You are correct, that was an uneducated guess on my part. I just glanced at the IR which was different for some attributes (nounwind vs mustprogress norecurse)

You are correct, that was an uneducated guess on my part. I just glanced at the IR which was different for some attributes (nounwind vs mustprogress norecurse), but the resulting assembly is 100% identical for every optimization level.