gas/expr.c

   1 /* expr.c -operands, expressions-
   2    Copyright (C) 1987, 1990, 1991, 1992, 1993 Free Software Foundation, Inc.
   3
   4    This file is part of GAS, the GNU Assembler.
   5
   6    GAS is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10
  11    GAS 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
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with GAS; see the file COPYING.  If not, write to
  18    the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA. */
  19
  20 /*
  21  * This is really a branch office of as-read.c. I split it out to clearly
  22  * distinguish the world of expressions from the world of statements.
  23  * (It also gives smaller files to re-compile.)
  24  * Here, "operand"s are of expressions, not instructions.
  25  */
  26
  27 #include <ctype.h>
  28 #include <string.h>
  29
  30 #include "as.h"
  31
  32 #include "obstack.h"
  33
  34 static void clean_up_expression PARAMS ((expressionS * expressionP));
  35 extern const char EXP_CHARS[], FLT_CHARS[];
  36
  37 /*
  38  * Build any floating-point literal here.
  39  * Also build any bignum literal here.
  40  */
  41
  42 /* Seems atof_machine can backscan through generic_bignum and hit whatever
  43    happens to be loaded before it in memory.  And its way too complicated
  44    for me to fix right.  Thus a hack.  JF:  Just make generic_bignum bigger,
  45    and never write into the early words, thus they'll always be zero.
  46    I hate Dean's floating-point code.  Bleh.  */
  47 LITTLENUM_TYPE generic_bignum[SIZE_OF_LARGE_NUMBER + 6];
  48 FLONUM_TYPE generic_floating_point_number =
  49 {
  50   &generic_bignum[6],           /* low (JF: Was 0) */
  51   &generic_bignum[SIZE_OF_LARGE_NUMBER + 6 - 1],        /* high JF: (added +6) */
  52   0,                            /* leader */
  53   0,                            /* exponent */
  54   0                             /* sign */
  55 };
  56 /* If nonzero, we've been asked to assemble nan, +inf or -inf */
  57 int generic_floating_point_magic;
  58 \f
  59 floating_constant (expressionP)
  60      expressionS *expressionP;
  61 {
  62   /* input_line_pointer->*/
  63   /* floating-point constant. */
  64   int error_code;
  65
  66   error_code = atof_generic
  67     (&input_line_pointer, ".", EXP_CHARS,
  68      &generic_floating_point_number);
  69
  70   if (error_code)
  71     {
  72       if (error_code == ERROR_EXPONENT_OVERFLOW)
  73         {
  74           as_bad ("bad floating-point constant: exponent overflow, probably assembling junk");
  75         }
  76       else
  77         {
  78           as_bad ("bad floating-point constant: unknown error code=%d.", error_code);
  79         }
  80     }
  81   expressionP->X_seg = big_section;
  82   /* input_line_pointer->just after constant, */
  83   /* which may point to whitespace. */
  84   expressionP->X_add_number = -1;
  85 }
  86
  87
  88
  89 integer_constant (radix, expressionP)
  90      int radix;
  91      expressionS *expressionP;
  92 {
  93   register char *digit_2;       /*->2nd digit of number. */
  94   char c;
  95
  96   register valueT number;       /* offset or (absolute) value */
  97   register short int digit;     /* value of next digit in current radix */
  98   register short int maxdig = 0;/* highest permitted digit value. */
  99   register int too_many_digits = 0;     /* if we see >= this number of */
 100   register char *name;          /* points to name of symbol */
 101   register symbolS *symbolP;    /* points to symbol */
 102
 103   int small;                    /* true if fits in 32 bits. */
 104   extern const char hex_value[]; /* in hex_value.c */
 105
 106   /* may be bignum, or may fit in 32 bits. */
 107   /*
 108    * most numbers fit into 32 bits, and we want this case to be fast.
 109    * so we pretend it will fit into 32 bits. if, after making up a 32
 110    * bit number, we realise that we have scanned more digits than
 111    * comfortably fit into 32 bits, we re-scan the digits coding
 112    * them into a bignum. for decimal and octal numbers we are conservative: some
 113    * numbers may be assumed bignums when in fact they do fit into 32 bits.
 114    * numbers of any radix can have excess leading zeros: we strive
 115    * to recognise this and cast them back into 32 bits.
 116    * we must check that the bignum really is more than 32
 117    * bits, and change it back to a 32-bit number if it fits.
 118    * the number we are looking for is expected to be positive, but
 119    * if it fits into 32 bits as an unsigned number, we let it be a 32-bit
 120    * number. the cavalier approach is for speed in ordinary cases.
