e_coshf.c revision 176451 
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#include <sys/cdefs.h>
17__FBSDID("$FreeBSD: head/lib/msun/src/e_coshf.c 176451 2008-02-22 02:30:36Z das $");
18
19#include "math.h"
20#include "math_private.h"
21
22static const float one = 1.0, half=0.5, huge = 1.0e30;
23
24float
25__ieee754_coshf(float x)
26{
27	float t,w;
28	int32_t ix;
29
30	GET_FLOAT_WORD(ix,x);
31	ix &= 0x7fffffff;
32
33    /* x is INF or NaN */
34	if(ix>=0x7f800000) return x*x;
35
36    /* |x| in [0,0.5*ln2], return 1+expm1(|x|)^2/(2*exp(|x|)) */
37	if(ix<0x3eb17218) {
38	    t = expm1f(fabsf(x));
39	    w = one+t;
40	    if (ix<0x39800000) return one;	/* cosh(tiny) = 1 */
41	    return one+(t*t)/(w+w);
42	}
43
44    /* |x| in [0.5*ln2,9], return (exp(|x|)+1/exp(|x|))/2; */
45	if (ix < 0x41100000) {
46		t = __ieee754_expf(fabsf(x));
47		return half*t+half/t;
48	}
49
50    /* |x| in [9, log(maxfloat)] return half*exp(|x|) */
51	if (ix < 0x42b17217)  return half*__ieee754_expf(fabsf(x));
52
53    /* |x| in [log(maxfloat), overflowthresold] */
54	if (ix<=0x42b2d4fc) {
55	    w = __ieee754_expf(half*fabsf(x));
56	    t = half*w;
57	    return t*w;
58	}
59
60    /* |x| > overflowthresold, cosh(x) overflow */
61	return huge*huge;
62}
63