Sop.v

(** Arithmetic and logical operators for Stanlight; a cut down version C/Clight Cop.v *)

Require Import Coqlib.
Require Import AST.
Require Import Integers.
Require Import Floats.
Require Import Values.
Require Import Memory.
Require Import Ctypes.
Require Archi.

(** * Syntax of operators. *)

Inductive unary_operation : Type :=
  | Onotbool : unary_operation          (**r boolean negation ([!] in C) *)
  | Onotint : unary_operation           (**r integer complement ([~] in C) *)
  | Oneg : unary_operation              (**r opposite (unary [-]) *)
  | Oabsfloat : unary_operation.        (**r floating-point absolute value *)

Inductive binary_operation : Type :=
  | Oadd : binary_operation             (**r addition (binary [+]) *)
  | Osub : binary_operation             (**r subtraction (binary [-]) *)
  | Omul : binary_operation             (**r multiplication (binary [*]) *)
  | Odiv : binary_operation             (**r division ([/]) *)
  | Omod : binary_operation             (**r remainder ([%]) *)
  | Oand : binary_operation             (**r bitwise and ([&]) *)
  | Oor : binary_operation              (**r bitwise or ([|]) *)
  | Oxor : binary_operation             (**r bitwise xor ([^]) *)
  | Oshl : binary_operation             (**r left shift ([<<]) *)
  | Oshr : binary_operation             (**r right shift ([>>]) *)
  | Oeq: binary_operation               (**r comparison ([==]) *)
  | One: binary_operation               (**r comparison ([!=]) *)
  | Olt: binary_operation               (**r comparison ([<]) *)
  | Ogt: binary_operation               (**r comparison ([>]) *)
  | Ole: binary_operation               (**r comparison ([<=]) *)
  | Oge: binary_operation.              (**r comparison ([>=]) *)

Inductive incr_or_decr : Type := Incr | Decr.

(** * Type classification and semantics of operators. *)

(** Most C operators are overloaded (they apply to arguments of various
  types) and their semantics depend on the types of their arguments.
  The following [classify_*] functions take as arguments the types
  of the arguments of an operation.  They return enough information
  to resolve overloading for this operator applications, such as
  ``both arguments are floats'', or ``the first is a pointer
  and the second is an integer''.  This classification is used in the
  compiler (module [Cshmgen]) to resolve overloading statically.

  The [sem_*] functions below compute the result of an operator
  application.  Since operators are overloaded, the result depends
  both on the static types of the arguments and on their run-time values.
  The corresponding [classify_*] function is first called on the
  types of the arguments to resolve static overloading.  It is then
  followed by a case analysis on the values of the arguments. *)

(** ** Casts and truth values *)

Inductive classify_cast_cases : Type :=
  | cast_case_pointer                              (**r between pointer types or intptr_t types *)
  | cast_case_i2i (sz2:intsize) (si2:signedness)   (**r int -> int *)
  | cast_case_f2f                                  (**r double -> double *)
  | cast_case_s2s                                  (**r single -> single *)
  | cast_case_f2s                                  (**r double -> single *)
  | cast_case_s2f                                  (**r single -> double *)
  | cast_case_i2f (si1: signedness)                (**r int -> double *)
  | cast_case_i2s (si1: signedness)                (**r int -> single *)
  | cast_case_f2i (sz2:intsize) (si2:signedness)   (**r double -> int *)
  | cast_case_s2i (sz2:intsize) (si2:signedness)   (**r single -> int *)
  | cast_case_l2l                       (**r long -> long *)
  | cast_case_i2l (si1: signedness)     (**r int -> long *)
  | cast_case_l2i (sz2: intsize) (si2: signedness) (**r long -> int *)
  | cast_case_l2f (si1: signedness)                (**r long -> double *)
  | cast_case_l2s (si1: signedness)                (**r long -> single *)
  | cast_case_f2l (si2:signedness)                 (**r double -> long *)
  | cast_case_s2l (si2:signedness)                 (**r single -> long *)
  | cast_case_i2bool                               (**r int -> bool *)
  | cast_case_l2bool                               (**r long -> bool *)
  | cast_case_f2bool                               (**r double -> bool *)
  | cast_case_s2bool                               (**r single -> bool *)
  | cast_case_struct (id1 id2: ident)              (**r struct -> struct *)
  | cast_case_union  (id1 id2: ident)              (**r union -> union *)
  | cast_case_void                                 (**r any -> void *)
  | cast_case_default.

Definition classify_cast (tfrom tto: type) : classify_cast_cases :=
  match tto, tfrom with
  (* To [void] *)
  | Tvoid, _ => cast_case_void
  (* To [_Bool] *)
  | Tint IBool _ _, Tint _ _ _ => cast_case_i2bool
  | Tint IBool _ _, Tlong _ _ => cast_case_l2bool
  | Tint IBool _ _, Tfloat F64 _ => cast_case_f2bool
  | Tint IBool _ _, Tfloat F32 _ => cast_case_s2bool
  | Tint IBool _ _, (Tpointer _ _ | Tarray _ _ _ | Tfunction _ _ _) => 
      if Archi.ptr64 then cast_case_l2bool else cast_case_i2bool
  (* To [int] other than [_Bool] *)
  | Tint sz2 si2 _, Tint _ _ _ =>
      if Archi.ptr64 then cast_case_i2i sz2 si2
      else if intsize_eq sz2 I32 then cast_case_pointer
      else cast_case_i2i sz2 si2
  | Tint sz2 si2 _, Tlong _ _ => cast_case_l2i sz2 si2
  | Tint sz2 si2 _, Tfloat F64 _ => cast_case_f2i sz2 si2
  | Tint sz2 si2 _, Tfloat F32 _ => cast_case_s2i sz2 si2
  | Tint sz2 si2 _, (Tpointer _ _ | Tarray _ _ _ | Tfunction _ _ _) =>
      if Archi.ptr64 then cast_case_l2i sz2 si2
      else if intsize_eq sz2 I32 then cast_case_pointer
      else cast_case_i2i sz2 si2
  (* To [long] *)
  | Tlong _ _, Tlong _ _ =>
      if Archi.ptr64 then cast_case_pointer else cast_case_l2l
  | Tlong _ _, Tint sz1 si1 _ => cast_case_i2l si1
  | Tlong si2 _, Tfloat F64 _ => cast_case_f2l si2
  | Tlong si2 _, Tfloat F32 _ => cast_case_s2l si2
  | Tlong si2 _, (Tpointer _ _ | Tarray _ _ _ | Tfunction _ _ _) =>
      if Archi.ptr64 then cast_case_pointer else cast_case_i2l si2
  (* To [float] *)
  | Tfloat F64 _, Tint sz1 si1 _ => cast_case_i2f si1
  | Tfloat F32 _, Tint sz1 si1 _ => cast_case_i2s si1
  | Tfloat F64 _, Tlong si1 _ => cast_case_l2f si1
  | Tfloat F32 _, Tlong si1 _ => cast_case_l2s si1
  | Tfloat F64 _, Tfloat F64 _ => cast_case_f2f
  | Tfloat F32 _, Tfloat F32 _ => cast_case_s2s
  | Tfloat F64 _, Tfloat F32 _ => cast_case_s2f
  | Tfloat F32 _, Tfloat F64 _ => cast_case_f2s
  (* To pointer types *)
  | Tpointer _ _, Tint _ si _ =>
      if Archi.ptr64 then cast_case_i2l si else cast_case_pointer
  | Tpointer _ _, Tlong _ _ =>
      if Archi.ptr64 then cast_case_pointer else cast_case_l2i I32 Unsigned
  | Tpointer _ _, (Tpointer _ _ | Tarray _ _ _ | Tfunction _ _ _) => cast_case_pointer
  (* To struct or union types *)
  | Tstruct id2 _, Tstruct id1 _ => cast_case_struct id1 id2
  | Tunion id2 _, Tunion id1 _ => cast_case_union id1 id2
  (* Catch-all *)
  | _, _ => cast_case_default
  end.

