[llvm] [InstCombine] Fold (1 << a) to (a + 1) and (2 >> a) to (2 - a) when a is in [0,1] (PR #207108)

[Yingwei Zheng via llvm-commits]

https://github.com/dtcxzyw edited https://github.com/llvm/llvm-project/pull/207108