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);
 172     } else if (region->is_Loop() && i == LoopNode::LoopBackControl &&
 173                n->is_Load() && can_move_to_inner_loop(n, region->as_Loop(), x)) {
 174       // it is not a win if 'x' moved from an outer to an inner loop
 175       // this edge case can only happen for Load nodes
 176       wins.reset();
 177       break;
 178     }
 179   }
 180   // Too few wins?
 181   if (!wins.profitable(policy)) {
 182     _igvn.remove_dead_node(phi);
 183     return nullptr;
 184   }
 185 
 186   // Record Phi
 187   register_new_node( phi, region );
 188 
 189   for (uint i2 = 1; i2 < phi->req(); i2++) {
 190     Node *x = phi->in(i2);
 191     // If we commoned up the cloned 'x' with another existing Node,
 192     // the existing Node picks up a new use.  We need to make the
 193     // existing Node occur higher up so it dominates its uses.
 194     Node *old_ctrl;
 195     IdealLoopTree *old_loop;
 196 
 197     if (x->is_Con()) {
 198       assert(get_ctrl(x) == C->root(), "constant control is not root");
 199       continue;
 200     }
 201     // The occasional new node
 202     if (x->_idx >= old_unique) {     // Found a new, unplaced node?
 203       old_ctrl = nullptr;
 204       old_loop = nullptr;               // Not in any prior loop
 205     } else {
 206       old_ctrl = get_ctrl(x);
 207       old_loop = get_loop(old_ctrl); // Get prior loop
 208     }
 209     // New late point must dominate new use
 210     Node *new_ctrl = dom_lca(old_ctrl, region->in(i2));
 211     if (new_ctrl == old_ctrl) // Nothing is changed
 212       continue;
 213 
 214     IdealLoopTree *new_loop = get_loop(new_ctrl);
 215 
 216     // Don't move x into a loop if its uses are
 217     // outside of loop. Otherwise x will be cloned
 218     // for each use outside of this loop.
 219     IdealLoopTree *use_loop = get_loop(region);
 220     if (!new_loop->is_member(use_loop) &&
 221         (old_loop == nullptr || !new_loop->is_member(old_loop))) {
 222       // Take early control, later control will be recalculated
 223       // during next iteration of loop optimizations.
 224       new_ctrl = get_early_ctrl(x);
 225       new_loop = get_loop(new_ctrl);
 226     }
 227     // Set new location
 228     set_ctrl(x, new_ctrl);
 229     // If changing loop bodies, see if we need to collect into new body
 230     if (old_loop != new_loop) {
 231       if (old_loop && !old_loop->_child)
 232         old_loop->_body.yank(x);
 233       if (!new_loop->_child)
 234         new_loop->_body.push(x);  // Collect body info
 235     }
 236   }
 237 
 238   split_thru_phi_yank_old_nodes(n, region);
 239   _igvn.replace_node(n, phi);
 240 
 241 #ifndef PRODUCT
 242   if (TraceLoopOpts) {
 243     tty->print_cr("Split %d %s through %d Phi in %d %s",
 244                   n->_idx, n->Name(), phi->_idx, region->_idx, region->Name());
 245   }
 246 #endif // !PRODUCT
 247 
 248   return phi;
 249 }
 250 
 251 // If the region is a Loop, we are removing the old n,
 252 // and need to yank it from the _body. If any phi we
 253 // just split through now has no use any more, it also
 254 // has to be removed.
 255 void PhaseIdealLoop::split_thru_phi_yank_old_nodes(Node* n, Node* region) {
 256   IdealLoopTree* region_loop = get_loop(region);
 257   if (region->is_Loop() && region_loop->is_innermost()) {
 258     region_loop->_body.yank(n);
 259     for (uint j = 1; j < n->req(); j++) {
 260       PhiNode* phi = n->in(j)->isa_Phi();
 261       // Check that phi belongs to the region and only has n as a use.
 262       if (phi != nullptr &&
 263           phi->in(0) == region &&
 264           phi->unique_multiple_edges_out_or_null() == n) {
 265         assert(get_ctrl(phi) == region, "sanity");
 266         assert(get_ctrl(n) == region, "sanity");
 267         region_loop->_body.yank(phi);
 268       }
 269     }
 270   }
 271 }
 272 
 273 // Test whether node 'x' can move into an inner loop relative to node 'n'.
 274 // Note: The test is not exact. Returns true if 'x' COULD end up in an inner loop,
 275 // BUT it can also return true and 'x' is in the outer loop
 276 bool PhaseIdealLoop::can_move_to_inner_loop(Node* n, LoopNode* n_loop, Node* x) {
 277   IdealLoopTree* n_loop_tree = get_loop(n_loop);
 278   IdealLoopTree* x_loop_tree = get_loop(get_early_ctrl(x));
 279   // x_loop_tree should be outer or same loop as n_loop_tree
 280   return !x_loop_tree->is_member(n_loop_tree);
 281 }
 282 
 283 // Subtype checks that carry profile data don't common so look for a replacement by following edges
 284 Node* PhaseIdealLoop::similar_subtype_check(const Node* x, Node* r_in) {
 285   if (x->is_SubTypeCheck()) {
 286     Node* in1 = x->in(1);
 287     for (DUIterator_Fast imax, i = in1->fast_outs(imax); i < imax; i++) {
 288       Node* u = in1->fast_out(i);
 289       if (u != x && u->is_SubTypeCheck() && u->in(1) == x->in(1) && u->in(2) == x->in(2)) {
 290         for (DUIterator_Fast jmax, j = u->fast_outs(jmax); j < jmax; j++) {
 291           Node* bol = u->fast_out(j);
 292           for (DUIterator_Fast kmax, k = bol->fast_outs(kmax); k < kmax; k++) {
 293             Node* iff = bol->fast_out(k);
 294             // Only dominating subtype checks are interesting: otherwise we risk replacing a subtype check by another with
 295             // unrelated profile
 296             if (iff->is_If() && is_dominator(iff, r_in)) {
 297               return u;
 298             }
 299           }
 300         }
 301       }
 302     }
 303   }
 304   return nullptr;
 305 }
 306 
 307 // Return true if 'n' is a Div or Mod node (without zero check If node which was removed earlier) with a loop phi divisor
 308 // of a trip-counted (integer or long) loop with a backedge input that could be zero (include zero in its type range). In
 309 // this case, we cannot split the division to the backedge as it could freely float above the loop exit check resulting in
 310 // a division by zero. This situation is possible because the type of an increment node of an iv phi (trip-counter) could
 311 // include zero while the iv phi does not (see PhiNode::Value() for trip-counted loops where we improve types of iv phis).
 312 // We also need to check other loop phis as they could have been created in the same split-if pass when applying
 313 // PhaseIdealLoop::split_thru_phi() to split nodes through an iv phi.
 314 bool PhaseIdealLoop::cannot_split_division(const Node* n, const Node* region) const {
 315   const Type* zero;
 316   switch (n->Opcode()) {
 317     case Op_DivI:
 318     case Op_ModI:
 319     case Op_UDivI:
 320     case Op_UModI:
 321       zero = TypeInt::ZERO;
 322       break;
 323     case Op_DivL:
 324     case Op_ModL:
 325     case Op_UDivL:
 326     case Op_UModL:
 327       zero = TypeLong::ZERO;
 328       break;
 329     default:
 330       return false;
 331   }
 332 
 333   if (n->in(0) != nullptr) {
 334     // Cannot split through phi if Div or Mod node has a control dependency to a zero check.
 335     return true;
 336   }
 337 
 338   Node* divisor = n->in(2);
 339   return is_divisor_loop_phi(divisor, region) &&
 340          loop_phi_backedge_type_contains_zero(divisor, zero);
 341 }
 342 
 343 bool PhaseIdealLoop::is_divisor_loop_phi(const Node* divisor, const Node* loop) {
 344   return loop->is_Loop() && divisor->is_Phi() && divisor->in(0) == loop;
 345 }
 346 
 347 bool PhaseIdealLoop::loop_phi_backedge_type_contains_zero(const Node* phi_divisor, const Type* zero) const {
 348     return _igvn.type(phi_divisor->in(LoopNode::LoopBackControl))->filter_speculative(zero) != Type::TOP;
 349 }
 350 
 351 //------------------------------dominated_by------------------------------------
 352 // Replace the dominated test with an obvious true or false.  Place it on the
 353 // IGVN worklist for later cleanup.  Move control-dependent data Nodes on the
 354 // live path up to the dominating control.
 355 void PhaseIdealLoop::dominated_by(IfProjNode* prevdom, IfNode* iff, bool flip, bool 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 = new AddPNode(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 = new AddPNode(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 = new AddPNode(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 = new AddPNode(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);
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     if (TraceLoopOpts) {
1655       tty->print_cr("Split-If");
1656     }
1657     do_split_if(iff);
1658     C->print_method(PHASE_AFTER_SPLIT_IF, 4, iff);
1659     return;
1660   }
1661 
1662   // Two identical ifs back to back can be merged
1663   if (try_merge_identical_ifs(n)) {
1664     return;
1665   }
1666 
1667   // Check for an IF ready to split; one that has its
1668   // condition codes input coming from a Phi at the block start.
1669   int n_op = n->Opcode();
1670 
1671   // Check for an IF being dominated by another IF same test
1672   if (n_op == Op_If ||
1673       n_op == Op_RangeCheck) {
1674     Node *bol = n->in(1);
1675     uint max = bol->outcnt();
1676     // Check for same test used more than once?
1677     if (bol->is_Bool() && (max > 1 || bol->in(1)->is_SubTypeCheck())) {
1678       // Search up IDOMs to see if this IF is dominated.
1679       Node* cmp = bol->in(1);
1680       Node *cutoff = cmp->is_SubTypeCheck() ? dom_lca(get_ctrl(cmp->in(1)), get_ctrl(cmp->in(2))) : get_ctrl(bol);
1681 
1682       // Now search up IDOMs till cutoff, looking for a dominating test
1683       Node *prevdom = n;
1684       Node *dom = idom(prevdom);
1685       while (dom != cutoff) {
1686         if (dom->req() > 1 && n->as_If()->same_condition(dom, &_igvn) && prevdom->in(0) == dom &&
1687             safe_for_if_replacement(dom)) {
1688           // It's invalid to move control dependent data nodes in the inner
1689           // strip-mined loop, because:
1690           //  1) break validation of LoopNode::verify_strip_mined()
1691           //  2) move code with side-effect in strip-mined loop
1692           // Move to the exit of outer strip-mined loop in that case.
1693           Node* out_le = is_inner_of_stripmined_loop(dom);
1694           if (out_le != nullptr) {
1695             prevdom = out_le;
1696           }
1697           // Replace the dominated test with an obvious true or false.
1698           // Place it on the IGVN worklist for later cleanup.
1699           C->set_major_progress();
1700           // Split if: pin array accesses that are control dependent on a range check and moved to a regular if,
1701           // to prevent an array load from floating above its range check. There are three cases:
1702           // 1. Move from RangeCheck "a" to RangeCheck "b": don't need to pin. If we ever remove b, then we pin
1703           //    all its array accesses at that point.
1704           // 2. We move from RangeCheck "a" to regular if "b": need to pin. If we ever remove b, then its array
1705           //    accesses would start to float, since we don't pin at that point.
1706           // 3. If we move from regular if: don't pin. All array accesses are already assumed to be pinned.
1707           bool pin_array_access_nodes =  n->Opcode() == Op_RangeCheck &&
1708                                          prevdom->in(0)->Opcode() != Op_RangeCheck;
1709           dominated_by(prevdom->as_IfProj(), n->as_If(), false, pin_array_access_nodes);
1710           DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
1711           return;
1712         }
1713         prevdom = dom;
1714         dom = idom(prevdom);
1715       }
1716     }
1717   }
1718 
1719   try_sink_out_of_loop(n);
1720   if (C->failing()) {
1721     return;
1722   }
1723 
1724   try_move_store_after_loop(n);
1725 
1726   // Remove multiple allocations of the same inline type
1727   if (n->is_InlineType()) {
1728     n->as_InlineType()->remove_redundant_allocations(this);
1729   }
1730 }
1731 
1732 // Transform:
1733 //
1734 // if (some_condition) {
1735 //   // body 1
1736 // } else {
1737 //   // body 2
1738 // }
1739 // if (some_condition) {
1740 //   // body 3
1741 // } else {
1742 //   // body 4
1743 // }
1744 //
1745 // into:
1746 //
1747 //
1748 // if (some_condition) {
1749 //   // body 1
1750 //   // body 3
1751 // } else {
1752 //   // body 2
1753 //   // body 4
1754 // }
1755 bool PhaseIdealLoop::try_merge_identical_ifs(Node* n) {
1756   if (identical_backtoback_ifs(n) && can_split_if(n->in(0))) {
1757     Node *n_ctrl = n->in(0);
1758     IfNode* dom_if = idom(n_ctrl)->as_If();
1759     if (n->in(1) != dom_if->in(1)) {
1760       assert(n->in(1)->in(1)->is_SubTypeCheck() &&
1761              (n->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr ||
1762               dom_if->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr), "only for subtype checks with profile data attached");
1763       _igvn.replace_input_of(n, 1, dom_if->in(1));
1764     }
1765     IfTrueNode* dom_proj_true = dom_if->true_proj();
1766     IfFalseNode* dom_proj_false = dom_if->false_proj();
1767 
1768     // Now split the IF
1769     RegionNode* new_false_region;
1770     RegionNode* new_true_region;
1771     do_split_if(n, &new_false_region, &new_true_region);
1772     assert(new_false_region->req() == new_true_region->req(), "");
1773 #ifdef ASSERT
1774     for (uint i = 1; i < new_false_region->req(); ++i) {
1775       assert(new_false_region->in(i)->in(0) == new_true_region->in(i)->in(0), "unexpected shape following split if");
1776       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");
1777     }
1778 #endif
1779     assert(new_false_region->in(1)->in(0)->in(1) == dom_if->in(1), "dominating if and dominated if after split must share test");
1780 
1781     // We now have:
1782     // if (some_condition) {
1783     //   // body 1
1784     //   if (some_condition) {
1785     //     body3: // new_true_region
1786     //     // body3
1787     //   } else {
1788     //     goto body4;
1789     //   }
1790     // } else {
1791     //   // body 2
1792     //  if (some_condition) {
1793     //     goto body3;
1794     //   } else {
1795     //     body4:   // new_false_region
1796     //     // body4;
1797     //   }
1798     // }
1799     //
1800 
1801     // clone pinned nodes thru the resulting regions
1802     push_pinned_nodes_thru_region(dom_if, new_true_region);
1803     push_pinned_nodes_thru_region(dom_if, new_false_region);
1804 
1805     // Optimize out the cloned ifs. Because pinned nodes were cloned, this also allows a CastPP that would be dependent
1806     // 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
1807     // unrelated control dependency.
1808     for (uint i = 1; i < new_false_region->req(); i++) {
1809       if (is_dominator(dom_proj_true, new_false_region->in(i))) {
1810         dominated_by(dom_proj_true, new_false_region->in(i)->in(0)->as_If());
1811       } else {
1812         assert(is_dominator(dom_proj_false, new_false_region->in(i)), "bad if");
1813         dominated_by(dom_proj_false, new_false_region->in(i)->in(0)->as_If());
1814       }
1815     }
1816     return true;
1817   }
1818   return false;
1819 }
1820 
1821 void PhaseIdealLoop::push_pinned_nodes_thru_region(IfNode* dom_if, Node* region) {
1822   for (DUIterator i = region->outs(); region->has_out(i); i++) {
1823     Node* u = region->out(i);
1824     if (!has_ctrl(u) || u->is_Phi() || !u->depends_only_on_test()) {
1825       continue;
1826     }
1827     assert(u->in(0) == region, "not a control dependent node?");
1828     uint j = 1;
1829     for (; j < u->req(); ++j) {
1830       Node* in = u->in(j);
1831       if (!is_dominator(ctrl_or_self(in), dom_if)) {
1832         break;
1833       }
1834     }
1835     if (j == u->req()) {
1836       Node *phi = PhiNode::make_blank(region, u);
1837       for (uint k = 1; k < region->req(); ++k) {
1838         Node* clone = u->clone();
1839         clone->set_req(0, region->in(k));
1840         register_new_node(clone, region->in(k));
1841         phi->init_req(k, clone);
1842       }
1843       register_new_node(phi, region);
1844       _igvn.replace_node(u, phi);
1845       --i;
1846     }
1847   }
1848 }
1849 
1850 bool PhaseIdealLoop::safe_for_if_replacement(const Node* dom) const {
1851   if (!dom->is_CountedLoopEnd()) {
1852     return true;
1853   }
1854   CountedLoopEndNode* le = dom->as_CountedLoopEnd();
1855   CountedLoopNode* cl = le->loopnode();
1856   if (cl == nullptr) {
1857     return true;
1858   }
1859   if (!cl->is_main_loop()) {
1860     return true;
1861   }
1862   if (cl->is_canonical_loop_entry() == nullptr) {
1863     return true;
1864   }
1865   // Further unrolling is possible so loop exit condition might change
1866   return false;
1867 }
1868 
1869 // See if a shared loop-varying computation has no loop-varying uses.
