xref: /llvm-project-15.0.7/clang/lib/CodeGen/CGDebugInfo.cpp (revision cc89063b)

//===--- CGDebugInfo.cpp - Emit Debug Information for a Module ------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This coordinates the debug information generation while generating code.
//
//===----------------------------------------------------------------------===//

#include "CGDebugInfo.h"
#include "CGBlocks.h"
#include "CGCXXABI.h"
#include "CGObjCRuntime.h"
#include "CGRecordLayout.h"
#include "CodeGenFunction.h"
#include "CodeGenModule.h"
#include "ConstantEmitter.h"
#include "clang/Analysis/Analyses/ExprMutationAnalyzer.h"
#include "clang/AST/ASTContext.h"
#include "clang/AST/DeclFriend.h"
#include "clang/AST/DeclObjC.h"
#include "clang/AST/DeclTemplate.h"
#include "clang/AST/Expr.h"
#include "clang/AST/RecordLayout.h"
#include "clang/Basic/CodeGenOptions.h"
#include "clang/Basic/FileManager.h"
#include "clang/Basic/SourceManager.h"
#include "clang/Basic/Version.h"
#include "clang/Frontend/FrontendOptions.h"
#include "clang/Lex/HeaderSearchOptions.h"
#include "clang/Lex/ModuleMap.h"
#include "clang/Lex/PreprocessorOptions.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/Intrinsics.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/Path.h"
using namespace clang;
using namespace clang::CodeGen;

static uint32_t getTypeAlignIfRequired(const Type *Ty, const ASTContext &Ctx) {
  auto TI = Ctx.getTypeInfo(Ty);
  return TI.AlignIsRequired ? TI.Align : 0;
}

static uint32_t getTypeAlignIfRequired(QualType Ty, const ASTContext &Ctx) {
  return getTypeAlignIfRequired(Ty.getTypePtr(), Ctx);
}

static uint32_t getDeclAlignIfRequired(const Decl *D, const ASTContext &Ctx) {
  return D->hasAttr<AlignedAttr>() ? D->getMaxAlignment() : 0;
}

CGDebugInfo::CGDebugInfo(CodeGenModule &CGM)
    : CGM(CGM), DebugKind(CGM.getCodeGenOpts().getDebugInfo()),
      DebugTypeExtRefs(CGM.getCodeGenOpts().DebugTypeExtRefs),
      DBuilder(CGM.getModule()) {
  for (const auto &KV : CGM.getCodeGenOpts().DebugPrefixMap)
    DebugPrefixMap[KV.first] = KV.second;
  CreateCompileUnit();
}

CGDebugInfo::~CGDebugInfo() {
  assert(LexicalBlockStack.empty() &&
         "Region stack mismatch, stack not empty!");
}

ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF,
                                       SourceLocation TemporaryLocation)
    : CGF(&CGF) {
  init(TemporaryLocation);
}

ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF,
                                       bool DefaultToEmpty,
                                       SourceLocation TemporaryLocation)
    : CGF(&CGF) {
  init(TemporaryLocation, DefaultToEmpty);
}

void ApplyDebugLocation::init(SourceLocation TemporaryLocation,
                              bool DefaultToEmpty) {
  auto *DI = CGF->getDebugInfo();
  if (!DI) {
    CGF = nullptr;
    return;
  }

  OriginalLocation = CGF->Builder.getCurrentDebugLocation();

  if (OriginalLocation && !DI->CGM.getExpressionLocationsEnabled())
    return;

  if (TemporaryLocation.isValid()) {
    DI->EmitLocation(CGF->Builder, TemporaryLocation);
    return;
  }

  if (DefaultToEmpty) {
    CGF->Builder.SetCurrentDebugLocation(llvm::DebugLoc());
    return;
  }

  // Construct a location that has a valid scope, but no line info.
  assert(!DI->LexicalBlockStack.empty());
  CGF->Builder.SetCurrentDebugLocation(llvm::DebugLoc::get(
      0, 0, DI->LexicalBlockStack.back(), DI->getInlinedAt()));
}

ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF, const Expr *E)
    : CGF(&CGF) {
  init(E->getExprLoc());
}

ApplyDebugLocation::ApplyDebugLocation(CodeGenFunction &CGF, llvm::DebugLoc Loc)
    : CGF(&CGF) {
  if (!CGF.getDebugInfo()) {
    this->CGF = nullptr;
    return;
  }
  OriginalLocation = CGF.Builder.getCurrentDebugLocation();
  if (Loc)
    CGF.Builder.SetCurrentDebugLocation(std::move(Loc));
}

ApplyDebugLocation::~ApplyDebugLocation() {
  // Query CGF so the location isn't overwritten when location updates are
  // temporarily disabled (for C++ default function arguments)
  if (CGF)
    CGF->Builder.SetCurrentDebugLocation(std::move(OriginalLocation));
}

ApplyInlineDebugLocation::ApplyInlineDebugLocation(CodeGenFunction &CGF,
                                                   GlobalDecl InlinedFn)
    : CGF(&CGF) {
  if (!CGF.getDebugInfo()) {
    this->CGF = nullptr;
    return;
  }
  auto &DI = *CGF.getDebugInfo();
  SavedLocation = DI.getLocation();
  assert((DI.getInlinedAt() ==
          CGF.Builder.getCurrentDebugLocation()->getInlinedAt()) &&
         "CGDebugInfo and IRBuilder are out of sync");

  DI.EmitInlineFunctionStart(CGF.Builder, InlinedFn);
}

ApplyInlineDebugLocation::~ApplyInlineDebugLocation() {
  if (!CGF)
    return;
  auto &DI = *CGF->getDebugInfo();
  DI.EmitInlineFunctionEnd(CGF->Builder);
  DI.EmitLocation(CGF->Builder, SavedLocation);
}

void CGDebugInfo::setLocation(SourceLocation Loc) {
  // If the new location isn't valid return.
  if (Loc.isInvalid())
    return;

  CurLoc = CGM.getContext().getSourceManager().getExpansionLoc(Loc);

  // If we've changed files in the middle of a lexical scope go ahead
  // and create a new lexical scope with file node if it's different
  // from the one in the scope.
  if (LexicalBlockStack.empty())
    return;

  SourceManager &SM = CGM.getContext().getSourceManager();
  auto *Scope = cast<llvm::DIScope>(LexicalBlockStack.back());
  PresumedLoc PCLoc = SM.getPresumedLoc(CurLoc);
  if (PCLoc.isInvalid() || Scope->getFile() == getOrCreateFile(CurLoc))
    return;

  if (auto *LBF = dyn_cast<llvm::DILexicalBlockFile>(Scope)) {
    LexicalBlockStack.pop_back();
    LexicalBlockStack.emplace_back(DBuilder.createLexicalBlockFile(
        LBF->getScope(), getOrCreateFile(CurLoc)));
  } else if (isa<llvm::DILexicalBlock>(Scope) ||
             isa<llvm::DISubprogram>(Scope)) {
    LexicalBlockStack.pop_back();
    LexicalBlockStack.emplace_back(
        DBuilder.createLexicalBlockFile(Scope, getOrCreateFile(CurLoc)));
  }
}

llvm::DIScope *CGDebugInfo::getDeclContextDescriptor(const Decl *D) {
  llvm::DIScope *Mod = getParentModuleOrNull(D);
  return getContextDescriptor(cast<Decl>(D->getDeclContext()),
                              Mod ? Mod : TheCU);
}

llvm::DIScope *CGDebugInfo::getContextDescriptor(const Decl *Context,
                                                 llvm::DIScope *Default) {
  if (!Context)
    return Default;

  auto I = RegionMap.find(Context);
  if (I != RegionMap.end()) {
    llvm::Metadata *V = I->second;
    return dyn_cast_or_null<llvm::DIScope>(V);
  }

  // Check namespace.
  if (const auto *NSDecl = dyn_cast<NamespaceDecl>(Context))
    return getOrCreateNamespace(NSDecl);

  if (const auto *RDecl = dyn_cast<RecordDecl>(Context))
    if (!RDecl->isDependentType())
      return getOrCreateType(CGM.getContext().getTypeDeclType(RDecl),
                             TheCU->getFile());
  return Default;
}

PrintingPolicy CGDebugInfo::getPrintingPolicy() const {
  PrintingPolicy PP = CGM.getContext().getPrintingPolicy();

  // If we're emitting codeview, it's important to try to match MSVC's naming so
  // that visualizers written for MSVC will trigger for our class names. In
  // particular, we can't have spaces between arguments of standard templates
  // like basic_string and vector.
  if (CGM.getCodeGenOpts().EmitCodeView)
    PP.MSVCFormatting = true;

  // Apply -fdebug-prefix-map.
  PP.RemapFilePaths = true;
  PP.remapPath = [this](StringRef Path) { return remapDIPath(Path); };
  return PP;
}

StringRef CGDebugInfo::getFunctionName(const FunctionDecl *FD) {
  assert(FD && "Invalid FunctionDecl!");
  IdentifierInfo *FII = FD->getIdentifier();
  FunctionTemplateSpecializationInfo *Info =
      FD->getTemplateSpecializationInfo();

  // Emit the unqualified name in normal operation. LLVM and the debugger can
  // compute the fully qualified name from the scope chain. If we're only
  // emitting line table info, there won't be any scope chains, so emit the
  // fully qualified name here so that stack traces are more accurate.
  // FIXME: Do this when emitting DWARF as well as when emitting CodeView after
  // evaluating the size impact.
  bool UseQualifiedName = DebugKind == codegenoptions::DebugLineTablesOnly &&
                          CGM.getCodeGenOpts().EmitCodeView;

  if (!Info && FII && !UseQualifiedName)
    return FII->getName();

  SmallString<128> NS;
  llvm::raw_svector_ostream OS(NS);
  if (!UseQualifiedName)
    FD->printName(OS);
  else
    FD->printQualifiedName(OS, getPrintingPolicy());

  // Add any template specialization args.
  if (Info) {
    const TemplateArgumentList *TArgs = Info->TemplateArguments;
    printTemplateArgumentList(OS, TArgs->asArray(), getPrintingPolicy());
  }

  // Copy this name on the side and use its reference.
  return internString(OS.str());
}

StringRef CGDebugInfo::getObjCMethodName(const ObjCMethodDecl *OMD) {
  SmallString<256> MethodName;
  llvm::raw_svector_ostream OS(MethodName);
  OS << (OMD->isInstanceMethod() ? '-' : '+') << '[';
  const DeclContext *DC = OMD->getDeclContext();
  if (const auto *OID = dyn_cast<ObjCImplementationDecl>(DC)) {
    OS << OID->getName();
  } else if (const auto *OID = dyn_cast<ObjCInterfaceDecl>(DC)) {
    OS << OID->getName();
  } else if (const auto *OC = dyn_cast<ObjCCategoryDecl>(DC)) {
    if (OC->IsClassExtension()) {
      OS << OC->getClassInterface()->getName();
    } else {
      OS << OC->getIdentifier()->getNameStart() << '('
         << OC->getIdentifier()->getNameStart() << ')';
    }
  } else if (const auto *OCD = dyn_cast<ObjCCategoryImplDecl>(DC)) {
    OS << OCD->getClassInterface()->getName() << '(' << OCD->getName() << ')';
  } else if (isa<ObjCProtocolDecl>(DC)) {
    // We can extract the type of the class from the self pointer.
    if (ImplicitParamDecl *SelfDecl = OMD->getSelfDecl()) {
      QualType ClassTy =
          cast<ObjCObjectPointerType>(SelfDecl->getType())->getPointeeType();
      ClassTy.print(OS, PrintingPolicy(LangOptions()));
    }
  }
  OS << ' ' << OMD->getSelector().getAsString() << ']';

  return internString(OS.str());
}

StringRef CGDebugInfo::getSelectorName(Selector S) {
  return internString(S.getAsString());
}

StringRef CGDebugInfo::getClassName(const RecordDecl *RD) {
  if (isa<ClassTemplateSpecializationDecl>(RD)) {
    SmallString<128> Name;
    llvm::raw_svector_ostream OS(Name);
    RD->getNameForDiagnostic(OS, getPrintingPolicy(),
                             /*Qualified*/ false);

    // Copy this name on the side and use its reference.
    return internString(Name);
  }

  // quick optimization to avoid having to intern strings that are already
  // stored reliably elsewhere
  if (const IdentifierInfo *II = RD->getIdentifier())
    return II->getName();

  // The CodeView printer in LLVM wants to see the names of unnamed types: it is
  // used to reconstruct the fully qualified type names.
  if (CGM.getCodeGenOpts().EmitCodeView) {
    if (const TypedefNameDecl *D = RD->getTypedefNameForAnonDecl()) {
      assert(RD->getDeclContext() == D->getDeclContext() &&
             "Typedef should not be in another decl context!");
      assert(D->getDeclName().getAsIdentifierInfo() &&
             "Typedef was not named!");
      return D->getDeclName().getAsIdentifierInfo()->getName();
    }

    if (CGM.getLangOpts().CPlusPlus) {
      StringRef Name;

      ASTContext &Context = CGM.getContext();
      if (const DeclaratorDecl *DD = Context.getDeclaratorForUnnamedTagDecl(RD))
        // Anonymous types without a name for linkage purposes have their
        // declarator mangled in if they have one.
        Name = DD->getName();
      else if (const TypedefNameDecl *TND =
                   Context.getTypedefNameForUnnamedTagDecl(RD))
        // Anonymous types without a name for linkage purposes have their
        // associate typedef mangled in if they have one.
        Name = TND->getName();

      if (!Name.empty()) {
        SmallString<256> UnnamedType("<unnamed-type-");
        UnnamedType += Name;
        UnnamedType += '>';
        return internString(UnnamedType);
      }
    }
  }

  return StringRef();
}

Optional<llvm::DIFile::ChecksumKind>
CGDebugInfo::computeChecksum(FileID FID, SmallString<32> &Checksum) const {
  Checksum.clear();

  if (!CGM.getCodeGenOpts().EmitCodeView &&
      CGM.getCodeGenOpts().DwarfVersion < 5)
    return None;

  SourceManager &SM = CGM.getContext().getSourceManager();
  bool Invalid;
  const llvm::MemoryBuffer *MemBuffer = SM.getBuffer(FID, &Invalid);
  if (Invalid)
    return None;

  llvm::MD5 Hash;
  llvm::MD5::MD5Result Result;

  Hash.update(MemBuffer->getBuffer());
  Hash.final(Result);

  Hash.stringifyResult(Result, Checksum);
  return llvm::DIFile::CSK_MD5;
}

Optional<StringRef> CGDebugInfo::getSource(const SourceManager &SM,
                                           FileID FID) {
  if (!CGM.getCodeGenOpts().EmbedSource)
    return None;

  bool SourceInvalid = false;
  StringRef Source = SM.getBufferData(FID, &SourceInvalid);

  if (SourceInvalid)
    return None;

  return Source;
}

llvm::DIFile *CGDebugInfo::getOrCreateFile(SourceLocation Loc) {
  if (!Loc.isValid())
    // If Location is not valid then use main input file.
    return TheCU->getFile();

  SourceManager &SM = CGM.getContext().getSourceManager();
  PresumedLoc PLoc = SM.getPresumedLoc(Loc);

  StringRef FileName = PLoc.getFilename();
  if (PLoc.isInvalid() || FileName.empty())
    // If the location is not valid then use main input file.
    return TheCU->getFile();

  // Cache the results.
  auto It = DIFileCache.find(FileName.data());
  if (It != DIFileCache.end()) {
    // Verify that the information still exists.
    if (llvm::Metadata *V = It->second)
      return cast<llvm::DIFile>(V);
  }

  SmallString<32> Checksum;

  // Compute the checksum if possible. If the location is affected by a #line
  // directive that refers to a file, PLoc will have an invalid FileID, and we
  // will correctly get no checksum.
  Optional<llvm::DIFile::ChecksumKind> CSKind =
      computeChecksum(PLoc.getFileID(), Checksum);
  Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo;
  if (CSKind)
    CSInfo.emplace(*CSKind, Checksum);
  return createFile(FileName, CSInfo, getSource(SM, SM.getFileID(Loc)));
}

llvm::DIFile *
CGDebugInfo::createFile(StringRef FileName,
                        Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo,
                        Optional<StringRef> Source) {
  StringRef Dir;
  StringRef File;
  std::string RemappedFile = remapDIPath(FileName);
  std::string CurDir = remapDIPath(getCurrentDirname());
  SmallString<128> DirBuf;
  SmallString<128> FileBuf;
  if (llvm::sys::path::is_absolute(RemappedFile)) {
    // Strip the common prefix (if it is more than just "/") from current
    // directory and FileName for a more space-efficient encoding.
    auto FileIt = llvm::sys::path::begin(RemappedFile);
    auto FileE = llvm::sys::path::end(RemappedFile);
    auto CurDirIt = llvm::sys::path::begin(CurDir);
    auto CurDirE = llvm::sys::path::end(CurDir);
    for (; CurDirIt != CurDirE && *CurDirIt == *FileIt; ++CurDirIt, ++FileIt)
      llvm::sys::path::append(DirBuf, *CurDirIt);
    if (std::distance(llvm::sys::path::begin(CurDir), CurDirIt) == 1) {
      // Don't strip the common prefix if it is only the root "/"
      // since that would make LLVM diagnostic locations confusing.
      Dir = {};
      File = RemappedFile;
    } else {
      for (; FileIt != FileE; ++FileIt)
        llvm::sys::path::append(FileBuf, *FileIt);
      Dir = DirBuf;
      File = FileBuf;
    }
  } else {
    Dir = CurDir;
    File = RemappedFile;
  }
  llvm::DIFile *F = DBuilder.createFile(File, Dir, CSInfo, Source);
  DIFileCache[FileName.data()].reset(F);
  return F;
}

std::string CGDebugInfo::remapDIPath(StringRef Path) const {
  for (const auto &Entry : DebugPrefixMap)
    if (Path.startswith(Entry.first))
      return (Twine(Entry.second) + Path.substr(Entry.first.size())).str();
  return Path.str();
}

unsigned CGDebugInfo::getLineNumber(SourceLocation Loc) {
  if (Loc.isInvalid() && CurLoc.isInvalid())
    return 0;
  SourceManager &SM = CGM.getContext().getSourceManager();
  PresumedLoc PLoc = SM.getPresumedLoc(Loc.isValid() ? Loc : CurLoc);
  return PLoc.isValid() ? PLoc.getLine() : 0;
}

unsigned CGDebugInfo::getColumnNumber(SourceLocation Loc, bool Force) {
  // We may not want column information at all.
  if (!Force && !CGM.getCodeGenOpts().DebugColumnInfo)
    return 0;

  // If the location is invalid then use the current column.
  if (Loc.isInvalid() && CurLoc.isInvalid())
    return 0;
  SourceManager &SM = CGM.getContext().getSourceManager();
  PresumedLoc PLoc = SM.getPresumedLoc(Loc.isValid() ? Loc : CurLoc);
  return PLoc.isValid() ? PLoc.getColumn() : 0;
}

StringRef CGDebugInfo::getCurrentDirname() {
  if (!CGM.getCodeGenOpts().DebugCompilationDir.empty())
    return CGM.getCodeGenOpts().DebugCompilationDir;

  if (!CWDName.empty())
    return CWDName;
  SmallString<256> CWD;
  llvm::sys::fs::current_path(CWD);
  return CWDName = internString(CWD);
}

void CGDebugInfo::CreateCompileUnit() {
  SmallString<32> Checksum;
  Optional<llvm::DIFile::ChecksumKind> CSKind;
  Optional<llvm::DIFile::ChecksumInfo<StringRef>> CSInfo;

  // Should we be asking the SourceManager for the main file name, instead of
  // accepting it as an argument? This just causes the main file name to
  // mismatch with source locations and create extra lexical scopes or
  // mismatched debug info (a CU with a DW_AT_file of "-", because that's what
  // the driver passed, but functions/other things have DW_AT_file of "<stdin>"
  // because that's what the SourceManager says)

  // Get absolute path name.
  SourceManager &SM = CGM.getContext().getSourceManager();
  std::string MainFileName = CGM.getCodeGenOpts().MainFileName;
  if (MainFileName.empty())
    MainFileName = "<stdin>";

  // The main file name provided via the "-main-file-name" option contains just
  // the file name itself with no path information. This file name may have had
  // a relative path, so we look into the actual file entry for the main
  // file to determine the real absolute path for the file.
  std::string MainFileDir;
  if (const FileEntry *MainFile = SM.getFileEntryForID(SM.getMainFileID())) {
    MainFileDir = remapDIPath(MainFile->getDir()->getName());
    if (MainFileDir != ".") {
      llvm::SmallString<1024> MainFileDirSS(MainFileDir);
      llvm::sys::path::append(MainFileDirSS, MainFileName);
      MainFileName = MainFileDirSS.str();
    }
    // If the main file name provided is identical to the input file name, and
    // if the input file is a preprocessed source, use the module name for
    // debug info. The module name comes from the name specified in the first
    // linemarker if the input is a preprocessed source.
    if (MainFile->getName() == MainFileName &&
        FrontendOptions::getInputKindForExtension(
            MainFile->getName().rsplit('.').second)
            .isPreprocessed())
      MainFileName = CGM.getModule().getName().str();

    CSKind = computeChecksum(SM.getMainFileID(), Checksum);
  }

  llvm::dwarf::SourceLanguage LangTag;
  const LangOptions &LO = CGM.getLangOpts();
  if (LO.CPlusPlus) {
    if (LO.ObjC)
      LangTag = llvm::dwarf::DW_LANG_ObjC_plus_plus;
    else
      LangTag = llvm::dwarf::DW_LANG_C_plus_plus;
  } else if (LO.ObjC) {
    LangTag = llvm::dwarf::DW_LANG_ObjC;
  } else if (LO.RenderScript) {
    LangTag = llvm::dwarf::DW_LANG_GOOGLE_RenderScript;
  } else if (LO.C99) {
    LangTag = llvm::dwarf::DW_LANG_C99;
  } else {
    LangTag = llvm::dwarf::DW_LANG_C89;
  }

  std::string Producer = getClangFullVersion();

  // Figure out which version of the ObjC runtime we have.
  unsigned RuntimeVers = 0;
  if (LO.ObjC)
    RuntimeVers = LO.ObjCRuntime.isNonFragile() ? 2 : 1;

  llvm::DICompileUnit::DebugEmissionKind EmissionKind;
  switch (DebugKind) {
  case codegenoptions::NoDebugInfo:
  case codegenoptions::LocTrackingOnly:
    EmissionKind = llvm::DICompileUnit::NoDebug;
    break;
  case codegenoptions::DebugLineTablesOnly:
    EmissionKind = llvm::DICompileUnit::LineTablesOnly;
    break;
  case codegenoptions::DebugDirectivesOnly:
    EmissionKind = llvm::DICompileUnit::DebugDirectivesOnly;
    break;
  case codegenoptions::LimitedDebugInfo:
  case codegenoptions::FullDebugInfo:
    EmissionKind = llvm::DICompileUnit::FullDebug;
    break;
  }

  uint64_t DwoId = 0;
  auto &CGOpts = CGM.getCodeGenOpts();
  // The DIFile used by the CU is distinct from the main source
  // file. Its directory part specifies what becomes the
  // DW_AT_comp_dir (the compilation directory), even if the source
  // file was specified with an absolute path.
  if (CSKind)
    CSInfo.emplace(*CSKind, Checksum);
  llvm::DIFile *CUFile = DBuilder.createFile(
      remapDIPath(MainFileName), remapDIPath(getCurrentDirname()), CSInfo,
      getSource(SM, SM.getMainFileID()));

  // Create new compile unit.
  TheCU = DBuilder.createCompileUnit(
      LangTag, CUFile, CGOpts.EmitVersionIdentMetadata ? Producer : "",
      LO.Optimize || CGOpts.PrepareForLTO || CGOpts.PrepareForThinLTO,
      CGOpts.DwarfDebugFlags, RuntimeVers, CGOpts.SplitDwarfFile, EmissionKind,
      DwoId, CGOpts.SplitDwarfInlining, CGOpts.DebugInfoForProfiling,
      CGM.getTarget().getTriple().isNVPTX()
          ? llvm::DICompileUnit::DebugNameTableKind::None
          : static_cast<llvm::DICompileUnit::DebugNameTableKind>(
                CGOpts.DebugNameTable),
      CGOpts.DebugRangesBaseAddress);
}

llvm::DIType *CGDebugInfo::CreateType(const BuiltinType *BT) {
  llvm::dwarf::TypeKind Encoding;
  StringRef BTName;
  switch (BT->getKind()) {
#define BUILTIN_TYPE(Id, SingletonId)
#define PLACEHOLDER_TYPE(Id, SingletonId) case BuiltinType::Id:
#include "clang/AST/BuiltinTypes.def"
  case BuiltinType::Dependent:
    llvm_unreachable("Unexpected builtin type");
  case BuiltinType::NullPtr:
    return DBuilder.createNullPtrType();
  case BuiltinType::Void:
    return nullptr;
  case BuiltinType::ObjCClass:
    if (!ClassTy)
      ClassTy =
          DBuilder.createForwardDecl(llvm::dwarf::DW_TAG_structure_type,
                                     "objc_class", TheCU, TheCU->getFile(), 0);
    return ClassTy;
  case BuiltinType::ObjCId: {
    // typedef struct objc_class *Class;
    // typedef struct objc_object {
    //  Class isa;
    // } *id;

    if (ObjTy)
      return ObjTy;

    if (!ClassTy)
      ClassTy =
          DBuilder.createForwardDecl(llvm::dwarf::DW_TAG_structure_type,
                                     "objc_class", TheCU, TheCU->getFile(), 0);

    unsigned Size = CGM.getContext().getTypeSize(CGM.getContext().VoidPtrTy);

    auto *ISATy = DBuilder.createPointerType(ClassTy, Size);

