src/math/sincos.c

   1 /* origin: FreeBSD /usr/src/lib/msun/src/s_sin.c */
   2 /*
   3  * ====================================================
   4  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
   5  *
   6  * Developed at SunPro, a Sun Microsystems, Inc. business.
   7  * Permission to use, copy, modify, and distribute this
   8  * software is freely granted, provided that this notice
   9  * is preserved.
  10  * ====================================================
  11  */
  12
  13 #define _GNU_SOURCE
  14 #include "libm.h"
  15
  16 void sincos(double x, double *sin, double *cos)
  17 {
  18         double y[2], s, c;
  19         uint32_t ix;
  20         unsigned n;
  21
  22         GET_HIGH_WORD(ix, x);
  23         ix &= 0x7fffffff;
  24
  25         /* |x| ~< pi/4 */
  26         if (ix <= 0x3fe921fb) {
  27                 /* if |x| < 2**-27 * sqrt(2) */
  28                 if (ix < 0x3e46a09e) {
  29                         /* raise inexact if x!=0 and underflow if subnormal */
  30                         FORCE_EVAL(ix < 0x00100000 ? x/0x1p120f : x+0x1p120f);
  31                         *sin = x;
  32                         *cos = 1.0;
  33                         return;
  34                 }
  35                 *sin = __sin(x, 0.0, 0);
  36                 *cos = __cos(x, 0.0);
  37                 return;
  38         }
  39
  40         /* sincos(Inf or NaN) is NaN */
  41         if (ix >= 0x7ff00000) {
  42                 *sin = *cos = x - x;
  43                 return;
  44         }
  45
  46         /* argument reduction needed */
  47         n = __rem_pio2(x, y);
  48         s = __sin(y[0], y[1], 1);
  49         c = __cos(y[0], y[1]);
  50         switch (n&3) {
  51         case 0:
  52                 *sin = s;
  53                 *cos = c;
  54                 break;
  55         case 1:
  56                 *sin = c;
  57                 *cos = -s;
  58                 break;
  59         case 2:
  60                 *sin = -s;
  61                 *cos = -c;
  62                 break;
  63         case 3:
  64         default:
  65                 *sin = -c;
  66                 *cos = s;
  67                 break;
  68         }
  69 }