tccasm.c

   1 /*
   2  *  GAS like assembler for TCC
   3  *
   4  *  Copyright (c) 2001, 2002 Fabrice Bellard
   5  *
   6  * This library is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU Lesser General Public
   8  * License as published by the Free Software Foundation; either
   9  * version 2 of the License, or (at your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14  * Lesser General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public
  17  * License along with this library; if not, write to the Free Software
  18  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  19  */
  20
  21 static int asm_get_local_label_name(TCCState *s1, unsigned int n)
  22 {
  23     char buf[64];
  24     TokenSym *ts;
  25
  26     snprintf(buf, sizeof(buf), "L..%u", n);
  27     ts = tok_alloc(buf, strlen(buf));
  28     return ts->tok;
  29 }
  30
  31 static void asm_expr(TCCState *s1, ExprValue *pe);
  32
  33 /* We do not use the C expression parser to handle symbols. Maybe the
  34    C expression parser could be tweaked to do so. */
  35
  36 static void asm_expr_unary(TCCState *s1, ExprValue *pe)
  37 {
  38     Sym *sym;
  39     int op, n, label;
  40     const char *p;
  41
  42     switch(tok) {
  43     case TOK_PPNUM:
  44         p = tokc.cstr->data;
  45         n = strtoul(p, (char **)&p, 0);
  46         if (*p == 'b' || *p == 'f') {
  47             /* backward or forward label */
  48             label = asm_get_local_label_name(s1, n);
  49             sym = label_find(label);
  50             if (*p == 'b') {
  51                 /* backward : find the last corresponding defined label */
  52                 if (sym && sym->r == 0)
  53                     sym = sym->prev_tok;
  54                 if (!sym)
  55                     error("local label '%d' not found backward", n);
  56             } else {
  57                 /* forward */
  58                 if (!sym || sym->r) {
  59                     /* if the last label is defined, then define a new one */
  60                     sym = label_push(&s1->asm_labels, label, 0);
  61                     sym->type.t = VT_STATIC | VT_VOID;
  62                 }
  63             }
  64             pe->v = 0;
  65             pe->sym = sym;
  66         } else if (*p == '\0') {
  67             pe->v = n;
  68             pe->sym = NULL;
  69         } else {
  70             error("invalid number syntax");
  71         }
  72         next();
  73         break;
  74     case '+':
  75         next();
  76         asm_expr_unary(s1, pe);
  77         break;
  78     case '-':
  79     case '~':
  80         op = tok;
  81         next();
  82         asm_expr_unary(s1, pe);
  83         if (pe->sym)
  84             error("invalid operation with label");
  85         if (op == '-')
  86             pe->v = -pe->v;
  87         else
  88             pe->v = ~pe->v;
  89         break;
  90     case TOK_CCHAR:
  91     case TOK_LCHAR:
  92         pe->v = tokc.i;
  93         pe->sym = NULL;
  94         next();
  95         break;
  96     case '(':
  97         next();
  98         asm_expr(s1, pe);
  99         skip(')');
 100         break;
 101     default:
 102         if (tok >= TOK_IDENT) {
 103             /* label case : if the label was not found, add one */
 104             sym = label_find(tok);
 105             if (!sym) {
 106                 sym = label_push(&s1->asm_labels, tok, 0);
 107                 /* NOTE: by default, the symbol is global */
 108                 sym->type.t = VT_VOID;
 109             }
 110             if (sym->r == SHN_ABS) {
 111                 /* if absolute symbol, no need to put a symbol value */
 112                 pe->v = (long)sym->next;
 113                 pe->sym = NULL;
 114             } else {
 115                 pe->v = 0;
 116                 pe->sym = sym;
 117             }
 118             next();
 119         } else {
 120             error("bad expression syntax [%s]", get_tok_str(tok, &tokc));
