1 /*
   2  * Copyright (c) 1997, 2025, 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 "gc/shared/barrierSet.hpp"
  26 #include "gc/shared/c2/barrierSetC2.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "memory/resourceArea.hpp"
  29 #include "oops/objArrayKlass.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/castnode.hpp"
  32 #include "opto/cfgnode.hpp"
  33 #include "opto/connode.hpp"
  34 #include "opto/convertnode.hpp"
  35 #include "opto/inlinetypenode.hpp"
  36 #include "opto/loopnode.hpp"
  37 #include "opto/machnode.hpp"
  38 #include "opto/movenode.hpp"
  39 #include "opto/mulnode.hpp"
  40 #include "opto/narrowptrnode.hpp"
  41 #include "opto/phaseX.hpp"
  42 #include "opto/regalloc.hpp"
  43 #include "opto/regmask.hpp"
  44 #include "opto/runtime.hpp"
  45 #include "opto/subnode.hpp"
  46 #include "opto/vectornode.hpp"
  47 #include "utilities/vmError.hpp"
  48 
  49 // Portions of code courtesy of Clifford Click
  50 
  51 // Optimization - Graph Style
  52 
  53 //=============================================================================
  54 //------------------------------Value------------------------------------------
  55 // Compute the type of the RegionNode.
  56 const Type* RegionNode::Value(PhaseGVN* phase) const {
  57   for( uint i=1; i<req(); ++i ) {       // For all paths in
  58     Node *n = in(i);            // Get Control source
  59     if( !n ) continue;          // Missing inputs are TOP
  60     if( phase->type(n) == Type::CONTROL )
  61       return Type::CONTROL;
  62   }
  63   return Type::TOP;             // All paths dead?  Then so are we
  64 }
  65 
  66 //------------------------------Identity---------------------------------------
  67 // Check for Region being Identity.
  68 Node* RegionNode::Identity(PhaseGVN* phase) {
  69   // Cannot have Region be an identity, even if it has only 1 input.
  70   // Phi users cannot have their Region input folded away for them,
  71   // since they need to select the proper data input
  72   return this;
  73 }
  74 
  75 //------------------------------merge_region-----------------------------------
  76 // If a Region flows into a Region, merge into one big happy merge.  This is
  77 // hard to do if there is stuff that has to happen
  78 static Node *merge_region(RegionNode *region, PhaseGVN *phase) {
  79   if( region->Opcode() != Op_Region ) // Do not do to LoopNodes
  80     return nullptr;
  81   Node *progress = nullptr;        // Progress flag
  82   PhaseIterGVN *igvn = phase->is_IterGVN();
  83 
  84   uint rreq = region->req();
  85   for( uint i = 1; i < rreq; i++ ) {
  86     Node *r = region->in(i);
  87     if( r && r->Opcode() == Op_Region && // Found a region?
  88         r->in(0) == r &&        // Not already collapsed?
  89         r != region &&          // Avoid stupid situations
  90         r->outcnt() == 2 ) {    // Self user and 'region' user only?
  91       assert(!r->as_Region()->has_phi(), "no phi users");
  92       if( !progress ) {         // No progress
  93         if (region->has_phi()) {
  94           return nullptr;        // Only flatten if no Phi users
  95           // igvn->hash_delete( phi );
  96         }
  97         igvn->hash_delete( region );
  98         progress = region;      // Making progress
  99       }
 100       igvn->hash_delete( r );
 101 
 102       // Append inputs to 'r' onto 'region'
 103       for( uint j = 1; j < r->req(); j++ ) {
 104         // Move an input from 'r' to 'region'
 105         region->add_req(r->in(j));
 106         r->set_req(j, phase->C->top());
 107         // Update phis of 'region'
 108         //for( uint k = 0; k < max; k++ ) {
 109         //  Node *phi = region->out(k);
 110         //  if( phi->is_Phi() ) {
 111         //    phi->add_req(phi->in(i));
 112         //  }
 113         //}
 114 
 115         rreq++;                 // One more input to Region
 116       } // Found a region to merge into Region
 117       igvn->_worklist.push(r);
 118       // Clobber pointer to the now dead 'r'
 119       region->set_req(i, phase->C->top());
 120     }
 121   }
 122 
 123   return progress;
 124 }
 125 
 126 
 127 
 128 //--------------------------------has_phi--------------------------------------
 129 // Helper function: Return any PhiNode that uses this region or null
 130 PhiNode* RegionNode::has_phi() const {
 131   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 132     Node* phi = fast_out(i);
 133     if (phi->is_Phi()) {   // Check for Phi users
 134       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 135       return phi->as_Phi();  // this one is good enough
 136     }
 137   }
 138 
 139   return nullptr;
 140 }
 141 
 142 
 143 //-----------------------------has_unique_phi----------------------------------
 144 // Helper function: Return the only PhiNode that uses this region or null
 145 PhiNode* RegionNode::has_unique_phi() const {
 146   // Check that only one use is a Phi
 147   PhiNode* only_phi = nullptr;
 148   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 149     Node* phi = fast_out(i);
 150     if (phi->is_Phi()) {   // Check for Phi users
 151       assert(phi->in(0) == (Node*)this, "phi uses region only via in(0)");
 152       if (only_phi == nullptr) {
 153         only_phi = phi->as_Phi();
 154       } else {
 155         return nullptr;  // multiple phis
 156       }
 157     }
 158   }
 159 
 160   return only_phi;
 161 }
 162 
 163 
 164 //------------------------------check_phi_clipping-----------------------------
 165 // Helper function for RegionNode's identification of FP clipping
 166 // Check inputs to the Phi
 167 static bool check_phi_clipping( PhiNode *phi, ConNode * &min, uint &min_idx, ConNode * &max, uint &max_idx, Node * &val, uint &val_idx ) {
 168   min     = nullptr;
 169   max     = nullptr;
 170   val     = nullptr;
 171   min_idx = 0;
 172   max_idx = 0;
 173   val_idx = 0;
 174   uint  phi_max = phi->req();
 175   if( phi_max == 4 ) {
 176     for( uint j = 1; j < phi_max; ++j ) {
 177       Node *n = phi->in(j);
 178       int opcode = n->Opcode();
 179       switch( opcode ) {
 180       case Op_ConI:
 181         {
 182           if( min == nullptr ) {
 183             min     = n->Opcode() == Op_ConI ? (ConNode*)n : nullptr;
 184             min_idx = j;
 185           } else {
 186             max     = n->Opcode() == Op_ConI ? (ConNode*)n : nullptr;
 187             max_idx = j;
 188             if( min->get_int() > max->get_int() ) {
 189               // Swap min and max
 190               ConNode *temp;
 191               uint     temp_idx;
 192               temp     = min;     min     = max;     max     = temp;
 193               temp_idx = min_idx; min_idx = max_idx; max_idx = temp_idx;
 194             }
 195           }
 196         }
 197         break;
 198       default:
 199         {
 200           val = n;
 201           val_idx = j;
 202         }
 203         break;
 204       }
 205     }
 206   }
 207   return ( min && max && val && (min->get_int() <= 0) && (max->get_int() >=0) );
 208 }
 209 
 210 
 211 //------------------------------check_if_clipping------------------------------
 212 // Helper function for RegionNode's identification of FP clipping
 213 // Check that inputs to Region come from two IfNodes,
 214 //
 215 //            If
 216 //      False    True
 217 //       If        |
 218 //  False  True    |
 219 //    |      |     |
 220 //  RegionNode_inputs
 221 //
 222 static bool check_if_clipping( const RegionNode *region, IfNode * &bot_if, IfNode * &top_if ) {
 223   top_if = nullptr;
 224   bot_if = nullptr;
 225 
 226   // Check control structure above RegionNode for (if  ( if  ) )
 227   Node *in1 = region->in(1);
 228   Node *in2 = region->in(2);
 229   Node *in3 = region->in(3);
 230   // Check that all inputs are projections
 231   if( in1->is_Proj() && in2->is_Proj() && in3->is_Proj() ) {
 232     Node *in10 = in1->in(0);
 233     Node *in20 = in2->in(0);
 234     Node *in30 = in3->in(0);
 235     // Check that #1 and #2 are ifTrue and ifFalse from same If
 236     if( in10 != nullptr && in10->is_If() &&
 237         in20 != nullptr && in20->is_If() &&
 238         in30 != nullptr && in30->is_If() && in10 == in20 &&
 239         (in1->Opcode() != in2->Opcode()) ) {
 240       Node  *in100 = in10->in(0);
 241       Node *in1000 = (in100 != nullptr && in100->is_Proj()) ? in100->in(0) : nullptr;
 242       // Check that control for in10 comes from other branch of IF from in3
 243       if( in1000 != nullptr && in1000->is_If() &&
 244           in30 == in1000 && (in3->Opcode() != in100->Opcode()) ) {
 245         // Control pattern checks
 246         top_if = (IfNode*)in1000;
 247         bot_if = (IfNode*)in10;
 248       }
 249     }
 250   }
 251 
 252   return (top_if != nullptr);
 253 }
 254 
 255 
 256 //------------------------------check_convf2i_clipping-------------------------
 257 // Helper function for RegionNode's identification of FP clipping
 258 // Verify that the value input to the phi comes from "ConvF2I; LShift; RShift"
 259 static bool check_convf2i_clipping( PhiNode *phi, uint idx, ConvF2INode * &convf2i, Node *min, Node *max) {
 260   convf2i = nullptr;
 261 
 262   // Check for the RShiftNode
 263   Node *rshift = phi->in(idx);
 264   assert( rshift, "Previous checks ensure phi input is present");
 265   if( rshift->Opcode() != Op_RShiftI )  { return false; }
 266 
 267   // Check for the LShiftNode
 268   Node *lshift = rshift->in(1);
 269   assert( lshift, "Previous checks ensure phi input is present");
 270   if( lshift->Opcode() != Op_LShiftI )  { return false; }
 271 
 272   // Check for the ConvF2INode
 273   Node *conv = lshift->in(1);
 274   if( conv->Opcode() != Op_ConvF2I ) { return false; }
 275 
 276   // Check that shift amounts are only to get sign bits set after F2I
 277   jint max_cutoff     = max->get_int();
 278   jint min_cutoff     = min->get_int();
 279   jint left_shift     = lshift->in(2)->get_int();
 280   jint right_shift    = rshift->in(2)->get_int();
 281   jint max_post_shift = nth_bit(BitsPerJavaInteger - left_shift - 1);
 282   if( left_shift != right_shift ||
 283       0 > left_shift || left_shift >= BitsPerJavaInteger ||
 284       max_post_shift < max_cutoff ||
 285       max_post_shift < -min_cutoff ) {
 286     // Shifts are necessary but current transformation eliminates them
 287     return false;
 288   }
 289 
 290   // OK to return the result of ConvF2I without shifting
 291   convf2i = (ConvF2INode*)conv;
 292   return true;
 293 }
 294 
 295 
 296 //------------------------------check_compare_clipping-------------------------
 297 // Helper function for RegionNode's identification of FP clipping
 298 static bool check_compare_clipping( bool less_than, IfNode *iff, ConNode *limit, Node * & input ) {
 299   Node *i1 = iff->in(1);
 300   if ( !i1->is_Bool() ) { return false; }
 301   BoolNode *bool1 = i1->as_Bool();
 302   if(       less_than && bool1->_test._test != BoolTest::le ) { return false; }
 303   else if( !less_than && bool1->_test._test != BoolTest::lt ) { return false; }
 304   const Node *cmpF = bool1->in(1);
 305   if( cmpF->Opcode() != Op_CmpF )      { return false; }
 306   // Test that the float value being compared against
 307   // is equivalent to the int value used as a limit
 308   Node *nodef = cmpF->in(2);
 309   if( nodef->Opcode() != Op_ConF ) { return false; }
 310   jfloat conf = nodef->getf();
 311   jint   coni = limit->get_int();
 312   if( ((int)conf) != coni )        { return false; }
 313   input = cmpF->in(1);
 314   return true;
 315 }
 316 
 317 //------------------------------is_unreachable_region--------------------------
 318 // Check if the RegionNode is part of an unsafe loop and unreachable from root.
 319 bool RegionNode::is_unreachable_region(const PhaseGVN* phase) {
 320   Node* top = phase->C->top();
 321   assert(req() == 2 || (req() == 3 && in(1) != nullptr && in(2) == top), "sanity check arguments");
 322   if (_is_unreachable_region) {
 323     // Return cached result from previous evaluation which should still be valid
 324     assert(is_unreachable_from_root(phase), "walk the graph again and check if its indeed unreachable");
 325     return true;
 326   }
 327 
 328   // First, cut the simple case of fallthrough region when NONE of
 329   // region's phis references itself directly or through a data node.
 330   if (is_possible_unsafe_loop(phase)) {
 331     // If we have a possible unsafe loop, check if the region node is actually unreachable from root.
 332     if (is_unreachable_from_root(phase)) {
 333       _is_unreachable_region = true;
 334       return true;
 335     }
 336   }
 337   return false;
 338 }
 339 
 340 bool RegionNode::is_possible_unsafe_loop(const PhaseGVN* phase) const {
 341   uint max = outcnt();
 342   uint i;
 343   for (i = 0; i < max; i++) {
 344     Node* n = raw_out(i);
 345     if (n != nullptr && n->is_Phi()) {
 346       PhiNode* phi = n->as_Phi();
 347       assert(phi->in(0) == this, "sanity check phi");
 348       if (phi->outcnt() == 0) {
 349         continue; // Safe case - no loops
 350       }
 351       if (phi->outcnt() == 1) {
 352         Node* u = phi->raw_out(0);
 353         // Skip if only one use is an other Phi or Call or Uncommon trap.
 354         // It is safe to consider this case as fallthrough.
 355         if (u != nullptr && (u->is_Phi() || u->is_CFG())) {
 356           continue;
 357         }
 358       }
 359       // Check when phi references itself directly or through an other node.
 360       if (phi->as_Phi()->simple_data_loop_check(phi->in(1)) >= PhiNode::Unsafe) {
 361         break; // Found possible unsafe data loop.
 362       }
 363     }
 364   }
 365   if (i >= max) {
 366     return false; // An unsafe case was NOT found - don't need graph walk.
 367   }
 368   return true;
 369 }
 370 
 371 bool RegionNode::is_unreachable_from_root(const PhaseGVN* phase) const {
 372   ResourceMark rm;
 373   Node_List nstack;
 374   VectorSet visited;
 375 
 376   // Mark all control nodes reachable from root outputs
 377   Node* n = (Node*)phase->C->root();
 378   nstack.push(n);
 379   visited.set(n->_idx);
 380   while (nstack.size() != 0) {
 381     n = nstack.pop();
 382     uint max = n->outcnt();
 383     for (uint i = 0; i < max; i++) {
 384       Node* m = n->raw_out(i);
 385       if (m != nullptr && m->is_CFG()) {
 386         if (m == this) {
 387           return false; // We reached the Region node - it is not dead.
 388         }
 389         if (!visited.test_set(m->_idx))
 390           nstack.push(m);
 391       }
 392     }
 393   }
 394   return true; // The Region node is unreachable - it is dead.
 395 }
 396 
 397 #ifdef ASSERT
 398 // Is this region in an infinite subgraph?
 399 // (no path to root except through false NeverBranch exit)
 400 bool RegionNode::is_in_infinite_subgraph() {
 401   ResourceMark rm;
 402   Unique_Node_List worklist;
 403   worklist.push(this);
 404   return RegionNode::are_all_nodes_in_infinite_subgraph(worklist);
 405 }
 406 
 407 // Are all nodes in worklist in infinite subgraph?
 408 // (no path to root except through false NeverBranch exit)
 409 // worklist is directly used for the traversal
 410 bool RegionNode::are_all_nodes_in_infinite_subgraph(Unique_Node_List& worklist) {
 411   // BFS traversal down the CFG, except through NeverBranch exits
 412   for (uint i = 0; i < worklist.size(); ++i) {
 413     Node* n = worklist.at(i);
 414     assert(n->is_CFG(), "only traverse CFG");
 415     if (n->is_Root()) {
 416       // Found root -> there was an exit!
 417       return false;
 418     } else if (n->is_NeverBranch()) {
 419       // Only follow the loop-internal projection, not the NeverBranch exit
 420       ProjNode* proj = n->as_NeverBranch()->proj_out_or_null(0);
 421       assert(proj != nullptr, "must find loop-internal projection of NeverBranch");
 422       worklist.push(proj);
 423     } else {
 424       // Traverse all CFG outputs
 425       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 426         Node* use = n->fast_out(i);
 427         if (use->is_CFG()) {
 428           worklist.push(use);
 429         }
 430       }
 431     }
 432   }
 433   // No exit found for any loop -> all are infinite
 434   return true;
 435 }
 436 #endif //ASSERT
 437 
 438 void RegionNode::set_loop_status(RegionNode::LoopStatus status) {
 439   assert(loop_status() == RegionNode::LoopStatus::NeverIrreducibleEntry, "why set our status again?");
 440   assert(status != RegionNode::LoopStatus::MaybeIrreducibleEntry || !is_Loop(), "LoopNode is never irreducible entry.");
 441   _loop_status = status;
 442 }
 443 
 444 // A Region can only be an irreducible entry if:
 445 // - It is marked as "maybe irreducible entry". Any other loop status would guarantee
 446 //   that it is never an irreducible loop entry.
