C++ StringRef::bytes_begin方法代码示例

// Populates the FileHeader reference by reading the first 32 bytes of the file.
Error readBinaryFormatHeader(StringRef Data, XRayFileHeader &FileHeader) {
  // FIXME: Maybe deduce whether the data is little or big-endian using some
  // magic bytes in the beginning of the file?

  // First 32 bytes of the file will always be the header. We assume a certain
  // format here:
  //
  //   (2)   uint16 : version
  //   (2)   uint16 : type
  //   (4)   uint32 : bitfield
  //   (8)   uint64 : cycle frequency
  //   (16)  -      : padding

  DataExtractor HeaderExtractor(Data, true, 8);
  uint32_t OffsetPtr = 0;
  FileHeader.Version = HeaderExtractor.getU16(&OffsetPtr);
  FileHeader.Type = HeaderExtractor.getU16(&OffsetPtr);
  uint32_t Bitfield = HeaderExtractor.getU32(&OffsetPtr);
  FileHeader.ConstantTSC = Bitfield & 1uL;
  FileHeader.NonstopTSC = Bitfield & 1uL << 1;
  FileHeader.CycleFrequency = HeaderExtractor.getU64(&OffsetPtr);
  std::memcpy(&FileHeader.FreeFormData, Data.bytes_begin() + OffsetPtr, 16);
  if (FileHeader.Version != 1)
    return make_error<StringError>(
        Twine("Unsupported XRay file version: ") + Twine(FileHeader.Version),
        std::make_error_code(std::errc::invalid_argument));
  return Error::success();
}

static bool isIntrinsicSourceOfDivergence(const TargetIntrinsicInfo *TII,
                                          const IntrinsicInst *I) {
  switch (I->getIntrinsicID()) {
  default:
    return false;
  case Intrinsic::not_intrinsic:
    // This means we have an intrinsic that isn't defined in
    // IntrinsicsAMDGPU.td
    break;

  case Intrinsic::amdgcn_interp_p1:
  case Intrinsic::amdgcn_interp_p2:
  case Intrinsic::amdgcn_mbcnt_hi:
  case Intrinsic::amdgcn_mbcnt_lo:
  case Intrinsic::r600_read_tidig_x:
  case Intrinsic::r600_read_tidig_y:
  case Intrinsic::r600_read_tidig_z:
    return true;
  }

  StringRef Name = I->getCalledFunction()->getName();
  switch (TII->lookupName((const char *)Name.bytes_begin(), Name.size())) {
  default:
    return false;
  case AMDGPUIntrinsic::SI_tid:
  case AMDGPUIntrinsic::SI_fs_interp:
  case AMDGPUIntrinsic::SI_fs_constant:
    return true;
  }
}

static bool isIntrinsicSourceOfDivergence(const TargetIntrinsicInfo *TII,
                                          const IntrinsicInst *I) {
  switch (I->getIntrinsicID()) {
  default:
    return false;
  case Intrinsic::not_intrinsic:
    // This means we have an intrinsic that isn't defined in
    // IntrinsicsAMDGPU.td
    break;

