A while ago I did a bunch of work for our compiler[0], one post of which got a decent amount of HN attention[1]. Same answers: use v2 and v3.
Our posts focused on floating point, but this one does not: it focuses on bit-related instructions. So I see an (expected) clear consistency: regardless of the kind of instruction area, use something more modern than x64 v1. Nice to see. I still hope to find the time for a followup post on integer instructions at some point.
[0] https://blogs.remobjects.com/2026/01/26/fast-math-in-six-lan...