[PATCH] WG-vectorizer: Re-enable LLVM vectorizers

[PATCH] WG-vectorizer: Re-enable LLVM vectorizers

The LLVM vectorizers were accidentally disabled when
transitioning to the new PM. This commit re-enables
them and exposes some new inefficiencies (to be continued...).

Yeah, we should also add a perf.regression test or at least a "smoke
test" for the WG vectorization.

(cherry picked from commit 19dc70bbe927a6f6210ccd45b6a4c2a49fe6da96)

Gbp-Pq: Name 0001-WG-vectorizer-Re-enable-LLVM-vectorizers.patch