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 "libadt/vectset.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "opto/cfgnode.hpp"
  29 #include "opto/connode.hpp"
  30 #include "opto/loopnode.hpp"
  31 #include "opto/machnode.hpp"
  32 #include "opto/matcher.hpp"
  33 #include "opto/node.hpp"
  34 #include "opto/opcodes.hpp"
  35 #include "opto/regmask.hpp"
  36 #include "opto/type.hpp"
  37 #include "utilities/copy.hpp"
  38 
  39 class RegMask;
  40 // #include "phase.hpp"
  41 class PhaseTransform;
  42 class PhaseGVN;
  43 
  44 // Arena we are currently building Nodes in
  45 const uint Node::NotAMachineReg = 0xffff0000;
  46 
  47 #ifndef PRODUCT
  48 extern int nodes_created;
  49 #endif
  50 
  51 #ifdef ASSERT
  52 
  53 //-------------------------- construct_node------------------------------------
  54 // Set a breakpoint here to identify where a particular node index is built.
  55 void Node::verify_construction() {
  56   _debug_orig = NULL;
  57   int old_debug_idx = Compile::debug_idx();
  58   int new_debug_idx = old_debug_idx+1;
  59   if (new_debug_idx > 0) {
  60     // Arrange that the lowest five decimal digits of _debug_idx
  61     // will repeat those of _idx. In case this is somehow pathological,
  62     // we continue to assign negative numbers (!) consecutively.
  63     const int mod = 100000;
  64     int bump = (int)(_idx - new_debug_idx) % mod;
  65     if (bump < 0)  bump += mod;
  66     assert(bump >= 0 && bump < mod, "");
  67     new_debug_idx += bump;
  68   }
  69   Compile::set_debug_idx(new_debug_idx);
  70   set_debug_idx( new_debug_idx );
  71   assert(Compile::current()->unique() < (UINT_MAX - 1), "Node limit exceeded UINT_MAX");
  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 *compile = Compile::current();
 476   uint s = size_of();           // Size of inherited Node
 477   Node *n = (Node*)compile->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     compile->add_macro_node(n);
 497   if (is_expensive())
 498     compile->add_expensive_node(n);
 499 
 500   n->set_idx(compile->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   compile->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(compile);
 523     }
 524   }
 525   // cloning CallNode may need to clone JVMState
 526   if (n->is_Call()) {
 527     CallNode *call = n->as_Call();
 528     call->clone_jvms();
 529   }
 530   return n;                     // Return the clone
 531 }
 532 
 533 //---------------------------setup_is_top--------------------------------------
 534 // Call this when changing the top node, to reassert the invariants
 535 // required by Node::is_top.  See Compile::set_cached_top_node.
 536 void Node::setup_is_top() {
 537   if (this == (Node*)Compile::current()->top()) {
 538     // This node has just become top.  Kill its out array.
 539     _outcnt = _outmax = 0;
 540     _out = NULL;                           // marker value for top
 541     assert(is_top(), "must be top");
 542   } else {
 543     if (_out == NULL)  _out = NO_OUT_ARRAY;
 544     assert(!is_top(), "must not be top");
 545   }
 546 }
 547 
 548 
 549 //------------------------------~Node------------------------------------------
 550 // Fancy destructor; eagerly attempt to reclaim Node numberings and storage
 551 extern int reclaim_idx ;
 552 extern int reclaim_in  ;
 553 extern int reclaim_node;
 554 void Node::destruct() {
 555   // Eagerly reclaim unique Node numberings
 556   Compile* compile = Compile::current();
 557   if ((uint)_idx+1 == compile->unique()) {
 558     compile->set_unique(compile->unique()-1);
 559 #ifdef ASSERT
 560     reclaim_idx++;
 561 #endif
 562   }
 563   // Clear debug info:
 564   Node_Notes* nn = compile->node_notes_at(_idx);
 565   if (nn != NULL)  nn->clear();
 566   // Walk the input array, freeing the corresponding output edges
 567   _cnt = _max;  // forget req/prec distinction
 568   uint i;
 569   for( i = 0; i < _max; i++ ) {
 570     set_req(i, NULL);
 571     //assert(def->out(def->outcnt()-1) == (Node *)this,"bad def-use hacking in reclaim");
 572   }
 573   assert(outcnt() == 0, "deleting a node must not leave a dangling use");
 574   // See if the input array was allocated just prior to the object
 575   int edge_size = _max*sizeof(void*);
 576   int out_edge_size = _outmax*sizeof(void*);
 577   char *edge_end = ((char*)_in) + edge_size;
 578   char *out_array = (char*)(_out == NO_OUT_ARRAY? NULL: _out);
 579   char *out_edge_end = out_array + out_edge_size;
 580   int node_size = size_of();
 581 
 582   // Free the output edge array
 583   if (out_edge_size > 0) {
 584 #ifdef ASSERT
 585     if( out_edge_end == compile->node_arena()->hwm() )
 586       reclaim_in  += out_edge_size;  // count reclaimed out edges with in edges
 587 #endif
 588     compile->node_arena()->Afree(out_array, out_edge_size);
 589   }
 590 
 591   // Free the input edge array and the node itself
 592   if( edge_end == (char*)this ) {
 593 #ifdef ASSERT
 594     if( edge_end+node_size == compile->node_arena()->hwm() ) {
 595       reclaim_in  += edge_size;
 596       reclaim_node+= node_size;
 597     }
 598 #else
 599     // It was; free the input array and object all in one hit
 600     compile->node_arena()->Afree(_in,edge_size+node_size);
 601 #endif
 602   } else {
 603 
 604     // Free just the input array
 605 #ifdef ASSERT
 606     if( edge_end == compile->node_arena()->hwm() )
 607       reclaim_in  += edge_size;
 608 #endif
 609     compile->node_arena()->Afree(_in,edge_size);
 610 
 611     // Free just the object
 612 #ifdef ASSERT
 613     if( ((char*)this) + node_size == compile->node_arena()->hwm() )
 614       reclaim_node+= node_size;
 615 #else
 616     compile->node_arena()->Afree(this,node_size);
 617 #endif
 618   }
 619   if (is_macro()) {
 620     compile->remove_macro_node(this);
 621   }
 622   if (is_expensive()) {
 623     compile->remove_expensive_node(this);
 624   }
 625 #ifdef ASSERT
 626   // We will not actually delete the storage, but we'll make the node unusable.
 627   *(address*)this = badAddress;  // smash the C++ vtbl, probably
 628   _in = _out = (Node**) badAddress;
 629   _max = _cnt = _outmax = _outcnt = 0;
 630 #endif
 631 }
 632 
 633 //------------------------------grow-------------------------------------------
 634 // Grow the input array, making space for more edges
 635 void Node::grow( uint len ) {
 636   Arena* arena = Compile::current()->node_arena();
 637   uint new_max = _max;
 638   if( new_max == 0 ) {
 639     _max = 4;
 640     _in = (Node**)arena->Amalloc(4*sizeof(Node*));
 641     Node** to = _in;
 642     to[0] = NULL;
 643     to[1] = NULL;
 644     to[2] = NULL;
 645     to[3] = NULL;
 646     return;
 647   }
 648   while( new_max <= len ) new_max <<= 1; // Find next power-of-2
 649   // Trimming to limit allows a uint8 to handle up to 255 edges.
 650   // Previously I was using only powers-of-2 which peaked at 128 edges.
 651   //if( new_max >= limit ) new_max = limit-1;
 652   _in = (Node**)arena->Arealloc(_in, _max*sizeof(Node*), new_max*sizeof(Node*));
 653   Copy::zero_to_bytes(&_in[_max], (new_max-_max)*sizeof(Node*)); // NULL all new space
 654   _max = new_max;               // Record new max length
 655   // This assertion makes sure that Node::_max is wide enough to
 656   // represent the numerical value of new_max.
 657   assert(_max == new_max && _max > len, "int width of _max is too small");
 658 }
 659 
 660 //-----------------------------out_grow----------------------------------------
 661 // Grow the input array, making space for more edges
 662 void Node::out_grow( uint len ) {
 663   assert(!is_top(), "cannot grow a top node's out array");
 664   Arena* arena = Compile::current()->node_arena();
 665   uint new_max = _outmax;
 666   if( new_max == 0 ) {
 667     _outmax = 4;
 668     _out = (Node **)arena->Amalloc(4*sizeof(Node*));
 669     return;
 670   }
 671   while( new_max <= len ) new_max <<= 1; // Find next power-of-2
 672   // Trimming to limit allows a uint8 to handle up to 255 edges.
 673   // Previously I was using only powers-of-2 which peaked at 128 edges.
