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  */
  22
  23 #include "smatch.h"
  24 #include "smatch_extra.h"
  25 #include "smatch_slist.h"
  26
  27 static int compare_id;
  28 static int link_id;
  29
  30 struct compare_data {
  31         const char *var1;
  32         struct var_sym_list *vsl1;
  33         int comparison;
  34         const char *var2;
  35         struct var_sym_list *vsl2;
  36 };
  37 ALLOCATOR(compare_data, "compare data");
  38
  39 int chunk_vsl_eq(const char *a, struct var_sym_list *a_vsl, const char *b, struct var_sym_list *b_vsl)
  40 {
  41         if (strcmp(a, b) == 0)
  42                 return 1;
  43         return 0;
  44 }
  45
  46 static struct symbol *vsl_to_sym(struct var_sym_list *vsl)
  47 {
  48         struct var_sym *vs;
  49
  50         if (!vsl)
  51                 return NULL;
  52         if (ptr_list_size((struct ptr_list *)vsl) != 1)
  53                 return NULL;
  54         vs = first_ptr_list((struct ptr_list *)vsl);
  55         return vs->sym;
  56 }
  57
  58 static struct smatch_state *alloc_compare_state(
  59                 const char *var1, struct var_sym_list *vsl1,
  60                 int comparison,
  61                 const char *var2, struct var_sym_list *vsl2)
  62 {
  63         struct smatch_state *state;
  64         struct compare_data *data;
  65
  66         state = __alloc_smatch_state(0);
  67         state->name = alloc_sname(show_special(comparison));
  68         data = __alloc_compare_data(0);
  69         data->var1 = alloc_sname(var1);
  70         data->vsl1 = clone_var_sym_list(vsl1);
  71         data->comparison = comparison;
  72         data->var2 = alloc_sname(var2);
  73         data->vsl2 = clone_var_sym_list(vsl2);
  74         state->data = data;
  75         return state;
  76 }
  77
  78 static int state_to_comparison(struct smatch_state *state)
  79 {
  80         if (!state || !state->data)
  81                 return 0;
  82         return ((struct compare_data *)state->data)->comparison;
  83 }
  84
  85 /*
  86  * flip_op() reverses the op left and right.  So "x >= y" becomes "y <= x".
  87  */
  88 static int flip_op(int op)
  89 {
  90         switch (op) {
  91         case 0:
  92                 return 0;
  93         case '<':
  94                 return '>';
  95         case SPECIAL_UNSIGNED_LT:
  96                 return SPECIAL_UNSIGNED_GT;
  97         case SPECIAL_LTE:
  98                 return SPECIAL_GTE;
  99         case SPECIAL_UNSIGNED_LTE:
 100                 return SPECIAL_UNSIGNED_GTE;
 101         case SPECIAL_EQUAL:
 102                 return SPECIAL_EQUAL;
 103         case SPECIAL_NOTEQUAL:
 104                 return SPECIAL_NOTEQUAL;
 105         case SPECIAL_GTE:
 106                 return SPECIAL_LTE;
 107         case SPECIAL_UNSIGNED_GTE:
 108                 return SPECIAL_UNSIGNED_LTE;
 109         case '>':
 110                 return '<';
 111         case SPECIAL_UNSIGNED_GT:
 112                 return SPECIAL_UNSIGNED_LT;
 113         default:
 114                 sm_msg("internal smatch bug.  unhandled comparison %d", op);
 115                 return op;
 116         }
 117 }
 118
 119 static int falsify_op(int op)
 120 {
 121         switch (op) {
 122         case 0:
 123                 return 0;
 124         case '<':
 125                 return SPECIAL_GTE;
 126         case SPECIAL_UNSIGNED_LT:
 127                 return SPECIAL_UNSIGNED_GTE;
 128         case SPECIAL_LTE:
 129                 return '>';
 130         case SPECIAL_UNSIGNED_LTE:
 131                 return SPECIAL_UNSIGNED_GT;
 132         case SPECIAL_EQUAL:
 133                 return SPECIAL_NOTEQUAL;
 134         case SPECIAL_NOTEQUAL:
 135                 return SPECIAL_EQUAL;
 136         case SPECIAL_GTE:
 137                 return '<';
 138         case SPECIAL_UNSIGNED_GTE:
 139                 return SPECIAL_UNSIGNED_LT;
 140         case '>':
 141                 return SPECIAL_LTE;
 142         case SPECIAL_UNSIGNED_GT:
 143                 return SPECIAL_UNSIGNED_LTE;
 144         default:
 145                 sm_msg("internal smatch bug.  unhandled comparison %d", op);
 146                 return op;
 147         }
 148 }
 149
 150 static int rl_comparison(struct range_list *left_rl, struct range_list *right_rl)
 151 {
 152         sval_t left_min, left_max, right_min, right_max;
 153
 154         if (!left_rl || !right_rl)
 155                 return 0;
 156
 157         left_min = rl_min(left_rl);
 158         left_max = rl_max(left_rl);
 159         right_min = rl_min(right_rl);