 121         }
 122         break;
 123     }
 124 }
 125
 126 static void asm_expr_prod(TCCState *s1, ExprValue *pe)
 127 {
 128     int op;
 129     ExprValue e2;
 130
 131     asm_expr_unary(s1, pe);
 132     for(;;) {
 133         op = tok;
 134         if (op != '*' && op != '/' && op != '%' &&
 135             op != TOK_SHL && op != TOK_SAR)
 136             break;
 137         next();
 138         asm_expr_unary(s1, &e2);
 139         if (pe->sym || e2.sym)
 140             error("invalid operation with label");
 141         switch(op) {
 142         case '*':
 143             pe->v *= e2.v;
 144             break;
 145         case '/':
 146             if (e2.v == 0) {
 147             div_error:
 148                 error("division by zero");
 149             }
 150             pe->v /= e2.v;
 151             break;
 152         case '%':
 153             if (e2.v == 0)
 154                 goto div_error;
 155             pe->v %= e2.v;
 156             break;
 157         case TOK_SHL:
 158             pe->v <<= e2.v;
 159             break;
 160         default:
 161         case TOK_SAR:
 162             pe->v >>= e2.v;
 163             break;
 164         }
 165     }
 166 }
 167
 168 static void asm_expr_logic(TCCState *s1, ExprValue *pe)
 169 {
 170     int op;
 171     ExprValue e2;
 172
 173     asm_expr_prod(s1, pe);
 174     for(;;) {
 175         op = tok;
 176         if (op != '&' && op != '|' && op != '^')
 177             break;
 178         next();
 179         asm_expr_prod(s1, &e2);
 180         if (pe->sym || e2.sym)
 181             error("invalid operation with label");
 182         switch(op) {
 183         case '&':
 184             pe->v &= e2.v;
 185             break;
 186         case '|':
 187             pe->v |= e2.v;
 188             break;
 189         default:
 190         case '^':
 191             pe->v ^= e2.v;
 192             break;
 193         }
 194     }
 195 }
 196
 197 static inline void asm_expr_sum(TCCState *s1, ExprValue *pe)
 198 {
 199     int op;
 200     ExprValue e2;
 201
 202     asm_expr_logic(s1, pe);
 203     for(;;) {
 204         op = tok;
 205         if (op != '+' && op != '-')
 206             break;
 207         next();
 208         asm_expr_logic(s1, &e2);
 209         if (op == '+') {
 210             if (pe->sym != NULL && e2.sym != NULL)
 211                 goto cannot_relocate;
 212             pe->v += e2.v;
 213             if (pe->sym == NULL && e2.sym != NULL)
 214                 pe->sym = e2.sym;
 215         } else {
 216             pe->v -= e2.v;
 217             /* NOTE: we are less powerful than gas in that case
 218                because we store only one symbol in the expression */
 219             if (!pe->sym && !e2.sym) {
 220                 /* OK */
 221             } else if (pe->sym && !e2.sym) {
 222                 /* OK */
 223             } else if (pe->sym && e2.sym) {
 224                 if (pe->sym == e2.sym) {
 225                     /* OK */
 226                 } else if (pe->sym->r == e2.sym->r && pe->sym->r != 0) {
 227                     /* we also accept defined symbols in the same section */
 228                     pe->v += (long)pe->sym->next - (long)e2.sym->next;
 229                 } else {
 230                     goto cannot_relocate;
 231                 }
 232                 pe->sym = NULL; /* same symbols can be substracted to NULL */
 233             } else {
 234             cannot_relocate:
 235                 error("invalid operation with label");
 236             }
 237         }
 238     }
 239 }
 240
 241 static void asm_expr(TCCState *s1, ExprValue *pe)
 242 {
 243     asm_expr_sum(s1, pe);
 244 }
 245
 246 static int asm_int_expr(TCCState *s1)
 247 {
 248     ExprValue e;
 249     asm_expr(s1, &e);
 250     if (e.sym)
 251         expect("constant");
 252     return e.v;
 253 }
 254
 255 /* NOTE: the same name space as C labels is used to avoid using too
