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 (inp->isa_InlineType()) {
 802         // TODO 8302217 This prevents PhiNode::push_inline_types_through
 803         return nullptr;
 804       }
 805       if (get_ctrl(inp) == proj) { // Found local op
 806         cost++;
 807         // Check for a chain of dependent ops; these will all become
 808         // speculative in a CMOV.
 809         for (uint k = 1; k < inp->req(); k++)
 810           if (get_ctrl(inp->in(k)) == proj)
 811             cost += ConditionalMoveLimit; // Too much speculative goo
 812       }
 813     }
 814     // See if the Phi is used by a Cmp or Narrow oop Decode/Encode.
 815     // This will likely Split-If, a higher-payoff operation.
 816     for (DUIterator_Fast kmax, k = phi->fast_outs(kmax); k < kmax; k++) {
 817       Node* use = phi->fast_out(k);
 818       if (use->is_Cmp() || use->is_DecodeNarrowPtr() || use->is_EncodeNarrowPtr())
 819         cost += ConditionalMoveLimit;
 820       // Is there a use inside the loop?
 821       // Note: check only basic types since CMoveP is pinned.
 822       if (!used_inside_loop && is_java_primitive(bt)) {
 823         IdealLoopTree* u_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use);
 824         if (r_loop == u_loop || r_loop->is_member(u_loop)) {
 825           used_inside_loop = true;
 826         }
 827       }
 828     }
 829   }//for
 830   Node* bol = iff->in(1);
 831   assert(!bol->is_OpaqueInitializedAssertionPredicate(), "Initialized Assertion Predicates cannot form a diamond with Halt");
 832   if (bol->is_OpaqueTemplateAssertionPredicate()) {
 833     // Ignore Template Assertion Predicates with OpaqueTemplateAssertionPredicate nodes.
 834     return nullptr;
 835   }
 836   if (bol->is_OpaqueMultiversioning()) {
 837     assert(bol->as_OpaqueMultiversioning()->is_useless(), "Must be useless, i.e. fast main loop has already disappeared.");
 838     // Ignore multiversion_if that just lost its loops. The OpaqueMultiversioning is marked useless,
 839     // and will make the multiversion_if constant fold in the next IGVN round.
 840     return nullptr;
 841   }
 842   if (!bol->is_Bool()) {
 843     assert(false, "Expected Bool, but got %s", NodeClassNames[bol->Opcode()]);
 844     return nullptr;
 845   }
 846   int cmp_op = bol->in(1)->Opcode();
 847   if (cmp_op == Op_SubTypeCheck) { // SubTypeCheck expansion expects an IfNode
 848     return nullptr;
 849   }
 850   // It is expensive to generate flags from a float compare.
 851   // Avoid duplicated float compare.
 852   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return nullptr;
 853 
 854   float infrequent_prob = PROB_UNLIKELY_MAG(3);
 855   // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
 856   if (used_inside_loop) {
 857     if (cost >= ConditionalMoveLimit) return nullptr; // Too much goo
 858 
 859     // BlockLayoutByFrequency optimization moves infrequent branch
 860     // from hot path. No point in CMOV'ing in such case (110 is used
 861     // instead of 100 to take into account not exactness of float value).
 862     if (BlockLayoutByFrequency) {
 863       infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
 864     }
 865   }
 866   // Check for highly predictable branch.  No point in CMOV'ing if
 867   // we are going to predict accurately all the time.
 868   if (C->use_cmove() && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) {
 869     //keep going
 870   } else if (iff->_prob < infrequent_prob ||
 871       iff->_prob > (1.0f - infrequent_prob))
 872     return nullptr;
 873 
 874   // --------------
 875   // Now replace all Phis with CMOV's
 876   Node *cmov_ctrl = iff->in(0);
 877   uint flip = (lp->Opcode() == Op_IfTrue);
 878   Node_List wq;
 879   while (1) {
 880     PhiNode* phi = nullptr;
 881     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 882       Node *out = region->fast_out(i);
 883       if (out->is_Phi()) {
 884         phi = out->as_Phi();
 885         break;
 886       }
 887     }
 888     if (phi == nullptr || _igvn.type(phi) == Type::TOP || !CMoveNode::supported(_igvn.type(phi))) {
 889       break;
 890     }
 891     // Move speculative ops
 892     wq.push(phi);
 893     while (wq.size() > 0) {
 894       Node *n = wq.pop();
 895       for (uint j = 1; j < n->req(); j++) {
 896         Node* m = n->in(j);
 897         if (m != nullptr && !is_dominator(get_ctrl(m), cmov_ctrl)) {
 898           set_ctrl(m, cmov_ctrl);
 899           wq.push(m);
 900         }
 901       }
 902     }
 903     Node* cmov = CMoveNode::make(iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi));
 904     register_new_node(cmov, cmov_ctrl);
 905     _igvn.replace_node(phi, cmov);
 906 #ifndef PRODUCT
 907     if (TraceLoopOpts) {
 908       tty->print("CMOV  ");
 909       r_loop->dump_head();
 910       if (Verbose) {
 911         bol->in(1)->dump(1);
 912         cmov->dump(1);
 913       }
 914     }
 915     DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
 916 #endif
 917   }
 918 
 919   // The useless CFG diamond will fold up later; see the optimization in
 920   // RegionNode::Ideal.
 921   _igvn._worklist.push(region);
 922 
 923   return iff->in(1);
 924 }
 925 
 926 static void enqueue_cfg_uses(Node* m, Unique_Node_List& wq) {
 927   for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
 928     Node* u = m->fast_out(i);
 929     if (u->is_CFG()) {
 930       if (u->is_NeverBranch()) {
 931         u = u->as_NeverBranch()->proj_out(0);
 932         enqueue_cfg_uses(u, wq);
 933       } else {
 934         wq.push(u);
 935       }
 936     }
 937   }
 938 }
 939 
 940 // Try moving a store out of a loop, right before the loop
 941 Node* PhaseIdealLoop::try_move_store_before_loop(Node* n, Node *n_ctrl) {
 942   // Store has to be first in the loop body
 943   IdealLoopTree *n_loop = get_loop(n_ctrl);
 944   if (n->is_Store() && n_loop != _ltree_root &&
 945       n_loop->is_loop() && n_loop->_head->is_Loop() &&
 946       n->in(0) != nullptr) {
 947     Node* address = n->in(MemNode::Address);
 948     Node* value = n->in(MemNode::ValueIn);
 949     Node* mem = n->in(MemNode::Memory);
 950 
 951     // - address and value must be loop invariant
 952     // - memory must be a memory Phi for the loop
 953     // - Store must be the only store on this memory slice in the
 954     // loop: if there's another store following this one then value
 955     // written at iteration i by the second store could be overwritten
 956     // at iteration i+n by the first store: it's not safe to move the
 957     // first store out of the loop
 958     // - nothing must observe the memory Phi: it guarantees no read
 959     // before the store, we are also guaranteed the store post
 960     // dominates the loop head (ignoring a possible early
 961     // exit). Otherwise there would be extra Phi involved between the
 962     // loop's Phi and the store.
 963     // - there must be no early exit from the loop before the Store
 964     // (such an exit most of the time would be an extra use of the
 965     // memory Phi but sometimes is a bottom memory Phi that takes the
 966     // store as input).
 967 
 968     if (!ctrl_is_member(n_loop, address) &&
 969         !ctrl_is_member(n_loop, value) &&
 970         mem->is_Phi() && mem->in(0) == n_loop->_head &&
 971         mem->outcnt() == 1 &&
 972         mem->in(LoopNode::LoopBackControl) == n) {
 973 
 974       assert(n_loop->_tail != nullptr, "need a tail");
 975       assert(is_dominator(n_ctrl, n_loop->_tail), "store control must not be in a branch in the loop");
 976 
 977       // Verify that there's no early exit of the loop before the store.
 978       bool ctrl_ok = false;
 979       {
 980         // Follow control from loop head until n, we exit the loop or
 981         // we reach the tail
 982         ResourceMark rm;
 983         Unique_Node_List wq;
 984         wq.push(n_loop->_head);
 985 
 986         for (uint next = 0; next < wq.size(); ++next) {
 987           Node *m = wq.at(next);
 988           if (m == n->in(0)) {
 989             ctrl_ok = true;
 990             continue;
 991           }
 992           assert(!has_ctrl(m), "should be CFG");
 993           if (!n_loop->is_member(get_loop(m)) || m == n_loop->_tail) {
 994             ctrl_ok = false;
 995             break;
 996           }
 997           enqueue_cfg_uses(m, wq);
 998           if (wq.size() > 10) {
 999             ctrl_ok = false;
1000             break;
1001           }
1002         }
1003       }
1004       if (ctrl_ok) {
1005         // move the Store
1006         _igvn.replace_input_of(mem, LoopNode::LoopBackControl, mem);
1007         _igvn.replace_input_of(n, 0, n_loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl));
1008         _igvn.replace_input_of(n, MemNode::Memory, mem->in(LoopNode::EntryControl));
1009         // Disconnect the phi now. An empty phi can confuse other
1010         // optimizations in this pass of loop opts.
1011         _igvn.replace_node(mem, mem->in(LoopNode::EntryControl));
1012         n_loop->_body.yank(mem);
1013 
1014         set_ctrl_and_loop(n, n->in(0));
1015 
1016         return n;
1017       }
1018     }
1019   }
1020   return nullptr;
1021 }
1022 
1023 // Try moving a store out of a loop, right after the loop
1024 void PhaseIdealLoop::try_move_store_after_loop(Node* n) {
1025   if (n->is_Store() && n->in(0) != nullptr) {
1026     Node *n_ctrl = get_ctrl(n);
1027     IdealLoopTree *n_loop = get_loop(n_ctrl);
1028     // Store must be in a loop
1029     if (n_loop != _ltree_root && !n_loop->_irreducible) {
1030       Node* address = n->in(MemNode::Address);
1031       Node* value = n->in(MemNode::ValueIn);
1032       // address must be loop invariant
1033       if (!ctrl_is_member(n_loop, address)) {
1034         // Store must be last on this memory slice in the loop and
1035         // nothing in the loop must observe it
1036         Node* phi = nullptr;
1037         for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1038           Node* u = n->fast_out(i);
1039           if (has_ctrl(u)) { // control use?
1040             if (!ctrl_is_member(n_loop, u)) {
1041               continue;
1042             }
1043             if (u->is_Phi() && u->in(0) == n_loop->_head) {
1044               assert(_igvn.type(u) == Type::MEMORY, "bad phi");
1045               // multiple phis on the same slice are possible
1046               if (phi != nullptr) {
1047                 return;
1048               }
1049               phi = u;
1050               continue;
1051             }
1052           }
1053           return;
1054         }
1055         if (phi != nullptr) {
1056           // Nothing in the loop before the store (next iteration)
1057           // must observe the stored value
1058           bool mem_ok = true;
1059           {
1060             ResourceMark rm;
1061             Unique_Node_List wq;
1062             wq.push(phi);
1063             for (uint next = 0; next < wq.size() && mem_ok; ++next) {
1064               Node *m = wq.at(next);
1065               for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax && mem_ok; i++) {
1066                 Node* u = m->fast_out(i);
1067                 if (u->is_Store() || u->is_Phi()) {
1068                   if (u != n) {
1069                     wq.push(u);
1070                     mem_ok = (wq.size() <= 10);
1071                   }
1072                 } else {
1073                   mem_ok = false;
1074                   break;
1075                 }
1076               }
1077             }
1078           }
1079           if (mem_ok) {
1080             // Move the store out of the loop if the LCA of all
1081             // users (except for the phi) is outside the loop.
1082             Node* hook = new Node(1);
1083             hook->init_req(0, n_ctrl); // Add an input to prevent hook from being dead
1084             _igvn.rehash_node_delayed(phi);
1085             int count = phi->replace_edge(n, hook, &_igvn);
1086             assert(count > 0, "inconsistent phi");
1087 
1088             // Compute latest point this store can go
1089             Node* lca = get_late_ctrl(n, get_ctrl(n));
1090             if (lca->is_OuterStripMinedLoop()) {
1091               lca = lca->in(LoopNode::EntryControl);
1092             }
1093             if (n_loop->is_member(get_loop(lca))) {
1094               // LCA is in the loop - bail out
1095               _igvn.replace_node(hook, n);
1096               return;
1097             }
1098 #ifdef ASSERT
1099             if (n_loop->_head->is_Loop() && n_loop->_head->as_Loop()->is_strip_mined()) {
1100               assert(n_loop->_head->Opcode() == Op_CountedLoop, "outer loop is a strip mined");
1101               n_loop->_head->as_Loop()->verify_strip_mined(1);
1102               Node* outer = n_loop->_head->as_CountedLoop()->outer_loop();
1103               IdealLoopTree* outer_loop = get_loop(outer);
1104               assert(n_loop->_parent == outer_loop, "broken loop tree");
1105               assert(get_loop(lca) == outer_loop, "safepoint in outer loop consume all memory state");
1106             }
1107 #endif
1108             lca = place_outside_loop(lca, n_loop);
1109             assert(!n_loop->is_member(get_loop(lca)), "control must not be back in the loop");
1110             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");
1111 
1112             // Move store out of the loop
1113             _igvn.replace_node(hook, n->in(MemNode::Memory));
1114             _igvn.replace_input_of(n, 0, lca);
1115             set_ctrl_and_loop(n, lca);
1116 
1117             // Disconnect the phi now. An empty phi can confuse other
1118             // optimizations in this pass of loop opts..
1119             if (phi->in(LoopNode::LoopBackControl) == phi) {
1120               _igvn.replace_node(phi, phi->in(LoopNode::EntryControl));
1121               n_loop->_body.yank(phi);
1122             }
1123           }
1124         }
1125       }
1126     }
1127   }
1128 }
1129 
1130 // We can't use immutable memory for the flat array check because we are loading the mark word which is
1131 // mutable. Although the bits we are interested in are immutable (we check for markWord::unlocked_value),
1132 // we need to use raw memory to not break anti dependency analysis. Below code will attempt to still move
1133 // flat array checks out of loops, mainly to enable loop unswitching.
1134 void PhaseIdealLoop::move_flat_array_check_out_of_loop(Node* n) {
1135   // Skip checks for more than one array
1136   if (n->req() > 3) {
1137     return;
1138   }
1139   Node* mem = n->in(FlatArrayCheckNode::Memory);
1140   Node* array = n->in(FlatArrayCheckNode::ArrayOrKlass)->uncast();
1141   IdealLoopTree* check_loop = get_loop(get_ctrl(n));
1142   IdealLoopTree* ary_loop = get_loop(get_ctrl(array));
1143 
1144   // Check if array is loop invariant
1145   if (!check_loop->is_member(ary_loop)) {
1146     // Walk up memory graph from the check until we leave the loop
1147     VectorSet wq;
1148     wq.set(mem->_idx);
1149     while (check_loop->is_member(get_loop(ctrl_or_self(mem)))) {
1150       if (mem->is_Phi()) {
1151         mem = mem->in(1);
1152       } else if (mem->is_MergeMem()) {
1153         mem = mem->as_MergeMem()->memory_at(Compile::AliasIdxRaw);
1154       } else if (mem->is_Proj()) {
1155         mem = mem->in(0);
1156       } else if (mem->is_MemBar() || mem->is_SafePoint()) {
1157         mem = mem->in(TypeFunc::Memory);
1158       } else if (mem->is_Store() || mem->is_LoadStore() || mem->is_ClearArray()) {
1159         mem = mem->in(MemNode::Memory);
1160       } else {
1161 #ifdef ASSERT
1162         mem->dump();
1163 #endif
1164         ShouldNotReachHere();
1165       }
1166       if (wq.test_set(mem->_idx)) {
1167         return;
1168       }
1169     }
1170     // Replace memory input and re-compute ctrl to move the check out of the loop
1171     _igvn.replace_input_of(n, 1, mem);
1172     set_ctrl_and_loop(n, get_early_ctrl(n));
1173     Node* bol = n->unique_out();
1174     set_ctrl_and_loop(bol, get_early_ctrl(bol));
1175   }
1176 }
1177 
1178 //------------------------------split_if_with_blocks_pre-----------------------
1179 // Do the real work in a non-recursive function.  Data nodes want to be
1180 // cloned in the pre-order so they can feed each other nicely.
1181 Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
1182   // Cloning these guys is unlikely to win
1183   int n_op = n->Opcode();
1184   if (n_op == Op_MergeMem) {
1185     return n;
1186   }
1187   if (n->is_Proj()) {
1188     return n;
1189   }
1190 
1191   if (n->isa_FlatArrayCheck()) {
1192     move_flat_array_check_out_of_loop(n);
1193     return n;
1194   }
1195 
1196   // Do not clone-up CmpFXXX variations, as these are always
1197   // followed by a CmpI
1198   if (n->is_Cmp()) {
1199     return n;
1200   }
1201   // Attempt to use a conditional move instead of a phi/branch
1202   if (ConditionalMoveLimit > 0 && n_op == Op_Region) {
1203     Node *cmov = conditional_move( n );
1204     if (cmov) {
1205       return cmov;
1206     }
1207   }
1208   if (n->is_CFG() || n->is_LoadStore()) {
1209     return n;
1210   }
1211   if (n->is_Opaque1()) { // Opaque nodes cannot be mod'd
1212     if (!C->major_progress()) {   // If chance of no more loop opts...
1213       _igvn._worklist.push(n);  // maybe we'll remove them
1214     }
1215     return n;
1216   }
1217 
1218   if (n->is_Con()) {
1219     return n;   // No cloning for Con nodes
1220   }
1221 
1222   Node *n_ctrl = get_ctrl(n);
1223   if (!n_ctrl) {
1224     return n;       // Dead node
1225   }
1226 
1227   Node* res = try_move_store_before_loop(n, n_ctrl);
1228   if (res != nullptr) {
1229     return n;
1230   }
1231 
1232   // Attempt to remix address expressions for loop invariants
1233   Node *m = remix_address_expressions( n );
1234   if( m ) return m;
1235 
1236   if (n_op == Op_AddI) {
1237     Node *nn = convert_add_to_muladd( n );
1238     if ( nn ) return nn;
1239   }
1240 
1241   if (n->is_ConstraintCast() && n->as_ConstraintCast()->dependency().narrows_type()) {
1242     Node* dom_cast = n->as_ConstraintCast()->dominating_cast(&_igvn, this);
1243     // ConstraintCastNode::dominating_cast() uses node control input to determine domination.
1244     // Node control inputs don't necessarily agree with loop control info (due to
1245     // transformations happened in between), thus additional dominance check is needed
1246     // to keep loop info valid.
1247     if (dom_cast != nullptr && is_dominator(get_ctrl(dom_cast), get_ctrl(n))) {
1248       _igvn.replace_node(n, dom_cast);
1249       return dom_cast;
1250     }
1251   }
1252 
1253   // Determine if the Node has inputs from some local Phi.
1254   // Returns the block to clone thru.
1255   Node *n_blk = has_local_phi_input( n );
1256   if( !n_blk ) return n;
1257 
1258   // Do not clone the trip counter through on a CountedLoop
1259   // (messes up the canonical shape).
1260   if (((n_blk->is_CountedLoop() || (n_blk->is_Loop() && n_blk->as_Loop()->is_loop_nest_inner_loop())) && n->Opcode() == Op_AddI) ||
1261       (n_blk->is_LongCountedLoop() && n->Opcode() == Op_AddL)) {
1262     return n;
1263   }
1264   // Pushing a shift through the iv Phi can get in the way of addressing optimizations or range check elimination
1265   if (n_blk->is_BaseCountedLoop() && n->Opcode() == Op_LShift(n_blk->as_BaseCountedLoop()->bt()) &&
1266       n->in(1) == n_blk->as_BaseCountedLoop()->phi()) {
1267     return n;
1268   }
1269 
1270   // Check for having no control input; not pinned.  Allow
1271   // dominating control.
1272   if (n->in(0)) {
1273     Node *dom = idom(n_blk);
1274     if (dom_lca(n->in(0), dom) != n->in(0)) {
1275       return n;
1276     }
1277   }
1278   // Policy: when is it profitable.  You must get more wins than
1279   // policy before it is considered profitable.  Policy is usually 0,
1280   // so 1 win is considered profitable.  Big merges will require big
1281   // cloning, so get a larger policy.
