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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 |