sysdeps/powerpc/fpu/k_cosf.c

   1 /* k_cosf.c -- float version of k_cos.c
   2    Copyright (C) 2011-2013 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Adhemerval Zanella <azanella@br.ibm.com>, 2011
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Library General Public License as
   8    published by the Free Software Foundation; either version 2 of the
   9    License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Library General Public License for more details.
  15
  16    You should have received a copy of the GNU Library General Public
  17    License along with the GNU C Library; see the file COPYING.LIB.  If
  18    not, see <http://www.gnu.org/licenses/>.  */
  19
  20 #include <math.h>
  21 #include <fenv.h>
  22 #include <math_private.h>
  23
  24 static const float twom27   = 7.4505806e-09;
  25 static const float dot3     = 3.0000001e-01;
  26 static const float dot78125 = 7.8125000e-01;
  27
  28 static const float one =  1.0000000000e+00;
  29 static const float C1  =  4.1666667908e-02;
  30 static const float C2  = -1.3888889225e-03;
  31 static const float C3  =  2.4801587642e-05;
  32 static const float C4  = -2.7557314297e-07;
  33 static const float C5  =  2.0875723372e-09;
  34 static const float C6  = -1.1359647598e-11;
  35
  36 float
  37 __kernel_cosf (float x, float y)
  38 {
  39   float a, hz, z, r, qx;
  40   float ix;
  41   ix = __builtin_fabsf (x);
  42   if (ix < twom27)
  43     {                           /* |x| < 2**-27 */
  44       __feraiseexcept (FE_INEXACT);
  45       return one;
  46     }
  47   z = x * x;
  48   r = z * (C1 + z * (C2 + z * (C3 + z * (C4 + z * (C5 + z * C6)))));
  49   if (ix < dot3)                /* if |x| < 0.3 */
  50     return one - ((float) 0.5 * z - (z * r - x * y));
  51   else
  52     {
  53       if (ix > dot78125)
  54         {                       /* x > 0.78125 */
  55           qx = (float) 0.28125;
  56         }
  57       else
  58         {
  59           qx = ix / 4.0;
  60         }
  61       hz = (float) 0.5 *z - qx;
  62       a = one - qx;
  63       return a - (hz - (z * r - x * y));
  64     }
  65 }