(** Semantics of casts.  [sem_cast v1 t1 t2 m = Some v2] if value [v1],
  viewed with static type [t1], can be converted  to type [t2],
  resulting in value [v2].  *)

Definition cast_int_int (sz: intsize) (sg: signedness) (i: int) : int :=
  match sz, sg with
  | I8, Signed => Int.sign_ext 8 i
  | I8, Unsigned => Int.zero_ext 8 i
  | I16, Signed => Int.sign_ext 16 i
  | I16, Unsigned => Int.zero_ext 16 i
  | I32, _ => i
  | IBool, _ => if Int.eq i Int.zero then Int.zero else Int.one
  end.

Definition cast_int_float (si: signedness) (i: int) : float :=
  match si with
  | Signed => Float.of_int i
  | Unsigned => Float.of_intu i
  end.

Definition cast_float_int (si : signedness) (f: float) : option int :=
  match si with
  | Signed => Float.to_int f
  | Unsigned => Float.to_intu f
  end.

Definition cast_int_single (si: signedness) (i: int) : float32 :=
  match si with
  | Signed => Float32.of_int i
  | Unsigned => Float32.of_intu i
  end.

Definition cast_single_int (si : signedness) (f: float32) : option int :=
  match si with
  | Signed => Float32.to_int f
  | Unsigned => Float32.to_intu f
  end.

Definition cast_int_long (si: signedness) (i: int) : int64 :=
  match si with
  | Signed => Int64.repr (Int.signed i)
  | Unsigned => Int64.repr (Int.unsigned i)
  end.

Definition cast_long_float (si: signedness) (i: int64) : float :=
  match si with
  | Signed => Float.of_long i
  | Unsigned => Float.of_longu i
  end.

Definition cast_long_single (si: signedness) (i: int64) : float32 :=
  match si with
  | Signed => Float32.of_long i
  | Unsigned => Float32.of_longu i
  end.

Definition cast_float_long (si : signedness) (f: float) : option int64 :=
  match si with
  | Signed => Float.to_long f
  | Unsigned => Float.to_longu f
  end.

Definition cast_single_long (si : signedness) (f: float32) : option int64 :=
  match si with
  | Signed => Float32.to_long f
  | Unsigned => Float32.to_longu f
  end.

Definition sem_cast (v: val) (t1 t2: type) : option val :=
  match classify_cast t1 t2 with
  | cast_case_pointer =>
      match v with
      | Vptr _ _ => Some v
      | Vint _ => if Archi.ptr64 then None else Some v
      | Vlong _ => if Archi.ptr64 then Some v else None
      | _ => None
      end
  | cast_case_i2i sz2 si2 =>
      match v with
      | Vint i => Some (Vint (cast_int_int sz2 si2 i))
      | _ => None
      end
  | cast_case_f2f =>
      match v with
      | Vfloat f => Some (Vfloat f)
      | _ => None
      end
  | cast_case_s2s =>
      match v with
      | Vsingle f => Some (Vsingle f)
      | _ => None
      end
  | cast_case_s2f =>
      match v with
      | Vsingle f => Some (Vfloat (Float.of_single f))
      | _ => None
      end
  | cast_case_f2s =>
      match v with
      | Vfloat f => Some (Vsingle (Float.to_single f))
      | _ => None
      end
  | cast_case_i2f si1 =>
      match v with
      | Vint i => Some (Vfloat (cast_int_float si1 i))
      | _ => None
      end
  | cast_case_i2s si1 =>
      match v with
      | Vint i => Some (Vsingle (cast_int_single si1 i))
      | _ => None
      end
  | cast_case_f2i sz2 si2 =>
      match v with
      | Vfloat f =>
          match cast_float_int si2 f with
          | Some i => Some (Vint (cast_int_int sz2 si2 i))
          | None => None
          end
      | _ => None
      end
  | cast_case_s2i sz2 si2 =>
      match v with
      | Vsingle f =>
          match cast_single_int si2 f with
          | Some i => Some (Vint (cast_int_int sz2 si2 i))
          | None => None
          end
      | _ => None
      end
  | cast_case_i2bool =>
      match v with
      | Vint n =>
          Some(Vint(if Int.eq n Int.zero then Int.zero else Int.one))
      | _ => None
      end
  | cast_case_l2bool =>
      match v with
      | Vlong n =>
          Some(Vint(if Int64.eq n Int64.zero then Int.zero else Int.one))
      | Vptr b ofs => None
      | _ => None
      end
  | cast_case_f2bool =>
      match v with
      | Vfloat f =>
          Some(Vint(if Float.cmp Ceq f Float.zero then Int.zero else Int.one))
      | _ => None
      end
  | cast_case_s2bool =>
      match v with
      | Vsingle f =>
          Some(Vint(if Float32.cmp Ceq f Float32.zero then Int.zero else Int.one))
      | _ => None
      end
  | cast_case_l2l =>
      match v with
      | Vlong n => Some (Vlong n)
      | _ => None
      end
  | cast_case_i2l si =>
      match v with
      | Vint n => Some(Vlong (cast_int_long si n))
      | _ => None
      end
  | cast_case_l2i sz si =>
      match v with
      | Vlong n => Some(Vint (cast_int_int sz si (Int.repr (Int64.unsigned n))))
      | _ => None
      end
  | cast_case_l2f si1 =>
      match v with
      | Vlong i => Some (Vfloat (cast_long_float si1 i))
      | _ => None
      end
  | cast_case_l2s si1 =>
      match v with
      | Vlong i => Some (Vsingle (cast_long_single si1 i))
      | _ => None
      end
  | cast_case_f2l si2 =>
      match v with
      | Vfloat f =>
          match cast_float_long si2 f with
          | Some i => Some (Vlong i)
          | None => None
          end
      | _ => None
      end
  | cast_case_s2l si2 =>
      match v with
      | Vsingle f =>
          match cast_single_long si2 f with
          | Some i => Some (Vlong i)
          | None => None
          end
      | _ => None
      end
  | cast_case_struct id1 id2 =>
      match v with
      | Vptr b ofs =>
          if ident_eq id1 id2 then Some v else None
      | _ => None
      end
  | cast_case_union id1 id2 =>
      match v with
      | Vptr b ofs =>
          if ident_eq id1 id2 then Some v else None
      | _ => None
      end
  | cast_case_void =>
      Some v
  | cast_case_default =>
      None
  end.

