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lustrec / src / optimize_machine.ml @ 521e2a6b

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(********************************************************************)
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(*                                                                  *)
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(*  The LustreC compiler toolset   /  The LustreC Development Team  *)
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(*  Copyright 2012 -    --   ONERA - CNRS - INPT                    *)
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(*                                                                  *)
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(*  LustreC is free software, distributed WITHOUT ANY WARRANTY      *)
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(*  under the terms of the GNU Lesser General Public License        *)
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(*  version 2.1.                                                    *)
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(*                                                                  *)
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(********************************************************************)
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open Utils
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open LustreSpec 
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open Corelang
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open Causality
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open Machine_code 
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open Dimension
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let pp_elim fmt elim =
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  begin
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    Format.fprintf fmt "@[{ /* elim table: */@ ";
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    IMap.iter (fun v expr -> Format.fprintf fmt "%s |-> %a@ " v pp_val expr) elim;
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    Format.fprintf fmt "}@ @]";
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  end
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let rec eliminate elim instr =
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  let e_expr = eliminate_expr elim in
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  match instr with
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  | MComment _         -> instr
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  | MLocalAssign (i,v) -> MLocalAssign (i, e_expr v)
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  | MStateAssign (i,v) -> MStateAssign (i, e_expr v)
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  | MReset i           -> instr
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  | MNoReset i         -> instr
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  | MStep (il, i, vl)  -> MStep(il, i, List.map e_expr vl)
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  | MBranch (g,hl)     -> 
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    MBranch
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      (e_expr g, 
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       (List.map 
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	  (fun (l, il) -> l, List.map (eliminate elim) il) 
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	  hl
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       )
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      )
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and eliminate_expr elim expr =
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  match expr.value_desc with
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  | LocalVar v -> (try IMap.find v.var_id elim with Not_found -> expr)
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  | Fun (id, vl) -> {expr with value_desc = Fun (id, List.map (eliminate_expr elim) vl)}
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  | Array(vl) -> {expr with value_desc = Array(List.map (eliminate_expr elim) vl)}
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  | Access(v1, v2) -> { expr with value_desc = Access(eliminate_expr elim v1, eliminate_expr elim v2)}
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  | Power(v1, v2) -> { expr with value_desc = Power(eliminate_expr elim v1, eliminate_expr elim v2)}
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  | Cst _ | StateVar _ -> expr
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let eliminate_dim elim dim =
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  Dimension.expr_replace_expr 
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    (fun v -> try
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		dimension_of_value (IMap.find v elim) 
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      with Not_found -> mkdim_ident dim.dim_loc v) 
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    dim
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(* 8th Jan 2016: issues when merging salsa with horn_encoding: The following
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   functions seem unsused. They have to be adapted to the new type for expr
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*)
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let unfold_expr_offset m offset expr =
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  List.fold_left
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    (fun res -> (function | Index i -> mk_val (Access (res, value_of_dimension m i))
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					      (Types.array_element_type res.value_type)
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                          | Field f -> Format.eprintf "internal error: not yet implemented !"; assert false))
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    expr offset
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let rec simplify_cst_expr m offset typ cst =
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    match offset, cst with
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    | []          , _
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      -> mk_val (Cst cst) typ
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    | Index i :: q, Const_array cl when Dimension.is_dimension_const i
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      -> let elt_typ = Types.array_element_type typ in
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         simplify_cst_expr m q elt_typ (List.nth cl (Dimension.size_const_dimension i))
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    | Index i :: q, Const_array cl
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      -> let elt_typ = Types.array_element_type typ in
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         unfold_expr_offset m [Index i] (mk_val (Array (List.map (simplify_cst_expr m q elt_typ) cl)) typ)
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    | Field f :: q, Const_struct fl
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      -> let fld_typ = Types.struct_field_type typ f in
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         simplify_cst_expr m q fld_typ (List.assoc f fl)
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    | _ -> (Format.eprintf "internal error: Optimize_machine.simplify_cst_expr %a@." Printers.pp_const cst; assert false)
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let simplify_expr_offset m expr =
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  let rec simplify offset expr =
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    match offset, expr.value_desc with
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    | Field f ::q , _                -> failwith "not yet implemented"
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    | _           , Fun (id, vl) when Basic_library.is_value_internal_fun expr
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                                     -> mk_val (Fun (id, List.map (simplify offset) vl)) expr.value_type
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    | _           , Fun _
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    | _           , StateVar _
