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.
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