1 /*
   2  * Copyright (c) 1997, 2012, 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 "libadt/vectset.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "opto/cfgnode.hpp"
  29 #include "opto/connode.hpp"
  30 #include "opto/machnode.hpp"
  31 #include "opto/matcher.hpp"
  32 #include "opto/node.hpp"
  33 #include "opto/opcodes.hpp"
  34 #include "opto/regmask.hpp"
  35 #include "opto/type.hpp"
  36 #include "utilities/copy.hpp"
  37 
  38 class RegMask;
  39 // #include "phase.hpp"
  40 class PhaseTransform;
  41 class PhaseGVN;
  42 
  43 // Arena we are currently building Nodes in
  44 const uint Node::NotAMachineReg = 0xffff0000;
  45 
  46 #ifndef PRODUCT
  47 extern int nodes_created;
  48 #endif
  49 
  50 #ifdef ASSERT
  51 
  52 //-------------------------- construct_node------------------------------------
  53 // Set a breakpoint here to identify where a particular node index is built.
  54 void Node::verify_construction() {
  55   _debug_orig = NULL;
  56   int old_debug_idx = Compile::debug_idx();
  57   int new_debug_idx = old_debug_idx+1;
  58   if (new_debug_idx > 0) {
  59     // Arrange that the lowest five decimal digits of _debug_idx
  60     // will repeat those of _idx. In case this is somehow pathological,
  61     // we continue to assign negative numbers (!) consecutively.
  62     const int mod = 100000;
  63     int bump = (int)(_idx - new_debug_idx) % mod;
  64     if (bump < 0)  bump += mod;
  65     assert(bump >= 0 && bump < mod, "");
  66     new_debug_idx += bump;
  67   }
  68   Compile::set_debug_idx(new_debug_idx);
  69   set_debug_idx( new_debug_idx );
  70   assert(Compile::current()->unique() < (INT_MAX - 1), "Node limit exceeded INT_MAX");
  71   assert(Compile::current()->live_nodes() < (uint)MaxNodeLimit, "Live Node limit exceeded limit");
  72   if (BreakAtNode != 0 && (_debug_idx == BreakAtNode || (int)_idx == BreakAtNode)) {
  73     tty->print_cr("BreakAtNode: _idx=%d _debug_idx=%d", _idx, _debug_idx);
  74     BREAKPOINT;
  75   }
  76 #if OPTO_DU_ITERATOR_ASSERT
  77   _last_del = NULL;
  78   _del_tick = 0;
  79 #endif
  80   _hash_lock = 0;
  81 }
  82 
  83 
  84 // #ifdef ASSERT ...
  85 
  86 #if OPTO_DU_ITERATOR_ASSERT
  87 void DUIterator_Common::sample(const Node* node) {
  88   _vdui     = VerifyDUIterators;
  89   _node     = node;
  90   _outcnt   = node->_outcnt;
  91   _del_tick = node->_del_tick;
  92   _last     = NULL;
  93 }
  94 
  95 void DUIterator_Common::verify(const Node* node, bool at_end_ok) {
  96   assert(_node     == node, "consistent iterator source");
  97   assert(_del_tick == node->_del_tick, "no unexpected deletions allowed");
  98 }
  99 
 100 void DUIterator_Common::verify_resync() {
 101   // Ensure that the loop body has just deleted the last guy produced.
 102   const Node* node = _node;
 103   // Ensure that at least one copy of the last-seen edge was deleted.
 104   // Note:  It is OK to delete multiple copies of the last-seen edge.
 105   // Unfortunately, we have no way to verify that all the deletions delete
 106   // that same edge.  On this point we must use the Honor System.
 107   assert(node->_del_tick >= _del_tick+1, "must have deleted an edge");
 108   assert(node->_last_del == _last, "must have deleted the edge just produced");
 109   // We liked this deletion, so accept the resulting outcnt and tick.
 110   _outcnt   = node->_outcnt;
 111   _del_tick = node->_del_tick;
 112 }
 113 
 114 void DUIterator_Common::reset(const DUIterator_Common& that) {
 115   if (this == &that)  return;  // ignore assignment to self
 116   if (!_vdui) {
 117     // We need to initialize everything, overwriting garbage values.
 118     _last = that._last;
 119     _vdui = that._vdui;
 120   }
 121   // Note:  It is legal (though odd) for an iterator over some node x
 122   // to be reassigned to iterate over another node y.  Some doubly-nested
 123   // progress loops depend on being able to do this.
 124   const Node* node = that._node;
 125   // Re-initialize everything, except _last.
 126   _node     = node;
 127   _outcnt   = node->_outcnt;
 128   _del_tick = node->_del_tick;
 129 }
 130 
 131 void DUIterator::sample(const Node* node) {
 132   DUIterator_Common::sample(node);      // Initialize the assertion data.
 133   _refresh_tick = 0;                    // No refreshes have happened, as yet.
 134 }
 135 
 136 void DUIterator::verify(const Node* node, bool at_end_ok) {
 137   DUIterator_Common::verify(node, at_end_ok);
 138   assert(_idx      <  node->_outcnt + (uint)at_end_ok, "idx in range");
 139 }
 140 
 141 void DUIterator::verify_increment() {
 142   if (_refresh_tick & 1) {
 143     // We have refreshed the index during this loop.
 144     // Fix up _idx to meet asserts.
 145     if (_idx > _outcnt)  _idx = _outcnt;
 146   }
 147   verify(_node, true);
 148 }
 149 
 150 void DUIterator::verify_resync() {
 151   // Note:  We do not assert on _outcnt, because insertions are OK here.
 152   DUIterator_Common::verify_resync();
 153   // Make sure we are still in sync, possibly with no more out-edges:
 154   verify(_node, true);
 155 }
 156 
 157 void DUIterator::reset(const DUIterator& that) {
 158   if (this == &that)  return;  // self assignment is always a no-op
 159   assert(that._refresh_tick == 0, "assign only the result of Node::outs()");
 160   assert(that._idx          == 0, "assign only the result of Node::outs()");
 161   assert(_idx               == that._idx, "already assigned _idx");
 162   if (!_vdui) {
 163     // We need to initialize everything, overwriting garbage values.
 164     sample(that._node);
 165   } else {
 166     DUIterator_Common::reset(that);
 167     if (_refresh_tick & 1) {
 168       _refresh_tick++;                  // Clear the "was refreshed" flag.
 169     }
 170     assert(_refresh_tick < 2*100000, "DU iteration must converge quickly");
 171   }
 172 }
 173 
 174 void DUIterator::refresh() {
 175   DUIterator_Common::sample(_node);     // Re-fetch assertion data.
 176   _refresh_tick |= 1;                   // Set the "was refreshed" flag.
 177 }
 178 
 179 void DUIterator::verify_finish() {
 180   // If the loop has killed the node, do not require it to re-run.
 181   if (_node->_outcnt == 0)  _refresh_tick &= ~1;
 182   // If this assert triggers, it means that a loop used refresh_out_pos
 183   // to re-synch an iteration index, but the loop did not correctly
 184   // re-run itself, using a "while (progress)" construct.
 185   // This iterator enforces the rule that you must keep trying the loop
 186   // until it "runs clean" without any need for refreshing.
 187   assert(!(_refresh_tick & 1), "the loop must run once with no refreshing");
 188 }
 189 
 190 
 191 void DUIterator_Fast::verify(const Node* node, bool at_end_ok) {
 192   DUIterator_Common::verify(node, at_end_ok);
 193   Node** out    = node->_out;
 194   uint   cnt    = node->_outcnt;
 195   assert(cnt == _outcnt, "no insertions allowed");
 196   assert(_outp >= out && _outp <= out + cnt - !at_end_ok, "outp in range");
 197   // This last check is carefully designed to work for NO_OUT_ARRAY.
 198 }
 199 
 200 void DUIterator_Fast::verify_limit() {
 201   const Node* node = _node;
 202   verify(node, true);
 203   assert(_outp == node->_out + node->_outcnt, "limit still correct");
 204 }
 205 
 206 void DUIterator_Fast::verify_resync() {
 207   const Node* node = _node;
 208   if (_outp == node->_out + _outcnt) {
 209     // Note that the limit imax, not the pointer i, gets updated with the
 210     // exact count of deletions.  (For the pointer it's always "--i".)
 211     assert(node->_outcnt+node->_del_tick == _outcnt+_del_tick, "no insertions allowed with deletion(s)");
 212     // This is a limit pointer, with a name like "imax".
 213     // Fudge the _last field so that the common assert will be happy.
 214     _last = (Node*) node->_last_del;
 215     DUIterator_Common::verify_resync();
 216   } else {
 217     assert(node->_outcnt < _outcnt, "no insertions allowed with deletion(s)");
 218     // A normal internal pointer.
 219     DUIterator_Common::verify_resync();
 220     // Make sure we are still in sync, possibly with no more out-edges:
 221     verify(node, true);
 222   }
 223 }
 224 
 225 void DUIterator_Fast::verify_relimit(uint n) {
 226   const Node* node = _node;
 227   assert((int)n > 0, "use imax -= n only with a positive count");
 228   // This must be a limit pointer, with a name like "imax".
 229   assert(_outp == node->_out + node->_outcnt, "apply -= only to a limit (imax)");
 230   // The reported number of deletions must match what the node saw.
 231   assert(node->_del_tick == _del_tick + n, "must have deleted n edges");
 232   // Fudge the _last field so that the common assert will be happy.
 233   _last = (Node*) node->_last_del;
 234   DUIterator_Common::verify_resync();
 235 }
 236 
 237 void DUIterator_Fast::reset(const DUIterator_Fast& that) {
 238   assert(_outp              == that._outp, "already assigned _outp");
 239   DUIterator_Common::reset(that);
 240 }
 241 
 242 void DUIterator_Last::verify(const Node* node, bool at_end_ok) {
 243   // at_end_ok means the _outp is allowed to underflow by 1
 244   _outp += at_end_ok;
 245   DUIterator_Fast::verify(node, at_end_ok);  // check _del_tick, etc.
 246   _outp -= at_end_ok;
 247   assert(_outp == (node->_out + node->_outcnt) - 1, "pointer must point to end of nodes");
 248 }
 249 
 250 void DUIterator_Last::verify_limit() {
 251   // Do not require the limit address to be resynched.
 252   //verify(node, true);
 253   assert(_outp == _node->_out, "limit still correct");
 254 }
 255 
 256 void DUIterator_Last::verify_step(uint num_edges) {
 257   assert((int)num_edges > 0, "need non-zero edge count for loop progress");
 258   _outcnt   -= num_edges;
 259   _del_tick += num_edges;
 260   // Make sure we are still in sync, possibly with no more out-edges:
 261   const Node* node = _node;
 262   verify(node, true);
 263   assert(node->_last_del == _last, "must have deleted the edge just produced");
 264 }
 265 
 266 #endif //OPTO_DU_ITERATOR_ASSERT
 267 
 268 
 269 #endif //ASSERT
 270 
 271 
 272 // This constant used to initialize _out may be any non-null value.
 273 // The value NULL is reserved for the top node only.
