smatch_math.c

   1 /*
   2  * smatch/smatch_math.c
   3  *
   4  * Copyright (C) 2010 Dan Carpenter.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 #include "symbol.h"
  11 #include "smatch.h"
  12 #include "smatch_slist.h"
  13 #include "smatch_extra.h"
  14
  15 static sval_t _get_value(struct expression *expr, int *undefined, int implied);
  16 static sval_t _get_implied_value(struct expression *expr, int *undefined, int implied);
  17
  18 #define BOGUS 12345
  19
  20 static sval_t zero  = {.type = &int_ctype, {.value = 0} };
  21 static sval_t one   = {.type = &int_ctype, {.value = 1} };
  22 static sval_t bogus = {.type = &int_ctype, {.value = BOGUS} };
  23
  24 enum {
  25         NOTIMPLIED,
  26         IMPLIED,
  27         IMPLIED_MIN,
  28         IMPLIED_MAX,
  29         FUZZY_MAX,
  30         FUZZY_MIN,
  31         ABSOLUTE_MIN,
  32         ABSOLUTE_MAX,
  33         HARD_MAX,
  34 };
  35
  36 static int opposite_implied(int implied)
  37 {
  38         if (implied == IMPLIED_MIN)
  39                 return IMPLIED_MAX;
  40         if (implied == IMPLIED_MAX)
  41                 return IMPLIED_MIN;
  42         if (implied == FUZZY_MIN)
  43                 return FUZZY_MAX;
  44         if (implied == FUZZY_MAX)
  45                 return FUZZY_MIN;
  46         if (implied == ABSOLUTE_MIN)
  47                 return ABSOLUTE_MAX;
  48         if (implied == ABSOLUTE_MAX)
  49                 return ABSOLUTE_MIN;
  50         if (implied == HARD_MAX)  /* we don't have a hard min.  */
  51                 return NOTIMPLIED;
  52
  53         return implied;
  54 }
  55
  56 static int last_stmt_sval(struct statement *stmt, sval_t *sval)
  57 {
  58         struct expression *expr;
  59
  60         if (!stmt)
  61                 return 0;
  62
  63         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  64         if (stmt->type != STMT_EXPRESSION)
  65                 return 0;
  66         expr = stmt->expression;
  67         if (!get_value(expr, sval))
  68                 return 0;
  69         return 1;
  70 }
  71
  72 static sval_t handle_expression_statement(struct expression *expr, int *undefined, int implied)
  73 {
  74         struct statement *stmt;
  75         sval_t ret;
  76
  77         stmt = get_expression_statement(expr);
  78         if (!last_stmt_sval(stmt, &ret)) {
  79                 *undefined = 1;
  80                 ret = bogus;
  81         }
  82
  83         return ret;
  84 }
  85
  86 static sval_t handle_ampersand(int *undefined, int implied)
  87 {
  88         sval_t ret;
  89
  90         ret.type = &ptr_ctype;
  91         ret.value = BOGUS;
  92
  93         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
  94                 return valid_ptr_min_sval;
  95         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
  96                 return valid_ptr_max_sval;
  97
  98         *undefined = 1;
  99         return ret;
 100 }
 101
 102 static sval_t handle_negate(struct expression *expr, int *undefined, int implied)
 103 {
 104         sval_t ret;
 105
 106         ret = sval_blank(expr->unop);
 107
 108         if (known_condition_true(expr->unop)) {
 109                 ret.value = 0;
 110                 return ret;
 111         }
 112
 113         if (implied == NOTIMPLIED) {
 114                 *undefined = 1;
 115                 return bogus;
 116         }
 117
 118         if (implied_condition_true(expr->unop)) {
 119                 ret.value = 0;
 120                 return ret;
 121         }
 122         if (implied_condition_false(expr->unop)) {
 123                 ret.value = 1;
 124                 return ret;
 125         }
 126         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN) {
 127                 ret.value = 0;
 128                 return ret;
 129         }
 130         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX) {
 131                 ret.value = 1;
 132                 return ret;
 133         }
 134         *undefined = 1;
 135         return bogus;
 136 }
 137
 138 static sval_t handle_preop(struct expression *expr, int *undefined, int implied)
 139 {
 140         sval_t ret;
 141
 142         switch (expr->op) {