 256    much memory when storing labels in TokenStrings */
 257 static void asm_new_label1(TCCState *s1, int label, int is_local,
 258                            int sh_num, int value)
 259 {
 260     Sym *sym;
 261
 262     sym = label_find(label);
 263     if (sym) {
 264         if (sym->r) {
 265             /* the label is already defined */
 266             if (!is_local) {
 267                 error("assembler label '%s' already defined",
 268                       get_tok_str(label, NULL));
 269             } else {
 270                 /* redefinition of local labels is possible */
 271                 goto new_label;
 272             }
 273         }
 274     } else {
 275     new_label:
 276         sym = label_push(&s1->asm_labels, label, 0);
 277         sym->type.t = VT_STATIC | VT_VOID;
 278     }
 279     sym->r = sh_num;
 280     sym->next = (void *)value;
 281 }
 282
 283 static void asm_new_label(TCCState *s1, int label, int is_local)
 284 {
 285     asm_new_label1(s1, label, is_local, cur_text_section->sh_num, ind);
 286 }
 287
 288 static void asm_free_labels(TCCState *st)
 289 {
 290     Sym *s, *s1;
 291     Section *sec;
 292
 293     for(s = st->asm_labels; s != NULL; s = s1) {
 294         s1 = s->prev;
 295         /* define symbol value in object file */
 296         if (s->r) {
 297             if (s->r == SHN_ABS)
 298                 sec = SECTION_ABS;
 299             else
 300                 sec = st->sections[s->r];
 301             put_extern_sym(s, sec, (long)s->next, 0);
 302         }
 303         /* remove label */
 304         table_ident[s->v - TOK_IDENT]->sym_label = NULL;
 305         tcc_free(s);
 306     }
 307     st->asm_labels = NULL;
 308 }
 309
 310 static void use_section1(TCCState *s1, Section *sec)
 311 {
 312     cur_text_section->data_offset = ind;
 313     cur_text_section = sec;
 314     ind = cur_text_section->data_offset;
 315 }
 316
 317 static void use_section(TCCState *s1, const char *name)
 318 {
 319     Section *sec;
 320     sec = find_section(s1, name);
 321     use_section1(s1, sec);
 322 }
 323
 324 static void asm_parse_directive(TCCState *s1)
 325 {
 326     int n, offset, v, size, tok1;
 327     Section *sec;
 328     uint8_t *ptr;
 329
 330     /* assembler directive */
 331     next();
 332     sec = cur_text_section;
 333     switch(tok) {
 334     case TOK_ASM_align:
 335     case TOK_ASM_skip:
 336     case TOK_ASM_space:
 337         tok1 = tok;
 338         next();
 339         n = asm_int_expr(s1);
 340         if (tok1 == TOK_ASM_align) {
 341             if (n < 0 || (n & (n-1)) != 0)
 342                 error("alignment must be a positive power of two");
 343             offset = (ind + n - 1) & -n;
 344             size = offset - ind;
 345             /* the section must have a compatible alignment */
 346             if (sec->sh_addralign < n)
 347                 sec->sh_addralign = n;
 348         } else {
 349             size = n;
 350         }
 351         v = 0;
 352         if (tok == ',') {
 353             next();
 354             v = asm_int_expr(s1);
 355         }
 356     zero_pad:
 357         if (sec->sh_type != SHT_NOBITS) {
 358             sec->data_offset = ind;
 359             ptr = section_ptr_add(sec, size);
 360             memset(ptr, v, size);
 361         }
 362         ind += size;
 363         break;
 364     case TOK_ASM_byte:
 365         size = 1;
 366         goto asm_data;
 367     case TOK_ASM_word:
 368     case TOK_SHORT:
 369         size = 2;
 370         goto asm_data;
 371     case TOK_LONG:
 372     case TOK_INT:
 373         size = 4;
 374     asm_data:
 375         next();
 376         for(;;) {
 377             ExprValue e;
 378             asm_expr(s1, &e);
 379             if (sec->sh_type != SHT_NOBITS) {
 380                 if (size == 4) {
 381                     gen_expr32(&e);
 382                 } else {
 383                     if (e.sym)