 274 #define NO_OUT_ARRAY ((Node**)-1)
 275 
 276 // This funny expression handshakes with Node::operator new
 277 // to pull Compile::current out of the new node's _out field,
 278 // and then calls a subroutine which manages most field
 279 // initializations.  The only one which is tricky is the
 280 // _idx field, which is const, and so must be initialized
 281 // by a return value, not an assignment.
 282 //
 283 // (Aren't you thankful that Java finals don't require so many tricks?)
 284 #define IDX_INIT(req) this->Init((req), (Compile*) this->_out)
 285 #ifdef _MSC_VER // the IDX_INIT hack falls foul of warning C4355
 286 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
 287 #endif
 288 
 289 // Out-of-line code from node constructors.
 290 // Executed only when extra debug info. is being passed around.
 291 static void init_node_notes(Compile* C, int idx, Node_Notes* nn) {
 292   C->set_node_notes_at(idx, nn);
 293 }
 294 
 295 // Shared initialization code.
 296 inline int Node::Init(int req, Compile* C) {
 297   assert(Compile::current() == C, "must use operator new(Compile*)");
 298   int idx = C->next_unique();
 299 
 300   // Allocate memory for the necessary number of edges.
 301   if (req > 0) {
 302     // Allocate space for _in array to have double alignment.
 303     _in = (Node **) ((char *) (C->node_arena()->Amalloc_D(req * sizeof(void*))));
 304 #ifdef ASSERT
 305     _in[req-1] = this; // magic cookie for assertion check
 306 #endif
 307   }
 308   // If there are default notes floating around, capture them:
 309   Node_Notes* nn = C->default_node_notes();
 310   if (nn != NULL)  init_node_notes(C, idx, nn);
 311 
 312   // Note:  At this point, C is dead,
 313   // and we begin to initialize the new Node.
 314 
 315   _cnt = _max = req;
 316   _outcnt = _outmax = 0;
 317   _class_id = Class_Node;
 318   _flags = 0;
 319   _out = NO_OUT_ARRAY;
 320   return idx;
 321 }
 322 
 323 //------------------------------Node-------------------------------------------
 324 // Create a Node, with a given number of required edges.
 325 Node::Node(uint req)
 326   : _idx(IDX_INIT(req))
 327 {
 328   assert( req < (uint)(MaxNodeLimit - NodeLimitFudgeFactor), "Input limit exceeded" );
 329   debug_only( verify_construction() );
 330   NOT_PRODUCT(nodes_created++);
 331   if (req == 0) {
 332     assert( _in == (Node**)this, "Must not pass arg count to 'new'" );
 333     _in = NULL;
 334   } else {
 335     assert( _in[req-1] == this, "Must pass arg count to 'new'" );
 336     Node** to = _in;
 337     for(uint i = 0; i < req; i++) {
 338       to[i] = NULL;
 339     }
 340   }
 341 }
 342 
 343 //------------------------------Node-------------------------------------------
 344 Node::Node(Node *n0)
 345   : _idx(IDX_INIT(1))
 346 {
 347   debug_only( verify_construction() );
 348   NOT_PRODUCT(nodes_created++);
 349   // Assert we allocated space for input array already
 350   assert( _in[0] == this, "Must pass arg count to 'new'" );
 351   assert( is_not_dead(n0), "can not use dead node");
 352   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 353 }
 354 
 355 //------------------------------Node-------------------------------------------
 356 Node::Node(Node *n0, Node *n1)
 357   : _idx(IDX_INIT(2))
 358 {
 359   debug_only( verify_construction() );
 360   NOT_PRODUCT(nodes_created++);
 361   // Assert we allocated space for input array already
 362   assert( _in[1] == this, "Must pass arg count to 'new'" );
 363   assert( is_not_dead(n0), "can not use dead node");
 364   assert( is_not_dead(n1), "can not use dead node");
 365   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 366   _in[1] = n1; if (n1 != NULL) n1->add_out((Node *)this);
 367 }
 368 
 369 //------------------------------Node-------------------------------------------
 370 Node::Node(Node *n0, Node *n1, Node *n2)
 371   : _idx(IDX_INIT(3))
 372 {
 373   debug_only( verify_construction() );
 374   NOT_PRODUCT(nodes_created++);
 375   // Assert we allocated space for input array already
 376   assert( _in[2] == this, "Must pass arg count to 'new'" );
 377   assert( is_not_dead(n0), "can not use dead node");
 378   assert( is_not_dead(n1), "can not use dead node");
 379   assert( is_not_dead(n2), "can not use dead node");
 380   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 381   _in[1] = n1; if (n1 != NULL) n1->add_out((Node *)this);
 382   _in[2] = n2; if (n2 != NULL) n2->add_out((Node *)this);
 383 }
 384 
 385 //------------------------------Node-------------------------------------------
 386 Node::Node(Node *n0, Node *n1, Node *n2, Node *n3)
 387   : _idx(IDX_INIT(4))
 388 {
 389   debug_only( verify_construction() );
 390   NOT_PRODUCT(nodes_created++);
 391   // Assert we allocated space for input array already
 392   assert( _in[3] == this, "Must pass arg count to 'new'" );
 393   assert( is_not_dead(n0), "can not use dead node");
 394   assert( is_not_dead(n1), "can not use dead node");
 395   assert( is_not_dead(n2), "can not use dead node");
 396   assert( is_not_dead(n3), "can not use dead node");
 397   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 398   _in[1] = n1; if (n1 != NULL) n1->add_out((Node *)this);
 399   _in[2] = n2; if (n2 != NULL) n2->add_out((Node *)this);
 400   _in[3] = n3; if (n3 != NULL) n3->add_out((Node *)this);
 401 }
 402 
 403 //------------------------------Node-------------------------------------------
 404 Node::Node(Node *n0, Node *n1, Node *n2, Node *n3, Node *n4)
 405   : _idx(IDX_INIT(5))
 406 {
 407   debug_only( verify_construction() );
 408   NOT_PRODUCT(nodes_created++);
 409   // Assert we allocated space for input array already
 410   assert( _in[4] == this, "Must pass arg count to 'new'" );
 411   assert( is_not_dead(n0), "can not use dead node");
 412   assert( is_not_dead(n1), "can not use dead node");
 413   assert( is_not_dead(n2), "can not use dead node");
 414   assert( is_not_dead(n3), "can not use dead node");
 415   assert( is_not_dead(n4), "can not use dead node");
 416   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 417   _in[1] = n1; if (n1 != NULL) n1->add_out((Node *)this);
 418   _in[2] = n2; if (n2 != NULL) n2->add_out((Node *)this);
 419   _in[3] = n3; if (n3 != NULL) n3->add_out((Node *)this);
 420   _in[4] = n4; if (n4 != NULL) n4->add_out((Node *)this);
 421 }
 422 
 423 //------------------------------Node-------------------------------------------
 424 Node::Node(Node *n0, Node *n1, Node *n2, Node *n3,
 425                      Node *n4, Node *n5)
 426   : _idx(IDX_INIT(6))
 427 {
 428   debug_only( verify_construction() );
 429   NOT_PRODUCT(nodes_created++);
 430   // Assert we allocated space for input array already
 431   assert( _in[5] == this, "Must pass arg count to 'new'" );
 432   assert( is_not_dead(n0), "can not use dead node");
 433   assert( is_not_dead(n1), "can not use dead node");
 434   assert( is_not_dead(n2), "can not use dead node");
 435   assert( is_not_dead(n3), "can not use dead node");
 436   assert( is_not_dead(n4), "can not use dead node");
 437   assert( is_not_dead(n5), "can not use dead node");
 438   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 439   _in[1] = n1; if (n1 != NULL) n1->add_out((Node *)this);
 440   _in[2] = n2; if (n2 != NULL) n2->add_out((Node *)this);
 441   _in[3] = n3; if (n3 != NULL) n3->add_out((Node *)this);
 442   _in[4] = n4; if (n4 != NULL) n4->add_out((Node *)this);
 443   _in[5] = n5; if (n5 != NULL) n5->add_out((Node *)this);
 444 }
 445 
 446 //------------------------------Node-------------------------------------------
 447 Node::Node(Node *n0, Node *n1, Node *n2, Node *n3,
 448                      Node *n4, Node *n5, Node *n6)
 449   : _idx(IDX_INIT(7))
 450 {
 451   debug_only( verify_construction() );
 452   NOT_PRODUCT(nodes_created++);
 453   // Assert we allocated space for input array already
 454   assert( _in[6] == this, "Must pass arg count to 'new'" );
 455   assert( is_not_dead(n0), "can not use dead node");
 456   assert( is_not_dead(n1), "can not use dead node");
 457   assert( is_not_dead(n2), "can not use dead node");
 458   assert( is_not_dead(n3), "can not use dead node");
 459   assert( is_not_dead(n4), "can not use dead node");
 460   assert( is_not_dead(n5), "can not use dead node");
 461   assert( is_not_dead(n6), "can not use dead node");
 462   _in[0] = n0; if (n0 != NULL) n0->add_out((Node *)this);
 463   _in[1] = n1; if (n1 != NULL) n1->add_out((Node *)this);
 464   _in[2] = n2; if (n2 != NULL) n2->add_out((Node *)this);
 465   _in[3] = n3; if (n3 != NULL) n3->add_out((Node *)this);
 466   _in[4] = n4; if (n4 != NULL) n4->add_out((Node *)this);
 467   _in[5] = n5; if (n5 != NULL) n5->add_out((Node *)this);
 468   _in[6] = n6; if (n6 != NULL) n6->add_out((Node *)this);
 469 }
 470 
 471 
 472 //------------------------------clone------------------------------------------
 473 // Clone a Node.
 474 Node *Node::clone() const {
 475   Compile* C = Compile::current();
 476   uint s = size_of();           // Size of inherited Node
 477   Node *n = (Node*)C->node_arena()->Amalloc_D(size_of() + _max*sizeof(Node*));
 478   Copy::conjoint_words_to_lower((HeapWord*)this, (HeapWord*)n, s);
 479   // Set the new input pointer array
 480   n->_in = (Node**)(((char*)n)+s);
 481   // Cannot share the old output pointer array, so kill it
 482   n->_out = NO_OUT_ARRAY;
 483   // And reset the counters to 0
 484   n->_outcnt = 0;
 485   n->_outmax = 0;
 486   // Unlock this guy, since he is not in any hash table.
 487   debug_only(n->_hash_lock = 0);
 488   // Walk the old node's input list to duplicate its edges
 489   uint i;
 490   for( i = 0; i < len(); i++ ) {
 491     Node *x = in(i);
 492     n->_in[i] = x;
 493     if (x != NULL) x->add_out(n);
 494   }
 495   if (is_macro())
 496     C->add_macro_node(n);
 497   if (is_expensive())
 498     C->add_expensive_node(n);
 499 
 500   n->set_idx(C->next_unique()); // Get new unique index as well
 501   debug_only( n->verify_construction() );
 502   NOT_PRODUCT(nodes_created++);
 503   // Do not patch over the debug_idx of a clone, because it makes it
 504   // impossible to break on the clone's moment of creation.
