecl GD, const TemplateArgumentList &TemplateArgs) {
  // <template-name> ::= <unscoped-template-name> <template-args>
  //                 ::= <substitution>
  // Always start with the unqualified name.

  // Templates have their own context for back references.
  ArgBackRefMap OuterFunArgsContext;
  ArgBackRefMap OuterTemplateArgsContext;
  BackRefVec OuterTemplateContext;
  PassObjectSizeArgsSet OuterPassObjectSizeArgs;
  NameBackReferences.swap(OuterTemplateContext);
  FunArgBackReferences.swap(OuterFunArgsContext);
  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
  PassObjectSizeArgs.swap(OuterPassObjectSizeArgs);

  mangleUnscopedTemplateName(GD);
  mangleTemplateArgs(cast<TemplateDecl>(GD.getDecl()), TemplateArgs);

  // Restore the previous back reference contexts.
  NameBackReferences.swap(OuterTemplateContext);
  FunArgBackReferences.swap(OuterFunArgsContext);
  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
  PassObjectSizeArgs.swap(OuterPassObjectSizeArgs);
}

void MicrosoftCXXNameMangler::mangleUnscopedTemplateName(GlobalDecl GD) {
  // <unscoped-template-name> ::= ?$ <unqualified-name>
  Out << "?$";
  mangleUnqualifiedName(GD);
}

void MicrosoftCXXNameMangler::mangleIntegerLiteral(
    const llvm::APSInt &Value, const NonTypeTemplateParmDecl *PD,
    QualType TemplateArgType) {
  // <integer-literal> ::= $0 <number>
  // <integer-literal> ::= <auto-nttp>
  //
  // <auto-nttp> ::= $ M <type> 0 <number>
  Out << "$";

  // Since MSVC 2019, add 'M[<type>]' after '$' for auto template parameter when
  // argument is integer.
  if (getASTContext().getLangOpts().isCompatibleWithMSVC(
          LangOptions::MSVC2019) &&
      PD && PD->getType()->getTypeClass() == Type::Auto &&
      !TemplateArgType.isNull()) {
    Out << "M";
    mangleType(TemplateArgType, SourceRange(), QMM_Drop);
  }

  Out << "0";

  mangleNumber(Value);
}

void MicrosoftCXXNameMangler::mangleExpression(
    const Expr *E, const NonTypeTemplateParmDecl *PD) {
  // See if this is a constant expression.
  if (std::optional<llvm::APSInt> Value =
          E->getIntegerConstantExpr(Context.getASTContext())) {
    mangleIntegerLiteral(*Value, PD, E->getType());
    return;
  }

  // As bad as this diagnostic is, it's better than crashing.
  Error(E->getExprLoc(), "expression type: ", E->getStmtClassName())
      << E->getSourceRange();
}

void MicrosoftCXXNameMangler::mangleTemplateArgs(
    const TemplateDecl *TD, const TemplateArgumentList &TemplateArgs) {
  // <template-args> ::= <template-arg>+
  const TemplateParameterList *TPL = TD->getTemplateParameters();
  assert(TPL->size() == TemplateArgs.size() &&
         "size mismatch between args and parms!");

  for (size_t i = 0; i < TemplateArgs.size(); ++i) {
    const TemplateArgument &TA = TemplateArgs[i];

    // Separate consecutive packs by $$Z.
    if (i > 0 && TA.getKind() == TemplateArgument::Pack &&
        TemplateArgs[i - 1].getKind() == TemplateArgument::Pack)
      Out << "$$Z";

    mangleTemplateArg(TD, TA, TPL->getParam(i));
  }
}

/// If value V (with type T) represents a decayed pointer to the first element
/// of an array, return that array.
static ValueDecl *getAsArrayToPointerDecayedDecl(QualType T, const APValue &V) {
  // Must be a pointer...
  if (!T->isPointerType() || !V.isLValue() || !V.hasLValuePath() ||
      !V.getLValueBase())
    return nullptr;
  // ... to element 0 of an array.
  QualType BaseT = V.getLValueBase().getType();
  if (!BaseT->isArrayType() || V.getLValuePath().size() != 1 ||
      V.getLValuePath()[0].getAsArrayIndex() != 0)
    return nullptr;
  return const_cast<ValueDecl *>(
      V.getLValueBase().dyn_cast<const ValueDecl *>());
}

void MicrosoftCXXNameMangler::mangleTemplateArg(const TemplateDecl *TD,
                                                const TemplateArgument &TA,
                                                const NamedDecl *Parm) {
  // <template-arg> ::= <type>
  //                ::= <integer-literal>
  //                ::= <member-data-pointer>
  //                ::= <member-function-pointer>
  //                ::= $ <constant-value>
  //                ::= $ <auto-nttp-constant-value>
  //                ::= <template-args>
  //
  // <auto-nttp-constant-value> ::= M <type> <constant-value>
  //
  // <constant-value> ::= 0 <number>                   # integer
  //                  ::= 1 <mangled-name>             # address of D
  //                  ::= 2 <type> <typed-constant-value>* @ # struct
  //                  ::= 3 <type> <constant-value>* @ # array
  //                  ::= 4 ???                        # string
  //                  ::= 5 <constant-value> @         # address of subobject
  //                  ::= 6 <constant-value> <unqualified-name> @ # a.b
  //                  ::= 7 <type> [<unqualified-name> <constant-value>] @
  //                      # union, with or without an active member
  //                  # pointer to member, symbolically
  //                  ::= 8 <class> <unqualified-name> @
  //                  ::= A <type> <non-negative integer>  # float
  //                  ::= B <type> <non-negative integer>  # double
  //                  # pointer to member, by component value
  //                  ::= F <number> <number>
  //                  ::= G <number> <number> <number>
  //                  ::= H <mangled-name> <number>
  //                  ::= I <mangled-name> <number> <number>
  //                  ::= J <mangled-name> <number> <number> <number>
  //
  // <typed-constant-value> ::= [<type>] <constant-value>
  //
  // The <type> appears to be included in a <typed-constant-value> only in the
  // '0', '1', '8', 'A', 'B', and 'E' cases.

  switch (TA.getKind()) {
  case TemplateArgument::Null:
    llvm_unreachable("Can't mangle null template arguments!");
  case TemplateArgument::TemplateExpansion:
    llvm_unreachable("Can't mangle template expansion arguments!");
  case TemplateArgument::Type: {
    QualType T = TA.getAsType();
    mangleType(T, SourceRange(), QMM_Escape);
    break;
  }
  case TemplateArgument::Declaration: {
    const NamedDecl *ND = TA.getAsDecl();
    if (isa<FieldDecl>(ND) || isa<IndirectFieldDecl>(ND)) {
      mangleMemberDataPointer(cast<CXXRecordDecl>(ND->getDeclContext())
                                  ->getMostRecentNonInjectedDecl(),
                              cast<ValueDecl>(ND),
                              cast<NonTypeTemplateParmDecl>(Parm),
                              TA.getParamTypeForDecl());
    } else if (const FunctionDecl *FD = dyn_cast<FunctionDecl>(ND)) {
      const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD);
      if (MD && MD->isInstance()) {
        mangleMemberFunctionPointer(
            MD->getParent()->getMostRecentNonInjectedDecl(), MD,
            cast<NonTypeTemplateParmDecl>(Parm), TA.getParamTypeForDecl());
      } else {
        mangleFunctionPointer(FD, cast<NonTypeTemplateParmDecl>(Parm),
                              TA.getParamTypeForDecl());
      }
    } else if (TA.getParamTypeForDecl()->isRecordType()) {
      Out << "$";
      auto *TPO = cast<TemplateParamObjectDecl>(ND);
      mangleTemplateArgValue(TPO->getType().getUnqualifiedType(),
                             TPO->getValue(), TplArgKind::ClassNTTP);
    } else if (const VarDecl *VD = dyn_cast<VarDecl>(ND)) {
      mangleVarDecl(VD, cast<NonTypeTemplateParmDecl>(Parm),
                    TA.getParamTypeForDecl());
    } else {
      mangle(ND, "$1?");
    }
    break;
  }
  case TemplateArgument::Integral: {
    QualType T = TA.getIntegralType();
    mangleIntegerLiteral(TA.getAsIntegral(),
                         cast<NonTypeTemplateParmDecl>(Parm), T);
    break;
  }
  case TemplateArgument::NullPtr: {
    QualType T = TA.getNullPtrType();
    if (const MemberPointerType *MPT = T->getAs<MemberPointerType>()) {
      const CXXRecordDecl *RD = MPT->getMostRecentCXXRecordDecl();
      if (MPT->isMemberFunctionPointerType() &&
          !isa<FunctionTemplateDecl>(TD)) {
        mangleMemberFunctionPointer(RD, nullptr, nullptr, QualType());
        return;
      }
      if (MPT->isMemberDataPointer()) {
        if (!isa<FunctionTemplateDecl>(TD)) {
          mangleMemberDataPointer(RD, nullptr, nullptr, QualType());
          return;
        }
        // nullptr data pointers are always represented with a single field
        // which is initialized with either 0 or -1.  Why -1?  Well, we need to
        // distinguish the case where the data member is at offset zero in the
        // record.
        // However, we are free to use 0 *if* we would use multiple fields for
        // non-nullptr member pointers.
        if (!RD->nullFieldOffsetIsZero()) {
          mangleIntegerLiteral(llvm::APSInt::get(-1),
                               cast<NonTypeTemplateParmDecl>(Parm), T);
          return;
        }
      }
    }
    mangleIntegerLiteral(llvm::APSInt::getUnsigned(0),
                         cast<NonTypeTemplateParmDecl>(Parm), T);
    break;
  }
  case TemplateArgument::StructuralValue:
    if (ValueDecl *D = getAsArrayToPointerDecayedDecl(
            TA.getStructuralValueType(), TA.getAsStructuralValue())) {
      // Mangle the result of array-to-pointer decay as if it were a reference
      // to the original declaration, to match MSVC's behavior. This can result
      // in mangling collisions in some cases!
      return mangleTemplateArg(
          TD, TemplateArgument(D, TA.getStructuralValueType()), Parm);
    }
    Out << "$";
    if (cast<NonTypeTemplateParmDecl>(Parm)
            ->getType()
            ->getContainedDeducedType()) {
      Out << "M";
      mangleType(TA.getNonTypeTemplateArgumentType(), SourceRange(), QMM_Drop);
    }
    mangleTemplateArgValue(TA.getStructuralValueType(),
                           TA.getAsStructuralValue(),
                           TplArgKind::StructuralValue,
                           /*WithScalarType=*/false);
    break;
  case TemplateArgument::Expression:
    mangleExpression(TA.getAsExpr(), cast<NonTypeTemplateParmDecl>(Parm));
    break;
  case TemplateArgument::Pack: {
    ArrayRef<TemplateArgument> TemplateArgs = TA.getPackAsArray();
    if (TemplateArgs.empty()) {
      if (isa<TemplateTypeParmDecl>(Parm) ||
          isa<TemplateTemplateParmDecl>(Parm))
        // MSVC 2015 changed the mangling for empty expanded template packs,
        // use the old mangling for link compatibility for old versions.
        Out << (Context.getASTContext().getLangOpts().isCompatibleWithMSVC(
                    LangOptions::MSVC2015)
                    ? "$$V"
                    : "$$$V");
      else if (isa<NonTypeTemplateParmDecl>(Parm))
        Out << "$S";
      else
        llvm_unreachable("unexpected template parameter decl!");
    } else {
      for (const TemplateArgument &PA : TemplateArgs)
        mangleTemplateArg(TD, PA, Parm);
    }
    break;
  }
  case TemplateArgument::Template: {
    const NamedDecl *ND =
        TA.getAsTemplate().getAsTemplateDecl()->getTemplatedDecl();
    if (const auto *TD = dyn_cast<TagDecl>(ND)) {
      mangleType(TD);
    } else if (isa<TypeAliasDecl>(ND)) {
      Out << "$$Y";
      mangleName(ND);
    } else {
      llvm_unreachable("unexpected template template NamedDecl!");
    }
    break;
  }
  }
}

void MicrosoftCXXNameMangler::mangleTemplateArgValue(QualType T,
                                                     const APValue &V,
                                                     TplArgKind TAK,
                                                     bool WithScalarType) {
  switch (V.getKind()) {
  case APValue::None:
  case APValue::Indeterminate:
    // FIXME: MSVC doesn't allow this, so we can't be sure how it should be
    // mangled.
    if (WithScalarType)
      mangleType(T, SourceRange(), QMM_Escape);
    Out << '@';
    return;

  case APValue::Int:
    if (WithScalarType)
      mangleType(T, SourceRange(), QMM_Escape);
    Out << '0';
    mangleNumber(V.getInt());
    return;

  case APValue::Float:
    if (WithScalarType)
      mangleType(T, SourceRange(), QMM_Escape);
    mangleFloat(V.getFloat());
    return;

  case APValue::LValue: {
    if (WithScalarType)
      mangleType(T, SourceRange(), QMM_Escape);

    APValue::LValueBase Base = V.getLValueBase();