(** The following describes types that can be interpreted as a boolean:
  integers, floats, pointers.  It is used for the semantics of
  the [!] and [?] operators, as well as the [if], [while],
  and [for] statements. *)

Inductive classify_bool_cases : Type :=
  | bool_case_i                           (**r integer *)
  | bool_case_l                           (**r long *)
  | bool_case_f                           (**r double float *)
  | bool_case_s                           (**r single float *)
  | bool_default.

Definition classify_bool (ty: type) : classify_bool_cases :=
  match typeconv ty with
  | Tint _ _ _ => bool_case_i
  | Tpointer _ _ => if Archi.ptr64 then bool_case_l else bool_case_i
  | Tfloat F64 _ => bool_case_f
  | Tfloat F32 _ => bool_case_s
  | Tlong _ _ => bool_case_l
  | _ => bool_default
  end.

(** Interpretation of values as truth values.
  Non-zero integers, non-zero floats and non-null pointers are
  considered as true.  The integer zero (which also represents
  the null pointer) and the float 0.0 are false. *)

Definition bool_val (v: val) (t: type) : option bool :=
  match classify_bool t with
  | bool_case_i =>
      match v with
      | Vint n => Some (negb (Int.eq n Int.zero))
      | Vptr b ofs => None
      | _ => None
      end
  | bool_case_l =>
      match v with
      | Vlong n => Some (negb (Int64.eq n Int64.zero))
      | Vptr b ofs => None
      | _ => None
      end
  | bool_case_f =>
      match v with
      | Vfloat f => Some (negb (Float.cmp Ceq f Float.zero))
      | _ => None
      end
  | bool_case_s =>
      match v with
      | Vsingle f => Some (negb (Float32.cmp Ceq f Float32.zero))
      | _ => None
      end
  | bool_default => None
  end.

(** ** Unary operators *)

(** *** Boolean negation *)

Definition sem_notbool (v: val) (ty: type): option val :=
  option_map (fun b => Val.of_bool (negb b)) (bool_val v ty).

(** *** Opposite and absolute value *)

Inductive classify_neg_cases : Type :=
  | neg_case_i(s: signedness)              (**r int *)
  | neg_case_f                             (**r double float *)
  | neg_case_s                             (**r single float *)
  | neg_case_l(s: signedness)              (**r long *)
  | neg_default.

Definition classify_neg (ty: type) : classify_neg_cases :=
  match ty with
  | Tint I32 Unsigned _ => neg_case_i Unsigned
  | Tint _ _ _ => neg_case_i Signed
  | Tfloat F64 _ => neg_case_f
  | Tfloat F32 _ => neg_case_s
  | Tlong si _ => neg_case_l si
  | _ => neg_default
  end.

Definition sem_neg (v: val) (ty: type) : option val :=
  match classify_neg ty with
  | neg_case_i sg =>
      match v with
      | Vint n => Some (Vint (Int.neg n))
      | _ => None
      end
  | neg_case_f =>
      match v with
      | Vfloat f => Some (Vfloat (Float.neg f))
      | _ => None
      end
  | neg_case_s =>
      match v with
      | Vsingle f => Some (Vsingle (Float32.neg f))
      | _ => None
      end
  | neg_case_l sg =>
      match v with
      | Vlong n => Some (Vlong (Int64.neg n))
      | _ => None
      end
  | neg_default => None
  end.

Definition sem_absfloat (v: val) (ty: type) : option val :=
  match classify_neg ty with
  | neg_case_i sg =>
      match v with
      | Vint n => Some (Vfloat (Float.abs (cast_int_float sg n)))
      | _ => None
      end
  | neg_case_f =>
      match v with
      | Vfloat f => Some (Vfloat (Float.abs f))
      | _ => None
      end
  | neg_case_s =>
      match v with
      | Vsingle f => Some (Vfloat (Float.abs (Float.of_single f)))
      | _ => None
      end
  | neg_case_l sg =>
      match v with
      | Vlong n => Some (Vfloat (Float.abs (cast_long_float sg n)))
      | _ => None
      end
  | neg_default => None
  end.

(** *** Bitwise complement *)

Inductive classify_notint_cases : Type :=
  | notint_case_i(s: signedness)              (**r int *)
  | notint_case_l(s: signedness)              (**r long *)
  | notint_default.

Definition classify_notint (ty: type) : classify_notint_cases :=
  match ty with
  | Tint I32 Unsigned _ => notint_case_i Unsigned
  | Tint _ _ _ => notint_case_i Signed
  | Tlong si _ => notint_case_l si
  | _ => notint_default
  end.

Definition sem_notint (v: val) (ty: type): option val :=
  match classify_notint ty with
  | notint_case_i sg =>
      match v with
      | Vint n => Some (Vint (Int.not n))
      | _ => None
      end
  | notint_case_l sg =>
      match v with
      | Vlong n => Some (Vlong (Int64.not n))
      | _ => None
      end
  | notint_default => None
  end.

(** ** Binary operators *)

(** For binary operations, the "usual binary conversions" consist in
- determining the type at which the operation is to be performed
  (a form of least upper bound of the types of the two arguments);
- casting the two arguments to this common type;
- performing the operation at that type.
*)

Inductive binarith_cases: Type :=
  | bin_case_i (s: signedness)         (**r at int type *)
  | bin_case_l (s: signedness)         (**r at long int type *)
  | bin_case_f                         (**r at double float type *)
  | bin_case_s                         (**r at single float type *)
  | bin_default.                       (**r error *)

Definition classify_binarith (ty1: type) (ty2: type) : binarith_cases :=
  match ty1, ty2 with
  | Tint I32 Unsigned _, Tint _ _ _ => bin_case_i Unsigned
  | Tint _ _ _, Tint I32 Unsigned _ => bin_case_i Unsigned
  | Tint _ _ _, Tint _ _ _ => bin_case_i Signed
  | Tlong Signed _, Tlong Signed _ => bin_case_l Signed
  | Tlong _ _, Tlong _ _ => bin_case_l Unsigned
  | Tlong sg _, Tint _ _ _ => bin_case_l sg
  | Tint _ _ _, Tlong sg _ => bin_case_l sg
  | Tfloat F32 _, Tfloat F32 _ => bin_case_s
  | Tfloat _ _, Tfloat _ _ => bin_case_f
  | Tfloat F64 _, (Tint _ _ _ | Tlong _ _) => bin_case_f
  | (Tint _ _ _ | Tlong _ _), Tfloat F64 _ => bin_case_f
  | Tfloat F32 _, (Tint _ _ _ | Tlong _ _) => bin_case_s
  | (Tint _ _ _ | Tlong _ _), Tfloat F32 _ => bin_case_s
  | _, _ => bin_default
  end.

