[llvm] [InstCombine] Simplify nonnull pointers (PR #128111)

[via llvm-commits]

asmok-g wrote:

I'm working on it; but to give a bit of explanation: the test that fails now is a death-test. It's heap-use-after-free access to a weak_ptr. The problem is, after this patch the test fails to die. It returns the object that should have already been destroyed. I'll try to get a better repro.

https://github.com/llvm/llvm-project/pull/128111