Use raise_without_backtrace in Map, Set

Map and Set use some exceptions for control flow that were being raised
with plain `raise`. This meant that stack traces were being created for
these exception that couldn't escape their outer function causing an
unfortunate performance loss. Raising these exceptions with
`raise_without_backtrace` avoids the performance problem.

Signed-off-by: Geoff Reedy <[email protected]>

src/map.ml

@@ -676,7 +676,7 @@ module Tree0 = struct
       match t with
       | Empty ->
         (match f None with
-         | None -> raise Change_no_op (* equivalent to returning: Empty *)
+         | None -> Exn.raise_without_backtrace Change_no_op (* equivalent to returning: Empty *)
          | Some data -> Leaf (key, data), length + 1)
       | Leaf (v, d) ->
         let c = compare_key key v in

src/set.ml

@@ -250,13 +250,13 @@ module Tree0 = struct
       | Leaf v ->
         let c = compare_elt x v in
         if c = 0
-        then raise Same
+        then Exn.raise_without_backtrace Same
         else if c < 0
         then create (Leaf x) v Empty
         else create Empty v (Leaf x)
       | Node (l, v, r, _, _) ->
         let c = compare_elt x v in
-        if c = 0 then raise Same else if c < 0 then bal (aux l) v r else bal l v (aux r)
+        if c = 0 then Exn.raise_without_backtrace Same else if c < 0 then bal (aux l) v r else bal l v (aux r)
     in
     try aux t with
     | Same -> t
@@ -419,8 +419,8 @@ module Tree0 = struct
   let remove t x ~compare_elt =
     let rec aux t =
       match t with
-      | Empty -> raise Same
-      | Leaf v -> if compare_elt x v = 0 then Empty else raise Same
+      | Empty -> Exn.raise_without_backtrace Same
+      | Leaf v -> if compare_elt x v = 0 then Empty else Exn.raise_without_backtrace Same
       | Node (l, v, r, _, _) ->
         let c = compare_elt x v in
         if c = 0 then merge l r else if c < 0 then bal (aux l) v r else bal l v (aux r)
@@ -432,8 +432,8 @@ module Tree0 = struct
   let remove_index t i ~compare_elt:_ =
     let rec aux t i =
       match t with
-      | Empty -> raise Same
-      | Leaf _ -> if i = 0 then Empty else raise Same
+      | Empty -> Exn.raise_without_backtrace Same
+      | Leaf _ -> if i = 0 then Empty else Exn.raise_without_backtrace Same
       | Node (l, v, r, _, _) ->
         let l_size = length l in
         let c = Poly.compare i l_size in