I tossed together a simple function using enumerate https://godbolt.org/z/PKsEdKvKK https://godbolt.org/z/PKsEdKvKK You get the same exact asm as the manual lo

I tossed together a simple function using enumerate https://godbolt.org/z/PKsEdKvKK https://godbolt.org/z/PKsEdKvKK You get the same exact asm as the manual loop. Of course, the idiom recognition seems to kick in, in both cases, as there's no actual loop here. I tossed in a +sum, which makes that fail, so you get some loops, check it out: https://godbolt.org/z/1ddf5ded7 https://godbolt.org/z/1ddf5ded7 They are one instruction different in length, which is kind of amusing to me. Some small differences.