1 /*
   2  * Copyright (c) 1997, 2014, 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 "memory/allocation.inline.hpp"
  27 #include "opto/block.hpp"
  28 #include "opto/callnode.hpp"
  29 #include "opto/castnode.hpp"
  30 #include "opto/cfgnode.hpp"
  31 #include "opto/idealGraphPrinter.hpp"
  32 #include "opto/loopnode.hpp"
  33 #include "opto/machnode.hpp"
  34 #include "opto/opcodes.hpp"
  35 #include "opto/phaseX.hpp"
  36 #include "opto/regalloc.hpp"
  37 #include "opto/rootnode.hpp"
  38 
  39 //=============================================================================
  40 #define NODE_HASH_MINIMUM_SIZE    255
  41 //------------------------------NodeHash---------------------------------------
  42 NodeHash::NodeHash(uint est_max_size) :
  43   _max( round_up(est_max_size < NODE_HASH_MINIMUM_SIZE ? NODE_HASH_MINIMUM_SIZE : est_max_size) ),
  44   _a(Thread::current()->resource_area()),
  45   _table( NEW_ARENA_ARRAY( _a , Node* , _max ) ), // (Node**)_a->Amalloc(_max * sizeof(Node*)) ),
  46   _inserts(0), _insert_limit( insert_limit() )
  47 #ifndef PRODUCT
  48   ,_look_probes(0), _lookup_hits(0), _lookup_misses(0),
  49   _delete_probes(0), _delete_hits(0), _delete_misses(0),
  50   _total_insert_probes(0), _total_inserts(0),
  51   _insert_probes(0), _grows(0)
  52 #endif
  53 {
  54   // _sentinel must be in the current node space
  55   _sentinel = new ProjNode(NULL, TypeFunc::Control);
  56   memset(_table,0,sizeof(Node*)*_max);
  57 }
  58 
  59 //------------------------------NodeHash---------------------------------------
  60 NodeHash::NodeHash(Arena *arena, uint est_max_size) :
  61   _max( round_up(est_max_size < NODE_HASH_MINIMUM_SIZE ? NODE_HASH_MINIMUM_SIZE : est_max_size) ),
  62   _a(arena),
  63   _table( NEW_ARENA_ARRAY( _a , Node* , _max ) ),
  64   _inserts(0), _insert_limit( insert_limit() )
  65 #ifndef PRODUCT
  66   ,_look_probes(0), _lookup_hits(0), _lookup_misses(0),
  67   _delete_probes(0), _delete_hits(0), _delete_misses(0),
  68   _total_insert_probes(0), _total_inserts(0),
  69   _insert_probes(0), _grows(0)
  70 #endif
  71 {
  72   // _sentinel must be in the current node space
  73   _sentinel = new ProjNode(NULL, TypeFunc::Control);
  74   memset(_table,0,sizeof(Node*)*_max);
  75 }
  76 
  77 //------------------------------NodeHash---------------------------------------
  78 NodeHash::NodeHash(NodeHash *nh) {
  79   debug_only(_table = (Node**)badAddress);   // interact correctly w/ operator=
  80   // just copy in all the fields
  81   *this = *nh;
  82   // nh->_sentinel must be in the current node space
  83 }
  84 
  85 void NodeHash::replace_with(NodeHash *nh) {
  86   debug_only(_table = (Node**)badAddress);   // interact correctly w/ operator=
  87   // just copy in all the fields
  88   *this = *nh;
  89   // nh->_sentinel must be in the current node space
  90 }
  91 
  92 //------------------------------hash_find--------------------------------------
  93 // Find in hash table
  94 Node *NodeHash::hash_find( const Node *n ) {
  95   // ((Node*)n)->set_hash( n->hash() );
  96   uint hash = n->hash();
  97   if (hash == Node::NO_HASH) {
  98     NOT_PRODUCT( _lookup_misses++ );
  99     return NULL;
 100   }
 101   uint key = hash & (_max-1);
 102   uint stride = key | 0x01;
 103   NOT_PRODUCT( _look_probes++ );
 104   Node *k = _table[key];        // Get hashed value
 105   if( !k ) {                    // ?Miss?
 106     NOT_PRODUCT( _lookup_misses++ );
 107     return NULL;                // Miss!
 108   }
 109 
 110   int op = n->Opcode();
 111   uint req = n->req();
 112   while( 1 ) {                  // While probing hash table
 113     if( k->req() == req &&      // Same count of inputs
 114         k->Opcode() == op ) {   // Same Opcode
 115       for( uint i=0; i<req; i++ )
 116         if( n->in(i)!=k->in(i)) // Different inputs?
 117           goto collision;       // "goto" is a speed hack...
 118       if( n->cmp(*k) ) {        // Check for any special bits
 119         NOT_PRODUCT( _lookup_hits++ );
 120         return k;               // Hit!
 121       }
 122     }
 123   collision:
 124     NOT_PRODUCT( _look_probes++ );
 125     key = (key + stride/*7*/) & (_max-1); // Stride through table with relative prime
 126     k = _table[key];            // Get hashed value
 127     if( !k ) {                  // ?Miss?
 128       NOT_PRODUCT( _lookup_misses++ );
 129       return NULL;              // Miss!
 130     }
 131   }
 132   ShouldNotReachHere();
 133   return NULL;
 134 }
 135 
 136 //------------------------------hash_find_insert-------------------------------
 137 // Find in hash table, insert if not already present
 138 // Used to preserve unique entries in hash table
 139 Node *NodeHash::hash_find_insert( Node *n ) {
 140   // n->set_hash( );
 141   uint hash = n->hash();
 142   if (hash == Node::NO_HASH) {
 143     NOT_PRODUCT( _lookup_misses++ );
 144     return NULL;
 145   }
 146   uint key = hash & (_max-1);
 147   uint stride = key | 0x01;     // stride must be relatively prime to table siz
 148   uint first_sentinel = 0;      // replace a sentinel if seen.
 149   NOT_PRODUCT( _look_probes++ );
 150   Node *k = _table[key];        // Get hashed value
 151   if( !k ) {                    // ?Miss?
 152     NOT_PRODUCT( _lookup_misses++ );
 153     _table[key] = n;            // Insert into table!
 154     debug_only(n->enter_hash_lock()); // Lock down the node while in the table.
 155     check_grow();               // Grow table if insert hit limit
 156     return NULL;                // Miss!
 157   }
 158   else if( k == _sentinel ) {
 159     first_sentinel = key;      // Can insert here
 160   }
 161 
 162   int op = n->Opcode();
 163   uint req = n->req();
 164   while( 1 ) {                  // While probing hash table
 165     if( k->req() == req &&      // Same count of inputs
 166         k->Opcode() == op ) {   // Same Opcode
 167       for( uint i=0; i<req; i++ )
 168         if( n->in(i)!=k->in(i)) // Different inputs?
 169           goto collision;       // "goto" is a speed hack...
 170       if( n->cmp(*k) ) {        // Check for any special bits
 171         NOT_PRODUCT( _lookup_hits++ );
 172         return k;               // Hit!
 173       }
 174     }
 175   collision:
 176     NOT_PRODUCT( _look_probes++ );
 177     key = (key + stride) & (_max-1); // Stride through table w/ relative prime
 178     k = _table[key];            // Get hashed value
 179     if( !k ) {                  // ?Miss?
 180       NOT_PRODUCT( _lookup_misses++ );
 181       key = (first_sentinel == 0) ? key : first_sentinel; // ?saw sentinel?
 182       _table[key] = n;          // Insert into table!
 183       debug_only(n->enter_hash_lock()); // Lock down the node while in the table.
 184       check_grow();             // Grow table if insert hit limit
 185       return NULL;              // Miss!
 186     }
 187     else if( first_sentinel == 0 && k == _sentinel ) {
 188       first_sentinel = key;    // Can insert here
 189     }
 190 
 191   }
 192   ShouldNotReachHere();
 193   return NULL;
 194 }
 195 
 196 //------------------------------hash_insert------------------------------------
 197 // Insert into hash table
 198 void NodeHash::hash_insert( Node *n ) {
 199   // // "conflict" comments -- print nodes that conflict
 200   // bool conflict = false;
 201   // n->set_hash();
 202   uint hash = n->hash();
 203   if (hash == Node::NO_HASH) {
 204     return;
 205   }
 206   check_grow();
 207   uint key = hash & (_max-1);
 208   uint stride = key | 0x01;
 209 
 210   while( 1 ) {                  // While probing hash table
 211     NOT_PRODUCT( _insert_probes++ );
 212     Node *k = _table[key];      // Get hashed value
 213     if( !k || (k == _sentinel) ) break;       // Found a slot
 214     assert( k != n, "already inserted" );
 215     // if( PrintCompilation && PrintOptoStatistics && Verbose ) { tty->print("  conflict: "); k->dump(); conflict = true; }
 216     key = (key + stride) & (_max-1); // Stride through table w/ relative prime
 217   }
 218   _table[key] = n;              // Insert into table!
 219   debug_only(n->enter_hash_lock()); // Lock down the node while in the table.
 220   // if( conflict ) { n->dump(); }
 221 }
 222 
 223 //------------------------------hash_delete------------------------------------
 224 // Replace in hash table with sentinel
 225 bool NodeHash::hash_delete( const Node *n ) {
 226   Node *k;
 227   uint hash = n->hash();
 228   if (hash == Node::NO_HASH) {
 229     NOT_PRODUCT( _delete_misses++ );
 230     return false;
 231   }
 232   uint key = hash & (_max-1);
 233   uint stride = key | 0x01;
 234   debug_only( uint counter = 0; );
 235   for( ; /* (k != NULL) && (k != _sentinel) */; ) {
 236     debug_only( counter++ );
 237     NOT_PRODUCT( _delete_probes++ );
 238     k = _table[key];            // Get hashed value
 239     if( !k ) {                  // Miss?
 240       NOT_PRODUCT( _delete_misses++ );
 241 #ifdef ASSERT
 242       if( VerifyOpto ) {
 243         for( uint i=0; i < _max; i++ )
 244           assert( _table[i] != n, "changed edges with rehashing" );
 245       }
 246 #endif
 247       return false;             // Miss! Not in chain
 248     }
 249     else if( n == k ) {
 250       NOT_PRODUCT( _delete_hits++ );
 251       _table[key] = _sentinel;  // Hit! Label as deleted entry
 252       debug_only(((Node*)n)->exit_hash_lock()); // Unlock the node upon removal from table.