 160         right_max = rl_max(right_rl);
 161
 162         if (left_min.value == left_max.value &&
 163             right_min.value == right_max.value &&
 164             left_min.value == right_min.value)
 165                 return SPECIAL_EQUAL;
 166
 167         if (sval_cmp(left_max, right_min) < 0)
 168                 return '<';
 169         if (sval_cmp(left_max, right_min) == 0)
 170                 return SPECIAL_LTE;
 171         if (sval_cmp(left_min, right_max) > 0)
 172                 return '>';
 173         if (sval_cmp(left_min, right_max) == 0)
 174                 return SPECIAL_GTE;
 175
 176         return 0;
 177 }
 178
 179 static struct range_list *get_orig_rl(struct var_sym_list *vsl)
 180 {
 181         struct symbol *sym;
 182         struct smatch_state *state;
 183
 184         if (!vsl)
 185                 return NULL;
 186         sym = vsl_to_sym(vsl);
 187         if (!sym || !sym->ident)
 188                 return NULL;
 189         state = get_orig_estate(sym->ident->name, sym);
 190         return estate_rl(state);
 191 }
 192
 193 static struct smatch_state *unmatched_comparison(struct sm_state *sm)
 194 {
 195         struct compare_data *data = sm->state->data;
 196         struct range_list *left_rl, *right_rl;
 197         int op;
 198
 199         if (!data)
 200                 return &undefined;
 201
 202         if (strstr(data->var1, " orig"))
 203                 left_rl = get_orig_rl(data->vsl1);
 204         else if (!get_implied_rl_var_sym(data->var1, vsl_to_sym(data->vsl1), &left_rl))
 205                 return &undefined;
 206         if (strstr(data->var2, " orig"))
 207                 right_rl = get_orig_rl(data->vsl2);
 208         else if (!get_implied_rl_var_sym(data->var2, vsl_to_sym(data->vsl2), &right_rl))
 209                 return &undefined;
 210
 211
 212         op = rl_comparison(left_rl, right_rl);
 213         if (op)
 214                 return alloc_compare_state(data->var1, data->vsl1, op, data->var2, data->vsl2);
 215
 216         return &undefined;
 217 }
 218
 219 /* remove_unsigned_from_comparison() is obviously a hack. */
 220 static int remove_unsigned_from_comparison(int op)
 221 {
 222         switch (op) {
 223         case SPECIAL_UNSIGNED_LT:
 224                 return '<';
 225         case SPECIAL_UNSIGNED_LTE:
 226                 return SPECIAL_LTE;
 227         case SPECIAL_UNSIGNED_GTE:
 228                 return SPECIAL_GTE;
 229         case SPECIAL_UNSIGNED_GT:
 230                 return '>';
 231         default:
 232                 return op;
 233         }
 234 }
 235
 236 /*
 237  * This is for when you merge states "a < b" and "a == b", the result is that
 238  * we can say for sure, "a <= b" after the merge.
 239  */
 240 static int merge_comparisons(int one, int two)
 241 {
 242         int LT, EQ, GT;
 243
 244         one = remove_unsigned_from_comparison(one);
 245         two = remove_unsigned_from_comparison(two);
 246
 247         LT = EQ = GT = 0;
 248
 249         switch (one) {
 250         case '<':
 251                 LT = 1;
 252                 break;
 253         case SPECIAL_LTE:
 254                 LT = 1;
 255                 EQ = 1;
 256                 break;
 257         case SPECIAL_EQUAL:
 258                 EQ = 1;
 259                 break;
 260         case SPECIAL_GTE:
 261                 GT = 1;
 262                 EQ = 1;
 263                 break;
 264         case '>':
 265                 GT = 1;
 266         }
 267
 268         switch (two) {
 269         case '<':
 270                 LT = 1;
 271                 break;
 272         case SPECIAL_LTE:
 273                 LT = 1;
 274                 EQ = 1;
 275                 break;
 276         case SPECIAL_EQUAL:
 277                 EQ = 1;
 278                 break;
 279         case SPECIAL_GTE:
 280                 GT = 1;
 281                 EQ = 1;
 282                 break;
 283         case '>':
 284                 GT = 1;
 285         }
 286
 287         if (LT && EQ && GT)
 288                 return 0;
 289         if (LT && EQ)
 290                 return SPECIAL_LTE;
 291         if (LT && GT)
 292                 return SPECIAL_NOTEQUAL;
 293         if (LT)
 294                 return '<';
 295         if (EQ && GT)
 296                 return SPECIAL_GTE;
 297         if (GT)
 298                 return '>';
 299         return 0;
 300 }
 301
 302 /*
 303  * This is for if you have "a < b" and "b <= c".  Or in other words,
 304  * "a < b <= c".  You would call this like get_combined_comparison('<', '<=').
 305  * The return comparison would be '<'.