    // this might not cover every case but did cover issue 97756
    // see test CodeGen/ms_mangler_templatearg_opte
    if (V.isLValueOnePastTheEnd()) {
      Out << "5E";
      auto *VD = Base.dyn_cast<const ValueDecl *>();
      if (VD)
        mangle(VD);
      Out << "@";
      return;
    }

    if (!V.hasLValuePath() || V.getLValuePath().empty()) {
      // Taking the address of a complete object has a special-case mangling.
      if (Base.isNull()) {
        // MSVC emits 0A@ for null pointers. Generalize this for arbitrary
        // integers cast to pointers.
        // FIXME: This mangles 0 cast to a pointer the same as a null pointer,
        // even in cases where the two are different values.
        Out << "0";
        mangleNumber(V.getLValueOffset().getQuantity());
      } else if (!V.hasLValuePath()) {
        // FIXME: This can only happen as an extension. Invent a mangling.
        Error("template argument (extension not comaptible with ms mangler)");
        return;
      } else if (auto *VD = Base.dyn_cast<const ValueDecl*>()) {
        Out << "E";
        mangle(VD);
      } else {
        Error("template argument (undeclared base)");
        return;
      }
    } else {
      if (TAK == TplArgKind::ClassNTTP && T->isPointerType())
        Out << "5";

      SmallVector<char, 2> EntryTypes;
      SmallVector<std::function<void()>, 2> EntryManglers;
      QualType ET = Base.getType();
      for (APValue::LValuePathEntry E : V.getLValuePath()) {
        if (auto *AT = ET->getAsArrayTypeUnsafe()) {
          EntryTypes.push_back('C');
          EntryManglers.push_back([this, I = E.getAsArrayIndex()] {
            Out << '0';
            mangleNumber(I);
            Out << '@';
          });
          ET = AT->getElementType();
          continue;
        }

        const Decl *D = E.getAsBaseOrMember().getPointer();
        if (auto *FD = dyn_cast<FieldDecl>(D)) {
          ET = FD->getType();
          if (const auto *RD = ET->getAsRecordDecl())
            if (RD->isAnonymousStructOrUnion())
              continue;
        } else {
          ET = getASTContext().getRecordType(cast<CXXRecordDecl>(D));
          // Bug in MSVC: fully qualified name of base class should be used for
          // mangling to prevent collisions e.g. on base classes with same names
          // in different namespaces.
        }

        EntryTypes.push_back('6');
        EntryManglers.push_back([this, D] {
          mangleUnqualifiedName(cast<NamedDecl>(D));
          Out << '@';
        });
      }

      for (auto I = EntryTypes.rbegin(), E = EntryTypes.rend(); I != E; ++I)
        Out << *I;

      auto *VD = Base.dyn_cast<const ValueDecl*>();
      if (!VD) {
        Error("template argument (null value decl)");
        return;
      }
      Out << (TAK == TplArgKind::ClassNTTP ? 'E' : '1');
      mangle(VD);

      for (const std::function<void()> &Mangler : EntryManglers)
        Mangler();
      if (TAK == TplArgKind::ClassNTTP && T->isPointerType())
        Out << '@';
    }

    return;
  }

  case APValue::MemberPointer: {
    if (WithScalarType)
      mangleType(T, SourceRange(), QMM_Escape);

    const CXXRecordDecl *RD =
        T->castAs<MemberPointerType>()->getMostRecentCXXRecordDecl();
    const ValueDecl *D = V.getMemberPointerDecl();
    if (TAK == TplArgKind::ClassNTTP) {
      if (T->isMemberDataPointerType())
        mangleMemberDataPointerInClassNTTP(RD, D);
      else
        mangleMemberFunctionPointerInClassNTTP(RD,
                                               cast_or_null<CXXMethodDecl>(D));
    } else {
      if (T->isMemberDataPointerType())
        mangleMemberDataPointer(RD, D, nullptr, QualType(), "");
      else
        mangleMemberFunctionPointer(RD, cast_or_null<CXXMethodDecl>(D), nullptr,
                                    QualType(), "");
    }
    return;
  }

  case APValue::Struct: {
    Out << '2';
    mangleType(T, SourceRange(), QMM_Escape);
    const CXXRecordDecl *RD = T->getAsCXXRecordDecl();
    assert(RD && "unexpected type for record value");

    unsigned BaseIndex = 0;
    for (const CXXBaseSpecifier &B : RD->bases())
      mangleTemplateArgValue(B.getType(), V.getStructBase(BaseIndex++), TAK);
    for (const FieldDecl *FD : RD->fields())
      if (!FD->isUnnamedBitField())
        mangleTemplateArgValue(FD->getType(),
                               V.getStructField(FD->getFieldIndex()), TAK,
                               /*WithScalarType*/ true);
    Out << '@';
    return;
  }

  case APValue::Union:
    Out << '7';
    mangleType(T, SourceRange(), QMM_Escape);
    if (const FieldDecl *FD = V.getUnionField()) {
      mangleUnqualifiedName(FD);
      mangleTemplateArgValue(FD->getType(), V.getUnionValue(), TAK);
    }
    Out << '@';
    return;

  case APValue::ComplexInt:
    // We mangle complex types as structs, so mangle the value as a struct too.
    Out << '2';
    mangleType(T, SourceRange(), QMM_Escape);
    Out << '0';
    mangleNumber(V.getComplexIntReal());
    Out << '0';
    mangleNumber(V.getComplexIntImag());
    Out << '@';
    return;

  case APValue::ComplexFloat:
    Out << '2';
    mangleType(T, SourceRange(), QMM_Escape);
    mangleFloat(V.getComplexFloatReal());
    mangleFloat(V.getComplexFloatImag());
    Out << '@';
    return;

  case APValue::Array: {
    Out << '3';
    QualType ElemT = getASTContext().getAsArrayType(T)->getElementType();
    mangleType(ElemT, SourceRange(), QMM_Escape);
    for (unsigned I = 0, N = V.getArraySize(); I != N; ++I) {
      const APValue &ElemV = I < V.getArrayInitializedElts()
                                 ? V.getArrayInitializedElt(I)
                                 : V.getArrayFiller();
      mangleTemplateArgValue(ElemT, ElemV, TAK);
      Out << '@';
    }
    Out << '@';
    return;
  }

  case APValue::Vector: {
    // __m128 is mangled as a struct containing an array. We follow this
    // approach for all vector types.
    Out << '2';
    mangleType(T, SourceRange(), QMM_Escape);
    Out << '3';
    QualType ElemT = T->castAs<VectorType>()->getElementType();
    mangleType(ElemT, SourceRange(), QMM_Escape);
    for (unsigned I = 0, N = V.getVectorLength(); I != N; ++I) {
      const APValue &ElemV = V.getVectorElt(I);
      mangleTemplateArgValue(ElemT, ElemV, TAK);
      Out << '@';
    }
    Out << "@@";
    return;
  }

  case APValue::AddrLabelDiff: {
    Error("template argument (value type: address label diff)");
    return;
  }

  case APValue::FixedPoint: {
    Error("template argument (value type: fixed point)");
    return;
  }
  }
}

void MicrosoftCXXNameMangler::mangleObjCProtocol(const ObjCProtocolDecl *PD) {
  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);

  Stream << "?$";
  Extra.mangleSourceName("Protocol");
  Extra.mangleArtificialTagType(TagTypeKind::Struct, PD->getName());

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__ObjC"});
}

void MicrosoftCXXNameMangler::mangleObjCLifetime(const QualType Type,
                                                 Qualifiers Quals,
                                                 SourceRange Range) {
  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);

  Stream << "?$";
  switch (Quals.getObjCLifetime()) {
  case Qualifiers::OCL_None:
  case Qualifiers::OCL_ExplicitNone:
    break;
  case Qualifiers::OCL_Autoreleasing:
    Extra.mangleSourceName("Autoreleasing");
    break;
  case Qualifiers::OCL_Strong:
    Extra.mangleSourceName("Strong");
    break;
  case Qualifiers::OCL_Weak:
    Extra.mangleSourceName("Weak");
    break;
  }
  Extra.manglePointerCVQualifiers(Quals);
  Extra.manglePointerExtQualifiers(Quals, Type);
  Extra.mangleType(Type, Range);

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__ObjC"});
}

void MicrosoftCXXNameMangler::mangleObjCKindOfType(const ObjCObjectType *T,
                                                   Qualifiers Quals,
                                                   SourceRange Range) {
  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);

  Stream << "?$";
  Extra.mangleSourceName("KindOf");
  Extra.mangleType(QualType(T, 0)
                       .stripObjCKindOfType(getASTContext())
                       ->castAs<ObjCObjectType>(),
                   Quals, Range);

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__ObjC"});
}

void MicrosoftCXXNameMangler::mangleQualifiers(Qualifiers Quals,
                                               bool IsMember) {
  // <cvr-qualifiers> ::= [E] [F] [I] <base-cvr-qualifiers>
  // 'E' means __ptr64 (32-bit only); 'F' means __unaligned (32/64-bit only);
  // 'I' means __restrict (32/64-bit).
  // Note that the MSVC __restrict keyword isn't the same as the C99 restrict
  // keyword!
  // <base-cvr-qualifiers> ::= A  # near
  //                       ::= B  # near const
  //                       ::= C  # near volatile
  //                       ::= D  # near const volatile
  //                       ::= E  # far (16-bit)
  //                       ::= F  # far const (16-bit)
  //                       ::= G  # far volatile (16-bit)
  //                       ::= H  # far const volatile (16-bit)
  //                       ::= I  # huge (16-bit)
  //                       ::= J  # huge const (16-bit)
  //                       ::= K  # huge volatile (16-bit)
  //                       ::= L  # huge const volatile (16-bit)
  //                       ::= M <basis> # based
  //                       ::= N <basis> # based const
  //                       ::= O <basis> # based volatile
  //                       ::= P <basis> # based const volatile
  //                       ::= Q  # near member
  //                       ::= R  # near const member
  //                       ::= S  # near volatile member
  //                       ::= T  # near const volatile member
  //                       ::= U  # far member (16-bit)
  //                       ::= V  # far const member (16-bit)
  //                       ::= W  # far volatile member (16-bit)
  //                       ::= X  # far const volatile member (16-bit)
  //                       ::= Y  # huge member (16-bit)
  //                       ::= Z  # huge const member (16-bit)
  //                       ::= 0  # huge volatile member (16-bit)
  //                       ::= 1  # huge const volatile member (16-bit)
  //                       ::= 2 <basis> # based member
  //                       ::= 3 <basis> # based const member
  //                       ::= 4 <basis> # based volatile member
  //                       ::= 5 <basis> # based const volatile member
  //                       ::= 6  # near function (pointers only)
  //                       ::= 7  # far function (pointers only)
  //                       ::= 8  # near method (pointers only)
  //                       ::= 9  # far method (pointers only)
  //                       ::= _A <basis> # based function (pointers only)
  //                       ::= _B <basis> # based function (far?) (pointers only)
  //                       ::= _C <basis> # based method (pointers only)
  //                       ::= _D <basis> # based method (far?) (pointers only)
  //                       ::= _E # block (Clang)
  // <basis> ::= 0 # __based(void)
  //         ::= 1 # __based(segment)?
  //         ::= 2 <name> # __based(name)
  //         ::= 3 # ?
  //         ::= 4 # ?
  //         ::= 5 # not really based
  bool HasConst = Quals.hasConst(),
       HasVolatile = Quals.hasVolatile();

  if (!IsMember) {
    if (HasConst && HasVolatile) {
      Out << 'D';
    } else if (HasVolatile) {
      Out << 'C';
    } else if (HasConst) {
      Out << 'B';
    } else {
      Out << 'A';
    }
  } else {
    if (HasConst && HasVolatile) {
      Out << 'T';
    } else if (HasVolatile) {
      Out << 'S';
    } else if (HasConst) {
      Out << 'R';
    } else {
      Out << 'Q';
    }
  }

  // FIXME: For now, just drop all extension qualifiers on the floor.
}

void
MicrosoftCXXNameMangler::mangleRefQualifier(RefQualifierKind RefQualifier) {
  // <ref-qualifier> ::= G                # lvalue reference
  //                 ::= H                # rvalue-reference
  switch (RefQualifier) {
  case RQ_None:
    break;

  case RQ_LValue:
    Out << 'G';
    break;

  case RQ_RValue:
    Out << 'H';
    break;
  }
}

void MicrosoftCXXNameMangler::manglePointerExtQualifiers(Qualifiers Quals,
                                                         QualType PointeeType) {
  // Check if this is a default 64-bit pointer or has __ptr64 qualifier.
  bool is64Bit = PointeeType.isNull() ? PointersAre64Bit :
      is64BitPointer(PointeeType.getQualifiers());
  if (is64Bit && (PointeeType.isNull() || !PointeeType->isFunctionType()))
    Out << 'E';

  if (Quals.hasRestrict())
    Out << 'I';

  if (Quals.hasUnaligned() ||
      (!PointeeType.isNull() && PointeeType.getLocalQualifiers().hasUnaligned()))
    Out << 'F';
}

void MicrosoftCXXNameMangler::manglePointerAuthQualifier(Qualifiers Quals) {
  PointerAuthQualifier PointerAuth = Quals.getPointerAuth();
  if (!PointerAuth)
    return;

  Out << "__ptrauth";
  mangleNumber(PointerAuth.getKey());
  mangleNumber(PointerAuth.isAddressDiscriminated());
  mangleNumber(PointerAuth.getExtraDiscriminator());
}

void MicrosoftCXXNameMangler::manglePointerCVQualifiers(Qualifiers Quals) {
  // <pointer-cv-qualifiers> ::= P  # no qualifiers
  //                         ::= Q  # const
  //                         ::= R  # volatile
  //                         ::= S  # const volatile
  bool HasConst = Quals.hasConst(),
       HasVolatile = Quals.hasVolatile();

  if (HasConst && HasVolatile) {
    Out << 'S';
  } else if (HasVolatile) {
    Out << 'R';
  } else if (HasConst) {
    Out << 'Q';
  } else {
    Out << 'P';
  }
}

void MicrosoftCXXNameMangler::mangleFunctionArgumentType(QualType T,
                                                         SourceRange Range) {
  // MSVC will backreference two canonically equivalent types that have slightly
  // different manglings when mangled alone.