 447 // - And it is not a LoopNode, those are guaranteed to be reducible loop entries.
 448 bool RegionNode::can_be_irreducible_entry() const {
 449   return loop_status() == RegionNode::LoopStatus::MaybeIrreducibleEntry &&
 450          !is_Loop();
 451 }
 452 
 453 void RegionNode::try_clean_mem_phis(PhaseIterGVN* igvn) {
 454   // Incremental inlining + PhaseStringOpts sometimes produce:
 455   //
 456   // cmpP with 1 top input
 457   //           |
 458   //          If
 459   //         /  \
 460   //   IfFalse  IfTrue  /- Some Node
 461   //         \  /      /    /
 462   //        Region    / /-MergeMem
 463   //             \---Phi
 464   //
 465   //
 466   // It's expected by PhaseStringOpts that the Region goes away and is
 467   // replaced by If's control input but because there's still a Phi,
 468   // the Region stays in the graph. The top input from the cmpP is
 469   // propagated forward and a subgraph that is useful goes away. The
 470   // code in PhiNode::try_clean_memory_phi() replaces the Phi with the
 471   // MergeMem in order to remove the Region if its last phi dies.
 472 
 473   if (!is_diamond()) {
 474     return;
 475   }
 476 
 477   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
 478     Node* phi = fast_out(i);
 479     if (phi->is_Phi() && phi->as_Phi()->try_clean_memory_phi(igvn)) {
 480       --i;
 481       --imax;
 482     }
 483   }
 484 }
 485 
 486 // Does this region merge a simple diamond formed by a proper IfNode?
 487 //
 488 //              Cmp
 489 //              /
 490 //     ctrl   Bool
 491 //       \    /
 492 //       IfNode
 493 //      /      \
 494 //  IfFalse   IfTrue
 495 //      \      /
 496 //       Region
 497 bool RegionNode::is_diamond() const {
 498   if (req() != 3) {
 499     return false;
 500   }
 501 
 502   Node* left_path = in(1);
 503   Node* right_path = in(2);
 504   if (left_path == nullptr || right_path == nullptr) {
 505     return false;
 506   }
 507   Node* diamond_if = left_path->in(0);
 508   if (diamond_if == nullptr || !diamond_if->is_If() || diamond_if != right_path->in(0)) {
 509     // Not an IfNode merging a diamond or TOP.
 510     return false;
 511   }
 512 
 513   // Check for a proper bool/cmp
 514   const Node* bol = diamond_if->in(1);
 515   if (!bol->is_Bool()) {
 516     return false;
 517   }
 518   const Node* cmp = bol->in(1);
 519   if (!cmp->is_Cmp()) {
 520     return false;
 521   }
 522   return true;
 523 }
 524 
 525 //------------------------------Ideal------------------------------------------
 526 // Return a node which is more "ideal" than the current node.  Must preserve
 527 // the CFG, but we can still strip out dead paths.
 528 Node *RegionNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 529   if( !can_reshape && !in(0) ) return nullptr;     // Already degraded to a Copy
 530   assert(!in(0) || !in(0)->is_Root(), "not a specially hidden merge");
 531 
 532   // Check for RegionNode with no Phi users and both inputs come from either
 533   // arm of the same IF.  If found, then the control-flow split is useless.
 534   bool has_phis = false;
 535   if (can_reshape) {            // Need DU info to check for Phi users
 536     try_clean_mem_phis(phase->is_IterGVN());
 537     has_phis = (has_phi() != nullptr);       // Cache result
 538 
 539     if (!has_phis) {            // No Phi users?  Nothing merging?
 540       for (uint i = 1; i < req()-1; i++) {
 541         Node *if1 = in(i);
 542         if( !if1 ) continue;
 543         Node *iff = if1->in(0);
 544         if( !iff || !iff->is_If() ) continue;
 545         for( uint j=i+1; j<req(); j++ ) {
 546           if( in(j) && in(j)->in(0) == iff &&
 547               if1->Opcode() != in(j)->Opcode() ) {
 548             // Add the IF Projections to the worklist. They (and the IF itself)
 549             // will be eliminated if dead.
 550             phase->is_IterGVN()->add_users_to_worklist(iff);
 551             set_req(i, iff->in(0));// Skip around the useless IF diamond
 552             set_req(j, nullptr);
 553             return this;      // Record progress
 554           }
 555         }
 556       }
 557     }
 558   }
 559 
 560   // Remove TOP or null input paths. If only 1 input path remains, this Region
 561   // degrades to a copy.
 562   bool add_to_worklist = true;
 563   bool modified = false;
 564   int cnt = 0;                  // Count of values merging
 565   DEBUG_ONLY( int cnt_orig = req(); ) // Save original inputs count
 566   DEBUG_ONLY( uint outcnt_orig = outcnt(); )
 567   int del_it = 0;               // The last input path we delete
 568   bool found_top = false; // irreducible loops need to check reachability if we find TOP
 569   // For all inputs...
 570   for( uint i=1; i<req(); ++i ){// For all paths in
 571     Node *n = in(i);            // Get the input
 572     if( n != nullptr ) {
 573       // Remove useless control copy inputs
 574       if( n->is_Region() && n->as_Region()->is_copy() ) {
 575         set_req(i, n->nonnull_req());
 576         modified = true;
 577         i--;
 578         continue;
 579       }
 580       if( n->is_Proj() ) {      // Remove useless rethrows
 581         Node *call = n->in(0);
 582         if (call->is_Call() && call->as_Call()->entry_point() == OptoRuntime::rethrow_stub()) {
 583           set_req(i, call->in(0));
 584           modified = true;
 585           i--;
 586           continue;
 587         }
 588       }
 589       if( phase->type(n) == Type::TOP ) {
 590         set_req_X(i, nullptr, phase); // Ignore TOP inputs
 591         modified = true;
 592         found_top = true;
 593         i--;
 594         continue;
 595       }
 596       cnt++;                    // One more value merging
 597     } else if (can_reshape) {   // Else found dead path with DU info
 598       PhaseIterGVN *igvn = phase->is_IterGVN();
 599       del_req(i);               // Yank path from self
 600       del_it = i;
 601 
 602       for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
 603         Node* use = fast_out(j);
 604 
 605         if (use->req() != req() && use->is_Phi()) {
 606           assert(use->in(0) == this, "unexpected control input");
 607           igvn->hash_delete(use);          // Yank from hash before hacking edges
 608           use->set_req_X(i, nullptr, igvn);// Correct DU info
 609           use->del_req(i);                 // Yank path from Phis
 610         }
 611       }
 612 
 613       if (add_to_worklist) {
 614         igvn->add_users_to_worklist(this);
 615         add_to_worklist = false;
 616       }
 617 
 618       i--;
 619     }
 620   }
 621 
 622   assert(outcnt() == outcnt_orig, "not expect to remove any use");
 623 
 624   if (can_reshape && found_top && loop_status() == RegionNode::LoopStatus::MaybeIrreducibleEntry) {
 625     // Is it a dead irreducible loop?
 626     // If an irreducible loop loses one of the multiple entries
 627     // that went into the loop head, or any secondary entries,
 628     // we need to verify if the irreducible loop is still reachable,
 629     // as the special logic in is_unreachable_region only works
 630     // for reducible loops.
 631     if (is_unreachable_from_root(phase)) {
 632       // The irreducible loop is dead - must remove it
 633       PhaseIterGVN* igvn = phase->is_IterGVN();
 634       remove_unreachable_subgraph(igvn);
 635       return nullptr;
 636     }
 637   } else if (can_reshape && cnt == 1) {
 638     // Is it dead loop?
 639     // If it is LoopNopde it had 2 (+1 itself) inputs and
 640     // one of them was cut. The loop is dead if it was EntryContol.
 641     // Loop node may have only one input because entry path
 642     // is removed in PhaseIdealLoop::Dominators().
 643     assert(!this->is_Loop() || cnt_orig <= 3, "Loop node should have 3 or less inputs");
 644     if ((this->is_Loop() && (del_it == LoopNode::EntryControl ||
 645                              (del_it == 0 && is_unreachable_region(phase)))) ||
 646         (!this->is_Loop() && has_phis && is_unreachable_region(phase))) {
 647       PhaseIterGVN* igvn = phase->is_IterGVN();
 648       remove_unreachable_subgraph(igvn);
 649       return nullptr;
 650     }
 651   }
 652 
 653   if( cnt <= 1 ) {              // Only 1 path in?
 654     set_req(0, nullptr);        // Null control input for region copy
 655     if( cnt == 0 && !can_reshape) { // Parse phase - leave the node as it is.
 656       // No inputs or all inputs are null.
 657       return nullptr;
 658     } else if (can_reshape) {   // Optimization phase - remove the node
 659       PhaseIterGVN *igvn = phase->is_IterGVN();
 660       // Strip mined (inner) loop is going away, remove outer loop.
 661       if (is_CountedLoop() &&
 662           as_Loop()->is_strip_mined()) {
 663         Node* outer_sfpt = as_CountedLoop()->outer_safepoint();
 664         Node* outer_out = as_CountedLoop()->outer_loop_exit();
 665         if (outer_sfpt != nullptr && outer_out != nullptr) {
 666           Node* in = outer_sfpt->in(0);
 667           igvn->replace_node(outer_out, in);
 668           LoopNode* outer = as_CountedLoop()->outer_loop();
 669           igvn->replace_input_of(outer, LoopNode::LoopBackControl, igvn->C->top());
 670         }
 671       }
 672       if (is_CountedLoop()) {
 673         Node* opaq = as_CountedLoop()->is_canonical_loop_entry();
 674         if (opaq != nullptr) {
 675           // 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
 676           // subject to further loop opts.
 677           assert(opaq->Opcode() == Op_OpaqueZeroTripGuard, "");
 678           igvn->replace_node(opaq, opaq->in(1));
 679         }
 680       }
 681       Node *parent_ctrl;
 682       if( cnt == 0 ) {
 683         assert( req() == 1, "no inputs expected" );
 684         // During IGVN phase such region will be subsumed by TOP node
 685         // so region's phis will have TOP as control node.
 686         // Kill phis here to avoid it.
 687         // Also set other user's input to top.
 688         parent_ctrl = phase->C->top();
 689       } else {
 690         // The fallthrough case since we already checked dead loops above.
 691         parent_ctrl = in(1);
 692         assert(parent_ctrl != nullptr, "Region is a copy of some non-null control");
 693         assert(parent_ctrl != this, "Close dead loop");
 694       }
 695       if (add_to_worklist) {
 696         igvn->add_users_to_worklist(this); // Check for further allowed opts
 697       }
 698       for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
 699         Node* n = last_out(i);
 700         igvn->hash_delete(n); // Remove from worklist before modifying edges
 701         if (n->outcnt() == 0) {
 702           int uses_found = n->replace_edge(this, phase->C->top(), igvn);
 703           if (uses_found > 1) { // (--i) done at the end of the loop.
 704             i -= (uses_found - 1);
 705           }
 706           continue;
 707         }
 708         if( n->is_Phi() ) {   // Collapse all Phis
 709           // Eagerly replace phis to avoid regionless phis.
 710           Node* in;
 711           if( cnt == 0 ) {
 712             assert( n->req() == 1, "No data inputs expected" );
 713             in = parent_ctrl; // replaced by top
 714           } else {
 715             assert( n->req() == 2 &&  n->in(1) != nullptr, "Only one data input expected" );
 716             in = n->in(1);               // replaced by unique input
 717             if( n->as_Phi()->is_unsafe_data_reference(in) )
 718               in = phase->C->top();      // replaced by top
 719           }
 720           igvn->replace_node(n, in);
 721         }
 722         else if( n->is_Region() ) { // Update all incoming edges
 723           assert(n != this, "Must be removed from DefUse edges");
 724           int uses_found = n->replace_edge(this, parent_ctrl, igvn);
 725           if (uses_found > 1) { // (--i) done at the end of the loop.
 726             i -= (uses_found - 1);
 727           }
 728         }
 729         else {
 730           assert(n->in(0) == this, "Expect RegionNode to be control parent");
 731           n->set_req(0, parent_ctrl);
 732         }
 733 #ifdef ASSERT
 734         for( uint k=0; k < n->req(); k++ ) {
 735           assert(n->in(k) != this, "All uses of RegionNode should be gone");
 736         }
 737 #endif
 738       }
 739       // Remove the RegionNode itself from DefUse info
 740       igvn->remove_dead_node(this);
 741       return nullptr;
 742     }
 743     return this;                // Record progress
 744   }
 745 
 746 
 747   // If a Region flows into a Region, merge into one big happy merge.
 748   if (can_reshape) {
 749     Node *m = merge_region(this, phase);
 750     if (m != nullptr)  return m;
 751   }
 752 
 753   // Check if this region is the root of a clipping idiom on floats
 754   if( ConvertFloat2IntClipping && can_reshape && req() == 4 ) {
 755     // Check that only one use is a Phi and that it simplifies to two constants +
 756     PhiNode* phi = has_unique_phi();
 757     if (phi != nullptr) {          // One Phi user
 758       // Check inputs to the Phi
 759       ConNode *min;
 760       ConNode *max;
 761       Node    *val;
 762       uint     min_idx;
 763       uint     max_idx;
 764       uint     val_idx;
 765       if( check_phi_clipping( phi, min, min_idx, max, max_idx, val, val_idx )  ) {
 766         IfNode *top_if;
 767         IfNode *bot_if;
 768         if( check_if_clipping( this, bot_if, top_if ) ) {
 769           // Control pattern checks, now verify compares
 770           Node   *top_in = nullptr;   // value being compared against
 771           Node   *bot_in = nullptr;
 772           if( check_compare_clipping( true,  bot_if, min, bot_in ) &&
 773               check_compare_clipping( false, top_if, max, top_in ) ) {
 774             if( bot_in == top_in ) {
 775               PhaseIterGVN *gvn = phase->is_IterGVN();
 776               assert( gvn != nullptr, "Only had DefUse info in IterGVN");
 777               // Only remaining check is that bot_in == top_in == (Phi's val + mods)
 778 
 779               // Check for the ConvF2INode
 780               ConvF2INode *convf2i;
 781               if( check_convf2i_clipping( phi, val_idx, convf2i, min, max ) &&
 782                 convf2i->in(1) == bot_in ) {
 783                 // Matched pattern, including LShiftI; RShiftI, replace with integer compares
 784                 // max test
 785                 Node *cmp   = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, min ));
 786                 Node *boo   = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::lt ));
 787                 IfNode *iff = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( top_if->in(0), boo, PROB_UNLIKELY_MAG(5), top_if->_fcnt ));
 788                 Node *if_min= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 789                 Node *ifF   = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 790                 // min test
 791                 cmp         = gvn->register_new_node_with_optimizer(new CmpINode( convf2i, max ));
 792                 boo         = gvn->register_new_node_with_optimizer(new BoolNode( cmp, BoolTest::gt ));
 793                 iff         = (IfNode*)gvn->register_new_node_with_optimizer(new IfNode( ifF, boo, PROB_UNLIKELY_MAG(5), bot_if->_fcnt ));
 794                 Node *if_max= gvn->register_new_node_with_optimizer(new IfTrueNode (iff));
 795                 ifF         = gvn->register_new_node_with_optimizer(new IfFalseNode(iff));
 796                 // update input edges to region node
 797                 set_req_X( min_idx, if_min, gvn );
 798                 set_req_X( max_idx, if_max, gvn );
 799                 set_req_X( val_idx, ifF,    gvn );
 800                 // remove unnecessary 'LShiftI; RShiftI' idiom
 801                 gvn->hash_delete(phi);
 802                 phi->set_req_X( val_idx, convf2i, gvn );
 803                 gvn->hash_find_insert(phi);
 804                 // Return transformed region node
 805                 return this;
 806               }
 807             }
 808           }
 809         }
 810       }
 811     }
 812   }
 813 
 814   if (can_reshape) {
 815     modified |= optimize_trichotomy(phase->is_IterGVN());
 816   }
 817 
 818   return modified ? this : nullptr;
 819 }
 820 
 821 //--------------------------remove_unreachable_subgraph----------------------
 822 // This region and therefore all nodes on the input control path(s) are unreachable
 823 // from root. To avoid incomplete removal of unreachable subgraphs, walk up the CFG
 824 // and aggressively replace all nodes by top.
 825 // If a control node "def" with a single control output "use" has its single output
 826 // "use" replaced with top, then "use" removes itself. This has the consequence that
 827 // when we visit "use", it already has all inputs removed. They are lost and we cannot
 828 // traverse them. This is why we fist find all unreachable nodes, and then remove
 829 // them in a second step.
