1 /*
   2  * Copyright (c) 2000, 2023, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciTypeFlow.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "memory/resourceArea.hpp"
  29 #include "opto/addnode.hpp"
  30 #include "opto/castnode.hpp"
  31 #include "opto/cfgnode.hpp"
  32 #include "opto/connode.hpp"
  33 #include "opto/loopnode.hpp"
  34 #include "opto/phaseX.hpp"
  35 #include "opto/predicates.hpp"
  36 #include "opto/runtime.hpp"
  37 #include "opto/rootnode.hpp"
  38 #include "opto/subnode.hpp"
  39 #include "opto/subtypenode.hpp"
  40 
  41 // Portions of code courtesy of Clifford Click
  42 
  43 // Optimization - Graph Style
  44 
  45 
  46 #ifndef PRODUCT
  47 extern uint explicit_null_checks_elided;
  48 #endif
  49 
  50 IfNode::IfNode(Node* control, Node* bol, float p, float fcnt)
  51     : MultiBranchNode(2),
  52       _prob(p),
  53       _fcnt(fcnt)
  54       NOT_PRODUCT(COMMA _assertion_predicate_type(AssertionPredicateType::None)) {
  55   init_node(control, bol);
  56 }
  57 
  58 #ifndef PRODUCT
  59 IfNode::IfNode(Node* control, Node* bol, float p, float fcnt, AssertionPredicateType assertion_predicate_type)
  60     : MultiBranchNode(2),
  61       _prob(p),
  62       _fcnt(fcnt),
  63       _assertion_predicate_type(assertion_predicate_type) {
  64   init_node(control, bol);
  65 }
  66 #endif // NOT_PRODUCT
  67 
  68 //=============================================================================
  69 //------------------------------Value------------------------------------------
  70 // Return a tuple for whichever arm of the IF is reachable
  71 const Type* IfNode::Value(PhaseGVN* phase) const {
  72   if( !in(0) ) return Type::TOP;
  73   if( phase->type(in(0)) == Type::TOP )
  74     return Type::TOP;
  75   const Type *t = phase->type(in(1));
  76   if( t == Type::TOP )          // data is undefined
  77     return TypeTuple::IFNEITHER; // unreachable altogether
  78   if( t == TypeInt::ZERO )      // zero, or false
  79     return TypeTuple::IFFALSE;  // only false branch is reachable
  80   if( t == TypeInt::ONE )       // 1, or true
  81     return TypeTuple::IFTRUE;   // only true branch is reachable
  82   assert( t == TypeInt::BOOL, "expected boolean type" );
  83 
  84   return TypeTuple::IFBOTH;     // No progress
  85 }
  86 
  87 const RegMask &IfNode::out_RegMask() const {
  88   return RegMask::Empty;
  89 }
  90 
  91 //------------------------------split_if---------------------------------------
  92 // Look for places where we merge constants, then test on the merged value.
  93 // If the IF test will be constant folded on the path with the constant, we
  94 // win by splitting the IF to before the merge point.
  95 static Node* split_if(IfNode *iff, PhaseIterGVN *igvn) {
  96   // I could be a lot more general here, but I'm trying to squeeze this
  97   // in before the Christmas '98 break so I'm gonna be kinda restrictive
  98   // on the patterns I accept.  CNC
  99 
 100   // Look for a compare of a constant and a merged value
 101   Node *i1 = iff->in(1);
 102   if( !i1->is_Bool() ) return nullptr;
 103   BoolNode *b = i1->as_Bool();
 104   Node *cmp = b->in(1);
 105   if( !cmp->is_Cmp() ) return nullptr;
 106   i1 = cmp->in(1);
 107   if( i1 == nullptr || !i1->is_Phi() ) return nullptr;
 108   PhiNode *phi = i1->as_Phi();
 109   Node *con2 = cmp->in(2);
 110   if( !con2->is_Con() ) return nullptr;
 111   // See that the merge point contains some constants
 112   Node *con1=nullptr;
 113   uint i4;
 114   RegionNode* phi_region = phi->region();
 115   for (i4 = 1; i4 < phi->req(); i4++ ) {
 116     con1 = phi->in(i4);
 117     // Do not optimize partially collapsed merges
 118     if (con1 == nullptr || phi_region->in(i4) == nullptr || igvn->type(phi_region->in(i4)) == Type::TOP) {
 119       igvn->_worklist.push(iff);
 120       return nullptr;
 121     }
 122     if( con1->is_Con() ) break; // Found a constant
 123     // Also allow null-vs-not-null checks
 124     const TypePtr *tp = igvn->type(con1)->isa_ptr();
 125     if( tp && tp->_ptr == TypePtr::NotNull )
 126       break;
 127   }
 128   if( i4 >= phi->req() ) return nullptr; // Found no constants
 129 
 130   igvn->C->set_has_split_ifs(true); // Has chance for split-if
 131 
 132   // Make sure that the compare can be constant folded away
 133   Node *cmp2 = cmp->clone();
 134   cmp2->set_req(1,con1);
 135   cmp2->set_req(2,con2);
 136   const Type *t = cmp2->Value(igvn);
 137   // This compare is dead, so whack it!
 138   igvn->remove_dead_node(cmp2);
 139   if( !t->singleton() ) return nullptr;
 140 
 141   // No intervening control, like a simple Call
 142   Node* r = iff->in(0);
 143   if (!r->is_Region() || r->is_Loop() || phi_region != r || r->as_Region()->is_copy()) {
 144     return nullptr;
 145   }
 146 
 147   // No other users of the cmp/bool
 148   if (b->outcnt() != 1 || cmp->outcnt() != 1) {
 149     //tty->print_cr("many users of cmp/bool");
 150     return nullptr;
 151   }
 152 
 153   // Make sure we can determine where all the uses of merged values go
 154   for (DUIterator_Fast jmax, j = r->fast_outs(jmax); j < jmax; j++) {
 155     Node* u = r->fast_out(j);
 156     if( u == r ) continue;
 157     if( u == iff ) continue;
 158     if( u->outcnt() == 0 ) continue; // use is dead & ignorable
 159     if( !u->is_Phi() ) {
 160       /*
 161       if( u->is_Start() ) {
 162         tty->print_cr("Region has inlined start use");
 163       } else {
 164         tty->print_cr("Region has odd use");
 165         u->dump(2);
 166       }*/
 167       return nullptr;
 168     }
 169     if( u != phi ) {
 170       // CNC - do not allow any other merged value
 171       //tty->print_cr("Merging another value");
 172       //u->dump(2);
 173       return nullptr;
 174     }
 175     // Make sure we can account for all Phi uses
 176     for (DUIterator_Fast kmax, k = u->fast_outs(kmax); k < kmax; k++) {
 177       Node* v = u->fast_out(k); // User of the phi
 178       // CNC - Allow only really simple patterns.
 179       // In particular I disallow AddP of the Phi, a fairly common pattern
 180       if (v == cmp) continue;  // The compare is OK
 181       if (v->is_ConstraintCast()) {
 182         // If the cast is derived from data flow edges, it may not have a control edge.
 183         // If so, it should be safe to split. But follow-up code can not deal with
 184         // this (l. 359). So skip.
 185         if (v->in(0) == nullptr) {
 186           return nullptr;
 187         }
 188         if (v->in(0)->in(0) == iff) {
 189           continue;               // CastPP/II of the IfNode is OK
 190         }
 191       }
 192       // Disabled following code because I cannot tell if exactly one
 193       // path dominates without a real dominator check. CNC 9/9/1999
 194       //uint vop = v->Opcode();
 195       //if( vop == Op_Phi ) {        // Phi from another merge point might be OK
 196       //  Node *r = v->in(0);        // Get controlling point
 197       //  if( !r ) return nullptr;   // Degraded to a copy
 198       //  // Find exactly one path in (either True or False doms, but not IFF)
 199       //  int cnt = 0;
 200       //  for( uint i = 1; i < r->req(); i++ )
 201       //    if( r->in(i) && r->in(i)->in(0) == iff )
 202       //      cnt++;
 203       //  if( cnt == 1 ) continue; // Exactly one of True or False guards Phi
 204       //}
 205       if( !v->is_Call() ) {
 206         /*
 207         if( v->Opcode() == Op_AddP ) {
 208           tty->print_cr("Phi has AddP use");
 209         } else if( v->Opcode() == Op_CastPP ) {
 210           tty->print_cr("Phi has CastPP use");
 211         } else if( v->Opcode() == Op_CastII ) {
 212           tty->print_cr("Phi has CastII use");
 213         } else {
 214           tty->print_cr("Phi has use I can't be bothered with");
 215         }
 216         */
 217       }
 218       return nullptr;
 219 
 220       /* CNC - Cut out all the fancy acceptance tests
 221       // Can we clone this use when doing the transformation?
 222       // If all uses are from Phis at this merge or constants, then YES.
 223       if( !v->in(0) && v != cmp ) {
 224         tty->print_cr("Phi has free-floating use");
 225         v->dump(2);
 226         return nullptr;
 227       }
 228       for( uint l = 1; l < v->req(); l++ ) {
 229         if( (!v->in(l)->is_Phi() || v->in(l)->in(0) != r) &&
 230             !v->in(l)->is_Con() ) {
 231           tty->print_cr("Phi has use");
 232           v->dump(2);
 233           return nullptr;
 234         } // End of if Phi-use input is neither Phi nor Constant
 235       } // End of for all inputs to Phi-use
 236       */
 237     } // End of for all uses of Phi
 238   } // End of for all uses of Region
 239 
 240   // Only do this if the IF node is in a sane state
 241   if (iff->outcnt() != 2)
 242     return nullptr;
 243 
 244   // Got a hit!  Do the Mondo Hack!
 245   //
 246   //ABC  a1c   def   ghi            B     1     e     h   A C   a c   d f   g i
 247   // R - Phi - Phi - Phi            Rc - Phi - Phi - Phi   Rx - Phi - Phi - Phi
 248   //     cmp - 2                         cmp - 2               cmp - 2
 249   //       bool                            bool_c                bool_x
 250   //       if                               if_c                  if_x
 251   //      T  F                              T  F                  T  F
 252   // ..s..    ..t ..                   ..s..    ..t..        ..s..    ..t..
 253   //
 254   // Split the paths coming into the merge point into 2 separate groups of
 255   // merges.  On the left will be all the paths feeding constants into the
 256   // Cmp's Phi.  On the right will be the remaining paths.  The Cmp's Phi
 257   // will fold up into a constant; this will let the Cmp fold up as well as
 258   // all the control flow.  Below the original IF we have 2 control
 259   // dependent regions, 's' and 't'.  Now we will merge the two paths
 260   // just prior to 's' and 't' from the two IFs.  At least 1 path (and quite
 261   // likely 2 or more) will promptly constant fold away.
 262   PhaseGVN *phase = igvn;
 263 
 264   // Make a region merging constants and a region merging the rest
 265   uint req_c = 0;
 266   for (uint ii = 1; ii < r->req(); ii++) {
 267     if (phi->in(ii) == con1) {
 268       req_c++;
 269     }
 270     if (Node::may_be_loop_entry(r->in(ii))) {
 271       // Bail out if splitting through a region with a Parse Predicate input (could
 272       // also be a loop header before loop opts creates a LoopNode for it).
 273       return nullptr;
 274     }
 275   }
 276 
 277   // If all the defs of the phi are the same constant, we already have the desired end state.
 278   // Skip the split that would create empty phi and region nodes.
 279   if ((r->req() - req_c) == 1) {
 280     return nullptr;
 281   }
 282 
 283   // At this point we know that we can apply the split if optimization. If the region is still on the worklist,
 284   // we should wait until it is processed. The region might be removed which makes this optimization redundant.
 285   // This also avoids the creation of dead data loops when rewiring data nodes below when a region is dying.
 286   if (igvn->_worklist.member(r)) {
 287     igvn->_worklist.push(iff); // retry split if later again
 288     return nullptr;
 289   }
 290 
 291   Node *region_c = new RegionNode(req_c + 1);
 292   Node *phi_c    = con1;
 293   uint  len      = r->req();
 294   Node *region_x = new RegionNode(len - req_c);
 295   Node *phi_x    = PhiNode::make_blank(region_x, phi);
 296   for (uint i = 1, i_c = 1, i_x = 1; i < len; i++) {
 297     if (phi->in(i) == con1) {
 298       region_c->init_req( i_c++, r  ->in(i) );
 299     } else {
 300       region_x->init_req( i_x,   r  ->in(i) );
 301       phi_x   ->init_req( i_x++, phi->in(i) );
 302     }
 303   }
 304 
 305   // Register the new RegionNodes but do not transform them.  Cannot
 306   // transform until the entire Region/Phi conglomerate has been hacked
 307   // as a single huge transform.