  // Decayed types do not match up with non-decayed versions of the same type.
  //
  // e.g.
  // void (*x)(void) will not form a backreference with void x(void)
  void *TypePtr;
  if (const auto *DT = T->getAs<DecayedType>()) {
    QualType OriginalType = DT->getOriginalType();
    // All decayed ArrayTypes should be treated identically; as-if they were
    // a decayed IncompleteArrayType.
    if (const auto *AT = getASTContext().getAsArrayType(OriginalType))
      OriginalType = getASTContext().getIncompleteArrayType(
          AT->getElementType(), AT->getSizeModifier(),
          AT->getIndexTypeCVRQualifiers());

    TypePtr = OriginalType.getCanonicalType().getAsOpaquePtr();
    // If the original parameter was textually written as an array,
    // instead treat the decayed parameter like it's const.
    //
    // e.g.
    // int [] -> int * const
    if (OriginalType->isArrayType())
      T = T.withConst();
  } else {
    TypePtr = T.getCanonicalType().getAsOpaquePtr();
  }

  ArgBackRefMap::iterator Found = FunArgBackReferences.find(TypePtr);

  if (Found == FunArgBackReferences.end()) {
    size_t OutSizeBefore = Out.tell();

    mangleType(T, Range, QMM_Drop);

    // See if it's worth creating a back reference.
    // Only types longer than 1 character are considered
    // and only 10 back references slots are available:
    bool LongerThanOneChar = (Out.tell() - OutSizeBefore > 1);
    if (LongerThanOneChar && FunArgBackReferences.size() < 10) {
      size_t Size = FunArgBackReferences.size();
      FunArgBackReferences[TypePtr] = Size;
    }
  } else {
    Out << Found->second;
  }
}

void MicrosoftCXXNameMangler::manglePassObjectSizeArg(
    const PassObjectSizeAttr *POSA) {
  int Type = POSA->getType();
  bool Dynamic = POSA->isDynamic();

  auto Iter = PassObjectSizeArgs.insert({Type, Dynamic}).first;
  auto *TypePtr = (const void *)&*Iter;
  ArgBackRefMap::iterator Found = FunArgBackReferences.find(TypePtr);

  if (Found == FunArgBackReferences.end()) {
    std::string Name =
        Dynamic ? "__pass_dynamic_object_size" : "__pass_object_size";
    mangleArtificialTagType(TagTypeKind::Enum, Name + llvm::utostr(Type),
                            {"__clang"});

    if (FunArgBackReferences.size() < 10) {
      size_t Size = FunArgBackReferences.size();
      FunArgBackReferences[TypePtr] = Size;
    }
  } else {
    Out << Found->second;
  }
}

void MicrosoftCXXNameMangler::mangleAddressSpaceType(QualType T,
                                                     Qualifiers Quals,
                                                     SourceRange Range) {
  // Address space is mangled as an unqualified templated type in the __clang
  // namespace. The demangled version of this is:
  // In the case of a language specific address space:
  // __clang::struct _AS[language_addr_space]<Type>
  // where:
  //  <language_addr_space> ::= <OpenCL-addrspace> | <CUDA-addrspace>
  //    <OpenCL-addrspace> ::= "CL" [ "global" | "local" | "constant" |
  //                                "private"| "generic" | "device" | "host" ]
  //    <CUDA-addrspace> ::= "CU" [ "device" | "constant" | "shared" ]
  //    Note that the above were chosen to match the Itanium mangling for this.
  //
  // In the case of a non-language specific address space:
  //  __clang::struct _AS<TargetAS, Type>
  assert(Quals.hasAddressSpace() && "Not valid without address space");
  llvm::SmallString<32> ASMangling;
  llvm::raw_svector_ostream Stream(ASMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);
  Stream << "?$";

  LangAS AS = Quals.getAddressSpace();
  if (Context.getASTContext().addressSpaceMapManglingFor(AS)) {
    unsigned TargetAS = Context.getASTContext().getTargetAddressSpace(AS);
    Extra.mangleSourceName("_AS");
    Extra.mangleIntegerLiteral(llvm::APSInt::getUnsigned(TargetAS));
  } else {
    switch (AS) {
    default:
      llvm_unreachable("Not a language specific address space");
    case LangAS::opencl_global:
      Extra.mangleSourceName("_ASCLglobal");
      break;
    case LangAS::opencl_global_device:
      Extra.mangleSourceName("_ASCLdevice");
      break;
    case LangAS::opencl_global_host:
      Extra.mangleSourceName("_ASCLhost");
      break;
    case LangAS::opencl_local:
      Extra.mangleSourceName("_ASCLlocal");
      break;
    case LangAS::opencl_constant:
      Extra.mangleSourceName("_ASCLconstant");
      break;
    case LangAS::opencl_private:
      Extra.mangleSourceName("_ASCLprivate");
      break;
    case LangAS::opencl_generic:
      Extra.mangleSourceName("_ASCLgeneric");
      break;
    case LangAS::cuda_device:
      Extra.mangleSourceName("_ASCUdevice");
      break;
    case LangAS::cuda_constant:
      Extra.mangleSourceName("_ASCUconstant");
      break;
    case LangAS::cuda_shared:
      Extra.mangleSourceName("_ASCUshared");
      break;
    case LangAS::ptr32_sptr:
    case LangAS::ptr32_uptr:
    case LangAS::ptr64:
      llvm_unreachable("don't mangle ptr address spaces with _AS");
    }
  }

  Extra.mangleType(T, Range, QMM_Escape);
  mangleQualifiers(Qualifiers(), false);
  mangleArtificialTagType(TagTypeKind::Struct, ASMangling, {"__clang"});
}

void MicrosoftCXXNameMangler::mangleAutoReturnType(QualType T,
                                                   QualifierMangleMode QMM) {
  assert(getASTContext().getLangOpts().isCompatibleWithMSVC(
             LangOptions::MSVC2019) &&
         "Cannot mangle MSVC 2017 auto return types!");

  if (isa<AutoType>(T)) {
    const auto *AT = T->getContainedAutoType();
    Qualifiers Quals = T.getLocalQualifiers();

    if (QMM == QMM_Result)
      Out << '?';
    if (QMM != QMM_Drop)
      mangleQualifiers(Quals, false);
    Out << (AT->isDecltypeAuto() ? "_T" : "_P");
    return;
  }

  T = T.getDesugaredType(getASTContext());
  Qualifiers Quals = T.getLocalQualifiers();

  switch (QMM) {
  case QMM_Drop:
  case QMM_Result:
    break;
  case QMM_Mangle:
    mangleQualifiers(Quals, false);
    break;
  default:
    llvm_unreachable("QMM_Escape unexpected");
  }

  const Type *ty = T.getTypePtr();
  switch (ty->getTypeClass()) {
  case Type::MemberPointer:
    mangleAutoReturnType(cast<MemberPointerType>(ty), Quals);
    break;
  case Type::Pointer:
    mangleAutoReturnType(cast<PointerType>(ty), Quals);
    break;
  case Type::LValueReference:
    mangleAutoReturnType(cast<LValueReferenceType>(ty), Quals);
    break;
  case Type::RValueReference:
    mangleAutoReturnType(cast<RValueReferenceType>(ty), Quals);
    break;
  default:
    llvm_unreachable("Invalid type expected");
  }
}

void MicrosoftCXXNameMangler::mangleType(QualType T, SourceRange Range,
                                         QualifierMangleMode QMM) {
  // Don't use the canonical types.  MSVC includes things like 'const' on
  // pointer arguments to function pointers that canonicalization strips away.
  T = T.getDesugaredType(getASTContext());
  Qualifiers Quals = T.getLocalQualifiers();

  if (const ArrayType *AT = getASTContext().getAsArrayType(T)) {
    // If there were any Quals, getAsArrayType() pushed them onto the array
    // element type.
    if (QMM == QMM_Mangle)
      Out << 'A';
    else if (QMM == QMM_Escape || QMM == QMM_Result)
      Out << "$$B";
    mangleArrayType(AT);
    return;
  }

  bool IsPointer = T->isAnyPointerType() || T->isMemberPointerType() ||
                   T->isReferenceType() || T->isBlockPointerType();

  switch (QMM) {
  case QMM_Drop:
    if (Quals.hasObjCLifetime())
      Quals = Quals.withoutObjCLifetime();
    break;
  case QMM_Mangle:
    if (const FunctionType *FT = dyn_cast<FunctionType>(T)) {
      Out << '6';
      mangleFunctionType(FT);
      return;
    }
    mangleQualifiers(Quals, false);
    break;
  case QMM_Escape:
    if (!IsPointer && Quals) {
      Out << "$$C";
      mangleQualifiers(Quals, false);
    }
    break;
  case QMM_Result:
    // Presence of __unaligned qualifier shouldn't affect mangling here.
    Quals.removeUnaligned();
    if (Quals.hasObjCLifetime())
      Quals = Quals.withoutObjCLifetime();
    if ((!IsPointer && Quals) || isa<TagType>(T) || isArtificialTagType(T)) {
      Out << '?';
      mangleQualifiers(Quals, false);
    }
    break;
  }

  const Type *ty = T.getTypePtr();

  switch (ty->getTypeClass()) {
#define ABSTRACT_TYPE(CLASS, PARENT)
#define NON_CANONICAL_TYPE(CLASS, PARENT) \
  case Type::CLASS: \
    llvm_unreachable("can't mangle non-canonical type " #CLASS "Type"); \
    return;
#define TYPE(CLASS, PARENT) \
  case Type::CLASS: \
    mangleType(cast<CLASS##Type>(ty), Quals, Range); \
    break;
#include "clang/AST/TypeNodes.inc"
#undef ABSTRACT_TYPE
#undef NON_CANONICAL_TYPE
#undef TYPE
  }
}

void MicrosoftCXXNameMangler::mangleType(const BuiltinType *T, Qualifiers,
                                         SourceRange Range) {
  //  <type>         ::= <builtin-type>
  //  <builtin-type> ::= X  # void
  //                 ::= C  # signed char
  //                 ::= D  # char
  //                 ::= E  # unsigned char
  //                 ::= F  # short
  //                 ::= G  # unsigned short (or wchar_t if it's not a builtin)
  //                 ::= H  # int
  //                 ::= I  # unsigned int
  //                 ::= J  # long
  //                 ::= K  # unsigned long
  //                     L  # <none>
  //                 ::= M  # float
  //                 ::= N  # double
  //                 ::= O  # long double (__float80 is mangled differently)
  //                 ::= _J # long long, __int64
  //                 ::= _K # unsigned long long, __int64
  //                 ::= _L # __int128
  //                 ::= _M # unsigned __int128
  //                 ::= _N # bool
  //                     _O # <array in parameter>
  //                 ::= _Q # char8_t
  //                 ::= _S # char16_t
  //                 ::= _T # __float80 (Intel)
  //                 ::= _U # char32_t
  //                 ::= _W # wchar_t
  //                 ::= _Z # __float80 (Digital Mars)
  switch (T->getKind()) {
  case BuiltinType::Void:
    Out << 'X';
    break;
  case BuiltinType::SChar:
    Out << 'C';
    break;
  case BuiltinType::Char_U:
  case BuiltinType::Char_S:
    Out << 'D';
    break;
  case BuiltinType::UChar:
    Out << 'E';
    break;
  case BuiltinType::Short:
    Out << 'F';
    break;
  case BuiltinType::UShort:
    Out << 'G';
    break;
  case BuiltinType::Int:
    Out << 'H';
    break;
  case BuiltinType::UInt:
    Out << 'I';
    break;
  case BuiltinType::Long:
    Out << 'J';
    break;
  case BuiltinType::ULong:
    Out << 'K';
    break;
  case BuiltinType::Float:
    Out << 'M';
    break;
  case BuiltinType::Double:
    Out << 'N';
    break;
  // TODO: Determine size and mangle accordingly
  case BuiltinType::LongDouble:
    Out << 'O';
    break;
  case BuiltinType::LongLong:
    Out << "_J";
    break;
  case BuiltinType::ULongLong:
    Out << "_K";
    break;
  case BuiltinType::Int128:
    Out << "_L";
    break;
  case BuiltinType::UInt128:
    Out << "_M";
    break;
  case BuiltinType::Bool:
    Out << "_N";
    break;
  case BuiltinType::Char8:
    Out << "_Q";
    break;
  case BuiltinType::Char16:
    Out << "_S";
    break;
  case BuiltinType::Char32:
    Out << "_U";
    break;
  case BuiltinType::WChar_S:
  case BuiltinType::WChar_U:
    Out << "_W";
    break;