 830 void RegionNode::remove_unreachable_subgraph(PhaseIterGVN* igvn) {
 831   Node* top = igvn->C->top();
 832   ResourceMark rm;
 833   Unique_Node_List unreachable; // visit each only once
 834   unreachable.push(this);
 835   // Recursively find all control inputs.
 836   for (uint i = 0; i < unreachable.size(); i++) {
 837     Node* n = unreachable.at(i);
 838     for (uint i = 0; i < n->req(); ++i) {
 839       Node* m = n->in(i);
 840       assert(m == nullptr || !m->is_Root(), "Should be unreachable from root");
 841       if (m != nullptr && m->is_CFG()) {
 842         unreachable.push(m);
 843       }
 844     }
 845   }
 846   // Remove all unreachable nodes.
 847   for (uint i = 0; i < unreachable.size(); i++) {
 848     Node* n = unreachable.at(i);
 849     if (n->is_Region()) {
 850       // Eagerly replace phis with top to avoid regionless phis.
 851       n->set_req(0, nullptr);
 852       bool progress = true;
 853       uint max = n->outcnt();
 854       DUIterator j;
 855       while (progress) {
 856         progress = false;
 857         for (j = n->outs(); n->has_out(j); j++) {
 858           Node* u = n->out(j);
 859           if (u->is_Phi()) {
 860             igvn->replace_node(u, top);
 861             if (max != n->outcnt()) {
 862               progress = true;
 863               j = n->refresh_out_pos(j);
 864               max = n->outcnt();
 865             }
 866           }
 867         }
 868       }
 869     }
 870     igvn->replace_node(n, top);
 871   }
 872 }
 873 
 874 //------------------------------optimize_trichotomy--------------------------
 875 // Optimize nested comparisons of the following kind:
 876 //
 877 // int compare(int a, int b) {
 878 //   return (a < b) ? -1 : (a == b) ? 0 : 1;
 879 // }
 880 //
 881 // Shape 1:
 882 // if (compare(a, b) == 1) { ... } -> if (a > b) { ... }
 883 //
 884 // Shape 2:
 885 // if (compare(a, b) == 0) { ... } -> if (a == b) { ... }
 886 //
 887 // Above code leads to the following IR shapes where both Ifs compare the
 888 // same value and two out of three region inputs idx1 and idx2 map to
 889 // the same value and control flow.
 890 //
 891 // (1)   If                 (2)   If
 892 //      /  \                     /  \
 893 //   Proj  Proj               Proj  Proj
 894 //     |      \                |      \
 895 //     |       If              |      If                      If
 896 //     |      /  \             |     /  \                    /  \
 897 //     |   Proj  Proj          |  Proj  Proj      ==>     Proj  Proj
 898 //     |   /      /            \    |    /                  |    /
 899 //    Region     /              \   |   /                   |   /
 900 //         \    /                \  |  /                    |  /
 901 //         Region                Region                    Region
 902 //
 903 // The method returns true if 'this' is modified and false otherwise.
 904 bool RegionNode::optimize_trichotomy(PhaseIterGVN* igvn) {
 905   int idx1 = 1, idx2 = 2;
 906   Node* region = nullptr;
 907   if (req() == 3 && in(1) != nullptr && in(2) != nullptr) {
 908     // Shape 1: Check if one of the inputs is a region that merges two control
 909     // inputs and has no other users (especially no Phi users).
 910     region = in(1)->isa_Region() ? in(1) : in(2)->isa_Region();
 911     if (region == nullptr || region->outcnt() != 2 || region->req() != 3) {
 912       return false; // No suitable region input found
 913     }
 914   } else if (req() == 4) {
 915     // Shape 2: Check if two control inputs map to the same value of the unique phi
 916     // user and treat these as if they would come from another region (shape (1)).
 917     PhiNode* phi = has_unique_phi();
 918     if (phi == nullptr) {
 919       return false; // No unique phi user
 920     }
 921     if (phi->in(idx1) != phi->in(idx2)) {
 922       idx2 = 3;
 923       if (phi->in(idx1) != phi->in(idx2)) {
 924         idx1 = 2;
 925         if (phi->in(idx1) != phi->in(idx2)) {
 926           return false; // No equal phi inputs found
 927         }
 928       }
 929     }
 930     assert(phi->in(idx1) == phi->in(idx2), "must be"); // Region is merging same value
 931     region = this;
 932   }
 933   if (region == nullptr || region->in(idx1) == nullptr || region->in(idx2) == nullptr) {
 934     return false; // Region does not merge two control inputs
 935   }
 936   // At this point we know that region->in(idx1) and region->(idx2) map to the same
 937   // value and control flow. Now search for ifs that feed into these region inputs.
 938   ProjNode* proj1 = region->in(idx1)->isa_Proj();
 939   ProjNode* proj2 = region->in(idx2)->isa_Proj();
 940   if (proj1 == nullptr || proj1->outcnt() != 1 ||
 941       proj2 == nullptr || proj2->outcnt() != 1) {
 942     return false; // No projection inputs with region as unique user found
 943   }
 944   assert(proj1 != proj2, "should be different projections");
 945   IfNode* iff1 = proj1->in(0)->isa_If();
 946   IfNode* iff2 = proj2->in(0)->isa_If();
 947   if (iff1 == nullptr || iff1->outcnt() != 2 ||
 948       iff2 == nullptr || iff2->outcnt() != 2) {
 949     return false; // No ifs found
 950   }
 951   if (iff1 == iff2) {
 952     igvn->add_users_to_worklist(iff1); // Make sure dead if is eliminated
 953     igvn->replace_input_of(region, idx1, iff1->in(0));
 954     igvn->replace_input_of(region, idx2, igvn->C->top());
 955     return (region == this); // Remove useless if (both projections map to the same control/value)
 956   }
 957   BoolNode* bol1 = iff1->in(1)->isa_Bool();
 958   BoolNode* bol2 = iff2->in(1)->isa_Bool();
 959   if (bol1 == nullptr || bol2 == nullptr) {
 960     return false; // No bool inputs found
 961   }
 962   Node* cmp1 = bol1->in(1);
 963   Node* cmp2 = bol2->in(1);
 964   bool commute = false;
 965   if (!cmp1->is_Cmp() || !cmp2->is_Cmp()) {
 966     return false; // No comparison
 967   } else if (cmp1->Opcode() == Op_CmpF || cmp1->Opcode() == Op_CmpD ||
 968              cmp2->Opcode() == Op_CmpF || cmp2->Opcode() == Op_CmpD ||
 969              cmp1->Opcode() == Op_CmpP || cmp1->Opcode() == Op_CmpN ||
 970              cmp2->Opcode() == Op_CmpP || cmp2->Opcode() == Op_CmpN ||
 971              cmp1->is_SubTypeCheck() || cmp2->is_SubTypeCheck() ||
 972              cmp1->is_FlatArrayCheck() || cmp2->is_FlatArrayCheck()) {
 973     // Floats and pointers don't exactly obey trichotomy. To be on the safe side, don't transform their tests.
 974     // SubTypeCheck is not commutative
 975     return false;
 976   } else if (cmp1 != cmp2) {
 977     if (cmp1->in(1) == cmp2->in(2) &&
 978         cmp1->in(2) == cmp2->in(1)) {
 979       commute = true; // Same but swapped inputs, commute the test
 980     } else {
 981       return false; // Ifs are not comparing the same values
 982     }
 983   }
 984   proj1 = proj1->other_if_proj();
 985   proj2 = proj2->other_if_proj();
 986   if (!((proj1->unique_ctrl_out_or_null() == iff2 &&
 987          proj2->unique_ctrl_out_or_null() == this) ||
 988         (proj2->unique_ctrl_out_or_null() == iff1 &&
 989          proj1->unique_ctrl_out_or_null() == this))) {
 990     return false; // Ifs are not connected through other projs
 991   }
 992   // Found 'iff -> proj -> iff -> proj -> this' shape where all other projs are merged
 993   // through 'region' and map to the same value. Merge the boolean tests and replace
 994   // the ifs by a single comparison.
 995   BoolTest test1 = (proj1->_con == 1) ? bol1->_test : bol1->_test.negate();
 996   BoolTest test2 = (proj2->_con == 1) ? bol2->_test : bol2->_test.negate();
 997   test1 = commute ? test1.commute() : test1;
 998   // After possibly commuting test1, if we can merge test1 & test2, then proj2/iff2/bol2 are the nodes to refine.
 999   BoolTest::mask res = test1.merge(test2);
1000   if (res == BoolTest::illegal) {
1001     return false; // Unable to merge tests
1002   }
1003   // Adjust iff1 to always pass (only iff2 will remain)
1004   igvn->replace_input_of(iff1, 1, igvn->intcon(proj1->_con));
1005   if (res == BoolTest::never) {
1006     // Merged test is always false, adjust iff2 to always fail
1007     igvn->replace_input_of(iff2, 1, igvn->intcon(1 - proj2->_con));
1008   } else {
1009     // Replace bool input of iff2 with merged test
1010     BoolNode* new_bol = new BoolNode(bol2->in(1), res);
1011     igvn->replace_input_of(iff2, 1, igvn->transform((proj2->_con == 1) ? new_bol : new_bol->negate(igvn)));
1012     if (new_bol->outcnt() == 0) {
1013       igvn->remove_dead_node(new_bol);
1014     }
1015   }
1016   return false;
1017 }
1018 
1019 const RegMask &RegionNode::out_RegMask() const {
1020   return RegMask::Empty;
1021 }
1022 
1023 #ifndef PRODUCT
1024 void RegionNode::dump_spec(outputStream* st) const {
1025   Node::dump_spec(st);
1026   switch (loop_status()) {
1027   case RegionNode::LoopStatus::MaybeIrreducibleEntry:
1028     st->print("#irreducible ");
1029     break;
1030   case RegionNode::LoopStatus::Reducible:
1031     st->print("#reducible ");
1032     break;
1033   case RegionNode::LoopStatus::NeverIrreducibleEntry:
1034     break; // nothing
1035   }
1036 }
1037 #endif
1038 
1039 // Find the one non-null required input.  RegionNode only
1040 Node *Node::nonnull_req() const {
1041   assert( is_Region(), "" );
1042   for( uint i = 1; i < _cnt; i++ )
1043     if( in(i) )
1044       return in(i);
1045   ShouldNotReachHere();
1046   return nullptr;
1047 }
1048 
1049 
1050 //=============================================================================
1051 // note that these functions assume that the _adr_type field is flat
1052 uint PhiNode::hash() const {
1053   const Type* at = _adr_type;
1054   return TypeNode::hash() + (at ? at->hash() : 0);
1055 }
1056 bool PhiNode::cmp( const Node &n ) const {
1057   return TypeNode::cmp(n) && _adr_type == ((PhiNode&)n)._adr_type;
1058 }
1059 static inline
1060 const TypePtr* flatten_phi_adr_type(const TypePtr* at) {
1061   if (at == nullptr || at == TypePtr::BOTTOM)  return at;
1062   return Compile::current()->alias_type(at)->adr_type();
1063 }
1064 
1065 //----------------------------make---------------------------------------------
1066 // create a new phi with edges matching r and set (initially) to x
1067 PhiNode* PhiNode::make(Node* r, Node* x, const Type *t, const TypePtr* at) {
1068   uint preds = r->req();   // Number of predecessor paths
1069   assert(t != Type::MEMORY || at == flatten_phi_adr_type(at) || (flatten_phi_adr_type(at) == TypeAryPtr::INLINES && Compile::current()->flat_accesses_share_alias()), "flatten at");
1070   PhiNode* p = new PhiNode(r, t, at);
1071   for (uint j = 1; j < preds; j++) {
1072     // Fill in all inputs, except those which the region does not yet have
1073     if (r->in(j) != nullptr)
1074       p->init_req(j, x);
1075   }
1076   return p;
1077 }
1078 PhiNode* PhiNode::make(Node* r, Node* x) {
1079   const Type*    t  = x->bottom_type();
1080   const TypePtr* at = nullptr;
1081   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
1082   return make(r, x, t, at);
1083 }
1084 PhiNode* PhiNode::make_blank(Node* r, Node* x) {
1085   const Type*    t  = x->bottom_type();
1086   const TypePtr* at = nullptr;
1087   if (t == Type::MEMORY)  at = flatten_phi_adr_type(x->adr_type());
1088   return new PhiNode(r, t, at);
1089 }
1090 
1091 
1092 //------------------------slice_memory-----------------------------------------
1093 // create a new phi with narrowed memory type
1094 PhiNode* PhiNode::slice_memory(const TypePtr* adr_type) const {
1095   PhiNode* mem = (PhiNode*) clone();
1096   *(const TypePtr**)&mem->_adr_type = adr_type;
1097   // convert self-loops, or else we get a bad graph
1098   for (uint i = 1; i < req(); i++) {
1099     if ((const Node*)in(i) == this)  mem->set_req(i, mem);
1100   }
1101   mem->verify_adr_type();
1102   return mem;
1103 }
1104 
1105 //------------------------split_out_instance-----------------------------------
1106 // Split out an instance type from a bottom phi.
1107 PhiNode* PhiNode::split_out_instance(const TypePtr* at, PhaseIterGVN *igvn) const {
1108   const TypeOopPtr *t_oop = at->isa_oopptr();
1109   assert(t_oop != nullptr && t_oop->is_known_instance(), "expecting instance oopptr");
1110 
1111   // Check if an appropriate node already exists.
1112   Node *region = in(0);
1113   for (DUIterator_Fast kmax, k = region->fast_outs(kmax); k < kmax; k++) {
1114     Node* use = region->fast_out(k);
1115     if( use->is_Phi()) {
1116       PhiNode *phi2 = use->as_Phi();
1117       if (phi2->type() == Type::MEMORY && phi2->adr_type() == at) {
1118         return phi2;
1119       }
1120     }
1121   }
1122   Compile *C = igvn->C;
1123   ResourceMark rm;
1124   Node_Array node_map;
1125   Node_Stack stack(C->live_nodes() >> 4);
1126   PhiNode *nphi = slice_memory(at);
1127   igvn->register_new_node_with_optimizer( nphi );
1128   node_map.map(_idx, nphi);
1129   stack.push((Node *)this, 1);
1130   while(!stack.is_empty()) {
1131     PhiNode *ophi = stack.node()->as_Phi();
1132     uint i = stack.index();
1133     assert(i >= 1, "not control edge");
1134     stack.pop();
1135     nphi = node_map[ophi->_idx]->as_Phi();
1136     for (; i < ophi->req(); i++) {
1137       Node *in = ophi->in(i);
1138       if (in == nullptr || igvn->type(in) == Type::TOP)
1139         continue;
1140       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, nullptr, igvn);
1141       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : nullptr;
1142       if (optphi != nullptr && optphi->adr_type() == TypePtr::BOTTOM) {
1143         opt = node_map[optphi->_idx];
1144         if (opt == nullptr) {
1145           stack.push(ophi, i);
1146           nphi = optphi->slice_memory(at);
1147           igvn->register_new_node_with_optimizer( nphi );
1148           node_map.map(optphi->_idx, nphi);
1149           ophi = optphi;
1150           i = 0; // will get incremented at top of loop
1151           continue;
1152         }
1153       }
1154       nphi->set_req(i, opt);
1155     }
1156   }
1157   return nphi;
1158 }
1159 
1160 //------------------------verify_adr_type--------------------------------------
1161 #ifdef ASSERT
1162 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1163   if (visited.test_set(_idx))  return;  //already visited
1164 
1165   // recheck constructor invariants:
1166   verify_adr_type(false);
1167 
1168   // recheck local phi/phi consistency:
1169   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1170          "adr_type must be consistent across phi nest");
1171 
1172   // walk around
1173   for (uint i = 1; i < req(); i++) {
1174     Node* n = in(i);
1175     if (n == nullptr)  continue;
1176     const Node* np = in(i);
1177     if (np->is_Phi()) {
1178       np->as_Phi()->verify_adr_type(visited, at);
1179     } else if (n->bottom_type() == Type::TOP
1180                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1181       // ignore top inputs
1182     } else {
1183       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1184       // recheck phi/non-phi consistency at leaves:
1185       assert((nat != nullptr) == (at != nullptr), "");
1186       assert(nat == at || nat == TypePtr::BOTTOM,
1187              "adr_type must be consistent at leaves of phi nest");
1188     }
1189   }
1190 }
1191 
1192 // Verify a whole nest of phis rooted at this one.
1193 void PhiNode::verify_adr_type(bool recursive) const {
1194   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1195   if (Node::in_dump())               return;  // muzzle asserts when printing
1196 
1197   assert((_type == Type::MEMORY) == (_adr_type != nullptr), "adr_type for memory phis only");
1198   // Flat array element shouldn't get their own memory slice until flat_accesses_share_alias is cleared.
