[sledge] Base implementation of localization on atoms instead of vars

Summary:
The computation of provable reachability through the heap currently
uses a set of variables whose values are either determined by the
desired roots or by the heap constraints. This requires globals to be
treated as variables. In preparation for distinguishing globals from
variables, this diff changes the reachability computation to use a set
of atomic terms instead of variables.

Reviewed By: jvillard

Differential Revision: D24886573

fbshipit-source-id: c0e6763b6

sledge/src/domain_sh.ml

@@ -73,39 +73,30 @@ let exec_intrinsic ~skip_throw r i es q =
     (List.map ~f:X.term es)
   |> Option.map ~f:(Option.map ~f:simplify)
 
-let term_eq_class_has_only_vars_in fvs ctx term =
-  [%Trace.call fun {pf} ->
-    pf "@[<v> fvs: @[%a@] @,ctx: @[%a@] @,term: @[%a@]@]" Var.Set.pp fvs
-      Context.pp ctx Term.pp term]
-  ;
-  let term_has_only_vars_in fvs term =
-    Var.Set.subset (Term.fv term) ~of_:fvs
-  in
-  let term_eq_class = Context.class_of ctx term in
-  List.exists ~f:(term_has_only_vars_in fvs) term_eq_class
-  |>
-  [%Trace.retn fun {pf} -> pf "%b"]
+let value_determined_by ctx us a =
+  List.exists (Context.class_of ctx a) ~f:(fun b ->
+      Term.Set.subset (Term.Set.of_iter (Term.atoms b)) ~of_:us )
 
-let garbage_collect (q : t) ~wrt =
+let garbage_collect (q : Sh.t) ~wrt =
   [%Trace.call fun {pf} -> pf "%a" pp q]
   ;
   (* only support DNF for now *)
   assert (List.is_empty q.djns) ;
   let rec all_reachable_vars previous current (q : t) =
-    if Var.Set.equal previous current then current
+    if Term.Set.equal previous current then current
     else
       let new_set =
         List.fold q.heap current ~f:(fun seg current ->
-            if term_eq_class_has_only_vars_in current q.ctx seg.loc then
+            if value_determined_by q.ctx current seg.loc then
               List.fold (Context.class_of q.ctx seg.seq) current
-                ~f:(fun e c -> Var.Set.union c (Term.fv e))
+                ~f:(fun e c ->
+                  Term.Set.union c (Term.Set.of_iter (Term.atoms e)) )
             else current )
       in
       all_reachable_vars current new_set q
   in
-  let r_vars = all_reachable_vars Var.Set.empty wrt q in
-  Sh.filter_heap q ~f:(fun seg ->
-      term_eq_class_has_only_vars_in r_vars q.ctx seg.loc )
+  let r_vars = all_reachable_vars Term.Set.empty wrt q in
+  Sh.filter_heap q ~f:(fun seg -> value_determined_by q.ctx r_vars seg.loc)
   |>
   [%Trace.retn fun {pf} -> pf "%a" pp]
 
@@ -120,10 +111,14 @@ let localize_entry globals actuals formals freturn locals shadow pre entry =
   (* Add the formals here to do garbage collection and then get rid of them *)
   let formals_set = Var.Set.of_list formals in
   let freturn_locals = X.regs (Llair.Reg.Set.add_option freturn locals) in
-  let function_summary_pre =
-    garbage_collect entry
-      ~wrt:(Var.Set.union formals_set (X.globals globals))
+  let wrt =
+    Term.Set.of_iter
+      (Iter.append
+         (Iter.map ~f:(Term.var << X.global)
+            (Llair.Global.Set.to_iter globals))
+         (Iter.map ~f:Term.var (List.to_iter formals)))
   in
+  let function_summary_pre = garbage_collect entry ~wrt in
   [%Trace.info "function summary pre %a" pp function_summary_pre] ;
   let foot = Sh.exists formals_set function_summary_pre in
   let xs, foot = Sh.bind_exists ~wrt:pre.Sh.us foot in
@@ -332,19 +327,19 @@ let%test_module _ =
     let seg_cycle = Sh.seg {loc= a; bas= b; len= n; siz= n; seq= main}
 