 674   //if( new_max >= limit ) new_max = limit-1;
 675   assert(_out != NULL && _out != NO_OUT_ARRAY, "out must have sensible value");
 676   _out = (Node**)arena->Arealloc(_out,_outmax*sizeof(Node*),new_max*sizeof(Node*));
 677   //Copy::zero_to_bytes(&_out[_outmax], (new_max-_outmax)*sizeof(Node*)); // NULL all new space
 678   _outmax = new_max;               // Record new max length
 679   // This assertion makes sure that Node::_max is wide enough to
 680   // represent the numerical value of new_max.
 681   assert(_outmax == new_max && _outmax > len, "int width of _outmax is too small");
 682 }
 683 
 684 #ifdef ASSERT
 685 //------------------------------is_dead----------------------------------------
 686 bool Node::is_dead() const {
 687   // Mach and pinch point nodes may look like dead.
 688   if( is_top() || is_Mach() || (Opcode() == Op_Node && _outcnt > 0) )
 689     return false;
 690   for( uint i = 0; i < _max; i++ )
 691     if( _in[i] != NULL )
 692       return false;
 693   dump();
 694   return true;
 695 }
 696 #endif
 697 
 698 
 699 //------------------------------is_unreachable---------------------------------
 700 bool Node::is_unreachable(PhaseIterGVN &igvn) const {
 701   assert(!is_Mach(), "doesn't work with MachNodes");
 702   return outcnt() == 0 || igvn.type(this) == Type::TOP || in(0)->is_top();
 703 }
 704 
 705 //------------------------------add_req----------------------------------------
 706 // Add a new required input at the end
 707 void Node::add_req( Node *n ) {
 708   assert( is_not_dead(n), "can not use dead node");
 709 
 710   // Look to see if I can move precedence down one without reallocating
 711   if( (_cnt >= _max) || (in(_max-1) != NULL) )
 712     grow( _max+1 );
 713 
 714   // Find a precedence edge to move
 715   if( in(_cnt) != NULL ) {       // Next precedence edge is busy?
 716     uint i;
 717     for( i=_cnt; i<_max; i++ )
 718       if( in(i) == NULL )       // Find the NULL at end of prec edge list
 719         break;                  // There must be one, since we grew the array
 720     _in[i] = in(_cnt);          // Move prec over, making space for req edge
 721   }
 722   _in[_cnt++] = n;            // Stuff over old prec edge
 723   if (n != NULL) n->add_out((Node *)this);
 724 }
 725 
 726 //---------------------------add_req_batch-------------------------------------
 727 // Add a new required input at the end
 728 void Node::add_req_batch( Node *n, uint m ) {
 729   assert( is_not_dead(n), "can not use dead node");
 730   // check various edge cases
 731   if ((int)m <= 1) {
 732     assert((int)m >= 0, "oob");
 733     if (m != 0)  add_req(n);
 734     return;
 735   }
 736 
 737   // Look to see if I can move precedence down one without reallocating
 738   if( (_cnt+m) > _max || _in[_max-m] )
 739     grow( _max+m );
 740 
 741   // Find a precedence edge to move
 742   if( _in[_cnt] != NULL ) {     // Next precedence edge is busy?
 743     uint i;
 744     for( i=_cnt; i<_max; i++ )
 745       if( _in[i] == NULL )      // Find the NULL at end of prec edge list
 746         break;                  // There must be one, since we grew the array
 747     // Slide all the precs over by m positions (assume #prec << m).
 748     Copy::conjoint_words_to_higher((HeapWord*)&_in[_cnt], (HeapWord*)&_in[_cnt+m], ((i-_cnt)*sizeof(Node*)));
 749   }
 750 
 751   // Stuff over the old prec edges
 752   for(uint i=0; i<m; i++ ) {
 753     _in[_cnt++] = n;
 754   }
 755 
 756   // Insert multiple out edges on the node.
 757   if (n != NULL && !n->is_top()) {
 758     for(uint i=0; i<m; i++ ) {
 759       n->add_out((Node *)this);
 760     }
 761   }
 762 }
 763 
 764 //------------------------------del_req----------------------------------------
 765 // Delete the required edge and compact the edge array
 766 void Node::del_req( uint idx ) {
 767   assert( idx < _cnt, "oob");
 768   assert( !VerifyHashTableKeys || _hash_lock == 0,
 769           "remove node from hash table before modifying it");
 770   // First remove corresponding def-use edge
 771   Node *n = in(idx);
 772   if (n != NULL) n->del_out((Node *)this);
 773   _in[idx] = in(--_cnt);  // Compact the array
 774   _in[_cnt] = NULL;       // NULL out emptied slot
 775 }
 776 
 777 //------------------------------ins_req----------------------------------------
 778 // Insert a new required input at the end
 779 void Node::ins_req( uint idx, Node *n ) {
 780   assert( is_not_dead(n), "can not use dead node");
 781   add_req(NULL);                // Make space
 782   assert( idx < _max, "Must have allocated enough space");
 783   // Slide over
 784   if(_cnt-idx-1 > 0) {
 785     Copy::conjoint_words_to_higher((HeapWord*)&_in[idx], (HeapWord*)&_in[idx+1], ((_cnt-idx-1)*sizeof(Node*)));
 786   }
 787   _in[idx] = n;                            // Stuff over old required edge
 788   if (n != NULL) n->add_out((Node *)this); // Add reciprocal def-use edge
 789 }
 790 
 791 //-----------------------------find_edge---------------------------------------
 792 int Node::find_edge(Node* n) {
 793   for (uint i = 0; i < len(); i++) {
 794     if (_in[i] == n)  return i;
 795   }
 796   return -1;
 797 }
 798 
 799 //----------------------------replace_edge-------------------------------------
 800 int Node::replace_edge(Node* old, Node* neww) {
 801   if (old == neww)  return 0;  // nothing to do
 802   uint nrep = 0;
 803   for (uint i = 0; i < len(); i++) {
 804     if (in(i) == old) {
 805       if (i < req())
 806         set_req(i, neww);
 807       else
 808         set_prec(i, neww);
 809       nrep++;
 810     }
 811   }
 812   return nrep;
 813 }
 814 
 815 //-------------------------disconnect_inputs-----------------------------------
 816 // NULL out all inputs to eliminate incoming Def-Use edges.
 817 // Return the number of edges between 'n' and 'this'
 818 int Node::disconnect_inputs(Node *n, Compile* C) {
 819   int edges_to_n = 0;
 820 
 821   uint cnt = req();
 822   for( uint i = 0; i < cnt; ++i ) {
 823     if( in(i) == 0 ) continue;
 824     if( in(i) == n ) ++edges_to_n;
 825     set_req(i, NULL);
 826   }
 827   // Remove precedence edges if any exist
 828   // Note: Safepoints may have precedence edges, even during parsing
 829   if( (req() != len()) && (in(req()) != NULL) ) {
 830     uint max = len();
 831     for( uint i = 0; i < max; ++i ) {
 832       if( in(i) == 0 ) continue;
 833       if( in(i) == n ) ++edges_to_n;
 834       set_prec(i, NULL);
 835     }
 836   }
 837 
 838   // Node::destruct requires all out edges be deleted first
 839   // debug_only(destruct();)   // no reuse benefit expected
 840   if (edges_to_n == 0) {
 841     C->record_dead_node(_idx);
 842   }
 843   return edges_to_n;
 844 }
 845 
 846 //-----------------------------uncast---------------------------------------
 847 // %%% Temporary, until we sort out CheckCastPP vs. CastPP.
 848 // Strip away casting.  (It is depth-limited.)
 849 Node* Node::uncast() const {
 850   // Should be inline:
 851   //return is_ConstraintCast() ? uncast_helper(this) : (Node*) this;
 852   if (is_ConstraintCast() || is_CheckCastPP())
 853     return uncast_helper(this);
 854   else
 855     return (Node*) this;
 856 }
 857 
 858 //---------------------------uncast_helper-------------------------------------
 859 Node* Node::uncast_helper(const Node* p) {
 860 #ifdef ASSERT
 861   uint depth_count = 0;
 862   const Node* orig_p = p;
 863 #endif
 864 
 865   while (true) {
 866 #ifdef ASSERT
 867     if (depth_count >= K) {
 868       orig_p->dump(4);
 869       if (p != orig_p)
 870         p->dump(1);
 871     }
 872     assert(depth_count++ < K, "infinite loop in Node::uncast_helper");
 873 #endif
 874     if (p == NULL || p->req() != 2) {
 875       break;
 876     } else if (p->is_ConstraintCast()) {
 877       p = p->in(1);
 878     } else if (p->is_CheckCastPP()) {
 879       p = p->in(1);
 880     } else {
 881       break;
 882     }
 883   }
 884   return (Node*) p;
 885 }
 886 
 887 //------------------------------add_prec---------------------------------------
 888 // Add a new precedence input.  Precedence inputs are unordered, with
 889 // duplicates removed and NULLs packed down at the end.
