[llvm] [InstCombine] fold `sub(zext(ptrtoint), zext(ptrtoint))` (PR #115369)

[Nikolay Panchenko via llvm-commits]

npanchen wrote:

> LGTM. For the future, please add less redundant tests. If I'm asking for a test with a non-global, I mean a single test, not a copy of _all_ existing tests.

Got it. Thanks.

https://github.com/llvm/llvm-project/pull/115369