[llvm] [InstCombine] Improve shamt range calculation (PR #72646)

[via llvm-commits]

goldsteinn wrote:

> It looks like this only affects tests using non-splat vectors. I'm usually not willing to accept improvements for non-splat vector support unless they are completely free in terms of complexity. Is there any particular reason why we would want this support?
> 
> (I'm not particularly strongly opposed though. If you think it has value I'm okay with it.)

The impl doesn't seem to go out of ways to handle non-splats, just they are a byproduct. Think you could create the same result with `(add (and X, ~Pow2), Pow2 * 3)` where we could get the knownbit but not the range.


https://github.com/llvm/llvm-project/pull/72646