[llvm] [LoopVectorize] Fix double-application of FindIV reduction expression in epilogue (PR #219362)

[via llvm-commits]

im-lunex wrote:

> underlying issue is still present?

This is confusing. I tested the same reproduction code locally was compiling fine, but in Godbolt the miscompilation was still there. Maybe something related to my config on my side.

https://github.com/llvm/llvm-project/pull/219362