1 /*
   2  * Copyright (c) 1997, 2023, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "gc/shared/barrierSet.hpp"
  27 #include "gc/shared/c2/barrierSetC2.hpp"
  28 #include "memory/allocation.inline.hpp"
  29 #include "memory/resourceArea.hpp"
  30 #include "oops/objArrayKlass.hpp"
  31 #include "opto/addnode.hpp"
  32 #include "opto/castnode.hpp"
  33 #include "opto/cfgnode.hpp"
  34 #include "opto/connode.hpp"
  35 #include "opto/convertnode.hpp"
  36 #include "opto/inlinetypenode.hpp"
  37 #include "opto/loopnode.hpp"
  38 #include "opto/machnode.hpp"
  39 #include "opto/movenode.hpp"
  40 #include "opto/narrowptrnode.hpp"
  41 #include "opto/mulnode.hpp"
  42 #include "opto/phaseX.hpp"
  43 #include "opto/regalloc.hpp"
  44 #include "opto/regmask.hpp"
  45 #include "opto/runtime.hpp"
  46 #include "opto/subnode.hpp"
  47 #include "opto/vectornode.hpp"
  48 #include "utilities/vmError.hpp"
  49 
  50 // Portions of code courtesy of Clifford Click
  51 
  52 // Optimization - Graph Style
  53 
  54 //=============================================================================
  55 //------------------------------Value------------------------------------------
  56 // Compute the type of the RegionNode.
  57 const Type* RegionNode::Value(PhaseGVN* phase) const {
  58   for( uint i=1; i<req(); ++i ) {       // For all paths in
  59     Node *n = in(i);            // Get Control source
  60     if( !n ) continue;          // Missing inputs are TOP
  61     if( phase->type(n) == Type::CONTROL )
  62       return Type::CONTROL;
  63   }
  64   return Type::TOP;             // All paths dead?  Then so are we
  65 }
  66 
  67 //------------------------------Identity---------------------------------------
  68 // Check for Region being Identity.
  69 Node* RegionNode::Identity(PhaseGVN* phase) {
  70   // Cannot have Region be an identity, even if it has only 1 input.
  71   // Phi users cannot have their Region input folded away for them,
  72   // since they need to select the proper data input
  73   return this;
  74 }
  75 
  76 //------------------------------merge_region-----------------------------------
  77 // If a Region flows into a Region, merge into one big happy merge.  This is
  78 // hard to do if there is stuff that has to happen
  79 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  80   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  81     return NULL;
  82   Node *progress = NULL;        // Progress flag
  83   PhaseIterGVN *igvn = phase->is_IterGVN();
  84 
  85   uint rreq = region->req();
  86   for( uint i = 1; i < rreq; i++ ) {
  87     Node *r = region->in(i);
  88     if( r && r->Opcode() == Op_Region && // Found a region?
  89         r->in(0) == r &&        // Not already collapsed?
  90         r != region &&          // Avoid stupid situations
  91         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  92       assert(!r->as_Region()->has_phi(), "no phi users");
  93       if( !progress ) {         // No progress
  94         if (region->has_phi()) {
  95           return NULL;        // Only flatten if no Phi users
  96           // igvn->hash_delete( phi );
  97         }
  98         igvn->hash_delete( region );
  99         progress = region;      // Making progress
 100       }
 101       igvn->hash_delete( r );
 102 
 103       // Append inputs to 'r' onto 'region'
 104       for( uint j = 1; j < r->req(); j++ ) {
 105         // Move an input from 'r' to 'region'
 106         region->add_req(r->in(j));
 107         r->set_req(j, phase->C->top());
 108         // Update phis of 'region'
 109         //for( uint k = 0; k < max; k++ ) {
 110         //  Node *phi = region->out(k);
 111         //  if( phi->is_Phi() ) {
 112         //    phi->add_req(phi->in(i));
 113         //  }
 114         //}
 115 
 116         rreq++;                 // One more input to Region
 117       } // Found a region to merge into Region
 118       igvn->_worklist.push(r);
 119       // Clobber pointer to the now dead 'r'
 120       region->set_req(i, phase->C->top());
 121     }
 122   }
 123 
 124   return progress;
 125 }
 126 
 127 
 128 
 129 //--------------------------------has_phi--------------------------------------
 130 // Helper function: Return any PhiNode that uses this region or NULL
 131 PhiNode* RegionNode::has_phi() const {
 132   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 133     Node* phi = fast_out(i);
 134     if (phi->is_Phi()) {   // Check for Phi users
 135       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 136       return phi->as_Phi();  // this one is good enough
 137     }
 138   }
 139 
 140   return NULL;
 141 }
 142 
 143 
 144 //-----------------------------has_unique_phi----------------------------------
 145 // Helper function: Return the only PhiNode that uses this region or NULL
 146 PhiNode* RegionNode::has_unique_phi() const {
 147   // Check that only one use is a Phi
 148   PhiNode* only_phi = NULL;
 149   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 150     Node* phi = fast_out(i);
 151     if (phi->is_Phi()) {   // Check for Phi users
 152       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 153       if (only_phi == NULL) {
 154         only_phi = phi->as_Phi();
 155       } else {
 156         return NULL;  // multiple phis
 157       }
 158     }
 159   }
 160 
 161   return only_phi;
 162 }
 163 
 164 
 165 //------------------------------check_phi_clipping-----------------------------
 166 // Helper function for RegionNode's identification of FP clipping
 167 // Check inputs to the Phi
 168 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 169   min     = NULL;
 170   max     = NULL;
 171   val     = NULL;
 172   min_idx = 0;
 173   max_idx = 0;
 174   val_idx = 0;
 175   uint  phi_max = phi->req();
 176   if( phi_max == 4 ) {
 177     for( uint j = 1; j < phi_max; ++j ) {
 178       Node *n = phi->in(j);
 179       int opcode = n->Opcode();
 180       switch( opcode ) {
 181       case Op_ConI:
 182         {
 183           if( min == NULL ) {
 184             min     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 185             min_idx = j;
 186           } else {
 187             max     = n->Opcode() == Op_ConI ? (ConNode*)n : NULL;
 188             max_idx = j;
 189             if( min->get_int() > max->get_int() ) {
 190               // Swap min and max
 191               ConNode *temp;
 192               uint     temp_idx;
 193               temp     = min;     min     = max;     max     = temp;
 194               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 195             }
 196           }
 197         }
 198         break;
 199       default:
 200         {
 201           val = n;
 202           val_idx = j;
 203         }
 204         break;
 205       }
 206     }
 207   }
 208   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 209 }
 210 
 211 
 212 //------------------------------check_if_clipping------------------------------
 213 // Helper function for RegionNode's identification of FP clipping
 214 // Check that inputs to Region come from two IfNodes,
 215 //
 216 //            If
 217 //      False    True
 218 //       If        |
 219 //  False  True    |
 220 //    |      |     |
 221 //  RegionNode_inputs
 222 //
 223 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 224   top_if = NULL;
 225   bot_if = NULL;
 226 
 227   // Check control structure above RegionNode for (if  ( if  ) )
 228   Node *in1 = region->in(1);
 229   Node *in2 = region->in(2);
 230   Node *in3 = region->in(3);
 231   // Check that all inputs are projections
 232   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 233     Node *in10 = in1->in(0);
 234     Node *in20 = in2->in(0);
 235     Node *in30 = in3->in(0);
 236     // Check that #1 and #2 are ifTrue and ifFalse from same If
 237     if( in10 != NULL && in10->is_If() &&
 238         in20 != NULL && in20->is_If() &&
 239         in30 != NULL && in30->is_If() && in10 == in20 &&
 240         (in1->Opcode() != in2->Opcode()) ) {
 241       Node  *in100 = in10->in(0);
 242       Node *in1000 = (in100 != NULL && in100->is_Proj()) ? in100->in(0) : NULL;
 243       // Check that control for in10 comes from other branch of IF from in3
 244       if( in1000 != NULL && in1000->is_If() &&
 245           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 246         // Control pattern checks
 247         top_if = (IfNode*)in1000;
 248         bot_if = (IfNode*)in10;
 249       }
 250     }
 251   }
 252 
 253   return (top_if != NULL);
 254 }
 255 
 256 
 257 //------------------------------check_convf2i_clipping-------------------------
 258 // Helper function for RegionNode's identification of FP clipping
 259 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 260 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 261   convf2i = NULL;
 262 
 263   // Check for the RShiftNode
 264   Node *rshift = phi->in(idx);
 265   assert( rshift, "Previous checks ensure phi input is present");
 266   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 267 
 268   // Check for the LShiftNode
 269   Node *lshift = rshift->in(1);
 270   assert( lshift, "Previous checks ensure phi input is present");
 271   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 272 
 273   // Check for the ConvF2INode
 274   Node *conv = lshift->in(1);
 275   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 276 
 277   // Check that shift amounts are only to get sign bits set after F2I
 278   jint max_cutoff     = max->get_int();
 279   jint min_cutoff     = min->get_int();
 280   jint left_shift     = lshift->in(2)->get_int();
 281   jint right_shift    = rshift->in(2)->get_int();
 282   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 283   if( left_shift != right_shift ||
 284       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 285       max_post_shift < max_cutoff ||
 286       max_post_shift < -min_cutoff ) {
 287     // Shifts are necessary but current transformation eliminates them
 288     return false;
 289   }
 290 
 291   // OK to return the result of ConvF2I without shifting
 292   convf2i = (ConvF2INode*)conv;
 293   return true;
 294 }
 295 
 296 
 297 //------------------------------check_compare_clipping-------------------------
 298 // Helper function for RegionNode's identification of FP clipping
 299 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 300   Node *i1 = iff->in(1);
 301   if ( !i1->is_Bool() ) { return false; }
 302   BoolNode *bool1 = i1->as_Bool();
 303   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 304   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 305   const Node *cmpF = bool1->in(1);
 306   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 307   // Test that the float value being compared against
 308   // is equivalent to the int value used as a limit
 309   Node *nodef = cmpF->in(2);
 310   if( nodef->Opcode() != Op_ConF ) { return false; }
 311   jfloat conf = nodef->getf();
 312   jint   coni = limit->get_int();
 313   if( ((int)conf) != coni )        { return false; }
 314   input = cmpF->in(1);
 315   return true;
 316 }
 317 
 318 //------------------------------is_unreachable_region--------------------------
 319 // Check if the RegionNode is part of an unsafe loop and unreachable from root.
 320 bool RegionNode::is_unreachable_region(const PhaseGVN* phase) {
 321   Node* top = phase->C->top();
 322   assert(req() == 2 || (req() == 3 && in(1) != NULL && in(2) == top), "sanity check arguments");
 323   if (_is_unreachable_region) {
 324     // Return cached result from previous evaluation which should still be valid
 325     assert(is_unreachable_from_root(phase), "walk the graph again and check if its indeed unreachable");
 326     return true;
 327   }
 328 
 329   // First, cut the simple case of fallthrough region when NONE of
 330   // region's phis references itself directly or through a data node.
 331   if (is_possible_unsafe_loop(phase)) {
 332     // If we have a possible unsafe loop, check if the region node is actually unreachable from root.
 333     if (is_unreachable_from_root(phase)) {
 334       _is_unreachable_region = true;
 335       return true;
 336     }
 337   }
 338   return false;
 339 }
 340 
 341 bool RegionNode::is_possible_unsafe_loop(const PhaseGVN* phase) const {
 342   uint max = outcnt();
 343   uint i;
 344   for (i = 0; i < max; i++) {
 345     Node* n = raw_out(i);
 346     if (n != NULL && n->is_Phi()) {
 347       PhiNode* phi = n->as_Phi();
 348       assert(phi->in(0) == this, "sanity check phi");
 349       if (phi->outcnt() == 0) {
 350         continue; // Safe case - no loops
 351       }
 352       if (phi->outcnt() == 1) {
 353         Node* u = phi->raw_out(0);
 354         // Skip if only one use is an other Phi or Call or Uncommon trap.
 355         // It is safe to consider this case as fallthrough.
 356         if (u != NULL && (u->is_Phi() || u->is_CFG())) {
 357           continue;
 358         }
 359       }
 360       // Check when phi references itself directly or through an other node.
 361       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe) {
 362         break; // Found possible unsafe data loop.
 363       }
 364     }
 365   }
 366   if (i >= max) {
 367     return false; // An unsafe case was NOT found - don't need graph walk.
 368   }
 369   return true;
 370 }
 371 
 372 bool RegionNode::is_unreachable_from_root(const PhaseGVN* phase) const {
 373   ResourceMark rm;
 374   Node_List nstack;
 375   VectorSet visited;
 376 
 377   // Mark all control nodes reachable from root outputs
 378   Node* n = (Node*)phase->C->root();
 379   nstack.push(n);
 380   visited.set(n->_idx);
 381   while (nstack.size() != 0) {
 382     n = nstack.pop();
 383     uint max = n->outcnt();
 384     for (uint i = 0; i < max; i++) {
 385       Node* m = n->raw_out(i);
 386       if (m != NULL && m->is_CFG()) {
 387         if (m == this) {
 388           return false; // We reached the Region node - it is not dead.
 389         }
 390         if (!visited.test_set(m->_idx))
 391           nstack.push(m);
 392       }
 393     }
 394   }
 395   return true; // The Region node is unreachable - it is dead.
 396 }
 397 
 398 #ifdef ASSERT
 399 // Is this region in an infinite subgraph?
 400 // (no path to root except through false NeverBranch exit)
 401 bool RegionNode::is_in_infinite_subgraph() {
 402   ResourceMark rm;
 403   Unique_Node_List worklist;
 404   worklist.push(this);
 405   return RegionNode::are_all_nodes_in_infinite_subgraph(worklist);
 406 }
 407 
 408 // Are all nodes in worklist in infinite subgraph?
