I have stumbled into this pretty accidentally, when rewriting some spaghetti-like code
into something more structured, which involved using some std::array<>s.
And to my surprise, the allocas remained, causing about +160% perf regression.
https://llvm-compile-time-tracker.com/compare.php?from=bb6f4d32aac3eecb51909f4facc625219307ee68&to=d563e66f40f9d4d145cb2050e41cb961e2b37785&stat=instructions
suggests that this has geomean compile-time cost of +0.08%.
This fixes PR40011, PR42794 and probably some other reports.
Remove -fno-experimental-new-pass-manager ? It was added to work around the NewPM/LegacyPM discrepancy.