 890 void Node::add_prec( Node *n ) {
 891   assert( is_not_dead(n), "can not use dead node");
 892 
 893   // Check for NULL at end
 894   if( _cnt >= _max || in(_max-1) )
 895     grow( _max+1 );
 896 
 897   // Find a precedence edge to move
 898   uint i = _cnt;
 899   while( in(i) != NULL ) i++;
 900   _in[i] = n;                                // Stuff prec edge over NULL
 901   if ( n != NULL) n->add_out((Node *)this);  // Add mirror edge
 902 }
 903 
 904 //------------------------------rm_prec----------------------------------------
 905 // Remove a precedence input.  Precedence inputs are unordered, with
 906 // duplicates removed and NULLs packed down at the end.
 907 void Node::rm_prec( uint j ) {
 908 
 909   // Find end of precedence list to pack NULLs
 910   uint i;
 911   for( i=j; i<_max; i++ )
 912     if( !_in[i] )               // Find the NULL at end of prec edge list
 913       break;
 914   if (_in[j] != NULL) _in[j]->del_out((Node *)this);
 915   _in[j] = _in[--i];            // Move last element over removed guy
 916   _in[i] = NULL;                // NULL out last element
 917 }
 918 
 919 //------------------------------size_of----------------------------------------
 920 uint Node::size_of() const { return sizeof(*this); }
 921 
 922 //------------------------------ideal_reg--------------------------------------
 923 uint Node::ideal_reg() const { return 0; }
 924 
 925 //------------------------------jvms-------------------------------------------
 926 JVMState* Node::jvms() const { return NULL; }
 927 
 928 #ifdef ASSERT
 929 //------------------------------jvms-------------------------------------------
 930 bool Node::verify_jvms(const JVMState* using_jvms) const {
 931   for (JVMState* jvms = this->jvms(); jvms != NULL; jvms = jvms->caller()) {
 932     if (jvms == using_jvms)  return true;
 933   }
 934   return false;
 935 }
 936 
 937 //------------------------------init_NodeProperty------------------------------
 938 void Node::init_NodeProperty() {
 939   assert(_max_classes <= max_jushort, "too many NodeProperty classes");
 940   assert(_max_flags <= max_jushort, "too many NodeProperty flags");
 941 }
 942 #endif
 943 
 944 //------------------------------format-----------------------------------------
 945 // Print as assembly
 946 void Node::format( PhaseRegAlloc *, outputStream *st ) const {}
 947 //------------------------------emit-------------------------------------------
 948 // Emit bytes starting at parameter 'ptr'.
 949 void Node::emit(CodeBuffer &cbuf, PhaseRegAlloc *ra_) const {}
 950 //------------------------------lateExpand-------------------------------------
 951 // Expand node after register allocation.
 952 void Node::lateExpand(GrowableArray <Node *> *nodes, PhaseRegAlloc *ra_) {}
 953 //------------------------------size-------------------------------------------
 954 // Size of instruction in bytes
 955 uint Node::size(PhaseRegAlloc *ra_) const { return 0; }
 956 
 957 //------------------------------CFG Construction-------------------------------
 958 // Nodes that end basic blocks, e.g. IfTrue/IfFalse, JumpProjNode, Root,
 959 // Goto and Return.
 960 const Node *Node::is_block_proj() const { return 0; }
 961 
 962 // Minimum guaranteed type
 963 const Type *Node::bottom_type() const { return Type::BOTTOM; }
 964 
 965 
 966 //------------------------------raise_bottom_type------------------------------
 967 // Get the worst-case Type output for this Node.
 968 void Node::raise_bottom_type(const Type* new_type) {
 969   if (is_Type()) {
 970     TypeNode *n = this->as_Type();
 971     if (VerifyAliases) {
 972       assert(new_type->higher_equal(n->type()), "new type must refine old type");
 973     }
 974     n->set_type(new_type);
 975   } else if (is_Load()) {
 976     LoadNode *n = this->as_Load();
 977     if (VerifyAliases) {
 978       assert(new_type->higher_equal(n->type()), "new type must refine old type");
 979     }
 980     n->set_type(new_type);
 981   }
 982 }
 983 
 984 //------------------------------Identity---------------------------------------
 985 // Return a node that the given node is equivalent to.
 986 Node *Node::Identity( PhaseTransform * ) {
 987   return this;                  // Default to no identities
 988 }
 989 
 990 //------------------------------Value------------------------------------------
 991 // Compute a new Type for a node using the Type of the inputs.
 992 const Type *Node::Value( PhaseTransform * ) const {
 993   return bottom_type();         // Default to worst-case Type
 994 }
 995 
 996 //------------------------------Ideal------------------------------------------
 997 //
 998 // 'Idealize' the graph rooted at this Node.
 999 //
1000 // In order to be efficient and flexible there are some subtle invariants
1001 // these Ideal calls need to hold.  Running with '+VerifyIterativeGVN' checks
1002 // these invariants, although its too slow to have on by default.  If you are
1003 // hacking an Ideal call, be sure to test with +VerifyIterativeGVN!
1004 //
1005 // The Ideal call almost arbitrarily reshape the graph rooted at the 'this'
1006 // pointer.  If ANY change is made, it must return the root of the reshaped
1007 // graph - even if the root is the same Node.  Example: swapping the inputs
1008 // to an AddINode gives the same answer and same root, but you still have to
1009 // return the 'this' pointer instead of NULL.
1010 //
1011 // You cannot return an OLD Node, except for the 'this' pointer.  Use the
1012 // Identity call to return an old Node; basically if Identity can find
1013 // another Node have the Ideal call make no change and return NULL.
1014 // Example: AddINode::Ideal must check for add of zero; in this case it
1015 // returns NULL instead of doing any graph reshaping.
1016 //
1017 // You cannot modify any old Nodes except for the 'this' pointer.  Due to
1018 // sharing there may be other users of the old Nodes relying on their current
1019 // semantics.  Modifying them will break the other users.
1020 // Example: when reshape "(X+3)+4" into "X+7" you must leave the Node for
1021 // "X+3" unchanged in case it is shared.
1022 //
1023 // If you modify the 'this' pointer's inputs, you should use
1024 // 'set_req'.  If you are making a new Node (either as the new root or
1025 // some new internal piece) you may use 'init_req' to set the initial
1026 // value.  You can make a new Node with either 'new' or 'clone'.  In
1027 // either case, def-use info is correctly maintained.
1028 //
1029 // Example: reshape "(X+3)+4" into "X+7":
1030 //    set_req(1, in(1)->in(1));
1031 //    set_req(2, phase->intcon(7));
1032 //    return this;
1033 // Example: reshape "X*4" into "X<<2"
1034 //    return new (C) LShiftINode(in(1), phase->intcon(2));
1035 //
1036 // You must call 'phase->transform(X)' on any new Nodes X you make, except
1037 // for the returned root node.  Example: reshape "X*31" with "(X<<5)-X".
1038 //    Node *shift=phase->transform(new(C)LShiftINode(in(1),phase->intcon(5)));
1039 //    return new (C) AddINode(shift, in(1));
1040 //
1041 // When making a Node for a constant use 'phase->makecon' or 'phase->intcon'.
1042 // These forms are faster than 'phase->transform(new (C) ConNode())' and Do
1043 // The Right Thing with def-use info.
1044 //
1045 // You cannot bury the 'this' Node inside of a graph reshape.  If the reshaped
1046 // graph uses the 'this' Node it must be the root.  If you want a Node with
1047 // the same Opcode as the 'this' pointer use 'clone'.
1048 //
1049 Node *Node::Ideal(PhaseGVN *phase, bool can_reshape) {
1050   return NULL;                  // Default to being Ideal already
1051 }
1052 
1053 // Some nodes have specific Ideal subgraph transformations only if they are
1054 // unique users of specific nodes. Such nodes should be put on IGVN worklist
1055 // for the transformations to happen.
1056 bool Node::has_special_unique_user() const {
1057   assert(outcnt() == 1, "match only for unique out");
1058   Node* n = unique_out();
1059   int op  = Opcode();
1060   if( this->is_Store() ) {
1061     // Condition for back-to-back stores folding.