 308   igvn->register_new_node_with_optimizer( region_c );
 309   igvn->register_new_node_with_optimizer( region_x );
 310   // Prevent the untimely death of phi_x.  Currently he has no uses.  He is
 311   // about to get one.  If this only use goes away, then phi_x will look dead.
 312   // However, he will be picking up some more uses down below.
 313   Node *hook = new Node(4);
 314   hook->init_req(0, phi_x);
 315   hook->init_req(1, phi_c);
 316   phi_x = phase->transform( phi_x );
 317 
 318   // Make the compare
 319   Node *cmp_c = phase->makecon(t);
 320   Node *cmp_x = cmp->clone();
 321   cmp_x->set_req(1,phi_x);
 322   cmp_x->set_req(2,con2);
 323   cmp_x = phase->transform(cmp_x);
 324   // Make the bool
 325   Node *b_c = phase->transform(new BoolNode(cmp_c,b->_test._test));
 326   Node *b_x = phase->transform(new BoolNode(cmp_x,b->_test._test));
 327   // Make the IfNode
 328   IfNode* iff_c = iff->clone()->as_If();
 329   iff_c->set_req(0, region_c);
 330   iff_c->set_req(1, b_c);
 331   igvn->set_type_bottom(iff_c);
 332   igvn->_worklist.push(iff_c);
 333   hook->init_req(2, iff_c);
 334 
 335   IfNode* iff_x = iff->clone()->as_If();
 336   iff_x->set_req(0, region_x);
 337   iff_x->set_req(1, b_x);
 338   igvn->set_type_bottom(iff_x);
 339   igvn->_worklist.push(iff_x);
 340   hook->init_req(3, iff_x);
 341 
 342   // Make the true/false arms
 343   Node *iff_c_t = phase->transform(new IfTrueNode (iff_c));
 344   Node *iff_c_f = phase->transform(new IfFalseNode(iff_c));
 345   Node *iff_x_t = phase->transform(new IfTrueNode (iff_x));
 346   Node *iff_x_f = phase->transform(new IfFalseNode(iff_x));
 347 
 348   // Merge the TRUE paths
 349   Node *region_s = new RegionNode(3);
 350   igvn->_worklist.push(region_s);
 351   region_s->init_req(1, iff_c_t);
 352   region_s->init_req(2, iff_x_t);
 353   igvn->register_new_node_with_optimizer( region_s );
 354 
 355   // Merge the FALSE paths
 356   Node *region_f = new RegionNode(3);
 357   igvn->_worklist.push(region_f);
 358   region_f->init_req(1, iff_c_f);
 359   region_f->init_req(2, iff_x_f);
 360   igvn->register_new_node_with_optimizer( region_f );
 361 
 362   igvn->hash_delete(cmp);// Remove soon-to-be-dead node from hash table.
 363   cmp->set_req(1,nullptr);  // Whack the inputs to cmp because it will be dead
 364   cmp->set_req(2,nullptr);
 365   // Check for all uses of the Phi and give them a new home.
 366   // The 'cmp' got cloned, but CastPP/IIs need to be moved.
 367   Node *phi_s = nullptr;     // do not construct unless needed
 368   Node *phi_f = nullptr;     // do not construct unless needed
 369   for (DUIterator_Last i2min, i2 = phi->last_outs(i2min); i2 >= i2min; --i2) {
 370     Node* v = phi->last_out(i2);// User of the phi
 371     igvn->rehash_node_delayed(v); // Have to fixup other Phi users
 372     uint vop = v->Opcode();
 373     Node *proj = nullptr;
 374     if( vop == Op_Phi ) {       // Remote merge point
 375       Node *r = v->in(0);
 376       for (uint i3 = 1; i3 < r->req(); i3++)
 377         if (r->in(i3) && r->in(i3)->in(0) == iff) {
 378           proj = r->in(i3);
 379           break;
 380         }
 381     } else if( v->is_ConstraintCast() ) {
 382       proj = v->in(0);          // Controlling projection
 383     } else {
 384       assert( 0, "do not know how to handle this guy" );
 385     }
 386     guarantee(proj != nullptr, "sanity");
 387 
 388     Node *proj_path_data, *proj_path_ctrl;
 389     if( proj->Opcode() == Op_IfTrue ) {
 390       if( phi_s == nullptr ) {
 391         // Only construct phi_s if needed, otherwise provides
 392         // interfering use.
 393         phi_s = PhiNode::make_blank(region_s,phi);
 394         phi_s->init_req( 1, phi_c );
 395         phi_s->init_req( 2, phi_x );
 396         hook->add_req(phi_s);
 397         phi_s = phase->transform(phi_s);
 398       }
 399       proj_path_data = phi_s;
 400       proj_path_ctrl = region_s;
 401     } else {
 402       if( phi_f == nullptr ) {
 403         // Only construct phi_f if needed, otherwise provides
 404         // interfering use.
 405         phi_f = PhiNode::make_blank(region_f,phi);
 406         phi_f->init_req( 1, phi_c );
 407         phi_f->init_req( 2, phi_x );
 408         hook->add_req(phi_f);
 409         phi_f = phase->transform(phi_f);
 410       }
 411       proj_path_data = phi_f;
 412       proj_path_ctrl = region_f;
 413     }
 414 
 415     // Fixup 'v' for for the split
 416     if( vop == Op_Phi ) {       // Remote merge point
 417       uint i;
 418       for( i = 1; i < v->req(); i++ )
 419         if( v->in(i) == phi )
 420           break;
 421       v->set_req(i, proj_path_data );
 422     } else if( v->is_ConstraintCast() ) {
 423       v->set_req(0, proj_path_ctrl );
 424       v->set_req(1, proj_path_data );
 425     } else
 426       ShouldNotReachHere();
 427   }
 428 
 429   // Now replace the original iff's True/False with region_s/region_t.
 430   // This makes the original iff go dead.
 431   for (DUIterator_Last i3min, i3 = iff->last_outs(i3min); i3 >= i3min; --i3) {
 432     Node* p = iff->last_out(i3);
 433     assert( p->Opcode() == Op_IfTrue || p->Opcode() == Op_IfFalse, "" );
 434     Node *u = (p->Opcode() == Op_IfTrue) ? region_s : region_f;
 435     // Replace p with u
 436     igvn->add_users_to_worklist(p);
 437     for (DUIterator_Last lmin, l = p->last_outs(lmin); l >= lmin;) {
 438       Node* x = p->last_out(l);
 439       igvn->hash_delete(x);
 440       uint uses_found = 0;
 441       for( uint j = 0; j < x->req(); j++ ) {
 442         if( x->in(j) == p ) {
 443           x->set_req(j, u);
 444           uses_found++;
 445         }
 446       }
 447       l -= uses_found;    // we deleted 1 or more copies of this edge
 448     }
 449     igvn->remove_dead_node(p);
 450   }
 451 
 452   // Force the original merge dead
 453   igvn->hash_delete(r);
 454   // First, remove region's dead users.
 455   for (DUIterator_Last lmin, l = r->last_outs(lmin); l >= lmin;) {
 456     Node* u = r->last_out(l);
 457     if( u == r ) {
 458       r->set_req(0, nullptr);
 459     } else {
 460       assert(u->outcnt() == 0, "only dead users");
 461       igvn->remove_dead_node(u);
 462     }
 463     l -= 1;
 464   }
 465   igvn->remove_dead_node(r);
 466 
 467   // Now remove the bogus extra edges used to keep things alive
 468   igvn->remove_dead_node( hook );
 469 
 470   // Must return either the original node (now dead) or a new node
 471   // (Do not return a top here, since that would break the uniqueness of top.)
 472   return new ConINode(TypeInt::ZERO);
 473 }
 474 
 475 IfNode* IfNode::make_with_same_profile(IfNode* if_node_profile, Node* ctrl, BoolNode* bol) {
 476   // Assert here that we only try to create a clone from an If node with the same profiling if that actually makes sense.
 477   // Some If node subtypes should not be cloned in this way. In theory, we should not clone BaseCountedLoopEndNodes.
 478   // But they can end up being used as normal If nodes when peeling a loop - they serve as zero-trip guard.
 479   // Allow them as well.
 480   assert(if_node_profile->Opcode() == Op_If || if_node_profile->is_RangeCheck()
 481          || if_node_profile->is_BaseCountedLoopEnd(), "should not clone other nodes");
 482   if (if_node_profile->is_RangeCheck()) {
 483     // RangeCheck nodes could be further optimized.
 484     return new RangeCheckNode(ctrl, bol, if_node_profile->_prob, if_node_profile->_fcnt);
 485   } else {
 486     // Not a RangeCheckNode? Fall back to IfNode.
 487     return new IfNode(ctrl, bol, if_node_profile->_prob, if_node_profile->_fcnt);
 488   }
 489 }
 490 
 491 // if this IfNode follows a range check pattern return the projection
 492 // for the failed path
 493 ProjNode* IfNode::range_check_trap_proj(int& flip_test, Node*& l, Node*& r) {
 494   if (outcnt() != 2) {
 495     return nullptr;
 496   }
 497   Node* b = in(1);
 498   if (b == nullptr || !b->is_Bool())  return nullptr;
 499   BoolNode* bn = b->as_Bool();
 500   Node* cmp = bn->in(1);
 501   if (cmp == nullptr)  return nullptr;
 502   if (cmp->Opcode() != Op_CmpU)  return nullptr;
 503 
 504   l = cmp->in(1);
 505   r = cmp->in(2);
 506   flip_test = 1;
 507   if (bn->_test._test == BoolTest::le) {
 508     l = cmp->in(2);
 509     r = cmp->in(1);
 510     flip_test = 2;
 511   } else if (bn->_test._test != BoolTest::lt) {
 512     return nullptr;
 513   }
 514   if (l->is_top())  return nullptr;   // Top input means dead test
 515   if (r->Opcode() != Op_LoadRange && !is_RangeCheck())  return nullptr;
 516 
 517   // We have recognized one of these forms:
 518   //  Flip 1:  If (Bool[<] CmpU(l, LoadRange)) ...
 519   //  Flip 2:  If (Bool[<=] CmpU(LoadRange, l)) ...
 520 
 521   ProjNode* iftrap = proj_out_or_null(flip_test == 2 ? true : false);
 522   return iftrap;
 523 }
 524 
 525 
 526 //------------------------------is_range_check---------------------------------
 527 // Return 0 if not a range check.  Return 1 if a range check and set index and
 528 // offset.  Return 2 if we had to negate the test.  Index is null if the check
 529 // is versus a constant.
 530 int RangeCheckNode::is_range_check(Node* &range, Node* &index, jint &offset) {
 531   int flip_test = 0;
 532   Node* l = nullptr;
 533   Node* r = nullptr;
 534   ProjNode* iftrap = range_check_trap_proj(flip_test, l, r);
 535 
 536   if (iftrap == nullptr) {
 537     return 0;
 538   }
 539 
 540   // Make sure it's a real range check by requiring an uncommon trap
 541   // along the OOB path.  Otherwise, it's possible that the user wrote
 542   // something which optimized to look like a range check but behaves
 543   // in some other way.
 544   if (iftrap->is_uncommon_trap_proj(Deoptimization::Reason_range_check) == nullptr) {
 545     return 0;
 546   }
 547 
 548   // Look for index+offset form
 549   Node* ind = l;
 550   jint  off = 0;
 551   if (l->is_top()) {
 552     return 0;
 553   } else if (l->Opcode() == Op_AddI) {
 554     if ((off = l->in(1)->find_int_con(0)) != 0) {
 555       ind = l->in(2)->uncast();
 556     } else if ((off = l->in(2)->find_int_con(0)) != 0) {
 557       ind = l->in(1)->uncast();
 558     }
 559   } else if ((off = l->find_int_con(-1)) >= 0) {
 560     // constant offset with no variable index
 561     ind = nullptr;
 562   } else {
 563     // variable index with no constant offset (or dead negative index)
 564     off = 0;
 565   }
 566 
 567   // Return all the values:
 568   index  = ind;
 569   offset = off;
 570   range  = r;
 571   return flip_test;
 572 }
 573 
 574 //------------------------------adjust_check-----------------------------------
 575 // Adjust (widen) a prior range check
 576 static void adjust_check(IfProjNode* proj, Node* range, Node* index,
 577                          int flip, jint off_lo, PhaseIterGVN* igvn) {
 578   PhaseGVN *gvn = igvn;
 579   // Break apart the old check
 580   Node *iff = proj->in(0);
 581   Node *bol = iff->in(1);
 582   if( bol->is_top() ) return;   // In case a partially dead range check appears
 583   // bail (or bomb[ASSERT/DEBUG]) if NOT projection-->IfNode-->BoolNode
 584   DEBUG_ONLY( if (!bol->is_Bool()) { proj->dump(3); fatal("Expect projection-->IfNode-->BoolNode"); } )
 585   if (!bol->is_Bool()) return;
 586 
 587   Node *cmp = bol->in(1);
 588   // Compute a new check
 589   Node *new_add = gvn->intcon(off_lo);
 590   if (index) {
 591     new_add = off_lo ? gvn->transform(new AddINode(index, new_add)) : index;
 592   }
 593   Node *new_cmp = (flip == 1)
 594     ? new CmpUNode(new_add, range)
 595     : new CmpUNode(range, new_add);
 596   new_cmp = gvn->transform(new_cmp);
 597   // See if no need to adjust the existing check
 598   if (new_cmp == cmp) return;
 599   // Else, adjust existing check
 600   Node* new_bol = gvn->transform(new BoolNode(new_cmp, bol->as_Bool()->_test._test));
 601   igvn->rehash_node_delayed(iff);
 602   iff->set_req_X(1, new_bol, igvn);
 603   // As part of range check smearing, this range check is widened. Loads and range check Cast nodes that are control
 604   // dependent on this range check now depend on multiple dominating range checks. These control dependent nodes end up
 605   // at the lowest/nearest dominating check in the graph. To ensure that these Loads/Casts do not float above any of the
 606   // dominating checks (even when the lowest dominating check is later replaced by yet another dominating check), we
 607   // need to pin them at the lowest dominating check.
