Hi all, Following a short chat in #ghc last week, I did a first attempt of reusing existing Iface logic to implement serialization for codegen-related Core. The implementation is included in the attached patch (~100 loc). As a quick and dirty validation of whether it works, I also modified the codegen pipeline logic to do a roundtrip: after CorePrep, the Core bits are converted to Iface, then we immediately convert it back and use it for later compiling. With the patch applied, stage-1 GHC would produce a "missing hi file" error like: : Bad interface file: _build/stage1/libraries/ghc-prim/build/GHC/Types.hi _build/stage1/libraries/ghc-prim/build/GHC/Types.hi: openBinaryFile: does not exist (No such file or directory) The error surprises me, since by the time we perform the Core-to-Core roundtrip, the .hi file should already have been written to disk. Is there anything obviously wrong with the implementation? I'd appreciate any pointers or further questions, thanks a lot! Best regards, Cheng