1062     return n->Opcode() == op && n->in(MemNode::Memory) == this;
1063   } else if( op == Op_AddL ) {
1064     // Condition for convL2I(addL(x,y)) ==> addI(convL2I(x),convL2I(y))
1065     return n->Opcode() == Op_ConvL2I && n->in(1) == this;
1066   } else if( op == Op_SubI || op == Op_SubL ) {
1067     // Condition for subI(x,subI(y,z)) ==> subI(addI(x,z),y)
1068     return n->Opcode() == op && n->in(2) == this;
1069   }
1070   return false;
1071 };
1072 
1073 //--------------------------find_exact_control---------------------------------
1074 // Skip Proj and CatchProj nodes chains. Check for Null and Top.
1075 Node* Node::find_exact_control(Node* ctrl) {
1076   if (ctrl == NULL && this->is_Region())
1077     ctrl = this->as_Region()->is_copy();
1078 
1079   if (ctrl != NULL && ctrl->is_CatchProj()) {
1080     if (ctrl->as_CatchProj()->_con == CatchProjNode::fall_through_index)
1081       ctrl = ctrl->in(0);
1082     if (ctrl != NULL && !ctrl->is_top())
1083       ctrl = ctrl->in(0);
1084   }
1085 
1086   if (ctrl != NULL && ctrl->is_Proj())
1087     ctrl = ctrl->in(0);
1088 
1089   return ctrl;
1090 }
1091 
1092 //--------------------------dominates------------------------------------------
1093 // Helper function for MemNode::all_controls_dominate().
1094 // Check if 'this' control node dominates or equal to 'sub' control node.
1095 // We already know that if any path back to Root or Start reaches 'this',
1096 // then all paths so, so this is a simple search for one example,
1097 // not an exhaustive search for a counterexample.
1098 bool Node::dominates(Node* sub, Node_List &nlist) {
1099   assert(this->is_CFG(), "expecting control");
1100   assert(sub != NULL && sub->is_CFG(), "expecting control");
1101 
1102   // detect dead cycle without regions
1103   int iterations_without_region_limit = DominatorSearchLimit;
1104 
1105   Node* orig_sub = sub;
1106   Node* dom      = this;
1107   bool  met_dom  = false;
1108   nlist.clear();
1109 
1110   // Walk 'sub' backward up the chain to 'dom', watching for regions.
1111   // After seeing 'dom', continue up to Root or Start.
1112   // If we hit a region (backward split point), it may be a loop head.
1113   // Keep going through one of the region's inputs.  If we reach the
1114   // same region again, go through a different input.  Eventually we
1115   // will either exit through the loop head, or give up.
1116   // (If we get confused, break out and return a conservative 'false'.)
1117   while (sub != NULL) {
1118     if (sub->is_top())  break; // Conservative answer for dead code.
1119     if (sub == dom) {
1120       if (nlist.size() == 0) {
1121         // No Region nodes except loops were visited before and the EntryControl
1122         // path was taken for loops: it did not walk in a cycle.
1123         return true;
1124       } else if (met_dom) {
1125         break;          // already met before: walk in a cycle
1126       } else {
1127         // Region nodes were visited. Continue walk up to Start or Root
1128         // to make sure that it did not walk in a cycle.
1129         met_dom = true; // first time meet
1130         iterations_without_region_limit = DominatorSearchLimit; // Reset
1131      }
1132     }
1133     if (sub->is_Start() || sub->is_Root()) {
1134       // Success if we met 'dom' along a path to Start or Root.
1135       // We assume there are no alternative paths that avoid 'dom'.
1136       // (This assumption is up to the caller to ensure!)
1137       return met_dom;
1138     }
1139     Node* up = sub->in(0);
1140     // Normalize simple pass-through regions and projections:
1141     up = sub->find_exact_control(up);
1142     // If sub == up, we found a self-loop.  Try to push past it.
1143     if (sub == up && sub->is_Loop()) {
1144       // Take loop entry path on the way up to 'dom'.
1145       up = sub->in(1); // in(LoopNode::EntryControl);
1146     } else if (sub == up && sub->is_Region() && sub->req() != 3) {
1147       // Always take in(1) path on the way up to 'dom' for clone regions
1148       // (with only one input) or regions which merge > 2 paths
1149       // (usually used to merge fast/slow paths).
1150       up = sub->in(1);
1151     } else if (sub == up && sub->is_Region()) {
1152       // Try both paths for Regions with 2 input paths (it may be a loop head).
1153       // It could give conservative 'false' answer without information
1154       // which region's input is the entry path.
1155       iterations_without_region_limit = DominatorSearchLimit; // Reset
1156 
1157       bool region_was_visited_before = false;
1158       // Was this Region node visited before?
1159       // If so, we have reached it because we accidentally took a
1160       // loop-back edge from 'sub' back into the body of the loop,
1161       // and worked our way up again to the loop header 'sub'.
1162       // So, take the first unexplored path on the way up to 'dom'.
1163       for (int j = nlist.size() - 1; j >= 0; j--) {
1164         intptr_t ni = (intptr_t)nlist.at(j);
1165         Node* visited = (Node*)(ni & ~1);
1166         bool  visited_twice_already = ((ni & 1) != 0);
1167         if (visited == sub) {
1168           if (visited_twice_already) {
1169             // Visited 2 paths, but still stuck in loop body.  Give up.
1170             return false;
1171           }
1172           // The Region node was visited before only once.
1173           // (We will repush with the low bit set, below.)
1174           nlist.remove(j);
1175           // We will find a new edge and re-insert.
1176           region_was_visited_before = true;
1177           break;
1178         }
1179       }
1180 
1181       // Find an incoming edge which has not been seen yet; walk through it.
1182       assert(up == sub, "");
1183       uint skip = region_was_visited_before ? 1 : 0;
1184       for (uint i = 1; i < sub->req(); i++) {
1185         Node* in = sub->in(i);
1186         if (in != NULL && !in->is_top() && in != sub) {
1187           if (skip == 0) {
1188             up = in;
1189             break;
1190           }
1191           --skip;               // skip this nontrivial input
1192         }
1193       }
1194 
1195       // Set 0 bit to indicate that both paths were taken.
1196       nlist.push((Node*)((intptr_t)sub + (region_was_visited_before ? 1 : 0)));
1197     }
1198 
1199     if (up == sub) {
1200       break;    // some kind of tight cycle
1201     }
1202     if (up == orig_sub && met_dom) {
1203       // returned back after visiting 'dom'
1204       break;    // some kind of cycle
1205     }
1206     if (--iterations_without_region_limit < 0) {
1207       break;    // dead cycle
1208     }
1209     sub = up;
1210   }
1211 
1212   // Did not meet Root or Start node in pred. chain.
1213   // Conservative answer for dead code.
1214   return false;
1215 }
1216 
1217 //------------------------------remove_dead_region-----------------------------
1218 // This control node is dead.  Follow the subgraph below it making everything
1219 // using it dead as well.  This will happen normally via the usual IterGVN
1220 // worklist but this call is more efficient.  Do not update use-def info
1221 // inside the dead region, just at the borders.
1222 static void kill_dead_code( Node *dead, PhaseIterGVN *igvn ) {
1223   // Con's are a popular node to re-hit in the hash table again.
1224   if( dead->is_Con() ) return;
1225 
1226   // Can't put ResourceMark here since igvn->_worklist uses the same arena
1227   // for verify pass with +VerifyOpto and we add/remove elements in it here.
1228   Node_List  nstack(Thread::current()->resource_area());
1229 
1230   Node *top = igvn->C->top();
1231   nstack.push(dead);
1232   bool has_irreducible_loop = igvn->C->has_irreducible_loop();
1233 
1234   while (nstack.size() > 0) {
1235     dead = nstack.pop();
1236     if (dead->outcnt() > 0) {
1237       // Keep dead node on stack until all uses are processed.
1238       nstack.push(dead);
1239       // For all Users of the Dead...    ;-)
1240       for (DUIterator_Last kmin, k = dead->last_outs(kmin); k >= kmin; ) {
1241         Node* use = dead->last_out(k);
1242         igvn->hash_delete(use);       // Yank from hash table prior to mod
1243         if (use->in(0) == dead) {     // Found another dead node
1244           assert (!use->is_Con(), "Control for Con node should be Root node.");
1245           use->set_req(0, top);       // Cut dead edge to prevent processing
1246           nstack.push(use);           // the dead node again.
