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 (sym)
 548                 *sym = NULL;
 549
 550         name = expr_to_var_sym(expr, &tmp);
 551         if (name && tmp) {
 552                 if (sym)
 553                         *sym = tmp;
 554                 return name;
 555         }
 556         if (name)
 557                 free_string(name);
 558
 559         if (expr->type != EXPR_BINOP)
 560                 return NULL;
 561         if (expr->op != '-' && expr->op != '+')
 562                 return NULL;
 563
 564         left_name = expr_to_var(expr->left);
 565         if (!left_name)
 566                 return NULL;
 567         right_name = expr_to_var(expr->right);
 568         if (!right_name) {
 569                 free_string(left_name);
 570                 return NULL;
 571         }
 572         snprintf(buf, sizeof(buf), "%s %s %s", left_name, show_special(expr->op), right_name);
 573         free_string(left_name);
 574         free_string(right_name);
 575         return alloc_string(buf);
 576 }
 577
 578 static char *chunk_to_var(struct expression *expr)
 579 {
 580         return chunk_to_var_sym(expr, NULL);
 581 }
 582
 583 static void save_link(struct expression *expr, char *link)
 584 {
 585         char *var;
 586         struct symbol *sym;
 587
 588         expr = strip_expr(expr);
 589         if (expr->type == EXPR_BINOP) {
 590                 char *chunk;
 591
 592                 chunk = chunk_to_var(expr);
 593                 if (!chunk)
 594                         return;
 595
 596                 save_link(expr->left, link);
 597                 save_link(expr->right, link);
 598                 save_link_var_sym(chunk, NULL, link);
 599                 return;
 600         }
 601
 602         var = expr_to_var_sym(expr, &sym);
 603         if (!var || !sym)
 604                 goto done;
 605
 606         save_link_var_sym(var, sym, link);
 607 done:
 608         free_string(var);
 609 }
 610
 611
 612
 613 static void update_tf_links(struct state_list *pre_slist,
 614                             const char *left_var, struct symbol *left_sym,
 615                             int left_comparison,
 616                             const char *mid_var, struct symbol *mid_sym,
 617                             struct string_list *links)
 618 {
 619         struct smatch_state *state;
 620         struct smatch_state *true_state, *false_state;
 621         struct compare_data *data;
 622         const char *right_var;
 623         struct symbol *right_sym;
 624         int right_comparison;
 625         int true_comparison;
 626         int false_comparison;
 627         char *tmp;
 628         char state_name[256];
 629
 630         FOR_EACH_PTR(links, tmp) {
 631                 state = get_state_slist(pre_slist, compare_id, tmp, NULL);
 632                 if (!state || !state->data)
 633                         continue;
 634                 data = state->data;
 635                 right_comparison = data->comparison;
 636                 right_var = data->var2;
 637                 right_sym = data->sym2;
 638                 if (var_sym_eq(mid_var, mid_sym, right_var, right_sym)) {
 639                         right_var = data->var1;
 640                         right_sym = data->sym1;
 641                         right_comparison = flip_op(right_comparison);
 642                 }
 643                 true_comparison = combine_comparisons(left_comparison, right_comparison);
 644                 false_comparison = combine_comparisons(falsify_op(left_comparison), right_comparison);
 645
 646                 if (strcmp(left_var, right_var) > 0) {
 647                         struct symbol *tmp_sym = left_sym;
 648                         const char *tmp_var = left_var;
 649
 650                         left_var = right_var;
 651                         left_sym = right_sym;
 652                         right_var = tmp_var;
 653                         right_sym = tmp_sym;
 654                         true_comparison = flip_op(true_comparison);
 655                         false_comparison = flip_op(false_comparison);
 656                 }
 657
 658                 if (!true_comparison && !false_comparison)
 659                         continue;
 660
 661                 if (true_comparison)
 662                         true_state = alloc_compare_state(left_var, left_sym, true_comparison, right_var, right_sym);
 663                 else
 664                         true_state = NULL;
