smatch_math.c

   1 /*
   2  * Copyright (C) 2010 Dan Carpenter.
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; either version 2
   7  * of the License, or (at your option) any later version.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, see http://www.gnu.org/copyleft/gpl.txt
  16  */
  17
  18 #include "symbol.h"
  19 #include "smatch.h"
  20 #include "smatch_slist.h"
  21 #include "smatch_extra.h"
  22
  23 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt);
  24 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt);
  25 static struct range_list *(*custom_handle_variable)(struct expression *expr);
  26
  27 static int get_implied_value_internal(struct expression *expr, sval_t *sval, int *recurse_cnt);
  28 static int get_absolute_rl_internal(struct expression *expr, struct range_list **rl, int *recurse_cnt);
  29
  30 static sval_t zero  = {.type = &int_ctype, {.value = 0} };
  31 static sval_t one   = {.type = &int_ctype, {.value = 1} };
  32
  33 struct range_list *rl_zero(void)
  34 {
  35         return alloc_rl(zero, zero);
  36 }
  37
  38 struct range_list *rl_one(void)
  39 {
  40         return alloc_rl(one, one);
  41 }
  42
  43 enum {
  44         RL_EXACT,
  45         RL_HARD,
  46         RL_FUZZY,
  47         RL_IMPLIED,
  48         RL_ABSOLUTE,
  49         RL_REAL_ABSOLUTE,
  50 };
  51
  52 static struct range_list *last_stmt_rl(struct statement *stmt, int implied, int *recurse_cnt)
  53 {
  54         struct expression *expr;
  55
  56         if (!stmt)
  57                 return NULL;
  58
  59         stmt = last_ptr_list((struct ptr_list *)stmt->stmts);
  60         if (stmt->type == STMT_LABEL) {
  61                 if (stmt->label_statement &&
  62                     stmt->label_statement->type == STMT_EXPRESSION)
  63                         expr = stmt->label_statement->expression;
  64                 else
  65                         return NULL;
  66         } else if (stmt->type == STMT_EXPRESSION) {
  67                 expr = stmt->expression;
  68         } else {
  69                 return NULL;
  70         }
  71         return _get_rl(expr, implied, recurse_cnt);
  72 }
  73
  74 static struct range_list *handle_expression_statement_rl(struct expression *expr, int implied, int *recurse_cnt)
  75 {
  76         return last_stmt_rl(get_expression_statement(expr), implied, recurse_cnt);
  77 }
  78
  79 static struct range_list *handle_ampersand_rl(struct expression *expr, int implied, int *recurse_cnt)
  80 {
  81         struct range_list *rl;
  82
  83         if (implied == RL_EXACT || implied == RL_HARD)
  84                 return NULL;
  85         if (get_address_rl(expr, &rl))
  86                 return rl;
  87         return alloc_rl(valid_ptr_min_sval, valid_ptr_max_sval);
  88 }
  89
  90 static struct range_list *handle_negate_rl(struct expression *expr, int implied, int *recurse_cnt)
  91 {
  92         if (known_condition_true(expr->unop))
  93                 return rl_zero();
  94         if (known_condition_false(expr->unop))
  95                 return rl_one();
  96
  97         if (implied == RL_EXACT)
  98                 return NULL;
  99
 100         if (implied_condition_true(expr->unop))
 101                 return rl_zero();
 102         if (implied_condition_false(expr->unop))
 103                 return rl_one();
 104         return alloc_rl(zero, one);
 105 }
 106
 107 static struct range_list *handle_bitwise_negate(struct expression *expr, int implied, int *recurse_cnt)
 108 {
 109         struct range_list *rl;
 110         sval_t sval;
 111
 112         rl = _get_rl(expr->unop, implied, recurse_cnt);
 113         if (!rl_to_sval(rl, &sval))
 114                 return NULL;
 115         sval = sval_preop(sval, '~');
 116         sval_cast(get_type(expr->unop), sval);
 117         return alloc_rl(sval, sval);
 118 }
 119
 120 static struct range_list *handle_minus_preop(struct expression *expr, int implied, int *recurse_cnt)
 121 {
 122         struct range_list *rl;
 123         sval_t min, max;
 124
 125         rl = _get_rl(expr->unop, implied, recurse_cnt);
 126         min = sval_preop(rl_max(rl), '-');
 127         max = sval_preop(rl_min(rl), '-');
 128         return alloc_rl(min, max);
 129 }
 130
 131 static struct range_list *handle_preop_rl(struct expression *expr, int implied, int *recurse_cnt)
 132 {
 133         switch (expr->op) {
 134         case '&':
 135                 return handle_ampersand_rl(expr, implied, recurse_cnt);
 136         case '!':
 137                 return handle_negate_rl(expr, implied, recurse_cnt);
 138         case '~':
 139                 return handle_bitwise_negate(expr, implied, recurse_cnt);
 140         case '-':
 141                 return handle_minus_preop(expr, implied, recurse_cnt);
 142         case '*':
 143                 return handle_variable(expr, implied, recurse_cnt);
 144         case '(':
 145                 return handle_expression_statement_rl(expr, implied, recurse_cnt);
 146         default:
 147                 return NULL;
 148         }
 149 }
 150
 151 static struct range_list *handle_divide_rl(struct expression *expr, int implied, int *recurse_cnt)
 152 {
 153         struct range_list *left_rl, *right_rl;
 154         struct symbol *type;
 155
 156         type = get_type(expr);
 157
 158         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 159         left_rl = cast_rl(type, left_rl);
 160         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 161         right_rl = cast_rl(type, right_rl);
 162
 163         if (!left_rl || !right_rl)
 164                 return NULL;
 165
 166         if (implied != RL_REAL_ABSOLUTE) {
 167                 if (is_whole_rl(left_rl) || is_whole_rl(right_rl))
 168                         return NULL;
 169         }
 170
 171         return rl_binop(left_rl, '/', right_rl);
 172 }
 173
 174 static int handle_offset_subtraction(struct expression *expr)
 175 {
 176         struct expression *left, *right;
 177         struct symbol *left_sym, *right_sym;
 178         struct symbol *type;
 179         int left_offset, right_offset;
 180
 181         type = get_type(expr);
 182         if (!type || type->type != SYM_PTR)
 183                 return -1;
 184         type = get_real_base_type(type);
 185         if (!type || (type_bits(type) != 8 && (type != &void_ctype)))
 186                 return -1;
 187
 188         left = strip_expr(expr->left);
 189         right = strip_expr(expr->right);
 190
 191         if (left->type != EXPR_PREOP || left->op != '&')
 192                 return -1;
 193         left = strip_expr(left->unop);
 194
 195         left_sym = expr_to_sym(left);
 196         right_sym = expr_to_sym(right);
 197         if (!left_sym || left_sym != right_sym)
