text: //===-- llvm-dwp.cpp - Split DWARF merging tool for llvm ------------------===//
  //
  // 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
  //
  //===----------------------------------------------------------------------===//
  //
  // A utility for merging DWARF 5 Split DWARF .dwo files into .dwp (DWARF
  // package files).
  //
  //===----------------------------------------------------------------------===//
  #include "DWPError.h"
  #include "DWPStringPool.h"
  #include "llvm/ADT/MapVector.h"
  #include "llvm/ADT/Optional.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/DebugInfo/DWARF/DWARFContext.h"
  #include "llvm/DebugInfo/DWARF/DWARFFormValue.h"
  #include "llvm/DebugInfo/DWARF/DWARFUnitIndex.h"
  #include "llvm/MC/MCAsmBackend.h"
  #include "llvm/MC/MCAsmInfo.h"
  #include "llvm/MC/MCCodeEmitter.h"
  #include "llvm/MC/MCContext.h"
  #include "llvm/MC/MCInstrInfo.h"
  #include "llvm/MC/MCObjectFileInfo.h"
  #include "llvm/MC/MCObjectWriter.h"
  #include "llvm/MC/MCRegisterInfo.h"
  #include "llvm/MC/MCStreamer.h"
  #include "llvm/MC/MCTargetOptionsCommandFlags.h"
  #include "llvm/Object/Decompressor.h"
  #include "llvm/Object/ObjectFile.h"
  #include "llvm/Support/CommandLine.h"
  #include "llvm/Support/DataExtractor.h"
  #include "llvm/Support/Error.h"
  #include "llvm/Support/FileSystem.h"
  #include "llvm/Support/InitLLVM.h"
  #include "llvm/Support/MathExtras.h"
  #include "llvm/Support/MemoryBuffer.h"
  #include "llvm/Support/Path.h"
  #include "llvm/Support/TargetRegistry.h"
  #include "llvm/Support/TargetSelect.h"
  #include "llvm/Support/ToolOutputFile.h"
  #include "llvm/Support/WithColor.h"
  #include "llvm/Support/raw_ostream.h"
  
  using namespace llvm;
  using namespace llvm::object;
  
  static mc::RegisterMCTargetOptionsFlags MCTargetOptionsFlags;
  
  cl::OptionCategory DwpCategory("Specific Options");
  static cl::list<std::string> InputFiles(cl::Positional, cl::ZeroOrMore,
                                          cl::desc("<input files>"),
                                          cl::cat(DwpCategory));
  
  static cl::list<std::string> ExecFilenames(
      "e", cl::ZeroOrMore,
      cl::desc("Specify the executable/library files to get the list of *.dwo from"),
      cl::value_desc("filename"), cl::cat(DwpCategory));
  
  static cl::opt<std::string> OutputFilename(cl::Required, "o",
                                             cl::desc("Specify the output file."),
                                             cl::value_desc("filename"),
                                             cl::cat(DwpCategory));
  
  static void writeStringsAndOffsets(MCStreamer &Out, DWPStringPool &Strings,
                                     MCSection *StrOffsetSection,
                                     StringRef CurStrSection,
                                     StringRef CurStrOffsetSection) {
    // Could possibly produce an error or warning if one of these was non-null but
    // the other was null.
    if (CurStrSection.empty() || CurStrOffsetSection.empty())
      return;
  
    DenseMap<uint64_t, uint32_t> OffsetRemapping;
  
    DataExtractor Data(CurStrSection, true, 0);
    uint64_t LocalOffset = 0;
    uint64_t PrevOffset = 0;
    while (const char *s = Data.getCStr(&LocalOffset)) {
      OffsetRemapping[PrevOffset] =
          Strings.getOffset(s, LocalOffset - PrevOffset);
      PrevOffset = LocalOffset;
    }
  
    Data = DataExtractor(CurStrOffsetSection, true, 0);
  
