1 /*
   2  * Copyright (c) 1999, 2025, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "gc/shared/barrierSet.hpp"
  26 #include "gc/shared/c2/barrierSetC2.hpp"
  27 #include "memory/allocation.inline.hpp"
  28 #include "memory/resourceArea.hpp"
  29 #include "opto/addnode.hpp"
  30 #include "opto/callnode.hpp"
  31 #include "opto/castnode.hpp"
  32 #include "opto/connode.hpp"
  33 #include "opto/divnode.hpp"
  34 #include "opto/inlinetypenode.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/matcher.hpp"
  37 #include "opto/movenode.hpp"
  38 #include "opto/mulnode.hpp"
  39 #include "opto/opaquenode.hpp"
  40 #include "opto/rootnode.hpp"
  41 #include "opto/subnode.hpp"
  42 #include "opto/subtypenode.hpp"
  43 #include "opto/superword.hpp"
  44 #include "opto/vectornode.hpp"
  45 #include "utilities/checkedCast.hpp"
  46 #include "utilities/macros.hpp"
  47 
  48 //=============================================================================
  49 //------------------------------split_thru_phi---------------------------------
  50 // Split Node 'n' through merge point if there is enough win.
  51 Node* PhaseIdealLoop::split_thru_phi(Node* n, Node* region, int policy) {
  52   if ((n->Opcode() == Op_ConvI2L && n->bottom_type() != TypeLong::LONG) ||
  53       (n->Opcode() == Op_ConvL2I && n->bottom_type() != TypeInt::INT)) {
  54     // ConvI2L/ConvL2I may have type information on it which is unsafe to push up
  55     // so disable this for now
  56     return nullptr;
  57   }
  58 
  59   // Splitting range check CastIIs through a loop induction Phi can
  60   // cause new Phis to be created that are left unrelated to the loop
  61   // induction Phi and prevent optimizations (vectorization)
  62   if (n->Opcode() == Op_CastII && region->is_CountedLoop() &&
  63       n->in(1) == region->as_CountedLoop()->phi()) {
  64     return nullptr;
  65   }
  66 
  67   // Inline types should not be split through Phis because they cannot be merged
  68   // through Phi nodes but each value input needs to be merged individually.
  69   if (n->is_InlineType()) {
  70     return nullptr;
  71   }
  72 
  73   if (cannot_split_division(n, region)) {
  74     return nullptr;
  75   }
  76 
  77   SplitThruPhiWins wins(region);
  78   assert(!n->is_CFG(), "");
  79   assert(region->is_Region(), "");
  80 
  81   const Type* type = n->bottom_type();
  82   const TypeOopPtr* t_oop = _igvn.type(n)->isa_oopptr();
  83   Node* phi;
  84   if (t_oop != nullptr && t_oop->is_known_instance_field()) {
  85     int iid    = t_oop->instance_id();
  86     int index  = C->get_alias_index(t_oop);
  87     int offset = t_oop->offset();
  88     phi = new PhiNode(region, type, nullptr, iid, index, offset);
  89   } else {
  90     phi = PhiNode::make_blank(region, n);
  91   }
  92   uint old_unique = C->unique();
  93   for (uint i = 1; i < region->req(); i++) {
  94     Node* x;
  95     Node* the_clone = nullptr;
  96     if (region->in(i) == C->top()) {
  97       x = C->top();             // Dead path?  Use a dead data op
  98     } else {
  99       x = n->clone();           // Else clone up the data op
 100       the_clone = x;            // Remember for possible deletion.
 101       // Alter data node to use pre-phi inputs
 102       if (n->in(0) == region)
 103         x->set_req( 0, region->in(i) );
 104       for (uint j = 1; j < n->req(); j++) {
 105         Node* in = n->in(j);
 106         if (in->is_Phi() && in->in(0) == region)
 107           x->set_req(j, in->in(i)); // Use pre-Phi input for the clone
 108       }
 109     }
 110     // Check for a 'win' on some paths
 111     const Type* t = x->Value(&_igvn);
 112 
 113     bool singleton = t->singleton();
 114 
 115     // A TOP singleton indicates that there are no possible values incoming
 116     // along a particular edge. In most cases, this is OK, and the Phi will
 117     // be eliminated later in an Ideal call. However, we can't allow this to
 118     // happen if the singleton occurs on loop entry, as the elimination of
 119     // the PhiNode may cause the resulting node to migrate back to a previous
 120     // loop iteration.
 121     if (singleton && t == Type::TOP) {
 122       // Is_Loop() == false does not confirm the absence of a loop (e.g., an
 123       // irreducible loop may not be indicated by an affirmative is_Loop());
 124       // therefore, the only top we can split thru a phi is on a backedge of
 125       // a loop.
 126       singleton &= region->is_Loop() && (i != LoopNode::EntryControl);
 127     }
 128 
 129     if (singleton) {
 130       wins.add_win(i);
 131       x = makecon(t);
 132     } else {
 133       // We now call Identity to try to simplify the cloned node.
 134       // Note that some Identity methods call phase->type(this).
 135       // Make sure that the type array is big enough for
 136       // our new node, even though we may throw the node away.
 137       // (Note: This tweaking with igvn only works because x is a new node.)
 138       _igvn.set_type(x, t);
 139       // If x is a TypeNode, capture any more-precise type permanently into Node
 140       // otherwise it will be not updated during igvn->transform since
 141       // igvn->type(x) is set to x->Value() already.
 142       x->raise_bottom_type(t);
 143       Node* y = x->Identity(&_igvn);
 144       if (y != x) {
 145         wins.add_win(i);
 146         x = y;
 147       } else {
 148         y = _igvn.hash_find(x);
 149         if (y == nullptr) {
 150           y = similar_subtype_check(x, region->in(i));
 151         }
 152         if (y) {
 153           wins.add_win(i);
 154           x = y;
 155         } else {
 156           // Else x is a new node we are keeping
 157           // We do not need register_new_node_with_optimizer
 158           // because set_type has already been called.
 159           _igvn._worklist.push(x);
 160         }
 161       }
 162     }
 163 
 164     phi->set_req( i, x );
 165 
 166     if (the_clone == nullptr) {
 167       continue;
 168     }
 169 
 170     if (the_clone != x) {
 171       _igvn.remove_dead_node(the_clone);
 172     } else if (region->is_Loop() && i == LoopNode::LoopBackControl &&
 173                n->is_Load() && can_move_to_inner_loop(n, region->as_Loop(), x)) {
 174       // it is not a win if 'x' moved from an outer to an inner loop
 175       // this edge case can only happen for Load nodes
 176       wins.reset();
 177       break;
 178     }
 179   }
 180   // Too few wins?
 181   if (!wins.profitable(policy)) {
 182     _igvn.remove_dead_node(phi);
 183     return nullptr;
 184   }
 185 
 186   // Record Phi
 187   register_new_node( phi, region );
 188 
 189   for (uint i2 = 1; i2 < phi->req(); i2++) {
 190     Node *x = phi->in(i2);
 191     // If we commoned up the cloned 'x' with another existing Node,
 192     // the existing Node picks up a new use.  We need to make the
 193     // existing Node occur higher up so it dominates its uses.
 194     Node *old_ctrl;
 195     IdealLoopTree *old_loop;
 196 
 197     if (x->is_Con()) {
 198       assert(get_ctrl(x) == C->root(), "constant control is not root");
 199       continue;
 200     }
 201     // The occasional new node
 202     if (x->_idx >= old_unique) {     // Found a new, unplaced node?
 203       old_ctrl = nullptr;
 204       old_loop = nullptr;               // Not in any prior loop
 205     } else {
 206       old_ctrl = get_ctrl(x);
 207       old_loop = get_loop(old_ctrl); // Get prior loop
 208     }
 209     // New late point must dominate new use
 210     Node *new_ctrl = dom_lca(old_ctrl, region->in(i2));
 211     if (new_ctrl == old_ctrl) // Nothing is changed
 212       continue;
 213 
 214     IdealLoopTree *new_loop = get_loop(new_ctrl);
 215 
 216     // Don't move x into a loop if its uses are
 217     // outside of loop. Otherwise x will be cloned
 218     // for each use outside of this loop.
 219     IdealLoopTree *use_loop = get_loop(region);
 220     if (!new_loop->is_member(use_loop) &&
 221         (old_loop == nullptr || !new_loop->is_member(old_loop))) {
 222       // Take early control, later control will be recalculated
 223       // during next iteration of loop optimizations.
 224       new_ctrl = get_early_ctrl(x);
 225       new_loop = get_loop(new_ctrl);
 226     }
 227     // Set new location
 228     set_ctrl(x, new_ctrl);
 229     // If changing loop bodies, see if we need to collect into new body
 230     if (old_loop != new_loop) {
 231       if (old_loop && !old_loop->_child)
 232         old_loop->_body.yank(x);
 233       if (!new_loop->_child)
 234         new_loop->_body.push(x);  // Collect body info
 235     }
 236   }
 237 
 238   split_thru_phi_yank_old_nodes(n, region);
 239   _igvn.replace_node(n, phi);
 240 
 241 #ifndef PRODUCT
 242   if (TraceLoopOpts) {
 243     tty->print_cr("Split %d %s through %d Phi in %d %s",
 244                   n->_idx, n->Name(), phi->_idx, region->_idx, region->Name());
 245   }
 246 #endif // !PRODUCT
 247 
 248   return phi;
 249 }
 250 
 251 // If the region is a Loop, we are removing the old n,
 252 // and need to yank it from the _body. If any phi we
 253 // just split through now has no use any more, it also
 254 // has to be removed.
 255 void PhaseIdealLoop::split_thru_phi_yank_old_nodes(Node* n, Node* region) {
 256   IdealLoopTree* region_loop = get_loop(region);
 257   if (region->is_Loop() && region_loop->is_innermost()) {
 258     region_loop->_body.yank(n);
 259     for (uint j = 1; j < n->req(); j++) {
 260       PhiNode* phi = n->in(j)->isa_Phi();
 261       // Check that phi belongs to the region and only has n as a use.
 262       if (phi != nullptr &&
 263           phi->in(0) == region &&
 264           phi->unique_multiple_edges_out_or_null() == n) {
 265         assert(get_ctrl(phi) == region, "sanity");
 266         assert(get_ctrl(n) == region, "sanity");
 267         region_loop->_body.yank(phi);
 268       }
 269     }
 270   }
 271 }
 272 
 273 // Test whether node 'x' can move into an inner loop relative to node 'n'.
 274 // Note: The test is not exact. Returns true if 'x' COULD end up in an inner loop,
 275 // BUT it can also return true and 'x' is in the outer loop
 276 bool PhaseIdealLoop::can_move_to_inner_loop(Node* n, LoopNode* n_loop, Node* x) {
 277   IdealLoopTree* n_loop_tree = get_loop(n_loop);
 278   IdealLoopTree* x_loop_tree = get_loop(get_early_ctrl(x));
 279   // x_loop_tree should be outer or same loop as n_loop_tree
 280   return !x_loop_tree->is_member(n_loop_tree);
 281 }
 282 
 283 // Subtype checks that carry profile data don't common so look for a replacement by following edges
 284 Node* PhaseIdealLoop::similar_subtype_check(const Node* x, Node* r_in) {
 285   if (x->is_SubTypeCheck()) {
 286     Node* in1 = x->in(1);
 287     for (DUIterator_Fast imax, i = in1->fast_outs(imax); i < imax; i++) {
 288       Node* u = in1->fast_out(i);
 289       if (u != x && u->is_SubTypeCheck() && u->in(1) == x->in(1) && u->in(2) == x->in(2)) {
 290         for (DUIterator_Fast jmax, j = u->fast_outs(jmax); j < jmax; j++) {
 291           Node* bol = u->fast_out(j);
 292           for (DUIterator_Fast kmax, k = bol->fast_outs(kmax); k < kmax; k++) {
 293             Node* iff = bol->fast_out(k);
 294             // Only dominating subtype checks are interesting: otherwise we risk replacing a subtype check by another with
 295             // unrelated profile
 296             if (iff->is_If() && is_dominator(iff, r_in)) {
 297               return u;
 298             }
 299           }
 300         }
 301       }
 302     }
 303   }
 304   return nullptr;
 305 }
 306 
 307 // Return true if 'n' is a Div or Mod node (without zero check If node which was removed earlier) with a loop phi divisor
 308 // of a trip-counted (integer or long) loop with a backedge input that could be zero (include zero in its type range). In
 309 // this case, we cannot split the division to the backedge as it could freely float above the loop exit check resulting in
 310 // a division by zero. This situation is possible because the type of an increment node of an iv phi (trip-counter) could
 311 // include zero while the iv phi does not (see PhiNode::Value() for trip-counted loops where we improve types of iv phis).
 312 // We also need to check other loop phis as they could have been created in the same split-if pass when applying
 313 // PhaseIdealLoop::split_thru_phi() to split nodes through an iv phi.
 314 bool PhaseIdealLoop::cannot_split_division(const Node* n, const Node* region) const {
 315   const Type* zero;
 316   switch (n->Opcode()) {
 317     case Op_DivI:
 318     case Op_ModI:
 319     case Op_UDivI:
 320     case Op_UModI:
 321       zero = TypeInt::ZERO;
 322       break;
 323     case Op_DivL:
 324     case Op_ModL:
 325     case Op_UDivL:
 326     case Op_UModL:
 327       zero = TypeLong::ZERO;
 328       break;
 329     default:
 330       return false;
 331   }
 332 
 333   if (n->in(0) != nullptr) {
 334     // Cannot split through phi if Div or Mod node has a control dependency to a zero check.
 335     return true;
 336   }
 337 
 338   Node* divisor = n->in(2);
 339   return is_divisor_loop_phi(divisor, region) &&
 340          loop_phi_backedge_type_contains_zero(divisor, zero);
 341 }
 342 
 343 bool PhaseIdealLoop::is_divisor_loop_phi(const Node* divisor, const Node* loop) {
 344   return loop->is_Loop() && divisor->is_Phi() && divisor->in(0) == loop;
 345 }
 346 
 347 bool PhaseIdealLoop::loop_phi_backedge_type_contains_zero(const Node* phi_divisor, const Type* zero) const {
 348     return _igvn.type(phi_divisor->in(LoopNode::LoopBackControl))->filter_speculative(zero) != Type::TOP;
 349 }
 350 
 351 //------------------------------dominated_by------------------------------------
 352 // Replace the dominated test with an obvious true or false.  Place it on the
 353 // IGVN worklist for later cleanup.  Move control-dependent data Nodes on the
 354 // live path up to the dominating control.
 355 void PhaseIdealLoop::dominated_by(IfProjNode* prevdom, IfNode* iff, bool flip, bool pin_array_access_nodes) {
 356   if (VerifyLoopOptimizations && PrintOpto) { tty->print_cr("dominating test"); }
 357 
 358   // prevdom is the dominating projection of the dominating test.
 359   assert(iff->Opcode() == Op_If ||
 360          iff->Opcode() == Op_CountedLoopEnd ||
 361          iff->Opcode() == Op_LongCountedLoopEnd ||
 362          iff->Opcode() == Op_RangeCheck ||
 363          iff->Opcode() == Op_ParsePredicate,
 364         "Check this code when new subtype is added");
 365 
 366   int pop = prevdom->Opcode();
 367   assert( pop == Op_IfFalse || pop == Op_IfTrue, "" );
 368   if (flip) {
 369     if (pop == Op_IfTrue)
 370       pop = Op_IfFalse;
 371     else
 372       pop = Op_IfTrue;
 373   }
 374   // 'con' is set to true or false to kill the dominated test.
 375   Node* con = makecon(pop == Op_IfTrue ? TypeInt::ONE : TypeInt::ZERO);
 376   // Hack the dominated test
 377   _igvn.replace_input_of(iff, 1, con);
 378 
 379   // If I don't have a reachable TRUE and FALSE path following the IfNode then
 380   // I can assume this path reaches an infinite loop.  In this case it's not
 381   // important to optimize the data Nodes - either the whole compilation will
 382   // be tossed or this path (and all data Nodes) will go dead.
 383   if (iff->outcnt() != 2) {
 384     return;
 385   }
 386 
 387   // Make control-dependent data Nodes on the live path (path that will remain
 388   // once the dominated IF is removed) become control-dependent on the
 389   // dominating projection.
 390   Node* dp = iff->proj_out_or_null(pop == Op_IfTrue);
 391 
 392   if (dp == nullptr) {
 393     return;
 394   }
 395 
 396   rewire_safe_outputs_to_dominator(dp, prevdom, pin_array_access_nodes);
 397 }
 398 
 399 void PhaseIdealLoop::rewire_safe_outputs_to_dominator(Node* source, Node* dominator, const bool pin_array_access_nodes) {
 400   IdealLoopTree* old_loop = get_loop(source);
 401 
 402   for (DUIterator_Fast imax, i = source->fast_outs(imax); i < imax; i++) {
 403     Node* out = source->fast_out(i); // Control-dependent node
 404     // Do not rewire Div and Mod nodes which could have a zero divisor to avoid skipping their zero check.
 405     if (out->depends_only_on_test() && _igvn.no_dependent_zero_check(out)) {
 406       assert(out->in(0) == source, "must be control dependent on source");
 407       _igvn.replace_input_of(out, 0, dominator);
 408       if (pin_array_access_nodes) {
 409         // Because of Loop Predication, Loads and range check Cast nodes that are control dependent on this range
 410         // check (that is about to be removed) now depend on multiple dominating Hoisted Check Predicates. After the
 411         // removal of this range check, these control dependent nodes end up at the lowest/nearest dominating predicate
 412         // in the graph. To ensure that these Loads/Casts do not float above any of the dominating checks (even when the
 413         // lowest dominating check is later replaced by yet another dominating check), we need to pin them at the lowest
 414         // dominating check.
 415         Node* clone = out->pin_array_access_node();
 416         if (clone != nullptr) {
 417           clone = _igvn.register_new_node_with_optimizer(clone, out);
 418           _igvn.replace_node(out, clone);
 419           out = clone;
 420         }
 421       }
 422       set_early_ctrl(out, false);
 423       IdealLoopTree* new_loop = get_loop(get_ctrl(out));
 424       if (old_loop != new_loop) {
 425         if (!old_loop->_child) {
 426           old_loop->_body.yank(out);
 427         }
 428         if (!new_loop->_child) {
 429           new_loop->_body.push(out);
 430         }
 431       }
 432       --i;
 433       --imax;
 434     }
 435   }
 436 }
 437 
 438 //------------------------------has_local_phi_input----------------------------
 439 // Return TRUE if 'n' has Phi inputs from its local block and no other
 440 // block-local inputs (all non-local-phi inputs come from earlier blocks)
 441 Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
 442   Node *n_ctrl = get_ctrl(n);
 443   // See if some inputs come from a Phi in this block, or from before
 444   // this block.
 445   uint i;
 446   for( i = 1; i < n->req(); i++ ) {
 447     Node *phi = n->in(i);
 448     if( phi->is_Phi() && phi->in(0) == n_ctrl )
 449       break;
 450   }
 451   if( i >= n->req() )
 452     return nullptr;                // No Phi inputs; nowhere to clone thru
 453 
 454   // Check for inputs created between 'n' and the Phi input.  These
 455   // must split as well; they have already been given the chance
 456   // (courtesy of a post-order visit) and since they did not we must
 457   // recover the 'cost' of splitting them by being very profitable
 458   // when splitting 'n'.  Since this is unlikely we simply give up.
 459   for( i = 1; i < n->req(); i++ ) {
 460     Node *m = n->in(i);
 461     if( get_ctrl(m) == n_ctrl && !m->is_Phi() ) {
 462       // We allow the special case of AddP's with no local inputs.
 463       // This allows us to split-up address expressions.
 464       if (m->is_AddP() &&
 465           get_ctrl(m->in(AddPNode::Base)) != n_ctrl &&
 466           get_ctrl(m->in(AddPNode::Address)) != n_ctrl &&
 467           get_ctrl(m->in(AddPNode::Offset)) != n_ctrl) {
 468         // Move the AddP up to the dominating point. That's fine because control of m's inputs
 469         // must dominate get_ctrl(m) == n_ctrl and we just checked that the input controls are != n_ctrl.
 470         Node* c = find_non_split_ctrl(idom(n_ctrl));
 471         if (c->is_OuterStripMinedLoop()) {
 472           c->as_Loop()->verify_strip_mined(1);
 473           c = c->in(LoopNode::EntryControl);
 474         }
 475         set_ctrl_and_loop(m, c);
 476         continue;
 477       }
 478       return nullptr;
 479     }
 480     assert(n->is_Phi() || m->is_Phi() || is_dominator(get_ctrl(m), n_ctrl), "m has strange control");
 481   }
 482 
 483   return n_ctrl;
 484 }
 485 
 486 // Replace expressions like ((V+I) << 2) with (V<<2 + I<<2).
 487 Node* PhaseIdealLoop::remix_address_expressions_add_left_shift(Node* n, IdealLoopTree* n_loop, Node* n_ctrl, BasicType bt) {
 488   assert(bt == T_INT || bt == T_LONG, "only for integers");
 489   int n_op = n->Opcode();
 490 
 491   if (n_op == Op_LShift(bt)) {
 492     // Scale is loop invariant
 493     Node* scale = n->in(2);
 494     Node* scale_ctrl = get_ctrl(scale);
 495     IdealLoopTree* scale_loop = get_loop(scale_ctrl);
 496     if (n_loop == scale_loop || !scale_loop->is_member(n_loop)) {
 497       return nullptr;
 498     }
 499     const TypeInt* scale_t = scale->bottom_type()->isa_int();
 500     if (scale_t != nullptr && scale_t->is_con() && scale_t->get_con() >= 16) {
 501       return nullptr;              // Dont bother with byte/short masking
 502     }
 503     // Add must vary with loop (else shift would be loop-invariant)
 504     Node* add = n->in(1);
 505     Node* add_ctrl = get_ctrl(add);
 506     IdealLoopTree* add_loop = get_loop(add_ctrl);
 507     if (n_loop != add_loop) {
 508       return nullptr;  // happens w/ evil ZKM loops
 509     }
 510 
 511     // Convert I-V into I+ (0-V); same for V-I
 512     if (add->Opcode() == Op_Sub(bt) &&
 513         _igvn.type(add->in(1)) != TypeInteger::zero(bt)) {
 514       assert(add->Opcode() == Op_SubI || add->Opcode() == Op_SubL, "");
 515       Node* zero = integercon(0, bt);
 516       Node* neg = SubNode::make(zero, add->in(2), bt);
 517       register_new_node_with_ctrl_of(neg, add->in(2));
 518       add = AddNode::make(add->in(1), neg, bt);
 519       register_new_node(add, add_ctrl);
 520     }
 521     if (add->Opcode() != Op_Add(bt)) return nullptr;
 522     assert(add->Opcode() == Op_AddI || add->Opcode() == Op_AddL, "");
 523     // See if one add input is loop invariant
 524     Node* add_var = add->in(1);
 525     Node* add_var_ctrl = get_ctrl(add_var);
 526     IdealLoopTree* add_var_loop = get_loop(add_var_ctrl);
 527     Node* add_invar = add->in(2);
 528     Node* add_invar_ctrl = get_ctrl(add_invar);
 529     IdealLoopTree* add_invar_loop = get_loop(add_invar_ctrl);
 530     if (add_invar_loop == n_loop) {
 531       // Swap to find the invariant part
 532       add_invar = add_var;
 533       add_invar_ctrl = add_var_ctrl;
 534       add_invar_loop = add_var_loop;
 535       add_var = add->in(2);
 536     } else if (add_var_loop != n_loop) { // Else neither input is loop invariant
 537       return nullptr;
 538     }
 539     if (n_loop == add_invar_loop || !add_invar_loop->is_member(n_loop)) {
 540       return nullptr;              // No invariant part of the add?
 541     }
 542 
 543     // Yes!  Reshape address expression!
 544     Node* inv_scale = LShiftNode::make(add_invar, scale, bt);
 545     Node* inv_scale_ctrl =
 546             dom_depth(add_invar_ctrl) > dom_depth(scale_ctrl) ?
 547             add_invar_ctrl : scale_ctrl;
 548     register_new_node(inv_scale, inv_scale_ctrl);
 549     Node* var_scale = LShiftNode::make(add_var, scale, bt);
 550     register_new_node(var_scale, n_ctrl);
 551     Node* var_add = AddNode::make(var_scale, inv_scale, bt);
 552     register_new_node(var_add, n_ctrl);
 553     _igvn.replace_node(n, var_add);
 554     return var_add;
 555   }
 556   return nullptr;
 557 }
 558 
 559 //------------------------------remix_address_expressions----------------------
 560 // Rework addressing expressions to get the most loop-invariant stuff
 561 // moved out.  We'd like to do all associative operators, but it's especially
 562 // important (common) to do address expressions.