 121    */
 122
 123   switch (radix)
 124     {
 125
 126     case 2:
 127       maxdig = 2;
 128       too_many_digits = 33;
 129       break;
 130     case 8:
 131       maxdig = radix = 8;
 132       too_many_digits = 11;
 133       break;
 134     case 16:
 135
 136
 137       maxdig = radix = 16;
 138       too_many_digits = 9;
 139       break;
 140     case 10:
 141       maxdig = radix = 10;
 142       too_many_digits = 11;
 143     }
 144   c = *input_line_pointer;
 145   input_line_pointer++;
 146   digit_2 = input_line_pointer;
 147   for (number = 0; (digit = hex_value[c]) < maxdig; c = *input_line_pointer++)
 148     {
 149       number = number * radix + digit;
 150     }
 151   /* c contains character after number. */
 152   /* input_line_pointer->char after c. */
 153   small = input_line_pointer - digit_2 < too_many_digits;
 154   if (!small)
 155     {
 156       /*
 157        * we saw a lot of digits. manufacture a bignum the hard way.
 158        */
 159       LITTLENUM_TYPE *leader;   /*->high order littlenum of the bignum. */
 160       LITTLENUM_TYPE *pointer;  /*->littlenum we are frobbing now. */
 161       long carry;
 162
 163       leader = generic_bignum;
 164       generic_bignum[0] = 0;
 165       generic_bignum[1] = 0;
 166       /* we could just use digit_2, but lets be mnemonic. */
 167       input_line_pointer = --digit_2;   /*->1st digit. */
 168       c = *input_line_pointer++;
 169       for (; (carry = hex_value[c]) < maxdig; c = *input_line_pointer++)
 170         {
 171           for (pointer = generic_bignum;
 172                pointer <= leader;
 173                pointer++)
 174             {
 175               long work;
 176
 177               work = carry + radix * *pointer;
 178               *pointer = work & LITTLENUM_MASK;
 179               carry = work >> LITTLENUM_NUMBER_OF_BITS;
 180             }
 181           if (carry)
 182             {
 183               if (leader < generic_bignum + SIZE_OF_LARGE_NUMBER - 1)
 184                 {               /* room to grow a longer bignum. */
 185                   *++leader = carry;
 186                 }
 187             }
 188         }
 189       /* again, c is char after number, */
 190       /* input_line_pointer->after c. */
 191       know (sizeof (int) * 8 == 32);
 192       know (LITTLENUM_NUMBER_OF_BITS == 16);
 193       /* hence the constant "2" in the next line. */
 194       if (leader < generic_bignum + 2)
 195         {                       /* will fit into 32 bits. */
 196           number =
 197             ((generic_bignum[1] & LITTLENUM_MASK) << LITTLENUM_NUMBER_OF_BITS)
 198             | (generic_bignum[0] & LITTLENUM_MASK);
 199           small = 1;
 200         }
 201       else
 202         {
 203           number = leader - generic_bignum + 1; /* number of littlenums in the bignum. */
 204         }
 205     }
 206   if (small)
 207     {
 208       /*
 209        * here with number, in correct radix. c is the next char.
 210        * note that unlike un*x, we allow "011f" "0x9f" to
 211        * both mean the same as the (conventional) "9f". this is simply easier
 212        * than checking for strict canonical form. syntax sux!
 213        */
 214
 215       switch (c)
 216         {
 217
 218 #ifdef LOCAL_LABELS_FB
 219         case 'b':
 220           {
 221             /*
 222              * backward ref to local label.
 223              * because it is backward, expect it to be defined.
 224              */
 225             /* Construct a local label.  */
 226             name = fb_label_name ((int) number, 0);
 227
 228             /* seen before, or symbol is defined: ok */
 229             symbolP = symbol_find (name);
 230             if ((symbolP != NULL) && (S_IS_DEFINED (symbolP)))
 231               {
 232
 233                 /* local labels are never absolute. don't waste time
 234                    checking absoluteness. */
 235                 know (SEG_NORMAL (S_GET_SEGMENT (symbolP)));
 236
 237                 expressionP->X_add_symbol = symbolP;
 238                 expressionP->X_seg = S_GET_SEGMENT (symbolP);
 239
 240               }
 241             else
 242               {                 /* either not seen or not defined. */
 243                 as_bad ("backw. ref to unknown label \"%d:\", 0 assumed.", number);
 244                 expressionP->X_seg = absolute_section;
 245               }
 246
 247             expressionP->X_add_number = 0;
 248             break;
 249           }                     /* case 'b' */
 250
 251         case 'f':
 252           {
 253             /*
 254              * forward reference. expect symbol to be undefined or
 255              * unknown. undefined: seen it before. unknown: never seen
 256              * it before.
 257              * construct a local label name, then an undefined symbol.
 258              * don't create a xseg frag for it: caller may do that.
 259              * just return it as never seen before.
