[llvm] [LV][POC] Use umin to avoid second-to-last iteration problems with EVL (PR #143434)

[Min-Yih Hsu via llvm-commits]

mshockwave wrote:

> > I think I'm less concerned about this as we're already reading vlenb in our current approach
> 
> I agree, just noting the potential issue.

Just chatted with Craig and realized that I blunderingly forgot my EVLIndVarSimplify Pass has effectively removed the vlenb reads

https://github.com/llvm/llvm-project/pull/143434