Are those results useless? The question posed early in the blog was whether Duff's Device is still relevant in 2021. The fact that the compiler can completely

Are those results useless? The question posed early in the blog was whether Duff's Device is still relevant in 2021. The fact that the compiler can completely elide the loop without it but cannot with it is a pretty good indicator that it's likely to cause more harm than good. It might prevent inlining of a function call in the loop body, which would make a loop much, much slower to execute. It will make the loop body larger (even without inlining) and likely cause an increase in cache misses. It will be unpredictable based on build: an unrelated change somewhere else might misalign it with a cache line. Different CPUs might have different cache behaviours and perform differently. The right view on this sort of thing hasn't changed for decades: don't optimize prematurely. Trust your compiler, check it with profiling, look first for algorithmic improvements because you can gain FAR more converting an O(n^2) algorithm to an O(nlogn) than you can by unrolling a loop. Duff's Device is obsolete in all but a vanishingly tiny number of edge cases.