 253       return true;
 254     }
 255     else {
 256       // collision: move through table with prime offset
 257       key = (key + stride/*7*/) & (_max-1);
 258       assert( counter <= _insert_limit, "Cycle in hash-table");
 259     }
 260   }
 261   ShouldNotReachHere();
 262   return false;
 263 }
 264 
 265 //------------------------------round_up---------------------------------------
 266 // Round up to nearest power of 2
 267 uint NodeHash::round_up( uint x ) {
 268   x += (x>>2);                  // Add 25% slop
 269   if( x <16 ) return 16;        // Small stuff
 270   uint i=16;
 271   while( i < x ) i <<= 1;       // Double to fit
 272   return i;                     // Return hash table size
 273 }
 274 
 275 //------------------------------grow-------------------------------------------
 276 // Grow _table to next power of 2 and insert old entries
 277 void  NodeHash::grow() {
 278   // Record old state
 279   uint   old_max   = _max;
 280   Node **old_table = _table;
 281   // Construct new table with twice the space
 282 #ifndef PRODUCT
 283   _grows++;
 284   _total_inserts       += _inserts;
 285   _total_insert_probes += _insert_probes;
 286   _insert_probes   = 0;
 287 #endif
 288   _inserts         = 0;
 289   _max     = _max << 1;
 290   _table   = NEW_ARENA_ARRAY( _a , Node* , _max ); // (Node**)_a->Amalloc( _max * sizeof(Node*) );
 291   memset(_table,0,sizeof(Node*)*_max);
 292   _insert_limit = insert_limit();
 293   // Insert old entries into the new table
 294   for( uint i = 0; i < old_max; i++ ) {
 295     Node *m = *old_table++;
 296     if( !m || m == _sentinel ) continue;
 297     debug_only(m->exit_hash_lock()); // Unlock the node upon removal from old table.
 298     hash_insert(m);
 299   }
 300 }
 301 
 302 //------------------------------clear------------------------------------------
 303 // Clear all entries in _table to NULL but keep storage
 304 void  NodeHash::clear() {
 305 #ifdef ASSERT
 306   // Unlock all nodes upon removal from table.
 307   for (uint i = 0; i < _max; i++) {
 308     Node* n = _table[i];
 309     if (!n || n == _sentinel)  continue;
 310     n->exit_hash_lock();
 311   }
 312 #endif
 313 
 314   memset( _table, 0, _max * sizeof(Node*) );
 315 }
 316 
 317 //-----------------------remove_useless_nodes----------------------------------
 318 // Remove useless nodes from value table,
 319 // implementation does not depend on hash function
 320 void NodeHash::remove_useless_nodes(VectorSet &useful) {
 321 
 322   // Dead nodes in the hash table inherited from GVN should not replace
 323   // existing nodes, remove dead nodes.
 324   uint max = size();
 325   Node *sentinel_node = sentinel();
 326   for( uint i = 0; i < max; ++i ) {
 327     Node *n = at(i);
 328     if(n != NULL && n != sentinel_node && !useful.test(n->_idx)) {
 329       debug_only(n->exit_hash_lock()); // Unlock the node when removed
 330       _table[i] = sentinel_node;       // Replace with placeholder
 331     }
 332   }
 333 }
 334 
 335 
 336 void NodeHash::check_no_speculative_types() {
 337 #ifdef ASSERT
 338   uint max = size();
 339   Node *sentinel_node = sentinel();
 340   for (uint i = 0; i < max; ++i) {
 341     Node *n = at(i);
 342     if(n != NULL && n != sentinel_node && n->is_Type() && n->outcnt() > 0) {
 343       TypeNode* tn = n->as_Type();
 344       const Type* t = tn->type();
 345       const Type* t_no_spec = t->remove_speculative();
 346       assert(t == t_no_spec, "dead node in hash table or missed node during speculative cleanup");
 347     }
 348   }
 349 #endif
 350 }
 351 
 352 #ifndef PRODUCT
 353 //------------------------------dump-------------------------------------------
 354 // Dump statistics for the hash table
 355 void NodeHash::dump() {
 356   _total_inserts       += _inserts;
 357   _total_insert_probes += _insert_probes;
 358   if (PrintCompilation && PrintOptoStatistics && Verbose && (_inserts > 0)) {
 359     if (WizardMode) {
 360       for (uint i=0; i<_max; i++) {
 361         if (_table[i])
 362           tty->print("%d/%d/%d ",i,_table[i]->hash()&(_max-1),_table[i]->_idx);
 363       }
 364     }
 365     tty->print("\nGVN Hash stats:  %d grows to %d max_size\n", _grows, _max);
 366     tty->print("  %d/%d (%8.1f%% full)\n", _inserts, _max, (double)_inserts/_max*100.0);
 367     tty->print("  %dp/(%dh+%dm) (%8.2f probes/lookup)\n", _look_probes, _lookup_hits, _lookup_misses, (double)_look_probes/(_lookup_hits+_lookup_misses));
 368     tty->print("  %dp/%di (%8.2f probes/insert)\n", _total_insert_probes, _total_inserts, (double)_total_insert_probes/_total_inserts);
 369     // sentinels increase lookup cost, but not insert cost
 370     assert((_lookup_misses+_lookup_hits)*4+100 >= _look_probes, "bad hash function");
 371     assert( _inserts+(_inserts>>3) < _max, "table too full" );
 372     assert( _inserts*3+100 >= _insert_probes, "bad hash function" );
 373   }
 374 }
 375 
 376 Node *NodeHash::find_index(uint idx) { // For debugging
 377   // Find an entry by its index value
 378   for( uint i = 0; i < _max; i++ ) {
 379     Node *m = _table[i];
 380     if( !m || m == _sentinel ) continue;
 381     if( m->_idx == (uint)idx ) return m;
 382   }
 383   return NULL;
 384 }
 385 #endif
 386 
 387 #ifdef ASSERT
 388 NodeHash::~NodeHash() {
 389   // Unlock all nodes upon destruction of table.
 390   if (_table != (Node**)badAddress)  clear();
 391 }
 392 
 393 void NodeHash::operator=(const NodeHash& nh) {
 394   // Unlock all nodes upon replacement of table.
 395   if (&nh == this)  return;
 396   if (_table != (Node**)badAddress)  clear();
 397   memcpy(this, &nh, sizeof(*this));
 398   // Do not increment hash_lock counts again.
 399   // Instead, be sure we never again use the source table.
 400   ((NodeHash*)&nh)->_table = (Node**)badAddress;
 401 }
 402 
 403 
 404 #endif
 405 
 406 
 407 //=============================================================================
 408 //------------------------------PhaseRemoveUseless-----------------------------
 409 // 1) Use a breadthfirst walk to collect useful nodes reachable from root.
 410 PhaseRemoveUseless::PhaseRemoveUseless(PhaseGVN *gvn, Unique_Node_List *worklist, PhaseNumber phase_num) : Phase(phase_num),
 411   _useful(Thread::current()->resource_area()) {
 412 
 413   // Implementation requires 'UseLoopSafepoints == true' and an edge from root
 414   // to each SafePointNode at a backward branch.  Inserted in add_safepoint().
 415   if( !UseLoopSafepoints || !OptoRemoveUseless ) return;
 416 
 417   // Identify nodes that are reachable from below, useful.
 418   C->identify_useful_nodes(_useful);
 419   // Update dead node list
 420   C->update_dead_node_list(_useful);
 421 
 422   // Remove all useless nodes from PhaseValues' recorded types
 423   // Must be done before disconnecting nodes to preserve hash-table-invariant
 424   gvn->remove_useless_nodes(_useful.member_set());
 425 
 426   // Remove all useless nodes from future worklist
 427   worklist->remove_useless_nodes(_useful.member_set());
 428 
 429   // Disconnect 'useless' nodes that are adjacent to useful nodes
 430   C->remove_useless_nodes(_useful);
 431 
 432   // Remove edges from "root" to each SafePoint at a backward branch.
 433   // They were inserted during parsing (see add_safepoint()) to make infinite
 434   // loops without calls or exceptions visible to root, i.e., useful.
 435   Node *root = C->root();
 436   if( root != NULL ) {
 437     for( uint i = root->req(); i < root->len(); ++i ) {
 438       Node *n = root->in(i);
 439       if( n != NULL && n->is_SafePoint() ) {
 440         root->rm_prec(i);
 441         --i;
 442       }
 443     }
 444   }
 445 }
 446 
 447 //=============================================================================
 448 //------------------------------PhaseRenumberLive------------------------------
 449 // First, remove useless nodes (equivalent to identifying live nodes).
 450 // Then, renumber live nodes.
 451 //
 452 // The set of live nodes is returned by PhaseRemoveUseless in the _useful structure.
 453 // If the number of live nodes is 'x' (where 'x' == _useful.size()), then the
 454 // PhaseRenumberLive updates the node ID of each node (the _idx field) with a unique
 455 // value in the range [0, x).
 456 //
 457 // At the end of the PhaseRenumberLive phase, the compiler's count of unique nodes is
 458 // updated to 'x' and the list of dead nodes is reset (as there are no dead nodes).
 459 //
 460 // The PhaseRenumberLive phase updates two data structures with the new node IDs.
 461 // (1) The worklist is used by the PhaseIterGVN phase to identify nodes that must be
 462 // processed. A new worklist (with the updated node IDs) is returned in 'new_worklist'.
 463 // (2) Type information (the field PhaseGVN::_types) maps type information to each
 464 // node ID. The mapping is updated to use the new node IDs as well. Updated type
 465 // information is returned in PhaseGVN::_types.
 466 //
 467 // The PhaseRenumberLive phase does not preserve the order of elements in the worklist.
 468 //
 469 // Other data structures used by the compiler are not updated. The hash table for value
 470 // numbering (the field PhaseGVN::_table) is not updated because computing the hash
 471 // values is not based on node IDs. The field PhaseGVN::_nodes is not updated either
 472 // because it is empty wherever PhaseRenumberLive is used.
 473 PhaseRenumberLive::PhaseRenumberLive(PhaseGVN* gvn,
 474                                      Unique_Node_List* worklist, Unique_Node_List* new_worklist,
 475                                      PhaseNumber phase_num) :
 476   PhaseRemoveUseless(gvn, worklist, Remove_Useless_And_Renumber_Live) {
 477 
 478   assert(RenumberLiveNodes, "RenumberLiveNodes must be set to true for node renumbering to take place");
 479   assert(C->live_nodes() == _useful.size(), "the number of live nodes must match the number of useful nodes");
 480   assert(gvn->nodes_size() == 0, "GVN must not contain any nodes at this point");
 481 
 482   uint old_unique_count = C->unique();
 483   uint live_node_count = C->live_nodes();
 484   uint worklist_size = worklist->size();
 485 
 486   // Storage for the updated type information.
 487   Type_Array new_type_array(C->comp_arena());
 488 
 489   // Iterate over the set of live nodes.
