1 /*
   2  * Copyright (c) 1999, 2026, 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, PhaseIterGVN::NodeOrigin::Speculative);
 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, PhaseIterGVN::NodeOrigin::Speculative);
 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 prevdom_not_imply_this) {
 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, prevdom_not_imply_this);
 397 }
 398 
 399 void PhaseIdealLoop::rewire_safe_outputs_to_dominator(Node* source, Node* dominator, const bool dominator_not_imply_source) {
 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     if (out->depends_only_on_test()) {
 405       assert(out->in(0) == source, "must be control dependent on source");
 406       _igvn.replace_input_of(out, 0, dominator);
 407       if (dominator_not_imply_source) {
 408         // Because of Loop Predication, Loads and range check Cast nodes that are control dependent on this range
 409         // check (that is about to be removed) now depend on multiple dominating Hoisted Check Predicates. After the
 410         // removal of this range check, these control dependent nodes end up at the lowest/nearest dominating predicate
 411         // in the graph. To ensure that these Loads/Casts do not float above any of the dominating checks (even when the
 412         // lowest dominating check is later replaced by yet another dominating check), we need to pin them at the lowest
 413         // dominating check.
 414         Node* clone = out->pin_node_under_control();
 415         if (clone != nullptr) {
 416           clone = _igvn.register_new_node_with_optimizer(clone, out);
 417           _igvn.replace_node(out, clone);
 418           out = clone;
 419         }
 420       }
 421       set_early_ctrl(out, false);
 422       IdealLoopTree* new_loop = get_loop(get_ctrl(out));
 423       if (old_loop != new_loop) {
 424         if (!old_loop->_child) {
 425           old_loop->_body.yank(out);
 426         }
 427         if (!new_loop->_child) {
 428           new_loop->_body.push(out);
 429         }
 430       }
 431       --i;
 432       --imax;
 433     }
 434   }
 435 }
 436 
 437 //------------------------------has_local_phi_input----------------------------
 438 // Return TRUE if 'n' has Phi inputs from its local block and no other
 439 // block-local inputs (all non-local-phi inputs come from earlier blocks)
 440 Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
 441   Node *n_ctrl = get_ctrl(n);
 442   // See if some inputs come from a Phi in this block, or from before
 443   // this block.
 444   uint i;
 445   for( i = 1; i < n->req(); i++ ) {
 446     Node *phi = n->in(i);
 447     if( phi->is_Phi() && phi->in(0) == n_ctrl )
 448       break;
 449   }
 450   if( i >= n->req() )
 451     return nullptr;                // No Phi inputs; nowhere to clone thru
 452 
 453   // Check for inputs created between 'n' and the Phi input.  These
 454   // must split as well; they have already been given the chance
 455   // (courtesy of a post-order visit) and since they did not we must
 456   // recover the 'cost' of splitting them by being very profitable
 457   // when splitting 'n'.  Since this is unlikely we simply give up.
 458   for( i = 1; i < n->req(); i++ ) {
 459     Node *m = n->in(i);
 460     if( get_ctrl(m) == n_ctrl && !m->is_Phi() ) {
 461       // We allow the special case of AddP's with no local inputs.
 462       // This allows us to split-up address expressions.
 463       if (m->is_AddP() &&
 464           get_ctrl(m->in(AddPNode::Base)) != n_ctrl &&
 465           get_ctrl(m->in(AddPNode::Address)) != n_ctrl &&
 466           get_ctrl(m->in(AddPNode::Offset)) != n_ctrl) {
 467         // Move the AddP up to the dominating point. That's fine because control of m's inputs
 468         // must dominate get_ctrl(m) == n_ctrl and we just checked that the input controls are != n_ctrl.
 469         Node* c = find_non_split_ctrl(idom(n_ctrl));
 470         if (c->is_OuterStripMinedLoop()) {
 471           c->as_Loop()->verify_strip_mined(1);
 472           c = c->in(LoopNode::EntryControl);
 473         }
 474         set_ctrl_and_loop(m, c);
 475         continue;
 476       }
 477       return nullptr;
 478     }
 479     assert(n->is_Phi() || m->is_Phi() || is_dominator(get_ctrl(m), n_ctrl), "m has strange control");
 480   }
 481 
 482   return n_ctrl;
 483 }
 484 
 485 // Replace expressions like ((V+I) << 2) with (V<<2 + I<<2).
 486 Node* PhaseIdealLoop::remix_address_expressions_add_left_shift(Node* n, IdealLoopTree* n_loop, Node* n_ctrl, BasicType bt) {
 487   assert(bt == T_INT || bt == T_LONG, "only for integers");
 488   int n_op = n->Opcode();
 489 
 490   if (n_op == Op_LShift(bt)) {
 491     // Scale is loop invariant
 492     Node* scale = n->in(2);
 493     Node* scale_ctrl = get_ctrl(scale);
 494     IdealLoopTree* scale_loop = get_loop(scale_ctrl);
 495     if (n_loop == scale_loop || !scale_loop->is_member(n_loop)) {
 496       return nullptr;
 497     }
 498     const TypeInt* scale_t = scale->bottom_type()->isa_int();
 499     if (scale_t != nullptr && scale_t->is_con() && scale_t->get_con() >= 16) {
 500       return nullptr;              // Dont bother with byte/short masking
 501     }
 502     // Add must vary with loop (else shift would be loop-invariant)
 503     Node* add = n->in(1);
 504     Node* add_ctrl = get_ctrl(add);
 505     IdealLoopTree* add_loop = get_loop(add_ctrl);
 506     if (n_loop != add_loop) {
 507       return nullptr;  // happens w/ evil ZKM loops
 508     }
 509 
 510     // Convert I-V into I+ (0-V); same for V-I
 511     if (add->Opcode() == Op_Sub(bt) &&
 512         _igvn.type(add->in(1)) != TypeInteger::zero(bt)) {
 513       assert(add->Opcode() == Op_SubI || add->Opcode() == Op_SubL, "");
 514       Node* zero = integercon(0, bt);
 515       Node* neg = SubNode::make(zero, add->in(2), bt);
 516       register_new_node_with_ctrl_of(neg, add->in(2));
 517       add = AddNode::make(add->in(1), neg, bt);
 518       register_new_node(add, add_ctrl);
 519     }
 520     if (add->Opcode() != Op_Add(bt)) return nullptr;
 521     assert(add->Opcode() == Op_AddI || add->Opcode() == Op_AddL, "");
 522     // See if one add input is loop invariant
 523     Node* add_var = add->in(1);
 524     Node* add_var_ctrl = get_ctrl(add_var);
 525     IdealLoopTree* add_var_loop = get_loop(add_var_ctrl);
 526     Node* add_invar = add->in(2);
 527     Node* add_invar_ctrl = get_ctrl(add_invar);
 528     IdealLoopTree* add_invar_loop = get_loop(add_invar_ctrl);
 529     if (add_invar_loop == n_loop) {
 530       // Swap to find the invariant part
 531       add_invar = add_var;
 532       add_invar_ctrl = add_var_ctrl;
 533       add_invar_loop = add_var_loop;
 534       add_var = add->in(2);
 535     } else if (add_var_loop != n_loop) { // Else neither input is loop invariant
 536       return nullptr;
 537     }
 538     if (n_loop == add_invar_loop || !add_invar_loop->is_member(n_loop)) {
 539       return nullptr;              // No invariant part of the add?
 540     }
 541 
 542     // Yes!  Reshape address expression!
 543     Node* inv_scale = LShiftNode::make(add_invar, scale, bt);
 544     Node* inv_scale_ctrl =
 545             dom_depth(add_invar_ctrl) > dom_depth(scale_ctrl) ?
 546             add_invar_ctrl : scale_ctrl;
 547     register_new_node(inv_scale, inv_scale_ctrl);
 548     Node* var_scale = LShiftNode::make(add_var, scale, bt);
 549     register_new_node(var_scale, n_ctrl);
 550     Node* var_add = AddNode::make(var_scale, inv_scale, bt);
 551     register_new_node(var_add, n_ctrl);
 552     _igvn.replace_node(n, var_add);
 553     return var_add;
 554   }
 555   return nullptr;
 556 }
 557 
 558 //------------------------------remix_address_expressions----------------------
 559 // Rework addressing expressions to get the most loop-invariant stuff
 560 // moved out.  We'd like to do all associative operators, but it's especially
 561 // important (common) to do address expressions.
 562 Node* PhaseIdealLoop::remix_address_expressions(Node* n) {
 563   if (!has_ctrl(n))  return nullptr;
 564   Node* n_ctrl = get_ctrl(n);
 565   IdealLoopTree* n_loop = get_loop(n_ctrl);
 566 
 567   // See if 'n' mixes loop-varying and loop-invariant inputs and
 568   // itself is loop-varying.
 569 
 570   // Only interested in binary ops (and AddP)
 571   if (n->req() < 3 || n->req() > 4) return nullptr;
 572 
 573   Node* n1_ctrl = get_ctrl(n->in(                    1));
 574   Node* n2_ctrl = get_ctrl(n->in(                    2));
 575   Node* n3_ctrl = get_ctrl(n->in(n->req() == 3 ? 2 : 3));
 576   IdealLoopTree* n1_loop = get_loop(n1_ctrl);
 577   IdealLoopTree* n2_loop = get_loop(n2_ctrl);
 578   IdealLoopTree* n3_loop = get_loop(n3_ctrl);
 579 
 580   // Does one of my inputs spin in a tighter loop than self?
 581   if ((n_loop->is_member(n1_loop) && n_loop != n1_loop) ||
 582       (n_loop->is_member(n2_loop) && n_loop != n2_loop) ||
 583       (n_loop->is_member(n3_loop) && n_loop != n3_loop)) {
 584     return nullptr;                // Leave well enough alone
 585   }
 586 
 587   // Is at least one of my inputs loop-invariant?
 588   if (n1_loop == n_loop &&
 589       n2_loop == n_loop &&
 590       n3_loop == n_loop) {
 591     return nullptr;                // No loop-invariant inputs
 592   }
 593 
 594   Node* res = remix_address_expressions_add_left_shift(n, n_loop, n_ctrl, T_INT);
 595   if (res != nullptr) {
 596     return res;
 597   }
 598   res = remix_address_expressions_add_left_shift(n, n_loop, n_ctrl, T_LONG);
 599   if (res != nullptr) {
 600     return res;
 601   }
 602 
 603   int n_op = n->Opcode();
 604   // Replace (I+V) with (V+I)
 605   if (n_op == Op_AddI ||
 606       n_op == Op_AddL ||
 607       n_op == Op_AddF ||
 608       n_op == Op_AddD ||
 609       n_op == Op_MulI ||
 610       n_op == Op_MulL ||
 611       n_op == Op_MulF ||
 612       n_op == Op_MulD) {
 613     if (n2_loop == n_loop) {
 614       assert(n1_loop != n_loop, "");
 615       n->swap_edges(1, 2);
 616     }
 617   }
 618 
 619   // Replace ((I1 +p V) +p I2) with ((I1 +p I2) +p V),
 620   // but not if I2 is a constant. Skip for irreducible loops.
 621   if (n_op == Op_AddP && n_loop->_head->is_Loop()) {
 622     if (n2_loop == n_loop && n3_loop != n_loop) {
 623       if (n->in(2)->Opcode() == Op_AddP && !n->in(3)->is_Con()) {
 624         Node* n22_ctrl = get_ctrl(n->in(2)->in(2));
 625         Node* n23_ctrl = get_ctrl(n->in(2)->in(3));
 626         IdealLoopTree* n22loop = get_loop(n22_ctrl);
 627         IdealLoopTree* n23_loop = get_loop(n23_ctrl);
 628         if (n22loop != n_loop && n22loop->is_member(n_loop) &&
 629             n23_loop == n_loop) {
 630           Node* add1 = AddPNode::make_with_base(n->in(1), n->in(2)->in(2), n->in(3));
 631           // Stuff new AddP in the loop preheader
 632           register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
 633           Node* add2 = AddPNode::make_with_base(n->in(1), add1, n->in(2)->in(3));
 634           register_new_node(add2, n_ctrl);
 635           _igvn.replace_node(n, add2);
 636           return add2;
 637         }
 638       }
 639     }
 640 
 641     // Replace (I1 +p (I2 + V)) with ((I1 +p I2) +p V)
 642     if (n2_loop != n_loop && n3_loop == n_loop) {
 643       if (n->in(3)->Opcode() == Op_AddX) {
 644         Node* V = n->in(3)->in(1);
 645         Node* I = n->in(3)->in(2);
 646         if (ctrl_is_member(n_loop, V)) {
 647         } else {
 648           Node *tmp = V; V = I; I = tmp;
 649         }
 650         if (!ctrl_is_member(n_loop, I)) {
 651           Node* add1 = AddPNode::make_with_base(n->in(1), n->in(2), I);
 652           // Stuff new AddP in the loop preheader
 653           register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
 654           Node* add2 = AddPNode::make_with_base(n->in(1), add1, V);
 655           register_new_node(add2, n_ctrl);
 656           _igvn.replace_node(n, add2);
 657           return add2;
 658         }
 659       }
 660     }
 661   }
 662 
 663   return nullptr;
 664 }
 665 
 666 // Optimize ((in1[2*i] * in2[2*i]) + (in1[2*i+1] * in2[2*i+1]))
 667 Node *PhaseIdealLoop::convert_add_to_muladd(Node* n) {
 668   assert(n->Opcode() == Op_AddI, "sanity");
 669   Node * nn = nullptr;
 670   Node * in1 = n->in(1);
 671   Node * in2 = n->in(2);
 672   if (in1->Opcode() == Op_MulI && in2->Opcode() == Op_MulI) {
 673     IdealLoopTree* loop_n = get_loop(get_ctrl(n));
 674     if (loop_n->is_counted() &&
 675         loop_n->_head->as_Loop()->is_valid_counted_loop(T_INT) &&
 676         Matcher::match_rule_supported(Op_MulAddVS2VI) &&
 677         Matcher::match_rule_supported(Op_MulAddS2I)) {
 678       Node* mul_in1 = in1->in(1);
 679       Node* mul_in2 = in1->in(2);
 680       Node* mul_in3 = in2->in(1);
 681       Node* mul_in4 = in2->in(2);
 682       if (mul_in1->Opcode() == Op_LoadS &&
 683           mul_in2->Opcode() == Op_LoadS &&
 684           mul_in3->Opcode() == Op_LoadS &&
 685           mul_in4->Opcode() == Op_LoadS) {
 686         IdealLoopTree* loop1 = get_loop(get_ctrl(mul_in1));
 687         IdealLoopTree* loop2 = get_loop(get_ctrl(mul_in2));
 688         IdealLoopTree* loop3 = get_loop(get_ctrl(mul_in3));
 689         IdealLoopTree* loop4 = get_loop(get_ctrl(mul_in4));
 690         IdealLoopTree* loop5 = get_loop(get_ctrl(in1));
 691         IdealLoopTree* loop6 = get_loop(get_ctrl(in2));
 692         // All nodes should be in the same counted loop.
 693         if (loop_n == loop1 && loop_n == loop2 && loop_n == loop3 &&
 694             loop_n == loop4 && loop_n == loop5 && loop_n == loop6) {
 695           Node* adr1 = mul_in1->in(MemNode::Address);
 696           Node* adr2 = mul_in2->in(MemNode::Address);
 697           Node* adr3 = mul_in3->in(MemNode::Address);
 698           Node* adr4 = mul_in4->in(MemNode::Address);
 699           if (adr1->is_AddP() && adr2->is_AddP() && adr3->is_AddP() && adr4->is_AddP()) {
 700             if ((adr1->in(AddPNode::Base) == adr3->in(AddPNode::Base)) &&
 701                 (adr2->in(AddPNode::Base) == adr4->in(AddPNode::Base))) {
 702               nn = new MulAddS2INode(mul_in1, mul_in2, mul_in3, mul_in4);
 703               register_new_node_with_ctrl_of(nn, n);
 704               _igvn.replace_node(n, nn);
 705               return nn;
 706             } else if ((adr1->in(AddPNode::Base) == adr4->in(AddPNode::Base)) &&
 707                        (adr2->in(AddPNode::Base) == adr3->in(AddPNode::Base))) {
 708               nn = new MulAddS2INode(mul_in1, mul_in2, mul_in4, mul_in3);
 709               register_new_node_with_ctrl_of(nn, n);
 710               _igvn.replace_node(n, nn);
 711               return nn;
 712             }
 713           }
 714         }
 715       }
 716     }
 717   }
 718   return nn;
 719 }
 720 
 721 //------------------------------conditional_move-------------------------------
 722 // Attempt to replace a Phi with a conditional move.  We have some pretty
 723 // strict profitability requirements.  All Phis at the merge point must
 724 // be converted, so we can remove the control flow.  We need to limit the
 725 // number of c-moves to a small handful.  All code that was in the side-arms
 726 // of the CFG diamond is now speculatively executed.  This code has to be
 727 // "cheap enough".  We are pretty much limited to CFG diamonds that merge
 728 // 1 or 2 items with a total of 1 or 2 ops executed speculatively.
 729 Node *PhaseIdealLoop::conditional_move( Node *region ) {
 730 
 731   assert(region->is_Region(), "sanity check");
 732   if (region->req() != 3) return nullptr;
 733 
 734   // Check for CFG diamond
 735   Node *lp = region->in(1);
 736   Node *rp = region->in(2);
 737   if (!lp || !rp) return nullptr;
 738   Node *lp_c = lp->in(0);
 739   if (lp_c == nullptr || lp_c != rp->in(0) || !lp_c->is_If()) return nullptr;
 740   IfNode *iff = lp_c->as_If();
 741 
 742   // Check for ops pinned in an arm of the diamond.
 743   // Can't remove the control flow in this case
 744   if (lp->outcnt() > 1) return nullptr;
 745   if (rp->outcnt() > 1) return nullptr;
 746 
 747   IdealLoopTree* r_loop = get_loop(region);
 748   assert(r_loop == get_loop(iff), "sanity");
 749   // Always convert to CMOVE if all results are used only outside this loop.
 750   bool used_inside_loop = (r_loop == _ltree_root);
 751 
 752   // Check profitability
 753   int cost = 0;
 754   int phis = 0;
 755   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 756     Node *out = region->fast_out(i);
 757     if (!out->is_Phi()) continue; // Ignore other control edges, etc
 758     phis++;
 759     PhiNode* phi = out->as_Phi();
 760     BasicType bt = phi->type()->basic_type();
 761     switch (bt) {
 762     case T_DOUBLE:
 763     case T_FLOAT:
 764       if (C->use_cmove()) {
 765         continue; //TODO: maybe we want to add some cost
 766       }
 767       cost += Matcher::float_cmove_cost(); // Could be very expensive
 768       break;
 769     case T_LONG: {
 770       cost += Matcher::long_cmove_cost(); // May encodes as 2 CMOV's
 771     }
 772     case T_INT:                 // These all CMOV fine
 773     case T_ADDRESS: {           // (RawPtr)
 774       cost++;
 775       break;
 776     }
 777     case T_NARROWOOP: // Fall through
 778     case T_OBJECT: {            // Base oops are OK, but not derived oops
 779       const TypeOopPtr *tp = phi->type()->make_ptr()->isa_oopptr();
 780       // Derived pointers are Bad (tm): what's the Base (for GC purposes) of a
 781       // CMOVE'd derived pointer?  It's a CMOVE'd derived base.  Thus
 782       // CMOVE'ing a derived pointer requires we also CMOVE the base.  If we
 783       // have a Phi for the base here that we convert to a CMOVE all is well
 784       // and good.  But if the base is dead, we'll not make a CMOVE.  Later
 785       // the allocator will have to produce a base by creating a CMOVE of the
 786       // relevant bases.  This puts the allocator in the business of
 787       // manufacturing expensive instructions, generally a bad plan.
 788       // Just Say No to Conditionally-Moved Derived Pointers.
 789       if (tp && tp->offset() != 0)
 790         return nullptr;
 791       cost++;
 792       break;
 793     }
 794     default:
 795       return nullptr;              // In particular, can't do memory or I/O
 796     }
 797     // Add in cost any speculative ops
 798     for (uint j = 1; j < region->req(); j++) {
 799       Node *proj = region->in(j);
 800       Node *inp = phi->in(j);
 801       if (get_ctrl(inp) == proj) { // Found local op
 802         cost++;
 803         // Check for a chain of dependent ops; these will all become
 804         // speculative in a CMOV.
 805         for (uint k = 1; k < inp->req(); k++)
 806           if (get_ctrl(inp->in(k)) == proj)
 807             cost += ConditionalMoveLimit; // Too much speculative goo
 808       }
 809     }
 810     // See if the Phi is used by a Cmp or Narrow oop Decode/Encode.
 811     // This will likely Split-If, a higher-payoff operation.
 812     for (DUIterator_Fast kmax, k = phi->fast_outs(kmax); k < kmax; k++) {
 813       Node* use = phi->fast_out(k);
 814       if (use->is_Cmp() || use->is_DecodeNarrowPtr() || use->is_EncodeNarrowPtr())
 815         cost += ConditionalMoveLimit;
 816       // Is there a use inside the loop?
 817       // Note: check only basic types since CMoveP is pinned.
 818       if (!used_inside_loop && is_java_primitive(bt)) {
 819         IdealLoopTree* u_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use);
 820         if (r_loop == u_loop || r_loop->is_member(u_loop)) {
 821           used_inside_loop = true;
 822         }
 823       }
 824     }
 825   }//for
 826   Node* bol = iff->in(1);
 827   assert(!bol->is_OpaqueInitializedAssertionPredicate(), "Initialized Assertion Predicates cannot form a diamond with Halt");
 828   if (bol->is_OpaqueTemplateAssertionPredicate()) {
 829     // Ignore Template Assertion Predicates with OpaqueTemplateAssertionPredicate nodes.
 830     return nullptr;
 831   }
 832   if (bol->is_OpaqueMultiversioning()) {
 833     assert(bol->as_OpaqueMultiversioning()->is_useless(), "Must be useless, i.e. fast main loop has already disappeared.");
 834     // Ignore multiversion_if that just lost its loops. The OpaqueMultiversioning is marked useless,
 835     // and will make the multiversion_if constant fold in the next IGVN round.
 836     return nullptr;
 837   }
 838   if (!bol->is_Bool()) {
 839     assert(false, "Expected Bool, but got %s", NodeClassNames[bol->Opcode()]);
 840     return nullptr;
 841   }
 842   int cmp_op = bol->in(1)->Opcode();
 843   if (cmp_op == Op_SubTypeCheck) { // SubTypeCheck expansion expects an IfNode
 844     return nullptr;
 845   }
 846   // It is expensive to generate flags from a float compare.
 847   // Avoid duplicated float compare.
