[llvm] [InstCombine] Fold expression using basic properties of floor and ceiling function (PR #107107)

[via llvm-commits]

c8ef wrote:

```
_bk;t=1725980729112Timed Out Tests (1):

_bk;t=1725980729112  lldb-api :: functionalities/fork/concurrent_vfork/TestConcurrentVFork.py
```

This seems irrelevant to my patch.

https://github.com/llvm/llvm-project/pull/107107