     let%expect_test _ =
-      pp (garbage_collect seg_main ~wrt:(Var.Set.of_list [])) ;
+      pp (garbage_collect seg_main ~wrt:(Term.Set.of_list [])) ;
       [%expect {| emp |}]
 
     let%expect_test _ =
       pp
         (garbage_collect (Sh.star seg_a seg_main)
-           ~wrt:(Var.Set.of_list [a_])) ;
+           ~wrt:(Term.Set.of_list [a])) ;
       [%expect {| %a_2 -[ %b_4, %n_3 )-> ⟨%n_3,%end_5⟩ |}]
 
     let%expect_test _ =
       pp
         (garbage_collect (Sh.star seg_a seg_main)
-           ~wrt:(Var.Set.of_list [main_])) ;
+           ~wrt:(Term.Set.of_list [main])) ;
       [%expect
         {|
           %main_1 -[ %b_4, %n_3 )-> ⟨%n_3,%a_2⟩
@@ -354,7 +349,7 @@ let%test_module _ =
       pp
         (garbage_collect
            (Sh.star seg_cycle seg_main)
-           ~wrt:(Var.Set.of_list [a_])) ;
+           ~wrt:(Term.Set.of_list [a])) ;
       [%expect
         {|
           %main_1 -[ %b_4, %n_3 )-> ⟨%n_3,%a_2⟩

sledge/src/fol/exp.ml

@@ -196,6 +196,7 @@ module Term = struct
   end
 
   include T
+  module Set = Set.Make (T)
   module Map = Map.Make (T)
 
   let ppx = ppx
@@ -269,6 +270,7 @@ module Term = struct
     match e with `Fml f -> iter_f f | #cnd as c -> iter_c c
 
   let vars = iter ~f:Trm.vars
+  let atoms = iter ~f:(fun e -> Iter.map ~f:(fun a -> `Trm a) (Trm.atoms e))
 
   (** Transform *)
 

sledge/src/fol/exp.mli

@@ -13,6 +13,7 @@ module rec Term : sig
   val ppx : Var.strength -> t pp
   val pp : t pp
 
+  module Set : Set.S with type elt := t
   module Map : Map.S with type key := t
 
   (** Construct *)
@@ -78,6 +79,7 @@ module rec Term : sig
   (** Traverse *)
 
   val vars : t -> Var.t iter
+  val atoms : t -> t iter
 
   (** Transform *)
 

sledge/src/fol/trm.ml

@@ -437,6 +437,13 @@ let trms = function
       Iter.(cons x (cons y (cons z empty)))
   | Concat xs | Apply (_, xs) -> Iter.of_array xs
 
+let is_atomic = function
+  | Var _ | Z _ | Q _ | Concat [||] | Apply (_, [||]) -> true
+  | Arith _ | Splat _ | Sized _ | Extract _ | Concat _ | Apply _ -> false
+
+let rec atoms e =
+  if is_atomic e then Iter.return e else Iter.flat_map ~f:atoms (trms e)
+
 (** Query *)
 
 let fv e = Var.Set.of_iter (vars e)

sledge/src/fol/trm.mli

@@ -89,8 +89,9 @@ val map : t -> f:(t -> t) -> t
 
 val seq_size_exn : t -> t
 val seq_size : t -> t option
-val fv : t -> Var.Set.t
+val is_atomic : t -> bool
 val height : t -> int
+val fv : t -> Var.Set.t
 
 (** Traverse *)
 
@@ -99,3 +100,6 @@ val trms : t -> t iter
 
 val vars : t -> Var.t iter
 (** The variables that occur in a term. *)
+
+val atoms : t -> t iter
+(** The atomic reflexive-transitive subterms of a term. *)