 198                 return -1;
 199
 200         left_offset = get_member_offset_from_deref(left);
 201         if (right->type == EXPR_SYMBOL)
 202                 right_offset = 0;
 203         else {
 204                 if (right->type != EXPR_PREOP || right->op != '&')
 205                         return -1;
 206                 right = strip_expr(right->unop);
 207                 right_offset = get_member_offset_from_deref(right);
 208         }
 209         if (left_offset < 0 || right_offset < 0)
 210                 return -1;
 211
 212         return left_offset - right_offset;
 213 }
 214
 215 static struct range_list *handle_subtract_rl(struct expression *expr, int implied, int *recurse_cnt)
 216 {
 217         struct symbol *type;
 218         struct range_list *left_orig, *right_orig;
 219         struct range_list *left_rl, *right_rl;
 220         sval_t max, min, tmp;
 221         int comparison;
 222         int offset;
 223
 224         type = get_type(expr);
 225
 226         offset = handle_offset_subtraction(expr);
 227         if (offset >= 0) {
 228                 tmp.type = type;
 229                 tmp.value = offset;
 230
 231                 return alloc_rl(tmp, tmp);
 232         }
 233
 234         comparison = get_comparison(expr->left, expr->right);
 235
 236         left_orig = _get_rl(expr->left, implied, recurse_cnt);
 237         left_rl = cast_rl(type, left_orig);
 238         right_orig = _get_rl(expr->right, implied, recurse_cnt);
 239         right_rl = cast_rl(type, right_orig);
 240
 241         if ((!left_rl || !right_rl) &&
 242             (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY))
 243                 return NULL;
 244
 245         if (!left_rl)
 246                 left_rl = alloc_whole_rl(type);
 247         if (!right_rl)
 248                 right_rl = alloc_whole_rl(type);
 249
 250         /* negative values complicate everything fix this later */
 251         if (sval_is_negative(rl_min(right_rl)))
 252                 return NULL;
 253         max = rl_max(left_rl);
 254         min = sval_type_min(type);
 255
 256         switch (comparison) {
 257         case '>':
 258         case SPECIAL_UNSIGNED_GT:
 259                 min = sval_type_val(type, 1);
 260                 max = rl_max(left_rl);
 261                 break;
 262         case SPECIAL_GTE:
 263         case SPECIAL_UNSIGNED_GTE:
 264                 min = sval_type_val(type, 0);
 265                 max = rl_max(left_rl);
 266                 break;
 267         case SPECIAL_EQUAL:
 268                 min = sval_type_val(type, 0);
 269                 max = sval_type_val(type, 0);
 270                 break;
 271         case '<':
 272         case SPECIAL_UNSIGNED_LT:
 273                 max = sval_type_val(type, -1);
 274                 break;
 275         case SPECIAL_LTE:
 276         case SPECIAL_UNSIGNED_LTE:
 277                 max = sval_type_val(type, 0);
 278                 break;
 279         default:
 280                 if (!left_orig || !right_orig)
 281                         return NULL;
 282                 return rl_binop(left_rl, '-', right_rl);
 283         }
 284
 285         if (!sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl))) {
 286                 tmp = sval_binop(rl_min(left_rl), '-', rl_max(right_rl));
 287                 if (sval_cmp(tmp, min) > 0)
 288                         min = tmp;
 289         }
 290
 291         if (!sval_is_max(rl_max(left_rl))) {
 292                 tmp = sval_binop(rl_max(left_rl), '-', rl_min(right_rl));
 293                 if (sval_cmp(tmp, max) < 0)
 294                         max = tmp;
 295         }
 296
 297         if (sval_is_min(min) && sval_is_max(max))
 298                 return NULL;
 299
 300         return cast_rl(type, alloc_rl(min, max));
 301 }
 302
 303 static struct range_list *handle_mod_rl(struct expression *expr, int implied, int *recurse_cnt)
 304 {
 305         struct range_list *rl;
 306         sval_t left, right, sval;
 307
 308         if (implied == RL_EXACT) {
 309                 if (!get_implied_value(expr->right, &right))
 310                         return NULL;
 311                 if (!get_implied_value(expr->left, &left))
 312                         return NULL;
 313                 sval = sval_binop(left, '%', right);
 314                 return alloc_rl(sval, sval);
 315         }
 316         /* if we can't figure out the right side it's probably hopeless */
 317         if (!get_implied_value_internal(expr->right, &right, recurse_cnt))
 318                 return NULL;
 319
 320         right = sval_cast(get_type(expr), right);
 321         right.value--;
 322
 323         rl = _get_rl(expr->left, implied, recurse_cnt);
 324         if (rl && rl_max(rl).uvalue < right.uvalue)
 325                 right.uvalue = rl_max(rl).uvalue;
 326
 327         return alloc_rl(sval_cast(right.type, zero), right);
 328 }
 329
 330 static sval_t sval_lowest_set_bit(sval_t sval)
 331 {
 332         int i;
 333         int found = 0;
 334
 335         for (i = 0; i < 64; i++) {
 336                 if (sval.uvalue & 1ULL << i) {
 337                         if (!found++)
 338                                 continue;
 339                         sval.uvalue &= ~(1ULL << i);
 340                 }
 341         }
 342         return sval;
 343 }
 344
 345 static struct range_list *handle_bitwise_AND(struct expression *expr, int implied, int *recurse_cnt)
 346 {
 347         struct symbol *type;
 348         struct range_list *left_rl, *right_rl;
 349         sval_t known;
 350         int new_recurse;
 351
 352         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE && implied != RL_REAL_ABSOLUTE)
 353                 return NULL;
 354
 355         type = get_type(expr);
 356
 357         if (get_implied_value_internal(expr->left, &known, recurse_cnt)) {
 358                 sval_t min;
 359
 360                 min = sval_lowest_set_bit(known);
 361                 left_rl = alloc_rl(min, known);
 362                 left_rl = cast_rl(type, left_rl);
 363                 add_range(&left_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 364         } else {
 365                 left_rl = _get_rl(expr->left, implied, recurse_cnt);
 366                 if (left_rl) {
 367                         left_rl = cast_rl(type, left_rl);
 368                         left_rl = alloc_rl(sval_type_val(type, 0), rl_max(left_rl));
 369                 } else {
 370                         if (implied == RL_HARD)
 371                                 return NULL;
 372                         left_rl = alloc_whole_rl(type);
 373                 }
 374         }
 375
 376         new_recurse = *recurse_cnt;
 377         if (*recurse_cnt >= 200)
 378                 new_recurse = 100;  /* Let's try super hard to get the mask */
