[llvm] [InstCombine] Support gep nuw in icmp folds (PR #118472)

[Nikita Popov via llvm-commits]

nikic wrote:

> We have found a couple of dozen of issues uncovered by this optimization, but I don't think in any of these cases ubsan was producing an error.

See https://clang.godbolt.org/z/azr7rbv3c for a sample of ubsan reporting this. Are you running ubsan in the cases that actually overflow? It's not going to report something if there is no overflow...

https://github.com/llvm/llvm-project/pull/118472