void MCMachOStreamer::Finish() {
  // We have to set the fragment atom associations so we can relax properly for
  // Mach-O.

  // First, scan the symbol table to build a lookup table from fragments to
  // defining symbols.
  DenseMap<const MCFragment*, MCSymbolData*> DefiningSymbolMap;
  for (MCAssembler::symbol_iterator it = getAssembler().symbol_begin(),
         ie = getAssembler().symbol_end(); it != ie; ++it) {
    if (getAssembler().isSymbolLinkerVisible(it->getSymbol()) &&
        it->getFragment()) {
      // An atom defining symbol should never be internal to a fragment.
      assert(it->getOffset() == 0 && "Invalid offset in atom defining symbol!");
      DefiningSymbolMap[it->getFragment()] = it;
    }
  }

  // Set the fragment atom associations by tracking the last seen atom defining
  // symbol.
  for (MCAssembler::iterator it = getAssembler().begin(),
         ie = getAssembler().end(); it != ie; ++it) {
    MCSymbolData *CurrentAtom = 0;
    for (MCSectionData::iterator it2 = it->begin(),
           ie2 = it->end(); it2 != ie2; ++it2) {
      if (MCSymbolData *SD = DefiningSymbolMap.lookup(it2))
        CurrentAtom = SD;
      it2->setAtom(CurrentAtom);
    }
  }

  this->MCObjectStreamer::Finish();
}
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/// ComputeSymbolTable - Compute the symbol table data
///
/// \param StringTable [out] - The string table data.
/// \param StringIndexMap [out] - Map from symbol names to offsets in the
/// string table.
void MachObjectWriter::
ComputeSymbolTable(MCAssembler &Asm, SmallString<256> &StringTable,
                   std::vector<MachSymbolData> &LocalSymbolData,
                   std::vector<MachSymbolData> &ExternalSymbolData,
                   std::vector<MachSymbolData> &UndefinedSymbolData) {
  // Build section lookup table.
  DenseMap<const MCSection*, uint8_t> SectionIndexMap;
  unsigned Index = 1;
  for (MCAssembler::iterator it = Asm.begin(),
         ie = Asm.end(); it != ie; ++it, ++Index)
    SectionIndexMap[&it->getSection()] = Index;
  assert(Index <= 256 && "Too many sections!");

  // Index 0 is always the empty string.
  StringMap<uint64_t> StringIndexMap;
  StringTable += '\x00';

  // Build the symbol arrays and the string table, but only for non-local
  // symbols.
  //
  // The particular order that we collect the symbols and create the string
  // table, then sort the symbols is chosen to match 'as'. Even though it
  // doesn't matter for correctness, this is important for letting us diff .o
  // files.
  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
         ie = Asm.symbol_end(); it != ie; ++it) {
    const MCSymbol &Symbol = it->getSymbol();

    // Ignore non-linker visible symbols.
    if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
      continue;

    if (!it->isExternal() && !Symbol.isUndefined())
      continue;

    uint64_t &Entry = StringIndexMap[Symbol.getName()];
    if (!Entry) {
      Entry = StringTable.size();
      StringTable += Symbol.getName();
      StringTable += '\x00';
    }

    MachSymbolData MSD;
    MSD.SymbolData = it;
    MSD.StringIndex = Entry;

    if (Symbol.isUndefined()) {
      MSD.SectionIndex = 0;
      UndefinedSymbolData.push_back(MSD);
    } else if (Symbol.isAbsolute()) {
      MSD.SectionIndex = 0;
      ExternalSymbolData.push_back(MSD);
    } else {
      MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
      assert(MSD.SectionIndex && "Invalid section index!");
      ExternalSymbolData.push_back(MSD);
    }
  }

  // Now add the data for local symbols.
  for (MCAssembler::symbol_iterator it = Asm.symbol_begin(),
         ie = Asm.symbol_end(); it != ie; ++it) {
    const MCSymbol &Symbol = it->getSymbol();

    // Ignore non-linker visible symbols.
    if (!Asm.isSymbolLinkerVisible(it->getSymbol()))
      continue;

    if (it->isExternal() || Symbol.isUndefined())
      continue;

    uint64_t &Entry = StringIndexMap[Symbol.getName()];
    if (!Entry) {
      Entry = StringTable.size();
      StringTable += Symbol.getName();
      StringTable += '\x00';
    }

    MachSymbolData MSD;
    MSD.SymbolData = it;
    MSD.StringIndex = Entry;

    if (Symbol.isAbsolute()) {
      MSD.SectionIndex = 0;
      LocalSymbolData.push_back(MSD);
    } else {
      MSD.SectionIndex = SectionIndexMap.lookup(&Symbol.getSection());
      assert(MSD.SectionIndex && "Invalid section index!");
      LocalSymbolData.push_back(MSD);
    }
  }

  // External and undefined symbols are required to be in lexicographic order.
  std::sort(ExternalSymbolData.begin(), ExternalSymbolData.end());
  std::sort(UndefinedSymbolData.begin(), UndefinedSymbolData.end());

  // Set the symbol indices.
  Index = 0;
  for (unsigned i = 0, e = LocalSymbolData.size(); i != e; ++i)
    LocalSymbolData[i].SymbolData->setIndex(Index++);
  for (unsigned i = 0, e = ExternalSymbolData.size(); i != e; ++i)
    ExternalSymbolData[i].SymbolData->setIndex(Index++);
  for (unsigned i = 0, e = UndefinedSymbolData.size(); i != e; ++i)
    UndefinedSymbolData[i].SymbolData->setIndex(Index++);

  // The string table is padded to a multiple of 4.
  while (StringTable.size() % 4)
    StringTable += '\x00';
}