[Bug target/81504] [7/8 Regression] gcc-7 regression: vec_st in loop misoptimized

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81504

--- Comment #6 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
Correction, the reconstruction happens *prior* to swap optimization so the
latter can't make the patterns unrecognizable.