smatch_comparison.c

   1 /*
   2  * smatch/smatch_comparison.c
   3  *
   4  * Copyright (C) 2012 Oracle.
   5  *
   6  * Licensed under the Open Software License version 1.1
   7  *
   8  */
   9
  10 /*
  11  * The point here is to store the relationships between two variables.
  12  * Ie:  y > x.
  13  * To do that we create a state with the two variables in alphabetical order:
  14  * ->name = "x vs y" and the state would be "<".  On the false path the state
  15  * would be ">=".
  16  *
  17  * Part of the trick of it is that if x or y is modified then we need to reset
  18  * the state.  We need to keep a list of all the states which depend on x and
  19  * all the states which depend on y.  The link_id code handles this.
  20  *
  21  * Future work:  If we know that x is greater than y and y is greater than z
  22  * then we know that x is greater than z.
  23  */
  24
  25 #include "smatch.h"
  26 #include "smatch_extra.h"
  27 #include "smatch_slist.h"
  28
  29 static int compare_id;
  30 static int link_id;
  31
  32 struct compare_data {
  33         const char *var1;
  34         struct symbol *sym1;
  35         int comparison;
  36         const char *var2;
  37         struct symbol *sym2;
  38 };
  39 ALLOCATOR(compare_data, "compare data");
  40
  41 int var_sym_eq(const char *a, struct symbol *a_sym, const char *b, struct symbol *b_sym)
  42 {
  43         if (a_sym != b_sym)
  44                 return 0;
  45         if (strcmp(a, b) == 0)
  46                 return 1;
  47         return 0;
  48 }
  49
  50 static struct smatch_state *alloc_compare_state(
  51                 const char *var1, struct symbol *sym1,
  52                 int comparison,
  53                 const char *var2, struct symbol *sym2)
  54 {
  55         struct smatch_state *state;
  56         struct compare_data *data;
  57
  58         state = __alloc_smatch_state(0);
  59         state->name = alloc_sname(show_special(comparison));
  60         data = __alloc_compare_data(0);
  61         data->var1 = alloc_sname(var1);
  62         data->sym1 = sym1;
  63         data->comparison = comparison;
  64         data->var2 = alloc_sname(var2);
  65         data->sym2 = sym2;
  66         state->data = data;
  67         return state;
  68 }
  69
  70 static int state_to_comparison(struct smatch_state *state)
  71 {
  72         if (!state || !state->data)
  73                 return 0;
  74         return ((struct compare_data *)state->data)->comparison;
  75 }
  76
  77 /*
  78  * flip_op() reverses the op left and right.  So "x >= y" becomes "y <= x".
  79  */
  80 static int flip_op(int op)
  81 {
  82         switch (op) {
  83         case 0:
  84                 return 0;
  85         case '<':
  86                 return '>';
  87         case SPECIAL_UNSIGNED_LT:
  88                 return SPECIAL_UNSIGNED_GT;
  89         case SPECIAL_LTE:
  90                 return SPECIAL_GTE;
  91         case SPECIAL_UNSIGNED_LTE:
  92                 return SPECIAL_UNSIGNED_GTE;
  93         case SPECIAL_EQUAL:
  94                 return SPECIAL_EQUAL;
  95         case SPECIAL_NOTEQUAL:
  96                 return SPECIAL_NOTEQUAL;
  97         case SPECIAL_GTE:
  98                 return SPECIAL_LTE;
  99         case SPECIAL_UNSIGNED_GTE:
 100                 return SPECIAL_UNSIGNED_LTE;
 101         case '>':
 102                 return '<';
 103         case SPECIAL_UNSIGNED_GT:
 104                 return SPECIAL_UNSIGNED_LT;
 105         default:
 106                 sm_msg("internal smatch bug.  unhandled comparison %d", op);
 107                 return op;
 108         }
 109 }
 110
 111 static int falsify_op(int op)
 112 {
 113         switch (op) {
 114         case 0:
 115                 return 0;
 116         case '<':
 117                 return SPECIAL_GTE;
