Comment by jandrewrogers

With the older microarchitectures there was a large penalty for crossing a cache line with AVX-512. In some cases, the performance could be worse than AVX2!

In older microarchitectures like Ice Lake it was pretty bad, so you wanted to avoid unaligned loads if you could. This penalty has rapidly shrunk across subsequent generations of microarchitectures. The penalty is still there but on recent microarchitectures it is small enough that the unaligned case often isn't a showstopper.

The main reason to use aligned loads in code is to denote cases where you expect the address to always be aligned i.e. it should blow up if it isn't. Forcing alignment still makes sense if you want predictable, maximum performance but it isn't strictly necessary for good performance on recent hardware in the way it used to be.