* gcc-interface/gigi.h (is_simple_additive_expression): Declare.
	* gcc-interface/trans.c (struct range_check_info_d): Add DISP and
	NEG_P fields.
	(find_loop_for): Add DISP and NEG_P parameters with default value.
	Call is_simple_additive_expression to handle additive expressions.
	(Loop_Statement_to_gnu): Deal with displacement in range checks.
	(Raise_Error_to_gnu): Likewise.
	(gnat_to_gnu): Add call to find_loop_for.
	(is_simple_additive_expression): New function extracted from...
	(gnat_invariant_expr): ...here.  Call it on the expression.

From-SVN: r231064