 505   //debug_only( n->set_debug_idx( debug_idx() ) );
 506 
 507   C->copy_node_notes_to(n, (Node*) this);
 508 
 509   // MachNode clone
 510   uint nopnds;
 511   if (this->is_Mach() && (nopnds = this->as_Mach()->num_opnds()) > 0) {
 512     MachNode *mach  = n->as_Mach();
 513     MachNode *mthis = this->as_Mach();
 514     // Get address of _opnd_array.
 515     // It should be the same offset since it is the clone of this node.
 516     MachOper **from = mthis->_opnds;
 517     MachOper **to = (MachOper **)((size_t)(&mach->_opnds) +
 518                     pointer_delta((const void*)from,
 519                                   (const void*)(&mthis->_opnds), 1));
 520     mach->_opnds = to;
 521     for ( uint i = 0; i < nopnds; ++i ) {
 522       to[i] = from[i]->clone(C);
 523     }
 524   }
 525   // cloning CallNode may need to clone JVMState
 526   if (n->is_Call()) {
 527     n->as_Call()->clone_jvms(C);
 528   }
 529   return n;                     // Return the clone
 530 }
 531 
 532 //---------------------------setup_is_top--------------------------------------
 533 // Call this when changing the top node, to reassert the invariants
 534 // required by Node::is_top.  See Compile::set_cached_top_node.
 535 void Node::setup_is_top() {
 536   if (this == (Node*)Compile::current()->top()) {
 537     // This node has just become top.  Kill its out array.
 538     _outcnt = _outmax = 0;
 539     _out = NULL;                           // marker value for top
 540     assert(is_top(), "must be top");
 541   } else {
 542     if (_out == NULL)  _out = NO_OUT_ARRAY;
 543     assert(!is_top(), "must not be top");
 544   }
 545 }
 546 
 547 
 548 //------------------------------~Node------------------------------------------
 549 // Fancy destructor; eagerly attempt to reclaim Node numberings and storage
 550 extern int reclaim_idx ;
 551 extern int reclaim_in  ;
 552 extern int reclaim_node;
 553 void Node::destruct() {
 554   // Eagerly reclaim unique Node numberings
 555   Compile* compile = Compile::current();
 556   if ((uint)_idx+1 == compile->unique()) {
 557     compile->set_unique(compile->unique()-1);
 558 #ifdef ASSERT
 559     reclaim_idx++;
 560 #endif
 561   }
 562   // Clear debug info:
 563   Node_Notes* nn = compile->node_notes_at(_idx);
 564   if (nn != NULL)  nn->clear();
 565   // Walk the input array, freeing the corresponding output edges
 566   _cnt = _max;  // forget req/prec distinction
 567   uint i;
 568   for( i = 0; i < _max; i++ ) {
 569     set_req(i, NULL);
 570     //assert(def->out(def->outcnt()-1) == (Node *)this,"bad def-use hacking in reclaim");
 571   }
 572   assert(outcnt() == 0, "deleting a node must not leave a dangling use");
 573   // See if the input array was allocated just prior to the object
 574   int edge_size = _max*sizeof(void*);
 575   int out_edge_size = _outmax*sizeof(void*);
 576   char *edge_end = ((char*)_in) + edge_size;
 577   char *out_array = (char*)(_out == NO_OUT_ARRAY? NULL: _out);
 578   char *out_edge_end = out_array + out_edge_size;
 579   int node_size = size_of();
 580 
 581   // Free the output edge array
 582   if (out_edge_size > 0) {
 583 #ifdef ASSERT
 584     if( out_edge_end == compile->node_arena()->hwm() )
 585       reclaim_in  += out_edge_size;  // count reclaimed out edges with in edges
 586 #endif
 587     compile->node_arena()->Afree(out_array, out_edge_size);
 588   }
 589 
 590   // Free the input edge array and the node itself
 591   if( edge_end == (char*)this ) {
 592 #ifdef ASSERT
 593     if( edge_end+node_size == compile->node_arena()->hwm() ) {
 594       reclaim_in  += edge_size;
 595       reclaim_node+= node_size;
 596     }
 597 #else
 598     // It was; free the input array and object all in one hit
 599     compile->node_arena()->Afree(_in,edge_size+node_size);
 600 #endif
 601   } else {
 602 
 603     // Free just the input array
 604 #ifdef ASSERT
 605     if( edge_end == compile->node_arena()->hwm() )
 606       reclaim_in  += edge_size;
 607 #endif
 608     compile->node_arena()->Afree(_in,edge_size);
 609 
 610     // Free just the object
 611 #ifdef ASSERT
 612     if( ((char*)this) + node_size == compile->node_arena()->hwm() )
 613       reclaim_node+= node_size;
 614 #else
 615     compile->node_arena()->Afree(this,node_size);
 616 #endif
 617   }
 618   if (is_macro()) {
 619     compile->remove_macro_node(this);
 620   }
 621   if (is_expensive()) {
 622     compile->remove_expensive_node(this);
 623   }
 624 #ifdef ASSERT
 625   // We will not actually delete the storage, but we'll make the node unusable.
 626   *(address*)this = badAddress;  // smash the C++ vtbl, probably
 627   _in = _out = (Node**) badAddress;
 628   _max = _cnt = _outmax = _outcnt = 0;
 629 #endif
 630 }
 631 
 632 //------------------------------grow-------------------------------------------
 633 // Grow the input array, making space for more edges
 634 void Node::grow( uint len ) {
 635   Arena* arena = Compile::current()->node_arena();
 636   uint new_max = _max;
 637   if( new_max == 0 ) {
 638     _max = 4;
 639     _in = (Node**)arena->Amalloc(4*sizeof(Node*));
 640     Node** to = _in;
 641     to[0] = NULL;
 642     to[1] = NULL;
 643     to[2] = NULL;
 644     to[3] = NULL;
 645     return;
 646   }
 647   while( new_max <= len ) new_max <<= 1; // Find next power-of-2
 648   // Trimming to limit allows a uint8 to handle up to 255 edges.
 649   // Previously I was using only powers-of-2 which peaked at 128 edges.
 650   //if( new_max >= limit ) new_max = limit-1;
 651   _in = (Node**)arena->Arealloc(_in, _max*sizeof(Node*), new_max*sizeof(Node*));
 652   Copy::zero_to_bytes(&_in[_max], (new_max-_max)*sizeof(Node*)); // NULL all new space
 653   _max = new_max;               // Record new max length
 654   // This assertion makes sure that Node::_max is wide enough to
 655   // represent the numerical value of new_max.
 656   assert(_max == new_max && _max > len, "int width of _max is too small");
 657 }
 658 
 659 //-----------------------------out_grow----------------------------------------
 660 // Grow the input array, making space for more edges
 661 void Node::out_grow( uint len ) {
 662   assert(!is_top(), "cannot grow a top node's out array");
 663   Arena* arena = Compile::current()->node_arena();
 664   uint new_max = _outmax;
 665   if( new_max == 0 ) {
 666     _outmax = 4;
 667     _out = (Node **)arena->Amalloc(4*sizeof(Node*));
 668     return;
 669   }
 670   while( new_max <= len ) new_max <<= 1; // Find next power-of-2
 671   // Trimming to limit allows a uint8 to handle up to 255 edges.
 672   // Previously I was using only powers-of-2 which peaked at 128 edges.
 673   //if( new_max >= limit ) new_max = limit-1;
 674   assert(_out != NULL && _out != NO_OUT_ARRAY, "out must have sensible value");
 675   _out = (Node**)arena->Arealloc(_out,_outmax*sizeof(Node*),new_max*sizeof(Node*));
 676   //Copy::zero_to_bytes(&_out[_outmax], (new_max-_outmax)*sizeof(Node*)); // NULL all new space
 677   _outmax = new_max;               // Record new max length
 678   // This assertion makes sure that Node::_max is wide enough to
 679   // represent the numerical value of new_max.
 680   assert(_outmax == new_max && _outmax > len, "int width of _outmax is too small");
 681 }
 682 
 683 #ifdef ASSERT
 684 //------------------------------is_dead----------------------------------------
 685 bool Node::is_dead() const {
 686   // Mach and pinch point nodes may look like dead.
 687   if( is_top() || is_Mach() || (Opcode() == Op_Node && _outcnt > 0) )
 688     return false;
 689   for( uint i = 0; i < _max; i++ )
 690     if( _in[i] != NULL )
 691       return false;
 692   dump();
 693   return true;
 694 }
 695 #endif
 696 
 697 
 698 //------------------------------is_unreachable---------------------------------
 699 bool Node::is_unreachable(PhaseIterGVN &igvn) const {
 700   assert(!is_Mach(), "doesn't work with MachNodes");
 701   return outcnt() == 0 || igvn.type(this) == Type::TOP || in(0)->is_top();
 702 }
 703 
 704 //------------------------------add_req----------------------------------------
 705 // Add a new required input at the end
 706 void Node::add_req( Node *n ) {
 707   assert( is_not_dead(n), "can not use dead node");
 708 
 709   // Look to see if I can move precedence down one without reallocating
 710   if( (_cnt >= _max) || (in(_max-1) != NULL) )
 711     grow( _max+1 );
 712 
 713   // Find a precedence edge to move
 714   if( in(_cnt) != NULL ) {       // Next precedence edge is busy?
 715     uint i;
 716     for( i=_cnt; i<_max; i++ )
 717       if( in(i) == NULL )       // Find the NULL at end of prec edge list
 718         break;                  // There must be one, since we grew the array
 719     _in[i] = in(_cnt);          // Move prec over, making space for req edge
 720   }
 721   _in[_cnt++] = n;            // Stuff over old prec edge
 722   if (n != NULL) n->add_out((Node *)this);
 723 }
 724 
 725 //---------------------------add_req_batch-------------------------------------
 726 // Add a new required input at the end
 727 void Node::add_req_batch( Node *n, uint m ) {
 728   assert( is_not_dead(n), "can not use dead node");
 729   // check various edge cases
 730   if ((int)m <= 1) {
 731     assert((int)m >= 0, "oob");
 732     if (m != 0)  add_req(n);
 733     return;
 734   }
 735 
 736   // Look to see if I can move precedence down one without reallocating
 737   if( (_cnt+m) > _max || _in[_max-m] )
 738     grow( _max+m );
 739 
 740   // Find a precedence edge to move
 741   if( _in[_cnt] != NULL ) {     // Next precedence edge is busy?
 742     uint i;
 743     for( i=_cnt; i<_max; i++ )
 744       if( _in[i] == NULL )      // Find the NULL at end of prec edge list
 745         break;                  // There must be one, since we grew the array
 746     // Slide all the precs over by m positions (assume #prec << m).
 747     Copy::conjoint_words_to_higher((HeapWord*)&_in[_cnt], (HeapWord*)&_in[_cnt+m], ((i-_cnt)*sizeof(Node*)));
 748   }
 749 
 750   // Stuff over the old prec edges
 751   for(uint i=0; i<m; i++ ) {
 752     _in[_cnt++] = n;
 753   }
 754 
 755   // Insert multiple out edges on the node.