1282   int policy = n_blk->req() >> 2;
1283 
1284   // If the loop is a candidate for range check elimination,
1285   // delay splitting through it's phi until a later loop optimization
1286   if (n_blk->is_BaseCountedLoop()) {
1287     IdealLoopTree *lp = get_loop(n_blk);
1288     if (lp && lp->_rce_candidate) {
1289       return n;
1290     }
1291   }
1292 
1293   if (must_throttle_split_if()) return n;
1294 
1295   // Split 'n' through the merge point if it is profitable, replacing it with a new phi.
1296   Node* phi = split_thru_phi(n, n_blk, policy);
1297   if (phi == nullptr) { return n; }
1298 
1299   // Moved a load around the loop, 'en-registering' something.
1300   if (n_blk->is_Loop() && n->is_Load() &&
1301       !phi->in(LoopNode::LoopBackControl)->is_Load())
1302     C->set_major_progress();
1303 
1304   return phi;
1305 }
1306 
1307 static bool merge_point_too_heavy(Compile* C, Node* region) {
1308   // Bail out if the region and its phis have too many users.
1309   int weight = 0;
1310   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1311     weight += region->fast_out(i)->outcnt();
1312   }
1313   int nodes_left = C->max_node_limit() - C->live_nodes();
1314   if (weight * 8 > nodes_left) {
1315     if (PrintOpto) {
1316       tty->print_cr("*** Split-if bails out:  %d nodes, region weight %d", C->unique(), weight);
1317     }
1318     return true;
1319   } else {
1320     return false;
1321   }
1322 }
1323 
1324 static bool merge_point_safe(Node* region) {
1325   // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
1326   // having a PhiNode input. This sidesteps the dangerous case where the split
1327   // ConvI2LNode may become TOP if the input Value() does not
1328   // overlap the ConvI2L range, leaving a node which may not dominate its
1329   // uses.
1330   // A better fix for this problem can be found in the BugTraq entry, but
1331   // expediency for Mantis demands this hack.
1332 #ifdef _LP64
1333   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1334     Node* n = region->fast_out(i);
1335     if (n->is_Phi()) {
1336       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
1337         Node* m = n->fast_out(j);
1338         if (m->Opcode() == Op_ConvI2L)
1339           return false;
1340         if (m->is_CastII()) {
1341           return false;
1342         }
1343       }
1344     }
1345   }
1346 #endif
1347   return true;
1348 }
1349 
1350 
1351 //------------------------------place_outside_loop---------------------------------
1352 // Place some computation outside of this loop on the path to the use passed as argument
1353 Node* PhaseIdealLoop::place_outside_loop(Node* useblock, IdealLoopTree* loop) const {
1354   Node* head = loop->_head;
1355   assert(!loop->is_member(get_loop(useblock)), "must be outside loop");
1356   if (head->is_Loop() && head->as_Loop()->is_strip_mined()) {
1357     loop = loop->_parent;
1358     assert(loop->_head->is_OuterStripMinedLoop(), "malformed strip mined loop");
1359   }
1360 
1361   // Pick control right outside the loop
1362   for (;;) {
1363     Node* dom = idom(useblock);
1364     if (loop->is_member(get_loop(dom))) {
1365       break;
1366     }
1367     useblock = dom;
1368   }
1369   assert(find_non_split_ctrl(useblock) == useblock, "should be non split control");
1370   return useblock;
1371 }
1372 
1373 
1374 bool PhaseIdealLoop::identical_backtoback_ifs(Node *n) {
1375   if (!n->is_If() || n->is_BaseCountedLoopEnd()) {
1376     return false;
1377   }
1378   if (!n->in(0)->is_Region()) {
1379     return false;
1380   }
1381 
1382   Node* region = n->in(0);
1383   Node* dom = idom(region);
1384   if (!dom->is_If() ||  !n->as_If()->same_condition(dom, &_igvn)) {
1385     return false;
1386   }
1387   IfNode* dom_if = dom->as_If();
1388   IfTrueNode* proj_true = dom_if->true_proj();
1389   IfFalseNode* proj_false = dom_if->false_proj();
1390 
1391   for (uint i = 1; i < region->req(); i++) {
1392     if (is_dominator(proj_true, region->in(i))) {
1393       continue;
1394     }
1395     if (is_dominator(proj_false, region->in(i))) {
1396       continue;
1397     }
1398     return false;
1399   }
1400 
1401   return true;
1402 }
1403 
1404 
1405 bool PhaseIdealLoop::can_split_if(Node* n_ctrl) {
1406   if (must_throttle_split_if()) {
1407     return false;
1408   }
1409 
1410   // Do not do 'split-if' if irreducible loops are present.
1411   if (_has_irreducible_loops) {
1412     return false;
1413   }
1414 
1415   if (merge_point_too_heavy(C, n_ctrl)) {
1416     return false;
1417   }
1418 
1419   // Do not do 'split-if' if some paths are dead.  First do dead code
1420   // elimination and then see if its still profitable.
1421   for (uint i = 1; i < n_ctrl->req(); i++) {
1422     if (n_ctrl->in(i) == C->top()) {
1423       return false;
1424     }
1425   }
1426 
1427   // If trying to do a 'Split-If' at the loop head, it is only
1428   // profitable if the cmp folds up on BOTH paths.  Otherwise we
1429   // risk peeling a loop forever.
1430 
1431   // CNC - Disabled for now.  Requires careful handling of loop
1432   // body selection for the cloned code.  Also, make sure we check
1433   // for any input path not being in the same loop as n_ctrl.  For
1434   // irreducible loops we cannot check for 'n_ctrl->is_Loop()'
1435   // because the alternative loop entry points won't be converted
1436   // into LoopNodes.
1437   IdealLoopTree *n_loop = get_loop(n_ctrl);
1438   for (uint j = 1; j < n_ctrl->req(); j++) {
1439     if (get_loop(n_ctrl->in(j)) != n_loop) {
1440       return false;
1441     }
1442   }
1443 
1444   // Check for safety of the merge point.
1445   if (!merge_point_safe(n_ctrl)) {
1446     return false;
1447   }
1448 
1449   return true;
1450 }
1451 
1452 // Detect if the node is the inner strip-mined loop
1453 // Return: null if it's not the case, or the exit of outer strip-mined loop
1454 static Node* is_inner_of_stripmined_loop(const Node* out) {
1455   Node* out_le = nullptr;
1456 
1457   if (out->is_CountedLoopEnd()) {
1458       const CountedLoopNode* loop = out->as_CountedLoopEnd()->loopnode();
1459 
1460       if (loop != nullptr && loop->is_strip_mined()) {
1461         out_le = loop->in(LoopNode::EntryControl)->as_OuterStripMinedLoop()->outer_loop_exit();
1462       }
1463   }
1464 
1465   return out_le;
1466 }
1467 
1468 bool PhaseIdealLoop::flat_array_element_type_check(Node *n) {
1469   // If the CmpP is a subtype check for a value that has just been
1470   // loaded from an array, the subtype check guarantees the value
1471   // can't be stored in a flat array and the load of the value
1472   // happens with a flat array check then: push the type check
1473   // through the phi of the flat array check. This needs special
1474   // logic because the subtype check's input is not a phi but a
1475   // LoadKlass that must first be cloned through the phi.
1476   if (n->Opcode() != Op_CmpP) {
1477     return false;
1478   }
1479 
1480   Node* klassptr = n->in(1);
1481   Node* klasscon = n->in(2);
1482 
1483   if (klassptr->is_DecodeNarrowPtr()) {
1484     klassptr = klassptr->in(1);
1485   }
1486 
1487   if (klassptr->Opcode() != Op_LoadKlass && klassptr->Opcode() != Op_LoadNKlass) {
1488     return false;
1489   }
1490 
1491   if (!klasscon->is_Con()) {
1492     return false;
1493   }
1494 
1495   Node* addr = klassptr->in(MemNode::Address);
1496 
1497   if (!addr->is_AddP()) {
1498     return false;
1499   }
1500 
1501   intptr_t offset;
1502   Node* obj = AddPNode::Ideal_base_and_offset(addr, &_igvn, offset);
1503 
1504   if (obj == nullptr) {
1505     return false;
1506   }
1507 
1508   // TODO 8378077: The code below does not work anymore with off-heap accesses which set their bases to top with
1509   // JDK-8373343. Also: flat_array_element_type_check() was introduced with JDK-8228622 for a specific check to enable
1510   // split-if but JDK-8245729 changed how that check looks like. Is it still relevant? This should be revisited.
1511   if (addr->in(AddPNode::Base)->is_top()) {
1512     return false;
1513   }
1514 
1515   if (obj->Opcode() == Op_CastPP) {
1516     obj = obj->in(1);
1517   }
1518 
1519   if (!obj->is_Phi()) {
1520     return false;
1521   }
1522 
1523   Node* region = obj->in(0);
1524 
1525   Node* phi = PhiNode::make_blank(region, n->in(1));
1526   for (uint i = 1; i < region->req(); i++) {
1527     Node* in = obj->in(i);
1528     Node* ctrl = region->in(i);
1529     if (addr->in(AddPNode::Base) != obj) {
1530       Node* cast = addr->in(AddPNode::Base);
1531       assert(cast->Opcode() == Op_CastPP && cast->in(0) != nullptr, "inconsistent subgraph");
1532       Node* cast_clone = cast->clone();
1533       cast_clone->set_req(0, ctrl);
1534       cast_clone->set_req(1, in);
1535       register_new_node(cast_clone, ctrl);
1536       const Type* tcast = cast_clone->Value(&_igvn);
1537       _igvn.set_type(cast_clone, tcast);
1538       cast_clone->as_Type()->set_type(tcast);
1539       in = cast_clone;
1540     }
1541     Node* addr_clone = addr->clone();
1542     addr_clone->set_req(AddPNode::Base, in);
1543     addr_clone->set_req(AddPNode::Address, in);
1544     register_new_node(addr_clone, ctrl);
1545     _igvn.set_type(addr_clone, addr_clone->Value(&_igvn));
1546     Node* klassptr_clone = klassptr->clone();
1547     klassptr_clone->set_req(2, addr_clone);
1548     register_new_node(klassptr_clone, ctrl);
1549     _igvn.set_type(klassptr_clone, klassptr_clone->Value(&_igvn));
1550     if (klassptr != n->in(1)) {
1551       Node* decode = n->in(1);
1552       assert(decode->is_DecodeNarrowPtr(), "inconsistent subgraph");
1553       Node* decode_clone = decode->clone();
1554       decode_clone->set_req(1, klassptr_clone);
1555       register_new_node(decode_clone, ctrl);
1556       _igvn.set_type(decode_clone, decode_clone->Value(&_igvn));
1557       klassptr_clone = decode_clone;
1558     }
1559     phi->set_req(i, klassptr_clone);
1560   }
1561   register_new_node(phi, region);
1562   Node* orig = n->in(1);
1563   _igvn.replace_input_of(n, 1, phi);
1564   split_if_with_blocks_post(n);
1565   if (n->outcnt() != 0) {
1566     _igvn.replace_input_of(n, 1, orig);
1567     _igvn.remove_dead_node(phi, PhaseIterGVN::NodeOrigin::Graph);
1568   }
1569   return true;
1570 }
1571 
1572 //------------------------------split_if_with_blocks_post----------------------
1573 // Do the real work in a non-recursive function.  CFG hackery wants to be
1574 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
1575 // info.
1576 void PhaseIdealLoop::split_if_with_blocks_post(Node *n) {
1577 
1578   if (flat_array_element_type_check(n)) {
1579     return;
1580   }
1581 
1582   // Cloning Cmp through Phi's involves the split-if transform.
1583   // FastLock is not used by an If
1584   if (n->is_Cmp() && !n->is_FastLock()) {
1585     Node *n_ctrl = get_ctrl(n);
1586     // Determine if the Node has inputs from some local Phi.
1587     // Returns the block to clone thru.
1588     Node *n_blk = has_local_phi_input(n);
1589     if (n_blk != n_ctrl) {
1590       return;
1591     }
1592 
1593     if (!can_split_if(n_ctrl)) {
1594       return;
1595     }
1596 
1597     if (n->outcnt() != 1) {
1598       return; // Multiple bool's from 1 compare?
1599     }
1600     Node *bol = n->unique_out();
1601     assert(bol->is_Bool(), "expect a bool here");
1602     if (bol->outcnt() != 1) {
1603       return;// Multiple branches from 1 compare?
1604     }
1605     Node *iff = bol->unique_out();
1606 
1607     // Check some safety conditions
1608     if (iff->is_If()) {        // Classic split-if?
1609       if (iff->in(0) != n_ctrl) {
1610         return; // Compare must be in same blk as if
1611       }
1612     } else if (iff->is_CMove()) { // Trying to split-up a CMOVE
1613       // Can't split CMove with different control.
1614       if (get_ctrl(iff) != n_ctrl) {
1615         return;
1616       }
1617       if (get_ctrl(iff->in(2)) == n_ctrl ||
1618           get_ctrl(iff->in(3)) == n_ctrl) {
1619         return;                 // Inputs not yet split-up
1620       }
1621       if (get_loop(n_ctrl) != get_loop(get_ctrl(iff))) {
1622         return;                 // Loop-invar test gates loop-varying CMOVE
1623       }
1624     } else {
1625       return;  // some other kind of node, such as an Allocate
1626     }
1627 
1628     // When is split-if profitable?  Every 'win' on means some control flow
1629     // goes dead, so it's almost always a win.
1630     int policy = 0;
1631     // Split compare 'n' through the merge point if it is profitable
1632     Node *phi = split_thru_phi( n, n_ctrl, policy);
1633     if (!phi) {
1634       return;
1635     }
1636 
1637     // Now split the bool up thru the phi
1638     Node* bolphi = split_thru_phi(bol, n_ctrl, -1);
1639     guarantee(bolphi != nullptr, "null boolean phi node");
1640     assert(iff->in(1) == bolphi, "");
1641 
1642     if (bolphi->Value(&_igvn)->singleton()) {
1643       return;
1644     }
1645 
1646     // Conditional-move?  Must split up now
1647     if (!iff->is_If()) {
1648       Node* cmovphi = split_thru_phi(iff, n_ctrl, -1);
1649       return;
1650     }
1651 
1652     // Now split the IF
1653     C->print_method(PHASE_BEFORE_SPLIT_IF, 4, iff);
1654 #ifndef PRODUCT
1655     if (TraceLoopOpts || TraceSplitIf) {
1656       tty->print_cr("Split-If: %d %s", iff->_idx, iff->Name());
1657     }
1658 #endif
1659     do_split_if(iff);
1660     C->print_method(PHASE_AFTER_SPLIT_IF, 4, iff);
1661     return;
1662   }
1663 
1664   // Two identical ifs back to back can be merged
1665   if (try_merge_identical_ifs(n)) {
1666     return;
1667   }
1668 
1669   // Check for an IF ready to split; one that has its
1670   // condition codes input coming from a Phi at the block start.
1671   int n_op = n->Opcode();
1672 
1673   // Check for an IF being dominated by another IF same test
1674   if (n_op == Op_If ||
1675       n_op == Op_RangeCheck) {
1676     Node *bol = n->in(1);
1677     uint max = bol->outcnt();
1678     // Check for same test used more than once?
1679     if (bol->is_Bool() && (max > 1 || bol->in(1)->is_SubTypeCheck())) {
1680       // Search up IDOMs to see if this IF is dominated.
1681       Node* cmp = bol->in(1);
1682       Node *cutoff = cmp->is_SubTypeCheck() ? dom_lca(get_ctrl(cmp->in(1)), get_ctrl(cmp->in(2))) : get_ctrl(bol);
1683 
1684       // Now search up IDOMs till cutoff, looking for a dominating test
1685       Node *prevdom = n;
1686       Node *dom = idom(prevdom);
1687       while (dom != cutoff) {
1688         if (dom->req() > 1 && n->as_If()->same_condition(dom, &_igvn) && prevdom->in(0) == dom &&
1689             safe_for_if_replacement(dom)) {
1690           // It's invalid to move control dependent data nodes in the inner
1691           // strip-mined loop, because:
1692           //  1) break validation of LoopNode::verify_strip_mined()
1693           //  2) move code with side-effect in strip-mined loop
1694           // Move to the exit of outer strip-mined loop in that case.
1695           Node* out_le = is_inner_of_stripmined_loop(dom);
1696           if (out_le != nullptr) {
1697             prevdom = out_le;
1698           }
1699           // Replace the dominated test with an obvious true or false.
1700           // Place it on the IGVN worklist for later cleanup.
1701           C->set_major_progress();
1702           // Split if: pin array accesses that are control dependent on a range check and moved to a regular if,
1703           // to prevent an array load from floating above its range check. There are three cases:
1704           // 1. Move from RangeCheck "a" to RangeCheck "b": don't need to pin. If we ever remove b, then we pin
1705           //    all its array accesses at that point.
1706           // 2. We move from RangeCheck "a" to regular if "b": need to pin. If we ever remove b, then its array
1707           //    accesses would start to float, since we don't pin at that point.
1708           // 3. If we move from regular if: don't pin. All array accesses are already assumed to be pinned.
1709           bool pin_array_access_nodes =  n->Opcode() == Op_RangeCheck &&
1710                                          prevdom->in(0)->Opcode() != Op_RangeCheck;
1711           dominated_by(prevdom->as_IfProj(), n->as_If(), false, pin_array_access_nodes);
1712           DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
1713           return;
1714         }
1715         prevdom = dom;
1716         dom = idom(prevdom);
1717       }
1718     }
1719   }
1720 
1721   try_sink_out_of_loop(n);
1722   if (C->failing()) {
1723     return;
1724   }
1725 
1726   try_move_store_after_loop(n);
1727 
1728   // Remove multiple allocations of the same inline type
1729   if (n->is_InlineType()) {
1730     n->as_InlineType()->remove_redundant_allocations(this);
1731   }
1732 }
1733 
1734 // Transform:
1735 //
1736 // if (some_condition) {
1737 //   // body 1
1738 // } else {
1739 //   // body 2
1740 // }
1741 // if (some_condition) {
1742 //   // body 3
1743 // } else {
1744 //   // body 4
1745 // }
1746 //
1747 // into:
1748 //
1749 //
1750 // if (some_condition) {
1751 //   // body 1
1752 //   // body 3
1753 // } else {
1754 //   // body 2
1755 //   // body 4
1756 // }
1757 bool PhaseIdealLoop::try_merge_identical_ifs(Node* n) {
1758   if (identical_backtoback_ifs(n) && can_split_if(n->in(0))) {
1759     Node *n_ctrl = n->in(0);
1760     IfNode* dom_if = idom(n_ctrl)->as_If();
1761     if (n->in(1) != dom_if->in(1)) {
1762       assert(n->in(1)->in(1)->is_SubTypeCheck() &&
1763              (n->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr ||
1764               dom_if->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr), "only for subtype checks with profile data attached");
1765       _igvn.replace_input_of(n, 1, dom_if->in(1));
1766     }
1767     IfTrueNode* dom_proj_true = dom_if->true_proj();
1768     IfFalseNode* dom_proj_false = dom_if->false_proj();
1769 
1770     // Now split the IF
1771     RegionNode* new_false_region;
1772     RegionNode* new_true_region;
1773 #ifndef PRODUCT
1774     if (TraceLoopOpts || TraceSplitIf) {
1775       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());
1776     }
1777 #endif
1778     do_split_if(n, &new_false_region, &new_true_region);
1779     assert(new_false_region->req() == new_true_region->req(), "");
1780 #ifdef ASSERT
1781     for (uint i = 1; i < new_false_region->req(); ++i) {
1782       assert(new_false_region->in(i)->in(0) == new_true_region->in(i)->in(0), "unexpected shape following split if");
1783       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");
1784     }
1785 #endif
1786     assert(new_false_region->in(1)->in(0)->in(1) == dom_if->in(1), "dominating if and dominated if after split must share test");
1787 
1788     // We now have:
1789     // if (some_condition) {
1790     //   // body 1
1791     //   if (some_condition) {
1792     //     body3: // new_true_region
1793     //     // body3
1794     //   } else {
1795     //     goto body4;
1796     //   }
1797     // } else {
1798     //   // body 2
1799     //  if (some_condition) {
1800     //     goto body3;
1801     //   } else {
1802     //     body4:   // new_false_region
1803     //     // body4;
1804     //   }
1805     // }
1806     //
1807 
1808     // clone pinned nodes thru the resulting regions
1809     push_pinned_nodes_thru_region(dom_if, new_true_region);
1810     push_pinned_nodes_thru_region(dom_if, new_false_region);
1811 
1812     // Optimize out the cloned ifs. Because pinned nodes were cloned, this also allows a CastPP that would be dependent
1813     // 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
1814     // unrelated control dependency.
