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/narrowptrnode.hpp"
  40 #include "opto/mulnode.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   Node_Array node_map;
1124   Node_Stack stack(C->live_nodes() >> 4);
1125   PhiNode *nphi = slice_memory(at);
1126   igvn->register_new_node_with_optimizer( nphi );
1127   node_map.map(_idx, nphi);
1128   stack.push((Node *)this, 1);
1129   while(!stack.is_empty()) {
1130     PhiNode *ophi = stack.node()->as_Phi();
1131     uint i = stack.index();
1132     assert(i >= 1, "not control edge");
1133     stack.pop();
1134     nphi = node_map[ophi->_idx]->as_Phi();
1135     for (; i < ophi->req(); i++) {
1136       Node *in = ophi->in(i);
1137       if (in == nullptr || igvn->type(in) == Type::TOP)
1138         continue;
1139       Node *opt = MemNode::optimize_simple_memory_chain(in, t_oop, nullptr, igvn);
1140       PhiNode *optphi = opt->is_Phi() ? opt->as_Phi() : nullptr;
1141       if (optphi != nullptr && optphi->adr_type() == TypePtr::BOTTOM) {
1142         opt = node_map[optphi->_idx];
1143         if (opt == nullptr) {
1144           stack.push(ophi, i);
1145           nphi = optphi->slice_memory(at);
1146           igvn->register_new_node_with_optimizer( nphi );
1147           node_map.map(optphi->_idx, nphi);
1148           ophi = optphi;
1149           i = 0; // will get incremented at top of loop
1150           continue;
1151         }
1152       }
1153       nphi->set_req(i, opt);
1154     }
1155   }
1156   return nphi;
1157 }
1158 
1159 //------------------------verify_adr_type--------------------------------------
1160 #ifdef ASSERT
1161 void PhiNode::verify_adr_type(VectorSet& visited, const TypePtr* at) const {
1162   if (visited.test_set(_idx))  return;  //already visited
1163 
1164   // recheck constructor invariants:
1165   verify_adr_type(false);
1166 
1167   // recheck local phi/phi consistency:
1168   assert(_adr_type == at || _adr_type == TypePtr::BOTTOM,
1169          "adr_type must be consistent across phi nest");
1170 
1171   // walk around
1172   for (uint i = 1; i < req(); i++) {
1173     Node* n = in(i);
1174     if (n == nullptr)  continue;
1175     const Node* np = in(i);
1176     if (np->is_Phi()) {
1177       np->as_Phi()->verify_adr_type(visited, at);
1178     } else if (n->bottom_type() == Type::TOP
1179                || (n->is_Mem() && n->in(MemNode::Address)->bottom_type() == Type::TOP)) {
1180       // ignore top inputs
1181     } else {
1182       const TypePtr* nat = flatten_phi_adr_type(n->adr_type());
1183       // recheck phi/non-phi consistency at leaves:
1184       assert((nat != nullptr) == (at != nullptr), "");
1185       assert(nat == at || nat == TypePtr::BOTTOM,
1186              "adr_type must be consistent at leaves of phi nest");
1187     }
1188   }
1189 }
1190 
1191 // Verify a whole nest of phis rooted at this one.
1192 void PhiNode::verify_adr_type(bool recursive) const {
1193   if (VMError::is_error_reported())  return;  // muzzle asserts when debugging an error
1194   if (Node::in_dump())               return;  // muzzle asserts when printing
1195 
1196   assert((_type == Type::MEMORY) == (_adr_type != nullptr), "adr_type for memory phis only");
1197   // Flat array element shouldn't get their own memory slice until flat_accesses_share_alias is cleared.
1198   // It could be the graph has no loads/stores and flat_accesses_share_alias is never cleared. EA could still
1199   // creates per element Phis but that wouldn't be a problem as there are no memory accesses for that array.
1200   assert(_adr_type == nullptr || _adr_type->isa_aryptr() == nullptr ||
1201          _adr_type->is_aryptr()->is_known_instance() ||
1202          !_adr_type->is_aryptr()->is_flat() ||
1203          !Compile::current()->flat_accesses_share_alias() ||
1204          _adr_type == TypeAryPtr::INLINES, "flat array element shouldn't get its own slice yet");
1205 
1206   if (!VerifyAliases)       return;  // verify thoroughly only if requested
1207 
1208   assert(_adr_type == flatten_phi_adr_type(_adr_type),
1209          "Phi::adr_type must be pre-normalized");
1210 
1211   if (recursive) {
1212     VectorSet visited;
1213     verify_adr_type(visited, _adr_type);
1214   }
1215 }
1216 #endif
1217 
1218 
1219 //------------------------------Value------------------------------------------
1220 // Compute the type of the PhiNode
1221 const Type* PhiNode::Value(PhaseGVN* phase) const {
1222   Node *r = in(0);              // RegionNode
1223   if( !r )                      // Copy or dead
1224     return in(1) ? phase->type(in(1)) : Type::TOP;
1225 
1226   // Note: During parsing, phis are often transformed before their regions.
1227   // This means we have to use type_or_null to defend against untyped regions.
1228   if( phase->type_or_null(r) == Type::TOP )  // Dead code?
1229     return Type::TOP;
1230 
1231   // Check for trip-counted loop.  If so, be smarter.
1232   BaseCountedLoopNode* l = r->is_BaseCountedLoop() ? r->as_BaseCountedLoop() : nullptr;
1233   if (l && ((const Node*)l->phi() == this)) { // Trip counted loop!
1234     // protect against init_trip() or limit() returning null
1235     if (l->can_be_counted_loop(phase)) {
1236       const Node* init = l->init_trip();
1237       const Node* limit = l->limit();
1238       const Node* stride = l->stride();
1239       if (init != nullptr && limit != nullptr && stride != nullptr) {
1240         const TypeInteger* lo = phase->type(init)->isa_integer(l->bt());
1241         const TypeInteger* hi = phase->type(limit)->isa_integer(l->bt());
1242         const TypeInteger* stride_t = phase->type(stride)->isa_integer(l->bt());
1243         if (lo != nullptr && hi != nullptr && stride_t != nullptr) { // Dying loops might have TOP here
1244           assert(stride_t->is_con(), "bad stride type");
1245           BoolTest::mask bt = l->loopexit()->test_trip();
1246           // If the loop exit condition is "not equal", the condition
1247           // would not trigger if init > limit (if stride > 0) or if
1248           // init < limit if (stride > 0) so we can't deduce bounds
1249           // for the iv from the exit condition.
1250           if (bt != BoolTest::ne) {
1251             jlong stride_con = stride_t->get_con_as_long(l->bt());
1252             if (stride_con < 0) {          // Down-counter loop
1253               swap(lo, hi);
1254               jlong iv_range_lower_limit = lo->lo_as_long();
1255               // Prevent overflow when adding one below
1256               if (iv_range_lower_limit < max_signed_integer(l->bt())) {
1257                 // The loop exit condition is: iv + stride > limit (iv is this Phi). So the loop iterates until
1258                 // iv + stride <= limit
1259                 // We know that: limit >= lo->lo_as_long() and stride <= -1
1260                 // So when the loop exits, iv has to be at most lo->lo_as_long() + 1
1261                 iv_range_lower_limit += 1; // lo is after decrement
1262                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1263                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != -1) {
1264                   julong uhi = static_cast<julong>(hi->lo_as_long());
1265                   julong ulo = static_cast<julong>(lo->hi_as_long());
1266                   julong diff = ((uhi - ulo - 1) / (-stride_con)) * (-stride_con);
1267                   julong ufirst = hi->lo_as_long() - diff;
1268                   iv_range_lower_limit = reinterpret_cast<jlong &>(ufirst);
1269                   assert(iv_range_lower_limit >= lo->lo_as_long() + 1, "should end up with narrower range");
1270                 }
1271               }
1272               return TypeInteger::make(MIN2(iv_range_lower_limit, hi->lo_as_long()), hi->hi_as_long(), 3, l->bt())->filter_speculative(_type);
1273             } else if (stride_con >= 0) {
1274               jlong iv_range_upper_limit = hi->hi_as_long();
1275               // Prevent overflow when subtracting one below
1276               if (iv_range_upper_limit > min_signed_integer(l->bt())) {
1277                 // The loop exit condition is: iv + stride < limit (iv is this Phi). So the loop iterates until
1278                 // iv + stride >= limit
1279                 // We know that: limit <= hi->hi_as_long() and stride >= 1
1280                 // So when the loop exits, iv has to be at most hi->hi_as_long() - 1
1281                 iv_range_upper_limit -= 1;
1282                 // Exact bounds for the phi can be computed when ABS(stride) greater than 1 if bounds are constant.
1283                 if (lo->is_con() && hi->is_con() && hi->lo_as_long() > lo->hi_as_long() && stride_con != 1) {
1284                   julong uhi = static_cast<julong>(hi->lo_as_long());
1285                   julong ulo = static_cast<julong>(lo->hi_as_long());
1286                   julong diff = ((uhi - ulo - 1) / stride_con) * stride_con;
1287                   julong ulast = lo->hi_as_long() + diff;
1288                   iv_range_upper_limit = reinterpret_cast<jlong &>(ulast);
1289                   assert(iv_range_upper_limit <= hi->hi_as_long() - 1, "should end up with narrower range");
1290                 }
1291               }
1292               return TypeInteger::make(lo->lo_as_long(), MAX2(lo->hi_as_long(), iv_range_upper_limit), 3, l->bt())->filter_speculative(_type);
1293             }
1294           }
1295         }
1296       }
1297     } else if (l->in(LoopNode::LoopBackControl) != nullptr &&
1298                in(LoopNode::EntryControl) != nullptr &&
1299                phase->type(l->in(LoopNode::LoopBackControl)) == Type::TOP) {
1300       // During CCP, if we saturate the type of a counted loop's Phi
1301       // before the special code for counted loop above has a chance
1302       // to run (that is as long as the type of the backedge's control
1303       // is top), we might end up with non monotonic types
1304       return phase->type(in(LoopNode::EntryControl))->filter_speculative(_type);
1305     }
1306   }
1307 
1308   // Default case: merge all inputs
1309   const Type *t = Type::TOP;        // Merged type starting value
1310   for (uint i = 1; i < req(); ++i) {// For all paths in
1311     // Reachable control path?
1312     if (r->in(i) && phase->type(r->in(i)) == Type::CONTROL) {
1313       const Type* ti = phase->type(in(i));
1314       t = t->meet_speculative(ti);
1315     }
1316   }
1317 
1318   // The worst-case type (from ciTypeFlow) should be consistent with "t".
1319   // That is, we expect that "t->higher_equal(_type)" holds true.
1320   // There are various exceptions:
1321   // - Inputs which are phis might in fact be widened unnecessarily.
1322   //   For example, an input might be a widened int while the phi is a short.
1323   // - Inputs might be BotPtrs but this phi is dependent on a null check,
1324   //   and postCCP has removed the cast which encodes the result of the check.
1325   // - The type of this phi is an interface, and the inputs are classes.
1326   // - Value calls on inputs might produce fuzzy results.
1327   //   (Occurrences of this case suggest improvements to Value methods.)
1328   //
1329   // It is not possible to see Type::BOTTOM values as phi inputs,
1330   // because the ciTypeFlow pre-pass produces verifier-quality types.
1331   const Type* ft = t->filter_speculative(_type);  // Worst case type
1332 
1333 #ifdef ASSERT
1334   // The following logic has been moved into TypeOopPtr::filter.
1335   const Type* jt = t->join_speculative(_type);
1336   if (jt->empty()) {           // Emptied out???
1337     // Otherwise it's something stupid like non-overlapping int ranges
1338     // found on dying counted loops.