    Out.SwitchSection(StrOffsetSection);
  
    uint64_t Offset = 0;
    uint64_t Size = CurStrOffsetSection.size();
    while (Offset < Size) {
      auto OldOffset = Data.getU32(&Offset);
      auto NewOffset = OffsetRemapping[OldOffset];
      Out.emitIntValue(NewOffset, 4);
    }
  }
  
  static uint64_t getCUAbbrev(StringRef Abbrev, uint64_t AbbrCode) {
    uint64_t CurCode;
    uint64_t Offset = 0;
    DataExtractor AbbrevData(Abbrev, true, 0);
    while ((CurCode = AbbrevData.getULEB128(&Offset)) != AbbrCode) {
      // Tag
      AbbrevData.getULEB128(&Offset);
      // DW_CHILDREN
      AbbrevData.getU8(&Offset);
      // Attributes
      while (AbbrevData.getULEB128(&Offset) | AbbrevData.getULEB128(&Offset))
        ;
    }
    return Offset;
  }
  
  struct CompileUnitIdentifiers {
    uint64_t Signature = 0;
    const char *Name = "";
    const char *DWOName = "";
  };
  
  static Expected<const char *>
  getIndexedString(dwarf::Form Form, DataExtractor InfoData,
                   uint64_t &InfoOffset, StringRef StrOffsets, StringRef Str) {
    if (Form == dwarf::DW_FORM_string)
      return InfoData.getCStr(&InfoOffset);
    if (Form != dwarf::DW_FORM_GNU_str_index)
      return make_error<DWPError>(
          "string field encoded without DW_FORM_string or DW_FORM_GNU_str_index");
    auto StrIndex = InfoData.getULEB128(&InfoOffset);
    DataExtractor StrOffsetsData(StrOffsets, true, 0);
    uint64_t StrOffsetsOffset = 4 * StrIndex;
    uint64_t StrOffset = StrOffsetsData.getU32(&StrOffsetsOffset);
    DataExtractor StrData(Str, true, 0);
    return StrData.getCStr(&StrOffset);
  }
  
  static Expected<CompileUnitIdentifiers> getCUIdentifiers(StringRef Abbrev,
                                                           StringRef Info,
                                                           StringRef StrOffsets,
                                                           StringRef Str) {
    uint64_t Offset = 0;
    DataExtractor InfoData(Info, true, 0);
    dwarf::DwarfFormat Format = dwarf::DwarfFormat::DWARF32;
    uint64_t Length = InfoData.getU32(&Offset);
    CompileUnitIdentifiers ID;
    Optional<uint64_t> Signature = None;
    // If the length is 0xffffffff, then this indictes that this is a DWARF 64
    // stream and the length is actually encoded into a 64 bit value that follows.
    if (Length == 0xffffffffU) {
      Format = dwarf::DwarfFormat::DWARF64;
      Length = InfoData.getU64(&Offset);
    }
    uint16_t Version = InfoData.getU16(&Offset);
    if (Version >= 5) {
      auto UnitType = InfoData.getU8(&Offset);
      if (UnitType != dwarf::DW_UT_split_compile)
        return make_error<DWPError>(
            std::string("unit type DW_UT_split_compile type not found in "
                        "debug_info header. Unexpected unit type 0x" +
                        utostr(UnitType) + " found"));
    }
    InfoData.getU32(&Offset); // Abbrev offset (should be zero)
    uint8_t AddrSize = InfoData.getU8(&Offset);
    if (Version >= 5)
      Signature = InfoData.getU64(&Offset);
    uint32_t AbbrCode = InfoData.getULEB128(&Offset);
  
    DataExtractor AbbrevData(Abbrev, true, 0);
    uint64_t AbbrevOffset = getCUAbbrev(Abbrev, AbbrCode);
    auto Tag = static_cast<dwarf::Tag>(AbbrevData.getULEB128(&AbbrevOffset));
    if (Tag != dwarf::DW_TAG_compile_unit)
      return make_error<DWPError>("top level DIE is not a compile unit");
    // DW_CHILDREN
    AbbrevData.getU8(&AbbrevOffset);
    uint32_t Name;
    dwarf::Form Form;
    while ((Name = AbbrevData.getULEB128(&AbbrevOffset)) |
           (Form = static_cast<dwarf::Form>(AbbrevData.getULEB128(&AbbrevOffset))) &&
           (Name != 0 || Form != 0)) {
      switch (Name) {
      case dwarf::DW_AT_name: {
        Expected<const char *> EName =
            getIndexedString(Form, InfoData, Offset, StrOffsets, Str);
        if (!EName)
          return EName.takeError();
        ID.Name = *EName;
        break;
      }
      case dwarf::DW_AT_GNU_dwo_name:
      case dwarf::DW_AT_dwo_name: {
        Expected<const char *> EName =
            getIndexedString(Form, InfoData, Offset, StrOffsets, Str);
        if (!EName)
          return EName.takeError();
        ID.DWOName = *EName;
        break;
      }
      case dwarf::DW_AT_GNU_dwo_id:
        Signature = InfoData.getU64(&Offset);
        break;
      default:
        DWARFFormValue::skipValue(Form, InfoData, &Offset,
                                  dwarf::FormParams({Version, AddrSize, Format}));
      }
    }
    if (!Signature)
      return make_error<DWPError>("compile unit missing dwo_id");
    ID.Signature = *Signature;
    return ID;
  }
  
