[llvm] [InstSimplify] Fold `getelementptr inbounds null, idx -> null` (PR #130742)

[Yingwei Zheng via llvm-commits]

dtcxzyw wrote:

> If this is causing a lot of issues can we possibly revert it while the fixes make their way through review, and then re-merge it with the fixes?

@efriedma-quic @nikic I am ok to just add a ubsan check in clang 21. Then we can reland this patch in llvm 22/23.


https://github.com/llvm/llvm-project/pull/130742