CristalCaveGem » LustreC

(* ----------------------------------------------------------------------------

 * SchedMCore - A MultiCore Scheduling Framework

 * Copyright (C) 2009-2011, ONERA, Toulouse, FRANCE - LIFL, Lille, FRANCE

 *

 * This file is part of Prelude

 *

 * Prelude is free software; you can redistribute it and/or

 * modify it under the terms of the GNU Lesser General Public License

 * as published by the Free Software Foundation ; either version 2 of

 * the License, or (at your option) any later version.

 *

 * Prelude is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY ; without even the implied warranty of

 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU

 * Lesser General Public License for more details.

 *

 * You should have received a copy of the GNU Lesser General Public

 * License along with this program ; if not, write to the Free Software

 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307

 * USA

 *---------------------------------------------------------------------------- *)

(** Simple modular syntactic causality analysis. Can reject correct

    programs, especially if the program is not flattened first. *)

open Utils

open LustreSpec

open Corelang

open Graph

open Format

exception Cycle of ident list

module IdentDepGraph = Graph.Imperative.Digraph.ConcreteBidirectional (IdentModule)

(*module IdentDepGraphUtil = Oper.P(IdentDepGraph)*)

(* Dependency of mem variables on mem variables is cut off 

   by duplication of some mem vars into local node vars.

   Thus, cylic dependency errors may only arise between no-mem vars.

no_mem' = combinational(no_mem, mem);

=> (mem -> no_mem' -> no_mem)

mem' = pre(no_mem, mem);

=> (mem' -> no_mem), (mem -> mem')

   Global roadmap:

   - compute two dep graphs g (non-mem/non-mem&mem) and g' (mem/mem)

   - check cycles in g (a cycle means a dependency error)

   - break cycles in g' (it's legal !):

     - check cycles in g'

     - if any, introduce aux var to break cycle, then start afresh

   - insert g' into g

   - return g

*)

let add_edges src tgt g =

(*List.iter (fun s -> List.iter (fun t -> Format.eprintf "add %s -> %s@." s t) tgt) src;*)

 List.iter

   (fun s ->

     List.iter

       (fun t -> IdentDepGraph.add_edge g s t)

       tgt)

   src;

  g

let add_vertices vtc g =

(*List.iter (fun t -> Format.eprintf "add %s@." t) vtc;*)

 List.iter (fun v -> IdentDepGraph.add_vertex g v) vtc;

  g

let new_graph () =

 IdentDepGraph.create ()

module ExprDep = struct

let eq_var_cpt = ref 0

let instance_var_cpt = ref 0

let mk_eq_var id =

 incr eq_var_cpt; sprintf "#%s_%d" id !eq_var_cpt

let mk_instance_var id =

 incr instance_var_cpt; sprintf "!%s_%d" id !instance_var_cpt

let is_eq_var v = v.[0] = '#'

let is_instance_var v = v.[0] = '!'

let is_ghost_var v = is_instance_var v || is_eq_var v

let eq_memory_variables mems eq =

  let rec match_mem lhs rhs mems =

    match rhs.expr_desc with

    | Expr_fby _

    | Expr_pre _    -> List.fold_right ISet.add lhs mems

    | Expr_tuple tl -> List.fold_right2 match_mem (transpose_list [lhs]) tl mems

    | _             -> mems in

  match_mem eq.eq_lhs eq.eq_rhs mems

let node_memory_variables nd =

 List.fold_left eq_memory_variables ISet.empty nd.node_eqs

(* computes the equivalence relation relating variables 

   in the same equation lhs, under the form of a table 

   of class representatives *)

let node_eq_equiv nd =

  let eq_equiv = Hashtbl.create 23 in

  List.iter (fun eq ->

    let first = List.hd eq.eq_lhs in

    List.iter (fun v -> Hashtbl.add eq_equiv v first) eq.eq_lhs

  )

    nd.node_eqs;

  eq_equiv

(* Create a tuple of right dimension, according to [expr] type, *)

