[llvm] [LoopVectorize][X86] Improve libmvec SSE/AVX/AVX-512 test coverage (PR #211863)

[Simon Pilgrim via llvm-commits]

https://github.com/RKSimon commented:

do we need libm-vector-calls-VF2-VF8.ll anymore? does libm-vector-calls.ll handle all its tests?

https://github.com/llvm/llvm-project/pull/211863