From 8675b9d1a574aceb9a9d40c9c135db9c042e00b1 Mon Sep 17 00:00:00 2001
From: Vincent Laporte
Date: Mon, 22 Jul 2019 12:47:53 +0000
Subject: [Int63] Implement all primitives in OCaml

Primitive operations addc, addcarryc, subc, subcarryc, and diveucl are
implemented in the kernel so that they can be used by OCaml code (e.g.,
extracted code) as the other primitives.
---
 kernel/uint63_amd64_63.ml | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

(limited to 'kernel/uint63_amd64_63.ml')

diff --git a/kernel/uint63_amd64_63.ml b/kernel/uint63_amd64_63.ml
index 20b2f58496..d6b077a9f5 100644
--- a/kernel/uint63_amd64_63.ml
+++ b/kernel/uint63_amd64_63.ml
@@ -82,6 +82,8 @@ let div (x : int) (y : int) =
 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))
 
@@ -225,3 +227,24 @@ let tail0 x =
 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
-- 
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