(* filled with variable [v] *)

let adjust_tuple v expr =

 match expr.expr_type.Types.tdesc with

 | Types.Ttuple tl -> duplicate v (List.length tl)

 | _         -> [v]

(* Add dependencies from lhs to rhs in [g, g'], *)

(* no-mem/no-mem and mem/no-mem in g            *)

(* mem/mem in g'                                *)

(* excluding all/[inputs]                       *)

let add_eq_dependencies mems inputs eq (g, g') =

  let rec add_dep lhs_is_mem lhs rhs g =

    let add_var x (g, g') =

      if ISet.mem x inputs then (g, g') else

      match (lhs_is_mem, ISet.mem x mems) with

      | (false, true ) -> (add_edges [x] lhs g, g'                  )

      | (false, false) -> (add_edges lhs [x] g, g'                  )

      | (true , false) -> (add_edges lhs [x] g, g'                  )

      | (true , true ) -> (g                  , add_edges [x] lhs g') in

(* Add mashup dependencies for a user-defined node instance [lhs] = [f]([e]) *)

(* i.e every input is connected to every output, through a ghost var *)

    let mashup_appl_dependencies f e g =

      let f_var = mk_instance_var (sprintf "%s_%d" f eq.eq_loc.Location.loc_start.Lexing.pos_lnum) in

      List.fold_right (fun rhs -> add_dep lhs_is_mem (adjust_tuple f_var rhs) rhs)

	(expr_list_of_expr e) (add_var f_var g) in

    match rhs.expr_desc with

    | Expr_const _    -> g

    | Expr_fby (e1, e2)  -> add_dep true lhs e2 (add_dep false lhs e1 g)

    | Expr_pre e      -> add_dep true lhs e g

    | Expr_ident x -> add_var x g

    | Expr_access (e1, _)

    | Expr_power (e1, _) -> add_dep lhs_is_mem lhs e1 g

    | Expr_array a -> List.fold_right (add_dep lhs_is_mem lhs) a g

    | Expr_tuple t -> List.fold_right2 (fun l r -> add_dep lhs_is_mem [l] r) lhs t g

    | Expr_merge (c, hl) -> add_var c (List.fold_right (fun (_, h) -> add_dep lhs_is_mem lhs h) hl g)

    | Expr_ite   (c, t, e) -> add_dep lhs_is_mem lhs c (add_dep lhs_is_mem lhs t (add_dep lhs_is_mem lhs e g))

    | Expr_arrow (e1, e2)  -> add_dep lhs_is_mem lhs e2 (add_dep lhs_is_mem lhs e1 g)

    | Expr_when  (e, c, _)  -> add_dep lhs_is_mem lhs e (add_var c g)

    | Expr_appl (f, e, None) ->

      if Basic_library.is_internal_fun f

    (* tuple component-wise dependency for internal operators *)

      then

	List.fold_right (add_dep lhs_is_mem lhs) (expr_list_of_expr e) g

    (* mashed up dependency for user-defined operators *)

      else

	mashup_appl_dependencies f e g

    | Expr_appl (f, e, Some (r, _)) ->

      mashup_appl_dependencies f e (add_var r g)

    | Expr_uclock  (e, _)

    | Expr_dclock  (e, _)

    | Expr_phclock (e, _) -> add_dep lhs_is_mem lhs e g 

  in

  add_dep false eq.eq_lhs eq.eq_rhs (add_vertices eq.eq_lhs g, g')

(* Returns the dependence graph for node [n] *)

let dependence_graph mems n =

  eq_var_cpt := 0;

  instance_var_cpt := 0;

  let g = new_graph (), new_graph () in

  let inputs = List.fold_left (fun inputs v -> ISet.add v.var_id inputs) ISet.empty n.node_inputs in