1870 // Happens if something is only used for JVM state in uncommon trap exits,
1871 // like various versions of induction variable+offset.  Clone the
1872 // computation per usage to allow it to sink out of the loop.
1873 void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
1874   bool is_raw_to_oop_cast = n->is_ConstraintCast() &&
1875                             n->in(1)->bottom_type()->isa_rawptr() &&
1876                             !n->bottom_type()->isa_rawptr();
1877 
1878   if (has_ctrl(n) &&
1879       !n->is_Phi() &&
1880       !n->is_Bool() &&
1881       !n->is_Proj() &&
1882       !n->is_MergeMem() &&
1883       !n->is_CMove() &&
1884       !n->is_OpaqueConstantBool() &&
1885       !n->is_OpaqueInitializedAssertionPredicate() &&
1886       !n->is_OpaqueTemplateAssertionPredicate() &&
1887       !is_raw_to_oop_cast && // don't extend live ranges of raw oops
1888       n->Opcode() != Op_CreateEx &&
1889       (KillPathsReachableByDeadTypeNode || !n->is_Type())
1890       ) {
1891     Node *n_ctrl = get_ctrl(n);
1892     IdealLoopTree *n_loop = get_loop(n_ctrl);
1893 
1894     if (n->in(0) != nullptr) {
1895       IdealLoopTree* loop_ctrl = get_loop(n->in(0));
1896       if (n_loop != loop_ctrl && n_loop->is_member(loop_ctrl)) {
1897         // n has a control input inside a loop but get_ctrl() is member of an outer loop. This could happen, for example,
1898         // for Div nodes inside a loop (control input inside loop) without a use except for an UCT (outside the loop).
1899         // Rewire control of n to right outside of the loop, regardless if its input(s) are later sunk or not.
1900         Node* maybe_pinned_n = n;
1901         Node* outside_ctrl = place_outside_loop(n_ctrl, loop_ctrl);
1902         if (!would_sink_below_pre_loop_exit(loop_ctrl, outside_ctrl)) {
1903           if (n->depends_only_on_test()) {
1904             // If this node depends_only_on_test, it will be rewired to a control input that is not
1905             // the correct test. As a result, it must be pinned otherwise it can be incorrectly
1906             // rewired to a dominating test equivalent to the new control.
1907             Node* pinned_clone = n->pin_node_under_control();
1908             if (pinned_clone != nullptr) {
1909               register_new_node(pinned_clone, n_ctrl);
1910               maybe_pinned_n = pinned_clone;
1911               _igvn.replace_node(n, pinned_clone);
1912             }
1913           }
1914           _igvn.replace_input_of(maybe_pinned_n, 0, outside_ctrl);
1915         }
1916       }
1917     }
1918     if (n_loop != _ltree_root && n->outcnt() > 1) {
1919       // Compute early control: needed for anti-dependence analysis. It's also possible that as a result of
1920       // previous transformations in this loop opts round, the node can be hoisted now: early control will tell us.
1921       Node* early_ctrl = compute_early_ctrl(n, n_ctrl);
1922       if (n_loop->is_member(get_loop(early_ctrl)) && // check that this one can't be hoisted now
1923           ctrl_of_all_uses_out_of_loop(n, early_ctrl, n_loop)) { // All uses in outer loops!
1924         if (n->is_Store() || n->is_LoadStore()) {
1925             assert(false, "no node with a side effect");
1926             C->record_failure("no node with a side effect");
1927             return;
1928         }
1929         Node* outer_loop_clone = nullptr;
1930         for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin;) {
1931           Node* u = n->last_out(j); // Clone private computation per use
1932           _igvn.rehash_node_delayed(u);
1933           Node* x = nullptr;
1934           if (n->in(0) != nullptr && n->depends_only_on_test()) {
1935             // If this node depends_only_on_test, it will be rewired to a control input that is not
1936             // the correct test. As a result, it must be pinned otherwise it can be incorrectly
1937             // rewired to a dominating test equivalent to the new control.
1938             x = n->pin_node_under_control();
1939           }
1940           if (x == nullptr) {
1941             x = n->clone();
1942           }
1943           Node* x_ctrl = nullptr;
1944           if (u->is_Phi()) {
1945             // Replace all uses of normal nodes.  Replace Phi uses
1946             // individually, so the separate Nodes can sink down
1947             // different paths.
1948             uint k = 1;
1949             while (u->in(k) != n) k++;
1950             u->set_req(k, x);
1951             // x goes next to Phi input path
1952             x_ctrl = u->in(0)->in(k);
1953             // Find control for 'x' next to use but not inside inner loops.
1954             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1955             --j;
1956           } else {              // Normal use
1957             if (has_ctrl(u)) {
1958               x_ctrl = get_ctrl(u);
1959             } else {
1960               x_ctrl = u->in(0);
1961             }
1962             // Find control for 'x' next to use but not inside inner loops.
1963             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1964             // Replace all uses
1965             if (u->is_ConstraintCast() && _igvn.type(n)->higher_equal(u->bottom_type()) && u->in(0) == x_ctrl) {
1966               // If we're sinking a chain of data nodes, we might have inserted a cast to pin the use which is not necessary
1967               // anymore now that we're going to pin n as well
1968               _igvn.replace_node(u, x);
1969               --j;
1970             } else {
1971               int nb = u->replace_edge(n, x, &_igvn);
1972               j -= nb;
1973             }
1974           }
1975 
1976           if (n->is_Load()) {
1977             // For loads, add a control edge to a CFG node outside of the loop
1978             // to force them to not combine and return back inside the loop
1979             // during GVN optimization (4641526).
1980             assert(x_ctrl == get_late_ctrl_with_anti_dep(x->as_Load(), early_ctrl, x_ctrl), "anti-dependences were already checked");
1981 
1982             IdealLoopTree* x_loop = get_loop(x_ctrl);
1983             Node* x_head = x_loop->_head;
1984             if (x_head->is_Loop() && x_head->is_OuterStripMinedLoop()) {
1985               // Do not add duplicate LoadNodes to the outer strip mined loop
1986               if (outer_loop_clone != nullptr) {
1987                 _igvn.replace_node(x, outer_loop_clone);
1988                 continue;
1989               }
1990               outer_loop_clone = x;
1991             }
1992             x->set_req(0, x_ctrl);
1993           } else if (n->in(0) != nullptr){
1994             x->set_req(0, x_ctrl);
1995           }
1996           assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
1997           assert(!n_loop->is_member(get_loop(x_ctrl)), "should have moved out of loop");
1998           register_new_node(x, x_ctrl);
1999 
2000           // Chain of AddP nodes: (AddP base (AddP base (AddP base )))
2001           // All AddP nodes must keep the same base after sinking so:
2002           // 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,
2003           // their bases remain the same.
2004           // (see 2- below)
2005           assert(!x->is_AddP() || !x->in(AddPNode::Address)->is_AddP() ||
2006                  x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base) ||
2007                  !x->in(AddPNode::Address)->in(AddPNode::Base)->eqv_uncast(x->in(AddPNode::Base)), "unexpected AddP shape");
2008           if (x->in(0) == nullptr && !x->is_DecodeNarrowPtr() &&
2009               !(x->is_AddP() && x->in(AddPNode::Address)->is_AddP() && x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base))) {
2010             assert(!x->is_Load(), "load should be pinned");
2011             // Use a cast node to pin clone out of loop
2012             Node* cast = nullptr;
2013             for (uint k = 0; k < x->req(); k++) {
2014               Node* in = x->in(k);
2015               if (in != nullptr && ctrl_is_member(n_loop, in)) {
2016                 const Type* in_t = _igvn.type(in);
2017                 cast = ConstraintCastNode::make_cast_for_type(x_ctrl, in, in_t,
2018                                                               ConstraintCastNode::DependencyType::NonFloatingNonNarrowing, nullptr);
2019               }
2020               if (cast != nullptr) {
2021                 Node* prev = _igvn.hash_find_insert(cast);
2022                 if (prev != nullptr && get_ctrl(prev) == x_ctrl) {
2023                   cast->destruct(&_igvn);
2024                   cast = prev;
2025                 } else {
2026                   register_new_node(cast, x_ctrl);
2027                 }
2028                 x->replace_edge(in, cast);
2029                 // Chain of AddP nodes:
2030                 // 2- A CastPP of the base is only added now that all AddP nodes are sunk
2031                 if (x->is_AddP() && k == AddPNode::Base) {
2032                   update_addp_chain_base(x, n->in(AddPNode::Base), cast);
2033                 }
2034                 break;
2035               }
2036             }
2037             assert(cast != nullptr, "must have added a cast to pin the node");
2038           }
2039         }
2040         _igvn.remove_dead_node(n);
2041       }
2042       _dom_lca_tags_round = 0;
2043     }
2044   }
2045 }
2046 
2047 void PhaseIdealLoop::update_addp_chain_base(Node* x, Node* old_base, Node* new_base) {
2048   ResourceMark rm;
2049   Node_List wq;
2050   wq.push(x);
2051   while (wq.size() != 0) {
2052     Node* n = wq.pop();
2053     for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2054       Node* u = n->fast_out(i);
2055       if (u->is_AddP() && u->in(AddPNode::Base) == old_base) {
2056         _igvn.replace_input_of(u, AddPNode::Base, new_base);
2057         wq.push(u);
2058       }
2059     }
2060   }
2061 }
2062 
2063 // Compute the early control of a node by following its inputs until we reach
2064 // nodes that are pinned. Then compute the LCA of the control of all pinned nodes.
2065 Node* PhaseIdealLoop::compute_early_ctrl(Node* n, Node* n_ctrl) {
2066   Node* early_ctrl = nullptr;
2067   ResourceMark rm;
2068   Unique_Node_List wq;
2069   wq.push(n);
2070   for (uint i = 0; i < wq.size(); i++) {
2071     Node* m = wq.at(i);
2072     Node* c = nullptr;
2073     if (m->is_CFG()) {
2074       c = m;
2075     } else if (m->pinned()) {
2076       c = m->in(0);
2077     } else {
2078       for (uint j = 0; j < m->req(); j++) {
2079         Node* in = m->in(j);
2080         if (in != nullptr) {
2081           wq.push(in);
2082         }
2083       }
2084     }
2085     if (c != nullptr) {
2086       assert(is_dominator(c, n_ctrl), "control input must dominate current control");
2087       if (early_ctrl == nullptr || is_dominator(early_ctrl, c)) {
2088         early_ctrl = c;
2089       }
2090     }
2091   }
2092   assert(is_dominator(early_ctrl, n_ctrl), "early control must dominate current control");
2093   return early_ctrl;
2094 }
2095 
2096 bool PhaseIdealLoop::ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop) {
2097   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2098     Node* u = n->fast_out(i);
2099     if (u->is_Opaque1()) {
2100       return false;  // Found loop limit, bugfix for 4677003
2101     }
2102     if (u->is_Phi()) {
2103       for (uint j = 1; j < u->req(); ++j) {
2104         if (u->in(j) == n && !ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, u->in(0)->in(j))) {
2105           return false;
2106         }
2107       }
2108     } else {
2109       Node* ctrl = has_ctrl(u) ? get_ctrl(u) : u->in(0);
2110       if (!ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, ctrl)) {
2111         return false;
2112       }
2113     }
2114   }
2115   return true;
2116 }
2117 
2118 // 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
2119 // to a check that's eliminated by range check elimination, it becomes input to an expression that feeds into the exit
2120 // 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
2121 // it would be to not eliminate the check in the main loop. Instead, we prevent sinking of the node here so better code
2122 // is generated for the main loop.
2123 bool PhaseIdealLoop::would_sink_below_pre_loop_exit(IdealLoopTree* n_loop, Node* ctrl) {
2124   if (n_loop->_head->is_CountedLoop() && n_loop->_head->as_CountedLoop()->is_pre_loop()) {
2125     CountedLoopNode* pre_loop = n_loop->_head->as_CountedLoop();
2126     if (is_dominator(pre_loop->loopexit(), ctrl)) {
2127       return true;
2128     }
2129   }
2130   return false;
2131 }
2132 
2133 bool PhaseIdealLoop::ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl) {
2134   if (n->is_Load()) {
2135     // We can't reuse tags in PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal() so make sure each call to
2136     // get_late_ctrl_with_anti_dep() uses its own tag
2137     _dom_lca_tags_round++;
2138     assert(_dom_lca_tags_round != 0, "shouldn't wrap around");
2139 
2140     ctrl = get_late_ctrl_with_anti_dep(n->as_Load(), n_ctrl, ctrl);
2141   }
2142   IdealLoopTree *u_loop = get_loop(ctrl);
2143   if (u_loop == n_loop) {
2144     return false; // Found loop-varying use
2145   }
2146   if (n_loop->is_member(u_loop)) {
2147     return false; // Found use in inner loop
2148   }
2149   if (would_sink_below_pre_loop_exit(n_loop, ctrl)) {
2150     return false;
2151   }
2152   return true;
2153 }
2154 
2155 //------------------------------split_if_with_blocks---------------------------
2156 // Check for aggressive application of 'split-if' optimization,
2157 // using basic block level info.
2158 void PhaseIdealLoop::split_if_with_blocks(VectorSet &visited, Node_Stack &nstack) {
2159   Node* root = C->root();
2160   visited.set(root->_idx); // first, mark root as visited
2161   // Do pre-visit work for root
2162   Node* n   = split_if_with_blocks_pre(root);
2163   uint  cnt = n->outcnt();
2164   uint  i   = 0;
2165 
2166   while (true) {
2167     // Visit all children
2168     if (i < cnt) {
2169       Node* use = n->raw_out(i);
2170       ++i;
2171       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
2172         // Now do pre-visit work for this use
2173         use = split_if_with_blocks_pre(use);
2174         nstack.push(n, i); // Save parent and next use's index.
2175         n   = use;         // Process all children of current use.
2176         cnt = use->outcnt();
2177         i   = 0;
2178       }
2179     }
2180     else {
2181       // All of n's children have been processed, complete post-processing.
2182       if (cnt != 0 && !n->is_Con()) {
2183         assert(has_node(n), "no dead nodes");
2184         split_if_with_blocks_post(n);
2185         if (C->failing()) {
2186           return;
2187         }
2188       }
2189       if (must_throttle_split_if()) {
2190         nstack.clear();
2191       }
2192       if (nstack.is_empty()) {
2193         // Finished all nodes on stack.
2194         break;
2195       }
2196       // Get saved parent node and next use's index. Visit the rest of uses.
2197       n   = nstack.node();
2198       cnt = n->outcnt();
2199       i   = nstack.index();
2200       nstack.pop();
2201     }
2202   }
2203 }
2204 
2205 
2206 //=============================================================================
2207 //
2208 //                   C L O N E   A   L O O P   B O D Y
2209 //
2210 
2211 //------------------------------clone_iff--------------------------------------
2212 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2213 // "Nearly" because all Nodes have been cloned from the original in the loop,
2214 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2215 // through the Phi recursively, and return a Bool.
2216 Node* PhaseIdealLoop::clone_iff(PhiNode* phi) {
2217 
2218   // Convert this Phi into a Phi merging Bools
2219   uint i;
2220   for (i = 1; i < phi->req(); i++) {
2221     Node* b = phi->in(i);
2222     if (b->is_Phi()) {
2223       _igvn.replace_input_of(phi, i, clone_iff(b->as_Phi()));
2224     } else {
2225       assert(b->is_Bool() || b->is_OpaqueConstantBool() || b->is_OpaqueInitializedAssertionPredicate(),
2226              "bool, non-null check with OpaqueConstantBool or Initialized Assertion Predicate with its Opaque node");
2227     }
2228   }
2229   Node* n = phi->in(1);
2230   Node* sample_opaque = nullptr;
2231   Node *sample_bool = nullptr;
2232   if (n->is_OpaqueConstantBool() || n->is_OpaqueInitializedAssertionPredicate()) {
2233     sample_opaque = n;
2234     sample_bool = n->in(1);
2235     assert(sample_bool->is_Bool(), "wrong type");
2236   } else {
2237     sample_bool = n;
2238   }
2239   Node* sample_cmp = sample_bool->in(1);
2240   const Type* t = Type::TOP;
2241   const TypePtr* at = nullptr;
2242   if (sample_cmp->is_FlatArrayCheck()) {
2243     // Left input of a FlatArrayCheckNode is memory, set the (adr) type of the phi accordingly
2244     assert(sample_cmp->in(1)->bottom_type() == Type::MEMORY, "unexpected input type");
2245     t = Type::MEMORY;
2246     at = TypeRawPtr::BOTTOM;
2247   }
2248 
2249   // Make Phis to merge the Cmp's inputs.
2250   PhiNode *phi1 = new PhiNode(phi->in(0), t, at);
2251   PhiNode *phi2 = new PhiNode(phi->in(0), Type::TOP);
2252   for (i = 1; i < phi->req(); i++) {
2253     Node *n1 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(1) : phi->in(i)->in(1)->in(1)->in(1);
2254     Node *n2 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(2) : phi->in(i)->in(1)->in(1)->in(2);
2255     phi1->set_req(i, n1);
2256     phi2->set_req(i, n2);
2257     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2258     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2259   }
2260   // See if these Phis have been made before.
