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8020a80887
Similar to various other bugs in this area, some atanh implementations do not raise the underflow exception for subnormal arguments, when the result is tiny and inexact. This patch forces the exception in a similar way to previous fixes. (No change in this regard is needed for the i386 implementation; special handling to force underflows in these cases will only be needed there when the spurious underflows, bug 18049, get fixed.) Tested for x86_64, x86, powerpc and mips64. [BZ #16352] * sysdeps/i386/fpu/e_atanh.S (dbl_min): New object. (__ieee754_atanh): Force underflow exception for results with small absolute value. * sysdeps/i386/fpu/e_atanhf.S (flt_min): New object. (__ieee754_atanhf): Force underflow exception for results with small absolute value. * sysdeps/ieee754/dbl-64/e_atanh.c: Include <float.h>. (__ieee754_atanh): Force underflow exception for results with small absolute value. * sysdeps/ieee754/flt-32/e_atanhf.c: Include <float.h>. (__ieee754_atanhf): Force underflow exception for results with small absolute value. * sysdeps/ieee754/ldbl-128/e_atanhl.c: Include <float.h>. (__ieee754_atanhl): Force underflow exception for results with small absolute value. * sysdeps/ieee754/ldbl-128ibm/e_atanhl.c: Include <float.h>. (__ieee754_atanhl): Force underflow exception for results with small absolute value. * sysdeps/ieee754/ldbl-96/e_atanhl.c: Include <float.h>. (__ieee754_atanhl): Force underflow exception for results with small absolute value. * math/auto-libm-test-in: Do not allow missing underflow exceptions from atanh. * math/auto-libm-test-out: Regenerated.
79 lines
2.1 KiB
C
79 lines
2.1 KiB
C
/* Copyright (C) 2011-2015 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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/* __ieee754_atanh(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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atanh(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------)
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2 1 - x 1 - x
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For x<0.5
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atanh(x) = 0.5*log1p(2x+2x*x/(1-x))
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Special cases:
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atanh(x) is NaN if |x| > 1 with signal;
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atanh(NaN) is that NaN with no signal;
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atanh(+-1) is +-INF with signal.
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*/
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#include <float.h>
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#include <inttypes.h>
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#include <math.h>
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#include <math_private.h>
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static const double huge = 1e300;
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double
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__ieee754_atanh (double x)
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{
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double xa = fabs (x);
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double t;
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if (isless (xa, 0.5))
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{
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if (__glibc_unlikely (xa < 0x1.0p-28))
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{
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math_force_eval (huge + x);
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if (fabs (x) < DBL_MIN)
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{
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double force_underflow = x * x;
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math_force_eval (force_underflow);
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}
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return x;
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}
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t = xa + xa;
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t = 0.5 * __log1p (t + t * xa / (1.0 - xa));
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}
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else if (__glibc_likely (isless (xa, 1.0)))
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t = 0.5 * __log1p ((xa + xa) / (1.0 - xa));
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else
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{
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if (isgreater (xa, 1.0))
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return (x - x) / (x - x);
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return x / 0.0;
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}
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return __copysign (t, x);
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}
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strong_alias (__ieee754_atanh, __atanh_finite)
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