tccasm.c

   1 /*
   2  *  GAS like assembler for TCC
   3  *
   4  *  Copyright (c) 2001-2004 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_sym2(s, sec, (long)s->next, 0, 0);
 302         }
 303         /* remove label */
 304         table_ident[s->v - TOK_IDENT]->sym_label = NULL;
 305         sym_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_quad:
 365         next();
 366         for(;;) {
 367             uint64_t vl;
 368             const char *p;
 369
 370             p = tokc.cstr->data;
 371             if (tok != TOK_PPNUM) {
 372             error_constant:
 373                 error("64 bit constant");
 374             }
 375             vl = strtoll(p, (char **)&p, 0);
 376             if (*p != '\0')
 377                 goto error_constant;
 378             next();
 379             if (sec->sh_type != SHT_NOBITS) {
 380                 /* XXX: endianness */
 381                 gen_le32(vl);
 382                 gen_le32(vl >> 32);
 383             } else {
 384                 ind += 8;
 385             }
 386             if (tok != ',')
 387                 break;
 388             next();
 389         }
 390         break;
 391     case TOK_ASM_byte:
 392         size = 1;
 393         goto asm_data;
 394     case TOK_ASM_word:
 395     case TOK_SHORT:
 396         size = 2;
 397         goto asm_data;
 398     case TOK_LONG:
 399     case TOK_INT:
 400         size = 4;
 401     asm_data:
 402         next();
 403         for(;;) {
 404             ExprValue e;
 405             asm_expr(s1, &e);
 406             if (sec->sh_type != SHT_NOBITS) {
 407                 if (size == 4) {
 408                     gen_expr32(&e);
 409                 } else {
 410                     if (e.sym)
 411                         expect("constant");
 412                     if (size == 1)
 413                         g(e.v);
 414                     else
 415                         gen_le16(e.v);
 416                 }
 417             } else {
 418                 ind += size;
 419             }
 420             if (tok != ',')
 421                 break;
 422             next();
 423         }
 424         break;
 425     case TOK_ASM_fill:
 426         {
 427             int repeat, size, val, i, j;
 428             uint8_t repeat_buf[8];
 429             next();
 430             repeat = asm_int_expr(s1);
 431             if (repeat < 0) {
 432                 error("repeat < 0; .fill ignored");
 433                 break;
 434             }
 435             size = 1;
 436             val = 0;
 437             if (tok == ',') {
 438                 next();
 439                 size = asm_int_expr(s1);
 440                 if (size < 0) {
 441                     error("size < 0; .fill ignored");
 442                     break;
 443                 }
 444                 if (size > 8)
 445                     size = 8;
 446                 if (tok == ',') {
 447                     next();
 448                     val = asm_int_expr(s1);
 449                 }
 450             }
 451             /* XXX: endianness */
 452             repeat_buf[0] = val;
 453             repeat_buf[1] = val >> 8;
 454             repeat_buf[2] = val >> 16;
 455             repeat_buf[3] = val >> 24;
 456             repeat_buf[4] = 0;
 457             repeat_buf[5] = 0;
 458             repeat_buf[6] = 0;
 459             repeat_buf[7] = 0;
 460             for(i = 0; i < repeat; i++) {
 461                 for(j = 0; j < size; j++) {
 462                     g(repeat_buf[j]);
 463                 }
 464             }
 465         }
 466         break;
 467     case TOK_ASM_org:
 468         {
 469             unsigned long n;
 470             next();
 471             /* XXX: handle section symbols too */
 472             n = asm_int_expr(s1);
 473             if (n < ind)
 474                 error("attempt to .org backwards");
 475             v = 0;
 476             size = n - ind;
 477             goto zero_pad;
 478         }
 479         break;
 480     case TOK_ASM_globl:
 481     case TOK_ASM_global:
 482         {
 483             Sym *sym;
 484
 485             next();
 486             sym = label_find(tok);
 487             if (!sym) {
 488                 sym = label_push(&s1->asm_labels, tok, 0);
 489                 sym->type.t = VT_VOID;
 490             }
