[llvm] [DemandedBits] Support non-constant shift amounts for funnel shifts (PR #180569)

[Panagiotis Karouzakis via llvm-commits]

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karouzakisp wrote:

I think we should skip normalization. In the Alive proof, it works fine without using fshl for fshr. I can add the extra cases

https://github.com/llvm/llvm-project/pull/180569