 118         case SPECIAL_UNSIGNED_LT:
 119                 return SPECIAL_UNSIGNED_GTE;
 120         case SPECIAL_LTE:
 121                 return '>';
 122         case SPECIAL_UNSIGNED_LTE:
 123                 return SPECIAL_UNSIGNED_GT;
 124         case SPECIAL_EQUAL:
 125                 return SPECIAL_NOTEQUAL;
 126         case SPECIAL_NOTEQUAL:
 127                 return SPECIAL_EQUAL;
 128         case SPECIAL_GTE:
 129                 return '<';
 130         case SPECIAL_UNSIGNED_GTE:
 131                 return SPECIAL_UNSIGNED_LT;
 132         case '>':
 133                 return SPECIAL_LTE;
 134         case SPECIAL_UNSIGNED_GT:
 135                 return SPECIAL_UNSIGNED_LTE;
 136         default:
 137                 sm_msg("internal smatch bug.  unhandled comparison %d", op);
 138                 return op;
 139         }
 140 }
 141
 142 static int rl_comparison(struct range_list *left_rl, struct range_list *right_rl)
 143 {
 144         sval_t left_min, left_max, right_min, right_max;
 145
 146         if (!left_rl || !right_rl)
 147                 return 0;
 148
 149         left_min = rl_min(left_rl);
 150         left_max = rl_max(left_rl);
 151         right_min = rl_min(right_rl);
 152         right_max = rl_max(right_rl);
 153
 154         if (left_min.value == left_max.value &&
 155             right_min.value == right_max.value &&
 156             left_min.value == right_min.value)
 157                 return SPECIAL_EQUAL;
 158
 159         if (sval_cmp(left_max, right_min) < 0)
 160                 return '<';
 161         if (sval_cmp(left_max, right_min) == 0)
 162                 return SPECIAL_LTE;
 163         if (sval_cmp(left_min, right_max) > 0)
 164                 return '>';
 165         if (sval_cmp(left_min, right_max) == 0)
 166                 return SPECIAL_GTE;
 167
 168         return 0;
 169 }
 170
 171 static struct range_list *get_orig_rl(struct symbol *sym)
 172 {
 173         struct smatch_state *state;
 174
 175         if (!sym || !sym->ident)
 176                 return NULL;
 177         state = get_orig_estate(sym->ident->name, sym);
 178         return estate_rl(state);
 179 }
 180
 181 static struct smatch_state *unmatched_comparison(struct sm_state *sm)
 182 {
 183         struct compare_data *data = sm->state->data;
 184         struct range_list *left_rl, *right_rl;
 185         int op;
 186
 187         if (!data)
 188                 return &undefined;
 189
 190         if (strstr(data->var1, " orig"))
 191                 left_rl = get_orig_rl(data->sym1);
 192         else if (!get_implied_rl_var_sym(data->var1, data->sym1, &left_rl))
 193                 return &undefined;
 194         if (strstr(data->var2, " orig"))
 195                 right_rl = get_orig_rl(data->sym2);
 196         else if (!get_implied_rl_var_sym(data->var2, data->sym2, &right_rl))
 197                 return &undefined;
 198
 199         op = rl_comparison(left_rl, right_rl);
 200         if (op)
 201                 return alloc_compare_state(data->var1, data->sym1, op, data->var2, data->sym2);
 202
 203         return &undefined;
 204 }
 205
 206 /* remove_unsigned_from_comparison() is obviously a hack. */
 207 static int remove_unsigned_from_comparison(int op)
 208 {
 209         switch (op) {
 210         case SPECIAL_UNSIGNED_LT:
 211                 return '<';
 212         case SPECIAL_UNSIGNED_LTE:
 213                 return SPECIAL_LTE;
 214         case SPECIAL_UNSIGNED_GTE:
 215                 return SPECIAL_GTE;
 216         case SPECIAL_UNSIGNED_GT:
 217                 return '>';
 218         default:
 219                 return op;
 220         }
 221 }
 222
 223 /*
 224  * This is for when you merge states "a < b" and "a == b", the result is that
 225  * we can say for sure, "a <= b" after the merge.
