unbox_specialised_args.ml

(**************************************************************************)
(*                                                                        *)
(*                                 OCaml                                  *)
(*                                                                        *)
(*                       Pierre Chambart, OCamlPro                        *)
(*           Mark Shinwell and Leo White, Jane Street Europe              *)
(*                                                                        *)
(*   Copyright 2013--2016 OCamlPro SAS                                    *)
(*   Copyright 2014--2016 Jane Street Group LLC                           *)
(*                                                                        *)
(*   All rights reserved.  This file is distributed under the terms of    *)
(*   the GNU Lesser General Public License version 2.1, with the          *)
(*   special exception on linking described in the file LICENSE.          *)
(*                                                                        *)
(**************************************************************************)

[@@@ocaml.warning "+a-4-9-30-40-41-42"]

module ASA = Augment_specialised_args
module W = ASA.What_to_specialise

module Transform = struct
  let pass_name = "unbox-specialised-args"

  let precondition ~env:_ ~(set_of_closures : Flambda.set_of_closures) =
    !Clflags.unbox_specialised_args
      && not (Variable.Map.is_empty set_of_closures.specialised_args)

  let what_to_specialise ~env ~(set_of_closures : Flambda.set_of_closures) =
    let what_to_specialise = W.create ~set_of_closures in
    if not (precondition ~env ~set_of_closures) then
      what_to_specialise
    else
      let projections_by_function =
        Variable.Map.filter_map set_of_closures.function_decls.funs
          ~f:(fun _fun_var (function_decl : Flambda.function_declaration) ->
              if function_decl.stub then None
              else
                Some (Extract_projections.from_function_decl ~env
                  ~function_decl
                  ~which_variables:set_of_closures.specialised_args))
      in
      (* CR-soon mshinwell: consider caching the Invariant_params *relation*
         as well as the "_in_recursion" map *)
      let invariant_params_flow =
        Invariant_params.invariant_param_sources set_of_closures.function_decls
          ~backend:(Inline_and_simplify_aux.Env.backend env)
      in
      Variable.Map.fold (fun fun_var extractions what_to_specialise ->
          Projection.Set.fold (fun (projection : Projection.t)
                  what_to_specialise ->
              let group = Projection.projecting_from projection in
              assert (Variable.Map.mem group set_of_closures.specialised_args);
              let what_to_specialise =
                W.new_specialised_arg what_to_specialise ~fun_var ~group
                  ~definition:(Projection_from_existing_specialised_arg
                      projection)
              in
              match Variable.Map.find group invariant_params_flow with
              | exception Not_found -> what_to_specialise
              | flow ->
                (* If for function [f] we would extract a projection expression
                   [e] from some specialised argument [x] of [f], and we know
                   from [Invariant_params] that a specialised argument [y] of
                   another function [g] flows to [x], we will add [e] with
                   [y] substituted for [x] throughout as a newly-specialised
                   argument for [g].  This should help reduce the number of
                   simplification rounds required for mutually-recursive
                   functions. *)
                Variable.Pair.Set.fold (fun (target_fun_var, target_spec_arg)
                          what_to_specialise ->
                    if Variable.equal fun_var target_fun_var
                      || not (Variable.Map.mem target_spec_arg
                          set_of_closures.specialised_args)
                    then begin
                      what_to_specialise
                    end else begin
                      (* Rewrite the projection (that was in terms of an inner
                         specialised arg of [fun_var]) to be in terms of the
                         corresponding inner specialised arg of
                         [target_fun_var].  (The outer vars referenced in the
                         projection remain unchanged.) *)
                      let projection =
                        Projection.map_projecting_from projection
                          ~f:(fun var ->
                            assert (Variable.equal var group);
                            target_spec_arg)
                      in
                      W.new_specialised_arg what_to_specialise
                        ~fun_var:target_fun_var ~group
                        ~definition:
                          (Projection_from_existing_specialised_arg projection)
                    end)
                  flow
                  what_to_specialise)
            extractions
            what_to_specialise)
        projections_by_function
        what_to_specialise
end

include ASA.Make (Transform)