1815     for (uint i = 1; i < new_false_region->req(); i++) {
1816       if (is_dominator(dom_proj_true, new_false_region->in(i))) {
1817         dominated_by(dom_proj_true, new_false_region->in(i)->in(0)->as_If());
1818       } else {
1819         assert(is_dominator(dom_proj_false, new_false_region->in(i)), "bad if");
1820         dominated_by(dom_proj_false, new_false_region->in(i)->in(0)->as_If());
1821       }
1822     }
1823     return true;
1824   }
1825   return false;
1826 }
1827 
1828 void PhaseIdealLoop::push_pinned_nodes_thru_region(IfNode* dom_if, Node* region) {
1829   for (DUIterator i = region->outs(); region->has_out(i); i++) {
1830     Node* u = region->out(i);
1831     if (!has_ctrl(u) || u->is_Phi() || !u->depends_only_on_test()) {
1832       continue;
1833     }
1834     assert(u->in(0) == region, "not a control dependent node?");
1835     uint j = 1;
1836     for (; j < u->req(); ++j) {
1837       Node* in = u->in(j);
1838       if (!is_dominator(ctrl_or_self(in), dom_if)) {
1839         break;
1840       }
1841     }
1842     if (j == u->req()) {
1843       Node *phi = PhiNode::make_blank(region, u);
1844       for (uint k = 1; k < region->req(); ++k) {
1845         Node* clone = u->clone();
1846         clone->set_req(0, region->in(k));
1847         register_new_node(clone, region->in(k));
1848         phi->init_req(k, clone);
1849       }
1850       register_new_node(phi, region);
1851       _igvn.replace_node(u, phi);
1852       --i;
1853     }
1854   }
1855 }
1856 
1857 bool PhaseIdealLoop::safe_for_if_replacement(const Node* dom) const {
1858   if (!dom->is_CountedLoopEnd()) {
1859     return true;
1860   }
1861   CountedLoopEndNode* le = dom->as_CountedLoopEnd();
1862   CountedLoopNode* cl = le->loopnode();
1863   if (cl == nullptr) {
1864     return true;
1865   }
1866   if (!cl->is_main_loop()) {
1867     return true;
1868   }
1869   if (cl->is_canonical_loop_entry() == nullptr) {
1870     return true;
1871   }
1872   // Further unrolling is possible so loop exit condition might change
1873   return false;
1874 }
1875 
1876 // See if a shared loop-varying computation has no loop-varying uses.
1877 // Happens if something is only used for JVM state in uncommon trap exits,
1878 // like various versions of induction variable+offset.  Clone the
1879 // computation per usage to allow it to sink out of the loop.
1880 void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
1881   bool is_raw_to_oop_cast = n->is_ConstraintCast() &&
1882                             n->in(1)->bottom_type()->isa_rawptr() &&
1883                             !n->bottom_type()->isa_rawptr();
1884 
1885   if (has_ctrl(n) &&
1886       !n->is_Phi() &&
1887       !n->is_Bool() &&
1888       !n->is_Proj() &&
1889       !n->is_MergeMem() &&
1890       !n->is_CMove() &&
1891       !n->is_OpaqueConstantBool() &&
1892       !n->is_OpaqueInitializedAssertionPredicate() &&
1893       !n->is_OpaqueTemplateAssertionPredicate() &&
1894       !is_raw_to_oop_cast && // don't extend live ranges of raw oops
1895       n->Opcode() != Op_CreateEx &&
1896       (KillPathsReachableByDeadTypeNode || !n->is_Type())
1897       ) {
1898     Node *n_ctrl = get_ctrl(n);
1899     IdealLoopTree *n_loop = get_loop(n_ctrl);
1900 
1901     if (n->in(0) != nullptr) {
1902       IdealLoopTree* loop_ctrl = get_loop(n->in(0));
1903       if (n_loop != loop_ctrl && n_loop->is_member(loop_ctrl)) {
1904         // n has a control input inside a loop but get_ctrl() is member of an outer loop. This could happen, for example,
1905         // for Div nodes inside a loop (control input inside loop) without a use except for an UCT (outside the loop).
1906         // Rewire control of n to right outside of the loop, regardless if its input(s) are later sunk or not.
1907         Node* maybe_pinned_n = n;
1908         Node* outside_ctrl = place_outside_loop(n_ctrl, loop_ctrl);
1909         if (!would_sink_below_pre_loop_exit(loop_ctrl, outside_ctrl)) {
1910           if (n->depends_only_on_test()) {
1911             // If this node depends_only_on_test, it will be rewired to a control input that is not
1912             // the correct test. As a result, it must be pinned otherwise it can be incorrectly
1913             // rewired to a dominating test equivalent to the new control.
1914             Node* pinned_clone = n->pin_node_under_control();
1915             if (pinned_clone != nullptr) {
1916               register_new_node(pinned_clone, n_ctrl);
1917               maybe_pinned_n = pinned_clone;
1918               _igvn.replace_node(n, pinned_clone);
1919             }
1920           }
1921           _igvn.replace_input_of(maybe_pinned_n, 0, outside_ctrl);
1922         }
1923       }
1924     }
1925     if (n_loop != _ltree_root && n->outcnt() > 1) {
1926       // Compute early control: needed for anti-dependence analysis. It's also possible that as a result of
1927       // previous transformations in this loop opts round, the node can be hoisted now: early control will tell us.
1928       Node* early_ctrl = compute_early_ctrl(n, n_ctrl);
1929       if (n_loop->is_member(get_loop(early_ctrl)) && // check that this one can't be hoisted now
1930           ctrl_of_all_uses_out_of_loop(n, early_ctrl, n_loop)) { // All uses in outer loops!
1931         if (n->is_Store() || n->is_LoadStore()) {
1932             assert(false, "no node with a side effect");
1933             C->record_failure("no node with a side effect");
1934             return;
1935         }
1936         Node* outer_loop_clone = nullptr;
1937         for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin;) {
1938           Node* u = n->last_out(j); // Clone private computation per use
1939           _igvn.rehash_node_delayed(u);
1940           Node* x = nullptr;
1941           if (n->in(0) != nullptr && n->depends_only_on_test()) {
1942             // If this node depends_only_on_test, it will be rewired to a control input that is not
1943             // the correct test. As a result, it must be pinned otherwise it can be incorrectly
1944             // rewired to a dominating test equivalent to the new control.
1945             x = n->pin_node_under_control();
1946           }
1947           if (x == nullptr) {
1948             x = n->clone();
1949           }
1950           Node* x_ctrl = nullptr;
1951           if (u->is_Phi()) {
1952             // Replace all uses of normal nodes.  Replace Phi uses
1953             // individually, so the separate Nodes can sink down
1954             // different paths.
1955             uint k = 1;
1956             while (u->in(k) != n) k++;
1957             u->set_req(k, x);
1958             // x goes next to Phi input path
1959             x_ctrl = u->in(0)->in(k);
1960             // Find control for 'x' next to use but not inside inner loops.
1961             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1962             --j;
1963           } else {              // Normal use
1964             if (has_ctrl(u)) {
1965               x_ctrl = get_ctrl(u);
1966             } else {
1967               x_ctrl = u->in(0);
1968             }
1969             // Find control for 'x' next to use but not inside inner loops.
1970             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1971             // Replace all uses
1972             if (u->is_ConstraintCast() && _igvn.type(n)->higher_equal(u->bottom_type()) && u->in(0) == x_ctrl) {
1973               // If we're sinking a chain of data nodes, we might have inserted a cast to pin the use which is not necessary
1974               // anymore now that we're going to pin n as well
1975               _igvn.replace_node(u, x);
1976               --j;
1977             } else {
1978               int nb = u->replace_edge(n, x, &_igvn);
1979               j -= nb;
1980             }
1981           }
1982 
1983           if (n->is_Load()) {
1984             // For loads, add a control edge to a CFG node outside of the loop
1985             // to force them to not combine and return back inside the loop
1986             // during GVN optimization (4641526).
1987             assert(x_ctrl == get_late_ctrl_with_anti_dep(x->as_Load(), early_ctrl, x_ctrl), "anti-dependences were already checked");
1988 
1989             IdealLoopTree* x_loop = get_loop(x_ctrl);
1990             Node* x_head = x_loop->_head;
1991             if (x_head->is_Loop() && x_head->is_OuterStripMinedLoop()) {
1992               // Do not add duplicate LoadNodes to the outer strip mined loop
1993               if (outer_loop_clone != nullptr) {
1994                 _igvn.replace_node(x, outer_loop_clone);
1995                 continue;
1996               }
1997               outer_loop_clone = x;
1998             }
1999             x->set_req(0, x_ctrl);
2000           } else if (n->in(0) != nullptr){
2001             x->set_req(0, x_ctrl);
2002           }
2003           assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
2004           assert(!n_loop->is_member(get_loop(x_ctrl)), "should have moved out of loop");
2005           register_new_node(x, x_ctrl);
2006 
2007           // Chain of AddP nodes: (AddP base (AddP base (AddP base )))
2008           // All AddP nodes must keep the same base after sinking so:
2009           // 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,
2010           // their bases remain the same.
2011           // (see 2- below)
2012           assert(!x->is_AddP() || !x->in(AddPNode::Address)->is_AddP() ||
2013                  x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base) ||
2014                  !x->in(AddPNode::Address)->in(AddPNode::Base)->eqv_uncast(x->in(AddPNode::Base)), "unexpected AddP shape");
2015           if (x->in(0) == nullptr && !x->is_DecodeNarrowPtr() &&
2016               !(x->is_AddP() && x->in(AddPNode::Address)->is_AddP() && x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base))) {
2017             assert(!x->is_Load(), "load should be pinned");
2018             // Use a cast node to pin clone out of loop
2019             Node* cast = nullptr;
2020             for (uint k = 0; k < x->req(); k++) {
2021               Node* in = x->in(k);
2022               if (in != nullptr && ctrl_is_member(n_loop, in)) {
2023                 const Type* in_t = _igvn.type(in);
2024                 cast = ConstraintCastNode::make_cast_for_type(x_ctrl, in, in_t,
2025                                                               ConstraintCastNode::DependencyType::NonFloatingNonNarrowing, nullptr);
2026               }
2027               if (cast != nullptr) {
2028                 Node* prev = _igvn.hash_find_insert(cast);
2029                 if (prev != nullptr && get_ctrl(prev) == x_ctrl) {
2030                   cast->destruct(&_igvn);
2031                   cast = prev;
2032                 } else {
2033                   register_new_node(cast, x_ctrl);
2034                 }
2035                 x->replace_edge(in, cast);
2036                 // Chain of AddP nodes:
2037                 // 2- A CastPP of the base is only added now that all AddP nodes are sunk
2038                 if (x->is_AddP() && k == AddPNode::Base) {
2039                   update_addp_chain_base(x, n->in(AddPNode::Base), cast);
2040                 }
2041                 break;
2042               }
2043             }
2044             assert(cast != nullptr, "must have added a cast to pin the node");
2045           }
2046         }
2047         _igvn.remove_dead_node(n, PhaseIterGVN::NodeOrigin::Graph);
2048       }
2049       _dom_lca_tags_round = 0;
2050     }
2051   }
2052 }
2053 
2054 void PhaseIdealLoop::update_addp_chain_base(Node* x, Node* old_base, Node* new_base) {
2055   ResourceMark rm;
2056   Node_List wq;
2057   wq.push(x);
2058   while (wq.size() != 0) {
2059     Node* n = wq.pop();
2060     for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2061       Node* u = n->fast_out(i);
2062       if (u->is_AddP() && u->in(AddPNode::Base) == old_base) {
2063         _igvn.replace_input_of(u, AddPNode::Base, new_base);
2064         wq.push(u);
2065       }
2066     }
2067   }
2068 }
2069 
2070 // Compute the early control of a node by following its inputs until we reach
2071 // nodes that are pinned. Then compute the LCA of the control of all pinned nodes.
2072 Node* PhaseIdealLoop::compute_early_ctrl(Node* n, Node* n_ctrl) {
2073   Node* early_ctrl = nullptr;
2074   ResourceMark rm;
2075   Unique_Node_List wq;
2076   wq.push(n);
2077   for (uint i = 0; i < wq.size(); i++) {
2078     Node* m = wq.at(i);
2079     Node* c = nullptr;
2080     if (m->is_CFG()) {
2081       c = m;
2082     } else if (m->pinned()) {
2083       c = m->in(0);
2084     } else {
2085       for (uint j = 0; j < m->req(); j++) {
2086         Node* in = m->in(j);
2087         if (in != nullptr) {
2088           wq.push(in);
2089         }
2090       }
2091     }
2092     if (c != nullptr) {
2093       assert(is_dominator(c, n_ctrl), "control input must dominate current control");
2094       if (early_ctrl == nullptr || is_dominator(early_ctrl, c)) {
2095         early_ctrl = c;
2096       }
2097     }
2098   }
2099   assert(is_dominator(early_ctrl, n_ctrl), "early control must dominate current control");
2100   return early_ctrl;
2101 }
2102 
2103 bool PhaseIdealLoop::ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop) {
2104   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2105     Node* u = n->fast_out(i);
2106     if (u->is_Opaque1()) {
2107       return false;  // Found loop limit, bugfix for 4677003
2108     }
2109     if (u->is_Phi()) {
2110       for (uint j = 1; j < u->req(); ++j) {
2111         if (u->in(j) == n && !ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, u->in(0)->in(j))) {
2112           return false;
2113         }
2114       }
2115     } else {
2116       Node* ctrl = has_ctrl(u) ? get_ctrl(u) : u->in(0);
2117       if (!ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, ctrl)) {
2118         return false;
2119       }
2120     }
2121   }
2122   return true;
2123 }
2124 
2125 // 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
2126 // to a check that's eliminated by range check elimination, it becomes input to an expression that feeds into the exit
2127 // 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
2128 // it would be to not eliminate the check in the main loop. Instead, we prevent sinking of the node here so better code
2129 // is generated for the main loop.
2130 bool PhaseIdealLoop::would_sink_below_pre_loop_exit(IdealLoopTree* n_loop, Node* ctrl) {
2131   if (n_loop->_head->is_CountedLoop() && n_loop->_head->as_CountedLoop()->is_pre_loop()) {
2132     CountedLoopNode* pre_loop = n_loop->_head->as_CountedLoop();
2133     if (is_dominator(pre_loop->loopexit(), ctrl)) {
2134       return true;
2135     }
2136   }
2137   return false;
2138 }
2139 
2140 bool PhaseIdealLoop::ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl) {
2141   if (n->is_Load()) {
2142     // We can't reuse tags in PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal() so make sure each call to
2143     // get_late_ctrl_with_anti_dep() uses its own tag
2144     _dom_lca_tags_round++;
2145     assert(_dom_lca_tags_round != 0, "shouldn't wrap around");
2146 
2147     ctrl = get_late_ctrl_with_anti_dep(n->as_Load(), n_ctrl, ctrl);
2148   }
2149   IdealLoopTree *u_loop = get_loop(ctrl);
2150   if (u_loop == n_loop) {
2151     return false; // Found loop-varying use
2152   }
2153   if (n_loop->is_member(u_loop)) {
2154     return false; // Found use in inner loop
2155   }
2156   if (would_sink_below_pre_loop_exit(n_loop, ctrl)) {
2157     return false;
2158   }
2159   return true;
2160 }
2161 
2162 //------------------------------split_if_with_blocks---------------------------
2163 // Check for aggressive application of 'split-if' optimization,
2164 // using basic block level info.
2165 void PhaseIdealLoop::split_if_with_blocks(VectorSet &visited, Node_Stack &nstack) {
2166   Node* root = C->root();
2167   visited.set(root->_idx); // first, mark root as visited
2168   // Do pre-visit work for root
2169   Node* n   = split_if_with_blocks_pre(root);
2170   uint  cnt = n->outcnt();
2171   uint  i   = 0;
2172 
2173   while (true) {
2174     // Visit all children
2175     if (i < cnt) {
2176       Node* use = n->raw_out(i);
2177       ++i;
2178       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
2179         // Now do pre-visit work for this use
2180         use = split_if_with_blocks_pre(use);
2181         nstack.push(n, i); // Save parent and next use's index.
2182         n   = use;         // Process all children of current use.
2183         cnt = use->outcnt();
2184         i   = 0;
2185       }
2186     }
2187     else {
2188       // All of n's children have been processed, complete post-processing.
2189       if (cnt != 0 && !n->is_Con()) {
2190         assert(has_node(n), "no dead nodes");
2191         split_if_with_blocks_post(n);
2192         if (C->failing()) {
2193           return;
2194         }
2195       }
2196       if (must_throttle_split_if()) {
2197         nstack.clear();
2198       }
2199       if (nstack.is_empty()) {
2200         // Finished all nodes on stack.
2201         break;
2202       }
2203       // Get saved parent node and next use's index. Visit the rest of uses.
2204       n   = nstack.node();
2205       cnt = n->outcnt();
2206       i   = nstack.index();
2207       nstack.pop();
2208     }
2209   }
2210 }
2211 
2212 
2213 //=============================================================================
2214 //
2215 //                   C L O N E   A   L O O P   B O D Y
2216 //
2217 
2218 //------------------------------clone_iff--------------------------------------
2219 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2220 // "Nearly" because all Nodes have been cloned from the original in the loop,
2221 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2222 // through the Phi recursively, and return a Bool.
2223 Node* PhaseIdealLoop::clone_iff(PhiNode* phi) {
2224 
2225   // Convert this Phi into a Phi merging Bools
2226   uint i;
2227   for (i = 1; i < phi->req(); i++) {
2228     Node* b = phi->in(i);
2229     if (b->is_Phi()) {
2230       _igvn.replace_input_of(phi, i, clone_iff(b->as_Phi()));
2231     } else {
2232       assert(b->is_Bool() || b->is_OpaqueConstantBool() || b->is_OpaqueInitializedAssertionPredicate(),
2233              "bool, non-null check with OpaqueConstantBool or Initialized Assertion Predicate with its Opaque node");
2234     }
2235   }
2236   Node* n = phi->in(1);
2237   Node* sample_opaque = nullptr;
2238   Node *sample_bool = nullptr;
2239   if (n->is_OpaqueConstantBool() || n->is_OpaqueInitializedAssertionPredicate()) {
2240     sample_opaque = n;
2241     sample_bool = n->in(1);
2242     assert(sample_bool->is_Bool(), "wrong type");
2243   } else {
2244     sample_bool = n;
2245   }
2246   Node* sample_cmp = sample_bool->in(1);
2247   const Type* t = Type::TOP;
2248   const TypePtr* at = nullptr;
2249   if (sample_cmp->is_FlatArrayCheck()) {
2250     // Left input of a FlatArrayCheckNode is memory, set the (adr) type of the phi accordingly
2251     assert(sample_cmp->in(1)->bottom_type() == Type::MEMORY, "unexpected input type");
2252     t = Type::MEMORY;
2253     at = TypeRawPtr::BOTTOM;
2254   }
2255 
2256   // Make Phis to merge the Cmp's inputs.
2257   PhiNode *phi1 = new PhiNode(phi->in(0), t, at);
2258   PhiNode *phi2 = new PhiNode(phi->in(0), Type::TOP);
2259   for (i = 1; i < phi->req(); i++) {
2260     Node *n1 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(1) : phi->in(i)->in(1)->in(1)->in(1);
2261     Node *n2 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(2) : phi->in(i)->in(1)->in(1)->in(2);
2262     phi1->set_req(i, n1);
2263     phi2->set_req(i, n2);
2264     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2265     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2266   }
2267   // See if these Phis have been made before.
