| 1 | /* i1620_fp.c: IBM 1620 floating point simulator\r |
| 2 | \r |
| 3 | Copyright (c) 2002-2008, Robert M. Supnik\r |
| 4 | \r |
| 5 | Permission is hereby granted, free of charge, to any person obtaining a\r |
| 6 | copy of this software and associated documentation files (the "Software"),\r |
| 7 | to deal in the Software without restriction, including without limitation\r |
| 8 | the rights to use, copy, modify, merge, publish, distribute, sublicense,\r |
| 9 | and/or sell copies of the Software, and to permit persons to whom the\r |
| 10 | Software is furnished to do so, subject to the following conditions:\r |
| 11 | \r |
| 12 | The above copyright notice and this permission notice shall be included in\r |
| 13 | all copies or substantial portions of the Software.\r |
| 14 | \r |
| 15 | THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR\r |
| 16 | IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,\r |
| 17 | FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL\r |
| 18 | ROBERT M SUPNIK BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER\r |
| 19 | IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN\r |
| 20 | CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.\r |
| 21 | \r |
| 22 | Except as contained in this notice, the name of Robert M Supnik shall not be\r |
| 23 | used in advertising or otherwise to promote the sale, use or other dealings\r |
| 24 | in this Software without prior written authorization from Robert M Supnik.\r |
| 25 | \r |
| 26 | The IBM 1620 uses a variable length floating point format, with a fixed\r |
| 27 | two digit decimal exponent and a variable length decimal mantissa:\r |
| 28 | \r |
| 29 | _ S_S\r |
| 30 | M.......MEE\r |
| 31 | \r |
| 32 | where S represents flag bits if the mantissa or exponent are negative.\r |
| 33 | \r |
| 34 | 31-May-2008 RMS Fixed add_field call (found by Peter Schorn)\r |
| 35 | */\r |
| 36 | \r |
| 37 | #include "i1620_defs.h"\r |
| 38 | \r |
| 39 | #define FP_LMAX 100 /* max fp mant lnt */\r |
| 40 | #define FP_EMAX 99 /* max fp exponent */\r |
| 41 | \r |
| 42 | /* Unpacked floating point operand */\r |
| 43 | \r |
| 44 | typedef struct {\r |
| 45 | int32 sign; /* 0 => +, 1 => - */\r |
| 46 | int32 exp; /* binary exponent */\r |
| 47 | uint32 lnt; /* mantissa length */\r |
| 48 | uint32 addr; /* mantissa addr */\r |
| 49 | uint32 zero; /* 0 => nz, 1 => zero */\r |
| 50 | } FPA;\r |
| 51 | \r |
| 52 | extern uint8 M[MAXMEMSIZE]; /* main memory */\r |
| 53 | extern uint8 ind[NUM_IND]; /* indicators */\r |
| 54 | extern UNIT cpu_unit;\r |
| 55 | \r |
| 56 | t_stat fp_scan_mant (uint32 ad, uint32 *lnt, uint32 *zro);\r |
| 57 | t_stat fp_zero (FPA *fp);\r |
| 58 | \r |
| 59 | extern t_stat xmt_field (uint32 d, uint32 s, uint32 skp);\r |