 665                 if (false_comparison)
 666                         false_state = alloc_compare_state(left_var, left_sym, false_comparison, right_var, right_sym);
 667                 else
 668                         false_state = NULL;
 669
 670                 snprintf(state_name, sizeof(state_name), "%s vs %s", left_var, right_var);
 671                 set_true_false_states(compare_id, state_name, NULL, true_state, false_state);
 672                 save_link_var_sym(left_var, left_sym, state_name);
 673                 save_link_var_sym(right_var, right_sym, state_name);
 674         } END_FOR_EACH_PTR(tmp);
 675 }
 676
 677 static void update_tf_data(struct state_list *pre_slist, struct compare_data *tdata)
 678 {
 679         struct smatch_state *state;
 680
 681         state = get_state_slist(pre_slist, link_id, tdata->var2, tdata->sym2);
 682         if (state)
 683                 update_tf_links(pre_slist, tdata->var1, tdata->sym1, tdata->comparison, tdata->var2, tdata->sym2, state->data);
 684
 685         state = get_state_slist(pre_slist, link_id, tdata->var1, tdata->sym1);
 686         if (state)
 687                 update_tf_links(pre_slist, tdata->var2, tdata->sym2, flip_op(tdata->comparison), tdata->var1, tdata->sym1, state->data);
 688 }
 689
 690 static void match_compare(struct expression *expr)
 691 {
 692         char *left = NULL;
 693         char *right = NULL;
 694         struct symbol *left_sym, *right_sym;
 695         int op, false_op;
 696         struct smatch_state *true_state, *false_state;
 697         char state_name[256];
 698         struct state_list *pre_slist;
 699
 700         if (expr->type != EXPR_COMPARE)
 701                 return;
 702         left = chunk_to_var_sym(expr->left, &left_sym);
 703         if (!left)
 704                 goto free;
 705         right = chunk_to_var_sym(expr->right, &right_sym);
 706         if (!right)
 707                 goto free;
 708
 709         if (strcmp(left, right) > 0) {
 710                 struct symbol *tmp_sym = left_sym;
 711                 char *tmp_name = left;
 712
 713                 left = right;
 714                 left_sym = right_sym;
 715                 right = tmp_name;
 716                 right_sym = tmp_sym;
 717                 op = flip_op(expr->op);
 718         } else {
 719                 op = expr->op;
 720         }
 721         false_op = falsify_op(op);
 722         snprintf(state_name, sizeof(state_name), "%s vs %s", left, right);
 723         true_state = alloc_compare_state(left, left_sym, op, right, right_sym);
 724         false_state = alloc_compare_state(left, left_sym, false_op, right, right_sym);
 725
 726         pre_slist = clone_slist(__get_cur_slist());
 727         update_tf_data(pre_slist, true_state->data);
 728         free_slist(&pre_slist);
 729
 730         set_true_false_states(compare_id, state_name, NULL, true_state, false_state);
 731         save_link(expr->left, state_name);
 732         save_link(expr->right, state_name);
 733 free:
 734         free_string(left);
 735         free_string(right);
 736 }
 737
 738 static void add_comparison_var_sym(const char *left_name, struct symbol *left_sym, int comparison, const char *right_name, struct symbol *right_sym)
 739 {
 740         struct smatch_state *state;
 741         char state_name[256];
 742
 743         if (strcmp(left_name, right_name) > 0) {
 744                 struct symbol *tmp_sym = left_sym;
 745                 const char *tmp_name = left_name;
 746
 747                 left_name = right_name;
 748                 left_sym = right_sym;
 749                 right_name = tmp_name;
 750                 right_sym = tmp_sym;
 751                 comparison = flip_op(comparison);
 752         }
 753         snprintf(state_name, sizeof(state_name), "%s vs %s", left_name, right_name);
 754         state = alloc_compare_state(left_name, left_sym, comparison, right_name, right_sym);
 755
 756         set_state(compare_id, state_name, NULL, state);
 757         save_link_var_sym(left_name, left_sym, state_name);
 758         save_link_var_sym(right_name, right_sym, state_name);
 759 }
 760
 761 static void add_comparison(struct expression *left, int comparison, struct expression *right)
 762 {
 763         char *left_name = NULL;
 764         char *right_name = NULL;
 765         struct symbol *left_sym, *right_sym;
 766
 767         left_name = chunk_to_var_sym(left, &left_sym);
 768         if (!left_name)
 769                 goto free;