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    | _           , LocalVar _       -> unfold_expr_offset m offset expr
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    | _           , Cst cst          -> simplify_cst_expr m offset expr.value_type cst
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    | _           , Access (expr, i) -> simplify (Index (dimension_of_value i) :: offset) expr
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    | []          , _                -> expr
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    | Index _ :: q, Power (expr, _)  -> simplify q expr
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    | Index i :: q, Array vl when Dimension.is_dimension_const i
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                                     -> simplify q (List.nth vl (Dimension.size_const_dimension i))
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    | Index i :: q, Array vl         -> unfold_expr_offset m [Index i] (mk_val (Array (List.map (simplify q) vl)) expr.value_type)
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    (*Format.eprintf "simplify_expr %a %a = %a@." pp_val expr (Utils.fprintf_list ~sep:"" Printers.pp_offset) offset pp_val res; res)
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     with e -> (Format.eprintf "simplify_expr %a %a = <FAIL>@." pp_val expr (Utils.fprintf_list ~sep:"" Printers.pp_offset) offset; raise e*)
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  in simplify [] expr
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let rec simplify_instr_offset m instr =
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  match instr with
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  | MLocalAssign (v, expr) -> MLocalAssign (v, simplify_expr_offset m expr)
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  | MStateAssign (v, expr) -> MStateAssign (v, simplify_expr_offset m expr)
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  | MReset id              -> instr
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  | MNoReset id            -> instr
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  | MStep (outputs, id, inputs) -> MStep (outputs, id, List.map (simplify_expr_offset m) inputs)
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  | MBranch (cond, brl)
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    -> MBranch(simplify_expr_offset m cond, List.map (fun (l, il) -> l, simplify_instrs_offset m il) brl)
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  | MComment _             -> instr
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and simplify_instrs_offset m instrs =
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  List.map (simplify_instr_offset m) instrs
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let is_scalar_const c =
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  match c with
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  | Const_real _
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  | Const_int _
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  | Const_tag _   -> true
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  | _             -> false
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(* An instruction v = expr may (and will) be unfolded iff:
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   - either expr is atomic
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     (no complex expressions, only const, vars and array/struct accesses)
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   - or v has a fanin <= 1 (used at most once)
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*)
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let is_unfoldable_expr fanin expr =
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  let rec unfold_const offset cst =
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    match offset, cst with
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    | _           , Const_int _
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    | _           , Const_real _
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    | _           , Const_tag _     -> true
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    | Field f :: q, Const_struct fl -> unfold_const q (List.assoc f fl)
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    | []          , Const_struct _  -> false
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    | Index i :: q, Const_array cl when Dimension.is_dimension_const i
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                                    -> unfold_const q (List.nth cl (Dimension.size_const_dimension i))
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    | _           , Const_array _   -> false
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    | _                             -> assert false in
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  let rec unfold offset expr =
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    match offset, expr.value_desc with
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    | _           , Cst cst                      -> unfold_const offset cst
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    | _           , LocalVar _
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    | _           , StateVar _                   -> true
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    | []          , Power _
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    | []          , Array _                      -> false
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    | Index i :: q, Power (v, _)                 -> unfold q v
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    | Index i :: q, Array vl when Dimension.is_dimension_const i
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                                                 -> unfold q (List.nth vl (Dimension.size_const_dimension i))
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    | _           , Array _                      -> false
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    | _           , Access (v, i)                -> unfold (Index (dimension_of_value i) :: offset) v
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    | _           , Fun (id, vl) when fanin < 2 && Basic_library.is_value_internal_fun expr
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                                                 -> List.for_all (unfold offset) vl
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    | _           , Fun _                        -> false
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    | _                                          -> assert false
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  in unfold [] expr
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let basic_unfoldable_assign fanin v expr =
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  try
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    let d = Hashtbl.find fanin v.var_id
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    in is_unfoldable_expr d expr
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  with Not_found -> false
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let unfoldable_assign fanin v expr =
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   (if !Options.mpfr then Mpfr.unfoldable_value expr else true)
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&& basic_unfoldable_assign fanin v expr
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let merge_elim elim1 elim2 =
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  let merge k e1 e2 =
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    match e1, e2 with
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    | Some e1, Some e2 -> if e1 = e2 then Some e1 else None
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    | _      , Some e2 -> Some e2
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    | Some e1, _       -> Some e1
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    | _                -> None
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  in IMap.merge merge elim1 elim2
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(* see if elim has to take in account the provided instr:
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   if so, update elim and return the remove flag,