  (* Basic dependencies *)

  let g = List.fold_right (add_eq_dependencies mems inputs) n.node_eqs g in

  g

end

module NodeDep = struct

  module ExprModule =

  struct

    type t = expr

    let compare = compare

    let hash n = Hashtbl.hash n

    let equal n1 n2 = n1 = n2

  end

  module ESet = Set.Make(ExprModule)

  let rec get_expr_calls prednode expr = 

    match expr.expr_desc with

      | Expr_const _ 

      | Expr_ident _ -> ESet.empty

      | Expr_access (e, _)

      | Expr_power (e, _) -> get_expr_calls prednode e

      | Expr_array t

      | Expr_tuple t -> List.fold_right (fun x set -> ESet.union (get_expr_calls prednode x) set) t ESet.empty

      | Expr_merge (_,hl) -> List.fold_right (fun (_,h) set -> ESet.union (get_expr_calls prednode h) set) hl ESet.empty

      | Expr_fby (e1,e2)

      | Expr_arrow (e1,e2) -> ESet.union (get_expr_calls prednode e1) (get_expr_calls prednode e2)

      | Expr_ite   (c, t, e) -> ESet.union (get_expr_calls prednode c) (ESet.union (get_expr_calls prednode t) (get_expr_calls prednode e))

      | Expr_pre e 

      | Expr_when (e,_,_)

      | Expr_uclock (e,_) 

      | Expr_dclock (e,_) 

      | Expr_phclock (e,_) -> get_expr_calls prednode e

      | Expr_appl (id,e, _) ->

	if not (Basic_library.is_internal_fun id) && prednode id

	then ESet.add expr (get_expr_calls prednode e)

	else (get_expr_calls prednode e)

  let get_callee expr =

    match expr.expr_desc with

    | Expr_appl (id, args, _) -> id, expr_list_of_expr args

    | _ -> assert false

  let get_calls prednode eqs =

    let deps =

      List.fold_left 

	(fun accu eq -> ESet.union accu (get_expr_calls prednode eq.eq_rhs))

	ESet.empty

	eqs in

    ESet.elements deps

  let dependence_graph prog =

  let g = new_graph () in

  let g = List.fold_right 

    (fun td accu -> (* for each node we add its dependencies *)

      match td.top_decl_desc with 

	| Node nd ->

	  (*Format.eprintf "Computing deps of node %s@.@?" nd.node_id; *)

	  let accu = add_vertices [nd.node_id] accu in

	  let deps = List.map (fun e -> fst (get_callee e)) (get_calls (fun _ -> true) nd.node_eqs) in

	   (*Format.eprintf "%a@.@?" (Utils.fprintf_list ~sep:"@." Format.pp_print_string) deps; *)

	  add_edges [nd.node_id] deps accu

	| _ -> assert false (* should not happen *)

    ) prog g in

  g   

  let rec filter_static_inputs inputs args =

   match inputs, args with

   | []   , [] -> []

   | v::vq, a::aq -> if v.var_dec_const then (dimension_of_expr a) :: filter_static_inputs vq aq else filter_static_inputs vq aq

   | _ -> assert false

  let compute_generic_calls prog =

    List.iter

      (fun td ->

	match td.top_decl_desc with 

	| Node nd ->

	  let prednode n = is_generic_node (Hashtbl.find node_table n) in

	  nd.node_gencalls <- get_calls prednode nd.node_eqs

	| _ -> ()

      ) prog

end

module CycleDetection = struct

(* ---- Look for cycles in a dependency graph *)

  module Cycles = Graph.Components.Make (IdentDepGraph)

  let mk_copy_var n id =

    mk_new_name (node_vars n) id

  let mk_copy_eq n var =

    let var_decl = node_var var n in

    let cp_var = mk_copy_var n var in

    let expr =

      { expr_tag = Utils.new_tag ();

	expr_desc = Expr_ident var;

	expr_type = var_decl.var_type;

	expr_clock = var_decl.var_clock;

	expr_delay = Delay.new_var ();

	expr_annot = None;

	expr_loc = var_decl.var_loc } in

    { var_decl with var_id = cp_var },

    mkeq var_decl.var_loc ([cp_var], expr)

  let wrong_partition g partition =

    match partition with

    | [id]    -> IdentDepGraph.mem_edge g id id

    | _::_::_ -> true

    | []      -> assert false

(* Checks that the dependency graph [g] does not contain a cycle. Raises

   [Cycle partition] if the succession of dependencies [partition] forms a cycle *)

  let check_cycles g =

    let scc_l = Cycles.scc_list g in

    List.iter (fun partition ->

      if wrong_partition g partition then

	raise (Cycle partition)

      else ()