2268   // Register with optimizer
2269   Node *hit1 = _igvn.hash_find_insert(phi1);
2270   if (hit1) {                   // Hit, toss just made Phi
2271     _igvn.remove_dead_node(phi1, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2272     assert(hit1->is_Phi(), "" );
2273     phi1 = (PhiNode*)hit1;      // Use existing phi
2274   } else {                      // Miss
2275     _igvn.register_new_node_with_optimizer(phi1);
2276   }
2277   Node *hit2 = _igvn.hash_find_insert(phi2);
2278   if (hit2) {                   // Hit, toss just made Phi
2279     _igvn.remove_dead_node(phi2, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2280     assert(hit2->is_Phi(), "" );
2281     phi2 = (PhiNode*)hit2;      // Use existing phi
2282   } else {                      // Miss
2283     _igvn.register_new_node_with_optimizer(phi2);
2284   }
2285   // Register Phis with loop/block info
2286   set_ctrl(phi1, phi->in(0));
2287   set_ctrl(phi2, phi->in(0));
2288   // Make a new Cmp
2289   Node *cmp = sample_cmp->clone();
2290   cmp->set_req(1, phi1);
2291   cmp->set_req(2, phi2);
2292   _igvn.register_new_node_with_optimizer(cmp);
2293   set_ctrl(cmp, phi->in(0));
2294 
2295   // Make a new Bool
2296   Node *b = sample_bool->clone();
2297   b->set_req(1,cmp);
2298   _igvn.register_new_node_with_optimizer(b);
2299   set_ctrl(b, phi->in(0));
2300 
2301   if (sample_opaque != nullptr) {
2302     Node* opaque = sample_opaque->clone();
2303     opaque->set_req(1, b);
2304     _igvn.register_new_node_with_optimizer(opaque);
2305     set_ctrl(opaque, phi->in(0));
2306     return opaque;
2307   }
2308 
2309   assert(b->is_Bool(), "");
2310   return b;
2311 }
2312 
2313 //------------------------------clone_bool-------------------------------------
2314 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2315 // "Nearly" because all Nodes have been cloned from the original in the loop,
2316 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2317 // through the Phi recursively, and return a Bool.
2318 CmpNode*PhaseIdealLoop::clone_bool(PhiNode* phi) {
2319   uint i;
2320   // Convert this Phi into a Phi merging Bools
2321   for( i = 1; i < phi->req(); i++ ) {
2322     Node *b = phi->in(i);
2323     if( b->is_Phi() ) {
2324       _igvn.replace_input_of(phi, i, clone_bool(b->as_Phi()));
2325     } else {
2326       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
2327     }
2328   }
2329 
2330   Node *sample_cmp = phi->in(1);
2331 
2332   // Make Phis to merge the Cmp's inputs.
2333   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
2334   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
2335   for( uint j = 1; j < phi->req(); j++ ) {
2336     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
2337     Node *n1, *n2;
2338     if( cmp_top->is_Cmp() ) {
2339       n1 = cmp_top->in(1);
2340       n2 = cmp_top->in(2);
2341     } else {
2342       n1 = n2 = cmp_top;
2343     }
2344     phi1->set_req( j, n1 );
2345     phi2->set_req( j, n2 );
2346     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2347     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2348   }
2349 
2350   // See if these Phis have been made before.
2351   // Register with optimizer
2352   Node *hit1 = _igvn.hash_find_insert(phi1);
2353   if( hit1 ) {                  // Hit, toss just made Phi
2354     _igvn.remove_dead_node(phi1, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2355     assert( hit1->is_Phi(), "" );
2356     phi1 = (PhiNode*)hit1;      // Use existing phi
2357   } else {                      // Miss
2358     _igvn.register_new_node_with_optimizer(phi1);
2359   }
2360   Node *hit2 = _igvn.hash_find_insert(phi2);
2361   if( hit2 ) {                  // Hit, toss just made Phi
2362     _igvn.remove_dead_node(phi2, PhaseIterGVN::NodeOrigin::Speculative); // Remove new phi
2363     assert( hit2->is_Phi(), "" );
2364     phi2 = (PhiNode*)hit2;      // Use existing phi
2365   } else {                      // Miss
2366     _igvn.register_new_node_with_optimizer(phi2);
2367   }
2368   // Register Phis with loop/block info
2369   set_ctrl(phi1, phi->in(0));
2370   set_ctrl(phi2, phi->in(0));
2371   // Make a new Cmp
2372   Node *cmp = sample_cmp->clone();
2373   cmp->set_req( 1, phi1 );
2374   cmp->set_req( 2, phi2 );
2375   _igvn.register_new_node_with_optimizer(cmp);
2376   set_ctrl(cmp, phi->in(0));
2377 
2378   assert( cmp->is_Cmp(), "" );
2379   return (CmpNode*)cmp;
2380 }
2381 
2382 void PhaseIdealLoop::clone_loop_handle_data_uses(Node* old, Node_List &old_new,
2383                                                  IdealLoopTree* loop, IdealLoopTree* outer_loop,
2384                                                  Node_List*& split_if_set, Node_List*& split_bool_set,
2385                                                  Node_List*& split_cex_set, Node_List& worklist,
2386                                                  uint new_counter, CloneLoopMode mode) {
2387   Node* nnn = old_new[old->_idx];
2388   // Copy uses to a worklist, so I can munge the def-use info
2389   // with impunity.
2390   for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
2391     worklist.push(old->fast_out(j));
2392 
2393   while( worklist.size() ) {
2394     Node *use = worklist.pop();
2395     if (!has_node(use))  continue; // Ignore dead nodes
2396     if (use->in(0) == C->top())  continue;
2397     IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
2398     // Check for data-use outside of loop - at least one of OLD or USE
2399     // must not be a CFG node.
2400 #ifdef ASSERT
2401     if (loop->_head->as_Loop()->is_strip_mined() && outer_loop->is_member(use_loop) && !loop->is_member(use_loop) && old_new[use->_idx] == nullptr) {
2402       Node* sfpt = loop->_head->as_CountedLoop()->outer_safepoint();
2403       assert(mode != IgnoreStripMined, "incorrect cloning mode");
2404       assert((mode == ControlAroundStripMined && use == sfpt) || !use->is_reachable_from_root(), "missed a node");
2405     }
2406 #endif
2407     if (!loop->is_member(use_loop) && !outer_loop->is_member(use_loop) && (!old->is_CFG() || !use->is_CFG())) {
2408 
2409       // If the Data use is an IF, that means we have an IF outside the
2410       // loop that is switching on a condition that is set inside the
2411       // loop.  Happens if people set a loop-exit flag; then test the flag
2412       // in the loop to break the loop, then test is again outside the
2413       // loop to determine which way the loop exited.
2414       //
2415       // For several uses we need to make sure that there is no phi between,
2416       // the use and the Bool/Cmp. We therefore clone the Bool/Cmp down here
2417       // to avoid such a phi in between.
2418       // For example, it is unexpected that there is a Phi between an
2419       // AllocateArray node and its ValidLengthTest input that could cause
2420       // split if to break.
2421       assert(!use->is_OpaqueTemplateAssertionPredicate(),
2422              "should not clone a Template Assertion Predicate which should be removed once it's useless");
2423       if (use->is_If() || use->is_CMove() || use->is_OpaqueConstantBool() || use->is_OpaqueInitializedAssertionPredicate() ||
2424           (use->Opcode() == Op_AllocateArray && use->in(AllocateNode::ValidLengthTest) == old)) {
2425         // Since this code is highly unlikely, we lazily build the worklist
2426         // of such Nodes to go split.
2427         if (!split_if_set) {
2428           split_if_set = new Node_List();
2429         }
2430         split_if_set->push(use);
2431       }
2432       if (use->is_Bool()) {
2433         if (!split_bool_set) {
2434           split_bool_set = new Node_List();
2435         }
2436         split_bool_set->push(use);
2437       }
2438       if (use->Opcode() == Op_CreateEx) {
2439         if (!split_cex_set) {
2440           split_cex_set = new Node_List();
2441         }
2442         split_cex_set->push(use);
2443       }
2444 
2445 
2446       // Get "block" use is in
2447       uint idx = 0;
2448       while( use->in(idx) != old ) idx++;
2449       Node *prev = use->is_CFG() ? use : get_ctrl(use);
2450       assert(!loop->is_member(get_loop(prev)) && !outer_loop->is_member(get_loop(prev)), "" );
2451       Node* cfg = (prev->_idx >= new_counter && prev->is_Region())
2452         ? prev->in(2)
2453         : idom(prev);
2454       if( use->is_Phi() )     // Phi use is in prior block
2455         cfg = prev->in(idx);  // NOT in block of Phi itself
2456       if (cfg->is_top()) {    // Use is dead?
2457         _igvn.replace_input_of(use, idx, C->top());
2458         continue;
2459       }
2460 
2461       // If use is referenced through control edge... (idx == 0)
2462       if (mode == IgnoreStripMined && idx == 0) {
2463         LoopNode *head = loop->_head->as_Loop();
2464         if (head->is_strip_mined() && is_dominator(head->outer_loop_exit(), prev)) {
2465           // That node is outside the inner loop, leave it outside the
2466           // outer loop as well to not confuse verification code.
2467           assert(!loop->_parent->is_member(use_loop), "should be out of the outer loop");
2468           _igvn.replace_input_of(use, 0, head->outer_loop_exit());
2469           continue;
2470         }
2471       }
2472 
2473       while(!outer_loop->is_member(get_loop(cfg))) {
2474         prev = cfg;
2475         cfg = (cfg->_idx >= new_counter && cfg->is_Region()) ? cfg->in(2) : idom(cfg);
2476       }
2477       // If the use occurs after merging several exits from the loop, then
2478       // old value must have dominated all those exits.  Since the same old
2479       // value was used on all those exits we did not need a Phi at this
2480       // merge point.  NOW we do need a Phi here.  Each loop exit value
2481       // is now merged with the peeled body exit; each exit gets its own
2482       // private Phi and those Phis need to be merged here.
2483       Node *phi;
2484       if( prev->is_Region() ) {
2485         if( idx == 0 ) {      // Updating control edge?
2486           phi = prev;         // Just use existing control
2487         } else {              // Else need a new Phi
2488           phi = PhiNode::make( prev, old );
2489           // Now recursively fix up the new uses of old!
2490           for( uint i = 1; i < prev->req(); i++ ) {
2491             worklist.push(phi); // Onto worklist once for each 'old' input
2492           }
2493         }
2494       } else {
2495         // Get new RegionNode merging old and new loop exits
2496         prev = old_new[prev->_idx];
2497         assert( prev, "just made this in step 7" );
2498         if( idx == 0) {      // Updating control edge?
2499           phi = prev;         // Just use existing control
2500         } else {              // Else need a new Phi
2501           // Make a new Phi merging data values properly
2502           phi = PhiNode::make( prev, old );
2503           phi->set_req( 1, nnn );
2504         }
2505       }
2506       // If inserting a new Phi, check for prior hits
2507       if( idx != 0 ) {
2508         Node *hit = _igvn.hash_find_insert(phi);
2509         if( hit == nullptr ) {
2510           _igvn.register_new_node_with_optimizer(phi); // Register new phi
2511         } else {                                      // or
2512           // Remove the new phi from the graph and use the hit
2513           _igvn.remove_dead_node(phi, phi == prev ? PhaseIterGVN::NodeOrigin::Graph : PhaseIterGVN::NodeOrigin::Speculative);
2514           phi = hit;                                  // Use existing phi
2515         }
2516         set_ctrl(phi, prev);
2517       }
2518       // Make 'use' use the Phi instead of the old loop body exit value
2519       assert(use->in(idx) == old, "old is still input of use");
2520       // We notify all uses of old, including use, and the indirect uses,
2521       // that may now be optimized because we have replaced old with phi.
2522       _igvn.add_users_to_worklist(old);
2523       if (idx == 0 && use->depends_only_on_test()) {
2524         // If this node depends_only_on_test, it will be rewired to a control input that is not the
2525         // correct test. As a result, it must be pinned otherwise it can be incorrectly rewired to
2526         // a dominating test equivalent to the new control.
2527         Node* pinned_clone = use->pin_node_under_control();
2528         if (pinned_clone != nullptr) {
2529           pinned_clone->set_req(0, phi);
2530           register_new_node_with_ctrl_of(pinned_clone, use);
2531           _igvn.replace_node(use, pinned_clone);
2532           continue;
2533         }
2534       }
2535       _igvn.replace_input_of(use, idx, phi);
2536       if( use->_idx >= new_counter ) { // If updating new phis
2537         // Not needed for correctness, but prevents a weak assert
2538         // in AddPNode from tripping (when we end up with different
2539         // base & derived Phis that will become the same after
2540         // IGVN does CSE).
2541         Node *hit = _igvn.hash_find_insert(use);
2542         if( hit )             // Go ahead and re-hash for hits.
2543           _igvn.replace_node( use, hit );
2544       }
2545     }
2546   }
2547 }
2548 
2549 static void collect_nodes_in_outer_loop_not_reachable_from_sfpt(Node* n, const IdealLoopTree *loop, const IdealLoopTree* outer_loop,
2550                                                                 const Node_List &old_new, Unique_Node_List& wq, PhaseIdealLoop* phase,
2551                                                                 bool check_old_new) {
2552   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2553     Node* u = n->fast_out(j);
2554     assert(check_old_new || old_new[u->_idx] == nullptr, "shouldn't have been cloned");
2555     if (!u->is_CFG() && (!check_old_new || old_new[u->_idx] == nullptr)) {
2556       assert(!phase->ctrl_is_member(loop, u) || !loop->_body.contains(u), "can be in outer loop or out of both loops only");
2557       if (!phase->ctrl_is_member(loop, u)) {
2558         if (phase->ctrl_is_member(outer_loop, u)) {
2559           wq.push(u);
2560         } else {
2561           // nodes pinned with control in the outer loop but not referenced from the safepoint must be moved out of
2562           // the outer loop too
2563           Node* u_c = u->in(0);
2564           if (u_c != nullptr) {
2565             IdealLoopTree* u_c_loop = phase->get_loop(u_c);
2566             if (outer_loop->is_member(u_c_loop) && !loop->is_member(u_c_loop)) {
2567               wq.push(u);
2568             }
2569           }
2570         }
2571       }
2572     }
2573   }
2574 }
2575 
2576 void PhaseIdealLoop::clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
2577                                       IdealLoopTree* outer_loop, int dd, Node_List &old_new,
2578                                       Node_List& extra_data_nodes) {
2579   if (head->is_strip_mined() && mode != IgnoreStripMined) {
2580     CountedLoopNode* cl = head->as_CountedLoop();
2581     Node* l = cl->outer_loop();
2582     Node* tail = cl->outer_loop_tail();
2583     IfNode* le = cl->outer_loop_end();
2584     Node* sfpt = cl->outer_safepoint();
2585     CountedLoopEndNode* cle = cl->loopexit();
2586     CountedLoopNode* new_cl = old_new[cl->_idx]->as_CountedLoop();
2587     CountedLoopEndNode* new_cle = new_cl->as_CountedLoop()->loopexit_or_null();
2588     IfFalseNode* cle_out = cle->false_proj();
2589 
2590     Node* new_sfpt = nullptr;
2591     Node* new_cle_out = cle_out->clone();
2592     old_new.map(cle_out->_idx, new_cle_out);
2593     if (mode == CloneIncludesStripMined) {
2594       // clone outer loop body
2595       Node* new_l = l->clone();
2596       Node* new_tail = tail->clone();
2597       IfNode* new_le = le->clone()->as_If();
2598       new_sfpt = sfpt->clone();
2599 
2600       set_loop(new_l, outer_loop->_parent);
2601       set_idom(new_l, new_l->in(LoopNode::EntryControl), dd);
2602       set_loop(new_cle_out, outer_loop->_parent);
2603       set_idom(new_cle_out, new_cle, dd);
2604       set_loop(new_sfpt, outer_loop->_parent);
2605       set_idom(new_sfpt, new_cle_out, dd);
2606       set_loop(new_le, outer_loop->_parent);
2607       set_idom(new_le, new_sfpt, dd);
2608       set_loop(new_tail, outer_loop->_parent);
2609       set_idom(new_tail, new_le, dd);
2610       set_idom(new_cl, new_l, dd);
2611 
2612       old_new.map(l->_idx, new_l);
2613       old_new.map(tail->_idx, new_tail);
2614       old_new.map(le->_idx, new_le);
2615       old_new.map(sfpt->_idx, new_sfpt);
2616 
2617       new_l->set_req(LoopNode::LoopBackControl, new_tail);
2618       new_l->set_req(0, new_l);
2619       new_tail->set_req(0, new_le);
2620       new_le->set_req(0, new_sfpt);
2621       new_sfpt->set_req(0, new_cle_out);
2622       new_cle_out->set_req(0, new_cle);
2623       new_cl->set_req(LoopNode::EntryControl, new_l);
2624 
2625       _igvn.register_new_node_with_optimizer(new_l);
2626       _igvn.register_new_node_with_optimizer(new_tail);
2627       _igvn.register_new_node_with_optimizer(new_le);
2628     } else {
2629       Node *newhead = old_new[loop->_head->_idx];
2630       newhead->as_Loop()->clear_strip_mined();
2631       _igvn.replace_input_of(newhead, LoopNode::EntryControl, newhead->in(LoopNode::EntryControl)->in(LoopNode::EntryControl));
2632       set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2633     }
2634     // Look at data node that were assigned a control in the outer
2635     // loop: they are kept in the outer loop by the safepoint so start
2636     // from the safepoint node's inputs.
2637     IdealLoopTree* outer_loop = get_loop(l);
2638     Node_Stack stack(2);
2639     stack.push(sfpt, 1);
2640     uint new_counter = C->unique();
2641     while (stack.size() > 0) {
2642       Node* n = stack.node();
2643       uint i = stack.index();
2644       while (i < n->req() &&
2645              (n->in(i) == nullptr ||
2646               !has_ctrl(n->in(i)) ||
2647               get_loop(get_ctrl(n->in(i))) != outer_loop ||
2648               (old_new[n->in(i)->_idx] != nullptr && old_new[n->in(i)->_idx]->_idx >= new_counter))) {
2649         i++;
2650       }
2651       if (i < n->req()) {
2652         stack.set_index(i+1);
2653         stack.push(n->in(i), 0);
2654       } else {
2655         assert(old_new[n->_idx] == nullptr || n == sfpt || old_new[n->_idx]->_idx < new_counter, "no clone yet");
2656         Node* m = n == sfpt ? new_sfpt : n->clone();
2657         if (m != nullptr) {
2658           for (uint i = 0; i < n->req(); i++) {
2659             if (m->in(i) != nullptr && old_new[m->in(i)->_idx] != nullptr) {
2660               m->set_req(i, old_new[m->in(i)->_idx]);
2661             }
2662           }
2663         } else {
2664           assert(n == sfpt && mode != CloneIncludesStripMined, "where's the safepoint clone?");
2665         }
2666         if (n != sfpt) {
2667           extra_data_nodes.push(n);
2668           _igvn.register_new_node_with_optimizer(m);
2669           assert(get_ctrl(n) == cle_out, "what other control?");
2670           set_ctrl(m, new_cle_out);
2671           old_new.map(n->_idx, m);
2672         }
2673         stack.pop();
2674       }
2675     }
2676     if (mode == CloneIncludesStripMined) {
2677       _igvn.register_new_node_with_optimizer(new_sfpt);
2678       _igvn.register_new_node_with_optimizer(new_cle_out);
2679     }
2680     // Some other transformation may have pessimistically assigned some
2681     // data nodes to the outer loop. Set their control so they are out
2682     // of the outer loop.
2683     ResourceMark rm;
2684     Unique_Node_List wq;
2685     for (uint i = 0; i < extra_data_nodes.size(); i++) {
2686       Node* old = extra_data_nodes.at(i);
2687       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2688     }
2689 
2690     for (uint i = 0; i < loop->_body.size(); i++) {
2691       Node* old = loop->_body.at(i);
2692       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2693     }
2694 
2695     Node* inner_out = sfpt->in(0);
2696     if (inner_out->outcnt() > 1) {
2697       collect_nodes_in_outer_loop_not_reachable_from_sfpt(inner_out, loop, outer_loop, old_new, wq, this, true);
2698     }
2699 
2700     Node* new_ctrl = cl->outer_loop_exit();
2701     assert(get_loop(new_ctrl) != outer_loop, "must be out of the loop nest");
2702     for (uint i = 0; i < wq.size(); i++) {
2703       Node* n = wq.at(i);
2704       set_ctrl(n, new_ctrl);
2705       if (n->in(0) != nullptr) {
2706         _igvn.replace_input_of(n, 0, new_ctrl);
2707       }
2708       collect_nodes_in_outer_loop_not_reachable_from_sfpt(n, loop, outer_loop, old_new, wq, this, false);
2709     }
2710   } else {
2711     Node *newhead = old_new[loop->_head->_idx];
2712     set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2713   }
2714 }
2715 
2716 //------------------------------clone_loop-------------------------------------
2717 //
2718 //                   C L O N E   A   L O O P   B O D Y
2719 //
2720 // This is the basic building block of the loop optimizations.  It clones an
2721 // entire loop body.  It makes an old_new loop body mapping; with this mapping
2722 // you can find the new-loop equivalent to an old-loop node.  All new-loop
2723 // nodes are exactly equal to their old-loop counterparts, all edges are the
2724 // same.  All exits from the old-loop now have a RegionNode that merges the
2725 // equivalent new-loop path.  This is true even for the normal "loop-exit"
2726 // condition.  All uses of loop-invariant old-loop values now come from (one
2727 // or more) Phis that merge their new-loop equivalents.
