1df930be7Sderaadt /* s_tanhf.c -- float version of s_tanh.c.
2df930be7Sderaadt * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3df930be7Sderaadt */
4df930be7Sderaadt
5df930be7Sderaadt /*
6df930be7Sderaadt * ====================================================
7df930be7Sderaadt * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8df930be7Sderaadt *
9df930be7Sderaadt * Developed at SunPro, a Sun Microsystems, Inc. business.
10df930be7Sderaadt * Permission to use, copy, modify, and distribute this
11df930be7Sderaadt * software is freely granted, provided that this notice
12df930be7Sderaadt * is preserved.
13df930be7Sderaadt * ====================================================
14df930be7Sderaadt */
15df930be7Sderaadt
16df930be7Sderaadt #include "math.h"
17df930be7Sderaadt #include "math_private.h"
18df930be7Sderaadt
19df930be7Sderaadt static const float one=1.0, two=2.0, tiny = 1.0e-30;
20df930be7Sderaadt
21e7beb4a7Smillert float
tanhf(float x)22e7beb4a7Smillert tanhf(float x)
23df930be7Sderaadt {
24df930be7Sderaadt float t,z;
25df930be7Sderaadt int32_t jx,ix;
26df930be7Sderaadt
27df930be7Sderaadt GET_FLOAT_WORD(jx,x);
28df930be7Sderaadt ix = jx&0x7fffffff;
29df930be7Sderaadt
30df930be7Sderaadt /* x is INF or NaN */
31df930be7Sderaadt if(ix>=0x7f800000) {
32df930be7Sderaadt if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
33df930be7Sderaadt else return one/x-one; /* tanh(NaN) = NaN */
34df930be7Sderaadt }
35df930be7Sderaadt
36df930be7Sderaadt /* |x| < 22 */
37df930be7Sderaadt if (ix < 0x41b00000) { /* |x|<22 */
38*6d7e72cbSmartynas if (ix == 0)
39*6d7e72cbSmartynas return x; /* x == +-0 */
40df930be7Sderaadt if (ix<0x24000000) /* |x|<2**-55 */
41df930be7Sderaadt return x*(one+x); /* tanh(small) = small */
42df930be7Sderaadt if (ix>=0x3f800000) { /* |x|>=1 */
43df930be7Sderaadt t = expm1f(two*fabsf(x));
44df930be7Sderaadt z = one - two/(t+two);
45df930be7Sderaadt } else {
46df930be7Sderaadt t = expm1f(-two*fabsf(x));
47df930be7Sderaadt z= -t/(t+two);
48df930be7Sderaadt }
49df930be7Sderaadt /* |x| > 22, return +-1 */
50df930be7Sderaadt } else {
51df930be7Sderaadt z = one - tiny; /* raised inexact flag */
52df930be7Sderaadt }
53df930be7Sderaadt return (jx>=0)? z: -z;
54df930be7Sderaadt }
55