let label_visible ff_opt inst label = match ff_opt with
| Isrc -> true
| Iproto -> false
| Iff (ff,_) ->
let m = !Db.Slicing.Slice.get_mark_from_label ff inst label in
let v = visible_mark m in
SlicingParameters.debug ~level:2
"[SlicingTransform.Visibility.label_visible] label %a is %svisible"
!Ast_printer.d_label label (if v then "" else "in");
v