1 /*
   2  * Copyright (c) 1998, 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 "ci/ciMethodData.hpp"
  26 #include "compiler/compileLog.hpp"
  27 #include "gc/shared/barrierSet.hpp"
  28 #include "gc/shared/c2/barrierSetC2.hpp"
  29 #include "libadt/vectset.hpp"
  30 #include "memory/allocation.inline.hpp"
  31 #include "memory/resourceArea.hpp"
  32 #include "opto/addnode.hpp"
  33 #include "opto/arraycopynode.hpp"
  34 #include "opto/c2_globals.hpp"
  35 #include "opto/callnode.hpp"
  36 #include "opto/castnode.hpp"
  37 #include "opto/connode.hpp"
  38 #include "opto/convertnode.hpp"
  39 #include "opto/divnode.hpp"
  40 #include "opto/idealGraphPrinter.hpp"
  41 #include "opto/loopnode.hpp"
  42 #include "opto/movenode.hpp"
  43 #include "opto/mulnode.hpp"
  44 #include "opto/opaquenode.hpp"
  45 #include "opto/opcodes.hpp"
  46 #include "opto/predicates.hpp"
  47 #include "opto/rootnode.hpp"
  48 #include "opto/runtime.hpp"
  49 #include "opto/vectorization.hpp"
  50 #include "runtime/sharedRuntime.hpp"
  51 #include "utilities/checkedCast.hpp"
  52 #include "utilities/powerOfTwo.hpp"
  53 
  54 //=============================================================================
  55 //--------------------------is_cloop_ind_var-----------------------------------
  56 // Determine if a node is a counted loop induction variable.
  57 // NOTE: The method is declared in "node.hpp".
  58 bool Node::is_cloop_ind_var() const {
  59   return (is_Phi() &&
  60           as_Phi()->region()->is_CountedLoop() &&
  61           as_Phi()->region()->as_CountedLoop()->phi() == this);
  62 }
  63 
  64 //=============================================================================
  65 //------------------------------dump_spec--------------------------------------
  66 // Dump special per-node info
  67 #ifndef PRODUCT
  68 void LoopNode::dump_spec(outputStream *st) const {
  69   RegionNode::dump_spec(st);
  70   if (is_inner_loop()) st->print( "inner " );
  71   if (is_partial_peel_loop()) st->print( "partial_peel " );
  72   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  73 }
  74 #endif
  75 
  76 //------------------------------is_valid_counted_loop-------------------------
  77 bool LoopNode::is_valid_counted_loop(BasicType bt) const {
  78   if (is_BaseCountedLoop() && as_BaseCountedLoop()->bt() == bt) {
  79     BaseCountedLoopNode*    l  = as_BaseCountedLoop();
  80     BaseCountedLoopEndNode* le = l->loopexit_or_null();
  81     if (le != nullptr &&
  82         le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  83       Node* phi  = l->phi();
  84       Node* exit = le->proj_out_or_null(0 /* false */);
  85       if (exit != nullptr && exit->Opcode() == Op_IfFalse &&
  86           phi != nullptr && phi->is_Phi() &&
  87           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  88           le->loopnode() == l && le->stride_is_con()) {
  89         return true;
  90       }
  91     }
  92   }
  93   return false;
  94 }
  95 
  96 //------------------------------get_early_ctrl---------------------------------
  97 // Compute earliest legal control
  98 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  99   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
 100   uint i;
 101   Node *early;
 102   if (n->in(0) && !n->is_expensive()) {
 103     early = n->in(0);
 104     if (!early->is_CFG()) // Might be a non-CFG multi-def
 105       early = get_ctrl(early);        // So treat input as a straight data input
 106     i = 1;
 107   } else {
 108     early = get_ctrl(n->in(1));
 109     i = 2;
 110   }
 111   uint e_d = dom_depth(early);
 112   assert( early, "" );
 113   for (; i < n->req(); i++) {
 114     Node *cin = get_ctrl(n->in(i));
 115     assert( cin, "" );
 116     // Keep deepest dominator depth
 117     uint c_d = dom_depth(cin);
 118     if (c_d > e_d) {           // Deeper guy?
 119       early = cin;              // Keep deepest found so far
 120       e_d = c_d;
 121     } else if (c_d == e_d &&    // Same depth?