 563 Node* PhaseIdealLoop::remix_address_expressions(Node* n) {
 564   if (!has_ctrl(n))  return nullptr;
 565   Node* n_ctrl = get_ctrl(n);
 566   IdealLoopTree* n_loop = get_loop(n_ctrl);
 567 
 568   // See if 'n' mixes loop-varying and loop-invariant inputs and
 569   // itself is loop-varying.
 570 
 571   // Only interested in binary ops (and AddP)
 572   if (n->req() < 3 || n->req() > 4) return nullptr;
 573 
 574   Node* n1_ctrl = get_ctrl(n->in(                    1));
 575   Node* n2_ctrl = get_ctrl(n->in(                    2));
 576   Node* n3_ctrl = get_ctrl(n->in(n->req() == 3 ? 2 : 3));
 577   IdealLoopTree* n1_loop = get_loop(n1_ctrl);
 578   IdealLoopTree* n2_loop = get_loop(n2_ctrl);
 579   IdealLoopTree* n3_loop = get_loop(n3_ctrl);
 580 
 581   // Does one of my inputs spin in a tighter loop than self?
 582   if ((n_loop->is_member(n1_loop) && n_loop != n1_loop) ||
 583       (n_loop->is_member(n2_loop) && n_loop != n2_loop) ||
 584       (n_loop->is_member(n3_loop) && n_loop != n3_loop)) {
 585     return nullptr;                // Leave well enough alone
 586   }
 587 
 588   // Is at least one of my inputs loop-invariant?
 589   if (n1_loop == n_loop &&
 590       n2_loop == n_loop &&
 591       n3_loop == n_loop) {
 592     return nullptr;                // No loop-invariant inputs
 593   }
 594 
 595   Node* res = remix_address_expressions_add_left_shift(n, n_loop, n_ctrl, T_INT);
 596   if (res != nullptr) {
 597     return res;
 598   }
 599   res = remix_address_expressions_add_left_shift(n, n_loop, n_ctrl, T_LONG);
 600   if (res != nullptr) {
 601     return res;
 602   }
 603 
 604   int n_op = n->Opcode();
 605   // Replace (I+V) with (V+I)
 606   if (n_op == Op_AddI ||
 607       n_op == Op_AddL ||
 608       n_op == Op_AddF ||
 609       n_op == Op_AddD ||
 610       n_op == Op_MulI ||
 611       n_op == Op_MulL ||
 612       n_op == Op_MulF ||
 613       n_op == Op_MulD) {
 614     if (n2_loop == n_loop) {
 615       assert(n1_loop != n_loop, "");
 616       n->swap_edges(1, 2);
 617     }
 618   }
 619 
 620   // Replace ((I1 +p V) +p I2) with ((I1 +p I2) +p V),
 621   // but not if I2 is a constant. Skip for irreducible loops.
 622   if (n_op == Op_AddP && n_loop->_head->is_Loop()) {
 623     if (n2_loop == n_loop && n3_loop != n_loop) {
 624       if (n->in(2)->Opcode() == Op_AddP && !n->in(3)->is_Con()) {
 625         Node* n22_ctrl = get_ctrl(n->in(2)->in(2));
 626         Node* n23_ctrl = get_ctrl(n->in(2)->in(3));
 627         IdealLoopTree* n22loop = get_loop(n22_ctrl);
 628         IdealLoopTree* n23_loop = get_loop(n23_ctrl);
 629         if (n22loop != n_loop && n22loop->is_member(n_loop) &&
 630             n23_loop == n_loop) {
 631           Node* add1 = new AddPNode(n->in(1), n->in(2)->in(2), n->in(3));
 632           // Stuff new AddP in the loop preheader
 633           register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
 634           Node* add2 = new AddPNode(n->in(1), add1, n->in(2)->in(3));
 635           register_new_node(add2, n_ctrl);
 636           _igvn.replace_node(n, add2);
 637           return add2;
 638         }
 639       }
 640     }
 641 
 642     // Replace (I1 +p (I2 + V)) with ((I1 +p I2) +p V)
 643     if (n2_loop != n_loop && n3_loop == n_loop) {
 644       if (n->in(3)->Opcode() == Op_AddX) {
 645         Node* V = n->in(3)->in(1);
 646         Node* I = n->in(3)->in(2);
 647         if (ctrl_is_member(n_loop, V)) {
 648         } else {
 649           Node *tmp = V; V = I; I = tmp;
 650         }
 651         if (!ctrl_is_member(n_loop, I)) {
 652           Node* add1 = new AddPNode(n->in(1), n->in(2), I);
 653           // Stuff new AddP in the loop preheader
 654           register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
 655           Node* add2 = new AddPNode(n->in(1), add1, V);
 656           register_new_node(add2, n_ctrl);
 657           _igvn.replace_node(n, add2);
 658           return add2;
 659         }
 660       }
 661     }
 662   }
 663 
 664   return nullptr;
 665 }
 666 
 667 // Optimize ((in1[2*i] * in2[2*i]) + (in1[2*i+1] * in2[2*i+1]))
 668 Node *PhaseIdealLoop::convert_add_to_muladd(Node* n) {
 669   assert(n->Opcode() == Op_AddI, "sanity");
 670   Node * nn = nullptr;
 671   Node * in1 = n->in(1);
 672   Node * in2 = n->in(2);
 673   if (in1->Opcode() == Op_MulI && in2->Opcode() == Op_MulI) {
 674     IdealLoopTree* loop_n = get_loop(get_ctrl(n));
 675     if (loop_n->is_counted() &&
 676         loop_n->_head->as_Loop()->is_valid_counted_loop(T_INT) &&
 677         Matcher::match_rule_supported(Op_MulAddVS2VI) &&
 678         Matcher::match_rule_supported(Op_MulAddS2I)) {
 679       Node* mul_in1 = in1->in(1);
 680       Node* mul_in2 = in1->in(2);
 681       Node* mul_in3 = in2->in(1);
 682       Node* mul_in4 = in2->in(2);
 683       if (mul_in1->Opcode() == Op_LoadS &&
 684           mul_in2->Opcode() == Op_LoadS &&
 685           mul_in3->Opcode() == Op_LoadS &&
 686           mul_in4->Opcode() == Op_LoadS) {
 687         IdealLoopTree* loop1 = get_loop(get_ctrl(mul_in1));
 688         IdealLoopTree* loop2 = get_loop(get_ctrl(mul_in2));
 689         IdealLoopTree* loop3 = get_loop(get_ctrl(mul_in3));
 690         IdealLoopTree* loop4 = get_loop(get_ctrl(mul_in4));
 691         IdealLoopTree* loop5 = get_loop(get_ctrl(in1));
 692         IdealLoopTree* loop6 = get_loop(get_ctrl(in2));
 693         // All nodes should be in the same counted loop.
 694         if (loop_n == loop1 && loop_n == loop2 && loop_n == loop3 &&
 695             loop_n == loop4 && loop_n == loop5 && loop_n == loop6) {
 696           Node* adr1 = mul_in1->in(MemNode::Address);
 697           Node* adr2 = mul_in2->in(MemNode::Address);
 698           Node* adr3 = mul_in3->in(MemNode::Address);
 699           Node* adr4 = mul_in4->in(MemNode::Address);
 700           if (adr1->is_AddP() && adr2->is_AddP() && adr3->is_AddP() && adr4->is_AddP()) {
 701             if ((adr1->in(AddPNode::Base) == adr3->in(AddPNode::Base)) &&
 702                 (adr2->in(AddPNode::Base) == adr4->in(AddPNode::Base))) {
 703               nn = new MulAddS2INode(mul_in1, mul_in2, mul_in3, mul_in4);
 704               register_new_node_with_ctrl_of(nn, n);
 705               _igvn.replace_node(n, nn);
 706               return nn;
 707             } else if ((adr1->in(AddPNode::Base) == adr4->in(AddPNode::Base)) &&
 708                        (adr2->in(AddPNode::Base) == adr3->in(AddPNode::Base))) {
 709               nn = new MulAddS2INode(mul_in1, mul_in2, mul_in4, mul_in3);
 710               register_new_node_with_ctrl_of(nn, n);
 711               _igvn.replace_node(n, nn);
 712               return nn;
 713             }
 714           }
 715         }
 716       }
 717     }
 718   }
 719   return nn;
 720 }
 721 
 722 //------------------------------conditional_move-------------------------------
 723 // Attempt to replace a Phi with a conditional move.  We have some pretty
 724 // strict profitability requirements.  All Phis at the merge point must
 725 // be converted, so we can remove the control flow.  We need to limit the
 726 // number of c-moves to a small handful.  All code that was in the side-arms
 727 // of the CFG diamond is now speculatively executed.  This code has to be
 728 // "cheap enough".  We are pretty much limited to CFG diamonds that merge
 729 // 1 or 2 items with a total of 1 or 2 ops executed speculatively.
 730 Node *PhaseIdealLoop::conditional_move( Node *region ) {
 731 
 732   assert(region->is_Region(), "sanity check");
 733   if (region->req() != 3) return nullptr;
 734 
 735   // Check for CFG diamond
 736   Node *lp = region->in(1);
 737   Node *rp = region->in(2);
 738   if (!lp || !rp) return nullptr;
 739   Node *lp_c = lp->in(0);
 740   if (lp_c == nullptr || lp_c != rp->in(0) || !lp_c->is_If()) return nullptr;
 741   IfNode *iff = lp_c->as_If();
 742 
 743   // Check for ops pinned in an arm of the diamond.
 744   // Can't remove the control flow in this case
 745   if (lp->outcnt() > 1) return nullptr;
 746   if (rp->outcnt() > 1) return nullptr;
 747 
 748   IdealLoopTree* r_loop = get_loop(region);
 749   assert(r_loop == get_loop(iff), "sanity");
 750   // Always convert to CMOVE if all results are used only outside this loop.
 751   bool used_inside_loop = (r_loop == _ltree_root);
 752 
 753   // Check profitability
 754   int cost = 0;
 755   int phis = 0;
 756   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 757     Node *out = region->fast_out(i);
 758     if (!out->is_Phi()) continue; // Ignore other control edges, etc
 759     phis++;
 760     PhiNode* phi = out->as_Phi();
 761     BasicType bt = phi->type()->basic_type();
 762     switch (bt) {
 763     case T_DOUBLE:
 764     case T_FLOAT:
 765       if (C->use_cmove()) {
 766         continue; //TODO: maybe we want to add some cost
 767       }
 768       cost += Matcher::float_cmove_cost(); // Could be very expensive
 769       break;
 770     case T_LONG: {
 771       cost += Matcher::long_cmove_cost(); // May encodes as 2 CMOV's
 772     }
 773     case T_INT:                 // These all CMOV fine
 774     case T_ADDRESS: {           // (RawPtr)
 775       cost++;
 776       break;
 777     }
 778     case T_NARROWOOP: // Fall through
 779     case T_OBJECT: {            // Base oops are OK, but not derived oops
 780       const TypeOopPtr *tp = phi->type()->make_ptr()->isa_oopptr();
 781       // Derived pointers are Bad (tm): what's the Base (for GC purposes) of a
 782       // CMOVE'd derived pointer?  It's a CMOVE'd derived base.  Thus
 783       // CMOVE'ing a derived pointer requires we also CMOVE the base.  If we
 784       // have a Phi for the base here that we convert to a CMOVE all is well
 785       // and good.  But if the base is dead, we'll not make a CMOVE.  Later
 786       // the allocator will have to produce a base by creating a CMOVE of the
 787       // relevant bases.  This puts the allocator in the business of
 788       // manufacturing expensive instructions, generally a bad plan.
 789       // Just Say No to Conditionally-Moved Derived Pointers.
 790       if (tp && tp->offset() != 0)
 791         return nullptr;
 792       cost++;
 793       break;
 794     }
 795     default:
 796       return nullptr;              // In particular, can't do memory or I/O
 797     }
 798     // Add in cost any speculative ops
 799     for (uint j = 1; j < region->req(); j++) {
 800       Node *proj = region->in(j);
 801       Node *inp = phi->in(j);
 802       if (inp->isa_InlineType()) {
 803         // TODO 8302217 This prevents PhiNode::push_inline_types_through
 804         return nullptr;
 805       }
 806       if (get_ctrl(inp) == proj) { // Found local op
 807         cost++;
 808         // Check for a chain of dependent ops; these will all become
 809         // speculative in a CMOV.
 810         for (uint k = 1; k < inp->req(); k++)
 811           if (get_ctrl(inp->in(k)) == proj)
 812             cost += ConditionalMoveLimit; // Too much speculative goo
 813       }
 814     }
 815     // See if the Phi is used by a Cmp or Narrow oop Decode/Encode.
 816     // This will likely Split-If, a higher-payoff operation.
 817     for (DUIterator_Fast kmax, k = phi->fast_outs(kmax); k < kmax; k++) {
 818       Node* use = phi->fast_out(k);
 819       if (use->is_Cmp() || use->is_DecodeNarrowPtr() || use->is_EncodeNarrowPtr())
 820         cost += ConditionalMoveLimit;
 821       // Is there a use inside the loop?
 822       // Note: check only basic types since CMoveP is pinned.
 823       if (!used_inside_loop && is_java_primitive(bt)) {
 824         IdealLoopTree* u_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use);
 825         if (r_loop == u_loop || r_loop->is_member(u_loop)) {
 826           used_inside_loop = true;
 827         }
 828       }
 829     }
 830   }//for
 831   Node* bol = iff->in(1);
 832   assert(!bol->is_OpaqueInitializedAssertionPredicate(), "Initialized Assertion Predicates cannot form a diamond with Halt");
 833   if (bol->is_OpaqueTemplateAssertionPredicate()) {
 834     // Ignore Template Assertion Predicates with OpaqueTemplateAssertionPredicate nodes.
 835     return nullptr;
 836   }
 837   if (bol->is_OpaqueMultiversioning()) {
 838     assert(bol->as_OpaqueMultiversioning()->is_useless(), "Must be useless, i.e. fast main loop has already disappeared.");
 839     // Ignore multiversion_if that just lost its loops. The OpaqueMultiversioning is marked useless,
 840     // and will make the multiversion_if constant fold in the next IGVN round.
 841     return nullptr;
 842   }
 843   if (!bol->is_Bool()) {
 844     assert(false, "Expected Bool, but got %s", NodeClassNames[bol->Opcode()]);
 845     return nullptr;
 846   }
 847   int cmp_op = bol->in(1)->Opcode();
 848   if (cmp_op == Op_SubTypeCheck) { // SubTypeCheck expansion expects an IfNode
 849     return nullptr;
 850   }
 851   // It is expensive to generate flags from a float compare.
 852   // Avoid duplicated float compare.
 853   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return nullptr;
 854 
 855   float infrequent_prob = PROB_UNLIKELY_MAG(3);
 856   // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
 857   if (used_inside_loop) {
 858     if (cost >= ConditionalMoveLimit) return nullptr; // Too much goo
 859 
 860     // BlockLayoutByFrequency optimization moves infrequent branch
 861     // from hot path. No point in CMOV'ing in such case (110 is used
 862     // instead of 100 to take into account not exactness of float value).
 863     if (BlockLayoutByFrequency) {
 864       infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
 865     }
 866   }
 867   // Check for highly predictable branch.  No point in CMOV'ing if
 868   // we are going to predict accurately all the time.
 869   if (C->use_cmove() && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) {
 870     //keep going
 871   } else if (iff->_prob < infrequent_prob ||
 872       iff->_prob > (1.0f - infrequent_prob))
 873     return nullptr;
 874 
 875   // --------------
 876   // Now replace all Phis with CMOV's
 877   Node *cmov_ctrl = iff->in(0);
 878   uint flip = (lp->Opcode() == Op_IfTrue);
 879   Node_List wq;
 880   while (1) {
 881     PhiNode* phi = nullptr;
 882     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 883       Node *out = region->fast_out(i);
 884       if (out->is_Phi()) {
 885         phi = out->as_Phi();
 886         break;
 887       }
 888     }
 889     if (phi == nullptr || _igvn.type(phi) == Type::TOP || !CMoveNode::supported(_igvn.type(phi))) {
 890       break;
 891     }
 892     // Move speculative ops
 893     wq.push(phi);
 894     while (wq.size() > 0) {
 895       Node *n = wq.pop();
 896       for (uint j = 1; j < n->req(); j++) {
 897         Node* m = n->in(j);
 898         if (m != nullptr && !is_dominator(get_ctrl(m), cmov_ctrl)) {
 899           set_ctrl(m, cmov_ctrl);
 900           wq.push(m);
 901         }
 902       }
 903     }
 904     Node* cmov = CMoveNode::make(iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi));
 905     register_new_node(cmov, cmov_ctrl);
 906     _igvn.replace_node(phi, cmov);
 907 #ifndef PRODUCT
 908     if (TraceLoopOpts) {
 909       tty->print("CMOV  ");
 910       r_loop->dump_head();
 911       if (Verbose) {
 912         bol->in(1)->dump(1);
 913         cmov->dump(1);
 914       }
 915     }
 916     DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
 917 #endif
 918   }
 919 
 920   // The useless CFG diamond will fold up later; see the optimization in
 921   // RegionNode::Ideal.
 922   _igvn._worklist.push(region);
 923 
 924   return iff->in(1);
 925 }
 926 
 927 static void enqueue_cfg_uses(Node* m, Unique_Node_List& wq) {
 928   for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
 929     Node* u = m->fast_out(i);
 930     if (u->is_CFG()) {
 931       if (u->is_NeverBranch()) {
 932         u = u->as_NeverBranch()->proj_out(0);
 933         enqueue_cfg_uses(u, wq);
 934       } else {
 935         wq.push(u);
 936       }
 937     }
 938   }
 939 }
 940 
 941 // Try moving a store out of a loop, right before the loop
 942 Node* PhaseIdealLoop::try_move_store_before_loop(Node* n, Node *n_ctrl) {
 943   // Store has to be first in the loop body
 944   IdealLoopTree *n_loop = get_loop(n_ctrl);
 945   if (n->is_Store() && n_loop != _ltree_root &&
 946       n_loop->is_loop() && n_loop->_head->is_Loop() &&
 947       n->in(0) != nullptr) {
 948     Node* address = n->in(MemNode::Address);
 949     Node* value = n->in(MemNode::ValueIn);
 950     Node* mem = n->in(MemNode::Memory);
 951 
 952     // - address and value must be loop invariant
 953     // - memory must be a memory Phi for the loop
 954     // - Store must be the only store on this memory slice in the
 955     // loop: if there's another store following this one then value
 956     // written at iteration i by the second store could be overwritten
 957     // at iteration i+n by the first store: it's not safe to move the
 958     // first store out of the loop
 959     // - nothing must observe the memory Phi: it guarantees no read
 960     // before the store, we are also guaranteed the store post
 961     // dominates the loop head (ignoring a possible early
 962     // exit). Otherwise there would be extra Phi involved between the
 963     // loop's Phi and the store.
 964     // - there must be no early exit from the loop before the Store
 965     // (such an exit most of the time would be an extra use of the
 966     // memory Phi but sometimes is a bottom memory Phi that takes the
 967     // store as input).
 968 
 969     if (!ctrl_is_member(n_loop, address) &&
 970         !ctrl_is_member(n_loop, value) &&
 971         mem->is_Phi() && mem->in(0) == n_loop->_head &&
 972         mem->outcnt() == 1 &&
 973         mem->in(LoopNode::LoopBackControl) == n) {
 974 
 975       assert(n_loop->_tail != nullptr, "need a tail");
 976       assert(is_dominator(n_ctrl, n_loop->_tail), "store control must not be in a branch in the loop");
 977 
 978       // Verify that there's no early exit of the loop before the store.
 979       bool ctrl_ok = false;
 980       {
 981         // Follow control from loop head until n, we exit the loop or
 982         // we reach the tail
 983         ResourceMark rm;
 984         Unique_Node_List wq;
 985         wq.push(n_loop->_head);
 986 
 987         for (uint next = 0; next < wq.size(); ++next) {
 988           Node *m = wq.at(next);
 989           if (m == n->in(0)) {
 990             ctrl_ok = true;
 991             continue;
 992           }
 993           assert(!has_ctrl(m), "should be CFG");
 994           if (!n_loop->is_member(get_loop(m)) || m == n_loop->_tail) {
 995             ctrl_ok = false;
 996             break;
 997           }
 998           enqueue_cfg_uses(m, wq);
 999           if (wq.size() > 10) {
1000             ctrl_ok = false;
1001             break;
1002           }
1003         }
1004       }
1005       if (ctrl_ok) {
1006         // move the Store
1007         _igvn.replace_input_of(mem, LoopNode::LoopBackControl, mem);
1008         _igvn.replace_input_of(n, 0, n_loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl));
1009         _igvn.replace_input_of(n, MemNode::Memory, mem->in(LoopNode::EntryControl));
1010         // Disconnect the phi now. An empty phi can confuse other
1011         // optimizations in this pass of loop opts.
1012         _igvn.replace_node(mem, mem->in(LoopNode::EntryControl));
1013         n_loop->_body.yank(mem);
1014 
1015         set_ctrl_and_loop(n, n->in(0));
1016 
1017         return n;
1018       }
1019     }
1020   }
1021   return nullptr;
1022 }
1023 
1024 // Try moving a store out of a loop, right after the loop
1025 void PhaseIdealLoop::try_move_store_after_loop(Node* n) {
1026   if (n->is_Store() && n->in(0) != nullptr) {
1027     Node *n_ctrl = get_ctrl(n);
1028     IdealLoopTree *n_loop = get_loop(n_ctrl);
1029     // Store must be in a loop
1030     if (n_loop != _ltree_root && !n_loop->_irreducible) {
1031       Node* address = n->in(MemNode::Address);
1032       Node* value = n->in(MemNode::ValueIn);
1033       // address must be loop invariant
1034       if (!ctrl_is_member(n_loop, address)) {
1035         // Store must be last on this memory slice in the loop and
1036         // nothing in the loop must observe it
1037         Node* phi = nullptr;
1038         for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1039           Node* u = n->fast_out(i);
1040           if (has_ctrl(u)) { // control use?
1041             if (!ctrl_is_member(n_loop, u)) {
1042               continue;
1043             }
1044             if (u->is_Phi() && u->in(0) == n_loop->_head) {
1045               assert(_igvn.type(u) == Type::MEMORY, "bad phi");
1046               // multiple phis on the same slice are possible
1047               if (phi != nullptr) {
1048                 return;
1049               }
1050               phi = u;
1051               continue;
1052             }
1053           }
1054           return;
1055         }
1056         if (phi != nullptr) {
1057           // Nothing in the loop before the store (next iteration)
1058           // must observe the stored value
1059           bool mem_ok = true;
1060           {
1061             ResourceMark rm;
1062             Unique_Node_List wq;
1063             wq.push(phi);
1064             for (uint next = 0; next < wq.size() && mem_ok; ++next) {
1065               Node *m = wq.at(next);
1066               for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax && mem_ok; i++) {
1067                 Node* u = m->fast_out(i);
1068                 if (u->is_Store() || u->is_Phi()) {
1069                   if (u != n) {
1070                     wq.push(u);
1071                     mem_ok = (wq.size() <= 10);
1072                   }
1073                 } else {
1074                   mem_ok = false;
1075                   break;
1076                 }
1077               }
1078             }
1079           }
1080           if (mem_ok) {
1081             // Move the store out of the loop if the LCA of all
1082             // users (except for the phi) is outside the loop.
1083             Node* hook = new Node(1);
1084             hook->init_req(0, n_ctrl); // Add an input to prevent hook from being dead
1085             _igvn.rehash_node_delayed(phi);
1086             int count = phi->replace_edge(n, hook, &_igvn);
1087             assert(count > 0, "inconsistent phi");
1088 
1089             // Compute latest point this store can go
1090             Node* lca = get_late_ctrl(n, get_ctrl(n));
1091             if (lca->is_OuterStripMinedLoop()) {
1092               lca = lca->in(LoopNode::EntryControl);
1093             }
1094             if (n_loop->is_member(get_loop(lca))) {
1095               // LCA is in the loop - bail out
1096               _igvn.replace_node(hook, n);
1097               return;
1098             }
1099 #ifdef ASSERT
1100             if (n_loop->_head->is_Loop() && n_loop->_head->as_Loop()->is_strip_mined()) {
1101               assert(n_loop->_head->Opcode() == Op_CountedLoop, "outer loop is a strip mined");
1102               n_loop->_head->as_Loop()->verify_strip_mined(1);
1103               Node* outer = n_loop->_head->as_CountedLoop()->outer_loop();
1104               IdealLoopTree* outer_loop = get_loop(outer);
1105               assert(n_loop->_parent == outer_loop, "broken loop tree");
1106               assert(get_loop(lca) == outer_loop, "safepoint in outer loop consume all memory state");
1107             }
1108 #endif
1109             lca = place_outside_loop(lca, n_loop);
1110             assert(!n_loop->is_member(get_loop(lca)), "control must not be back in the loop");
1111             assert(get_loop(lca)->_nest < n_loop->_nest || get_loop(lca)->_head->as_Loop()->is_in_infinite_subgraph(), "must not be moved into inner loop");
1112 
1113             // Move store out of the loop
1114             _igvn.replace_node(hook, n->in(MemNode::Memory));
1115             _igvn.replace_input_of(n, 0, lca);
1116             set_ctrl_and_loop(n, lca);
1117 
1118             // Disconnect the phi now. An empty phi can confuse other
1119             // optimizations in this pass of loop opts..