 491             sym->type.t &= ~VT_STATIC;
 492             next();
 493         }
 494         break;
 495     case TOK_ASM_string:
 496     case TOK_ASM_ascii:
 497     case TOK_ASM_asciz:
 498         {
 499             const uint8_t *p;
 500             int i, size, t;
 501
 502             t = tok;
 503             next();
 504             for(;;) {
 505                 if (tok != TOK_STR)
 506                     expect("string constant");
 507                 p = tokc.cstr->data;
 508                 size = tokc.cstr->size;
 509                 if (t == TOK_ASM_ascii && size > 0)
 510                     size--;
 511                 for(i = 0; i < size; i++)
 512                     g(p[i]);
 513                 next();
 514                 if (tok == ',') {
 515                     next();
 516                 } else if (tok != TOK_STR) {
 517                     break;
 518                 }
 519             }
 520         }
 521         break;
 522     case TOK_ASM_text:
 523     case TOK_ASM_data:
 524     case TOK_ASM_bss:
 525         {
 526             char sname[64];
 527             tok1 = tok;
 528             n = 0;
 529             next();
 530             if (tok != ';' && tok != TOK_LINEFEED) {
 531                 n = asm_int_expr(s1);
 532                 next();
 533             }
 534             sprintf(sname, (n?".%s%d":".%s"), get_tok_str(tok1, NULL), n);
 535             use_section(s1, sname);
 536         }
 537         break;
 538     case TOK_SECTION1:
 539         {
 540             char sname[256];
 541
 542             /* XXX: support more options */
 543             next();
 544             sname[0] = '\0';
 545             while (tok != ';' && tok != TOK_LINEFEED && tok != ',') {
 546                 if (tok == TOK_STR)
 547                     pstrcat(sname, sizeof(sname), tokc.cstr->data);
 548                 else
 549                     pstrcat(sname, sizeof(sname), get_tok_str(tok, NULL));
 550                 next();
 551             }
 552             if (tok == ',') {
 553                 /* skip section options */
 554                 next();
 555                 if (tok != TOK_STR)
 556                     expect("string constant");
 557                 next();
 558             }
 559             last_text_section = cur_text_section;
 560             use_section(s1, sname);
 561         }
 562         break;
 563     case TOK_ASM_previous:
 564         {
 565             Section *sec;
 566             next();
 567             if (!last_text_section)
 568                 error("no previous section referenced");
 569             sec = cur_text_section;
 570             use_section1(s1, last_text_section);
 571             last_text_section = sec;
 572         }
 573         break;
 574     default:
 575         error("unknown assembler directive '.%s'", get_tok_str(tok, NULL));
 576         break;
 577     }
 578 }
 579
 580
 581 /* assemble a file */
 582 static int tcc_assemble_internal(TCCState *s1, int do_preprocess)
 583 {
 584     int opcode;
 585
 586 #if 0
 587     /* print stats about opcodes */
 588     {
 589         const ASMInstr *pa;
 590         int freq[4];
 591         int op_vals[500];
 592         int nb_op_vals, i, j;
 593
 594         nb_op_vals = 0;
 595         memset(freq, 0, sizeof(freq));
 596         for(pa = asm_instrs; pa->sym != 0; pa++) {
 597             freq[pa->nb_ops]++;
 598             for(i=0;i<pa->nb_ops;i++) {
 599                 for(j=0;j<nb_op_vals;j++) {
 600                     if (pa->op_type[i] == op_vals[j])
 601                         goto found;
 602                 }
 603                 op_vals[nb_op_vals++] = pa->op_type[i];
 604             found: ;
 605             }
 606         }
 607         for(i=0;i<nb_op_vals;i++) {
 608             int v = op_vals[i];
 609             if ((v & (v - 1)) != 0)
 610                 printf("%3d: %08x\n", i, v);
 611         }
 612         printf("size=%d nb=%d f0=%d f1=%d f2=%d f3=%d\n",
 613                sizeof(asm_instrs), sizeof(asm_instrs) / sizeof(ASMInstr),
 614                freq[0], freq[1], freq[2], freq[3]);
 615     }
 616 #endif
 617
 618     /* XXX: undefine C labels */
 619
 620     ch = file->buf_ptr[0];
 621     tok_flags = TOK_FLAG_BOL | TOK_FLAG_BOF;
 622     parse_flags = PARSE_FLAG_ASM_COMMENTS;
 623     if (do_preprocess)
