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
 183
 184         if (!type || type->type != SYM_PTR)
 185                 return -1;
 186         type = get_real_base_type(type);
 187         if (!type || (type_bits(type) != 8 && (type != &void_ctype)))
 188                 return -1;
 189
 190         left = strip_expr(expr->left);
 191         right = strip_expr(expr->right);
 192
 193         if (left->type != EXPR_PREOP || left->op != '&')
 194                 return -1;
 195         left = strip_expr(left->unop);
 196
 197         left_sym = expr_to_sym(left);
 198         right_sym = expr_to_sym(right);
 199         if (!left_sym || left_sym != right_sym)
 200                 return -1;
 201
 202         left_offset = get_member_offset_from_deref(left);
 203         if (right->type == EXPR_SYMBOL)
 204                 right_offset = 0;
 205         else {
 206                 if (right->type != EXPR_PREOP || right->op != '&')
 207                         return -1;
 208                 right = strip_expr(right->unop);
 209                 right_offset = get_member_offset_from_deref(right);
 210         }
 211         if (left_offset < 0 || right_offset < 0)
 212                 return -1;
 213
 214         return left_offset - right_offset;
 215 }
 216
 217 static struct range_list *handle_subtract_rl(struct expression *expr, int implied, int *recurse_cnt)
 218 {
 219         struct symbol *type;
 220         struct range_list *left_rl, *right_rl;
 221         sval_t max, min, tmp;
 222         int comparison;
 223         int offset;
 224
 225         type = get_type(expr);
 226
 227         offset = handle_offset_subtraction(expr);
 228         if (offset >= 0) {
 229                 tmp.type = type;
 230                 tmp.value = offset;
 231
 232                 return alloc_rl(tmp, tmp);
 233         }
 234
 235         comparison = get_comparison(expr->left, expr->right);
 236
 237         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 238         left_rl = cast_rl(type, left_rl);
 239         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 240         right_rl = cast_rl(type, right_rl);
 241
 242         if ((!left_rl || !right_rl) &&
 243             (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY))
 244                 return NULL;
 245
 246         if (!left_rl)
 247                 left_rl = alloc_whole_rl(type);
 248         if (!right_rl)
 249                 right_rl = alloc_whole_rl(type);
 250
 251         /* negative values complicate everything fix this later */
 252         if (sval_is_negative(rl_min(right_rl)))
 253                 return NULL;
 254         max = rl_max(left_rl);
 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 (sval_binop_overflows(rl_min(left_rl), '-', rl_max(right_rl)))
 281                         return NULL;
 282                 min = sval_type_min(type);
 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                 return clone_rl(estate_rl(state));
 579
 580         type = get_type(expr);
 581         left_rl = _get_rl(expr->left, implied, recurse_cnt);
 582         left_rl = cast_rl(type, left_rl);
 583         right_rl = _get_rl(expr->right, implied, recurse_cnt);
 584         right_rl = cast_rl(type, right_rl);
 585
 586         if (!left_rl && !right_rl)
 587                 return NULL;
 588
 589         rl = handle_implied_binop(left_rl, expr->op, right_rl);
 590         if (rl)
 591                 return rl;
 592
 593         switch (expr->op) {
 594         case '%':
 595                 return handle_mod_rl(expr, implied, recurse_cnt);
 596         case '&':
 597                 return handle_bitwise_AND(expr, implied, recurse_cnt);
 598         case '|':
 599         case '^':
 600                 return use_rl_binop(expr, implied, recurse_cnt);
 601         case SPECIAL_RIGHTSHIFT:
 602                 return handle_right_shift(expr, implied, recurse_cnt);
 603         case SPECIAL_LEFTSHIFT:
 604                 return handle_left_shift(expr, implied, recurse_cnt);
 605         case '-':
 606                 return handle_subtract_rl(expr, implied, recurse_cnt);
 607         case '/':
 608                 return handle_divide_rl(expr, implied, recurse_cnt);
 609         }
 610
 611         if (!left_rl || !right_rl)
 612                 return NULL;
 613
 614         if (sval_binop_overflows(rl_min(left_rl), expr->op, rl_min(right_rl)))
 615                 return NULL;
 616         if (sval_binop_overflows(rl_max(left_rl), expr->op, rl_max(right_rl)))
 617                 return NULL;
 618
