1 /* sf_tanh.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 #include "fdlibm.h"
17
18 static const volatile float one = 1.0, two = 2.0, tiny = 1.0e-30;
19
20 float
tanhf(float x)21 tanhf(float x)
22 {
23 float t, z;
24 __int32_t jx, ix;
25
26 GET_FLOAT_WORD(jx, x);
27 ix = jx & 0x7fffffff;
28
29 /* x is INF or NaN */
30 if (!FLT_UWORD_IS_FINITE(ix)) {
31 if (jx >= 0)
32 return one / x + one; /* tanh(+-inf)=+-1 */
33 else
34 return one / x - one; /* tanh(NaN) = NaN */
35 }
36
37 /* |x| < 22 */
38 if (ix < 0x41b00000) { /* |x|<22 */
39 if (ix < 0x24000000) /* |x|<2**-55 */
40 return x * (one + x); /* tanh(small) = small */
41 if (ix >= 0x3f800000) { /* |x|>=1 */
42 t = expm1f(two * fabsf(x));
43 z = one - two / (t + two);
44 } else {
45 t = expm1f(-two * fabsf(x));
46 z = -t / (t + two);
47 }
48 /* |x| > 22, return +-1 */
49 } else {
50 z = one - tiny; /* raised inexact flag */
51 }
52 return (jx >= 0) ? z : -z;
53 }
54
55 _MATH_ALIAS_f_f(tanh)
56
