[llvm] [VectorCombine][X86] Use updated getVectorInstrCost hook (PR #137823)

[Luke Lau via llvm-commits]

lukel97 wrote:

> Alive seems to approve of this transformation: https://alive2.llvm.org/ce/z/xUNKWG

FWIW this patch didn't actually change the transformation, but just changed the cost model so it might kick in more places. So I guess if the transformation was faulty it would have already existed before this patch.

Is it possible to reduce the test case with llvm-reduce somehow?

https://github.com/llvm/llvm-project/pull/137823