 756   if (n != NULL && !n->is_top()) {
 757     for(uint i=0; i<m; i++ ) {
 758       n->add_out((Node *)this);
 759     }
 760   }
 761 }
 762 
 763 //------------------------------del_req----------------------------------------
 764 // Delete the required edge and compact the edge array
 765 void Node::del_req( uint idx ) {
 766   assert( idx < _cnt, "oob");
 767   assert( !VerifyHashTableKeys || _hash_lock == 0,
 768           "remove node from hash table before modifying it");
 769   // First remove corresponding def-use edge
 770   Node *n = in(idx);
 771   if (n != NULL) n->del_out((Node *)this);
 772   _in[idx] = in(--_cnt);  // Compact the array
 773   _in[_cnt] = NULL;       // NULL out emptied slot
 774 }
 775 
 776 //------------------------------ins_req----------------------------------------
 777 // Insert a new required input at the end
 778 void Node::ins_req( uint idx, Node *n ) {
 779   assert( is_not_dead(n), "can not use dead node");
 780   add_req(NULL);                // Make space
 781   assert( idx < _max, "Must have allocated enough space");
 782   // Slide over
 783   if(_cnt-idx-1 > 0) {
 784     Copy::conjoint_words_to_higher((HeapWord*)&_in[idx], (HeapWord*)&_in[idx+1], ((_cnt-idx-1)*sizeof(Node*)));
 785   }
 786   _in[idx] = n;                            // Stuff over old required edge
 787   if (n != NULL) n->add_out((Node *)this); // Add reciprocal def-use edge
 788 }
 789 
 790 //-----------------------------find_edge---------------------------------------
 791 int Node::find_edge(Node* n) {
 792   for (uint i = 0; i < len(); i++) {
 793     if (_in[i] == n)  return i;
 794   }
 795   return -1;
 796 }
 797 
 798 //----------------------------replace_edge-------------------------------------
 799 int Node::replace_edge(Node* old, Node* neww) {
 800   if (old == neww)  return 0;  // nothing to do
 801   uint nrep = 0;
 802   for (uint i = 0; i < len(); i++) {
 803     if (in(i) == old) {
 804       if (i < req())
 805         set_req(i, neww);
 806       else
 807         set_prec(i, neww);
 808       nrep++;
 809     }
 810   }
 811   return nrep;
 812 }
 813 
 814 /**
 815  * Replace input edges in the range pointing to 'old' node.
 816  */
 817 int Node::replace_edges_in_range(Node* old, Node* neww, int start, int end) {
 818   if (old == neww)  return 0;  // nothing to do
 819   uint nrep = 0;
 820   for (int i = start; i < end; i++) {
 821     if (in(i) == old) {
 822       set_req(i, neww);
 823       nrep++;
 824     }
 825   }
 826   return nrep;
 827 }
 828 
 829 //-------------------------disconnect_inputs-----------------------------------
 830 // NULL out all inputs to eliminate incoming Def-Use edges.
 831 // Return the number of edges between 'n' and 'this'
 832 int Node::disconnect_inputs(Node *n, Compile* C) {
 833   int edges_to_n = 0;
 834 
 835   uint cnt = req();
 836   for( uint i = 0; i < cnt; ++i ) {
 837     if( in(i) == 0 ) continue;
 838     if( in(i) == n ) ++edges_to_n;
 839     set_req(i, NULL);
 840   }
 841   // Remove precedence edges if any exist
 842   // Note: Safepoints may have precedence edges, even during parsing
 843   if( (req() != len()) && (in(req()) != NULL) ) {
 844     uint max = len();
 845     for( uint i = 0; i < max; ++i ) {
 846       if( in(i) == 0 ) continue;
 847       if( in(i) == n ) ++edges_to_n;
 848       set_prec(i, NULL);
 849     }
 850   }
 851 
 852   // Node::destruct requires all out edges be deleted first
 853   // debug_only(destruct();)   // no reuse benefit expected
 854   if (edges_to_n == 0) {
 855     C->record_dead_node(_idx);
 856   }
 857   return edges_to_n;
 858 }
 859 
 860 //-----------------------------uncast---------------------------------------
 861 // %%% Temporary, until we sort out CheckCastPP vs. CastPP.
 862 // Strip away casting.  (It is depth-limited.)
 863 Node* Node::uncast() const {
 864   // Should be inline:
 865   //return is_ConstraintCast() ? uncast_helper(this) : (Node*) this;
 866   if (is_ConstraintCast() || is_CheckCastPP())
 867     return uncast_helper(this);
 868   else
 869     return (Node*) this;
 870 }
 871 
 872 //---------------------------uncast_helper-------------------------------------
 873 Node* Node::uncast_helper(const Node* p) {
 874 #ifdef ASSERT
 875   uint depth_count = 0;
 876   const Node* orig_p = p;
 877 #endif
 878 
 879   while (true) {
 880 #ifdef ASSERT
 881     if (depth_count >= K) {
 882       orig_p->dump(4);
 883       if (p != orig_p)
 884         p->dump(1);
 885     }
 886     assert(depth_count++ < K, "infinite loop in Node::uncast_helper");
 887 #endif
 888     if (p == NULL || p->req() != 2) {
 889       break;
 890     } else if (p->is_ConstraintCast()) {
 891       p = p->in(1);
 892     } else if (p->is_CheckCastPP()) {
 893       p = p->in(1);
 894     } else {
 895       break;
 896     }
 897   }
 898   return (Node*) p;
 899 }
 900 
 901 //------------------------------add_prec---------------------------------------
 902 // Add a new precedence input.  Precedence inputs are unordered, with
 903 // duplicates removed and NULLs packed down at the end.
 904 void Node::add_prec( Node *n ) {
 905   assert( is_not_dead(n), "can not use dead node");
 906 
 907   // Check for NULL at end
 908   if( _cnt >= _max || in(_max-1) )
 909     grow( _max+1 );
 910 
 911   // Find a precedence edge to move
 912   uint i = _cnt;
 913   while( in(i) != NULL ) i++;
 914   _in[i] = n;                                // Stuff prec edge over NULL
 915   if ( n != NULL) n->add_out((Node *)this);  // Add mirror edge
 916 }
 917 
 918 //------------------------------rm_prec----------------------------------------
 919 // Remove a precedence input.  Precedence inputs are unordered, with
 920 // duplicates removed and NULLs packed down at the end.
 921 void Node::rm_prec( uint j ) {
 922 
 923   // Find end of precedence list to pack NULLs
 924   uint i;
 925   for( i=j; i<_max; i++ )
 926     if( !_in[i] )               // Find the NULL at end of prec edge list
 927       break;
 928   if (_in[j] != NULL) _in[j]->del_out((Node *)this);
 929   _in[j] = _in[--i];            // Move last element over removed guy
 930   _in[i] = NULL;                // NULL out last element
 931 }
 932 
 933 //------------------------------size_of----------------------------------------
 934 uint Node::size_of() const { return sizeof(*this); }
 935 
 936 //------------------------------ideal_reg--------------------------------------
 937 uint Node::ideal_reg() const { return 0; }
 938 
 939 //------------------------------jvms-------------------------------------------
 940 JVMState* Node::jvms() const { return NULL; }
 941 
 942 #ifdef ASSERT
 943 //------------------------------jvms-------------------------------------------
 944 bool Node::verify_jvms(const JVMState* using_jvms) const {
 945   for (JVMState* jvms = this->jvms(); jvms != NULL; jvms = jvms->caller()) {
 946     if (jvms == using_jvms)  return true;
 947   }
 948   return false;
 949 }
 950 
 951 //------------------------------init_NodeProperty------------------------------
 952 void Node::init_NodeProperty() {
 953   assert(_max_classes <= max_jushort, "too many NodeProperty classes");
 954   assert(_max_flags <= max_jushort, "too many NodeProperty flags");
 955 }
 956 #endif
 957 
 958 //------------------------------format-----------------------------------------
 959 // Print as assembly
 960 void Node::format( PhaseRegAlloc *, outputStream *st ) const {}
 961 //------------------------------emit-------------------------------------------
 962 // Emit bytes starting at parameter 'ptr'.
 963 void Node::emit(CodeBuffer &cbuf, PhaseRegAlloc *ra_) const {}
 964 //------------------------------size-------------------------------------------
 965 // Size of instruction in bytes
 966 uint Node::size(PhaseRegAlloc *ra_) const { return 0; }
 967 
 968 //------------------------------CFG Construction-------------------------------
 969 // Nodes that end basic blocks, e.g. IfTrue/IfFalse, JumpProjNode, Root,
 970 // Goto and Return.
 971 const Node *Node::is_block_proj() const { return 0; }
 972 
 973 // Minimum guaranteed type
 974 const Type *Node::bottom_type() const { return Type::BOTTOM; }
 975 
 976 
 977 //------------------------------raise_bottom_type------------------------------
 978 // Get the worst-case Type output for this Node.
 979 void Node::raise_bottom_type(const Type* new_type) {
 980   if (is_Type()) {
 981     TypeNode *n = this->as_Type();
 982     if (VerifyAliases) {
 983       assert(new_type->higher_equal(n->type()), "new type must refine old type");
 984     }
 985     n->set_type(new_type);
 986   } else if (is_Load()) {
 987     LoadNode *n = this->as_Load();
 988     if (VerifyAliases) {
 989       assert(new_type->higher_equal(n->type()), "new type must refine old type");
 990     }
 991     n->set_type(new_type);
 992   }
 993 }
 994 
 995 //------------------------------Identity---------------------------------------
 996 // Return a node that the given node is equivalent to.
 997 Node *Node::Identity( PhaseTransform * ) {
 998   return this;                  // Default to no identities
 999 }
1000 
1001 //------------------------------Value------------------------------------------
1002 // Compute a new Type for a node using the Type of the inputs.
1003 const Type *Node::Value( PhaseTransform * ) const {
1004   return bottom_type();         // Default to worst-case Type
1005 }
1006 
1007 //------------------------------Ideal------------------------------------------
1008 //
1009 // 'Idealize' the graph rooted at this Node.
1010 //
1011 // In order to be efficient and flexible there are some subtle invariants
1012 // these Ideal calls need to hold.  Running with '+VerifyIterativeGVN' checks
1013 // these invariants, although its too slow to have on by default.  If you are
1014 // hacking an Ideal call, be sure to test with +VerifyIterativeGVN!
1015 //
1016 // The Ideal call almost arbitrarily reshape the graph rooted at the 'this'
1017 // pointer.  If ANY change is made, it must return the root of the reshaped
1018 // graph - even if the root is the same Node.  Example: swapping the inputs
1019 // to an AddINode gives the same answer and same root, but you still have to
1020 // return the 'this' pointer instead of NULL.
1021 //
1022 // You cannot return an OLD Node, except for the 'this' pointer.  Use the
1023 // Identity call to return an old Node; basically if Identity can find
1024 // another Node have the Ideal call make no change and return NULL.
1025 // Example: AddINode::Ideal must check for add of zero; in this case it
1026 // returns NULL instead of doing any graph reshaping.
1027 //
1028 // You cannot modify any old Nodes except for the 'this' pointer.  Due to
1029 // sharing there may be other users of the old Nodes relying on their current
1030 // semantics.  Modifying them will break the other users.
1031 // Example: when reshape "(X+3)+4" into "X+7" you must leave the Node for
1032 // "X+3" unchanged in case it is shared.