2261   // Register with optimizer
2262   Node *hit1 = _igvn.hash_find_insert(phi1);
2263   if (hit1) {                   // Hit, toss just made Phi
2264     _igvn.remove_dead_node(phi1); // Remove new phi
2265     assert(hit1->is_Phi(), "" );
2266     phi1 = (PhiNode*)hit1;      // Use existing phi
2267   } else {                      // Miss
2268     _igvn.register_new_node_with_optimizer(phi1);
2269   }
2270   Node *hit2 = _igvn.hash_find_insert(phi2);
2271   if (hit2) {                   // Hit, toss just made Phi
2272     _igvn.remove_dead_node(phi2); // Remove new phi
2273     assert(hit2->is_Phi(), "" );
2274     phi2 = (PhiNode*)hit2;      // Use existing phi
2275   } else {                      // Miss
2276     _igvn.register_new_node_with_optimizer(phi2);
2277   }
2278   // Register Phis with loop/block info
2279   set_ctrl(phi1, phi->in(0));
2280   set_ctrl(phi2, phi->in(0));
2281   // Make a new Cmp
2282   Node *cmp = sample_cmp->clone();
2283   cmp->set_req(1, phi1);
2284   cmp->set_req(2, phi2);
2285   _igvn.register_new_node_with_optimizer(cmp);
2286   set_ctrl(cmp, phi->in(0));
2287 
2288   // Make a new Bool
2289   Node *b = sample_bool->clone();
2290   b->set_req(1,cmp);
2291   _igvn.register_new_node_with_optimizer(b);
2292   set_ctrl(b, phi->in(0));
2293 
2294   if (sample_opaque != nullptr) {
2295     Node* opaque = sample_opaque->clone();
2296     opaque->set_req(1, b);
2297     _igvn.register_new_node_with_optimizer(opaque);
2298     set_ctrl(opaque, phi->in(0));
2299     return opaque;
2300   }
2301 
2302   assert(b->is_Bool(), "");
2303   return b;
2304 }
2305 
2306 //------------------------------clone_bool-------------------------------------
2307 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2308 // "Nearly" because all Nodes have been cloned from the original in the loop,
2309 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2310 // through the Phi recursively, and return a Bool.
2311 CmpNode*PhaseIdealLoop::clone_bool(PhiNode* phi) {
2312   uint i;
2313   // Convert this Phi into a Phi merging Bools
2314   for( i = 1; i < phi->req(); i++ ) {
2315     Node *b = phi->in(i);
2316     if( b->is_Phi() ) {
2317       _igvn.replace_input_of(phi, i, clone_bool(b->as_Phi()));
2318     } else {
2319       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
2320     }
2321   }
2322 
2323   Node *sample_cmp = phi->in(1);
2324 
2325   // Make Phis to merge the Cmp's inputs.
2326   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
2327   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
2328   for( uint j = 1; j < phi->req(); j++ ) {
2329     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
2330     Node *n1, *n2;
2331     if( cmp_top->is_Cmp() ) {
2332       n1 = cmp_top->in(1);
2333       n2 = cmp_top->in(2);
2334     } else {
2335       n1 = n2 = cmp_top;
2336     }
2337     phi1->set_req( j, n1 );
2338     phi2->set_req( j, n2 );
2339     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2340     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2341   }
2342 
2343   // See if these Phis have been made before.
2344   // Register with optimizer
2345   Node *hit1 = _igvn.hash_find_insert(phi1);
2346   if( hit1 ) {                  // Hit, toss just made Phi
2347     _igvn.remove_dead_node(phi1); // Remove new phi
2348     assert( hit1->is_Phi(), "" );
2349     phi1 = (PhiNode*)hit1;      // Use existing phi
2350   } else {                      // Miss
2351     _igvn.register_new_node_with_optimizer(phi1);
2352   }
2353   Node *hit2 = _igvn.hash_find_insert(phi2);
2354   if( hit2 ) {                  // Hit, toss just made Phi
2355     _igvn.remove_dead_node(phi2); // Remove new phi
2356     assert( hit2->is_Phi(), "" );
2357     phi2 = (PhiNode*)hit2;      // Use existing phi
2358   } else {                      // Miss
2359     _igvn.register_new_node_with_optimizer(phi2);
2360   }
2361   // Register Phis with loop/block info
2362   set_ctrl(phi1, phi->in(0));
2363   set_ctrl(phi2, phi->in(0));
2364   // Make a new Cmp
2365   Node *cmp = sample_cmp->clone();
2366   cmp->set_req( 1, phi1 );
2367   cmp->set_req( 2, phi2 );
2368   _igvn.register_new_node_with_optimizer(cmp);
2369   set_ctrl(cmp, phi->in(0));
2370 
2371   assert( cmp->is_Cmp(), "" );
2372   return (CmpNode*)cmp;
2373 }
2374 
2375 void PhaseIdealLoop::clone_loop_handle_data_uses(Node* old, Node_List &old_new,
2376                                                  IdealLoopTree* loop, IdealLoopTree* outer_loop,
2377                                                  Node_List*& split_if_set, Node_List*& split_bool_set,
2378                                                  Node_List*& split_cex_set, Node_List& worklist,
2379                                                  uint new_counter, CloneLoopMode mode) {
2380   Node* nnn = old_new[old->_idx];
2381   // Copy uses to a worklist, so I can munge the def-use info
2382   // with impunity.
2383   for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
2384     worklist.push(old->fast_out(j));
2385 
2386   while( worklist.size() ) {
2387     Node *use = worklist.pop();
2388     if (!has_node(use))  continue; // Ignore dead nodes
2389     if (use->in(0) == C->top())  continue;
2390     IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
2391     // Check for data-use outside of loop - at least one of OLD or USE
2392     // must not be a CFG node.
2393 #ifdef ASSERT
2394     if (loop->_head->as_Loop()->is_strip_mined() && outer_loop->is_member(use_loop) && !loop->is_member(use_loop) && old_new[use->_idx] == nullptr) {
2395       Node* sfpt = loop->_head->as_CountedLoop()->outer_safepoint();
2396       assert(mode != IgnoreStripMined, "incorrect cloning mode");
2397       assert((mode == ControlAroundStripMined && use == sfpt) || !use->is_reachable_from_root(), "missed a node");
2398     }
2399 #endif
2400     if (!loop->is_member(use_loop) && !outer_loop->is_member(use_loop) && (!old->is_CFG() || !use->is_CFG())) {
2401 
2402       // If the Data use is an IF, that means we have an IF outside the
2403       // loop that is switching on a condition that is set inside the
2404       // loop.  Happens if people set a loop-exit flag; then test the flag
2405       // in the loop to break the loop, then test is again outside the
2406       // loop to determine which way the loop exited.
2407       //
2408       // For several uses we need to make sure that there is no phi between,
2409       // the use and the Bool/Cmp. We therefore clone the Bool/Cmp down here
2410       // to avoid such a phi in between.
2411       // For example, it is unexpected that there is a Phi between an
2412       // AllocateArray node and its ValidLengthTest input that could cause
2413       // split if to break.
2414       assert(!use->is_OpaqueTemplateAssertionPredicate(),
2415              "should not clone a Template Assertion Predicate which should be removed once it's useless");
2416       if (use->is_If() || use->is_CMove() || use->is_OpaqueConstantBool() || use->is_OpaqueInitializedAssertionPredicate() ||
2417           (use->Opcode() == Op_AllocateArray && use->in(AllocateNode::ValidLengthTest) == old)) {
2418         // Since this code is highly unlikely, we lazily build the worklist
2419         // of such Nodes to go split.
2420         if (!split_if_set) {
2421           split_if_set = new Node_List();
2422         }
2423         split_if_set->push(use);
2424       }
2425       if (use->is_Bool()) {
2426         if (!split_bool_set) {
2427           split_bool_set = new Node_List();
2428         }
2429         split_bool_set->push(use);
2430       }
2431       if (use->Opcode() == Op_CreateEx) {
2432         if (!split_cex_set) {
2433           split_cex_set = new Node_List();
2434         }
2435         split_cex_set->push(use);
2436       }
2437 
2438 
2439       // Get "block" use is in
2440       uint idx = 0;
2441       while( use->in(idx) != old ) idx++;
2442       Node *prev = use->is_CFG() ? use : get_ctrl(use);
2443       assert(!loop->is_member(get_loop(prev)) && !outer_loop->is_member(get_loop(prev)), "" );
2444       Node* cfg = (prev->_idx >= new_counter && prev->is_Region())
2445         ? prev->in(2)
2446         : idom(prev);
2447       if( use->is_Phi() )     // Phi use is in prior block
2448         cfg = prev->in(idx);  // NOT in block of Phi itself
2449       if (cfg->is_top()) {    // Use is dead?
2450         _igvn.replace_input_of(use, idx, C->top());
2451         continue;
2452       }
2453 
2454       // If use is referenced through control edge... (idx == 0)
2455       if (mode == IgnoreStripMined && idx == 0) {
2456         LoopNode *head = loop->_head->as_Loop();
2457         if (head->is_strip_mined() && is_dominator(head->outer_loop_exit(), prev)) {
2458           // That node is outside the inner loop, leave it outside the
2459           // outer loop as well to not confuse verification code.
2460           assert(!loop->_parent->is_member(use_loop), "should be out of the outer loop");
2461           _igvn.replace_input_of(use, 0, head->outer_loop_exit());
2462           continue;
2463         }
2464       }
2465 
2466       while(!outer_loop->is_member(get_loop(cfg))) {
2467         prev = cfg;
2468         cfg = (cfg->_idx >= new_counter && cfg->is_Region()) ? cfg->in(2) : idom(cfg);
2469       }
2470       // If the use occurs after merging several exits from the loop, then
2471       // old value must have dominated all those exits.  Since the same old
2472       // value was used on all those exits we did not need a Phi at this
2473       // merge point.  NOW we do need a Phi here.  Each loop exit value
2474       // is now merged with the peeled body exit; each exit gets its own
2475       // private Phi and those Phis need to be merged here.
2476       Node *phi;
2477       if( prev->is_Region() ) {
2478         if( idx == 0 ) {      // Updating control edge?
2479           phi = prev;         // Just use existing control
2480         } else {              // Else need a new Phi
2481           phi = PhiNode::make( prev, old );
2482           // Now recursively fix up the new uses of old!
2483           for( uint i = 1; i < prev->req(); i++ ) {
2484             worklist.push(phi); // Onto worklist once for each 'old' input
2485           }
2486         }
2487       } else {
2488         // Get new RegionNode merging old and new loop exits
2489         prev = old_new[prev->_idx];
2490         assert( prev, "just made this in step 7" );
2491         if( idx == 0) {      // Updating control edge?
2492           phi = prev;         // Just use existing control
2493         } else {              // Else need a new Phi
2494           // Make a new Phi merging data values properly
2495           phi = PhiNode::make( prev, old );
2496           phi->set_req( 1, nnn );
2497         }
2498       }
2499       // If inserting a new Phi, check for prior hits
2500       if( idx != 0 ) {
2501         Node *hit = _igvn.hash_find_insert(phi);
2502         if( hit == nullptr ) {
2503           _igvn.register_new_node_with_optimizer(phi); // Register new phi
2504         } else {                                      // or
2505           // Remove the new phi from the graph and use the hit
2506           _igvn.remove_dead_node(phi);
2507           phi = hit;                                  // Use existing phi
2508         }
2509         set_ctrl(phi, prev);
2510       }
2511       // Make 'use' use the Phi instead of the old loop body exit value
2512       assert(use->in(idx) == old, "old is still input of use");
2513       // We notify all uses of old, including use, and the indirect uses,
2514       // that may now be optimized because we have replaced old with phi.
2515       _igvn.add_users_to_worklist(old);
2516       if (idx == 0 && use->depends_only_on_test()) {
2517         // If this node depends_only_on_test, it will be rewired to a control input that is not the
2518         // correct test. As a result, it must be pinned otherwise it can be incorrectly rewired to
2519         // a dominating test equivalent to the new control.
2520         Node* pinned_clone = use->pin_node_under_control();
2521         if (pinned_clone != nullptr) {
2522           pinned_clone->set_req(0, phi);
2523           register_new_node_with_ctrl_of(pinned_clone, use);
2524           _igvn.replace_node(use, pinned_clone);
2525           continue;
2526         }
2527       }
2528       _igvn.replace_input_of(use, idx, phi);
2529       if( use->_idx >= new_counter ) { // If updating new phis
2530         // Not needed for correctness, but prevents a weak assert
2531         // in AddPNode from tripping (when we end up with different
2532         // base & derived Phis that will become the same after
2533         // IGVN does CSE).
2534         Node *hit = _igvn.hash_find_insert(use);
2535         if( hit )             // Go ahead and re-hash for hits.
2536           _igvn.replace_node( use, hit );
2537       }
2538     }
2539   }
2540 }
2541 
2542 static void collect_nodes_in_outer_loop_not_reachable_from_sfpt(Node* n, const IdealLoopTree *loop, const IdealLoopTree* outer_loop,
2543                                                                 const Node_List &old_new, Unique_Node_List& wq, PhaseIdealLoop* phase,
2544                                                                 bool check_old_new) {
2545   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2546     Node* u = n->fast_out(j);
2547     assert(check_old_new || old_new[u->_idx] == nullptr, "shouldn't have been cloned");
2548     if (!u->is_CFG() && (!check_old_new || old_new[u->_idx] == nullptr)) {
2549       assert(!phase->ctrl_is_member(loop, u) || !loop->_body.contains(u), "can be in outer loop or out of both loops only");
2550       if (!phase->ctrl_is_member(loop, u)) {
2551         if (phase->ctrl_is_member(outer_loop, u)) {
2552           wq.push(u);
2553         } else {
2554           // nodes pinned with control in the outer loop but not referenced from the safepoint must be moved out of
2555           // the outer loop too
2556           Node* u_c = u->in(0);
2557           if (u_c != nullptr) {
2558             IdealLoopTree* u_c_loop = phase->get_loop(u_c);
2559             if (outer_loop->is_member(u_c_loop) && !loop->is_member(u_c_loop)) {
2560               wq.push(u);
2561             }
2562           }
2563         }
2564       }
2565     }
2566   }
2567 }
2568 
2569 void PhaseIdealLoop::clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
2570                                       IdealLoopTree* outer_loop, int dd, Node_List &old_new,
2571                                       Node_List& extra_data_nodes) {
2572   if (head->is_strip_mined() && mode != IgnoreStripMined) {
2573     CountedLoopNode* cl = head->as_CountedLoop();
2574     Node* l = cl->outer_loop();
2575     Node* tail = cl->outer_loop_tail();
2576     IfNode* le = cl->outer_loop_end();
2577     Node* sfpt = cl->outer_safepoint();
2578     CountedLoopEndNode* cle = cl->loopexit();
2579     CountedLoopNode* new_cl = old_new[cl->_idx]->as_CountedLoop();
2580     CountedLoopEndNode* new_cle = new_cl->as_CountedLoop()->loopexit_or_null();
2581     IfFalseNode* cle_out = cle->false_proj();
2582 
2583     Node* new_sfpt = nullptr;
2584     Node* new_cle_out = cle_out->clone();
2585     old_new.map(cle_out->_idx, new_cle_out);
2586     if (mode == CloneIncludesStripMined) {
2587       // clone outer loop body
2588       Node* new_l = l->clone();
2589       Node* new_tail = tail->clone();
2590       IfNode* new_le = le->clone()->as_If();
2591       new_sfpt = sfpt->clone();
2592 
2593       set_loop(new_l, outer_loop->_parent);
2594       set_idom(new_l, new_l->in(LoopNode::EntryControl), dd);
2595       set_loop(new_cle_out, outer_loop->_parent);
2596       set_idom(new_cle_out, new_cle, dd);
2597       set_loop(new_sfpt, outer_loop->_parent);
2598       set_idom(new_sfpt, new_cle_out, dd);
2599       set_loop(new_le, outer_loop->_parent);
2600       set_idom(new_le, new_sfpt, dd);
2601       set_loop(new_tail, outer_loop->_parent);
2602       set_idom(new_tail, new_le, dd);
2603       set_idom(new_cl, new_l, dd);
2604 
2605       old_new.map(l->_idx, new_l);
2606       old_new.map(tail->_idx, new_tail);
2607       old_new.map(le->_idx, new_le);
2608       old_new.map(sfpt->_idx, new_sfpt);
2609 
2610       new_l->set_req(LoopNode::LoopBackControl, new_tail);
2611       new_l->set_req(0, new_l);
2612       new_tail->set_req(0, new_le);
2613       new_le->set_req(0, new_sfpt);
2614       new_sfpt->set_req(0, new_cle_out);
2615       new_cle_out->set_req(0, new_cle);
2616       new_cl->set_req(LoopNode::EntryControl, new_l);
2617 
2618       _igvn.register_new_node_with_optimizer(new_l);
2619       _igvn.register_new_node_with_optimizer(new_tail);
2620       _igvn.register_new_node_with_optimizer(new_le);
2621     } else {
2622       Node *newhead = old_new[loop->_head->_idx];
2623       newhead->as_Loop()->clear_strip_mined();
2624       _igvn.replace_input_of(newhead, LoopNode::EntryControl, newhead->in(LoopNode::EntryControl)->in(LoopNode::EntryControl));
2625       set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2626     }
2627     // Look at data node that were assigned a control in the outer
2628     // loop: they are kept in the outer loop by the safepoint so start
2629     // from the safepoint node's inputs.
