We run the builder, then use a small program that converts the JSON output into C code that generates the data. Compile that into a bundle, then load it as the prespecializations library. Then scan all the entries in the table and compare them with what the runtime builds dynamically.
We were doing a linear scan of the table contents as a stopgap. Stop doing that, and compute the proper key for the lookup, matching the one used in the builder.
This library uses GenericMetadataBuilder with a ReaderWriter that can read data and resolve pointers from MachO files, and emit a JSON representation of a dylib containing the built metadata.
We use LLVM's binary file readers to parse the MachO files and resolve fixups so we can follow pointers. This code is somewhat MachO specific, but could be generalized to other formats that LLVM supports.
rdar://116592577