#define BUILTIN_TYPE(Id, SingletonId)
#define PLACEHOLDER_TYPE(Id, SingletonId) \
  case BuiltinType::Id:
#include "clang/AST/BuiltinTypes.def"
  case BuiltinType::Dependent:
    llvm_unreachable("placeholder types shouldn't get to name mangling");

  case BuiltinType::ObjCId:
    mangleArtificialTagType(TagTypeKind::Struct, "objc_object");
    break;
  case BuiltinType::ObjCClass:
    mangleArtificialTagType(TagTypeKind::Struct, "objc_class");
    break;
  case BuiltinType::ObjCSel:
    mangleArtificialTagType(TagTypeKind::Struct, "objc_selector");
    break;

#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix) \
  case BuiltinType::Id: \
    Out << "PAUocl_" #ImgType "_" #Suffix "@@"; \
    break;
#include "clang/Basic/OpenCLImageTypes.def"
  case BuiltinType::OCLSampler:
    Out << "PA";
    mangleArtificialTagType(TagTypeKind::Struct, "ocl_sampler");
    break;
  case BuiltinType::OCLEvent:
    Out << "PA";
    mangleArtificialTagType(TagTypeKind::Struct, "ocl_event");
    break;
  case BuiltinType::OCLClkEvent:
    Out << "PA";
    mangleArtificialTagType(TagTypeKind::Struct, "ocl_clkevent");
    break;
  case BuiltinType::OCLQueue:
    Out << "PA";
    mangleArtificialTagType(TagTypeKind::Struct, "ocl_queue");
    break;
  case BuiltinType::OCLReserveID:
    Out << "PA";
    mangleArtificialTagType(TagTypeKind::Struct, "ocl_reserveid");
    break;
#define EXT_OPAQUE_TYPE(ExtType, Id, Ext)                                      \
  case BuiltinType::Id:                                                        \
    mangleArtificialTagType(TagTypeKind::Struct, "ocl_" #ExtType);             \
    break;
#include "clang/Basic/OpenCLExtensionTypes.def"

  case BuiltinType::NullPtr:
    Out << "$$T";
    break;

  case BuiltinType::Float16:
    mangleArtificialTagType(TagTypeKind::Struct, "_Float16", {"__clang"});
    break;

  case BuiltinType::Half:
    if (!getASTContext().getLangOpts().HLSL)
      mangleArtificialTagType(TagTypeKind::Struct, "_Half", {"__clang"});
    else if (getASTContext().getLangOpts().NativeHalfType)
      Out << "$f16@";
    else
      Out << "$halff@";
    break;

  case BuiltinType::BFloat16:
    mangleArtificialTagType(TagTypeKind::Struct, "__bf16", {"__clang"});
    break;

  case BuiltinType::MFloat8:
    mangleArtificialTagType(TagTypeKind::Struct, "__mfp8", {"__clang"});
    break;

#define WASM_REF_TYPE(InternalName, MangledName, Id, SingletonId, AS)          \
  case BuiltinType::Id:                                                        \
    mangleArtificialTagType(TagTypeKind::Struct, MangledName);                 \
    mangleArtificialTagType(TagTypeKind::Struct, MangledName, {"__clang"});    \
    break;

#include "clang/Basic/WebAssemblyReferenceTypes.def"

#define HLSL_INTANGIBLE_TYPE(Name, Id, SingletonId)                            \
  case BuiltinType::Id:                                                        \
    mangleArtificialTagType(TagTypeKind::Struct, #Name);                       \
    break;
#include "clang/Basic/HLSLIntangibleTypes.def"

#define SVE_TYPE(Name, Id, SingletonId)                                        \
  case BuiltinType::Id:                                                        \
    mangleArtificialTagType(TagTypeKind::Struct, #Name, {"__clang"});          \
    break;
#define SVE_SCALAR_TYPE(Name, MangledName, Id, SingletonId, Bits)
#include "clang/Basic/AArch64ACLETypes.def"

    // Issue an error for any type not explicitly handled.
  default:
    Error(Range.getBegin(), "built-in type: ",
          T->getName(Context.getASTContext().getPrintingPolicy()))
        << Range;
    break;
  }
}

// <type>          ::= <function-type>
void MicrosoftCXXNameMangler::mangleType(const FunctionProtoType *T, Qualifiers,
                                         SourceRange) {
  // Structors only appear in decls, so at this point we know it's not a
  // structor type.
  // FIXME: This may not be lambda-friendly.
  if (T->getMethodQuals() || T->getRefQualifier() != RQ_None) {
    Out << "$$A8@@";
    mangleFunctionType(T, /*D=*/nullptr, /*ForceThisQuals=*/true);
  } else {
    Out << "$$A6";
    mangleFunctionType(T);
  }
}
void MicrosoftCXXNameMangler::mangleType(const FunctionNoProtoType *T,
                                         Qualifiers, SourceRange) {
  Out << "$$A6";
  mangleFunctionType(T);
}

void MicrosoftCXXNameMangler::mangleFunctionType(const FunctionType *T,
                                                 const FunctionDecl *D,
                                                 bool ForceThisQuals,
                                                 bool MangleExceptionSpec) {
  // <function-type> ::= <this-cvr-qualifiers> <calling-convention>
  //                     <return-type> <argument-list> <throw-spec>
  const FunctionProtoType *Proto = dyn_cast<FunctionProtoType>(T);

  SourceRange Range;
  if (D) Range = D->getSourceRange();

  bool IsInLambda = false;
  bool IsStructor = false, HasThisQuals = ForceThisQuals, IsCtorClosure = false;
  CallingConv CC = T->getCallConv();
  if (const CXXMethodDecl *MD = dyn_cast_or_null<CXXMethodDecl>(D)) {
    if (MD->getParent()->isLambda())
      IsInLambda = true;
    if (MD->isImplicitObjectMemberFunction())
      HasThisQuals = true;
    if (isa<CXXDestructorDecl>(MD)) {
      IsStructor = true;
    } else if (isa<CXXConstructorDecl>(MD)) {
      IsStructor = true;
      IsCtorClosure = (StructorType == Ctor_CopyingClosure ||
                       StructorType == Ctor_DefaultClosure) &&
                      isStructorDecl(MD);
      if (IsCtorClosure)
        CC = getASTContext().getDefaultCallingConvention(
            /*IsVariadic=*/false, /*IsCXXMethod=*/true);
    }
  }

  // If this is a C++ instance method, mangle the CVR qualifiers for the
  // this pointer.
  if (HasThisQuals) {
    Qualifiers Quals = Proto->getMethodQuals();
    manglePointerExtQualifiers(Quals, /*PointeeType=*/QualType());
    mangleRefQualifier(Proto->getRefQualifier());
    mangleQualifiers(Quals, /*IsMember=*/false);
  }

  mangleCallingConvention(CC, Range);

  // <return-type> ::= <type>
  //               ::= @ # structors (they have no declared return type)
  if (IsStructor) {
    if (isa<CXXDestructorDecl>(D) && isStructorDecl(D)) {
      // The scalar deleting destructor takes an extra int argument which is not
      // reflected in the AST.
      if (StructorType == Dtor_Deleting) {
        Out << (PointersAre64Bit ? "PEAXI@Z" : "PAXI@Z");
        return;
      }
      // The vbase destructor returns void which is not reflected in the AST.
      if (StructorType == Dtor_Complete) {
        Out << "XXZ";
        return;
      }
    }
    if (IsCtorClosure) {
      // Default constructor closure and copy constructor closure both return
      // void.
      Out << 'X';

      if (StructorType == Ctor_DefaultClosure) {
        // Default constructor closure always has no arguments.
        Out << 'X';
      } else if (StructorType == Ctor_CopyingClosure) {
        // Copy constructor closure always takes an unqualified reference.
        mangleFunctionArgumentType(getASTContext().getLValueReferenceType(
                                       Proto->getParamType(0)
                                           ->castAs<LValueReferenceType>()
                                           ->getPointeeType(),
                                       /*SpelledAsLValue=*/true),
                                   Range);
        Out << '@';
      } else {
        llvm_unreachable("unexpected constructor closure!");
      }
      Out << 'Z';
      return;
    }
    Out << '@';
  } else if (IsInLambda && isa_and_nonnull<CXXConversionDecl>(D)) {
    // The only lambda conversion operators are to function pointers, which
    // can differ by their calling convention and are typically deduced.  So
    // we make sure that this type gets mangled properly.
    mangleType(T->getReturnType(), Range, QMM_Result);
  } else {
    QualType ResultType = T->getReturnType();
    if (IsInLambda && isa<CXXConversionDecl>(D)) {
      // The only lambda conversion operators are to function pointers, which
      // can differ by their calling convention and are typically deduced.  So
      // we make sure that this type gets mangled properly.
      mangleType(ResultType, Range, QMM_Result);
    } else if (IsInLambda) {
      if (const auto *AT = ResultType->getContainedAutoType()) {
        assert(AT->getKeyword() != AutoTypeKeyword::GNUAutoType &&
               "shouldn't need to mangle __auto_type!");
        Out << '?';
        mangleQualifiers(ResultType.getLocalQualifiers(), /*IsMember=*/false);
        Out << '?';
        mangleSourceName(AT->isDecltypeAuto() ? "<decltype-auto>" : "<auto>");
        Out << '@';
      } else {
        Out << '@';
      }
    } else if (const auto *AT = ResultType->getContainedAutoType()) {
      assert(AT->getKeyword() != AutoTypeKeyword::GNUAutoType &&
             "shouldn't need to mangle __auto_type!");

      // If we have any pointer types with the clang address space extension
      // then defer to the custom clang mangling to keep backwards
      // compatibility. See `mangleType(const PointerType *T, Qualifiers Quals,
      // SourceRange Range)` for details.
      auto UseClangMangling = [](QualType ResultType) {
        QualType T = ResultType;
        while (isa<PointerType>(T.getTypePtr())) {
          T = T->getPointeeType();
          if (T.getQualifiers().hasAddressSpace())
            return true;
        }
        return false;
      };

      if (getASTContext().getLangOpts().isCompatibleWithMSVC(
              LangOptions::MSVC2019) &&
          !UseClangMangling(ResultType)) {
        if (D && !D->getPrimaryTemplate()) {
          Out << '@';
        } else {
          if (D && D->getPrimaryTemplate()) {
            const FunctionProtoType *FPT = D->getPrimaryTemplate()
                                               ->getTemplatedDecl()
                                               ->getFirstDecl()
                                               ->getType()
                                               ->castAs<FunctionProtoType>();
            ResultType = FPT->getReturnType();
          }
          mangleAutoReturnType(ResultType, QMM_Result);
        }
      } else {
        Out << '?';
        mangleQualifiers(ResultType.getLocalQualifiers(), /*IsMember=*/false);
        Out << '?';
        mangleSourceName(AT->isDecltypeAuto() ? "<decltype-auto>" : "<auto>");
        Out << '@';
      }
    } else {
      if (ResultType->isVoidType())
        ResultType = ResultType.getUnqualifiedType();
      mangleType(ResultType, Range, QMM_Result);
    }
  }