2630     IdealLoopTree* outer_loop = get_loop(l);
2631     Node_Stack stack(2);
2632     stack.push(sfpt, 1);
2633     uint new_counter = C->unique();
2634     while (stack.size() > 0) {
2635       Node* n = stack.node();
2636       uint i = stack.index();
2637       while (i < n->req() &&
2638              (n->in(i) == nullptr ||
2639               !has_ctrl(n->in(i)) ||
2640               get_loop(get_ctrl(n->in(i))) != outer_loop ||
2641               (old_new[n->in(i)->_idx] != nullptr && old_new[n->in(i)->_idx]->_idx >= new_counter))) {
2642         i++;
2643       }
2644       if (i < n->req()) {
2645         stack.set_index(i+1);
2646         stack.push(n->in(i), 0);
2647       } else {
2648         assert(old_new[n->_idx] == nullptr || n == sfpt || old_new[n->_idx]->_idx < new_counter, "no clone yet");
2649         Node* m = n == sfpt ? new_sfpt : n->clone();
2650         if (m != nullptr) {
2651           for (uint i = 0; i < n->req(); i++) {
2652             if (m->in(i) != nullptr && old_new[m->in(i)->_idx] != nullptr) {
2653               m->set_req(i, old_new[m->in(i)->_idx]);
2654             }
2655           }
2656         } else {
2657           assert(n == sfpt && mode != CloneIncludesStripMined, "where's the safepoint clone?");
2658         }
2659         if (n != sfpt) {
2660           extra_data_nodes.push(n);
2661           _igvn.register_new_node_with_optimizer(m);
2662           assert(get_ctrl(n) == cle_out, "what other control?");
2663           set_ctrl(m, new_cle_out);
2664           old_new.map(n->_idx, m);
2665         }
2666         stack.pop();
2667       }
2668     }
2669     if (mode == CloneIncludesStripMined) {
2670       _igvn.register_new_node_with_optimizer(new_sfpt);
2671       _igvn.register_new_node_with_optimizer(new_cle_out);
2672     }
2673     // Some other transformation may have pessimistically assigned some
2674     // data nodes to the outer loop. Set their control so they are out
2675     // of the outer loop.
2676     ResourceMark rm;
2677     Unique_Node_List wq;
2678     for (uint i = 0; i < extra_data_nodes.size(); i++) {
2679       Node* old = extra_data_nodes.at(i);
2680       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2681     }
2682 
2683     for (uint i = 0; i < loop->_body.size(); i++) {
2684       Node* old = loop->_body.at(i);
2685       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2686     }
2687 
2688     Node* inner_out = sfpt->in(0);
2689     if (inner_out->outcnt() > 1) {
2690       collect_nodes_in_outer_loop_not_reachable_from_sfpt(inner_out, loop, outer_loop, old_new, wq, this, true);
2691     }
2692 
2693     Node* new_ctrl = cl->outer_loop_exit();
2694     assert(get_loop(new_ctrl) != outer_loop, "must be out of the loop nest");
2695     for (uint i = 0; i < wq.size(); i++) {
2696       Node* n = wq.at(i);
2697       set_ctrl(n, new_ctrl);
2698       if (n->in(0) != nullptr) {
2699         _igvn.replace_input_of(n, 0, new_ctrl);
2700       }
2701       collect_nodes_in_outer_loop_not_reachable_from_sfpt(n, loop, outer_loop, old_new, wq, this, false);
2702     }
2703   } else {
2704     Node *newhead = old_new[loop->_head->_idx];
2705     set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2706   }
2707 }
2708 
2709 //------------------------------clone_loop-------------------------------------
2710 //
2711 //                   C L O N E   A   L O O P   B O D Y
2712 //
2713 // This is the basic building block of the loop optimizations.  It clones an
2714 // entire loop body.  It makes an old_new loop body mapping; with this mapping
2715 // you can find the new-loop equivalent to an old-loop node.  All new-loop
2716 // nodes are exactly equal to their old-loop counterparts, all edges are the
2717 // same.  All exits from the old-loop now have a RegionNode that merges the
2718 // equivalent new-loop path.  This is true even for the normal "loop-exit"
2719 // condition.  All uses of loop-invariant old-loop values now come from (one
2720 // or more) Phis that merge their new-loop equivalents.
2721 //
2722 // This operation leaves the graph in an illegal state: there are two valid
2723 // control edges coming from the loop pre-header to both loop bodies.  I'll
2724 // definitely have to hack the graph after running this transform.
2725 //
2726 // From this building block I will further edit edges to perform loop peeling
2727 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
2728 //
2729 // Parameter side_by_size_idom:
2730 //   When side_by_size_idom is null, the dominator tree is constructed for
2731 //      the clone loop to dominate the original.  Used in construction of
2732 //      pre-main-post loop sequence.
2733 //   When nonnull, the clone and original are side-by-side, both are
2734 //      dominated by the side_by_side_idom node.  Used in construction of
2735 //      unswitched loops.
2736 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
2737                                 CloneLoopMode mode, Node* side_by_side_idom) {
2738 
2739   LoopNode* head = loop->_head->as_Loop();
2740   head->verify_strip_mined(1);
2741 
2742   if (C->do_vector_loop() && PrintOpto) {
2743     const char* mname = C->method()->name()->as_quoted_ascii();
2744     if (mname != nullptr) {
2745       tty->print("PhaseIdealLoop::clone_loop: for vectorize method %s\n", mname);
2746     }
2747   }
2748 
2749   CloneMap& cm = C->clone_map();
2750   if (C->do_vector_loop()) {
2751     cm.set_clone_idx(cm.max_gen()+1);
2752 #ifndef PRODUCT
2753     if (PrintOpto) {
2754       tty->print_cr("PhaseIdealLoop::clone_loop: _clone_idx %d", cm.clone_idx());
2755       loop->dump_head();
2756     }
2757 #endif
2758   }
2759 
2760   // Step 1: Clone the loop body.  Make the old->new mapping.
2761   clone_loop_body(loop->_body, old_new, &cm);
2762 
2763   IdealLoopTree* outer_loop = (head->is_strip_mined() && mode != IgnoreStripMined) ? get_loop(head->as_CountedLoop()->outer_loop()) : loop;
2764 
2765   // Step 2: Fix the edges in the new body.  If the old input is outside the
2766   // loop use it.  If the old input is INside the loop, use the corresponding
2767   // new node instead.
2768   fix_body_edges(loop->_body, loop, old_new, dd, outer_loop->_parent, false);
2769 
2770   Node_List extra_data_nodes; // data nodes in the outer strip mined loop
2771   clone_outer_loop(head, mode, loop, outer_loop, dd, old_new, extra_data_nodes);
2772 
2773   // Step 3: Now fix control uses.  Loop varying control uses have already
2774   // been fixed up (as part of all input edges in Step 2).  Loop invariant
2775   // control uses must be either an IfFalse or an IfTrue.  Make a merge
2776   // point to merge the old and new IfFalse/IfTrue nodes; make the use
2777   // refer to this.
2778   Node_List worklist;
2779   uint new_counter = C->unique();
2780   fix_ctrl_uses(loop->_body, loop, old_new, mode, side_by_side_idom, &cm, worklist);
2781 
2782   // Step 4: If loop-invariant use is not control, it must be dominated by a
2783   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
2784   // there if needed.  Make a Phi there merging old and new used values.
2785   Node_List *split_if_set = nullptr;
2786   Node_List *split_bool_set = nullptr;
2787   Node_List *split_cex_set = nullptr;
2788   fix_data_uses(loop->_body, loop, mode, outer_loop, new_counter, old_new, worklist, split_if_set, split_bool_set, split_cex_set);
2789 
2790   for (uint i = 0; i < extra_data_nodes.size(); i++) {
2791     Node* old = extra_data_nodes.at(i);
2792     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2793                                 split_bool_set, split_cex_set, worklist, new_counter,
2794                                 mode);
2795   }
2796 
2797   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
2798   // the loop uses a condition set in the loop.  The original IF probably
2799   // takes control from one or more OLD Regions (which in turn get from NEW
2800   // Regions).  In any case, there will be a set of Phis for each merge point
2801   // from the IF up to where the original BOOL def exists the loop.
2802   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
2803 
2804 }
2805 
2806 void PhaseIdealLoop::finish_clone_loop(Node_List* split_if_set, Node_List* split_bool_set, Node_List* split_cex_set) {
2807   if (split_if_set) {
2808     while (split_if_set->size()) {
2809       Node *iff = split_if_set->pop();
2810       uint input = iff->Opcode() == Op_AllocateArray ? AllocateNode::ValidLengthTest : 1;
2811       if (iff->in(input)->is_Phi()) {
2812         Node *b = clone_iff(iff->in(input)->as_Phi());
2813         _igvn.replace_input_of(iff, input, b);
2814       }
2815     }
2816   }
2817   if (split_bool_set) {
2818     while (split_bool_set->size()) {
2819       Node *b = split_bool_set->pop();
2820       Node *phi = b->in(1);
2821       assert(phi->is_Phi(), "");
2822       CmpNode *cmp = clone_bool((PhiNode*) phi);
2823       _igvn.replace_input_of(b, 1, cmp);
2824     }
2825   }
2826   if (split_cex_set) {
2827     while (split_cex_set->size()) {
2828       Node *b = split_cex_set->pop();
2829       assert(b->in(0)->is_Region(), "");
2830       assert(b->in(1)->is_Phi(), "");
2831       assert(b->in(0)->in(0) == b->in(1)->in(0), "");
2832       split_up(b, b->in(0), nullptr);
2833     }
2834   }
2835 }
2836 
2837 void PhaseIdealLoop::fix_data_uses(Node_List& body, IdealLoopTree* loop, CloneLoopMode mode, IdealLoopTree* outer_loop,
2838                                    uint new_counter, Node_List &old_new, Node_List &worklist, Node_List*& split_if_set,
2839                                    Node_List*& split_bool_set, Node_List*& split_cex_set) {
2840   for(uint i = 0; i < body.size(); i++ ) {
2841     Node* old = body.at(i);
2842     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2843                                 split_bool_set, split_cex_set, worklist, new_counter,
2844                                 mode);
2845   }
2846 }
2847 
2848 void PhaseIdealLoop::fix_ctrl_uses(const Node_List& body, const IdealLoopTree* loop, Node_List &old_new, CloneLoopMode mode,
2849                                    Node* side_by_side_idom, CloneMap* cm, Node_List &worklist) {
2850   LoopNode* head = loop->_head->as_Loop();
2851   for(uint i = 0; i < body.size(); i++ ) {
2852     Node* old = body.at(i);
2853     if( !old->is_CFG() ) continue;
2854 
2855     // Copy uses to a worklist, so I can munge the def-use info
2856     // with impunity.
2857     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++) {
2858       worklist.push(old->fast_out(j));
2859     }
2860 
2861     while (worklist.size()) {  // Visit all uses
2862       Node *use = worklist.pop();
2863       if (!has_node(use))  continue; // Ignore dead nodes
2864       IdealLoopTree *use_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use );
2865       if (!loop->is_member(use_loop) && use->is_CFG()) {
2866         // Both OLD and USE are CFG nodes here.
2867         assert(use->is_Proj(), "" );
2868         Node* nnn = old_new[old->_idx];
2869 
2870         Node* newuse = nullptr;
2871         if (head->is_strip_mined() && mode != IgnoreStripMined) {
2872           CountedLoopNode* cl = head->as_CountedLoop();
2873           CountedLoopEndNode* cle = cl->loopexit();
2874           // is use the projection that exits the loop from the CountedLoopEndNode?
2875           if (use->in(0) == cle) {
2876             IfFalseNode* cle_out = use->as_IfFalse();
2877             IfNode* le = cl->outer_loop_end();
2878             use = le->false_proj();
2879             use_loop = get_loop(use);
2880             if (mode == CloneIncludesStripMined) {
2881               nnn = old_new[le->_idx];
2882             } else {
2883               newuse = old_new[cle_out->_idx];
2884             }
2885           }
2886         }
2887         if (newuse == nullptr) {
2888           newuse = use->clone();
2889         }
2890 
2891         // Clone the loop exit control projection
2892         if (C->do_vector_loop() && cm != nullptr) {
2893           cm->verify_insert_and_clone(use, newuse, cm->clone_idx());
2894         }
2895         newuse->set_req(0,nnn);
2896         _igvn.register_new_node_with_optimizer(newuse);
2897         set_loop(newuse, use_loop);
2898         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
2899 
2900         // We need a Region to merge the exit from the peeled body and the
2901         // exit from the old loop body.
2902         RegionNode *r = new RegionNode(3);
2903         uint dd_r = MIN2(dom_depth(newuse), dom_depth(use));
2904         assert(dd_r >= dom_depth(dom_lca(newuse, use)), "" );
2905 
2906         // The original user of 'use' uses 'r' instead.
2907         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
2908           Node* useuse = use->last_out(l);
2909           _igvn.rehash_node_delayed(useuse);
2910           uint uses_found = 0;
2911           if (useuse->in(0) == use) {
2912             useuse->set_req(0, r);
2913             uses_found++;
2914             if (useuse->is_CFG()) {
2915               // This is not a dom_depth > dd_r because when new
2916               // control flow is constructed by a loop opt, a node and
2917               // its dominator can end up at the same dom_depth
2918               assert(dom_depth(useuse) >= dd_r, "");
2919               set_idom(useuse, r, dom_depth(useuse));
2920             }
2921           }
2922           for (uint k = 1; k < useuse->req(); k++) {
2923             if( useuse->in(k) == use ) {
2924               useuse->set_req(k, r);
2925               uses_found++;
2926               if (useuse->is_Loop() && k == LoopNode::EntryControl) {
2927                 // This is not a dom_depth > dd_r because when new
2928                 // control flow is constructed by a loop opt, a node
2929                 // and its dominator can end up at the same dom_depth
2930                 assert(dom_depth(useuse) >= dd_r , "");
2931                 set_idom(useuse, r, dom_depth(useuse));
2932               }
2933             }
2934           }
2935           l -= uses_found;    // we deleted 1 or more copies of this edge
2936         }
2937 
2938         assert(use->is_Proj(), "loop exit should be projection");
2939         // replace_node_and_forward_ctrl() below moves all nodes that are:
2940         // - control dependent on the loop exit or
2941         // - have control set to the loop exit
2942         // below the post-loop merge point.
2943         // replace_node_and_forward_ctrl() takes a dead control as first input.
2944         // To make it possible to use it, the loop exit projection is cloned and becomes the
2945         // new exit projection. The initial one becomes dead and is "replaced" by the region.
2946         Node* use_clone = use->clone();
2947         register_control(use_clone, use_loop, idom(use), dom_depth(use));
2948         // Now finish up 'r'
2949         r->set_req(1, newuse);
2950         r->set_req(2, use_clone);
2951         _igvn.register_new_node_with_optimizer(r);
2952         set_loop(r, use_loop);
2953         set_idom(r, (side_by_side_idom == nullptr) ? newuse->in(0) : side_by_side_idom, dd_r);
2954         replace_node_and_forward_ctrl(use, r);
2955         // Map the (cloned) old use to the new merge point
2956         old_new.map(use_clone->_idx, r);
2957       } // End of if a loop-exit test
2958     }
2959   }
2960 }
2961 
2962 void PhaseIdealLoop::fix_body_edges(const Node_List &body, IdealLoopTree* loop, const Node_List &old_new, int dd,
2963                                     IdealLoopTree* parent, bool partial) {
2964   for(uint i = 0; i < body.size(); i++ ) {
2965     Node *old = body.at(i);
2966     Node *nnn = old_new[old->_idx];
2967     // Fix CFG/Loop controlling the new node
2968     if (has_ctrl(old)) {
2969       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
2970     } else {
2971       set_loop(nnn, parent);
2972       if (old->outcnt() > 0) {
2973         Node* dom = idom(old);
2974         if (old_new[dom->_idx] != nullptr) {
2975           dom = old_new[dom->_idx];
2976           set_idom(nnn, dom, dd );
2977         }
2978       }
2979     }
2980     // Correct edges to the new node
2981     for (uint j = 0; j < nnn->req(); j++) {
2982         Node *n = nnn->in(j);
2983         if (n != nullptr) {
2984           IdealLoopTree *old_in_loop = get_loop(has_ctrl(n) ? get_ctrl(n) : n);
2985           if (loop->is_member(old_in_loop)) {
2986             if (old_new[n->_idx] != nullptr) {
2987               nnn->set_req(j, old_new[n->_idx]);
2988             } else {
2989               assert(!body.contains(n), "");
2990               assert(partial, "node not cloned");
2991             }
2992           }
2993         }
2994     }
2995     _igvn.hash_find_insert(nnn);
2996   }
2997 }
2998 
2999 void PhaseIdealLoop::clone_loop_body(const Node_List& body, Node_List &old_new, CloneMap* cm) {
3000   for (uint i = 0; i < body.size(); i++) {
3001     Node* old = body.at(i);
3002     Node* nnn = old->clone();
3003     old_new.map(old->_idx, nnn);
3004     if (C->do_vector_loop() && cm != nullptr) {
3005       cm->verify_insert_and_clone(old, nnn, cm->clone_idx());
3006     }
3007     _igvn.register_new_node_with_optimizer(nnn);
3008   }
3009 }
3010 
3011 
3012 //---------------------- stride_of_possible_iv -------------------------------------
3013 // Looks for an iff/bool/comp with one operand of the compare
3014 // being a cycle involving an add and a phi,
3015 // with an optional truncation (left-shift followed by a right-shift)
3016 // of the add. Returns zero if not an iv.
