funcnode.cc

   1 #include "funcnode.h"
   2
   3 FuncNode::FuncNode(ModelHistory * history) :
   4         history(history),
   5         exit_count(0),
   6         func_inst_map(),
   7         inst_list(),
   8         entry_insts(),
   9         predicate_tree_position(),
  10         edge_table(32),
  11         out_edges()
  12 {
  13         predicate_tree_entry = new Predicate(NULL, true);
  14         predicate_tree_entry->add_predicate_expr(NOPREDICATE, NULL, true);
  15
  16         // Memories that are reclaimed after each execution
  17         action_list_buffer = new SnapList<action_list_t *>();
  18         read_locations = new loc_set_t();
  19         write_locations = new loc_set_t();
  20         val_loc_map = new HashTable<uint64_t, loc_set_t *, uint64_t, 0>();
  21         loc_may_equal_map = new HashTable<void *, loc_set_t *, uintptr_t, 0>();
  22         thrd_inst_act_map = new SnapVector<inst_act_map_t *>();
  23
  24         //values_may_read_from = new value_set_t();
  25 }
  26
  27 /* Reallocate snapshotted memories when new executions start */
  28 void FuncNode::set_new_exec_flag()
  29 {
  30         for (mllnode<FuncInst *> * it = inst_list.begin(); it != NULL; it = it->getNext()) {
  31                 FuncInst * inst = it->getVal();
  32                 inst->unset_location();
  33         }
  34
  35         action_list_buffer = new SnapList<action_list_t *>();
  36         read_locations = new loc_set_t();
  37         write_locations = new loc_set_t();
  38         val_loc_map = new HashTable<uint64_t, loc_set_t *, uint64_t, 0>();
  39         loc_may_equal_map = new HashTable<void *, loc_set_t *, uintptr_t, 0>();
  40         thrd_inst_act_map = new SnapVector<inst_act_map_t *>();
  41
  42         //values_may_read_from = new value_set_t();
  43 }
  44
  45 /* Check whether FuncInst with the same type, position, and location
  46  * as act has been added to func_inst_map or not. If not, add it.
  47  *
  48  * Note: currently, actions with the same position are filtered out by process_action,
  49  * so the collision list of FuncInst is not used. May remove it later.
  50  */
  51 void FuncNode::add_inst(ModelAction *act)
  52 {
  53         ASSERT(act);
  54         const char * position = act->get_position();
  55
  56         /* THREAD* actions, ATOMIC_LOCK, ATOMIC_TRYLOCK, and ATOMIC_UNLOCK
  57          * actions are not tagged with their source line numbers
  58          */
  59         if (position == NULL)
  60                 return;
  61
  62         if ( func_inst_map.contains(position) ) {
  63                 FuncInst * inst = func_inst_map.get(position);
  64
  65                 ASSERT(inst->get_type() == act->get_type());
  66
  67                 // locations are set to NULL when new executions start
  68                 if (inst->get_location() == NULL)
  69                         inst->set_location(act->get_location());
  70
  71                 if (inst->get_location() != act->get_location())
  72                         inst->not_single_location();
  73
  74                 return;
  75         }
  76
  77         FuncInst * func_inst = new FuncInst(act, this);
  78
  79         func_inst_map.put(position, func_inst);
  80         inst_list.push_back(func_inst);
  81 }
  82
  83 /* Get the FuncInst with the same type, position, and location
  84  * as act
  85  *
  86  * @return FuncInst with the same type, position, and location as act */
  87 FuncInst * FuncNode::get_inst(ModelAction *act)
  88 {
  89         ASSERT(act);
  90         const char * position = act->get_position();
  91
  92         /* THREAD* actions, ATOMIC_LOCK, ATOMIC_TRYLOCK, and ATOMIC_UNLOCK
  93          * actions are not tagged with their source line numbers
  94          */
  95         if (position == NULL)
  96                 return NULL;
  97
  98         FuncInst * inst = func_inst_map.get(position);
  99         if (inst == NULL)
 100                 return NULL;
 101
 102         action_type inst_type = inst->get_type();
 103         action_type act_type = act->get_type();
 104
 105         // else if branch: an RMWRCAS action is converted to a RMW or READ action
 106         if (inst_type == act_type)