 260              */
 261             name = fb_label_name ((int) number, 1);
 262             symbolP = symbol_find_or_make (name);
 263             /* we have no need to check symbol properties. */
 264 #ifndef many_segments
 265             /* since "know" puts its arg into a "string", we
 266                can't have newlines in the argument.  */
 267             know (S_GET_SEGMENT (symbolP) == undefined_section || S_GET_SEGMENT (symbolP) == text_section || S_GET_SEGMENT (symbolP) == data_section);
 268 #endif
 269             expressionP->X_add_symbol = symbolP;
 270             expressionP->X_seg = undefined_section;
 271             expressionP->X_subtract_symbol = NULL;
 272             expressionP->X_add_number = 0;
 273
 274             break;
 275           }                     /* case 'f' */
 276
 277 #endif /* LOCAL_LABELS_FB */
 278
 279 #ifdef LOCAL_LABELS_DOLLAR
 280
 281         case '$':
 282           {
 283
 284             /* If the dollar label is *currently* defined, then this is just
 285                another reference to it.  If it is not *currently* defined,
 286                then this is a fresh instantiation of that number, so create
 287                it.  */
 288
 289             if (dollar_label_defined (number))
 290               {
 291                 name = dollar_label_name (number, 0);
 292                 symbolP = symbol_find (name);
 293                 know (symbolP != NULL);
 294               }
 295             else
 296               {
 297                 name = dollar_label_name (number, 1);
 298                 symbolP = symbol_find_or_make (name);
 299               }
 300
 301             expressionP->X_add_symbol = symbolP;
 302             expressionP->X_add_number = 0;
 303             expressionP->X_seg = S_GET_SEGMENT (symbolP);
 304
 305             break;
 306           }                     /* case '$' */
 307
 308 #endif /* LOCAL_LABELS_DOLLAR */
 309
 310         default:
 311           {
 312             expressionP->X_add_number = number;
 313             expressionP->X_seg = absolute_section;
 314             input_line_pointer--;       /* restore following character. */
 315             break;
 316           }                     /* really just a number */
 317
 318         }                       /* switch on char following the number */
 319
 320
 321     }
 322   else
 323     {                           /* not a small number */
 324       expressionP->X_add_number = number;
 325       expressionP->X_seg = big_section;
 326       input_line_pointer--;     /*->char following number. */
 327     }                           /* if (small) */
 328 }                               /* integer_constant() */
 329
 330
 331 /*
 332  * Summary of operand().
 333  *
 334  * in:  Input_line_pointer points to 1st char of operand, which may
 335  *      be a space.
 336  *
 337  * out: A expressionS. X_seg determines how to understand the rest of the
 338  *      expressionS.
 339  *      The operand may have been empty: in this case X_seg == SEG_ABSENT.
 340  *      Input_line_pointer->(next non-blank) char after operand.
 341  *
 342  */
 343 \f
 344
 345
 346 static segT
 347 operand (expressionP)
 348      register expressionS *expressionP;
 349 {
 350   register char c;
 351   register symbolS *symbolP;    /* points to symbol */
 352   register char *name;          /* points to name of symbol */
 353   /* invented for humans only, hope */
 354   /* optimising compiler flushes it! */
 355   register short int radix;     /* 2, 8, 10 or 16, 0 when floating */
 356   /* 0 means we saw start of a floating- */
 357   /* point constant. */
 358
 359   /* digits, assume it is a bignum. */
 360
 361   SKIP_WHITESPACE ();           /* leading whitespace is part of operand. */
 362   c = *input_line_pointer++;    /* input_line_pointer->past char in c. */
 363
 364   switch (c)
 365     {
 366 #ifdef MRI
 367     case '%':
 368       integer_constant (2, expressionP);
 369       break;
 370     case '@':
 371       integer_constant (8, expressionP);
 372       break;
 373     case '$':
 374       integer_constant (16, expressionP);
 375       break;
 376 #endif
 377     case '1':
 378     case '2':
 379     case '3':
 380     case '4':
 381     case '5':
 382     case '6':
 383     case '7':
 384     case '8':
 385     case '9':
 386       input_line_pointer--;
 387
 388       integer_constant (10, expressionP);
 389       break;
 390
 391     case '0':
 392       /* non-decimal radix */
 393
 394
 395       c = *input_line_pointer;
 396       switch (c)
 397         {
 398
 399         default:
 400           if (c && strchr (FLT_CHARS, c))
 401             {
 402               input_line_pointer++;
 403               floating_constant (expressionP);
 404             }
 405           else
 406             {
 407               /* The string was only zero */
 408               expressionP->X_add_symbol = 0;
 409               expressionP->X_add_number = 0;
 410               expressionP->X_seg = absolute_section;
 411             }
 412
 413           break;
 414
 415         case 'x':
 416         case 'X':
 417           input_line_pointer++;
 418           integer_constant (16, expressionP);
 419           break;
 420
 421         case 'b':
 422 #ifdef LOCAL_LABELS_FB
 423           if (!*input_line_pointer
 424               || (!strchr ("+-.0123456789", *input_line_pointer)
 425                   && !strchr (EXP_CHARS, *input_line_pointer)))
 426             {
 427               input_line_pointer--;
 428               integer_constant (10, expressionP);
