The list of relevant changes to the compiler is the empty set. We wanted to certify the compiler without forking it or restricting the supported language features.

We do build and test some targets to a higher tier level than upstream rust and do have support for custom proprietary targets which the rust project will never support (1), but that makes for a tiny change set. (Measured in literally tens of lines).

Most of Ferrocene is the LTS support and the qualification documentation, both of which upstream has no interest in providing. The documentation also describes our QA process and unless you’ll adopt our procedures, you’ll have to adjust the documentation and then re-certify.

(1) to a large extend because the rust project cannot sign an NDA and support proprietary hardware in its CI.