 226  */
 227 static int merge_comparisons(int one, int two)
 228 {
 229         int LT, EQ, GT;
 230
 231         one = remove_unsigned_from_comparison(one);
 232         two = remove_unsigned_from_comparison(two);
 233
 234         LT = EQ = GT = 0;
 235
 236         switch (one) {
 237         case '<':
 238                 LT = 1;
 239                 break;
 240         case SPECIAL_LTE:
 241                 LT = 1;
 242                 EQ = 1;
 243                 break;
 244         case SPECIAL_EQUAL:
 245                 EQ = 1;
 246                 break;
 247         case SPECIAL_GTE:
 248                 GT = 1;
 249                 EQ = 1;
 250                 break;
 251         case '>':
 252                 GT = 1;
 253         }
 254
 255         switch (two) {
 256         case '<':
 257                 LT = 1;
 258                 break;
 259         case SPECIAL_LTE:
 260                 LT = 1;
 261                 EQ = 1;
 262                 break;
 263         case SPECIAL_EQUAL:
 264                 EQ = 1;
 265                 break;
 266         case SPECIAL_GTE:
 267                 GT = 1;
 268                 EQ = 1;
 269                 break;
 270         case '>':
 271                 GT = 1;
 272         }
 273
 274         if (LT && EQ && GT)
 275                 return 0;
 276         if (LT && EQ)
 277                 return SPECIAL_LTE;
 278         if (LT && GT)
 279                 return SPECIAL_NOTEQUAL;
 280         if (LT)
 281                 return '<';
 282         if (EQ && GT)
 283                 return SPECIAL_GTE;
 284         if (GT)
 285                 return '>';
 286         return 0;
 287 }
 288
 289 /*
 290  * This is for if you have "a < b" and "b <= c".  Or in other words,
 291  * "a < b <= c".  You would call this like get_combined_comparison('<', '<=').
 292  * The return comparison would be '<'.
 293  *
 294  * This function is different from merge_comparisons(), for example:
 295  * merge_comparison('<', '==') returns '<='
 296  * get_combined_comparison('<', '==') returns '<'
 297  */
 298 static int combine_comparisons(int left_compare, int right_compare)
 299 {
 300         int LT, EQ, GT;
 301
 302         left_compare = remove_unsigned_from_comparison(left_compare);
 303         right_compare = remove_unsigned_from_comparison(right_compare);
 304
 305         LT = EQ = GT = 0;
 306
 307         switch (left_compare) {
 308         case '<':
 309                 LT++;
 310                 break;
 311         case SPECIAL_LTE:
 312                 LT++;
 313                 EQ++;
 314                 break;
 315         case SPECIAL_EQUAL:
 316                 return right_compare;
 317         case SPECIAL_GTE:
 318                 GT++;
 319                 EQ++;
 320                 break;
 321         case '>':
 322                 GT++;
 323         }
 324
 325         switch (right_compare) {
 326         case '<':
 327                 LT++;
 328                 break;
 329         case SPECIAL_LTE:
 330                 LT++;
 331                 EQ++;
 332                 break;
 333         case SPECIAL_EQUAL:
 334                 return left_compare;
 335         case SPECIAL_GTE:
 336                 GT++;
 337                 EQ++;
 338                 break;
 339         case '>':
 340                 GT++;
 341         }
 342
 343         if (LT == 2) {
 344                 if (EQ == 2)
 345                         return SPECIAL_LTE;
 346                 return '<';
 347         }
 348
 349         if (GT == 2) {
 350                 if (EQ == 2)
 351                         return SPECIAL_GTE;
 352                 return '>';
 353         }
 354         return 0;
 355 }
 356
 357 static struct smatch_state *merge_compare_states(struct smatch_state *s1, struct smatch_state *s2)
 358 {
 359         struct compare_data *data = s1->data;
 360         int op;
 361
 362         op = merge_comparisons(state_to_comparison(s1), state_to_comparison(s2));
 363         if (op)
 364                 return alloc_compare_state(data->var1, data->sym1, op, data->var2, data->sym2);
 365         return &undefined;
 366 }
 367
 368 struct smatch_state *alloc_link_state(struct string_list *links)
 369 {
 370         struct smatch_state *state;
 371         static char buf[256];
 372         char *tmp;
 373         int i;
 374
 375         state = __alloc_smatch_state(0);
 376
 377         i = 0;
 378         FOR_EACH_PTR(links, tmp) {
 379                 if (!i++) {
 380                         snprintf(buf, sizeof(buf), "%s", tmp);
 381                 } else {
 382                         append(buf, ", ", sizeof(buf));
 383                         append(buf, tmp, sizeof(buf));
 384                 }
 385         } END_FOR_EACH_PTR(tmp);