 848   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return nullptr;
 849 
 850   float infrequent_prob = PROB_UNLIKELY_MAG(3);
 851   // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
 852   if (used_inside_loop) {
 853     if (cost >= ConditionalMoveLimit) return nullptr; // Too much goo
 854 
 855     // BlockLayoutByFrequency optimization moves infrequent branch
 856     // from hot path. No point in CMOV'ing in such case (110 is used
 857     // instead of 100 to take into account not exactness of float value).
 858     if (BlockLayoutByFrequency) {
 859       infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
 860     }
 861   }
 862   // Check for highly predictable branch.  No point in CMOV'ing if
 863   // we are going to predict accurately all the time.
 864   if (C->use_cmove() && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) {
 865     //keep going
 866   } else if (iff->_prob < infrequent_prob ||
 867       iff->_prob > (1.0f - infrequent_prob))
 868     return nullptr;
 869 
 870   // --------------
 871   // Now replace all Phis with CMOV's
 872   Node *cmov_ctrl = iff->in(0);
 873   uint flip = (lp->Opcode() == Op_IfTrue);
 874   Node_List wq;
 875   while (1) {
 876     PhiNode* phi = nullptr;
 877     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 878       Node *out = region->fast_out(i);
 879       if (out->is_Phi()) {
 880         phi = out->as_Phi();
 881         break;
 882       }
 883     }
 884     if (phi == nullptr || _igvn.type(phi) == Type::TOP || !CMoveNode::supported(_igvn.type(phi))) {
 885       break;
 886     }
 887     // Move speculative ops
 888     wq.push(phi);
 889     while (wq.size() > 0) {
 890       Node *n = wq.pop();
 891       for (uint j = 1; j < n->req(); j++) {
 892         Node* m = n->in(j);
 893         if (m != nullptr && !is_dominator(get_ctrl(m), cmov_ctrl)) {
 894           set_ctrl(m, cmov_ctrl);
 895           wq.push(m);
 896         }
 897       }
 898     }
 899     Node* cmov = CMoveNode::make(iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi));
 900     register_new_node(cmov, cmov_ctrl);
 901     _igvn.replace_node(phi, cmov);
 902 #ifndef PRODUCT
 903     if (TraceLoopOpts) {
 904       tty->print("CMOV  ");
 905       r_loop->dump_head();
 906       if (Verbose) {
 907         bol->in(1)->dump(1);
 908         cmov->dump(1);
 909       }
 910     }
 911     DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
 912 #endif
 913   }
 914 
 915   // The useless CFG diamond will fold up later; see the optimization in
 916   // RegionNode::Ideal.
 917   _igvn._worklist.push(region);
 918 
 919   return iff->in(1);
 920 }
 921 
 922 static void enqueue_cfg_uses(Node* m, Unique_Node_List& wq) {
 923   for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
 924     Node* u = m->fast_out(i);
 925     if (u->is_CFG()) {
 926       if (u->is_NeverBranch()) {
 927         u = u->as_NeverBranch()->proj_out(0);
 928         enqueue_cfg_uses(u, wq);
 929       } else {
 930         wq.push(u);
 931       }
 932     }
 933   }
 934 }
 935 
 936 // Try moving a store out of a loop, right before the loop
 937 Node* PhaseIdealLoop::try_move_store_before_loop(Node* n, Node *n_ctrl) {
 938   // Store has to be first in the loop body
 939   IdealLoopTree *n_loop = get_loop(n_ctrl);
 940   if (n->is_Store() && n_loop != _ltree_root &&
 941       n_loop->is_loop() && n_loop->_head->is_Loop() &&
 942       n->in(0) != nullptr) {
 943     Node* address = n->in(MemNode::Address);
 944     Node* value = n->in(MemNode::ValueIn);
 945     Node* mem = n->in(MemNode::Memory);
 946 
 947     // - address and value must be loop invariant
 948     // - memory must be a memory Phi for the loop
 949     // - Store must be the only store on this memory slice in the
 950     // loop: if there's another store following this one then value
 951     // written at iteration i by the second store could be overwritten
 952     // at iteration i+n by the first store: it's not safe to move the
 953     // first store out of the loop
 954     // - nothing must observe the memory Phi: it guarantees no read
 955     // before the store, we are also guaranteed the store post
 956     // dominates the loop head (ignoring a possible early
 957     // exit). Otherwise there would be extra Phi involved between the
 958     // loop's Phi and the store.
 959     // - there must be no early exit from the loop before the Store
 960     // (such an exit most of the time would be an extra use of the
 961     // memory Phi but sometimes is a bottom memory Phi that takes the
 962     // store as input).
 963 
 964     if (!ctrl_is_member(n_loop, address) &&
 965         !ctrl_is_member(n_loop, value) &&
 966         mem->is_Phi() && mem->in(0) == n_loop->_head &&
 967         mem->outcnt() == 1 &&
 968         mem->in(LoopNode::LoopBackControl) == n) {
 969 
 970       assert(n_loop->_tail != nullptr, "need a tail");
 971       assert(is_dominator(n_ctrl, n_loop->_tail), "store control must not be in a branch in the loop");
 972 
 973       // Verify that there's no early exit of the loop before the store.
 974       bool ctrl_ok = false;
 975       {
 976         // Follow control from loop head until n, we exit the loop or
 977         // we reach the tail
 978         ResourceMark rm;
 979         Unique_Node_List wq;
 980         wq.push(n_loop->_head);
 981 
 982         for (uint next = 0; next < wq.size(); ++next) {
 983           Node *m = wq.at(next);
 984           if (m == n->in(0)) {
 985             ctrl_ok = true;
 986             continue;
 987           }
 988           assert(!has_ctrl(m), "should be CFG");
 989           if (!n_loop->is_member(get_loop(m)) || m == n_loop->_tail) {
 990             ctrl_ok = false;
 991             break;
 992           }
 993           enqueue_cfg_uses(m, wq);
 994           if (wq.size() > 10) {
 995             ctrl_ok = false;
 996             break;
 997           }
 998         }
 999       }
1000       if (ctrl_ok) {
1001         // move the Store
1002         _igvn.replace_input_of(mem, LoopNode::LoopBackControl, mem);
1003         _igvn.replace_input_of(n, 0, n_loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl));
1004         _igvn.replace_input_of(n, MemNode::Memory, mem->in(LoopNode::EntryControl));
1005         // Disconnect the phi now. An empty phi can confuse other
1006         // optimizations in this pass of loop opts.
1007         _igvn.replace_node(mem, mem->in(LoopNode::EntryControl));
1008         n_loop->_body.yank(mem);
1009 
1010         set_ctrl_and_loop(n, n->in(0));
1011 
1012         return n;
1013       }
1014     }
1015   }
1016   return nullptr;
1017 }
1018 
1019 // Try moving a store out of a loop, right after the loop
1020 void PhaseIdealLoop::try_move_store_after_loop(Node* n) {
1021   if (n->is_Store() && n->in(0) != nullptr) {
1022     Node *n_ctrl = get_ctrl(n);
1023     IdealLoopTree *n_loop = get_loop(n_ctrl);
1024     // Store must be in a loop
1025     if (n_loop != _ltree_root && !n_loop->_irreducible) {
1026       Node* address = n->in(MemNode::Address);
1027       Node* value = n->in(MemNode::ValueIn);
1028       // address must be loop invariant
1029       if (!ctrl_is_member(n_loop, address)) {
1030         // Store must be last on this memory slice in the loop and
1031         // nothing in the loop must observe it
1032         Node* phi = nullptr;
1033         for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1034           Node* u = n->fast_out(i);
1035           if (has_ctrl(u)) { // control use?
1036             if (!ctrl_is_member(n_loop, u)) {
1037               continue;
1038             }
1039             if (u->is_Phi() && u->in(0) == n_loop->_head) {
1040               assert(_igvn.type(u) == Type::MEMORY, "bad phi");
1041               // multiple phis on the same slice are possible
1042               if (phi != nullptr) {
1043                 return;
1044               }
1045               phi = u;
1046               continue;
1047             }
1048           }
1049           return;
1050         }
1051         if (phi != nullptr) {
1052           // Nothing in the loop before the store (next iteration)
1053           // must observe the stored value
1054           bool mem_ok = true;
1055           {
1056             ResourceMark rm;
1057             Unique_Node_List wq;
1058             wq.push(phi);
1059             for (uint next = 0; next < wq.size() && mem_ok; ++next) {
1060               Node *m = wq.at(next);
1061               for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax && mem_ok; i++) {
1062                 Node* u = m->fast_out(i);
1063                 if (u->is_Store() || u->is_Phi()) {
1064                   if (u != n) {
1065                     wq.push(u);
1066                     mem_ok = (wq.size() <= 10);
1067                   }
1068                 } else {
1069                   mem_ok = false;
1070                   break;
1071                 }
1072               }
1073             }
1074           }
1075           if (mem_ok) {
1076             // Move the store out of the loop if the LCA of all
1077             // users (except for the phi) is outside the loop.
1078             Node* hook = new Node(1);
1079             hook->init_req(0, n_ctrl); // Add an input to prevent hook from being dead
1080             _igvn.rehash_node_delayed(phi);
1081             int count = phi->replace_edge(n, hook, &_igvn);
1082             assert(count > 0, "inconsistent phi");
1083 
1084             // Compute latest point this store can go
1085             Node* lca = get_late_ctrl(n, get_ctrl(n));
1086             if (lca->is_OuterStripMinedLoop()) {
1087               lca = lca->in(LoopNode::EntryControl);
1088             }
1089             if (n_loop->is_member(get_loop(lca))) {
1090               // LCA is in the loop - bail out
1091               _igvn.replace_node(hook, n);
1092               return;
1093             }
1094 #ifdef ASSERT
1095             if (n_loop->_head->is_Loop() && n_loop->_head->as_Loop()->is_strip_mined()) {
1096               assert(n_loop->_head->Opcode() == Op_CountedLoop, "outer loop is a strip mined");
1097               n_loop->_head->as_Loop()->verify_strip_mined(1);
1098               Node* outer = n_loop->_head->as_CountedLoop()->outer_loop();
1099               IdealLoopTree* outer_loop = get_loop(outer);
1100               assert(n_loop->_parent == outer_loop, "broken loop tree");
1101               assert(get_loop(lca) == outer_loop, "safepoint in outer loop consume all memory state");
1102             }
1103 #endif
1104             lca = place_outside_loop(lca, n_loop);
1105             assert(!n_loop->is_member(get_loop(lca)), "control must not be back in the loop");
1106             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");
1107 
1108             // Move store out of the loop
1109             _igvn.replace_node(hook, n->in(MemNode::Memory));
1110             _igvn.replace_input_of(n, 0, lca);
1111             set_ctrl_and_loop(n, lca);
1112 
1113             // Disconnect the phi now. An empty phi can confuse other
1114             // optimizations in this pass of loop opts..
1115             if (phi->in(LoopNode::LoopBackControl) == phi) {
1116               _igvn.replace_node(phi, phi->in(LoopNode::EntryControl));
1117               n_loop->_body.yank(phi);
1118             }
1119           }
1120         }
1121       }
1122     }
1123   }
1124 }
1125 
1126 // We can't use immutable memory for the flat array check because we are loading the mark word which is
1127 // mutable. Although the bits we are interested in are immutable (we check for markWord::unlocked_value),
1128 // we need to use raw memory to not break anti dependency analysis. Below code will attempt to still move
1129 // flat array checks out of loops, mainly to enable loop unswitching.
1130 void PhaseIdealLoop::move_flat_array_check_out_of_loop(Node* n) {
1131   // Skip checks for more than one array
1132   if (n->req() > 3) {
1133     return;
1134   }
1135   Node* mem = n->in(FlatArrayCheckNode::Memory);
1136   Node* array = n->in(FlatArrayCheckNode::ArrayOrKlass)->uncast();
1137   IdealLoopTree* check_loop = get_loop(get_ctrl(n));
1138   IdealLoopTree* ary_loop = get_loop(get_ctrl(array));
1139 
1140   // Check if array is loop invariant
1141   if (!check_loop->is_member(ary_loop)) {
1142     // Walk up memory graph from the check until we leave the loop
1143     VectorSet wq;
1144     wq.set(mem->_idx);
1145     while (check_loop->is_member(get_loop(ctrl_or_self(mem)))) {
1146       if (mem->is_Phi()) {
1147         mem = mem->in(1);
1148       } else if (mem->is_MergeMem()) {
1149         mem = mem->as_MergeMem()->memory_at(Compile::AliasIdxRaw);
1150       } else if (mem->is_Proj()) {
1151         mem = mem->in(0);
1152       } else if (mem->is_MemBar() || mem->is_SafePoint()) {
1153         mem = mem->in(TypeFunc::Memory);
1154       } else if (mem->is_Store() || mem->is_LoadStore() || mem->is_ClearArray()) {
1155         mem = mem->in(MemNode::Memory);
1156       } else {
1157 #ifdef ASSERT
1158         mem->dump();
1159 #endif
1160         ShouldNotReachHere();
1161       }
1162       if (wq.test_set(mem->_idx)) {
1163         return;
1164       }
1165     }
1166     // Replace memory input and re-compute ctrl to move the check out of the loop
1167     _igvn.replace_input_of(n, 1, mem);
1168     set_ctrl_and_loop(n, get_early_ctrl(n));
1169     Node* bol = n->unique_out();
1170     set_ctrl_and_loop(bol, get_early_ctrl(bol));
1171   }
1172 }
1173 
1174 //------------------------------split_if_with_blocks_pre-----------------------
1175 // Do the real work in a non-recursive function.  Data nodes want to be
1176 // cloned in the pre-order so they can feed each other nicely.
1177 Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
1178   // Cloning these guys is unlikely to win
1179   int n_op = n->Opcode();
1180   if (n_op == Op_MergeMem) {
1181     return n;
1182   }
1183   if (n->is_Proj()) {
1184     return n;
1185   }
1186 
1187   if (n->isa_FlatArrayCheck()) {
1188     move_flat_array_check_out_of_loop(n);
1189     return n;
1190   }
1191 
1192   // Do not clone-up CmpFXXX variations, as these are always
1193   // followed by a CmpI
1194   if (n->is_Cmp()) {
1195     return n;
1196   }
1197   // Attempt to use a conditional move instead of a phi/branch
1198   if (ConditionalMoveLimit > 0 && n_op == Op_Region) {
1199     Node *cmov = conditional_move( n );
1200     if (cmov) {
1201       return cmov;
1202     }
1203   }
1204   if (n->is_CFG() || n->is_LoadStore()) {
1205     return n;
1206   }
1207   if (n->is_Opaque1()) { // Opaque nodes cannot be mod'd
1208     if (!C->major_progress()) {   // If chance of no more loop opts...
1209       _igvn._worklist.push(n);  // maybe we'll remove them
1210     }
1211     return n;
1212   }
1213 
1214   if (n->is_Con()) {
1215     return n;   // No cloning for Con nodes
1216   }
1217 
1218   Node *n_ctrl = get_ctrl(n);
1219   if (!n_ctrl) {
1220     return n;       // Dead node
1221   }
1222 
1223   Node* res = try_move_store_before_loop(n, n_ctrl);
1224   if (res != nullptr) {
1225     return n;
1226   }
1227 
1228   // Attempt to remix address expressions for loop invariants
1229   Node *m = remix_address_expressions( n );
1230   if( m ) return m;
1231 
1232   if (n_op == Op_AddI) {
1233     Node *nn = convert_add_to_muladd( n );
1234     if ( nn ) return nn;
1235   }
1236 
1237   if (n->is_ConstraintCast() && n->as_ConstraintCast()->dependency().narrows_type()) {
1238     Node* dom_cast = n->as_ConstraintCast()->dominating_cast(&_igvn, this);
1239     // ConstraintCastNode::dominating_cast() uses node control input to determine domination.
1240     // Node control inputs don't necessarily agree with loop control info (due to
1241     // transformations happened in between), thus additional dominance check is needed
1242     // to keep loop info valid.
1243     if (dom_cast != nullptr && is_dominator(get_ctrl(dom_cast), get_ctrl(n))) {
1244       _igvn.replace_node(n, dom_cast);
1245       return dom_cast;
1246     }
1247   }
1248 
1249   // Determine if the Node has inputs from some local Phi.
1250   // Returns the block to clone thru.
1251   Node *n_blk = has_local_phi_input( n );
1252   if( !n_blk ) return n;
1253 
1254   // Do not clone the trip counter through on a CountedLoop
1255   // (messes up the canonical shape).
1256   if (((n_blk->is_CountedLoop() || (n_blk->is_Loop() && n_blk->as_Loop()->is_loop_nest_inner_loop())) && n->Opcode() == Op_AddI) ||
1257       (n_blk->is_LongCountedLoop() && n->Opcode() == Op_AddL)) {
1258     return n;
1259   }
1260   // Pushing a shift through the iv Phi can get in the way of addressing optimizations or range check elimination
1261   if (n_blk->is_BaseCountedLoop() && n->Opcode() == Op_LShift(n_blk->as_BaseCountedLoop()->bt()) &&
1262       n->in(1) == n_blk->as_BaseCountedLoop()->phi()) {
1263     return n;
1264   }
1265 
1266   // Check for having no control input; not pinned.  Allow
1267   // dominating control.
1268   if (n->in(0)) {
1269     Node *dom = idom(n_blk);
1270     if (dom_lca(n->in(0), dom) != n->in(0)) {
1271       return n;
1272     }
1273   }
1274   // Policy: when is it profitable.  You must get more wins than
1275   // policy before it is considered profitable.  Policy is usually 0,
1276   // so 1 win is considered profitable.  Big merges will require big
1277   // cloning, so get a larger policy.
1278   int policy = n_blk->req() >> 2;
1279 
1280   // If the loop is a candidate for range check elimination,
1281   // delay splitting through it's phi until a later loop optimization
1282   if (n_blk->is_BaseCountedLoop()) {
1283     IdealLoopTree *lp = get_loop(n_blk);
1284     if (lp && lp->_rce_candidate) {
1285       return n;
1286     }
1287   }
1288 
1289   if (must_throttle_split_if()) return n;
1290 
1291   // Split 'n' through the merge point if it is profitable, replacing it with a new phi.
1292   Node* phi = split_thru_phi(n, n_blk, policy);
1293   if (phi == nullptr) { return n; }
1294 
1295   // Moved a load around the loop, 'en-registering' something.
1296   if (n_blk->is_Loop() && n->is_Load() &&
1297       !phi->in(LoopNode::LoopBackControl)->is_Load())
1298     C->set_major_progress();
1299 
1300   return phi;
1301 }
1302 
1303 static bool merge_point_too_heavy(Compile* C, Node* region) {
1304   // Bail out if the region and its phis have too many users.
1305   int weight = 0;
1306   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1307     weight += region->fast_out(i)->outcnt();
1308   }
1309   int nodes_left = C->max_node_limit() - C->live_nodes();
1310   if (weight * 8 > nodes_left) {
1311     if (PrintOpto) {
1312       tty->print_cr("*** Split-if bails out:  %d nodes, region weight %d", C->unique(), weight);
1313     }
1314     return true;
1315   } else {
1316     return false;
1317   }
1318 }
1319 
1320 static bool merge_point_safe(Node* region) {
1321   // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
1322   // having a PhiNode input. This sidesteps the dangerous case where the split
1323   // ConvI2LNode may become TOP if the input Value() does not
1324   // overlap the ConvI2L range, leaving a node which may not dominate its
1325   // uses.
1326   // A better fix for this problem can be found in the BugTraq entry, but
1327   // expediency for Mantis demands this hack.
1328 #ifdef _LP64
1329   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1330     Node* n = region->fast_out(i);
1331     if (n->is_Phi()) {
1332       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
1333         Node* m = n->fast_out(j);
1334         if (m->Opcode() == Op_ConvI2L)
1335           return false;
1336         if (m->is_CastII()) {
1337           return false;
1338         }
1339       }
1340     }
1341   }
1342 #endif
1343   return true;
1344 }
1345 
1346 
1347 //------------------------------place_outside_loop---------------------------------
1348 // Place some computation outside of this loop on the path to the use passed as argument
1349 Node* PhaseIdealLoop::place_outside_loop(Node* useblock, IdealLoopTree* loop) const {
1350   Node* head = loop->_head;
1351   assert(!loop->is_member(get_loop(useblock)), "must be outside loop");
1352   if (head->is_Loop() && head->as_Loop()->is_strip_mined()) {
1353     loop = loop->_parent;
1354     assert(loop->_head->is_OuterStripMinedLoop(), "malformed strip mined loop");
1355   }
1356 
1357   // Pick control right outside the loop
1358   for (;;) {
1359     Node* dom = idom(useblock);
1360     if (loop->is_member(get_loop(dom))) {
1361       break;
1362     }
1363     useblock = dom;
1364   }
1365   assert(find_non_split_ctrl(useblock) == useblock, "should be non split control");
1366   return useblock;
1367 }
1368 
1369 
1370 bool PhaseIdealLoop::identical_backtoback_ifs(Node *n) {
1371   if (!n->is_If()) {
1372     return false;
1373   }
1374   if (n->outcnt() != n->as_If()->required_outcnt()) {
1375     assert(false, "malformed IfNode with %d outputs", n->outcnt());
1376     return false;
1377   }
1378   if (n->is_BaseCountedLoopEnd()) {
1379     return false;
1380   }
1381   if (!n->in(0)->is_Region()) {
1382     return false;
1383   }
1384 
1385   Node* region = n->in(0);
1386   Node* dom = idom(region);
1387   if (!dom->is_If() ||  !n->as_If()->same_condition(dom, &_igvn)) {
1388     return false;
1389   }
1390   IfNode* dom_if = dom->as_If();
1391   IfTrueNode* proj_true = dom_if->true_proj();
1392   IfFalseNode* proj_false = dom_if->false_proj();
1393 
1394   for (uint i = 1; i < region->req(); i++) {
1395     if (is_dominator(proj_true, region->in(i))) {
1396       continue;
1397     }
1398     if (is_dominator(proj_false, region->in(i))) {
1399       continue;
1400     }
1401     return false;
1402   }
1403 
1404   return true;
1405 }
1406 
1407 
1408 bool PhaseIdealLoop::can_split_if(Node* n_ctrl) {
1409   if (must_throttle_split_if()) {
1410     return false;
1411   }
1412 
1413   // Do not do 'split-if' if irreducible loops are present.
1414   if (_has_irreducible_loops) {
1415     return false;
1416   }
1417 
1418   if (merge_point_too_heavy(C, n_ctrl)) {
1419     return false;
1420   }
1421 
1422   // Do not do 'split-if' if some paths are dead.  First do dead code
1423   // elimination and then see if its still profitable.
1424   for (uint i = 1; i < n_ctrl->req(); i++) {
1425     if (n_ctrl->in(i) == C->top()) {
1426       return false;
1427     }
1428   }
1429 
1430   // If trying to do a 'Split-If' at the loop head, it is only
1431   // profitable if the cmp folds up on BOTH paths.  Otherwise we
1432   // risk peeling a loop forever.
