Hilarious [Or Not So Hilarious] Code Optimizations

Question

Raymond Chen has this to say on his recent post on code optimizations... Obvious optimizations - one that begs to be optimized - tend to be \"de-optimizations\" if you conside

Answer 1

Duff's Device, which is so twisted that it looks like it shouldn't even compile in ISO C:

int n = (count + 7) / 8;
switch (count % 8) {
case 0: do { *to = *from++;
case 7:      *to = *from++;
case 6:      *to = *from++;
case 5:      *to = *from++;
case 4:      *to = *from++;
case 3:      *to = *from++;
case 2:      *to = *from++;
case 1:      *to = *from++;
           } while (--n > 0);
}