 770         right_name = chunk_to_var_sym(right, &right_sym);
 771         if (!right_name)
 772                 goto free;
 773
 774         add_comparison_var_sym(left_name, left_sym, comparison, right_name, right_sym);
 775
 776 free:
 777         free_string(left_name);
 778         free_string(right_name);
 779 }
 780
 781 static void match_assign_add(struct expression *expr)
 782 {
 783         struct expression *right;
 784         struct expression *r_left, *r_right;
 785         sval_t left_tmp, right_tmp;
 786
 787         right = strip_expr(expr->right);
 788         r_left = strip_expr(right->left);
 789         r_right = strip_expr(right->right);
 790
 791         get_absolute_min(r_left, &left_tmp);
 792         get_absolute_min(r_right, &right_tmp);
 793
 794         if (left_tmp.value > 0)
 795                 add_comparison(expr->left, '>', r_right);
 796         else if (left_tmp.value == 0)
 797                 add_comparison(expr->left, SPECIAL_GTE, r_right);
 798
 799         if (right_tmp.value > 0)
 800                 add_comparison(expr->left, '>', r_left);
 801         else if (right_tmp.value == 0)
 802                 add_comparison(expr->left, SPECIAL_GTE, r_left);
 803 }
 804
 805 static void match_assign_sub(struct expression *expr)
 806 {
 807         struct expression *right;
 808         struct expression *r_left, *r_right;
 809         int comparison;
 810         sval_t min;
 811
 812         right = strip_expr(expr->right);
 813         r_left = strip_expr(right->left);
 814         r_right = strip_expr(right->right);
 815
 816         if (get_absolute_min(r_right, &min) && sval_is_negative(min))
 817                 return;
 818
 819         comparison = get_comparison(r_left, r_right);
 820
 821         switch (comparison) {
 822         case '>':
 823         case SPECIAL_GTE:
 824                 if (implied_not_equal(r_right, 0))
 825                         add_comparison(expr->left, '>', r_left);
 826                 else
 827                         add_comparison(expr->left, SPECIAL_GTE, r_left);
 828                 return;
 829         }
 830 }
 831
 832 static void match_assign_divide(struct expression *expr)
 833 {
 834         struct expression *right;
 835         struct expression *r_left, *r_right;
 836         sval_t min;
 837
 838         right = strip_expr(expr->right);
 839         r_left = strip_expr(right->left);
 840         r_right = strip_expr(right->right);
 841         if (!get_implied_min(r_right, &min) || min.value <= 1)
 842                 return;
 843
 844         add_comparison(expr->left, '<', r_left);
 845 }
 846
 847 static void match_binop_assign(struct expression *expr)
 848 {
 849         struct expression *right;
 850
 851         right = strip_expr(expr->right);
 852         if (right->op == '+')
 853                 match_assign_add(expr);
 854         if (right->op == '-')
 855                 match_assign_sub(expr);
 856         if (right->op == '/')
 857                 match_assign_divide(expr);
 858 }
 859
 860 static void copy_comparisons(struct expression *left, struct expression *right)
 861 {
 862         struct string_list *links;
 863         struct smatch_state *state;
 864         struct compare_data *data;
 865         struct symbol *left_sym, *right_sym;
 866         char *left_var = NULL;
 867         char *right_var = NULL;
 868         const char *var;
 869         struct symbol *sym;
 870         int comparison;
 871         char *tmp;
 872
 873         left_var = chunk_to_var_sym(left, &left_sym);
 874         if (!left_var)
 875                 goto done;
 876         right_var = chunk_to_var_sym(right, &right_sym);
 877         if (!right_var)
 878                 goto done;
 879
 880         state = get_state(link_id, right_var, right_sym);
 881         if (!state)
 882                 return;
 883         links = state->data;
 884
 885         FOR_EACH_PTR(links, tmp) {
 886                 state = get_state(compare_id, tmp, NULL);
 887                 if (!state || !state->data)
 888                         continue;
 889                 data = state->data;
 890                 comparison = data->comparison;
 891                 var = data->var2;
 892                 sym = data->sym2;
 893                 if (var_sym_eq(var, sym, right_var, right_sym)) {
 894                         var = data->var1;
 895                         sym = data->sym1;
 896                         comparison = flip_op(comparison);
 897                 }
