usr/src/lib/libm/common/R/tanf.c

   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  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  23  */
  24 /*
  25  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
  26  * Use is subject to license terms.
  27  */
  28
  29 #pragma weak __tanf = tanf
  30
  31 #include "libm.h"
  32
  33 extern const int _TBL_ipio2_inf[];
  34 extern int __rem_pio2m(double *, double *, int, int, int, const int *);
  35 #if defined(__i386) && !defined(__amd64)
  36 extern int __swapRP(int);
  37 #endif
  38
  39 static const double C[] = {
  40         1.0,
  41         4.46066928428959230679140546271810308098793029785e-0003,
  42         4.92165316309189027066395283327437937259674072266e+0000,
  43         -7.11410648161473480044492134766187518835067749023e-0001,
  44         4.08549808374053391446523164631798863410949707031e+0000,
  45         2.50411070398050927821032018982805311679840087891e+0000,
  46         1.11492064560251158411574579076841473579406738281e+0001,
  47         -1.50565540968422650891511693771462887525558471680e+0000,
  48         -1.81484378878349295050043110677506774663925170898e+0000,
  49         3.333335997532835641297409611782510896641e-0001,
  50         2.999997598248363761541668282006867229939e+00,
  51         0.636619772367581343075535,     /* 2^ -1  * 1.45F306DC9C883 */
  52         0.5,
  53         1.570796326734125614166,        /* 2^  0  * 1.921FB54400000 */
  54         6.077100506506192601475e-11,    /* 2^-34  * 1.0B4611A626331 */
  55 };
  56
  57 #define one     C[0]
  58 #define P0      C[1]
  59 #define P1      C[2]
  60 #define P2      C[3]
  61 #define P3      C[4]
  62 #define P4      C[5]
  63 #define P5      C[6]
  64 #define P6      C[7]
  65 #define P7      C[8]
  66 #define T0      C[9]
  67 #define T1      C[10]
  68 #define invpio2 C[11]
  69 #define half    C[12]
  70 #define pio2_1  C[13]
  71 #define pio2_t  C[14]
  72
  73 float
  74 tanf(float x)
  75 {
  76         double  y, z, w;
  77         float   f;
  78         int     n, ix, hx, hy;
  79         volatile int i;
  80
  81         hx = *((int *)&x);
  82         ix = hx & 0x7fffffff;
  83
  84         y = (double)x;
  85
  86         if (ix <= 0x4016cbe4) {         /* |x| < 3*pi/4 */
  87                 if (ix <= 0x3f490fdb) {         /* |x| < pi/4 */
  88                         if (ix < 0x3c000000) {          /* |x| < 2**-7 */
  89                                 if (ix <= 0x39800000) { /* |x| < 2**-12 */
  90                                         i = (int)y;
  91                                         return (x);
  92                                 }
  93                                 return ((float)((y * T0) * (T1 + y * y)));
  94                         }
  95                         z = y * y;
  96                         return ((float)(((P0 * y) * (P1 + z * (P2 + z)) *
  97                             (P3 + z * (P4 + z))) *
  98                             (P5 + z * (P6 + z * (P7 + z)))));
  99                 }
 100                 if (hx > 0)
 101                         y = (y - pio2_1) - pio2_t;
 102                 else
 103                         y = (y + pio2_1) + pio2_t;
 104                 hy = ((int *)&y)[HIWORD] & ~0x80000000;
 105                 if (hy < 0x3f800000) {          /* |y| < 2**-7 */
 106                         z = (y * T0) * (T1 + y * y);
 107                         return ((float)(-one / z));
 108                 }
 109                 z = y * y;
 110                 w = ((P0 * y) * (P1 + z * (P2 + z)) * (P3 + z * (P4 + z))) *
 111                     (P5 + z * (P6 + z * (P7 + z)));
 112                 return ((float)(-one / w));
 113         }
 114
 115         if (ix <= 0x49c90fdb) { /* |x| < 2^19*pi */
 116 #if defined(__i386) && !defined(__amd64)
 117                 int     rp;
 118
 119                 rp = __swapRP(fp_extended);
 120 #endif
 121                 w = y * invpio2;
 122                 if (hx < 0)
 123                         n = (int)(w - half);
 124                 else
 125                         n = (int)(w + half);
 126                 y = (y - n * pio2_1) - n * pio2_t;
 127 #if defined(__i386) && !defined(__amd64)
 128                 if (rp != fp_extended)
 129                         (void) __swapRP(rp);
 130 #endif
 131         } else {
 132                 if (ix >= 0x7f800000)
 133                         return (x / x); /* sin(Inf or NaN) is NaN */
 134                 hy = ((int *)&y)[HIWORD];
 135                 n = ((hy >> 20) & 0x7ff) - 1046;
 136                 ((int *)&w)[HIWORD] = (hy & 0xfffff) | 0x41600000;
 137                 ((int *)&w)[LOWORD] = ((int *)&y)[LOWORD];
 138                 n = __rem_pio2m(&w, &y, n, 1, 0, _TBL_ipio2_inf);
 139                 if (hy < 0) {
 140                         y = -y;
 141                         n = -n;
 142                 }
 143         }
 144
 145         hy = ((int *)&y)[HIWORD] & ~0x80000000;
 146         if (hy < 0x3f800000) {          /* |y| < 2**-7 */
 147                 z = (y * T0) * (T1 + y * y);
 148                 f = ((n & 1) == 0)? (float)z : (float)(-one / z);
 149                 return (f);
 150         }
 151         z = y * y;
 152         w = ((P0 * y) * (P1 + z * (P2 + z)) * (P3 + z * (P4 + z))) *
 153             (P5 + z * (P6 + z * (P7 + z)));
 154         f = ((n & 1) == 0)? (float)w : (float)(-one / w);
 155         return (f);
 156 }