 384                         expect("constant");
 385                     if (size == 1)
 386                         g(e.v);
 387                     else
 388                         gen_le16(e.v);
 389                 }
 390             } else {
 391                 ind += size;
 392             }
 393             if (tok != ',')
 394                 break;
 395             next();
 396         }
 397         break;
 398     case TOK_ASM_fill:
 399         {
 400             int repeat, size, val, i, j;
 401             uint8_t repeat_buf[8];
 402             next();
 403             repeat = asm_int_expr(s1);
 404             if (repeat < 0) {
 405                 error("repeat < 0; .fill ignored");
 406                 break;
 407             }
 408             size = 1;
 409             val = 0;
 410             if (tok == ',') {
 411                 next();
 412                 size = asm_int_expr(s1);
 413                 if (size < 0) {
 414                     error("size < 0; .fill ignored");
 415                     break;
 416                 }
 417                 if (size > 8)
 418                     size = 8;
 419                 if (tok == ',') {
 420                     next();
 421                     val = asm_int_expr(s1);
 422                 }
 423             }
 424             /* XXX: endianness */
 425             repeat_buf[0] = val;
 426             repeat_buf[1] = val >> 8;
 427             repeat_buf[2] = val >> 16;
 428             repeat_buf[3] = val >> 24;
 429             repeat_buf[4] = 0;
 430             repeat_buf[5] = 0;
 431             repeat_buf[6] = 0;
 432             repeat_buf[7] = 0;
 433             for(i = 0; i < repeat; i++) {
 434                 for(j = 0; j < size; j++) {
 435                     g(repeat_buf[j]);
 436                 }
 437             }
 438         }
 439         break;
 440     case TOK_ASM_org:
 441         {
 442             unsigned long n;
 443             next();
 444             /* XXX: handle section symbols too */
 445             n = asm_int_expr(s1);
 446             if (n < ind)
 447                 error("attempt to .org backwards");
 448             v = 0;
 449             size = n - ind;
 450             goto zero_pad;
 451         }
 452         break;
 453     case TOK_ASM_globl:
 454     case TOK_ASM_global:
 455         {
 456             Sym *sym;
 457
 458             next();
 459             sym = label_find(tok);
 460             if (!sym) {
 461                 sym = label_push(&s1->asm_labels, tok, 0);
 462                 sym->type.t = VT_VOID;
 463             }
 464             sym->type.t &= ~VT_STATIC;
 465             next();
 466         }
 467         break;
 468     case TOK_ASM_string:
 469     case TOK_ASM_ascii:
 470     case TOK_ASM_asciz:
 471         {
 472             const uint8_t *p;
 473             int i, size, t;
 474
 475             t = tok;
 476             next();
 477             for(;;) {
 478                 if (tok != TOK_STR)
 479                     expect("string constant");
 480                 p = tokc.cstr->data;
 481                 size = tokc.cstr->size;
 482                 if (t == TOK_ASM_ascii && size > 0)
 483                     size--;
 484                 for(i = 0; i < size; i++)
 485                     g(p[i]);
 486                 next();
 487                 if (tok == ',') {
 488                     next();
 489                 } else if (tok != TOK_STR) {
 490                     break;
 491                 }
 492             }
 493         }
 494         break;
 495     case TOK_ASM_text:
 496     case TOK_ASM_data:
 497     case TOK_ASM_bss:
 498         {
 499             char sname[64];
 500             tok1 = tok;
 501             n = 0;
 502             next();
 503             if (tok != ';' && tok != TOK_LINEFEED) {
 504                 n = asm_int_expr(s1);
 505                 next();
 506             }
 507             sprintf(sname, (n?".%s%d":".%s"), get_tok_str(tok1, NULL), n);
