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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 | /*---------------------------------------------------------------------------+ | reg_add_sub.c | | | | Functions to add or subtract two registers and put the result in a third. | | | | Copyright (C) 1992,1993 | | W. Metzenthen, 22 Parker St, Ormond, Vic 3163, | | Australia. E-mail billm@vaxc.cc.monash.edu.au | | | | | +---------------------------------------------------------------------------*/ /*---------------------------------------------------------------------------+ | For each function, the destination may be any FPU_REG, including one of | | the source FPU_REGs. | +---------------------------------------------------------------------------*/ #include "exception.h" #include "reg_constant.h" #include "fpu_emu.h" #include "control_w.h" #include "fpu_system.h" int reg_add(FPU_REG const *a, FPU_REG const *b, FPU_REG *dest, int control_w) { char saved_sign = dest->sign; int diff; if ( !(a->tag | b->tag) ) { /* Both registers are valid */ if (!(a->sign ^ b->sign)) { /* signs are the same */ dest->sign = a->sign; if ( reg_u_add(a, b, dest, control_w) ) { dest->sign = saved_sign; return 1; } return 0; } /* The signs are different, so do a subtraction */ diff = a->exp - b->exp; if (!diff) { diff = a->sigh - b->sigh; /* Works only if ms bits are identical */ if (!diff) { diff = a->sigl > b->sigl; if (!diff) diff = -(a->sigl < b->sigl); } } if (diff > 0) { dest->sign = a->sign; if ( reg_u_sub(a, b, dest, control_w) ) { dest->sign = saved_sign; return 1; } } else if ( diff == 0 ) { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(&CONST_Z, dest); /* sign depends upon rounding mode */ dest->sign = ((control_w & CW_RC) != RC_DOWN) ? SIGN_POS : SIGN_NEG; } else { dest->sign = b->sign; if ( reg_u_sub(b, a, dest, control_w) ) { dest->sign = saved_sign; return 1; } } return 0; } else { if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) ) { return real_2op_NaN(a, b, dest); } else if (a->tag == TW_Zero) { if (b->tag == TW_Zero) { char different_signs = a->sign ^ b->sign; /* Both are zero, result will be zero. */ reg_move(a, dest); if (different_signs) { /* Signs are different. */ /* Sign of answer depends upon rounding mode. */ dest->sign = ((control_w & CW_RC) != RC_DOWN) ? SIGN_POS : SIGN_NEG; } } else { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(b, dest); } return 0; } else if (b->tag == TW_Zero) { #ifdef DENORM_OPERAND if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(a, dest); return 0; } else if (a->tag == TW_Infinity) { if (b->tag != TW_Infinity) { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(a, dest); return 0; } if (a->sign == b->sign) { /* They are both + or - infinity */ reg_move(a, dest); return 0; } return arith_invalid(dest); /* Infinity-Infinity is undefined. */ } else if (b->tag == TW_Infinity) { #ifdef DENORM_OPERAND if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(b, dest); return 0; } } #ifdef PARANOID EXCEPTION(EX_INTERNAL|0x101); #endif return 1; } /* Subtract b from a. (a-b) -> dest */ int reg_sub(FPU_REG const *a, FPU_REG const *b, FPU_REG *dest, int control_w) { char saved_sign = dest->sign; int diff; if ( !(a->tag | b->tag) ) { /* Both registers are valid */ diff = a->exp - b->exp; if (!diff) { diff = a->sigh - b->sigh; /* Works only if ms bits are identical */ if (!diff) { diff = a->sigl > b->sigl; if (!diff) diff = -(a->sigl < b->sigl); } } switch (a->sign*2 + b->sign) { case 0: /* P - P */ case 3: /* N - N */ if (diff > 0) { /* |a| > |b| */ dest->sign = a->sign; if ( reg_u_sub(a, b, dest, control_w) ) { dest->sign = saved_sign; return 1; } return 0; } else if ( diff == 0 ) { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(&CONST_Z, dest); /* sign depends upon rounding mode */ dest->sign = ((control_w & CW_RC) != RC_DOWN) ? SIGN_POS : SIGN_NEG; } else { dest->sign = a->sign ^ SIGN_POS^SIGN_NEG; if ( reg_u_sub(b, a, dest, control_w) ) { dest->sign = saved_sign; return 1; } } break; case 1: /* P - N */ dest->sign = SIGN_POS; if ( reg_u_add(a, b, dest, control_w) ) { dest->sign = saved_sign; return 1; } break; case 2: /* N - P */ dest->sign = SIGN_NEG; if ( reg_u_add(a, b, dest, control_w) ) { dest->sign = saved_sign; return 1; } break; } return 0; } else { if ( (a->tag == TW_NaN) || (b->tag == TW_NaN) ) { return real_2op_NaN(b, a, dest); } else if (b->tag == TW_Zero) { if (a->tag == TW_Zero) { char same_signs = !(a->sign ^ b->sign); /* Both are zero, result will be zero. */ reg_move(a, dest); /* Answer for different signs. */ if (same_signs) { /* Sign depends upon rounding mode */ dest->sign = ((control_w & CW_RC) != RC_DOWN) ? SIGN_POS : SIGN_NEG; } } else { #ifdef DENORM_OPERAND if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(a, dest); } return 0; } else if (a->tag == TW_Zero) { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(b, dest); dest->sign ^= SIGN_POS^SIGN_NEG; return 0; } else if (a->tag == TW_Infinity) { if (b->tag != TW_Infinity) { #ifdef DENORM_OPERAND if ( (b->tag == TW_Valid) && (b->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(a, dest); return 0; } /* Both args are Infinity */ if (a->sign == b->sign) { /* Infinity-Infinity is undefined. */ return arith_invalid(dest); } reg_move(a, dest); return 0; } else if (b->tag == TW_Infinity) { #ifdef DENORM_OPERAND if ( (a->tag == TW_Valid) && (a->exp <= EXP_UNDER) && denormal_operand() ) return 1; #endif DENORM_OPERAND reg_move(b, dest); dest->sign ^= SIGN_POS^SIGN_NEG; return 0; } } #ifdef PARANOID EXCEPTION(EX_INTERNAL|0x110); #endif return 1; } |