 429               break;
 430             }
 431 #endif
 432         case 'B':
 433           input_line_pointer++;
 434           integer_constant (2, expressionP);
 435           break;
 436
 437         case '0':
 438         case '1':
 439         case '2':
 440         case '3':
 441         case '4':
 442         case '5':
 443         case '6':
 444         case '7':
 445           integer_constant (8, expressionP);
 446           break;
 447
 448         case 'f':
 449 #ifdef LOCAL_LABELS_FB
 450           /* if it says '0f' and the line ends or it doesn't look like
 451              a floating point #, its a local label ref.  dtrt */
 452           /* likewise for the b's.  xoxorich. */
 453           if (c == 'f'
 454               && (!*input_line_pointer ||
 455                   (!strchr ("+-.0123456789", *input_line_pointer) &&
 456                    !strchr (EXP_CHARS, *input_line_pointer))))
 457             {
 458               input_line_pointer -= 1;
 459               integer_constant (10, expressionP);
 460               break;
 461             }
 462 #endif
 463
 464         case 'd':
 465         case 'D':
 466         case 'F':
 467         case 'r':
 468         case 'e':
 469         case 'E':
 470         case 'g':
 471         case 'G':
 472
 473           input_line_pointer++;
 474           floating_constant (expressionP);
 475           expressionP->X_add_number = -(isupper (c) ? tolower (c) : c);
 476           break;
 477
 478 #ifdef LOCAL_LABELS_DOLLAR
 479         case '$':
 480           integer_constant (10, expressionP);
 481           break;
 482 #endif
 483         }
 484
 485       break;
 486     case '(':
 487       /* didn't begin with digit & not a name */
 488       {
 489         (void) expression (expressionP);
 490         /* Expression() will pass trailing whitespace */
 491         if (*input_line_pointer++ != ')')
 492           {
 493             as_bad ("Missing ')' assumed");
 494             input_line_pointer--;
 495           }
 496         /* here with input_line_pointer->char after "(...)" */
 497       }
 498       return expressionP->X_seg;
 499
 500
 501     case '\'':
 502       /* Warning: to conform to other people's assemblers NO ESCAPEMENT is
 503          permitted for a single quote. The next character, parity errors and
 504          all, is taken as the value of the operand. VERY KINKY.  */
 505       expressionP->X_add_number = *input_line_pointer++;
 506       expressionP->X_seg = absolute_section;
 507       break;
 508
 509     case '~':
 510     case '-':
 511     case '+':
 512       {
 513         /* unary operator: hope for SEG_ABSOLUTE */
 514         segT opseg = operand (expressionP);
 515         if (opseg == absolute_section)
 516           {
 517             /* input_line_pointer -> char after operand */
 518             if (c == '-')
 519               {
 520                 expressionP->X_add_number = -expressionP->X_add_number;
 521                 /* Notice: '-' may overflow: no warning is given. This is
 522                    compatible with other people's assemblers. Sigh.  */
 523               }
 524             else
 525               {
 526                 expressionP->X_add_number = ~expressionP->X_add_number;
 527               }
 528           }
 529         else if (opseg == text_section
 530                  || opseg == data_section
 531                  || opseg == bss_section
 532                  || opseg == pass1_section
 533                  || opseg == undefined_section)
 534           {
 535             if (c == '-')
 536               {
 537                 expressionP->X_subtract_symbol = expressionP->X_add_symbol;
 538                 expressionP->X_add_symbol = 0;
 539                 expressionP->X_seg = diff_section;
 540               }
 541             else
 542               as_warn ("Unary operator %c ignored because bad operand follows",
 543                        c);
 544           }
 545         else
 546           as_warn ("Unary operator %c ignored because bad operand follows", c);
 547       }
 548       break;
 549
 550     case '.':
 551       if (!is_part_of_name (*input_line_pointer))
 552         {
 553           char *fake;
 554           extern struct obstack frags;
 555
 556           /* JF: '.' is pseudo symbol with value of current location
 557              in current segment.  */
 558 #ifdef DOT_LABEL_PREFIX
 559           fake = ".L0\001";
 560 #else
 561           fake = "L0\001";
 562 #endif
 563           symbolP = symbol_new (fake,
 564                                 now_seg,
 565                (valueT) (obstack_next_free (&frags) - frag_now->fr_literal),
 566                                 frag_now);
 567
 568           expressionP->X_add_number = 0;
 569           expressionP->X_add_symbol = symbolP;
 570           expressionP->X_seg = now_seg;
 571           break;
 572
 573         }
 574       else
 575         {
 576           goto isname;
 577
 578
 579         }
 580     case ',':
 581     case '\n':
 582     case '\0':
 583     eol:
 584       /* can't imagine any other kind of operand */
 585       expressionP->X_seg = absent_section;
 586       input_line_pointer--;
 587       md_operand (expressionP);
 588       break;
 589
 590     default:
 591       if (is_end_of_line[c])
 592         goto eol;
 593       if (is_name_beginner (c)) /* here if did not begin with a digit */
 594         {
 595           /*
 596            * Identifier begins here.
 597            * This is kludged for speed, so code is repeated.
