[llvm] [InstCombine] Fold `ceil(X / (2 ^ C)) == 0` -> `X == 0` (PR #143683)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

IIRC the regression can be fixed by handling this pattern in `isKnownNonZero`. It would be better to add a helper `stripNullTest` to find patterns in the form of `f(x) == 0 <-> x == 0`.


https://github.com/llvm/llvm-project/pull/143683