 608   proj->pin_array_access_nodes(igvn);
 609 }
 610 
 611 //------------------------------up_one_dom-------------------------------------
 612 // Walk up the dominator tree one step.  Return null at root or true
 613 // complex merges.  Skips through small diamonds.
 614 Node* IfNode::up_one_dom(Node *curr, bool linear_only) {
 615   Node *dom = curr->in(0);
 616   if( !dom )                    // Found a Region degraded to a copy?
 617     return curr->nonnull_req(); // Skip thru it
 618 
 619   if( curr != dom )             // Normal walk up one step?
 620     return dom;
 621 
 622   // Use linear_only if we are still parsing, since we cannot
 623   // trust the regions to be fully filled in.
 624   if (linear_only)
 625     return nullptr;
 626 
 627   if( dom->is_Root() )
 628     return nullptr;
 629 
 630   // Else hit a Region.  Check for a loop header
 631   if( dom->is_Loop() )
 632     return dom->in(1);          // Skip up thru loops
 633 
 634   // Check for small diamonds
 635   Node *din1, *din2, *din3, *din4;
 636   if( dom->req() == 3 &&        // 2-path merge point
 637       (din1 = dom ->in(1)) &&   // Left  path exists
 638       (din2 = dom ->in(2)) &&   // Right path exists
 639       (din3 = din1->in(0)) &&   // Left  path up one
 640       (din4 = din2->in(0)) ) {  // Right path up one
 641     if( din3->is_Call() &&      // Handle a slow-path call on either arm
 642         (din3 = din3->in(0)) )
 643       din3 = din3->in(0);
 644     if( din4->is_Call() &&      // Handle a slow-path call on either arm
 645         (din4 = din4->in(0)) )
 646       din4 = din4->in(0);
 647     if (din3 != nullptr && din3 == din4 && din3->is_If()) // Regions not degraded to a copy
 648       return din3;              // Skip around diamonds
 649   }
 650 
 651   // Give up the search at true merges
 652   return nullptr;                  // Dead loop?  Or hit root?
 653 }
 654 
 655 
 656 //------------------------------filtered_int_type--------------------------------
 657 // Return a possibly more restrictive type for val based on condition control flow for an if
 658 const TypeInt* IfNode::filtered_int_type(PhaseGVN* gvn, Node* val, Node* if_proj) {
 659   assert(if_proj &&
 660          (if_proj->Opcode() == Op_IfTrue || if_proj->Opcode() == Op_IfFalse), "expecting an if projection");
 661   if (if_proj->in(0) && if_proj->in(0)->is_If()) {
 662     IfNode* iff = if_proj->in(0)->as_If();
 663     if (iff->in(1) && iff->in(1)->is_Bool()) {
 664       BoolNode* bol = iff->in(1)->as_Bool();
 665       if (bol->in(1) && bol->in(1)->is_Cmp()) {
 666         const CmpNode* cmp  = bol->in(1)->as_Cmp();
 667         if (cmp->in(1) == val) {
 668           const TypeInt* cmp2_t = gvn->type(cmp->in(2))->isa_int();
 669           if (cmp2_t != nullptr) {
 670             jint lo = cmp2_t->_lo;
 671             jint hi = cmp2_t->_hi;
 672             BoolTest::mask msk = if_proj->Opcode() == Op_IfTrue ? bol->_test._test : bol->_test.negate();
 673             switch (msk) {
 674             case BoolTest::ne: {
 675               // If val is compared to its lower or upper bound, we can narrow the type
 676               const TypeInt* val_t = gvn->type(val)->isa_int();
 677               if (val_t != nullptr && !val_t->singleton() && cmp2_t->is_con()) {
 678                 if (val_t->_lo == lo) {
 679                   return TypeInt::make(val_t->_lo + 1, val_t->_hi, val_t->_widen);
 680                 } else if (val_t->_hi == hi) {
 681                   return TypeInt::make(val_t->_lo, val_t->_hi - 1, val_t->_widen);
 682                 }
 683               }
 684               // Can't refine type
 685               return nullptr;
 686             }
 687             case BoolTest::eq:
 688               return cmp2_t;
 689             case BoolTest::lt:
 690               lo = TypeInt::INT->_lo;
 691               if (hi != min_jint) {
 692                 hi = hi - 1;
 693               }
 694               break;
 695             case BoolTest::le:
 696               lo = TypeInt::INT->_lo;
 697               break;
 698             case BoolTest::gt:
 699               if (lo != max_jint) {
 700                 lo = lo + 1;
 701               }
 702               hi = TypeInt::INT->_hi;
 703               break;
 704             case BoolTest::ge:
 705               // lo unchanged
 706               hi = TypeInt::INT->_hi;
 707               break;
 708             default:
 709               break;
 710             }
 711             const TypeInt* rtn_t = TypeInt::make(lo, hi, cmp2_t->_widen);
 712             return rtn_t;
 713           }
 714         }
 715       }
 716     }
 717   }
 718   return nullptr;
 719 }
 720 
 721 //------------------------------fold_compares----------------------------
 722 // See if a pair of CmpIs can be converted into a CmpU.  In some cases
 723 // the direction of this if is determined by the preceding if so it
 724 // can be eliminate entirely.
 725 //
 726 // Given an if testing (CmpI n v) check for an immediately control
 727 // dependent if that is testing (CmpI n v2) and has one projection
 728 // leading to this if and the other projection leading to a region
 729 // that merges one of this ifs control projections.
 730 //
 731 //                   If
 732 //                  / |
 733 //                 /  |
 734 //                /   |
 735 //              If    |
 736 //              /\    |
 737 //             /  \   |
 738 //            /    \  |
 739 //           /    Region
 740 //
 741 // Or given an if testing (CmpI n v) check for a dominating if that is
 742 // testing (CmpI n v2), both having one projection leading to an
 743 // uncommon trap. Allow Another independent guard in between to cover
 744 // an explicit range check:
 745 // if (index < 0 || index >= array.length) {
 746 // which may need a null check to guard the LoadRange
 747 //
 748 //                   If
 749 //                  / \
 750 //                 /   \
 751 //                /     \
 752 //              If      unc
 753 //              /\
 754 //             /  \
 755 //            /    \
 756 //           /      unc
 757 //
 758 
 759 // Is the comparison for this If suitable for folding?
 760 bool IfNode::cmpi_folds(PhaseIterGVN* igvn, bool fold_ne) {
 761   return in(1) != nullptr &&
 762     in(1)->is_Bool() &&
 763     in(1)->in(1) != nullptr &&
 764     in(1)->in(1)->Opcode() == Op_CmpI &&
 765     in(1)->in(1)->in(2) != nullptr &&
 766     in(1)->in(1)->in(2) != igvn->C->top() &&
 767     (in(1)->as_Bool()->_test.is_less() ||
 768      in(1)->as_Bool()->_test.is_greater() ||
 769      (fold_ne && in(1)->as_Bool()->_test._test == BoolTest::ne));
 770 }
 771 
 772 // Is a dominating control suitable for folding with this if?
 773 bool IfNode::is_ctrl_folds(Node* ctrl, PhaseIterGVN* igvn) {
 774   return ctrl != nullptr &&
 775     ctrl->is_Proj() &&
 776     ctrl->outcnt() == 1 && // No side-effects
 777     ctrl->in(0) != nullptr &&
 778     ctrl->in(0)->Opcode() == Op_If &&
 779     ctrl->in(0)->outcnt() == 2 &&
 780     ctrl->in(0)->as_If()->cmpi_folds(igvn, true) &&
 781     // Must compare same value
 782     ctrl->in(0)->in(1)->in(1)->in(1) != nullptr &&
 783     ctrl->in(0)->in(1)->in(1)->in(1) != igvn->C->top() &&
 784     ctrl->in(0)->in(1)->in(1)->in(1) == in(1)->in(1)->in(1);
 785 }
 786 
 787 // Do this If and the dominating If share a region?
 788 bool IfNode::has_shared_region(ProjNode* proj, ProjNode*& success, ProjNode*& fail) {
 789   ProjNode* otherproj = proj->other_if_proj();
 790   Node* otherproj_ctrl_use = otherproj->unique_ctrl_out_or_null();
 791   RegionNode* region = (otherproj_ctrl_use != nullptr && otherproj_ctrl_use->is_Region()) ? otherproj_ctrl_use->as_Region() : nullptr;
 792   success = nullptr;
 793   fail = nullptr;
 794 
 795   if (otherproj->outcnt() == 1 && region != nullptr && !region->has_phi()) {
 796     for (int i = 0; i < 2; i++) {
 797       ProjNode* proj = proj_out(i);
 798       if (success == nullptr && proj->outcnt() == 1 && proj->unique_out() == region) {
 799         success = proj;
 800       } else if (fail == nullptr) {
 801         fail = proj;
 802       } else {
 803         success = fail = nullptr;
 804       }
 805     }
 806   }
 807   return success != nullptr && fail != nullptr;
 808 }
 809 
 810 bool IfNode::is_dominator_unc(CallStaticJavaNode* dom_unc, CallStaticJavaNode* unc) {
 811   // Different methods and methods containing jsrs are not supported.
 812   ciMethod* method = unc->jvms()->method();
 813   ciMethod* dom_method = dom_unc->jvms()->method();
 814   if (method != dom_method || method->has_jsrs()) {
 815     return false;
 816   }
 817   // Check that both traps are in the same activation of the method (instead
 818   // of two activations being inlined through different call sites) by verifying
 819   // that the call stacks are equal for both JVMStates.
 820   JVMState* dom_caller = dom_unc->jvms()->caller();
 821   JVMState* caller = unc->jvms()->caller();
 822   if ((dom_caller == nullptr) != (caller == nullptr)) {
 823     // The current method must either be inlined into both dom_caller and
 824     // caller or must not be inlined at all (top method). Bail out otherwise.
 825     return false;
 826   } else if (dom_caller != nullptr && !dom_caller->same_calls_as(caller)) {
 827     return false;
 828   }
 829   // Check that the bci of the dominating uncommon trap dominates the bci
 830   // of the dominated uncommon trap. Otherwise we may not re-execute
 831   // the dominated check after deoptimization from the merged uncommon trap.
