CristalCaveGem » LustreC

open Graph

(* computes the cone of influence of a given [var] wrt a dependency graph [g].

*)

let cone_of_influence g var =

 (*Format.printf "coi: %s@." var;*)

 let frontier = ref (ISet.add var ISet.empty) in

 let coi = ref ISet.empty in

 while not (ISet.is_empty !frontier)

 do

   let head = ISet.min_elt !frontier in

   (*Format.printf "head: %s@." head;*)

   frontier := ISet.remove head !frontier;

   if ExprDep.is_read_var head then coi := ISet.add (ExprDep.undo_read_var head) !coi;

   List.iter (fun s -> frontier := ISet.add s !frontier) (IdentDepGraph.succ g head);

 done;

 !coi

let compute_unused n g =

  let inputs = ExprDep.node_input_variables n in

  let mems = ExprDep.node_memory_variables n in

  let outputs = ExprDep.node_output_variables n in

  ISet.fold

    (fun var unused -> ISet.diff unused (cone_of_influence g var))

    (ISet.union outputs mems)

    (ISet.union inputs mems)