  // <argument-list> ::= X # void
  //                 ::= <type>+ @
  //                 ::= <type>* Z # varargs
  if (!Proto) {
    // Function types without prototypes can arise when mangling a function type
    // within an overloadable function in C. We mangle these as the absence of
    // any parameter types (not even an empty parameter list).
    Out << '@';
  } else if (Proto->getNumParams() == 0 && !Proto->isVariadic()) {
    Out << 'X';
  } else {
    // Happens for function pointer type arguments for example.
    for (unsigned I = 0, E = Proto->getNumParams(); I != E; ++I) {
      // Explicit object parameters are prefixed by "_V".
      if (I == 0 && D && D->getParamDecl(I)->isExplicitObjectParameter())
        Out << "_V";

      mangleFunctionArgumentType(Proto->getParamType(I), Range);
      // Mangle each pass_object_size parameter as if it's a parameter of enum
      // type passed directly after the parameter with the pass_object_size
      // attribute. The aforementioned enum's name is __pass_object_size, and we
      // pretend it resides in a top-level namespace called __clang.
      //
      // FIXME: Is there a defined extension notation for the MS ABI, or is it
      // necessary to just cross our fingers and hope this type+namespace
      // combination doesn't conflict with anything?
      if (D)
        if (const auto *P = D->getParamDecl(I)->getAttr<PassObjectSizeAttr>())
          manglePassObjectSizeArg(P);
    }
    // <builtin-type>      ::= Z  # ellipsis
    if (Proto->isVariadic())
      Out << 'Z';
    else
      Out << '@';
  }

  if (MangleExceptionSpec && getASTContext().getLangOpts().CPlusPlus17 &&
      getASTContext().getLangOpts().isCompatibleWithMSVC(
          LangOptions::MSVC2017_5))
    mangleThrowSpecification(Proto);
  else
    Out << 'Z';
}

void MicrosoftCXXNameMangler::mangleFunctionClass(const FunctionDecl *FD) {
  // <function-class>  ::= <member-function> E? # E designates a 64-bit 'this'
  //                                            # pointer. in 64-bit mode *all*
  //                                            # 'this' pointers are 64-bit.
  //                   ::= <global-function>
  // <member-function> ::= A # private: near
  //                   ::= B # private: far
  //                   ::= C # private: static near
  //                   ::= D # private: static far
  //                   ::= E # private: virtual near
  //                   ::= F # private: virtual far
  //                   ::= I # protected: near
  //                   ::= J # protected: far
  //                   ::= K # protected: static near
  //                   ::= L # protected: static far
  //                   ::= M # protected: virtual near
  //                   ::= N # protected: virtual far
  //                   ::= Q # public: near
  //                   ::= R # public: far
  //                   ::= S # public: static near
  //                   ::= T # public: static far
  //                   ::= U # public: virtual near
  //                   ::= V # public: virtual far
  // <global-function> ::= Y # global near
  //                   ::= Z # global far
  if (const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(FD)) {
    bool IsVirtual = MD->isVirtual();
    // When mangling vbase destructor variants, ignore whether or not the
    // underlying destructor was defined to be virtual.
    if (isa<CXXDestructorDecl>(MD) && isStructorDecl(MD) &&
        StructorType == Dtor_Complete) {
      IsVirtual = false;
    }
    switch (MD->getAccess()) {
      case AS_none:
        llvm_unreachable("Unsupported access specifier");
      case AS_private:
        if (!MD->isImplicitObjectMemberFunction())
          Out << 'C';
        else if (IsVirtual)
          Out << 'E';
        else
          Out << 'A';
        break;
      case AS_protected:
        if (!MD->isImplicitObjectMemberFunction())
          Out << 'K';
        else if (IsVirtual)
          Out << 'M';
        else
          Out << 'I';
        break;
      case AS_public:
        if (!MD->isImplicitObjectMemberFunction())
          Out << 'S';
        else if (IsVirtual)
          Out << 'U';
        else
          Out << 'Q';
    }
  } else {
    Out << 'Y';
  }
}
void MicrosoftCXXNameMangler::mangleCallingConvention(CallingConv CC,
                                                      SourceRange Range) {
  // <calling-convention> ::= A # __cdecl
  //                      ::= B # __export __cdecl
  //                      ::= C # __pascal
  //                      ::= D # __export __pascal
  //                      ::= E # __thiscall
  //                      ::= F # __export __thiscall
  //                      ::= G # __stdcall
  //                      ::= H # __export __stdcall
  //                      ::= I # __fastcall
  //                      ::= J # __export __fastcall
  //                      ::= Q # __vectorcall
  //                      ::= S # __attribute__((__swiftcall__)) // Clang-only
  //                      ::= W # __attribute__((__swiftasynccall__))
  //                      ::= U # __attribute__((__preserve_most__))
  //                      ::= V # __attribute__((__preserve_none__)) //
  //                      Clang-only
  //                            // Clang-only
  //                      ::= w # __regcall
  //                      ::= x # __regcall4
  // The 'export' calling conventions are from a bygone era
  // (*cough*Win16*cough*) when functions were declared for export with
  // that keyword. (It didn't actually export them, it just made them so
  // that they could be in a DLL and somebody from another module could call
  // them.)

  switch (CC) {
    default:
      break;
    case CC_Win64:
    case CC_X86_64SysV:
    case CC_C:
      Out << 'A';
      return;
    case CC_X86Pascal:
      Out << 'C';
      return;
    case CC_X86ThisCall:
      Out << 'E';
      return;
    case CC_X86StdCall:
      Out << 'G';
      return;
    case CC_X86FastCall:
      Out << 'I';
      return;
    case CC_X86VectorCall:
      Out << 'Q';
      return;
    case CC_Swift:
      Out << 'S';
      return;
    case CC_SwiftAsync:
      Out << 'W';
      return;
    case CC_PreserveMost:
      Out << 'U';
      return;
    case CC_PreserveNone:
      Out << 'V';
      return;
    case CC_X86RegCall:
      if (getASTContext().getLangOpts().RegCall4)
        Out << "x";
      else
        Out << "w";
      return;
  }

  Error(Range.getBegin(), "calling convention") << Range;
}
void MicrosoftCXXNameMangler::mangleCallingConvention(const FunctionType *T,
                                                      SourceRange Range) {
  mangleCallingConvention(T->getCallConv(), Range);
}

void MicrosoftCXXNameMangler::mangleThrowSpecification(
                                                const FunctionProtoType *FT) {
  // <throw-spec> ::= Z # (default)
  //              ::= _E # noexcept
  if (FT->canThrow())
    Out << 'Z';
  else
    Out << "_E";
}

void MicrosoftCXXNameMangler::mangleType(const UnresolvedUsingType *T,
                                         Qualifiers, SourceRange Range) {
  // Probably should be mangled as a template instantiation; need to see what
  // VC does first.
  Error(Range.getBegin(), "unresolved dependent type") << Range;
}

// <type>        ::= <union-type> | <struct-type> | <class-type> | <enum-type>
// <union-type>  ::= T <name>
// <struct-type> ::= U <name>
// <class-type>  ::= V <name>
// <enum-type>   ::= W4 <name>
void MicrosoftCXXNameMangler::mangleTagTypeKind(TagTypeKind TTK) {
  switch (TTK) {
  case TagTypeKind::Union:
    Out << 'T';
    break;
  case TagTypeKind::Struct:
  case TagTypeKind::Interface:
    Out << 'U';
    break;
  case TagTypeKind::Class:
    Out << 'V';
    break;
  case TagTypeKind::Enum:
    Out << "W4";
    break;
  }
}
void MicrosoftCXXNameMangler::mangleType(const EnumType *T, Qualifiers,
                                         SourceRange) {
  mangleType(cast<TagType>(T)->getDecl());
}
void MicrosoftCXXNameMangler::mangleType(const RecordType *T, Qualifiers,
                                         SourceRange) {
  mangleType(cast<TagType>(T)->getDecl());
}
void MicrosoftCXXNameMangler::mangleType(const TagDecl *TD) {
  mangleTagTypeKind(TD->getTagKind());
  mangleName(TD);
}

// If you add a call to this, consider updating isArtificialTagType() too.
void MicrosoftCXXNameMangler::mangleArtificialTagType(
    TagTypeKind TK, StringRef UnqualifiedName,
    ArrayRef<StringRef> NestedNames) {
  // <name> ::= <unscoped-name> {[<named-scope>]+ | [<nested-name>]}? @
  mangleTagTypeKind(TK);

  // Always start with the unqualified name.
  mangleSourceName(UnqualifiedName);

  for (StringRef N : llvm::reverse(NestedNames))
    mangleSourceName(N);

  // Terminate the whole name with an '@'.
  Out << '@';
}

// <type>       ::= <array-type>
// <array-type> ::= <pointer-cvr-qualifiers> <cvr-qualifiers>
//                  [Y <dimension-count> <dimension>+]
//                  <element-type> # as global, E is never required
// It's supposed to be the other way around, but for some strange reason, it
// isn't. Today this behavior is retained for the sole purpose of backwards
// compatibility.
void MicrosoftCXXNameMangler::mangleDecayedArrayType(const ArrayType *T) {
  // This isn't a recursive mangling, so now we have to do it all in this
  // one call.
  manglePointerCVQualifiers(T->getElementType().getQualifiers());
  mangleType(T->getElementType(), SourceRange());
}
void MicrosoftCXXNameMangler::mangleType(const ConstantArrayType *T, Qualifiers,
                                         SourceRange) {
  llvm_unreachable("Should have been special cased");
}
void MicrosoftCXXNameMangler::mangleType(const VariableArrayType *T, Qualifiers,
                                         SourceRange) {
  llvm_unreachable("Should have been special cased");
}
void MicrosoftCXXNameMangler::mangleType(const DependentSizedArrayType *T,
                                         Qualifiers, SourceRange) {
  llvm_unreachable("Should have been special cased");
}
void MicrosoftCXXNameMangler::mangleType(const IncompleteArrayType *T,
                                         Qualifiers, SourceRange) {
  llvm_unreachable("Should have been special cased");
}
void MicrosoftCXXNameMangler::mangleArrayType(const ArrayType *T) {
  QualType ElementTy(T, 0);
  SmallVector<llvm::APInt, 3> Dimensions;
  for (;;) {
    if (ElementTy->isConstantArrayType()) {
      const ConstantArrayType *CAT =
          getASTContext().getAsConstantArrayType(ElementTy);
      Dimensions.push_back(CAT->getSize());
      ElementTy = CAT->getElementType();
    } else if (ElementTy->isIncompleteArrayType()) {
      const IncompleteArrayType *IAT =
          getASTContext().getAsIncompleteArrayType(ElementTy);
      Dimensions.push_back(llvm::APInt(32, 0));
      ElementTy = IAT->getElementType();
    } else if (ElementTy->isVariableArrayType()) {
      const VariableArrayType *VAT =
        getASTContext().getAsVariableArrayType(ElementTy);
      Dimensions.push_back(llvm::APInt(32, 0));
      ElementTy = VAT->getElementType();
    } else if (ElementTy->isDependentSizedArrayType()) {
      // The dependent expression has to be folded into a constant (TODO).
      const DependentSizedArrayType *DSAT =
        getASTContext().getAsDependentSizedArrayType(ElementTy);
      Error(DSAT->getSizeExpr()->getExprLoc(), "dependent-length")
          << DSAT->getSizeExpr()->getSourceRange();
      return;
    } else {
      break;
    }
  }
  Out << 'Y';
  // <dimension-count> ::= <number> # number of extra dimensions
  mangleNumber(Dimensions.size());
  for (const llvm::APInt &Dimension : Dimensions)
    mangleNumber(Dimension.getLimitedValue());
  mangleType(ElementTy, SourceRange(), QMM_Escape);
}

void MicrosoftCXXNameMangler::mangleType(const ArrayParameterType *T,
                                         Qualifiers, SourceRange) {
  mangleArrayType(cast<ConstantArrayType>(T));
}

// <type>                   ::= <pointer-to-member-type>
// <pointer-to-member-type> ::= <pointer-cvr-qualifiers> <cvr-qualifiers>
//                                                          <class name> <type>
void MicrosoftCXXNameMangler::mangleType(const MemberPointerType *T,
                                         Qualifiers Quals, SourceRange Range) {
  QualType PointeeType = T->getPointeeType();
  manglePointerCVQualifiers(Quals);
  manglePointerExtQualifiers(Quals, PointeeType);
  if (const FunctionProtoType *FPT = PointeeType->getAs<FunctionProtoType>()) {
    Out << '8';
    mangleName(T->getMostRecentCXXRecordDecl());
    mangleFunctionType(FPT, nullptr, true);
  } else {
    mangleQualifiers(PointeeType.getQualifiers(), true);
    mangleName(T->getMostRecentCXXRecordDecl());
    mangleType(PointeeType, Range, QMM_Drop);
  }
}

void MicrosoftCXXNameMangler::mangleType(const TemplateTypeParmType *T,
                                         Qualifiers, SourceRange Range) {
  Out << '?';

  llvm::SmallString<64> Name;
  Name += "<TTPT_";
  Name += llvm::utostr(T->getDepth());
  Name += "_";
  Name += llvm::utostr(T->getIndex());
  Name += ">";
  mangleSourceName(Name);
}

void MicrosoftCXXNameMangler::mangleType(const SubstTemplateTypeParmPackType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "substituted parameter pack") << Range;
}

// <type> ::= <pointer-type>
// <pointer-type> ::= E? <pointer-cvr-qualifiers> <cvr-qualifiers> <type>
//                       # the E is required for 64-bit non-static pointers
void MicrosoftCXXNameMangler::mangleType(const PointerType *T, Qualifiers Quals,
                                         SourceRange Range) {
  QualType PointeeType = T->getPointeeType();
  manglePointerCVQualifiers(Quals);
  manglePointerExtQualifiers(Quals, PointeeType);
  manglePointerAuthQualifier(Quals);

