Well I created the 16 bit .c file, because I'm not that curious. gcc -O0 completed immediately and made a 1,5MB executable. -O1 took about 10 minutes for a 1,8 MB executable. -O2 has been running for 1h15m so far... i7-14700K
I'm in too deep now, so I'll let it run while I'm at work.
GCC -O2 made a 1,8 MB executable after a bit over four hours. I'm not trying -O3 :D
I don't know enough about compilers to answer why this doesn't get optimised down to something tiny, or why it took so long. I'm not sure what we've learned tonight, but there you go.
I'm in too deep now, so I'll let it run while I'm at work.