  struct UnitIndexEntry {
    DWARFUnitIndex::Entry::SectionContribution Contributions[8];
    std::string Name;
    std::string DWOName;
    StringRef DWPName;
  };
  
  static bool isSupportedSectionKind(DWARFSectionKind Kind) {
    return Kind != DW_SECT_EXT_unknown;
  }
  
  // Convert an internal section identifier into the index to use with
  // UnitIndexEntry::Contributions.
  static unsigned getContributionIndex(DWARFSectionKind Kind) {
    // Assuming the pre-standard DWP format.
    assert(serializeSectionKind(Kind, 2) >= DW_SECT_INFO);
    return serializeSectionKind(Kind, 2) - DW_SECT_INFO;
  }
  
  // Convert a UnitIndexEntry::Contributions index to the corresponding on-disk
  // value of the section identifier.
  static unsigned getOnDiskSectionId(unsigned Index) {
    return Index + DW_SECT_INFO;
  }
  
  static StringRef getSubsection(StringRef Section,
                                 const DWARFUnitIndex::Entry &Entry,
                                 DWARFSectionKind Kind) {
    const auto *Off = Entry.getContribution(Kind);
    if (!Off)
      return StringRef();
    return Section.substr(Off->Offset, Off->Length);
  }
  
  static void addAllTypesFromDWP(
      MCStreamer &Out, MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
      const DWARFUnitIndex &TUIndex, MCSection *OutputTypes, StringRef Types,
      const UnitIndexEntry &TUEntry, uint32_t &TypesOffset) {
    Out.SwitchSection(OutputTypes);
    for (const DWARFUnitIndex::Entry &E : TUIndex.getRows()) {
      auto *I = E.getContributions();
      if (!I)
        continue;
      auto P = TypeIndexEntries.insert(std::make_pair(E.getSignature(), TUEntry));
      if (!P.second)
        continue;
      auto &Entry = P.first->second;
      // Zero out the debug_info contribution
      Entry.Contributions[0] = {};
      for (auto Kind : TUIndex.getColumnKinds()) {
        if (!isSupportedSectionKind(Kind))
          continue;
        auto &C = Entry.Contributions[getContributionIndex(Kind)];
        C.Offset += I->Offset;
        C.Length = I->Length;
        ++I;
      }
      unsigned TypesIndex = getContributionIndex(DW_SECT_EXT_TYPES);
      auto &C = Entry.Contributions[TypesIndex];
      Out.emitBytes(Types.substr(
          C.Offset - TUEntry.Contributions[TypesIndex].Offset, C.Length));
      C.Offset = TypesOffset;
      TypesOffset += C.Length;
    }
  }
  
  static void addAllTypes(MCStreamer &Out,
                          MapVector<uint64_t, UnitIndexEntry> &TypeIndexEntries,
                          MCSection *OutputTypes,
                          const std::vector<StringRef> &TypesSections,
                          const UnitIndexEntry &CUEntry, uint32_t &TypesOffset) {
    for (StringRef Types : TypesSections) {
      Out.SwitchSection(OutputTypes);
      uint64_t Offset = 0;
      DataExtractor Data(Types, true, 0);
      while (Data.isValidOffset(Offset)) {
        UnitIndexEntry Entry = CUEntry;
        // Zero out the debug_info contribution
        Entry.Contributions[0] = {};
        auto &C = Entry.Contributions[getContributionIndex(DW_SECT_EXT_TYPES)];
        C.Offset = TypesOffset;
        auto PrevOffset = Offset;
        // Length of the unit, including the 4 byte length field.
        C.Length = Data.getU32(&Offset) + 4;
  
