Similar to 806761a7629df268c8aed49657aeccffa6bca449
-mtriple= specifies the full target triple while -march= merely sets the
architecture part of the default target triple, leaving a target triple which
may not make sense.
Therefore, -march= is error-prone and not recommended for tests without a target
triple. The issue has been benign as we recognize avr-apple-darwin as ELF instead
of rejecting it outrightly.
There was a bug where we would hit an assertion if 'Q' was used as a
constraint.
I also removed hardcoded register names to prefer regexes so the tests
don't break when the register allocator changes.
llvm-svn: 289325
