common/m9x/modfl.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
 */
/*
 * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#pragma weak modfl = __modfl

#include "libm.h"

#if defined(__sparc)

long double
__modfl(long double x, long double *iptr) {
    union {
        unsigned i[4];
        long double q;
    } xx, yy;
    unsigned hx, s;

    xx.q = x;
    hx = xx.i[0] & ~0x80000000;

    if (hx >= 0x406f0000) { /* x is NaN, infinite, or integral */
        *iptr = x;
        if (hx < 0x7fff0000 || (hx == 0x7fff0000 &&
            (xx.i[1] | xx.i[2] | xx.i[3]) == 0)) {
            xx.i[0] &= 0x80000000;
            xx.i[1] = xx.i[2] = xx.i[3] = 0;
        }
        return (xx.q);
    }

    if (hx < 0x3fff0000) {  /* |x| < 1 */
        xx.i[0] &= 0x80000000;
        xx.i[1] = xx.i[2] = xx.i[3] = 0;
        *iptr = xx.q;
        return (x);
    }

    /* split x at the binary point */
    s = xx.i[0] & 0x80000000;
    if (hx < 0x40100000) {
        yy.i[0] = xx.i[0] & ~((1 << (0x400f - (hx >> 16))) - 1);
        yy.i[1] = yy.i[2] = yy.i[3] = 0;
    } else if (hx < 0x40300000) {
        yy.i[0] = xx.i[0];
        yy.i[1] = xx.i[1] & ~((1 << (0x402f - (hx >> 16))) - 1);
        yy.i[2] = yy.i[3] = 0;
    } else if (hx < 0x40500000) {
        yy.i[0] = xx.i[0];
        yy.i[1] = xx.i[1];
        yy.i[2] = xx.i[2] & ~((1 << (0x404f - (hx >> 16))) - 1);
        yy.i[3] = 0;
    } else {
        yy.i[0] = xx.i[0];
        yy.i[1] = xx.i[1];
        yy.i[2] = xx.i[2];
        yy.i[3] = xx.i[3] & ~((1 << (0x406f - (hx >> 16))) - 1);
    }
    *iptr = yy.q;

    /*
     * we could implement the following more efficiently than by using
     * software emulation of fsubq, but we'll do it this way for now
     * (and hope hardware support becomes commonplace)
     */
    xx.q -= yy.q;
    xx.i[0] = (xx.i[0] & ~0x80000000) | s;  /* keep sign of x */
    return (xx.q);
}

#elif defined(__x86)

long double
__modfl(long double x, long double *iptr) {
    union {
        unsigned i[3];
        long double e;
    } xx, yy;
    unsigned hx, s;

    /*
     * It might be faster to use one of the x86 fpops instead of
     * the following.
     */
    xx.e = x;
    hx = xx.i[2] & 0x7fff;

    if (hx >= 0x403e) { /* x is NaN, infinite, or integral */
        *iptr = x;
        if (hx < 0x7fff || (hx == 0x7fff &&
            ((xx.i[1] << 1) | xx.i[0]) == 0)) {
            xx.i[2] &= 0x8000;
            xx.i[1] = xx.i[0] = 0;
        }
        return (xx.e);
    }

    if (hx < 0x3fff) {  /* |x| < 1 */
        xx.i[2] &= 0x8000;
        xx.i[1] = xx.i[0] = 0;
        *iptr = xx.e;
        return (x);
    }

    /* split x at the binary point */
    s = xx.i[2] & 0x8000;
    yy.i[2] = xx.i[2];
    if (hx < 0x401f) {
        yy.i[1] = xx.i[1] & ~((1 << (0x401e - hx)) - 1);
        yy.i[0] = 0;
    } else {
        yy.i[1] = xx.i[1];
        yy.i[0] = xx.i[0] & ~((1 << (0x403e - hx)) - 1);
    }
    *iptr = yy.e;
    xx.e -= yy.e;
    xx.i[2] = (xx.i[2] & ~0x8000) | s;  /* keep sign of x */
    return (xx.e);
}

#else
#error Unknown architecture
#endif