e_coshf.c revision 152352 
1/* e_coshf.c -- float version of e_cosh.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#ifndef lint
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/e_coshf.c 152352 2005-11-13 00:08:23Z bde $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23static const float one = 1.0, half=0.5, huge = 1.0e30;
24
25float
26__ieee754_coshf(float x)
27{
28	float t,w;
29	int32_t ix;
30
31	GET_FLOAT_WORD(ix,x);
32	ix &= 0x7fffffff;
33
34    /* x is INF or NaN */
35	if(ix>=0x7f800000) return x*x;
36
37    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
38	if(ix<0x3eb17218) {
39	    t = expm1f(fabsf(x));
40	    w = one+t;
41	    if (ix<0x39800000) return one;	/* cosh(tiny) = 1 */
42	    return one+(t*t)/(w+w);
43	}
44
45    /* |x| in [0.5*ln2,9], return (exp(|x|)+1/exp(|x|))/2; */
46	if (ix < 0x41100000) {
47		t = __ieee754_expf(fabsf(x));
48		return half*t+half/t;
49	}
50
51    /* |x| in [9, log(maxfloat)] return half*exp(|x|) */
52	if (ix < 0x42b17217)  return half*__ieee754_expf(fabsf(x));
53
54    /* |x| in [log(maxfloat), overflowthresold] */
55	if (ix<=0x42b2d4fc) {
56	    w = __ieee754_expf(half*fabsf(x));
57	    t = half*w;
58	    return t*w;
59	}
60
61    /* |x| > overflowthresold, cosh(x) overflow */
62	return huge*huge;
63}
64