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 #include "libm.h"
  32 
  33 
  34 /*
  35  * float __k_tan(double x);
  36  * kernel (float) tan function on [-pi/4, pi/4], pi/4 ~ 0.785398164
  37  * Input x is in double and assumed to be bounded by ~pi/4 in magnitude.
  38  *
  39  * Constants:
  40  * The hexadecimal values are the intended ones for the following constants.
  41  * The decimal values may be used, provided that the compiler will convert
  42  * from decimal to binary accurately enough to produce the hexadecimal values
  43  * shown.
  44  */
  45 
  46 static const double q[] = {
  47 /* one */
  48         1.0,
  49 /* P0 */ 4.46066928428959230679140546271810308098793029785e-0003,
  50 /* P1 */ 4.92165316309189027066395283327437937259674072266e+0000,
  51 /* P2 */ -7.11410648161473480044492134766187518835067749023e-0001,
  52 /* P3 */ 4.08549808374053391446523164631798863410949707031e+0000,
  53 /* P4 */ 2.50411070398050927821032018982805311679840087891e+0000,
  54 /* P5 */ 1.11492064560251158411574579076841473579406738281e+0001,
  55 /* P6 */ -1.50565540968422650891511693771462887525558471680e+0000,
  56 /* P7 */ -1.81484378878349295050043110677506774663925170898e+0000,
  57 /* T0 */ 3.333335997532835641297409611782510896641e-0001,
  58 /* T1 */ 2.999997598248363761541668282006867229939e+00,
  59 };
  60 
  61 
  62 #define one             q[0]
  63 #define P0              q[1]
  64 #define P1              q[2]
  65 #define P2              q[3]
  66 #define P3              q[4]
  67 #define P4              q[5]
  68 #define P5              q[6]
  69 #define P6              q[7]
  70 #define P7              q[8]
  71 #define T0              q[9]
  72 #define T1              q[10]
  73 
  74 float
  75 __k_tanf(double x, int n)
  76 {
  77         float ft = 0.0;
  78         double z, w;
  79         int ix;
  80 
  81         ix = ((int *)&x)[HIWORD] & ~0x80000000; /* ix = leading |x| */
  82 
  83         /* small argument */
  84         if (ix < 0x3f800000) {                       /* if |x| < 0.0078125 = 2**-7 */
  85                 if (ix < 0x3f100000) {               /* if |x| < 2**-14 */
  86                         if ((int)x == 0)        /* raise inexact if x != 0 */
  87                                 ft = n == 0 ? (float)x : (float)(-one / x);
  88 
  89                         return (ft);
  90                 }
  91 
  92                 z = (x * T0) * (T1 + x * x);
  93                 ft = n == 0 ? (float)z : (float)(-one / z);
  94                 return (ft);
  95         }
  96 
  97         z = x * x;
  98         w = ((P0 * x) * (P1 + z * (P2 + z)) * (P3 + z * (P4 + z))) * (P5 + z *
  99             (P6 + z * (P7 + z)));
 100         ft = n == 0 ? (float)w : (float)(-one / w);
 101         return (ft);
 102 }