Cleaning up expand optabs code

[Mikael Pettersson]

Richard Sandiford writes:
 > Andreas Krebbel <krebbel@linux.vnet.ibm.com> writes:
 > > On 03/22/2011 06:48 PM, Richard Henderson wrote:
 > >
 > >> Ok.  Watch out for other target problems this week.
 > >
 > > This unfortunately broke bootstrap on s390.
 > 
 > This is PR 48263.  Since it seems to be affecting several targets,
 > and since my bootstrap seems to be taking a looong time, I'll post
 > the patch here before testing has finished.
 > 
 > > Just copying the pre-patch behaviour fixes the problem for me:
 > 
 > I think we need to undo more of the patch, and leave the conversion
 > outside of the new interface.
 > 
 > Sorry for the breakage.
 > 
 > Richard
 > 
 > 
 > gcc/
 > 	PR rtl-optimization/48263
 > 	* optabs.c (expand_binop_directly): Reinstate convert_modes code
 > 	and original commutative_p handling.  Use maybe_gen_insn.

Unfortunately this fix (r171418) broke m68k-linux, see
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=48332

/Mikael