1120             if (phi->in(LoopNode::LoopBackControl) == phi) {
1121               _igvn.replace_node(phi, phi->in(LoopNode::EntryControl));
1122               n_loop->_body.yank(phi);
1123             }
1124           }
1125         }
1126       }
1127     }
1128   }
1129 }
1130 
1131 // We can't use immutable memory for the flat array check because we are loading the mark word which is
1132 // mutable. Although the bits we are interested in are immutable (we check for markWord::unlocked_value),
1133 // we need to use raw memory to not break anti dependency analysis. Below code will attempt to still move
1134 // flat array checks out of loops, mainly to enable loop unswitching.
1135 void PhaseIdealLoop::move_flat_array_check_out_of_loop(Node* n) {
1136   // Skip checks for more than one array
1137   if (n->req() > 3) {
1138     return;
1139   }
1140   Node* mem = n->in(FlatArrayCheckNode::Memory);
1141   Node* array = n->in(FlatArrayCheckNode::ArrayOrKlass)->uncast();
1142   IdealLoopTree* check_loop = get_loop(get_ctrl(n));
1143   IdealLoopTree* ary_loop = get_loop(get_ctrl(array));
1144 
1145   // Check if array is loop invariant
1146   if (!check_loop->is_member(ary_loop)) {
1147     // Walk up memory graph from the check until we leave the loop
1148     VectorSet wq;
1149     wq.set(mem->_idx);
1150     while (check_loop->is_member(get_loop(ctrl_or_self(mem)))) {
1151       if (mem->is_Phi()) {
1152         mem = mem->in(1);
1153       } else if (mem->is_MergeMem()) {
1154         mem = mem->as_MergeMem()->memory_at(Compile::AliasIdxRaw);
1155       } else if (mem->is_Proj()) {
1156         mem = mem->in(0);
1157       } else if (mem->is_MemBar() || mem->is_SafePoint()) {
1158         mem = mem->in(TypeFunc::Memory);
1159       } else if (mem->is_Store() || mem->is_LoadStore() || mem->is_ClearArray()) {
1160         mem = mem->in(MemNode::Memory);
1161       } else {
1162 #ifdef ASSERT
1163         mem->dump();
1164 #endif
1165         ShouldNotReachHere();
1166       }
1167       if (wq.test_set(mem->_idx)) {
1168         return;
1169       }
1170     }
1171     // Replace memory input and re-compute ctrl to move the check out of the loop
1172     _igvn.replace_input_of(n, 1, mem);
1173     set_ctrl_and_loop(n, get_early_ctrl(n));
1174     Node* bol = n->unique_out();
1175     set_ctrl_and_loop(bol, get_early_ctrl(bol));
1176   }
1177 }
1178 
1179 //------------------------------split_if_with_blocks_pre-----------------------
1180 // Do the real work in a non-recursive function.  Data nodes want to be
1181 // cloned in the pre-order so they can feed each other nicely.
1182 Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
1183   // Cloning these guys is unlikely to win
1184   int n_op = n->Opcode();
1185   if (n_op == Op_MergeMem) {
1186     return n;
1187   }
1188   if (n->is_Proj()) {
1189     return n;
1190   }
1191 
1192   if (n->isa_FlatArrayCheck()) {
1193     move_flat_array_check_out_of_loop(n);
1194     return n;
1195   }
1196 
1197   // Do not clone-up CmpFXXX variations, as these are always
1198   // followed by a CmpI
1199   if (n->is_Cmp()) {
1200     return n;
1201   }
1202   // Attempt to use a conditional move instead of a phi/branch
1203   if (ConditionalMoveLimit > 0 && n_op == Op_Region) {
1204     Node *cmov = conditional_move( n );
1205     if (cmov) {
1206       return cmov;
1207     }
1208   }
1209   if (n->is_CFG() || n->is_LoadStore()) {
1210     return n;
1211   }
1212   if (n->is_Opaque1()) { // Opaque nodes cannot be mod'd
1213     if (!C->major_progress()) {   // If chance of no more loop opts...
1214       _igvn._worklist.push(n);  // maybe we'll remove them
1215     }
1216     return n;
1217   }
1218 
1219   if (n->is_Con()) {
1220     return n;   // No cloning for Con nodes
1221   }
1222 
1223   Node *n_ctrl = get_ctrl(n);
1224   if (!n_ctrl) {
1225     return n;       // Dead node
1226   }
1227 
1228   Node* res = try_move_store_before_loop(n, n_ctrl);
1229   if (res != nullptr) {
1230     return n;
1231   }
1232 
1233   // Attempt to remix address expressions for loop invariants
1234   Node *m = remix_address_expressions( n );
1235   if( m ) return m;
1236 
1237   if (n_op == Op_AddI) {
1238     Node *nn = convert_add_to_muladd( n );
1239     if ( nn ) return nn;
1240   }
1241 
1242   if (n->is_ConstraintCast() && n->as_ConstraintCast()->dependency().narrows_type()) {
1243     Node* dom_cast = n->as_ConstraintCast()->dominating_cast(&_igvn, this);
1244     // ConstraintCastNode::dominating_cast() uses node control input to determine domination.
1245     // Node control inputs don't necessarily agree with loop control info (due to
1246     // transformations happened in between), thus additional dominance check is needed
1247     // to keep loop info valid.
1248     if (dom_cast != nullptr && is_dominator(get_ctrl(dom_cast), get_ctrl(n))) {
1249       _igvn.replace_node(n, dom_cast);
1250       return dom_cast;
1251     }
1252   }
1253 
1254   // Determine if the Node has inputs from some local Phi.
1255   // Returns the block to clone thru.
1256   Node *n_blk = has_local_phi_input( n );
1257   if( !n_blk ) return n;
1258 
1259   // Do not clone the trip counter through on a CountedLoop
1260   // (messes up the canonical shape).
1261   if (((n_blk->is_CountedLoop() || (n_blk->is_Loop() && n_blk->as_Loop()->is_loop_nest_inner_loop())) && n->Opcode() == Op_AddI) ||
1262       (n_blk->is_LongCountedLoop() && n->Opcode() == Op_AddL)) {
1263     return n;
1264   }
1265   // Pushing a shift through the iv Phi can get in the way of addressing optimizations or range check elimination
1266   if (n_blk->is_BaseCountedLoop() && n->Opcode() == Op_LShift(n_blk->as_BaseCountedLoop()->bt()) &&
1267       n->in(1) == n_blk->as_BaseCountedLoop()->phi()) {
1268     return n;
1269   }
1270 
1271   // Check for having no control input; not pinned.  Allow
1272   // dominating control.
1273   if (n->in(0)) {
1274     Node *dom = idom(n_blk);
1275     if (dom_lca(n->in(0), dom) != n->in(0)) {
1276       return n;
1277     }
1278   }
1279   // Policy: when is it profitable.  You must get more wins than
1280   // policy before it is considered profitable.  Policy is usually 0,
1281   // so 1 win is considered profitable.  Big merges will require big
1282   // cloning, so get a larger policy.
1283   int policy = n_blk->req() >> 2;
1284 
1285   // If the loop is a candidate for range check elimination,
1286   // delay splitting through it's phi until a later loop optimization
1287   if (n_blk->is_BaseCountedLoop()) {
1288     IdealLoopTree *lp = get_loop(n_blk);
1289     if (lp && lp->_rce_candidate) {
1290       return n;
1291     }
1292   }
1293 
1294   if (must_throttle_split_if()) return n;
1295 
1296   // Split 'n' through the merge point if it is profitable, replacing it with a new phi.
1297   Node* phi = split_thru_phi(n, n_blk, policy);
1298   if (phi == nullptr) { return n; }
1299 
1300   // Moved a load around the loop, 'en-registering' something.
1301   if (n_blk->is_Loop() && n->is_Load() &&
1302       !phi->in(LoopNode::LoopBackControl)->is_Load())
1303     C->set_major_progress();
1304 
1305   return phi;
1306 }
1307 
1308 static bool merge_point_too_heavy(Compile* C, Node* region) {
1309   // Bail out if the region and its phis have too many users.
1310   int weight = 0;
1311   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1312     weight += region->fast_out(i)->outcnt();
1313   }
1314   int nodes_left = C->max_node_limit() - C->live_nodes();
1315   if (weight * 8 > nodes_left) {
1316     if (PrintOpto) {
1317       tty->print_cr("*** Split-if bails out:  %d nodes, region weight %d", C->unique(), weight);
1318     }
1319     return true;
1320   } else {
1321     return false;
1322   }
1323 }
1324 
1325 static bool merge_point_safe(Node* region) {
1326   // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
1327   // having a PhiNode input. This sidesteps the dangerous case where the split
1328   // ConvI2LNode may become TOP if the input Value() does not
1329   // overlap the ConvI2L range, leaving a node which may not dominate its
1330   // uses.
1331   // A better fix for this problem can be found in the BugTraq entry, but
1332   // expediency for Mantis demands this hack.
1333 #ifdef _LP64
1334   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1335     Node* n = region->fast_out(i);
1336     if (n->is_Phi()) {
1337       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
1338         Node* m = n->fast_out(j);
1339         if (m->Opcode() == Op_ConvI2L)
1340           return false;
1341         if (m->is_CastII()) {
1342           return false;
1343         }
1344       }
1345     }
1346   }
1347 #endif
1348   return true;
1349 }
1350 
1351 
1352 //------------------------------place_outside_loop---------------------------------
1353 // Place some computation outside of this loop on the path to the use passed as argument
1354 Node* PhaseIdealLoop::place_outside_loop(Node* useblock, IdealLoopTree* loop) const {
1355   Node* head = loop->_head;
1356   assert(!loop->is_member(get_loop(useblock)), "must be outside loop");
1357   if (head->is_Loop() && head->as_Loop()->is_strip_mined()) {
1358     loop = loop->_parent;
1359     assert(loop->_head->is_OuterStripMinedLoop(), "malformed strip mined loop");
1360   }
1361 
1362   // Pick control right outside the loop
1363   for (;;) {
1364     Node* dom = idom(useblock);
1365     if (loop->is_member(get_loop(dom))) {
1366       break;
1367     }
1368     useblock = dom;
1369   }
1370   assert(find_non_split_ctrl(useblock) == useblock, "should be non split control");
1371   return useblock;
1372 }
1373 
1374 
1375 bool PhaseIdealLoop::identical_backtoback_ifs(Node *n) {
1376   if (!n->is_If() || n->is_BaseCountedLoopEnd()) {
1377     return false;
1378   }
1379   if (!n->in(0)->is_Region()) {
1380     return false;
1381   }
1382 
1383   Node* region = n->in(0);
1384   Node* dom = idom(region);
1385   if (!dom->is_If() ||  !n->as_If()->same_condition(dom, &_igvn)) {
1386     return false;
1387   }
1388   IfNode* dom_if = dom->as_If();
1389   IfTrueNode* proj_true = dom_if->true_proj();
1390   IfFalseNode* proj_false = dom_if->false_proj();
1391 
1392   for (uint i = 1; i < region->req(); i++) {
1393     if (is_dominator(proj_true, region->in(i))) {
1394       continue;
1395     }
1396     if (is_dominator(proj_false, region->in(i))) {
1397       continue;
1398     }
1399     return false;
1400   }
1401 
1402   return true;
1403 }
1404 
1405 
1406 bool PhaseIdealLoop::can_split_if(Node* n_ctrl) {
1407   if (must_throttle_split_if()) {
1408     return false;
1409   }
1410 
1411   // Do not do 'split-if' if irreducible loops are present.
1412   if (_has_irreducible_loops) {
1413     return false;
1414   }
1415 
1416   if (merge_point_too_heavy(C, n_ctrl)) {
1417     return false;
1418   }
1419 
1420   // Do not do 'split-if' if some paths are dead.  First do dead code
1421   // elimination and then see if its still profitable.
1422   for (uint i = 1; i < n_ctrl->req(); i++) {
1423     if (n_ctrl->in(i) == C->top()) {
1424       return false;
1425     }
1426   }
1427 
1428   // If trying to do a 'Split-If' at the loop head, it is only
1429   // profitable if the cmp folds up on BOTH paths.  Otherwise we
1430   // risk peeling a loop forever.
1431 
1432   // CNC - Disabled for now.  Requires careful handling of loop
1433   // body selection for the cloned code.  Also, make sure we check
1434   // for any input path not being in the same loop as n_ctrl.  For
1435   // irreducible loops we cannot check for 'n_ctrl->is_Loop()'
1436   // because the alternative loop entry points won't be converted
1437   // into LoopNodes.
1438   IdealLoopTree *n_loop = get_loop(n_ctrl);
1439   for (uint j = 1; j < n_ctrl->req(); j++) {
1440     if (get_loop(n_ctrl->in(j)) != n_loop) {
1441       return false;
1442     }
1443   }
1444 
1445   // Check for safety of the merge point.
1446   if (!merge_point_safe(n_ctrl)) {
1447     return false;
1448   }
1449 
1450   return true;
1451 }
1452 
1453 // Detect if the node is the inner strip-mined loop
1454 // Return: null if it's not the case, or the exit of outer strip-mined loop
1455 static Node* is_inner_of_stripmined_loop(const Node* out) {
1456   Node* out_le = nullptr;
1457 
1458   if (out->is_CountedLoopEnd()) {
1459       const CountedLoopNode* loop = out->as_CountedLoopEnd()->loopnode();
1460 
1461       if (loop != nullptr && loop->is_strip_mined()) {
1462         out_le = loop->in(LoopNode::EntryControl)->as_OuterStripMinedLoop()->outer_loop_exit();
1463       }
1464   }
1465 
1466   return out_le;
1467 }
1468 
1469 bool PhaseIdealLoop::flat_array_element_type_check(Node *n) {
1470   // If the CmpP is a subtype check for a value that has just been
1471   // loaded from an array, the subtype check guarantees the value
1472   // can't be stored in a flat array and the load of the value
1473   // happens with a flat array check then: push the type check
1474   // through the phi of the flat array check. This needs special
1475   // logic because the subtype check's input is not a phi but a
1476   // LoadKlass that must first be cloned through the phi.
1477   if (n->Opcode() != Op_CmpP) {
1478     return false;
1479   }
1480 
1481   Node* klassptr = n->in(1);
1482   Node* klasscon = n->in(2);
1483 
1484   if (klassptr->is_DecodeNarrowPtr()) {
1485     klassptr = klassptr->in(1);
1486   }
1487 
1488   if (klassptr->Opcode() != Op_LoadKlass && klassptr->Opcode() != Op_LoadNKlass) {
1489     return false;
1490   }
1491 
1492   if (!klasscon->is_Con()) {
1493     return false;
1494   }
1495 
1496   Node* addr = klassptr->in(MemNode::Address);
1497 
1498   if (!addr->is_AddP()) {
1499     return false;
1500   }
1501 
1502   intptr_t offset;
1503   Node* obj = AddPNode::Ideal_base_and_offset(addr, &_igvn, offset);
1504 
1505   if (obj == nullptr) {
1506     return false;
1507   }
1508 
1509   assert(obj != nullptr && addr->in(AddPNode::Base) == addr->in(AddPNode::Address), "malformed AddP?");
1510   if (obj->Opcode() == Op_CastPP) {
1511     obj = obj->in(1);
1512   }
1513 
1514   if (!obj->is_Phi()) {
1515     return false;
1516   }
1517 
1518   Node* region = obj->in(0);
1519 
1520   Node* phi = PhiNode::make_blank(region, n->in(1));
1521   for (uint i = 1; i < region->req(); i++) {
1522     Node* in = obj->in(i);
1523     Node* ctrl = region->in(i);
1524     if (addr->in(AddPNode::Base) != obj) {
1525       Node* cast = addr->in(AddPNode::Base);
1526       assert(cast->Opcode() == Op_CastPP && cast->in(0) != nullptr, "inconsistent subgraph");
1527       Node* cast_clone = cast->clone();
1528       cast_clone->set_req(0, ctrl);
1529       cast_clone->set_req(1, in);
1530       register_new_node(cast_clone, ctrl);
1531       const Type* tcast = cast_clone->Value(&_igvn);
1532       _igvn.set_type(cast_clone, tcast);
1533       cast_clone->as_Type()->set_type(tcast);
1534       in = cast_clone;
1535     }
1536     Node* addr_clone = addr->clone();
1537     addr_clone->set_req(AddPNode::Base, in);
1538     addr_clone->set_req(AddPNode::Address, in);
1539     register_new_node(addr_clone, ctrl);
1540     _igvn.set_type(addr_clone, addr_clone->Value(&_igvn));
1541     Node* klassptr_clone = klassptr->clone();
1542     klassptr_clone->set_req(2, addr_clone);
1543     register_new_node(klassptr_clone, ctrl);
1544     _igvn.set_type(klassptr_clone, klassptr_clone->Value(&_igvn));
1545     if (klassptr != n->in(1)) {
1546       Node* decode = n->in(1);
1547       assert(decode->is_DecodeNarrowPtr(), "inconsistent subgraph");
1548       Node* decode_clone = decode->clone();
1549       decode_clone->set_req(1, klassptr_clone);
1550       register_new_node(decode_clone, ctrl);
1551       _igvn.set_type(decode_clone, decode_clone->Value(&_igvn));
1552       klassptr_clone = decode_clone;
1553     }
1554     phi->set_req(i, klassptr_clone);
1555   }
1556   register_new_node(phi, region);
1557   Node* orig = n->in(1);
1558   _igvn.replace_input_of(n, 1, phi);
1559   split_if_with_blocks_post(n);
1560   if (n->outcnt() != 0) {
1561     _igvn.replace_input_of(n, 1, orig);
1562     _igvn.remove_dead_node(phi);
1563   }
1564   return true;
1565 }
1566 
1567 //------------------------------split_if_with_blocks_post----------------------
1568 // Do the real work in a non-recursive function.  CFG hackery wants to be
1569 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
1570 // info.
1571 void PhaseIdealLoop::split_if_with_blocks_post(Node *n) {
1572 
1573   if (flat_array_element_type_check(n)) {
1574     return;
1575   }
1576 
1577   // Cloning Cmp through Phi's involves the split-if transform.
1578   // FastLock is not used by an If
1579   if (n->is_Cmp() && !n->is_FastLock()) {
1580     Node *n_ctrl = get_ctrl(n);
1581     // Determine if the Node has inputs from some local Phi.
1582     // Returns the block to clone thru.
1583     Node *n_blk = has_local_phi_input(n);
1584     if (n_blk != n_ctrl) {
1585       return;
1586     }
1587 
1588     if (!can_split_if(n_ctrl)) {
1589       return;
1590     }
1591 
1592     if (n->outcnt() != 1) {
1593       return; // Multiple bool's from 1 compare?
1594     }
1595     Node *bol = n->unique_out();
1596     assert(bol->is_Bool(), "expect a bool here");
1597     if (bol->outcnt() != 1) {
1598       return;// Multiple branches from 1 compare?
1599     }
1600     Node *iff = bol->unique_out();
1601 
1602     // Check some safety conditions
1603     if (iff->is_If()) {        // Classic split-if?
1604       if (iff->in(0) != n_ctrl) {
1605         return; // Compare must be in same blk as if
1606       }
1607     } else if (iff->is_CMove()) { // Trying to split-up a CMOVE
1608       // Can't split CMove with different control.
1609       if (get_ctrl(iff) != n_ctrl) {
1610         return;
1611       }
1612       if (get_ctrl(iff->in(2)) == n_ctrl ||
1613           get_ctrl(iff->in(3)) == n_ctrl) {
1614         return;                 // Inputs not yet split-up
1615       }
1616       if (get_loop(n_ctrl) != get_loop(get_ctrl(iff))) {
1617         return;                 // Loop-invar test gates loop-varying CMOVE
1618       }
1619     } else {
1620       return;  // some other kind of node, such as an Allocate
1621     }
1622 
1623     // When is split-if profitable?  Every 'win' on means some control flow
1624     // goes dead, so it's almost always a win.
1625     int policy = 0;
1626     // Split compare 'n' through the merge point if it is profitable
1627     Node *phi = split_thru_phi( n, n_ctrl, policy);
1628     if (!phi) {
1629       return;
1630     }
1631 
1632     // Now split the bool up thru the phi
1633     Node* bolphi = split_thru_phi(bol, n_ctrl, -1);
1634     guarantee(bolphi != nullptr, "null boolean phi node");
1635     assert(iff->in(1) == bolphi, "");
1636 
1637     if (bolphi->Value(&_igvn)->singleton()) {
1638       return;
1639     }
1640 
1641     // Conditional-move?  Must split up now
1642     if (!iff->is_If()) {
1643       Node* cmovphi = split_thru_phi(iff, n_ctrl, -1);
1644       return;
1645     }
1646 
1647     // Now split the IF
1648     C->print_method(PHASE_BEFORE_SPLIT_IF, 4, iff);
1649     if (TraceLoopOpts) {
1650       tty->print_cr("Split-If");
1651     }
1652     do_split_if(iff);
1653     C->print_method(PHASE_AFTER_SPLIT_IF, 4, iff);
1654     return;
1655   }
1656 
1657   // Two identical ifs back to back can be merged
1658   if (try_merge_identical_ifs(n)) {
1659     return;
1660   }
1661 
1662   // Check for an IF ready to split; one that has its
1663   // condition codes input coming from a Phi at the block start.
1664   int n_op = n->Opcode();
1665 
1666   // Check for an IF being dominated by another IF same test
1667   if (n_op == Op_If ||
1668       n_op == Op_RangeCheck) {
1669     Node *bol = n->in(1);
1670     uint max = bol->outcnt();
1671     // Check for same test used more than once?
1672     if (bol->is_Bool() && (max > 1 || bol->in(1)->is_SubTypeCheck())) {
1673       // Search up IDOMs to see if this IF is dominated.
1674       Node* cmp = bol->in(1);
1675       Node *cutoff = cmp->is_SubTypeCheck() ? dom_lca(get_ctrl(cmp->in(1)), get_ctrl(cmp->in(2))) : get_ctrl(bol);
1676 
1677       // Now search up IDOMs till cutoff, looking for a dominating test
1678       Node *prevdom = n;
1679       Node *dom = idom(prevdom);
1680       while (dom != cutoff) {
1681         if (dom->req() > 1 && n->as_If()->same_condition(dom, &_igvn) && prevdom->in(0) == dom &&
1682             safe_for_if_replacement(dom)) {
1683           // It's invalid to move control dependent data nodes in the inner
1684           // strip-mined loop, because:
1685           //  1) break validation of LoopNode::verify_strip_mined()
1686           //  2) move code with side-effect in strip-mined loop
1687           // Move to the exit of outer strip-mined loop in that case.
1688           Node* out_le = is_inner_of_stripmined_loop(dom);
1689           if (out_le != nullptr) {
1690             prevdom = out_le;
1691           }
1692           // Replace the dominated test with an obvious true or false.
1693           // Place it on the IGVN worklist for later cleanup.
1694           C->set_major_progress();
1695           // Split if: pin array accesses that are control dependent on a range check and moved to a regular if,
1696           // to prevent an array load from floating above its range check. There are three cases:
1697           // 1. Move from RangeCheck "a" to RangeCheck "b": don't need to pin. If we ever remove b, then we pin
1698           //    all its array accesses at that point.
1699           // 2. We move from RangeCheck "a" to regular if "b": need to pin. If we ever remove b, then its array
1700           //    accesses would start to float, since we don't pin at that point.
1701           // 3. If we move from regular if: don't pin. All array accesses are already assumed to be pinned.
