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 #ifndef PRODUCT
 239   if (TraceLoopOpts) {
 240     tty->print_cr("Split %d %s through %d Phi in %d %s",
 241                   n->_idx, n->Name(), phi->_idx, region->_idx, region->Name());
 242   }
 243 #endif // !PRODUCT
 244 
 245   return phi;
 246 }
 247 
 248 // Test whether node 'x' can move into an inner loop relative to node 'n'.
 249 // Note: The test is not exact. Returns true if 'x' COULD end up in an inner loop,
 250 // BUT it can also return true and 'x' is in the outer loop
 251 bool PhaseIdealLoop::can_move_to_inner_loop(Node* n, LoopNode* n_loop, Node* x) {
 252   IdealLoopTree* n_loop_tree = get_loop(n_loop);
 253   IdealLoopTree* x_loop_tree = get_loop(get_early_ctrl(x));
 254   // x_loop_tree should be outer or same loop as n_loop_tree
 255   return !x_loop_tree->is_member(n_loop_tree);
 256 }
 257 
 258 // Subtype checks that carry profile data don't common so look for a replacement by following edges
 259 Node* PhaseIdealLoop::similar_subtype_check(const Node* x, Node* r_in) {
 260   if (x->is_SubTypeCheck()) {
 261     Node* in1 = x->in(1);
 262     for (DUIterator_Fast imax, i = in1->fast_outs(imax); i < imax; i++) {
 263       Node* u = in1->fast_out(i);
 264       if (u != x && u->is_SubTypeCheck() && u->in(1) == x->in(1) && u->in(2) == x->in(2)) {
 265         for (DUIterator_Fast jmax, j = u->fast_outs(jmax); j < jmax; j++) {
 266           Node* bol = u->fast_out(j);
 267           for (DUIterator_Fast kmax, k = bol->fast_outs(kmax); k < kmax; k++) {
 268             Node* iff = bol->fast_out(k);
 269             // Only dominating subtype checks are interesting: otherwise we risk replacing a subtype check by another with
 270             // unrelated profile
 271             if (iff->is_If() && is_dominator(iff, r_in)) {
 272               return u;
 273             }
 274           }
 275         }
 276       }
 277     }
 278   }
 279   return nullptr;
 280 }
 281 
 282 // Return true if 'n' is a Div or Mod node (without zero check If node which was removed earlier) with a loop phi divisor
 283 // of a trip-counted (integer or long) loop with a backedge input that could be zero (include zero in its type range). In
 284 // this case, we cannot split the division to the backedge as it could freely float above the loop exit check resulting in
 285 // a division by zero. This situation is possible because the type of an increment node of an iv phi (trip-counter) could
 286 // include zero while the iv phi does not (see PhiNode::Value() for trip-counted loops where we improve types of iv phis).
 287 // We also need to check other loop phis as they could have been created in the same split-if pass when applying
 288 // PhaseIdealLoop::split_thru_phi() to split nodes through an iv phi.
 289 bool PhaseIdealLoop::cannot_split_division(const Node* n, const Node* region) const {
 290   const Type* zero;
 291   switch (n->Opcode()) {
 292     case Op_DivI:
 293     case Op_ModI:
 294     case Op_UDivI:
 295     case Op_UModI:
 296       zero = TypeInt::ZERO;
 297       break;
 298     case Op_DivL:
 299     case Op_ModL:
 300     case Op_UDivL:
 301     case Op_UModL:
 302       zero = TypeLong::ZERO;
 303       break;
 304     default:
 305       return false;
 306   }
 307 
 308   if (n->in(0) != nullptr) {
 309     // Cannot split through phi if Div or Mod node has a control dependency to a zero check.
 310     return true;
 311   }
 312 
 313   Node* divisor = n->in(2);
 314   return is_divisor_loop_phi(divisor, region) &&
 315          loop_phi_backedge_type_contains_zero(divisor, zero);
 316 }
 317 
 318 bool PhaseIdealLoop::is_divisor_loop_phi(const Node* divisor, const Node* loop) {
 319   return loop->is_Loop() && divisor->is_Phi() && divisor->in(0) == loop;
 320 }
 321 
 322 bool PhaseIdealLoop::loop_phi_backedge_type_contains_zero(const Node* phi_divisor, const Type* zero) const {
 323     return _igvn.type(phi_divisor->in(LoopNode::LoopBackControl))->filter_speculative(zero) != Type::TOP;
 324 }
 325 
 326 //------------------------------dominated_by------------------------------------
 327 // Replace the dominated test with an obvious true or false.  Place it on the
 328 // IGVN worklist for later cleanup.  Move control-dependent data Nodes on the
 329 // live path up to the dominating control.
 330 void PhaseIdealLoop::dominated_by(IfProjNode* prevdom, IfNode* iff, bool flip, bool pin_array_access_nodes) {
 331   if (VerifyLoopOptimizations && PrintOpto) { tty->print_cr("dominating test"); }
 332 
 333   // prevdom is the dominating projection of the dominating test.
 334   assert(iff->Opcode() == Op_If ||
 335          iff->Opcode() == Op_CountedLoopEnd ||
 336          iff->Opcode() == Op_LongCountedLoopEnd ||
 337          iff->Opcode() == Op_RangeCheck ||
 338          iff->Opcode() == Op_ParsePredicate,
 339         "Check this code when new subtype is added");
 340 
 341   int pop = prevdom->Opcode();
 342   assert( pop == Op_IfFalse || pop == Op_IfTrue, "" );
 343   if (flip) {
 344     if (pop == Op_IfTrue)
 345       pop = Op_IfFalse;
 346     else
 347       pop = Op_IfTrue;
 348   }
 349   // 'con' is set to true or false to kill the dominated test.
 350   Node* con = makecon(pop == Op_IfTrue ? TypeInt::ONE : TypeInt::ZERO);
 351   // Hack the dominated test
 352   _igvn.replace_input_of(iff, 1, con);
 353 
 354   // If I don't have a reachable TRUE and FALSE path following the IfNode then
 355   // I can assume this path reaches an infinite loop.  In this case it's not
 356   // important to optimize the data Nodes - either the whole compilation will
 357   // be tossed or this path (and all data Nodes) will go dead.
 358   if (iff->outcnt() != 2) {
 359     return;
 360   }
 361 
 362   // Make control-dependent data Nodes on the live path (path that will remain
 363   // once the dominated IF is removed) become control-dependent on the
 364   // dominating projection.
 365   Node* dp = iff->proj_out_or_null(pop == Op_IfTrue);
 366 
 367   if (dp == nullptr) {
 368     return;
 369   }
 370 
 371   rewire_safe_outputs_to_dominator(dp, prevdom, pin_array_access_nodes);
 372 }
 373 
 374 void PhaseIdealLoop::rewire_safe_outputs_to_dominator(Node* source, Node* dominator, const bool pin_array_access_nodes) {
 375   IdealLoopTree* old_loop = get_loop(source);
 376 
 377   for (DUIterator_Fast imax, i = source->fast_outs(imax); i < imax; i++) {
 378     Node* out = source->fast_out(i); // Control-dependent node
 379     // Do not rewire Div and Mod nodes which could have a zero divisor to avoid skipping their zero check.
 380     if (out->depends_only_on_test() && _igvn.no_dependent_zero_check(out)) {
 381       assert(out->in(0) == source, "must be control dependent on source");
 382       _igvn.replace_input_of(out, 0, dominator);
 383       if (pin_array_access_nodes) {
 384         // Because of Loop Predication, Loads and range check Cast nodes that are control dependent on this range
 385         // check (that is about to be removed) now depend on multiple dominating Hoisted Check Predicates. After the
 386         // removal of this range check, these control dependent nodes end up at the lowest/nearest dominating predicate
 387         // in the graph. To ensure that these Loads/Casts do not float above any of the dominating checks (even when the
 388         // lowest dominating check is later replaced by yet another dominating check), we need to pin them at the lowest
 389         // dominating check.
 390         Node* clone = out->pin_array_access_node();
 391         if (clone != nullptr) {
 392           clone = _igvn.register_new_node_with_optimizer(clone, out);
 393           _igvn.replace_node(out, clone);
 394           out = clone;
 395         }
 396       }
 397       set_early_ctrl(out, false);
 398       IdealLoopTree* new_loop = get_loop(get_ctrl(out));
 399       if (old_loop != new_loop) {
 400         if (!old_loop->_child) {
 401           old_loop->_body.yank(out);
 402         }
 403         if (!new_loop->_child) {
 404           new_loop->_body.push(out);
 405         }
 406       }
 407       --i;
 408       --imax;
 409     }
 410   }
 411 }
 412 
 413 //------------------------------has_local_phi_input----------------------------
 414 // Return TRUE if 'n' has Phi inputs from its local block and no other
 415 // block-local inputs (all non-local-phi inputs come from earlier blocks)
 416 Node *PhaseIdealLoop::has_local_phi_input( Node *n ) {
 417   Node *n_ctrl = get_ctrl(n);
 418   // See if some inputs come from a Phi in this block, or from before
 419   // this block.
 420   uint i;
 421   for( i = 1; i < n->req(); i++ ) {
 422     Node *phi = n->in(i);
 423     if( phi->is_Phi() && phi->in(0) == n_ctrl )
 424       break;
 425   }
 426   if( i >= n->req() )
 427     return nullptr;                // No Phi inputs; nowhere to clone thru
 428 
 429   // Check for inputs created between 'n' and the Phi input.  These
 430   // must split as well; they have already been given the chance
 431   // (courtesy of a post-order visit) and since they did not we must
 432   // recover the 'cost' of splitting them by being very profitable
 433   // when splitting 'n'.  Since this is unlikely we simply give up.
 434   for( i = 1; i < n->req(); i++ ) {
 435     Node *m = n->in(i);
 436     if( get_ctrl(m) == n_ctrl && !m->is_Phi() ) {
 437       // We allow the special case of AddP's with no local inputs.
 438       // This allows us to split-up address expressions.
 439       if (m->is_AddP() &&
 440           get_ctrl(m->in(AddPNode::Base)) != n_ctrl &&
 441           get_ctrl(m->in(AddPNode::Address)) != n_ctrl &&
 442           get_ctrl(m->in(AddPNode::Offset)) != n_ctrl) {
 443         // Move the AddP up to the dominating point. That's fine because control of m's inputs
 444         // must dominate get_ctrl(m) == n_ctrl and we just checked that the input controls are != n_ctrl.
 445         Node* c = find_non_split_ctrl(idom(n_ctrl));
 446         if (c->is_OuterStripMinedLoop()) {
 447           c->as_Loop()->verify_strip_mined(1);
 448           c = c->in(LoopNode::EntryControl);
 449         }
 450         set_ctrl_and_loop(m, c);
 451         continue;
 452       }
 453       return nullptr;
 454     }
 455     assert(n->is_Phi() || m->is_Phi() || is_dominator(get_ctrl(m), n_ctrl), "m has strange control");
 456   }
 457 
 458   return n_ctrl;
 459 }
 460 
 461 // Replace expressions like ((V+I) << 2) with (V<<2 + I<<2).
 462 Node* PhaseIdealLoop::remix_address_expressions_add_left_shift(Node* n, IdealLoopTree* n_loop, Node* n_ctrl, BasicType bt) {
 463   assert(bt == T_INT || bt == T_LONG, "only for integers");
 464   int n_op = n->Opcode();
 465 
 466   if (n_op == Op_LShift(bt)) {
 467     // Scale is loop invariant
 468     Node* scale = n->in(2);
 469     Node* scale_ctrl = get_ctrl(scale);
 470     IdealLoopTree* scale_loop = get_loop(scale_ctrl);
 471     if (n_loop == scale_loop || !scale_loop->is_member(n_loop)) {
 472       return nullptr;
 473     }
 474     const TypeInt* scale_t = scale->bottom_type()->isa_int();
 475     if (scale_t != nullptr && scale_t->is_con() && scale_t->get_con() >= 16) {
 476       return nullptr;              // Dont bother with byte/short masking
 477     }
 478     // Add must vary with loop (else shift would be loop-invariant)
 479     Node* add = n->in(1);
 480     Node* add_ctrl = get_ctrl(add);
 481     IdealLoopTree* add_loop = get_loop(add_ctrl);
 482     if (n_loop != add_loop) {
 483       return nullptr;  // happens w/ evil ZKM loops
 484     }
 485 
 486     // Convert I-V into I+ (0-V); same for V-I
 487     if (add->Opcode() == Op_Sub(bt) &&
 488         _igvn.type(add->in(1)) != TypeInteger::zero(bt)) {
 489       assert(add->Opcode() == Op_SubI || add->Opcode() == Op_SubL, "");
 490       Node* zero = integercon(0, bt);
 491       Node* neg = SubNode::make(zero, add->in(2), bt);
 492       register_new_node_with_ctrl_of(neg, add->in(2));
 493       add = AddNode::make(add->in(1), neg, bt);
 494       register_new_node(add, add_ctrl);
 495     }
 496     if (add->Opcode() != Op_Add(bt)) return nullptr;
 497     assert(add->Opcode() == Op_AddI || add->Opcode() == Op_AddL, "");
 498     // See if one add input is loop invariant
 499     Node* add_var = add->in(1);
 500     Node* add_var_ctrl = get_ctrl(add_var);
 501     IdealLoopTree* add_var_loop = get_loop(add_var_ctrl);
 502     Node* add_invar = add->in(2);
 503     Node* add_invar_ctrl = get_ctrl(add_invar);
 504     IdealLoopTree* add_invar_loop = get_loop(add_invar_ctrl);
 505     if (add_invar_loop == n_loop) {
 506       // Swap to find the invariant part
 507       add_invar = add_var;
 508       add_invar_ctrl = add_var_ctrl;
 509       add_invar_loop = add_var_loop;
 510       add_var = add->in(2);
 511     } else if (add_var_loop != n_loop) { // Else neither input is loop invariant
 512       return nullptr;
 513     }
 514     if (n_loop == add_invar_loop || !add_invar_loop->is_member(n_loop)) {
 515       return nullptr;              // No invariant part of the add?
 516     }
 517 
 518     // Yes!  Reshape address expression!
 519     Node* inv_scale = LShiftNode::make(add_invar, scale, bt);
 520     Node* inv_scale_ctrl =
 521             dom_depth(add_invar_ctrl) > dom_depth(scale_ctrl) ?
 522             add_invar_ctrl : scale_ctrl;
 523     register_new_node(inv_scale, inv_scale_ctrl);
 524     Node* var_scale = LShiftNode::make(add_var, scale, bt);
 525     register_new_node(var_scale, n_ctrl);
 526     Node* var_add = AddNode::make(var_scale, inv_scale, bt);
 527     register_new_node(var_add, n_ctrl);
 528     _igvn.replace_node(n, var_add);
 529     return var_add;
 530   }
 531   return nullptr;
 532 }
 533 
 534 //------------------------------remix_address_expressions----------------------
 535 // Rework addressing expressions to get the most loop-invariant stuff
 536 // moved out.  We'd like to do all associative operators, but it's especially
 537 // important (common) to do address expressions.
 538 Node* PhaseIdealLoop::remix_address_expressions(Node* n) {
 539   if (!has_ctrl(n))  return nullptr;
 540   Node* n_ctrl = get_ctrl(n);
 541   IdealLoopTree* n_loop = get_loop(n_ctrl);
 542 
 543   // See if 'n' mixes loop-varying and loop-invariant inputs and
 544   // itself is loop-varying.
 545 
 546   // Only interested in binary ops (and AddP)
 547   if (n->req() < 3 || n->req() > 4) return nullptr;
 548 
 549   Node* n1_ctrl = get_ctrl(n->in(                    1));
 550   Node* n2_ctrl = get_ctrl(n->in(                    2));
 551   Node* n3_ctrl = get_ctrl(n->in(n->req() == 3 ? 2 : 3));
 552   IdealLoopTree* n1_loop = get_loop(n1_ctrl);
 553   IdealLoopTree* n2_loop = get_loop(n2_ctrl);
 554   IdealLoopTree* n3_loop = get_loop(n3_ctrl);
 555 
 556   // Does one of my inputs spin in a tighter loop than self?
 557   if ((n_loop->is_member(n1_loop) && n_loop != n1_loop) ||
 558       (n_loop->is_member(n2_loop) && n_loop != n2_loop) ||
 559       (n_loop->is_member(n3_loop) && n_loop != n3_loop)) {
 560     return nullptr;                // Leave well enough alone
 561   }
 562 
 563   // Is at least one of my inputs loop-invariant?
 564   if (n1_loop == n_loop &&
 565       n2_loop == n_loop &&
 566       n3_loop == n_loop) {
 567     return nullptr;                // No loop-invariant inputs
 568   }
 569 
 570   Node* res = remix_address_expressions_add_left_shift(n, n_loop, n_ctrl, T_INT);
 571   if (res != nullptr) {
 572     return res;
 573   }
 574   res = remix_address_expressions_add_left_shift(n, n_loop, n_ctrl, T_LONG);
 575   if (res != nullptr) {
 576     return res;
 577   }
 578 
 579   int n_op = n->Opcode();
 580   // Replace (I+V) with (V+I)
 581   if (n_op == Op_AddI ||
 582       n_op == Op_AddL ||
 583       n_op == Op_AddF ||
 584       n_op == Op_AddD ||
 585       n_op == Op_MulI ||
 586       n_op == Op_MulL ||
 587       n_op == Op_MulF ||
 588       n_op == Op_MulD) {
 589     if (n2_loop == n_loop) {
 590       assert(n1_loop != n_loop, "");
 591       n->swap_edges(1, 2);
 592     }
 593   }
 594 
 595   // Replace ((I1 +p V) +p I2) with ((I1 +p I2) +p V),
 596   // but not if I2 is a constant. Skip for irreducible loops.
 597   if (n_op == Op_AddP && n_loop->_head->is_Loop()) {
 598     if (n2_loop == n_loop && n3_loop != n_loop) {
 599       if (n->in(2)->Opcode() == Op_AddP && !n->in(3)->is_Con()) {
 600         Node* n22_ctrl = get_ctrl(n->in(2)->in(2));
 601         Node* n23_ctrl = get_ctrl(n->in(2)->in(3));
 602         IdealLoopTree* n22loop = get_loop(n22_ctrl);
 603         IdealLoopTree* n23_loop = get_loop(n23_ctrl);
 604         if (n22loop != n_loop && n22loop->is_member(n_loop) &&
 605             n23_loop == n_loop) {
 606           Node* add1 = new AddPNode(n->in(1), n->in(2)->in(2), n->in(3));
 607           // Stuff new AddP in the loop preheader
 608           register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
 609           Node* add2 = new AddPNode(n->in(1), add1, n->in(2)->in(3));
 610           register_new_node(add2, n_ctrl);
 611           _igvn.replace_node(n, add2);
 612           return add2;
 613         }
 614       }
 615     }
 616 
 617     // Replace (I1 +p (I2 + V)) with ((I1 +p I2) +p V)
 618     if (n2_loop != n_loop && n3_loop == n_loop) {
 619       if (n->in(3)->Opcode() == Op_AddX) {
 620         Node* V = n->in(3)->in(1);
 621         Node* I = n->in(3)->in(2);
 622         if (is_member(n_loop,get_ctrl(V))) {
 623         } else {
 624           Node *tmp = V; V = I; I = tmp;
 625         }
 626         if (!is_member(n_loop,get_ctrl(I))) {
 627           Node* add1 = new AddPNode(n->in(1), n->in(2), I);
 628           // Stuff new AddP in the loop preheader
 629           register_new_node(add1, n_loop->_head->as_Loop()->skip_strip_mined(1)->in(LoopNode::EntryControl));
 630           Node* add2 = new AddPNode(n->in(1), add1, V);
 631           register_new_node(add2, n_ctrl);
 632           _igvn.replace_node(n, add2);
 633           return add2;
 634         }
 635       }
 636     }
 637   }
 638 
 639   return nullptr;
 640 }
 641 
 642 // Optimize ((in1[2*i] * in2[2*i]) + (in1[2*i+1] * in2[2*i+1]))
 643 Node *PhaseIdealLoop::convert_add_to_muladd(Node* n) {
 644   assert(n->Opcode() == Op_AddI, "sanity");
 645   Node * nn = nullptr;
 646   Node * in1 = n->in(1);
 647   Node * in2 = n->in(2);
 648   if (in1->Opcode() == Op_MulI && in2->Opcode() == Op_MulI) {
 649     IdealLoopTree* loop_n = get_loop(get_ctrl(n));
 650     if (loop_n->is_counted() &&
 651         loop_n->_head->as_Loop()->is_valid_counted_loop(T_INT) &&
 652         Matcher::match_rule_supported(Op_MulAddVS2VI) &&
 653         Matcher::match_rule_supported(Op_MulAddS2I)) {
 654       Node* mul_in1 = in1->in(1);
 655       Node* mul_in2 = in1->in(2);
 656       Node* mul_in3 = in2->in(1);
 657       Node* mul_in4 = in2->in(2);
 658       if (mul_in1->Opcode() == Op_LoadS &&
 659           mul_in2->Opcode() == Op_LoadS &&
 660           mul_in3->Opcode() == Op_LoadS &&
 661           mul_in4->Opcode() == Op_LoadS) {
 662         IdealLoopTree* loop1 = get_loop(get_ctrl(mul_in1));
 663         IdealLoopTree* loop2 = get_loop(get_ctrl(mul_in2));
 664         IdealLoopTree* loop3 = get_loop(get_ctrl(mul_in3));
 665         IdealLoopTree* loop4 = get_loop(get_ctrl(mul_in4));
 666         IdealLoopTree* loop5 = get_loop(get_ctrl(in1));
 667         IdealLoopTree* loop6 = get_loop(get_ctrl(in2));
 668         // All nodes should be in the same counted loop.
 669         if (loop_n == loop1 && loop_n == loop2 && loop_n == loop3 &&
 670             loop_n == loop4 && loop_n == loop5 && loop_n == loop6) {
 671           Node* adr1 = mul_in1->in(MemNode::Address);
 672           Node* adr2 = mul_in2->in(MemNode::Address);
 673           Node* adr3 = mul_in3->in(MemNode::Address);
 674           Node* adr4 = mul_in4->in(MemNode::Address);
 675           if (adr1->is_AddP() && adr2->is_AddP() && adr3->is_AddP() && adr4->is_AddP()) {
 676             if ((adr1->in(AddPNode::Base) == adr3->in(AddPNode::Base)) &&
 677                 (adr2->in(AddPNode::Base) == adr4->in(AddPNode::Base))) {
 678               nn = new MulAddS2INode(mul_in1, mul_in2, mul_in3, mul_in4);
 679               register_new_node_with_ctrl_of(nn, n);
 680               _igvn.replace_node(n, nn);
 681               return nn;
 682             } else if ((adr1->in(AddPNode::Base) == adr4->in(AddPNode::Base)) &&
 683                        (adr2->in(AddPNode::Base) == adr3->in(AddPNode::Base))) {
 684               nn = new MulAddS2INode(mul_in1, mul_in2, mul_in4, mul_in3);
 685               register_new_node_with_ctrl_of(nn, n);
 686               _igvn.replace_node(n, nn);
 687               return nn;
 688             }
 689           }
 690         }
 691       }
 692     }
 693   }
 694   return nn;
 695 }
 696 
 697 //------------------------------conditional_move-------------------------------
 698 // Attempt to replace a Phi with a conditional move.  We have some pretty
 699 // strict profitability requirements.  All Phis at the merge point must
 700 // be converted, so we can remove the control flow.  We need to limit the
 701 // number of c-moves to a small handful.  All code that was in the side-arms
 702 // of the CFG diamond is now speculatively executed.  This code has to be
 703 // "cheap enough".  We are pretty much limited to CFG diamonds that merge
 704 // 1 or 2 items with a total of 1 or 2 ops executed speculatively.
 705 Node *PhaseIdealLoop::conditional_move( Node *region ) {
 706 
 707   assert(region->is_Region(), "sanity check");
 708   if (region->req() != 3) return nullptr;
 709 
 710   // Check for CFG diamond
 711   Node *lp = region->in(1);
 712   Node *rp = region->in(2);
 713   if (!lp || !rp) return nullptr;
 714   Node *lp_c = lp->in(0);
 715   if (lp_c == nullptr || lp_c != rp->in(0) || !lp_c->is_If()) return nullptr;
 716   IfNode *iff = lp_c->as_If();
 717 
 718   // Check for ops pinned in an arm of the diamond.
 719   // Can't remove the control flow in this case
 720   if (lp->outcnt() > 1) return nullptr;
 721   if (rp->outcnt() > 1) return nullptr;
 722 
 723   IdealLoopTree* r_loop = get_loop(region);
 724   assert(r_loop == get_loop(iff), "sanity");
 725   // Always convert to CMOVE if all results are used only outside this loop.
 726   bool used_inside_loop = (r_loop == _ltree_root);
 727 
 728   // Check profitability
 729   int cost = 0;
 730   int phis = 0;
 731   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 732     Node *out = region->fast_out(i);
 733     if (!out->is_Phi()) continue; // Ignore other control edges, etc
 734     phis++;
 735     PhiNode* phi = out->as_Phi();
 736     BasicType bt = phi->type()->basic_type();
 737     switch (bt) {
 738     case T_DOUBLE:
 739     case T_FLOAT:
 740       if (C->use_cmove()) {
 741         continue; //TODO: maybe we want to add some cost
 742       }
 743       cost += Matcher::float_cmove_cost(); // Could be very expensive
 744       break;
 745     case T_LONG: {
 746       cost += Matcher::long_cmove_cost(); // May encodes as 2 CMOV's
 747     }
 748     case T_INT:                 // These all CMOV fine
 749     case T_ADDRESS: {           // (RawPtr)
 750       cost++;
 751       break;
 752     }
 753     case T_NARROWOOP: // Fall through
 754     case T_OBJECT: {            // Base oops are OK, but not derived oops
 755       const TypeOopPtr *tp = phi->type()->make_ptr()->isa_oopptr();
 756       // Derived pointers are Bad (tm): what's the Base (for GC purposes) of a
 757       // CMOVE'd derived pointer?  It's a CMOVE'd derived base.  Thus
 758       // CMOVE'ing a derived pointer requires we also CMOVE the base.  If we
 759       // have a Phi for the base here that we convert to a CMOVE all is well
 760       // and good.  But if the base is dead, we'll not make a CMOVE.  Later
 761       // the allocator will have to produce a base by creating a CMOVE of the
 762       // relevant bases.  This puts the allocator in the business of
 763       // manufacturing expensive instructions, generally a bad plan.