 832   ciTypeFlow* flow = dom_method->get_flow_analysis();
 833   int bci = unc->jvms()->bci();
 834   int dom_bci = dom_unc->jvms()->bci();
 835   if (!flow->is_dominated_by(bci, dom_bci)) {
 836     return false;
 837   }
 838 
 839   return true;
 840 }
 841 
 842 // Return projection that leads to an uncommon trap if any
 843 ProjNode* IfNode::uncommon_trap_proj(CallStaticJavaNode*& call, Deoptimization::DeoptReason reason) const {
 844   for (int i = 0; i < 2; i++) {
 845     call = proj_out(i)->is_uncommon_trap_proj(reason);
 846     if (call != nullptr) {
 847       return proj_out(i);
 848     }
 849   }
 850   return nullptr;
 851 }
 852 
 853 // Do this If and the dominating If both branch out to an uncommon trap
 854 bool IfNode::has_only_uncommon_traps(ProjNode* proj, ProjNode*& success, ProjNode*& fail, PhaseIterGVN* igvn) {
 855   ProjNode* otherproj = proj->other_if_proj();
 856   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();
 857 
 858   if (otherproj->outcnt() == 1 && dom_unc != nullptr) {
 859     // We need to re-execute the folded Ifs after deoptimization from the merged traps
 860     if (!dom_unc->jvms()->should_reexecute()) {
 861       return false;
 862     }
 863 
 864     CallStaticJavaNode* unc = nullptr;
 865     ProjNode* unc_proj = uncommon_trap_proj(unc);
 866     if (unc_proj != nullptr && unc_proj->outcnt() == 1) {
 867       if (dom_unc == unc) {
 868         // Allow the uncommon trap to be shared through a region
 869         RegionNode* r = unc->in(0)->as_Region();
 870         if (r->outcnt() != 2 || r->req() != 3 || r->find_edge(otherproj) == -1 || r->find_edge(unc_proj) == -1) {
 871           return false;
 872         }
 873         assert(r->has_phi() == nullptr, "simple region shouldn't have a phi");
 874       } else if (dom_unc->in(0) != otherproj || unc->in(0) != unc_proj) {
 875         return false;
 876       }
 877 
 878       if (!is_dominator_unc(dom_unc, unc)) {
 879         return false;
 880       }
 881 
 882       // See merge_uncommon_traps: the reason of the uncommon trap
 883       // will be changed and the state of the dominating If will be
 884       // used. Checked that we didn't apply this transformation in a
 885       // previous compilation and it didn't cause too many traps
 886       ciMethod* dom_method = dom_unc->jvms()->method();
 887       int dom_bci = dom_unc->jvms()->bci();
 888       if (!igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_unstable_fused_if) &&
 889           !igvn->C->too_many_traps(dom_method, dom_bci, Deoptimization::Reason_range_check) &&
 890           // Return true if c2 manages to reconcile with UnstableIf optimization. See the comments for it.
 891           igvn->C->remove_unstable_if_trap(dom_unc, true/*yield*/)) {
 892         success = unc_proj;
 893         fail = unc_proj->other_if_proj();
 894         return true;
 895       }
 896     }
 897   }
 898   return false;
 899 }
 900 
 901 // Check that the 2 CmpI can be folded into as single CmpU and proceed with the folding
 902 bool IfNode::fold_compares_helper(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
 903   Node* this_cmp = in(1)->in(1);
 904   BoolNode* this_bool = in(1)->as_Bool();
 905   IfNode* dom_iff = proj->in(0)->as_If();
 906   BoolNode* dom_bool = dom_iff->in(1)->as_Bool();
 907   Node* lo = dom_iff->in(1)->in(1)->in(2);
 908   Node* hi = this_cmp->in(2);
 909   Node* n = this_cmp->in(1);
 910   ProjNode* otherproj = proj->other_if_proj();
 911 
 912   const TypeInt* lo_type = IfNode::filtered_int_type(igvn, n, otherproj);
 913   const TypeInt* hi_type = IfNode::filtered_int_type(igvn, n, success);
 914 
 915   BoolTest::mask lo_test = dom_bool->_test._test;
 916   BoolTest::mask hi_test = this_bool->_test._test;
 917   BoolTest::mask cond = hi_test;
 918 
 919   // convert:
 920   //
 921   //          dom_bool = x {<,<=,>,>=} a
 922   //                           / \
 923   //     proj = {True,False}  /   \ otherproj = {False,True}
 924   //                         /
 925   //        this_bool = x {<,<=} b
 926   //                       / \
 927   //  fail = {True,False} /   \ success = {False,True}
 928   //                     /
 929   //
 930   // (Second test guaranteed canonicalized, first one may not have
 931   // been canonicalized yet)
 932   //
 933   // into:
 934   //
 935   // cond = (x - lo) {<u,<=u,>u,>=u} adjusted_lim
 936   //                       / \
 937   //                 fail /   \ success
 938   //                     /
 939   //
 940 
 941   // Figure out which of the two tests sets the upper bound and which
 942   // sets the lower bound if any.
 943   Node* adjusted_lim = nullptr;
 944   if (lo_type != nullptr && hi_type != nullptr && hi_type->_lo > lo_type->_hi &&
 945       hi_type->_hi == max_jint && lo_type->_lo == min_jint && lo_test != BoolTest::ne) {
 946     assert((dom_bool->_test.is_less() && !proj->_con) ||
 947            (dom_bool->_test.is_greater() && proj->_con), "incorrect test");
 948 
 949     // this_bool = <
 950     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 951     //     x in [a, b[ on the fail (= True) projection, b > a-1 (because of hi_type->_lo > lo_type->_hi test above):
 952     //     lo = a, hi = b, adjusted_lim = b-a, cond = <u
 953     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 954     //     x in ]a, b[ on the fail (= True) projection, b > a:
 955     //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <u
 956     // this_bool = <=
 957     //   dom_bool = >= (proj = True) or dom_bool = < (proj = False)
 958     //     x in [a, b] on the fail (= True) projection, b+1 > a-1:
 959     //     lo = a, hi = b, adjusted_lim = b-a+1, cond = <u
 960     //     lo = a, hi = b, adjusted_lim = b-a, cond = <=u doesn't work because b = a - 1 is possible, then b-a = -1
 961     //   dom_bool = > (proj = True) or dom_bool = <= (proj = False)
 962     //     x in ]a, b] on the fail (= True) projection b+1 > a:
 963     //     lo = a+1, hi = b, adjusted_lim = b-a, cond = <u
 964     //     lo = a+1, hi = b, adjusted_lim = b-a-1, cond = <=u doesn't work because a = b is possible, then b-a-1 = -1
 965 
 966     if (hi_test == BoolTest::lt) {
 967       if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
 968         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 969       }
 970     } else if (hi_test == BoolTest::le) {
 971       if (lo_test == BoolTest::ge || lo_test == BoolTest::lt) {
 972         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 973         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
 974         cond = BoolTest::lt;
 975       } else if (lo_test == BoolTest::gt || lo_test == BoolTest::le) {
 976         adjusted_lim = igvn->transform(new SubINode(hi, lo));
 977         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
 978         cond = BoolTest::lt;
 979       } else {
 980         assert(false, "unhandled lo_test: %d", lo_test);
 981         return false;
 982       }
 983     } else {
 984       assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled hi_test: %d", hi_test);
 985       return false;
 986     }
 987     // this test was canonicalized
 988     assert(this_bool->_test.is_less() && fail->_con, "incorrect test");
 989   } else if (lo_type != nullptr && hi_type != nullptr && lo_type->_lo > hi_type->_hi &&
 990              lo_type->_hi == max_jint && hi_type->_lo == min_jint && lo_test != BoolTest::ne) {
 991 
 992     // this_bool = <
 993     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
 994     //     x in [b, a[ on the fail (= False) projection, a > b-1 (because of lo_type->_lo > hi_type->_hi above):
 995     //     lo = b, hi = a, adjusted_lim = a-b, cond = >=u
 996     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
 997     //     x in [b, a] on the fail (= False) projection, a+1 > b-1:
 998     //     lo = b, hi = a, adjusted_lim = a-b+1, cond = >=u
 999     //     lo = b, hi = a, adjusted_lim = a-b, cond = >u doesn't work because a = b - 1 is possible, then b-a = -1
1000     // this_bool = <=
1001     //   dom_bool = < (proj = True) or dom_bool = >= (proj = False)
1002     //     x in ]b, a[ on the fail (= False) projection, a > b:
1003     //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >=u
1004     //   dom_bool = <= (proj = True) or dom_bool = > (proj = False)
1005     //     x in ]b, a] on the fail (= False) projection, a+1 > b:
1006     //     lo = b+1, hi = a, adjusted_lim = a-b, cond = >=u
1007     //     lo = b+1, hi = a, adjusted_lim = a-b-1, cond = >u doesn't work because a = b is possible, then b-a-1 = -1
1008 
1009     swap(lo, hi);
1010     swap(lo_type, hi_type);
1011     swap(lo_test, hi_test);
1012 
1013     assert((dom_bool->_test.is_less() && proj->_con) ||
1014            (dom_bool->_test.is_greater() && !proj->_con), "incorrect test");
1015 
1016     cond = (hi_test == BoolTest::le || hi_test == BoolTest::gt) ? BoolTest::gt : BoolTest::ge;
1017 
1018     if (lo_test == BoolTest::lt) {
1019       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
1020         cond = BoolTest::ge;
1021       } else if (hi_test == BoolTest::le || hi_test == BoolTest::gt) {
1022         adjusted_lim = igvn->transform(new SubINode(hi, lo));
1023         adjusted_lim = igvn->transform(new AddINode(adjusted_lim, igvn->intcon(1)));
1024         cond = BoolTest::ge;
1025       } else {
1026         assert(false, "unhandled hi_test: %d", hi_test);
1027         return false;
1028       }
1029     } else if (lo_test == BoolTest::le) {
1030       if (hi_test == BoolTest::lt || hi_test == BoolTest::ge) {
1031         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
1032         cond = BoolTest::ge;
1033       } else if (hi_test == BoolTest::le || hi_test == BoolTest::gt) {
1034         adjusted_lim = igvn->transform(new SubINode(hi, lo));
1035         lo = igvn->transform(new AddINode(lo, igvn->intcon(1)));
1036         cond = BoolTest::ge;
1037       } else {
1038         assert(false, "unhandled hi_test: %d", hi_test);
1039         return false;
1040       }
1041     } else {
1042       assert(igvn->_worklist.member(in(1)) && in(1)->Value(igvn) != igvn->type(in(1)), "unhandled lo_test: %d", lo_test);
1043       return false;
1044     }
1045     // this test was canonicalized
1046     assert(this_bool->_test.is_less() && !fail->_con, "incorrect test");
1047   } else {
1048     const TypeInt* failtype = filtered_int_type(igvn, n, proj);
1049     if (failtype != nullptr) {
1050       const TypeInt* type2 = filtered_int_type(igvn, n, fail);
1051       if (type2 != nullptr) {
1052         failtype = failtype->join(type2)->is_int();
1053         if (failtype->empty()) {
1054           // previous if determines the result of this if so
1055           // replace Bool with constant
1056           igvn->replace_input_of(this, 1, igvn->intcon(success->_con));
1057           return true;
1058         }
1059       }
1060     }
1061     return false;
1062   }
1063 
1064   assert(lo != nullptr && hi != nullptr, "sanity");
1065   Node* hook = new Node(lo); // Add a use to lo to prevent him from dying
1066   // Merge the two compares into a single unsigned compare by building (CmpU (n - lo) (hi - lo))
1067   Node* adjusted_val = igvn->transform(new SubINode(n,  lo));
1068   if (adjusted_lim == nullptr) {
1069     adjusted_lim = igvn->transform(new SubINode(hi, lo));
1070   }
1071   hook->destruct(igvn);
1072 
1073   if (adjusted_val->is_top() || adjusted_lim->is_top()) {
1074     return false;
1075   }
1076 
1077   if (igvn->type(adjusted_lim)->is_int()->_lo < 0 &&
1078       !igvn->C->post_loop_opts_phase()) {
1079     // If range check elimination applies to this comparison, it includes code to protect from overflows that may
1080     // cause the main loop to be skipped entirely. Delay this transformation.
1081     // Example:
1082     // for (int i = 0; i < limit; i++) {
1083     //   if (i < max_jint && i > min_jint) {...