 508             use_section(s1, sname);
 509         }
 510         break;
 511     case TOK_SECTION1:
 512         {
 513             char sname[256];
 514
 515             /* XXX: support more options */
 516             next();
 517             sname[0] = '\0';
 518             while (tok != ';' && tok != TOK_LINEFEED && tok != ',') {
 519                 if (tok == TOK_STR)
 520                     pstrcat(sname, sizeof(sname), tokc.cstr->data);
 521                 else
 522                     pstrcat(sname, sizeof(sname), get_tok_str(tok, NULL));
 523                 next();
 524             }
 525             if (tok == ',') {
 526                 /* skip section options */
 527                 next();
 528                 if (tok != TOK_STR)
 529                     expect("string constant");
 530                 next();
 531             }
 532             last_text_section = cur_text_section;
 533             use_section(s1, sname);
 534         }
 535         break;
 536     case TOK_ASM_previous:
 537         {
 538             Section *sec;
 539             next();
 540             if (!last_text_section)
 541                 error("no previous section referenced");
 542             sec = cur_text_section;
 543             use_section1(s1, last_text_section);
 544             last_text_section = sec;
 545         }
 546         break;
 547     default:
 548         error("unknown assembler directive '.%s'", get_tok_str(tok, NULL));
 549         break;
 550     }
 551 }
 552
 553
 554 /* assemble a file */
 555 static int tcc_assemble_internal(TCCState *s1, int do_preprocess)
 556 {
 557     int opcode;
 558
 559 #if 0
 560     /* print stats about opcodes */
 561     {
 562         const ASMInstr *pa;
 563         int freq[4];
 564         int op_vals[500];
 565         int nb_op_vals, i, j;
 566
 567         nb_op_vals = 0;
 568         memset(freq, 0, sizeof(freq));
 569         for(pa = asm_instrs; pa->sym != 0; pa++) {
 570             freq[pa->nb_ops]++;
 571             for(i=0;i<pa->nb_ops;i++) {
 572                 for(j=0;j<nb_op_vals;j++) {
 573                     if (pa->op_type[i] == op_vals[j])
 574                         goto found;
 575                 }
 576                 op_vals[nb_op_vals++] = pa->op_type[i];
 577             found: ;
 578             }
 579         }
 580         for(i=0;i<nb_op_vals;i++) {
 581             int v = op_vals[i];
 582             if ((v & (v - 1)) != 0)
 583                 printf("%3d: %08x\n", i, v);
 584         }
 585         printf("size=%d nb=%d f0=%d f1=%d f2=%d f3=%d\n",
 586                sizeof(asm_instrs), sizeof(asm_instrs) / sizeof(ASMInstr),
 587                freq[0], freq[1], freq[2], freq[3]);
 588     }
 589 #endif
 590
 591     /* XXX: undefine C labels */
 592
 593     ch = file->buf_ptr[0];
 594     tok_flags = TOK_FLAG_BOL | TOK_FLAG_BOF;
 595     parse_flags = PARSE_FLAG_ASM_COMMENTS;
 596     if (do_preprocess)
 597         parse_flags |= PARSE_FLAG_PREPROCESS;
 598     next();
 599     for(;;) {
 600         if (tok == TOK_EOF)
 601             break;
 602         parse_flags |= PARSE_FLAG_LINEFEED; /* XXX: suppress that hack */
 603     redo:
 604         if (tok == '#') {
 605             /* horrible gas comment */
 606             while (tok != TOK_LINEFEED)
 607                 next();
 608         } else if (tok == '.') {
 609             asm_parse_directive(s1);
 610         } else if (tok == TOK_PPNUM) {
 611             const char *p;
 612             int n;
 613             p = tokc.cstr->data;
 614             n = strtoul(p, (char **)&p, 10);
 615             if (*p != '\0')
 616                 expect("':'");
 617             /* new local label */
 618             asm_new_label(s1, asm_get_local_label_name(s1, n), 1);
 619             next();
 620             skip(':');
 621             goto redo;
 622         } else if (tok >= TOK_IDENT) {
 623             /* instruction or label */