    ObjTy = DBuilder.createStructType(TheCU, "objc_object", TheCU->getFile(), 0,
                                      0, 0, llvm::DINode::FlagZero, nullptr,
                                      llvm::DINodeArray());

    DBuilder.replaceArrays(
        ObjTy, DBuilder.getOrCreateArray(&*DBuilder.createMemberType(
                   ObjTy, "isa", TheCU->getFile(), 0, Size, 0, 0,
                   llvm::DINode::FlagZero, ISATy)));
    return ObjTy;
  }
  case BuiltinType::ObjCSel: {
    if (!SelTy)
      SelTy = DBuilder.createForwardDecl(llvm::dwarf::DW_TAG_structure_type,
                                         "objc_selector", TheCU,
                                         TheCU->getFile(), 0);
    return SelTy;
  }

#define IMAGE_TYPE(ImgType, Id, SingletonId, Access, Suffix)                   \
  case BuiltinType::Id:                                                        \
    return getOrCreateStructPtrType("opencl_" #ImgType "_" #Suffix "_t",       \
                                    SingletonId);
#include "clang/Basic/OpenCLImageTypes.def"
  case BuiltinType::OCLSampler:
    return getOrCreateStructPtrType("opencl_sampler_t", OCLSamplerDITy);
  case BuiltinType::OCLEvent:
    return getOrCreateStructPtrType("opencl_event_t", OCLEventDITy);
  case BuiltinType::OCLClkEvent:
    return getOrCreateStructPtrType("opencl_clk_event_t", OCLClkEventDITy);
  case BuiltinType::OCLQueue:
    return getOrCreateStructPtrType("opencl_queue_t", OCLQueueDITy);
  case BuiltinType::OCLReserveID:
    return getOrCreateStructPtrType("opencl_reserve_id_t", OCLReserveIDDITy);
#define EXT_OPAQUE_TYPE(ExtType, Id, Ext) \
  case BuiltinType::Id: \
    return getOrCreateStructPtrType("opencl_" #ExtType, Id##Ty);
#include "clang/Basic/OpenCLExtensionTypes.def"
  // TODO: real support for SVE types requires more infrastructure
  // to be added first.  The types have a variable length and are
  // represented in debug info as types whose length depends on a
  // target-specific pseudo register.
#define SVE_TYPE(Name, Id, SingletonId) \
  case BuiltinType::Id:
#include "clang/Basic/AArch64SVEACLETypes.def"
  {
    unsigned DiagID = CGM.getDiags().getCustomDiagID(
        DiagnosticsEngine::Error,
        "cannot yet generate debug info for SVE type '%0'");
    auto Name = BT->getName(CGM.getContext().getPrintingPolicy());
    CGM.getDiags().Report(DiagID) << Name;
    // Return something safe.
    return CreateType(cast<const BuiltinType>(CGM.getContext().IntTy));
  }

  case BuiltinType::UChar:
  case BuiltinType::Char_U:
    Encoding = llvm::dwarf::DW_ATE_unsigned_char;
    break;
  case BuiltinType::Char_S:
  case BuiltinType::SChar:
    Encoding = llvm::dwarf::DW_ATE_signed_char;
    break;
  case BuiltinType::Char8:
  case BuiltinType::Char16:
  case BuiltinType::Char32:
    Encoding = llvm::dwarf::DW_ATE_UTF;
    break;
  case BuiltinType::UShort:
  case BuiltinType::UInt:
  case BuiltinType::UInt128:
  case BuiltinType::ULong:
  case BuiltinType::WChar_U:
  case BuiltinType::ULongLong:
    Encoding = llvm::dwarf::DW_ATE_unsigned;
    break;
  case BuiltinType::Short:
  case BuiltinType::Int:
  case BuiltinType::Int128:
  case BuiltinType::Long:
  case BuiltinType::WChar_S:
  case BuiltinType::LongLong:
    Encoding = llvm::dwarf::DW_ATE_signed;
    break;
  case BuiltinType::Bool:
    Encoding = llvm::dwarf::DW_ATE_boolean;
    break;
  case BuiltinType::Half:
  case BuiltinType::Float:
  case BuiltinType::LongDouble:
  case BuiltinType::Float16:
  case BuiltinType::Float128:
  case BuiltinType::Double:
    // FIXME: For targets where long double and __float128 have the same size,
    // they are currently indistinguishable in the debugger without some
    // special treatment. However, there is currently no consensus on encoding
    // and this should be updated once a DWARF encoding exists for distinct
    // floating point types of the same size.
    Encoding = llvm::dwarf::DW_ATE_float;
    break;
  case BuiltinType::ShortAccum:
  case BuiltinType::Accum:
  case BuiltinType::LongAccum:
  case BuiltinType::ShortFract:
  case BuiltinType::Fract:
  case BuiltinType::LongFract:
  case BuiltinType::SatShortFract:
  case BuiltinType::SatFract:
  case BuiltinType::SatLongFract:
  case BuiltinType::SatShortAccum:
  case BuiltinType::SatAccum:
  case BuiltinType::SatLongAccum:
    Encoding = llvm::dwarf::DW_ATE_signed_fixed;
    break;
  case BuiltinType::UShortAccum:
  case BuiltinType::UAccum:
  case BuiltinType::ULongAccum:
  case BuiltinType::UShortFract:
  case BuiltinType::UFract:
  case BuiltinType::ULongFract:
  case BuiltinType::SatUShortAccum:
  case BuiltinType::SatUAccum:
  case BuiltinType::SatULongAccum:
  case BuiltinType::SatUShortFract:
  case BuiltinType::SatUFract:
  case BuiltinType::SatULongFract:
    Encoding = llvm::dwarf::DW_ATE_unsigned_fixed;
    break;
  }

  switch (BT->getKind()) {
  case BuiltinType::Long:
    BTName = "long int";
    break;
  case BuiltinType::LongLong:
    BTName = "long long int";
    break;
  case BuiltinType::ULong:
    BTName = "long unsigned int";
    break;
  case BuiltinType::ULongLong:
    BTName = "long long unsigned int";
    break;
  default:
    BTName = BT->getName(CGM.getLangOpts());
    break;
  }
  // Bit size and offset of the type.
  uint64_t Size = CGM.getContext().getTypeSize(BT);
  return DBuilder.createBasicType(BTName, Size, Encoding);
}

llvm::DIType *CGDebugInfo::CreateType(const ComplexType *Ty) {
  // Bit size and offset of the type.
  llvm::dwarf::TypeKind Encoding = llvm::dwarf::DW_ATE_complex_float;
  if (Ty->isComplexIntegerType())
    Encoding = llvm::dwarf::DW_ATE_lo_user;

  uint64_t Size = CGM.getContext().getTypeSize(Ty);
  return DBuilder.createBasicType("complex", Size, Encoding);
}

llvm::DIType *CGDebugInfo::CreateQualifiedType(QualType Ty,
                                               llvm::DIFile *Unit) {
  QualifierCollector Qc;
  const Type *T = Qc.strip(Ty);

  // Ignore these qualifiers for now.
  Qc.removeObjCGCAttr();
  Qc.removeAddressSpace();
  Qc.removeObjCLifetime();

  // We will create one Derived type for one qualifier and recurse to handle any
  // additional ones.
  llvm::dwarf::Tag Tag;
  if (Qc.hasConst()) {
    Tag = llvm::dwarf::DW_TAG_const_type;
    Qc.removeConst();
  } else if (Qc.hasVolatile()) {
    Tag = llvm::dwarf::DW_TAG_volatile_type;
    Qc.removeVolatile();
  } else if (Qc.hasRestrict()) {
    Tag = llvm::dwarf::DW_TAG_restrict_type;
    Qc.removeRestrict();
  } else {
    assert(Qc.empty() && "Unknown type qualifier for debug info");
    return getOrCreateType(QualType(T, 0), Unit);
  }

  auto *FromTy = getOrCreateType(Qc.apply(CGM.getContext(), T), Unit);

  // No need to fill in the Name, Line, Size, Alignment, Offset in case of
  // CVR derived types.
  return DBuilder.createQualifiedType(Tag, FromTy);
}

llvm::DIType *CGDebugInfo::CreateType(const ObjCObjectPointerType *Ty,
                                      llvm::DIFile *Unit) {

  // The frontend treats 'id' as a typedef to an ObjCObjectType,
  // whereas 'id<protocol>' is treated as an ObjCPointerType. For the
  // debug info, we want to emit 'id' in both cases.
  if (Ty->isObjCQualifiedIdType())
    return getOrCreateType(CGM.getContext().getObjCIdType(), Unit);

  return CreatePointerLikeType(llvm::dwarf::DW_TAG_pointer_type, Ty,
                               Ty->getPointeeType(), Unit);
}

llvm::DIType *CGDebugInfo::CreateType(const PointerType *Ty,
                                      llvm::DIFile *Unit) {
  return CreatePointerLikeType(llvm::dwarf::DW_TAG_pointer_type, Ty,
                               Ty->getPointeeType(), Unit);
}

/// \return whether a C++ mangling exists for the type defined by TD.
static bool hasCXXMangling(const TagDecl *TD, llvm::DICompileUnit *TheCU) {
  switch (TheCU->getSourceLanguage()) {
  case llvm::dwarf::DW_LANG_C_plus_plus:
    return true;
  case llvm::dwarf::DW_LANG_ObjC_plus_plus:
    return isa<CXXRecordDecl>(TD) || isa<EnumDecl>(TD);
  default:
    return false;
  }
}

// Determines if the debug info for this tag declaration needs a type
// identifier. The purpose of the unique identifier is to deduplicate type
// information for identical types across TUs. Because of the C++ one definition
// rule (ODR), it is valid to assume that the type is defined the same way in
// every TU and its debug info is equivalent.
//
// C does not have the ODR, and it is common for codebases to contain multiple
// different definitions of a struct with the same name in different TUs.
// Therefore, if the type doesn't have a C++ mangling, don't give it an
// identifer. Type information in C is smaller and simpler than C++ type
// information, so the increase in debug info size is negligible.
//
// If the type is not externally visible, it should be unique to the current TU,
// and should not need an identifier to participate in type deduplication.
// However, when emitting CodeView, the format internally uses these
// unique type name identifers for references between debug info. For example,
// the method of a class in an anonymous namespace uses the identifer to refer
// to its parent class. The Microsoft C++ ABI attempts to provide unique names
// for such types, so when emitting CodeView, always use identifiers for C++
// types. This may create problems when attempting to emit CodeView when the MS
// C++ ABI is not in use.
static bool needsTypeIdentifier(const TagDecl *TD, CodeGenModule &CGM,
                                llvm::DICompileUnit *TheCU) {
  // We only add a type identifier for types with C++ name mangling.
  if (!hasCXXMangling(TD, TheCU))
    return false;

  // Externally visible types with C++ mangling need a type identifier.
  if (TD->isExternallyVisible())
    return true;

  // CodeView types with C++ mangling need a type identifier.
  if (CGM.getCodeGenOpts().EmitCodeView)
    return true;

  return false;
}

// Returns a unique type identifier string if one exists, or an empty string.
static SmallString<256> getTypeIdentifier(const TagType *Ty, CodeGenModule &CGM,
                                          llvm::DICompileUnit *TheCU) {
  SmallString<256> Identifier;
  const TagDecl *TD = Ty->getDecl();

  if (!needsTypeIdentifier(TD, CGM, TheCU))
    return Identifier;
  if (const auto *RD = dyn_cast<CXXRecordDecl>(TD))
    if (RD->getDefinition())
      if (RD->isDynamicClass() &&
          CGM.getVTableLinkage(RD) == llvm::GlobalValue::ExternalLinkage)
        return Identifier;

  // TODO: This is using the RTTI name. Is there a better way to get
  // a unique string for a type?
  llvm::raw_svector_ostream Out(Identifier);
  CGM.getCXXABI().getMangleContext().mangleCXXRTTIName(QualType(Ty, 0), Out);
  return Identifier;
}

/// \return the appropriate DWARF tag for a composite type.
static llvm::dwarf::Tag getTagForRecord(const RecordDecl *RD) {
  llvm::dwarf::Tag Tag;
  if (RD->isStruct() || RD->isInterface())
    Tag = llvm::dwarf::DW_TAG_structure_type;
  else if (RD->isUnion())
    Tag = llvm::dwarf::DW_TAG_union_type;
  else {
    // FIXME: This could be a struct type giving a default visibility different
    // than C++ class type, but needs llvm metadata changes first.
    assert(RD->isClass());
    Tag = llvm::dwarf::DW_TAG_class_type;
  }
  return Tag;
}

llvm::DICompositeType *
CGDebugInfo::getOrCreateRecordFwdDecl(const RecordType *Ty,
                                      llvm::DIScope *Ctx) {
  const RecordDecl *RD = Ty->getDecl();
  if (llvm::DIType *T = getTypeOrNull(CGM.getContext().getRecordType(RD)))
    return cast<llvm::DICompositeType>(T);
  llvm::DIFile *DefUnit = getOrCreateFile(RD->getLocation());
  unsigned Line = getLineNumber(RD->getLocation());
  StringRef RDName = getClassName(RD);

  uint64_t Size = 0;
  uint32_t Align = 0;

  // Create the type.
  SmallString<256> Identifier = getTypeIdentifier(Ty, CGM, TheCU);
  llvm::DICompositeType *RetTy = DBuilder.createReplaceableCompositeType(
      getTagForRecord(RD), RDName, Ctx, DefUnit, Line, 0, Size, Align,
      llvm::DINode::FlagFwdDecl, Identifier);
  if (CGM.getCodeGenOpts().DebugFwdTemplateParams)
    if (auto *TSpecial = dyn_cast<ClassTemplateSpecializationDecl>(RD))
      DBuilder.replaceArrays(RetTy, llvm::DINodeArray(),
                             CollectCXXTemplateParams(TSpecial, DefUnit));
  ReplaceMap.emplace_back(
      std::piecewise_construct, std::make_tuple(Ty),
      std::make_tuple(static_cast<llvm::Metadata *>(RetTy)));
  return RetTy;
}

llvm::DIType *CGDebugInfo::CreatePointerLikeType(llvm::dwarf::Tag Tag,
                                                 const Type *Ty,
                                                 QualType PointeeTy,
                                                 llvm::DIFile *Unit) {
  // Bit size, align and offset of the type.
  // Size is always the size of a pointer. We can't use getTypeSize here
  // because that does not return the correct value for references.
  unsigned AddressSpace = CGM.getContext().getTargetAddressSpace(PointeeTy);
  uint64_t Size = CGM.getTarget().getPointerWidth(AddressSpace);
  auto Align = getTypeAlignIfRequired(Ty, CGM.getContext());
  Optional<unsigned> DWARFAddressSpace =
      CGM.getTarget().getDWARFAddressSpace(AddressSpace);

  if (Tag == llvm::dwarf::DW_TAG_reference_type ||
      Tag == llvm::dwarf::DW_TAG_rvalue_reference_type)
    return DBuilder.createReferenceType(Tag, getOrCreateType(PointeeTy, Unit),
                                        Size, Align, DWARFAddressSpace);
  else
    return DBuilder.createPointerType(getOrCreateType(PointeeTy, Unit), Size,
                                      Align, DWARFAddressSpace);
}

llvm::DIType *CGDebugInfo::getOrCreateStructPtrType(StringRef Name,
                                                    llvm::DIType *&Cache) {
  if (Cache)
    return Cache;
  Cache = DBuilder.createForwardDecl(llvm::dwarf::DW_TAG_structure_type, Name,
                                     TheCU, TheCU->getFile(), 0);
  unsigned Size = CGM.getContext().getTypeSize(CGM.getContext().VoidPtrTy);
  Cache = DBuilder.createPointerType(Cache, Size);
  return Cache;
}

uint64_t CGDebugInfo::collectDefaultElementTypesForBlockPointer(
    const BlockPointerType *Ty, llvm::DIFile *Unit, llvm::DIDerivedType *DescTy,
    unsigned LineNo, SmallVectorImpl<llvm::Metadata *> &EltTys) {
  QualType FType;

  // Advanced by calls to CreateMemberType in increments of FType, then
  // returned as the overall size of the default elements.
  uint64_t FieldOffset = 0;

  // Blocks in OpenCL have unique constraints which make the standard fields
  // redundant while requiring size and align fields for enqueue_kernel. See
  // initializeForBlockHeader in CGBlocks.cpp
  if (CGM.getLangOpts().OpenCL) {
    FType = CGM.getContext().IntTy;
    EltTys.push_back(CreateMemberType(Unit, FType, "__size", &FieldOffset));
    EltTys.push_back(CreateMemberType(Unit, FType, "__align", &FieldOffset));
  } else {
    FType = CGM.getContext().getPointerType(CGM.getContext().VoidTy);
    EltTys.push_back(CreateMemberType(Unit, FType, "__isa", &FieldOffset));
    FType = CGM.getContext().IntTy;
    EltTys.push_back(CreateMemberType(Unit, FType, "__flags", &FieldOffset));
    EltTys.push_back(CreateMemberType(Unit, FType, "__reserved", &FieldOffset));
    FType = CGM.getContext().getPointerType(Ty->getPointeeType());
    EltTys.push_back(CreateMemberType(Unit, FType, "__FuncPtr", &FieldOffset));
    FType = CGM.getContext().getPointerType(CGM.getContext().VoidTy);
    uint64_t FieldSize = CGM.getContext().getTypeSize(Ty);
    uint32_t FieldAlign = CGM.getContext().getTypeAlign(Ty);
    EltTys.push_back(DBuilder.createMemberType(
        Unit, "__descriptor", nullptr, LineNo, FieldSize, FieldAlign,
        FieldOffset, llvm::DINode::FlagZero, DescTy));
    FieldOffset += FieldSize;
  }

  return FieldOffset;
}

llvm::DIType *CGDebugInfo::CreateType(const BlockPointerType *Ty,
                                      llvm::DIFile *Unit) {
  SmallVector<llvm::Metadata *, 8> EltTys;
  QualType FType;
  uint64_t FieldOffset;
  llvm::DINodeArray Elements;

  FieldOffset = 0;
  FType = CGM.getContext().UnsignedLongTy;
  EltTys.push_back(CreateMemberType(Unit, FType, "reserved", &FieldOffset));
  EltTys.push_back(CreateMemberType(Unit, FType, "Size", &FieldOffset));

  Elements = DBuilder.getOrCreateArray(EltTys);
  EltTys.clear();

  llvm::DINode::DIFlags Flags = llvm::DINode::FlagAppleBlock;

  auto *EltTy =
      DBuilder.createStructType(Unit, "__block_descriptor", nullptr, 0,
                                FieldOffset, 0, Flags, nullptr, Elements);

  // Bit size, align and offset of the type.
  uint64_t Size = CGM.getContext().getTypeSize(Ty);

  auto *DescTy = DBuilder.createPointerType(EltTy, Size);

  FieldOffset = collectDefaultElementTypesForBlockPointer(Ty, Unit, DescTy,
                                                          0, EltTys);

  Elements = DBuilder.getOrCreateArray(EltTys);

  // The __block_literal_generic structs are marked with a special
  // DW_AT_APPLE_BLOCK attribute and are an implementation detail only
  // the debugger needs to know about. To allow type uniquing, emit
  // them without a name or a location.
  EltTy = DBuilder.createStructType(Unit, "", nullptr, 0, FieldOffset, 0,
                                    Flags, nullptr, Elements);

  return DBuilder.createPointerType(EltTy, Size);
}

llvm::DIType *CGDebugInfo::CreateType(const TemplateSpecializationType *Ty,
                                      llvm::DIFile *Unit) {
  assert(Ty->isTypeAlias());
  llvm::DIType *Src = getOrCreateType(Ty->getAliasedType(), Unit);

  auto *AliasDecl =
      cast<TypeAliasTemplateDecl>(Ty->getTemplateName().getAsTemplateDecl())
          ->getTemplatedDecl();

  if (AliasDecl->hasAttr<NoDebugAttr>())
    return Src;

  SmallString<128> NS;
  llvm::raw_svector_ostream OS(NS);
  Ty->getTemplateName().print(OS, getPrintingPolicy(), /*qualified*/ false);
  printTemplateArgumentList(OS, Ty->template_arguments(), getPrintingPolicy());

  SourceLocation Loc = AliasDecl->getLocation();
  return DBuilder.createTypedef(Src, OS.str(), getOrCreateFile(Loc),
                                getLineNumber(Loc),
                                getDeclContextDescriptor(AliasDecl));
}

llvm::DIType *CGDebugInfo::CreateType(const TypedefType *Ty,
                                      llvm::DIFile *Unit) {
  llvm::DIType *Underlying =
      getOrCreateType(Ty->getDecl()->getUnderlyingType(), Unit);

  if (Ty->getDecl()->hasAttr<NoDebugAttr>())
    return Underlying;

  // We don't set size information, but do specify where the typedef was
  // declared.
  SourceLocation Loc = Ty->getDecl()->getLocation();

  // Typedefs are derived from some other type.
  return DBuilder.createTypedef(Underlying, Ty->getDecl()->getName(),
                                getOrCreateFile(Loc), getLineNumber(Loc),
                                getDeclContextDescriptor(Ty->getDecl()));
}

static unsigned getDwarfCC(CallingConv CC) {
  switch (CC) {
  case CC_C:
    // Avoid emitting DW_AT_calling_convention if the C convention was used.
    return 0;

  case CC_X86StdCall:
    return llvm::dwarf::DW_CC_BORLAND_stdcall;
  case CC_X86FastCall:
    return llvm::dwarf::DW_CC_BORLAND_msfastcall;
  case CC_X86ThisCall:
    return llvm::dwarf::DW_CC_BORLAND_thiscall;
  case CC_X86VectorCall:
    return llvm::dwarf::DW_CC_LLVM_vectorcall;
  case CC_X86Pascal:
    return llvm::dwarf::DW_CC_BORLAND_pascal;
  case CC_Win64:
    return llvm::dwarf::DW_CC_LLVM_Win64;
  case CC_X86_64SysV:
    return llvm::dwarf::DW_CC_LLVM_X86_64SysV;
  case CC_AAPCS:
  case CC_AArch64VectorCall:
    return llvm::dwarf::DW_CC_LLVM_AAPCS;
  case CC_AAPCS_VFP:
    return llvm::dwarf::DW_CC_LLVM_AAPCS_VFP;
  case CC_IntelOclBicc:
    return llvm::dwarf::DW_CC_LLVM_IntelOclBicc;
  case CC_SpirFunction:
    return llvm::dwarf::DW_CC_LLVM_SpirFunction;
  case CC_OpenCLKernel:
    return llvm::dwarf::DW_CC_LLVM_OpenCLKernel;
  case CC_Swift:
    return llvm::dwarf::DW_CC_LLVM_Swift;
  case CC_PreserveMost:
    return llvm::dwarf::DW_CC_LLVM_PreserveMost;
  case CC_PreserveAll:
    return llvm::dwarf::DW_CC_LLVM_PreserveAll;
  case CC_X86RegCall:
    return llvm::dwarf::DW_CC_LLVM_X86RegCall;
  }
  return 0;
}

llvm::DIType *CGDebugInfo::CreateType(const FunctionType *Ty,
                                      llvm::DIFile *Unit) {
  SmallVector<llvm::Metadata *, 16> EltTys;

  // Add the result type at least.
  EltTys.push_back(getOrCreateType(Ty->getReturnType(), Unit));

  // Set up remainder of arguments if there is a prototype.
  // otherwise emit it as a variadic function.
  if (isa<FunctionNoProtoType>(Ty))
    EltTys.push_back(DBuilder.createUnspecifiedParameter());
  else if (const auto *FPT = dyn_cast<FunctionProtoType>(Ty)) {
    for (const QualType &ParamType : FPT->param_types())
      EltTys.push_back(getOrCreateType(ParamType, Unit));
    if (FPT->isVariadic())
      EltTys.push_back(DBuilder.createUnspecifiedParameter());
  }

  llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(EltTys);
  return DBuilder.createSubroutineType(EltTypeArray, llvm::DINode::FlagZero,
                                       getDwarfCC(Ty->getCallConv()));
}

/// Convert an AccessSpecifier into the corresponding DINode flag.
/// As an optimization, return 0 if the access specifier equals the
/// default for the containing type.
static llvm::DINode::DIFlags getAccessFlag(AccessSpecifier Access,
                                           const RecordDecl *RD) {
  AccessSpecifier Default = clang::AS_none;
  if (RD && RD->isClass())
    Default = clang::AS_private;
  else if (RD && (RD->isStruct() || RD->isUnion()))
    Default = clang::AS_public;

  if (Access == Default)
    return llvm::DINode::FlagZero;

  switch (Access) {
  case clang::AS_private:
    return llvm::DINode::FlagPrivate;
  case clang::AS_protected:
    return llvm::DINode::FlagProtected;
  case clang::AS_public:
    return llvm::DINode::FlagPublic;
  case clang::AS_none:
    return llvm::DINode::FlagZero;
  }
  llvm_unreachable("unexpected access enumerator");
}

llvm::DIType *CGDebugInfo::createBitFieldType(const FieldDecl *BitFieldDecl,
                                              llvm::DIScope *RecordTy,
                                              const RecordDecl *RD) {
  StringRef Name = BitFieldDecl->getName();
  QualType Ty = BitFieldDecl->getType();
  SourceLocation Loc = BitFieldDecl->getLocation();
  llvm::DIFile *VUnit = getOrCreateFile(Loc);
  llvm::DIType *DebugType = getOrCreateType(Ty, VUnit);