        Data.getU16(&Offset); // Version
        Data.getU32(&Offset); // Abbrev offset
        Data.getU8(&Offset);  // Address size
        auto Signature = Data.getU64(&Offset);
        Offset = PrevOffset + C.Length;
  
        auto P = TypeIndexEntries.insert(std::make_pair(Signature, Entry));
        if (!P.second)
          continue;
  
        Out.emitBytes(Types.substr(PrevOffset, C.Length));
        TypesOffset += C.Length;
      }
    }
  }
  
  static void
  writeIndexTable(MCStreamer &Out, ArrayRef<unsigned> ContributionOffsets,
                  const MapVector<uint64_t, UnitIndexEntry> &IndexEntries,
                  uint32_t DWARFUnitIndex::Entry::SectionContribution::*Field) {
    for (const auto &E : IndexEntries)
      for (size_t i = 0; i != array_lengthof(E.second.Contributions); ++i)
        if (ContributionOffsets[i])
          Out.emitIntValue(E.second.Contributions[i].*Field, 4);
  }
  
  static void
  writeIndex(MCStreamer &Out, MCSection *Section,
             ArrayRef<unsigned> ContributionOffsets,
             const MapVector<uint64_t, UnitIndexEntry> &IndexEntries) {
    if (IndexEntries.empty())
      return;
  
    unsigned Columns = 0;
    for (auto &C : ContributionOffsets)
      if (C)
        ++Columns;
  
    std::vector<unsigned> Buckets(NextPowerOf2(3 * IndexEntries.size() / 2));
    uint64_t Mask = Buckets.size() - 1;
    size_t i = 0;
    for (const auto &P : IndexEntries) {
      auto S = P.first;
      auto H = S & Mask;
      auto HP = ((S >> 32) & Mask) | 1;
      while (Buckets[H]) {
        assert(S != IndexEntries.begin()[Buckets[H] - 1].first &&
               "Duplicate unit");
        H = (H + HP) & Mask;
      }
      Buckets[H] = i + 1;
      ++i;
    }
  
    Out.SwitchSection(Section);
    Out.emitIntValue(2, 4);                   // Version
    Out.emitIntValue(Columns, 4);             // Columns
    Out.emitIntValue(IndexEntries.size(), 4); // Num Units
    Out.emitIntValue(Buckets.size(), 4);      // Num Buckets
  
    // Write the signatures.
    for (const auto &I : Buckets)
      Out.emitIntValue(I ? IndexEntries.begin()[I - 1].first : 0, 8);
  
    // Write the indexes.
    for (const auto &I : Buckets)
      Out.emitIntValue(I, 4);
  
    // Write the column headers (which sections will appear in the table)
    for (size_t i = 0; i != ContributionOffsets.size(); ++i)
      if (ContributionOffsets[i])
        Out.emitIntValue(getOnDiskSectionId(i), 4);
  
    // Write the offsets.
    writeIndexTable(Out, ContributionOffsets, IndexEntries,
                    &DWARFUnitIndex::Entry::SectionContribution::Offset);
  
    // Write the lengths.
    writeIndexTable(Out, ContributionOffsets, IndexEntries,
                    &DWARFUnitIndex::Entry::SectionContribution::Length);
  }
  
  static std::string buildDWODescription(StringRef Name, StringRef DWPName,
                                         StringRef DWOName) {
    std::string Text = "\'";
    Text += Name;
    Text += '\'';
    if (!DWPName.empty()) {
      Text += " (from ";
      if (!DWOName.empty()) {
        Text += '\'';
        Text += DWOName;
        Text += "' in ";
      }
      Text += '\'';
      Text += DWPName;
      Text += "')";
    }
    return Text;
  }
  
  static Error createError(StringRef Name, Error E) {
    return make_error<DWPError>(
        ("failure while decompressing compressed section: '" + Name + "', " +
         llvm::toString(std::move(E)))
            .str());
  }
  
  static Error
  handleCompressedSection(std::deque<SmallString<32>> &UncompressedSections,
                          StringRef &Name, StringRef &Contents) {
    if (!Decompressor::isGnuStyle(Name))
      return Error::success();
  
    Expected<Decompressor> Dec =
        Decompressor::create(Name, Contents, false /*IsLE*/, false /*Is64Bit*/);
    if (!Dec)
      return createError(Name, Dec.takeError());
  