1199   // It could be the graph has no loads/stores and flat_accesses_share_alias is never cleared. EA could still
1200   // creates per element Phis but that wouldn't be a problem as there are no memory accesses for that array.
1201   assert(_adr_type == nullptr || _adr_type->isa_aryptr() == nullptr ||
1202          _adr_type->is_aryptr()->is_known_instance() ||
1203          !_adr_type->is_aryptr()->is_flat() ||
1204          !Compile::current()->flat_accesses_share_alias() ||
1205          _adr_type == TypeAryPtr::INLINES, "flat array element shouldn't get its own slice yet");
1206 
1207   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1208 
1209   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1210          "Phi::adr_type must be pre-normalized");
1211 
1212   if (recursive) {
1213     VectorSet visited;
1214     verify_adr_type(visited, _adr_type);
1215   }
1216 }
1217 #endif
1218 
1219 
1220 //------------------------------Value------------------------------------------
1221 // Compute the type of the PhiNode
1222 const Type* PhiNode::Value(PhaseGVN* phase) const {
1223   Node *r = in(0);              // RegionNode
1224   if( !r )                      // Copy or dead
1225     return in(1) ? phase->type(in(1)) : Type::TOP;
1226 
1227   // Note: During parsing, phis are often transformed before their regions.
1228   // This means we have to use type_or_null to defend against untyped regions.
1229   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1230     return Type::TOP;
1231 
1232   // Check for trip-counted loop.  If so, be smarter.
1233   BaseCountedLoopNode* l = r->is_BaseCountedLoop() ? r->as_BaseCountedLoop() : nullptr;
1234   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1235     // protect against init_trip() or limit() returning null
1236     if (l->can_be_counted_loop(phase)) {
1237       const Node* init = l->init_trip();
1238       const Node* limit = l->limit();
1239       const Node* stride = l->stride();
1240       if (init != nullptr && limit != nullptr && stride != nullptr) {
1241         const TypeInteger* lo = phase->type(init)->isa_integer(l->bt());
1242         const TypeInteger* hi = phase->type(limit)->isa_integer(l->bt());
1243         const TypeInteger* stride_t = phase->type(stride)->isa_integer(l->bt());
1244         if (lo != nullptr && hi != nullptr && stride_t != nullptr) { // Dying loops might have TOP here
1245           assert(stride_t->is_con(), "bad stride type");
1246           BoolTest::mask bt = l->loopexit()->test_trip();
1247           // If the loop exit condition is "not equal", the condition
1248           // would not trigger if init > limit (if stride > 0) or if
1249           // init < limit if (stride > 0) so we can't deduce bounds
1250           // for the iv from the exit condition.
1251           if (bt != BoolTest::ne) {
1252             jlong stride_con = stride_t->get_con_as_long(l->bt());
1253             if (stride_con < 0) {          // Down-counter loop
1254               swap(lo, hi);
1255               jlong iv_range_lower_limit = lo->lo_as_long();
1256               // Prevent overflow when adding one below
1257               if (iv_range_lower_limit < max_signed_integer(l->bt())) {
1258                 // The loop exit condition is: iv + stride > limit (iv is this Phi). So the loop iterates until
1259                 // iv + stride <= limit
1260                 // We know that: limit >= lo->lo_as_long() and stride <= -1
1261                 // So when the loop exits, iv has to be at most lo->lo_as_long() + 1
1262                 iv_range_lower_limit += 1; // lo is after decrement
1263                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1264                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != -1) {
1265                   julong uhi = static_cast<julong>(hi->lo_as_long());
1266                   julong ulo = static_cast<julong>(lo->hi_as_long());
1267                   julong diff = ((uhi - ulo - 1) / (-stride_con)) * (-stride_con);
1268                   julong ufirst = hi->lo_as_long() - diff;
1269                   iv_range_lower_limit = reinterpret_cast<jlong &>(ufirst);
1270                   assert(iv_range_lower_limit >= lo->lo_as_long() + 1, "should end up with narrower range");
1271                 }
1272               }
1273               return TypeInteger::make(MIN2(iv_range_lower_limit, hi->lo_as_long()), hi->hi_as_long(), 3, l->bt())->filter_speculative(_type);
1274             } else if (stride_con >= 0) {
1275               jlong iv_range_upper_limit = hi->hi_as_long();
1276               // Prevent overflow when subtracting one below
1277               if (iv_range_upper_limit > min_signed_integer(l->bt())) {
1278                 // The loop exit condition is: iv + stride < limit (iv is this Phi). So the loop iterates until
1279                 // iv + stride >= limit
1280                 // We know that: limit <= hi->hi_as_long() and stride >= 1
1281                 // So when the loop exits, iv has to be at most hi->hi_as_long() - 1
1282                 iv_range_upper_limit -= 1;
1283                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1284                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != 1) {
1285                   julong uhi = static_cast<julong>(hi->lo_as_long());
1286                   julong ulo = static_cast<julong>(lo->hi_as_long());
1287                   julong diff = ((uhi - ulo - 1) / stride_con) * stride_con;
1288                   julong ulast = lo->hi_as_long() + diff;
1289                   iv_range_upper_limit = reinterpret_cast<jlong &>(ulast);
1290                   assert(iv_range_upper_limit <= hi->hi_as_long() - 1, "should end up with narrower range");
1291                 }
1292               }
1293               return TypeInteger::make(lo->lo_as_long(), MAX2(lo->hi_as_long(), iv_range_upper_limit), 3, l->bt())->filter_speculative(_type);
1294             }
1295           }
1296         }
1297       }
1298     } else if (l->in(LoopNode::LoopBackControl) != nullptr &&
1299                in(LoopNode::EntryControl) != nullptr &&
1300                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1301       // During CCP, if we saturate the type of a counted loop's Phi
1302       // before the special code for counted loop above has a chance
1303       // to run (that is as long as the type of the backedge's control
1304       // is top), we might end up with non monotonic types
1305       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1306     }
1307   }
1308 
1309   // Default case: merge all inputs
1310   const Type *t = Type::TOP;        // Merged type starting value
1311   for (uint i = 1; i < req(); ++i) {// For all paths in
1312     // Reachable control path?
1313     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1314       const Type* ti = phase->type(in(i));
1315       t = t->meet_speculative(ti);
1316     }
1317   }
1318 
1319   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1320   // That is, we expect that "t->higher_equal(_type)" holds true.
1321   // There are various exceptions:
1322   // - Inputs which are phis might in fact be widened unnecessarily.
1323   //   For example, an input might be a widened int while the phi is a short.
1324   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1325   //   and postCCP has removed the cast which encodes the result of the check.
1326   // - The type of this phi is an interface, and the inputs are classes.
1327   // - Value calls on inputs might produce fuzzy results.
1328   //   (Occurrences of this case suggest improvements to Value methods.)
1329   //
1330   // It is not possible to see Type::BOTTOM values as phi inputs,
1331   // because the ciTypeFlow pre-pass produces verifier-quality types.
1332   const Type* ft = t->filter_speculative(_type);  // Worst case type
1333 
1334 #ifdef ASSERT
1335   // The following logic has been moved into TypeOopPtr::filter.
1336   const Type* jt = t->join_speculative(_type);
1337   if (jt->empty()) {           // Emptied out???
1338     // Otherwise it's something stupid like non-overlapping int ranges
1339     // found on dying counted loops.
1340     assert(ft == Type::TOP, ""); // Canonical empty value
1341   }
1342 
1343   else {
1344 
1345     if (jt != ft && jt->base() == ft->base()) {
1346       if (jt->isa_int() &&
1347           jt->is_int()->_lo == ft->is_int()->_lo &&
1348           jt->is_int()->_hi == ft->is_int()->_hi)
1349         jt = ft;
1350       if (jt->isa_long() &&
1351           jt->is_long()->_lo == ft->is_long()->_lo &&
1352           jt->is_long()->_hi == ft->is_long()->_hi)
1353         jt = ft;
1354     }
1355     if (jt != ft) {
1356       tty->print("merge type:  "); t->dump(); tty->cr();
1357       tty->print("kill type:   "); _type->dump(); tty->cr();
1358       tty->print("join type:   "); jt->dump(); tty->cr();
1359       tty->print("filter type: "); ft->dump(); tty->cr();
1360     }
1361     assert(jt == ft, "");
1362   }
1363 #endif //ASSERT
1364 
1365   // Deal with conversion problems found in data loops.
1366   ft = phase->saturate_and_maybe_push_to_igvn_worklist(this, ft);
1367   return ft;
1368 }
1369 
1370 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1371 // index of the true path or 0 otherwise.
1372 int PhiNode::is_diamond_phi() const {
1373   Node* region = in(0);
1374   assert(region != nullptr && region->is_Region(), "phi must have region");
1375   if (!region->as_Region()->is_diamond()) {
1376     return 0;
1377   }
1378 
1379   if (region->in(1)->is_IfTrue()) {
1380     assert(region->in(2)->is_IfFalse(), "bad If");
1381     return 1;
1382   } else {
1383     // Flipped projections.
1384     assert(region->in(2)->is_IfTrue(), "bad If");
1385     return 2;
1386   }
1387 }
1388 
1389 // Do the following transformation if we find the corresponding graph shape, remove the involved memory phi and return
1390 // true. Otherwise, return false if the transformation cannot be applied.
1391 //
1392 //           If                                     If
1393 //          /  \                                   /  \
1394 //    IfFalse  IfTrue  /- Some Node          IfFalse  IfTrue
1395 //          \  /      /    /                       \  /        Some Node
1396 //         Region    / /-MergeMem     ===>        Region          |
1397 //          /   \---Phi                             |          MergeMem
1398 // [other phis]      \                        [other phis]        |
1399 //                   use                                         use
1400 bool PhiNode::try_clean_memory_phi(PhaseIterGVN* igvn) {
1401   if (_type != Type::MEMORY) {
1402     return false;
1403   }
1404   assert(is_diamond_phi() > 0, "sanity");
1405   assert(req() == 3, "same as region");
1406   const Node* region = in(0);
1407   for (uint i = 1; i < 3; i++) {
1408     Node* phi_input = in(i);
1409     if (phi_input != nullptr && phi_input->is_MergeMem() && region->in(i)->outcnt() == 1) {
1410       // Nothing is control-dependent on path #i except the region itself.
1411       MergeMemNode* merge_mem = phi_input->as_MergeMem();
1412       uint j = 3 - i;
1413       Node* other_phi_input = in(j);
1414       if (other_phi_input != nullptr && other_phi_input == merge_mem->base_memory()) {
1415         // merge_mem is a successor memory to other_phi_input, and is not pinned inside the diamond, so push it out.
1416         // This will allow the diamond to collapse completely if there are no other phis left.
1417         igvn->replace_node(this, merge_mem);
1418         return true;
1419       }
1420     }
1421   }
1422   return false;
1423 }
1424 
1425 //----------------------------check_cmove_id-----------------------------------
1426 // Check for CMove'ing a constant after comparing against the constant.
1427 // Happens all the time now, since if we compare equality vs a constant in
1428 // the parser, we "know" the variable is constant on one path and we force
1429 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1430 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1431 // general in that we don't need constants.  Since CMove's are only inserted
1432 // in very special circumstances, we do it here on generic Phi's.
1433 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1434   assert(true_path !=0, "only diamond shape graph expected");
1435 
1436   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1437   // phi->region->if_proj->ifnode->bool->cmp
1438   Node*     region = in(0);
1439   Node*     iff    = region->in(1)->in(0);
1440   BoolNode* b      = iff->in(1)->as_Bool();
1441   Node*     cmp    = b->in(1);
1442   Node*     tval   = in(true_path);
1443   Node*     fval   = in(3-true_path);
1444   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1445   if (id == nullptr)
1446     return nullptr;
1447 
1448   // Either value might be a cast that depends on a branch of 'iff'.
1449   // Since the 'id' value will float free of the diamond, either
1450   // decast or return failure.
1451   Node* ctl = id->in(0);
1452   if (ctl != nullptr && ctl->in(0) == iff) {
1453     if (id->is_ConstraintCast()) {
1454       return id->in(1);
1455     } else {
1456       // Don't know how to disentangle this value.
1457       return nullptr;
1458     }
1459   }
1460 
1461   return id;
1462 }
1463 
1464 //------------------------------Identity---------------------------------------
1465 // Check for Region being Identity.
1466 Node* PhiNode::Identity(PhaseGVN* phase) {
1467   if (must_wait_for_region_in_irreducible_loop(phase)) {
1468     return this;
1469   }
1470   // Check for no merging going on
1471   // (There used to be special-case code here when this->region->is_Loop.
1472   // It would check for a tributary phi on the backedge that the main phi
1473   // trivially, perhaps with a single cast.  The unique_input method
1474   // does all this and more, by reducing such tributaries to 'this'.)
1475   Node* uin = unique_input(phase, false);
1476   if (uin != nullptr) {
1477     return uin;
1478   }
1479   uin = unique_constant_input_recursive(phase);
1480   if (uin != nullptr) {
1481     return uin;
1482   }
1483 
1484   int true_path = is_diamond_phi();
1485   // Delay CMove'ing identity if Ideal has not had the chance to handle unsafe cases, yet.
1486   if (true_path != 0 && !(phase->is_IterGVN() && wait_for_region_igvn(phase))) {
1487     Node* id = is_cmove_id(phase, true_path);
1488     if (id != nullptr) {
1489       return id;
1490     }
1491   }
1492 
1493   // Looking for phis with identical inputs.  If we find one that has
1494   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1495   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1496       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1497     uint phi_len = req();
1498     Node* phi_reg = region();
1499     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1500       Node* u = phi_reg->fast_out(i);
1501       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1502           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1503           u->req() == phi_len) {
1504         for (uint j = 1; j < phi_len; j++) {
1505           if (in(j) != u->in(j)) {
1506             u = nullptr;
1507             break;
1508           }
1509         }
1510         if (u != nullptr) {
1511           return u;
1512         }
1513       }
1514     }
1515   }
1516 
1517   return this;                     // No identity
1518 }
1519 
1520 //-----------------------------unique_input------------------------------------
1521 // Find the unique value, discounting top, self-loops, and casts.
1522 // Return top if there are no inputs, and self if there are multiple.
1523 Node* PhiNode::unique_input(PhaseValues* phase, bool uncast) {
1524   //  1) One unique direct input,
1525   // or if uncast is true:
1526   //  2) some of the inputs have an intervening ConstraintCast
1527   //  3) an input is a self loop
1528   //
1529   //  1) input   or   2) input     or   3) input __
1530   //     /   \           /   \               \  /  \
1531   //     \   /          |    cast             phi  cast
1532   //      phi            \   /               /  \  /
1533   //                      phi               /    --
1534 
1535   Node* r = in(0);                      // RegionNode
1536   Node* input = nullptr; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1537 
1538   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1539     Node* rc = r->in(i);
1540     if (rc == nullptr || phase->type(rc) == Type::TOP)
1541       continue;                 // ignore unreachable control path
1542     Node* n = in(i);
1543     if (n == nullptr)
1544       continue;
1545     Node* un = n;
1546     if (uncast) {
1547 #ifdef ASSERT
1548       Node* m = un->uncast();
1549 #endif
1550       while (un != nullptr && un->req() == 2 && un->is_ConstraintCast()) {
1551         Node* next = un->in(1);
1552         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1553           // risk exposing raw ptr at safepoint
1554           break;
1555         }
1556         un = next;
1557       }
1558       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1559     }
1560     if (un == nullptr || un == this || phase->type(un) == Type::TOP) {
1561       continue; // ignore if top, or in(i) and "this" are in a data cycle
1562     }
1563     // Check for a unique input (maybe uncasted)
1564     if (input == nullptr) {
1565       input = un;
1566     } else if (input != un) {
1567       input = NodeSentinel; // no unique input
1568     }
1569   }
1570   if (input == nullptr) {
1571     return phase->C->top();        // no inputs
1572   }
1573 
1574   if (input != NodeSentinel) {
1575     return input;           // one unique direct input
1576   }
1577 
1578   // Nothing.
1579   return nullptr;
1580 }
1581 
1582 // Find the unique input, try to look recursively through input Phis
1583 Node* PhiNode::unique_constant_input_recursive(PhaseGVN* phase) {
1584   if (!phase->is_IterGVN()) {
1585     return nullptr;
1586   }
1587 
1588   ResourceMark rm;
1589   Node* unique = nullptr;
1590   Unique_Node_List visited;
1591   visited.push(this);
1592 
1593   for (uint visited_idx = 0; visited_idx < visited.size(); visited_idx++) {
1594     Node* current = visited.at(visited_idx);
1595     for (uint i = 1; i < current->req(); i++) {
1596       Node* phi_in = current->in(i);
1597       if (phi_in == nullptr) {
1598         continue;
1599       }
1600 
1601       if (phi_in->is_Phi()) {
1602         visited.push(phi_in);
1603       } else {
1604         if (unique == nullptr) {
1605           if (!phi_in->is_Con()) {
1606             return nullptr;
1607           }
1608           unique = phi_in;
1609         } else if (unique != phi_in) {
1610           return nullptr;
1611         }
1612       }
1613     }
1614   }
1615   return unique;
1616 }
1617 
1618 //------------------------------is_x2logic-------------------------------------
1619 // Check for simple convert-to-boolean pattern
1620 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1621 // Convert Phi to an ConvIB.
