1/* s_tanhf.c -- float version of s_tanh.c.
2 */
3
4/*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15#if defined(LIBM_SCCS) && !defined(lint)
16static char rcsid[] = "$NetBSD: s_tanhf.c,v 1.4 1995/05/10 20:48:24 jtc Exp $";
17#endif
18
19#include <float.h>
20#include <math.h>
21#include <math_private.h>
22#include <math-underflow.h>
23#include <libm-alias-float.h>
24
25static const float one=1.0, two=2.0, tiny = 1.0e-30;
26
27float __tanhf(float x)
28{
29 float t,z;
30 int32_t jx,ix;
31
32 GET_FLOAT_WORD(jx,x);
33 ix = jx&0x7fffffff;
34
35 /* x is INF or NaN */
36 if(ix>=0x7f800000) {
37 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
38 else return one/x-one; /* tanh(NaN) = NaN */
39 }
40
41 /* |x| < 22 */
42 if (ix < 0x41b00000) { /* |x|<22 */
43 if (ix == 0)
44 return x; /* x == +-0 */
45 if (ix<0x24000000) /* |x|<2**-55 */
46 {
47 math_check_force_underflow (x);
48 return x*(one+x); /* tanh(small) = small */
49 }
50 if (ix>=0x3f800000) { /* |x|>=1 */
51 t = __expm1f(x: two*fabsf(x: x));
52 z = one - two/(t+two);
53 } else {
54 t = __expm1f(x: -two*fabsf(x: x));
55 z= -t/(t+two);
56 }
57 /* |x| > 22, return +-1 */
58 } else {
59 z = one - tiny; /* raised inexact flag */
60 }
61 return (jx>=0)? z: -z;
62}
63libm_alias_float (__tanh, tanh)
64

source code of glibc/sysdeps/ieee754/flt-32/s_tanhf.c