 409 // (no path to root except through false NeverBranch exit)
 410 // worklist is directly used for the traversal
 411 bool RegionNode::are_all_nodes_in_infinite_subgraph(Unique_Node_List& worklist) {
 412   // BFS traversal down the CFG, except through NeverBranch exits
 413   for (uint i = 0; i < worklist.size(); ++i) {
 414     Node* n = worklist.at(i);
 415     assert(n->is_CFG(), "only traverse CFG");
 416     if (n->is_Root()) {
 417       // Found root -> there was an exit!
 418       return false;
 419     } else if (n->is_NeverBranch()) {
 420       // Only follow the loop-internal projection, not the NeverBranch exit
 421       ProjNode* proj = n->as_NeverBranch()->proj_out_or_null(0);
 422       assert(proj != nullptr, "must find loop-internal projection of NeverBranch");
 423       worklist.push(proj);
 424     } else {
 425       // Traverse all CFG outputs
 426       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 427         Node* use = n->fast_out(i);
 428         if (use->is_CFG()) {
 429           worklist.push(use);
 430         }
 431       }
 432     }
 433   }
 434   // No exit found for any loop -> all are infinite
 435   return true;
 436 }
 437 #endif //ASSERT
 438 
 439 Node* PhiNode::try_clean_mem_phi(PhaseGVN *phase) {
 440   // Incremental inlining + PhaseStringOpts sometimes produce:
 441   //
 442   // cmpP with 1 top input
 443   //           |
 444   //          If
 445   //         /  \
 446   //   IfFalse  IfTrue  /- Some Node
 447   //         \  /      /    /
 448   //        Region    / /-MergeMem
 449   //             \---Phi
 450   //
 451   //
 452   // It's expected by PhaseStringOpts that the Region goes away and is
 453   // replaced by If's control input but because there's still a Phi,
 454   // the Region stays in the graph. The top input from the cmpP is
 455   // propagated forward and a subgraph that is useful goes away. The
 456   // code below replaces the Phi with the MergeMem so that the Region
 457   // is simplified.
 458 
 459   if (type() == Type::MEMORY && is_diamond_phi(true)) {
 460     MergeMemNode* m = NULL;
 461     assert(req() == 3, "same as region");
 462     Node* r = in(0);
 463     for (uint i = 1; i < 3; ++i) {
 464       Node *mem = in(i);
 465       if (mem && mem->is_MergeMem() && r->in(i)->outcnt() == 1) {
 466         // Nothing is control-dependent on path #i except the region itself.
 467         m = mem->as_MergeMem();
 468         uint j = 3 - i;
 469         Node* other = in(j);
 470         if (other && other == m->base_memory()) {
 471           // m is a successor memory to other, and is not pinned inside the diamond, so push it out.
 472           // This will allow the diamond to collapse completely.
 473           return m;
 474         }
 475       }
 476     }
 477   }
 478   return NULL;
 479 }
 480 
 481 //------------------------------Ideal------------------------------------------
 482 // Return a node which is more "ideal" than the current node.  Must preserve
 483 // the CFG, but we can still strip out dead paths.
 484 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 485   if( !can_reshape && !in(0) ) return NULL;     // Already degraded to a Copy
 486   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 487 
 488   // Check for RegionNode with no Phi users and both inputs come from either
 489   // arm of the same IF.  If found, then the control-flow split is useless.
 490   bool has_phis = false;
 491   if (can_reshape) {            // Need DU info to check for Phi users
 492     has_phis = (has_phi() != NULL);       // Cache result
 493     if (has_phis) {
 494       PhiNode* phi = has_unique_phi();
 495       if (phi != NULL) {
 496         Node* m = phi->try_clean_mem_phi(phase);
 497         if (m != NULL) {
 498           phase->is_IterGVN()->replace_node(phi, m);
 499           has_phis = false;
 500         }
 501       }
 502     }
 503 
 504     if (!has_phis) {            // No Phi users?  Nothing merging?
 505       for (uint i = 1; i < req()-1; i++) {
 506         Node *if1 = in(i);
 507         if( !if1 ) continue;
 508         Node *iff = if1->in(0);
 509         if( !iff || !iff->is_If() ) continue;
 510         for( uint j=i+1; j<req(); j++ ) {
 511           if( in(j) && in(j)->in(0) == iff &&
 512               if1->Opcode() != in(j)->Opcode() ) {
 513             // Add the IF Projections to the worklist. They (and the IF itself)
 514             // will be eliminated if dead.
 515             phase->is_IterGVN()->add_users_to_worklist(iff);
 516             set_req(i, iff->in(0));// Skip around the useless IF diamond
 517             set_req(j, NULL);
 518             return this;      // Record progress
 519           }
 520         }
 521       }
 522     }
 523   }
 524 
 525   // Remove TOP or NULL input paths. If only 1 input path remains, this Region
 526   // degrades to a copy.
 527   bool add_to_worklist = true;
 528   bool modified = false;
 529   int cnt = 0;                  // Count of values merging
 530   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 531   int del_it = 0;               // The last input path we delete
 532   // For all inputs...
 533   for( uint i=1; i<req(); ++i ){// For all paths in
 534     Node *n = in(i);            // Get the input
 535     if( n != NULL ) {
 536       // Remove useless control copy inputs
 537       if( n->is_Region() && n->as_Region()->is_copy() ) {
 538         set_req(i, n->nonnull_req());
 539         modified = true;
 540         i--;
 541         continue;
 542       }
 543       if( n->is_Proj() ) {      // Remove useless rethrows
 544         Node *call = n->in(0);
 545         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 546           set_req(i, call->in(0));
 547           modified = true;
 548           i--;
 549           continue;
 550         }
 551       }
 552       if( phase->type(n) == Type::TOP ) {
 553         set_req_X(i, NULL, phase); // Ignore TOP inputs
 554         modified = true;
 555         i--;
 556         continue;
 557       }
 558       cnt++;                    // One more value merging
 559 
 560     } else if (can_reshape) {   // Else found dead path with DU info
 561       PhaseIterGVN *igvn = phase->is_IterGVN();
 562       del_req(i);               // Yank path from self
 563       del_it = i;
 564       uint max = outcnt();
 565       DUIterator j;
 566       bool progress = true;
 567       while(progress) {         // Need to establish property over all users
 568         progress = false;
 569         for (j = outs(); has_out(j); j++) {
 570           Node *n = out(j);
 571           if( n->req() != req() && n->is_Phi() ) {
 572             assert( n->in(0) == this, "" );
 573             igvn->hash_delete(n); // Yank from hash before hacking edges
 574             n->set_req_X(i,NULL,igvn);// Correct DU info
 575             n->del_req(i);        // Yank path from Phis
 576             if( max != outcnt() ) {
 577               progress = true;
 578               j = refresh_out_pos(j);
 579               max = outcnt();
 580             }
 581           }
 582         }
 583       }
 584       add_to_worklist = false;
 585       phase->is_IterGVN()->add_users_to_worklist(this);
 586       i--;
 587     }
 588   }
 589 
 590   if (can_reshape && cnt == 1) {
 591     // Is it dead loop?
 592     // If it is LoopNopde it had 2 (+1 itself) inputs and
 593     // one of them was cut. The loop is dead if it was EntryContol.
 594     // Loop node may have only one input because entry path
 595     // is removed in PhaseIdealLoop::Dominators().
 596     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 597     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 598                              (del_it == 0 && is_unreachable_region(phase)))) ||
 599         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 600       // This region and therefore all nodes on the input control path(s) are unreachable
 601       // from root. To avoid incomplete removal of unreachable subgraphs, walk up the CFG
 602       // and aggressively replace all nodes by top.
 603       PhaseIterGVN* igvn = phase->is_IterGVN();
 604       Node* top = phase->C->top();
 605       ResourceMark rm;
 606       Node_List nstack;
 607       VectorSet visited;
 608       nstack.push(this);
 609       visited.set(_idx);
 610       while (nstack.size() != 0) {
 611         Node* n = nstack.pop();
 612         for (uint i = 0; i < n->req(); ++i) {
 613           Node* m = n->in(i);
 614           assert(m != (Node*)phase->C->root(), "Should be unreachable from root");
 615           if (m != NULL && m->is_CFG() && !visited.test_set(m->_idx)) {
 616             nstack.push(m);
 617           }
 618         }
 619         if (n->is_Region()) {
 620           // Eagerly replace phis with top to avoid regionless phis.
 621           n->set_req(0, NULL);
 622           bool progress = true;
 623           uint max = n->outcnt();
 624           DUIterator j;
 625           while (progress) {
 626             progress = false;
 627             for (j = n->outs(); n->has_out(j); j++) {
 628               Node* u = n->out(j);
 629               if (u->is_Phi()) {
 630                 igvn->replace_node(u, top);
 631                 if (max != n->outcnt()) {
 632                   progress = true;
 633                   j = n->refresh_out_pos(j);
 634                   max = n->outcnt();
 635                 }
 636               }
 637             }
 638           }
 639         }
 640         igvn->replace_node(n, top);
 641       }
 642       return NULL;
 643     }
 644   }
 645 
 646   if( cnt <= 1 ) {              // Only 1 path in?
 647     set_req(0, NULL);           // Null control input for region copy
 648     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 649       // No inputs or all inputs are NULL.
 650       return NULL;
 651     } else if (can_reshape) {   // Optimization phase - remove the node
 652       PhaseIterGVN *igvn = phase->is_IterGVN();
 653       // Strip mined (inner) loop is going away, remove outer loop.
 654       if (is_CountedLoop() &&
 655           as_Loop()->is_strip_mined()) {
 656         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 657         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 658         if (outer_sfpt != NULL && outer_out != NULL) {
 659           Node* in = outer_sfpt->in(0);
 660           igvn->replace_node(outer_out, in);
 661           LoopNode* outer = as_CountedLoop()->outer_loop();
 662           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 663         }
 664       }
 665       if (is_CountedLoop()) {
 666         Node* opaq = as_CountedLoop()->is_canonical_loop_entry();
 667         if (opaq != NULL) {
 668           // This is not a loop anymore. No need to keep the Opaque1 node on the test that guards the loop as it won't be
 669           // subject to further loop opts.
 670           assert(opaq->Opcode() == Op_OpaqueZeroTripGuard, "");
 671           igvn->replace_node(opaq, opaq->in(1));
 672         }
 673       }
 674       Node *parent_ctrl;
 675       if( cnt == 0 ) {
 676         assert( req() == 1, "no inputs expected" );
 677         // During IGVN phase such region will be subsumed by TOP node
 678         // so region's phis will have TOP as control node.
 679         // Kill phis here to avoid it.
 680         // Also set other user's input to top.
 681         parent_ctrl = phase->C->top();
 682       } else {
 683         // The fallthrough case since we already checked dead loops above.
 684         parent_ctrl = in(1);
 685         assert(parent_ctrl != NULL, "Region is a copy of some non-null control");
 686         assert(parent_ctrl != this, "Close dead loop");
 687       }
 688       if (add_to_worklist) {
 689         igvn->add_users_to_worklist(this); // Check for further allowed opts
 690       }
 691       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 692         Node* n = last_out(i);
 693         igvn->hash_delete(n); // Remove from worklist before modifying edges
 694         if (n->outcnt() == 0) {
 695           int uses_found = n->replace_edge(this, phase->C->top(), igvn);
 696           if (uses_found > 1) { // (--i) done at the end of the loop.
 697             i -= (uses_found - 1);
 698           }
 699           continue;
 700         }
 701         if( n->is_Phi() ) {   // Collapse all Phis
 702           // Eagerly replace phis to avoid regionless phis.
 703           Node* in;
 704           if( cnt == 0 ) {
 705             assert( n->req() == 1, "No data inputs expected" );
 706             in = parent_ctrl; // replaced by top
 707           } else {
 708             assert( n->req() == 2 &&  n->in(1) != NULL, "Only one data input expected" );
 709             in = n->in(1);               // replaced by unique input
 710             if( n->as_Phi()->is_unsafe_data_reference(in) )
 711               in = phase->C->top();      // replaced by top
 712           }
 713           igvn->replace_node(n, in);
 714         }
 715         else if( n->is_Region() ) { // Update all incoming edges
 716           assert(n != this, "Must be removed from DefUse edges");
 717           int uses_found = n->replace_edge(this, parent_ctrl, igvn);
 718           if (uses_found > 1) { // (--i) done at the end of the loop.
 719             i -= (uses_found - 1);
 720           }
 721         }
 722         else {
 723           assert(n->in(0) == this, "Expect RegionNode to be control parent");
 724           n->set_req(0, parent_ctrl);
 725         }
 726 #ifdef ASSERT
 727         for( uint k=0; k < n->req(); k++ ) {
 728           assert(n->in(k) != this, "All uses of RegionNode should be gone");
 729         }
 730 #endif
 731       }
 732       // Remove the RegionNode itself from DefUse info
 733       igvn->remove_dead_node(this);
 734       return NULL;
 735     }
 736     return this;                // Record progress
 737   }
 738 
 739 
 740   // If a Region flows into a Region, merge into one big happy merge.
