fix for wasm

Author: hhugo

compiler/lib/deadcode.ml

@@ -193,18 +193,26 @@ let empty_body b =
 
 let remove_empty_blocks ~live_vars (p : Code.program) : Code.program =
   let shortcuts = Hashtbl.create 16 in
-  let rec resolve_rec visited ((pc, args) as cont) =
+  let rec resolve_rec keep_empty visited ((pc, args) as cont0) =
     if Addr.Set.mem pc visited
-    then cont
+    then cont0
     else
       match Hashtbl.find_opt shortcuts pc with
       | Some (params, cont) ->
-          let pc', args' = resolve_rec (Addr.Set.add pc visited) cont in
-          let s = Subst.from_map (Subst.build_mapping params args) in
-          pc', List.map ~f:s args'
-      | None -> cont
+          let pc', args' = resolve_rec keep_empty (Addr.Set.add pc visited) cont in
+          if keep_empty && not (List.is_empty args')
+          then cont0
+          else
+            let s = Subst.from_map (Subst.build_mapping params args) in
+            pc', List.map ~f:s args'
+      | None -> cont0
+  in
+  let resolve cont = resolve_rec false Addr.Set.empty cont in
+  let resolve_inside_switch =
+    match Config.target () with
+    | `JavaScript -> resolve
+    | `Wasm -> resolve_rec true Addr.Set.empty
   in
-  let resolve cont = resolve_rec Addr.Set.empty cont in
   Addr.Map.iter
     (fun pc block ->
       match block with
@@ -233,7 +241,7 @@ let remove_empty_blocks ~live_vars (p : Code.program) : Code.program =
              match branch with
              | Branch cont -> Branch (resolve cont)
              | Cond (x, cont1, cont2) -> Cond (x, resolve cont1, resolve cont2)
-             | Switch (x, a1) -> Switch (x, Array.map ~f:resolve a1)
+             | Switch (x, a1) -> Switch (x, Array.map ~f:resolve_inside_switch a1)
              | Pushtrap (cont1, x, cont2) -> Pushtrap (resolve cont1, x, resolve cont2)
              | Poptrap cont -> Poptrap (resolve cont)
              | Return _ | Raise _ | Stop -> branch)