 379         if (get_implied_value_internal(expr->right, &known, &new_recurse)) {
 380                 sval_t min, left_max, mod;
 381
 382                 *recurse_cnt = new_recurse;
 383
 384                 min = sval_lowest_set_bit(known);
 385                 right_rl = alloc_rl(min, known);
 386                 right_rl = cast_rl(type, right_rl);
 387                 add_range(&right_rl, sval_type_val(type, 0), sval_type_val(type, 0));
 388
 389                 if (min.value != 0) {
 390                         left_max = rl_max(left_rl);
 391                         mod = sval_binop(left_max, '%', min);
 392                         if (mod.value) {
 393                                 left_max = sval_binop(left_max, '-', mod);
 394                                 left_max.value++;
 395                                 if (left_max.value > 0 && sval_cmp(left_max, rl_max(left_rl)) < 0)
 396                                         left_rl = remove_range(left_rl, left_max, rl_max(left_rl));
 397                         }
 398                 }
 399         } else {
 400                 right_rl = _get_rl(expr->right, implied, recurse_cnt);
 401                 if (right_rl) {
 402                         right_rl = cast_rl(type, right_rl);
 403                         right_rl = alloc_rl(sval_type_val(type, 0), rl_max(right_rl));
 404                 } else {
 405                         if (implied == RL_HARD)
 406                                 return NULL;
 407                         right_rl = alloc_whole_rl(type);
 408                 }
 409         }
 410
 411         return rl_intersection(left_rl, right_rl);
 412 }
 413
 414 static struct range_list *use_rl_binop(struct expression *expr, int implied, int *recurse_cnt)
 415 {
 416         struct symbol *type;
 417         struct range_list *left_rl, *right_rl;
 418
 419         if (implied != RL_IMPLIED && implied != RL_ABSOLUTE && implied != RL_REAL_ABSOLUTE)
 420                 return NULL;
 421
 422         type = get_type(expr);
 423
 424         get_absolute_rl_internal(expr->left, &left_rl, recurse_cnt);
 425         get_absolute_rl_internal(expr->right, &right_rl, recurse_cnt);
 426         left_rl = cast_rl(type, left_rl);
 427         right_rl = cast_rl(type, right_rl);
 428         if (!left_rl || !right_rl)
 429                 return NULL;
 430
 431         return rl_binop(left_rl, expr->op, right_rl);
 432 }
 433
 434 static struct range_list *handle_right_shift(struct expression *expr, int implied, int *recurse_cnt)
 435 {
 436         struct range_list *left_rl;
 437         sval_t right;
 438         sval_t min, max;
 439
 440         if (implied == RL_EXACT || implied == RL_HARD)
 441                 return NULL;
 442
 443         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 444         if (left_rl) {
 445                 max = rl_max(left_rl);
 446                 min = rl_min(left_rl);
 447         } else {
 448                 if (implied == RL_FUZZY)
 449                         return NULL;
 450                 max = sval_type_max(get_type(expr->left));
 451                 min = sval_type_val(get_type(expr->left), 0);
 452         }
 453
 454         if (get_implied_value_internal(expr->right, &right, recurse_cnt)) {
 455                 min = sval_binop(min, SPECIAL_RIGHTSHIFT, right);
 456                 max = sval_binop(max, SPECIAL_RIGHTSHIFT, right);
 457         } else if (!sval_is_negative(min)) {
 458                 min.value = 0;
 459                 max = sval_type_max(max.type);
 460         } else {
 461                 return NULL;
 462         }
 463
 464         return alloc_rl(min, max);
 465 }
 466
 467 static struct range_list *handle_left_shift(struct expression *expr, int implied, int *recurse_cnt)
 468 {
 469         struct range_list *left_rl, *res;
 470         sval_t right;
 471         sval_t min, max;
 472         int add_zero = 0;
 473
 474         if (implied == RL_EXACT || implied == RL_HARD)
 475                 return NULL;
 476         /* this is hopeless without the right side */
 477         if (!get_implied_value_internal(expr->right, &right, recurse_cnt))
 478                 return NULL;
 479         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 480         if (left_rl) {
 481                 max = rl_max(left_rl);
 482                 min = rl_min(left_rl);
 483                 if (min.value == 0) {
 484                         min.value = 1;
 485                         add_zero = 1;
 486                 }
 487         } else {
 488                 if (implied == RL_FUZZY)
 489                         return NULL;
 490                 max = sval_type_max(get_type(expr->left));
 491                 min = sval_type_val(get_type(expr->left), 1);
 492                 add_zero = 1;
 493         }
 494
 495         max = sval_binop(max, SPECIAL_LEFTSHIFT, right);
 496         min = sval_binop(min, SPECIAL_LEFTSHIFT, right);
 497         res = alloc_rl(min, max);
 498         if (add_zero)
 499                 res = rl_union(res, rl_zero());
 500         return res;
 501 }
 502
 503 static struct range_list *handle_known_binop(struct expression *expr)
 504 {
 505         sval_t left, right;
 506
 507         if (!get_value(expr->left, &left))
 508                 return NULL;
 509         if (!get_value(expr->right, &right))
 510                 return NULL;
 511         left = sval_binop(left, expr->op, right);
 512         return alloc_rl(left, left);
 513 }
 514
 515 static int has_actual_ranges(struct range_list *rl)
 516 {
 517         struct data_range *tmp;
 518
 519         FOR_EACH_PTR(rl, tmp) {
 520                 if (sval_cmp(tmp->min, tmp->max) != 0)
 521                         return 1;
 522         } END_FOR_EACH_PTR(tmp);
 523         return 0;
 524 }
 525
 526 static struct range_list *handle_implied_binop(struct range_list *left_rl, int op, struct range_list *right_rl)
 527 {
 528         struct range_list *res_rl;
 529         struct data_range *left_drange, *right_drange;
 530         sval_t res;
 531
 532         if (!left_rl || !right_rl)
 533                 return NULL;
 534         if (has_actual_ranges(left_rl))
 535                 return NULL;
 536         if (has_actual_ranges(right_rl))
 537                 return NULL;
 538
 539         if (ptr_list_size((struct ptr_list *)left_rl) * ptr_list_size((struct ptr_list *)right_rl) > 20)
 540                 return NULL;
 541
 542         res_rl = NULL;
 543
 544         FOR_EACH_PTR(left_rl, left_drange) {
 545                 FOR_EACH_PTR(right_rl, right_drange) {
 546                         if ((op == '%' || op == '/') &&
 547                             right_drange->min.value == 0)
 548                                 return NULL;