 490   uint current_idx = 0; // The current new node ID. Incremented after every assignment.
 491   for (uint i = 0; i < _useful.size(); i++) {
 492     Node* n = _useful.at(i);
 493     const Type* type = gvn->type_or_null(n);
 494     new_type_array.map(current_idx, type);
 495 
 496     bool in_worklist = false;
 497     if (worklist->member(n)) {
 498       in_worklist = true;
 499     }
 500 
 501     n->set_idx(current_idx); // Update node ID.
 502 
 503     if (in_worklist) {
 504       new_worklist->push(n);
 505     }
 506 
 507     current_idx++;
 508   }
 509 
 510   assert(worklist_size == new_worklist->size(), "the new worklist must have the same size as the original worklist");
 511   assert(live_node_count == current_idx, "all live nodes must be processed");
 512 
 513   // Replace the compiler's type information with the updated type information.
 514   gvn->replace_types(new_type_array);
 515 
 516   // Update the unique node count of the compilation to the number of currently live nodes.
 517   C->set_unique(live_node_count);
 518 
 519   // Set the dead node count to 0 and reset dead node list.
 520   C->reset_dead_node_list();
 521 }
 522 
 523 
 524 //=============================================================================
 525 //------------------------------PhaseTransform---------------------------------
 526 PhaseTransform::PhaseTransform( PhaseNumber pnum ) : Phase(pnum),
 527   _arena(Thread::current()->resource_area()),
 528   _nodes(_arena),
 529   _types(_arena)
 530 {
 531   init_con_caches();
 532 #ifndef PRODUCT
 533   clear_progress();
 534   clear_transforms();
 535   set_allow_progress(true);
 536 #endif
 537   // Force allocation for currently existing nodes
 538   _types.map(C->unique(), NULL);
 539 }
 540 
 541 //------------------------------PhaseTransform---------------------------------
 542 PhaseTransform::PhaseTransform( Arena *arena, PhaseNumber pnum ) : Phase(pnum),
 543   _arena(arena),
 544   _nodes(arena),
 545   _types(arena)
 546 {
 547   init_con_caches();
 548 #ifndef PRODUCT
 549   clear_progress();
 550   clear_transforms();
 551   set_allow_progress(true);
 552 #endif
 553   // Force allocation for currently existing nodes
 554   _types.map(C->unique(), NULL);
 555 }
 556 
 557 //------------------------------PhaseTransform---------------------------------
 558 // Initialize with previously generated type information
 559 PhaseTransform::PhaseTransform( PhaseTransform *pt, PhaseNumber pnum ) : Phase(pnum),
 560   _arena(pt->_arena),
 561   _nodes(pt->_nodes),
 562   _types(pt->_types)
 563 {
 564   init_con_caches();
 565 #ifndef PRODUCT
 566   clear_progress();
 567   clear_transforms();
 568   set_allow_progress(true);
 569 #endif
 570 }
 571 
 572 void PhaseTransform::init_con_caches() {
 573   memset(_icons,0,sizeof(_icons));
 574   memset(_lcons,0,sizeof(_lcons));
 575   memset(_zcons,0,sizeof(_zcons));
 576 }
 577 
 578 
 579 //--------------------------------find_int_type--------------------------------
 580 const TypeInt* PhaseTransform::find_int_type(Node* n) {
 581   if (n == NULL)  return NULL;
 582   // Call type_or_null(n) to determine node's type since we might be in
 583   // parse phase and call n->Value() may return wrong type.
 584   // (For example, a phi node at the beginning of loop parsing is not ready.)
 585   const Type* t = type_or_null(n);
 586   if (t == NULL)  return NULL;
 587   return t->isa_int();
 588 }
 589 
 590 
 591 //-------------------------------find_long_type--------------------------------
 592 const TypeLong* PhaseTransform::find_long_type(Node* n) {
 593   if (n == NULL)  return NULL;
 594   // (See comment above on type_or_null.)
 595   const Type* t = type_or_null(n);
 596   if (t == NULL)  return NULL;
 597   return t->isa_long();
 598 }
 599 
 600 
 601 #ifndef PRODUCT
 602 void PhaseTransform::dump_old2new_map() const {
 603   _nodes.dump();
 604 }
 605 
 606 void PhaseTransform::dump_new( uint nidx ) const {
 607   for( uint i=0; i<_nodes.Size(); i++ )
 608     if( _nodes[i] && _nodes[i]->_idx == nidx ) {
 609       _nodes[i]->dump();
 610       tty->cr();
 611       tty->print_cr("Old index= %d",i);
 612       return;
 613     }
 614   tty->print_cr("Node %d not found in the new indices", nidx);
 615 }
 616 
 617 //------------------------------dump_types-------------------------------------
 618 void PhaseTransform::dump_types( ) const {
 619   _types.dump();
 620 }
 621 
 622 //------------------------------dump_nodes_and_types---------------------------
 623 void PhaseTransform::dump_nodes_and_types(const Node *root, uint depth, bool only_ctrl) {
 624   VectorSet visited(Thread::current()->resource_area());
 625   dump_nodes_and_types_recur( root, depth, only_ctrl, visited );
 626 }
 627 
 628 //------------------------------dump_nodes_and_types_recur---------------------
 629 void PhaseTransform::dump_nodes_and_types_recur( const Node *n, uint depth, bool only_ctrl, VectorSet &visited) {
 630   if( !n ) return;
 631   if( depth == 0 ) return;
 632   if( visited.test_set(n->_idx) ) return;
 633   for( uint i=0; i<n->len(); i++ ) {
 634     if( only_ctrl && !(n->is_Region()) && i != TypeFunc::Control ) continue;
 635     dump_nodes_and_types_recur( n->in(i), depth-1, only_ctrl, visited );
 636   }
 637   n->dump();
 638   if (type_or_null(n) != NULL) {
 639     tty->print("      "); type(n)->dump(); tty->cr();
 640   }
 641 }
 642 
 643 #endif
 644 
 645 
 646 //=============================================================================
 647 //------------------------------PhaseValues------------------------------------
 648 // Set minimum table size to "255"
 649 PhaseValues::PhaseValues( Arena *arena, uint est_max_size ) : PhaseTransform(arena, GVN), _table(arena, est_max_size) {
 650   NOT_PRODUCT( clear_new_values(); )
 651 }
 652 
 653 //------------------------------PhaseValues------------------------------------
 654 // Set minimum table size to "255"
 655 PhaseValues::PhaseValues( PhaseValues *ptv ) : PhaseTransform( ptv, GVN ),
 656   _table(&ptv->_table) {
 657   NOT_PRODUCT( clear_new_values(); )
 658 }
 659 
 660 //------------------------------PhaseValues------------------------------------
 661 // Used by +VerifyOpto.  Clear out hash table but copy _types array.
 662 PhaseValues::PhaseValues( PhaseValues *ptv, const char *dummy ) : PhaseTransform( ptv, GVN ),
 663   _table(ptv->arena(),ptv->_table.size()) {
 664   NOT_PRODUCT( clear_new_values(); )
 665 }
 666 
 667 //------------------------------~PhaseValues-----------------------------------
 668 #ifndef PRODUCT
 669 PhaseValues::~PhaseValues() {
 670   _table.dump();
 671 
 672   // Statistics for value progress and efficiency
 673   if( PrintCompilation && Verbose && WizardMode ) {
 674     tty->print("\n%sValues: %d nodes ---> %d/%d (%d)",
 675       is_IterGVN() ? "Iter" : "    ", C->unique(), made_progress(), made_transforms(), made_new_values());
 676     if( made_transforms() != 0 ) {
 677       tty->print_cr("  ratio %f", made_progress()/(float)made_transforms() );
 678     } else {
 679       tty->cr();
 680     }
 681   }
 682 }
 683 #endif
 684 
 685 //------------------------------makecon----------------------------------------
 686 ConNode* PhaseTransform::makecon(const Type *t) {
 687   assert(t->singleton(), "must be a constant");
 688   assert(!t->empty() || t == Type::TOP, "must not be vacuous range");
 689   switch (t->base()) {  // fast paths
 690   case Type::Half:
 691   case Type::Top:  return (ConNode*) C->top();
 692   case Type::Int:  return intcon( t->is_int()->get_con() );
 693   case Type::Long: return longcon( t->is_long()->get_con() );
 694   }
 695   if (t->is_zero_type())
 696     return zerocon(t->basic_type());
 697   return uncached_makecon(t);
 698 }
 699 
 700 //--------------------------uncached_makecon-----------------------------------
 701 // Make an idealized constant - one of ConINode, ConPNode, etc.
 702 ConNode* PhaseValues::uncached_makecon(const Type *t) {
 703   assert(t->singleton(), "must be a constant");
 704   ConNode* x = ConNode::make(t);
 705   ConNode* k = (ConNode*)hash_find_insert(x); // Value numbering
 706   if (k == NULL) {
 707     set_type(x, t);             // Missed, provide type mapping
 708     GrowableArray<Node_Notes*>* nna = C->node_note_array();
 709     if (nna != NULL) {
 710       Node_Notes* loc = C->locate_node_notes(nna, x->_idx, true);
 711       loc->clear(); // do not put debug info on constants
 712     }
 713   } else {
 714     x->destruct();              // Hit, destroy duplicate constant
 715     x = k;                      // use existing constant
 716   }
 717   return x;
 718 }
 719 
 720 //------------------------------intcon-----------------------------------------
 721 // Fast integer constant.  Same as "transform(new ConINode(TypeInt::make(i)))"
 722 ConINode* PhaseTransform::intcon(int i) {
 723   // Small integer?  Check cache! Check that cached node is not dead
 724   if (i >= _icon_min && i <= _icon_max) {
 725     ConINode* icon = _icons[i-_icon_min];
 726     if (icon != NULL && icon->in(TypeFunc::Control) != NULL)
 727       return icon;
 728   }
 729   ConINode* icon = (ConINode*) uncached_makecon(TypeInt::make(i));
 730   assert(icon->is_Con(), "");
 731   if (i >= _icon_min && i <= _icon_max)
 732     _icons[i-_icon_min] = icon;   // Cache small integers
 733   return icon;
 734 }
 735 
 736 //------------------------------longcon----------------------------------------
 737 // Fast long constant.
