re PR c++/78655 (gcc doesn't exploit the fact that the result of pointer…

re PR c++/78655 (gcc doesn't exploit the fact that the result of pointer addition can not be nullptr)

2018-08-20  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/78655
	* tree-vrp.c (extract_range_from_binary_expr_1): Make
	pointer + offset nonnull if either operand is nonnull work.

	* gcc.dg/tree-ssa/evrp11.c: New testcase.

From-SVN: r263662

gcc/ChangeLog

+2018-08-20  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78655
+	* tree-vrp.c (extract_range_from_binary_expr_1): Make
+	pointer + offset nonnull if either operand is nonnull work.
+
 2018-08-20  Tom de Vries  <tdevries@suse.de>
 
 	* dwarf2out.c (add_scalar_info): Don't add reference to existing die

gcc/testsuite/ChangeLog

+2018-08-20  Richard Biener  <rguenther@suse.de>
+
+	PR tree-optimization/78655
+	* gcc.dg/tree-ssa/evrp11.c: New testcase.
+
 2018-08-18  Iain Sandoe  <iain@sandoe.co.uk>
 
 	* gcc.dg/debug/dwarf2/pr80263.c: Suppress pubtypes output

gcc/testsuite/gcc.dg/tree-ssa/evrp11.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-evrp" } */
+
+extern void link_error ();
+
+void foo (int *x)
+{
+  int *p = x + 1;
+  if (p == 0)
+    link_error ();
+}
+
+void bar (char *x, int a)
+{
+  if (a != 0)
+    {
+      char *p = x + a;
+      if (p == 0)
+	link_error ();
+    }
+}
+
+/* { dg-final { scan-tree-dump-not "link_error" "evrp" } }  */

gcc/tree-vrp.c

@@ -1437,6 +1437,7 @@ extract_range_from_binary_expr_1 (value_range *vr,
       && code != PLUS_EXPR
       && code != MINUS_EXPR
       && code != RSHIFT_EXPR
+      && code != POINTER_PLUS_EXPR
       && (vr0.type == VR_VARYING
 	  || vr1.type == VR_VARYING
 	  || vr0.type != vr1.type
@@ -1467,7 +1468,11 @@ extract_range_from_binary_expr_1 (value_range *vr,
 	{
 	  /* For pointer types, we are really only interested in asserting
 	     whether the expression evaluates to non-NULL.  */
-	  if (range_is_nonnull (&vr0) || range_is_nonnull (&vr1))
+	  if (range_is_nonnull (&vr0)
+	      || range_is_nonnull (&vr1)
+	      || (vr1.type == VR_RANGE
+		  && !symbolic_range_p (&vr1)
+		  && !range_includes_zero_p (vr1.min, vr1.max)))
 	    set_value_range_to_nonnull (vr, expr_type);
 	  else if (range_is_null (&vr0) && range_is_null (&vr1))
 	    set_value_range_to_null (vr, expr_type);