[cogman10]

This isn't a microbenchmark. In fact, I haven't even bothered to benchmark it (perhaps the non-simd version actually is faster?)

This is purely me looking at the emitted assembly and being surprised at when the compilers decide to deploy it and not deploy it. It may be the case that the SIMD instructions are in fact slower even though they should theoretically end up faster.

Both compilers are simply using heuristics to determine when it's fruitful to deploy SIMD instructions.