[llvm] [WIP] Fold (bitwiseop X, (add (not Y), Z)) -> (bitwiseop X, (not (sub Y, Z))). (PR #141476)

[Jay Foad via llvm-commits]

jayfoad wrote:

As well as `~y+z --> ~(y-z)` you can also do `~y-z --> ~(y+z)` right?

https://github.com/llvm/llvm-project/pull/141476