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
30ieee754sp ieee754sp_add(ieee754sp x, ieee754sp y)
31{
32	COMPXSP;
33	COMPYSP;
34
35	EXPLODEXSP;
36	EXPLODEYSP;
37
38	CLEARCX;
39
40	FLUSHXSP;
41	FLUSHYSP;
42
43	switch (CLPAIR(xc, yc)) {
44	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
45	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
46	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
47	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
48	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
49	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
50	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
51	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
52	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
53	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
54	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
55		SETCX(IEEE754_INVALID_OPERATION);
56		return ieee754sp_nanxcpt(ieee754sp_indef(), "add", x, y);
57
58	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
59	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
60	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
61	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
62		return y;
63
64	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
65	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
66	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
67	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
68	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
69		return x;
70
71
72		/* Infinity handling
73		 */
74
75	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
76		if (xs == ys)
77			return x;
78		SETCX(IEEE754_INVALID_OPERATION);
79		return ieee754sp_xcpt(ieee754sp_indef(), "add", x, y);
80
81	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
82	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
83	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
84		return y;
85
86	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
87	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
88	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
89		return x;
90
91		/* Zero handling
92		 */
93
94	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
95		if (xs == ys)
96			return x;
97		else
98			return ieee754sp_zero(ieee754_csr.rm ==
99					      IEEE754_RD);
100
101	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
102	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
103		return x;
104
105	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
106	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
107		return y;
108
109	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
110		SPDNORMX;
111
112	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
113		SPDNORMY;
114		break;
115
116	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
117		SPDNORMX;
118		break;
119
120	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
121		break;
122	}
123	assert(xm & SP_HIDDEN_BIT);
124	assert(ym & SP_HIDDEN_BIT);
125
126	/* provide guard,round and stick bit space */
127	xm <<= 3;
128	ym <<= 3;
129
130	if (xe > ye) {
131		/* have to shift y fraction right to align
132		 */
133		int s = xe - ye;
134		SPXSRSYn(s);
135	} else if (ye > xe) {
136		/* have to shift x fraction right to align
137		 */
138		int s = ye - xe;
139		SPXSRSXn(s);
140	}
141	assert(xe == ye);
142	assert(xe <= SP_EMAX);
143
144	if (xs == ys) {
145		/* generate 28 bit result of adding two 27 bit numbers
146		 * leaving result in xm,xs,xe
147		 */
148		xm = xm + ym;
149		xe = xe;
150		xs = xs;
151
152		if (xm >> (SP_MBITS + 1 + 3)) {	/* carry out */
153			SPXSRSX1();
154		}
155	} else {
156		if (xm >= ym) {
157			xm = xm - ym;
158			xe = xe;
159			xs = xs;
160		} else {
161			xm = ym - xm;
162			xe = xe;
163			xs = ys;
164		}
165		if (xm == 0)
166			return ieee754sp_zero(ieee754_csr.rm ==
167					      IEEE754_RD);
168
169		/* normalize in extended single precision */
170		while ((xm >> (SP_MBITS + 3)) == 0) {
171			xm <<= 1;
172			xe--;
173		}
174
175	}
176	SPNORMRET2(xs, xe, xm, "add", x, y);
177}
178