 107                 return inst;
 108         else if (inst_type == ATOMIC_RMWRCAS &&
 109                         (act_type == ATOMIC_RMW || act_type == ATOMIC_READ))
 110                 return inst;
 111
 112         return NULL;
 113 }
 114
 115
 116 void FuncNode::add_entry_inst(FuncInst * inst)
 117 {
 118         if (inst == NULL)
 119                 return;
 120
 121         mllnode<FuncInst *> * it;
 122         for (it = entry_insts.begin(); it != NULL; it = it->getNext()) {
 123                 if (inst == it->getVal())
 124                         return;
 125         }
 126
 127         entry_insts.push_back(inst);
 128 }
 129
 130 /**
 131  * @brief Convert ModelAdtion list to FuncInst list
 132  * @param act_list A list of ModelActions
 133  */
 134 void FuncNode::update_tree(action_list_t * act_list)
 135 {
 136         if (act_list == NULL || act_list->size() == 0)
 137                 return;
 138
 139         HashTable<void *, value_set_t *, uintptr_t, 4> * write_history = history->getWriteHistory();
 140
 141         /* build inst_list from act_list for later processing */
 142         func_inst_list_t inst_list;
 143         action_list_t rw_act_list;
 144
 145         for (sllnode<ModelAction *> * it = act_list->begin(); it != NULL; it = it->getNext()) {
 146                 ModelAction * act = it->getVal();
 147                 FuncInst * func_inst = get_inst(act);
 148                 void * loc = act->get_location();
 149
 150                 if (func_inst == NULL)
 151                         continue;
 152
 153                 inst_list.push_back(func_inst);
 154                 bool act_added = false;
 155
 156                 if (act->is_write()) {
 157                         rw_act_list.push_back(act);
 158                         act_added = true;
 159                         if (!write_locations->contains(loc)) {
 160                                 write_locations->add(loc);
 161                                 history->update_loc_wr_func_nodes_map(loc, this);
 162                         }
 163
 164                 }
 165
 166                 if (act->is_read()) {
 167                         if (!act_added)
 168                                 rw_act_list.push_back(act);
 169
 170                         /* If func_inst may only read_from a single location, then:
 171                          *
 172                          * The first time an action reads from some location,
 173                          * import all the values that have been written to this
 174                          * location from ModelHistory and notify ModelHistory
 175                          * that this FuncNode may read from this location.
 176                          */
 177                         if (!read_locations->contains(loc) && func_inst->is_single_location()) {
 178                                 read_locations->add(loc);
 179                                 value_set_t * write_values = write_history->get(loc);
 180                                 add_to_val_loc_map(write_values, loc);
 181                                 history->update_loc_func_nodes_map(loc, this);
 182                         }
 183                 }
 184         }
 185
 186 //      model_print("function %s\n", func_name);
 187 //      print_val_loc_map();
 188
 189         update_inst_tree(&inst_list);
 190         update_predicate_tree(&rw_act_list);
 191
 192 //      print_predicate_tree();
 193 }
 194
 195 /**
 196  * @brief Link FuncInsts in inst_list  - add one FuncInst to another's predecessors and successors
 197  * @param inst_list A list of FuncInsts
 198  */
 199 void FuncNode::update_inst_tree(func_inst_list_t * inst_list)
 200 {
 201         if (inst_list == NULL)
 202                 return;
 203         else if (inst_list->size() == 0)
 204                 return;
 205
 206         /* start linking */
 207         sllnode<FuncInst *>* it = inst_list->begin();
 208         sllnode<FuncInst *>* prev;
 209
 210         /* add the first instruction to the list of entry insts */
 211         FuncInst * entry_inst = it->getVal();
 212         add_entry_inst(entry_inst);
 213
 214         it = it->getNext();