 598            */
 599         isname:
 600           name = --input_line_pointer;
 601           c = get_symbol_end ();
 602           symbolP = symbol_find_or_make (name);
 603           /* If we have an absolute symbol or a reg, then we know its value
 604              now.  */
 605           expressionP->X_seg = S_GET_SEGMENT (symbolP);
 606           if (expressionP->X_seg == absolute_section
 607               || expressionP->X_seg == reg_section)
 608             expressionP->X_add_number = S_GET_VALUE (symbolP);
 609           else
 610             {
 611               expressionP->X_add_number = 0;
 612               expressionP->X_add_symbol = symbolP;
 613             }
 614           *input_line_pointer = c;
 615           expressionP->X_subtract_symbol = NULL;
 616         }
 617       else
 618         {
 619           as_bad ("Bad expression");
 620           expressionP->X_add_number = 0;
 621           expressionP->X_seg = absolute_section;
 622         }
 623     }
 624
 625   /*
 626    * It is more 'efficient' to clean up the expressionS when they are created.
 627    * Doing it here saves lines of code.
 628    */
 629   clean_up_expression (expressionP);
 630   SKIP_WHITESPACE ();           /*->1st char after operand. */
 631   know (*input_line_pointer != ' ');
 632   return (expressionP->X_seg);
 633 }                               /* operand() */
 634 \f
 635
 636 /* Internal. Simplify a struct expression for use by expr() */
 637
 638 /*
 639  * In:  address of a expressionS.
 640  *      The X_seg field of the expressionS may only take certain values.
 641  *      Now, we permit SEG_PASS1 to make code smaller & faster.
 642  *      Elsewise we waste time special-case testing. Sigh. Ditto SEG_ABSENT.
 643  * Out: expressionS may have been modified:
 644  *      'foo-foo' symbol references cancelled to 0,
 645  *              which changes X_seg from SEG_DIFFERENCE to SEG_ABSOLUTE;
 646  *      Unused fields zeroed to help expr().
 647  */
 648
 649 static void
 650 clean_up_expression (expressionP)
 651      register expressionS *expressionP;
 652 {
 653   segT s = expressionP->X_seg;
 654   if (s == absent_section
 655       || s == pass1_section)
 656     {
 657       expressionP->X_add_symbol = NULL;
 658       expressionP->X_subtract_symbol = NULL;
 659       expressionP->X_add_number = 0;
 660     }
 661   else if (s == big_section
 662            || s == absolute_section)
 663     {
 664       expressionP->X_subtract_symbol = NULL;
 665       expressionP->X_add_symbol = NULL;
 666     }
 667   else if (s == undefined_section)
 668     expressionP->X_subtract_symbol = NULL;
 669   else if (s == diff_section)
 670     {
 671       /*
 672        * It does not hurt to 'cancel' NULL==NULL
 673        * when comparing symbols for 'eq'ness.
 674        * It is faster to re-cancel them to NULL
 675        * than to check for this special case.
 676        */
 677       if (expressionP->X_subtract_symbol == expressionP->X_add_symbol
 678           || (expressionP->X_subtract_symbol
 679               && expressionP->X_add_symbol
 680               && expressionP->X_subtract_symbol->sy_frag == expressionP->X_add_symbol->sy_frag
 681               && S_GET_VALUE (expressionP->X_subtract_symbol) == S_GET_VALUE (expressionP->X_add_symbol)))
 682         {
 683           expressionP->X_subtract_symbol = NULL;
 684           expressionP->X_add_symbol = NULL;
 685           expressionP->X_seg = absolute_section;
 686         }
 687     }
 688   else if (s == reg_section)
 689     {
 690       expressionP->X_add_symbol = NULL;
 691       expressionP->X_subtract_symbol = NULL;
 692     }
 693   else
 694     {
 695       if (SEG_NORMAL (expressionP->X_seg))
 696         {
 697           expressionP->X_subtract_symbol = NULL;
 698         }
 699       else
 700         {
 701           BAD_CASE (expressionP->X_seg);
 702         }
 703     }
 704 }
 705 \f
 706 /*
 707  *                      expr_part ()
 708  *
 709  * Internal. Made a function because this code is used in 2 places.
 710  * Generate error or correct X_?????_symbol of expressionS.
 711  */
 712
 713 /*
 714  * symbol_1 += symbol_2 ... well ... sort of.
