fusl/src/math/tanf.c

/* origin: FreeBSD /usr/src/lib/msun/src/s_tanf.c */
/*
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 * Optimized by Bruce D. Evans.
 */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#include "libm.h"

/* Small multiples of pi/2 rounded to double precision. */
static const double t1pio2 = 1 * M_PI_2, /* 0x3FF921FB, 0x54442D18 */
    t2pio2 = 2 * M_PI_2,                 /* 0x400921FB, 0x54442D18 */
    t3pio2 = 3 * M_PI_2,                 /* 0x4012D97C, 0x7F3321D2 */
    t4pio2 = 4 * M_PI_2;                 /* 0x401921FB, 0x54442D18 */

float tanf(float x) {
  double y;
  uint32_t ix;
  unsigned n, sign;

  GET_FLOAT_WORD(ix, x);
  sign = ix >> 31;
  ix &= 0x7fffffff;

  if (ix <= 0x3f490fda) {  /* |x| ~<= pi/4 */
    if (ix < 0x39800000) { /* |x| < 2**-12 */
      /* raise inexact if x!=0 and underflow if subnormal */
      FORCE_EVAL(ix < 0x00800000 ? x / 0x1p120f : x + 0x1p120f);
      return x;
    }
    return __tandf(x, 0);
  }
  if (ix <= 0x407b53d1) { /* |x| ~<= 5*pi/4 */
    if (ix <= 0x4016cbe3) /* |x| ~<= 3pi/4 */
      return __tandf((sign ? x + t1pio2 : x - t1pio2), 1);
    else
      return __tandf((sign ? x + t2pio2 : x - t2pio2), 0);
  }
  if (ix <= 0x40e231d5) { /* |x| ~<= 9*pi/4 */
    if (ix <= 0x40afeddf) /* |x| ~<= 7*pi/4 */
      return __tandf((sign ? x + t3pio2 : x - t3pio2), 1);
    else
      return __tandf((sign ? x + t4pio2 : x - t4pio2), 0);
  }

  /* tan(Inf or NaN) is NaN */
  if (ix >= 0x7f800000)
    return x - x;

  /* argument reduction */
  n = __rem_pio2f(x, &y);
  return __tandf(y, n & 1);
}