 738 ConLNode* PhaseTransform::longcon(jlong l) {
 739   // Small integer?  Check cache! Check that cached node is not dead
 740   if (l >= _lcon_min && l <= _lcon_max) {
 741     ConLNode* lcon = _lcons[l-_lcon_min];
 742     if (lcon != NULL && lcon->in(TypeFunc::Control) != NULL)
 743       return lcon;
 744   }
 745   ConLNode* lcon = (ConLNode*) uncached_makecon(TypeLong::make(l));
 746   assert(lcon->is_Con(), "");
 747   if (l >= _lcon_min && l <= _lcon_max)
 748     _lcons[l-_lcon_min] = lcon;      // Cache small integers
 749   return lcon;
 750 }
 751 
 752 //------------------------------zerocon-----------------------------------------
 753 // Fast zero or null constant. Same as "transform(ConNode::make(Type::get_zero_type(bt)))"
 754 ConNode* PhaseTransform::zerocon(BasicType bt) {
 755   assert((uint)bt <= _zcon_max, "domain check");
 756   ConNode* zcon = _zcons[bt];
 757   if (zcon != NULL && zcon->in(TypeFunc::Control) != NULL)
 758     return zcon;
 759   zcon = (ConNode*) uncached_makecon(Type::get_zero_type(bt));
 760   _zcons[bt] = zcon;
 761   return zcon;
 762 }
 763 
 764 
 765 
 766 //=============================================================================
 767 //------------------------------transform--------------------------------------
 768 // Return a node which computes the same function as this node, but in a
 769 // faster or cheaper fashion.
 770 Node *PhaseGVN::transform( Node *n ) {
 771   return transform_no_reclaim(n);
 772 }
 773 
 774 //------------------------------transform--------------------------------------
 775 // Return a node which computes the same function as this node, but
 776 // in a faster or cheaper fashion.
 777 Node *PhaseGVN::transform_no_reclaim( Node *n ) {
 778   NOT_PRODUCT( set_transforms(); )
 779 
 780   // Apply the Ideal call in a loop until it no longer applies
 781   Node *k = n;
 782   NOT_PRODUCT( uint loop_count = 0; )
 783   while( 1 ) {
 784     Node *i = k->Ideal(this, /*can_reshape=*/false);
 785     if( !i ) break;
 786     assert( i->_idx >= k->_idx, "Idealize should return new nodes, use Identity to return old nodes" );
 787     k = i;
 788     assert(loop_count++ < K, "infinite loop in PhaseGVN::transform");
 789   }
 790   NOT_PRODUCT( if( loop_count != 0 ) { set_progress(); } )
 791 
 792 
 793   // If brand new node, make space in type array.
 794   ensure_type_or_null(k);
 795 
 796   // Since I just called 'Value' to compute the set of run-time values
 797   // for this Node, and 'Value' is non-local (and therefore expensive) I'll
 798   // cache Value.  Later requests for the local phase->type of this Node can
 799   // use the cached Value instead of suffering with 'bottom_type'.
 800   const Type *t = k->Value(this); // Get runtime Value set
 801   assert(t != NULL, "value sanity");
 802   if (type_or_null(k) != t) {
 803 #ifndef PRODUCT
 804     // Do not count initial visit to node as a transformation
 805     if (type_or_null(k) == NULL) {
 806       inc_new_values();
 807       set_progress();
 808     }
 809 #endif
 810     set_type(k, t);
 811     // If k is a TypeNode, capture any more-precise type permanently into Node
 812     k->raise_bottom_type(t);
 813   }
 814 
 815   if( t->singleton() && !k->is_Con() ) {
 816     NOT_PRODUCT( set_progress(); )
 817     return makecon(t);          // Turn into a constant
 818   }
 819 
 820   // Now check for Identities
 821   Node *i = k->Identity(this);  // Look for a nearby replacement
 822   if( i != k ) {                // Found? Return replacement!
 823     NOT_PRODUCT( set_progress(); )
 824     return i;
 825   }
 826 
 827   // Global Value Numbering
 828   i = hash_find_insert(k);      // Insert if new
 829   if( i && (i != k) ) {
 830     // Return the pre-existing node
 831     NOT_PRODUCT( set_progress(); )
 832     return i;
 833   }
 834 
 835   // Return Idealized original
 836   return k;
 837 }
 838 
 839 bool PhaseGVN::is_dominator_helper(Node *d, Node *n, bool linear_only) {
 840   if (d->is_top() || n->is_top()) {
 841     return false;
 842   }
 843   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
 844   int i = 0;
 845   while (d != n) {
 846     n = IfNode::up_one_dom(n, linear_only);
 847     i++;
 848     if (n == NULL || i >= 10) {
 849       return false;
 850     }
 851   }
 852   return true;
 853 }
 854 
 855 #ifdef ASSERT
 856 //------------------------------dead_loop_check--------------------------------
 857 // Check for a simple dead loop when a data node references itself directly
 858 // or through an other data node excluding cons and phis.
 859 void PhaseGVN::dead_loop_check( Node *n ) {
 860   // Phi may reference itself in a loop
 861   if (n != NULL && !n->is_dead_loop_safe() && !n->is_CFG()) {
 862     // Do 2 levels check and only data inputs.
 863     bool no_dead_loop = true;
 864     uint cnt = n->req();
 865     for (uint i = 1; i < cnt && no_dead_loop; i++) {
 866       Node *in = n->in(i);
 867       if (in == n) {
 868         no_dead_loop = false;
 869       } else if (in != NULL && !in->is_dead_loop_safe()) {
 870         uint icnt = in->req();
 871         for (uint j = 1; j < icnt && no_dead_loop; j++) {
 872           if (in->in(j) == n || in->in(j) == in)
 873             no_dead_loop = false;
 874         }
 875       }
 876     }
 877     if (!no_dead_loop) n->dump(3);
 878     assert(no_dead_loop, "dead loop detected");
 879   }
 880 }
 881 #endif
 882 
 883 //=============================================================================
 884 //------------------------------PhaseIterGVN-----------------------------------
 885 // Initialize hash table to fresh and clean for +VerifyOpto
 886 PhaseIterGVN::PhaseIterGVN( PhaseIterGVN *igvn, const char *dummy ) : PhaseGVN(igvn,dummy), _worklist( ),
 887                                                                       _stack(C->live_nodes() >> 1),
 888                                                                       _delay_transform(false) {
 889 }
 890 
 891 //------------------------------PhaseIterGVN-----------------------------------
 892 // Initialize with previous PhaseIterGVN info; used by PhaseCCP
 893 PhaseIterGVN::PhaseIterGVN( PhaseIterGVN *igvn ) : PhaseGVN(igvn),
 894                                                    _worklist( igvn->_worklist ),
 895                                                    _stack( igvn->_stack ),
 896                                                    _delay_transform(igvn->_delay_transform)
 897 {
 898 }
 899 
 900 //------------------------------PhaseIterGVN-----------------------------------
 901 // Initialize with previous PhaseGVN info from Parser
 902 PhaseIterGVN::PhaseIterGVN( PhaseGVN *gvn ) : PhaseGVN(gvn),
 903                                               _worklist(*C->for_igvn()),
 904 // TODO: Before incremental inlining it was allocated only once and it was fine. Now that
 905 //       the constructor is used in incremental inlining, this consumes too much memory:
 906 //                                            _stack(C->live_nodes() >> 1),
 907 //       So, as a band-aid, we replace this by:
 908                                               _stack(C->comp_arena(), 32),
 909                                               _delay_transform(false)
 910 {
 911   uint max;
 912 
 913   // Dead nodes in the hash table inherited from GVN were not treated as
 914   // roots during def-use info creation; hence they represent an invisible
 915   // use.  Clear them out.
 916   max = _table.size();
 917   for( uint i = 0; i < max; ++i ) {
 918     Node *n = _table.at(i);
 919     if(n != NULL && n != _table.sentinel() && n->outcnt() == 0) {
 920       if( n->is_top() ) continue;
 921       assert( false, "Parse::remove_useless_nodes missed this node");
 922       hash_delete(n);
 923     }
 924   }
 925 
 926   // Any Phis or Regions on the worklist probably had uses that could not
 927   // make more progress because the uses were made while the Phis and Regions
 928   // were in half-built states.  Put all uses of Phis and Regions on worklist.
 929   max = _worklist.size();
 930   for( uint j = 0; j < max; j++ ) {
 931     Node *n = _worklist.at(j);
 932     uint uop = n->Opcode();
 933     if( uop == Op_Phi || uop == Op_Region ||
 934         n->is_Type() ||
 935         n->is_Mem() )
 936       add_users_to_worklist(n);
 937   }
 938 }
 939 
 940 /**
 941  * Initialize worklist for each node.
 942  */
 943 void PhaseIterGVN::init_worklist(Node* first) {
 944   Unique_Node_List to_process;
 945   to_process.push(first);
 946 
 947   while (to_process.size() > 0) {
 948     Node* n = to_process.pop();
 949     if (!_worklist.member(n)) {
 950       _worklist.push(n);
 951 
 952       uint cnt = n->req();
 953       for(uint i = 0; i < cnt; i++) {
 954         Node* m = n->in(i);
 955         if (m != NULL) {
 956           to_process.push(m);
 957         }
 958       }
 959     }
 960   }
 961 }
 962 
 963 #ifndef PRODUCT
 964 void PhaseIterGVN::verify_step(Node* n) {
 965   if (VerifyIterativeGVN) {
 966     _verify_window[_verify_counter % _verify_window_size] = n;
 967     ++_verify_counter;
 968     ResourceMark rm;
 969     ResourceArea* area = Thread::current()->resource_area();
 970     VectorSet old_space(area), new_space(area);
 971     if (C->unique() < 1000 ||
 972         0 == _verify_counter % (C->unique() < 10000 ? 10 : 100)) {
 973       ++_verify_full_passes;
 974       Node::verify_recur(C->root(), -1, old_space, new_space);
 975     }
 976     const int verify_depth = 4;
 977     for ( int i = 0; i < _verify_window_size; i++ ) {
 978       Node* n = _verify_window[i];
 979       if ( n == NULL )  continue;
 980       if( n->in(0) == NodeSentinel ) {  // xform_idom
 981         _verify_window[i] = n->in(1);
 982         --i; continue;
 983       }
 984       // Typical fanout is 1-2, so this call visits about 6 nodes.