 215         while (it != NULL) {
 216                 prev = it->getPrev();
 217
 218                 FuncInst * prev_inst = prev->getVal();
 219                 FuncInst * curr_inst = it->getVal();
 220
 221                 prev_inst->add_succ(curr_inst);
 222                 curr_inst->add_pred(prev_inst);
 223
 224                 it = it->getNext();
 225         }
 226 }
 227
 228 void FuncNode::update_predicate_tree(action_list_t * act_list)
 229 {
 230         if (act_list == NULL || act_list->size() == 0)
 231                 return;
 232
 233         /* map a FuncInst to the its predicate */
 234         HashTable<FuncInst *, Predicate *, uintptr_t, 0> inst_pred_map(128);
 235
 236         // number FuncInsts to detect loops
 237         HashTable<FuncInst *, uint32_t, uintptr_t, 0> inst_id_map(128);
 238         uint32_t inst_counter = 0;
 239
 240         HashTable<void *, ModelAction *, uintptr_t, 0> loc_act_map(128);
 241         HashTable<FuncInst *, ModelAction *, uintptr_t, 0> inst_act_map(128);
 242
 243         sllnode<ModelAction *> *it = act_list->begin();
 244         Predicate * curr_pred = predicate_tree_entry;
 245         while (it != NULL) {
 246                 ModelAction * next_act = it->getVal();
 247                 FuncInst * next_inst = get_inst(next_act);
 248
 249                 SnapVector<Predicate *> unset_predicates = SnapVector<Predicate *>();
 250                 bool branch_found = follow_branch(&curr_pred, next_inst, next_act, &inst_act_map, &unset_predicates);
 251
 252                 // A branch with unset predicate expression is detected
 253                 if (!branch_found && unset_predicates.size() != 0) {
 254                         ASSERT(unset_predicates.size() == 1);
 255                         Predicate * one_branch = unset_predicates[0];
 256
 257                         bool amended = amend_predicate_expr(&curr_pred, next_inst, next_act);
 258                         if (amended)
 259                                 continue;
 260                         else {
 261                                 curr_pred = one_branch;
 262                                 branch_found = true;
 263                         }
 264                 }
 265
 266                 // Detect loops
 267                 if (!branch_found && inst_id_map.contains(next_inst)) {
 268                         FuncInst * curr_inst = curr_pred->get_func_inst();
 269                         uint32_t curr_id = inst_id_map.get(curr_inst);
 270                         uint32_t next_id = inst_id_map.get(next_inst);
 271
 272                         if (curr_id >= next_id) {
 273                                 Predicate * old_pred = inst_pred_map.get(next_inst);
 274                                 Predicate * back_pred = old_pred->get_parent();
 275
 276                                 curr_pred->add_backedge(back_pred);
 277                                 curr_pred = back_pred;
 278
 279                                 continue;
 280                         }
 281                 }
 282
 283                 // Generate new branches
 284                 if (!branch_found) {
 285                         SnapVector<struct half_pred_expr *> half_pred_expressions;
 286                         infer_predicates(next_inst, next_act, &loc_act_map, &half_pred_expressions);
 287                         generate_predicates(&curr_pred, next_inst, &half_pred_expressions);
 288                         continue;
 289                 }
 290
 291                 if (next_act->is_write())
 292                         curr_pred->set_write(true);
 293
 294                 inst_pred_map.put(next_inst, curr_pred);
 295                 if (!inst_id_map.contains(next_inst))
 296                         inst_id_map.put(next_inst, inst_counter++);
 297
 298                 loc_act_map.put(next_act->get_location(), next_act);
 299                 inst_act_map.put(next_inst, next_act);
 300                 it = it->getNext();
 301         }
 302 }
 303
 304 /* Given curr_pred and next_inst, find the branch following curr_pred that
 305  * contains next_inst and the correct predicate.
 306  * @return true if branch found, false otherwise.