 619         min = sval_binop(rl_min(left_rl), expr->op, rl_min(right_rl));
 620         max = sval_binop(rl_max(left_rl), expr->op, rl_max(right_rl));
 621
 622         return alloc_rl(min, max);
 623 }
 624
 625 static int do_comparison(struct expression *expr)
 626 {
 627         struct range_list *left_ranges = NULL;
 628         struct range_list *right_ranges = NULL;
 629         int poss_true, poss_false;
 630         struct symbol *type;
 631
 632         type = get_type(expr);
 633         get_absolute_rl(expr->left, &left_ranges);
 634         get_absolute_rl(expr->right, &right_ranges);
 635
 636         left_ranges = cast_rl(type, left_ranges);
 637         right_ranges = cast_rl(type, right_ranges);
 638
 639         poss_true = possibly_true_rl(left_ranges, expr->op, right_ranges);
 640         poss_false = possibly_false_rl(left_ranges, expr->op, right_ranges);
 641
 642         free_rl(&left_ranges);
 643         free_rl(&right_ranges);
 644
 645         if (!poss_true && !poss_false)
 646                 return 0x0;
 647         if (poss_true && !poss_false)
 648                 return 0x1;
 649         if (!poss_true && poss_false)
 650                 return 0x2;
 651         return 0x3;
 652 }
 653
 654 static struct range_list *handle_comparison_rl(struct expression *expr, int implied, int *recurse_cnt)
 655 {
 656         sval_t left, right;
 657         int res;
 658
 659         if (expr->op == SPECIAL_EQUAL && expr->left->type == EXPR_TYPE) {
 660                 struct symbol *left, *right;
 661
 662                 left = get_real_base_type(expr->left->symbol);
 663                 right = get_real_base_type(expr->left->symbol);
 664                 if (left == right)
 665                         return rl_one();
 666                 return rl_zero();
 667         }
 668
 669         if (get_value(expr->left, &left) && get_value(expr->right, &right)) {
 670                 struct data_range tmp_left, tmp_right;
 671
 672                 tmp_left.min = left;
 673                 tmp_left.max = left;
 674                 tmp_right.min = right;
 675                 tmp_right.max = right;
 676                 if (true_comparison_range(&tmp_left, expr->op, &tmp_right))
 677                         return rl_one();
 678                 return rl_zero();
 679         }
 680
 681         if (implied == RL_EXACT)
 682                 return NULL;
 683
 684         res = do_comparison(expr);
 685         if (res == 1)
 686                 return rl_one();
 687         if (res == 2)
 688                 return rl_zero();
 689
 690         return alloc_rl(zero, one);
 691 }
 692
 693 static struct range_list *handle_logical_rl(struct expression *expr, int implied, int *recurse_cnt)
 694 {
 695         sval_t left, right;
 696         int left_known = 0;
 697         int right_known = 0;
 698
 699         if (implied == RL_EXACT) {
 700                 if (get_value(expr->left, &left))
 701                         left_known = 1;
 702                 if (get_value(expr->right, &right))
 703                         right_known = 1;
 704         } else {
 705                 if (get_implied_value_internal(expr->left, &left, recurse_cnt))
 706                         left_known = 1;
 707                 if (get_implied_value_internal(expr->right, &right, recurse_cnt))
 708                         right_known = 1;
 709         }
 710
 711         switch (expr->op) {
 712         case SPECIAL_LOGICAL_OR:
 713                 if (left_known && left.value)
 714                         return rl_one();
 715                 if (right_known && right.value)
 716                         return rl_one();
 717                 if (left_known && right_known)
 718                         return rl_zero();
 719                 break;
 720         case SPECIAL_LOGICAL_AND:
 721                 if (left_known && right_known) {
 722                         if (left.value && right.value)
 723                                 return rl_one();
 724                         return rl_zero();
 725                 }
 726                 break;
 727         default:
 728                 return NULL;
 729         }
 730
 731         if (implied == RL_EXACT)
 732                 return NULL;
 733
 734         return alloc_rl(zero, one);
 735 }
 736
 737 static struct range_list *handle_conditional_rl(struct expression *expr, int implied, int *recurse_cnt)
 738 {
 739         struct range_list *true_rl, *false_rl;
 740         struct symbol *type;
 741         int final_pass_orig = final_pass;
 742
 743         if (known_condition_true(expr->conditional))