1033 //
1034 // If you modify the 'this' pointer's inputs, you should use
1035 // 'set_req'.  If you are making a new Node (either as the new root or
1036 // some new internal piece) you may use 'init_req' to set the initial
1037 // value.  You can make a new Node with either 'new' or 'clone'.  In
1038 // either case, def-use info is correctly maintained.
1039 //
1040 // Example: reshape "(X+3)+4" into "X+7":
1041 //    set_req(1, in(1)->in(1));
1042 //    set_req(2, phase->intcon(7));
1043 //    return this;
1044 // Example: reshape "X*4" into "X<<2"
1045 //    return new (C) LShiftINode(in(1), phase->intcon(2));
1046 //
1047 // You must call 'phase->transform(X)' on any new Nodes X you make, except
1048 // for the returned root node.  Example: reshape "X*31" with "(X<<5)-X".
1049 //    Node *shift=phase->transform(new(C)LShiftINode(in(1),phase->intcon(5)));
1050 //    return new (C) AddINode(shift, in(1));
1051 //
1052 // When making a Node for a constant use 'phase->makecon' or 'phase->intcon'.
1053 // These forms are faster than 'phase->transform(new (C) ConNode())' and Do
1054 // The Right Thing with def-use info.
1055 //
1056 // You cannot bury the 'this' Node inside of a graph reshape.  If the reshaped
1057 // graph uses the 'this' Node it must be the root.  If you want a Node with
1058 // the same Opcode as the 'this' pointer use 'clone'.
1059 //
1060 Node *Node::Ideal(PhaseGVN *phase, bool can_reshape) {
1061   return NULL;                  // Default to being Ideal already
1062 }
1063 
1064 // Some nodes have specific Ideal subgraph transformations only if they are
1065 // unique users of specific nodes. Such nodes should be put on IGVN worklist
1066 // for the transformations to happen.
1067 bool Node::has_special_unique_user() const {
1068   assert(outcnt() == 1, "match only for unique out");
1069   Node* n = unique_out();
1070   int op  = Opcode();
1071   if( this->is_Store() ) {
1072     // Condition for back-to-back stores folding.
1073     return n->Opcode() == op && n->in(MemNode::Memory) == this;
1074   } else if( op == Op_AddL ) {
1075     // Condition for convL2I(addL(x,y)) ==> addI(convL2I(x),convL2I(y))
1076     return n->Opcode() == Op_ConvL2I && n->in(1) == this;
1077   } else if( op == Op_SubI || op == Op_SubL ) {
1078     // Condition for subI(x,subI(y,z)) ==> subI(addI(x,z),y)
1079     return n->Opcode() == op && n->in(2) == this;
1080   }
1081   return false;
1082 };
1083 
1084 //--------------------------find_exact_control---------------------------------
1085 // Skip Proj and CatchProj nodes chains. Check for Null and Top.
1086 Node* Node::find_exact_control(Node* ctrl) {
1087   if (ctrl == NULL && this->is_Region())
1088     ctrl = this->as_Region()->is_copy();
1089 
1090   if (ctrl != NULL && ctrl->is_CatchProj()) {
1091     if (ctrl->as_CatchProj()->_con == CatchProjNode::fall_through_index)
1092       ctrl = ctrl->in(0);
1093     if (ctrl != NULL && !ctrl->is_top())
1094       ctrl = ctrl->in(0);
1095   }
1096 
1097   if (ctrl != NULL && ctrl->is_Proj())
1098     ctrl = ctrl->in(0);
1099 
1100   return ctrl;
1101 }
1102 
1103 //--------------------------dominates------------------------------------------
1104 // Helper function for MemNode::all_controls_dominate().
1105 // Check if 'this' control node dominates or equal to 'sub' control node.
1106 // We already know that if any path back to Root or Start reaches 'this',
1107 // then all paths so, so this is a simple search for one example,
1108 // not an exhaustive search for a counterexample.
1109 bool Node::dominates(Node* sub, Node_List &nlist) {
1110   assert(this->is_CFG(), "expecting control");
1111   assert(sub != NULL && sub->is_CFG(), "expecting control");
1112 
1113   // detect dead cycle without regions
1114   int iterations_without_region_limit = DominatorSearchLimit;
1115 
1116   Node* orig_sub = sub;
1117   Node* dom      = this;
1118   bool  met_dom  = false;
1119   nlist.clear();
1120 
1121   // Walk 'sub' backward up the chain to 'dom', watching for regions.
1122   // After seeing 'dom', continue up to Root or Start.
1123   // If we hit a region (backward split point), it may be a loop head.
1124   // Keep going through one of the region's inputs.  If we reach the
1125   // same region again, go through a different input.  Eventually we
1126   // will either exit through the loop head, or give up.
1127   // (If we get confused, break out and return a conservative 'false'.)
1128   while (sub != NULL) {
1129     if (sub->is_top())  break; // Conservative answer for dead code.
1130     if (sub == dom) {
1131       if (nlist.size() == 0) {
1132         // No Region nodes except loops were visited before and the EntryControl
1133         // path was taken for loops: it did not walk in a cycle.
1134         return true;
1135       } else if (met_dom) {
1136         break;          // already met before: walk in a cycle
1137       } else {
1138         // Region nodes were visited. Continue walk up to Start or Root
1139         // to make sure that it did not walk in a cycle.
1140         met_dom = true; // first time meet
1141         iterations_without_region_limit = DominatorSearchLimit; // Reset
1142      }
1143     }
1144     if (sub->is_Start() || sub->is_Root()) {
1145       // Success if we met 'dom' along a path to Start or Root.
1146       // We assume there are no alternative paths that avoid 'dom'.
1147       // (This assumption is up to the caller to ensure!)
1148       return met_dom;
1149     }
1150     Node* up = sub->in(0);
1151     // Normalize simple pass-through regions and projections:
1152     up = sub->find_exact_control(up);
1153     // If sub == up, we found a self-loop.  Try to push past it.
1154     if (sub == up && sub->is_Loop()) {
1155       // Take loop entry path on the way up to 'dom'.
1156       up = sub->in(1); // in(LoopNode::EntryControl);
1157     } else if (sub == up && sub->is_Region() && sub->req() != 3) {
1158       // Always take in(1) path on the way up to 'dom' for clone regions
1159       // (with only one input) or regions which merge > 2 paths
1160       // (usually used to merge fast/slow paths).
1161       up = sub->in(1);
1162     } else if (sub == up && sub->is_Region()) {
1163       // Try both paths for Regions with 2 input paths (it may be a loop head).
1164       // It could give conservative 'false' answer without information
1165       // which region's input is the entry path.
1166       iterations_without_region_limit = DominatorSearchLimit; // Reset
1167 
1168       bool region_was_visited_before = false;
1169       // Was this Region node visited before?
1170       // If so, we have reached it because we accidentally took a
1171       // loop-back edge from 'sub' back into the body of the loop,
1172       // and worked our way up again to the loop header 'sub'.
1173       // So, take the first unexplored path on the way up to 'dom'.
1174       for (int j = nlist.size() - 1; j >= 0; j--) {
1175         intptr_t ni = (intptr_t)nlist.at(j);
1176         Node* visited = (Node*)(ni & ~1);
1177         bool  visited_twice_already = ((ni & 1) != 0);
1178         if (visited == sub) {
1179           if (visited_twice_already) {
1180             // Visited 2 paths, but still stuck in loop body.  Give up.
1181             return false;
1182           }
1183           // The Region node was visited before only once.
1184           // (We will repush with the low bit set, below.)
1185           nlist.remove(j);
1186           // We will find a new edge and re-insert.
1187           region_was_visited_before = true;
1188           break;
1189         }
1190       }
1191 
1192       // Find an incoming edge which has not been seen yet; walk through it.
1193       assert(up == sub, "");
1194       uint skip = region_was_visited_before ? 1 : 0;
1195       for (uint i = 1; i < sub->req(); i++) {
1196         Node* in = sub->in(i);
1197         if (in != NULL && !in->is_top() && in != sub) {
1198           if (skip == 0) {
1199             up = in;
1200             break;
1201           }
1202           --skip;               // skip this nontrivial input
1203         }
1204       }
1205 
1206       // Set 0 bit to indicate that both paths were taken.
1207       nlist.push((Node*)((intptr_t)sub + (region_was_visited_before ? 1 : 0)));
1208     }
1209 
1210     if (up == sub) {
1211       break;    // some kind of tight cycle
1212     }
1213     if (up == orig_sub && met_dom) {
1214       // returned back after visiting 'dom'
1215       break;    // some kind of cycle
1216     }
1217     if (--iterations_without_region_limit < 0) {
1218       break;    // dead cycle
1219     }
1220     sub = up;
1221   }
1222 
1223   // Did not meet Root or Start node in pred. chain.
1224   // Conservative answer for dead code.
1225   return false;
1226 }
1227 
1228 //------------------------------remove_dead_region-----------------------------
1229 // This control node is dead.  Follow the subgraph below it making everything
1230 // using it dead as well.  This will happen normally via the usual IterGVN
1231 // worklist but this call is more efficient.  Do not update use-def info
1232 // inside the dead region, just at the borders.
1233 static void kill_dead_code( Node *dead, PhaseIterGVN *igvn ) {
1234   // Con's are a popular node to re-hit in the hash table again.
1235   if( dead->is_Con() ) return;
1236 
1237   // Can't put ResourceMark here since igvn->_worklist uses the same arena
1238   // for verify pass with +VerifyOpto and we add/remove elements in it here.
1239   Node_List  nstack(Thread::current()->resource_area());
1240 
1241   Node *top = igvn->C->top();
1242   nstack.push(dead);
1243 
1244   while (nstack.size() > 0) {
1245     dead = nstack.pop();
1246     if (dead->outcnt() > 0) {
1247       // Keep dead node on stack until all uses are processed.
1248       nstack.push(dead);
1249       // For all Users of the Dead...    ;-)
1250       for (DUIterator_Last kmin, k = dead->last_outs(kmin); k >= kmin; ) {
1251         Node* use = dead->last_out(k);
1252         igvn->hash_delete(use);       // Yank from hash table prior to mod
1253         if (use->in(0) == dead) {     // Found another dead node
1254           assert (!use->is_Con(), "Control for Con node should be Root node.");
1255           use->set_req(0, top);       // Cut dead edge to prevent processing
1256           nstack.push(use);           // the dead node again.
1257         } else {                      // Else found a not-dead user
1258           for (uint j = 1; j < use->req(); j++) {
1259             if (use->in(j) == dead) { // Turn all dead inputs into TOP
1260               use->set_req(j, top);
1261             }
1262           }
1263           igvn->_worklist.push(use);
1264         }
1265         // Refresh the iterator, since any number of kills might have happened.
1266         k = dead->last_outs(kmin);
1267       }
1268     } else { // (dead->outcnt() == 0)
1269       // Done with outputs.
1270       igvn->hash_delete(dead);
1271       igvn->_worklist.remove(dead);
1272       igvn->set_type(dead, Type::TOP);
1273       if (dead->is_macro()) {
1274         igvn->C->remove_macro_node(dead);
1275       }
1276       if (dead->is_expensive()) {
1277         igvn->C->remove_expensive_node(dead);
1278       }
1279       igvn->C->record_dead_node(dead->_idx);
1280       // Kill all inputs to the dead guy
1281       for (uint i=0; i < dead->req(); i++) {
1282         Node *n = dead->in(i);      // Get input to dead guy
1283         if (n != NULL && !n->is_top()) { // Input is valid?
