[llvm] [InstCombine] ptrmask of gep for dynamic pointer aligment (PR #80002)

[Jon Chesterfield via llvm-commits]

JonChesterfield wrote:

Not forgotten, merely sidetracked. LHSKnown instead of alignment works as expected, need to add the tests and update the PR.

https://github.com/llvm/llvm-project/pull/80002