1433 
1434   // CNC - Disabled for now.  Requires careful handling of loop
1435   // body selection for the cloned code.  Also, make sure we check
1436   // for any input path not being in the same loop as n_ctrl.  For
1437   // irreducible loops we cannot check for 'n_ctrl->is_Loop()'
1438   // because the alternative loop entry points won't be converted
1439   // into LoopNodes.
1440   IdealLoopTree *n_loop = get_loop(n_ctrl);
1441   for (uint j = 1; j < n_ctrl->req(); j++) {
1442     if (get_loop(n_ctrl->in(j)) != n_loop) {
1443       return false;
1444     }
1445   }
1446 
1447   // Check for safety of the merge point.
1448   if (!merge_point_safe(n_ctrl)) {
1449     return false;
1450   }
1451 
1452   return true;
1453 }
1454 
1455 // Detect if the node is the inner strip-mined loop
1456 // Return: null if it's not the case, or the exit of outer strip-mined loop
1457 static Node* is_inner_of_stripmined_loop(const Node* out) {
1458   Node* out_le = nullptr;
1459 
1460   if (out->is_CountedLoopEnd()) {
1461       const CountedLoopNode* loop = out->as_CountedLoopEnd()->loopnode();
1462 
1463       if (loop != nullptr && loop->is_strip_mined()) {
1464         out_le = loop->in(LoopNode::EntryControl)->as_OuterStripMinedLoop()->outer_loop_exit();
1465       }
1466   }
1467 
1468   return out_le;
1469 }
1470 
1471 bool PhaseIdealLoop::flat_array_element_type_check(Node *n) {
1472   // If the CmpP is a subtype check for a value that has just been
1473   // loaded from an array, the subtype check guarantees the value
1474   // can't be stored in a flat array and the load of the value
1475   // happens with a flat array check then: push the type check
1476   // through the phi of the flat array check. This needs special
1477   // logic because the subtype check's input is not a phi but a
1478   // LoadKlass that must first be cloned through the phi.
1479   if (n->Opcode() != Op_CmpP) {
1480     return false;
1481   }
1482 
1483   Node* klassptr = n->in(1);
1484   Node* klasscon = n->in(2);
1485 
1486   if (klassptr->is_DecodeNarrowPtr()) {
1487     klassptr = klassptr->in(1);
1488   }
1489 
1490   if (klassptr->Opcode() != Op_LoadKlass && klassptr->Opcode() != Op_LoadNKlass) {
1491     return false;
1492   }
1493 
1494   if (!klasscon->is_Con()) {
1495     return false;
1496   }
1497 
1498   Node* addr = klassptr->in(MemNode::Address);
1499 
1500   if (!addr->is_AddP()) {
1501     return false;
1502   }
1503 
1504   intptr_t offset;
1505   Node* obj = AddPNode::Ideal_base_and_offset(addr, &_igvn, offset);
1506 
1507   if (obj == nullptr) {
1508     return false;
1509   }
1510 
1511   // TODO 8378077: The code below does not work anymore with off-heap accesses which set their bases to top with
1512   // JDK-8373343. Also: flat_array_element_type_check() was introduced with JDK-8228622 for a specific check to enable
1513   // split-if but JDK-8245729 changed how that check looks like. Is it still relevant? This should be revisited.
1514   if (addr->in(AddPNode::Base)->is_top()) {
1515     return false;
1516   }
1517 
1518   if (obj->Opcode() == Op_CastPP) {
1519     obj = obj->in(1);
1520   }
1521 
1522   if (!obj->is_Phi()) {
1523     return false;
1524   }
1525 
1526   Node* region = obj->in(0);
1527 
1528   Node* phi = PhiNode::make_blank(region, n->in(1));
1529   for (uint i = 1; i < region->req(); i++) {
1530     Node* in = obj->in(i);
1531     Node* ctrl = region->in(i);
1532     if (addr->in(AddPNode::Base) != obj) {
1533       Node* cast = addr->in(AddPNode::Base);
1534       assert(cast->Opcode() == Op_CastPP && cast->in(0) != nullptr, "inconsistent subgraph");
1535       Node* cast_clone = cast->clone();
1536       cast_clone->set_req(0, ctrl);
1537       cast_clone->set_req(1, in);
1538       register_new_node(cast_clone, ctrl);
1539       const Type* tcast = cast_clone->Value(&_igvn);
1540       _igvn.set_type(cast_clone, tcast);
1541       cast_clone->as_Type()->set_type(tcast);
1542       in = cast_clone;
1543     }
1544     Node* addr_clone = addr->clone();
1545     addr_clone->set_req(AddPNode::Base, in);
1546     addr_clone->set_req(AddPNode::Address, in);
1547     register_new_node(addr_clone, ctrl);
1548     _igvn.set_type(addr_clone, addr_clone->Value(&_igvn));
1549     Node* klassptr_clone = klassptr->clone();
1550     klassptr_clone->set_req(2, addr_clone);
1551     register_new_node(klassptr_clone, ctrl);
1552     _igvn.set_type(klassptr_clone, klassptr_clone->Value(&_igvn));
1553     if (klassptr != n->in(1)) {
1554       Node* decode = n->in(1);
1555       assert(decode->is_DecodeNarrowPtr(), "inconsistent subgraph");
1556       Node* decode_clone = decode->clone();
1557       decode_clone->set_req(1, klassptr_clone);
1558       register_new_node(decode_clone, ctrl);
1559       _igvn.set_type(decode_clone, decode_clone->Value(&_igvn));
1560       klassptr_clone = decode_clone;
1561     }
1562     phi->set_req(i, klassptr_clone);
1563   }
1564   register_new_node(phi, region);
1565   Node* orig = n->in(1);
1566   _igvn.replace_input_of(n, 1, phi);
1567   split_if_with_blocks_post(n);
1568   if (n->outcnt() != 0) {
1569     _igvn.replace_input_of(n, 1, orig);
1570     _igvn.remove_dead_node(phi, PhaseIterGVN::NodeOrigin::Graph);
1571   }
1572   return true;
1573 }
1574 
1575 //------------------------------split_if_with_blocks_post----------------------
1576 // Do the real work in a non-recursive function.  CFG hackery wants to be
1577 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
1578 // info.
1579 void PhaseIdealLoop::split_if_with_blocks_post(Node *n) {
1580 
1581   if (flat_array_element_type_check(n)) {
1582     return;
1583   }
1584 
1585   // Cloning Cmp through Phi's involves the split-if transform.
1586   // FastLock is not used by an If
1587   if (n->is_Cmp() && !n->is_FastLock()) {
1588     Node *n_ctrl = get_ctrl(n);
1589     // Determine if the Node has inputs from some local Phi.
1590     // Returns the block to clone thru.
1591     Node *n_blk = has_local_phi_input(n);
1592     if (n_blk != n_ctrl) {
1593       return;
1594     }
1595 
1596     if (!can_split_if(n_ctrl)) {
1597       return;
1598     }
1599 
1600     if (n->outcnt() != 1) {
1601       return; // Multiple bool's from 1 compare?
1602     }
1603     Node *bol = n->unique_out();
1604     assert(bol->is_Bool(), "expect a bool here");
1605     if (bol->outcnt() != 1) {
1606       return;// Multiple branches from 1 compare?
1607     }
1608     Node *iff = bol->unique_out();
1609 
1610     // Check some safety conditions
1611     if (iff->is_If()) {        // Classic split-if?
1612       if (iff->outcnt() != iff->as_If()->required_outcnt()) {
1613         assert(false, "malformed IfNode with %d outputs", iff->outcnt());
1614         return;
1615       } else if (iff->in(0) != n_ctrl) {
1616         return; // Compare must be in same blk as if
1617       }
1618     } else if (iff->is_CMove()) { // Trying to split-up a CMOVE
1619       // Can't split CMove with different control.
1620       if (get_ctrl(iff) != n_ctrl) {
1621         return;
1622       }
1623       if (get_ctrl(iff->in(2)) == n_ctrl ||
1624           get_ctrl(iff->in(3)) == n_ctrl) {
1625         return;                 // Inputs not yet split-up
1626       }
1627       if (get_loop(n_ctrl) != get_loop(get_ctrl(iff))) {
1628         return;                 // Loop-invar test gates loop-varying CMOVE
1629       }
1630     } else {
1631       return;  // some other kind of node, such as an Allocate
1632     }
1633 
1634     // When is split-if profitable?  Every 'win' on means some control flow
1635     // goes dead, so it's almost always a win.
1636     int policy = 0;
1637     // Split compare 'n' through the merge point if it is profitable
1638     Node *phi = split_thru_phi( n, n_ctrl, policy);
1639     if (!phi) {
1640       return;
1641     }
1642 
1643     // Now split the bool up thru the phi
1644     Node* bolphi = split_thru_phi(bol, n_ctrl, -1);
1645     guarantee(bolphi != nullptr, "null boolean phi node");
1646     assert(iff->in(1) == bolphi, "");
1647 
1648     if (bolphi->Value(&_igvn)->singleton()) {
1649       return;
1650     }
1651 
1652     // Conditional-move?  Must split up now
1653     if (!iff->is_If()) {
1654       Node* cmovphi = split_thru_phi(iff, n_ctrl, -1);
1655       return;
1656     }
1657 
1658     // Now split the IF
1659     C->print_method(PHASE_BEFORE_SPLIT_IF, 4, iff);
1660 #ifndef PRODUCT
1661     if (TraceLoopOpts || TraceSplitIf) {
1662       tty->print_cr("Split-If: %d %s", iff->_idx, iff->Name());
1663     }
1664 #endif
1665     do_split_if(iff);
1666     C->print_method(PHASE_AFTER_SPLIT_IF, 4, iff);
1667     return;
1668   }
1669 
1670   // Two identical ifs back to back can be merged
1671   if (try_merge_identical_ifs(n)) {
1672     return;
1673   }
1674 
1675   // Check for an IF ready to split; one that has its
1676   // condition codes input coming from a Phi at the block start.
1677   int n_op = n->Opcode();
1678 
1679   // Check for an IF being dominated by another IF same test
1680   if (n_op == Op_If ||
1681       n_op == Op_RangeCheck) {
1682     Node *bol = n->in(1);
1683     uint max = bol->outcnt();
1684     // Check for same test used more than once?
1685     if (bol->is_Bool() && (max > 1 || bol->in(1)->is_SubTypeCheck())) {
1686       // Search up IDOMs to see if this IF is dominated.
1687       Node* cmp = bol->in(1);
1688       Node *cutoff = cmp->is_SubTypeCheck() ? dom_lca(get_ctrl(cmp->in(1)), get_ctrl(cmp->in(2))) : get_ctrl(bol);
1689 
1690       // Now search up IDOMs till cutoff, looking for a dominating test
1691       Node *prevdom = n;
1692       Node *dom = idom(prevdom);
1693       while (dom != cutoff) {
1694         if (dom->req() > 1 && n->as_If()->same_condition(dom, &_igvn) && prevdom->in(0) == dom &&
1695             safe_for_if_replacement(dom)) {
1696           // It's invalid to move control dependent data nodes in the inner
1697           // strip-mined loop, because:
1698           //  1) break validation of LoopNode::verify_strip_mined()
1699           //  2) move code with side-effect in strip-mined loop
1700           // Move to the exit of outer strip-mined loop in that case.
1701           Node* out_le = is_inner_of_stripmined_loop(dom);
1702           if (out_le != nullptr) {
1703             prevdom = out_le;
1704           }
1705           // Replace the dominated test with an obvious true or false.
1706           // Place it on the IGVN worklist for later cleanup.
1707           C->set_major_progress();
1708           // Split if: pin array accesses that are control dependent on a range check and moved to a regular if,
1709           // to prevent an array load from floating above its range check. There are three cases:
1710           // 1. Move from RangeCheck "a" to RangeCheck "b": don't need to pin. If we ever remove b, then we pin
1711           //    all its array accesses at that point.
1712           // 2. We move from RangeCheck "a" to regular if "b": need to pin. If we ever remove b, then its array
1713           //    accesses would start to float, since we don't pin at that point.
1714           // 3. If we move from regular if: don't pin. All array accesses are already assumed to be pinned.
1715           bool pin_array_access_nodes =  n->Opcode() == Op_RangeCheck &&
1716                                          prevdom->in(0)->Opcode() != Op_RangeCheck;
1717           dominated_by(prevdom->as_IfProj(), n->as_If(), false, pin_array_access_nodes);
1718           DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
1719           return;
1720         }
1721         prevdom = dom;
1722         dom = idom(prevdom);
1723       }
1724     }
1725   }
1726 
1727   try_sink_out_of_loop(n);
1728   if (C->failing()) {
1729     return;
1730   }
1731 
1732   try_move_store_after_loop(n);
1733 
1734   // Remove multiple allocations of the same inline type
1735   if (n->is_InlineType()) {
1736     n->as_InlineType()->remove_redundant_allocations(this);
1737   }
1738 }
1739 
1740 // Transform:
1741 //
1742 // if (some_condition) {
1743 //   // body 1
1744 // } else {
1745 //   // body 2
1746 // }
1747 // if (some_condition) {
1748 //   // body 3
1749 // } else {
1750 //   // body 4
1751 // }
1752 //
1753 // into:
1754 //
1755 //
1756 // if (some_condition) {
1757 //   // body 1
1758 //   // body 3
1759 // } else {
1760 //   // body 2
1761 //   // body 4
1762 // }
1763 bool PhaseIdealLoop::try_merge_identical_ifs(Node* n) {
1764   if (identical_backtoback_ifs(n) && can_split_if(n->in(0))) {
1765     Node *n_ctrl = n->in(0);
1766     IfNode* dom_if = idom(n_ctrl)->as_If();
1767     if (n->in(1) != dom_if->in(1)) {
1768       assert(n->in(1)->in(1)->is_SubTypeCheck() &&
1769              (n->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr ||
1770               dom_if->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr), "only for subtype checks with profile data attached");
1771       _igvn.replace_input_of(n, 1, dom_if->in(1));
1772     }
1773     IfTrueNode* dom_proj_true = dom_if->true_proj();
1774     IfFalseNode* dom_proj_false = dom_if->false_proj();
1775 
1776     // Now split the IF
1777     RegionNode* new_false_region;
1778     RegionNode* new_true_region;
1779 #ifndef PRODUCT
1780     if (TraceLoopOpts || TraceSplitIf) {
1781       tty->print_cr("Split-If Merging Identical Ifs: Dom-If: %d %s, If: %d %s", dom_if->_idx, dom_if->Name(), n->_idx, n->Name());
1782     }
1783 #endif
1784     do_split_if(n, &new_false_region, &new_true_region);
1785     assert(new_false_region->req() == new_true_region->req(), "");
1786 #ifdef ASSERT
1787     for (uint i = 1; i < new_false_region->req(); ++i) {
1788       assert(new_false_region->in(i)->in(0) == new_true_region->in(i)->in(0), "unexpected shape following split if");
1789       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");
1790     }
1791 #endif
1792     assert(new_false_region->in(1)->in(0)->in(1) == dom_if->in(1), "dominating if and dominated if after split must share test");
1793 
1794     // We now have:
1795     // if (some_condition) {
1796     //   // body 1
1797     //   if (some_condition) {
1798     //     body3: // new_true_region
1799     //     // body3
1800     //   } else {
1801     //     goto body4;
1802     //   }
1803     // } else {
1804     //   // body 2
1805     //  if (some_condition) {
1806     //     goto body3;
1807     //   } else {
1808     //     body4:   // new_false_region
1809     //     // body4;
1810     //   }
1811     // }
1812     //
1813 
1814     // clone pinned nodes thru the resulting regions
1815     push_pinned_nodes_thru_region(dom_if, new_true_region);
1816     push_pinned_nodes_thru_region(dom_if, new_false_region);
1817 
1818     // Optimize out the cloned ifs. Because pinned nodes were cloned, this also allows a CastPP that would be dependent
1819     // 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
1820     // unrelated control dependency.
1821     for (uint i = 1; i < new_false_region->req(); i++) {
1822       if (is_dominator(dom_proj_true, new_false_region->in(i))) {
1823         dominated_by(dom_proj_true, new_false_region->in(i)->in(0)->as_If());
1824       } else {
1825         assert(is_dominator(dom_proj_false, new_false_region->in(i)), "bad if");
1826         dominated_by(dom_proj_false, new_false_region->in(i)->in(0)->as_If());
1827       }
1828     }
1829     return true;
1830   }
1831   return false;
1832 }
1833 
1834 void PhaseIdealLoop::push_pinned_nodes_thru_region(IfNode* dom_if, Node* region) {
1835   for (DUIterator i = region->outs(); region->has_out(i); i++) {
1836     Node* u = region->out(i);
1837     if (!has_ctrl(u) || u->is_Phi() || !u->depends_only_on_test()) {
1838       continue;
1839     }
1840     assert(u->in(0) == region, "not a control dependent node?");
1841     uint j = 1;
1842     for (; j < u->req(); ++j) {
1843       Node* in = u->in(j);
1844       if (!is_dominator(ctrl_or_self(in), dom_if)) {
1845         break;
1846       }
1847     }
1848     if (j == u->req()) {
1849       Node *phi = PhiNode::make_blank(region, u);
1850       for (uint k = 1; k < region->req(); ++k) {
1851         Node* clone = u->clone();
1852         clone->set_req(0, region->in(k));
1853         register_new_node(clone, region->in(k));
1854         phi->init_req(k, clone);
1855       }
1856       register_new_node(phi, region);
1857       _igvn.replace_node(u, phi);
1858       --i;
1859     }
1860   }
1861 }
1862 
1863 bool PhaseIdealLoop::safe_for_if_replacement(const Node* dom) const {
1864   if (!dom->is_CountedLoopEnd()) {
1865     return true;
1866   }
1867   CountedLoopEndNode* le = dom->as_CountedLoopEnd();
1868   CountedLoopNode* cl = le->loopnode();
1869   if (cl == nullptr) {
1870     return true;
1871   }
1872   if (!cl->is_main_loop()) {
1873     return true;
1874   }
1875   if (cl->is_canonical_loop_entry() == nullptr) {
1876     return true;
1877   }
1878   // Further unrolling is possible so loop exit condition might change
1879   return false;
1880 }
1881 
1882 // See if a shared loop-varying computation has no loop-varying uses.
1883 // Happens if something is only used for JVM state in uncommon trap exits,
1884 // like various versions of induction variable+offset.  Clone the
1885 // computation per usage to allow it to sink out of the loop.
1886 void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
1887   bool is_raw_to_oop_cast = n->is_ConstraintCast() &&
1888                             n->in(1)->bottom_type()->isa_rawptr() &&
1889                             !n->bottom_type()->isa_rawptr();
1890 
1891   if (has_ctrl(n) &&
1892       !n->is_Phi() &&
1893       !n->is_Bool() &&
1894       !n->is_Proj() &&
1895       !n->is_MergeMem() &&
1896       !n->is_CMove() &&
1897       !n->is_OpaqueConstantBool() &&
1898       !n->is_OpaqueInitializedAssertionPredicate() &&
1899       !n->is_OpaqueTemplateAssertionPredicate() &&
1900       !is_raw_to_oop_cast && // don't extend live ranges of raw oops
1901       n->Opcode() != Op_CreateEx &&
1902       (KillPathsReachableByDeadTypeNode || !n->is_Type())
1903       ) {
1904     Node *n_ctrl = get_ctrl(n);
1905     IdealLoopTree *n_loop = get_loop(n_ctrl);
1906 
1907     if (n->in(0) != nullptr) {
1908       IdealLoopTree* loop_ctrl = get_loop(n->in(0));
1909       if (n_loop != loop_ctrl && n_loop->is_member(loop_ctrl)) {
1910         // n has a control input inside a loop but get_ctrl() is member of an outer loop. This could happen, for example,
1911         // for Div nodes inside a loop (control input inside loop) without a use except for an UCT (outside the loop).
1912         // Rewire control of n to right outside of the loop, regardless if its input(s) are later sunk or not.
1913         Node* maybe_pinned_n = n;
1914         Node* outside_ctrl = place_outside_loop(n_ctrl, loop_ctrl);
1915         if (!would_sink_below_pre_loop_exit(loop_ctrl, outside_ctrl)) {
1916           if (n->depends_only_on_test()) {
1917             // If this node depends_only_on_test, it will be rewired to a control input that is not
1918             // the correct test. As a result, it must be pinned otherwise it can be incorrectly
1919             // rewired to a dominating test equivalent to the new control.
1920             Node* pinned_clone = n->pin_node_under_control();
1921             if (pinned_clone != nullptr) {
1922               register_new_node(pinned_clone, n_ctrl);
1923               maybe_pinned_n = pinned_clone;
1924               _igvn.replace_node(n, pinned_clone);
1925             }
1926           }
1927           _igvn.replace_input_of(maybe_pinned_n, 0, outside_ctrl);
1928         }
1929       }
1930     }
1931     if (n_loop != _ltree_root && n->outcnt() > 1) {
1932       // Compute early control: needed for anti-dependence analysis. It's also possible that as a result of
1933       // previous transformations in this loop opts round, the node can be hoisted now: early control will tell us.
1934       Node* early_ctrl = compute_early_ctrl(n, n_ctrl);
1935       if (n_loop->is_member(get_loop(early_ctrl)) && // check that this one can't be hoisted now
1936           ctrl_of_all_uses_out_of_loop(n, early_ctrl, n_loop)) { // All uses in outer loops!
1937         if (n->is_Store() || n->is_LoadStore()) {
1938             assert(false, "no node with a side effect");
1939             C->record_failure("no node with a side effect");
1940             return;
1941         }
1942         Node* outer_loop_clone = nullptr;
1943         for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin;) {
1944           Node* u = n->last_out(j); // Clone private computation per use
1945           _igvn.rehash_node_delayed(u);
1946           Node* x = nullptr;
1947           if (n->in(0) != nullptr && n->depends_only_on_test()) {
1948             // If this node depends_only_on_test, it will be rewired to a control input that is not
1949             // the correct test. As a result, it must be pinned otherwise it can be incorrectly
1950             // rewired to a dominating test equivalent to the new control.
1951             x = n->pin_node_under_control();
1952           }
1953           if (x == nullptr) {
1954             x = n->clone();
1955           }
1956           Node* x_ctrl = nullptr;
1957           if (u->is_Phi()) {
1958             // Replace all uses of normal nodes.  Replace Phi uses
1959             // individually, so the separate Nodes can sink down
1960             // different paths.
1961             uint k = 1;
1962             while (u->in(k) != n) k++;
1963             u->set_req(k, x);
1964             // x goes next to Phi input path
1965             x_ctrl = u->in(0)->in(k);
1966             // Find control for 'x' next to use but not inside inner loops.
1967             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1968             --j;
1969           } else {              // Normal use
1970             if (has_ctrl(u)) {
1971               x_ctrl = get_ctrl(u);
1972             } else {
1973               x_ctrl = u->in(0);
1974             }
1975             // Find control for 'x' next to use but not inside inner loops.