 764       // Just Say No to Conditionally-Moved Derived Pointers.
 765       if (tp && tp->offset() != 0)
 766         return nullptr;
 767       cost++;
 768       break;
 769     }
 770     default:
 771       return nullptr;              // In particular, can't do memory or I/O
 772     }
 773     // Add in cost any speculative ops
 774     for (uint j = 1; j < region->req(); j++) {
 775       Node *proj = region->in(j);
 776       Node *inp = phi->in(j);
 777       if (inp->isa_InlineType()) {
 778         // TODO 8302217 This prevents PhiNode::push_inline_types_through
 779         return nullptr;
 780       }
 781       if (get_ctrl(inp) == proj) { // Found local op
 782         cost++;
 783         // Check for a chain of dependent ops; these will all become
 784         // speculative in a CMOV.
 785         for (uint k = 1; k < inp->req(); k++)
 786           if (get_ctrl(inp->in(k)) == proj)
 787             cost += ConditionalMoveLimit; // Too much speculative goo
 788       }
 789     }
 790     // See if the Phi is used by a Cmp or Narrow oop Decode/Encode.
 791     // This will likely Split-If, a higher-payoff operation.
 792     for (DUIterator_Fast kmax, k = phi->fast_outs(kmax); k < kmax; k++) {
 793       Node* use = phi->fast_out(k);
 794       if (use->is_Cmp() || use->is_DecodeNarrowPtr() || use->is_EncodeNarrowPtr())
 795         cost += ConditionalMoveLimit;
 796       // Is there a use inside the loop?
 797       // Note: check only basic types since CMoveP is pinned.
 798       if (!used_inside_loop && is_java_primitive(bt)) {
 799         IdealLoopTree* u_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use);
 800         if (r_loop == u_loop || r_loop->is_member(u_loop)) {
 801           used_inside_loop = true;
 802         }
 803       }
 804     }
 805   }//for
 806   Node* bol = iff->in(1);
 807   assert(!bol->is_OpaqueInitializedAssertionPredicate(), "Initialized Assertion Predicates cannot form a diamond with Halt");
 808   if (bol->is_OpaqueTemplateAssertionPredicate()) {
 809     // Ignore Template Assertion Predicates with OpaqueTemplateAssertionPredicate nodes.
 810     return nullptr;
 811   }
 812   if (bol->is_OpaqueMultiversioning()) {
 813     assert(bol->as_OpaqueMultiversioning()->is_useless(), "Must be useless, i.e. fast main loop has already disappeared.");
 814     // Ignore multiversion_if that just lost its loops. The OpaqueMultiversioning is marked useless,
 815     // and will make the multiversion_if constant fold in the next IGVN round.
 816     return nullptr;
 817   }
 818   if (!bol->is_Bool()) {
 819     assert(false, "Expected Bool, but got %s", NodeClassNames[bol->Opcode()]);
 820     return nullptr;
 821   }
 822   int cmp_op = bol->in(1)->Opcode();
 823   if (cmp_op == Op_SubTypeCheck) { // SubTypeCheck expansion expects an IfNode
 824     return nullptr;
 825   }
 826   // It is expensive to generate flags from a float compare.
 827   // Avoid duplicated float compare.
 828   if (phis > 1 && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) return nullptr;
 829 
 830   float infrequent_prob = PROB_UNLIKELY_MAG(3);
 831   // Ignore cost and blocks frequency if CMOVE can be moved outside the loop.
 832   if (used_inside_loop) {
 833     if (cost >= ConditionalMoveLimit) return nullptr; // Too much goo
 834 
 835     // BlockLayoutByFrequency optimization moves infrequent branch
 836     // from hot path. No point in CMOV'ing in such case (110 is used
 837     // instead of 100 to take into account not exactness of float value).
 838     if (BlockLayoutByFrequency) {
 839       infrequent_prob = MAX2(infrequent_prob, (float)BlockLayoutMinDiamondPercentage/110.0f);
 840     }
 841   }
 842   // Check for highly predictable branch.  No point in CMOV'ing if
 843   // we are going to predict accurately all the time.
 844   if (C->use_cmove() && (cmp_op == Op_CmpF || cmp_op == Op_CmpD)) {
 845     //keep going
 846   } else if (iff->_prob < infrequent_prob ||
 847       iff->_prob > (1.0f - infrequent_prob))
 848     return nullptr;
 849 
 850   // --------------
 851   // Now replace all Phis with CMOV's
 852   Node *cmov_ctrl = iff->in(0);
 853   uint flip = (lp->Opcode() == Op_IfTrue);
 854   Node_List wq;
 855   while (1) {
 856     PhiNode* phi = nullptr;
 857     for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
 858       Node *out = region->fast_out(i);
 859       if (out->is_Phi()) {
 860         phi = out->as_Phi();
 861         break;
 862       }
 863     }
 864     if (phi == nullptr || _igvn.type(phi) == Type::TOP || !CMoveNode::supported(_igvn.type(phi))) {
 865       break;
 866     }
 867     // Move speculative ops
 868     wq.push(phi);
 869     while (wq.size() > 0) {
 870       Node *n = wq.pop();
 871       for (uint j = 1; j < n->req(); j++) {
 872         Node* m = n->in(j);
 873         if (m != nullptr && !is_dominator(get_ctrl(m), cmov_ctrl)) {
 874           set_ctrl(m, cmov_ctrl);
 875           wq.push(m);
 876         }
 877       }
 878     }
 879     Node* cmov = CMoveNode::make(iff->in(1), phi->in(1+flip), phi->in(2-flip), _igvn.type(phi));
 880     register_new_node(cmov, cmov_ctrl);
 881     _igvn.replace_node(phi, cmov);
 882 #ifndef PRODUCT
 883     if (TraceLoopOpts) {
 884       tty->print("CMOV  ");
 885       r_loop->dump_head();
 886       if (Verbose) {
 887         bol->in(1)->dump(1);
 888         cmov->dump(1);
 889       }
 890     }
 891     DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
 892 #endif
 893   }
 894 
 895   // The useless CFG diamond will fold up later; see the optimization in
 896   // RegionNode::Ideal.
 897   _igvn._worklist.push(region);
 898 
 899   return iff->in(1);
 900 }
 901 
 902 static void enqueue_cfg_uses(Node* m, Unique_Node_List& wq) {
 903   for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax; i++) {
 904     Node* u = m->fast_out(i);
 905     if (u->is_CFG()) {
 906       if (u->is_NeverBranch()) {
 907         u = u->as_NeverBranch()->proj_out(0);
 908         enqueue_cfg_uses(u, wq);
 909       } else {
 910         wq.push(u);
 911       }
 912     }
 913   }
 914 }
 915 
 916 // Try moving a store out of a loop, right before the loop
 917 Node* PhaseIdealLoop::try_move_store_before_loop(Node* n, Node *n_ctrl) {
 918   // Store has to be first in the loop body
 919   IdealLoopTree *n_loop = get_loop(n_ctrl);
 920   if (n->is_Store() && n_loop != _ltree_root &&
 921       n_loop->is_loop() && n_loop->_head->is_Loop() &&
 922       n->in(0) != nullptr) {
 923     Node* address = n->in(MemNode::Address);
 924     Node* value = n->in(MemNode::ValueIn);
 925     Node* mem = n->in(MemNode::Memory);
 926     IdealLoopTree* address_loop = get_loop(get_ctrl(address));
 927     IdealLoopTree* value_loop = get_loop(get_ctrl(value));
 928 
 929     // - address and value must be loop invariant
 930     // - memory must be a memory Phi for the loop
 931     // - Store must be the only store on this memory slice in the
 932     // loop: if there's another store following this one then value
 933     // written at iteration i by the second store could be overwritten
 934     // at iteration i+n by the first store: it's not safe to move the
 935     // first store out of the loop
 936     // - nothing must observe the memory Phi: it guarantees no read
 937     // before the store, we are also guaranteed the store post
 938     // dominates the loop head (ignoring a possible early
 939     // exit). Otherwise there would be extra Phi involved between the
 940     // loop's Phi and the store.
 941     // - there must be no early exit from the loop before the Store
 942     // (such an exit most of the time would be an extra use of the
 943     // memory Phi but sometimes is a bottom memory Phi that takes the
 944     // store as input).
 945 
 946     if (!n_loop->is_member(address_loop) &&
 947         !n_loop->is_member(value_loop) &&
 948         mem->is_Phi() && mem->in(0) == n_loop->_head &&
 949         mem->outcnt() == 1 &&
 950         mem->in(LoopNode::LoopBackControl) == n) {
 951 
 952       assert(n_loop->_tail != nullptr, "need a tail");
 953       assert(is_dominator(n_ctrl, n_loop->_tail), "store control must not be in a branch in the loop");
 954 
 955       // Verify that there's no early exit of the loop before the store.
 956       bool ctrl_ok = false;
 957       {
 958         // Follow control from loop head until n, we exit the loop or
 959         // we reach the tail
 960         ResourceMark rm;
 961         Unique_Node_List wq;
 962         wq.push(n_loop->_head);
 963 
 964         for (uint next = 0; next < wq.size(); ++next) {
 965           Node *m = wq.at(next);
 966           if (m == n->in(0)) {
 967             ctrl_ok = true;
 968             continue;
 969           }
 970           assert(!has_ctrl(m), "should be CFG");
 971           if (!n_loop->is_member(get_loop(m)) || m == n_loop->_tail) {
 972             ctrl_ok = false;
 973             break;
 974           }
 975           enqueue_cfg_uses(m, wq);
 976           if (wq.size() > 10) {
 977             ctrl_ok = false;
 978             break;
 979           }
 980         }
 981       }
 982       if (ctrl_ok) {
 983         // move the Store
 984         _igvn.replace_input_of(mem, LoopNode::LoopBackControl, mem);
 985         _igvn.replace_input_of(n, 0, n_loop->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl));
 986         _igvn.replace_input_of(n, MemNode::Memory, mem->in(LoopNode::EntryControl));
 987         // Disconnect the phi now. An empty phi can confuse other
 988         // optimizations in this pass of loop opts.
 989         _igvn.replace_node(mem, mem->in(LoopNode::EntryControl));
 990         n_loop->_body.yank(mem);
 991 
 992         set_ctrl_and_loop(n, n->in(0));
 993 
 994         return n;
 995       }
 996     }
 997   }
 998   return nullptr;
 999 }
1000 
1001 // Try moving a store out of a loop, right after the loop
1002 void PhaseIdealLoop::try_move_store_after_loop(Node* n) {
1003   if (n->is_Store() && n->in(0) != nullptr) {
1004     Node *n_ctrl = get_ctrl(n);
1005     IdealLoopTree *n_loop = get_loop(n_ctrl);
1006     // Store must be in a loop
1007     if (n_loop != _ltree_root && !n_loop->_irreducible) {
1008       Node* address = n->in(MemNode::Address);
1009       Node* value = n->in(MemNode::ValueIn);
1010       IdealLoopTree* address_loop = get_loop(get_ctrl(address));
1011       // address must be loop invariant
1012       if (!n_loop->is_member(address_loop)) {
1013         // Store must be last on this memory slice in the loop and
1014         // nothing in the loop must observe it
1015         Node* phi = nullptr;
1016         for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1017           Node* u = n->fast_out(i);
1018           if (has_ctrl(u)) { // control use?
1019             IdealLoopTree *u_loop = get_loop(get_ctrl(u));
1020             if (!n_loop->is_member(u_loop)) {
1021               continue;
1022             }
1023             if (u->is_Phi() && u->in(0) == n_loop->_head) {
1024               assert(_igvn.type(u) == Type::MEMORY, "bad phi");
1025               // multiple phis on the same slice are possible
1026               if (phi != nullptr) {
1027                 return;
1028               }
1029               phi = u;
1030               continue;
1031             }
1032           }
1033           return;
1034         }
1035         if (phi != nullptr) {
1036           // Nothing in the loop before the store (next iteration)
1037           // must observe the stored value
1038           bool mem_ok = true;
1039           {
1040             ResourceMark rm;
1041             Unique_Node_List wq;
1042             wq.push(phi);
1043             for (uint next = 0; next < wq.size() && mem_ok; ++next) {
1044               Node *m = wq.at(next);
1045               for (DUIterator_Fast imax, i = m->fast_outs(imax); i < imax && mem_ok; i++) {
1046                 Node* u = m->fast_out(i);
1047                 if (u->is_Store() || u->is_Phi()) {
1048                   if (u != n) {
1049                     wq.push(u);
1050                     mem_ok = (wq.size() <= 10);
1051                   }
1052                 } else {
1053                   mem_ok = false;
1054                   break;
1055                 }
1056               }
1057             }
1058           }
1059           if (mem_ok) {
1060             // Move the store out of the loop if the LCA of all
1061             // users (except for the phi) is outside the loop.
1062             Node* hook = new Node(1);
1063             hook->init_req(0, n_ctrl); // Add an input to prevent hook from being dead
1064             _igvn.rehash_node_delayed(phi);
1065             int count = phi->replace_edge(n, hook, &_igvn);
1066             assert(count > 0, "inconsistent phi");
1067 
1068             // Compute latest point this store can go
1069             Node* lca = get_late_ctrl(n, get_ctrl(n));
1070             if (lca->is_OuterStripMinedLoop()) {
1071               lca = lca->in(LoopNode::EntryControl);
1072             }
1073             if (n_loop->is_member(get_loop(lca))) {
1074               // LCA is in the loop - bail out
1075               _igvn.replace_node(hook, n);
1076               return;
1077             }
1078 #ifdef ASSERT
1079             if (n_loop->_head->is_Loop() && n_loop->_head->as_Loop()->is_strip_mined()) {
1080               assert(n_loop->_head->Opcode() == Op_CountedLoop, "outer loop is a strip mined");
1081               n_loop->_head->as_Loop()->verify_strip_mined(1);
1082               Node* outer = n_loop->_head->as_CountedLoop()->outer_loop();
1083               IdealLoopTree* outer_loop = get_loop(outer);
1084               assert(n_loop->_parent == outer_loop, "broken loop tree");
1085               assert(get_loop(lca) == outer_loop, "safepoint in outer loop consume all memory state");
1086             }
1087 #endif
1088             lca = place_outside_loop(lca, n_loop);
1089             assert(!n_loop->is_member(get_loop(lca)), "control must not be back in the loop");
1090             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");
1091 
1092             // Move store out of the loop
1093             _igvn.replace_node(hook, n->in(MemNode::Memory));
1094             _igvn.replace_input_of(n, 0, lca);
1095             set_ctrl_and_loop(n, lca);
1096 
1097             // Disconnect the phi now. An empty phi can confuse other
1098             // optimizations in this pass of loop opts..
1099             if (phi->in(LoopNode::LoopBackControl) == phi) {
1100               _igvn.replace_node(phi, phi->in(LoopNode::EntryControl));
1101               n_loop->_body.yank(phi);
1102             }
1103           }
1104         }
1105       }
1106     }
1107   }
1108 }
1109 
1110 // We can't use immutable memory for the flat array check because we are loading the mark word which is
1111 // mutable. Although the bits we are interested in are immutable (we check for markWord::unlocked_value),
1112 // we need to use raw memory to not break anti dependency analysis. Below code will attempt to still move
1113 // flat array checks out of loops, mainly to enable loop unswitching.
1114 void PhaseIdealLoop::move_flat_array_check_out_of_loop(Node* n) {
1115   // Skip checks for more than one array
1116   if (n->req() > 3) {
1117     return;
1118   }
1119   Node* mem = n->in(FlatArrayCheckNode::Memory);
1120   Node* array = n->in(FlatArrayCheckNode::ArrayOrKlass)->uncast();
1121   IdealLoopTree* check_loop = get_loop(get_ctrl(n));
1122   IdealLoopTree* ary_loop = get_loop(get_ctrl(array));
1123 
1124   // Check if array is loop invariant
1125   if (!check_loop->is_member(ary_loop)) {
1126     // Walk up memory graph from the check until we leave the loop
1127     VectorSet wq;
1128     wq.set(mem->_idx);
1129     while (check_loop->is_member(get_loop(ctrl_or_self(mem)))) {
1130       if (mem->is_Phi()) {
1131         mem = mem->in(1);
1132       } else if (mem->is_MergeMem()) {
1133         mem = mem->as_MergeMem()->memory_at(Compile::AliasIdxRaw);
1134       } else if (mem->is_Proj()) {
1135         mem = mem->in(0);
1136       } else if (mem->is_MemBar() || mem->is_SafePoint()) {
1137         mem = mem->in(TypeFunc::Memory);
1138       } else if (mem->is_Store() || mem->is_LoadStore() || mem->is_ClearArray()) {
1139         mem = mem->in(MemNode::Memory);
1140       } else {
1141 #ifdef ASSERT
1142         mem->dump();
1143 #endif
1144         ShouldNotReachHere();
1145       }
1146       if (wq.test_set(mem->_idx)) {
1147         return;
1148       }
1149     }
1150     // Replace memory input and re-compute ctrl to move the check out of the loop
1151     _igvn.replace_input_of(n, 1, mem);
1152     set_ctrl_and_loop(n, get_early_ctrl(n));
1153     Node* bol = n->unique_out();
1154     set_ctrl_and_loop(bol, get_early_ctrl(bol));
1155   }
1156 }
1157 
1158 //------------------------------split_if_with_blocks_pre-----------------------
1159 // Do the real work in a non-recursive function.  Data nodes want to be
1160 // cloned in the pre-order so they can feed each other nicely.
1161 Node *PhaseIdealLoop::split_if_with_blocks_pre( Node *n ) {
1162   // Cloning these guys is unlikely to win
1163   int n_op = n->Opcode();
1164   if (n_op == Op_MergeMem) {
1165     return n;
1166   }
1167   if (n->is_Proj()) {
1168     return n;
1169   }
1170 
1171   if (n->isa_FlatArrayCheck()) {
1172     move_flat_array_check_out_of_loop(n);
1173     return n;
1174   }
1175 
1176   // Do not clone-up CmpFXXX variations, as these are always
1177   // followed by a CmpI
1178   if (n->is_Cmp()) {
1179     return n;
1180   }
1181   // Attempt to use a conditional move instead of a phi/branch
1182   if (ConditionalMoveLimit > 0 && n_op == Op_Region) {
1183     Node *cmov = conditional_move( n );
1184     if (cmov) {
1185       return cmov;
1186     }
1187   }
1188   if (n->is_CFG() || n->is_LoadStore()) {
1189     return n;
1190   }
1191   if (n->is_Opaque1()) { // Opaque nodes cannot be mod'd
1192     if (!C->major_progress()) {   // If chance of no more loop opts...
1193       _igvn._worklist.push(n);  // maybe we'll remove them
1194     }
1195     return n;
1196   }
1197 
1198   if (n->is_Con()) {
1199     return n;   // No cloning for Con nodes
1200   }
1201 
1202   Node *n_ctrl = get_ctrl(n);
1203   if (!n_ctrl) {
1204     return n;       // Dead node
1205   }
1206 
1207   Node* res = try_move_store_before_loop(n, n_ctrl);
1208   if (res != nullptr) {
1209     return n;
1210   }
1211 
1212   // Attempt to remix address expressions for loop invariants
1213   Node *m = remix_address_expressions( n );
1214   if( m ) return m;
1215 
1216   if (n_op == Op_AddI) {
1217     Node *nn = convert_add_to_muladd( n );
1218     if ( nn ) return nn;
1219   }
1220 
1221   if (n->is_ConstraintCast()) {
1222     Node* dom_cast = n->as_ConstraintCast()->dominating_cast(&_igvn, this);
1223     // ConstraintCastNode::dominating_cast() uses node control input to determine domination.
1224     // Node control inputs don't necessarily agree with loop control info (due to
1225     // transformations happened in between), thus additional dominance check is needed
1226     // to keep loop info valid.
1227     if (dom_cast != nullptr && is_dominator(get_ctrl(dom_cast), get_ctrl(n))) {
1228       _igvn.replace_node(n, dom_cast);
1229       return dom_cast;
1230     }
1231   }
1232 
1233   // Determine if the Node has inputs from some local Phi.
1234   // Returns the block to clone thru.
1235   Node *n_blk = has_local_phi_input( n );
1236   if( !n_blk ) return n;
1237 
1238   // Do not clone the trip counter through on a CountedLoop
1239   // (messes up the canonical shape).
1240   if (((n_blk->is_CountedLoop() || (n_blk->is_Loop() && n_blk->as_Loop()->is_loop_nest_inner_loop())) && n->Opcode() == Op_AddI) ||
1241       (n_blk->is_LongCountedLoop() && n->Opcode() == Op_AddL)) {
1242     return n;
1243   }
1244   // Pushing a shift through the iv Phi can get in the way of addressing optimizations or range check elimination
1245   if (n_blk->is_BaseCountedLoop() && n->Opcode() == Op_LShift(n_blk->as_BaseCountedLoop()->bt()) &&
1246       n->in(1) == n_blk->as_BaseCountedLoop()->phi()) {
1247     return n;
1248   }
1249 
1250   // Check for having no control input; not pinned.  Allow
1251   // dominating control.
1252   if (n->in(0)) {
1253     Node *dom = idom(n_blk);
1254     if (dom_lca(n->in(0), dom) != n->in(0)) {
1255       return n;
1256     }
1257   }
1258   // Policy: when is it profitable.  You must get more wins than
1259   // policy before it is considered profitable.  Policy is usually 0,
1260   // so 1 win is considered profitable.  Big merges will require big
1261   // cloning, so get a larger policy.
1262   int policy = n_blk->req() >> 2;
1263 
1264   // If the loop is a candidate for range check elimination,
1265   // delay splitting through it's phi until a later loop optimization
1266   if (n_blk->is_BaseCountedLoop()) {
1267     IdealLoopTree *lp = get_loop(n_blk);
1268     if (lp && lp->_rce_candidate) {
1269       return n;
1270     }
1271   }
1272 
1273   if (must_throttle_split_if()) return n;
1274 
1275   // Split 'n' through the merge point if it is profitable
1276   Node *phi = split_thru_phi( n, n_blk, policy );
1277   if (!phi) return n;
1278 
1279   // Found a Phi to split thru!
1280   // Replace 'n' with the new phi
1281   _igvn.replace_node( n, phi );
1282   // Moved a load around the loop, 'en-registering' something.
1283   if (n_blk->is_Loop() && n->is_Load() &&
1284       !phi->in(LoopNode::LoopBackControl)->is_Load())
1285     C->set_major_progress();
1286 
1287   return phi;
1288 }
1289 
1290 static bool merge_point_too_heavy(Compile* C, Node* region) {
1291   // Bail out if the region and its phis have too many users.
1292   int weight = 0;
1293   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1294     weight += region->fast_out(i)->outcnt();
1295   }
1296   int nodes_left = C->max_node_limit() - C->live_nodes();
1297   if (weight * 8 > nodes_left) {
1298     if (PrintOpto) {
1299       tty->print_cr("*** Split-if bails out:  %d nodes, region weight %d", C->unique(), weight);
1300     }
1301     return true;
1302   } else {
1303     return false;
1304   }
1305 }
1306 
1307 static bool merge_point_safe(Node* region) {
1308   // 4799512: Stop split_if_with_blocks from splitting a block with a ConvI2LNode
1309   // having a PhiNode input. This sidesteps the dangerous case where the split
1310   // ConvI2LNode may become TOP if the input Value() does not
1311   // overlap the ConvI2L range, leaving a node which may not dominate its
1312   // uses.
1313   // A better fix for this problem can be found in the BugTraq entry, but
1314   // expediency for Mantis demands this hack.
1315 #ifdef _LP64
1316   for (DUIterator_Fast imax, i = region->fast_outs(imax); i < imax; i++) {
1317     Node* n = region->fast_out(i);
1318     if (n->is_Phi()) {
1319       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
1320         Node* m = n->fast_out(j);
1321         if (m->Opcode() == Op_ConvI2L)
1322           return false;
1323         if (m->is_CastII()) {
1324           return false;
1325         }
1326       }
1327     }
1328   }
1329 #endif
1330   return true;
1331 }
1332 
1333 
1334 //------------------------------place_outside_loop---------------------------------
1335 // Place some computation outside of this loop on the path to the use passed as argument
1336 Node* PhaseIdealLoop::place_outside_loop(Node* useblock, IdealLoopTree* loop) const {
1337   Node* head = loop->_head;
1338   assert(!loop->is_member(get_loop(useblock)), "must be outside loop");
1339   if (head->is_Loop() && head->as_Loop()->is_strip_mined()) {
1340     loop = loop->_parent;
1341     assert(loop->_head->is_OuterStripMinedLoop(), "malformed strip mined loop");
1342   }
1343 
1344   // Pick control right outside the loop
1345   for (;;) {
1346     Node* dom = idom(useblock);
1347     if (loop->is_member(get_loop(dom))) {
1348       break;
1349     }
1350     useblock = dom;
1351   }
1352   assert(find_non_split_ctrl(useblock) == useblock, "should be non split control");
1353   return useblock;
1354 }
1355 
1356 
1357 bool PhaseIdealLoop::identical_backtoback_ifs(Node *n) {
1358   if (!n->is_If() || n->is_BaseCountedLoopEnd()) {
1359     return false;
1360   }
1361   if (!n->in(0)->is_Region()) {
1362     return false;
1363   }
1364 
1365   Node* region = n->in(0);
1366   Node* dom = idom(region);
1367   if (!dom->is_If() ||  !n->as_If()->same_condition(dom, &_igvn)) {
1368     return false;
1369   }
1370   IfNode* dom_if = dom->as_If();
1371   Node* proj_true = dom_if->proj_out(1);
1372   Node* proj_false = dom_if->proj_out(0);
1373 
1374   for (uint i = 1; i < region->req(); i++) {
1375     if (is_dominator(proj_true, region->in(i))) {
1376       continue;
1377     }
1378     if (is_dominator(proj_false, region->in(i))) {
1379       continue;
1380     }
1381     return false;
1382   }
1383 
1384   return true;
1385 }
1386 
1387 
1388 bool PhaseIdealLoop::can_split_if(Node* n_ctrl) {
1389   if (must_throttle_split_if()) {
1390     return false;
1391   }
1392 
1393   // Do not do 'split-if' if irreducible loops are present.
