source: vendor/FreeBSD-msun/current/src/s_cosf.c

/* s_cosf.c -- float version of s_cos.c.
 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
 */

/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunPro, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */

#ifndef lint
static char rcsid[] = "$FreeBSD: src/lib/msun/src/s_cosf.c,v 1.7 2002/05/28 18:15:04 alfred Exp $";
#endif

#include "math.h"
#include "math_private.h"

static const float one=1.0;

float
cosf(float x)
{
        float y[2],z=0.0;
        int32_t n,ix;

        GET_FLOAT_WORD(ix,x);

    /* |x| ~< pi/4 */
        ix &= 0x7fffffff;
        if(ix <= 0x3f490fd8) return __kernel_cosf(x,z);

    /* cos(Inf or NaN) is NaN */
        else if (ix>=0x7f800000) return x-x;

    /* argument reduction needed */
        else {
            n = __ieee754_rem_pio2f(x,y);
            switch(n&3) {
                case 0: return  __kernel_cosf(y[0],y[1]);
                case 1: return -__kernel_sinf(y[0],y[1],1);
                case 2: return -__kernel_cosf(y[0],y[1]);
                default:
                        return  __kernel_sinf(y[0],y[1],1);
            }
        }
}