 744                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 745         if (known_condition_false(expr->conditional))
 746                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 747
 748         if (implied == RL_EXACT)
 749                 return NULL;
 750
 751         if (implied_condition_true(expr->conditional))
 752                 return _get_rl(expr->cond_true, implied, recurse_cnt);
 753         if (implied_condition_false(expr->conditional))
 754                 return _get_rl(expr->cond_false, implied, recurse_cnt);
 755
 756
 757         /* this becomes a problem with deeply nested conditional statements */
 758         if (low_on_memory())
 759                 return NULL;
 760
 761         type = get_type(expr);
 762
 763         __push_fake_cur_stree();
 764         final_pass = 0;
 765         __split_whole_condition(expr->conditional);
 766         true_rl = _get_rl(expr->cond_true, implied, recurse_cnt);
 767         __push_true_states();
 768         __use_false_states();
 769         false_rl = _get_rl(expr->cond_false, implied, recurse_cnt);
 770         __merge_true_states();
 771         __free_fake_cur_stree();
 772         final_pass = final_pass_orig;
 773
 774         if (!true_rl || !false_rl)
 775                 return NULL;
 776         true_rl = cast_rl(type, true_rl);
 777         false_rl = cast_rl(type, false_rl);
 778
 779         return rl_union(true_rl, false_rl);
 780 }
 781
 782 static int get_fuzzy_max_helper(struct expression *expr, sval_t *max)
 783 {
 784         struct smatch_state *state;
 785         sval_t sval;
 786
 787         if (get_hard_max(expr, &sval)) {
 788                 *max = sval;
 789                 return 1;
 790         }
 791
 792         state = get_extra_state(expr);
 793         if (!state || !estate_has_fuzzy_max(state))
 794                 return 0;
 795         *max = sval_cast(get_type(expr), estate_get_fuzzy_max(state));
 796         return 1;
 797 }
 798
 799 static int get_fuzzy_min_helper(struct expression *expr, sval_t *min)
 800 {
 801         struct smatch_state *state;
 802         sval_t sval;
 803
 804         state = get_extra_state(expr);
 805         if (!state || !estate_rl(state))
 806                 return 0;
 807
 808         sval = estate_min(state);
 809         if (sval_is_negative(sval) && sval_is_min(sval))
 810                 return 0;
 811
 812         if (sval_is_max(sval))
 813                 return 0;
 814
 815         *min = sval_cast(get_type(expr), sval);
 816         return 1;
 817 }
 818
 819 int get_const_value(struct expression *expr, sval_t *sval)
 820 {
 821         struct symbol *sym;
 822         sval_t right;
 823
 824         if (expr->type != EXPR_SYMBOL || !expr->symbol)
 825                 return 0;
 826         sym = expr->symbol;
 827         if (!(sym->ctype.modifiers & MOD_CONST))
 828                 return 0;
 829         if (get_value(sym->initializer, &right)) {
 830                 *sval = sval_cast(get_type(expr), right);
 831                 return 1;
 832         }
 833         return 0;
 834 }
 835
 836 struct range_list *var_to_absolute_rl(struct expression *expr)
 837 {
 838         struct smatch_state *state;
 839         struct range_list *rl;
 840
 841         state = get_extra_state(expr);
 842         if (!state || is_whole_rl(estate_rl(state))) {
 843                 state = get_real_absolute_state(expr);
 844                 if (state && state->data && !estate_is_whole(state))
 845                         return clone_rl(estate_rl(state));
 846                 if (get_local_rl(expr, &rl) && !is_whole_rl(rl))
 847                         return rl;
 848                 if (get_db_type_rl(expr, &rl) && !is_whole_rl(rl))
 849                         return rl;
 850                 return alloc_whole_rl(get_type(expr));
 851         }
 852         /* err on the side of saying things are possible */
 853         if (!estate_rl(state))
 854                 return alloc_whole_rl(get_type(expr));
 855         return clone_rl(estate_rl(state));
 856 }
 857
 858 static struct range_list *handle_variable(struct expression *expr, int implied, int *recurse_cnt)
 859 {
 860         struct smatch_state *state;
 861         struct range_list *rl;
 862         sval_t sval, min, max;
 863         struct symbol *type;
 864
 865         if (get_const_value(expr, &sval))
 866                 return alloc_rl(sval, sval);
 867
 868         if (custom_handle_variable) {
 869                 rl = custom_handle_variable(expr);
 870                 if (!rl)
 871                         return var_to_absolute_rl(expr);