1702           bool pin_array_access_nodes =  n->Opcode() == Op_RangeCheck &&
1703                                          prevdom->in(0)->Opcode() != Op_RangeCheck;
1704           dominated_by(prevdom->as_IfProj(), n->as_If(), false, pin_array_access_nodes);
1705           DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
1706           return;
1707         }
1708         prevdom = dom;
1709         dom = idom(prevdom);
1710       }
1711     }
1712   }
1713 
1714   try_sink_out_of_loop(n);
1715   if (C->failing()) {
1716     return;
1717   }
1718 
1719   try_move_store_after_loop(n);
1720 
1721   // Remove multiple allocations of the same inline type
1722   if (n->is_InlineType()) {
1723     n->as_InlineType()->remove_redundant_allocations(this);
1724   }
1725 }
1726 
1727 // Transform:
1728 //
1729 // if (some_condition) {
1730 //   // body 1
1731 // } else {
1732 //   // body 2
1733 // }
1734 // if (some_condition) {
1735 //   // body 3
1736 // } else {
1737 //   // body 4
1738 // }
1739 //
1740 // into:
1741 //
1742 //
1743 // if (some_condition) {
1744 //   // body 1
1745 //   // body 3
1746 // } else {
1747 //   // body 2
1748 //   // body 4
1749 // }
1750 bool PhaseIdealLoop::try_merge_identical_ifs(Node* n) {
1751   if (identical_backtoback_ifs(n) && can_split_if(n->in(0))) {
1752     Node *n_ctrl = n->in(0);
1753     IfNode* dom_if = idom(n_ctrl)->as_If();
1754     if (n->in(1) != dom_if->in(1)) {
1755       assert(n->in(1)->in(1)->is_SubTypeCheck() &&
1756              (n->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr ||
1757               dom_if->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr), "only for subtype checks with profile data attached");
1758       _igvn.replace_input_of(n, 1, dom_if->in(1));
1759     }
1760     IfTrueNode* dom_proj_true = dom_if->true_proj();
1761     IfFalseNode* dom_proj_false = dom_if->false_proj();
1762 
1763     // Now split the IF
1764     RegionNode* new_false_region;
1765     RegionNode* new_true_region;
1766     do_split_if(n, &new_false_region, &new_true_region);
1767     assert(new_false_region->req() == new_true_region->req(), "");
1768 #ifdef ASSERT
1769     for (uint i = 1; i < new_false_region->req(); ++i) {
1770       assert(new_false_region->in(i)->in(0) == new_true_region->in(i)->in(0), "unexpected shape following split if");
1771       assert(i == new_false_region->req() - 1 || new_false_region->in(i)->in(0)->in(1) == new_false_region->in(i + 1)->in(0)->in(1), "unexpected shape following split if");
1772     }
1773 #endif
1774     assert(new_false_region->in(1)->in(0)->in(1) == dom_if->in(1), "dominating if and dominated if after split must share test");
1775 
1776     // We now have:
1777     // if (some_condition) {
1778     //   // body 1
1779     //   if (some_condition) {
1780     //     body3: // new_true_region
1781     //     // body3
1782     //   } else {
1783     //     goto body4;
1784     //   }
1785     // } else {
1786     //   // body 2
1787     //  if (some_condition) {
1788     //     goto body3;
1789     //   } else {
1790     //     body4:   // new_false_region
1791     //     // body4;
1792     //   }
1793     // }
1794     //
1795 
1796     // clone pinned nodes thru the resulting regions
1797     push_pinned_nodes_thru_region(dom_if, new_true_region);
1798     push_pinned_nodes_thru_region(dom_if, new_false_region);
1799 
1800     // Optimize out the cloned ifs. Because pinned nodes were cloned, this also allows a CastPP that would be dependent
1801     // on a projection of n to have the dom_if as a control dependency. We don't want the CastPP to end up with an
1802     // unrelated control dependency.
1803     for (uint i = 1; i < new_false_region->req(); i++) {
1804       if (is_dominator(dom_proj_true, new_false_region->in(i))) {
1805         dominated_by(dom_proj_true, new_false_region->in(i)->in(0)->as_If());
1806       } else {
1807         assert(is_dominator(dom_proj_false, new_false_region->in(i)), "bad if");
1808         dominated_by(dom_proj_false, new_false_region->in(i)->in(0)->as_If());
1809       }
1810     }
1811     return true;
1812   }
1813   return false;
1814 }
1815 
1816 void PhaseIdealLoop::push_pinned_nodes_thru_region(IfNode* dom_if, Node* region) {
1817   for (DUIterator i = region->outs(); region->has_out(i); i++) {
1818     Node* u = region->out(i);
1819     if (!has_ctrl(u) || u->is_Phi() || !u->depends_only_on_test() || !_igvn.no_dependent_zero_check(u)) {
1820       continue;
1821     }
1822     assert(u->in(0) == region, "not a control dependent node?");
1823     uint j = 1;
1824     for (; j < u->req(); ++j) {
1825       Node* in = u->in(j);
1826       if (!is_dominator(ctrl_or_self(in), dom_if)) {
1827         break;
1828       }
1829     }
1830     if (j == u->req()) {
1831       Node *phi = PhiNode::make_blank(region, u);
1832       for (uint k = 1; k < region->req(); ++k) {
1833         Node* clone = u->clone();
1834         clone->set_req(0, region->in(k));
1835         register_new_node(clone, region->in(k));
1836         phi->init_req(k, clone);
1837       }
1838       register_new_node(phi, region);
1839       _igvn.replace_node(u, phi);
1840       --i;
1841     }
1842   }
1843 }
1844 
1845 bool PhaseIdealLoop::safe_for_if_replacement(const Node* dom) const {
1846   if (!dom->is_CountedLoopEnd()) {
1847     return true;
1848   }
1849   CountedLoopEndNode* le = dom->as_CountedLoopEnd();
1850   CountedLoopNode* cl = le->loopnode();
1851   if (cl == nullptr) {
1852     return true;
1853   }
1854   if (!cl->is_main_loop()) {
1855     return true;
1856   }
1857   if (cl->is_canonical_loop_entry() == nullptr) {
1858     return true;
1859   }
1860   // Further unrolling is possible so loop exit condition might change
1861   return false;
1862 }
1863 
1864 // See if a shared loop-varying computation has no loop-varying uses.
1865 // Happens if something is only used for JVM state in uncommon trap exits,
1866 // like various versions of induction variable+offset.  Clone the
1867 // computation per usage to allow it to sink out of the loop.
1868 void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
1869   bool is_raw_to_oop_cast = n->is_ConstraintCast() &&
1870                             n->in(1)->bottom_type()->isa_rawptr() &&
1871                             !n->bottom_type()->isa_rawptr();
1872 
1873   if (has_ctrl(n) &&
1874       !n->is_Phi() &&
1875       !n->is_Bool() &&
1876       !n->is_Proj() &&
1877       !n->is_MergeMem() &&
1878       !n->is_CMove() &&
1879       !n->is_OpaqueNotNull() &&
1880       !n->is_OpaqueInitializedAssertionPredicate() &&
1881       !n->is_OpaqueTemplateAssertionPredicate() &&
1882       !is_raw_to_oop_cast && // don't extend live ranges of raw oops
1883       (KillPathsReachableByDeadTypeNode || !n->is_Type())
1884       ) {
1885     Node *n_ctrl = get_ctrl(n);
1886     IdealLoopTree *n_loop = get_loop(n_ctrl);
1887 
1888     if (n->in(0) != nullptr) {
1889       IdealLoopTree* loop_ctrl = get_loop(n->in(0));
1890       if (n_loop != loop_ctrl && n_loop->is_member(loop_ctrl)) {
1891         // n has a control input inside a loop but get_ctrl() is member of an outer loop. This could happen, for example,
1892         // for Div nodes inside a loop (control input inside loop) without a use except for an UCT (outside the loop).
1893         // Rewire control of n to right outside of the loop, regardless if its input(s) are later sunk or not.
1894         Node* maybe_pinned_n = n;
1895         Node* outside_ctrl = place_outside_loop(n_ctrl, loop_ctrl);
1896         if (!would_sink_below_pre_loop_exit(loop_ctrl, outside_ctrl)) {
1897           if (n->depends_only_on_test()) {
1898             Node* pinned_clone = n->pin_array_access_node();
1899             if (pinned_clone != nullptr) {
1900               // Pin array access nodes: if this is an array load, it's going to be dependent on a condition that's not a
1901               // range check for that access. If that condition is replaced by an identical dominating one, then an
1902               // unpinned load would risk floating above its range check.
1903               register_new_node(pinned_clone, n_ctrl);
1904               maybe_pinned_n = pinned_clone;
1905               _igvn.replace_node(n, pinned_clone);
1906             }
1907           }
1908           _igvn.replace_input_of(maybe_pinned_n, 0, outside_ctrl);
1909         }
1910       }
1911     }
1912     if (n_loop != _ltree_root && n->outcnt() > 1) {
1913       // Compute early control: needed for anti-dependence analysis. It's also possible that as a result of
1914       // previous transformations in this loop opts round, the node can be hoisted now: early control will tell us.
1915       Node* early_ctrl = compute_early_ctrl(n, n_ctrl);
1916       if (n_loop->is_member(get_loop(early_ctrl)) && // check that this one can't be hoisted now
1917           ctrl_of_all_uses_out_of_loop(n, early_ctrl, n_loop)) { // All uses in outer loops!
1918         if (n->is_Store() || n->is_LoadStore()) {
1919             assert(false, "no node with a side effect");
1920             C->record_failure("no node with a side effect");
1921             return;
1922         }
1923         Node* outer_loop_clone = nullptr;
1924         for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin;) {
1925           Node* u = n->last_out(j); // Clone private computation per use
1926           _igvn.rehash_node_delayed(u);
1927           Node* x = nullptr;
1928           if (n->depends_only_on_test()) {
1929             // Pin array access nodes: if this is an array load, it's going to be dependent on a condition that's not a
1930             // range check for that access. If that condition is replaced by an identical dominating one, then an
1931             // unpinned load would risk floating above its range check.
1932             x = n->pin_array_access_node();
1933           }
1934           if (x == nullptr) {
1935             x = n->clone();
1936           }
1937           Node* x_ctrl = nullptr;
1938           if (u->is_Phi()) {
1939             // Replace all uses of normal nodes.  Replace Phi uses
1940             // individually, so the separate Nodes can sink down
1941             // different paths.
1942             uint k = 1;
1943             while (u->in(k) != n) k++;
1944             u->set_req(k, x);
1945             // x goes next to Phi input path
1946             x_ctrl = u->in(0)->in(k);
1947             // Find control for 'x' next to use but not inside inner loops.
1948             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1949             --j;
1950           } else {              // Normal use
1951             if (has_ctrl(u)) {
1952               x_ctrl = get_ctrl(u);
1953             } else {
1954               x_ctrl = u->in(0);
1955             }
1956             // Find control for 'x' next to use but not inside inner loops.
1957             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1958             // Replace all uses
1959             if (u->is_ConstraintCast() && _igvn.type(n)->higher_equal(u->bottom_type()) && u->in(0) == x_ctrl) {
1960               // If we're sinking a chain of data nodes, we might have inserted a cast to pin the use which is not necessary
1961               // anymore now that we're going to pin n as well
1962               _igvn.replace_node(u, x);
1963               --j;
1964             } else {
1965               int nb = u->replace_edge(n, x, &_igvn);
1966               j -= nb;
1967             }
1968           }
1969 
1970           if (n->is_Load()) {
1971             // For loads, add a control edge to a CFG node outside of the loop
1972             // to force them to not combine and return back inside the loop
1973             // during GVN optimization (4641526).
1974             assert(x_ctrl == get_late_ctrl_with_anti_dep(x->as_Load(), early_ctrl, x_ctrl), "anti-dependences were already checked");
1975 
1976             IdealLoopTree* x_loop = get_loop(x_ctrl);
1977             Node* x_head = x_loop->_head;
1978             if (x_head->is_Loop() && x_head->is_OuterStripMinedLoop()) {
1979               // Do not add duplicate LoadNodes to the outer strip mined loop
1980               if (outer_loop_clone != nullptr) {
1981                 _igvn.replace_node(x, outer_loop_clone);
1982                 continue;
1983               }
1984               outer_loop_clone = x;
1985             }
1986             x->set_req(0, x_ctrl);
1987           } else if (n->in(0) != nullptr){
1988             x->set_req(0, x_ctrl);
1989           }
1990           assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
1991           assert(!n_loop->is_member(get_loop(x_ctrl)), "should have moved out of loop");
1992           register_new_node(x, x_ctrl);
1993 
1994           // Chain of AddP nodes: (AddP base (AddP base (AddP base )))
1995           // All AddP nodes must keep the same base after sinking so:
1996           // 1- We don't add a CastPP here until the last one of the chain is sunk: if part of the chain is not sunk,
1997           // their bases remain the same.
1998           // (see 2- below)
1999           assert(!x->is_AddP() || !x->in(AddPNode::Address)->is_AddP() ||
2000                  x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base) ||
2001                  !x->in(AddPNode::Address)->in(AddPNode::Base)->eqv_uncast(x->in(AddPNode::Base)), "unexpected AddP shape");
2002           if (x->in(0) == nullptr && !x->is_DecodeNarrowPtr() &&
2003               !(x->is_AddP() && x->in(AddPNode::Address)->is_AddP() && x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base))) {
2004             assert(!x->is_Load(), "load should be pinned");
2005             // Use a cast node to pin clone out of loop
2006             Node* cast = nullptr;
2007             for (uint k = 0; k < x->req(); k++) {
2008               Node* in = x->in(k);
2009               if (in != nullptr && ctrl_is_member(n_loop, in)) {
2010                 const Type* in_t = _igvn.type(in);
2011                 cast = ConstraintCastNode::make_cast_for_type(x_ctrl, in, in_t,
2012                                                               ConstraintCastNode::DependencyType::NonFloatingNonNarrowing, nullptr);
2013               }
2014               if (cast != nullptr) {
2015                 Node* prev = _igvn.hash_find_insert(cast);
2016                 if (prev != nullptr && get_ctrl(prev) == x_ctrl) {
2017                   cast->destruct(&_igvn);
2018                   cast = prev;
2019                 } else {
2020                   register_new_node(cast, x_ctrl);
2021                 }
2022                 x->replace_edge(in, cast);
2023                 // Chain of AddP nodes:
2024                 // 2- A CastPP of the base is only added now that all AddP nodes are sunk
2025                 if (x->is_AddP() && k == AddPNode::Base) {
2026                   update_addp_chain_base(x, n->in(AddPNode::Base), cast);
2027                 }
2028                 break;
2029               }
2030             }
2031             assert(cast != nullptr, "must have added a cast to pin the node");
2032           }
2033         }
2034         _igvn.remove_dead_node(n);
2035       }
2036       _dom_lca_tags_round = 0;
2037     }
2038   }
2039 }
2040 
2041 void PhaseIdealLoop::update_addp_chain_base(Node* x, Node* old_base, Node* new_base) {
2042   ResourceMark rm;
2043   Node_List wq;
2044   wq.push(x);
2045   while (wq.size() != 0) {
2046     Node* n = wq.pop();
2047     for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2048       Node* u = n->fast_out(i);
2049       if (u->is_AddP() && u->in(AddPNode::Base) == old_base) {
2050         _igvn.replace_input_of(u, AddPNode::Base, new_base);
2051         wq.push(u);
2052       }
2053     }
2054   }
2055 }
2056 
2057 // Compute the early control of a node by following its inputs until we reach
2058 // nodes that are pinned. Then compute the LCA of the control of all pinned nodes.
2059 Node* PhaseIdealLoop::compute_early_ctrl(Node* n, Node* n_ctrl) {
2060   Node* early_ctrl = nullptr;
2061   ResourceMark rm;
2062   Unique_Node_List wq;
2063   wq.push(n);
2064   for (uint i = 0; i < wq.size(); i++) {
2065     Node* m = wq.at(i);
2066     Node* c = nullptr;
2067     if (m->is_CFG()) {
2068       c = m;
2069     } else if (m->pinned()) {
2070       c = m->in(0);
2071     } else {
2072       for (uint j = 0; j < m->req(); j++) {
2073         Node* in = m->in(j);
2074         if (in != nullptr) {
2075           wq.push(in);
2076         }
2077       }
2078     }
2079     if (c != nullptr) {
2080       assert(is_dominator(c, n_ctrl), "control input must dominate current control");
2081       if (early_ctrl == nullptr || is_dominator(early_ctrl, c)) {
2082         early_ctrl = c;
2083       }
2084     }
2085   }
2086   assert(is_dominator(early_ctrl, n_ctrl), "early control must dominate current control");
2087   return early_ctrl;
2088 }
2089 
2090 bool PhaseIdealLoop::ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop) {
2091   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2092     Node* u = n->fast_out(i);
2093     if (u->is_Opaque1()) {
2094       return false;  // Found loop limit, bugfix for 4677003
2095     }
2096     // We can't reuse tags in PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal() so make sure calls to
2097     // get_late_ctrl_with_anti_dep() use their own tag
2098     _dom_lca_tags_round++;
2099     assert(_dom_lca_tags_round != 0, "shouldn't wrap around");
2100 
2101     if (u->is_Phi()) {
2102       for (uint j = 1; j < u->req(); ++j) {
2103         if (u->in(j) == n && !ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, u->in(0)->in(j))) {
2104           return false;
2105         }
2106       }
2107     } else {
2108       Node* ctrl = has_ctrl(u) ? get_ctrl(u) : u->in(0);
2109       if (!ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, ctrl)) {
2110         return false;
2111       }
2112     }
2113   }
2114   return true;
2115 }
2116 
2117 // Sinking a node from a pre loop to its main loop pins the node between the pre and main loops. If that node is input
2118 // to a check that's eliminated by range check elimination, it becomes input to an expression that feeds into the exit
2119 // test of the pre loop above the point in the graph where it's pinned. This results in a broken graph. One way to avoid
2120 // it would be to not eliminate the check in the main loop. Instead, we prevent sinking of the node here so better code
2121 // is generated for the main loop.
2122 bool PhaseIdealLoop::would_sink_below_pre_loop_exit(IdealLoopTree* n_loop, Node* ctrl) {
2123   if (n_loop->_head->is_CountedLoop() && n_loop->_head->as_CountedLoop()->is_pre_loop()) {
2124     CountedLoopNode* pre_loop = n_loop->_head->as_CountedLoop();
2125     if (is_dominator(pre_loop->loopexit(), ctrl)) {
2126       return true;
2127     }
2128   }
2129   return false;
2130 }
2131 
2132 bool PhaseIdealLoop::ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl) {
2133   if (n->is_Load()) {
2134     ctrl = get_late_ctrl_with_anti_dep(n->as_Load(), n_ctrl, ctrl);
2135   }
2136   IdealLoopTree *u_loop = get_loop(ctrl);
2137   if (u_loop == n_loop) {
2138     return false; // Found loop-varying use
2139   }
2140   if (n_loop->is_member(u_loop)) {
2141     return false; // Found use in inner loop
2142   }
2143   if (would_sink_below_pre_loop_exit(n_loop, ctrl)) {
2144     return false;
2145   }
2146   return true;
2147 }
2148 
2149 //------------------------------split_if_with_blocks---------------------------
2150 // Check for aggressive application of 'split-if' optimization,
2151 // using basic block level info.
2152 void PhaseIdealLoop::split_if_with_blocks(VectorSet &visited, Node_Stack &nstack) {
2153   Node* root = C->root();
2154   visited.set(root->_idx); // first, mark root as visited
2155   // Do pre-visit work for root
2156   Node* n   = split_if_with_blocks_pre(root);
2157   uint  cnt = n->outcnt();
2158   uint  i   = 0;
2159 
2160   while (true) {
2161     // Visit all children
2162     if (i < cnt) {
2163       Node* use = n->raw_out(i);
2164       ++i;
2165       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
2166         // Now do pre-visit work for this use
2167         use = split_if_with_blocks_pre(use);
2168         nstack.push(n, i); // Save parent and next use's index.
2169         n   = use;         // Process all children of current use.
2170         cnt = use->outcnt();
2171         i   = 0;
2172       }
2173     }
2174     else {
2175       // All of n's children have been processed, complete post-processing.
2176       if (cnt != 0 && !n->is_Con()) {
2177         assert(has_node(n), "no dead nodes");
2178         split_if_with_blocks_post(n);
2179         if (C->failing()) {
2180           return;
2181         }
2182       }
2183       if (must_throttle_split_if()) {
2184         nstack.clear();
2185       }
2186       if (nstack.is_empty()) {
2187         // Finished all nodes on stack.
2188         break;
2189       }
2190       // Get saved parent node and next use's index. Visit the rest of uses.
2191       n   = nstack.node();
2192       cnt = n->outcnt();
2193       i   = nstack.index();
2194       nstack.pop();
2195     }
2196   }
2197 }
2198 
2199 
2200 //=============================================================================
2201 //
2202 //                   C L O N E   A   L O O P   B O D Y
2203 //
2204 
2205 //------------------------------clone_iff--------------------------------------
2206 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2207 // "Nearly" because all Nodes have been cloned from the original in the loop,
2208 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2209 // through the Phi recursively, and return a Bool.
2210 Node* PhaseIdealLoop::clone_iff(PhiNode* phi) {
2211 
2212   // Convert this Phi into a Phi merging Bools
2213   uint i;
2214   for (i = 1; i < phi->req(); i++) {
2215     Node* b = phi->in(i);
2216     if (b->is_Phi()) {
2217       _igvn.replace_input_of(phi, i, clone_iff(b->as_Phi()));
2218     } else {
2219       assert(b->is_Bool() || b->is_OpaqueNotNull() || b->is_OpaqueInitializedAssertionPredicate(),
2220              "bool, non-null check with OpaqueNotNull or Initialized Assertion Predicate with its Opaque node");
2221     }
2222   }
2223   Node* n = phi->in(1);
2224   Node* sample_opaque = nullptr;
2225   Node *sample_bool = nullptr;
2226   if (n->is_OpaqueNotNull() || n->is_OpaqueInitializedAssertionPredicate()) {
2227     sample_opaque = n;
2228     sample_bool = n->in(1);
2229     assert(sample_bool->is_Bool(), "wrong type");
2230   } else {
2231     sample_bool = n;
2232   }
2233   Node* sample_cmp = sample_bool->in(1);
2234   const Type* t = Type::TOP;
2235   const TypePtr* at = nullptr;
2236   if (sample_cmp->is_FlatArrayCheck()) {
2237     // Left input of a FlatArrayCheckNode is memory, set the (adr) type of the phi accordingly
2238     assert(sample_cmp->in(1)->bottom_type() == Type::MEMORY, "unexpected input type");
2239     t = Type::MEMORY;
2240     at = TypeRawPtr::BOTTOM;
2241   }
2242 
2243   // Make Phis to merge the Cmp's inputs.
2244   PhiNode *phi1 = new PhiNode(phi->in(0), t, at);
2245   PhiNode *phi2 = new PhiNode(phi->in(0), Type::TOP);
2246   for (i = 1; i < phi->req(); i++) {
2247     Node *n1 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(1) : phi->in(i)->in(1)->in(1)->in(1);
2248     Node *n2 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(2) : phi->in(i)->in(1)->in(1)->in(2);
2249     phi1->set_req(i, n1);
2250     phi2->set_req(i, n2);
2251     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2252     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2253   }
2254   // See if these Phis have been made before.
2255   // Register with optimizer
2256   Node *hit1 = _igvn.hash_find_insert(phi1);
2257   if (hit1) {                   // Hit, toss just made Phi
2258     _igvn.remove_dead_node(phi1); // Remove new phi
2259     assert(hit1->is_Phi(), "" );
2260     phi1 = (PhiNode*)hit1;      // Use existing phi
2261   } else {                      // Miss
2262     _igvn.register_new_node_with_optimizer(phi1);
2263   }
2264   Node *hit2 = _igvn.hash_find_insert(phi2);
2265   if (hit2) {                   // Hit, toss just made Phi
2266     _igvn.remove_dead_node(phi2); // Remove new phi
2267     assert(hit2->is_Phi(), "" );
2268     phi2 = (PhiNode*)hit2;      // Use existing phi
2269   } else {                      // Miss
2270     _igvn.register_new_node_with_optimizer(phi2);
2271   }
2272   // Register Phis with loop/block info
2273   set_ctrl(phi1, phi->in(0));
2274   set_ctrl(phi2, phi->in(0));
2275   // Make a new Cmp
2276   Node *cmp = sample_cmp->clone();
2277   cmp->set_req(1, phi1);
2278   cmp->set_req(2, phi2);
2279   _igvn.register_new_node_with_optimizer(cmp);
2280   set_ctrl(cmp, phi->in(0));
2281 
2282   // Make a new Bool
2283   Node *b = sample_bool->clone();
2284   b->set_req(1,cmp);
2285   _igvn.register_new_node_with_optimizer(b);
2286   set_ctrl(b, phi->in(0));
2287 
2288   if (sample_opaque != nullptr) {
2289     Node* opaque = sample_opaque->clone();
2290     opaque->set_req(1, b);
2291     _igvn.register_new_node_with_optimizer(opaque);
2292     set_ctrl(opaque, phi->in(0));
2293     return opaque;
2294   }
2295 
2296   assert(b->is_Bool(), "");
2297   return b;
2298 }
2299 
2300 //------------------------------clone_bool-------------------------------------
2301 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2302 // "Nearly" because all Nodes have been cloned from the original in the loop,
2303 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2304 // through the Phi recursively, and return a Bool.
2305 CmpNode*PhaseIdealLoop::clone_bool(PhiNode* phi) {
2306   uint i;
2307   // Convert this Phi into a Phi merging Bools
2308   for( i = 1; i < phi->req(); i++ ) {
2309     Node *b = phi->in(i);
2310     if( b->is_Phi() ) {
2311       _igvn.replace_input_of(phi, i, clone_bool(b->as_Phi()));
2312     } else {
2313       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
2314     }
2315   }
2316 
2317   Node *sample_cmp = phi->in(1);
2318 
2319   // Make Phis to merge the Cmp's inputs.
