[llvm] Reapply "[ValueTracking] Propagate sign information out of loop" (PR #182512)

[Antonio Frighetto via llvm-commits]

antoniofrighetto wrote:

May be worth adding a small test coming from the reproducer at https://github.com/llvm/llvm-project/pull/180355#issuecomment-3933327966 to confirm the fix.

https://github.com/llvm/llvm-project/pull/182512