 985       Node::verify_recur(n, verify_depth, old_space, new_space);
 986     }
 987   }
 988 }
 989 
 990 void PhaseIterGVN::trace_PhaseIterGVN(Node* n, Node* nn, const Type* oldtype) {
 991   if (TraceIterativeGVN) {
 992     uint wlsize = _worklist.size();
 993     const Type* newtype = type_or_null(n);
 994     if (nn != n) {
 995       // print old node
 996       tty->print("< ");
 997       if (oldtype != newtype && oldtype != NULL) {
 998         oldtype->dump();
 999       }
1000       do { tty->print("\t"); } while (tty->position() < 16);
1001       tty->print("<");
1002       n->dump();
1003     }
1004     if (oldtype != newtype || nn != n) {
1005       // print new node and/or new type
1006       if (oldtype == NULL) {
1007         tty->print("* ");
1008       } else if (nn != n) {
1009         tty->print("> ");
1010       } else {
1011         tty->print("= ");
1012       }
1013       if (newtype == NULL) {
1014         tty->print("null");
1015       } else {
1016         newtype->dump();
1017       }
1018       do { tty->print("\t"); } while (tty->position() < 16);
1019       nn->dump();
1020     }
1021     if (Verbose && wlsize < _worklist.size()) {
1022       tty->print("  Push {");
1023       while (wlsize != _worklist.size()) {
1024         Node* pushed = _worklist.at(wlsize++);
1025         tty->print(" %d", pushed->_idx);
1026       }
1027       tty->print_cr(" }");
1028     }
1029     if (nn != n) {
1030       // ignore n, it might be subsumed
1031       verify_step((Node*) NULL);
1032     }
1033   }
1034 }
1035 
1036 void PhaseIterGVN::init_verifyPhaseIterGVN() {
1037   _verify_counter = 0;
1038   _verify_full_passes = 0;
1039   for (int i = 0; i < _verify_window_size; i++) {
1040     _verify_window[i] = NULL;
1041   }
1042 #ifdef ASSERT
1043   // Verify that all modified nodes are on _worklist
1044   Unique_Node_List* modified_list = C->modified_nodes();
1045   while (modified_list != NULL && modified_list->size()) {
1046     Node* n = modified_list->pop();
1047     if (n->outcnt() != 0 && !n->is_Con() && !_worklist.member(n)) {
1048       n->dump();
1049       assert(false, "modified node is not on IGVN._worklist");
1050     }
1051   }
1052 #endif
1053 }
1054 
1055 void PhaseIterGVN::verify_PhaseIterGVN() {
1056 #ifdef ASSERT
1057   // Verify nodes with changed inputs.
1058   Unique_Node_List* modified_list = C->modified_nodes();
1059   while (modified_list != NULL && modified_list->size()) {
1060     Node* n = modified_list->pop();
1061     if (n->outcnt() != 0 && !n->is_Con()) { // skip dead and Con nodes
1062       n->dump();
1063       assert(false, "modified node was not processed by IGVN.transform_old()");
1064     }
1065   }
1066 #endif
1067 
1068   C->verify_graph_edges();
1069   if( VerifyOpto && allow_progress() ) {
1070     // Must turn off allow_progress to enable assert and break recursion
1071     C->root()->verify();
1072     { // Check if any progress was missed using IterGVN
1073       // Def-Use info enables transformations not attempted in wash-pass
1074       // e.g. Region/Phi cleanup, ...
1075       // Null-check elision -- may not have reached fixpoint
1076       //                       do not propagate to dominated nodes
1077       ResourceMark rm;
1078       PhaseIterGVN igvn2(this,"Verify"); // Fresh and clean!
1079       // Fill worklist completely
1080       igvn2.init_worklist(C->root());
1081 
1082       igvn2.set_allow_progress(false);
1083       igvn2.optimize();
1084       igvn2.set_allow_progress(true);
1085     }
1086   }
1087   if (VerifyIterativeGVN && PrintOpto) {
1088     if (_verify_counter == _verify_full_passes) {
1089       tty->print_cr("VerifyIterativeGVN: %d transforms and verify passes",
1090                     (int) _verify_full_passes);
1091     } else {
1092       tty->print_cr("VerifyIterativeGVN: %d transforms, %d full verify passes",
1093                   (int) _verify_counter, (int) _verify_full_passes);
1094     }
1095   }
1096 
1097 #ifdef ASSERT
1098   while (modified_list->size()) {
1099     Node* n = modified_list->pop();
1100     n->dump();
1101     assert(false, "VerifyIterativeGVN: new modified node was added");
1102   }
1103 #endif
1104 }
1105 #endif /* PRODUCT */
1106 
1107 #ifdef ASSERT
1108 /**
1109  * Dumps information that can help to debug the problem. A debug
1110  * build fails with an assert.
1111  */
1112 void PhaseIterGVN::dump_infinite_loop_info(Node* n) {
1113   n->dump(4);
1114   _worklist.dump();
1115   assert(false, "infinite loop in PhaseIterGVN::optimize");
1116 }
1117 
1118 /**
1119  * Prints out information about IGVN if the 'verbose' option is used.
1120  */
1121 void PhaseIterGVN::trace_PhaseIterGVN_verbose(Node* n, int num_processed) {
1122   if (TraceIterativeGVN && Verbose) {
1123     tty->print("  Pop ");
1124     n->dump();
1125     if ((num_processed % 100) == 0) {
1126       _worklist.print_set();
1127     }
1128   }
1129 }
1130 #endif /* ASSERT */
1131 
1132 void PhaseIterGVN::optimize() {
1133   DEBUG_ONLY(uint num_processed  = 0;)
1134   NOT_PRODUCT(init_verifyPhaseIterGVN();)
1135 
1136   uint loop_count = 0;
1137   // Pull from worklist and transform the node. If the node has changed,
1138   // update edge info and put uses on worklist.
1139   while(_worklist.size()) {
1140     if (C->check_node_count(NodeLimitFudgeFactor * 2, "Out of nodes")) {
1141       return;
1142     }
1143     Node* n  = _worklist.pop();
1144     if (++loop_count >= K * C->live_nodes()) {
1145       DEBUG_ONLY(dump_infinite_loop_info(n);)
1146       C->record_method_not_compilable("infinite loop in PhaseIterGVN::optimize");
1147       return;
1148     }
1149     DEBUG_ONLY(trace_PhaseIterGVN_verbose(n, num_processed++);)
1150     if (n->outcnt() != 0) {
1151       NOT_PRODUCT(const Type* oldtype = type_or_null(n));
1152       // Do the transformation
1153       Node* nn = transform_old(n);
1154       NOT_PRODUCT(trace_PhaseIterGVN(n, nn, oldtype);)
1155     } else if (!n->is_top()) {
1156       remove_dead_node(n);
1157     }
1158   }
1159   NOT_PRODUCT(verify_PhaseIterGVN();)
1160 }
1161 
1162 
1163 /**
1164  * Register a new node with the optimizer.  Update the types array, the def-use
1165  * info.  Put on worklist.
1166  */
1167 Node* PhaseIterGVN::register_new_node_with_optimizer(Node* n, Node* orig) {
1168   set_type_bottom(n);
1169   _worklist.push(n);
1170   if (orig != NULL)  C->copy_node_notes_to(n, orig);
1171   return n;
1172 }
1173 
1174 //------------------------------transform--------------------------------------
1175 // Non-recursive: idealize Node 'n' with respect to its inputs and its value
1176 Node *PhaseIterGVN::transform( Node *n ) {
1177   if (_delay_transform) {
1178     // Register the node but don't optimize for now
1179     register_new_node_with_optimizer(n);
1180     return n;
1181   }
1182 
1183   // If brand new node, make space in type array, and give it a type.
1184   ensure_type_or_null(n);
1185   if (type_or_null(n) == NULL) {
1186     set_type_bottom(n);
1187   }
1188 
1189   return transform_old(n);
1190 }
1191 
1192 Node *PhaseIterGVN::transform_old(Node* n) {
1193   DEBUG_ONLY(uint loop_count = 0;);
1194   NOT_PRODUCT(set_transforms());
1195 
1196   // Remove 'n' from hash table in case it gets modified
1197   _table.hash_delete(n);
1198   if (VerifyIterativeGVN) {
1199    assert(!_table.find_index(n->_idx), "found duplicate entry in table");
1200   }
1201 
1202   // Apply the Ideal call in a loop until it no longer applies
1203   Node* k = n;
1204   DEBUG_ONLY(dead_loop_check(k);)
1205   DEBUG_ONLY(bool is_new = (k->outcnt() == 0);)
1206   C->remove_modified_node(k);
1207   Node* i = k->Ideal(this, /*can_reshape=*/true);
1208   assert(i != k || is_new || i->outcnt() > 0, "don't return dead nodes");
1209 #ifndef PRODUCT
1210   verify_step(k);
1211   if (i && VerifyOpto ) {
1212     if (!allow_progress()) {
1213       if (i->is_Add() && (i->outcnt() == 1)) {
1214         // Switched input to left side because this is the only use
1215       } else if (i->is_If() && (i->in(0) == NULL)) {
1216         // This IF is dead because it is dominated by an equivalent IF When
1217         // dominating if changed, info is not propagated sparsely to 'this'
1218         // Propagating this info further will spuriously identify other
1219         // progress.
1220         return i;
1221       } else
1222         set_progress();
1223     } else {
1224       set_progress();
1225     }
1226   }
1227 #endif
1228 
1229   while (i != NULL) {
1230 #ifdef ASSERT
1231     if (loop_count >= K) {
1232       dump_infinite_loop_info(i);
1233     }
1234     loop_count++;
1235 #endif
1236     assert((i->_idx >= k->_idx) || i->is_top(), "Idealize should return new nodes, use Identity to return old nodes");
1237     // Made a change; put users of original Node on worklist
1238     add_users_to_worklist(k);
1239     // Replacing root of transform tree?
1240     if (k != i) {
1241       // Make users of old Node now use new.
1242       subsume_node(k, i);
1243       k = i;
1244     }
1245     DEBUG_ONLY(dead_loop_check(k);)
1246     // Try idealizing again
1247     DEBUG_ONLY(is_new = (k->outcnt() == 0);)
1248     C->remove_modified_node(k);
1249     i = k->Ideal(this, /*can_reshape=*/true);
1250     assert(i != k || is_new || (i->outcnt() > 0), "don't return dead nodes");
1251 #ifndef PRODUCT
1252     verify_step(k);
1253     if (i && VerifyOpto) {
1254       set_progress();
1255     }
1256 #endif
1257   }
1258 
1259   // If brand new node, make space in type array.
1260   ensure_type_or_null(k);
1261 
1262   // See what kind of values 'k' takes on at runtime
1263   const Type* t = k->Value(this);
1264   assert(t != NULL, "value sanity");
1265 
1266   // Since I just called 'Value' to compute the set of run-time values
1267   // for this Node, and 'Value' is non-local (and therefore expensive) I'll
1268   // cache Value.  Later requests for the local phase->type of this Node can
1269   // use the cached Value instead of suffering with 'bottom_type'.