2320   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
2321   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
2322   for( uint j = 1; j < phi->req(); j++ ) {
2323     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
2324     Node *n1, *n2;
2325     if( cmp_top->is_Cmp() ) {
2326       n1 = cmp_top->in(1);
2327       n2 = cmp_top->in(2);
2328     } else {
2329       n1 = n2 = cmp_top;
2330     }
2331     phi1->set_req( j, n1 );
2332     phi2->set_req( j, n2 );
2333     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2334     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2335   }
2336 
2337   // See if these Phis have been made before.
2338   // Register with optimizer
2339   Node *hit1 = _igvn.hash_find_insert(phi1);
2340   if( hit1 ) {                  // Hit, toss just made Phi
2341     _igvn.remove_dead_node(phi1); // Remove new phi
2342     assert( hit1->is_Phi(), "" );
2343     phi1 = (PhiNode*)hit1;      // Use existing phi
2344   } else {                      // Miss
2345     _igvn.register_new_node_with_optimizer(phi1);
2346   }
2347   Node *hit2 = _igvn.hash_find_insert(phi2);
2348   if( hit2 ) {                  // Hit, toss just made Phi
2349     _igvn.remove_dead_node(phi2); // Remove new phi
2350     assert( hit2->is_Phi(), "" );
2351     phi2 = (PhiNode*)hit2;      // Use existing phi
2352   } else {                      // Miss
2353     _igvn.register_new_node_with_optimizer(phi2);
2354   }
2355   // Register Phis with loop/block info
2356   set_ctrl(phi1, phi->in(0));
2357   set_ctrl(phi2, phi->in(0));
2358   // Make a new Cmp
2359   Node *cmp = sample_cmp->clone();
2360   cmp->set_req( 1, phi1 );
2361   cmp->set_req( 2, phi2 );
2362   _igvn.register_new_node_with_optimizer(cmp);
2363   set_ctrl(cmp, phi->in(0));
2364 
2365   assert( cmp->is_Cmp(), "" );
2366   return (CmpNode*)cmp;
2367 }
2368 
2369 void PhaseIdealLoop::clone_loop_handle_data_uses(Node* old, Node_List &old_new,
2370                                                  IdealLoopTree* loop, IdealLoopTree* outer_loop,
2371                                                  Node_List*& split_if_set, Node_List*& split_bool_set,
2372                                                  Node_List*& split_cex_set, Node_List& worklist,
2373                                                  uint new_counter, CloneLoopMode mode) {
2374   Node* nnn = old_new[old->_idx];
2375   // Copy uses to a worklist, so I can munge the def-use info
2376   // with impunity.
2377   for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
2378     worklist.push(old->fast_out(j));
2379 
2380   while( worklist.size() ) {
2381     Node *use = worklist.pop();
2382     if (!has_node(use))  continue; // Ignore dead nodes
2383     if (use->in(0) == C->top())  continue;
2384     IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
2385     // Check for data-use outside of loop - at least one of OLD or USE
2386     // must not be a CFG node.
2387 #ifdef ASSERT
2388     if (loop->_head->as_Loop()->is_strip_mined() && outer_loop->is_member(use_loop) && !loop->is_member(use_loop) && old_new[use->_idx] == nullptr) {
2389       Node* sfpt = loop->_head->as_CountedLoop()->outer_safepoint();
2390       assert(mode != IgnoreStripMined, "incorrect cloning mode");
2391       assert((mode == ControlAroundStripMined && use == sfpt) || !use->is_reachable_from_root(), "missed a node");
2392     }
2393 #endif
2394     if (!loop->is_member(use_loop) && !outer_loop->is_member(use_loop) && (!old->is_CFG() || !use->is_CFG())) {
2395 
2396       // If the Data use is an IF, that means we have an IF outside the
2397       // loop that is switching on a condition that is set inside the
2398       // loop.  Happens if people set a loop-exit flag; then test the flag
2399       // in the loop to break the loop, then test is again outside the
2400       // loop to determine which way the loop exited.
2401       //
2402       // For several uses we need to make sure that there is no phi between,
2403       // the use and the Bool/Cmp. We therefore clone the Bool/Cmp down here
2404       // to avoid such a phi in between.
2405       // For example, it is unexpected that there is a Phi between an
2406       // AllocateArray node and its ValidLengthTest input that could cause
2407       // split if to break.
2408       assert(!use->is_OpaqueTemplateAssertionPredicate(),
2409              "should not clone a Template Assertion Predicate which should be removed once it's useless");
2410       if (use->is_If() || use->is_CMove() || use->is_OpaqueNotNull() || use->is_OpaqueInitializedAssertionPredicate() ||
2411           (use->Opcode() == Op_AllocateArray && use->in(AllocateNode::ValidLengthTest) == old)) {
2412         // Since this code is highly unlikely, we lazily build the worklist
2413         // of such Nodes to go split.
2414         if (!split_if_set) {
2415           split_if_set = new Node_List();
2416         }
2417         split_if_set->push(use);
2418       }
2419       if (use->is_Bool()) {
2420         if (!split_bool_set) {
2421           split_bool_set = new Node_List();
2422         }
2423         split_bool_set->push(use);
2424       }
2425       if (use->Opcode() == Op_CreateEx) {
2426         if (!split_cex_set) {
2427           split_cex_set = new Node_List();
2428         }
2429         split_cex_set->push(use);
2430       }
2431 
2432 
2433       // Get "block" use is in
2434       uint idx = 0;
2435       while( use->in(idx) != old ) idx++;
2436       Node *prev = use->is_CFG() ? use : get_ctrl(use);
2437       assert(!loop->is_member(get_loop(prev)) && !outer_loop->is_member(get_loop(prev)), "" );
2438       Node* cfg = (prev->_idx >= new_counter && prev->is_Region())
2439         ? prev->in(2)
2440         : idom(prev);
2441       if( use->is_Phi() )     // Phi use is in prior block
2442         cfg = prev->in(idx);  // NOT in block of Phi itself
2443       if (cfg->is_top()) {    // Use is dead?
2444         _igvn.replace_input_of(use, idx, C->top());
2445         continue;
2446       }
2447 
2448       // If use is referenced through control edge... (idx == 0)
2449       if (mode == IgnoreStripMined && idx == 0) {
2450         LoopNode *head = loop->_head->as_Loop();
2451         if (head->is_strip_mined() && is_dominator(head->outer_loop_exit(), prev)) {
2452           // That node is outside the inner loop, leave it outside the
2453           // outer loop as well to not confuse verification code.
2454           assert(!loop->_parent->is_member(use_loop), "should be out of the outer loop");
2455           _igvn.replace_input_of(use, 0, head->outer_loop_exit());
2456           continue;
2457         }
2458       }
2459 
2460       while(!outer_loop->is_member(get_loop(cfg))) {
2461         prev = cfg;
2462         cfg = (cfg->_idx >= new_counter && cfg->is_Region()) ? cfg->in(2) : idom(cfg);
2463       }
2464       // If the use occurs after merging several exits from the loop, then
2465       // old value must have dominated all those exits.  Since the same old
2466       // value was used on all those exits we did not need a Phi at this
2467       // merge point.  NOW we do need a Phi here.  Each loop exit value
2468       // is now merged with the peeled body exit; each exit gets its own
2469       // private Phi and those Phis need to be merged here.
2470       Node *phi;
2471       if( prev->is_Region() ) {
2472         if( idx == 0 ) {      // Updating control edge?
2473           phi = prev;         // Just use existing control
2474         } else {              // Else need a new Phi
2475           phi = PhiNode::make( prev, old );
2476           // Now recursively fix up the new uses of old!
2477           for( uint i = 1; i < prev->req(); i++ ) {
2478             worklist.push(phi); // Onto worklist once for each 'old' input
2479           }
2480         }
2481       } else {
2482         // Get new RegionNode merging old and new loop exits
2483         prev = old_new[prev->_idx];
2484         assert( prev, "just made this in step 7" );
2485         if( idx == 0) {      // Updating control edge?
2486           phi = prev;         // Just use existing control
2487         } else {              // Else need a new Phi
2488           // Make a new Phi merging data values properly
2489           phi = PhiNode::make( prev, old );
2490           phi->set_req( 1, nnn );
2491         }
2492       }
2493       // If inserting a new Phi, check for prior hits
2494       if( idx != 0 ) {
2495         Node *hit = _igvn.hash_find_insert(phi);
2496         if( hit == nullptr ) {
2497           _igvn.register_new_node_with_optimizer(phi); // Register new phi
2498         } else {                                      // or
2499           // Remove the new phi from the graph and use the hit
2500           _igvn.remove_dead_node(phi);
2501           phi = hit;                                  // Use existing phi
2502         }
2503         set_ctrl(phi, prev);
2504       }
2505       // Make 'use' use the Phi instead of the old loop body exit value
2506       assert(use->in(idx) == old, "old is still input of use");
2507       // We notify all uses of old, including use, and the indirect uses,
2508       // that may now be optimized because we have replaced old with phi.
2509       _igvn.add_users_to_worklist(old);
2510       if (idx == 0 &&
2511           use->depends_only_on_test()) {
2512         Node* pinned_clone = use->pin_array_access_node();
2513         if (pinned_clone != nullptr) {
2514           // Pin array access nodes: control is updated here to a region. If, after some transformations, only one path
2515           // into the region is left, an array load could become dependent on a condition that's not a range check for
2516           // that access. If that condition is replaced by an identical dominating one, then an unpinned load would risk
2517           // floating above its range check.
2518           pinned_clone->set_req(0, phi);
2519           register_new_node_with_ctrl_of(pinned_clone, use);
2520           _igvn.replace_node(use, pinned_clone);
2521           continue;
2522         }
2523       }
2524       _igvn.replace_input_of(use, idx, phi);
2525       if( use->_idx >= new_counter ) { // If updating new phis
2526         // Not needed for correctness, but prevents a weak assert
2527         // in AddPNode from tripping (when we end up with different
2528         // base & derived Phis that will become the same after
2529         // IGVN does CSE).
2530         Node *hit = _igvn.hash_find_insert(use);
2531         if( hit )             // Go ahead and re-hash for hits.
2532           _igvn.replace_node( use, hit );
2533       }
2534     }
2535   }
2536 }
2537 
2538 static void collect_nodes_in_outer_loop_not_reachable_from_sfpt(Node* n, const IdealLoopTree *loop, const IdealLoopTree* outer_loop,
2539                                                                 const Node_List &old_new, Unique_Node_List& wq, PhaseIdealLoop* phase,
2540                                                                 bool check_old_new) {
2541   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2542     Node* u = n->fast_out(j);
2543     assert(check_old_new || old_new[u->_idx] == nullptr, "shouldn't have been cloned");
2544     if (!u->is_CFG() && (!check_old_new || old_new[u->_idx] == nullptr)) {
2545       assert(!phase->ctrl_is_member(loop, u) || !loop->_body.contains(u), "can be in outer loop or out of both loops only");
2546       if (!phase->ctrl_is_member(loop, u)) {
2547         if (phase->ctrl_is_member(outer_loop, u)) {
2548           wq.push(u);
2549         } else {
2550           // nodes pinned with control in the outer loop but not referenced from the safepoint must be moved out of
2551           // the outer loop too
2552           Node* u_c = u->in(0);
2553           if (u_c != nullptr) {
2554             IdealLoopTree* u_c_loop = phase->get_loop(u_c);
2555             if (outer_loop->is_member(u_c_loop) && !loop->is_member(u_c_loop)) {
2556               wq.push(u);
2557             }
2558           }
2559         }
2560       }
2561     }
2562   }
2563 }
2564 
2565 void PhaseIdealLoop::clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
2566                                       IdealLoopTree* outer_loop, int dd, Node_List &old_new,
2567                                       Node_List& extra_data_nodes) {
2568   if (head->is_strip_mined() && mode != IgnoreStripMined) {
2569     CountedLoopNode* cl = head->as_CountedLoop();
2570     Node* l = cl->outer_loop();
2571     Node* tail = cl->outer_loop_tail();
2572     IfNode* le = cl->outer_loop_end();
2573     Node* sfpt = cl->outer_safepoint();
2574     CountedLoopEndNode* cle = cl->loopexit();
2575     CountedLoopNode* new_cl = old_new[cl->_idx]->as_CountedLoop();
2576     CountedLoopEndNode* new_cle = new_cl->as_CountedLoop()->loopexit_or_null();
2577     IfFalseNode* cle_out = cle->false_proj();
2578 
2579     Node* new_sfpt = nullptr;
2580     Node* new_cle_out = cle_out->clone();
2581     old_new.map(cle_out->_idx, new_cle_out);
2582     if (mode == CloneIncludesStripMined) {
2583       // clone outer loop body
2584       Node* new_l = l->clone();
2585       Node* new_tail = tail->clone();
2586       IfNode* new_le = le->clone()->as_If();
2587       new_sfpt = sfpt->clone();
2588 
2589       set_loop(new_l, outer_loop->_parent);
2590       set_idom(new_l, new_l->in(LoopNode::EntryControl), dd);
2591       set_loop(new_cle_out, outer_loop->_parent);
2592       set_idom(new_cle_out, new_cle, dd);
2593       set_loop(new_sfpt, outer_loop->_parent);
2594       set_idom(new_sfpt, new_cle_out, dd);
2595       set_loop(new_le, outer_loop->_parent);
2596       set_idom(new_le, new_sfpt, dd);
2597       set_loop(new_tail, outer_loop->_parent);
2598       set_idom(new_tail, new_le, dd);
2599       set_idom(new_cl, new_l, dd);
2600 
2601       old_new.map(l->_idx, new_l);
2602       old_new.map(tail->_idx, new_tail);
2603       old_new.map(le->_idx, new_le);
2604       old_new.map(sfpt->_idx, new_sfpt);
2605 
2606       new_l->set_req(LoopNode::LoopBackControl, new_tail);
2607       new_l->set_req(0, new_l);
2608       new_tail->set_req(0, new_le);
2609       new_le->set_req(0, new_sfpt);
2610       new_sfpt->set_req(0, new_cle_out);
2611       new_cle_out->set_req(0, new_cle);
2612       new_cl->set_req(LoopNode::EntryControl, new_l);
2613 
2614       _igvn.register_new_node_with_optimizer(new_l);
2615       _igvn.register_new_node_with_optimizer(new_tail);
2616       _igvn.register_new_node_with_optimizer(new_le);
2617     } else {
2618       Node *newhead = old_new[loop->_head->_idx];
2619       newhead->as_Loop()->clear_strip_mined();
2620       _igvn.replace_input_of(newhead, LoopNode::EntryControl, newhead->in(LoopNode::EntryControl)->in(LoopNode::EntryControl));
2621       set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2622     }
2623     // Look at data node that were assigned a control in the outer
2624     // loop: they are kept in the outer loop by the safepoint so start
2625     // from the safepoint node's inputs.
2626     IdealLoopTree* outer_loop = get_loop(l);
2627     Node_Stack stack(2);
2628     stack.push(sfpt, 1);
2629     uint new_counter = C->unique();
2630     while (stack.size() > 0) {
2631       Node* n = stack.node();
2632       uint i = stack.index();
2633       while (i < n->req() &&
2634              (n->in(i) == nullptr ||
2635               !has_ctrl(n->in(i)) ||
2636               get_loop(get_ctrl(n->in(i))) != outer_loop ||
2637               (old_new[n->in(i)->_idx] != nullptr && old_new[n->in(i)->_idx]->_idx >= new_counter))) {
2638         i++;
2639       }
2640       if (i < n->req()) {
2641         stack.set_index(i+1);
2642         stack.push(n->in(i), 0);
2643       } else {
2644         assert(old_new[n->_idx] == nullptr || n == sfpt || old_new[n->_idx]->_idx < new_counter, "no clone yet");
2645         Node* m = n == sfpt ? new_sfpt : n->clone();
2646         if (m != nullptr) {
2647           for (uint i = 0; i < n->req(); i++) {
2648             if (m->in(i) != nullptr && old_new[m->in(i)->_idx] != nullptr) {
2649               m->set_req(i, old_new[m->in(i)->_idx]);
2650             }
2651           }
2652         } else {
2653           assert(n == sfpt && mode != CloneIncludesStripMined, "where's the safepoint clone?");
2654         }
2655         if (n != sfpt) {
2656           extra_data_nodes.push(n);
2657           _igvn.register_new_node_with_optimizer(m);
2658           assert(get_ctrl(n) == cle_out, "what other control?");
2659           set_ctrl(m, new_cle_out);
2660           old_new.map(n->_idx, m);
2661         }
2662         stack.pop();
2663       }
2664     }
2665     if (mode == CloneIncludesStripMined) {
2666       _igvn.register_new_node_with_optimizer(new_sfpt);
2667       _igvn.register_new_node_with_optimizer(new_cle_out);
2668     }
2669     // Some other transformation may have pessimistically assigned some
2670     // data nodes to the outer loop. Set their control so they are out
2671     // of the outer loop.
2672     ResourceMark rm;
2673     Unique_Node_List wq;
2674     for (uint i = 0; i < extra_data_nodes.size(); i++) {
2675       Node* old = extra_data_nodes.at(i);
2676       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2677     }
2678 
2679     for (uint i = 0; i < loop->_body.size(); i++) {
2680       Node* old = loop->_body.at(i);
2681       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2682     }
2683 
2684     Node* inner_out = sfpt->in(0);
2685     if (inner_out->outcnt() > 1) {
2686       collect_nodes_in_outer_loop_not_reachable_from_sfpt(inner_out, loop, outer_loop, old_new, wq, this, true);
2687     }
2688 
2689     Node* new_ctrl = cl->outer_loop_exit();
2690     assert(get_loop(new_ctrl) != outer_loop, "must be out of the loop nest");
2691     for (uint i = 0; i < wq.size(); i++) {
2692       Node* n = wq.at(i);
2693       set_ctrl(n, new_ctrl);
2694       if (n->in(0) != nullptr) {
2695         _igvn.replace_input_of(n, 0, new_ctrl);
2696       }
2697       collect_nodes_in_outer_loop_not_reachable_from_sfpt(n, loop, outer_loop, old_new, wq, this, false);
2698     }
2699   } else {
2700     Node *newhead = old_new[loop->_head->_idx];
2701     set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2702   }
2703 }
2704 
2705 //------------------------------clone_loop-------------------------------------
2706 //
2707 //                   C L O N E   A   L O O P   B O D Y
2708 //
2709 // This is the basic building block of the loop optimizations.  It clones an
2710 // entire loop body.  It makes an old_new loop body mapping; with this mapping
2711 // you can find the new-loop equivalent to an old-loop node.  All new-loop
2712 // nodes are exactly equal to their old-loop counterparts, all edges are the
2713 // same.  All exits from the old-loop now have a RegionNode that merges the
2714 // equivalent new-loop path.  This is true even for the normal "loop-exit"
2715 // condition.  All uses of loop-invariant old-loop values now come from (one
2716 // or more) Phis that merge their new-loop equivalents.
2717 //
2718 // This operation leaves the graph in an illegal state: there are two valid
2719 // control edges coming from the loop pre-header to both loop bodies.  I'll
2720 // definitely have to hack the graph after running this transform.
2721 //
2722 // From this building block I will further edit edges to perform loop peeling
2723 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
2724 //
2725 // Parameter side_by_size_idom:
2726 //   When side_by_size_idom is null, the dominator tree is constructed for
2727 //      the clone loop to dominate the original.  Used in construction of
2728 //      pre-main-post loop sequence.
2729 //   When nonnull, the clone and original are side-by-side, both are
2730 //      dominated by the side_by_side_idom node.  Used in construction of
2731 //      unswitched loops.
2732 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
2733                                 CloneLoopMode mode, Node* side_by_side_idom) {
2734 
2735   LoopNode* head = loop->_head->as_Loop();
2736   head->verify_strip_mined(1);
2737 
2738   if (C->do_vector_loop() && PrintOpto) {
2739     const char* mname = C->method()->name()->as_quoted_ascii();
2740     if (mname != nullptr) {
2741       tty->print("PhaseIdealLoop::clone_loop: for vectorize method %s\n", mname);
2742     }
2743   }
2744 
2745   CloneMap& cm = C->clone_map();
2746   if (C->do_vector_loop()) {
2747     cm.set_clone_idx(cm.max_gen()+1);
2748 #ifndef PRODUCT
2749     if (PrintOpto) {
2750       tty->print_cr("PhaseIdealLoop::clone_loop: _clone_idx %d", cm.clone_idx());
2751       loop->dump_head();
2752     }
2753 #endif
2754   }
2755 
2756   // Step 1: Clone the loop body.  Make the old->new mapping.
2757   clone_loop_body(loop->_body, old_new, &cm);
2758 
2759   IdealLoopTree* outer_loop = (head->is_strip_mined() && mode != IgnoreStripMined) ? get_loop(head->as_CountedLoop()->outer_loop()) : loop;
2760 
2761   // Step 2: Fix the edges in the new body.  If the old input is outside the
2762   // loop use it.  If the old input is INside the loop, use the corresponding
2763   // new node instead.
2764   fix_body_edges(loop->_body, loop, old_new, dd, outer_loop->_parent, false);
2765 
2766   Node_List extra_data_nodes; // data nodes in the outer strip mined loop
2767   clone_outer_loop(head, mode, loop, outer_loop, dd, old_new, extra_data_nodes);
2768 
2769   // Step 3: Now fix control uses.  Loop varying control uses have already
2770   // been fixed up (as part of all input edges in Step 2).  Loop invariant
2771   // control uses must be either an IfFalse or an IfTrue.  Make a merge
2772   // point to merge the old and new IfFalse/IfTrue nodes; make the use
2773   // refer to this.
2774   Node_List worklist;
2775   uint new_counter = C->unique();
2776   fix_ctrl_uses(loop->_body, loop, old_new, mode, side_by_side_idom, &cm, worklist);
2777 
2778   // Step 4: If loop-invariant use is not control, it must be dominated by a
2779   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
2780   // there if needed.  Make a Phi there merging old and new used values.
2781   Node_List *split_if_set = nullptr;
2782   Node_List *split_bool_set = nullptr;
2783   Node_List *split_cex_set = nullptr;
2784   fix_data_uses(loop->_body, loop, mode, outer_loop, new_counter, old_new, worklist, split_if_set, split_bool_set, split_cex_set);
2785 
2786   for (uint i = 0; i < extra_data_nodes.size(); i++) {
2787     Node* old = extra_data_nodes.at(i);
2788     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2789                                 split_bool_set, split_cex_set, worklist, new_counter,
2790                                 mode);
2791   }
2792 
2793   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
2794   // the loop uses a condition set in the loop.  The original IF probably
2795   // takes control from one or more OLD Regions (which in turn get from NEW
2796   // Regions).  In any case, there will be a set of Phis for each merge point
2797   // from the IF up to where the original BOOL def exists the loop.
2798   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
2799 
2800 }
2801 
2802 void PhaseIdealLoop::finish_clone_loop(Node_List* split_if_set, Node_List* split_bool_set, Node_List* split_cex_set) {
2803   if (split_if_set) {
2804     while (split_if_set->size()) {
2805       Node *iff = split_if_set->pop();
2806       uint input = iff->Opcode() == Op_AllocateArray ? AllocateNode::ValidLengthTest : 1;
2807       if (iff->in(input)->is_Phi()) {
2808         Node *b = clone_iff(iff->in(input)->as_Phi());
2809         _igvn.replace_input_of(iff, input, b);
2810       }
2811     }
2812   }
2813   if (split_bool_set) {
2814     while (split_bool_set->size()) {
2815       Node *b = split_bool_set->pop();
2816       Node *phi = b->in(1);
2817       assert(phi->is_Phi(), "");
2818       CmpNode *cmp = clone_bool((PhiNode*) phi);
2819       _igvn.replace_input_of(b, 1, cmp);
2820     }
2821   }
2822   if (split_cex_set) {
2823     while (split_cex_set->size()) {
2824       Node *b = split_cex_set->pop();
2825       assert(b->in(0)->is_Region(), "");
2826       assert(b->in(1)->is_Phi(), "");
2827       assert(b->in(0)->in(0) == b->in(1)->in(0), "");
2828       split_up(b, b->in(0), nullptr);
2829     }
2830   }
2831 }
2832 
2833 void PhaseIdealLoop::fix_data_uses(Node_List& body, IdealLoopTree* loop, CloneLoopMode mode, IdealLoopTree* outer_loop,
2834                                    uint new_counter, Node_List &old_new, Node_List &worklist, Node_List*& split_if_set,
2835                                    Node_List*& split_bool_set, Node_List*& split_cex_set) {
2836   for(uint i = 0; i < body.size(); i++ ) {
2837     Node* old = body.at(i);
2838     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2839                                 split_bool_set, split_cex_set, worklist, new_counter,
2840                                 mode);
2841   }
2842 }
2843 
2844 void PhaseIdealLoop::fix_ctrl_uses(const Node_List& body, const IdealLoopTree* loop, Node_List &old_new, CloneLoopMode mode,
2845                                    Node* side_by_side_idom, CloneMap* cm, Node_List &worklist) {
2846   LoopNode* head = loop->_head->as_Loop();
2847   for(uint i = 0; i < body.size(); i++ ) {
2848     Node* old = body.at(i);
2849     if( !old->is_CFG() ) continue;
2850 
2851     // Copy uses to a worklist, so I can munge the def-use info
2852     // with impunity.