1622 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1623   assert(true_path !=0, "only diamond shape graph expected");
1624 
1625   // If we're late in the optimization process, we may have already expanded Conv2B nodes
1626   if (phase->C->post_loop_opts_phase() && !Matcher::match_rule_supported(Op_Conv2B)) {
1627     return nullptr;
1628   }
1629 
1630   // Convert the true/false index into an expected 0/1 return.
1631   // Map 2->0 and 1->1.
1632   int flipped = 2-true_path;
1633 
1634   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1635   // phi->region->if_proj->ifnode->bool->cmp
1636   Node *region = phi->in(0);
1637   Node *iff = region->in(1)->in(0);
1638   BoolNode *b = (BoolNode*)iff->in(1);
1639   const CmpNode *cmp = (CmpNode*)b->in(1);
1640 
1641   Node *zero = phi->in(1);
1642   Node *one  = phi->in(2);
1643   const Type *tzero = phase->type( zero );
1644   const Type *tone  = phase->type( one  );
1645 
1646   // Check for compare vs 0
1647   const Type *tcmp = phase->type(cmp->in(2));
1648   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1649     // Allow cmp-vs-1 if the other input is bounded by 0-1
1650     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1651       return nullptr;
1652     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1653   }
1654 
1655   // Check for setting zero/one opposite expected
1656   if( tzero == TypeInt::ZERO ) {
1657     if( tone == TypeInt::ONE ) {
1658     } else return nullptr;
1659   } else if( tzero == TypeInt::ONE ) {
1660     if( tone == TypeInt::ZERO ) {
1661       flipped = 1-flipped;
1662     } else return nullptr;
1663   } else return nullptr;
1664 
1665   // Check for boolean test backwards
1666   if( b->_test._test == BoolTest::ne ) {
1667   } else if( b->_test._test == BoolTest::eq ) {
1668     flipped = 1-flipped;
1669   } else return nullptr;
1670 
1671   // Build int->bool conversion
1672   Node* n = new Conv2BNode(cmp->in(1));
1673   if (flipped) {
1674     n = new XorINode(phase->transform(n), phase->intcon(1));
1675   }
1676 
1677   return n;
1678 }
1679 
1680 //------------------------------is_cond_add------------------------------------
1681 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1682 // To be profitable the control flow has to disappear; there can be no other
1683 // values merging here.  We replace the test-and-branch with:
1684 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1685 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1686 // Then convert Y to 0-or-Y and finally add.
1687 // This is a key transform for SpecJava _201_compress.
1688 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1689   assert(true_path !=0, "only diamond shape graph expected");
1690 
1691   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1692   // phi->region->if_proj->ifnode->bool->cmp
1693   RegionNode *region = (RegionNode*)phi->in(0);
1694   Node *iff = region->in(1)->in(0);
1695   BoolNode* b = iff->in(1)->as_Bool();
1696   const CmpNode *cmp = (CmpNode*)b->in(1);
1697 
1698   // Make sure only merging this one phi here
1699   if (region->has_unique_phi() != phi)  return nullptr;
1700 
1701   // Make sure each arm of the diamond has exactly one output, which we assume
1702   // is the region.  Otherwise, the control flow won't disappear.
1703   if (region->in(1)->outcnt() != 1) return nullptr;
1704   if (region->in(2)->outcnt() != 1) return nullptr;
1705 
1706   // Check for "(P < Q)" of type signed int
1707   if (b->_test._test != BoolTest::lt)  return nullptr;
1708   if (cmp->Opcode() != Op_CmpI)        return nullptr;
1709 
1710   Node *p = cmp->in(1);
1711   Node *q = cmp->in(2);
1712   Node *n1 = phi->in(  true_path);
1713   Node *n2 = phi->in(3-true_path);
1714 
1715   int op = n1->Opcode();
1716   if( op != Op_AddI           // Need zero as additive identity
1717       /*&&op != Op_SubI &&
1718       op != Op_AddP &&
1719       op != Op_XorI &&
1720       op != Op_OrI*/ )
1721     return nullptr;
1722 
1723   Node *x = n2;
1724   Node *y = nullptr;
1725   if( x == n1->in(1) ) {
1726     y = n1->in(2);
1727   } else if( x == n1->in(2) ) {
1728     y = n1->in(1);
1729   } else return nullptr;
1730 
1731   // Not so profitable if compare and add are constants
1732   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1733     return nullptr;
1734 
1735   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1736   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1737   return new AddINode(j_and,x);
1738 }
1739 
1740 //------------------------------is_absolute------------------------------------
1741 // Check for absolute value.
1742 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1743   assert(true_path !=0, "only diamond shape graph expected");
1744 
1745   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1746   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1747 
1748   // ABS ends with the merge of 2 control flow paths.
1749   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1750   int false_path = 3 - true_path;
1751 
1752   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1753   // phi->region->if_proj->ifnode->bool->cmp
1754   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1755   Node *cmp = bol->in(1);
1756 
1757   // Check bool sense
1758   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1759     switch (bol->_test._test) {
1760     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1761     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1762     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1763     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1764     default:           return nullptr;                           break;
1765     }
1766   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1767     switch (bol->_test._test) {
1768     case BoolTest::lt:
1769     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1770     case BoolTest::gt:
1771     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1772     default:           return nullptr;                           break;
1773     }
1774   }
1775 
1776   // Test is next
1777   const Type *tzero = nullptr;
1778   switch (cmp->Opcode()) {
1779   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1780   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1781   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1782   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1783   default: return nullptr;
1784   }
1785 
1786   // Find zero input of compare; the other input is being abs'd
1787   Node *x = nullptr;
1788   bool flip = false;
1789   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1790     x = cmp->in(3 - cmp_zero_idx);
1791   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1792     // The test is inverted, we should invert the result...
1793     x = cmp->in(cmp_zero_idx);
1794     flip = true;
1795   } else {
1796     return nullptr;
1797   }
1798 
1799   // Next get the 2 pieces being selected, one is the original value
1800   // and the other is the negated value.
1801   if( phi_root->in(phi_x_idx) != x ) return nullptr;
1802 
1803   // Check other phi input for subtract node
1804   Node *sub = phi_root->in(3 - phi_x_idx);
1805 
1806   bool is_sub = sub->Opcode() == Op_SubF || sub->Opcode() == Op_SubD ||
1807                 sub->Opcode() == Op_SubI || sub->Opcode() == Op_SubL;
1808 
1809   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1810   if (!is_sub || phase->type(sub->in(1)) != tzero || sub->in(2) != x) return nullptr;
1811 
1812   if (tzero == TypeF::ZERO) {
1813     x = new AbsFNode(x);
1814     if (flip) {
1815       x = new SubFNode(sub->in(1), phase->transform(x));
1816     }
1817   } else if (tzero == TypeD::ZERO) {
1818     x = new AbsDNode(x);
1819     if (flip) {
1820       x = new SubDNode(sub->in(1), phase->transform(x));
1821     }
1822   } else if (tzero == TypeInt::ZERO && Matcher::match_rule_supported(Op_AbsI)) {
1823     x = new AbsINode(x);
1824     if (flip) {
1825       x = new SubINode(sub->in(1), phase->transform(x));
1826     }
1827   } else if (tzero == TypeLong::ZERO && Matcher::match_rule_supported(Op_AbsL)) {
1828     x = new AbsLNode(x);
1829     if (flip) {
1830       x = new SubLNode(sub->in(1), phase->transform(x));
1831     }
1832   } else return nullptr;
1833 
1834   return x;
1835 }
1836 
1837 //------------------------------split_once-------------------------------------
1838 // Helper for split_flow_path
1839 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1840   igvn->hash_delete(n);         // Remove from hash before hacking edges
1841 
1842   uint j = 1;
1843   for (uint i = phi->req()-1; i > 0; i--) {
1844     if (phi->in(i) == val) {   // Found a path with val?
1845       // Add to NEW Region/Phi, no DU info
1846       newn->set_req( j++, n->in(i) );
1847       // Remove from OLD Region/Phi
1848       n->del_req(i);
1849     }
1850   }
1851 
1852   // Register the new node but do not transform it.  Cannot transform until the
1853   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1854   igvn->register_new_node_with_optimizer( newn );
1855 
1856   // Now I can point to the new node.
1857   n->add_req(newn);
1858   igvn->_worklist.push(n);
1859 }
1860 
1861 //------------------------------split_flow_path--------------------------------
1862 // Check for merging identical values and split flow paths
1863 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1864   // This optimization tries to find two or more inputs of phi with the same constant value
1865   // It then splits them into a separate Phi, and according Region. If this is a loop-entry,
1866   // and the loop entry has multiple fall-in edges, and some of those fall-in edges have that
1867   // constant, and others not, we may split the fall-in edges into separate Phi's, and create
1868   // an irreducible loop. For reducible loops, this never seems to happen, as the multiple
1869   // fall-in edges are already merged before the loop head during parsing. But with irreducible
1870   // loops present the order or merging during parsing can sometimes prevent this.
1871   if (phase->C->has_irreducible_loop()) {
1872     // Avoid this optimization if any irreducible loops are present. Else we may create
1873     // an irreducible loop that we do not detect.
1874     return nullptr;
1875   }
1876   BasicType bt = phi->type()->basic_type();
1877   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1878     return nullptr;             // Bail out on funny non-value stuff
1879   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1880     return nullptr;             // third unequal input to be worth doing
1881 
1882   // Scan for a constant
1883   uint i;
1884   for( i = 1; i < phi->req()-1; i++ ) {
1885     Node *n = phi->in(i);
1886     if( !n ) return nullptr;
1887     if( phase->type(n) == Type::TOP ) return nullptr;
1888     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1889       break;
1890   }
1891   if( i >= phi->req() )         // Only split for constants
1892     return nullptr;
1893 
1894   Node *val = phi->in(i);       // Constant to split for
1895   uint hit = 0;                 // Number of times it occurs
1896   Node *r = phi->region();
1897 
1898   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1899     Node *n = phi->in(i);
1900     if( !n ) return nullptr;
1901     if( phase->type(n) == Type::TOP ) return nullptr;
1902     if( phi->in(i) == val ) {
1903       hit++;
1904       if (Node::may_be_loop_entry(r->in(i))) {
1905         return nullptr; // don't split loop entry path
1906       }
1907     }
1908   }
1909 
1910   if( hit <= 1 ||               // Make sure we find 2 or more
1911       hit == phi->req()-1 )     // and not ALL the same value
1912     return nullptr;
1913 
1914   // Now start splitting out the flow paths that merge the same value.
1915   // Split first the RegionNode.
1916   PhaseIterGVN *igvn = phase->is_IterGVN();
1917   RegionNode *newr = new RegionNode(hit+1);
1918   split_once(igvn, phi, val, r, newr);
1919 
1920   // Now split all other Phis than this one
1921   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1922     Node* phi2 = r->fast_out(k);
1923     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1924       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1925       split_once(igvn, phi, val, phi2, newphi);
1926     }
1927   }
1928 
1929   // Clean up this guy
1930   igvn->hash_delete(phi);
1931   for( i = phi->req()-1; i > 0; i-- ) {
1932     if( phi->in(i) == val ) {
1933       phi->del_req(i);
1934     }
1935   }
1936   phi->add_req(val);
1937 
1938   return phi;
1939 }
1940 
1941 // Returns the BasicType of a given convert node and a type, with special handling to ensure that conversions to
1942 // and from half float will return the SHORT basic type, as that wouldn't be returned typically from TypeInt.
1943 static BasicType get_convert_type(Node* convert, const Type* type) {
1944   int convert_op = convert->Opcode();
1945   if (type->isa_int() && (convert_op == Op_ConvHF2F || convert_op == Op_ConvF2HF)) {
1946     return T_SHORT;
1947   }
1948 
1949   return type->basic_type();
1950 }
1951 
1952 //=============================================================================
1953 //------------------------------simple_data_loop_check-------------------------
1954 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1955 //  Returns:
1956 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1957 // Safe       - safe case when the phi and it's inputs reference only safe data
1958 //              nodes;
1959 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1960 //              is no reference back to the phi - need a graph walk
1961 //              to determine if it is in a loop;
1962 // UnsafeLoop - unsafe case when the phi references itself directly or through
1963 //              unsafe data node.
1964 //  Note: a safe data node is a node which could/never reference itself during
1965 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1966 //  I mark Phi nodes as safe node not only because they can reference itself
1967 //  but also to prevent mistaking the fallthrough case inside an outer loop
1968 //  as dead loop when the phi references itself through an other phi.
1969 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1970   // It is unsafe loop if the phi node references itself directly.
1971   if (in == (Node*)this)
1972     return UnsafeLoop; // Unsafe loop
1973   // Unsafe loop if the phi node references itself through an unsafe data node.
1974   // Exclude cases with null inputs or data nodes which could reference
1975   // itself (safe for dead loops).
1976   if (in != nullptr && !in->is_dead_loop_safe()) {
1977     // Check inputs of phi's inputs also.
1978     // It is much less expensive then full graph walk.
1979     uint cnt = in->req();
1980     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1981     for (; i < cnt; ++i) {
1982       Node* m = in->in(i);
1983       if (m == (Node*)this)
1984         return UnsafeLoop; // Unsafe loop
1985       if (m != nullptr && !m->is_dead_loop_safe()) {
1986         // Check the most common case (about 30% of all cases):
1987         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1988         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : nullptr;
1989         if (m1 == (Node*)this)
1990           return UnsafeLoop; // Unsafe loop
1991         if (m1 != nullptr && m1 == m->in(2) &&
1992             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1993           continue; // Safe case
1994         }
1995         // The phi references an unsafe node - need full analysis.
1996         return Unsafe;
1997       }
1998     }
1999   }
2000   return Safe; // Safe case - we can optimize the phi node.
2001 }
2002 
2003 //------------------------------is_unsafe_data_reference-----------------------
2004 // If phi can be reached through the data input - it is data loop.
2005 bool PhiNode::is_unsafe_data_reference(Node *in) const {
2006   assert(req() > 1, "");
2007   // First, check simple cases when phi references itself directly or
2008   // through an other node.
2009   LoopSafety safety = simple_data_loop_check(in);
2010   if (safety == UnsafeLoop)
2011     return true;  // phi references itself - unsafe loop
2012   else if (safety == Safe)
2013     return false; // Safe case - phi could be replaced with the unique input.
2014 
2015   // Unsafe case when we should go through data graph to determine
2016   // if the phi references itself.
2017 
2018   ResourceMark rm;
2019 
2020   Node_List nstack;
2021   VectorSet visited;
2022 
2023   nstack.push(in); // Start with unique input.
2024   visited.set(in->_idx);
2025   while (nstack.size() != 0) {
2026     Node* n = nstack.pop();
2027     uint cnt = n->req();
2028     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
2029     for (; i < cnt; i++) {
2030       Node* m = n->in(i);
2031       if (m == (Node*)this) {
2032         return true;    // Data loop
2033       }
2034       if (m != nullptr && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
2035         if (!visited.test_set(m->_idx))
2036           nstack.push(m);
2037       }
2038     }
2039   }
2040   return false; // The phi is not reachable from its inputs
2041 }
2042 
2043 // Is this Phi's region or some inputs to the region enqueued for IGVN
2044 // and so could cause the region to be optimized out?
2045 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
2046   PhaseIterGVN* igvn = phase->is_IterGVN();
2047   Unique_Node_List& worklist = igvn->_worklist;
2048   bool delay = false;
2049   Node* r = in(0);
2050   for (uint j = 1; j < req(); j++) {
2051     Node* rc = r->in(j);
2052     Node* n = in(j);
2053 
2054     if (rc == nullptr || !rc->is_Proj()) { continue; }
2055     if (worklist.member(rc)) {
2056       delay = true;
2057       break;
2058     }
2059 
2060     if (rc->in(0) == nullptr || !rc->in(0)->is_If()) { continue; }
2061     if (worklist.member(rc->in(0))) {
2062       delay = true;
2063       break;
2064     }
2065 
2066     if (rc->in(0)->in(1) == nullptr || !rc->in(0)->in(1)->is_Bool()) { continue; }
2067     if (worklist.member(rc->in(0)->in(1))) {
2068       delay = true;
2069       break;
2070     }
2071 
2072     if (rc->in(0)->in(1)->in(1) == nullptr || !rc->in(0)->in(1)->in(1)->is_Cmp()) { continue; }
2073     if (worklist.member(rc->in(0)->in(1)->in(1))) {
2074       delay = true;
2075       break;
2076     }
2077   }
2078 
2079   if (delay) {
2080     worklist.push(this);
2081   }
2082   return delay;
2083 }
2084 
2085 // Push inline type input nodes (and null) down through the phi recursively (can handle data loops).