1247         } else if (!has_irreducible_loop && // Backedge could be alive in irreducible loop
1248                    use->is_Loop() && !use->is_Root() &&       // Don't kill Root (RootNode extends LoopNode)
1249                    use->in(LoopNode::EntryControl) == dead) { // Dead loop if its entry is dead
1250           use->set_req(LoopNode::EntryControl, top);          // Cut dead edge to prevent processing
1251           use->set_req(0, top);       // Cut self edge
1252           nstack.push(use);
1253         } else {                      // Else found a not-dead user
1254           // Dead if all inputs are top or null
1255           bool dead_use = !use->is_Root(); // Keep empty graph alive
1256           for (uint j = 1; j < use->req(); j++) {
1257             Node* in = use->in(j);
1258             if (in == dead) {         // Turn all dead inputs into TOP
1259               use->set_req(j, top);
1260             } else if (in != NULL && !in->is_top()) {
1261               dead_use = false;
1262             }
1263           }
1264           if (dead_use) {
1265             if (use->is_Region()) {
1266               use->set_req(0, top);   // Cut self edge
1267             }
1268             nstack.push(use);
1269           } else {
1270             igvn->_worklist.push(use);
1271           }
1272         }
1273         // Refresh the iterator, since any number of kills might have happened.
1274         k = dead->last_outs(kmin);
1275       }
1276     } else { // (dead->outcnt() == 0)
1277       // Done with outputs.
1278       igvn->hash_delete(dead);
1279       igvn->_worklist.remove(dead);
1280       igvn->set_type(dead, Type::TOP);
1281       if (dead->is_macro()) {
1282         igvn->C->remove_macro_node(dead);
1283       }
1284       if (dead->is_expensive()) {
1285         igvn->C->remove_expensive_node(dead);
1286       }
1287       igvn->C->record_dead_node(dead->_idx);
1288       // Kill all inputs to the dead guy
1289       for (uint i=0; i < dead->req(); i++) {
1290         Node *n = dead->in(i);      // Get input to dead guy
1291         if (n != NULL && !n->is_top()) { // Input is valid?
1292           dead->set_req(i, top);    // Smash input away
1293           if (n->outcnt() == 0) {   // Input also goes dead?
1294             if (!n->is_Con())
1295               nstack.push(n);       // Clear it out as well
1296           } else if (n->outcnt() == 1 &&
1297                      n->has_special_unique_user()) {
1298             igvn->add_users_to_worklist( n );
1299           } else if (n->outcnt() <= 2 && n->is_Store()) {
1300             // Push store's uses on worklist to enable folding optimization for
1301             // store/store and store/load to the same address.
1302             // The restriction (outcnt() <= 2) is the same as in set_req_X()
1303             // and remove_globally_dead_node().
1304             igvn->add_users_to_worklist( n );
1305           }
1306         }
1307       }
1308     } // (dead->outcnt() == 0)
1309   }   // while (nstack.size() > 0) for outputs
1310   return;
1311 }
1312 
1313 //------------------------------remove_dead_region-----------------------------
1314 bool Node::remove_dead_region(PhaseGVN *phase, bool can_reshape) {
1315   Node *n = in(0);
1316   if( !n ) return false;
1317   // Lost control into this guy?  I.e., it became unreachable?
1318   // Aggressively kill all unreachable code.
1319   if (can_reshape && n->is_top()) {
1320     kill_dead_code(this, phase->is_IterGVN());
1321     return false; // Node is dead.
1322   }
1323 
1324   if( n->is_Region() && n->as_Region()->is_copy() ) {
1325     Node *m = n->nonnull_req();
1326     set_req(0, m);
1327     return true;
1328   }
1329   return false;
1330 }
1331 
1332 //------------------------------Ideal_DU_postCCP-------------------------------
1333 // Idealize graph, using DU info.  Must clone result into new-space
1334 Node *Node::Ideal_DU_postCCP( PhaseCCP * ) {
1335   return NULL;                 // Default to no change
1336 }
1337 
1338 //------------------------------hash-------------------------------------------
1339 // Hash function over Nodes.
1340 uint Node::hash() const {
1341   uint sum = 0;
1342   for( uint i=0; i<_cnt; i++ )  // Add in all inputs
1343     sum = (sum<<1)-(uintptr_t)in(i);        // Ignore embedded NULLs
1344   return (sum>>2) + _cnt + Opcode();
1345 }
1346 
1347 //------------------------------cmp--------------------------------------------
1348 // Compare special parts of simple Nodes
1349 uint Node::cmp( const Node &n ) const {
1350   return 1;                     // Must be same
1351 }
1352 
1353 //------------------------------rematerialize-----------------------------------
1354 // Should we clone rather than spill this instruction?
1355 bool Node::rematerialize() const {
1356   if ( is_Mach() )
1357     return this->as_Mach()->rematerialize();
1358   else
1359     return (_flags & Flag_rematerialize) != 0;
1360 }
1361 
1362 //------------------------------needs_anti_dependence_check---------------------
1363 // Nodes which use memory without consuming it, hence need antidependences.
1364 bool Node::needs_anti_dependence_check() const {
1365   if( req() < 2 || (_flags & Flag_needs_anti_dependence_check) == 0 )
1366     return false;
1367   else
1368     return in(1)->bottom_type()->has_memory();
1369 }
1370 
1371 
1372 // Get an integer constant from a ConNode (or CastIINode).
1373 // Return a default value if there is no apparent constant here.
1374 const TypeInt* Node::find_int_type() const {
1375   if (this->is_Type()) {
1376     return this->as_Type()->type()->isa_int();
1377   } else if (this->is_Con()) {
1378     assert(is_Mach(), "should be ConNode(TypeNode) or else a MachNode");
1379     return this->bottom_type()->isa_int();
1380   }
1381   return NULL;
1382 }
1383 
1384 // Get a pointer constant from a ConstNode.
1385 // Returns the constant if it is a pointer ConstNode
1386 intptr_t Node::get_ptr() const {
1387   assert( Opcode() == Op_ConP, "" );
1388   return ((ConPNode*)this)->type()->is_ptr()->get_con();
1389 }
1390 
1391 // Get a narrow oop constant from a ConNNode.
1392 intptr_t Node::get_narrowcon() const {
1393   assert( Opcode() == Op_ConN, "" );
1394   return ((ConNNode*)this)->type()->is_narrowoop()->get_con();
1395 }
1396 
1397 // Get a long constant from a ConNode.
1398 // Return a default value if there is no apparent constant here.
1399 const TypeLong* Node::find_long_type() const {
1400   if (this->is_Type()) {
1401     return this->as_Type()->type()->isa_long();
1402   } else if (this->is_Con()) {
1403     assert(is_Mach(), "should be ConNode(TypeNode) or else a MachNode");
1404     return this->bottom_type()->isa_long();
1405   }
1406   return NULL;
1407 }
1408 
1409 
1410 /**
1411  * Return a ptr type for nodes which should have it.
1412  */
1413 const TypePtr* Node::get_ptr_type() const {
1414   const TypePtr* tp = this->bottom_type()->make_ptr();
1415 #ifdef ASSERT
1416   if (tp == NULL) {
1417     this->dump(1);
1418     assert((tp != NULL), "unexpected node type");
1419   }
1420 #endif
1421   return tp;
1422 }
1423 
1424 // Get a double constant from a ConstNode.
1425 // Returns the constant if it is a double ConstNode
1426 jdouble Node::getd() const {
1427   assert( Opcode() == Op_ConD, "" );
1428   return ((ConDNode*)this)->type()->is_double_constant()->getd();
1429 }
1430 
1431 // Get a float constant from a ConstNode.
1432 // Returns the constant if it is a float ConstNode
1433 jfloat Node::getf() const {
1434   assert( Opcode() == Op_ConF, "" );
1435   return ((ConFNode*)this)->type()->is_float_constant()->getf();
1436 }
1437 
1438 #ifndef PRODUCT
1439 
1440 //----------------------------NotANode----------------------------------------
1441 // Used in debugging code to avoid walking across dead or uninitialized edges.
1442 static inline bool NotANode(const Node* n) {
1443   if (n == NULL)                   return true;
1444   if (((intptr_t)n & 1) != 0)      return true;  // uninitialized, etc.
1445   if (*(address*)n == badAddress)  return true;  // kill by Node::destruct
1446   return false;
1447 }
1448 
1449 
1450 //------------------------------find------------------------------------------
1451 // Find a neighbor of this Node with the given _idx
1452 // If idx is negative, find its absolute value, following both _in and _out.
1453 static void find_recur(Compile* C,  Node* &result, Node *n, int idx, bool only_ctrl,
1454                         VectorSet* old_space, VectorSet* new_space ) {
1455   int node_idx = (idx >= 0) ? idx : -idx;
1456   if (NotANode(n))  return;  // Gracefully handle NULL, -1, 0xabababab, etc.
1457   // Contained in new_space or old_space?   Check old_arena first since it's mostly empty.
