I have a lot of sympathy for wanting efficient code. But let's indeed have a look: https://github.com/FFmpeg/FFmpeg/blob/7bbad32d5ab69cb52bc92a5ec30c7b9838daa08

I have a lot of sympathy for wanting efficient code. But let's indeed have a look: https://github.com/FFmpeg/FFmpeg/blob/7bbad32d5ab69cb52bc92a5ec30c7b9838daa08a/libavfilter/x86/vf_gblur.asm#L180 https://github.com/FFmpeg/FFmpeg/blob/7bbad32d5ab69cb52bc92a... There are so many macros, %if and clutter here that it's difficult (for me?) to keep the big picture in mind. This reminds me of a retrospective of an OS/window manager written in assembly - they were great about avoiding tiny overheads, but expressed regret that the whole system ended up slow because it was hard to reason about bigger things such as how often to redraw everything, similar to what people are saying here. To be clear: let's indeed optimize and vectorize, but better to build on intrinsics than go all the way down to assembly.