int.c

   1 /* neatcc intermediate code generation */
   2 #include <stdlib.h>
   3 #include <stdio.h>
   4 #include <string.h>
   5 #include "ncc.h"
   6
   7 static struct ic *ic;           /* intermediate code */
   8 static long ic_n, ic_sz;        /* number of instructions in ic[] */
   9 static long iv[NTMPS];          /* operand stack */
  10 static long iv_n;               /* number of values in iv[] */
  11 static long *lab_loc;           /* label locations */
  12 static long lab_n, lab_sz;      /* number of labels in lab_loc[] */
  13 static long lab_last;           /* the last label target */
  14
  15 static int io_num(void);
  16 static int io_mul2(void);
  17 static int io_cmp(void);
  18 static int io_jmp(void);
  19 static int io_addr(void);
  20 static int io_loc(void);
  21 static int io_imm(void);
  22 static int io_call(void);
  23 static void io_deadcode(void);
  24
  25 static void iv_put(long n);
  26
  27 static struct ic *ic_put(long op, long arg1, long arg2, long arg3)
  28 {
  29         struct ic *c;
  30         if (ic_n == ic_sz) {
  31                 ic_sz = MAX(128, ic_sz * 2);
  32                 ic = mextend(ic, ic_n, ic_sz, sizeof(*ic));
  33         }
  34         c = &ic[ic_n++];
  35         c->op = op;
  36         c->a1 = arg1;
  37         c->a2 = arg2;
  38         c->a3 = arg3;
  39         if (op & O_OUT)
  40                 iv_put(ic_n - 1);
  41         return c;
  42 }
  43
  44 static void ic_back(long pos)
  45 {
  46         int i;
  47         for (i = pos; i < ic_n; i++)
  48                 if (ic[i].op & O_CALL)
  49                         free(ic[i].args);
  50         ic_n = pos;
  51 }
  52
  53 static long iv_pop(void)
  54 {
  55         return iv[--iv_n];
  56 }
  57
  58 static long iv_get(int n)
  59 {
  60         return iv[iv_n - n - 1];
  61 }
  62
  63 static void iv_put(long n)
  64 {
  65         iv[iv_n++] = n;
  66 }
  67
  68 static void iv_drop(int n)
  69 {
  70         iv_n = MAX(0, iv_n - n);
  71 }
  72
  73 static void iv_swap(int x, int y)
  74 {
  75         long v = iv[iv_n - x - 1];
  76         iv[iv_n - x - 1] = iv[iv_n - y - 1];
  77         iv[iv_n - y - 1] = v;
  78 }
  79
  80 static void iv_dup(void)
  81 {
  82         iv[iv_n] = iv[iv_n - 1];
  83         iv_n++;
  84 }
  85
  86 void o_num(long n)
  87 {
  88         ic_put(O_MOV | O_NUM, n, 0, 0);
  89 }
  90
  91 void o_local(long id)
  92 {
  93         ic_put(O_MOV | O_LOC, id, 0, 0);
  94 }
  95
  96 void o_sym(char *sym)
  97 {
  98         ic_put(O_MOV | O_SYM, out_sym(sym), 0, 0);
  99 }
 100
 101 void o_tmpdrop(int n)
 102 {
 103         iv_drop(n >= 0 ? n : iv_n);
 104 }
 105
 106 void o_tmpswap(void)
 107 {
 108         iv_swap(0, 1);
 109 }
 110
 111 void o_tmpcopy(void)
 112 {
 113         iv_dup();
 114 }
 115
 116 /* return one if the given value is constant */
 117 static int ic_const(long iv)
 118 {
 119         long oc = O_C(ic[iv].op);
 120         return oc & O_MOV && oc & (O_NUM | O_SYM | O_LOC);
 121 }
 122
 123 /* return one if the given value is a simple load */
 124 static int ic_load(long iv)
 125 {
 126         long oc = O_C(ic[iv].op);
 127         int i;
 128         if (oc & O_LD && oc & (O_NUM | O_SYM | O_LOC)) {
 129                 for (i = iv + 1; i < ic_n; i++)
 130                         if (ic[i].op & O_ST)
 131                                 return 0;
 132                 return 1;
 133         }
 134         return 0;
 135 }
 136
 137 void o_bop(long op)
 138 {
 139         int r1 = iv_pop();
 140         int r2 = iv_pop();
 141         /* load constants as late as possible */
 142         if (opt(1) && ic_const(r2) && !ic_const(r1)) {
