Method getLTOInfo

src/lib/Bitcode/Reader/BitcodeReader.cpp:5973–6019

Check if the given bitcode buffer contains a global value summary block.

// Check if the given bitcode buffer contains a global value summary block.
Expected<BitcodeLTOInfo> BitcodeModule::getLTOInfo() {
  BitstreamCursor Stream(Buffer);
  Stream.JumpToBit(ModuleBit);

  if (Stream.EnterSubBlock(bitc::MODULE_BLOCK_ID))
    return error("Invalid record");

  while (true) {
    BitstreamEntry Entry = Stream.advance();

    switch (Entry.Kind) {
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      return BitcodeLTOInfo{/*IsThinLTO=*/false, /*HasSummary=*/false,
                            /*EnableSplitLTOUnit=*/false};

    case BitstreamEntry::SubBlock:
      if (Entry.ID == bitc::GLOBALVAL_SUMMARY_BLOCK_ID) {
        Expected<bool> EnableSplitLTOUnit =
            getEnableSplitLTOUnitFlag(Stream, Entry.ID);
        if (!EnableSplitLTOUnit)
          return EnableSplitLTOUnit.takeError();
        return BitcodeLTOInfo{/*IsThinLTO=*/true, /*HasSummary=*/true,
                              *EnableSplitLTOUnit};
      }

      if (Entry.ID == bitc::FULL_LTO_GLOBALVAL_SUMMARY_BLOCK_ID) {
        Expected<bool> EnableSplitLTOUnit =
            getEnableSplitLTOUnitFlag(Stream, Entry.ID);
        if (!EnableSplitLTOUnit)
          return EnableSplitLTOUnit.takeError();
        return BitcodeLTOInfo{/*IsThinLTO=*/false, /*HasSummary=*/true,
                              *EnableSplitLTOUnit};
      }

      // Ignore other sub-blocks.
      if (Stream.SkipBlock())
        return error("Malformed block");
      continue;

    case BitstreamEntry::Record:
      Stream.skipRecord(Entry.ID);
      continue;
    }
  }
}

static Expected<BitcodeModule> getSingleModule(MemoryBufferRef Buffer) {
  Expected<std::vector<BitcodeModule>> MsOrErr = getBitcodeModuleList(Buffer);