1284           dead->set_req(i, top);    // Smash input away
1285           if (n->outcnt() == 0) {   // Input also goes dead?
1286             if (!n->is_Con())
1287               nstack.push(n);       // Clear it out as well
1288           } else if (n->outcnt() == 1 &&
1289                      n->has_special_unique_user()) {
1290             igvn->add_users_to_worklist( n );
1291           } else if (n->outcnt() <= 2 && n->is_Store()) {
1292             // Push store's uses on worklist to enable folding optimization for
1293             // store/store and store/load to the same address.
1294             // The restriction (outcnt() <= 2) is the same as in set_req_X()
1295             // and remove_globally_dead_node().
1296             igvn->add_users_to_worklist( n );
1297           }
1298         }
1299       }
1300     } // (dead->outcnt() == 0)
1301   }   // while (nstack.size() > 0) for outputs
1302   return;
1303 }
1304 
1305 //------------------------------remove_dead_region-----------------------------
1306 bool Node::remove_dead_region(PhaseGVN *phase, bool can_reshape) {
1307   Node *n = in(0);
1308   if( !n ) return false;
1309   // Lost control into this guy?  I.e., it became unreachable?
1310   // Aggressively kill all unreachable code.
1311   if (can_reshape && n->is_top()) {
1312     kill_dead_code(this, phase->is_IterGVN());
1313     return false; // Node is dead.
1314   }
1315 
1316   if( n->is_Region() && n->as_Region()->is_copy() ) {
1317     Node *m = n->nonnull_req();
1318     set_req(0, m);
1319     return true;
1320   }
1321   return false;
1322 }
1323 
1324 //------------------------------Ideal_DU_postCCP-------------------------------
1325 // Idealize graph, using DU info.  Must clone result into new-space
1326 Node *Node::Ideal_DU_postCCP( PhaseCCP * ) {
1327   return NULL;                 // Default to no change
1328 }
1329 
1330 //------------------------------hash-------------------------------------------
1331 // Hash function over Nodes.
1332 uint Node::hash() const {
1333   uint sum = 0;
1334   for( uint i=0; i<_cnt; i++ )  // Add in all inputs
1335     sum = (sum<<1)-(uintptr_t)in(i);        // Ignore embedded NULLs
1336   return (sum>>2) + _cnt + Opcode();
1337 }
1338 
1339 //------------------------------cmp--------------------------------------------
1340 // Compare special parts of simple Nodes
1341 uint Node::cmp( const Node &n ) const {
1342   return 1;                     // Must be same
1343 }
1344 
1345 //------------------------------rematerialize-----------------------------------
1346 // Should we clone rather than spill this instruction?
1347 bool Node::rematerialize() const {
1348   if ( is_Mach() )
1349     return this->as_Mach()->rematerialize();
1350   else
1351     return (_flags & Flag_rematerialize) != 0;
1352 }
1353 
1354 //------------------------------needs_anti_dependence_check---------------------
1355 // Nodes which use memory without consuming it, hence need antidependences.
1356 bool Node::needs_anti_dependence_check() const {
1357   if( req() < 2 || (_flags & Flag_needs_anti_dependence_check) == 0 )
1358     return false;
1359   else
1360     return in(1)->bottom_type()->has_memory();
1361 }
1362 
1363 
1364 // Get an integer constant from a ConNode (or CastIINode).
1365 // Return a default value if there is no apparent constant here.
1366 const TypeInt* Node::find_int_type() const {
1367   if (this->is_Type()) {
1368     return this->as_Type()->type()->isa_int();
1369   } else if (this->is_Con()) {
1370     assert(is_Mach(), "should be ConNode(TypeNode) or else a MachNode");
1371     return this->bottom_type()->isa_int();
1372   }
1373   return NULL;
1374 }
1375 
1376 // Get a pointer constant from a ConstNode.
1377 // Returns the constant if it is a pointer ConstNode
1378 intptr_t Node::get_ptr() const {
1379   assert( Opcode() == Op_ConP, "" );
1380   return ((ConPNode*)this)->type()->is_ptr()->get_con();
1381 }
1382 
1383 // Get a narrow oop constant from a ConNNode.
1384 intptr_t Node::get_narrowcon() const {
1385   assert( Opcode() == Op_ConN, "" );
1386   return ((ConNNode*)this)->type()->is_narrowoop()->get_con();
1387 }
1388 
1389 // Get a long constant from a ConNode.
1390 // Return a default value if there is no apparent constant here.
1391 const TypeLong* Node::find_long_type() const {
1392   if (this->is_Type()) {
1393     return this->as_Type()->type()->isa_long();
1394   } else if (this->is_Con()) {
1395     assert(is_Mach(), "should be ConNode(TypeNode) or else a MachNode");
1396     return this->bottom_type()->isa_long();
1397   }
1398   return NULL;
1399 }
1400 
1401 
1402 /**
1403  * Return a ptr type for nodes which should have it.
1404  */
1405 const TypePtr* Node::get_ptr_type() const {
1406   const TypePtr* tp = this->bottom_type()->make_ptr();
1407 #ifdef ASSERT
1408   if (tp == NULL) {
1409     this->dump(1);
1410     assert((tp != NULL), "unexpected node type");
1411   }
1412 #endif
1413   return tp;
1414 }
1415 
1416 // Get a double constant from a ConstNode.
1417 // Returns the constant if it is a double ConstNode
1418 jdouble Node::getd() const {
1419   assert( Opcode() == Op_ConD, "" );
1420   return ((ConDNode*)this)->type()->is_double_constant()->getd();
1421 }
1422 
1423 // Get a float constant from a ConstNode.
1424 // Returns the constant if it is a float ConstNode
1425 jfloat Node::getf() const {
1426   assert( Opcode() == Op_ConF, "" );
1427   return ((ConFNode*)this)->type()->is_float_constant()->getf();
1428 }
1429 
1430 #ifndef PRODUCT
1431 
1432 //----------------------------NotANode----------------------------------------
1433 // Used in debugging code to avoid walking across dead or uninitialized edges.
1434 static inline bool NotANode(const Node* n) {
1435   if (n == NULL)                   return true;
1436   if (((intptr_t)n & 1) != 0)      return true;  // uninitialized, etc.
1437   if (*(address*)n == badAddress)  return true;  // kill by Node::destruct
1438   return false;
1439 }
1440 
1441 
1442 //------------------------------find------------------------------------------
1443 // Find a neighbor of this Node with the given _idx
1444 // If idx is negative, find its absolute value, following both _in and _out.
1445 static void find_recur(Compile* C,  Node* &result, Node *n, int idx, bool only_ctrl,
1446                         VectorSet* old_space, VectorSet* new_space ) {
1447   int node_idx = (idx >= 0) ? idx : -idx;
1448   if (NotANode(n))  return;  // Gracefully handle NULL, -1, 0xabababab, etc.
1449   // Contained in new_space or old_space?   Check old_arena first since it's mostly empty.
1450   VectorSet *v = C->old_arena()->contains(n) ? old_space : new_space;
1451   if( v->test(n->_idx) ) return;
1452   if( (int)n->_idx == node_idx
1453       debug_only(|| n->debug_idx() == node_idx) ) {
1454     if (result != NULL)
1455       tty->print("find: " INTPTR_FORMAT " and " INTPTR_FORMAT " both have idx==%d\n",
1456                  (uintptr_t)result, (uintptr_t)n, node_idx);
1457     result = n;
1458   }
1459   v->set(n->_idx);
1460   for( uint i=0; i<n->len(); i++ ) {
1461     if( only_ctrl && !(n->is_Region()) && (n->Opcode() != Op_Root) && (i != TypeFunc::Control) ) continue;
1462     find_recur(C, result, n->in(i), idx, only_ctrl, old_space, new_space );
1463   }
1464   // Search along forward edges also:
1465   if (idx < 0 && !only_ctrl) {
1466     for( uint j=0; j<n->outcnt(); j++ ) {
1467       find_recur(C, result, n->raw_out(j), idx, only_ctrl, old_space, new_space );
1468     }
1469   }
1470 #ifdef ASSERT
1471   // Search along debug_orig edges last, checking for cycles
1472   Node* orig = n->debug_orig();
1473   if (orig != NULL) {
1474     do {
1475       if (NotANode(orig))  break;
1476       find_recur(C, result, orig, idx, only_ctrl, old_space, new_space );
1477       orig = orig->debug_orig();
1478     } while (orig != NULL && orig != n->debug_orig());
1479   }
1480 #endif //ASSERT
1481 }
1482 
1483 // call this from debugger:
1484 Node* find_node(Node* n, int idx) {
1485   return n->find(idx);
1486 }
1487 
1488 //------------------------------find-------------------------------------------
1489 Node* Node::find(int idx) const {
1490   ResourceArea *area = Thread::current()->resource_area();
1491   VectorSet old_space(area), new_space(area);
1492   Node* result = NULL;
1493   find_recur(Compile::current(), result, (Node*) this, idx, false, &old_space, &new_space );
1494   return result;
1495 }
1496 
1497 //------------------------------find_ctrl--------------------------------------
1498 // Find an ancestor to this node in the control history with given _idx
1499 Node* Node::find_ctrl(int idx) const {
1500   ResourceArea *area = Thread::current()->resource_area();
1501   VectorSet old_space(area), new_space(area);
1502   Node* result = NULL;
1503   find_recur(Compile::current(), result, (Node*) this, idx, true, &old_space, &new_space );
1504   return result;
1505 }
1506 #endif
1507 
1508 
1509 
1510 #ifndef PRODUCT
1511 int Node::_in_dump_cnt = 0;
1512 
1513 // -----------------------------Name-------------------------------------------
1514 extern const char *NodeClassNames[];
1515 const char *Node::Name() const { return NodeClassNames[Opcode()]; }
1516 
1517 static bool is_disconnected(const Node* n) {
1518   for (uint i = 0; i < n->req(); i++) {
1519     if (n->in(i) != NULL)  return false;
1520   }
1521   return true;
1522 }
1523 
1524 #ifdef ASSERT
1525 static void dump_orig(Node* orig, outputStream *st) {
1526   Compile* C = Compile::current();
1527   if (NotANode(orig)) orig = NULL;
1528   if (orig != NULL && !C->node_arena()->contains(orig)) orig = NULL;
1529   if (orig == NULL) return;
1530   st->print(" !orig=");
1531   Node* fast = orig->debug_orig(); // tortoise & hare algorithm to detect loops
1532   if (NotANode(fast)) fast = NULL;
1533   while (orig != NULL) {