 143                 ic_put(ic[r2].op, ic[r2].a1, ic[r2].a2, ic[r2].a3);
 144                 r2 = iv_pop();
 145         }
 146         ic_put(op, r2, r1, 0);
 147         if (opt(1)) {
 148                 io_num();
 149                 io_mul2();
 150                 io_addr();
 151                 io_imm();
 152         }
 153 }
 154
 155 void o_uop(long op)
 156 {
 157         int r1 = iv_pop();
 158         ic_put(op, r1, 0, 0);
 159         if (opt(1)) {
 160                 io_num();
 161                 io_cmp();
 162         }
 163 }
 164
 165 void o_assign(long bt)
 166 {
 167         int rv = iv_pop();
 168         int lv = iv_pop();
 169         /* load constants as late as possible */
 170         if (opt(1) && (ic_const(lv) || ic_load(lv))) {
 171                 ic_put(ic[lv].op, ic[lv].a1, ic[lv].a2, ic[lv].a3);
 172                 lv = iv_pop();
 173         }
 174         ic_put(O_MK(O_ST | O_NUM, bt), rv, lv, 0);
 175         iv_put(rv);
 176         if (opt(1))
 177                 io_loc();
 178 }
 179
 180 void o_deref(long bt)
 181 {
 182         int r1 = iv_pop();
 183         ic_put(O_MK(O_LD | O_NUM, bt), r1, 0, 0);
 184         if (opt(1))
 185                 io_loc();
 186 }
 187
 188 void o_cast(long bt)
 189 {
 190         if (T_SZ(bt) != ULNG) {
 191                 int r1 = iv_pop();
 192                 ic_put(O_MK(O_MOV, bt), r1, 0, 0);
 193                 if (opt(1))
 194                         io_num();
 195         }
 196 }
 197
 198 void o_memcpy(void)
 199 {
 200         int r2 = iv_pop();
 201         int r1 = iv_pop();
 202         int r0 = iv_pop();
 203         ic_put(O_MCPY, r0, r1, r2);
 204 }
 205
 206 void o_memset(void)
 207 {
 208         int r2 = iv_pop();
 209         int r1 = iv_pop();
 210         int r0 = iv_pop();
 211         ic_put(O_MSET, r0, r1, r2);
 212 }
 213
 214 void o_call(int argc, int ret)
 215 {
 216         struct ic *c;
 217         long *args = malloc(argc * sizeof(c->args[0]));
 218         int r1, i;
 219         for (i = argc - 1; i >= 0; --i)
 220                 args[i] = iv_pop();
 221         for (i = argc - 1; i >= 0; --i) {
 222                 int iv = args[i];
 223                 /* load constants as late as possible */
 224                 if (opt(1) && (ic_const(iv) || ic_load(iv))) {
 225                         ic_put(ic[iv].op, ic[iv].a1, ic[iv].a2, ic[iv].a3);
 226                         args[i] = iv_pop();
 227                 }
 228         }
 229         r1 = iv_pop();
 230         c = ic_put(O_CALL, r1, 0, argc);
 231         c->args = args;
 232         iv_drop(ret == 0);
 233         if (opt(1))
 234                 io_call();
 235 }
 236
 237 void o_ret(int ret)
 238 {
 239         if (!ret)
 240                 o_num(0);
 241         ic_put(O_RET, iv_pop(), 0, 0);
 242 }
 243
 244 void o_label(long id)
 245 {
 246         while (id >= lab_sz) {
 247                 lab_sz = MAX(128, lab_sz * 2);
 248                 lab_loc = mextend(lab_loc, lab_n, lab_sz, sizeof(*lab_loc));
 249         }
 250         while (lab_n <= id)
 251                 lab_loc[lab_n++] = -1;
 252         lab_loc[id] = ic_n;
 253         lab_last = ic_n;
 254 }
 255
 256 void o_jmp(long id)
 257 {
 258         ic_put(O_JMP, 0, 0, id);
 259 }
 260
 261 void o_jz(long id)
 262 {
 263         ic_put(O_JZ, iv_pop(), 0, id);
 264         if (opt(1))
 265                 io_jmp();
 266 }
 267
 268 int o_popnum(long *n)
 269 {
 270         if (ic_num(ic, iv_get(0), n))
 271                 return 1;
 272         iv_drop(1);
 273         return 0;
 274 }
 275
 276 int o_popsym(long *sym, long *off)
 277 {
 278         if (ic_sym(ic, iv_get(0), sym, off))
 279                 return 1;