3017 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
3018   const TypeInteger* ttype = nullptr;
3019   if (!iff->is_If() || iff->in(1) == nullptr || !iff->in(1)->is_Bool()) {
3020     return 0;
3021   }
3022   BoolNode* bl = iff->in(1)->as_Bool();
3023   Node* cmp = bl->in(1);
3024   if (!cmp || (cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU)) {
3025     return 0;
3026   }
3027   // Must have an invariant operand
3028   if (ctrl_is_member(get_loop(iff), cmp->in(2))) {
3029     return 0;
3030   }
3031   Node* add2 = nullptr;
3032   Node* cmp1 = cmp->in(1);
3033   if (cmp1->is_Phi()) {
3034     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
3035     Node* phi = cmp1;
3036     for (uint i = 1; i < phi->req(); i++) {
3037       Node* in = phi->in(i);
3038       CountedLoopConverter::TruncatedIncrement add(T_INT);
3039       add.build(in);
3040       if (add.is_valid() && add.incr()->in(1) == phi) {
3041         add2 = add.incr()->in(2);
3042         break;
3043       }
3044     }
3045   } else {
3046     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
3047     Node* addtrunc = cmp1;
3048     CountedLoopConverter::TruncatedIncrement add(T_INT);
3049     add.build(addtrunc);
3050     if (add.is_valid() && add.incr()->in(1)->is_Phi()) {
3051       Node* phi = add.incr()->in(1);
3052       for (uint i = 1; i < phi->req(); i++) {
3053         if (phi->in(i) == addtrunc) {
3054           add2 = add.incr()->in(2);
3055           break;
3056         }
3057       }
3058     }
3059   }
3060   if (add2 != nullptr) {
3061     const TypeInt* add2t = _igvn.type(add2)->is_int();
3062     if (add2t->is_con()) {
3063       return add2t->get_con();
3064     }
3065   }
3066   return 0;
3067 }
3068 
3069 
3070 //---------------------- stay_in_loop -------------------------------------
3071 // Return the (unique) control output node that's in the loop (if it exists.)
3072 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
3073   Node* unique = nullptr;
3074   if (!n) return nullptr;
3075   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3076     Node* use = n->fast_out(i);
3077     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
3078       if (unique != nullptr) {
3079         return nullptr;
3080       }
3081       unique = use;
3082     }
3083   }
3084   return unique;
3085 }
3086 
3087 //------------------------------ register_node -------------------------------------
3088 // Utility to register node "n" with PhaseIdealLoop
3089 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree* loop, Node* pred, uint ddepth) {
3090   _igvn.register_new_node_with_optimizer(n);
3091   loop->_body.push(n);
3092   if (n->is_CFG()) {
3093     set_loop(n, loop);
3094     set_idom(n, pred, ddepth);
3095   } else {
3096     set_ctrl(n, pred);
3097   }
3098 }
3099 
3100 //------------------------------ proj_clone -------------------------------------
3101 // Utility to create an if-projection
3102 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
3103   ProjNode* c = p->clone()->as_Proj();
3104   c->set_req(0, iff);
3105   return c;
3106 }
3107 
3108 //------------------------------ short_circuit_if -------------------------------------
3109 // Force the iff control output to be the live_proj
3110 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
3111   guarantee(live_proj != nullptr, "null projection");
3112   int proj_con = live_proj->_con;
3113   assert(proj_con == 0 || proj_con == 1, "false or true projection");
3114   Node* con = intcon(proj_con);
3115   if (iff) {
3116     iff->set_req(1, con);
3117   }
3118   return con;
3119 }
3120 
3121 //------------------------------ insert_if_before_proj -------------------------------------
3122 // Insert a new if before an if projection (* - new node)
3123 //
3124 // before
3125 //           if(test)
3126 //           /     \
3127 //          v       v
3128 //    other-proj   proj (arg)
3129 //
3130 // after
3131 //           if(test)
3132 //           /     \
3133 //          /       v
3134 //         |      * proj-clone
3135 //         v          |
3136 //    other-proj      v
3137 //                * new_if(relop(cmp[IU](left,right)))
3138 //                  /  \
3139 //                 v    v
3140 //         * new-proj  proj
3141 //         (returned)
3142 //
3143 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
3144   IfNode* iff = proj->in(0)->as_If();
3145   IdealLoopTree *loop = get_loop(proj);
3146   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3147   uint ddepth = dom_depth(proj);
3148 
3149   _igvn.rehash_node_delayed(iff);
3150   _igvn.rehash_node_delayed(proj);
3151 
3152   proj->set_req(0, nullptr);  // temporary disconnect
3153   ProjNode* proj2 = proj_clone(proj, iff);
3154   register_node(proj2, loop, iff, ddepth);
3155 
3156   Node* cmp = Signed ? (Node*) new CmpINode(left, right) : (Node*) new CmpUNode(left, right);
3157   register_node(cmp, loop, proj2, ddepth);
3158 
3159   BoolNode* bol = new BoolNode(cmp, relop);
3160   register_node(bol, loop, proj2, ddepth);
3161 
3162   int opcode = iff->Opcode();
3163   assert(opcode == Op_If || opcode == Op_RangeCheck, "unexpected opcode");
3164   IfNode* new_if = IfNode::make_with_same_profile(iff, proj2, bol);
3165   register_node(new_if, loop, proj2, ddepth);
3166 
3167   proj->set_req(0, new_if); // reattach
3168   set_idom(proj, new_if, ddepth);
3169 
3170   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
3171   guarantee(new_exit != nullptr, "null exit node");
3172   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
3173 
3174   return new_exit;
3175 }
3176 
3177 //------------------------------ insert_region_before_proj -------------------------------------
3178 // Insert a region before an if projection (* - new node)
3179 //
3180 // before
3181 //           if(test)
3182 //          /      |
3183 //         v       |
3184 //       proj      v
3185 //               other-proj
3186 //
3187 // after
3188 //           if(test)
3189 //          /      |
3190 //         v       |
3191 // * proj-clone    v
3192 //         |     other-proj
3193 //         v
3194 // * new-region
3195 //         |
3196 //         v
3197 // *      dum_if
3198 //       /     \
3199 //      v       \
3200 // * dum-proj    v
3201 //              proj
3202 //
3203 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
3204   IfNode* iff = proj->in(0)->as_If();
3205   IdealLoopTree *loop = get_loop(proj);
3206   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3207   uint ddepth = dom_depth(proj);
3208 
3209   _igvn.rehash_node_delayed(iff);
3210   _igvn.rehash_node_delayed(proj);
3211 
3212   proj->set_req(0, nullptr);  // temporary disconnect
3213   ProjNode* proj2 = proj_clone(proj, iff);
3214   register_node(proj2, loop, iff, ddepth);
3215 
3216   RegionNode* reg = new RegionNode(2);
3217   reg->set_req(1, proj2);
3218   register_node(reg, loop, iff, ddepth);
3219 
3220   IfNode* dum_if = new IfNode(reg, short_circuit_if(nullptr, proj), iff->_prob, iff->_fcnt);
3221   register_node(dum_if, loop, reg, ddepth);
3222 
3223   proj->set_req(0, dum_if); // reattach
3224   set_idom(proj, dum_if, ddepth);
3225 
3226   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
3227   register_node(dum_proj, loop, dum_if, ddepth);
3228 
3229   return reg;
3230 }
3231 
3232 // Idea
3233 // ----
3234 // Partial Peeling tries to rotate the loop in such a way that it can later be turned into a counted loop. Counted loops
3235 // require a signed loop exit test. When calling this method, we've only found a suitable unsigned test to partial peel
3236 // with. Therefore, we try to split off a signed loop exit test from the unsigned test such that it can be used as new
3237 // loop exit while keeping the unsigned test unchanged and preserving the same behavior as if we've used the unsigned
3238 // test alone instead:
3239 //
3240 // Before Partial Peeling:
3241 //   Loop:
3242 //     <peeled section>
3243 //     Split off signed loop exit test
3244 //     <-- CUT HERE -->
3245 //     Unchanged unsigned loop exit test
3246 //     <rest of unpeeled section>
3247 //     goto Loop
3248 //
3249 // After Partial Peeling:
3250 //   <cloned peeled section>
3251 //   Cloned split off signed loop exit test
3252 //   Loop:
3253 //     Unchanged unsigned loop exit test
3254 //     <rest of unpeeled section>
3255 //     <peeled section>
3256 //     Split off signed loop exit test
3257 //     goto Loop
3258 //
3259 // Details
3260 // -------
3261 // Before:
3262 //          if (i <u limit)    Unsigned loop exit condition
3263 //         /       |
3264 //        v        v
3265 //   exit-proj   stay-in-loop-proj
3266 //
3267 // Split off a signed loop exit test (i.e. with CmpI) from an unsigned loop exit test (i.e. with CmpU) and insert it
3268 // before the CmpU on the stay-in-loop path and keep both tests:
3269 //
3270 //          if (i <u limit)    Signed loop exit test
3271 //        /        |
3272 //       /  if (i <u limit)    Unsigned loop exit test
3273 //      /  /       |
3274 //     v  v        v
3275 //  exit-region  stay-in-loop-proj
3276 //
3277 // Implementation
3278 // --------------
3279 // We need to make sure that the new signed loop exit test is properly inserted into the graph such that the unsigned
3280 // loop exit test still dominates the same set of control nodes, the ctrl() relation from data nodes to both loop
3281 // exit tests is preserved, and their loop nesting is correct.
3282 //
3283 // To achieve that, we clone the unsigned loop exit test completely (leave it unchanged), insert the signed loop exit
3284 // test above it and kill the original unsigned loop exit test by setting it's condition to a constant
3285 // (i.e. stay-in-loop-const in graph below) such that IGVN can fold it later:
3286 //
3287 //           if (stay-in-loop-const)  Killed original unsigned loop exit test
3288 //          /       |
3289 //         /        v
3290 //        /  if (i <  limit)          Split off signed loop exit test
3291 //       /  /       |
3292 //      /  /        v
3293 //     /  /  if (i <u limit)          Cloned unsigned loop exit test
3294 //    /  /   /      |
3295 //   v  v  v        |
3296 //  exit-region     |
3297 //        |         |
3298 //    dummy-if      |
3299 //     /  |         |
3300 // dead   |         |
3301 //        v         v
3302 //   exit-proj   stay-in-loop-proj
3303 //
3304 // Note: The dummy-if is inserted to create a region to merge the loop exits between the original to be killed unsigned
3305 //       loop exit test and its exit projection while keeping the exit projection (also see insert_region_before_proj()).
3306 //
3307 // Requirements
3308 // ------------
3309 // Note that we can only split off a signed loop exit test from the unsigned loop exit test when the behavior is exactly
3310 // the same as before with only a single unsigned test. This is only possible if certain requirements are met.
3311 // Otherwise, we need to bail out (see comments in the code below).
3312 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree* loop) {
3313   const bool Signed   = true;
3314   const bool Unsigned = false;
3315 
3316   BoolNode* bol = if_cmpu->in(1)->as_Bool();
3317   if (bol->_test._test != BoolTest::lt) {
3318     return nullptr;
3319   }
3320   CmpNode* cmpu = bol->in(1)->as_Cmp();
3321   assert(cmpu->Opcode() == Op_CmpU, "must be unsigned comparison");
3322 
3323   int stride = stride_of_possible_iv(if_cmpu);
3324   if (stride == 0) {
3325     return nullptr;
3326   }
3327 
3328   Node* lp_proj = stay_in_loop(if_cmpu, loop);
3329   guarantee(lp_proj != nullptr, "null loop node");
3330 
3331   ProjNode* lp_continue = lp_proj->as_Proj();
3332   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
3333   if (!lp_exit->is_IfFalse()) {
3334     // The loop exit condition is (i <u limit) ==> (i >= 0 && i < limit).
3335     // We therefore can't add a single exit condition.
3336     return nullptr;
3337   }
3338   // The unsigned loop exit condition is
3339   //   !(i <u  limit)
3340   // =   i >=u limit
3341   //
3342   // First, we note that for any x for which
3343   //   0 <= x <= INT_MAX
3344   // we can convert x to an unsigned int and still get the same guarantee:
3345   //   0 <=  (uint) x <=  INT_MAX = (uint) INT_MAX
3346   //   0 <=u (uint) x <=u INT_MAX = (uint) INT_MAX   (LEMMA)
3347   //
3348   // With that in mind, if
3349   //   limit >= 0             (COND)
3350   // then the unsigned loop exit condition
3351   //   i >=u limit            (ULE)
3352   // is equivalent to
3353   //   i < 0 || i >= limit    (SLE-full)
3354   // because either i is negative and therefore always greater than MAX_INT when converting to unsigned
3355   //   (uint) i >=u MAX_INT >= limit >= 0
3356   // or otherwise
3357   //   i >= limit >= 0
3358   // holds due to (LEMMA).
3359   //
3360   // For completeness, a counterexample with limit < 0:
3361   // Assume i = -3 and limit = -2:
3362   //   i  < 0
3363   //   -2 < 0
3364   // is true and thus also "i < 0 || i >= limit". But
3365   //   i  >=u limit
3366   //   -3 >=u -2
3367   // is false.
3368   Node* limit = cmpu->in(2);
3369   const TypeInt* type_limit = _igvn.type(limit)->is_int();
3370   if (type_limit->_lo < 0) {
3371     return nullptr;
3372   }
3373 
3374   // We prove below that we can extract a single signed loop exit condition from (SLE-full), depending on the stride:
3375   //   stride < 0:
3376   //     i < 0        (SLE = SLE-negative)
3377   //   stride > 0:
3378   //     i >= limit   (SLE = SLE-positive)
3379   // such that we have the following graph before Partial Peeling with stride > 0 (similar for stride < 0):
3380   //
3381   // Loop:
3382   //   <peeled section>
3383   //   i >= limit    (SLE-positive)
3384   //   <-- CUT HERE -->
3385   //   i >=u limit   (ULE)
3386   //   <rest of unpeeled section>
3387   //   goto Loop
3388   //
3389   // We exit the loop if:
3390   //   (SLE) is true OR (ULE) is true
3391   // However, if (SLE) is true then (ULE) also needs to be true to ensure the exact same behavior. Otherwise, we wrongly
3392   // exit a loop that should not have been exited if we did not apply Partial Peeling. More formally, we need to ensure:
3393   //   (SLE) IMPLIES (ULE)
3394   // This indeed holds when (COND) is given:
3395   // - stride > 0:
3396   //       i >=  limit             // (SLE = SLE-positive)
3397   //       i >=  limit >= 0        // (COND)
3398   //       i >=u limit >= 0        // (LEMMA)
3399   //     which is the unsigned loop exit condition (ULE).
3400   // - stride < 0:
3401   //       i        <  0           // (SLE = SLE-negative)
3402   //       (uint) i >u MAX_INT     // (NEG) all negative values are greater than MAX_INT when converted to unsigned
3403   //       MAX_INT >= limit >= 0   // (COND)
3404   //       MAX_INT >=u limit >= 0  // (LEMMA)
3405   //     and thus from (NEG) and (LEMMA):
3406   //       i >=u limit
3407   //     which is the unsigned loop exit condition (ULE).
3408   //
3409   //
3410   // After Partial Peeling, we have the following structure for stride > 0 (similar for stride < 0):
3411   //   <cloned peeled section>
3412   //   i >= limit (SLE-positive)
3413   //   Loop:
3414   //     i >=u limit (ULE)
3415   //     <rest of unpeeled section>
3416   //     <peeled section>
3417   //     i >= limit (SLE-positive)
3418   //     goto Loop
3419   Node* rhs_cmpi;
3420   if (stride > 0) {
3421     rhs_cmpi = limit; // For i >= limit
3422   } else {
3423     rhs_cmpi = makecon(TypeInt::ZERO); // For i < 0
3424   }
3425   // Create a new region on the exit path
3426   RegionNode* reg = insert_region_before_proj(lp_exit);
3427   guarantee(reg != nullptr, "null region node");
3428 
3429   // Clone the if-cmpu-true-false using a signed compare
3430   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
3431   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, rhs_cmpi, lp_continue);
3432   reg->add_req(cmpi_exit);
3433 
3434   // Clone the if-cmpu-true-false
3435   BoolTest::mask rel_u = bol->_test._test;
3436   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
3437   reg->add_req(cmpu_exit);
3438 
3439   // Force original if to stay in loop.
