gcc/ada/s-expllu.adb

   1 ------------------------------------------------------------------------------
   2 --                                                                          --
   3 --                         GNAT RUNTIME COMPONENTS                          --
   4 --                                                                          --
   5 --                        S Y S T E M . X P _ B M L                         --
   6 --                                                                          --
   7 --                                 B o d y                                  --
   8 --                                                                          --
   9 --                            $Revision: 1.7 $                              --
  10 --                                                                          --
  11 --        Copyright (C) 1992,1993,1994 Free Software Foundation, Inc.       --
  12 --                                                                          --
  13 -- GNAT is free software;  you can  redistribute it  and/or modify it under --
  14 -- terms of the  GNU General Public License as published  by the Free Soft- --
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  19 -- for  more details.  You should have  received  a copy of the GNU General --
  20 -- Public License  distributed with GNAT;  see file COPYING.  If not, write --
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  22 -- MA 02111-1307, USA.                                                      --
  23 --                                                                          --
  24 -- As a special exception,  if other files  instantiate  generics from this --
  25 -- unit, or you link  this unit with other files  to produce an executable, --
  26 -- this  unit  does not  by itself cause  the resulting  executable  to  be --
  27 -- covered  by the  GNU  General  Public  License.  This exception does not --
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  29 -- covered by the  GNU Public License.                                      --
  30 --                                                                          --
  31 -- GNAT was originally developed  by the GNAT team at  New York University. --
  32 -- It is now maintained by Ada Core Technologies Inc (http://www.gnat.com). --
  33 --                                                                          --
  34 ------------------------------------------------------------------------------
  35
  36 with System.Unsigned_Types; use System.Unsigned_Types;
  37
  38 package body System.Exp_LLU is
  39
  40    ----------------------------
  41    -- Exp_Long_Long_Unsigned --
  42    ----------------------------
  43
  44    function Exp_Long_Long_Unsigned
  45      (Left  : Long_Long_Unsigned;
  46       Right : Natural)
  47       return  Long_Long_Unsigned
  48    is
  49       Result : Long_Long_Unsigned := 1;
  50       Factor : Long_Long_Unsigned := Left;
  51       Exp    : Natural := Right;
  52
  53    begin
  54       --  We use the standard logarithmic approach, Exp gets shifted right
  55       --  testing successive low order bits and Factor is the value of the
  56       --  base raised to the next power of 2.
  57
  58       --  Note: it is not worth special casing the cases of base values -1,0,+1
  59       --  since the expander does this when the base is a literal, and other
  60       --  cases will be extremely rare.
  61
  62       if Exp /= 0 then
  63          loop
  64             if Exp rem 2 /= 0 then
  65                Result := Result * Factor;
  66             end if;
  67
  68             Exp := Exp / 2;
  69             exit when Exp = 0;
  70             Factor := Factor * Factor;
  71          end loop;
  72       end if;
  73
  74       return Result;
  75
  76    end Exp_Long_Long_Unsigned;
  77
  78 end System.Exp_LLU;