Revert "Fix CSE equations on params (#2628)"

This reverts commit 7676c07.

Author: mshinwell

middle_end/flambda2/simplify/common_subexpression_elimination.ml

@@ -105,33 +105,18 @@ end
 
 let cse_with_eligible_lhs ~typing_env_at_fork ~cse_at_each_use ~params prev_cse
     (extra_bindings : EPA.t) extra_equations =
-  let params_set =
-    List.map params ~f:Bound_parameter.name |> Name.Set.of_list
-  in
-  let params = List.map params ~f:Bound_parameter.simple in
+  let params = List.map params ~f:Bound_parameter.name |> Name.Set.of_list in
   let is_param simple =
     Simple.pattern_match simple
-      ~name:(fun name ~coercion:_ -> Name.Set.mem name params_set)
+      ~name:(fun name ~coercion:_ -> Name.Set.mem name params)
       ~const:(fun _ -> false)
   in
   List.fold_left cse_at_each_use ~init:EP.Map.empty
     ~f:(fun eligible (env_at_use, id, cse) ->
       let find_new_name =
-        let find_param simple params =
-          List.find_opt
-            ~f:(fun param ->
-              match
-                TE.get_canonical_simple_exn env_at_use param
-                  ~min_name_mode:NM.normal
-                  ~name_mode_of_existing_simple:NM.normal
-              with
-              | exception Not_found -> false
-              | arg -> Simple.equal arg simple)
-            params
-        in
         match (extra_bindings : EPA.t) with
-        | Empty -> fun arg -> find_param arg params
-        | Non_empty { extra_args; extra_params } -> (
+        | Empty -> fun _arg -> None
+        | Non_empty { extra_args; extra_params } ->
           let extra_args = RI.Map.find id extra_args in
           let rec find_name simple params args =
             match args, params with
@@ -152,10 +137,7 @@ let cse_with_eligible_lhs ~typing_env_at_fork ~cse_at_each_use ~params prev_cse
                 find_name simple params args)
           in
           fun arg ->
-            match find_param arg params with
-            | None ->
-              find_name arg (Bound_parameters.to_list extra_params) extra_args
-            | Some _ as r -> r)
+            find_name arg (Bound_parameters.to_list extra_params) extra_args
       in
       EP.Map.fold
         (fun prim bound_to eligible ->