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  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27  * Use is subject to license terms.
  28  */
  29 
  30 #pragma weak tan = __tan
  31 
  32 /* INDENT OFF */
  33 /*
  34  * tan(x)
  35  * Table look-up algorithm by K.C. Ng, November, 1989.
  36  *
  37  * kernel function:
  38  *      __k_tan         ... tangent function on [-pi/4,pi/4]
  39  *      __rem_pio2      ... argument reduction routine
  40  */
  41 /* INDENT ON */
  42 
  43 #include "libm.h"
  44 #include "libm_synonyms.h"
  45 #include "libm_protos.h"
  46 #include <math.h>
  47 
  48 double
  49 tan(double x) {
  50         double y[2], z = 0.0;
  51         int n, ix;
  52 
  53         /* high word of x */
  54         ix = ((int *) &x)[HIWORD];
  55 
  56         /* |x| ~< pi/4 */
  57         ix &= 0x7fffffff;
  58         if (ix <= 0x3fe921fb)
  59                 return (__k_tan(x, z, 0));
  60 
  61         /* tan(Inf or NaN) is NaN */
  62         else if (ix >= 0x7ff00000) {
  63 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
  64                 return (ix >= 0x7ff80000 ? x : x - x);       /* NaN */
  65                 /* assumes sparc-like QNaN */
  66 #else
  67                 return (x - x);                         /* NaN */
  68 #endif
  69         }
  70 
  71         /* argument reduction needed */
  72         else {
  73                 n = __rem_pio2(x, y);
  74                 return (__k_tan(y[0], y[1], n & 1));
  75         }
  76 }