[Bug tree-optimization/91934] Performance regression on 8.3.0 with -O3 and avx

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91934

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |missed-optimization
             Status|UNCONFIRMED                 |WAITING
   Last reconfirmed|                            |2019-09-30
                 CC|                            |matz at gcc dot gnu.org,
                   |                            |rguenth at gcc dot gnu.org
          Component|c                           |tree-optimization
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
I guess you are talking about the new unroll-and-jam transform transforming
your loop and that making the vectorized variant slower somehow.  You can try
if -fno-loop-unroll-and-jam fixes the slowness.

But I'm not sure what "strange SIMD instructions" you are refering to.

I'm also not sure what exactly unroll-and-jam keyed onto.