2853     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++) {
2854       worklist.push(old->fast_out(j));
2855     }
2856 
2857     while (worklist.size()) {  // Visit all uses
2858       Node *use = worklist.pop();
2859       if (!has_node(use))  continue; // Ignore dead nodes
2860       IdealLoopTree *use_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use );
2861       if (!loop->is_member(use_loop) && use->is_CFG()) {
2862         // Both OLD and USE are CFG nodes here.
2863         assert(use->is_Proj(), "" );
2864         Node* nnn = old_new[old->_idx];
2865 
2866         Node* newuse = nullptr;
2867         if (head->is_strip_mined() && mode != IgnoreStripMined) {
2868           CountedLoopNode* cl = head->as_CountedLoop();
2869           CountedLoopEndNode* cle = cl->loopexit();
2870           // is use the projection that exits the loop from the CountedLoopEndNode?
2871           if (use->in(0) == cle) {
2872             IfFalseNode* cle_out = use->as_IfFalse();
2873             IfNode* le = cl->outer_loop_end();
2874             use = le->false_proj();
2875             use_loop = get_loop(use);
2876             if (mode == CloneIncludesStripMined) {
2877               nnn = old_new[le->_idx];
2878             } else {
2879               newuse = old_new[cle_out->_idx];
2880             }
2881           }
2882         }
2883         if (newuse == nullptr) {
2884           newuse = use->clone();
2885         }
2886 
2887         // Clone the loop exit control projection
2888         if (C->do_vector_loop() && cm != nullptr) {
2889           cm->verify_insert_and_clone(use, newuse, cm->clone_idx());
2890         }
2891         newuse->set_req(0,nnn);
2892         _igvn.register_new_node_with_optimizer(newuse);
2893         set_loop(newuse, use_loop);
2894         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
2895 
2896         // We need a Region to merge the exit from the peeled body and the
2897         // exit from the old loop body.
2898         RegionNode *r = new RegionNode(3);
2899         uint dd_r = MIN2(dom_depth(newuse), dom_depth(use));
2900         assert(dd_r >= dom_depth(dom_lca(newuse, use)), "" );
2901 
2902         // The original user of 'use' uses 'r' instead.
2903         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
2904           Node* useuse = use->last_out(l);
2905           _igvn.rehash_node_delayed(useuse);
2906           uint uses_found = 0;
2907           if (useuse->in(0) == use) {
2908             useuse->set_req(0, r);
2909             uses_found++;
2910             if (useuse->is_CFG()) {
2911               // This is not a dom_depth > dd_r because when new
2912               // control flow is constructed by a loop opt, a node and
2913               // its dominator can end up at the same dom_depth
2914               assert(dom_depth(useuse) >= dd_r, "");
2915               set_idom(useuse, r, dom_depth(useuse));
2916             }
2917           }
2918           for (uint k = 1; k < useuse->req(); k++) {
2919             if( useuse->in(k) == use ) {
2920               useuse->set_req(k, r);
2921               uses_found++;
2922               if (useuse->is_Loop() && k == LoopNode::EntryControl) {
2923                 // This is not a dom_depth > dd_r because when new
2924                 // control flow is constructed by a loop opt, a node
2925                 // and its dominator can end up at the same dom_depth
2926                 assert(dom_depth(useuse) >= dd_r , "");
2927                 set_idom(useuse, r, dom_depth(useuse));
2928               }
2929             }
2930           }
2931           l -= uses_found;    // we deleted 1 or more copies of this edge
2932         }
2933 
2934         assert(use->is_Proj(), "loop exit should be projection");
2935         // replace_node_and_forward_ctrl() below moves all nodes that are:
2936         // - control dependent on the loop exit or
2937         // - have control set to the loop exit
2938         // below the post-loop merge point.
2939         // replace_node_and_forward_ctrl() takes a dead control as first input.
2940         // To make it possible to use it, the loop exit projection is cloned and becomes the
2941         // new exit projection. The initial one becomes dead and is "replaced" by the region.
2942         Node* use_clone = use->clone();
2943         register_control(use_clone, use_loop, idom(use), dom_depth(use));
2944         // Now finish up 'r'
2945         r->set_req(1, newuse);
2946         r->set_req(2, use_clone);
2947         _igvn.register_new_node_with_optimizer(r);
2948         set_loop(r, use_loop);
2949         set_idom(r, (side_by_side_idom == nullptr) ? newuse->in(0) : side_by_side_idom, dd_r);
2950         replace_node_and_forward_ctrl(use, r);
2951         // Map the (cloned) old use to the new merge point
2952         old_new.map(use_clone->_idx, r);
2953       } // End of if a loop-exit test
2954     }
2955   }
2956 }
2957 
2958 void PhaseIdealLoop::fix_body_edges(const Node_List &body, IdealLoopTree* loop, const Node_List &old_new, int dd,
2959                                     IdealLoopTree* parent, bool partial) {
2960   for(uint i = 0; i < body.size(); i++ ) {
2961     Node *old = body.at(i);
2962     Node *nnn = old_new[old->_idx];
2963     // Fix CFG/Loop controlling the new node
2964     if (has_ctrl(old)) {
2965       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
2966     } else {
2967       set_loop(nnn, parent);
2968       if (old->outcnt() > 0) {
2969         Node* dom = idom(old);
2970         if (old_new[dom->_idx] != nullptr) {
2971           dom = old_new[dom->_idx];
2972           set_idom(nnn, dom, dd );
2973         }
2974       }
2975     }
2976     // Correct edges to the new node
2977     for (uint j = 0; j < nnn->req(); j++) {
2978         Node *n = nnn->in(j);
2979         if (n != nullptr) {
2980           IdealLoopTree *old_in_loop = get_loop(has_ctrl(n) ? get_ctrl(n) : n);
2981           if (loop->is_member(old_in_loop)) {
2982             if (old_new[n->_idx] != nullptr) {
2983               nnn->set_req(j, old_new[n->_idx]);
2984             } else {
2985               assert(!body.contains(n), "");
2986               assert(partial, "node not cloned");
2987             }
2988           }
2989         }
2990     }
2991     _igvn.hash_find_insert(nnn);
2992   }
2993 }
2994 
2995 void PhaseIdealLoop::clone_loop_body(const Node_List& body, Node_List &old_new, CloneMap* cm) {
2996   for (uint i = 0; i < body.size(); i++) {
2997     Node* old = body.at(i);
2998     Node* nnn = old->clone();
2999     old_new.map(old->_idx, nnn);
3000     if (C->do_vector_loop() && cm != nullptr) {
3001       cm->verify_insert_and_clone(old, nnn, cm->clone_idx());
3002     }
3003     _igvn.register_new_node_with_optimizer(nnn);
3004   }
3005 }
3006 
3007 
3008 //---------------------- stride_of_possible_iv -------------------------------------
3009 // Looks for an iff/bool/comp with one operand of the compare
3010 // being a cycle involving an add and a phi,
3011 // with an optional truncation (left-shift followed by a right-shift)
3012 // of the add. Returns zero if not an iv.
3013 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
3014   Node* trunc1 = nullptr;
3015   Node* trunc2 = nullptr;
3016   const TypeInteger* ttype = nullptr;
3017   if (!iff->is_If() || iff->in(1) == nullptr || !iff->in(1)->is_Bool()) {
3018     return 0;
3019   }
3020   BoolNode* bl = iff->in(1)->as_Bool();
3021   Node* cmp = bl->in(1);
3022   if (!cmp || (cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU)) {
3023     return 0;
3024   }
3025   // Must have an invariant operand
3026   if (ctrl_is_member(get_loop(iff), cmp->in(2))) {
3027     return 0;
3028   }
3029   Node* add2 = nullptr;
3030   Node* cmp1 = cmp->in(1);
3031   if (cmp1->is_Phi()) {
3032     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
3033     Node* phi = cmp1;
3034     for (uint i = 1; i < phi->req(); i++) {
3035       Node* in = phi->in(i);
3036       Node* add = CountedLoopNode::match_incr_with_optional_truncation(in,
3037                                 &trunc1, &trunc2, &ttype, T_INT);
3038       if (add && add->in(1) == phi) {
3039         add2 = add->in(2);
3040         break;
3041       }
3042     }
3043   } else {
3044     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
3045     Node* addtrunc = cmp1;
3046     Node* add = CountedLoopNode::match_incr_with_optional_truncation(addtrunc,
3047                                 &trunc1, &trunc2, &ttype, T_INT);
3048     if (add && add->in(1)->is_Phi()) {
3049       Node* phi = add->in(1);
3050       for (uint i = 1; i < phi->req(); i++) {
3051         if (phi->in(i) == addtrunc) {
3052           add2 = add->in(2);
3053           break;
3054         }
3055       }
3056     }
3057   }
3058   if (add2 != nullptr) {
3059     const TypeInt* add2t = _igvn.type(add2)->is_int();
3060     if (add2t->is_con()) {
3061       return add2t->get_con();
3062     }
3063   }
3064   return 0;
3065 }
3066 
3067 
3068 //---------------------- stay_in_loop -------------------------------------
3069 // Return the (unique) control output node that's in the loop (if it exists.)
3070 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
3071   Node* unique = nullptr;
3072   if (!n) return nullptr;
3073   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3074     Node* use = n->fast_out(i);
3075     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
3076       if (unique != nullptr) {
3077         return nullptr;
3078       }
3079       unique = use;
3080     }
3081   }
3082   return unique;
3083 }
3084 
3085 //------------------------------ register_node -------------------------------------
3086 // Utility to register node "n" with PhaseIdealLoop
3087 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree* loop, Node* pred, uint ddepth) {
3088   _igvn.register_new_node_with_optimizer(n);
3089   loop->_body.push(n);
3090   if (n->is_CFG()) {
3091     set_loop(n, loop);
3092     set_idom(n, pred, ddepth);
3093   } else {
3094     set_ctrl(n, pred);
3095   }
3096 }
3097 
3098 //------------------------------ proj_clone -------------------------------------
3099 // Utility to create an if-projection
3100 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
3101   ProjNode* c = p->clone()->as_Proj();
3102   c->set_req(0, iff);
3103   return c;
3104 }
3105 
3106 //------------------------------ short_circuit_if -------------------------------------
3107 // Force the iff control output to be the live_proj
3108 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
3109   guarantee(live_proj != nullptr, "null projection");
3110   int proj_con = live_proj->_con;
3111   assert(proj_con == 0 || proj_con == 1, "false or true projection");
3112   Node* con = intcon(proj_con);
3113   if (iff) {
3114     iff->set_req(1, con);
3115   }
3116   return con;
3117 }
3118 
3119 //------------------------------ insert_if_before_proj -------------------------------------
3120 // Insert a new if before an if projection (* - new node)
3121 //
3122 // before
3123 //           if(test)
3124 //           /     \
3125 //          v       v
3126 //    other-proj   proj (arg)
3127 //
3128 // after
3129 //           if(test)
3130 //           /     \
3131 //          /       v
3132 //         |      * proj-clone
3133 //         v          |
3134 //    other-proj      v
3135 //                * new_if(relop(cmp[IU](left,right)))
3136 //                  /  \
3137 //                 v    v
3138 //         * new-proj  proj
3139 //         (returned)
3140 //
3141 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
3142   IfNode* iff = proj->in(0)->as_If();
3143   IdealLoopTree *loop = get_loop(proj);
3144   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3145   uint ddepth = dom_depth(proj);
3146 
3147   _igvn.rehash_node_delayed(iff);
3148   _igvn.rehash_node_delayed(proj);
3149 
3150   proj->set_req(0, nullptr);  // temporary disconnect
3151   ProjNode* proj2 = proj_clone(proj, iff);
3152   register_node(proj2, loop, iff, ddepth);
3153 
3154   Node* cmp = Signed ? (Node*) new CmpINode(left, right) : (Node*) new CmpUNode(left, right);
3155   register_node(cmp, loop, proj2, ddepth);
3156 
3157   BoolNode* bol = new BoolNode(cmp, relop);
3158   register_node(bol, loop, proj2, ddepth);
3159 
3160   int opcode = iff->Opcode();
3161   assert(opcode == Op_If || opcode == Op_RangeCheck, "unexpected opcode");
3162   IfNode* new_if = IfNode::make_with_same_profile(iff, proj2, bol);
3163   register_node(new_if, loop, proj2, ddepth);
3164 
3165   proj->set_req(0, new_if); // reattach
3166   set_idom(proj, new_if, ddepth);
3167 
3168   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
3169   guarantee(new_exit != nullptr, "null exit node");
3170   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
3171 
3172   return new_exit;
3173 }
3174 
3175 //------------------------------ insert_region_before_proj -------------------------------------
3176 // Insert a region before an if projection (* - new node)
3177 //
3178 // before
3179 //           if(test)
3180 //          /      |
3181 //         v       |
3182 //       proj      v
3183 //               other-proj
3184 //
3185 // after
3186 //           if(test)
3187 //          /      |
3188 //         v       |
3189 // * proj-clone    v
3190 //         |     other-proj
3191 //         v
3192 // * new-region
3193 //         |
3194 //         v
3195 // *      dum_if
3196 //       /     \
3197 //      v       \
3198 // * dum-proj    v
3199 //              proj
3200 //
3201 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
3202   IfNode* iff = proj->in(0)->as_If();
3203   IdealLoopTree *loop = get_loop(proj);
3204   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3205   uint ddepth = dom_depth(proj);
3206 
3207   _igvn.rehash_node_delayed(iff);
3208   _igvn.rehash_node_delayed(proj);
3209 
3210   proj->set_req(0, nullptr);  // temporary disconnect
3211   ProjNode* proj2 = proj_clone(proj, iff);
3212   register_node(proj2, loop, iff, ddepth);
3213 
3214   RegionNode* reg = new RegionNode(2);
3215   reg->set_req(1, proj2);
3216   register_node(reg, loop, iff, ddepth);
3217 
3218   IfNode* dum_if = new IfNode(reg, short_circuit_if(nullptr, proj), iff->_prob, iff->_fcnt);
3219   register_node(dum_if, loop, reg, ddepth);
3220 
3221   proj->set_req(0, dum_if); // reattach
3222   set_idom(proj, dum_if, ddepth);
3223 
3224   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
3225   register_node(dum_proj, loop, dum_if, ddepth);
3226 
3227   return reg;
3228 }
3229 
3230 // Idea
3231 // ----
3232 // Partial Peeling tries to rotate the loop in such a way that it can later be turned into a counted loop. Counted loops
3233 // require a signed loop exit test. When calling this method, we've only found a suitable unsigned test to partial peel
3234 // with. Therefore, we try to split off a signed loop exit test from the unsigned test such that it can be used as new
3235 // loop exit while keeping the unsigned test unchanged and preserving the same behavior as if we've used the unsigned
3236 // test alone instead:
3237 //
3238 // Before Partial Peeling:
3239 //   Loop:
3240 //     <peeled section>
3241 //     Split off signed loop exit test
3242 //     <-- CUT HERE -->
3243 //     Unchanged unsigned loop exit test
3244 //     <rest of unpeeled section>
3245 //     goto Loop
3246 //
3247 // After Partial Peeling:
3248 //   <cloned peeled section>
3249 //   Cloned split off signed loop exit test
3250 //   Loop:
3251 //     Unchanged unsigned loop exit test
3252 //     <rest of unpeeled section>
3253 //     <peeled section>
3254 //     Split off signed loop exit test
3255 //     goto Loop
3256 //
3257 // Details
3258 // -------
3259 // Before:
3260 //          if (i <u limit)    Unsigned loop exit condition
3261 //         /       |
3262 //        v        v
3263 //   exit-proj   stay-in-loop-proj
3264 //
3265 // Split off a signed loop exit test (i.e. with CmpI) from an unsigned loop exit test (i.e. with CmpU) and insert it
3266 // before the CmpU on the stay-in-loop path and keep both tests:
3267 //
3268 //          if (i <u limit)    Signed loop exit test
3269 //        /        |
3270 //       /  if (i <u limit)    Unsigned loop exit test
3271 //      /  /       |
3272 //     v  v        v
3273 //  exit-region  stay-in-loop-proj
3274 //
3275 // Implementation
3276 // --------------
3277 // We need to make sure that the new signed loop exit test is properly inserted into the graph such that the unsigned
3278 // loop exit test still dominates the same set of control nodes, the ctrl() relation from data nodes to both loop
3279 // exit tests is preserved, and their loop nesting is correct.
3280 //
3281 // To achieve that, we clone the unsigned loop exit test completely (leave it unchanged), insert the signed loop exit
3282 // test above it and kill the original unsigned loop exit test by setting it's condition to a constant
3283 // (i.e. stay-in-loop-const in graph below) such that IGVN can fold it later:
3284 //
3285 //           if (stay-in-loop-const)  Killed original unsigned loop exit test
3286 //          /       |
3287 //         /        v
3288 //        /  if (i <  limit)          Split off signed loop exit test
3289 //       /  /       |
3290 //      /  /        v
3291 //     /  /  if (i <u limit)          Cloned unsigned loop exit test
3292 //    /  /   /      |
3293 //   v  v  v        |
3294 //  exit-region     |
3295 //        |         |
3296 //    dummy-if      |
3297 //     /  |         |
3298 // dead   |         |
3299 //        v         v
3300 //   exit-proj   stay-in-loop-proj
3301 //
3302 // Note: The dummy-if is inserted to create a region to merge the loop exits between the original to be killed unsigned
3303 //       loop exit test and its exit projection while keeping the exit projection (also see insert_region_before_proj()).
3304 //
3305 // Requirements
3306 // ------------
3307 // Note that we can only split off a signed loop exit test from the unsigned loop exit test when the behavior is exactly
3308 // the same as before with only a single unsigned test. This is only possible if certain requirements are met.
3309 // Otherwise, we need to bail out (see comments in the code below).
3310 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree* loop) {
3311   const bool Signed   = true;
3312   const bool Unsigned = false;
3313 
3314   BoolNode* bol = if_cmpu->in(1)->as_Bool();
3315   if (bol->_test._test != BoolTest::lt) {
3316     return nullptr;
3317   }
3318   CmpNode* cmpu = bol->in(1)->as_Cmp();
3319   assert(cmpu->Opcode() == Op_CmpU, "must be unsigned comparison");
3320 
3321   int stride = stride_of_possible_iv(if_cmpu);
3322   if (stride == 0) {
3323     return nullptr;
3324   }
3325 
3326   Node* lp_proj = stay_in_loop(if_cmpu, loop);
3327   guarantee(lp_proj != nullptr, "null loop node");
3328 
3329   ProjNode* lp_continue = lp_proj->as_Proj();
3330   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
3331   if (!lp_exit->is_IfFalse()) {
3332     // The loop exit condition is (i <u limit) ==> (i >= 0 && i < limit).
3333     // We therefore can't add a single exit condition.
3334     return nullptr;
3335   }
3336   // The unsigned loop exit condition is
3337   //   !(i <u  limit)
3338   // =   i >=u limit
3339   //
3340   // First, we note that for any x for which
3341   //   0 <= x <= INT_MAX
3342   // we can convert x to an unsigned int and still get the same guarantee:
3343   //   0 <=  (uint) x <=  INT_MAX = (uint) INT_MAX
3344   //   0 <=u (uint) x <=u INT_MAX = (uint) INT_MAX   (LEMMA)
3345   //
3346   // With that in mind, if
3347   //   limit >= 0             (COND)
3348   // then the unsigned loop exit condition
3349   //   i >=u limit            (ULE)
3350   // is equivalent to
3351   //   i < 0 || i >= limit    (SLE-full)
3352   // because either i is negative and therefore always greater than MAX_INT when converting to unsigned
3353   //   (uint) i >=u MAX_INT >= limit >= 0
3354   // or otherwise
3355   //   i >= limit >= 0
3356   // holds due to (LEMMA).
3357   //
3358   // For completeness, a counterexample with limit < 0:
3359   // Assume i = -3 and limit = -2:
3360   //   i  < 0
3361   //   -2 < 0
3362   // is true and thus also "i < 0 || i >= limit". But
3363   //   i  >=u limit
3364   //   -3 >=u -2
3365   // is false.
3366   Node* limit = cmpu->in(2);
3367   const TypeInt* type_limit = _igvn.type(limit)->is_int();
3368   if (type_limit->_lo < 0) {
3369     return nullptr;
3370   }
3371 
3372   // We prove below that we can extract a single signed loop exit condition from (SLE-full), depending on the stride:
3373   //   stride < 0:
3374   //     i < 0        (SLE = SLE-negative)
3375   //   stride > 0:
3376   //     i >= limit   (SLE = SLE-positive)
3377   // such that we have the following graph before Partial Peeling with stride > 0 (similar for stride < 0):
3378   //
3379   // Loop:
3380   //   <peeled section>
3381   //   i >= limit    (SLE-positive)
3382   //   <-- CUT HERE -->
3383   //   i >=u limit   (ULE)
3384   //   <rest of unpeeled section>
3385   //   goto Loop
3386   //
3387   // We exit the loop if:
3388   //   (SLE) is true OR (ULE) is true
3389   // However, if (SLE) is true then (ULE) also needs to be true to ensure the exact same behavior. Otherwise, we wrongly
3390   // exit a loop that should not have been exited if we did not apply Partial Peeling. More formally, we need to ensure:
3391   //   (SLE) IMPLIES (ULE)
3392   // This indeed holds when (COND) is given:
3393   // - stride > 0:
3394   //       i >=  limit             // (SLE = SLE-positive)
3395   //       i >=  limit >= 0        // (COND)
3396   //       i >=u limit >= 0        // (LEMMA)
3397   //     which is the unsigned loop exit condition (ULE).
3398   // - stride < 0:
3399   //       i        <  0           // (SLE = SLE-negative)
3400   //       (uint) i >u MAX_INT     // (NEG) all negative values are greater than MAX_INT when converted to unsigned
3401   //       MAX_INT >= limit >= 0   // (COND)
3402   //       MAX_INT >=u limit >= 0  // (LEMMA)
3403   //     and thus from (NEG) and (LEMMA):
3404   //       i >=u limit
3405   //     which is the unsigned loop exit condition (ULE).
3406   //
3407   //
3408   // After Partial Peeling, we have the following structure for stride > 0 (similar for stride < 0):
3409   //   <cloned peeled section>
3410   //   i >= limit (SLE-positive)
3411   //   Loop:
3412   //     i >=u limit (ULE)
3413   //     <rest of unpeeled section>
3414   //     <peeled section>
3415   //     i >= limit (SLE-positive)
3416   //     goto Loop
3417   Node* rhs_cmpi;
3418   if (stride > 0) {
3419     rhs_cmpi = limit; // For i >= limit
3420   } else {
3421     rhs_cmpi = makecon(TypeInt::ZERO); // For i < 0
3422   }
3423   // Create a new region on the exit path
3424   RegionNode* reg = insert_region_before_proj(lp_exit);
3425   guarantee(reg != nullptr, "null region node");
3426 
3427   // Clone the if-cmpu-true-false using a signed compare
3428   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
3429   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, rhs_cmpi, lp_continue);
3430   reg->add_req(cmpi_exit);
3431 
3432   // Clone the if-cmpu-true-false
3433   BoolTest::mask rel_u = bol->_test._test;
3434   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
3435   reg->add_req(cmpu_exit);
3436 
3437   // Force original if to stay in loop.
3438   short_circuit_if(if_cmpu, lp_continue);
3439 
3440   return cmpi_exit->in(0)->as_If();
3441 }
3442 
3443 //------------------------------ remove_cmpi_loop_exit -------------------------------------
3444 // Remove a previously inserted signed compare loop exit.
3445 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
3446   Node* lp_proj = stay_in_loop(if_cmp, loop);
3447   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
3448          stay_in_loop(lp_proj, loop)->is_If() &&
3449          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
3450   Node* con = makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
3451   if_cmp->set_req(1, con);
3452 }
3453 
3454 //------------------------------ scheduled_nodelist -------------------------------------
3455 // Create a post order schedule of nodes that are in the
3456 // "member" set.  The list is returned in "sched".
3457 // The first node in "sched" is the loop head, followed by
3458 // nodes which have no inputs in the "member" set, and then
3459 // followed by the nodes that have an immediate input dependence
3460 // on a node in "sched".