 306  *
 307  * This function is different from merge_comparisons(), for example:
 308  * merge_comparison('<', '==') returns '<='
 309  * get_combined_comparison('<', '==') returns '<'
 310  */
 311 static int combine_comparisons(int left_compare, int right_compare)
 312 {
 313         int LT, EQ, GT;
 314
 315         left_compare = remove_unsigned_from_comparison(left_compare);
 316         right_compare = remove_unsigned_from_comparison(right_compare);
 317
 318         LT = EQ = GT = 0;
 319
 320         switch (left_compare) {
 321         case '<':
 322                 LT++;
 323                 break;
 324         case SPECIAL_LTE:
 325                 LT++;
 326                 EQ++;
 327                 break;
 328         case SPECIAL_EQUAL:
 329                 return right_compare;
 330         case SPECIAL_GTE:
 331                 GT++;
 332                 EQ++;
 333                 break;
 334         case '>':
 335                 GT++;
 336         }
 337
 338         switch (right_compare) {
 339         case '<':
 340                 LT++;
 341                 break;
 342         case SPECIAL_LTE:
 343                 LT++;
 344                 EQ++;
 345                 break;
 346         case SPECIAL_EQUAL:
 347                 return left_compare;
 348         case SPECIAL_GTE:
 349                 GT++;
 350                 EQ++;
 351                 break;
 352         case '>':
 353                 GT++;
 354         }
 355
 356         if (LT == 2) {
 357                 if (EQ == 2)
 358                         return SPECIAL_LTE;
 359                 return '<';
 360         }
 361
 362         if (GT == 2) {
 363                 if (EQ == 2)
 364                         return SPECIAL_GTE;
 365                 return '>';
 366         }
 367         return 0;
 368 }
 369
 370 static struct smatch_state *merge_compare_states(struct smatch_state *s1, struct smatch_state *s2)
 371 {
 372         struct compare_data *data = s1->data;
 373         int op;
 374
 375         op = merge_comparisons(state_to_comparison(s1), state_to_comparison(s2));
 376         if (op)
 377                 return alloc_compare_state(data->var1, data->vsl1, op, data->var2, data->vsl2);
 378         return &undefined;
 379 }
 380
 381 struct smatch_state *alloc_link_state(struct string_list *links)
 382 {
 383         struct smatch_state *state;
 384         static char buf[256];
 385         char *tmp;
 386         int i;
 387
 388         state = __alloc_smatch_state(0);
 389
 390         i = 0;
 391         FOR_EACH_PTR(links, tmp) {
 392                 if (!i++) {
 393                         snprintf(buf, sizeof(buf), "%s", tmp);
 394                 } else {
 395                         append(buf, ", ", sizeof(buf));
 396                         append(buf, tmp, sizeof(buf));
 397                 }
 398         } END_FOR_EACH_PTR(tmp);
 399
 400         state->name = alloc_sname(buf);
 401         state->data = links;
 402         return state;
 403 }
 404
 405 static void save_start_states(struct statement *stmt)
 406 {
 407         struct symbol *param;
 408         char orig[64];
 409         char state_name[128];
 410         struct smatch_state *state;
 411         struct string_list *links;
 412         char *link;
 413
 414         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
 415                 struct var_sym_list *vsl1 = NULL;
 416                 struct var_sym_list *vsl2 = NULL;
 417
 418                 if (!param->ident)
 419                         continue;
 420                 snprintf(orig, sizeof(orig), "%s orig", param->ident->name);
 421                 snprintf(state_name, sizeof(state_name), "%s vs %s", param->ident->name, orig);
 422                 add_var_sym(&vsl1, param->ident->name, param);
 423                 add_var_sym(&vsl2, orig, param);
 424                 state = alloc_compare_state(param->ident->name, vsl1, SPECIAL_EQUAL, alloc_sname(orig), vsl2);
 425                 set_state(compare_id, state_name, NULL, state);
 426
 427                 link = alloc_sname(state_name);
 428                 links = NULL;
 429                 insert_string(&links, link);
 430                 state = alloc_link_state(links);
 431                 set_state(link_id, param->ident->name, param, state);
 432         } END_FOR_EACH_PTR(param);
 433 }
 434
 435 static struct smatch_state *merge_links(struct smatch_state *s1, struct smatch_state *s2)
 436 {
 437         struct smatch_state *ret;
 438         struct string_list *links;
 439
 440         links = combine_string_lists(s1->data, s2->data);
 441         ret = alloc_link_state(links);
 442         return ret;
 443 }
 444
 445 static void save_link_var_sym(const char *var, struct symbol *sym, const char *link)
 446 {
 447         struct smatch_state *old_state, *new_state;
 448         struct string_list *links;
 449         char *new;
 450
 451         old_state = get_state(link_id, var, sym);
 452         if (old_state)
 453                 links = clone_str_list(old_state->data);
 454         else
 455                 links = NULL;
 456
 457         new = alloc_sname(link);
 458         insert_string(&links, new);
 459
 460         new_state = alloc_link_state(links);
