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/arch/mips/math-emu/dp_add.c

https://bitbucket.org/evzijst/gittest
C | 183 lines | 114 code | 29 blank | 40 comment | 19 complexity | 502ca9623b829d85ded25dbfe3316dbe MD5 | raw file
  1/* IEEE754 floating point arithmetic
  2 * double precision: common utilities
  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
 29#include "ieee754dp.h"
 30
 31ieee754dp ieee754dp_add(ieee754dp x, ieee754dp y)
 32{
 33	COMPXDP;
 34	COMPYDP;
 35
 36	EXPLODEXDP;
 37	EXPLODEYDP;
 38
 39	CLEARCX;
 40
 41	FLUSHXDP;
 42	FLUSHYDP;
 43
 44	switch (CLPAIR(xc, yc)) {
 45	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN):
 46	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN):
 47	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN):
 48	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN):
 49	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN):
 50	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN):
 51	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN):
 52	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO):
 53	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM):
 54	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM):
 55	case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF):
 56		SETCX(IEEE754_INVALID_OPERATION);
 57		return ieee754dp_nanxcpt(ieee754dp_indef(), "add", x, y);
 58
 59	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN):
 60	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN):
 61	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN):
 62	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN):
 63		return y;
 64
 65	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN):
 66	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO):
 67	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM):
 68	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM):
 69	case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF):
 70		return x;
 71
 72
 73		/* Infinity handling
 74		 */
 75
 76	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF):
 77		if (xs == ys)
 78			return x;
 79		SETCX(IEEE754_INVALID_OPERATION);
 80		return ieee754dp_xcpt(ieee754dp_indef(), "add", x, y);
 81
 82	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF):
 83	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF):
 84	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF):
 85		return y;
 86
 87	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO):
 88	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM):
 89	case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM):
 90		return x;
 91
 92		/* Zero handling
 93		 */
 94
 95	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO):
 96		if (xs == ys)
 97			return x;
 98		else
 99			return ieee754dp_zero(ieee754_csr.rm ==
100					      IEEE754_RD);
101
102	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO):
103	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO):
104		return x;
105
106	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM):
107	case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM):
108		return y;
109
110	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM):
111		DPDNORMX;
112
113		/* FALL THROUGH */
114
115	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM):
116		DPDNORMY;
117		break;
118
119	case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM):
120		DPDNORMX;
121		break;
122
123	case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM):
124		break;
125	}
126	assert(xm & DP_HIDDEN_BIT);
127	assert(ym & DP_HIDDEN_BIT);
128
129	/* provide guard,round and stick bit space */
130	xm <<= 3;
131	ym <<= 3;
132
133	if (xe > ye) {
134		/* have to shift y fraction right to align
135		 */
136		int s = xe - ye;
137		ym = XDPSRS(ym, s);
138		ye += s;
139	} else if (ye > xe) {
140		/* have to shift x fraction right to align
141		 */
142		int s = ye - xe;
143		xm = XDPSRS(xm, s);
144		xe += s;
145	}
146	assert(xe == ye);
147	assert(xe <= DP_EMAX);
148
149	if (xs == ys) {
150		/* generate 28 bit result of adding two 27 bit numbers
151		 * leaving result in xm,xs,xe
152		 */
153		xm = xm + ym;
154		xe = xe;
155		xs = xs;
156
157		if (xm >> (DP_MBITS + 1 + 3)) {	/* carry out */
158			xm = XDPSRS1(xm);
159			xe++;
160		}
161	} else {
162		if (xm >= ym) {
163			xm = xm - ym;
164			xe = xe;
165			xs = xs;
166		} else {
167			xm = ym - xm;
168			xe = xe;
169			xs = ys;
170		}
171		if (xm == 0)
172			return ieee754dp_zero(ieee754_csr.rm ==
173					      IEEE754_RD);
174
175		/* normalize to rounding precision */
176		while ((xm >> (DP_MBITS + 3)) == 0) {
177			xm <<= 1;
178			xe--;
179		}
180
181	}
182	DPNORMRET2(xs, xe, xm, "add", x, y);
183}