 143         case '&':
 144                 ret = handle_ampersand(undefined, implied);
 145                 break;
 146         case '!':
 147                 ret = handle_negate(expr, undefined, implied);
 148                 break;
 149         case '~':
 150                 ret = _get_value(expr->unop, undefined, implied);
 151                 ret = sval_preop(ret, '~');
 152                 ret = sval_cast(get_type(expr->unop), ret);
 153                 break;
 154         case '-':
 155                 ret = _get_value(expr->unop, undefined, implied);
 156                 ret = sval_preop(ret, '-');
 157                 break;
 158         case '*':
 159                 ret = _get_implied_value(expr, undefined, implied);
 160                 break;
 161         case '(':
 162                 ret = handle_expression_statement(expr, undefined, implied);
 163                 break;
 164         default:
 165                 *undefined = 1;
 166                 ret = sval_blank(expr);
 167         }
 168         ret = sval_cast(get_type(expr), ret);
 169         return ret;
 170 }
 171
 172 static sval_t handle_divide(struct expression *expr, int *undefined, int implied)
 173 {
 174         sval_t left, right;
 175
 176         left = _get_value(expr->left, undefined, implied);
 177         right = _get_value(expr->right, undefined, opposite_implied(implied));
 178
 179         if (right.value == 0) {
 180                 *undefined = 1;
 181                 return bogus;
 182         }
 183
 184         return sval_binop(left, '/', right);
 185 }
 186
 187 static sval_t handle_subtract(struct expression *expr, int *undefined, int implied)
 188 {
 189         struct symbol *type;
 190         sval_t left, right, ret;
 191         int left_undefined = 0;
 192         int right_undefined = 0;
 193         int known_but_negative = 0;
 194         int comparison;
 195
 196         left = _get_value(expr->left, &left_undefined, implied);
 197         right = _get_value(expr->right, &right_undefined, opposite_implied(implied));
 198
 199         if (!left_undefined && !right_undefined) {
 200                 ret = sval_binop(left, '-', right);
 201                 if (sval_is_negative(ret))
 202                         known_but_negative = 1;
 203                 else
 204                         return ret;  /* best case scenario */
 205         }
 206
 207         comparison = get_comparison(expr->left, expr->right);
 208         if (!comparison)
 209                 goto bogus;
 210
 211         type = get_type(expr);
 212
 213         switch (comparison) {
 214         case '>':
 215         case SPECIAL_UNSIGNED_GT:
 216                 switch (implied) {
 217                 case IMPLIED_MIN:
 218                 case FUZZY_MIN:
 219                 case ABSOLUTE_MIN:
 220                         return sval_type_val(type, 1);
 221                 case IMPLIED_MAX:
 222                 case FUZZY_MAX:
 223                 case ABSOLUTE_MAX:
 224                         return _get_value(expr->left, undefined, implied);
 225                 }
 226                 break;
 227         case SPECIAL_GTE:
 228         case SPECIAL_UNSIGNED_GTE:
 229                 switch (implied) {
 230                 case IMPLIED_MIN:
 231                 case FUZZY_MIN:
 232                 case ABSOLUTE_MIN:
 233                         return sval_type_val(type, 0);
 234                 case IMPLIED_MAX:
 235                 case FUZZY_MAX:
 236                 case ABSOLUTE_MAX:
 237                         return _get_value(expr->left, undefined, implied);
 238                 }
 239                 break;
 240         }
 241
 242         if (known_but_negative)
 243                 return ret;
 244
 245 bogus:
 246         *undefined = 1;
 247         return bogus;
 248 }
 249
 250 static sval_t handle_mod(struct expression *expr, int *undefined, int implied)
 251 {
 252         sval_t left, right;
 253
 254         /* if we can't figure out the right side it's probably hopeless */
 255         right = _get_value(expr->right, undefined, implied);
 256         if (*undefined || right.value == 0) {
 257                 *undefined = 1;
 258                 return bogus;
 259         }