 549                         res = sval_binop(left_drange->min, op, right_drange->min);
 550                         add_range(&res_rl, res, res);
 551                 } END_FOR_EACH_PTR(right_drange);
 552         } END_FOR_EACH_PTR(left_drange);
 553
 554         return res_rl;
 555 }
 556
 557 static struct range_list *handle_binop_rl(struct expression *expr, int implied, int *recurse_cnt)
 558 {
 559         struct smatch_state *state;
 560         struct symbol *type;
 561         struct range_list *left_rl, *right_rl, *rl;
 562         sval_t min, max;
 563
 564         rl = handle_known_binop(expr);
 565         if (rl)
 566                 return rl;
 567         if (implied == RL_EXACT)
 568                 return NULL;
 569
 570         if (custom_handle_variable) {
 571                 rl = custom_handle_variable(expr);
 572                 if (rl)
 573                         return rl;
 574         }
 575
 576         state = get_extra_state(expr);
 577         if (state && !is_whole_rl(estate_rl(state))) {
 578                 if (implied != RL_HARD || estate_has_hard_max(state))
 579                         return clone_rl(estate_rl(state));
 580         }
 581
 582         type = get_type(expr);
 583         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 584         left_rl = cast_rl(type, left_rl);
 585         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 586         right_rl = cast_rl(type, right_rl);
 587
 588         if (!left_rl && !right_rl)
 589                 return NULL;
 590
 591         rl = handle_implied_binop(left_rl, expr->op, right_rl);
 592         if (rl)
 593                 return rl;
 594
 595         switch (expr->op) {
 596         case '%':
 597                 return handle_mod_rl(expr, implied, recurse_cnt);
 598         case '&':
 599                 return handle_bitwise_AND(expr, implied, recurse_cnt);
 600         case '|':
 601         case '^':
 602                 return use_rl_binop(expr, implied, recurse_cnt);
 603         case SPECIAL_RIGHTSHIFT:
 604                 return handle_right_shift(expr, implied, recurse_cnt);
 605         case SPECIAL_LEFTSHIFT:
 606                 return handle_left_shift(expr, implied, recurse_cnt);
 607         case '-':
 608                 return handle_subtract_rl(expr, implied, recurse_cnt);
 609         case '/':
 610                 return handle_divide_rl(expr, implied, recurse_cnt);
 611         }
 612
 613         if (!left_rl || !right_rl)
 614                 return NULL;
 615
 616         if (sval_binop_overflows(rl_min(left_rl), expr->op, rl_min(right_rl)))
 617                 return NULL;
 618         if (sval_binop_overflows(rl_max(left_rl), expr->op, rl_max(right_rl)))
 619                 return NULL;
 620
 621         min = sval_binop(rl_min(left_rl), expr->op, rl_min(right_rl));
 622         max = sval_binop(rl_max(left_rl), expr->op, rl_max(right_rl));
 623
 624         return alloc_rl(min, max);
 625 }
 626
 627 static int do_comparison(struct expression *expr)
 628 {
 629         struct range_list *left_ranges = NULL;
 630         struct range_list *right_ranges = NULL;
 631         int poss_true, poss_false;
 632         struct symbol *type;
 633
 634         type = get_type(expr);
 635         get_absolute_rl(expr->left, &left_ranges);
 636         get_absolute_rl(expr->right, &right_ranges);
 637
 638         left_ranges = cast_rl(type, left_ranges);
 639         right_ranges = cast_rl(type, right_ranges);
 640
 641         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 642         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 643
 644         free_rl(&left_ranges);
 645         free_rl(&right_ranges);
 646
 647         if (!poss_true && !poss_false)
 648                 return 0x0;
 649         if (poss_true && !poss_false)
 650                 return 0x1;
 651         if (!poss_true && poss_false)
 652                 return 0x2;
 653         return 0x3;
 654 }
 655
 656 static struct range_list *handle_comparison_rl(struct expression *expr, int implied, int *recurse_cnt)
 657 {
 658         sval_t left, right;
 659         int res;
 660
 661         if (expr->op == SPECIAL_EQUAL && expr->left->type == EXPR_TYPE) {
 662                 struct symbol *left, *right;
 663
 664                 left = get_real_base_type(expr->left->symbol);
 665                 right = get_real_base_type(expr->left->symbol);
 666                 if (left == right)
 667                         return rl_one();
 668                 return rl_zero();
 669         }
 670
 671         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 672                 struct data_range tmp_left, tmp_right;
 673
 674                 tmp_left.min = left;
 675                 tmp_left.max = left;
 676                 tmp_right.min = right;
 677                 tmp_right.max = right;
 678                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 679                         return rl_one();
 680                 return rl_zero();
 681         }
 682
 683         if (implied == RL_EXACT)
 684                 return NULL;
 685
 686         res = do_comparison(expr);
 687         if (res == 1)
 688                 return rl_one();
 689         if (res == 2)
 690                 return rl_zero();
 691
 692         return alloc_rl(zero, one);
 693 }
 694
 695 static struct range_list *handle_logical_rl(struct expression *expr, int implied, int *recurse_cnt)
 696 {
 697         sval_t left, right;
 698         int left_known = 0;
 699         int right_known = 0;
 700
 701         if (implied == RL_EXACT) {
 702                 if (get_value(expr->left, &left))
 703                         left_known = 1;
 704                 if (get_value(expr->right, &right))
 705                         right_known = 1;
 706         } else {
 707                 if (get_implied_value_internal(expr->left, &left, recurse_cnt))
 708                         left_known = 1;
 709                 if (get_implied_value_internal(expr->right, &right, recurse_cnt))
 710                         right_known = 1;
 711         }
 712
 713         switch (expr->op) {
 714         case SPECIAL_LOGICAL_OR:
 715                 if (left_known && left.value)
 716                         return rl_one();
 717                 if (right_known && right.value)
 718                         return rl_one();
 719                 if (left_known && right_known)
 720                         return rl_zero();
 721                 break;
 722         case SPECIAL_LOGICAL_AND:
 723                 if (left_known && right_known) {
 724                         if (left.value && right.value)
 725                                 return rl_one();
 726                         return rl_zero();
 727                 }
 728                 break;
 729         default:
 730                 return NULL;