 280         iv_drop(1);
 281         return 0;
 282 }
 283
 284 long o_mark(void)
 285 {
 286         return ic_n;
 287 }
 288
 289 void o_back(long mark)
 290 {
 291         ic_back(mark);
 292 }
 293
 294 void ic_get(struct ic **c, long *n)
 295 {
 296         int i;
 297         if (!ic_n || ~ic[ic_n - 1].op & O_RET || lab_last == ic_n)
 298                 o_ret(0);
 299         for (i = 0; i < ic_n; i++)      /* filling branch targets */
 300                 if (ic[i].op & O_JXX)
 301                         ic[i].a3 = lab_loc[ic[i].a3];
 302         io_deadcode();                  /* removing dead code */
 303         *c = ic;
 304         *n = ic_n;
 305         ic = NULL;
 306         ic_n = 0;
 307         ic_sz = 0;
 308         iv_n = 0;
 309         free(lab_loc);
 310         lab_loc = NULL;
 311         lab_n = 0;
 312         lab_sz = 0;
 313         lab_last = 0;
 314 }
 315
 316 void ic_free(struct ic *ic)
 317 {
 318         if (ic->op & O_CALL)
 319                 free(ic->args);
 320 }
 321
 322 /* intermediate code queries */
 323
 324 static long cb(long op, long a, long b)
 325 {
 326         switch (O_C(op)) {
 327         case O_ADD:
 328                 return a + b;
 329         case O_SUB:
 330                 return a - b;
 331         case O_AND:
 332                 return a & b;
 333         case O_OR:
 334                 return a | b;
 335         case O_XOR:
 336                 return a ^ b;
 337         case O_MUL:
 338                 return a * b;
 339         case O_DIV:
 340                 return a / b;
 341         case O_MOD:
 342                 return a % b;
 343         case O_SHL:
 344                 return a << b;
 345         case O_SHR:
 346                 return O_T(op) & T_MSIGN ? a >> b : (unsigned long) a >> b;
 347         case O_LT:
 348                 return a < b;
 349         case O_GT:
 350                 return a > b;
 351         case O_LE:
 352                 return a <= b;
 353         case O_GE:
 354                 return a >= b;
 355         case O_EQ:
 356                 return a == b;
 357         case O_NE:
 358                 return a != b;
 359         }
 360         return 0;
 361 }
 362
 363 static long cu(int op, long i)
 364 {
 365         switch (O_C(op)) {
 366         case O_NEG:
 367                 return -i;
 368         case O_NOT:
 369                 return ~i;
 370         case O_LNOT:
 371                 return !i;
 372         }
 373         return 0;
 374 }
 375
 376 static long c_cast(long n, unsigned bt)
 377 {
 378         if (!(bt & T_MSIGN) && T_SZ(bt) != ULNG)
 379                 n &= ((1l << (long) (T_SZ(bt) * 8)) - 1);
 380         if (bt & T_MSIGN && T_SZ(bt) != ULNG &&
 381                                 n > (1l << (T_SZ(bt) * 8 - 1)))
 382                 n = -((1l << (T_SZ(bt) * 8)) - n);
 383         return n;
 384 }
 385
 386 int ic_num(struct ic *ic, long iv, long *n)
 387 {
 388         long n1, n2;
 389         long oc = O_C(ic[iv].op);
 390         long bt = O_T(ic[iv].op);
 391         if (oc & O_MOV && oc & O_NUM) {
 392                 *n = ic[iv].a1;
 393                 return 0;
 394         }
 395         if (oc & O_BOP) {
 396                 if (ic_num(ic, ic[iv].a1, &n1))
 397                         return 1;
 398                 if (ic_num(ic, ic[iv].a2, &n2))
 399                         return 1;
 400                 *n = cb(ic[iv].op, n1, n2);
 401                 return 0;
 402         }
 403         if (oc & O_UOP) {
 404                 if (ic_num(ic, ic[iv].a1, &n1))
 405                         return 1;
 406                 *n = cu(ic[iv].op, n1);
 407                 return 0;
