[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 #7 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
Created attachment 42041
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=42041&action=edit
Patch under test