3440   short_circuit_if(if_cmpu, lp_continue);
3441 
3442   return cmpi_exit->in(0)->as_If();
3443 }
3444 
3445 //------------------------------ remove_cmpi_loop_exit -------------------------------------
3446 // Remove a previously inserted signed compare loop exit.
3447 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
3448   Node* lp_proj = stay_in_loop(if_cmp, loop);
3449   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
3450          stay_in_loop(lp_proj, loop)->is_If() &&
3451          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
3452   Node* con = makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
3453   if_cmp->set_req(1, con);
3454 }
3455 
3456 //------------------------------ scheduled_nodelist -------------------------------------
3457 // Create a post order schedule of nodes that are in the
3458 // "member" set.  The list is returned in "sched".
3459 // The first node in "sched" is the loop head, followed by
3460 // nodes which have no inputs in the "member" set, and then
3461 // followed by the nodes that have an immediate input dependence
3462 // on a node in "sched".
3463 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
3464 
3465   assert(member.test(loop->_head->_idx), "loop head must be in member set");
3466   VectorSet visited;
3467   Node_Stack nstack(loop->_body.size());
3468 
3469   Node* n  = loop->_head;  // top of stack is cached in "n"
3470   uint idx = 0;
3471   visited.set(n->_idx);
3472 
3473   // Initially push all with no inputs from within member set
3474   for(uint i = 0; i < loop->_body.size(); i++ ) {
3475     Node *elt = loop->_body.at(i);
3476     if (member.test(elt->_idx)) {
3477       bool found = false;
3478       for (uint j = 0; j < elt->req(); j++) {
3479         Node* def = elt->in(j);
3480         if (def && member.test(def->_idx) && def != elt) {
3481           found = true;
3482           break;
3483         }
3484       }
3485       if (!found && elt != loop->_head) {
3486         nstack.push(n, idx);
3487         n = elt;
3488         assert(!visited.test(n->_idx), "not seen yet");
3489         visited.set(n->_idx);
3490       }
3491     }
3492   }
3493 
3494   // traverse out's that are in the member set
3495   while (true) {
3496     if (idx < n->outcnt()) {
3497       Node* use = n->raw_out(idx);
3498       idx++;
3499       if (!visited.test_set(use->_idx)) {
3500         if (member.test(use->_idx)) {
3501           nstack.push(n, idx);
3502           n = use;
3503           idx = 0;
3504         }
3505       }
3506     } else {
3507       // All outputs processed
3508       sched.push(n);
3509       if (nstack.is_empty()) break;
3510       n   = nstack.node();
3511       idx = nstack.index();
3512       nstack.pop();
3513     }
3514   }
3515 }
3516 
3517 
3518 //------------------------------ has_use_in_set -------------------------------------
3519 // Has a use in the vector set
3520 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
3521   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3522     Node* use = n->fast_out(j);
3523     if (vset.test(use->_idx)) {
3524       return true;
3525     }
3526   }
3527   return false;
3528 }
3529 
3530 
3531 //------------------------------ has_use_internal_to_set -------------------------------------
3532 // Has use internal to the vector set (ie. not in a phi at the loop head)
3533 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
3534   Node* head  = loop->_head;
3535   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3536     Node* use = n->fast_out(j);
3537     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
3538       return true;
3539     }
3540   }
3541   return false;
3542 }
3543 
3544 
3545 //------------------------------ clone_for_use_outside_loop -------------------------------------
3546 // clone "n" for uses that are outside of loop
3547 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
3548   int cloned = 0;
3549   assert(worklist.size() == 0, "should be empty");
3550   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3551     Node* use = n->fast_out(j);
3552     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
3553       worklist.push(use);
3554     }
3555   }
3556 
3557   if (C->check_node_count(worklist.size() + NodeLimitFudgeFactor,
3558                           "Too many clones required in clone_for_use_outside_loop in partial peeling")) {
3559     return -1;
3560   }
3561 
3562   while( worklist.size() ) {
3563     Node *use = worklist.pop();
3564     if (!has_node(use) || use->in(0) == C->top()) continue;
3565     uint j;
3566     for (j = 0; j < use->req(); j++) {
3567       if (use->in(j) == n) break;
3568     }
3569     assert(j < use->req(), "must be there");
3570 
3571     // clone "n" and insert it between the inputs of "n" and the use outside the loop
3572     Node* n_clone = n->clone();
3573     _igvn.replace_input_of(use, j, n_clone);
3574     cloned++;
3575     Node* use_c;
3576     if (!use->is_Phi()) {
3577       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
3578     } else {
3579       // Use in a phi is considered a use in the associated predecessor block
3580       use_c = use->in(0)->in(j);
3581     }
3582     set_ctrl(n_clone, use_c);
3583     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
3584     get_loop(use_c)->_body.push(n_clone);
3585     _igvn.register_new_node_with_optimizer(n_clone);
3586 #ifndef PRODUCT
3587     if (TracePartialPeeling) {
3588       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
3589     }
3590 #endif
3591   }
3592   return cloned;
3593 }
3594 
3595 
3596 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
3597 // clone "n" for special uses that are in the not_peeled region.
3598 // If these def-uses occur in separate blocks, the code generator
3599 // marks the method as not compilable.  For example, if a "BoolNode"
3600 // is in a different basic block than the "IfNode" that uses it, then
3601 // the compilation is aborted in the code generator.
3602 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
3603                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
3604   if (n->is_Phi() || n->is_Load()) {
3605     return;
3606   }
3607   assert(worklist.size() == 0, "should be empty");
3608   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3609     Node* use = n->fast_out(j);
3610     if ( not_peel.test(use->_idx) &&
3611          (use->is_If() || use->is_CMove() || use->is_Bool() || use->is_OpaqueInitializedAssertionPredicate()) &&
3612          use->in(1) == n)  {
3613       worklist.push(use);
3614     }
3615   }
3616   if (worklist.size() > 0) {
3617     // clone "n" and insert it between inputs of "n" and the use
3618     Node* n_clone = n->clone();
3619     loop->_body.push(n_clone);
3620     _igvn.register_new_node_with_optimizer(n_clone);
3621     set_ctrl(n_clone, get_ctrl(n));
3622     sink_list.push(n_clone);
3623     not_peel.set(n_clone->_idx);
3624 #ifndef PRODUCT
3625     if (TracePartialPeeling) {
3626       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
3627     }
3628 #endif
3629     while( worklist.size() ) {
3630       Node *use = worklist.pop();
3631       _igvn.rehash_node_delayed(use);
3632       for (uint j = 1; j < use->req(); j++) {
3633         if (use->in(j) == n) {
3634           use->set_req(j, n_clone);
3635         }
3636       }
3637     }
3638   }
3639 }
3640 
3641 
3642 //------------------------------ insert_phi_for_loop -------------------------------------
3643 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
3644 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
3645   Node *phi = PhiNode::make(lp, back_edge_val);
3646   phi->set_req(LoopNode::EntryControl, lp_entry_val);
3647   // Use existing phi if it already exists
3648   Node *hit = _igvn.hash_find_insert(phi);
3649   if( hit == nullptr ) {
3650     _igvn.register_new_node_with_optimizer(phi);
3651     set_ctrl(phi, lp);
3652   } else {
3653     // Remove the new phi from the graph and use the hit
3654     _igvn.remove_dead_node(phi);
3655     phi = hit;
3656   }
3657   _igvn.replace_input_of(use, idx, phi);
3658 }
3659 
3660 #ifdef ASSERT
3661 //------------------------------ is_valid_loop_partition -------------------------------------
3662 // Validate the loop partition sets: peel and not_peel
3663 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
3664                                               VectorSet& not_peel ) {
3665   uint i;
3666   // Check that peel_list entries are in the peel set
3667   for (i = 0; i < peel_list.size(); i++) {
3668     if (!peel.test(peel_list.at(i)->_idx)) {
3669       return false;
3670     }
3671   }
3672   // Check at loop members are in one of peel set or not_peel set
3673   for (i = 0; i < loop->_body.size(); i++ ) {
3674     Node *def  = loop->_body.at(i);
3675     uint di = def->_idx;
3676     // Check that peel set elements are in peel_list
3677     if (peel.test(di)) {
3678       if (not_peel.test(di)) {
3679         return false;
3680       }
3681       // Must be in peel_list also
3682       bool found = false;
3683       for (uint j = 0; j < peel_list.size(); j++) {
3684         if (peel_list.at(j)->_idx == di) {
3685           found = true;
3686           break;
3687         }
3688       }
3689       if (!found) {
3690         return false;
3691       }
3692     } else if (not_peel.test(di)) {
3693       if (peel.test(di)) {
3694         return false;
3695       }
3696     } else {
3697       return false;
3698     }
3699   }
3700   return true;
3701 }
3702 
3703 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
3704 // Ensure a use outside of loop is of the right form
3705 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
3706   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3707   return (use->is_Phi() &&
3708           use_c->is_Region() && use_c->req() == 3 &&
3709           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
3710            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
3711            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
3712           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
3713 }
3714 
3715 //------------------------------ is_valid_clone_loop_form -------------------------------------
3716 // Ensure that all uses outside of loop are of the right form
3717 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
3718                                                uint orig_exit_idx, uint clone_exit_idx) {
3719   uint len = peel_list.size();
3720   for (uint i = 0; i < len; i++) {
3721     Node *def = peel_list.at(i);
3722 
3723     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
3724       Node *use = def->fast_out(j);
3725       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3726       if (!loop->is_member(get_loop(use_c))) {
3727         // use is not in the loop, check for correct structure
3728         if (use->in(0) == def) {
3729           // Okay
3730         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
3731           return false;
3732         }
3733       }
3734     }
3735   }
3736   return true;
3737 }
3738 #endif
3739 
3740 //------------------------------ partial_peel -------------------------------------
3741 // Partially peel (aka loop rotation) the top portion of a loop (called
3742 // the peel section below) by cloning it and placing one copy just before
3743 // the new loop head and the other copy at the bottom of the new loop.
3744 //
3745 //    before                       after                where it came from
3746 //
3747 //    stmt1                        stmt1
3748 //  loop:                          stmt2                     clone
3749 //    stmt2                        if condA goto exitA       clone
3750 //    if condA goto exitA        new_loop:                   new
3751 //    stmt3                        stmt3                     clone
3752 //    if !condB goto loop          if condB goto exitB       clone
3753 //  exitB:                         stmt2                     orig
3754 //    stmt4                        if !condA goto new_loop   orig
3755 //  exitA:                         goto exitA
3756 //                               exitB:
3757 //                                 stmt4
3758 //                               exitA:
3759 //
3760 // Step 1: find the cut point: an exit test on probable
3761 //         induction variable.
3762 // Step 2: schedule (with cloning) operations in the peel
3763 //         section that can be executed after the cut into
3764 //         the section that is not peeled.  This may need
3765 //         to clone operations into exit blocks.  For
3766 //         instance, a reference to A[i] in the not-peel
3767 //         section and a reference to B[i] in an exit block
3768 //         may cause a left-shift of i by 2 to be placed
3769 //         in the peel block.  This step will clone the left
3770 //         shift into the exit block and sink the left shift
3771 //         from the peel to the not-peel section.
3772 // Step 3: clone the loop, retarget the control, and insert
3773 //         phis for values that are live across the new loop
3774 //         head.  This is very dependent on the graph structure
3775 //         from clone_loop.  It creates region nodes for
3776 //         exit control and associated phi nodes for values
3777 //         flow out of the loop through that exit.  The region
3778 //         node is dominated by the clone's control projection.
3779 //         So the clone's peel section is placed before the
3780 //         new loop head, and the clone's not-peel section is
3781 //         forms the top part of the new loop.  The original
3782 //         peel section forms the tail of the new loop.
3783 // Step 4: update the dominator tree and recompute the
3784 //         dominator depth.
3785 //
3786 //                   orig
3787 //
3788 //                   stmt1
3789 //                     |
3790 //                     v
3791 //                 predicates
3792 //                     |
3793 //                     v
3794 //                   loop<----+
3795 //                     |      |
3796 //                   stmt2    |
3797 //                     |      |
3798 //                     v      |
3799 //                    ifA     |
3800 //                   / |      |
3801 //                  v  v      |
3802 //               false true   ^  <-- last_peel
3803 //               /     |      |
3804 //              /   ===|==cut |
3805 //             /     stmt3    |  <-- first_not_peel
3806 //            /        |      |
3807 //            |        v      |
3808 //            v       ifB     |
3809 //          exitA:   / \      |
3810 //                  /   \     |
3811 //                 v     v    |
3812 //               false true   |
3813 //               /       \    |
3814 //              /         ----+
3815 //             |
3816 //             v
3817 //           exitB:
3818 //           stmt4
3819 //
3820 //
3821 //            after clone loop
3822 //
3823 //                   stmt1
3824 //                     |
3825 //                     v
3826 //                predicates
3827 //                 /       \
3828 //        clone   /         \   orig
3829 //               /           \
3830 //              /             \
3831 //             v               v
3832 //   +---->loop                loop<----+
3833 //   |      |                    |      |
3834 //   |    stmt2                stmt2    |
3835 //   |      |                    |      |
3836 //   |      v                    v      |
3837 //   |      ifA                 ifA     |
3838 //   |      | \                / |      |
3839 //   |      v  v              v  v      |
3840 //   ^    true  false      false true   ^  <-- last_peel
3841 //   |      |   ^   \       /    |      |
3842 //   | cut==|==  \   \     /  ===|==cut |
3843 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
3844 //   |      |    dom   | |       |      |
3845 //   |      v      \  1v v2      v      |
3846 //   |      ifB     regionA     ifB     |
3847 //   |      / \        |       / \      |
3848 //   |     /   \       v      /   \     |
3849 //   |    v     v    exitA:  v     v    |
3850 //   |    true  false      false true   |
3851 //   |    /     ^   \      /       \    |
3852 //   +----       \   \    /         ----+
3853 //               dom  \  /
3854 //                 \  1v v2
3855 //                  regionB
3856 //                     |
3857 //                     v
3858 //                   exitB:
3859 //                   stmt4
3860 //
3861 //
3862 //           after partial peel
3863 //
3864 //                  stmt1
3865 //                     |
3866 //                     v
3867 //                predicates
3868 //                 /
3869 //        clone   /             orig
3870 //               /          TOP
3871 //              /             \
3872 //             v               v
3873 //    TOP->loop                loop----+
3874 //          |                    |      |
3875 //        stmt2                stmt2    |
3876 //          |                    |      |
3877 //          v                    v      |
3878 //          ifA                 ifA     |
3879 //          | \                / |      |
3880 //          v  v              v  v      |
3881 //        true  false      false true   |     <-- last_peel
3882 //          |   ^   \       /    +------|---+
3883 //  +->newloop   \   \     /  === ==cut |   |
3884 //  |     stmt3   \   \   /     TOP     |   |
3885 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
3886 //  |       v      \  1v v2      v      |   |
3887 //  |       ifB     regionA     ifB     ^   v
3888 //  |       / \        |       / \      |   |
3889 //  |      /   \       v      /   \     |   |
3890 //  |     v     v    exitA:  v     v    |   |
3891 //  |     true  false      false true   |   |
3892 //  |     /     ^   \      /       \    |   |
3893 //  |    |       \   \    /         v   |   |
3894 //  |    |       dom  \  /         TOP  |   |
3895 //  |    |         \  1v v2             |   |
3896 //  ^    v          regionB             |   |
3897 //  |    |             |                |   |
3898 //  |    |             v                ^   v
3899 //  |    |           exitB:             |   |
3900 //  |    |           stmt4              |   |
3901 //  |    +------------>-----------------+   |
3902 //  |                                       |
3903 //  +-----------------<---------------------+
3904 //
3905 //
3906 //              final graph
3907 //
3908 //                  stmt1
3909 //                    |
3910 //                    v
3911 //                predicates
3912 //                    |
3913 //                    v
3914 //                  stmt2 clone
3915 //                    |
3916 //                    v
3917 //         ........> ifA clone
3918 //         :        / |
3919 //        dom      /  |
3920 //         :      v   v
3921 //         :  false   true
3922 //         :  |       |
3923 //         :  |       v
3924 //         :  |    newloop<-----+
3925 //         :  |        |        |
3926 //         :  |     stmt3 clone |
3927 //         :  |        |        |
3928 //         :  |        v        |
3929 //         :  |       ifB       |
3930 //         :  |      / \        |
3931 //         :  |     v   v       |
3932 //         :  |  false true     |
3933 //         :  |   |     |       |
3934 //         :  |   v    stmt2    |
3935 //         :  | exitB:  |       |
3936 //         :  | stmt4   v       |
3937 //         :  |       ifA orig  |
3938 //         :  |      /  \       |
3939 //         :  |     /    \      |
3940 //         :  |    v     v      |
3941 //         :  |  false  true    |
3942 //         :  |  /        \     |
3943 //         :  v  v         -----+
3944 //          RegionA
3945 //             |
3946 //             v
3947 //           exitA
3948 //
3949 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
3950 
3951   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
3952   if (!loop->_head->is_Loop()) {
3953     return false;
3954   }
3955   LoopNode *head = loop->_head->as_Loop();
3956 
3957   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
3958     return false;
3959   }
3960 
3961   // Check for complex exit control
3962   for (uint ii = 0; ii < loop->_body.size(); ii++) {
3963     Node *n = loop->_body.at(ii);
3964     int opc = n->Opcode();
3965     if (n->is_Call()        ||
3966         opc == Op_Catch     ||
3967         opc == Op_CatchProj ||
3968         opc == Op_Jump      ||
3969         opc == Op_JumpProj) {
3970 #ifndef PRODUCT
3971       if (TracePartialPeeling) {
3972         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
3973       }
3974 #endif
3975       return false;
3976     }
3977   }
3978 
3979   int dd = dom_depth(head);
3980 
3981   // Step 1: find cut point
3982 
3983   // Walk up dominators to loop head looking for first loop exit
3984   // which is executed on every path thru loop.
