1 | /* s_tanhf.c -- float version of s_tanh.c. |
2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. |
3 | */ |
4 | |
5 | /* |
6 | * ==================================================== |
7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
8 | * |
9 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
10 | * Permission to use, copy, modify, and distribute this |
11 | * software is freely granted, provided that this notice |
12 | * is preserved. |
13 | * ==================================================== |
14 | */ |
15 | |
16 | #if defined(LIBM_SCCS) && !defined(lint) |
17 | static char rcsid[] = "$NetBSD: s_tanhf.c,v 1.4 1995/05/10 20:48:24 jtc Exp $" ; |
18 | #endif |
19 | |
20 | #include <float.h> |
21 | #include <math.h> |
22 | #include <math_private.h> |
23 | |
24 | static const float one=1.0, two=2.0, tiny = 1.0e-30; |
25 | |
26 | float __tanhf(float x) |
27 | { |
28 | float t,z; |
29 | int32_t jx,ix; |
30 | |
31 | GET_FLOAT_WORD(jx,x); |
32 | ix = jx&0x7fffffff; |
33 | |
34 | /* x is INF or NaN */ |
35 | if(ix>=0x7f800000) { |
36 | if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */ |
37 | else return one/x-one; /* tanh(NaN) = NaN */ |
38 | } |
39 | |
40 | /* |x| < 22 */ |
41 | if (ix < 0x41b00000) { /* |x|<22 */ |
42 | if (ix == 0) |
43 | return x; /* x == +-0 */ |
44 | if (ix<0x24000000) /* |x|<2**-55 */ |
45 | { |
46 | math_check_force_underflow (x); |
47 | return x*(one+x); /* tanh(small) = small */ |
48 | } |
49 | if (ix>=0x3f800000) { /* |x|>=1 */ |
50 | t = __expm1f(two*fabsf(x)); |
51 | z = one - two/(t+two); |
52 | } else { |
53 | t = __expm1f(-two*fabsf(x)); |
54 | z= -t/(t+two); |
55 | } |
56 | /* |x| > 22, return +-1 */ |
57 | } else { |
58 | z = one - tiny; /* raised inexact flag */ |
59 | } |
60 | return (jx>=0)? z: -z; |
61 | } |
62 | weak_alias (__tanhf, tanhf) |
63 | |