[Bug target/70957] testsuite/gcc.target/powerpc/vsx-elemrev-4.c fails on power7

[wschmidt at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70957

--- Comment #5 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
I applied the same patch to gcc-6-branch, and the test works correctly on a
Power7 machine.  Thus we appear to be exposing a recent problem introduced on
trunk.  I'll try to bisect this.