1339     assert(ft == Type::TOP, ""); // Canonical empty value
1340   }
1341 
1342   else {
1343 
1344     if (jt != ft && jt->base() == ft->base()) {
1345       if (jt->isa_int() &&
1346           jt->is_int()->_lo == ft->is_int()->_lo &&
1347           jt->is_int()->_hi == ft->is_int()->_hi)
1348         jt = ft;
1349       if (jt->isa_long() &&
1350           jt->is_long()->_lo == ft->is_long()->_lo &&
1351           jt->is_long()->_hi == ft->is_long()->_hi)
1352         jt = ft;
1353     }
1354     if (jt != ft) {
1355       tty->print("merge type:  "); t->dump(); tty->cr();
1356       tty->print("kill type:   "); _type->dump(); tty->cr();
1357       tty->print("join type:   "); jt->dump(); tty->cr();
1358       tty->print("filter type: "); ft->dump(); tty->cr();
1359     }
1360     assert(jt == ft, "");
1361   }
1362 #endif //ASSERT
1363 
1364   // Deal with conversion problems found in data loops.
1365   ft = phase->saturate_and_maybe_push_to_igvn_worklist(this, ft);
1366   return ft;
1367 }
1368 
1369 // Does this Phi represent a simple well-shaped diamond merge?  Return the
1370 // index of the true path or 0 otherwise.
1371 int PhiNode::is_diamond_phi() const {
1372   Node* region = in(0);
1373   assert(region != nullptr && region->is_Region(), "phi must have region");
1374   if (!region->as_Region()->is_diamond()) {
1375     return 0;
1376   }
1377 
1378   if (region->in(1)->is_IfTrue()) {
1379     assert(region->in(2)->is_IfFalse(), "bad If");
1380     return 1;
1381   } else {
1382     // Flipped projections.
1383     assert(region->in(2)->is_IfTrue(), "bad If");
1384     return 2;
1385   }
1386 }
1387 
1388 // Do the following transformation if we find the corresponding graph shape, remove the involved memory phi and return
1389 // true. Otherwise, return false if the transformation cannot be applied.
1390 //
1391 //           If                                     If
1392 //          /  \                                   /  \
1393 //    IfFalse  IfTrue  /- Some Node          IfFalse  IfTrue
1394 //          \  /      /    /                       \  /        Some Node
1395 //         Region    / /-MergeMem     ===>        Region          |
1396 //          /   \---Phi                             |          MergeMem
1397 // [other phis]      \                        [other phis]        |
1398 //                   use                                         use
1399 bool PhiNode::try_clean_memory_phi(PhaseIterGVN* igvn) {
1400   if (_type != Type::MEMORY) {
1401     return false;
1402   }
1403   assert(is_diamond_phi() > 0, "sanity");
1404   assert(req() == 3, "same as region");
1405   const Node* region = in(0);
1406   for (uint i = 1; i < 3; i++) {
1407     Node* phi_input = in(i);
1408     if (phi_input != nullptr && phi_input->is_MergeMem() && region->in(i)->outcnt() == 1) {
1409       // Nothing is control-dependent on path #i except the region itself.
1410       MergeMemNode* merge_mem = phi_input->as_MergeMem();
1411       uint j = 3 - i;
1412       Node* other_phi_input = in(j);
1413       if (other_phi_input != nullptr && other_phi_input == merge_mem->base_memory()) {
1414         // merge_mem is a successor memory to other_phi_input, and is not pinned inside the diamond, so push it out.
1415         // This will allow the diamond to collapse completely if there are no other phis left.
1416         igvn->replace_node(this, merge_mem);
1417         return true;
1418       }
1419     }
1420   }
1421   return false;
1422 }
1423 
1424 //----------------------------check_cmove_id-----------------------------------
1425 // Check for CMove'ing a constant after comparing against the constant.
1426 // Happens all the time now, since if we compare equality vs a constant in
1427 // the parser, we "know" the variable is constant on one path and we force
1428 // it.  Thus code like "if( x==0 ) {/*EMPTY*/}" ends up inserting a
1429 // conditional move: "x = (x==0)?0:x;".  Yucko.  This fix is slightly more
1430 // general in that we don't need constants.  Since CMove's are only inserted
1431 // in very special circumstances, we do it here on generic Phi's.
1432 Node* PhiNode::is_cmove_id(PhaseTransform* phase, int true_path) {
1433   assert(true_path !=0, "only diamond shape graph expected");
1434 
1435   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1436   // phi->region->if_proj->ifnode->bool->cmp
1437   Node*     region = in(0);
1438   Node*     iff    = region->in(1)->in(0);
1439   BoolNode* b      = iff->in(1)->as_Bool();
1440   Node*     cmp    = b->in(1);
1441   Node*     tval   = in(true_path);
1442   Node*     fval   = in(3-true_path);
1443   Node*     id     = CMoveNode::is_cmove_id(phase, cmp, tval, fval, b);
1444   if (id == nullptr)
1445     return nullptr;
1446 
1447   // Either value might be a cast that depends on a branch of 'iff'.
1448   // Since the 'id' value will float free of the diamond, either
1449   // decast or return failure.
1450   Node* ctl = id->in(0);
1451   if (ctl != nullptr && ctl->in(0) == iff) {
1452     if (id->is_ConstraintCast()) {
1453       return id->in(1);
1454     } else {
1455       // Don't know how to disentangle this value.
1456       return nullptr;
1457     }
1458   }
1459 
1460   return id;
1461 }
1462 
1463 //------------------------------Identity---------------------------------------
1464 // Check for Region being Identity.
1465 Node* PhiNode::Identity(PhaseGVN* phase) {
1466   if (must_wait_for_region_in_irreducible_loop(phase)) {
1467     return this;
1468   }
1469   // Check for no merging going on
1470   // (There used to be special-case code here when this->region->is_Loop.
1471   // It would check for a tributary phi on the backedge that the main phi
1472   // trivially, perhaps with a single cast.  The unique_input method
1473   // does all this and more, by reducing such tributaries to 'this'.)
1474   Node* uin = unique_input(phase, false);
1475   if (uin != nullptr) {
1476     return uin;
1477   }
1478 
1479   int true_path = is_diamond_phi();
1480   // Delay CMove'ing identity if Ideal has not had the chance to handle unsafe cases, yet.
1481   if (true_path != 0 && !(phase->is_IterGVN() && wait_for_region_igvn(phase))) {
1482     Node* id = is_cmove_id(phase, true_path);
1483     if (id != nullptr) {
1484       return id;
1485     }
1486   }
1487 
1488   // Looking for phis with identical inputs.  If we find one that has
1489   // type TypePtr::BOTTOM, replace the current phi with the bottom phi.
1490   if (phase->is_IterGVN() && type() == Type::MEMORY && adr_type() !=
1491       TypePtr::BOTTOM && !adr_type()->is_known_instance()) {
1492     uint phi_len = req();
1493     Node* phi_reg = region();
1494     for (DUIterator_Fast imax, i = phi_reg->fast_outs(imax); i < imax; i++) {
1495       Node* u = phi_reg->fast_out(i);
1496       if (u->is_Phi() && u->as_Phi()->type() == Type::MEMORY &&
1497           u->adr_type() == TypePtr::BOTTOM && u->in(0) == phi_reg &&
1498           u->req() == phi_len) {
1499         for (uint j = 1; j < phi_len; j++) {
1500           if (in(j) != u->in(j)) {
1501             u = nullptr;
1502             break;
1503           }
1504         }
1505         if (u != nullptr) {
1506           return u;
1507         }
1508       }
1509     }
1510   }
1511 
1512   return this;                     // No identity
1513 }
1514 
1515 //-----------------------------unique_input------------------------------------
1516 // Find the unique value, discounting top, self-loops, and casts.
1517 // Return top if there are no inputs, and self if there are multiple.
1518 Node* PhiNode::unique_input(PhaseValues* phase, bool uncast) {
1519   //  1) One unique direct input,
1520   // or if uncast is true:
1521   //  2) some of the inputs have an intervening ConstraintCast
1522   //  3) an input is a self loop
1523   //
1524   //  1) input   or   2) input     or   3) input __
1525   //     /   \           /   \               \  /  \
1526   //     \   /          |    cast             phi  cast
1527   //      phi            \   /               /  \  /
1528   //                      phi               /    --
1529 
1530   Node* r = in(0);                      // RegionNode
1531   Node* input = nullptr; // The unique direct input (maybe uncasted = ConstraintCasts removed)
1532 
1533   for (uint i = 1, cnt = req(); i < cnt; ++i) {
1534     Node* rc = r->in(i);
1535     if (rc == nullptr || phase->type(rc) == Type::TOP)
1536       continue;                 // ignore unreachable control path
1537     Node* n = in(i);
1538     if (n == nullptr)
1539       continue;
1540     Node* un = n;
1541     if (uncast) {
1542 #ifdef ASSERT
1543       Node* m = un->uncast();
1544 #endif
1545       while (un != nullptr && un->req() == 2 && un->is_ConstraintCast()) {
1546         Node* next = un->in(1);
1547         if (phase->type(next)->isa_rawptr() && phase->type(un)->isa_oopptr()) {
1548           // risk exposing raw ptr at safepoint
1549           break;
1550         }
1551         un = next;
1552       }
1553       assert(m == un || un->in(1) == m, "Only expected at CheckCastPP from allocation");
1554     }
1555     if (un == nullptr || un == this || phase->type(un) == Type::TOP) {
1556       continue; // ignore if top, or in(i) and "this" are in a data cycle
1557     }
1558     // Check for a unique input (maybe uncasted)
1559     if (input == nullptr) {
1560       input = un;
1561     } else if (input != un) {
1562       input = NodeSentinel; // no unique input
1563     }
1564   }
1565   if (input == nullptr) {
1566     return phase->C->top();        // no inputs
1567   }
1568 
1569   if (input != NodeSentinel) {
1570     return input;           // one unique direct input
1571   }
1572 
1573   // Nothing.
1574   return nullptr;
1575 }
1576 
1577 //------------------------------is_x2logic-------------------------------------
1578 // Check for simple convert-to-boolean pattern
1579 // If:(C Bool) Region:(IfF IfT) Phi:(Region 0 1)
1580 // Convert Phi to an ConvIB.
1581 static Node *is_x2logic( PhaseGVN *phase, PhiNode *phi, int true_path ) {
1582   assert(true_path !=0, "only diamond shape graph expected");
1583 
1584   // If we're late in the optimization process, we may have already expanded Conv2B nodes
1585   if (phase->C->post_loop_opts_phase() && !Matcher::match_rule_supported(Op_Conv2B)) {
1586     return nullptr;
1587   }
1588 
1589   // Convert the true/false index into an expected 0/1 return.
1590   // Map 2->0 and 1->1.
1591   int flipped = 2-true_path;
1592 
1593   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1594   // phi->region->if_proj->ifnode->bool->cmp
1595   Node *region = phi->in(0);
1596   Node *iff = region->in(1)->in(0);
1597   BoolNode *b = (BoolNode*)iff->in(1);
1598   const CmpNode *cmp = (CmpNode*)b->in(1);
1599 
1600   Node *zero = phi->in(1);
1601   Node *one  = phi->in(2);
1602   const Type *tzero = phase->type( zero );
1603   const Type *tone  = phase->type( one  );
1604 
1605   // Check for compare vs 0
1606   const Type *tcmp = phase->type(cmp->in(2));
1607   if( tcmp != TypeInt::ZERO && tcmp != TypePtr::NULL_PTR ) {
1608     // Allow cmp-vs-1 if the other input is bounded by 0-1
1609     if( !(tcmp == TypeInt::ONE && phase->type(cmp->in(1)) == TypeInt::BOOL) )
1610       return nullptr;
1611     flipped = 1-flipped;        // Test is vs 1 instead of 0!