  // Get the location for the field.
  llvm::DIFile *File = getOrCreateFile(Loc);
  unsigned Line = getLineNumber(Loc);

  const CGBitFieldInfo &BitFieldInfo =
      CGM.getTypes().getCGRecordLayout(RD).getBitFieldInfo(BitFieldDecl);
  uint64_t SizeInBits = BitFieldInfo.Size;
  assert(SizeInBits > 0 && "found named 0-width bitfield");
  uint64_t StorageOffsetInBits =
      CGM.getContext().toBits(BitFieldInfo.StorageOffset);
  uint64_t Offset = BitFieldInfo.Offset;
  // The bit offsets for big endian machines are reversed for big
  // endian target, compensate for that as the DIDerivedType requires
  // un-reversed offsets.
  if (CGM.getDataLayout().isBigEndian())
    Offset = BitFieldInfo.StorageSize - BitFieldInfo.Size - Offset;
  uint64_t OffsetInBits = StorageOffsetInBits + Offset;
  llvm::DINode::DIFlags Flags = getAccessFlag(BitFieldDecl->getAccess(), RD);
  return DBuilder.createBitFieldMemberType(
      RecordTy, Name, File, Line, SizeInBits, OffsetInBits, StorageOffsetInBits,
      Flags, DebugType);
}

llvm::DIType *
CGDebugInfo::createFieldType(StringRef name, QualType type, SourceLocation loc,
                             AccessSpecifier AS, uint64_t offsetInBits,
                             uint32_t AlignInBits, llvm::DIFile *tunit,
                             llvm::DIScope *scope, const RecordDecl *RD) {
  llvm::DIType *debugType = getOrCreateType(type, tunit);

  // Get the location for the field.
  llvm::DIFile *file = getOrCreateFile(loc);
  unsigned line = getLineNumber(loc);

  uint64_t SizeInBits = 0;
  auto Align = AlignInBits;
  if (!type->isIncompleteArrayType()) {
    TypeInfo TI = CGM.getContext().getTypeInfo(type);
    SizeInBits = TI.Width;
    if (!Align)
      Align = getTypeAlignIfRequired(type, CGM.getContext());
  }

  llvm::DINode::DIFlags flags = getAccessFlag(AS, RD);
  return DBuilder.createMemberType(scope, name, file, line, SizeInBits, Align,
                                   offsetInBits, flags, debugType);
}

void CGDebugInfo::CollectRecordLambdaFields(
    const CXXRecordDecl *CXXDecl, SmallVectorImpl<llvm::Metadata *> &elements,
    llvm::DIType *RecordTy) {
  // For C++11 Lambdas a Field will be the same as a Capture, but the Capture
  // has the name and the location of the variable so we should iterate over
  // both concurrently.
  const ASTRecordLayout &layout = CGM.getContext().getASTRecordLayout(CXXDecl);
  RecordDecl::field_iterator Field = CXXDecl->field_begin();
  unsigned fieldno = 0;
  for (CXXRecordDecl::capture_const_iterator I = CXXDecl->captures_begin(),
                                             E = CXXDecl->captures_end();
       I != E; ++I, ++Field, ++fieldno) {
    const LambdaCapture &C = *I;
    if (C.capturesVariable()) {
      SourceLocation Loc = C.getLocation();
      assert(!Field->isBitField() && "lambdas don't have bitfield members!");
      VarDecl *V = C.getCapturedVar();
      StringRef VName = V->getName();
      llvm::DIFile *VUnit = getOrCreateFile(Loc);
      auto Align = getDeclAlignIfRequired(V, CGM.getContext());
      llvm::DIType *FieldType = createFieldType(
          VName, Field->getType(), Loc, Field->getAccess(),
          layout.getFieldOffset(fieldno), Align, VUnit, RecordTy, CXXDecl);
      elements.push_back(FieldType);
    } else if (C.capturesThis()) {
      // TODO: Need to handle 'this' in some way by probably renaming the
      // this of the lambda class and having a field member of 'this' or
      // by using AT_object_pointer for the function and having that be
      // used as 'this' for semantic references.
      FieldDecl *f = *Field;
      llvm::DIFile *VUnit = getOrCreateFile(f->getLocation());
      QualType type = f->getType();
      llvm::DIType *fieldType = createFieldType(
          "this", type, f->getLocation(), f->getAccess(),
          layout.getFieldOffset(fieldno), VUnit, RecordTy, CXXDecl);

      elements.push_back(fieldType);
    }
  }
}

llvm::DIDerivedType *
CGDebugInfo::CreateRecordStaticField(const VarDecl *Var, llvm::DIType *RecordTy,
                                     const RecordDecl *RD) {
  // Create the descriptor for the static variable, with or without
  // constant initializers.
  Var = Var->getCanonicalDecl();
  llvm::DIFile *VUnit = getOrCreateFile(Var->getLocation());
  llvm::DIType *VTy = getOrCreateType(Var->getType(), VUnit);

  unsigned LineNumber = getLineNumber(Var->getLocation());
  StringRef VName = Var->getName();
  llvm::Constant *C = nullptr;
  if (Var->getInit()) {
    const APValue *Value = Var->evaluateValue();
    if (Value) {
      if (Value->isInt())
        C = llvm::ConstantInt::get(CGM.getLLVMContext(), Value->getInt());
      if (Value->isFloat())
        C = llvm::ConstantFP::get(CGM.getLLVMContext(), Value->getFloat());
    }
  }

  llvm::DINode::DIFlags Flags = getAccessFlag(Var->getAccess(), RD);
  auto Align = getDeclAlignIfRequired(Var, CGM.getContext());
  llvm::DIDerivedType *GV = DBuilder.createStaticMemberType(
      RecordTy, VName, VUnit, LineNumber, VTy, Flags, C, Align);
  StaticDataMemberCache[Var->getCanonicalDecl()].reset(GV);
  return GV;
}

void CGDebugInfo::CollectRecordNormalField(
    const FieldDecl *field, uint64_t OffsetInBits, llvm::DIFile *tunit,
    SmallVectorImpl<llvm::Metadata *> &elements, llvm::DIType *RecordTy,
    const RecordDecl *RD) {
  StringRef name = field->getName();
  QualType type = field->getType();

  // Ignore unnamed fields unless they're anonymous structs/unions.
  if (name.empty() && !type->isRecordType())
    return;

  llvm::DIType *FieldType;
  if (field->isBitField()) {
    FieldType = createBitFieldType(field, RecordTy, RD);
  } else {
    auto Align = getDeclAlignIfRequired(field, CGM.getContext());
    FieldType =
        createFieldType(name, type, field->getLocation(), field->getAccess(),
                        OffsetInBits, Align, tunit, RecordTy, RD);
  }

  elements.push_back(FieldType);
}

void CGDebugInfo::CollectRecordNestedType(
    const TypeDecl *TD, SmallVectorImpl<llvm::Metadata *> &elements) {
  QualType Ty = CGM.getContext().getTypeDeclType(TD);
  // Injected class names are not considered nested records.
  if (isa<InjectedClassNameType>(Ty))
    return;
  SourceLocation Loc = TD->getLocation();
  llvm::DIType *nestedType = getOrCreateType(Ty, getOrCreateFile(Loc));
  elements.push_back(nestedType);
}

void CGDebugInfo::CollectRecordFields(
    const RecordDecl *record, llvm::DIFile *tunit,
    SmallVectorImpl<llvm::Metadata *> &elements,
    llvm::DICompositeType *RecordTy) {
  const auto *CXXDecl = dyn_cast<CXXRecordDecl>(record);

  if (CXXDecl && CXXDecl->isLambda())
    CollectRecordLambdaFields(CXXDecl, elements, RecordTy);
  else {
    const ASTRecordLayout &layout = CGM.getContext().getASTRecordLayout(record);

    // Field number for non-static fields.
    unsigned fieldNo = 0;

    // Static and non-static members should appear in the same order as
    // the corresponding declarations in the source program.
    for (const auto *I : record->decls())
      if (const auto *V = dyn_cast<VarDecl>(I)) {
        if (V->hasAttr<NoDebugAttr>())
          continue;

        // Skip variable template specializations when emitting CodeView. MSVC
        // doesn't emit them.
        if (CGM.getCodeGenOpts().EmitCodeView &&
            isa<VarTemplateSpecializationDecl>(V))
          continue;

        if (isa<VarTemplatePartialSpecializationDecl>(V))
          continue;

        // Reuse the existing static member declaration if one exists
        auto MI = StaticDataMemberCache.find(V->getCanonicalDecl());
        if (MI != StaticDataMemberCache.end()) {
          assert(MI->second &&
                 "Static data member declaration should still exist");
          elements.push_back(MI->second);
        } else {
          auto Field = CreateRecordStaticField(V, RecordTy, record);
          elements.push_back(Field);
        }
      } else if (const auto *field = dyn_cast<FieldDecl>(I)) {
        CollectRecordNormalField(field, layout.getFieldOffset(fieldNo), tunit,
                                 elements, RecordTy, record);

        // Bump field number for next field.
        ++fieldNo;
      } else if (CGM.getCodeGenOpts().EmitCodeView) {
        // Debug info for nested types is included in the member list only for
        // CodeView.
        if (const auto *nestedType = dyn_cast<TypeDecl>(I))
          if (!nestedType->isImplicit() &&
              nestedType->getDeclContext() == record)
            CollectRecordNestedType(nestedType, elements);
      }
  }
}

llvm::DISubroutineType *
CGDebugInfo::getOrCreateMethodType(const CXXMethodDecl *Method,
                                   llvm::DIFile *Unit) {
  const FunctionProtoType *Func = Method->getType()->getAs<FunctionProtoType>();
  if (Method->isStatic())
    return cast_or_null<llvm::DISubroutineType>(
        getOrCreateType(QualType(Func, 0), Unit));
  return getOrCreateInstanceMethodType(Method->getThisType(), Func, Unit);
}

llvm::DISubroutineType *CGDebugInfo::getOrCreateInstanceMethodType(
    QualType ThisPtr, const FunctionProtoType *Func, llvm::DIFile *Unit) {
  // Add "this" pointer.
  llvm::DITypeRefArray Args(
      cast<llvm::DISubroutineType>(getOrCreateType(QualType(Func, 0), Unit))
          ->getTypeArray());
  assert(Args.size() && "Invalid number of arguments!");

  SmallVector<llvm::Metadata *, 16> Elts;

  // First element is always return type. For 'void' functions it is NULL.
  Elts.push_back(Args[0]);

  // "this" pointer is always first argument.
  const CXXRecordDecl *RD = ThisPtr->getPointeeCXXRecordDecl();
  if (isa<ClassTemplateSpecializationDecl>(RD)) {
    // Create pointer type directly in this case.
    const PointerType *ThisPtrTy = cast<PointerType>(ThisPtr);
    QualType PointeeTy = ThisPtrTy->getPointeeType();
    unsigned AS = CGM.getContext().getTargetAddressSpace(PointeeTy);
    uint64_t Size = CGM.getTarget().getPointerWidth(AS);
    auto Align = getTypeAlignIfRequired(ThisPtrTy, CGM.getContext());
    llvm::DIType *PointeeType = getOrCreateType(PointeeTy, Unit);
    llvm::DIType *ThisPtrType =
        DBuilder.createPointerType(PointeeType, Size, Align);
    TypeCache[ThisPtr.getAsOpaquePtr()].reset(ThisPtrType);
    // TODO: This and the artificial type below are misleading, the
    // types aren't artificial the argument is, but the current
    // metadata doesn't represent that.
    ThisPtrType = DBuilder.createObjectPointerType(ThisPtrType);
    Elts.push_back(ThisPtrType);
  } else {
    llvm::DIType *ThisPtrType = getOrCreateType(ThisPtr, Unit);
    TypeCache[ThisPtr.getAsOpaquePtr()].reset(ThisPtrType);
    ThisPtrType = DBuilder.createObjectPointerType(ThisPtrType);
    Elts.push_back(ThisPtrType);
  }

  // Copy rest of the arguments.
  for (unsigned i = 1, e = Args.size(); i != e; ++i)
    Elts.push_back(Args[i]);

  llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(Elts);

  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  if (Func->getExtProtoInfo().RefQualifier == RQ_LValue)
    Flags |= llvm::DINode::FlagLValueReference;
  if (Func->getExtProtoInfo().RefQualifier == RQ_RValue)
    Flags |= llvm::DINode::FlagRValueReference;

  return DBuilder.createSubroutineType(EltTypeArray, Flags,
                                       getDwarfCC(Func->getCallConv()));
}

/// isFunctionLocalClass - Return true if CXXRecordDecl is defined
/// inside a function.
static bool isFunctionLocalClass(const CXXRecordDecl *RD) {
  if (const auto *NRD = dyn_cast<CXXRecordDecl>(RD->getDeclContext()))
    return isFunctionLocalClass(NRD);
  if (isa<FunctionDecl>(RD->getDeclContext()))
    return true;
  return false;
}

llvm::DISubprogram *CGDebugInfo::CreateCXXMemberFunction(
    const CXXMethodDecl *Method, llvm::DIFile *Unit, llvm::DIType *RecordTy) {
  bool IsCtorOrDtor =
      isa<CXXConstructorDecl>(Method) || isa<CXXDestructorDecl>(Method);

  StringRef MethodName = getFunctionName(Method);
  llvm::DISubroutineType *MethodTy = getOrCreateMethodType(Method, Unit);

  // Since a single ctor/dtor corresponds to multiple functions, it doesn't
  // make sense to give a single ctor/dtor a linkage name.
  StringRef MethodLinkageName;
  // FIXME: 'isFunctionLocalClass' seems like an arbitrary/unintentional
  // property to use here. It may've been intended to model "is non-external
  // type" but misses cases of non-function-local but non-external classes such
  // as those in anonymous namespaces as well as the reverse - external types
  // that are function local, such as those in (non-local) inline functions.
  if (!IsCtorOrDtor && !isFunctionLocalClass(Method->getParent()))
    MethodLinkageName = CGM.getMangledName(Method);

  // Get the location for the method.
  llvm::DIFile *MethodDefUnit = nullptr;
  unsigned MethodLine = 0;
  if (!Method->isImplicit()) {
    MethodDefUnit = getOrCreateFile(Method->getLocation());
    MethodLine = getLineNumber(Method->getLocation());
  }

  // Collect virtual method info.
  llvm::DIType *ContainingType = nullptr;
  unsigned VIndex = 0;
  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  llvm::DISubprogram::DISPFlags SPFlags = llvm::DISubprogram::SPFlagZero;
  int ThisAdjustment = 0;

  if (Method->isVirtual()) {
    if (Method->isPure())
      SPFlags |= llvm::DISubprogram::SPFlagPureVirtual;
    else
      SPFlags |= llvm::DISubprogram::SPFlagVirtual;

    if (CGM.getTarget().getCXXABI().isItaniumFamily()) {
      // It doesn't make sense to give a virtual destructor a vtable index,
      // since a single destructor has two entries in the vtable.
      if (!isa<CXXDestructorDecl>(Method))
        VIndex = CGM.getItaniumVTableContext().getMethodVTableIndex(Method);
    } else {
      // Emit MS ABI vftable information.  There is only one entry for the
      // deleting dtor.
      const auto *DD = dyn_cast<CXXDestructorDecl>(Method);
      GlobalDecl GD = DD ? GlobalDecl(DD, Dtor_Deleting) : GlobalDecl(Method);
      MethodVFTableLocation ML =
          CGM.getMicrosoftVTableContext().getMethodVFTableLocation(GD);
      VIndex = ML.Index;

      // CodeView only records the vftable offset in the class that introduces
      // the virtual method. This is possible because, unlike Itanium, the MS
      // C++ ABI does not include all virtual methods from non-primary bases in
      // the vtable for the most derived class. For example, if C inherits from
      // A and B, C's primary vftable will not include B's virtual methods.
      if (Method->size_overridden_methods() == 0)
        Flags |= llvm::DINode::FlagIntroducedVirtual;

      // The 'this' adjustment accounts for both the virtual and non-virtual
      // portions of the adjustment. Presumably the debugger only uses it when
      // it knows the dynamic type of an object.
      ThisAdjustment = CGM.getCXXABI()
                           .getVirtualFunctionPrologueThisAdjustment(GD)
                           .getQuantity();
    }
    ContainingType = RecordTy;
  }

  if (Method->isStatic())
    Flags |= llvm::DINode::FlagStaticMember;
  if (Method->isImplicit())
    Flags |= llvm::DINode::FlagArtificial;
  Flags |= getAccessFlag(Method->getAccess(), Method->getParent());
  if (const auto *CXXC = dyn_cast<CXXConstructorDecl>(Method)) {
    if (CXXC->isExplicit())
      Flags |= llvm::DINode::FlagExplicit;
  } else if (const auto *CXXC = dyn_cast<CXXConversionDecl>(Method)) {
    if (CXXC->isExplicit())
      Flags |= llvm::DINode::FlagExplicit;
  }
  if (Method->hasPrototype())
    Flags |= llvm::DINode::FlagPrototyped;
  if (Method->getRefQualifier() == RQ_LValue)
    Flags |= llvm::DINode::FlagLValueReference;
  if (Method->getRefQualifier() == RQ_RValue)
    Flags |= llvm::DINode::FlagRValueReference;
  if (CGM.getLangOpts().Optimize)
    SPFlags |= llvm::DISubprogram::SPFlagOptimized;

  llvm::DINodeArray TParamsArray = CollectFunctionTemplateParams(Method, Unit);
  llvm::DISubprogram *SP = DBuilder.createMethod(
      RecordTy, MethodName, MethodLinkageName, MethodDefUnit, MethodLine,
      MethodTy, VIndex, ThisAdjustment, ContainingType, Flags, SPFlags,
      TParamsArray.get());

  SPCache[Method->getCanonicalDecl()].reset(SP);

  return SP;
}

void CGDebugInfo::CollectCXXMemberFunctions(
    const CXXRecordDecl *RD, llvm::DIFile *Unit,
    SmallVectorImpl<llvm::Metadata *> &EltTys, llvm::DIType *RecordTy) {

  // Since we want more than just the individual member decls if we
  // have templated functions iterate over every declaration to gather
  // the functions.
  for (const auto *I : RD->decls()) {
    const auto *Method = dyn_cast<CXXMethodDecl>(I);
    // If the member is implicit, don't add it to the member list. This avoids
    // the member being added to type units by LLVM, while still allowing it
    // to be emitted into the type declaration/reference inside the compile
    // unit.
    // Ditto 'nodebug' methods, for consistency with CodeGenFunction.cpp.
    // FIXME: Handle Using(Shadow?)Decls here to create
    // DW_TAG_imported_declarations inside the class for base decls brought into
    // derived classes. GDB doesn't seem to notice/leverage these when I tried
    // it, so I'm not rushing to fix this. (GCC seems to produce them, if
    // referenced)
    if (!Method || Method->isImplicit() || Method->hasAttr<NoDebugAttr>())
      continue;

    if (Method->getType()->getAs<FunctionProtoType>()->getContainedAutoType())
      continue;

    // Reuse the existing member function declaration if it exists.
    // It may be associated with the declaration of the type & should be
    // reused as we're building the definition.
    //
    // This situation can arise in the vtable-based debug info reduction where
    // implicit members are emitted in a non-vtable TU.
    auto MI = SPCache.find(Method->getCanonicalDecl());
    EltTys.push_back(MI == SPCache.end()
                         ? CreateCXXMemberFunction(Method, Unit, RecordTy)
                         : static_cast<llvm::Metadata *>(MI->second));
  }
}

void CGDebugInfo::CollectCXXBases(const CXXRecordDecl *RD, llvm::DIFile *Unit,
                                  SmallVectorImpl<llvm::Metadata *> &EltTys,
                                  llvm::DIType *RecordTy) {
  llvm::DenseSet<CanonicalDeclPtr<const CXXRecordDecl>> SeenTypes;
  CollectCXXBasesAux(RD, Unit, EltTys, RecordTy, RD->bases(), SeenTypes,
                     llvm::DINode::FlagZero);

  // If we are generating CodeView debug info, we also need to emit records for
  // indirect virtual base classes.
  if (CGM.getCodeGenOpts().EmitCodeView) {
    CollectCXXBasesAux(RD, Unit, EltTys, RecordTy, RD->vbases(), SeenTypes,
                       llvm::DINode::FlagIndirectVirtualBase);
  }
}

void CGDebugInfo::CollectCXXBasesAux(
    const CXXRecordDecl *RD, llvm::DIFile *Unit,
    SmallVectorImpl<llvm::Metadata *> &EltTys, llvm::DIType *RecordTy,
    const CXXRecordDecl::base_class_const_range &Bases,
    llvm::DenseSet<CanonicalDeclPtr<const CXXRecordDecl>> &SeenTypes,
    llvm::DINode::DIFlags StartingFlags) {
  const ASTRecordLayout &RL = CGM.getContext().getASTRecordLayout(RD);
  for (const auto &BI : Bases) {
    const auto *Base =
        cast<CXXRecordDecl>(BI.getType()->getAs<RecordType>()->getDecl());
    if (!SeenTypes.insert(Base).second)
      continue;
    auto *BaseTy = getOrCreateType(BI.getType(), Unit);
    llvm::DINode::DIFlags BFlags = StartingFlags;
    uint64_t BaseOffset;
    uint32_t VBPtrOffset = 0;

    if (BI.isVirtual()) {
      if (CGM.getTarget().getCXXABI().isItaniumFamily()) {
        // virtual base offset offset is -ve. The code generator emits dwarf
        // expression where it expects +ve number.
        BaseOffset = 0 - CGM.getItaniumVTableContext()
                             .getVirtualBaseOffsetOffset(RD, Base)
                             .getQuantity();
      } else {
        // In the MS ABI, store the vbtable offset, which is analogous to the
        // vbase offset offset in Itanium.
        BaseOffset =
            4 * CGM.getMicrosoftVTableContext().getVBTableIndex(RD, Base);
        VBPtrOffset = CGM.getContext()
                          .getASTRecordLayout(RD)
                          .getVBPtrOffset()
                          .getQuantity();
      }
      BFlags |= llvm::DINode::FlagVirtual;
    } else
      BaseOffset = CGM.getContext().toBits(RL.getBaseClassOffset(Base));
    // FIXME: Inconsistent units for BaseOffset. It is in bytes when
    // BI->isVirtual() and bits when not.