 386
 387         state->name = alloc_sname(buf);
 388         state->data = links;
 389         return state;
 390 }
 391
 392 static void save_start_states(struct statement *stmt)
 393 {
 394         struct symbol *param;
 395         char orig[64];
 396         char state_name[128];
 397         struct smatch_state *state;
 398         struct string_list *links;
 399         char *link;
 400
 401         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
 402                 if (!param->ident)
 403                         continue;
 404                 snprintf(orig, sizeof(orig), "%s orig", param->ident->name);
 405                 snprintf(state_name, sizeof(state_name), "%s vs %s", param->ident->name, orig);
 406                 state = alloc_compare_state(param->ident->name, param, SPECIAL_EQUAL, alloc_sname(orig), param);
 407                 set_state(compare_id, state_name, NULL, state);
 408
 409                 link = alloc_sname(state_name);
 410                 links = NULL;
 411                 insert_string(&links, link);
 412                 state = alloc_link_state(links);
 413                 set_state(link_id, param->ident->name, param, state);
 414         } END_FOR_EACH_PTR(param);
 415 }
 416
 417 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
 418 {
 419         struct smatch_state *ret;
 420         struct string_list *links;
 421
 422         links = combine_string_lists(s1->data, s2->data);
 423         ret = alloc_link_state(links);
 424         return ret;
 425 }
 426
 427 static void save_link_var_sym(const char *var, struct symbol *sym, const char *link)
 428 {
 429         struct smatch_state *old_state, *new_state;
 430         struct string_list *links;
 431         char *new;
 432
 433         old_state = get_state(link_id, var, sym);
 434         if (old_state)
 435                 links = clone_str_list(old_state->data);
 436         else
 437                 links = NULL;
 438
 439         new = alloc_sname(link);
 440         insert_string(&links, new);
 441
 442         new_state = alloc_link_state(links);
 443         set_state(link_id, var, sym, new_state);
 444 }
 445
 446 static void match_inc(struct sm_state *sm)
 447 {
 448         struct string_list *links;
 449         struct smatch_state *state;
 450         char *tmp;
 451
 452         links = sm->state->data;
 453
 454         FOR_EACH_PTR(links, tmp) {
 455                 state = get_state(compare_id, tmp, NULL);
 456
 457                 switch (state_to_comparison(state)) {
 458                 case SPECIAL_EQUAL:
 459                 case SPECIAL_GTE:
 460                 case SPECIAL_UNSIGNED_GTE:
 461                 case '>':
 462                 case SPECIAL_UNSIGNED_GT: {
 463                         struct compare_data *data = state->data;
 464                         struct smatch_state *new;
 465
 466                         new = alloc_compare_state(data->var1, data->sym1, '>', data->var2, data->sym2);
 467                         set_state(compare_id, tmp, NULL, new);
 468                         break;
 469                         }
 470                 default:
 471                         set_state(compare_id, tmp, NULL, &undefined);
 472                 }
 473         } END_FOR_EACH_PTR(tmp);
 474 }
 475
 476 static void match_dec(struct sm_state *sm)
 477 {
 478         struct string_list *links;
 479         struct smatch_state *state;
 480         char *tmp;
 481
 482         links = sm->state->data;
 483
 484         FOR_EACH_PTR(links, tmp) {
 485                 state = get_state(compare_id, tmp, NULL);
 486
 487                 switch (state_to_comparison(state)) {
 488                 case SPECIAL_EQUAL:
 489                 case SPECIAL_LTE:
 490                 case SPECIAL_UNSIGNED_LTE:
 491                 case '<':
 492                 case SPECIAL_UNSIGNED_LT: {
 493                         struct compare_data *data = state->data;
 494                         struct smatch_state *new;
 495
 496                         new = alloc_compare_state(data->var1, data->sym1, '<', data->var2, data->sym2);
 497                         set_state(compare_id, tmp, NULL, new);
 498                         break;
 499                         }
 500                 default:
 501                         set_state(compare_id, tmp, NULL, &undefined);
 502                 }
 503         } END_FOR_EACH_PTR(tmp);
 504 }
 505
 506 static int match_inc_dec(struct sm_state *sm, struct expression *mod_expr)
 507 {
 508         if (!mod_expr)
 509                 return 0;
 510         if (mod_expr->type != EXPR_PREOP && mod_expr->type != EXPR_POSTOP)
 511                 return 0;
 512
 513         if (mod_expr->op == SPECIAL_INCREMENT) {