 122                early != cin) { // If not equal, must use slower algorithm
 123       // If same depth but not equal, one _must_ dominate the other
 124       // and we want the deeper (i.e., dominated) guy.
 125       Node *n1 = early;
 126       Node *n2 = cin;
 127       while (1) {
 128         n1 = idom(n1);          // Walk up until break cycle
 129         n2 = idom(n2);
 130         if (n1 == cin ||        // Walked early up to cin
 131             dom_depth(n2) < c_d)
 132           break;                // early is deeper; keep him
 133         if (n2 == early ||      // Walked cin up to early
 134             dom_depth(n1) < c_d) {
 135           early = cin;          // cin is deeper; keep him
 136           break;
 137         }
 138       }
 139       e_d = dom_depth(early);   // Reset depth register cache
 140     }
 141   }
 142 
 143   // Return earliest legal location
 144   assert(early == find_non_split_ctrl(early), "unexpected early control");
 145 
 146   if (n->is_expensive() && !_verify_only && !_verify_me) {
 147     assert(n->in(0), "should have control input");
 148     early = get_early_ctrl_for_expensive(n, early);
 149   }
 150 
 151   return early;
 152 }
 153 
 154 //------------------------------get_early_ctrl_for_expensive---------------------------------
 155 // Move node up the dominator tree as high as legal while still beneficial
 156 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 157   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 158   assert(OptimizeExpensiveOps, "optimization off?");
 159 
 160   Node* ctl = n->in(0);
 161   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 162   uint min_dom_depth = dom_depth(earliest);
 163 #ifdef ASSERT
 164   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 165     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 166     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 167   }
 168 #endif
 169   if (dom_depth(ctl) < min_dom_depth) {
 170     return earliest;
 171   }
 172 
 173   while (true) {
 174     Node* next = ctl;
 175     // Moving the node out of a loop on the projection of an If
 176     // confuses Loop Predication. So, once we hit a loop in an If branch
 177     // that doesn't branch to an UNC, we stop. The code that process
 178     // expensive nodes will notice the loop and skip over it to try to
 179     // move the node further up.
 180     if (ctl->is_CountedLoop() && ctl->in(1) != nullptr && ctl->in(1)->in(0) != nullptr && ctl->in(1)->in(0)->is_If()) {
 181       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern()) {
 182         break;
 183       }
 184       next = idom(ctl->in(1)->in(0));
 185     } else if (ctl->is_Proj()) {
 186       // We only move it up along a projection if the projection is
 187       // the single control projection for its parent: same code path,
 188       // if it's a If with UNC or fallthrough of a call.
 189       Node* parent_ctl = ctl->in(0);
 190       if (parent_ctl == nullptr) {
 191         break;
 192       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != nullptr) {
 193         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 194       } else if (parent_ctl->is_If()) {
 195         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern()) {
 196           break;
 197         }
 198         assert(idom(ctl) == parent_ctl, "strange");
 199         next = idom(parent_ctl);
 200       } else if (ctl->is_CatchProj()) {
 201         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 202           break;
 203         }
 204         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 205         next = parent_ctl->in(0)->in(0)->in(0);
 206       } else {
 207         // Check if parent control has a single projection (this
 208         // control is the only possible successor of the parent
 209         // control). If so, we can try to move the node above the
 210         // parent control.
 211         int nb_ctl_proj = 0;
 212         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 213           Node *p = parent_ctl->fast_out(i);
 214           if (p->is_Proj() && p->is_CFG()) {
 215             nb_ctl_proj++;
 216             if (nb_ctl_proj > 1) {
 217               break;
 218             }
 219           }
 220         }
 221 
 222         if (nb_ctl_proj > 1) {
 223           break;
 224         }
 225         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
 226                BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
 227         assert(idom(ctl) == parent_ctl, "strange");
 228         next = idom(parent_ctl);
 229       }
 230     } else {
 231       next = idom(ctl);
 232     }
 233     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 234       break;
 235     }
 236     ctl = next;
 237   }
 238 
 239   if (ctl != n->in(0)) {
 240     _igvn.replace_input_of(n, 0, ctl);
 241     _igvn.hash_insert(n);
 242   }
 243 
 244   return ctl;
 245 }
 246 
 247 
 248 //------------------------------set_early_ctrl---------------------------------
 249 // Set earliest legal control
 250 void PhaseIdealLoop::set_early_ctrl(Node* n, bool update_body) {
 251   Node *early = get_early_ctrl(n);
 252 
 253   // Record earliest legal location
 254   set_ctrl(n, early);
 255   IdealLoopTree *loop = get_loop(early);
 256   if (update_body && loop->_child == nullptr) {
 257     loop->_body.push(n);
 258   }
 259 }
 260 
 261 //------------------------------set_subtree_ctrl-------------------------------
 262 // set missing _ctrl entries on new nodes
 263 void PhaseIdealLoop::set_subtree_ctrl(Node* n, bool update_body) {
 264   // Already set?  Get out.