1976             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1977             // Replace all uses
1978             if (u->is_ConstraintCast() && _igvn.type(n)->higher_equal(u->bottom_type()) && u->in(0) == x_ctrl) {
1979               // If we're sinking a chain of data nodes, we might have inserted a cast to pin the use which is not necessary
1980               // anymore now that we're going to pin n as well
1981               _igvn.replace_node(u, x);
1982               --j;
1983             } else {
1984               int nb = u->replace_edge(n, x, &_igvn);
1985               j -= nb;
1986             }
1987           }
1988 
1989           if (n->is_Load()) {
1990             // For loads, add a control edge to a CFG node outside of the loop
1991             // to force them to not combine and return back inside the loop
1992             // during GVN optimization (4641526).
1993             assert(x_ctrl == get_late_ctrl_with_anti_dep(x->as_Load(), early_ctrl, x_ctrl), "anti-dependences were already checked");
1994 
1995             IdealLoopTree* x_loop = get_loop(x_ctrl);
1996             Node* x_head = x_loop->_head;
1997             if (x_head->is_Loop() && x_head->is_OuterStripMinedLoop()) {
1998               // Do not add duplicate LoadNodes to the outer strip mined loop
1999               if (outer_loop_clone != nullptr) {
2000                 _igvn.replace_node(x, outer_loop_clone);
2001                 continue;
2002               }
2003               outer_loop_clone = x;
2004             }
2005             x->set_req(0, x_ctrl);
2006           } else if (n->in(0) != nullptr){
2007             x->set_req(0, x_ctrl);
2008           }
2009           assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
2010           assert(!n_loop->is_member(get_loop(x_ctrl)), "should have moved out of loop");
2011           register_new_node(x, x_ctrl);
2012 
2013           // Chain of AddP nodes: (AddP base (AddP base (AddP base )))
2014           // All AddP nodes must keep the same base after sinking so:
2015           // 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,
2016           // their bases remain the same.
2017           // (see 2- below)
2018           assert(!x->is_AddP() || !x->in(AddPNode::Address)->is_AddP() ||
2019                  x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base) ||
2020                  !x->in(AddPNode::Address)->in(AddPNode::Base)->eqv_uncast(x->in(AddPNode::Base)), "unexpected AddP shape");
2021           if (x->in(0) == nullptr && !x->is_DecodeNarrowPtr() &&
2022               !(x->is_AddP() && x->in(AddPNode::Address)->is_AddP() && x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base))) {
2023             assert(!x->is_Load(), "load should be pinned");
2024             // Use a cast node to pin clone out of loop
2025             Node* cast = nullptr;
2026             for (uint k = 0; k < x->req(); k++) {
2027               Node* in = x->in(k);
2028               if (in != nullptr && ctrl_is_member(n_loop, in)) {
2029                 const Type* in_t = _igvn.type(in);
2030                 cast = ConstraintCastNode::make_cast_for_type(x_ctrl, in, in_t,
2031                                                               ConstraintCastNode::DependencyType::NonFloatingNonNarrowing, nullptr);
2032               }
2033               if (cast != nullptr) {
2034                 Node* prev = _igvn.hash_find_insert(cast);
2035                 if (prev != nullptr && get_ctrl(prev) == x_ctrl) {
2036                   cast->destruct(&_igvn);
2037                   cast = prev;
2038                 } else {
2039                   register_new_node(cast, x_ctrl);
2040                 }
2041                 x->replace_edge(in, cast);
2042                 // Chain of AddP nodes:
2043                 // 2- A CastPP of the base is only added now that all AddP nodes are sunk
2044                 if (x->is_AddP() && k == AddPNode::Base) {
2045                   update_addp_chain_base(x, n->in(AddPNode::Base), cast);
2046                 }
2047                 break;
2048               }
2049             }
2050             assert(cast != nullptr, "must have added a cast to pin the node");
2051           }
2052         }
2053         _igvn.remove_dead_node(n, PhaseIterGVN::NodeOrigin::Graph);
2054       }
2055       _dom_lca_tags_round = 0;
2056     }
2057   }
2058 }
2059 
2060 void PhaseIdealLoop::update_addp_chain_base(Node* x, Node* old_base, Node* new_base) {
2061   ResourceMark rm;
2062   Node_List wq;
2063   wq.push(x);
2064   while (wq.size() != 0) {
2065     Node* n = wq.pop();
2066     for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2067       Node* u = n->fast_out(i);
2068       if (u->is_AddP() && u->in(AddPNode::Base) == old_base) {
2069         _igvn.replace_input_of(u, AddPNode::Base, new_base);
2070         wq.push(u);
2071       }
2072     }
2073   }
2074 }
2075 
2076 // Compute the early control of a node by following its inputs until we reach
2077 // nodes that are pinned. Then compute the LCA of the control of all pinned nodes.
2078 Node* PhaseIdealLoop::compute_early_ctrl(Node* n, Node* n_ctrl) {
2079   Node* early_ctrl = nullptr;
2080   ResourceMark rm;
2081   Unique_Node_List wq;
2082   wq.push(n);
2083   for (uint i = 0; i < wq.size(); i++) {
2084     Node* m = wq.at(i);
2085     Node* c = nullptr;
2086     if (m->is_CFG()) {
2087       c = m;
2088     } else if (m->pinned()) {
2089       c = m->in(0);
2090     } else {
2091       for (uint j = 0; j < m->req(); j++) {
2092         Node* in = m->in(j);
2093         if (in != nullptr) {
2094           wq.push(in);
2095         }
2096       }
2097     }
2098     if (c != nullptr) {
2099       assert(is_dominator(c, n_ctrl), "control input must dominate current control");
2100       if (early_ctrl == nullptr || is_dominator(early_ctrl, c)) {
2101         early_ctrl = c;
2102       }
2103     }
2104   }
2105   assert(is_dominator(early_ctrl, n_ctrl), "early control must dominate current control");
2106   return early_ctrl;
2107 }
2108 
2109 bool PhaseIdealLoop::ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop) {
2110   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2111     Node* u = n->fast_out(i);
2112     if (u->is_Opaque1()) {
2113       return false;  // Found loop limit, bugfix for 4677003
2114     }
2115     if (u->is_Phi()) {
2116       for (uint j = 1; j < u->req(); ++j) {
2117         if (u->in(j) == n && !ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, u->in(0)->in(j))) {
2118           return false;
2119         }
2120       }
2121     } else {
2122       Node* ctrl = has_ctrl(u) ? get_ctrl(u) : u->in(0);
2123       if (!ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, ctrl)) {
2124         return false;
2125       }
2126     }
2127   }
2128   return true;
2129 }
2130 
2131 // 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
2132 // to a check that's eliminated by range check elimination, it becomes input to an expression that feeds into the exit
2133 // 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
2134 // it would be to not eliminate the check in the main loop. Instead, we prevent sinking of the node here so better code
2135 // is generated for the main loop.
2136 bool PhaseIdealLoop::would_sink_below_pre_loop_exit(IdealLoopTree* n_loop, Node* ctrl) {
2137   if (n_loop->_head->is_CountedLoop() && n_loop->_head->as_CountedLoop()->is_pre_loop()) {
2138     CountedLoopNode* pre_loop = n_loop->_head->as_CountedLoop();
2139     if (is_dominator(pre_loop->loopexit(), ctrl)) {
2140       return true;
2141     }
2142   }
2143   return false;
2144 }
2145 
2146 bool PhaseIdealLoop::ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl) {
2147   if (n->is_Load()) {
2148     // We can't reuse tags in PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal() so make sure each call to
2149     // get_late_ctrl_with_anti_dep() uses its own tag
2150     _dom_lca_tags_round++;
2151     assert(_dom_lca_tags_round != 0, "shouldn't wrap around");
2152 
2153     ctrl = get_late_ctrl_with_anti_dep(n->as_Load(), n_ctrl, ctrl);
2154   }
2155   IdealLoopTree *u_loop = get_loop(ctrl);
2156   if (u_loop == n_loop) {
2157     return false; // Found loop-varying use
2158   }
2159   if (n_loop->is_member(u_loop)) {
2160     return false; // Found use in inner loop
2161   }
2162   if (would_sink_below_pre_loop_exit(n_loop, ctrl)) {
2163     return false;
2164   }
2165   return true;
2166 }
2167 
2168 //------------------------------split_if_with_blocks---------------------------
2169 // Check for aggressive application of 'split-if' optimization,
2170 // using basic block level info.
2171 void PhaseIdealLoop::split_if_with_blocks(VectorSet &visited, Node_Stack &nstack) {
2172   Node* root = C->root();
2173   visited.set(root->_idx); // first, mark root as visited
2174   // Do pre-visit work for root
2175   Node* n   = split_if_with_blocks_pre(root);
2176   uint  cnt = n->outcnt();
2177   uint  i   = 0;
2178 
2179   while (true) {
2180     // Visit all children
2181     if (i < cnt) {
2182       Node* use = n->raw_out(i);
2183       ++i;
2184       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
2185         // Now do pre-visit work for this use
2186         use = split_if_with_blocks_pre(use);
2187         nstack.push(n, i); // Save parent and next use's index.
2188         n   = use;         // Process all children of current use.
2189         cnt = use->outcnt();
2190         i   = 0;
2191       }
2192     }
2193     else {
2194       // All of n's children have been processed, complete post-processing.
2195       if (cnt != 0 && !n->is_Con()) {
2196         assert(has_node(n), "no dead nodes");
2197         split_if_with_blocks_post(n);
2198         if (C->failing()) {
2199           return;
2200         }
2201       }
2202       if (must_throttle_split_if()) {
2203         nstack.clear();
2204       }
2205       if (nstack.is_empty()) {
2206         // Finished all nodes on stack.
2207         break;
2208       }
2209       // Get saved parent node and next use's index. Visit the rest of uses.
2210       n   = nstack.node();
2211       cnt = n->outcnt();
2212       i   = nstack.index();
2213       nstack.pop();
2214     }
2215   }
2216 }
2217 
2218 
2219 //=============================================================================
2220 //
2221 //                   C L O N E   A   L O O P   B O D Y
2222 //
2223 
2224 //------------------------------clone_iff--------------------------------------
2225 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2226 // "Nearly" because all Nodes have been cloned from the original in the loop,
2227 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2228 // through the Phi recursively, and return a Bool.
2229 Node* PhaseIdealLoop::clone_iff(PhiNode* phi) {
2230 
2231   // Convert this Phi into a Phi merging Bools
2232   uint i;
2233   for (i = 1; i < phi->req(); i++) {
2234     Node* b = phi->in(i);
2235     if (b->is_Phi()) {
2236       _igvn.replace_input_of(phi, i, clone_iff(b->as_Phi()));
2237     } else {
2238       assert(b->is_Bool() || b->is_OpaqueConstantBool() || b->is_OpaqueInitializedAssertionPredicate(),
2239              "bool, non-null check with OpaqueConstantBool or Initialized Assertion Predicate with its Opaque node");
2240     }
2241   }
2242   Node* n = phi->in(1);
2243   Node* sample_opaque = nullptr;
2244   Node *sample_bool = nullptr;
2245   if (n->is_OpaqueConstantBool() || n->is_OpaqueInitializedAssertionPredicate()) {
2246     sample_opaque = n;
2247     sample_bool = n->in(1);
2248     assert(sample_bool->is_Bool(), "wrong type");
2249   } else {
2250     sample_bool = n;
2251   }
2252   Node* sample_cmp = sample_bool->in(1);
2253   const Type* t = Type::TOP;
2254   const TypePtr* at = nullptr;
2255   if (sample_cmp->is_FlatArrayCheck()) {
2256     // Left input of a FlatArrayCheckNode is memory, set the (adr) type of the phi accordingly
2257     assert(sample_cmp->in(1)->bottom_type() == Type::MEMORY, "unexpected input type");
2258     t = Type::MEMORY;
2259     at = TypeRawPtr::BOTTOM;
2260   }
2261 
2262   // Make Phis to merge the Cmp's inputs.
2263   PhiNode *phi1 = new PhiNode(phi->in(0), t, at);
2264   PhiNode *phi2 = new PhiNode(phi->in(0), Type::TOP);
2265   for (i = 1; i < phi->req(); i++) {
2266     Node *n1 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(1) : phi->in(i)->in(1)->in(1)->in(1);
2267     Node *n2 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(2) : phi->in(i)->in(1)->in(1)->in(2);
2268     phi1->set_req(i, n1);
2269     phi2->set_req(i, n2);
2270     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2271     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2272   }
2273   // See if these Phis have been made before.
2274   // Register with optimizer
2275   Node *hit1 = _igvn.hash_find_insert(phi1);
2276   if (hit1) {                   // Hit, toss just made Phi
2277     _igvn.remove_dead_node(phi1, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2278     assert(hit1->is_Phi(), "" );
2279     phi1 = (PhiNode*)hit1;      // Use existing phi
2280   } else {                      // Miss
2281     _igvn.register_new_node_with_optimizer(phi1);
2282   }
2283   Node *hit2 = _igvn.hash_find_insert(phi2);
2284   if (hit2) {                   // Hit, toss just made Phi
2285     _igvn.remove_dead_node(phi2, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2286     assert(hit2->is_Phi(), "" );
2287     phi2 = (PhiNode*)hit2;      // Use existing phi
2288   } else {                      // Miss
2289     _igvn.register_new_node_with_optimizer(phi2);
2290   }
2291   // Register Phis with loop/block info
2292   set_ctrl(phi1, phi->in(0));
2293   set_ctrl(phi2, phi->in(0));
2294   // Make a new Cmp
2295   Node *cmp = sample_cmp->clone();
2296   cmp->set_req(1, phi1);
2297   cmp->set_req(2, phi2);
2298   _igvn.register_new_node_with_optimizer(cmp);
2299   set_ctrl(cmp, phi->in(0));
2300 
2301   // Make a new Bool
2302   Node *b = sample_bool->clone();
2303   b->set_req(1,cmp);
2304   _igvn.register_new_node_with_optimizer(b);
2305   set_ctrl(b, phi->in(0));
2306 
2307   if (sample_opaque != nullptr) {
2308     Node* opaque = sample_opaque->clone();
2309     opaque->set_req(1, b);
2310     _igvn.register_new_node_with_optimizer(opaque);
2311     set_ctrl(opaque, phi->in(0));
2312     return opaque;
2313   }
2314 
2315   assert(b->is_Bool(), "");
2316   return b;
2317 }
2318 
2319 //------------------------------clone_bool-------------------------------------
2320 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2321 // "Nearly" because all Nodes have been cloned from the original in the loop,
2322 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2323 // through the Phi recursively, and return a Bool.
2324 CmpNode*PhaseIdealLoop::clone_bool(PhiNode* phi) {
2325   uint i;
2326   // Convert this Phi into a Phi merging Bools
2327   for( i = 1; i < phi->req(); i++ ) {
2328     Node *b = phi->in(i);
2329     if( b->is_Phi() ) {
2330       _igvn.replace_input_of(phi, i, clone_bool(b->as_Phi()));
2331     } else {
2332       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
2333     }
2334   }
2335 
2336   Node *sample_cmp = phi->in(1);
2337 
2338   // Make Phis to merge the Cmp's inputs.
2339   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
2340   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
2341   for( uint j = 1; j < phi->req(); j++ ) {
2342     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
2343     Node *n1, *n2;
2344     if( cmp_top->is_Cmp() ) {
2345       n1 = cmp_top->in(1);
2346       n2 = cmp_top->in(2);
2347     } else {
2348       n1 = n2 = cmp_top;
2349     }
2350     phi1->set_req( j, n1 );
2351     phi2->set_req( j, n2 );
2352     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2353     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2354   }
2355 
2356   // See if these Phis have been made before.
2357   // Register with optimizer
2358   Node *hit1 = _igvn.hash_find_insert(phi1);
2359   if( hit1 ) {                  // Hit, toss just made Phi
2360     _igvn.remove_dead_node(phi1, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2361     assert( hit1->is_Phi(), "" );
2362     phi1 = (PhiNode*)hit1;      // Use existing phi
2363   } else {                      // Miss
2364     _igvn.register_new_node_with_optimizer(phi1);
2365   }
2366   Node *hit2 = _igvn.hash_find_insert(phi2);
2367   if( hit2 ) {                  // Hit, toss just made Phi
2368     _igvn.remove_dead_node(phi2, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2369     assert( hit2->is_Phi(), "" );
2370     phi2 = (PhiNode*)hit2;      // Use existing phi
2371   } else {                      // Miss
2372     _igvn.register_new_node_with_optimizer(phi2);
2373   }
2374   // Register Phis with loop/block info
2375   set_ctrl(phi1, phi->in(0));
2376   set_ctrl(phi2, phi->in(0));
2377   // Make a new Cmp
2378   Node *cmp = sample_cmp->clone();
2379   cmp->set_req( 1, phi1 );
2380   cmp->set_req( 2, phi2 );
2381   _igvn.register_new_node_with_optimizer(cmp);
2382   set_ctrl(cmp, phi->in(0));
2383 
2384   assert( cmp->is_Cmp(), "" );
2385   return (CmpNode*)cmp;
2386 }
2387 
2388 void PhaseIdealLoop::clone_loop_handle_data_uses(Node* old, Node_List &old_new,
2389                                                  IdealLoopTree* loop, IdealLoopTree* outer_loop,
2390                                                  Node_List*& split_if_set, Node_List*& split_bool_set,
2391                                                  Node_List*& split_cex_set, Node_List& worklist,
2392                                                  uint new_counter, CloneLoopMode mode) {
2393   Node* nnn = old_new[old->_idx];
2394   // Copy uses to a worklist, so I can munge the def-use info
2395   // with impunity.
2396   for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
2397     worklist.push(old->fast_out(j));
2398 
2399   while( worklist.size() ) {
2400     Node *use = worklist.pop();
2401     if (!has_node(use))  continue; // Ignore dead nodes
2402     if (use->in(0) == C->top())  continue;
2403     IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
2404     // Check for data-use outside of loop - at least one of OLD or USE
2405     // must not be a CFG node.
2406 #ifdef ASSERT
2407     if (loop->_head->as_Loop()->is_strip_mined() && outer_loop->is_member(use_loop) && !loop->is_member(use_loop) && old_new[use->_idx] == nullptr) {
2408       Node* sfpt = loop->_head->as_CountedLoop()->outer_safepoint();
2409       assert(mode != IgnoreStripMined, "incorrect cloning mode");
2410       assert((mode == ControlAroundStripMined && use == sfpt) || !use->is_reachable_from_root(), "missed a node");
2411     }
2412 #endif
2413     if (!loop->is_member(use_loop) && !outer_loop->is_member(use_loop) && (!old->is_CFG() || !use->is_CFG())) {
2414 
2415       // If the Data use is an IF, that means we have an IF outside the
2416       // loop that is switching on a condition that is set inside the
2417       // loop.  Happens if people set a loop-exit flag; then test the flag
2418       // in the loop to break the loop, then test is again outside the
2419       // loop to determine which way the loop exited.
2420       //
2421       // For several uses we need to make sure that there is no phi between,
2422       // the use and the Bool/Cmp. We therefore clone the Bool/Cmp down here
2423       // to avoid such a phi in between.
2424       // For example, it is unexpected that there is a Phi between an
2425       // AllocateArray node and its ValidLengthTest input that could cause
2426       // split if to break.
2427       assert(!use->is_OpaqueTemplateAssertionPredicate(),
2428              "should not clone a Template Assertion Predicate which should be removed once it's useless");
2429       if (use->is_If() || use->is_CMove() || use->is_OpaqueConstantBool() || use->is_OpaqueInitializedAssertionPredicate() ||
2430           (use->Opcode() == Op_AllocateArray && use->in(AllocateNode::ValidLengthTest) == old)) {
2431         // Since this code is highly unlikely, we lazily build the worklist
2432         // of such Nodes to go split.
2433         if (!split_if_set) {
2434           split_if_set = new Node_List();
2435         }
2436         split_if_set->push(use);
2437       }
2438       if (use->is_Bool()) {
2439         if (!split_bool_set) {
2440           split_bool_set = new Node_List();
2441         }
2442         split_bool_set->push(use);
2443       }
2444       if (use->Opcode() == Op_CreateEx) {
2445         if (!split_cex_set) {
2446           split_cex_set = new Node_List();
2447         }
2448         split_cex_set->push(use);
2449       }
2450 
2451 
2452       // Get "block" use is in
2453       uint idx = 0;
2454       while( use->in(idx) != old ) idx++;
2455       Node *prev = use->is_CFG() ? use : get_ctrl(use);
2456       assert(!loop->is_member(get_loop(prev)) && !outer_loop->is_member(get_loop(prev)), "" );
2457       Node* cfg = (prev->_idx >= new_counter && prev->is_Region())
2458         ? prev->in(2)
2459         : idom(prev);
2460       if( use->is_Phi() )     // Phi use is in prior block
2461         cfg = prev->in(idx);  // NOT in block of Phi itself
2462       if (cfg->is_top()) {    // Use is dead?
2463         _igvn.replace_input_of(use, idx, C->top());
2464         continue;
2465       }
2466 
2467       // If use is referenced through control edge... (idx == 0)
2468       if (mode == IgnoreStripMined && idx == 0) {
2469         LoopNode *head = loop->_head->as_Loop();
2470         if (head->is_strip_mined() && is_dominator(head->outer_loop_exit(), prev)) {
2471           // That node is outside the inner loop, leave it outside the
2472           // outer loop as well to not confuse verification code.
2473           assert(!loop->_parent->is_member(use_loop), "should be out of the outer loop");
2474           _igvn.replace_input_of(use, 0, head->outer_loop_exit());
2475           continue;
2476         }
2477       }
2478 
2479       while(!outer_loop->is_member(get_loop(cfg))) {
2480         prev = cfg;
2481         cfg = (cfg->_idx >= new_counter && cfg->is_Region()) ? cfg->in(2) : idom(cfg);
2482       }
2483       // If the use occurs after merging several exits from the loop, then
2484       // old value must have dominated all those exits.  Since the same old
2485       // value was used on all those exits we did not need a Phi at this
2486       // merge point.  NOW we do need a Phi here.  Each loop exit value
2487       // is now merged with the peeled body exit; each exit gets its own
2488       // private Phi and those Phis need to be merged here.
2489       Node *phi;
2490       if( prev->is_Region() ) {
2491         if( idx == 0 ) {      // Updating control edge?
2492           phi = prev;         // Just use existing control
2493         } else {              // Else need a new Phi
2494           phi = PhiNode::make( prev, old );
2495           // Now recursively fix up the new uses of old!
2496           for( uint i = 1; i < prev->req(); i++ ) {
2497             worklist.push(phi); // Onto worklist once for each 'old' input
2498           }
2499         }
2500       } else {
2501         // Get new RegionNode merging old and new loop exits
2502         prev = old_new[prev->_idx];
2503         assert( prev, "just made this in step 7" );
2504         if( idx == 0) {      // Updating control edge?