| 60 | extern t_stat add_field (uint32 d, uint32 s, t_bool sub, t_bool sto, uint32 skp, int32 *sta);\r |
| 61 | extern t_stat mul_field (uint32 d, uint32 s);\r |
| 62 | extern t_stat xmt_divd (uint32 d, uint32 s);\r |
| 63 | extern t_stat div_field (uint32 dvd, uint32 dvr, int32 *ez);\r |
| 64 | \r |
| 65 | /* Unpack and validate a floating point argument */\r |
| 66 | \r |
| 67 | t_stat fp_unpack (uint32 ad, FPA *fp)\r |
| 68 | {\r |
| 69 | uint8 d0, d1, esign;\r |
| 70 | \r |
| 71 | esign = M[ad] & FLAG; /* get exp sign */\r |
| 72 | d0 = M[ad] & DIGIT; /* get exp lo digit */\r |
| 73 | MM (ad);\r |
| 74 | if ((M[ad] & FLAG) == 0) return STOP_FPMF; /* no flag on hi exp? */\r |
| 75 | d1 = M[ad] & DIGIT; /* get exp hi digit */\r |
| 76 | MM (ad);\r |
| 77 | fp->addr = ad; /* save mant addr */\r |
| 78 | if (BAD_DIGIT (d1) || BAD_DIGIT (d0)) return STOP_INVDIG; /* exp bad dig? */\r |
| 79 | fp->exp = ((d1 * 10) + d0) * (esign? -1: 1); /* convert exponent */\r |
| 80 | fp->sign = (M[ad] & FLAG)? 1: 0; /* get mantissa sign */\r |
| 81 | return fp_scan_mant (fp->addr, &(fp->lnt), &(fp->zero));\r |
| 82 | }\r |
| 83 | \r |
| 84 | /* Unpack and validate source and destination arguments */\r |
| 85 | \r |
| 86 | t_stat fp_unpack_two (uint32 dad, uint32 sad, FPA *dfp, FPA *sfp)\r |
| 87 | {\r |
| 88 | t_stat r;\r |
| 89 | \r |
| 90 | if ((r = fp_unpack (dad, dfp)) != SCPE_OK) return r; /* unpack dst */\r |
| 91 | if ((r = fp_unpack (sad, sfp)) != SCPE_OK) return r; /* unpack src */\r |
| 92 | if (sfp->lnt != dfp->lnt) return STOP_FPUNL; /* lnts must be equal */\r |
| 93 | return SCPE_OK;\r |
| 94 | }\r |
| 95 | \r |
| 96 | /* Pack floating point result */\r |
| 97 | \r |
| 98 | t_stat fp_pack (FPA *fp)\r |
| 99 | {\r |
| 100 | int32 e;\r |
| 101 | uint32 i, mad;\r |
| 102 | \r |
| 103 | e = (fp->exp >= 0)? fp->exp: -fp->exp; /* get |exp| */ \r |
| 104 | if (e > FP_EMAX) { /* too big? */\r |
| 105 | ind[IN_EXPCHK] = 1; /* set indicator */\r |
| 106 | if (fp->exp < 0) return fp_zero (fp); /* underflow? */\r |
| 107 | mad = fp->addr;\r |
| 108 | for (i = 0; i < fp->lnt; i++) { /* mant = 99...99 */\r |
| 109 | M[mad] = (M[mad] & FLAG) | 9;\r |
| 110 | MM (mad);\r |
| 111 | }\r |
| 112 | e = FP_EMAX; /* cap at max */\r |
| 113 | }\r |
| 114 | M[ADDR_A (fp->addr, 1)] = (e / 10) | FLAG; /* high exp digit */\r |
| 115 | M[ADDR_A (fp->addr, 2)] = (e % 10) | /* low exp digit */\r |
| 116 | ((fp->exp < 0)? FLAG: 0);\r |
| 117 | return SCPE_OK;\r |
| 118 | }\r |
| 119 | \r |
| 120 | /* Shift mantissa right n positions */\r |
| 121 | \r |
| 122 | void fp_rsh (FPA *fp, uint32 n)\r |
| 123 | {\r |
| 124 | uint32 i, sad, dad;\r |
| 125 | \r |
| 126 | if (n == 0) return; /* zero? done */\r |