2728 //
2729 // This operation leaves the graph in an illegal state: there are two valid
2730 // control edges coming from the loop pre-header to both loop bodies.  I'll
2731 // definitely have to hack the graph after running this transform.
2732 //
2733 // From this building block I will further edit edges to perform loop peeling
2734 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
2735 //
2736 // Parameter side_by_size_idom:
2737 //   When side_by_size_idom is null, the dominator tree is constructed for
2738 //      the clone loop to dominate the original.  Used in construction of
2739 //      pre-main-post loop sequence.
2740 //   When nonnull, the clone and original are side-by-side, both are
2741 //      dominated by the side_by_side_idom node.  Used in construction of
2742 //      unswitched loops.
2743 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
2744                                 CloneLoopMode mode, Node* side_by_side_idom) {
2745 
2746   LoopNode* head = loop->_head->as_Loop();
2747   head->verify_strip_mined(1);
2748 
2749   if (C->do_vector_loop() && PrintOpto) {
2750     const char* mname = C->method()->name()->as_quoted_ascii();
2751     if (mname != nullptr) {
2752       tty->print("PhaseIdealLoop::clone_loop: for vectorize method %s\n", mname);
2753     }
2754   }
2755 
2756   CloneMap& cm = C->clone_map();
2757   if (C->do_vector_loop()) {
2758     cm.set_clone_idx(cm.max_gen()+1);
2759 #ifndef PRODUCT
2760     if (PrintOpto) {
2761       tty->print_cr("PhaseIdealLoop::clone_loop: _clone_idx %d", cm.clone_idx());
2762       loop->dump_head();
2763     }
2764 #endif
2765   }
2766 
2767   // Step 1: Clone the loop body.  Make the old->new mapping.
2768   clone_loop_body(loop->_body, old_new, &cm);
2769 
2770   IdealLoopTree* outer_loop = (head->is_strip_mined() && mode != IgnoreStripMined) ? get_loop(head->as_CountedLoop()->outer_loop()) : loop;
2771 
2772   // Step 2: Fix the edges in the new body.  If the old input is outside the
2773   // loop use it.  If the old input is INside the loop, use the corresponding
2774   // new node instead.
2775   fix_body_edges(loop->_body, loop, old_new, dd, outer_loop->_parent, false);
2776 
2777   Node_List extra_data_nodes; // data nodes in the outer strip mined loop
2778   clone_outer_loop(head, mode, loop, outer_loop, dd, old_new, extra_data_nodes);
2779 
2780   // Step 3: Now fix control uses.  Loop varying control uses have already
2781   // been fixed up (as part of all input edges in Step 2).  Loop invariant
2782   // control uses must be either an IfFalse or an IfTrue.  Make a merge
2783   // point to merge the old and new IfFalse/IfTrue nodes; make the use
2784   // refer to this.
2785   Node_List worklist;
2786   uint new_counter = C->unique();
2787   fix_ctrl_uses(loop->_body, loop, old_new, mode, side_by_side_idom, &cm, worklist);
2788 
2789   // Step 4: If loop-invariant use is not control, it must be dominated by a
2790   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
2791   // there if needed.  Make a Phi there merging old and new used values.
2792   Node_List *split_if_set = nullptr;
2793   Node_List *split_bool_set = nullptr;
2794   Node_List *split_cex_set = nullptr;
2795   fix_data_uses(loop->_body, loop, mode, outer_loop, new_counter, old_new, worklist, split_if_set, split_bool_set, split_cex_set);
2796 
2797   for (uint i = 0; i < extra_data_nodes.size(); i++) {
2798     Node* old = extra_data_nodes.at(i);
2799     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2800                                 split_bool_set, split_cex_set, worklist, new_counter,
2801                                 mode);
2802   }
2803 
2804   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
2805   // the loop uses a condition set in the loop.  The original IF probably
2806   // takes control from one or more OLD Regions (which in turn get from NEW
2807   // Regions).  In any case, there will be a set of Phis for each merge point
2808   // from the IF up to where the original BOOL def exists the loop.
2809   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
2810 
2811 }
2812 
2813 void PhaseIdealLoop::finish_clone_loop(Node_List* split_if_set, Node_List* split_bool_set, Node_List* split_cex_set) {
2814   if (split_if_set) {
2815     while (split_if_set->size()) {
2816       Node *iff = split_if_set->pop();
2817       uint input = iff->Opcode() == Op_AllocateArray ? AllocateNode::ValidLengthTest : 1;
2818       if (iff->in(input)->is_Phi()) {
2819         Node *b = clone_iff(iff->in(input)->as_Phi());
2820         _igvn.replace_input_of(iff, input, b);
2821       }
2822     }
2823   }
2824   if (split_bool_set) {
2825     while (split_bool_set->size()) {
2826       Node *b = split_bool_set->pop();
2827       Node *phi = b->in(1);
2828       assert(phi->is_Phi(), "");
2829       CmpNode *cmp = clone_bool((PhiNode*) phi);
2830       _igvn.replace_input_of(b, 1, cmp);
2831     }
2832   }
2833   if (split_cex_set) {
2834     while (split_cex_set->size()) {
2835       Node *b = split_cex_set->pop();
2836       assert(b->in(0)->is_Region(), "");
2837       assert(b->in(1)->is_Phi(), "");
2838       assert(b->in(0)->in(0) == b->in(1)->in(0), "");
2839       split_up(b, b->in(0), nullptr);
2840     }
2841   }
2842 }
2843 
2844 void PhaseIdealLoop::fix_data_uses(Node_List& body, IdealLoopTree* loop, CloneLoopMode mode, IdealLoopTree* outer_loop,
2845                                    uint new_counter, Node_List &old_new, Node_List &worklist, Node_List*& split_if_set,
2846                                    Node_List*& split_bool_set, Node_List*& split_cex_set) {
2847   for(uint i = 0; i < body.size(); i++ ) {
2848     Node* old = body.at(i);
2849     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2850                                 split_bool_set, split_cex_set, worklist, new_counter,
2851                                 mode);
2852   }
2853 }
2854 
2855 void PhaseIdealLoop::fix_ctrl_uses(const Node_List& body, const IdealLoopTree* loop, Node_List &old_new, CloneLoopMode mode,
2856                                    Node* side_by_side_idom, CloneMap* cm, Node_List &worklist) {
2857   LoopNode* head = loop->_head->as_Loop();
2858   for(uint i = 0; i < body.size(); i++ ) {
2859     Node* old = body.at(i);
2860     if( !old->is_CFG() ) continue;
2861 
2862     // Copy uses to a worklist, so I can munge the def-use info
2863     // with impunity.
2864     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++) {
2865       worklist.push(old->fast_out(j));
2866     }
2867 
2868     while (worklist.size()) {  // Visit all uses
2869       Node *use = worklist.pop();
2870       if (!has_node(use))  continue; // Ignore dead nodes
2871       IdealLoopTree *use_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use );
2872       if (!loop->is_member(use_loop) && use->is_CFG()) {
2873         // Both OLD and USE are CFG nodes here.
2874         assert(use->is_Proj(), "" );
2875         Node* nnn = old_new[old->_idx];
2876 
2877         Node* newuse = nullptr;
2878         if (head->is_strip_mined() && mode != IgnoreStripMined) {
2879           CountedLoopNode* cl = head->as_CountedLoop();
2880           CountedLoopEndNode* cle = cl->loopexit();
2881           // is use the projection that exits the loop from the CountedLoopEndNode?
2882           if (use->in(0) == cle) {
2883             IfFalseNode* cle_out = use->as_IfFalse();
2884             IfNode* le = cl->outer_loop_end();
2885             use = le->false_proj();
2886             use_loop = get_loop(use);
2887             if (mode == CloneIncludesStripMined) {
2888               nnn = old_new[le->_idx];
2889             } else {
2890               newuse = old_new[cle_out->_idx];
2891             }
2892           }
2893         }
2894         if (newuse == nullptr) {
2895           newuse = use->clone();
2896         }
2897 
2898         // Clone the loop exit control projection
2899         if (C->do_vector_loop() && cm != nullptr) {
2900           cm->verify_insert_and_clone(use, newuse, cm->clone_idx());
2901         }
2902         newuse->set_req(0,nnn);
2903         _igvn.register_new_node_with_optimizer(newuse);
2904         set_loop(newuse, use_loop);
2905         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
2906 
2907         // We need a Region to merge the exit from the peeled body and the
2908         // exit from the old loop body.
2909         RegionNode *r = new RegionNode(3);
2910         uint dd_r = MIN2(dom_depth(newuse), dom_depth(use));
2911         assert(dd_r >= dom_depth(dom_lca(newuse, use)), "" );
2912 
2913         // The original user of 'use' uses 'r' instead.
2914         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
2915           Node* useuse = use->last_out(l);
2916           _igvn.rehash_node_delayed(useuse);
2917           uint uses_found = 0;
2918           if (useuse->in(0) == use) {
2919             useuse->set_req(0, r);
2920             uses_found++;
2921             if (useuse->is_CFG()) {
2922               // This is not a dom_depth > dd_r because when new
2923               // control flow is constructed by a loop opt, a node and
2924               // its dominator can end up at the same dom_depth
2925               assert(dom_depth(useuse) >= dd_r, "");
2926               set_idom(useuse, r, dom_depth(useuse));
2927             }
2928           }
2929           for (uint k = 1; k < useuse->req(); k++) {
2930             if( useuse->in(k) == use ) {
2931               useuse->set_req(k, r);
2932               uses_found++;
2933               if (useuse->is_Loop() && k == LoopNode::EntryControl) {
2934                 // This is not a dom_depth > dd_r because when new
2935                 // control flow is constructed by a loop opt, a node
2936                 // and its dominator can end up at the same dom_depth
2937                 assert(dom_depth(useuse) >= dd_r , "");
2938                 set_idom(useuse, r, dom_depth(useuse));
2939               }
2940             }
2941           }
2942           l -= uses_found;    // we deleted 1 or more copies of this edge
2943         }
2944 
2945         assert(use->is_Proj(), "loop exit should be projection");
2946         // replace_node_and_forward_ctrl() below moves all nodes that are:
2947         // - control dependent on the loop exit or
2948         // - have control set to the loop exit
2949         // below the post-loop merge point.
2950         // replace_node_and_forward_ctrl() takes a dead control as first input.
2951         // To make it possible to use it, the loop exit projection is cloned and becomes the
2952         // new exit projection. The initial one becomes dead and is "replaced" by the region.
2953         Node* use_clone = use->clone();
2954         register_control(use_clone, use_loop, idom(use), dom_depth(use));
2955         // Now finish up 'r'
2956         r->set_req(1, newuse);
2957         r->set_req(2, use_clone);
2958         _igvn.register_new_node_with_optimizer(r);
2959         set_loop(r, use_loop);
2960         set_idom(r, (side_by_side_idom == nullptr) ? newuse->in(0) : side_by_side_idom, dd_r);
2961         replace_node_and_forward_ctrl(use, r);
2962         // Map the (cloned) old use to the new merge point
2963         old_new.map(use_clone->_idx, r);
2964       } // End of if a loop-exit test
2965     }
2966   }
2967 }
2968 
2969 void PhaseIdealLoop::fix_body_edges(const Node_List &body, IdealLoopTree* loop, const Node_List &old_new, int dd,
2970                                     IdealLoopTree* parent, bool partial) {
2971   for(uint i = 0; i < body.size(); i++ ) {
2972     Node *old = body.at(i);
2973     Node *nnn = old_new[old->_idx];
2974     // Fix CFG/Loop controlling the new node
2975     if (has_ctrl(old)) {
2976       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
2977     } else {
2978       set_loop(nnn, parent);
2979       if (old->outcnt() > 0) {
2980         Node* dom = idom(old);
2981         if (old_new[dom->_idx] != nullptr) {
2982           dom = old_new[dom->_idx];
2983           set_idom(nnn, dom, dd );
2984         }
2985       }
2986     }
2987     // Correct edges to the new node
2988     for (uint j = 0; j < nnn->req(); j++) {
2989         Node *n = nnn->in(j);
2990         if (n != nullptr) {
2991           IdealLoopTree *old_in_loop = get_loop(has_ctrl(n) ? get_ctrl(n) : n);
2992           if (loop->is_member(old_in_loop)) {
2993             if (old_new[n->_idx] != nullptr) {
2994               nnn->set_req(j, old_new[n->_idx]);
2995             } else {
2996               assert(!body.contains(n), "");
2997               assert(partial, "node not cloned");
2998             }
2999           }
3000         }
3001     }
3002     _igvn.hash_find_insert(nnn);
3003   }
3004 }
3005 
3006 void PhaseIdealLoop::clone_loop_body(const Node_List& body, Node_List &old_new, CloneMap* cm) {
3007   for (uint i = 0; i < body.size(); i++) {
3008     Node* old = body.at(i);
3009     Node* nnn = old->clone();
3010     old_new.map(old->_idx, nnn);
3011     if (C->do_vector_loop() && cm != nullptr) {
3012       cm->verify_insert_and_clone(old, nnn, cm->clone_idx());
3013     }
3014     _igvn.register_new_node_with_optimizer(nnn);
3015   }
3016 }
3017 
3018 
3019 //---------------------- stride_of_possible_iv -------------------------------------
3020 // Looks for an iff/bool/comp with one operand of the compare
3021 // being a cycle involving an add and a phi,
3022 // with an optional truncation (left-shift followed by a right-shift)
3023 // of the add. Returns zero if not an iv.
3024 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
3025   const TypeInteger* ttype = nullptr;
3026   if (!iff->is_If() || iff->in(1) == nullptr || !iff->in(1)->is_Bool()) {
3027     return 0;
3028   }
3029   BoolNode* bl = iff->in(1)->as_Bool();
3030   Node* cmp = bl->in(1);
3031   if (!cmp || (cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU)) {
3032     return 0;
3033   }
3034   // Must have an invariant operand
3035   if (ctrl_is_member(get_loop(iff), cmp->in(2))) {
3036     return 0;
3037   }
3038   Node* add2 = nullptr;
3039   Node* cmp1 = cmp->in(1);
3040   if (cmp1->is_Phi()) {
3041     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
3042     Node* phi = cmp1;
3043     for (uint i = 1; i < phi->req(); i++) {
3044       Node* in = phi->in(i);
3045       CountedLoopConverter::TruncatedIncrement add(T_INT);
3046       add.build(in);
3047       if (add.is_valid() && add.incr()->in(1) == phi) {
3048         add2 = add.incr()->in(2);
3049         break;
3050       }
3051     }
3052   } else {
3053     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
3054     Node* addtrunc = cmp1;
3055     CountedLoopConverter::TruncatedIncrement add(T_INT);
3056     add.build(addtrunc);
3057     if (add.is_valid() && add.incr()->in(1)->is_Phi()) {
3058       Node* phi = add.incr()->in(1);
3059       for (uint i = 1; i < phi->req(); i++) {
3060         if (phi->in(i) == addtrunc) {
3061           add2 = add.incr()->in(2);
3062           break;
3063         }
3064       }
3065     }
3066   }
3067   if (add2 != nullptr) {
3068     const TypeInt* add2t = _igvn.type(add2)->is_int();
3069     if (add2t->is_con()) {
3070       return add2t->get_con();
3071     }
3072   }
3073   return 0;
3074 }
3075 
3076 
3077 //---------------------- stay_in_loop -------------------------------------
3078 // Return the (unique) control output node that's in the loop (if it exists.)
3079 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
3080   Node* unique = nullptr;
3081   if (!n) return nullptr;
3082   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3083     Node* use = n->fast_out(i);
3084     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
3085       if (unique != nullptr) {
3086         return nullptr;
3087       }
3088       unique = use;
3089     }
3090   }
3091   return unique;
3092 }
3093 
3094 //------------------------------ register_node -------------------------------------
3095 // Utility to register node "n" with PhaseIdealLoop
3096 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree* loop, Node* pred, uint ddepth) {
3097   _igvn.register_new_node_with_optimizer(n);
3098   loop->_body.push(n);
3099   if (n->is_CFG()) {
3100     set_loop(n, loop);
3101     set_idom(n, pred, ddepth);
3102   } else {
3103     set_ctrl(n, pred);
3104   }
3105 }
3106 
3107 //------------------------------ proj_clone -------------------------------------
3108 // Utility to create an if-projection
3109 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
3110   ProjNode* c = p->clone()->as_Proj();
3111   c->set_req(0, iff);
3112   return c;
3113 }
3114 
3115 //------------------------------ short_circuit_if -------------------------------------
3116 // Force the iff control output to be the live_proj
3117 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
3118   guarantee(live_proj != nullptr, "null projection");
3119   int proj_con = live_proj->_con;
3120   assert(proj_con == 0 || proj_con == 1, "false or true projection");
3121   Node* con = intcon(proj_con);
3122   if (iff) {
3123     iff->set_req(1, con);
3124   }
3125   return con;
3126 }
3127 
3128 //------------------------------ insert_if_before_proj -------------------------------------
3129 // Insert a new if before an if projection (* - new node)
3130 //
3131 // before
3132 //           if(test)
3133 //           /     \
3134 //          v       v
3135 //    other-proj   proj (arg)
3136 //
3137 // after
3138 //           if(test)
3139 //           /     \
3140 //          /       v
3141 //         |      * proj-clone
3142 //         v          |
3143 //    other-proj      v
3144 //                * new_if(relop(cmp[IU](left,right)))
3145 //                  /  \
3146 //                 v    v
3147 //         * new-proj  proj
3148 //         (returned)
3149 //
3150 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
3151   IfNode* iff = proj->in(0)->as_If();
3152   IdealLoopTree *loop = get_loop(proj);
3153   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3154   uint ddepth = dom_depth(proj);
3155 
3156   _igvn.rehash_node_delayed(iff);
3157   _igvn.rehash_node_delayed(proj);
3158 
3159   proj->set_req(0, nullptr);  // temporary disconnect
3160   ProjNode* proj2 = proj_clone(proj, iff);
3161   register_node(proj2, loop, iff, ddepth);
3162 
3163   Node* cmp = Signed ? (Node*) new CmpINode(left, right) : (Node*) new CmpUNode(left, right);
3164   register_node(cmp, loop, proj2, ddepth);
3165 
3166   BoolNode* bol = new BoolNode(cmp, relop);
3167   register_node(bol, loop, proj2, ddepth);
3168 
3169   int opcode = iff->Opcode();
3170   assert(opcode == Op_If || opcode == Op_RangeCheck, "unexpected opcode");
3171   IfNode* new_if = IfNode::make_with_same_profile(iff, proj2, bol);
3172   register_node(new_if, loop, proj2, ddepth);
3173 
3174   proj->set_req(0, new_if); // reattach
3175   set_idom(proj, new_if, ddepth);
3176 
3177   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
3178   guarantee(new_exit != nullptr, "null exit node");
3179   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
3180 
3181   return new_exit;
3182 }
3183 
3184 //------------------------------ insert_region_before_proj -------------------------------------
3185 // Insert a region before an if projection (* - new node)
3186 //
3187 // before
3188 //           if(test)
3189 //          /      |
3190 //         v       |
3191 //       proj      v
3192 //               other-proj
3193 //
3194 // after
3195 //           if(test)
3196 //          /      |
3197 //         v       |
3198 // * proj-clone    v
3199 //         |     other-proj
3200 //         v
3201 // * new-region
3202 //         |
3203 //         v
3204 // *      dum_if
3205 //       /     \
3206 //      v       \
3207 // * dum-proj    v
3208 //              proj
3209 //
3210 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
3211   IfNode* iff = proj->in(0)->as_If();
3212   IdealLoopTree *loop = get_loop(proj);
3213   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3214   uint ddepth = dom_depth(proj);
3215 
3216   _igvn.rehash_node_delayed(iff);
3217   _igvn.rehash_node_delayed(proj);
3218 
3219   proj->set_req(0, nullptr);  // temporary disconnect
3220   ProjNode* proj2 = proj_clone(proj, iff);
3221   register_node(proj2, loop, iff, ddepth);
3222 
3223   RegionNode* reg = new RegionNode(2);
3224   reg->set_req(1, proj2);
3225   register_node(reg, loop, iff, ddepth);
3226 
3227   IfNode* dum_if = new IfNode(reg, short_circuit_if(nullptr, proj), iff->_prob, iff->_fcnt);
3228   register_node(dum_if, loop, reg, ddepth);
3229 
3230   proj->set_req(0, dum_if); // reattach
3231   set_idom(proj, dum_if, ddepth);
3232 
3233   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
3234   register_node(dum_proj, loop, dum_if, ddepth);
3235 
3236   return reg;
3237 }
3238 
3239 // Idea
3240 // ----
3241 // Partial Peeling tries to rotate the loop in such a way that it can later be turned into a counted loop. Counted loops
3242 // require a signed loop exit test. When calling this method, we've only found a suitable unsigned test to partial peel
3243 // with. Therefore, we try to split off a signed loop exit test from the unsigned test such that it can be used as new
3244 // loop exit while keeping the unsigned test unchanged and preserving the same behavior as if we've used the unsigned
3245 // test alone instead:
3246 //
3247 // Before Partial Peeling:
3248 //   Loop:
3249 //     <peeled section>
3250 //     Split off signed loop exit test
3251 //     <-- CUT HERE -->
3252 //     Unchanged unsigned loop exit test
3253 //     <rest of unpeeled section>
3254 //     goto Loop
3255 //
3256 // After Partial Peeling:
3257 //   <cloned peeled section>
3258 //   Cloned split off signed loop exit test
3259 //   Loop:
3260 //     Unchanged unsigned loop exit test
3261 //     <rest of unpeeled section>
3262 //     <peeled section>
3263 //     Split off signed loop exit test
3264 //     goto Loop
3265 //
3266 // Details
3267 // -------
3268 // Before:
3269 //          if (i <u limit)    Unsigned loop exit condition
3270 //         /       |
3271 //        v        v
3272 //   exit-proj   stay-in-loop-proj
3273 //
3274 // Split off a signed loop exit test (i.e. with CmpI) from an unsigned loop exit test (i.e. with CmpU) and insert it
3275 // before the CmpU on the stay-in-loop path and keep both tests:
3276 //
3277 //          if (i <u limit)    Signed loop exit test
3278 //        /        |
3279 //       /  if (i <u limit)    Unsigned loop exit test
3280 //      /  /       |
3281 //     v  v        v
3282 //  exit-region  stay-in-loop-proj
3283 //
3284 // Implementation
3285 // --------------
3286 // We need to make sure that the new signed loop exit test is properly inserted into the graph such that the unsigned
3287 // loop exit test still dominates the same set of control nodes, the ctrl() relation from data nodes to both loop
3288 // exit tests is preserved, and their loop nesting is correct.