1394   if (_has_irreducible_loops) {
1395     return false;
1396   }
1397 
1398   if (merge_point_too_heavy(C, n_ctrl)) {
1399     return false;
1400   }
1401 
1402   // Do not do 'split-if' if some paths are dead.  First do dead code
1403   // elimination and then see if its still profitable.
1404   for (uint i = 1; i < n_ctrl->req(); i++) {
1405     if (n_ctrl->in(i) == C->top()) {
1406       return false;
1407     }
1408   }
1409 
1410   // If trying to do a 'Split-If' at the loop head, it is only
1411   // profitable if the cmp folds up on BOTH paths.  Otherwise we
1412   // risk peeling a loop forever.
1413 
1414   // CNC - Disabled for now.  Requires careful handling of loop
1415   // body selection for the cloned code.  Also, make sure we check
1416   // for any input path not being in the same loop as n_ctrl.  For
1417   // irreducible loops we cannot check for 'n_ctrl->is_Loop()'
1418   // because the alternative loop entry points won't be converted
1419   // into LoopNodes.
1420   IdealLoopTree *n_loop = get_loop(n_ctrl);
1421   for (uint j = 1; j < n_ctrl->req(); j++) {
1422     if (get_loop(n_ctrl->in(j)) != n_loop) {
1423       return false;
1424     }
1425   }
1426 
1427   // Check for safety of the merge point.
1428   if (!merge_point_safe(n_ctrl)) {
1429     return false;
1430   }
1431 
1432   return true;
1433 }
1434 
1435 // Detect if the node is the inner strip-mined loop
1436 // Return: null if it's not the case, or the exit of outer strip-mined loop
1437 static Node* is_inner_of_stripmined_loop(const Node* out) {
1438   Node* out_le = nullptr;
1439 
1440   if (out->is_CountedLoopEnd()) {
1441       const CountedLoopNode* loop = out->as_CountedLoopEnd()->loopnode();
1442 
1443       if (loop != nullptr && loop->is_strip_mined()) {
1444         out_le = loop->in(LoopNode::EntryControl)->as_OuterStripMinedLoop()->outer_loop_exit();
1445       }
1446   }
1447 
1448   return out_le;
1449 }
1450 
1451 bool PhaseIdealLoop::flat_array_element_type_check(Node *n) {
1452   // If the CmpP is a subtype check for a value that has just been
1453   // loaded from an array, the subtype check guarantees the value
1454   // can't be stored in a flat array and the load of the value
1455   // happens with a flat array check then: push the type check
1456   // through the phi of the flat array check. This needs special
1457   // logic because the subtype check's input is not a phi but a
1458   // LoadKlass that must first be cloned through the phi.
1459   if (n->Opcode() != Op_CmpP) {
1460     return false;
1461   }
1462 
1463   Node* klassptr = n->in(1);
1464   Node* klasscon = n->in(2);
1465 
1466   if (klassptr->is_DecodeNarrowPtr()) {
1467     klassptr = klassptr->in(1);
1468   }
1469 
1470   if (klassptr->Opcode() != Op_LoadKlass && klassptr->Opcode() != Op_LoadNKlass) {
1471     return false;
1472   }
1473 
1474   if (!klasscon->is_Con()) {
1475     return false;
1476   }
1477 
1478   Node* addr = klassptr->in(MemNode::Address);
1479 
1480   if (!addr->is_AddP()) {
1481     return false;
1482   }
1483 
1484   intptr_t offset;
1485   Node* obj = AddPNode::Ideal_base_and_offset(addr, &_igvn, offset);
1486 
1487   if (obj == nullptr) {
1488     return false;
1489   }
1490 
1491   assert(obj != nullptr && addr->in(AddPNode::Base) == addr->in(AddPNode::Address), "malformed AddP?");
1492   if (obj->Opcode() == Op_CastPP) {
1493     obj = obj->in(1);
1494   }
1495 
1496   if (!obj->is_Phi()) {
1497     return false;
1498   }
1499 
1500   Node* region = obj->in(0);
1501 
1502   Node* phi = PhiNode::make_blank(region, n->in(1));
1503   for (uint i = 1; i < region->req(); i++) {
1504     Node* in = obj->in(i);
1505     Node* ctrl = region->in(i);
1506     if (addr->in(AddPNode::Base) != obj) {
1507       Node* cast = addr->in(AddPNode::Base);
1508       assert(cast->Opcode() == Op_CastPP && cast->in(0) != nullptr, "inconsistent subgraph");
1509       Node* cast_clone = cast->clone();
1510       cast_clone->set_req(0, ctrl);
1511       cast_clone->set_req(1, in);
1512       register_new_node(cast_clone, ctrl);
1513       const Type* tcast = cast_clone->Value(&_igvn);
1514       _igvn.set_type(cast_clone, tcast);
1515       cast_clone->as_Type()->set_type(tcast);
1516       in = cast_clone;
1517     }
1518     Node* addr_clone = addr->clone();
1519     addr_clone->set_req(AddPNode::Base, in);
1520     addr_clone->set_req(AddPNode::Address, in);
1521     register_new_node(addr_clone, ctrl);
1522     _igvn.set_type(addr_clone, addr_clone->Value(&_igvn));
1523     Node* klassptr_clone = klassptr->clone();
1524     klassptr_clone->set_req(2, addr_clone);
1525     register_new_node(klassptr_clone, ctrl);
1526     _igvn.set_type(klassptr_clone, klassptr_clone->Value(&_igvn));
1527     if (klassptr != n->in(1)) {
1528       Node* decode = n->in(1);
1529       assert(decode->is_DecodeNarrowPtr(), "inconsistent subgraph");
1530       Node* decode_clone = decode->clone();
1531       decode_clone->set_req(1, klassptr_clone);
1532       register_new_node(decode_clone, ctrl);
1533       _igvn.set_type(decode_clone, decode_clone->Value(&_igvn));
1534       klassptr_clone = decode_clone;
1535     }
1536     phi->set_req(i, klassptr_clone);
1537   }
1538   register_new_node(phi, region);
1539   Node* orig = n->in(1);
1540   _igvn.replace_input_of(n, 1, phi);
1541   split_if_with_blocks_post(n);
1542   if (n->outcnt() != 0) {
1543     _igvn.replace_input_of(n, 1, orig);
1544     _igvn.remove_dead_node(phi);
1545   }
1546   return true;
1547 }
1548 
1549 //------------------------------split_if_with_blocks_post----------------------
1550 // Do the real work in a non-recursive function.  CFG hackery wants to be
1551 // in the post-order, so it can dirty the I-DOM info and not use the dirtied
1552 // info.
1553 void PhaseIdealLoop::split_if_with_blocks_post(Node *n) {
1554 
1555   if (flat_array_element_type_check(n)) {
1556     return;
1557   }
1558 
1559   // Cloning Cmp through Phi's involves the split-if transform.
1560   // FastLock is not used by an If
1561   if (n->is_Cmp() && !n->is_FastLock()) {
1562     Node *n_ctrl = get_ctrl(n);
1563     // Determine if the Node has inputs from some local Phi.
1564     // Returns the block to clone thru.
1565     Node *n_blk = has_local_phi_input(n);
1566     if (n_blk != n_ctrl) {
1567       return;
1568     }
1569 
1570     if (!can_split_if(n_ctrl)) {
1571       return;
1572     }
1573 
1574     if (n->outcnt() != 1) {
1575       return; // Multiple bool's from 1 compare?
1576     }
1577     Node *bol = n->unique_out();
1578     assert(bol->is_Bool(), "expect a bool here");
1579     if (bol->outcnt() != 1) {
1580       return;// Multiple branches from 1 compare?
1581     }
1582     Node *iff = bol->unique_out();
1583 
1584     // Check some safety conditions
1585     if (iff->is_If()) {        // Classic split-if?
1586       if (iff->in(0) != n_ctrl) {
1587         return; // Compare must be in same blk as if
1588       }
1589     } else if (iff->is_CMove()) { // Trying to split-up a CMOVE
1590       // Can't split CMove with different control.
1591       if (get_ctrl(iff) != n_ctrl) {
1592         return;
1593       }
1594       if (get_ctrl(iff->in(2)) == n_ctrl ||
1595           get_ctrl(iff->in(3)) == n_ctrl) {
1596         return;                 // Inputs not yet split-up
1597       }
1598       if (get_loop(n_ctrl) != get_loop(get_ctrl(iff))) {
1599         return;                 // Loop-invar test gates loop-varying CMOVE
1600       }
1601     } else {
1602       return;  // some other kind of node, such as an Allocate
1603     }
1604 
1605     // When is split-if profitable?  Every 'win' on means some control flow
1606     // goes dead, so it's almost always a win.
1607     int policy = 0;
1608     // Split compare 'n' through the merge point if it is profitable
1609     Node *phi = split_thru_phi( n, n_ctrl, policy);
1610     if (!phi) {
1611       return;
1612     }
1613 
1614     // Found a Phi to split thru!
1615     // Replace 'n' with the new phi
1616     _igvn.replace_node(n, phi);
1617 
1618     // Now split the bool up thru the phi
1619     Node *bolphi = split_thru_phi(bol, n_ctrl, -1);
1620     guarantee(bolphi != nullptr, "null boolean phi node");
1621 
1622     _igvn.replace_node(bol, bolphi);
1623     assert(iff->in(1) == bolphi, "");
1624 
1625     if (bolphi->Value(&_igvn)->singleton()) {
1626       return;
1627     }
1628 
1629     // Conditional-move?  Must split up now
1630     if (!iff->is_If()) {
1631       Node *cmovphi = split_thru_phi(iff, n_ctrl, -1);
1632       _igvn.replace_node(iff, cmovphi);
1633       return;
1634     }
1635 
1636     // Now split the IF
1637     C->print_method(PHASE_BEFORE_SPLIT_IF, 4, iff);
1638     if (TraceLoopOpts) {
1639       tty->print_cr("Split-If");
1640     }
1641     do_split_if(iff);
1642     C->print_method(PHASE_AFTER_SPLIT_IF, 4, iff);
1643     return;
1644   }
1645 
1646   // Two identical ifs back to back can be merged
1647   if (try_merge_identical_ifs(n)) {
1648     return;
1649   }
1650 
1651   // Check for an IF ready to split; one that has its
1652   // condition codes input coming from a Phi at the block start.
1653   int n_op = n->Opcode();
1654 
1655   // Check for an IF being dominated by another IF same test
1656   if (n_op == Op_If ||
1657       n_op == Op_RangeCheck) {
1658     Node *bol = n->in(1);
1659     uint max = bol->outcnt();
1660     // Check for same test used more than once?
1661     if (bol->is_Bool() && (max > 1 || bol->in(1)->is_SubTypeCheck())) {
1662       // Search up IDOMs to see if this IF is dominated.
1663       Node* cmp = bol->in(1);
1664       Node *cutoff = cmp->is_SubTypeCheck() ? dom_lca(get_ctrl(cmp->in(1)), get_ctrl(cmp->in(2))) : get_ctrl(bol);
1665 
1666       // Now search up IDOMs till cutoff, looking for a dominating test
1667       Node *prevdom = n;
1668       Node *dom = idom(prevdom);
1669       while (dom != cutoff) {
1670         if (dom->req() > 1 && n->as_If()->same_condition(dom, &_igvn) && prevdom->in(0) == dom &&
1671             safe_for_if_replacement(dom)) {
1672           // It's invalid to move control dependent data nodes in the inner
1673           // strip-mined loop, because:
1674           //  1) break validation of LoopNode::verify_strip_mined()
1675           //  2) move code with side-effect in strip-mined loop
1676           // Move to the exit of outer strip-mined loop in that case.
1677           Node* out_le = is_inner_of_stripmined_loop(dom);
1678           if (out_le != nullptr) {
1679             prevdom = out_le;
1680           }
1681           // Replace the dominated test with an obvious true or false.
1682           // Place it on the IGVN worklist for later cleanup.
1683           C->set_major_progress();
1684           // Split if: pin array accesses that are control dependent on a range check and moved to a regular if,
1685           // to prevent an array load from floating above its range check. There are three cases:
1686           // 1. Move from RangeCheck "a" to RangeCheck "b": don't need to pin. If we ever remove b, then we pin
1687           //    all its array accesses at that point.
1688           // 2. We move from RangeCheck "a" to regular if "b": need to pin. If we ever remove b, then its array
1689           //    accesses would start to float, since we don't pin at that point.
1690           // 3. If we move from regular if: don't pin. All array accesses are already assumed to be pinned.
1691           bool pin_array_access_nodes =  n->Opcode() == Op_RangeCheck &&
1692                                          prevdom->in(0)->Opcode() != Op_RangeCheck;
1693           dominated_by(prevdom->as_IfProj(), n->as_If(), false, pin_array_access_nodes);
1694           DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
1695           return;
1696         }
1697         prevdom = dom;
1698         dom = idom(prevdom);
1699       }
1700     }
1701   }
1702 
1703   try_sink_out_of_loop(n);
1704   if (C->failing()) {
1705     return;
1706   }
1707 
1708   try_move_store_after_loop(n);
1709 
1710   // Remove multiple allocations of the same inline type
1711   if (n->is_InlineType()) {
1712     n->as_InlineType()->remove_redundant_allocations(this);
1713   }
1714 }
1715 
1716 // Transform:
1717 //
1718 // if (some_condition) {
1719 //   // body 1
1720 // } else {
1721 //   // body 2
1722 // }
1723 // if (some_condition) {
1724 //   // body 3
1725 // } else {
1726 //   // body 4
1727 // }
1728 //
1729 // into:
1730 //
1731 //
1732 // if (some_condition) {
1733 //   // body 1
1734 //   // body 3
1735 // } else {
1736 //   // body 2
1737 //   // body 4
1738 // }
1739 bool PhaseIdealLoop::try_merge_identical_ifs(Node* n) {
1740   if (identical_backtoback_ifs(n) && can_split_if(n->in(0))) {
1741     Node *n_ctrl = n->in(0);
1742     IfNode* dom_if = idom(n_ctrl)->as_If();
1743     if (n->in(1) != dom_if->in(1)) {
1744       assert(n->in(1)->in(1)->is_SubTypeCheck() &&
1745              (n->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr ||
1746               dom_if->in(1)->in(1)->as_SubTypeCheck()->method() != nullptr), "only for subtype checks with profile data attached");
1747       _igvn.replace_input_of(n, 1, dom_if->in(1));
1748     }
1749     ProjNode* dom_proj_true = dom_if->proj_out(1);
1750     ProjNode* dom_proj_false = dom_if->proj_out(0);
1751 
1752     // Now split the IF
1753     RegionNode* new_false_region;
1754     RegionNode* new_true_region;
1755     do_split_if(n, &new_false_region, &new_true_region);
1756     assert(new_false_region->req() == new_true_region->req(), "");
1757 #ifdef ASSERT
1758     for (uint i = 1; i < new_false_region->req(); ++i) {
1759       assert(new_false_region->in(i)->in(0) == new_true_region->in(i)->in(0), "unexpected shape following split if");
1760       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");
1761     }
1762 #endif
1763     assert(new_false_region->in(1)->in(0)->in(1) == dom_if->in(1), "dominating if and dominated if after split must share test");
1764 
1765     // We now have:
1766     // if (some_condition) {
1767     //   // body 1
1768     //   if (some_condition) {
1769     //     body3: // new_true_region
1770     //     // body3
1771     //   } else {
1772     //     goto body4;
1773     //   }
1774     // } else {
1775     //   // body 2
1776     //  if (some_condition) {
1777     //     goto body3;
1778     //   } else {
1779     //     body4:   // new_false_region
1780     //     // body4;
1781     //   }
1782     // }
1783     //
1784 
1785     // clone pinned nodes thru the resulting regions
1786     push_pinned_nodes_thru_region(dom_if, new_true_region);
1787     push_pinned_nodes_thru_region(dom_if, new_false_region);
1788 
1789     // Optimize out the cloned ifs. Because pinned nodes were cloned, this also allows a CastPP that would be dependent
1790     // 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
1791     // unrelated control dependency.
1792     for (uint i = 1; i < new_false_region->req(); i++) {
1793       if (is_dominator(dom_proj_true, new_false_region->in(i))) {
1794         dominated_by(dom_proj_true->as_IfProj(), new_false_region->in(i)->in(0)->as_If());
1795       } else {
1796         assert(is_dominator(dom_proj_false, new_false_region->in(i)), "bad if");
1797         dominated_by(dom_proj_false->as_IfProj(), new_false_region->in(i)->in(0)->as_If());
1798       }
1799     }
1800     return true;
1801   }
1802   return false;
1803 }
1804 
1805 void PhaseIdealLoop::push_pinned_nodes_thru_region(IfNode* dom_if, Node* region) {
1806   for (DUIterator i = region->outs(); region->has_out(i); i++) {
1807     Node* u = region->out(i);
1808     if (!has_ctrl(u) || u->is_Phi() || !u->depends_only_on_test() || !_igvn.no_dependent_zero_check(u)) {
1809       continue;
1810     }
1811     assert(u->in(0) == region, "not a control dependent node?");
1812     uint j = 1;
1813     for (; j < u->req(); ++j) {
1814       Node* in = u->in(j);
1815       if (!is_dominator(ctrl_or_self(in), dom_if)) {
1816         break;
1817       }
1818     }
1819     if (j == u->req()) {
1820       Node *phi = PhiNode::make_blank(region, u);
1821       for (uint k = 1; k < region->req(); ++k) {
1822         Node* clone = u->clone();
1823         clone->set_req(0, region->in(k));
1824         register_new_node(clone, region->in(k));
1825         phi->init_req(k, clone);
1826       }
1827       register_new_node(phi, region);
1828       _igvn.replace_node(u, phi);
1829       --i;
1830     }
1831   }
1832 }
1833 
1834 bool PhaseIdealLoop::safe_for_if_replacement(const Node* dom) const {
1835   if (!dom->is_CountedLoopEnd()) {
1836     return true;
1837   }
1838   CountedLoopEndNode* le = dom->as_CountedLoopEnd();
1839   CountedLoopNode* cl = le->loopnode();
1840   if (cl == nullptr) {
1841     return true;
1842   }
1843   if (!cl->is_main_loop()) {
1844     return true;
1845   }
1846   if (cl->is_canonical_loop_entry() == nullptr) {
1847     return true;
1848   }
1849   // Further unrolling is possible so loop exit condition might change
1850   return false;
1851 }
1852 
1853 // See if a shared loop-varying computation has no loop-varying uses.
1854 // Happens if something is only used for JVM state in uncommon trap exits,
1855 // like various versions of induction variable+offset.  Clone the
1856 // computation per usage to allow it to sink out of the loop.
1857 void PhaseIdealLoop::try_sink_out_of_loop(Node* n) {
1858   bool is_raw_to_oop_cast = n->is_ConstraintCast() &&
1859                             n->in(1)->bottom_type()->isa_rawptr() &&
1860                             !n->bottom_type()->isa_rawptr();
1861 
1862   if (has_ctrl(n) &&
1863       !n->is_Phi() &&
1864       !n->is_Bool() &&
1865       !n->is_Proj() &&
1866       !n->is_MergeMem() &&
1867       !n->is_CMove() &&
1868       !n->is_OpaqueNotNull() &&
1869       !n->is_OpaqueInitializedAssertionPredicate() &&
1870       !n->is_OpaqueTemplateAssertionPredicate() &&
1871       !is_raw_to_oop_cast && // don't extend live ranges of raw oops
1872       (KillPathsReachableByDeadTypeNode || !n->is_Type())
1873       ) {
1874     Node *n_ctrl = get_ctrl(n);
1875     IdealLoopTree *n_loop = get_loop(n_ctrl);
1876 
1877     if (n->in(0) != nullptr) {
1878       IdealLoopTree* loop_ctrl = get_loop(n->in(0));
1879       if (n_loop != loop_ctrl && n_loop->is_member(loop_ctrl)) {
1880         // n has a control input inside a loop but get_ctrl() is member of an outer loop. This could happen, for example,
1881         // for Div nodes inside a loop (control input inside loop) without a use except for an UCT (outside the loop).
1882         // Rewire control of n to right outside of the loop, regardless if its input(s) are later sunk or not.
1883         Node* maybe_pinned_n = n;
1884         Node* outside_ctrl = place_outside_loop(n_ctrl, loop_ctrl);
1885         if (!would_sink_below_pre_loop_exit(loop_ctrl, outside_ctrl)) {
1886           if (n->depends_only_on_test()) {
1887             Node* pinned_clone = n->pin_array_access_node();
1888             if (pinned_clone != nullptr) {
1889               // Pin array access nodes: if this is an array load, it's going to be dependent on a condition that's not a
1890               // range check for that access. If that condition is replaced by an identical dominating one, then an
1891               // unpinned load would risk floating above its range check.
1892               register_new_node(pinned_clone, n_ctrl);
1893               maybe_pinned_n = pinned_clone;
1894               _igvn.replace_node(n, pinned_clone);
1895             }
1896           }
1897           _igvn.replace_input_of(maybe_pinned_n, 0, outside_ctrl);
1898         }
1899       }
1900     }
1901     if (n_loop != _ltree_root && n->outcnt() > 1) {
1902       // Compute early control: needed for anti-dependence analysis. It's also possible that as a result of
1903       // previous transformations in this loop opts round, the node can be hoisted now: early control will tell us.
1904       Node* early_ctrl = compute_early_ctrl(n, n_ctrl);
1905       if (n_loop->is_member(get_loop(early_ctrl)) && // check that this one can't be hoisted now
1906           ctrl_of_all_uses_out_of_loop(n, early_ctrl, n_loop)) { // All uses in outer loops!
1907         if (n->is_Store() || n->is_LoadStore()) {
1908             assert(false, "no node with a side effect");
1909             C->record_failure("no node with a side effect");
1910             return;
1911         }
1912         Node* outer_loop_clone = nullptr;
1913         for (DUIterator_Last jmin, j = n->last_outs(jmin); j >= jmin;) {
1914           Node* u = n->last_out(j); // Clone private computation per use
1915           _igvn.rehash_node_delayed(u);
1916           Node* x = nullptr;
1917           if (n->depends_only_on_test()) {
1918             // Pin array access nodes: if this is an array load, it's going to be dependent on a condition that's not a
1919             // range check for that access. If that condition is replaced by an identical dominating one, then an
1920             // unpinned load would risk floating above its range check.
1921             x = n->pin_array_access_node();
1922           }
1923           if (x == nullptr) {
1924             x = n->clone();
1925           }
1926           Node* x_ctrl = nullptr;
1927           if (u->is_Phi()) {
1928             // Replace all uses of normal nodes.  Replace Phi uses
1929             // individually, so the separate Nodes can sink down
1930             // different paths.
1931             uint k = 1;
1932             while (u->in(k) != n) k++;
1933             u->set_req(k, x);
1934             // x goes next to Phi input path
1935             x_ctrl = u->in(0)->in(k);
1936             // Find control for 'x' next to use but not inside inner loops.
1937             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1938             --j;
1939           } else {              // Normal use
1940             if (has_ctrl(u)) {
1941               x_ctrl = get_ctrl(u);
1942             } else {
1943               x_ctrl = u->in(0);
1944             }
1945             // Find control for 'x' next to use but not inside inner loops.
1946             x_ctrl = place_outside_loop(x_ctrl, n_loop);
1947             // Replace all uses
1948             if (u->is_ConstraintCast() && _igvn.type(n)->higher_equal(u->bottom_type()) && u->in(0) == x_ctrl) {
1949               // If we're sinking a chain of data nodes, we might have inserted a cast to pin the use which is not necessary
1950               // anymore now that we're going to pin n as well
1951               _igvn.replace_node(u, x);
1952               --j;
1953             } else {
1954               int nb = u->replace_edge(n, x, &_igvn);
1955               j -= nb;
1956             }
1957           }
1958 
1959           if (n->is_Load()) {
1960             // For loads, add a control edge to a CFG node outside of the loop
1961             // to force them to not combine and return back inside the loop
1962             // during GVN optimization (4641526).
1963             assert(x_ctrl == get_late_ctrl_with_anti_dep(x->as_Load(), early_ctrl, x_ctrl), "anti-dependences were already checked");
1964 
1965             IdealLoopTree* x_loop = get_loop(x_ctrl);
1966             Node* x_head = x_loop->_head;
1967             if (x_head->is_Loop() && x_head->is_OuterStripMinedLoop()) {
1968               // Do not add duplicate LoadNodes to the outer strip mined loop
1969               if (outer_loop_clone != nullptr) {
1970                 _igvn.replace_node(x, outer_loop_clone);
1971                 continue;
1972               }
1973               outer_loop_clone = x;
1974             }
1975             x->set_req(0, x_ctrl);
1976           } else if (n->in(0) != nullptr){
1977             x->set_req(0, x_ctrl);
1978           }
1979           assert(dom_depth(n_ctrl) <= dom_depth(x_ctrl), "n is later than its clone");
1980           assert(!n_loop->is_member(get_loop(x_ctrl)), "should have moved out of loop");
1981           register_new_node(x, x_ctrl);
1982 
1983           // Chain of AddP nodes: (AddP base (AddP base (AddP base )))
1984           // All AddP nodes must keep the same base after sinking so:
1985           // 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,
1986           // their bases remain the same.
