let is_call_to_change ci f_to_call =
let old_called = get_f_called ci in
match old_called, f_to_call with
| None, None -> false
| None, _ -> true
| Some (T.CallSrc _), Some (T.CallSrc _) -> false
| Some (T.CallSrc _), _ -> true
| Some (T.CallSlice _), Some (T.CallSrc _) -> true
| Some (T.CallSlice _), None -> true
| Some (T.CallSlice ff_called), Some (T.CallSlice ff_to_call) ->
if (M.equal_ff ff_called ff_to_call) then false else true