Mercurial > hg > CbC > CbC_gcc
comparison libquadmath/math/tanhq.c @ 68:561a7518be6b
update gcc-4.6
author | Nobuyasu Oshiro <dimolto@cr.ie.u-ryukyu.ac.jp> |
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date | Sun, 21 Aug 2011 07:07:55 +0900 |
parents | |
children | 04ced10e8804 |
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67:f6334be47118 | 68:561a7518be6b |
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1 /* s_tanhl.c -- __float128 version of s_tanh.c. | |
2 * Conversion to __float128 by Ulrich Drepper, | |
3 * Cygnus Support, drepper@cygnus.com. | |
4 */ | |
5 | |
6 /* | |
7 * ==================================================== | |
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
9 * | |
10 * Developed at SunPro, a Sun Microsystems, Inc. business. | |
11 * Permission to use, copy, modify, and distribute this | |
12 * software is freely granted, provided that this notice | |
13 * is preserved. | |
14 * ==================================================== | |
15 */ | |
16 | |
17 /* Changes for 128-bit __float128 contributed by | |
18 Stephen L. Moshier <moshier@na-net.ornl.gov> */ | |
19 | |
20 /* tanhl(x) | |
21 * Return the Hyperbolic Tangent of x | |
22 * | |
23 * Method : | |
24 * x -x | |
25 * e - e | |
26 * 0. tanhl(x) is defined to be ----------- | |
27 * x -x | |
28 * e + e | |
29 * 1. reduce x to non-negative by tanhl(-x) = -tanhl(x). | |
30 * 2. 0 <= x <= 2**-57 : tanhl(x) := x*(one+x) | |
31 * -t | |
32 * 2**-57 < x <= 1 : tanhl(x) := -----; t = expm1l(-2x) | |
33 * t + 2 | |
34 * 2 | |
35 * 1 <= x <= 40.0 : tanhl(x) := 1- ----- ; t=expm1l(2x) | |
36 * t + 2 | |
37 * 40.0 < x <= INF : tanhl(x) := 1. | |
38 * | |
39 * Special cases: | |
40 * tanhl(NaN) is NaN; | |
41 * only tanhl(0)=0 is exact for finite argument. | |
42 */ | |
43 | |
44 #include "quadmath-imp.h" | |
45 | |
46 static const __float128 one = 1.0Q, two = 2.0Q, tiny = 1.0e-4900Q; | |
47 | |
48 __float128 | |
49 tanhq (__float128 x) | |
50 { | |
51 __float128 t, z; | |
52 uint32_t jx, ix; | |
53 ieee854_float128 u; | |
54 | |
55 /* Words of |x|. */ | |
56 u.value = x; | |
57 jx = u.words32.w0; | |
58 ix = jx & 0x7fffffff; | |
59 /* x is INF or NaN */ | |
60 if (ix >= 0x7fff0000) | |
61 { | |
62 /* for NaN it's not important which branch: tanhl(NaN) = NaN */ | |
63 if (jx & 0x80000000) | |
64 return one / x - one; /* tanhl(-inf)= -1; */ | |
65 else | |
66 return one / x + one; /* tanhl(+inf)=+1 */ | |
67 } | |
68 | |
69 /* |x| < 40 */ | |
70 if (ix < 0x40044000) | |
71 { | |
72 if (u.value == 0) | |
73 return x; /* x == +- 0 */ | |
74 if (ix < 0x3fc60000) /* |x| < 2^-57 */ | |
75 return x * (one + tiny); /* tanh(small) = small */ | |
76 u.words32.w0 = ix; /* Absolute value of x. */ | |
77 if (ix >= 0x3fff0000) | |
78 { /* |x| >= 1 */ | |
79 t = expm1q (two * u.value); | |
80 z = one - two / (t + two); | |
81 } | |
82 else | |
83 { | |
84 t = expm1q (-two * u.value); | |
85 z = -t / (t + two); | |
86 } | |
87 /* |x| > 40, return +-1 */ | |
88 } | |
89 else | |
90 { | |
91 z = one - tiny; /* raised inexact flag */ | |
92 } | |
93 return (jx & 0x80000000) ? -z : z; | |
94 } |