* config/arm/elf.h (ASM_OUTPUT_ALIGNED_COMMON): Remove definition.
[official-gcc.git] / gcc / ada / s-expmod.adb
blob67c2bf148135a334f1fd5f855cef421cb8a0d0f0
1 ------------------------------------------------------------------------------
2 -- --
3 -- GNAT RUNTIME COMPONENTS --
4 -- --
5 -- S Y S T E M . E X P _ M O D --
6 -- --
7 -- B o d y --
8 -- --
9 -- Copyright (C) 1992,1993,1994,1995 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 2, 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. See the GNU General Public License --
17 -- for more details. You should have received a copy of the GNU General --
18 -- Public License distributed with GNAT; see file COPYING. If not, write --
19 -- to the Free Software Foundation, 59 Temple Place - Suite 330, Boston, --
20 -- MA 02111-1307, USA. --
21 -- --
22 -- As a special exception, if other files instantiate generics from this --
23 -- unit, or you link this unit with other files to produce an executable, --
24 -- this unit does not by itself cause the resulting executable to be --
25 -- covered by the GNU General Public License. This exception does not --
26 -- however invalidate any other reasons why the executable file might be --
27 -- covered by the GNU Public License. --
28 -- --
29 -- GNAT was originally developed by the GNAT team at New York University. --
30 -- Extensive contributions were provided by Ada Core Technologies Inc. --
31 -- --
32 ------------------------------------------------------------------------------
34 package body System.Exp_Mod is
36 -----------------
37 -- Exp_Modular --
38 -----------------
40 function Exp_Modular
41 (Left : Integer;
42 Modulus : Integer;
43 Right : Natural)
44 return Integer
46 Result : Integer := 1;
47 Factor : Integer := Left;
48 Exp : Natural := Right;
50 function Mult (X, Y : Integer) return Integer;
51 pragma Inline (Mult);
52 -- Modular multiplication. Note that we can't take advantage of the
53 -- compiler's circuit, because the modulus is not known statically.
55 function Mult (X, Y : Integer) return Integer is
56 begin
57 return Integer
58 (Long_Long_Integer (X) * Long_Long_Integer (Y)
59 mod Long_Long_Integer (Modulus));
60 end Mult;
62 -- Start of processing for Exp_Modular
64 begin
65 -- We use the standard logarithmic approach, Exp gets shifted right
66 -- testing successive low order bits and Factor is the value of the
67 -- base raised to the next power of 2.
69 -- Note: it is not worth special casing the cases of base values -1,0,+1
70 -- since the expander does this when the base is a literal, and other
71 -- cases will be extremely rare.
73 if Exp /= 0 then
74 loop
75 if Exp rem 2 /= 0 then
76 Result := Mult (Result, Factor);
77 end if;
79 Exp := Exp / 2;
80 exit when Exp = 0;
81 Factor := Mult (Factor, Factor);
82 end loop;
83 end if;
85 return Result;
87 end Exp_Modular;
89 end System.Exp_Mod;