tanf.c raw

   1  /* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.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  t1pio2 = 1*M_PI_2, /* 0x3FF921FB, 0x54442D18 */
  22  t2pio2 = 2*M_PI_2, /* 0x400921FB, 0x54442D18 */
  23  t3pio2 = 3*M_PI_2, /* 0x4012D97C, 0x7F3321D2 */
  24  t4pio2 = 4*M_PI_2; /* 0x401921FB, 0x54442D18 */
  25  
  26  float tanf(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 and underflow if subnormal */
  39  			FORCE_EVAL(ix < 0x00800000 ? x/0x1p120f : x+0x1p120f);
  40  			return x;
  41  		}
  42  		return __tandf(x, 0);
  43  	}
  44  	if (ix <= 0x407b53d1) {  /* |x| ~<= 5*pi/4 */
  45  		if (ix <= 0x4016cbe3)  /* |x| ~<= 3pi/4 */
  46  			return __tandf((sign ? x+t1pio2 : x-t1pio2), 1);
  47  		else
  48  			return __tandf((sign ? x+t2pio2 : x-t2pio2), 0);
  49  	}
  50  	if (ix <= 0x40e231d5) {  /* |x| ~<= 9*pi/4 */
  51  		if (ix <= 0x40afeddf)  /* |x| ~<= 7*pi/4 */
  52  			return __tandf((sign ? x+t3pio2 : x-t3pio2), 1);
  53  		else
  54  			return __tandf((sign ? x+t4pio2 : x-t4pio2), 0);
  55  	}
  56  
  57  	/* tan(Inf or NaN) is NaN */
  58  	if (ix >= 0x7f800000)
  59  		return x - x;
  60  
  61  	/* argument reduction */
  62  	n = __rem_pio2f(x, &y);
  63  	return __tandf(y, n&1);
  64  }
  65