Optimize sourcemap processing

CHANGES.md

@@ -1,3 +1,8 @@
+# dev (2024-??) - ??
+
+## Features/Changes
+* Compiler: optimize sourcemap processing, improving linking performance #1617
+
 # 5.8.2 (2024-05-26) - Luc
 
 ## Bug fixes

compiler/bin-js_of_ocaml/cmd_arg.ml

@@ -312,9 +312,10 @@ let options =
             ; file
             ; sourceroot = sourcemap_root
             ; sources = []
-            ; sources_content = (if sourcemap_don't_inline_content then None else Some [])
+            ; sources_contents =
+                (if sourcemap_don't_inline_content then None else Some [])
             ; names = []
-            ; mappings = []
+            ; mappings = Source_map.Mappings.empty
             } )
       else None
     in
@@ -551,9 +552,10 @@ let options_runtime_only =
             ; file
             ; sourceroot = sourcemap_root
             ; sources = []
-            ; sources_content = (if sourcemap_don't_inline_content then None else Some [])
+            ; sources_contents =
+                (if sourcemap_don't_inline_content then None else Some [])
             ; names = []
-            ; mappings = []
+            ; mappings = Source_map.Mappings.empty
             } )
       else None
     in

compiler/bin-js_of_ocaml/link.ml

@@ -106,9 +106,9 @@ let options =
             ; file
             ; sourceroot = sourcemap_root
             ; sources = []
-            ; sources_content = Some []
+            ; sources_contents = Some []
             ; names = []
-            ; mappings = []
+            ; mappings = Source_map.Mappings.empty
             } )
       else None
     in

compiler/lib/js_output.ml

@@ -1903,10 +1903,10 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
   let temp_mappings = ref [] in
   let files = Hashtbl.create 17 in
   let names = Hashtbl.create 17 in
-  let contents : string option list ref option =
+  let contents : Source_map.Source_text.t list ref option =
     match source_map with
-    | None | Some { Source_map.sources_content = None; _ } -> None
-    | Some { Source_map.sources_content = Some _; _ } -> Some (ref [])
+    | None | Some { Source_map.sources_contents = None; _ } -> None
+    | Some { Source_map.sources_contents = Some _; _ } -> Some (ref [])
   in
   let push_mapping, get_file_index, get_name_index, source_map_enabled =
     let source_map_enabled =
@@ -1918,27 +1918,28 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
             | [], _ -> ()
             | x :: xs, [] ->
                 Hashtbl.add files x (Hashtbl.length files);
-                Option.iter contents ~f:(fun r -> r := None :: !r);
+                Option.iter contents ~f:(fun r -> r := Source_map.Source_text.empty :: !r);
                 loop xs []
             | x :: xs, y :: ys ->
                 Hashtbl.add files x (Hashtbl.length files);
                 Option.iter contents ~f:(fun r -> r := y :: !r);
                 loop xs ys
           in
-          loop sm.sources (Option.value ~default:[] sm.sources_content);
+          loop sm.sources (Option.value ~default:[] sm.sources_contents);
           List.iter sm.Source_map.names ~f:(fun f ->
               Hashtbl.add names f (Hashtbl.length names));
           true
     in
     let find_source file =
-      match Builtins.find file with
-      | Some f -> Some (Builtins.File.content f)
-      | None ->
-          if Sys.file_exists file && not (Sys.is_directory file)
-          then
-            let content = Fs.read_file file in
-            Some content
-          else None
+      Source_map.Source_text.encode
+        (match Builtins.find file with
+        | Some f -> Some (Builtins.File.content f)
+        | None ->
+            if Sys.file_exists file && not (Sys.is_directory file)
+            then
+              let content = Fs.read_file file in
+              Some content
+            else None)
     in
     ( (fun pos m -> temp_mappings := (pos, m) :: !temp_mappings)
     , (fun file ->
@@ -1979,19 +1980,20 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
     | Some sm ->
         let sources = hashtbl_to_list files in
         let names = hashtbl_to_list names in
-        let sources_content =
-          match contents with
-          | None -> None
-          | Some r -> Some (List.rev !r)
+        let sources_contents =
+          let open Option.Syntax in
+          let* r = contents in
+          Option.return (List.rev !r)
         in
         let sources =
           List.map sources ~f:(fun filename ->
               match Builtins.find filename with
               | None -> filename
               | Some _ -> Filename.concat "/builtin" filename)
         in
+        let sm_mappings = Source_map.Mappings.decode sm.mappings in
         let mappings =
-          List.rev_append_map !temp_mappings sm.mappings ~f:(fun (pos, m) ->
+          List.rev_append_map !temp_mappings sm_mappings ~f:(fun (pos, m) ->
               let gen_line = pos.PP.p_line + 1 in
               let gen_col = pos.PP.p_col in
               match m with
@@ -2006,7 +2008,8 @@ let program ?(accept_unnamed_var = false) f ?source_map p =
                   Source_map.Gen_Ori_Name
                     { gen_line; gen_col; ori_source; ori_line; ori_col; ori_name })
         in
-        Some { sm with Source_map.sources; names; sources_content; mappings }
+        let mappings = Source_map.Mappings.encode mappings in
+        Some { sm with Source_map.sources; names; sources_contents; mappings }
   in
   PP.check f;
   (if stats ()