  case Intrinsic::amdgcn_workitem_id_x:
  case Intrinsic::amdgcn_workitem_id_y:
  case Intrinsic::amdgcn_workitem_id_z:
  case Intrinsic::amdgcn_interp_p1:
  case Intrinsic::amdgcn_interp_p2:
  case Intrinsic::amdgcn_mbcnt_hi:
  case Intrinsic::amdgcn_mbcnt_lo:
  case Intrinsic::r600_read_tidig_x:
  case Intrinsic::r600_read_tidig_y:
  case Intrinsic::r600_read_tidig_z:
  case Intrinsic::amdgcn_image_atomic_swap:
  case Intrinsic::amdgcn_image_atomic_add:
  case Intrinsic::amdgcn_image_atomic_sub:
  case Intrinsic::amdgcn_image_atomic_smin:
  case Intrinsic::amdgcn_image_atomic_umin:
  case Intrinsic::amdgcn_image_atomic_smax:
  case Intrinsic::amdgcn_image_atomic_umax:
  case Intrinsic::amdgcn_image_atomic_and:
  case Intrinsic::amdgcn_image_atomic_or:
  case Intrinsic::amdgcn_image_atomic_xor:
  case Intrinsic::amdgcn_image_atomic_inc:
  case Intrinsic::amdgcn_image_atomic_dec:
  case Intrinsic::amdgcn_image_atomic_cmpswap:
  case Intrinsic::amdgcn_buffer_atomic_swap:
  case Intrinsic::amdgcn_buffer_atomic_add:
  case Intrinsic::amdgcn_buffer_atomic_sub:
  case Intrinsic::amdgcn_buffer_atomic_smin:
  case Intrinsic::amdgcn_buffer_atomic_umin:
  case Intrinsic::amdgcn_buffer_atomic_smax:
  case Intrinsic::amdgcn_buffer_atomic_umax:
  case Intrinsic::amdgcn_buffer_atomic_and:
  case Intrinsic::amdgcn_buffer_atomic_or:
  case Intrinsic::amdgcn_buffer_atomic_xor:
  case Intrinsic::amdgcn_buffer_atomic_cmpswap:
    return true;
  }

  StringRef Name = I->getCalledFunction()->getName();
  switch (TII->lookupName((const char *)Name.bytes_begin(), Name.size())) {
  default:
    return false;
  case AMDGPUIntrinsic::SI_tid:
  case AMDGPUIntrinsic::SI_fs_interp:
    return true;
  }
}

Error llvm::codeview::consume(ArrayRef<uint8_t> &Data, StringRef &Item) {
  if (Data.empty())
    return make_error<CodeViewError>(cv_error_code::corrupt_record,
                                     "Null terminated string buffer is empty!");

  StringRef Rest;
  std::tie(Item, Rest) = getBytesAsCharacters(Data).split('\0');
  // We expect this to be null terminated.  If it was not, it is an error.
  if (Data.size() == Item.size())
    return make_error<CodeViewError>(cv_error_code::corrupt_record,
                                     "Expected null terminator!");

  Data = ArrayRef<uint8_t>(Rest.bytes_begin(), Rest.bytes_end());
  return Error::success();
}

static Error
loadObj(StringRef Filename, object::OwningBinary<object::ObjectFile> &ObjFile,
          InstrumentationMap::SledContainer &Sleds,
          InstrumentationMap::FunctionAddressMap &FunctionAddresses,
          InstrumentationMap::FunctionAddressReverseMap &FunctionIds) {
  InstrumentationMap Map;

  // Find the section named "xray_instr_map".
  if ((!ObjFile.getBinary()->isELF() && !ObjFile.getBinary()->isMachO()) ||
      !(ObjFile.getBinary()->getArch() == Triple::x86_64 ||
        ObjFile.getBinary()->getArch() == Triple::ppc64le))
    return make_error<StringError>(
        "File format not supported (only does ELF and Mach-O little endian 64-bit).",
        std::make_error_code(std::errc::not_supported));

  StringRef Contents = "";
  const auto &Sections = ObjFile.getBinary()->sections();
  auto I = llvm::find_if(Sections, [&](object::SectionRef Section) {
    StringRef Name = "";
    if (Section.getName(Name))
      return false;
    return Name == "xray_instr_map";
  });

  if (I == Sections.end())
    return make_error<StringError>(
        "Failed to find XRay instrumentation map.",
        std::make_error_code(std::errc::executable_format_error));

  if (I->getContents(Contents))
    return errorCodeToError(
        std::make_error_code(std::errc::executable_format_error));