  // For pointer size address spaces, go down the same type mangling path as
  // non address space types.
  LangAS AddrSpace = PointeeType.getQualifiers().getAddressSpace();
  if (isPtrSizeAddressSpace(AddrSpace) || AddrSpace == LangAS::Default)
    mangleType(PointeeType, Range);
  else
    mangleAddressSpaceType(PointeeType, PointeeType.getQualifiers(), Range);
}

void MicrosoftCXXNameMangler::mangleType(const ObjCObjectPointerType *T,
                                         Qualifiers Quals, SourceRange Range) {
  QualType PointeeType = T->getPointeeType();
  switch (Quals.getObjCLifetime()) {
  case Qualifiers::OCL_None:
  case Qualifiers::OCL_ExplicitNone:
    break;
  case Qualifiers::OCL_Autoreleasing:
  case Qualifiers::OCL_Strong:
  case Qualifiers::OCL_Weak:
    return mangleObjCLifetime(PointeeType, Quals, Range);
  }
  manglePointerCVQualifiers(Quals);
  manglePointerExtQualifiers(Quals, PointeeType);
  mangleType(PointeeType, Range);
}

// <type> ::= <reference-type>
// <reference-type> ::= A E? <cvr-qualifiers> <type>
//                 # the E is required for 64-bit non-static lvalue references
void MicrosoftCXXNameMangler::mangleType(const LValueReferenceType *T,
                                         Qualifiers Quals, SourceRange Range) {
  QualType PointeeType = T->getPointeeType();
  assert(!Quals.hasConst() && !Quals.hasVolatile() && "unexpected qualifier!");
  Out << 'A';
  manglePointerExtQualifiers(Quals, PointeeType);
  mangleType(PointeeType, Range);
}

// <type> ::= <r-value-reference-type>
// <r-value-reference-type> ::= $$Q E? <cvr-qualifiers> <type>
//                 # the E is required for 64-bit non-static rvalue references
void MicrosoftCXXNameMangler::mangleType(const RValueReferenceType *T,
                                         Qualifiers Quals, SourceRange Range) {
  QualType PointeeType = T->getPointeeType();
  assert(!Quals.hasConst() && !Quals.hasVolatile() && "unexpected qualifier!");
  Out << "$$Q";
  manglePointerExtQualifiers(Quals, PointeeType);
  mangleType(PointeeType, Range);
}

void MicrosoftCXXNameMangler::mangleType(const ComplexType *T, Qualifiers,
                                         SourceRange Range) {
  QualType ElementType = T->getElementType();

  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);
  Stream << "?$";
  Extra.mangleSourceName("_Complex");
  Extra.mangleType(ElementType, Range, QMM_Escape);

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__clang"});
}

// Returns true for types that mangleArtificialTagType() gets called for with
// TagTypeKind Union, Struct, Class and where compatibility with MSVC's
// mangling matters.
// (It doesn't matter for Objective-C types and the like that cl.exe doesn't
// support.)
bool MicrosoftCXXNameMangler::isArtificialTagType(QualType T) const {
  const Type *ty = T.getTypePtr();
  switch (ty->getTypeClass()) {
  default:
    return false;

  case Type::Vector: {
    // For ABI compatibility only __m64, __m128(id), and __m256(id) matter,
    // but since mangleType(VectorType*) always calls mangleArtificialTagType()
    // just always return true (the other vector types are clang-only).
    return true;
  }
  }
}

void MicrosoftCXXNameMangler::mangleType(const VectorType *T, Qualifiers Quals,
                                         SourceRange Range) {
  QualType EltTy = T->getElementType();
  const BuiltinType *ET = EltTy->getAs<BuiltinType>();
  const BitIntType *BitIntTy = EltTy->getAs<BitIntType>();
  assert((ET || BitIntTy) &&
         "vectors with non-builtin/_BitInt elements are unsupported");
  uint64_t Width = getASTContext().getTypeSize(T);
  // Pattern match exactly the typedefs in our intrinsic headers.  Anything that
  // doesn't match the Intel types uses a custom mangling below.
  size_t OutSizeBefore = Out.tell();
  if (!isa<ExtVectorType>(T)) {
    if (getASTContext().getTargetInfo().getTriple().isX86() && ET) {
      if (Width == 64 && ET->getKind() == BuiltinType::LongLong) {
        mangleArtificialTagType(TagTypeKind::Union, "__m64");
      } else if (Width >= 128) {
        if (ET->getKind() == BuiltinType::Float)
          mangleArtificialTagType(TagTypeKind::Union,
                                  "__m" + llvm::utostr(Width));
        else if (ET->getKind() == BuiltinType::LongLong)
          mangleArtificialTagType(TagTypeKind::Union,
                                  "__m" + llvm::utostr(Width) + 'i');
        else if (ET->getKind() == BuiltinType::Double)
          mangleArtificialTagType(TagTypeKind::Struct,
                                  "__m" + llvm::utostr(Width) + 'd');
      }
    }
  }

  bool IsBuiltin = Out.tell() != OutSizeBefore;
  if (!IsBuiltin) {
    // The MS ABI doesn't have a special mangling for vector types, so we define
    // our own mangling to handle uses of __vector_size__ on user-specified
    // types, and for extensions like __v4sf.

    llvm::SmallString<64> TemplateMangling;
    llvm::raw_svector_ostream Stream(TemplateMangling);
    MicrosoftCXXNameMangler Extra(Context, Stream);
    Stream << "?$";
    Extra.mangleSourceName("__vector");
    Extra.mangleType(QualType(ET ? static_cast<const Type *>(ET) : BitIntTy, 0),
                     Range, QMM_Escape);
    Extra.mangleIntegerLiteral(llvm::APSInt::getUnsigned(T->getNumElements()));

    mangleArtificialTagType(TagTypeKind::Union, TemplateMangling, {"__clang"});
  }
}

void MicrosoftCXXNameMangler::mangleType(const ExtVectorType *T,
                                         Qualifiers Quals, SourceRange Range) {
  mangleType(static_cast<const VectorType *>(T), Quals, Range);
}

void MicrosoftCXXNameMangler::mangleType(const DependentVectorType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "dependent-sized vector type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const DependentSizedExtVectorType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "dependent-sized extended vector type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const ConstantMatrixType *T,
                                         Qualifiers quals, SourceRange Range) {
  QualType EltTy = T->getElementType();

  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);

  Stream << "?$";

  Extra.mangleSourceName("__matrix");
  Extra.mangleType(EltTy, Range, QMM_Escape);

  Extra.mangleIntegerLiteral(llvm::APSInt::getUnsigned(T->getNumRows()));
  Extra.mangleIntegerLiteral(llvm::APSInt::getUnsigned(T->getNumColumns()));

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__clang"});
}

void MicrosoftCXXNameMangler::mangleType(const DependentSizedMatrixType *T,
                                         Qualifiers quals, SourceRange Range) {
  Error(Range.getBegin(), "dependent-sized matrix type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const DependentAddressSpaceType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "dependent address space type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const ObjCInterfaceType *T, Qualifiers,
                                         SourceRange) {
  // ObjC interfaces have structs underlying them.
  mangleTagTypeKind(TagTypeKind::Struct);
  mangleName(T->getDecl());
}

void MicrosoftCXXNameMangler::mangleType(const ObjCObjectType *T,
                                         Qualifiers Quals, SourceRange Range) {
  if (T->isKindOfType())
    return mangleObjCKindOfType(T, Quals, Range);

  if (T->qual_empty() && !T->isSpecialized())
    return mangleType(T->getBaseType(), Range, QMM_Drop);

  ArgBackRefMap OuterFunArgsContext;
  ArgBackRefMap OuterTemplateArgsContext;
  BackRefVec OuterTemplateContext;

  FunArgBackReferences.swap(OuterFunArgsContext);
  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
  NameBackReferences.swap(OuterTemplateContext);

  mangleTagTypeKind(TagTypeKind::Struct);

  Out << "?$";
  if (T->isObjCId())
    mangleSourceName("objc_object");
  else if (T->isObjCClass())
    mangleSourceName("objc_class");
  else
    mangleSourceName(T->getInterface()->getName());

  for (const auto &Q : T->quals())
    mangleObjCProtocol(Q);

  if (T->isSpecialized())
    for (const auto &TA : T->getTypeArgs())
      mangleType(TA, Range, QMM_Drop);

  Out << '@';

  Out << '@';

  FunArgBackReferences.swap(OuterFunArgsContext);
  TemplateArgBackReferences.swap(OuterTemplateArgsContext);
  NameBackReferences.swap(OuterTemplateContext);
}

void MicrosoftCXXNameMangler::mangleType(const BlockPointerType *T,
                                         Qualifiers Quals, SourceRange Range) {
  QualType PointeeType = T->getPointeeType();
  manglePointerCVQualifiers(Quals);
  manglePointerExtQualifiers(Quals, PointeeType);

  Out << "_E";

  mangleFunctionType(PointeeType->castAs<FunctionProtoType>());
}

void MicrosoftCXXNameMangler::mangleType(const InjectedClassNameType *,
                                         Qualifiers, SourceRange) {
  llvm_unreachable("Cannot mangle injected class name type.");
}

void MicrosoftCXXNameMangler::mangleType(const TemplateSpecializationType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "template specialization type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const DependentNameType *T, Qualifiers,
                                         SourceRange Range) {
  Error(Range.getBegin(), "dependent name type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(
    const DependentTemplateSpecializationType *T, Qualifiers,
    SourceRange Range) {
  Error(Range.getBegin(), "dependent template specialization type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const PackExpansionType *T, Qualifiers,
                                         SourceRange Range) {
  Error(Range.getBegin(), "pack expansion") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const PackIndexingType *T,
                                         Qualifiers Quals, SourceRange Range) {
  manglePointerCVQualifiers(Quals);
  mangleType(T->getSelectedType(), Range);
}

void MicrosoftCXXNameMangler::mangleType(const TypeOfType *T, Qualifiers,
                                         SourceRange Range) {
  Error(Range.getBegin(), "typeof(type)") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const TypeOfExprType *T, Qualifiers,
                                         SourceRange Range) {
  Error(Range.getBegin(), "typeof(expression)") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const DecltypeType *T, Qualifiers,
                                         SourceRange Range) {
  Error(Range.getBegin(), "decltype()") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const UnaryTransformType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "unary transform type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const AutoType *T, Qualifiers,
                                         SourceRange Range) {
  assert(T->getDeducedType().isNull() && "expecting a dependent type!");

  Error(Range.getBegin(), "'auto' type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(
    const DeducedTemplateSpecializationType *T, Qualifiers, SourceRange Range) {
  assert(T->getDeducedType().isNull() && "expecting a dependent type!");

  Error(Range.getBegin(), "deduced class template specialization type")
      << Range;
}

void MicrosoftCXXNameMangler::mangleType(const AtomicType *T, Qualifiers,
                                         SourceRange Range) {
  QualType ValueType = T->getValueType();

  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);
  Stream << "?$";
  Extra.mangleSourceName("_Atomic");
  Extra.mangleType(ValueType, Range, QMM_Escape);

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__clang"});
}

void MicrosoftCXXNameMangler::mangleType(const PipeType *T, Qualifiers,
                                         SourceRange Range) {
  QualType ElementType = T->getElementType();

  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);
  Stream << "?$";
  Extra.mangleSourceName("ocl_pipe");
  Extra.mangleType(ElementType, Range, QMM_Escape);
  Extra.mangleIntegerLiteral(llvm::APSInt::get(T->isReadOnly()));

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__clang"});
}

void MicrosoftMangleContextImpl::mangleCXXName(GlobalDecl GD,
                                               raw_ostream &Out) {
  const NamedDecl *D = cast<NamedDecl>(GD.getDecl());
  PrettyStackTraceDecl CrashInfo(D, SourceLocation(),
                                 getASTContext().getSourceManager(),
                                 "Mangling declaration");

  msvc_hashing_ostream MHO(Out);

  if (auto *CD = dyn_cast<CXXConstructorDecl>(D)) {
    auto Type = GD.getCtorType();
    MicrosoftCXXNameMangler mangler(*this, MHO, CD, Type);
    return mangler.mangle(GD);
  }

  if (auto *DD = dyn_cast<CXXDestructorDecl>(D)) {
    auto Type = GD.getDtorType();
    MicrosoftCXXNameMangler mangler(*this, MHO, DD, Type);
    return mangler.mangle(GD);
  }

  MicrosoftCXXNameMangler Mangler(*this, MHO);
  return Mangler.mangle(GD);
}

void MicrosoftCXXNameMangler::mangleType(const BitIntType *T, Qualifiers,
                                         SourceRange Range) {
  llvm::SmallString<64> TemplateMangling;
  llvm::raw_svector_ostream Stream(TemplateMangling);
  MicrosoftCXXNameMangler Extra(Context, Stream);
  Stream << "?$";
  if (T->isUnsigned())
    Extra.mangleSourceName("_UBitInt");
  else
    Extra.mangleSourceName("_BitInt");
  Extra.mangleIntegerLiteral(llvm::APSInt::getUnsigned(T->getNumBits()));

  mangleArtificialTagType(TagTypeKind::Struct, TemplateMangling, {"__clang"});
}

void MicrosoftCXXNameMangler::mangleType(const DependentBitIntType *T,
                                         Qualifiers, SourceRange Range) {
  Error(Range.getBegin(), "DependentBitInt type") << Range;
}

void MicrosoftCXXNameMangler::mangleType(const HLSLAttributedResourceType *T,
                                         Qualifiers, SourceRange Range) {
  llvm_unreachable("HLSL uses Itanium name mangling");
}

void MicrosoftCXXNameMangler::mangleType(const HLSLInlineSpirvType *T,
                                         Qualifiers, SourceRange Range) {
  llvm_unreachable("HLSL uses Itanium name mangling");
}