 741   if (can_reshape) {
 742     Node *m = merge_region(this, phase);
 743     if (m != NULL)  return m;
 744   }
 745 
 746   // Check if this region is the root of a clipping idiom on floats
 747   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 748     // Check that only one use is a Phi and that it simplifies to two constants +
 749     PhiNode* phi = has_unique_phi();
 750     if (phi != NULL) {          // One Phi user
 751       // Check inputs to the Phi
 752       ConNode *min;
 753       ConNode *max;
 754       Node    *val;
 755       uint     min_idx;
 756       uint     max_idx;
 757       uint     val_idx;
 758       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 759         IfNode *top_if;
 760         IfNode *bot_if;
 761         if( check_if_clipping( this, bot_if, top_if ) ) {
 762           // Control pattern checks, now verify compares
 763           Node   *top_in = NULL;   // value being compared against
 764           Node   *bot_in = NULL;
 765           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 766               check_compare_clipping( false, top_if, max, top_in ) ) {
 767             if( bot_in == top_in ) {
 768               PhaseIterGVN *gvn = phase->is_IterGVN();
 769               assert( gvn != NULL, "Only had DefUse info in IterGVN");
 770               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 771 
 772               // Check for the ConvF2INode
 773               ConvF2INode *convf2i;
 774               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 775                 convf2i->in(1) == bot_in ) {
 776                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 777                 // max test
 778                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 779                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 780                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 781                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 782                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 783                 // min test
 784                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 785                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 786                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 787                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 788                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 789                 // update input edges to region node
 790                 set_req_X( min_idx, if_min, gvn );
 791                 set_req_X( max_idx, if_max, gvn );
 792                 set_req_X( val_idx, ifF,    gvn );
 793                 // remove unnecessary 'LShiftI; RShiftI' idiom
 794                 gvn->hash_delete(phi);
 795                 phi->set_req_X( val_idx, convf2i, gvn );
 796                 gvn->hash_find_insert(phi);
 797                 // Return transformed region node
 798                 return this;
 799               }
 800             }
 801           }
 802         }
 803       }
 804     }
 805   }
 806 
 807   if (can_reshape) {
 808     modified |= optimize_trichotomy(phase->is_IterGVN());
 809   }
 810 
 811   return modified ? this : NULL;
 812 }
 813 
 814 //------------------------------optimize_trichotomy--------------------------
 815 // Optimize nested comparisons of the following kind:
 816 //
 817 // int compare(int a, int b) {
 818 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 819 // }
 820 //
 821 // Shape 1:
 822 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 823 //
 824 // Shape 2:
 825 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 826 //
 827 // Above code leads to the following IR shapes where both Ifs compare the
 828 // same value and two out of three region inputs idx1 and idx2 map to
 829 // the same value and control flow.
 830 //
 831 // (1)   If                 (2)   If
 832 //      /  \                     /  \
 833 //   Proj  Proj               Proj  Proj
 834 //     |      \                |      \
 835 //     |       If              |      If                      If
 836 //     |      /  \             |     /  \                    /  \
 837 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 838 //     |   /      /            \    |    /                  |    /
 839 //    Region     /              \   |   /                   |   /
 840 //         \    /                \  |  /                    |  /
 841 //         Region                Region                    Region
 842 //
 843 // The method returns true if 'this' is modified and false otherwise.
 844 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 845   int idx1 = 1, idx2 = 2;
 846   Node* region = NULL;
 847   if (req() == 3 && in(1) != NULL && in(2) != NULL) {
 848     // Shape 1: Check if one of the inputs is a region that merges two control
 849     // inputs and has no other users (especially no Phi users).
 850     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 851     if (region == NULL || region->outcnt() != 2 || region->req() != 3) {
 852       return false; // No suitable region input found
 853     }
 854   } else if (req() == 4) {
 855     // Shape 2: Check if two control inputs map to the same value of the unique phi
 856     // user and treat these as if they would come from another region (shape (1)).
 857     PhiNode* phi = has_unique_phi();
 858     if (phi == NULL) {
 859       return false; // No unique phi user
 860     }
 861     if (phi->in(idx1) != phi->in(idx2)) {
 862       idx2 = 3;
 863       if (phi->in(idx1) != phi->in(idx2)) {
 864         idx1 = 2;
 865         if (phi->in(idx1) != phi->in(idx2)) {
 866           return false; // No equal phi inputs found
 867         }
 868       }
 869     }
 870     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 871     region = this;
 872   }
 873   if (region == NULL || region->in(idx1) == NULL || region->in(idx2) == NULL) {
 874     return false; // Region does not merge two control inputs
 875   }
 876   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 877   // value and control flow. Now search for ifs that feed into these region inputs.
 878   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 879   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 880   if (proj1 == NULL || proj1->outcnt() != 1 ||
 881       proj2 == NULL || proj2->outcnt() != 1) {
 882     return false; // No projection inputs with region as unique user found
 883   }
 884   assert(proj1 != proj2, "should be different projections");
 885   IfNode* iff1 = proj1->in(0)->isa_If();
 886   IfNode* iff2 = proj2->in(0)->isa_If();
 887   if (iff1 == NULL || iff1->outcnt() != 2 ||
 888       iff2 == NULL || iff2->outcnt() != 2) {
 889     return false; // No ifs found
 890   }
 891   if (iff1 == iff2) {
 892     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 893     igvn->replace_input_of(region, idx1, iff1->in(0));
 894     igvn->replace_input_of(region, idx2, igvn->C->top());
 895     return (region == this); // Remove useless if (both projections map to the same control/value)
 896   }
 897   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 898   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 899   if (bol1 == NULL || bol2 == NULL) {
 900     return false; // No bool inputs found
 901   }
 902   Node* cmp1 = bol1->in(1);
 903   Node* cmp2 = bol2->in(1);
 904   bool commute = false;
 905   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 906     return false; // No comparison
 907   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 908              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 909              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 910              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN ||
 911              cmp1->is_SubTypeCheck() || cmp2->is_SubTypeCheck() ||
 912              cmp1->is_FlatArrayCheck() || cmp2->is_FlatArrayCheck()) {
 913     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 914     // SubTypeCheck is not commutative
 915     return false;
 916   } else if (cmp1 != cmp2) {
 917     if (cmp1->in(1) == cmp2->in(2) &&
 918         cmp1->in(2) == cmp2->in(1)) {
 919       commute = true; // Same but swapped inputs, commute the test
 920     } else {
 921       return false; // Ifs are not comparing the same values
 922     }
 923   }
 924   proj1 = proj1->other_if_proj();
 925   proj2 = proj2->other_if_proj();
 926   if (!((proj1->unique_ctrl_out_or_null() == iff2 &&
 927          proj2->unique_ctrl_out_or_null() == this) ||
 928         (proj2->unique_ctrl_out_or_null() == iff1 &&
 929          proj1->unique_ctrl_out_or_null() == this))) {
 930     return false; // Ifs are not connected through other projs
 931   }
 932   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 933   // through 'region' and map to the same value. Merge the boolean tests and replace
 934   // the ifs by a single comparison.
 935   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 936   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 937   test1 = commute ? test1.commute() : test1;
 938   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 939   BoolTest::mask res = test1.merge(test2);
 940   if (res == BoolTest::illegal) {
 941     return false; // Unable to merge tests
 942   }
 943   // Adjust iff1 to always pass (only iff2 will remain)
 944   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
 945   if (res == BoolTest::never) {
 946     // Merged test is always false, adjust iff2 to always fail
 947     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
 948   } else {
 949     // Replace bool input of iff2 with merged test
 950     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
 951     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
 952     if (new_bol->outcnt() == 0) {
 953       igvn->remove_dead_node(new_bol);
 954     }
 955   }
 956   return false;
 957 }
 958 
 959 const RegMask &RegionNode::out_RegMask() const {
 960   return RegMask::Empty;
 961 }
 962 
 963 // Find the one non-null required input.  RegionNode only
 964 Node *Node::nonnull_req() const {
 965   assert( is_Region(), "" );
 966   for( uint i = 1; i < _cnt; i++ )
 967     if( in(i) )
 968       return in(i);
 969   ShouldNotReachHere();
 970   return NULL;
 971 }
 972 
 973 
 974 //=============================================================================
 975 // note that these functions assume that the _adr_type field is flattened
 976 uint PhiNode::hash() const {
 977   const Type* at = _adr_type;
 978   return TypeNode::hash() + (at ? at->hash() : 0);
 979 }
 980 bool PhiNode::cmp( const Node &n ) const {
 981   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
 982 }
 983 static inline
 984 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
 985   if (at == NULL || at == TypePtr::BOTTOM)  return at;
 986   return Compile::current()->alias_type(at)->adr_type();
 987 }
 988 
 989 //----------------------------make---------------------------------------------
 990 // create a new phi with edges matching r and set (initially) to x
 991 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
 992   uint preds = r->req();   // Number of predecessor paths
 993   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at) || (flatten_phi_adr_type(at) == TypeAryPtr::INLINES && Compile::current()->flattened_accesses_share_alias()), "flatten at");
 994   PhiNode* p = new PhiNode(r, t, at);
 995   for (uint j = 1; j < preds; j++) {
 996     // Fill in all inputs, except those which the region does not yet have
 997     if (r->in(j) != NULL)
 998       p->init_req(j, x);
 999   }
1000   return p;
1001 }
1002 PhiNode* PhiNode::make(Node* r, Node* x) {
1003   const Type*    t  = x->bottom_type();
1004   const TypePtr* at = NULL;
1005   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
1006   return make(r, x, t, at);
1007 }
1008 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
1009   const Type*    t  = x->bottom_type();
1010   const TypePtr* at = NULL;
1011   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
1012   return new PhiNode(r, t, at);
1013 }
1014 
1015 
1016 //------------------------slice_memory-----------------------------------------
1017 // create a new phi with narrowed memory type
1018 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
1019   PhiNode* mem = (PhiNode*) clone();
1020   *(const TypePtr**)&mem->_adr_type = adr_type;
1021   // convert self-loops, or else we get a bad graph
1022   for (uint i = 1; i < req(); i++) {
1023     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
1024   }
1025   mem->verify_adr_type();
1026   return mem;
1027 }
1028 
1029 //------------------------split_out_instance-----------------------------------
1030 // Split out an instance type from a bottom phi.
1031 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
1032   const TypeOopPtr *t_oop = at->isa_oopptr();
1033   assert(t_oop != NULL && t_oop->is_known_instance(), "expecting instance oopptr");
1034 
1035   // Check if an appropriate node already exists.
1036   Node *region = in(0);
1037   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
1038     Node* use = region->fast_out(k);
1039     if( use->is_Phi()) {
1040       PhiNode *phi2 = use->as_Phi();
1041       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
1042         return phi2;
1043       }
1044     }
1045   }
1046   Compile *C = igvn->C;
1047   Arena *a = Thread::current()->resource_area();
1048   Node_Array node_map = new Node_Array(a);
1049   Node_Stack stack(a, C->live_nodes() >> 4);
1050   PhiNode *nphi = slice_memory(at);
1051   igvn->register_new_node_with_optimizer( nphi );
1052   node_map.map(_idx, nphi);
1053   stack.push((Node *)this, 1);
1054   while(!stack.is_empty()) {
1055     PhiNode *ophi = stack.node()->as_Phi();
1056     uint i = stack.index();
1057     assert(i >= 1, "not control edge");
1058     stack.pop();
1059     nphi = node_map[ophi->_idx]->as_Phi();
1060     for (; i < ophi->req(); i++) {
1061       Node *in = ophi->in(i);
1062       if (in == NULL || igvn->type(in) == Type::TOP)
1063         continue;
1064       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, NULL, igvn);
1065       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : NULL;
1066       if (optphi != NULL && optphi->adr_type() == TypePtr::BOTTOM) {
1067         opt = node_map[optphi->_idx];
1068         if (opt == NULL) {
1069           stack.push(ophi, i);
1070           nphi = optphi->slice_memory(at);
1071           igvn->register_new_node_with_optimizer( nphi );
1072           node_map.map(optphi->_idx, nphi);
1073           ophi = optphi;
1074           i = 0; // will get incremented at top of loop
1075           continue;
1076         }
1077       }
1078       nphi->set_req(i, opt);
1079     }
1080   }
1081   return nphi;
1082 }
1083 
1084 //------------------------verify_adr_type--------------------------------------
1085 #ifdef ASSERT
1086 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1087   if (visited.test_set(_idx))  return;  //already visited
1088 
1089   // recheck constructor invariants:
1090   verify_adr_type(false);
1091 
1092   // recheck local phi/phi consistency:
1093   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1094          "adr_type must be consistent across phi nest");
1095 
1096   // walk around
1097   for (uint i = 1; i < req(); i++) {
1098     Node* n = in(i);
1099     if (n == NULL)  continue;
1100     const Node* np = in(i);
1101     if (np->is_Phi()) {
1102       np->as_Phi()->verify_adr_type(visited, at);
1103     } else if (n->bottom_type() == Type::TOP
1104                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1105       // ignore top inputs
1106     } else {
1107       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1108       // recheck phi/non-phi consistency at leaves:
1109       assert((nat != NULL) == (at != NULL), "");
1110       assert(nat == at || nat == TypePtr::BOTTOM,
1111              "adr_type must be consistent at leaves of phi nest");
1112     }
1113   }
1114 }
1115 
1116 // Verify a whole nest of phis rooted at this one.
1117 void PhiNode::verify_adr_type(bool recursive) const {
1118   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1119   if (Node::in_dump())               return;  // muzzle asserts when printing
1120 
1121   assert((_type == Type::MEMORY) == (_adr_type != NULL), "adr_type for memory phis only");
1122   // Flat array element shouldn't get their own memory slice until flattened_accesses_share_alias is cleared.
1123   // It could be the graph has no loads/stores and flattened_accesses_share_alias is never cleared. EA could still
1124   // creates per element Phis but that wouldn't be a problem as there are no memory accesses for that array.
1125   assert(_adr_type == NULL || _adr_type->isa_aryptr() == NULL ||
1126          _adr_type->is_aryptr()->is_known_instance() ||
1127          !_adr_type->is_aryptr()->is_flat() ||
1128          !Compile::current()->flattened_accesses_share_alias() ||
1129          _adr_type == TypeAryPtr::INLINES, "flat array element shouldn't get its own slice yet");
1130 
1131   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1132 
1133   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1134          "Phi::adr_type must be pre-normalized");
1135 
1136   if (recursive) {
1137     VectorSet visited;
1138     verify_adr_type(visited, _adr_type);
1139   }
1140 }
1141 #endif
1142 
1143 
1144 //------------------------------Value------------------------------------------
1145 // Compute the type of the PhiNode
1146 const Type* PhiNode::Value(PhaseGVN* phase) const {
1147   Node *r = in(0);              // RegionNode
1148   if( !r )                      // Copy or dead
1149     return in(1) ? phase->type(in(1)) : Type::TOP;
1150 
1151   // Note: During parsing, phis are often transformed before their regions.
1152   // This means we have to use type_or_null to defend against untyped regions.
1153   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1154     return Type::TOP;
1155 
1156   // Check for trip-counted loop.  If so, be smarter.
