If you’re processing N things at a time and your “scalar tail” is N-1 why can’t you put in a dummy value for the last entry, run one last SIMD iteration, and discard the dummy return value?
You can, but usually the code may have problems with this. For example, storing out of bounds is often going to give you a bad time. Some platforms that are all SIMD all the time will support masked operations for this kind of thing.