[llvm] SimplifyIndVar: teach widenLoopCompare about samesign (PR #125764)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> I'm also wondering why the nested loops are needed for these tests. Shouldn't it be possible to show the same behavior without them and simplify the tests?

For this patch itself, yes. I merely re-used the tests that Yingwei had provided from the original regression: for that, I'm not able to reproduce the behavior without nested loops.

https://github.com/llvm/llvm-project/pull/125764