performance of random floats (amended)

After I found some issues with my benchmark which invalidated my previous results, I have substantially revised my previous blog entry. There are two main differences:

A proper baseline revealed that my amd64 numbers were nonsense because I wasn’t fencing enough, and after tearing my hair out and eventually fixing that I found that the bithack conversion is one or two cycles faster.
A newer compiler can radically improve the multiply conversion on arm64 so it’s the same speed as the bithack conversion; I've added some source and assembly snippets to the blog post to highlight how nice arm64 is compared to amd64 for this task.