 715  */
 716
 717 static segT
 718 expr_part (symbol_1_PP, symbol_2_P)
 719      symbolS **symbol_1_PP;
 720      symbolS *symbol_2_P;
 721 {
 722   segT return_value;
 723 #ifndef MANY_SEGMENTS
 724   assert ((*symbol_1_PP) == NULL \
 725           || (S_GET_SEGMENT (*symbol_1_PP) == text_section) \
 726           || (S_GET_SEGMENT (*symbol_1_PP) == data_section) \
 727           || (S_GET_SEGMENT (*symbol_1_PP) == bss_section) \
 728           || (!S_IS_DEFINED (*symbol_1_PP)));
 729   assert (symbol_2_P == NULL \
 730           || (S_GET_SEGMENT (symbol_2_P) == text_section) \
 731           || (S_GET_SEGMENT (symbol_2_P) == data_section) \
 732           || (S_GET_SEGMENT (symbol_2_P) == bss_section) \
 733           || (!S_IS_DEFINED (symbol_2_P)));
 734 #endif
 735   if (*symbol_1_PP)
 736     {
 737       if (!S_IS_DEFINED (*symbol_1_PP))
 738         {
 739           if (symbol_2_P)
 740             {
 741               return_value = pass1_section;
 742               *symbol_1_PP = NULL;
 743             }
 744           else
 745             {
 746               know (!S_IS_DEFINED (*symbol_1_PP));
 747               return_value = undefined_section;
 748             }
 749         }
 750       else
 751         {
 752           if (symbol_2_P)
 753             {
 754               if (!S_IS_DEFINED (symbol_2_P))
 755                 {
 756                   *symbol_1_PP = NULL;
 757                   return_value = pass1_section;
 758                 }
 759               else
 760                 {
 761                   /* {seg1} - {seg2} */
 762                   as_bad ("Expression too complex, 2 symbolS forgotten: \"%s\" \"%s\"",
 763                         S_GET_NAME (*symbol_1_PP), S_GET_NAME (symbol_2_P));
 764                   *symbol_1_PP = NULL;
 765                   return_value = absolute_section;
 766                 }
 767             }
 768           else
 769             {
 770               return_value = S_GET_SEGMENT (*symbol_1_PP);
 771             }
 772         }
 773     }
 774   else
 775     {                           /* (* symbol_1_PP) == NULL */
 776       if (symbol_2_P)
 777         {
 778           *symbol_1_PP = symbol_2_P;
 779           return_value = S_GET_SEGMENT (symbol_2_P);
 780         }
 781       else
 782         {
 783           *symbol_1_PP = NULL;
 784           return_value = absolute_section;
 785         }
 786     }
 787 #ifndef MANY_SEGMENTS
 788   assert (return_value == absolute_section \
 789           || return_value == text_section \
 790           || return_value == data_section \
 791           || return_value == bss_section \
 792           || return_value == undefined_section \
 793           || return_value == pass1_section);
 794 #endif
 795   know ((*symbol_1_PP) == NULL
 796         || (S_GET_SEGMENT (*symbol_1_PP) == return_value));
 797   return (return_value);
 798 }
 799 \f
 800 /* Expression parser. */
 801
 802 /*
 803  * We allow an empty expression, and just assume (absolute,0) silently.
 804  * Unary operators and parenthetical expressions are treated as operands.
 805  * As usual, Q==quantity==operand, O==operator, X==expression mnemonics.
 806  *
 807  * We used to do a aho/ullman shift-reduce parser, but the logic got so
 808  * warped that I flushed it and wrote a recursive-descent parser instead.
 809  * Now things are stable, would anybody like to write a fast parser?
 810  * Most expressions are either register (which does not even reach here)
 811  * or 1 symbol. Then "symbol+constant" and "symbol-symbol" are common.
 812  * So I guess it doesn't really matter how inefficient more complex expressions
 813  * are parsed.
 814  *
 815  * After expr(RANK,resultP) input_line_pointer->operator of rank <= RANK.
 816  * Also, we have consumed any leading or trailing spaces (operand does that)
 817  * and done all intervening operators.
 818  */
 819
 820 typedef enum
 821 {
 822   O_illegal,                    /* (0)  what we get for illegal op */
 823
 824   O_multiply,                   /* (1)  * */
 825   O_divide,                     /* (2)  / */
 826   O_modulus,                    /* (3)  % */
 827   O_left_shift,                 /* (4)  < */
 828   O_right_shift,                /* (5)  > */
 829   O_bit_inclusive_or,           /* (6)  | */
 830   O_bit_or_not,                 /* (7)  ! */
 831   O_bit_exclusive_or,           /* (8)  ^ */
 832   O_bit_and,                    /* (9)  & */
 833   O_add,                        /* (10) + */
 834   O_subtract                    /* (11) - */
 835 }
 836
 837 operatorT;
 838
 839 #define __ O_illegal
 840
 841 static const operatorT op_encoding[256] =
 842 {                               /* maps ASCII->operators */
 843
 844   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 845   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 846
 847   __, O_bit_or_not, __, __, __, O_modulus, O_bit_and, __,
 848   __, __, O_multiply, O_add, __, O_subtract, __, O_divide,
 849   __, __, __, __, __, __, __, __,
 850   __, __, __, __, O_left_shift, __, O_right_shift, __,
 851   __, __, __, __, __, __, __, __,
 852   __, __, __, __, __, __, __, __,
 853   __, __, __, __, __, __, __, __,
 854   __, __, __, __, __, __, O_bit_exclusive_or, __,
 855   __, __, __, __, __, __, __, __,
 856   __, __, __, __, __, __, __, __,
 857   __, __, __, __, __, __, __, __,
 858   __, __, __, __, O_bit_inclusive_or, __, __, __,
 859
 860   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 861   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 862   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 863   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 864   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 865   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 866   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __,
