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Diffstat (limited to 'gcc/ada/s-exnllf.adb')
| -rw-r--r-- | gcc/ada/s-exnllf.adb | 97 |
1 files changed, 97 insertions, 0 deletions
diff --git a/gcc/ada/s-exnllf.adb b/gcc/ada/s-exnllf.adb new file mode 100644 index 000000000..a1e59c179 --- /dev/null +++ b/gcc/ada/s-exnllf.adb @@ -0,0 +1,97 @@ +------------------------------------------------------------------------------ +-- -- +-- GNAT RUN-TIME COMPONENTS -- +-- -- +-- S Y S T E M . E X N _ L L F -- +-- -- +-- B o d y -- +-- -- +-- Copyright (C) 1992-2009 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 3, 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. -- +-- -- +-- As a special exception under Section 7 of GPL version 3, you are granted -- +-- additional permissions described in the GCC Runtime Library Exception, -- +-- version 3.1, as published by the Free Software Foundation. -- +-- -- +-- You should have received a copy of the GNU General Public License and -- +-- a copy of the GCC Runtime Library Exception along with this program; -- +-- see the files COPYING3 and COPYING.RUNTIME respectively. If not, see -- +-- <http://www.gnu.org/licenses/>. -- +-- -- +-- 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. If the low order bit or Exp is + -- set, multiply the result by this factor. For negative exponents, + -- invert result upon return. + + 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; |