 624         parse_flags |= PARSE_FLAG_PREPROCESS;
 625     next();
 626     for(;;) {
 627         if (tok == TOK_EOF)
 628             break;
 629         parse_flags |= PARSE_FLAG_LINEFEED; /* XXX: suppress that hack */
 630     redo:
 631         if (tok == '#') {
 632             /* horrible gas comment */
 633             while (tok != TOK_LINEFEED)
 634                 next();
 635         } else if (tok == '.') {
 636             asm_parse_directive(s1);
 637         } else if (tok == TOK_PPNUM) {
 638             const char *p;
 639             int n;
 640             p = tokc.cstr->data;
 641             n = strtoul(p, (char **)&p, 10);
 642             if (*p != '\0')
 643                 expect("':'");
 644             /* new local label */
 645             asm_new_label(s1, asm_get_local_label_name(s1, n), 1);
 646             next();
 647             skip(':');
 648             goto redo;
 649         } else if (tok >= TOK_IDENT) {
 650             /* instruction or label */
 651             opcode = tok;
 652             next();
 653             if (tok == ':') {
 654                 /* new label */
 655                 asm_new_label(s1, opcode, 0);
 656                 next();
 657                 goto redo;
 658             } else if (tok == '=') {
 659                 int n;
 660                 next();
 661                 n = asm_int_expr(s1);
 662                 asm_new_label1(s1, opcode, 0, SHN_ABS, n);
 663                 goto redo;
 664             } else {
 665                 asm_opcode(s1, opcode);
 666             }
 667         }
 668         /* end of line */
 669         if (tok != ';' && tok != TOK_LINEFEED){
 670             expect("end of line");
 671         }
 672         parse_flags &= ~PARSE_FLAG_LINEFEED; /* XXX: suppress that hack */
 673         next();
 674     }
 675
 676     asm_free_labels(s1);
 677
 678     return 0;
 679 }
 680
 681 /* Assemble the current file */
 682 static int tcc_assemble(TCCState *s1, int do_preprocess)
 683 {
 684     Sym *define_start;
 685     int ret;
 686
 687     preprocess_init(s1);
 688
 689     /* default section is text */
 690     cur_text_section = text_section;
 691     ind = cur_text_section->data_offset;
 692
 693     define_start = define_stack;
 694
 695     ret = tcc_assemble_internal(s1, do_preprocess);
 696
 697     cur_text_section->data_offset = ind;
 698
 699     free_defines(define_start);
 700
 701     return ret;
 702 }
 703
 704 /********************************************************************/
 705 /* GCC inline asm support */
 706
 707 /* assemble the string 'str' in the current C compilation unit without
 708    C preprocessing. NOTE: str is modified by modifying the '\0' at the
 709    end */
 710 static void tcc_assemble_inline(TCCState *s1, char *str, int len)
 711 {
 712     BufferedFile *bf, *saved_file;
 713     int saved_parse_flags, *saved_macro_ptr;
 714
 715     bf = tcc_malloc(sizeof(BufferedFile));
 716     memset(bf, 0, sizeof(BufferedFile));
 717     bf->fd = -1;
 718     bf->buf_ptr = str;
 719     bf->buf_end = str + len;
 720     str[len] = CH_EOB;
 721     /* same name as current file so that errors are correctly
 722        reported */
 723     pstrcpy(bf->filename, sizeof(bf->filename), file->filename);
 724     bf->line_num = file->line_num;
 725     saved_file = file;
 726     file = bf;
 727     saved_parse_flags = parse_flags;
 728     saved_macro_ptr = macro_ptr;
 729     macro_ptr = NULL;
 730
 731     tcc_assemble_internal(s1, 0);
 732
 733     parse_flags = saved_parse_flags;
 734     macro_ptr = saved_macro_ptr;
 735     file = saved_file;
 736     tcc_free(bf);
 737 }
 738
 739 /* find a constraint by its number or id (gcc 3 extended
 740    syntax). return -1 if not found. Return in *pp in char after the
 741    constraint */
 742 static int find_constraint(ASMOperand *operands, int nb_operands,
 743                            const char *name, const char **pp)
 744 {
 745     int index;
 746     TokenSym *ts;
 747     const char *p;
 748
 749     if (isnum(*name)) {
 750         index = 0;
 751         while (isnum(*name)) {
 752             index = (index * 10) + (*name) - '0';
 753             name++;
 754         }
 755         if ((unsigned)index >= nb_operands)
 756             index = -1;
 757     } else if (*name == '[') {
 758         name++;
