[llvm] [DemandedBits] Support non-constant shift amounts (PR #148880)

[Panagiotis Karouzakis via llvm-commits]

karouzakisp wrote:

> > my transformation contains a loop and the Alive syntax doesn't permit loops
> 
> You can use a smaller integer bitwidth (e.g., i4/i8), then unroll the loop with `-src-unroll=8 -tgt-unroll=8`.

Thanks for the tip. Here is the updated proof --> https://alive2.llvm.org/ce/z/tCvUT6

https://github.com/llvm/llvm-project/pull/148880