 307  */
 308 bool FuncNode::follow_branch(Predicate ** curr_pred, FuncInst * next_inst, ModelAction * next_act,
 309         HashTable<FuncInst *, ModelAction *, uintptr_t, 0> * inst_act_map,
 310         SnapVector<Predicate *> * unset_predicates)
 311 {
 312         /* check if a branch with func_inst and corresponding predicate exists */
 313         bool branch_found = false;
 314         ModelVector<Predicate *> * branches = (*curr_pred)->get_children();
 315         for (uint i = 0; i < branches->size(); i++) {
 316                 Predicate * branch = (*branches)[i];
 317                 if (branch->get_func_inst() != next_inst)
 318                         continue;
 319
 320                 /* check against predicate expressions */
 321                 bool predicate_correct = true;
 322                 PredExprSet * pred_expressions = branch->get_pred_expressions();
 323                 PredExprSetIter * pred_expr_it = pred_expressions->iterator();
 324
 325                 /* Only read and rmw actions my have unset predicate expressions */
 326                 if (pred_expressions->getSize() == 0) {
 327                         predicate_correct = false;
 328                         unset_predicates->push_back(branch);
 329                 }
 330
 331                 while (pred_expr_it->hasNext()) {
 332                         pred_expr * pred_expression = pred_expr_it->next();
 333                         uint64_t last_read, next_read;
 334                         bool equality;
 335
 336                         switch(pred_expression->token) {
 337                                 case NOPREDICATE:
 338                                         predicate_correct = true;
 339                                         break;
 340                                 case EQUALITY:
 341                                         FuncInst * to_be_compared;
 342                                         ModelAction * last_act;
 343
 344                                         to_be_compared = pred_expression->func_inst;
 345                                         last_act = inst_act_map->get(to_be_compared);
 346
 347                                         last_read = last_act->get_reads_from_value();
 348                                         next_read = next_act->get_reads_from_value();
 349                                         equality = (last_read == next_read);
 350                                         if (equality != pred_expression->value)
 351                                                 predicate_correct = false;
 352
 353                                         break;
 354                                 case NULLITY:
 355                                         next_read = next_act->get_reads_from_value();
 356                                         equality = ((void*)next_read == NULL);
 357                                         if (equality != pred_expression->value)
 358                                                 predicate_correct = false;
 359                                         break;
 360                                 default:
 361                                         predicate_correct = false;
 362                                         model_print("unkown predicate token\n");
 363                                         break;
 364                         }
 365                 }
 366
 367                 if (predicate_correct) {
 368                         *curr_pred = branch;
 369                         branch_found = true;
 370                         break;
 371                 }
 372         }
 373
 374         return branch_found;
 375 }
 376
 377 /* Infer predicate expressions, which are generated in FuncNode::generate_predicates */
 378 void FuncNode::infer_predicates(FuncInst * next_inst, ModelAction * next_act,
 379         HashTable<void *, ModelAction *, uintptr_t, 0> * loc_act_map,
 380         SnapVector<struct half_pred_expr *> * half_pred_expressions)
 381 {
 382         void * loc = next_act->get_location();
 383
 384         if (next_inst->is_read()) {
 385                 /* read + rmw */
 386                 if ( loc_act_map->contains(loc) ) {
 387                         ModelAction * last_act = loc_act_map->get(loc);
 388                         FuncInst * last_inst = get_inst(last_act);
 389                         struct half_pred_expr * expression = new half_pred_expr(EQUALITY, last_inst);
 390                         half_pred_expressions->push_back(expression);
 391                 } else if ( next_inst->is_single_location() ){
 392                         loc_set_t * loc_may_equal = loc_may_equal_map->get(loc);
 393
 394                         if (loc_may_equal != NULL) {
 395                                 loc_set_iter * loc_it = loc_may_equal->iterator();
 396                                 while (loc_it->hasNext()) {
 397                                         void * neighbor = loc_it->next();
 398                                         if (loc_act_map->contains(neighbor)) {
 399                                                 ModelAction * last_act = loc_act_map->get(neighbor);
 400                                                 FuncInst * last_inst = get_inst(last_act);
 401
 402                                                 struct half_pred_expr * expression = new half_pred_expr(EQUALITY, last_inst);
 403                                                 half_pred_expressions->push_back(expression);
 404                                         }
 405                                 }
 406                         }
 407                 } else {
 408                         // next_inst is not single location
 409                         uint64_t read_val = next_act->get_reads_from_value();
 410
 411                         // only infer NULLITY predicate when it is actually NULL.
 412                         if ( (void*)read_val == NULL) {
 413                                 struct half_pred_expr * expression = new half_pred_expr(NULLITY, NULL);
 414                                 half_pred_expressions->push_back(expression);
 415                         }
 416                 }
 417         } else {
 418                 /* Pure writes */
 419                 // TODO: do anything here?
