If this code only runs on one compiler version/CPU arch, then ASSUMING the compiler will do the RIGHT THING and auto-vectorize the code is okay.
But if your code will be cross-platform/run on different OSes/CPU arch's, then a SWAR version may be more consistently performant - no need to guess if the compiler's optimization heuristics decided to go with the general purpose CPU registers or faster SIMD registers.
Downside is that the devs are exposed to the gnarly optimized code.
But if your code will be cross-platform/run on different OSes/CPU arch's, then a SWAR version may be more consistently performant - no need to guess if the compiler's optimization heuristics decided to go with the general purpose CPU registers or faster SIMD registers.
Downside is that the devs are exposed to the gnarly optimized code.