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 #include "math.h"
17 #include "math_private.h"
18
19 static const float one=1.0, two=2.0, tiny = 1.0e-30;
20
21 float
tanhf(float x)22 tanhf(float x)
23 {
24 float t,z;
25 int32_t jx,ix;
26
27 GET_FLOAT_WORD(jx,x);
28 ix = jx&0x7fffffff;
29
30 /* x is INF or NaN */
31 if(ix>=0x7f800000) {
32 if (jx>=0) return one/x+one; /* tanh(+-inf)=+-1 */
33 else return one/x-one; /* tanh(NaN) = NaN */
34 }
35
36 /* |x| < 22 */
37 if (ix < 0x41b00000) { /* |x|<22 */
38 if (ix == 0)
39 return x; /* x == +-0 */
40 if (ix<0x24000000) /* |x|<2**-55 */
41 return x*(one+x); /* tanh(small) = small */
42 if (ix>=0x3f800000) { /* |x|>=1 */
43 t = expm1f(two*fabsf(x));
44 z = one - two/(t+two);
45 } else {
46 t = expm1f(-two*fabsf(x));
47 z= -t/(t+two);
48 }
49 /* |x| > 22, return +-1 */
50 } else {
51 z = one - tiny; /* raised inexact flag */
52 }
53 return (jx>=0)? z: -z;
54 }
55