2505           phi = prev;         // Just use existing control
2506         } else {              // Else need a new Phi
2507           // Make a new Phi merging data values properly
2508           phi = PhiNode::make( prev, old );
2509           phi->set_req( 1, nnn );
2510         }
2511       }
2512       // If inserting a new Phi, check for prior hits
2513       if( idx != 0 ) {
2514         Node *hit = _igvn.hash_find_insert(phi);
2515         if( hit == nullptr ) {
2516           _igvn.register_new_node_with_optimizer(phi); // Register new phi
2517         } else {                                      // or
2518           // Remove the new phi from the graph and use the hit
2519           _igvn.remove_dead_node(phi, phi == prev ? PhaseIterGVN::NodeOrigin::Graph : PhaseIterGVN::NodeOrigin::Speculative);
2520           phi = hit;                                  // Use existing phi
2521         }
2522         set_ctrl(phi, prev);
2523       }
2524       // Make 'use' use the Phi instead of the old loop body exit value
2525       assert(use->in(idx) == old, "old is still input of use");
2526       // We notify all uses of old, including use, and the indirect uses,
2527       // that may now be optimized because we have replaced old with phi.
2528       _igvn.add_users_to_worklist(old);
2529       if (idx == 0 && use->depends_only_on_test()) {
2530         // If this node depends_only_on_test, it will be rewired to a control input that is not the
2531         // correct test. As a result, it must be pinned otherwise it can be incorrectly rewired to
2532         // a dominating test equivalent to the new control.
2533         Node* pinned_clone = use->pin_node_under_control();
2534         if (pinned_clone != nullptr) {
2535           pinned_clone->set_req(0, phi);
2536           register_new_node_with_ctrl_of(pinned_clone, use);
2537           _igvn.replace_node(use, pinned_clone);
2538           continue;
2539         }
2540       }
2541       _igvn.replace_input_of(use, idx, phi);
2542       if( use->_idx >= new_counter ) { // If updating new phis
2543         // Not needed for correctness, but prevents a weak assert
2544         // in AddPNode from tripping (when we end up with different
2545         // base & derived Phis that will become the same after
2546         // IGVN does CSE).
2547         Node *hit = _igvn.hash_find_insert(use);
2548         if( hit )             // Go ahead and re-hash for hits.
2549           _igvn.replace_node( use, hit );
2550       }
2551     }
2552   }
2553 }
2554 
2555 static void collect_nodes_in_outer_loop_not_reachable_from_sfpt(Node* n, const IdealLoopTree *loop, const IdealLoopTree* outer_loop,
2556                                                                 const Node_List &old_new, Unique_Node_List& wq, PhaseIdealLoop* phase,
2557                                                                 bool check_old_new) {
2558   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2559     Node* u = n->fast_out(j);
2560     assert(check_old_new || old_new[u->_idx] == nullptr, "shouldn't have been cloned");
2561     if (!u->is_CFG() && (!check_old_new || old_new[u->_idx] == nullptr)) {
2562       assert(!phase->ctrl_is_member(loop, u) || !loop->_body.contains(u), "can be in outer loop or out of both loops only");
2563       if (!phase->ctrl_is_member(loop, u)) {
2564         if (phase->ctrl_is_member(outer_loop, u)) {
2565           wq.push(u);
2566         } else {
2567           // nodes pinned with control in the outer loop but not referenced from the safepoint must be moved out of
2568           // the outer loop too
2569           Node* u_c = u->in(0);
2570           if (u_c != nullptr) {
2571             IdealLoopTree* u_c_loop = phase->get_loop(u_c);
2572             if (outer_loop->is_member(u_c_loop) && !loop->is_member(u_c_loop)) {
2573               wq.push(u);
2574             }
2575           }
2576         }
2577       }
2578     }
2579   }
2580 }
2581 
2582 void PhaseIdealLoop::clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
2583                                       IdealLoopTree* outer_loop, int dd, Node_List &old_new,
2584                                       Node_List& extra_data_nodes) {
2585   if (head->is_strip_mined() && mode != IgnoreStripMined) {
2586     CountedLoopNode* cl = head->as_CountedLoop();
2587     Node* l = cl->outer_loop();
2588     Node* tail = cl->outer_loop_tail();
2589     IfNode* le = cl->outer_loop_end();
2590     Node* sfpt = cl->outer_safepoint();
2591     CountedLoopEndNode* cle = cl->loopexit();
2592     CountedLoopNode* new_cl = old_new[cl->_idx]->as_CountedLoop();
2593     CountedLoopEndNode* new_cle = new_cl->as_CountedLoop()->loopexit_or_null();
2594     IfFalseNode* cle_out = cle->false_proj();
2595 
2596     Node* new_sfpt = nullptr;
2597     Node* new_cle_out = cle_out->clone();
2598     old_new.map(cle_out->_idx, new_cle_out);
2599     if (mode == CloneIncludesStripMined) {
2600       // clone outer loop body
2601       Node* new_l = l->clone();
2602       Node* new_tail = tail->clone();
2603       IfNode* new_le = le->clone()->as_If();
2604       new_sfpt = sfpt->clone();
2605 
2606       set_loop(new_l, outer_loop->_parent);
2607       set_idom(new_l, new_l->in(LoopNode::EntryControl), dd);
2608       set_loop(new_cle_out, outer_loop->_parent);
2609       set_idom(new_cle_out, new_cle, dd);
2610       set_loop(new_sfpt, outer_loop->_parent);
2611       set_idom(new_sfpt, new_cle_out, dd);
2612       set_loop(new_le, outer_loop->_parent);
2613       set_idom(new_le, new_sfpt, dd);
2614       set_loop(new_tail, outer_loop->_parent);
2615       set_idom(new_tail, new_le, dd);
2616       set_idom(new_cl, new_l, dd);
2617 
2618       old_new.map(l->_idx, new_l);
2619       old_new.map(tail->_idx, new_tail);
2620       old_new.map(le->_idx, new_le);
2621       old_new.map(sfpt->_idx, new_sfpt);
2622 
2623       new_l->set_req(LoopNode::LoopBackControl, new_tail);
2624       new_l->set_req(0, new_l);
2625       new_tail->set_req(0, new_le);
2626       new_le->set_req(0, new_sfpt);
2627       new_sfpt->set_req(0, new_cle_out);
2628       new_cle_out->set_req(0, new_cle);
2629       new_cl->set_req(LoopNode::EntryControl, new_l);
2630 
2631       _igvn.register_new_node_with_optimizer(new_l);
2632       _igvn.register_new_node_with_optimizer(new_tail);
2633       _igvn.register_new_node_with_optimizer(new_le);
2634     } else {
2635       Node *newhead = old_new[loop->_head->_idx];
2636       newhead->as_Loop()->clear_strip_mined();
2637       _igvn.replace_input_of(newhead, LoopNode::EntryControl, newhead->in(LoopNode::EntryControl)->in(LoopNode::EntryControl));
2638       set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2639     }
2640     // Look at data node that were assigned a control in the outer
2641     // loop: they are kept in the outer loop by the safepoint so start
2642     // from the safepoint node's inputs.
2643     IdealLoopTree* outer_loop = get_loop(l);
2644     Node_Stack stack(2);
2645     stack.push(sfpt, 1);
2646     uint new_counter = C->unique();
2647     while (stack.size() > 0) {
2648       Node* n = stack.node();
2649       uint i = stack.index();
2650       while (i < n->req() &&
2651              (n->in(i) == nullptr ||
2652               !has_ctrl(n->in(i)) ||
2653               get_loop(get_ctrl(n->in(i))) != outer_loop ||
2654               (old_new[n->in(i)->_idx] != nullptr && old_new[n->in(i)->_idx]->_idx >= new_counter))) {
2655         i++;
2656       }
2657       if (i < n->req()) {
2658         stack.set_index(i+1);
2659         stack.push(n->in(i), 0);
2660       } else {
2661         assert(old_new[n->_idx] == nullptr || n == sfpt || old_new[n->_idx]->_idx < new_counter, "no clone yet");
2662         Node* m = n == sfpt ? new_sfpt : n->clone();
2663         if (m != nullptr) {
2664           for (uint i = 0; i < n->req(); i++) {
2665             if (m->in(i) != nullptr && old_new[m->in(i)->_idx] != nullptr) {
2666               m->set_req(i, old_new[m->in(i)->_idx]);
2667             }
2668           }
2669         } else {
2670           assert(n == sfpt && mode != CloneIncludesStripMined, "where's the safepoint clone?");
2671         }
2672         if (n != sfpt) {
2673           extra_data_nodes.push(n);
2674           _igvn.register_new_node_with_optimizer(m);
2675           assert(get_ctrl(n) == cle_out, "what other control?");
2676           set_ctrl(m, new_cle_out);
2677           old_new.map(n->_idx, m);
2678         }
2679         stack.pop();
2680       }
2681     }
2682     if (mode == CloneIncludesStripMined) {
2683       _igvn.register_new_node_with_optimizer(new_sfpt);
2684       _igvn.register_new_node_with_optimizer(new_cle_out);
2685     }
2686     // Some other transformation may have pessimistically assigned some
2687     // data nodes to the outer loop. Set their control so they are out
2688     // of the outer loop.
2689     ResourceMark rm;
2690     Unique_Node_List wq;
2691     for (uint i = 0; i < extra_data_nodes.size(); i++) {
2692       Node* old = extra_data_nodes.at(i);
2693       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2694     }
2695 
2696     for (uint i = 0; i < loop->_body.size(); i++) {
2697       Node* old = loop->_body.at(i);
2698       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2699     }
2700 
2701     Node* inner_out = sfpt->in(0);
2702     if (inner_out->outcnt() > 1) {
2703       collect_nodes_in_outer_loop_not_reachable_from_sfpt(inner_out, loop, outer_loop, old_new, wq, this, true);
2704     }
2705 
2706     Node* new_ctrl = cl->outer_loop_exit();
2707     assert(get_loop(new_ctrl) != outer_loop, "must be out of the loop nest");
2708     for (uint i = 0; i < wq.size(); i++) {
2709       Node* n = wq.at(i);
2710       set_ctrl(n, new_ctrl);
2711       if (n->in(0) != nullptr) {
2712         _igvn.replace_input_of(n, 0, new_ctrl);
2713       }
2714       collect_nodes_in_outer_loop_not_reachable_from_sfpt(n, loop, outer_loop, old_new, wq, this, false);
2715     }
2716   } else {
2717     Node *newhead = old_new[loop->_head->_idx];
2718     set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2719   }
2720 }
2721 
2722 //------------------------------clone_loop-------------------------------------
2723 //
2724 //                   C L O N E   A   L O O P   B O D Y
2725 //
2726 // This is the basic building block of the loop optimizations.  It clones an
2727 // entire loop body.  It makes an old_new loop body mapping; with this mapping
2728 // you can find the new-loop equivalent to an old-loop node.  All new-loop
2729 // nodes are exactly equal to their old-loop counterparts, all edges are the
2730 // same.  All exits from the old-loop now have a RegionNode that merges the
2731 // equivalent new-loop path.  This is true even for the normal "loop-exit"
2732 // condition.  All uses of loop-invariant old-loop values now come from (one
2733 // or more) Phis that merge their new-loop equivalents.
2734 //
2735 // This operation leaves the graph in an illegal state: there are two valid
2736 // control edges coming from the loop pre-header to both loop bodies.  I'll
2737 // definitely have to hack the graph after running this transform.
2738 //
2739 // From this building block I will further edit edges to perform loop peeling
2740 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
2741 //
2742 // Parameter side_by_size_idom:
2743 //   When side_by_size_idom is null, the dominator tree is constructed for
2744 //      the clone loop to dominate the original.  Used in construction of
2745 //      pre-main-post loop sequence.
2746 //   When nonnull, the clone and original are side-by-side, both are
2747 //      dominated by the side_by_side_idom node.  Used in construction of
2748 //      unswitched loops.
2749 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
2750                                 CloneLoopMode mode, Node* side_by_side_idom) {
2751 
2752   LoopNode* head = loop->_head->as_Loop();
2753   head->verify_strip_mined(1);
2754 
2755   if (C->do_vector_loop() && PrintOpto) {
2756     const char* mname = C->method()->name()->as_quoted_ascii();
2757     if (mname != nullptr) {
2758       tty->print("PhaseIdealLoop::clone_loop: for vectorize method %s\n", mname);
2759     }
2760   }
2761 
2762   CloneMap& cm = C->clone_map();
2763   if (C->do_vector_loop()) {
2764     cm.set_clone_idx(cm.max_gen()+1);
2765 #ifndef PRODUCT
2766     if (PrintOpto) {
2767       tty->print_cr("PhaseIdealLoop::clone_loop: _clone_idx %d", cm.clone_idx());
2768       loop->dump_head();
2769     }
2770 #endif
2771   }
2772 
2773   // Step 1: Clone the loop body.  Make the old->new mapping.
2774   clone_loop_body(loop->_body, old_new, &cm);
2775 
2776   IdealLoopTree* outer_loop = (head->is_strip_mined() && mode != IgnoreStripMined) ? get_loop(head->as_CountedLoop()->outer_loop()) : loop;
2777 
2778   // Step 2: Fix the edges in the new body.  If the old input is outside the
2779   // loop use it.  If the old input is INside the loop, use the corresponding
2780   // new node instead.
2781   fix_body_edges(loop->_body, loop, old_new, dd, outer_loop->_parent, false);
2782 
2783   Node_List extra_data_nodes; // data nodes in the outer strip mined loop
2784   clone_outer_loop(head, mode, loop, outer_loop, dd, old_new, extra_data_nodes);
2785 
2786   // Step 3: Now fix control uses.  Loop varying control uses have already
2787   // been fixed up (as part of all input edges in Step 2).  Loop invariant
2788   // control uses must be either an IfFalse or an IfTrue.  Make a merge
2789   // point to merge the old and new IfFalse/IfTrue nodes; make the use
2790   // refer to this.
2791   Node_List worklist;
2792   uint new_counter = C->unique();
2793   fix_ctrl_uses(loop->_body, loop, old_new, mode, side_by_side_idom, &cm, worklist);
2794 
2795   // Step 4: If loop-invariant use is not control, it must be dominated by a
2796   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
2797   // there if needed.  Make a Phi there merging old and new used values.
2798   Node_List *split_if_set = nullptr;
2799   Node_List *split_bool_set = nullptr;
2800   Node_List *split_cex_set = nullptr;
2801   fix_data_uses(loop->_body, loop, mode, outer_loop, new_counter, old_new, worklist, split_if_set, split_bool_set, split_cex_set);
2802 
2803   for (uint i = 0; i < extra_data_nodes.size(); i++) {
2804     Node* old = extra_data_nodes.at(i);
2805     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2806                                 split_bool_set, split_cex_set, worklist, new_counter,
2807                                 mode);
2808   }
2809 
2810   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
2811   // the loop uses a condition set in the loop.  The original IF probably
2812   // takes control from one or more OLD Regions (which in turn get from NEW
2813   // Regions).  In any case, there will be a set of Phis for each merge point
2814   // from the IF up to where the original BOOL def exists the loop.
2815   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
2816 
2817 }
2818 
2819 void PhaseIdealLoop::finish_clone_loop(Node_List* split_if_set, Node_List* split_bool_set, Node_List* split_cex_set) {
2820   if (split_if_set) {
2821     while (split_if_set->size()) {
2822       Node *iff = split_if_set->pop();
2823       uint input = iff->Opcode() == Op_AllocateArray ? AllocateNode::ValidLengthTest : 1;
2824       if (iff->in(input)->is_Phi()) {
2825         Node *b = clone_iff(iff->in(input)->as_Phi());
2826         _igvn.replace_input_of(iff, input, b);
2827       }
2828     }
2829   }
2830   if (split_bool_set) {
2831     while (split_bool_set->size()) {
2832       Node *b = split_bool_set->pop();
2833       Node *phi = b->in(1);
2834       assert(phi->is_Phi(), "");
2835       CmpNode *cmp = clone_bool((PhiNode*) phi);
2836       _igvn.replace_input_of(b, 1, cmp);
2837     }
2838   }
2839   if (split_cex_set) {
2840     while (split_cex_set->size()) {
2841       Node *b = split_cex_set->pop();
2842       assert(b->in(0)->is_Region(), "");
2843       assert(b->in(1)->is_Phi(), "");
2844       assert(b->in(0)->in(0) == b->in(1)->in(0), "");
2845       split_up(b, b->in(0), nullptr);
2846     }
2847   }
2848 }
2849 
2850 void PhaseIdealLoop::fix_data_uses(Node_List& body, IdealLoopTree* loop, CloneLoopMode mode, IdealLoopTree* outer_loop,
2851                                    uint new_counter, Node_List &old_new, Node_List &worklist, Node_List*& split_if_set,
2852                                    Node_List*& split_bool_set, Node_List*& split_cex_set) {
2853   for(uint i = 0; i < body.size(); i++ ) {
2854     Node* old = body.at(i);
2855     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2856                                 split_bool_set, split_cex_set, worklist, new_counter,
2857                                 mode);
2858   }
2859 }
2860 
2861 void PhaseIdealLoop::fix_ctrl_uses(const Node_List& body, const IdealLoopTree* loop, Node_List &old_new, CloneLoopMode mode,
2862                                    Node* side_by_side_idom, CloneMap* cm, Node_List &worklist) {
2863   LoopNode* head = loop->_head->as_Loop();
2864   for(uint i = 0; i < body.size(); i++ ) {
2865     Node* old = body.at(i);
2866     if( !old->is_CFG() ) continue;
2867 
2868     // Copy uses to a worklist, so I can munge the def-use info
2869     // with impunity.
2870     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++) {
2871       worklist.push(old->fast_out(j));
2872     }
2873 
2874     while (worklist.size()) {  // Visit all uses
2875       Node *use = worklist.pop();
2876       if (!has_node(use))  continue; // Ignore dead nodes
2877       IdealLoopTree *use_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use );
2878       if (!loop->is_member(use_loop) && use->is_CFG()) {
2879         // Both OLD and USE are CFG nodes here.
2880         assert(use->is_Proj(), "" );
2881         Node* nnn = old_new[old->_idx];
2882 
2883         Node* newuse = nullptr;
2884         if (head->is_strip_mined() && mode != IgnoreStripMined) {
2885           CountedLoopNode* cl = head->as_CountedLoop();
2886           CountedLoopEndNode* cle = cl->loopexit();
2887           // is use the projection that exits the loop from the CountedLoopEndNode?
2888           if (use->in(0) == cle) {
2889             IfFalseNode* cle_out = use->as_IfFalse();
2890             IfNode* le = cl->outer_loop_end();
2891             use = le->false_proj();
2892             use_loop = get_loop(use);
2893             if (mode == CloneIncludesStripMined) {
2894               nnn = old_new[le->_idx];
2895             } else {
2896               newuse = old_new[cle_out->_idx];
2897             }
2898           }
2899         }
2900         if (newuse == nullptr) {
2901           newuse = use->clone();
2902         }
2903 
2904         // Clone the loop exit control projection
2905         if (C->do_vector_loop() && cm != nullptr) {
2906           cm->verify_insert_and_clone(use, newuse, cm->clone_idx());
2907         }
2908         newuse->set_req(0,nnn);
2909         _igvn.register_new_node_with_optimizer(newuse);
2910         set_loop(newuse, use_loop);
2911         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
2912 
2913         // We need a Region to merge the exit from the peeled body and the
2914         // exit from the old loop body.
2915         RegionNode *r = new RegionNode(3);
2916         uint dd_r = MIN2(dom_depth(newuse), dom_depth(use));
2917         assert(dd_r >= dom_depth(dom_lca(newuse, use)), "" );
2918 
2919         // The original user of 'use' uses 'r' instead.
2920         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
2921           Node* useuse = use->last_out(l);
2922           _igvn.rehash_node_delayed(useuse);
2923           uint uses_found = 0;
2924           if (useuse->in(0) == use) {
2925             useuse->set_req(0, r);
2926             uses_found++;
2927             if (useuse->is_CFG()) {
2928               // This is not a dom_depth > dd_r because when new
2929               // control flow is constructed by a loop opt, a node and
2930               // its dominator can end up at the same dom_depth
2931               assert(dom_depth(useuse) >= dd_r, "");
2932               set_idom(useuse, r, dom_depth(useuse));
2933             }
2934           }
2935           for (uint k = 1; k < useuse->req(); k++) {
2936             if( useuse->in(k) == use ) {
2937               useuse->set_req(k, r);
2938               uses_found++;
2939               if (useuse->is_Loop() && k == LoopNode::EntryControl) {
2940                 // This is not a dom_depth > dd_r because when new
2941                 // control flow is constructed by a loop opt, a node
2942                 // and its dominator can end up at the same dom_depth
2943                 assert(dom_depth(useuse) >= dd_r , "");
2944                 set_idom(useuse, r, dom_depth(useuse));
2945               }
2946             }
2947           }
2948           l -= uses_found;    // we deleted 1 or more copies of this edge
2949         }
2950 
2951         assert(use->is_Proj(), "loop exit should be projection");
2952         // replace_node_and_forward_ctrl() below moves all nodes that are:
2953         // - control dependent on the loop exit or
2954         // - have control set to the loop exit
2955         // below the post-loop merge point.
2956         // replace_node_and_forward_ctrl() takes a dead control as first input.
2957         // To make it possible to use it, the loop exit projection is cloned and becomes the
2958         // new exit projection. The initial one becomes dead and is "replaced" by the region.
2959         Node* use_clone = use->clone();
2960         register_control(use_clone, use_loop, idom(use), dom_depth(use));
2961         // Now finish up 'r'
2962         r->set_req(1, newuse);
2963         r->set_req(2, use_clone);
2964         _igvn.register_new_node_with_optimizer(r);
2965         set_loop(r, use_loop);
2966         set_idom(r, (side_by_side_idom == nullptr) ? newuse->in(0) : side_by_side_idom, dd_r);
2967         replace_node_and_forward_ctrl(use, r);
2968         // Map the (cloned) old use to the new merge point
2969         old_new.map(use_clone->_idx, r);
2970       } // End of if a loop-exit test
2971     }
2972   }
2973 }
2974 
2975 void PhaseIdealLoop::fix_body_edges(const Node_List &body, IdealLoopTree* loop, const Node_List &old_new, int dd,
2976                                     IdealLoopTree* parent, bool partial) {
2977   for(uint i = 0; i < body.size(); i++ ) {
2978     Node *old = body.at(i);
2979     Node *nnn = old_new[old->_idx];
2980     // Fix CFG/Loop controlling the new node
2981     if (has_ctrl(old)) {
2982       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
2983     } else {
2984       set_loop(nnn, parent);
2985       if (old->outcnt() > 0) {
2986         Node* dom = idom(old);
2987         if (old_new[dom->_idx] != nullptr) {
2988           dom = old_new[dom->_idx];
2989           set_idom(nnn, dom, dd );
2990         }
2991       }
2992     }
2993     // Correct edges to the new node
2994     for (uint j = 0; j < nnn->req(); j++) {
2995         Node *n = nnn->in(j);
2996         if (n != nullptr) {
2997           IdealLoopTree *old_in_loop = get_loop(has_ctrl(n) ? get_ctrl(n) : n);
2998           if (loop->is_member(old_in_loop)) {
2999             if (old_new[n->_idx] != nullptr) {
3000               nnn->set_req(j, old_new[n->_idx]);
3001             } else {
3002               assert(!body.contains(n), "");
3003               assert(partial, "node not cloned");
3004             }
3005           }
3006         }
3007     }
3008     _igvn.hash_find_insert(nnn);
3009   }
3010 }
3011 
3012 void PhaseIdealLoop::clone_loop_body(const Node_List& body, Node_List &old_new, CloneMap* cm) {
3013   for (uint i = 0; i < body.size(); i++) {
3014     Node* old = body.at(i);
3015     Node* nnn = old->clone();
3016     old_new.map(old->_idx, nnn);
3017     if (C->do_vector_loop() && cm != nullptr) {
3018       cm->verify_insert_and_clone(old, nnn, cm->clone_idx());
3019     }
3020     _igvn.register_new_node_with_optimizer(nnn);
3021   }
3022 }
3023 
3024 
3025 //---------------------- stride_of_possible_iv -------------------------------------
3026 // Looks for an iff/bool/comp with one operand of the compare
3027 // being a cycle involving an add and a phi,
3028 // with an optional truncation (left-shift followed by a right-shift)
3029 // of the add. Returns zero if not an iv.
