1/* IEEE754 floating point arithmetic
2 * single precision
3 */
4/*
5 * MIPS floating point support
6 * Copyright (C) 1994-2000 Algorithmics Ltd.
7 * http://www.algor.co.uk
8 *
9 * ########################################################################
10 *
11 *  This program is free software; you can distribute it and/or modify it
12 *  under the terms of the GNU General Public License (Version 2) as
13 *  published by the Free Software Foundation.
14 *
15 *  This program is distributed in the hope it will be useful, but WITHOUT
16 *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
17 *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
18 *  for more details.
19 *
20 *  You should have received a copy of the GNU General Public License along
21 *  with this program; if not, write to the Free Software Foundation, Inc.,
22 *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
23 *
24 * ########################################################################
25 */
26
27
28#include "ieee754sp.h"
29
30int ieee754sp_class(ieee754sp x)
31{
32	COMPXSP;
33	EXPLODEXSP;
34	return xc;
35}
36
37int ieee754sp_isnan(ieee754sp x)
38{
39	return ieee754sp_class(x) >= IEEE754_CLASS_SNAN;
40}
41
42int ieee754sp_issnan(ieee754sp x)
43{
44	assert(ieee754sp_isnan(x));
45	return (SPMANT(x) & SP_MBIT(SP_MBITS-1));
46}
47
48
49ieee754sp ieee754sp_xcpt(ieee754sp r, const char *op, ...)
50{
51	struct ieee754xctx ax;
52
53	if (!TSTX())
54		return r;
55
56	ax.op = op;
57	ax.rt = IEEE754_RT_SP;
58	ax.rv.sp = r;
59	va_start(ax.ap, op);
60	ieee754_xcpt(&ax);
61	return ax.rv.sp;
62}
63
64ieee754sp ieee754sp_nanxcpt(ieee754sp r, const char *op, ...)
65{
66	struct ieee754xctx ax;
67
68	assert(ieee754sp_isnan(r));
69
70	if (!ieee754sp_issnan(r))	/* QNAN does not cause invalid op !! */
71		return r;
72
73	if (!SETANDTESTCX(IEEE754_INVALID_OPERATION)) {
74		/* not enabled convert to a quiet NaN */
75		SPMANT(r) &= (~SP_MBIT(SP_MBITS-1));
76		if (ieee754sp_isnan(r))
77			return r;
78		else
79			return ieee754sp_indef();
80	}
81
82	ax.op = op;
83	ax.rt = 0;
84	ax.rv.sp = r;
85	va_start(ax.ap, op);
86	ieee754_xcpt(&ax);
87	return ax.rv.sp;
88}
89
90ieee754sp ieee754sp_bestnan(ieee754sp x, ieee754sp y)
91{
92	assert(ieee754sp_isnan(x));
93	assert(ieee754sp_isnan(y));
94
95	if (SPMANT(x) > SPMANT(y))
96		return x;
97	else
98		return y;
99}
100
101
102static unsigned get_rounding(int sn, unsigned xm)
103{
104	/* inexact must round of 3 bits
105	 */
106	if (xm & (SP_MBIT(3) - 1)) {
107		switch (ieee754_csr.rm) {
108		case IEEE754_RZ:
109			break;
110		case IEEE754_RN:
111			xm += 0x3 + ((xm >> 3) & 1);
112			/* xm += (xm&0x8)?0x4:0x3 */
113			break;
114		case IEEE754_RU:	/* toward +Infinity */
115			if (!sn)	/* ?? */
116				xm += 0x8;
117			break;
118		case IEEE754_RD:	/* toward -Infinity */
119			if (sn)	/* ?? */
120				xm += 0x8;
121			break;
122		}
123	}
124	return xm;
125}
126
127
128/* generate a normal/denormal number with over,under handling
129 * sn is sign
130 * xe is an unbiased exponent
131 * xm is 3bit extended precision value.
