k_cosf.c

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/* k_cosf.c -- float version of k_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.
 * ====================================================
 */

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

static const float 
one =  1.0000000000e+00, /* 0x3f800000 */
C1  =  4.1666667908e-02, /* 0x3d2aaaab */
C2  = -1.3888889225e-03, /* 0xbab60b61 */
C3  =  2.4801587642e-05, /* 0x37d00d01 */
C4  = -2.7557314297e-07, /* 0xb493f27c */
C5  =  2.0875723372e-09, /* 0x310f74f6 */
C6  = -1.1359647598e-11; /* 0xad47d74e */

float
__kernel_cosf(float x, float y)
{
    float a,hz,z,r,qx;
    int32_t ix;
    GET_FLOAT_WORD(ix,x);
    ix &= 0x7fffffff;           /* ix = |x|'s high word*/
    if(ix<0x32000000) {         /* if x < 2**27 */
        if(((int)x)==0) return one;     /* generate inexact */
    }
    z  = x*x;
    r  = z*(C1+z*(C2+z*(C3+z*(C4+z*(C5+z*C6)))));
    if(ix < 0x3e99999a)             /* if |x| < 0.3 */ 
        return one - ((float)0.5*z - (z*r - x*y));
    else {
        if(ix > 0x3f480000) {       /* x > 0.78125 */
        qx = (float)0.28125;
        } else {
            SET_FLOAT_WORD(qx,ix-0x01000000);   /* x/4 */
        }
        hz = (float)0.5*z-qx;
        a  = one-qx;
        return a - (hz - (z*r-x*y));
    }
}