1270   if (type_or_null(k) != t) {
1271 #ifndef PRODUCT
1272     inc_new_values();
1273     set_progress();
1274 #endif
1275     set_type(k, t);
1276     // If k is a TypeNode, capture any more-precise type permanently into Node
1277     k->raise_bottom_type(t);
1278     // Move users of node to worklist
1279     add_users_to_worklist(k);
1280   }
1281   // If 'k' computes a constant, replace it with a constant
1282   if (t->singleton() && !k->is_Con()) {
1283     NOT_PRODUCT(set_progress();)
1284     Node* con = makecon(t);     // Make a constant
1285     add_users_to_worklist(k);
1286     subsume_node(k, con);       // Everybody using k now uses con
1287     return con;
1288   }
1289 
1290   // Now check for Identities
1291   i = k->Identity(this);      // Look for a nearby replacement
1292   if (i != k) {                // Found? Return replacement!
1293     NOT_PRODUCT(set_progress();)
1294     add_users_to_worklist(k);
1295     subsume_node(k, i);       // Everybody using k now uses i
1296     return i;
1297   }
1298 
1299   // Global Value Numbering
1300   i = hash_find_insert(k);      // Check for pre-existing node
1301   if (i && (i != k)) {
1302     // Return the pre-existing node if it isn't dead
1303     NOT_PRODUCT(set_progress();)
1304     add_users_to_worklist(k);
1305     subsume_node(k, i);       // Everybody using k now uses i
1306     return i;
1307   }
1308 
1309   // Return Idealized original
1310   return k;
1311 }
1312 
1313 //---------------------------------saturate------------------------------------
1314 const Type* PhaseIterGVN::saturate(const Type* new_type, const Type* old_type,
1315                                    const Type* limit_type) const {
1316   return new_type->narrow(old_type);
1317 }
1318 
1319 //------------------------------remove_globally_dead_node----------------------
1320 // Kill a globally dead Node.  All uses are also globally dead and are
1321 // aggressively trimmed.
1322 void PhaseIterGVN::remove_globally_dead_node( Node *dead ) {
1323   enum DeleteProgress {
1324     PROCESS_INPUTS,
1325     PROCESS_OUTPUTS
1326   };
1327   assert(_stack.is_empty(), "not empty");
1328   _stack.push(dead, PROCESS_INPUTS);
1329 
1330   while (_stack.is_nonempty()) {
1331     dead = _stack.node();
1332     uint progress_state = _stack.index();
1333     assert(dead != C->root(), "killing root, eh?");
1334     assert(!dead->is_top(), "add check for top when pushing");
1335     NOT_PRODUCT( set_progress(); )
1336     if (progress_state == PROCESS_INPUTS) {
1337       // After following inputs, continue to outputs
1338       _stack.set_index(PROCESS_OUTPUTS);
1339       if (!dead->is_Con()) { // Don't kill cons but uses
1340         bool recurse = false;
1341         // Remove from hash table
1342         _table.hash_delete( dead );
1343         // Smash all inputs to 'dead', isolating him completely
1344         for (uint i = 0; i < dead->req(); i++) {
1345           Node *in = dead->in(i);
1346           if (in != NULL && in != C->top()) {  // Points to something?
1347             int nrep = dead->replace_edge(in, NULL);  // Kill edges
1348             assert((nrep > 0), "sanity");
1349             if (in->outcnt() == 0) { // Made input go dead?
1350               _stack.push(in, PROCESS_INPUTS); // Recursively remove
1351               recurse = true;
1352             } else if (in->outcnt() == 1 &&
1353                        in->has_special_unique_user()) {
1354               _worklist.push(in->unique_out());
1355             } else if (in->outcnt() <= 2 && dead->is_Phi()) {
1356               if (in->Opcode() == Op_Region) {
1357                 _worklist.push(in);
1358               } else if (in->is_Store()) {
1359                 DUIterator_Fast imax, i = in->fast_outs(imax);
1360                 _worklist.push(in->fast_out(i));
1361                 i++;
1362                 if (in->outcnt() == 2) {
1363                   _worklist.push(in->fast_out(i));
1364                   i++;
1365                 }
1366                 assert(!(i < imax), "sanity");
1367               }
1368             }
1369             if (ReduceFieldZeroing && dead->is_Load() && i == MemNode::Memory &&
1370                 in->is_Proj() && in->in(0) != NULL && in->in(0)->is_Initialize()) {
1371               // A Load that directly follows an InitializeNode is
1372               // going away. The Stores that follow are candidates
1373               // again to be captured by the InitializeNode.
1374               for (DUIterator_Fast jmax, j = in->fast_outs(jmax); j < jmax; j++) {
1375                 Node *n = in->fast_out(j);
1376                 if (n->is_Store()) {
1377                   _worklist.push(n);
1378                 }
1379               }
1380             }
1381           } // if (in != NULL && in != C->top())
1382         } // for (uint i = 0; i < dead->req(); i++)
1383         if (recurse) {
1384           continue;
1385         }
1386       } // if (!dead->is_Con())
1387     } // if (progress_state == PROCESS_INPUTS)
1388 
1389     // Aggressively kill globally dead uses
1390     // (Rather than pushing all the outs at once, we push one at a time,
1391     // plus the parent to resume later, because of the indefinite number
1392     // of edge deletions per loop trip.)
1393     if (dead->outcnt() > 0) {
1394       // Recursively remove output edges
1395       _stack.push(dead->raw_out(0), PROCESS_INPUTS);
1396     } else {
1397       // Finished disconnecting all input and output edges.
1398       _stack.pop();
1399       // Remove dead node from iterative worklist
1400       _worklist.remove(dead);
1401       C->remove_modified_node(dead);
1402       // Constant node that has no out-edges and has only one in-edge from
1403       // root is usually dead. However, sometimes reshaping walk makes
1404       // it reachable by adding use edges. So, we will NOT count Con nodes
1405       // as dead to be conservative about the dead node count at any
1406       // given time.
1407       if (!dead->is_Con()) {
1408         C->record_dead_node(dead->_idx);
1409       }
1410       if (dead->is_macro()) {
1411         C->remove_macro_node(dead);
1412       }
1413       if (dead->is_expensive()) {
1414         C->remove_expensive_node(dead);
1415       }
1416       CastIINode* cast = dead->isa_CastII();
1417       if (cast != NULL && cast->has_range_check()) {
1418         C->remove_range_check_cast(cast);
1419       }
1420     }
1421   } // while (_stack.is_nonempty())
1422 }
1423 
1424 //------------------------------subsume_node-----------------------------------
1425 // Remove users from node 'old' and add them to node 'nn'.
1426 void PhaseIterGVN::subsume_node( Node *old, Node *nn ) {
1427   assert( old != hash_find(old), "should already been removed" );
1428   assert( old != C->top(), "cannot subsume top node");
1429   // Copy debug or profile information to the new version:
1430   C->copy_node_notes_to(nn, old);
1431   // Move users of node 'old' to node 'nn'
1432   for (DUIterator_Last imin, i = old->last_outs(imin); i >= imin; ) {
1433     Node* use = old->last_out(i);  // for each use...
1434     // use might need re-hashing (but it won't if it's a new node)
1435     rehash_node_delayed(use);
1436     // Update use-def info as well
1437     // We remove all occurrences of old within use->in,
1438     // so as to avoid rehashing any node more than once.
1439     // The hash table probe swamps any outer loop overhead.
1440     uint num_edges = 0;
1441     for (uint jmax = use->len(), j = 0; j < jmax; j++) {
1442       if (use->in(j) == old) {
1443         use->set_req(j, nn);
1444         ++num_edges;
1445       }
1446     }
1447     i -= num_edges;    // we deleted 1 or more copies of this edge
1448   }
1449 
1450   // Smash all inputs to 'old', isolating him completely
1451   Node *temp = new Node(1);
1452   temp->init_req(0,nn);     // Add a use to nn to prevent him from dying
1453   remove_dead_node( old );
1454   temp->del_req(0);         // Yank bogus edge
1455 #ifndef PRODUCT
1456   if( VerifyIterativeGVN ) {
1457     for ( int i = 0; i < _verify_window_size; i++ ) {
1458       if ( _verify_window[i] == old )
1459         _verify_window[i] = nn;
1460     }
1461   }
1462 #endif
1463   _worklist.remove(temp);   // this can be necessary
1464   temp->destruct();         // reuse the _idx of this little guy
1465 }
1466 
1467 //------------------------------add_users_to_worklist--------------------------
1468 void PhaseIterGVN::add_users_to_worklist0( Node *n ) {
1469   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1470     _worklist.push(n->fast_out(i));  // Push on worklist
1471   }
1472 }
1473 
1474 // Return counted loop Phi if as a counted loop exit condition, cmp
1475 // compares the the induction variable with n
1476 static PhiNode* countedloop_phi_from_cmp(CmpINode* cmp, Node* n) {
1477   for (DUIterator_Fast imax, i = cmp->fast_outs(imax); i < imax; i++) {
1478     Node* bol = cmp->fast_out(i);
1479     for (DUIterator_Fast i2max, i2 = bol->fast_outs(i2max); i2 < i2max; i2++) {
1480       Node* iff = bol->fast_out(i2);
1481       if (iff->is_CountedLoopEnd()) {
1482         CountedLoopEndNode* cle = iff->as_CountedLoopEnd();
1483         if (cle->limit() == n) {
1484           PhiNode* phi = cle->phi();
1485           if (phi != NULL) {
1486             return phi;
1487           }
1488         }
1489       }
1490     }
1491   }
1492   return NULL;
1493 }
1494 
1495 void PhaseIterGVN::add_users_to_worklist( Node *n ) {
1496   add_users_to_worklist0(n);
1497 
1498   // Move users of node to worklist
1499   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1500     Node* use = n->fast_out(i); // Get use
1501 
1502     if( use->is_Multi() ||      // Multi-definer?  Push projs on worklist
1503         use->is_Store() )       // Enable store/load same address
1504       add_users_to_worklist0(use);
1505 
1506     // If we changed the receiver type to a call, we need to revisit
1507     // the Catch following the call.  It's looking for a non-NULL
1508     // receiver to know when to enable the regular fall-through path
1509     // in addition to the NullPtrException path.
1510     if (use->is_CallDynamicJava() && n == use->in(TypeFunc::Parms)) {
1511       Node* p = use->as_CallDynamicJava()->proj_out(TypeFunc::Control);
1512       if (p != NULL) {
1513         add_users_to_worklist0(p);
1514       }
1515     }
1516 
1517     uint use_op = use->Opcode();
1518     if(use->is_Cmp()) {       // Enable CMP/BOOL optimization
1519       add_users_to_worklist(use); // Put Bool on worklist
1520       if (use->outcnt() > 0) {
1521         Node* bol = use->raw_out(0);
1522         if (bol->outcnt() > 0) {
1523           Node* iff = bol->raw_out(0);
1524           if (iff->outcnt() == 2) {
1525             // Look for the 'is_x2logic' pattern: "x ? : 0 : 1" and put the
1526             // phi merging either 0 or 1 onto the worklist
1527             Node* ifproj0 = iff->raw_out(0);
1528             Node* ifproj1 = iff->raw_out(1);
1529             if (ifproj0->outcnt() > 0 && ifproj1->outcnt() > 0) {
1530               Node* region0 = ifproj0->raw_out(0);
1531               Node* region1 = ifproj1->raw_out(0);
1532               if( region0 == region1 )
1533                 add_users_to_worklist0(region0);
1534             }
1535           }
1536         }
1537       }
1538       if (use_op == Op_CmpI) {
1539         Node* phi = countedloop_phi_from_cmp((CmpINode*)use, n);
1540         if (phi != NULL) {
1541           // If an opaque node feeds into the limit condition of a
1542           // CountedLoop, we need to process the Phi node for the
1543           // induction variable when the opaque node is removed:
1544           // the range of values taken by the Phi is now known and
1545           // so its type is also known.