 408         }
 409         if (oc & O_MOV && !(oc & (O_NUM | O_LOC | O_SYM))) {
 410                 if (ic_num(ic, ic[iv].a1, &n1))
 411                         return 1;
 412                 *n = c_cast(n1, bt);
 413                 return 0;
 414         }
 415         return 1;
 416 }
 417
 418 int ic_sym(struct ic *ic, long iv, long *sym, long *off)
 419 {
 420         long n;
 421         long oc = O_C(ic[iv].op);
 422         if (oc & O_MOV && oc & O_SYM) {
 423                 *sym = ic[iv].a1;
 424                 *off = ic[iv].a2;
 425                 return 0;
 426         }
 427         if (oc == O_ADD) {
 428                 if ((ic_sym(ic, ic[iv].a1, sym, off) ||
 429                                 ic_num(ic, ic[iv].a2, &n)) &&
 430                         (ic_sym(ic, ic[iv].a2, sym, off) ||
 431                                 ic_num(ic, ic[iv].a1, &n)))
 432                         return 1;
 433                 *off += n;
 434                 return 0;
 435         }
 436         if (oc == O_SUB) {
 437                 if (ic_sym(ic, ic[iv].a1, sym, off) ||
 438                                 ic_num(ic, ic[iv].a2, &n))
 439                         return 1;
 440                 *off -= n;
 441                 return 0;
 442         }
 443         return 1;
 444 }
 445
 446 static int ic_off(struct ic *ic, long iv, long *base_iv, long *off)
 447 {
 448         long n;
 449         long oc = O_C(ic[iv].op);
 450         if (oc == (O_ADD | O_NUM)) {
 451                 *base_iv = ic[iv].a1;
 452                 *off = ic[iv].a2;
 453                 return 0;
 454         }
 455         if (oc == (O_SUB | O_NUM)) {
 456                 *base_iv = ic[iv].a1;
 457                 *off = -ic[iv].a2;
 458                 return 0;
 459         }
 460         if (oc == O_ADD) {
 461                 if ((ic_off(ic, ic[iv].a1, base_iv, off) ||
 462                                 ic_num(ic, ic[iv].a2, &n)) &&
 463                         (ic_off(ic, ic[iv].a2, base_iv, off) ||
 464                                 ic_num(ic, ic[iv].a1, &n)))
 465                         return 1;
 466                 *off += n;
 467                 return 0;
 468         }
 469         if (oc == O_SUB) {
 470                 if (ic_off(ic, ic[iv].a1, base_iv, off) ||
 471                                 ic_num(ic, ic[iv].a2, &n))
 472                         return 1;
 473                 *off -= n;
 474                 return 0;
 475         }
 476         *base_iv = iv;
 477         *off = 0;
 478         return 0;
 479 }
 480
 481 /* number of register arguments */
 482 int ic_regcnt(struct ic *ic)
 483 {
 484         long o = ic->op;
 485         if (o & O_BOP)
 486                 return o & (O_NUM | O_SYM | O_LOC) ? 1 : 2;
 487         if (o & O_UOP)
 488                 return o & (O_NUM | O_SYM | O_LOC) ? 0 : 1;
 489         if (o & O_CALL)
 490                 return o & (O_NUM | O_SYM | O_LOC) ? 0 : 1;
 491         if (o & O_MOV)
 492                 return o & (O_NUM | O_SYM | O_LOC) ? 0 : 1;
 493         if (o & O_MEM)
 494                 return 3;
 495         if (o & O_JMP)
 496                 return 0;
 497         if (o & O_JZ)
 498                 return 1;
 499         if (o & O_JCC)
 500                 return o & (O_NUM | O_SYM | O_LOC) ? 1 : 2;
 501         if (o & O_RET)
 502                 return 1;
 503         if (o & O_LD)
 504                 return ((o & O_NUM) != 0);
 505         if (o & O_ST)
 506                 return 1 + ((o & O_NUM) != 0);
 507         return 0;
 508 }
 509
 510 /*
 511  * The returned array indicates the last instruction in
 512  * which the value produced by each instruction is used.
