open Netlist_ast
open Graph
 
exception Combinational_cycle
 
let read_exp (_,exp) = 
    let f a = match a with | Avar x -> [x] | _ -> [] in
    match exp with
    | Earg a | Enot a | Eslice (_,_,a) | Eselect (_,a) -> f a
    | Ebinop (_,a,b) | Econcat (a,b) -> (f a)@(f b)
    | Emux (a,b,c) -> (f a)@(f b)@(f c)
    | Ereg _ | Erom _ | Eram _ -> []
 
let schedule p =
    let g = mk_graph () in
    List.iter (add_node g) p.p_eqs;
    let addlinks (v,e) =
        let rec is_in x = function
            | t::q when t=x -> true
            | t::q -> is_in x q
            | [] -> false
        in
        List.iter (add_edge g (v,e))
            (List.filter (fun f -> is_in v (read_exp f)) p.p_eqs )
    in
 
    try (List.iter addlinks p.p_eqs) with Cycle -> (raise Combinational_cycle) ;
 
    { p_eqs=topological g;
      p_inputs=p.p_inputs;
      p_outputs=p.p_outputs;
      p_vars=p.p_vars }