1546           _worklist.push(phi);
1547         }
1548         Node* in1 = use->in(1);
1549         for (uint i = 0; i < in1->outcnt(); i++) {
1550           if (in1->raw_out(i)->Opcode() == Op_CastII) {
1551             Node* castii = in1->raw_out(i);
1552             if (castii->in(0) != NULL && castii->in(0)->in(0) != NULL && castii->in(0)->in(0)->is_If()) {
1553               Node* ifnode = castii->in(0)->in(0);
1554               if (ifnode->in(1) != NULL && ifnode->in(1)->is_Bool() && ifnode->in(1)->in(1) == use) {
1555                 // Reprocess a CastII node that may depend on an
1556                 // opaque node value when the opaque node is
1557                 // removed. In case it carries a dependency we can do
1558                 // a better job of computing its type.
1559                 _worklist.push(castii);
1560               }
1561             }
1562           }
1563         }
1564       }
1565     }
1566 
1567     // If changed Cast input, check Phi users for simple cycles
1568     if (use->is_ConstraintCast()) {
1569       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1570         Node* u = use->fast_out(i2);
1571         if (u->is_Phi())
1572           _worklist.push(u);
1573       }
1574     }
1575     // If changed LShift inputs, check RShift users for useless sign-ext
1576     if( use_op == Op_LShiftI ) {
1577       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1578         Node* u = use->fast_out(i2);
1579         if (u->Opcode() == Op_RShiftI)
1580           _worklist.push(u);
1581       }
1582     }
1583     // If changed AddI/SubI inputs, check CmpU for range check optimization.
1584     if (use_op == Op_AddI || use_op == Op_SubI) {
1585       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1586         Node* u = use->fast_out(i2);
1587         if (u->is_Cmp() && (u->Opcode() == Op_CmpU)) {
1588           _worklist.push(u);
1589         }
1590       }
1591     }
1592     // If changed AddP inputs, check Stores for loop invariant
1593     if( use_op == Op_AddP ) {
1594       for (DUIterator_Fast i2max, i2 = use->fast_outs(i2max); i2 < i2max; i2++) {
1595         Node* u = use->fast_out(i2);
1596         if (u->is_Mem())
1597           _worklist.push(u);
1598       }
1599     }
1600     // If changed initialization activity, check dependent Stores
1601     if (use_op == Op_Allocate || use_op == Op_AllocateArray) {
1602       InitializeNode* init = use->as_Allocate()->initialization();
1603       if (init != NULL) {
1604         Node* imem = init->proj_out(TypeFunc::Memory);
1605         if (imem != NULL)  add_users_to_worklist0(imem);
1606       }
1607     }
1608     if (use_op == Op_Initialize) {
1609       Node* imem = use->as_Initialize()->proj_out(TypeFunc::Memory);
1610       if (imem != NULL)  add_users_to_worklist0(imem);
1611     }
1612   }
1613 }
1614 
1615 /**
1616  * Remove the speculative part of all types that we know of
1617  */
1618 void PhaseIterGVN::remove_speculative_types()  {
1619   assert(UseTypeSpeculation, "speculation is off");
1620   for (uint i = 0; i < _types.Size(); i++)  {
1621     const Type* t = _types.fast_lookup(i);
1622     if (t != NULL) {
1623       _types.map(i, t->remove_speculative());
1624     }
1625   }
1626   _table.check_no_speculative_types();
1627 }
1628 
1629 //=============================================================================
1630 #ifndef PRODUCT
1631 uint PhaseCCP::_total_invokes   = 0;
1632 uint PhaseCCP::_total_constants = 0;
1633 #endif
1634 //------------------------------PhaseCCP---------------------------------------
1635 // Conditional Constant Propagation, ala Wegman & Zadeck
1636 PhaseCCP::PhaseCCP( PhaseIterGVN *igvn ) : PhaseIterGVN(igvn) {
1637   NOT_PRODUCT( clear_constants(); )
1638   assert( _worklist.size() == 0, "" );
1639   // Clear out _nodes from IterGVN.  Must be clear to transform call.
1640   _nodes.clear();               // Clear out from IterGVN
1641   analyze();
1642 }
1643 
1644 #ifndef PRODUCT
1645 //------------------------------~PhaseCCP--------------------------------------
1646 PhaseCCP::~PhaseCCP() {
1647   inc_invokes();
1648   _total_constants += count_constants();
1649 }
1650 #endif
1651 
1652 
1653 #ifdef ASSERT
1654 static bool ccp_type_widens(const Type* t, const Type* t0) {
1655   assert(t->meet(t0) == t, "Not monotonic");
1656   switch (t->base() == t0->base() ? t->base() : Type::Top) {
1657   case Type::Int:
1658     assert(t0->isa_int()->_widen <= t->isa_int()->_widen, "widen increases");
1659     break;
1660   case Type::Long:
1661     assert(t0->isa_long()->_widen <= t->isa_long()->_widen, "widen increases");
1662     break;
1663   }
1664   return true;
1665 }
1666 #endif //ASSERT
1667 
1668 //------------------------------analyze----------------------------------------
1669 void PhaseCCP::analyze() {
1670   // Initialize all types to TOP, optimistic analysis
1671   for (int i = C->unique() - 1; i >= 0; i--)  {
1672     _types.map(i,Type::TOP);
1673   }
1674 
1675   // Push root onto worklist
1676   Unique_Node_List worklist;
1677   worklist.push(C->root());
1678 
1679   // Pull from worklist; compute new value; push changes out.
1680   // This loop is the meat of CCP.
1681   while( worklist.size() ) {
1682     Node *n = worklist.pop();
1683     const Type *t = n->Value(this);
1684     if (t != type(n)) {
1685       assert(ccp_type_widens(t, type(n)), "ccp type must widen");
1686 #ifndef PRODUCT
1687       if( TracePhaseCCP ) {
1688         t->dump();
1689         do { tty->print("\t"); } while (tty->position() < 16);
1690         n->dump();
1691       }
1692 #endif
1693       set_type(n, t);
1694       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1695         Node* m = n->fast_out(i);   // Get user
1696         if (m->is_Region()) {  // New path to Region?  Must recheck Phis too
1697           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1698             Node* p = m->fast_out(i2); // Propagate changes to uses
1699             if (p->bottom_type() != type(p)) { // If not already bottomed out
1700               worklist.push(p); // Propagate change to user
1701             }
1702           }
1703         }
1704         // If we changed the receiver type to a call, we need to revisit
1705         // the Catch following the call.  It's looking for a non-NULL
1706         // receiver to know when to enable the regular fall-through path
1707         // in addition to the NullPtrException path
1708         if (m->is_Call()) {
1709           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1710             Node* p = m->fast_out(i2);  // Propagate changes to uses
1711             if (p->is_Proj() && p->as_Proj()->_con == TypeFunc::Control && p->outcnt() == 1) {
1712               worklist.push(p->unique_out());
1713             }
1714           }
1715         }
1716         if (m->bottom_type() != type(m)) { // If not already bottomed out
1717           worklist.push(m);     // Propagate change to user
1718         }
1719 
1720         // CmpU nodes can get their type information from two nodes up in the
1721         // graph (instead of from the nodes immediately above). Make sure they
1722         // are added to the worklist if nodes they depend on are updated, since
1723         // they could be missed and get wrong types otherwise.
1724         uint m_op = m->Opcode();
1725         if (m_op == Op_AddI || m_op == Op_SubI) {
1726           for (DUIterator_Fast i2max, i2 = m->fast_outs(i2max); i2 < i2max; i2++) {
1727             Node* p = m->fast_out(i2); // Propagate changes to uses
1728             if (p->Opcode() == Op_CmpU) {
1729               // Got a CmpU which might need the new type information from node n.
1730               if(p->bottom_type() != type(p)) { // If not already bottomed out
1731                 worklist.push(p); // Propagate change to user
1732               }
1733             }
1734           }
1735         }
1736         // If n is used in a counted loop exit condition then the type
1737         // of the counted loop's Phi depends on the type of n. See
1738         // PhiNode::Value().
1739         if (m_op == Op_CmpI) {
1740           PhiNode* phi = countedloop_phi_from_cmp((CmpINode*)m, n);
1741           if (phi != NULL) {
1742             worklist.push(phi);
1743           }
1744         }
1745       }
1746     }
1747   }
1748 }
1749 
1750 //------------------------------do_transform-----------------------------------
1751 // Top level driver for the recursive transformer
1752 void PhaseCCP::do_transform() {
1753   // Correct leaves of new-space Nodes; they point to old-space.
1754   C->set_root( transform(C->root())->as_Root() );
1755   assert( C->top(),  "missing TOP node" );
1756   assert( C->root(), "missing root" );
1757 }
1758 
1759 //------------------------------transform--------------------------------------
1760 // Given a Node in old-space, clone him into new-space.
1761 // Convert any of his old-space children into new-space children.
1762 Node *PhaseCCP::transform( Node *n ) {
1763   Node *new_node = _nodes[n->_idx]; // Check for transformed node
1764   if( new_node != NULL )
1765     return new_node;                // Been there, done that, return old answer
1766   new_node = transform_once(n);     // Check for constant
1767   _nodes.map( n->_idx, new_node );  // Flag as having been cloned
1768 
1769   // Allocate stack of size _nodes.Size()/2 to avoid frequent realloc
1770   GrowableArray <Node *> trstack(C->live_nodes() >> 1);
1771 
1772   trstack.push(new_node);           // Process children of cloned node
1773   while ( trstack.is_nonempty() ) {
1774     Node *clone = trstack.pop();
1775     uint cnt = clone->req();
1776     for( uint i = 0; i < cnt; i++ ) {          // For all inputs do
1777       Node *input = clone->in(i);
1778       if( input != NULL ) {                    // Ignore NULLs
1779         Node *new_input = _nodes[input->_idx]; // Check for cloned input node
1780         if( new_input == NULL ) {
1781           new_input = transform_once(input);   // Check for constant
1782           _nodes.map( input->_idx, new_input );// Flag as having been cloned
1783           trstack.push(new_input);
1784         }
1785         assert( new_input == clone->in(i), "insanity check");
1786       }
1787     }
1788   }
1789   return new_node;
1790 }
1791 
1792 
1793 //------------------------------transform_once---------------------------------
1794 // For PhaseCCP, transformation is IDENTITY unless Node computed a constant.