1987           // (see 2- below)
1988           assert(!x->is_AddP() || !x->in(AddPNode::Address)->is_AddP() ||
1989                  x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base) ||
1990                  !x->in(AddPNode::Address)->in(AddPNode::Base)->eqv_uncast(x->in(AddPNode::Base)), "unexpected AddP shape");
1991           if (x->in(0) == nullptr && !x->is_DecodeNarrowPtr() &&
1992               !(x->is_AddP() && x->in(AddPNode::Address)->is_AddP() && x->in(AddPNode::Address)->in(AddPNode::Base) == x->in(AddPNode::Base))) {
1993             assert(!x->is_Load(), "load should be pinned");
1994             // Use a cast node to pin clone out of loop
1995             Node* cast = nullptr;
1996             for (uint k = 0; k < x->req(); k++) {
1997               Node* in = x->in(k);
1998               if (in != nullptr && n_loop->is_member(get_loop(get_ctrl(in)))) {
1999                 const Type* in_t = _igvn.type(in);
2000                 cast = ConstraintCastNode::make_cast_for_type(x_ctrl, in, in_t,
2001                                                               ConstraintCastNode::UnconditionalDependency, nullptr);
2002               }
2003               if (cast != nullptr) {
2004                 Node* prev = _igvn.hash_find_insert(cast);
2005                 if (prev != nullptr && get_ctrl(prev) == x_ctrl) {
2006                   cast->destruct(&_igvn);
2007                   cast = prev;
2008                 } else {
2009                   register_new_node(cast, x_ctrl);
2010                 }
2011                 x->replace_edge(in, cast);
2012                 // Chain of AddP nodes:
2013                 // 2- A CastPP of the base is only added now that all AddP nodes are sunk
2014                 if (x->is_AddP() && k == AddPNode::Base) {
2015                   update_addp_chain_base(x, n->in(AddPNode::Base), cast);
2016                 }
2017                 break;
2018               }
2019             }
2020             assert(cast != nullptr, "must have added a cast to pin the node");
2021           }
2022         }
2023         _igvn.remove_dead_node(n);
2024       }
2025       _dom_lca_tags_round = 0;
2026     }
2027   }
2028 }
2029 
2030 void PhaseIdealLoop::update_addp_chain_base(Node* x, Node* old_base, Node* new_base) {
2031   ResourceMark rm;
2032   Node_List wq;
2033   wq.push(x);
2034   while (wq.size() != 0) {
2035     Node* n = wq.pop();
2036     for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2037       Node* u = n->fast_out(i);
2038       if (u->is_AddP() && u->in(AddPNode::Base) == old_base) {
2039         _igvn.replace_input_of(u, AddPNode::Base, new_base);
2040         wq.push(u);
2041       }
2042     }
2043   }
2044 }
2045 
2046 // Compute the early control of a node by following its inputs until we reach
2047 // nodes that are pinned. Then compute the LCA of the control of all pinned nodes.
2048 Node* PhaseIdealLoop::compute_early_ctrl(Node* n, Node* n_ctrl) {
2049   Node* early_ctrl = nullptr;
2050   ResourceMark rm;
2051   Unique_Node_List wq;
2052   wq.push(n);
2053   for (uint i = 0; i < wq.size(); i++) {
2054     Node* m = wq.at(i);
2055     Node* c = nullptr;
2056     if (m->is_CFG()) {
2057       c = m;
2058     } else if (m->pinned()) {
2059       c = m->in(0);
2060     } else {
2061       for (uint j = 0; j < m->req(); j++) {
2062         Node* in = m->in(j);
2063         if (in != nullptr) {
2064           wq.push(in);
2065         }
2066       }
2067     }
2068     if (c != nullptr) {
2069       assert(is_dominator(c, n_ctrl), "control input must dominate current control");
2070       if (early_ctrl == nullptr || is_dominator(early_ctrl, c)) {
2071         early_ctrl = c;
2072       }
2073     }
2074   }
2075   assert(is_dominator(early_ctrl, n_ctrl), "early control must dominate current control");
2076   return early_ctrl;
2077 }
2078 
2079 bool PhaseIdealLoop::ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop) {
2080   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2081     Node* u = n->fast_out(i);
2082     if (u->is_Opaque1()) {
2083       return false;  // Found loop limit, bugfix for 4677003
2084     }
2085     // We can't reuse tags in PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal() so make sure calls to
2086     // get_late_ctrl_with_anti_dep() use their own tag
2087     _dom_lca_tags_round++;
2088     assert(_dom_lca_tags_round != 0, "shouldn't wrap around");
2089 
2090     if (u->is_Phi()) {
2091       for (uint j = 1; j < u->req(); ++j) {
2092         if (u->in(j) == n && !ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, u->in(0)->in(j))) {
2093           return false;
2094         }
2095       }
2096     } else {
2097       Node* ctrl = has_ctrl(u) ? get_ctrl(u) : u->in(0);
2098       if (!ctrl_of_use_out_of_loop(n, n_ctrl, n_loop, ctrl)) {
2099         return false;
2100       }
2101     }
2102   }
2103   return true;
2104 }
2105 
2106 // 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
2107 // to a check that's eliminated by range check elimination, it becomes input to an expression that feeds into the exit
2108 // 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
2109 // it would be to not eliminate the check in the main loop. Instead, we prevent sinking of the node here so better code
2110 // is generated for the main loop.
2111 bool PhaseIdealLoop::would_sink_below_pre_loop_exit(IdealLoopTree* n_loop, Node* ctrl) {
2112   if (n_loop->_head->is_CountedLoop() && n_loop->_head->as_CountedLoop()->is_pre_loop()) {
2113     CountedLoopNode* pre_loop = n_loop->_head->as_CountedLoop();
2114     if (is_dominator(pre_loop->loopexit(), ctrl)) {
2115       return true;
2116     }
2117   }
2118   return false;
2119 }
2120 
2121 bool PhaseIdealLoop::ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl) {
2122   if (n->is_Load()) {
2123     ctrl = get_late_ctrl_with_anti_dep(n->as_Load(), n_ctrl, ctrl);
2124   }
2125   IdealLoopTree *u_loop = get_loop(ctrl);
2126   if (u_loop == n_loop) {
2127     return false; // Found loop-varying use
2128   }
2129   if (n_loop->is_member(u_loop)) {
2130     return false; // Found use in inner loop
2131   }
2132   if (would_sink_below_pre_loop_exit(n_loop, ctrl)) {
2133     return false;
2134   }
2135   return true;
2136 }
2137 
2138 //------------------------------split_if_with_blocks---------------------------
2139 // Check for aggressive application of 'split-if' optimization,
2140 // using basic block level info.
2141 void PhaseIdealLoop::split_if_with_blocks(VectorSet &visited, Node_Stack &nstack) {
2142   Node* root = C->root();
2143   visited.set(root->_idx); // first, mark root as visited
2144   // Do pre-visit work for root
2145   Node* n   = split_if_with_blocks_pre(root);
2146   uint  cnt = n->outcnt();
2147   uint  i   = 0;
2148 
2149   while (true) {
2150     // Visit all children
2151     if (i < cnt) {
2152       Node* use = n->raw_out(i);
2153       ++i;
2154       if (use->outcnt() != 0 && !visited.test_set(use->_idx)) {
2155         // Now do pre-visit work for this use
2156         use = split_if_with_blocks_pre(use);
2157         nstack.push(n, i); // Save parent and next use's index.
2158         n   = use;         // Process all children of current use.
2159         cnt = use->outcnt();
2160         i   = 0;
2161       }
2162     }
2163     else {
2164       // All of n's children have been processed, complete post-processing.
2165       if (cnt != 0 && !n->is_Con()) {
2166         assert(has_node(n), "no dead nodes");
2167         split_if_with_blocks_post(n);
2168         if (C->failing()) {
2169           return;
2170         }
2171       }
2172       if (must_throttle_split_if()) {
2173         nstack.clear();
2174       }
2175       if (nstack.is_empty()) {
2176         // Finished all nodes on stack.
2177         break;
2178       }
2179       // Get saved parent node and next use's index. Visit the rest of uses.
2180       n   = nstack.node();
2181       cnt = n->outcnt();
2182       i   = nstack.index();
2183       nstack.pop();
2184     }
2185   }
2186 }
2187 
2188 
2189 //=============================================================================
2190 //
2191 //                   C L O N E   A   L O O P   B O D Y
2192 //
2193 
2194 //------------------------------clone_iff--------------------------------------
2195 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2196 // "Nearly" because all Nodes have been cloned from the original in the loop,
2197 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2198 // through the Phi recursively, and return a Bool.
2199 Node* PhaseIdealLoop::clone_iff(PhiNode* phi) {
2200 
2201   // Convert this Phi into a Phi merging Bools
2202   uint i;
2203   for (i = 1; i < phi->req(); i++) {
2204     Node* b = phi->in(i);
2205     if (b->is_Phi()) {
2206       _igvn.replace_input_of(phi, i, clone_iff(b->as_Phi()));
2207     } else {
2208       assert(b->is_Bool() || b->is_OpaqueNotNull() || b->is_OpaqueInitializedAssertionPredicate(),
2209              "bool, non-null check with OpaqueNotNull or Initialized Assertion Predicate with its Opaque node");
2210     }
2211   }
2212   Node* n = phi->in(1);
2213   Node* sample_opaque = nullptr;
2214   Node *sample_bool = nullptr;
2215   if (n->is_OpaqueNotNull() || n->is_OpaqueInitializedAssertionPredicate()) {
2216     sample_opaque = n;
2217     sample_bool = n->in(1);
2218     assert(sample_bool->is_Bool(), "wrong type");
2219   } else {
2220     sample_bool = n;
2221   }
2222   Node* sample_cmp = sample_bool->in(1);
2223   const Type* t = Type::TOP;
2224   const TypePtr* at = nullptr;
2225   if (sample_cmp->is_FlatArrayCheck()) {
2226     // Left input of a FlatArrayCheckNode is memory, set the (adr) type of the phi accordingly
2227     assert(sample_cmp->in(1)->bottom_type() == Type::MEMORY, "unexpected input type");
2228     t = Type::MEMORY;
2229     at = TypeRawPtr::BOTTOM;
2230   }
2231 
2232   // Make Phis to merge the Cmp's inputs.
2233   PhiNode *phi1 = new PhiNode(phi->in(0), t, at);
2234   PhiNode *phi2 = new PhiNode(phi->in(0), Type::TOP);
2235   for (i = 1; i < phi->req(); i++) {
2236     Node *n1 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(1) : phi->in(i)->in(1)->in(1)->in(1);
2237     Node *n2 = sample_opaque == nullptr ? phi->in(i)->in(1)->in(2) : phi->in(i)->in(1)->in(1)->in(2);
2238     phi1->set_req(i, n1);
2239     phi2->set_req(i, n2);
2240     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2241     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2242   }
2243   // See if these Phis have been made before.
2244   // Register with optimizer
2245   Node *hit1 = _igvn.hash_find_insert(phi1);
2246   if (hit1) {                   // Hit, toss just made Phi
2247     _igvn.remove_dead_node(phi1); // Remove new phi
2248     assert(hit1->is_Phi(), "" );
2249     phi1 = (PhiNode*)hit1;      // Use existing phi
2250   } else {                      // Miss
2251     _igvn.register_new_node_with_optimizer(phi1);
2252   }
2253   Node *hit2 = _igvn.hash_find_insert(phi2);
2254   if (hit2) {                   // Hit, toss just made Phi
2255     _igvn.remove_dead_node(phi2); // Remove new phi
2256     assert(hit2->is_Phi(), "" );
2257     phi2 = (PhiNode*)hit2;      // Use existing phi
2258   } else {                      // Miss
2259     _igvn.register_new_node_with_optimizer(phi2);
2260   }
2261   // Register Phis with loop/block info
2262   set_ctrl(phi1, phi->in(0));
2263   set_ctrl(phi2, phi->in(0));
2264   // Make a new Cmp
2265   Node *cmp = sample_cmp->clone();
2266   cmp->set_req(1, phi1);
2267   cmp->set_req(2, phi2);
2268   _igvn.register_new_node_with_optimizer(cmp);
2269   set_ctrl(cmp, phi->in(0));
2270 
2271   // Make a new Bool
2272   Node *b = sample_bool->clone();
2273   b->set_req(1,cmp);
2274   _igvn.register_new_node_with_optimizer(b);
2275   set_ctrl(b, phi->in(0));
2276 
2277   if (sample_opaque != nullptr) {
2278     Node* opaque = sample_opaque->clone();
2279     opaque->set_req(1, b);
2280     _igvn.register_new_node_with_optimizer(opaque);
2281     set_ctrl(opaque, phi->in(0));
2282     return opaque;
2283   }
2284 
2285   assert(b->is_Bool(), "");
2286   return b;
2287 }
2288 
2289 //------------------------------clone_bool-------------------------------------
2290 // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
2291 // "Nearly" because all Nodes have been cloned from the original in the loop,
2292 // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
2293 // through the Phi recursively, and return a Bool.
2294 CmpNode*PhaseIdealLoop::clone_bool(PhiNode* phi) {
2295   uint i;
2296   // Convert this Phi into a Phi merging Bools
2297   for( i = 1; i < phi->req(); i++ ) {
2298     Node *b = phi->in(i);
2299     if( b->is_Phi() ) {
2300       _igvn.replace_input_of(phi, i, clone_bool(b->as_Phi()));
2301     } else {
2302       assert( b->is_Cmp() || b->is_top(), "inputs are all Cmp or TOP" );
2303     }
2304   }
2305 
2306   Node *sample_cmp = phi->in(1);
2307 
2308   // Make Phis to merge the Cmp's inputs.
2309   PhiNode *phi1 = new PhiNode( phi->in(0), Type::TOP );
2310   PhiNode *phi2 = new PhiNode( phi->in(0), Type::TOP );
2311   for( uint j = 1; j < phi->req(); j++ ) {
2312     Node *cmp_top = phi->in(j); // Inputs are all Cmp or TOP
2313     Node *n1, *n2;
2314     if( cmp_top->is_Cmp() ) {
2315       n1 = cmp_top->in(1);
2316       n2 = cmp_top->in(2);
2317     } else {
2318       n1 = n2 = cmp_top;
2319     }
2320     phi1->set_req( j, n1 );
2321     phi2->set_req( j, n2 );
2322     phi1->set_type(phi1->type()->meet_speculative(n1->bottom_type()));
2323     phi2->set_type(phi2->type()->meet_speculative(n2->bottom_type()));
2324   }
2325 
2326   // See if these Phis have been made before.
2327   // Register with optimizer
2328   Node *hit1 = _igvn.hash_find_insert(phi1);
2329   if( hit1 ) {                  // Hit, toss just made Phi
2330     _igvn.remove_dead_node(phi1); // Remove new phi
2331     assert( hit1->is_Phi(), "" );
2332     phi1 = (PhiNode*)hit1;      // Use existing phi
2333   } else {                      // Miss
2334     _igvn.register_new_node_with_optimizer(phi1);
2335   }
2336   Node *hit2 = _igvn.hash_find_insert(phi2);
2337   if( hit2 ) {                  // Hit, toss just made Phi
2338     _igvn.remove_dead_node(phi2); // Remove new phi
2339     assert( hit2->is_Phi(), "" );
2340     phi2 = (PhiNode*)hit2;      // Use existing phi
2341   } else {                      // Miss
2342     _igvn.register_new_node_with_optimizer(phi2);
2343   }
2344   // Register Phis with loop/block info
2345   set_ctrl(phi1, phi->in(0));
2346   set_ctrl(phi2, phi->in(0));
2347   // Make a new Cmp
2348   Node *cmp = sample_cmp->clone();
2349   cmp->set_req( 1, phi1 );
2350   cmp->set_req( 2, phi2 );
2351   _igvn.register_new_node_with_optimizer(cmp);
2352   set_ctrl(cmp, phi->in(0));
2353 
2354   assert( cmp->is_Cmp(), "" );
2355   return (CmpNode*)cmp;
2356 }
2357 
2358 void PhaseIdealLoop::clone_loop_handle_data_uses(Node* old, Node_List &old_new,
2359                                                  IdealLoopTree* loop, IdealLoopTree* outer_loop,
2360                                                  Node_List*& split_if_set, Node_List*& split_bool_set,
2361                                                  Node_List*& split_cex_set, Node_List& worklist,
2362                                                  uint new_counter, CloneLoopMode mode) {
2363   Node* nnn = old_new[old->_idx];
2364   // Copy uses to a worklist, so I can munge the def-use info
2365   // with impunity.
2366   for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++)
2367     worklist.push(old->fast_out(j));
2368 
2369   while( worklist.size() ) {
2370     Node *use = worklist.pop();
2371     if (!has_node(use))  continue; // Ignore dead nodes
2372     if (use->in(0) == C->top())  continue;
2373     IdealLoopTree *use_loop = get_loop( has_ctrl(use) ? get_ctrl(use) : use );
2374     // Check for data-use outside of loop - at least one of OLD or USE
2375     // must not be a CFG node.
2376 #ifdef ASSERT
2377     if (loop->_head->as_Loop()->is_strip_mined() && outer_loop->is_member(use_loop) && !loop->is_member(use_loop) && old_new[use->_idx] == nullptr) {
2378       Node* sfpt = loop->_head->as_CountedLoop()->outer_safepoint();
2379       assert(mode != IgnoreStripMined, "incorrect cloning mode");
2380       assert((mode == ControlAroundStripMined && use == sfpt) || !use->is_reachable_from_root(), "missed a node");
2381     }
2382 #endif
2383     if (!loop->is_member(use_loop) && !outer_loop->is_member(use_loop) && (!old->is_CFG() || !use->is_CFG())) {
2384 
2385       // If the Data use is an IF, that means we have an IF outside the
2386       // loop that is switching on a condition that is set inside the
2387       // loop.  Happens if people set a loop-exit flag; then test the flag
2388       // in the loop to break the loop, then test is again outside the
2389       // loop to determine which way the loop exited.
2390       //
2391       // For several uses we need to make sure that there is no phi between,
2392       // the use and the Bool/Cmp. We therefore clone the Bool/Cmp down here
2393       // to avoid such a phi in between.
2394       // For example, it is unexpected that there is a Phi between an
2395       // AllocateArray node and its ValidLengthTest input that could cause
2396       // split if to break.
2397       assert(!use->is_OpaqueTemplateAssertionPredicate(),
2398              "should not clone a Template Assertion Predicate which should be removed once it's useless");
2399       if (use->is_If() || use->is_CMove() || use->is_OpaqueNotNull() || use->is_OpaqueInitializedAssertionPredicate() ||
2400           (use->Opcode() == Op_AllocateArray && use->in(AllocateNode::ValidLengthTest) == old)) {
2401         // Since this code is highly unlikely, we lazily build the worklist
2402         // of such Nodes to go split.
2403         if (!split_if_set) {
2404           split_if_set = new Node_List();
2405         }
2406         split_if_set->push(use);
2407       }
2408       if (use->is_Bool()) {
2409         if (!split_bool_set) {
2410           split_bool_set = new Node_List();
2411         }
2412         split_bool_set->push(use);
2413       }
2414       if (use->Opcode() == Op_CreateEx) {
2415         if (!split_cex_set) {
2416           split_cex_set = new Node_List();
2417         }
2418         split_cex_set->push(use);
2419       }
2420 
2421 
2422       // Get "block" use is in
2423       uint idx = 0;
2424       while( use->in(idx) != old ) idx++;
2425       Node *prev = use->is_CFG() ? use : get_ctrl(use);
2426       assert(!loop->is_member(get_loop(prev)) && !outer_loop->is_member(get_loop(prev)), "" );
2427       Node* cfg = (prev->_idx >= new_counter && prev->is_Region())
2428         ? prev->in(2)
2429         : idom(prev);
2430       if( use->is_Phi() )     // Phi use is in prior block
2431         cfg = prev->in(idx);  // NOT in block of Phi itself
2432       if (cfg->is_top()) {    // Use is dead?
2433         _igvn.replace_input_of(use, idx, C->top());
2434         continue;
2435       }
2436 
2437       // If use is referenced through control edge... (idx == 0)
2438       if (mode == IgnoreStripMined && idx == 0) {
2439         LoopNode *head = loop->_head->as_Loop();
2440         if (head->is_strip_mined() && is_dominator(head->outer_loop_exit(), prev)) {
2441           // That node is outside the inner loop, leave it outside the
2442           // outer loop as well to not confuse verification code.
2443           assert(!loop->_parent->is_member(use_loop), "should be out of the outer loop");
2444           _igvn.replace_input_of(use, 0, head->outer_loop_exit());
2445           continue;
2446         }
2447       }
2448 
2449       while(!outer_loop->is_member(get_loop(cfg))) {
2450         prev = cfg;
2451         cfg = (cfg->_idx >= new_counter && cfg->is_Region()) ? cfg->in(2) : idom(cfg);
2452       }
2453       // If the use occurs after merging several exits from the loop, then
2454       // old value must have dominated all those exits.  Since the same old
2455       // value was used on all those exits we did not need a Phi at this
2456       // merge point.  NOW we do need a Phi here.  Each loop exit value
2457       // is now merged with the peeled body exit; each exit gets its own
2458       // private Phi and those Phis need to be merged here.
2459       Node *phi;
2460       if( prev->is_Region() ) {
2461         if( idx == 0 ) {      // Updating control edge?
2462           phi = prev;         // Just use existing control
2463         } else {              // Else need a new Phi
2464           phi = PhiNode::make( prev, old );
2465           // Now recursively fix up the new uses of old!
2466           for( uint i = 1; i < prev->req(); i++ ) {
2467             worklist.push(phi); // Onto worklist once for each 'old' input
2468           }
2469         }
2470       } else {
2471         // Get new RegionNode merging old and new loop exits
2472         prev = old_new[prev->_idx];
2473         assert( prev, "just made this in step 7" );
2474         if( idx == 0) {      // Updating control edge?
2475           phi = prev;         // Just use existing control
2476         } else {              // Else need a new Phi
2477           // Make a new Phi merging data values properly
2478           phi = PhiNode::make( prev, old );
2479           phi->set_req( 1, nnn );
2480         }
2481       }
2482       // If inserting a new Phi, check for prior hits
2483       if( idx != 0 ) {
2484         Node *hit = _igvn.hash_find_insert(phi);
2485         if( hit == nullptr ) {
2486           _igvn.register_new_node_with_optimizer(phi); // Register new phi
2487         } else {                                      // or
2488           // Remove the new phi from the graph and use the hit
2489           _igvn.remove_dead_node(phi);
2490           phi = hit;                                  // Use existing phi
2491         }
2492         set_ctrl(phi, prev);
2493       }
2494       // Make 'use' use the Phi instead of the old loop body exit value
2495       assert(use->in(idx) == old, "old is still input of use");
2496       // We notify all uses of old, including use, and the indirect uses,
2497       // that may now be optimized because we have replaced old with phi.
2498       _igvn.add_users_to_worklist(old);
2499       if (idx == 0 &&
2500           use->depends_only_on_test()) {
2501         Node* pinned_clone = use->pin_array_access_node();
2502         if (pinned_clone != nullptr) {
2503           // Pin array access nodes: control is updated here to a region. If, after some transformations, only one path
2504           // into the region is left, an array load could become dependent on a condition that's not a range check for
2505           // that access. If that condition is replaced by an identical dominating one, then an unpinned load would risk
2506           // floating above its range check.
2507           pinned_clone->set_req(0, phi);
2508           register_new_node_with_ctrl_of(pinned_clone, use);
2509           _igvn.replace_node(use, pinned_clone);
2510           continue;
2511         }
2512       }
2513       _igvn.replace_input_of(use, idx, phi);
2514       if( use->_idx >= new_counter ) { // If updating new phis
2515         // Not needed for correctness, but prevents a weak assert
2516         // in AddPNode from tripping (when we end up with different
2517         // base & derived Phis that will become the same after
2518         // IGVN does CSE).
2519         Node *hit = _igvn.hash_find_insert(use);
2520         if( hit )             // Go ahead and re-hash for hits.