    UncompressedSections.emplace_back();
    if (Error E = Dec->resizeAndDecompress(UncompressedSections.back()))
      return createError(Name, std::move(E));
  
    Name = Name.substr(2); // Drop ".z"
    Contents = UncompressedSections.back();
    return Error::success();
  }
  
  static Error handleSection(
      const StringMap<std::pair<MCSection *, DWARFSectionKind>> &KnownSections,
      const MCSection *StrSection, const MCSection *StrOffsetSection,
      const MCSection *TypesSection, const MCSection *CUIndexSection,
      const MCSection *TUIndexSection, const SectionRef &Section, MCStreamer &Out,
      std::deque<SmallString<32>> &UncompressedSections,
      uint32_t (&ContributionOffsets)[8], UnitIndexEntry &CurEntry,
      StringRef &CurStrSection, StringRef &CurStrOffsetSection,
      std::vector<StringRef> &CurTypesSection, StringRef &InfoSection,
      StringRef &AbbrevSection, StringRef &CurCUIndexSection,
      StringRef &CurTUIndexSection) {
    if (Section.isBSS())
      return Error::success();
  
    if (Section.isVirtual())
      return Error::success();
  
    Expected<StringRef> NameOrErr = Section.getName();
    if (!NameOrErr)
      return NameOrErr.takeError();
    StringRef Name = *NameOrErr;
  
    Expected<StringRef> ContentsOrErr = Section.getContents();
    if (!ContentsOrErr)
      return ContentsOrErr.takeError();
    StringRef Contents = *ContentsOrErr;
  
    if (auto Err = handleCompressedSection(UncompressedSections, Name, Contents))
      return Err;
  
    Name = Name.substr(Name.find_first_not_of("._"));
  
    auto SectionPair = KnownSections.find(Name);
    if (SectionPair == KnownSections.end())
      return Error::success();
  
    if (DWARFSectionKind Kind = SectionPair->second.second) {
      auto Index = getContributionIndex(Kind);
      if (Kind != DW_SECT_EXT_TYPES) {
        CurEntry.Contributions[Index].Offset = ContributionOffsets[Index];
        ContributionOffsets[Index] +=
            (CurEntry.Contributions[Index].Length = Contents.size());
      }
  
      switch (Kind) {
      case DW_SECT_INFO:
        InfoSection = Contents;
        break;
      case DW_SECT_ABBREV:
        AbbrevSection = Contents;
        break;
      default:
        break;
      }
    }
  
    MCSection *OutSection = SectionPair->second.first;
    if (OutSection == StrOffsetSection)
      CurStrOffsetSection = Contents;
    else if (OutSection == StrSection)
      CurStrSection = Contents;
    else if (OutSection == TypesSection)
      CurTypesSection.push_back(Contents);
    else if (OutSection == CUIndexSection)
      CurCUIndexSection = Contents;
    else if (OutSection == TUIndexSection)
      CurTUIndexSection = Contents;
    else {
      Out.SwitchSection(OutSection);
      Out.emitBytes(Contents);
    }
    return Error::success();
  }
  
  static Error
  buildDuplicateError(const std::pair<uint64_t, UnitIndexEntry> &PrevE,
                      const CompileUnitIdentifiers &ID, StringRef DWPName) {
    return make_error<DWPError>(
        std::string("duplicate DWO ID (") + utohexstr(PrevE.first) + ") in " +
        buildDWODescription(PrevE.second.Name, PrevE.second.DWPName,
                            PrevE.second.DWOName) +
        " and " + buildDWODescription(ID.Name, DWPName, ID.DWOName));
  }
  
  static Expected<SmallVector<std::string, 16>>
  getDWOFilenames(StringRef ExecFilename) {
    auto ErrOrObj = object::ObjectFile::createObjectFile(ExecFilename);
    if (!ErrOrObj)
      return ErrOrObj.takeError();
  
    const ObjectFile &Obj = *ErrOrObj.get().getBinary();
    std::unique_ptr<DWARFContext> DWARFCtx = DWARFContext::create(Obj);
  
