[cft] subreg validation round 2

[Andrew Pinski]

On Nov 17, 2004, at 5:31 PM, Janis Johnson wrote:

> That change also causes several new test failures for powerpc64-linux
> with -m64, which now ICE in gen_lowpart_common for a BLKmode argument.

Yes this is because subreg of a register which is BLKmode is invalid
now.
See <http://gcc.gnu.org/ml/gcc/2004-11/msg00573.html> for another
target which did the same thing and how to fix it.

Thanks,
Andrew Pinski