 872                 return rl;
 873         }
 874
 875         if (implied == RL_EXACT)
 876                 return NULL;
 877
 878         type = get_type(expr);
 879         if (type && type->type == SYM_FN)
 880                 return alloc_rl(fn_ptr_min, fn_ptr_max);
 881
 882         switch (implied) {
 883         case RL_HARD:
 884         case RL_IMPLIED:
 885         case RL_ABSOLUTE:
 886                 state = get_extra_state(expr);
 887                 if (!state || !state->data) {
 888                         if (implied == RL_HARD)
 889                                 return NULL;
 890                         if (get_local_rl(expr, &rl))
 891                                 return rl;
 892                         if (get_db_type_rl(expr, &rl))
 893                                 return rl;
 894                         return NULL;
 895                 }
 896                 if (implied == RL_HARD && !estate_has_hard_max(state))
 897                         return NULL;
 898                 return clone_rl(estate_rl(state));
 899         case RL_REAL_ABSOLUTE: {
 900                 struct smatch_state *abs_state;
 901
 902                 state = get_extra_state(expr);
 903                 abs_state = get_real_absolute_state(expr);
 904
 905                 if (estate_rl(state) && estate_rl(abs_state)) {
 906                         return clone_rl(rl_intersection(estate_rl(state),
 907                                                         estate_rl(abs_state)));
 908                 } else if (estate_rl(state)) {
 909                         return clone_rl(estate_rl(state));
 910                 } else if (state && estate_is_empty(state)) {
 911                         /*
 912                          * FIXME: we don't handle empty extra states correctly.
 913                          *
 914                          * The real abs rl is supposed to be filtered by the
 915                          * extra state if there is one.  We don't bother keeping
 916                          * the abs state in sync all the time because we know it
 917                          * will be filtered later.
 918                          *
 919                          * It's not totally obvious to me how they should be
 920                          * handled.  Perhaps we should take the whole rl and
 921                          * filter by the imaginary states.  Perhaps we should
 922                          * just go with the empty state.
 923                          *
 924                          * Anyway what we currently do is return NULL here and
 925                          * that gets translated into the whole range in
 926                          * get_real_absolute_rl().
 927                          *
 928                          */
 929                         return NULL;
 930                 } else if (estate_rl(abs_state)) {
 931                         return clone_rl(estate_rl(abs_state));
 932                 }
 933
 934                 if (get_local_rl(expr, &rl))
 935                         return rl;
 936                 if (get_db_type_rl(expr, &rl))
 937                         return rl;
 938                 return NULL;
 939         }
 940         case RL_FUZZY:
 941                 if (!get_fuzzy_min_helper(expr, &min))
 942                         min = sval_type_min(get_type(expr));
 943                 if (!get_fuzzy_max_helper(expr, &max))
 944                         return NULL;
 945                 /* fuzzy ranges are often inverted */
 946                 if (sval_cmp(min, max) > 0) {
 947                         sval = min;
 948                         min = max;
 949                         max = sval;
 950                 }
 951                 return alloc_rl(min, max);
 952         }
 953         return NULL;
 954 }
 955
 956 static sval_t handle_sizeof(struct expression *expr)
 957 {
 958         struct symbol *sym;
 959         sval_t ret;
 960
 961         ret = sval_blank(expr);
 962         sym = expr->cast_type;
 963         if (!sym) {
 964                 sym = evaluate_expression(expr->cast_expression);
 965                 if (!sym)
 966                         sym = &int_ctype;
 967 #if 0
 968                 /*
 969                  * Expressions of restricted types will possibly get
 970                  * promoted - check that here.  I'm not sure how this works,
 971                  * the problem is that sizeof(le16) shouldn't be promoted and
 972                  * the original code did that...  Let's if zero this out and
 973                  * see what breaks.
