[Bug tree-optimization/71271] SLP loop vectorized twice

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71271

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-05-25
     Ever confirmed|0                           |1

--- Comment #3 from Richard Biener <rguenth at gcc dot gnu.org> ---
Heh.  I suppose the vectorizer could annotate the unvectorized loop copy with
some flag.  But OTOH BB vectorization might end up partially vectorizing the
loop - it sounds hard to detect the case where it would be equivalent to
full loop vectorization.

So, confirmed.  But as missed loop vectorization / unnecessary versioning for
aliasing.  It's perfectly fine to SLP vectorize this w/o alias versioning.