[clang] [llvm] [Transforms][Utils][PromoteMem2Reg] Propagate nnan flag on par with the nsz flag (PR #114271)

[Nikita Popov via cfe-commits]

nikic wrote:

> I've rebased my PR so this branch could also contain phase-ordering test for vectorizing predicated selects introduced by commit [577c7dd](https://github.com/llvm/llvm-project/commit/577c7dd7cc4c5a9f62f9654cfa30ee9d55709426)

Do I understand correctly that this PR doesn't change the PhaseOrdering test because the motivating issue was already addressed by 0f919444adfa74b46df50aa2da12e7137c23a02c?

https://github.com/llvm/llvm-project/pull/114271