 265   if (_loop_or_ctrl[n->_idx]) return;
 266   // Recursively set _loop_or_ctrl array to indicate where the Node goes
 267   uint i;
 268   for (i = 0; i < n->req(); ++i) {
 269     Node *m = n->in(i);
 270     if (m && m != C->root()) {
 271       set_subtree_ctrl(m, update_body);
 272     }
 273   }
 274 
 275   // Fixup self
 276   set_early_ctrl(n, update_body);
 277 }
 278 
 279 IdealLoopTree* PhaseIdealLoop::insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift) {
 280   IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
 281   IdealLoopTree* parent = loop->_parent;
 282   IdealLoopTree* sibling = parent->_child;
 283   if (sibling == loop) {
 284     parent->_child = outer_ilt;
 285   } else {
 286     while (sibling->_next != loop) {
 287       sibling = sibling->_next;
 288     }
 289     sibling->_next = outer_ilt;
 290   }
 291   outer_ilt->_next = loop->_next;
 292   outer_ilt->_parent = parent;
 293   outer_ilt->_child = loop;
 294   outer_ilt->_nest = loop->_nest;
 295   loop->_parent = outer_ilt;
 296   loop->_next = nullptr;
 297   loop->_nest++;
 298   assert(loop->_nest <= SHRT_MAX, "sanity");
 299   return outer_ilt;
 300 }
 301 
 302 // Create a skeleton strip mined outer loop: an OuterStripMinedLoop head before the inner strip mined CountedLoop, a
 303 // SafePoint on exit of the inner CountedLoopEnd and an OuterStripMinedLoopEnd test that can't constant fold until loop
 304 // optimizations are over. The inner strip mined loop is left as it is. Only once loop optimizations are over, do we
 305 // adjust the inner loop exit condition to limit its number of iterations, set the outer loop exit condition and add
 306 // Phis to the outer loop head. Some loop optimizations that operate on the inner strip mined loop need to be aware of
 307 // the outer strip mined loop: loop unswitching needs to clone the outer loop as well as the inner, unrolling needs to
 308 // only clone the inner loop etc. No optimizations need to change the outer strip mined loop as it is only a skeleton.
 309 //
 310 // Schematically:
 311 //
 312 // OuterStripMinedLoop -------|
 313 //       |                    |
 314 // CountedLoop ----------- |  |
 315 //     \- Phi (iv) -|      |  |
 316 //       /  \       |      |  |
 317 //     CmpI  AddI --|      |  |
 318 //       \                 |  |
 319 //        Bool             |  |
 320 //         \               |  |
 321 // CountedLoopEnd          |  |
 322 //       /  \              |  |
 323 // IfFalse   IfTrue--------|  |
 324 //      |                     |
 325 // SafePoint                  |
 326 //      |                     |
 327 // OuterStripMinedLoopEnd     |
 328 //       /   \                |
 329 // IfFalse   IfTrue-----------|
 330 //      |
 331 //
 332 //
 333 // As loop optimizations transform the inner loop, the outer strip mined loop stays mostly unchanged. The only exception
 334 // is nodes referenced from the SafePoint and sunk from the inner loop: they end up in the outer strip mined loop.