3289 //
3290 // To achieve that, we clone the unsigned loop exit test completely (leave it unchanged), insert the signed loop exit
3291 // test above it and kill the original unsigned loop exit test by setting it's condition to a constant
3292 // (i.e. stay-in-loop-const in graph below) such that IGVN can fold it later:
3293 //
3294 //           if (stay-in-loop-const)  Killed original unsigned loop exit test
3295 //          /       |
3296 //         /        v
3297 //        /  if (i <  limit)          Split off signed loop exit test
3298 //       /  /       |
3299 //      /  /        v
3300 //     /  /  if (i <u limit)          Cloned unsigned loop exit test
3301 //    /  /   /      |
3302 //   v  v  v        |
3303 //  exit-region     |
3304 //        |         |
3305 //    dummy-if      |
3306 //     /  |         |
3307 // dead   |         |
3308 //        v         v
3309 //   exit-proj   stay-in-loop-proj
3310 //
3311 // Note: The dummy-if is inserted to create a region to merge the loop exits between the original to be killed unsigned
3312 //       loop exit test and its exit projection while keeping the exit projection (also see insert_region_before_proj()).
3313 //
3314 // Requirements
3315 // ------------
3316 // Note that we can only split off a signed loop exit test from the unsigned loop exit test when the behavior is exactly
3317 // the same as before with only a single unsigned test. This is only possible if certain requirements are met.
3318 // Otherwise, we need to bail out (see comments in the code below).
3319 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree* loop) {
3320   const bool Signed   = true;
3321   const bool Unsigned = false;
3322 
3323   BoolNode* bol = if_cmpu->in(1)->as_Bool();
3324   if (bol->_test._test != BoolTest::lt) {
3325     return nullptr;
3326   }
3327   CmpNode* cmpu = bol->in(1)->as_Cmp();
3328   assert(cmpu->Opcode() == Op_CmpU, "must be unsigned comparison");
3329 
3330   int stride = stride_of_possible_iv(if_cmpu);
3331   if (stride == 0) {
3332     return nullptr;
3333   }
3334 
3335   Node* lp_proj = stay_in_loop(if_cmpu, loop);
3336   guarantee(lp_proj != nullptr, "null loop node");
3337 
3338   ProjNode* lp_continue = lp_proj->as_Proj();
3339   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
3340   if (!lp_exit->is_IfFalse()) {
3341     // The loop exit condition is (i <u limit) ==> (i >= 0 && i < limit).
3342     // We therefore can't add a single exit condition.
3343     return nullptr;
3344   }
3345   // The unsigned loop exit condition is
3346   //   !(i <u  limit)
3347   // =   i >=u limit
3348   //
3349   // First, we note that for any x for which
3350   //   0 <= x <= INT_MAX
3351   // we can convert x to an unsigned int and still get the same guarantee:
3352   //   0 <=  (uint) x <=  INT_MAX = (uint) INT_MAX
3353   //   0 <=u (uint) x <=u INT_MAX = (uint) INT_MAX   (LEMMA)
3354   //
3355   // With that in mind, if
3356   //   limit >= 0             (COND)
3357   // then the unsigned loop exit condition
3358   //   i >=u limit            (ULE)
3359   // is equivalent to
3360   //   i < 0 || i >= limit    (SLE-full)
3361   // because either i is negative and therefore always greater than MAX_INT when converting to unsigned
3362   //   (uint) i >=u MAX_INT >= limit >= 0
3363   // or otherwise
3364   //   i >= limit >= 0
3365   // holds due to (LEMMA).
3366   //
3367   // For completeness, a counterexample with limit < 0:
3368   // Assume i = -3 and limit = -2:
3369   //   i  < 0
3370   //   -2 < 0
3371   // is true and thus also "i < 0 || i >= limit". But
3372   //   i  >=u limit
3373   //   -3 >=u -2
3374   // is false.
3375   Node* limit = cmpu->in(2);
3376   const TypeInt* type_limit = _igvn.type(limit)->is_int();
3377   if (type_limit->_lo < 0) {
3378     return nullptr;
3379   }
3380 
3381   // We prove below that we can extract a single signed loop exit condition from (SLE-full), depending on the stride:
3382   //   stride < 0:
3383   //     i < 0        (SLE = SLE-negative)
3384   //   stride > 0:
3385   //     i >= limit   (SLE = SLE-positive)
3386   // such that we have the following graph before Partial Peeling with stride > 0 (similar for stride < 0):
3387   //
3388   // Loop:
3389   //   <peeled section>
3390   //   i >= limit    (SLE-positive)
3391   //   <-- CUT HERE -->
3392   //   i >=u limit   (ULE)
3393   //   <rest of unpeeled section>
3394   //   goto Loop
3395   //
3396   // We exit the loop if:
3397   //   (SLE) is true OR (ULE) is true
3398   // However, if (SLE) is true then (ULE) also needs to be true to ensure the exact same behavior. Otherwise, we wrongly
3399   // exit a loop that should not have been exited if we did not apply Partial Peeling. More formally, we need to ensure:
3400   //   (SLE) IMPLIES (ULE)
3401   // This indeed holds when (COND) is given:
3402   // - stride > 0:
3403   //       i >=  limit             // (SLE = SLE-positive)
3404   //       i >=  limit >= 0        // (COND)
3405   //       i >=u limit >= 0        // (LEMMA)
3406   //     which is the unsigned loop exit condition (ULE).
3407   // - stride < 0:
3408   //       i        <  0           // (SLE = SLE-negative)
3409   //       (uint) i >u MAX_INT     // (NEG) all negative values are greater than MAX_INT when converted to unsigned
3410   //       MAX_INT >= limit >= 0   // (COND)
3411   //       MAX_INT >=u limit >= 0  // (LEMMA)
3412   //     and thus from (NEG) and (LEMMA):
3413   //       i >=u limit
3414   //     which is the unsigned loop exit condition (ULE).
3415   //
3416   //
3417   // After Partial Peeling, we have the following structure for stride > 0 (similar for stride < 0):
3418   //   <cloned peeled section>
3419   //   i >= limit (SLE-positive)
3420   //   Loop:
3421   //     i >=u limit (ULE)
3422   //     <rest of unpeeled section>
3423   //     <peeled section>
3424   //     i >= limit (SLE-positive)
3425   //     goto Loop
3426   Node* rhs_cmpi;
3427   if (stride > 0) {
3428     rhs_cmpi = limit; // For i >= limit
3429   } else {
3430     rhs_cmpi = makecon(TypeInt::ZERO); // For i < 0
3431   }
3432   // Create a new region on the exit path
3433   RegionNode* reg = insert_region_before_proj(lp_exit);
3434   guarantee(reg != nullptr, "null region node");
3435 
3436   // Clone the if-cmpu-true-false using a signed compare
3437   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
3438   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, rhs_cmpi, lp_continue);
3439   reg->add_req(cmpi_exit);
3440 
3441   // Clone the if-cmpu-true-false
3442   BoolTest::mask rel_u = bol->_test._test;
3443   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
3444   reg->add_req(cmpu_exit);
3445 
3446   // Force original if to stay in loop.
3447   short_circuit_if(if_cmpu, lp_continue);
3448 
3449   return cmpi_exit->in(0)->as_If();
3450 }
3451 
3452 //------------------------------ remove_cmpi_loop_exit -------------------------------------
3453 // Remove a previously inserted signed compare loop exit.
3454 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
3455   Node* lp_proj = stay_in_loop(if_cmp, loop);
3456   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
3457          stay_in_loop(lp_proj, loop)->is_If() &&
3458          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
3459   Node* con = makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
3460   if_cmp->set_req(1, con);
3461 }
3462 
3463 //------------------------------ scheduled_nodelist -------------------------------------
3464 // Create a post order schedule of nodes that are in the
3465 // "member" set.  The list is returned in "sched".
3466 // The first node in "sched" is the loop head, followed by
3467 // nodes which have no inputs in the "member" set, and then
3468 // followed by the nodes that have an immediate input dependence
3469 // on a node in "sched".
3470 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
3471 
3472   assert(member.test(loop->_head->_idx), "loop head must be in member set");
3473   VectorSet visited;
3474   Node_Stack nstack(loop->_body.size());
3475 
3476   Node* n  = loop->_head;  // top of stack is cached in "n"
3477   uint idx = 0;
3478   visited.set(n->_idx);
3479 
3480   // Initially push all with no inputs from within member set
3481   for(uint i = 0; i < loop->_body.size(); i++ ) {
3482     Node *elt = loop->_body.at(i);
3483     if (member.test(elt->_idx)) {
3484       bool found = false;
3485       for (uint j = 0; j < elt->req(); j++) {
3486         Node* def = elt->in(j);
3487         if (def && member.test(def->_idx) && def != elt) {
3488           found = true;
3489           break;
3490         }
3491       }
3492       if (!found && elt != loop->_head) {
3493         nstack.push(n, idx);
3494         n = elt;
3495         assert(!visited.test(n->_idx), "not seen yet");
3496         visited.set(n->_idx);
3497       }
3498     }
3499   }
3500 
3501   // traverse out's that are in the member set
3502   while (true) {
3503     if (idx < n->outcnt()) {
3504       Node* use = n->raw_out(idx);
3505       idx++;
3506       if (!visited.test_set(use->_idx)) {
3507         if (member.test(use->_idx)) {
3508           nstack.push(n, idx);
3509           n = use;
3510           idx = 0;
3511         }
3512       }
3513     } else {
3514       // All outputs processed
3515       sched.push(n);
3516       if (nstack.is_empty()) break;
3517       n   = nstack.node();
3518       idx = nstack.index();
3519       nstack.pop();
3520     }
3521   }
3522 }
3523 
3524 
3525 //------------------------------ has_use_in_set -------------------------------------
3526 // Has a use in the vector set
3527 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
3528   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3529     Node* use = n->fast_out(j);
3530     if (vset.test(use->_idx)) {
3531       return true;
3532     }
3533   }
3534   return false;
3535 }
3536 
3537 
3538 //------------------------------ has_use_internal_to_set -------------------------------------
3539 // Has use internal to the vector set (ie. not in a phi at the loop head)
3540 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
3541   Node* head  = loop->_head;
3542   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3543     Node* use = n->fast_out(j);
3544     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
3545       return true;
3546     }
3547   }
3548   return false;
3549 }
3550 
3551 
3552 //------------------------------ clone_for_use_outside_loop -------------------------------------
3553 // clone "n" for uses that are outside of loop
3554 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
3555   int cloned = 0;
3556   assert(worklist.size() == 0, "should be empty");
3557   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3558     Node* use = n->fast_out(j);
3559     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
3560       worklist.push(use);
3561     }
3562   }
3563 
3564   if (C->check_node_count(worklist.size() + NodeLimitFudgeFactor,
3565                           "Too many clones required in clone_for_use_outside_loop in partial peeling")) {
3566     return -1;
3567   }
3568 
3569   while( worklist.size() ) {
3570     Node *use = worklist.pop();
3571     if (!has_node(use) || use->in(0) == C->top()) continue;
3572     uint j;
3573     for (j = 0; j < use->req(); j++) {
3574       if (use->in(j) == n) break;
3575     }
3576     assert(j < use->req(), "must be there");
3577 
3578     // clone "n" and insert it between the inputs of "n" and the use outside the loop
3579     Node* n_clone = n->clone();
3580     _igvn.replace_input_of(use, j, n_clone);
3581     cloned++;
3582     Node* use_c;
3583     if (!use->is_Phi()) {
3584       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
3585     } else {
3586       // Use in a phi is considered a use in the associated predecessor block
3587       use_c = use->in(0)->in(j);
3588     }
3589     set_ctrl(n_clone, use_c);
3590     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
3591     get_loop(use_c)->_body.push(n_clone);
3592     _igvn.register_new_node_with_optimizer(n_clone);
3593 #ifndef PRODUCT
3594     if (TracePartialPeeling) {
3595       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
3596     }
3597 #endif
3598   }
3599   return cloned;
3600 }
3601 
3602 
3603 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
3604 // clone "n" for special uses that are in the not_peeled region.
3605 // If these def-uses occur in separate blocks, the code generator
3606 // marks the method as not compilable.  For example, if a "BoolNode"
3607 // is in a different basic block than the "IfNode" that uses it, then
3608 // the compilation is aborted in the code generator.
3609 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
3610                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
3611   if (n->is_Phi() || n->is_Load()) {
3612     return;
3613   }
3614   assert(worklist.size() == 0, "should be empty");
3615   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3616     Node* use = n->fast_out(j);
3617     if ( not_peel.test(use->_idx) &&
3618          (use->is_If() || use->is_CMove() || use->is_Bool() || use->is_OpaqueInitializedAssertionPredicate()) &&
3619          use->in(1) == n)  {
3620       worklist.push(use);
3621     }
3622   }
3623   if (worklist.size() > 0) {
3624     // clone "n" and insert it between inputs of "n" and the use
3625     Node* n_clone = n->clone();
3626     loop->_body.push(n_clone);
3627     _igvn.register_new_node_with_optimizer(n_clone);
3628     set_ctrl(n_clone, get_ctrl(n));
3629     sink_list.push(n_clone);
3630     not_peel.set(n_clone->_idx);
3631 #ifndef PRODUCT
3632     if (TracePartialPeeling) {
3633       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
3634     }
3635 #endif
3636     while( worklist.size() ) {
3637       Node *use = worklist.pop();
3638       _igvn.rehash_node_delayed(use);
3639       for (uint j = 1; j < use->req(); j++) {
3640         if (use->in(j) == n) {
3641           use->set_req(j, n_clone);
3642         }
3643       }
3644     }
3645   }
3646 }
3647 
3648 
3649 //------------------------------ insert_phi_for_loop -------------------------------------
3650 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
3651 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
3652   Node *phi = PhiNode::make(lp, back_edge_val);
3653   phi->set_req(LoopNode::EntryControl, lp_entry_val);
3654   // Use existing phi if it already exists
3655   Node *hit = _igvn.hash_find_insert(phi);
3656   if( hit == nullptr ) {
3657     _igvn.register_new_node_with_optimizer(phi);
3658     set_ctrl(phi, lp);
3659   } else {
3660     // Remove the new phi from the graph and use the hit
3661     _igvn.remove_dead_node(phi, PhaseIterGVN::NodeOrigin::Speculative);
3662     phi = hit;
3663   }
3664   _igvn.replace_input_of(use, idx, phi);
3665 }
3666 
3667 #ifdef ASSERT
3668 //------------------------------ is_valid_loop_partition -------------------------------------
3669 // Validate the loop partition sets: peel and not_peel
3670 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
3671                                               VectorSet& not_peel ) {
3672   uint i;
3673   // Check that peel_list entries are in the peel set
3674   for (i = 0; i < peel_list.size(); i++) {
3675     if (!peel.test(peel_list.at(i)->_idx)) {
3676       return false;
3677     }
3678   }
3679   // Check at loop members are in one of peel set or not_peel set
3680   for (i = 0; i < loop->_body.size(); i++ ) {
3681     Node *def  = loop->_body.at(i);
3682     uint di = def->_idx;
3683     // Check that peel set elements are in peel_list
3684     if (peel.test(di)) {
3685       if (not_peel.test(di)) {
3686         return false;
3687       }
3688       // Must be in peel_list also
3689       bool found = false;
3690       for (uint j = 0; j < peel_list.size(); j++) {
3691         if (peel_list.at(j)->_idx == di) {
3692           found = true;
3693           break;
3694         }
3695       }
3696       if (!found) {
3697         return false;
3698       }
3699     } else if (not_peel.test(di)) {
3700       if (peel.test(di)) {
3701         return false;
3702       }
3703     } else {
3704       return false;
3705     }
3706   }
3707   return true;
3708 }
3709 
3710 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
3711 // Ensure a use outside of loop is of the right form
3712 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
3713   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3714   return (use->is_Phi() &&
3715           use_c->is_Region() && use_c->req() == 3 &&
3716           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
3717            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
3718            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
3719           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
3720 }
3721 
3722 //------------------------------ is_valid_clone_loop_form -------------------------------------
3723 // Ensure that all uses outside of loop are of the right form
3724 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
3725                                                uint orig_exit_idx, uint clone_exit_idx) {
3726   uint len = peel_list.size();
3727   for (uint i = 0; i < len; i++) {
3728     Node *def = peel_list.at(i);
3729 
3730     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
3731       Node *use = def->fast_out(j);
3732       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3733       if (!loop->is_member(get_loop(use_c))) {
3734         // use is not in the loop, check for correct structure
3735         if (use->in(0) == def) {
3736           // Okay
3737         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
3738           return false;
3739         }
3740       }
3741     }
3742   }
3743   return true;
3744 }
3745 #endif
3746 
3747 //------------------------------ partial_peel -------------------------------------
3748 // Partially peel (aka loop rotation) the top portion of a loop (called
3749 // the peel section below) by cloning it and placing one copy just before
3750 // the new loop head and the other copy at the bottom of the new loop.
3751 //
3752 //    before                       after                where it came from
3753 //
3754 //    stmt1                        stmt1
3755 //  loop:                          stmt2                     clone
3756 //    stmt2                        if condA goto exitA       clone
3757 //    if condA goto exitA        new_loop:                   new
3758 //    stmt3                        stmt3                     clone
3759 //    if !condB goto loop          if condB goto exitB       clone
3760 //  exitB:                         stmt2                     orig
3761 //    stmt4                        if !condA goto new_loop   orig
3762 //  exitA:                         goto exitA
3763 //                               exitB:
3764 //                                 stmt4
3765 //                               exitA:
3766 //
3767 // Step 1: find the cut point: an exit test on probable
3768 //         induction variable.