 513  */
 514 long *ic_lastuse(struct ic *ic, long ic_n)
 515 {
 516         long *luse = calloc(ic_n, sizeof(luse[0]));
 517         int i, j;
 518         for (i = ic_n - 1; i >= 0; --i) {
 519                 int n = ic_regcnt(ic + i);
 520                 if (!luse[i])
 521                         if (!(ic[i].op & O_OUT) || ic[i].op & O_CALL)
 522                                 luse[i] = -1;
 523                 if (!luse[i])
 524                         continue;
 525                 if (n >= 1 && !luse[ic[i].a1])
 526                         luse[ic[i].a1] = i;
 527                 if (n >= 2 && !luse[ic[i].a2])
 528                         luse[ic[i].a2] = i;
 529                 if (n >= 3 && !luse[ic[i].a3])
 530                         luse[ic[i].a3] = i;
 531                 if (ic[i].op & O_CALL)
 532                         for (j = 0; j < ic[i].a3; j++)
 533                                 if (!luse[ic[i].args[j]])
 534                                         luse[ic[i].args[j]] = i;
 535         }
 536         return luse;
 537 }
 538
 539 /* intermediate code optimisations */
 540
 541 /* constant folding */
 542 static int io_num(void)
 543 {
 544         long n;
 545         if (!ic_num(ic, iv_get(0), &n)) {
 546                 iv_drop(1);
 547                 o_num(n);
 548                 return 0;
 549         }
 550         return 1;
 551 }
 552
 553 static int log2a(unsigned long n)
 554 {
 555         int i = 0;
 556         for (i = 0; i < LONGSZ * 8; i++)
 557                 if (n & (1u << i))
 558                         break;
 559         if (i == LONGSZ * 8 || !(n >> (i + 1)))
 560                 return i;
 561         return -1;
 562 }
 563
 564 static long iv_num(long n)
 565 {
 566         o_num(n);
 567         return iv_pop();
 568 }
 569
 570 /* optimised multiplication operations for powers of two */
 571 static int io_mul2(void)
 572 {
 573         long iv = iv_get(0);
 574         long n, p;
 575         long r1, r2;
 576         long oc = O_C(ic[iv].op);
 577         long bt = O_T(ic[iv].op);
 578         if (!(oc & O_MUL))
 579                 return 1;
 580         if (oc == O_MUL && !ic_num(ic, ic[iv].a1, &n)) {
 581                 long t = ic[iv].a1;
 582                 ic[iv].a1 = ic[iv].a2;
 583                 ic[iv].a2 = t;
 584         }
 585         if (ic_num(ic, ic[iv].a2, &n))
 586                 return 1;
 587         p = log2a(n);
 588         if (n && p < 0)
 589                 return 1;
 590         if (oc == O_MUL) {
 591                 iv_drop(1);
 592                 if (n == 1) {
 593                         iv_put(ic[iv].a1);
 594                         return 0;
 595                 }
 596                 if (n == 0) {
 597                         o_num(0);
 598                         return 0;
 599                 }
 600                 r2 = iv_num(p);
 601                 ic_put(O_MK(O_SHL, ULNG), ic[iv].a1, r2, 0);
 602                 return 0;
 603         }
 604         if (oc == O_DIV && ~bt & T_MSIGN) {
 605                 iv_drop(1);
 606                 if (n == 1) {
 607                         iv_put(ic[iv].a1);
 608                         return 0;
 609                 }
 610                 r2 = iv_num(p);
 611                 ic_put(O_MK(O_SHR, ULNG), ic[iv].a1, r2, 0);
 612                 return 0;
 613         }
 614         if (oc == O_MOD && ~bt & T_MSIGN) {
 615                 iv_drop(1);
 616                 if (n == 1) {
 617                         o_num(0);
 618                         return 0;
 619                 }
 620                 r2 = iv_num(LONGSZ * 8 - p);
 621                 ic_put(O_MK(O_SHL, ULNG), ic[iv].a1, r2, 0);
 622                 r1 = iv_pop();
 623                 r2 = iv_num(LONGSZ * 8 - p);
 624                 ic_put(O_MK(O_SHR, ULNG), r1, r2, 0);
 625                 return 0;
 626         }
 627         return 1;
 628 }
 629
 630 /* optimise comparison */
 631 static int io_cmp(void)
 632 {
