From 3083b2dcd9da8108df8118be2bc87f955311d2bd Mon Sep 17 00:00:00 2001
From: Gaëtan Gilbert
Date: Fri, 5 Jul 2019 15:01:26 +0200
Subject: Simplify picking between uint63_63.ml and uint63_31.ml

- remove the architecture component (we don't do anything
  arch-specific so it was just a rewording of int_size)
- have configure tell the make build system about int_size instead of
  reimplementing cp

As a bonus, add the copyright header to uint63.mli.
---
 kernel/uint63_63.ml | 227 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 227 insertions(+)
 create mode 100644 kernel/uint63_63.ml

(limited to 'kernel/uint63_63.ml')

diff --git a/kernel/uint63_63.ml b/kernel/uint63_63.ml
new file mode 100644
index 0000000000..5c4028e1c8
--- /dev/null
+++ b/kernel/uint63_63.ml
@@ -0,0 +1,227 @@
+(************************************************************************)
+(*         *   The Coq Proof Assistant / The Coq Development Team       *)
+(*  v      *   INRIA, CNRS and contributors - Copyright 1999-2019       *)
+(* <O___,, *       (see CREDITS file for the list of authors)           *)
+(*   \VV/  **************************************************************)
+(*    //   *    This file is distributed under the terms of the         *)
+(*         *     GNU Lesser General Public License Version 2.1          *)
+(*         *     (see LICENSE file for the text of the license)         *)
+(************************************************************************)
+
+type t = int
+
+let _ = assert (Sys.word_size = 64)
+
+let uint_size = 63
+
+let maxuint63 = Int64.of_string "0x7FFFFFFFFFFFFFFF"
+let maxuint31 = 0x7FFFFFFF
+
+    (* conversion from an int *)
+let to_uint64 i = Int64.logand (Int64.of_int i) maxuint63
+
+let of_int i = i
+[@@ocaml.inline always]
+
+let to_int2 i = (0,i)
+
+let of_int64 _i = assert false
+
+let hash i = i
+[@@ocaml.inline always]
+
+    (* conversion of an uint63 to a string *)
+let to_string i = Int64.to_string (to_uint64 i)
+
+let of_string s =
+  let i64 = Int64.of_string s in
+  if Int64.compare Int64.zero i64 <= 0
+      && Int64.compare i64 maxuint63 <= 0
+  then Int64.to_int i64
+  else raise (Failure "Int64.of_string")
+
+(* Compiles an unsigned int to OCaml code *)
+let compile i = Printf.sprintf "Uint63.of_int (%i)" i
+
+let zero = 0
+let one = 1
+
+    (* logical shift *)
+let l_sl x y =
+  if 0 <= y && y < 63 then x lsl y else 0
+
+let l_sr x y =
+  if 0 <= y && y < 63 then x lsr y else 0
+
+let l_and x y = x land y
+[@@ocaml.inline always]
+
+let l_or x y = x lor y
+[@@ocaml.inline always]
+
+let l_xor x y = x lxor y
+[@@ocaml.inline always]
+
+    (* addition of int63 *)
+let add x y = x + y
+[@@ocaml.inline always]
+
+    (* subtraction *)
+let sub x y = x - y
+[@@ocaml.inline always]
+
+    (* multiplication *)
+let mul x y = x * y
+[@@ocaml.inline always]
+
+    (* division *)
+let div (x : int) (y : int) =
+  if y = 0 then 0 else Int64.to_int (Int64.div (to_uint64 x) (to_uint64 y))
+
+    (* modulo *)
+let rem (x : int) (y : int) =
+  if y = 0 then 0 else Int64.to_int (Int64.rem (to_uint64 x) (to_uint64 y))
+
+let diveucl x y = (div x y, rem x y)
+
+let addmuldiv p x y =
+  l_or (l_sl x p) (l_sr y (uint_size - p))
+
+    (* comparison *)
+let lt (x : int) (y : int) =
+  (x lxor 0x4000000000000000) < (y lxor 0x4000000000000000)
+[@@ocaml.inline always]
+
+let le (x : int) (y : int) =
+  (x lxor 0x4000000000000000) <= (y lxor 0x4000000000000000)
+[@@ocaml.inline always]
+
+    (* division of two numbers by one *)
+(* precondition: xh < y *)
+(* outputs: q, r s.t. x = q * y + r, r < y *)
+let div21 xh xl y =
+  (* nh might temporarily grow as large as 2*y - 1 in the loop body,
+     so we store it as a 64-bit unsigned integer *)
+  let nh = ref xh in