| 127 | sad = ADDR_S (fp->addr, n); /* src = addr - n */\r |
| 128 | dad = fp->addr; /* dst = n */\r |
| 129 | for (i = 0; i < fp->lnt; i++) { /* move digits */\r |
| 130 | if (i >= (fp->lnt - n)) M[dad] = M[dad] & FLAG;\r |
| 131 | else M[dad] = (M[dad] & FLAG) | (M[sad] & DIGIT);\r |
| 132 | MM (dad);\r |
| 133 | MM (sad);\r |
| 134 | }\r |
| 135 | return;\r |
| 136 | }\r |
| 137 | \r |
| 138 | /* Shift mantissa left 1 position */\r |
| 139 | \r |
| 140 | void fp_lsh_1 (FPA *fp)\r |
| 141 | {\r |
| 142 | uint32 i, mad, nxt;\r |
| 143 | \r |
| 144 | mad = ADDR_S (fp->addr, fp->lnt - 1); /* hi order digit */\r |
| 145 | for (i = 0; i < (fp->lnt - 1); i++) { /* move lnt-1 digits */\r |
| 146 | nxt = ADDR_A (mad, 1);\r |
| 147 | M[mad] = (M[mad] & FLAG) | (M[nxt] & DIGIT);\r |
| 148 | mad = nxt;\r |
| 149 | }\r |
| 150 | M[mad] = M[mad] & FLAG; /* clear last digit */\r |
| 151 | return;\r |
| 152 | }\r |
| 153 | \r |
| 154 | /* Clear floating point number */\r |
| 155 | \r |
| 156 | t_stat fp_zero (FPA *fp)\r |
| 157 | {\r |
| 158 | uint32 i, mad = fp->addr;\r |
| 159 | \r |
| 160 | for (i = 0; i < fp->lnt; i++) { /* clear mantissa */\r |
| 161 | M[mad] = (i? M[mad] & FLAG: 0); /* clear sign bit */\r |
| 162 | MM (mad);\r |
| 163 | }\r |
| 164 | M[ADDR_A (fp->addr, 1)] = FLAG + 9; /* exp = -99 */\r |
| 165 | M[ADDR_A (fp->addr, 2)] = FLAG + 9; /* exp = -99 */\r |
| 166 | ind[IN_EZ] = 1; /* result = 0 */\r |
| 167 | ind[IN_HP] = 0;\r |
| 168 | return SCPE_OK;\r |
| 169 | }\r |
| 170 | \r |
| 171 | /* Scan floating point mantissa for length and (optionally) zero */\r |
| 172 | \r |
| 173 | t_stat fp_scan_mant (uint32 ad, uint32 *lnt, uint32 *zro)\r |
| 174 | {\r |
| 175 | uint8 d, l, z;\r |
| 176 | \r |
| 177 | z = 1; /* assume zero */\r |
| 178 | for (l = 1; l <= FP_LMAX; l++) { /* scan to get length */\r |
| 179 | d = M[ad] & DIGIT; /* get mant digit */\r |
| 180 | if (d) z = 0; /* non-zero? */\r |
| 181 | if ((l != 1) && (M[ad] & FLAG)) { /* flag past first dig? */\r |
| 182 | *lnt = l; /* set returns */\r |
| 183 | if (zro) *zro = z;\r |
| 184 | return SCPE_OK;\r |
| 185 | }\r |
| 186 | MM (ad);\r |
| 187 | }\r |
| 188 | return STOP_FPLNT; /* too long */\r |
| 189 | }\r |
| 190 | \r |
| 191 | /* Copy floating point mantissa */\r |
| 192 | \r |
| 193 | void fp_copy_mant (uint32 d, uint32 s, uint32 l)\r |
| 194 | {\r |
| 195 | uint32 i;\r |
| 196 | \r |
| 197 | if (ind[IN_HP]) M[d] = M[d] & ~FLAG; /* clr/set sign */\r |
| 198 | else M[d] = M[d] | FLAG;\r |
| 199 | for (i = 0; i < l; i++) { /* copy src */\r |
| 200 | M[d] = (M[d] & FLAG) | (M[s] & DIGIT); /* preserve flags */\r |
| 201 | MM (d);\r |
| 202 | MM (s);\r |
| 203 | }\r |
| 204 | return;\r |
| 205 | }\r |
| 206 | \r |
| 207 | /* Compare floating point mantissa */\r |
| 208 | \r |