    BFlags |= getAccessFlag(BI.getAccessSpecifier(), RD);
    llvm::DIType *DTy = DBuilder.createInheritance(RecordTy, BaseTy, BaseOffset,
                                                   VBPtrOffset, BFlags);
    EltTys.push_back(DTy);
  }
}

llvm::DINodeArray
CGDebugInfo::CollectTemplateParams(const TemplateParameterList *TPList,
                                   ArrayRef<TemplateArgument> TAList,
                                   llvm::DIFile *Unit) {
  SmallVector<llvm::Metadata *, 16> TemplateParams;
  for (unsigned i = 0, e = TAList.size(); i != e; ++i) {
    const TemplateArgument &TA = TAList[i];
    StringRef Name;
    if (TPList)
      Name = TPList->getParam(i)->getName();
    switch (TA.getKind()) {
    case TemplateArgument::Type: {
      llvm::DIType *TTy = getOrCreateType(TA.getAsType(), Unit);
      TemplateParams.push_back(
          DBuilder.createTemplateTypeParameter(TheCU, Name, TTy));
    } break;
    case TemplateArgument::Integral: {
      llvm::DIType *TTy = getOrCreateType(TA.getIntegralType(), Unit);
      TemplateParams.push_back(DBuilder.createTemplateValueParameter(
          TheCU, Name, TTy,
          llvm::ConstantInt::get(CGM.getLLVMContext(), TA.getAsIntegral())));
    } break;
    case TemplateArgument::Declaration: {
      const ValueDecl *D = TA.getAsDecl();
      QualType T = TA.getParamTypeForDecl().getDesugaredType(CGM.getContext());
      llvm::DIType *TTy = getOrCreateType(T, Unit);
      llvm::Constant *V = nullptr;
      // Skip retrieve the value if that template parameter has cuda device
      // attribute, i.e. that value is not available at the host side.
      if (!CGM.getLangOpts().CUDA || CGM.getLangOpts().CUDAIsDevice ||
          !D->hasAttr<CUDADeviceAttr>()) {
        const CXXMethodDecl *MD;
        // Variable pointer template parameters have a value that is the address
        // of the variable.
        if (const auto *VD = dyn_cast<VarDecl>(D))
          V = CGM.GetAddrOfGlobalVar(VD);
        // Member function pointers have special support for building them,
        // though this is currently unsupported in LLVM CodeGen.
        else if ((MD = dyn_cast<CXXMethodDecl>(D)) && MD->isInstance())
          V = CGM.getCXXABI().EmitMemberFunctionPointer(MD);
        else if (const auto *FD = dyn_cast<FunctionDecl>(D))
          V = CGM.GetAddrOfFunction(FD);
        // Member data pointers have special handling too to compute the fixed
        // offset within the object.
        else if (const auto *MPT =
                     dyn_cast<MemberPointerType>(T.getTypePtr())) {
          // These five lines (& possibly the above member function pointer
          // handling) might be able to be refactored to use similar code in
          // CodeGenModule::getMemberPointerConstant
          uint64_t fieldOffset = CGM.getContext().getFieldOffset(D);
          CharUnits chars =
              CGM.getContext().toCharUnitsFromBits((int64_t)fieldOffset);
          V = CGM.getCXXABI().EmitMemberDataPointer(MPT, chars);
        }
        V = V->stripPointerCasts();
      }
      TemplateParams.push_back(DBuilder.createTemplateValueParameter(
          TheCU, Name, TTy, cast_or_null<llvm::Constant>(V)));
    } break;
    case TemplateArgument::NullPtr: {
      QualType T = TA.getNullPtrType();
      llvm::DIType *TTy = getOrCreateType(T, Unit);
      llvm::Constant *V = nullptr;
      // Special case member data pointer null values since they're actually -1
      // instead of zero.
      if (const auto *MPT = dyn_cast<MemberPointerType>(T.getTypePtr()))
        // But treat member function pointers as simple zero integers because
        // it's easier than having a special case in LLVM's CodeGen. If LLVM
        // CodeGen grows handling for values of non-null member function
        // pointers then perhaps we could remove this special case and rely on
        // EmitNullMemberPointer for member function pointers.
        if (MPT->isMemberDataPointer())
          V = CGM.getCXXABI().EmitNullMemberPointer(MPT);
      if (!V)
        V = llvm::ConstantInt::get(CGM.Int8Ty, 0);
      TemplateParams.push_back(
          DBuilder.createTemplateValueParameter(TheCU, Name, TTy, V));
    } break;
    case TemplateArgument::Template:
      TemplateParams.push_back(DBuilder.createTemplateTemplateParameter(
          TheCU, Name, nullptr,
          TA.getAsTemplate().getAsTemplateDecl()->getQualifiedNameAsString()));
      break;
    case TemplateArgument::Pack:
      TemplateParams.push_back(DBuilder.createTemplateParameterPack(
          TheCU, Name, nullptr,
          CollectTemplateParams(nullptr, TA.getPackAsArray(), Unit)));
      break;
    case TemplateArgument::Expression: {
      const Expr *E = TA.getAsExpr();
      QualType T = E->getType();
      if (E->isGLValue())
        T = CGM.getContext().getLValueReferenceType(T);
      llvm::Constant *V = ConstantEmitter(CGM).emitAbstract(E, T);
      assert(V && "Expression in template argument isn't constant");
      llvm::DIType *TTy = getOrCreateType(T, Unit);
      TemplateParams.push_back(DBuilder.createTemplateValueParameter(
          TheCU, Name, TTy, V->stripPointerCasts()));
    } break;
    // And the following should never occur:
    case TemplateArgument::TemplateExpansion:
    case TemplateArgument::Null:
      llvm_unreachable(
          "These argument types shouldn't exist in concrete types");
    }
  }
  return DBuilder.getOrCreateArray(TemplateParams);
}

llvm::DINodeArray
CGDebugInfo::CollectFunctionTemplateParams(const FunctionDecl *FD,
                                           llvm::DIFile *Unit) {
  if (FD->getTemplatedKind() ==
      FunctionDecl::TK_FunctionTemplateSpecialization) {
    const TemplateParameterList *TList = FD->getTemplateSpecializationInfo()
                                             ->getTemplate()
                                             ->getTemplateParameters();
    return CollectTemplateParams(
        TList, FD->getTemplateSpecializationArgs()->asArray(), Unit);
  }
  return llvm::DINodeArray();
}

llvm::DINodeArray CGDebugInfo::CollectVarTemplateParams(const VarDecl *VL,
                                                        llvm::DIFile *Unit) {
  // Always get the full list of parameters, not just the ones from the
  // specialization. A partial specialization may have fewer parameters than
  // there are arguments.
  auto *TS = dyn_cast<VarTemplateSpecializationDecl>(VL);
  if (!TS)
    return llvm::DINodeArray();
  VarTemplateDecl *T = TS->getSpecializedTemplate();
  const TemplateParameterList *TList = T->getTemplateParameters();
  auto TA = TS->getTemplateArgs().asArray();
  return CollectTemplateParams(TList, TA, Unit);
}

llvm::DINodeArray CGDebugInfo::CollectCXXTemplateParams(
    const ClassTemplateSpecializationDecl *TSpecial, llvm::DIFile *Unit) {
  // Always get the full list of parameters, not just the ones from the
  // specialization. A partial specialization may have fewer parameters than
  // there are arguments.
  TemplateParameterList *TPList =
      TSpecial->getSpecializedTemplate()->getTemplateParameters();
  const TemplateArgumentList &TAList = TSpecial->getTemplateArgs();
  return CollectTemplateParams(TPList, TAList.asArray(), Unit);
}

llvm::DIType *CGDebugInfo::getOrCreateVTablePtrType(llvm::DIFile *Unit) {
  if (VTablePtrType)
    return VTablePtrType;

  ASTContext &Context = CGM.getContext();

  /* Function type */
  llvm::Metadata *STy = getOrCreateType(Context.IntTy, Unit);
  llvm::DITypeRefArray SElements = DBuilder.getOrCreateTypeArray(STy);
  llvm::DIType *SubTy = DBuilder.createSubroutineType(SElements);
  unsigned Size = Context.getTypeSize(Context.VoidPtrTy);
  unsigned VtblPtrAddressSpace = CGM.getTarget().getVtblPtrAddressSpace();
  Optional<unsigned> DWARFAddressSpace =
      CGM.getTarget().getDWARFAddressSpace(VtblPtrAddressSpace);

  llvm::DIType *vtbl_ptr_type = DBuilder.createPointerType(
      SubTy, Size, 0, DWARFAddressSpace, "__vtbl_ptr_type");
  VTablePtrType = DBuilder.createPointerType(vtbl_ptr_type, Size);
  return VTablePtrType;
}

StringRef CGDebugInfo::getVTableName(const CXXRecordDecl *RD) {
  // Copy the gdb compatible name on the side and use its reference.
  return internString("_vptr$", RD->getNameAsString());
}

StringRef CGDebugInfo::getDynamicInitializerName(const VarDecl *VD,
                                                 DynamicInitKind StubKind,
                                                 llvm::Function *InitFn) {
  // If we're not emitting codeview, use the mangled name. For Itanium, this is
  // arbitrary.
  if (!CGM.getCodeGenOpts().EmitCodeView)
    return InitFn->getName();

  // Print the normal qualified name for the variable, then break off the last
  // NNS, and add the appropriate other text. Clang always prints the global
  // variable name without template arguments, so we can use rsplit("::") and
  // then recombine the pieces.
  SmallString<128> QualifiedGV;
  StringRef Quals;
  StringRef GVName;
  {
    llvm::raw_svector_ostream OS(QualifiedGV);
    VD->printQualifiedName(OS, getPrintingPolicy());
    std::tie(Quals, GVName) = OS.str().rsplit("::");
    if (GVName.empty())
      std::swap(Quals, GVName);
  }

  SmallString<128> InitName;
  llvm::raw_svector_ostream OS(InitName);
  if (!Quals.empty())
    OS << Quals << "::";

  switch (StubKind) {
  case DynamicInitKind::NoStub:
    llvm_unreachable("not an initializer");
  case DynamicInitKind::Initializer:
    OS << "`dynamic initializer for '";
    break;
  case DynamicInitKind::AtExit:
    OS << "`dynamic atexit destructor for '";
    break;
  }

  OS << GVName;

  // Add any template specialization args.
  if (const auto *VTpl = dyn_cast<VarTemplateSpecializationDecl>(VD)) {
    printTemplateArgumentList(OS, VTpl->getTemplateArgs().asArray(),
                              getPrintingPolicy());
  }

  OS << '\'';

  return internString(OS.str());
}

void CGDebugInfo::CollectVTableInfo(const CXXRecordDecl *RD, llvm::DIFile *Unit,
                                    SmallVectorImpl<llvm::Metadata *> &EltTys,
                                    llvm::DICompositeType *RecordTy) {
  // If this class is not dynamic then there is not any vtable info to collect.
  if (!RD->isDynamicClass())
    return;

  // Don't emit any vtable shape or vptr info if this class doesn't have an
  // extendable vfptr. This can happen if the class doesn't have virtual
  // methods, or in the MS ABI if those virtual methods only come from virtually
  // inherited bases.
  const ASTRecordLayout &RL = CGM.getContext().getASTRecordLayout(RD);
  if (!RL.hasExtendableVFPtr())
    return;

  // CodeView needs to know how large the vtable of every dynamic class is, so
  // emit a special named pointer type into the element list. The vptr type
  // points to this type as well.
  llvm::DIType *VPtrTy = nullptr;
  bool NeedVTableShape = CGM.getCodeGenOpts().EmitCodeView &&
                         CGM.getTarget().getCXXABI().isMicrosoft();
  if (NeedVTableShape) {
    uint64_t PtrWidth =
        CGM.getContext().getTypeSize(CGM.getContext().VoidPtrTy);
    const VTableLayout &VFTLayout =
        CGM.getMicrosoftVTableContext().getVFTableLayout(RD, CharUnits::Zero());
    unsigned VSlotCount =
        VFTLayout.vtable_components().size() - CGM.getLangOpts().RTTIData;
    unsigned VTableWidth = PtrWidth * VSlotCount;
    unsigned VtblPtrAddressSpace = CGM.getTarget().getVtblPtrAddressSpace();
    Optional<unsigned> DWARFAddressSpace =
        CGM.getTarget().getDWARFAddressSpace(VtblPtrAddressSpace);

    // Create a very wide void* type and insert it directly in the element list.
    llvm::DIType *VTableType = DBuilder.createPointerType(
        nullptr, VTableWidth, 0, DWARFAddressSpace, "__vtbl_ptr_type");
    EltTys.push_back(VTableType);

    // The vptr is a pointer to this special vtable type.
    VPtrTy = DBuilder.createPointerType(VTableType, PtrWidth);
  }

  // If there is a primary base then the artificial vptr member lives there.
  if (RL.getPrimaryBase())
    return;

  if (!VPtrTy)
    VPtrTy = getOrCreateVTablePtrType(Unit);

  unsigned Size = CGM.getContext().getTypeSize(CGM.getContext().VoidPtrTy);
  llvm::DIType *VPtrMember =
      DBuilder.createMemberType(Unit, getVTableName(RD), Unit, 0, Size, 0, 0,
                                llvm::DINode::FlagArtificial, VPtrTy);
  EltTys.push_back(VPtrMember);
}

llvm::DIType *CGDebugInfo::getOrCreateRecordType(QualType RTy,
                                                 SourceLocation Loc) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  llvm::DIType *T = getOrCreateType(RTy, getOrCreateFile(Loc));
  return T;
}

llvm::DIType *CGDebugInfo::getOrCreateInterfaceType(QualType D,
                                                    SourceLocation Loc) {
  return getOrCreateStandaloneType(D, Loc);
}

llvm::DIType *CGDebugInfo::getOrCreateStandaloneType(QualType D,
                                                     SourceLocation Loc) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  assert(!D.isNull() && "null type");
  llvm::DIType *T = getOrCreateType(D, getOrCreateFile(Loc));
  assert(T && "could not create debug info for type");

  RetainedTypes.push_back(D.getAsOpaquePtr());
  return T;
}

void CGDebugInfo::addHeapAllocSiteMetadata(llvm::Instruction *CI,
                                           QualType D,
                                           SourceLocation Loc) {
  llvm::MDNode *node;
  if (D.getTypePtr()->isVoidPointerType()) {
    node = llvm::MDNode::get(CGM.getLLVMContext(), None);
  } else {
    QualType PointeeTy = D.getTypePtr()->getPointeeType();
    node = getOrCreateType(PointeeTy, getOrCreateFile(Loc));
  }

  CI->setMetadata("heapallocsite", node);
}

void CGDebugInfo::completeType(const EnumDecl *ED) {
  if (DebugKind <= codegenoptions::DebugLineTablesOnly)
    return;
  QualType Ty = CGM.getContext().getEnumType(ED);
  void *TyPtr = Ty.getAsOpaquePtr();
  auto I = TypeCache.find(TyPtr);
  if (I == TypeCache.end() || !cast<llvm::DIType>(I->second)->isForwardDecl())
    return;
  llvm::DIType *Res = CreateTypeDefinition(Ty->castAs<EnumType>());
  assert(!Res->isForwardDecl());
  TypeCache[TyPtr].reset(Res);
}

void CGDebugInfo::completeType(const RecordDecl *RD) {
  if (DebugKind > codegenoptions::LimitedDebugInfo ||
      !CGM.getLangOpts().CPlusPlus)
    completeRequiredType(RD);
}

/// Return true if the class or any of its methods are marked dllimport.
static bool isClassOrMethodDLLImport(const CXXRecordDecl *RD) {
  if (RD->hasAttr<DLLImportAttr>())
    return true;
  for (const CXXMethodDecl *MD : RD->methods())
    if (MD->hasAttr<DLLImportAttr>())
      return true;
  return false;
}

/// Does a type definition exist in an imported clang module?
static bool isDefinedInClangModule(const RecordDecl *RD) {
  // Only definitions that where imported from an AST file come from a module.
  if (!RD || !RD->isFromASTFile())
    return false;
  // Anonymous entities cannot be addressed. Treat them as not from module.
  if (!RD->isExternallyVisible() && RD->getName().empty())
    return false;
  if (auto *CXXDecl = dyn_cast<CXXRecordDecl>(RD)) {
    if (!CXXDecl->isCompleteDefinition())
      return false;
    // Check wether RD is a template.
    auto TemplateKind = CXXDecl->getTemplateSpecializationKind();
    if (TemplateKind != TSK_Undeclared) {
      // Unfortunately getOwningModule() isn't accurate enough to find the
      // owning module of a ClassTemplateSpecializationDecl that is inside a
      // namespace spanning multiple modules.
      bool Explicit = false;
      if (auto *TD = dyn_cast<ClassTemplateSpecializationDecl>(CXXDecl))
        Explicit = TD->isExplicitInstantiationOrSpecialization();
      if (!Explicit && CXXDecl->getEnclosingNamespaceContext())
        return false;
      // This is a template, check the origin of the first member.
      if (CXXDecl->field_begin() == CXXDecl->field_end())
        return TemplateKind == TSK_ExplicitInstantiationDeclaration;
      if (!CXXDecl->field_begin()->isFromASTFile())
        return false;
    }
  }
  return true;
}

void CGDebugInfo::completeClassData(const RecordDecl *RD) {
  if (auto *CXXRD = dyn_cast<CXXRecordDecl>(RD))
    if (CXXRD->isDynamicClass() &&
        CGM.getVTableLinkage(CXXRD) ==
            llvm::GlobalValue::AvailableExternallyLinkage &&
        !isClassOrMethodDLLImport(CXXRD))
      return;

  if (DebugTypeExtRefs && isDefinedInClangModule(RD->getDefinition()))
    return;

  completeClass(RD);
}

void CGDebugInfo::completeClass(const RecordDecl *RD) {
  if (DebugKind <= codegenoptions::DebugLineTablesOnly)
    return;
  QualType Ty = CGM.getContext().getRecordType(RD);
  void *TyPtr = Ty.getAsOpaquePtr();
  auto I = TypeCache.find(TyPtr);
  if (I != TypeCache.end() && !cast<llvm::DIType>(I->second)->isForwardDecl())
    return;
  llvm::DIType *Res = CreateTypeDefinition(Ty->castAs<RecordType>());
  assert(!Res->isForwardDecl());
  TypeCache[TyPtr].reset(Res);
}

static bool hasExplicitMemberDefinition(CXXRecordDecl::method_iterator I,
                                        CXXRecordDecl::method_iterator End) {
  for (CXXMethodDecl *MD : llvm::make_range(I, End))
    if (FunctionDecl *Tmpl = MD->getInstantiatedFromMemberFunction())
      if (!Tmpl->isImplicit() && Tmpl->isThisDeclarationADefinition() &&
          !MD->getMemberSpecializationInfo()->isExplicitSpecialization())
        return true;
  return false;
}

static bool shouldOmitDefinition(codegenoptions::DebugInfoKind DebugKind,
                                 bool DebugTypeExtRefs, const RecordDecl *RD,
                                 const LangOptions &LangOpts) {
  if (DebugTypeExtRefs && isDefinedInClangModule(RD->getDefinition()))
    return true;

  if (auto *ES = RD->getASTContext().getExternalSource())
    if (ES->hasExternalDefinitions(RD) == ExternalASTSource::EK_Always)
      return true;

  if (DebugKind > codegenoptions::LimitedDebugInfo)
    return false;

  if (!LangOpts.CPlusPlus)
    return false;

  if (!RD->isCompleteDefinitionRequired())
    return true;

  const auto *CXXDecl = dyn_cast<CXXRecordDecl>(RD);

  if (!CXXDecl)
    return false;

  // Only emit complete debug info for a dynamic class when its vtable is
  // emitted.  However, Microsoft debuggers don't resolve type information
  // across DLL boundaries, so skip this optimization if the class or any of its
  // methods are marked dllimport. This isn't a complete solution, since objects
  // without any dllimport methods can be used in one DLL and constructed in
  // another, but it is the current behavior of LimitedDebugInfo.
  if (CXXDecl->hasDefinition() && CXXDecl->isDynamicClass() &&
      !isClassOrMethodDLLImport(CXXDecl))
    return true;

  TemplateSpecializationKind Spec = TSK_Undeclared;
  if (const auto *SD = dyn_cast<ClassTemplateSpecializationDecl>(RD))
    Spec = SD->getSpecializationKind();

  if (Spec == TSK_ExplicitInstantiationDeclaration &&
      hasExplicitMemberDefinition(CXXDecl->method_begin(),
                                  CXXDecl->method_end()))
    return true;

  return false;
}

void CGDebugInfo::completeRequiredType(const RecordDecl *RD) {
  if (shouldOmitDefinition(DebugKind, DebugTypeExtRefs, RD, CGM.getLangOpts()))
    return;

  QualType Ty = CGM.getContext().getRecordType(RD);
  llvm::DIType *T = getTypeOrNull(Ty);
  if (T && T->isForwardDecl())
    completeClassData(RD);
}

llvm::DIType *CGDebugInfo::CreateType(const RecordType *Ty) {
  RecordDecl *RD = Ty->getDecl();
  llvm::DIType *T = cast_or_null<llvm::DIType>(getTypeOrNull(QualType(Ty, 0)));
  if (T || shouldOmitDefinition(DebugKind, DebugTypeExtRefs, RD,
                                CGM.getLangOpts())) {
    if (!T)
      T = getOrCreateRecordFwdDecl(Ty, getDeclContextDescriptor(RD));
    return T;
  }

  return CreateTypeDefinition(Ty);
}

llvm::DIType *CGDebugInfo::CreateTypeDefinition(const RecordType *Ty) {
  RecordDecl *RD = Ty->getDecl();

  // Get overall information about the record type for the debug info.
  llvm::DIFile *DefUnit = getOrCreateFile(RD->getLocation());

  // Records and classes and unions can all be recursive.  To handle them, we
  // first generate a debug descriptor for the struct as a forward declaration.
  // Then (if it is a definition) we go through and get debug info for all of
  // its members.  Finally, we create a descriptor for the complete type (which
  // may refer to the forward decl if the struct is recursive) and replace all
  // uses of the forward declaration with the final definition.
  llvm::DICompositeType *FwdDecl = getOrCreateLimitedType(Ty, DefUnit);

  const RecordDecl *D = RD->getDefinition();
  if (!D || !D->isCompleteDefinition())
    return FwdDecl;

  if (const auto *CXXDecl = dyn_cast<CXXRecordDecl>(RD))
    CollectContainingType(CXXDecl, FwdDecl);

  // Push the struct on region stack.
  LexicalBlockStack.emplace_back(&*FwdDecl);
  RegionMap[Ty->getDecl()].reset(FwdDecl);

  // Convert all the elements.
  SmallVector<llvm::Metadata *, 16> EltTys;
  // what about nested types?

  // Note: The split of CXXDecl information here is intentional, the
  // gdb tests will depend on a certain ordering at printout. The debug
  // information offsets are still correct if we merge them all together
  // though.
  const auto *CXXDecl = dyn_cast<CXXRecordDecl>(RD);
  if (CXXDecl) {
    CollectCXXBases(CXXDecl, DefUnit, EltTys, FwdDecl);
    CollectVTableInfo(CXXDecl, DefUnit, EltTys, FwdDecl);
  }

  // Collect data fields (including static variables and any initializers).
  CollectRecordFields(RD, DefUnit, EltTys, FwdDecl);
  if (CXXDecl)
    CollectCXXMemberFunctions(CXXDecl, DefUnit, EltTys, FwdDecl);

  LexicalBlockStack.pop_back();
  RegionMap.erase(Ty->getDecl());

  llvm::DINodeArray Elements = DBuilder.getOrCreateArray(EltTys);
  DBuilder.replaceArrays(FwdDecl, Elements);

  if (FwdDecl->isTemporary())
    FwdDecl =
        llvm::MDNode::replaceWithPermanent(llvm::TempDICompositeType(FwdDecl));

  RegionMap[Ty->getDecl()].reset(FwdDecl);
  return FwdDecl;
}

llvm::DIType *CGDebugInfo::CreateType(const ObjCObjectType *Ty,
                                      llvm::DIFile *Unit) {
  // Ignore protocols.
  return getOrCreateType(Ty->getBaseType(), Unit);
}

llvm::DIType *CGDebugInfo::CreateType(const ObjCTypeParamType *Ty,
                                      llvm::DIFile *Unit) {
  // Ignore protocols.
  SourceLocation Loc = Ty->getDecl()->getLocation();

  // Use Typedefs to represent ObjCTypeParamType.
  return DBuilder.createTypedef(
      getOrCreateType(Ty->getDecl()->getUnderlyingType(), Unit),
      Ty->getDecl()->getName(), getOrCreateFile(Loc), getLineNumber(Loc),
      getDeclContextDescriptor(Ty->getDecl()));
}

/// \return true if Getter has the default name for the property PD.
static bool hasDefaultGetterName(const ObjCPropertyDecl *PD,
                                 const ObjCMethodDecl *Getter) {
  assert(PD);
  if (!Getter)
    return true;

  assert(Getter->getDeclName().isObjCZeroArgSelector());
  return PD->getName() ==
         Getter->getDeclName().getObjCSelector().getNameForSlot(0);
}

/// \return true if Setter has the default name for the property PD.
static bool hasDefaultSetterName(const ObjCPropertyDecl *PD,
                                 const ObjCMethodDecl *Setter) {
  assert(PD);
  if (!Setter)
    return true;

  assert(Setter->getDeclName().isObjCOneArgSelector());
  return SelectorTable::constructSetterName(PD->getName()) ==
         Setter->getDeclName().getObjCSelector().getNameForSlot(0);
}

llvm::DIType *CGDebugInfo::CreateType(const ObjCInterfaceType *Ty,
                                      llvm::DIFile *Unit) {
  ObjCInterfaceDecl *ID = Ty->getDecl();
  if (!ID)
    return nullptr;

  // Return a forward declaration if this type was imported from a clang module,
  // and this is not the compile unit with the implementation of the type (which
  // may contain hidden ivars).
  if (DebugTypeExtRefs && ID->isFromASTFile() && ID->getDefinition() &&
      !ID->getImplementation())
    return DBuilder.createForwardDecl(llvm::dwarf::DW_TAG_structure_type,
                                      ID->getName(),
                                      getDeclContextDescriptor(ID), Unit, 0);

  // Get overall information about the record type for the debug info.
  llvm::DIFile *DefUnit = getOrCreateFile(ID->getLocation());
  unsigned Line = getLineNumber(ID->getLocation());
  auto RuntimeLang =
      static_cast<llvm::dwarf::SourceLanguage>(TheCU->getSourceLanguage());

  // If this is just a forward declaration return a special forward-declaration
  // debug type since we won't be able to lay out the entire type.
  ObjCInterfaceDecl *Def = ID->getDefinition();
  if (!Def || !Def->getImplementation()) {
    llvm::DIScope *Mod = getParentModuleOrNull(ID);
    llvm::DIType *FwdDecl = DBuilder.createReplaceableCompositeType(
        llvm::dwarf::DW_TAG_structure_type, ID->getName(), Mod ? Mod : TheCU,
        DefUnit, Line, RuntimeLang);
    ObjCInterfaceCache.push_back(ObjCInterfaceCacheEntry(Ty, FwdDecl, Unit));
    return FwdDecl;
  }

  return CreateTypeDefinition(Ty, Unit);
}

llvm::DIModule *
CGDebugInfo::getOrCreateModuleRef(ExternalASTSource::ASTSourceDescriptor Mod,
                                  bool CreateSkeletonCU) {
  // Use the Module pointer as the key into the cache. This is a
  // nullptr if the "Module" is a PCH, which is safe because we don't
  // support chained PCH debug info, so there can only be a single PCH.
  const Module *M = Mod.getModuleOrNull();
  auto ModRef = ModuleCache.find(M);
  if (ModRef != ModuleCache.end())
    return cast<llvm::DIModule>(ModRef->second);