1612   }
1613 
1614   // Check for setting zero/one opposite expected
1615   if( tzero == TypeInt::ZERO ) {
1616     if( tone == TypeInt::ONE ) {
1617     } else return nullptr;
1618   } else if( tzero == TypeInt::ONE ) {
1619     if( tone == TypeInt::ZERO ) {
1620       flipped = 1-flipped;
1621     } else return nullptr;
1622   } else return nullptr;
1623 
1624   // Check for boolean test backwards
1625   if( b->_test._test == BoolTest::ne ) {
1626   } else if( b->_test._test == BoolTest::eq ) {
1627     flipped = 1-flipped;
1628   } else return nullptr;
1629 
1630   // Build int->bool conversion
1631   Node* n = new Conv2BNode(cmp->in(1));
1632   if (flipped) {
1633     n = new XorINode(phase->transform(n), phase->intcon(1));
1634   }
1635 
1636   return n;
1637 }
1638 
1639 //------------------------------is_cond_add------------------------------------
1640 // Check for simple conditional add pattern:  "(P < Q) ? X+Y : X;"
1641 // To be profitable the control flow has to disappear; there can be no other
1642 // values merging here.  We replace the test-and-branch with:
1643 // "(sgn(P-Q))&Y) + X".  Basically, convert "(P < Q)" into 0 or -1 by
1644 // moving the carry bit from (P-Q) into a register with 'sbb EAX,EAX'.
1645 // Then convert Y to 0-or-Y and finally add.
1646 // This is a key transform for SpecJava _201_compress.
1647 static Node* is_cond_add(PhaseGVN *phase, PhiNode *phi, int true_path) {
1648   assert(true_path !=0, "only diamond shape graph expected");
1649 
1650   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1651   // phi->region->if_proj->ifnode->bool->cmp
1652   RegionNode *region = (RegionNode*)phi->in(0);
1653   Node *iff = region->in(1)->in(0);
1654   BoolNode* b = iff->in(1)->as_Bool();
1655   const CmpNode *cmp = (CmpNode*)b->in(1);
1656 
1657   // Make sure only merging this one phi here
1658   if (region->has_unique_phi() != phi)  return nullptr;
1659 
1660   // Make sure each arm of the diamond has exactly one output, which we assume
1661   // is the region.  Otherwise, the control flow won't disappear.
1662   if (region->in(1)->outcnt() != 1) return nullptr;
1663   if (region->in(2)->outcnt() != 1) return nullptr;
1664 
1665   // Check for "(P < Q)" of type signed int
1666   if (b->_test._test != BoolTest::lt)  return nullptr;
1667   if (cmp->Opcode() != Op_CmpI)        return nullptr;
1668 
1669   Node *p = cmp->in(1);
1670   Node *q = cmp->in(2);
1671   Node *n1 = phi->in(  true_path);
1672   Node *n2 = phi->in(3-true_path);
1673 
1674   int op = n1->Opcode();
1675   if( op != Op_AddI           // Need zero as additive identity
1676       /*&&op != Op_SubI &&
1677       op != Op_AddP &&
1678       op != Op_XorI &&
1679       op != Op_OrI*/ )
1680     return nullptr;
1681 
1682   Node *x = n2;
1683   Node *y = nullptr;
1684   if( x == n1->in(1) ) {
1685     y = n1->in(2);
1686   } else if( x == n1->in(2) ) {
1687     y = n1->in(1);
1688   } else return nullptr;
1689 
1690   // Not so profitable if compare and add are constants
1691   if( q->is_Con() && phase->type(q) != TypeInt::ZERO && y->is_Con() )
1692     return nullptr;
1693 
1694   Node *cmplt = phase->transform( new CmpLTMaskNode(p,q) );
1695   Node *j_and   = phase->transform( new AndINode(cmplt,y) );
1696   return new AddINode(j_and,x);
1697 }
1698 
1699 //------------------------------is_absolute------------------------------------
1700 // Check for absolute value.
1701 static Node* is_absolute( PhaseGVN *phase, PhiNode *phi_root, int true_path) {
1702   assert(true_path !=0, "only diamond shape graph expected");
1703 
1704   int  cmp_zero_idx = 0;        // Index of compare input where to look for zero
1705   int  phi_x_idx = 0;           // Index of phi input where to find naked x
1706 
1707   // ABS ends with the merge of 2 control flow paths.
1708   // Find the false path from the true path. With only 2 inputs, 3 - x works nicely.
1709   int false_path = 3 - true_path;
1710 
1711   // is_diamond_phi() has guaranteed the correctness of the nodes sequence:
1712   // phi->region->if_proj->ifnode->bool->cmp
1713   BoolNode *bol = phi_root->in(0)->in(1)->in(0)->in(1)->as_Bool();
1714   Node *cmp = bol->in(1);
1715 
1716   // Check bool sense
1717   if (cmp->Opcode() == Op_CmpF || cmp->Opcode() == Op_CmpD) {
1718     switch (bol->_test._test) {
1719     case BoolTest::lt: cmp_zero_idx = 1; phi_x_idx = true_path;  break;
1720     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1721     case BoolTest::gt: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1722     case BoolTest::ge: cmp_zero_idx = 1; phi_x_idx = false_path; break;
1723     default:           return nullptr;                           break;
1724     }
1725   } else if (cmp->Opcode() == Op_CmpI || cmp->Opcode() == Op_CmpL) {
1726     switch (bol->_test._test) {
1727     case BoolTest::lt:
1728     case BoolTest::le: cmp_zero_idx = 2; phi_x_idx = false_path; break;
1729     case BoolTest::gt:
1730     case BoolTest::ge: cmp_zero_idx = 2; phi_x_idx = true_path;  break;
1731     default:           return nullptr;                           break;
1732     }
1733   }
1734 
1735   // Test is next
1736   const Type *tzero = nullptr;
1737   switch (cmp->Opcode()) {
1738   case Op_CmpI:    tzero = TypeInt::ZERO; break;  // Integer ABS
1739   case Op_CmpL:    tzero = TypeLong::ZERO; break; // Long ABS
1740   case Op_CmpF:    tzero = TypeF::ZERO; break; // Float ABS
1741   case Op_CmpD:    tzero = TypeD::ZERO; break; // Double ABS
1742   default: return nullptr;
1743   }
1744 
1745   // Find zero input of compare; the other input is being abs'd
1746   Node *x = nullptr;
1747   bool flip = false;
1748   if( phase->type(cmp->in(cmp_zero_idx)) == tzero ) {
1749     x = cmp->in(3 - cmp_zero_idx);
1750   } else if( phase->type(cmp->in(3 - cmp_zero_idx)) == tzero ) {
1751     // The test is inverted, we should invert the result...
1752     x = cmp->in(cmp_zero_idx);
1753     flip = true;
1754   } else {
1755     return nullptr;
1756   }
1757 
1758   // Next get the 2 pieces being selected, one is the original value
1759   // and the other is the negated value.
1760   if( phi_root->in(phi_x_idx) != x ) return nullptr;
1761 
1762   // Check other phi input for subtract node
1763   Node *sub = phi_root->in(3 - phi_x_idx);
1764 
1765   bool is_sub = sub->Opcode() == Op_SubF || sub->Opcode() == Op_SubD ||
1766                 sub->Opcode() == Op_SubI || sub->Opcode() == Op_SubL;
1767 
1768   // Allow only Sub(0,X) and fail out for all others; Neg is not OK
1769   if (!is_sub || phase->type(sub->in(1)) != tzero || sub->in(2) != x) return nullptr;
1770 
1771   if (tzero == TypeF::ZERO) {
1772     x = new AbsFNode(x);
1773     if (flip) {
1774       x = new SubFNode(sub->in(1), phase->transform(x));
1775     }
1776   } else if (tzero == TypeD::ZERO) {
1777     x = new AbsDNode(x);
1778     if (flip) {
1779       x = new SubDNode(sub->in(1), phase->transform(x));
1780     }
1781   } else if (tzero == TypeInt::ZERO && Matcher::match_rule_supported(Op_AbsI)) {
1782     x = new AbsINode(x);
1783     if (flip) {
1784       x = new SubINode(sub->in(1), phase->transform(x));
1785     }
1786   } else if (tzero == TypeLong::ZERO && Matcher::match_rule_supported(Op_AbsL)) {
1787     x = new AbsLNode(x);
1788     if (flip) {
1789       x = new SubLNode(sub->in(1), phase->transform(x));
1790     }
1791   } else return nullptr;
1792 
1793   return x;
1794 }
1795 
1796 //------------------------------split_once-------------------------------------
1797 // Helper for split_flow_path
1798 static void split_once(PhaseIterGVN *igvn, Node *phi, Node *val, Node *n, Node *newn) {
1799   igvn->hash_delete(n);         // Remove from hash before hacking edges
1800 
1801   uint j = 1;
1802   for (uint i = phi->req()-1; i > 0; i--) {
1803     if (phi->in(i) == val) {   // Found a path with val?
1804       // Add to NEW Region/Phi, no DU info
1805       newn->set_req( j++, n->in(i) );
1806       // Remove from OLD Region/Phi
1807       n->del_req(i);
1808     }
1809   }
1810 
1811   // Register the new node but do not transform it.  Cannot transform until the
1812   // entire Region/Phi conglomerate has been hacked as a single huge transform.
1813   igvn->register_new_node_with_optimizer( newn );
1814 
1815   // Now I can point to the new node.
1816   n->add_req(newn);
1817   igvn->_worklist.push(n);
1818 }
1819 
1820 //------------------------------split_flow_path--------------------------------
1821 // Check for merging identical values and split flow paths
1822 static Node* split_flow_path(PhaseGVN *phase, PhiNode *phi) {
1823   // This optimization tries to find two or more inputs of phi with the same constant value
1824   // It then splits them into a separate Phi, and according Region. If this is a loop-entry,
1825   // and the loop entry has multiple fall-in edges, and some of those fall-in edges have that
1826   // constant, and others not, we may split the fall-in edges into separate Phi's, and create
1827   // an irreducible loop. For reducible loops, this never seems to happen, as the multiple
1828   // fall-in edges are already merged before the loop head during parsing. But with irreducible
1829   // loops present the order or merging during parsing can sometimes prevent this.
1830   if (phase->C->has_irreducible_loop()) {
1831     // Avoid this optimization if any irreducible loops are present. Else we may create
1832     // an irreducible loop that we do not detect.
1833     return nullptr;
1834   }
1835   BasicType bt = phi->type()->basic_type();
1836   if( bt == T_ILLEGAL || type2size[bt] <= 0 )
1837     return nullptr;             // Bail out on funny non-value stuff
1838   if( phi->req() <= 3 )         // Need at least 2 matched inputs and a
1839     return nullptr;             // third unequal input to be worth doing
1840 
1841   // Scan for a constant
1842   uint i;
1843   for( i = 1; i < phi->req()-1; i++ ) {
1844     Node *n = phi->in(i);
1845     if( !n ) return nullptr;
1846     if( phase->type(n) == Type::TOP ) return nullptr;
1847     if( n->Opcode() == Op_ConP || n->Opcode() == Op_ConN || n->Opcode() == Op_ConNKlass )
1848       break;
1849   }
1850   if( i >= phi->req() )         // Only split for constants
1851     return nullptr;
1852 
1853   Node *val = phi->in(i);       // Constant to split for
1854   uint hit = 0;                 // Number of times it occurs
1855   Node *r = phi->region();
1856 
1857   for( ; i < phi->req(); i++ ){ // Count occurrences of constant
1858     Node *n = phi->in(i);
1859     if( !n ) return nullptr;
1860     if( phase->type(n) == Type::TOP ) return nullptr;
1861     if( phi->in(i) == val ) {
1862       hit++;
1863       if (Node::may_be_loop_entry(r->in(i))) {
1864         return nullptr; // don't split loop entry path
1865       }
1866     }
1867   }
1868 
1869   if( hit <= 1 ||               // Make sure we find 2 or more
1870       hit == phi->req()-1 )     // and not ALL the same value
1871     return nullptr;
1872 
1873   // Now start splitting out the flow paths that merge the same value.
