Eliminate dead lambdas

src/main/compile/dune

@@ -12,6 +12,7 @@
     ast_typed
     transpiler
     mini_c
+    self_mini_c
     compiler
     self_michelson
   )

src/main/compile/of_mini_c.ml

@@ -33,14 +33,17 @@ let compile_function = fun e ->
 
 let compile_expression_as_function_entry = fun program name ->
   let%bind aggregated = aggregate_entry program name true in
+  let%bind aggregated = Self_mini_c.all_expression aggregated in
   compile_function aggregated
 
 let compile_function_entry = fun program name ->
   let%bind aggregated = aggregate_entry program name false in
+  let%bind aggregated = Self_mini_c.all_expression aggregated in
   compile_function aggregated
 
 let compile_contract_entry = fun program name ->
   let%bind aggregated = aggregate_entry program name false in
+  let%bind aggregated = Self_mini_c.all_expression aggregated in
   let%bind compiled = compile_function aggregated in
   let%bind (param_ty , storage_ty) =
     let%bind fun_ty = get_t_function aggregated.type_value in

src/passes/7-self_mini_c/self_mini_c.ml

@@ -0,0 +1,29 @@
+open Mini_c
+open Trace
+
+(* Overly conservative for now: ok to treat pure things as impure,
+   must not treat impure things as pure. *)
+let is_pure : expression -> bool = fun e ->
+  match e.content with
+  | E_closure _ -> true
+  | _ -> false
+
+let rec elim_dead_lambdas : expression -> expression result = fun e ->
+  let changed = ref false in (* ugh *)
+  let mapper : Helpers.mapper = fun e ->
+    match e.content with
+    | E_let_in ((x, _), e1, e2) when is_pure e1 ->
+      let fvs = Free_variables.expression [] e2 in
+      if Free_variables.mem x fvs
+      then ok e
+      else
+        (* pure e1 is not used, eliminate! *)
+        (changed := true ; ok e2)
+    | _ -> ok e in
+  let%bind e = Helpers.map_expression mapper e in
+  if !changed
+  then elim_dead_lambdas e
+  else ok e
+
+let all_expression : expression -> expression result =
+  elim_dead_lambdas