re PR tree-optimization/22117 (VRP thinks <ptr type> + <ptr type> is always nonnull.)

gcc/
	PR tree-optimization/22117
	* tree-vrp.c (extract_range_from_binary_expr): Compute a
	correct range when adding two pointers.

testsuite/
	PR tree-optimization/22117
	* gcc.dg/tree-ssa/pr22117.c: New.

From-SVN: r101272

gcc/ChangeLog

+2005-06-23  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/22117
+	* tree-vrp.c (extract_range_from_binary_expr): Compute a
+	correct range when adding two pointers.
+
 2005-06-23  Jason Merrill  <jason@redhat.com>
 
 	PR c++/19317

gcc/testsuite/ChangeLog

+2005-06-23  Kazu Hirata  <kazu@codesourcery.com>
+
+	PR tree-optimization/22117
+	* gcc.dg/tree-ssa/pr22117.c: New.
+
 2005-06-23  James A. Morrison  <phython@gcc.gnu.org>
 
 	PR testsuite/22123

gcc/testsuite/gcc.dg/tree-ssa/pr22117.c

+/* PR tree-optimization/22117
+   VRP used think that &p[q] is nonzero even though p and q are both
+   known to be zero after entering the first two "if" statements.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp" } */
+
+void
+foo (int *p, int q)
+{
+  if (p == 0)
+    {
+      if (q == 0)
+	{
+	  int *r = &p[q];
+	  if (r != 0)
+	    link_error ();
+	}
+    }
+}
+
+/* { dg-final { scan-tree-dump-times "Folding predicate r_.* != 0B to 0" 1 "vrp" } } */
+/* { dg-final { cleanup-tree-dump "vrp" } } */

gcc/tree-vrp.c

@@ -1073,7 +1073,14 @@ extract_range_from_binary_expr (value_range_t *vr, tree expr)
 	 ivopts is generating expressions with pointer multiplication
 	 in them.  */
       if (code == PLUS_EXPR)
-	set_value_range_to_nonnull (vr, TREE_TYPE (expr));
+	{
+	  if (range_is_nonnull (&vr0) || range_is_nonnull (&vr1))
+	    set_value_range_to_nonnull (vr, TREE_TYPE (expr));
+	  else if (range_is_null (&vr0) && range_is_null (&vr1))
+	    set_value_range_to_null (vr, TREE_TYPE (expr));
+	  else
+	    set_value_range_to_varying (vr);
+	}
       else
 	{
 	  /* Subtracting from a pointer, may yield 0, so just drop the