1157   BaseCountedLoopNode* l = r->is_BaseCountedLoop() ? r->as_BaseCountedLoop() : NULL;
1158   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1159     // protect against init_trip() or limit() returning NULL
1160     if (l->can_be_counted_loop(phase)) {
1161       const Node* init = l->init_trip();
1162       const Node* limit = l->limit();
1163       const Node* stride = l->stride();
1164       if (init != NULL && limit != NULL && stride != NULL) {
1165         const TypeInteger* lo = phase->type(init)->isa_integer(l->bt());
1166         const TypeInteger* hi = phase->type(limit)->isa_integer(l->bt());
1167         const TypeInteger* stride_t = phase->type(stride)->isa_integer(l->bt());
1168         if (lo != NULL && hi != NULL && stride_t != NULL) { // Dying loops might have TOP here
1169           assert(stride_t->is_con(), "bad stride type");
1170           BoolTest::mask bt = l->loopexit()->test_trip();
1171           // If the loop exit condition is "not equal", the condition
1172           // would not trigger if init > limit (if stride > 0) or if
1173           // init < limit if (stride > 0) so we can't deduce bounds
1174           // for the iv from the exit condition.
1175           if (bt != BoolTest::ne) {
1176             jlong stride_con = stride_t->get_con_as_long(l->bt());
1177             if (stride_con < 0) {          // Down-counter loop
1178               swap(lo, hi);
1179               jlong iv_range_lower_limit = lo->lo_as_long();
1180               // Prevent overflow when adding one below
1181               if (iv_range_lower_limit < max_signed_integer(l->bt())) {
1182                 // The loop exit condition is: iv + stride > limit (iv is this Phi). So the loop iterates until
1183                 // iv + stride <= limit
1184                 // We know that: limit >= lo->lo_as_long() and stride <= -1
1185                 // So when the loop exits, iv has to be at most lo->lo_as_long() + 1
1186                 iv_range_lower_limit += 1; // lo is after decrement
1187                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1188                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != -1) {
1189                   julong uhi = static_cast<julong>(hi->lo_as_long());
1190                   julong ulo = static_cast<julong>(lo->hi_as_long());
1191                   julong diff = ((uhi - ulo - 1) / (-stride_con)) * (-stride_con);
1192                   julong ufirst = hi->lo_as_long() - diff;
1193                   iv_range_lower_limit = reinterpret_cast<jlong &>(ufirst);
1194                   assert(iv_range_lower_limit >= lo->lo_as_long() + 1, "should end up with narrower range");
1195                 }
1196               }
1197               return TypeInteger::make(MIN2(iv_range_lower_limit, hi->lo_as_long()), hi->hi_as_long(), 3, l->bt())->filter_speculative(_type);
1198             } else if (stride_con >= 0) {
1199               jlong iv_range_upper_limit = hi->hi_as_long();
1200               // Prevent overflow when subtracting one below
1201               if (iv_range_upper_limit > min_signed_integer(l->bt())) {
1202                 // The loop exit condition is: iv + stride < limit (iv is this Phi). So the loop iterates until
1203                 // iv + stride >= limit
1204                 // We know that: limit <= hi->hi_as_long() and stride >= 1
1205                 // So when the loop exits, iv has to be at most hi->hi_as_long() - 1
1206                 iv_range_upper_limit -= 1;
1207                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1208                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != 1) {
1209                   julong uhi = static_cast<julong>(hi->lo_as_long());
1210                   julong ulo = static_cast<julong>(lo->hi_as_long());
1211                   julong diff = ((uhi - ulo - 1) / stride_con) * stride_con;
1212                   julong ulast = lo->hi_as_long() + diff;
1213                   iv_range_upper_limit = reinterpret_cast<jlong &>(ulast);
1214                   assert(iv_range_upper_limit <= hi->hi_as_long() - 1, "should end up with narrower range");
1215                 }
1216               }
1217               return TypeInteger::make(lo->lo_as_long(), MAX2(lo->hi_as_long(), iv_range_upper_limit), 3, l->bt())->filter_speculative(_type);
1218             }
1219           }
1220         }
1221       }
1222     } else if (l->in(LoopNode::LoopBackControl) != NULL &&
1223                in(LoopNode::EntryControl) != NULL &&
1224                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1225       // During CCP, if we saturate the type of a counted loop's Phi
1226       // before the special code for counted loop above has a chance
1227       // to run (that is as long as the type of the backedge's control
1228       // is top), we might end up with non monotonic types
1229       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1230     }
1231   }
1232 
1233   // Default case: merge all inputs
1234   const Type *t = Type::TOP;        // Merged type starting value
1235   for (uint i = 1; i < req(); ++i) {// For all paths in
1236     // Reachable control path?
1237     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1238       const Type* ti = phase->type(in(i));
1239       t = t->meet_speculative(ti);
1240     }
1241   }
1242 
1243   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1244   // That is, we expect that "t->higher_equal(_type)" holds true.
1245   // There are various exceptions:
1246   // - Inputs which are phis might in fact be widened unnecessarily.
1247   //   For example, an input might be a widened int while the phi is a short.
1248   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1249   //   and postCCP has removed the cast which encodes the result of the check.
1250   // - The type of this phi is an interface, and the inputs are classes.
1251   // - Value calls on inputs might produce fuzzy results.
1252   //   (Occurrences of this case suggest improvements to Value methods.)
1253   //
1254   // It is not possible to see Type::BOTTOM values as phi inputs,
1255   // because the ciTypeFlow pre-pass produces verifier-quality types.
1256   const Type* ft = t->filter_speculative(_type);  // Worst case type
1257 
1258 #ifdef ASSERT
1259   // The following logic has been moved into TypeOopPtr::filter.
1260   const Type* jt = t->join_speculative(_type);
1261   if (jt->empty()) {           // Emptied out???
1262     // Otherwise it's something stupid like non-overlapping int ranges
1263     // found on dying counted loops.
1264     assert(ft == Type::TOP, ""); // Canonical empty value
1265   }
1266 
1267   else {
1268 
1269     if (jt != ft && jt->base() == ft->base()) {
1270       if (jt->isa_int() &&
1271           jt->is_int()->_lo == ft->is_int()->_lo &&
1272           jt->is_int()->_hi == ft->is_int()->_hi)
1273         jt = ft;
1274       if (jt->isa_long() &&
1275           jt->is_long()->_lo == ft->is_long()->_lo &&
1276           jt->is_long()->_hi == ft->is_long()->_hi)
1277         jt = ft;
1278     }
1279     if (jt != ft) {
1280       tty->print("merge type:  "); t->dump(); tty->cr();
1281       tty->print("kill type:   "); _type->dump(); tty->cr();
1282       tty->print("join type:   "); jt->dump(); tty->cr();
1283       tty->print("filter type: "); ft->dump(); tty->cr();
1284     }
1285     assert(jt == ft, "");
1286   }
1287 #endif //ASSERT
1288 
1289   // Deal with conversion problems found in data loops.
1290   ft = phase->saturate(ft, phase->type_or_null(this), _type);
1291 
1292   return ft;
1293 }
1294 
1295 
1296 //------------------------------is_diamond_phi---------------------------------
1297 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1298 // index of the true path or 0 otherwise.
1299 // If check_control_only is true, do not inspect the If node at the
1300 // top, and return -1 (not an edge number) on success.
1301 int PhiNode::is_diamond_phi(bool check_control_only) const {
1302   // Check for a 2-path merge
1303   Node *region = in(0);
1304   if( !region ) return 0;
1305   if( region->req() != 3 ) return 0;
1306   if(         req() != 3 ) return 0;
1307   // Check that both paths come from the same If
1308   Node *ifp1 = region->in(1);
1309   Node *ifp2 = region->in(2);
1310   if( !ifp1 || !ifp2 ) return 0;
1311   Node *iff = ifp1->in(0);
1312   if( !iff || !iff->is_If() ) return 0;
1313   if( iff != ifp2->in(0) ) return 0;
1314   if (check_control_only)  return -1;
1315   // Check for a proper bool/cmp
1316   const Node *b = iff->in(1);
1317   if( !b->is_Bool() ) return 0;
1318   const Node *cmp = b->in(1);
1319   if( !cmp->is_Cmp() ) return 0;
1320 
1321   // Check for branching opposite expected
1322   if( ifp2->Opcode() == Op_IfTrue ) {
1323     assert( ifp1->Opcode() == Op_IfFalse, "" );
1324     return 2;
1325   } else {
1326     assert( ifp1->Opcode() == Op_IfTrue, "" );
1327     return 1;
1328   }
1329 }
1330 
1331 //----------------------------check_cmove_id-----------------------------------
1332 // Check for CMove'ing a constant after comparing against the constant.
1333 // Happens all the time now, since if we compare equality vs a constant in
1334 // the parser, we "know" the variable is constant on one path and we force
1335 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1336 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1337 // general in that we don't need constants.  Since CMove's are only inserted
1338 // in very special circumstances, we do it here on generic Phi's.
1339 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1340   assert(true_path !=0, "only diamond shape graph expected");
1341 
1342   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1343   // phi->region->if_proj->ifnode->bool->cmp
1344   Node*     region = in(0);
1345   Node*     iff    = region->in(1)->in(0);
1346   BoolNode* b      = iff->in(1)->as_Bool();
1347   Node*     cmp    = b->in(1);
1348   Node*     tval   = in(true_path);
1349   Node*     fval   = in(3-true_path);
1350   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1351   if (id == NULL)
1352     return NULL;
1353 
1354   // Either value might be a cast that depends on a branch of 'iff'.
1355   // Since the 'id' value will float free of the diamond, either
1356   // decast or return failure.
1357   Node* ctl = id->in(0);
1358   if (ctl != NULL && ctl->in(0) == iff) {
1359     if (id->is_ConstraintCast()) {
1360       return id->in(1);
1361     } else {
1362       // Don't know how to disentangle this value.
1363       return NULL;
1364     }
1365   }
1366 
1367   return id;
1368 }
1369 
1370 //------------------------------Identity---------------------------------------
1371 // Check for Region being Identity.
1372 Node* PhiNode::Identity(PhaseGVN* phase) {
1373   // Check for no merging going on
1374   // (There used to be special-case code here when this->region->is_Loop.
1375   // It would check for a tributary phi on the backedge that the main phi
1376   // trivially, perhaps with a single cast.  The unique_input method
1377   // does all this and more, by reducing such tributaries to 'this'.)
1378   Node* uin = unique_input(phase, false);
1379   if (uin != NULL) {
1380     return uin;
1381   }
1382 
1383   int true_path = is_diamond_phi();
1384   // Delay CMove'ing identity if Ideal has not had the chance to handle unsafe cases, yet.
1385   if (true_path != 0 && !(phase->is_IterGVN() && wait_for_region_igvn(phase))) {
1386     Node* id = is_cmove_id(phase, true_path);
1387     if (id != NULL) {
1388       return id;
1389     }
1390   }
1391 
1392   if (phase->is_IterGVN()) {
1393     Node* m = try_clean_mem_phi(phase);
1394     if (m != NULL) {
1395       return m;
1396     }
1397   }
1398 
1399 
1400   // Looking for phis with identical inputs.  If we find one that has
1401   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1402   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1403       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1404     uint phi_len = req();
1405     Node* phi_reg = region();
1406     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1407       Node* u = phi_reg->fast_out(i);
1408       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1409           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1410           u->req() == phi_len) {
1411         for (uint j = 1; j < phi_len; j++) {
1412           if (in(j) != u->in(j)) {
1413             u = NULL;
1414             break;
1415           }
1416         }
1417         if (u != NULL) {
1418           return u;
1419         }
1420       }
1421     }
1422   }
1423 
1424   return this;                     // No identity
1425 }
1426 
1427 //-----------------------------unique_input------------------------------------
1428 // Find the unique value, discounting top, self-loops, and casts.
1429 // Return top if there are no inputs, and self if there are multiple.
1430 Node* PhiNode::unique_input(PhaseTransform* phase, bool uncast) {
1431   //  1) One unique direct input,
1432   // or if uncast is true:
1433   //  2) some of the inputs have an intervening ConstraintCast
1434   //  3) an input is a self loop
1435   //
1436   //  1) input   or   2) input     or   3) input __
1437   //     /   \           /   \               \  /  \
1438   //     \   /          |    cast             phi  cast
1439   //      phi            \   /               /  \  /
1440   //                      phi               /    --
1441 
1442   Node* r = in(0);                      // RegionNode
1443   Node* input = NULL; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1444 
1445   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1446     Node* rc = r->in(i);
1447     if (rc == NULL || phase->type(rc) == Type::TOP)
1448       continue;                 // ignore unreachable control path
1449     Node* n = in(i);
1450     if (n == NULL)
1451       continue;
1452     Node* un = n;
1453     if (uncast) {
1454 #ifdef ASSERT
1455       Node* m = un->uncast();
1456 #endif
1457       while (un != NULL && un->req() == 2 && un->is_ConstraintCast()) {
1458         Node* next = un->in(1);
1459         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1460           // risk exposing raw ptr at safepoint
1461           break;
1462         }
1463         un = next;
1464       }
1465       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1466     }
1467     if (un == NULL || un == this || phase->type(un) == Type::TOP) {
1468       continue; // ignore if top, or in(i) and "this" are in a data cycle
1469     }
1470     // Check for a unique input (maybe uncasted)
1471     if (input == NULL) {
1472       input = un;
1473     } else if (input != un) {
1474       input = NodeSentinel; // no unique input
1475     }
1476   }
1477   if (input == NULL) {
1478     return phase->C->top();        // no inputs
1479   }
1480 
1481   if (input != NodeSentinel) {
1482     return input;           // one unique direct input
1483   }
1484 
1485   // Nothing.
1486   return NULL;
1487 }
1488 
1489 //------------------------------is_x2logic-------------------------------------
1490 // Check for simple convert-to-boolean pattern
1491 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1492 // Convert Phi to an ConvIB.
1493 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1494   assert(true_path !=0, "only diamond shape graph expected");
1495   // Convert the true/false index into an expected 0/1 return.
