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Source file congruences.ml

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(****************************************************************************)
(*                                                                          *)
(* This file is part of MOPSA, a Modular Open Platform for Static Analysis. *)
(*                                                                          *)
(* Copyright (C) 2017-2019 The MOPSA Project.                               *)
(*                                                                          *)
(* This program 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 3 of the License, or     *)
(* (at your option) any later version.                                      *)
(*                                                                          *)
(* This program 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, see <http://www.gnu.org/licenses/>.    *)
(*                                                                          *)
(****************************************************************************)

(** Congruence abstraction of integer values. *)

open Mopsa
open Sig.Abstraction.Simplified_value
open Ast
open Bot


module Value =
struct

  module C = CongUtils.IntCong

  type v = C.t
  type t = v with_bot

  include GenValueId(
    struct
        type nonrec t = t
        let name = "universal.numeric.values.congruences"
        let display = "congruences"
    end
    )

  let accept_type = function
    | T_int | T_bool -> true
    | _ -> false

  let bottom = BOT

  let top = Nb (C.minf_inf)

  let is_bottom abs =
    bot_dfl1 true (fun itv -> not (C.is_valid itv)) abs

  let subset (a1:t) (a2:t) : bool = C.included_bot a1 a2

  let join (a1:t) (a2:t) : t = C.join_bot a1 a2

  let meet (a1:t) (a2:t) : t = C.meet_bot a1 a2

  let widen ctx (a1:t) (a2:t) : t = join a1 a2

  let print printer (a:t) = unformat C.fprint_bot printer a

  include DefaultValueFunctions

  let constant c t =
    match c with
    | C_bool true -> Nb (C.cst_int 1)
    | C_bool false -> Nb (C.cst_int 0)
    | C_int i -> Nb (C.cst i)
    | C_int_interval (i1,i2) -> Nb (C.of_bound i1 i2)
    | C_avalue(Common.V_int_congr_interval,(_,c)) -> c
    | _ -> top

  let unop op t a tr =
    match op with
    | O_log_not -> bot_lift1 C.log_not a
    | O_minus -> bot_lift1 C.neg a
    | O_plus -> a
    | O_abs -> bot_lift1 C.abs a
    | O_wrap(l,u) -> bot_lift1 (fun a -> C.wrap a l u) a
    | O_bit_invert -> bot_lift1 C.bit_not a
    | _ -> top

  let binop op t1 a1 t2 a2 tr =
    match op with
    | O_plus   -> bot_lift2 C.add a1 a2
    | O_minus  -> bot_lift2 C.sub a1 a2
    | O_mult   -> bot_lift2 C.mul a1 a2
    | O_div    -> bot_absorb2 C.div a1 a2
    | O_log_or   -> bot_lift2 C.log_or a1 a2
    | O_log_and  -> bot_lift2 C.log_and a1 a2
    | O_log_xor -> bot_lift2 C.log_xor a1 a2
    | O_mod    -> bot_absorb2 C.rem a1 a2
    | O_bit_rshift -> bot_absorb2 C.shift_right a1 a2
    | O_bit_lshift -> bot_absorb2 C.shift_left a1 a2
    | _     -> top

  let filter b t a =
    if b then bot_absorb1 C.meet_nonzero a
    else bot_absorb1 C.meet_zero a

  let backward_unop op t a tr r =
    try
      let a, r = bot_to_exn a, bot_to_exn r in
      let aa = match op with
        | O_minus  -> bot_to_exn (C.bwd_neg a r)
        | _ -> a
      in
      Nb aa
    with Found_BOT ->
      bottom

  let backward_binop op t1 a1 t2 a2 tr r =
    try
      let a1, a2, r = bot_to_exn a1, bot_to_exn a2, bot_to_exn r in
      let aa1, aa2 =
        match op with
        | O_plus   -> bot_to_exn (C.bwd_add a1 a2 r)
        | O_minus  -> bot_to_exn (C.bwd_sub a1 a2 r)
        | O_mult   -> bot_to_exn (C.bwd_mul a1 a2 r)
        | O_div    -> bot_to_exn (C.bwd_div a1 a2 r)
        | O_mod    -> bot_to_exn (C.bwd_rem a1 a2 r)
        | O_bit_rshift -> bot_to_exn (C.bwd_shift_right a1 a2 r)
        | O_bit_lshift -> bot_to_exn (C.bwd_shift_left a1 a2 r)
        | _ -> a1, a2
      in
      Nb aa1, Nb aa2
    with Found_BOT ->
      bottom, bottom

  let compare op b t1 a1 t2 a2 =
    try
      let a1, a2 = bot_to_exn a1, bot_to_exn a2 in
      let op = if b then op else negate_comparison_op op in
      let aa1, aa2 =
        match op with
        | O_eq -> bot_to_exn (C.filter_eq a1 a2)
        | O_ne -> bot_to_exn (C.filter_neq a1 a2)
        | O_lt -> bot_to_exn (C.filter_lt a1 a2)
        | O_gt -> bot_to_exn (C.filter_gt a1 a2)
        | O_le -> bot_to_exn (C.filter_leq a1 a2)
        | O_ge -> bot_to_exn (C.filter_geq a1 a2)
        | _ -> a1, a2
      in
      Nb aa1, Nb aa2
    with Found_BOT ->
      bottom, bottom


  let avalue : type r. r avalue_kind -> t -> r option =
    fun aval c ->
    match aval with
    | Common.V_int_congr_interval ->
      let ret =
        match c with
        | BOT -> Intervals.Integer.Value.bottom, bottom
        | _ -> Intervals.Integer.Value.top, c
      in
      OptionExt.return ret

    | _ -> None

end

let () =
  register_simplified_value_abstraction (module Value)
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