3461 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
3462 
3463   assert(member.test(loop->_head->_idx), "loop head must be in member set");
3464   VectorSet visited;
3465   Node_Stack nstack(loop->_body.size());
3466 
3467   Node* n  = loop->_head;  // top of stack is cached in "n"
3468   uint idx = 0;
3469   visited.set(n->_idx);
3470 
3471   // Initially push all with no inputs from within member set
3472   for(uint i = 0; i < loop->_body.size(); i++ ) {
3473     Node *elt = loop->_body.at(i);
3474     if (member.test(elt->_idx)) {
3475       bool found = false;
3476       for (uint j = 0; j < elt->req(); j++) {
3477         Node* def = elt->in(j);
3478         if (def && member.test(def->_idx) && def != elt) {
3479           found = true;
3480           break;
3481         }
3482       }
3483       if (!found && elt != loop->_head) {
3484         nstack.push(n, idx);
3485         n = elt;
3486         assert(!visited.test(n->_idx), "not seen yet");
3487         visited.set(n->_idx);
3488       }
3489     }
3490   }
3491 
3492   // traverse out's that are in the member set
3493   while (true) {
3494     if (idx < n->outcnt()) {
3495       Node* use = n->raw_out(idx);
3496       idx++;
3497       if (!visited.test_set(use->_idx)) {
3498         if (member.test(use->_idx)) {
3499           nstack.push(n, idx);
3500           n = use;
3501           idx = 0;
3502         }
3503       }
3504     } else {
3505       // All outputs processed
3506       sched.push(n);
3507       if (nstack.is_empty()) break;
3508       n   = nstack.node();
3509       idx = nstack.index();
3510       nstack.pop();
3511     }
3512   }
3513 }
3514 
3515 
3516 //------------------------------ has_use_in_set -------------------------------------
3517 // Has a use in the vector set
3518 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
3519   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3520     Node* use = n->fast_out(j);
3521     if (vset.test(use->_idx)) {
3522       return true;
3523     }
3524   }
3525   return false;
3526 }
3527 
3528 
3529 //------------------------------ has_use_internal_to_set -------------------------------------
3530 // Has use internal to the vector set (ie. not in a phi at the loop head)
3531 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
3532   Node* head  = loop->_head;
3533   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3534     Node* use = n->fast_out(j);
3535     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
3536       return true;
3537     }
3538   }
3539   return false;
3540 }
3541 
3542 
3543 //------------------------------ clone_for_use_outside_loop -------------------------------------
3544 // clone "n" for uses that are outside of loop
3545 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
3546   int cloned = 0;
3547   assert(worklist.size() == 0, "should be empty");
3548   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3549     Node* use = n->fast_out(j);
3550     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
3551       worklist.push(use);
3552     }
3553   }
3554 
3555   if (C->check_node_count(worklist.size() + NodeLimitFudgeFactor,
3556                           "Too many clones required in clone_for_use_outside_loop in partial peeling")) {
3557     return -1;
3558   }
3559 
3560   while( worklist.size() ) {
3561     Node *use = worklist.pop();
3562     if (!has_node(use) || use->in(0) == C->top()) continue;
3563     uint j;
3564     for (j = 0; j < use->req(); j++) {
3565       if (use->in(j) == n) break;
3566     }
3567     assert(j < use->req(), "must be there");
3568 
3569     // clone "n" and insert it between the inputs of "n" and the use outside the loop
3570     Node* n_clone = n->clone();
3571     _igvn.replace_input_of(use, j, n_clone);
3572     cloned++;
3573     Node* use_c;
3574     if (!use->is_Phi()) {
3575       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
3576     } else {
3577       // Use in a phi is considered a use in the associated predecessor block
3578       use_c = use->in(0)->in(j);
3579     }
3580     set_ctrl(n_clone, use_c);
3581     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
3582     get_loop(use_c)->_body.push(n_clone);
3583     _igvn.register_new_node_with_optimizer(n_clone);
3584 #ifndef PRODUCT
3585     if (TracePartialPeeling) {
3586       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
3587     }
3588 #endif
3589   }
3590   return cloned;
3591 }
3592 
3593 
3594 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
3595 // clone "n" for special uses that are in the not_peeled region.
3596 // If these def-uses occur in separate blocks, the code generator
3597 // marks the method as not compilable.  For example, if a "BoolNode"
3598 // is in a different basic block than the "IfNode" that uses it, then
3599 // the compilation is aborted in the code generator.
3600 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
3601                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
3602   if (n->is_Phi() || n->is_Load()) {
3603     return;
3604   }
3605   assert(worklist.size() == 0, "should be empty");
3606   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3607     Node* use = n->fast_out(j);
3608     if ( not_peel.test(use->_idx) &&
3609          (use->is_If() || use->is_CMove() || use->is_Bool() || use->is_OpaqueInitializedAssertionPredicate()) &&
3610          use->in(1) == n)  {
3611       worklist.push(use);
3612     }
3613   }
3614   if (worklist.size() > 0) {
3615     // clone "n" and insert it between inputs of "n" and the use
3616     Node* n_clone = n->clone();
3617     loop->_body.push(n_clone);
3618     _igvn.register_new_node_with_optimizer(n_clone);
3619     set_ctrl(n_clone, get_ctrl(n));
3620     sink_list.push(n_clone);
3621     not_peel.set(n_clone->_idx);
3622 #ifndef PRODUCT
3623     if (TracePartialPeeling) {
3624       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
3625     }
3626 #endif
3627     while( worklist.size() ) {
3628       Node *use = worklist.pop();
3629       _igvn.rehash_node_delayed(use);
3630       for (uint j = 1; j < use->req(); j++) {
3631         if (use->in(j) == n) {
3632           use->set_req(j, n_clone);
3633         }
3634       }
3635     }
3636   }
3637 }
3638 
3639 
3640 //------------------------------ insert_phi_for_loop -------------------------------------
3641 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
3642 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
3643   Node *phi = PhiNode::make(lp, back_edge_val);
3644   phi->set_req(LoopNode::EntryControl, lp_entry_val);
3645   // Use existing phi if it already exists
3646   Node *hit = _igvn.hash_find_insert(phi);
3647   if( hit == nullptr ) {
3648     _igvn.register_new_node_with_optimizer(phi);
3649     set_ctrl(phi, lp);
3650   } else {
3651     // Remove the new phi from the graph and use the hit
3652     _igvn.remove_dead_node(phi);
3653     phi = hit;
3654   }
3655   _igvn.replace_input_of(use, idx, phi);
3656 }
3657 
3658 #ifdef ASSERT
3659 //------------------------------ is_valid_loop_partition -------------------------------------
3660 // Validate the loop partition sets: peel and not_peel
3661 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
3662                                               VectorSet& not_peel ) {
3663   uint i;
3664   // Check that peel_list entries are in the peel set
3665   for (i = 0; i < peel_list.size(); i++) {
3666     if (!peel.test(peel_list.at(i)->_idx)) {
3667       return false;
3668     }
3669   }
3670   // Check at loop members are in one of peel set or not_peel set
3671   for (i = 0; i < loop->_body.size(); i++ ) {
3672     Node *def  = loop->_body.at(i);
3673     uint di = def->_idx;
3674     // Check that peel set elements are in peel_list
3675     if (peel.test(di)) {
3676       if (not_peel.test(di)) {
3677         return false;
3678       }
3679       // Must be in peel_list also
3680       bool found = false;
3681       for (uint j = 0; j < peel_list.size(); j++) {
3682         if (peel_list.at(j)->_idx == di) {
3683           found = true;
3684           break;
3685         }
3686       }
3687       if (!found) {
3688         return false;
3689       }
3690     } else if (not_peel.test(di)) {
3691       if (peel.test(di)) {
3692         return false;
3693       }
3694     } else {
3695       return false;
3696     }
3697   }
3698   return true;
3699 }
3700 
3701 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
3702 // Ensure a use outside of loop is of the right form
3703 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
3704   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3705   return (use->is_Phi() &&
3706           use_c->is_Region() && use_c->req() == 3 &&
3707           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
3708            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
3709            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
3710           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
3711 }
3712 
3713 //------------------------------ is_valid_clone_loop_form -------------------------------------
3714 // Ensure that all uses outside of loop are of the right form
3715 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
3716                                                uint orig_exit_idx, uint clone_exit_idx) {
3717   uint len = peel_list.size();
3718   for (uint i = 0; i < len; i++) {
3719     Node *def = peel_list.at(i);
3720 
3721     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
3722       Node *use = def->fast_out(j);
3723       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3724       if (!loop->is_member(get_loop(use_c))) {
3725         // use is not in the loop, check for correct structure
3726         if (use->in(0) == def) {
3727           // Okay
3728         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
3729           return false;
3730         }
3731       }
3732     }
3733   }
3734   return true;
3735 }
3736 #endif
3737 
3738 //------------------------------ partial_peel -------------------------------------
3739 // Partially peel (aka loop rotation) the top portion of a loop (called
3740 // the peel section below) by cloning it and placing one copy just before
3741 // the new loop head and the other copy at the bottom of the new loop.
3742 //
3743 //    before                       after                where it came from
3744 //
3745 //    stmt1                        stmt1
3746 //  loop:                          stmt2                     clone
3747 //    stmt2                        if condA goto exitA       clone
3748 //    if condA goto exitA        new_loop:                   new
3749 //    stmt3                        stmt3                     clone
3750 //    if !condB goto loop          if condB goto exitB       clone
3751 //  exitB:                         stmt2                     orig
3752 //    stmt4                        if !condA goto new_loop   orig
3753 //  exitA:                         goto exitA
3754 //                               exitB:
3755 //                                 stmt4
3756 //                               exitA:
3757 //
3758 // Step 1: find the cut point: an exit test on probable
3759 //         induction variable.
3760 // Step 2: schedule (with cloning) operations in the peel
3761 //         section that can be executed after the cut into
3762 //         the section that is not peeled.  This may need
3763 //         to clone operations into exit blocks.  For
3764 //         instance, a reference to A[i] in the not-peel
3765 //         section and a reference to B[i] in an exit block
3766 //         may cause a left-shift of i by 2 to be placed
3767 //         in the peel block.  This step will clone the left
3768 //         shift into the exit block and sink the left shift
3769 //         from the peel to the not-peel section.
3770 // Step 3: clone the loop, retarget the control, and insert
3771 //         phis for values that are live across the new loop
3772 //         head.  This is very dependent on the graph structure
3773 //         from clone_loop.  It creates region nodes for
3774 //         exit control and associated phi nodes for values
3775 //         flow out of the loop through that exit.  The region
3776 //         node is dominated by the clone's control projection.
3777 //         So the clone's peel section is placed before the
3778 //         new loop head, and the clone's not-peel section is
3779 //         forms the top part of the new loop.  The original
3780 //         peel section forms the tail of the new loop.
3781 // Step 4: update the dominator tree and recompute the
3782 //         dominator depth.
3783 //
3784 //                   orig
3785 //
3786 //                   stmt1
3787 //                     |
3788 //                     v
3789 //                 predicates
3790 //                     |
3791 //                     v
3792 //                   loop<----+
3793 //                     |      |
3794 //                   stmt2    |
3795 //                     |      |
3796 //                     v      |
3797 //                    ifA     |
3798 //                   / |      |
3799 //                  v  v      |
3800 //               false true   ^  <-- last_peel
3801 //               /     |      |
3802 //              /   ===|==cut |
3803 //             /     stmt3    |  <-- first_not_peel
3804 //            /        |      |
3805 //            |        v      |
3806 //            v       ifB     |
3807 //          exitA:   / \      |
3808 //                  /   \     |
3809 //                 v     v    |
3810 //               false true   |
3811 //               /       \    |
3812 //              /         ----+
3813 //             |
3814 //             v
3815 //           exitB:
3816 //           stmt4
3817 //
3818 //
3819 //            after clone loop
3820 //
3821 //                   stmt1
3822 //                     |
3823 //                     v
3824 //                predicates
3825 //                 /       \
3826 //        clone   /         \   orig
3827 //               /           \
3828 //              /             \
3829 //             v               v
3830 //   +---->loop                loop<----+
3831 //   |      |                    |      |
3832 //   |    stmt2                stmt2    |
3833 //   |      |                    |      |
3834 //   |      v                    v      |
3835 //   |      ifA                 ifA     |
3836 //   |      | \                / |      |
3837 //   |      v  v              v  v      |
3838 //   ^    true  false      false true   ^  <-- last_peel
3839 //   |      |   ^   \       /    |      |
3840 //   | cut==|==  \   \     /  ===|==cut |
3841 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
3842 //   |      |    dom   | |       |      |
3843 //   |      v      \  1v v2      v      |
3844 //   |      ifB     regionA     ifB     |
3845 //   |      / \        |       / \      |
3846 //   |     /   \       v      /   \     |
3847 //   |    v     v    exitA:  v     v    |
3848 //   |    true  false      false true   |
3849 //   |    /     ^   \      /       \    |
3850 //   +----       \   \    /         ----+
3851 //               dom  \  /
3852 //                 \  1v v2
3853 //                  regionB
3854 //                     |
3855 //                     v
3856 //                   exitB:
3857 //                   stmt4
3858 //
3859 //
3860 //           after partial peel
3861 //
3862 //                  stmt1
3863 //                     |
3864 //                     v
3865 //                predicates
3866 //                 /
3867 //        clone   /             orig
3868 //               /          TOP
3869 //              /             \
3870 //             v               v
3871 //    TOP->loop                loop----+
3872 //          |                    |      |
3873 //        stmt2                stmt2    |
3874 //          |                    |      |
3875 //          v                    v      |
3876 //          ifA                 ifA     |
3877 //          | \                / |      |
3878 //          v  v              v  v      |
3879 //        true  false      false true   |     <-- last_peel
3880 //          |   ^   \       /    +------|---+
3881 //  +->newloop   \   \     /  === ==cut |   |
3882 //  |     stmt3   \   \   /     TOP     |   |
3883 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
3884 //  |       v      \  1v v2      v      |   |
3885 //  |       ifB     regionA     ifB     ^   v
3886 //  |       / \        |       / \      |   |
3887 //  |      /   \       v      /   \     |   |
3888 //  |     v     v    exitA:  v     v    |   |
3889 //  |     true  false      false true   |   |
3890 //  |     /     ^   \      /       \    |   |
3891 //  |    |       \   \    /         v   |   |
3892 //  |    |       dom  \  /         TOP  |   |
3893 //  |    |         \  1v v2             |   |
3894 //  ^    v          regionB             |   |
3895 //  |    |             |                |   |
3896 //  |    |             v                ^   v
3897 //  |    |           exitB:             |   |
3898 //  |    |           stmt4              |   |
3899 //  |    +------------>-----------------+   |
3900 //  |                                       |
3901 //  +-----------------<---------------------+
3902 //
3903 //
3904 //              final graph
3905 //
3906 //                  stmt1
3907 //                    |
3908 //                    v
3909 //                predicates
3910 //                    |
3911 //                    v
3912 //                  stmt2 clone
3913 //                    |
3914 //                    v
3915 //         ........> ifA clone
3916 //         :        / |
3917 //        dom      /  |
3918 //         :      v   v
3919 //         :  false   true
3920 //         :  |       |
3921 //         :  |       v
3922 //         :  |    newloop<-----+
3923 //         :  |        |        |
3924 //         :  |     stmt3 clone |
3925 //         :  |        |        |
3926 //         :  |        v        |
3927 //         :  |       ifB       |
3928 //         :  |      / \        |
3929 //         :  |     v   v       |
3930 //         :  |  false true     |
3931 //         :  |   |     |       |
3932 //         :  |   v    stmt2    |
3933 //         :  | exitB:  |       |
3934 //         :  | stmt4   v       |
3935 //         :  |       ifA orig  |
3936 //         :  |      /  \       |
3937 //         :  |     /    \      |
3938 //         :  |    v     v      |
3939 //         :  |  false  true    |
3940 //         :  |  /        \     |
3941 //         :  v  v         -----+
3942 //          RegionA
3943 //             |
3944 //             v
3945 //           exitA
3946 //
3947 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
3948 
3949   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
3950   if (!loop->_head->is_Loop()) {
3951     return false;
3952   }
3953   LoopNode *head = loop->_head->as_Loop();
3954 
3955   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
3956     return false;
3957   }
3958 
3959   // Check for complex exit control
3960   for (uint ii = 0; ii < loop->_body.size(); ii++) {
3961     Node *n = loop->_body.at(ii);
3962     int opc = n->Opcode();
3963     if (n->is_Call()        ||
3964         opc == Op_Catch     ||
3965         opc == Op_CatchProj ||
3966         opc == Op_Jump      ||
3967         opc == Op_JumpProj) {
3968 #ifndef PRODUCT
3969       if (TracePartialPeeling) {
3970         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
3971       }
3972 #endif
3973       return false;
3974     }
3975   }
3976 
3977   int dd = dom_depth(head);
3978 
3979   // Step 1: find cut point
3980 
3981   // Walk up dominators to loop head looking for first loop exit
3982   // which is executed on every path thru loop.
3983   IfNode *peel_if = nullptr;
3984   IfNode *peel_if_cmpu = nullptr;
3985 
3986   Node *iff = loop->tail();
3987   while (iff != head) {
3988     if (iff->is_If()) {
3989       Node *ctrl = get_ctrl(iff->in(1));
3990       if (ctrl->is_top()) return false; // Dead test on live IF.
3991       // If loop-varying exit-test, check for induction variable
3992       if (loop->is_member(get_loop(ctrl)) &&
3993           loop->is_loop_exit(iff) &&
3994           is_possible_iv_test(iff)) {
3995         Node* cmp = iff->in(1)->in(1);
3996         if (cmp->Opcode() == Op_CmpI) {
3997           peel_if = iff->as_If();
3998         } else {
3999           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
4000           peel_if_cmpu = iff->as_If();
4001         }
4002       }
4003     }
4004     iff = idom(iff);
4005   }
4006 
4007   // Prefer signed compare over unsigned compare.
4008   IfNode* new_peel_if = nullptr;
4009   if (peel_if == nullptr) {
4010     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == nullptr) {
4011       return false;   // No peel point found
4012     }
4013     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
4014     if (new_peel_if == nullptr) {
4015       return false;   // No peel point found
4016     }
4017     peel_if = new_peel_if;
4018   }
4019   Node* last_peel        = stay_in_loop(peel_if, loop);
4020   Node* first_not_peeled = stay_in_loop(last_peel, loop);
4021   if (first_not_peeled == nullptr || first_not_peeled == head) {
4022     return false;
4023   }
4024 
4025 #ifndef PRODUCT
4026   if (TraceLoopOpts) {
4027     tty->print("PartialPeel  ");
4028     loop->dump_head();
4029   }
4030 
4031   if (TracePartialPeeling) {
4032     tty->print_cr("before partial peel one iteration");
4033     Node_List wl;
4034     Node* t = head->in(2);
4035     while (true) {
4036       wl.push(t);
4037       if (t == head) break;
4038       t = idom(t);
4039     }
4040     while (wl.size() > 0) {
4041       Node* tt = wl.pop();
4042       tt->dump();
4043       if (tt == last_peel) tty->print_cr("-- cut --");
4044     }
4045   }
4046 #endif
4047 
4048   C->print_method(PHASE_BEFORE_PARTIAL_PEELING, 4, head);
4049 
4050   VectorSet peel;
4051   VectorSet not_peel;
4052   Node_List peel_list;
4053   Node_List worklist;
4054   Node_List sink_list;
4055 
4056   uint estimate = loop->est_loop_clone_sz(1);
4057   if (exceeding_node_budget(estimate)) {
4058     return false;
4059   }
4060 
4061   // Set of cfg nodes to peel are those that are executable from
4062   // the head through last_peel.
4063   assert(worklist.size() == 0, "should be empty");
4064   worklist.push(head);
4065   peel.set(head->_idx);
4066   while (worklist.size() > 0) {
4067     Node *n = worklist.pop();
4068     if (n != last_peel) {
4069       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
4070         Node* use = n->fast_out(j);
4071         if (use->is_CFG() &&
4072             loop->is_member(get_loop(use)) &&
4073             !peel.test_set(use->_idx)) {
4074           worklist.push(use);
4075         }
4076       }
4077     }
4078   }
4079 
4080   // Set of non-cfg nodes to peel are those that are control
4081   // dependent on the cfg nodes.
4082   for (uint i = 0; i < loop->_body.size(); i++) {
4083     Node *n = loop->_body.at(i);
4084     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
4085     if (peel.test(n_c->_idx)) {
4086       peel.set(n->_idx);
4087     } else {
4088       not_peel.set(n->_idx);
4089     }
4090   }
4091 
4092   // Step 2: move operations from the peeled section down into the
4093   //         not-peeled section
4094 
4095   // Get a post order schedule of nodes in the peel region
4096   // Result in right-most operand.
4097   scheduled_nodelist(loop, peel, peel_list);
4098 
4099   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4100 
4101   // For future check for too many new phis
4102   uint old_phi_cnt = 0;
4103   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
4104     Node* use = head->fast_out(j);
4105     if (use->is_Phi()) old_phi_cnt++;
4106   }
4107 
4108 #ifndef PRODUCT
4109   if (TracePartialPeeling) {
4110     tty->print_cr("\npeeled list");
4111   }
4112 #endif
4113 
4114   // Evacuate nodes in peel region into the not_peeled region if possible
4115   bool too_many_clones = false;
4116   uint new_phi_cnt = 0;
4117   uint cloned_for_outside_use = 0;
4118   for (uint i = 0; i < peel_list.size();) {
4119     Node* n = peel_list.at(i);
4120 #ifndef PRODUCT
4121   if (TracePartialPeeling) n->dump();
4122 #endif
4123     bool incr = true;
4124     if (!n->is_CFG()) {
4125       if (has_use_in_set(n, not_peel)) {
4126         // If not used internal to the peeled region,
4127         // move "n" from peeled to not_peeled region.
4128         if (!has_use_internal_to_set(n, peel, loop)) {
4129           // if not pinned and not a load (which maybe anti-dependent on a store)
4130           // and not a CMove (Matcher expects only bool->cmove).
4131           if (n->in(0) == nullptr && !n->is_Load() && !n->is_CMove()) {
4132             int new_clones = clone_for_use_outside_loop(loop, n, worklist);
4133             if (C->failing()) return false;
4134             if (new_clones == -1) {
4135               too_many_clones = true;
4136               break;
4137             }
4138             cloned_for_outside_use += new_clones;
4139             sink_list.push(n);
4140             peel.remove(n->_idx);
4141             not_peel.set(n->_idx);
4142             peel_list.remove(i);
4143             incr = false;
4144 #ifndef PRODUCT
4145             if (TracePartialPeeling) {
4146               tty->print_cr("sink to not_peeled region: %d newbb: %d",
4147                             n->_idx, get_ctrl(n)->_idx);
4148             }
4149 #endif
4150           }
4151         } else {
4152           // Otherwise check for special def-use cases that span
4153           // the peel/not_peel boundary such as bool->if
4154           clone_for_special_use_inside_loop(loop, n, not_peel, sink_list, worklist);
4155           new_phi_cnt++;
4156         }
4157       }
4158     }
4159     if (incr) i++;
4160   }
4161 
4162   estimate += cloned_for_outside_use + new_phi_cnt;
4163   bool exceed_node_budget = !may_require_nodes(estimate);
4164   bool exceed_phi_limit = new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta;
4165 
4166   if (too_many_clones || exceed_node_budget || exceed_phi_limit) {
4167 #ifndef PRODUCT
4168     if (TracePartialPeeling && exceed_phi_limit) {
4169       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
4170                     new_phi_cnt, old_phi_cnt, new_peel_if != nullptr?'T':'F');
4171     }
4172 #endif
4173     if (new_peel_if != nullptr) {
4174       remove_cmpi_loop_exit(new_peel_if, loop);
4175     }
4176     // Inhibit more partial peeling on this loop
4177     assert(!head->is_partial_peel_loop(), "not partial peeled");
4178     head->mark_partial_peel_failed();
4179     if (cloned_for_outside_use > 0) {
4180       // Terminate this round of loop opts because
4181       // the graph outside this loop was changed.
4182       C->set_major_progress();
4183       return true;
4184     }
4185     return false;
4186   }
4187 
4188   // Step 3: clone loop, retarget control, and insert new phis
4189 
4190   // Create new loop head for new phis and to hang
4191   // the nodes being moved (sinked) from the peel region.