 974                  */
 975
 976                 if (is_restricted_type(sym)) {
 977                         if (type_bits(sym) < bits_in_int)
 978                                 sym = &int_ctype;
 979                 }
 980 #endif
 981                 if (is_fouled_type(sym))
 982                         sym = &int_ctype;
 983         }
 984         examine_symbol_type(sym);
 985
 986         ret.type = size_t_ctype;
 987         if (type_bits(sym) <= 0) /* sizeof(void) */ {
 988                 if (get_real_base_type(sym) == &void_ctype)
 989                         ret.value = 1;
 990                 else
 991                         ret.value = 0;
 992         } else
 993                 ret.value = type_bytes(sym);
 994
 995         return ret;
 996 }
 997
 998 static struct range_list *handle_strlen(struct expression *expr, int implied, int *recurse_cnt)
 999 {
1000         struct range_list *rl;
1001         struct expression *arg;
1002         sval_t sval = { .type = &ulong_ctype };
1003
1004         if (implied == RL_EXACT)
1005                 return NULL;
1006
1007         arg = get_argument_from_call_expr(expr->args, 0);
1008         if (!arg)
1009                 return NULL;
1010         if (arg->type == EXPR_STRING) {
1011                 sval.value = arg->string->length - 1;
1012                 return alloc_rl(sval, sval);
1013         }
1014
1015         if (implied == RL_HARD || implied == RL_FUZZY)
1016                 return NULL;
1017
1018         if (get_implied_return(expr, &rl))
1019                 return rl;
1020
1021         return NULL;
1022 }
1023
1024 static struct range_list *handle_call_rl(struct expression *expr, int implied, int *recurse_cnt)
1025 {
1026         struct range_list *rl;
1027
1028         if (sym_name_is("__builtin_expect", expr->fn) ||
1029             sym_name_is("__builtin_bswap16", expr->fn) ||
1030             sym_name_is("__builtin_bswap32", expr->fn) ||
1031             sym_name_is("__builtin_bswap64", expr->fn)) {
1032                 struct expression *arg;
1033
1034                 arg = get_argument_from_call_expr(expr->args, 0);
1035                 return _get_rl(arg, implied, recurse_cnt);
1036         }
1037
1038         if (sym_name_is("strlen", expr->fn))
1039                 return handle_strlen(expr, implied, recurse_cnt);
1040
1041         if (implied == RL_EXACT || implied == RL_HARD || implied == RL_FUZZY)
1042                 return NULL;
1043
1044         if (custom_handle_variable) {
1045                 rl = custom_handle_variable(expr);
1046                 if (rl)
1047                         return rl;
1048         }
1049
1050         if (get_implied_return(expr, &rl))
1051                 return rl;
1052         return db_return_vals(expr);
1053 }
1054
1055 static struct range_list *handle_cast(struct expression *expr, int implied, int *recurse_cnt)
1056 {
1057         struct range_list *rl;
1058         struct symbol *type;
1059
1060         type = get_type(expr);
1061         rl = _get_rl(expr->cast_expression, implied, recurse_cnt);
1062         if (rl)
1063                 return cast_rl(type, rl);
1064         if (implied == RL_ABSOLUTE || implied == RL_REAL_ABSOLUTE)
1065                 return alloc_whole_rl(type);
1066         if (implied == RL_IMPLIED && type &&
1067             type_bits(type) > 0 && type_bits(type) < 32)
1068                 return alloc_whole_rl(type);
1069         return NULL;
1070 }
1071
1072 static struct range_list *_get_rl(struct expression *expr, int implied, int *recurse_cnt)
1073 {
1074         struct range_list *rl;
1075         struct symbol *type;
1076         sval_t sval;
1077
1078         type = get_type(expr);
