1------------------------------------------------------------------------------
2--                                                                          --
3--                         GNAT COMPILER COMPONENTS                         --
4--                                                                          --
5--                      S Y S T E M . A R I T H _ 6 4                       --
6--                                                                          --
7--                                 S p e c                                  --
8--                                                                          --
9--          Copyright (C) 1992-2018, Free Software Foundation, Inc.         --
10--                                                                          --
11-- GNAT is free software;  you can  redistribute it  and/or modify it under --
12-- terms of the  GNU General Public License as published  by the Free Soft- --
13-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
14-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
15-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
16-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
17--                                                                          --
18-- As a special exception under Section 7 of GPL version 3, you are granted --
19-- additional permissions described in the GCC Runtime Library Exception,   --
20-- version 3.1, as published by the Free Software Foundation.               --
21--                                                                          --
22-- You should have received a copy of the GNU General Public License and    --
23-- a copy of the GCC Runtime Library Exception along with this program;     --
24-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
25-- <http://www.gnu.org/licenses/>.                                          --
26--                                                                          --
27-- GNAT was originally developed  by the GNAT team at  New York University. --
28-- Extensive contributions were provided by Ada Core Technologies Inc.      --
29--                                                                          --
30------------------------------------------------------------------------------
31
32--  This unit provides software routines for doing arithmetic on 64-bit
33--  signed integer values in cases where either overflow checking is
34--  required, or intermediate results are longer than 64 bits.
35
36pragma Restrictions (No_Elaboration_Code);
37--  Allow direct call from gigi generated code
38
39with Interfaces;
40
41package System.Arith_64 is
42   pragma Pure;
43
44   subtype Int64 is Interfaces.Integer_64;
45
46   function Add_With_Ovflo_Check (X, Y : Int64) return Int64;
47   --  Raises Constraint_Error if sum of operands overflows 64 bits,
48   --  otherwise returns the 64-bit signed integer sum.
49
50   function Subtract_With_Ovflo_Check (X, Y : Int64) return Int64;
51   --  Raises Constraint_Error if difference of operands overflows 64
52   --  bits, otherwise returns the 64-bit signed integer difference.
53
54   function Multiply_With_Ovflo_Check (X, Y : Int64) return Int64;
55   pragma Export (C, Multiply_With_Ovflo_Check, "__gnat_mulv64");
56   --  Raises Constraint_Error if product of operands overflows 64
57   --  bits, otherwise returns the 64-bit signed integer product.
58   --  GIGI may also call this routine directly.
59
60   procedure Scaled_Divide
61     (X, Y, Z : Int64;
62      Q, R    : out Int64;
63      Round   : Boolean);
64   --  Performs the division of (X * Y) / Z, storing the quotient in Q
65   --  and the remainder in R. Constraint_Error is raised if Z is zero,
66   --  or if the quotient does not fit in 64-bits. Round indicates if
67   --  the result should be rounded. If Round is False, then Q, R are
68   --  the normal quotient and remainder from a truncating division.
69   --  If Round is True, then Q is the rounded quotient. The remainder
70   --  R is not affected by the setting of the Round flag.
71
72   procedure Double_Divide
73     (X, Y, Z : Int64;
74      Q, R    : out Int64;
75      Round   : Boolean);
76   --  Performs the division X / (Y * Z), storing the quotient in Q and
77   --  the remainder in R. Constraint_Error is raised if Y or Z is zero,
78   --  or if the quotient does not fit in 64-bits. Round indicates if the
79   --  result should be rounded. If Round is False, then Q, R are the normal
80   --  quotient and remainder from a truncating division. If Round is True,
81   --  then Q is the rounded quotient. The remainder R is not affected by the
82   --  setting of the Round flag.
83
84end System.Arith_64;
85