 335 //
 336 // Not adding Phis to the outer loop head from the beginning, and only adding them after loop optimizations does not
 337 // conform to C2's IR rules: any variable or memory slice that is mutated in a loop should have a Phi. The main
 338 // motivation for such a design that doesn't conform to C2's IR rules is to allow existing loop optimizations to be
 339 // mostly unaffected by the outer strip mined loop: the only extra step needed in most cases is to step over the
 340 // OuterStripMinedLoop. The main drawback is that once loop optimizations are over, an extra step is needed to finish
 341 // constructing the outer loop. This is handled by OuterStripMinedLoopNode::adjust_strip_mined_loop().
 342 //
 343 // Adding Phis to the outer loop is largely straightforward: there needs to be one Phi in the outer loop for every Phi
 344 // in the inner loop. Things may be more complicated for sunk Store nodes: there may not be any inner loop Phi left
 345 // after sinking for a particular memory slice but the outer loop needs a Phi. See
 346 // OuterStripMinedLoopNode::handle_sunk_stores_when_finishing_construction()
 347 IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(Node* init_control,
 348                                                              IdealLoopTree* loop, float cl_prob, float le_fcnt,
 349                                                              Node*& entry_control, Node*& iffalse) {
 350   Node* outer_test = intcon(0);
 351   Node *orig = iffalse;
 352   iffalse = iffalse->clone();
 353   _igvn.register_new_node_with_optimizer(iffalse);
 354   set_idom(iffalse, idom(orig), dom_depth(orig));
 355 
 356   IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
 357   Node *outer_ift = new IfTrueNode (outer_le);
 358   Node* outer_iff = orig;
 359   _igvn.replace_input_of(outer_iff, 0, outer_le);
 360 
 361   LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
 362   entry_control = outer_l;
 363 
 364   IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_l, outer_ift);
 365 
 366   set_loop(iffalse, outer_ilt);
 367   // When this code runs, loop bodies have not yet been populated.
 368   const bool body_populated = false;
 369   register_control(outer_le, outer_ilt, iffalse, body_populated);
 370   register_control(outer_ift, outer_ilt, outer_le, body_populated);
 371   set_idom(outer_iff, outer_le, dom_depth(outer_le));
 372   _igvn.register_new_node_with_optimizer(outer_l);
 373   set_loop(outer_l, outer_ilt);
 374   set_idom(outer_l, init_control, dom_depth(init_control)+1);
 375 
 376   return outer_ilt;
 377 }
 378 
 379 void PhaseIdealLoop::insert_loop_limit_check_predicate(ParsePredicateSuccessProj* loop_limit_check_parse_proj,
 380                                                        Node* cmp_limit, Node* bol) {
 381   assert(loop_limit_check_parse_proj->in(0)->is_ParsePredicate(), "must be parse predicate");
 382   Node* new_predicate_proj = create_new_if_for_predicate(loop_limit_check_parse_proj, nullptr,
 383                                                          Deoptimization::Reason_loop_limit_check,
 384                                                          Op_If);
 385   Node* iff = new_predicate_proj->in(0);
 386   cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 387   bol = _igvn.register_new_node_with_optimizer(bol);
 388   set_subtree_ctrl(bol, false);
 389   _igvn.replace_input_of(iff, 1, bol);
 390 
 391 #ifndef PRODUCT
 392   // report that the loop predication has been actually performed
 393   // for this loop
 394   if (TraceLoopLimitCheck) {
 395     tty->print_cr("Counted Loop Limit Check generated:");
 396     DEBUG_ONLY( bol->dump(2); )
 397   }
 398 #endif
 399 }
 400 
 401 Node* PhaseIdealLoop::loop_exit_control(Node* x, IdealLoopTree* loop) {
 402   // Counted loop head must be a good RegionNode with only 3 not null
 403   // control input edges: Self, Entry, LoopBack.
 404   if (x->in(LoopNode::Self) == nullptr || x->req() != 3 || loop->_irreducible) {
 405     return nullptr;
 406   }
 407   Node *init_control = x->in(LoopNode::EntryControl);
 408   Node *back_control = x->in(LoopNode::LoopBackControl);
 409   if (init_control == nullptr || back_control == nullptr) {   // Partially dead
 410     return nullptr;
 411   }
 412   // Must also check for TOP when looking for a dead loop
 413   if (init_control->is_top() || back_control->is_top()) {
 414     return nullptr;
 415   }
 416 
 417   // Allow funny placement of Safepoint
 418   if (back_control->Opcode() == Op_SafePoint) {
 419     back_control = back_control->in(TypeFunc::Control);
 420   }
 421 
 422   // Controlling test for loop
 423   Node *iftrue = back_control;
 424   uint iftrue_op = iftrue->Opcode();
 425   if (iftrue_op != Op_IfTrue &&
 426       iftrue_op != Op_IfFalse) {
 427     // I have a weird back-control.  Probably the loop-exit test is in
 428     // the middle of the loop and I am looking at some trailing control-flow
 429     // merge point.  To fix this I would have to partially peel the loop.