 624             opcode = tok;
 625             next();
 626             if (tok == ':') {
 627                 /* new label */
 628                 asm_new_label(s1, opcode, 0);
 629                 next();
 630                 goto redo;
 631             } else if (tok == '=') {
 632                 int n;
 633                 next();
 634                 n = asm_int_expr(s1);
 635                 asm_new_label1(s1, opcode, 0, SHN_ABS, n);
 636                 goto redo;
 637             } else {
 638                 asm_opcode(s1, opcode);
 639             }
 640         }
 641         /* end of line */
 642         if (tok != ';' && tok != TOK_LINEFEED){
 643             expect("end of line");
 644         }
 645         parse_flags &= ~PARSE_FLAG_LINEFEED; /* XXX: suppress that hack */
 646         next();
 647     }
 648
 649     asm_free_labels(s1);
 650
 651     return 0;
 652 }
 653
 654 /* Assemble the current file */
 655 static int tcc_assemble(TCCState *s1, int do_preprocess)
 656 {
 657     Sym *define_start;
 658     int ret;
 659
 660     preprocess_init(s1);
 661
 662     /* default section is text */
 663     cur_text_section = text_section;
 664     ind = cur_text_section->data_offset;
 665
 666     define_start = define_stack;
 667
 668     ret = tcc_assemble_internal(s1, do_preprocess);
 669
 670     cur_text_section->data_offset = ind;
 671
 672     free_defines(define_start);
 673
 674     return ret;
 675 }
 676
 677 /********************************************************************/
 678 /* GCC inline asm support */
 679
 680 /* assemble the string 'str' in the current C compilation unit without
 681    C preprocessing. NOTE: str is modified by modifying the '\0' at the
 682    end */
 683 static void tcc_assemble_inline(TCCState *s1, char *str, int len)
 684 {
 685     BufferedFile *bf, *saved_file;
 686     int saved_parse_flags, *saved_macro_ptr;
 687
 688     bf = tcc_malloc(sizeof(BufferedFile));
 689     memset(bf, 0, sizeof(BufferedFile));
 690     bf->fd = -1;
 691     bf->buf_ptr = str;
 692     bf->buf_end = str + len;
 693     str[len] = CH_EOB;
 694     /* same name as current file so that errors are correctly
 695        reported */
 696     pstrcpy(bf->filename, sizeof(bf->filename), file->filename);
 697     bf->line_num = file->line_num;
 698     saved_file = file;
 699     file = bf;
 700     saved_parse_flags = parse_flags;
 701     saved_macro_ptr = macro_ptr;
 702     macro_ptr = NULL;
 703
 704     tcc_assemble_internal(s1, 0);
 705
 706     parse_flags = saved_parse_flags;
 707     macro_ptr = saved_macro_ptr;
 708     file = saved_file;
 709     tcc_free(bf);
 710 }
 711
 712 /* find a constraint by its number or id (gcc 3 extended
 713    syntax). return -1 if not found. Return in *pp in char after the
 714    constraint */
 715 static int find_constraint(ASMOperand *operands, int nb_operands,
 716                            const char *name, const char **pp)
 717 {
 718     int index;
 719     TokenSym *ts;
 720     const char *p;
 721
 722     if (isnum(*name)) {
 723         index = 0;
 724         while (isnum(*name)) {
 725             index = (index * 10) + (*name) - '0';
 726             name++;
 727         }
 728         if ((unsigned)index >= nb_operands)
 729             index = -1;
 730     } else if (*name == '[') {
 731         name++;
 732         p = strchr(name, ']');
 733         if (p) {
 734             ts = tok_alloc(name, p - name);
 735             for(index = 0; index < nb_operands; index++) {
 736                 if (operands[index].id == ts->tok)
 737                     goto found;
 738             }
 739             index = -1;
 740         found:
 741             name = p + 1;
 742         } else {
 743             index = -1;
 744         }
 745     } else {
 746         index = -1;
 747     }
 748     if (pp)
 749         *pp = name;
 750     return index;
 751 }
 752
 753 static void subst_asm_operands(ASMOperand *operands, int nb_operands,
