1 /*
   2  * Copyright (c) 1997, 2021, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/shared/barrierSet.hpp"
  27 #include "gc/shared/c2/barrierSetC2.hpp"
  28 #include "memory/allocation.inline.hpp"
  29 #include "memory/resourceArea.hpp"
  30 #include "opto/block.hpp"
  31 #include "opto/callnode.hpp"
  32 #include "opto/castnode.hpp"
  33 #include "opto/cfgnode.hpp"
  34 #include "opto/idealGraphPrinter.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/machnode.hpp"
  37 #include "opto/opcodes.hpp"
  38 #include "opto/phaseX.hpp"
  39 #include "opto/regalloc.hpp"
  40 #include "opto/rootnode.hpp"
  41 #include "utilities/macros.hpp"
  42 #include "utilities/powerOfTwo.hpp"
  43 
  44 //=============================================================================
  45 #define NODE_HASH_MINIMUM_SIZE    255
  46 //------------------------------NodeHash---------------------------------------
  47 NodeHash::NodeHash(uint est_max_size) :
  48   _a(Thread::current()->resource_area()),
  49   _max( round_up(est_max_size < NODE_HASH_MINIMUM_SIZE ? NODE_HASH_MINIMUM_SIZE : est_max_size) ),
  50   _inserts(0), _insert_limit( insert_limit() ),
  51   _table( NEW_ARENA_ARRAY( _a , Node* , _max ) ) // (Node**)_a->Amalloc(_max * sizeof(Node*)) ),
  52 #ifndef PRODUCT
  53   , _grows(0),_look_probes(0), _lookup_hits(0), _lookup_misses(0),
  54   _insert_probes(0), _delete_probes(0), _delete_hits(0), _delete_misses(0),
  55    _total_inserts(0), _total_insert_probes(0)
  56 #endif
  57 {
  58   // _sentinel must be in the current node space
  59   _sentinel = new ProjNode(NULL, TypeFunc::Control);
  60   memset(_table,0,sizeof(Node*)*_max);
  61 }
  62 
  63 //------------------------------NodeHash---------------------------------------
  64 NodeHash::NodeHash(Arena *arena, uint est_max_size) :
  65   _a(arena),
  66   _max( round_up(est_max_size < NODE_HASH_MINIMUM_SIZE ? NODE_HASH_MINIMUM_SIZE : est_max_size) ),
  67   _inserts(0), _insert_limit( insert_limit() ),
  68   _table( NEW_ARENA_ARRAY( _a , Node* , _max ) )
  69 #ifndef PRODUCT
  70   , _grows(0),_look_probes(0), _lookup_hits(0), _lookup_misses(0),
  71   _insert_probes(0), _delete_probes(0), _delete_hits(0), _delete_misses(0),
  72    _total_inserts(0), _total_insert_probes(0)
  73 #endif
  74 {
  75   // _sentinel must be in the current node space
  76   _sentinel = new ProjNode(NULL, TypeFunc::Control);
  77   memset(_table,0,sizeof(Node*)*_max);
  78 }
  79 
  80 //------------------------------NodeHash---------------------------------------
  81 NodeHash::NodeHash(NodeHash *nh) {
  82   debug_only(_table = (Node**)badAddress);   // interact correctly w/ operator=
  83   // just copy in all the fields
  84   *this = *nh;
  85   // nh->_sentinel must be in the current node space
  86 }
  87 
  88 void NodeHash::replace_with(NodeHash *nh) {
  89   debug_only(_table = (Node**)badAddress);   // interact correctly w/ operator=
  90   // just copy in all the fields
  91   *this = *nh;
  92   // nh->_sentinel must be in the current node space
  93 }
  94 
  95 //------------------------------hash_find--------------------------------------
  96 // Find in hash table
  97 Node *NodeHash::hash_find( const Node *n ) {
  98   // ((Node*)n)->set_hash( n->hash() );
  99   uint hash = n->hash();
 100   if (hash == Node::NO_HASH) {
 101     NOT_PRODUCT( _lookup_misses++ );
 102     return NULL;
 103   }
 104   uint key = hash & (_max-1);
 105   uint stride = key | 0x01;
 106   NOT_PRODUCT( _look_probes++ );
 107   Node *k = _table[key];        // Get hashed value
 108   if( !k ) {                    // ?Miss?
 109     NOT_PRODUCT( _lookup_misses++ );
 110     return NULL;                // Miss!
 111   }
 112 
 113   int op = n->Opcode();
 114   uint req = n->req();
 115   while( 1 ) {                  // While probing hash table
 116     if( k->req() == req &&      // Same count of inputs
 117         k->Opcode() == op ) {   // Same Opcode
 118       for( uint i=0; i<req; i++ )
 119         if( n->in(i)!=k->in(i)) // Different inputs?
 120           goto collision;       // "goto" is a speed hack...
 121       if( n->cmp(*k) ) {        // Check for any special bits
 122         NOT_PRODUCT( _lookup_hits++ );
 123         return k;               // Hit!
 124       }
 125     }
 126   collision:
 127     NOT_PRODUCT( _look_probes++ );
 128     key = (key + stride/*7*/) & (_max-1); // Stride through table with relative prime
 129     k = _table[key];            // Get hashed value
 130     if( !k ) {                  // ?Miss?
 131       NOT_PRODUCT( _lookup_misses++ );
 132       return NULL;              // Miss!
 133     }
 134   }
 135   ShouldNotReachHere();
 136   return NULL;
 137 }
 138 
 139 //------------------------------hash_find_insert-------------------------------
 140 // Find in hash table, insert if not already present
 141 // Used to preserve unique entries in hash table
 142 Node *NodeHash::hash_find_insert( Node *n ) {
 143   // n->set_hash( );
 144   uint hash = n->hash();
 145   if (hash == Node::NO_HASH) {
 146     NOT_PRODUCT( _lookup_misses++ );
 147     return NULL;
 148   }
 149   uint key = hash & (_max-1);
 150   uint stride = key | 0x01;     // stride must be relatively prime to table siz
 151   uint first_sentinel = 0;      // replace a sentinel if seen.
 152   NOT_PRODUCT( _look_probes++ );
 153   Node *k = _table[key];        // Get hashed value
 154   if( !k ) {                    // ?Miss?
 155     NOT_PRODUCT( _lookup_misses++ );
 156     _table[key] = n;            // Insert into table!
 157     debug_only(n->enter_hash_lock()); // Lock down the node while in the table.
 158     check_grow();               // Grow table if insert hit limit
 159     return NULL;                // Miss!
 160   }
 161   else if( k == _sentinel ) {
 162     first_sentinel = key;      // Can insert here
 163   }
 164 
 165   int op = n->Opcode();
 166   uint req = n->req();
 167   while( 1 ) {                  // While probing hash table
 168     if( k->req() == req &&      // Same count of inputs
 169         k->Opcode() == op ) {   // Same Opcode
 170       for( uint i=0; i<req; i++ )
 171         if( n->in(i)!=k->in(i)) // Different inputs?
 172           goto collision;       // "goto" is a speed hack...
 173       if( n->cmp(*k) ) {        // Check for any special bits
 174         NOT_PRODUCT( _lookup_hits++ );
 175         return k;               // Hit!
 176       }
 177     }
 178   collision:
 179     NOT_PRODUCT( _look_probes++ );
 180     key = (key + stride) & (_max-1); // Stride through table w/ relative prime
 181     k = _table[key];            // Get hashed value
 182     if( !k ) {                  // ?Miss?
 183       NOT_PRODUCT( _lookup_misses++ );
 184       key = (first_sentinel == 0) ? key : first_sentinel; // ?saw sentinel?
 185       _table[key] = n;          // Insert into table!
 186       debug_only(n->enter_hash_lock()); // Lock down the node while in the table.
 187       check_grow();             // Grow table if insert hit limit
 188       return NULL;              // Miss!
 189     }
 190     else if( first_sentinel == 0 && k == _sentinel ) {
 191       first_sentinel = key;    // Can insert here
 192     }
 193 
 194   }
 195   ShouldNotReachHere();
 196   return NULL;
 197 }
 198 
 199 //------------------------------hash_insert------------------------------------
 200 // Insert into hash table
 201 void NodeHash::hash_insert( Node *n ) {
 202   // // "conflict" comments -- print nodes that conflict
 203   // bool conflict = false;
 204   // n->set_hash();
 205   uint hash = n->hash();
 206   if (hash == Node::NO_HASH) {
 207     return;
 208   }
 209   check_grow();
 210   uint key = hash & (_max-1);
 211   uint stride = key | 0x01;
 212 
 213   while( 1 ) {                  // While probing hash table
 214     NOT_PRODUCT( _insert_probes++ );
 215     Node *k = _table[key];      // Get hashed value
 216     if( !k || (k == _sentinel) ) break;       // Found a slot
 217     assert( k != n, "already inserted" );
 218     // if( PrintCompilation && PrintOptoStatistics && Verbose ) { tty->print("  conflict: "); k->dump(); conflict = true; }
 219     key = (key + stride) & (_max-1); // Stride through table w/ relative prime
 220   }
 221   _table[key] = n;              // Insert into table!
 222   debug_only(n->enter_hash_lock()); // Lock down the node while in the table.
 223   // if( conflict ) { n->dump(); }
 224 }
 225 
 226 //------------------------------hash_delete------------------------------------
 227 // Replace in hash table with sentinel
 228 bool NodeHash::hash_delete( const Node *n ) {
 229   Node *k;
 230   uint hash = n->hash();
 231   if (hash == Node::NO_HASH) {
 232     NOT_PRODUCT( _delete_misses++ );
 233     return false;
 234   }
 235   uint key = hash & (_max-1);
 236   uint stride = key | 0x01;
 237   debug_only( uint counter = 0; );
 238   for( ; /* (k != NULL) && (k != _sentinel) */; ) {
 239     debug_only( counter++ );
 240     NOT_PRODUCT( _delete_probes++ );
 241     k = _table[key];            // Get hashed value
 242     if( !k ) {                  // Miss?
 243       NOT_PRODUCT( _delete_misses++ );
 244       return false;             // Miss! Not in chain
 245     }
 246     else if( n == k ) {
 247       NOT_PRODUCT( _delete_hits++ );
 248       _table[key] = _sentinel;  // Hit! Label as deleted entry
 249       debug_only(((Node*)n)->exit_hash_lock()); // Unlock the node upon removal from table.
 250       return true;
 251     }
 252     else {
 253       // collision: move through table with prime offset
 254       key = (key + stride/*7*/) & (_max-1);
 255       assert( counter <= _insert_limit, "Cycle in hash-table");
 256     }
 257   }
 258   ShouldNotReachHere();
 259   return false;
 260 }
 261 
 262 //------------------------------round_up---------------------------------------
 263 // Round up to nearest power of 2
 264 uint NodeHash::round_up(uint x) {
 265   x += (x >> 2);                  // Add 25% slop
 266   return MAX2(16U, round_up_power_of_2(x));
 267 }
 268 
 269 //------------------------------grow-------------------------------------------
 270 // Grow _table to next power of 2 and insert old entries
 271 void  NodeHash::grow() {
 272   // Record old state
 273   uint   old_max   = _max;
 274   Node **old_table = _table;
 275   // Construct new table with twice the space
 276 #ifndef PRODUCT
 277   _grows++;
 278   _total_inserts       += _inserts;
 279   _total_insert_probes += _insert_probes;
 280   _insert_probes   = 0;
 281 #endif
 282   _inserts         = 0;
 283   _max     = _max << 1;
 284   _table   = NEW_ARENA_ARRAY( _a , Node* , _max ); // (Node**)_a->Amalloc( _max * sizeof(Node*) );
 285   memset(_table,0,sizeof(Node*)*_max);
 286   _insert_limit = insert_limit();
 287   // Insert old entries into the new table
 288   for( uint i = 0; i < old_max; i++ ) {
 289     Node *m = *old_table++;
 290     if( !m || m == _sentinel ) continue;
 291     debug_only(m->exit_hash_lock()); // Unlock the node upon removal from old table.
