tree-vrp.c (vrp_visit_phi_node): Allow a last iteration if the currently…

tree-vrp.c (vrp_visit_phi_node): Allow a last iteration if the currently executable edges have fixed ranges.

2016-08-12  Richard Biener  <rguenther@suse.de>

	* tree-vrp.c (vrp_visit_phi_node): Allow a last iteration if
	the currently executable edges have fixed ranges.  Always
	go through update_value_range.

From-SVN: r239404

gcc/ChangeLog

+2016-08-12  Richard Biener  <rguenther@suse.de>
+
+	* tree-vrp.c (vrp_visit_phi_node): Allow a last iteration if
+	the currently executable edges have fixed ranges.  Always
+	go through update_value_range.
+
 2016-08-12  Alexandre Oliva <aoliva@redhat.com>
 
 	PR debug/63240

gcc/tree-vrp.c

@@ -8725,6 +8725,7 @@ vrp_visit_phi_node (gphi *phi)
       print_gimple_stmt (dump_file, phi, 0, dump_flags);
     }
 
+  bool may_simulate_again = false;
   edges = 0;
   for (i = 0; i < gimple_phi_num_args (phi); i++)
     {
@@ -8747,6 +8748,12 @@ vrp_visit_phi_node (gphi *phi)
 
 	  if (TREE_CODE (arg) == SSA_NAME)
 	    {
+	      /* See if we are eventually going to change one of the args.  */
+	      gimple *def_stmt = SSA_NAME_DEF_STMT (arg);
+	      if (! gimple_nop_p (def_stmt)
+		  && prop_simulate_again_p (def_stmt))
+		may_simulate_again = true;
+
 	      vr_arg = *(get_value_range (arg));
 	      /* Do not allow equivalences or symbolic ranges to leak in from
 		 backedges.  That creates invalid equivalencies.
@@ -8822,11 +8829,14 @@ vrp_visit_phi_node (gphi *phi)
      previous one.  We don't do this if we have seen a new executable
      edge; this helps us avoid an overflow infinity for conditionals
      which are not in a loop.  If the old value-range was VR_UNDEFINED
-     use the updated range and iterate one more time.  */
+     use the updated range and iterate one more time.  If we will not
+     simulate this PHI again with the same number of edges then iterate
+     one more time.  */
   if (edges > 0
       && gimple_phi_num_args (phi) > 1
       && edges == old_edges
-      && lhs_vr->type != VR_UNDEFINED)
+      && lhs_vr->type != VR_UNDEFINED
+      && may_simulate_again)
     {
       /* Compare old and new ranges, fall back to varying if the
          values are not comparable.  */
@@ -8880,28 +8890,7 @@ vrp_visit_phi_node (gphi *phi)
       goto infinite_check;
     }
 
-  /* If the new range is different than the previous value, keep
-     iterating.  */
-update_range:
-  if (update_value_range (lhs, &vr_result))
-    {
-      if (dump_file && (dump_flags & TDF_DETAILS))
-	{
-	  fprintf (dump_file, "Found new range for ");
-	  print_generic_expr (dump_file, lhs, 0);
-	  fprintf (dump_file, ": ");
-	  dump_value_range (dump_file, &vr_result);
-	  fprintf (dump_file, "\n");
-	}
-
-      if (vr_result.type == VR_VARYING)
-	return SSA_PROP_VARYING;
-
-      return SSA_PROP_INTERESTING;
-    }
-
-  /* Nothing changed, don't add outgoing edges.  */
-  return SSA_PROP_NOT_INTERESTING;
+  goto update_range;
 
 varying:
   set_value_range_to_varying (&vr_result);
@@ -8922,11 +8911,32 @@ infinite_check:
   if ((vr_result.type == VR_RANGE || vr_result.type == VR_ANTI_RANGE)
       && !((vrp_val_is_max (vr_result.max) && vrp_val_is_min (vr_result.min))
 	   || compare_values (vr_result.min, vr_result.max) > 0))
-    goto update_range;
+    ;
+  else
+    set_value_range_to_varying (&vr_result);
 
-  /* No match found.  Set the LHS to VARYING.  */
-  set_value_range_to_varying (lhs_vr);
+  /* If the new range is different than the previous value, keep
+     iterating.  */
+update_range:
+  if (update_value_range (lhs, &vr_result))
+    {
+      if (dump_file && (dump_flags & TDF_DETAILS))
+	{
+	  fprintf (dump_file, "Found new range for ");
+	  print_generic_expr (dump_file, lhs, 0);
+	  fprintf (dump_file, ": ");
+	  dump_value_range (dump_file, &vr_result);
+	  fprintf (dump_file, "\n");
+	}
+
+      if (vr_result.type == VR_VARYING)
 	return SSA_PROP_VARYING;
+
+      return SSA_PROP_INTERESTING;
+    }
+
+  /* Nothing changed, don't add outgoing edges.  */
+  return SSA_PROP_NOT_INTERESTING;
 }
 
 /* Simplify boolean operations if the source is known