  // Macro definitions that were defined with "-D" on the command line.
  SmallString<128> ConfigMacros;
  {
    llvm::raw_svector_ostream OS(ConfigMacros);
    const auto &PPOpts = CGM.getPreprocessorOpts();
    unsigned I = 0;
    // Translate the macro definitions back into a command line.
    for (auto &M : PPOpts.Macros) {
      if (++I > 1)
        OS << " ";
      const std::string &Macro = M.first;
      bool Undef = M.second;
      OS << "\"-" << (Undef ? 'U' : 'D');
      for (char c : Macro)
        switch (c) {
        case '\\':
          OS << "\\\\";
          break;
        case '"':
          OS << "\\\"";
          break;
        default:
          OS << c;
        }
      OS << '\"';
    }
  }

  bool IsRootModule = M ? !M->Parent : true;
  // When a module name is specified as -fmodule-name, that module gets a
  // clang::Module object, but it won't actually be built or imported; it will
  // be textual.
  if (CreateSkeletonCU && IsRootModule && Mod.getASTFile().empty() && M)
    assert(StringRef(M->Name).startswith(CGM.getLangOpts().ModuleName) &&
           "clang module without ASTFile must be specified by -fmodule-name");

  if (CreateSkeletonCU && IsRootModule && !Mod.getASTFile().empty()) {
    // PCH files don't have a signature field in the control block,
    // but LLVM detects skeleton CUs by looking for a non-zero DWO id.
    // We use the lower 64 bits for debug info.
    uint64_t Signature =
        Mod.getSignature()
            ? (uint64_t)Mod.getSignature()[1] << 32 | Mod.getSignature()[0]
            : ~1ULL;
    llvm::DIBuilder DIB(CGM.getModule());
    DIB.createCompileUnit(TheCU->getSourceLanguage(),
                          // TODO: Support "Source" from external AST providers?
                          DIB.createFile(Mod.getModuleName(), Mod.getPath()),
                          TheCU->getProducer(), true, StringRef(), 0,
                          Mod.getASTFile(), llvm::DICompileUnit::FullDebug,
                          Signature);
    DIB.finalize();
  }

  llvm::DIModule *Parent =
      IsRootModule ? nullptr
                   : getOrCreateModuleRef(
                         ExternalASTSource::ASTSourceDescriptor(*M->Parent),
                         CreateSkeletonCU);
  llvm::DIModule *DIMod =
      DBuilder.createModule(Parent, Mod.getModuleName(), ConfigMacros,
                            Mod.getPath(), CGM.getHeaderSearchOpts().Sysroot);
  ModuleCache[M].reset(DIMod);
  return DIMod;
}

llvm::DIType *CGDebugInfo::CreateTypeDefinition(const ObjCInterfaceType *Ty,
                                                llvm::DIFile *Unit) {
  ObjCInterfaceDecl *ID = Ty->getDecl();
  llvm::DIFile *DefUnit = getOrCreateFile(ID->getLocation());
  unsigned Line = getLineNumber(ID->getLocation());
  unsigned RuntimeLang = TheCU->getSourceLanguage();

  // Bit size, align and offset of the type.
  uint64_t Size = CGM.getContext().getTypeSize(Ty);
  auto Align = getTypeAlignIfRequired(Ty, CGM.getContext());

  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  if (ID->getImplementation())
    Flags |= llvm::DINode::FlagObjcClassComplete;

  llvm::DIScope *Mod = getParentModuleOrNull(ID);
  llvm::DICompositeType *RealDecl = DBuilder.createStructType(
      Mod ? Mod : Unit, ID->getName(), DefUnit, Line, Size, Align, Flags,
      nullptr, llvm::DINodeArray(), RuntimeLang);

  QualType QTy(Ty, 0);
  TypeCache[QTy.getAsOpaquePtr()].reset(RealDecl);

  // Push the struct on region stack.
  LexicalBlockStack.emplace_back(RealDecl);
  RegionMap[Ty->getDecl()].reset(RealDecl);

  // Convert all the elements.
  SmallVector<llvm::Metadata *, 16> EltTys;

  ObjCInterfaceDecl *SClass = ID->getSuperClass();
  if (SClass) {
    llvm::DIType *SClassTy =
        getOrCreateType(CGM.getContext().getObjCInterfaceType(SClass), Unit);
    if (!SClassTy)
      return nullptr;

    llvm::DIType *InhTag = DBuilder.createInheritance(RealDecl, SClassTy, 0, 0,
                                                      llvm::DINode::FlagZero);
    EltTys.push_back(InhTag);
  }

  // Create entries for all of the properties.
  auto AddProperty = [&](const ObjCPropertyDecl *PD) {
    SourceLocation Loc = PD->getLocation();
    llvm::DIFile *PUnit = getOrCreateFile(Loc);
    unsigned PLine = getLineNumber(Loc);
    ObjCMethodDecl *Getter = PD->getGetterMethodDecl();
    ObjCMethodDecl *Setter = PD->getSetterMethodDecl();
    llvm::MDNode *PropertyNode = DBuilder.createObjCProperty(
        PD->getName(), PUnit, PLine,
        hasDefaultGetterName(PD, Getter) ? ""
                                         : getSelectorName(PD->getGetterName()),
        hasDefaultSetterName(PD, Setter) ? ""
                                         : getSelectorName(PD->getSetterName()),
        PD->getPropertyAttributes(), getOrCreateType(PD->getType(), PUnit));
    EltTys.push_back(PropertyNode);
  };
  {
    llvm::SmallPtrSet<const IdentifierInfo *, 16> PropertySet;
    for (const ObjCCategoryDecl *ClassExt : ID->known_extensions())
      for (auto *PD : ClassExt->properties()) {
        PropertySet.insert(PD->getIdentifier());
        AddProperty(PD);
      }
    for (const auto *PD : ID->properties()) {
      // Don't emit duplicate metadata for properties that were already in a
      // class extension.
      if (!PropertySet.insert(PD->getIdentifier()).second)
        continue;
      AddProperty(PD);
    }
  }

  const ASTRecordLayout &RL = CGM.getContext().getASTObjCInterfaceLayout(ID);
  unsigned FieldNo = 0;
  for (ObjCIvarDecl *Field = ID->all_declared_ivar_begin(); Field;
       Field = Field->getNextIvar(), ++FieldNo) {
    llvm::DIType *FieldTy = getOrCreateType(Field->getType(), Unit);
    if (!FieldTy)
      return nullptr;

    StringRef FieldName = Field->getName();

    // Ignore unnamed fields.
    if (FieldName.empty())
      continue;

    // Get the location for the field.
    llvm::DIFile *FieldDefUnit = getOrCreateFile(Field->getLocation());
    unsigned FieldLine = getLineNumber(Field->getLocation());
    QualType FType = Field->getType();
    uint64_t FieldSize = 0;
    uint32_t FieldAlign = 0;

    if (!FType->isIncompleteArrayType()) {

      // Bit size, align and offset of the type.
      FieldSize = Field->isBitField()
                      ? Field->getBitWidthValue(CGM.getContext())
                      : CGM.getContext().getTypeSize(FType);
      FieldAlign = getTypeAlignIfRequired(FType, CGM.getContext());
    }

    uint64_t FieldOffset;
    if (CGM.getLangOpts().ObjCRuntime.isNonFragile()) {
      // We don't know the runtime offset of an ivar if we're using the
      // non-fragile ABI.  For bitfields, use the bit offset into the first
      // byte of storage of the bitfield.  For other fields, use zero.
      if (Field->isBitField()) {
        FieldOffset =
            CGM.getObjCRuntime().ComputeBitfieldBitOffset(CGM, ID, Field);
        FieldOffset %= CGM.getContext().getCharWidth();
      } else {
        FieldOffset = 0;
      }
    } else {
      FieldOffset = RL.getFieldOffset(FieldNo);
    }

    llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
    if (Field->getAccessControl() == ObjCIvarDecl::Protected)
      Flags = llvm::DINode::FlagProtected;
    else if (Field->getAccessControl() == ObjCIvarDecl::Private)
      Flags = llvm::DINode::FlagPrivate;
    else if (Field->getAccessControl() == ObjCIvarDecl::Public)
      Flags = llvm::DINode::FlagPublic;

    llvm::MDNode *PropertyNode = nullptr;
    if (ObjCImplementationDecl *ImpD = ID->getImplementation()) {
      if (ObjCPropertyImplDecl *PImpD =
              ImpD->FindPropertyImplIvarDecl(Field->getIdentifier())) {
        if (ObjCPropertyDecl *PD = PImpD->getPropertyDecl()) {
          SourceLocation Loc = PD->getLocation();
          llvm::DIFile *PUnit = getOrCreateFile(Loc);
          unsigned PLine = getLineNumber(Loc);
          ObjCMethodDecl *Getter = PD->getGetterMethodDecl();
          ObjCMethodDecl *Setter = PD->getSetterMethodDecl();
          PropertyNode = DBuilder.createObjCProperty(
              PD->getName(), PUnit, PLine,
              hasDefaultGetterName(PD, Getter)
                  ? ""
                  : getSelectorName(PD->getGetterName()),
              hasDefaultSetterName(PD, Setter)
                  ? ""
                  : getSelectorName(PD->getSetterName()),
              PD->getPropertyAttributes(),
              getOrCreateType(PD->getType(), PUnit));
        }
      }
    }
    FieldTy = DBuilder.createObjCIVar(FieldName, FieldDefUnit, FieldLine,
                                      FieldSize, FieldAlign, FieldOffset, Flags,
                                      FieldTy, PropertyNode);
    EltTys.push_back(FieldTy);
  }

  llvm::DINodeArray Elements = DBuilder.getOrCreateArray(EltTys);
  DBuilder.replaceArrays(RealDecl, Elements);

  LexicalBlockStack.pop_back();
  return RealDecl;
}

llvm::DIType *CGDebugInfo::CreateType(const VectorType *Ty,
                                      llvm::DIFile *Unit) {
  llvm::DIType *ElementTy = getOrCreateType(Ty->getElementType(), Unit);
  int64_t Count = Ty->getNumElements();

  llvm::Metadata *Subscript;
  QualType QTy(Ty, 0);
  auto SizeExpr = SizeExprCache.find(QTy);
  if (SizeExpr != SizeExprCache.end())
    Subscript = DBuilder.getOrCreateSubrange(0, SizeExpr->getSecond());
  else
    Subscript = DBuilder.getOrCreateSubrange(0, Count ? Count : -1);
  llvm::DINodeArray SubscriptArray = DBuilder.getOrCreateArray(Subscript);

  uint64_t Size = CGM.getContext().getTypeSize(Ty);
  auto Align = getTypeAlignIfRequired(Ty, CGM.getContext());

  return DBuilder.createVectorType(Size, Align, ElementTy, SubscriptArray);
}

llvm::DIType *CGDebugInfo::CreateType(const ArrayType *Ty, llvm::DIFile *Unit) {
  uint64_t Size;
  uint32_t Align;

  // FIXME: make getTypeAlign() aware of VLAs and incomplete array types
  if (const auto *VAT = dyn_cast<VariableArrayType>(Ty)) {
    Size = 0;
    Align = getTypeAlignIfRequired(CGM.getContext().getBaseElementType(VAT),
                                   CGM.getContext());
  } else if (Ty->isIncompleteArrayType()) {
    Size = 0;
    if (Ty->getElementType()->isIncompleteType())
      Align = 0;
    else
      Align = getTypeAlignIfRequired(Ty->getElementType(), CGM.getContext());
  } else if (Ty->isIncompleteType()) {
    Size = 0;
    Align = 0;
  } else {
    // Size and align of the whole array, not the element type.
    Size = CGM.getContext().getTypeSize(Ty);
    Align = getTypeAlignIfRequired(Ty, CGM.getContext());
  }

  // Add the dimensions of the array.  FIXME: This loses CV qualifiers from
  // interior arrays, do we care?  Why aren't nested arrays represented the
  // obvious/recursive way?
  SmallVector<llvm::Metadata *, 8> Subscripts;
  QualType EltTy(Ty, 0);
  while ((Ty = dyn_cast<ArrayType>(EltTy))) {
    // If the number of elements is known, then count is that number. Otherwise,
    // it's -1. This allows us to represent a subrange with an array of 0
    // elements, like this:
    //
    //   struct foo {
    //     int x[0];
    //   };
    int64_t Count = -1; // Count == -1 is an unbounded array.
    if (const auto *CAT = dyn_cast<ConstantArrayType>(Ty))
      Count = CAT->getSize().getZExtValue();
    else if (const auto *VAT = dyn_cast<VariableArrayType>(Ty)) {
      if (Expr *Size = VAT->getSizeExpr()) {
        Expr::EvalResult Result;
        if (Size->EvaluateAsInt(Result, CGM.getContext()))
          Count = Result.Val.getInt().getExtValue();
      }
    }

    auto SizeNode = SizeExprCache.find(EltTy);
    if (SizeNode != SizeExprCache.end())
      Subscripts.push_back(
          DBuilder.getOrCreateSubrange(0, SizeNode->getSecond()));
    else
      Subscripts.push_back(DBuilder.getOrCreateSubrange(0, Count));
    EltTy = Ty->getElementType();
  }

  llvm::DINodeArray SubscriptArray = DBuilder.getOrCreateArray(Subscripts);

  return DBuilder.createArrayType(Size, Align, getOrCreateType(EltTy, Unit),
                                  SubscriptArray);
}

llvm::DIType *CGDebugInfo::CreateType(const LValueReferenceType *Ty,
                                      llvm::DIFile *Unit) {
  return CreatePointerLikeType(llvm::dwarf::DW_TAG_reference_type, Ty,
                               Ty->getPointeeType(), Unit);
}

llvm::DIType *CGDebugInfo::CreateType(const RValueReferenceType *Ty,
                                      llvm::DIFile *Unit) {
  return CreatePointerLikeType(llvm::dwarf::DW_TAG_rvalue_reference_type, Ty,
                               Ty->getPointeeType(), Unit);
}

llvm::DIType *CGDebugInfo::CreateType(const MemberPointerType *Ty,
                                      llvm::DIFile *U) {
  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  uint64_t Size = 0;

  if (!Ty->isIncompleteType()) {
    Size = CGM.getContext().getTypeSize(Ty);

    // Set the MS inheritance model. There is no flag for the unspecified model.
    if (CGM.getTarget().getCXXABI().isMicrosoft()) {
      switch (Ty->getMostRecentCXXRecordDecl()->getMSInheritanceModel()) {
      case MSInheritanceAttr::Keyword_single_inheritance:
        Flags |= llvm::DINode::FlagSingleInheritance;
        break;
      case MSInheritanceAttr::Keyword_multiple_inheritance:
        Flags |= llvm::DINode::FlagMultipleInheritance;
        break;
      case MSInheritanceAttr::Keyword_virtual_inheritance:
        Flags |= llvm::DINode::FlagVirtualInheritance;
        break;
      case MSInheritanceAttr::Keyword_unspecified_inheritance:
        break;
      }
    }
  }

  llvm::DIType *ClassType = getOrCreateType(QualType(Ty->getClass(), 0), U);
  if (Ty->isMemberDataPointerType())
    return DBuilder.createMemberPointerType(
        getOrCreateType(Ty->getPointeeType(), U), ClassType, Size, /*Align=*/0,
        Flags);

  const FunctionProtoType *FPT =
      Ty->getPointeeType()->getAs<FunctionProtoType>();
  return DBuilder.createMemberPointerType(
      getOrCreateInstanceMethodType(
          CXXMethodDecl::getThisType(FPT, Ty->getMostRecentCXXRecordDecl()),
          FPT, U),
      ClassType, Size, /*Align=*/0, Flags);
}

llvm::DIType *CGDebugInfo::CreateType(const AtomicType *Ty, llvm::DIFile *U) {
  auto *FromTy = getOrCreateType(Ty->getValueType(), U);
  return DBuilder.createQualifiedType(llvm::dwarf::DW_TAG_atomic_type, FromTy);
}

llvm::DIType *CGDebugInfo::CreateType(const PipeType *Ty, llvm::DIFile *U) {
  return getOrCreateType(Ty->getElementType(), U);
}

llvm::DIType *CGDebugInfo::CreateEnumType(const EnumType *Ty) {
  const EnumDecl *ED = Ty->getDecl();

  uint64_t Size = 0;
  uint32_t Align = 0;
  if (!ED->getTypeForDecl()->isIncompleteType()) {
    Size = CGM.getContext().getTypeSize(ED->getTypeForDecl());
    Align = getDeclAlignIfRequired(ED, CGM.getContext());
  }

  SmallString<256> Identifier = getTypeIdentifier(Ty, CGM, TheCU);

  bool isImportedFromModule =
      DebugTypeExtRefs && ED->isFromASTFile() && ED->getDefinition();

  // If this is just a forward declaration, construct an appropriately
  // marked node and just return it.
  if (isImportedFromModule || !ED->getDefinition()) {
    // Note that it is possible for enums to be created as part of
    // their own declcontext. In this case a FwdDecl will be created
    // twice. This doesn't cause a problem because both FwdDecls are
    // entered into the ReplaceMap: finalize() will replace the first
    // FwdDecl with the second and then replace the second with
    // complete type.
    llvm::DIScope *EDContext = getDeclContextDescriptor(ED);
    llvm::DIFile *DefUnit = getOrCreateFile(ED->getLocation());
    llvm::TempDIScope TmpContext(DBuilder.createReplaceableCompositeType(
        llvm::dwarf::DW_TAG_enumeration_type, "", TheCU, DefUnit, 0));

    unsigned Line = getLineNumber(ED->getLocation());
    StringRef EDName = ED->getName();
    llvm::DIType *RetTy = DBuilder.createReplaceableCompositeType(
        llvm::dwarf::DW_TAG_enumeration_type, EDName, EDContext, DefUnit, Line,
        0, Size, Align, llvm::DINode::FlagFwdDecl, Identifier);

    ReplaceMap.emplace_back(
        std::piecewise_construct, std::make_tuple(Ty),
        std::make_tuple(static_cast<llvm::Metadata *>(RetTy)));
    return RetTy;
  }

  return CreateTypeDefinition(Ty);
}

llvm::DIType *CGDebugInfo::CreateTypeDefinition(const EnumType *Ty) {
  const EnumDecl *ED = Ty->getDecl();
  uint64_t Size = 0;
  uint32_t Align = 0;
  if (!ED->getTypeForDecl()->isIncompleteType()) {
    Size = CGM.getContext().getTypeSize(ED->getTypeForDecl());
    Align = getDeclAlignIfRequired(ED, CGM.getContext());
  }

  SmallString<256> Identifier = getTypeIdentifier(Ty, CGM, TheCU);

  // Create elements for each enumerator.
  SmallVector<llvm::Metadata *, 16> Enumerators;
  ED = ED->getDefinition();
  bool IsSigned = ED->getIntegerType()->isSignedIntegerType();
  for (const auto *Enum : ED->enumerators()) {
    const auto &InitVal = Enum->getInitVal();
    auto Value = IsSigned ? InitVal.getSExtValue() : InitVal.getZExtValue();
    Enumerators.push_back(
        DBuilder.createEnumerator(Enum->getName(), Value, !IsSigned));
  }

  // Return a CompositeType for the enum itself.
  llvm::DINodeArray EltArray = DBuilder.getOrCreateArray(Enumerators);

  llvm::DIFile *DefUnit = getOrCreateFile(ED->getLocation());
  unsigned Line = getLineNumber(ED->getLocation());
  llvm::DIScope *EnumContext = getDeclContextDescriptor(ED);
  llvm::DIType *ClassTy = getOrCreateType(ED->getIntegerType(), DefUnit);
  return DBuilder.createEnumerationType(EnumContext, ED->getName(), DefUnit,
                                        Line, Size, Align, EltArray, ClassTy,
                                        Identifier, ED->isScoped());
}

llvm::DIMacro *CGDebugInfo::CreateMacro(llvm::DIMacroFile *Parent,
                                        unsigned MType, SourceLocation LineLoc,
                                        StringRef Name, StringRef Value) {
  unsigned Line = LineLoc.isInvalid() ? 0 : getLineNumber(LineLoc);
  return DBuilder.createMacro(Parent, Line, MType, Name, Value);
}

llvm::DIMacroFile *CGDebugInfo::CreateTempMacroFile(llvm::DIMacroFile *Parent,
                                                    SourceLocation LineLoc,
                                                    SourceLocation FileLoc) {
  llvm::DIFile *FName = getOrCreateFile(FileLoc);
  unsigned Line = LineLoc.isInvalid() ? 0 : getLineNumber(LineLoc);
  return DBuilder.createTempMacroFile(Parent, Line, FName);
}

static QualType UnwrapTypeForDebugInfo(QualType T, const ASTContext &C) {
  Qualifiers Quals;
  do {
    Qualifiers InnerQuals = T.getLocalQualifiers();
    // Qualifiers::operator+() doesn't like it if you add a Qualifier
    // that is already there.
    Quals += Qualifiers::removeCommonQualifiers(Quals, InnerQuals);
    Quals += InnerQuals;
    QualType LastT = T;
    switch (T->getTypeClass()) {
    default:
      return C.getQualifiedType(T.getTypePtr(), Quals);
    case Type::TemplateSpecialization: {
      const auto *Spec = cast<TemplateSpecializationType>(T);
      if (Spec->isTypeAlias())
        return C.getQualifiedType(T.getTypePtr(), Quals);
      T = Spec->desugar();
      break;
    }
    case Type::TypeOfExpr:
      T = cast<TypeOfExprType>(T)->getUnderlyingExpr()->getType();
      break;
    case Type::TypeOf:
      T = cast<TypeOfType>(T)->getUnderlyingType();
      break;
    case Type::Decltype:
      T = cast<DecltypeType>(T)->getUnderlyingType();
      break;
    case Type::UnaryTransform:
      T = cast<UnaryTransformType>(T)->getUnderlyingType();
      break;
    case Type::Attributed:
      T = cast<AttributedType>(T)->getEquivalentType();
      break;
    case Type::Elaborated:
      T = cast<ElaboratedType>(T)->getNamedType();
      break;
    case Type::Paren:
      T = cast<ParenType>(T)->getInnerType();
      break;
    case Type::MacroQualified:
      T = cast<MacroQualifiedType>(T)->getUnderlyingType();
      break;
    case Type::SubstTemplateTypeParm:
      T = cast<SubstTemplateTypeParmType>(T)->getReplacementType();
      break;
    case Type::Auto:
    case Type::DeducedTemplateSpecialization: {
      QualType DT = cast<DeducedType>(T)->getDeducedType();
      assert(!DT.isNull() && "Undeduced types shouldn't reach here.");
      T = DT;
      break;
    }
    case Type::Adjusted:
    case Type::Decayed:
      // Decayed and adjusted types use the adjusted type in LLVM and DWARF.
      T = cast<AdjustedType>(T)->getAdjustedType();
      break;
    }

    assert(T != LastT && "Type unwrapping failed to unwrap!");
    (void)LastT;
  } while (true);
}

llvm::DIType *CGDebugInfo::getTypeOrNull(QualType Ty) {

  // Unwrap the type as needed for debug information.
  Ty = UnwrapTypeForDebugInfo(Ty, CGM.getContext());

  auto It = TypeCache.find(Ty.getAsOpaquePtr());
  if (It != TypeCache.end()) {
    // Verify that the debug info still exists.
    if (llvm::Metadata *V = It->second)
      return cast<llvm::DIType>(V);
  }

  return nullptr;
}

void CGDebugInfo::completeTemplateDefinition(
    const ClassTemplateSpecializationDecl &SD) {
  if (DebugKind <= codegenoptions::DebugLineTablesOnly)
    return;
  completeUnusedClass(SD);
}

void CGDebugInfo::completeUnusedClass(const CXXRecordDecl &D) {
  if (DebugKind <= codegenoptions::DebugLineTablesOnly)
    return;

  completeClassData(&D);
  // In case this type has no member function definitions being emitted, ensure
  // it is retained
  RetainedTypes.push_back(CGM.getContext().getRecordType(&D).getAsOpaquePtr());
}

llvm::DIType *CGDebugInfo::getOrCreateType(QualType Ty, llvm::DIFile *Unit) {
  if (Ty.isNull())
    return nullptr;

  // Unwrap the type as needed for debug information.
  Ty = UnwrapTypeForDebugInfo(Ty, CGM.getContext());

  if (auto *T = getTypeOrNull(Ty))
    return T;

  llvm::DIType *Res = CreateTypeNode(Ty, Unit);
  void *TyPtr = Ty.getAsOpaquePtr();

  // And update the type cache.
  TypeCache[TyPtr].reset(Res);

  return Res;
}

llvm::DIModule *CGDebugInfo::getParentModuleOrNull(const Decl *D) {
  // A forward declaration inside a module header does not belong to the module.
  if (isa<RecordDecl>(D) && !cast<RecordDecl>(D)->getDefinition())
    return nullptr;
  if (DebugTypeExtRefs && D->isFromASTFile()) {
    // Record a reference to an imported clang module or precompiled header.
    auto *Reader = CGM.getContext().getExternalSource();
    auto Idx = D->getOwningModuleID();
    auto Info = Reader->getSourceDescriptor(Idx);
    if (Info)
      return getOrCreateModuleRef(*Info, /*SkeletonCU=*/true);
  } else if (ClangModuleMap) {
    // We are building a clang module or a precompiled header.
    //
    // TODO: When D is a CXXRecordDecl or a C++ Enum, the ODR applies
    // and it wouldn't be necessary to specify the parent scope
    // because the type is already unique by definition (it would look
    // like the output of -fno-standalone-debug). On the other hand,
    // the parent scope helps a consumer to quickly locate the object
    // file where the type's definition is located, so it might be
    // best to make this behavior a command line or debugger tuning
    // option.
    if (Module *M = D->getOwningModule()) {
      // This is a (sub-)module.
      auto Info = ExternalASTSource::ASTSourceDescriptor(*M);
      return getOrCreateModuleRef(Info, /*SkeletonCU=*/false);
    } else {
      // This the precompiled header being built.
      return getOrCreateModuleRef(PCHDescriptor, /*SkeletonCU=*/false);
    }
  }

  return nullptr;
}

llvm::DIType *CGDebugInfo::CreateTypeNode(QualType Ty, llvm::DIFile *Unit) {
  // Handle qualifiers, which recursively handles what they refer to.
  if (Ty.hasLocalQualifiers())
    return CreateQualifiedType(Ty, Unit);