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   otherwise, the expression should be kept and elim is left untouched *)
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let rec instrs_unfold fanin elim instrs =
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  let elim, rev_instrs = 
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    List.fold_left (fun (elim, instrs) instr ->
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      (* each subexpression in instr that could be rewritten by the elim set is
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	 rewritten *)
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      let instr = eliminate elim instr in
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      (* if instr is a simple local assign, then (a) elim is simplified with it (b) it
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	 is stored as the elim set *)
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      instr_unfold fanin instrs elim instr
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    ) (elim, []) instrs
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  in elim, List.rev rev_instrs
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and instr_unfold fanin instrs elim instr =
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(*  Format.eprintf "SHOULD WE STORE THE EXPRESSION IN INSTR %a TO ELIMINATE IT@." pp_instr instr;*)
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  match instr with
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  (* Simple cases*)
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  | MStep([v], id, vl) when Basic_library.is_value_internal_fun (mk_val (Fun (id, vl)) v.var_type)
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    -> instr_unfold fanin instrs elim (MLocalAssign (v, mk_val (Fun (id, vl)) v.var_type))
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  | MLocalAssign(v, expr) when unfoldable_assign fanin v expr
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    -> (IMap.add v.var_id expr elim, instrs)
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  | MBranch(g, hl) when false
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    -> let elim_branches = List.map (fun (h, l) -> (h, instrs_unfold fanin elim l)) hl in
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       let (elim, branches) =
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	 List.fold_right
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	   (fun (h, (e, l)) (elim, branches) -> (merge_elim elim e, (h, l)::branches))
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	   elim_branches (elim, [])
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       in elim, (MBranch (g, branches) :: instrs)
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  | _
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    -> (elim, instr :: instrs)
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    (* default case, we keep the instruction and do not modify elim *)
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(** We iterate in the order, recording simple local assigns in an accumulator
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    1. each expression is rewritten according to the accumulator
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    2. local assigns then rewrite occurrences of the lhs in the computed accumulator
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*)
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let static_call_unfold elim (inst, (n, args)) =
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  let replace v =
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    try
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      Machine_code.dimension_of_value (IMap.find v elim)
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    with Not_found -> Dimension.mkdim_ident Location.dummy_loc v
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  in (inst, (n, List.map (Dimension.expr_replace_expr replace) args))
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(** Perform optimization on machine code:
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    - iterate through step instructions and remove simple local assigns
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233
*)
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let machine_unfold fanin elim machine =
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  (*Log.report ~level:1 (fun fmt -> Format.fprintf fmt "machine_unfold %a@." pp_elim elim);*)
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  let elim_consts, mconst = instrs_unfold fanin elim machine.mconst in
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  let elim_vars, instrs = instrs_unfold fanin elim_consts machine.mstep.step_instrs in
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  let instrs = simplify_instrs_offset machine instrs in
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  let checks = List.map (fun (loc, check) -> loc, eliminate_expr elim_vars check) machine.mstep.step_checks in
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  let locals = List.filter (fun v -> not (IMap.mem v.var_id elim_vars)) machine.mstep.step_locals in
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  let minstances = List.map (static_call_unfold elim_consts) machine.minstances in
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  let mcalls = List.map (static_call_unfold elim_consts) machine.mcalls
243
  in
244
  {
245
    machine with
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      mstep = { 
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	machine.mstep with 
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	  step_locals = locals;
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	  step_instrs = instrs;
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	  step_checks = checks
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      };
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      mconst = mconst;
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      minstances = minstances;
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      mcalls = mcalls;
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  },
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  elim_vars
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let instr_of_const top_const =
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  let const = const_of_top top_const in
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  let vdecl = mkvar_decl Location.dummy_loc (const.const_id, mktyp Location.dummy_loc Tydec_any, mkclock Location.dummy_loc Ckdec_any, true, None) in
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  let vdecl = { vdecl with var_type = const.const_type }
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  in MLocalAssign (vdecl, mk_val (Cst const.const_value) vdecl.var_type)
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let machines_unfold consts node_schs machines =
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  List.fold_right (fun m (machines, removed) ->
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    let fanin = (IMap.find m.mname.node_id node_schs).Scheduling.fanin_table in
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    let elim_consts, _ = instrs_unfold fanin IMap.empty (List.map instr_of_const consts) in
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    let (m, removed_m) =  machine_unfold fanin elim_consts m in
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    (m::machines, IMap.add m.mname.node_id removed_m removed)
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    )
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    machines
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    ([], IMap.empty)
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let get_assign_lhs instr =
275
  match instr with
276
  | MLocalAssign(v, e) -> mk_val (LocalVar v) e.value_type
277
  | MStateAssign(v, e) -> mk_val (StateVar v) e.value_type
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  | _                  -> assert false
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280
let get_assign_rhs instr =
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  match instr with
282
  | MLocalAssign(_, e)
283
  | MStateAssign(_, e) -> e
284
  | _                  -> assert false
285