1496   // Map 2->0 and 1->1.
1497   int flipped = 2-true_path;
1498 
1499   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1500   // phi->region->if_proj->ifnode->bool->cmp
1501   Node *region = phi->in(0);
1502   Node *iff = region->in(1)->in(0);
1503   BoolNode *b = (BoolNode*)iff->in(1);
1504   const CmpNode *cmp = (CmpNode*)b->in(1);
1505 
1506   Node *zero = phi->in(1);
1507   Node *one  = phi->in(2);
1508   const Type *tzero = phase->type( zero );
1509   const Type *tone  = phase->type( one  );
1510 
1511   // Check for compare vs 0
1512   const Type *tcmp = phase->type(cmp->in(2));
1513   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1514     // Allow cmp-vs-1 if the other input is bounded by 0-1
1515     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1516       return NULL;
1517     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1518   }
1519 
1520   // Check for setting zero/one opposite expected
1521   if( tzero == TypeInt::ZERO ) {
1522     if( tone == TypeInt::ONE ) {
1523     } else return NULL;
1524   } else if( tzero == TypeInt::ONE ) {
1525     if( tone == TypeInt::ZERO ) {
1526       flipped = 1-flipped;
1527     } else return NULL;
1528   } else return NULL;
1529 
1530   // Check for boolean test backwards
1531   if( b->_test._test == BoolTest::ne ) {
1532   } else if( b->_test._test == BoolTest::eq ) {
1533     flipped = 1-flipped;
1534   } else return NULL;
1535 
1536   // Build int->bool conversion
1537   Node *n = new Conv2BNode(cmp->in(1));
1538   if( flipped )
1539     n = new XorINode( phase->transform(n), phase->intcon(1) );
1540 
1541   return n;
1542 }
1543 
1544 //------------------------------is_cond_add------------------------------------
1545 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1546 // To be profitable the control flow has to disappear; there can be no other
1547 // values merging here.  We replace the test-and-branch with:
1548 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1549 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1550 // Then convert Y to 0-or-Y and finally add.
1551 // This is a key transform for SpecJava _201_compress.
1552 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1553   assert(true_path !=0, "only diamond shape graph expected");
1554 
1555   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1556   // phi->region->if_proj->ifnode->bool->cmp
1557   RegionNode *region = (RegionNode*)phi->in(0);
1558   Node *iff = region->in(1)->in(0);
1559   BoolNode* b = iff->in(1)->as_Bool();
1560   const CmpNode *cmp = (CmpNode*)b->in(1);
1561 
1562   // Make sure only merging this one phi here
1563   if (region->has_unique_phi() != phi)  return NULL;
1564 
1565   // Make sure each arm of the diamond has exactly one output, which we assume
1566   // is the region.  Otherwise, the control flow won't disappear.
1567   if (region->in(1)->outcnt() != 1) return NULL;
1568   if (region->in(2)->outcnt() != 1) return NULL;
1569 
1570   // Check for "(P < Q)" of type signed int
1571   if (b->_test._test != BoolTest::lt)  return NULL;
1572   if (cmp->Opcode() != Op_CmpI)        return NULL;
1573 
1574   Node *p = cmp->in(1);
1575   Node *q = cmp->in(2);
1576   Node *n1 = phi->in(  true_path);
1577   Node *n2 = phi->in(3-true_path);
1578 
1579   int op = n1->Opcode();
1580   if( op != Op_AddI           // Need zero as additive identity
1581       /*&&op != Op_SubI &&
1582       op != Op_AddP &&
1583       op != Op_XorI &&
1584       op != Op_OrI*/ )
1585     return NULL;
1586 
1587   Node *x = n2;
1588   Node *y = NULL;
1589   if( x == n1->in(1) ) {
1590     y = n1->in(2);
1591   } else if( x == n1->in(2) ) {
1592     y = n1->in(1);
1593   } else return NULL;
1594 
1595   // Not so profitable if compare and add are constants
1596   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1597     return NULL;
1598 
1599   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1600   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1601   return new AddINode(j_and,x);
1602 }
1603 
1604 //------------------------------is_absolute------------------------------------
1605 // Check for absolute value.
1606 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1607   assert(true_path !=0, "only diamond shape graph expected");
1608 
1609   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1610   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1611 
1612   // ABS ends with the merge of 2 control flow paths.
1613   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1614   int false_path = 3 - true_path;
1615 
1616   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1617   // phi->region->if_proj->ifnode->bool->cmp
1618   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1619   Node *cmp = bol->in(1);
1620 
1621   // Check bool sense
1622   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1623     switch (bol->_test._test) {
1624     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1625     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1626     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1627     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1628     default:           return NULL;                              break;
1629     }
1630   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1631     switch (bol->_test._test) {
1632     case BoolTest::lt:
1633     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1634     case BoolTest::gt:
1635     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1636     default:           return NULL;                              break;
1637     }
1638   }
1639 
1640   // Test is next
1641   const Type *tzero = NULL;
1642   switch (cmp->Opcode()) {
1643   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1644   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1645   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1646   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1647   default: return NULL;
1648   }
1649 
1650   // Find zero input of compare; the other input is being abs'd
1651   Node *x = NULL;
1652   bool flip = false;
1653   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1654     x = cmp->in(3 - cmp_zero_idx);
1655   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1656     // The test is inverted, we should invert the result...
1657     x = cmp->in(cmp_zero_idx);
1658     flip = true;
1659   } else {
1660     return NULL;
1661   }
1662 
1663   // Next get the 2 pieces being selected, one is the original value
1664   // and the other is the negated value.
1665   if( phi_root->in(phi_x_idx) != x ) return NULL;
1666 
1667   // Check other phi input for subtract node
1668   Node *sub = phi_root->in(3 - phi_x_idx);
1669 
1670   bool is_sub = sub->Opcode() == Op_SubF || sub->Opcode() == Op_SubD ||
1671                 sub->Opcode() == Op_SubI || sub->Opcode() == Op_SubL;
1672 
1673   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1674   if (!is_sub || phase->type(sub->in(1)) != tzero || sub->in(2) != x) return NULL;
1675 
1676   if (tzero == TypeF::ZERO) {
1677     x = new AbsFNode(x);
1678     if (flip) {
1679       x = new SubFNode(sub->in(1), phase->transform(x));
1680     }
1681   } else if (tzero == TypeD::ZERO) {
1682     x = new AbsDNode(x);
1683     if (flip) {
1684       x = new SubDNode(sub->in(1), phase->transform(x));
1685     }
1686   } else if (tzero == TypeInt::ZERO && Matcher::match_rule_supported(Op_AbsI)) {
1687     x = new AbsINode(x);
1688     if (flip) {
1689       x = new SubINode(sub->in(1), phase->transform(x));
1690     }
1691   } else if (tzero == TypeLong::ZERO && Matcher::match_rule_supported(Op_AbsL)) {
1692     x = new AbsLNode(x);
1693     if (flip) {
1694       x = new SubLNode(sub->in(1), phase->transform(x));
1695     }
1696   } else return NULL;
1697 
1698   return x;
1699 }
1700 
1701 //------------------------------split_once-------------------------------------
1702 // Helper for split_flow_path
1703 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1704   igvn->hash_delete(n);         // Remove from hash before hacking edges
1705 
1706   uint j = 1;
1707   for (uint i = phi->req()-1; i > 0; i--) {
1708     if (phi->in(i) == val) {   // Found a path with val?
1709       // Add to NEW Region/Phi, no DU info
1710       newn->set_req( j++, n->in(i) );
1711       // Remove from OLD Region/Phi
1712       n->del_req(i);
1713     }
1714   }
1715 
1716   // Register the new node but do not transform it.  Cannot transform until the
1717   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1718   igvn->register_new_node_with_optimizer( newn );
1719 
1720   // Now I can point to the new node.
1721   n->add_req(newn);
1722   igvn->_worklist.push(n);
1723 }
1724 
1725 //------------------------------split_flow_path--------------------------------
1726 // Check for merging identical values and split flow paths
1727 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1728   BasicType bt = phi->type()->basic_type();
1729   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1730     return NULL;                // Bail out on funny non-value stuff
1731   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1732     return NULL;                // third unequal input to be worth doing
1733 
1734   // Scan for a constant
1735   uint i;
1736   for( i = 1; i < phi->req()-1; i++ ) {
1737     Node *n = phi->in(i);
1738     if( !n ) return NULL;
1739     if( phase->type(n) == Type::TOP ) return NULL;
1740     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1741       break;
1742   }
1743   if( i >= phi->req() )         // Only split for constants
1744     return NULL;
1745 
1746   Node *val = phi->in(i);       // Constant to split for
1747   uint hit = 0;                 // Number of times it occurs
1748   Node *r = phi->region();
1749 
1750   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1751     Node *n = phi->in(i);
1752     if( !n ) return NULL;
1753     if( phase->type(n) == Type::TOP ) return NULL;
1754     if( phi->in(i) == val ) {
1755       hit++;
1756       if (PhaseIdealLoop::find_predicate(r->in(i)) != NULL) {
1757         return NULL;            // don't split loop entry path
1758       }
1759     }
1760   }
1761 
1762   if( hit <= 1 ||               // Make sure we find 2 or more
1763       hit == phi->req()-1 )     // and not ALL the same value
1764     return NULL;
1765 
1766   // Now start splitting out the flow paths that merge the same value.
1767   // Split first the RegionNode.
1768   PhaseIterGVN *igvn = phase->is_IterGVN();
1769   RegionNode *newr = new RegionNode(hit+1);
1770   split_once(igvn, phi, val, r, newr);
1771 
1772   // Now split all other Phis than this one
1773   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1774     Node* phi2 = r->fast_out(k);
1775     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1776       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1777       split_once(igvn, phi, val, phi2, newphi);
1778     }
1779   }
1780 
1781   // Clean up this guy
1782   igvn->hash_delete(phi);
1783   for( i = phi->req()-1; i > 0; i-- ) {
1784     if( phi->in(i) == val ) {
1785       phi->del_req(i);
1786     }
1787   }
1788   phi->add_req(val);
1789 
1790   return phi;
1791 }
1792 
1793 //=============================================================================
1794 //------------------------------simple_data_loop_check-------------------------
1795 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1796 //  Returns:
1797 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1798 // Safe       - safe case when the phi and it's inputs reference only safe data
1799 //              nodes;
1800 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1801 //              is no reference back to the phi - need a graph walk
1802 //              to determine if it is in a loop;
1803 // UnsafeLoop - unsafe case when the phi references itself directly or through
1804 //              unsafe data node.
1805 //  Note: a safe data node is a node which could/never reference itself during
1806 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1807 //  I mark Phi nodes as safe node not only because they can reference itself
1808 //  but also to prevent mistaking the fallthrough case inside an outer loop
1809 //  as dead loop when the phi references itself through an other phi.
1810 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1811   // It is unsafe loop if the phi node references itself directly.
1812   if (in == (Node*)this)
1813     return UnsafeLoop; // Unsafe loop
1814   // Unsafe loop if the phi node references itself through an unsafe data node.
1815   // Exclude cases with null inputs or data nodes which could reference
1816   // itself (safe for dead loops).
1817   if (in != NULL && !in->is_dead_loop_safe()) {
1818     // Check inputs of phi's inputs also.
1819     // It is much less expensive then full graph walk.
1820     uint cnt = in->req();
1821     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1822     for (; i < cnt; ++i) {
1823       Node* m = in->in(i);
1824       if (m == (Node*)this)
1825         return UnsafeLoop; // Unsafe loop
1826       if (m != NULL && !m->is_dead_loop_safe()) {
1827         // Check the most common case (about 30% of all cases):
1828         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1829         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : NULL;
1830         if (m1 == (Node*)this)
1831           return UnsafeLoop; // Unsafe loop
1832         if (m1 != NULL && m1 == m->in(2) &&
1833             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1834           continue; // Safe case
1835         }
1836         // The phi references an unsafe node - need full analysis.
1837         return Unsafe;
1838       }
1839     }
1840   }
1841   return Safe; // Safe case - we can optimize the phi node.
1842 }
1843 
1844 //------------------------------is_unsafe_data_reference-----------------------
1845 // If phi can be reached through the data input - it is data loop.
1846 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1847   assert(req() > 1, "");
1848   // First, check simple cases when phi references itself directly or
1849   // through an other node.
1850   LoopSafety safety = simple_data_loop_check(in);
1851   if (safety == UnsafeLoop)
1852     return true;  // phi references itself - unsafe loop
1853   else if (safety == Safe)
1854     return false; // Safe case - phi could be replaced with the unique input.
1855 
1856   // Unsafe case when we should go through data graph to determine
1857   // if the phi references itself.
1858 
1859   ResourceMark rm;
1860 
1861   Node_List nstack;
1862   VectorSet visited;
1863 
1864   nstack.push(in); // Start with unique input.
1865   visited.set(in->_idx);
1866   while (nstack.size() != 0) {
1867     Node* n = nstack.pop();
1868     uint cnt = n->req();
1869     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1870     for (; i < cnt; i++) {
1871       Node* m = n->in(i);
1872       if (m == (Node*)this) {
1873         return true;    // Data loop
1874       }
1875       if (m != NULL && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1876         if (!visited.test_set(m->_idx))
1877           nstack.push(m);
1878       }
1879     }
1880   }
1881   return false; // The phi is not reachable from its inputs
1882 }
1883 
1884 // Is this Phi's region or some inputs to the region enqueued for IGVN
1885 // and so could cause the region to be optimized out?