 731         }
 732
 733         if (implied == RL_EXACT)
 734                 return NULL;
 735
 736         return alloc_rl(zero, one);
 737 }
 738
 739 static struct range_list *handle_conditional_rl(struct expression *expr, int implied, int *recurse_cnt)
 740 {
 741         struct range_list *true_rl, *false_rl;
 742         struct symbol *type;
 743         int final_pass_orig = final_pass;
 744
 745         if (known_condition_true(expr->conditional))
 746                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 747         if (known_condition_false(expr->conditional))
 748                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 749
 750         if (implied == RL_EXACT)
 751                 return NULL;
 752
 753         if (implied_condition_true(expr->conditional))
 754                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 755         if (implied_condition_false(expr->conditional))
 756                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 757
 758
 759         /* this becomes a problem with deeply nested conditional statements */
 760         if (low_on_memory())
 761                 return NULL;
 762
 763         type = get_type(expr);
 764
 765         __push_fake_cur_stree();
 766         final_pass = 0;
 767         __split_whole_condition(expr->conditional);
 768         true_rl = _get_rl(expr->cond_true, implied, recurse_cnt);
 769         __push_true_states();
 770         __use_false_states();
 771         false_rl = _get_rl(expr->cond_false, implied, recurse_cnt);
 772         __merge_true_states();
 773         __free_fake_cur_stree();
 774         final_pass = final_pass_orig;
 775
 776         if (!true_rl || !false_rl)
 777                 return NULL;
 778         true_rl = cast_rl(type, true_rl);
 779         false_rl = cast_rl(type, false_rl);
 780
 781         return rl_union(true_rl, false_rl);
 782 }
 783
 784 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 785 {
 786         struct smatch_state *state;
 787         sval_t sval;
 788
 789         if (get_hard_max(expr, &sval)) {
 790                 *max = sval;
 791                 return 1;
 792         }
 793
 794         state = get_extra_state(expr);
 795         if (!state || !estate_has_fuzzy_max(state))
 796                 return 0;
 797         *max = sval_cast(get_type(expr), estate_get_fuzzy_max(state));
 798         return 1;
 799 }
 800
 801 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 802 {
 803         struct smatch_state *state;
 804         sval_t sval;
 805
 806         state = get_extra_state(expr);
 807         if (!state || !estate_rl(state))
 808                 return 0;
 809
 810         sval = estate_min(state);
 811         if (sval_is_negative(sval) && sval_is_min(sval))
 812                 return 0;
 813
 814         if (sval_is_max(sval))
 815                 return 0;
 816
 817         *min = sval_cast(get_type(expr), sval);
 818         return 1;
 819 }
 820
 821 int get_const_value(struct expression *expr, sval_t *sval)
 822 {
 823         struct symbol *sym;
 824         sval_t right;
 825
 826         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 827                 return 0;
 828         sym = expr->symbol;
 829         if (!(sym->ctype.modifiers & MOD_CONST))
 830                 return 0;
 831         if (get_value(sym->initializer, &right)) {
 832                 *sval = sval_cast(get_type(expr), right);
 833                 return 1;
 834         }
 835         return 0;
 836 }
 837
 838 struct range_list *var_to_absolute_rl(struct expression *expr)
 839 {
 840         struct smatch_state *state;
 841         struct range_list *rl;
 842
 843         state = get_extra_state(expr);
 844         if (!state || is_whole_rl(estate_rl(state))) {
 845                 state = get_real_absolute_state(expr);
 846                 if (state && state->data && !estate_is_whole(state))
 847                         return clone_rl(estate_rl(state));
 848                 if (get_local_rl(expr, &rl) && !is_whole_rl(rl))
 849                         return rl;
 850                 if (get_db_type_rl(expr, &rl) && !is_whole_rl(rl))
 851                         return rl;
 852                 return alloc_whole_rl(get_type(expr));
 853         }
 854         /* err on the side of saying things are possible */
 855         if (!estate_rl(state))
 856                 return alloc_whole_rl(get_type(expr));
 857         return clone_rl(estate_rl(state));
 858 }
 859
 860 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt)
 861 {
 862         struct smatch_state *state;
 863         struct range_list *rl;
 864         sval_t sval, min, max;
 865         struct symbol *type;
 866
 867         if (get_const_value(expr, &sval))
 868                 return alloc_rl(sval, sval);
 869
 870         if (custom_handle_variable) {
 871                 rl = custom_handle_variable(expr);
 872                 if (!rl)
 873                         return var_to_absolute_rl(expr);
 874                 return rl;
 875         }
 876
 877         if (implied == RL_EXACT)
 878                 return NULL;
 879
 880         type = get_type(expr);
 881         if (type && type->type == SYM_FN)
 882                 return alloc_rl(fn_ptr_min, fn_ptr_max);
 883
 884         switch (implied) {
 885         case RL_HARD:
 886         case RL_IMPLIED:
 887         case RL_ABSOLUTE:
 888                 state = get_extra_state(expr);
 889                 if (!state || !state->data) {
 890                         if (implied == RL_HARD)
 891                                 return NULL;
 892                         if (get_local_rl(expr, &rl))
 893                                 return rl;
 894                         if (get_db_type_rl(expr, &rl))
 895                                 return rl;
 896                         return NULL;
 897                 }
 898                 if (implied == RL_HARD && !estate_has_hard_max(state))
 899                         return NULL;
 900                 return clone_rl(estate_rl(state));
 901         case RL_REAL_ABSOLUTE: {
 902                 struct smatch_state *abs_state;
 903
 904                 state = get_extra_state(expr);
 905                 abs_state = get_real_absolute_state(expr);
 906
 907                 if (estate_rl(state) && estate_rl(abs_state)) {
 908                         return clone_rl(rl_intersection(estate_rl(state),
 909                                                         estate_rl(abs_state)));
 910                 } else if (estate_rl(state)) {
 911                         return clone_rl(estate_rl(state));
 912                 } else if (estate_is_empty(state)) {
 913                         /*
 914                          * FIXME: we don't handle empty extra states correctly.