 292     hash_insert(m);
 293   }
 294 }
 295 
 296 //------------------------------clear------------------------------------------
 297 // Clear all entries in _table to NULL but keep storage
 298 void  NodeHash::clear() {
 299 #ifdef ASSERT
 300   // Unlock all nodes upon removal from table.
 301   for (uint i = 0; i < _max; i++) {
 302     Node* n = _table[i];
 303     if (!n || n == _sentinel)  continue;
 304     n->exit_hash_lock();
 305   }
 306 #endif
 307 
 308   memset( _table, 0, _max * sizeof(Node*) );
 309 }
 310 
 311 //-----------------------remove_useless_nodes----------------------------------
 312 // Remove useless nodes from value table,
 313 // implementation does not depend on hash function
 314 void NodeHash::remove_useless_nodes(VectorSet &useful) {
 315 
 316   // Dead nodes in the hash table inherited from GVN should not replace
 317   // existing nodes, remove dead nodes.
 318   uint max = size();
 319   Node *sentinel_node = sentinel();
 320   for( uint i = 0; i < max; ++i ) {
 321     Node *n = at(i);
 322     if(n != NULL && n != sentinel_node && !useful.test(n->_idx)) {
 323       debug_only(n->exit_hash_lock()); // Unlock the node when removed
 324       _table[i] = sentinel_node;       // Replace with placeholder
 325     }
 326   }
 327 }
 328 
 329 
 330 void NodeHash::check_no_speculative_types() {
 331 #ifdef ASSERT
 332   uint max = size();
 333   Unique_Node_List live_nodes;
 334   Compile::current()->identify_useful_nodes(live_nodes);
 335   Node *sentinel_node = sentinel();
 336   for (uint i = 0; i < max; ++i) {
 337     Node *n = at(i);
 338     if (n != NULL &&
 339         n != sentinel_node &&
 340         n->is_Type() &&
 341         live_nodes.member(n)) {
 342       TypeNode* tn = n->as_Type();
 343       const Type* t = tn->type();
 344       const Type* t_no_spec = t->remove_speculative();
 345       assert(t == t_no_spec, "dead node in hash table or missed node during speculative cleanup");
 346     }
 347   }
 348 #endif
 349 }
 350 
 351 #ifndef PRODUCT
 352 //------------------------------dump-------------------------------------------
 353 // Dump statistics for the hash table
 354 void NodeHash::dump() {
 355   _total_inserts       += _inserts;
 356   _total_insert_probes += _insert_probes;
 357   if (PrintCompilation && PrintOptoStatistics && Verbose && (_inserts > 0)) {
 358     if (WizardMode) {
 359       for (uint i=0; i<_max; i++) {
 360         if (_table[i])
 361           tty->print("%d/%d/%d ",i,_table[i]->hash()&(_max-1),_table[i]->_idx);
 362       }
 363     }
 364     tty->print("\nGVN Hash stats:  %d grows to %d max_size\n", _grows, _max);
 365     tty->print("  %d/%d (%8.1f%% full)\n", _inserts, _max, (double)_inserts/_max*100.0);
 366     tty->print("  %dp/(%dh+%dm) (%8.2f probes/lookup)\n", _look_probes, _lookup_hits, _lookup_misses, (double)_look_probes/(_lookup_hits+_lookup_misses));
 367     tty->print("  %dp/%di (%8.2f probes/insert)\n", _total_insert_probes, _total_inserts, (double)_total_insert_probes/_total_inserts);
 368     // sentinels increase lookup cost, but not insert cost
 369     assert((_lookup_misses+_lookup_hits)*4+100 >= _look_probes, "bad hash function");
 370     assert( _inserts+(_inserts>>3) < _max, "table too full" );
 371     assert( _inserts*3+100 >= _insert_probes, "bad hash function" );
 372   }
 373 }
 374 
 375 Node *NodeHash::find_index(uint idx) { // For debugging
 376   // Find an entry by its index value
 377   for( uint i = 0; i < _max; i++ ) {
 378     Node *m = _table[i];
 379     if( !m || m == _sentinel ) continue;
 380     if( m->_idx == (uint)idx ) return m;
 381   }
 382   return NULL;
 383 }
 384 #endif
 385 
 386 #ifdef ASSERT
 387 NodeHash::~NodeHash() {
 388   // Unlock all nodes upon destruction of table.
 389   if (_table != (Node**)badAddress)  clear();
 390 }
 391 
 392 void NodeHash::operator=(const NodeHash& nh) {
 393   // Unlock all nodes upon replacement of table.
 394   if (&nh == this)  return;
 395   if (_table != (Node**)badAddress)  clear();
 396   memcpy((void*)this, (void*)&nh, sizeof(*this));
 397   // Do not increment hash_lock counts again.
 398   // Instead, be sure we never again use the source table.
 399   ((NodeHash*)&nh)->_table = (Node**)badAddress;
 400 }
 401 
 402 
 403 #endif
 404 
 405 
 406 //=============================================================================
 407 //------------------------------PhaseRemoveUseless-----------------------------
 408 // 1) Use a breadthfirst walk to collect useful nodes reachable from root.
 409 PhaseRemoveUseless::PhaseRemoveUseless(PhaseGVN* gvn, Unique_Node_List* worklist, PhaseNumber phase_num) : Phase(phase_num) {
 410   // Implementation requires an edge from root to each SafePointNode
 411   // at a backward branch. Inserted in add_safepoint().
 412 
 413   // Identify nodes that are reachable from below, useful.
 414   C->identify_useful_nodes(_useful);
 415   // Update dead node list
 416   C->update_dead_node_list(_useful);
 417 
 418   // Remove all useless nodes from PhaseValues' recorded types
 419   // Must be done before disconnecting nodes to preserve hash-table-invariant
 420   gvn->remove_useless_nodes(_useful.member_set());
 421 
 422   // Remove all useless nodes from future worklist
 423   worklist->remove_useless_nodes(_useful.member_set());
 424 
 425   // Disconnect 'useless' nodes that are adjacent to useful nodes
 426   C->remove_useless_nodes(_useful);
 427 }
 428 
 429 //=============================================================================
 430 //------------------------------PhaseRenumberLive------------------------------
 431 // First, remove useless nodes (equivalent to identifying live nodes).
 432 // Then, renumber live nodes.
 433 //
 434 // The set of live nodes is returned by PhaseRemoveUseless in the _useful structure.
 435 // If the number of live nodes is 'x' (where 'x' == _useful.size()), then the
 436 // PhaseRenumberLive updates the node ID of each node (the _idx field) with a unique
 437 // value in the range [0, x).
 438 //
 439 // At the end of the PhaseRenumberLive phase, the compiler's count of unique nodes is
 440 // updated to 'x' and the list of dead nodes is reset (as there are no dead nodes).
 441 //
 442 // The PhaseRenumberLive phase updates two data structures with the new node IDs.
 443 // (1) The worklist is used by the PhaseIterGVN phase to identify nodes that must be
 444 // processed. A new worklist (with the updated node IDs) is returned in 'new_worklist'.
 445 // 'worklist' is cleared upon returning.
 446 // (2) Type information (the field PhaseGVN::_types) maps type information to each
 447 // node ID. The mapping is updated to use the new node IDs as well. Updated type
 448 // information is returned in PhaseGVN::_types.
 449 //
 450 // The PhaseRenumberLive phase does not preserve the order of elements in the worklist.
 451 //
 452 // Other data structures used by the compiler are not updated. The hash table for value
 453 // numbering (the field PhaseGVN::_table) is not updated because computing the hash
 454 // values is not based on node IDs. The field PhaseGVN::_nodes is not updated either
 455 // because it is empty wherever PhaseRenumberLive is used.
 456 PhaseRenumberLive::PhaseRenumberLive(PhaseGVN* gvn,
 457                                      Unique_Node_List* worklist, Unique_Node_List* new_worklist,
 458                                      PhaseNumber phase_num) :
 459   PhaseRemoveUseless(gvn, worklist, Remove_Useless_And_Renumber_Live),
 460   _new_type_array(C->comp_arena()),
 461   _old2new_map(C->unique(), C->unique(), -1),
 462   _is_pass_finished(false),
 463   _live_node_count(C->live_nodes())
 464 {
 465   assert(RenumberLiveNodes, "RenumberLiveNodes must be set to true for node renumbering to take place");
 466   assert(C->live_nodes() == _useful.size(), "the number of live nodes must match the number of useful nodes");
 467   assert(gvn->nodes_size() == 0, "GVN must not contain any nodes at this point");
 468   assert(_delayed.size() == 0, "should be empty");
 469 
 470   uint worklist_size = worklist->size();
 471 
 472   // Iterate over the set of live nodes.
 473   for (uint current_idx = 0; current_idx < _useful.size(); current_idx++) {
 474     Node* n = _useful.at(current_idx);
 475 
 476     bool in_worklist = false;
 477     if (worklist->member(n)) {
 478       in_worklist = true;
 479     }
 480 
 481     const Type* type = gvn->type_or_null(n);
 482     _new_type_array.map(current_idx, type);
 483 
 484     assert(_old2new_map.at(n->_idx) == -1, "already seen");
 485     _old2new_map.at_put(n->_idx, current_idx);
 486 
 487     n->set_idx(current_idx); // Update node ID.
 488 
 489     if (in_worklist) {
 490       new_worklist->push(n);
 491     }
 492 
 493     if (update_embedded_ids(n) < 0) {
 494       _delayed.push(n); // has embedded IDs; handle later
 495     }
 496   }
 497 
 498   assert(worklist_size == new_worklist->size(), "the new worklist must have the same size as the original worklist");
 499   assert(_live_node_count == _useful.size(), "all live nodes must be processed");
 500 
 501   _is_pass_finished = true; // pass finished; safe to process delayed updates
 502 
 503   while (_delayed.size() > 0) {
 504     Node* n = _delayed.pop();
 505     int no_of_updates = update_embedded_ids(n);
 506     assert(no_of_updates > 0, "should be updated");
 507   }
 508 
 509   // Replace the compiler's type information with the updated type information.
 510   gvn->replace_types(_new_type_array);
 511 
 512   // Update the unique node count of the compilation to the number of currently live nodes.
 513   C->set_unique(_live_node_count);
 514 
 515   // Set the dead node count to 0 and reset dead node list.
