1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21 
  22 /*
  23  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24  */
  25 
  26 /*
  27  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  28  * Use is subject to license terms.
  29  */
  30 
  31 #pragma weak __tanl = tanl
  32 
  33 /* BEGIN CSTYLED */
  34 /*
  35  * cosl(x)
  36  * Table look-up algorithm by K.C. Ng, November, 1989.
  37  *
  38  * kernel function:
  39  *      __k_tanl        ... tangent function on [-pi/4,pi/4]
  40  *      __rem_pio2l     ... argument reduction routine
  41  *
  42  * Method.
  43  *      Let S and C denote the sin and cos respectively on [-PI/4, +PI/4].
  44  *      1. Assume the argument x is reduced to y1+y2 = x-k*pi/2 in
  45  *         [-pi/2 , +pi/2], and let n = k mod 4.
  46  *      2. Let S=S(y1+y2), C=C(y1+y2). Depending on n, we have
  47  *
  48  *          n        sin(x)      cos(x)        tan(x)
  49  *     ----------------------------------------------------------
  50  *          0          S           C             S/C
  51  *          1          C          -S            -C/S
  52  *          2         -S          -C             S/C
  53  *          3         -C           S            -C/S
  54  *     ----------------------------------------------------------
  55  *
  56  * Special cases:
  57  *      Let trig be any of sin, cos, or tan.
  58  *      trig(+-INF)  is NaN, with signals;
  59  *      trig(NaN)    is that NaN;
  60  *
  61  * Accuracy:
  62  *      computer TRIG(x) returns trig(x) nearly rounded.
  63  */
  64 /* END CSTYLED */
  65 
  66 #include "libm.h"
  67 #include "longdouble.h"
  68 
  69 #include <sys/isa_defs.h>
  70 
  71 long double
  72 tanl(long double x)
  73 {
  74         long double y[2], z = 0.0L;
  75         int n, ix;
  76 
  77 #if defined(__i386) || defined(__amd64)
  78         int *px = (int *)&x;
  79 #endif
  80 
  81         /* trig(Inf or NaN) is NaN */
  82         if (!finitel(x))
  83                 return (x - x);
  84 
  85         /* High word of x. */
  86 #if defined(__i386) || defined(__amd64)
  87         XTOI(px, ix);
  88 #else
  89         ix = *(int *)&x;
  90 #endif
  91 
  92         /* |x| ~< pi/4 */
  93         ix &= 0x7fffffff;
  94 
  95         if (ix <= 0x3ffe9220) {
  96                 return (__k_tanl(x, z, 0));
  97         }
  98         /* argument reduction needed */
  99         else {
 100                 n = __rem_pio2l(x, y);
 101                 return (__k_tanl(y[0], y[1], n & 1));
 102         }
 103 }