@AndyZzzZzzZzz
Thanks for reaching out.
Given the size of the project I’m not super keen for work to start on it early because it risks me having to significantly rework the proposal.
OTOH, you can technically submit patches but these would be considered as part of normal open source contributions to LLVM and would not imply mentorship. Please note having accepted patches does not guarantee acceptance of your proposal but they might increase your chances.