    
286
let is_assign instr =
287
  match instr with
288
  | MLocalAssign _
289
  | MStateAssign _ -> true
290
  | _              -> false
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292
let mk_assign v e =
293
 match v.value_desc with
294
 | LocalVar v -> MLocalAssign(v, e)
295
 | StateVar v -> MStateAssign(v, e)
296
 | _          -> assert false
297

    
298
let rec assigns_instr instr assign =
299
  match instr with  
300
  | MLocalAssign (i,_)
301
  | MStateAssign (i,_) -> ISet.add i assign
302
  | MStep (ol, _, _)   -> List.fold_right ISet.add ol assign
303
  | MBranch (_,hl)     -> List.fold_right (fun (_, il) -> assigns_instrs il) hl assign
304
  | _                  -> assign
305

    
306
and assigns_instrs instrs assign =
307
  List.fold_left (fun assign instr -> assigns_instr instr assign) assign instrs
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(*    
310
and substitute_expr subst expr =
311
  match expr with
312
  | StateVar v
313
  | LocalVar v -> (try IMap.find expr subst with Not_found -> expr)
314
  | Fun (id, vl) -> Fun (id, List.map (substitute_expr subst) vl)
315
  | Array(vl) -> Array(List.map (substitute_expr subst) vl)
316
  | Access(v1, v2) -> Access(substitute_expr subst v1, substitute_expr subst v2)
317
  | Power(v1, v2) -> Power(substitute_expr subst v1, substitute_expr subst v2)
318
  | Cst _  -> expr
319
*)
320
(** Finds a substitute for [instr] in [instrs], 
321
   i.e. another instr' with the same rhs expression.
322
   Then substitute this expression with the first assigned var
323
*)
324
let subst_instr subst instrs instr =
325
  (*Format.eprintf "subst instr: %a@." Machine_code.pp_instr instr;*)
326
  let instr = eliminate subst instr in
327
  let v = get_assign_lhs instr in
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  let e = get_assign_rhs instr in
329
  (* Difficulties to merge with unstable. Here is the other code:
330

