[clang] [llvm] [InstCombine] Infer nuw for gep inbounds from base of object (PR #119225)

[Alexander Kornienko via llvm-commits]

alexfh wrote:

> > Heads up: apart from a number of instances of actual UB in the code (which are quite tedious to localize and understand due to a lack of specialized tooling) we're investigating a bad interaction of this commit with msan, which seems to result in a miscompilation.
> 
> Thanks for the heads up! As I mentioned on another thread, I'm happy to just entirely revert this patch due to lack of good sanitizer support (I can do it tomorrow, but feel free to do it yourself earlier). Having a reproducer for the msan issue is probably still valuable, as it may indicate a larger problem.

Thanks! Sent a PR with a revert: https://github.com/llvm/llvm-project/pull/120460

As mentioned, a test case is in the works.

https://github.com/llvm/llvm-project/pull/119225