(** The static type of the result. Both arguments are converted to this type
    before the actual computation. *)

Definition binarith_type (c: binarith_cases) : type :=
  match c with
  | bin_case_i sg => Tint I32 sg noattr
  | bin_case_l sg => Tlong sg noattr
  | bin_case_f    => Tfloat F64 noattr
  | bin_case_s    => Tfloat F32 noattr
  | bin_default   => Tvoid
  end.

Definition sem_binarith
    (sem_int: signedness -> int -> int -> option val)
    (sem_long: signedness -> int64 -> int64 -> option val)
    (sem_float: float -> float -> option val)
    (sem_single: float32 -> float32 -> option val)
    (v1: val) (t1: type) (v2: val) (t2: type) : option val :=
  let c := classify_binarith t1 t2 in
  let t := binarith_type c in
  match sem_cast v1 t1 t with
  | None => None
  | Some v1' =>
  match sem_cast v2 t2 t with
  | None => None
  | Some v2' =>
  match c with
  | bin_case_i sg =>
      match v1', v2' with
      | Vint n1, Vint n2 => sem_int sg n1 n2
      | _,  _ => None
      end
  | bin_case_f =>
      match v1', v2' with
      | Vfloat n1, Vfloat n2 => sem_float n1 n2
      | _,  _ => None
      end
  | bin_case_s =>
      match v1', v2' with
      | Vsingle n1, Vsingle n2 => sem_single n1 n2
      | _,  _ => None
      end
  | bin_case_l sg =>
      match v1', v2' with
      | Vlong n1, Vlong n2 => sem_long sg n1 n2
      | _,  _ => None
      end
  | bin_default => None
  end end end.

(** *** Addition *)

Inductive classify_add_cases : Type :=
  | add_case_pi (ty: type) (si: signedness)     (**r pointer, int *)
  | add_case_pl (ty: type)     (**r pointer, long *)
  | add_case_ip (si: signedness) (ty: type)     (**r int, pointer *)
  | add_case_lp (ty: type)     (**r long, pointer *)
  | add_default.               (**r numerical type, numerical type *)

Definition classify_add (ty1: type) (ty2: type) :=
  match typeconv ty1, typeconv ty2 with
  | Tpointer ty _, Tint _ si _ => add_case_pi ty si
  | Tpointer ty _, Tlong _ _ => add_case_pl ty
  | Tint _ si _, Tpointer ty _ => add_case_ip si ty
  | Tlong _ _, Tpointer ty _ => add_case_lp ty
  | _, _ => add_default
  end.

Definition ptrofs_of_int (si: signedness) (n: int) : ptrofs :=
  match si with
  | Signed => Ptrofs.of_ints n
  | Unsigned => Ptrofs.of_intu n
  end.

Definition sem_add_ptr_int (cenv: composite_env) (ty: type) (si: signedness) (v1 v2: val): option val :=
  match v1, v2 with
  | Vptr b1 ofs1, Vint n2 =>
      let n2 := ptrofs_of_int si n2 in
      Some (Vptr b1 (Ptrofs.add ofs1 (Ptrofs.mul (Ptrofs.repr (sizeof cenv ty)) n2)))
  | Vint n1, Vint n2 =>
      if Archi.ptr64 then None else Some (Vint (Int.add n1 (Int.mul (Int.repr (sizeof cenv ty)) n2)))
  | Vlong n1, Vint n2 =>
      let n2 := cast_int_long si n2 in
      if Archi.ptr64 then Some (Vlong (Int64.add n1 (Int64.mul (Int64.repr (sizeof cenv ty)) n2))) else None
  | _,  _ => None
  end.

Definition sem_add_ptr_long (cenv: composite_env) (ty: type) (v1 v2: val): option val :=
  match v1, v2 with
  | Vptr b1 ofs1, Vlong n2 =>
      let n2 := Ptrofs.of_int64 n2 in
      Some (Vptr b1 (Ptrofs.add ofs1 (Ptrofs.mul (Ptrofs.repr (sizeof cenv ty)) n2)))
  | Vint n1, Vlong n2 =>
      let n2 := Int.repr (Int64.unsigned n2) in
      if Archi.ptr64 then None else Some (Vint (Int.add n1 (Int.mul (Int.repr (sizeof cenv ty)) n2)))
  | Vlong n1, Vlong n2 =>
      if Archi.ptr64 then Some (Vlong (Int64.add n1 (Int64.mul (Int64.repr (sizeof cenv ty)) n2))) else None
  | _,  _ => None
  end.

Definition sem_add (cenv: composite_env) (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  match classify_add t1 t2 with
  | add_case_pi ty si =>             (**r pointer plus integer *)
      sem_add_ptr_int cenv ty si v1 v2
  | add_case_pl ty =>                (**r pointer plus long *)
      sem_add_ptr_long cenv ty v1 v2
  | add_case_ip si ty =>             (**r integer plus pointer *)
      sem_add_ptr_int cenv ty si v2 v1
  | add_case_lp ty =>                (**r long plus pointer *)
      sem_add_ptr_long cenv ty v2 v1
  | add_default =>
      sem_binarith
        (fun sg n1 n2 => Some(Vint(Int.add n1 n2)))
        (fun sg n1 n2 => Some(Vlong(Int64.add n1 n2)))
        (fun n1 n2 => Some(Vfloat(Float.add n1 n2)))
        (fun n1 n2 => Some(Vsingle(Float32.add n1 n2)))
        v1 t1 v2 t2
  end.

(** *** Subtraction *)

Inductive classify_sub_cases : Type :=
  | sub_case_pi (ty: type) (si: signedness)  (**r pointer, int *)
  | sub_case_pp (ty: type)               (**r pointer, pointer *)
  | sub_case_pl (ty: type)               (**r pointer, long *)
  | sub_default.                         (**r numerical type, numerical type *)

Definition classify_sub (ty1: type) (ty2: type) :=
  match typeconv ty1, typeconv ty2 with
  | Tpointer ty _, Tint _ si _ => sub_case_pi ty si
  | Tpointer ty _ , Tpointer _ _ => sub_case_pp ty
  | Tpointer ty _, Tlong _ _ => sub_case_pl ty
  | _, _ => sub_default
  end.