// <this-adjustment> ::= <no-adjustment> | <static-adjustment> |
//                       <virtual-adjustment>
// <no-adjustment>      ::= A # private near
//                      ::= B # private far
//                      ::= I # protected near
//                      ::= J # protected far
//                      ::= Q # public near
//                      ::= R # public far
// <static-adjustment>  ::= G <static-offset> # private near
//                      ::= H <static-offset> # private far
//                      ::= O <static-offset> # protected near
//                      ::= P <static-offset> # protected far
//                      ::= W <static-offset> # public near
//                      ::= X <static-offset> # public far
// <virtual-adjustment> ::= $0 <virtual-shift> <static-offset> # private near
//                      ::= $1 <virtual-shift> <static-offset> # private far
//                      ::= $2 <virtual-shift> <static-offset> # protected near
//                      ::= $3 <virtual-shift> <static-offset> # protected far
//                      ::= $4 <virtual-shift> <static-offset> # public near
//                      ::= $5 <virtual-shift> <static-offset> # public far
// <virtual-shift>      ::= <vtordisp-shift> | <vtordispex-shift>
// <vtordisp-shift>     ::= <offset-to-vtordisp>
// <vtordispex-shift>   ::= <offset-to-vbptr> <vbase-offset-offset>
//                          <offset-to-vtordisp>
static void mangleThunkThisAdjustment(AccessSpecifier AS,
                                      const ThisAdjustment &Adjustment,
                                      MicrosoftCXXNameMangler &Mangler,
                                      raw_ostream &Out) {
  if (!Adjustment.Virtual.isEmpty()) {
    Out << '$';
    char AccessSpec;
    switch (AS) {
    case AS_none:
      llvm_unreachable("Unsupported access specifier");
    case AS_private:
      AccessSpec = '0';
      break;
    case AS_protected:
      AccessSpec = '2';
      break;
    case AS_public:
      AccessSpec = '4';
    }
    if (Adjustment.Virtual.Microsoft.VBPtrOffset) {
      Out << 'R' << AccessSpec;
      Mangler.mangleNumber(
          static_cast<uint32_t>(Adjustment.Virtual.Microsoft.VBPtrOffset));
      Mangler.mangleNumber(
          static_cast<uint32_t>(Adjustment.Virtual.Microsoft.VBOffsetOffset));
      Mangler.mangleNumber(
          static_cast<uint32_t>(Adjustment.Virtual.Microsoft.VtordispOffset));
      Mangler.mangleNumber(static_cast<uint32_t>(Adjustment.NonVirtual));
    } else {
      Out << AccessSpec;
      Mangler.mangleNumber(
          static_cast<uint32_t>(Adjustment.Virtual.Microsoft.VtordispOffset));
      Mangler.mangleNumber(-static_cast<uint32_t>(Adjustment.NonVirtual));
    }
  } else if (Adjustment.NonVirtual != 0) {
    switch (AS) {
    case AS_none:
      llvm_unreachable("Unsupported access specifier");
    case AS_private:
      Out << 'G';
      break;
    case AS_protected:
      Out << 'O';
      break;
    case AS_public:
      Out << 'W';
    }
    Mangler.mangleNumber(-static_cast<uint32_t>(Adjustment.NonVirtual));
  } else {
    switch (AS) {
    case AS_none:
      llvm_unreachable("Unsupported access specifier");
    case AS_private:
      Out << 'A';
      break;
    case AS_protected:
      Out << 'I';
      break;
    case AS_public:
      Out << 'Q';
    }
  }
}

void MicrosoftMangleContextImpl::mangleVirtualMemPtrThunk(
    const CXXMethodDecl *MD, const MethodVFTableLocation &ML,
    raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << '?';
  Mangler.mangleVirtualMemPtrThunk(MD, ML);
}

void MicrosoftMangleContextImpl::mangleThunk(const CXXMethodDecl *MD,
                                             const ThunkInfo &Thunk,
                                             bool /*ElideOverrideInfo*/,
                                             raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << '?';
  Mangler.mangleName(MD);

  // Usually the thunk uses the access specifier of the new method, but if this
  // is a covariant return thunk, then MSVC always uses the public access
  // specifier, and we do the same.
  AccessSpecifier AS = Thunk.Return.isEmpty() ? MD->getAccess() : AS_public;
  mangleThunkThisAdjustment(AS, Thunk.This, Mangler, MHO);

  if (!Thunk.Return.isEmpty())
    assert(Thunk.Method != nullptr &&
           "Thunk info should hold the overridee decl");

  const CXXMethodDecl *DeclForFPT = Thunk.Method ? Thunk.Method : MD;
  Mangler.mangleFunctionType(
      DeclForFPT->getType()->castAs<FunctionProtoType>(), MD);
}

void MicrosoftMangleContextImpl::mangleCXXDtorThunk(const CXXDestructorDecl *DD,
                                                    CXXDtorType Type,
                                                    const ThunkInfo &Thunk,
                                                    bool /*ElideOverrideInfo*/,
                                                    raw_ostream &Out) {
  // FIXME: Actually, the dtor thunk should be emitted for vector deleting
  // dtors rather than scalar deleting dtors. Just use the vector deleting dtor
  // mangling manually until we support both deleting dtor types.
  assert(Type == Dtor_Deleting);
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO, DD, Type);
  Mangler.getStream() << "??_E";
  Mangler.mangleName(DD->getParent());
  auto &Adjustment = Thunk.This;
  mangleThunkThisAdjustment(DD->getAccess(), Adjustment, Mangler, MHO);
  Mangler.mangleFunctionType(DD->getType()->castAs<FunctionProtoType>(), DD);
}

void MicrosoftMangleContextImpl::mangleCXXVFTable(
    const CXXRecordDecl *Derived, ArrayRef<const CXXRecordDecl *> BasePath,
    raw_ostream &Out) {
  // <mangled-name> ::= ?_7 <class-name> <storage-class>
  //                    <cvr-qualifiers> [<name>] @
  // NOTE: <cvr-qualifiers> here is always 'B' (const). <storage-class>
  // is always '6' for vftables.
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  if (Derived->hasAttr<DLLImportAttr>())
    Mangler.getStream() << "??_S";
  else
    Mangler.getStream() << "??_7";
  Mangler.mangleName(Derived);
  Mangler.getStream() << "6B"; // '6' for vftable, 'B' for const.
  for (const CXXRecordDecl *RD : BasePath)
    Mangler.mangleName(RD);
  Mangler.getStream() << '@';
}

void MicrosoftMangleContextImpl::mangleCXXVTable(const CXXRecordDecl *Derived,
                                                 raw_ostream &Out) {
  // TODO: Determine appropriate mangling for MSABI
  mangleCXXVFTable(Derived, {}, Out);
}

void MicrosoftMangleContextImpl::mangleCXXVBTable(
    const CXXRecordDecl *Derived, ArrayRef<const CXXRecordDecl *> BasePath,
    raw_ostream &Out) {
  // <mangled-name> ::= ?_8 <class-name> <storage-class>
  //                    <cvr-qualifiers> [<name>] @
  // NOTE: <cvr-qualifiers> here is always 'B' (const). <storage-class>
  // is always '7' for vbtables.
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??_8";
  Mangler.mangleName(Derived);
  Mangler.getStream() << "7B";  // '7' for vbtable, 'B' for const.
  for (const CXXRecordDecl *RD : BasePath)
    Mangler.mangleName(RD);
  Mangler.getStream() << '@';
}

void MicrosoftMangleContextImpl::mangleCXXRTTI(QualType T, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??_R0";
  Mangler.mangleType(T, SourceRange(), MicrosoftCXXNameMangler::QMM_Result);
  Mangler.getStream() << "@8";
}

void MicrosoftMangleContextImpl::mangleCXXRTTIName(
    QualType T, raw_ostream &Out, bool NormalizeIntegers = false) {
  MicrosoftCXXNameMangler Mangler(*this, Out);
  Mangler.getStream() << '.';
  Mangler.mangleType(T, SourceRange(), MicrosoftCXXNameMangler::QMM_Result);
}

void MicrosoftMangleContextImpl::mangleCXXVirtualDisplacementMap(
    const CXXRecordDecl *SrcRD, const CXXRecordDecl *DstRD, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??_K";
  Mangler.mangleName(SrcRD);
  Mangler.getStream() << "$C";
  Mangler.mangleName(DstRD);
}

void MicrosoftMangleContextImpl::mangleCXXThrowInfo(QualType T, bool IsConst,
                                                    bool IsVolatile,
                                                    bool IsUnaligned,
                                                    uint32_t NumEntries,
                                                    raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "_TI";
  if (IsConst)
    Mangler.getStream() << 'C';
  if (IsVolatile)
    Mangler.getStream() << 'V';
  if (IsUnaligned)
    Mangler.getStream() << 'U';
  Mangler.getStream() << NumEntries;
  Mangler.mangleType(T, SourceRange(), MicrosoftCXXNameMangler::QMM_Result);
}

void MicrosoftMangleContextImpl::mangleCXXCatchableTypeArray(
    QualType T, uint32_t NumEntries, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "_CTA";
  Mangler.getStream() << NumEntries;
  Mangler.mangleType(T, SourceRange(), MicrosoftCXXNameMangler::QMM_Result);
}

void MicrosoftMangleContextImpl::mangleCXXCatchableType(
    QualType T, const CXXConstructorDecl *CD, CXXCtorType CT, uint32_t Size,
    uint32_t NVOffset, int32_t VBPtrOffset, uint32_t VBIndex,
    raw_ostream &Out) {
  MicrosoftCXXNameMangler Mangler(*this, Out);
  Mangler.getStream() << "_CT";

  llvm::SmallString<64> RTTIMangling;
  {
    llvm::raw_svector_ostream Stream(RTTIMangling);
    msvc_hashing_ostream MHO(Stream);
    mangleCXXRTTI(T, MHO);
  }
  Mangler.getStream() << RTTIMangling;

  // VS2015 and VS2017.1 omit the copy-constructor in the mangled name but
  // both older and newer versions include it.
  // FIXME: It is known that the Ctor is present in 2013, and in 2017.7
  // (_MSC_VER 1914) and newer, and that it's omitted in 2015 and 2017.4
  // (_MSC_VER 1911), but it's unknown when exactly it reappeared (1914?
  // Or 1912, 1913 already?).
  bool OmitCopyCtor = getASTContext().getLangOpts().isCompatibleWithMSVC(
                          LangOptions::MSVC2015) &&
                      !getASTContext().getLangOpts().isCompatibleWithMSVC(
                          LangOptions::MSVC2017_7);
  llvm::SmallString<64> CopyCtorMangling;
  if (!OmitCopyCtor && CD) {
    llvm::raw_svector_ostream Stream(CopyCtorMangling);
    msvc_hashing_ostream MHO(Stream);
    mangleCXXName(GlobalDecl(CD, CT), MHO);
  }
  Mangler.getStream() << CopyCtorMangling;

  Mangler.getStream() << Size;
  if (VBPtrOffset == -1) {
    if (NVOffset) {
      Mangler.getStream() << NVOffset;
    }
  } else {
    Mangler.getStream() << NVOffset;
    Mangler.getStream() << VBPtrOffset;
    Mangler.getStream() << VBIndex;
  }
}

void MicrosoftMangleContextImpl::mangleCXXRTTIBaseClassDescriptor(
    const CXXRecordDecl *Derived, uint32_t NVOffset, int32_t VBPtrOffset,
    uint32_t VBTableOffset, uint32_t Flags, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??_R1";
  Mangler.mangleNumber(NVOffset);
  Mangler.mangleNumber(VBPtrOffset);
  Mangler.mangleNumber(VBTableOffset);
  Mangler.mangleNumber(Flags);
  Mangler.mangleName(Derived);
  Mangler.getStream() << "8";
}

void MicrosoftMangleContextImpl::mangleCXXRTTIBaseClassArray(
    const CXXRecordDecl *Derived, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??_R2";
  Mangler.mangleName(Derived);
  Mangler.getStream() << "8";
}

void MicrosoftMangleContextImpl::mangleCXXRTTIClassHierarchyDescriptor(
    const CXXRecordDecl *Derived, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??_R3";
  Mangler.mangleName(Derived);
  Mangler.getStream() << "8";
}

void MicrosoftMangleContextImpl::mangleCXXRTTICompleteObjectLocator(
    const CXXRecordDecl *Derived, ArrayRef<const CXXRecordDecl *> BasePath,
    raw_ostream &Out) {
  // <mangled-name> ::= ?_R4 <class-name> <storage-class>
  //                    <cvr-qualifiers> [<name>] @
  // NOTE: <cvr-qualifiers> here is always 'B' (const). <storage-class>
  // is always '6' for vftables.
  llvm::SmallString<64> VFTableMangling;
  llvm::raw_svector_ostream Stream(VFTableMangling);
  mangleCXXVFTable(Derived, BasePath, Stream);

  if (VFTableMangling.starts_with("??@")) {
    assert(VFTableMangling.ends_with("@"));
    Out << VFTableMangling << "??_R4@";
    return;
  }

  assert(VFTableMangling.starts_with("??_7") ||
         VFTableMangling.starts_with("??_S"));