 915                          *
 916                          * The real abs rl is supposed to be filtered by the
 917                          * extra state if there is one.  We don't bother keeping
 918                          * the abs state in sync all the time because we know it
 919                          * will be filtered later.
 920                          *
 921                          * It's not totally obvious to me how they should be
 922                          * handled.  Perhaps we should take the whole rl and
 923                          * filter by the imaginary states.  Perhaps we should
 924                          * just go with the empty state.
 925                          *
 926                          * Anyway what we currently do is return NULL here and
 927                          * that gets translated into the whole range in
 928                          * get_real_absolute_rl().
 929                          *
 930                          */
 931                         return NULL;
 932                 } else if (estate_rl(abs_state)) {
 933                         return clone_rl(estate_rl(abs_state));
 934                 }
 935
 936                 if (get_local_rl(expr, &rl))
 937                         return rl;
 938                 if (get_db_type_rl(expr, &rl))
 939                         return rl;
 940                 return NULL;
 941         }
 942         case RL_FUZZY:
 943                 if (!get_fuzzy_min_helper(expr, &min))
 944                         min = sval_type_min(get_type(expr));
 945                 if (!get_fuzzy_max_helper(expr, &max))
 946                         return NULL;
 947                 /* fuzzy ranges are often inverted */
 948                 if (sval_cmp(min, max) > 0) {
 949                         sval = min;
 950                         min = max;
 951                         max = sval;
 952                 }
 953                 return alloc_rl(min, max);
 954         }
 955         return NULL;
 956 }
 957
 958 static sval_t handle_sizeof(struct expression *expr)
 959 {
 960         struct symbol *sym;
 961         sval_t ret;
 962
 963         ret = sval_blank(expr);
 964         sym = expr->cast_type;
 965         if (!sym) {
 966                 sym = evaluate_expression(expr->cast_expression);
 967                 if (!sym) {
 968                         __silence_warnings_for_stmt = true;
 969                         sym = &int_ctype;
 970                 }
 971 #if 0
 972                 /*
 973                  * Expressions of restricted types will possibly get
 974                  * promoted - check that here.  I'm not sure how this works,
 975                  * the problem is that sizeof(le16) shouldn't be promoted and
 976                  * the original code did that...  Let's if zero this out and
 977                  * see what breaks.
 978                  */
 979
 980                 if (is_restricted_type(sym)) {
 981                         if (type_bits(sym) < bits_in_int)
 982                                 sym = &int_ctype;
 983                 }
 984 #endif
 985                 if (is_fouled_type(sym))
 986                         sym = &int_ctype;
 987         }
 988         examine_symbol_type(sym);
 989
 990         ret.type = size_t_ctype;
 991         if (type_bits(sym) <= 0) /* sizeof(void) */ {
 992                 if (get_real_base_type(sym) == &void_ctype)
 993                         ret.value = 1;
 994                 else
 995                         ret.value = 0;
 996         } else
 997                 ret.value = type_bytes(sym);
 998
 999         return ret;
1000 }
1001
1002 static struct range_list *handle_strlen(struct expression *expr, int implied, int *recurse_cnt)
1003 {
1004         struct range_list *rl;
1005         struct expression *arg;
1006         sval_t sval = { .type = &ulong_ctype };
1007
1008         if (implied == RL_EXACT)
1009                 return NULL;
1010
1011         arg = get_argument_from_call_expr(expr->args, 0);
1012         if (!arg)
1013                 return NULL;
1014         if (arg->type == EXPR_STRING) {
1015                 sval.value = arg->string->length - 1;
1016                 return alloc_rl(sval, sval);
1017         }
1018
1019         if (implied == RL_HARD || implied == RL_FUZZY)
1020                 return NULL;
1021
1022         if (get_implied_return(expr, &rl))
1023                 return rl;
1024
1025         return NULL;
1026 }
1027
1028 static struct range_list *handle_call_rl(struct expression *expr, int implied, int *recurse_cnt)
1029 {
1030         struct range_list *rl;
1031
1032         if (sym_name_is("__builtin_expect", expr->fn) ||
1033             sym_name_is("__builtin_bswap16", expr->fn) ||
1034             sym_name_is("__builtin_bswap32", expr->fn) ||
1035             sym_name_is("__builtin_bswap64", expr->fn)) {
1036                 struct expression *arg;
1037
1038                 arg = get_argument_from_call_expr(expr->args, 0);
1039                 return _get_rl(arg, implied, recurse_cnt);
1040         }
1041
1042         if (sym_name_is("strlen", expr->fn))
1043                 return handle_strlen(expr, implied, recurse_cnt);
1044
1045         if (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY)
1046                 return NULL;
1047
1048         if (custom_handle_variable) {
1049                 rl = custom_handle_variable(expr);
1050                 if (rl)
1051                         return rl;
1052         }
1053
1054         if (get_implied_return(expr, &rl))
1055                 return rl;
1056         return db_return_vals(expr);
1057 }
1058
1059 static struct range_list *handle_cast(struct expression *expr, int implied, int *recurse_cnt)
1060 {
1061         struct range_list *rl;
1062         struct symbol *type;
1063
1064         type = get_type(expr);
1065         rl = _get_rl(expr->cast_expression, implied, recurse_cnt);
1066         if (rl)
1067                 return cast_rl(type, rl);
1068         if (implied == RL_ABSOLUTE || implied == RL_REAL_ABSOLUTE)
1069                 return alloc_whole_rl(type);
1070         if (implied == RL_IMPLIED && type &&
1071             type_bits(type) > 0 && type_bits(type) < 32)
1072                 return alloc_whole_rl(type);
1073         return NULL;
1074 }
1075
1076 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt)
1077 {
1078         struct range_list *rl;
1079         struct symbol *type;
1080         sval_t sval;
1081