 260
 261         switch (implied) {
 262         case NOTIMPLIED:
 263         case IMPLIED:
 264                 left = _get_value(expr->left, undefined, implied);
 265                 if (!*undefined)
 266                         return sval_binop(left, '%', right);
 267                 return bogus;
 268         case IMPLIED_MIN:
 269         case FUZZY_MIN:
 270         case ABSOLUTE_MIN:
 271                 *undefined = 0;
 272                 return sval_type_val(get_type(expr->left), 0);
 273         case IMPLIED_MAX:
 274         case FUZZY_MAX:
 275         case ABSOLUTE_MAX:
 276                 *undefined = 0;
 277                 right = sval_cast(get_type(expr), right);
 278                 right.value--;
 279                 return right;
 280         }
 281         return bogus;
 282 }
 283
 284 static sval_t handle_binop(struct expression *expr, int *undefined, int implied)
 285 {
 286         struct symbol *type;
 287         sval_t left, right;
 288         sval_t ret = {.type = &int_ctype, {.value = 123456} };
 289         int local_undef = 0;
 290
 291         switch (expr->op) {
 292         case '%':
 293                 return handle_mod(expr, undefined, implied);
 294         case '&':
 295                 left = _get_value(expr->left, &local_undef, implied);
 296                 if (local_undef) {
 297                         if (implied == IMPLIED_MIN || implied == ABSOLUTE_MIN) {
 298                                 ret = sval_blank(expr->left);
 299                                 ret.value = 0;
 300                                 return ret;
 301                         }
 302                         if (implied != IMPLIED_MAX && implied != ABSOLUTE_MAX)
 303                                 *undefined = 1;
 304                         if (!get_absolute_max(expr->left, &left))
 305                                 *undefined = 1;
 306                 }
 307                 right = _get_value(expr->right, undefined, implied);
 308                 if (*undefined)
 309                         return bogus;
 310                 return sval_binop(left, '&', right);
 311
 312         case SPECIAL_RIGHTSHIFT:
 313                 left = _get_value(expr->left, &local_undef, implied);
 314                 if (local_undef) {
 315                         if (implied == IMPLIED_MIN || implied == ABSOLUTE_MIN) {
 316                                 ret = sval_blank(expr->left);
 317                                 ret.value = 0;
 318                                 return ret;
 319                         }
 320                         if (implied != IMPLIED_MAX && implied != ABSOLUTE_MAX)
 321                                 *undefined = 1;
 322                         if (!get_absolute_max(expr->left, &left))
 323                                 *undefined = 1;
 324                 }
 325                 right = _get_value(expr->right, undefined, implied);
 326                 if (*undefined)
 327                         return bogus;
 328                 return sval_binop(left, SPECIAL_RIGHTSHIFT, right);
 329         case '-':
 330                 return handle_subtract(expr, undefined, implied);
 331         }
 332
 333         left = _get_value(expr->left, undefined, implied);
 334         right = _get_value(expr->right, undefined, implied);
 335
 336         if (*undefined)
 337                 return bogus;
 338
 339         type = get_type(expr);
 340         left = sval_cast(type, left);
 341         right = sval_cast(type, right);
 342
 343         switch (implied) {
 344         case IMPLIED_MAX:
 345         case ABSOLUTE_MAX:
 346                 if (sval_binop_overflows(left, expr->op, right))
 347                         return sval_type_max(get_type(expr));
 348                 break;
 349         case HARD_MAX:
 350         case FUZZY_MAX:
 351                 if (sval_binop_overflows(left, expr->op, right)) {
 352                         *undefined = 1;
 353                         return bogus;
 354                 }
 355         }
 356
 357         switch (expr->op) {
 358         case '/':
 359                 return handle_divide(expr, undefined, implied);
 360         case '%':
 361                 if (right.value == 0) {
