[llvm] [LV] Vectorize selecting last IV of min/max element. (PR #141431)

[Florian Hahn via llvm-commits]

https://github.com/fhahn commented:

> May be good to also have end-to-end test(s), to confirm vectorized result is the same as original; and subsequently check relative costs and overall performance benefits.

There was a set of tests in llvm-test-suite, but the coverage was relatively limited. Put up https://github.com/llvm/llvm-test-suite/pull/299 to generalize and extend coverage

https://github.com/llvm/llvm-project/pull/141431