3030 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
3031   const TypeInteger* ttype = nullptr;
3032   if (!iff->is_If() || iff->in(1) == nullptr || !iff->in(1)->is_Bool()) {
3033     return 0;
3034   }
3035   BoolNode* bl = iff->in(1)->as_Bool();
3036   Node* cmp = bl->in(1);
3037   if (!cmp || (cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU)) {
3038     return 0;
3039   }
3040   // Must have an invariant operand
3041   if (ctrl_is_member(get_loop(iff), cmp->in(2))) {
3042     return 0;
3043   }
3044   Node* add2 = nullptr;
3045   Node* cmp1 = cmp->in(1);
3046   if (cmp1->is_Phi()) {
3047     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
3048     Node* phi = cmp1;
3049     for (uint i = 1; i < phi->req(); i++) {
3050       Node* in = phi->in(i);
3051       CountedLoopConverter::TruncatedIncrement add(T_INT);
3052       add.build(in);
3053       if (add.is_valid() && add.incr()->in(1) == phi) {
3054         add2 = add.incr()->in(2);
3055         break;
3056       }
3057     }
3058   } else {
3059     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
3060     Node* addtrunc = cmp1;
3061     CountedLoopConverter::TruncatedIncrement add(T_INT);
3062     add.build(addtrunc);
3063     if (add.is_valid() && add.incr()->in(1)->is_Phi()) {
3064       Node* phi = add.incr()->in(1);
3065       for (uint i = 1; i < phi->req(); i++) {
3066         if (phi->in(i) == addtrunc) {
3067           add2 = add.incr()->in(2);
3068           break;
3069         }
3070       }
3071     }
3072   }
3073   if (add2 != nullptr) {
3074     const TypeInt* add2t = _igvn.type(add2)->is_int();
3075     if (add2t->is_con()) {
3076       return add2t->get_con();
3077     }
3078   }
3079   return 0;
3080 }
3081 
3082 
3083 //---------------------- stay_in_loop -------------------------------------
3084 // Return the (unique) control output node that's in the loop (if it exists.)
3085 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
3086   Node* unique = nullptr;
3087   if (!n) return nullptr;
3088   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3089     Node* use = n->fast_out(i);
3090     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
3091       if (unique != nullptr) {
3092         return nullptr;
3093       }
3094       unique = use;
3095     }
3096   }
3097   return unique;
3098 }
3099 
3100 //------------------------------ register_node -------------------------------------
3101 // Utility to register node "n" with PhaseIdealLoop
3102 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree* loop, Node* pred, uint ddepth) {
3103   _igvn.register_new_node_with_optimizer(n);
3104   loop->_body.push(n);
3105   if (n->is_CFG()) {
3106     set_loop(n, loop);
3107     set_idom(n, pred, ddepth);
3108   } else {
3109     set_ctrl(n, pred);
3110   }
3111 }
3112 
3113 //------------------------------ proj_clone -------------------------------------
3114 // Utility to create an if-projection
3115 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
3116   ProjNode* c = p->clone()->as_Proj();
3117   c->set_req(0, iff);
3118   return c;
3119 }
3120 
3121 //------------------------------ short_circuit_if -------------------------------------
3122 // Force the iff control output to be the live_proj
3123 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
3124   guarantee(live_proj != nullptr, "null projection");
3125   int proj_con = live_proj->_con;
3126   assert(proj_con == 0 || proj_con == 1, "false or true projection");
3127   Node* con = intcon(proj_con);
3128   if (iff) {
3129     iff->set_req(1, con);
3130   }
3131   return con;
3132 }
3133 
3134 //------------------------------ insert_if_before_proj -------------------------------------
3135 // Insert a new if before an if projection (* - new node)
3136 //
3137 // before
3138 //           if(test)
3139 //           /     \
3140 //          v       v
3141 //    other-proj   proj (arg)
3142 //
3143 // after
3144 //           if(test)
3145 //           /     \
3146 //          /       v
3147 //         |      * proj-clone
3148 //         v          |
3149 //    other-proj      v
3150 //                * new_if(relop(cmp[IU](left,right)))
3151 //                  /  \
3152 //                 v    v
3153 //         * new-proj  proj
3154 //         (returned)
3155 //
3156 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
3157   IfNode* iff = proj->in(0)->as_If();
3158   IdealLoopTree *loop = get_loop(proj);
3159   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3160   uint ddepth = dom_depth(proj);
3161 
3162   _igvn.rehash_node_delayed(iff);
3163   _igvn.rehash_node_delayed(proj);
3164 
3165   proj->set_req(0, nullptr);  // temporary disconnect
3166   ProjNode* proj2 = proj_clone(proj, iff);
3167   register_node(proj2, loop, iff, ddepth);
3168 
3169   Node* cmp = Signed ? (Node*) new CmpINode(left, right) : (Node*) new CmpUNode(left, right);
3170   register_node(cmp, loop, proj2, ddepth);
3171 
3172   BoolNode* bol = new BoolNode(cmp, relop);
3173   register_node(bol, loop, proj2, ddepth);
3174 
3175   int opcode = iff->Opcode();
3176   assert(opcode == Op_If || opcode == Op_RangeCheck, "unexpected opcode");
3177   IfNode* new_if = IfNode::make_with_same_profile(iff, proj2, bol);
3178   register_node(new_if, loop, proj2, ddepth);
3179 
3180   proj->set_req(0, new_if); // reattach
3181   set_idom(proj, new_if, ddepth);
3182 
3183   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
3184   guarantee(new_exit != nullptr, "null exit node");
3185   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
3186 
3187   return new_exit;
3188 }
3189 
3190 //------------------------------ insert_region_before_proj -------------------------------------
3191 // Insert a region before an if projection (* - new node)
3192 //
3193 // before
3194 //           if(test)
3195 //          /      |
3196 //         v       |
3197 //       proj      v
3198 //               other-proj
3199 //
3200 // after
3201 //           if(test)
3202 //          /      |
3203 //         v       |
3204 // * proj-clone    v
3205 //         |     other-proj
3206 //         v
3207 // * new-region
3208 //         |
3209 //         v
3210 // *      dum_if
3211 //       /     \
3212 //      v       \
3213 // * dum-proj    v
3214 //              proj
3215 //
3216 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
3217   IfNode* iff = proj->in(0)->as_If();
3218   IdealLoopTree *loop = get_loop(proj);
3219   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3220   uint ddepth = dom_depth(proj);
3221 
3222   _igvn.rehash_node_delayed(iff);
3223   _igvn.rehash_node_delayed(proj);
3224 
3225   proj->set_req(0, nullptr);  // temporary disconnect
3226   ProjNode* proj2 = proj_clone(proj, iff);
3227   register_node(proj2, loop, iff, ddepth);
3228 
3229   RegionNode* reg = new RegionNode(2);
3230   reg->set_req(1, proj2);
3231   register_node(reg, loop, iff, ddepth);
3232 
3233   IfNode* dum_if = new IfNode(reg, short_circuit_if(nullptr, proj), iff->_prob, iff->_fcnt);
3234   register_node(dum_if, loop, reg, ddepth);
3235 
3236   proj->set_req(0, dum_if); // reattach
3237   set_idom(proj, dum_if, ddepth);
3238 
3239   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
3240   register_node(dum_proj, loop, dum_if, ddepth);
3241 
3242   return reg;
3243 }
3244 
3245 // Idea
3246 // ----
3247 // Partial Peeling tries to rotate the loop in such a way that it can later be turned into a counted loop. Counted loops
3248 // require a signed loop exit test. When calling this method, we've only found a suitable unsigned test to partial peel
3249 // with. Therefore, we try to split off a signed loop exit test from the unsigned test such that it can be used as new
3250 // loop exit while keeping the unsigned test unchanged and preserving the same behavior as if we've used the unsigned
3251 // test alone instead:
3252 //
3253 // Before Partial Peeling:
3254 //   Loop:
3255 //     <peeled section>
3256 //     Split off signed loop exit test
3257 //     <-- CUT HERE -->
3258 //     Unchanged unsigned loop exit test
3259 //     <rest of unpeeled section>
3260 //     goto Loop
3261 //
3262 // After Partial Peeling:
3263 //   <cloned peeled section>
3264 //   Cloned split off signed loop exit test
3265 //   Loop:
3266 //     Unchanged unsigned loop exit test
3267 //     <rest of unpeeled section>
3268 //     <peeled section>
3269 //     Split off signed loop exit test
3270 //     goto Loop
3271 //
3272 // Details
3273 // -------
3274 // Before:
3275 //          if (i <u limit)    Unsigned loop exit condition
3276 //         /       |
3277 //        v        v
3278 //   exit-proj   stay-in-loop-proj
3279 //
3280 // Split off a signed loop exit test (i.e. with CmpI) from an unsigned loop exit test (i.e. with CmpU) and insert it
3281 // before the CmpU on the stay-in-loop path and keep both tests:
3282 //
3283 //          if (i <u limit)    Signed loop exit test
3284 //        /        |
3285 //       /  if (i <u limit)    Unsigned loop exit test
3286 //      /  /       |
3287 //     v  v        v
3288 //  exit-region  stay-in-loop-proj
3289 //
3290 // Implementation
3291 // --------------
3292 // We need to make sure that the new signed loop exit test is properly inserted into the graph such that the unsigned
3293 // loop exit test still dominates the same set of control nodes, the ctrl() relation from data nodes to both loop
3294 // exit tests is preserved, and their loop nesting is correct.
3295 //
3296 // To achieve that, we clone the unsigned loop exit test completely (leave it unchanged), insert the signed loop exit
3297 // test above it and kill the original unsigned loop exit test by setting it's condition to a constant
3298 // (i.e. stay-in-loop-const in graph below) such that IGVN can fold it later:
3299 //
3300 //           if (stay-in-loop-const)  Killed original unsigned loop exit test
3301 //          /       |
3302 //         /        v
3303 //        /  if (i <  limit)          Split off signed loop exit test
3304 //       /  /       |
3305 //      /  /        v
3306 //     /  /  if (i <u limit)          Cloned unsigned loop exit test
3307 //    /  /   /      |
3308 //   v  v  v        |
3309 //  exit-region     |
3310 //        |         |
3311 //    dummy-if      |
3312 //     /  |         |
3313 // dead   |         |
3314 //        v         v
3315 //   exit-proj   stay-in-loop-proj
3316 //
3317 // Note: The dummy-if is inserted to create a region to merge the loop exits between the original to be killed unsigned
3318 //       loop exit test and its exit projection while keeping the exit projection (also see insert_region_before_proj()).
3319 //
3320 // Requirements
3321 // ------------
3322 // Note that we can only split off a signed loop exit test from the unsigned loop exit test when the behavior is exactly
3323 // the same as before with only a single unsigned test. This is only possible if certain requirements are met.
3324 // Otherwise, we need to bail out (see comments in the code below).
3325 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree* loop) {
3326   const bool Signed   = true;
3327   const bool Unsigned = false;
3328 
3329   BoolNode* bol = if_cmpu->in(1)->as_Bool();
3330   if (bol->_test._test != BoolTest::lt) {
3331     return nullptr;
3332   }
3333   CmpNode* cmpu = bol->in(1)->as_Cmp();
3334   assert(cmpu->Opcode() == Op_CmpU, "must be unsigned comparison");
3335 
3336   int stride = stride_of_possible_iv(if_cmpu);
3337   if (stride == 0) {
3338     return nullptr;
3339   }
3340 
3341   Node* lp_proj = stay_in_loop(if_cmpu, loop);
3342   guarantee(lp_proj != nullptr, "null loop node");
3343 
3344   ProjNode* lp_continue = lp_proj->as_Proj();
3345   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
3346   if (!lp_exit->is_IfFalse()) {
3347     // The loop exit condition is (i <u limit) ==> (i >= 0 && i < limit).
3348     // We therefore can't add a single exit condition.
3349     return nullptr;
3350   }
3351   // The unsigned loop exit condition is
3352   //   !(i <u  limit)
3353   // =   i >=u limit
3354   //
3355   // First, we note that for any x for which
3356   //   0 <= x <= INT_MAX
3357   // we can convert x to an unsigned int and still get the same guarantee:
3358   //   0 <=  (uint) x <=  INT_MAX = (uint) INT_MAX
3359   //   0 <=u (uint) x <=u INT_MAX = (uint) INT_MAX   (LEMMA)
3360   //
3361   // With that in mind, if
3362   //   limit >= 0             (COND)
3363   // then the unsigned loop exit condition
3364   //   i >=u limit            (ULE)
3365   // is equivalent to
3366   //   i < 0 || i >= limit    (SLE-full)
3367   // because either i is negative and therefore always greater than MAX_INT when converting to unsigned
3368   //   (uint) i >=u MAX_INT >= limit >= 0
3369   // or otherwise
3370   //   i >= limit >= 0
3371   // holds due to (LEMMA).
3372   //
3373   // For completeness, a counterexample with limit < 0:
3374   // Assume i = -3 and limit = -2:
3375   //   i  < 0
3376   //   -2 < 0
3377   // is true and thus also "i < 0 || i >= limit". But
3378   //   i  >=u limit
3379   //   -3 >=u -2
3380   // is false.
3381   Node* limit = cmpu->in(2);
3382   const TypeInt* type_limit = _igvn.type(limit)->is_int();
3383   if (type_limit->_lo < 0) {
3384     return nullptr;
3385   }
3386 
3387   // We prove below that we can extract a single signed loop exit condition from (SLE-full), depending on the stride:
3388   //   stride < 0:
3389   //     i < 0        (SLE = SLE-negative)
3390   //   stride > 0:
3391   //     i >= limit   (SLE = SLE-positive)
3392   // such that we have the following graph before Partial Peeling with stride > 0 (similar for stride < 0):
3393   //
3394   // Loop:
3395   //   <peeled section>
3396   //   i >= limit    (SLE-positive)
3397   //   <-- CUT HERE -->
3398   //   i >=u limit   (ULE)
3399   //   <rest of unpeeled section>
3400   //   goto Loop
3401   //
3402   // We exit the loop if:
3403   //   (SLE) is true OR (ULE) is true
3404   // However, if (SLE) is true then (ULE) also needs to be true to ensure the exact same behavior. Otherwise, we wrongly
3405   // exit a loop that should not have been exited if we did not apply Partial Peeling. More formally, we need to ensure:
3406   //   (SLE) IMPLIES (ULE)
3407   // This indeed holds when (COND) is given:
3408   // - stride > 0:
3409   //       i >=  limit             // (SLE = SLE-positive)
3410   //       i >=  limit >= 0        // (COND)
3411   //       i >=u limit >= 0        // (LEMMA)
3412   //     which is the unsigned loop exit condition (ULE).
3413   // - stride < 0:
3414   //       i        <  0           // (SLE = SLE-negative)
3415   //       (uint) i >u MAX_INT     // (NEG) all negative values are greater than MAX_INT when converted to unsigned
3416   //       MAX_INT >= limit >= 0   // (COND)
3417   //       MAX_INT >=u limit >= 0  // (LEMMA)
3418   //     and thus from (NEG) and (LEMMA):
3419   //       i >=u limit
3420   //     which is the unsigned loop exit condition (ULE).
3421   //
3422   //
3423   // After Partial Peeling, we have the following structure for stride > 0 (similar for stride < 0):
3424   //   <cloned peeled section>
3425   //   i >= limit (SLE-positive)
3426   //   Loop:
3427   //     i >=u limit (ULE)
3428   //     <rest of unpeeled section>
3429   //     <peeled section>
3430   //     i >= limit (SLE-positive)
3431   //     goto Loop
3432   Node* rhs_cmpi;
3433   if (stride > 0) {
3434     rhs_cmpi = limit; // For i >= limit
3435   } else {
3436     rhs_cmpi = makecon(TypeInt::ZERO); // For i < 0
3437   }
3438   // Create a new region on the exit path
3439   RegionNode* reg = insert_region_before_proj(lp_exit);
3440   guarantee(reg != nullptr, "null region node");
3441 
3442   // Clone the if-cmpu-true-false using a signed compare
3443   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
3444   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, rhs_cmpi, lp_continue);
3445   reg->add_req(cmpi_exit);
3446 
3447   // Clone the if-cmpu-true-false
3448   BoolTest::mask rel_u = bol->_test._test;
3449   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
3450   reg->add_req(cmpu_exit);
3451 
3452   // Force original if to stay in loop.
3453   short_circuit_if(if_cmpu, lp_continue);
3454 
3455   return cmpi_exit->in(0)->as_If();
3456 }
3457 
3458 //------------------------------ remove_cmpi_loop_exit -------------------------------------
3459 // Remove a previously inserted signed compare loop exit.
3460 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
3461   Node* lp_proj = stay_in_loop(if_cmp, loop);
3462   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
3463          stay_in_loop(lp_proj, loop)->is_If() &&
3464          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
3465   Node* con = makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
3466   if_cmp->set_req(1, con);
3467 }
3468 
3469 //------------------------------ scheduled_nodelist -------------------------------------
3470 // Create a post order schedule of nodes that are in the
3471 // "member" set.  The list is returned in "sched".
3472 // The first node in "sched" is the loop head, followed by
3473 // nodes which have no inputs in the "member" set, and then
3474 // followed by the nodes that have an immediate input dependence
3475 // on a node in "sched".
3476 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
3477 
3478   assert(member.test(loop->_head->_idx), "loop head must be in member set");
3479   VectorSet visited;
3480   Node_Stack nstack(loop->_body.size());
3481 
3482   Node* n  = loop->_head;  // top of stack is cached in "n"
3483   uint idx = 0;
3484   visited.set(n->_idx);
3485 
3486   // Initially push all with no inputs from within member set
3487   for(uint i = 0; i < loop->_body.size(); i++ ) {
3488     Node *elt = loop->_body.at(i);
3489     if (member.test(elt->_idx)) {
3490       bool found = false;
3491       for (uint j = 0; j < elt->req(); j++) {
3492         Node* def = elt->in(j);
3493         if (def && member.test(def->_idx) && def != elt) {
3494           found = true;
3495           break;
3496         }
3497       }
3498       if (!found && elt != loop->_head) {
3499         nstack.push(n, idx);
3500         n = elt;
3501         assert(!visited.test(n->_idx), "not seen yet");
3502         visited.set(n->_idx);
3503       }
3504     }
3505   }
3506 
3507   // traverse out's that are in the member set
3508   while (true) {
3509     if (idx < n->outcnt()) {
3510       Node* use = n->raw_out(idx);
3511       idx++;
3512       if (!visited.test_set(use->_idx)) {
3513         if (member.test(use->_idx)) {
3514           nstack.push(n, idx);
3515           n = use;
3516           idx = 0;
3517         }
3518       }
3519     } else {
3520       // All outputs processed
3521       sched.push(n);
3522       if (nstack.is_empty()) break;
3523       n   = nstack.node();
3524       idx = nstack.index();
3525       nstack.pop();
3526     }
3527   }
3528 }
3529 
3530 
3531 //------------------------------ has_use_in_set -------------------------------------
3532 // Has a use in the vector set
3533 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
3534   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3535     Node* use = n->fast_out(j);
3536     if (vset.test(use->_idx)) {
3537       return true;
3538     }
3539   }
3540   return false;
3541 }
3542 
3543 
3544 //------------------------------ has_use_internal_to_set -------------------------------------
3545 // Has use internal to the vector set (ie. not in a phi at the loop head)
3546 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
3547   Node* head  = loop->_head;
3548   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3549     Node* use = n->fast_out(j);
3550     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
3551       return true;
3552     }
3553   }
3554   return false;
3555 }
3556 
3557 
3558 //------------------------------ clone_for_use_outside_loop -------------------------------------
3559 // clone "n" for uses that are outside of loop
3560 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
3561   int cloned = 0;
3562   assert(worklist.size() == 0, "should be empty");
3563   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3564     Node* use = n->fast_out(j);
3565     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
3566       worklist.push(use);
3567     }
3568   }
3569 
3570   if (C->check_node_count(worklist.size() + NodeLimitFudgeFactor,
3571                           "Too many clones required in clone_for_use_outside_loop in partial peeling")) {
3572     return -1;
3573   }
3574 
3575   while( worklist.size() ) {
3576     Node *use = worklist.pop();
3577     if (!has_node(use) || use->in(0) == C->top()) continue;
3578     uint j;
3579     for (j = 0; j < use->req(); j++) {
3580       if (use->in(j) == n) break;
3581     }
3582     assert(j < use->req(), "must be there");
3583 
3584     // clone "n" and insert it between the inputs of "n" and the use outside the loop
3585     Node* n_clone = n->clone();
3586     _igvn.replace_input_of(use, j, n_clone);
3587     cloned++;
3588     Node* use_c;
3589     if (!use->is_Phi()) {
3590       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
3591     } else {
3592       // Use in a phi is considered a use in the associated predecessor block
3593       use_c = use->in(0)->in(j);
3594     }
3595     set_ctrl(n_clone, use_c);
3596     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
3597     get_loop(use_c)->_body.push(n_clone);
3598     _igvn.register_new_node_with_optimizer(n_clone);
3599 #ifndef PRODUCT
3600     if (TracePartialPeeling) {
3601       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
3602     }
3603 #endif
3604   }
3605   return cloned;
3606 }
3607 
3608 
3609 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
3610 // clone "n" for special uses that are in the not_peeled region.
3611 // If these def-uses occur in separate blocks, the code generator
3612 // marks the method as not compilable.  For example, if a "BoolNode"
3613 // is in a different basic block than the "IfNode" that uses it, then
3614 // the compilation is aborted in the code generator.