 420         }
 421 }
 422
 423 /* Able to generate complex predicates when there are multiple predciate expressions */
 424 void FuncNode::generate_predicates(Predicate ** curr_pred, FuncInst * next_inst,
 425         SnapVector<struct half_pred_expr *> * half_pred_expressions)
 426 {
 427         if (half_pred_expressions->size() == 0) {
 428                 Predicate * new_pred = new Predicate(next_inst);
 429                 (*curr_pred)->add_child(new_pred);
 430                 new_pred->set_parent(*curr_pred);
 431
 432                 /* entry predicates and predicates containing pure write actions
 433                  * have no predicate expressions */
 434                 if ( (*curr_pred)->is_entry_predicate() )
 435                         new_pred->add_predicate_expr(NOPREDICATE, NULL, true);
 436                 else if (next_inst->is_write()) {
 437                         /* next_inst->is_write() <==> pure writes */
 438                         new_pred->add_predicate_expr(NOPREDICATE, NULL, true);
 439                 }
 440
 441                 return;
 442         }
 443
 444         SnapVector<Predicate *> predicates;
 445
 446         struct half_pred_expr * half_expr = (*half_pred_expressions)[0];
 447         predicates.push_back(new Predicate(next_inst));
 448         predicates.push_back(new Predicate(next_inst));
 449
 450         predicates[0]->add_predicate_expr(half_expr->token, half_expr->func_inst, true);
 451         predicates[1]->add_predicate_expr(half_expr->token, half_expr->func_inst, false);
 452
 453         for (uint i = 1; i < half_pred_expressions->size(); i++) {
 454                 half_expr = (*half_pred_expressions)[i];
 455
 456                 uint old_size = predicates.size();
 457                 for (uint j = 0; j < old_size; j++) {
 458                         Predicate * pred = predicates[j];
 459                         Predicate * new_pred = new Predicate(next_inst);
 460                         new_pred->copy_predicate_expr(pred);
 461
 462                         pred->add_predicate_expr(half_expr->token, half_expr->func_inst, true);
 463                         new_pred->add_predicate_expr(half_expr->token, half_expr->func_inst, false);
 464
 465                         predicates.push_back(new_pred);
 466                 }
 467         }
 468
 469         for (uint i = 0; i < predicates.size(); i++) {
 470                 Predicate * pred= predicates[i];
 471                 (*curr_pred)->add_child(pred);
 472                 pred->set_parent(*curr_pred);
 473         }
 474 }
 475
 476 /* Amend predicates that contain no predicate expressions. Currenlty only amend with NULLITY predicates */
 477 bool FuncNode::amend_predicate_expr(Predicate ** curr_pred, FuncInst * next_inst, ModelAction * next_act)
 478 {
 479         // there should only be only child
 480         Predicate * unset_pred = (*curr_pred)->get_children()->back();
 481         uint64_t read_val = next_act->get_reads_from_value();
 482
 483         // only generate NULLITY predicate when it is actually NULL.
 484         if ( !next_inst->is_single_location() && (void*)read_val == NULL ) {
 485                 Predicate * new_pred = new Predicate(next_inst);
 486
 487                 (*curr_pred)->add_child(new_pred);
 488                 new_pred->set_parent(*curr_pred);
 489
 490                 unset_pred->add_predicate_expr(NULLITY, NULL, false);
 491                 new_pred->add_predicate_expr(NULLITY, NULL, true);
 492
 493                 return true;
 494         }
 495
 496         return false;
 497 }
 498
 499 void FuncNode::add_to_val_loc_map(uint64_t val, void * loc)
 500 {
 501         loc_set_t * locations = val_loc_map->get(val);
 502
 503         if (locations == NULL) {
 504                 locations = new loc_set_t();
 505                 val_loc_map->put(val, locations);
 506         }
 507
 508         update_loc_may_equal_map(loc, locations);
 509         locations->add(loc);
 510         // values_may_read_from->add(val);
 511 }
 512
 513 void FuncNode::add_to_val_loc_map(value_set_t * values, void * loc)
 514 {
 515         if (values == NULL)
 516                 return;
 517
 518         value_set_iter * it = values->iterator();
 519         while (it->hasNext()) {
 520                 uint64_t val = it->next();
 521                 add_to_val_loc_map(val, loc);
 522         }
 523 }
 524
 525 void FuncNode::update_loc_may_equal_map(void * new_loc, loc_set_t * old_locations)
 526 {
 527         if ( old_locations->contains(new_loc) )
 528                 return;
 529
 530         loc_set_t * neighbors = loc_may_equal_map->get(new_loc);
