FFmpeg developers aren't stupid and aren't doing things because of historical accident. If you don't mind writing platform specific code, it simply works better this way. Here's clang messing up x86 intrinsics code. x.com/ffmpeg/status/1852913590258618852 The other reason to do it is that, since x86 intrinsics are named in Hungarian notation, they're so hard to read that the asm is actually more maintainable.

FFMPEG uses hand written assembly across their code base, and while 94x may not be representative everywhere, it's generally true that they regularly outperform the compiler with assembly: x.com/FFmpeg/status/1852913590258618852 x.com/FFmpeg/status/1850475265455251704