re PR c++/69902 (Bogus -Wnonnull-compare for: dynamic_cast<T*>(&ref) == nullptr)

	PR c++/69902
	* fold-const.c (fold_truth_not_expr): Propagate TREE_NO_WARNING
	when inverting comparison.

	* g++.dg/warn/Wnonnull-compare-5.C: New test.

From-SVN: r233631

gcc/ChangeLog

 2016-02-23  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/69902
+	* fold-const.c (fold_truth_not_expr): Propagate TREE_NO_WARNING
+	when inverting comparison.
+
 	PR c/69900
 	* common.opt (Wunreachable-code): Add Warning flag.
 

gcc/fold-const.c

@@ -3589,8 +3589,11 @@ fold_truth_not_expr (location_t loc, tree arg)
       if (code == ERROR_MARK)
 	return NULL_TREE;
 
-      return build2_loc (loc, code, type, TREE_OPERAND (arg, 0),
-			 TREE_OPERAND (arg, 1));
+      tree ret = build2_loc (loc, code, type, TREE_OPERAND (arg, 0),
+			     TREE_OPERAND (arg, 1));
+      if (TREE_NO_WARNING (arg))
+	TREE_NO_WARNING (ret) = 1;
+      return ret;
     }
 
   switch (code)

gcc/testsuite/ChangeLog

 2016-02-23  Jakub Jelinek  <jakub@redhat.com>
 
+	PR c++/69902
+	* g++.dg/warn/Wnonnull-compare-5.C: New test.
+
 	PR c/69900
 	* gcc.dg/pr69900.c: New test.
 

gcc/testsuite/g++.dg/warn/Wnonnull-compare-5.C

+// PR c++/69902
+// { dg-do compile }
+// { dg-options "-Wall" }
+
+struct A { virtual ~A (); };
+struct B : A {};
+
+bool
+foo (A &a)
+{
+  return dynamic_cast<B *>(&a) == (B *) 0;	// { dg-bogus "nonnull argument" }
+}
+
+bool
+bar (A &a)
+{
+  return dynamic_cast<B *>(&a) != (B *) 0;	// { dg-bogus "nonnull argument" }
+}