mn10300: Force lower-subreg pass to run.

There are a number of tests that fail -- generally ones involving
generic vectorization -- at -O0 because we run out of registers.
The lower-subreg pass cleans things up sufficiently to allow these
tests to succeed.

From-SVN: r168721

gcc/ChangeLog

 2011-01-12  Richard Henderson  <rth@redhat.com>
 
+	* config/mn10300/mn10300.c (mn10300_option_override): Force enable
+	flag_split_wide_types.
+
 	* config/mn10300/mn10300.c (mn10300_asm_trampoline_template): Remove.
 	(mn10300_trampoline_init): Rewrite without a template, an immediate
 	load and a direct branch.

gcc/config/mn10300/mn10300.c

@@ -127,6 +127,12 @@ mn10300_option_override (void)
 	 not have timing information available for it.  */
       flag_schedule_insns = 0;
       flag_schedule_insns_after_reload = 0;
+
+      /* Force enable splitting of wide types, as otherwise it is trivial
+	 to run out of registers.  Indeed, this works so well that register
+	 allocation problems are now more common *without* optimization,
+	 when this flag is not enabled by default.  */
+      flag_split_wide_types = 1;
     }
   
   if (mn10300_tune_string)