[llvm] [VPlan] Add visited set for onlyFirstLaneUsed() (PR #228438)

[Ramkumar Ramachandra via llvm-commits]

https://github.com/artagnon commented:

Hm, not sure. I've also been thinking about the problem, and I think the solution is to avoid calls to onlyFirstLaneUsed in usesFirstLaneOnly, rewrite onlyFirstLaneUsed to have a visited set, and change the problematic calls to usesFirstLaneOnly? I can offer to do this work if you like, but it might take a few days, as I'm currently a bit under the weather?

https://github.com/llvm/llvm-project/pull/228438