[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 #11 from Bill Schmidt <wschmidt at gcc dot gnu.org> ---
OK, I've traced this down to its sordid origins.  The problem arises when the
test case is run on a machine using an old target assembler.  If the assembler
doesn't support POWER8 instructions, this causes TARGET_P8_VECTOR to be
disabled.  If TARGET_P8_VECTOR is disabled, TARGET_P9_VECTOR is likewise
disabled, which means that the P9-specific built-ins are not tied to the
built-in overload table.

So even though these tests are compile-only, the configuration test that
determines the assembler isn't up to speed causes these tests to fail.  I'll
have to add a dg-require-effective-target to fix this.