2086 InlineTypeNode* PhiNode::push_inline_types_down(PhaseGVN* phase, bool can_reshape, ciInlineKlass* inline_klass) {
2087   assert(inline_klass != nullptr, "must be");
2088   InlineTypeNode* vt = InlineTypeNode::make_null(*phase, inline_klass, /* transform = */ false)->clone_with_phis(phase, in(0), nullptr, !_type->maybe_null(), true);
2089   if (can_reshape) {
2090     // Replace phi right away to be able to use the inline
2091     // type node when reaching the phi again through data loops.
2092     PhaseIterGVN* igvn = phase->is_IterGVN();
2093     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2094       Node* u = fast_out(i);
2095       igvn->rehash_node_delayed(u);
2096       imax -= u->replace_edge(this, vt);
2097       --i;
2098     }
2099     igvn->rehash_node_delayed(this);
2100     assert(outcnt() == 0, "should be dead now");
2101   }
2102   ResourceMark rm;
2103   Node_List casts;
2104   for (uint i = 1; i < req(); ++i) {
2105     Node* n = in(i);
2106     while (n->is_ConstraintCast()) {
2107       casts.push(n);
2108       n = n->in(1);
2109     }
2110     if (phase->type(n)->is_zero_type()) {
2111       n = InlineTypeNode::make_null(*phase, inline_klass);
2112     } else if (n->is_Phi()) {
2113       assert(can_reshape, "can only handle phis during IGVN");
2114       n = phase->transform(n->as_Phi()->push_inline_types_down(phase, can_reshape, inline_klass));
2115     }
2116     while (casts.size() != 0) {
2117       // Push the cast(s) through the InlineTypeNode
2118       // TODO 8302217 Can we avoid cloning? See InlineTypeNode::clone_if_required
2119       Node* cast = casts.pop()->clone();
2120       cast->set_req_X(1, n->as_InlineType()->get_oop(), phase);
2121       n = n->clone();
2122       n->as_InlineType()->set_oop(*phase, phase->transform(cast));
2123       n = phase->transform(n);
2124       if (n->is_top()) {
2125         break;
2126       }
2127     }
2128     bool transform = !can_reshape && (i == (req()-1)); // Transform phis on last merge
2129     assert(n->is_top() || n->is_InlineType(), "Only InlineType or top at this point.");
2130     if (n->is_InlineType()) {
2131       vt->merge_with(phase, n->as_InlineType(), i, transform);
2132     } // else nothing to do: phis above vt created by clone_with_phis are initialized to top already.
2133   }
2134   return vt;
2135 }
2136 
2137 // If the Phi's Region is in an irreducible loop, and the Region
2138 // has had an input removed, but not yet transformed, it could be
2139 // that the Region (and this Phi) are not reachable from Root.
2140 // If we allow the Phi to collapse before the Region, this may lead
2141 // to dead-loop data. Wait for the Region to check for reachability,
2142 // and potentially remove the dead code.
2143 bool PhiNode::must_wait_for_region_in_irreducible_loop(PhaseGVN* phase) const {
2144   RegionNode* region = in(0)->as_Region();
2145   if (region->loop_status() == RegionNode::LoopStatus::MaybeIrreducibleEntry) {
2146     Node* top = phase->C->top();
2147     for (uint j = 1; j < req(); j++) {
2148       Node* rc = region->in(j); // for each control input
2149       if (rc == nullptr || phase->type(rc) == Type::TOP) {
2150         // Region is missing a control input
2151         Node* n = in(j);
2152         if (n != nullptr && n != top) {
2153           // Phi still has its input, so region just lost its input
2154           return true;
2155         }
2156       }
2157     }
2158   }
2159   return false;
2160 }
2161 
2162 // Check if splitting a bot memory Phi through a parent MergeMem may lead to
2163 // non-termination. For more details, see comments at the call site in
2164 // PhiNode::Ideal.
2165 bool PhiNode::is_split_through_mergemem_terminating() const {
2166   ResourceMark rm;
2167   VectorSet visited;
2168   GrowableArray<const Node*> worklist;
2169   worklist.push(this);
2170   visited.set(this->_idx);
2171   auto maybe_add_to_worklist = [&](Node* input) {
2172     if (input != nullptr &&
2173         (input->is_MergeMem() || input->is_memory_phi()) &&
2174         !visited.test_set(input->_idx)) {
2175       worklist.push(input);
2176       assert(input->adr_type() == TypePtr::BOTTOM,
2177           "should only visit bottom memory");
2178     }
2179   };
2180   while (worklist.length() > 0) {
2181     const Node* n = worklist.pop();
2182     if (n->is_MergeMem()) {
2183       Node* input = n->as_MergeMem()->base_memory();
2184       if (input == this) {
2185         return false;
2186       }
2187       maybe_add_to_worklist(input);
2188     } else {
2189       assert(n->is_memory_phi(), "invariant");
2190       for (uint i = PhiNode::Input; i < n->req(); i++) {
2191         Node* input = n->in(i);
2192         if (input == this) {
2193           return false;
2194         }
2195         maybe_add_to_worklist(input);
2196       }
2197     }
2198   }
2199   return true;
2200 }
2201 
2202 //------------------------------Ideal------------------------------------------
2203 // Return a node which is more "ideal" than the current node.  Must preserve
2204 // the CFG, but we can still strip out dead paths.
2205 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2206   Node *r = in(0);              // RegionNode
2207   assert(r != nullptr && r->is_Region(), "this phi must have a region");
2208   assert(r->in(0) == nullptr || !r->in(0)->is_Root(), "not a specially hidden merge");
2209 
2210   // Note: During parsing, phis are often transformed before their regions.
2211   // This means we have to use type_or_null to defend against untyped regions.
2212   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
2213     return nullptr;                // No change
2214 
2215   Node *top = phase->C->top();
2216   bool new_phi = (outcnt() == 0); // transforming new Phi
2217   // No change for igvn if new phi is not hooked
2218   if (new_phi && can_reshape)
2219     return nullptr;
2220 
2221   if (must_wait_for_region_in_irreducible_loop(phase)) {
2222     return nullptr;
2223   }
2224 
2225   // The are 2 situations when only one valid phi's input is left
2226   // (in addition to Region input).
2227   // One: region is not loop - replace phi with this input.
2228   // Two: region is loop - replace phi with top since this data path is dead
2229   //                       and we need to break the dead data loop.
2230   Node* progress = nullptr;        // Record if any progress made
2231   for( uint j = 1; j < req(); ++j ){ // For all paths in
2232     // Check unreachable control paths
2233     Node* rc = r->in(j);
2234     Node* n = in(j);            // Get the input
2235     if (rc == nullptr || phase->type(rc) == Type::TOP) {
2236       if (n != top) {           // Not already top?
2237         PhaseIterGVN *igvn = phase->is_IterGVN();
2238         if (can_reshape && igvn != nullptr) {
2239           igvn->_worklist.push(r);
2240         }
2241         // Nuke it down
2242         set_req_X(j, top, phase);
2243         progress = this;        // Record progress
2244       }
2245     }
2246   }
2247 
2248   if (can_reshape && outcnt() == 0) {
2249     // set_req() above may kill outputs if Phi is referenced
2250     // only by itself on the dead (top) control path.
2251     return top;
2252   }
2253 
2254   bool uncasted = false;
2255   Node* uin = unique_input(phase, false);
2256   if (uin == nullptr && can_reshape &&
2257       // If there is a chance that the region can be optimized out do
2258       // not add a cast node that we can't remove yet.
2259       !wait_for_region_igvn(phase)) {
2260     uncasted = true;
2261     uin = unique_input(phase, true);
2262   }
2263   if (uin == top) {             // Simplest case: no alive inputs.
2264     if (can_reshape)            // IGVN transformation
2265       return top;
2266     else
2267       return nullptr;              // Identity will return TOP
2268   } else if (uin != nullptr) {
2269     // Only one not-null unique input path is left.
2270     // Determine if this input is backedge of a loop.
2271     // (Skip new phis which have no uses and dead regions).
2272     if (outcnt() > 0 && r->in(0) != nullptr) {
2273       if (is_data_loop(r->as_Region(), uin, phase)) {
2274         // Break this data loop to avoid creation of a dead loop.
2275         if (can_reshape) {
2276           return top;
2277         } else {
2278           // We can't return top if we are in Parse phase - cut inputs only
2279           // let Identity to handle the case.
2280           replace_edge(uin, top, phase);
2281           return nullptr;
2282         }
2283       }
2284     }
2285 
2286     if (uncasted) {
2287       // Add cast nodes between the phi to be removed and its unique input.
2288       // Wait until after parsing for the type information to propagate from the casts.
2289       assert(can_reshape, "Invalid during parsing");
2290       const Type* phi_type = bottom_type();
2291       // Add casts to carry the control dependency of the Phi that is
2292       // going away
2293       Node* cast = nullptr;
2294       const TypeTuple* extra_types = collect_types(phase);
2295       if (phi_type->isa_ptr()) {
2296         const Type* uin_type = phase->type(uin);
2297         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
2298           cast = new CastPPNode(r, uin, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2299         } else {
2300           // Use a CastPP for a cast to not null and a CheckCastPP for
2301           // a cast to a new klass (and both if both null-ness and
2302           // klass change).
2303 
2304           // If the type of phi is not null but the type of uin may be
2305           // null, uin's type must be casted to not null
2306           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
2307               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
2308             cast = new CastPPNode(r, uin, TypePtr::NOTNULL, ConstraintCastNode::StrongDependency, extra_types);
2309           }
2310 
2311           // If the type of phi and uin, both casted to not null,
2312           // differ the klass of uin must be (check)cast'ed to match
2313           // that of phi
2314           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
2315             Node* n = uin;
2316             if (cast != nullptr) {
2317               cast = phase->transform(cast);
2318               n = cast;
2319             }
2320             cast = new CheckCastPPNode(r, n, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2321           }
2322           if (cast == nullptr) {
2323             cast = new CastPPNode(r, uin, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2324           }
2325         }
2326       } else {
2327         cast = ConstraintCastNode::make_cast_for_type(r, uin, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2328       }
2329       assert(cast != nullptr, "cast should be set");
2330       cast = phase->transform(cast);
2331       // set all inputs to the new cast(s) so the Phi is removed by Identity
2332       PhaseIterGVN* igvn = phase->is_IterGVN();
2333       for (uint i = 1; i < req(); i++) {
2334         set_req_X(i, cast, igvn);
2335       }
2336       uin = cast;
2337     }
2338 
2339     // One unique input.
2340     DEBUG_ONLY(Node* ident = Identity(phase));
2341     // The unique input must eventually be detected by the Identity call.
2342 #ifdef ASSERT
2343     if (ident != uin && !ident->is_top() && !must_wait_for_region_in_irreducible_loop(phase)) {
2344       // print this output before failing assert
2345       r->dump(3);
2346       this->dump(3);
2347       ident->dump();
2348       uin->dump();
2349     }
2350 #endif
2351     // Identity may not return the expected uin, if it has to wait for the region, in irreducible case
2352     assert(ident == uin || ident->is_top() || must_wait_for_region_in_irreducible_loop(phase), "Identity must clean this up");
2353     return nullptr;
2354   }
2355 
2356   Node* opt = nullptr;
2357   int true_path = is_diamond_phi();
2358   if (true_path != 0 &&
2359       // If one of the diamond's branch is in the process of dying then, the Phi's input for that branch might transform
2360       // to top. If that happens replacing the Phi with an operation that consumes the Phi's inputs will cause the Phi
2361       // to be replaced by top. To prevent that, delay the transformation until the branch has a chance to be removed.
2362       !(can_reshape && wait_for_region_igvn(phase))) {
2363     // Check for CMove'ing identity. If it would be unsafe,
2364     // handle it here. In the safe case, let Identity handle it.
2365     Node* unsafe_id = is_cmove_id(phase, true_path);
2366     if( unsafe_id != nullptr && is_unsafe_data_reference(unsafe_id) )
2367       opt = unsafe_id;
2368 
2369     // Check for simple convert-to-boolean pattern
2370     if( opt == nullptr )
2371       opt = is_x2logic(phase, this, true_path);
2372 
2373     // Check for absolute value
2374     if( opt == nullptr )
2375       opt = is_absolute(phase, this, true_path);
2376 
2377     // Check for conditional add
2378     if( opt == nullptr && can_reshape )
2379       opt = is_cond_add(phase, this, true_path);
2380 
2381     // These 4 optimizations could subsume the phi:
2382     // have to check for a dead data loop creation.
2383     if( opt != nullptr ) {
2384       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2385         // Found dead loop.
2386         if( can_reshape )
2387           return top;
2388         // We can't return top if we are in Parse phase - cut inputs only
2389         // to stop further optimizations for this phi. Identity will return TOP.
2390         assert(req() == 3, "only diamond merge phi here");
2391         set_req(1, top);
2392         set_req(2, top);
2393         return nullptr;
2394       } else {
2395         return opt;
2396       }
2397     }
2398   }
2399 
2400   // Check for merging identical values and split flow paths
2401   if (can_reshape) {
2402     opt = split_flow_path(phase, this);
2403     // This optimization only modifies phi - don't need to check for dead loop.
2404     assert(opt == nullptr || opt == this, "do not elide phi");
2405     if (opt != nullptr)  return opt;
2406   }
2407 
2408   if (in(1) != nullptr && in(1)->Opcode() == Op_AddP && can_reshape) {
2409     // Try to undo Phi of AddP:
2410     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2411     // becomes:
2412     // newbase := (Phi base base2)
2413     // newaddress := (Phi address address2)
2414     // newoffset := (Phi offset offset2)
2415     // (AddP newbase newaddress newoffset)
2416     //
2417     // This occurs as a result of unsuccessful split_thru_phi and
2418     // interferes with taking advantage of addressing modes. See the
2419     // clone_shift_expressions code in matcher.cpp
2420     Node* addp = in(1);
2421     Node* base = addp->in(AddPNode::Base);
2422     Node* address = addp->in(AddPNode::Address);
2423     Node* offset = addp->in(AddPNode::Offset);
2424     if (base != nullptr && address != nullptr && offset != nullptr &&
2425         !base->is_top() && !address->is_top() && !offset->is_top()) {
2426       const Type* base_type = base->bottom_type();
2427       const Type* address_type = address->bottom_type();
2428       // make sure that all the inputs are similar to the first one,
2429       // i.e. AddP with base == address and same offset as first AddP
2430       bool doit = true;
2431       for (uint i = 2; i < req(); i++) {
2432         if (in(i) == nullptr ||
2433             in(i)->Opcode() != Op_AddP ||
2434             in(i)->in(AddPNode::Base) == nullptr ||
2435             in(i)->in(AddPNode::Address) == nullptr ||
2436             in(i)->in(AddPNode::Offset) == nullptr ||
2437             in(i)->in(AddPNode::Base)->is_top() ||
2438             in(i)->in(AddPNode::Address)->is_top() ||
2439             in(i)->in(AddPNode::Offset)->is_top()) {
2440           doit = false;
2441           break;
2442         }
2443         if (in(i)->in(AddPNode::Base) != base) {
2444           base = nullptr;
2445         }
2446         if (in(i)->in(AddPNode::Offset) != offset) {
2447           offset = nullptr;
2448         }
2449         if (in(i)->in(AddPNode::Address) != address) {
2450           address = nullptr;
2451         }
2452         // Accumulate type for resulting Phi
2453         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2454         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2455       }
2456       if (doit && base == nullptr) {
2457         // Check for neighboring AddP nodes in a tree.
2458         // If they have a base, use that it.
2459         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2460           Node* u = this->fast_out(k);
2461           if (u->is_AddP()) {
2462             Node* base2 = u->in(AddPNode::Base);
2463             if (base2 != nullptr && !base2->is_top()) {
2464               if (base == nullptr)
2465                 base = base2;
2466               else if (base != base2)
2467                 { doit = false; break; }
2468             }
2469           }
2470         }
2471       }
2472       if (doit) {
2473         if (base == nullptr) {
2474           base = new PhiNode(in(0), base_type, nullptr);
2475           for (uint i = 1; i < req(); i++) {
2476             base->init_req(i, in(i)->in(AddPNode::Base));
2477           }
2478           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2479         }
2480         if (address == nullptr) {
2481           address = new PhiNode(in(0), address_type, nullptr);
2482           for (uint i = 1; i < req(); i++) {
2483             address->init_req(i, in(i)->in(AddPNode::Address));
2484           }
2485           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2486         }
2487         if (offset == nullptr) {
2488           offset = new PhiNode(in(0), TypeX_X, nullptr);
2489           for (uint i = 1; i < req(); i++) {
2490             offset->init_req(i, in(i)->in(AddPNode::Offset));
2491           }
2492           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2493         }
2494         return new AddPNode(base, address, offset);
2495       }
2496     }
2497   }
2498 
2499   // Split phis through memory merges, so that the memory merges will go away.
