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awilliam
GitHub Repository: awilliam/linux-vfio
 Path: blob/master/arch/mips/math-emu/dp_div.c
10818 views
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/* IEEE754 floating point arithmetic

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 * double precision: common utilities

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 */

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/*

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 * MIPS floating point support

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 * Copyright (C) 1994-2000 Algorithmics Ltd.

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 *

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 * ########################################################################

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 *

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 *  This program is free software; you can distribute it and/or modify it

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 *  under the terms of the GNU General Public License (Version 2) as

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 *  published by the Free Software Foundation.

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 *

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 *  This program is distributed in the hope it will be useful, but WITHOUT

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 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or

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 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

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 *  for more details.

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 *

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 *  You should have received a copy of the GNU General Public License along

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 *  with this program; if not, write to the Free Software Foundation, Inc.,

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 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.

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 *

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 * ########################################################################

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 */

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#include "ieee754dp.h"

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ieee754dp ieee754dp_div(ieee754dp x, ieee754dp y)

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{

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	COMPXDP;

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	COMPYDP;

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	EXPLODEXDP;

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	EXPLODEYDP;

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	CLEARCX;

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	FLUSHXDP;

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	FLUSHYDP;

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	switch (CLPAIR(xc, yc)) {

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	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):

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	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):

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	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):

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	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):

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	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):

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	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):

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	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):

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	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):

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	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):

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	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):

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	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):

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		SETCX(IEEE754_INVALID_OPERATION);

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		return ieee754dp_nanxcpt(ieee754dp_indef(), "div", x, y);

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	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):

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	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):

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	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):

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	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):

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		return y;

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	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):

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	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):

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	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):

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	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):

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	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):

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		return x;

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		/* Infinity handling

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		 */

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	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):

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		SETCX(IEEE754_INVALID_OPERATION);

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		return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);

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	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):

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	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):

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	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):

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		return ieee754dp_zero(xs ^ ys);

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	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):

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	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):

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	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):

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		return ieee754dp_inf(xs ^ ys);

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		/* Zero handling

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		 */

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	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):

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		SETCX(IEEE754_INVALID_OPERATION);

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		return ieee754dp_xcpt(ieee754dp_indef(), "div", x, y);

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	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):

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	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):

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		SETCX(IEEE754_ZERO_DIVIDE);

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		return ieee754dp_xcpt(ieee754dp_inf(xs ^ ys), "div", x, y);

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	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):

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	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):

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		return ieee754dp_zero(xs == ys ? 0 : 1);

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	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):

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		DPDNORMX;

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	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):

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		DPDNORMY;

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		break;

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	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):

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		DPDNORMX;

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		break;

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	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):

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		break;

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	}

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	assert(xm & DP_HIDDEN_BIT);

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	assert(ym & DP_HIDDEN_BIT);

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	/* provide rounding space */

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	xm <<= 3;

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	ym <<= 3;

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	{

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		/* now the dirty work */

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		u64 rm = 0;

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		int re = xe - ye;

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		u64 bm;

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		for (bm = DP_MBIT(DP_MBITS + 2); bm; bm >>= 1) {

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			if (xm >= ym) {

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				xm -= ym;

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				rm |= bm;

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				if (xm == 0)

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					break;

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			}

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			xm <<= 1;

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		}

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		rm <<= 1;

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		if (xm)

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			rm |= 1;	/* have remainder, set sticky */

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		assert(rm);

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		/* normalise rm to rounding precision ?

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		 */

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		while ((rm >> (DP_MBITS + 3)) == 0) {

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			rm <<= 1;

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			re--;

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		}

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		DPNORMRET2(xs == ys ? 0 : 1, re, rm, "div", x, y);

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	}

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}

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