 430     return nullptr; // Obscure back-control
 431   }
 432 
 433   // Get boolean guarding loop-back test
 434   Node *iff = iftrue->in(0);
 435   if (get_loop(iff) != loop || !iff->in(1)->is_Bool()) {
 436     return nullptr;
 437   }
 438   return iftrue;
 439 }
 440 
 441 Node* PhaseIdealLoop::loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob) {
 442   Node* iftrue = back_control;
 443   uint iftrue_op = iftrue->Opcode();
 444   Node* iff = iftrue->in(0);
 445   BoolNode* test = iff->in(1)->as_Bool();
 446   bt = test->_test._test;
 447   cl_prob = iff->as_If()->_prob;
 448   if (iftrue_op == Op_IfFalse) {
 449     bt = BoolTest(bt).negate();
 450     cl_prob = 1.0 - cl_prob;
 451   }
 452   // Get backedge compare
 453   Node* cmp = test->in(1);
 454   if (!cmp->is_Cmp()) {
 455     return nullptr;
 456   }
 457 
 458   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 459   incr  = cmp->in(1);
 460   limit = cmp->in(2);
 461 
 462   // ---------
 463   // need 'loop()' test to tell if limit is loop invariant
 464   // ---------
 465 
 466   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 467     Node* tmp = incr;            // Then reverse order into the CmpI
 468     incr = limit;
 469     limit = tmp;
 470     bt = BoolTest(bt).commute(); // And commute the exit test
 471   }
 472   if (is_member(loop, get_ctrl(limit))) { // Limit must be loop-invariant
 473     return nullptr;
 474   }
 475   if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
 476     return nullptr;
 477   }
 478   return cmp;
 479 }
 480 
 481 Node* PhaseIdealLoop::loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr) {
 482   if (incr->is_Phi()) {
 483     if (incr->as_Phi()->region() != x || incr->req() != 3) {
 484       return nullptr; // Not simple trip counter expression
 485     }
 486     phi_incr = incr;
 487     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 488     if (!is_member(loop, get_ctrl(incr))) { // Trip counter must be loop-variant
 489       return nullptr;
 490     }
 491   }
 492   return incr;
 493 }
 494 
 495 Node* PhaseIdealLoop::loop_iv_stride(Node* incr, Node*& xphi) {
 496   assert(incr->Opcode() == Op_AddI || incr->Opcode() == Op_AddL, "caller resp.");
 497   // Get merge point
 498   xphi = incr->in(1);
 499   Node *stride = incr->in(2);
 500   if (!stride->is_Con()) {     // Oops, swap these
 501     if (!xphi->is_Con()) {     // Is the other guy a constant?
 502       return nullptr;          // Nope, unknown stride, bail out
 503     }
 504     Node *tmp = xphi;          // 'incr' is commutative, so ok to swap
 505     xphi = stride;
 506     stride = tmp;
 507   }
 508   return stride;
 509 }
 510 
 511 PhiNode* PhaseIdealLoop::loop_iv_phi(Node* xphi, Node* phi_incr, Node* x) {
 512   if (!xphi->is_Phi()) {
 513     return nullptr; // Too much math on the trip counter
 514   }
 515   if (phi_incr != nullptr && phi_incr != xphi) {
 516     return nullptr;
 517   }
 518   PhiNode *phi = xphi->as_Phi();
 519 
 520   // Phi must be of loop header; backedge must wrap to increment
 521   if (phi->region() != x) {
 522     return nullptr;
 523   }
 524   return phi;
 525 }
 526 
 527 static int check_stride_overflow(jlong final_correction, const TypeInteger* limit_t, BasicType bt) {
 528   if (final_correction > 0) {
 529     if (limit_t->lo_as_long() > (max_signed_integer(bt) - final_correction)) {
 530       return -1;
 531     }
 532     if (limit_t->hi_as_long() > (max_signed_integer(bt) - final_correction)) {
 533       return 1;
 534     }
 535   } else {
 536     if (limit_t->hi_as_long() < (min_signed_integer(bt) - final_correction)) {
 537       return -1;
 538     }
 539     if (limit_t->lo_as_long() < (min_signed_integer(bt) - final_correction)) {
 540       return 1;
 541     }
 542   }
 543   return 0;
 544 }
 545 
 546 static bool condition_stride_ok(BoolTest::mask bt, jlong stride_con) {
 547   // If the condition is inverted and we will be rolling
 548   // through MININT to MAXINT, then bail out.
