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 <sys/cdefs.h>
17 __FBSDID("$FreeBSD$");
18 
19 #include "math.h"
20 #include "math_private.h"
21 
22 static const volatile float tiny = 1.0e-30;
23 static const float one=1.0, two=2.0, huge = 1.0e30;
24 
25 float
tanhf(float x)26 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| < 9 */
41 	if (ix < 0x41100000) {		/* |x|<9 */
42 	    if (ix<0x39800000) {	/* |x|<2**-12 */
43 		if(huge+x>one) return x; /* tanh(tiny) = tiny with inexact */
44 	    }
45 	    if (ix>=0x3f800000) {	/* |x|>=1  */
46 		t = expm1f(two*fabsf(x));
47 		z = one - two/(t+two);
48 	    } else {
49 	        t = expm1f(-two*fabsf(x));
50 	        z= -t/(t+two);
51 	    }
52     /* |x| >= 9, return +-1 */
53 	} else {
54 	    z = one - tiny;		/* raise inexact flag */
55 	}
56 	return (jx>=0)? z: -z;
57 }
58