 633         long iv = iv_get(0);
 634         long cmp = ic[iv].a1;
 635         if (O_C(ic[iv].op) == O_LNOT && ic[cmp].op & O_CMP) {
 636                 iv_drop(1);
 637                 ic[cmp].op ^= 1;
 638                 iv_put(cmp);
 639                 return 0;
 640         }
 641         return 1;
 642 }
 643
 644 /* optimise branch instructions after comparison */
 645 static int io_jmp(void)
 646 {
 647         struct ic *c = &ic[ic_n - 1];
 648         long oc = O_C(c->op);
 649         if (oc & O_JZ && O_C(ic[c->a1].op) == O_LNOT) {
 650                 c->a1 = ic[c->a1].a1;
 651                 c->op ^= 1;
 652                 return 0;
 653         }
 654         if (oc & O_JZ && O_C(ic[c->a1].op) & O_CMP) {
 655                 long cop = (ic[c->a1].op & ~O_CMP) | O_JCC;
 656                 c->op = O_C(c->op) == O_JZ ? cop ^ 1 : cop;
 657                 c->a2 = ic[c->a1].a2;
 658                 c->a1 = ic[c->a1].a1;
 659                 return 0;
 660         }
 661         return 1;
 662 }
 663
 664 /* optimise accessing locals or symbols with an offset */
 665 static int io_addr(void)
 666 {
 667         long iv, off;
 668         if (ic_off(ic, iv_get(0), &iv, &off) || iv == iv_get(0))
 669                 return 1;
 670         if (ic[iv].op & O_MOV && ic[iv].op & O_LOC) {
 671                 iv_drop(1);
 672                 ic_put(O_MOV | O_LOC, ic[iv].a1, ic[iv].a2 + off, 0);
 673                 return 0;
 674         }
 675         if (ic[iv].op & O_MOV && ic[iv].op & O_SYM) {
 676                 iv_drop(1);
 677                 ic_put(O_MOV | O_SYM, ic[iv].a1, ic[iv].a2 + off, 0);
 678                 return 0;
 679         }
 680         return 1;
 681 }
 682
 683 static int imm_ok(long op, long n, int arg)
 684 {
 685         long m[5];
 686         if (i_reg(op | O_NUM, m + 0, m + 1, m + 2, m + 3, m + 4))
 687                 return 0;
 688         return i_imm(m[arg], n);
 689 }
 690
 691 /* optimise loading and storing locals */
 692 static int io_loc(void)
 693 {
 694         struct ic *c = &ic[ic_n - 1];
 695         long iv, off;
 696         if (c->op & O_LD && c->op & O_NUM) {
 697                 if (ic_off(ic, c->a1, &iv, &off))
 698                         return 1;
 699                 if (ic[iv].op & O_MOV && ic[iv].op & O_LOC) {
 700                         c->op = (c->op & ~O_NUM) | O_LOC;
 701                         c->a1 = ic[iv].a1;
 702                         c->a2 += ic[iv].a2 + off;
 703                         return 0;
 704                 }
 705                 if (imm_ok(c->op, off, 2)) {
 706                         c->a1 = iv;
 707                         c->a2 += off;
 708                 }
 709                 return 0;
 710         }
 711         if (c->op & O_ST && c->op & O_NUM) {
 712                 if (ic_off(ic, c->a2, &iv, &off))
 713                         return 1;
 714                 if (ic[iv].op & O_MOV && ic[iv].op & O_LOC) {
 715                         c->op = (c->op & ~O_NUM) | O_LOC;
 716                         c->a2 = ic[iv].a1;
 717                         c->a3 += ic[iv].a2 + off;
 718                         return 0;
 719                 }
 720                 if (imm_ok(c->op, off, 3)) {
 721                         c->a2 = iv;
 722                         c->a3 += off;
 723                 }
 724                 return 0;
 725         }
 726         return 1;
 727 }
 728
 729 /* use instruction immediates */
 730 static int io_imm(void)
 731 {
 732         struct ic *c = &ic[ic_n - 1];
 733         long oc = O_C(c->op);
 734         long n;
 735         if (oc & (O_NUM | O_LOC | O_SYM))
 736                 return 1;
 737         if (oc == O_ADD || oc == O_MUL || oc == O_AND || oc == O_OR ||
 738                         oc == O_XOR || oc == O_EQ || oc == O_NE) {
 739                 if (!ic_num(ic, c->a1, &n)) {
 740                         long t = c->a1;
 741                         c->a1 = c->a2;
 742                         c->a2 = t;