2500   // Piggy-back this transformation on the search for a unique input....
2501   // It will be as if the merged memory is the unique value of the phi.
2502   // (Do not attempt this optimization unless parsing is complete.
2503   // It would make the parser's memory-merge logic sick.)
2504   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2505   if (progress == nullptr && can_reshape && type() == Type::MEMORY) {
2506 
2507     // See if this Phi should be sliced. Determine the merge width of input
2508     // MergeMems and check if there is a direct loop to self, as illustrated
2509     // below.
2510     //
2511     //               +-------------+
2512     //               |             |
2513     // (base_memory) v             |
2514     //              MergeMem       |
2515     //                 |           |
2516     //                 v           |
2517     //                Phi (this)   |
2518     //                 |           |
2519     //                 +-----------+
2520     //
2521     // Generally, there are issues with non-termination with such circularity
2522     // (see comment further below). However, if there is a direct loop to self,
2523     // splitting the Phi through the MergeMem will result in the below.
2524     //
2525     //               +---+
2526     //               |   |
2527     //               v   |
2528     //              Phi  |
2529     //               |\  |
2530     //               | +-+
2531     // (base_memory) v
2532     //              MergeMem
2533     //
2534     // This split breaks the circularity and consequently does not lead to
2535     // non-termination.
2536     uint merge_width = 0;
2537     // TODO revisit this with JDK-8247216
2538     bool mergemem_only = true;
2539     bool split_always_terminates = false; // Is splitting guaranteed to terminate?
2540     for( uint i=1; i<req(); ++i ) {// For all paths in
2541       Node *ii = in(i);
2542       // TOP inputs should not be counted as safe inputs because if the
2543       // Phi references itself through all other inputs then splitting the
2544       // Phi through memory merges would create dead loop at later stage.
2545       if (ii == top) {
2546         return nullptr; // Delay optimization until graph is cleaned.
2547       }
2548       if (ii->is_MergeMem()) {
2549         MergeMemNode* n = ii->as_MergeMem();
2550         merge_width = MAX2(merge_width, n->req());
2551         if (n->base_memory() == this) {
2552           split_always_terminates = true;
2553         }
2554       } else {
2555         mergemem_only = false;
2556       }
2557     }
2558 
2559     // There are cases with circular dependencies between bottom Phis
2560     // and MergeMems. Below is a minimal example.
2561     //
2562     //               +------------+
2563     //               |            |
2564     // (base_memory) v            |
2565     //              MergeMem      |
2566     //                 |          |
2567     //                 v          |
2568     //                Phi (this)  |
2569     //                 |          |
2570     //                 v          |
2571     //                Phi         |
2572     //                 |          |
2573     //                 +----------+
2574     //
2575     // Here, we cannot break the circularity through a self-loop as there
2576     // are two Phis involved. Repeatedly splitting the Phis through the
2577     // MergeMem leads to non-termination. We check for non-termination below.
2578     // Only check for non-termination if necessary.
2579     if (!mergemem_only && !split_always_terminates && adr_type() == TypePtr::BOTTOM &&
2580         merge_width > Compile::AliasIdxRaw) {
2581       split_always_terminates = is_split_through_mergemem_terminating();
2582     }
2583 
2584     if (merge_width > Compile::AliasIdxRaw) {
2585       // found at least one non-empty MergeMem
2586       const TypePtr* at = adr_type();
2587       if (at != TypePtr::BOTTOM) {
2588         // Patch the existing phi to select an input from the merge:
2589         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2590         //     Phi:AT1(...m1...)
2591         int alias_idx = phase->C->get_alias_index(at);
2592         for (uint i=1; i<req(); ++i) {
2593           Node *ii = in(i);
2594           if (ii->is_MergeMem()) {
2595             MergeMemNode* n = ii->as_MergeMem();
2596             // compress paths and change unreachable cycles to TOP
2597             // If not, we can update the input infinitely along a MergeMem cycle
2598             // Equivalent code is in MemNode::Ideal_common
2599             Node *m  = phase->transform(n);
2600             if (outcnt() == 0) {  // Above transform() may kill us!
2601               return top;
2602             }
2603             // If transformed to a MergeMem, get the desired slice
2604             // Otherwise the returned node represents memory for every slice
2605             Node *new_mem = (m->is_MergeMem()) ?
2606                              m->as_MergeMem()->memory_at(alias_idx) : m;
2607             // Update input if it is progress over what we have now
2608             if (new_mem != ii) {
2609               set_req_X(i, new_mem, phase->is_IterGVN());
2610               progress = this;
2611             }
2612           }
2613         }
2614       } else if (mergemem_only || split_always_terminates) {
2615         // If all inputs reference this phi (directly or through data nodes) -
2616         // it is a dead loop.
2617         bool saw_safe_input = false;
2618         for (uint j = 1; j < req(); ++j) {
2619           Node* n = in(j);
2620           if (n->is_MergeMem()) {
2621             MergeMemNode* mm = n->as_MergeMem();
2622             if (mm->base_memory() == this || mm->base_memory() == mm->empty_memory()) {
2623               // Skip this input if it references back to this phi or if the memory path is dead
2624               continue;
2625             }
2626           }
2627           if (!is_unsafe_data_reference(n)) {
2628             saw_safe_input = true; // found safe input
2629             break;
2630           }
2631         }
2632         if (!saw_safe_input) {
2633           // There is a dead loop: All inputs are either dead or reference back to this phi
2634           return top;
2635         }
2636 
2637         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2638         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2639         PhaseIterGVN* igvn = phase->is_IterGVN();
2640         assert(igvn != nullptr, "sanity check");
2641         PhiNode* new_base = (PhiNode*) clone();
2642         // Must eagerly register phis, since they participate in loops.
2643         igvn->register_new_node_with_optimizer(new_base);
2644 
2645         MergeMemNode* result = MergeMemNode::make(new_base);
2646         for (uint i = 1; i < req(); ++i) {
2647           Node *ii = in(i);
2648           if (ii->is_MergeMem()) {
2649             MergeMemNode* n = ii->as_MergeMem();
2650             if (igvn) {
2651               // TODO revisit this with JDK-8247216
2652               // Put 'n' on the worklist because it might be modified by MergeMemStream::iteration_setup
2653               igvn->_worklist.push(n);
2654             }
2655             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2656               // If we have not seen this slice yet, make a phi for it.
2657               bool made_new_phi = false;
2658               if (mms.is_empty()) {
2659                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2660                 made_new_phi = true;
2661                 igvn->register_new_node_with_optimizer(new_phi);
2662                 mms.set_memory(new_phi);
2663               }
2664               Node* phi = mms.memory();
2665               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2666               phi->set_req(i, mms.memory2());
2667             }
2668           }
2669         }
2670         // Distribute all self-loops.
2671         { // (Extra braces to hide mms.)
2672           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2673             Node* phi = mms.memory();
2674             for (uint i = 1; i < req(); ++i) {
2675               if (phi->in(i) == this)  phi->set_req(i, phi);
2676             }
2677           }
2678         }
2679 
2680         // We could immediately transform the new Phi nodes here, but that can
2681         // result in creating an excessive number of new nodes within a single
2682         // IGVN iteration. We have put the Phi nodes on the IGVN worklist, so
2683         // they are transformed later on in any case.
2684 
2685         // Replace self with the result.
2686         return result;
2687       }
2688     }
2689     //
2690     // Other optimizations on the memory chain
2691     //
2692     const TypePtr* at = adr_type();
2693     for( uint i=1; i<req(); ++i ) {// For all paths in
2694       Node *ii = in(i);
2695       Node *new_in = MemNode::optimize_memory_chain(ii, at, nullptr, phase);
2696       if (ii != new_in ) {
2697         set_req(i, new_in);
2698         progress = this;
2699       }
2700     }
2701   }
2702 
2703 #ifdef _LP64
2704   // Push DecodeN/DecodeNKlass down through phi.
2705   // The rest of phi graph will transform by split EncodeP node though phis up.
2706   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == nullptr) {
2707     bool may_push = true;
2708     bool has_decodeN = false;
2709     bool is_decodeN = false;
2710     for (uint i=1; i<req(); ++i) {// For all paths in
2711       Node *ii = in(i);
2712       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2713         // Do optimization if a non dead path exist.
2714         if (ii->in(1)->bottom_type() != Type::TOP) {
2715           has_decodeN = true;
2716           is_decodeN = ii->is_DecodeN();
2717         }
2718       } else if (!ii->is_Phi()) {
2719         may_push = false;
2720       }
2721     }
2722 
2723     if (has_decodeN && may_push) {
2724       PhaseIterGVN *igvn = phase->is_IterGVN();
2725       // Make narrow type for new phi.
2726       const Type* narrow_t;
2727       if (is_decodeN) {
2728         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2729       } else {
2730         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2731       }
2732       PhiNode* new_phi = new PhiNode(r, narrow_t);
2733       uint orig_cnt = req();
2734       for (uint i=1; i<req(); ++i) {// For all paths in
2735         Node *ii = in(i);
2736         Node* new_ii = nullptr;
2737         if (ii->is_DecodeNarrowPtr()) {
2738           assert(ii->bottom_type() == bottom_type(), "sanity");
2739           new_ii = ii->in(1);
2740         } else {
2741           assert(ii->is_Phi(), "sanity");
2742           if (ii->as_Phi() == this) {
2743             new_ii = new_phi;
2744           } else {
2745             if (is_decodeN) {
2746               new_ii = new EncodePNode(ii, narrow_t);
2747             } else {
2748               new_ii = new EncodePKlassNode(ii, narrow_t);
2749             }
2750             igvn->register_new_node_with_optimizer(new_ii);
2751           }
2752         }
2753         new_phi->set_req(i, new_ii);
2754       }
2755       igvn->register_new_node_with_optimizer(new_phi, this);
2756       if (is_decodeN) {
2757         progress = new DecodeNNode(new_phi, bottom_type());
2758       } else {
2759         progress = new DecodeNKlassNode(new_phi, bottom_type());
2760       }
2761     }
2762   }
2763 #endif
2764 
2765   Node* inline_type = try_push_inline_types_down(phase, can_reshape);
2766   if (inline_type != this) {
2767     return inline_type;
2768   }
2769 
2770   // Try to convert a Phi with two duplicated convert nodes into a phi of the pre-conversion type and the convert node
2771   // proceeding the phi, to de-duplicate the convert node and compact the IR.
2772   if (can_reshape && progress == nullptr) {
2773     ConvertNode* convert = in(1)->isa_Convert();
2774     if (convert != nullptr) {
2775       int conv_op = convert->Opcode();
2776       bool ok = true;
2777 
2778       // Check the rest of the inputs
2779       for (uint i = 2; i < req(); i++) {
2780         // Make sure that all inputs are of the same type of convert node
2781         if (in(i)->Opcode() != conv_op) {
2782           ok = false;
2783           break;
2784         }
2785       }
2786 
2787       if (ok) {
2788         // Find the local bottom type to set as the type of the phi
2789         const Type* source_type = Type::get_const_basic_type(convert->in_type()->basic_type());
2790         const Type* dest_type = convert->bottom_type();
2791 
2792         PhiNode* newphi = new PhiNode(in(0), source_type, nullptr);
2793         // Set inputs to the new phi be the inputs of the convert
2794         for (uint i = 1; i < req(); i++) {
2795           newphi->init_req(i, in(i)->in(1));
2796         }
2797 
2798         phase->is_IterGVN()->register_new_node_with_optimizer(newphi, this);
2799 
2800         return ConvertNode::create_convert(get_convert_type(convert, source_type), get_convert_type(convert, dest_type), newphi);
2801       }
2802     }
2803   }
2804 
2805   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2806   if (EnableVectorReboxing && can_reshape && progress == nullptr && type()->isa_oopptr()) {
2807     progress = merge_through_phi(this, phase->is_IterGVN());
2808   }
2809 
2810   return progress;              // Return any progress
2811 }
2812 
2813 // Check recursively if inputs are either an inline type, constant null
2814 // or another Phi (including self references through data loops). If so,
2815 // push the inline types down through the phis to enable folding of loads.
2816 Node* PhiNode::try_push_inline_types_down(PhaseGVN* phase, const bool can_reshape) {
2817   if (!can_be_inline_type()) {
2818     return this;
2819   }
2820 
2821   ciInlineKlass* inline_klass;
2822   if (can_push_inline_types_down(phase, can_reshape, inline_klass)) {
2823     assert(inline_klass != nullptr, "must be");
2824     return push_inline_types_down(phase, can_reshape, inline_klass);
2825   }
2826   return this;
2827 }
2828 
2829 bool PhiNode::can_push_inline_types_down(PhaseGVN* phase, const bool can_reshape, ciInlineKlass*& inline_klass) {
2830   if (req() <= 2) {
2831     // Dead phi.
2832     return false;
2833   }
2834   inline_klass = nullptr;
2835 
2836   // TODO 8302217 We need to prevent endless pushing through
2837   bool only_phi = (outcnt() != 0);
2838   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2839     Node* n = fast_out(i);
2840     if (n->is_InlineType() && n->in(1) == this) {
2841       return false;
2842     }
2843     if (!n->is_Phi()) {
2844       only_phi = false;
2845     }
2846   }
2847   if (only_phi) {
2848     return false;
2849   }
2850 
2851   ResourceMark rm;
2852   Unique_Node_List worklist;
2853   worklist.push(this);
2854   Node_List casts;
2855 
2856   for (uint next = 0; next < worklist.size(); next++) {
2857     Node* phi = worklist.at(next);
2858     for (uint i = 1; i < phi->req(); i++) {
2859       Node* n = phi->in(i);
2860       if (n == nullptr) {
2861         return false;
2862       }
2863       while (n->is_ConstraintCast()) {
2864         if (n->in(0) != nullptr && n->in(0)->is_top()) {
2865           // Will die, don't optimize
2866           return false;
2867         }
2868         casts.push(n);
2869         n = n->in(1);
2870       }
2871       const Type* type = phase->type(n);
2872       if (n->is_InlineType() && (inline_klass == nullptr || inline_klass == type->inline_klass())) {
2873         inline_klass = type->inline_klass();
2874       } else if (n->is_Phi() && can_reshape && n->bottom_type()->isa_ptr()) {
2875         worklist.push(n);
2876       } else if (!type->is_zero_type()) {
2877         return false;
2878       }
2879     }
2880   }
2881   if (inline_klass == nullptr) {
2882     return false;
2883   }
2884 
2885   // Check if cast nodes can be pushed through
2886   const Type* t = Type::get_const_type(inline_klass);
2887   while (casts.size() != 0 && t != nullptr) {
2888     Node* cast = casts.pop();
2889     if (t->filter(cast->bottom_type()) == Type::TOP) {
2890       return false;
2891     }
2892   }
2893 
2894   return true;
2895 }
2896 
2897 #ifdef ASSERT
2898 bool PhiNode::can_push_inline_types_down(PhaseGVN* phase) {
2899   if (!can_be_inline_type()) {
2900     return false;
2901   }
2902 
2903   ciInlineKlass* inline_klass;
2904   return can_push_inline_types_down(phase, true, inline_klass);
2905 }
2906 #endif // ASSERT
2907 
2908 static int compare_types(const Type* const& e1, const Type* const& e2) {
2909   return (intptr_t)e1 - (intptr_t)e2;
2910 }
2911 
2912 // Collect types at casts that are going to be eliminated at that Phi and store them in a TypeTuple.