| 209 | int32 fp_comp_mant (uint32 d, uint32 s, uint32 l)\r |
| 210 | {\r |
| 211 | uint8 i, dd, sd;\r |
| 212 | \r |
| 213 | d = ADDR_S (d, l - 1); /* start of mantissa */\r |
| 214 | s = ADDR_S (s, l - 1);\r |
| 215 | for (i = 0; i < l; i++) { /* compare dst:src */\r |
| 216 | dd = M[d] & DIGIT; /* get dst digit */\r |
| 217 | sd = M[s] & DIGIT; /* get src digit */\r |
| 218 | if (dd > sd) return 1; /* >? done */\r |
| 219 | if (dd < sd) return -1; /* <? done */\r |
| 220 | PP (d); /* =? continue */\r |
| 221 | PP (s);\r |
| 222 | }\r |
| 223 | return 0; /* done, equal */\r |
| 224 | }\r |
| 225 | \r |
| 226 | /* Floating point add */\r |
| 227 | \r |
| 228 | t_stat fp_add (uint32 d, uint32 s, t_bool sub)\r |
| 229 | {\r |
| 230 | FPA sfp, dfp;\r |
| 231 | uint32 i, sad, hi;\r |
| 232 | int32 dif, sta;\r |
| 233 | uint8 sav_src[FP_LMAX];\r |
| 234 | t_stat r;\r |
| 235 | \r |
| 236 | r = fp_unpack_two (d, s, &dfp, &sfp); /* unpack operands */\r |
| 237 | if (r != SCPE_OK) return r; /* error? */\r |
| 238 | dif = dfp.exp - sfp.exp; /* exp difference */\r |
| 239 | \r |
| 240 | if (sfp.zero || (dif >= ((int32) dfp.lnt))) { /* src = 0, or too small? */\r |
| 241 | if (dfp.zero) return fp_zero (&dfp); /* res = dst, zero? */ \r |
| 242 | ind[IN_EZ] = 0; /* res nz, set EZ, HP */\r |
| 243 | ind[IN_HP] = (dfp.sign == 0);\r |
| 244 | return SCPE_OK;\r |
| 245 | }\r |
| 246 | if (dfp.zero || (dif <= -((int32) dfp.lnt))) { /* dst = 0, or too small? */\r |
| 247 | if (sfp.zero) return fp_zero (&dfp); /* res = src, zero? */\r |
| 248 | r = xmt_field (d, s, 3); /* copy src to dst */\r |
| 249 | ind[IN_EZ] = 0; /* res nz, set EZ, HP */\r |
| 250 | ind[IN_HP] = (dfp.sign == 0);\r |
| 251 | return r;\r |
| 252 | }\r |
| 253 | \r |
| 254 | if (dif > 0) { /* dst exp > src exp? */\r |
| 255 | sad = sfp.addr; /* save src in save area */\r |
| 256 | for (i = 0; i < sfp.lnt; i++) {\r |
| 257 | sav_src[i] = M[sad];\r |
| 258 | MM (sad);\r |
| 259 | }\r |
| 260 | fp_rsh (&sfp, dif); /* denormalize src */\r |
| 261 | }\r |
| 262 | else if (dif < 0) { /* dst exp < src exp? */\r |
| 263 | dfp.exp = sfp.exp; /* res exp = src exp */\r |
| 264 | fp_rsh (&dfp, -dif); /* denormalize dst */\r |
| 265 | }\r |
| 266 | r = add_field (dfp.addr, sfp.addr, sub, TRUE, 0, &sta); /* add mant, set EZ, HP */\r |
| 267 | if (dif > 0) { /* src denormalized? */\r |
| 268 | sad = sfp.addr; /* restore src from */\r |
| 269 | for (i = 0; i < sfp.lnt; i++) { /* save area */\r |
| 270 | M[sad] = sav_src[i];\r |
| 271 | MM (sad);\r |
| 272 | }\r |
| 273 | }\r |
| 274 | if (r != SCPE_OK) return r; /* add error? */\r |
| 275 | \r |
| 276 | hi = ADDR_S (dfp.addr, dfp.lnt - 1); /* addr of hi digit */\r |
| 277 | if (sta == ADD_CARRY) { /* carry out? */\r |