4192   LoopNode* new_head = new LoopNode(last_peel, last_peel);
4193   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
4194   _igvn.register_new_node_with_optimizer(new_head);
4195   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
4196   _igvn.replace_input_of(first_not_peeled, 0, new_head);
4197   set_loop(new_head, loop);
4198   loop->_body.push(new_head);
4199   not_peel.set(new_head->_idx);
4200   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
4201   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
4202 
4203   while (sink_list.size() > 0) {
4204     Node* n = sink_list.pop();
4205     set_ctrl(n, new_head);
4206   }
4207 
4208   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4209 
4210   clone_loop(loop, old_new, dd, IgnoreStripMined);
4211 
4212   const uint clone_exit_idx = 1;
4213   const uint orig_exit_idx  = 2;
4214   assert(is_valid_clone_loop_form(loop, peel_list, orig_exit_idx, clone_exit_idx), "bad clone loop");
4215 
4216   Node* head_clone             = old_new[head->_idx];
4217   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
4218   Node* orig_tail_clone        = head_clone->in(2);
4219 
4220   // Add phi if "def" node is in peel set and "use" is not
4221 
4222   for (uint i = 0; i < peel_list.size(); i++) {
4223     Node *def  = peel_list.at(i);
4224     if (!def->is_CFG()) {
4225       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
4226         Node *use = def->fast_out(j);
4227         if (has_node(use) && use->in(0) != C->top() &&
4228             (!peel.test(use->_idx) ||
4229              (use->is_Phi() && use->in(0) == head)) ) {
4230           worklist.push(use);
4231         }
4232       }
4233       while( worklist.size() ) {
4234         Node *use = worklist.pop();
4235         for (uint j = 1; j < use->req(); j++) {
4236           Node* n = use->in(j);
4237           if (n == def) {
4238 
4239             // "def" is in peel set, "use" is not in peel set
4240             // or "use" is in the entry boundary (a phi) of the peel set
4241 
4242             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
4243 
4244             if ( loop->is_member(get_loop( use_c )) ) {
4245               // use is in loop
4246               if (old_new[use->_idx] != nullptr) { // null for dead code
4247                 Node* use_clone = old_new[use->_idx];
4248                 _igvn.replace_input_of(use, j, C->top());
4249                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
4250               }
4251             } else {
4252               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
4253               // use is not in the loop, check if the live range includes the cut
4254               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
4255               if (not_peel.test(lp_if->_idx)) {
4256                 assert(j == orig_exit_idx, "use from original loop");
4257                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
4258               }
4259             }
4260           }
4261         }
4262       }
4263     }
4264   }
4265 
4266   // Step 3b: retarget control
4267 
4268   // Redirect control to the new loop head if a cloned node in
4269   // the not_peeled region has control that points into the peeled region.
4270   // This necessary because the cloned peeled region will be outside
4271   // the loop.
4272   //                            from    to
4273   //          cloned-peeled    <---+
4274   //    new_head_clone:            |    <--+
4275   //          cloned-not_peeled  in(0)    in(0)
4276   //          orig-peeled
4277 
4278   for (uint i = 0; i < loop->_body.size(); i++) {
4279     Node *n = loop->_body.at(i);
4280     if (!n->is_CFG()           && n->in(0) != nullptr        &&
4281         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
4282       Node* n_clone = old_new[n->_idx];
4283       if (n_clone->depends_only_on_test()) {
4284         // Pin array access nodes: control is updated here to the loop head. If, after some transformations, the
4285         // backedge is removed, an array load could become dependent on a condition that's not a range check for that
4286         // access. If that condition is replaced by an identical dominating one, then an unpinned load would risk
4287         // floating above its range check.
4288         Node* pinned_clone = n_clone->pin_array_access_node();
4289         if (pinned_clone != nullptr) {
4290           register_new_node_with_ctrl_of(pinned_clone, n_clone);
4291           old_new.map(n->_idx, pinned_clone);
4292           _igvn.replace_node(n_clone, pinned_clone);
4293           n_clone = pinned_clone;
4294         }
4295       }
4296       _igvn.replace_input_of(n_clone, 0, new_head_clone);
4297     }
4298   }
4299 
4300   // Backedge of the surviving new_head (the clone) is original last_peel
4301   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
4302 
4303   // Cut first node in original not_peel set
4304   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
4305   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
4306   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
4307 
4308   // Copy head_clone back-branch info to original head
4309   // and remove original head's loop entry and
4310   // clone head's back-branch
4311   _igvn.rehash_node_delayed(head); // Multiple edge updates
4312   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
4313   head->set_req(LoopNode::LoopBackControl, C->top());
4314   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
4315 
4316   // Similarly modify the phis
4317   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
4318     Node* use = head->fast_out(k);
4319     if (use->is_Phi() && use->outcnt() > 0) {
4320       Node* use_clone = old_new[use->_idx];
4321       _igvn.rehash_node_delayed(use); // Multiple edge updates
4322       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
4323       use->set_req(LoopNode::LoopBackControl, C->top());
4324       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
4325     }
4326   }
4327 
4328   // Step 4: update dominator tree and dominator depth
4329 
4330   set_idom(head, orig_tail_clone, dd);
4331   recompute_dom_depth();
4332 
4333   // Inhibit more partial peeling on this loop
4334   new_head_clone->set_partial_peel_loop();
4335   C->set_major_progress();
4336   loop->record_for_igvn();
4337 
4338 #ifndef PRODUCT
4339   if (TracePartialPeeling) {
4340     tty->print_cr("\nafter partial peel one iteration");
4341     Node_List wl;
4342     Node* t = last_peel;
4343     while (true) {
4344       wl.push(t);
4345       if (t == head_clone) break;
4346       t = idom(t);
4347     }
4348     while (wl.size() > 0) {
4349       Node* tt = wl.pop();
4350       if (tt == head) tty->print_cr("orig head");
4351       else if (tt == new_head_clone) tty->print_cr("new head");
4352       else if (tt == head_clone) tty->print_cr("clone head");
4353       tt->dump();
4354     }
4355   }
4356 #endif
4357 
4358   C->print_method(PHASE_AFTER_PARTIAL_PEELING, 4, new_head_clone);
4359 
4360   return true;
4361 }
4362 
4363 #ifdef ASSERT
4364 
4365 // Moves Template Assertion Predicates to a target loop by cloning and killing the old ones. The target loop is the
4366 // original, not-cloned loop. This is currently only used with StressLoopBackedge which is a develop flag only and
4367 // false with product builds. We can therefore guard it with an ifdef. More details can be found at the use-site.
4368 class MoveAssertionPredicatesVisitor : public PredicateVisitor {
4369   ClonePredicateToTargetLoop _clone_predicate_to_loop;
4370   PhaseIdealLoop* const _phase;
4371 
4372 public:
4373   MoveAssertionPredicatesVisitor(LoopNode* target_loop_head,
4374                                  const NodeInSingleLoopBody &node_in_loop_body,
4375                                  PhaseIdealLoop* phase)
4376     : _clone_predicate_to_loop(target_loop_head, node_in_loop_body, phase),
4377       _phase(phase) {
4378   }
4379   NONCOPYABLE(MoveAssertionPredicatesVisitor);
4380 
4381   using PredicateVisitor::visit;
4382 
4383   void visit(const TemplateAssertionPredicate& template_assertion_predicate) override {
4384     _clone_predicate_to_loop.clone_template_assertion_predicate(template_assertion_predicate);
4385     template_assertion_predicate.kill(_phase->igvn());
4386   }
4387 };
4388 #endif // ASSERT
4389 
4390 // Transform:
4391 //
4392 // loop<-----------------+
4393 //  |                    |
4394 // stmt1 stmt2 .. stmtn  |
4395 //  |     |        |     |
4396 //  \     |       /      |
4397 //    v   v     v        |
4398 //       region          |
4399 //         |             |
4400 //     shared_stmt       |
4401 //         |             |
4402 //         v             |
4403 //         if            |
4404 //         / \           |
4405 //        |   -----------+
4406 //        v
4407 //
4408 // into:
4409 //
4410 //    loop<-------------------+
4411 //     |                      |
4412 //     v                      |
4413 // +->loop                    |
4414 // |   |                      |
4415 // |  stmt1 stmt2 .. stmtn    |
4416 // |   |     |        |       |
4417 // |   |      \       /       |
4418 // |   |       v     v        |
4419 // |   |        region1       |
4420 // |   |           |          |
4421 // |  shared_stmt shared_stmt |
4422 // |   |           |          |
4423 // |   v           v          |
4424 // |   if          if         |
4425 // |   /\          / \        |
4426 // +--   |         |   -------+
4427 //       \         /
4428 //        v       v
4429 //         region2
4430 //
4431 // (region2 is shown to merge mirrored projections of the loop exit
4432 // ifs to make the diagram clearer but they really merge the same
4433 // projection)
4434 //
4435 // Conditions for this transformation to trigger:
4436 // - the path through stmt1 is frequent enough
4437 // - the inner loop will be turned into a counted loop after transformation
4438 bool PhaseIdealLoop::duplicate_loop_backedge(IdealLoopTree *loop, Node_List &old_new) {
4439   if (!DuplicateBackedge) {
4440     return false;
4441   }
4442   assert(!loop->_head->is_CountedLoop() || StressDuplicateBackedge, "Non-counted loop only");
4443   if (!loop->_head->is_Loop()) {
4444     return false;
4445   }
4446 
4447   uint estimate = loop->est_loop_clone_sz(1);
4448   if (exceeding_node_budget(estimate)) {
4449     return false;
4450   }
4451 
4452   LoopNode *head = loop->_head->as_Loop();
4453 
4454   Node* region = nullptr;
4455   IfNode* exit_test = nullptr;
4456   uint inner;
4457   float f;
4458 #ifdef ASSERT
4459   if (StressDuplicateBackedge) {
4460     if (head->is_strip_mined()) {
4461       return false;
4462     }
4463     Node* c = head->in(LoopNode::LoopBackControl);
4464 
4465     while (c != head) {
4466       if (c->is_Region()) {
4467         region = c;
4468       }
4469       c = idom(c);
4470     }
4471 
4472     if (region == nullptr) {
4473       return false;
4474     }
4475 
4476     inner = 1;
4477   } else
4478 #endif //ASSERT
4479   {
4480     // Is the shape of the loop that of a counted loop...
4481     Node* back_control = loop_exit_control(head, loop);
4482     if (back_control == nullptr) {
4483       return false;
4484     }
4485 
4486     BoolTest::mask bt = BoolTest::illegal;
4487     float cl_prob = 0;
4488     Node* incr = nullptr;
4489     Node* limit = nullptr;
4490     Node* cmp = loop_exit_test(back_control, loop, incr, limit, bt, cl_prob);
4491     if (cmp == nullptr || cmp->Opcode() != Op_CmpI) {
4492       return false;
4493     }
4494 
4495     // With an extra phi for the candidate iv?
4496     // Or the region node is the loop head
4497     if (!incr->is_Phi() || incr->in(0) == head) {
4498       return false;
4499     }
4500 
4501     PathFrequency pf(head, this);
4502     region = incr->in(0);
4503 
4504     // Go over all paths for the extra phi's region and see if that
4505     // path is frequent enough and would match the expected iv shape
4506     // if the extra phi is removed
4507     inner = 0;
4508     for (uint i = 1; i < incr->req(); ++i) {
4509       Node* in = incr->in(i);
4510       Node* trunc1 = nullptr;
4511       Node* trunc2 = nullptr;
4512       const TypeInteger* iv_trunc_t = nullptr;
4513       Node* orig_in = in;
4514       if (!(in = CountedLoopNode::match_incr_with_optional_truncation(in, &trunc1, &trunc2, &iv_trunc_t, T_INT))) {
4515         continue;
4516       }
4517       assert(in->Opcode() == Op_AddI, "wrong increment code");
4518       Node* xphi = nullptr;
4519       Node* stride = loop_iv_stride(in, xphi);
4520 
4521       if (stride == nullptr) {
4522         continue;
4523       }
4524 
4525       PhiNode* phi = loop_iv_phi(xphi, nullptr, head);
4526       if (phi == nullptr ||
4527           (trunc1 == nullptr && phi->in(LoopNode::LoopBackControl) != incr) ||
4528           (trunc1 != nullptr && phi->in(LoopNode::LoopBackControl) != trunc1)) {
4529         return false;
4530       }
4531 
4532       f = pf.to(region->in(i));
4533       if (f > 0.5) {
4534         inner = i;
4535         break;
4536       }
4537     }
4538 
4539     if (inner == 0) {
4540       return false;
4541     }
4542 
4543     exit_test = back_control->in(0)->as_If();
4544   }
4545 
4546   if (idom(region)->is_Catch()) {
4547     return false;
4548   }
4549 
4550   // Collect all control nodes that need to be cloned (shared_stmt in the diagram)
4551   Unique_Node_List wq;
4552   wq.push(head->in(LoopNode::LoopBackControl));
4553   for (uint i = 0; i < wq.size(); i++) {
4554     Node* c = wq.at(i);
4555     assert(get_loop(c) == loop, "not in the right loop?");
4556     if (c->is_Region()) {
4557       if (c != region) {
4558         for (uint j = 1; j < c->req(); ++j) {
4559           wq.push(c->in(j));
4560         }
4561       }
4562     } else {
4563       wq.push(c->in(0));
4564     }
4565     assert(!is_strict_dominator(c, region), "shouldn't go above region");
4566   }
4567 
4568   Node* region_dom = idom(region);
4569 
4570   // Can't do the transformation if this would cause a membar pair to
4571   // be split
4572   for (uint i = 0; i < wq.size(); i++) {
4573     Node* c = wq.at(i);
4574     if (c->is_MemBar() && (c->as_MemBar()->trailing_store() || c->as_MemBar()->trailing_load_store())) {
4575       assert(c->as_MemBar()->leading_membar()->trailing_membar() == c, "bad membar pair");
4576       if (!wq.member(c->as_MemBar()->leading_membar())) {
4577         return false;
4578       }
4579     }
4580   }
4581   C->print_method(PHASE_BEFORE_DUPLICATE_LOOP_BACKEDGE, 4, head);
4582 
4583   // Collect data nodes that need to be clones as well
4584   int dd = dom_depth(head);
4585 
4586   for (uint i = 0; i < loop->_body.size(); ++i) {
4587     Node* n = loop->_body.at(i);
4588     if (has_ctrl(n)) {
4589       Node* c = get_ctrl(n);
4590       if (wq.member(c)) {
4591         wq.push(n);
4592       }
4593     } else {
4594       set_idom(n, idom(n), dd);
4595     }
4596   }
4597 
4598   // clone shared_stmt
4599   clone_loop_body(wq, old_new, nullptr);
4600 
4601   Node* region_clone = old_new[region->_idx];
4602   region_clone->set_req(inner, C->top());
4603   set_idom(region, region->in(inner), dd);
4604 
4605   // Prepare the outer loop
4606   Node* outer_head = new LoopNode(head->in(LoopNode::EntryControl), old_new[head->in(LoopNode::LoopBackControl)->_idx]);
4607   register_control(outer_head, loop->_parent, outer_head->in(LoopNode::EntryControl));
4608   _igvn.replace_input_of(head, LoopNode::EntryControl, outer_head);
4609   set_idom(head, outer_head, dd);
4610 
4611   fix_body_edges(wq, loop, old_new, dd, loop->_parent, true);
4612 
4613   // Make one of the shared_stmt copies only reachable from stmt1, the
4614   // other only from stmt2..stmtn.
4615   Node* dom = nullptr;
4616   for (uint i = 1; i < region->req(); ++i) {
4617     if (i != inner) {
4618       _igvn.replace_input_of(region, i, C->top());
4619     }
4620     Node* in = region_clone->in(i);
4621     if (in->is_top()) {
4622       continue;
4623     }
4624     if (dom == nullptr) {
4625       dom = in;
4626     } else {
4627       dom = dom_lca(dom, in);
4628     }
4629   }
4630 
4631   set_idom(region_clone, dom, dd);
4632 
4633   // Set up the outer loop
4634   for (uint i = 0; i < head->outcnt(); i++) {
4635     Node* u = head->raw_out(i);
4636     if (u->is_Phi()) {
4637       Node* outer_phi = u->clone();
4638       outer_phi->set_req(0, outer_head);
4639       Node* backedge = old_new[u->in(LoopNode::LoopBackControl)->_idx];
4640       if (backedge == nullptr) {
4641         backedge = u->in(LoopNode::LoopBackControl);
4642       }
4643       outer_phi->set_req(LoopNode::LoopBackControl, backedge);
4644       register_new_node(outer_phi, outer_head);
4645       _igvn.replace_input_of(u, LoopNode::EntryControl, outer_phi);
4646     }
4647   }
4648 
4649   // create control and data nodes for out of loop uses (including region2)
4650   Node_List worklist;
4651   uint new_counter = C->unique();
4652   fix_ctrl_uses(wq, loop, old_new, ControlAroundStripMined, outer_head, nullptr, worklist);
4653 
4654   Node_List *split_if_set = nullptr;
4655   Node_List *split_bool_set = nullptr;
4656   Node_List *split_cex_set = nullptr;
4657   fix_data_uses(wq, loop, ControlAroundStripMined, loop->skip_strip_mined(), new_counter, old_new, worklist,
4658                 split_if_set, split_bool_set, split_cex_set);
4659 
4660   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
4661 
4662   if (exit_test != nullptr) {
4663     float cnt = exit_test->_fcnt;
4664     if (cnt != COUNT_UNKNOWN) {
4665       exit_test->_fcnt = cnt * f;
4666       old_new[exit_test->_idx]->as_If()->_fcnt = cnt * (1 - f);
4667     }
4668   }
4669 
4670 #ifdef ASSERT
4671   if (StressDuplicateBackedge && head->is_CountedLoop()) {
4672     // The Template Assertion Predicates from the old counted loop are now at the new outer loop - clone them to
4673     // the inner counted loop and kill the old ones. We only need to do this with debug builds because
4674     // StressDuplicateBackedge is a devlop flag and false by default. Without StressDuplicateBackedge 'head' will be a
4675     // non-counted loop, and thus we have no Template Assertion Predicates above the old loop to move down.
4676     PredicateIterator predicate_iterator(outer_head->in(LoopNode::EntryControl));
4677     NodeInSingleLoopBody node_in_body(this, loop);
4678     MoveAssertionPredicatesVisitor move_assertion_predicates_visitor(head, node_in_body, this);
4679     predicate_iterator.for_each(move_assertion_predicates_visitor);
4680   }
4681 #endif // ASSERT
4682 
4683   C->set_major_progress();
4684 
4685   C->print_method(PHASE_AFTER_DUPLICATE_LOOP_BACKEDGE, 4, outer_head);
4686 
4687   return true;
4688 }
4689 
4690 // AutoVectorize the loop: replace scalar ops with vector ops.
4691 PhaseIdealLoop::AutoVectorizeStatus
4692 PhaseIdealLoop::auto_vectorize(IdealLoopTree* lpt, VSharedData &vshared) {
4693   // Counted loop only
4694   if (!lpt->is_counted()) {
4695     return AutoVectorizeStatus::Impossible;
4696   }
4697 
4698   // Main-loop only
4699   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4700   if (!cl->is_main_loop()) {
4701     return AutoVectorizeStatus::Impossible;
4702   }
4703 
4704   VLoop vloop(lpt, false);
4705   if (!vloop.check_preconditions()) {
4706     return AutoVectorizeStatus::TriedAndFailed;
4707   }
4708 
4709   // Ensure the shared data is cleared before each use
4710   vshared.clear();
4711 
4712   const VLoopAnalyzer vloop_analyzer(vloop, vshared);
4713   if (!vloop_analyzer.success()) {
4714     return AutoVectorizeStatus::TriedAndFailed;
4715   }
4716 
4717   SuperWord sw(vloop_analyzer);
4718   if (!sw.transform_loop()) {
4719     return AutoVectorizeStatus::TriedAndFailed;
4720   }
4721 
4722   return AutoVectorizeStatus::Success;
4723 }
4724 
4725 // Just before insert_pre_post_loops, we can multiversion the loop:
4726 //
4727 //              multiversion_if
4728 //               |       |
4729 //         fast_loop   slow_loop
4730 //
4731 // In the fast_loop we can make speculative assumptions, and put the
4732 // conditions into the multiversion_if. If the conditions hold at runtime,
4733 // we enter the fast_loop, if the conditions fail, we take the slow_loop
4734 // instead which does not make any of the speculative assumptions.
4735 //
4736 // Note: we only multiversion the loop if the loop does not have any
4737 //       auto vectorization check Predicate. If we have that predicate,
4738 //       then we can simply add the speculative assumption checks to
4739 //       that Predicate. This means we do not need to duplicate the
4740 //       loop - we have a smaller graph and save compile time. Should
4741 //       the conditions ever fail, then we deopt / trap at the Predicate
4742 //       and recompile without that Predicate. At that point we will
4743 //       multiversion the loop, so that we can still have speculative
4744 //       runtime checks.
4745 //
4746 // We perform the multiversioning when the loop is still in its single
4747 // iteration form, even before we insert pre and post loops. This makes
4748 // the cloning much simpler. However, this means that both the fast
4749 // and the slow loop have to be optimized independently (adding pre
4750 // and post loops, unrolling the main loop, auto-vectorize etc.). And
4751 // we may end up not needing any speculative assumptions in the fast_loop
4752 // and then rejecting the slow_loop by constant folding the multiversion_if.
4753 //
4754 // Therefore, we "delay" the optimization of the slow_loop until we add
4755 // at least one speculative assumption for the fast_loop. If we never
4756 // add such a speculative runtime check, the OpaqueMultiversioningNode
4757 // of the multiversion_if constant folds to true after loop opts, and the
4758 // multiversion_if folds away the "delayed" slow_loop. If we add any
4759 // speculative assumption, then we notify the OpaqueMultiversioningNode
4760 // with "notify_slow_loop_that_it_can_resume_optimizations".
4761 //
4762 // Note: new runtime checks can be added to the multiversion_if with
4763 //       PhaseIdealLoop::create_new_if_for_multiversion
4764 void PhaseIdealLoop::maybe_multiversion_for_auto_vectorization_runtime_checks(IdealLoopTree* lpt, Node_List& old_new) {
4765   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4766   LoopNode* outer_loop = cl->skip_strip_mined();
4767   Node* entry = outer_loop->in(LoopNode::EntryControl);
4768 
4769   // Check we have multiversioning enabled, and are not already multiversioned.
4770   if (!LoopMultiversioning || cl->is_multiversion()) { return; }
4771 
4772   // Check that we do not have a parse-predicate where we can add the runtime checks
4773   // during auto-vectorization.
4774   const Predicates predicates(entry);
4775   const PredicateBlock* predicate_block = predicates.auto_vectorization_check_block();
4776   if (predicate_block->has_parse_predicate()) { return; }
4777 
4778   // Check node budget.
4779   uint estimate = lpt->est_loop_clone_sz(2);
4780   if (!may_require_nodes(estimate)) { return; }
4781 
4782   do_multiversioning(lpt, old_new);
4783 }
4784 
4785 void DataNodeGraph::clone_data_nodes(Node* new_ctrl) {
4786   for (uint i = 0; i < _data_nodes.size(); i++) {
4787     clone(_data_nodes[i], new_ctrl);
4788   }
4789 }
4790 
4791 // Clone the given node and set it up properly. Set 'new_ctrl' as ctrl.
4792 void DataNodeGraph::clone(Node* node, Node* new_ctrl) {
4793   Node* clone = node->clone();
4794   _phase->igvn().register_new_node_with_optimizer(clone);
4795   _orig_to_new.put(node, clone);
4796   _phase->set_ctrl(clone, new_ctrl);
4797   if (node->is_CastII()) {
4798     clone->set_req(0, new_ctrl);
4799   }
4800 }
4801 
4802 // Rewire the data inputs of all (unprocessed) cloned nodes, whose inputs are still pointing to the same inputs as their
4803 // corresponding orig nodes, to the newly cloned inputs to create a separate cloned graph.
4804 void DataNodeGraph::rewire_clones_to_cloned_inputs() {
4805   _orig_to_new.iterate_all([&](Node* node, Node* clone) {
4806     for (uint i = 1; i < node->req(); i++) {
4807       Node** cloned_input = _orig_to_new.get(node->in(i));
4808       if (cloned_input != nullptr) {
4809         // Input was also cloned -> rewire clone to the cloned input.
4810         _phase->igvn().replace_input_of(clone, i, *cloned_input);
4811       }
4812     }
4813   });
4814 }
4815 
4816 // Clone all non-OpaqueLoop* nodes and apply the provided transformation strategy for OpaqueLoop* nodes.
4817 // Set 'new_ctrl' as ctrl for all cloned non-OpaqueLoop* nodes.
4818 void DataNodeGraph::clone_data_nodes_and_transform_opaque_loop_nodes(
4819     const TransformStrategyForOpaqueLoopNodes& transform_strategy,
4820     Node* new_ctrl) {
4821   for (uint i = 0; i < _data_nodes.size(); i++) {
4822     Node* data_node = _data_nodes[i];
4823     if (data_node->is_Opaque1()) {
4824       transform_opaque_node(transform_strategy, data_node);
4825     } else {
4826       clone(data_node, new_ctrl);
4827     }
4828   }
4829 }
4830 
4831 void DataNodeGraph::transform_opaque_node(const TransformStrategyForOpaqueLoopNodes& transform_strategy, Node* node) {
4832   Node* transformed_node;
4833   if (node->is_OpaqueLoopInit()) {
4834     transformed_node = transform_strategy.transform_opaque_init(node->as_OpaqueLoopInit());
4835   } else {
4836     assert(node->is_OpaqueLoopStride(), "must be OpaqueLoopStrideNode");
4837     transformed_node = transform_strategy.transform_opaque_stride(node->as_OpaqueLoopStride());
4838   }
4839   // Add an orig->new mapping to correctly update the inputs of the copied graph in rewire_clones_to_cloned_inputs().
4840   _orig_to_new.put(node, transformed_node);
4841 }
--- EOF ---