2521           _igvn.replace_node( use, hit );
2522       }
2523     }
2524   }
2525 }
2526 
2527 static void collect_nodes_in_outer_loop_not_reachable_from_sfpt(Node* n, const IdealLoopTree *loop, const IdealLoopTree* outer_loop,
2528                                                                 const Node_List &old_new, Unique_Node_List& wq, PhaseIdealLoop* phase,
2529                                                                 bool check_old_new) {
2530   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
2531     Node* u = n->fast_out(j);
2532     assert(check_old_new || old_new[u->_idx] == nullptr, "shouldn't have been cloned");
2533     if (!u->is_CFG() && (!check_old_new || old_new[u->_idx] == nullptr)) {
2534       Node* c = phase->get_ctrl(u);
2535       IdealLoopTree* u_loop = phase->get_loop(c);
2536       assert(!loop->is_member(u_loop) || !loop->_body.contains(u), "can be in outer loop or out of both loops only");
2537       if (!loop->is_member(u_loop)) {
2538         if (outer_loop->is_member(u_loop)) {
2539           wq.push(u);
2540         } else {
2541           // nodes pinned with control in the outer loop but not referenced from the safepoint must be moved out of
2542           // the outer loop too
2543           Node* u_c = u->in(0);
2544           if (u_c != nullptr) {
2545             IdealLoopTree* u_c_loop = phase->get_loop(u_c);
2546             if (outer_loop->is_member(u_c_loop) && !loop->is_member(u_c_loop)) {
2547               wq.push(u);
2548             }
2549           }
2550         }
2551       }
2552     }
2553   }
2554 }
2555 
2556 void PhaseIdealLoop::clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
2557                                       IdealLoopTree* outer_loop, int dd, Node_List &old_new,
2558                                       Node_List& extra_data_nodes) {
2559   if (head->is_strip_mined() && mode != IgnoreStripMined) {
2560     CountedLoopNode* cl = head->as_CountedLoop();
2561     Node* l = cl->outer_loop();
2562     Node* tail = cl->outer_loop_tail();
2563     IfNode* le = cl->outer_loop_end();
2564     Node* sfpt = cl->outer_safepoint();
2565     CountedLoopEndNode* cle = cl->loopexit();
2566     CountedLoopNode* new_cl = old_new[cl->_idx]->as_CountedLoop();
2567     CountedLoopEndNode* new_cle = new_cl->as_CountedLoop()->loopexit_or_null();
2568     Node* cle_out = cle->proj_out(false);
2569 
2570     Node* new_sfpt = nullptr;
2571     Node* new_cle_out = cle_out->clone();
2572     old_new.map(cle_out->_idx, new_cle_out);
2573     if (mode == CloneIncludesStripMined) {
2574       // clone outer loop body
2575       Node* new_l = l->clone();
2576       Node* new_tail = tail->clone();
2577       IfNode* new_le = le->clone()->as_If();
2578       new_sfpt = sfpt->clone();
2579 
2580       set_loop(new_l, outer_loop->_parent);
2581       set_idom(new_l, new_l->in(LoopNode::EntryControl), dd);
2582       set_loop(new_cle_out, outer_loop->_parent);
2583       set_idom(new_cle_out, new_cle, dd);
2584       set_loop(new_sfpt, outer_loop->_parent);
2585       set_idom(new_sfpt, new_cle_out, dd);
2586       set_loop(new_le, outer_loop->_parent);
2587       set_idom(new_le, new_sfpt, dd);
2588       set_loop(new_tail, outer_loop->_parent);
2589       set_idom(new_tail, new_le, dd);
2590       set_idom(new_cl, new_l, dd);
2591 
2592       old_new.map(l->_idx, new_l);
2593       old_new.map(tail->_idx, new_tail);
2594       old_new.map(le->_idx, new_le);
2595       old_new.map(sfpt->_idx, new_sfpt);
2596 
2597       new_l->set_req(LoopNode::LoopBackControl, new_tail);
2598       new_l->set_req(0, new_l);
2599       new_tail->set_req(0, new_le);
2600       new_le->set_req(0, new_sfpt);
2601       new_sfpt->set_req(0, new_cle_out);
2602       new_cle_out->set_req(0, new_cle);
2603       new_cl->set_req(LoopNode::EntryControl, new_l);
2604 
2605       _igvn.register_new_node_with_optimizer(new_l);
2606       _igvn.register_new_node_with_optimizer(new_tail);
2607       _igvn.register_new_node_with_optimizer(new_le);
2608     } else {
2609       Node *newhead = old_new[loop->_head->_idx];
2610       newhead->as_Loop()->clear_strip_mined();
2611       _igvn.replace_input_of(newhead, LoopNode::EntryControl, newhead->in(LoopNode::EntryControl)->in(LoopNode::EntryControl));
2612       set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2613     }
2614     // Look at data node that were assigned a control in the outer
2615     // loop: they are kept in the outer loop by the safepoint so start
2616     // from the safepoint node's inputs.
2617     IdealLoopTree* outer_loop = get_loop(l);
2618     Node_Stack stack(2);
2619     stack.push(sfpt, 1);
2620     uint new_counter = C->unique();
2621     while (stack.size() > 0) {
2622       Node* n = stack.node();
2623       uint i = stack.index();
2624       while (i < n->req() &&
2625              (n->in(i) == nullptr ||
2626               !has_ctrl(n->in(i)) ||
2627               get_loop(get_ctrl(n->in(i))) != outer_loop ||
2628               (old_new[n->in(i)->_idx] != nullptr && old_new[n->in(i)->_idx]->_idx >= new_counter))) {
2629         i++;
2630       }
2631       if (i < n->req()) {
2632         stack.set_index(i+1);
2633         stack.push(n->in(i), 0);
2634       } else {
2635         assert(old_new[n->_idx] == nullptr || n == sfpt || old_new[n->_idx]->_idx < new_counter, "no clone yet");
2636         Node* m = n == sfpt ? new_sfpt : n->clone();
2637         if (m != nullptr) {
2638           for (uint i = 0; i < n->req(); i++) {
2639             if (m->in(i) != nullptr && old_new[m->in(i)->_idx] != nullptr) {
2640               m->set_req(i, old_new[m->in(i)->_idx]);
2641             }
2642           }
2643         } else {
2644           assert(n == sfpt && mode != CloneIncludesStripMined, "where's the safepoint clone?");
2645         }
2646         if (n != sfpt) {
2647           extra_data_nodes.push(n);
2648           _igvn.register_new_node_with_optimizer(m);
2649           assert(get_ctrl(n) == cle_out, "what other control?");
2650           set_ctrl(m, new_cle_out);
2651           old_new.map(n->_idx, m);
2652         }
2653         stack.pop();
2654       }
2655     }
2656     if (mode == CloneIncludesStripMined) {
2657       _igvn.register_new_node_with_optimizer(new_sfpt);
2658       _igvn.register_new_node_with_optimizer(new_cle_out);
2659     }
2660     // Some other transformation may have pessimistically assigned some
2661     // data nodes to the outer loop. Set their control so they are out
2662     // of the outer loop.
2663     ResourceMark rm;
2664     Unique_Node_List wq;
2665     for (uint i = 0; i < extra_data_nodes.size(); i++) {
2666       Node* old = extra_data_nodes.at(i);
2667       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2668     }
2669 
2670     for (uint i = 0; i < loop->_body.size(); i++) {
2671       Node* old = loop->_body.at(i);
2672       collect_nodes_in_outer_loop_not_reachable_from_sfpt(old, loop, outer_loop, old_new, wq, this, true);
2673     }
2674 
2675     Node* inner_out = sfpt->in(0);
2676     if (inner_out->outcnt() > 1) {
2677       collect_nodes_in_outer_loop_not_reachable_from_sfpt(inner_out, loop, outer_loop, old_new, wq, this, true);
2678     }
2679 
2680     Node* new_ctrl = cl->outer_loop_exit();
2681     assert(get_loop(new_ctrl) != outer_loop, "must be out of the loop nest");
2682     for (uint i = 0; i < wq.size(); i++) {
2683       Node* n = wq.at(i);
2684       set_ctrl(n, new_ctrl);
2685       if (n->in(0) != nullptr) {
2686         _igvn.replace_input_of(n, 0, new_ctrl);
2687       }
2688       collect_nodes_in_outer_loop_not_reachable_from_sfpt(n, loop, outer_loop, old_new, wq, this, false);
2689     }
2690   } else {
2691     Node *newhead = old_new[loop->_head->_idx];
2692     set_idom(newhead, newhead->in(LoopNode::EntryControl), dd);
2693   }
2694 }
2695 
2696 //------------------------------clone_loop-------------------------------------
2697 //
2698 //                   C L O N E   A   L O O P   B O D Y
2699 //
2700 // This is the basic building block of the loop optimizations.  It clones an
2701 // entire loop body.  It makes an old_new loop body mapping; with this mapping
2702 // you can find the new-loop equivalent to an old-loop node.  All new-loop
2703 // nodes are exactly equal to their old-loop counterparts, all edges are the
2704 // same.  All exits from the old-loop now have a RegionNode that merges the
2705 // equivalent new-loop path.  This is true even for the normal "loop-exit"
2706 // condition.  All uses of loop-invariant old-loop values now come from (one
2707 // or more) Phis that merge their new-loop equivalents.
2708 //
2709 // This operation leaves the graph in an illegal state: there are two valid
2710 // control edges coming from the loop pre-header to both loop bodies.  I'll
2711 // definitely have to hack the graph after running this transform.
2712 //
2713 // From this building block I will further edit edges to perform loop peeling
2714 // or loop unrolling or iteration splitting (Range-Check-Elimination), etc.
2715 //
2716 // Parameter side_by_size_idom:
2717 //   When side_by_size_idom is null, the dominator tree is constructed for
2718 //      the clone loop to dominate the original.  Used in construction of
2719 //      pre-main-post loop sequence.
2720 //   When nonnull, the clone and original are side-by-side, both are
2721 //      dominated by the side_by_side_idom node.  Used in construction of
2722 //      unswitched loops.
2723 void PhaseIdealLoop::clone_loop( IdealLoopTree *loop, Node_List &old_new, int dd,
2724                                 CloneLoopMode mode, Node* side_by_side_idom) {
2725 
2726   LoopNode* head = loop->_head->as_Loop();
2727   head->verify_strip_mined(1);
2728 
2729   if (C->do_vector_loop() && PrintOpto) {
2730     const char* mname = C->method()->name()->as_quoted_ascii();
2731     if (mname != nullptr) {
2732       tty->print("PhaseIdealLoop::clone_loop: for vectorize method %s\n", mname);
2733     }
2734   }
2735 
2736   CloneMap& cm = C->clone_map();
2737   if (C->do_vector_loop()) {
2738     cm.set_clone_idx(cm.max_gen()+1);
2739 #ifndef PRODUCT
2740     if (PrintOpto) {
2741       tty->print_cr("PhaseIdealLoop::clone_loop: _clone_idx %d", cm.clone_idx());
2742       loop->dump_head();
2743     }
2744 #endif
2745   }
2746 
2747   // Step 1: Clone the loop body.  Make the old->new mapping.
2748   clone_loop_body(loop->_body, old_new, &cm);
2749 
2750   IdealLoopTree* outer_loop = (head->is_strip_mined() && mode != IgnoreStripMined) ? get_loop(head->as_CountedLoop()->outer_loop()) : loop;
2751 
2752   // Step 2: Fix the edges in the new body.  If the old input is outside the
2753   // loop use it.  If the old input is INside the loop, use the corresponding
2754   // new node instead.
2755   fix_body_edges(loop->_body, loop, old_new, dd, outer_loop->_parent, false);
2756 
2757   Node_List extra_data_nodes; // data nodes in the outer strip mined loop
2758   clone_outer_loop(head, mode, loop, outer_loop, dd, old_new, extra_data_nodes);
2759 
2760   // Step 3: Now fix control uses.  Loop varying control uses have already
2761   // been fixed up (as part of all input edges in Step 2).  Loop invariant
2762   // control uses must be either an IfFalse or an IfTrue.  Make a merge
2763   // point to merge the old and new IfFalse/IfTrue nodes; make the use
2764   // refer to this.
2765   Node_List worklist;
2766   uint new_counter = C->unique();
2767   fix_ctrl_uses(loop->_body, loop, old_new, mode, side_by_side_idom, &cm, worklist);
2768 
2769   // Step 4: If loop-invariant use is not control, it must be dominated by a
2770   // loop exit IfFalse/IfTrue.  Find "proper" loop exit.  Make a Region
2771   // there if needed.  Make a Phi there merging old and new used values.
2772   Node_List *split_if_set = nullptr;
2773   Node_List *split_bool_set = nullptr;
2774   Node_List *split_cex_set = nullptr;
2775   fix_data_uses(loop->_body, loop, mode, outer_loop, new_counter, old_new, worklist, split_if_set, split_bool_set, split_cex_set);
2776 
2777   for (uint i = 0; i < extra_data_nodes.size(); i++) {
2778     Node* old = extra_data_nodes.at(i);
2779     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2780                                 split_bool_set, split_cex_set, worklist, new_counter,
2781                                 mode);
2782   }
2783 
2784   // Check for IFs that need splitting/cloning.  Happens if an IF outside of
2785   // the loop uses a condition set in the loop.  The original IF probably
2786   // takes control from one or more OLD Regions (which in turn get from NEW
2787   // Regions).  In any case, there will be a set of Phis for each merge point
2788   // from the IF up to where the original BOOL def exists the loop.
2789   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
2790 
2791 }
2792 
2793 void PhaseIdealLoop::finish_clone_loop(Node_List* split_if_set, Node_List* split_bool_set, Node_List* split_cex_set) {
2794   if (split_if_set) {
2795     while (split_if_set->size()) {
2796       Node *iff = split_if_set->pop();
2797       uint input = iff->Opcode() == Op_AllocateArray ? AllocateNode::ValidLengthTest : 1;
2798       if (iff->in(input)->is_Phi()) {
2799         Node *b = clone_iff(iff->in(input)->as_Phi());
2800         _igvn.replace_input_of(iff, input, b);
2801       }
2802     }
2803   }
2804   if (split_bool_set) {
2805     while (split_bool_set->size()) {
2806       Node *b = split_bool_set->pop();
2807       Node *phi = b->in(1);
2808       assert(phi->is_Phi(), "");
2809       CmpNode *cmp = clone_bool((PhiNode*) phi);
2810       _igvn.replace_input_of(b, 1, cmp);
2811     }
2812   }
2813   if (split_cex_set) {
2814     while (split_cex_set->size()) {
2815       Node *b = split_cex_set->pop();
2816       assert(b->in(0)->is_Region(), "");
2817       assert(b->in(1)->is_Phi(), "");
2818       assert(b->in(0)->in(0) == b->in(1)->in(0), "");
2819       split_up(b, b->in(0), nullptr);
2820     }
2821   }
2822 }
2823 
2824 void PhaseIdealLoop::fix_data_uses(Node_List& body, IdealLoopTree* loop, CloneLoopMode mode, IdealLoopTree* outer_loop,
2825                                    uint new_counter, Node_List &old_new, Node_List &worklist, Node_List*& split_if_set,
2826                                    Node_List*& split_bool_set, Node_List*& split_cex_set) {
2827   for(uint i = 0; i < body.size(); i++ ) {
2828     Node* old = body.at(i);
2829     clone_loop_handle_data_uses(old, old_new, loop, outer_loop, split_if_set,
2830                                 split_bool_set, split_cex_set, worklist, new_counter,
2831                                 mode);
2832   }
2833 }
2834 
2835 void PhaseIdealLoop::fix_ctrl_uses(const Node_List& body, const IdealLoopTree* loop, Node_List &old_new, CloneLoopMode mode,
2836                                    Node* side_by_side_idom, CloneMap* cm, Node_List &worklist) {
2837   LoopNode* head = loop->_head->as_Loop();
2838   for(uint i = 0; i < body.size(); i++ ) {
2839     Node* old = body.at(i);
2840     if( !old->is_CFG() ) continue;
2841 
2842     // Copy uses to a worklist, so I can munge the def-use info
2843     // with impunity.
2844     for (DUIterator_Fast jmax, j = old->fast_outs(jmax); j < jmax; j++) {
2845       worklist.push(old->fast_out(j));
2846     }
2847 
2848     while (worklist.size()) {  // Visit all uses
2849       Node *use = worklist.pop();
2850       if (!has_node(use))  continue; // Ignore dead nodes
2851       IdealLoopTree *use_loop = get_loop(has_ctrl(use) ? get_ctrl(use) : use );
2852       if (!loop->is_member(use_loop) && use->is_CFG()) {
2853         // Both OLD and USE are CFG nodes here.
2854         assert(use->is_Proj(), "" );
2855         Node* nnn = old_new[old->_idx];
2856 
2857         Node* newuse = nullptr;
2858         if (head->is_strip_mined() && mode != IgnoreStripMined) {
2859           CountedLoopNode* cl = head->as_CountedLoop();
2860           CountedLoopEndNode* cle = cl->loopexit();
2861           Node* cle_out = cle->proj_out_or_null(false);
2862           if (use == cle_out) {
2863             IfNode* le = cl->outer_loop_end();
2864             use = le->proj_out(false);
2865             use_loop = get_loop(use);
2866             if (mode == CloneIncludesStripMined) {
2867               nnn = old_new[le->_idx];
2868             } else {
2869               newuse = old_new[cle_out->_idx];
2870             }
2871           }
2872         }
2873         if (newuse == nullptr) {
2874           newuse = use->clone();
2875         }
2876 
2877         // Clone the loop exit control projection
2878         if (C->do_vector_loop() && cm != nullptr) {
2879           cm->verify_insert_and_clone(use, newuse, cm->clone_idx());
2880         }
2881         newuse->set_req(0,nnn);
2882         _igvn.register_new_node_with_optimizer(newuse);
2883         set_loop(newuse, use_loop);
2884         set_idom(newuse, nnn, dom_depth(nnn) + 1 );
2885 
2886         // We need a Region to merge the exit from the peeled body and the
2887         // exit from the old loop body.
2888         RegionNode *r = new RegionNode(3);
2889         uint dd_r = MIN2(dom_depth(newuse), dom_depth(use));
2890         assert(dd_r >= dom_depth(dom_lca(newuse, use)), "" );
2891 
2892         // The original user of 'use' uses 'r' instead.
2893         for (DUIterator_Last lmin, l = use->last_outs(lmin); l >= lmin;) {
2894           Node* useuse = use->last_out(l);
2895           _igvn.rehash_node_delayed(useuse);
2896           uint uses_found = 0;
2897           if (useuse->in(0) == use) {
2898             useuse->set_req(0, r);
2899             uses_found++;
2900             if (useuse->is_CFG()) {
2901               // This is not a dom_depth > dd_r because when new
2902               // control flow is constructed by a loop opt, a node and
2903               // its dominator can end up at the same dom_depth
2904               assert(dom_depth(useuse) >= dd_r, "");
2905               set_idom(useuse, r, dom_depth(useuse));
2906             }
2907           }
2908           for (uint k = 1; k < useuse->req(); k++) {
2909             if( useuse->in(k) == use ) {
2910               useuse->set_req(k, r);
2911               uses_found++;
2912               if (useuse->is_Loop() && k == LoopNode::EntryControl) {
2913                 // This is not a dom_depth > dd_r because when new
2914                 // control flow is constructed by a loop opt, a node
2915                 // and its dominator can end up at the same dom_depth
2916                 assert(dom_depth(useuse) >= dd_r , "");
2917                 set_idom(useuse, r, dom_depth(useuse));
2918               }
2919             }
2920           }
2921           l -= uses_found;    // we deleted 1 or more copies of this edge
2922         }
2923 
2924         assert(use->is_Proj(), "loop exit should be projection");
2925         // lazy_replace() below moves all nodes that are:
2926         // - control dependent on the loop exit or
2927         // - have control set to the loop exit
2928         // below the post-loop merge point. lazy_replace() takes a dead control as first input. To make it
2929         // possible to use it, the loop exit projection is cloned and becomes the new exit projection. The initial one
2930         // becomes dead and is "replaced" by the region.
2931         Node* use_clone = use->clone();
2932         register_control(use_clone, use_loop, idom(use), dom_depth(use));
2933         // Now finish up 'r'
2934         r->set_req(1, newuse);
2935         r->set_req(2, use_clone);
2936         _igvn.register_new_node_with_optimizer(r);
2937         set_loop(r, use_loop);
2938         set_idom(r, (side_by_side_idom == nullptr) ? newuse->in(0) : side_by_side_idom, dd_r);
2939         lazy_replace(use, r);
2940         // Map the (cloned) old use to the new merge point
2941         old_new.map(use_clone->_idx, r);
2942       } // End of if a loop-exit test
2943     }
2944   }
2945 }
2946 
2947 void PhaseIdealLoop::fix_body_edges(const Node_List &body, IdealLoopTree* loop, const Node_List &old_new, int dd,
2948                                     IdealLoopTree* parent, bool partial) {
2949   for(uint i = 0; i < body.size(); i++ ) {
2950     Node *old = body.at(i);
2951     Node *nnn = old_new[old->_idx];
2952     // Fix CFG/Loop controlling the new node
2953     if (has_ctrl(old)) {
2954       set_ctrl(nnn, old_new[get_ctrl(old)->_idx]);
2955     } else {
2956       set_loop(nnn, parent);
2957       if (old->outcnt() > 0) {
2958         Node* dom = idom(old);
2959         if (old_new[dom->_idx] != nullptr) {
2960           dom = old_new[dom->_idx];
2961           set_idom(nnn, dom, dd );
2962         }
2963       }
2964     }
2965     // Correct edges to the new node
2966     for (uint j = 0; j < nnn->req(); j++) {
2967         Node *n = nnn->in(j);
2968         if (n != nullptr) {
2969           IdealLoopTree *old_in_loop = get_loop(has_ctrl(n) ? get_ctrl(n) : n);
2970           if (loop->is_member(old_in_loop)) {
2971             if (old_new[n->_idx] != nullptr) {
2972               nnn->set_req(j, old_new[n->_idx]);
2973             } else {
2974               assert(!body.contains(n), "");
2975               assert(partial, "node not cloned");
2976             }
2977           }
2978         }
2979     }
2980     _igvn.hash_find_insert(nnn);
2981   }
2982 }
2983 
2984 void PhaseIdealLoop::clone_loop_body(const Node_List& body, Node_List &old_new, CloneMap* cm) {
2985   for (uint i = 0; i < body.size(); i++) {
2986     Node* old = body.at(i);
2987     Node* nnn = old->clone();
2988     old_new.map(old->_idx, nnn);
2989     if (C->do_vector_loop() && cm != nullptr) {
2990       cm->verify_insert_and_clone(old, nnn, cm->clone_idx());
2991     }
2992     _igvn.register_new_node_with_optimizer(nnn);
2993   }
2994 }
2995 
2996 
2997 //---------------------- stride_of_possible_iv -------------------------------------
2998 // Looks for an iff/bool/comp with one operand of the compare
2999 // being a cycle involving an add and a phi,
3000 // with an optional truncation (left-shift followed by a right-shift)
3001 // of the add. Returns zero if not an iv.
3002 int PhaseIdealLoop::stride_of_possible_iv(Node* iff) {
3003   Node* trunc1 = nullptr;
3004   Node* trunc2 = nullptr;
3005   const TypeInteger* ttype = nullptr;
3006   if (!iff->is_If() || iff->in(1) == nullptr || !iff->in(1)->is_Bool()) {
3007     return 0;
3008   }
3009   BoolNode* bl = iff->in(1)->as_Bool();
3010   Node* cmp = bl->in(1);
3011   if (!cmp || (cmp->Opcode() != Op_CmpI && cmp->Opcode() != Op_CmpU)) {
3012     return 0;
3013   }
3014   // Must have an invariant operand
3015   if (is_member(get_loop(iff), get_ctrl(cmp->in(2)))) {
3016     return 0;
3017   }
3018   Node* add2 = nullptr;
3019   Node* cmp1 = cmp->in(1);
3020   if (cmp1->is_Phi()) {
3021     // (If (Bool (CmpX phi:(Phi ...(Optional-trunc(AddI phi add2))) )))
3022     Node* phi = cmp1;
3023     for (uint i = 1; i < phi->req(); i++) {
3024       Node* in = phi->in(i);
3025       Node* add = CountedLoopNode::match_incr_with_optional_truncation(in,
3026                                 &trunc1, &trunc2, &ttype, T_INT);
3027       if (add && add->in(1) == phi) {
3028         add2 = add->in(2);
3029         break;
3030       }
3031     }
3032   } else {
3033     // (If (Bool (CmpX addtrunc:(Optional-trunc((AddI (Phi ...addtrunc...) add2)) )))
3034     Node* addtrunc = cmp1;
3035     Node* add = CountedLoopNode::match_incr_with_optional_truncation(addtrunc,
3036                                 &trunc1, &trunc2, &ttype, T_INT);
3037     if (add && add->in(1)->is_Phi()) {
3038       Node* phi = add->in(1);
3039       for (uint i = 1; i < phi->req(); i++) {
3040         if (phi->in(i) == addtrunc) {
3041           add2 = add->in(2);
3042           break;
3043         }
3044       }
3045     }
3046   }
3047   if (add2 != nullptr) {
3048     const TypeInt* add2t = _igvn.type(add2)->is_int();
3049     if (add2t->is_con()) {
3050       return add2t->get_con();
3051     }
3052   }
3053   return 0;
3054 }
3055 
3056 
3057 //---------------------- stay_in_loop -------------------------------------
3058 // Return the (unique) control output node that's in the loop (if it exists.)