3615 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
3616                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
3617   if (n->is_Phi() || n->is_Load()) {
3618     return;
3619   }
3620   assert(worklist.size() == 0, "should be empty");
3621   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3622     Node* use = n->fast_out(j);
3623     if ( not_peel.test(use->_idx) &&
3624          (use->is_If() || use->is_CMove() || use->is_Bool() || use->is_OpaqueInitializedAssertionPredicate()) &&
3625          use->in(1) == n)  {
3626       worklist.push(use);
3627     }
3628   }
3629   if (worklist.size() > 0) {
3630     // clone "n" and insert it between inputs of "n" and the use
3631     Node* n_clone = n->clone();
3632     loop->_body.push(n_clone);
3633     _igvn.register_new_node_with_optimizer(n_clone);
3634     set_ctrl(n_clone, get_ctrl(n));
3635     sink_list.push(n_clone);
3636     not_peel.set(n_clone->_idx);
3637 #ifndef PRODUCT
3638     if (TracePartialPeeling) {
3639       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
3640     }
3641 #endif
3642     while( worklist.size() ) {
3643       Node *use = worklist.pop();
3644       _igvn.rehash_node_delayed(use);
3645       for (uint j = 1; j < use->req(); j++) {
3646         if (use->in(j) == n) {
3647           use->set_req(j, n_clone);
3648         }
3649       }
3650     }
3651   }
3652 }
3653 
3654 
3655 //------------------------------ insert_phi_for_loop -------------------------------------
3656 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
3657 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
3658   Node *phi = PhiNode::make(lp, back_edge_val);
3659   phi->set_req(LoopNode::EntryControl, lp_entry_val);
3660   // Use existing phi if it already exists
3661   Node *hit = _igvn.hash_find_insert(phi);
3662   if( hit == nullptr ) {
3663     _igvn.register_new_node_with_optimizer(phi);
3664     set_ctrl(phi, lp);
3665   } else {
3666     // Remove the new phi from the graph and use the hit
3667     _igvn.remove_dead_node(phi, PhaseIterGVN::NodeOrigin::Speculative);
3668     phi = hit;
3669   }
3670   _igvn.replace_input_of(use, idx, phi);
3671 }
3672 
3673 #ifdef ASSERT
3674 //------------------------------ is_valid_loop_partition -------------------------------------
3675 // Validate the loop partition sets: peel and not_peel
3676 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
3677                                               VectorSet& not_peel ) {
3678   uint i;
3679   // Check that peel_list entries are in the peel set
3680   for (i = 0; i < peel_list.size(); i++) {
3681     if (!peel.test(peel_list.at(i)->_idx)) {
3682       return false;
3683     }
3684   }
3685   // Check at loop members are in one of peel set or not_peel set
3686   for (i = 0; i < loop->_body.size(); i++ ) {
3687     Node *def  = loop->_body.at(i);
3688     uint di = def->_idx;
3689     // Check that peel set elements are in peel_list
3690     if (peel.test(di)) {
3691       if (not_peel.test(di)) {
3692         return false;
3693       }
3694       // Must be in peel_list also
3695       bool found = false;
3696       for (uint j = 0; j < peel_list.size(); j++) {
3697         if (peel_list.at(j)->_idx == di) {
3698           found = true;
3699           break;
3700         }
3701       }
3702       if (!found) {
3703         return false;
3704       }
3705     } else if (not_peel.test(di)) {
3706       if (peel.test(di)) {
3707         return false;
3708       }
3709     } else {
3710       return false;
3711     }
3712   }
3713   return true;
3714 }
3715 
3716 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
3717 // Ensure a use outside of loop is of the right form
3718 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
3719   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3720   return (use->is_Phi() &&
3721           use_c->is_Region() && use_c->req() == 3 &&
3722           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
3723            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
3724            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
3725           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
3726 }
3727 
3728 //------------------------------ is_valid_clone_loop_form -------------------------------------
3729 // Ensure that all uses outside of loop are of the right form
3730 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
3731                                                uint orig_exit_idx, uint clone_exit_idx) {
3732   uint len = peel_list.size();
3733   for (uint i = 0; i < len; i++) {
3734     Node *def = peel_list.at(i);
3735 
3736     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
3737       Node *use = def->fast_out(j);
3738       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3739       if (!loop->is_member(get_loop(use_c))) {
3740         // use is not in the loop, check for correct structure
3741         if (use->in(0) == def) {
3742           // Okay
3743         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
3744           return false;
3745         }
3746       }
3747     }
3748   }
3749   return true;
3750 }
3751 #endif
3752 
3753 //------------------------------ partial_peel -------------------------------------
3754 // Partially peel (aka loop rotation) the top portion of a loop (called
3755 // the peel section below) by cloning it and placing one copy just before
3756 // the new loop head and the other copy at the bottom of the new loop.
3757 //
3758 //    before                       after                where it came from
3759 //
3760 //    stmt1                        stmt1
3761 //  loop:                          stmt2                     clone
3762 //    stmt2                        if condA goto exitA       clone
3763 //    if condA goto exitA        new_loop:                   new
3764 //    stmt3                        stmt3                     clone
3765 //    if !condB goto loop          if condB goto exitB       clone
3766 //  exitB:                         stmt2                     orig
3767 //    stmt4                        if !condA goto new_loop   orig
3768 //  exitA:                         goto exitA
3769 //                               exitB:
3770 //                                 stmt4
3771 //                               exitA:
3772 //
3773 // Step 1: find the cut point: an exit test on probable
3774 //         induction variable.
3775 // Step 2: schedule (with cloning) operations in the peel
3776 //         section that can be executed after the cut into
3777 //         the section that is not peeled.  This may need
3778 //         to clone operations into exit blocks.  For
3779 //         instance, a reference to A[i] in the not-peel
3780 //         section and a reference to B[i] in an exit block
3781 //         may cause a left-shift of i by 2 to be placed
3782 //         in the peel block.  This step will clone the left
3783 //         shift into the exit block and sink the left shift
3784 //         from the peel to the not-peel section.
3785 // Step 3: clone the loop, retarget the control, and insert
3786 //         phis for values that are live across the new loop
3787 //         head.  This is very dependent on the graph structure
3788 //         from clone_loop.  It creates region nodes for
3789 //         exit control and associated phi nodes for values
3790 //         flow out of the loop through that exit.  The region
3791 //         node is dominated by the clone's control projection.
3792 //         So the clone's peel section is placed before the
3793 //         new loop head, and the clone's not-peel section is
3794 //         forms the top part of the new loop.  The original
3795 //         peel section forms the tail of the new loop.
3796 // Step 4: update the dominator tree and recompute the
3797 //         dominator depth.
3798 //
3799 //                   orig
3800 //
3801 //                   stmt1
3802 //                     |
3803 //                     v
3804 //                 predicates
3805 //                     |
3806 //                     v
3807 //                   loop<----+
3808 //                     |      |
3809 //                   stmt2    |
3810 //                     |      |
3811 //                     v      |
3812 //                    ifA     |
3813 //                   / |      |
3814 //                  v  v      |
3815 //               false true   ^  <-- last_peel
3816 //               /     |      |
3817 //              /   ===|==cut |
3818 //             /     stmt3    |  <-- first_not_peel
3819 //            /        |      |
3820 //            |        v      |
3821 //            v       ifB     |
3822 //          exitA:   / \      |
3823 //                  /   \     |
3824 //                 v     v    |
3825 //               false true   |
3826 //               /       \    |
3827 //              /         ----+
3828 //             |
3829 //             v
3830 //           exitB:
3831 //           stmt4
3832 //
3833 //
3834 //            after clone loop
3835 //
3836 //                   stmt1
3837 //                     |
3838 //                     v
3839 //                predicates
3840 //                 /       \
3841 //        clone   /         \   orig
3842 //               /           \
3843 //              /             \
3844 //             v               v
3845 //   +---->loop                loop<----+
3846 //   |      |                    |      |
3847 //   |    stmt2                stmt2    |
3848 //   |      |                    |      |
3849 //   |      v                    v      |
3850 //   |      ifA                 ifA     |
3851 //   |      | \                / |      |
3852 //   |      v  v              v  v      |
3853 //   ^    true  false      false true   ^  <-- last_peel
3854 //   |      |   ^   \       /    |      |
3855 //   | cut==|==  \   \     /  ===|==cut |
3856 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
3857 //   |      |    dom   | |       |      |
3858 //   |      v      \  1v v2      v      |
3859 //   |      ifB     regionA     ifB     |
3860 //   |      / \        |       / \      |
3861 //   |     /   \       v      /   \     |
3862 //   |    v     v    exitA:  v     v    |
3863 //   |    true  false      false true   |
3864 //   |    /     ^   \      /       \    |
3865 //   +----       \   \    /         ----+
3866 //               dom  \  /
3867 //                 \  1v v2
3868 //                  regionB
3869 //                     |
3870 //                     v
3871 //                   exitB:
3872 //                   stmt4
3873 //
3874 //
3875 //           after partial peel
3876 //
3877 //                  stmt1
3878 //                     |
3879 //                     v
3880 //                predicates
3881 //                 /
3882 //        clone   /             orig
3883 //               /          TOP
3884 //              /             \
3885 //             v               v
3886 //    TOP->loop                loop----+
3887 //          |                    |      |
3888 //        stmt2                stmt2    |
3889 //          |                    |      |
3890 //          v                    v      |
3891 //          ifA                 ifA     |
3892 //          | \                / |      |
3893 //          v  v              v  v      |
3894 //        true  false      false true   |     <-- last_peel
3895 //          |   ^   \       /    +------|---+
3896 //  +->newloop   \   \     /  === ==cut |   |
3897 //  |     stmt3   \   \   /     TOP     |   |
3898 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
3899 //  |       v      \  1v v2      v      |   |
3900 //  |       ifB     regionA     ifB     ^   v
3901 //  |       / \        |       / \      |   |
3902 //  |      /   \       v      /   \     |   |
3903 //  |     v     v    exitA:  v     v    |   |
3904 //  |     true  false      false true   |   |
3905 //  |     /     ^   \      /       \    |   |
3906 //  |    |       \   \    /         v   |   |
3907 //  |    |       dom  \  /         TOP  |   |
3908 //  |    |         \  1v v2             |   |
3909 //  ^    v          regionB             |   |
3910 //  |    |             |                |   |
3911 //  |    |             v                ^   v
3912 //  |    |           exitB:             |   |
3913 //  |    |           stmt4              |   |
3914 //  |    +------------>-----------------+   |
3915 //  |                                       |
3916 //  +-----------------<---------------------+
3917 //
3918 //
3919 //              final graph
3920 //
3921 //                  stmt1
3922 //                    |
3923 //                    v
3924 //                predicates
3925 //                    |
3926 //                    v
3927 //                  stmt2 clone
3928 //                    |
3929 //                    v
3930 //         ........> ifA clone
3931 //         :        / |
3932 //        dom      /  |
3933 //         :      v   v
3934 //         :  false   true
3935 //         :  |       |
3936 //         :  |       v
3937 //         :  |    newloop<-----+
3938 //         :  |        |        |
3939 //         :  |     stmt3 clone |
3940 //         :  |        |        |
3941 //         :  |        v        |
3942 //         :  |       ifB       |
3943 //         :  |      / \        |
3944 //         :  |     v   v       |
3945 //         :  |  false true     |
3946 //         :  |   |     |       |
3947 //         :  |   v    stmt2    |
3948 //         :  | exitB:  |       |
3949 //         :  | stmt4   v       |
3950 //         :  |       ifA orig  |
3951 //         :  |      /  \       |
3952 //         :  |     /    \      |
3953 //         :  |    v     v      |
3954 //         :  |  false  true    |
3955 //         :  |  /        \     |
3956 //         :  v  v         -----+
3957 //          RegionA
3958 //             |
3959 //             v
3960 //           exitA
3961 //
3962 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
3963 
3964   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
3965   if (!loop->_head->is_Loop()) {
3966     return false;
3967   }
3968   LoopNode *head = loop->_head->as_Loop();
3969 
3970   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
3971     return false;
3972   }
3973 
3974   // Check for complex exit control
3975   for (uint ii = 0; ii < loop->_body.size(); ii++) {
3976     Node *n = loop->_body.at(ii);
3977     int opc = n->Opcode();
3978     if (n->is_Call()        ||
3979         opc == Op_Catch     ||
3980         opc == Op_CatchProj ||
3981         opc == Op_Jump      ||
3982         opc == Op_JumpProj) {
3983 #ifndef PRODUCT
3984       if (TracePartialPeeling) {
3985         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
3986       }
3987 #endif
3988       return false;
3989     }
3990   }
3991 
3992   int dd = dom_depth(head);
3993 
3994   // Step 1: find cut point
3995 
3996   // Walk up dominators to loop head looking for first loop exit
3997   // which is executed on every path thru loop.
3998   IfNode *peel_if = nullptr;
3999   IfNode *peel_if_cmpu = nullptr;
4000 
4001   Node *iff = loop->tail();
4002   while (iff != head) {
4003     if (iff->is_If()) {
4004       Node *ctrl = get_ctrl(iff->in(1));
4005       if (ctrl->is_top()) return false; // Dead test on live IF.
4006       // If loop-varying exit-test, check for induction variable
4007       if (loop->is_member(get_loop(ctrl)) &&
4008           loop->is_loop_exit(iff) &&
4009           is_possible_iv_test(iff)) {
4010         Node* cmp = iff->in(1)->in(1);
4011         if (cmp->Opcode() == Op_CmpI) {
4012           peel_if = iff->as_If();
4013         } else {
4014           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
4015           peel_if_cmpu = iff->as_If();
4016         }
4017       }
4018     }
4019     iff = idom(iff);
4020   }
4021 
4022   // Prefer signed compare over unsigned compare.
4023   IfNode* new_peel_if = nullptr;
4024   if (peel_if == nullptr) {
4025     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == nullptr) {
4026       return false;   // No peel point found
4027     }
4028     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
4029     if (new_peel_if == nullptr) {
4030       return false;   // No peel point found
4031     }
4032     peel_if = new_peel_if;
4033   }
4034   Node* last_peel        = stay_in_loop(peel_if, loop);
4035   Node* first_not_peeled = stay_in_loop(last_peel, loop);
4036   if (first_not_peeled == nullptr || first_not_peeled == head) {
4037     return false;
4038   }
4039 
4040 #ifndef PRODUCT
4041   if (TraceLoopOpts) {
4042     tty->print("PartialPeel  ");
4043     loop->dump_head();
4044   }
4045 
4046   if (TracePartialPeeling) {
4047     tty->print_cr("before partial peel one iteration");
4048     Node_List wl;
4049     Node* t = head->in(2);
4050     while (true) {
4051       wl.push(t);
4052       if (t == head) break;
4053       t = idom(t);
4054     }
4055     while (wl.size() > 0) {
4056       Node* tt = wl.pop();
4057       tt->dump();
4058       if (tt == last_peel) tty->print_cr("-- cut --");
4059     }
4060   }
4061 #endif
4062 
4063   C->print_method(PHASE_BEFORE_PARTIAL_PEELING, 4, head);
4064 
4065   VectorSet peel;
4066   VectorSet not_peel;
4067   Node_List peel_list;
4068   Node_List worklist;
4069   Node_List sink_list;
4070 
4071   uint estimate = loop->est_loop_clone_sz(1);
4072   if (exceeding_node_budget(estimate)) {
4073     return false;
4074   }
4075 
4076   // Set of cfg nodes to peel are those that are executable from
4077   // the head through last_peel.
4078   assert(worklist.size() == 0, "should be empty");
4079   worklist.push(head);
4080   peel.set(head->_idx);
4081   while (worklist.size() > 0) {
4082     Node *n = worklist.pop();
4083     if (n != last_peel) {
4084       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
4085         Node* use = n->fast_out(j);
4086         if (use->is_CFG() &&
4087             loop->is_member(get_loop(use)) &&
4088             !peel.test_set(use->_idx)) {
4089           worklist.push(use);
4090         }
4091       }
4092     }
4093   }
4094 
4095   // Set of non-cfg nodes to peel are those that are control
4096   // dependent on the cfg nodes.
4097   for (uint i = 0; i < loop->_body.size(); i++) {
4098     Node *n = loop->_body.at(i);
4099     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
4100     if (peel.test(n_c->_idx)) {
4101       peel.set(n->_idx);
4102     } else {
4103       not_peel.set(n->_idx);
4104     }
4105   }
4106 
4107   // Step 2: move operations from the peeled section down into the
4108   //         not-peeled section
4109 
4110   // Get a post order schedule of nodes in the peel region
4111   // Result in right-most operand.
4112   scheduled_nodelist(loop, peel, peel_list);
4113 
4114   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4115 
4116   // For future check for too many new phis
4117   uint old_phi_cnt = 0;
4118   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
4119     Node* use = head->fast_out(j);
4120     if (use->is_Phi()) old_phi_cnt++;
4121   }
4122 
4123 #ifndef PRODUCT
4124   if (TracePartialPeeling) {
4125     tty->print_cr("\npeeled list");
4126   }
4127 #endif
4128 
4129   // Evacuate nodes in peel region into the not_peeled region if possible
4130   bool too_many_clones = false;
4131   uint new_phi_cnt = 0;
4132   uint cloned_for_outside_use = 0;
4133   for (uint i = 0; i < peel_list.size();) {
4134     Node* n = peel_list.at(i);
4135 #ifndef PRODUCT
4136   if (TracePartialPeeling) n->dump();
4137 #endif
4138     bool incr = true;
4139     if (!n->is_CFG()) {
4140       if (has_use_in_set(n, not_peel)) {
4141         // If not used internal to the peeled region,
4142         // move "n" from peeled to not_peeled region.
4143         if (!has_use_internal_to_set(n, peel, loop)) {
4144           // if not pinned and not a load (which maybe anti-dependent on a store)
4145           // and not a CMove (Matcher expects only bool->cmove).
4146           if (n->in(0) == nullptr && !n->is_Load() && !n->is_CMove()) {
4147             int new_clones = clone_for_use_outside_loop(loop, n, worklist);
4148             if (C->failing()) return false;
4149             if (new_clones == -1) {
4150               too_many_clones = true;
4151               break;
4152             }
4153             cloned_for_outside_use += new_clones;
4154             sink_list.push(n);
4155             peel.remove(n->_idx);
4156             not_peel.set(n->_idx);
4157             peel_list.remove(i);
4158             incr = false;
4159 #ifndef PRODUCT
4160             if (TracePartialPeeling) {
4161               tty->print_cr("sink to not_peeled region: %d newbb: %d",
4162                             n->_idx, get_ctrl(n)->_idx);
4163             }
4164 #endif
4165           }
4166         } else {
4167           // Otherwise check for special def-use cases that span
4168           // the peel/not_peel boundary such as bool->if
4169           clone_for_special_use_inside_loop(loop, n, not_peel, sink_list, worklist);
4170           new_phi_cnt++;
4171         }
4172       }
4173     }
4174     if (incr) i++;
4175   }
4176 
4177   estimate += cloned_for_outside_use + new_phi_cnt;
4178   bool exceed_node_budget = !may_require_nodes(estimate);
4179   bool exceed_phi_limit = new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta;
4180 
4181   if (too_many_clones || exceed_node_budget || exceed_phi_limit) {
4182 #ifndef PRODUCT
4183     if (TracePartialPeeling && exceed_phi_limit) {
4184       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
4185                     new_phi_cnt, old_phi_cnt, new_peel_if != nullptr?'T':'F');
4186     }
4187 #endif
4188     if (new_peel_if != nullptr) {
4189       remove_cmpi_loop_exit(new_peel_if, loop);
4190     }
4191     // Inhibit more partial peeling on this loop
4192     assert(!head->is_partial_peel_loop(), "not partial peeled");
4193     head->mark_partial_peel_failed();
4194     if (cloned_for_outside_use > 0) {
4195       // Terminate this round of loop opts because
4196       // the graph outside this loop was changed.
4197       C->set_major_progress();
4198       return true;
4199     }
4200     return false;
4201   }
4202 
4203   // Step 3: clone loop, retarget control, and insert new phis
4204 
4205   // Create new loop head for new phis and to hang
4206   // the nodes being moved (sinked) from the peel region.
4207   LoopNode* new_head = new LoopNode(last_peel, last_peel);
4208   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
4209   _igvn.register_new_node_with_optimizer(new_head);
4210   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
4211   _igvn.replace_input_of(first_not_peeled, 0, new_head);
4212   set_loop(new_head, loop);
4213   loop->_body.push(new_head);
4214   not_peel.set(new_head->_idx);
4215   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
4216   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
4217 
4218   while (sink_list.size() > 0) {
4219     Node* n = sink_list.pop();
4220     set_ctrl(n, new_head);
4221   }
4222 
4223   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4224 
4225   clone_loop(loop, old_new, dd, IgnoreStripMined);
4226 
4227   const uint clone_exit_idx = 1;
4228   const uint orig_exit_idx  = 2;
4229   assert(is_valid_clone_loop_form(loop, peel_list, orig_exit_idx, clone_exit_idx), "bad clone loop");
4230 
4231   Node* head_clone             = old_new[head->_idx];
4232   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
4233   Node* orig_tail_clone        = head_clone->in(2);
4234 
4235   // Add phi if "def" node is in peel set and "use" is not
4236 
4237   for (uint i = 0; i < peel_list.size(); i++) {
4238     Node *def  = peel_list.at(i);
4239     if (!def->is_CFG()) {
4240       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
4241         Node *use = def->fast_out(j);
4242         if (has_node(use) && use->in(0) != C->top() &&
4243             (!peel.test(use->_idx) ||
4244              (use->is_Phi() && use->in(0) == head)) ) {
4245           worklist.push(use);
4246         }
4247       }
4248       while( worklist.size() ) {
4249         Node *use = worklist.pop();
4250         for (uint j = 1; j < use->req(); j++) {
4251           Node* n = use->in(j);
4252           if (n == def) {
4253 
4254             // "def" is in peel set, "use" is not in peel set
4255             // or "use" is in the entry boundary (a phi) of the peel set
4256 
4257             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
4258 
4259             if ( loop->is_member(get_loop( use_c )) ) {
4260               // use is in loop
4261               if (old_new[use->_idx] != nullptr) { // null for dead code
4262                 Node* use_clone = old_new[use->_idx];
4263                 _igvn.replace_input_of(use, j, C->top());
4264                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
4265               }
4266             } else {
4267               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
4268               // use is not in the loop, check if the live range includes the cut
4269               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
4270               if (not_peel.test(lp_if->_idx)) {
4271                 assert(j == orig_exit_idx, "use from original loop");
4272                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
4273               }
4274             }
4275           }
4276         }
4277       }
4278     }
4279   }
4280 
4281   // Step 3b: retarget control
4282 
4283   // Redirect control to the new loop head if a cloned node in
4284   // the not_peeled region has control that points into the peeled region.
4285   // This necessary because the cloned peeled region will be outside
4286   // the loop.