1534     bool discon = is_disconnected(orig);  // if discon, print [123] else 123
1535     if (discon) st->print("[");
1536     if (!Compile::current()->node_arena()->contains(orig))
1537       st->print("o");
1538     st->print("%d", orig->_idx);
1539     if (discon) st->print("]");
1540     orig = orig->debug_orig();
1541     if (NotANode(orig)) orig = NULL;
1542     if (orig != NULL && !C->node_arena()->contains(orig)) orig = NULL;
1543     if (orig != NULL) st->print(",");
1544     if (fast != NULL) {
1545       // Step fast twice for each single step of orig:
1546       fast = fast->debug_orig();
1547       if (NotANode(fast)) fast = NULL;
1548       if (fast != NULL && fast != orig) {
1549         fast = fast->debug_orig();
1550         if (NotANode(fast)) fast = NULL;
1551       }
1552       if (fast == orig) {
1553         st->print("...");
1554         break;
1555       }
1556     }
1557   }
1558 }
1559 
1560 void Node::set_debug_orig(Node* orig) {
1561   _debug_orig = orig;
1562   if (BreakAtNode == 0)  return;
1563   if (NotANode(orig))  orig = NULL;
1564   int trip = 10;
1565   while (orig != NULL) {
1566     if (orig->debug_idx() == BreakAtNode || (int)orig->_idx == BreakAtNode) {
1567       tty->print_cr("BreakAtNode: _idx=%d _debug_idx=%d orig._idx=%d orig._debug_idx=%d",
1568                     this->_idx, this->debug_idx(), orig->_idx, orig->debug_idx());
1569       BREAKPOINT;
1570     }
1571     orig = orig->debug_orig();
1572     if (NotANode(orig))  orig = NULL;
1573     if (trip-- <= 0)  break;
1574   }
1575 }
1576 #endif //ASSERT
1577 
1578 //------------------------------dump------------------------------------------
1579 // Dump a Node
1580 void Node::dump(const char* suffix, outputStream *st) const {
1581   Compile* C = Compile::current();
1582   bool is_new = C->node_arena()->contains(this);
1583   _in_dump_cnt++;
1584   st->print("%c%d\t%s\t=== ", is_new ? ' ' : 'o', _idx, Name());
1585 
1586   // Dump the required and precedence inputs
1587   dump_req(st);
1588   dump_prec(st);
1589   // Dump the outputs
1590   dump_out(st);
1591 
1592   if (is_disconnected(this)) {
1593 #ifdef ASSERT
1594     st->print("  [%d]",debug_idx());
1595     dump_orig(debug_orig(), st);
1596 #endif
1597     st->cr();
1598     _in_dump_cnt--;
1599     return;                     // don't process dead nodes
1600   }
1601 
1602   // Dump node-specific info
1603   dump_spec(st);
1604 #ifdef ASSERT
1605   // Dump the non-reset _debug_idx
1606   if (Verbose && WizardMode) {
1607     st->print("  [%d]",debug_idx());
1608   }
1609 #endif
1610 
1611   const Type *t = bottom_type();
1612 
1613   if (t != NULL && (t->isa_instptr() || t->isa_klassptr())) {
1614     const TypeInstPtr  *toop = t->isa_instptr();
1615     const TypeKlassPtr *tkls = t->isa_klassptr();
1616     ciKlass*           klass = toop ? toop->klass() : (tkls ? tkls->klass() : NULL );
1617     if (klass && klass->is_loaded() && klass->is_interface()) {
1618       st->print("  Interface:");
1619     } else if (toop) {
1620       st->print("  Oop:");
1621     } else if (tkls) {
1622       st->print("  Klass:");
1623     }
1624     t->dump_on(st);
1625   } else if (t == Type::MEMORY) {
1626     st->print("  Memory:");
1627     MemNode::dump_adr_type(this, adr_type(), st);
1628   } else if (Verbose || WizardMode) {
1629     st->print("  Type:");
1630     if (t) {
1631       t->dump_on(st);
1632     } else {
1633       st->print("no type");
1634     }
1635   } else if (t->isa_vect() && this->is_MachSpillCopy()) {
1636     // Dump MachSpillcopy vector type.
1637     t->dump_on(st);
1638   }
1639   if (is_new) {
1640     debug_only(dump_orig(debug_orig(), st));
1641     Node_Notes* nn = C->node_notes_at(_idx);
1642     if (nn != NULL && !nn->is_clear()) {
1643       if (nn->jvms() != NULL) {
1644         st->print(" !jvms:");
1645         nn->jvms()->dump_spec(st);
1646       }
1647     }
1648   }
1649   if (suffix) st->print(suffix);
1650   _in_dump_cnt--;
1651 }
1652 
1653 //------------------------------dump_req--------------------------------------
1654 void Node::dump_req(outputStream *st) const {
1655   // Dump the required input edges
1656   for (uint i = 0; i < req(); i++) {    // For all required inputs
1657     Node* d = in(i);
1658     if (d == NULL) {
1659       st->print("_ ");
1660     } else if (NotANode(d)) {
1661       st->print("NotANode ");  // uninitialized, sentinel, garbage, etc.
1662     } else {
1663       st->print("%c%d ", Compile::current()->node_arena()->contains(d) ? ' ' : 'o', d->_idx);
1664     }
1665   }
1666 }
1667 
1668 
1669 //------------------------------dump_prec-------------------------------------
1670 void Node::dump_prec(outputStream *st) const {
1671   // Dump the precedence edges
1672   int any_prec = 0;
1673   for (uint i = req(); i < len(); i++) {       // For all precedence inputs
1674     Node* p = in(i);
1675     if (p != NULL) {
1676       if (!any_prec++) st->print(" |");
1677       if (NotANode(p)) { st->print("NotANode "); continue; }
1678       st->print("%c%d ", Compile::current()->node_arena()->contains(in(i)) ? ' ' : 'o', in(i)->_idx);
1679     }
1680   }
1681 }
1682 
1683 //------------------------------dump_out--------------------------------------
1684 void Node::dump_out(outputStream *st) const {
1685   // Delimit the output edges
1686   st->print(" [[");
1687   // Dump the output edges
1688   for (uint i = 0; i < _outcnt; i++) {    // For all outputs
1689     Node* u = _out[i];
1690     if (u == NULL) {
1691       st->print("_ ");
1692     } else if (NotANode(u)) {
1693       st->print("NotANode ");
1694     } else {
1695       st->print("%c%d ", Compile::current()->node_arena()->contains(u) ? ' ' : 'o', u->_idx);
1696     }
1697   }
1698   st->print("]] ");
1699 }
1700 
1701 //------------------------------dump_nodes-------------------------------------
1702 static void dump_nodes(const Node* start, int d, bool only_ctrl) {
1703   Node* s = (Node*)start; // remove const
1704   if (NotANode(s)) return;
1705 
1706   uint depth = (uint)ABS(d);
1707   int direction = d;
1708   Compile* C = Compile::current();
1709   GrowableArray <Node *> nstack(C->unique());
1710 
1711   nstack.append(s);
1712   int begin = 0;
1713   int end = 0;
1714   for(uint i = 0; i < depth; i++) {
1715     end = nstack.length();
1716     for(int j = begin; j < end; j++) {
1717       Node* tp  = nstack.at(j);
1718       uint limit = direction > 0 ? tp->len() : tp->outcnt();
1719       for(uint k = 0; k < limit; k++) {
1720         Node* n = direction > 0 ? tp->in(k) : tp->raw_out(k);
1721 
1722         if (NotANode(n))  continue;
1723         // do not recurse through top or the root (would reach unrelated stuff)
1724         if (n->is_Root() || n->is_top())  continue;
1725         if (only_ctrl && !n->is_CFG()) continue;
1726 
1727         bool on_stack = nstack.contains(n);
1728         if (!on_stack) {
1729           nstack.append(n);
1730         }
1731       }
1732     }
1733     begin = end;
1734   }
1735   end = nstack.length();
1736   if (direction > 0) {
1737     for(int j = end-1; j >= 0; j--) {
1738       nstack.at(j)->dump();
1739     }
1740   } else {
1741     for(int j = 0; j < end; j++) {
1742       nstack.at(j)->dump();
1743     }
1744   }
1745 }
1746 
1747 //------------------------------dump-------------------------------------------
1748 void Node::dump(int d) const {
1749   dump_nodes(this, d, false);
1750 }
1751 
1752 //------------------------------dump_ctrl--------------------------------------
1753 // Dump a Node's control history to depth
1754 void Node::dump_ctrl(int d) const {
1755   dump_nodes(this, d, true);
1756 }
1757 
1758 // VERIFICATION CODE
1759 // For each input edge to a node (ie - for each Use-Def edge), verify that
1760 // there is a corresponding Def-Use edge.
1761 //------------------------------verify_edges-----------------------------------
1762 void Node::verify_edges(Unique_Node_List &visited) {
1763   uint i, j, idx;
1764   int  cnt;
1765   Node *n;
1766 
1767   // Recursive termination test
1768   if (visited.member(this))  return;
1769   visited.push(this);
1770 
1771   // Walk over all input edges, checking for correspondence
1772   for( i = 0; i < len(); i++ ) {
1773     n = in(i);
1774     if (n != NULL && !n->is_top()) {
1775       // Count instances of (Node *)this
1776       cnt = 0;
1777       for (idx = 0; idx < n->_outcnt; idx++ ) {
1778         if (n->_out[idx] == (Node *)this)  cnt++;
1779       }
1780       assert( cnt > 0,"Failed to find Def-Use edge." );
1781       // Check for duplicate edges
1782       // walk the input array downcounting the input edges to n
1783       for( j = 0; j < len(); j++ ) {
1784         if( in(j) == n ) cnt--;
1785       }
1786       assert( cnt == 0,"Mismatched edge count.");
1787     } else if (n == NULL) {
1788       assert(i >= req() || i == 0 || is_Region() || is_Phi(), "only regions or phis have null data edges");
1789     } else {
1790       assert(n->is_top(), "sanity");
1791       // Nothing to check.
1792     }
1793   }
1794   // Recursive walk over all input edges
1795   for( i = 0; i < len(); i++ ) {
1796     n = in(i);
1797     if( n != NULL )
1798       in(i)->verify_edges(visited);
1799   }
1800 }
1801 
1802 //------------------------------verify_recur-----------------------------------
1803 static const Node *unique_top = NULL;
1804 
1805 void Node::verify_recur(const Node *n, int verify_depth,
1806                         VectorSet &old_space, VectorSet &new_space) {
1807   if ( verify_depth == 0 )  return;
1808   if (verify_depth > 0)  --verify_depth;
1809 
1810   Compile* C = Compile::current();
1811 
1812   // Contained in new_space or old_space?
1813   VectorSet *v = C->node_arena()->contains(n) ? &new_space : &old_space;
1814   // Check for visited in the proper space.  Numberings are not unique
1815   // across spaces so we need a separate VectorSet for each space.