3985   IfNode *peel_if = nullptr;
3986   IfNode *peel_if_cmpu = nullptr;
3987 
3988   Node *iff = loop->tail();
3989   while (iff != head) {
3990     if (iff->is_If()) {
3991       Node *ctrl = get_ctrl(iff->in(1));
3992       if (ctrl->is_top()) return false; // Dead test on live IF.
3993       // If loop-varying exit-test, check for induction variable
3994       if (loop->is_member(get_loop(ctrl)) &&
3995           loop->is_loop_exit(iff) &&
3996           is_possible_iv_test(iff)) {
3997         Node* cmp = iff->in(1)->in(1);
3998         if (cmp->Opcode() == Op_CmpI) {
3999           peel_if = iff->as_If();
4000         } else {
4001           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
4002           peel_if_cmpu = iff->as_If();
4003         }
4004       }
4005     }
4006     iff = idom(iff);
4007   }
4008 
4009   // Prefer signed compare over unsigned compare.
4010   IfNode* new_peel_if = nullptr;
4011   if (peel_if == nullptr) {
4012     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == nullptr) {
4013       return false;   // No peel point found
4014     }
4015     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
4016     if (new_peel_if == nullptr) {
4017       return false;   // No peel point found
4018     }
4019     peel_if = new_peel_if;
4020   }
4021   Node* last_peel        = stay_in_loop(peel_if, loop);
4022   Node* first_not_peeled = stay_in_loop(last_peel, loop);
4023   if (first_not_peeled == nullptr || first_not_peeled == head) {
4024     return false;
4025   }
4026 
4027 #ifndef PRODUCT
4028   if (TraceLoopOpts) {
4029     tty->print("PartialPeel  ");
4030     loop->dump_head();
4031   }
4032 
4033   if (TracePartialPeeling) {
4034     tty->print_cr("before partial peel one iteration");
4035     Node_List wl;
4036     Node* t = head->in(2);
4037     while (true) {
4038       wl.push(t);
4039       if (t == head) break;
4040       t = idom(t);
4041     }
4042     while (wl.size() > 0) {
4043       Node* tt = wl.pop();
4044       tt->dump();
4045       if (tt == last_peel) tty->print_cr("-- cut --");
4046     }
4047   }
4048 #endif
4049 
4050   C->print_method(PHASE_BEFORE_PARTIAL_PEELING, 4, head);
4051 
4052   VectorSet peel;
4053   VectorSet not_peel;
4054   Node_List peel_list;
4055   Node_List worklist;
4056   Node_List sink_list;
4057 
4058   uint estimate = loop->est_loop_clone_sz(1);
4059   if (exceeding_node_budget(estimate)) {
4060     return false;
4061   }
4062 
4063   // Set of cfg nodes to peel are those that are executable from
4064   // the head through last_peel.
4065   assert(worklist.size() == 0, "should be empty");
4066   worklist.push(head);
4067   peel.set(head->_idx);
4068   while (worklist.size() > 0) {
4069     Node *n = worklist.pop();
4070     if (n != last_peel) {
4071       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
4072         Node* use = n->fast_out(j);
4073         if (use->is_CFG() &&
4074             loop->is_member(get_loop(use)) &&
4075             !peel.test_set(use->_idx)) {
4076           worklist.push(use);
4077         }
4078       }
4079     }
4080   }
4081 
4082   // Set of non-cfg nodes to peel are those that are control
4083   // dependent on the cfg nodes.
4084   for (uint i = 0; i < loop->_body.size(); i++) {
4085     Node *n = loop->_body.at(i);
4086     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
4087     if (peel.test(n_c->_idx)) {
4088       peel.set(n->_idx);
4089     } else {
4090       not_peel.set(n->_idx);
4091     }
4092   }
4093 
4094   // Step 2: move operations from the peeled section down into the
4095   //         not-peeled section
4096 
4097   // Get a post order schedule of nodes in the peel region
4098   // Result in right-most operand.
4099   scheduled_nodelist(loop, peel, peel_list);
4100 
4101   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4102 
4103   // For future check for too many new phis
4104   uint old_phi_cnt = 0;
4105   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
4106     Node* use = head->fast_out(j);
4107     if (use->is_Phi()) old_phi_cnt++;
4108   }
4109 
4110 #ifndef PRODUCT
4111   if (TracePartialPeeling) {
4112     tty->print_cr("\npeeled list");
4113   }
4114 #endif
4115 
4116   // Evacuate nodes in peel region into the not_peeled region if possible
4117   bool too_many_clones = false;
4118   uint new_phi_cnt = 0;
4119   uint cloned_for_outside_use = 0;
4120   for (uint i = 0; i < peel_list.size();) {
4121     Node* n = peel_list.at(i);
4122 #ifndef PRODUCT
4123   if (TracePartialPeeling) n->dump();
4124 #endif
4125     bool incr = true;
4126     if (!n->is_CFG()) {
4127       if (has_use_in_set(n, not_peel)) {
4128         // If not used internal to the peeled region,
4129         // move "n" from peeled to not_peeled region.
4130         if (!has_use_internal_to_set(n, peel, loop)) {
4131           // if not pinned and not a load (which maybe anti-dependent on a store)
4132           // and not a CMove (Matcher expects only bool->cmove).
4133           if (n->in(0) == nullptr && !n->is_Load() && !n->is_CMove()) {
4134             int new_clones = clone_for_use_outside_loop(loop, n, worklist);
4135             if (C->failing()) return false;
4136             if (new_clones == -1) {
4137               too_many_clones = true;
4138               break;
4139             }
4140             cloned_for_outside_use += new_clones;
4141             sink_list.push(n);
4142             peel.remove(n->_idx);
4143             not_peel.set(n->_idx);
4144             peel_list.remove(i);
4145             incr = false;
4146 #ifndef PRODUCT
4147             if (TracePartialPeeling) {
4148               tty->print_cr("sink to not_peeled region: %d newbb: %d",
4149                             n->_idx, get_ctrl(n)->_idx);
4150             }
4151 #endif
4152           }
4153         } else {
4154           // Otherwise check for special def-use cases that span
4155           // the peel/not_peel boundary such as bool->if
4156           clone_for_special_use_inside_loop(loop, n, not_peel, sink_list, worklist);
4157           new_phi_cnt++;
4158         }
4159       }
4160     }
4161     if (incr) i++;
4162   }
4163 
4164   estimate += cloned_for_outside_use + new_phi_cnt;
4165   bool exceed_node_budget = !may_require_nodes(estimate);
4166   bool exceed_phi_limit = new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta;
4167 
4168   if (too_many_clones || exceed_node_budget || exceed_phi_limit) {
4169 #ifndef PRODUCT
4170     if (TracePartialPeeling && exceed_phi_limit) {
4171       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
4172                     new_phi_cnt, old_phi_cnt, new_peel_if != nullptr?'T':'F');
4173     }
4174 #endif
4175     if (new_peel_if != nullptr) {
4176       remove_cmpi_loop_exit(new_peel_if, loop);
4177     }
4178     // Inhibit more partial peeling on this loop
4179     assert(!head->is_partial_peel_loop(), "not partial peeled");
4180     head->mark_partial_peel_failed();
4181     if (cloned_for_outside_use > 0) {
4182       // Terminate this round of loop opts because
4183       // the graph outside this loop was changed.
4184       C->set_major_progress();
4185       return true;
4186     }
4187     return false;
4188   }
4189 
4190   // Step 3: clone loop, retarget control, and insert new phis
4191 
4192   // Create new loop head for new phis and to hang
4193   // the nodes being moved (sinked) from the peel region.
4194   LoopNode* new_head = new LoopNode(last_peel, last_peel);
4195   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
4196   _igvn.register_new_node_with_optimizer(new_head);
4197   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
4198   _igvn.replace_input_of(first_not_peeled, 0, new_head);
4199   set_loop(new_head, loop);
4200   loop->_body.push(new_head);
4201   not_peel.set(new_head->_idx);
4202   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
4203   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
4204 
4205   while (sink_list.size() > 0) {
4206     Node* n = sink_list.pop();
4207     set_ctrl(n, new_head);
4208   }
4209 
4210   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4211 
4212   clone_loop(loop, old_new, dd, IgnoreStripMined);
4213 
4214   const uint clone_exit_idx = 1;
4215   const uint orig_exit_idx  = 2;
4216   assert(is_valid_clone_loop_form(loop, peel_list, orig_exit_idx, clone_exit_idx), "bad clone loop");
4217 
4218   Node* head_clone             = old_new[head->_idx];
4219   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
4220   Node* orig_tail_clone        = head_clone->in(2);
4221 
4222   // Add phi if "def" node is in peel set and "use" is not
4223 
4224   for (uint i = 0; i < peel_list.size(); i++) {
4225     Node *def  = peel_list.at(i);
4226     if (!def->is_CFG()) {
4227       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
4228         Node *use = def->fast_out(j);
4229         if (has_node(use) && use->in(0) != C->top() &&
4230             (!peel.test(use->_idx) ||
4231              (use->is_Phi() && use->in(0) == head)) ) {
4232           worklist.push(use);
4233         }
4234       }
4235       while( worklist.size() ) {
4236         Node *use = worklist.pop();
4237         for (uint j = 1; j < use->req(); j++) {
4238           Node* n = use->in(j);
4239           if (n == def) {
4240 
4241             // "def" is in peel set, "use" is not in peel set
4242             // or "use" is in the entry boundary (a phi) of the peel set
4243 
4244             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
4245 
4246             if ( loop->is_member(get_loop( use_c )) ) {
4247               // use is in loop
4248               if (old_new[use->_idx] != nullptr) { // null for dead code
4249                 Node* use_clone = old_new[use->_idx];
4250                 _igvn.replace_input_of(use, j, C->top());
4251                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
4252               }
4253             } else {
4254               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
4255               // use is not in the loop, check if the live range includes the cut
4256               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
4257               if (not_peel.test(lp_if->_idx)) {
4258                 assert(j == orig_exit_idx, "use from original loop");
4259                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
4260               }
4261             }
4262           }
4263         }
4264       }
4265     }
4266   }
4267 
4268   // Step 3b: retarget control
4269 
4270   // Redirect control to the new loop head if a cloned node in
4271   // the not_peeled region has control that points into the peeled region.
4272   // This necessary because the cloned peeled region will be outside
4273   // the loop.
4274   //                            from    to
4275   //          cloned-peeled    <---+
4276   //    new_head_clone:            |    <--+
4277   //          cloned-not_peeled  in(0)    in(0)
4278   //          orig-peeled
4279 
4280   for (uint i = 0; i < loop->_body.size(); i++) {
4281     Node *n = loop->_body.at(i);
4282     if (!n->is_CFG()           && n->in(0) != nullptr        &&
4283         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
4284       Node* n_clone = old_new[n->_idx];
4285       if (n_clone->depends_only_on_test()) {
4286         // If this node depends_only_on_test, it will be rewire to the loop head, which is not the
4287         // correct test
4288         Node* pinned_clone = n_clone->pin_node_under_control();
4289         if (pinned_clone != nullptr) {
4290           register_new_node_with_ctrl_of(pinned_clone, n_clone);
4291           old_new.map(n->_idx, pinned_clone);
4292           _igvn.replace_node(n_clone, pinned_clone);
4293           n_clone = pinned_clone;
4294         }
4295       }
4296       _igvn.replace_input_of(n_clone, 0, new_head_clone);
4297     }
4298   }
4299 
4300   // Backedge of the surviving new_head (the clone) is original last_peel
4301   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
4302 
4303   // Cut first node in original not_peel set
4304   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
4305   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
4306   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
4307 
4308   // Copy head_clone back-branch info to original head
4309   // and remove original head's loop entry and
4310   // clone head's back-branch
4311   _igvn.rehash_node_delayed(head); // Multiple edge updates
4312   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
4313   head->set_req(LoopNode::LoopBackControl, C->top());
4314   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
4315 
4316   // Similarly modify the phis
4317   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
4318     Node* use = head->fast_out(k);
4319     if (use->is_Phi() && use->outcnt() > 0) {
4320       Node* use_clone = old_new[use->_idx];
4321       _igvn.rehash_node_delayed(use); // Multiple edge updates
4322       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
4323       use->set_req(LoopNode::LoopBackControl, C->top());
4324       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
4325     }
4326   }
4327 
4328   // Step 4: update dominator tree and dominator depth
4329 
4330   set_idom(head, orig_tail_clone, dd);
4331   recompute_dom_depth();
4332 
4333   // Inhibit more partial peeling on this loop
4334   new_head_clone->set_partial_peel_loop();
4335   C->set_major_progress();
4336   loop->record_for_igvn();
4337 
4338 #ifndef PRODUCT
4339   if (TracePartialPeeling) {
4340     tty->print_cr("\nafter partial peel one iteration");
4341     Node_List wl;
4342     Node* t = last_peel;
4343     while (true) {
4344       wl.push(t);
4345       if (t == head_clone) break;
4346       t = idom(t);
4347     }
4348     while (wl.size() > 0) {
4349       Node* tt = wl.pop();
4350       if (tt == head) tty->print_cr("orig head");
4351       else if (tt == new_head_clone) tty->print_cr("new head");
4352       else if (tt == head_clone) tty->print_cr("clone head");
4353       tt->dump();
4354     }
4355   }
4356 #endif
4357 
4358   C->print_method(PHASE_AFTER_PARTIAL_PEELING, 4, new_head_clone);
4359 
4360   return true;
4361 }
4362 
4363 #ifdef ASSERT
4364 
4365 // Moves Template Assertion Predicates to a target loop by cloning and killing the old ones. The target loop is the
4366 // original, not-cloned loop. This is currently only used with StressLoopBackedge which is a develop flag only and
4367 // false with product builds. We can therefore guard it with an ifdef. More details can be found at the use-site.
4368 class MoveAssertionPredicatesVisitor : public PredicateVisitor {
4369   ClonePredicateToTargetLoop _clone_predicate_to_loop;
4370   PhaseIdealLoop* const _phase;
4371 
4372 public:
4373   MoveAssertionPredicatesVisitor(LoopNode* target_loop_head,
4374                                  const NodeInSingleLoopBody &node_in_loop_body,
4375                                  PhaseIdealLoop* phase)
4376     : _clone_predicate_to_loop(target_loop_head, node_in_loop_body, phase),
4377       _phase(phase) {
4378   }
4379   NONCOPYABLE(MoveAssertionPredicatesVisitor);
4380 
4381   using PredicateVisitor::visit;
4382 
4383   void visit(const TemplateAssertionPredicate& template_assertion_predicate) override {
4384     _clone_predicate_to_loop.clone_template_assertion_predicate(template_assertion_predicate);
4385     template_assertion_predicate.kill(_phase->igvn());
4386   }
4387 };
4388 #endif // ASSERT
4389 
4390 // Transform:
4391 //
4392 // loop<-----------------+
4393 //  |                    |
4394 // stmt1 stmt2 .. stmtn  |
4395 //  |     |        |     |
4396 //  \     |       /      |
4397 //    v   v     v        |
4398 //       region          |
4399 //         |             |
4400 //     shared_stmt       |
4401 //         |             |
4402 //         v             |
4403 //         if            |
4404 //         / \           |
4405 //        |   -----------+
4406 //        v
4407 //
4408 // into:
4409 //
4410 //    loop<-------------------+
4411 //     |                      |
4412 //     v                      |
4413 // +->loop                    |
4414 // |   |                      |
4415 // |  stmt1 stmt2 .. stmtn    |
4416 // |   |     |        |       |
4417 // |   |      \       /       |
4418 // |   |       v     v        |
4419 // |   |        region1       |
4420 // |   |           |          |
4421 // |  shared_stmt shared_stmt |
4422 // |   |           |          |
4423 // |   v           v          |
4424 // |   if          if         |
4425 // |   /\          / \        |
4426 // +--   |         |   -------+
4427 //       \         /
4428 //        v       v
4429 //         region2
4430 //
4431 // (region2 is shown to merge mirrored projections of the loop exit
4432 // ifs to make the diagram clearer but they really merge the same
4433 // projection)
4434 //
4435 // Conditions for this transformation to trigger:
4436 // - the path through stmt1 is frequent enough
4437 // - the inner loop will be turned into a counted loop after transformation
4438 bool PhaseIdealLoop::duplicate_loop_backedge(IdealLoopTree *loop, Node_List &old_new) {
4439   if (!DuplicateBackedge) {
4440     return false;
4441   }
4442   assert(!loop->_head->is_CountedLoop() || StressDuplicateBackedge, "Non-counted loop only");
4443   if (!loop->_head->is_Loop()) {
4444     return false;
4445   }
4446 
4447   uint estimate = loop->est_loop_clone_sz(1);
4448   if (exceeding_node_budget(estimate)) {
4449     return false;
4450   }
4451 
4452   LoopNode *head = loop->_head->as_Loop();
4453 
4454   Node* region = nullptr;
4455   IfNode* exit_test = nullptr;
4456   uint inner;
4457   float f;
4458 #ifdef ASSERT
4459   if (StressDuplicateBackedge) {
4460     if (head->is_strip_mined()) {
4461       return false;
4462     }
4463     Node* c = head->in(LoopNode::LoopBackControl);
4464 
4465     while (c != head) {
4466       if (c->is_Region()) {
4467         region = c;
4468       }
4469       c = idom(c);
4470     }
4471 
4472     if (region == nullptr) {
4473       return false;
4474     }
4475 
4476     inner = 1;
4477   } else
4478 #endif //ASSERT
4479   {
4480     // Is the shape of the loop that of a counted loop...