1458   VectorSet *v = C->old_arena()->contains(n) ? old_space : new_space;
1459   if( v->test(n->_idx) ) return;
1460   if( (int)n->_idx == node_idx
1461       debug_only(|| n->debug_idx() == node_idx) ) {
1462     if (result != NULL)
1463       tty->print("find: " INTPTR_FORMAT " and " INTPTR_FORMAT " both have idx==%d\n",
1464                  (uintptr_t)result, (uintptr_t)n, node_idx);
1465     result = n;
1466   }
1467   v->set(n->_idx);
1468   for( uint i=0; i<n->len(); i++ ) {
1469     if( only_ctrl && !(n->is_Region()) && (n->Opcode() != Op_Root) && (i != TypeFunc::Control) ) continue;
1470     find_recur(C, result, n->in(i), idx, only_ctrl, old_space, new_space );
1471   }
1472   // Search along forward edges also:
1473   if (idx < 0 && !only_ctrl) {
1474     for( uint j=0; j<n->outcnt(); j++ ) {
1475       find_recur(C, result, n->raw_out(j), idx, only_ctrl, old_space, new_space );
1476     }
1477   }
1478 #ifdef ASSERT
1479   // Search along debug_orig edges last, checking for cycles
1480   Node* orig = n->debug_orig();
1481   if (orig != NULL) {
1482     do {
1483       if (NotANode(orig))  break;
1484       find_recur(C, result, orig, idx, only_ctrl, old_space, new_space );
1485       orig = orig->debug_orig();
1486     } while (orig != NULL && orig != n->debug_orig());
1487   }
1488 #endif //ASSERT
1489 }
1490 
1491 // call this from debugger:
1492 Node* find_node(Node* n, int idx) {
1493   return n->find(idx);
1494 }
1495 
1496 //------------------------------find-------------------------------------------
1497 Node* Node::find(int idx) const {
1498   ResourceArea *area = Thread::current()->resource_area();
1499   VectorSet old_space(area), new_space(area);
1500   Node* result = NULL;
1501   find_recur(Compile::current(), result, (Node*) this, idx, false, &old_space, &new_space );
1502   return result;
1503 }
1504 
1505 //------------------------------find_ctrl--------------------------------------
1506 // Find an ancestor to this node in the control history with given _idx
1507 Node* Node::find_ctrl(int idx) const {
1508   ResourceArea *area = Thread::current()->resource_area();
1509   VectorSet old_space(area), new_space(area);
1510   Node* result = NULL;
1511   find_recur(Compile::current(), result, (Node*) this, idx, true, &old_space, &new_space );
1512   return result;
1513 }
1514 #endif
1515 
1516 
1517 
1518 #ifndef PRODUCT
1519 
1520 // -----------------------------Name-------------------------------------------
1521 extern const char *NodeClassNames[];
1522 const char *Node::Name() const { return NodeClassNames[Opcode()]; }
1523 
1524 static bool is_disconnected(const Node* n) {
1525   for (uint i = 0; i < n->req(); i++) {
1526     if (n->in(i) != NULL)  return false;
1527   }
1528   return true;
1529 }
1530 
1531 #ifdef ASSERT
1532 static void dump_orig(Node* orig, outputStream *st) {
1533   Compile* C = Compile::current();
1534   if (NotANode(orig)) orig = NULL;
1535   if (orig != NULL && !C->node_arena()->contains(orig)) orig = NULL;
1536   if (orig == NULL) return;
1537   st->print(" !orig=");
1538   Node* fast = orig->debug_orig(); // tortoise & hare algorithm to detect loops
1539   if (NotANode(fast)) fast = NULL;
1540   while (orig != NULL) {
1541     bool discon = is_disconnected(orig);  // if discon, print [123] else 123
1542     if (discon) st->print("[");
1543     if (!Compile::current()->node_arena()->contains(orig))
1544       st->print("o");
1545     st->print("%d", orig->_idx);
1546     if (discon) st->print("]");
1547     orig = orig->debug_orig();
1548     if (NotANode(orig)) orig = NULL;
1549     if (orig != NULL && !C->node_arena()->contains(orig)) orig = NULL;
1550     if (orig != NULL) st->print(",");
1551     if (fast != NULL) {
1552       // Step fast twice for each single step of orig:
1553       fast = fast->debug_orig();
1554       if (NotANode(fast)) fast = NULL;
1555       if (fast != NULL && fast != orig) {
1556         fast = fast->debug_orig();
1557         if (NotANode(fast)) fast = NULL;
1558       }
1559       if (fast == orig) {
1560         st->print("...");
1561         break;
1562       }
1563     }
1564   }
1565 }
1566 
1567 void Node::set_debug_orig(Node* orig) {
1568   _debug_orig = orig;
1569   if (BreakAtNode == 0)  return;
1570   if (NotANode(orig))  orig = NULL;
1571   int trip = 10;
1572   while (orig != NULL) {
1573     if (orig->debug_idx() == BreakAtNode || (int)orig->_idx == BreakAtNode) {
1574       tty->print_cr("BreakAtNode: _idx=%d _debug_idx=%d orig._idx=%d orig._debug_idx=%d",
1575                     this->_idx, this->debug_idx(), orig->_idx, orig->debug_idx());
1576       BREAKPOINT;
1577     }
1578     orig = orig->debug_orig();
1579     if (NotANode(orig))  orig = NULL;
1580     if (trip-- <= 0)  break;
1581   }
1582 }
1583 #endif //ASSERT
1584 
1585 //------------------------------dump------------------------------------------
1586 // Dump a Node
1587 void Node::dump(const char* suffix, outputStream *st) const {
1588   Compile* C = Compile::current();
1589   bool is_new = C->node_arena()->contains(this);
1590   C->_in_dump_cnt++;
1591   st->print("%c%d\t%s\t=== ", is_new ? ' ' : 'o', _idx, Name());
1592 
1593   // Dump the required and precedence inputs
1594   dump_req(st);
1595   dump_prec(st);
1596   // Dump the outputs
1597   dump_out(st);
1598 
1599   if (is_disconnected(this)) {
1600 #ifdef ASSERT
1601     st->print("  [%d]",debug_idx());
1602     dump_orig(debug_orig(), st);
1603 #endif
1604     st->cr();
1605     C->_in_dump_cnt--;
1606     return;                     // don't process dead nodes
1607   }
1608 
1609   // Dump node-specific info
1610   dump_spec(st);
1611 #ifdef ASSERT
1612   // Dump the non-reset _debug_idx
1613   if (Verbose && WizardMode) {
1614     st->print("  [%d]",debug_idx());
1615   }
1616 #endif
1617 
1618   const Type *t = bottom_type();
1619 
1620   if (t != NULL && (t->isa_instptr() || t->isa_klassptr())) {
1621     const TypeInstPtr  *toop = t->isa_instptr();
1622     const TypeKlassPtr *tkls = t->isa_klassptr();
1623     ciKlass*           klass = toop ? toop->klass() : (tkls ? tkls->klass() : NULL );
1624     if (klass && klass->is_loaded() && klass->is_interface()) {
1625       st->print("  Interface:");
1626     } else if (toop) {
1627       st->print("  Oop:");
1628     } else if (tkls) {
1629       st->print("  Klass:");
1630     }
1631     t->dump_on(st);
1632   } else if (t == Type::MEMORY) {
1633     st->print("  Memory:");
1634     MemNode::dump_adr_type(this, adr_type(), st);
1635   } else if (Verbose || WizardMode) {
1636     st->print("  Type:");
1637     if (t) {
1638       t->dump_on(st);
1639     } else {
1640       st->print("no type");
1641     }
1642   } else if (t->isa_vect() && this->is_MachSpillCopy()) {
1643     // Dump MachSpillcopy vector type.
1644     t->dump_on(st);
1645   }
1646   if (is_new) {
1647     debug_only(dump_orig(debug_orig(), st));
1648     Node_Notes* nn = C->node_notes_at(_idx);
1649     if (nn != NULL && !nn->is_clear()) {
1650       if (nn->jvms() != NULL) {
1651         st->print(" !jvms:");
1652         nn->jvms()->dump_spec(st);
1653       }
1654     }
1655   }
1656   if (suffix) st->print(suffix);
1657   C->_in_dump_cnt--;
1658 }
1659 
1660 //------------------------------dump_req--------------------------------------
1661 void Node::dump_req(outputStream *st) const {
1662   // Dump the required input edges
1663   for (uint i = 0; i < req(); i++) {    // For all required inputs
1664     Node* d = in(i);
1665     if (d == NULL) {
1666       st->print("_ ");
1667     } else if (NotANode(d)) {
1668       st->print("NotANode ");  // uninitialized, sentinel, garbage, etc.