 516   C->reset_dead_node_list();
 517 
 518   // Clear the original worklist
 519   worklist->clear();
 520 }
 521 
 522 int PhaseRenumberLive::new_index(int old_idx) {
 523   assert(_is_pass_finished, "not finished");
 524   if (_old2new_map.at(old_idx) == -1) { // absent
 525     // Allocate a placeholder to preserve uniqueness
 526     _old2new_map.at_put(old_idx, _live_node_count);
 527     _live_node_count++;
 528   }
 529   return _old2new_map.at(old_idx);
 530 }
 531 
 532 int PhaseRenumberLive::update_embedded_ids(Node* n) {
 533   int no_of_updates = 0;
 534   if (n->is_Phi()) {
 535     PhiNode* phi = n->as_Phi();
 536     if (phi->_inst_id != -1) {
 537       if (!_is_pass_finished) {
 538         return -1; // delay
 539       }
 540       int new_idx = new_index(phi->_inst_id);
 541       assert(new_idx != -1, "");
 542       phi->_inst_id = new_idx;
 543       no_of_updates++;
 544     }
 545     if (phi->_inst_mem_id != -1) {
 546       if (!_is_pass_finished) {
 547         return -1; // delay
 548       }
 549       int new_idx = new_index(phi->_inst_mem_id);
 550       assert(new_idx != -1, "");
 551       phi->_inst_mem_id = new_idx;
 552       no_of_updates++;
 553     }
 554   }
 555 
 556   const Type* type = _new_type_array.fast_lookup(n->_idx);
 557   if (type != NULL && type->isa_oopptr() && type->is_oopptr()->is_known_instance()) {
 558     if (!_is_pass_finished) {
 559         return -1; // delay
 560     }
 561     int old_idx = type->is_oopptr()->instance_id();
 562     int new_idx = new_index(old_idx);
 563     const Type* new_type = type->is_oopptr()->with_instance_id(new_idx);
 564     _new_type_array.map(n->_idx, new_type);
 565     no_of_updates++;
 566   }
 567 
 568   return no_of_updates;
 569 }
 570 
 571 //=============================================================================
 572 //------------------------------PhaseTransform---------------------------------
 573 PhaseTransform::PhaseTransform( PhaseNumber pnum ) : Phase(pnum),
 574   _arena(Thread::current()->resource_area()),
 575   _nodes(_arena),
 576   _types(_arena)
 577 {
 578   init_con_caches();
 579 #ifndef PRODUCT
 580   clear_progress();
 581   clear_transforms();
 582   set_allow_progress(true);
 583 #endif
 584   // Force allocation for currently existing nodes
 585   _types.map(C->unique(), NULL);
 586 }
 587 
 588 //------------------------------PhaseTransform---------------------------------
 589 PhaseTransform::PhaseTransform( Arena *arena, PhaseNumber pnum ) : Phase(pnum),
 590   _arena(arena),
 591   _nodes(arena),
 592   _types(arena)
 593 {
 594   init_con_caches();
 595 #ifndef PRODUCT
 596   clear_progress();
 597   clear_transforms();
 598   set_allow_progress(true);
 599 #endif
 600   // Force allocation for currently existing nodes
 601   _types.map(C->unique(), NULL);
 602 }
 603 
 604 //------------------------------PhaseTransform---------------------------------
 605 // Initialize with previously generated type information
 606 PhaseTransform::PhaseTransform( PhaseTransform *pt, PhaseNumber pnum ) : Phase(pnum),
 607   _arena(pt->_arena),
 608   _nodes(pt->_nodes),
 609   _types(pt->_types)
 610 {
 611   init_con_caches();
 612 #ifndef PRODUCT
 613   clear_progress();
 614   clear_transforms();
 615   set_allow_progress(true);
 616 #endif
 617 }
 618 
 619 void PhaseTransform::init_con_caches() {
 620   memset(_icons,0,sizeof(_icons));
 621   memset(_lcons,0,sizeof(_lcons));
 622   memset(_zcons,0,sizeof(_zcons));
 623 }
 624 
 625 
 626 //--------------------------------find_int_type--------------------------------
 627 const TypeInt* PhaseTransform::find_int_type(Node* n) {
 628   if (n == NULL)  return NULL;
 629   // Call type_or_null(n) to determine node's type since we might be in
 630   // parse phase and call n->Value() may return wrong type.
 631   // (For example, a phi node at the beginning of loop parsing is not ready.)
 632   const Type* t = type_or_null(n);
 633   if (t == NULL)  return NULL;
 634   return t->isa_int();
 635 }
 636 
 637 
 638 //-------------------------------find_long_type--------------------------------
 639 const TypeLong* PhaseTransform::find_long_type(Node* n) {
 640   if (n == NULL)  return NULL;
 641   // (See comment above on type_or_null.)
 642   const Type* t = type_or_null(n);
 643   if (t == NULL)  return NULL;
 644   return t->isa_long();
 645 }
 646 
 647 
 648 #ifndef PRODUCT
 649 void PhaseTransform::dump_old2new_map() const {
 650   _nodes.dump();
 651 }
 652 
 653 void PhaseTransform::dump_new( uint nidx ) const {
 654   for( uint i=0; i<_nodes.Size(); i++ )
 655     if( _nodes[i] && _nodes[i]->_idx == nidx ) {
 656       _nodes[i]->dump();
 657       tty->cr();
 658       tty->print_cr("Old index= %d",i);
 659       return;
 660     }
 661   tty->print_cr("Node %d not found in the new indices", nidx);
 662 }
 663 
 664 //------------------------------dump_types-------------------------------------
 665 void PhaseTransform::dump_types( ) const {
 666   _types.dump();
 667 }
 668 
 669 //------------------------------dump_nodes_and_types---------------------------
 670 void PhaseTransform::dump_nodes_and_types(const Node* root, uint depth, bool only_ctrl) {
 671   VectorSet visited;
 672   dump_nodes_and_types_recur(root, depth, only_ctrl, visited);
 673 }
 674 
 675 //------------------------------dump_nodes_and_types_recur---------------------
 676 void PhaseTransform::dump_nodes_and_types_recur( const Node *n, uint depth, bool only_ctrl, VectorSet &visited) {
 677   if( !n ) return;
 678   if( depth == 0 ) return;
 679   if( visited.test_set(n->_idx) ) return;
 680   for( uint i=0; i<n->len(); i++ ) {
 681     if( only_ctrl && !(n->is_Region()) && i != TypeFunc::Control ) continue;
 682     dump_nodes_and_types_recur( n->in(i), depth-1, only_ctrl, visited );
 683   }
 684   n->dump();
 685   if (type_or_null(n) != NULL) {
 686     tty->print("      "); type(n)->dump(); tty->cr();
 687   }
 688 }
 689 
 690 #endif
 691 
 692 
 693 //=============================================================================
 694 //------------------------------PhaseValues------------------------------------
 695 // Set minimum table size to "255"
 696 PhaseValues::PhaseValues( Arena *arena, uint est_max_size )
 697   : PhaseTransform(arena, GVN), _table(arena, est_max_size), _iterGVN(false) {
 698   NOT_PRODUCT( clear_new_values(); )
 699 }
 700 
 701 //------------------------------PhaseValues------------------------------------
 702 // Set minimum table size to "255"
 703 PhaseValues::PhaseValues(PhaseValues* ptv)
 704   : PhaseTransform(ptv, GVN), _table(&ptv->_table), _iterGVN(false) {
 705   NOT_PRODUCT( clear_new_values(); )
 706 }
 707 
 708 //------------------------------~PhaseValues-----------------------------------
 709 #ifndef PRODUCT
 710 PhaseValues::~PhaseValues() {
 711   _table.dump();
 712 
 713   // Statistics for value progress and efficiency
 714   if( PrintCompilation && Verbose && WizardMode ) {
 715     tty->print("\n%sValues: %d nodes ---> %d/%d (%d)",
 716       is_IterGVN() ? "Iter" : "    ", C->unique(), made_progress(), made_transforms(), made_new_values());
 717     if( made_transforms() != 0 ) {
 718       tty->print_cr("  ratio %f", made_progress()/(float)made_transforms() );
 719     } else {
 720       tty->cr();
 721     }
 722   }
 723 }
 724 #endif
 725 
 726 //------------------------------makecon----------------------------------------
 727 ConNode* PhaseTransform::makecon(const Type *t) {
 728   assert(t->singleton(), "must be a constant");
 729   assert(!t->empty() || t == Type::TOP, "must not be vacuous range");
 730   switch (t->base()) {  // fast paths
 731   case Type::Half:
 732   case Type::Top:  return (ConNode*) C->top();
 733   case Type::Int:  return intcon( t->is_int()->get_con() );
 734   case Type::Long: return longcon( t->is_long()->get_con() );
 735   default:         break;
 736   }
 737   if (t->is_zero_type())
 738     return zerocon(t->basic_type());
 739   return uncached_makecon(t);
 740 }
 741 
 742 //--------------------------uncached_makecon-----------------------------------
 743 // Make an idealized constant - one of ConINode, ConPNode, etc.
 744 ConNode* PhaseValues::uncached_makecon(const Type *t) {
 745   assert(t->singleton(), "must be a constant");
 746   ConNode* x = ConNode::make(t);
 747   ConNode* k = (ConNode*)hash_find_insert(x); // Value numbering
 748   if (k == NULL) {
 749     set_type(x, t);             // Missed, provide type mapping
 750     GrowableArray<Node_Notes*>* nna = C->node_note_array();
 751     if (nna != NULL) {
 752       Node_Notes* loc = C->locate_node_notes(nna, x->_idx, true);
 753       loc->clear(); // do not put debug info on constants
 754     }
 755   } else {
 756     x->destruct(this);          // Hit, destroy duplicate constant
 757     x = k;                      // use existing constant
 758   }
 759   return x;
 760 }
 761 
 762 //------------------------------intcon-----------------------------------------
 763 // Fast integer constant.  Same as "transform(new ConINode(TypeInt::make(i)))"
 764 ConINode* PhaseTransform::intcon(jint i) {
 765   // Small integer?  Check cache! Check that cached node is not dead
 766   if (i >= _icon_min && i <= _icon_max) {
 767     ConINode* icon = _icons[i-_icon_min];
 768     if (icon != NULL && icon->in(TypeFunc::Control) != NULL)
 769       return icon;
 770   }
 771   ConINode* icon = (ConINode*) uncached_makecon(TypeInt::make(i));
 772   assert(icon->is_Con(), "");
 773   if (i >= _icon_min && i <= _icon_max)
 774     _icons[i-_icon_min] = icon;   // Cache small integers
 775   return icon;
 776 }
 777 
 778 //------------------------------longcon----------------------------------------
 779 // Fast long constant.