 362                         *undefined = 1;
 363                         return bogus;
 364                 } else {
 365                         return sval_binop(left, '%', right);
 366                 }
 367         default:
 368                 ret = sval_binop(left, expr->op, right);
 369         }
 370         return ret;
 371 }
 372
 373 static int do_comparison(struct expression *expr)
 374 {
 375         struct range_list *left_ranges = NULL;
 376         struct range_list *right_ranges = NULL;
 377         int poss_true, poss_false;
 378
 379         get_implied_rl(expr->left, &left_ranges);
 380         get_implied_rl(expr->right, &right_ranges);
 381
 382         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 383         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 384
 385         free_rl(&left_ranges);
 386         free_rl(&right_ranges);
 387
 388         if (!poss_true && !poss_false)
 389                 return 0;
 390         if (poss_true && !poss_false)
 391                 return 1;
 392         if (!poss_true && poss_false)
 393                 return 2;
 394         return 3;
 395 }
 396
 397 static sval_t handle_comparison(struct expression *expr, int *undefined, int implied)
 398 {
 399         sval_t left, right;
 400         int res;
 401
 402         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 403                 struct data_range tmp_left, tmp_right;
 404
 405                 tmp_left.min = left;
 406                 tmp_left.max = left;
 407                 tmp_right.min = right;
 408                 tmp_right.max = right;
 409                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 410                         return one;
 411                 return zero;
 412         }
 413
 414         if (implied == NOTIMPLIED) {
 415                 *undefined = 1;
 416                 return bogus;
 417         }
 418
 419         res = do_comparison(expr);
 420         if (res == 1)
 421                 return one;
 422         if (res == 2)
 423                 return zero;
 424
 425         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 426                 return zero;
 427         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 428                 return one;
 429
 430         *undefined = 1;
 431         return bogus;
 432 }
 433
 434 static sval_t handle_logical(struct expression *expr, int *undefined, int implied)
 435 {
 436         sval_t left, right;
 437         int left_known = 0;
 438         int right_known = 0;
 439
 440         if (implied == NOTIMPLIED) {
 441                 if (get_value(expr->left, &left))
 442                         left_known = 1;
 443                 if (get_value(expr->right, &right))
 444                         right_known = 1;
 445         } else {
 446                 if (get_implied_value(expr->left, &left))
 447                         left_known = 1;
 448                 if (get_implied_value(expr->right, &right))
 449                         right_known = 1;
 450         }
 451
 452         switch (expr->op) {
 453         case SPECIAL_LOGICAL_OR:
 454                 if (left_known && left.value)
 455                         return one;
 456                 if (right_known && right.value)
 457                         return one;
 458                 if (left_known && right_known)
 459                         return zero;
 460                 break;
 461         case SPECIAL_LOGICAL_AND:
 462                 if (left_known && right_known) {
 463                         if (left.value && right.value)
 464                                 return one;
 465                         return zero;
 466                 }
 467                 break;
 468         default:
 469                 *undefined = 1;
 470                 return bogus;
 471         }
 472
 473         if (implied == IMPLIED_MIN || implied == FUZZY_MIN || implied == ABSOLUTE_MIN)
 474                 return zero;
 475         if (implied == IMPLIED_MAX || implied == FUZZY_MAX || implied == ABSOLUTE_MAX)
 476                 return one;
 477
 478         *undefined = 1;
 479         return bogus;
 480 }
 481
 482 static sval_t handle_conditional(struct expression *expr, int *undefined, int implied)