1669     } else {
1670       st->print("%c%d ", Compile::current()->node_arena()->contains(d) ? ' ' : 'o', d->_idx);
1671     }
1672   }
1673 }
1674 
1675 
1676 //------------------------------dump_prec-------------------------------------
1677 void Node::dump_prec(outputStream *st) const {
1678   // Dump the precedence edges
1679   int any_prec = 0;
1680   for (uint i = req(); i < len(); i++) {       // For all precedence inputs
1681     Node* p = in(i);
1682     if (p != NULL) {
1683       if (!any_prec++) st->print(" |");
1684       if (NotANode(p)) { st->print("NotANode "); continue; }
1685       st->print("%c%d ", Compile::current()->node_arena()->contains(in(i)) ? ' ' : 'o', in(i)->_idx);
1686     }
1687   }
1688 }
1689 
1690 //------------------------------dump_out--------------------------------------
1691 void Node::dump_out(outputStream *st) const {
1692   // Delimit the output edges
1693   st->print(" [[");
1694   // Dump the output edges
1695   for (uint i = 0; i < _outcnt; i++) {    // For all outputs
1696     Node* u = _out[i];
1697     if (u == NULL) {
1698       st->print("_ ");
1699     } else if (NotANode(u)) {
1700       st->print("NotANode ");
1701     } else {
1702       st->print("%c%d ", Compile::current()->node_arena()->contains(u) ? ' ' : 'o', u->_idx);
1703     }
1704   }
1705   st->print("]] ");
1706 }
1707 
1708 //------------------------------dump_nodes-------------------------------------
1709 static void dump_nodes(const Node* start, int d, bool only_ctrl) {
1710   Node* s = (Node*)start; // remove const
1711   if (NotANode(s)) return;
1712 
1713   uint depth = (uint)ABS(d);
1714   int direction = d;
1715   Compile* C = Compile::current();
1716   GrowableArray <Node *> nstack(C->unique());
1717 
1718   nstack.append(s);
1719   int begin = 0;
1720   int end = 0;
1721   for(uint i = 0; i < depth; i++) {
1722     end = nstack.length();
1723     for(int j = begin; j < end; j++) {
1724       Node* tp  = nstack.at(j);
1725       uint limit = direction > 0 ? tp->len() : tp->outcnt();
1726       for(uint k = 0; k < limit; k++) {
1727         Node* n = direction > 0 ? tp->in(k) : tp->raw_out(k);
1728 
1729         if (NotANode(n))  continue;
1730         // do not recurse through top or the root (would reach unrelated stuff)
1731         if (n->is_Root() || n->is_top())  continue;
1732         if (only_ctrl && !n->is_CFG()) continue;
1733 
1734         bool on_stack = nstack.contains(n);
1735         if (!on_stack) {
1736           nstack.append(n);
1737         }
1738       }
1739     }
1740     begin = end;
1741   }
1742   end = nstack.length();
1743   if (direction > 0) {
1744     for(int j = end-1; j >= 0; j--) {
1745       nstack.at(j)->dump();
1746     }
1747   } else {
1748     for(int j = 0; j < end; j++) {
1749       nstack.at(j)->dump();
1750     }
1751   }
1752 }
1753 
1754 //------------------------------dump-------------------------------------------
1755 void Node::dump(int d) const {
1756   dump_nodes(this, d, false);
1757 }
1758 
1759 //------------------------------dump_ctrl--------------------------------------
1760 // Dump a Node's control history to depth
1761 void Node::dump_ctrl(int d) const {
1762   dump_nodes(this, d, true);
1763 }
1764 
1765 // VERIFICATION CODE
1766 // For each input edge to a node (ie - for each Use-Def edge), verify that
1767 // there is a corresponding Def-Use edge.
1768 //------------------------------verify_edges-----------------------------------
1769 void Node::verify_edges(Unique_Node_List &visited) {
1770   uint i, j, idx;
1771   int  cnt;
1772   Node *n;
1773 
1774   // Recursive termination test
1775   if (visited.member(this))  return;
1776   visited.push(this);
1777 
1778   // Walk over all input edges, checking for correspondence
1779   for( i = 0; i < len(); i++ ) {
1780     n = in(i);
1781     if (n != NULL && !n->is_top()) {
1782       // Count instances of (Node *)this
1783       cnt = 0;
1784       for (idx = 0; idx < n->_outcnt; idx++ ) {
1785         if (n->_out[idx] == (Node *)this)  cnt++;
1786       }
1787       assert( cnt > 0,"Failed to find Def-Use edge." );
1788       // Check for duplicate edges
1789       // walk the input array downcounting the input edges to n
1790       for( j = 0; j < len(); j++ ) {
1791         if( in(j) == n ) cnt--;
1792       }
1793       assert( cnt == 0,"Mismatched edge count.");
1794     } else if (n == NULL) {
1795       assert(i >= req() || i == 0 || is_Region() || is_Phi(), "only regions or phis have null data edges");
1796     } else {
1797       assert(n->is_top(), "sanity");
1798       // Nothing to check.
1799     }
1800   }
1801   // Recursive walk over all input edges
1802   for( i = 0; i < len(); i++ ) {
1803     n = in(i);
1804     if( n != NULL )
1805       in(i)->verify_edges(visited);
1806   }
1807 }
1808 
1809 //------------------------------verify_recur-----------------------------------
1810 static const Node *unique_top = NULL;
1811 
1812 void Node::verify_recur(const Node *n, int verify_depth,
1813                         VectorSet &old_space, VectorSet &new_space) {
1814   if ( verify_depth == 0 )  return;
1815   if (verify_depth > 0)  --verify_depth;
1816 
1817   Compile* C = Compile::current();
1818 
1819   // Contained in new_space or old_space?
1820   VectorSet *v = C->node_arena()->contains(n) ? &new_space : &old_space;
1821   // Check for visited in the proper space.  Numberings are not unique
1822   // across spaces so we need a separate VectorSet for each space.
1823   if( v->test_set(n->_idx) ) return;
1824 
1825   if (n->is_Con() && n->bottom_type() == Type::TOP) {
1826     if (C->cached_top_node() == NULL)
1827       C->set_cached_top_node((Node*)n);
1828     assert(C->cached_top_node() == n, "TOP node must be unique");
1829   }
1830 
1831   for( uint i = 0; i < n->len(); i++ ) {
1832     Node *x = n->in(i);
1833     if (!x || x->is_top()) continue;
1834 
1835     // Verify my input has a def-use edge to me
1836     if (true /*VerifyDefUse*/) {
1837       // Count use-def edges from n to x
1838       int cnt = 0;
1839       for( uint j = 0; j < n->len(); j++ )
1840         if( n->in(j) == x )
1841           cnt++;
1842       // Count def-use edges from x to n
1843       uint max = x->_outcnt;
1844       for( uint k = 0; k < max; k++ )
1845         if (x->_out[k] == n)
1846           cnt--;
1847       assert( cnt == 0, "mismatched def-use edge counts" );
1848     }
1849 
1850     verify_recur(x, verify_depth, old_space, new_space);
1851   }
1852 
1853 }
1854 
1855 //------------------------------verify-----------------------------------------
1856 // Check Def-Use info for my subgraph
1857 void Node::verify() const {
1858   Compile* C = Compile::current();
1859   Node* old_top = C->cached_top_node();
1860   ResourceMark rm;
1861   ResourceArea *area = Thread::current()->resource_area();
1862   VectorSet old_space(area), new_space(area);
1863   verify_recur(this, -1, old_space, new_space);
1864   C->set_cached_top_node(old_top);
1865 }
1866 #endif
1867 
1868 
1869 //------------------------------walk-------------------------------------------
1870 // Graph walk, with both pre-order and post-order functions
1871 void Node::walk(NFunc pre, NFunc post, void *env) {
1872   VectorSet visited(Thread::current()->resource_area()); // Setup for local walk
1873   walk_(pre, post, env, visited);
1874 }
1875 
1876 void Node::walk_(NFunc pre, NFunc post, void *env, VectorSet &visited) {
1877   if( visited.test_set(_idx) ) return;
1878   pre(*this,env);               // Call the pre-order walk function
1879   for( uint i=0; i<_max; i++ )
1880     if( in(i) )                 // Input exists and is not walked?
1881       in(i)->walk_(pre,post,env,visited); // Walk it with pre & post functions
1882   post(*this,env);              // Call the post-order walk function
1883 }
1884 
1885 void Node::nop(Node &, void*) {}
1886 
1887 //------------------------------Registers--------------------------------------
1888 // Do we Match on this edge index or not?  Generally false for Control
1889 // and true for everything else.  Weird for calls & returns.
