[deliverable/linux.git] / arch / mips / math-emu / ieee754sp.c

/* 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 <linux/compiler.h>

#include "ieee754sp.h"

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

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

static inline int ieee754sp_issnan(union ieee754sp x)
{
	assert(ieee754sp_isnan(x));
	return (SPMANT(x) & SP_MBIT(SP_FBITS-1));
}


union ieee754sp __cold ieee754sp_nanxcpt(union ieee754sp r)
{
	assert(ieee754sp_isnan(r));

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

	if (!ieee754_setandtestcx(IEEE754_INVALID_OPERATION)) {
		/* not enabled convert to a quiet NaN */
		SPMANT(r) &= (~SP_MBIT(SP_FBITS-1));
		if (ieee754sp_isnan(r))
			return r;
		else
			return ieee754sp_indef();
	}

	return r;
}

static unsigned ieee754sp_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.
 */
union ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
{
	assert(xm);		/* we don't gen exact zeros (probably should) */

	assert((xm >> (SP_FBITS + 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) {
			ieee754_setcx(IEEE754_UNDERFLOW);
			ieee754_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 &&
		    ieee754sp_get_rounding(sn, xm) >> (SP_FBITS + 1 + 3))
		{
			/* Not tiny after rounding */
			ieee754_setcx(IEEE754_INEXACT);
			xm = ieee754sp_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)) {
		ieee754_setcx(IEEE754_INEXACT);
		if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
			ieee754_setcx(IEEE754_UNDERFLOW);
		}

		/* inexact must round of 3 bits
		 */
		xm = ieee754sp_get_rounding(sn, xm);
		/* adjust exponent for rounding add overflowing
		 */
		if (xm >> (SP_FBITS + 1 + 3)) {
			/* add causes mantissa overflow */
			xm >>= 1;
			xe++;
		}
	}
	/* strip grs bits */
	xm >>= 3;

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

	if (xe > SP_EMAX) {
		ieee754_setcx(IEEE754_OVERFLOW);
		ieee754_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)
			ieee754_setcx(IEEE754_UNDERFLOW);
		return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
	} else {
		assert((xm >> (SP_FBITS + 1)) == 0);	/* no execess */
		assert(xm & SP_HIDDEN_BIT);

