common/m9x/roundl.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 __roundl = roundl

#include "libm.h"

#if defined(__sparc)
long double
roundl(long double x) {
    union {
        unsigned i[4];
        long double q;
    } xx;
    unsigned hx, sx, v;
    int j;

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

    /* handle trivial cases */
    if (hx >= 0x406f0000) /* |x| >= 2^112 + ... or x is nan */
        return (hx >= 0x7fff0000 ? x + x : x);

    /* handle |x| < 1 */
    if (hx < 0x3fff0000) {
        if (hx >= 0x3ffe0000)
            return (sx ? -1.0L : 1.0L);
        return (sx ? -0.0L : 0.0L);
    }

    xx.i[0] = hx;
    j = 0x406f - (hx >> 16);        /* 1 <= j <= 112 */
    if (j >= 96) {              /* 96 <= j <= 112 */
        v = (1U << (j - 96)) >> 1;
        if (v) {
            if (xx.i[0] & v)
                xx.i[0] += v;
            xx.i[0] &= ~(v - 1);
        } else if (xx.i[1] & 0x80000000)
                ++xx.i[0];
        xx.i[1] = xx.i[2] = xx.i[3] = 0;
    } else if (j >= 64) {           /* 64 <= j <= 95 */
        v = (1U << (j - 64)) >> 1;
        if (v) {
            if (xx.i[1] & v) {
                xx.i[1] += v;
                if (xx.i[1] < v)
                    ++xx.i[0];
            }
            xx.i[1] &= ~(v - 1);
        } else if (xx.i[2] & 0x80000000) {
                if (++xx.i[1] == 0)
                    ++xx.i[0];
        }
        xx.i[2] = xx.i[3] = 0;
    } else if (j >= 32) {           /* 32 <= j <= 63 */
        v = (1U << (j - 32)) >> 1;
        if (v) {
            if (xx.i[2] & v) {
                xx.i[2] += v;
                if (xx.i[2] < v) {
                    if (++xx.i[1] == 0)
                        ++xx.i[0];
                }
            }
            xx.i[2] &= ~(v - 1);
        } else if (xx.i[3] & 0x80000000) {
                if (++xx.i[2] == 0) {
                    if (++xx.i[1] == 0)
                        ++xx.i[0];
                }
        }
        xx.i[3] = 0;
    } else {                /* 1 <= j <= 31 */
        v = 1U << (j - 1);
        if (xx.i[3] & v) {
            xx.i[3] += v;
            if (xx.i[3] < v) {
                if (++xx.i[2] == 0) {
                    if (++xx.i[1] == 0)
                        ++xx.i[0];
                }
            }
        }
        xx.i[3] &= ~(v - 1);
    }

    /* negate result if need be */
    if (sx)
        xx.i[0] |= 0x80000000;
    return (xx.q);
}
#elif defined(__x86)
long double
roundl(long double x) {
    union {
        unsigned i[3];
        long double e;
    } xx;
    int ex, sx, i;

    xx.e = x;
    ex = xx.i[2] & 0x7fff;
    sx = xx.i[2] & 0x8000;
    if (ex < 0x403e) {  /* |x| < 2^63 */
        if (ex < 0x3fff) {  /* |x| < 1 */
            if (ex >= 0x3ffe)
                return (sx ? -1.0L : 1.0L);
            return (sx ? -0.0L : 0.0L);
        }

        /* round x at the integer bit */
        if (ex < 0x401e) {
            i = 1 << (0x401d - ex);
            xx.i[1] = (xx.i[1] + i) & ~(i | (i - 1));
            xx.i[0] = 0;
        } else {
            i = 1 << (0x403d - ex);
            xx.i[0] += i;
            if (xx.i[0] < i)
                xx.i[1]++;
            xx.i[0] &= ~(i | (i - 1));
        }
        if (xx.i[1] == 0) {
            xx.i[2] = sx | ++ex;
            xx.i[1] = 0x80000000U;
        }
        return (xx.e);
    } else if (ex < 0x7fff) /* x is integral */
        return (x);
    else            /* inf or nan */
        return (x + x);
}
#else
#error Unknown architecture
#endif  /* defined(__sparc) || defined(__x86) */