[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.

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