[Bug middle-end/68542] [6 Regression] 10% 481.wrf performance regression

["rguenth at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68542

--- Comment #2 from Richard Biener <rguenth at gcc dot gnu.org> ---
Ok, so previously we if-converted but with versioning and thus the if-converted
loop was not vectorized and thrown away?

So yes, for such cases we'd ideally have vector control-flow

 if (!all-zero)
  {
...
  }

but best by not if-converting this in the first place.  Note that the
above also applies to "regular" vectorization of if-converted code,
not only to 'masks' as with Yuris patch.  I wonder if we can extend
that to re-introduce control flow.  A vector == 0 check should be
fairly cheap and the transform keyed on how much code we can execute
conditionally.