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  * Optimized by Bruce D. Evans.
   4  */
   5
   6 /*
   7  * ====================================================
   8  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   9  *
  10  * Developed at SunPro, a Sun Microsystems, Inc. business.
  11  * Permission to use, copy, modify, and distribute this
  12  * software is freely granted, provided that this notice
  13  * is preserved.
  14  * ====================================================
  15  *
  16  * $FreeBSD: head/lib/msun/src/s_cosf.c 176569 2008-02-25 22:19:17Z bde $
  17  */
  18
  19 #include <float.h>
  20
  21 #include "math.h"
  22 #define INLINE_KERNEL_COSDF
  23 #define INLINE_KERNEL_SINDF
  24 #define INLINE_REM_PIO2F
  25 #include "math_private.h"
  26 #include "e_rem_pio2f.c"
  27 #include "k_cosf.c"
  28 #include "k_sinf.c"
  29
  30 /* Small multiples of pi/2 rounded to double precision. */
  31 static const double
  32 c1pio2 = 1*M_PI_2,                      /* 0x3FF921FB, 0x54442D18 */
  33 c2pio2 = 2*M_PI_2,                      /* 0x400921FB, 0x54442D18 */
  34 c3pio2 = 3*M_PI_2,                      /* 0x4012D97C, 0x7F3321D2 */
  35 c4pio2 = 4*M_PI_2;                      /* 0x401921FB, 0x54442D18 */
  36
  37 float
  38 cosf(float x)
  39 {
  40         double y;
  41         int32_t n, hx, ix;
  42
  43         GET_FLOAT_WORD(hx,x);
  44         ix = hx & 0x7fffffff;
  45
  46         if(ix <= 0x3f490fda) {          /* |x| ~<= pi/4 */
  47             if(ix<0x39800000)           /* |x| < 2**-12 */
  48                 if(((int)x)==0) return 1.0;     /* 1 with inexact if x != 0 */
  49             return __kernel_cosdf(x);
  50         }
  51         if(ix<=0x407b53d1) {            /* |x| ~<= 5*pi/4 */
  52             if(ix>0x4016cbe3)           /* |x|  ~> 3*pi/4 */
  53                 return -__kernel_cosdf(x + (hx > 0 ? -c2pio2 : c2pio2));
  54             else {
  55                 if(hx>0)
  56                     return __kernel_sindf(c1pio2 - x);
  57                 else
  58                     return __kernel_sindf(x + c1pio2);
  59             }
  60         }
  61         if(ix<=0x40e231d5) {            /* |x| ~<= 9*pi/4 */
  62             if(ix>0x40afeddf)           /* |x|  ~> 7*pi/4 */
  63                 return __kernel_cosdf(x + (hx > 0 ? -c4pio2 : c4pio2));
  64             else {
  65                 if(hx>0)
  66                     return __kernel_sindf(x - c3pio2);
  67                 else
  68                     return __kernel_sindf(-c3pio2 - x);
  69             }
  70         }
  71
  72     /* cos(Inf or NaN) is NaN */
  73         else if (ix>=0x7f800000) return x-x;
  74
  75     /* general argument reduction needed */
  76         else {
  77             n = __ieee754_rem_pio2f(x,&y);
  78             switch(n&3) {
  79                 case 0: return  __kernel_cosdf(y);
  80                 case 1: return  __kernel_sindf(-y);
  81                 case 2: return -__kernel_cosdf(y);
  82                 default:
  83                         return  __kernel_sindf(y);
  84             }
  85         }
  86 }