Fixes to One_bit_fewer (#677)

* One_bit_fewer: simplify signature

* One_bit_fewer: fix shift_right_logical, remove unneeded sign extensions

Author: lthls

middle_end/flambda2/numbers/one_bit_fewer.ml

@@ -205,7 +205,8 @@ module Make (I : S) : S with type t = I.t = struct
 
   let mul x y = sign_extend (I.mul x y)
 
-  let mod_ x y = sign_extend (I.mod_ x y)
+  (* No sign-extension: the result is always in the correct range *)
+  let mod_ = I.mod_
 
   let div x y = sign_extend (I.div x y)
 
@@ -217,9 +218,11 @@ module Make (I : S) : S with type t = I.t = struct
 
   let shift_left t i = sign_extend (I.shift_left t i)
 
-  let shift_right t i = sign_extend (I.shift_right t i)
+  (* No sign-extension: the result is always in the correct range *)
+  let shift_right = I.shift_right
 
-  let shift_right_logical t i = I.shift_right_logical (I.shift_left t 1) (i + 1)
+  let shift_right_logical t i =
+    I.shift_right (I.shift_right_logical (I.shift_left t 1) i) 1
 
   let max = I.max
 

middle_end/flambda2/numbers/one_bit_fewer.mli

@@ -90,94 +90,4 @@ module type S = sig
   val min : t -> t -> t
 end
 
-module Make : functor (I : S) -> sig
-  type t = I.t
-
-  val compare : t -> t -> int
-
-  val equal : t -> t -> bool
-
-  val hash : t -> int
-
-  val print : Format.formatter -> t -> unit
-
-  val min_value : t
-
-  val max_value : t
-
-  val max_string_length : t
-
-  val minus_one : t
-
-  val zero : t
-
-  val one : t
-
-  val ten : t
-
-  val hex_ff : t
-
-  val ( <= ) : t -> t -> bool
-
-  val ( < ) : t -> t -> bool
-
-  val bottom_byte_to_int : t -> int
-
-  val of_char : char -> t
-
-  val of_int : int -> t
-
-  val of_int_option : int -> t option
-
-  val of_int32 : int32 -> t
-
-  val of_int64 : int64 -> t
-
-  val of_targetint : Targetint_32_64.t -> t
-
-  val of_float : float -> t
-
-  val to_float : t -> float
-
-  val to_int : t -> int
-
-  val to_int_exn : t -> int
-
-  val to_int_option : t -> int option
-
-  val to_int32 : t -> int32
-
-  val to_int64 : t -> int64
-
-  val to_targetint : t -> Targetint_32_64.t
-
-  val neg : t -> t
-
-  val get_least_significant_16_bits_then_byte_swap : t -> t
-
-  val add : t -> t -> t
-
-  val sub : t -> t -> t
-
-  val mul : t -> t -> t
-
-  val mod_ : t -> t -> t
-
-  val div : t -> t -> t
-
-  val and_ : t -> t -> t
-
-  val or_ : t -> t -> t
-
-  val xor : t -> t -> t
-
-  val shift_left : t -> int -> t
-
-  val shift_right : t -> int -> t
-
-  val shift_right_logical : t -> int -> t
-
-  val max : t -> t -> t
-
-  val min : t -> t -> t
-end
+module Make : functor (I : S) -> S with type t = I.t