1795 Node *PhaseCCP::transform_once( Node *n ) {
1796   const Type *t = type(n);
1797   // Constant?  Use constant Node instead
1798   if( t->singleton() ) {
1799     Node *nn = n;               // Default is to return the original constant
1800     if( t == Type::TOP ) {
1801       // cache my top node on the Compile instance
1802       if( C->cached_top_node() == NULL || C->cached_top_node()->in(0) == NULL ) {
1803         C->set_cached_top_node(ConNode::make(Type::TOP));
1804         set_type(C->top(), Type::TOP);
1805       }
1806       nn = C->top();
1807     }
1808     if( !n->is_Con() ) {
1809       if( t != Type::TOP ) {
1810         nn = makecon(t);        // ConNode::make(t);
1811         NOT_PRODUCT( inc_constants(); )
1812       } else if( n->is_Region() ) { // Unreachable region
1813         // Note: nn == C->top()
1814         n->set_req(0, NULL);        // Cut selfreference
1815         // Eagerly remove dead phis to avoid phis copies creation.
1816         for (DUIterator i = n->outs(); n->has_out(i); i++) {
1817           Node* m = n->out(i);
1818           if( m->is_Phi() ) {
1819             assert(type(m) == Type::TOP, "Unreachable region should not have live phis.");
1820             replace_node(m, nn);
1821             --i; // deleted this phi; rescan starting with next position
1822           }
1823         }
1824       }
1825       replace_node(n,nn);       // Update DefUse edges for new constant
1826     }
1827     return nn;
1828   }
1829 
1830   // If x is a TypeNode, capture any more-precise type permanently into Node
1831   if (t != n->bottom_type()) {
1832     hash_delete(n);             // changing bottom type may force a rehash
1833     n->raise_bottom_type(t);
1834     _worklist.push(n);          // n re-enters the hash table via the worklist
1835   }
1836 
1837   // TEMPORARY fix to ensure that 2nd GVN pass eliminates NULL checks
1838   switch( n->Opcode() ) {
1839   case Op_FastLock:      // Revisit FastLocks for lock coarsening
1840   case Op_If:
1841   case Op_CountedLoopEnd:
1842   case Op_Region:
1843   case Op_Loop:
1844   case Op_CountedLoop:
1845   case Op_Conv2B:
1846   case Op_Opaque1:
1847   case Op_Opaque2:
1848     _worklist.push(n);
1849     break;
1850   default:
1851     break;
1852   }
1853 
1854   return  n;
1855 }
1856 
1857 //---------------------------------saturate------------------------------------
1858 const Type* PhaseCCP::saturate(const Type* new_type, const Type* old_type,
1859                                const Type* limit_type) const {
1860   const Type* wide_type = new_type->widen(old_type, limit_type);
1861   if (wide_type != new_type) {          // did we widen?
1862     // If so, we may have widened beyond the limit type.  Clip it back down.
1863     new_type = wide_type->filter(limit_type);
1864   }
1865   return new_type;
1866 }
1867 
1868 //------------------------------print_statistics-------------------------------
1869 #ifndef PRODUCT
1870 void PhaseCCP::print_statistics() {
1871   tty->print_cr("CCP: %d  constants found: %d", _total_invokes, _total_constants);
1872 }
1873 #endif
1874 
1875 
1876 //=============================================================================
1877 #ifndef PRODUCT
1878 uint PhasePeephole::_total_peepholes = 0;
1879 #endif
1880 //------------------------------PhasePeephole----------------------------------
1881 // Conditional Constant Propagation, ala Wegman & Zadeck
1882 PhasePeephole::PhasePeephole( PhaseRegAlloc *regalloc, PhaseCFG &cfg )
1883   : PhaseTransform(Peephole), _regalloc(regalloc), _cfg(cfg) {
1884   NOT_PRODUCT( clear_peepholes(); )
1885 }
1886 
1887 #ifndef PRODUCT
1888 //------------------------------~PhasePeephole---------------------------------
1889 PhasePeephole::~PhasePeephole() {
1890   _total_peepholes += count_peepholes();
1891 }
1892 #endif
1893 
1894 //------------------------------transform--------------------------------------
1895 Node *PhasePeephole::transform( Node *n ) {
1896   ShouldNotCallThis();
1897   return NULL;
1898 }
1899 
1900 //------------------------------do_transform-----------------------------------
1901 void PhasePeephole::do_transform() {
1902   bool method_name_not_printed = true;
1903 
1904   // Examine each basic block
1905   for (uint block_number = 1; block_number < _cfg.number_of_blocks(); ++block_number) {
1906     Block* block = _cfg.get_block(block_number);
1907     bool block_not_printed = true;
1908 
1909     // and each instruction within a block
1910     uint end_index = block->number_of_nodes();
1911     // block->end_idx() not valid after PhaseRegAlloc
1912     for( uint instruction_index = 1; instruction_index < end_index; ++instruction_index ) {
1913       Node     *n = block->get_node(instruction_index);
1914       if( n->is_Mach() ) {
1915         MachNode *m = n->as_Mach();
1916         int deleted_count = 0;
1917         // check for peephole opportunities
1918         MachNode *m2 = m->peephole(block, instruction_index, _regalloc, deleted_count);
1919         if( m2 != NULL ) {
1920 #ifndef PRODUCT
1921           if( PrintOptoPeephole ) {
1922             // Print method, first time only
1923             if( C->method() && method_name_not_printed ) {
1924               C->method()->print_short_name(); tty->cr();
1925               method_name_not_printed = false;
1926             }
1927             // Print this block
1928             if( Verbose && block_not_printed) {
1929               tty->print_cr("in block");
1930               block->dump();
1931               block_not_printed = false;
1932             }
1933             // Print instructions being deleted
1934             for( int i = (deleted_count - 1); i >= 0; --i ) {
1935               block->get_node(instruction_index-i)->as_Mach()->format(_regalloc); tty->cr();
1936             }
1937             tty->print_cr("replaced with");
1938             // Print new instruction
1939             m2->format(_regalloc);
1940             tty->print("\n\n");
1941           }
1942 #endif
1943           // Remove old nodes from basic block and update instruction_index
1944           // (old nodes still exist and may have edges pointing to them
1945           //  as register allocation info is stored in the allocator using
1946           //  the node index to live range mappings.)
1947           uint safe_instruction_index = (instruction_index - deleted_count);
1948           for( ; (instruction_index > safe_instruction_index); --instruction_index ) {
1949             block->remove_node( instruction_index );
1950           }
1951           // install new node after safe_instruction_index
1952           block->insert_node(m2, safe_instruction_index + 1);
1953           end_index = block->number_of_nodes() - 1; // Recompute new block size
1954           NOT_PRODUCT( inc_peepholes(); )
1955         }
1956       }
1957     }
1958   }
1959 }
1960 
1961 //------------------------------print_statistics-------------------------------
1962 #ifndef PRODUCT
1963 void PhasePeephole::print_statistics() {
1964   tty->print_cr("Peephole: peephole rules applied: %d",  _total_peepholes);
1965 }
1966 #endif
1967 
1968 
1969 //=============================================================================
1970 //------------------------------set_req_X--------------------------------------
1971 void Node::set_req_X( uint i, Node *n, PhaseIterGVN *igvn ) {
1972   assert( is_not_dead(n), "can not use dead node");
1973   assert( igvn->hash_find(this) != this, "Need to remove from hash before changing edges" );
1974   Node *old = in(i);
1975   set_req(i, n);
1976 
1977   // old goes dead?
1978   if( old ) {
1979     switch (old->outcnt()) {
1980     case 0:
1981       // Put into the worklist to kill later. We do not kill it now because the
1982       // recursive kill will delete the current node (this) if dead-loop exists
1983       if (!old->is_top())
1984         igvn->_worklist.push( old );
1985       break;
1986     case 1:
1987       if( old->is_Store() || old->has_special_unique_user() )
1988         igvn->add_users_to_worklist( old );
1989       break;
1990     case 2:
1991       if( old->is_Store() )
1992         igvn->add_users_to_worklist( old );
1993       if( old->Opcode() == Op_Region )
1994         igvn->_worklist.push(old);
1995       break;
1996     case 3:
1997       if( old->Opcode() == Op_Region ) {
1998         igvn->_worklist.push(old);
1999         igvn->add_users_to_worklist( old );
2000       }
2001       break;
2002     default:
2003       break;
2004     }
2005   }
2006 
2007 }
2008 
2009 //-------------------------------replace_by-----------------------------------
2010 // Using def-use info, replace one node for another.  Follow the def-use info
2011 // to all users of the OLD node.  Then make all uses point to the NEW node.
2012 void Node::replace_by(Node *new_node) {
2013   assert(!is_top(), "top node has no DU info");
2014   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; ) {
2015     Node* use = last_out(i);
2016     uint uses_found = 0;
2017     for (uint j = 0; j < use->len(); j++) {
2018       if (use->in(j) == this) {
2019         if (j < use->req())
2020               use->set_req(j, new_node);
2021         else  use->set_prec(j, new_node);
2022         uses_found++;
2023       }
2024     }
2025     i -= uses_found;    // we deleted 1 or more copies of this edge
2026   }
2027 }
2028 
2029 //=============================================================================
2030 //-----------------------------------------------------------------------------
2031 void Type_Array::grow( uint i ) {
2032   if( !_max ) {
2033     _max = 1;
2034     _types = (const Type**)_a->Amalloc( _max * sizeof(Type*) );
2035     _types[0] = NULL;
2036   }
2037   uint old = _max;
2038   while( i >= _max ) _max <<= 1;        // Double to fit
2039   _types = (const Type**)_a->Arealloc( _types, old*sizeof(Type*),_max*sizeof(Type*));
2040   memset( &_types[old], 0, (_max-old)*sizeof(Type*) );
2041 }
2042 
2043 //------------------------------dump-------------------------------------------
2044 #ifndef PRODUCT
2045 void Type_Array::dump() const {
2046   uint max = Size();
2047   for( uint i = 0; i < max; i++ ) {
2048     if( _types[i] != NULL ) {
2049       tty->print("  %d\t== ", i); _types[i]->dump(); tty->cr();
2050     }
2051   }
2052 }
2053 #endif