| 278 | fp_rsh (&dfp, 1); /* shift mantissa */\r |
| 279 | M[hi] = FLAG + 1; /* high order 1 */\r |
| 280 | dfp.exp = dfp.exp + 1;\r |
| 281 | ind[IN_EZ] = 0; /* not zero */\r |
| 282 | ind[IN_HP] = (dfp.sign == 0); /* set HP */\r |
| 283 | }\r |
| 284 | else if (ind[IN_EZ]) return fp_zero (&dfp); /* result zero? */\r |
| 285 | else {\r |
| 286 | while ((M[hi] & DIGIT) == 0) { /* until normalized */\r |
| 287 | fp_lsh_1 (&dfp); /* left shift */\r |
| 288 | dfp.exp = dfp.exp - 1; /* decr exponent */\r |
| 289 | }\r |
| 290 | }\r |
| 291 | \r |
| 292 | return fp_pack (&dfp); /* pack and exit */\r |
| 293 | }\r |
| 294 | \r |
| 295 | /* Floating point multiply */\r |
| 296 | \r |
| 297 | t_stat fp_mul (uint32 d, uint32 s)\r |
| 298 | {\r |
| 299 | FPA sfp, dfp;\r |
| 300 | uint32 pad;\r |
| 301 | t_stat r;\r |
| 302 | \r |
| 303 | r = fp_unpack_two (d, s, &dfp, &sfp); /* unpack operands */\r |
| 304 | if (r != SCPE_OK) return r; /* error? */\r |
| 305 | if (sfp.zero || dfp.zero) return fp_zero (&dfp); /* either zero? */\r |
| 306 | \r |
| 307 | r = mul_field (dfp.addr, sfp.addr); /* mul, set EZ, HP */\r |
| 308 | if (r != SCPE_OK) return r;\r |
| 309 | if (M[ADDR_S (PROD_AREA_END, 2 * dfp.lnt)] & DIGIT) { /* hi prod dig set? */\r |
| 310 | pad = ADDR_S (PROD_AREA_END - 1, dfp.lnt); /* no normalization */\r |
| 311 | dfp.exp = dfp.exp + sfp.exp; /* res exp = sum */\r |
| 312 | }\r |
| 313 | else {\r |
| 314 | pad = ADDR_S (PROD_AREA_END, dfp.lnt); /* 'normalize' 1 */\r |
| 315 | dfp.exp = dfp.exp + sfp.exp - 1; /* res exp = sum - 1 */\r |
| 316 | }\r |
| 317 | fp_copy_mant (dfp.addr, pad, dfp.lnt); /* copy prod to mant */\r |
| 318 | \r |
| 319 | return fp_pack (&dfp); /* pack and exit */\r |
| 320 | }\r |
| 321 | \r |
| 322 | /* Floating point divide */\r |
| 323 | \r |
| 324 | t_stat fp_div (uint32 d, uint32 s)\r |
| 325 | {\r |
| 326 | FPA sfp, dfp;\r |
| 327 | uint32 i, pad, a100ml, a99ml;\r |
| 328 | int32 ez;\r |
| 329 | t_stat r;\r |
| 330 | \r |
| 331 | r = fp_unpack_two (d, s, &dfp, &sfp); /* unpack operands */\r |
| 332 | if (r != SCPE_OK) return r; /* error? */\r |
| 333 | if (sfp.zero) { /* divide by zero? */\r |
| 334 | ind[IN_OVF] = 1; /* dead jim */\r |
| 335 | return SCPE_OK;\r |
| 336 | }\r |
| 337 | if (dfp.zero) return fp_zero (&dfp); /* divide into zero? */\r |
| 338 | \r |
| 339 | for (i = 0; i < PROD_AREA_LEN; i++) /* clear prod area */\r |
| 340 | M[PROD_AREA + i] = 0;\r |
| 341 | a100ml = ADDR_S (PROD_AREA_END, dfp.lnt); /* 100 - lnt */\r |
| 342 | a99ml = ADDR_S (PROD_AREA_END - 1, dfp.lnt); /* 99 - lnt */\r |
| 343 | if (fp_comp_mant (dfp.addr, sfp.addr, dfp.lnt) >= 0) { /* |Mdst| >= |Msrc|? */\r |
| 344 | pad = a100ml;\r |
| 345 | dfp.exp = dfp.exp - sfp.exp + 1; /* res exp = diff + 1 */\r |