1886 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
1887   PhaseIterGVN* igvn = phase->is_IterGVN();
1888   Unique_Node_List& worklist = igvn->_worklist;
1889   bool delay = false;
1890   Node* r = in(0);
1891   for (uint j = 1; j < req(); j++) {
1892     Node* rc = r->in(j);
1893     Node* n = in(j);
1894     if (rc != NULL &&
1895         rc->is_Proj()) {
1896       if (worklist.member(rc)) {
1897         delay = true;
1898       } else if (rc->in(0) != NULL &&
1899                  rc->in(0)->is_If()) {
1900         if (worklist.member(rc->in(0))) {
1901           delay = true;
1902         } else if (rc->in(0)->in(1) != NULL &&
1903                    rc->in(0)->in(1)->is_Bool()) {
1904           if (worklist.member(rc->in(0)->in(1))) {
1905             delay = true;
1906           } else if (rc->in(0)->in(1)->in(1) != NULL &&
1907                      rc->in(0)->in(1)->in(1)->is_Cmp()) {
1908             if (worklist.member(rc->in(0)->in(1)->in(1))) {
1909               delay = true;
1910             }
1911           }
1912         }
1913       }
1914     }
1915   }
1916   if (delay) {
1917     worklist.push(this);
1918   }
1919   return delay;
1920 }
1921 
1922 // Push inline type input nodes (and null) down through the phi recursively (can handle data loops).
1923 InlineTypeNode* PhiNode::push_inline_types_through(PhaseGVN* phase, bool can_reshape, ciInlineKlass* vk, bool is_init) {
1924   InlineTypeNode* vt = InlineTypeNode::make_null(*phase, vk)->clone_with_phis(phase, in(0), is_init);
1925   if (can_reshape) {
1926     // Replace phi right away to be able to use the inline
1927     // type node when reaching the phi again through data loops.
1928     PhaseIterGVN* igvn = phase->is_IterGVN();
1929     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
1930       Node* u = fast_out(i);
1931       igvn->rehash_node_delayed(u);
1932       imax -= u->replace_edge(this, vt);
1933       --i;
1934     }
1935     igvn->rehash_node_delayed(this);
1936     assert(outcnt() == 0, "should be dead now");
1937   }
1938   ResourceMark rm;
1939   Node_List casts;
1940   for (uint i = 1; i < req(); ++i) {
1941     Node* n = in(i);
1942     while (n->is_ConstraintCast()) {
1943       casts.push(n);
1944       n = n->in(1);
1945     }
1946     if (phase->type(n)->is_zero_type()) {
1947       n = InlineTypeNode::make_null(*phase, vk);
1948     } else if (n->is_Phi()) {
1949       assert(can_reshape, "can only handle phis during IGVN");
1950       n = phase->transform(n->as_Phi()->push_inline_types_through(phase, can_reshape, vk, is_init));
1951     }
1952     while (casts.size() != 0) {
1953       // Push the cast(s) through the InlineTypeNode
1954       Node* cast = casts.pop()->clone();
1955       cast->set_req_X(1, n->as_InlineType()->get_oop(), phase);
1956       n = n->clone();
1957       n->as_InlineType()->set_oop(phase->transform(cast));
1958       n = phase->transform(n);
1959     }
1960     bool transform = !can_reshape && (i == (req()-1)); // Transform phis on last merge
1961     vt->merge_with(phase, n->as_InlineType(), i, transform);
1962   }
1963   return vt;
1964 }
1965 
1966 //------------------------------Ideal------------------------------------------
1967 // Return a node which is more "ideal" than the current node.  Must preserve
1968 // the CFG, but we can still strip out dead paths.
1969 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1970   Node *r = in(0);              // RegionNode
1971   assert(r != NULL && r->is_Region(), "this phi must have a region");
1972   assert(r->in(0) == NULL || !r->in(0)->is_Root(), "not a specially hidden merge");
1973 
1974   // Note: During parsing, phis are often transformed before their regions.
1975   // This means we have to use type_or_null to defend against untyped regions.
1976   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
1977     return NULL;                // No change
1978 
1979   Node *top = phase->C->top();
1980   bool new_phi = (outcnt() == 0); // transforming new Phi
1981   // No change for igvn if new phi is not hooked
1982   if (new_phi && can_reshape)
1983     return NULL;
1984 
1985   // The are 2 situations when only one valid phi's input is left
1986   // (in addition to Region input).
1987   // One: region is not loop - replace phi with this input.
1988   // Two: region is loop - replace phi with top since this data path is dead
1989   //                       and we need to break the dead data loop.
1990   Node* progress = NULL;        // Record if any progress made
1991   for( uint j = 1; j < req(); ++j ){ // For all paths in
1992     // Check unreachable control paths
1993     Node* rc = r->in(j);
1994     Node* n = in(j);            // Get the input
1995     if (rc == NULL || phase->type(rc) == Type::TOP) {
1996       if (n != top) {           // Not already top?
1997         PhaseIterGVN *igvn = phase->is_IterGVN();
1998         if (can_reshape && igvn != NULL) {
1999           igvn->_worklist.push(r);
2000         }
2001         // Nuke it down
2002         set_req_X(j, top, phase);
2003         progress = this;        // Record progress
2004       }
2005     }
2006   }
2007 
2008   if (can_reshape && outcnt() == 0) {
2009     // set_req() above may kill outputs if Phi is referenced
2010     // only by itself on the dead (top) control path.
2011     return top;
2012   }
2013 
2014   bool uncasted = false;
2015   Node* uin = unique_input(phase, false);
2016   if (uin == NULL && can_reshape &&
2017       // If there is a chance that the region can be optimized out do
2018       // not add a cast node that we can't remove yet.
2019       !wait_for_region_igvn(phase)) {
2020     uncasted = true;
2021     uin = unique_input(phase, true);
2022   }
2023   if (uin == top) {             // Simplest case: no alive inputs.
2024     if (can_reshape)            // IGVN transformation
2025       return top;
2026     else
2027       return NULL;              // Identity will return TOP
2028   } else if (uin != NULL) {
2029     // Only one not-NULL unique input path is left.
2030     // Determine if this input is backedge of a loop.
2031     // (Skip new phis which have no uses and dead regions).
2032     if (outcnt() > 0 && r->in(0) != NULL) {
2033       if (is_data_loop(r->as_Region(), uin, phase)) {
2034         // Break this data loop to avoid creation of a dead loop.
2035         if (can_reshape) {
2036           return top;
2037         } else {
2038           // We can't return top if we are in Parse phase - cut inputs only
2039           // let Identity to handle the case.
2040           replace_edge(uin, top, phase);
2041           return NULL;
2042         }
2043       }
2044     }
2045 
2046     if (uncasted) {
2047       // Add cast nodes between the phi to be removed and its unique input.
2048       // Wait until after parsing for the type information to propagate from the casts.
2049       assert(can_reshape, "Invalid during parsing");
2050       const Type* phi_type = bottom_type();
2051       // Add casts to carry the control dependency of the Phi that is
2052       // going away
2053       Node* cast = NULL;
2054       if (phi_type->isa_ptr()) {
2055         const Type* uin_type = phase->type(uin);
2056         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
2057           cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2058         } else {
2059           // Use a CastPP for a cast to not null and a CheckCastPP for
2060           // a cast to a new klass (and both if both null-ness and
2061           // klass change).
2062 
2063           // If the type of phi is not null but the type of uin may be
2064           // null, uin's type must be casted to not null
2065           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
2066               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
2067             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, TypePtr::NOTNULL, ConstraintCastNode::StrongDependency);
2068           }
2069 
2070           // If the type of phi and uin, both casted to not null,
2071           // differ the klass of uin must be (check)cast'ed to match
2072           // that of phi
2073           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
2074             Node* n = uin;
2075             if (cast != NULL) {
2076               cast = phase->transform(cast);
2077               n = cast;
2078             }
2079             cast = ConstraintCastNode::make_cast(Op_CheckCastPP, r, n, phi_type, ConstraintCastNode::StrongDependency);
2080           }
2081           if (cast == NULL) {
2082             cast = ConstraintCastNode::make_cast(Op_CastPP, r, uin, phi_type, ConstraintCastNode::StrongDependency);
2083           }
2084         }
2085       } else {
2086         cast = ConstraintCastNode::make_cast_for_type(r, uin, phi_type, ConstraintCastNode::StrongDependency);
2087       }
2088       assert(cast != NULL, "cast should be set");
2089       cast = phase->transform(cast);
2090       // set all inputs to the new cast(s) so the Phi is removed by Identity
2091       PhaseIterGVN* igvn = phase->is_IterGVN();
2092       for (uint i = 1; i < req(); i++) {
2093         set_req_X(i, cast, igvn);
2094       }
2095       uin = cast;
2096     }
2097 
2098     // One unique input.
2099     debug_only(Node* ident = Identity(phase));
2100     // The unique input must eventually be detected by the Identity call.
2101 #ifdef ASSERT
2102     if (ident != uin && !ident->is_top()) {
2103       // print this output before failing assert
2104       r->dump(3);
2105       this->dump(3);
2106       ident->dump();
2107       uin->dump();
2108     }
2109 #endif
2110     assert(ident == uin || ident->is_top(), "Identity must clean this up");
2111     return NULL;
2112   }
2113 
2114   Node* opt = NULL;
2115   int true_path = is_diamond_phi();
2116   if (true_path != 0 &&
2117       // If one of the diamond's branch is in the process of dying then, the Phi's input for that branch might transform
2118       // to top. If that happens replacing the Phi with an operation that consumes the Phi's inputs will cause the Phi
2119       // to be replaced by top. To prevent that, delay the transformation until the branch has a chance to be removed.
2120       !(can_reshape && wait_for_region_igvn(phase))) {
2121     // Check for CMove'ing identity. If it would be unsafe,
2122     // handle it here. In the safe case, let Identity handle it.
2123     Node* unsafe_id = is_cmove_id(phase, true_path);
2124     if( unsafe_id != NULL && is_unsafe_data_reference(unsafe_id) )
2125       opt = unsafe_id;
2126 
2127     // Check for simple convert-to-boolean pattern
2128     if( opt == NULL )
2129       opt = is_x2logic(phase, this, true_path);
2130 
2131     // Check for absolute value
2132     if( opt == NULL )
2133       opt = is_absolute(phase, this, true_path);
2134 
2135     // Check for conditional add
2136     if( opt == NULL && can_reshape )
2137       opt = is_cond_add(phase, this, true_path);
2138 
2139     // These 4 optimizations could subsume the phi:
2140     // have to check for a dead data loop creation.
2141     if( opt != NULL ) {
2142       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2143         // Found dead loop.
2144         if( can_reshape )
2145           return top;
2146         // We can't return top if we are in Parse phase - cut inputs only
2147         // to stop further optimizations for this phi. Identity will return TOP.
2148         assert(req() == 3, "only diamond merge phi here");
2149         set_req(1, top);
2150         set_req(2, top);
2151         return NULL;
2152       } else {
2153         return opt;
2154       }
2155     }
2156   }
2157 
2158   // Check for merging identical values and split flow paths
2159   if (can_reshape) {
2160     opt = split_flow_path(phase, this);
2161     // This optimization only modifies phi - don't need to check for dead loop.
2162     assert(opt == NULL || opt == this, "do not elide phi");
2163     if (opt != NULL)  return opt;
2164   }
2165 
2166   if (in(1) != NULL && in(1)->Opcode() == Op_AddP && can_reshape) {
2167     // Try to undo Phi of AddP:
2168     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2169     // becomes:
2170     // newbase := (Phi base base2)
2171     // newaddress := (Phi address address2)
2172     // newoffset := (Phi offset offset2)
2173     // (AddP newbase newaddress newoffset)
2174     //
2175     // This occurs as a result of unsuccessful split_thru_phi and
2176     // interferes with taking advantage of addressing modes. See the
2177     // clone_shift_expressions code in matcher.cpp
2178     Node* addp = in(1);
2179     Node* base = addp->in(AddPNode::Base);
2180     Node* address = addp->in(AddPNode::Address);
2181     Node* offset = addp->in(AddPNode::Offset);
2182     if (base != NULL && address != NULL && offset != NULL &&
2183         !base->is_top() && !address->is_top() && !offset->is_top()) {
2184       const Type* base_type = base->bottom_type();
2185       const Type* address_type = address->bottom_type();
2186       // make sure that all the inputs are similar to the first one,
2187       // i.e. AddP with base == address and same offset as first AddP
2188       bool doit = true;
2189       for (uint i = 2; i < req(); i++) {
2190         if (in(i) == NULL ||
2191             in(i)->Opcode() != Op_AddP ||
2192             in(i)->in(AddPNode::Base) == NULL ||
2193             in(i)->in(AddPNode::Address) == NULL ||
2194             in(i)->in(AddPNode::Offset) == NULL ||
2195             in(i)->in(AddPNode::Base)->is_top() ||
2196             in(i)->in(AddPNode::Address)->is_top() ||
2197             in(i)->in(AddPNode::Offset)->is_top()) {
2198           doit = false;
2199           break;
2200         }
2201         if (in(i)->in(AddPNode::Base) != base) {
2202           base = NULL;
2203         }
2204         if (in(i)->in(AddPNode::Offset) != offset) {
2205           offset = NULL;
2206         }
2207         if (in(i)->in(AddPNode::Address) != address) {
2208           address = NULL;
2209         }
2210         // Accumulate type for resulting Phi
2211         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2212         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2213       }
2214       if (doit && base == NULL) {
2215         // Check for neighboring AddP nodes in a tree.
2216         // If they have a base, use that it.
2217         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2218           Node* u = this->fast_out(k);
2219           if (u->is_AddP()) {
2220             Node* base2 = u->in(AddPNode::Base);
2221             if (base2 != NULL && !base2->is_top()) {
2222               if (base == NULL)
2223                 base = base2;
2224               else if (base != base2)
2225                 { doit = false; break; }
2226             }
2227           }
2228         }
2229       }
2230       if (doit) {
2231         if (base == NULL) {
2232           base = new PhiNode(in(0), base_type, NULL);
2233           for (uint i = 1; i < req(); i++) {
2234             base->init_req(i, in(i)->in(AddPNode::Base));
2235           }
2236           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2237         }
2238         if (address == NULL) {
2239           address = new PhiNode(in(0), address_type, NULL);
2240           for (uint i = 1; i < req(); i++) {
2241             address->init_req(i, in(i)->in(AddPNode::Address));
2242           }
2243           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2244         }
2245         if (offset == NULL) {
2246           offset = new PhiNode(in(0), TypeX_X, NULL);
2247           for (uint i = 1; i < req(); i++) {
2248             offset->init_req(i, in(i)->in(AddPNode::Offset));
2249           }
2250           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2251         }
2252         return new AddPNode(base, address, offset);
2253       }
2254     }
2255   }
2256 
2257   // Split phis through memory merges, so that the memory merges will go away.