 759         p = strchr(name, ']');
 760         if (p) {
 761             ts = tok_alloc(name, p - name);
 762             for(index = 0; index < nb_operands; index++) {
 763                 if (operands[index].id == ts->tok)
 764                     goto found;
 765             }
 766             index = -1;
 767         found:
 768             name = p + 1;
 769         } else {
 770             index = -1;
 771         }
 772     } else {
 773         index = -1;
 774     }
 775     if (pp)
 776         *pp = name;
 777     return index;
 778 }
 779
 780 static void subst_asm_operands(ASMOperand *operands, int nb_operands,
 781                                int nb_outputs,
 782                                CString *out_str, CString *in_str)
 783 {
 784     int c, index, modifier;
 785     const char *str;
 786     ASMOperand *op;
 787     SValue sv;
 788
 789     cstr_new(out_str);
 790     str = in_str->data;
 791     for(;;) {
 792         c = *str++;
 793         if (c == '%') {
 794             if (*str == '%') {
 795                 str++;
 796                 goto add_char;
 797             }
 798             modifier = 0;
 799             if (*str == 'c' || *str == 'n' ||
 800                 *str == 'b' || *str == 'w' || *str == 'h')
 801                 modifier = *str++;
 802             index = find_constraint(operands, nb_operands, str, &str);
 803             if (index < 0)
 804                 error("invalid operand reference after %%");
 805             op = &operands[index];
 806             sv = *op->vt;
 807             if (op->reg >= 0) {
 808                 sv.r = op->reg;
 809                 if ((op->vt->r & VT_VALMASK) == VT_LLOCAL && op->is_memory)
 810                     sv.r |= VT_LVAL;
 811             }
 812             subst_asm_operand(out_str, &sv, modifier);
 813         } else {
 814         add_char:
 815             cstr_ccat(out_str, c);
 816             if (c == '\0')
 817                 break;
 818         }
 819     }
 820 }
 821
 822
 823 static void parse_asm_operands(ASMOperand *operands, int *nb_operands_ptr,
 824                                int is_output)
 825 {
 826     ASMOperand *op;
 827     int nb_operands;
 828
 829     if (tok != ':') {
 830         nb_operands = *nb_operands_ptr;
 831         for(;;) {
 832             if (nb_operands >= MAX_ASM_OPERANDS)
 833                 error("too many asm operands");
 834             op = &operands[nb_operands++];
 835             op->id = 0;
 836             if (tok == '[') {
 837                 next();
 838                 if (tok < TOK_IDENT)
 839                     expect("identifier");
 840                 op->id = tok;
 841                 next();
 842                 skip(']');
 843             }
 844             if (tok != TOK_STR)
 845                 expect("string constant");
 846             op->constraint = tcc_malloc(tokc.cstr->size);
 847             strcpy(op->constraint, tokc.cstr->data);
 848             next();
 849             skip('(');
 850             gexpr();
 851             if (is_output) {
 852                 test_lvalue();
 853             } else {
 854                 /* we want to avoid LLOCAL case, except when the 'm'
 855                    constraint is used. Note that it may come from
 856                    register storage, so we need to convert (reg)
 857                    case */
 858                 if ((vtop->r & VT_LVAL) &&
 859                     ((vtop->r & VT_VALMASK) == VT_LLOCAL ||
 860                      (vtop->r & VT_VALMASK) < VT_CONST) &&
 861                     !strchr(op->constraint, 'm')) {
 862                     gv(RC_INT);
 863                 }
 864             }
 865             op->vt = vtop;
 866             skip(')');
 867             if (tok == ',') {
 868                 next();
 869             } else {
 870                 break;
 871             }
 872         }
 873         *nb_operands_ptr = nb_operands;
 874     }
 875 }
 876
 877 static void parse_asm_str(CString *astr)
 878 {
 879     skip('(');
 880     /* read the string */
 881     if (tok != TOK_STR)
 882         expect("string constant");
 883     cstr_new(astr);
 884     while (tok == TOK_STR) {
 885         /* XXX: add \0 handling too ? */
 886         cstr_cat(astr, tokc.cstr->data);
 887         next();
 888     }