Definition sem_sub (cenv: composite_env) (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  match classify_sub t1 t2 with
  | sub_case_pi ty si =>            (**r pointer minus integer *)
      match v1, v2 with
      | Vptr b1 ofs1, Vint n2 =>
          let n2 := ptrofs_of_int si n2 in
          Some (Vptr b1 (Ptrofs.sub ofs1 (Ptrofs.mul (Ptrofs.repr (sizeof cenv ty)) n2)))
      | Vint n1, Vint n2 =>
          if Archi.ptr64 then None else Some (Vint (Int.sub n1 (Int.mul (Int.repr (sizeof cenv ty)) n2)))
      | Vlong n1, Vint n2 =>
          let n2 := cast_int_long si n2 in
          if Archi.ptr64 then Some (Vlong (Int64.sub n1 (Int64.mul (Int64.repr (sizeof cenv ty)) n2))) else None
      | _,  _ => None
      end
  | sub_case_pl ty =>            (**r pointer minus long *)
      match v1, v2 with
      | Vptr b1 ofs1, Vlong n2 =>
          let n2 := Ptrofs.of_int64 n2 in
          Some (Vptr b1 (Ptrofs.sub ofs1 (Ptrofs.mul (Ptrofs.repr (sizeof cenv ty)) n2)))
      | Vint n1, Vlong n2 =>
          let n2 := Int.repr (Int64.unsigned n2) in
          if Archi.ptr64 then None else Some (Vint (Int.sub n1 (Int.mul (Int.repr (sizeof cenv ty)) n2)))
      | Vlong n1, Vlong n2 =>
          if Archi.ptr64 then Some (Vlong (Int64.sub n1 (Int64.mul (Int64.repr (sizeof cenv ty)) n2))) else None
      | _,  _ => None
      end
  | sub_case_pp ty =>          (**r pointer minus pointer *)
      match v1,v2 with
      | Vptr b1 ofs1, Vptr b2 ofs2 =>
          if eq_block b1 b2 then
            let sz := sizeof cenv ty in
            if zlt 0 sz && zle sz Ptrofs.max_signed
            then Some (Vptrofs (Ptrofs.divs (Ptrofs.sub ofs1 ofs2) (Ptrofs.repr sz)))
            else None
          else None
      | _, _ => None
      end
  | sub_default =>
      sem_binarith
        (fun sg n1 n2 => Some(Vint(Int.sub n1 n2)))
        (fun sg n1 n2 => Some(Vlong(Int64.sub n1 n2)))
        (fun n1 n2 => Some(Vfloat(Float.sub n1 n2)))
        (fun n1 n2 => Some(Vsingle(Float32.sub n1 n2)))
        v1 t1 v2 t2
  end.

(** *** Multiplication, division, modulus *)

Definition sem_mul (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_binarith
    (fun sg n1 n2 => Some(Vint(Int.mul n1 n2)))
    (fun sg n1 n2 => Some(Vlong(Int64.mul n1 n2)))
    (fun n1 n2 => Some(Vfloat(Float.mul n1 n2)))
    (fun n1 n2 => Some(Vsingle(Float32.mul n1 n2)))
    v1 t1 v2 t2.

Definition sem_div (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_binarith
    (fun sg n1 n2 =>
      match sg with
      | Signed =>
          if Int.eq n2 Int.zero
          || Int.eq n1 (Int.repr Int.min_signed) && Int.eq n2 Int.mone
          then None else Some(Vint(Int.divs n1 n2))
      | Unsigned =>
          if Int.eq n2 Int.zero
          then None else Some(Vint(Int.divu n1 n2))
      end)
    (fun sg n1 n2 =>
      match sg with
      | Signed =>
          if Int64.eq n2 Int64.zero
          || Int64.eq n1 (Int64.repr Int64.min_signed) && Int64.eq n2 Int64.mone
          then None else Some(Vlong(Int64.divs n1 n2))
      | Unsigned =>
          if Int64.eq n2 Int64.zero
          then None else Some(Vlong(Int64.divu n1 n2))
      end)
    (fun n1 n2 => Some(Vfloat(Float.div n1 n2)))
    (fun n1 n2 => Some(Vsingle(Float32.div n1 n2)))
    v1 t1 v2 t2.

Definition sem_mod (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_binarith
    (fun sg n1 n2 =>
      match sg with
      | Signed =>
          if Int.eq n2 Int.zero
          || Int.eq n1 (Int.repr Int.min_signed) && Int.eq n2 Int.mone
          then None else Some(Vint(Int.mods n1 n2))
      | Unsigned =>
          if Int.eq n2 Int.zero
          then None else Some(Vint(Int.modu n1 n2))
      end)
    (fun sg n1 n2 =>
      match sg with
      | Signed =>
          if Int64.eq n2 Int64.zero
          || Int64.eq n1 (Int64.repr Int64.min_signed) && Int64.eq n2 Int64.mone
          then None else Some(Vlong(Int64.mods n1 n2))
      | Unsigned =>
          if Int64.eq n2 Int64.zero
          then None else Some(Vlong(Int64.modu n1 n2))
      end)
    (fun n1 n2 => None)
    (fun n1 n2 => None)
    v1 t1 v2 t2.

Definition sem_and (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_binarith
    (fun sg n1 n2 => Some(Vint(Int.and n1 n2)))
    (fun sg n1 n2 => Some(Vlong(Int64.and n1 n2)))
    (fun n1 n2 => None)
    (fun n1 n2 => None)
    v1 t1 v2 t2.

Definition sem_or (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_binarith
    (fun sg n1 n2 => Some(Vint(Int.or n1 n2)))
    (fun sg n1 n2 => Some(Vlong(Int64.or n1 n2)))
    (fun n1 n2 => None)
    (fun n1 n2 => None)
    v1 t1 v2 t2.

Definition sem_xor (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_binarith
    (fun sg n1 n2 => Some(Vint(Int.xor n1 n2)))
    (fun sg n1 n2 => Some(Vlong(Int64.xor n1 n2)))
    (fun n1 n2 => None)
    (fun n1 n2 => None)
    v1 t1 v2 t2.

(** *** Shifts *)

(** Shifts do not perform the usual binary conversions.  Instead,
  each argument is converted independently, and the signedness
  of the result is always that of the first argument. *)

Inductive classify_shift_cases : Type:=
  | shift_case_ii(s: signedness)         (**r int , int *)
  | shift_case_ll(s: signedness)         (**r long, long *)
  | shift_case_il(s: signedness)         (**r int, long *)
  | shift_case_li(s: signedness)         (**r long, int *)
  | shift_default.

Definition classify_shift (ty1: type) (ty2: type) :=
  match typeconv ty1, typeconv ty2 with
  | Tint I32 Unsigned _, Tint _ _ _ => shift_case_ii Unsigned
  | Tint _ _ _, Tint _ _ _ => shift_case_ii Signed
  | Tint I32 Unsigned _, Tlong _ _ => shift_case_il Unsigned
  | Tint _ _ _, Tlong _ _ => shift_case_il Signed
  | Tlong s _, Tint _ _ _ => shift_case_li s
  | Tlong s _, Tlong _ _ => shift_case_ll s
  | _,_  => shift_default
  end.

