boost/numeric/interval/ext/x86_fast_rounding_control.hpp

   1 /* Boost interval/detail/x86gcc_rounding_control.hpp file
   2  *
   3  * This header provides a rounding control policy
   4  * that avoids flushing results to memory. In
   5  * order for this optimization to be reliable, it
   6  * should be used only when no underflow or
   7  * overflow would happen without it. Indeed, only
   8  * values in range are correctly rounded.
   9  *
  10  * Copyright 2002 Hervé Brönnimann, Guillaume Melquiond, Sylvain Pion
  11  *
  12  * Distributed under the Boost Software License, Version 1.0.
  13  * (See accompanying file LICENSE_1_0.txt or
  14  * copy at http://www.boost.org/LICENSE_1_0.txt)
  15  */
  16
  17 #ifndef BOOST_NUMERIC_INTERVAL_EXT_X86_FAST_ROUNDING_CONTROL_HPP
  18 #define BOOST_NUMERIC_INTERVAL_EXT_X86_FAST_ROUNDING_CONTROL_HPP
  19
  20 namespace boost {
  21 namespace numeric {
  22 namespace interval_lib {
  23
  24 namespace detail {
  25
  26 // exceptions masked, expected precision (the mask is 0x0300)
  27 static const fpu_rounding_modes rnd_mode_f = { 0x107f, 0x147f, 0x187f, 0x1c7f };
  28 static const fpu_rounding_modes rnd_mode_d = { 0x127f, 0x167f, 0x1a7f, 0x1e7f };
  29 static const fpu_rounding_modes rnd_mode_l = { 0x137f, 0x177f, 0x1b7f, 0x1f7f };
  30
  31 } // namespace detail
  32
  33 template<class T>
  34 struct x86_fast_rounding_control;
  35
  36 template<>
  37 struct x86_fast_rounding_control<float>: detail::x86_rounding
  38 {
  39   static void to_nearest()  { set_rounding_mode(detail::rnd_mode_f.to_nearest);  }
  40   static void downward()    { set_rounding_mode(detail::rnd_mode_f.downward);    }
  41   static void upward()      { set_rounding_mode(detail::rnd_mode_f.upward);      }
  42   static void toward_zero() { set_rounding_mode(detail::rnd_mode_f.toward_zero); }
  43   static const float& force_rounding(const float& r) { return r; }
  44 };
  45
  46 template<>
  47 struct x86_fast_rounding_control<double>: detail::x86_rounding
  48 {
  49   static void to_nearest()  { set_rounding_mode(detail::rnd_mode_d.to_nearest);  }
  50   static void downward()    { set_rounding_mode(detail::rnd_mode_d.downward);    }
  51   static void upward()      { set_rounding_mode(detail::rnd_mode_d.upward);      }
  52   static void toward_zero() { set_rounding_mode(detail::rnd_mode_d.toward_zero); }
  53   static const double& force_rounding(const double& r) { return r; }
  54 };
  55
  56 template<>
  57 struct x86_fast_rounding_control<long double>: detail::x86_rounding
  58 {
  59   static void to_nearest()  { set_rounding_mode(detail::rnd_mode_l.to_nearest);  }
  60   static void downward()    { set_rounding_mode(detail::rnd_mode_l.downward);    }
  61   static void upward()      { set_rounding_mode(detail::rnd_mode_l.upward);      }
  62   static void toward_zero() { set_rounding_mode(detail::rnd_mode_l.toward_zero); }
  63   static const long double& force_rounding(const long double& r) { return r; }
  64 };
  65
  66 } // namespace interval_lib
  67 } // namespace numeric
  68 } // namespace boost
  69
  70 #endif // BOOST_NUMERIC_INTERVAL_EXT_X86_FAST_ROUNDING_CONTROL_HPP