 461         set_state(link_id, var, sym, new_state);
 462 }
 463
 464 static void match_inc(struct sm_state *sm)
 465 {
 466         struct string_list *links;
 467         struct smatch_state *state;
 468         char *tmp;
 469
 470         links = sm->state->data;
 471
 472         FOR_EACH_PTR(links, tmp) {
 473                 state = get_state(compare_id, tmp, NULL);
 474
 475                 switch (state_to_comparison(state)) {
 476                 case SPECIAL_EQUAL:
 477                 case SPECIAL_GTE:
 478                 case SPECIAL_UNSIGNED_GTE:
 479                 case '>':
 480                 case SPECIAL_UNSIGNED_GT: {
 481                         struct compare_data *data = state->data;
 482                         struct smatch_state *new;
 483
 484                         new = alloc_compare_state(data->var1, data->vsl1, '>', data->var2, data->vsl2);
 485                         set_state(compare_id, tmp, NULL, new);
 486                         break;
 487                         }
 488                 default:
 489                         set_state(compare_id, tmp, NULL, &undefined);
 490                 }
 491         } END_FOR_EACH_PTR(tmp);
 492 }
 493
 494 static void match_dec(struct sm_state *sm)
 495 {
 496         struct string_list *links;
 497         struct smatch_state *state;
 498         char *tmp;
 499
 500         links = sm->state->data;
 501
 502         FOR_EACH_PTR(links, tmp) {
 503                 state = get_state(compare_id, tmp, NULL);
 504
 505                 switch (state_to_comparison(state)) {
 506                 case SPECIAL_EQUAL:
 507                 case SPECIAL_LTE:
 508                 case SPECIAL_UNSIGNED_LTE:
 509                 case '<':
 510                 case SPECIAL_UNSIGNED_LT: {
 511                         struct compare_data *data = state->data;
 512                         struct smatch_state *new;
 513
 514                         new = alloc_compare_state(data->var1, data->vsl1, '<', data->var2, data->vsl2);
 515                         set_state(compare_id, tmp, NULL, new);
 516                         break;
 517                         }
 518                 default:
 519                         set_state(compare_id, tmp, NULL, &undefined);
 520                 }
 521         } END_FOR_EACH_PTR(tmp);
 522 }
 523
 524 static int match_inc_dec(struct sm_state *sm, struct expression *mod_expr)
 525 {
 526         if (!mod_expr)
 527                 return 0;
 528         if (mod_expr->type != EXPR_PREOP && mod_expr->type != EXPR_POSTOP)
 529                 return 0;
 530
 531         if (mod_expr->op == SPECIAL_INCREMENT) {
 532                 match_inc(sm);
 533                 return 1;
 534         }
 535         if (mod_expr->op == SPECIAL_DECREMENT) {
 536                 match_dec(sm);
 537                 return 1;
 538         }
 539         return 0;
 540 }
 541
 542 static void match_modify(struct sm_state *sm, struct expression *mod_expr)
 543 {
 544         struct string_list *links;
 545         char *tmp;
 546
 547         if (match_inc_dec(sm, mod_expr))
 548                 return;
 549
 550         links = sm->state->data;
 551
 552         FOR_EACH_PTR(links, tmp) {
 553                 set_state(compare_id, tmp, NULL, &undefined);
 554         } END_FOR_EACH_PTR(tmp);
 555         set_state(link_id, sm->name, sm->sym, &undefined);
 556
 557
 558 }
 559
 560 static char *chunk_to_var_sym(struct expression *expr, struct symbol **sym)
 561 {
 562         char *name, *left_name, *right_name;
 563         struct symbol *tmp;
 564         char buf[128];
 565
 566         expr = strip_expr(expr);
 567         if (!expr)
 568                 return NULL;
 569         if (sym)
 570                 *sym = NULL;
 571
 572         name = expr_to_var_sym(expr, &tmp);
 573         if (name && tmp) {
 574                 if (sym)
 575                         *sym = tmp;
 576                 return name;
 577         }
 578         if (name)
 579                 free_string(name);
 580
 581         if (expr->type != EXPR_BINOP)
 582                 return NULL;
 583         if (expr->op != '-' && expr->op != '+')
 584                 return NULL;
 585
 586         left_name = expr_to_var(expr->left);
 587         if (!left_name)
 588                 return NULL;
 589         right_name = expr_to_var(expr->right);
 590         if (!right_name) {
 591                 free_string(left_name);
 592                 return NULL;
 593         }
 594         snprintf(buf, sizeof(buf), "%s %s %s", left_name, show_special(expr->op), right_name);
 595         free_string(left_name);
 596         free_string(right_name);
 597         return alloc_string(buf);
 598 }
 599
 600 static char *chunk_to_var(struct expression *expr)
 601 {
 602         return chunk_to_var_sym(expr, NULL);
 603 }
 604
 605 static void save_link(struct expression *expr, char *link)
 606 {
 607         char *var;
 608         struct symbol *sym;
 609
 610         expr = strip_expr(expr);
 611         if (expr->type == EXPR_BINOP) {
 612                 char *chunk;
 613
 614                 chunk = chunk_to_var(expr);
 615                 if (!chunk)
 616                         return;
 617
