rep movsb has been quite optimized recently and I suspect it will continue to be. Today you can be faster with more complex solutions in some cases, and dependi

rep movsb has been quite optimized recently and I suspect it will continue to be. Today you can be faster with more complex solutions in some cases, and depending on your precise microarch alternate solution for small copies, etc., but I suspect eventually rep movsb will just be good enough for everything but the most demanding memcpy, which I'm not even sure has a good definition because in an ever increasing number of cases it will depend on what the other cores are doing... Intel seems to be improving rep movsb from gen to gen, and on the AMD side it seems Zen3 is getting ERMS and FRMS. Given how useful it is when you can't do AVX or just because it is insanely compact, I think its usage will only increase in the near/medium future. Long term, who knows, but like anything.