 549   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 550       // Odd stride
 551       (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
 552       // Count down loop rolls through MAXINT
 553       ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
 554       // Count up loop rolls through MININT
 555       ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
 556     return false; // Bail out
 557   }
 558   return true;
 559 }
 560 
 561 Node* PhaseIdealLoop::loop_nest_replace_iv(Node* iv_to_replace, Node* inner_iv, Node* outer_phi, Node* inner_head,
 562                                            BasicType bt) {
 563   Node* iv_as_long;
 564   if (bt == T_LONG) {
 565     iv_as_long = new ConvI2LNode(inner_iv, TypeLong::INT);
 566     register_new_node(iv_as_long, inner_head);
 567   } else {
 568     iv_as_long = inner_iv;
 569   }
 570   Node* iv_replacement = AddNode::make(outer_phi, iv_as_long, bt);
 571   register_new_node(iv_replacement, inner_head);
 572   for (DUIterator_Last imin, i = iv_to_replace->last_outs(imin); i >= imin;) {
 573     Node* u = iv_to_replace->last_out(i);
 574 #ifdef ASSERT
 575     if (!is_dominator(inner_head, ctrl_or_self(u))) {
 576       assert(u->is_Phi(), "should be a Phi");
 577       for (uint j = 1; j < u->req(); j++) {
 578         if (u->in(j) == iv_to_replace) {
 579           assert(is_dominator(inner_head, u->in(0)->in(j)), "iv use above loop?");
 580         }
 581       }
 582     }
 583 #endif
 584     _igvn.rehash_node_delayed(u);
 585     int nb = u->replace_edge(iv_to_replace, iv_replacement, &_igvn);
 586     i -= nb;
 587   }
 588   return iv_replacement;
 589 }
 590 
 591 // Add a Parse Predicate with an uncommon trap on the failing/false path. Normal control will continue on the true path.
 592 void PhaseIdealLoop::add_parse_predicate(Deoptimization::DeoptReason reason, Node* inner_head, IdealLoopTree* loop,
 593                                          SafePointNode* sfpt) {
 594   if (!C->too_many_traps(reason)) {
 595     ParsePredicateNode* parse_predicate = new ParsePredicateNode(inner_head->in(LoopNode::EntryControl), reason, &_igvn);
 596     register_control(parse_predicate, loop, inner_head->in(LoopNode::EntryControl));
 597     Node* if_false = new IfFalseNode(parse_predicate);
 598     register_control(if_false, _ltree_root, parse_predicate);
 599     Node* if_true = new IfTrueNode(parse_predicate);
 600     register_control(if_true, loop, parse_predicate);
 601 
 602     int trap_request = Deoptimization::make_trap_request(reason, Deoptimization::Action_maybe_recompile);
 603     address call_addr = OptoRuntime::uncommon_trap_blob()->entry_point();
 604     const TypePtr* no_memory_effects = nullptr;
 605     CallNode* unc = new CallStaticJavaNode(OptoRuntime::uncommon_trap_Type(), call_addr, "uncommon_trap",
 606                                            no_memory_effects);
 607 
 608     Node* mem = nullptr;
 609     Node* i_o = nullptr;
 610     if (sfpt->is_Call()) {
 611       mem = sfpt->proj_out(TypeFunc::Memory);
 612       i_o = sfpt->proj_out(TypeFunc::I_O);
 613     } else {
 614       mem = sfpt->memory();
 615       i_o = sfpt->i_o();
 616     }
 617 
 618     Node *frame = new ParmNode(C->start(), TypeFunc::FramePtr);
 619     register_new_node(frame, C->start());
 620     Node *ret = new ParmNode(C->start(), TypeFunc::ReturnAdr);
 621     register_new_node(ret, C->start());
 622 
 623     unc->init_req(TypeFunc::Control, if_false);
 624     unc->init_req(TypeFunc::I_O, i_o);
 625     unc->init_req(TypeFunc::Memory, mem); // may gc ptrs
 626     unc->init_req(TypeFunc::FramePtr, frame);
 627     unc->init_req(TypeFunc::ReturnAdr, ret);
 628     unc->init_req(TypeFunc::Parms+0, _igvn.intcon(trap_request));
 629     unc->set_cnt(PROB_UNLIKELY_MAG(4));
 630     unc->copy_call_debug_info(&_igvn, sfpt);