 867   __, __, __, __, __, __, __, __, __, __, __, __, __, __, __, __
 868 };
 869
 870
 871 /*
 872  *      Rank    Examples
 873  *      0       operand, (expression)
 874  *      1       + -
 875  *      2       & ^ ! |
 876  *      3       * / % << >>
 877  */
 878 static const operator_rankT
 879   op_rank[] =
 880 {0, 3, 3, 3, 3, 3, 2, 2, 2, 2, 1, 1};
 881 \f
 882 /* Return resultP->X_seg. */
 883 segT
 884 expr (rank, resultP)
 885      register operator_rankT rank;      /* Larger # is higher rank. */
 886      register expressionS *resultP;     /* Deliver result here. */
 887 {
 888   expressionS right;
 889   register operatorT op_left;
 890   register char c_left;         /* 1st operator character. */
 891   register operatorT op_right;
 892   register char c_right;
 893
 894   know (rank >= 0);
 895   (void) operand (resultP);
 896   know (*input_line_pointer != ' ');    /* Operand() gobbles spaces. */
 897   c_left = *input_line_pointer; /* Potential operator character. */
 898   op_left = op_encoding[c_left];
 899   while (op_left != O_illegal && op_rank[(int) op_left] > rank)
 900     {
 901       input_line_pointer++;     /*->after 1st character of operator. */
 902       /* Operators "<<" and ">>" have 2 characters. */
 903       if (*input_line_pointer == c_left && (c_left == '<' || c_left == '>'))
 904         {
 905           input_line_pointer++;
 906         }                       /*->after operator. */
 907       if (absent_section == expr (op_rank[(int) op_left], &right))
 908         {
 909           as_warn ("Missing operand value assumed absolute 0.");
 910           resultP->X_add_number = 0;
 911           resultP->X_subtract_symbol = NULL;
 912           resultP->X_add_symbol = NULL;
 913           resultP->X_seg = absolute_section;
 914         }
 915       know (*input_line_pointer != ' ');
 916       c_right = *input_line_pointer;
 917       op_right = op_encoding[c_right];
 918       if (*input_line_pointer == c_right && (c_right == '<' || c_right == '>'))
 919         {
 920           input_line_pointer++;
 921         }                       /*->after operator. */
 922       know ((int) op_right == 0 || op_rank[(int) op_right] <= op_rank[(int) op_left]);
 923       /* input_line_pointer->after right-hand quantity. */
 924       /* left-hand quantity in resultP */
 925       /* right-hand quantity in right. */
 926       /* operator in op_left. */
 927       if (resultP->X_seg == pass1_section || right.X_seg == pass1_section)
 928         {
 929           resultP->X_seg = pass1_section;
 930         }
 931       else
 932         {
 933           if (resultP->X_seg == big_section)
 934             {
 935               as_warn ("Left operand of %c is a %s.  Integer 0 assumed.",
 936                     c_left, resultP->X_add_number > 0 ? "bignum" : "float");
 937               resultP->X_seg = absolute_section;
 938               resultP->X_add_symbol = 0;
 939               resultP->X_subtract_symbol = 0;
 940               resultP->X_add_number = 0;
 941             }
 942           if (right.X_seg == big_section)
 943             {
 944               as_warn ("Right operand of %c is a %s.  Integer 0 assumed.",
 945                        c_left, right.X_add_number > 0 ? "bignum" : "float");
 946               right.X_seg = absolute_section;
 947               right.X_add_symbol = 0;
 948               right.X_subtract_symbol = 0;
 949               right.X_add_number = 0;
 950             }
 951           if (op_left == O_subtract)
 952             {
 953               /*
 954                * Convert - into + by exchanging symbolS and negating number.
 955                * I know -infinity can't be negated in 2's complement:
 956                * but then it can't be subtracted either. This trick
 957                * does not cause any further inaccuracy.
 958                */
 959
 960               register symbolS *symbolP;
 961
 962               right.X_add_number = -right.X_add_number;
 963               symbolP = right.X_add_symbol;
 964               right.X_add_symbol = right.X_subtract_symbol;
 965               right.X_subtract_symbol = symbolP;
 966               if (symbolP)
 967                 {
 968                   right.X_seg = diff_section;
 969                 }
 970               op_left = O_add;
 971             }
 972 \f
 973           if (op_left == O_add)
 974             {
 975               segT seg1;
 976               segT seg2;
 977 #ifndef MANY_SEGMENTS
 978
 979               know (resultP->X_seg == data_section || resultP->X_seg == text_section || resultP->X_seg == bss_section || resultP->X_seg == undefined_section || resultP->X_seg == diff_section || resultP->X_seg == absolute_section || resultP->X_seg == pass1_section || resultP->X_seg == reg_section);
 980
 981               know (right.X_seg == data_section || right.X_seg == text_section || right.X_seg == bss_section || right.X_seg == undefined_section || right.X_seg == diff_section || right.X_seg == absolute_section || right.X_seg == pass1_section);
 982 #endif
 983               clean_up_expression (&right);
 984               clean_up_expression (resultP);
 985
 986               seg1 = expr_part (&resultP->X_add_symbol, right.X_add_symbol);
 987               seg2 = expr_part (&resultP->X_subtract_symbol, right.X_subtract_symbol);
 988               if (seg1 == pass1_section || seg2 == pass1_section)
 989                 {
 990                   need_pass_2 = 1;
 991                   resultP->X_seg = pass1_section;
 992                 }
 993               else if (seg2 == absolute_section)
 994                 resultP->X_seg = seg1;
 995               else if (seg1 != undefined_section
 996                        && seg1 != absolute_section
 997                        && seg2 != undefined_section
 998                        && seg1 != seg2)
 999                 {
