[Bug tree-optimization/81655] [7/8 Regression] new test case gcc.dg/tree-ssa/pr81588.c fails on powerpc64

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81655

--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 41891
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41891&action=edit
gcc7-pr81655.patch

As that is a new optimization, I think we should just tweak the testcase for
7.x.