See post-commit discussion on https://reviews.llvm.org/D120305. This change breaks the clang-ppc64le-rhel buildbot, though there is suspicion that it's an issue with the bot. The change also had a larger than expected impact on compile-time and code-size. This reverts commit 3c4ed02698afec021c6bca80740d1e58e3ee019e and some followup changes.