This is quite a hardcore trip down to optimising single CPU instructions. I need to tip off my hat to the author. Though not sure what kind of motivation and project goals warrant this deep and detailed problem tackling.
The thing about optimization work is that it's incredibly addicting once you get into it. Seeing consistent, measurable improvement and watching the frame times shrink is so satisfying, plus the process itself is really enjoyable in and of itself.
I definitely agree that the optimizations here are overkill for the actual application itself. However, it served as a great learning experience for me personally and allowed me to write this blog post as well!
While this might be a bit overkill, I wish more developers spent at least 10% as much effort as here, the modern world of software really feels bloated often. The core engines are getting faster and the cpus are getting faster but the web feels slower.
And another important factor is that more and more software runs on battery powered portable devices in some form. Instructions saved is battery saved = happier users :)
I'd be amazed to see what this level of profiling skill could do on a fancier algorithm.