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Diffstat (limited to 'gcc/ada/s-exnllf.adb')
-rw-r--r-- | gcc/ada/s-exnllf.adb | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/gcc/ada/s-exnllf.adb b/gcc/ada/s-exnllf.adb new file mode 100644 index 00000000000..a66bc43030c --- /dev/null +++ b/gcc/ada/s-exnllf.adb @@ -0,0 +1,99 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT RUNTIME COMPONENTS -- +-- -- +-- S Y S T E M . E X N _ L L F -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1992-2003, Free Software Foundation, Inc. -- +-- -- +-- 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, 59 Temple Place - Suite 330, Boston, -- +-- MA 02111-1307, USA. -- +-- -- +-- As a special exception, if other files instantiate generics from this -- +-- unit, or you link this unit with other files to produce an executable, -- +-- this unit does not by itself cause the resulting executable to be -- +-- covered by the GNU General Public License. This exception does not -- +-- however invalidate any other reasons why the executable file might be -- +-- covered by the GNU Public License. -- +-- -- +-- GNAT was originally developed by the GNAT team at New York University. -- +-- Extensive contributions were provided by Ada Core Technologies Inc. -- +-- -- +------------------------------------------------------------------------------ + +package body System.Exn_LLF is + + ------------------------- + -- Exn_Long_Long_Float -- + ------------------------- + + function Exn_Long_Long_Float + (Left : Long_Long_Float; + Right : Integer) + return Long_Long_Float + is + Result : Long_Long_Float := 1.0; + Factor : Long_Long_Float := Left; + Exp : Integer := 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. For positive exponents we + -- multiply the result by this factor, for negative exponents, we + -- Division by this factor. + + if Exp >= 0 then + loop + if Exp rem 2 /= 0 then + Result := Result * Factor; + end if; + + Exp := Exp / 2; + exit when Exp = 0; + Factor := Factor * Factor; + end loop; + + return Result; + + -- Here we have a negative exponent, and we compute the result as: + + -- 1.0 / (Left ** (-Right)) + + -- Note that the case of Left being zero is not special, it will + -- simply result in a division by zero at the end, yielding a + -- correctly signed infinity, or possibly generating an overflow. + + -- Note on overflow: The coding of this routine assumes that the + -- target generates infinities with standard IEEE semantics. If this + -- is not the case, then the code below may raise Constraint_Error. + -- This follows the implementation permission given in RM 4.5.6(12). + + else + begin + loop + if Exp rem 2 /= 0 then + Result := Result * Factor; + end if; + + Exp := Exp / 2; + exit when Exp = 0; + Factor := Factor * Factor; + end loop; + + return 1.0 / Result; + end; + end if; + end Exn_Long_Long_Float; + +end System.Exn_LLF; |