1084     // }
1085     // Comparisons folded as:
1086     // i - min_jint - 1 <u -2
1087     // when RC applies, main loop limit becomes:
1088     // min(limit, max(-2 + min_jint + 1, min_jint))
1089     // = min(limit, min_jint)
1090     // = min_jint
1091     if (adjusted_val->outcnt() == 0) {
1092       igvn->remove_dead_node(adjusted_val);
1093     }
1094     if (adjusted_lim->outcnt() == 0) {
1095       igvn->remove_dead_node(adjusted_lim);
1096     }
1097     igvn->C->record_for_post_loop_opts_igvn(this);
1098     return false;
1099   }
1100 
1101   Node* newcmp = igvn->transform(new CmpUNode(adjusted_val, adjusted_lim));
1102   Node* newbool = igvn->transform(new BoolNode(newcmp, cond));
1103 
1104   igvn->replace_input_of(dom_iff, 1, igvn->intcon(proj->_con));
1105   igvn->replace_input_of(this, 1, newbool);
1106 
1107   return true;
1108 }
1109 
1110 // Merge the branches that trap for this If and the dominating If into
1111 // a single region that branches to the uncommon trap for the
1112 // dominating If
1113 Node* IfNode::merge_uncommon_traps(ProjNode* proj, ProjNode* success, ProjNode* fail, PhaseIterGVN* igvn) {
1114   Node* res = this;
1115   assert(success->in(0) == this, "bad projection");
1116 
1117   ProjNode* otherproj = proj->other_if_proj();
1118 
1119   CallStaticJavaNode* unc = success->is_uncommon_trap_proj();
1120   CallStaticJavaNode* dom_unc = otherproj->is_uncommon_trap_proj();
1121 
1122   if (unc != dom_unc) {
1123     Node* r = new RegionNode(3);
1124 
1125     r->set_req(1, otherproj);
1126     r->set_req(2, success);
1127     r = igvn->transform(r);
1128     assert(r->is_Region(), "can't go away");
1129 
1130     // Make both If trap at the state of the first If: once the CmpI
1131     // nodes are merged, if we trap we don't know which of the CmpI
1132     // nodes would have caused the trap so we have to restart
1133     // execution at the first one
1134     igvn->replace_input_of(dom_unc, 0, r);
1135     igvn->replace_input_of(unc, 0, igvn->C->top());
1136   }
1137   int trap_request = dom_unc->uncommon_trap_request();
1138   Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1139   Deoptimization::DeoptAction action = Deoptimization::trap_request_action(trap_request);
1140 
1141   int flip_test = 0;
1142   Node* l = nullptr;
1143   Node* r = nullptr;
1144 
1145   if (success->in(0)->as_If()->range_check_trap_proj(flip_test, l, r) != nullptr) {
1146     // If this looks like a range check, change the trap to
1147     // Reason_range_check so the compiler recognizes it as a range
1148     // check and applies the corresponding optimizations
1149     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_range_check, action);
1150 
1151     improve_address_types(l, r, fail, igvn);
1152 
1153     res = igvn->transform(new RangeCheckNode(in(0), in(1), _prob, _fcnt));
1154   } else if (unc != dom_unc) {
1155     // If we trap we won't know what CmpI would have caused the trap
1156     // so use a special trap reason to mark this pair of CmpI nodes as
1157     // bad candidate for folding. On recompilation we won't fold them
1158     // and we may trap again but this time we'll know what branch
1159     // traps
1160     trap_request = Deoptimization::make_trap_request(Deoptimization::Reason_unstable_fused_if, action);
1161   }
1162   igvn->replace_input_of(dom_unc, TypeFunc::Parms, igvn->intcon(trap_request));
1163   return res;
1164 }
1165 
1166 // If we are turning 2 CmpI nodes into a CmpU that follows the pattern
1167 // of a rangecheck on index i, on 64 bit the compares may be followed
1168 // by memory accesses using i as index. In that case, the CmpU tells
1169 // us something about the values taken by i that can help the compiler
1170 // (see Compile::conv_I2X_index())
1171 void IfNode::improve_address_types(Node* l, Node* r, ProjNode* fail, PhaseIterGVN* igvn) {
1172 #ifdef _LP64
1173   ResourceMark rm;
1174   Node_Stack stack(2);
1175 
1176   assert(r->Opcode() == Op_LoadRange, "unexpected range check");
1177   const TypeInt* array_size = igvn->type(r)->is_int();
1178 
1179   stack.push(l, 0);
1180 
1181   while(stack.size() > 0) {
1182     Node* n = stack.node();
1183     uint start = stack.index();
1184 
1185     uint i = start;
1186     for (; i < n->outcnt(); i++) {
1187       Node* use = n->raw_out(i);
1188       if (stack.size() == 1) {
1189         if (use->Opcode() == Op_ConvI2L) {
1190           const TypeLong* bounds = use->as_Type()->type()->is_long();
1191           if (bounds->_lo <= array_size->_lo && bounds->_hi >= array_size->_hi &&
1192               (bounds->_lo != array_size->_lo || bounds->_hi != array_size->_hi)) {
1193             stack.set_index(i+1);
1194             stack.push(use, 0);
1195             break;
1196           }
1197         }
1198       } else if (use->is_Mem()) {
1199         Node* ctrl = use->in(0);
1200         for (int i = 0; i < 10 && ctrl != nullptr && ctrl != fail; i++) {
1201           ctrl = up_one_dom(ctrl);
1202         }
1203         if (ctrl == fail) {
1204           Node* init_n = stack.node_at(1);
1205           assert(init_n->Opcode() == Op_ConvI2L, "unexpected first node");
1206           // Create a new narrow ConvI2L node that is dependent on the range check
1207           Node* new_n = igvn->C->conv_I2X_index(igvn, l, array_size, fail);
1208 
1209           // The type of the ConvI2L may be widen and so the new
1210           // ConvI2L may not be better than an existing ConvI2L
1211           if (new_n != init_n) {
1212             for (uint j = 2; j < stack.size(); j++) {
1213               Node* n = stack.node_at(j);
1214               Node* clone = n->clone();
1215               int rep = clone->replace_edge(init_n, new_n, igvn);
1216               assert(rep > 0, "can't find expected node?");
1217               clone = igvn->transform(clone);
1218               init_n = n;
1219               new_n = clone;
1220             }
1221             igvn->hash_delete(use);
1222             int rep = use->replace_edge(init_n, new_n, igvn);
1223             assert(rep > 0, "can't find expected node?");
1224             igvn->transform(use);
1225             if (init_n->outcnt() == 0) {
1226               igvn->_worklist.push(init_n);
1227             }
1228           }
1229         }
1230       } else if (use->in(0) == nullptr && (igvn->type(use)->isa_long() ||
1231                                         igvn->type(use)->isa_ptr())) {
1232         stack.set_index(i+1);
1233         stack.push(use, 0);
1234         break;
1235       }
1236     }
1237     if (i == n->outcnt()) {
1238       stack.pop();
1239     }
1240   }
1241 #endif
1242 }
1243 
1244 bool IfNode::is_cmp_with_loadrange(ProjNode* proj) {
1245   if (in(1) != nullptr &&
1246       in(1)->in(1) != nullptr &&
1247       in(1)->in(1)->in(2) != nullptr) {
1248     Node* other = in(1)->in(1)->in(2);
1249     if (other->Opcode() == Op_LoadRange &&
1250         ((other->in(0) != nullptr && other->in(0) == proj) ||
1251          (other->in(0) == nullptr &&
1252           other->in(2) != nullptr &&
1253           other->in(2)->is_AddP() &&
1254           other->in(2)->in(1) != nullptr &&
1255           other->in(2)->in(1)->Opcode() == Op_CastPP &&
1256           other->in(2)->in(1)->in(0) == proj))) {
1257       return true;
1258     }
1259   }
1260   return false;
1261 }
1262 
1263 bool IfNode::is_null_check(ProjNode* proj, PhaseIterGVN* igvn) {
1264   Node* other = in(1)->in(1)->in(2);
1265   if (other->in(MemNode::Address) != nullptr &&
1266       proj->in(0)->in(1) != nullptr &&
1267       proj->in(0)->in(1)->is_Bool() &&
1268       proj->in(0)->in(1)->in(1) != nullptr &&
1269       proj->in(0)->in(1)->in(1)->Opcode() == Op_CmpP &&
1270       proj->in(0)->in(1)->in(1)->in(2) != nullptr &&
1271       proj->in(0)->in(1)->in(1)->in(1) == other->in(MemNode::Address)->in(AddPNode::Address)->uncast() &&
1272       igvn->type(proj->in(0)->in(1)->in(1)->in(2)) == TypePtr::NULL_PTR) {
1273     return true;
1274   }
1275   return false;
1276 }
1277 
1278 // Returns true if this IfNode belongs to a flat array check
1279 // and returns the corresponding array in the 'array' parameter.
1280 bool IfNode::is_flat_array_check(PhaseTransform* phase, Node** array) {
1281   Node* bol = in(1);
1282   if (!bol->is_Bool()) {
1283     return false;
1284   }
1285   Node* cmp = bol->in(1);
1286   if (cmp->isa_FlatArrayCheck()) {
1287     if (array != nullptr) {
1288       *array = cmp->in(FlatArrayCheckNode::ArrayOrKlass);
1289     }
1290     return true;
1291   }
1292   return false;
1293 }
1294 
1295 // Check that the If that is in between the 2 integer comparisons has
1296 // no side effect
1297 bool IfNode::is_side_effect_free_test(ProjNode* proj, PhaseIterGVN* igvn) {
1298   if (proj == nullptr) {
1299     return false;
1300   }
1301   CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1302   if (unc != nullptr && proj->outcnt() <= 2) {
1303     if (proj->outcnt() == 1 ||
1304         // Allow simple null check from LoadRange
1305         (is_cmp_with_loadrange(proj) && is_null_check(proj, igvn))) {
1306       CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1307       CallStaticJavaNode* dom_unc = proj->in(0)->in(0)->as_Proj()->is_uncommon_trap_if_pattern();
1308       assert(dom_unc != nullptr, "is_uncommon_trap_if_pattern returned null");
1309 
1310       // reroute_side_effect_free_unc changes the state of this
1311       // uncommon trap to restart execution at the previous
1312       // CmpI. Check that this change in a previous compilation didn't
1313       // cause too many traps.
1314       int trap_request = unc->uncommon_trap_request();
1315       Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(trap_request);
1316 
1317       if (igvn->C->too_many_traps(dom_unc->jvms()->method(), dom_unc->jvms()->bci(), reason)) {
1318         return false;
1319       }
1320 
1321       if (!is_dominator_unc(dom_unc, unc)) {
1322         return false;
1323       }
1324 
1325       return true;
1326     }
1327   }
1328   return false;
1329 }
1330 
1331 // Make the If between the 2 integer comparisons trap at the state of
1332 // the first If: the last CmpI is the one replaced by a CmpU and the
1333 // first CmpI is eliminated, so the test between the 2 CmpI nodes
1334 // won't be guarded by the first CmpI anymore. It can trap in cases
1335 // where the first CmpI would have prevented it from executing: on a
1336 // trap, we need to restart execution at the state of the first CmpI
1337 void IfNode::reroute_side_effect_free_unc(ProjNode* proj, ProjNode* dom_proj, PhaseIterGVN* igvn) {
1338   CallStaticJavaNode* dom_unc = dom_proj->is_uncommon_trap_if_pattern();
1339   ProjNode* otherproj = proj->other_if_proj();
1340   CallStaticJavaNode* unc = proj->is_uncommon_trap_if_pattern();
1341   Node* call_proj = dom_unc->unique_ctrl_out();
1342   Node* halt = call_proj->unique_ctrl_out();
1343 
1344   Node* new_unc = dom_unc->clone();
1345   call_proj = call_proj->clone();
1346   halt = halt->clone();
1347   Node* c = otherproj->clone();
1348 
1349   c = igvn->transform(c);
1350   new_unc->set_req(TypeFunc::Parms, unc->in(TypeFunc::Parms));
1351   new_unc->set_req(0, c);
1352   new_unc = igvn->transform(new_unc);
1353   call_proj->set_req(0, new_unc);
1354   call_proj = igvn->transform(call_proj);
1355   halt->set_req(0, call_proj);
1356   halt = igvn->transform(halt);
1357 
1358   igvn->replace_node(otherproj, igvn->C->top());
1359   igvn->C->root()->add_req(halt);
1360 }
1361 
1362 Node* IfNode::fold_compares(PhaseIterGVN* igvn) {
1363   if (Opcode() != Op_If) return nullptr;
1364 
1365   if (cmpi_folds(igvn)) {
1366     Node* ctrl = in(0);
1367     if (is_ctrl_folds(ctrl, igvn)) {
1368       // A integer comparison immediately dominated by another integer
1369       // comparison
1370       ProjNode* success = nullptr;
1371       ProjNode* fail = nullptr;
1372       ProjNode* dom_cmp = ctrl->as_Proj();
1373       if (has_shared_region(dom_cmp, success, fail) &&
1374           // Next call modifies graph so must be last
1375           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1376         return this;
1377       }
1378       if (has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1379           // Next call modifies graph so must be last
1380           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1381         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1382       }
1383       return nullptr;
1384     } else if (ctrl->in(0) != nullptr &&
1385                ctrl->in(0)->in(0) != nullptr) {
1386       ProjNode* success = nullptr;
1387       ProjNode* fail = nullptr;
1388       Node* dom = ctrl->in(0)->in(0);
1389       ProjNode* dom_cmp = dom->isa_Proj();
1390       ProjNode* other_cmp = ctrl->isa_Proj();
1391 
1392       // Check if it's an integer comparison dominated by another
1393       // integer comparison with another test in between
1394       if (is_ctrl_folds(dom, igvn) &&
1395           has_only_uncommon_traps(dom_cmp, success, fail, igvn) &&
1396           is_side_effect_free_test(other_cmp, igvn) &&
1397           // Next call modifies graph so must be last
1398           fold_compares_helper(dom_cmp, success, fail, igvn)) {
1399         reroute_side_effect_free_unc(other_cmp, dom_cmp, igvn);
1400         return merge_uncommon_traps(dom_cmp, success, fail, igvn);
1401       }
1402     }
1403   }
1404   return nullptr;
1405 }
1406 
1407 //------------------------------remove_useless_bool----------------------------
1408 // Check for people making a useless boolean: things like
1409 // if( (x < y ? true : false) ) { ... }
1410 // Replace with if( x < y ) { ... }
1411 static Node *remove_useless_bool(IfNode *iff, PhaseGVN *phase) {
1412   Node *i1 = iff->in(1);
1413   if( !i1->is_Bool() ) return nullptr;
1414   BoolNode *bol = i1->as_Bool();
1415 
1416   Node *cmp = bol->in(1);
1417   if( cmp->Opcode() != Op_CmpI ) return nullptr;
1418 
1419   // Must be comparing against a bool
1420   const Type *cmp2_t = phase->type( cmp->in(2) );
1421   if( cmp2_t != TypeInt::ZERO &&
1422       cmp2_t != TypeInt::ONE )
1423     return nullptr;
1424 
1425   // Find a prior merge point merging the boolean
1426   i1 = cmp->in(1);
1427   if( !i1->is_Phi() ) return nullptr;
1428   PhiNode *phi = i1->as_Phi();
1429   if( phase->type( phi ) != TypeInt::BOOL )
1430     return nullptr;
1431 
1432   // Check for diamond pattern
1433   int true_path = phi->is_diamond_phi();
1434   if( true_path == 0 ) return nullptr;
1435 
1436   // Make sure that iff and the control of the phi are different. This
1437   // should really only happen for dead control flow since it requires
1438   // an illegal cycle.
