1  /* s_tanf.c -- float version of s_tan.c.
       2   */
       3  
       4  /*
       5   * ====================================================
       6   * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
       7   *
       8   * Developed at SunPro, a Sun Microsystems, Inc. business.
       9   * Permission to use, copy, modify, and distribute this
      10   * software is freely granted, provided that this notice
      11   * is preserved.
      12   * ====================================================
      13   */
      14  
      15  #if defined(LIBM_SCCS) && !defined(lint)
      16  static char rcsid[] = "$NetBSD: s_tanf.c,v 1.4 1995/05/10 20:48:20 jtc Exp $";
      17  #endif
      18  
      19  #include <errno.h>
      20  #include <math.h>
      21  #include <math_private.h>
      22  #include <libm-alias-float.h>
      23  #include "s_sincosf.h"
      24  
      25  /* Reduce range of X to a multiple of PI/2.  The modulo result is between
      26     -PI/4 and PI/4 and returned as a high part y[0] and a low part y[1].
      27     The low bit in the return value indicates the first or 2nd half of tanf.  */
      28  static inline int32_t
      29  rem_pio2f (float x, float *y)
      30  {
      31    double dx = x;
      32    int n;
      33    const sincos_t *p = &__sincosf_table[0];
      34  
      35    if (__glibc_likely (abstop12 (x) < abstop12 (120.0f)))
      36      dx = reduce_fast (dx, p, &n);
      37    else
      38      {
      39        uint32_t xi = asuint (x);
      40        int sign = xi >> 31;
      41  
      42        dx = reduce_large (xi, &n);
      43        dx = sign ? -dx : dx;
      44      }
      45  
      46    y[0] = dx;
      47    y[1] = dx - y[0];
      48    return n;
      49  }
      50  
      51  float __tanf(float x)
      52  {
      53  	float y[2],z=0.0;
      54  	int32_t n, ix;
      55  
      56  	GET_FLOAT_WORD(ix,x);
      57  
      58      /* |x| ~< pi/4 */
      59  	ix &= 0x7fffffff;
      60  	if(ix <= 0x3f490fda) return __kernel_tanf(x,z,1);
      61  
      62      /* tan(Inf or NaN) is NaN */
      63  	else if (ix>=0x7f800000) {
      64  	  if (ix==0x7f800000)
      65  	    __set_errno (EDOM);
      66  	  return x-x;		/* NaN */
      67  	}
      68  
      69      /* argument reduction needed */
      70  	else {
      71  	    n = rem_pio2f(x,y);
      72  	    return __kernel_tanf(y[0],y[1],1-((n&1)<<1)); /*   1 -- n even
      73  							      -1 -- n odd */
      74  	}
      75  }
      76  libm_alias_float (__tan, tan)