 898                 add_comparison_var_sym(left_var, left_sym, comparison, var, sym);
 899         } END_FOR_EACH_PTR(tmp);
 900
 901 done:
 902         free_string(right_var);
 903 }
 904
 905 static void match_assign(struct expression *expr)
 906 {
 907         struct expression *right;
 908
 909         if (expr->op != '=')
 910                 return;
 911
 912         copy_comparisons(expr->left, expr->right);
 913         add_comparison(expr->left, SPECIAL_EQUAL, expr->right);
 914
 915         right = strip_expr(expr->right);
 916         if (right->type == EXPR_BINOP)
 917                 match_binop_assign(expr);
 918 }
 919
 920 static int get_comparison_strings(char *one, char *two)
 921 {
 922         char buf[256];
 923         struct smatch_state *state;
 924         int invert = 0;
 925         int ret = 0;
 926
 927         if (strcmp(one, two) > 0) {
 928                 char *tmp = one;
 929
 930                 one = two;
 931                 two = tmp;
 932                 invert = 1;
 933         }
 934
 935         snprintf(buf, sizeof(buf), "%s vs %s", one, two);
 936         state = get_state(compare_id, buf, NULL);
 937         if (state)
 938                 ret = state_to_comparison(state);
 939
 940         if (invert)
 941                 ret = flip_op(ret);
 942
 943         return ret;
 944 }
 945
 946 int get_comparison(struct expression *a, struct expression *b)
 947 {
 948         char *one = NULL;
 949         char *two = NULL;
 950         int ret = 0;
 951
 952         one = chunk_to_var(a);
 953         if (!one)
 954                 goto free;
 955         two = chunk_to_var(b);
 956         if (!two)
 957                 goto free;
 958
 959         ret = get_comparison_strings(one, two);
 960 free:
 961         free_string(one);
 962         free_string(two);
 963         return ret;
 964 }
 965
 966 void __add_comparison_info(struct expression *expr, struct expression *call, const char *range)
 967 {
 968         struct expression *arg;
 969         int comparison;
 970         const char *c = range;
 971
 972         if (!str_to_comparison_arg(c, call, &comparison, &arg))
 973                 return;
 974         add_comparison(expr, comparison, arg);
 975 }
 976
 977 static char *range_comparison_to_param_helper(struct expression *expr, char starts_with)
 978 {
 979         struct symbol *param;
 980         char *var = NULL;
 981         char buf[256];
 982         char *ret_str = NULL;
 983         int compare;
 984         int i;
 985
 986         var = chunk_to_var(expr);
 987         if (!var)
 988                 goto free;
 989
 990         i = -1;
 991         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
 992                 i++;
 993                 if (!param->ident)
 994                         continue;
 995                 snprintf(buf, sizeof(buf), "%s orig", param->ident->name);
 996                 compare = get_comparison_strings(var, buf);
 997                 if (!compare)
 998                         continue;
 999                 if (show_special(compare)[0] != starts_with)
1000                         continue;
1001                 snprintf(buf, sizeof(buf), "[%sp%d]", show_special(compare), i);
1002                 ret_str = alloc_sname(buf);
1003                 break;
1004         } END_FOR_EACH_PTR(param);
1005
1006 free:
1007         free_string(var);
1008         return ret_str;
1009 }
1010
1011 char *expr_equal_to_param(struct expression *expr)
1012 {
1013         return range_comparison_to_param_helper(expr, '=');
1014 }
1015
1016 char *expr_lte_to_param(struct expression *expr)
1017 {
1018         return range_comparison_to_param_helper(expr, '<');
1019 }
1020
1021 static void free_data(struct symbol *sym)
1022 {
1023         if (__inline_fn)
1024                 return;
1025         clear_compare_data_alloc();
1026 }
1027
1028 void register_comparison(int id)
1029 {
1030         compare_id = id;
1031         add_hook(&match_compare, CONDITION_HOOK);
1032         add_hook(&match_assign, ASSIGNMENT_HOOK);
1033         add_hook(&save_start_states, AFTER_DEF_HOOK);
1034         add_unmatched_state_hook(compare_id, unmatched_comparison);
1035         add_merge_hook(compare_id, &merge_compare_states);
1036         add_hook(&free_data, AFTER_FUNC_HOOK);
1037 }
1038
1039 void register_comparison_links(int id)
1040 {
1041         link_id = id;
1042         add_merge_hook(link_id, &merge_links);
1043         add_modification_hook(link_id, &match_modify);
1044 }