[Bug tree-optimization/80631] [6/7/8 Regression] Compiling with -O3 -mavx2 gives wrong code

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80631

--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Related to PR81179 and http://gcc.gnu.org/ml/gcc-patches/2017-11/msg02054.html
As the patch doesn't apply cleanly, can't easily verify it.