 483 {
 484         if (known_condition_true(expr->conditional))
 485                 return _get_value(expr->cond_true, undefined, implied);
 486         if (known_condition_false(expr->conditional))
 487                 return _get_value(expr->cond_false, undefined, implied);
 488
 489         if (implied == NOTIMPLIED) {
 490                 *undefined = 1;
 491                 return bogus;
 492         }
 493
 494         if (implied_condition_true(expr->conditional))
 495                 return _get_value(expr->cond_true, undefined, implied);
 496         if (implied_condition_false(expr->conditional))
 497                 return _get_value(expr->cond_false, undefined, implied);
 498
 499         *undefined = 1;
 500         return bogus;
 501 }
 502
 503 static int get_implied_value_helper(struct expression *expr, sval_t *sval, int implied)
 504 {
 505         struct smatch_state *state;
 506         struct symbol *sym;
 507         char *name;
 508
 509         /* fixme: this should return the casted value */
 510
 511         expr = strip_expr(expr);
 512
 513         if (get_value(expr, sval))
 514                 return 1;
 515
 516         name = expr_to_var_sym(expr, &sym);
 517         if (!name)
 518                 return 0;
 519         *sval = sval_blank(expr);
 520         state = get_state(SMATCH_EXTRA, name, sym);
 521         free_string(name);
 522         if (!state || !state->data)
 523                 return 0;
 524         if (implied == IMPLIED) {
 525                 if (estate_get_single_value(state, sval))
 526                         return 1;
 527                 return 0;
 528         }
 529         if (implied == HARD_MAX) {
 530                 if (estate_get_hard_max(state, sval))
 531                         return 1;
 532                 return 0;
 533         }
 534         if (implied == IMPLIED_MAX || implied == ABSOLUTE_MAX) {
 535                 *sval = estate_max(state);
 536                 return 1;
 537         }
 538         *sval = estate_min(state);
 539         return 1;
 540 }
 541
 542 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 543 {
 544         struct sm_state *sm;
 545         struct sm_state *tmp;
 546         sval_t sval;
 547
 548         if (get_hard_max(expr, &sval)) {
 549                 *max = sval;
 550                 return 1;
 551         }
 552
 553         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 554         if (!sm)
 555                 return 0;
 556
 557         sval = sval_type_min(estate_type(sm->state));
 558         FOR_EACH_PTR(sm->possible, tmp) {
 559                 sval_t new_min;
 560
 561                 new_min = estate_min(tmp->state);
 562                 if (sval_cmp(new_min, sval) > 0)
 563                         sval = new_min;
 564         } END_FOR_EACH_PTR(tmp);
 565
 566         if (sval_is_min(sval))
 567                 return 0;
 568         if (sval.value == sval_type_min(sval.type).value + 1)  /* it's common to be on off */
 569                 return 0;
 570
 571         *max = sval_cast(get_type(expr), sval);
 572         return 1;
 573 }
 574
 575 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 576 {
 577         struct sm_state *sm;
 578         struct sm_state *tmp;
 579         sval_t sval;
 580
 581         sm = get_sm_state_expr(SMATCH_EXTRA, expr);
 582         if (!sm)
 583                 return 0;
 584
 585         if (!sval_is_min(estate_min(sm->state))) {
 586                 *min = estate_min(sm->state);
 587                 return 1;
 588         }
 589
 590         sval = sval_type_max(estate_type(sm->state));
 591         FOR_EACH_PTR(sm->possible, tmp) {
 592                 sval_t new_max;
 593
 594                 new_max = estate_max(tmp->state);
 595                 if (sval_cmp(new_max, sval) < 0)
 596                         sval = new_max;
 597         } END_FOR_EACH_PTR(tmp);
 598
 599         if (sval_is_max(sval))
 600                 return 0;
 601         *min = sval_cast(get_type(expr), sval);
 602         return 1;
 603 }
 604
 605 static sval_t _get_implied_value(struct expression *expr, int *undefined, int implied)
 606 {
 607         sval_t ret;
 608
 609         ret = sval_blank(expr);
 610