4287   //                            from    to
4288   //          cloned-peeled    <---+
4289   //    new_head_clone:            |    <--+
4290   //          cloned-not_peeled  in(0)    in(0)
4291   //          orig-peeled
4292 
4293   for (uint i = 0; i < loop->_body.size(); i++) {
4294     Node *n = loop->_body.at(i);
4295     if (!n->is_CFG()           && n->in(0) != nullptr        &&
4296         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
4297       Node* n_clone = old_new[n->_idx];
4298       if (n_clone->depends_only_on_test()) {
4299         // If this node depends_only_on_test, it will be rewire to the loop head, which is not the
4300         // correct test
4301         Node* pinned_clone = n_clone->pin_node_under_control();
4302         if (pinned_clone != nullptr) {
4303           register_new_node_with_ctrl_of(pinned_clone, n_clone);
4304           old_new.map(n->_idx, pinned_clone);
4305           _igvn.replace_node(n_clone, pinned_clone);
4306           n_clone = pinned_clone;
4307         }
4308       }
4309       _igvn.replace_input_of(n_clone, 0, new_head_clone);
4310     }
4311   }
4312 
4313   // Backedge of the surviving new_head (the clone) is original last_peel
4314   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
4315 
4316   // Cut first node in original not_peel set
4317   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
4318   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
4319   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
4320 
4321   // Copy head_clone back-branch info to original head
4322   // and remove original head's loop entry and
4323   // clone head's back-branch
4324   _igvn.rehash_node_delayed(head); // Multiple edge updates
4325   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
4326   head->set_req(LoopNode::LoopBackControl, C->top());
4327   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
4328 
4329   // Similarly modify the phis
4330   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
4331     Node* use = head->fast_out(k);
4332     if (use->is_Phi() && use->outcnt() > 0) {
4333       Node* use_clone = old_new[use->_idx];
4334       _igvn.rehash_node_delayed(use); // Multiple edge updates
4335       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
4336       use->set_req(LoopNode::LoopBackControl, C->top());
4337       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
4338     }
4339   }
4340 
4341   // Step 4: update dominator tree and dominator depth
4342 
4343   set_idom(head, orig_tail_clone, dd);
4344   recompute_dom_depth();
4345 
4346   // Inhibit more partial peeling on this loop
4347   new_head_clone->set_partial_peel_loop();
4348   C->set_major_progress();
4349   loop->record_for_igvn();
4350 
4351 #ifndef PRODUCT
4352   if (TracePartialPeeling) {
4353     tty->print_cr("\nafter partial peel one iteration");
4354     Node_List wl;
4355     Node* t = last_peel;
4356     while (true) {
4357       wl.push(t);
4358       if (t == head_clone) break;
4359       t = idom(t);
4360     }
4361     while (wl.size() > 0) {
4362       Node* tt = wl.pop();
4363       if (tt == head) tty->print_cr("orig head");
4364       else if (tt == new_head_clone) tty->print_cr("new head");
4365       else if (tt == head_clone) tty->print_cr("clone head");
4366       tt->dump();
4367     }
4368   }
4369 #endif
4370 
4371   C->print_method(PHASE_AFTER_PARTIAL_PEELING, 4, new_head_clone);
4372 
4373   return true;
4374 }
4375 
4376 #ifdef ASSERT
4377 
4378 // Moves Template Assertion Predicates to a target loop by cloning and killing the old ones. The target loop is the
4379 // original, not-cloned loop. This is currently only used with StressLoopBackedge which is a develop flag only and
4380 // false with product builds. We can therefore guard it with an ifdef. More details can be found at the use-site.
4381 class MoveAssertionPredicatesVisitor : public PredicateVisitor {
4382   ClonePredicateToTargetLoop _clone_predicate_to_loop;
4383   PhaseIdealLoop* const _phase;
4384 
4385 public:
4386   MoveAssertionPredicatesVisitor(LoopNode* target_loop_head,
4387                                  const NodeInSingleLoopBody &node_in_loop_body,
4388                                  PhaseIdealLoop* phase)
4389     : _clone_predicate_to_loop(target_loop_head, node_in_loop_body, phase),
4390       _phase(phase) {
4391   }
4392   NONCOPYABLE(MoveAssertionPredicatesVisitor);
4393 
4394   using PredicateVisitor::visit;
4395 
4396   void visit(const TemplateAssertionPredicate& template_assertion_predicate) override {
4397     _clone_predicate_to_loop.clone_template_assertion_predicate(template_assertion_predicate);
4398     template_assertion_predicate.kill(_phase->igvn());
4399   }
4400 };
4401 #endif // ASSERT
4402 
4403 // Transform:
4404 //
4405 // loop<-----------------+
4406 //  |                    |
4407 // stmt1 stmt2 .. stmtn  |
4408 //  |     |        |     |
4409 //  \     |       /      |
4410 //    v   v     v        |
4411 //       region          |
4412 //         |             |
4413 //     shared_stmt       |
4414 //         |             |
4415 //         v             |
4416 //         if            |
4417 //         / \           |
4418 //        |   -----------+
4419 //        v
4420 //
4421 // into:
4422 //
4423 //    loop<-------------------+
4424 //     |                      |
4425 //     v                      |
4426 // +->loop                    |
4427 // |   |                      |
4428 // |  stmt1 stmt2 .. stmtn    |
4429 // |   |     |        |       |
4430 // |   |      \       /       |
4431 // |   |       v     v        |
4432 // |   |        region1       |
4433 // |   |           |          |
4434 // |  shared_stmt shared_stmt |
4435 // |   |           |          |
4436 // |   v           v          |
4437 // |   if          if         |
4438 // |   /\          / \        |
4439 // +--   |         |   -------+
4440 //       \         /
4441 //        v       v
4442 //         region2
4443 //
4444 // (region2 is shown to merge mirrored projections of the loop exit
4445 // ifs to make the diagram clearer but they really merge the same
4446 // projection)
4447 //
4448 // Conditions for this transformation to trigger:
4449 // - the path through stmt1 is frequent enough
4450 // - the inner loop will be turned into a counted loop after transformation
4451 bool PhaseIdealLoop::duplicate_loop_backedge(IdealLoopTree *loop, Node_List &old_new) {
4452   if (!DuplicateBackedge) {
4453     return false;
4454   }
4455   assert(!loop->_head->is_CountedLoop() || StressDuplicateBackedge, "Non-counted loop only");
4456   if (!loop->_head->is_Loop()) {
4457     return false;
4458   }
4459 
4460   uint estimate = loop->est_loop_clone_sz(1);
4461   if (exceeding_node_budget(estimate)) {
4462     return false;
4463   }
4464 
4465   LoopNode *head = loop->_head->as_Loop();
4466 
4467   Node* region = nullptr;
4468   IfNode* exit_test = nullptr;
4469   uint inner;
4470   float f;
4471 #ifdef ASSERT
4472   if (StressDuplicateBackedge) {
4473     if (head->is_strip_mined()) {
4474       return false;
4475     }
4476     Node* c = head->in(LoopNode::LoopBackControl);
4477 
4478     while (c != head) {
4479       if (c->is_Region()) {
4480         region = c;
4481       }
4482       c = idom(c);
4483     }
4484 
4485     if (region == nullptr) {
4486       return false;
4487     }
4488 
4489     inner = 1;
4490   } else
4491 #endif //ASSERT
4492   {
4493     // Is the shape of the loop that of a counted loop...
4494     Node* back_control = loop_exit_control(loop);
4495     if (back_control == nullptr) {
4496       return false;
4497     }
4498 
4499     LoopExitTest loop_exit(back_control, loop, this);
4500     loop_exit.build();
4501     if (!loop_exit.is_valid_with_bt(T_INT)) {
4502       return false;
4503     }
4504 
4505     const Node* loop_incr = loop_exit.incr();
4506 
4507     // With an extra phi for the candidate iv?
4508     // Or the region node is the loop head
4509     if (!loop_incr->is_Phi() || loop_incr->in(0) == head) {
4510       return false;
4511     }
4512 
4513     PathFrequency pf(head, this);
4514     region = loop_incr->in(0);
4515 
4516     // Go over all paths for the extra phi's region and see if that
4517     // path is frequent enough and would match the expected iv shape
4518     // if the extra phi is removed
4519     inner = 0;
4520     for (uint i = 1; i < loop_incr->req(); ++i) {
4521       CountedLoopConverter::TruncatedIncrement increment(T_INT);
4522       increment.build(loop_incr->in(i));
4523       if (!increment.is_valid()) {
4524         continue;
4525       }
4526       assert(increment.incr()->Opcode() == Op_AddI, "wrong increment code");
4527 
4528       LoopIVStride stride = LoopIVStride(T_INT);
4529       stride.build(increment.incr());
4530       if (!stride.is_valid()) {
4531         continue;
4532       }
4533 
4534       PhiNode* phi = loop_iv_phi(stride.xphi(), nullptr, head);
4535       if (phi == nullptr ||
4536           (increment.outer_trunc() == nullptr && phi->in(LoopNode::LoopBackControl) != loop_exit.incr()) ||
4537           (increment.outer_trunc() != nullptr && phi->in(LoopNode::LoopBackControl) != increment.outer_trunc())) {
4538         return false;
4539       }
4540 
4541       f = pf.to(region->in(i));
4542       if (f > 0.5) {
4543         inner = i;
4544         break;
4545       }
4546     }
4547 
4548     if (inner == 0) {
4549       return false;
4550     }
4551 
4552     exit_test = back_control->in(0)->as_If();
4553   }
4554 
4555   if (idom(region)->is_Catch()) {
4556     return false;
4557   }
4558 
4559   // Collect all control nodes that need to be cloned (shared_stmt in the diagram)
4560   Unique_Node_List wq;
4561   wq.push(head->in(LoopNode::LoopBackControl));
4562   for (uint i = 0; i < wq.size(); i++) {
4563     Node* c = wq.at(i);
4564     assert(get_loop(c) == loop, "not in the right loop?");
4565     if (c->is_Region()) {
4566       if (c != region) {
4567         for (uint j = 1; j < c->req(); ++j) {
4568           wq.push(c->in(j));
4569         }
4570       }
4571     } else {
4572       wq.push(c->in(0));
4573     }
4574     assert(!is_strict_dominator(c, region), "shouldn't go above region");
4575   }
4576 
4577   Node* region_dom = idom(region);
4578 
4579   // Can't do the transformation if this would cause a membar pair to
4580   // be split
4581   for (uint i = 0; i < wq.size(); i++) {
4582     Node* c = wq.at(i);
4583     if (c->is_MemBar() && (c->as_MemBar()->trailing_store() || c->as_MemBar()->trailing_load_store())) {
4584       assert(c->as_MemBar()->leading_membar()->trailing_membar() == c, "bad membar pair");
4585       if (!wq.member(c->as_MemBar()->leading_membar())) {
4586         return false;
4587       }
4588     }
4589   }
4590   C->print_method(PHASE_BEFORE_DUPLICATE_LOOP_BACKEDGE, 4, head);
4591 
4592   // Collect data nodes that need to be clones as well
4593   int dd = dom_depth(head);
4594 
4595   for (uint i = 0; i < loop->_body.size(); ++i) {
4596     Node* n = loop->_body.at(i);
4597     if (has_ctrl(n)) {
4598       Node* c = get_ctrl(n);
4599       if (wq.member(c)) {
4600         wq.push(n);
4601       }
4602     } else {
4603       set_idom(n, idom(n), dd);
4604     }
4605   }
4606 
4607   // clone shared_stmt
4608   clone_loop_body(wq, old_new, nullptr);
4609 
4610   Node* region_clone = old_new[region->_idx];
4611   region_clone->set_req(inner, C->top());
4612   set_idom(region, region->in(inner), dd);
4613 
4614   // Prepare the outer loop
4615   Node* outer_head = new LoopNode(head->in(LoopNode::EntryControl), old_new[head->in(LoopNode::LoopBackControl)->_idx]);
4616   register_control(outer_head, loop->_parent, outer_head->in(LoopNode::EntryControl));
4617   _igvn.replace_input_of(head, LoopNode::EntryControl, outer_head);
4618   set_idom(head, outer_head, dd);
4619 
4620   fix_body_edges(wq, loop, old_new, dd, loop->_parent, true);
4621 
4622   // Make one of the shared_stmt copies only reachable from stmt1, the
4623   // other only from stmt2..stmtn.
4624   Node* dom = nullptr;
4625   for (uint i = 1; i < region->req(); ++i) {
4626     if (i != inner) {
4627       _igvn.replace_input_of(region, i, C->top());
4628     }
4629     Node* in = region_clone->in(i);
4630     if (in->is_top()) {
4631       continue;
4632     }
4633     if (dom == nullptr) {
4634       dom = in;
4635     } else {
4636       dom = dom_lca(dom, in);
4637     }
4638   }
4639 
4640   set_idom(region_clone, dom, dd);
4641 
4642   // Set up the outer loop
4643   for (uint i = 0; i < head->outcnt(); i++) {
4644     Node* u = head->raw_out(i);
4645     if (u->is_Phi()) {
4646       Node* outer_phi = u->clone();
4647       outer_phi->set_req(0, outer_head);
4648       Node* backedge = old_new[u->in(LoopNode::LoopBackControl)->_idx];
4649       if (backedge == nullptr) {
4650         backedge = u->in(LoopNode::LoopBackControl);
4651       }
4652       outer_phi->set_req(LoopNode::LoopBackControl, backedge);
4653       register_new_node(outer_phi, outer_head);
4654       _igvn.replace_input_of(u, LoopNode::EntryControl, outer_phi);
4655     }
4656   }
4657 
4658   // create control and data nodes for out of loop uses (including region2)
4659   Node_List worklist;
4660   uint new_counter = C->unique();
4661   fix_ctrl_uses(wq, loop, old_new, ControlAroundStripMined, outer_head, nullptr, worklist);
4662 
4663   Node_List *split_if_set = nullptr;
4664   Node_List *split_bool_set = nullptr;
4665   Node_List *split_cex_set = nullptr;
4666   fix_data_uses(wq, loop, ControlAroundStripMined, loop->skip_strip_mined(), new_counter, old_new, worklist,
4667                 split_if_set, split_bool_set, split_cex_set);
4668 
4669   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
4670 
4671   if (exit_test != nullptr) {
4672     float cnt = exit_test->_fcnt;
4673     if (cnt != COUNT_UNKNOWN) {
4674       exit_test->_fcnt = cnt * f;
4675       old_new[exit_test->_idx]->as_If()->_fcnt = cnt * (1 - f);
4676     }
4677   }
4678 
4679 #ifdef ASSERT
4680   if (StressDuplicateBackedge && head->is_CountedLoop()) {
4681     // The Template Assertion Predicates from the old counted loop are now at the new outer loop - clone them to
4682     // the inner counted loop and kill the old ones. We only need to do this with debug builds because
4683     // StressDuplicateBackedge is a devlop flag and false by default. Without StressDuplicateBackedge 'head' will be a
4684     // non-counted loop, and thus we have no Template Assertion Predicates above the old loop to move down.
4685     PredicateIterator predicate_iterator(outer_head->in(LoopNode::EntryControl));
4686     NodeInSingleLoopBody node_in_body(this, loop);
4687     MoveAssertionPredicatesVisitor move_assertion_predicates_visitor(head, node_in_body, this);
4688     predicate_iterator.for_each(move_assertion_predicates_visitor);
4689   }
4690 #endif // ASSERT
4691 
4692   C->set_major_progress();
4693 
4694   C->print_method(PHASE_AFTER_DUPLICATE_LOOP_BACKEDGE, 4, outer_head);
4695 
4696   return true;
4697 }
4698 
4699 // AutoVectorize the loop: replace scalar ops with vector ops.
4700 PhaseIdealLoop::AutoVectorizeStatus
4701 PhaseIdealLoop::auto_vectorize(IdealLoopTree* lpt, VSharedData &vshared) {
4702   // Counted loop only
4703   if (!lpt->is_counted()) {
4704     return AutoVectorizeStatus::Impossible;
4705   }
4706 
4707   // Main-loop only
4708   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4709   if (!cl->is_main_loop()) {
4710     return AutoVectorizeStatus::Impossible;
4711   }
4712 
4713   VLoop vloop(lpt, false);
4714   if (!vloop.check_preconditions()) {
4715     return AutoVectorizeStatus::TriedAndFailed;
4716   }
4717 
4718   // Ensure the shared data is cleared before each use
4719   vshared.clear();
4720 
4721   const VLoopAnalyzer vloop_analyzer(vloop, vshared);
4722   if (!vloop_analyzer.success()) {
4723     return AutoVectorizeStatus::TriedAndFailed;
4724   }
4725 
4726   SuperWord sw(vloop_analyzer);
4727   if (!sw.transform_loop()) {
4728     return AutoVectorizeStatus::TriedAndFailed;
4729   }
4730 
4731   return AutoVectorizeStatus::Success;
4732 }
4733 
4734 // Just before insert_pre_post_loops, we can multiversion the loop:
4735 //
4736 //              multiversion_if
4737 //               |       |
4738 //         fast_loop   slow_loop
4739 //
4740 // In the fast_loop we can make speculative assumptions, and put the
4741 // conditions into the multiversion_if. If the conditions hold at runtime,
4742 // we enter the fast_loop, if the conditions fail, we take the slow_loop
4743 // instead which does not make any of the speculative assumptions.
4744 //
4745 // Note: we only multiversion the loop if the loop does not have any
4746 //       auto vectorization check Predicate. If we have that predicate,
4747 //       then we can simply add the speculative assumption checks to
4748 //       that Predicate. This means we do not need to duplicate the
4749 //       loop - we have a smaller graph and save compile time. Should
4750 //       the conditions ever fail, then we deopt / trap at the Predicate
4751 //       and recompile without that Predicate. At that point we will
4752 //       multiversion the loop, so that we can still have speculative
4753 //       runtime checks.
4754 //
4755 // We perform the multiversioning when the loop is still in its single
4756 // iteration form, even before we insert pre and post loops. This makes
4757 // the cloning much simpler. However, this means that both the fast
4758 // and the slow loop have to be optimized independently (adding pre
4759 // and post loops, unrolling the main loop, auto-vectorize etc.). And
4760 // we may end up not needing any speculative assumptions in the fast_loop
4761 // and then rejecting the slow_loop by constant folding the multiversion_if.
4762 //
4763 // Therefore, we "delay" the optimization of the slow_loop until we add
4764 // at least one speculative assumption for the fast_loop. If we never
4765 // add such a speculative runtime check, the OpaqueMultiversioningNode
4766 // of the multiversion_if constant folds to true after loop opts, and the
4767 // multiversion_if folds away the "delayed" slow_loop. If we add any
4768 // speculative assumption, then we notify the OpaqueMultiversioningNode
4769 // with "notify_slow_loop_that_it_can_resume_optimizations".
4770 //
4771 // Note: new runtime checks can be added to the multiversion_if with
4772 //       PhaseIdealLoop::create_new_if_for_multiversion
4773 void PhaseIdealLoop::maybe_multiversion_for_auto_vectorization_runtime_checks(IdealLoopTree* lpt, Node_List& old_new) {
4774   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4775   LoopNode* outer_loop = cl->skip_strip_mined();
4776   Node* entry = outer_loop->in(LoopNode::EntryControl);
4777 
4778   // Check we have multiversioning enabled, and are not already multiversioned.
4779   if (!LoopMultiversioning || cl->is_multiversion()) { return; }
4780 
4781   // Check that we do not have a parse-predicate where we can add the runtime checks
4782   // during auto-vectorization.
4783   const Predicates predicates(entry);
4784   const PredicateBlock* predicate_block = predicates.auto_vectorization_check_block();
4785   if (predicate_block->has_parse_predicate()) { return; }
4786 
4787   // Check node budget.
4788   uint estimate = lpt->est_loop_clone_sz(2);
4789   if (!may_require_nodes(estimate)) { return; }
4790 
4791   do_multiversioning(lpt, old_new);
4792 }
4793 
4794 void DataNodeGraph::clone_data_nodes(Node* new_ctrl) {
4795   for (uint i = 0; i < _data_nodes.size(); i++) {
4796     clone(_data_nodes[i], new_ctrl);
4797   }
4798 }
4799 
4800 // Clone the given node and set it up properly. Set 'new_ctrl' as ctrl.
4801 void DataNodeGraph::clone(Node* node, Node* new_ctrl) {
4802   Node* clone = node->clone();
4803   _phase->igvn().register_new_node_with_optimizer(clone);
4804   _orig_to_new.put(node, clone);
4805   _phase->set_ctrl(clone, new_ctrl);
4806   if (node->is_CastII()) {
4807     clone->set_req(0, new_ctrl);
4808   }
4809 }
4810 
4811 // Rewire the data inputs of all (unprocessed) cloned nodes, whose inputs are still pointing to the same inputs as their
4812 // corresponding orig nodes, to the newly cloned inputs to create a separate cloned graph.
4813 void DataNodeGraph::rewire_clones_to_cloned_inputs() {
4814   _orig_to_new.iterate_all([&](Node* node, Node* clone) {
4815     for (uint i = 1; i < node->req(); i++) {
4816       Node** cloned_input = _orig_to_new.get(node->in(i));
4817       if (cloned_input != nullptr) {
4818         // Input was also cloned -> rewire clone to the cloned input.
4819         _phase->igvn().replace_input_of(clone, i, *cloned_input);
4820       }
4821     }
4822   });
4823 }
4824 
4825 // Clone all non-OpaqueLoop* nodes and apply the provided transformation strategy for OpaqueLoop* nodes.
4826 // Set 'new_ctrl' as ctrl for all cloned non-OpaqueLoop* nodes.
4827 void DataNodeGraph::clone_data_nodes_and_transform_opaque_loop_nodes(
4828     const TransformStrategyForOpaqueLoopNodes& transform_strategy,
4829     Node* new_ctrl) {
4830   for (uint i = 0; i < _data_nodes.size(); i++) {
4831     Node* data_node = _data_nodes[i];
4832     if (data_node->is_Opaque1()) {
4833       transform_opaque_node(transform_strategy, data_node);
4834     } else {
4835       clone(data_node, new_ctrl);
4836     }
4837   }
4838 }
4839 
4840 void DataNodeGraph::transform_opaque_node(const TransformStrategyForOpaqueLoopNodes& transform_strategy, Node* node) {
4841   Node* transformed_node;
4842   if (node->is_OpaqueLoopInit()) {
4843     transformed_node = transform_strategy.transform_opaque_init(node->as_OpaqueLoopInit());
4844   } else {
4845     assert(node->is_OpaqueLoopStride(), "must be OpaqueLoopStrideNode");
4846     transformed_node = transform_strategy.transform_opaque_stride(node->as_OpaqueLoopStride());
4847   }
4848   // Add an orig->new mapping to correctly update the inputs of the copied graph in rewire_clones_to_cloned_inputs().
4849   _orig_to_new.put(node, transformed_node);
4850 }
--- EOF ---