sparc/fp/_Q_qtod.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (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 (c) 1994-1997, by Sun Microsystems, Inc.
 * All rights reserved.
 */

#pragma ident   "%Z%%M% %I% %E% SMI"

#include "quad.h"

#ifdef __sparcv9
#define _Q_qtod _Qp_qtod
#endif

/*
 * _Q_qtod(x) returns (double)*x.
 */
double
_Q_qtod(const union longdouble *x)
{
    union xdouble   u;
    unsigned int    xm, round, sticky, fsr, rm;
    int     subnormal, e;

    xm = x->l.msw & 0x7fffffff;

    /* get the rounding mode, fudging directed rounding modes */
    /* as though the result were positive */
    __quad_getfsrp(&fsr);
    rm = fsr >> 30;
    if (x->l.msw & 0x80000000)
        rm ^= (rm >> 1);

    /* handle nan, inf, and out-of-range cases */
    if (xm >= 0x43ff0000) {
        if (xm >= 0x7fff0000) {
            if ((xm & 0xffff) | x->l.frac2 | x->l.frac3 |
                x->l.frac4) {
                /* x is nan */
                u.l.hi = (x->l.msw & 0x80000000) | 0x7ff80000;
                u.l.hi |= ((xm & 0x7fff) << 4) |
                    (x->l.frac2 >> 28);
                u.l.lo = (x->l.frac2 << 4) |
                    (x->l.frac3 >> 28);
                if (!(xm & 0x8000)) {
                    /* snan, signal invalid */
                    if (fsr & FSR_NVM) {
                        __quad_fqtod(x, &u.d);
                    } else {
                        fsr = (fsr & ~FSR_CEXC) |
                            FSR_NVA | FSR_NVC;
                        __quad_setfsrp(&fsr);
                    }
                }
                return (u.d);
            }
            /* x is inf */
            u.l.hi = (x->l.msw & 0x80000000) | 0x7ff00000;
            u.l.lo = 0;
            return (u.d);
        }
        /* x is too big, overflow */
        if (rm == FSR_RN || rm == FSR_RP) {
            u.l.hi = 0x7ff00000;
            u.l.lo = 0;
        } else {
            u.l.hi = 0x7fefffff;
            u.l.lo = 0xffffffff;
        }
        u.l.hi |= (x->l.msw & 0x80000000);
        if (fsr & (FSR_OFM | FSR_NXM)) {
            __quad_fqtod(x, &u.d);
        } else {
            fsr = (fsr & ~FSR_CEXC) | FSR_OFA | FSR_OFC |
                FSR_NXA | FSR_NXC;
            __quad_setfsrp(&fsr);
        }
        return (u.d);
    }

    subnormal = 0;
    if (xm < 0x3c010000) {
        if (xm < 0x3bcc0000) {
            if (QUAD_ISZERO(*x)) {
                u.l.hi = (x->l.msw & 0x80000000);
                u.l.lo = 0;
                return (u.d);
            }
            /* x is too small, underflow */
            u.l.hi = (x->l.msw & 0x80000000);
            u.l.lo = ((rm == FSR_RP)? 1 : 0);
            if (fsr & (FSR_UFM | FSR_NXM)) {
                __quad_fqtod(x, &u.d);
            } else {
                fsr = (fsr & ~FSR_CEXC) | FSR_UFA | FSR_UFC |
                    FSR_NXA | FSR_NXC;
                __quad_setfsrp(&fsr);
            }
            return (u.d);
        }

        /* x is in the subnormal range for double */
        subnormal = 1;
        u.l.hi = 0x80000 | ((xm & 0xffff) << 3) | (x->l.frac2 >> 29);
        u.l.lo = (x->l.frac2 << 3) | (x->l.frac3 >> 29);
        round = x->l.frac3 & 0x10000000;
        sticky = (x->l.frac3 & 0xfffffff) | x->l.frac4;
        e = 0x3c00 - (xm >> 16);
        if (e >= 32) {
            sticky |= round | (u.l.lo & 0x7fffffff);
            round = u.l.lo & 0x80000000;
            u.l.lo = u.l.hi;
            u.l.hi = 0;
            e -= 32;
        }
        if (e) {
            sticky |= round | (u.l.lo & ((1 << (e - 1)) - 1));
            round = u.l.lo & (1 << (e - 1));
            u.l.lo = (u.l.lo >> e) | (u.l.hi << (32 - e));
            u.l.hi >>= e;
        }
    } else {
        /* x is in the normal range for double */
        u.l.hi = ((xm - 0x3c000000) << 4) | (x->l.frac2 >> 28);
        u.l.lo = (x->l.frac2 << 4) | (x->l.frac3 >> 28);
        round = x->l.frac3 & 0x8000000;
        sticky = (x->l.frac3 & 0x7ffffff) | x->l.frac4;
    }

    /* see if we need to round */
    fsr &= ~FSR_CEXC;
    if (round | sticky) {
        fsr |= FSR_NXC;
        if (subnormal)
            fsr |= FSR_UFC;

        /* round up if necessary */
        if (rm == FSR_RP || (rm == FSR_RN && round && (sticky ||
            (u.l.lo & 1)))) {
            /* round up and check for overflow */
            if (++u.l.lo == 0)
                if (++u.l.hi >= 0x7ff00000)
                    fsr |= FSR_OFC;
        }
    }

    /* if result is exact and subnormal but underflow trapping is */
    /* enabled, signal underflow */
    else if (subnormal && (fsr & FSR_UFM))
        fsr |= FSR_UFC;

    /* attach the sign and raise exceptions as need be */
    u.l.hi |= (x->l.msw & 0x80000000);
    if ((fsr & FSR_CEXC) & (fsr >> 23)) {
        __quad_setfsrp(&fsr);
        __quad_fqtod(x, &u.d);
    } else {
        fsr |= (fsr & 0x1f) << 5;
        __quad_setfsrp(&fsr);
    }
    return (u.d);
}