1816   if( v->test_set(n->_idx) ) return;
1817 
1818   if (n->is_Con() && n->bottom_type() == Type::TOP) {
1819     if (C->cached_top_node() == NULL)
1820       C->set_cached_top_node((Node*)n);
1821     assert(C->cached_top_node() == n, "TOP node must be unique");
1822   }
1823 
1824   for( uint i = 0; i < n->len(); i++ ) {
1825     Node *x = n->in(i);
1826     if (!x || x->is_top()) continue;
1827 
1828     // Verify my input has a def-use edge to me
1829     if (true /*VerifyDefUse*/) {
1830       // Count use-def edges from n to x
1831       int cnt = 0;
1832       for( uint j = 0; j < n->len(); j++ )
1833         if( n->in(j) == x )
1834           cnt++;
1835       // Count def-use edges from x to n
1836       uint max = x->_outcnt;
1837       for( uint k = 0; k < max; k++ )
1838         if (x->_out[k] == n)
1839           cnt--;
1840       assert( cnt == 0, "mismatched def-use edge counts" );
1841     }
1842 
1843     verify_recur(x, verify_depth, old_space, new_space);
1844   }
1845 
1846 }
1847 
1848 //------------------------------verify-----------------------------------------
1849 // Check Def-Use info for my subgraph
1850 void Node::verify() const {
1851   Compile* C = Compile::current();
1852   Node* old_top = C->cached_top_node();
1853   ResourceMark rm;
1854   ResourceArea *area = Thread::current()->resource_area();
1855   VectorSet old_space(area), new_space(area);
1856   verify_recur(this, -1, old_space, new_space);
1857   C->set_cached_top_node(old_top);
1858 }
1859 #endif
1860 
1861 
1862 //------------------------------walk-------------------------------------------
1863 // Graph walk, with both pre-order and post-order functions
1864 void Node::walk(NFunc pre, NFunc post, void *env) {
1865   VectorSet visited(Thread::current()->resource_area()); // Setup for local walk
1866   walk_(pre, post, env, visited);
1867 }
1868 
1869 void Node::walk_(NFunc pre, NFunc post, void *env, VectorSet &visited) {
1870   if( visited.test_set(_idx) ) return;
1871   pre(*this,env);               // Call the pre-order walk function
1872   for( uint i=0; i<_max; i++ )
1873     if( in(i) )                 // Input exists and is not walked?
1874       in(i)->walk_(pre,post,env,visited); // Walk it with pre & post functions
1875   post(*this,env);              // Call the post-order walk function
1876 }
1877 
1878 void Node::nop(Node &, void*) {}
1879 
1880 //------------------------------Registers--------------------------------------
1881 // Do we Match on this edge index or not?  Generally false for Control
1882 // and true for everything else.  Weird for calls & returns.
1883 uint Node::match_edge(uint idx) const {
1884   return idx;                   // True for other than index 0 (control)
1885 }
1886 
1887 static RegMask _not_used_at_all;
1888 // Register classes are defined for specific machines
1889 const RegMask &Node::out_RegMask() const {
1890   ShouldNotCallThis();
1891   return _not_used_at_all;
1892 }
1893 
1894 const RegMask &Node::in_RegMask(uint) const {
1895   ShouldNotCallThis();
1896   return _not_used_at_all;
1897 }
1898 
1899 //=============================================================================
1900 //-----------------------------------------------------------------------------
1901 void Node_Array::reset( Arena *new_arena ) {
1902   _a->Afree(_nodes,_max*sizeof(Node*));
1903   _max   = 0;
1904   _nodes = NULL;
1905   _a     = new_arena;
1906 }
1907 
1908 //------------------------------clear------------------------------------------
1909 // Clear all entries in _nodes to NULL but keep storage
1910 void Node_Array::clear() {
1911   Copy::zero_to_bytes( _nodes, _max*sizeof(Node*) );
1912 }
1913 
1914 //-----------------------------------------------------------------------------
1915 void Node_Array::grow( uint i ) {
1916   if( !_max ) {
1917     _max = 1;
1918     _nodes = (Node**)_a->Amalloc( _max * sizeof(Node*) );
1919     _nodes[0] = NULL;
1920   }
1921   uint old = _max;
1922   while( i >= _max ) _max <<= 1;        // Double to fit
1923   _nodes = (Node**)_a->Arealloc( _nodes, old*sizeof(Node*),_max*sizeof(Node*));
1924   Copy::zero_to_bytes( &_nodes[old], (_max-old)*sizeof(Node*) );
1925 }
1926 
1927 //-----------------------------------------------------------------------------
1928 void Node_Array::insert( uint i, Node *n ) {
1929   if( _nodes[_max-1] ) grow(_max);      // Get more space if full
1930   Copy::conjoint_words_to_higher((HeapWord*)&_nodes[i], (HeapWord*)&_nodes[i+1], ((_max-i-1)*sizeof(Node*)));
1931   _nodes[i] = n;
1932 }
1933 
1934 //-----------------------------------------------------------------------------
1935 void Node_Array::remove( uint i ) {
1936   Copy::conjoint_words_to_lower((HeapWord*)&_nodes[i+1], (HeapWord*)&_nodes[i], ((_max-i-1)*sizeof(Node*)));
1937   _nodes[_max-1] = NULL;
1938 }
1939 
1940 //-----------------------------------------------------------------------------
1941 void Node_Array::sort( C_sort_func_t func) {
1942   qsort( _nodes, _max, sizeof( Node* ), func );
1943 }
1944 
1945 //-----------------------------------------------------------------------------
1946 void Node_Array::dump() const {
1947 #ifndef PRODUCT
1948   for( uint i = 0; i < _max; i++ ) {
1949     Node *nn = _nodes[i];
1950     if( nn != NULL ) {
1951       tty->print("%5d--> ",i); nn->dump();
1952     }
1953   }
1954 #endif
1955 }
1956 
1957 //--------------------------is_iteratively_computed------------------------------
1958 // Operation appears to be iteratively computed (such as an induction variable)
1959 // It is possible for this operation to return false for a loop-varying
1960 // value, if it appears (by local graph inspection) to be computed by a simple conditional.
1961 bool Node::is_iteratively_computed() {
1962   if (ideal_reg()) { // does operation have a result register?
1963     for (uint i = 1; i < req(); i++) {
1964       Node* n = in(i);
1965       if (n != NULL && n->is_Phi()) {
1966         for (uint j = 1; j < n->req(); j++) {
1967           if (n->in(j) == this) {
1968             return true;
1969           }
1970         }
1971       }
1972     }
1973   }
1974   return false;
1975 }
1976 
1977 //--------------------------find_similar------------------------------
1978 // Return a node with opcode "opc" and same inputs as "this" if one can
1979 // be found; Otherwise return NULL;
1980 Node* Node::find_similar(int opc) {
1981   if (req() >= 2) {
1982     Node* def = in(1);
1983     if (def && def->outcnt() >= 2) {
1984       for (DUIterator_Fast dmax, i = def->fast_outs(dmax); i < dmax; i++) {
1985         Node* use = def->fast_out(i);
1986         if (use->Opcode() == opc &&
1987             use->req() == req()) {
1988           uint j;
1989           for (j = 0; j < use->req(); j++) {
1990             if (use->in(j) != in(j)) {
1991               break;
1992             }
1993           }
1994           if (j == use->req()) {
1995             return use;
1996           }
1997         }
1998       }
1999     }
2000   }
2001   return NULL;
2002 }
2003 
2004 
2005 //--------------------------unique_ctrl_out------------------------------
2006 // Return the unique control out if only one. Null if none or more than one.
2007 Node* Node::unique_ctrl_out() {
2008   Node* found = NULL;
2009   for (uint i = 0; i < outcnt(); i++) {
2010     Node* use = raw_out(i);
2011     if (use->is_CFG() && use != this) {
2012       if (found != NULL) return NULL;
2013       found = use;
2014     }
2015   }
2016   return found;
2017 }
2018 
2019 //=============================================================================
2020 //------------------------------yank-------------------------------------------
2021 // Find and remove
2022 void Node_List::yank( Node *n ) {
2023   uint i;
2024   for( i = 0; i < _cnt; i++ )
2025     if( _nodes[i] == n )
2026       break;
2027 
2028   if( i < _cnt )
2029     _nodes[i] = _nodes[--_cnt];
2030 }
2031 
2032 //------------------------------dump-------------------------------------------
2033 void Node_List::dump() const {
2034 #ifndef PRODUCT
2035   for( uint i = 0; i < _cnt; i++ )
2036     if( _nodes[i] ) {
2037       tty->print("%5d--> ",i);
2038       _nodes[i]->dump();
2039     }
2040 #endif
2041 }
2042 
2043 //=============================================================================
2044 //------------------------------remove-----------------------------------------
2045 void Unique_Node_List::remove( Node *n ) {
2046   if( _in_worklist[n->_idx] ) {
2047     for( uint i = 0; i < size(); i++ )
2048       if( _nodes[i] == n ) {
2049         map(i,Node_List::pop());
2050         _in_worklist >>= n->_idx;
2051         return;
2052       }
2053     ShouldNotReachHere();
2054   }
2055 }
2056 
2057 //-----------------------remove_useless_nodes----------------------------------
2058 // Remove useless nodes from worklist
2059 void Unique_Node_List::remove_useless_nodes(VectorSet &useful) {
2060 
2061   for( uint i = 0; i < size(); ++i ) {
2062     Node *n = at(i);
2063     assert( n != NULL, "Did not expect null entries in worklist");
2064     if( ! useful.test(n->_idx) ) {
2065       _in_worklist >>= n->_idx;
2066       map(i,Node_List::pop());
2067       // Node *replacement = Node_List::pop();
2068       // if( i != size() ) { // Check if removing last entry
2069       //   _nodes[i] = replacement;
2070       // }
2071       --i;  // Visit popped node
2072       // If it was last entry, loop terminates since size() was also reduced
2073     }
2074   }
2075 }
2076 
2077 //=============================================================================
2078 void Node_Stack::grow() {
2079   size_t old_top = pointer_delta(_inode_top,_inodes,sizeof(INode)); // save _top
2080   size_t old_max = pointer_delta(_inode_max,_inodes,sizeof(INode));
2081   size_t max = old_max << 1;             // max * 2
2082   _inodes = REALLOC_ARENA_ARRAY(_a, INode, _inodes, old_max, max);
2083   _inode_max = _inodes + max;
2084   _inode_top = _inodes + old_top;        // restore _top
2085 }
2086 
2087 // Node_Stack is used to map nodes.
2088 Node* Node_Stack::find(uint idx) const {
2089   uint sz = size();
2090   for (uint i=0; i < sz; i++) {
2091     if (idx == index_at(i) )
2092       return node_at(i);
2093   }
2094   return NULL;
2095 }
2096 
2097 //=============================================================================
2098 uint TypeNode::size_of() const { return sizeof(*this); }
2099 #ifndef PRODUCT
2100 void TypeNode::dump_spec(outputStream *st) const {
2101   if( !Verbose && !WizardMode ) {
2102     // standard dump does this in Verbose and WizardMode
2103     st->print(" #"); _type->dump_on(st);
2104   }
2105 }
2106 #endif
2107 uint TypeNode::hash() const {
2108   return Node::hash() + _type->hash();
2109 }
2110 uint TypeNode::cmp( const Node &n ) const
2111 { return !Type::cmp( _type, ((TypeNode&)n)._type ); }
2112 const Type *TypeNode::bottom_type() const { return _type; }
2113 const Type *TypeNode::Value( PhaseTransform * ) const { return _type; }
2114 
2115 //------------------------------ideal_reg--------------------------------------
2116 uint TypeNode::ideal_reg() const {
2117   return _type->ideal_reg();
2118 }