re PR tree-optimization/21563 (A trivial VRP opportunity missed)

gcc/
	PR tree-optimization/21563
	* tree-vrp.c (compare_value): Return boolean_false_node when
	SSA_NAME in "if (SSA_NAME == CST)" is strictly smaller than or
	strictly larger than CST.

testsuite/
	PR tree-optimization/21563
	* gcc.dg/tree-ssa/pr21563.c: New.

From-SVN: r99705

gcc/ChangeLog

@@ -3,6 +3,11 @@
 	* tree-optimize.c (init_tree_optimization_passes): Move
 	pass_cd_dce in place of the last pass_dce.
 
+	PR tree-optimization/21563
+	* tree-vrp.c (compare_value): Return boolean_false_node when
+	SSA_NAME in "if (SSA_NAME == CST)" is strictly smaller than or
+	strictly larger than CST.
+
 2005-05-14  Nathan Sidwell  <nathan@codesourcery.com>
 	    Jan-Benedict Glaw  <jbglaw@lug-owl.de>
 

gcc/testsuite/ChangeLog

+2005-05-14  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/21563
+	* gcc.dg/tree-ssa/pr21563.c: New.
+
 2005-05-14  Jan Hubicka  <jh@suse.cz>
 
 	* gcc.dg/noreturn-7.c: Allow control reaches warning.

gcc/testsuite/gcc.dg/tree-ssa/pr21563.c

+/* PR tree-optimization/21563
+   Make sure VRP folds the second "if" statement.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-vrp-details" } */
+
+int
+foo (int a)
+{
+  if (a > 1)
+    if (a == 0)
+      return 1;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Folding predicate" 1 "vrp"} } */
+/* { dg-final { cleanup-tree-dump "vrp" } } */

gcc/tree-vrp.c

@@ -1204,6 +1204,9 @@ compare_range_with_value (enum tree_code comp, value_range *vr, tree val)
 	  else if (cmp == -1 || cmp == 1 || cmp == 2)
 	    return boolean_false_node;
 	}
+      else if (compare_values (val, vr->min) == -1
+	       || compare_values (vr->max, val) == -1)
+	return boolean_false_node;
 
       return NULL_TREE;
     }