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0b87419b69
Similar to various other bugs in this area, ctan and ctanh can fail to raise the underflow exception for some cases of results that are tiny and inexact. This patch forces the exception in a similar way to previous fixes. Tested for x86_64 and x86. [BZ #18595] * math/s_ctan.c (__ctan): Force underflow exception for results whose real or imaginary part has small absolute value. * math/s_ctanf.c (__ctanf): Likewise. * math/s_ctanh.c (__ctanh): Likewise. * math/s_ctanhf.c (__ctanhf): Likewise. * math/s_ctanhl.c (__ctanhl): Likewise. * math/s_ctanl.c (__ctanl): Likewise. * math/auto-libm-test-in: Do not allow missing underflow for ctan and ctanh. Add more tests of ctan and ctanh.
132 lines
3.4 KiB
C
132 lines
3.4 KiB
C
/* Complex tangent function for double.
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Copyright (C) 1997-2015 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@cygnus.com>, 1997.
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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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#include <complex.h>
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#include <fenv.h>
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#include <math.h>
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#include <math_private.h>
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#include <float.h>
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__complex__ double
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__ctan (__complex__ double x)
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{
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__complex__ double res;
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if (__glibc_unlikely (!isfinite (__real__ x) || !isfinite (__imag__ x)))
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{
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if (__isinf_ns (__imag__ x))
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{
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__real__ res = __copysign (0.0, __real__ x);
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__imag__ res = __copysign (1.0, __imag__ x);
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}
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else if (__real__ x == 0.0)
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{
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res = x;
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}
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else
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{
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__real__ res = __nan ("");
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__imag__ res = __nan ("");
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if (__isinf_ns (__real__ x))
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feraiseexcept (FE_INVALID);
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}
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}
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else
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{
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double sinrx, cosrx;
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double den;
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const int t = (int) ((DBL_MAX_EXP - 1) * M_LN2 / 2);
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/* tan(x+iy) = (sin(2x) + i*sinh(2y))/(cos(2x) + cosh(2y))
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= (sin(x)*cos(x) + i*sinh(y)*cosh(y)/(cos(x)^2 + sinh(y)^2). */
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if (__glibc_likely (fabs (__real__ x) > DBL_MIN))
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{
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__sincos (__real__ x, &sinrx, &cosrx);
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}
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else
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{
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sinrx = __real__ x;
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cosrx = 1.0;
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}
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if (fabs (__imag__ x) > t)
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{
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/* Avoid intermediate overflow when the real part of the
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result may be subnormal. Ignoring negligible terms, the
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imaginary part is +/- 1, the real part is
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sin(x)*cos(x)/sinh(y)^2 = 4*sin(x)*cos(x)/exp(2y). */
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double exp_2t = __ieee754_exp (2 * t);
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__imag__ res = __copysign (1.0, __imag__ x);
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__real__ res = 4 * sinrx * cosrx;
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__imag__ x = fabs (__imag__ x);
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__imag__ x -= t;
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__real__ res /= exp_2t;
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if (__imag__ x > t)
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{
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/* Underflow (original imaginary part of x has absolute
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value > 2t). */
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__real__ res /= exp_2t;
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}
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else
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__real__ res /= __ieee754_exp (2 * __imag__ x);
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}
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else
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{
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double sinhix, coshix;
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if (fabs (__imag__ x) > DBL_MIN)
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{
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sinhix = __ieee754_sinh (__imag__ x);
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coshix = __ieee754_cosh (__imag__ x);
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}
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else
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{
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sinhix = __imag__ x;
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coshix = 1.0;
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}
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if (fabs (sinhix) > fabs (cosrx) * DBL_EPSILON)
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den = cosrx * cosrx + sinhix * sinhix;
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else
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den = cosrx * cosrx;
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__real__ res = sinrx * cosrx / den;
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__imag__ res = sinhix * coshix / den;
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}
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if (fabs (__real__ res) < DBL_MIN)
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{
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double force_underflow = __real__ res * __real__ res;
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math_force_eval (force_underflow);
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}
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if (fabs (__imag__ res) < DBL_MIN)
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{
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double force_underflow = __imag__ res * __imag__ res;
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math_force_eval (force_underflow);
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}
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}
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return res;
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}
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weak_alias (__ctan, ctan)
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#ifdef NO_LONG_DOUBLE
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strong_alias (__ctan, __ctanl)
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weak_alias (__ctan, ctanl)
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#endif
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