 780 ConLNode* PhaseTransform::longcon(jlong l) {
 781   // Small integer?  Check cache! Check that cached node is not dead
 782   if (l >= _lcon_min && l <= _lcon_max) {
 783     ConLNode* lcon = _lcons[l-_lcon_min];
 784     if (lcon != NULL && lcon->in(TypeFunc::Control) != NULL)
 785       return lcon;
 786   }
 787   ConLNode* lcon = (ConLNode*) uncached_makecon(TypeLong::make(l));
 788   assert(lcon->is_Con(), "");
 789   if (l >= _lcon_min && l <= _lcon_max)
 790     _lcons[l-_lcon_min] = lcon;      // Cache small integers
 791   return lcon;
 792 }
 793 ConNode* PhaseTransform::integercon(jlong l, BasicType bt) {
 794   if (bt == T_INT) {
 795     jint int_con = (jint)l;
 796     assert(((long)int_con) == l, "not an int");
 797     return intcon(int_con);
 798   }
 799   assert(bt == T_LONG, "not an integer");
 800   return longcon(l);
 801 }
 802 
 803 
 804 //------------------------------zerocon-----------------------------------------
 805 // Fast zero or null constant. Same as "transform(ConNode::make(Type::get_zero_type(bt)))"
 806 ConNode* PhaseTransform::zerocon(BasicType bt) {
 807   assert((uint)bt <= _zcon_max, "domain check");
 808   ConNode* zcon = _zcons[bt];
 809   if (zcon != NULL && zcon->in(TypeFunc::Control) != NULL)
 810     return zcon;
 811   zcon = (ConNode*) uncached_makecon(Type::get_zero_type(bt));
 812   _zcons[bt] = zcon;
 813   return zcon;
 814 }
 815 
 816 
 817 
 818 //=============================================================================
 819 Node* PhaseGVN::apply_ideal(Node* k, bool can_reshape) {
 820   Node* i = BarrierSet::barrier_set()->barrier_set_c2()->ideal_node(this, k, can_reshape);
 821   if (i == NULL) {
 822     i = k->Ideal(this, can_reshape);
 823   }
 824   return i;
 825 }
 826 
 827 //------------------------------transform--------------------------------------
 828 // Return a node which computes the same function as this node, but in a
 829 // faster or cheaper fashion.
 830 Node *PhaseGVN::transform( Node *n ) {
 831   return transform_no_reclaim(n);
 832 }
 833 
 834 //------------------------------transform--------------------------------------
 835 // Return a node which computes the same function as this node, but
 836 // in a faster or cheaper fashion.
 837 Node *PhaseGVN::transform_no_reclaim(Node *n) {
 838   NOT_PRODUCT( set_transforms(); )
 839 
 840   // Apply the Ideal call in a loop until it no longer applies
 841   Node* k = n;
 842   Node* i = apply_ideal(k, /*can_reshape=*/false);
 843   NOT_PRODUCT(uint loop_count = 1;)
 844   while (i != NULL) {
 845     assert(i->_idx >= k->_idx, "Idealize should return new nodes, use Identity to return old nodes" );
 846     k = i;
 847 #ifdef ASSERT
 848     if (loop_count >= K + C->live_nodes()) {
 849       dump_infinite_loop_info(i, "PhaseGVN::transform_no_reclaim");
 850     }
 851 #endif
 852     i = apply_ideal(k, /*can_reshape=*/false);
 853     NOT_PRODUCT(loop_count++;)
 854   }
 855   NOT_PRODUCT(if (loop_count != 0) { set_progress(); })
 856 
 857   // If brand new node, make space in type array.
 858   ensure_type_or_null(k);
 859 
 860   // Since I just called 'Value' to compute the set of run-time values
 861   // for this Node, and 'Value' is non-local (and therefore expensive) I'll
 862   // cache Value.  Later requests for the local phase->type of this Node can
 863   // use the cached Value instead of suffering with 'bottom_type'.
 864   const Type* t = k->Value(this); // Get runtime Value set
 865   assert(t != NULL, "value sanity");
 866   if (type_or_null(k) != t) {
 867 #ifndef PRODUCT
 868     // Do not count initial visit to node as a transformation
 869     if (type_or_null(k) == NULL) {
 870       inc_new_values();
 871       set_progress();
 872     }
 873 #endif
 874     set_type(k, t);
 875     // If k is a TypeNode, capture any more-precise type permanently into Node
 876     k->raise_bottom_type(t);
 877   }
 878 
 879   if (t->singleton() && !k->is_Con()) {
 880     NOT_PRODUCT(set_progress();)
 881     return makecon(t);          // Turn into a constant
 882   }
 883 
 884   // Now check for Identities
 885   i = k->Identity(this);        // Look for a nearby replacement
 886   if (i != k) {                 // Found? Return replacement!
 887     NOT_PRODUCT(set_progress();)
 888     return i;
 889   }
 890 
 891   // Global Value Numbering
 892   i = hash_find_insert(k);      // Insert if new
 893   if (i && (i != k)) {
 894     // Return the pre-existing node
 895     NOT_PRODUCT(set_progress();)
 896     return i;
 897   }
 898 
 899   // Return Idealized original
 900   return k;
 901 }
 902 
 903 bool PhaseGVN::is_dominator_helper(Node *d, Node *n, bool linear_only) {
 904   if (d->is_top() || (d->is_Proj() && d->in(0)->is_top())) {
 905     return false;
 906   }
 907   if (n->is_top() || (n->is_Proj() && n->in(0)->is_top())) {
 908     return false;
 909   }
 910   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
 911   int i = 0;
 912   while (d != n) {
 913     n = IfNode::up_one_dom(n, linear_only);
 914     i++;
 915     if (n == NULL || i >= 100) {
 916       return false;
 917     }
 918   }
 919   return true;
 920 }
 921 
 922 #ifdef ASSERT
 923 //------------------------------dead_loop_check--------------------------------
 924 // Check for a simple dead loop when a data node references itself directly
 925 // or through an other data node excluding cons and phis.
 926 void PhaseGVN::dead_loop_check( Node *n ) {
 927   // Phi may reference itself in a loop
 928   if (n != NULL && !n->is_dead_loop_safe() && !n->is_CFG()) {
 929     // Do 2 levels check and only data inputs.
 930     bool no_dead_loop = true;
 931     uint cnt = n->req();
 932     for (uint i = 1; i < cnt && no_dead_loop; i++) {
 933       Node *in = n->in(i);
 934       if (in == n) {
 935         no_dead_loop = false;
 936       } else if (in != NULL && !in->is_dead_loop_safe()) {
 937         uint icnt = in->req();
 938         for (uint j = 1; j < icnt && no_dead_loop; j++) {
 939           if (in->in(j) == n || in->in(j) == in)
 940             no_dead_loop = false;
 941         }
 942       }
 943     }
 944     if (!no_dead_loop) n->dump(3);
 945     assert(no_dead_loop, "dead loop detected");
 946   }
 947 }
 948 
 949 
 950 /**
 951  * Dumps information that can help to debug the problem. A debug
 952  * build fails with an assert.
 953  */
 954 void PhaseGVN::dump_infinite_loop_info(Node* n, const char* where) {
 955   n->dump(4);
 956   assert(false, "infinite loop in %s", where);
 957 }
 958 #endif
 959 
 960 //=============================================================================
 961 //------------------------------PhaseIterGVN-----------------------------------
 962 // Initialize with previous PhaseIterGVN info; used by PhaseCCP
 963 PhaseIterGVN::PhaseIterGVN(PhaseIterGVN* igvn) : PhaseGVN(igvn),
 964                                                  _delay_transform(igvn->_delay_transform),
 965                                                  _stack(igvn->_stack ),
 966                                                  _worklist(igvn->_worklist)
 967 {
 968   _iterGVN = true;
 969 }
 970 
 971 //------------------------------PhaseIterGVN-----------------------------------
 972 // Initialize with previous PhaseGVN info from Parser
 973 PhaseIterGVN::PhaseIterGVN(PhaseGVN* gvn) : PhaseGVN(gvn),
 974                                             _delay_transform(false),
 975 // TODO: Before incremental inlining it was allocated only once and it was fine. Now that
 976 //       the constructor is used in incremental inlining, this consumes too much memory:
 977 //                                            _stack(C->live_nodes() >> 1),
 978 //       So, as a band-aid, we replace this by:
 979                                             _stack(C->comp_arena(), 32),
 980                                             _worklist(*C->for_igvn())
 981 {
 982   _iterGVN = true;
 983   uint max;
 984 
 985   // Dead nodes in the hash table inherited from GVN were not treated as
 986   // roots during def-use info creation; hence they represent an invisible
 987   // use.  Clear them out.
 988   max = _table.size();
 989   for( uint i = 0; i < max; ++i ) {
 990     Node *n = _table.at(i);
 991     if(n != NULL && n != _table.sentinel() && n->outcnt() == 0) {
 992       if( n->is_top() ) continue;
 993       // If remove_useless_nodes() has run, we expect no such nodes left.
 994       assert(false, "remove_useless_nodes missed this node");
 995       hash_delete(n);
 996     }
 997   }
 998 
 999   // Any Phis or Regions on the worklist probably had uses that could not
1000   // make more progress because the uses were made while the Phis and Regions
1001   // were in half-built states.  Put all uses of Phis and Regions on worklist.
1002   max = _worklist.size();
1003   for( uint j = 0; j < max; j++ ) {
1004     Node *n = _worklist.at(j);
1005     uint uop = n->Opcode();
1006     if( uop == Op_Phi || uop == Op_Region ||
1007         n->is_Type() ||
1008         n->is_Mem() )
1009       add_users_to_worklist(n);
1010   }
1011 }
1012 
1013 void PhaseIterGVN::shuffle_worklist() {
1014   if (_worklist.size() < 2) return;
1015   for (uint i = _worklist.size() - 1; i >= 1; i--) {
1016     uint j = C->random() % (i + 1);
1017     swap(_worklist.adr()[i], _worklist.adr()[j]);
1018   }
1019 }
1020 
1021 #ifndef PRODUCT
1022 void PhaseIterGVN::verify_step(Node* n) {
1023   if (VerifyIterativeGVN) {
1024     ResourceMark rm;
1025     VectorSet visited;
1026     Node_List worklist;
1027 
1028     _verify_window[_verify_counter % _verify_window_size] = n;
1029     ++_verify_counter;
1030     if (C->unique() < 1000 || 0 == _verify_counter % (C->unique() < 10000 ? 10 : 100)) {
1031       ++_verify_full_passes;
1032       worklist.push(C->root());
1033       Node::verify(-1, visited, worklist);
1034       return;
1035     }
1036     for (int i = 0; i < _verify_window_size; i++) {
1037       Node* n = _verify_window[i];
1038       if (n == NULL) {
1039         continue;
1040       }
1041       if (n->in(0) == NodeSentinel) { // xform_idom
1042         _verify_window[i] = n->in(1);
1043         --i;
1044         continue;
1045       }
1046       // Typical fanout is 1-2, so this call visits about 6 nodes.
1047       if (!visited.test_set(n->_idx)) {
1048         worklist.push(n);
1049       }
1050     }
1051     Node::verify(4, visited, worklist);
1052   }
1053 }
1054 
1055 void PhaseIterGVN::trace_PhaseIterGVN(Node* n, Node* nn, const Type* oldtype) {
1056   if (TraceIterativeGVN) {
1057     uint wlsize = _worklist.size();
1058     const Type* newtype = type_or_null(n);
1059     if (nn != n) {
1060       // print old node
1061       tty->print("< ");
1062       if (oldtype != newtype && oldtype != NULL) {
1063         oldtype->dump();
1064       }
1065       do { tty->print("\t"); } while (tty->position() < 16);
1066       tty->print("<");
1067       n->dump();
1068     }
1069     if (oldtype != newtype || nn != n) {
1070       // print new node and/or new type
1071       if (oldtype == NULL) {
1072         tty->print("* ");
1073       } else if (nn != n) {
1074         tty->print("> ");
1075       } else {
1076         tty->print("= ");
1077       }
1078       if (newtype == NULL) {
1079         tty->print("null");
1080       } else {
1081         newtype->dump();
1082       }
1083       do { tty->print("\t"); } while (tty->position() < 16);
1084       nn->dump();
1085     }
1086     if (Verbose && wlsize < _worklist.size()) {
1087       tty->print("  Push {");
1088       while (wlsize != _worklist.size()) {
1089         Node* pushed = _worklist.at(wlsize++);
1090         tty->print(" %d", pushed->_idx);
1091       }
1092       tty->print_cr(" }");
1093     }
1094     if (nn != n) {
1095       // ignore n, it might be subsumed
1096       verify_step((Node*) NULL);
1097     }
1098   }
1099 }
1100 
1101 void PhaseIterGVN::init_verifyPhaseIterGVN() {
1102   _verify_counter = 0;
1103   _verify_full_passes = 0;
1104   for (int i = 0; i < _verify_window_size; i++) {
1105     _verify_window[i] = NULL;
1106   }
1107 #ifdef ASSERT
1108   // Verify that all modified nodes are on _worklist
1109   Unique_Node_List* modified_list = C->modified_nodes();
1110   while (modified_list != NULL && modified_list->size()) {
1111     Node* n = modified_list->pop();
1112     if (!n->is_Con() && !_worklist.member(n)) {
1113       n->dump();
1114       fatal("modified node is not on IGVN._worklist");
1115     }
1116   }
1117 #endif
1118 }
1119 
1120 void PhaseIterGVN::verify_PhaseIterGVN() {
1121 #ifdef ASSERT
1122   // Verify nodes with changed inputs.
