Even if true, SIMD is doing the heavy lifting here. Probably followed by the fact that almost any rewrite of a code base will result in performance improvements due to the nature of being more familiar with the domain and where the bottle necks are. I would be surprised if the assembly was responsible for more then about 1% of the gains here. So why highlight the fact assembly was used here? It is just missleading. If you want to show how ASM is so much better you need a much better example then this. For all we know the use of ASM could have made things slower and harder to develop. There is just no details at all as to why ASM is beneficial here except some author seems to love it.