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| -rw-r--r-- | sysdeps/ieee754/ldbl-128/s_tanhl.c | 106 |
1 files changed, 106 insertions, 0 deletions
diff --git a/sysdeps/ieee754/ldbl-128/s_tanhl.c b/sysdeps/ieee754/ldbl-128/s_tanhl.c new file mode 100644 index 0000000000..fcbf300a10 --- /dev/null +++ b/sysdeps/ieee754/ldbl-128/s_tanhl.c @@ -0,0 +1,106 @@ +/* s_tanhl.c -- long double version of s_tanh.c. + * Conversion to long double by Ulrich Drepper, + * Cygnus Support, drepper@cygnus.com. + */ + +/* + * ==================================================== + * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. + * + * Developed at SunPro, a Sun Microsystems, Inc. business. + * Permission to use, copy, modify, and distribute this + * software is freely granted, provided that this notice + * is preserved. + * ==================================================== + */ + +/* Changes for 128-bit long double contributed by + Stephen L. Moshier <moshier@na-net.ornl.gov> */ + +/* tanhl(x) + * Return the Hyperbolic Tangent of x + * + * Method : + * x -x + * e - e + * 0. tanhl(x) is defined to be ----------- + * x -x + * e + e + * 1. reduce x to non-negative by tanhl(-x) = -tanhl(x). + * 2. 0 <= x <= 2**-57 : tanhl(x) := x*(one+x) + * -t + * 2**-57 < x <= 1 : tanhl(x) := -----; t = expm1l(-2x) + * t + 2 + * 2 + * 1 <= x <= 40.0 : tanhl(x) := 1- ----- ; t=expm1l(2x) + * t + 2 + * 40.0 < x <= INF : tanhl(x) := 1. + * + * Special cases: + * tanhl(NaN) is NaN; + * only tanhl(0)=0 is exact for finite argument. + */ + +#include "math.h" +#include "math_private.h" + +#ifdef __STDC__ +static const long double one = 1.0, two = 2.0, tiny = 1.0e-4900L; +#else +static long double one = 1.0, two = 2.0, tiny = 1.0e-4900L; +#endif + +#ifdef __STDC__ +long double +__tanhl (long double x) +#else +long double +__tanhl (x) + long double x; +#endif +{ + long double t, z; + u_int32_t jx, ix; + ieee854_long_double_shape_type u; + + /* Words of |x|. */ + u.value = x; + jx = u.parts32.w0; + ix = jx & 0x7fffffff; + /* x is INF or NaN */ + if (ix >= 0x7fff0000) + { + /* for NaN it's not important which branch: tanhl(NaN) = NaN */ + if (jx & 0x80000000) + return one / x - one; /* tanhl(-inf)= -1; */ + else + return one / x + one; /* tanhl(+inf)=+1 */ + } + + /* |x| < 40 */ + if (ix < 0x40044000) + { + if (u.value == 0) + return x; /* x == +- 0 */ + if (ix < 0x3fc60000) /* |x| < 2^-57 */ + return x * (one + tiny); /* tanh(small) = small */ + u.parts32.w0 = ix; /* Absolute value of x. */ + if (ix >= 0x3fff0000) + { /* |x| >= 1 */ + t = __expm1l (two * u.value); + z = one - two / (t + two); + } + else + { + t = __expm1l (-two * u.value); + z = -t / (t + two); + } + /* |x| > 40, return +-1 */ + } + else + { + z = one - tiny; /* raised inexact flag */ + } + return (jx & 0x80000000) ? -z : z; +} +weak_alias (__tanhl, tanhl) |