1874   // Split first the RegionNode.
1875   PhaseIterGVN *igvn = phase->is_IterGVN();
1876   RegionNode *newr = new RegionNode(hit+1);
1877   split_once(igvn, phi, val, r, newr);
1878 
1879   // Now split all other Phis than this one
1880   for (DUIterator_Fast kmax, k = r->fast_outs(kmax); k < kmax; k++) {
1881     Node* phi2 = r->fast_out(k);
1882     if( phi2->is_Phi() && phi2->as_Phi() != phi ) {
1883       PhiNode *newphi = PhiNode::make_blank(newr, phi2);
1884       split_once(igvn, phi, val, phi2, newphi);
1885     }
1886   }
1887 
1888   // Clean up this guy
1889   igvn->hash_delete(phi);
1890   for( i = phi->req()-1; i > 0; i-- ) {
1891     if( phi->in(i) == val ) {
1892       phi->del_req(i);
1893     }
1894   }
1895   phi->add_req(val);
1896 
1897   return phi;
1898 }
1899 
1900 // Returns the BasicType of a given convert node and a type, with special handling to ensure that conversions to
1901 // and from half float will return the SHORT basic type, as that wouldn't be returned typically from TypeInt.
1902 static BasicType get_convert_type(Node* convert, const Type* type) {
1903   int convert_op = convert->Opcode();
1904   if (type->isa_int() && (convert_op == Op_ConvHF2F || convert_op == Op_ConvF2HF)) {
1905     return T_SHORT;
1906   }
1907 
1908   return type->basic_type();
1909 }
1910 
1911 //=============================================================================
1912 //------------------------------simple_data_loop_check-------------------------
1913 //  Try to determining if the phi node in a simple safe/unsafe data loop.
1914 //  Returns:
1915 // enum LoopSafety { Safe = 0, Unsafe, UnsafeLoop };
1916 // Safe       - safe case when the phi and it's inputs reference only safe data
1917 //              nodes;
1918 // Unsafe     - the phi and it's inputs reference unsafe data nodes but there
1919 //              is no reference back to the phi - need a graph walk
1920 //              to determine if it is in a loop;
1921 // UnsafeLoop - unsafe case when the phi references itself directly or through
1922 //              unsafe data node.
1923 //  Note: a safe data node is a node which could/never reference itself during
1924 //  GVN transformations. For now it is Con, Proj, Phi, CastPP, CheckCastPP.
1925 //  I mark Phi nodes as safe node not only because they can reference itself
1926 //  but also to prevent mistaking the fallthrough case inside an outer loop
1927 //  as dead loop when the phi references itself through an other phi.
1928 PhiNode::LoopSafety PhiNode::simple_data_loop_check(Node *in) const {
1929   // It is unsafe loop if the phi node references itself directly.
1930   if (in == (Node*)this)
1931     return UnsafeLoop; // Unsafe loop
1932   // Unsafe loop if the phi node references itself through an unsafe data node.
1933   // Exclude cases with null inputs or data nodes which could reference
1934   // itself (safe for dead loops).
1935   if (in != nullptr && !in->is_dead_loop_safe()) {
1936     // Check inputs of phi's inputs also.
1937     // It is much less expensive then full graph walk.
1938     uint cnt = in->req();
1939     uint i = (in->is_Proj() && !in->is_CFG())  ? 0 : 1;
1940     for (; i < cnt; ++i) {
1941       Node* m = in->in(i);
1942       if (m == (Node*)this)
1943         return UnsafeLoop; // Unsafe loop
1944       if (m != nullptr && !m->is_dead_loop_safe()) {
1945         // Check the most common case (about 30% of all cases):
1946         // phi->Load/Store->AddP->(ConP ConP Con)/(Parm Parm Con).
1947         Node *m1 = (m->is_AddP() && m->req() > 3) ? m->in(1) : nullptr;
1948         if (m1 == (Node*)this)
1949           return UnsafeLoop; // Unsafe loop
1950         if (m1 != nullptr && m1 == m->in(2) &&
1951             m1->is_dead_loop_safe() && m->in(3)->is_Con()) {
1952           continue; // Safe case
1953         }
1954         // The phi references an unsafe node - need full analysis.
1955         return Unsafe;
1956       }
1957     }
1958   }
1959   return Safe; // Safe case - we can optimize the phi node.
1960 }
1961 
1962 //------------------------------is_unsafe_data_reference-----------------------
1963 // If phi can be reached through the data input - it is data loop.
1964 bool PhiNode::is_unsafe_data_reference(Node *in) const {
1965   assert(req() > 1, "");
1966   // First, check simple cases when phi references itself directly or
1967   // through an other node.
1968   LoopSafety safety = simple_data_loop_check(in);
1969   if (safety == UnsafeLoop)
1970     return true;  // phi references itself - unsafe loop
1971   else if (safety == Safe)
1972     return false; // Safe case - phi could be replaced with the unique input.
1973 
1974   // Unsafe case when we should go through data graph to determine
1975   // if the phi references itself.
1976 
1977   ResourceMark rm;
1978 
1979   Node_List nstack;
1980   VectorSet visited;
1981 
1982   nstack.push(in); // Start with unique input.
1983   visited.set(in->_idx);
1984   while (nstack.size() != 0) {
1985     Node* n = nstack.pop();
1986     uint cnt = n->req();
1987     uint i = (n->is_Proj() && !n->is_CFG()) ? 0 : 1;
1988     for (; i < cnt; i++) {
1989       Node* m = n->in(i);
1990       if (m == (Node*)this) {
1991         return true;    // Data loop
1992       }
1993       if (m != nullptr && !m->is_dead_loop_safe()) { // Only look for unsafe cases.
1994         if (!visited.test_set(m->_idx))
1995           nstack.push(m);
1996       }
1997     }
1998   }
1999   return false; // The phi is not reachable from its inputs
2000 }
2001 
2002 // Is this Phi's region or some inputs to the region enqueued for IGVN
2003 // and so could cause the region to be optimized out?
2004 bool PhiNode::wait_for_region_igvn(PhaseGVN* phase) {
2005   PhaseIterGVN* igvn = phase->is_IterGVN();
2006   Unique_Node_List& worklist = igvn->_worklist;
2007   bool delay = false;
2008   Node* r = in(0);
2009   for (uint j = 1; j < req(); j++) {
2010     Node* rc = r->in(j);
2011     Node* n = in(j);
2012 
2013     if (rc == nullptr || !rc->is_Proj()) { continue; }
2014     if (worklist.member(rc)) {
2015       delay = true;
2016       break;
2017     }
2018 
2019     if (rc->in(0) == nullptr || !rc->in(0)->is_If()) { continue; }
2020     if (worklist.member(rc->in(0))) {
2021       delay = true;
2022       break;
2023     }
2024 
2025     if (rc->in(0)->in(1) == nullptr || !rc->in(0)->in(1)->is_Bool()) { continue; }
2026     if (worklist.member(rc->in(0)->in(1))) {
2027       delay = true;
2028       break;
2029     }
2030 
2031     if (rc->in(0)->in(1)->in(1) == nullptr || !rc->in(0)->in(1)->in(1)->is_Cmp()) { continue; }
2032     if (worklist.member(rc->in(0)->in(1)->in(1))) {
2033       delay = true;
2034       break;
2035     }
2036   }
2037 
2038   if (delay) {
2039     worklist.push(this);
2040   }
2041   return delay;
2042 }
2043 
2044 // Push inline type input nodes (and null) down through the phi recursively (can handle data loops).
2045 InlineTypeNode* PhiNode::push_inline_types_down(PhaseGVN* phase, bool can_reshape, ciInlineKlass* inline_klass) {
2046   assert(inline_klass != nullptr, "must be");
2047   InlineTypeNode* vt = InlineTypeNode::make_null(*phase, inline_klass, /* transform = */ false)->clone_with_phis(phase, in(0), nullptr, !_type->maybe_null());
2048   if (can_reshape) {
2049     // Replace phi right away to be able to use the inline
2050     // type node when reaching the phi again through data loops.
2051     PhaseIterGVN* igvn = phase->is_IterGVN();
2052     for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2053       Node* u = fast_out(i);
2054       igvn->rehash_node_delayed(u);
2055       imax -= u->replace_edge(this, vt);
2056       --i;
2057     }
2058     igvn->rehash_node_delayed(this);
2059     assert(outcnt() == 0, "should be dead now");
2060   }
2061   ResourceMark rm;
2062   Node_List casts;
2063   for (uint i = 1; i < req(); ++i) {
2064     Node* n = in(i);
2065     while (n->is_ConstraintCast()) {
2066       casts.push(n);
2067       n = n->in(1);
2068     }
2069     if (phase->type(n)->is_zero_type()) {
2070       n = InlineTypeNode::make_null(*phase, inline_klass);
2071     } else if (n->is_Phi()) {
2072       assert(can_reshape, "can only handle phis during IGVN");
2073       n = phase->transform(n->as_Phi()->push_inline_types_down(phase, can_reshape, inline_klass));
2074     }
2075     while (casts.size() != 0) {
2076       // Push the cast(s) through the InlineTypeNode
2077       // TODO 8302217 Can we avoid cloning? See InlineTypeNode::clone_if_required
2078       Node* cast = casts.pop()->clone();
2079       cast->set_req_X(1, n->as_InlineType()->get_oop(), phase);
2080       n = n->clone();
2081       n->as_InlineType()->set_oop(*phase, phase->transform(cast));
2082       n = phase->transform(n);
2083     }
2084     bool transform = !can_reshape && (i == (req()-1)); // Transform phis on last merge
2085     vt->merge_with(phase, n->as_InlineType(), i, transform);
2086   }
2087   return vt;
2088 }
2089 
2090 // If the Phi's Region is in an irreducible loop, and the Region
2091 // has had an input removed, but not yet transformed, it could be
2092 // that the Region (and this Phi) are not reachable from Root.
2093 // If we allow the Phi to collapse before the Region, this may lead
2094 // to dead-loop data. Wait for the Region to check for reachability,
2095 // and potentially remove the dead code.
2096 bool PhiNode::must_wait_for_region_in_irreducible_loop(PhaseGVN* phase) const {
2097   RegionNode* region = in(0)->as_Region();
2098   if (region->loop_status() == RegionNode::LoopStatus::MaybeIrreducibleEntry) {
2099     Node* top = phase->C->top();
2100     for (uint j = 1; j < req(); j++) {
2101       Node* rc = region->in(j); // for each control input
2102       if (rc == nullptr || phase->type(rc) == Type::TOP) {
2103         // Region is missing a control input
2104         Node* n = in(j);
2105         if (n != nullptr && n != top) {
2106           // Phi still has its input, so region just lost its input
2107           return true;
2108         }
2109       }
2110     }
2111   }
2112   return false;
2113 }
2114 
2115 //------------------------------Ideal------------------------------------------
2116 // Return a node which is more "ideal" than the current node.  Must preserve
2117 // the CFG, but we can still strip out dead paths.
2118 Node *PhiNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2119   Node *r = in(0);              // RegionNode
2120   assert(r != nullptr && r->is_Region(), "this phi must have a region");
2121   assert(r->in(0) == nullptr || !r->in(0)->is_Root(), "not a specially hidden merge");
2122 
2123   // Note: During parsing, phis are often transformed before their regions.
2124   // This means we have to use type_or_null to defend against untyped regions.
2125   if( phase->type_or_null(r) == Type::TOP ) // Dead code?
