[sledge] Improve using extended open

Summary:
OCaml 4.08 supports `open` of arbitrary module expressions. This
enables some code simplifications.

Reviewed By: ngorogiannis

Differential Revision: D18736381

fbshipit-source-id: c729dcfbd

sledge/src/llair/frontend.ml

@@ -37,30 +37,29 @@ let scope_tbl :
     Hashtbl.t =
   Hashtbl.Poly.create ~size:32_768 ()
 
-let ( (scan_names_and_locs : Llvm.llmodule -> unit)
-    , (find_name : Llvm.llvalue -> string)
-    , (find_loc : Llvm.llvalue -> Loc.t) ) =
+open struct
+  open struct
     let loc_of_global g =
       Loc.mk
         ?dir:(Llvm.get_debug_loc_directory g)
         ?file:(Llvm.get_debug_loc_filename g)
         ~line:(Llvm.get_debug_loc_line g)
         ?col:None
-  in
+
     let loc_of_function f =
       Loc.mk
         ?dir:(Llvm.get_debug_loc_directory f)
         ?file:(Llvm.get_debug_loc_filename f)
         ~line:(Llvm.get_debug_loc_line f)
         ?col:None
-  in
+
     let loc_of_instr i =
       Loc.mk
         ?dir:(Llvm.get_debug_loc_directory i)
         ?file:(Llvm.get_debug_loc_filename i)
         ~line:(Llvm.get_debug_loc_line i)
         ~col:(Llvm.get_debug_loc_column i)
-  in
+
     let add_sym llv loc =
       let maybe_scope =
         match Llvm.classify_value llv with
@@ -121,8 +120,10 @@ let ( (scan_names_and_locs : Llvm.llmodule -> unit)
                 | exception _ -> name ) )
           in
           Hashtbl.set sym_tbl ~key:llv ~data:(name, loc)
-  in
-  let scan_names_and_locs m =
+  end
+
+  let scan_names_and_locs : Llvm.llmodule -> unit =
+   fun m ->
     let scan_global g = add_sym g (loc_of_global g) in
     let scan_instr i =
       let loc = loc_of_instr i in
@@ -152,10 +153,13 @@ let ( (scan_names_and_locs : Llvm.llmodule -> unit)
     in
     Llvm.iter_globals scan_global m ;
     Llvm.iter_functions scan_function m
-  in
-  let find_name v = fst (Hashtbl.find_exn sym_tbl v) in
-  let find_loc v = snd (Hashtbl.find_exn sym_tbl v) in
-  (scan_names_and_locs, find_name, find_loc)
+
+  let find_name : Llvm.llvalue -> string =
+   fun v -> fst (Hashtbl.find_exn sym_tbl v)
+
+  let find_loc : Llvm.llvalue -> Loc.t =
+   fun v -> snd (Hashtbl.find_exn sym_tbl v)
+end
 
 let label_of_block : Llvm.llbasicblock -> string =
  fun blk -> find_name (Llvm.value_of_block blk)