+  let nl = ref xl in
+  let q = ref 0 in
+  for _i = 0 to 62 do
+    (* invariants: 0 <= nh < y, nl = (xl*2^i) % 2^63,
+       (q*y + nh) * 2^(63-i) + (xl % 2^(63-i)) = (xh%y) * 2^63 + xl *)
+    nh := Int64.logor (Int64.shift_left !nh 1) (Int64.of_int (!nl lsr 62));
+    nl := !nl lsl 1;
+    q := !q lsl 1;
+    (* TODO: use "Int64.unsigned_compare !nh y >= 0",
+       once OCaml 4.08 becomes the minimal required version *)
+    if Int64.compare !nh 0L < 0 || Int64.compare !nh y >= 0 then
+      begin q := !q lor 1; nh := Int64.sub !nh y; end
+  done;
+  !q, Int64.to_int !nh
+
+let div21 xh xl y =
+  let xh = to_uint64 xh in
+  let y = to_uint64 y in
+  if Int64.compare y xh <= 0 then 0, 0 else div21 xh xl y
+
+     (* exact multiplication *)
+(* TODO: check that none of these additions could be a logical or *)
+
+
+(* size = 32 + 31
+   (hx << 31 + lx) * (hy << 31 + ly) =
+   hxhy << 62 + (hxly + lxhy) << 31 + lxly
+*)
+
+(* precondition : (x lsr 62 = 0 || y lsr 62 = 0) *)
+let mulc_aux x y =
+  let lx = x land maxuint31 in
+  let ly = y land maxuint31 in
+  let hx = x lsr 31  in
+  let hy = y lsr 31 in
+    (* hx and hy are 32 bits value but at most one is 32 *)
+  let hxy  = hx * hy in (* 63 bits *)
+  let hxly = hx * ly in (* 63 bits *)
+  let lxhy = lx * hy in (* 63 bits *)
+  let lxy  = lx * ly in (* 62 bits *)
+  let l  = lxy lor (hxy lsl 62) (* 63 bits *) in
+  let h  = hxy lsr 1 in (* 62 bits *)
+  let hl = hxly + lxhy in (* We can have a carry *)
+  let h  = if lt hl hxly then h + (1 lsl 31) else h in
+  let hl'= hl lsl 31 in
+  let l  = l + hl' in
+  let h  = if lt l hl' then h + 1 else h in
+  let h  = h + (hl lsr 32) in
+  (h,l)
+
+let mulc x y =
+  if (x lsr 62 = 0 || y lsr 62 = 0) then mulc_aux x y
+  else
+    let yl = y lxor (1 lsl 62) in
+    let (h,l) = mulc_aux x yl in
+    (* h << 63 + l = x * yl
+       x * y = x * (1 << 62 + yl)  =
+       x << 62 + x*yl = x << 62 + h << 63 + l *)
+    let l' = l + (x lsl 62) in
+    let h = if lt l' l then h + 1 else h in
+    (h + (x lsr 1), l')
+
+let equal (x : int) (y : int) = x = y
+[@@ocaml.inline always]
+
+let compare (x:int) (y:int) =
+  let x = x lxor 0x4000000000000000 in
+  let y = y lxor 0x4000000000000000 in
+  if x > y then 1
+  else if y > x then -1
+  else 0
+
+    (* head tail *)
+
+let head0 x =
+  let r = ref 0 in
+  let x = ref x in
+  if !x land 0x7FFFFFFF00000000 = 0 then r := !r + 31
+  else x := !x lsr 31;
+  if !x land 0xFFFF0000 = 0 then (x := !x lsl 16; r := !r + 16);
+  if !x land 0xFF000000 = 0 then (x := !x lsl 8; r := !r + 8);
+  if !x land 0xF0000000 = 0 then (x := !x lsl 4; r := !r + 4);
+  if !x land 0xC0000000 = 0 then (x := !x lsl 2; r := !r + 2);
+  if !x land 0x80000000 = 0 then (x := !x lsl 1; r := !r + 1);
+  if !x land 0x80000000 = 0 then (               r := !r + 1);
+  !r;;
+
+let tail0 x =
+  let r = ref 0 in
+  let x = ref x in
+  if !x land 0xFFFFFFFF = 0 then (x := !x lsr 32; r := !r + 32);
+  if !x land 0xFFFF = 0 then (x := !x lsr 16; r := !r + 16);
+  if !x land 0xFF = 0   then (x := !x lsr 8;  r := !r + 8);
+  if !x land 0xF = 0    then (x := !x lsr 4;  r := !r + 4);
+  if !x land 0x3 = 0    then (x := !x lsr 2;  r := !r + 2);
+  if !x land 0x1 = 0    then (                r := !r + 1);
+  !r
+
+let is_uint63 t =
+  Obj.is_int t
+[@@ocaml.inline always]
+
+(* Arithmetic with explicit carries *)
+
+(* Analog of Numbers.Abstract.Cyclic.carry *)
+type 'a carry = C0 of 'a | C1 of 'a
+
+let addc x y =
+  let r = x + y in
+  if lt r x then C1 r else C0 r
+
+let addcarryc x y =
+  let r = x + y + 1 in
+  if le r x then C1 r else C0 r
+
+let subc x y =
+  let r = x - y in
+  if le y x then C0 r else C1 r
+
+let subcarryc x y =
+  let r = x - y - 1 in
+  if lt y x then C0 r else C1 r
-- 
cgit v1.2.3