 514                 match_inc(sm);
 515                 return 1;
 516         }
 517         if (mod_expr->op == SPECIAL_DECREMENT) {
 518                 match_dec(sm);
 519                 return 1;
 520         }
 521         return 0;
 522 }
 523
 524 static void match_modify(struct sm_state *sm, struct expression *mod_expr)
 525 {
 526         struct string_list *links;
 527         char *tmp;
 528
 529         if (match_inc_dec(sm, mod_expr))
 530                 return;
 531
 532         links = sm->state->data;
 533
 534         FOR_EACH_PTR(links, tmp) {
 535                 set_state(compare_id, tmp, NULL, &undefined);
 536         } END_FOR_EACH_PTR(tmp);
 537         set_state(link_id, sm->name, sm->sym, &undefined);
 538 }
 539
 540 static char *chunk_to_var_sym(struct expression *expr, struct symbol **sym)
 541 {
 542         char *name, *left_name, *right_name;
 543         struct symbol *tmp;
 544         char buf[128];
 545
 546         expr = strip_expr(expr);
 547         if (!expr)
 548                 return NULL;
 549         if (sym)
 550                 *sym = NULL;
 551
 552         name = expr_to_var_sym(expr, &tmp);
 553         if (name && tmp) {
 554                 if (sym)
 555                         *sym = tmp;
 556                 return name;
 557         }
 558         if (name)
 559                 free_string(name);
 560
 561         if (expr->type != EXPR_BINOP)
 562                 return NULL;
 563         if (expr->op != '-' && expr->op != '+')
 564                 return NULL;
 565
 566         left_name = expr_to_var(expr->left);
 567         if (!left_name)
 568                 return NULL;
 569         right_name = expr_to_var(expr->right);
 570         if (!right_name) {
 571                 free_string(left_name);
 572                 return NULL;
 573         }
 574         snprintf(buf, sizeof(buf), "%s %s %s", left_name, show_special(expr->op), right_name);
 575         free_string(left_name);
 576         free_string(right_name);
 577         return alloc_string(buf);
 578 }
 579
 580 static char *chunk_to_var(struct expression *expr)
 581 {
 582         return chunk_to_var_sym(expr, NULL);
 583 }
 584
 585 static void save_link(struct expression *expr, char *link)
 586 {
 587         char *var;
 588         struct symbol *sym;
 589
 590         expr = strip_expr(expr);
 591         if (expr->type == EXPR_BINOP) {
 592                 char *chunk;
 593
 594                 chunk = chunk_to_var(expr);
 595                 if (!chunk)
 596                         return;
 597
 598                 save_link(expr->left, link);
 599                 save_link(expr->right, link);
 600                 save_link_var_sym(chunk, NULL, link);
 601                 return;
 602         }
 603
 604         var = expr_to_var_sym(expr, &sym);
 605         if (!var || !sym)
 606                 goto done;
 607
 608         save_link_var_sym(var, sym, link);
 609 done:
 610         free_string(var);
 611 }
 612
 613
 614
 615 static void update_tf_links(struct state_list *pre_slist,
 616                             const char *left_var, struct symbol *left_sym,
 617                             int left_comparison,
 618                             const char *mid_var, struct symbol *mid_sym,
 619                             struct string_list *links)
 620 {
 621         struct smatch_state *state;
 622         struct smatch_state *true_state, *false_state;
 623         struct compare_data *data;
 624         const char *right_var;
 625         struct symbol *right_sym;
 626         int right_comparison;
 627         int true_comparison;
 628         int false_comparison;
 629         char *tmp;
 630         char state_name[256];
 631
 632         FOR_EACH_PTR(links, tmp) {
 633                 state = get_state_slist(pre_slist, compare_id, tmp, NULL);
 634                 if (!state || !state->data)
 635                         continue;
 636                 data = state->data;
 637                 right_comparison = data->comparison;
 638                 right_var = data->var2;
 639                 right_sym = data->sym2;
 640                 if (var_sym_eq(mid_var, mid_sym, right_var, right_sym)) {
 641                         right_var = data->var1;
 642                         right_sym = data->sym1;
 643                         right_comparison = flip_op(right_comparison);
 644                 }
 645                 true_comparison = combine_comparisons(left_comparison, right_comparison);
 646                 false_comparison = combine_comparisons(falsify_op(left_comparison), right_comparison);
 647
 648                 if (strcmp(left_var, right_var) > 0) {
 649                         struct symbol *tmp_sym = left_sym;
 650                         const char *tmp_var = left_var;