  RelocMap Relocs;
  if (ObjFile.getBinary()->isELF()) {
    uint32_t RelativeRelocation = [](object::ObjectFile *ObjFile) {
      if (const auto *ELFObj = dyn_cast<object::ELF32LEObjectFile>(ObjFile))
        return ELFObj->getELFFile()->getRelativeRelocationType();
      else if (const auto *ELFObj = dyn_cast<object::ELF32BEObjectFile>(ObjFile))
        return ELFObj->getELFFile()->getRelativeRelocationType();
      else if (const auto *ELFObj = dyn_cast<object::ELF64LEObjectFile>(ObjFile))
        return ELFObj->getELFFile()->getRelativeRelocationType();
      else if (const auto *ELFObj = dyn_cast<object::ELF64BEObjectFile>(ObjFile))
        return ELFObj->getELFFile()->getRelativeRelocationType();
      else
        return static_cast<uint32_t>(0);
    }(ObjFile.getBinary());

    for (const object::SectionRef &Section : Sections) {
      for (const object::RelocationRef &Reloc : Section.relocations()) {
        if (Reloc.getType() != RelativeRelocation)
          continue;
        if (auto AddendOrErr = object::ELFRelocationRef(Reloc).getAddend())
          Relocs.insert({Reloc.getOffset(), *AddendOrErr});
      }
    }
  }

  // Copy the instrumentation map data into the Sleds data structure.
  auto C = Contents.bytes_begin();
  static constexpr size_t ELF64SledEntrySize = 32;

  if ((C - Contents.bytes_end()) % ELF64SledEntrySize != 0)
    return make_error<StringError>(
        Twine("Instrumentation map entries not evenly divisible by size of "
              "an XRay sled entry in ELF64."),
        std::make_error_code(std::errc::executable_format_error));

  auto RelocateOrElse = [&](uint32_t Offset, uint64_t Address) {
    if (!Address) {
      uint64_t A = I->getAddress() + C - Contents.bytes_begin() + Offset;
      RelocMap::const_iterator R = Relocs.find(A);
      if (R != Relocs.end())
        return R->second;
    }
    return Address;
  };

  int32_t FuncId = 1;
  uint64_t CurFn = 0;
  for (; C != Contents.bytes_end(); C += ELF64SledEntrySize) {
    DataExtractor Extractor(
        StringRef(reinterpret_cast<const char *>(C), ELF64SledEntrySize), true,
        8);
    Sleds.push_back({});
    auto &Entry = Sleds.back();
    uint32_t OffsetPtr = 0;
    uint32_t AddrOff = OffsetPtr;
    Entry.Address = RelocateOrElse(AddrOff, Extractor.getU64(&OffsetPtr));
    uint32_t FuncOff = OffsetPtr;
    Entry.Function = RelocateOrElse(FuncOff, Extractor.getU64(&OffsetPtr));
    auto Kind = Extractor.getU8(&OffsetPtr);
    static constexpr SledEntry::FunctionKinds Kinds[] = {
        SledEntry::FunctionKinds::ENTRY, SledEntry::FunctionKinds::EXIT,
        SledEntry::FunctionKinds::TAIL,
        SledEntry::FunctionKinds::LOG_ARGS_ENTER,
        SledEntry::FunctionKinds::CUSTOM_EVENT};
    if (Kind >= sizeof(Kinds))
      return errorCodeToError(
          std::make_error_code(std::errc::executable_format_error));
//.........这里部分代码省略.........

Error llvm::codeview::consume(StringRef &Data, uint32_t &Item) {
  ArrayRef<uint8_t> Bytes(Data.bytes_begin(), Data.bytes_end());
  auto EC = consume(Bytes, Item);
  Data = StringRef(reinterpret_cast<const char *>(Bytes.data()), Bytes.size());
  return EC;
}

// Returns true if S encloses T.
static bool encloses(StringRef S, StringRef T) {
  return S.bytes_begin() <= T.bytes_begin() && T.bytes_end() <= S.bytes_end();
}

Error BinaryStreamWriter::writeFixedString(StringRef Str) {
  return writeBytes(ArrayRef<uint8_t>(Str.bytes_begin(), Str.bytes_end()));
}

BinaryStreamRef::BinaryStreamRef(StringRef Data, endianness Endian)
    : BinaryStreamRef(makeArrayRef(Data.bytes_begin(), Data.bytes_end()),
                      Endian) {}