 754                                int nb_outputs,
 755                                CString *out_str, CString *in_str)
 756 {
 757     int c, index, modifier;
 758     const char *str;
 759     ASMOperand *op;
 760     SValue sv;
 761
 762     cstr_new(out_str);
 763     str = in_str->data;
 764     for(;;) {
 765         c = *str++;
 766         if (c == '%') {
 767             if (*str == '%') {
 768                 str++;
 769                 goto add_char;
 770             }
 771             modifier = 0;
 772             if (*str == 'c' || *str == 'n' ||
 773                 *str == 'b' || *str == 'w' || *str == 'h')
 774                 modifier = *str++;
 775             index = find_constraint(operands, nb_operands, str, &str);
 776             if (index < 0)
 777                 error("invalid operand reference after %%");
 778             op = &operands[index];
 779             sv = *op->vt;
 780             if (op->reg >= 0) {
 781                 sv.r = op->reg;
 782                 if ((op->vt->r & VT_VALMASK) == VT_LLOCAL)
 783                     sv.r |= VT_LVAL;
 784             }
 785             subst_asm_operand(out_str, &sv, modifier);
 786         } else {
 787         add_char:
 788             cstr_ccat(out_str, c);
 789             if (c == '\0')
 790                 break;
 791         }
 792     }
 793 }
 794
 795
 796 static void parse_asm_operands(ASMOperand *operands, int *nb_operands_ptr,
 797                                int is_output)
 798 {
 799     ASMOperand *op;
 800     int nb_operands;
 801
 802     if (tok != ':') {
 803         nb_operands = *nb_operands_ptr;
 804         for(;;) {
 805             if (nb_operands >= MAX_ASM_OPERANDS)
 806                 error("too many asm operands");
 807             op = &operands[nb_operands++];
 808             op->id = 0;
 809             if (tok == '[') {
 810                 next();
 811                 if (tok < TOK_IDENT)
 812                     expect("identifier");
 813                 op->id = tok;
 814                 next();
 815                 skip(']');
 816             }
 817             if (tok != TOK_STR)
 818                 expect("string constant");
 819             op->constraint = tcc_malloc(tokc.cstr->size);
 820             strcpy(op->constraint, tokc.cstr->data);
 821             next();
 822             skip('(');
 823             gexpr();
 824             if (is_output) {
 825                 test_lvalue();
 826             } else {
 827                 /* we want to avoid LLOCAL case, except when the 'm'
 828                    constraint is used. Note that it may come from
 829                    register storage, so we need to convert (reg)
 830                    case */
 831                 if ((vtop->r & VT_LVAL) &&
 832                     ((vtop->r & VT_VALMASK) == VT_LLOCAL ||
 833                      (vtop->r & VT_VALMASK) < VT_CONST) &&
 834                     !strchr(op->constraint, 'm')) {
 835                     gv(RC_INT);
 836                 }
 837             }
 838             op->vt = vtop;
 839             skip(')');
 840             if (tok == ',') {
 841                 next();
 842             } else {
 843                 break;
 844             }
 845         }
 846         *nb_operands_ptr = nb_operands;
 847     }
 848 }
 849
 850 static void parse_asm_str(CString *astr)
 851 {
 852     skip('(');
 853     /* read the string */
 854     if (tok != TOK_STR)
 855         expect("string constant");
 856     cstr_new(astr);
 857     while (tok == TOK_STR) {
 858         /* XXX: add \0 handling too ? */
 859         cstr_cat(astr, tokc.cstr->data);
 860         next();
 861     }
 862     cstr_ccat(astr, '\0');
 863 }
 864
 865 /* parse the GCC asm() instruction */
 866 static void asm_instr(void)
 867 {
 868     CString astr, astr1;
 869     ASMOperand operands[MAX_ASM_OPERANDS];
 870     int nb_inputs, nb_outputs, nb_operands, i, must_subst, out_reg;
