https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88398
--- Comment #18 from Jakub Jelinek <jakub at gcc dot gnu.org> --- The duffs device doesn't need to be done with computed jump, it can be done with 3 conditional branches + 3 comparisons too. The advantage of doing that is especially if the iter isn't really very small, by doing it that way you don't need those 4 unrolled iterations + one scalar loop. if (n & 2) { if (n & 1) { n++; goto loop3; } { n += 2; goto loop2; } } else if (n & 1) { n += 3; goto loop1; } else if (n == 0) goto end; do { iter; loop3: iter; loop2: iter; loop1: iter; n -= 4; } while (n != 0); end:; Of course, if iter is very short, it might be easier/more efficient to duplicate iter more times than 4 and do something else.