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1994-05-19
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------------------------------------------------------------------------------
-- --
-- GNAT RUNTIME COMPONENTS --
-- --
-- S Y S T E M . X P _ B M L --
-- --
-- B o d y --
-- --
-- $Revision: 1.1 $ --
-- --
-- Copyright (c) 1992,1993,1994 NYU, All Rights Reserved --
-- --
-- GNAT is free software; you can redistribute it and/or modify it under --
-- terms of the GNU General Public License as published by the Free Soft- --
-- ware Foundation; either version 2, or (at your option) any later ver- --
-- sion. GNAT is distributed in the hope that it will be useful, but WITH- --
-- OUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY --
-- or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License --
-- for more details. You should have received a copy of the GNU General --
-- Public License distributed with GNAT; see file COPYING. If not, write --
-- to the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. --
-- --
------------------------------------------------------------------------------
function System.Xp_BML
(Left : Long_Long_Unsigned;
Right : Natural)
return Long_Long_Unsigned
is
Result : Long_Long_Unsigned := 1;
Factor : Long_Long_Unsigned := Left;
Exp : Natural := Right;
begin
-- We use the standard logarithmic approach, Exp gets shifted right
-- testing successive low order bits and Factor is the value of the
-- base raised to the next power of 2.
-- Note: it is not worth special casing the cases of base values -1,0,+1
-- since the expander does this when the base is a literal, and other
-- cases will be extremely rare.
while Exp /= 0 loop
if Exp rem 2 /= 0 then
Result := Result * Factor;
end if;
Factor := Factor * Factor;
Exp := Exp / 2;
end loop;
return Result;
end System.Xp_BML;