 871     uint8_t clobber_regs[NB_ASM_REGS];
 872
 873     next();
 874     /* since we always generate the asm() instruction, we can ignore
 875        volatile */
 876     if (tok == TOK_VOLATILE1 || tok == TOK_VOLATILE2 || tok == TOK_VOLATILE3) {
 877         next();
 878     }
 879     parse_asm_str(&astr);
 880     nb_operands = 0;
 881     nb_outputs = 0;
 882     must_subst = 0;
 883     memset(clobber_regs, 0, sizeof(clobber_regs));
 884     if (tok == ':') {
 885         next();
 886         must_subst = 1;
 887         /* output args */
 888         parse_asm_operands(operands, &nb_operands, 1);
 889         nb_outputs = nb_operands;
 890         if (tok == ':') {
 891             next();
 892             /* input args */
 893             parse_asm_operands(operands, &nb_operands, 0);
 894             if (tok == ':') {
 895                 /* clobber list */
 896                 /* XXX: handle registers */
 897                 next();
 898                 for(;;) {
 899                     if (tok != TOK_STR)
 900                         expect("string constant");
 901                     asm_clobber(clobber_regs, tokc.cstr->data);
 902                     next();
 903                     if (tok == ',') {
 904                         next();
 905                     } else {
 906                         break;
 907                     }
 908                 }
 909             }
 910         }
 911     }
 912     skip(')');
 913     /* NOTE: we do not eat the ';' so that we can restore the current
 914        token after the assembler parsing */
 915     if (tok != ';')
 916         expect("';'");
 917     nb_inputs = nb_operands - nb_outputs;
 918
 919     /* save all values in the memory */
 920     save_regs(0);
 921
 922     /* compute constraints */
 923     asm_compute_constraints(operands, nb_operands, nb_outputs,
 924                             clobber_regs, &out_reg);
 925
 926     /* substitute the operands in the asm string. No substitution is
 927        done if no operands (GCC behaviour) */
 928 #ifdef ASM_DEBUG
 929     printf("asm: \"%s\"\n", (char *)astr.data);
 930 #endif
 931     if (must_subst) {
 932         subst_asm_operands(operands, nb_operands, nb_outputs, &astr1, &astr);
 933         cstr_free(&astr);
 934     } else {
 935         astr1 = astr;
 936     }
 937 #ifdef ASM_DEBUG
 938     printf("subst_asm: \"%s\"\n", (char *)astr1.data);
 939 #endif
 940
 941     /* generate loads */
 942     asm_gen_code(operands, nb_operands, nb_outputs, 0,
 943                  clobber_regs, out_reg);
 944
 945     /* assemble the string with tcc internal assembler */
 946     tcc_assemble_inline(tcc_state, astr1.data, astr1.size - 1);
 947
 948     /* restore the current C token */
 949     next();
 950
 951     /* store the output values if needed */
 952     asm_gen_code(operands, nb_operands, nb_outputs, 1,
 953                  clobber_regs, out_reg);
 954
 955     /* free everything */
 956     for(i=0;i<nb_operands;i++) {
 957         ASMOperand *op;
 958         op = &operands[i];
 959         tcc_free(op->constraint);
 960         vpop();
 961     }
 962     cstr_free(&astr1);
 963 }
 964
 965 static void asm_global_instr(void)
 966 {
 967     CString astr;
 968
 969     next();
 970     parse_asm_str(&astr);
 971     skip(')');
 972     /* NOTE: we do not eat the ';' so that we can restore the current
 973        token after the assembler parsing */
 974     if (tok != ';')
 975         expect("';'");
 976
 977 #ifdef ASM_DEBUG
 978     printf("asm_global: \"%s\"\n", (char *)astr.data);
 979 #endif
 980     cur_text_section = text_section;
 981     ind = cur_text_section->data_offset;
 982
 983     /* assemble the string with tcc internal assembler */
 984     tcc_assemble_inline(tcc_state, astr.data, astr.size - 1);
 985
 986     cur_text_section->data_offset = ind;
 987
 988     /* restore the current C token */
 989     next();
 990
 991     cstr_free(&astr);
 992 }