re PR rtl-optimization/49890 (IRA spill with plenty of available registers)

2011-08-18  Vladimir Makarov  <vmakarov@redhat.com>

	PR rtl-optimization/49890
	* ira-costs.c (setup_regno_cost_classes_by_aclass): Don't exclude
	subclasses of class which is superset of a pressure class.

From-SVN: r177874

1 files changed, 27 insertions, 5 deletions

diff --git a/gcc/ira-costs.c b/gcc/ira-costs.c
index 12d3ed67fa7..dc983fd3a70 100644
--- a/gcc/ira-costs.c
+++ b/gcc/ira-costs.c
@@ -232,20 +232,42 @@ setup_regno_cost_classes_by_aclass (int regno, enum reg_class aclass)
   int i;
   PTR *slot;
   HARD_REG_SET temp, temp2;
+  bool exclude_p;
 
   if ((classes_ptr = cost_classes_aclass_cache[aclass]) == NULL)
     {
       COPY_HARD_REG_SET (temp, reg_class_contents[aclass]);
       AND_COMPL_HARD_REG_SET (temp, ira_no_alloc_regs);
+      /* We exclude classes from consideration which are subsets of
+	 ACLASS only if ACLASS is a pressure class or subset of a
+	 pressure class.  It means by the definition of pressure classes
+	 that cost of moving between susbets of ACLASS is cheaper than
+	 load or store.  */
+      for (i = 0; i < ira_pressure_classes_num; i++)
+	{
+	  cl = ira_pressure_classes[i];
+	  if (cl == aclass)
+	    break;
+	  COPY_HARD_REG_SET (temp2, reg_class_contents[cl]);
+	  AND_COMPL_HARD_REG_SET (temp2, ira_no_alloc_regs);
+	  if (hard_reg_set_subset_p (temp, temp2))
+	    break;
+	}
+      exclude_p = i < ira_pressure_classes_num;
       classes.num = 0;
       for (i = 0; i < ira_important_classes_num; i++)
 	{
 	  cl = ira_important_classes[i];
-	  COPY_HARD_REG_SET (temp2, reg_class_contents[cl]);
-	  AND_COMPL_HARD_REG_SET (temp2, ira_no_alloc_regs);
-	  if (! ira_reg_pressure_class_p[cl]
-	      && hard_reg_set_subset_p (temp2, temp) && cl != aclass)
-	    continue;
+	  if (exclude_p)
+	    {
+	      /* Exclude no-pressure classes which are subsets of
+		 ACLASS.  */
+	      COPY_HARD_REG_SET (temp2, reg_class_contents[cl]);
+	      AND_COMPL_HARD_REG_SET (temp2, ira_no_alloc_regs);
+	      if (! ira_reg_pressure_class_p[cl]
+		  && hard_reg_set_subset_p (temp2, temp) && cl != aclass)
+		continue;
+	    }
 	  classes.classes[classes.num++] = cl;
 	}
       slot = htab_find_slot (cost_classes_htab, &classes, INSERT);