2126     return nullptr;                // No change
2127 
2128   Node *top = phase->C->top();
2129   bool new_phi = (outcnt() == 0); // transforming new Phi
2130   // No change for igvn if new phi is not hooked
2131   if (new_phi && can_reshape)
2132     return nullptr;
2133 
2134   if (must_wait_for_region_in_irreducible_loop(phase)) {
2135     return nullptr;
2136   }
2137 
2138   // The are 2 situations when only one valid phi's input is left
2139   // (in addition to Region input).
2140   // One: region is not loop - replace phi with this input.
2141   // Two: region is loop - replace phi with top since this data path is dead
2142   //                       and we need to break the dead data loop.
2143   Node* progress = nullptr;        // Record if any progress made
2144   for( uint j = 1; j < req(); ++j ){ // For all paths in
2145     // Check unreachable control paths
2146     Node* rc = r->in(j);
2147     Node* n = in(j);            // Get the input
2148     if (rc == nullptr || phase->type(rc) == Type::TOP) {
2149       if (n != top) {           // Not already top?
2150         PhaseIterGVN *igvn = phase->is_IterGVN();
2151         if (can_reshape && igvn != nullptr) {
2152           igvn->_worklist.push(r);
2153         }
2154         // Nuke it down
2155         set_req_X(j, top, phase);
2156         progress = this;        // Record progress
2157       }
2158     }
2159   }
2160 
2161   if (can_reshape && outcnt() == 0) {
2162     // set_req() above may kill outputs if Phi is referenced
2163     // only by itself on the dead (top) control path.
2164     return top;
2165   }
2166 
2167   bool uncasted = false;
2168   Node* uin = unique_input(phase, false);
2169   if (uin == nullptr && can_reshape &&
2170       // If there is a chance that the region can be optimized out do
2171       // not add a cast node that we can't remove yet.
2172       !wait_for_region_igvn(phase)) {
2173     uncasted = true;
2174     uin = unique_input(phase, true);
2175   }
2176   if (uin == top) {             // Simplest case: no alive inputs.
2177     if (can_reshape)            // IGVN transformation
2178       return top;
2179     else
2180       return nullptr;              // Identity will return TOP
2181   } else if (uin != nullptr) {
2182     // Only one not-null unique input path is left.
2183     // Determine if this input is backedge of a loop.
2184     // (Skip new phis which have no uses and dead regions).
2185     if (outcnt() > 0 && r->in(0) != nullptr) {
2186       if (is_data_loop(r->as_Region(), uin, phase)) {
2187         // Break this data loop to avoid creation of a dead loop.
2188         if (can_reshape) {
2189           return top;
2190         } else {
2191           // We can't return top if we are in Parse phase - cut inputs only
2192           // let Identity to handle the case.
2193           replace_edge(uin, top, phase);
2194           return nullptr;
2195         }
2196       }
2197     }
2198 
2199     if (uncasted) {
2200       // Add cast nodes between the phi to be removed and its unique input.
2201       // Wait until after parsing for the type information to propagate from the casts.
2202       assert(can_reshape, "Invalid during parsing");
2203       const Type* phi_type = bottom_type();
2204       // Add casts to carry the control dependency of the Phi that is
2205       // going away
2206       Node* cast = nullptr;
2207       const TypeTuple* extra_types = collect_types(phase);
2208       if (phi_type->isa_ptr()) {
2209         const Type* uin_type = phase->type(uin);
2210         if (!phi_type->isa_oopptr() && !uin_type->isa_oopptr()) {
2211           cast = new CastPPNode(r, uin, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2212         } else {
2213           // Use a CastPP for a cast to not null and a CheckCastPP for
2214           // a cast to a new klass (and both if both null-ness and
2215           // klass change).
2216 
2217           // If the type of phi is not null but the type of uin may be
2218           // null, uin's type must be casted to not null
2219           if (phi_type->join(TypePtr::NOTNULL) == phi_type->remove_speculative() &&
2220               uin_type->join(TypePtr::NOTNULL) != uin_type->remove_speculative()) {
2221             cast = new CastPPNode(r, uin, TypePtr::NOTNULL, ConstraintCastNode::StrongDependency, extra_types);
2222           }
2223 
2224           // If the type of phi and uin, both casted to not null,
2225           // differ the klass of uin must be (check)cast'ed to match
2226           // that of phi
2227           if (phi_type->join_speculative(TypePtr::NOTNULL) != uin_type->join_speculative(TypePtr::NOTNULL)) {
2228             Node* n = uin;
2229             if (cast != nullptr) {
2230               cast = phase->transform(cast);
2231               n = cast;
2232             }
2233             cast = new CheckCastPPNode(r, n, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2234           }
2235           if (cast == nullptr) {
2236             cast = new CastPPNode(r, uin, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2237           }
2238         }
2239       } else {
2240         cast = ConstraintCastNode::make_cast_for_type(r, uin, phi_type, ConstraintCastNode::StrongDependency, extra_types);
2241       }
2242       assert(cast != nullptr, "cast should be set");
2243       cast = phase->transform(cast);
2244       // set all inputs to the new cast(s) so the Phi is removed by Identity
2245       PhaseIterGVN* igvn = phase->is_IterGVN();
2246       for (uint i = 1; i < req(); i++) {
2247         set_req_X(i, cast, igvn);
2248       }
2249       uin = cast;
2250     }
2251 
2252     // One unique input.
2253     debug_only(Node* ident = Identity(phase));
2254     // The unique input must eventually be detected by the Identity call.
2255 #ifdef ASSERT
2256     if (ident != uin && !ident->is_top() && !must_wait_for_region_in_irreducible_loop(phase)) {
2257       // print this output before failing assert
2258       r->dump(3);
2259       this->dump(3);
2260       ident->dump();
2261       uin->dump();
2262     }
2263 #endif
2264     // Identity may not return the expected uin, if it has to wait for the region, in irreducible case
2265     assert(ident == uin || ident->is_top() || must_wait_for_region_in_irreducible_loop(phase), "Identity must clean this up");
2266     return nullptr;
2267   }
2268 
2269   Node* opt = nullptr;
2270   int true_path = is_diamond_phi();
2271   if (true_path != 0 &&
2272       // If one of the diamond's branch is in the process of dying then, the Phi's input for that branch might transform
2273       // to top. If that happens replacing the Phi with an operation that consumes the Phi's inputs will cause the Phi
2274       // to be replaced by top. To prevent that, delay the transformation until the branch has a chance to be removed.
2275       !(can_reshape && wait_for_region_igvn(phase))) {
2276     // Check for CMove'ing identity. If it would be unsafe,
2277     // handle it here. In the safe case, let Identity handle it.
2278     Node* unsafe_id = is_cmove_id(phase, true_path);
2279     if( unsafe_id != nullptr && is_unsafe_data_reference(unsafe_id) )
2280       opt = unsafe_id;
2281 
2282     // Check for simple convert-to-boolean pattern
2283     if( opt == nullptr )
2284       opt = is_x2logic(phase, this, true_path);
2285 
2286     // Check for absolute value
2287     if( opt == nullptr )
2288       opt = is_absolute(phase, this, true_path);
2289 
2290     // Check for conditional add
2291     if( opt == nullptr && can_reshape )
2292       opt = is_cond_add(phase, this, true_path);
2293 
2294     // These 4 optimizations could subsume the phi:
2295     // have to check for a dead data loop creation.
2296     if( opt != nullptr ) {
2297       if( opt == unsafe_id || is_unsafe_data_reference(opt) ) {
2298         // Found dead loop.
2299         if( can_reshape )
2300           return top;
2301         // We can't return top if we are in Parse phase - cut inputs only
2302         // to stop further optimizations for this phi. Identity will return TOP.
2303         assert(req() == 3, "only diamond merge phi here");
2304         set_req(1, top);
2305         set_req(2, top);
2306         return nullptr;
2307       } else {
2308         return opt;
2309       }
2310     }
2311   }
2312 
2313   // Check for merging identical values and split flow paths
2314   if (can_reshape) {
2315     opt = split_flow_path(phase, this);
2316     // This optimization only modifies phi - don't need to check for dead loop.
2317     assert(opt == nullptr || opt == this, "do not elide phi");
2318     if (opt != nullptr)  return opt;
2319   }
2320 
2321   if (in(1) != nullptr && in(1)->Opcode() == Op_AddP && can_reshape) {
2322     // Try to undo Phi of AddP:
2323     // (Phi (AddP base address offset) (AddP base2 address2 offset2))
2324     // becomes:
2325     // newbase := (Phi base base2)
2326     // newaddress := (Phi address address2)
2327     // newoffset := (Phi offset offset2)
2328     // (AddP newbase newaddress newoffset)
2329     //
2330     // This occurs as a result of unsuccessful split_thru_phi and
2331     // interferes with taking advantage of addressing modes. See the
2332     // clone_shift_expressions code in matcher.cpp
2333     Node* addp = in(1);
2334     Node* base = addp->in(AddPNode::Base);
2335     Node* address = addp->in(AddPNode::Address);
2336     Node* offset = addp->in(AddPNode::Offset);
2337     if (base != nullptr && address != nullptr && offset != nullptr &&
2338         !base->is_top() && !address->is_top() && !offset->is_top()) {
2339       const Type* base_type = base->bottom_type();
2340       const Type* address_type = address->bottom_type();
2341       // make sure that all the inputs are similar to the first one,
2342       // i.e. AddP with base == address and same offset as first AddP
2343       bool doit = true;
2344       for (uint i = 2; i < req(); i++) {
2345         if (in(i) == nullptr ||
2346             in(i)->Opcode() != Op_AddP ||
2347             in(i)->in(AddPNode::Base) == nullptr ||
2348             in(i)->in(AddPNode::Address) == nullptr ||
2349             in(i)->in(AddPNode::Offset) == nullptr ||
2350             in(i)->in(AddPNode::Base)->is_top() ||
2351             in(i)->in(AddPNode::Address)->is_top() ||
2352             in(i)->in(AddPNode::Offset)->is_top()) {
2353           doit = false;
2354           break;
2355         }
2356         if (in(i)->in(AddPNode::Base) != base) {
2357           base = nullptr;
2358         }
2359         if (in(i)->in(AddPNode::Offset) != offset) {
2360           offset = nullptr;
2361         }
2362         if (in(i)->in(AddPNode::Address) != address) {
2363           address = nullptr;
2364         }
2365         // Accumulate type for resulting Phi
2366         base_type = base_type->meet_speculative(in(i)->in(AddPNode::Base)->bottom_type());
2367         address_type = address_type->meet_speculative(in(i)->in(AddPNode::Address)->bottom_type());
2368       }
2369       if (doit && base == nullptr) {
2370         // Check for neighboring AddP nodes in a tree.
2371         // If they have a base, use that it.
2372         for (DUIterator_Fast kmax, k = this->fast_outs(kmax); k < kmax; k++) {
2373           Node* u = this->fast_out(k);
2374           if (u->is_AddP()) {
2375             Node* base2 = u->in(AddPNode::Base);
2376             if (base2 != nullptr && !base2->is_top()) {
2377               if (base == nullptr)
2378                 base = base2;
2379               else if (base != base2)
2380                 { doit = false; break; }
2381             }
2382           }
2383         }
2384       }
2385       if (doit) {
2386         if (base == nullptr) {
2387           base = new PhiNode(in(0), base_type, nullptr);
2388           for (uint i = 1; i < req(); i++) {
2389             base->init_req(i, in(i)->in(AddPNode::Base));
2390           }
2391           phase->is_IterGVN()->register_new_node_with_optimizer(base);
2392         }
2393         if (address == nullptr) {
2394           address = new PhiNode(in(0), address_type, nullptr);
2395           for (uint i = 1; i < req(); i++) {
2396             address->init_req(i, in(i)->in(AddPNode::Address));
2397           }
2398           phase->is_IterGVN()->register_new_node_with_optimizer(address);
2399         }
2400         if (offset == nullptr) {
2401           offset = new PhiNode(in(0), TypeX_X, nullptr);
2402           for (uint i = 1; i < req(); i++) {
2403             offset->init_req(i, in(i)->in(AddPNode::Offset));
2404           }
2405           phase->is_IterGVN()->register_new_node_with_optimizer(offset);
2406         }
2407         return new AddPNode(base, address, offset);
2408       }
2409     }
2410   }
2411 
2412   // Split phis through memory merges, so that the memory merges will go away.