    
331
try
332
    let instr' = List.find (fun instr' -> is_assign instr' && get_assign_rhs instr' = e) instrs in
333
    match v.value_desc with
334
    | LocalVar v ->
335
      IMap.add v.var_id (get_assign_lhs instr') subst, instrs
336
    | StateVar v ->
337
      let lhs' = get_assign_lhs instr' in
338
      let typ' = lhs'.value_type in
339
      (match lhs'.value_desc with
340
      | LocalVar v' ->
341
	let instr = eliminate subst (mk_assign (mk_val (StateVar v) typ') (mk_val (LocalVar v') typ')) in
342
	subst, instr :: instrs
343
      | StateVar v' ->
344
	let subst_v' = IMap.add v'.var_id (mk_val (StateVar v) typ') IMap.empty in
345
let instrs' = snd (List.fold_right (fun instr (ok, instrs) -> (ok || instr = instr', if ok then instr :: instrs else if instr = instr' then instrs else eliminate subst_v' instr :: instrs)) instrs (false, [])) in
346
	IMap.add v'.var_id (mk_val (StateVar v) typ') subst, instr :: instrs'
347
      | _           -> assert false)
348
    | _          -> assert false
349
  with Not_found -> subst, instr :: instrs
350
 
351
*)
352

    
353
try
354
    let instr' = List.find (fun instr' -> is_assign instr' && get_assign_rhs instr' = e) instrs in
355
    match v.value_desc with
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    | LocalVar v ->
357
      IMap.add v.var_id (get_assign_lhs instr') subst, instrs
358
    | StateVar stv ->
359
       let lhs = get_assign_lhs instr' in
360
      (match lhs.value_desc with
361
      | LocalVar v' ->
362
        let instr = eliminate subst (mk_assign v lhs) in
363
	subst, instr :: instrs
364
      | StateVar stv' ->
365
	let subst_v' = IMap.add stv'.var_id v IMap.empty in
366
	let instrs' = snd (List.fold_right (fun instr (ok, instrs) -> (ok || instr = instr', if ok then instr :: instrs else if instr = instr' then instrs else eliminate subst_v' instr :: instrs)) instrs (false, [])) in
367
	IMap.add stv'.var_id v subst, instr :: instrs'
368
      | _           -> assert false)
369
    | _          -> assert false
370
  with Not_found -> subst, instr :: instrs
371
 
372
(** Common sub-expression elimination for machine instructions *)
373
(* - [subst] : hashtable from ident to (simple) definition
374
               it is an equivalence table
375
   - [elim]   : set of eliminated variables
376
   - [instrs] : previous instructions, which [instr] is compared against
377
   - [instr] : current instruction, normalized by [subst]
378
*)
379
let rec instr_cse (subst, instrs) instr =
380
  match instr with
381
  (* Simple cases*)
382
  | MStep([v], id, vl) when Basic_library.is_internal_fun id (List.map (fun v -> v.value_type) vl)
383
      -> instr_cse (subst, instrs) (MLocalAssign (v, mk_val (Fun (id, vl)) v.var_type))
384
  | MLocalAssign(v, expr) when is_unfoldable_expr 2 expr
385
      -> (IMap.add v.var_id expr subst, instr :: instrs)
386
  | _ when is_assign instr
387
      -> subst_instr subst instrs instr
388
  | _ -> (subst, instr :: instrs)
389

    
390
(** Apply common sub-expression elimination to a sequence of instrs
391
*)
392
let rec instrs_cse subst instrs =
393
  let subst, rev_instrs = 
394
    List.fold_left instr_cse (subst, []) instrs
395
  in subst, List.rev rev_instrs
396

    
397
(** Apply common sub-expression elimination to a machine
398
    - iterate through step instructions and remove simple local assigns
399
*)
400
let machine_cse subst machine =
401
  (*Log.report ~level:1 (fun fmt -> Format.fprintf fmt "machine_cse %a@." pp_elim subst);*)
402
  let subst, instrs = instrs_cse subst machine.mstep.step_instrs in
403
  let assigned = assigns_instrs instrs ISet.empty
404
  in
405
  {
406
    machine with
407
      mmemory = List.filter (fun vdecl -> ISet.mem vdecl assigned) machine.mmemory;
408
      mstep = { 
409
	machine.mstep with 
410
	  step_locals = List.filter (fun vdecl -> ISet.mem vdecl assigned) machine.mstep.step_locals;
411
	  step_instrs = instrs
412
      }
413
  }
414

