Home | History | Annotate | Line # | Download | only in src 
      1 /*	$NetBSD: s_tanl.c,v 1.3 2024/04/03 18:53:42 christos Exp $	*/
      2 
      3 /*-
      4  * SPDX-License-Identifier: BSD-2-Clause
      5  *
      6  * Copyright (c) 2007 Steven G. Kargl
      7  * All rights reserved.
      8  *
      9  * Redistribution and use in source and binary forms, with or without
     10  * modification, are permitted provided that the following conditions
     11  * are met:
     12  * 1. Redistributions of source code must retain the above copyright
     13  *    notice unmodified, this list of conditions, and the following
     14  *    disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
     20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
     21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
     22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
     23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
     25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
     26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
     28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     29  */
     30 
     31 #include <sys/cdefs.h>
     32 __RCSID("$NetBSD: s_tanl.c,v 1.3 2024/04/03 18:53:42 christos Exp $");
     33 
     34 /*
     35  * Limited testing on pseudorandom numbers drawn within [0:4e8] shows
     36  * an accuracy of <= 1.5 ULP where 247024 values of x out of 40 million
     37  * possibles resulted in tan(x) that exceeded 0.5 ULP (ie., 0.6%).
     38  */
     39 #include "namespace.h"
     40 #include <float.h>
     41 
     42 #include "math.h"
     43 #include "math_private.h"
     44 
     45 #ifdef __weak_alias
     46 __weak_alias(tanl, _tanl)
     47 #endif
     48 
     49 #ifdef __HAVE_LONG_DOUBLE
     50 
     51 #if LDBL_MANT_DIG == 64
     52 #include "../ld80/e_rem_pio2l.h"
     53 #include "../ld80/k_tanl.c"
     54 #elif LDBL_MANT_DIG == 113
     55 #include "../ld128/e_rem_pio2l.h"
     56 #include "../ld128/k_tanl.c"
     57 #else
     58 #error "Unsupported long double format"
     59 #endif
     60 
     61 long double
     62 tanl(long double x)
     63 {
     64 	union ieee_ext_u z;
     65 	int e0, s;
     66 	long double y[2];
     67 	long double hi, lo;
     68 
     69 	z.extu_ld = x;
     70 	s = z.extu_sign;
     71 	z.extu_sign = 0;
     72 
     73 	/* If x = +-0 or x is subnormal, then tan(x) = x. */
     74 	if (z.extu_exp == 0)
     75 		return (x);
     76 
     77 	/* If x = NaN or Inf, then tan(x) = NaN. */
     78 	if (z.extu_exp == 32767)
     79 		return ((x - x) / (x - x));
     80 
     81 	ENTERI();
     82 
     83 	/* Optimize the case where x is already within range. */
     84 	if (z.extu_ld < M_PI_4) {
     85 		hi = __kernel_tanl(z.extu_ld, 0, 0);
     86 		RETURNI(s ? -hi : hi);
     87 	}
     88 
     89 	e0 = __ieee754_rem_pio2l(x, y);
     90 	hi = y[0];
     91 	lo = y[1];
     92 
     93 	switch (e0 & 3) {
     94 	case 0:
     95 	case 2:
     96 	    hi = __kernel_tanl(hi, lo, 0);
     97 	    break;
     98 	case 1:
     99 	case 3:
    100 	    hi = __kernel_tanl(hi, lo, 1);
    101 	    break;
    102 	}
    103 
    104 	RETURNI(hi);
    105 }
    106 
    107 #else
    108 
    109 long double
    110 tanl(long double x)
    111 {
    112 	return tan(x);
    113 }
    114 
    115 #endif
    116