[llvm] InstSimplify: lookthru casts, binops in folding shuffles (PR #92668)

[Nikita Popov via llvm-commits]

nikic wrote:

@artagnon See https://llvm.org/docs/InstCombineContributorGuide.html#pick-the-correct-optimization-pass for basic guidance on which pass to put things. Putting this in InstCombine may be fine -- but if VectorCombine support is already on the way, no point in doing that.

https://github.com/llvm/llvm-project/pull/92668