 611         switch (implied) {
 612         case IMPLIED:
 613         case IMPLIED_MAX:
 614         case IMPLIED_MIN:
 615         case HARD_MAX:
 616         case ABSOLUTE_MIN:
 617         case ABSOLUTE_MAX:
 618                 if (!get_implied_value_helper(expr, &ret, implied))
 619                         *undefined = 1;
 620                 break;
 621         case FUZZY_MAX:
 622                 if (!get_fuzzy_max_helper(expr, &ret))
 623                         *undefined = 1;
 624                 break;
 625         case FUZZY_MIN:
 626                 if (!get_fuzzy_min_helper(expr, &ret))
 627                         *undefined = 1;
 628                 break;
 629         default:
 630                 *undefined = 1;
 631         }
 632         return ret;
 633 }
 634
 635 static int get_const_value(struct expression *expr, sval_t *sval)
 636 {
 637         struct symbol *sym;
 638         sval_t right;
 639
 640         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 641                 return 0;
 642         sym = expr->symbol;
 643         if (!(sym->ctype.modifiers & MOD_CONST))
 644                 return 0;
 645         if (get_value(sym->initializer, &right)) {
 646                 *sval = sval_cast(get_type(expr), right);
 647                 return 1;
 648         }
 649         return 0;
 650 }
 651
 652 static sval_t handle_sizeof(struct expression *expr)
 653 {
 654         struct symbol *sym;
 655         sval_t ret;
 656
 657         ret = sval_blank(expr);
 658         sym = expr->cast_type;
 659         if (!sym) {
 660                 sym = evaluate_expression(expr->cast_expression);
 661                 /*
 662                  * Expressions of restricted types will possibly get
 663                  * promoted - check that here
 664                  */
 665                 if (is_restricted_type(sym)) {
 666                         if (sym->bit_size < bits_in_int)
 667                                 sym = &int_ctype;
 668                 } else if (is_fouled_type(sym)) {
 669                         sym = &int_ctype;
 670                 }
 671         }
 672         examine_symbol_type(sym);
 673
 674         ret.type = size_t_ctype;
 675         if (sym->bit_size <= 0) /* sizeof(void) */
 676                 ret.value = 1;
 677         else
 678                 ret.value = bits_to_bytes(sym->bit_size);
 679
 680         return ret;
 681 }
 682
 683 static sval_t _get_value(struct expression *expr, int *undefined, int implied)
 684 {
 685         sval_t ret;
 686
 687         if (!expr) {
 688                 *undefined = 1;
 689                 return bogus;
 690         }
 691         if (*undefined)
 692                 return bogus;
 693
 694         expr = strip_parens(expr);
 695
 696         switch (expr->type) {
 697         case EXPR_VALUE:
 698                 ret = sval_from_val(expr, expr->value);
 699                 break;
 700         case EXPR_PREOP:
 701                 ret = handle_preop(expr, undefined, implied);
 702                 break;
 703         case EXPR_POSTOP:
 704                 ret = _get_value(expr->unop, undefined, implied);
 705                 break;
 706         case EXPR_CAST:
 707         case EXPR_FORCE_CAST:
 708         case EXPR_IMPLIED_CAST:
 709                 ret = _get_value(expr->cast_expression, undefined, implied);
 710                 ret = sval_cast(get_type(expr), ret);
 711                 break;
 712         case EXPR_BINOP:
 713                 ret = handle_binop(expr, undefined, implied);
 714                 break;
 715         case EXPR_COMPARE:
 716                 ret = handle_comparison(expr, undefined, implied);
 717                 break;
 718         case EXPR_LOGICAL:
 719                 ret = handle_logical(expr, undefined, implied);
 720                 break;
 721         case EXPR_PTRSIZEOF:
 722         case EXPR_SIZEOF:
 723                 ret = handle_sizeof(expr);
 724                 break;
 725         case EXPR_SYMBOL:
 726                 if (get_const_value(expr, &ret)) {
 727                         break;
 728                 }
 729                 ret = _get_implied_value(expr, undefined, implied);
 730                 break;
