[llvm] [InstCombine][ValueTracking] Improve logic for shift flags. (PR #67758)

[via llvm-commits]

goldsteinn wrote:

> The first commit looks good to me, please land it. For the last commit, what is the compile-time impact of the change, if any?

The first commit being the ValueTracking one? (thats the one I imagine would have compile-time impact).

https://github.com/llvm/llvm-project/pull/67758