Comment by inkyoto

There is (long abandoned tho) a GNU superoptimiser that supports multiple hardware architectures including HP PA-RISC, Motorola 68k and 88k, Intel i960 amongst others – https://www.gnu.org/software/superopt/

It is based on the exhaustive search with backtracking, kind of what Prolog is best for, and given a function that takes an input vector of integers, it attempts to find the most optimal instruction sequence that produces an output integer.