[clang] Reland "[clang] Add nuw attribute to GEPs (#105496)" (PR #107257)

[Nikita Popov via cfe-commits]

nikic wrote:

Reduced: https://llvm.godbolt.org/z/TPdd9qore

I believe the problem is this line: https://github.com/llvm/llvm-project/blob/c05e29bff036060f0811b887a92715104abdceb5/llvm/lib/Transforms/InstCombine/InstructionCombining.cpp#L2513 This does an in-place modification of the GEP, but only updates the inbounds flag.

https://github.com/llvm/llvm-project/pull/107257