Definition sem_shift
    (sem_int: signedness -> int -> int -> int)
    (sem_long: signedness -> int64 -> int64 -> int64)
    (v1: val) (t1: type) (v2: val) (t2: type) : option val :=
  match classify_shift t1 t2 with
  | shift_case_ii sg =>
      match v1, v2 with
      | Vint n1, Vint n2 =>
          if Int.ltu n2 Int.iwordsize
          then Some(Vint(sem_int sg n1 n2)) else None
      | _, _ => None
      end
  | shift_case_il sg =>
      match v1, v2 with
      | Vint n1, Vlong n2 =>
          if Int64.ltu n2 (Int64.repr 32)
          then Some(Vint(sem_int sg n1 (Int64.loword n2))) else None
      | _, _ => None
      end
  | shift_case_li sg =>
      match v1, v2 with
      | Vlong n1, Vint n2 =>
          if Int.ltu n2 Int64.iwordsize'
          then Some(Vlong(sem_long sg n1 (Int64.repr (Int.unsigned n2)))) else None
      | _, _ => None
      end
  | shift_case_ll sg =>
      match v1, v2 with
      | Vlong n1, Vlong n2 =>
          if Int64.ltu n2 Int64.iwordsize
          then Some(Vlong(sem_long sg n1 n2)) else None
      | _, _ => None
      end
  | shift_default => None
  end.

Definition sem_shl (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_shift
    (fun sg n1 n2 => Int.shl n1 n2)
    (fun sg n1 n2 => Int64.shl n1 n2)
    v1 t1 v2 t2.

Definition sem_shr (v1:val) (t1:type) (v2: val) (t2:type) : option val :=
  sem_shift
    (fun sg n1 n2 => match sg with Signed => Int.shr n1 n2 | Unsigned => Int.shru n1 n2 end)
    (fun sg n1 n2 => match sg with Signed => Int64.shr n1 n2 | Unsigned => Int64.shru n1 n2 end)
    v1 t1 v2 t2.

(** *** Comparisons *)

Inductive classify_cmp_cases : Type :=
  | cmp_case_pp                       (**r pointer, pointer *)
  | cmp_case_pi (si: signedness)      (**r pointer, int *)
  | cmp_case_ip (si: signedness)      (**r int, pointer *)
  | cmp_case_pl                       (**r pointer, long *)
  | cmp_case_lp                       (**r long, pointer *)
  | cmp_default.                      (**r numerical, numerical *)

Definition classify_cmp (ty1: type) (ty2: type) :=
  match typeconv ty1, typeconv ty2 with
  | Tpointer _ _ , Tpointer _ _ => cmp_case_pp
  | Tpointer _ _ , Tint _ si _ => cmp_case_pi si
  | Tint _ si _, Tpointer _ _ => cmp_case_ip si
  | Tpointer _ _ , Tlong _ _ => cmp_case_pl
  | Tlong _ _ , Tpointer _ _ => cmp_case_lp
  | _, _ => cmp_default
  end.

Definition sem_cmp (c:comparison)
                  (v1: val) (t1: type) (v2: val) (t2: type)
                  : option val :=
  match classify_cmp t1 t2 with
  | cmp_case_pp => None
  | cmp_case_pi si => None
  | cmp_case_ip si => None
  | cmp_case_pl => None
  | cmp_case_lp => None
  | cmp_default =>
      sem_binarith
        (fun sg n1 n2 =>
            Some(Val.of_bool(match sg with Signed => Int.cmp c n1 n2 | Unsigned => Int.cmpu c n1 n2 end)))
        (fun sg n1 n2 =>
            Some(Val.of_bool(match sg with Signed => Int64.cmp c n1 n2 | Unsigned => Int64.cmpu c n1 n2 end)))
        (fun n1 n2 =>
            Some(Val.of_bool(Float.cmp c n1 n2)))
        (fun n1 n2 =>
            Some(Val.of_bool(Float32.cmp c n1 n2)))
        v1 t1 v2 t2
  end.

(** ** Function applications *)

Inductive classify_fun_cases : Type :=
  | fun_case_f (targs: typelist) (tres: type) (cc: calling_convention) (**r (pointer to) function *)
  | fun_default.

Definition classify_fun (ty: type) :=
  match ty with
  | Tfunction args res cc => fun_case_f args res cc
  | Tpointer (Tfunction args res cc) _ => fun_case_f args res cc
  | _ => fun_default
  end.

(** ** Argument of a [switch] statement *)

Inductive classify_switch_cases : Type :=
  | switch_case_i
  | switch_case_l
  | switch_default.

Definition classify_switch (ty: type) :=
  match ty with
  | Tint _ _ _ => switch_case_i
  | Tlong _ _ => switch_case_l
  | _ => switch_default
  end.

Definition sem_switch_arg (v: val) (ty: type): option Z :=
  match classify_switch ty with
  | switch_case_i =>
      match v with Vint n => Some(Int.unsigned n) | _ => None end
  | switch_case_l =>
      match v with Vlong n => Some(Int64.unsigned n) | _ => None end
  | switch_default =>
      None
  end.

(** * Combined semantics of unary and binary operators *)

Definition sem_unary_operation
            (op: unary_operation) (v: val) (ty: type) : option val :=
  match op with
  | Onotbool => sem_notbool v ty
  | Onotint => sem_notint v ty
  | Oneg => sem_neg v ty
  | Oabsfloat => sem_absfloat v ty
  end.

Definition sem_binary_operation
    (cenv: composite_env)
    (op: binary_operation)
    (v1: val) (t1: type) (v2: val) (t2:type)
    : option val :=
  match op with
  | Oadd => sem_add cenv v1 t1 v2 t2
  | Osub => sem_sub cenv v1 t1 v2 t2
  | Omul => sem_mul v1 t1 v2 t2 
  | Omod => sem_mod v1 t1 v2 t2
  | Odiv => sem_div v1 t1 v2 t2
  | Oand => sem_and v1 t1 v2 t2
  | Oor  => sem_or v1 t1 v2 t2
  | Oxor  => sem_xor v1 t1 v2 t2
  | Oshl => sem_shl v1 t1 v2 t2
  | Oshr  => sem_shr v1 t1 v2 t2
  | Oeq => sem_cmp Ceq v1 t1 v2 t2
  | One => sem_cmp Cne v1 t1 v2 t2
  | Olt => sem_cmp Clt v1 t1 v2 t2
  | Ogt => sem_cmp Cgt v1 t1 v2 t2
  | Ole => sem_cmp Cle v1 t1 v2 t2
  | Oge => sem_cmp Cge v1 t1 v2 t2
  end.

Definition sem_incrdecr (cenv: composite_env) (id: incr_or_decr) (v: val) (ty: type) :=
  match id with
  | Incr => sem_add cenv v ty (Vint Int.one) type_int32s
  | Decr => sem_sub cenv v ty (Vint Int.one) type_int32s
  end.

Definition incrdecr_type (ty: type) :=
  match typeconv ty with
  | Tpointer ty a => Tpointer ty a
  | Tint sz sg a => Tint sz sg noattr
  | Tlong sg a => Tlong sg noattr
  | Tfloat sz a => Tfloat sz noattr
  | _ => Tvoid
  end.

