[llvm] [Support] Adding fast-path for KnownBits's udiv when RHS is contant (PR #189779)

[Jay Foad via llvm-commits]

jayfoad wrote:

> [Support] Adding fast-path for KnownBits's udiv when RHS is contant

Calling it a "fast-path" seems misleading since it also changes (improves) behavior. Was making it faster the original motivation?

Also typo "contant"

https://github.com/llvm/llvm-project/pull/189779