 618                 save_link(expr->left, link);
 619                 save_link(expr->right, link);
 620                 save_link_var_sym(chunk, NULL, link);
 621                 return;
 622         }
 623
 624         var = expr_to_var_sym(expr, &sym);
 625         if (!var || !sym)
 626                 goto done;
 627
 628         save_link_var_sym(var, sym, link);
 629 done:
 630         free_string(var);
 631 }
 632
 633 static void update_tf_links(struct state_list *pre_slist,
 634                             const char *left_var, struct var_sym_list *left_vsl,
 635                             int left_comparison,
 636                             const char *mid_var, struct var_sym_list *mid_vsl,
 637                             struct string_list *links)
 638 {
 639         struct smatch_state *state;
 640         struct smatch_state *true_state, *false_state;
 641         struct compare_data *data;
 642         const char *right_var;
 643         struct var_sym_list *right_vsl;
 644         int right_comparison;
 645         int true_comparison;
 646         int false_comparison;
 647         char *tmp;
 648         char state_name[256];
 649         struct var_sym *vs;
 650
 651         FOR_EACH_PTR(links, tmp) {
 652                 state = get_state_slist(pre_slist, compare_id, tmp, NULL);
 653                 if (!state || !state->data)
 654                         continue;
 655                 data = state->data;
 656                 right_comparison = data->comparison;
 657                 right_var = data->var2;
 658                 right_vsl = data->vsl2;
 659                 if (chunk_vsl_eq(mid_var, mid_vsl, right_var, right_vsl)) {
 660                         right_var = data->var1;
 661                         right_vsl = data->vsl1;
 662                         right_comparison = flip_op(right_comparison);
 663                 }
 664                 true_comparison = combine_comparisons(left_comparison, right_comparison);
 665                 false_comparison = combine_comparisons(falsify_op(left_comparison), right_comparison);
 666
 667                 if (strcmp(left_var, right_var) > 0) {
 668                         const char *tmp_var = left_var;
 669                         struct var_sym_list *tmp_vsl = left_vsl;
 670
 671                         left_var = right_var;
 672                         left_vsl = right_vsl;
 673                         right_var = tmp_var;
 674                         right_vsl = tmp_vsl;
 675                         true_comparison = flip_op(true_comparison);
 676                         false_comparison = flip_op(false_comparison);
 677                 }
 678
 679                 if (!true_comparison && !false_comparison)
 680                         continue;
 681
 682                 if (true_comparison)
 683                         true_state = alloc_compare_state(left_var, left_vsl, true_comparison, right_var, right_vsl);
 684                 else
 685                         true_state = NULL;
 686                 if (false_comparison)
 687                         false_state = alloc_compare_state(left_var, left_vsl, false_comparison, right_var, right_vsl);
 688                 else
 689                         false_state = NULL;
 690
 691                 snprintf(state_name, sizeof(state_name), "%s vs %s", left_var, right_var);
 692                 set_true_false_states(compare_id, state_name, NULL, true_state, false_state);
 693                 FOR_EACH_PTR(left_vsl, vs) {
 694                         save_link_var_sym(vs->var, vs->sym, state_name);
 695                 } END_FOR_EACH_PTR(vs);
 696                 FOR_EACH_PTR(right_vsl, vs) {
 697                         save_link_var_sym(vs->var, vs->sym, state_name);
 698                 } END_FOR_EACH_PTR(vs);
 699                 if (!vsl_to_sym(left_vsl))
 700                         save_link_var_sym(left_var, NULL, state_name);
 701                 if (!vsl_to_sym(right_vsl))
 702                         save_link_var_sym(right_var, NULL, state_name);
 703         } END_FOR_EACH_PTR(tmp);
 704 }
 705
 706 static void update_tf_data(struct state_list *pre_slist,
 707                 const char *left_name, struct symbol *left_sym,
 708                 const char *right_name, struct symbol *right_sym,
 709                 struct compare_data *tdata)
 710 {
 711         struct smatch_state *state;
 712
 713         state = get_state_slist(pre_slist, link_id, tdata->var2, vsl_to_sym(tdata->vsl2));
 714         if (state)
 715                 update_tf_links(pre_slist, tdata->var1, tdata->vsl1, tdata->comparison, tdata->var2, tdata->vsl2, state->data);
 716
 717         state = get_state_slist(pre_slist, link_id, tdata->var1, vsl_to_sym(tdata->vsl1));
 718         if (state)
 719                 update_tf_links(pre_slist, tdata->var2, tdata->vsl2, flip_op(tdata->comparison), tdata->var1, tdata->vsl1, state->data);
 720 }
 721
 722 static void match_compare(struct expression *expr)
 723 {
 724         char *left = NULL;
 725         char *right = NULL;
 726         struct symbol *left_sym, *right_sym;
 727         struct var_sym_list *left_vsl, *right_vsl;
 728         int op, false_op;
 729         struct smatch_state *true_state, *false_state;