 743                 }
 744         }
 745         if (oc == O_LT || oc == O_GE || oc == O_LE || oc == O_GT) {
 746                 if (!ic_num(ic, c->a1, &n)) {
 747                         int t = c->a1;
 748                         c->a1 = c->a2;
 749                         c->a2 = t;
 750                         c->op ^= 1;
 751                 }
 752         }
 753         if (oc & O_JCC && !ic_num(ic, c->a1, &n)) {
 754                 int t = c->a1;
 755                 c->a1 = c->a2;
 756                 c->a2 = t;
 757                 c->op ^= 1;
 758         }
 759         if (oc & O_JCC && !ic_num(ic, c->a2, &n) && imm_ok(c->op, n, 1)) {
 760                 c->op |= O_NUM;
 761                 c->a2 = n;
 762                 return 0;
 763         }
 764         if (!(oc & O_BOP) || ic_num(ic, c->a2, &n))
 765                 return 1;
 766         if ((oc == O_ADD || oc == O_SUB || oc & O_SHL) && n == 0) {
 767                 iv_drop(1);
 768                 iv_put(c->a1);
 769                 return 0;
 770         }
 771         if (imm_ok(c->op, n, 2)) {
 772                 c->op |= O_NUM;
 773                 c->a2 = n;
 774                 return 0;
 775         }
 776         return 1;
 777 }
 778
 779 /* calling symbols */
 780 static int io_call(void)
 781 {
 782         struct ic *c = &ic[ic_n - 1];
 783         long sym, off;
 784         if (c->op & O_CALL && !ic_sym(ic, c->a1, &sym, &off) && !off) {
 785                 c->op |= O_SYM;
 786                 c->a1 = sym;
 787                 return 0;
 788         }
 789         return 1;
 790 }
 791
 792 /* remove dead code */
 793 static void io_deadcode(void)
 794 {
 795         char *live;
 796         long *nidx;
 797         long src = 0, dst = 0;
 798         int i, j;
 799         /* liveness analysis */
 800         live = calloc(ic_n, sizeof(live[0]));
 801         for (i = ic_n - 1; i >= 0; i--) {
 802                 int n = ic_regcnt(ic + i);
 803                 if (!(ic[i].op & O_OUT) || ic[i].op & O_CALL)
 804                         live[i] = 1;
 805                 if (!live[i])
 806                         continue;
 807                 if (n >= 1)
 808                         live[ic[i].a1] = 1;
 809                 if (n >= 2)
 810                         live[ic[i].a2] = 1;
 811                 if (n >= 3)
 812                         live[ic[i].a3] = 1;
 813                 if (ic[i].op & O_CALL)
 814                         for (j = 0; j < ic[i].a3; j++)
 815                                 live[ic[i].args[j]] = 1;
 816         }
 817         /* the new indices of intermediate instructions */
 818         nidx = calloc(ic_n, sizeof(nidx[0]));
 819         while (src < ic_n) {
 820                 while (src < ic_n && !live[src]) {
 821                         nidx[src] = dst;
 822                         ic_free(&ic[src++]);
 823                 }
 824                 if (src < ic_n) {
 825                         nidx[src] = dst;
 826                         if (src != dst)
 827                                 memcpy(ic + dst, ic + src, sizeof(ic[src]));
 828                         src++;
 829                         dst++;
 830                 }
 831         }
 832         ic_n = dst;
 833         /* adjusting arguments and branch targets */
 834         for (i = 0; i < ic_n; i++) {
 835                 int n = ic_regcnt(ic + i);
 836                 if (n >= 1)
 837                         ic[i].a1 = nidx[ic[i].a1];
 838                 if (n >= 2)
 839                         ic[i].a2 = nidx[ic[i].a2];
 840                 if (n >= 3)
 841                         ic[i].a3 = nidx[ic[i].a3];
 842                 if (ic[i].op & O_JXX)
 843                         ic[i].a3 = nidx[ic[i].a3];
 844                 if (ic[i].op & O_CALL)
 845                         for (j = 0; j < ic[i].a3; j++)
 846                                 ic[i].args[j] = nidx[ic[i].args[j]];
 847         }
 848         free(live);
 849         free(nidx);
 850 }