    
415
let machines_cse machines =
416
  List.map
417
    (machine_cse IMap.empty)
418
    machines
419

    
420
(* variable substitution for optimizing purposes *)
421

    
422
(* checks whether an [instr] is skip and can be removed from program *)
423
let rec instr_is_skip instr =
424
  match instr with
425
  | MLocalAssign (i, { value_desc = (LocalVar v) ; _}) when i = v -> true
426
  | MStateAssign (i, { value_desc = StateVar v; _}) when i = v -> true
427
  | MBranch (g, hl) -> List.for_all (fun (_, il) -> instrs_are_skip il) hl
428
  | _               -> false
429
and instrs_are_skip instrs =
430
  List.for_all instr_is_skip instrs
431

    
432
let instr_cons instr cont =
433
 if instr_is_skip instr then cont else instr::cont
434

    
435
let rec instr_remove_skip instr cont =
436
  match instr with
437
  | MLocalAssign (i, { value_desc = LocalVar v; _ }) when i = v -> cont
438
  | MStateAssign (i, { value_desc = StateVar v; _ }) when i = v -> cont
439
  | MBranch (g, hl) -> MBranch (g, List.map (fun (h, il) -> (h, instrs_remove_skip il [])) hl) :: cont
440
  | _               -> instr::cont
441

    
442
and instrs_remove_skip instrs cont =
443
  List.fold_right instr_remove_skip instrs cont
444

    
445
let rec value_replace_var fvar value =
446
  match value.value_desc with
447
  | Cst c -> value
448
  | LocalVar v -> { value with value_desc = LocalVar (fvar v) }
449
  | StateVar v -> value
450
  | Fun (id, args) -> { value with value_desc = Fun (id, List.map (value_replace_var fvar) args) }
451
  | Array vl -> { value with value_desc = Array (List.map (value_replace_var fvar) vl)}
452
  | Access (t, i) -> { value with value_desc = Access(value_replace_var fvar t, i)}
453
  | Power (v, n) -> { value with value_desc = Power(value_replace_var fvar v, n)}
454

    
455
let rec instr_replace_var fvar instr cont =
456
  match instr with
457
  | MComment _          -> instr_cons instr cont
458
  | MLocalAssign (i, v) -> instr_cons (MLocalAssign (fvar i, value_replace_var fvar v)) cont
459
  | MStateAssign (i, v) -> instr_cons (MStateAssign (i, value_replace_var fvar v)) cont
460
  | MReset i            -> instr_cons instr cont
461
  | MNoReset i          -> instr_cons instr cont
462
  | MStep (il, i, vl)   -> instr_cons (MStep (List.map fvar il, i, List.map (value_replace_var fvar) vl)) cont
463
  | MBranch (g, hl)     -> instr_cons (MBranch (value_replace_var fvar g, List.map (fun (h, il) -> (h, instrs_replace_var fvar il [])) hl)) cont
464

    
465
and instrs_replace_var fvar instrs cont =
466
  List.fold_right (instr_replace_var fvar) instrs cont
467

    
468
let step_replace_var fvar step =
469
  (* Some outputs may have been replaced by locals.
470
     We then need to rename those outputs
471
     without changing their clocks, etc *)
472
  let outputs' =
473
    List.map (fun o -> { o with var_id = (fvar o).var_id }) step.step_outputs in
474
  let locals'  =
475
    List.fold_left (fun res l ->
476
      let l' = fvar l in
477
      if List.exists (fun o -> o.var_id = l'.var_id) outputs'
478
      then res
479
      else Utils.add_cons l' res)
480
      [] step.step_locals in
481
  { step with
482
    step_checks = List.map (fun (l, v) -> (l, value_replace_var fvar v)) step.step_checks;
483
    step_outputs = outputs';
484
    step_locals = locals';
485
    step_instrs = instrs_replace_var fvar step.step_instrs [];
486
}
487