3769 // Step 2: schedule (with cloning) operations in the peel
3770 //         section that can be executed after the cut into
3771 //         the section that is not peeled.  This may need
3772 //         to clone operations into exit blocks.  For
3773 //         instance, a reference to A[i] in the not-peel
3774 //         section and a reference to B[i] in an exit block
3775 //         may cause a left-shift of i by 2 to be placed
3776 //         in the peel block.  This step will clone the left
3777 //         shift into the exit block and sink the left shift
3778 //         from the peel to the not-peel section.
3779 // Step 3: clone the loop, retarget the control, and insert
3780 //         phis for values that are live across the new loop
3781 //         head.  This is very dependent on the graph structure
3782 //         from clone_loop.  It creates region nodes for
3783 //         exit control and associated phi nodes for values
3784 //         flow out of the loop through that exit.  The region
3785 //         node is dominated by the clone's control projection.
3786 //         So the clone's peel section is placed before the
3787 //         new loop head, and the clone's not-peel section is
3788 //         forms the top part of the new loop.  The original
3789 //         peel section forms the tail of the new loop.
3790 // Step 4: update the dominator tree and recompute the
3791 //         dominator depth.
3792 //
3793 //                   orig
3794 //
3795 //                   stmt1
3796 //                     |
3797 //                     v
3798 //                 predicates
3799 //                     |
3800 //                     v
3801 //                   loop<----+
3802 //                     |      |
3803 //                   stmt2    |
3804 //                     |      |
3805 //                     v      |
3806 //                    ifA     |
3807 //                   / |      |
3808 //                  v  v      |
3809 //               false true   ^  <-- last_peel
3810 //               /     |      |
3811 //              /   ===|==cut |
3812 //             /     stmt3    |  <-- first_not_peel
3813 //            /        |      |
3814 //            |        v      |
3815 //            v       ifB     |
3816 //          exitA:   / \      |
3817 //                  /   \     |
3818 //                 v     v    |
3819 //               false true   |
3820 //               /       \    |
3821 //              /         ----+
3822 //             |
3823 //             v
3824 //           exitB:
3825 //           stmt4
3826 //
3827 //
3828 //            after clone loop
3829 //
3830 //                   stmt1
3831 //                     |
3832 //                     v
3833 //                predicates
3834 //                 /       \
3835 //        clone   /         \   orig
3836 //               /           \
3837 //              /             \
3838 //             v               v
3839 //   +---->loop                loop<----+
3840 //   |      |                    |      |
3841 //   |    stmt2                stmt2    |
3842 //   |      |                    |      |
3843 //   |      v                    v      |
3844 //   |      ifA                 ifA     |
3845 //   |      | \                / |      |
3846 //   |      v  v              v  v      |
3847 //   ^    true  false      false true   ^  <-- last_peel
3848 //   |      |   ^   \       /    |      |
3849 //   | cut==|==  \   \     /  ===|==cut |
3850 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
3851 //   |      |    dom   | |       |      |
3852 //   |      v      \  1v v2      v      |
3853 //   |      ifB     regionA     ifB     |
3854 //   |      / \        |       / \      |
3855 //   |     /   \       v      /   \     |
3856 //   |    v     v    exitA:  v     v    |
3857 //   |    true  false      false true   |
3858 //   |    /     ^   \      /       \    |
3859 //   +----       \   \    /         ----+
3860 //               dom  \  /
3861 //                 \  1v v2
3862 //                  regionB
3863 //                     |
3864 //                     v
3865 //                   exitB:
3866 //                   stmt4
3867 //
3868 //
3869 //           after partial peel
3870 //
3871 //                  stmt1
3872 //                     |
3873 //                     v
3874 //                predicates
3875 //                 /
3876 //        clone   /             orig
3877 //               /          TOP
3878 //              /             \
3879 //             v               v
3880 //    TOP->loop                loop----+
3881 //          |                    |      |
3882 //        stmt2                stmt2    |
3883 //          |                    |      |
3884 //          v                    v      |
3885 //          ifA                 ifA     |
3886 //          | \                / |      |
3887 //          v  v              v  v      |
3888 //        true  false      false true   |     <-- last_peel
3889 //          |   ^   \       /    +------|---+
3890 //  +->newloop   \   \     /  === ==cut |   |
3891 //  |     stmt3   \   \   /     TOP     |   |
3892 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
3893 //  |       v      \  1v v2      v      |   |
3894 //  |       ifB     regionA     ifB     ^   v
3895 //  |       / \        |       / \      |   |
3896 //  |      /   \       v      /   \     |   |
3897 //  |     v     v    exitA:  v     v    |   |
3898 //  |     true  false      false true   |   |
3899 //  |     /     ^   \      /       \    |   |
3900 //  |    |       \   \    /         v   |   |
3901 //  |    |       dom  \  /         TOP  |   |
3902 //  |    |         \  1v v2             |   |
3903 //  ^    v          regionB             |   |
3904 //  |    |             |                |   |
3905 //  |    |             v                ^   v
3906 //  |    |           exitB:             |   |
3907 //  |    |           stmt4              |   |
3908 //  |    +------------>-----------------+   |
3909 //  |                                       |
3910 //  +-----------------<---------------------+
3911 //
3912 //
3913 //              final graph
3914 //
3915 //                  stmt1
3916 //                    |
3917 //                    v
3918 //                predicates
3919 //                    |
3920 //                    v
3921 //                  stmt2 clone
3922 //                    |
3923 //                    v
3924 //         ........> ifA clone
3925 //         :        / |
3926 //        dom      /  |
3927 //         :      v   v
3928 //         :  false   true
3929 //         :  |       |
3930 //         :  |       v
3931 //         :  |    newloop<-----+
3932 //         :  |        |        |
3933 //         :  |     stmt3 clone |
3934 //         :  |        |        |
3935 //         :  |        v        |
3936 //         :  |       ifB       |
3937 //         :  |      / \        |
3938 //         :  |     v   v       |
3939 //         :  |  false true     |
3940 //         :  |   |     |       |
3941 //         :  |   v    stmt2    |
3942 //         :  | exitB:  |       |
3943 //         :  | stmt4   v       |
3944 //         :  |       ifA orig  |
3945 //         :  |      /  \       |
3946 //         :  |     /    \      |
3947 //         :  |    v     v      |
3948 //         :  |  false  true    |
3949 //         :  |  /        \     |
3950 //         :  v  v         -----+
3951 //          RegionA
3952 //             |
3953 //             v
3954 //           exitA
3955 //
3956 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
3957 
3958   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
3959   if (!loop->_head->is_Loop()) {
3960     return false;
3961   }
3962   LoopNode *head = loop->_head->as_Loop();
3963 
3964   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
3965     return false;
3966   }
3967 
3968   // Check for complex exit control
3969   for (uint ii = 0; ii < loop->_body.size(); ii++) {
3970     Node *n = loop->_body.at(ii);
3971     int opc = n->Opcode();
3972     if (n->is_Call()        ||
3973         opc == Op_Catch     ||
3974         opc == Op_CatchProj ||
3975         opc == Op_Jump      ||
3976         opc == Op_JumpProj) {
3977 #ifndef PRODUCT
3978       if (TracePartialPeeling) {
3979         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
3980       }
3981 #endif
3982       return false;
3983     }
3984   }
3985 
3986   int dd = dom_depth(head);
3987 
3988   // Step 1: find cut point
3989 
3990   // Walk up dominators to loop head looking for first loop exit
3991   // which is executed on every path thru loop.
3992   IfNode *peel_if = nullptr;
3993   IfNode *peel_if_cmpu = nullptr;
3994 
3995   Node *iff = loop->tail();
3996   while (iff != head) {
3997     if (iff->is_If()) {
3998       Node *ctrl = get_ctrl(iff->in(1));
3999       if (ctrl->is_top()) return false; // Dead test on live IF.
4000       // If loop-varying exit-test, check for induction variable
4001       if (loop->is_member(get_loop(ctrl)) &&
4002           loop->is_loop_exit(iff) &&
4003           is_possible_iv_test(iff)) {
4004         Node* cmp = iff->in(1)->in(1);
4005         if (cmp->Opcode() == Op_CmpI) {
4006           peel_if = iff->as_If();
4007         } else {
4008           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
4009           peel_if_cmpu = iff->as_If();
4010         }
4011       }
4012     }
4013     iff = idom(iff);
4014   }
4015 
4016   // Prefer signed compare over unsigned compare.
4017   IfNode* new_peel_if = nullptr;
4018   if (peel_if == nullptr) {
4019     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == nullptr) {
4020       return false;   // No peel point found
4021     }
4022     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
4023     if (new_peel_if == nullptr) {
4024       return false;   // No peel point found
4025     }
4026     peel_if = new_peel_if;
4027   }
4028   Node* last_peel        = stay_in_loop(peel_if, loop);
4029   Node* first_not_peeled = stay_in_loop(last_peel, loop);
4030   if (first_not_peeled == nullptr || first_not_peeled == head) {
4031     return false;
4032   }
4033 
4034 #ifndef PRODUCT
4035   if (TraceLoopOpts) {
4036     tty->print("PartialPeel  ");
4037     loop->dump_head();
4038   }
4039 
4040   if (TracePartialPeeling) {
4041     tty->print_cr("before partial peel one iteration");
4042     Node_List wl;
4043     Node* t = head->in(2);
4044     while (true) {
4045       wl.push(t);
4046       if (t == head) break;
4047       t = idom(t);
4048     }
4049     while (wl.size() > 0) {
4050       Node* tt = wl.pop();
4051       tt->dump();
4052       if (tt == last_peel) tty->print_cr("-- cut --");
4053     }
4054   }
4055 #endif
4056 
4057   C->print_method(PHASE_BEFORE_PARTIAL_PEELING, 4, head);
4058 
4059   VectorSet peel;
4060   VectorSet not_peel;
4061   Node_List peel_list;
4062   Node_List worklist;
4063   Node_List sink_list;
4064 
4065   uint estimate = loop->est_loop_clone_sz(1);
4066   if (exceeding_node_budget(estimate)) {
4067     return false;
4068   }
4069 
4070   // Set of cfg nodes to peel are those that are executable from
4071   // the head through last_peel.
4072   assert(worklist.size() == 0, "should be empty");
4073   worklist.push(head);
4074   peel.set(head->_idx);
4075   while (worklist.size() > 0) {
4076     Node *n = worklist.pop();
4077     if (n != last_peel) {
4078       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
4079         Node* use = n->fast_out(j);
4080         if (use->is_CFG() &&
4081             loop->is_member(get_loop(use)) &&
4082             !peel.test_set(use->_idx)) {
4083           worklist.push(use);
4084         }
4085       }
4086     }
4087   }
4088 
4089   // Set of non-cfg nodes to peel are those that are control
4090   // dependent on the cfg nodes.
4091   for (uint i = 0; i < loop->_body.size(); i++) {
4092     Node *n = loop->_body.at(i);
4093     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
4094     if (peel.test(n_c->_idx)) {
4095       peel.set(n->_idx);
4096     } else {
4097       not_peel.set(n->_idx);
4098     }
4099   }
4100 
4101   // Step 2: move operations from the peeled section down into the
4102   //         not-peeled section
4103 
4104   // Get a post order schedule of nodes in the peel region
4105   // Result in right-most operand.
4106   scheduled_nodelist(loop, peel, peel_list);
4107 
4108   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4109 
4110   // For future check for too many new phis
4111   uint old_phi_cnt = 0;
4112   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
4113     Node* use = head->fast_out(j);
4114     if (use->is_Phi()) old_phi_cnt++;
4115   }
4116 
4117 #ifndef PRODUCT
4118   if (TracePartialPeeling) {
4119     tty->print_cr("\npeeled list");
4120   }
4121 #endif
4122 
4123   // Evacuate nodes in peel region into the not_peeled region if possible
4124   bool too_many_clones = false;
4125   uint new_phi_cnt = 0;
4126   uint cloned_for_outside_use = 0;
4127   for (uint i = 0; i < peel_list.size();) {
4128     Node* n = peel_list.at(i);
4129 #ifndef PRODUCT
4130   if (TracePartialPeeling) n->dump();
4131 #endif
4132     bool incr = true;
4133     if (!n->is_CFG()) {
4134       if (has_use_in_set(n, not_peel)) {
4135         // If not used internal to the peeled region,
4136         // move "n" from peeled to not_peeled region.
4137         if (!has_use_internal_to_set(n, peel, loop)) {
4138           // if not pinned and not a load (which maybe anti-dependent on a store)
4139           // and not a CMove (Matcher expects only bool->cmove).
4140           if (n->in(0) == nullptr && !n->is_Load() && !n->is_CMove()) {
4141             int new_clones = clone_for_use_outside_loop(loop, n, worklist);
4142             if (C->failing()) return false;
4143             if (new_clones == -1) {
4144               too_many_clones = true;
4145               break;
4146             }
4147             cloned_for_outside_use += new_clones;
4148             sink_list.push(n);
4149             peel.remove(n->_idx);
4150             not_peel.set(n->_idx);
4151             peel_list.remove(i);
4152             incr = false;
4153 #ifndef PRODUCT
4154             if (TracePartialPeeling) {
4155               tty->print_cr("sink to not_peeled region: %d newbb: %d",
4156                             n->_idx, get_ctrl(n)->_idx);
4157             }
4158 #endif
4159           }
4160         } else {
4161           // Otherwise check for special def-use cases that span
4162           // the peel/not_peel boundary such as bool->if
4163           clone_for_special_use_inside_loop(loop, n, not_peel, sink_list, worklist);
4164           new_phi_cnt++;
4165         }
4166       }
4167     }
4168     if (incr) i++;
4169   }
4170 
4171   estimate += cloned_for_outside_use + new_phi_cnt;
4172   bool exceed_node_budget = !may_require_nodes(estimate);
4173   bool exceed_phi_limit = new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta;
4174 
4175   if (too_many_clones || exceed_node_budget || exceed_phi_limit) {
4176 #ifndef PRODUCT
4177     if (TracePartialPeeling && exceed_phi_limit) {
4178       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
4179                     new_phi_cnt, old_phi_cnt, new_peel_if != nullptr?'T':'F');
4180     }
4181 #endif
4182     if (new_peel_if != nullptr) {
4183       remove_cmpi_loop_exit(new_peel_if, loop);
4184     }
4185     // Inhibit more partial peeling on this loop
4186     assert(!head->is_partial_peel_loop(), "not partial peeled");
4187     head->mark_partial_peel_failed();
4188     if (cloned_for_outside_use > 0) {
4189       // Terminate this round of loop opts because
4190       // the graph outside this loop was changed.
4191       C->set_major_progress();
4192       return true;
4193     }
4194     return false;
4195   }
4196 
4197   // Step 3: clone loop, retarget control, and insert new phis
4198 
4199   // Create new loop head for new phis and to hang
4200   // the nodes being moved (sinked) from the peel region.
4201   LoopNode* new_head = new LoopNode(last_peel, last_peel);
4202   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
4203   _igvn.register_new_node_with_optimizer(new_head);
4204   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
4205   _igvn.replace_input_of(first_not_peeled, 0, new_head);
4206   set_loop(new_head, loop);
4207   loop->_body.push(new_head);
4208   not_peel.set(new_head->_idx);
4209   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
4210   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
4211 
4212   while (sink_list.size() > 0) {
4213     Node* n = sink_list.pop();
4214     set_ctrl(n, new_head);
4215   }
4216 
4217   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4218 
4219   clone_loop(loop, old_new, dd, IgnoreStripMined);
4220 
4221   const uint clone_exit_idx = 1;
4222   const uint orig_exit_idx  = 2;
4223   assert(is_valid_clone_loop_form(loop, peel_list, orig_exit_idx, clone_exit_idx), "bad clone loop");
4224 
4225   Node* head_clone             = old_new[head->_idx];
4226   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
4227   Node* orig_tail_clone        = head_clone->in(2);
4228 
4229   // Add phi if "def" node is in peel set and "use" is not
4230 
4231   for (uint i = 0; i < peel_list.size(); i++) {
4232     Node *def  = peel_list.at(i);
4233     if (!def->is_CFG()) {
4234       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
4235         Node *use = def->fast_out(j);
4236         if (has_node(use) && use->in(0) != C->top() &&
4237             (!peel.test(use->_idx) ||
4238              (use->is_Phi() && use->in(0) == head)) ) {
4239           worklist.push(use);
4240         }
4241       }
4242       while( worklist.size() ) {
4243         Node *use = worklist.pop();
4244         for (uint j = 1; j < use->req(); j++) {
4245           Node* n = use->in(j);
4246           if (n == def) {
4247 
4248             // "def" is in peel set, "use" is not in peel set
4249             // or "use" is in the entry boundary (a phi) of the peel set
4250 
4251             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
4252 
4253             if ( loop->is_member(get_loop( use_c )) ) {
4254               // use is in loop
4255               if (old_new[use->_idx] != nullptr) { // null for dead code
4256                 Node* use_clone = old_new[use->_idx];
4257                 _igvn.replace_input_of(use, j, C->top());
4258                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
4259               }
4260             } else {
4261               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
4262               // use is not in the loop, check if the live range includes the cut
4263               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
4264               if (not_peel.test(lp_if->_idx)) {
4265                 assert(j == orig_exit_idx, "use from original loop");
4266                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
4267               }
4268             }
4269           }
4270         }
4271       }
4272     }
4273   }
4274 
4275   // Step 3b: retarget control
4276 
4277   // Redirect control to the new loop head if a cloned node in
4278   // the not_peeled region has control that points into the peeled region.
4279   // This necessary because the cloned peeled region will be outside
4280   // the loop.
4281   //                            from    to
4282   //          cloned-peeled    <---+
4283   //    new_head_clone:            |    <--+
4284   //          cloned-not_peeled  in(0)    in(0)
4285   //          orig-peeled
4286 
4287   for (uint i = 0; i < loop->_body.size(); i++) {
4288     Node *n = loop->_body.at(i);
4289     if (!n->is_CFG()           && n->in(0) != nullptr        &&
4290         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
4291       Node* n_clone = old_new[n->_idx];
4292       if (n_clone->depends_only_on_test()) {
4293         // If this node depends_only_on_test, it will be rewire to the loop head, which is not the
4294         // correct test
4295         Node* pinned_clone = n_clone->pin_node_under_control();
4296         if (pinned_clone != nullptr) {
4297           register_new_node_with_ctrl_of(pinned_clone, n_clone);
4298           old_new.map(n->_idx, pinned_clone);
4299           _igvn.replace_node(n_clone, pinned_clone);
4300           n_clone = pinned_clone;
4301         }
4302       }
4303       _igvn.replace_input_of(n_clone, 0, new_head_clone);
4304     }
4305   }
4306 
4307   // Backedge of the surviving new_head (the clone) is original last_peel
4308   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
4309 
4310   // Cut first node in original not_peel set
4311   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
4312   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
4313   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
4314 
4315   // Copy head_clone back-branch info to original head
4316   // and remove original head's loop entry and
4317   // clone head's back-branch
4318   _igvn.rehash_node_delayed(head); // Multiple edge updates
4319   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
4320   head->set_req(LoopNode::LoopBackControl, C->top());
4321   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
4322 
4323   // Similarly modify the phis
4324   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
4325     Node* use = head->fast_out(k);
4326     if (use->is_Phi() && use->outcnt() > 0) {
4327       Node* use_clone = old_new[use->_idx];
4328       _igvn.rehash_node_delayed(use); // Multiple edge updates
4329       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
4330       use->set_req(LoopNode::LoopBackControl, C->top());
4331       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
4332     }
4333   }
4334 
4335   // Step 4: update dominator tree and dominator depth
4336 
4337   set_idom(head, orig_tail_clone, dd);
4338   recompute_dom_depth();
4339 
4340   // Inhibit more partial peeling on this loop
4341   new_head_clone->set_partial_peel_loop();
4342   C->set_major_progress();
4343   loop->record_for_igvn();
4344 
4345 #ifndef PRODUCT
4346   if (TracePartialPeeling) {
4347     tty->print_cr("\nafter partial peel one iteration");
4348     Node_List wl;
4349     Node* t = last_peel;
4350     while (true) {
4351       wl.push(t);
4352       if (t == head_clone) break;
4353       t = idom(t);
4354     }
4355     while (wl.size() > 0) {
4356       Node* tt = wl.pop();
4357       if (tt == head) tty->print_cr("orig head");
4358       else if (tt == new_head_clone) tty->print_cr("new head");
4359       else if (tt == head_clone) tty->print_cr("clone head");
4360       tt->dump();
4361     }
4362   }
4363 #endif
4364 
4365   C->print_method(PHASE_AFTER_PARTIAL_PEELING, 4, new_head_clone);
4366 
4367   return true;
4368 }
4369 
4370 #ifdef ASSERT
4371 
4372 // Moves Template Assertion Predicates to a target loop by cloning and killing the old ones. The target loop is the
4373 // original, not-cloned loop. This is currently only used with StressLoopBackedge which is a develop flag only and
4374 // false with product builds. We can therefore guard it with an ifdef. More details can be found at the use-site.