1123   Unique_Node_List* modified_list = C->modified_nodes();
1124   while (modified_list != NULL && modified_list->size()) {
1125     Node* n = modified_list->pop();
1126     if (!n->is_Con()) { // skip Con nodes
1127       n->dump();
1128       fatal("modified node was not processed by IGVN.transform_old()");
1129     }
1130   }
1131 #endif
1132 
1133   C->verify_graph_edges();
1134   if (VerifyIterativeGVN && PrintOpto) {
1135     if (_verify_counter == _verify_full_passes) {
1136       tty->print_cr("VerifyIterativeGVN: %d transforms and verify passes",
1137                     (int) _verify_full_passes);
1138     } else {
1139       tty->print_cr("VerifyIterativeGVN: %d transforms, %d full verify passes",
1140                   (int) _verify_counter, (int) _verify_full_passes);
1141     }
1142   }
1143 
1144 #ifdef ASSERT
1145   if (modified_list != NULL) {
1146     while (modified_list->size() > 0) {
1147       Node* n = modified_list->pop();
1148       n->dump();
1149       assert(false, "VerifyIterativeGVN: new modified node was added");
1150     }
1151   }
1152 #endif
1153 }
1154 #endif /* PRODUCT */
1155 
1156 #ifdef ASSERT
1157 /**
1158  * Dumps information that can help to debug the problem. A debug
1159  * build fails with an assert.
1160  */
1161 void PhaseIterGVN::dump_infinite_loop_info(Node* n, const char* where) {
1162   n->dump(4);
1163   _worklist.dump();
1164   assert(false, "infinite loop in %s", where);
1165 }
1166 
1167 /**
1168  * Prints out information about IGVN if the 'verbose' option is used.
1169  */
1170 void PhaseIterGVN::trace_PhaseIterGVN_verbose(Node* n, int num_processed) {
1171   if (TraceIterativeGVN && Verbose) {
1172     tty->print("  Pop ");
1173     n->dump();
1174     if ((num_processed % 100) == 0) {
1175       _worklist.print_set();
1176     }
1177   }
1178 }
1179 #endif /* ASSERT */
1180 
1181 void PhaseIterGVN::optimize() {
1182   DEBUG_ONLY(uint num_processed  = 0;)
1183   NOT_PRODUCT(init_verifyPhaseIterGVN();)
1184   if (StressIGVN) {
1185     shuffle_worklist();
1186   }
1187 
1188   uint loop_count = 0;
1189   // Pull from worklist and transform the node. If the node has changed,
1190   // update edge info and put uses on worklist.
1191   while(_worklist.size()) {
1192     if (C->check_node_count(NodeLimitFudgeFactor * 2, "Out of nodes")) {
1193       return;
1194     }
1195     Node* n  = _worklist.pop();
1196     if (loop_count >= K * C->live_nodes()) {
1197       DEBUG_ONLY(dump_infinite_loop_info(n, "PhaseIterGVN::optimize");)
1198       C->record_method_not_compilable("infinite loop in PhaseIterGVN::optimize");
1199       return;
1200     }
1201     DEBUG_ONLY(trace_PhaseIterGVN_verbose(n, num_processed++);)
1202     if (n->outcnt() != 0) {
1203       NOT_PRODUCT(const Type* oldtype = type_or_null(n));
1204       // Do the transformation
1205       Node* nn = transform_old(n);
1206       NOT_PRODUCT(trace_PhaseIterGVN(n, nn, oldtype);)
1207     } else if (!n->is_top()) {
1208       remove_dead_node(n);
1209     }
1210     loop_count++;
1211   }
1212   NOT_PRODUCT(verify_PhaseIterGVN();)
1213 }
1214 
1215 
1216 /**
1217  * Register a new node with the optimizer.  Update the types array, the def-use
1218  * info.  Put on worklist.
1219  */
1220 Node* PhaseIterGVN::register_new_node_with_optimizer(Node* n, Node* orig) {
1221   set_type_bottom(n);
1222   _worklist.push(n);
1223   if (orig != NULL)  C->copy_node_notes_to(n, orig);
1224   return n;
1225 }
1226 
1227 //------------------------------transform--------------------------------------
1228 // Non-recursive: idealize Node 'n' with respect to its inputs and its value
1229 Node *PhaseIterGVN::transform( Node *n ) {
1230   if (_delay_transform) {
1231     // Register the node but don't optimize for now
1232     register_new_node_with_optimizer(n);
1233     return n;
1234   }
1235 
1236   // If brand new node, make space in type array, and give it a type.
1237   ensure_type_or_null(n);
1238   if (type_or_null(n) == NULL) {
1239     set_type_bottom(n);
1240   }
1241 
1242   return transform_old(n);
1243 }
1244 
1245 Node *PhaseIterGVN::transform_old(Node* n) {
1246   NOT_PRODUCT(set_transforms());
1247   // Remove 'n' from hash table in case it gets modified
1248   _table.hash_delete(n);
1249   if (VerifyIterativeGVN) {
1250     assert(!_table.find_index(n->_idx), "found duplicate entry in table");
1251   }
1252 
1253   // Apply the Ideal call in a loop until it no longer applies
1254   Node* k = n;
1255   DEBUG_ONLY(dead_loop_check(k);)
1256   DEBUG_ONLY(bool is_new = (k->outcnt() == 0);)
1257   C->remove_modified_node(k);
1258   Node* i = apply_ideal(k, /*can_reshape=*/true);
1259   assert(i != k || is_new || i->outcnt() > 0, "don't return dead nodes");
1260 #ifndef PRODUCT
1261   verify_step(k);
1262 #endif
1263 
1264   DEBUG_ONLY(uint loop_count = 1;)
1265   while (i != NULL) {
1266 #ifdef ASSERT
1267     if (loop_count >= K + C->live_nodes()) {
1268       dump_infinite_loop_info(i, "PhaseIterGVN::transform_old");
1269     }
1270 #endif
1271     assert((i->_idx >= k->_idx) || i->is_top(), "Idealize should return new nodes, use Identity to return old nodes");
1272     // Made a change; put users of original Node on worklist
1273     add_users_to_worklist(k);
1274     // Replacing root of transform tree?
1275     if (k != i) {
1276       // Make users of old Node now use new.
1277       subsume_node(k, i);
1278       k = i;
1279     }
1280     DEBUG_ONLY(dead_loop_check(k);)
1281     // Try idealizing again
1282     DEBUG_ONLY(is_new = (k->outcnt() == 0);)
1283     C->remove_modified_node(k);
1284     i = apply_ideal(k, /*can_reshape=*/true);
1285     assert(i != k || is_new || (i->outcnt() > 0), "don't return dead nodes");
1286 #ifndef PRODUCT
1287     verify_step(k);
1288 #endif
1289     DEBUG_ONLY(loop_count++;)
1290   }
1291 
1292   // If brand new node, make space in type array.
1293   ensure_type_or_null(k);
1294 
1295   // See what kind of values 'k' takes on at runtime
1296   const Type* t = k->Value(this);
1297   assert(t != NULL, "value sanity");
1298 
1299   // Since I just called 'Value' to compute the set of run-time values
1300   // for this Node, and 'Value' is non-local (and therefore expensive) I'll
1301   // cache Value.  Later requests for the local phase->type of this Node can
1302   // use the cached Value instead of suffering with 'bottom_type'.
1303   if (type_or_null(k) != t) {
1304 #ifndef PRODUCT
1305     inc_new_values();
1306     set_progress();
1307 #endif
1308     set_type(k, t);
1309     // If k is a TypeNode, capture any more-precise type permanently into Node
1310     k->raise_bottom_type(t);
1311     // Move users of node to worklist
1312     add_users_to_worklist(k);
1313   }
1314   // If 'k' computes a constant, replace it with a constant
1315   if (t->singleton() && !k->is_Con()) {
1316     NOT_PRODUCT(set_progress();)
1317     Node* con = makecon(t);     // Make a constant
1318     add_users_to_worklist(k);
1319     subsume_node(k, con);       // Everybody using k now uses con
1320     return con;
1321   }
1322 
1323   // Now check for Identities
1324   i = k->Identity(this);      // Look for a nearby replacement
1325   if (i != k) {                // Found? Return replacement!
1326     NOT_PRODUCT(set_progress();)
1327     add_users_to_worklist(k);
1328     subsume_node(k, i);       // Everybody using k now uses i
1329     return i;
1330   }
1331 
1332   // Global Value Numbering
1333   i = hash_find_insert(k);      // Check for pre-existing node
1334   if (i && (i != k)) {
1335     // Return the pre-existing node if it isn't dead
1336     NOT_PRODUCT(set_progress();)
1337     add_users_to_worklist(k);
1338     subsume_node(k, i);       // Everybody using k now uses i
1339     return i;
1340   }
1341 
1342   // Return Idealized original
1343   return k;
1344 }
1345 
1346 //---------------------------------saturate------------------------------------
1347 const Type* PhaseIterGVN::saturate(const Type* new_type, const Type* old_type,
1348                                    const Type* limit_type) const {
1349   return new_type->narrow(old_type);
1350 }
1351 
1352 //------------------------------remove_globally_dead_node----------------------
1353 // Kill a globally dead Node.  All uses are also globally dead and are
1354 // aggressively trimmed.
1355 void PhaseIterGVN::remove_globally_dead_node( Node *dead ) {
1356   enum DeleteProgress {
1357     PROCESS_INPUTS,
1358     PROCESS_OUTPUTS
1359   };
1360   assert(_stack.is_empty(), "not empty");
1361   _stack.push(dead, PROCESS_INPUTS);
1362 
1363   while (_stack.is_nonempty()) {
1364     dead = _stack.node();
1365     if (dead->Opcode() == Op_SafePoint) {
1366       dead->as_SafePoint()->disconnect_from_root(this);
1367     }
1368     uint progress_state = _stack.index();
1369     assert(dead != C->root(), "killing root, eh?");
1370     assert(!dead->is_top(), "add check for top when pushing");
1371     NOT_PRODUCT( set_progress(); )
1372     if (progress_state == PROCESS_INPUTS) {
1373       // After following inputs, continue to outputs
1374       _stack.set_index(PROCESS_OUTPUTS);
1375       if (!dead->is_Con()) { // Don't kill cons but uses
1376         bool recurse = false;
1377         // Remove from hash table
1378         _table.hash_delete( dead );
1379         // Smash all inputs to 'dead', isolating him completely
1380         for (uint i = 0; i < dead->req(); i++) {
1381           Node *in = dead->in(i);
1382           if (in != NULL && in != C->top()) {  // Points to something?
