Method parseMetadata

src/lib/Bitcode/Reader/MetadataLoader.cpp:840–910

Parse a METADATA_BLOCK. If ModuleLevel is true then we are parsing module level metadata.

/// Parse a METADATA_BLOCK. If ModuleLevel is true then we are parsing
/// module level metadata.
Error MetadataLoader::MetadataLoaderImpl::parseMetadata(bool ModuleLevel) {
  if (!ModuleLevel && MetadataList.hasFwdRefs())
    return error("Invalid metadata: fwd refs into function blocks");

  // Record the entry position so that we can jump back here and efficiently
  // skip the whole block in case we lazy-load.
  auto EntryPos = Stream.GetCurrentBitNo();

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

  SmallVector<uint64_t, 64> Record;
  PlaceholderQueue Placeholders;

  // We lazy-load module-level metadata: we build an index for each record, and
  // then load individual record as needed, starting with the named metadata.
  if (ModuleLevel && IsImporting && MetadataList.empty() &&
      !DisableLazyLoading) {
    auto SuccessOrErr = lazyLoadModuleMetadataBlock();
    if (!SuccessOrErr)
      return SuccessOrErr.takeError();
    if (SuccessOrErr.get()) {
      // An index was successfully created and we will be able to load metadata
      // on-demand.
      MetadataList.resize(MDStringRef.size() +
                          GlobalMetadataBitPosIndex.size());

      // Reading the named metadata created forward references and/or
      // placeholders, that we flush here.
      resolveForwardRefsAndPlaceholders(Placeholders);
      upgradeDebugInfo();
      // Return at the beginning of the block, since it is easy to skip it
      // entirely from there.
      Stream.ReadBlockEnd(); // Pop the abbrev block context.
      Stream.JumpToBit(EntryPos);
      if (Stream.SkipBlock())
        return error("Invalid record");
      return Error::success();
    }
    // Couldn't load an index, fallback to loading all the block "old-style".
  }

  unsigned NextMetadataNo = MetadataList.size();

  // Read all the records.
  while (true) {
    BitstreamEntry Entry = Stream.advanceSkippingSubblocks();

    switch (Entry.Kind) {
    case BitstreamEntry::SubBlock: // Handled for us already.
    case BitstreamEntry::Error:
      return error("Malformed block");
    case BitstreamEntry::EndBlock:
      resolveForwardRefsAndPlaceholders(Placeholders);
      upgradeDebugInfo();
      return Error::success();
    case BitstreamEntry::Record:
      // The interesting case.