4375 class MoveAssertionPredicatesVisitor : public PredicateVisitor {
4376   ClonePredicateToTargetLoop _clone_predicate_to_loop;
4377   PhaseIdealLoop* const _phase;
4378 
4379 public:
4380   MoveAssertionPredicatesVisitor(LoopNode* target_loop_head,
4381                                  const NodeInSingleLoopBody &node_in_loop_body,
4382                                  PhaseIdealLoop* phase)
4383     : _clone_predicate_to_loop(target_loop_head, node_in_loop_body, phase),
4384       _phase(phase) {
4385   }
4386   NONCOPYABLE(MoveAssertionPredicatesVisitor);
4387 
4388   using PredicateVisitor::visit;
4389 
4390   void visit(const TemplateAssertionPredicate& template_assertion_predicate) override {
4391     _clone_predicate_to_loop.clone_template_assertion_predicate(template_assertion_predicate);
4392     template_assertion_predicate.kill(_phase->igvn());
4393   }
4394 };
4395 #endif // ASSERT
4396 
4397 // Transform:
4398 //
4399 // loop<-----------------+
4400 //  |                    |
4401 // stmt1 stmt2 .. stmtn  |
4402 //  |     |        |     |
4403 //  \     |       /      |
4404 //    v   v     v        |
4405 //       region          |
4406 //         |             |
4407 //     shared_stmt       |
4408 //         |             |
4409 //         v             |
4410 //         if            |
4411 //         / \           |
4412 //        |   -----------+
4413 //        v
4414 //
4415 // into:
4416 //
4417 //    loop<-------------------+
4418 //     |                      |
4419 //     v                      |
4420 // +->loop                    |
4421 // |   |                      |
4422 // |  stmt1 stmt2 .. stmtn    |
4423 // |   |     |        |       |
4424 // |   |      \       /       |
4425 // |   |       v     v        |
4426 // |   |        region1       |
4427 // |   |           |          |
4428 // |  shared_stmt shared_stmt |
4429 // |   |           |          |
4430 // |   v           v          |
4431 // |   if          if         |
4432 // |   /\          / \        |
4433 // +--   |         |   -------+
4434 //       \         /
4435 //        v       v
4436 //         region2
4437 //
4438 // (region2 is shown to merge mirrored projections of the loop exit
4439 // ifs to make the diagram clearer but they really merge the same
4440 // projection)
4441 //
4442 // Conditions for this transformation to trigger:
4443 // - the path through stmt1 is frequent enough
4444 // - the inner loop will be turned into a counted loop after transformation
4445 bool PhaseIdealLoop::duplicate_loop_backedge(IdealLoopTree *loop, Node_List &old_new) {
4446   if (!DuplicateBackedge) {
4447     return false;
4448   }
4449   assert(!loop->_head->is_CountedLoop() || StressDuplicateBackedge, "Non-counted loop only");
4450   if (!loop->_head->is_Loop()) {
4451     return false;
4452   }
4453 
4454   uint estimate = loop->est_loop_clone_sz(1);
4455   if (exceeding_node_budget(estimate)) {
4456     return false;
4457   }
4458 
4459   LoopNode *head = loop->_head->as_Loop();
4460 
4461   Node* region = nullptr;
4462   IfNode* exit_test = nullptr;
4463   uint inner;
4464   float f;
4465 #ifdef ASSERT
4466   if (StressDuplicateBackedge) {
4467     if (head->is_strip_mined()) {
4468       return false;
4469     }
4470     Node* c = head->in(LoopNode::LoopBackControl);
4471 
4472     while (c != head) {
4473       if (c->is_Region()) {
4474         region = c;
4475       }
4476       c = idom(c);
4477     }
4478 
4479     if (region == nullptr) {
4480       return false;
4481     }
4482 
4483     inner = 1;
4484   } else
4485 #endif //ASSERT
4486   {
4487     // Is the shape of the loop that of a counted loop...
4488     Node* back_control = loop_exit_control(loop);
4489     if (back_control == nullptr) {
4490       return false;
4491     }
4492 
4493     LoopExitTest loop_exit(back_control, loop, this);
4494     loop_exit.build();
4495     if (!loop_exit.is_valid_with_bt(T_INT)) {
4496       return false;
4497     }
4498 
4499     const Node* loop_incr = loop_exit.incr();
4500 
4501     // With an extra phi for the candidate iv?
4502     // Or the region node is the loop head
4503     if (!loop_incr->is_Phi() || loop_incr->in(0) == head) {
4504       return false;
4505     }
4506 
4507     PathFrequency pf(head, this);
4508     region = loop_incr->in(0);
4509 
4510     // Go over all paths for the extra phi's region and see if that
4511     // path is frequent enough and would match the expected iv shape
4512     // if the extra phi is removed
4513     inner = 0;
4514     for (uint i = 1; i < loop_incr->req(); ++i) {
4515       CountedLoopConverter::TruncatedIncrement increment(T_INT);
4516       increment.build(loop_incr->in(i));
4517       if (!increment.is_valid()) {
4518         continue;
4519       }
4520       assert(increment.incr()->Opcode() == Op_AddI, "wrong increment code");
4521 
4522       LoopIVStride stride = LoopIVStride(T_INT);
4523       stride.build(increment.incr());
4524       if (!stride.is_valid()) {
4525         continue;
4526       }
4527 
4528       PhiNode* phi = loop_iv_phi(stride.xphi(), nullptr, head);
4529       if (phi == nullptr ||
4530           (increment.outer_trunc() == nullptr && phi->in(LoopNode::LoopBackControl) != loop_exit.incr()) ||
4531           (increment.outer_trunc() != nullptr && phi->in(LoopNode::LoopBackControl) != increment.outer_trunc())) {
4532         return false;
4533       }
4534 
4535       f = pf.to(region->in(i));
4536       if (f > 0.5) {
4537         inner = i;
4538         break;
4539       }
4540     }
4541 
4542     if (inner == 0) {
4543       return false;
4544     }
4545 
4546     exit_test = back_control->in(0)->as_If();
4547   }
4548 
4549   if (idom(region)->is_Catch()) {
4550     return false;
4551   }
4552 
4553   // Collect all control nodes that need to be cloned (shared_stmt in the diagram)
4554   Unique_Node_List wq;
4555   wq.push(head->in(LoopNode::LoopBackControl));
4556   for (uint i = 0; i < wq.size(); i++) {
4557     Node* c = wq.at(i);
4558     assert(get_loop(c) == loop, "not in the right loop?");
4559     if (c->is_Region()) {
4560       if (c != region) {
4561         for (uint j = 1; j < c->req(); ++j) {
4562           wq.push(c->in(j));
4563         }
4564       }
4565     } else {
4566       wq.push(c->in(0));
4567     }
4568     assert(!is_strict_dominator(c, region), "shouldn't go above region");
4569   }
4570 
4571   Node* region_dom = idom(region);
4572 
4573   // Can't do the transformation if this would cause a membar pair to
4574   // be split
4575   for (uint i = 0; i < wq.size(); i++) {
4576     Node* c = wq.at(i);
4577     if (c->is_MemBar() && (c->as_MemBar()->trailing_store() || c->as_MemBar()->trailing_load_store())) {
4578       assert(c->as_MemBar()->leading_membar()->trailing_membar() == c, "bad membar pair");
4579       if (!wq.member(c->as_MemBar()->leading_membar())) {
4580         return false;
4581       }
4582     }
4583   }
4584   C->print_method(PHASE_BEFORE_DUPLICATE_LOOP_BACKEDGE, 4, head);
4585 
4586   // Collect data nodes that need to be clones as well
4587   int dd = dom_depth(head);
4588 
4589   for (uint i = 0; i < loop->_body.size(); ++i) {
4590     Node* n = loop->_body.at(i);
4591     if (has_ctrl(n)) {
4592       Node* c = get_ctrl(n);
4593       if (wq.member(c)) {
4594         wq.push(n);
4595       }
4596     } else {
4597       set_idom(n, idom(n), dd);
4598     }
4599   }
4600 
4601   // clone shared_stmt
4602   clone_loop_body(wq, old_new, nullptr);
4603 
4604   Node* region_clone = old_new[region->_idx];
4605   region_clone->set_req(inner, C->top());
4606   set_idom(region, region->in(inner), dd);
4607 
4608   // Prepare the outer loop
4609   Node* outer_head = new LoopNode(head->in(LoopNode::EntryControl), old_new[head->in(LoopNode::LoopBackControl)->_idx]);
4610   register_control(outer_head, loop->_parent, outer_head->in(LoopNode::EntryControl));
4611   _igvn.replace_input_of(head, LoopNode::EntryControl, outer_head);
4612   set_idom(head, outer_head, dd);
4613 
4614   fix_body_edges(wq, loop, old_new, dd, loop->_parent, true);
4615 
4616   // Make one of the shared_stmt copies only reachable from stmt1, the
4617   // other only from stmt2..stmtn.
4618   Node* dom = nullptr;
4619   for (uint i = 1; i < region->req(); ++i) {
4620     if (i != inner) {
4621       _igvn.replace_input_of(region, i, C->top());
4622     }
4623     Node* in = region_clone->in(i);
4624     if (in->is_top()) {
4625       continue;
4626     }
4627     if (dom == nullptr) {
4628       dom = in;
4629     } else {
4630       dom = dom_lca(dom, in);
4631     }
4632   }
4633 
4634   set_idom(region_clone, dom, dd);
4635 
4636   // Set up the outer loop
4637   for (uint i = 0; i < head->outcnt(); i++) {
4638     Node* u = head->raw_out(i);
4639     if (u->is_Phi()) {
4640       Node* outer_phi = u->clone();
4641       outer_phi->set_req(0, outer_head);
4642       Node* backedge = old_new[u->in(LoopNode::LoopBackControl)->_idx];
4643       if (backedge == nullptr) {
4644         backedge = u->in(LoopNode::LoopBackControl);
4645       }
4646       outer_phi->set_req(LoopNode::LoopBackControl, backedge);
4647       register_new_node(outer_phi, outer_head);
4648       _igvn.replace_input_of(u, LoopNode::EntryControl, outer_phi);
4649     }
4650   }
4651 
4652   // create control and data nodes for out of loop uses (including region2)
4653   Node_List worklist;
4654   uint new_counter = C->unique();
4655   fix_ctrl_uses(wq, loop, old_new, ControlAroundStripMined, outer_head, nullptr, worklist);
4656 
4657   Node_List *split_if_set = nullptr;
4658   Node_List *split_bool_set = nullptr;
4659   Node_List *split_cex_set = nullptr;
4660   fix_data_uses(wq, loop, ControlAroundStripMined, loop->skip_strip_mined(), new_counter, old_new, worklist,
4661                 split_if_set, split_bool_set, split_cex_set);
4662 
4663   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
4664 
4665   if (exit_test != nullptr) {
4666     float cnt = exit_test->_fcnt;
4667     if (cnt != COUNT_UNKNOWN) {
4668       exit_test->_fcnt = cnt * f;
4669       old_new[exit_test->_idx]->as_If()->_fcnt = cnt * (1 - f);
4670     }
4671   }
4672 
4673 #ifdef ASSERT
4674   if (StressDuplicateBackedge && head->is_CountedLoop()) {
4675     // The Template Assertion Predicates from the old counted loop are now at the new outer loop - clone them to
4676     // the inner counted loop and kill the old ones. We only need to do this with debug builds because
4677     // StressDuplicateBackedge is a devlop flag and false by default. Without StressDuplicateBackedge 'head' will be a
4678     // non-counted loop, and thus we have no Template Assertion Predicates above the old loop to move down.
4679     PredicateIterator predicate_iterator(outer_head->in(LoopNode::EntryControl));
4680     NodeInSingleLoopBody node_in_body(this, loop);
4681     MoveAssertionPredicatesVisitor move_assertion_predicates_visitor(head, node_in_body, this);
4682     predicate_iterator.for_each(move_assertion_predicates_visitor);
4683   }
4684 #endif // ASSERT
4685 
4686   C->set_major_progress();
4687 
4688   C->print_method(PHASE_AFTER_DUPLICATE_LOOP_BACKEDGE, 4, outer_head);
4689 
4690   return true;
4691 }
4692 
4693 // AutoVectorize the loop: replace scalar ops with vector ops.
4694 PhaseIdealLoop::AutoVectorizeStatus
4695 PhaseIdealLoop::auto_vectorize(IdealLoopTree* lpt, VSharedData &vshared) {
4696   // Counted loop only
4697   if (!lpt->is_counted()) {
4698     return AutoVectorizeStatus::Impossible;
4699   }
4700 
4701   // Main-loop only
4702   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4703   if (!cl->is_main_loop()) {
4704     return AutoVectorizeStatus::Impossible;
4705   }
4706 
4707   VLoop vloop(lpt, false);
4708   if (!vloop.check_preconditions()) {
4709     return AutoVectorizeStatus::TriedAndFailed;
4710   }
4711 
4712   // Ensure the shared data is cleared before each use
4713   vshared.clear();
4714 
4715   const VLoopAnalyzer vloop_analyzer(vloop, vshared);
4716   if (!vloop_analyzer.success()) {
4717     return AutoVectorizeStatus::TriedAndFailed;
4718   }
4719 
4720   SuperWord sw(vloop_analyzer);
4721   if (!sw.transform_loop()) {
4722     return AutoVectorizeStatus::TriedAndFailed;
4723   }
4724 
4725   return AutoVectorizeStatus::Success;
4726 }
4727 
4728 // Just before insert_pre_post_loops, we can multiversion the loop:
4729 //
4730 //              multiversion_if
4731 //               |       |
4732 //         fast_loop   slow_loop
4733 //
4734 // In the fast_loop we can make speculative assumptions, and put the
4735 // conditions into the multiversion_if. If the conditions hold at runtime,
4736 // we enter the fast_loop, if the conditions fail, we take the slow_loop
4737 // instead which does not make any of the speculative assumptions.
4738 //
4739 // Note: we only multiversion the loop if the loop does not have any
4740 //       auto vectorization check Predicate. If we have that predicate,
4741 //       then we can simply add the speculative assumption checks to
4742 //       that Predicate. This means we do not need to duplicate the
4743 //       loop - we have a smaller graph and save compile time. Should
4744 //       the conditions ever fail, then we deopt / trap at the Predicate
4745 //       and recompile without that Predicate. At that point we will
4746 //       multiversion the loop, so that we can still have speculative
4747 //       runtime checks.
4748 //
4749 // We perform the multiversioning when the loop is still in its single
4750 // iteration form, even before we insert pre and post loops. This makes
4751 // the cloning much simpler. However, this means that both the fast
4752 // and the slow loop have to be optimized independently (adding pre
4753 // and post loops, unrolling the main loop, auto-vectorize etc.). And
4754 // we may end up not needing any speculative assumptions in the fast_loop
4755 // and then rejecting the slow_loop by constant folding the multiversion_if.
4756 //
4757 // Therefore, we "delay" the optimization of the slow_loop until we add
4758 // at least one speculative assumption for the fast_loop. If we never
4759 // add such a speculative runtime check, the OpaqueMultiversioningNode
4760 // of the multiversion_if constant folds to true after loop opts, and the
4761 // multiversion_if folds away the "delayed" slow_loop. If we add any
4762 // speculative assumption, then we notify the OpaqueMultiversioningNode
4763 // with "notify_slow_loop_that_it_can_resume_optimizations".
4764 //
4765 // Note: new runtime checks can be added to the multiversion_if with
4766 //       PhaseIdealLoop::create_new_if_for_multiversion
4767 void PhaseIdealLoop::maybe_multiversion_for_auto_vectorization_runtime_checks(IdealLoopTree* lpt, Node_List& old_new) {
4768   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4769   LoopNode* outer_loop = cl->skip_strip_mined();
4770   Node* entry = outer_loop->in(LoopNode::EntryControl);
4771 
4772   // Check we have multiversioning enabled, and are not already multiversioned.
4773   if (!LoopMultiversioning || cl->is_multiversion()) { return; }
4774 
4775   // Check that we do not have a parse-predicate where we can add the runtime checks
4776   // during auto-vectorization.
4777   const Predicates predicates(entry);
4778   const PredicateBlock* predicate_block = predicates.auto_vectorization_check_block();
4779   if (predicate_block->has_parse_predicate()) { return; }
4780 
4781   // Check node budget.
4782   uint estimate = lpt->est_loop_clone_sz(2);
4783   if (!may_require_nodes(estimate)) { return; }
4784 
4785   do_multiversioning(lpt, old_new);
4786 }
4787 
4788 void DataNodeGraph::clone_data_nodes(Node* new_ctrl) {
4789   for (uint i = 0; i < _data_nodes.size(); i++) {
4790     clone(_data_nodes[i], new_ctrl);
4791   }
4792 }
4793 
4794 // Clone the given node and set it up properly. Set 'new_ctrl' as ctrl.
4795 void DataNodeGraph::clone(Node* node, Node* new_ctrl) {
4796   Node* clone = node->clone();
4797   _phase->igvn().register_new_node_with_optimizer(clone);
4798   _orig_to_new.put(node, clone);
4799   _phase->set_ctrl(clone, new_ctrl);
4800   if (node->is_CastII()) {
4801     clone->set_req(0, new_ctrl);
4802   }
4803 }
4804 
4805 // Rewire the data inputs of all (unprocessed) cloned nodes, whose inputs are still pointing to the same inputs as their
4806 // corresponding orig nodes, to the newly cloned inputs to create a separate cloned graph.
4807 void DataNodeGraph::rewire_clones_to_cloned_inputs() {
4808   _orig_to_new.iterate_all([&](Node* node, Node* clone) {
4809     for (uint i = 1; i < node->req(); i++) {
4810       Node** cloned_input = _orig_to_new.get(node->in(i));
4811       if (cloned_input != nullptr) {
4812         // Input was also cloned -> rewire clone to the cloned input.
4813         _phase->igvn().replace_input_of(clone, i, *cloned_input);
4814       }
4815     }
4816   });
4817 }
4818 
4819 // Clone all non-OpaqueLoop* nodes and apply the provided transformation strategy for OpaqueLoop* nodes.
4820 // Set 'new_ctrl' as ctrl for all cloned non-OpaqueLoop* nodes.
4821 void DataNodeGraph::clone_data_nodes_and_transform_opaque_loop_nodes(
4822     const TransformStrategyForOpaqueLoopNodes& transform_strategy,
4823     Node* new_ctrl) {
4824   for (uint i = 0; i < _data_nodes.size(); i++) {
4825     Node* data_node = _data_nodes[i];
4826     if (data_node->is_Opaque1()) {
4827       transform_opaque_node(transform_strategy, data_node);
4828     } else {
4829       clone(data_node, new_ctrl);
4830     }
4831   }
4832 }
4833 
4834 void DataNodeGraph::transform_opaque_node(const TransformStrategyForOpaqueLoopNodes& transform_strategy, Node* node) {
4835   Node* transformed_node;
4836   if (node->is_OpaqueLoopInit()) {
4837     transformed_node = transform_strategy.transform_opaque_init(node->as_OpaqueLoopInit());
4838   } else {
4839     assert(node->is_OpaqueLoopStride(), "must be OpaqueLoopStrideNode");
4840     transformed_node = transform_strategy.transform_opaque_stride(node->as_OpaqueLoopStride());
4841   }
4842   // Add an orig->new mapping to correctly update the inputs of the copied graph in rewire_clones_to_cloned_inputs().
4843   _orig_to_new.put(node, transformed_node);
4844 }
--- EOF ---