(***********************************************************************)
(*                                                                     *)
(*                           Objective Caml                            *)
(*                                                                     *)
(*            Xavier Leroy, projet Cristal, INRIA Rocquencourt         *)
(*                                                                     *)
(*  Copyright 1997 Institut National de Recherche en Informatique et   *)
(*  en Automatique.  All rights reserved.  This file is distributed    *)
(*  under the terms of the Q Public License version 1.0.               *)
(*                                                                     *)
(***********************************************************************)

(* $Id: selection.ml,v 1.6 2004/06/19 16:13:33 xleroy Exp $ *)

(* Instruction selection for the Power PC processor *)

open Misc
open Cmm
open Reg
open Arch
open Mach

(* Recognition of addressing modes *)

type addressing_expr =
    Asymbol of string
  | Alinear of expression
  | Aadd of expression * expression

let rec select_addr = function
    Cconst_symbol s ->
      (Asymbol s, 0)
  | Cop((Caddi | Cadda), [arg; Cconst_int m]) ->
      let (a, n) = select_addr arg in (a, n + m)
  | Cop((Caddi | Cadda), [Cconst_int m; arg]) ->
      let (a, n) = select_addr arg in (a, n + m)
  | Cop((Caddi | Cadda), [arg1; arg2]) ->
      begin match (select_addr arg1, select_addr arg2) with
          ((Alinear e1, n1), (Alinear e2, n2)) ->
              (Aadd(e1, e2), n1 + n2)
        | _ ->
              (Aadd(arg1, arg2), 0)
      end
  | exp ->
      (Alinear exp, 0)

(* Instruction selection *)

class selector = object (self)

inherit Selectgen.selector_generic as super

method is_immediate n = (n <= 32767) && (n >= -32768)

method select_addressing exp =
  match select_addr exp with
    (Asymbol s, d) ->
      (Ibased(s, d), Ctuple [])
  | (Alinear e, d) ->
      (Iindexed d, e)
  | (Aadd(e1, e2), d) ->
      if d = 0
      then (Iindexed2, Ctuple[e1; e2])
      else (Iindexed d, Cop(Cadda, [e1; e2]))

method select_operation op args =
  match (op, args) with
  (* Prevent the recognition of (x / cst) and (x % cst) when cst is not
     a power of 2, which do not correspond to an instruction. *)
    (Cdivi, [arg; Cconst_int n]) when n = 1 lsl (Misc.log2 n) ->
      (Iintop_imm(Idiv, n), [arg])
  | (Cdivi, _) -> 
      (Iintop Idiv, args)
  | (Cmodi, [arg; Cconst_int n]) when n = 1 lsl (Misc.log2 n) ->
      (Iintop_imm(Imod, n), [arg])
  | (Cmodi, _) ->
      (Iintop Imod, args)
  (* The and, or and xor instructions have a different range of immediate
     operands than the other instructions *)
  | (Cand, _) -> self#select_logical Iand args
  | (Cor, _) -> self#select_logical Ior args
  | (Cxor, _) -> self#select_logical Ixor args
  (* Recognize mult-add and mult-sub instructions *)
  | (Caddf, [Cop(Cmulf, [arg1; arg2]); arg3]) ->
      (Ispecific Imultaddf, [arg1; arg2; arg3])
  | (Caddf, [arg3; Cop(Cmulf, [arg1; arg2])]) ->
      (Ispecific Imultaddf, [arg1; arg2; arg3])
  | (Csubf, [Cop(Cmulf, [arg1; arg2]); arg3]) ->
      (Ispecific Imultsubf, [arg1; arg2; arg3])
  | _ ->
      super#select_operation op args

method select_logical op = function
    [arg; Cconst_int n] when n >= 0 && n <= 0xFFFF ->
      (Iintop_imm(op, n), [arg])
  | [Cconst_int n; arg] when n >= 0 && n <= 0xFFFF ->
      (Iintop_imm(op, n), [arg])
  | args ->
      (Iintop op, args)

end

let fundecl f = (new selector)#emit_fundecl f