3059 Node* PhaseIdealLoop::stay_in_loop( Node* n, IdealLoopTree *loop) {
3060   Node* unique = nullptr;
3061   if (!n) return nullptr;
3062   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3063     Node* use = n->fast_out(i);
3064     if (!has_ctrl(use) && loop->is_member(get_loop(use))) {
3065       if (unique != nullptr) {
3066         return nullptr;
3067       }
3068       unique = use;
3069     }
3070   }
3071   return unique;
3072 }
3073 
3074 //------------------------------ register_node -------------------------------------
3075 // Utility to register node "n" with PhaseIdealLoop
3076 void PhaseIdealLoop::register_node(Node* n, IdealLoopTree* loop, Node* pred, uint ddepth) {
3077   _igvn.register_new_node_with_optimizer(n);
3078   loop->_body.push(n);
3079   if (n->is_CFG()) {
3080     set_loop(n, loop);
3081     set_idom(n, pred, ddepth);
3082   } else {
3083     set_ctrl(n, pred);
3084   }
3085 }
3086 
3087 //------------------------------ proj_clone -------------------------------------
3088 // Utility to create an if-projection
3089 ProjNode* PhaseIdealLoop::proj_clone(ProjNode* p, IfNode* iff) {
3090   ProjNode* c = p->clone()->as_Proj();
3091   c->set_req(0, iff);
3092   return c;
3093 }
3094 
3095 //------------------------------ short_circuit_if -------------------------------------
3096 // Force the iff control output to be the live_proj
3097 Node* PhaseIdealLoop::short_circuit_if(IfNode* iff, ProjNode* live_proj) {
3098   guarantee(live_proj != nullptr, "null projection");
3099   int proj_con = live_proj->_con;
3100   assert(proj_con == 0 || proj_con == 1, "false or true projection");
3101   Node* con = intcon(proj_con);
3102   if (iff) {
3103     iff->set_req(1, con);
3104   }
3105   return con;
3106 }
3107 
3108 //------------------------------ insert_if_before_proj -------------------------------------
3109 // Insert a new if before an if projection (* - new node)
3110 //
3111 // before
3112 //           if(test)
3113 //           /     \
3114 //          v       v
3115 //    other-proj   proj (arg)
3116 //
3117 // after
3118 //           if(test)
3119 //           /     \
3120 //          /       v
3121 //         |      * proj-clone
3122 //         v          |
3123 //    other-proj      v
3124 //                * new_if(relop(cmp[IU](left,right)))
3125 //                  /  \
3126 //                 v    v
3127 //         * new-proj  proj
3128 //         (returned)
3129 //
3130 ProjNode* PhaseIdealLoop::insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj) {
3131   IfNode* iff = proj->in(0)->as_If();
3132   IdealLoopTree *loop = get_loop(proj);
3133   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3134   uint ddepth = dom_depth(proj);
3135 
3136   _igvn.rehash_node_delayed(iff);
3137   _igvn.rehash_node_delayed(proj);
3138 
3139   proj->set_req(0, nullptr);  // temporary disconnect
3140   ProjNode* proj2 = proj_clone(proj, iff);
3141   register_node(proj2, loop, iff, ddepth);
3142 
3143   Node* cmp = Signed ? (Node*) new CmpINode(left, right) : (Node*) new CmpUNode(left, right);
3144   register_node(cmp, loop, proj2, ddepth);
3145 
3146   BoolNode* bol = new BoolNode(cmp, relop);
3147   register_node(bol, loop, proj2, ddepth);
3148 
3149   int opcode = iff->Opcode();
3150   assert(opcode == Op_If || opcode == Op_RangeCheck, "unexpected opcode");
3151   IfNode* new_if = IfNode::make_with_same_profile(iff, proj2, bol);
3152   register_node(new_if, loop, proj2, ddepth);
3153 
3154   proj->set_req(0, new_if); // reattach
3155   set_idom(proj, new_if, ddepth);
3156 
3157   ProjNode* new_exit = proj_clone(other_proj, new_if)->as_Proj();
3158   guarantee(new_exit != nullptr, "null exit node");
3159   register_node(new_exit, get_loop(other_proj), new_if, ddepth);
3160 
3161   return new_exit;
3162 }
3163 
3164 //------------------------------ insert_region_before_proj -------------------------------------
3165 // Insert a region before an if projection (* - new node)
3166 //
3167 // before
3168 //           if(test)
3169 //          /      |
3170 //         v       |
3171 //       proj      v
3172 //               other-proj
3173 //
3174 // after
3175 //           if(test)
3176 //          /      |
3177 //         v       |
3178 // * proj-clone    v
3179 //         |     other-proj
3180 //         v
3181 // * new-region
3182 //         |
3183 //         v
3184 // *      dum_if
3185 //       /     \
3186 //      v       \
3187 // * dum-proj    v
3188 //              proj
3189 //
3190 RegionNode* PhaseIdealLoop::insert_region_before_proj(ProjNode* proj) {
3191   IfNode* iff = proj->in(0)->as_If();
3192   IdealLoopTree *loop = get_loop(proj);
3193   ProjNode *other_proj = iff->proj_out(!proj->is_IfTrue())->as_Proj();
3194   uint ddepth = dom_depth(proj);
3195 
3196   _igvn.rehash_node_delayed(iff);
3197   _igvn.rehash_node_delayed(proj);
3198 
3199   proj->set_req(0, nullptr);  // temporary disconnect
3200   ProjNode* proj2 = proj_clone(proj, iff);
3201   register_node(proj2, loop, iff, ddepth);
3202 
3203   RegionNode* reg = new RegionNode(2);
3204   reg->set_req(1, proj2);
3205   register_node(reg, loop, iff, ddepth);
3206 
3207   IfNode* dum_if = new IfNode(reg, short_circuit_if(nullptr, proj), iff->_prob, iff->_fcnt);
3208   register_node(dum_if, loop, reg, ddepth);
3209 
3210   proj->set_req(0, dum_if); // reattach
3211   set_idom(proj, dum_if, ddepth);
3212 
3213   ProjNode* dum_proj = proj_clone(other_proj, dum_if);
3214   register_node(dum_proj, loop, dum_if, ddepth);
3215 
3216   return reg;
3217 }
3218 
3219 // Idea
3220 // ----
3221 // Partial Peeling tries to rotate the loop in such a way that it can later be turned into a counted loop. Counted loops
3222 // require a signed loop exit test. When calling this method, we've only found a suitable unsigned test to partial peel
3223 // with. Therefore, we try to split off a signed loop exit test from the unsigned test such that it can be used as new
3224 // loop exit while keeping the unsigned test unchanged and preserving the same behavior as if we've used the unsigned
3225 // test alone instead:
3226 //
3227 // Before Partial Peeling:
3228 //   Loop:
3229 //     <peeled section>
3230 //     Split off signed loop exit test
3231 //     <-- CUT HERE -->
3232 //     Unchanged unsigned loop exit test
3233 //     <rest of unpeeled section>
3234 //     goto Loop
3235 //
3236 // After Partial Peeling:
3237 //   <cloned peeled section>
3238 //   Cloned split off signed loop exit test
3239 //   Loop:
3240 //     Unchanged unsigned loop exit test
3241 //     <rest of unpeeled section>
3242 //     <peeled section>
3243 //     Split off signed loop exit test
3244 //     goto Loop
3245 //
3246 // Details
3247 // -------
3248 // Before:
3249 //          if (i <u limit)    Unsigned loop exit condition
3250 //         /       |
3251 //        v        v
3252 //   exit-proj   stay-in-loop-proj
3253 //
3254 // Split off a signed loop exit test (i.e. with CmpI) from an unsigned loop exit test (i.e. with CmpU) and insert it
3255 // before the CmpU on the stay-in-loop path and keep both tests:
3256 //
3257 //          if (i <u limit)    Signed loop exit test
3258 //        /        |
3259 //       /  if (i <u limit)    Unsigned loop exit test
3260 //      /  /       |
3261 //     v  v        v
3262 //  exit-region  stay-in-loop-proj
3263 //
3264 // Implementation
3265 // --------------
3266 // We need to make sure that the new signed loop exit test is properly inserted into the graph such that the unsigned
3267 // loop exit test still dominates the same set of control nodes, the ctrl() relation from data nodes to both loop
3268 // exit tests is preserved, and their loop nesting is correct.
3269 //
3270 // To achieve that, we clone the unsigned loop exit test completely (leave it unchanged), insert the signed loop exit
3271 // test above it and kill the original unsigned loop exit test by setting it's condition to a constant
3272 // (i.e. stay-in-loop-const in graph below) such that IGVN can fold it later:
3273 //
3274 //           if (stay-in-loop-const)  Killed original unsigned loop exit test
3275 //          /       |
3276 //         /        v
3277 //        /  if (i <  limit)          Split off signed loop exit test
3278 //       /  /       |
3279 //      /  /        v
3280 //     /  /  if (i <u limit)          Cloned unsigned loop exit test
3281 //    /  /   /      |
3282 //   v  v  v        |
3283 //  exit-region     |
3284 //        |         |
3285 //    dummy-if      |
3286 //     /  |         |
3287 // dead   |         |
3288 //        v         v
3289 //   exit-proj   stay-in-loop-proj
3290 //
3291 // Note: The dummy-if is inserted to create a region to merge the loop exits between the original to be killed unsigned
3292 //       loop exit test and its exit projection while keeping the exit projection (also see insert_region_before_proj()).
3293 //
3294 // Requirements
3295 // ------------
3296 // Note that we can only split off a signed loop exit test from the unsigned loop exit test when the behavior is exactly
3297 // the same as before with only a single unsigned test. This is only possible if certain requirements are met.
3298 // Otherwise, we need to bail out (see comments in the code below).
3299 IfNode* PhaseIdealLoop::insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree* loop) {
3300   const bool Signed   = true;
3301   const bool Unsigned = false;
3302 
3303   BoolNode* bol = if_cmpu->in(1)->as_Bool();
3304   if (bol->_test._test != BoolTest::lt) {
3305     return nullptr;
3306   }
3307   CmpNode* cmpu = bol->in(1)->as_Cmp();
3308   assert(cmpu->Opcode() == Op_CmpU, "must be unsigned comparison");
3309 
3310   int stride = stride_of_possible_iv(if_cmpu);
3311   if (stride == 0) {
3312     return nullptr;
3313   }
3314 
3315   Node* lp_proj = stay_in_loop(if_cmpu, loop);
3316   guarantee(lp_proj != nullptr, "null loop node");
3317 
3318   ProjNode* lp_continue = lp_proj->as_Proj();
3319   ProjNode* lp_exit     = if_cmpu->proj_out(!lp_continue->is_IfTrue())->as_Proj();
3320   if (!lp_exit->is_IfFalse()) {
3321     // The loop exit condition is (i <u limit) ==> (i >= 0 && i < limit).
3322     // We therefore can't add a single exit condition.
3323     return nullptr;
3324   }
3325   // The unsigned loop exit condition is
3326   //   !(i <u  limit)
3327   // =   i >=u limit
3328   //
3329   // First, we note that for any x for which
3330   //   0 <= x <= INT_MAX
3331   // we can convert x to an unsigned int and still get the same guarantee:
3332   //   0 <=  (uint) x <=  INT_MAX = (uint) INT_MAX
3333   //   0 <=u (uint) x <=u INT_MAX = (uint) INT_MAX   (LEMMA)
3334   //
3335   // With that in mind, if
3336   //   limit >= 0             (COND)
3337   // then the unsigned loop exit condition
3338   //   i >=u limit            (ULE)
3339   // is equivalent to
3340   //   i < 0 || i >= limit    (SLE-full)
3341   // because either i is negative and therefore always greater than MAX_INT when converting to unsigned
3342   //   (uint) i >=u MAX_INT >= limit >= 0
3343   // or otherwise
3344   //   i >= limit >= 0
3345   // holds due to (LEMMA).
3346   //
3347   // For completeness, a counterexample with limit < 0:
3348   // Assume i = -3 and limit = -2:
3349   //   i  < 0
3350   //   -2 < 0
3351   // is true and thus also "i < 0 || i >= limit". But
3352   //   i  >=u limit
3353   //   -3 >=u -2
3354   // is false.
3355   Node* limit = cmpu->in(2);
3356   const TypeInt* type_limit = _igvn.type(limit)->is_int();
3357   if (type_limit->_lo < 0) {
3358     return nullptr;
3359   }
3360 
3361   // We prove below that we can extract a single signed loop exit condition from (SLE-full), depending on the stride:
3362   //   stride < 0:
3363   //     i < 0        (SLE = SLE-negative)
3364   //   stride > 0:
3365   //     i >= limit   (SLE = SLE-positive)
3366   // such that we have the following graph before Partial Peeling with stride > 0 (similar for stride < 0):
3367   //
3368   // Loop:
3369   //   <peeled section>
3370   //   i >= limit    (SLE-positive)
3371   //   <-- CUT HERE -->
3372   //   i >=u limit   (ULE)
3373   //   <rest of unpeeled section>
3374   //   goto Loop
3375   //
3376   // We exit the loop if:
3377   //   (SLE) is true OR (ULE) is true
3378   // However, if (SLE) is true then (ULE) also needs to be true to ensure the exact same behavior. Otherwise, we wrongly
3379   // exit a loop that should not have been exited if we did not apply Partial Peeling. More formally, we need to ensure:
3380   //   (SLE) IMPLIES (ULE)
3381   // This indeed holds when (COND) is given:
3382   // - stride > 0:
3383   //       i >=  limit             // (SLE = SLE-positive)
3384   //       i >=  limit >= 0        // (COND)
3385   //       i >=u limit >= 0        // (LEMMA)
3386   //     which is the unsigned loop exit condition (ULE).
3387   // - stride < 0:
3388   //       i        <  0           // (SLE = SLE-negative)
3389   //       (uint) i >u MAX_INT     // (NEG) all negative values are greater than MAX_INT when converted to unsigned
3390   //       MAX_INT >= limit >= 0   // (COND)
3391   //       MAX_INT >=u limit >= 0  // (LEMMA)
3392   //     and thus from (NEG) and (LEMMA):
3393   //       i >=u limit
3394   //     which is the unsigned loop exit condition (ULE).
3395   //
3396   //
3397   // After Partial Peeling, we have the following structure for stride > 0 (similar for stride < 0):
3398   //   <cloned peeled section>
3399   //   i >= limit (SLE-positive)
3400   //   Loop:
3401   //     i >=u limit (ULE)
3402   //     <rest of unpeeled section>
3403   //     <peeled section>
3404   //     i >= limit (SLE-positive)
3405   //     goto Loop
3406   Node* rhs_cmpi;
3407   if (stride > 0) {
3408     rhs_cmpi = limit; // For i >= limit
3409   } else {
3410     rhs_cmpi = makecon(TypeInt::ZERO); // For i < 0
3411   }
3412   // Create a new region on the exit path
3413   RegionNode* reg = insert_region_before_proj(lp_exit);
3414   guarantee(reg != nullptr, "null region node");
3415 
3416   // Clone the if-cmpu-true-false using a signed compare
3417   BoolTest::mask rel_i = stride > 0 ? bol->_test._test : BoolTest::ge;
3418   ProjNode* cmpi_exit = insert_if_before_proj(cmpu->in(1), Signed, rel_i, rhs_cmpi, lp_continue);
3419   reg->add_req(cmpi_exit);
3420 
3421   // Clone the if-cmpu-true-false
3422   BoolTest::mask rel_u = bol->_test._test;
3423   ProjNode* cmpu_exit = insert_if_before_proj(cmpu->in(1), Unsigned, rel_u, cmpu->in(2), lp_continue);
3424   reg->add_req(cmpu_exit);
3425 
3426   // Force original if to stay in loop.
3427   short_circuit_if(if_cmpu, lp_continue);
3428 
3429   return cmpi_exit->in(0)->as_If();
3430 }
3431 
3432 //------------------------------ remove_cmpi_loop_exit -------------------------------------
3433 // Remove a previously inserted signed compare loop exit.
3434 void PhaseIdealLoop::remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop) {
3435   Node* lp_proj = stay_in_loop(if_cmp, loop);
3436   assert(if_cmp->in(1)->in(1)->Opcode() == Op_CmpI &&
3437          stay_in_loop(lp_proj, loop)->is_If() &&
3438          stay_in_loop(lp_proj, loop)->in(1)->in(1)->Opcode() == Op_CmpU, "inserted cmpi before cmpu");
3439   Node* con = makecon(lp_proj->is_IfTrue() ? TypeInt::ONE : TypeInt::ZERO);
3440   if_cmp->set_req(1, con);
3441 }
3442 
3443 //------------------------------ scheduled_nodelist -------------------------------------
3444 // Create a post order schedule of nodes that are in the
3445 // "member" set.  The list is returned in "sched".
3446 // The first node in "sched" is the loop head, followed by
3447 // nodes which have no inputs in the "member" set, and then
3448 // followed by the nodes that have an immediate input dependence
3449 // on a node in "sched".
3450 void PhaseIdealLoop::scheduled_nodelist( IdealLoopTree *loop, VectorSet& member, Node_List &sched ) {
3451 
3452   assert(member.test(loop->_head->_idx), "loop head must be in member set");
3453   VectorSet visited;
3454   Node_Stack nstack(loop->_body.size());
3455 
3456   Node* n  = loop->_head;  // top of stack is cached in "n"
3457   uint idx = 0;
3458   visited.set(n->_idx);
3459 
3460   // Initially push all with no inputs from within member set
3461   for(uint i = 0; i < loop->_body.size(); i++ ) {
3462     Node *elt = loop->_body.at(i);
3463     if (member.test(elt->_idx)) {
3464       bool found = false;
3465       for (uint j = 0; j < elt->req(); j++) {
3466         Node* def = elt->in(j);
3467         if (def && member.test(def->_idx) && def != elt) {
3468           found = true;
3469           break;
3470         }
3471       }
3472       if (!found && elt != loop->_head) {
3473         nstack.push(n, idx);
3474         n = elt;
3475         assert(!visited.test(n->_idx), "not seen yet");
3476         visited.set(n->_idx);
3477       }
3478     }
3479   }
3480 
3481   // traverse out's that are in the member set
3482   while (true) {
3483     if (idx < n->outcnt()) {
3484       Node* use = n->raw_out(idx);
3485       idx++;
3486       if (!visited.test_set(use->_idx)) {
3487         if (member.test(use->_idx)) {
3488           nstack.push(n, idx);
3489           n = use;
3490           idx = 0;
3491         }
3492       }
3493     } else {
3494       // All outputs processed
3495       sched.push(n);
3496       if (nstack.is_empty()) break;
3497       n   = nstack.node();
3498       idx = nstack.index();
3499       nstack.pop();
3500     }
3501   }
3502 }
3503 
3504 
3505 //------------------------------ has_use_in_set -------------------------------------
3506 // Has a use in the vector set
3507 bool PhaseIdealLoop::has_use_in_set( Node* n, VectorSet& vset ) {
3508   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3509     Node* use = n->fast_out(j);
3510     if (vset.test(use->_idx)) {
3511       return true;
3512     }
3513   }
3514   return false;
3515 }
3516 
3517 
3518 //------------------------------ has_use_internal_to_set -------------------------------------
3519 // Has use internal to the vector set (ie. not in a phi at the loop head)
3520 bool PhaseIdealLoop::has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop ) {
3521   Node* head  = loop->_head;
3522   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3523     Node* use = n->fast_out(j);
3524     if (vset.test(use->_idx) && !(use->is_Phi() && use->in(0) == head)) {
3525       return true;
3526     }
3527   }
3528   return false;
3529 }
3530 
3531 
3532 //------------------------------ clone_for_use_outside_loop -------------------------------------
3533 // clone "n" for uses that are outside of loop
3534 int PhaseIdealLoop::clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist ) {
3535   int cloned = 0;
3536   assert(worklist.size() == 0, "should be empty");
3537   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3538     Node* use = n->fast_out(j);
3539     if( !loop->is_member(get_loop(has_ctrl(use) ? get_ctrl(use) : use)) ) {
3540       worklist.push(use);
3541     }
3542   }
3543 
3544   if (C->check_node_count(worklist.size() + NodeLimitFudgeFactor,
3545                           "Too many clones required in clone_for_use_outside_loop in partial peeling")) {
3546     return -1;
3547   }
3548 
3549   while( worklist.size() ) {
3550     Node *use = worklist.pop();
3551     if (!has_node(use) || use->in(0) == C->top()) continue;
3552     uint j;
3553     for (j = 0; j < use->req(); j++) {
3554       if (use->in(j) == n) break;
3555     }
3556     assert(j < use->req(), "must be there");
3557 
3558     // clone "n" and insert it between the inputs of "n" and the use outside the loop
3559     Node* n_clone = n->clone();
3560     _igvn.replace_input_of(use, j, n_clone);
3561     cloned++;
3562     Node* use_c;
3563     if (!use->is_Phi()) {
3564       use_c = has_ctrl(use) ? get_ctrl(use) : use->in(0);
3565     } else {
3566       // Use in a phi is considered a use in the associated predecessor block
3567       use_c = use->in(0)->in(j);
3568     }
3569     set_ctrl(n_clone, use_c);
3570     assert(!loop->is_member(get_loop(use_c)), "should be outside loop");
3571     get_loop(use_c)->_body.push(n_clone);
3572     _igvn.register_new_node_with_optimizer(n_clone);
3573 #ifndef PRODUCT
3574     if (TracePartialPeeling) {
3575       tty->print_cr("loop exit cloning old: %d new: %d newbb: %d", n->_idx, n_clone->_idx, get_ctrl(n_clone)->_idx);
3576     }
3577 #endif
3578   }
3579   return cloned;
3580 }
3581 
3582 
3583 //------------------------------ clone_for_special_use_inside_loop -------------------------------------
3584 // clone "n" for special uses that are in the not_peeled region.
3585 // If these def-uses occur in separate blocks, the code generator
3586 // marks the method as not compilable.  For example, if a "BoolNode"
3587 // is in a different basic block than the "IfNode" that uses it, then
3588 // the compilation is aborted in the code generator.
3589 void PhaseIdealLoop::clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
3590                                                         VectorSet& not_peel, Node_List& sink_list, Node_List& worklist ) {
3591   if (n->is_Phi() || n->is_Load()) {
3592     return;
3593   }
3594   assert(worklist.size() == 0, "should be empty");
3595   for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
3596     Node* use = n->fast_out(j);
3597     if ( not_peel.test(use->_idx) &&
3598          (use->is_If() || use->is_CMove() || use->is_Bool() || use->is_OpaqueInitializedAssertionPredicate()) &&
3599          use->in(1) == n)  {
3600       worklist.push(use);
3601     }
3602   }
3603   if (worklist.size() > 0) {
3604     // clone "n" and insert it between inputs of "n" and the use
3605     Node* n_clone = n->clone();
3606     loop->_body.push(n_clone);
3607     _igvn.register_new_node_with_optimizer(n_clone);
3608     set_ctrl(n_clone, get_ctrl(n));
3609     sink_list.push(n_clone);
3610     not_peel.set(n_clone->_idx);
3611 #ifndef PRODUCT
3612     if (TracePartialPeeling) {
3613       tty->print_cr("special not_peeled cloning old: %d new: %d", n->_idx, n_clone->_idx);
3614     }
3615 #endif
3616     while( worklist.size() ) {
3617       Node *use = worklist.pop();
3618       _igvn.rehash_node_delayed(use);
3619       for (uint j = 1; j < use->req(); j++) {
3620         if (use->in(j) == n) {
3621           use->set_req(j, n_clone);
3622         }
3623       }
3624     }
3625   }
3626 }
3627 
3628 
3629 //------------------------------ insert_phi_for_loop -------------------------------------
3630 // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
3631 void PhaseIdealLoop::insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp ) {
3632   Node *phi = PhiNode::make(lp, back_edge_val);
3633   phi->set_req(LoopNode::EntryControl, lp_entry_val);
3634   // Use existing phi if it already exists
3635   Node *hit = _igvn.hash_find_insert(phi);
3636   if( hit == nullptr ) {
3637     _igvn.register_new_node_with_optimizer(phi);
3638     set_ctrl(phi, lp);
3639   } else {
3640     // Remove the new phi from the graph and use the hit
3641     _igvn.remove_dead_node(phi);
3642     phi = hit;
3643   }
3644   _igvn.replace_input_of(use, idx, phi);
3645 }
3646 
3647 #ifdef ASSERT
3648 //------------------------------ is_valid_loop_partition -------------------------------------
3649 // Validate the loop partition sets: peel and not_peel
3650 bool PhaseIdealLoop::is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list,
3651                                               VectorSet& not_peel ) {
3652   uint i;
3653   // Check that peel_list entries are in the peel set
3654   for (i = 0; i < peel_list.size(); i++) {
3655     if (!peel.test(peel_list.at(i)->_idx)) {
3656       return false;
3657     }
3658   }
3659   // Check at loop members are in one of peel set or not_peel set
3660   for (i = 0; i < loop->_body.size(); i++ ) {
3661     Node *def  = loop->_body.at(i);
3662     uint di = def->_idx;
3663     // Check that peel set elements are in peel_list
3664     if (peel.test(di)) {
3665       if (not_peel.test(di)) {
3666         return false;
3667       }
3668       // Must be in peel_list also
3669       bool found = false;
3670       for (uint j = 0; j < peel_list.size(); j++) {
3671         if (peel_list.at(j)->_idx == di) {
3672           found = true;
3673           break;
3674         }
3675       }
3676       if (!found) {
3677         return false;
3678       }
3679     } else if (not_peel.test(di)) {
3680       if (peel.test(di)) {
3681         return false;
3682       }
3683     } else {
3684       return false;
3685     }
3686   }
3687   return true;
3688 }
3689 
3690 //------------------------------ is_valid_clone_loop_exit_use -------------------------------------
3691 // Ensure a use outside of loop is of the right form
3692 bool PhaseIdealLoop::is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx) {
3693   Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3694   return (use->is_Phi() &&
3695           use_c->is_Region() && use_c->req() == 3 &&
3696           (use_c->in(exit_idx)->Opcode() == Op_IfTrue ||
3697            use_c->in(exit_idx)->Opcode() == Op_IfFalse ||
3698            use_c->in(exit_idx)->Opcode() == Op_JumpProj) &&
3699           loop->is_member( get_loop( use_c->in(exit_idx)->in(0) ) ) );
3700 }
3701 
3702 //------------------------------ is_valid_clone_loop_form -------------------------------------
3703 // Ensure that all uses outside of loop are of the right form
3704 bool PhaseIdealLoop::is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
3705                                                uint orig_exit_idx, uint clone_exit_idx) {
3706   uint len = peel_list.size();
3707   for (uint i = 0; i < len; i++) {
3708     Node *def = peel_list.at(i);
3709 
3710     for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
3711       Node *use = def->fast_out(j);
3712       Node *use_c = has_ctrl(use) ? get_ctrl(use) : use;
3713       if (!loop->is_member(get_loop(use_c))) {
3714         // use is not in the loop, check for correct structure
3715         if (use->in(0) == def) {
3716           // Okay
3717         } else if (!is_valid_clone_loop_exit_use(loop, use, orig_exit_idx)) {
3718           return false;
3719         }
3720       }
3721     }
3722   }
3723   return true;
3724 }
3725 #endif
3726 
3727 //------------------------------ partial_peel -------------------------------------
3728 // Partially peel (aka loop rotation) the top portion of a loop (called
3729 // the peel section below) by cloning it and placing one copy just before
3730 // the new loop head and the other copy at the bottom of the new loop.