 889     cstr_ccat(astr, '\0');
 890 }
 891
 892 /* parse the GCC asm() instruction */
 893 static void asm_instr(void)
 894 {
 895     CString astr, astr1;
 896     ASMOperand operands[MAX_ASM_OPERANDS];
 897     int nb_inputs, nb_outputs, nb_operands, i, must_subst, out_reg;
 898     uint8_t clobber_regs[NB_ASM_REGS];
 899
 900     next();
 901     /* since we always generate the asm() instruction, we can ignore
 902        volatile */
 903     if (tok == TOK_VOLATILE1 || tok == TOK_VOLATILE2 || tok == TOK_VOLATILE3) {
 904         next();
 905     }
 906     parse_asm_str(&astr);
 907     nb_operands = 0;
 908     nb_outputs = 0;
 909     must_subst = 0;
 910     memset(clobber_regs, 0, sizeof(clobber_regs));
 911     if (tok == ':') {
 912         next();
 913         must_subst = 1;
 914         /* output args */
 915         parse_asm_operands(operands, &nb_operands, 1);
 916         nb_outputs = nb_operands;
 917         if (tok == ':') {
 918             next();
 919             if (tok != ')') {
 920                 /* input args */
 921                 parse_asm_operands(operands, &nb_operands, 0);
 922                 if (tok == ':') {
 923                     /* clobber list */
 924                     /* XXX: handle registers */
 925                     next();
 926                     for(;;) {
 927                         if (tok != TOK_STR)
 928                             expect("string constant");
 929                         asm_clobber(clobber_regs, tokc.cstr->data);
 930                         next();
 931                         if (tok == ',') {
 932                             next();
 933                         } else {
 934                             break;
 935                         }
 936                     }
 937                 }
 938             }
 939         }
 940     }
 941     skip(')');
 942     /* NOTE: we do not eat the ';' so that we can restore the current
 943        token after the assembler parsing */
 944     if (tok != ';')
 945         expect("';'");
 946     nb_inputs = nb_operands - nb_outputs;
 947
 948     /* save all values in the memory */
 949     save_regs(0);
 950
 951     /* compute constraints */
 952     asm_compute_constraints(operands, nb_operands, nb_outputs,
 953                             clobber_regs, &out_reg);
 954
 955     /* substitute the operands in the asm string. No substitution is
 956        done if no operands (GCC behaviour) */
 957 #ifdef ASM_DEBUG
 958     printf("asm: \"%s\"\n", (char *)astr.data);
 959 #endif
 960     if (must_subst) {
 961         subst_asm_operands(operands, nb_operands, nb_outputs, &astr1, &astr);
 962         cstr_free(&astr);
 963     } else {
 964         astr1 = astr;
 965     }
 966 #ifdef ASM_DEBUG
 967     printf("subst_asm: \"%s\"\n", (char *)astr1.data);
 968 #endif
 969
 970     /* generate loads */
 971     asm_gen_code(operands, nb_operands, nb_outputs, 0,
 972                  clobber_regs, out_reg);
 973
 974     /* assemble the string with tcc internal assembler */
 975     tcc_assemble_inline(tcc_state, astr1.data, astr1.size - 1);
 976
 977     /* restore the current C token */
 978     next();
 979
 980     /* store the output values if needed */
 981     asm_gen_code(operands, nb_operands, nb_outputs, 1,
 982                  clobber_regs, out_reg);
 983
 984     /* free everything */
 985     for(i=0;i<nb_operands;i++) {
 986         ASMOperand *op;
 987         op = &operands[i];
 988         tcc_free(op->constraint);
 989         vpop();
 990     }
 991     cstr_free(&astr1);
 992 }
 993
 994 static void asm_global_instr(void)
 995 {
 996     CString astr;
 997
 998     next();
 999     parse_asm_str(&astr);
1000     skip(')');
1001     /* NOTE: we do not eat the ';' so that we can restore the current
1002        token after the assembler parsing */
1003     if (tok != ';')
1004         expect("';'");
1005
1006 #ifdef ASM_DEBUG
1007     printf("asm_global: \"%s\"\n", (char *)astr.data);
1008 #endif
1009     cur_text_section = text_section;
1010     ind = cur_text_section->data_offset;
1011
1012     /* assemble the string with tcc internal assembler */
1013     tcc_assemble_inline(tcc_state, astr.data, astr.size - 1);
1014
1015     cur_text_section->data_offset = ind;
1016
1017     /* restore the current C token */
1018     next();
1019
1020     cstr_free(&astr);
1021 }