  // Work out details of type.
  switch (Ty->getTypeClass()) {
#define TYPE(Class, Base)
#define ABSTRACT_TYPE(Class, Base)
#define NON_CANONICAL_TYPE(Class, Base)
#define DEPENDENT_TYPE(Class, Base) case Type::Class:
#include "clang/AST/TypeNodes.def"
    llvm_unreachable("Dependent types cannot show up in debug information");

  case Type::ExtVector:
  case Type::Vector:
    return CreateType(cast<VectorType>(Ty), Unit);
  case Type::ObjCObjectPointer:
    return CreateType(cast<ObjCObjectPointerType>(Ty), Unit);
  case Type::ObjCObject:
    return CreateType(cast<ObjCObjectType>(Ty), Unit);
  case Type::ObjCTypeParam:
    return CreateType(cast<ObjCTypeParamType>(Ty), Unit);
  case Type::ObjCInterface:
    return CreateType(cast<ObjCInterfaceType>(Ty), Unit);
  case Type::Builtin:
    return CreateType(cast<BuiltinType>(Ty));
  case Type::Complex:
    return CreateType(cast<ComplexType>(Ty));
  case Type::Pointer:
    return CreateType(cast<PointerType>(Ty), Unit);
  case Type::BlockPointer:
    return CreateType(cast<BlockPointerType>(Ty), Unit);
  case Type::Typedef:
    return CreateType(cast<TypedefType>(Ty), Unit);
  case Type::Record:
    return CreateType(cast<RecordType>(Ty));
  case Type::Enum:
    return CreateEnumType(cast<EnumType>(Ty));
  case Type::FunctionProto:
  case Type::FunctionNoProto:
    return CreateType(cast<FunctionType>(Ty), Unit);
  case Type::ConstantArray:
  case Type::VariableArray:
  case Type::IncompleteArray:
    return CreateType(cast<ArrayType>(Ty), Unit);

  case Type::LValueReference:
    return CreateType(cast<LValueReferenceType>(Ty), Unit);
  case Type::RValueReference:
    return CreateType(cast<RValueReferenceType>(Ty), Unit);

  case Type::MemberPointer:
    return CreateType(cast<MemberPointerType>(Ty), Unit);

  case Type::Atomic:
    return CreateType(cast<AtomicType>(Ty), Unit);

  case Type::Pipe:
    return CreateType(cast<PipeType>(Ty), Unit);

  case Type::TemplateSpecialization:
    return CreateType(cast<TemplateSpecializationType>(Ty), Unit);

  case Type::Auto:
  case Type::Attributed:
  case Type::Adjusted:
  case Type::Decayed:
  case Type::DeducedTemplateSpecialization:
  case Type::Elaborated:
  case Type::Paren:
  case Type::MacroQualified:
  case Type::SubstTemplateTypeParm:
  case Type::TypeOfExpr:
  case Type::TypeOf:
  case Type::Decltype:
  case Type::UnaryTransform:
  case Type::PackExpansion:
    break;
  }

  llvm_unreachable("type should have been unwrapped!");
}

llvm::DICompositeType *CGDebugInfo::getOrCreateLimitedType(const RecordType *Ty,
                                                           llvm::DIFile *Unit) {
  QualType QTy(Ty, 0);

  auto *T = cast_or_null<llvm::DICompositeType>(getTypeOrNull(QTy));

  // We may have cached a forward decl when we could have created
  // a non-forward decl. Go ahead and create a non-forward decl
  // now.
  if (T && !T->isForwardDecl())
    return T;

  // Otherwise create the type.
  llvm::DICompositeType *Res = CreateLimitedType(Ty);

  // Propagate members from the declaration to the definition
  // CreateType(const RecordType*) will overwrite this with the members in the
  // correct order if the full type is needed.
  DBuilder.replaceArrays(Res, T ? T->getElements() : llvm::DINodeArray());

  // And update the type cache.
  TypeCache[QTy.getAsOpaquePtr()].reset(Res);
  return Res;
}

// TODO: Currently used for context chains when limiting debug info.
llvm::DICompositeType *CGDebugInfo::CreateLimitedType(const RecordType *Ty) {
  RecordDecl *RD = Ty->getDecl();

  // Get overall information about the record type for the debug info.
  llvm::DIFile *DefUnit = getOrCreateFile(RD->getLocation());
  unsigned Line = getLineNumber(RD->getLocation());
  StringRef RDName = getClassName(RD);

  llvm::DIScope *RDContext = getDeclContextDescriptor(RD);

  // If we ended up creating the type during the context chain construction,
  // just return that.
  auto *T = cast_or_null<llvm::DICompositeType>(
      getTypeOrNull(CGM.getContext().getRecordType(RD)));
  if (T && (!T->isForwardDecl() || !RD->getDefinition()))
    return T;

  // If this is just a forward or incomplete declaration, construct an
  // appropriately marked node and just return it.
  const RecordDecl *D = RD->getDefinition();
  if (!D || !D->isCompleteDefinition())
    return getOrCreateRecordFwdDecl(Ty, RDContext);

  uint64_t Size = CGM.getContext().getTypeSize(Ty);
  auto Align = getDeclAlignIfRequired(D, CGM.getContext());

  SmallString<256> Identifier = getTypeIdentifier(Ty, CGM, TheCU);

  // Explicitly record the calling convention for C++ records.
  auto Flags = llvm::DINode::FlagZero;
  if (auto CXXRD = dyn_cast<CXXRecordDecl>(RD)) {
    if (CGM.getCXXABI().getRecordArgABI(CXXRD) == CGCXXABI::RAA_Indirect)
      Flags |= llvm::DINode::FlagTypePassByReference;
    else
      Flags |= llvm::DINode::FlagTypePassByValue;

    // Record if a C++ record is non-trivial type.
    if (!CXXRD->isTrivial())
      Flags |= llvm::DINode::FlagNonTrivial;
  }

  llvm::DICompositeType *RealDecl = DBuilder.createReplaceableCompositeType(
      getTagForRecord(RD), RDName, RDContext, DefUnit, Line, 0, Size, Align,
      Flags, Identifier);

  // Elements of composite types usually have back to the type, creating
  // uniquing cycles.  Distinct nodes are more efficient.
  switch (RealDecl->getTag()) {
  default:
    llvm_unreachable("invalid composite type tag");

  case llvm::dwarf::DW_TAG_array_type:
  case llvm::dwarf::DW_TAG_enumeration_type:
    // Array elements and most enumeration elements don't have back references,
    // so they don't tend to be involved in uniquing cycles and there is some
    // chance of merging them when linking together two modules.  Only make
    // them distinct if they are ODR-uniqued.
    if (Identifier.empty())
      break;
    LLVM_FALLTHROUGH;

  case llvm::dwarf::DW_TAG_structure_type:
  case llvm::dwarf::DW_TAG_union_type:
  case llvm::dwarf::DW_TAG_class_type:
    // Immediately resolve to a distinct node.
    RealDecl =
        llvm::MDNode::replaceWithDistinct(llvm::TempDICompositeType(RealDecl));
    break;
  }

  RegionMap[Ty->getDecl()].reset(RealDecl);
  TypeCache[QualType(Ty, 0).getAsOpaquePtr()].reset(RealDecl);

  if (const auto *TSpecial = dyn_cast<ClassTemplateSpecializationDecl>(RD))
    DBuilder.replaceArrays(RealDecl, llvm::DINodeArray(),
                           CollectCXXTemplateParams(TSpecial, DefUnit));
  return RealDecl;
}

void CGDebugInfo::CollectContainingType(const CXXRecordDecl *RD,
                                        llvm::DICompositeType *RealDecl) {
  // A class's primary base or the class itself contains the vtable.
  llvm::DICompositeType *ContainingType = nullptr;
  const ASTRecordLayout &RL = CGM.getContext().getASTRecordLayout(RD);
  if (const CXXRecordDecl *PBase = RL.getPrimaryBase()) {
    // Seek non-virtual primary base root.
    while (1) {
      const ASTRecordLayout &BRL = CGM.getContext().getASTRecordLayout(PBase);
      const CXXRecordDecl *PBT = BRL.getPrimaryBase();
      if (PBT && !BRL.isPrimaryBaseVirtual())
        PBase = PBT;
      else
        break;
    }
    ContainingType = cast<llvm::DICompositeType>(
        getOrCreateType(QualType(PBase->getTypeForDecl(), 0),
                        getOrCreateFile(RD->getLocation())));
  } else if (RD->isDynamicClass())
    ContainingType = RealDecl;

  DBuilder.replaceVTableHolder(RealDecl, ContainingType);
}

llvm::DIType *CGDebugInfo::CreateMemberType(llvm::DIFile *Unit, QualType FType,
                                            StringRef Name, uint64_t *Offset) {
  llvm::DIType *FieldTy = CGDebugInfo::getOrCreateType(FType, Unit);
  uint64_t FieldSize = CGM.getContext().getTypeSize(FType);
  auto FieldAlign = getTypeAlignIfRequired(FType, CGM.getContext());
  llvm::DIType *Ty =
      DBuilder.createMemberType(Unit, Name, Unit, 0, FieldSize, FieldAlign,
                                *Offset, llvm::DINode::FlagZero, FieldTy);
  *Offset += FieldSize;
  return Ty;
}

void CGDebugInfo::collectFunctionDeclProps(GlobalDecl GD, llvm::DIFile *Unit,
                                           StringRef &Name,
                                           StringRef &LinkageName,
                                           llvm::DIScope *&FDContext,
                                           llvm::DINodeArray &TParamsArray,
                                           llvm::DINode::DIFlags &Flags) {
  const auto *FD = cast<FunctionDecl>(GD.getDecl());
  Name = getFunctionName(FD);
  // Use mangled name as linkage name for C/C++ functions.
  if (FD->hasPrototype()) {
    LinkageName = CGM.getMangledName(GD);
    Flags |= llvm::DINode::FlagPrototyped;
  }
  // No need to replicate the linkage name if it isn't different from the
  // subprogram name, no need to have it at all unless coverage is enabled or
  // debug is set to more than just line tables or extra debug info is needed.
  if (LinkageName == Name || (!CGM.getCodeGenOpts().EmitGcovArcs &&
                              !CGM.getCodeGenOpts().EmitGcovNotes &&
                              !CGM.getCodeGenOpts().DebugInfoForProfiling &&
                              DebugKind <= codegenoptions::DebugLineTablesOnly))
    LinkageName = StringRef();

  if (DebugKind >= codegenoptions::LimitedDebugInfo) {
    if (const NamespaceDecl *NSDecl =
            dyn_cast_or_null<NamespaceDecl>(FD->getDeclContext()))
      FDContext = getOrCreateNamespace(NSDecl);
    else if (const RecordDecl *RDecl =
                 dyn_cast_or_null<RecordDecl>(FD->getDeclContext())) {
      llvm::DIScope *Mod = getParentModuleOrNull(RDecl);
      FDContext = getContextDescriptor(RDecl, Mod ? Mod : TheCU);
    }
    // Check if it is a noreturn-marked function
    if (FD->isNoReturn())
      Flags |= llvm::DINode::FlagNoReturn;
    // Collect template parameters.
    TParamsArray = CollectFunctionTemplateParams(FD, Unit);
  }
}

void CGDebugInfo::collectVarDeclProps(const VarDecl *VD, llvm::DIFile *&Unit,
                                      unsigned &LineNo, QualType &T,
                                      StringRef &Name, StringRef &LinkageName,
                                      llvm::MDTuple *&TemplateParameters,
                                      llvm::DIScope *&VDContext) {
  Unit = getOrCreateFile(VD->getLocation());
  LineNo = getLineNumber(VD->getLocation());

  setLocation(VD->getLocation());

  T = VD->getType();
  if (T->isIncompleteArrayType()) {
    // CodeGen turns int[] into int[1] so we'll do the same here.
    llvm::APInt ConstVal(32, 1);
    QualType ET = CGM.getContext().getAsArrayType(T)->getElementType();

    T = CGM.getContext().getConstantArrayType(ET, ConstVal, ArrayType::Normal,
                                              0);
  }

  Name = VD->getName();
  if (VD->getDeclContext() && !isa<FunctionDecl>(VD->getDeclContext()) &&
      !isa<ObjCMethodDecl>(VD->getDeclContext()))
    LinkageName = CGM.getMangledName(VD);
  if (LinkageName == Name)
    LinkageName = StringRef();

  if (isa<VarTemplateSpecializationDecl>(VD)) {
    llvm::DINodeArray parameterNodes = CollectVarTemplateParams(VD, &*Unit);
    TemplateParameters = parameterNodes.get();
  } else {
    TemplateParameters = nullptr;
  }

  // Since we emit declarations (DW_AT_members) for static members, place the
  // definition of those static members in the namespace they were declared in
  // in the source code (the lexical decl context).
  // FIXME: Generalize this for even non-member global variables where the
  // declaration and definition may have different lexical decl contexts, once
  // we have support for emitting declarations of (non-member) global variables.
  const DeclContext *DC = VD->isStaticDataMember() ? VD->getLexicalDeclContext()
                                                   : VD->getDeclContext();
  // When a record type contains an in-line initialization of a static data
  // member, and the record type is marked as __declspec(dllexport), an implicit
  // definition of the member will be created in the record context.  DWARF
  // doesn't seem to have a nice way to describe this in a form that consumers
  // are likely to understand, so fake the "normal" situation of a definition
  // outside the class by putting it in the global scope.
  if (DC->isRecord())
    DC = CGM.getContext().getTranslationUnitDecl();

  llvm::DIScope *Mod = getParentModuleOrNull(VD);
  VDContext = getContextDescriptor(cast<Decl>(DC), Mod ? Mod : TheCU);
}

llvm::DISubprogram *CGDebugInfo::getFunctionFwdDeclOrStub(GlobalDecl GD,
                                                          bool Stub) {
  llvm::DINodeArray TParamsArray;
  StringRef Name, LinkageName;
  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  llvm::DISubprogram::DISPFlags SPFlags = llvm::DISubprogram::SPFlagZero;
  SourceLocation Loc = GD.getDecl()->getLocation();
  llvm::DIFile *Unit = getOrCreateFile(Loc);
  llvm::DIScope *DContext = Unit;
  unsigned Line = getLineNumber(Loc);
  collectFunctionDeclProps(GD, Unit, Name, LinkageName, DContext, TParamsArray,
                           Flags);
  auto *FD = dyn_cast<FunctionDecl>(GD.getDecl());

  // Build function type.
  SmallVector<QualType, 16> ArgTypes;
  if (FD)
    for (const ParmVarDecl *Parm : FD->parameters())
      ArgTypes.push_back(Parm->getType());
  CallingConv CC = FD->getType()->castAs<FunctionType>()->getCallConv();
  QualType FnType = CGM.getContext().getFunctionType(
      FD->getReturnType(), ArgTypes, FunctionProtoType::ExtProtoInfo(CC));
  if (!FD->isExternallyVisible())
    SPFlags |= llvm::DISubprogram::SPFlagLocalToUnit;
  if (CGM.getLangOpts().Optimize)
    SPFlags |= llvm::DISubprogram::SPFlagOptimized;

  if (Stub) {
    Flags |= getCallSiteRelatedAttrs();
    SPFlags |= llvm::DISubprogram::SPFlagDefinition;
    return DBuilder.createFunction(
        DContext, Name, LinkageName, Unit, Line,
        getOrCreateFunctionType(GD.getDecl(), FnType, Unit), 0, Flags, SPFlags,
        TParamsArray.get(), getFunctionDeclaration(FD));
  }

  llvm::DISubprogram *SP = DBuilder.createTempFunctionFwdDecl(
      DContext, Name, LinkageName, Unit, Line,
      getOrCreateFunctionType(GD.getDecl(), FnType, Unit), 0, Flags, SPFlags,
      TParamsArray.get(), getFunctionDeclaration(FD));
  const FunctionDecl *CanonDecl = FD->getCanonicalDecl();
  FwdDeclReplaceMap.emplace_back(std::piecewise_construct,
                                 std::make_tuple(CanonDecl),
                                 std::make_tuple(SP));
  return SP;
}

llvm::DISubprogram *CGDebugInfo::getFunctionForwardDeclaration(GlobalDecl GD) {
  return getFunctionFwdDeclOrStub(GD, /* Stub = */ false);
}

llvm::DISubprogram *CGDebugInfo::getFunctionStub(GlobalDecl GD) {
  return getFunctionFwdDeclOrStub(GD, /* Stub = */ true);
}

llvm::DIGlobalVariable *
CGDebugInfo::getGlobalVariableForwardDeclaration(const VarDecl *VD) {
  QualType T;
  StringRef Name, LinkageName;
  SourceLocation Loc = VD->getLocation();
  llvm::DIFile *Unit = getOrCreateFile(Loc);
  llvm::DIScope *DContext = Unit;
  unsigned Line = getLineNumber(Loc);
  llvm::MDTuple *TemplateParameters = nullptr;

  collectVarDeclProps(VD, Unit, Line, T, Name, LinkageName, TemplateParameters,
                      DContext);
  auto Align = getDeclAlignIfRequired(VD, CGM.getContext());
  auto *GV = DBuilder.createTempGlobalVariableFwdDecl(
      DContext, Name, LinkageName, Unit, Line, getOrCreateType(T, Unit),
      !VD->isExternallyVisible(), nullptr, TemplateParameters, Align);
  FwdDeclReplaceMap.emplace_back(
      std::piecewise_construct,
      std::make_tuple(cast<VarDecl>(VD->getCanonicalDecl())),
      std::make_tuple(static_cast<llvm::Metadata *>(GV)));
  return GV;
}

llvm::DINode *CGDebugInfo::getDeclarationOrDefinition(const Decl *D) {
  // We only need a declaration (not a definition) of the type - so use whatever
  // we would otherwise do to get a type for a pointee. (forward declarations in
  // limited debug info, full definitions (if the type definition is available)
  // in unlimited debug info)
  if (const auto *TD = dyn_cast<TypeDecl>(D))
    return getOrCreateType(CGM.getContext().getTypeDeclType(TD),
                           getOrCreateFile(TD->getLocation()));
  auto I = DeclCache.find(D->getCanonicalDecl());

  if (I != DeclCache.end()) {
    auto N = I->second;
    if (auto *GVE = dyn_cast_or_null<llvm::DIGlobalVariableExpression>(N))
      return GVE->getVariable();
    return dyn_cast_or_null<llvm::DINode>(N);
  }

  // No definition for now. Emit a forward definition that might be
  // merged with a potential upcoming definition.
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    return getFunctionForwardDeclaration(FD);
  else if (const auto *VD = dyn_cast<VarDecl>(D))
    return getGlobalVariableForwardDeclaration(VD);

  return nullptr;
}

llvm::DISubprogram *CGDebugInfo::getFunctionDeclaration(const Decl *D) {
  if (!D || DebugKind <= codegenoptions::DebugLineTablesOnly)
    return nullptr;

  const auto *FD = dyn_cast<FunctionDecl>(D);
  if (!FD)
    return nullptr;

  // Setup context.
  auto *S = getDeclContextDescriptor(D);

  auto MI = SPCache.find(FD->getCanonicalDecl());
  if (MI == SPCache.end()) {
    if (const auto *MD = dyn_cast<CXXMethodDecl>(FD->getCanonicalDecl())) {
      return CreateCXXMemberFunction(MD, getOrCreateFile(MD->getLocation()),
                                     cast<llvm::DICompositeType>(S));
    }
  }
  if (MI != SPCache.end()) {
    auto *SP = dyn_cast_or_null<llvm::DISubprogram>(MI->second);
    if (SP && !SP->isDefinition())
      return SP;
  }

  for (auto NextFD : FD->redecls()) {
    auto MI = SPCache.find(NextFD->getCanonicalDecl());
    if (MI != SPCache.end()) {
      auto *SP = dyn_cast_or_null<llvm::DISubprogram>(MI->second);
      if (SP && !SP->isDefinition())
        return SP;
    }
  }
  return nullptr;
}

// getOrCreateFunctionType - Construct type. If it is a c++ method, include
// implicit parameter "this".
llvm::DISubroutineType *CGDebugInfo::getOrCreateFunctionType(const Decl *D,
                                                             QualType FnType,
                                                             llvm::DIFile *F) {
  if (!D || DebugKind <= codegenoptions::DebugLineTablesOnly)
    // Create fake but valid subroutine type. Otherwise -verify would fail, and
    // subprogram DIE will miss DW_AT_decl_file and DW_AT_decl_line fields.
    return DBuilder.createSubroutineType(DBuilder.getOrCreateTypeArray(None));

  if (const auto *Method = dyn_cast<CXXMethodDecl>(D))
    return getOrCreateMethodType(Method, F);

  const auto *FTy = FnType->getAs<FunctionType>();
  CallingConv CC = FTy ? FTy->getCallConv() : CallingConv::CC_C;

  if (const auto *OMethod = dyn_cast<ObjCMethodDecl>(D)) {
    // Add "self" and "_cmd"
    SmallVector<llvm::Metadata *, 16> Elts;

    // First element is always return type. For 'void' functions it is NULL.
    QualType ResultTy = OMethod->getReturnType();

    // Replace the instancetype keyword with the actual type.
    if (ResultTy == CGM.getContext().getObjCInstanceType())
      ResultTy = CGM.getContext().getPointerType(
          QualType(OMethod->getClassInterface()->getTypeForDecl(), 0));

    Elts.push_back(getOrCreateType(ResultTy, F));
    // "self" pointer is always first argument.
    QualType SelfDeclTy;
    if (auto *SelfDecl = OMethod->getSelfDecl())
      SelfDeclTy = SelfDecl->getType();
    else if (auto *FPT = dyn_cast<FunctionProtoType>(FnType))
      if (FPT->getNumParams() > 1)
        SelfDeclTy = FPT->getParamType(0);
    if (!SelfDeclTy.isNull())
      Elts.push_back(
          CreateSelfType(SelfDeclTy, getOrCreateType(SelfDeclTy, F)));
    // "_cmd" pointer is always second argument.
    Elts.push_back(DBuilder.createArtificialType(
        getOrCreateType(CGM.getContext().getObjCSelType(), F)));
    // Get rest of the arguments.
    for (const auto *PI : OMethod->parameters())
      Elts.push_back(getOrCreateType(PI->getType(), F));
    // Variadic methods need a special marker at the end of the type list.
    if (OMethod->isVariadic())
      Elts.push_back(DBuilder.createUnspecifiedParameter());

    llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(Elts);
    return DBuilder.createSubroutineType(EltTypeArray, llvm::DINode::FlagZero,
                                         getDwarfCC(CC));
  }

  // Handle variadic function types; they need an additional
  // unspecified parameter.
  if (const auto *FD = dyn_cast<FunctionDecl>(D))
    if (FD->isVariadic()) {
      SmallVector<llvm::Metadata *, 16> EltTys;
      EltTys.push_back(getOrCreateType(FD->getReturnType(), F));
      if (const auto *FPT = dyn_cast<FunctionProtoType>(FnType))
        for (QualType ParamType : FPT->param_types())
          EltTys.push_back(getOrCreateType(ParamType, F));
      EltTys.push_back(DBuilder.createUnspecifiedParameter());
      llvm::DITypeRefArray EltTypeArray = DBuilder.getOrCreateTypeArray(EltTys);
      return DBuilder.createSubroutineType(EltTypeArray, llvm::DINode::FlagZero,
                                           getDwarfCC(CC));
    }

  return cast<llvm::DISubroutineType>(getOrCreateType(FnType, F));
}

void CGDebugInfo::EmitFunctionStart(GlobalDecl GD, SourceLocation Loc,
                                    SourceLocation ScopeLoc, QualType FnType,
                                    llvm::Function *Fn, bool CurFuncIsThunk,
                                    CGBuilderTy &Builder) {

  StringRef Name;
  StringRef LinkageName;

  FnBeginRegionCount.push_back(LexicalBlockStack.size());

  const Decl *D = GD.getDecl();
  bool HasDecl = (D != nullptr);

  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  llvm::DISubprogram::DISPFlags SPFlags = llvm::DISubprogram::SPFlagZero;
  llvm::DIFile *Unit = getOrCreateFile(Loc);
  llvm::DIScope *FDContext = Unit;
  llvm::DINodeArray TParamsArray;
  if (!HasDecl) {
    // Use llvm function name.
    LinkageName = Fn->getName();
  } else if (const auto *FD = dyn_cast<FunctionDecl>(D)) {
    // If there is a subprogram for this function available then use it.
    auto FI = SPCache.find(FD->getCanonicalDecl());
    if (FI != SPCache.end()) {
      auto *SP = dyn_cast_or_null<llvm::DISubprogram>(FI->second);
      if (SP && SP->isDefinition()) {
        LexicalBlockStack.emplace_back(SP);
        RegionMap[D].reset(SP);
        return;
      }
    }
    collectFunctionDeclProps(GD, Unit, Name, LinkageName, FDContext,
                             TParamsArray, Flags);
  } else if (const auto *OMD = dyn_cast<ObjCMethodDecl>(D)) {
    Name = getObjCMethodName(OMD);
    Flags |= llvm::DINode::FlagPrototyped;
  } else if (isa<VarDecl>(D) &&
             GD.getDynamicInitKind() != DynamicInitKind::NoStub) {
    // This is a global initializer or atexit destructor for a global variable.
    Name = getDynamicInitializerName(cast<VarDecl>(D), GD.getDynamicInitKind(),
                                     Fn);
  } else {
    // Use llvm function name.
    Name = Fn->getName();
    Flags |= llvm::DINode::FlagPrototyped;
  }
  if (Name.startswith("\01"))
    Name = Name.substr(1);

  if (!HasDecl || D->isImplicit() || D->hasAttr<ArtificialAttr>() ||
      (isa<VarDecl>(D) && GD.getDynamicInitKind() == DynamicInitKind::AtExit)) {
    Flags |= llvm::DINode::FlagArtificial;
    // Artificial functions should not silently reuse CurLoc.
    CurLoc = SourceLocation();
  }

  if (CurFuncIsThunk)
    Flags |= llvm::DINode::FlagThunk;

  if (Fn->hasLocalLinkage())
    SPFlags |= llvm::DISubprogram::SPFlagLocalToUnit;
  if (CGM.getLangOpts().Optimize)
    SPFlags |= llvm::DISubprogram::SPFlagOptimized;

  llvm::DINode::DIFlags FlagsForDef = Flags | getCallSiteRelatedAttrs();
  llvm::DISubprogram::DISPFlags SPFlagsForDef =
      SPFlags | llvm::DISubprogram::SPFlagDefinition;

  unsigned LineNo = getLineNumber(Loc);
  unsigned ScopeLine = getLineNumber(ScopeLoc);