    ) scc_l

(* Creates the sub-graph of [g] restricted to vertices and edges in partition *)

  let copy_partition g partition =

    let copy_g = IdentDepGraph.create () in

    IdentDepGraph.iter_edges

      (fun src tgt ->

	if List.mem src partition && List.mem tgt partition

	then IdentDepGraph.add_edge copy_g src tgt)

      g

(* Breaks dependency cycles in a graph [g] by inserting aux variables.

  [head] is a head of a non-trivial scc of [g]. 

   In Lustre, this is legal only for mem/mem cycles *)

  let break_cycle head cp_head g =

    let succs = IdentDepGraph.succ g head in

    IdentDepGraph.add_edge g head cp_head;

    List.iter

      (fun s ->

	IdentDepGraph.remove_edge g head s;

	IdentDepGraph.add_edge    g s cp_head)

      succs

(* Breaks cycles of the dependency graph [g] of memory variables [mems]

   belonging in node [node]. Returns:

   - a list of new auxiliary variable declarations

   - a list of new equations

   - a modified acyclic version of [g]

*)

  let break_cycles node mems g =

    let (mem_eqs, non_mem_eqs) = List.partition (fun eq -> List.exists (fun v -> ISet.mem v mems) eq.eq_lhs) node.node_eqs in

    let rec break vdecls mem_eqs g =

      let scc_l = Cycles.scc_list g in

      let wrong = List.filter (wrong_partition g) scc_l in

      match wrong with

      | []              -> (vdecls, non_mem_eqs@mem_eqs, g)

      | [head]::_       ->

	begin

	  IdentDepGraph.remove_edge g head head;

	  break vdecls mem_eqs g

	end

      | (head::part)::_ -> 

	begin

	  let vdecl_cp_head, cp_eq = mk_copy_eq node head in

	  let pvar v = List.mem v part in

	  let fvar v = if v = head then vdecl_cp_head.var_id else v in

	  let mem_eqs' = List.map (eq_replace_rhs_var pvar fvar) mem_eqs in

	  break_cycle head vdecl_cp_head.var_id g;

	  break (vdecl_cp_head::vdecls) (cp_eq::mem_eqs') g

	end

      | _               -> assert false

    in break [] mem_eqs g

end

let pp_dep_graph fmt g =

  begin

    Format.fprintf fmt "{ /* graph */@.";

    IdentDepGraph.iter_edges (fun s t -> Format.fprintf fmt "%s -> %s@." s t) g;

    Format.fprintf fmt "}@."

  end

let pp_error fmt trace =

  fprintf fmt "@.Causality error, cyclic data dependencies: %a@."

    (fprintf_list ~sep:"->" pp_print_string) trace

(* Merges elements of graph [g2] into graph [g1] *)

  let merge_with g1 g2 =

    IdentDepGraph.iter_vertex (fun v -> IdentDepGraph.add_vertex g1 v) g2;

    IdentDepGraph.iter_edges (fun s t -> IdentDepGraph.add_edge g1 s t) g2

let global_dependency node =

  let mems = ExprDep.node_memory_variables node in

  let (g_non_mems, g_mems) = ExprDep.dependence_graph mems node in

  (*Format.eprintf "g_non_mems: %a" pp_dep_graph g_non_mems;

  Format.eprintf "g_mems: %a" pp_dep_graph g_mems;*)

  CycleDetection.check_cycles g_non_mems;

  let (vdecls', eqs', g_mems') = CycleDetection.break_cycles node mems g_mems in

  (*Format.eprintf "g_mems': %a" pp_dep_graph g_mems';*)

  merge_with g_non_mems g_mems';

  { node with node_eqs = eqs'; node_locals = vdecls'@node.node_locals }, 

  g_non_mems

(* Local Variables: *)

(* compile-command:"make -C .." *)

(* End: *)