[llvm] [InstCombine] Improve shamt range calculation (PR #72535)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> Does this have any compile-time impact?

Compile-time impact: https://llvm-compile-time-tracker.com/compare.php?from=59b2301508ecd97175f4093039bbf887f6d5b484&to=561a3c51afb2816ca1ab20fef16fafc69f590681&stat=instructions:u

https://github.com/llvm/llvm-project/pull/72535