1439   if (phi->in(0)->in(1)->in(0) == iff) return nullptr;
1440 
1441   // phi->region->if_proj->ifnode->bool->cmp
1442   BoolNode *bol2 = phi->in(0)->in(1)->in(0)->in(1)->as_Bool();
1443 
1444   // Now get the 'sense' of the test correct so we can plug in
1445   // either iff2->in(1) or its complement.
1446   int flip = 0;
1447   if( bol->_test._test == BoolTest::ne ) flip = 1-flip;
1448   else if( bol->_test._test != BoolTest::eq ) return nullptr;
1449   if( cmp2_t == TypeInt::ZERO ) flip = 1-flip;
1450 
1451   const Type *phi1_t = phase->type( phi->in(1) );
1452   const Type *phi2_t = phase->type( phi->in(2) );
1453   // Check for Phi(0,1) and flip
1454   if( phi1_t == TypeInt::ZERO ) {
1455     if( phi2_t != TypeInt::ONE ) return nullptr;
1456     flip = 1-flip;
1457   } else {
1458     // Check for Phi(1,0)
1459     if( phi1_t != TypeInt::ONE  ) return nullptr;
1460     if( phi2_t != TypeInt::ZERO ) return nullptr;
1461   }
1462   if( true_path == 2 ) {
1463     flip = 1-flip;
1464   }
1465 
1466   Node* new_bol = (flip ? phase->transform( bol2->negate(phase) ) : bol2);
1467   assert(new_bol != iff->in(1), "must make progress");
1468   iff->set_req_X(1, new_bol, phase);
1469   // Intervening diamond probably goes dead
1470   phase->C->set_major_progress();
1471   return iff;
1472 }
1473 
1474 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff);
1475 
1476 struct RangeCheck {
1477   IfProjNode* ctl;
1478   jint off;
1479 };
1480 
1481 Node* IfNode::Ideal_common(PhaseGVN *phase, bool can_reshape) {
1482   if (remove_dead_region(phase, can_reshape))  return this;
1483   // No Def-Use info?
1484   if (!can_reshape)  return nullptr;
1485 
1486   // Don't bother trying to transform a dead if
1487   if (in(0)->is_top())  return nullptr;
1488   // Don't bother trying to transform an if with a dead test
1489   if (in(1)->is_top())  return nullptr;
1490   // Another variation of a dead test
1491   if (in(1)->is_Con())  return nullptr;
1492   // Another variation of a dead if
1493   if (outcnt() < 2)  return nullptr;
1494 
1495   // Canonicalize the test.
1496   Node* idt_if = idealize_test(phase, this);
1497   if (idt_if != nullptr)  return idt_if;
1498 
1499   // Try to split the IF
1500   PhaseIterGVN *igvn = phase->is_IterGVN();
1501   Node *s = split_if(this, igvn);
1502   if (s != nullptr)  return s;
1503 
1504   return NodeSentinel;
1505 }
1506 
1507 //------------------------------Ideal------------------------------------------
1508 // Return a node which is more "ideal" than the current node.  Strip out
1509 // control copies
1510 Node* IfNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1511   Node* res = Ideal_common(phase, can_reshape);
1512   if (res != NodeSentinel) {
1513     return res;
1514   }
1515 
1516   // Check for people making a useless boolean: things like
1517   // if( (x < y ? true : false) ) { ... }
1518   // Replace with if( x < y ) { ... }
1519   Node* bol2 = remove_useless_bool(this, phase);
1520   if (bol2) return bol2;
1521 
1522   if (in(0) == nullptr) return nullptr;     // Dead loop?
1523 
1524   PhaseIterGVN* igvn = phase->is_IterGVN();
1525   Node* result = fold_compares(igvn);
1526   if (result != nullptr) {
1527     return result;
1528   }
1529 
1530   // Scan for an equivalent test
1531   int dist = 4;               // Cutoff limit for search
1532   if (is_If() && in(1)->is_Bool()) {
1533     Node* cmp = in(1)->in(1);
1534     if (cmp->Opcode() == Op_CmpP &&
1535         cmp->in(2) != nullptr && // make sure cmp is not already dead
1536         cmp->in(2)->bottom_type() == TypePtr::NULL_PTR) {
1537       dist = 64;              // Limit for null-pointer scans
1538     }
1539   }
1540 
1541   Node* prev_dom = search_identical(dist, igvn);
1542 
1543   if (prev_dom != nullptr) {
1544     // Replace dominated IfNode
1545     return dominated_by(prev_dom, igvn, false);
1546   }
1547 
1548   return simple_subsuming(igvn);
1549 }
1550 
1551 //------------------------------dominated_by-----------------------------------
1552 Node* IfNode::dominated_by(Node* prev_dom, PhaseIterGVN* igvn, bool pin_array_access_nodes) {
1553 #ifndef PRODUCT
1554   if (TraceIterativeGVN) {
1555     tty->print("   Removing IfNode: "); this->dump();
1556   }
1557 #endif
1558 
1559   igvn->hash_delete(this);      // Remove self to prevent spurious V-N
1560   Node *idom = in(0);
1561   // Need opcode to decide which way 'this' test goes
1562   int prev_op = prev_dom->Opcode();
1563   Node *top = igvn->C->top(); // Shortcut to top
1564 
1565   // Now walk the current IfNode's projections.
1566   // Loop ends when 'this' has no more uses.
1567   for (DUIterator_Last imin, i = last_outs(imin); i >= imin; --i) {
1568     Node *ifp = last_out(i);     // Get IfTrue/IfFalse
1569     igvn->add_users_to_worklist(ifp);
1570     // Check which projection it is and set target.
1571     // Data-target is either the dominating projection of the same type
1572     // or TOP if the dominating projection is of opposite type.
1573     // Data-target will be used as the new control edge for the non-CFG
1574     // nodes like Casts and Loads.
1575     Node *data_target = (ifp->Opcode() == prev_op) ? prev_dom : top;
1576     // Control-target is just the If's immediate dominator or TOP.
1577     Node *ctrl_target = (ifp->Opcode() == prev_op) ?     idom : top;
1578 
1579     // For each child of an IfTrue/IfFalse projection, reroute.
1580     // Loop ends when projection has no more uses.
1581     for (DUIterator_Last jmin, j = ifp->last_outs(jmin); j >= jmin; --j) {
1582       Node* s = ifp->last_out(j);   // Get child of IfTrue/IfFalse
1583       if (s->depends_only_on_test() && igvn->no_dependent_zero_check(s)) {
1584         // For control producers.
1585         // Do not rewire Div and Mod nodes which could have a zero divisor to avoid skipping their zero check.
1586         igvn->replace_input_of(s, 0, data_target); // Move child to data-target
1587         if (pin_array_access_nodes && data_target != top) {
1588           // As a result of range check smearing, Loads and range check Cast nodes that are control dependent on this
1589           // range check (that is about to be removed) now depend on multiple dominating range checks. After the removal
1590           // of this range check, these control dependent nodes end up at the lowest/nearest dominating check in the
1591           // graph. To ensure that these Loads/Casts do not float above any of the dominating checks (even when the
1592           // lowest dominating check is later replaced by yet another dominating check), we need to pin them at the
1593           // lowest dominating check.
1594           Node* clone = s->pin_array_access_node();
1595           if (clone != nullptr) {
1596             clone = igvn->transform(clone);
1597             igvn->replace_node(s, clone);
1598           }
1599         }
1600       } else {
1601         // Find the control input matching this def-use edge.
1602         // For Regions it may not be in slot 0.
1603         uint l;
1604         for (l = 0; s->in(l) != ifp; l++) { }
1605         igvn->replace_input_of(s, l, ctrl_target);
1606       }
1607     } // End for each child of a projection
1608 
1609     igvn->remove_dead_node(ifp);
1610   } // End for each IfTrue/IfFalse child of If
1611 
1612   // Kill the IfNode
1613   igvn->remove_dead_node(this);
1614 
1615   // Must return either the original node (now dead) or a new node
1616   // (Do not return a top here, since that would break the uniqueness of top.)
1617   return new ConINode(TypeInt::ZERO);
1618 }
1619 
1620 Node* IfNode::search_identical(int dist, PhaseIterGVN* igvn) {
1621   // Setup to scan up the CFG looking for a dominating test
1622   Node* dom = in(0);
1623   Node* prev_dom = this;
1624   int op = Opcode();
1625   // Search up the dominator tree for an If with an identical test
1626   while (dom->Opcode() != op ||  // Not same opcode?
1627          !same_condition(dom, igvn) ||  // Not same input 1?
1628          prev_dom->in(0) != dom) {  // One path of test does not dominate?
1629     if (dist < 0) return nullptr;
1630 
1631     dist--;
1632     prev_dom = dom;
1633     dom = up_one_dom(dom);
1634     if (!dom) return nullptr;
1635   }
1636 
1637   // Check that we did not follow a loop back to ourselves
1638   if (this == dom) {
1639     return nullptr;
1640   }
1641 
1642 #ifndef PRODUCT
1643   if (dist > 2) { // Add to count of null checks elided
1644     explicit_null_checks_elided++;
1645   }
1646 #endif
1647 
1648   return prev_dom;
1649 }
1650 
1651 bool IfNode::same_condition(const Node* dom, PhaseIterGVN* igvn) const {
1652   Node* dom_bool = dom->in(1);
1653   Node* this_bool = in(1);
1654   if (dom_bool == this_bool) {
1655     return true;
1656   }
1657 
1658   if (dom_bool == nullptr || !dom_bool->is_Bool() ||
1659       this_bool == nullptr || !this_bool->is_Bool()) {
1660     return false;
1661   }
1662   Node* dom_cmp = dom_bool->in(1);
1663   Node* this_cmp = this_bool->in(1);
1664 
1665   // If the comparison is a subtype check, then SubTypeCheck nodes may have profile data attached to them and may be
1666   // different nodes even-though they perform the same subtype check
1667   if (dom_cmp == nullptr || !dom_cmp->is_SubTypeCheck() ||
1668       this_cmp == nullptr || !this_cmp->is_SubTypeCheck()) {
1669     return false;
1670   }
1671 
1672   if (dom_cmp->in(1) != this_cmp->in(1) ||
1673       dom_cmp->in(2) != this_cmp->in(2) ||
1674       dom_bool->as_Bool()->_test._test != this_bool->as_Bool()->_test._test) {
1675     return false;
1676   }
1677 
1678   return true;
1679 }
1680 
1681 
1682 static int subsuming_bool_test_encode(Node*);
1683 
1684 // Check if dominating test is subsuming 'this' one.
