[llvm] [KnownBits] Add fast path for udiv by pow2 and overloads for shift ops by constant (PR #189779)

[Jay Foad via llvm-commits]

jayfoad wrote:

There are some places in ScalarEvolution's `getRangeForUnknownRecurrence` that could use the new overloads too. (Doesn't have to be done in this PR.)

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