1082         type = get_type(expr);
1083         expr = strip_parens(expr);
1084         if (!expr)
1085                 return NULL;
1086
1087         if (++(*recurse_cnt) >= 200)
1088                 return NULL;
1089
1090         switch(expr->type) {
1091         case EXPR_CAST:
1092         case EXPR_FORCE_CAST:
1093         case EXPR_IMPLIED_CAST:
1094                 rl = handle_cast(expr, implied, recurse_cnt);
1095                 goto out_cast;
1096         }
1097
1098         expr = strip_expr(expr);
1099         if (!expr)
1100                 return NULL;
1101
1102         switch (expr->type) {
1103         case EXPR_VALUE:
1104                 sval = sval_from_val(expr, expr->value);
1105                 rl = alloc_rl(sval, sval);
1106                 break;
1107         case EXPR_PREOP:
1108                 rl = handle_preop_rl(expr, implied, recurse_cnt);
1109                 break;
1110         case EXPR_POSTOP:
1111                 rl = _get_rl(expr->unop, implied, recurse_cnt);
1112                 break;
1113         case EXPR_BINOP:
1114                 rl = handle_binop_rl(expr, implied, recurse_cnt);
1115                 break;
1116         case EXPR_COMPARE:
1117                 rl = handle_comparison_rl(expr, implied, recurse_cnt);
1118                 break;
1119         case EXPR_LOGICAL:
1120                 rl = handle_logical_rl(expr, implied, recurse_cnt);
1121                 break;
1122         case EXPR_PTRSIZEOF:
1123         case EXPR_SIZEOF:
1124                 sval = handle_sizeof(expr);
1125                 rl = alloc_rl(sval, sval);
1126                 break;
1127         case EXPR_SELECT:
1128         case EXPR_CONDITIONAL:
1129                 rl = handle_conditional_rl(expr, implied, recurse_cnt);
1130                 break;
1131         case EXPR_CALL:
1132                 rl = handle_call_rl(expr, implied, recurse_cnt);
1133                 break;
1134         default:
1135                 rl = handle_variable(expr, implied, recurse_cnt);
1136         }
1137
1138 out_cast:
1139         if (rl)
1140                 return rl;
1141         if (type && (implied == RL_ABSOLUTE || implied == RL_REAL_ABSOLUTE))
1142                 return alloc_whole_rl(type);
1143         return NULL;
1144 }
1145
1146 /* returns 1 if it can get a value literal or else returns 0 */
1147 int get_value(struct expression *expr, sval_t *sval)
1148 {
1149         struct range_list *rl;
1150         int recurse_cnt = 0;
1151
1152         rl = _get_rl(expr, RL_EXACT, &recurse_cnt);
1153         if (!rl_to_sval(rl, sval))
1154                 return 0;
1155         return 1;
1156 }
1157
1158 static int get_implied_value_internal(struct expression *expr, sval_t *sval, int *recurse_cnt)
1159 {
1160         struct range_list *rl;
1161
1162         rl =  _get_rl(expr, RL_IMPLIED, recurse_cnt);
1163         if (!rl_to_sval(rl, sval))
1164                 return 0;
1165         return 1;
1166 }
1167
1168 int get_implied_value(struct expression *expr, sval_t *sval)
1169 {
1170         struct range_list *rl;
1171         int recurse_cnt = 0;
1172
1173         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1174         if (!rl_to_sval(rl, sval))
1175                 return 0;
1176         return 1;
1177 }
1178
1179 int get_implied_min(struct expression *expr, sval_t *sval)
1180 {
1181         struct range_list *rl;
1182         int recurse_cnt = 0;
1183
1184         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1185         if (!rl)
1186                 return 0;
1187         *sval = rl_min(rl);
1188         return 1;
1189 }
1190
1191 int get_implied_max(struct expression *expr, sval_t *sval)
1192 {
1193         struct range_list *rl;
1194         int recurse_cnt = 0;
1195
1196         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1197         if (!rl)
1198                 return 0;
1199         *sval = rl_max(rl);
1200         return 1;
1201 }
1202
1203 int get_implied_rl(struct expression *expr, struct range_list **rl)
1204 {
1205         int recurse_cnt = 0;
1206
1207         *rl = _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1208         if (*rl)
1209                 return 1;
1210         return 0;
1211 }
1212
1213 static int get_absolute_rl_internal(struct expression *expr, struct range_list **rl, int *recurse_cnt)
1214 {
1215         *rl = _get_rl(expr, RL_ABSOLUTE, recurse_cnt);
1216         if (!*rl)
1217                 *rl = alloc_whole_rl(get_type(expr));
1218         return 1;
1219 }
1220
1221 int get_absolute_rl(struct expression *expr, struct range_list **rl)
1222 {
1223         int recurse_cnt = 0;
1224
1225         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1226         if (!*rl)
1227                 *rl = alloc_whole_rl(get_type(expr));
1228         return 1;
1229 }
1230
1231 int get_real_absolute_rl(struct expression *expr, struct range_list **rl)
1232 {
1233         int recurse_cnt = 0;
1234
1235         *rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1236         if (!*rl)
1237                 *rl = alloc_whole_rl(get_type(expr));
1238         return 1;
1239 }
1240
1241 int custom_get_absolute_rl(struct expression *expr,
1242                            struct range_list *(*fn)(struct expression *expr),
1243                            struct range_list **rl)
1244 {
1245         int recurse_cnt = 0;
1246
1247         *rl = NULL;
1248         custom_handle_variable = fn;
1249         *rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1250         custom_handle_variable = NULL;
1251         return 1;
1252 }
1253
1254 int get_implied_rl_var_sym(const char *var, struct symbol *sym, struct range_list **rl)
1255 {
1256         struct smatch_state *state;
1257
1258         state = get_state(SMATCH_EXTRA, var, sym);
1259         *rl = estate_rl(state);
1260         if (*rl)
1261                 return 1;
1262         return 0;
1263 }
1264
1265 int get_hard_max(struct expression *expr, sval_t *sval)
1266 {
1267         struct range_list *rl;
1268         int recurse_cnt = 0;
1269
1270         rl =  _get_rl(expr, RL_HARD, &recurse_cnt);
1271         if (!rl)
1272                 return 0;
1273         *sval = rl_max(rl);
1274         return 1;
1275 }
1276
1277 int get_fuzzy_min(struct expression *expr, sval_t *sval)
1278 {
1279         struct range_list *rl;
1280         sval_t tmp;
1281         int recurse_cnt = 0;
1282
1283         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1284         if (!rl)
1285                 return 0;
1286         tmp = rl_min(rl);