2413   // Piggy-back this transformation on the search for a unique input....
2414   // It will be as if the merged memory is the unique value of the phi.
2415   // (Do not attempt this optimization unless parsing is complete.
2416   // It would make the parser's memory-merge logic sick.)
2417   // (MergeMemNode is not dead_loop_safe - need to check for dead loop.)
2418   if (progress == nullptr && can_reshape && type() == Type::MEMORY) {
2419     // see if this phi should be sliced
2420     uint merge_width = 0;
2421     bool saw_self = false;
2422     // TODO revisit this with JDK-8247216
2423     bool mergemem_only = true;
2424     for( uint i=1; i<req(); ++i ) {// For all paths in
2425       Node *ii = in(i);
2426       // TOP inputs should not be counted as safe inputs because if the
2427       // Phi references itself through all other inputs then splitting the
2428       // Phi through memory merges would create dead loop at later stage.
2429       if (ii == top) {
2430         return nullptr; // Delay optimization until graph is cleaned.
2431       }
2432       if (ii->is_MergeMem()) {
2433         MergeMemNode* n = ii->as_MergeMem();
2434         merge_width = MAX2(merge_width, n->req());
2435         saw_self = saw_self || (n->base_memory() == this);
2436       } else {
2437         mergemem_only = false;
2438       }
2439     }
2440 
2441     // This restriction is temporarily necessary to ensure termination:
2442     if (!mergemem_only && !saw_self && adr_type() == TypePtr::BOTTOM)  merge_width = 0;
2443 
2444     if (merge_width > Compile::AliasIdxRaw) {
2445       // found at least one non-empty MergeMem
2446       const TypePtr* at = adr_type();
2447       if (at != TypePtr::BOTTOM) {
2448         // Patch the existing phi to select an input from the merge:
2449         // Phi:AT1(...MergeMem(m0, m1, m2)...) into
2450         //     Phi:AT1(...m1...)
2451         int alias_idx = phase->C->get_alias_index(at);
2452         for (uint i=1; i<req(); ++i) {
2453           Node *ii = in(i);
2454           if (ii->is_MergeMem()) {
2455             MergeMemNode* n = ii->as_MergeMem();
2456             // compress paths and change unreachable cycles to TOP
2457             // If not, we can update the input infinitely along a MergeMem cycle
2458             // Equivalent code is in MemNode::Ideal_common
2459             Node *m  = phase->transform(n);
2460             if (outcnt() == 0) {  // Above transform() may kill us!
2461               return top;
2462             }
2463             // If transformed to a MergeMem, get the desired slice
2464             // Otherwise the returned node represents memory for every slice
2465             Node *new_mem = (m->is_MergeMem()) ?
2466                              m->as_MergeMem()->memory_at(alias_idx) : m;
2467             // Update input if it is progress over what we have now
2468             if (new_mem != ii) {
2469               set_req_X(i, new_mem, phase->is_IterGVN());
2470               progress = this;
2471             }
2472           }
2473         }
2474       } else {
2475         // We know that at least one MergeMem->base_memory() == this
2476         // (saw_self == true). If all other inputs also references this phi
2477         // (directly or through data nodes) - it is a dead loop.
2478         bool saw_safe_input = false;
2479         for (uint j = 1; j < req(); ++j) {
2480           Node* n = in(j);
2481           if (n->is_MergeMem()) {
2482             MergeMemNode* mm = n->as_MergeMem();
2483             if (mm->base_memory() == this || mm->base_memory() == mm->empty_memory()) {
2484               // Skip this input if it references back to this phi or if the memory path is dead
2485               continue;
2486             }
2487           }
2488           if (!is_unsafe_data_reference(n)) {
2489             saw_safe_input = true; // found safe input
2490             break;
2491           }
2492         }
2493         if (!saw_safe_input) {
2494           // There is a dead loop: All inputs are either dead or reference back to this phi
2495           return top;
2496         }
2497 
2498         // Phi(...MergeMem(m0, m1:AT1, m2:AT2)...) into
2499         //     MergeMem(Phi(...m0...), Phi:AT1(...m1...), Phi:AT2(...m2...))
2500         PhaseIterGVN* igvn = phase->is_IterGVN();
2501         assert(igvn != nullptr, "sanity check");
2502         Node* hook = new Node(1);
2503         PhiNode* new_base = (PhiNode*) clone();
2504         // Must eagerly register phis, since they participate in loops.
2505         igvn->register_new_node_with_optimizer(new_base);
2506         hook->add_req(new_base);
2507 
2508         MergeMemNode* result = MergeMemNode::make(new_base);
2509         for (uint i = 1; i < req(); ++i) {
2510           Node *ii = in(i);
2511           if (ii->is_MergeMem()) {
2512             MergeMemNode* n = ii->as_MergeMem();
2513             if (igvn) {
2514               // TODO revisit this with JDK-8247216
2515               // Put 'n' on the worklist because it might be modified by MergeMemStream::iteration_setup
2516               igvn->_worklist.push(n);
2517             }
2518             for (MergeMemStream mms(result, n); mms.next_non_empty2(); ) {
2519               // If we have not seen this slice yet, make a phi for it.
2520               bool made_new_phi = false;
2521               if (mms.is_empty()) {
2522                 Node* new_phi = new_base->slice_memory(mms.adr_type(phase->C));
2523                 made_new_phi = true;
2524                 igvn->register_new_node_with_optimizer(new_phi);
2525                 hook->add_req(new_phi);
2526                 mms.set_memory(new_phi);
2527               }
2528               Node* phi = mms.memory();
2529               assert(made_new_phi || phi->in(i) == n, "replace the i-th merge by a slice");
2530               phi->set_req(i, mms.memory2());
2531             }
2532           }
2533         }
2534         // Distribute all self-loops.
2535         { // (Extra braces to hide mms.)
2536           for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2537             Node* phi = mms.memory();
2538             for (uint i = 1; i < req(); ++i) {
2539               if (phi->in(i) == this)  phi->set_req(i, phi);
2540             }
2541           }
2542         }
2543         // Already replace this phi node to cut it off from the graph to not interfere in dead loop checks during the
2544         // transformations of the new phi nodes below. Otherwise, we could wrongly conclude that there is no dead loop
2545         // because we are finding this phi node again. Also set the type of the new MergeMem node in case we are also
2546         // visiting it in the transformations below.
2547         igvn->replace_node(this, result);
2548         igvn->set_type(result, result->bottom_type());
2549 
2550         // now transform the new nodes, and return the mergemem
2551         for (MergeMemStream mms(result); mms.next_non_empty(); ) {
2552           Node* phi = mms.memory();
2553           mms.set_memory(phase->transform(phi));
2554         }
2555         hook->destruct(igvn);
2556         // Replace self with the result.
2557         return result;
2558       }
2559     }
2560     //
2561     // Other optimizations on the memory chain
2562     //
2563     const TypePtr* at = adr_type();
2564     for( uint i=1; i<req(); ++i ) {// For all paths in
2565       Node *ii = in(i);
2566       Node *new_in = MemNode::optimize_memory_chain(ii, at, nullptr, phase);
2567       if (ii != new_in ) {
2568         set_req(i, new_in);
2569         progress = this;
2570       }
2571     }
2572   }
2573 
2574 #ifdef _LP64
2575   // Push DecodeN/DecodeNKlass down through phi.
2576   // The rest of phi graph will transform by split EncodeP node though phis up.
2577   if ((UseCompressedOops || UseCompressedClassPointers) && can_reshape && progress == nullptr) {
2578     bool may_push = true;
2579     bool has_decodeN = false;
2580     bool is_decodeN = false;
2581     for (uint i=1; i<req(); ++i) {// For all paths in
2582       Node *ii = in(i);
2583       if (ii->is_DecodeNarrowPtr() && ii->bottom_type() == bottom_type()) {
2584         // Do optimization if a non dead path exist.
2585         if (ii->in(1)->bottom_type() != Type::TOP) {
2586           has_decodeN = true;
2587           is_decodeN = ii->is_DecodeN();
2588         }
2589       } else if (!ii->is_Phi()) {
2590         may_push = false;
2591       }
2592     }
2593 
2594     if (has_decodeN && may_push) {
2595       PhaseIterGVN *igvn = phase->is_IterGVN();
2596       // Make narrow type for new phi.
2597       const Type* narrow_t;
2598       if (is_decodeN) {
2599         narrow_t = TypeNarrowOop::make(this->bottom_type()->is_ptr());
2600       } else {
2601         narrow_t = TypeNarrowKlass::make(this->bottom_type()->is_ptr());
2602       }
2603       PhiNode* new_phi = new PhiNode(r, narrow_t);
2604       uint orig_cnt = req();
2605       for (uint i=1; i<req(); ++i) {// For all paths in
2606         Node *ii = in(i);
2607         Node* new_ii = nullptr;
2608         if (ii->is_DecodeNarrowPtr()) {
2609           assert(ii->bottom_type() == bottom_type(), "sanity");
2610           new_ii = ii->in(1);
2611         } else {
2612           assert(ii->is_Phi(), "sanity");
2613           if (ii->as_Phi() == this) {
2614             new_ii = new_phi;
2615           } else {
2616             if (is_decodeN) {
2617               new_ii = new EncodePNode(ii, narrow_t);
2618             } else {
2619               new_ii = new EncodePKlassNode(ii, narrow_t);
2620             }
2621             igvn->register_new_node_with_optimizer(new_ii);
2622           }
2623         }
2624         new_phi->set_req(i, new_ii);
2625       }
2626       igvn->register_new_node_with_optimizer(new_phi, this);
2627       if (is_decodeN) {
2628         progress = new DecodeNNode(new_phi, bottom_type());
2629       } else {
2630         progress = new DecodeNKlassNode(new_phi, bottom_type());
2631       }
2632     }
2633   }
2634 #endif
2635 
2636   Node* inline_type = try_push_inline_types_down(phase, can_reshape);
2637   if (inline_type != this) {
2638     return inline_type;
2639   }
2640 
2641   // Try to convert a Phi with two duplicated convert nodes into a phi of the pre-conversion type and the convert node
2642   // proceeding the phi, to de-duplicate the convert node and compact the IR.
2643   if (can_reshape && progress == nullptr) {
2644     ConvertNode* convert = in(1)->isa_Convert();
2645     if (convert != nullptr) {
2646       int conv_op = convert->Opcode();
2647       bool ok = true;
2648 
2649       // Check the rest of the inputs
2650       for (uint i = 2; i < req(); i++) {
2651         // Make sure that all inputs are of the same type of convert node
2652         if (in(i)->Opcode() != conv_op) {
2653           ok = false;
2654           break;
2655         }
2656       }
2657 
2658       if (ok) {
2659         // Find the local bottom type to set as the type of the phi
2660         const Type* source_type = Type::get_const_basic_type(convert->in_type()->basic_type());
2661         const Type* dest_type = convert->bottom_type();
2662 
2663         PhiNode* newphi = new PhiNode(in(0), source_type, nullptr);
2664         // Set inputs to the new phi be the inputs of the convert
2665         for (uint i = 1; i < req(); i++) {
2666           newphi->init_req(i, in(i)->in(1));
2667         }
2668 
2669         phase->is_IterGVN()->register_new_node_with_optimizer(newphi, this);
2670 
2671         return ConvertNode::create_convert(get_convert_type(convert, source_type), get_convert_type(convert, dest_type), newphi);
2672       }
2673     }
2674   }
2675 
2676   // Phi (VB ... VB) => VB (Phi ...) (Phi ...)
