re PR rtl-optimization/49936 (IRA handles CANNOT_CHANGE_MODE_CLASS poorly, +…

re PR rtl-optimization/49936 (IRA handles CANNOT_CHANGE_MODE_CLASS poorly, + spills to memory on 4.7)

2011-08-19  Vladimir Makarov  <vmakarov@redhat.com>

	PR rtl-optimization/49936
	* ira.c (ira_init_register_move_cost): Ignore too small subclasses
	for calculation of max register move costs.

From-SVN: r177916

gcc/ChangeLog

+2011-08-19  Vladimir Makarov  <vmakarov@redhat.com>
+
+	PR rtl-optimization/49936
+	* ira.c (ira_init_register_move_cost): Ignore too small subclasses
+	for calculation of max register move costs.
+
 2011-08-19  Joseph Myers  <joseph@codesourcery.com>
 
 	* c-parser.c (c_parser_postfix_expression): Convert operands of

gcc/ira.c

@@ -1501,6 +1501,10 @@ ira_init_register_move_cost (enum machine_mode mode)
 	  sizeof (move_table) * N_REG_CLASSES);
   for (cl1 = 0; cl1 < N_REG_CLASSES; cl1++)
     {
+      /* Some subclasses are to small to have enough registers to hold
+	 a value of MODE.  Just ignore them.  */
+      if (! contains_reg_of_mode[cl1][mode])
+	continue;
       COPY_HARD_REG_SET (temp_hard_regset, reg_class_contents[cl1]);
       AND_COMPL_HARD_REG_SET (temp_hard_regset, no_unit_alloc_regs);
       if (hard_reg_set_empty_p (temp_hard_regset))