2258   // Piggy-back this transformation on the search for a unique input....
2259   // It will be as if the merged memory is the unique value of the phi.
2260   // (Do not attempt this optimization unless parsing is complete.
2261   // It would make the parser's memory-merge logic sick.)
2262   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2263   if (progress == NULL && can_reshape && type() == Type::MEMORY) {
2264     // see if this phi should be sliced
2265     uint merge_width = 0;
2266     bool saw_self = false;
2267     // TODO revisit this with JDK-8247216
2268     bool mergemem_only = true;
2269     for( uint i=1; i<req(); ++i ) {// For all paths in
2270       Node *ii = in(i);
2271       // TOP inputs should not be counted as safe inputs because if the
2272       // Phi references itself through all other inputs then splitting the
2273       // Phi through memory merges would create dead loop at later stage.
2274       if (ii == top) {
2275         return NULL; // Delay optimization until graph is cleaned.
2276       }
2277       if (ii->is_MergeMem()) {
2278         MergeMemNode* n = ii->as_MergeMem();
2279         merge_width = MAX2(merge_width, n->req());
2280         saw_self = saw_self || (n->base_memory() == this);
2281       } else {
2282         mergemem_only = false;
2283       }
2284     }
2285 
2286     // This restriction is temporarily necessary to ensure termination:
2287     if (!mergemem_only && !saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2288 
2289     if (merge_width > Compile::AliasIdxRaw) {
2290       // found at least one non-empty MergeMem
2291       const TypePtr* at = adr_type();
2292       if (at != TypePtr::BOTTOM) {
2293         // Patch the existing phi to select an input from the merge:
2294         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2295         //     Phi:AT1(...m1...)
2296         int alias_idx = phase->C->get_alias_index(at);
2297         for (uint i=1; i<req(); ++i) {
2298           Node *ii = in(i);
2299           if (ii->is_MergeMem()) {
2300             MergeMemNode* n = ii->as_MergeMem();
2301             // compress paths and change unreachable cycles to TOP
2302             // If not, we can update the input infinitely along a MergeMem cycle
2303             // Equivalent code is in MemNode::Ideal_common
2304             Node *m  = phase->transform(n);
2305             if (outcnt() == 0) {  // Above transform() may kill us!
2306               return top;
2307             }
2308             // If transformed to a MergeMem, get the desired slice
2309             // Otherwise the returned node represents memory for every slice
2310             Node *new_mem = (m->is_MergeMem()) ?
2311                              m->as_MergeMem()->memory_at(alias_idx) : m;
2312             // Update input if it is progress over what we have now
2313             if (new_mem != ii) {
2314               set_req_X(i, new_mem, phase->is_IterGVN());
2315               progress = this;
2316             }
2317           }
2318         }
2319       } else {
2320         // We know that at least one MergeMem->base_memory() == this
2321         // (saw_self == true). If all other inputs also references this phi
2322         // (directly or through data nodes) - it is a dead loop.
2323         bool saw_safe_input = false;
2324         for (uint j = 1; j < req(); ++j) {
2325           Node* n = in(j);
2326           if (n->is_MergeMem()) {
2327             MergeMemNode* mm = n->as_MergeMem();
2328             if (mm->base_memory() == this || mm->base_memory() == mm->empty_memory()) {
2329               // Skip this input if it references back to this phi or if the memory path is dead
2330               continue;
2331             }
2332           }
2333           if (!is_unsafe_data_reference(n)) {
2334             saw_safe_input = true; // found safe input
2335             break;
2336           }
2337         }
2338         if (!saw_safe_input) {
2339           // There is a dead loop: All inputs are either dead or reference back to this phi
2340           return top;
2341         }
2342 
2343         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2344         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2345         PhaseIterGVN* igvn = phase->is_IterGVN();
2346         assert(igvn != NULL, "sanity check");
2347         Node* hook = new Node(1);
2348         PhiNode* new_base = (PhiNode*) clone();
2349         // Must eagerly register phis, since they participate in loops.
2350         igvn->register_new_node_with_optimizer(new_base);
2351         hook->add_req(new_base);
2352 
2353         MergeMemNode* result = MergeMemNode::make(new_base);
2354         for (uint i = 1; i < req(); ++i) {
2355           Node *ii = in(i);
2356           if (ii->is_MergeMem()) {
2357             MergeMemNode* n = ii->as_MergeMem();
2358             if (igvn) {
2359               // TODO revisit this with JDK-8247216
2360               // Put 'n' on the worklist because it might be modified by MergeMemStream::iteration_setup
2361               igvn->_worklist.push(n);
2362             }
2363             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2364               // If we have not seen this slice yet, make a phi for it.
2365               bool made_new_phi = false;
2366               if (mms.is_empty()) {
2367                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2368                 made_new_phi = true;
2369                 igvn->register_new_node_with_optimizer(new_phi);
2370                 hook->add_req(new_phi);
2371                 mms.set_memory(new_phi);
2372               }
2373               Node* phi = mms.memory();
2374               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2375               phi->set_req(i, mms.memory2());
2376             }
2377           }
2378         }
2379         // Distribute all self-loops.
2380         { // (Extra braces to hide mms.)
2381           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2382             Node* phi = mms.memory();
2383             for (uint i = 1; i < req(); ++i) {
2384               if (phi->in(i) == this)  phi->set_req(i, phi);
2385             }
2386           }
2387         }
2388         // Already replace this phi node to cut it off from the graph to not interfere in dead loop checks during the
2389         // transformations of the new phi nodes below. Otherwise, we could wrongly conclude that there is no dead loop
2390         // because we are finding this phi node again. Also set the type of the new MergeMem node in case we are also
2391         // visiting it in the transformations below.
2392         igvn->replace_node(this, result);
2393         igvn->set_type(result, result->bottom_type());
2394 
2395         // now transform the new nodes, and return the mergemem
2396         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2397           Node* phi = mms.memory();
2398           mms.set_memory(phase->transform(phi));
2399         }
2400         hook->destruct(igvn);
2401         // Replace self with the result.
2402         return result;
2403       }
2404     }
2405     //
2406     // Other optimizations on the memory chain
2407     //
2408     const TypePtr* at = adr_type();
2409     for( uint i=1; i<req(); ++i ) {// For all paths in
2410       Node *ii = in(i);
2411       Node *new_in = MemNode::optimize_memory_chain(ii, at, NULL, phase);
2412       if (ii != new_in ) {
2413         set_req(i, new_in);
2414         progress = this;
2415       }
2416     }
2417   }
2418 
2419 #ifdef _LP64
2420   // Push DecodeN/DecodeNKlass down through phi.
2421   // The rest of phi graph will transform by split EncodeP node though phis up.
2422   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == NULL) {
2423     bool may_push = true;
2424     bool has_decodeN = false;
2425     bool is_decodeN = false;
2426     for (uint i=1; i<req(); ++i) {// For all paths in
2427       Node *ii = in(i);
2428       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2429         // Do optimization if a non dead path exist.
2430         if (ii->in(1)->bottom_type() != Type::TOP) {
2431           has_decodeN = true;
2432           is_decodeN = ii->is_DecodeN();
2433         }
2434       } else if (!ii->is_Phi()) {
2435         may_push = false;
2436       }
2437     }
2438 
2439     if (has_decodeN && may_push) {
2440       PhaseIterGVN *igvn = phase->is_IterGVN();
2441       // Make narrow type for new phi.
2442       const Type* narrow_t;
2443       if (is_decodeN) {
2444         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2445       } else {
2446         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2447       }
2448       PhiNode* new_phi = new PhiNode(r, narrow_t);
2449       uint orig_cnt = req();
2450       for (uint i=1; i<req(); ++i) {// For all paths in
2451         Node *ii = in(i);
2452         Node* new_ii = NULL;
2453         if (ii->is_DecodeNarrowPtr()) {
2454           assert(ii->bottom_type() == bottom_type(), "sanity");
2455           new_ii = ii->in(1);
2456         } else {
2457           assert(ii->is_Phi(), "sanity");
2458           if (ii->as_Phi() == this) {
2459             new_ii = new_phi;
2460           } else {
2461             if (is_decodeN) {
2462               new_ii = new EncodePNode(ii, narrow_t);
2463             } else {
2464               new_ii = new EncodePKlassNode(ii, narrow_t);
2465             }
2466             igvn->register_new_node_with_optimizer(new_ii);
2467           }
2468         }
2469         new_phi->set_req(i, new_ii);
2470       }
2471       igvn->register_new_node_with_optimizer(new_phi, this);
2472       if (is_decodeN) {
2473         progress = new DecodeNNode(new_phi, bottom_type());
2474       } else {
2475         progress = new DecodeNKlassNode(new_phi, bottom_type());
2476       }
2477     }
2478   }
2479 #endif
2480 
2481   // Check recursively if inputs are either an inline type, constant null
2482   // or another Phi (including self references through data loops). If so,
2483   // push the inline types down through the phis to enable folding of loads.
2484   if (EnableValhalla && _type->isa_ptr() && req() > 2) {
2485     ResourceMark rm;
2486     Unique_Node_List worklist;
2487     worklist.push(this);
2488     bool can_optimize = true;
2489     ciInlineKlass* vk = NULL;
2490     // true if all IsInit inputs of all InlineType* nodes are true
2491     bool is_init = true;
2492     Node_List casts;
2493 
2494     // TODO 8302217 We need to prevent endless pushing through
2495     bool only_phi = (outcnt() != 0);
2496     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2497       Node* n = fast_out(i);
2498       if (n->is_InlineType() && n->in(1) == this) {
2499         can_optimize = false;
2500         break;
2501       }
2502       if (!n->is_Phi()) {
2503         only_phi = false;
2504       }
2505     }
2506     if (only_phi) {
2507       can_optimize = false;
2508     }
2509     for (uint next = 0; next < worklist.size() && can_optimize; next++) {
2510       Node* phi = worklist.at(next);
2511       for (uint i = 1; i < phi->req() && can_optimize; i++) {
2512         Node* n = phi->in(i);
2513         if (n == NULL) {
2514           can_optimize = false;
2515           break;
2516         }
2517         while (n->is_ConstraintCast()) {
2518           if (n->in(0) != NULL && n->in(0)->is_top()) {
2519             // Will die, don't optimize
2520             can_optimize = false;
2521             break;
2522           }
2523           casts.push(n);
2524           n = n->in(1);
2525         }
2526         const Type* t = phase->type(n);
2527         if (n->is_InlineType() && (vk == NULL || vk == t->inline_klass())) {
2528           vk = (vk == NULL) ? t->inline_klass() : vk;
2529           if (phase->find_int_con(n->as_InlineType()->get_is_init(), 0) != 1) {
2530             is_init = false;
2531           }
2532         } else if (n->is_Phi() && can_reshape && n->bottom_type()->isa_ptr()) {
2533           worklist.push(n);
2534         } else if (t->is_zero_type()) {
2535           is_init = false;
2536         } else {
2537           can_optimize = false;
2538         }
2539       }
2540     }
2541     // Check if cast nodes can be pushed through
2542     const Type* t = Type::get_const_type(vk);
2543     while (casts.size() != 0 && can_optimize && t != NULL) {
2544       Node* cast = casts.pop();
2545       if (t->filter(cast->bottom_type()) == Type::TOP) {
2546         can_optimize = false;
2547       }
2548     }
2549     if (can_optimize && vk != NULL) {
2550 // TODO 8302217
2551 //      assert(!_type->isa_ptr() || _type->maybe_null() || is_init, "Phi not null but a possible null was seen");
2552       return push_inline_types_through(phase, can_reshape, vk, is_init);
2553     }
2554   }
2555 
2556   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2557   if (EnableVectorReboxing && can_reshape && progress == NULL && type()->isa_oopptr()) {
2558     progress = merge_through_phi(this, phase->is_IterGVN());
2559   }
2560 
2561   return progress;              // Return any progress
2562 }
2563 
2564 Node* PhiNode::clone_through_phi(Node* root_phi, const Type* t, uint c, PhaseIterGVN* igvn) {
2565   Node_Stack stack(1);
2566   VectorSet  visited;
2567   Node_List  node_map;
2568 
2569   stack.push(root_phi, 1); // ignore control
2570   visited.set(root_phi->_idx);
2571 
2572   Node* new_phi = new PhiNode(root_phi->in(0), t);
2573   node_map.map(root_phi->_idx, new_phi);
2574 
2575   while (stack.is_nonempty()) {
2576     Node* n   = stack.node();
2577     uint  idx = stack.index();
2578     assert(n->is_Phi(), "not a phi");
2579     if (idx < n->req()) {
2580       stack.set_index(idx + 1);
2581       Node* def = n->in(idx);
2582       if (def == NULL) {
2583         continue; // ignore dead path
2584       } else if (def->is_Phi()) { // inner node
2585         Node* new_phi = node_map[n->_idx];
2586         if (!visited.test_set(def->_idx)) { // not visited yet
2587           node_map.map(def->_idx, new PhiNode(def->in(0), t));
2588           stack.push(def, 1); // ignore control
2589         }
2590         Node* new_in = node_map[def->_idx];
2591         new_phi->set_req(idx, new_in);
2592       } else if (def->Opcode() == Op_VectorBox) { // leaf
2593         assert(n->is_Phi(), "not a phi");
2594         Node* new_phi = node_map[n->_idx];
2595         new_phi->set_req(idx, def->in(c));
2596       } else {
2597         assert(false, "not optimizeable");
2598         return NULL;
2599       }
2600     } else {
2601       Node* new_phi = node_map[n->_idx];
2602       igvn->register_new_node_with_optimizer(new_phi, n);
2603       stack.pop();
2604     }
2605   }
2606   return new_phi;
2607 }
2608 
2609 Node* PhiNode::merge_through_phi(Node* root_phi, PhaseIterGVN* igvn) {
2610   Node_Stack stack(1);
2611   VectorSet  visited;
2612 
2613   stack.push(root_phi, 1); // ignore control
2614   visited.set(root_phi->_idx);
2615 
2616   VectorBoxNode* cached_vbox = NULL;
2617   while (stack.is_nonempty()) {
2618     Node* n   = stack.node();
2619     uint  idx = stack.index();
2620     if (idx < n->req()) {
2621       stack.set_index(idx + 1);
2622       Node* in = n->in(idx);
2623       if (in == NULL) {
2624         continue; // ignore dead path
2625       } else if (in->isa_Phi()) {
2626         if (!visited.test_set(in->_idx)) {
2627           stack.push(in, 1); // ignore control
2628         }
2629       } else if (in->Opcode() == Op_VectorBox) {
2630         VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in);
2631         if (cached_vbox == NULL) {
2632           cached_vbox = vbox;
2633         } else if (vbox->vec_type() != cached_vbox->vec_type()) {
2634           // TODO: vector type mismatch can be handled with additional reinterpret casts
2635           assert(Type::cmp(vbox->vec_type(), cached_vbox->vec_type()) != 0, "inconsistent");
2636           return NULL; // not optimizable: vector type mismatch
2637         } else if (vbox->box_type() != cached_vbox->box_type()) {
2638           assert(Type::cmp(vbox->box_type(), cached_vbox->box_type()) != 0, "inconsistent");
2639           return NULL; // not optimizable: box type mismatch
2640         }
2641       } else {
2642         return NULL; // not optimizable: neither Phi nor VectorBox
2643       }
2644     } else {
2645       stack.pop();
2646     }
2647   }
2648 
2649   assert(cached_vbox != NULL, "sanity");
2650   const TypeInstPtr* btype = cached_vbox->box_type();
2651   const TypeVect*    vtype = cached_vbox->vec_type();
2652   Node* new_vbox_phi = clone_through_phi(root_phi, btype, VectorBoxNode::Box,   igvn);
2653   Node* new_vect_phi = clone_through_phi(root_phi, vtype, VectorBoxNode::Value, igvn);
2654   return new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, btype, vtype);
2655 }
2656 
2657 bool PhiNode::is_data_loop(RegionNode* r, Node* uin, const PhaseGVN* phase) {
2658   // First, take the short cut when we know it is a loop and the EntryControl data path is dead.
