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|
(* *********************************************************************)
(* *)
(* The Compcert verified compiler *)
(* *)
(* Xavier Leroy, INRIA Paris-Rocquencourt *)
(* *)
(* Copyright Institut National de Recherche en Informatique et en *)
(* Automatique. All rights reserved. This file is distributed *)
(* under the terms of the GNU General Public License as published by *)
(* the Free Software Foundation, either version 2 of the License, or *)
(* (at your option) any later version. This file is also distributed *)
(* under the terms of the INRIA Non-Commercial License Agreement. *)
(* *)
(* *********************************************************************)
(* Expand assignments between structs and between unions *)
(* Assumes: unblocked code.
Preserves: unblocked code *)
open C
open Machine
open Cutil
open Env
open Errors
open Transform
(* Finding appropriate memcpy functions *)
let memcpy_decl = ref (None : ident option)
let memcpy_type =
TFun(TPtr(TVoid [], []),
Some [(Env.fresh_ident "", TPtr(TVoid [], []));
(Env.fresh_ident "", TPtr(TVoid [AConst], []));
(Env.fresh_ident "", TInt(size_t_ikind, []))],
false, [])
let lookup_function env name =
match Env.lookup_ident env name with
| (id, II_ident(sto, ty)) -> (id, ty)
| (id, II_enum _) -> raise (Env.Error(Env.Unbound_identifier name))
let default_memcpy () =
match !memcpy_decl with
| Some id ->
(id, memcpy_type)
| None ->
let id = Env.fresh_ident "memcpy" in
memcpy_decl := Some id;
(id, memcpy_type)
let find_memcpy env =
try
(lookup_function env "__builtin_memcpy_aligned", true)
with Env.Error _ ->
try
(lookup_function env "__builtin_memcpy", false)
with Env.Error _ ->
try
(lookup_function env "memcpy", false)
with Env.Error _ ->
(default_memcpy(), false)
(* Smart constructor for "," expressions *)
let comma e1 e2 =
match e1.edesc, e2.edesc with
| EConst _, _ -> e2
| _, EConst _ -> e1
| _, _ -> ecomma e1 e2
(* Smart constructor for "&" expressions *)
let rec addrof e =
match e.edesc with
| EBinop(Ocomma, e1, e2, _) -> ecomma e1 (addrof e2)
| _ -> eaddrof e
(* Translate an assignment [lhs = rhs] between composite types.
[lhs] and [rhs] must be l-values. *)
let transf_assign env lhs rhs =
let al =
match Cutil.alignof env lhs.etyp with Some al -> al | None -> 1 in
let ((ident, ty), four_args) = find_memcpy env in
let memcpy = {edesc = EVar(ident); etyp = ty} in
let e_lhs = addrof lhs
and e_rhs = addrof rhs
and e_size = {edesc = ESizeof(lhs.etyp); etyp = TInt(size_t_ikind, [])}
and e_align = intconst (Int64.of_int al) size_t_ikind in
let args =
if four_args
then [e_lhs; e_rhs; e_size; e_align]
else [e_lhs; e_rhs; e_size] in
{edesc = ECall(memcpy, args); etyp = TVoid[]}
(* Detect invariant l-values *)
let not_volatile env ty = not (List.mem AVolatile (attributes_of_type env ty))
let rec invariant_lvalue env e =
match e.edesc with
| EVar _ -> true
| EUnop(Oderef, {edesc = EVar _; etyp = ty}) -> not_volatile env ty
| EUnop(Odot _, e1) -> invariant_lvalue env e1
| _ -> false
(* Bind a l-value to a temporary variable if it is not invariant. *)
let bind_lvalue env e fn =
if invariant_lvalue env e then
fn e
else begin
let tmp = new_temp (TPtr(e.etyp, [])) in
ecomma (eassign tmp (addrof e))
(fn {edesc = EUnop(Oderef, tmp); etyp = e.etyp})
end
(* Transformation of expressions. *)
type context = Val | Effects
let rec transf_expr env ctx e =
match e.edesc with
| EBinop(Oassign, lhs, rhs, _) when is_composite_type env lhs.etyp ->
let lhs' = transf_expr env Val lhs in
let rhs' = transf_expr env Val rhs in
begin match ctx with
| Effects ->
transf_assign env lhs' rhs'
| Val ->
bind_lvalue env lhs' (fun l -> ecomma (transf_assign env l rhs') l)
end
| EConst c -> e
| ESizeof ty -> e
| EVar x -> e
| EUnop(op, e1) ->
{edesc = EUnop(op, transf_expr env Val e1); etyp = e.etyp}
| EBinop(Ocomma, e1, e2, ty) ->
{edesc = EBinop(Ocomma, transf_expr env Effects e1,
transf_expr env ctx e2, ty);
etyp = e.etyp}
| EBinop(op, e1, e2, ty) ->
{edesc = EBinop(op, transf_expr env Val e1,
transf_expr env Val e2, ty);
etyp = e.etyp}
| EConditional(e1, e2, e3) ->
{edesc = EConditional(transf_expr env Val e1,
transf_expr env ctx e2, transf_expr env ctx e3);
etyp = e.etyp}
| ECast(ty, e1) ->
{edesc = ECast(ty, transf_expr env Val e1); etyp = e.etyp}
| ECall(e1, el) ->
{edesc = ECall(transf_expr env Val e1,
List.map (transf_expr env Val) el);
etyp = e.etyp}
(* Transformation of statements *)
let rec transf_stmt env s =
match s.sdesc with
| Sskip -> s
| Sdo e -> {s with sdesc = Sdo(transf_expr env Effects e)}
| Sseq(s1, s2) ->
{s with sdesc = Sseq(transf_stmt env s1, transf_stmt env s2)}
| Sif(e, s1, s2) ->
{s with sdesc = Sif(transf_expr env Val e,
transf_stmt env s1, transf_stmt env s2)}
| Swhile(e, s1) ->
{s with sdesc = Swhile(transf_expr env Val e, transf_stmt env s1)}
| Sdowhile(s1, e) ->
{s with sdesc = Sdowhile(transf_stmt env s1, transf_expr env Val e)}
| Sfor(s1, e, s2, s3) ->
{s with sdesc = Sfor(transf_stmt env s1, transf_expr env Val e,
transf_stmt env s2, transf_stmt env s3)}
| Sbreak -> s
| Scontinue -> s
| Sswitch(e, s1) ->
{s with sdesc = Sswitch(transf_expr env Val e, transf_stmt env s1)}
| Slabeled(lbl, s1) ->
{s with sdesc = Slabeled(lbl, transf_stmt env s1)}
| Sgoto lbl -> s
| Sreturn None -> s
| Sreturn (Some e) -> {s with sdesc = Sreturn(Some(transf_expr env Val e))}
| Sblock _ | Sdecl _ -> assert false (* not in unblocked code *)
let transf_fundef env f =
reset_temps();
let newbody = transf_stmt env f.fd_body in
let temps = get_temps() in
{f with fd_locals = f.fd_locals @ temps; fd_body = newbody}
let program p =
memcpy_decl := None;
let p' = Transform.program ~fundef:transf_fundef p in
match !memcpy_decl with
| None -> p'
| Some id ->
{gdesc = Gdecl(Storage_extern, id, memcpy_type, None); gloc = no_loc}
:: p'
|
