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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [gcc/] [ada/] [s-expint.adb] - Blame information for rev 706

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1 706 jeremybenn
------------------------------------------------------------------------------
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--                                                                          --
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--                         GNAT RUN-TIME COMPONENTS                         --
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--                                                                          --
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--                        S Y S T E M . E X P I N T                         --
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--                                                                          --
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--                                 B o d y                                  --
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--                                                                          --
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--          Copyright (C) 1992-2009 Free Software Foundation, Inc.          --
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--                                                                          --
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-- GNAT is free software;  you can  redistribute it  and/or modify it under --
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-- terms of the  GNU General Public License as published  by the Free Soft- --
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-- ware  Foundation;  either version 3,  or (at your option) any later ver- --
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-- sion.  GNAT is distributed in the hope that it will be useful, but WITH- --
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-- OUT ANY WARRANTY;  without even the  implied warranty of MERCHANTABILITY --
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-- or FITNESS FOR A PARTICULAR PURPOSE.                                     --
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--                                                                          --
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-- As a special exception under Section 7 of GPL version 3, you are granted --
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-- additional permissions described in the GCC Runtime Library Exception,   --
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-- version 3.1, as published by the Free Software Foundation.               --
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--                                                                          --
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-- You should have received a copy of the GNU General Public License and    --
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-- a copy of the GCC Runtime Library Exception along with this program;     --
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-- see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see    --
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-- <http://www.gnu.org/licenses/>.                                          --
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--                                                                          --
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-- GNAT was originally developed  by the GNAT team at  New York University. --
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-- Extensive contributions were provided by Ada Core Technologies Inc.      --
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--                                                                          --
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------------------------------------------------------------------------------
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package body System.Exp_Int is
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   -----------------
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   -- Exp_Integer --
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   -----------------
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   --  Note that negative exponents get a constraint error because the
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   --  subtype of the Right argument (the exponent) is Natural.
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   function Exp_Integer
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     (Left  : Integer;
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      Right : Natural)
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      return  Integer
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   is
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      Result : Integer := 1;
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      Factor : Integer := Left;
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      Exp    : Natural := Right;
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   begin
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      --  We use the standard logarithmic approach, Exp gets shifted right
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      --  testing successive low order bits and Factor is the value of the
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      --  base raised to the next power of 2.
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      --  Note: it is not worth special casing base values -1, 0, +1 since
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      --  the expander does this when the base is a literal, and other cases
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      --  will be extremely rare.
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      if Exp /= 0 then
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         loop
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            if Exp rem 2 /= 0 then
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               declare
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                  pragma Unsuppress (All_Checks);
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               begin
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                  Result := Result * Factor;
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               end;
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            end if;
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            Exp := Exp / 2;
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            exit when Exp = 0;
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            declare
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               pragma Unsuppress (All_Checks);
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            begin
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               Factor := Factor * Factor;
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            end;
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         end loop;
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      end if;
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      return Result;
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   end Exp_Integer;
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end System.Exp_Int;

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