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 * 8 * This program is free software; you can distribute it and/or modify it 9 * under the terms of the GNU General Public License (Version 2) as 10 * published by the Free Software Foundation. 11 * 12 * This program is distributed in the hope it will be useful, but WITHOUT 13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 15 * for more details. 16 * 17 * You should have received a copy of the GNU General Public License along 18 * with this program; if not, write to the Free Software Foundation, Inc., 19 * 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 */ 21 22 #include "ieee754dp.h" 23 24 union ieee754dp ieee754dp_add(union ieee754dp x, union ieee754dp y) 25 { 26 int s; 27 28 COMPXDP; 29 COMPYDP; 30 31 EXPLODEXDP; 32 EXPLODEYDP; 33 34 ieee754_clearcx(); 35 36 FLUSHXDP; 37 FLUSHYDP; 38 39 switch (CLPAIR(xc, yc)) { 40 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_QNAN): 41 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_SNAN): 42 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_SNAN): 43 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_SNAN): 44 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_SNAN): 45 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_SNAN): 46 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_SNAN): 47 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_ZERO): 48 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_NORM): 49 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_DNORM): 50 case CLPAIR(IEEE754_CLASS_SNAN, IEEE754_CLASS_INF): 51 ieee754_setcx(IEEE754_INVALID_OPERATION); 52 return ieee754dp_nanxcpt(ieee754dp_indef()); 53 54 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_QNAN): 55 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_QNAN): 56 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_QNAN): 57 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_QNAN): 58 return y; 59 60 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_QNAN): 61 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_ZERO): 62 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_NORM): 63 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_DNORM): 64 case CLPAIR(IEEE754_CLASS_QNAN, IEEE754_CLASS_INF): 65 return x; 66 67 68 /* 69 * Infinity handling 70 */ 71 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_INF): 72 if (xs == ys) 73 return x; 74 ieee754_setcx(IEEE754_INVALID_OPERATION); 75 return ieee754dp_indef(); 76 77 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_INF): 78 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_INF): 79 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_INF): 80 return y; 81 82 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_ZERO): 83 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_NORM): 84 case CLPAIR(IEEE754_CLASS_INF, IEEE754_CLASS_DNORM): 85 return x; 86 87 /* 88 * Zero handling 89 */ 90 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_ZERO): 91 if (xs == ys) 92 return x; 93 else 94 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD); 95 96 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_ZERO): 97 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_ZERO): 98 return x; 99 100 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_NORM): 101 case CLPAIR(IEEE754_CLASS_ZERO, IEEE754_CLASS_DNORM): 102 return y; 103 104 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_DNORM): 105 DPDNORMX; 106 107 /* FALL THROUGH */ 108 109 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_DNORM): 110 DPDNORMY; 111 break; 112 113 case CLPAIR(IEEE754_CLASS_DNORM, IEEE754_CLASS_NORM): 114 DPDNORMX; 115 break; 116 117 case CLPAIR(IEEE754_CLASS_NORM, IEEE754_CLASS_NORM): 118 break; 119 } 120 assert(xm & DP_HIDDEN_BIT); 121 assert(ym & DP_HIDDEN_BIT); 122 123 /* 124 * Provide guard,round and stick bit space. 125 */ 126 xm <<= 3; 127 ym <<= 3; 128 129 if (xe > ye) { 130 /* 131 * Have to shift y fraction right to align. 132 */ 133 s = xe - ye; 134 ym = XDPSRS(ym, s); 135 ye += s; 136 } else if (ye > xe) { 137 /* 138 * Have to shift x fraction right to align. 139 */ 140 s = ye - xe; 141 xm = XDPSRS(xm, s); 142 xe += s; 143 } 144 assert(xe == ye); 145 assert(xe <= DP_EMAX); 146 147 if (xs == ys) { 148 /* 149 * Generate 28 bit result of adding two 27 bit numbers 150 * leaving result in xm, xs and xe. 151 */ 152 xm = xm + ym; 153 xe = xe; 154 xs = xs; 155 156 if (xm >> (DP_FBITS + 1 + 3)) { /* carry out */ 157 xm = XDPSRS1(xm); 158 xe++; 159 } 160 } else { 161 if (xm >= ym) { 162 xm = xm - ym; 163 xe = xe; 164 xs = xs; 165 } else { 166 xm = ym - xm; 167 xe = xe; 168 xs = ys; 169 } 170 if (xm == 0) 171 return ieee754dp_zero(ieee754_csr.rm == FPU_CSR_RD); 172 173 /* 174 * Normalize to rounding precision. 175 */ 176 while ((xm >> (DP_FBITS + 3)) == 0) { 177 xm <<= 1; 178 xe--; 179 } 180 } 181 182 return ieee754dp_format(xs, xe, xm); 183 } 184