 531
 532         if (neighbors == NULL) {
 533                 neighbors = new loc_set_t();
 534                 loc_may_equal_map->put(new_loc, neighbors);
 535         }
 536
 537         loc_set_iter * loc_it = old_locations->iterator();
 538         while (loc_it->hasNext()) {
 539                 // new_loc: { old_locations, ... }
 540                 void * member = loc_it->next();
 541                 neighbors->add(member);
 542
 543                 // for each i in old_locations, i : { new_loc, ... }
 544                 loc_set_t * _neighbors = loc_may_equal_map->get(member);
 545                 if (_neighbors == NULL) {
 546                         _neighbors = new loc_set_t();
 547                         loc_may_equal_map->put(member, _neighbors);
 548                 }
 549                 _neighbors->add(new_loc);
 550         }
 551 }
 552
 553 /* Every time a thread enters a function, set its position to the predicate tree entry */
 554 void FuncNode::init_predicate_tree_position(thread_id_t tid)
 555 {
 556         int thread_id = id_to_int(tid);
 557         if (predicate_tree_position.size() <= (uint) thread_id)
 558                 predicate_tree_position.resize(thread_id + 1);
 559
 560         predicate_tree_position[thread_id] = predicate_tree_entry;
 561 }
 562
 563 void FuncNode::set_predicate_tree_position(thread_id_t tid, Predicate * pred)
 564 {
 565         int thread_id = id_to_int(tid);
 566         predicate_tree_position[thread_id] = pred;
 567 }
 568
 569 /* @return The position of a thread in a predicate tree */
 570 Predicate * FuncNode::get_predicate_tree_position(thread_id_t tid)
 571 {
 572         int thread_id = id_to_int(tid);
 573         return predicate_tree_position[thread_id];
 574 }
 575
 576 /* Make sure elements of thrd_inst_act_map are initialized properly when threads enter functions */
 577 void FuncNode::init_inst_act_map(thread_id_t tid)
 578 {
 579         int thread_id = id_to_int(tid);
 580         uint old_size = thrd_inst_act_map->size();
 581
 582         if (thrd_inst_act_map->size() <= (uint) thread_id) {
 583                 uint new_size = thread_id + 1;
 584                 thrd_inst_act_map->resize(new_size);
 585
 586                 for (uint i = old_size; i < new_size; i++)
 587                         (*thrd_inst_act_map)[i] = new inst_act_map_t(128);
 588         }
 589 }
 590
 591 /* Reset elements of thrd_inst_act_map when threads exit functions */
 592 void FuncNode::reset_inst_act_map(thread_id_t tid)
 593 {
 594         int thread_id = id_to_int(tid);
 595         inst_act_map_t * map = (*thrd_inst_act_map)[thread_id];
 596         map->reset();
 597 }
 598
 599 void FuncNode::update_inst_act_map(thread_id_t tid, ModelAction * read_act)
 600 {
 601         int thread_id = id_to_int(tid);
 602         inst_act_map_t * map = (*thrd_inst_act_map)[thread_id];
 603         FuncInst * read_inst = get_inst(read_act);
 604         map->put(read_inst, read_act);
 605 }
 606
 607 inst_act_map_t * FuncNode::get_inst_act_map(thread_id_t tid)
 608 {
 609         int thread_id = id_to_int(tid);
 610         return (*thrd_inst_act_map)[thread_id];
 611 }
 612
 613 /* Add FuncNodes that this node may follow */
 614 void FuncNode::add_out_edge(FuncNode * other)
 615 {
 616         if ( !edge_table.contains(other) ) {
 617                 edge_table.put(other, OUT_EDGE);
 618                 out_edges.push_back(other);
 619                 return;
 620         }
 621
 622         edge_type_t edge = edge_table.get(other);
 623         if (edge == IN_EDGE) {
 624                 edge_table.put(other, BI_EDGE);
 625                 out_edges.push_back(other);
 626         }
 627 }
 628
 629 void FuncNode::print_predicate_tree()
 630 {
 631         model_print("digraph function_%s {\n", func_name);
 632         predicate_tree_entry->print_pred_subtree();
 633         model_print("}\n");     // end of graph
 634 }
 635
 636 void FuncNode::print_val_loc_map()
 637 {
 638 /*
 639         value_set_iter * val_it = values_may_read_from->iterator();
 640         while (val_it->hasNext()) {
 641                 uint64_t value = val_it->next();
 642                 model_print("val %llx: ", value);
 643
 644                 loc_set_t * locations = val_loc_map->get(value);
 645                 loc_set_iter * loc_it = locations->iterator();
 646                 while (loc_it->hasNext()) {
 647                         void * location = loc_it->next();
 648                         model_print("%p ", location);
 649                 }
 650                 model_print("\n");
 651         }
 652 */
 653 }