File: model_integer_exact.why

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(**************************************************************************)
(*                                                                        *)
(*  This file is part of Frama-C.                                         *)
(*                                                                        *)
(*  Copyright (C) 2007-2010                                               *)
(*    CEA   (Commissariat  l'nergie atomique et aux nergies            *)
(*           alternatives)                                                *)
(*    INRIA (Institut National de Recherche en Informatique et en         *)
(*           Automatique)                                                 *)
(*                                                                        *)
(*  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, version 2.1.                                              *)
(*                                                                        *)
(*  It 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.                   *)
(*                                                                        *)
(*  See the GNU Lesser General Public License version v2.1                *)
(*  for more details (enclosed in the file licenses/LGPLv2.1).            *)
(*                                                                        *)
(**************************************************************************)

(* Integer modulo definitions as in compcert integers*)

logic modul : int

axiom modul_pos : modul > 0

logic eqmod: int ,int -> prop

axiom eqmod_def : 
 forall x,y:int. 
   exists k:int. x =k*modul + y 


axiom eqmod_refl : 
  forall x:int. 
     eqmod(x,x)

axiom eqmod_refl2 : 
  forall x,y:int. 
     x=y -> 
     eqmod(x,y)

axiom eqmod_sym : 
  forall x,y:int. 
     eqmod(x,y) -> 
     eqmod(y,x)

axiom eqmod_trans: 
  forall x,y,z:int. 
     eqmod(x,y) -> 
     eqmod(y,z) -> 
     eqmod(x,z)

axiom eqmod_small_eq : 
  forall x,y:int. 
    eqmod(x,y)    ->
    0<= x < modul ->  
    0<= y < modul ->
    x=y  

axiom eqmod_mod_eq: 
  forall x,y:int. 
    eqmod(x,y) ->
    x % modul = y% modul 

axiom eqmod_mod: 
  forall x:int. 
    eqmod(x,x %modul) 

axiom eqmod_neg: 
  forall x,y:int. 
    eqmod(x,y) ->
    eqmod(-x,-y)

axiom eqmod_add: 
  forall a,b,c,d:int. 
    eqmod(a,b) ->
    eqmod(c,d) ->
    eqmod(a+c,b+d)

axiom eqmod_sub: 
  forall a,b,c,d:int. 
    eqmod(a,b) ->
    eqmod(c,d) ->
    eqmod(a-c,b-d)

axiom eqmod_mult: 
  forall a,b,c,d:int. 
    eqmod(a,b) ->
    eqmod(c,d) ->
    eqmod(a*c,b*d)


axiom mod_in_range : 
 forall x:int. 
    0 <= x%modul < modul

(* integer definition *) 

type Int

logic intval   : Int -> int  (* Z representation of the int *)
logic intrange : Int -> prop (* range property of the int vs a modul *)
logic unsigned : Int -> int 
logic signed   : Int -> int
logic repr     : int -> Int
logic Int_eq   : Int equality



logic half_modul   : int
logic max_unsigned : int
logic max_signed   : int
logic min_signed   : int


axiom half_modul_value   : half_modul = modul /2
axiom max_unsigned_value : max_signed = modul - 1 
axiom max_signed_value   : max_signed = half_modul - 1
axiom min_signed_value   : min_signed =- half_modul 

axiom unsigned_def : 
  forall i:Int. 
   unsigned(i) = intval(i)

axiom signed_lt : 
  forall i:Int. 
   intval(i) < half_modul ->
   signed(i) = unsigned(i)

axiom signed_ge : 
  forall i:Int. 
   intval(i) >= half_modul ->
   signed(i) = unsigned(i) - modul 

axiom mod_in_range : 
 forall x:Int. 0 <= (intval(x))%modul < modul

axiom repr_intval : 
  forall x:int. intval(repr(x))=x

axiom repr_intrange : 
   forall x:int. intrange(repr(x))

logic zero : Int
logic one  : Int
logic mone : Int

axiom zero_def : zero = repr(0) 
axiom one_def  : one  = repr(1)
axiom mone_def : mone = repr(-1)