1890 uint Node::match_edge(uint idx) const {
1891   return idx;                   // True for other than index 0 (control)
1892 }
1893 
1894 // Register classes are defined for specific machines
1895 const RegMask &Node::out_RegMask() const {
1896   ShouldNotCallThis();
1897   return *(new RegMask());
1898 }
1899 
1900 const RegMask &Node::in_RegMask(uint) const {
1901   ShouldNotCallThis();
1902   return *(new RegMask());
1903 }
1904 
1905 //=============================================================================
1906 //-----------------------------------------------------------------------------
1907 void Node_Array::reset( Arena *new_arena ) {
1908   _a->Afree(_nodes,_max*sizeof(Node*));
1909   _max   = 0;
1910   _nodes = NULL;
1911   _a     = new_arena;
1912 }
1913 
1914 //------------------------------clear------------------------------------------
1915 // Clear all entries in _nodes to NULL but keep storage
1916 void Node_Array::clear() {
1917   Copy::zero_to_bytes( _nodes, _max*sizeof(Node*) );
1918 }
1919 
1920 //-----------------------------------------------------------------------------
1921 void Node_Array::grow( uint i ) {
1922   if( !_max ) {
1923     _max = 1;
1924     _nodes = (Node**)_a->Amalloc( _max * sizeof(Node*) );
1925     _nodes[0] = NULL;
1926   }
1927   uint old = _max;
1928   while( i >= _max ) _max <<= 1;        // Double to fit
1929   _nodes = (Node**)_a->Arealloc( _nodes, old*sizeof(Node*),_max*sizeof(Node*));
1930   Copy::zero_to_bytes( &_nodes[old], (_max-old)*sizeof(Node*) );
1931 }
1932 
1933 //-----------------------------------------------------------------------------
1934 void Node_Array::insert( uint i, Node *n ) {
1935   if( _nodes[_max-1] ) grow(_max);      // Get more space if full
1936   Copy::conjoint_words_to_higher((HeapWord*)&_nodes[i], (HeapWord*)&_nodes[i+1], ((_max-i-1)*sizeof(Node*)));
1937   _nodes[i] = n;
1938 }
1939 
1940 //-----------------------------------------------------------------------------
1941 void Node_Array::remove( uint i ) {
1942   Copy::conjoint_words_to_lower((HeapWord*)&_nodes[i+1], (HeapWord*)&_nodes[i], ((_max-i-1)*sizeof(Node*)));
1943   _nodes[_max-1] = NULL;
1944 }
1945 
1946 //-----------------------------------------------------------------------------
1947 void Node_Array::sort( C_sort_func_t func) {
1948   qsort( _nodes, _max, sizeof( Node* ), func );
1949 }
1950 
1951 //-----------------------------------------------------------------------------
1952 void Node_Array::dump() const {
1953 #ifndef PRODUCT
1954   for( uint i = 0; i < _max; i++ ) {
1955     Node *nn = _nodes[i];
1956     if( nn != NULL ) {
1957       tty->print("%5d--> ",i); nn->dump();
1958     }
1959   }
1960 #endif
1961 }
1962 
1963 //--------------------------is_iteratively_computed------------------------------
1964 // Operation appears to be iteratively computed (such as an induction variable)
1965 // It is possible for this operation to return false for a loop-varying
1966 // value, if it appears (by local graph inspection) to be computed by a simple conditional.
1967 bool Node::is_iteratively_computed() {
1968   if (ideal_reg()) { // does operation have a result register?
1969     for (uint i = 1; i < req(); i++) {
1970       Node* n = in(i);
1971       if (n != NULL && n->is_Phi()) {
1972         for (uint j = 1; j < n->req(); j++) {
1973           if (n->in(j) == this) {
1974             return true;
1975           }
1976         }
1977       }
1978     }
1979   }
1980   return false;
1981 }
1982 
1983 //--------------------------find_similar------------------------------
1984 // Return a node with opcode "opc" and same inputs as "this" if one can
1985 // be found; Otherwise return NULL;
1986 Node* Node::find_similar(int opc) {
1987   if (req() >= 2) {
1988     Node* def = in(1);
1989     if (def && def->outcnt() >= 2) {
1990       for (DUIterator_Fast dmax, i = def->fast_outs(dmax); i < dmax; i++) {
1991         Node* use = def->fast_out(i);
1992         if (use->Opcode() == opc &&
1993             use->req() == req()) {
1994           uint j;
1995           for (j = 0; j < use->req(); j++) {
1996             if (use->in(j) != in(j)) {
1997               break;
1998             }
1999           }
2000           if (j == use->req()) {
2001             return use;
2002           }
2003         }
2004       }
2005     }
2006   }
2007   return NULL;
2008 }
2009 
2010 
2011 //--------------------------unique_ctrl_out------------------------------
2012 // Return the unique control out if only one. Null if none or more than one.
2013 Node* Node::unique_ctrl_out() {
2014   Node* found = NULL;
2015   for (uint i = 0; i < outcnt(); i++) {
2016     Node* use = raw_out(i);
2017     if (use->is_CFG() && use != this) {
2018       if (found != NULL) return NULL;
2019       found = use;
2020     }
2021   }
2022   return found;
2023 }
2024 
2025 //=============================================================================
2026 //------------------------------yank-------------------------------------------
2027 // Find and remove
2028 void Node_List::yank( Node *n ) {
2029   uint i;
2030   for( i = 0; i < _cnt; i++ )
2031     if( _nodes[i] == n )
2032       break;
2033 
2034   if( i < _cnt )
2035     _nodes[i] = _nodes[--_cnt];
2036 }
2037 
2038 //------------------------------dump-------------------------------------------
2039 void Node_List::dump() const {
2040 #ifndef PRODUCT
2041   for( uint i = 0; i < _cnt; i++ )
2042     if( _nodes[i] ) {
2043       tty->print("%5d--> ",i);
2044       _nodes[i]->dump();
2045     }
2046 #endif
2047 }
2048 
2049 //=============================================================================
2050 //------------------------------remove-----------------------------------------
2051 void Unique_Node_List::remove( Node *n ) {
2052   if( _in_worklist[n->_idx] ) {
2053     for( uint i = 0; i < size(); i++ )
2054       if( _nodes[i] == n ) {
2055         map(i,Node_List::pop());
2056         _in_worklist >>= n->_idx;
2057         return;
2058       }
2059     ShouldNotReachHere();
2060   }
2061 }
2062 
2063 //-----------------------remove_useless_nodes----------------------------------
2064 // Remove useless nodes from worklist
2065 void Unique_Node_List::remove_useless_nodes(VectorSet &useful) {
2066 
2067   for( uint i = 0; i < size(); ++i ) {
2068     Node *n = at(i);
2069     assert( n != NULL, "Did not expect null entries in worklist");
2070     if( ! useful.test(n->_idx) ) {
2071       _in_worklist >>= n->_idx;
2072       map(i,Node_List::pop());
2073       // Node *replacement = Node_List::pop();
2074       // if( i != size() ) { // Check if removing last entry
2075       //   _nodes[i] = replacement;
2076       // }
2077       --i;  // Visit popped node
2078       // If it was last entry, loop terminates since size() was also reduced
2079     }
2080   }
2081 }
2082 
2083 //=============================================================================
2084 void Node_Stack::grow() {
2085   size_t old_top = pointer_delta(_inode_top,_inodes,sizeof(INode)); // save _top
2086   size_t old_max = pointer_delta(_inode_max,_inodes,sizeof(INode));
2087   size_t max = old_max << 1;             // max * 2
2088   _inodes = REALLOC_ARENA_ARRAY(_a, INode, _inodes, old_max, max);
2089   _inode_max = _inodes + max;
2090   _inode_top = _inodes + old_top;        // restore _top
2091 }
2092 
2093 // Node_Stack is used to map nodes.
2094 Node* Node_Stack::find(uint idx) const {
2095   uint sz = size();
2096   for (uint i=0; i < sz; i++) {
2097     if (idx == index_at(i) )
2098       return node_at(i);
2099   }
2100   return NULL;
2101 }
2102 
2103 //=============================================================================
2104 uint TypeNode::size_of() const { return sizeof(*this); }
2105 #ifndef PRODUCT
2106 void TypeNode::dump_spec(outputStream *st) const {
2107   if( !Verbose && !WizardMode ) {
2108     // standard dump does this in Verbose and WizardMode
2109     st->print(" #"); _type->dump_on(st);
2110   }
2111 }
2112 #endif
2113 uint TypeNode::hash() const {
2114   return Node::hash() + _type->hash();
2115 }
2116 uint TypeNode::cmp( const Node &n ) const
2117 { return !Type::cmp( _type, ((TypeNode&)n)._type ); }
2118 const Type *TypeNode::bottom_type() const { return _type; }
2119 const Type *TypeNode::Value( PhaseTransform * ) const { return _type; }
2120 
2121 //------------------------------ideal_reg--------------------------------------
2122 uint TypeNode::ideal_reg() const {
2123   return Matcher::base2reg[_type->base()];
2124 }