Wow. I love your work. Thank you for coming here and talking about it. You could write Hacker's Delight 2nd edition for a new generation.

would totally love to read a modern `Hacker's Delight`. My mind was so blown away the first time I learned about low-level optimizations. I wish I did more of that on a day to day

Hacker's Delight already has a 2nd edition.

https://www.oreilly.com/library/view/hackers-delight-second/...

Let's add it to ClickHouse: https://github.com/ClickHouse/ClickHouse/blob/master/base/ba...

It should significantly improve the performance on ARM.

> However, developers often encounter problems with Arm NEON instructions being expensive to move to scalar code and back.

I remember talking to an ARM engineer easily 10 years ago and he told us in that nice british accent: "You know, NEON is like 'back in the yard'" :-D. This has changed a lot, but not enough from what you wrote... Bit sad that these SIMD optimizations are still hand written...

The VSHRN trick is nice (I used it only two hours ago!), but it really does feel like a crutch; I don't understand why they couldn't simply implement a PMOVMSKB-like instruction to begin with (it cannot possibly be very expensive in silicon, at least not if it moved into a vector register). One-bit-per-byte is really the sweet spot for almost any kind of text manipulation, and often requires less setup/post-fixup on either side of the POVMSKB/VSHRN.