(** coercions between int and Int **) 


axiom eqm_unsigned_repr : 
 forall z:int. eqmod(z,unsigned(repr(z)))

axiom eqm_unsigned_repr_l : 
 forall a,b:int. 
    eqmod(a,b) -> 
    eqmod(unsigned(repr(a)),b)

axiom eqm_unsigned_repr_r : 
 forall a,b:int. 
    eqmod(a,b) ->
    eqmod(a,unsigned(repr(b)))

axiom eqm_signed_unsigned :
 forall x:Int. 
    eqmod(signed(x),unsigned(x)) 

axiom unsigned_range: 
 forall i:Int. 0 <= unsigned(i) < max_unsigned

axiom unsigned_range_2: 
 forall i:Int. 0 <= unsigned(i) <= max_unsigned





(** boolean intepretation **)

axiom is_true : 
  forall i: Int. i <> zero

axiom is_false : 
  forall i:Int. i = zero 

(** arithmetics operations **) 


(** comparisons definition **)
logic cmpi_eq  : Int,Int -> Int
logic cmpi_lt  : Int,Int -> Int
logic cmpi_ltu : Int,Int -> Int

axiom cmpi_eq_def_true: 
 forall x,y:Int. 
   unsigned(x) = unsigned(y) -> 
   cmpi_eq(x,y) = one

axiom cmpi_eq_def_false: 
 forall x,y:Int. 
   unsigned(x) <> unsigned(y) -> 
   cmpi_eq(x,y) = zero


axiom cmpi_lt_def_true : 
 forall x,y:Int. 
   signed(x) < signed(y) ->
   cmpi_lt(x,y) = one 

axiom cmpi_lt_def_false : 
 forall x,y:Int. 
   signed(x) >= signed(y) ->
   cmpi_lt(x,y) = zero


axiom cmpi_ltu_def_true : 
 forall x,y:Int. 
   unsigned(x) < unsigned(y) ->
   cmpi_lt(x,y) = one 

axiom cmpi_ltu_def_false : 
 forall x,y:Int. 
   unsigned(x) >= unsigned(y) ->
   cmpi_lt(x,y) = zero


(** negation of a Int definition and properties **)
logic i_neg: Int -> Int

axiom neg_def : 
 forall i:Int. i_neg(i) = repr(-unsigned(i))

axiom neg_repr : 
 forall i:int . i_neg(repr(i)) = repr(-i)

axiom neg_zero : 
 i_neg(zero) = zero

axiom neg_involutive : 
 forall i:Int. i_neg (i_neg(i)) = i

(** addition of int definition and properties **)
logic i_add : Int,Int -> Int

axiom i_add_unsigned : 
 forall x,y:Int. 
     i_add(x,y) = repr (unsigned(x)+unsigned(y))

axiom add_signed : 
 forall x,y:Int. 
     i_add(x,y) = repr(signed(x)+signed(y))

axiom add_commut : 
 forall x,y:Int. 
   i_add(x,y) = i_add(y,x)

axiom add_permut : 
 forall x,y,z:Int. 
   i_add(x,i_add(y,z)) = i_add(y,i_add(x,z)) 

axiom add_neg_zero : 
 forall x:Int. i_add(x,i_neg(x)) = zero


axiom neg_add_distr : 
 forall x,y:Int. 
     i_neg(i_add(x,y)) = i_add (i_neg(x),i_neg(y))

(** subtraction of Int definition and properties **)
logic i_sub : Int,Int -> Int

axiom i_sub_def : 
 forall x,y:Int. 
     i_sub(x,y) = repr (unsigned(x)-unsigned(y))

axiom sub_zero_l : 
 forall x:Int. i_sub(x,zero) = x

axiom sub_zero_r : 
 forall x:Int. i_sub(zero,x) = i_neg(x)

axiom sub_add_opp : 
 forall x,y:Int. i_sub(x,y) = i_add(x,i_neg(y))

axiom sub_idem : 
 forall x:Int. i_sub(x,x) = zero

axiom sub_add_l : 
 forall x,y,z:Int. i_sub (i_add(x,y),z) = i_add(i_sub(x,z),y) 
 
axiom sub_add_r: 
 forall x,y,z:Int. i_sub(x,i_add(y,z)) = i_add(i_sub(x,z),i_neg(y)) 

axiom sub_shifted:
 forall x,y,z:Int. i_sub(i_add(x,z),i_add(y,z)) =i_sub(x,y)

