Review: Comment + cleanup in matching.ml

lambda/matching.ml

@@ -2835,11 +2835,15 @@ let combine_constructor loc arg pat_env cstr partial ctx def
             match
               (cstr.cstr_consts, cstr.cstr_nonconsts, consts, nonconsts)
             with
-            | 1, 1, [ (0, act1) ], [ (0, act2) ]
-              when not !Clflags.native_code ->
-                (* Typically, match on lists, will avoid isint primitive in that
-              case *)
-                Lifthenelse (arg, act2, act1)
+            | 1, 1, [ (0, act1) ], [ (0, act2) ] ->
+                if !Clflags.native_code then
+                  Lifthenelse(Lprim (Pisint, [ arg ], loc), act1, act2)
+                else
+                  (* PR#10681: we use [arg] directly as the test here;
+                     it generates better bytecode for this common case
+                     (typically options and lists), but would prevent
+                     some optimizations with the native compiler. *)
+                  Lifthenelse (arg, act2, act1)
             | n, 0, _, [] ->
                 (* The type defines constant constructors only *)
                 call_switcher loc fail_opt arg 0 (n - 1) consts