Comment by userbinator

I do wish Intel would make the other string instructions faster, just like they did with MOVS, because the alternatives are so insanely bloated.

it is never used with a prefix (the value would be overwritten for each repetition)

...which is still useful for extreme size-optimisation; I remember seeing "rep lodsb" in a demo, as a slower-but-tiny (2 bytes) way of [1] adding cx to si, [2] zeroing cx, [3] putting the byte at [cx + si - 1] into al, and [4] conditionally leaving al and si unchanged if cx is 0, all effectively as a single instruction. Not something any optimising compiler I know of would be able to do, but perhaps within the possibility of an LLM these days.