Not really IMO. Seems pretty by the books SIMD optimization at the high level (main body vs manually peeled iteration for the tail), just using a nice instructi

Not really IMO. Seems pretty by the books SIMD optimization at the high level (main body vs manually peeled iteration for the tail), just using a nice instruction set. Straightforward vectorization of the original code. I suspect modern AVX is probably not much worse. You're more-or-less programming in assembly here using these intrinsics, using C for goodies like for loops, and at the moment that's about as good as you can do while scalable autovectorization is still WIP/NIH in most compilers, so it's not really surprising or noteworthy. For experienced SIMD programmers, this is the standard approach to getting data parallelism out of many "boring" algorithms.