about 400 bytes of compiled machine code.
approximately 80 hours of work (2 weeks) - just coding and tweaking, not including any prior research (sunk cost)
i.e. 0.2 hr per byte of machine code.
If a "monte carlo tree search", ala AlphaGo, can be applied to compilers, it could lower that cost to 1e-4 seconds per byte of machine code, i think.
what needs to happen is to have
John Regehr, http://blog.regehr.org/
Chris Lattner, http://clang.llvm.org/
Demis Hassabis, https://en.wikipedia.org/wiki/Google_DeepMind