64 characters with AVX-512? =)

DannyBee · on March 28, 2014

I didn't check to see if the instructions exist, but possibly :)

You do start to hit two issues though as oyu increase the size of the skipping:

1. Alignment 2. If the average block comment/line is < 64 characters, you may lose more time performing the instruction and then counting the trailing zeros in the result to find the place it ended.

I have no numbers to back up whether this matters, of course :)

pbsd · on March 29, 2014

AVX-512 does not seem to have PMOVMSKB, which is how I assume it is being done with SSE2. There are other ways to skin that cat, but it's unclear whether they have any advantage over using AVX2 with VPMOVMSKB.

DannyBee · on March 30, 2014

I posted a patch here: https://gist.github.com/dberlin/9867614

It adds AVX2 and SSE4.2 instruction support. It makes no discernible difference performance wise that i can find :)

jevinskie · on March 31, 2014

Heh, awesome! I'll try it out today.