Mercurial > hg > CbC > CbC_gcc
comparison libquadmath/math/atanhq.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_atanhl.c -- __float128 version of s_atan.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 /* __ieee754_atanhl(x) | |
18 * Method : | |
19 * 1.Reduced x to positive by atanh(-x) = -atanh(x) | |
20 * 2.For x>=0.5 | |
21 * 1 2x x | |
22 * atanhl(x) = --- * log(1 + -------) = 0.5 * log1p(2 * --------) | |
23 * 2 1 - x 1 - x | |
24 * | |
25 * For x<0.5 | |
26 * atanhl(x) = 0.5*log1pl(2x+2x*x/(1-x)) | |
27 * | |
28 * Special cases: | |
29 * atanhl(x) is NaN if |x| > 1 with signal; | |
30 * atanhl(NaN) is that NaN with no signal; | |
31 * atanhl(+-1) is +-INF with signal. | |
32 * | |
33 */ | |
34 | |
35 #include "quadmath-imp.h" | |
36 | |
37 static const __float128 one = 1.0Q, huge = 1e4900Q; | |
38 static const __float128 zero = 0.0Q; | |
39 | |
40 __float128 | |
41 atanhq (__float128 x) | |
42 { | |
43 __float128 t; | |
44 uint32_t jx, ix; | |
45 ieee854_float128 u; | |
46 | |
47 u.value = x; | |
48 jx = u.words32.w0; | |
49 ix = jx & 0x7fffffff; | |
50 u.words32.w0 = ix; | |
51 if (ix >= 0x3fff0000) /* |x| >= 1.0 or infinity or NaN */ | |
52 { | |
53 if (u.value == one) | |
54 return x/zero; | |
55 else | |
56 return (x-x)/(x-x); | |
57 } | |
58 if(ix<0x3fc60000 && (huge+x)>zero) return x; /* x < 2^-57 */ | |
59 | |
60 if(ix<0x3ffe0000) { /* x < 0.5 */ | |
61 t = u.value+u.value; | |
62 t = 0.5*log1pq(t+t*u.value/(one-u.value)); | |
63 } else | |
64 t = 0.5*log1pq((u.value+u.value)/(one-u.value)); | |
65 if(jx & 0x80000000) return -t; else return t; | |
66 } |