4481     Node* back_control = loop_exit_control(loop);
4482     if (back_control == nullptr) {
4483       return false;
4484     }
4485 
4486     LoopExitTest loop_exit(back_control, loop, this);
4487     loop_exit.build();
4488     if (!loop_exit.is_valid_with_bt(T_INT)) {
4489       return false;
4490     }
4491 
4492     const Node* loop_incr = loop_exit.incr();
4493 
4494     // With an extra phi for the candidate iv?
4495     // Or the region node is the loop head
4496     if (!loop_incr->is_Phi() || loop_incr->in(0) == head) {
4497       return false;
4498     }
4499 
4500     PathFrequency pf(head, this);
4501     region = loop_incr->in(0);
4502 
4503     // Go over all paths for the extra phi's region and see if that
4504     // path is frequent enough and would match the expected iv shape
4505     // if the extra phi is removed
4506     inner = 0;
4507     for (uint i = 1; i < loop_incr->req(); ++i) {
4508       CountedLoopConverter::TruncatedIncrement increment(T_INT);
4509       increment.build(loop_incr->in(i));
4510       if (!increment.is_valid()) {
4511         continue;
4512       }
4513       assert(increment.incr()->Opcode() == Op_AddI, "wrong increment code");
4514 
4515       LoopIVStride stride = LoopIVStride(T_INT);
4516       stride.build(increment.incr());
4517       if (!stride.is_valid()) {
4518         continue;
4519       }
4520 
4521       PhiNode* phi = loop_iv_phi(stride.xphi(), nullptr, head);
4522       if (phi == nullptr ||
4523           (increment.outer_trunc() == nullptr && phi->in(LoopNode::LoopBackControl) != loop_exit.incr()) ||
4524           (increment.outer_trunc() != nullptr && phi->in(LoopNode::LoopBackControl) != increment.outer_trunc())) {
4525         return false;
4526       }
4527 
4528       f = pf.to(region->in(i));
4529       if (f > 0.5) {
4530         inner = i;
4531         break;
4532       }
4533     }
4534 
4535     if (inner == 0) {
4536       return false;
4537     }
4538 
4539     exit_test = back_control->in(0)->as_If();
4540   }
4541 
4542   if (idom(region)->is_Catch()) {
4543     return false;
4544   }
4545 
4546   // Collect all control nodes that need to be cloned (shared_stmt in the diagram)
4547   Unique_Node_List wq;
4548   wq.push(head->in(LoopNode::LoopBackControl));
4549   for (uint i = 0; i < wq.size(); i++) {
4550     Node* c = wq.at(i);
4551     assert(get_loop(c) == loop, "not in the right loop?");
4552     if (c->is_Region()) {
4553       if (c != region) {
4554         for (uint j = 1; j < c->req(); ++j) {
4555           wq.push(c->in(j));
4556         }
4557       }
4558     } else {
4559       wq.push(c->in(0));
4560     }
4561     assert(!is_strict_dominator(c, region), "shouldn't go above region");
4562   }
4563 
4564   Node* region_dom = idom(region);
4565 
4566   // Can't do the transformation if this would cause a membar pair to
4567   // be split
4568   for (uint i = 0; i < wq.size(); i++) {
4569     Node* c = wq.at(i);
4570     if (c->is_MemBar() && (c->as_MemBar()->trailing_store() || c->as_MemBar()->trailing_load_store())) {
4571       assert(c->as_MemBar()->leading_membar()->trailing_membar() == c, "bad membar pair");
4572       if (!wq.member(c->as_MemBar()->leading_membar())) {
4573         return false;
4574       }
4575     }
4576   }
4577   C->print_method(PHASE_BEFORE_DUPLICATE_LOOP_BACKEDGE, 4, head);
4578 
4579   // Collect data nodes that need to be clones as well
4580   int dd = dom_depth(head);
4581 
4582   for (uint i = 0; i < loop->_body.size(); ++i) {
4583     Node* n = loop->_body.at(i);
4584     if (has_ctrl(n)) {
4585       Node* c = get_ctrl(n);
4586       if (wq.member(c)) {
4587         wq.push(n);
4588       }
4589     } else {
4590       set_idom(n, idom(n), dd);
4591     }
4592   }
4593 
4594   // clone shared_stmt
4595   clone_loop_body(wq, old_new, nullptr);
4596 
4597   Node* region_clone = old_new[region->_idx];
4598   region_clone->set_req(inner, C->top());
4599   set_idom(region, region->in(inner), dd);
4600 
4601   // Prepare the outer loop
4602   Node* outer_head = new LoopNode(head->in(LoopNode::EntryControl), old_new[head->in(LoopNode::LoopBackControl)->_idx]);
4603   register_control(outer_head, loop->_parent, outer_head->in(LoopNode::EntryControl));
4604   _igvn.replace_input_of(head, LoopNode::EntryControl, outer_head);
4605   set_idom(head, outer_head, dd);
4606 
4607   fix_body_edges(wq, loop, old_new, dd, loop->_parent, true);
4608 
4609   // Make one of the shared_stmt copies only reachable from stmt1, the
4610   // other only from stmt2..stmtn.
4611   Node* dom = nullptr;
4612   for (uint i = 1; i < region->req(); ++i) {
4613     if (i != inner) {
4614       _igvn.replace_input_of(region, i, C->top());
4615     }
4616     Node* in = region_clone->in(i);
4617     if (in->is_top()) {
4618       continue;
4619     }
4620     if (dom == nullptr) {
4621       dom = in;
4622     } else {
4623       dom = dom_lca(dom, in);
4624     }
4625   }
4626 
4627   set_idom(region_clone, dom, dd);
4628 
4629   // Set up the outer loop
4630   for (uint i = 0; i < head->outcnt(); i++) {
4631     Node* u = head->raw_out(i);
4632     if (u->is_Phi()) {
4633       Node* outer_phi = u->clone();
4634       outer_phi->set_req(0, outer_head);
4635       Node* backedge = old_new[u->in(LoopNode::LoopBackControl)->_idx];
4636       if (backedge == nullptr) {
4637         backedge = u->in(LoopNode::LoopBackControl);
4638       }
4639       outer_phi->set_req(LoopNode::LoopBackControl, backedge);
4640       register_new_node(outer_phi, outer_head);
4641       _igvn.replace_input_of(u, LoopNode::EntryControl, outer_phi);
4642     }
4643   }
4644 
4645   // create control and data nodes for out of loop uses (including region2)
4646   Node_List worklist;
4647   uint new_counter = C->unique();
4648   fix_ctrl_uses(wq, loop, old_new, ControlAroundStripMined, outer_head, nullptr, worklist);
4649 
4650   Node_List *split_if_set = nullptr;
4651   Node_List *split_bool_set = nullptr;
4652   Node_List *split_cex_set = nullptr;
4653   fix_data_uses(wq, loop, ControlAroundStripMined, loop->skip_strip_mined(), new_counter, old_new, worklist,
4654                 split_if_set, split_bool_set, split_cex_set);
4655 
4656   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
4657 
4658   if (exit_test != nullptr) {
4659     float cnt = exit_test->_fcnt;
4660     if (cnt != COUNT_UNKNOWN) {
4661       exit_test->_fcnt = cnt * f;
4662       old_new[exit_test->_idx]->as_If()->_fcnt = cnt * (1 - f);
4663     }
4664   }
4665 
4666 #ifdef ASSERT
4667   if (StressDuplicateBackedge && head->is_CountedLoop()) {
4668     // The Template Assertion Predicates from the old counted loop are now at the new outer loop - clone them to
4669     // the inner counted loop and kill the old ones. We only need to do this with debug builds because
4670     // StressDuplicateBackedge is a devlop flag and false by default. Without StressDuplicateBackedge 'head' will be a
4671     // non-counted loop, and thus we have no Template Assertion Predicates above the old loop to move down.
4672     PredicateIterator predicate_iterator(outer_head->in(LoopNode::EntryControl));
4673     NodeInSingleLoopBody node_in_body(this, loop);
4674     MoveAssertionPredicatesVisitor move_assertion_predicates_visitor(head, node_in_body, this);
4675     predicate_iterator.for_each(move_assertion_predicates_visitor);
4676   }
4677 #endif // ASSERT
4678 
4679   C->set_major_progress();
4680 
4681   C->print_method(PHASE_AFTER_DUPLICATE_LOOP_BACKEDGE, 4, outer_head);
4682 
4683   return true;
4684 }
4685 
4686 // AutoVectorize the loop: replace scalar ops with vector ops.
4687 PhaseIdealLoop::AutoVectorizeStatus
4688 PhaseIdealLoop::auto_vectorize(IdealLoopTree* lpt, VSharedData &vshared) {
4689   // Counted loop only
4690   if (!lpt->is_counted()) {
4691     return AutoVectorizeStatus::Impossible;
4692   }
4693 
4694   // Main-loop only
4695   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4696   if (!cl->is_main_loop()) {
4697     return AutoVectorizeStatus::Impossible;
4698   }
4699 
4700   VLoop vloop(lpt, false);
4701   if (!vloop.check_preconditions()) {
4702     return AutoVectorizeStatus::TriedAndFailed;
4703   }
4704 
4705   // Ensure the shared data is cleared before each use
4706   vshared.clear();
4707 
4708   const VLoopAnalyzer vloop_analyzer(vloop, vshared);
4709   if (!vloop_analyzer.success()) {
4710     return AutoVectorizeStatus::TriedAndFailed;
4711   }
4712 
4713   SuperWord sw(vloop_analyzer);
4714   if (!sw.transform_loop()) {
4715     return AutoVectorizeStatus::TriedAndFailed;
4716   }
4717 
4718   return AutoVectorizeStatus::Success;
4719 }
4720 
4721 // Just before insert_pre_post_loops, we can multiversion the loop:
4722 //
4723 //              multiversion_if
4724 //               |       |
4725 //         fast_loop   slow_loop
4726 //
4727 // In the fast_loop we can make speculative assumptions, and put the
4728 // conditions into the multiversion_if. If the conditions hold at runtime,
4729 // we enter the fast_loop, if the conditions fail, we take the slow_loop
4730 // instead which does not make any of the speculative assumptions.
4731 //
4732 // Note: we only multiversion the loop if the loop does not have any
4733 //       auto vectorization check Predicate. If we have that predicate,
4734 //       then we can simply add the speculative assumption checks to
4735 //       that Predicate. This means we do not need to duplicate the
4736 //       loop - we have a smaller graph and save compile time. Should
4737 //       the conditions ever fail, then we deopt / trap at the Predicate
4738 //       and recompile without that Predicate. At that point we will
4739 //       multiversion the loop, so that we can still have speculative
4740 //       runtime checks.
4741 //
4742 // We perform the multiversioning when the loop is still in its single
4743 // iteration form, even before we insert pre and post loops. This makes
4744 // the cloning much simpler. However, this means that both the fast
4745 // and the slow loop have to be optimized independently (adding pre
4746 // and post loops, unrolling the main loop, auto-vectorize etc.). And
4747 // we may end up not needing any speculative assumptions in the fast_loop
4748 // and then rejecting the slow_loop by constant folding the multiversion_if.
4749 //
4750 // Therefore, we "delay" the optimization of the slow_loop until we add
4751 // at least one speculative assumption for the fast_loop. If we never
4752 // add such a speculative runtime check, the OpaqueMultiversioningNode
4753 // of the multiversion_if constant folds to true after loop opts, and the
4754 // multiversion_if folds away the "delayed" slow_loop. If we add any
4755 // speculative assumption, then we notify the OpaqueMultiversioningNode
4756 // with "notify_slow_loop_that_it_can_resume_optimizations".
4757 //
4758 // Note: new runtime checks can be added to the multiversion_if with
4759 //       PhaseIdealLoop::create_new_if_for_multiversion
4760 void PhaseIdealLoop::maybe_multiversion_for_auto_vectorization_runtime_checks(IdealLoopTree* lpt, Node_List& old_new) {
4761   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4762   LoopNode* outer_loop = cl->skip_strip_mined();
4763   Node* entry = outer_loop->in(LoopNode::EntryControl);
4764 
4765   // Check we have multiversioning enabled, and are not already multiversioned.
4766   if (!LoopMultiversioning || cl->is_multiversion()) { return; }
4767 
4768   // Check that we do not have a parse-predicate where we can add the runtime checks
4769   // during auto-vectorization.
4770   const Predicates predicates(entry);
4771   const PredicateBlock* predicate_block = predicates.auto_vectorization_check_block();
4772   if (predicate_block->has_parse_predicate()) { return; }
4773 
4774   // Check node budget.
4775   uint estimate = lpt->est_loop_clone_sz(2);
4776   if (!may_require_nodes(estimate)) { return; }
4777 
4778   do_multiversioning(lpt, old_new);
4779 }
4780 
4781 void DataNodeGraph::clone_data_nodes(Node* new_ctrl) {
4782   for (uint i = 0; i < _data_nodes.size(); i++) {
4783     clone(_data_nodes[i], new_ctrl);
4784   }
4785 }
4786 
4787 // Clone the given node and set it up properly. Set 'new_ctrl' as ctrl.
4788 void DataNodeGraph::clone(Node* node, Node* new_ctrl) {
4789   Node* clone = node->clone();
4790   _phase->igvn().register_new_node_with_optimizer(clone);
4791   _orig_to_new.put(node, clone);
4792   _phase->set_ctrl(clone, new_ctrl);
4793   if (node->is_CastII()) {
4794     clone->set_req(0, new_ctrl);
4795   }
4796 }
4797 
4798 // Rewire the data inputs of all (unprocessed) cloned nodes, whose inputs are still pointing to the same inputs as their
4799 // corresponding orig nodes, to the newly cloned inputs to create a separate cloned graph.
4800 void DataNodeGraph::rewire_clones_to_cloned_inputs() {
4801   _orig_to_new.iterate_all([&](Node* node, Node* clone) {
4802     for (uint i = 1; i < node->req(); i++) {
4803       Node** cloned_input = _orig_to_new.get(node->in(i));
4804       if (cloned_input != nullptr) {
4805         // Input was also cloned -> rewire clone to the cloned input.
4806         _phase->igvn().replace_input_of(clone, i, *cloned_input);
4807       }
4808     }
4809   });
4810 }
4811 
4812 // Clone all non-OpaqueLoop* nodes and apply the provided transformation strategy for OpaqueLoop* nodes.
4813 // Set 'new_ctrl' as ctrl for all cloned non-OpaqueLoop* nodes.
4814 void DataNodeGraph::clone_data_nodes_and_transform_opaque_loop_nodes(
4815     const TransformStrategyForOpaqueLoopNodes& transform_strategy,
4816     Node* new_ctrl) {
4817   for (uint i = 0; i < _data_nodes.size(); i++) {
4818     Node* data_node = _data_nodes[i];
4819     if (data_node->is_Opaque1()) {
4820       transform_opaque_node(transform_strategy, data_node);
4821     } else {
4822       clone(data_node, new_ctrl);
4823     }
4824   }
4825 }
4826 
4827 void DataNodeGraph::transform_opaque_node(const TransformStrategyForOpaqueLoopNodes& transform_strategy, Node* node) {
4828   Node* transformed_node;
4829   if (node->is_OpaqueLoopInit()) {
4830     transformed_node = transform_strategy.transform_opaque_init(node->as_OpaqueLoopInit());
4831   } else {
4832     assert(node->is_OpaqueLoopStride(), "must be OpaqueLoopStrideNode");
4833     transformed_node = transform_strategy.transform_opaque_stride(node->as_OpaqueLoopStride());
4834   }
4835   // Add an orig->new mapping to correctly update the inputs of the copied graph in rewire_clones_to_cloned_inputs().
4836   _orig_to_new.put(node, transformed_node);
4837 }
--- EOF ---