    
488
let rec machine_replace_variables fvar m =
489
  { m with
490
    mstep = step_replace_var fvar m.mstep
491
  }
492

    
493
let machine_reuse_variables m reuse =
494
  let fvar v =
495
    try
496
      Hashtbl.find reuse v.var_id
497
    with Not_found -> v in
498
  machine_replace_variables fvar m
499

    
500
let machines_reuse_variables prog reuse_tables =
501
  List.map 
502
    (fun m -> 
503
      machine_reuse_variables m (Utils.IMap.find m.mname.node_id reuse_tables)
504
    ) prog
505

    
506
let rec instr_assign res instr =
507
  match instr with
508
  | MLocalAssign (i, _) -> Disjunction.CISet.add i res
509
  | MStateAssign (i, _) -> Disjunction.CISet.add i res
510
  | MBranch (g, hl)     -> List.fold_left (fun res (h, b) -> instrs_assign res b) res hl
511
  | MStep (il, _, _)    -> List.fold_right Disjunction.CISet.add il res
512
  | _                   -> res
513

    
514
and instrs_assign res instrs =
515
  List.fold_left instr_assign res instrs
516

    
517
let rec instr_constant_assign var instr =
518
  match instr with
519
  | MLocalAssign (i, { value_desc = Cst (Const_tag _); _ })
520
  | MStateAssign (i, { value_desc = Cst (Const_tag _); _ }) -> i = var
521
  | MBranch (g, hl)                     -> List.for_all (fun (h, b) -> instrs_constant_assign var b) hl
522
  | _                                   -> false
523

    
524
and instrs_constant_assign var instrs =
525
  List.fold_left (fun res i -> if Disjunction.CISet.mem var (instr_assign Disjunction.CISet.empty i) then instr_constant_assign var i else res) false instrs
526

    
527
let rec instr_reduce branches instr1 cont =
528
  match instr1 with
529
  | MLocalAssign (_, { value_desc = Cst (Const_tag c); _}) -> instr1 :: (List.assoc c branches @ cont)
530
  | MStateAssign (_, { value_desc = Cst (Const_tag c); _}) -> instr1 :: (List.assoc c branches @ cont)
531
  | MBranch (g, hl)                     -> MBranch (g, List.map (fun (h, b) -> (h, instrs_reduce branches b [])) hl) :: cont
532
  | _                                   -> instr1 :: cont
533

    
534
and instrs_reduce branches instrs cont =
535
 match instrs with
536
 | []        -> cont
537
 | [i]       -> instr_reduce branches i cont
538
 | i1::i2::q -> i1 :: instrs_reduce branches (i2::q) cont
539

    
540
let rec instrs_fusion instrs =
541
  match instrs with
542
  | []
543
  | [_]                                                               ->
544
    instrs
545
  | i1::(MBranch ({ value_desc = LocalVar v; _}, hl))::q when instr_constant_assign v i1 ->
546
    instr_reduce (List.map (fun (h, b) -> h, instrs_fusion b) hl) i1 (instrs_fusion q)
547
  | i1::(MBranch ({ value_desc = StateVar v; _}, hl))::q when instr_constant_assign v i1 ->
548
    instr_reduce (List.map (fun (h, b) -> h, instrs_fusion b) hl) i1 (instrs_fusion q) 
549
  | i1::i2::q                                                         ->
550
    i1 :: instrs_fusion (i2::q)
551

    
552
let step_fusion step =
553
  { step with
554
    step_instrs = instrs_fusion step.step_instrs;
555
  }
556

    
557
let rec machine_fusion m =
558
  { m with
559
    mstep = step_fusion m.mstep
560
  }
561

    
562
let machines_fusion prog =
563
  List.map machine_fusion prog
564

    
565
(* Local Variables: *)
566
(* compile-command:"make -C .." *)
567
(* End: *)