 731         case EXPR_SELECT:
 732         case EXPR_CONDITIONAL:
 733                 ret = handle_conditional(expr, undefined, implied);
 734                 break;
 735         default:
 736                 ret = _get_implied_value(expr, undefined, implied);
 737         }
 738         if (*undefined)
 739                 return bogus;
 740         return ret;
 741 }
 742
 743 /* returns 1 if it can get a value literal or else returns 0 */
 744 int get_value(struct expression *expr, sval_t *sval)
 745 {
 746         int undefined = 0;
 747         sval_t ret;
 748
 749         ret = _get_value(expr, &undefined, NOTIMPLIED);
 750         if (undefined)
 751                 return 0;
 752         *sval = ret;
 753         return 1;
 754 }
 755
 756 int get_implied_value(struct expression *expr, sval_t *sval)
 757 {
 758         int undefined = 0;
 759         sval_t ret;
 760
 761         ret =  _get_value(expr, &undefined, IMPLIED);
 762         if (undefined)
 763                 return 0;
 764         *sval = ret;
 765         return 1;
 766 }
 767
 768 int get_implied_min(struct expression *expr, sval_t *sval)
 769 {
 770         int undefined = 0;
 771         sval_t ret;
 772
 773         ret =  _get_value(expr, &undefined, IMPLIED_MIN);
 774         if (undefined)
 775                 return 0;
 776         *sval = ret;
 777         return 1;
 778 }
 779
 780 int get_implied_max(struct expression *expr, sval_t *sval)
 781 {
 782         int undefined = 0;
 783         sval_t ret;
 784
 785         ret =  _get_value(expr, &undefined, IMPLIED_MAX);
 786         if (undefined)
 787                 return 0;
 788         *sval = ret;
 789         return 1;
 790 }
 791
 792 int get_implied_rl(struct expression *expr, struct range_list **rl)
 793 {
 794         sval_t sval;
 795         struct smatch_state *state;
 796         sval_t min, max;
 797         int min_known = 0;
 798         int max_known = 0;
 799
 800         *rl = NULL;
 801
 802         expr = strip_parens(expr);
 803         if (!expr)
 804                 return 0;
 805
 806         state = get_state_expr(SMATCH_EXTRA, expr);
 807         if (state) {
 808                 *rl = clone_rl(estate_rl(state));
 809                 return 1;
 810         }
 811
 812         if (expr->type == EXPR_CALL) {
 813                 if (get_implied_return(expr, rl))
 814                         return 1;
 815                 *rl = db_return_vals(expr);
 816                 if (*rl)
 817                         return 1;
 818                 return 0;
 819         }
 820
 821         if (get_implied_value(expr, &sval)) {
 822                 add_range(rl, sval, sval);
 823                 return 1;
 824         }
 825
 826         min_known = get_implied_min(expr, &min);
 827         max_known = get_implied_max(expr, &max);
 828         if (!min_known && !max_known)
 829                 return 0;
 830         if (!min_known)
 831                 get_absolute_min(expr, &min);
 832         if (!max_known)
 833                 get_absolute_max(expr, &max);
 834
 835         *rl = alloc_rl(min, max);
 836         return 1;
 837 }
 838
 839 int get_hard_max(struct expression *expr, sval_t *sval)
 840 {
 841         int undefined = 0;
 842         sval_t ret;
 843
 844         ret =  _get_value(expr, &undefined, HARD_MAX);
 845         if (undefined)
 846                 return 0;
 847         *sval = ret;
 848         return 1;
 849 }
 850
 851 int get_fuzzy_min(struct expression *expr, sval_t *sval)
 852 {
 853         int undefined = 0;
 854         sval_t ret;
 855
 856         ret =  _get_value(expr, &undefined, FUZZY_MIN);
 857         if (undefined)
 858                 return 0;
 859         *sval = ret;
 860         return 1;
 861 }
 862
 863 int get_fuzzy_max(struct expression *expr, sval_t *sval)
 864 {
 865         int undefined = 0;
 866         sval_t ret;
 867
 868         ret =  _get_value(expr, &undefined, FUZZY_MAX);
 869         if (undefined)
 870                 return 0;
 871         if (ret.uvalue > INT_MAX - 10000)
 872                 return 0;
 873         *sval = ret;
 874         return 1;
 875 }
 876
 877 int get_absolute_min(struct expression *expr, sval_t *sval)
 878 {
 879         int undefined = 0;
