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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libquadmath/] [math/] [tanhq.c] - Blame information for rev 755

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Line No. Rev Author Line
1 740 jeremybenn 
/* s_tanhl.c -- __float128 version of s_tanh.c.
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 * Conversion to __float128 by Ulrich Drepper,
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 * Cygnus Support, drepper@cygnus.com.
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 */
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/*
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 * ====================================================
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 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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 *
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 * Developed at SunPro, a Sun Microsystems, Inc. business.
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 * Permission to use, copy, modify, and distribute this
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 * software is freely granted, provided that this notice
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 * is preserved.
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 * ====================================================
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 */
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/* Changes for 128-bit __float128 contributed by
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   Stephen L. Moshier <moshier@na-net.ornl.gov> */
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/* tanhl(x)
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 * Return the Hyperbolic Tangent of x
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 *
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 * Method :
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 *                                      x    -x
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 *                                     e  - e
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 *      0. tanhl(x) is defined to be -----------
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 *                                      x    -x
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 *                                     e  + e
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 *      1. reduce x to non-negative by tanhl(-x) = -tanhl(x).
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 *      2.  0      <= x <= 2**-57 : tanhl(x) := x*(one+x)
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 *                                               -t
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 *          2**-57 <  x <=  1     : tanhl(x) := -----; t = expm1l(-2x)
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 *                                              t + 2
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 *                                                    2
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 *          1      <= x <=  40.0  : tanhl(x) := 1-  ----- ; t=expm1l(2x)
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 *                                                  t + 2
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 *          40.0   <  x <= INF    : tanhl(x) := 1.
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 *
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 * Special cases:
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 *      tanhl(NaN) is NaN;
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 *      only tanhl(0)=0 is exact for finite argument.
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 */
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#include "quadmath-imp.h"
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static const __float128 one = 1.0Q, two = 2.0Q, tiny = 1.0e-4900Q;
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__float128
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tanhq (__float128 x)
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{
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  __float128 t, z;
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  uint32_t jx, ix;
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  ieee854_float128 u;
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  /* Words of |x|. */
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  u.value = x;
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  jx = u.words32.w0;
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  ix = jx & 0x7fffffff;
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  /* x is INF or NaN */
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  if (ix >= 0x7fff0000)
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    {
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      /* for NaN it's not important which branch: tanhl(NaN) = NaN */
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      if (jx & 0x80000000)
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        return one / x - one;   /* tanhl(-inf)= -1; */
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      else
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        return one / x + one;   /* tanhl(+inf)=+1 */
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    }
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  /* |x| < 40 */
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  if (ix < 0x40044000)
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    {
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      if (u.value == 0)
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        return x;               /* x == +- 0 */
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      if (ix < 0x3fc60000)      /* |x| < 2^-57 */
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        return x * (one + tiny); /* tanh(small) = small */
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      u.words32.w0 = ix;        /* Absolute value of x.  */
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      if (ix >= 0x3fff0000)
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        {                       /* |x| >= 1  */
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          t = expm1q (two * u.value);
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          z = one - two / (t + two);
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        }
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      else
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        {
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          t = expm1q (-two * u.value);
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          z = -t / (t + two);
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        }
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      /* |x| > 40, return +-1 */
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    }
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  else
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    {
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      z = one - tiny;           /* raised inexact flag */
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    }
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  return (jx & 0x80000000) ? -z : z;
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}

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