    SmallVector<std::string, 16> DWOPaths;
    for (const auto &CU : DWARFCtx->compile_units()) {
      const DWARFDie &Die = CU->getUnitDIE();
      std::string DWOName = dwarf::toString(
          Die.find({dwarf::DW_AT_dwo_name, dwarf::DW_AT_GNU_dwo_name}), "");
      if (DWOName.empty())
        continue;
      std::string DWOCompDir =
          dwarf::toString(Die.find(dwarf::DW_AT_comp_dir), "");
      if (!DWOCompDir.empty()) {
        SmallString<16> DWOPath(std::move(DWOName));
        sys::fs::make_absolute(DWOCompDir, DWOPath);
        DWOPaths.emplace_back(DWOPath.data(), DWOPath.size());
      } else {
        DWOPaths.push_back(std::move(DWOName));
      }
    }
    return std::move(DWOPaths);
  }
  
  static Error write(MCStreamer &Out, ArrayRef<std::string> Inputs) {
    const auto &MCOFI = *Out.getContext().getObjectFileInfo();
    MCSection *const StrSection = MCOFI.getDwarfStrDWOSection();
    MCSection *const StrOffsetSection = MCOFI.getDwarfStrOffDWOSection();
    MCSection *const TypesSection = MCOFI.getDwarfTypesDWOSection();
    MCSection *const CUIndexSection = MCOFI.getDwarfCUIndexSection();
    MCSection *const TUIndexSection = MCOFI.getDwarfTUIndexSection();
    const StringMap<std::pair<MCSection *, DWARFSectionKind>> KnownSections = {
        {"debug_info.dwo", {MCOFI.getDwarfInfoDWOSection(), DW_SECT_INFO}},
        {"debug_types.dwo", {MCOFI.getDwarfTypesDWOSection(), DW_SECT_EXT_TYPES}},
        {"debug_str_offsets.dwo", {StrOffsetSection, DW_SECT_STR_OFFSETS}},
        {"debug_str.dwo", {StrSection, static_cast<DWARFSectionKind>(0)}},
        {"debug_loc.dwo", {MCOFI.getDwarfLocDWOSection(), DW_SECT_EXT_LOC}},
        {"debug_line.dwo", {MCOFI.getDwarfLineDWOSection(), DW_SECT_LINE}},
        {"debug_abbrev.dwo", {MCOFI.getDwarfAbbrevDWOSection(), DW_SECT_ABBREV}},
        {"debug_cu_index", {CUIndexSection, static_cast<DWARFSectionKind>(0)}},
        {"debug_tu_index", {TUIndexSection, static_cast<DWARFSectionKind>(0)}}};
  
    MapVector<uint64_t, UnitIndexEntry> IndexEntries;
    MapVector<uint64_t, UnitIndexEntry> TypeIndexEntries;
  
    uint32_t ContributionOffsets[8] = {};
  
    DWPStringPool Strings(Out, StrSection);
  
    SmallVector<OwningBinary<object::ObjectFile>, 128> Objects;
    Objects.reserve(Inputs.size());
  
    std::deque<SmallString<32>> UncompressedSections;
  
    for (const auto &Input : Inputs) {
      auto ErrOrObj = object::ObjectFile::createObjectFile(Input);
      if (!ErrOrObj)
        return ErrOrObj.takeError();
  
      auto &Obj = *ErrOrObj->getBinary();
      Objects.push_back(std::move(*ErrOrObj));
  
      UnitIndexEntry CurEntry = {};
  
      StringRef CurStrSection;
      StringRef CurStrOffsetSection;
      std::vector<StringRef> CurTypesSection;
      StringRef InfoSection;
      StringRef AbbrevSection;
      StringRef CurCUIndexSection;
      StringRef CurTUIndexSection;
  
      for (const auto &Section : Obj.sections())
        if (auto Err = handleSection(
                KnownSections, StrSection, StrOffsetSection, TypesSection,
                CUIndexSection, TUIndexSection, Section, Out,
                UncompressedSections, ContributionOffsets, CurEntry,
                CurStrSection, CurStrOffsetSection, CurTypesSection, InfoSection,
                AbbrevSection, CurCUIndexSection, CurTUIndexSection))
          return Err;
  
      if (InfoSection.empty())
        continue;
  
      writeStringsAndOffsets(Out, Strings, StrOffsetSection, CurStrSection,
                             CurStrOffsetSection);
  
      if (CurCUIndexSection.empty()) {
        Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
            AbbrevSection, InfoSection, CurStrOffsetSection, CurStrSection);
        if (!EID)
          return createFileError(Input, EID.takeError());
        const auto &ID = *EID;
        auto P = IndexEntries.insert(std::make_pair(ID.Signature, CurEntry));
        if (!P.second)
          return buildDuplicateError(*P.first, ID, "");
        P.first->second.Name = ID.Name;
        P.first->second.DWOName = ID.DWOName;
        addAllTypes(Out, TypeIndexEntries, TypesSection, CurTypesSection,
                    CurEntry,
                    ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES)]);
        continue;
      }
  