1079         expr = strip_parens(expr);
1080         if (!expr)
1081                 return NULL;
1082
1083         if (++(*recurse_cnt) >= 200)
1084                 return NULL;
1085
1086         switch(expr->type) {
1087         case EXPR_CAST:
1088         case EXPR_FORCE_CAST:
1089         case EXPR_IMPLIED_CAST:
1090                 rl = handle_cast(expr, implied, recurse_cnt);
1091                 goto out_cast;
1092         }
1093
1094         expr = strip_expr(expr);
1095         if (!expr)
1096                 return NULL;
1097
1098         switch (expr->type) {
1099         case EXPR_VALUE:
1100                 sval = sval_from_val(expr, expr->value);
1101                 rl = alloc_rl(sval, sval);
1102                 break;
1103         case EXPR_PREOP:
1104                 rl = handle_preop_rl(expr, implied, recurse_cnt);
1105                 break;
1106         case EXPR_POSTOP:
1107                 rl = _get_rl(expr->unop, implied, recurse_cnt);
1108                 break;
1109         case EXPR_BINOP:
1110                 rl = handle_binop_rl(expr, implied, recurse_cnt);
1111                 break;
1112         case EXPR_COMPARE:
1113                 rl = handle_comparison_rl(expr, implied, recurse_cnt);
1114                 break;
1115         case EXPR_LOGICAL:
1116                 rl = handle_logical_rl(expr, implied, recurse_cnt);
1117                 break;
1118         case EXPR_PTRSIZEOF:
1119         case EXPR_SIZEOF:
1120                 sval = handle_sizeof(expr);
1121                 rl = alloc_rl(sval, sval);
1122                 break;
1123         case EXPR_SELECT:
1124         case EXPR_CONDITIONAL:
1125                 rl = handle_conditional_rl(expr, implied, recurse_cnt);
1126                 break;
1127         case EXPR_CALL:
1128                 rl = handle_call_rl(expr, implied, recurse_cnt);
1129                 break;
1130         default:
1131                 rl = handle_variable(expr, implied, recurse_cnt);
1132         }
1133
1134 out_cast:
1135         if (rl)
1136                 return rl;
1137         if (type && (implied == RL_ABSOLUTE || implied == RL_REAL_ABSOLUTE))
1138                 return alloc_whole_rl(type);
1139         return NULL;
1140 }
1141
1142 /* returns 1 if it can get a value literal or else returns 0 */
1143 int get_value(struct expression *expr, sval_t *sval)
1144 {
1145         struct range_list *rl;
1146         int recurse_cnt = 0;
1147
1148         rl = _get_rl(expr, RL_EXACT, &recurse_cnt);
1149         if (!rl_to_sval(rl, sval))
1150                 return 0;
1151         return 1;
1152 }
1153
1154 static int get_implied_value_internal(struct expression *expr, sval_t *sval, int *recurse_cnt)
1155 {
1156         struct range_list *rl;
1157
1158         rl =  _get_rl(expr, RL_IMPLIED, recurse_cnt);
1159         if (!rl_to_sval(rl, sval))
1160                 return 0;
1161         return 1;
1162 }
1163
1164 int get_implied_value(struct expression *expr, sval_t *sval)
1165 {
1166         struct range_list *rl;
1167         int recurse_cnt = 0;
1168
1169         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1170         if (!rl_to_sval(rl, sval))
1171                 return 0;
1172         return 1;
1173 }
1174
1175 int get_implied_min(struct expression *expr, sval_t *sval)
1176 {
1177         struct range_list *rl;
1178         int recurse_cnt = 0;
1179
1180         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1181         if (!rl)
1182                 return 0;
1183         *sval = rl_min(rl);
1184         return 1;
1185 }
1186
1187 int get_implied_max(struct expression *expr, sval_t *sval)
1188 {
1189         struct range_list *rl;
1190         int recurse_cnt = 0;
1191