2677   if (EnableVectorReboxing && can_reshape && progress == nullptr && type()->isa_oopptr()) {
2678     progress = merge_through_phi(this, phase->is_IterGVN());
2679   }
2680 
2681   return progress;              // Return any progress
2682 }
2683 
2684 // Check recursively if inputs are either an inline type, constant null
2685 // or another Phi (including self references through data loops). If so,
2686 // push the inline types down through the phis to enable folding of loads.
2687 Node* PhiNode::try_push_inline_types_down(PhaseGVN* phase, const bool can_reshape) {
2688   if (!can_be_inline_type()) {
2689     return this;
2690   }
2691 
2692   ciInlineKlass* inline_klass;
2693   if (can_push_inline_types_down(phase, can_reshape, inline_klass)) {
2694     assert(inline_klass != nullptr, "must be");
2695     return push_inline_types_down(phase, can_reshape, inline_klass);
2696   }
2697   return this;
2698 }
2699 
2700 bool PhiNode::can_push_inline_types_down(PhaseGVN* phase, const bool can_reshape, ciInlineKlass*& inline_klass) {
2701   if (req() <= 2) {
2702     // Dead phi.
2703     return false;
2704   }
2705   inline_klass = nullptr;
2706 
2707   // TODO 8302217 We need to prevent endless pushing through
2708   bool only_phi = (outcnt() != 0);
2709   for (DUIterator_Fast imax, i = fast_outs(imax); i < imax; i++) {
2710     Node* n = fast_out(i);
2711     if (n->is_InlineType() && n->in(1) == this) {
2712       return false;
2713     }
2714     if (!n->is_Phi()) {
2715       only_phi = false;
2716     }
2717   }
2718   if (only_phi) {
2719     return false;
2720   }
2721 
2722   ResourceMark rm;
2723   Unique_Node_List worklist;
2724   worklist.push(this);
2725   Node_List casts;
2726 
2727   for (uint next = 0; next < worklist.size(); next++) {
2728     Node* phi = worklist.at(next);
2729     for (uint i = 1; i < phi->req(); i++) {
2730       Node* n = phi->in(i);
2731       if (n == nullptr) {
2732         return false;
2733       }
2734       while (n->is_ConstraintCast()) {
2735         if (n->in(0) != nullptr && n->in(0)->is_top()) {
2736           // Will die, don't optimize
2737           return false;
2738         }
2739         casts.push(n);
2740         n = n->in(1);
2741       }
2742       const Type* type = phase->type(n);
2743       if (n->is_InlineType() && (inline_klass == nullptr || inline_klass == type->inline_klass())) {
2744         inline_klass = type->inline_klass();
2745       } else if (n->is_Phi() && can_reshape && n->bottom_type()->isa_ptr()) {
2746         worklist.push(n);
2747       } else if (!type->is_zero_type()) {
2748         return false;
2749       }
2750     }
2751   }
2752   if (inline_klass == nullptr) {
2753     return false;
2754   }
2755 
2756   // Check if cast nodes can be pushed through
2757   const Type* t = Type::get_const_type(inline_klass);
2758   while (casts.size() != 0 && t != nullptr) {
2759     Node* cast = casts.pop();
2760     if (t->filter(cast->bottom_type()) == Type::TOP) {
2761       return false;
2762     }
2763   }
2764 
2765   return true;
2766 }
2767 
2768 #ifdef ASSERT
2769 bool PhiNode::can_push_inline_types_down(PhaseGVN* phase) {
2770   if (!can_be_inline_type()) {
2771     return false;
2772   }
2773 
2774   ciInlineKlass* inline_klass;
2775   return can_push_inline_types_down(phase, true, inline_klass);
2776 }
2777 #endif // ASSERT
2778 
2779 static int compare_types(const Type* const& e1, const Type* const& e2) {
2780   return (intptr_t)e1 - (intptr_t)e2;
2781 }
2782 
2783 // Collect types at casts that are going to be eliminated at that Phi and store them in a TypeTuple.
2784 // Sort the types using an arbitrary order so a list of some types always hashes to the same TypeTuple (and TypeTuple
2785 // pointer comparison is enough to tell if 2 list of types are the same or not)
2786 const TypeTuple* PhiNode::collect_types(PhaseGVN* phase) const {
2787   const Node* region = in(0);
2788   const Type* phi_type = bottom_type();
2789   ResourceMark rm;
2790   GrowableArray<const Type*> types;
2791   for (uint i = 1; i < req(); i++) {
2792     if (region->in(i) == nullptr || phase->type(region->in(i)) == Type::TOP) {
2793       continue;
2794     }
2795     Node* in = Node::in(i);
2796     const Type* t = phase->type(in);
2797     if (in == nullptr || in == this || t == Type::TOP) {
2798       continue;
2799     }
2800     if (t != phi_type && t->higher_equal_speculative(phi_type)) {
2801       types.insert_sorted<compare_types>(t);
2802     }
2803     while (in != nullptr && in->is_ConstraintCast()) {
2804       Node* next = in->in(1);
2805       if (phase->type(next)->isa_rawptr() && phase->type(in)->isa_oopptr()) {
2806         break;
2807       }
2808       ConstraintCastNode* cast = in->as_ConstraintCast();
2809       for (int j = 0; j < cast->extra_types_count(); ++j) {
2810         const Type* extra_t = cast->extra_type_at(j);
2811         if (extra_t != phi_type && extra_t->higher_equal_speculative(phi_type)) {
2812           types.insert_sorted<compare_types>(extra_t);
2813         }
2814       }
2815       in = next;
2816     }
2817   }
2818   const Type **flds = (const Type **)(phase->C->type_arena()->AmallocWords(types.length()*sizeof(Type*)));
2819   for (int i = 0; i < types.length(); ++i) {
2820     flds[i] = types.at(i);
2821   }
2822   return TypeTuple::make(types.length(), flds);
2823 }
2824 
2825 Node* PhiNode::clone_through_phi(Node* root_phi, const Type* t, uint c, PhaseIterGVN* igvn) {
2826   Node_Stack stack(1);
2827   VectorSet  visited;
2828   Node_List  node_map;
2829 
2830   stack.push(root_phi, 1); // ignore control
2831   visited.set(root_phi->_idx);
2832 
2833   Node* new_phi = new PhiNode(root_phi->in(0), t);
2834   node_map.map(root_phi->_idx, new_phi);
2835 
2836   while (stack.is_nonempty()) {
2837     Node* n   = stack.node();
2838     uint  idx = stack.index();
2839     assert(n->is_Phi(), "not a phi");
2840     if (idx < n->req()) {
2841       stack.set_index(idx + 1);
2842       Node* def = n->in(idx);
2843       if (def == nullptr) {
2844         continue; // ignore dead path
2845       } else if (def->is_Phi()) { // inner node
2846         Node* new_phi = node_map[n->_idx];
2847         if (!visited.test_set(def->_idx)) { // not visited yet
2848           node_map.map(def->_idx, new PhiNode(def->in(0), t));
2849           stack.push(def, 1); // ignore control
2850         }
2851         Node* new_in = node_map[def->_idx];
2852         new_phi->set_req(idx, new_in);
2853       } else if (def->Opcode() == Op_VectorBox) { // leaf
2854         assert(n->is_Phi(), "not a phi");
2855         Node* new_phi = node_map[n->_idx];
2856         new_phi->set_req(idx, def->in(c));
2857       } else {
2858         assert(false, "not optimizeable");
2859         return nullptr;
2860       }
2861     } else {
2862       Node* new_phi = node_map[n->_idx];
2863       igvn->register_new_node_with_optimizer(new_phi, n);
2864       stack.pop();
2865     }
2866   }
2867   return new_phi;
2868 }
2869 
2870 Node* PhiNode::merge_through_phi(Node* root_phi, PhaseIterGVN* igvn) {
2871   Node_Stack stack(1);
2872   VectorSet  visited;
2873 
2874   stack.push(root_phi, 1); // ignore control
2875   visited.set(root_phi->_idx);
2876 
2877   VectorBoxNode* cached_vbox = nullptr;
2878   while (stack.is_nonempty()) {
2879     Node* n   = stack.node();
2880     uint  idx = stack.index();
2881     if (idx < n->req()) {
2882       stack.set_index(idx + 1);
2883       Node* in = n->in(idx);
2884       if (in == nullptr) {
2885         continue; // ignore dead path
2886       } else if (in->isa_Phi()) {
2887         if (!visited.test_set(in->_idx)) {
2888           stack.push(in, 1); // ignore control
2889         }
2890       } else if (in->Opcode() == Op_VectorBox) {
2891         VectorBoxNode* vbox = static_cast<VectorBoxNode*>(in);
2892         if (cached_vbox == nullptr) {
2893           cached_vbox = vbox;
2894         } else if (vbox->vec_type() != cached_vbox->vec_type()) {
2895           // TODO: vector type mismatch can be handled with additional reinterpret casts
2896           assert(!Type::equals(vbox->vec_type(), cached_vbox->vec_type()), "inconsistent");
2897           return nullptr; // not optimizable: vector type mismatch
2898         } else if (vbox->box_type() != cached_vbox->box_type()) {
2899           assert(!Type::equals(vbox->box_type(), cached_vbox->box_type()), "inconsistent");
2900           return nullptr; // not optimizable: box type mismatch
2901         }
2902       } else {
2903         return nullptr; // not optimizable: neither Phi nor VectorBox
2904       }
2905     } else {
2906       stack.pop();
2907     }
2908   }
2909   if (cached_vbox == nullptr) {
2910     // We have a Phi dead-loop (no data-input). Phi nodes are considered safe,
2911     // so just avoid this optimization.
2912     return nullptr;
2913   }
2914   const TypeInstPtr* btype = cached_vbox->box_type();
2915   const TypeVect*    vtype = cached_vbox->vec_type();
2916   Node* new_vbox_phi = clone_through_phi(root_phi, btype, VectorBoxNode::Box,   igvn);
2917   Node* new_vect_phi = clone_through_phi(root_phi, vtype, VectorBoxNode::Value, igvn);
2918   return new VectorBoxNode(igvn->C, new_vbox_phi, new_vect_phi, btype, vtype);
2919 }
2920 
2921 bool PhiNode::is_data_loop(RegionNode* r, Node* uin, const PhaseGVN* phase) {
2922   // First, take the short cut when we know it is a loop and the EntryControl data path is dead.
2923   // The loop node may only have one input because the entry path was removed in PhaseIdealLoop::Dominators().
2924   // Then, check if there is a data loop when the phi references itself directly or through other data nodes.
2925   assert(!r->is_Loop() || r->req() <= 3, "Loop node should have 3 or less inputs");
2926   const bool is_loop = (r->is_Loop() && r->req() == 3);
2927   const Node* top = phase->C->top();
2928   if (is_loop) {
2929     return !uin->eqv_uncast(in(LoopNode::EntryControl));
2930   } else {
2931     // We have a data loop either with an unsafe data reference or if a region is unreachable.