  // FIXME: The function declaration we're constructing here is mostly reusing
  // declarations from CXXMethodDecl and not constructing new ones for arbitrary
  // FunctionDecls. When/if we fix this we can have FDContext be TheCU/null for
  // all subprograms instead of the actual context since subprogram definitions
  // are emitted as CU level entities by the backend.
  llvm::DISubprogram *SP = DBuilder.createFunction(
      FDContext, Name, LinkageName, Unit, LineNo,
      getOrCreateFunctionType(D, FnType, Unit), ScopeLine, FlagsForDef,
      SPFlagsForDef, TParamsArray.get(), getFunctionDeclaration(D));
  Fn->setSubprogram(SP);
  // We might get here with a VarDecl in the case we're generating
  // code for the initialization of globals. Do not record these decls
  // as they will overwrite the actual VarDecl Decl in the cache.
  if (HasDecl && isa<FunctionDecl>(D))
    DeclCache[D->getCanonicalDecl()].reset(SP);

  // We use the SPDefCache only in the case when the debug entry values option
  // is set, in order to speed up parameters modification analysis.
  //
  // FIXME: Use AbstractCallee here to support ObjCMethodDecl.
  if (CGM.getCodeGenOpts().EnableDebugEntryValues && HasDecl)
    if (auto *FD = dyn_cast<FunctionDecl>(D))
      if (FD->hasBody() && !FD->param_empty())
        SPDefCache[FD].reset(SP);

  if (CGM.getCodeGenOpts().DwarfVersion >= 5) {
    // Starting with DWARF V5 method declarations are emitted as children of
    // the interface type.
    if (const auto *OMD = dyn_cast_or_null<ObjCMethodDecl>(D)) {
      const ObjCInterfaceDecl *ID = OMD->getClassInterface();
      QualType QTy(ID->getTypeForDecl(), 0);
      auto It = TypeCache.find(QTy.getAsOpaquePtr());
      if (It != TypeCache.end()) {
        llvm::DICompositeType *InterfaceDecl =
            cast<llvm::DICompositeType>(It->second);
        llvm::DISubprogram *FD = DBuilder.createFunction(
            InterfaceDecl, Name, LinkageName, Unit, LineNo,
            getOrCreateFunctionType(D, FnType, Unit), ScopeLine, Flags, SPFlags,
            TParamsArray.get());
        DBuilder.finalizeSubprogram(FD);
        ObjCMethodCache[ID].push_back(FD);
      }
    }
  }

  // Push the function onto the lexical block stack.
  LexicalBlockStack.emplace_back(SP);

  if (HasDecl)
    RegionMap[D].reset(SP);
}

void CGDebugInfo::EmitFunctionDecl(GlobalDecl GD, SourceLocation Loc,
                                   QualType FnType, llvm::Function *Fn) {
  StringRef Name;
  StringRef LinkageName;

  const Decl *D = GD.getDecl();
  if (!D)
    return;

  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  llvm::DIFile *Unit = getOrCreateFile(Loc);
  bool IsDeclForCallSite = Fn ? true : false;
  llvm::DIScope *FDContext =
      IsDeclForCallSite ? Unit : getDeclContextDescriptor(D);
  llvm::DINodeArray TParamsArray;
  if (isa<FunctionDecl>(D)) {
    // If there is a DISubprogram for this function available then use it.
    collectFunctionDeclProps(GD, Unit, Name, LinkageName, FDContext,
                             TParamsArray, Flags);
  } else if (const auto *OMD = dyn_cast<ObjCMethodDecl>(D)) {
    Name = getObjCMethodName(OMD);
    Flags |= llvm::DINode::FlagPrototyped;
  } else {
    llvm_unreachable("not a function or ObjC method");
  }
  if (!Name.empty() && Name[0] == '\01')
    Name = Name.substr(1);

  if (D->isImplicit()) {
    Flags |= llvm::DINode::FlagArtificial;
    // Artificial functions without a location should not silently reuse CurLoc.
    if (Loc.isInvalid())
      CurLoc = SourceLocation();
  }
  unsigned LineNo = getLineNumber(Loc);
  unsigned ScopeLine = 0;
  llvm::DISubprogram::DISPFlags SPFlags = llvm::DISubprogram::SPFlagZero;
  if (CGM.getLangOpts().Optimize)
    SPFlags |= llvm::DISubprogram::SPFlagOptimized;

  llvm::DISubprogram *SP = DBuilder.createFunction(
      FDContext, Name, LinkageName, Unit, LineNo,
      getOrCreateFunctionType(D, FnType, Unit), ScopeLine, Flags, SPFlags,
      TParamsArray.get(), getFunctionDeclaration(D));

  if (IsDeclForCallSite)
    Fn->setSubprogram(SP);

  DBuilder.retainType(SP);
}

void CGDebugInfo::EmitFuncDeclForCallSite(llvm::CallBase *CallOrInvoke,
                                          QualType CalleeType,
                                          const FunctionDecl *CalleeDecl) {
  auto &CGOpts = CGM.getCodeGenOpts();
  if (!CGOpts.EnableDebugEntryValues || !CGM.getLangOpts().Optimize ||
      !CallOrInvoke ||
      CGM.getCodeGenOpts().getDebugInfo() < codegenoptions::LimitedDebugInfo)
    return;

  auto *Func = CallOrInvoke->getCalledFunction();
  if (!Func)
    return;

  // If there is no DISubprogram attached to the function being called,
  // create the one describing the function in order to have complete
  // call site debug info.
  if (Func->getSubprogram())
    return;

  if (!CalleeDecl->isStatic() && !CalleeDecl->isInlined())
    EmitFunctionDecl(CalleeDecl, CalleeDecl->getLocation(), CalleeType, Func);
}

void CGDebugInfo::EmitInlineFunctionStart(CGBuilderTy &Builder, GlobalDecl GD) {
  const auto *FD = cast<FunctionDecl>(GD.getDecl());
  // If there is a subprogram for this function available then use it.
  auto FI = SPCache.find(FD->getCanonicalDecl());
  llvm::DISubprogram *SP = nullptr;
  if (FI != SPCache.end())
    SP = dyn_cast_or_null<llvm::DISubprogram>(FI->second);
  if (!SP || !SP->isDefinition())
    SP = getFunctionStub(GD);
  FnBeginRegionCount.push_back(LexicalBlockStack.size());
  LexicalBlockStack.emplace_back(SP);
  setInlinedAt(Builder.getCurrentDebugLocation());
  EmitLocation(Builder, FD->getLocation());
}

void CGDebugInfo::EmitInlineFunctionEnd(CGBuilderTy &Builder) {
  assert(CurInlinedAt && "unbalanced inline scope stack");
  EmitFunctionEnd(Builder, nullptr);
  setInlinedAt(llvm::DebugLoc(CurInlinedAt).getInlinedAt());
}

void CGDebugInfo::EmitLocation(CGBuilderTy &Builder, SourceLocation Loc) {
  // Update our current location
  setLocation(Loc);

  if (CurLoc.isInvalid() || CurLoc.isMacroID() || LexicalBlockStack.empty())
    return;

  llvm::MDNode *Scope = LexicalBlockStack.back();
  Builder.SetCurrentDebugLocation(llvm::DebugLoc::get(
      getLineNumber(CurLoc), getColumnNumber(CurLoc), Scope, CurInlinedAt));
}

void CGDebugInfo::CreateLexicalBlock(SourceLocation Loc) {
  llvm::MDNode *Back = nullptr;
  if (!LexicalBlockStack.empty())
    Back = LexicalBlockStack.back().get();
  LexicalBlockStack.emplace_back(DBuilder.createLexicalBlock(
      cast<llvm::DIScope>(Back), getOrCreateFile(CurLoc), getLineNumber(CurLoc),
      getColumnNumber(CurLoc)));
}

void CGDebugInfo::AppendAddressSpaceXDeref(
    unsigned AddressSpace, SmallVectorImpl<int64_t> &Expr) const {
  Optional<unsigned> DWARFAddressSpace =
      CGM.getTarget().getDWARFAddressSpace(AddressSpace);
  if (!DWARFAddressSpace)
    return;

  Expr.push_back(llvm::dwarf::DW_OP_constu);
  Expr.push_back(DWARFAddressSpace.getValue());
  Expr.push_back(llvm::dwarf::DW_OP_swap);
  Expr.push_back(llvm::dwarf::DW_OP_xderef);
}

void CGDebugInfo::EmitLexicalBlockStart(CGBuilderTy &Builder,
                                        SourceLocation Loc) {
  // Set our current location.
  setLocation(Loc);

  // Emit a line table change for the current location inside the new scope.
  Builder.SetCurrentDebugLocation(
      llvm::DebugLoc::get(getLineNumber(Loc), getColumnNumber(Loc),
                          LexicalBlockStack.back(), CurInlinedAt));

  if (DebugKind <= codegenoptions::DebugLineTablesOnly)
    return;

  // Create a new lexical block and push it on the stack.
  CreateLexicalBlock(Loc);
}

void CGDebugInfo::EmitLexicalBlockEnd(CGBuilderTy &Builder,
                                      SourceLocation Loc) {
  assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");

  // Provide an entry in the line table for the end of the block.
  EmitLocation(Builder, Loc);

  if (DebugKind <= codegenoptions::DebugLineTablesOnly)
    return;

  LexicalBlockStack.pop_back();
}

void CGDebugInfo::EmitFunctionEnd(CGBuilderTy &Builder, llvm::Function *Fn) {
  assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
  unsigned RCount = FnBeginRegionCount.back();
  assert(RCount <= LexicalBlockStack.size() && "Region stack mismatch");

  // Pop all regions for this function.
  while (LexicalBlockStack.size() != RCount) {
    // Provide an entry in the line table for the end of the block.
    EmitLocation(Builder, CurLoc);
    LexicalBlockStack.pop_back();
  }
  FnBeginRegionCount.pop_back();

  if (Fn && Fn->getSubprogram())
    DBuilder.finalizeSubprogram(Fn->getSubprogram());
}

CGDebugInfo::BlockByRefType
CGDebugInfo::EmitTypeForVarWithBlocksAttr(const VarDecl *VD,
                                          uint64_t *XOffset) {
  SmallVector<llvm::Metadata *, 5> EltTys;
  QualType FType;
  uint64_t FieldSize, FieldOffset;
  uint32_t FieldAlign;

  llvm::DIFile *Unit = getOrCreateFile(VD->getLocation());
  QualType Type = VD->getType();

  FieldOffset = 0;
  FType = CGM.getContext().getPointerType(CGM.getContext().VoidTy);
  EltTys.push_back(CreateMemberType(Unit, FType, "__isa", &FieldOffset));
  EltTys.push_back(CreateMemberType(Unit, FType, "__forwarding", &FieldOffset));
  FType = CGM.getContext().IntTy;
  EltTys.push_back(CreateMemberType(Unit, FType, "__flags", &FieldOffset));
  EltTys.push_back(CreateMemberType(Unit, FType, "__size", &FieldOffset));

  bool HasCopyAndDispose = CGM.getContext().BlockRequiresCopying(Type, VD);
  if (HasCopyAndDispose) {
    FType = CGM.getContext().getPointerType(CGM.getContext().VoidTy);
    EltTys.push_back(
        CreateMemberType(Unit, FType, "__copy_helper", &FieldOffset));
    EltTys.push_back(
        CreateMemberType(Unit, FType, "__destroy_helper", &FieldOffset));
  }
  bool HasByrefExtendedLayout;
  Qualifiers::ObjCLifetime Lifetime;
  if (CGM.getContext().getByrefLifetime(Type, Lifetime,
                                        HasByrefExtendedLayout) &&
      HasByrefExtendedLayout) {
    FType = CGM.getContext().getPointerType(CGM.getContext().VoidTy);
    EltTys.push_back(
        CreateMemberType(Unit, FType, "__byref_variable_layout", &FieldOffset));
  }

  CharUnits Align = CGM.getContext().getDeclAlign(VD);
  if (Align > CGM.getContext().toCharUnitsFromBits(
                  CGM.getTarget().getPointerAlign(0))) {
    CharUnits FieldOffsetInBytes =
        CGM.getContext().toCharUnitsFromBits(FieldOffset);
    CharUnits AlignedOffsetInBytes = FieldOffsetInBytes.alignTo(Align);
    CharUnits NumPaddingBytes = AlignedOffsetInBytes - FieldOffsetInBytes;

    if (NumPaddingBytes.isPositive()) {
      llvm::APInt pad(32, NumPaddingBytes.getQuantity());
      FType = CGM.getContext().getConstantArrayType(CGM.getContext().CharTy,
                                                    pad, ArrayType::Normal, 0);
      EltTys.push_back(CreateMemberType(Unit, FType, "", &FieldOffset));
    }
  }

  FType = Type;
  llvm::DIType *WrappedTy = getOrCreateType(FType, Unit);
  FieldSize = CGM.getContext().getTypeSize(FType);
  FieldAlign = CGM.getContext().toBits(Align);

  *XOffset = FieldOffset;
  llvm::DIType *FieldTy = DBuilder.createMemberType(
      Unit, VD->getName(), Unit, 0, FieldSize, FieldAlign, FieldOffset,
      llvm::DINode::FlagZero, WrappedTy);
  EltTys.push_back(FieldTy);
  FieldOffset += FieldSize;

  llvm::DINodeArray Elements = DBuilder.getOrCreateArray(EltTys);
  return {DBuilder.createStructType(Unit, "", Unit, 0, FieldOffset, 0,
                                    llvm::DINode::FlagZero, nullptr, Elements),
          WrappedTy};
}

llvm::DILocalVariable *CGDebugInfo::EmitDeclare(const VarDecl *VD,
                                                llvm::Value *Storage,
                                                llvm::Optional<unsigned> ArgNo,
                                                CGBuilderTy &Builder,
                                                const bool UsePointerValue) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");
  if (VD->hasAttr<NoDebugAttr>())
    return nullptr;

  bool Unwritten =
      VD->isImplicit() || (isa<Decl>(VD->getDeclContext()) &&
                           cast<Decl>(VD->getDeclContext())->isImplicit());
  llvm::DIFile *Unit = nullptr;
  if (!Unwritten)
    Unit = getOrCreateFile(VD->getLocation());
  llvm::DIType *Ty;
  uint64_t XOffset = 0;
  if (VD->hasAttr<BlocksAttr>())
    Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset).WrappedType;
  else
    Ty = getOrCreateType(VD->getType(), Unit);

  // If there is no debug info for this type then do not emit debug info
  // for this variable.
  if (!Ty)
    return nullptr;

  // Get location information.
  unsigned Line = 0;
  unsigned Column = 0;
  if (!Unwritten) {
    Line = getLineNumber(VD->getLocation());
    Column = getColumnNumber(VD->getLocation());
  }
  SmallVector<int64_t, 13> Expr;
  llvm::DINode::DIFlags Flags = llvm::DINode::FlagZero;
  if (VD->isImplicit())
    Flags |= llvm::DINode::FlagArtificial;

  auto Align = getDeclAlignIfRequired(VD, CGM.getContext());

  unsigned AddressSpace = CGM.getContext().getTargetAddressSpace(VD->getType());
  AppendAddressSpaceXDeref(AddressSpace, Expr);

  // If this is implicit parameter of CXXThis or ObjCSelf kind, then give it an
  // object pointer flag.
  if (const auto *IPD = dyn_cast<ImplicitParamDecl>(VD)) {
    if (IPD->getParameterKind() == ImplicitParamDecl::CXXThis ||
        IPD->getParameterKind() == ImplicitParamDecl::ObjCSelf)
      Flags |= llvm::DINode::FlagObjectPointer;
  }

  // Note: Older versions of clang used to emit byval references with an extra
  // DW_OP_deref, because they referenced the IR arg directly instead of
  // referencing an alloca. Newer versions of LLVM don't treat allocas
  // differently from other function arguments when used in a dbg.declare.
  auto *Scope = cast<llvm::DIScope>(LexicalBlockStack.back());
  StringRef Name = VD->getName();
  if (!Name.empty()) {
    if (VD->hasAttr<BlocksAttr>()) {
      // Here, we need an offset *into* the alloca.
      CharUnits offset = CharUnits::fromQuantity(32);
      Expr.push_back(llvm::dwarf::DW_OP_plus_uconst);
      // offset of __forwarding field
      offset = CGM.getContext().toCharUnitsFromBits(
          CGM.getTarget().getPointerWidth(0));
      Expr.push_back(offset.getQuantity());
      Expr.push_back(llvm::dwarf::DW_OP_deref);
      Expr.push_back(llvm::dwarf::DW_OP_plus_uconst);
      // offset of x field
      offset = CGM.getContext().toCharUnitsFromBits(XOffset);
      Expr.push_back(offset.getQuantity());
    }
  } else if (const auto *RT = dyn_cast<RecordType>(VD->getType())) {
    // If VD is an anonymous union then Storage represents value for
    // all union fields.
    const RecordDecl *RD = RT->getDecl();
    if (RD->isUnion() && RD->isAnonymousStructOrUnion()) {
      // GDB has trouble finding local variables in anonymous unions, so we emit
      // artificial local variables for each of the members.
      //
      // FIXME: Remove this code as soon as GDB supports this.
      // The debug info verifier in LLVM operates based on the assumption that a
      // variable has the same size as its storage and we had to disable the
      // check for artificial variables.
      for (const auto *Field : RD->fields()) {
        llvm::DIType *FieldTy = getOrCreateType(Field->getType(), Unit);
        StringRef FieldName = Field->getName();

        // Ignore unnamed fields. Do not ignore unnamed records.
        if (FieldName.empty() && !isa<RecordType>(Field->getType()))
          continue;

        // Use VarDecl's Tag, Scope and Line number.
        auto FieldAlign = getDeclAlignIfRequired(Field, CGM.getContext());
        auto *D = DBuilder.createAutoVariable(
            Scope, FieldName, Unit, Line, FieldTy, CGM.getLangOpts().Optimize,
            Flags | llvm::DINode::FlagArtificial, FieldAlign);

        // Insert an llvm.dbg.declare into the current block.
        DBuilder.insertDeclare(
            Storage, D, DBuilder.createExpression(Expr),
            llvm::DebugLoc::get(Line, Column, Scope, CurInlinedAt),
            Builder.GetInsertBlock());
      }
    }
  }

  // Clang stores the sret pointer provided by the caller in a static alloca.
  // Use DW_OP_deref to tell the debugger to load the pointer and treat it as
  // the address of the variable.
  if (UsePointerValue) {
    assert(std::find(Expr.begin(), Expr.end(), llvm::dwarf::DW_OP_deref) ==
               Expr.end() &&
           "Debug info already contains DW_OP_deref.");
    Expr.push_back(llvm::dwarf::DW_OP_deref);
  }

  // Create the descriptor for the variable.
  auto *D = ArgNo ? DBuilder.createParameterVariable(
                        Scope, Name, *ArgNo, Unit, Line, Ty,
                        CGM.getLangOpts().Optimize, Flags)
                  : DBuilder.createAutoVariable(Scope, Name, Unit, Line, Ty,
                                                CGM.getLangOpts().Optimize,
                                                Flags, Align);

  // Insert an llvm.dbg.declare into the current block.
  DBuilder.insertDeclare(Storage, D, DBuilder.createExpression(Expr),
                         llvm::DebugLoc::get(Line, Column, Scope, CurInlinedAt),
                         Builder.GetInsertBlock());

  if (CGM.getCodeGenOpts().EnableDebugEntryValues && ArgNo) {
    if (auto *PD = dyn_cast<ParmVarDecl>(VD))
      ParamCache[PD].reset(D);
  }

  return D;
}

llvm::DILocalVariable *
CGDebugInfo::EmitDeclareOfAutoVariable(const VarDecl *VD, llvm::Value *Storage,
                                       CGBuilderTy &Builder,
                                       const bool UsePointerValue) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  return EmitDeclare(VD, Storage, llvm::None, Builder, UsePointerValue);
}

void CGDebugInfo::EmitLabel(const LabelDecl *D, CGBuilderTy &Builder) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");

  if (D->hasAttr<NoDebugAttr>())
    return;

  auto *Scope = cast<llvm::DIScope>(LexicalBlockStack.back());
  llvm::DIFile *Unit = getOrCreateFile(D->getLocation());

  // Get location information.
  unsigned Line = getLineNumber(D->getLocation());
  unsigned Column = getColumnNumber(D->getLocation());

  StringRef Name = D->getName();

  // Create the descriptor for the label.
  auto *L =
      DBuilder.createLabel(Scope, Name, Unit, Line, CGM.getLangOpts().Optimize);

  // Insert an llvm.dbg.label into the current block.
  DBuilder.insertLabel(L,
                       llvm::DebugLoc::get(Line, Column, Scope, CurInlinedAt),
                       Builder.GetInsertBlock());
}

llvm::DIType *CGDebugInfo::CreateSelfType(const QualType &QualTy,
                                          llvm::DIType *Ty) {
  llvm::DIType *CachedTy = getTypeOrNull(QualTy);
  if (CachedTy)
    Ty = CachedTy;
  return DBuilder.createObjectPointerType(Ty);
}

void CGDebugInfo::EmitDeclareOfBlockDeclRefVariable(
    const VarDecl *VD, llvm::Value *Storage, CGBuilderTy &Builder,
    const CGBlockInfo &blockInfo, llvm::Instruction *InsertPoint) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  assert(!LexicalBlockStack.empty() && "Region stack mismatch, stack empty!");

  if (Builder.GetInsertBlock() == nullptr)
    return;
  if (VD->hasAttr<NoDebugAttr>())
    return;

  bool isByRef = VD->hasAttr<BlocksAttr>();

  uint64_t XOffset = 0;
  llvm::DIFile *Unit = getOrCreateFile(VD->getLocation());
  llvm::DIType *Ty;
  if (isByRef)
    Ty = EmitTypeForVarWithBlocksAttr(VD, &XOffset).WrappedType;
  else
    Ty = getOrCreateType(VD->getType(), Unit);

  // Self is passed along as an implicit non-arg variable in a
  // block. Mark it as the object pointer.
  if (const auto *IPD = dyn_cast<ImplicitParamDecl>(VD))
    if (IPD->getParameterKind() == ImplicitParamDecl::ObjCSelf)
      Ty = CreateSelfType(VD->getType(), Ty);

  // Get location information.
  unsigned Line = getLineNumber(VD->getLocation());
  unsigned Column = getColumnNumber(VD->getLocation());

  const llvm::DataLayout &target = CGM.getDataLayout();

  CharUnits offset = CharUnits::fromQuantity(
      target.getStructLayout(blockInfo.StructureType)
          ->getElementOffset(blockInfo.getCapture(VD).getIndex()));

  SmallVector<int64_t, 9> addr;
  addr.push_back(llvm::dwarf::DW_OP_deref);
  addr.push_back(llvm::dwarf::DW_OP_plus_uconst);
  addr.push_back(offset.getQuantity());
  if (isByRef) {
    addr.push_back(llvm::dwarf::DW_OP_deref);
    addr.push_back(llvm::dwarf::DW_OP_plus_uconst);
    // offset of __forwarding field
    offset =
        CGM.getContext().toCharUnitsFromBits(target.getPointerSizeInBits(0));
    addr.push_back(offset.getQuantity());
    addr.push_back(llvm::dwarf::DW_OP_deref);
    addr.push_back(llvm::dwarf::DW_OP_plus_uconst);
    // offset of x field
    offset = CGM.getContext().toCharUnitsFromBits(XOffset);
    addr.push_back(offset.getQuantity());
  }

  // Create the descriptor for the variable.
  auto Align = getDeclAlignIfRequired(VD, CGM.getContext());
  auto *D = DBuilder.createAutoVariable(
      cast<llvm::DILocalScope>(LexicalBlockStack.back()), VD->getName(), Unit,
      Line, Ty, false, llvm::DINode::FlagZero, Align);