 880         struct symbol *type;
 881
 882         type = get_type(expr);
 883         if (!type)
 884                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
 885         *sval =  _get_value(expr, &undefined, ABSOLUTE_MIN);
 886         if (undefined) {
 887                 *sval = sval_type_min(type);
 888                 return 1;
 889         }
 890
 891         if (sval_cmp(*sval, sval_type_min(type)) < 0)
 892                 *sval = sval_type_min(type);
 893         return 1;
 894 }
 895
 896 int get_absolute_max(struct expression *expr, sval_t *sval)
 897 {
 898         int undefined = 0;
 899         struct symbol *type;
 900
 901         type = get_type(expr);
 902         if (!type)
 903                 type = &llong_ctype;
 904         *sval = _get_value(expr, &undefined, ABSOLUTE_MAX);
 905         if (undefined) {
 906                 *sval = sval_type_max(type);
 907                 return 1;
 908         }
 909
 910         if (sval_cmp(sval_type_max(type), *sval) < 0)
 911                 *sval = sval_type_max(type);
 912         return 1;
 913 }
 914
 915 int known_condition_true(struct expression *expr)
 916 {
 917         sval_t tmp;
 918
 919         if (!expr)
 920                 return 0;
 921
 922         if (get_value(expr, &tmp) && tmp.value)
 923                 return 1;
 924
 925         return 0;
 926 }
 927
 928 int known_condition_false(struct expression *expr)
 929 {
 930         if (!expr)
 931                 return 0;
 932
 933         if (is_zero(expr))
 934                 return 1;
 935
 936         if (expr->type == EXPR_CALL) {
 937                 if (sym_name_is("__builtin_constant_p", expr->fn))
 938                         return 1;
 939         }
 940         return 0;
 941 }
 942
 943 int implied_condition_true(struct expression *expr)
 944 {
 945         sval_t tmp;
 946
 947         if (!expr)
 948                 return 0;
 949
 950         if (known_condition_true(expr))
 951                 return 1;
 952         if (get_implied_value(expr, &tmp) && tmp.value)
 953                 return 1;
 954
 955         if (expr->type == EXPR_POSTOP)
 956                 return implied_condition_true(expr->unop);
 957
 958         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
 959                 return implied_not_equal(expr->unop, 1);
 960         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
 961                 return implied_not_equal(expr->unop, -1);
 962
 963         expr = strip_expr(expr);
 964         switch (expr->type) {
 965         case EXPR_COMPARE:
 966                 if (do_comparison(expr) == 1)
 967                         return 1;
 968                 break;
 969         case EXPR_PREOP:
 970                 if (expr->op == '!') {
 971                         if (implied_condition_false(expr->unop))
 972                                 return 1;
 973                         break;
 974                 }
 975                 break;
 976         default:
 977                 if (implied_not_equal(expr, 0) == 1)
 978                         return 1;
 979                 break;
 980         }
 981         return 0;
 982 }
 983
 984 int implied_condition_false(struct expression *expr)
 985 {
 986         struct expression *tmp;
 987         sval_t sval;
 988
 989         if (!expr)
 990                 return 0;
 991
 992         if (known_condition_false(expr))
 993                 return 1;
 994
 995         switch (expr->type) {
 996         case EXPR_COMPARE:
 997                 if (do_comparison(expr) == 2)
 998                         return 1;
 999         case EXPR_PREOP:
1000                 if (expr->op == '!') {
1001                         if (implied_condition_true(expr->unop))
1002                                 return 1;
1003                         break;
1004                 }
1005                 tmp = strip_expr(expr);
1006                 if (tmp != expr)
1007                         return implied_condition_false(tmp);
1008                 break;
1009         default:
1010                 if (get_implied_value(expr, &sval) && sval.value == 0)
1011                         return 1;
1012                 break;
1013         }
1014         return 0;
1015 }