Make more progress on generating the symbolic AST for the backward

functions

3 files changed, 25 insertions, 11 deletions

diff --git a/src/Interpreter.ml b/src/Interpreter.ml
index c7cdc329..bcfb9a78 100644
--- a/src/Interpreter.ml
+++ b/src/Interpreter.ml
@@ -43,7 +43,7 @@ let initialize_context (m : M.cfim_module) (type_vars : T.type_var list) :
       signature.
  *)
 let initialize_symbolic_context_for_fun (m : M.cfim_module) (fdef : A.fun_def) :
-    C.eval_ctx =
+    C.eval_ctx * A.inst_fun_sig =
   (* The abstractions are not initialized the same way as for function
    * calls: they contain *loan* projectors, because they "provide" us
    * with the input values (which behave as if they had been returned
@@ -93,7 +93,7 @@ let initialize_symbolic_context_for_fun (m : M.cfim_module) (fdef : A.fun_def) :
   (* Push the remaining local variables (initialized with ⊥) *)
   let ctx = C.ctx_push_uninitialized_vars ctx local_vars in
   (* Return *)
-  ctx
+  (ctx, inst_sg)
 
 (** Small helper.
 
@@ -184,7 +184,7 @@ let evaluate_function_symbolic (config : C.partial_config) (synthesize : bool)
   log#ldebug (lazy ("evaluate_function_symbolic: " ^ name_to_string ()));
 
   (* Create the evaluation context *)
-  let ctx = initialize_symbolic_context_for_fun m fdef in
+  let ctx, inst_sg = initialize_symbolic_context_for_fun m fdef in
 
   (* Create the continuation to finish the evaluation *)
   let config = C.config_of_partial C.SymbolicMode config in
@@ -205,7 +205,7 @@ let evaluate_function_symbolic (config : C.partial_config) (synthesize : bool)
               let cf_move = move_return_value config in
               (* Generate the Return node *)
               let cf_return ret_value : m_fun =
-               fun _ -> Some (SA.Return ret_value)
+               fun _ -> Some (SA.Return (Some ret_value))
               in
               (* Apply *)
               cf_move cf_return ctx
diff --git a/src/SymbolicAst.ml b/src/SymbolicAst.ml
index 9dc20468..f0873aa3 100644
--- a/src/SymbolicAst.ml
+++ b/src/SymbolicAst.ml
@@ -28,9 +28,11 @@ type call = {
     used in CFIM: they are a first step towards lambda-calculus expressions.
  *)
 type expression =
-  | Return of V.typed_value
-      (** The typed value stored in [Return] is the value contained in the return
-          variable upon returning
+  | Return of V.typed_value option
+      (** There are two cases:
+          - the AST is for a forward function: the typed value should contain
+            the value which was in the return variable
+          - the AST is for a backward function: the typed value should be `None`
        *)
   | Panic
   | FunCall of call * expression
diff --git a/src/SymbolicToPure.ml b/src/SymbolicToPure.ml
index 51d3c170..67d5cc45 100644
--- a/src/SymbolicToPure.ml
+++ b/src/SymbolicToPure.ml
@@ -190,7 +190,7 @@ type call_info = {
 type bs_ctx = {
   type_context : type_context;
   fun_context : fun_context;
-  bid : T.RegionGroupId.id option;
+  bid : T.RegionGroupId.id option;  (** TODO: rename *)
   sv_to_var : var V.SymbolicValueId.Map.t;
       (** Whenever we encounter a new symbolic value (introduced because of
       a symbolic expansion or upon ending an abstraction, for instance)
@@ -834,9 +834,7 @@ let get_abs_ancestors (ctx : bs_ctx) (abs : V.abs) : S.call * V.abs list =
 
 let rec translate_expression (e : S.expression) (ctx : bs_ctx) : expression =
   match e with
-  | S.Return v ->
-      let v = typed_value_to_rvalue ctx v in
-      Return v
+  | S.Return opt_v -> translate_return opt_v ctx
   | Panic -> Panic
   | FunCall (call, e) -> translate_function_call call e ctx
   | EndAbstraction (abs, e) -> translate_end_abstraction abs e ctx
@@ -845,6 +843,20 @@ let rec translate_expression (e : S.expression) (ctx : bs_ctx) : expression =
       (* We ignore the meta information *)
       translate_expression e ctx
 
+and translate_return (opt_v : V.typed_value option) (ctx : bs_ctx) : expression
+    =
+  (* There are two cases:
+     - either we are translating a forward function, in which case the optional
+       value should be `Some` (it is the returned value)
+     - or we are translating a backward function, in which case it should be `None`
+  *)
+  match ctx.bid with
+  | None ->
+      let v = Option.get opt_v in
+      let v = typed_value_to_rvalue ctx v in
+      Return v
+  | Some bid -> raise Unimplemented
+
 and translate_function_call (call : S.call) (e : S.expression) (ctx : bs_ctx) :
     expression =
   (* Translate the function call *)