		return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
	}
}
Commit	Line	Data
1da177e4 LT	1	/* IEEE754 floating point arithmetic
	2	* single precision
	3	*/
	4	/*
	5	* MIPS floating point support
	6	* Copyright (C) 1994-2000 Algorithmics Ltd.
1da177e4 LT	7	*
	8	* ########################################################################
	9	*
	10	* This program is free software; you can distribute it and/or modify it
	11	* under the terms of the GNU General Public License (Version 2) as
	12	* published by the Free Software Foundation.
	13	*
	14	* This program is distributed in the hope it will be useful, but WITHOUT
	15	* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
	16	* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	17	* for more details.
	18	*
	19	* You should have received a copy of the GNU General Public License along
	20	* with this program; if not, write to the Free Software Foundation, Inc.,
	21	* 59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
	22	*
	23	* ########################################################################
	24	*/
	25
cae55066	26	#include <linux/compiler.h>
1da177e4 LT	27
	28	#include "ieee754sp.h"
	29
2209bcb1	30	int ieee754sp_class(union ieee754sp x)
1da177e4 LT	31	{
	32	COMPXSP;
	33	EXPLODEXSP;
	34	return xc;
	35	}
	36
2209bcb1	37	int ieee754sp_isnan(union ieee754sp x)
1da177e4 LT	38	{
	39	return ieee754sp_class(x) >= IEEE754_CLASS_SNAN;
	40	}
	41
f71baa11	42	static inline int ieee754sp_issnan(union ieee754sp x)
1da177e4 LT	43	{
1da177e4 LT	44	assert(ieee754sp_isnan(x));
ad8fb553	45	return (SPMANT(x) & SP_MBIT(SP_FBITS-1));
1da177e4 LT	46	}
	47
	48
90efba36	49	union ieee754sp __cold ieee754sp_nanxcpt(union ieee754sp r)
1da177e4	50	{
1da177e4 LT	51	assert(ieee754sp_isnan(r));
	52
	53	if (!ieee754sp_issnan(r)) /* QNAN does not cause invalid op !! */
	54	return r;
	55
9e8bad1f	56	if (!ieee754_setandtestcx(IEEE754_INVALID_OPERATION)) {
1da177e4	57	/* not enabled convert to a quiet NaN */
ad8fb553	58	SPMANT(r) &= (~SP_MBIT(SP_FBITS-1));
1da177e4 LT	59	if (ieee754sp_isnan(r))
	60	return r;
	61	else
	62	return ieee754sp_indef();
	63	}
	64
90efba36	65	return r;
1da177e4 LT	66	}
1da177e4 LT	67
de2fc342	68	static unsigned ieee754sp_get_rounding(int sn, unsigned xm)
1da177e4 LT	69	{
	70	/* inexact must round of 3 bits
	71	*/
	72	if (xm & (SP_MBIT(3) - 1)) {
	73	switch (ieee754_csr.rm) {
	74	case IEEE754_RZ:
	75	break;
	76	case IEEE754_RN:
	77	xm += 0x3 + ((xm >> 3) & 1);
	78	/* xm += (xm&0x8)?0x4:0x3 */
	79	break;
	80	case IEEE754_RU: /* toward +Infinity */
	81	if (!sn) /* ?? */
	82	xm += 0x8;
	83	break;
	84	case IEEE754_RD: /* toward -Infinity */
70342287	85	if (sn) /* ?? */
1da177e4 LT	86	xm += 0x8;
	87	break;
	88	}
	89	}
	90	return xm;
	91	}
	92
	93
	94	/* generate a normal/denormal number with over,under handling
	95	* sn is sign
	96	* xe is an unbiased exponent
	97	* xm is 3bit extended precision value.
	98	*/
2209bcb1	99	union ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
1da177e4 LT	100	{
	101	assert(xm); /* we don't gen exact zeros (probably should) */
	102
ad8fb553	103	assert((xm >> (SP_FBITS + 1 + 3)) == 0); /* no execess */
1da177e4 LT	104	assert(xm & (SP_HIDDEN_BIT << 3));
	105
	106	if (xe < SP_EMIN) {
	107	/* strip lower bits */
	108	int es = SP_EMIN - xe;
	109
	110	if (ieee754_csr.nod) {
9e8bad1f RB	111	ieee754_setcx(IEEE754_UNDERFLOW);
9e8bad1f RB	112	ieee754_setcx(IEEE754_INEXACT);
1da177e4 LT	113
	114	switch(ieee754_csr.rm) {
	115	case IEEE754_RN:
1da177e4 LT	116	case IEEE754_RZ:
	117	return ieee754sp_zero(sn);
	118	case IEEE754_RU: /* toward +Infinity */
47fa0c02	119	if (sn == 0)
1da177e4 LT	120	return ieee754sp_min(0);
	121	else
	122	return ieee754sp_zero(1);
	123	case IEEE754_RD: /* toward -Infinity */
47fa0c02	124	if (sn == 0)
1da177e4 LT	125	return ieee754sp_zero(0);
	126	else
	127	return ieee754sp_min(1);
	128	}
	129	}
	130
de2fc342 RB	131	if (xe == SP_EMIN - 1 &&
de2fc342 RB	132	ieee754sp_get_rounding(sn, xm) >> (SP_FBITS + 1 + 3))
1da177e4 LT	133	{
1da177e4 LT	134	/* Not tiny after rounding */
9e8bad1f	135	ieee754_setcx(IEEE754_INEXACT);
de2fc342	136	xm = ieee754sp_get_rounding(sn, xm);
1da177e4 LT	137	xm >>= 1;
	138	/* Clear grs bits */
	139	xm &= ~(SP_MBIT(3) - 1);
	140	xe++;
47fa0c02	141	} else {
1da177e4 LT	142	/* sticky right shift es bits
	143	*/
	144	SPXSRSXn(es);
	145	assert((xm & (SP_HIDDEN_BIT << 3)) == 0);
	146	assert(xe == SP_EMIN);
	147	}
	148	}
	149	if (xm & (SP_MBIT(3) - 1)) {
9e8bad1f	150	ieee754_setcx(IEEE754_INEXACT);
1da177e4	151	if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
9e8bad1f	152	ieee754_setcx(IEEE754_UNDERFLOW);
1da177e4 LT	153	}
	154
	155	/* inexact must round of 3 bits
	156	*/
de2fc342	157	xm = ieee754sp_get_rounding(sn, xm);
1da177e4 LT	158	/* adjust exponent for rounding add overflowing
1da177e4 LT	159	*/
ad8fb553	160	if (xm >> (SP_FBITS + 1 + 3)) {
1da177e4 LT	161	/* add causes mantissa overflow */
	162	xm >>= 1;
	163	xe++;
	164	}
	165	}
	166	/* strip grs bits */
	167	xm >>= 3;
	168
ad8fb553	169	assert((xm >> (SP_FBITS + 1)) == 0); /* no execess */
1da177e4 LT	170	assert(xe >= SP_EMIN);
	171
	172	if (xe > SP_EMAX) {
9e8bad1f RB	173	ieee754_setcx(IEEE754_OVERFLOW);
9e8bad1f RB	174	ieee754_setcx(IEEE754_INEXACT);
1da177e4 LT	175	/* -O can be table indexed by (rm,sn) */
	176	switch (ieee754_csr.rm) {
	177	case IEEE754_RN:
	178	return ieee754sp_inf(sn);
	179	case IEEE754_RZ:
	180	return ieee754sp_max(sn);
	181	case IEEE754_RU: /* toward +Infinity */
	182	if (sn == 0)
	183	return ieee754sp_inf(0);
	184	else
	185	return ieee754sp_max(1);
	186	case IEEE754_RD: /* toward -Infinity */
	187	if (sn == 0)
	188	return ieee754sp_max(0);
	189	else
	190	return ieee754sp_inf(1);
	191	}
	192	}
	193	/* gen norm/denorm/zero */
	194
	195	if ((xm & SP_HIDDEN_BIT) == 0) {
	196	/* we underflow (tiny/zero) */
	197	assert(xe == SP_EMIN);
	198	if (ieee754_csr.mx & IEEE754_UNDERFLOW)
9e8bad1f	199	ieee754_setcx(IEEE754_UNDERFLOW);
1da177e4 LT	200	return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
1da177e4 LT	201	} else {
ad8fb553	202	assert((xm >> (SP_FBITS + 1)) == 0); /* no execess */
1da177e4 LT	203	assert(xm & SP_HIDDEN_BIT);
	204
	205	return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
	206	}
	207	}