[llvm] [InstCombine] Fold (trunc X to i1) & !iszero(X & Pow2)) -> (X & (1 | Pow2)) == (1 | Pow2) (PR #119196)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> many of the places already have decomposeBitTestICmp so maybe good to make a decomposeBitTest that only have a Value as input that handle trunc and then call decomposeBitTestICmp for icmp.

Thank you for the detailed investigation! I agree that we can continue to migrate to `trunc X to i1`.


https://github.com/llvm/llvm-project/pull/119196