2659   // The loop node may only have one input because the entry path was removed in PhaseIdealLoop::Dominators().
2660   // Then, check if there is a data loop when the phi references itself directly or through other data nodes.
2661   assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
2662   const bool is_loop = (r->is_Loop() && r->req() == 3);
2663   const Node* top = phase->C->top();
2664   if (is_loop) {
2665     return !uin->eqv_uncast(in(LoopNode::EntryControl));
2666   } else {
2667     // We have a data loop either with an unsafe data reference or if a region is unreachable.
2668     return is_unsafe_data_reference(uin)
2669            || (r->req() == 3 && (r->in(1) != top && r->in(2) == top && r->is_unreachable_region(phase)));
2670   }
2671 }
2672 
2673 //------------------------------is_tripcount-----------------------------------
2674 bool PhiNode::is_tripcount(BasicType bt) const {
2675   return (in(0) != NULL && in(0)->is_BaseCountedLoop() &&
2676           in(0)->as_BaseCountedLoop()->bt() == bt &&
2677           in(0)->as_BaseCountedLoop()->phi() == this);
2678 }
2679 
2680 //------------------------------out_RegMask------------------------------------
2681 const RegMask &PhiNode::in_RegMask(uint i) const {
2682   return i ? out_RegMask() : RegMask::Empty;
2683 }
2684 
2685 const RegMask &PhiNode::out_RegMask() const {
2686   uint ideal_reg = _type->ideal_reg();
2687   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2688   if( ideal_reg == 0 ) return RegMask::Empty;
2689   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2690   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2691 }
2692 
2693 #ifndef PRODUCT
2694 void PhiNode::dump_spec(outputStream *st) const {
2695   TypeNode::dump_spec(st);
2696   if (is_tripcount(T_INT) || is_tripcount(T_LONG)) {
2697     st->print(" #tripcount");
2698   }
2699 }
2700 #endif
2701 
2702 
2703 //=============================================================================
2704 const Type* GotoNode::Value(PhaseGVN* phase) const {
2705   // If the input is reachable, then we are executed.
2706   // If the input is not reachable, then we are not executed.
2707   return phase->type(in(0));
2708 }
2709 
2710 Node* GotoNode::Identity(PhaseGVN* phase) {
2711   return in(0);                // Simple copy of incoming control
2712 }
2713 
2714 const RegMask &GotoNode::out_RegMask() const {
2715   return RegMask::Empty;
2716 }
2717 
2718 //=============================================================================
2719 const RegMask &JumpNode::out_RegMask() const {
2720   return RegMask::Empty;
2721 }
2722 
2723 //=============================================================================
2724 const RegMask &JProjNode::out_RegMask() const {
2725   return RegMask::Empty;
2726 }
2727 
2728 //=============================================================================
2729 const RegMask &CProjNode::out_RegMask() const {
2730   return RegMask::Empty;
2731 }
2732 
2733 
2734 
2735 //=============================================================================
2736 
2737 uint PCTableNode::hash() const { return Node::hash() + _size; }
2738 bool PCTableNode::cmp( const Node &n ) const
2739 { return _size == ((PCTableNode&)n)._size; }
2740 
2741 const Type *PCTableNode::bottom_type() const {
2742   const Type** f = TypeTuple::fields(_size);
2743   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2744   return TypeTuple::make(_size, f);
2745 }
2746 
2747 //------------------------------Value------------------------------------------
2748 // Compute the type of the PCTableNode.  If reachable it is a tuple of
2749 // Control, otherwise the table targets are not reachable
2750 const Type* PCTableNode::Value(PhaseGVN* phase) const {
2751   if( phase->type(in(0)) == Type::CONTROL )
2752     return bottom_type();
2753   return Type::TOP;             // All paths dead?  Then so are we
2754 }
2755 
2756 //------------------------------Ideal------------------------------------------
2757 // Return a node which is more "ideal" than the current node.  Strip out
2758 // control copies
2759 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2760   return remove_dead_region(phase, can_reshape) ? this : NULL;
2761 }
2762 
2763 //=============================================================================
2764 uint JumpProjNode::hash() const {
2765   return Node::hash() + _dest_bci;
2766 }
2767 
2768 bool JumpProjNode::cmp( const Node &n ) const {
2769   return ProjNode::cmp(n) &&
2770     _dest_bci == ((JumpProjNode&)n)._dest_bci;
2771 }
2772 
2773 #ifndef PRODUCT
2774 void JumpProjNode::dump_spec(outputStream *st) const {
2775   ProjNode::dump_spec(st);
2776   st->print("@bci %d ",_dest_bci);
2777 }
2778 
2779 void JumpProjNode::dump_compact_spec(outputStream *st) const {
2780   ProjNode::dump_compact_spec(st);
2781   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
2782 }
2783 #endif
2784 
2785 //=============================================================================
2786 //------------------------------Value------------------------------------------
2787 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
2788 // have the default "fall_through_index" path.
2789 const Type* CatchNode::Value(PhaseGVN* phase) const {
2790   // Unreachable?  Then so are all paths from here.
2791   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
2792   // First assume all paths are reachable
2793   const Type** f = TypeTuple::fields(_size);
2794   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
2795   // Identify cases that will always throw an exception
2796   // () rethrow call
2797   // () virtual or interface call with NULL receiver
2798   // () call is a check cast with incompatible arguments
2799   if( in(1)->is_Proj() ) {
2800     Node *i10 = in(1)->in(0);
2801     if( i10->is_Call() ) {
2802       CallNode *call = i10->as_Call();
2803       // Rethrows always throw exceptions, never return
2804       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
2805         f[CatchProjNode::fall_through_index] = Type::TOP;
2806       } else if (call->is_AllocateArray()) {
2807         Node* klass_node = call->in(AllocateNode::KlassNode);
2808         Node* length = call->in(AllocateNode::ALength);
2809         const Type* length_type = phase->type(length);
2810         const Type* klass_type = phase->type(klass_node);
2811         Node* valid_length_test = call->in(AllocateNode::ValidLengthTest);
2812         const Type* valid_length_test_t = phase->type(valid_length_test);
2813         if (length_type == Type::TOP || klass_type == Type::TOP || valid_length_test_t == Type::TOP ||
2814             valid_length_test_t->is_int()->is_con(0)) {
2815           f[CatchProjNode::fall_through_index] = Type::TOP;
2816         }
2817       } else if( call->req() > TypeFunc::Parms ) {
2818         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
2819         // Check for null receiver to virtual or interface calls
2820         if( call->is_CallDynamicJava() &&
2821             arg0->higher_equal(TypePtr::NULL_PTR) ) {
2822           f[CatchProjNode::fall_through_index] = Type::TOP;
2823         }
2824       } // End of if not a runtime stub
2825     } // End of if have call above me
2826   } // End of slot 1 is not a projection
2827   return TypeTuple::make(_size, f);
2828 }
2829 
2830 //=============================================================================
2831 uint CatchProjNode::hash() const {
2832   return Node::hash() + _handler_bci;
2833 }
2834 
2835 
2836 bool CatchProjNode::cmp( const Node &n ) const {
2837   return ProjNode::cmp(n) &&
2838     _handler_bci == ((CatchProjNode&)n)._handler_bci;
2839 }
2840 
2841 
2842 //------------------------------Identity---------------------------------------
2843 // If only 1 target is possible, choose it if it is the main control
2844 Node* CatchProjNode::Identity(PhaseGVN* phase) {
2845   // If my value is control and no other value is, then treat as ID
2846   const TypeTuple *t = phase->type(in(0))->is_tuple();
2847   if (t->field_at(_con) != Type::CONTROL)  return this;
2848   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
2849   // also remove any exception table entry.  Thus we must know the call
2850   // feeding the Catch will not really throw an exception.  This is ok for
2851   // the main fall-thru control (happens when we know a call can never throw
2852   // an exception) or for "rethrow", because a further optimization will
2853   // yank the rethrow (happens when we inline a function that can throw an
2854   // exception and the caller has no handler).  Not legal, e.g., for passing
2855   // a NULL receiver to a v-call, or passing bad types to a slow-check-cast.
2856   // These cases MUST throw an exception via the runtime system, so the VM
2857   // will be looking for a table entry.
2858   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
2859   CallNode *call;
2860   if (_con != TypeFunc::Control && // Bail out if not the main control.
2861       !(proj->is_Proj() &&      // AND NOT a rethrow
2862         proj->in(0)->is_Call() &&
2863         (call = proj->in(0)->as_Call()) &&
2864         call->entry_point() == OptoRuntime::rethrow_stub()))
2865     return this;
2866 
2867   // Search for any other path being control
2868   for (uint i = 0; i < t->cnt(); i++) {
2869     if (i != _con && t->field_at(i) == Type::CONTROL)
2870       return this;
2871   }
2872   // Only my path is possible; I am identity on control to the jump
2873   return in(0)->in(0);
2874 }
2875 
2876 
2877 #ifndef PRODUCT
2878 void CatchProjNode::dump_spec(outputStream *st) const {
2879   ProjNode::dump_spec(st);
2880   st->print("@bci %d ",_handler_bci);
2881 }
2882 #endif
2883 
2884 //=============================================================================
2885 //------------------------------Identity---------------------------------------
2886 // Check for CreateEx being Identity.
2887 Node* CreateExNode::Identity(PhaseGVN* phase) {
2888   if( phase->type(in(1)) == Type::TOP ) return in(1);
2889   if( phase->type(in(0)) == Type::TOP ) return in(0);
2890   // We only come from CatchProj, unless the CatchProj goes away.
2891   // If the CatchProj is optimized away, then we just carry the
2892   // exception oop through.
2893 
2894   // CheckCastPPNode::Ideal() for inline types reuses the exception
2895   // paths of a call to perform an allocation: we can see a Phi here.
2896   if (in(1)->is_Phi()) {
2897     return this;
2898   }
2899   CallNode *call = in(1)->in(0)->as_Call();
2900 
2901   return (in(0)->is_CatchProj() && in(0)->in(0)->is_Catch() &&
2902           in(0)->in(0)->in(1) == in(1)) ? this : call->in(TypeFunc::Parms);
2903 }
2904 
2905 //=============================================================================
2906 //------------------------------Value------------------------------------------
2907 // Check for being unreachable.
2908 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
2909   if (!in(0) || in(0)->is_top()) return Type::TOP;
2910   return bottom_type();
2911 }
2912 
2913 //------------------------------Ideal------------------------------------------
2914 // Check for no longer being part of a loop
2915 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2916   if (can_reshape && !in(0)->is_Region()) {
2917     // Dead code elimination can sometimes delete this projection so
2918     // if it's not there, there's nothing to do.
2919     Node* fallthru = proj_out_or_null(0);
2920     if (fallthru != NULL) {
2921       phase->is_IterGVN()->replace_node(fallthru, in(0));
2922     }
2923     return phase->C->top();
2924   }
2925   return NULL;
2926 }
2927 
2928 #ifndef PRODUCT
2929 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
2930   st->print("%s", Name());
2931 }
2932 #endif
2933 
2934 #ifndef PRODUCT
2935 void BlackholeNode::format(PhaseRegAlloc* ra, outputStream* st) const {
2936   st->print("blackhole ");
2937   bool first = true;
2938   for (uint i = 0; i < req(); i++) {
2939     Node* n = in(i);
2940     if (n != NULL && OptoReg::is_valid(ra->get_reg_first(n))) {
2941       if (first) {
2942         first = false;
2943       } else {
2944         st->print(", ");
2945       }
2946       char buf[128];
2947       ra->dump_register(n, buf);
2948       st->print("%s", buf);
2949     }
2950   }
2951   st->cr();
2952 }
2953 #endif
2954