OpenCores
URL https://opencores.org/ocsvn/openrisc_2011-10-31/openrisc_2011-10-31/trunk

Subversion Repositories openrisc_2011-10-31

[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.18.0/] [newlib/] [libm/] [math/] [s_cos.c] - Blame information for rev 617

Go to most recent revision | Details | Compare with Previous | View Log

Line No. Rev Author Line
1 207 jeremybenn 
 
2 
/* @(#)s_cos.c 5.1 93/09/24 */
3 
/*
4 
 * ====================================================
5 
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 
 *
7 
 * Developed at SunPro, a Sun Microsystems, Inc. business.
8 
 * Permission to use, copy, modify, and distribute this
9 
 * software is freely granted, provided that this notice
10 
 * is preserved.
11 
 * ====================================================
12 
 */
13 
 
14 
/* cos(x)
15 
 * Return cosine function of x.
16 
 *
17 
 * kernel function:
18 
 *      __kernel_sin            ... sine function on [-pi/4,pi/4]
19 
 *      __kernel_cos            ... cosine function on [-pi/4,pi/4]
20 
 *      __ieee754_rem_pio2      ... argument reduction routine
21 
 *
22 
 * Method.
23 
 *      Let S,C and T denote the sin, cos and tan respectively on
24 
 *      [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
25 
 *      in [-pi/4 , +pi/4], and let n = k mod 4.
26 
 *      We have
27 
 *
28 
 *          n        sin(x)      cos(x)        tan(x)
29 
 *     ----------------------------------------------------------
30 
 *          0          S           C             T
31 
 *          1          C          -S            -1/T
32 
 *          2         -S          -C             T
33 
 *          3         -C           S            -1/T
34 
 *     ----------------------------------------------------------
35 
 *
36 
 * Special cases:
37 
 *      Let trig be any of sin, cos, or tan.
38 
 *      trig(+-INF)  is NaN, with signals;
39 
 *      trig(NaN)    is that NaN;
40 
 *
41 
 * Accuracy:
42 
 *      TRIG(x) returns trig(x) nearly rounded
43 
 */
44 
 
45 
#include "fdlibm.h"
46 
 
47 
#ifndef _DOUBLE_IS_32BITS
48 
 
49 
#ifdef __STDC__
50 
        double cos(double x)
51 
#else
52 
        double cos(x)
53 
        double x;
54 
#endif
55 
{
56 
        double y[2],z=0.0;
57 
        __int32_t n,ix;
58 
 
59 
    /* High word of x. */
60 
        GET_HIGH_WORD(ix,x);
61 
 
62 
    /* |x| ~< pi/4 */
63 
        ix &= 0x7fffffff;
64 
        if(ix <= 0x3fe921fb) return __kernel_cos(x,z);
65 
 
66 
    /* cos(Inf or NaN) is NaN */
67 
        else if (ix>=0x7ff00000) return x-x;
68 
 
69 
    /* argument reduction needed */
70 
        else {
71 
            n = __ieee754_rem_pio2(x,y);
72 
            switch(n&3) {
73 
                case 0: return  __kernel_cos(y[0],y[1]);
74 
                case 1: return -__kernel_sin(y[0],y[1],1);
75 
                case 2: return -__kernel_cos(y[0],y[1]);
76 
                default:
77 
                        return  __kernel_sin(y[0],y[1],1);
78 
            }
79 
        }
80 
}
81 
 
82 
#endif /* _DOUBLE_IS_32BITS */

powered by: WebSVN 2.1.0

© copyright 1999-2024 OpenCores.org, equivalent to Oliscience, all rights reserved. OpenCores®, registered trademark.