1383             int nrep = dead->replace_edge(in, NULL, this);  // Kill edges
1384             assert((nrep > 0), "sanity");
1385             if (in->outcnt() == 0) { // Made input go dead?
1386               _stack.push(in, PROCESS_INPUTS); // Recursively remove
1387               recurse = true;
1388             } else if (in->outcnt() == 1 &&
1389                        in->has_special_unique_user()) {
1390               _worklist.push(in->unique_out());
1391             } else if (in->outcnt() <= 2 && dead->is_Phi()) {
1392               if (in->Opcode() == Op_Region) {
1393                 _worklist.push(in);
1394               } else if (in->is_Store()) {
1395                 DUIterator_Fast imax, i = in->fast_outs(imax);
1396                 _worklist.push(in->fast_out(i));
1397                 i++;
1398                 if (in->outcnt() == 2) {
1399                   _worklist.push(in->fast_out(i));
1400                   i++;
1401                 }
1402                 assert(!(i < imax), "sanity");
1403               }
1404             } else {
1405               BarrierSet::barrier_set()->barrier_set_c2()->enqueue_useful_gc_barrier(this, in);
1406             }
1407             if (ReduceFieldZeroing && dead->is_Load() && i == MemNode::Memory &&
1408                 in->is_Proj() && in->in(0) != NULL && in->in(0)->is_Initialize()) {
1409               // A Load that directly follows an InitializeNode is
1410               // going away. The Stores that follow are candidates
1411               // again to be captured by the InitializeNode.
1412               for (DUIterator_Fast jmax, j = in->fast_outs(jmax); j < jmax; j++) {
1413                 Node *n = in->fast_out(j);
1414                 if (n->is_Store()) {
1415                   _worklist.push(n);
1416                 }
1417               }
1418             }
1419           } // if (in != NULL && in != C->top())
1420         } // for (uint i = 0; i < dead->req(); i++)
1421         if (recurse) {
1422           continue;
1423         }
1424       } // if (!dead->is_Con())
1425     } // if (progress_state == PROCESS_INPUTS)
1426 
1427     // Aggressively kill globally dead uses
1428     // (Rather than pushing all the outs at once, we push one at a time,
1429     // plus the parent to resume later, because of the indefinite number
1430     // of edge deletions per loop trip.)
1431     if (dead->outcnt() > 0) {
1432       // Recursively remove output edges
1433       _stack.push(dead->raw_out(0), PROCESS_INPUTS);
1434     } else {
1435       // Finished disconnecting all input and output edges.
1436       _stack.pop();
1437       // Remove dead node from iterative worklist
1438       _worklist.remove(dead);
1439       C->remove_useless_node(dead);
1440     }
1441   } // while (_stack.is_nonempty())
1442 }
1443 
1444 //------------------------------subsume_node-----------------------------------
1445 // Remove users from node 'old' and add them to node 'nn'.
1446 void PhaseIterGVN::subsume_node( Node *old, Node *nn ) {
1447   if (old->Opcode() == Op_SafePoint) {
1448     old->as_SafePoint()->disconnect_from_root(this);
1449   }
1450   assert( old != hash_find(old), "should already been removed" );
1451   assert( old != C->top(), "cannot subsume top node");
1452   // Copy debug or profile information to the new version:
1453   C->copy_node_notes_to(nn, old);
1454   // Move users of node 'old' to node 'nn'
1455   for (DUIterator_Last imin, i = old->last_outs(imin); i >= imin; ) {
1456     Node* use = old->last_out(i);  // for each use...
1457     // use might need re-hashing (but it won't if it's a new node)
1458     rehash_node_delayed(use);
1459     // Update use-def info as well
1460     // We remove all occurrences of old within use->in,
1461     // so as to avoid rehashing any node more than once.
1462     // The hash table probe swamps any outer loop overhead.
1463     uint num_edges = 0;
1464     for (uint jmax = use->len(), j = 0; j < jmax; j++) {
1465       if (use->in(j) == old) {
1466         use->set_req(j, nn);
1467         ++num_edges;
1468       }
1469     }
1470     i -= num_edges;    // we deleted 1 or more copies of this edge
1471   }
1472 
1473   // Search for instance field data PhiNodes in the same region pointing to the old
1474   // memory PhiNode and update their instance memory ids to point to the new node.
1475   if (old->is_Phi() && old->as_Phi()->type()->has_memory() && old->in(0) != NULL) {
1476     Node* region = old->in(0);
1477     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1478       PhiNode* phi = region->fast_out(i)->isa_Phi();
1479       if (phi != NULL && phi->inst_mem_id() == (int)old->_idx) {
1480         phi->set_inst_mem_id((int)nn->_idx);
1481       }
1482     }
1483   }
1484 
1485   // Smash all inputs to 'old', isolating him completely
1486   Node *temp = new Node(1);
1487   temp->init_req(0,nn);     // Add a use to nn to prevent him from dying
1488   remove_dead_node( old );
1489   temp->del_req(0);         // Yank bogus edge
1490   if (nn != NULL && nn->outcnt() == 0) {
1491     _worklist.push(nn);
1492   }
1493 #ifndef PRODUCT
1494   if( VerifyIterativeGVN ) {
1495     for ( int i = 0; i < _verify_window_size; i++ ) {
1496       if ( _verify_window[i] == old )
1497         _verify_window[i] = nn;
1498     }
1499   }
1500 #endif
1501   temp->destruct(this);     // reuse the _idx of this little guy
1502 }
1503 
1504 //------------------------------add_users_to_worklist--------------------------
1505 void PhaseIterGVN::add_users_to_worklist0( Node *n ) {
1506   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1507     _worklist.push(n->fast_out(i));  // Push on worklist
1508   }
1509 }
1510 
1511 // Return counted loop Phi if as a counted loop exit condition, cmp
1512 // compares the the induction variable with n
1513 static PhiNode* countedloop_phi_from_cmp(CmpINode* cmp, Node* n) {
1514   for (DUIterator_Fast imax, i = cmp->fast_outs(imax); i < imax; i++) {
1515     Node* bol = cmp->fast_out(i);
1516     for (DUIterator_Fast i2max, i2 = bol->fast_outs(i2max); i2 < i2max; i2++) {
1517       Node* iff = bol->fast_out(i2);
1518       if (iff->is_CountedLoopEnd()) {
1519         CountedLoopEndNode* cle = iff->as_CountedLoopEnd();
1520         if (cle->limit() == n) {
1521           PhiNode* phi = cle->phi();
1522           if (phi != NULL) {
1523             return phi;
1524           }
1525         }
1526       }
1527     }
1528   }
1529   return NULL;
1530 }
1531 
1532 void PhaseIterGVN::add_users_to_worklist( Node *n ) {
1533   add_users_to_worklist0(n);
1534 
1535   // Move users of node to worklist
1536   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1537     Node* use = n->fast_out(i); // Get use
1538 
1539     if( use->is_Multi() ||      // Multi-definer?  Push projs on worklist
1540         use->is_Store() )       // Enable store/load same address
1541       add_users_to_worklist0(use);
1542 
1543     // If we changed the receiver type to a call, we need to revisit
1544     // the Catch following the call.  It's looking for a non-NULL
1545     // receiver to know when to enable the regular fall-through path
1546     // in addition to the NullPtrException path.
1547     if (use->is_CallDynamicJava() && n == use->in(TypeFunc::Parms)) {
1548       Node* p = use->as_CallDynamicJava()->proj_out_or_null(TypeFunc::Control);
1549       if (p != NULL) {
1550         add_users_to_worklist0(p);
1551       }
1552     }
1553 
1554     uint use_op = use->Opcode();
1555     if(use->is_Cmp()) {       // Enable CMP/BOOL optimization
1556       add_users_to_worklist(use); // Put Bool on worklist
1557       if (use->outcnt() > 0) {
1558         Node* bol = use->raw_out(0);
1559         if (bol->outcnt() > 0) {
1560           Node* iff = bol->raw_out(0);
1561           if (iff->outcnt() == 2) {
1562             // Look for the 'is_x2logic' pattern: "x ? : 0 : 1" and put the
1563             // phi merging either 0 or 1 onto the worklist
1564             Node* ifproj0 = iff->raw_out(0);
1565             Node* ifproj1 = iff->raw_out(1);
1566             if (ifproj0->outcnt() > 0 && ifproj1->outcnt() > 0) {
1567               Node* region0 = ifproj0->raw_out(0);
1568               Node* region1 = ifproj1->raw_out(0);
1569               if( region0 == region1 )
1570                 add_users_to_worklist0(region0);
1571             }
1572           }
1573         }
1574       }
1575       if (use_op == Op_CmpI) {
1576         Node* phi = countedloop_phi_from_cmp((CmpINode*)use, n);
1577         if (phi != NULL) {
1578           // If an opaque node feeds into the limit condition of a
1579           // CountedLoop, we need to process the Phi node for the
1580           // induction variable when the opaque node is removed:
1581           // the range of values taken by the Phi is now known and
1582           // so its type is also known.
1583           _worklist.push(phi);
1584         }
1585         Node* in1 = use->in(1);
1586         for (uint i = 0; i < in1->outcnt(); i++) {
1587           if (in1->raw_out(i)->Opcode() == Op_CastII) {
1588             Node* castii = in1->raw_out(i);
1589             if (castii->in(0) != NULL && castii->in(0)->in(0) != NULL && castii->in(0)->in(0)->is_If()) {
1590               Node* ifnode = castii->in(0)->in(0);
1591               if (ifnode->in(1) != NULL && ifnode->in(1)->is_Bool() && ifnode->in(1)->in(1) == use) {
1592                 // Reprocess a CastII node that may depend on an
1593                 // opaque node value when the opaque node is
1594                 // removed. In case it carries a dependency we can do
1595                 // a better job of computing its type.
1596                 _worklist.push(castii);
1597               }
1598             }
1599           }
1600         }
1601       }
1602     }
1603 
1604     // If changed Cast input, check Phi users for simple cycles
1605     if (use->is_ConstraintCast()) {
1606       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1607         Node* u = use->fast_out(i2);
1608         if (u->is_Phi())
1609           _worklist.push(u);
1610       }
1611     }
1612     // If changed LShift inputs, check RShift users for useless sign-ext
1613     if( use_op == Op_LShiftI ) {
1614       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1615         Node* u = use->fast_out(i2);
1616         if (u->Opcode() == Op_RShiftI)
1617           _worklist.push(u);
1618       }
1619     }
1620     // If changed AddI/SubI inputs, check CmpU for range check optimization.