      DWARFUnitIndex CUIndex(DW_SECT_INFO);
      DataExtractor CUIndexData(CurCUIndexSection, Obj.isLittleEndian(), 0);
      if (!CUIndex.parse(CUIndexData))
        return make_error<DWPError>("failed to parse cu_index");
      if (CUIndex.getVersion() != 2)
        return make_error<DWPError>(
            "unsupported cu_index version: " + utostr(CUIndex.getVersion()) +
            " (only version 2 is supported)");
  
      for (const DWARFUnitIndex::Entry &E : CUIndex.getRows()) {
        auto *I = E.getContributions();
        if (!I)
          continue;
        auto P = IndexEntries.insert(std::make_pair(E.getSignature(), CurEntry));
        Expected<CompileUnitIdentifiers> EID = getCUIdentifiers(
            getSubsection(AbbrevSection, E, DW_SECT_ABBREV),
            getSubsection(InfoSection, E, DW_SECT_INFO),
            getSubsection(CurStrOffsetSection, E, DW_SECT_STR_OFFSETS),
            CurStrSection);
        if (!EID)
          return createFileError(Input, EID.takeError());
        const auto &ID = *EID;
        if (!P.second)
          return buildDuplicateError(*P.first, ID, Input);
        auto &NewEntry = P.first->second;
        NewEntry.Name = ID.Name;
        NewEntry.DWOName = ID.DWOName;
        NewEntry.DWPName = Input;
        for (auto Kind : CUIndex.getColumnKinds()) {
          if (!isSupportedSectionKind(Kind))
            continue;
          auto &C = NewEntry.Contributions[getContributionIndex(Kind)];
          C.Offset += I->Offset;
          C.Length = I->Length;
          ++I;
        }
      }
  
      if (!CurTypesSection.empty()) {
        if (CurTypesSection.size() != 1)
          return make_error<DWPError>("multiple type unit sections in .dwp file");
        DWARFUnitIndex TUIndex(DW_SECT_EXT_TYPES);
        DataExtractor TUIndexData(CurTUIndexSection, Obj.isLittleEndian(), 0);
        if (!TUIndex.parse(TUIndexData))
          return make_error<DWPError>("failed to parse tu_index");
        if (TUIndex.getVersion() != 2)
          return make_error<DWPError>(
              "unsupported tu_index version: " + utostr(TUIndex.getVersion()) +
              " (only version 2 is supported)");
  
        addAllTypesFromDWP(
            Out, TypeIndexEntries, TUIndex, TypesSection, CurTypesSection.front(),
            CurEntry,
            ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES)]);
      }
    }
  
    // Lie about there being no info contributions so the TU index only includes
    // the type unit contribution
    ContributionOffsets[0] = 0;
    writeIndex(Out, MCOFI.getDwarfTUIndexSection(), ContributionOffsets,
               TypeIndexEntries);
  
    // Lie about the type contribution
    ContributionOffsets[getContributionIndex(DW_SECT_EXT_TYPES)] = 0;
    // Unlie about the info contribution
    ContributionOffsets[0] = 1;
  
    writeIndex(Out, MCOFI.getDwarfCUIndexSection(), ContributionOffsets,
               IndexEntries);
  
    return Error::success();
  }
  
  static int error(const Twine &Error, const Twine &Context) {
    errs() << Twine("while processing ") + Context + ":\n";
    errs() << Twine("error: ") + Error + "\n";
    return 1;
  }
  
  static Expected<Triple> readTargetTriple(StringRef FileName) {
    auto ErrOrObj = object::ObjectFile::createObjectFile(FileName);
    if (!ErrOrObj)
      return ErrOrObj.takeError();
  
    return ErrOrObj->getBinary()->makeTriple();
  }
  
  int main(int argc, char **argv) {
    InitLLVM X(argc, argv);
  
