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37d83a089d
Similar to various other bugs in this area, some tanh 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. Tested for x86_64, x86, mips64 and powerpc. [BZ #16520] * sysdeps/ieee754/dbl-64/s_tanh.c: Include <float.h>. (__tanh): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/flt-32/s_tanhf.c: Include <float.h>. (__tanhf): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-128/s_tanhl.c: Include <float.h>. (__tanhl): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-128ibm/s_tanhl.c: Include <float.h>. (__tanhl): Force underflow exception for arguments with small absolute value. * sysdeps/ieee754/ldbl-96/s_tanhl.c: Include <float.h>. (__tanhl): Force underflow exception for arguments with small absolute value. * math/auto-libm-test-in: Add more tests of tanh. * math/auto-libm-test-out: Regenerated. * sysdeps/i386/fpu/libm-test-ulps: Update.
95 lines
2.4 KiB
C
95 lines
2.4 KiB
C
/* s_tanhl.c -- long double version of s_tanh.c.
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* Conversion to long double 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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#if defined(LIBM_SCCS) && !defined(lint)
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static char rcsid[] = "$NetBSD: $";
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#endif
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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**-55 : tanhl(x) := x*(one+x)
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* -t
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* 2**-55 < x <= 1 : tanhl(x) := -----; t = expm1l(-2x)
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* t + 2
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* 2
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* 1 <= x <= 23.0 : tanhl(x) := 1- ----- ; t=expm1l(2x)
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* t + 2
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* 23.0 < 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 <float.h>
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#include <math.h>
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#include <math_private.h>
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static const long double one=1.0, two=2.0, tiny = 1.0e-4900L;
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long double __tanhl(long double x)
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{
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long double t,z;
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int32_t se;
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u_int32_t j0,j1,ix;
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/* High word of |x|. */
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GET_LDOUBLE_WORDS(se,j0,j1,x);
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ix = se&0x7fff;
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/* x is INF or NaN */
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if(ix==0x7fff) {
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/* for NaN it's not important which branch: tanhl(NaN) = NaN */
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if (se&0x8000) return one/x-one; /* tanhl(-inf)= -1; */
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else return one/x+one; /* tanhl(+inf)=+1 */
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}
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/* |x| < 23 */
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if (ix < 0x4003 || (ix == 0x4003 && j0 < 0xb8000000u)) {/* |x|<23 */
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if ((ix|j0|j1) == 0)
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return x; /* x == +- 0 */
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if (ix<0x3fc8) /* |x|<2**-55 */
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{
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if (fabsl (x) < LDBL_MIN)
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{
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long double force_underflow = x * x;
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math_force_eval (force_underflow);
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}
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return x*(one+tiny); /* tanh(small) = small */
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}
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if (ix>=0x3fff) { /* |x|>=1 */
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t = __expm1l(two*fabsl(x));
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z = one - two/(t+two);
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} else {
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t = __expm1l(-two*fabsl(x));
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z= -t/(t+two);
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}
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/* |x| > 23, return +-1 */
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} else {
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z = one - tiny; /* raised inexact flag */
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}
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return (se&0x8000)? -z: z;
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}
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weak_alias (__tanhl, tanhl)
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