[Bug testsuite/51251] conflicting -mcpu switches during testing

[joel at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51251

--- Comment #8 from Joel Sherrill <joel at gcc dot gnu.org> 2011-11-21 14:06:27 UTC ---
(In reply to comment #7)

> > The issue is that when running on real hardware, you can't use arbitrary cpu
> > flags and expect it to work.  And it is wrong to say xfail on sparc-rtems
> > because they could work on another board running rtems. Just not this one.
> 
> ...yes, that's why we have the dg-require-effective-target framework now.

I am thinking this may be a broader case than just that the CPU model on the
target doesn't have a particular feature.  sparc-rtems is different from
sparc64-rtems.  sparc-rtems is ONLY 32-bit v7 and v8.  

What's the simplest way to indicate that no 64-bit, VIS, etc tests are
applicable?