    cl::ParseCommandLineOptions(argc, argv, "merge split dwarf (.dwo) files\n");
  
    llvm::InitializeAllTargetInfos();
    llvm::InitializeAllTargetMCs();
    llvm::InitializeAllTargets();
    llvm::InitializeAllAsmPrinters();
  
    std::vector<std::string> DWOFilenames = InputFiles;
    for (const auto &ExecFilename : ExecFilenames) {
      auto DWOs = getDWOFilenames(ExecFilename);
      if (!DWOs) {
        logAllUnhandledErrors(DWOs.takeError(), WithColor::error());
        return 1;
      }
      DWOFilenames.insert(DWOFilenames.end(),
                          std::make_move_iterator(DWOs->begin()),
                          std::make_move_iterator(DWOs->end()));
    }
  
    if (DWOFilenames.empty())
      return 0;
  
    std::string ErrorStr;
    StringRef Context = "dwarf streamer init";
  
    auto ErrOrTriple = readTargetTriple(DWOFilenames.front());
    if (!ErrOrTriple) {
      logAllUnhandledErrors(ErrOrTriple.takeError(), WithColor::error());
      return 1;
    }
  
    // Get the target.
    const Target *TheTarget =
        TargetRegistry::lookupTarget("", *ErrOrTriple, ErrorStr);
    if (!TheTarget)
      return error(ErrorStr, Context);
    std::string TripleName = ErrOrTriple->getTriple();
  
    // Create all the MC Objects.
    std::unique_ptr<MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TripleName));
    if (!MRI)
      return error(Twine("no register info for target ") + TripleName, Context);
  
    MCTargetOptions MCOptions = llvm::mc::InitMCTargetOptionsFromFlags();
    std::unique_ptr<MCAsmInfo> MAI(
        TheTarget->createMCAsmInfo(*MRI, TripleName, MCOptions));
    if (!MAI)
      return error("no asm info for target " + TripleName, Context);
  
    MCObjectFileInfo MOFI;
    MCContext MC(MAI.get(), MRI.get(), &MOFI);
    MOFI.InitMCObjectFileInfo(*ErrOrTriple, /*PIC*/ false, MC);
  
    std::unique_ptr<MCSubtargetInfo> MSTI(
        TheTarget->createMCSubtargetInfo(TripleName, "", ""));
    if (!MSTI)
      return error("no subtarget info for target " + TripleName, Context);
  
    MCTargetOptions Options;
    auto MAB = TheTarget->createMCAsmBackend(*MSTI, *MRI, Options);
    if (!MAB)
      return error("no asm backend for target " + TripleName, Context);
  
    std::unique_ptr<MCInstrInfo> MII(TheTarget->createMCInstrInfo());
    if (!MII)
      return error("no instr info info for target " + TripleName, Context);
  
    MCCodeEmitter *MCE = TheTarget->createMCCodeEmitter(*MII, *MRI, MC);
    if (!MCE)
      return error("no code emitter for target " + TripleName, Context);
  
    // Create the output file.
    std::error_code EC;
    ToolOutputFile OutFile(OutputFilename, EC, sys::fs::OF_None);
    Optional<buffer_ostream> BOS;
    raw_pwrite_stream *OS;
    if (EC)
      return error(Twine(OutputFilename) + ": " + EC.message(), Context);
    if (OutFile.os().supportsSeeking()) {
      OS = &OutFile.os();
    } else {
      BOS.emplace(OutFile.os());
      OS = BOS.getPointer();
    }
  
    std::unique_ptr<MCStreamer> MS(TheTarget->createMCObjectStreamer(
        *ErrOrTriple, MC, std::unique_ptr<MCAsmBackend>(MAB),
        MAB->createObjectWriter(*OS), std::unique_ptr<MCCodeEmitter>(MCE), *MSTI,
        MCOptions.MCRelaxAll, MCOptions.MCIncrementalLinkerCompatible,
        /*DWARFMustBeAtTheEnd*/ false));
    if (!MS)
      return error("no object streamer for target " + TripleName, Context);
  
    if (auto Err = write(*MS, DWOFilenames)) {
      logAllUnhandledErrors(std::move(Err), WithColor::error());
      return 1;
    }
  
    MS->Finish();
    OutFile.keep();
    return 0;
  }
  