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