sparc/fp/_Q_qtos.c

	_Q_qtos.c revision 7c478bd95313f5f23a4c958a745db2134aa03244
/*
 * 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_qtos _Qp_qtos
#endif

/*
 * _Q_qtos(x) returns (float)*x.
 */
float
_Q_qtos(const union longdouble *x)
{
    union {
        float       f;
        unsigned int    l;
    } 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 >= 0x407f0000) {
        if (xm >= 0x7fff0000) {
            if ((xm & 0xffff) | x->l.frac2 | x->l.frac3 |
                x->l.frac4) {
                /* x is nan */
                u.l = (x->l.msw & 0x80000000) | 0x7fc00000;
                u.l |= ((xm & 0x7fff) << 7) |
                    (x->l.frac2 >> 25);
                if (!(xm & 0x8000)) {
                    /* snan, signal invalid */
                    if (fsr & FSR_NVM) {
                        __quad_fqtos(x, &u.f);
                    } else {
                        fsr = (fsr & ~FSR_CEXC) |
                            FSR_NVA | FSR_NVC;
                        __quad_setfsrp(&fsr);
                    }
                }
                return (u.f);
            }
            /* x is inf */
            u.l = (x->l.msw & 0x80000000) | 0x7f800000;
            return (u.f);
        }
        /* x is too big, overflow */
        if (rm == FSR_RN || rm == FSR_RP)
            u.l = 0x7f800000;
        else
            u.l = 0x7f7fffff;
        u.l |= (x->l.msw & 0x80000000);
        if (fsr & (FSR_OFM | FSR_NXM)) {
            __quad_fqtos(x, &u.f);
        } else {
            fsr = (fsr & ~FSR_CEXC) | FSR_OFA | FSR_OFC |
                FSR_NXA | FSR_NXC;
            __quad_setfsrp(&fsr);
        }
        return (u.f);
    }

    subnormal = 0;
    if (xm < 0x3f810000) {
        if (xm < 0x3f690000) {
            if (QUAD_ISZERO(*x)) {
                u.l = (x->l.msw & 0x80000000);
                return (u.f);
            }
            /* x is too small, underflow */
            u.l = ((rm == FSR_RP)? 1 : 0);
            u.l |= (x->l.msw & 0x80000000);
            if (fsr & (FSR_UFM | FSR_NXM)) {
                __quad_fqtos(x, &u.f);
            } else {
                fsr = (fsr & ~FSR_CEXC) | FSR_UFA | FSR_UFC |
                    FSR_NXA | FSR_NXC;
                __quad_setfsrp(&fsr);
            }
            return (u.f);
        }

        /* x is in the subnormal range for single */
        subnormal = 1;
        u.l = 0x800000 | ((xm & 0xffff) << 7) | (x->l.frac2 >> 25);
        e = 0x3f80 - (xm >> 16);
        round = u.l & (1 << e);
        sticky = (u.l & ((1 << e) - 1)) | (x->l.frac2 & 0x1ffffff) |
            x->l.frac3 | x->l.frac4;
        u.l >>= e + 1;
    } else {
        /* x is in the normal range for single */
        u.l = ((xm - 0x3f800000) << 7) | (x->l.frac2 >> 25);
        round = x->l.frac2 & 0x1000000;
        sticky = (x->l.frac2 & 0xffffff) | x->l.frac3 | 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 & 1)))) {
            /* round up and check for overflow */
            if (++u.l >= 0x7f800000)
                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 |= (x->l.msw & 0x80000000);
    if ((fsr & FSR_CEXC) & (fsr >> 23)) {
        __quad_setfsrp(&fsr);
        __quad_fqtos(x, &u.f);
    } else {
        fsr |= (fsr & 0x1f) << 5;
        __quad_setfsrp(&fsr);
    }
    return (u.f);
}