1192         rl =  _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1193         if (!rl)
1194                 return 0;
1195         *sval = rl_max(rl);
1196         return 1;
1197 }
1198
1199 int get_implied_rl(struct expression *expr, struct range_list **rl)
1200 {
1201         int recurse_cnt = 0;
1202
1203         *rl = _get_rl(expr, RL_IMPLIED, &recurse_cnt);
1204         if (*rl)
1205                 return 1;
1206         return 0;
1207 }
1208
1209 static int get_absolute_rl_internal(struct expression *expr, struct range_list **rl, int *recurse_cnt)
1210 {
1211         *rl = _get_rl(expr, RL_ABSOLUTE, recurse_cnt);
1212         if (!*rl)
1213                 *rl = alloc_whole_rl(get_type(expr));
1214         return 1;
1215 }
1216
1217 int get_absolute_rl(struct expression *expr, struct range_list **rl)
1218 {
1219         int recurse_cnt = 0;
1220
1221         *rl = _get_rl(expr, RL_ABSOLUTE, &recurse_cnt);
1222         if (!*rl)
1223                 *rl = alloc_whole_rl(get_type(expr));
1224         return 1;
1225 }
1226
1227 int get_real_absolute_rl(struct expression *expr, struct range_list **rl)
1228 {
1229         int recurse_cnt = 0;
1230
1231         *rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1232         if (!*rl)
1233                 *rl = alloc_whole_rl(get_type(expr));
1234         return 1;
1235 }
1236
1237 int custom_get_absolute_rl(struct expression *expr,
1238                            struct range_list *(*fn)(struct expression *expr),
1239                            struct range_list **rl)
1240 {
1241         int recurse_cnt = 0;
1242
1243         *rl = NULL;
1244         custom_handle_variable = fn;
1245         *rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1246         custom_handle_variable = NULL;
1247         return 1;
1248 }
1249
1250 int get_implied_rl_var_sym(const char *var, struct symbol *sym, struct range_list **rl)
1251 {
1252         struct smatch_state *state;
1253
1254         state = get_state(SMATCH_EXTRA, var, sym);
1255         *rl = estate_rl(state);
1256         if (*rl)
1257                 return 1;
1258         return 0;
1259 }
1260
1261 int get_hard_max(struct expression *expr, sval_t *sval)
1262 {
1263         struct range_list *rl;
1264         int recurse_cnt = 0;
1265
1266         rl =  _get_rl(expr, RL_HARD, &recurse_cnt);
1267         if (!rl)
1268                 return 0;
1269         *sval = rl_max(rl);
1270         return 1;
1271 }
1272
1273 int get_fuzzy_min(struct expression *expr, sval_t *sval)
1274 {
1275         struct range_list *rl;
1276         sval_t tmp;
1277         int recurse_cnt = 0;
1278
1279         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1280         if (!rl)
1281                 return 0;
1282         tmp = rl_min(rl);
1283         if (sval_is_negative(tmp) && sval_is_min(tmp))
1284                 return 0;
1285         *sval = tmp;
1286         return 1;
1287 }
1288
1289 int get_fuzzy_max(struct expression *expr, sval_t *sval)
1290 {
1291         struct range_list *rl;
1292         sval_t max;
1293         int recurse_cnt = 0;
1294
1295         rl =  _get_rl(expr, RL_FUZZY, &recurse_cnt);
1296         if (!rl)
1297                 return 0;
1298         max = rl_max(rl);
1299         if (max.uvalue > INT_MAX - 10000)
1300                 return 0;
1301         *sval = max;
1302         return 1;
1303 }
1304
1305 int get_absolute_min(struct expression *expr, sval_t *sval)
1306 {
1307         struct range_list *rl;
1308         struct symbol *type;
1309         int recurse_cnt = 0;
1310
1311         type = get_type(expr);
1312         if (!type)
1313                 type = &llong_ctype;  // FIXME: this is wrong but places assume get type can't fail.