1621     if (use_op == Op_AddI || use_op == Op_SubI) {
1622       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1623         Node* u = use->fast_out(i2);
1624         if (u->is_Cmp() && (u->Opcode() == Op_CmpU)) {
1625           _worklist.push(u);
1626         }
1627       }
1628     }
1629     // If changed AddP inputs, check Stores for loop invariant
1630     if( use_op == Op_AddP ) {
1631       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1632         Node* u = use->fast_out(i2);
1633         if (u->is_Mem())
1634           _worklist.push(u);
1635       }
1636     }
1637     // If changed initialization activity, check dependent Stores
1638     if (use_op == Op_Allocate || use_op == Op_AllocateArray) {
1639       InitializeNode* init = use->as_Allocate()->initialization();
1640       if (init != NULL) {
1641         Node* imem = init->proj_out_or_null(TypeFunc::Memory);
1642         if (imem != NULL)  add_users_to_worklist0(imem);
1643       }
1644     }
1645     if (use_op == Op_Initialize) {
1646       Node* imem = use->as_Initialize()->proj_out_or_null(TypeFunc::Memory);
1647       if (imem != NULL)  add_users_to_worklist0(imem);
1648     }
1649     // Loading the java mirror from a Klass requires two loads and the type
1650     // of the mirror load depends on the type of 'n'. See LoadNode::Value().
1651     //   LoadBarrier?(LoadP(LoadP(AddP(foo:Klass, #java_mirror))))
1652     BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1653     bool has_load_barrier_nodes = bs->has_load_barrier_nodes();
1654 
1655     if (use_op == Op_LoadP && use->bottom_type()->isa_rawptr()) {
1656       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1657         Node* u = use->fast_out(i2);
1658         const Type* ut = u->bottom_type();
1659         if (u->Opcode() == Op_LoadP && ut->isa_instptr()) {
1660           if (has_load_barrier_nodes) {
1661             // Search for load barriers behind the load
1662             for (DUIterator_Fast i3max, i3 = u->fast_outs(i3max); i3 < i3max; i3++) {
1663               Node* b = u->fast_out(i3);
1664               if (bs->is_gc_barrier_node(b)) {
1665                 _worklist.push(b);
1666               }
1667             }
1668           }
1669           _worklist.push(u);
1670         }
1671       }
1672     }
1673   }
1674 }
1675 
1676 /**
1677  * Remove the speculative part of all types that we know of
1678  */
1679 void PhaseIterGVN::remove_speculative_types()  {
1680   assert(UseTypeSpeculation, "speculation is off");
1681   for (uint i = 0; i < _types.Size(); i++)  {
1682     const Type* t = _types.fast_lookup(i);
1683     if (t != NULL) {
1684       _types.map(i, t->remove_speculative());
1685     }
1686   }
1687   _table.check_no_speculative_types();
1688 }
1689 
1690 // Check if the type of a divisor of a Div or Mod node includes zero.
1691 bool PhaseIterGVN::no_dependent_zero_check(Node* n) const {
1692   switch (n->Opcode()) {
1693     case Op_DivI:
1694     case Op_ModI: {
1695       // Type of divisor includes 0?
1696       if (n->in(2)->is_top()) {
1697         // 'n' is dead. Treat as if zero check is still there to avoid any further optimizations.
1698         return false;
1699       }
1700       const TypeInt* type_divisor = type(n->in(2))->is_int();
1701       return (type_divisor->_hi < 0 || type_divisor->_lo > 0);
1702     }
1703     case Op_DivL:
1704     case Op_ModL: {
1705       // Type of divisor includes 0?
1706       if (n->in(2)->is_top()) {
1707         // 'n' is dead. Treat as if zero check is still there to avoid any further optimizations.
1708         return false;
1709       }
1710       const TypeLong* type_divisor = type(n->in(2))->is_long();
1711       return (type_divisor->_hi < 0 || type_divisor->_lo > 0);
1712     }
1713   }
1714   return true;
1715 }
1716 
1717 //=============================================================================
1718 #ifndef PRODUCT
1719 uint PhaseCCP::_total_invokes   = 0;
1720 uint PhaseCCP::_total_constants = 0;
1721 #endif
1722 //------------------------------PhaseCCP---------------------------------------
1723 // Conditional Constant Propagation, ala Wegman & Zadeck
1724 PhaseCCP::PhaseCCP( PhaseIterGVN *igvn ) : PhaseIterGVN(igvn) {
1725   NOT_PRODUCT( clear_constants(); )
1726   assert( _worklist.size() == 0, "" );
1727   // Clear out _nodes from IterGVN.  Must be clear to transform call.
1728   _nodes.clear();               // Clear out from IterGVN
1729   analyze();
1730 }
1731 
1732 #ifndef PRODUCT
1733 //------------------------------~PhaseCCP--------------------------------------
1734 PhaseCCP::~PhaseCCP() {
1735   inc_invokes();
1736   _total_constants += count_constants();
1737 }
1738 #endif
1739 
1740 
1741 #ifdef ASSERT
1742 static bool ccp_type_widens(const Type* t, const Type* t0) {
1743   assert(t->meet(t0) == t, "Not monotonic");
1744   switch (t->base() == t0->base() ? t->base() : Type::Top) {
1745   case Type::Int:
1746     assert(t0->isa_int()->_widen <= t->isa_int()->_widen, "widen increases");
1747     break;
1748   case Type::Long:
1749     assert(t0->isa_long()->_widen <= t->isa_long()->_widen, "widen increases");
1750     break;
1751   default:
1752     break;
1753   }
1754   return true;
1755 }
1756 #endif //ASSERT
1757 
1758 //------------------------------analyze----------------------------------------
1759 void PhaseCCP::analyze() {
1760   // Initialize all types to TOP, optimistic analysis
1761   for (int i = C->unique() - 1; i >= 0; i--)  {
1762     _types.map(i,Type::TOP);
1763   }
1764 
1765   // Push root onto worklist
1766   Unique_Node_List worklist;
1767   worklist.push(C->root());
1768 
1769   // Pull from worklist; compute new value; push changes out.
1770   // This loop is the meat of CCP.
1771   while( worklist.size() ) {
1772     Node* n; // Node to be examined in this iteration
1773     if (StressCCP) {
1774       n = worklist.remove(C->random() % worklist.size());
1775     } else {
1776       n = worklist.pop();
1777     }
1778     const Type *t = n->Value(this);
1779     if (t != type(n)) {
1780       assert(ccp_type_widens(t, type(n)), "ccp type must widen");
1781 #ifndef PRODUCT
1782       if( TracePhaseCCP ) {
1783         t->dump();
1784         do { tty->print("\t"); } while (tty->position() < 16);
1785         n->dump();
1786       }
1787 #endif
1788       set_type(n, t);
1789       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1790         Node* m = n->fast_out(i);   // Get user
1791         if (m->is_Region()) {  // New path to Region?  Must recheck Phis too
1792           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1793             Node* p = m->fast_out(i2); // Propagate changes to uses
1794             if (p->bottom_type() != type(p)) { // If not already bottomed out
1795               worklist.push(p); // Propagate change to user
1796             }
1797           }
1798         }
1799         // If we changed the receiver type to a call, we need to revisit
1800         // the Catch following the call.  It's looking for a non-NULL
1801         // receiver to know when to enable the regular fall-through path
1802         // in addition to the NullPtrException path
1803         if (m->is_Call()) {
1804           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1805             Node* p = m->fast_out(i2);  // Propagate changes to uses
1806             if (p->is_Proj() && p->as_Proj()->_con == TypeFunc::Control) {
1807               Node* catch_node = p->find_out_with(Op_Catch);
1808               if (catch_node != NULL) {
1809                 worklist.push(catch_node);
1810               }
1811             }
1812           }
1813         }
1814         if (m->bottom_type() != type(m)) { // If not already bottomed out
1815           worklist.push(m);     // Propagate change to user
1816         }
1817 
1818         // CmpU nodes can get their type information from two nodes up in the
1819         // graph (instead of from the nodes immediately above). Make sure they
1820         // are added to the worklist if nodes they depend on are updated, since
1821         // they could be missed and get wrong types otherwise.
1822         uint m_op = m->Opcode();
1823         if (m_op == Op_AddI || m_op == Op_SubI) {
1824           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1825             Node* p = m->fast_out(i2); // Propagate changes to uses
1826             if (p->Opcode() == Op_CmpU) {
1827               // Got a CmpU which might need the new type information from node n.
1828               if(p->bottom_type() != type(p)) { // If not already bottomed out
1829                 worklist.push(p); // Propagate change to user
1830               }
1831             }
1832           }
1833         }
1834         // If n is used in a counted loop exit condition then the type
1835         // of the counted loop's Phi depends on the type of n. See
1836         // PhiNode::Value().
1837         if (m_op == Op_CmpI) {
1838           PhiNode* phi = countedloop_phi_from_cmp((CmpINode*)m, n);
1839           if (phi != NULL) {
1840             worklist.push(phi);
1841           }
1842         }
1843         // Loading the java mirror from a Klass requires two loads and the type
1844         // of the mirror load depends on the type of 'n'. See LoadNode::Value().
1845         BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
1846         bool has_load_barrier_nodes = bs->has_load_barrier_nodes();
1847 
1848         if (m_op == Op_LoadP && m->bottom_type()->isa_rawptr()) {
1849           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1850             Node* u = m->fast_out(i2);
1851             const Type* ut = u->bottom_type();
1852             if (u->Opcode() == Op_LoadP && ut->isa_instptr() && ut != type(u)) {
1853               if (has_load_barrier_nodes) {
1854                 // Search for load barriers behind the load
1855                 for (DUIterator_Fast i3max, i3 = u->fast_outs(i3max); i3 < i3max; i3++) {
1856                   Node* b = u->fast_out(i3);
1857                   if (bs->is_gc_barrier_node(b)) {
1858                     worklist.push(b);
1859                   }
1860                 }
1861               }
1862               worklist.push(u);
1863             }
1864           }
1865         }
1866       }
1867     }
1868   }
1869 }
1870 
1871 //------------------------------do_transform-----------------------------------
1872 // Top level driver for the recursive transformer
1873 void PhaseCCP::do_transform() {
1874   // Correct leaves of new-space Nodes; they point to old-space.
1875   C->set_root( transform(C->root())->as_Root() );
1876   assert( C->top(),  "missing TOP node" );
1877   assert( C->root(), "missing root" );
1878 }
1879 
1880 //------------------------------transform--------------------------------------
1881 // Given a Node in old-space, clone him into new-space.
1882 // Convert any of his old-space children into new-space children.
1883 Node *PhaseCCP::transform( Node *n ) {
1884   Node *new_node = _nodes[n->_idx]; // Check for transformed node
1885   if( new_node != NULL )
1886     return new_node;                // Been there, done that, return old answer
1887   new_node = transform_once(n);     // Check for constant
1888   _nodes.map( n->_idx, new_node );  // Flag as having been cloned
1889 
1890   // Allocate stack of size _nodes.Size()/2 to avoid frequent realloc
1891   GrowableArray <Node *> trstack(C->live_nodes() >> 1);
1892 
1893   trstack.push(new_node);           // Process children of cloned node
1894   while ( trstack.is_nonempty() ) {
1895     Node *clone = trstack.pop();
1896     uint cnt = clone->req();
1897     for( uint i = 0; i < cnt; i++ ) {          // For all inputs do
1898       Node *input = clone->in(i);
1899       if( input != NULL ) {                    // Ignore NULLs
1900         Node *new_input = _nodes[input->_idx]; // Check for cloned input node
1901         if( new_input == NULL ) {
1902           new_input = transform_once(input);   // Check for constant
1903           _nodes.map( input->_idx, new_input );// Flag as having been cloned
1904           trstack.push(new_input);
1905         }
1906         assert( new_input == clone->in(i), "insanity check");
1907       }
1908     }
1909   }
1910   return new_node;
1911 }
1912 
1913 
1914 //------------------------------transform_once---------------------------------
1915 // For PhaseCCP, transformation is IDENTITY unless Node computed a constant.
