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[/] [openrisc/] [trunk/] [gnu-dev/] [or1k-gcc/] [libquadmath/] [math/] [atanhq.c] - Blame information for rev 760

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1 740 jeremybenn
/* s_atanhl.c -- __float128 version of s_atan.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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/* __ieee754_atanhl(x)
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 * Method :
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 *    1.Reduced x to positive by atanh(-x) = -atanh(x)
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 *    2.For x>=0.5
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 *                   1              2x                          x
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 *      atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
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 *                   2             1 - x                      1 - x
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 *
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 *      For x<0.5
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 *      atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x))
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 *
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 * Special cases:
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 *      atanhl(x) is NaN if |x| > 1 with signal;
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 *      atanhl(NaN) is that NaN with no signal;
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 *      atanhl(+-1) is +-INF with signal.
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 *
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 */
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#include "quadmath-imp.h"
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static const __float128 one = 1.0Q, huge = 1e4900Q;
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static const __float128 zero = 0.0Q;
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__float128
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atanhq (__float128 x)
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{
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        __float128 t;
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        uint32_t jx, ix;
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        ieee854_float128 u;
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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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        u.words32.w0 = ix;
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        if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */
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          {
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            if (u.value == one)
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              return x/zero;
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            else
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              return (x-x)/(x-x);
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          }
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        if(ix<0x3fc60000 && (huge+x)>zero) return x;    /* x < 2^-57 */
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        if(ix<0x3ffe0000) {             /* x < 0.5 */
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            t = u.value+u.value;
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            t = 0.5*log1pq(t+t*u.value/(one-u.value));
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        } else
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            t = 0.5*log1pq((u.value+u.value)/(one-u.value));
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        if(jx & 0x80000000) return -t; else return t;
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}

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