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 #include "libm.h"
  31 
  32 /* INDENT OFF */
  33 /*
  34  * float __k_tan(double x);
  35  * kernel (float) tan function on [-pi/4, pi/4], pi/4 ~ 0.785398164
  36  * Input x is in double and assumed to be bounded by ~pi/4 in magnitude.
  37  *
  38  * Constants:
  39  * The hexadecimal values are the intended ones for the following constants.
  40  * The decimal values may be used, provided that the compiler will convert
  41  * from decimal to binary accurately enough to produce the hexadecimal values
  42  * shown.
  43  */
  44 
  45 static const double q[] = {
  46 /* one */ 1.0,
  47 /* P0 */  4.46066928428959230679140546271810308098793029785e-0003,
  48 /* P1 */  4.92165316309189027066395283327437937259674072266e+0000,
  49 /* P2 */ -7.11410648161473480044492134766187518835067749023e-0001,
  50 /* P3 */  4.08549808374053391446523164631798863410949707031e+0000,
  51 /* P4 */  2.50411070398050927821032018982805311679840087891e+0000,
  52 /* P5 */  1.11492064560251158411574579076841473579406738281e+0001,
  53 /* P6 */ -1.50565540968422650891511693771462887525558471680e+0000,
  54 /* P7 */ -1.81484378878349295050043110677506774663925170898e+0000,
  55 /* T0 */  3.333335997532835641297409611782510896641e-0001,
  56 /* T1 */  2.999997598248363761541668282006867229939e+00,
  57 };
  58 /* INDENT ON */
  59 
  60 #define one q[0]
  61 #define P0 q[1]
  62 #define P1 q[2]
  63 #define P2 q[3]
  64 #define P3 q[4]
  65 #define P4 q[5]
  66 #define P5 q[6]
  67 #define P6 q[7]
  68 #define P7 q[8]
  69 #define T0 q[9]
  70 #define T1 q[10]
  71 
  72 float
  73 __k_tanf(double x, int n) {
  74         float ft = 0.0;
  75         double z, w;
  76         int ix;
  77 
  78         ix = ((int *) &x)[HIWORD] & ~0x80000000;        /* ix = leading |x| */
  79         /* small argument */
  80         if (ix < 0x3f800000) {               /* if |x| < 0.0078125 = 2**-7 */
  81                 if (ix < 0x3f100000) {       /* if |x| < 2**-14 */
  82                         if ((int) x == 0) {     /* raise inexact if x!=0 */
  83                                 ft = n == 0 ? (float) x : (float) (-one / x);
  84                         }
  85                         return (ft);
  86                 }
  87                 z = (x * T0) * (T1 + x * x);
  88                 ft = n == 0 ? (float) z : (float) (-one / z);
  89                 return (ft);
  90         }
  91         z = x * x;
  92         w = ((P0 * x) * (P1 + z * (P2 + z)) * (P3 + z * (P4 + z)))
  93                 * (P5 + z * (P6 + z * (P7 + z)));
  94         ft = n == 0 ? (float) w : (float) (-one / w);
  95         return (ft);
  96 }