[PATCH] PR target/34814 Force SDmode function args into FP registers per the ABI

[David Edelsohn]

	The rs6000 port-specific pieces generally are okay.

	I'm not sure if it is faster to check all scalar float modes of
that size or check DECIMAL_FLOAT_MODE_P, if that only is scalar decimal
float modes.

	I would reverse the test in rs6000_secondary_memory_needed_rtx
because SDmode is the rare case and it would be better to fall through and
return immediately.

	I do not see why you need to duplicate so much code in
rs6000_secondary_reload_class.

	Also, the new UNSPECS cannot use values 49 and 50.  50 already is
used by Altivec.  I would place the define_constant in dfp.md and start a
new range at 400.

David