/* IEEE754 floating point arithmetic
 * single precision
 */
/*
 * MIPS floating point support
 * Copyright (C) 1994-2000 Algorithmics Ltd.
 *
 * ########################################################################
 *
 *  This program is free software; you can distribute it and/or modify it
 *  under the terms of the GNU General Public License (Version 2) as
 *  published by the Free Software Foundation.
 *
 *  This program is distributed in the hope it will be useful, but WITHOUT
 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 *  for more details.
 *
 *  You should have received a copy of the GNU General Public License along
 *  with this program; if not, write to the Free Software Foundation, Inc.,
 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
 *
 * ########################################################################
 */


#include "ieee754sp.h"

int ieee754sp_class(ieee754sp x)
{
        COMPXSP;
        EXPLODEXSP;
        return xc;
}

int ieee754sp_isnan(ieee754sp x)
{
        return ieee754sp_class(x) >= IEEE754_CLASS_SNAN;
}

int ieee754sp_issnan(ieee754sp x)
{
        assert(ieee754sp_isnan(x));
        return (SPMANT(x) & SP_MBIT(SP_MBITS-1));
}


ieee754sp ieee754sp_xcpt(ieee754sp r, const char *op, ...)
{
        struct ieee754xctx ax;

        if (!TSTX())
                return r;

        ax.op = op;
        ax.rt = IEEE754_RT_SP;
        ax.rv.sp = r;
        va_start(ax.ap, op);
        ieee754_xcpt(&ax);
        va_end(ax.ap);
        return ax.rv.sp;
}

ieee754sp ieee754sp_nanxcpt(ieee754sp r, const char *op, ...)
{
        struct ieee754xctx ax;

        assert(ieee754sp_isnan(r));

        if (!ieee754sp_issnan(r))       /* QNAN does not cause invalid op !! */
                return r;

        if (!SETANDTESTCX(IEEE754_INVALID_OPERATION)) {
                /* not enabled convert to a quiet NaN */
                SPMANT(r) &= (~SP_MBIT(SP_MBITS-1));
                if (ieee754sp_isnan(r))
                        return r;
                else
                        return ieee754sp_indef();
        }

        ax.op = op;
        ax.rt = 0;
        ax.rv.sp = r;
        va_start(ax.ap, op);
        ieee754_xcpt(&ax);
        va_end(ax.ap);
        return ax.rv.sp;
}

ieee754sp ieee754sp_bestnan(ieee754sp x, ieee754sp y)
{
        assert(ieee754sp_isnan(x));
        assert(ieee754sp_isnan(y));

        if (SPMANT(x) > SPMANT(y))
                return x;
        else
                return y;
}


static unsigned get_rounding(int sn, unsigned xm)
{
        /* inexact must round of 3 bits
         */
        if (xm & (SP_MBIT(3) - 1)) {
                switch (ieee754_csr.rm) {
                case IEEE754_RZ:
                        break;
                case IEEE754_RN:
                        xm += 0x3 + ((xm >> 3) & 1);
                        /* xm += (xm&0x8)?0x4:0x3 */
                        break;
                case IEEE754_RU:        /* toward +Infinity */
                        if (!sn)        /* ?? */
                                xm += 0x8;
                        break;
                case IEEE754_RD:        /* toward -Infinity */
                        if (sn) /* ?? */
                                xm += 0x8;
                        break;
                }
        }
        return xm;
}


/* generate a normal/denormal number with over,under handling
 * sn is sign
 * xe is an unbiased exponent
 * xm is 3bit extended precision value.
 */
ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
{
        assert(xm);             /* we don't gen exact zeros (probably should) */

        assert((xm >> (SP_MBITS + 1 + 3)) == 0);        /* no execess */
        assert(xm & (SP_HIDDEN_BIT << 3));

        if (xe < SP_EMIN) {
                /* strip lower bits */
                int es = SP_EMIN - xe;

                if (ieee754_csr.nod) {
                        SETCX(IEEE754_UNDERFLOW);
                        SETCX(IEEE754_INEXACT);

                        switch(ieee754_csr.rm) {
                        case IEEE754_RN:
                        case IEEE754_RZ:
                                return ieee754sp_zero(sn);
                        case IEEE754_RU:      /* toward +Infinity */
                                if(sn == 0)
                                        return ieee754sp_min(0);
                                else
                                        return ieee754sp_zero(1);
                        case IEEE754_RD:      /* toward -Infinity */
                                if(sn == 0)
                                        return ieee754sp_zero(0);
                                else
                                        return ieee754sp_min(1);
                        }
                }

                if (xe == SP_EMIN - 1
                                && get_rounding(sn, xm) >> (SP_MBITS + 1 + 3))
                {
                        /* Not tiny after rounding */
                        SETCX(IEEE754_INEXACT);
                        xm = get_rounding(sn, xm);
                        xm >>= 1;
                        /* Clear grs bits */
                        xm &= ~(SP_MBIT(3) - 1);
                        xe++;
                }
                else {
                        /* sticky right shift es bits
                         */
                        SPXSRSXn(es);
                        assert((xm & (SP_HIDDEN_BIT << 3)) == 0);
                        assert(xe == SP_EMIN);
                }
        }
        if (xm & (SP_MBIT(3) - 1)) {
                SETCX(IEEE754_INEXACT);
                if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
                        SETCX(IEEE754_UNDERFLOW);
                }

                /* inexact must round of 3 bits
                 */
                xm = get_rounding(sn, xm);
                /* adjust exponent for rounding add overflowing
                 */
                if (xm >> (SP_MBITS + 1 + 3)) {
                        /* add causes mantissa overflow */
                        xm >>= 1;
                        xe++;
                }
        }
        /* strip grs bits */
        xm >>= 3;

        assert((xm >> (SP_MBITS + 1)) == 0);    /* no execess */
        assert(xe >= SP_EMIN);

        if (xe > SP_EMAX) {
                SETCX(IEEE754_OVERFLOW);
                SETCX(IEEE754_INEXACT);
                /* -O can be table indexed by (rm,sn) */
                switch (ieee754_csr.rm) {
                case IEEE754_RN:
                        return ieee754sp_inf(sn);
                case IEEE754_RZ:
                        return ieee754sp_max(sn);
                case IEEE754_RU:        /* toward +Infinity */
                        if (sn == 0)
                                return ieee754sp_inf(0);
                        else
                                return ieee754sp_max(1);
                case IEEE754_RD:        /* toward -Infinity */
                        if (sn == 0)
                                return ieee754sp_max(0);
                        else
                                return ieee754sp_inf(1);
                }
        }
        /* gen norm/denorm/zero */

        if ((xm & SP_HIDDEN_BIT) == 0) {
                /* we underflow (tiny/zero) */
                assert(xe == SP_EMIN);
                if (ieee754_csr.mx & IEEE754_UNDERFLOW)
                        SETCX(IEEE754_UNDERFLOW);
                return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
        } else {
                assert((xm >> (SP_MBITS + 1)) == 0);    /* no execess */
                assert(xm & SP_HIDDEN_BIT);

                return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
        }
}