lib/libm/src/s_cosf.c

   1 /* s_cosf.c -- float version of s_cos.c.
   2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   3  */
   4
   5 /*
   6  * ====================================================
   7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   8  *
   9  * Developed at SunPro, a Sun Microsystems, Inc. business.
  10  * Permission to use, copy, modify, and distribute this
  11  * software is freely granted, provided that this notice
  12  * is preserved.
  13  * ====================================================
  14  */
  15
  16 #include "math.h"
  17 #include "math_private.h"
  18
  19 float
  20 cosf(float x)
  21 {
  22         float y[2],z=0.0;
  23         int32_t n,ix;
  24
  25         GET_FLOAT_WORD(ix,x);
  26
  27     /* |x| ~< pi/4 */
  28         ix &= 0x7fffffff;
  29         if(ix <= 0x3f490fd8) return __kernel_cosf(x,z);
  30
  31     /* cos(Inf or NaN) is NaN */
  32         else if (ix>=0x7f800000) return x-x;
  33
  34     /* argument reduction needed */
  35         else {
  36             n = __ieee754_rem_pio2f(x,y);
  37             switch(n&3) {
  38                 case 0: return  __kernel_cosf(y[0],y[1]);
  39                 case 1: return -__kernel_sinf(y[0],y[1],1);
  40                 case 2: return -__kernel_cosf(y[0],y[1]);
  41                 default:
  42                         return  __kernel_sinf(y[0],y[1],1);
  43             }
  44         }
  45 }