3731 //
3732 //    before                       after                where it came from
3733 //
3734 //    stmt1                        stmt1
3735 //  loop:                          stmt2                     clone
3736 //    stmt2                        if condA goto exitA       clone
3737 //    if condA goto exitA        new_loop:                   new
3738 //    stmt3                        stmt3                     clone
3739 //    if !condB goto loop          if condB goto exitB       clone
3740 //  exitB:                         stmt2                     orig
3741 //    stmt4                        if !condA goto new_loop   orig
3742 //  exitA:                         goto exitA
3743 //                               exitB:
3744 //                                 stmt4
3745 //                               exitA:
3746 //
3747 // Step 1: find the cut point: an exit test on probable
3748 //         induction variable.
3749 // Step 2: schedule (with cloning) operations in the peel
3750 //         section that can be executed after the cut into
3751 //         the section that is not peeled.  This may need
3752 //         to clone operations into exit blocks.  For
3753 //         instance, a reference to A[i] in the not-peel
3754 //         section and a reference to B[i] in an exit block
3755 //         may cause a left-shift of i by 2 to be placed
3756 //         in the peel block.  This step will clone the left
3757 //         shift into the exit block and sink the left shift
3758 //         from the peel to the not-peel section.
3759 // Step 3: clone the loop, retarget the control, and insert
3760 //         phis for values that are live across the new loop
3761 //         head.  This is very dependent on the graph structure
3762 //         from clone_loop.  It creates region nodes for
3763 //         exit control and associated phi nodes for values
3764 //         flow out of the loop through that exit.  The region
3765 //         node is dominated by the clone's control projection.
3766 //         So the clone's peel section is placed before the
3767 //         new loop head, and the clone's not-peel section is
3768 //         forms the top part of the new loop.  The original
3769 //         peel section forms the tail of the new loop.
3770 // Step 4: update the dominator tree and recompute the
3771 //         dominator depth.
3772 //
3773 //                   orig
3774 //
3775 //                   stmt1
3776 //                     |
3777 //                     v
3778 //                 predicates
3779 //                     |
3780 //                     v
3781 //                   loop<----+
3782 //                     |      |
3783 //                   stmt2    |
3784 //                     |      |
3785 //                     v      |
3786 //                    ifA     |
3787 //                   / |      |
3788 //                  v  v      |
3789 //               false true   ^  <-- last_peel
3790 //               /     |      |
3791 //              /   ===|==cut |
3792 //             /     stmt3    |  <-- first_not_peel
3793 //            /        |      |
3794 //            |        v      |
3795 //            v       ifB     |
3796 //          exitA:   / \      |
3797 //                  /   \     |
3798 //                 v     v    |
3799 //               false true   |
3800 //               /       \    |
3801 //              /         ----+
3802 //             |
3803 //             v
3804 //           exitB:
3805 //           stmt4
3806 //
3807 //
3808 //            after clone loop
3809 //
3810 //                   stmt1
3811 //                     |
3812 //                     v
3813 //                predicates
3814 //                 /       \
3815 //        clone   /         \   orig
3816 //               /           \
3817 //              /             \
3818 //             v               v
3819 //   +---->loop                loop<----+
3820 //   |      |                    |      |
3821 //   |    stmt2                stmt2    |
3822 //   |      |                    |      |
3823 //   |      v                    v      |
3824 //   |      ifA                 ifA     |
3825 //   |      | \                / |      |
3826 //   |      v  v              v  v      |
3827 //   ^    true  false      false true   ^  <-- last_peel
3828 //   |      |   ^   \       /    |      |
3829 //   | cut==|==  \   \     /  ===|==cut |
3830 //   |    stmt3   \   \   /    stmt3    |  <-- first_not_peel
3831 //   |      |    dom   | |       |      |
3832 //   |      v      \  1v v2      v      |
3833 //   |      ifB     regionA     ifB     |
3834 //   |      / \        |       / \      |
3835 //   |     /   \       v      /   \     |
3836 //   |    v     v    exitA:  v     v    |
3837 //   |    true  false      false true   |
3838 //   |    /     ^   \      /       \    |
3839 //   +----       \   \    /         ----+
3840 //               dom  \  /
3841 //                 \  1v v2
3842 //                  regionB
3843 //                     |
3844 //                     v
3845 //                   exitB:
3846 //                   stmt4
3847 //
3848 //
3849 //           after partial peel
3850 //
3851 //                  stmt1
3852 //                     |
3853 //                     v
3854 //                predicates
3855 //                 /
3856 //        clone   /             orig
3857 //               /          TOP
3858 //              /             \
3859 //             v               v
3860 //    TOP->loop                loop----+
3861 //          |                    |      |
3862 //        stmt2                stmt2    |
3863 //          |                    |      |
3864 //          v                    v      |
3865 //          ifA                 ifA     |
3866 //          | \                / |      |
3867 //          v  v              v  v      |
3868 //        true  false      false true   |     <-- last_peel
3869 //          |   ^   \       /    +------|---+
3870 //  +->newloop   \   \     /  === ==cut |   |
3871 //  |     stmt3   \   \   /     TOP     |   |
3872 //  |       |    dom   | |      stmt3   |   | <-- first_not_peel
3873 //  |       v      \  1v v2      v      |   |
3874 //  |       ifB     regionA     ifB     ^   v
3875 //  |       / \        |       / \      |   |
3876 //  |      /   \       v      /   \     |   |
3877 //  |     v     v    exitA:  v     v    |   |
3878 //  |     true  false      false true   |   |
3879 //  |     /     ^   \      /       \    |   |
3880 //  |    |       \   \    /         v   |   |
3881 //  |    |       dom  \  /         TOP  |   |
3882 //  |    |         \  1v v2             |   |
3883 //  ^    v          regionB             |   |
3884 //  |    |             |                |   |
3885 //  |    |             v                ^   v
3886 //  |    |           exitB:             |   |
3887 //  |    |           stmt4              |   |
3888 //  |    +------------>-----------------+   |
3889 //  |                                       |
3890 //  +-----------------<---------------------+
3891 //
3892 //
3893 //              final graph
3894 //
3895 //                  stmt1
3896 //                    |
3897 //                    v
3898 //                predicates
3899 //                    |
3900 //                    v
3901 //                  stmt2 clone
3902 //                    |
3903 //                    v
3904 //         ........> ifA clone
3905 //         :        / |
3906 //        dom      /  |
3907 //         :      v   v
3908 //         :  false   true
3909 //         :  |       |
3910 //         :  |       v
3911 //         :  |    newloop<-----+
3912 //         :  |        |        |
3913 //         :  |     stmt3 clone |
3914 //         :  |        |        |
3915 //         :  |        v        |
3916 //         :  |       ifB       |
3917 //         :  |      / \        |
3918 //         :  |     v   v       |
3919 //         :  |  false true     |
3920 //         :  |   |     |       |
3921 //         :  |   v    stmt2    |
3922 //         :  | exitB:  |       |
3923 //         :  | stmt4   v       |
3924 //         :  |       ifA orig  |
3925 //         :  |      /  \       |
3926 //         :  |     /    \      |
3927 //         :  |    v     v      |
3928 //         :  |  false  true    |
3929 //         :  |  /        \     |
3930 //         :  v  v         -----+
3931 //          RegionA
3932 //             |
3933 //             v
3934 //           exitA
3935 //
3936 bool PhaseIdealLoop::partial_peel( IdealLoopTree *loop, Node_List &old_new ) {
3937 
3938   assert(!loop->_head->is_CountedLoop(), "Non-counted loop only");
3939   if (!loop->_head->is_Loop()) {
3940     return false;
3941   }
3942   LoopNode *head = loop->_head->as_Loop();
3943 
3944   if (head->is_partial_peel_loop() || head->partial_peel_has_failed()) {
3945     return false;
3946   }
3947 
3948   // Check for complex exit control
3949   for (uint ii = 0; ii < loop->_body.size(); ii++) {
3950     Node *n = loop->_body.at(ii);
3951     int opc = n->Opcode();
3952     if (n->is_Call()        ||
3953         opc == Op_Catch     ||
3954         opc == Op_CatchProj ||
3955         opc == Op_Jump      ||
3956         opc == Op_JumpProj) {
3957 #ifndef PRODUCT
3958       if (TracePartialPeeling) {
3959         tty->print_cr("\nExit control too complex: lp: %d", head->_idx);
3960       }
3961 #endif
3962       return false;
3963     }
3964   }
3965 
3966   int dd = dom_depth(head);
3967 
3968   // Step 1: find cut point
3969 
3970   // Walk up dominators to loop head looking for first loop exit
3971   // which is executed on every path thru loop.
3972   IfNode *peel_if = nullptr;
3973   IfNode *peel_if_cmpu = nullptr;
3974 
3975   Node *iff = loop->tail();
3976   while (iff != head) {
3977     if (iff->is_If()) {
3978       Node *ctrl = get_ctrl(iff->in(1));
3979       if (ctrl->is_top()) return false; // Dead test on live IF.
3980       // If loop-varying exit-test, check for induction variable
3981       if (loop->is_member(get_loop(ctrl)) &&
3982           loop->is_loop_exit(iff) &&
3983           is_possible_iv_test(iff)) {
3984         Node* cmp = iff->in(1)->in(1);
3985         if (cmp->Opcode() == Op_CmpI) {
3986           peel_if = iff->as_If();
3987         } else {
3988           assert(cmp->Opcode() == Op_CmpU, "must be CmpI or CmpU");
3989           peel_if_cmpu = iff->as_If();
3990         }
3991       }
3992     }
3993     iff = idom(iff);
3994   }
3995 
3996   // Prefer signed compare over unsigned compare.
3997   IfNode* new_peel_if = nullptr;
3998   if (peel_if == nullptr) {
3999     if (!PartialPeelAtUnsignedTests || peel_if_cmpu == nullptr) {
4000       return false;   // No peel point found
4001     }
4002     new_peel_if = insert_cmpi_loop_exit(peel_if_cmpu, loop);
4003     if (new_peel_if == nullptr) {
4004       return false;   // No peel point found
4005     }
4006     peel_if = new_peel_if;
4007   }
4008   Node* last_peel        = stay_in_loop(peel_if, loop);
4009   Node* first_not_peeled = stay_in_loop(last_peel, loop);
4010   if (first_not_peeled == nullptr || first_not_peeled == head) {
4011     return false;
4012   }
4013 
4014 #ifndef PRODUCT
4015   if (TraceLoopOpts) {
4016     tty->print("PartialPeel  ");
4017     loop->dump_head();
4018   }
4019 
4020   if (TracePartialPeeling) {
4021     tty->print_cr("before partial peel one iteration");
4022     Node_List wl;
4023     Node* t = head->in(2);
4024     while (true) {
4025       wl.push(t);
4026       if (t == head) break;
4027       t = idom(t);
4028     }
4029     while (wl.size() > 0) {
4030       Node* tt = wl.pop();
4031       tt->dump();
4032       if (tt == last_peel) tty->print_cr("-- cut --");
4033     }
4034   }
4035 #endif
4036 
4037   C->print_method(PHASE_BEFORE_PARTIAL_PEELING, 4, head);
4038 
4039   VectorSet peel;
4040   VectorSet not_peel;
4041   Node_List peel_list;
4042   Node_List worklist;
4043   Node_List sink_list;
4044 
4045   uint estimate = loop->est_loop_clone_sz(1);
4046   if (exceeding_node_budget(estimate)) {
4047     return false;
4048   }
4049 
4050   // Set of cfg nodes to peel are those that are executable from
4051   // the head through last_peel.
4052   assert(worklist.size() == 0, "should be empty");
4053   worklist.push(head);
4054   peel.set(head->_idx);
4055   while (worklist.size() > 0) {
4056     Node *n = worklist.pop();
4057     if (n != last_peel) {
4058       for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
4059         Node* use = n->fast_out(j);
4060         if (use->is_CFG() &&
4061             loop->is_member(get_loop(use)) &&
4062             !peel.test_set(use->_idx)) {
4063           worklist.push(use);
4064         }
4065       }
4066     }
4067   }
4068 
4069   // Set of non-cfg nodes to peel are those that are control
4070   // dependent on the cfg nodes.
4071   for (uint i = 0; i < loop->_body.size(); i++) {
4072     Node *n = loop->_body.at(i);
4073     Node *n_c = has_ctrl(n) ? get_ctrl(n) : n;
4074     if (peel.test(n_c->_idx)) {
4075       peel.set(n->_idx);
4076     } else {
4077       not_peel.set(n->_idx);
4078     }
4079   }
4080 
4081   // Step 2: move operations from the peeled section down into the
4082   //         not-peeled section
4083 
4084   // Get a post order schedule of nodes in the peel region
4085   // Result in right-most operand.
4086   scheduled_nodelist(loop, peel, peel_list);
4087 
4088   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4089 
4090   // For future check for too many new phis
4091   uint old_phi_cnt = 0;
4092   for (DUIterator_Fast jmax, j = head->fast_outs(jmax); j < jmax; j++) {
4093     Node* use = head->fast_out(j);
4094     if (use->is_Phi()) old_phi_cnt++;
4095   }
4096 
4097 #ifndef PRODUCT
4098   if (TracePartialPeeling) {
4099     tty->print_cr("\npeeled list");
4100   }
4101 #endif
4102 
4103   // Evacuate nodes in peel region into the not_peeled region if possible
4104   bool too_many_clones = false;
4105   uint new_phi_cnt = 0;
4106   uint cloned_for_outside_use = 0;
4107   for (uint i = 0; i < peel_list.size();) {
4108     Node* n = peel_list.at(i);
4109 #ifndef PRODUCT
4110   if (TracePartialPeeling) n->dump();
4111 #endif
4112     bool incr = true;
4113     if (!n->is_CFG()) {
4114       if (has_use_in_set(n, not_peel)) {
4115         // If not used internal to the peeled region,
4116         // move "n" from peeled to not_peeled region.
4117         if (!has_use_internal_to_set(n, peel, loop)) {
4118           // if not pinned and not a load (which maybe anti-dependent on a store)
4119           // and not a CMove (Matcher expects only bool->cmove).
4120           if (n->in(0) == nullptr && !n->is_Load() && !n->is_CMove()) {
4121             int new_clones = clone_for_use_outside_loop(loop, n, worklist);
4122             if (C->failing()) return false;
4123             if (new_clones == -1) {
4124               too_many_clones = true;
4125               break;
4126             }
4127             cloned_for_outside_use += new_clones;
4128             sink_list.push(n);
4129             peel.remove(n->_idx);
4130             not_peel.set(n->_idx);
4131             peel_list.remove(i);
4132             incr = false;
4133 #ifndef PRODUCT
4134             if (TracePartialPeeling) {
4135               tty->print_cr("sink to not_peeled region: %d newbb: %d",
4136                             n->_idx, get_ctrl(n)->_idx);
4137             }
4138 #endif
4139           }
4140         } else {
4141           // Otherwise check for special def-use cases that span
4142           // the peel/not_peel boundary such as bool->if
4143           clone_for_special_use_inside_loop(loop, n, not_peel, sink_list, worklist);
4144           new_phi_cnt++;
4145         }
4146       }
4147     }
4148     if (incr) i++;
4149   }
4150 
4151   estimate += cloned_for_outside_use + new_phi_cnt;
4152   bool exceed_node_budget = !may_require_nodes(estimate);
4153   bool exceed_phi_limit = new_phi_cnt > old_phi_cnt + PartialPeelNewPhiDelta;
4154 
4155   if (too_many_clones || exceed_node_budget || exceed_phi_limit) {
4156 #ifndef PRODUCT
4157     if (TracePartialPeeling && exceed_phi_limit) {
4158       tty->print_cr("\nToo many new phis: %d  old %d new cmpi: %c",
4159                     new_phi_cnt, old_phi_cnt, new_peel_if != nullptr?'T':'F');
4160     }
4161 #endif
4162     if (new_peel_if != nullptr) {
4163       remove_cmpi_loop_exit(new_peel_if, loop);
4164     }
4165     // Inhibit more partial peeling on this loop
4166     assert(!head->is_partial_peel_loop(), "not partial peeled");
4167     head->mark_partial_peel_failed();
4168     if (cloned_for_outside_use > 0) {
4169       // Terminate this round of loop opts because
4170       // the graph outside this loop was changed.
4171       C->set_major_progress();
4172       return true;
4173     }
4174     return false;
4175   }
4176 
4177   // Step 3: clone loop, retarget control, and insert new phis
4178 
4179   // Create new loop head for new phis and to hang
4180   // the nodes being moved (sinked) from the peel region.
4181   LoopNode* new_head = new LoopNode(last_peel, last_peel);
4182   new_head->set_unswitch_count(head->unswitch_count()); // Preserve
4183   _igvn.register_new_node_with_optimizer(new_head);
4184   assert(first_not_peeled->in(0) == last_peel, "last_peel <- first_not_peeled");
4185   _igvn.replace_input_of(first_not_peeled, 0, new_head);
4186   set_loop(new_head, loop);
4187   loop->_body.push(new_head);
4188   not_peel.set(new_head->_idx);
4189   set_idom(new_head, last_peel, dom_depth(first_not_peeled));
4190   set_idom(first_not_peeled, new_head, dom_depth(first_not_peeled));
4191 
4192   while (sink_list.size() > 0) {
4193     Node* n = sink_list.pop();
4194     set_ctrl(n, new_head);
4195   }
4196 
4197   assert(is_valid_loop_partition(loop, peel, peel_list, not_peel), "bad partition");
4198 
4199   clone_loop(loop, old_new, dd, IgnoreStripMined);
4200 
4201   const uint clone_exit_idx = 1;
4202   const uint orig_exit_idx  = 2;
4203   assert(is_valid_clone_loop_form(loop, peel_list, orig_exit_idx, clone_exit_idx), "bad clone loop");
4204 
4205   Node* head_clone             = old_new[head->_idx];
4206   LoopNode* new_head_clone     = old_new[new_head->_idx]->as_Loop();
4207   Node* orig_tail_clone        = head_clone->in(2);
4208 
4209   // Add phi if "def" node is in peel set and "use" is not
4210 
4211   for (uint i = 0; i < peel_list.size(); i++) {
4212     Node *def  = peel_list.at(i);
4213     if (!def->is_CFG()) {
4214       for (DUIterator_Fast jmax, j = def->fast_outs(jmax); j < jmax; j++) {
4215         Node *use = def->fast_out(j);
4216         if (has_node(use) && use->in(0) != C->top() &&
4217             (!peel.test(use->_idx) ||
4218              (use->is_Phi() && use->in(0) == head)) ) {
4219           worklist.push(use);
4220         }
4221       }
4222       while( worklist.size() ) {
4223         Node *use = worklist.pop();
4224         for (uint j = 1; j < use->req(); j++) {
4225           Node* n = use->in(j);
4226           if (n == def) {
4227 
4228             // "def" is in peel set, "use" is not in peel set
4229             // or "use" is in the entry boundary (a phi) of the peel set
4230 
4231             Node* use_c = has_ctrl(use) ? get_ctrl(use) : use;
4232 
4233             if ( loop->is_member(get_loop( use_c )) ) {
4234               // use is in loop
4235               if (old_new[use->_idx] != nullptr) { // null for dead code
4236                 Node* use_clone = old_new[use->_idx];
4237                 _igvn.replace_input_of(use, j, C->top());
4238                 insert_phi_for_loop( use_clone, j, old_new[def->_idx], def, new_head_clone );
4239               }
4240             } else {
4241               assert(is_valid_clone_loop_exit_use(loop, use, orig_exit_idx), "clone loop format");
4242               // use is not in the loop, check if the live range includes the cut
4243               Node* lp_if = use_c->in(orig_exit_idx)->in(0);
4244               if (not_peel.test(lp_if->_idx)) {
4245                 assert(j == orig_exit_idx, "use from original loop");
4246                 insert_phi_for_loop( use, clone_exit_idx, old_new[def->_idx], def, new_head_clone );
4247               }
4248             }
4249           }
4250         }
4251       }
4252     }
4253   }
4254 
4255   // Step 3b: retarget control
4256 
4257   // Redirect control to the new loop head if a cloned node in
4258   // the not_peeled region has control that points into the peeled region.
4259   // This necessary because the cloned peeled region will be outside
4260   // the loop.
4261   //                            from    to
4262   //          cloned-peeled    <---+
4263   //    new_head_clone:            |    <--+
4264   //          cloned-not_peeled  in(0)    in(0)
4265   //          orig-peeled
4266 
4267   for (uint i = 0; i < loop->_body.size(); i++) {
4268     Node *n = loop->_body.at(i);
4269     if (!n->is_CFG()           && n->in(0) != nullptr        &&
4270         not_peel.test(n->_idx) && peel.test(n->in(0)->_idx)) {
4271       Node* n_clone = old_new[n->_idx];
4272       if (n_clone->depends_only_on_test()) {
4273         // Pin array access nodes: control is updated here to the loop head. If, after some transformations, the
4274         // backedge is removed, an array load could become dependent on a condition that's not a range check for that
4275         // access. If that condition is replaced by an identical dominating one, then an unpinned load would risk
4276         // floating above its range check.
4277         Node* pinned_clone = n_clone->pin_array_access_node();
4278         if (pinned_clone != nullptr) {
4279           register_new_node_with_ctrl_of(pinned_clone, n_clone);
4280           old_new.map(n->_idx, pinned_clone);
4281           _igvn.replace_node(n_clone, pinned_clone);
4282           n_clone = pinned_clone;
4283         }
4284       }
4285       _igvn.replace_input_of(n_clone, 0, new_head_clone);
4286     }
4287   }
4288 
4289   // Backedge of the surviving new_head (the clone) is original last_peel
4290   _igvn.replace_input_of(new_head_clone, LoopNode::LoopBackControl, last_peel);
4291 
4292   // Cut first node in original not_peel set
4293   _igvn.rehash_node_delayed(new_head);                     // Multiple edge updates:
4294   new_head->set_req(LoopNode::EntryControl,    C->top());  //   use rehash_node_delayed / set_req instead of
4295   new_head->set_req(LoopNode::LoopBackControl, C->top());  //   multiple replace_input_of calls
4296 
4297   // Copy head_clone back-branch info to original head
4298   // and remove original head's loop entry and
4299   // clone head's back-branch
4300   _igvn.rehash_node_delayed(head); // Multiple edge updates
4301   head->set_req(LoopNode::EntryControl,    head_clone->in(LoopNode::LoopBackControl));
4302   head->set_req(LoopNode::LoopBackControl, C->top());
4303   _igvn.replace_input_of(head_clone, LoopNode::LoopBackControl, C->top());
4304 
4305   // Similarly modify the phis
4306   for (DUIterator_Fast kmax, k = head->fast_outs(kmax); k < kmax; k++) {
4307     Node* use = head->fast_out(k);
4308     if (use->is_Phi() && use->outcnt() > 0) {
4309       Node* use_clone = old_new[use->_idx];
4310       _igvn.rehash_node_delayed(use); // Multiple edge updates
4311       use->set_req(LoopNode::EntryControl,    use_clone->in(LoopNode::LoopBackControl));
4312       use->set_req(LoopNode::LoopBackControl, C->top());
4313       _igvn.replace_input_of(use_clone, LoopNode::LoopBackControl, C->top());
4314     }
4315   }
4316 
4317   // Step 4: update dominator tree and dominator depth
4318 
4319   set_idom(head, orig_tail_clone, dd);
4320   recompute_dom_depth();
4321 
4322   // Inhibit more partial peeling on this loop
4323   new_head_clone->set_partial_peel_loop();
4324   C->set_major_progress();
4325   loop->record_for_igvn();
4326 
4327 #ifndef PRODUCT
4328   if (TracePartialPeeling) {
4329     tty->print_cr("\nafter partial peel one iteration");
4330     Node_List wl;
4331     Node* t = last_peel;
4332     while (true) {
4333       wl.push(t);
4334       if (t == head_clone) break;
4335       t = idom(t);
4336     }
4337     while (wl.size() > 0) {
4338       Node* tt = wl.pop();
4339       if (tt == head) tty->print_cr("orig head");
4340       else if (tt == new_head_clone) tty->print_cr("new head");
4341       else if (tt == head_clone) tty->print_cr("clone head");
4342       tt->dump();
4343     }
4344   }
4345 #endif
4346 
4347   C->print_method(PHASE_AFTER_PARTIAL_PEELING, 4, new_head_clone);
4348 
4349   return true;
4350 }
4351 
4352 // Transform:
4353 //
4354 // loop<-----------------+
4355 //  |                    |
4356 // stmt1 stmt2 .. stmtn  |
4357 //  |     |        |     |
4358 //  \     |       /      |
4359 //    v   v     v        |
4360 //       region          |
4361 //         |             |
4362 //     shared_stmt       |
4363 //         |             |
4364 //         v             |
4365 //         if            |
4366 //         / \           |
4367 //        |   -----------+
4368 //        v
4369 //
4370 // into:
4371 //
4372 //    loop<-------------------+
4373 //     |                      |
4374 //     v                      |
4375 // +->loop                    |
4376 // |   |                      |
4377 // |  stmt1 stmt2 .. stmtn    |
4378 // |   |     |        |       |
4379 // |   |      \       /       |
4380 // |   |       v     v        |
4381 // |   |        region1       |
4382 // |   |           |          |
4383 // |  shared_stmt shared_stmt |
4384 // |   |           |          |
4385 // |   v           v          |
4386 // |   if          if         |
4387 // |   /\          / \        |
4388 // +--   |         |   -------+
4389 //       \         /
4390 //        v       v
4391 //         region2
4392 //
4393 // (region2 is shown to merge mirrored projections of the loop exit
4394 // ifs to make the diagram clearer but they really merge the same
4395 // projection)
4396 //
4397 // Conditions for this transformation to trigger:
4398 // - the path through stmt1 is frequent enough
4399 // - the inner loop will be turned into a counted loop after transformation
4400 bool PhaseIdealLoop::duplicate_loop_backedge(IdealLoopTree *loop, Node_List &old_new) {
4401   if (!DuplicateBackedge) {
4402     return false;
4403   }
4404   assert(!loop->_head->is_CountedLoop() || StressDuplicateBackedge, "Non-counted loop only");
4405   if (!loop->_head->is_Loop()) {
4406     return false;
4407   }
4408 
4409   uint estimate = loop->est_loop_clone_sz(1);
4410   if (exceeding_node_budget(estimate)) {
4411     return false;
4412   }
4413 
4414   LoopNode *head = loop->_head->as_Loop();
4415 
4416   Node* region = nullptr;
4417   IfNode* exit_test = nullptr;
4418   uint inner;
4419   float f;
4420   if (StressDuplicateBackedge) {
4421     if (head->is_strip_mined()) {
4422       return false;
4423     }
4424     Node* c = head->in(LoopNode::LoopBackControl);
4425 
4426     while (c != head) {
4427       if (c->is_Region()) {
4428         region = c;
4429       }
4430       c = idom(c);
4431     }
4432 
4433     if (region == nullptr) {
4434       return false;
4435     }
4436 
4437     inner = 1;
4438   } else {
4439     // Is the shape of the loop that of a counted loop...
