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

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

LGTM, though I'd suggest to replace the "store double poison" with zero stores. There doesn't seem to be a need to use poison here.

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?

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