===================================================================
@@ -2080,14 +2080,19 @@ Attribute_to_gnu (Node_Id gnat_node, tre
gnu_result = bitsize_int (bitpos % BITS_PER_UNIT);
gnu_result = size_binop (PLUS_EXPR, gnu_result,
TYPE_SIZE (TREE_TYPE (gnu_prefix)));
- gnu_result = size_binop (MINUS_EXPR, gnu_result,
- bitsize_one_node);
+ /* ??? Avoid a large unsigned result that will overflow when
+ converted to the signed universal_integer. */
+ if (integer_zerop (gnu_result))
+ gnu_result = integer_minus_one_node;
+ else
+ gnu_result
+ = size_binop (MINUS_EXPR, gnu_result, bitsize_one_node);
break;
case Attr_Bit_Position:
gnu_result = gnu_field_bitpos;
break;
- }
+ }
/* If this has a PLACEHOLDER_EXPR, qualify it by the object we are
handling. */