(** * Compatibility with extensions and injections *)

(** * Some properties of operator semantics *)

(** This section collects some common-sense properties about the type
  classification and semantic functions above.  Some properties are used
  in the CompCert semantics preservation proofs.  Others are not, but increase
  confidence in the specification and its relation with the ISO C99 standard. *)

(** Relation between Boolean value and casting to [_Bool] type. *)

Lemma cast_bool_bool_val:
  forall v t,
  sem_cast v t (Tint IBool Signed noattr) =
  match bool_val v t with None => None | Some b => Some(Val.of_bool b) end.
  intros.
  assert (A: classify_bool t =
    match t with
    | Tint _ _ _ => bool_case_i
    | Tpointer _ _ | Tarray _ _ _ | Tfunction _ _ _ => if Archi.ptr64 then bool_case_l else bool_case_i
    | Tfloat F64 _ => bool_case_f
    | Tfloat F32 _ => bool_case_s
    | Tlong _ _ => bool_case_l
    | _ => bool_default
    end).
  {
    unfold classify_bool; destruct t; simpl; auto. destruct i; auto.
  }
  unfold bool_val. rewrite A.
  unfold sem_cast, classify_cast; remember Archi.ptr64 as ptr64; destruct t; simpl; auto; destruct v; auto.
  destruct (Int.eq i0 Int.zero); auto.
  destruct ptr64; auto.
  destruct (Int64.eq i Int64.zero); auto.
  destruct (Int64.eq i Int64.zero); auto.
  destruct f; auto.
  destruct f; auto.
  destruct f; auto.
  destruct f; auto.
  destruct (Float.cmp Ceq f0 Float.zero); auto.
  destruct f; auto.
  destruct (Float32.cmp Ceq f0 Float32.zero); auto.
  destruct f; auto. 
  destruct ptr64; auto.
  destruct (Int.eq i Int.zero); auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto. destruct (Int64.eq i Int64.zero); auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto. destruct (Int.eq i Int.zero); auto.
  destruct ptr64; auto. destruct (Int64.eq i Int64.zero); auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto. destruct (Int.eq i Int.zero); auto.
  destruct ptr64; auto. destruct (Int64.eq i Int64.zero); auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
  destruct ptr64; auto.
Qed.

(** Relation between Boolean value and Boolean negation. *)

Lemma notbool_bool_val:
  forall v t,
  sem_notbool v t =
  match bool_val v t with None => None | Some b => Some(Val.of_bool (negb b)) end.
Proof.
  intros. unfold sem_notbool. destruct (bool_val v t) as [[] | ]; reflexivity.
Qed.

(** Properties of values obtained by casting to a given type. *)

Section VAL_CASTED.

Inductive val_casted: val -> type -> Prop :=
  | val_casted_int: forall sz si attr n,
      cast_int_int sz si n = n ->
      val_casted (Vint n) (Tint sz si attr)
  | val_casted_float: forall attr n,
       val_casted (Vfloat n) (Tfloat F64 attr)
  | val_casted_single: forall attr n,
       val_casted (Vsingle n) (Tfloat F32 attr)
  | val_casted_long: forall si attr n,
      val_casted (Vlong n) (Tlong si attr)
  | val_casted_ptr_ptr: forall b ofs ty attr,
      val_casted (Vptr b ofs) (Tpointer ty attr)
  | val_casted_int_ptr: forall n ty attr,
      Archi.ptr64 = false -> val_casted (Vint n) (Tpointer ty attr)
  | val_casted_ptr_int: forall b ofs si attr,
      Archi.ptr64 = false -> val_casted (Vptr b ofs) (Tint I32 si attr)
  | val_casted_long_ptr: forall n ty attr,
      Archi.ptr64 = true -> val_casted (Vlong n) (Tpointer ty attr)
  | val_casted_ptr_long: forall b ofs si attr,
      Archi.ptr64 = true -> val_casted (Vptr b ofs) (Tlong si attr)
  | val_casted_struct: forall id attr b ofs,
      val_casted (Vptr b ofs) (Tstruct id attr)
  | val_casted_union: forall id attr b ofs,
      val_casted (Vptr b ofs) (Tunion id attr)
  | val_casted_void: forall v,
      val_casted v Tvoid.

Local Hint Constructors val_casted : core.

Remark cast_int_int_idem:
  forall sz sg i, cast_int_int sz sg (cast_int_int sz sg i) = cast_int_int sz sg i.
Proof.
  intros. destruct sz; simpl; auto.
  destruct sg; [apply Int.sign_ext_idem|apply Int.zero_ext_idem]; compute; intuition congruence.
  destruct sg; [apply Int.sign_ext_idem|apply Int.zero_ext_idem]; compute; intuition congruence.
  destruct (Int.eq i Int.zero); auto.
Qed.

Ltac DestructCases :=
  match goal with
  | [H: match match ?x with _ => _ end with _ => _ end = Some _ |- _ ] => destruct x eqn:?; DestructCases
  | [H: match ?x with _ => _ end = Some _ |- _ ] => destruct x eqn:?; DestructCases
  | [H: Some _ = Some _ |- _ ] => inv H; DestructCases
  | [H: None = Some _ |- _ ] => discriminate H
  | [H: @eq intsize _ _ |- _ ] => discriminate H || (clear H; DestructCases)
  | [ |- val_casted (Vint (if ?x then Int.zero else Int.one)) _ ] =>
       try (constructor; destruct x; reflexivity)
  | [ |- val_casted (Vint _) (Tint ?sz ?sg _) ] =>
       try (constructor; apply (cast_int_int_idem sz sg))
  | _ => idtac
  end.

Lemma cast_val_is_casted:
  forall v ty ty' v', sem_cast v ty ty' = Some v' -> val_casted v' ty'.
Proof.
  unfold sem_cast; intros.
  destruct ty, ty'; simpl in H; DestructCases; constructor; auto.
Qed.

End VAL_CASTED.

(** As a consequence, casting twice is equivalent to casting once. *)

Lemma cast_val_casted:
  forall v ty, val_casted v ty -> sem_cast v ty ty = Some v.
Proof.
  intros. unfold sem_cast; inversion H; clear H; subst v ty; simpl.
- destruct Archi.ptr64; [ | destruct (intsize_eq sz I32)].
+ destruct sz; f_equal; f_equal; assumption.
+ subst sz; auto.
+ destruct sz; f_equal; f_equal; assumption.
- auto.
- auto.
- destruct Archi.ptr64; auto.
- auto.
- rewrite H0; auto.
- rewrite H0; auto.
- rewrite H0; auto.
- rewrite H0; auto.
- rewrite dec_eq_true; auto.
- rewrite dec_eq_true; auto.
- auto. 
Qed.

Lemma cast_idempotent:
  forall v ty ty' v', sem_cast v ty ty' = Some v' -> sem_cast v' ty' ty' = Some v'.
Proof.
  intros. apply cast_val_casted. eapply cast_val_is_casted; eauto.
Qed.