 730         char state_name[256];
 731         struct state_list *pre_slist;
 732
 733         if (expr->type != EXPR_COMPARE)
 734                 return;
 735         left = chunk_to_var_sym(expr->left, &left_sym);
 736         if (!left)
 737                 goto free;
 738         left_vsl = expr_to_vsl(expr->left);
 739         right = chunk_to_var_sym(expr->right, &right_sym);
 740         if (!right)
 741                 goto free;
 742         right_vsl = expr_to_vsl(expr->right);
 743
 744         if (strcmp(left, right) > 0) {
 745                 struct symbol *tmp_sym = left_sym;
 746                 char *tmp_name = left;
 747                 struct var_sym_list *tmp_vsl = left_vsl;
 748
 749                 left = right;
 750                 left_sym = right_sym;
 751                 left_vsl = right_vsl;
 752                 right = tmp_name;
 753                 right_sym = tmp_sym;
 754                 right_vsl = tmp_vsl;
 755                 op = flip_op(expr->op);
 756         } else {
 757                 op = expr->op;
 758         }
 759         false_op = falsify_op(op);
 760         snprintf(state_name, sizeof(state_name), "%s vs %s", left, right);
 761         true_state = alloc_compare_state(left, left_vsl, op, right, right_vsl);
 762         false_state = alloc_compare_state(left, left_vsl, false_op, right, right_vsl);
 763
 764         pre_slist = clone_slist(__get_cur_slist());
 765         update_tf_data(pre_slist, left, left_sym, right, right_sym, true_state->data);
 766         free_slist(&pre_slist);
 767
 768         set_true_false_states(compare_id, state_name, NULL, true_state, false_state);
 769         save_link(expr->left, state_name);
 770         save_link(expr->right, state_name);
 771 free:
 772         free_string(left);
 773         free_string(right);
 774 }
 775
 776 static void add_comparison_var_sym(const char *left_name,
 777                 struct var_sym_list *left_vsl,
 778                 int comparison,
 779                 const char *right_name, struct var_sym_list *right_vsl)
 780 {
 781         struct smatch_state *state;
 782         struct var_sym *vs;
 783         char state_name[256];
 784
 785         if (strcmp(left_name, right_name) > 0) {
 786                 const char *tmp_name = left_name;
 787                 struct var_sym_list *tmp_vsl = left_vsl;
 788
 789                 left_name = right_name;
 790                 left_vsl = right_vsl;
 791                 right_name = tmp_name;
 792                 right_vsl = tmp_vsl;
 793                 comparison = flip_op(comparison);
 794         }
 795         snprintf(state_name, sizeof(state_name), "%s vs %s", left_name, right_name);
 796         state = alloc_compare_state(left_name, left_vsl, comparison, right_name, right_vsl);
 797
 798         set_state(compare_id, state_name, NULL, state);
 799
 800         FOR_EACH_PTR(left_vsl, vs) {
 801                 save_link_var_sym(vs->var, vs->sym, state_name);
 802         } END_FOR_EACH_PTR(vs);
 803         FOR_EACH_PTR(right_vsl, vs) {
 804                 save_link_var_sym(vs->var, vs->sym, state_name);
 805         } END_FOR_EACH_PTR(vs);
 806 }
 807
 808 static void add_comparison(struct expression *left, int comparison, struct expression *right)
 809 {
 810         char *left_name = NULL;
 811         char *right_name = NULL;
 812         struct symbol *left_sym, *right_sym;
 813         struct var_sym_list *left_vsl, *right_vsl;
 814         struct smatch_state *state;
 815         char state_name[256];
 816
 817         left_name = chunk_to_var_sym(left, &left_sym);
 818         if (!left_name)
 819                 goto free;
 820         left_vsl = expr_to_vsl(left);
 821         right_name = chunk_to_var_sym(right, &right_sym);
 822         if (!right_name)
 823                 goto free;
 824         right_vsl = expr_to_vsl(right);
 825
 826         if (strcmp(left_name, right_name) > 0) {
 827                 struct symbol *tmp_sym = left_sym;
 828                 char *tmp_name = left_name;
 829                 struct var_sym_list *tmp_vsl = left_vsl;
 830
 831                 left_name = right_name;
 832                 left_sym = right_sym;
 833                 left_vsl = right_vsl;
 834                 right_name = tmp_name;
 835                 right_sym = tmp_sym;
 836                 right_vsl = tmp_vsl;
 837                 comparison = flip_op(comparison);
 838         }
 839         snprintf(state_name, sizeof(state_name), "%s vs %s", left_name, right_name);
 840         state = alloc_compare_state(left_name, left_vsl, comparison, right_name, right_vsl);
 841
 842         set_state(compare_id, state_name, NULL, state);
 843         save_link(left, state_name);
 844         save_link(right, state_name);
 845
 846 free:
 847         free_string(left_name);
 848         free_string(right_name);
 849 }
 850
 851 static void match_assign_add(struct expression *expr)
 852 {
 853         struct expression *right;
 854         struct expression *r_left, *r_right;
 855         sval_t left_tmp, right_tmp;
 856
 857         right = strip_expr(expr->right);
 858         r_left = strip_expr(right->left);
 859         r_right = strip_expr(right->right);
 860
 861         get_absolute_min(r_left, &left_tmp);