 631 
 632     for (uint i = TypeFunc::Parms; i < unc->req(); i++) {
 633       set_subtree_ctrl(unc->in(i), false);
 634     }
 635     register_control(unc, _ltree_root, if_false);
 636 
 637     Node* ctrl = new ProjNode(unc, TypeFunc::Control);
 638     register_control(ctrl, _ltree_root, unc);
 639     Node* halt = new HaltNode(ctrl, frame, "uncommon trap returned which should never happen" PRODUCT_ONLY(COMMA /*reachable*/false));
 640     register_control(halt, _ltree_root, ctrl);
 641     _igvn.add_input_to(C->root(), halt);
 642 
 643     _igvn.replace_input_of(inner_head, LoopNode::EntryControl, if_true);
 644     set_idom(inner_head, if_true, dom_depth(inner_head));
 645   }
 646 }
 647 
 648 // Find a safepoint node that dominates the back edge. We need a
 649 // SafePointNode so we can use its jvm state to create empty
 650 // predicates.
 651 static bool no_side_effect_since_safepoint(Compile* C, Node* x, Node* mem, MergeMemNode* mm, PhaseIdealLoop* phase) {
 652   SafePointNode* safepoint = nullptr;
 653   for (DUIterator_Fast imax, i = x->fast_outs(imax); i < imax; i++) {
 654     Node* u = x->fast_out(i);
 655     if (u->is_memory_phi()) {
 656       Node* m = u->in(LoopNode::LoopBackControl);
 657       if (u->adr_type() == TypePtr::BOTTOM) {
 658         if (m->is_MergeMem() && mem->is_MergeMem()) {
 659           if (m != mem DEBUG_ONLY(|| true)) {
 660             // MergeMemStream can modify m, for example to adjust the length to mem.
 661             // This is unfortunate, and probably unnecessary. But as it is, we need
 662             // to add m to the igvn worklist, else we may have a modified node that
 663             // is not on the igvn worklist.
 664             phase->igvn()._worklist.push(m);
 665             for (MergeMemStream mms(m->as_MergeMem(), mem->as_MergeMem()); mms.next_non_empty2(); ) {
 666               if (!mms.is_empty()) {
 667                 if (mms.memory() != mms.memory2()) {
 668                   return false;
 669                 }
 670 #ifdef ASSERT
 671                 if (mms.alias_idx() != Compile::AliasIdxBot) {
 672                   mm->set_memory_at(mms.alias_idx(), mem->as_MergeMem()->base_memory());
 673                 }
 674 #endif
 675               }
 676             }
 677           }
 678         } else if (mem->is_MergeMem()) {
 679           if (m != mem->as_MergeMem()->base_memory()) {
 680             return false;
 681           }
 682         } else {
 683           return false;
 684         }
 685       } else {
 686         if (mem->is_MergeMem()) {
 687           if (m != mem->as_MergeMem()->memory_at(C->get_alias_index(u->adr_type()))) {
 688             return false;
 689           }
 690 #ifdef ASSERT
 691           mm->set_memory_at(C->get_alias_index(u->adr_type()), mem->as_MergeMem()->base_memory());
 692 #endif
 693         } else {
 694           if (m != mem) {
 695             return false;
 696           }
 697         }
 698       }
 699     }
 700   }
 701   return true;
 702 }
 703 
 704 SafePointNode* PhaseIdealLoop::find_safepoint(Node* back_control, Node* x, IdealLoopTree* loop) {
 705   IfNode* exit_test = back_control->in(0)->as_If();
 706   SafePointNode* safepoint = nullptr;
 707   if (exit_test->in(0)->is_SafePoint() && exit_test->in(0)->outcnt() == 1) {
 708     safepoint = exit_test->in(0)->as_SafePoint();
 709   } else {
 710     Node* c = back_control;
 711     while (c != x && c->Opcode() != Op_SafePoint) {
 712       c = idom(c);
 713     }
 714 
 715     if (c->Opcode() == Op_SafePoint) {
 716       safepoint = c->as_SafePoint();
 717     }
 718 
 719     if (safepoint == nullptr) {
 720       return nullptr;
 721     }
 722 
 723     Node* mem = safepoint->in(TypeFunc::Memory);
 724 
 725     // We can only use that safepoint if there's no side effect between the backedge and the safepoint.