 651
 652                         left_var = right_var;
 653                         left_sym = right_sym;
 654                         right_var = tmp_var;
 655                         right_sym = tmp_sym;
 656                         true_comparison = flip_op(true_comparison);
 657                         false_comparison = flip_op(false_comparison);
 658                 }
 659
 660                 if (!true_comparison && !false_comparison)
 661                         continue;
 662
 663                 if (true_comparison)
 664                         true_state = alloc_compare_state(left_var, left_sym, true_comparison, right_var, right_sym);
 665                 else
 666                         true_state = NULL;
 667                 if (false_comparison)
 668                         false_state = alloc_compare_state(left_var, left_sym, false_comparison, right_var, right_sym);
 669                 else
 670                         false_state = NULL;
 671
 672                 snprintf(state_name, sizeof(state_name), "%s vs %s", left_var, right_var);
 673                 set_true_false_states(compare_id, state_name, NULL, true_state, false_state);
 674                 save_link_var_sym(left_var, left_sym, state_name);
 675                 save_link_var_sym(right_var, right_sym, state_name);
 676         } END_FOR_EACH_PTR(tmp);
 677 }
 678
 679 static void update_tf_data(struct state_list *pre_slist, struct compare_data *tdata)
 680 {
 681         struct smatch_state *state;
 682
 683         state = get_state_slist(pre_slist, link_id, tdata->var2, tdata->sym2);
 684         if (state)
 685                 update_tf_links(pre_slist, tdata->var1, tdata->sym1, tdata->comparison, tdata->var2, tdata->sym2, state->data);
 686
 687         state = get_state_slist(pre_slist, link_id, tdata->var1, tdata->sym1);
 688         if (state)
 689                 update_tf_links(pre_slist, tdata->var2, tdata->sym2, flip_op(tdata->comparison), tdata->var1, tdata->sym1, state->data);
 690 }
 691
 692 static void match_compare(struct expression *expr)
 693 {
 694         char *left = NULL;
 695         char *right = NULL;
 696         struct symbol *left_sym, *right_sym;
 697         int op, false_op;
 698         struct smatch_state *true_state, *false_state;
 699         char state_name[256];
 700         struct state_list *pre_slist;
 701
 702         if (expr->type != EXPR_COMPARE)
 703                 return;
 704         left = chunk_to_var_sym(expr->left, &left_sym);
 705         if (!left)
 706                 goto free;
 707         right = chunk_to_var_sym(expr->right, &right_sym);
 708         if (!right)
 709                 goto free;
 710
 711         if (strcmp(left, right) > 0) {
 712                 struct symbol *tmp_sym = left_sym;
 713                 char *tmp_name = left;
 714
 715                 left = right;
 716                 left_sym = right_sym;
 717                 right = tmp_name;
 718                 right_sym = tmp_sym;
 719                 op = flip_op(expr->op);
 720         } else {
 721                 op = expr->op;
 722         }
 723         false_op = falsify_op(op);
 724         snprintf(state_name, sizeof(state_name), "%s vs %s", left, right);
 725         true_state = alloc_compare_state(left, left_sym, op, right, right_sym);
 726         false_state = alloc_compare_state(left, left_sym, false_op, right, right_sym);
 727
 728         pre_slist = clone_slist(__get_cur_slist());
 729         update_tf_data(pre_slist, true_state->data);
 730         free_slist(&pre_slist);
 731
 732         set_true_false_states(compare_id, state_name, NULL, true_state, false_state);
 733         save_link(expr->left, state_name);
 734         save_link(expr->right, state_name);
 735 free:
 736         free_string(left);
 737         free_string(right);
 738 }
 739
 740 static void add_comparison_var_sym(const char *left_name, struct symbol *left_sym, int comparison, const char *right_name, struct symbol *right_sym)
 741 {
 742         struct smatch_state *state;
 743         char state_name[256];
 744
 745         if (strcmp(left_name, right_name) > 0) {
 746                 struct symbol *tmp_sym = left_sym;
 747                 const char *tmp_name = left_name;
 748
 749                 left_name = right_name;
 750                 left_sym = right_sym;
 751                 right_name = tmp_name;
 752                 right_sym = tmp_sym;
 753                 comparison = flip_op(comparison);
 754         }
 755         snprintf(state_name, sizeof(state_name), "%s vs %s", left_name, right_name);
 756         state = alloc_compare_state(left_name, left_sym, comparison, right_name, right_sym);
 757
 758         set_state(compare_id, state_name, NULL, state);