  Out << "??_R4" << VFTableMangling.str().drop_front(4);
}

void MicrosoftMangleContextImpl::mangleSEHFilterExpression(
    GlobalDecl EnclosingDecl, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  // The function body is in the same comdat as the function with the handler,
  // so the numbering here doesn't have to be the same across TUs.
  //
  // <mangled-name> ::= ?filt$ <filter-number> @0
  Mangler.getStream() << "?filt$" << SEHFilterIds[EnclosingDecl]++ << "@0@";
  Mangler.mangleName(EnclosingDecl);
}

void MicrosoftMangleContextImpl::mangleSEHFinallyBlock(
    GlobalDecl EnclosingDecl, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  // The function body is in the same comdat as the function with the handler,
  // so the numbering here doesn't have to be the same across TUs.
  //
  // <mangled-name> ::= ?fin$ <filter-number> @0
  Mangler.getStream() << "?fin$" << SEHFinallyIds[EnclosingDecl]++ << "@0@";
  Mangler.mangleName(EnclosingDecl);
}

void MicrosoftMangleContextImpl::mangleCanonicalTypeName(
    QualType T, raw_ostream &Out, bool NormalizeIntegers = false) {
  // This is just a made up unique string for the purposes of tbaa.  undname
  // does *not* know how to demangle it.
  MicrosoftCXXNameMangler Mangler(*this, Out);
  Mangler.getStream() << '?';
  Mangler.mangleType(T.getCanonicalType(), SourceRange());
}

void MicrosoftMangleContextImpl::mangleReferenceTemporary(
    const VarDecl *VD, unsigned ManglingNumber, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);

  Mangler.getStream() << "?";
  Mangler.mangleSourceName("$RT" + llvm::utostr(ManglingNumber));
  Mangler.mangle(VD, "");
}

void MicrosoftMangleContextImpl::mangleThreadSafeStaticGuardVariable(
    const VarDecl *VD, unsigned GuardNum, raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);

  Mangler.getStream() << "?";
  Mangler.mangleSourceName("$TSS" + llvm::utostr(GuardNum));
  Mangler.mangleNestedName(VD);
  Mangler.getStream() << "@4HA";
}

void MicrosoftMangleContextImpl::mangleStaticGuardVariable(const VarDecl *VD,
                                                           raw_ostream &Out) {
  // <guard-name> ::= ?_B <postfix> @5 <scope-depth>
  //              ::= ?__J <postfix> @5 <scope-depth>
  //              ::= ?$S <guard-num> @ <postfix> @4IA

  // The first mangling is what MSVC uses to guard static locals in inline
  // functions.  It uses a different mangling in external functions to support
  // guarding more than 32 variables.  MSVC rejects inline functions with more
  // than 32 static locals.  We don't fully implement the second mangling
  // because those guards are not externally visible, and instead use LLVM's
  // default renaming when creating a new guard variable.
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);

  bool Visible = VD->isExternallyVisible();
  if (Visible) {
    Mangler.getStream() << (VD->getTLSKind() ? "??__J" : "??_B");
  } else {
    Mangler.getStream() << "?$S1@";
  }
  unsigned ScopeDepth = 0;
  if (Visible && !getNextDiscriminator(VD, ScopeDepth))
    // If we do not have a discriminator and are emitting a guard variable for
    // use at global scope, then mangling the nested name will not be enough to
    // remove ambiguities.
    Mangler.mangle(VD, "");
  else
    Mangler.mangleNestedName(VD);
  Mangler.getStream() << (Visible ? "@5" : "@4IA");
  if (ScopeDepth)
    Mangler.mangleNumber(ScopeDepth);
}

void MicrosoftMangleContextImpl::mangleInitFiniStub(const VarDecl *D,
                                                    char CharCode,
                                                    raw_ostream &Out) {
  msvc_hashing_ostream MHO(Out);
  MicrosoftCXXNameMangler Mangler(*this, MHO);
  Mangler.getStream() << "??__" << CharCode;
  if (D->isStaticDataMember()) {
    Mangler.getStream() << '?';
    Mangler.mangleName(D);
    Mangler.mangleVariableEncoding(D);
    Mangler.getStream() << "@@";
  } else {
    Mangler.mangleName(D);
  }
  // This is the function class mangling.  These stubs are global, non-variadic,
  // cdecl functions that return void and take no args.
  Mangler.getStream() << "YAXXZ";
}

void MicrosoftMangleContextImpl::mangleDynamicInitializer(const VarDecl *D,
                                                          raw_ostream &Out) {
  // <initializer-name> ::= ?__E <name> YAXXZ
  mangleInitFiniStub(D, 'E', Out);
}

void
MicrosoftMangleContextImpl::mangleDynamicAtExitDestructor(const VarDecl *D,
                                                          raw_ostream &Out) {
  // <destructor-name> ::= ?__F <name> YAXXZ
  mangleInitFiniStub(D, 'F', Out);
}

void MicrosoftMangleContextImpl::mangleStringLiteral(const StringLiteral *SL,
                                                     raw_ostream &Out) {
  // <char-type> ::= 0   # char, char16_t, char32_t
  //                     # (little endian char data in mangling)
  //             ::= 1   # wchar_t (big endian char data in mangling)
  //
  // <literal-length> ::= <non-negative integer>  # the length of the literal
  //
  // <encoded-crc>    ::= <hex digit>+ @          # crc of the literal including
  //                                              # trailing null bytes
  //
  // <encoded-string> ::= <simple character>           # uninteresting character
  //                  ::= '?$' <hex digit> <hex digit> # these two nibbles
  //                                                   # encode the byte for the
  //                                                   # character
  //                  ::= '?' [a-z]                    # \xe1 - \xfa
  //                  ::= '?' [A-Z]                    # \xc1 - \xda
  //                  ::= '?' [0-9]                    # [,/\:. \n\t'-]
  //
  // <literal> ::= '??_C@_' <char-type> <literal-length> <encoded-crc>
  //               <encoded-string> '@'
  MicrosoftCXXNameMangler Mangler(*this, Out);
  Mangler.getStream() << "??_C@_";

  // The actual string length might be different from that of the string literal
  // in cases like:
  // char foo[3] = "foobar";
  // char bar[42] = "foobar";
  // Where it is truncated or zero-padded to fit the array. This is the length
  // used for mangling, and any trailing null-bytes also need to be mangled.
  unsigned StringLength =
      getASTContext().getAsConstantArrayType(SL->getType())->getZExtSize();
  unsigned StringByteLength = StringLength * SL->getCharByteWidth();

  // <char-type>: The "kind" of string literal is encoded into the mangled name.
  if (SL->isWide())
    Mangler.getStream() << '1';
  else
    Mangler.getStream() << '0';

  // <literal-length>: The next part of the mangled name consists of the length
  // of the string in bytes.
  Mangler.mangleNumber(StringByteLength);

  auto GetLittleEndianByte = [&SL](unsigned Index) {
    unsigned CharByteWidth = SL->getCharByteWidth();
    if (Index / CharByteWidth >= SL->getLength())
      return static_cast<char>(0);
    uint32_t CodeUnit = SL->getCodeUnit(Index / CharByteWidth);
    unsigned OffsetInCodeUnit = Index % CharByteWidth;
    return static_cast<char>((CodeUnit >> (8 * OffsetInCodeUnit)) & 0xff);
  };

  auto GetBigEndianByte = [&SL](unsigned Index) {
    unsigned CharByteWidth = SL->getCharByteWidth();
    if (Index / CharByteWidth >= SL->getLength())
      return static_cast<char>(0);
    uint32_t CodeUnit = SL->getCodeUnit(Index / CharByteWidth);
    unsigned OffsetInCodeUnit = (CharByteWidth - 1) - (Index % CharByteWidth);
    return static_cast<char>((CodeUnit >> (8 * OffsetInCodeUnit)) & 0xff);
  };

  // CRC all the bytes of the StringLiteral.
  llvm::JamCRC JC;
  for (unsigned I = 0, E = StringByteLength; I != E; ++I)
    JC.update(GetLittleEndianByte(I));

  // <encoded-crc>: The CRC is encoded utilizing the standard number mangling
  // scheme.
  Mangler.mangleNumber(JC.getCRC());

  // <encoded-string>: The mangled name also contains the first 32 bytes
  // (including null-terminator bytes) of the encoded StringLiteral.
  // Each character is encoded by splitting them into bytes and then encoding
  // the constituent bytes.
  auto MangleByte = [&Mangler](char Byte) {
    // There are five different manglings for characters:
    // - [a-zA-Z0-9_$]: A one-to-one mapping.
    // - ?[a-z]: The range from \xe1 to \xfa.
    // - ?[A-Z]: The range from \xc1 to \xda.
    // - ?[0-9]: The set of [,/\:. \n\t'-].
    // - ?$XX: A fallback which maps nibbles.
    if (isAsciiIdentifierContinue(Byte, /*AllowDollar=*/true)) {
      Mangler.getStream() << Byte;
    } else if (isLetter(Byte & 0x7f)) {
      Mangler.getStream() << '?' << static_cast<char>(Byte & 0x7f);
    } else {
      const char SpecialChars[] = {',', '/',  '\\', ':',  '.',
                                   ' ', '\n', '\t', '\'', '-'};
      const char *Pos = llvm::find(SpecialChars, Byte);
      if (Pos != std::end(SpecialChars)) {
        Mangler.getStream() << '?' << (Pos - std::begin(SpecialChars));
      } else {
        Mangler.getStream() << "?$";
        Mangler.getStream() << static_cast<char>('A' + ((Byte >> 4) & 0xf));
        Mangler.getStream() << static_cast<char>('A' + (Byte & 0xf));
      }
    }
  };

  // Enforce our 32 bytes max, except wchar_t which gets 32 chars instead.
  unsigned MaxBytesToMangle = SL->isWide() ? 64U : 32U;
  unsigned NumBytesToMangle = std::min(MaxBytesToMangle, StringByteLength);
  for (unsigned I = 0; I != NumBytesToMangle; ++I) {
    if (SL->isWide())
      MangleByte(GetBigEndianByte(I));
    else
      MangleByte(GetLittleEndianByte(I));
  }

  Mangler.getStream() << '@';
}

void MicrosoftCXXNameMangler::mangleAutoReturnType(const MemberPointerType *T,
                                                   Qualifiers Quals) {
  QualType PointeeType = T->getPointeeType();
  manglePointerCVQualifiers(Quals);
  manglePointerExtQualifiers(Quals, PointeeType);
  if (const FunctionProtoType *FPT = PointeeType->getAs<FunctionProtoType>()) {
    Out << '8';
    mangleName(T->getMostRecentCXXRecordDecl());
    mangleFunctionType(FPT, nullptr, true);
  } else {
    mangleQualifiers(PointeeType.getQualifiers(), true);
    mangleName(T->getMostRecentCXXRecordDecl());
    mangleAutoReturnType(PointeeType, QMM_Drop);
  }
}

void MicrosoftCXXNameMangler::mangleAutoReturnType(const PointerType *T,
                                                   Qualifiers Quals) {
  QualType PointeeType = T->getPointeeType();
  assert(!PointeeType.getQualifiers().hasAddressSpace() &&
         "Unexpected address space mangling required");

  manglePointerCVQualifiers(Quals);
  manglePointerExtQualifiers(Quals, PointeeType);

  if (const FunctionProtoType *FPT = PointeeType->getAs<FunctionProtoType>()) {
    Out << '6';
    mangleFunctionType(FPT);
  } else {
    mangleAutoReturnType(PointeeType, QMM_Mangle);
  }
}

void MicrosoftCXXNameMangler::mangleAutoReturnType(const LValueReferenceType *T,
                                                   Qualifiers Quals) {
  QualType PointeeType = T->getPointeeType();
  assert(!Quals.hasConst() && !Quals.hasVolatile() && "unexpected qualifier!");
  Out << 'A';
  manglePointerExtQualifiers(Quals, PointeeType);
  mangleAutoReturnType(PointeeType, QMM_Mangle);
}

void MicrosoftCXXNameMangler::mangleAutoReturnType(const RValueReferenceType *T,
                                                   Qualifiers Quals) {
  QualType PointeeType = T->getPointeeType();
  assert(!Quals.hasConst() && !Quals.hasVolatile() && "unexpected qualifier!");
  Out << "$$Q";
  manglePointerExtQualifiers(Quals, PointeeType);
  mangleAutoReturnType(PointeeType, QMM_Mangle);
}

MicrosoftMangleContext *MicrosoftMangleContext::create(ASTContext &Context,
                                                       DiagnosticsEngine &Diags,
                                                       bool IsAux) {
  return new MicrosoftMangleContextImpl(Context, Diags, IsAux);
}