2913 // Sort the types using an arbitrary order so a list of some types always hashes to the same TypeTuple (and TypeTuple
2914 // pointer comparison is enough to tell if 2 list of types are the same or not)
2915 const TypeTuple* PhiNode::collect_types(PhaseGVN* phase) const {
2916   const Node* region = in(0);
2917   const Type* phi_type = bottom_type();
2918   ResourceMark rm;
2919   GrowableArray<const Type*> types;
2920   for (uint i = 1; i < req(); i++) {
2921     if (region->in(i) == nullptr || phase->type(region->in(i)) == Type::TOP) {
2922       continue;
2923     }
2924     Node* in = Node::in(i);
2925     const Type* t = phase->type(in);
2926     if (in == nullptr || in == this || t == Type::TOP) {
2927       continue;
2928     }
2929     if (t != phi_type && t->higher_equal_speculative(phi_type)) {
2930       types.insert_sorted<compare_types>(t);
2931     }
2932     while (in != nullptr && in->is_ConstraintCast()) {
2933       Node* next = in->in(1);
2934       if (phase->type(next)->isa_rawptr() && phase->type(in)->isa_oopptr()) {
2935         break;
2936       }
2937       ConstraintCastNode* cast = in->as_ConstraintCast();
2938       for (int j = 0; j < cast->extra_types_count(); ++j) {
2939         const Type* extra_t = cast->extra_type_at(j);
2940         if (extra_t != phi_type && extra_t->higher_equal_speculative(phi_type)) {
2941           types.insert_sorted<compare_types>(extra_t);
2942         }
2943       }
2944       in = next;
2945     }
2946   }
2947   const Type **flds = (const Type **)(phase->C->type_arena()->AmallocWords(types.length()*sizeof(Type*)));
2948   for (int i = 0; i < types.length(); ++i) {
2949     flds[i] = types.at(i);
2950   }
2951   return TypeTuple::make(types.length(), flds);
2952 }
2953 
2954 Node* PhiNode::clone_through_phi(Node* root_phi, const Type* t, uint c, PhaseIterGVN* igvn) {
2955   Node_Stack stack(1);
2956   VectorSet  visited;
2957   Node_List  node_map;
2958 
2959   stack.push(root_phi, 1); // ignore control
2960   visited.set(root_phi->_idx);
2961 
2962   Node* new_phi = new PhiNode(root_phi->in(0), t);
2963   node_map.map(root_phi->_idx, new_phi);
2964 
2965   while (stack.is_nonempty()) {
2966     Node* n   = stack.node();
2967     uint  idx = stack.index();
2968     assert(n->is_Phi(), "not a phi");
2969     if (idx < n->req()) {
2970       stack.set_index(idx + 1);
2971       Node* def = n->in(idx);
2972       if (def == nullptr) {
2973         continue; // ignore dead path
2974       } else if (def->is_Phi()) { // inner node
2975         Node* new_phi = node_map[n->_idx];
2976         if (!visited.test_set(def->_idx)) { // not visited yet
2977           node_map.map(def->_idx, new PhiNode(def->in(0), t));
2978           stack.push(def, 1); // ignore control
2979         }
2980         Node* new_in = node_map[def->_idx];
2981         new_phi->set_req(idx, new_in);
2982       } else if (def->Opcode() == Op_VectorBox) { // leaf
2983         assert(n->is_Phi(), "not a phi");
2984         Node* new_phi = node_map[n->_idx];
2985         new_phi->set_req(idx, def->in(c));
2986       } else {
2987         assert(false, "not optimizeable");
2988         return nullptr;
2989       }
2990     } else {
2991       Node* new_phi = node_map[n->_idx];
2992       igvn->register_new_node_with_optimizer(new_phi, n);
2993       stack.pop();
2994     }
2995   }
2996   return new_phi;
2997 }
2998 
2999 Node* PhiNode::merge_through_phi(Node* root_phi, PhaseIterGVN* igvn) {
3000   Node_Stack stack(1);
3001   VectorSet  visited;
3002 
3003   stack.push(root_phi, 1); // ignore control
3004   visited.set(root_phi->_idx);
3005 
3006   VectorBoxNode* cached_vbox = nullptr;
3007   while (stack.is_nonempty()) {
3008     Node* n   = stack.node();
3009     uint  idx = stack.index();
3010     if (idx < n->req()) {
3011       stack.set_index(idx + 1);
3012       Node* in = n->in(idx);
3013       if (in == nullptr) {
3014         continue; // ignore dead path
3015       } else if (in->isa_Phi()) {
3016         if (!visited.test_set(in->_idx)) {
3017           stack.push(in, 1); // ignore control
3018         }
3019       } else if (in->Opcode() == Op_VectorBox) {
3020         VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in);
3021         if (cached_vbox == nullptr) {
3022           cached_vbox = vbox;
3023         } else if (vbox->vec_type() != cached_vbox->vec_type()) {
3024           // TODO: vector type mismatch can be handled with additional reinterpret casts
3025           assert(!Type::equals(vbox->vec_type(), cached_vbox->vec_type()), "inconsistent");
3026           return nullptr; // not optimizable: vector type mismatch
3027         } else if (vbox->box_type() != cached_vbox->box_type()) {
3028           assert(!Type::equals(vbox->box_type(), cached_vbox->box_type()), "inconsistent");
3029           return nullptr; // not optimizable: box type mismatch
3030         }
3031       } else {
3032         return nullptr; // not optimizable: neither Phi nor VectorBox
3033       }
3034     } else {
3035       stack.pop();
3036     }
3037   }
3038   if (cached_vbox == nullptr) {
3039     // We have a Phi dead-loop (no data-input). Phi nodes are considered safe,
3040     // so just avoid this optimization.
3041     return nullptr;
3042   }
3043   const TypeInstPtr* btype = cached_vbox->box_type();
3044   const TypeVect*    vtype = cached_vbox->vec_type();
3045   Node* new_vbox_phi = clone_through_phi(root_phi, btype, VectorBoxNode::Box,   igvn);
3046   Node* new_vect_phi = clone_through_phi(root_phi, vtype, VectorBoxNode::Value, igvn);
3047   return new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, btype, vtype);
3048 }
3049 
3050 bool PhiNode::is_data_loop(RegionNode* r, Node* uin, const PhaseGVN* phase) {
3051   // First, take the short cut when we know it is a loop and the EntryControl data path is dead.
3052   // The loop node may only have one input because the entry path was removed in PhaseIdealLoop::Dominators().
3053   // Then, check if there is a data loop when the phi references itself directly or through other data nodes.
3054   assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
3055   const bool is_loop = (r->is_Loop() && r->req() == 3);
3056   const Node* top = phase->C->top();
3057   if (is_loop) {
3058     return !uin->eqv_uncast(in(LoopNode::EntryControl));
3059   } else {
3060     // We have a data loop either with an unsafe data reference or if a region is unreachable.
3061     return is_unsafe_data_reference(uin)
3062            || (r->req() == 3 && (r->in(1) != top && r->in(2) == top && r->is_unreachable_region(phase)));
3063   }
3064 }
3065 
3066 //------------------------------is_tripcount-----------------------------------
3067 bool PhiNode::is_tripcount(BasicType bt) const {
3068   return (in(0) != nullptr && in(0)->is_BaseCountedLoop() &&
3069           in(0)->as_BaseCountedLoop()->bt() == bt &&
3070           in(0)->as_BaseCountedLoop()->phi() == this);
3071 }
3072 
3073 //------------------------------out_RegMask------------------------------------
3074 const RegMask &PhiNode::in_RegMask(uint i) const {
3075   return i ? out_RegMask() : RegMask::Empty;
3076 }
3077 
3078 const RegMask &PhiNode::out_RegMask() const {
3079   uint ideal_reg = _type->ideal_reg();
3080   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
3081   if( ideal_reg == 0 ) return RegMask::Empty;
3082   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
3083   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
3084 }
3085 
3086 #ifndef PRODUCT
3087 void PhiNode::dump_spec(outputStream *st) const {
3088   TypeNode::dump_spec(st);
3089   if (is_tripcount(T_INT) || is_tripcount(T_LONG)) {
3090     st->print(" #tripcount");
3091   }
3092 }
3093 #endif
3094 
3095 
3096 //=============================================================================
3097 const Type* GotoNode::Value(PhaseGVN* phase) const {
3098   // If the input is reachable, then we are executed.
3099   // If the input is not reachable, then we are not executed.
3100   return phase->type(in(0));
3101 }
3102 
3103 Node* GotoNode::Identity(PhaseGVN* phase) {
3104   return in(0);                // Simple copy of incoming control
3105 }
3106 
3107 const RegMask &GotoNode::out_RegMask() const {
3108   return RegMask::Empty;
3109 }
3110 
3111 //=============================================================================
3112 const RegMask &JumpNode::out_RegMask() const {
3113   return RegMask::Empty;
3114 }
3115 
3116 //=============================================================================
3117 const RegMask &JProjNode::out_RegMask() const {
3118   return RegMask::Empty;
3119 }
3120 
3121 //=============================================================================
3122 const RegMask &CProjNode::out_RegMask() const {
3123   return RegMask::Empty;
3124 }
3125 
3126 
3127 
3128 //=============================================================================
3129 
3130 uint PCTableNode::hash() const { return Node::hash() + _size; }
3131 bool PCTableNode::cmp( const Node &n ) const
3132 { return _size == ((PCTableNode&)n)._size; }
3133 
3134 const Type *PCTableNode::bottom_type() const {
3135   const Type** f = TypeTuple::fields(_size);
3136   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
3137   return TypeTuple::make(_size, f);
3138 }
3139 
3140 //------------------------------Value------------------------------------------
3141 // Compute the type of the PCTableNode.  If reachable it is a tuple of
3142 // Control, otherwise the table targets are not reachable
3143 const Type* PCTableNode::Value(PhaseGVN* phase) const {
3144   if( phase->type(in(0)) == Type::CONTROL )
3145     return bottom_type();
3146   return Type::TOP;             // All paths dead?  Then so are we
3147 }
3148 
3149 //------------------------------Ideal------------------------------------------
3150 // Return a node which is more "ideal" than the current node.  Strip out
3151 // control copies
3152 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3153   return remove_dead_region(phase, can_reshape) ? this : nullptr;
3154 }
3155 
3156 //=============================================================================
3157 uint JumpProjNode::hash() const {
3158   return Node::hash() + _dest_bci;
3159 }
3160 
3161 bool JumpProjNode::cmp( const Node &n ) const {
3162   return ProjNode::cmp(n) &&
3163     _dest_bci == ((JumpProjNode&)n)._dest_bci;
3164 }
3165 
3166 #ifndef PRODUCT
3167 void JumpProjNode::dump_spec(outputStream *st) const {
3168   ProjNode::dump_spec(st);
3169   st->print("@bci %d ",_dest_bci);
3170 }
3171 
3172 void JumpProjNode::dump_compact_spec(outputStream *st) const {
3173   ProjNode::dump_compact_spec(st);
3174   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
3175 }
3176 #endif
3177 
3178 //=============================================================================
3179 //------------------------------Value------------------------------------------
3180 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
3181 // have the default "fall_through_index" path.
3182 const Type* CatchNode::Value(PhaseGVN* phase) const {
3183   // Unreachable?  Then so are all paths from here.
3184   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
3185   // First assume all paths are reachable
3186   const Type** f = TypeTuple::fields(_size);
3187   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
3188   // Identify cases that will always throw an exception
3189   // () rethrow call
3190   // () virtual or interface call with null receiver
3191   // () call is a check cast with incompatible arguments
3192   if( in(1)->is_Proj() ) {
3193     Node *i10 = in(1)->in(0);
3194     if( i10->is_Call() ) {
3195       CallNode *call = i10->as_Call();
3196       // Rethrows always throw exceptions, never return
3197       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
3198         f[CatchProjNode::fall_through_index] = Type::TOP;
3199       } else if (call->is_AllocateArray()) {
3200         Node* klass_node = call->in(AllocateNode::KlassNode);
3201         Node* length = call->in(AllocateNode::ALength);
3202         const Type* length_type = phase->type(length);
3203         const Type* klass_type = phase->type(klass_node);
3204         Node* valid_length_test = call->in(AllocateNode::ValidLengthTest);
3205         const Type* valid_length_test_t = phase->type(valid_length_test);
3206         if (length_type == Type::TOP || klass_type == Type::TOP || valid_length_test_t == Type::TOP ||
3207             valid_length_test_t->is_int()->is_con(0)) {
3208           f[CatchProjNode::fall_through_index] = Type::TOP;
3209         }
3210       } else if( call->req() > TypeFunc::Parms ) {
3211         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
3212         // Check for null receiver to virtual or interface calls
3213         if( call->is_CallDynamicJava() &&
3214             arg0->higher_equal(TypePtr::NULL_PTR) ) {
3215           f[CatchProjNode::fall_through_index] = Type::TOP;
3216         }
3217       } // End of if not a runtime stub
3218     } // End of if have call above me
3219   } // End of slot 1 is not a projection
3220   return TypeTuple::make(_size, f);
3221 }
3222 
3223 //=============================================================================
3224 uint CatchProjNode::hash() const {
3225   return Node::hash() + _handler_bci;
3226 }
3227 
3228 
3229 bool CatchProjNode::cmp( const Node &n ) const {
3230   return ProjNode::cmp(n) &&
3231     _handler_bci == ((CatchProjNode&)n)._handler_bci;
3232 }
3233 
3234 
3235 //------------------------------Identity---------------------------------------
3236 // If only 1 target is possible, choose it if it is the main control
3237 Node* CatchProjNode::Identity(PhaseGVN* phase) {
3238   // If my value is control and no other value is, then treat as ID
3239   const TypeTuple *t = phase->type(in(0))->is_tuple();
3240   if (t->field_at(_con) != Type::CONTROL)  return this;
3241   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
3242   // also remove any exception table entry.  Thus we must know the call
3243   // feeding the Catch will not really throw an exception.  This is ok for
3244   // the main fall-thru control (happens when we know a call can never throw
3245   // an exception) or for "rethrow", because a further optimization will
3246   // yank the rethrow (happens when we inline a function that can throw an
3247   // exception and the caller has no handler).  Not legal, e.g., for passing
3248   // a null receiver to a v-call, or passing bad types to a slow-check-cast.
3249   // These cases MUST throw an exception via the runtime system, so the VM
3250   // will be looking for a table entry.
3251   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
3252   CallNode *call;
3253   if (_con != TypeFunc::Control && // Bail out if not the main control.
3254       !(proj->is_Proj() &&      // AND NOT a rethrow
3255         proj->in(0)->is_Call() &&
3256         (call = proj->in(0)->as_Call()) &&
3257         call->entry_point() == OptoRuntime::rethrow_stub()))
3258     return this;
3259 
3260   // Search for any other path being control
3261   for (uint i = 0; i < t->cnt(); i++) {
3262     if (i != _con && t->field_at(i) == Type::CONTROL)
3263       return this;
3264   }
3265   // Only my path is possible; I am identity on control to the jump
3266   return in(0)->in(0);
3267 }
3268 
3269 
3270 #ifndef PRODUCT
3271 void CatchProjNode::dump_spec(outputStream *st) const {
3272   ProjNode::dump_spec(st);
3273   st->print("@bci %d ",_handler_bci);
3274 }
3275 #endif
3276 
3277 //=============================================================================
3278 //------------------------------Identity---------------------------------------
3279 // Check for CreateEx being Identity.
3280 Node* CreateExNode::Identity(PhaseGVN* phase) {
3281   if( phase->type(in(1)) == Type::TOP ) return in(1);
3282   if( phase->type(in(0)) == Type::TOP ) return in(0);
3283   if (phase->type(in(0)->in(0)) == Type::TOP) {
3284     assert(in(0)->is_CatchProj(), "control is CatchProj");
3285     return phase->C->top(); // dead code
3286   }
3287   // We only come from CatchProj, unless the CatchProj goes away.
3288   // If the CatchProj is optimized away, then we just carry the
3289   // exception oop through.
3290 
3291   // CheckCastPPNode::Ideal() for inline types reuses the exception
3292   // paths of a call to perform an allocation: we can see a Phi here.
3293   if (in(1)->is_Phi()) {
3294     return this;
3295   }
3296   CallNode *call = in(1)->in(0)->as_Call();
3297 
3298   return (in(0)->is_CatchProj() && in(0)->in(0)->is_Catch() &&
3299           in(0)->in(0)->in(1) == in(1)) ? this : call->in(TypeFunc::Parms);
3300 }
3301 
3302 //=============================================================================
3303 //------------------------------Value------------------------------------------
3304 // Check for being unreachable.
3305 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
3306   if (!in(0) || in(0)->is_top()) return Type::TOP;
3307   return bottom_type();
3308 }
3309 
3310 //------------------------------Ideal------------------------------------------
3311 // Check for no longer being part of a loop
3312 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3313   if (can_reshape && !in(0)->is_Region()) {
3314     // Dead code elimination can sometimes delete this projection so
3315     // if it's not there, there's nothing to do.
3316     Node* fallthru = proj_out_or_null(0);
3317     if (fallthru != nullptr) {
3318       phase->is_IterGVN()->replace_node(fallthru, in(0));
3319     }
3320     return phase->C->top();
3321   }
3322   return nullptr;
3323 }
3324 
3325 #ifndef PRODUCT
3326 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
3327   st->print("%s", Name());
3328 }
3329 #endif
3330 
3331 Node* BlackholeNode::Ideal(PhaseGVN* phase, bool can_reshape) {
3332   return remove_dead_region(phase, can_reshape) ? this : nullptr;
3333 }
3334 
3335 #ifndef PRODUCT
3336 void BlackholeNode::format(PhaseRegAlloc* ra, outputStream* st) const {
3337   st->print("blackhole ");
3338   bool first = true;
3339   for (uint i = 0; i < req(); i++) {
3340     Node* n = in(i);
3341     if (n != nullptr && OptoReg::is_valid(ra->get_reg_first(n))) {
3342       if (first) {
3343         first = false;
3344       } else {
3345         st->print(", ");
3346       }
3347       char buf[128];
3348       ra->dump_register(n, buf, sizeof(buf));
3349       st->print("%s", buf);
3350     }
3351   }
3352   st->cr();
3353 }
3354 #endif
3355