1685 //
1686 //              cmp
1687 //              / \
1688 //     (r1)  bool  \
1689 //            /    bool (r2)
1690 //    (dom) if       \
1691 //            \       )
1692 //    (pre)  if[TF]  /
1693 //               \  /
1694 //                if (this)
1695 //   \r1
1696 //  r2\  eqT  eqF  neT  neF  ltT  ltF  leT  leF  gtT  gtF  geT  geF
1697 //  eq    t    f    f    t    f    -    -    f    f    -    -    f
1698 //  ne    f    t    t    f    t    -    -    t    t    -    -    t
1699 //  lt    f    -    -    f    t    f    -    f    f    -    f    t
1700 //  le    t    -    -    t    t    -    t    f    f    t    -    t
1701 //  gt    f    -    -    f    f    -    f    t    t    f    -    f
1702 //  ge    t    -    -    t    f    t    -    t    t    -    t    f
1703 //
1704 Node* IfNode::simple_subsuming(PhaseIterGVN* igvn) {
1705   // Table encoding: N/A (na), True-branch (tb), False-branch (fb).
1706   static enum { na, tb, fb } s_short_circuit_map[6][12] = {
1707   /*rel: eq+T eq+F ne+T ne+F lt+T lt+F le+T le+F gt+T gt+F ge+T ge+F*/
1708   /*eq*/{ tb,  fb,  fb,  tb,  fb,  na,  na,  fb,  fb,  na,  na,  fb },
1709   /*ne*/{ fb,  tb,  tb,  fb,  tb,  na,  na,  tb,  tb,  na,  na,  tb },
1710   /*lt*/{ fb,  na,  na,  fb,  tb,  fb,  na,  fb,  fb,  na,  fb,  tb },
1711   /*le*/{ tb,  na,  na,  tb,  tb,  na,  tb,  fb,  fb,  tb,  na,  tb },
1712   /*gt*/{ fb,  na,  na,  fb,  fb,  na,  fb,  tb,  tb,  fb,  na,  fb },
1713   /*ge*/{ tb,  na,  na,  tb,  fb,  tb,  na,  tb,  tb,  na,  tb,  fb }};
1714 
1715   Node* pre = in(0);
1716   if (!pre->is_IfTrue() && !pre->is_IfFalse()) {
1717     return nullptr;
1718   }
1719   Node* dom = pre->in(0);
1720   if (!dom->is_If()) {
1721     return nullptr;
1722   }
1723   Node* bol = in(1);
1724   if (!bol->is_Bool()) {
1725     return nullptr;
1726   }
1727   Node* cmp = in(1)->in(1);
1728   if (!cmp->is_Cmp()) {
1729     return nullptr;
1730   }
1731 
1732   if (!dom->in(1)->is_Bool()) {
1733     return nullptr;
1734   }
1735   if (dom->in(1)->in(1) != cmp) {  // Not same cond?
1736     return nullptr;
1737   }
1738 
1739   int drel = subsuming_bool_test_encode(dom->in(1));
1740   int trel = subsuming_bool_test_encode(bol);
1741   int bout = pre->is_IfFalse() ? 1 : 0;
1742 
1743   if (drel < 0 || trel < 0) {
1744     return nullptr;
1745   }
1746   int br = s_short_circuit_map[trel][2*drel+bout];
1747   if (br == na) {
1748     return nullptr;
1749   }
1750 #ifndef PRODUCT
1751   if (TraceIterativeGVN) {
1752     tty->print("   Subsumed IfNode: "); dump();
1753   }
1754 #endif
1755   // Replace condition with constant True(1)/False(0).
1756   bool is_always_true = br == tb;
1757   set_req(1, igvn->intcon(is_always_true ? 1 : 0));
1758 
1759   // Update any data dependencies to the directly dominating test. This subsumed test is not immediately removed by igvn
1760   // and therefore subsequent optimizations might miss these data dependencies otherwise. There might be a dead loop
1761   // ('always_taken_proj' == 'pre') that is cleaned up later. Skip this case to make the iterator work properly.
1762   Node* always_taken_proj = proj_out(is_always_true);
1763   if (always_taken_proj != pre) {
1764     for (DUIterator_Fast imax, i = always_taken_proj->fast_outs(imax); i < imax; i++) {
1765       Node* u = always_taken_proj->fast_out(i);
1766       if (!u->is_CFG()) {
1767         igvn->replace_input_of(u, 0, pre);
1768         --i;
1769         --imax;
1770       }
1771     }
1772   }
1773 
1774   if (bol->outcnt() == 0) {
1775     igvn->remove_dead_node(bol);    // Kill the BoolNode.
1776   }
1777   return this;
1778 }
1779 
1780 // Map BoolTest to local table encoding. The BoolTest (e)numerals
1781 //   { eq = 0, ne = 4, le = 5, ge = 7, lt = 3, gt = 1 }
1782 // are mapped to table indices, while the remaining (e)numerals in BoolTest
1783 //   { overflow = 2, no_overflow = 6, never = 8, illegal = 9 }
1784 // are ignored (these are not modeled in the table).
1785 //
1786 static int subsuming_bool_test_encode(Node* node) {
1787   precond(node->is_Bool());
1788   BoolTest::mask x = node->as_Bool()->_test._test;
1789   switch (x) {
1790     case BoolTest::eq: return 0;
1791     case BoolTest::ne: return 1;
1792     case BoolTest::lt: return 2;
1793     case BoolTest::le: return 3;
1794     case BoolTest::gt: return 4;
1795     case BoolTest::ge: return 5;
1796     case BoolTest::overflow:
1797     case BoolTest::no_overflow:
1798     case BoolTest::never:
1799     case BoolTest::illegal:
1800     default:
1801       return -1;
1802   }
1803 }
1804 
1805 //------------------------------Identity---------------------------------------
1806 // If the test is constant & we match, then we are the input Control
1807 Node* IfProjNode::Identity(PhaseGVN* phase) {
1808   // Can only optimize if cannot go the other way
1809   const TypeTuple *t = phase->type(in(0))->is_tuple();
1810   if (t == TypeTuple::IFNEITHER || (always_taken(t) &&
1811        // During parsing (GVN) we don't remove dead code aggressively.
1812        // Cut off dead branch and let PhaseRemoveUseless take care of it.
1813       (!phase->is_IterGVN() ||
1814        // During IGVN, first wait for the dead branch to be killed.
1815        // Otherwise, the IfNode's control will have two control uses (the IfNode
1816        // that doesn't go away because it still has uses and this branch of the
1817        // If) which breaks other optimizations. Node::has_special_unique_user()
1818        // will cause this node to be reprocessed once the dead branch is killed.
1819        in(0)->outcnt() == 1))) {
1820     // IfNode control
1821     if (in(0)->is_BaseCountedLoopEnd()) {
1822       // CountedLoopEndNode may be eliminated by if subsuming, replace CountedLoopNode with LoopNode to
1823       // avoid mismatching between CountedLoopNode and CountedLoopEndNode in the following optimization.
1824       Node* head = unique_ctrl_out_or_null();
1825       if (head != nullptr && head->is_BaseCountedLoop() && head->in(LoopNode::LoopBackControl) == this) {
1826         Node* new_head = new LoopNode(head->in(LoopNode::EntryControl), this);
1827         phase->is_IterGVN()->register_new_node_with_optimizer(new_head);
1828         phase->is_IterGVN()->replace_node(head, new_head);
1829       }
1830     }
1831     return in(0)->in(0);
1832   }
1833   // no progress
1834   return this;
1835 }
1836 
1837 bool IfNode::is_zero_trip_guard() const {
1838   if (in(1)->is_Bool() && in(1)->in(1)->is_Cmp()) {
1839     return in(1)->in(1)->in(1)->Opcode() == Op_OpaqueZeroTripGuard;
1840   }
1841   return false;
1842 }
1843 
1844 void IfProjNode::pin_array_access_nodes(PhaseIterGVN* igvn) {
1845   for (DUIterator i = outs(); has_out(i); i++) {
1846     Node* u = out(i);
1847     if (!u->depends_only_on_test()) {
1848       continue;
1849     }
1850     Node* clone = u->pin_array_access_node();
1851     if (clone != nullptr) {
1852       clone = igvn->transform(clone);
1853       assert(clone != u, "shouldn't common");
1854       igvn->replace_node(u, clone);
1855       --i;
1856     }
1857   }
1858 }
1859 
1860 #ifndef PRODUCT
1861 void IfNode::dump_spec(outputStream* st) const {
1862   switch (_assertion_predicate_type) {
1863     case AssertionPredicateType::InitValue:
1864       st->print("#Init Value Assertion Predicate  ");
1865       break;
1866     case AssertionPredicateType::LastValue:
1867       st->print("#Last Value Assertion Predicate  ");
1868       break;
1869     case AssertionPredicateType::None:
1870       // No Assertion Predicate
1871       break;
1872     default:
1873       fatal("Unknown Assertion Predicate type");
1874   }
1875   st->print("P=%f, C=%f", _prob, _fcnt);
1876 }
1877 #endif // NOT PRODUCT
1878 
1879 //------------------------------idealize_test----------------------------------
1880 // Try to canonicalize tests better.  Peek at the Cmp/Bool/If sequence and
1881 // come up with a canonical sequence.  Bools getting 'eq', 'gt' and 'ge' forms
1882 // converted to 'ne', 'le' and 'lt' forms.  IfTrue/IfFalse get swapped as
1883 // needed.
1884 static IfNode* idealize_test(PhaseGVN* phase, IfNode* iff) {
1885   assert(iff->in(0) != nullptr, "If must be live");
1886 
1887   if (iff->outcnt() != 2)  return nullptr; // Malformed projections.
1888   Node* old_if_f = iff->proj_out(false);
1889   Node* old_if_t = iff->proj_out(true);
1890 
1891   // CountedLoopEnds want the back-control test to be TRUE, regardless of
1892   // whether they are testing a 'gt' or 'lt' condition.  The 'gt' condition
1893   // happens in count-down loops
1894   if (iff->is_BaseCountedLoopEnd())  return nullptr;
1895   if (!iff->in(1)->is_Bool())  return nullptr; // Happens for partially optimized IF tests
1896   BoolNode *b = iff->in(1)->as_Bool();
1897   BoolTest bt = b->_test;
1898   // Test already in good order?
1899   if( bt.is_canonical() )
1900     return nullptr;
1901 
1902   // Flip test to be canonical.  Requires flipping the IfFalse/IfTrue and
1903   // cloning the IfNode.
1904   Node* new_b = phase->transform( new BoolNode(b->in(1), bt.negate()) );
1905   if( !new_b->is_Bool() ) return nullptr;
1906   b = new_b->as_Bool();
1907 
1908   PhaseIterGVN *igvn = phase->is_IterGVN();
1909   assert( igvn, "Test is not canonical in parser?" );
1910 
1911   // The IF node never really changes, but it needs to be cloned
1912   iff = iff->clone()->as_If();
1913   iff->set_req(1, b);
1914   iff->_prob = 1.0-iff->_prob;
1915 
1916   Node *prior = igvn->hash_find_insert(iff);
1917   if( prior ) {
1918     igvn->remove_dead_node(iff);
1919     iff = (IfNode*)prior;
1920   } else {
1921     // Cannot call transform on it just yet
1922     igvn->set_type_bottom(iff);
1923   }
1924   igvn->_worklist.push(iff);
1925 
1926   // Now handle projections.  Cloning not required.
1927   Node* new_if_f = (Node*)(new IfFalseNode( iff ));
1928   Node* new_if_t = (Node*)(new IfTrueNode ( iff ));
1929 
1930   igvn->register_new_node_with_optimizer(new_if_f);
1931   igvn->register_new_node_with_optimizer(new_if_t);
1932   // Flip test, so flip trailing control
1933   igvn->replace_node(old_if_f, new_if_t);
1934   igvn->replace_node(old_if_t, new_if_f);
1935 
1936   // Progress
1937   return iff;
1938 }
1939 
1940 Node* RangeCheckNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1941   Node* res = Ideal_common(phase, can_reshape);
1942   if (res != NodeSentinel) {
1943     return res;
1944   }
1945 
1946   PhaseIterGVN *igvn = phase->is_IterGVN();
1947   // Setup to scan up the CFG looking for a dominating test
1948   Node* prev_dom = this;
1949 
1950   // Check for range-check vs other kinds of tests
1951   Node* index1;
1952   Node* range1;
1953   jint offset1;
1954   int flip1 = is_range_check(range1, index1, offset1);
1955   if (flip1) {
1956     Node* dom = in(0);
1957     // Try to remove extra range checks.  All 'up_one_dom' gives up at merges
1958     // so all checks we inspect post-dominate the top-most check we find.
1959     // If we are going to fail the current check and we reach the top check
1960     // then we are guaranteed to fail, so just start interpreting there.
1961     // We 'expand' the top 3 range checks to include all post-dominating
1962     // checks.