1314         rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1315         if (rl)
1316                 *sval = rl_min(rl);
1317         else
1318                 *sval = sval_type_min(type);
1319
1320         if (sval_cmp(*sval, sval_type_min(type)) < 0)
1321                 *sval = sval_type_min(type);
1322         return 1;
1323 }
1324
1325 int get_absolute_max(struct expression *expr, sval_t *sval)
1326 {
1327         struct range_list *rl;
1328         struct symbol *type;
1329         int recurse_cnt = 0;
1330
1331         type = get_type(expr);
1332         if (!type)
1333                 type = &llong_ctype;
1334         rl = _get_rl(expr, RL_REAL_ABSOLUTE, &recurse_cnt);
1335         if (rl)
1336                 *sval = rl_max(rl);
1337         else
1338                 *sval = sval_type_max(type);
1339
1340         if (sval_cmp(sval_type_max(type), *sval) < 0)
1341                 *sval = sval_type_max(type);
1342         return 1;
1343 }
1344
1345 int known_condition_true(struct expression *expr)
1346 {
1347         sval_t tmp;
1348
1349         if (!expr)
1350                 return 0;
1351
1352         if (get_value(expr, &tmp) && tmp.value)
1353                 return 1;
1354
1355         return 0;
1356 }
1357
1358 int known_condition_false(struct expression *expr)
1359 {
1360         if (!expr)
1361                 return 0;
1362
1363         if (is_zero(expr))
1364                 return 1;
1365
1366         if (expr->type == EXPR_CALL) {
1367                 if (sym_name_is("__builtin_constant_p", expr->fn))
1368                         return 1;
1369         }
1370         return 0;
1371 }
1372
1373 int implied_condition_true(struct expression *expr)
1374 {
1375         sval_t tmp;
1376
1377         if (!expr)
1378                 return 0;
1379
1380         if (known_condition_true(expr))
1381                 return 1;
1382         if (get_implied_value(expr, &tmp) && tmp.value)
1383                 return 1;
1384
1385         if (expr->type == EXPR_POSTOP)
1386                 return implied_condition_true(expr->unop);
1387
1388         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_DECREMENT)
1389                 return implied_not_equal(expr->unop, 1);
1390         if (expr->type == EXPR_PREOP && expr->op == SPECIAL_INCREMENT)
1391                 return implied_not_equal(expr->unop, -1);
1392
1393         expr = strip_expr(expr);
1394         switch (expr->type) {
1395         case EXPR_COMPARE:
1396                 if (do_comparison(expr) == 1)
1397                         return 1;
1398                 break;
1399         case EXPR_PREOP:
1400                 if (expr->op == '!') {
1401                         if (implied_condition_false(expr->unop))
1402                                 return 1;
1403                         break;
1404                 }
1405                 break;
1406         default:
1407                 if (implied_not_equal(expr, 0) == 1)
1408                         return 1;
1409                 break;
1410         }
1411         return 0;
1412 }
1413
1414 int implied_condition_false(struct expression *expr)
1415 {
1416         struct expression *tmp;
1417         sval_t sval;
1418
1419         if (!expr)
1420                 return 0;
1421
1422         if (known_condition_false(expr))
1423                 return 1;
1424
1425         switch (expr->type) {
1426         case EXPR_COMPARE:
1427                 if (do_comparison(expr) == 2)
1428                         return 1;
1429         case EXPR_PREOP:
1430                 if (expr->op == '!') {
1431                         if (implied_condition_true(expr->unop))
1432                                 return 1;
1433                         break;
1434                 }
1435                 tmp = strip_expr(expr);
1436                 if (tmp != expr)
1437                         return implied_condition_false(tmp);
1438                 break;
1439         default:
1440                 if (get_implied_value(expr, &sval) && sval.value == 0)
1441                         return 1;
1442                 break;
1443         }
1444         return 0;
1445 }
1446
1447 int can_integer_overflow(struct symbol *type, struct expression *expr)
1448 {
1449         int op;
1450         sval_t lmax, rmax, res;
1451
1452         if (!type)
1453                 type = &int_ctype;
1454
1455         expr = strip_expr(expr);
1456
1457         if (expr->type == EXPR_ASSIGNMENT) {
1458                 switch(expr->op) {
1459                 case SPECIAL_MUL_ASSIGN:
1460                         op = '*';
1461                         break;
1462                 case SPECIAL_ADD_ASSIGN:
1463                         op = '+';
1464                         break;
1465                 case SPECIAL_SHL_ASSIGN:
1466                         op = SPECIAL_LEFTSHIFT;
1467                         break;
1468                 default:
1469                         return 0;
1470                 }
1471         } else if (expr->type == EXPR_BINOP) {
1472                 if (expr->op != '*' && expr->op != '+' && expr->op != SPECIAL_LEFTSHIFT)
1473                         return 0;
1474                 op = expr->op;
1475         } else {
1476                 return 0;
1477         }
1478
1479         get_absolute_max(expr->left, &lmax);
1480         get_absolute_max(expr->right, &rmax);
1481
1482         if (sval_binop_overflows(lmax, op, rmax))
1483                 return 1;
1484
1485         res = sval_binop(lmax, op, rmax);
1486         if (sval_cmp(res, sval_type_max(type)) > 0)
1487                 return 1;
1488         return 0;
1489 }