5261 libm should stop using synonyms.h
5298 fabs is 0-sized, confuses dis(1) and others
Reviewed by: Josef 'Jeff' Sipek <jeffpc@josefsipek.net>
Approved by: Gordon Ross <gwr@nexenta.com>

          --- old/usr/src/lib/libm/common/C/tanh.c
          +++ new/usr/src/lib/libm/common/C/tanh.c

   1    1  /*
   2    2   * CDDL HEADER START
   3    3   *
   4    4   * The contents of this file are subject to the terms of the
   5    5   * Common Development and Distribution License (the "License").
   6    6   * You may not use this file except in compliance with the License.
   7    7   *
   8    8   * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9    9   * or http://www.opensolaris.org/os/licensing.
  10   10   * See the License for the specific language governing permissions
  11   11   * and limitations under the License.
  12   12   *
  13   13   * When distributing Covered Code, include this CDDL HEADER in each
  14   14   * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15   15   * If applicable, add the following below this CDDL HEADER, with the
  16   16   * fields enclosed by brackets "[]" replaced with your own identifying
  17   17   * information: Portions Copyright [yyyy] [name of copyright owner]
  18   18   *
  19   19   * CDDL HEADER END

  20   20   */
  21   21  
  22   22  /*
  23   23   * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
  24   24   */
  25   25  /*
  26   26   * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
  27   27   * Use is subject to license terms.
  28   28   */
  29   29  
  30      -#pragma weak tanh = __tanh
       30 +#pragma weak __tanh = tanh
  31   31  
  32   32  /* INDENT OFF */
  33   33  /*
  34   34   * TANH(X)
  35   35   * RETURN THE HYPERBOLIC TANGENT OF X
  36   36   * code based on 4.3bsd
  37   37   * Modified by K.C. Ng for sun 4.0, Jan 31, 1987
  38   38   *
  39   39   * Method :
  40   40   *      1. reduce x to non-negative by tanh(-x) = - tanh(x).

  41   41   *      2.
  42   42   *          0      <  x <=  1.e-10 :  tanh(x) := x
  43   43   *                                                -expm1(-2x)
  44   44   *          1.e-10 <  x <=  1      :  tanh(x) := --------------
  45   45   *                                               expm1(-2x) + 2
  46   46   *                                                        2
  47   47   *          1      <= x <=  22.0   :  tanh(x) := 1 -  ---------------
  48   48   *                                                    expm1(2x) + 2

  49   49   *          22.0   <  x <= INF     :  tanh(x) := 1.
  50   50   *
  51   51   *      Note: 22 was chosen so that fl(1.0+2/(expm1(2*22)+2)) == 1.
  52   52   *
  53   53   * Special cases:
  54   54   *      tanh(NaN) is NaN;
  55   55   *      only tanh(0)=0 is exact for finite argument.
  56   56   */
  57   57  
  58   58  #include "libm.h"
  59      -#include "libm_synonyms.h"
  60   59  #include "libm_protos.h"
  61   60  #include <math.h>
  62   61  
  63   62  static const double
  64   63          one = 1.0,
  65   64          two = 2.0,
  66   65          small = 1.0e-10,
  67   66          big = 1.0e10;
  68   67  /* INDENT ON */
  69   68  

  70   69  double
  71   70  tanh(double x) {
  72   71          double t, y, z;
  73   72          int signx;
  74   73          volatile double dummy;
  75   74  
  76   75          if (isnan(x))
  77   76                  return (x * x); /* + -> * for Cheetah */
  78   77          signx = signbit(x);
  79   78          t = fabs(x);
  80   79          z = one;
  81   80          if (t <= 22.0) {
  82   81                  if (t > one)
  83   82                          z = one - two / (expm1(t + t) + two);
  84   83                  else if (t > small) {
  85   84                          y = expm1(-t - t);
  86   85                          z = -y / (y + two);
  87   86                  } else {
  88   87                          /* raise the INEXACT flag for non-zero t */
  89   88                          dummy = t + big;
  90   89  #ifdef lint
  91   90                          dummy = dummy;
  92   91  #endif
  93   92                          return (x);
  94   93                  }
  95   94          } else if (!finite(t))
  96   95                  return (copysign(1.0, x));
  97   96          else
  98   97                  return (signx == 1 ? -z + small * small : z - small * small);
  99   98  
 100   99          return (signx == 1 ? -z : z);
 101  100  }

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