[llvm] Preserve inbound of transformed GEPs (PR #86885)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

This is obviously incorrect if the indices have different signs. Please do refrain from submitting patches without alive2 proofs in the future, see https://llvm.org/docs/InstCombineContributorGuide.html#proofs.

https://github.com/llvm/llvm-project/pull/86885