132 */
133ieee754sp ieee754sp_format(int sn, int xe, unsigned xm)
134{
135	assert(xm);		/* we don't gen exact zeros (probably should) */
136
137	assert((xm >> (SP_MBITS + 1 + 3)) == 0);	/* no execess */
138	assert(xm & (SP_HIDDEN_BIT << 3));
139
140	if (xe < SP_EMIN) {
141		/* strip lower bits */
142		int es = SP_EMIN - xe;
143
144		if (ieee754_csr.nod) {
145			SETCX(IEEE754_UNDERFLOW);
146			SETCX(IEEE754_INEXACT);
147
148			switch(ieee754_csr.rm) {
149			case IEEE754_RN:
150				return ieee754sp_zero(sn);
151			case IEEE754_RZ:
152				return ieee754sp_zero(sn);
153			case IEEE754_RU:      /* toward +Infinity */
154				if(sn == 0)
155					return ieee754sp_min(0);
156				else
157					return ieee754sp_zero(1);
158			case IEEE754_RD:      /* toward -Infinity */
159				if(sn == 0)
160					return ieee754sp_zero(0);
161				else
162					return ieee754sp_min(1);
163			}
164		}
165
166		if (xe == SP_EMIN - 1
167				&& get_rounding(sn, xm) >> (SP_MBITS + 1 + 3))
168		{
169			/* Not tiny after rounding */
170			SETCX(IEEE754_INEXACT);
171			xm = get_rounding(sn, xm);
172			xm >>= 1;
173			/* Clear grs bits */
174			xm &= ~(SP_MBIT(3) - 1);
175			xe++;
176		}
177		else {
178			/* sticky right shift es bits
179			 */
180			SPXSRSXn(es);
181			assert((xm & (SP_HIDDEN_BIT << 3)) == 0);
182			assert(xe == SP_EMIN);
183		}
184	}
185	if (xm & (SP_MBIT(3) - 1)) {
186		SETCX(IEEE754_INEXACT);
187		if ((xm & (SP_HIDDEN_BIT << 3)) == 0) {
188			SETCX(IEEE754_UNDERFLOW);
189		}
190
191		/* inexact must round of 3 bits
192		 */
193		xm = get_rounding(sn, xm);
194		/* adjust exponent for rounding add overflowing
195		 */
196		if (xm >> (SP_MBITS + 1 + 3)) {
197			/* add causes mantissa overflow */
198			xm >>= 1;
199			xe++;
200		}
201	}
202	/* strip grs bits */
203	xm >>= 3;
204
205	assert((xm >> (SP_MBITS + 1)) == 0);	/* no execess */
206	assert(xe >= SP_EMIN);
207
208	if (xe > SP_EMAX) {
209		SETCX(IEEE754_OVERFLOW);
210		SETCX(IEEE754_INEXACT);
211		/* -O can be table indexed by (rm,sn) */
212		switch (ieee754_csr.rm) {
213		case IEEE754_RN:
214			return ieee754sp_inf(sn);
215		case IEEE754_RZ:
216			return ieee754sp_max(sn);
217		case IEEE754_RU:	/* toward +Infinity */
218			if (sn == 0)
219				return ieee754sp_inf(0);
220			else
221				return ieee754sp_max(1);
222		case IEEE754_RD:	/* toward -Infinity */
223			if (sn == 0)
224				return ieee754sp_max(0);
225			else
226				return ieee754sp_inf(1);
227		}
228	}
229	/* gen norm/denorm/zero */
230
231	if ((xm & SP_HIDDEN_BIT) == 0) {
232		/* we underflow (tiny/zero) */
233		assert(xe == SP_EMIN);
234		if (ieee754_csr.mx & IEEE754_UNDERFLOW)
235			SETCX(IEEE754_UNDERFLOW);
236		return buildsp(sn, SP_EMIN - 1 + SP_EBIAS, xm);
237	} else {
238		assert((xm >> (SP_MBITS + 1)) == 0);	/* no execess */
239		assert(xm & SP_HIDDEN_BIT);
240
241		return buildsp(sn, xe + SP_EBIAS, xm & ~SP_HIDDEN_BIT);
242	}
243}
244