let result_visible _kf ff = match ff with
| Isrc | Iproto -> true
| Iff (slice, _) ->
let key = PdgIndex.Key.output_key in
let _, ff_marks = slice.T.ff_marks in
try
let m = PdgIndex.FctIndex.find_info ff_marks key in
visible_mark m
with PdgIndex.NotFound -> false