decl.c (annotate_value): Deal specially with negative constants.

	* gcc-interface/decl.c (annotate_value) <INTEGER_CST>: Deal specially
	with negative constants.

From-SVN: r242360

gcc/ada/ChangeLog

 2016-11-13  Eric Botcazou  <ebotcazou@adacore.com>
 
+	* gcc-interface/decl.c (annotate_value) <INTEGER_CST>: Deal specially
+	with negative constants.
+
+2016-11-13  Eric Botcazou  <ebotcazou@adacore.com>
+
 	* gcc-interface/utils2.c (gnat_protect_expr): Also protect only the
 	address if the expression is the component of a dereference.
 	Do not use a reference type for the final temporary reference.

gcc/ada/gcc-interface/decl.c

@@ -8022,6 +8022,14 @@ annotate_value (tree gnu_size)
   switch (TREE_CODE (gnu_size))
     {
     case INTEGER_CST:
+      /* For negative values, build NEGATE_EXPR of the opposite.  Such values
+	 can appear for discriminants in expressions for variants.  */
+      if (tree_int_cst_sgn (gnu_size) < 0)
+	{
+	  tree t = wide_int_to_tree (sizetype, wi::neg (gnu_size));
+	  return annotate_value (build1 (NEGATE_EXPR, sizetype, t));
+	}
+
       return TREE_OVERFLOW (gnu_size) ? No_Uint : UI_From_gnu (gnu_size);
 
     case COMPONENT_REF: