Ocaml code

open Ssa module H = Hashtbl.Make(Ssa.G.V) module VH = Vine.VarHash module PDG = Vine_pdg.SSA_PDG let in_slice ?(keep_asserts=true) cfg variables = let pdg = PDG.compute_pdg cfg in let live = H.create cfg#length in let is_live = H.mem live in let rec add_to_slice id = if not(is_live id) then ( H.add live id (); PDG.iter_pred add_to_slice pdg id ) in let vh = VH.create (List.length variables) in let () = List.iter (fun x -> VH.add vh x ()) variables in let rec live_stmt = function | Attr(s,_) -> live_stmt s | Move(v,_) -> VH.mem vh v | Assert _ -> keep_asserts | Label _ | Comment _ -> true | _ -> false in let live_bb bb = List.exists live_stmt (cfg#get_info bb) in cfg#iter_bb (fun bb -> if live_bb bb then add_to_slice (cfg#get_id bb)); add_to_slice Vine_cfg.BB_Exit; is_live let slice ?(keep_asserts=false) cfg variables = let id_live = in_slice ~keep_asserts:keep_asserts cfg variables in let bb_dead bb = not(id_live (cfg#get_id bb)) in let for_later = ref [] in let remove_simple bb = let action = match cfg#succ bb with | [s] -> `Remove s | [s;s'] when s = s' -> `Remove s | [s;s'] when s' = bb -> `Remove s | [s';s] when s' = bb -> `Remove s | [] -> `Drop | _ -> `Postpone in match action with | `Remove s -> cfg#iter_pred (fun p -> cfg#add_edge p s) bb; cfg#remove_bb bb | `Drop -> cfg#remove_bb bb | `Postpone -> for_later := bb :: !for_later in cfg#iter_bb (fun bb -> if bb_dead bb then remove_simple bb); while !for_later <> [] do let toremove = !for_later in let size = cfg#length in for_later := []; List.iter remove_simple toremove; (* Hmm, there exist cases this won't be able to deal with... Would requiring reducible loops be enough? *) assert(size <> cfg#length) done can anyone explain this part of code??