(** multiplication of Int definition and properties **)
logic i_mul : Int,Int -> Int

axiom i_mul_def : 
 forall x,y:Int. 
     i_mul(x,y) = repr (unsigned(x)*unsigned(y))

axiom mul_commut: 
 forall x,y:Int. i_mul(x,y) = i_mul(y,x)

axiom mul_zero: 
 forall x:Int. i_mul(x,zero) = zero 

axiom mul_one: 
 forall x:Int. i_mul(x,one) = x

axiom mul_assoc: 
 forall x,y,z:Int. i_mul(i_mul(x,y),z) = i_mul(x,i_mul(y,z))

axiom mul_add_distr_l : 
 forall x,y,z:Int. i_mul(i_add(x,y),z) = i_add(i_mul(x,z),i_mul(y,z))

axiom mul_add_distr_r :
 forall x,y,z:Int. i_mul(x,i_add(y,z)) = i_add(i_mul(x,y),i_mul(x,z))

axiom neg_mul_distr_l: 
 forall x,y:Int. i_neg(i_mul(x,y)) = i_mul (i_neg(x),y)

axiom neg_mul_distr_l: 
 forall x,y:Int. i_neg(i_mul(x,y)) = i_mul (x,i_neg(y))

(** divisions on signed Int definition and properties **) 

logic divs:Int,Int -> Int

axiom divs_neg_neg : 
 forall x,y:Int. 
   signed(x) < 0 ->
   signed(y) < 0 ->
   divs(x,y) = repr (-signed(x)/(-signed(y)))

axiom divs_neg_pos : 
 forall x,y:Int. 
   signed(x) < 0  ->
   signed(y) >= 0 ->
   divs(x,y) = repr (-((-signed(x))/signed(y)))

axiom divs_pos_neg : 
 forall x,y:Int. 
   signed(x)>= 0 ->
   signed(y) < 0 ->
   divs(x,y) = repr(-(signed(x)/(-signed(y))))

axiom divs_pos_pos : 
 forall x,y:Int. 
   signed(x)>= 0 ->
   signed(y)>= 0 ->
   divs(x,y) = repr (signed(x)/signed(y))

(** divisions of unsigned Int definition and properties **) 

logic divu : Int,Int -> Int 

axiom divu_def : 
 forall x,y:Int. divu(x,y) = repr (unsigned(x)/unsigned(y))

(** Modulo of signed Int definition and properties **)

logic mods :Int,Int -> Int

axiom mods_neg_neg: 
  forall x,y:Int. 
   signed(x) < 0 ->
   signed(y) < 0 ->
   mods(x,y) = repr (signed(x)-(((-signed(x))/(-signed(y)))*signed(y)))

axiom divs_neg_pos : 
 forall x,y:Int. 
   signed(x) < 0  ->
   signed(y) >= 0 ->
   mods(x,y) = repr (signed(x) +(((-signed(x))/signed(y))*signed(y)))

axiom divs_pos_neg : 
 forall x,y:Int. 
   signed(x)>= 0 ->
   signed(y) < 0 ->
   mods(x,y) = repr(signed(x)+((signed(x)/(-signed(y)))*signed(y)))

axiom divs_pos_pos : 
 forall x,y:Int. 
   signed(x)>= 0 ->
   signed(y)>= 0 ->
   divs(x,y) = repr(signed(x)-((signed(x)/signed(y))*signed(y)))

(** Modulo of unsigned Int definition and properties **)

logic modu:Int,Int ->Int

axiom modu_def: 
 forall x,y:Int. modu(x,y)=repr (unsigned(x)%unsigned(y))