2932     return is_unsafe_data_reference(uin)
2933            || (r->req() == 3 && (r->in(1) != top && r->in(2) == top && r->is_unreachable_region(phase)));
2934   }
2935 }
2936 
2937 //------------------------------is_tripcount-----------------------------------
2938 bool PhiNode::is_tripcount(BasicType bt) const {
2939   return (in(0) != nullptr && in(0)->is_BaseCountedLoop() &&
2940           in(0)->as_BaseCountedLoop()->bt() == bt &&
2941           in(0)->as_BaseCountedLoop()->phi() == this);
2942 }
2943 
2944 //------------------------------out_RegMask------------------------------------
2945 const RegMask &PhiNode::in_RegMask(uint i) const {
2946   return i ? out_RegMask() : RegMask::Empty;
2947 }
2948 
2949 const RegMask &PhiNode::out_RegMask() const {
2950   uint ideal_reg = _type->ideal_reg();
2951   assert( ideal_reg != Node::NotAMachineReg, "invalid type at Phi" );
2952   if( ideal_reg == 0 ) return RegMask::Empty;
2953   assert(ideal_reg != Op_RegFlags, "flags register is not spillable");
2954   return *(Compile::current()->matcher()->idealreg2spillmask[ideal_reg]);
2955 }
2956 
2957 #ifndef PRODUCT
2958 void PhiNode::dump_spec(outputStream *st) const {
2959   TypeNode::dump_spec(st);
2960   if (is_tripcount(T_INT) || is_tripcount(T_LONG)) {
2961     st->print(" #tripcount");
2962   }
2963 }
2964 #endif
2965 
2966 
2967 //=============================================================================
2968 const Type* GotoNode::Value(PhaseGVN* phase) const {
2969   // If the input is reachable, then we are executed.
2970   // If the input is not reachable, then we are not executed.
2971   return phase->type(in(0));
2972 }
2973 
2974 Node* GotoNode::Identity(PhaseGVN* phase) {
2975   return in(0);                // Simple copy of incoming control
2976 }
2977 
2978 const RegMask &GotoNode::out_RegMask() const {
2979   return RegMask::Empty;
2980 }
2981 
2982 //=============================================================================
2983 const RegMask &JumpNode::out_RegMask() const {
2984   return RegMask::Empty;
2985 }
2986 
2987 //=============================================================================
2988 const RegMask &JProjNode::out_RegMask() const {
2989   return RegMask::Empty;
2990 }
2991 
2992 //=============================================================================
2993 const RegMask &CProjNode::out_RegMask() const {
2994   return RegMask::Empty;
2995 }
2996 
2997 
2998 
2999 //=============================================================================
3000 
3001 uint PCTableNode::hash() const { return Node::hash() + _size; }
3002 bool PCTableNode::cmp( const Node &n ) const
3003 { return _size == ((PCTableNode&)n)._size; }
3004 
3005 const Type *PCTableNode::bottom_type() const {
3006   const Type** f = TypeTuple::fields(_size);
3007   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
3008   return TypeTuple::make(_size, f);
3009 }
3010 
3011 //------------------------------Value------------------------------------------
3012 // Compute the type of the PCTableNode.  If reachable it is a tuple of
3013 // Control, otherwise the table targets are not reachable
3014 const Type* PCTableNode::Value(PhaseGVN* phase) const {
3015   if( phase->type(in(0)) == Type::CONTROL )
3016     return bottom_type();
3017   return Type::TOP;             // All paths dead?  Then so are we
3018 }
3019 
3020 //------------------------------Ideal------------------------------------------
3021 // Return a node which is more "ideal" than the current node.  Strip out
3022 // control copies
3023 Node *PCTableNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3024   return remove_dead_region(phase, can_reshape) ? this : nullptr;
3025 }
3026 
3027 //=============================================================================
3028 uint JumpProjNode::hash() const {
3029   return Node::hash() + _dest_bci;
3030 }
3031 
3032 bool JumpProjNode::cmp( const Node &n ) const {
3033   return ProjNode::cmp(n) &&
3034     _dest_bci == ((JumpProjNode&)n)._dest_bci;
3035 }
3036 
3037 #ifndef PRODUCT
3038 void JumpProjNode::dump_spec(outputStream *st) const {
3039   ProjNode::dump_spec(st);
3040   st->print("@bci %d ",_dest_bci);
3041 }
3042 
3043 void JumpProjNode::dump_compact_spec(outputStream *st) const {
3044   ProjNode::dump_compact_spec(st);
3045   st->print("(%d)%d@%d", _switch_val, _proj_no, _dest_bci);
3046 }
3047 #endif
3048 
3049 //=============================================================================
3050 //------------------------------Value------------------------------------------
3051 // Check for being unreachable, or for coming from a Rethrow.  Rethrow's cannot
3052 // have the default "fall_through_index" path.
3053 const Type* CatchNode::Value(PhaseGVN* phase) const {
3054   // Unreachable?  Then so are all paths from here.
3055   if( phase->type(in(0)) == Type::TOP ) return Type::TOP;
3056   // First assume all paths are reachable
3057   const Type** f = TypeTuple::fields(_size);
3058   for( uint i = 0; i < _size; i++ ) f[i] = Type::CONTROL;
3059   // Identify cases that will always throw an exception
3060   // () rethrow call
3061   // () virtual or interface call with null receiver
3062   // () call is a check cast with incompatible arguments
3063   if( in(1)->is_Proj() ) {
3064     Node *i10 = in(1)->in(0);
3065     if( i10->is_Call() ) {
3066       CallNode *call = i10->as_Call();
3067       // Rethrows always throw exceptions, never return
3068       if (call->entry_point() == OptoRuntime::rethrow_stub()) {
3069         f[CatchProjNode::fall_through_index] = Type::TOP;
3070       } else if (call->is_AllocateArray()) {
3071         Node* klass_node = call->in(AllocateNode::KlassNode);
3072         Node* length = call->in(AllocateNode::ALength);
3073         const Type* length_type = phase->type(length);
3074         const Type* klass_type = phase->type(klass_node);
3075         Node* valid_length_test = call->in(AllocateNode::ValidLengthTest);
3076         const Type* valid_length_test_t = phase->type(valid_length_test);
3077         if (length_type == Type::TOP || klass_type == Type::TOP || valid_length_test_t == Type::TOP ||
3078             valid_length_test_t->is_int()->is_con(0)) {
3079           f[CatchProjNode::fall_through_index] = Type::TOP;
3080         }
3081       } else if( call->req() > TypeFunc::Parms ) {
3082         const Type *arg0 = phase->type( call->in(TypeFunc::Parms) );
3083         // Check for null receiver to virtual or interface calls
3084         if( call->is_CallDynamicJava() &&
3085             arg0->higher_equal(TypePtr::NULL_PTR) ) {
3086           f[CatchProjNode::fall_through_index] = Type::TOP;
3087         }
3088       } // End of if not a runtime stub
3089     } // End of if have call above me
3090   } // End of slot 1 is not a projection
3091   return TypeTuple::make(_size, f);
3092 }
3093 
3094 //=============================================================================
3095 uint CatchProjNode::hash() const {
3096   return Node::hash() + _handler_bci;
3097 }
3098 
3099 
3100 bool CatchProjNode::cmp( const Node &n ) const {
3101   return ProjNode::cmp(n) &&
3102     _handler_bci == ((CatchProjNode&)n)._handler_bci;
3103 }
3104 
3105 
3106 //------------------------------Identity---------------------------------------
3107 // If only 1 target is possible, choose it if it is the main control
3108 Node* CatchProjNode::Identity(PhaseGVN* phase) {
3109   // If my value is control and no other value is, then treat as ID
3110   const TypeTuple *t = phase->type(in(0))->is_tuple();
3111   if (t->field_at(_con) != Type::CONTROL)  return this;
3112   // If we remove the last CatchProj and elide the Catch/CatchProj, then we
3113   // also remove any exception table entry.  Thus we must know the call
3114   // feeding the Catch will not really throw an exception.  This is ok for
3115   // the main fall-thru control (happens when we know a call can never throw
3116   // an exception) or for "rethrow", because a further optimization will
3117   // yank the rethrow (happens when we inline a function that can throw an
3118   // exception and the caller has no handler).  Not legal, e.g., for passing
3119   // a null receiver to a v-call, or passing bad types to a slow-check-cast.
3120   // These cases MUST throw an exception via the runtime system, so the VM
3121   // will be looking for a table entry.
3122   Node *proj = in(0)->in(1);    // Expect a proj feeding CatchNode
3123   CallNode *call;
3124   if (_con != TypeFunc::Control && // Bail out if not the main control.
3125       !(proj->is_Proj() &&      // AND NOT a rethrow
3126         proj->in(0)->is_Call() &&
3127         (call = proj->in(0)->as_Call()) &&
3128         call->entry_point() == OptoRuntime::rethrow_stub()))
3129     return this;
3130 
3131   // Search for any other path being control
3132   for (uint i = 0; i < t->cnt(); i++) {
3133     if (i != _con && t->field_at(i) == Type::CONTROL)
3134       return this;
3135   }
3136   // Only my path is possible; I am identity on control to the jump
3137   return in(0)->in(0);
3138 }
3139 
3140 
3141 #ifndef PRODUCT
3142 void CatchProjNode::dump_spec(outputStream *st) const {
3143   ProjNode::dump_spec(st);
3144   st->print("@bci %d ",_handler_bci);
3145 }
3146 #endif
3147 
3148 //=============================================================================
3149 //------------------------------Identity---------------------------------------
3150 // Check for CreateEx being Identity.
3151 Node* CreateExNode::Identity(PhaseGVN* phase) {
3152   if( phase->type(in(1)) == Type::TOP ) return in(1);
3153   if( phase->type(in(0)) == Type::TOP ) return in(0);
3154   if (phase->type(in(0)->in(0)) == Type::TOP) {
3155     assert(in(0)->is_CatchProj(), "control is CatchProj");
3156     return phase->C->top(); // dead code
3157   }
3158   // We only come from CatchProj, unless the CatchProj goes away.
3159   // If the CatchProj is optimized away, then we just carry the
3160   // exception oop through.
3161 
3162   // CheckCastPPNode::Ideal() for inline types reuses the exception
3163   // paths of a call to perform an allocation: we can see a Phi here.
3164   if (in(1)->is_Phi()) {
3165     return this;
3166   }
3167   CallNode *call = in(1)->in(0)->as_Call();
3168 
3169   return (in(0)->is_CatchProj() && in(0)->in(0)->is_Catch() &&
3170           in(0)->in(0)->in(1) == in(1)) ? this : call->in(TypeFunc::Parms);
3171 }
3172 
3173 //=============================================================================
3174 //------------------------------Value------------------------------------------
3175 // Check for being unreachable.
3176 const Type* NeverBranchNode::Value(PhaseGVN* phase) const {
3177   if (!in(0) || in(0)->is_top()) return Type::TOP;
3178   return bottom_type();
3179 }
3180 
3181 //------------------------------Ideal------------------------------------------
3182 // Check for no longer being part of a loop
3183 Node *NeverBranchNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3184   if (can_reshape && !in(0)->is_Region()) {
3185     // Dead code elimination can sometimes delete this projection so
3186     // if it's not there, there's nothing to do.
3187     Node* fallthru = proj_out_or_null(0);
3188     if (fallthru != nullptr) {
3189       phase->is_IterGVN()->replace_node(fallthru, in(0));
3190     }
3191     return phase->C->top();
3192   }
3193   return nullptr;
3194 }
3195 
3196 #ifndef PRODUCT
3197 void NeverBranchNode::format( PhaseRegAlloc *ra_, outputStream *st) const {
3198   st->print("%s", Name());
3199 }
3200 #endif
3201 
3202 #ifndef PRODUCT
3203 void BlackholeNode::format(PhaseRegAlloc* ra, outputStream* st) const {
3204   st->print("blackhole ");
3205   bool first = true;
3206   for (uint i = 0; i < req(); i++) {
3207     Node* n = in(i);
3208     if (n != nullptr && OptoReg::is_valid(ra->get_reg_first(n))) {
3209       if (first) {
3210         first = false;
3211       } else {
3212         st->print(", ");
3213       }
3214       char buf[128];
3215       ra->dump_register(n, buf, sizeof(buf));
3216       st->print("%s", buf);
3217     }
3218   }
3219   st->cr();
3220 }
3221 #endif
3222