C++ MCSection::getAlignment方法代码示例

void MCWinCOFFStreamer::EmitCOFFSafeSEH(MCSymbol const *Symbol) {
  // SafeSEH is a feature specific to 32-bit x86.  It does not exist (and is
  // unnecessary) on all platforms which use table-based exception dispatch.
  if (getContext().getObjectFileInfo()->getTargetTriple().getArch() !=
      Triple::x86)
    return;

  const MCSymbolCOFF *CSymbol = cast<MCSymbolCOFF>(Symbol);
  if (CSymbol->isSafeSEH())
    return;

  MCSection *SXData = getContext().getObjectFileInfo()->getSXDataSection();
  getAssembler().registerSection(*SXData);
  if (SXData->getAlignment() < 4)
    SXData->setAlignment(4);

  new MCSafeSEHFragment(Symbol, SXData);

  getAssembler().registerSymbol(*Symbol);
  CSymbol->setIsSafeSEH();

  // The Microsoft linker requires that the symbol type of a handler be
  // function. Go ahead and oblige it here.
  CSymbol->setType(COFF::IMAGE_SYM_DTYPE_FUNCTION
                   << COFF::SCT_COMPLEX_TYPE_SHIFT);
}

void ELFObjectWriter::writeSectionData(const MCAssembler &Asm, MCSection &Sec,
                                       const MCAsmLayout &Layout) {
  MCSectionELF &Section = static_cast<MCSectionELF &>(Sec);
  StringRef SectionName = Section.getSectionName();

  auto &MC = Asm.getContext();
  const auto &MAI = MC.getAsmInfo();

  // Compressing debug_frame requires handling alignment fragments which is
  // more work (possibly generalizing MCAssembler.cpp:writeFragment to allow
  // for writing to arbitrary buffers) for little benefit.
  bool CompressionEnabled =
      MAI->compressDebugSections() != DebugCompressionType::None;
  if (!CompressionEnabled || !SectionName.startswith(".debug_") ||
      SectionName == ".debug_frame") {
    Asm.writeSectionData(&Section, Layout);
    return;
  }

  assert((MAI->compressDebugSections() == DebugCompressionType::Z ||
          MAI->compressDebugSections() == DebugCompressionType::GNU) &&
         "expected zlib or zlib-gnu style compression");

  SmallVector<char, 128> UncompressedData;
  raw_svector_ostream VecOS(UncompressedData);
  raw_pwrite_stream &OldStream = getStream();
  setStream(VecOS);
  Asm.writeSectionData(&Section, Layout);
  setStream(OldStream);

  SmallVector<char, 128> CompressedContents;
  if (Error E = zlib::compress(
          StringRef(UncompressedData.data(), UncompressedData.size()),
          CompressedContents)) {
    consumeError(std::move(E));
    getStream() << UncompressedData;
    return;
  }

  bool ZlibStyle = MAI->compressDebugSections() == DebugCompressionType::Z;
  if (!maybeWriteCompression(UncompressedData.size(), CompressedContents,
                             ZlibStyle, Sec.getAlignment())) {
    getStream() << UncompressedData;
    return;
  }

  if (ZlibStyle)
    // Set the compressed flag. That is zlib style.
    Section.setFlags(Section.getFlags() | ELF::SHF_COMPRESSED);
  else
    // Add "z" prefix to section name. This is zlib-gnu style.
    MC.renameELFSection(&Section, (".z" + SectionName.drop_front(1)).str());
  getStream() << CompressedContents;
}

void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
                                            int64_t Value,
                                            unsigned ValueSize,
                                            unsigned MaxBytesToEmit) {
  if (MaxBytesToEmit == 0)
    MaxBytesToEmit = ByteAlignment;
  insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));

  // Update the maximum alignment on the current section if necessary.
  MCSection *CurSec = getCurrentSection().first;
  if (ByteAlignment > CurSec->getAlignment())
    CurSec->setAlignment(ByteAlignment);
}

void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *Symbol, uint64_t Size,
                                              unsigned ByteAlignment) {
  assert(!Symbol->isInSection() && "Symbol must not already have a section!");

  MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
  getAssembler().registerSection(*Section);
  if (Section->getAlignment() < ByteAlignment)
    Section->setAlignment(ByteAlignment);

  getAssembler().registerSymbol(*Symbol);
  Symbol->setExternal(false);

  if (ByteAlignment != 1)
    new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0,
                        ByteAlignment, Section);

  MCFillFragment *Fragment = new MCFillFragment(
      /*Value=*/0, Size, Section);
  Symbol->setFragment(Fragment);
}

void MCWinCOFFStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
                                              unsigned ByteAlignment) {
  auto *Symbol = cast<MCSymbolCOFF>(S);

  MCSection *Section = getContext().getObjectFileInfo()->getBSSSection();
  getAssembler().registerSection(*Section);
  if (Section->getAlignment() < ByteAlignment)
    Section->setAlignment(ByteAlignment);

  getAssembler().registerSymbol(*Symbol);
  Symbol->setExternal(false);

  if (ByteAlignment != 1)
    new MCAlignFragment(ByteAlignment, /*Value=*/0, /*ValueSize=*/0,
                        ByteAlignment, Section);

  MCFillFragment *Fragment = new MCFillFragment(
      /*Value=*/0, Size, Section);
  Symbol->setFragment(Fragment);
}