That's not my experience. Plain old SIMD code ages fairly well - but if you port to a new arch, you will need to look at it again. This isn't a question of pr

That's not my experience. Plain old SIMD code ages fairly well - but if you port to a new arch, you will need to look at it again. This isn't a question of precise instruction timing, it's a question of compilers being pretty bad at leveraging SIMD in general, even in 2020. Also, while I'm sure lots of projects have hand-tuned assembly, even higher level stuff like intrinsics help a lot, and need manual porting.