 759         save_link_var_sym(left_name, left_sym, state_name);
 760         save_link_var_sym(right_name, right_sym, state_name);
 761 }
 762
 763 static void add_comparison(struct expression *left, int comparison, struct expression *right)
 764 {
 765         char *left_name = NULL;
 766         char *right_name = NULL;
 767         struct symbol *left_sym, *right_sym;
 768
 769         left_name = chunk_to_var_sym(left, &left_sym);
 770         if (!left_name)
 771                 goto free;
 772         right_name = chunk_to_var_sym(right, &right_sym);
 773         if (!right_name)
 774                 goto free;
 775
 776         add_comparison_var_sym(left_name, left_sym, comparison, right_name, right_sym);
 777
 778 free:
 779         free_string(left_name);
 780         free_string(right_name);
 781 }
 782
 783 static void match_assign_add(struct expression *expr)
 784 {
 785         struct expression *right;
 786         struct expression *r_left, *r_right;
 787         sval_t left_tmp, right_tmp;
 788
 789         right = strip_expr(expr->right);
 790         r_left = strip_expr(right->left);
 791         r_right = strip_expr(right->right);
 792
 793         get_absolute_min(r_left, &left_tmp);
 794         get_absolute_min(r_right, &right_tmp);
 795
 796         if (left_tmp.value > 0)
 797                 add_comparison(expr->left, '>', r_right);
 798         else if (left_tmp.value == 0)
 799                 add_comparison(expr->left, SPECIAL_GTE, r_right);
 800
 801         if (right_tmp.value > 0)
 802                 add_comparison(expr->left, '>', r_left);
 803         else if (right_tmp.value == 0)
 804                 add_comparison(expr->left, SPECIAL_GTE, r_left);
 805 }
 806
 807 static void match_assign_sub(struct expression *expr)
 808 {
 809         struct expression *right;
 810         struct expression *r_left, *r_right;
 811         int comparison;
 812         sval_t min;
 813
 814         right = strip_expr(expr->right);
 815         r_left = strip_expr(right->left);
 816         r_right = strip_expr(right->right);
 817
 818         if (get_absolute_min(r_right, &min) && sval_is_negative(min))
 819                 return;
 820
 821         comparison = get_comparison(r_left, r_right);
 822
 823         switch (comparison) {
 824         case '>':
 825         case SPECIAL_GTE:
 826                 if (implied_not_equal(r_right, 0))
 827                         add_comparison(expr->left, '>', r_left);
 828                 else
 829                         add_comparison(expr->left, SPECIAL_GTE, r_left);
 830                 return;
 831         }
 832 }
 833
 834 static void match_assign_divide(struct expression *expr)
 835 {
 836         struct expression *right;
 837         struct expression *r_left, *r_right;
 838         sval_t min;
 839
 840         right = strip_expr(expr->right);
 841         r_left = strip_expr(right->left);
 842         r_right = strip_expr(right->right);
 843         if (!get_implied_min(r_right, &min) || min.value <= 1)
 844                 return;
 845
 846         add_comparison(expr->left, '<', r_left);
 847 }
 848
 849 static void match_binop_assign(struct expression *expr)
 850 {
 851         struct expression *right;
 852
 853         right = strip_expr(expr->right);
 854         if (right->op == '+')
 855                 match_assign_add(expr);
 856         if (right->op == '-')
 857                 match_assign_sub(expr);
 858         if (right->op == '/')
 859                 match_assign_divide(expr);
 860 }
 861
 862 static void copy_comparisons(struct expression *left, struct expression *right)
 863 {
 864         struct string_list *links;
 865         struct smatch_state *state;
 866         struct compare_data *data;
 867         struct symbol *left_sym, *right_sym;
 868         char *left_var = NULL;
 869         char *right_var = NULL;
 870         const char *var;
 871         struct symbol *sym;
 872         int comparison;
 873         char *tmp;
 874
 875         left_var = chunk_to_var_sym(left, &left_sym);
 876         if (!left_var)
 877                 goto done;
 878         right_var = chunk_to_var_sym(right, &right_sym);
 879         if (!right_var)
 880                 goto done;
 881
 882         state = get_state(link_id, right_var, right_sym);
 883         if (!state)
 884                 return;
 885         links = state->data;
 886
 887         FOR_EACH_PTR(links, tmp) {
 888                 state = get_state(compare_id, tmp, NULL);
 889                 if (!state || !state->data)
 890                         continue;
 891                 data = state->data;
 892                 comparison = data->comparison;
 893                 var = data->var2;
 894                 sym = data->sym2;