4440     Node* back_control = loop_exit_control(head, loop);
4441     if (back_control == nullptr) {
4442       return false;
4443     }
4444 
4445     BoolTest::mask bt = BoolTest::illegal;
4446     float cl_prob = 0;
4447     Node* incr = nullptr;
4448     Node* limit = nullptr;
4449     Node* cmp = loop_exit_test(back_control, loop, incr, limit, bt, cl_prob);
4450     if (cmp == nullptr || cmp->Opcode() != Op_CmpI) {
4451       return false;
4452     }
4453 
4454     // With an extra phi for the candidate iv?
4455     // Or the region node is the loop head
4456     if (!incr->is_Phi() || incr->in(0) == head) {
4457       return false;
4458     }
4459 
4460     PathFrequency pf(head, this);
4461     region = incr->in(0);
4462 
4463     // Go over all paths for the extra phi's region and see if that
4464     // path is frequent enough and would match the expected iv shape
4465     // if the extra phi is removed
4466     inner = 0;
4467     for (uint i = 1; i < incr->req(); ++i) {
4468       Node* in = incr->in(i);
4469       Node* trunc1 = nullptr;
4470       Node* trunc2 = nullptr;
4471       const TypeInteger* iv_trunc_t = nullptr;
4472       Node* orig_in = in;
4473       if (!(in = CountedLoopNode::match_incr_with_optional_truncation(in, &trunc1, &trunc2, &iv_trunc_t, T_INT))) {
4474         continue;
4475       }
4476       assert(in->Opcode() == Op_AddI, "wrong increment code");
4477       Node* xphi = nullptr;
4478       Node* stride = loop_iv_stride(in, xphi);
4479 
4480       if (stride == nullptr) {
4481         continue;
4482       }
4483 
4484       PhiNode* phi = loop_iv_phi(xphi, nullptr, head);
4485       if (phi == nullptr ||
4486           (trunc1 == nullptr && phi->in(LoopNode::LoopBackControl) != incr) ||
4487           (trunc1 != nullptr && phi->in(LoopNode::LoopBackControl) != trunc1)) {
4488         return false;
4489       }
4490 
4491       f = pf.to(region->in(i));
4492       if (f > 0.5) {
4493         inner = i;
4494         break;
4495       }
4496     }
4497 
4498     if (inner == 0) {
4499       return false;
4500     }
4501 
4502     exit_test = back_control->in(0)->as_If();
4503   }
4504 
4505   if (idom(region)->is_Catch()) {
4506     return false;
4507   }
4508 
4509   // Collect all control nodes that need to be cloned (shared_stmt in the diagram)
4510   Unique_Node_List wq;
4511   wq.push(head->in(LoopNode::LoopBackControl));
4512   for (uint i = 0; i < wq.size(); i++) {
4513     Node* c = wq.at(i);
4514     assert(get_loop(c) == loop, "not in the right loop?");
4515     if (c->is_Region()) {
4516       if (c != region) {
4517         for (uint j = 1; j < c->req(); ++j) {
4518           wq.push(c->in(j));
4519         }
4520       }
4521     } else {
4522       wq.push(c->in(0));
4523     }
4524     assert(!is_strict_dominator(c, region), "shouldn't go above region");
4525   }
4526 
4527   Node* region_dom = idom(region);
4528 
4529   // Can't do the transformation if this would cause a membar pair to
4530   // be split
4531   for (uint i = 0; i < wq.size(); i++) {
4532     Node* c = wq.at(i);
4533     if (c->is_MemBar() && (c->as_MemBar()->trailing_store() || c->as_MemBar()->trailing_load_store())) {
4534       assert(c->as_MemBar()->leading_membar()->trailing_membar() == c, "bad membar pair");
4535       if (!wq.member(c->as_MemBar()->leading_membar())) {
4536         return false;
4537       }
4538     }
4539   }
4540   C->print_method(PHASE_BEFORE_DUPLICATE_LOOP_BACKEDGE, 4, head);
4541 
4542   // Collect data nodes that need to be clones as well
4543   int dd = dom_depth(head);
4544 
4545   for (uint i = 0; i < loop->_body.size(); ++i) {
4546     Node* n = loop->_body.at(i);
4547     if (has_ctrl(n)) {
4548       Node* c = get_ctrl(n);
4549       if (wq.member(c)) {
4550         wq.push(n);
4551       }
4552     } else {
4553       set_idom(n, idom(n), dd);
4554     }
4555   }
4556 
4557   // clone shared_stmt
4558   clone_loop_body(wq, old_new, nullptr);
4559 
4560   Node* region_clone = old_new[region->_idx];
4561   region_clone->set_req(inner, C->top());
4562   set_idom(region, region->in(inner), dd);
4563 
4564   // Prepare the outer loop
4565   Node* outer_head = new LoopNode(head->in(LoopNode::EntryControl), old_new[head->in(LoopNode::LoopBackControl)->_idx]);
4566   register_control(outer_head, loop->_parent, outer_head->in(LoopNode::EntryControl));
4567   _igvn.replace_input_of(head, LoopNode::EntryControl, outer_head);
4568   set_idom(head, outer_head, dd);
4569 
4570   fix_body_edges(wq, loop, old_new, dd, loop->_parent, true);
4571 
4572   // Make one of the shared_stmt copies only reachable from stmt1, the
4573   // other only from stmt2..stmtn.
4574   Node* dom = nullptr;
4575   for (uint i = 1; i < region->req(); ++i) {
4576     if (i != inner) {
4577       _igvn.replace_input_of(region, i, C->top());
4578     }
4579     Node* in = region_clone->in(i);
4580     if (in->is_top()) {
4581       continue;
4582     }
4583     if (dom == nullptr) {
4584       dom = in;
4585     } else {
4586       dom = dom_lca(dom, in);
4587     }
4588   }
4589 
4590   set_idom(region_clone, dom, dd);
4591 
4592   // Set up the outer loop
4593   for (uint i = 0; i < head->outcnt(); i++) {
4594     Node* u = head->raw_out(i);
4595     if (u->is_Phi()) {
4596       Node* outer_phi = u->clone();
4597       outer_phi->set_req(0, outer_head);
4598       Node* backedge = old_new[u->in(LoopNode::LoopBackControl)->_idx];
4599       if (backedge == nullptr) {
4600         backedge = u->in(LoopNode::LoopBackControl);
4601       }
4602       outer_phi->set_req(LoopNode::LoopBackControl, backedge);
4603       register_new_node(outer_phi, outer_head);
4604       _igvn.replace_input_of(u, LoopNode::EntryControl, outer_phi);
4605     }
4606   }
4607 
4608   // create control and data nodes for out of loop uses (including region2)
4609   Node_List worklist;
4610   uint new_counter = C->unique();
4611   fix_ctrl_uses(wq, loop, old_new, ControlAroundStripMined, outer_head, nullptr, worklist);
4612 
4613   Node_List *split_if_set = nullptr;
4614   Node_List *split_bool_set = nullptr;
4615   Node_List *split_cex_set = nullptr;
4616   fix_data_uses(wq, loop, ControlAroundStripMined, loop->skip_strip_mined(), new_counter, old_new, worklist,
4617                 split_if_set, split_bool_set, split_cex_set);
4618 
4619   finish_clone_loop(split_if_set, split_bool_set, split_cex_set);
4620 
4621   if (exit_test != nullptr) {
4622     float cnt = exit_test->_fcnt;
4623     if (cnt != COUNT_UNKNOWN) {
4624       exit_test->_fcnt = cnt * f;
4625       old_new[exit_test->_idx]->as_If()->_fcnt = cnt * (1 - f);
4626     }
4627   }
4628 
4629   C->set_major_progress();
4630 
4631   C->print_method(PHASE_AFTER_DUPLICATE_LOOP_BACKEDGE, 4, outer_head);
4632 
4633   return true;
4634 }
4635 
4636 // AutoVectorize the loop: replace scalar ops with vector ops.
4637 PhaseIdealLoop::AutoVectorizeStatus
4638 PhaseIdealLoop::auto_vectorize(IdealLoopTree* lpt, VSharedData &vshared) {
4639   // Counted loop only
4640   if (!lpt->is_counted()) {
4641     return AutoVectorizeStatus::Impossible;
4642   }
4643 
4644   // Main-loop only
4645   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4646   if (!cl->is_main_loop()) {
4647     return AutoVectorizeStatus::Impossible;
4648   }
4649 
4650   VLoop vloop(lpt, false);
4651   if (!vloop.check_preconditions()) {
4652     return AutoVectorizeStatus::TriedAndFailed;
4653   }
4654 
4655   // Ensure the shared data is cleared before each use
4656   vshared.clear();
4657 
4658   const VLoopAnalyzer vloop_analyzer(vloop, vshared);
4659   if (!vloop_analyzer.success()) {
4660     return AutoVectorizeStatus::TriedAndFailed;
4661   }
4662 
4663   SuperWord sw(vloop_analyzer);
4664   if (!sw.transform_loop()) {
4665     return AutoVectorizeStatus::TriedAndFailed;
4666   }
4667 
4668   return AutoVectorizeStatus::Success;
4669 }
4670 
4671 // Just before insert_pre_post_loops, we can multiversion the loop:
4672 //
4673 //              multiversion_if
4674 //               |       |
4675 //         fast_loop   slow_loop
4676 //
4677 // In the fast_loop we can make speculative assumptions, and put the
4678 // conditions into the multiversion_if. If the conditions hold at runtime,
4679 // we enter the fast_loop, if the conditions fail, we take the slow_loop
4680 // instead which does not make any of the speculative assumptions.
4681 //
4682 // Note: we only multiversion the loop if the loop does not have any
4683 //       auto vectorization check Predicate. If we have that predicate,
4684 //       then we can simply add the speculative assumption checks to
4685 //       that Predicate. This means we do not need to duplicate the
4686 //       loop - we have a smaller graph and save compile time. Should
4687 //       the conditions ever fail, then we deopt / trap at the Predicate
4688 //       and recompile without that Predicate. At that point we will
4689 //       multiversion the loop, so that we can still have speculative
4690 //       runtime checks.
4691 //
4692 // We perform the multiversioning when the loop is still in its single
4693 // iteration form, even before we insert pre and post loops. This makes
4694 // the cloning much simpler. However, this means that both the fast
4695 // and the slow loop have to be optimized independently (adding pre
4696 // and post loops, unrolling the main loop, auto-vectorize etc.). And
4697 // we may end up not needing any speculative assumptions in the fast_loop
4698 // and then rejecting the slow_loop by constant folding the multiversion_if.
4699 //
4700 // Therefore, we "delay" the optimization of the slow_loop until we add
4701 // at least one speculative assumption for the fast_loop. If we never
4702 // add such a speculative runtime check, the OpaqueMultiversioningNode
4703 // of the multiversion_if constant folds to true after loop opts, and the
4704 // multiversion_if folds away the "delayed" slow_loop. If we add any
4705 // speculative assumption, then we notify the OpaqueMultiversioningNode
4706 // with "notify_slow_loop_that_it_can_resume_optimizations".
4707 //
4708 // Note: new runtime checks can be added to the multiversion_if with
4709 //       PhaseIdealLoop::create_new_if_for_multiversion
4710 void PhaseIdealLoop::maybe_multiversion_for_auto_vectorization_runtime_checks(IdealLoopTree* lpt, Node_List& old_new) {
4711   CountedLoopNode* cl = lpt->_head->as_CountedLoop();
4712   LoopNode* outer_loop = cl->skip_strip_mined();
4713   Node* entry = outer_loop->in(LoopNode::EntryControl);
4714 
4715   // Check we have multiversioning enabled, and are not already multiversioned.
4716   if (!LoopMultiversioning || cl->is_multiversion()) { return; }
4717 
4718   // Check that we do not have a parse-predicate where we can add the runtime checks
4719   // during auto-vectorization.
4720   const Predicates predicates(entry);
4721   const PredicateBlock* predicate_block = predicates.auto_vectorization_check_block();
4722   if (predicate_block->has_parse_predicate()) { return; }
4723 
4724   // Check node budget.
4725   uint estimate = lpt->est_loop_clone_sz(2);
4726   if (!may_require_nodes(estimate)) { return; }
4727 
4728   do_multiversioning(lpt, old_new);
4729 }
4730 
4731 // Returns true if the Reduction node is unordered.
4732 static bool is_unordered_reduction(Node* n) {
4733   return n->is_Reduction() && !n->as_Reduction()->requires_strict_order();
4734 }
4735 
4736 // Having ReductionNodes in the loop is expensive. They need to recursively
4737 // fold together the vector values, for every vectorized loop iteration. If
4738 // we encounter the following pattern, we can vector accumulate the values
4739 // inside the loop, and only have a single UnorderedReduction after the loop.
4740 //
4741 // Note: UnorderedReduction represents a ReductionNode which does not require
4742 // calculating in strict order.
4743 //
4744 // CountedLoop     init
4745 //          |        |
4746 //          +------+ | +-----------------------+
4747 //                 | | |                       |
4748 //                PhiNode (s)                  |
4749 //                  |                          |
4750 //                  |          Vector          |
4751 //                  |            |             |
4752 //               UnorderedReduction (first_ur) |
4753 //                  |                          |
4754 //                 ...         Vector          |
4755 //                  |            |             |
4756 //               UnorderedReduction (last_ur)  |
4757 //                       |                     |
4758 //                       +---------------------+
4759 //
4760 // We patch the graph to look like this:
4761 //
4762 // CountedLoop   identity_vector
4763 //         |         |
4764 //         +-------+ | +---------------+
4765 //                 | | |               |
4766 //                PhiNode (v)          |
4767 //                   |                 |
4768 //                   |         Vector  |
4769 //                   |           |     |
4770 //                 VectorAccumulator   |
4771 //                   |                 |
4772 //                  ...        Vector  |
4773 //                   |           |     |
4774 //      init       VectorAccumulator   |
4775 //        |          |     |           |
4776 //     UnorderedReduction  +-----------+
4777 //
4778 // We turned the scalar (s) Phi into a vectorized one (v). In the loop, we
4779 // use vector_accumulators, which do the same reductions, but only element
4780 // wise. This is a single operation per vector_accumulator, rather than many
4781 // for a UnorderedReduction. We can then reduce the last vector_accumulator
4782 // after the loop, and also reduce the init value into it.
4783 //
4784 // We can not do this with all reductions. Some reductions do not allow the
4785 // reordering of operations (for example float addition/multiplication require
4786 // strict order).
4787 void PhaseIdealLoop::move_unordered_reduction_out_of_loop(IdealLoopTree* loop) {
4788   assert(!C->major_progress() && loop->is_counted() && loop->is_innermost(), "sanity");
4789 
4790   // Find all Phi nodes with an unordered Reduction on backedge.
4791   CountedLoopNode* cl = loop->_head->as_CountedLoop();
4792   for (DUIterator_Fast jmax, j = cl->fast_outs(jmax); j < jmax; j++) {
4793     Node* phi = cl->fast_out(j);
4794     // We have a phi with a single use, and an unordered Reduction on the backedge.
4795     if (!phi->is_Phi() || phi->outcnt() != 1 || !is_unordered_reduction(phi->in(2))) {
4796       continue;
4797     }
4798 
4799     ReductionNode* last_ur = phi->in(2)->as_Reduction();
4800     assert(!last_ur->requires_strict_order(), "must be");
4801 
4802     // Determine types
4803     const TypeVect* vec_t = last_ur->vect_type();
4804     uint vector_length    = vec_t->length();
4805     BasicType bt          = vec_t->element_basic_type();
4806 
4807     // Convert opcode from vector-reduction -> scalar -> normal-vector-op
4808     const int sopc        = VectorNode::scalar_opcode(last_ur->Opcode(), bt);
4809     const int vopc        = VectorNode::opcode(sopc, bt);
4810     if (!Matcher::match_rule_supported_vector(vopc, vector_length, bt)) {
4811         DEBUG_ONLY( last_ur->dump(); )
4812         assert(false, "do not have normal vector op for this reduction");
4813         continue; // not implemented -> fails
4814     }
4815 
4816     // Traverse up the chain of unordered Reductions, checking that it loops back to
4817     // the phi. Check that all unordered Reductions only have a single use, except for
4818     // the last (last_ur), which only has phi as a use in the loop, and all other uses
4819     // are outside the loop.
4820     ReductionNode* current = last_ur;
4821     ReductionNode* first_ur = nullptr;
4822     while (true) {
4823       assert(!current->requires_strict_order(), "sanity");
4824 
4825       // Expect no ctrl and a vector_input from within the loop.
4826       Node* ctrl = current->in(0);
4827       Node* vector_input = current->in(2);
4828       if (ctrl != nullptr || get_ctrl(vector_input) != cl) {
4829         DEBUG_ONLY( current->dump(1); )
4830         assert(false, "reduction has ctrl or bad vector_input");
4831         break; // Chain traversal fails.
4832       }
4833 
4834       assert(current->vect_type() != nullptr, "must have vector type");
4835       if (current->vect_type() != last_ur->vect_type()) {
4836         // Reductions do not have the same vector type (length and element type).
4837         break; // Chain traversal fails.
4838       }
4839 
4840       // Expect single use of an unordered Reduction, except for last_ur.
4841       if (current == last_ur) {
4842         // Expect all uses to be outside the loop, except phi.
4843         for (DUIterator_Fast kmax, k = current->fast_outs(kmax); k < kmax; k++) {
4844           Node* use = current->fast_out(k);
4845           if (use != phi && ctrl_or_self(use) == cl) {
4846             DEBUG_ONLY( current->dump(-1); )
4847             assert(false, "reduction has use inside loop");
4848             // Should not be allowed by SuperWord::mark_reductions
4849             return; // bail out of optimization
4850           }
4851         }
4852       } else {
4853         if (current->outcnt() != 1) {
4854           break; // Chain traversal fails.
4855         }
4856       }
4857 
4858       // Expect another unordered Reduction or phi as the scalar input.
4859       Node* scalar_input = current->in(1);
4860       if (is_unordered_reduction(scalar_input) &&
4861           scalar_input->Opcode() == current->Opcode()) {
4862         // Move up the unordered Reduction chain.
4863         current = scalar_input->as_Reduction();
4864         assert(!current->requires_strict_order(), "must be");
4865       } else if (scalar_input == phi) {
4866         // Chain terminates at phi.
4867         first_ur = current;
4868         current = nullptr;
4869         break; // Success.
4870       } else {
4871         // scalar_input is neither phi nor a matching reduction
4872         // Can for example be scalar reduction when we have
4873         // partial vectorization.
4874         break; // Chain traversal fails.
4875       }
4876     }
4877     if (current != nullptr) {
4878       // Chain traversal was not successful.
4879       continue;
4880     }
4881     assert(first_ur != nullptr, "must have successfully terminated chain traversal");
4882 
4883     Node* identity_scalar = ReductionNode::make_identity_con_scalar(_igvn, sopc, bt);
4884     set_root_as_ctrl(identity_scalar);
4885     VectorNode* identity_vector = VectorNode::scalar2vector(identity_scalar, vector_length, bt);
4886     register_new_node(identity_vector, C->root());
4887     assert(vec_t == identity_vector->vect_type(), "matching vector type");
4888     VectorNode::trace_new_vector(identity_vector, "Unordered Reduction");
4889 
4890     // Turn the scalar phi into a vector phi.
4891     _igvn.rehash_node_delayed(phi);
4892     Node* init = phi->in(1); // Remember init before replacing it.
4893     phi->set_req_X(1, identity_vector, &_igvn);
4894     phi->as_Type()->set_type(vec_t);
4895     _igvn.set_type(phi, vec_t);
4896 
4897     // Traverse down the chain of unordered Reductions, and replace them with vector_accumulators.
4898     current = first_ur;
4899     while (true) {
4900       // Create vector_accumulator to replace current.
4901       Node* last_vector_accumulator = current->in(1);
4902       Node* vector_input            = current->in(2);
4903       VectorNode* vector_accumulator = VectorNode::make(vopc, last_vector_accumulator, vector_input, vec_t);
4904       register_new_node(vector_accumulator, cl);
4905       _igvn.replace_node(current, vector_accumulator);
4906       VectorNode::trace_new_vector(vector_accumulator, "Unordered Reduction");
4907       if (current == last_ur) {
4908         break;
4909       }
4910       current = vector_accumulator->unique_out()->as_Reduction();
4911       assert(!current->requires_strict_order(), "must be");
4912     }
4913 
4914     // Create post-loop reduction.
4915     Node* last_accumulator = phi->in(2);
4916     Node* post_loop_reduction = ReductionNode::make(sopc, nullptr, init, last_accumulator, bt);
4917 
4918     // Take over uses of last_accumulator that are not in the loop.
4919     for (DUIterator i = last_accumulator->outs(); last_accumulator->has_out(i); i++) {
4920       Node* use = last_accumulator->out(i);
4921       if (use != phi && use != post_loop_reduction) {
4922         assert(ctrl_or_self(use) != cl, "use must be outside loop");
4923         use->replace_edge(last_accumulator, post_loop_reduction,  &_igvn);
4924         --i;
4925       }
4926     }
4927     register_new_node(post_loop_reduction, get_late_ctrl(post_loop_reduction, cl));
4928     VectorNode::trace_new_vector(post_loop_reduction, "Unordered Reduction");
4929 
4930     assert(last_accumulator->outcnt() == 2, "last_accumulator has 2 uses: phi and post_loop_reduction");
4931     assert(post_loop_reduction->outcnt() > 0, "should have taken over all non loop uses of last_accumulator");
4932     assert(phi->outcnt() == 1, "accumulator is the only use of phi");
4933   }
4934 }
4935 
4936 void DataNodeGraph::clone_data_nodes(Node* new_ctrl) {
4937   for (uint i = 0; i < _data_nodes.size(); i++) {
4938     clone(_data_nodes[i], new_ctrl);
4939   }
4940 }
4941 
4942 // Clone the given node and set it up properly. Set 'new_ctrl' as ctrl.
4943 void DataNodeGraph::clone(Node* node, Node* new_ctrl) {
4944   Node* clone = node->clone();
4945   _phase->igvn().register_new_node_with_optimizer(clone);
4946   _orig_to_new.put(node, clone);
4947   _phase->set_ctrl(clone, new_ctrl);
4948   if (node->is_CastII()) {
4949     clone->set_req(0, new_ctrl);
4950   }
4951 }
4952 
4953 // Rewire the data inputs of all (unprocessed) cloned nodes, whose inputs are still pointing to the same inputs as their
4954 // corresponding orig nodes, to the newly cloned inputs to create a separate cloned graph.
4955 void DataNodeGraph::rewire_clones_to_cloned_inputs() {
4956   _orig_to_new.iterate_all([&](Node* node, Node* clone) {
4957     for (uint i = 1; i < node->req(); i++) {
4958       Node** cloned_input = _orig_to_new.get(node->in(i));
4959       if (cloned_input != nullptr) {
4960         // Input was also cloned -> rewire clone to the cloned input.
4961         _phase->igvn().replace_input_of(clone, i, *cloned_input);
4962       }
4963     }
4964   });
4965 }
4966 
4967 // Clone all non-OpaqueLoop* nodes and apply the provided transformation strategy for OpaqueLoop* nodes.
4968 // Set 'new_ctrl' as ctrl for all cloned non-OpaqueLoop* nodes.
4969 void DataNodeGraph::clone_data_nodes_and_transform_opaque_loop_nodes(
4970     const TransformStrategyForOpaqueLoopNodes& transform_strategy,
4971     Node* new_ctrl) {
4972   for (uint i = 0; i < _data_nodes.size(); i++) {
4973     Node* data_node = _data_nodes[i];
4974     if (data_node->is_Opaque1()) {
4975       transform_opaque_node(transform_strategy, data_node);
4976     } else {
4977       clone(data_node, new_ctrl);
4978     }
4979   }
4980 }
4981 
4982 void DataNodeGraph::transform_opaque_node(const TransformStrategyForOpaqueLoopNodes& transform_strategy, Node* node) {
4983   Node* transformed_node;
4984   if (node->is_OpaqueLoopInit()) {
4985     transformed_node = transform_strategy.transform_opaque_init(node->as_OpaqueLoopInit());
4986   } else {
4987     assert(node->is_OpaqueLoopStride(), "must be OpaqueLoopStrideNode");
4988     transformed_node = transform_strategy.transform_opaque_stride(node->as_OpaqueLoopStride());
4989   }
4990   // Add an orig->new mapping to correctly update the inputs of the copied graph in rewire_clones_to_cloned_inputs().
4991   _orig_to_new.put(node, transformed_node);
4992 }
--- EOF ---