 862         get_absolute_min(r_right, &right_tmp);
 863
 864         if (left_tmp.value > 0)
 865                 add_comparison(expr->left, '>', r_right);
 866         else if (left_tmp.value == 0)
 867                 add_comparison(expr->left, SPECIAL_GTE, r_right);
 868
 869         if (right_tmp.value > 0)
 870                 add_comparison(expr->left, '>', r_left);
 871         else if (right_tmp.value == 0)
 872                 add_comparison(expr->left, SPECIAL_GTE, r_left);
 873 }
 874
 875 static void match_assign_sub(struct expression *expr)
 876 {
 877         struct expression *right;
 878         struct expression *r_left, *r_right;
 879         int comparison;
 880         sval_t min;
 881
 882         right = strip_expr(expr->right);
 883         r_left = strip_expr(right->left);
 884         r_right = strip_expr(right->right);
 885
 886         if (get_absolute_min(r_right, &min) && sval_is_negative(min))
 887                 return;
 888
 889         comparison = get_comparison(r_left, r_right);
 890
 891         switch (comparison) {
 892         case '>':
 893         case SPECIAL_GTE:
 894                 if (implied_not_equal(r_right, 0))
 895                         add_comparison(expr->left, '>', r_left);
 896                 else
 897                         add_comparison(expr->left, SPECIAL_GTE, r_left);
 898                 return;
 899         }
 900 }
 901
 902 static void match_assign_divide(struct expression *expr)
 903 {
 904         struct expression *right;
 905         struct expression *r_left, *r_right;
 906         sval_t min;
 907
 908         right = strip_expr(expr->right);
 909         r_left = strip_expr(right->left);
 910         r_right = strip_expr(right->right);
 911         if (!get_implied_min(r_right, &min) || min.value <= 1)
 912                 return;
 913
 914         add_comparison(expr->left, '<', r_left);
 915 }
 916
 917 static void match_binop_assign(struct expression *expr)
 918 {
 919         struct expression *right;
 920
 921         right = strip_expr(expr->right);
 922         if (right->op == '+')
 923                 match_assign_add(expr);
 924         if (right->op == '-')
 925                 match_assign_sub(expr);
 926         if (right->op == '/')
 927                 match_assign_divide(expr);
 928 }
 929
 930 static void copy_comparisons(struct expression *left, struct expression *right)
 931 {
 932         struct string_list *links;
 933         struct smatch_state *state;
 934         struct compare_data *data;
 935         struct symbol *left_sym, *right_sym;
 936         char *left_var = NULL;
 937         char *right_var = NULL;
 938         struct var_sym_list *left_vsl;
 939         const char *var;
 940         struct var_sym_list *vsl;
 941         int comparison;
 942         char *tmp;
 943
 944         left_var = chunk_to_var_sym(left, &left_sym);
 945         if (!left_var)
 946                 goto done;
 947         left_vsl = expr_to_vsl(left);
 948         right_var = chunk_to_var_sym(right, &right_sym);
 949         if (!right_var)
 950                 goto done;
 951
 952         state = get_state(link_id, right_var, right_sym);
 953         if (!state)
 954                 return;
 955         links = state->data;
 956
 957         FOR_EACH_PTR(links, tmp) {
 958                 state = get_state(compare_id, tmp, NULL);
 959                 if (!state || !state->data)
 960                         continue;
 961                 data = state->data;
 962                 comparison = data->comparison;
 963                 var = data->var2;
 964                 vsl = data->vsl2;
 965                 if (chunk_vsl_eq(var, vsl, right_var, NULL)) {
 966                         var = data->var1;
 967                         vsl = data->vsl1;
 968                         comparison = flip_op(comparison);
 969                 }
 970                 add_comparison_var_sym(left_var, left_vsl, comparison, var, vsl);
 971         } END_FOR_EACH_PTR(tmp);
 972
 973 done:
 974         free_string(right_var);
 975 }
 976
 977 static void match_assign(struct expression *expr)
 978 {
 979         struct expression *right;
 980
 981         if (expr->op != '=')
 982                 return;
 983
 984         copy_comparisons(expr->left, expr->right);
 985         add_comparison(expr->left, SPECIAL_EQUAL, expr->right);
 986
 987         right = strip_expr(expr->right);
 988         if (right->type == EXPR_BINOP)
 989                 match_binop_assign(expr);
 990 }
 991
 992 static int get_comparison_strings(char *one, char *two)
 993 {
 994         char buf[256];
 995         struct smatch_state *state;
 996         int invert = 0;
 997         int ret = 0;
 998
 999         if (strcmp(one, two) > 0) {
1000                 char *tmp = one;
1001
1002                 one = two;
1003                 two = tmp;
1004                 invert = 1;
1005         }
1006
1007         snprintf(buf, sizeof(buf), "%s vs %s", one, two);
1008         state = get_state(compare_id, buf, NULL);
1009         if (state)
1010                 ret = state_to_comparison(state);
1011
1012         if (invert)
1013                 ret = flip_op(ret);
1014
1015         return ret;
1016 }