 895                 if (var_sym_eq(var, sym, right_var, right_sym)) {
 896                         var = data->var1;
 897                         sym = data->sym1;
 898                         comparison = flip_op(comparison);
 899                 }
 900                 add_comparison_var_sym(left_var, left_sym, comparison, var, sym);
 901         } END_FOR_EACH_PTR(tmp);
 902
 903 done:
 904         free_string(right_var);
 905 }
 906
 907 static void match_assign(struct expression *expr)
 908 {
 909         struct expression *right;
 910
 911         if (expr->op != '=')
 912                 return;
 913
 914         copy_comparisons(expr->left, expr->right);
 915         add_comparison(expr->left, SPECIAL_EQUAL, expr->right);
 916
 917         right = strip_expr(expr->right);
 918         if (right->type == EXPR_BINOP)
 919                 match_binop_assign(expr);
 920 }
 921
 922 static int get_comparison_strings(char *one, char *two)
 923 {
 924         char buf[256];
 925         struct smatch_state *state;
 926         int invert = 0;
 927         int ret = 0;
 928
 929         if (strcmp(one, two) > 0) {
 930                 char *tmp = one;
 931
 932                 one = two;
 933                 two = tmp;
 934                 invert = 1;
 935         }
 936
 937         snprintf(buf, sizeof(buf), "%s vs %s", one, two);
 938         state = get_state(compare_id, buf, NULL);
 939         if (state)
 940                 ret = state_to_comparison(state);
 941
 942         if (invert)
 943                 ret = flip_op(ret);
 944
 945         return ret;
 946 }
 947
 948 int get_comparison(struct expression *a, struct expression *b)
 949 {
 950         char *one = NULL;
 951         char *two = NULL;
 952         int ret = 0;
 953
 954         one = chunk_to_var(a);
 955         if (!one)
 956                 goto free;
 957         two = chunk_to_var(b);
 958         if (!two)
 959                 goto free;
 960
 961         ret = get_comparison_strings(one, two);
 962 free:
 963         free_string(one);
 964         free_string(two);
 965         return ret;
 966 }
 967
 968 void __add_comparison_info(struct expression *expr, struct expression *call, const char *range)
 969 {
 970         struct expression *arg;
 971         int comparison;
 972         const char *c = range;
 973
 974         if (!str_to_comparison_arg(c, call, &comparison, &arg))
 975                 return;
 976         add_comparison(expr, comparison, arg);
 977 }
 978
 979 static char *range_comparison_to_param_helper(struct expression *expr, char starts_with)
 980 {
 981         struct symbol *param;
 982         char *var = NULL;
 983         char buf[256];
 984         char *ret_str = NULL;
 985         int compare;
 986         int i;
 987
 988         var = chunk_to_var(expr);
 989         if (!var)
 990                 goto free;
 991
 992         i = -1;
 993         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
 994                 i++;
 995                 if (!param->ident)
 996                         continue;
 997                 snprintf(buf, sizeof(buf), "%s orig", param->ident->name);
 998                 compare = get_comparison_strings(var, buf);
 999                 if (!compare)
1000                         continue;
1001                 if (show_special(compare)[0] != starts_with)
1002                         continue;
1003                 snprintf(buf, sizeof(buf), "[%sp%d]", show_special(compare), i);
1004                 ret_str = alloc_sname(buf);
1005                 break;
1006         } END_FOR_EACH_PTR(param);
1007
1008 free:
1009         free_string(var);
1010         return ret_str;
1011 }
1012
1013 char *expr_equal_to_param(struct expression *expr)
1014 {
1015         return range_comparison_to_param_helper(expr, '=');
1016 }
1017
1018 char *expr_lte_to_param(struct expression *expr)
1019 {
1020         return range_comparison_to_param_helper(expr, '<');
1021 }
1022
1023 static void free_data(struct symbol *sym)
1024 {
1025         if (__inline_fn)
1026                 return;
1027         clear_compare_data_alloc();
1028 }
1029
1030 void register_comparison(int id)
1031 {
1032         compare_id = id;
1033         add_hook(&match_compare, CONDITION_HOOK);
1034         add_hook(&match_assign, ASSIGNMENT_HOOK);
1035         add_hook(&save_start_states, AFTER_DEF_HOOK);
1036         add_unmatched_state_hook(compare_id, unmatched_comparison);
1037         add_merge_hook(compare_id, &merge_compare_states);
1038         add_hook(&free_data, AFTER_FUNC_HOOK);
1039 }
1040
1041 void register_comparison_links(int id)
1042 {
1043         link_id = id;
1044         add_merge_hook(link_id, &merge_links);
1045         add_modification_hook(link_id, &match_modify);
1046 }