1000                   know (seg2 != absolute_section);
1001                   know (resultP->X_subtract_symbol);
1002 #ifndef MANY_SEGMENTS
1003                   know (seg1 == text_section || seg1 == data_section || seg1 == bss_section);
1004                   know (seg2 == text_section || seg2 == data_section || seg2 == bss_section);
1005 #endif
1006                   know (resultP->X_add_symbol);
1007                   know (resultP->X_subtract_symbol);
1008                   as_bad ("Expression too complex: forgetting %s - %s",
1009                           S_GET_NAME (resultP->X_add_symbol),
1010                           S_GET_NAME (resultP->X_subtract_symbol));
1011                   resultP->X_seg = absolute_section;
1012                   /* Clean_up_expression() will do the rest. */
1013                 }
1014               else
1015                 resultP->X_seg = diff_section;
1016
1017               resultP->X_add_number += right.X_add_number;
1018               clean_up_expression (resultP);
1019             }
1020           else
1021             {                   /* Not +. */
1022               if (resultP->X_seg == undefined_section || right.X_seg == undefined_section)
1023                 {
1024                   resultP->X_seg = pass1_section;
1025                   need_pass_2 = 1;
1026                 }
1027               else
1028                 {
1029                   resultP->X_subtract_symbol = NULL;
1030                   resultP->X_add_symbol = NULL;
1031                   /* Will be absolute_section. */
1032                   if (resultP->X_seg != absolute_section || right.X_seg != absolute_section)
1033                     {
1034                       as_bad ("Relocation error. Absolute 0 assumed.");
1035                       resultP->X_seg = absolute_section;
1036                       resultP->X_add_number = 0;
1037                     }
1038                   else
1039                     {
1040                       switch (op_left)
1041                         {
1042                         case O_bit_inclusive_or:
1043                           resultP->X_add_number |= right.X_add_number;
1044                           break;
1045
1046                         case O_modulus:
1047                           if (right.X_add_number)
1048                             {
1049                               resultP->X_add_number %= right.X_add_number;
1050                             }
1051                           else
1052                             {
1053                               as_warn ("Division by 0. 0 assumed.");
1054                               resultP->X_add_number = 0;
1055                             }
1056                           break;
1057
1058                         case O_bit_and:
1059                           resultP->X_add_number &= right.X_add_number;
1060                           break;
1061
1062                         case O_multiply:
1063                           resultP->X_add_number *= right.X_add_number;
1064                           break;
1065
1066                         case O_divide:
1067                           if (right.X_add_number)
1068                             {
1069                               resultP->X_add_number /= right.X_add_number;
1070                             }
1071                           else
1072                             {
1073                               as_warn ("Division by 0. 0 assumed.");
1074                               resultP->X_add_number = 0;
1075                             }
1076                           break;
1077
1078                         case O_left_shift:
1079                           resultP->X_add_number <<= right.X_add_number;
1080                           break;
1081
1082                         case O_right_shift:
1083                           resultP->X_add_number >>= right.X_add_number;
1084                           break;
1085
1086                         case O_bit_exclusive_or:
1087                           resultP->X_add_number ^= right.X_add_number;
1088                           break;
1089
1090                         case O_bit_or_not:
1091                           resultP->X_add_number |= ~right.X_add_number;
1092                           break;
1093
1094                         default:
1095                           BAD_CASE (op_left);
1096                           break;
1097                         }       /* switch(operator) */
1098                     }
1099                 }               /* If we have to force need_pass_2. */
1100             }                   /* If operator was +. */
1101         }                       /* If we didn't set need_pass_2. */
1102       op_left = op_right;
1103     }                           /* While next operator is >= this rank. */
1104   return (resultP->X_seg);
1105 }
1106 \f
1107 /*
1108  *                      get_symbol_end()
1109  *
1110  * This lives here because it belongs equally in expr.c & read.c.
1111  * Expr.c is just a branch office read.c anyway, and putting it
1112  * here lessens the crowd at read.c.
1113  *
1114  * Assume input_line_pointer is at start of symbol name.
1115  * Advance input_line_pointer past symbol name.
1116  * Turn that character into a '\0', returning its former value.
1117  * This allows a string compare (RMS wants symbol names to be strings)
1118  * of the symbol name.
1119  * There will always be a char following symbol name, because all good
1120  * lines end in end-of-line.
1121  */
1122 char
1123 get_symbol_end ()
1124 {
1125   register char c;
1126
1127   while (is_part_of_name (c = *input_line_pointer++))
1128     ;
1129   *--input_line_pointer = 0;
1130   return (c);
1131 }
1132
1133
1134 unsigned int
1135 get_single_number ()
1136 {
1137   expressionS exp;
1138   operand (&exp);
1139   return exp.X_add_number;
1140
1141 }
1142
1143 /* end of expr.c */