1017
1018 int get_comparison(struct expression *a, struct expression *b)
1019 {
1020         char *one = NULL;
1021         char *two = NULL;
1022         int ret = 0;
1023
1024         one = chunk_to_var(a);
1025         if (!one)
1026                 goto free;
1027         two = chunk_to_var(b);
1028         if (!two)
1029                 goto free;
1030
1031         ret = get_comparison_strings(one, two);
1032 free:
1033         free_string(one);
1034         free_string(two);
1035         return ret;
1036 }
1037
1038 static void update_links_from_call(struct expression *left,
1039                                    int left_compare,
1040                                    struct expression *right)
1041 {
1042         struct string_list *links;
1043         struct smatch_state *state;
1044         struct compare_data *data;
1045         struct symbol *left_sym, *right_sym;
1046         char *left_var = NULL;
1047         char *right_var = NULL;
1048         struct var_sym_list *left_vsl;
1049         const char *var;
1050         struct var_sym_list *vsl;
1051         int comparison;
1052         char *tmp;
1053
1054         left_var = chunk_to_var_sym(left, &left_sym);
1055         if (!left_var)
1056                 goto done;
1057         left_vsl = expr_to_vsl(left);
1058         right_var = chunk_to_var_sym(right, &right_sym);
1059         if (!right_var)
1060                 goto done;
1061
1062         state = get_state(link_id, right_var, right_sym);
1063         if (!state)
1064                 return;
1065         links = state->data;
1066
1067         FOR_EACH_PTR(links, tmp) {
1068                 state = get_state(compare_id, tmp, NULL);
1069                 if (!state || !state->data)
1070                         continue;
1071                 data = state->data;
1072                 comparison = data->comparison;
1073                 var = data->var2;
1074                 vsl = data->vsl2;
1075                 if (chunk_vsl_eq(var, vsl, right_var, NULL)) {
1076                         var = data->var1;
1077                         vsl = data->vsl1;
1078                         comparison = flip_op(comparison);
1079                 }
1080                 comparison = combine_comparisons(left_compare, comparison);
1081                 if (!comparison)
1082                         continue;
1083                 add_comparison_var_sym(left_var, left_vsl, comparison, var, vsl);
1084         } END_FOR_EACH_PTR(tmp);
1085
1086 done:
1087         free_string(right_var);
1088 }
1089
1090 void __add_comparison_info(struct expression *expr, struct expression *call, const char *range)
1091 {
1092         struct expression *arg;
1093         int comparison;
1094         const char *c = range;
1095
1096         if (!str_to_comparison_arg(c, call, &comparison, &arg))
1097                 return;
1098         update_links_from_call(expr, comparison, arg);
1099         add_comparison(expr, comparison, arg);
1100 }
1101
1102 static char *range_comparison_to_param_helper(struct expression *expr, char starts_with)
1103 {
1104         struct symbol *param;
1105         char *var = NULL;
1106         char buf[256];
1107         char *ret_str = NULL;
1108         int compare;
1109         int i;
1110
1111         var = chunk_to_var(expr);
1112         if (!var)
1113                 goto free;
1114
1115         i = -1;
1116         FOR_EACH_PTR(cur_func_sym->ctype.base_type->arguments, param) {
1117                 i++;
1118                 if (!param->ident)
1119                         continue;
1120                 snprintf(buf, sizeof(buf), "%s orig", param->ident->name);
1121                 compare = get_comparison_strings(var, buf);
1122                 if (!compare)
1123                         continue;
1124                 if (show_special(compare)[0] != starts_with)
1125                         continue;
1126                 snprintf(buf, sizeof(buf), "[%sp%d]", show_special(compare), i);
1127                 ret_str = alloc_sname(buf);
1128                 break;
1129         } END_FOR_EACH_PTR(param);
1130
1131 free:
1132         free_string(var);
1133         return ret_str;
1134 }
1135
1136 char *expr_equal_to_param(struct expression *expr)
1137 {
1138         return range_comparison_to_param_helper(expr, '=');
1139 }
1140
1141 char *expr_lte_to_param(struct expression *expr)
1142 {
1143         return range_comparison_to_param_helper(expr, '<');
1144 }
1145
1146 static void free_data(struct symbol *sym)
1147 {
1148         if (__inline_fn)
1149                 return;
1150         clear_compare_data_alloc();
1151 }
1152
1153 void register_comparison(int id)
1154 {
1155         compare_id = id;
1156         add_hook(&match_compare, CONDITION_HOOK);
1157         add_hook(&match_assign, ASSIGNMENT_HOOK);
1158         add_hook(&save_start_states, AFTER_DEF_HOOK);
1159         add_unmatched_state_hook(compare_id, unmatched_comparison);
1160         add_merge_hook(compare_id, &merge_compare_states);
1161         add_hook(&free_data, AFTER_FUNC_HOOK);
1162 }
1163
1164 void register_comparison_links(int id)
1165 {
1166         link_id = id;
1167         add_merge_hook(link_id, &merge_links);
1168         add_modification_hook(link_id, &match_modify);
1169 }