  // Insert an llvm.dbg.declare into the current block.
  auto DL =
      llvm::DebugLoc::get(Line, Column, LexicalBlockStack.back(), CurInlinedAt);
  auto *Expr = DBuilder.createExpression(addr);
  if (InsertPoint)
    DBuilder.insertDeclare(Storage, D, Expr, DL, InsertPoint);
  else
    DBuilder.insertDeclare(Storage, D, Expr, DL, Builder.GetInsertBlock());
}

void CGDebugInfo::EmitDeclareOfArgVariable(const VarDecl *VD, llvm::Value *AI,
                                           unsigned ArgNo,
                                           CGBuilderTy &Builder) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  EmitDeclare(VD, AI, ArgNo, Builder);
}

namespace {
struct BlockLayoutChunk {
  uint64_t OffsetInBits;
  const BlockDecl::Capture *Capture;
};
bool operator<(const BlockLayoutChunk &l, const BlockLayoutChunk &r) {
  return l.OffsetInBits < r.OffsetInBits;
}
} // namespace

void CGDebugInfo::collectDefaultFieldsForBlockLiteralDeclare(
    const CGBlockInfo &Block, const ASTContext &Context, SourceLocation Loc,
    const llvm::StructLayout &BlockLayout, llvm::DIFile *Unit,
    SmallVectorImpl<llvm::Metadata *> &Fields) {
  // Blocks in OpenCL have unique constraints which make the standard fields
  // redundant while requiring size and align fields for enqueue_kernel. See
  // initializeForBlockHeader in CGBlocks.cpp
  if (CGM.getLangOpts().OpenCL) {
    Fields.push_back(createFieldType("__size", Context.IntTy, Loc, AS_public,
                                     BlockLayout.getElementOffsetInBits(0),
                                     Unit, Unit));
    Fields.push_back(createFieldType("__align", Context.IntTy, Loc, AS_public,
                                     BlockLayout.getElementOffsetInBits(1),
                                     Unit, Unit));
  } else {
    Fields.push_back(createFieldType("__isa", Context.VoidPtrTy, Loc, AS_public,
                                     BlockLayout.getElementOffsetInBits(0),
                                     Unit, Unit));
    Fields.push_back(createFieldType("__flags", Context.IntTy, Loc, AS_public,
                                     BlockLayout.getElementOffsetInBits(1),
                                     Unit, Unit));
    Fields.push_back(
        createFieldType("__reserved", Context.IntTy, Loc, AS_public,
                        BlockLayout.getElementOffsetInBits(2), Unit, Unit));
    auto *FnTy = Block.getBlockExpr()->getFunctionType();
    auto FnPtrType = CGM.getContext().getPointerType(FnTy->desugar());
    Fields.push_back(createFieldType("__FuncPtr", FnPtrType, Loc, AS_public,
                                     BlockLayout.getElementOffsetInBits(3),
                                     Unit, Unit));
    Fields.push_back(createFieldType(
        "__descriptor",
        Context.getPointerType(Block.NeedsCopyDispose
                                   ? Context.getBlockDescriptorExtendedType()
                                   : Context.getBlockDescriptorType()),
        Loc, AS_public, BlockLayout.getElementOffsetInBits(4), Unit, Unit));
  }
}

void CGDebugInfo::EmitDeclareOfBlockLiteralArgVariable(const CGBlockInfo &block,
                                                       StringRef Name,
                                                       unsigned ArgNo,
                                                       llvm::AllocaInst *Alloca,
                                                       CGBuilderTy &Builder) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  ASTContext &C = CGM.getContext();
  const BlockDecl *blockDecl = block.getBlockDecl();

  // Collect some general information about the block's location.
  SourceLocation loc = blockDecl->getCaretLocation();
  llvm::DIFile *tunit = getOrCreateFile(loc);
  unsigned line = getLineNumber(loc);
  unsigned column = getColumnNumber(loc);

  // Build the debug-info type for the block literal.
  getDeclContextDescriptor(blockDecl);

  const llvm::StructLayout *blockLayout =
      CGM.getDataLayout().getStructLayout(block.StructureType);

  SmallVector<llvm::Metadata *, 16> fields;
  collectDefaultFieldsForBlockLiteralDeclare(block, C, loc, *blockLayout, tunit,
                                             fields);

  // We want to sort the captures by offset, not because DWARF
  // requires this, but because we're paranoid about debuggers.
  SmallVector<BlockLayoutChunk, 8> chunks;

  // 'this' capture.
  if (blockDecl->capturesCXXThis()) {
    BlockLayoutChunk chunk;
    chunk.OffsetInBits =
        blockLayout->getElementOffsetInBits(block.CXXThisIndex);
    chunk.Capture = nullptr;
    chunks.push_back(chunk);
  }

  // Variable captures.
  for (const auto &capture : blockDecl->captures()) {
    const VarDecl *variable = capture.getVariable();
    const CGBlockInfo::Capture &captureInfo = block.getCapture(variable);

    // Ignore constant captures.
    if (captureInfo.isConstant())
      continue;

    BlockLayoutChunk chunk;
    chunk.OffsetInBits =
        blockLayout->getElementOffsetInBits(captureInfo.getIndex());
    chunk.Capture = &capture;
    chunks.push_back(chunk);
  }

  // Sort by offset.
  llvm::array_pod_sort(chunks.begin(), chunks.end());

  for (const BlockLayoutChunk &Chunk : chunks) {
    uint64_t offsetInBits = Chunk.OffsetInBits;
    const BlockDecl::Capture *capture = Chunk.Capture;

    // If we have a null capture, this must be the C++ 'this' capture.
    if (!capture) {
      QualType type;
      if (auto *Method =
              cast_or_null<CXXMethodDecl>(blockDecl->getNonClosureContext()))
        type = Method->getThisType();
      else if (auto *RDecl = dyn_cast<CXXRecordDecl>(blockDecl->getParent()))
        type = QualType(RDecl->getTypeForDecl(), 0);
      else
        llvm_unreachable("unexpected block declcontext");

      fields.push_back(createFieldType("this", type, loc, AS_public,
                                       offsetInBits, tunit, tunit));
      continue;
    }

    const VarDecl *variable = capture->getVariable();
    StringRef name = variable->getName();

    llvm::DIType *fieldType;
    if (capture->isByRef()) {
      TypeInfo PtrInfo = C.getTypeInfo(C.VoidPtrTy);
      auto Align = PtrInfo.AlignIsRequired ? PtrInfo.Align : 0;
      // FIXME: This recomputes the layout of the BlockByRefWrapper.
      uint64_t xoffset;
      fieldType =
          EmitTypeForVarWithBlocksAttr(variable, &xoffset).BlockByRefWrapper;
      fieldType = DBuilder.createPointerType(fieldType, PtrInfo.Width);
      fieldType = DBuilder.createMemberType(tunit, name, tunit, line,
                                            PtrInfo.Width, Align, offsetInBits,
                                            llvm::DINode::FlagZero, fieldType);
    } else {
      auto Align = getDeclAlignIfRequired(variable, CGM.getContext());
      fieldType = createFieldType(name, variable->getType(), loc, AS_public,
                                  offsetInBits, Align, tunit, tunit);
    }
    fields.push_back(fieldType);
  }

  SmallString<36> typeName;
  llvm::raw_svector_ostream(typeName)
      << "__block_literal_" << CGM.getUniqueBlockCount();

  llvm::DINodeArray fieldsArray = DBuilder.getOrCreateArray(fields);

  llvm::DIType *type =
      DBuilder.createStructType(tunit, typeName.str(), tunit, line,
                                CGM.getContext().toBits(block.BlockSize), 0,
                                llvm::DINode::FlagZero, nullptr, fieldsArray);
  type = DBuilder.createPointerType(type, CGM.PointerWidthInBits);

  // Get overall information about the block.
  llvm::DINode::DIFlags flags = llvm::DINode::FlagArtificial;
  auto *scope = cast<llvm::DILocalScope>(LexicalBlockStack.back());

  // Create the descriptor for the parameter.
  auto *debugVar = DBuilder.createParameterVariable(
      scope, Name, ArgNo, tunit, line, type, CGM.getLangOpts().Optimize, flags);

  // Insert an llvm.dbg.declare into the current block.
  DBuilder.insertDeclare(Alloca, debugVar, DBuilder.createExpression(),
                         llvm::DebugLoc::get(line, column, scope, CurInlinedAt),
                         Builder.GetInsertBlock());
}

llvm::DIDerivedType *
CGDebugInfo::getOrCreateStaticDataMemberDeclarationOrNull(const VarDecl *D) {
  if (!D || !D->isStaticDataMember())
    return nullptr;

  auto MI = StaticDataMemberCache.find(D->getCanonicalDecl());
  if (MI != StaticDataMemberCache.end()) {
    assert(MI->second && "Static data member declaration should still exist");
    return MI->second;
  }

  // If the member wasn't found in the cache, lazily construct and add it to the
  // type (used when a limited form of the type is emitted).
  auto DC = D->getDeclContext();
  auto *Ctxt = cast<llvm::DICompositeType>(getDeclContextDescriptor(D));
  return CreateRecordStaticField(D, Ctxt, cast<RecordDecl>(DC));
}

llvm::DIGlobalVariableExpression *CGDebugInfo::CollectAnonRecordDecls(
    const RecordDecl *RD, llvm::DIFile *Unit, unsigned LineNo,
    StringRef LinkageName, llvm::GlobalVariable *Var, llvm::DIScope *DContext) {
  llvm::DIGlobalVariableExpression *GVE = nullptr;

  for (const auto *Field : RD->fields()) {
    llvm::DIType *FieldTy = getOrCreateType(Field->getType(), Unit);
    StringRef FieldName = Field->getName();

    // Ignore unnamed fields, but recurse into anonymous records.
    if (FieldName.empty()) {
      if (const auto *RT = dyn_cast<RecordType>(Field->getType()))
        GVE = CollectAnonRecordDecls(RT->getDecl(), Unit, LineNo, LinkageName,
                                     Var, DContext);
      continue;
    }
    // Use VarDecl's Tag, Scope and Line number.
    GVE = DBuilder.createGlobalVariableExpression(
        DContext, FieldName, LinkageName, Unit, LineNo, FieldTy,
        Var->hasLocalLinkage());
    Var->addDebugInfo(GVE);
  }
  return GVE;
}

void CGDebugInfo::EmitGlobalVariable(llvm::GlobalVariable *Var,
                                     const VarDecl *D) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  if (D->hasAttr<NoDebugAttr>())
    return;

  // If we already created a DIGlobalVariable for this declaration, just attach
  // it to the llvm::GlobalVariable.
  auto Cached = DeclCache.find(D->getCanonicalDecl());
  if (Cached != DeclCache.end())
    return Var->addDebugInfo(
        cast<llvm::DIGlobalVariableExpression>(Cached->second));

  // Create global variable debug descriptor.
  llvm::DIFile *Unit = nullptr;
  llvm::DIScope *DContext = nullptr;
  unsigned LineNo;
  StringRef DeclName, LinkageName;
  QualType T;
  llvm::MDTuple *TemplateParameters = nullptr;
  collectVarDeclProps(D, Unit, LineNo, T, DeclName, LinkageName,
                      TemplateParameters, DContext);

  // Attempt to store one global variable for the declaration - even if we
  // emit a lot of fields.
  llvm::DIGlobalVariableExpression *GVE = nullptr;

  // If this is an anonymous union then we'll want to emit a global
  // variable for each member of the anonymous union so that it's possible
  // to find the name of any field in the union.
  if (T->isUnionType() && DeclName.empty()) {
    const RecordDecl *RD = T->castAs<RecordType>()->getDecl();
    assert(RD->isAnonymousStructOrUnion() &&
           "unnamed non-anonymous struct or union?");
    GVE = CollectAnonRecordDecls(RD, Unit, LineNo, LinkageName, Var, DContext);
  } else {
    auto Align = getDeclAlignIfRequired(D, CGM.getContext());

    SmallVector<int64_t, 4> Expr;
    unsigned AddressSpace =
        CGM.getContext().getTargetAddressSpace(D->getType());
    if (CGM.getLangOpts().CUDA && CGM.getLangOpts().CUDAIsDevice) {
      if (D->hasAttr<CUDASharedAttr>())
        AddressSpace =
            CGM.getContext().getTargetAddressSpace(LangAS::cuda_shared);
      else if (D->hasAttr<CUDAConstantAttr>())
        AddressSpace =
            CGM.getContext().getTargetAddressSpace(LangAS::cuda_constant);
    }
    AppendAddressSpaceXDeref(AddressSpace, Expr);

    GVE = DBuilder.createGlobalVariableExpression(
        DContext, DeclName, LinkageName, Unit, LineNo, getOrCreateType(T, Unit),
        Var->hasLocalLinkage(),
        Expr.empty() ? nullptr : DBuilder.createExpression(Expr),
        getOrCreateStaticDataMemberDeclarationOrNull(D), TemplateParameters,
        Align);
    Var->addDebugInfo(GVE);
  }
  DeclCache[D->getCanonicalDecl()].reset(GVE);
}

void CGDebugInfo::EmitGlobalVariable(const ValueDecl *VD, const APValue &Init) {
  assert(DebugKind >= codegenoptions::LimitedDebugInfo);
  if (VD->hasAttr<NoDebugAttr>())
    return;
  auto Align = getDeclAlignIfRequired(VD, CGM.getContext());
  // Create the descriptor for the variable.
  llvm::DIFile *Unit = getOrCreateFile(VD->getLocation());
  StringRef Name = VD->getName();
  llvm::DIType *Ty = getOrCreateType(VD->getType(), Unit);

  // Do not use global variables for enums, unless in CodeView.
  if (const auto *ECD = dyn_cast<EnumConstantDecl>(VD)) {
    const auto *ED = cast<EnumDecl>(ECD->getDeclContext());
    assert(isa<EnumType>(ED->getTypeForDecl()) && "Enum without EnumType?");
    (void)ED;

    // If CodeView, emit enums as global variables, unless they are defined
    // inside a class. We do this because MSVC doesn't emit S_CONSTANTs for
    // enums in classes, and because it is difficult to attach this scope
    // information to the global variable.
    if (!CGM.getCodeGenOpts().EmitCodeView ||
        isa<RecordDecl>(ED->getDeclContext()))
      return;
  }

  llvm::DIScope *DContext = nullptr;

  // Do not emit separate definitions for function local consts.
  if (isa<FunctionDecl>(VD->getDeclContext()))
    return;

  // Emit definition for static members in CodeView.
  VD = cast<ValueDecl>(VD->getCanonicalDecl());
  auto *VarD = dyn_cast<VarDecl>(VD);
  if (VarD && VarD->isStaticDataMember()) {
    auto *RD = cast<RecordDecl>(VarD->getDeclContext());
    getDeclContextDescriptor(VarD);
    // Ensure that the type is retained even though it's otherwise unreferenced.
    //
    // FIXME: This is probably unnecessary, since Ty should reference RD
    // through its scope.
    RetainedTypes.push_back(
        CGM.getContext().getRecordType(RD).getAsOpaquePtr());

    if (!CGM.getCodeGenOpts().EmitCodeView)
      return;

    // Use the global scope for static members.
    DContext = getContextDescriptor(
        cast<Decl>(CGM.getContext().getTranslationUnitDecl()), TheCU);
  } else {
    DContext = getDeclContextDescriptor(VD);
  }

  auto &GV = DeclCache[VD];
  if (GV)
    return;
  llvm::DIExpression *InitExpr = nullptr;
  if (CGM.getContext().getTypeSize(VD->getType()) <= 64) {
    // FIXME: Add a representation for integer constants wider than 64 bits.
    if (Init.isInt())
      InitExpr =
          DBuilder.createConstantValueExpression(Init.getInt().getExtValue());
    else if (Init.isFloat())
      InitExpr = DBuilder.createConstantValueExpression(
          Init.getFloat().bitcastToAPInt().getZExtValue());
  }

  llvm::MDTuple *TemplateParameters = nullptr;

  if (isa<VarTemplateSpecializationDecl>(VD))
    if (VarD) {
      llvm::DINodeArray parameterNodes = CollectVarTemplateParams(VarD, &*Unit);
      TemplateParameters = parameterNodes.get();
    }

  GV.reset(DBuilder.createGlobalVariableExpression(
      DContext, Name, StringRef(), Unit, getLineNumber(VD->getLocation()), Ty,
      true, InitExpr, getOrCreateStaticDataMemberDeclarationOrNull(VarD),
      TemplateParameters, Align));
}

llvm::DIScope *CGDebugInfo::getCurrentContextDescriptor(const Decl *D) {
  if (!LexicalBlockStack.empty())
    return LexicalBlockStack.back();
  llvm::DIScope *Mod = getParentModuleOrNull(D);
  return getContextDescriptor(D, Mod ? Mod : TheCU);
}

void CGDebugInfo::EmitUsingDirective(const UsingDirectiveDecl &UD) {
  if (CGM.getCodeGenOpts().getDebugInfo() < codegenoptions::LimitedDebugInfo)
    return;
  const NamespaceDecl *NSDecl = UD.getNominatedNamespace();
  if (!NSDecl->isAnonymousNamespace() ||
      CGM.getCodeGenOpts().DebugExplicitImport) {
    auto Loc = UD.getLocation();
    DBuilder.createImportedModule(
        getCurrentContextDescriptor(cast<Decl>(UD.getDeclContext())),
        getOrCreateNamespace(NSDecl), getOrCreateFile(Loc), getLineNumber(Loc));
  }
}

void CGDebugInfo::EmitUsingDecl(const UsingDecl &UD) {
  if (CGM.getCodeGenOpts().getDebugInfo() < codegenoptions::LimitedDebugInfo)
    return;
  assert(UD.shadow_size() &&
         "We shouldn't be codegening an invalid UsingDecl containing no decls");
  // Emitting one decl is sufficient - debuggers can detect that this is an
  // overloaded name & provide lookup for all the overloads.
  const UsingShadowDecl &USD = **UD.shadow_begin();

  // FIXME: Skip functions with undeduced auto return type for now since we
  // don't currently have the plumbing for separate declarations & definitions
  // of free functions and mismatched types (auto in the declaration, concrete
  // return type in the definition)
  if (const auto *FD = dyn_cast<FunctionDecl>(USD.getUnderlyingDecl()))
    if (const auto *AT =
            FD->getType()->getAs<FunctionProtoType>()->getContainedAutoType())
      if (AT->getDeducedType().isNull())
        return;
  if (llvm::DINode *Target =
          getDeclarationOrDefinition(USD.getUnderlyingDecl())) {
    auto Loc = USD.getLocation();
    DBuilder.createImportedDeclaration(
        getCurrentContextDescriptor(cast<Decl>(USD.getDeclContext())), Target,
        getOrCreateFile(Loc), getLineNumber(Loc));
  }
}

void CGDebugInfo::EmitImportDecl(const ImportDecl &ID) {
  if (CGM.getCodeGenOpts().getDebuggerTuning() != llvm::DebuggerKind::LLDB)
    return;
  if (Module *M = ID.getImportedModule()) {
    auto Info = ExternalASTSource::ASTSourceDescriptor(*M);
    auto Loc = ID.getLocation();
    DBuilder.createImportedDeclaration(
        getCurrentContextDescriptor(cast<Decl>(ID.getDeclContext())),
        getOrCreateModuleRef(Info, DebugTypeExtRefs), getOrCreateFile(Loc),
        getLineNumber(Loc));
  }
}

llvm::DIImportedEntity *
CGDebugInfo::EmitNamespaceAlias(const NamespaceAliasDecl &NA) {
  if (CGM.getCodeGenOpts().getDebugInfo() < codegenoptions::LimitedDebugInfo)
    return nullptr;
  auto &VH = NamespaceAliasCache[&NA];
  if (VH)
    return cast<llvm::DIImportedEntity>(VH);
  llvm::DIImportedEntity *R;
  auto Loc = NA.getLocation();
  if (const auto *Underlying =
          dyn_cast<NamespaceAliasDecl>(NA.getAliasedNamespace()))
    // This could cache & dedup here rather than relying on metadata deduping.
    R = DBuilder.createImportedDeclaration(
        getCurrentContextDescriptor(cast<Decl>(NA.getDeclContext())),
        EmitNamespaceAlias(*Underlying), getOrCreateFile(Loc),
        getLineNumber(Loc), NA.getName());
  else
    R = DBuilder.createImportedDeclaration(
        getCurrentContextDescriptor(cast<Decl>(NA.getDeclContext())),
        getOrCreateNamespace(cast<NamespaceDecl>(NA.getAliasedNamespace())),
        getOrCreateFile(Loc), getLineNumber(Loc), NA.getName());
  VH.reset(R);
  return R;
}

llvm::DINamespace *
CGDebugInfo::getOrCreateNamespace(const NamespaceDecl *NSDecl) {
  // Don't canonicalize the NamespaceDecl here: The DINamespace will be uniqued
  // if necessary, and this way multiple declarations of the same namespace in
  // different parent modules stay distinct.
  auto I = NamespaceCache.find(NSDecl);
  if (I != NamespaceCache.end())
    return cast<llvm::DINamespace>(I->second);

  llvm::DIScope *Context = getDeclContextDescriptor(NSDecl);
  // Don't trust the context if it is a DIModule (see comment above).
  llvm::DINamespace *NS =
      DBuilder.createNameSpace(Context, NSDecl->getName(), NSDecl->isInline());
  NamespaceCache[NSDecl].reset(NS);
  return NS;
}

void CGDebugInfo::setDwoId(uint64_t Signature) {
  assert(TheCU && "no main compile unit");
  TheCU->setDWOId(Signature);
}

/// Analyzes each function parameter to determine whether it is constant
/// throughout the function body.
static void analyzeParametersModification(
    ASTContext &Ctx,
    llvm::DenseMap<const FunctionDecl *, llvm::TrackingMDRef> &SPDefCache,
    llvm::DenseMap<const ParmVarDecl *, llvm::TrackingMDRef> &ParamCache) {
  for (auto &SP : SPDefCache) {
    auto *FD = SP.first;
    assert(FD->hasBody() && "Functions must have body here");
    const Stmt *FuncBody = (*FD).getBody();
    for (auto Parm : FD->parameters()) {
      ExprMutationAnalyzer FuncAnalyzer(*FuncBody, Ctx);
      if (FuncAnalyzer.isMutated(Parm))
        continue;

      auto I = ParamCache.find(Parm);
      assert(I != ParamCache.end() && "Parameters should be already cached");
      auto *DIParm = cast<llvm::DILocalVariable>(I->second);
      DIParm->setIsNotModified();
    }
  }
}

void CGDebugInfo::finalize() {
  // Creating types might create further types - invalidating the current
  // element and the size(), so don't cache/reference them.
  for (size_t i = 0; i != ObjCInterfaceCache.size(); ++i) {
    ObjCInterfaceCacheEntry E = ObjCInterfaceCache[i];
    llvm::DIType *Ty = E.Type->getDecl()->getDefinition()
                           ? CreateTypeDefinition(E.Type, E.Unit)
                           : E.Decl;
    DBuilder.replaceTemporary(llvm::TempDIType(E.Decl), Ty);
  }

  if (CGM.getCodeGenOpts().DwarfVersion >= 5) {
    // Add methods to interface.
    for (const auto &P : ObjCMethodCache) {
      if (P.second.empty())
        continue;

      QualType QTy(P.first->getTypeForDecl(), 0);
      auto It = TypeCache.find(QTy.getAsOpaquePtr());
      assert(It != TypeCache.end());

      llvm::DICompositeType *InterfaceDecl =
          cast<llvm::DICompositeType>(It->second);

      SmallVector<llvm::Metadata *, 16> EltTys;
      auto CurrenetElts = InterfaceDecl->getElements();
      EltTys.append(CurrenetElts.begin(), CurrenetElts.end());
      for (auto &MD : P.second)
        EltTys.push_back(MD);
      llvm::DINodeArray Elements = DBuilder.getOrCreateArray(EltTys);
      DBuilder.replaceArrays(InterfaceDecl, Elements);
    }
  }

  for (const auto &P : ReplaceMap) {
    assert(P.second);
    auto *Ty = cast<llvm::DIType>(P.second);
    assert(Ty->isForwardDecl());

    auto It = TypeCache.find(P.first);
    assert(It != TypeCache.end());
    assert(It->second);

    DBuilder.replaceTemporary(llvm::TempDIType(Ty),
                              cast<llvm::DIType>(It->second));
  }

  for (const auto &P : FwdDeclReplaceMap) {
    assert(P.second);
    llvm::TempMDNode FwdDecl(cast<llvm::MDNode>(P.second));
    llvm::Metadata *Repl;

    auto It = DeclCache.find(P.first);
    // If there has been no definition for the declaration, call RAUW
    // with ourselves, that will destroy the temporary MDNode and
    // replace it with a standard one, avoiding leaking memory.
    if (It == DeclCache.end())
      Repl = P.second;
    else
      Repl = It->second;

    if (auto *GVE = dyn_cast_or_null<llvm::DIGlobalVariableExpression>(Repl))
      Repl = GVE->getVariable();
    DBuilder.replaceTemporary(std::move(FwdDecl), cast<llvm::MDNode>(Repl));
  }

  // We keep our own list of retained types, because we need to look
  // up the final type in the type cache.
  for (auto &RT : RetainedTypes)
    if (auto MD = TypeCache[RT])
      DBuilder.retainType(cast<llvm::DIType>(MD));

  if (CGM.getCodeGenOpts().EnableDebugEntryValues)
    // This will be used to emit debug entry values.
    analyzeParametersModification(CGM.getContext(), SPDefCache, ParamCache);

  DBuilder.finalize();
}

void CGDebugInfo::EmitExplicitCastType(QualType Ty) {
  if (CGM.getCodeGenOpts().getDebugInfo() < codegenoptions::LimitedDebugInfo)
    return;

  if (auto *DieTy = getOrCreateType(Ty, TheCU->getFile()))
    // Don't ignore in case of explicit cast where it is referenced indirectly.
    DBuilder.retainType(DieTy);
}

llvm::DebugLoc CGDebugInfo::SourceLocToDebugLoc(SourceLocation Loc) {
  if (LexicalBlockStack.empty())
    return llvm::DebugLoc();

  llvm::MDNode *Scope = LexicalBlockStack.back();
  return llvm::DebugLoc::get(getLineNumber(Loc), getColumnNumber(Loc), Scope);
}

llvm::DINode::DIFlags CGDebugInfo::getCallSiteRelatedAttrs() const {
  // Call site-related attributes are only useful in optimized programs, and
  // when there's a possibility of debugging backtraces.
  if (!CGM.getLangOpts().Optimize || DebugKind == codegenoptions::NoDebugInfo ||
      DebugKind == codegenoptions::LocTrackingOnly)
    return llvm::DINode::FlagZero;

  // Call site-related attributes are available in DWARF v5. Some debuggers,
  // while not fully DWARF v5-compliant, may accept these attributes as if they
  // were part of DWARF v4.
  bool SupportsDWARFv4Ext =
      CGM.getCodeGenOpts().DwarfVersion == 4 &&
      (CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::LLDB ||
       (CGM.getCodeGenOpts().EnableDebugEntryValues &&
       CGM.getCodeGenOpts().getDebuggerTuning() == llvm::DebuggerKind::GDB));

  if (!SupportsDWARFv4Ext && CGM.getCodeGenOpts().DwarfVersion < 5)
    return llvm::DINode::FlagZero;

  return llvm::DINode::FlagAllCallsDescribed;
}