I’m not sure you’ve though this through.

Any C function that manipulates pointers (or arrays) can alias those pointers, type pun, and otherwise touch the same block of memory through different paths and/or treating the bits as different types.

Vast areas of optimization are completely closed to you if you want code to be resilient in the face of aliasing.

You should sit down with pen and paper to figure out how to optimize a simple function while preserving invariants but without UB. It would be very illuminating.