1287         if (sval_is_negative(tmp) && sval_is_min(tmp))
1288                 return 0;
1289         *sval = tmp;
1290         return 1;
1291 }
1292
1293 int get_fuzzy_max(struct expression *expr, sval_t *sval)
1294 {
1295         struct range_list *rl;
1296         sval_t max;
1297         int recurse_cnt = 0;
1298
1299         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1300         if (!rl)
1301                 return 0;
1302         max = rl_max(rl);
1303         if (max.uvalue > INT_MAX - 10000)
1304                 return 0;
1305         *sval = max;
1306         return 1;
1307 }
1308
1309 int get_absolute_min(struct expression *expr, sval_t *sval)
1310 {
1311         struct range_list *rl;
1312         struct symbol *type;
1313         int recurse_cnt = 0;
1314
1315         type = get_type(expr);
1316         if (!type)
1317                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
1318         rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1319         if (rl)
1320                 *sval = rl_min(rl);
1321         else
1322                 *sval = sval_type_min(type);
1323
1324         if (sval_cmp(*sval, sval_type_min(type)) < 0)
1325                 *sval = sval_type_min(type);
1326         return 1;
1327 }
1328
1329 int get_absolute_max(struct expression *expr, sval_t *sval)
1330 {
1331         struct range_list *rl;
1332         struct symbol *type;
1333         int recurse_cnt = 0;
1334
1335         type = get_type(expr);
1336         if (!type)
1337                 type = &llong_ctype;
1338         rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1339         if (rl)
1340                 *sval = rl_max(rl);
1341         else
1342                 *sval = sval_type_max(type);
1343
1344         if (sval_cmp(sval_type_max(type), *sval) < 0)
1345                 *sval = sval_type_max(type);
1346         return 1;
1347 }
1348
1349 int known_condition_true(struct expression *expr)
1350 {
1351         sval_t tmp;
1352
1353         if (!expr)
1354                 return 0;
1355
1356         if (get_value(expr, &tmp) && tmp.value)
1357                 return 1;
1358
1359         return 0;
1360 }
1361
1362 int known_condition_false(struct expression *expr)
1363 {
1364         if (!expr)
1365                 return 0;
1366
1367         if (is_zero(expr))
1368                 return 1;
1369
1370         if (expr->type == EXPR_CALL) {
1371                 if (sym_name_is("__builtin_constant_p", expr->fn))
1372                         return 1;
1373         }
1374         return 0;
1375 }
1376
1377 int implied_condition_true(struct expression *expr)
1378 {
1379         sval_t tmp;
1380
1381         if (!expr)
1382                 return 0;
1383
1384         if (known_condition_true(expr))
1385                 return 1;
1386         if (get_implied_value(expr, &tmp) && tmp.value)
1387                 return 1;
1388
1389         if (expr->type == EXPR_POSTOP)
1390                 return implied_condition_true(expr->unop);
1391
1392         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
1393                 return implied_not_equal(expr->unop, 1);
1394         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
1395                 return implied_not_equal(expr->unop, -1);
1396
1397         expr = strip_expr(expr);
1398         switch (expr->type) {
1399         case EXPR_COMPARE:
1400                 if (do_comparison(expr) == 1)
1401                         return 1;
1402                 break;
1403         case EXPR_PREOP:
1404                 if (expr->op == '!') {
1405                         if (implied_condition_false(expr->unop))
1406                                 return 1;
1407                         break;
1408                 }
1409                 break;
1410         default:
1411                 if (implied_not_equal(expr, 0) == 1)
1412                         return 1;
1413                 break;
1414         }
1415         return 0;
1416 }
1417
1418 int implied_condition_false(struct expression *expr)
1419 {
1420         struct expression *tmp;
1421         sval_t sval;
1422
1423         if (!expr)
1424                 return 0;
1425
1426         if (known_condition_false(expr))
1427                 return 1;
1428
1429         switch (expr->type) {
1430         case EXPR_COMPARE:
1431                 if (do_comparison(expr) == 2)
1432                         return 1;
1433         case EXPR_PREOP:
1434                 if (expr->op == '!') {
1435                         if (implied_condition_true(expr->unop))
1436                                 return 1;
1437                         break;
1438                 }
1439                 tmp = strip_expr(expr);
1440                 if (tmp != expr)
1441                         return implied_condition_false(tmp);
1442                 break;
1443         default:
1444                 if (get_implied_value(expr, &sval) && sval.value == 0)
1445                         return 1;
1446                 break;
1447         }
1448         return 0;
1449 }
1450
1451 int can_integer_overflow(struct symbol *type, struct expression *expr)
1452 {
1453         int op;
1454         sval_t lmax, rmax, res;
1455
1456         if (!type)
1457                 type = &int_ctype;
1458
1459         expr = strip_expr(expr);
1460
1461         if (expr->type == EXPR_ASSIGNMENT) {
1462                 switch(expr->op) {
1463                 case SPECIAL_MUL_ASSIGN:
1464                         op = '*';
1465                         break;
1466                 case SPECIAL_ADD_ASSIGN:
1467                         op = '+';
1468                         break;
1469                 case SPECIAL_SHL_ASSIGN:
1470                         op = SPECIAL_LEFTSHIFT;
1471                         break;
1472                 default:
1473                         return 0;
1474                 }
1475         } else if (expr->type == EXPR_BINOP) {
1476                 if (expr->op != '*' && expr->op != '+' && expr->op != SPECIAL_LEFTSHIFT)
1477                         return 0;
1478                 op = expr->op;
1479         } else {
1480                 return 0;
1481         }
1482
1483         get_absolute_max(expr->left, &lmax);
1484         get_absolute_max(expr->right, &rmax);
1485
1486         if (sval_binop_overflows(lmax, op, rmax))
1487                 return 1;
1488
1489         res = sval_binop(lmax, op, rmax);
1490         if (sval_cmp(res, sval_type_max(type)) > 0)
1491                 return 1;
1492         return 0;
1493 }