1916 Node *PhaseCCP::transform_once( Node *n ) {
1917   const Type *t = type(n);
1918   // Constant?  Use constant Node instead
1919   if( t->singleton() ) {
1920     Node *nn = n;               // Default is to return the original constant
1921     if( t == Type::TOP ) {
1922       // cache my top node on the Compile instance
1923       if( C->cached_top_node() == NULL || C->cached_top_node()->in(0) == NULL ) {
1924         C->set_cached_top_node(ConNode::make(Type::TOP));
1925         set_type(C->top(), Type::TOP);
1926       }
1927       nn = C->top();
1928     }
1929     if( !n->is_Con() ) {
1930       if( t != Type::TOP ) {
1931         nn = makecon(t);        // ConNode::make(t);
1932         NOT_PRODUCT( inc_constants(); )
1933       } else if( n->is_Region() ) { // Unreachable region
1934         // Note: nn == C->top()
1935         n->set_req(0, NULL);        // Cut selfreference
1936         bool progress = true;
1937         uint max = n->outcnt();
1938         DUIterator i;
1939         while (progress) {
1940           progress = false;
1941           // Eagerly remove dead phis to avoid phis copies creation.
1942           for (i = n->outs(); n->has_out(i); i++) {
1943             Node* m = n->out(i);
1944             if (m->is_Phi()) {
1945               assert(type(m) == Type::TOP, "Unreachable region should not have live phis.");
1946               replace_node(m, nn);
1947               if (max != n->outcnt()) {
1948                 progress = true;
1949                 i = n->refresh_out_pos(i);
1950                 max = n->outcnt();
1951               }
1952             }
1953           }
1954         }
1955       }
1956       replace_node(n,nn);       // Update DefUse edges for new constant
1957     }
1958     return nn;
1959   }
1960 
1961   // If x is a TypeNode, capture any more-precise type permanently into Node
1962   if (t != n->bottom_type()) {
1963     hash_delete(n);             // changing bottom type may force a rehash
1964     n->raise_bottom_type(t);
1965     _worklist.push(n);          // n re-enters the hash table via the worklist
1966   }
1967 
1968   // TEMPORARY fix to ensure that 2nd GVN pass eliminates NULL checks
1969   switch( n->Opcode() ) {
1970   case Op_CallStaticJava:  // Give post-parse call devirtualization a chance
1971   case Op_CallDynamicJava:
1972   case Op_FastLock:        // Revisit FastLocks for lock coarsening
1973   case Op_If:
1974   case Op_CountedLoopEnd:
1975   case Op_Region:
1976   case Op_Loop:
1977   case Op_CountedLoop:
1978   case Op_Conv2B:
1979   case Op_Opaque1:
1980   case Op_Opaque2:
1981     _worklist.push(n);
1982     break;
1983   default:
1984     break;
1985   }
1986 
1987   return  n;
1988 }
1989 
1990 //---------------------------------saturate------------------------------------
1991 const Type* PhaseCCP::saturate(const Type* new_type, const Type* old_type,
1992                                const Type* limit_type) const {
1993   const Type* wide_type = new_type->widen(old_type, limit_type);
1994   if (wide_type != new_type) {          // did we widen?
1995     // If so, we may have widened beyond the limit type.  Clip it back down.
1996     new_type = wide_type->filter(limit_type);
1997   }
1998   return new_type;
1999 }
2000 
2001 //------------------------------print_statistics-------------------------------
2002 #ifndef PRODUCT
2003 void PhaseCCP::print_statistics() {
2004   tty->print_cr("CCP: %d  constants found: %d", _total_invokes, _total_constants);
2005 }
2006 #endif
2007 
2008 
2009 //=============================================================================
2010 #ifndef PRODUCT
2011 uint PhasePeephole::_total_peepholes = 0;
2012 #endif
2013 //------------------------------PhasePeephole----------------------------------
2014 // Conditional Constant Propagation, ala Wegman & Zadeck
2015 PhasePeephole::PhasePeephole( PhaseRegAlloc *regalloc, PhaseCFG &cfg )
2016   : PhaseTransform(Peephole), _regalloc(regalloc), _cfg(cfg) {
2017   NOT_PRODUCT( clear_peepholes(); )
2018 }
2019 
2020 #ifndef PRODUCT
2021 //------------------------------~PhasePeephole---------------------------------
2022 PhasePeephole::~PhasePeephole() {
2023   _total_peepholes += count_peepholes();
2024 }
2025 #endif
2026 
2027 //------------------------------transform--------------------------------------
2028 Node *PhasePeephole::transform( Node *n ) {
2029   ShouldNotCallThis();
2030   return NULL;
2031 }
2032 
2033 //------------------------------do_transform-----------------------------------
2034 void PhasePeephole::do_transform() {
2035   bool method_name_not_printed = true;
2036 
2037   // Examine each basic block
2038   for (uint block_number = 1; block_number < _cfg.number_of_blocks(); ++block_number) {
2039     Block* block = _cfg.get_block(block_number);
2040     bool block_not_printed = true;
2041 
2042     // and each instruction within a block
2043     uint end_index = block->number_of_nodes();
2044     // block->end_idx() not valid after PhaseRegAlloc
2045     for( uint instruction_index = 1; instruction_index < end_index; ++instruction_index ) {
2046       Node     *n = block->get_node(instruction_index);
2047       if( n->is_Mach() ) {
2048         MachNode *m = n->as_Mach();
2049         int deleted_count = 0;
2050         // check for peephole opportunities
2051         MachNode *m2 = m->peephole(block, instruction_index, _regalloc, deleted_count);
2052         if( m2 != NULL ) {
2053 #ifndef PRODUCT
2054           if( PrintOptoPeephole ) {
2055             // Print method, first time only
2056             if( C->method() && method_name_not_printed ) {
2057               C->method()->print_short_name(); tty->cr();
2058               method_name_not_printed = false;
2059             }
2060             // Print this block
2061             if( Verbose && block_not_printed) {
2062               tty->print_cr("in block");
2063               block->dump();
2064               block_not_printed = false;
2065             }
2066             // Print instructions being deleted
2067             for( int i = (deleted_count - 1); i >= 0; --i ) {
2068               block->get_node(instruction_index-i)->as_Mach()->format(_regalloc); tty->cr();
2069             }
2070             tty->print_cr("replaced with");
2071             // Print new instruction
2072             m2->format(_regalloc);
2073             tty->print("\n\n");
2074           }
2075 #endif
2076           // Remove old nodes from basic block and update instruction_index
2077           // (old nodes still exist and may have edges pointing to them
2078           //  as register allocation info is stored in the allocator using
2079           //  the node index to live range mappings.)
2080           uint safe_instruction_index = (instruction_index - deleted_count);
2081           for( ; (instruction_index > safe_instruction_index); --instruction_index ) {
2082             block->remove_node( instruction_index );
2083           }
2084           // install new node after safe_instruction_index
2085           block->insert_node(m2, safe_instruction_index + 1);
2086           end_index = block->number_of_nodes() - 1; // Recompute new block size
2087           NOT_PRODUCT( inc_peepholes(); )
2088         }
2089       }
2090     }
2091   }
2092 }
2093 
2094 //------------------------------print_statistics-------------------------------
2095 #ifndef PRODUCT
2096 void PhasePeephole::print_statistics() {
2097   tty->print_cr("Peephole: peephole rules applied: %d",  _total_peepholes);
2098 }
2099 #endif
2100 
2101 
2102 //=============================================================================
2103 //------------------------------set_req_X--------------------------------------
2104 void Node::set_req_X( uint i, Node *n, PhaseIterGVN *igvn ) {
2105   assert( is_not_dead(n), "can not use dead node");
2106   assert( igvn->hash_find(this) != this, "Need to remove from hash before changing edges" );
2107   Node *old = in(i);
2108   set_req(i, n);
2109 
2110   // old goes dead?
2111   if( old ) {
2112     switch (old->outcnt()) {
2113     case 0:
2114       // Put into the worklist to kill later. We do not kill it now because the
2115       // recursive kill will delete the current node (this) if dead-loop exists
2116       if (!old->is_top())
2117         igvn->_worklist.push( old );
2118       break;
2119     case 1:
2120       if( old->is_Store() || old->has_special_unique_user() )
2121         igvn->add_users_to_worklist( old );
2122       break;
2123     case 2:
2124       if( old->is_Store() )
2125         igvn->add_users_to_worklist( old );
2126       if( old->Opcode() == Op_Region )
2127         igvn->_worklist.push(old);
2128       break;
2129     case 3:
2130       if( old->Opcode() == Op_Region ) {
2131         igvn->_worklist.push(old);
2132         igvn->add_users_to_worklist( old );
2133       }
2134       break;
2135     default:
2136       break;
2137     }
2138 
2139     BarrierSet::barrier_set()->barrier_set_c2()->enqueue_useful_gc_barrier(igvn, old);
2140   }
2141 }
2142 
2143 void Node::set_req_X(uint i, Node *n, PhaseGVN *gvn) {
2144   PhaseIterGVN* igvn = gvn->is_IterGVN();
2145   if (igvn == NULL) {
2146     set_req(i, n);
2147     return;
2148   }
2149   set_req_X(i, n, igvn);
2150 }
2151 
2152 //-------------------------------replace_by-----------------------------------
2153 // Using def-use info, replace one node for another.  Follow the def-use info
2154 // to all users of the OLD node.  Then make all uses point to the NEW node.
2155 void Node::replace_by(Node *new_node) {
2156   assert(!is_top(), "top node has no DU info");
2157   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; ) {
2158     Node* use = last_out(i);
2159     uint uses_found = 0;
2160     for (uint j = 0; j < use->len(); j++) {
2161       if (use->in(j) == this) {
2162         if (j < use->req())
2163               use->set_req(j, new_node);
2164         else  use->set_prec(j, new_node);
2165         uses_found++;
2166       }
2167     }
2168     i -= uses_found;    // we deleted 1 or more copies of this edge
2169   }
2170 }
2171 
2172 //=============================================================================
2173 //-----------------------------------------------------------------------------
2174 void Type_Array::grow( uint i ) {
2175   if( !_max ) {
2176     _max = 1;
2177     _types = (const Type**)_a->Amalloc( _max * sizeof(Type*) );
2178     _types[0] = NULL;
2179   }
2180   uint old = _max;
2181   _max = next_power_of_2(i);
2182   _types = (const Type**)_a->Arealloc( _types, old*sizeof(Type*),_max*sizeof(Type*));
2183   memset( &_types[old], 0, (_max-old)*sizeof(Type*) );
2184 }
2185 
2186 //------------------------------dump-------------------------------------------
2187 #ifndef PRODUCT
2188 void Type_Array::dump() const {
2189   uint max = Size();
2190   for( uint i = 0; i < max; i++ ) {
2191     if( _types[i] != NULL ) {
2192       tty->print("  %d\t== ", i); _types[i]->dump(); tty->cr();
2193     }
2194   }
2195 }
2196 #endif