(** Moreover, casted values belong to the machine type corresponding to the
    C type. *)

Lemma val_casted_has_type:
  forall v ty, val_casted v ty -> ty <> Tvoid -> Val.has_type v (typ_of_type ty).
Proof.
  intros. inv H; simpl typ_of_type.
- exact I.
- exact I.
- exact I.
- exact I.
- apply Val.Vptr_has_type.
- red; unfold Tptr; rewrite H1; auto.
- red; unfold Tptr; rewrite H1; auto.
- red; unfold Tptr; rewrite H1; auto.
- red; unfold Tptr; rewrite H1; auto.
- apply Val.Vptr_has_type.
- apply Val.Vptr_has_type.
- congruence.
Qed.

(** Relation with the arithmetic conversions of ISO C99, section 6.3.1 *)

Module ArithConv.

(** This is the ISO C algebra of arithmetic types, without qualifiers.
    [S] stands for "signed" and [U] for "unsigned".  *)

Inductive int_type : Type :=
  | _Bool
  | Char | SChar | UChar
  | Short | UShort
  | Int | UInt
  | Long | ULong
  | Longlong | ULonglong.

Inductive arith_type : Type :=
  | I (it: int_type)
  | Float
  | Double
  | Longdouble.

Definition eq_int_type: forall (x y: int_type), {x=y} + {x<>y}.
Proof. decide equality. Defined.

Definition is_unsigned (t: int_type) : bool :=
  match t with
  | _Bool => true
  | Char => false    (**r as in most of CompCert's target ABIs *)
  | SChar => false
  | UChar => true
  | Short => false
  | UShort => true
  | Int => false
  | UInt => true
  | Long => false
  | ULong => true
  | Longlong => false
  | ULonglong => true
  end.

Definition unsigned_type (t: int_type) : int_type :=
  match t with
  | Char => UChar
  | SChar => UChar
  | Short => UShort
  | Int => UInt
  | Long => ULong
  | Longlong => ULonglong
  | _ => t
  end.

Definition int_sizeof (t: int_type) : Z :=
  match t with
  | _Bool | Char | SChar | UChar => 1
  | Short | UShort => 2
  | Int | UInt | Long | ULong => 4
  | Longlong | ULonglong => 8
  end.

(** 6.3.1.1 para 1: integer conversion rank *)

Definition rank (t: int_type) : Z :=
  match t with
  | _Bool => 1
  | Char | SChar | UChar => 2
  | Short | UShort => 3
  | Int | UInt => 4
  | Long | ULong => 5
  | Longlong | ULonglong => 6
  end.

(** 6.3.1.1 para 2: integer promotions, a.k.a. usual unary conversions *)

Definition integer_promotion (t: int_type) : int_type :=
  if zlt (rank t) (rank Int) then Int else t.

(** 6.3.1.8: Usual arithmetic conversions, a.k.a. binary conversions.
  This function returns the type to which the two operands must be
  converted. *)

Definition usual_arithmetic_conversion (t1 t2: arith_type) : arith_type :=
  match t1, t2 with
  (* First, if the corresponding real type of either operand is long
     double, the other operand is converted, without change of type domain,
     to a type whose corresponding real type is long double. *)
  | Longdouble, _ | _, Longdouble => Longdouble
  (* Otherwise, if the corresponding real type of either operand is
     double, the other operand is converted, without change of type domain,
     to a type whose corresponding real type is double. *)
  | Double, _ | _, Double => Double
  (* Otherwise, if the corresponding real type of either operand is
     float, the other operand is converted, without change of type domain,
     to a type whose corresponding real type is float. *)
  | Float, _ | _, Float => Float
  (* Otherwise, the integer promotions are performed on both operands. *)
  | I i1, I i2 =>
    let j1 := integer_promotion i1 in
    let j2 := integer_promotion i2 in
    (* Then the following rules are applied to the promoted operands:
       If both operands have the same type, then no further conversion
       is needed. *)
    if eq_int_type j1 j2 then I j1 else
    match is_unsigned j1, is_unsigned j2 with
    (* Otherwise, if both operands have signed integer types or both
       have unsigned integer types, the operand with the type of lesser
       integer conversion rank is converted to the type of the operand with
       greater rank. *)
    | true, true | false, false =>
        if zlt (rank j1) (rank j2) then I j2 else I j1
    | true, false =>
    (* Otherwise, if the operand that has unsigned integer type has
       rank greater or equal to the rank of the type of the other operand,
       then the operand with signed integer type is converted to the type of
       the operand with unsigned integer type. *)
        if zle (rank j2) (rank j1) then I j1 else
    (* Otherwise, if the type of the operand with signed integer type
       can represent all of the values of the type of the operand with
       unsigned integer type, then the operand with unsigned integer type is
       converted to the type of the operand with signed integer type. *)
        if zlt (int_sizeof j1) (int_sizeof j2) then I j2 else
    (* Otherwise, both operands are converted to the unsigned integer type
       corresponding to the type of the operand with signed integer type. *)
        I (unsigned_type j2)
    | false, true =>
    (* Same logic as above, swapping the roles of j1 and j2 *)
        if zle (rank j1) (rank j2) then I j2 else
        if zlt (int_sizeof j2) (int_sizeof j1) then I j1 else
        I (unsigned_type j1)
    end
  end.

(** Mapping ISO arithmetic types to CompCert types *)

Definition proj_type (t: arith_type) : type :=
  match t with
  | I _Bool => Tint IBool Unsigned noattr
  | I Char => Tint I8 Unsigned noattr
  | I SChar => Tint I8 Signed noattr
  | I UChar => Tint I8 Unsigned noattr
  | I Short => Tint I16 Signed noattr
  | I UShort => Tint I16 Unsigned noattr
  | I Int => Tint I32 Signed noattr
  | I UInt => Tint I32 Unsigned noattr
  | I Long => Tint I32 Signed noattr
  | I ULong => Tint I32 Unsigned noattr
  | I Longlong => Tlong Signed noattr
  | I ULonglong => Tlong Unsigned noattr
  | Float => Tfloat F32 noattr
  | Double => Tfloat F64 noattr
  | Longdouble => Tfloat F64 noattr
  end.

(** Relation between [typeconv] and integer promotion. *)

Lemma typeconv_integer_promotion:
  forall i, typeconv (proj_type (I i)) = proj_type (I (integer_promotion i)).
Proof.
  destruct i; reflexivity.
Qed.

(** Relation between [classify_binarith] and arithmetic conversion. *)

Lemma classify_binarith_arithmetic_conversion:
  forall t1 t2,
  binarith_type (classify_binarith (proj_type t1) (proj_type t2)) =
  proj_type (usual_arithmetic_conversion t1 t2).
Proof.
  destruct t1; destruct t2; try reflexivity.
- destruct it; destruct it0; reflexivity.
- destruct it; reflexivity.
- destruct it; reflexivity.
- destruct it; reflexivity.
- destruct it; reflexivity.
- destruct it; reflexivity.
- destruct it; reflexivity.
Qed.

End ArithConv.