[src][state][loc_dep][2/n] add cache for external uids

Author: fantazio

src/state/location_dependencies.ml

@@ -48,18 +48,31 @@ let fill_from_cmt_tbl uid_to_decl res_uid_to_loc =
   UidTbl.iter add_uid_loc uid_to_decl;
   res_uid_to_loc
 
-let find_opt_external_uid_loc ~cm_paths = function
-  | Shape.Uid.(Compilation_unit _ | Internal | Predef _) -> None
-  | Item {comp_unit; _} as uid ->
-    let ( let* ) x f = Option.bind x f in
-    let* cm_path =
-        Utils.StringSet.elements cm_paths
-        |> List.rev
-        |> List.find_opt (fun path -> Utils.Filepath.unit path = comp_unit)
-    in
-    let* cmt_infos = Cmt_format.read cm_path |> snd in
-    let* item_decl = UidTbl.find_opt cmt_infos.cmt_uid_to_decl uid in
-    loc_opt_of_item_decl item_decl
+let find_opt_external_uid_loc, clear_external_cache =
+  let cache = Hashtbl.create 16 in
+  let clear_external_cache () = Hashtbl.reset cache in
+  let find_opt_external_uid_loc ~cm_paths = function
+    | Shape.Uid.(Compilation_unit _ | Internal | Predef _) -> None
+    | Item {comp_unit; _} as uid ->
+      let ( let* ) x f = Option.bind x f in
+      let* cmt_uid_to_decl =
+        match Hashtbl.find_opt cache comp_unit with
+        | Some _ as cmt_uid_to_decl -> cmt_uid_to_decl
+        | None ->
+            let* cm_path =
+                Utils.StringSet.elements cm_paths
+                |> List.rev
+                |> List.find_opt (fun path -> Utils.Filepath.unit path = comp_unit)
+            in
+            let* cmt_infos = Cmt_format.read cm_path |> snd in
+            let cmt_uid_to_decl = cmt_infos.cmt_uid_to_decl in
+            Hashtbl.add cache comp_unit cmt_uid_to_decl;
+            Some cmt_uid_to_decl
+      in
+      let* item_decl = UidTbl.find_opt cmt_uid_to_decl uid in
+      loc_opt_of_item_decl item_decl
+  in
+  find_opt_external_uid_loc, clear_external_cache
 
 let cmt_decl_dep_to_loc_dep ~cm_paths cmt_decl_dep uid_to_loc =
   let convert_pair (_dep_kind, uid_def, uid_decl) =
@@ -73,7 +86,9 @@ let cmt_decl_dep_to_loc_dep ~cm_paths cmt_decl_dep uid_to_loc =
     let* decl_loc = loc_opt_of_uid uid_decl in
     Some (def_loc, decl_loc)
   in
-  List.filter_map convert_pair cmt_decl_dep
+  let res = List.filter_map convert_pair cmt_decl_dep in
+  clear_external_cache ();
+  res
 
 let init ~cm_paths cmt_infos cmti_uid_to_decl =
   match cmt_infos.Cmt_format.cmt_annots with