1963     //
1964     // Example:
1965     // a[i+x] // (1) 1 < x < 6
1966     // a[i+3] // (2)
1967     // a[i+4] // (3)
1968     // a[i+6] // max = max of all constants
1969     // a[i+2]
1970     // a[i+1] // min = min of all constants
1971     //
1972     // If x < 3:
1973     //   (1) a[i+x]: Leave unchanged
1974     //   (2) a[i+3]: Replace with a[i+max] = a[i+6]: i+x < i+3 <= i+6  -> (2) is covered
1975     //   (3) a[i+4]: Replace with a[i+min] = a[i+1]: i+1 < i+4 <= i+6  -> (3) and all following checks are covered
1976     //   Remove all other a[i+c] checks
1977     //
1978     // If x >= 3:
1979     //   (1) a[i+x]: Leave unchanged
1980     //   (2) a[i+3]: Replace with a[i+min] = a[i+1]: i+1 < i+3 <= i+x  -> (2) is covered
1981     //   (3) a[i+4]: Replace with a[i+max] = a[i+6]: i+1 < i+4 <= i+6  -> (3) and all following checks are covered
1982     //   Remove all other a[i+c] checks
1983     //
1984     // We only need the top 2 range checks if x is the min or max of all constants.
1985     //
1986     // This, however, only works if the interval [i+min,i+max] is not larger than max_int (i.e. abs(max - min) < max_int):
1987     // The theoretical max size of an array is max_int with:
1988     // - Valid index space: [0,max_int-1]
1989     // - Invalid index space: [max_int,-1] // max_int, min_int, min_int - 1 ..., -1
1990     //
1991     // The size of the consecutive valid index space is smaller than the size of the consecutive invalid index space.
1992     // If we choose min and max in such a way that:
1993     // - abs(max - min) < max_int
1994     // - i+max and i+min are inside the valid index space
1995     // then all indices [i+min,i+max] must be in the valid index space. Otherwise, the invalid index space must be
1996     // smaller than the valid index space which is never the case for any array size.
1997     //
1998     // Choosing a smaller array size only makes the valid index space smaller and the invalid index space larger and
1999     // the argument above still holds.
2000     //
2001     // Note that the same optimization with the same maximal accepted interval size can also be found in C1.
2002     const jlong maximum_number_of_min_max_interval_indices = (jlong)max_jint;
2003 
2004     // The top 3 range checks seen
2005     const int NRC = 3;
2006     RangeCheck prev_checks[NRC];
2007     int nb_checks = 0;
2008 
2009     // Low and high offsets seen so far
2010     jint off_lo = offset1;
2011     jint off_hi = offset1;
2012 
2013     bool found_immediate_dominator = false;
2014 
2015     // Scan for the top checks and collect range of offsets
2016     for (int dist = 0; dist < 999; dist++) { // Range-Check scan limit
2017       if (dom->Opcode() == Op_RangeCheck &&  // Not same opcode?
2018           prev_dom->in(0) == dom) { // One path of test does dominate?
2019         if (dom == this) return nullptr; // dead loop
2020         // See if this is a range check
2021         Node* index2;
2022         Node* range2;
2023         jint offset2;
2024         int flip2 = dom->as_RangeCheck()->is_range_check(range2, index2, offset2);
2025         // See if this is a _matching_ range check, checking against
2026         // the same array bounds.
2027         if (flip2 == flip1 && range2 == range1 && index2 == index1 &&
2028             dom->outcnt() == 2) {
2029           if (nb_checks == 0 && dom->in(1) == in(1)) {
2030             // Found an immediately dominating test at the same offset.
2031             // This kind of back-to-back test can be eliminated locally,
2032             // and there is no need to search further for dominating tests.
2033             assert(offset2 == offset1, "Same test but different offsets");
2034             found_immediate_dominator = true;
2035             break;
2036           }
2037 
2038           // "x - y" -> must add one to the difference for number of elements in [x,y]
2039           const jlong diff = (jlong)MIN2(offset2, off_lo) - (jlong)MAX2(offset2, off_hi);
2040           if (ABS(diff) < maximum_number_of_min_max_interval_indices) {
2041             // Gather expanded bounds
2042             off_lo = MIN2(off_lo, offset2);
2043             off_hi = MAX2(off_hi, offset2);
2044             // Record top NRC range checks
2045             prev_checks[nb_checks % NRC].ctl = prev_dom->as_IfProj();
2046             prev_checks[nb_checks % NRC].off = offset2;
2047             nb_checks++;
2048           }
2049         }
2050       }
2051       prev_dom = dom;
2052       dom = up_one_dom(dom);
2053       if (!dom) break;
2054     }
2055 
2056     if (!found_immediate_dominator) {
2057       // Attempt to widen the dominating range check to cover some later
2058       // ones.  Since range checks "fail" by uncommon-trapping to the
2059       // interpreter, widening a check can make us speculatively enter
2060       // the interpreter.  If we see range-check deopt's, do not widen!
2061       if (!phase->C->allow_range_check_smearing())  return nullptr;
2062 
2063       if (can_reshape && !phase->C->post_loop_opts_phase()) {
2064         // We are about to perform range check smearing (i.e. remove this RangeCheck if it is dominated by
2065         // a series of RangeChecks which have a range that covers this RangeCheck). This can cause array access nodes to
2066         // be pinned. We want to avoid that and first allow range check elimination a chance to remove the RangeChecks
2067         // from loops. Hence, we delay range check smearing until after loop opts.
2068         phase->C->record_for_post_loop_opts_igvn(this);
2069         return nullptr;
2070       }
2071 
2072       // Didn't find prior covering check, so cannot remove anything.
2073       if (nb_checks == 0) {
2074         return nullptr;
2075       }
2076       // Constant indices only need to check the upper bound.
2077       // Non-constant indices must check both low and high.
2078       int chk0 = (nb_checks - 1) % NRC;
2079       if (index1) {
2080         if (nb_checks == 1) {
2081           return nullptr;
2082         } else {
2083           // If the top range check's constant is the min or max of
2084           // all constants we widen the next one to cover the whole
2085           // range of constants.
2086           RangeCheck rc0 = prev_checks[chk0];
2087           int chk1 = (nb_checks - 2) % NRC;
2088           RangeCheck rc1 = prev_checks[chk1];
2089           if (rc0.off == off_lo) {
2090             adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
2091             prev_dom = rc1.ctl;
2092           } else if (rc0.off == off_hi) {
2093             adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
2094             prev_dom = rc1.ctl;
2095           } else {
2096             // If the top test's constant is not the min or max of all
2097             // constants, we need 3 range checks. We must leave the
2098             // top test unchanged because widening it would allow the
2099             // accesses it protects to successfully read/write out of
2100             // bounds.
2101             if (nb_checks == 2) {
2102               return nullptr;
2103             }
2104             int chk2 = (nb_checks - 3) % NRC;
2105             RangeCheck rc2 = prev_checks[chk2];
2106             // The top range check a+i covers interval: -a <= i < length-a
2107             // The second range check b+i covers interval: -b <= i < length-b
2108             if (rc1.off <= rc0.off) {
2109               // if b <= a, we change the second range check to:
2110               // -min_of_all_constants <= i < length-min_of_all_constants
2111               // Together top and second range checks now cover:
2112               // -min_of_all_constants <= i < length-a
2113               // which is more restrictive than -b <= i < length-b:
2114               // -b <= -min_of_all_constants <= i < length-a <= length-b
2115               // The third check is then changed to:
2116               // -max_of_all_constants <= i < length-max_of_all_constants
2117               // so 2nd and 3rd checks restrict allowed values of i to:
2118               // -min_of_all_constants <= i < length-max_of_all_constants
2119               adjust_check(rc1.ctl, range1, index1, flip1, off_lo, igvn);
2120               adjust_check(rc2.ctl, range1, index1, flip1, off_hi, igvn);
2121             } else {
2122               // if b > a, we change the second range check to:
2123               // -max_of_all_constants <= i < length-max_of_all_constants
2124               // Together top and second range checks now cover:
2125               // -a <= i < length-max_of_all_constants
2126               // which is more restrictive than -b <= i < length-b:
2127               // -b < -a <= i < length-max_of_all_constants <= length-b
2128               // The third check is then changed to:
2129               // -max_of_all_constants <= i < length-max_of_all_constants
2130               // so 2nd and 3rd checks restrict allowed values of i to:
2131               // -min_of_all_constants <= i < length-max_of_all_constants
2132               adjust_check(rc1.ctl, range1, index1, flip1, off_hi, igvn);
2133               adjust_check(rc2.ctl, range1, index1, flip1, off_lo, igvn);
2134             }
2135             prev_dom = rc2.ctl;
2136           }
2137         }
2138       } else {
2139         RangeCheck rc0 = prev_checks[chk0];
2140         // 'Widen' the offset of the 1st and only covering check
2141         adjust_check(rc0.ctl, range1, index1, flip1, off_hi, igvn);
2142         // Test is now covered by prior checks, dominate it out
2143         prev_dom = rc0.ctl;
2144       }
2145       // The last RangeCheck is found to be redundant with a sequence of n (n >= 2) preceding RangeChecks.
2146       // If an array load is control dependent on the eliminated range check, the array load nodes (CastII and Load)
2147       // become control dependent on the last range check of the sequence, but they are really dependent on the entire
2148       // sequence of RangeChecks. If RangeCheck#n is later replaced by a dominating identical check, the array load
2149       // nodes must not float above the n-1 other RangeCheck in the sequence. We pin the array load nodes here to
2150       // guarantee it doesn't happen.
2151       //
2152       // RangeCheck#1                 RangeCheck#1
2153       //    |      \                     |      \
2154       //    |      uncommon trap         |      uncommon trap
2155       //    ..                           ..
2156       // RangeCheck#n              -> RangeCheck#n
2157       //    |      \                     |      \
2158       //    |      uncommon trap        CastII  uncommon trap
2159       // RangeCheck                     Load
2160       //    |      \
2161       //   CastII  uncommon trap
2162       //   Load
2163 
2164       return dominated_by(prev_dom, igvn, true);
2165     }
2166   } else {
2167     prev_dom = search_identical(4, igvn);
2168 
2169     if (prev_dom == nullptr) {
2170       return nullptr;
2171     }
2172   }
2173 
2174   // Replace dominated IfNode
2175   return dominated_by(prev_dom, igvn, false);
2176 }
2177 
2178 ParsePredicateNode::ParsePredicateNode(Node* control, Deoptimization::DeoptReason deopt_reason, PhaseGVN* gvn)
2179     : IfNode(control, gvn->intcon(1), PROB_MAX, COUNT_UNKNOWN),
2180       _deopt_reason(deopt_reason),
2181       _useless(false) {
2182   init_class_id(Class_ParsePredicate);
2183   gvn->C->add_parse_predicate(this);
2184   gvn->C->record_for_post_loop_opts_igvn(this);
2185 #ifdef ASSERT
2186   switch (deopt_reason) {
2187     case Deoptimization::Reason_predicate:
2188     case Deoptimization::Reason_profile_predicate:
2189     case Deoptimization::Reason_loop_limit_check:
2190       break;
2191     default:
2192       assert(false, "unsupported deoptimization reason for Parse Predicate");
2193   }
2194 #endif // ASSERT
2195 }
2196 
2197 Node* ParsePredicateNode::uncommon_trap() const {
2198   ParsePredicateUncommonProj* uncommon_proj = proj_out(0)->as_IfFalse();
2199   Node* uct_region_or_call = uncommon_proj->unique_ctrl_out();
2200   assert(uct_region_or_call->is_Region() || uct_region_or_call->is_Call(), "must be a region or call uct");
2201   return uct_region_or_call;
2202 }
2203 
2204 // Fold this node away once it becomes useless or at latest in post loop opts IGVN.
2205 const Type* ParsePredicateNode::Value(PhaseGVN* phase) const {
2206   if (phase->type(in(0)) == Type::TOP) {
2207     return Type::TOP;
2208   }
2209   if (_useless || phase->C->post_loop_opts_phase()) {
2210     return TypeTuple::IFTRUE;
2211   } else {
2212     return bottom_type();
2213   }
2214 }
2215 
2216 #ifndef PRODUCT
2217 void ParsePredicateNode::dump_spec(outputStream* st) const {
2218   st->print(" #");
2219   switch (_deopt_reason) {
2220     case Deoptimization::DeoptReason::Reason_predicate:
2221       st->print("Loop ");
2222       break;
2223     case Deoptimization::DeoptReason::Reason_profile_predicate:
2224       st->print("Profiled_Loop ");
2225       break;
2226     case Deoptimization::DeoptReason::Reason_loop_limit_check:
2227       st->print("Loop_Limit_Check ");
2228       break;
2229     default:
2230       fatal("unknown kind");
2231   }
2232   if (_useless) {
2233     st->print("#useless ");
2234   }
2235 }
2236 #endif // NOT PRODUCT