cosf.c raw

   1  /* origin: FreeBSD /usr/src/lib/msun/src/s_cosf.c */
   2  /*
   3   * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
   4   * Optimized by Bruce D. Evans.
   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  
  17  #include "libm.h"
  18  
  19  /* Small multiples of pi/2 rounded to double precision. */
  20  static const double
  21  c1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
  22  c2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
  23  c3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
  24  c4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
  25  
  26  float cosf(float x)
  27  {
  28  	double y;
  29  	uint32_t ix;
  30  	unsigned n, sign;
  31  
  32  	GET_FLOAT_WORD(ix, x);
  33  	sign = ix >> 31;
  34  	ix &= 0x7fffffff;
  35  
  36  	if (ix <= 0x3f490fda) {  /* |x| ~<= pi/4 */
  37  		if (ix < 0x39800000) {  /* |x| < 2**-12 */
  38  			/* raise inexact if x != 0 */
  39  			FORCE_EVAL(x + 0x1p120f);
  40  			return 1.0f;
  41  		}
  42  		return __cosdf(x);
  43  	}
  44  	if (ix <= 0x407b53d1) {  /* |x| ~<= 5*pi/4 */
  45  		if (ix > 0x4016cbe3)  /* |x|  ~> 3*pi/4 */
  46  			return -__cosdf(sign ? x+c2pio2 : x-c2pio2);
  47  		else {
  48  			if (sign)
  49  				return __sindf(x + c1pio2);
  50  			else
  51  				return __sindf(c1pio2 - x);
  52  		}
  53  	}
  54  	if (ix <= 0x40e231d5) {  /* |x| ~<= 9*pi/4 */
  55  		if (ix > 0x40afeddf)  /* |x| ~> 7*pi/4 */
  56  			return __cosdf(sign ? x+c4pio2 : x-c4pio2);
  57  		else {
  58  			if (sign)
  59  				return __sindf(-x - c3pio2);
  60  			else
  61  				return __sindf(x - c3pio2);
  62  		}
  63  	}
  64  
  65  	/* cos(Inf or NaN) is NaN */
  66  	if (ix >= 0x7f800000)
  67  		return x-x;
  68  
  69  	/* general argument reduction needed */
  70  	n = __rem_pio2f(x,&y);
  71  	switch (n&3) {
  72  	case 0: return  __cosdf(y);
  73  	case 1: return  __sindf(-y);
  74  	case 2: return -__cosdf(y);
  75  	default:
  76  		return  __sindf(y);
  77  	}
  78  }
  79