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|
(** Compute various information, including:
- can a function fail (by having `Fail` in its body, or transitively
calling a function which can fail - this is false for globals)
- can a function diverge (by being recursive, containing a loop or
transitively calling a function which can diverge)
- does a function perform stateful operations (i.e., do we need a state
to translate it)
*)
open LlbcAst
module EU = ExpressionsUtils
(** Various information about a function.
Note that not all this information is used yet to adjust the extraction yet.
*)
type fun_info = {
can_fail : bool;
(* Not used yet: all the extracted functions use an error monad *)
stateful : bool;
divergent : bool; (* Not used yet *)
}
[@@deriving show]
(** Various information about a module's functions *)
type modules_funs_info = fun_info FunDeclId.Map.t
let analyze_module (m : crate) (funs_map : fun_decl FunDeclId.Map.t)
(globals_map : global_decl GlobalDeclId.Map.t) (use_state : bool) :
modules_funs_info =
let infos = ref FunDeclId.Map.empty in
let register_info (id : FunDeclId.id) (info : fun_info) : unit =
assert (not (FunDeclId.Map.mem id !infos));
infos := FunDeclId.Map.add id info !infos
in
(* Analyze a group of mutually recursive functions.
* As the functions can call each other, we compute the same information
* for all of them (if one of the functions can fail, then all of them
* can fail, etc.).
*
* We simply check if the functions contains panic statements, loop statements,
* recursive calls, etc. We use the previously computed information in case
* of function calls.
*)
let analyze_fun_decls (fun_ids : FunDeclId.Set.t) (d : fun_decl list) :
fun_info =
let can_fail = ref false in
let stateful = ref false in
let divergent = ref false in
let visit_fun (f : fun_decl) : unit =
let obj =
object (self)
inherit [_] iter_statement as super
method may_fail b = can_fail := !can_fail || b
method! visit_Assert env a =
self#may_fail true;
super#visit_Assert env a
method! visit_rvalue _env rv =
match rv with
| Use _ | Ref _ | Global _ | Discriminant _ | Aggregate _ -> ()
| UnaryOp (uop, _) -> can_fail := EU.unop_can_fail uop || !can_fail
| BinaryOp (bop, _, _) ->
can_fail := EU.binop_can_fail bop || !can_fail
method! visit_Call env call =
(match call.func with
| Regular id ->
if FunDeclId.Set.mem id fun_ids then divergent := true
else
let info = FunDeclId.Map.find id !infos in
self#may_fail info.can_fail;
stateful := !stateful || info.stateful;
divergent := !divergent || info.divergent
| Assumed id ->
(* None of the assumed functions is stateful for now *)
can_fail := !can_fail || Assumed.assumed_can_fail id);
super#visit_Call env call
method! visit_Panic env =
self#may_fail true;
super#visit_Panic env
method! visit_Loop env loop =
divergent := true;
super#visit_Loop env loop
end
in
(* Sanity check: global bodies don't contain stateful calls *)
assert ((not f.is_global_decl_body) || not !stateful);
match f.body with
| None ->
(* Opaque function: we consider they fail by default *)
obj#may_fail true;
stateful := (not f.is_global_decl_body) && use_state
| Some body -> obj#visit_statement () body.body
in
List.iter visit_fun d;
(* We need to know if the declaration group contains a global - note that
* groups containing globals contain exactly one declaration *)
let is_global_decl_body = List.exists (fun f -> f.is_global_decl_body) d in
assert ((not is_global_decl_body) || List.length d = 1);
(* We ignore on purpose functions that cannot fail and consider they *can*
* fail: the result of the analysis is not used yet to adjust the translation
* so that the functions which syntactically can't fail don't use an error monad.
* However, we do keep the result of the analysis for global bodies.
* *)
can_fail := (not is_global_decl_body) || !can_fail;
{ can_fail = !can_fail; stateful = !stateful; divergent = !divergent }
in
let analyze_fun_decl_group (d : fun_declaration_group) : unit =
(* Retrieve the function declarations *)
let funs = match d with NonRec id -> [ id ] | Rec ids -> ids in
let funs = List.map (fun id -> FunDeclId.Map.find id funs_map) funs in
let fun_ids = List.map (fun (d : fun_decl) -> d.def_id) funs in
let fun_ids = FunDeclId.Set.of_list fun_ids in
let info = analyze_fun_decls fun_ids funs in
List.iter (fun (f : fun_decl) -> register_info f.def_id info) funs
in
let rec analyze_decl_groups (decls : declaration_group list) : unit =
match decls with
| [] -> ()
| Type _ :: decls' -> analyze_decl_groups decls'
| Fun decl :: decls' ->
analyze_fun_decl_group decl;
analyze_decl_groups decls'
| Global id :: decls' ->
(* Analyze a global by analyzing its body function *)
let global = GlobalDeclId.Map.find id globals_map in
analyze_fun_decl_group (NonRec global.body_id);
analyze_decl_groups decls'
in
analyze_decl_groups m.declarations;
!infos
|