| 346 | }\r |
| 347 | else {\r |
| 348 | pad = a99ml;\r |
| 349 | dfp.exp = dfp.exp - sfp.exp; /* res exp = diff */\r |
| 350 | }\r |
| 351 | r = xmt_divd (pad, dfp.addr); /* xmt dividend */\r |
| 352 | if (r != SCPE_OK) return r; /* error? */\r |
| 353 | r = div_field (a100ml, sfp.addr, &ez); /* divide fractions */\r |
| 354 | if (r != SCPE_OK) return r; /* error? */\r |
| 355 | if (ez) return fp_zero (&dfp); /* result zero? */\r |
| 356 | \r |
| 357 | ind[IN_HP] = ((dfp.sign ^ sfp.sign) == 0); /* set res sign */\r |
| 358 | ind[IN_EZ] = 0; /* not zero */\r |
| 359 | fp_copy_mant (dfp.addr, a99ml, dfp.lnt); /* copy result */\r |
| 360 | \r |
| 361 | return fp_pack (&dfp);\r |
| 362 | }\r |
| 363 | \r |
| 364 | /* Floating shift right */\r |
| 365 | \r |
| 366 | t_stat fp_fsr (uint32 d, uint32 s)\r |
| 367 | {\r |
| 368 | uint32 cnt;\r |
| 369 | uint8 t;\r |
| 370 | \r |
| 371 | if (d == s) return SCPE_OK; /* no move? */\r |
| 372 | \r |
| 373 | cnt = 0;\r |
| 374 | M[d] = (M[d] & FLAG) | (M[s] & DIGIT); /* move 1st wo flag */\r |
| 375 | do {\r |
| 376 | MM (d); /* decr ptrs */\r |
| 377 | MM (s);\r |
| 378 | t = M[d] = M[s] & (FLAG | DIGIT); /* copy others */\r |
| 379 | if (cnt++ > MEMSIZE) return STOP_FWRAP; /* (stop runaway) */\r |
| 380 | } while ((t & FLAG) == 0); /* until src flag */\r |
| 381 | \r |
| 382 | cnt = 0;\r |
| 383 | do {\r |
| 384 | MM (d); /* decr pointer */\r |
| 385 | t = M[d]; /* save old val */\r |
| 386 | M[d] = 0; /* zero field */\r |
| 387 | if (cnt++ > MEMSIZE) return STOP_FWRAP; /* (stop runaway) */\r |
| 388 | } while ((t & FLAG) == 0); /* until dst flag */\r |
| 389 | return SCPE_OK;\r |
| 390 | } \r |
| 391 | \r |
| 392 | /* Floating shift left - note that dst is addr of high order digit */\r |
| 393 | \r |
| 394 | t_stat fp_fsl (uint32 d, uint32 s)\r |
| 395 | {\r |
| 396 | uint32 i, lnt;\r |
| 397 | uint8 sign;\r |
| 398 | t_stat r;\r |
| 399 | \r |
| 400 | if (d == s) return SCPE_OK;\r |
| 401 | sign = M[s] & FLAG; /* get src sign */\r |
| 402 | r = fp_scan_mant (s, &lnt, NULL); /* get src length */\r |
| 403 | if (r != SCPE_OK) return r; /* error? */\r |
| 404 | s = ADDR_S (s, lnt - 1); /* hi order src */\r |
| 405 | M[d] = M[s] & (FLAG | DIGIT); /* move 1st w flag */\r |
| 406 | M[s] = M[s] & ~FLAG; /* clr flag from src */\r |
| 407 | for (i = 1; i < lnt; i++) { /* move src to dst */\r |
| 408 | PP (d); /* incr ptrs */\r |
| 409 | PP (s);\r |
| 410 | M[d] = M[s] & DIGIT; /* move just digit */\r |
| 411 | }\r |
| 412 | PP (d); /* incr pointer */\r |
| 413 | while ((M[d] & FLAG) == 0) { /* until flag */\r |
| 414 | M[d] = 0; /* clear field */\r |
| 415 | PP (d);\r |
| 416 | }\r |
| 417 | if (sign) M[d] = FLAG; /* -? zero under sign */\r |
| 418 | return SCPE_OK;\r |
| 419 | }\r |