s_cosf.c revision 152596 
1/* s_cosf.c -- float version of s_cos.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/s_cosf.c 152596 2005-11-19 02:38:27Z bde $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23/* Small multiples of pi/2 rounded to double precision. */
24static const double
25c1pio2 = 1*M_PI_2,			/* 0x3FF921FB, 0x54442D18 */
26c2pio2 = 2*M_PI_2,			/* 0x400921FB, 0x54442D18 */
27c3pio2 = 3*M_PI_2,			/* 0x4012D97C, 0x7F3321D2 */
28c4pio2 = 4*M_PI_2;			/* 0x401921FB, 0x54442D18 */
29
30static inline float
31__kernel_cosdf(double x)
32{
33	return __kernel_cosf((float)x, x - (float)x);
34}
35
36static inline float
37__kernel_sindf(double x)
38{
39	return __kernel_sinf((float)x, x - (float)x, 1);
40}
41
42float
43cosf(float x)
44{
45	float y[2];
46	int32_t n,ix;
47
48	x = fabsf(x);
49	GET_FLOAT_WORD(ix,x);
50
51	if(ix <= 0x3f490fda) {		/* |x| ~<= pi/4 */
52	    if(ix<0x39800000)		/* |x| < 2**-12 */
53		if(((int)x)==0) return 1.0;	/* 1 with inexact if x != 0 */
54	    return __kernel_cosf(x,0.0);
55	}
56	if(ix<=0x407b53d1) {		/* |x| <= ~5*pi/4 */
57	    if(ix<=0x4016cbe3)		/* |x| <= ~3pi/4 */
58		return -__kernel_sindf(x - c1pio2);
59	    else
60		return -__kernel_cosdf(x - c2pio2);
61	}
62	if(ix<=0x40e231d5) {		/* |x| <= ~9*pi/4 */
63	    if(ix<=0x40afeddf)		/* |x| <= ~7*pi/4 */
64		return __kernel_sindf(x - c3pio2);
65	    else
66		return __kernel_cosdf(x - c4pio2);
67	}
68
69    /* cos(Inf or NaN) is NaN */
70	else if (ix>=0x7f800000) return x-x;
71
72    /* general argument reduction needed */
73	else {
74	    n = __ieee754_rem_pio2f(x,y);
75	    switch(n&3) {
76		case 0: return  __kernel_cosf(y[0],y[1]);
77		case 1: return -__kernel_sinf(y[0],y[1],1);
78		case 2: return -__kernel_cosf(y[0],y[1]);
79		default:
80		        return  __kernel_sinf(y[0],y[1],1);
81	    }
82	}
83}
84