re PR sanitizer/81097 (UBSAN: false positive for not existing negation operator…

re PR sanitizer/81097 (UBSAN: false positive for not existing negation operator and a bogus message)

2017-06-20  Richard Biener  <rguenther@suse.de>

	PR middle-end/81097
	* fold-const.c (split_tree): Fold to type before negating.

	* c-c++-common/ubsan/pr81097.c: New testcase.

From-SVN: r249407

gcc/ChangeLog

+2017-06-20  Richard Biener  <rguenther@suse.de>
+
+	PR middle-end/81097
+	* fold-const.c (split_tree): Fold to type before negating.
+
 2017-06-20  David Malcolm  <dmalcolm@redhat.com>
 
 	* diagnostic-show-locus.c

gcc/fold-const.c

@@ -853,9 +853,9 @@ split_tree (location_t loc, tree in, tree type, enum tree_code code,
 	   && code == PLUS_EXPR)
     {
       /* -X - 1 is folded to ~X, undo that here.  Do _not_ do this
-         when IN is constant.  */
-      *minus_litp = build_one_cst (TREE_TYPE (in));
-      var = negate_expr (TREE_OPERAND (in, 0));
+         when IN is constant.  Convert to TYPE before negating.  */
+      *minus_litp = build_one_cst (type);
+      var = negate_expr (fold_convert_loc (loc, type, TREE_OPERAND (in, 0)));
     }
   else
     var = in;

gcc/testsuite/ChangeLog

 2017-06-20  Richard Biener  <rguenther@suse.de>
 
+	PR middle-end/81097
+	* c-c++-common/ubsan/pr81097.c: New testcase.
+
+2017-06-20  Richard Biener  <rguenther@suse.de>
+
 	* gcc.dg/vect/pr65947-9.c: Adjust.
 
 2017-06-20  Prakhar Bahuguna  <prakhar.bahuguna@arm.com>

gcc/testsuite/c-c++-common/ubsan/pr81097.c

+/* { dg-do run } */
+/* { dg-options "-fsanitize=undefined -fsanitize-undefined-trap-on-error" } */
+
+unsigned int a = 3309568;
+unsigned int b = -1204857327;
+short c = -10871;
+short x;
+int main()
+{
+  x = ((short)(~a) | ~c) +  ((short)(~b) | ~c);
+  return 0;
+}