 726 
 727     // mm is the memory state at the safepoint (when it's a MergeMem)
 728     // no_side_effect_since_safepoint() goes over the memory state at the backedge. It resets the mm input for each
 729     // component of the memory state it encounters so it points to the base memory. Once no_side_effect_since_safepoint()
 730     // is done, if no side effect after the safepoint was found, mm should transform to the base memory: the states at
 731     // the backedge and safepoint are the same so all components of the memory state at the safepoint should have been
 732     // reset.
 733     MergeMemNode* mm = nullptr;
 734 #ifdef ASSERT
 735     if (mem->is_MergeMem()) {
 736       mm = mem->clone()->as_MergeMem();
 737       _igvn._worklist.push(mm);
 738       for (MergeMemStream mms(mem->as_MergeMem()); mms.next_non_empty(); ) {
 739         // Loop invariant memory state won't be reset by no_side_effect_since_safepoint(). Do it here.
 740         // Escape Analysis can add state to mm that it doesn't add to the backedge memory Phis, breaking verification
 741         // code that relies on mm. Clear that extra state here.
 742         if (mms.alias_idx() != Compile::AliasIdxBot &&
 743             (loop != get_loop(ctrl_or_self(mms.memory())) ||
 744              (mms.adr_type()->isa_oop_ptr() && mms.adr_type()->is_known_instance()))) {
 745           mm->set_memory_at(mms.alias_idx(), mem->as_MergeMem()->base_memory());
 746         }
 747       }
 748     }
 749 #endif
 750     if (!no_side_effect_since_safepoint(C, x, mem, mm, this)) {
 751       safepoint = nullptr;
 752     } else {
 753       assert(mm == nullptr|| _igvn.transform(mm) == mem->as_MergeMem()->base_memory(), "all memory state should have been processed");
 754     }
 755 #ifdef ASSERT
 756     if (mm != nullptr) {
 757       _igvn.remove_dead_node(mm);
 758     }
 759 #endif
 760   }
 761   return safepoint;
 762 }
 763 
 764 // If the loop has the shape of a counted loop but with a long
 765 // induction variable, transform the loop in a loop nest: an inner
 766 // loop that iterates for at most max int iterations with an integer
 767 // induction variable and an outer loop that iterates over the full
 768 // range of long values from the initial loop in (at most) max int
 769 // steps. That is:
 770 //
 771 // x: for (long phi = init; phi < limit; phi += stride) {
 772 //   // phi := Phi(L, init, incr)
 773 //   // incr := AddL(phi, longcon(stride))
 774 //   long incr = phi + stride;
 775 //   ... use phi and incr ...
 776 // }
 777 //
 778 // OR:
 779 //
 780 // x: for (long phi = init; (phi += stride) < limit; ) {
 781 //   // phi := Phi(L, AddL(init, stride), incr)
 782 //   // incr := AddL(phi, longcon(stride))
 783 //   long incr = phi + stride;
 784 //   ... use phi and (phi + stride) ...
 785 // }
 786 //
 787 // ==transform=>
 788 //
 789 // const ulong inner_iters_limit = INT_MAX - stride - 1;  //near 0x7FFFFFF0
 790 // assert(stride <= inner_iters_limit);  // else abort transform
 791 // assert((extralong)limit + stride <= LONG_MAX);  // else deopt
 792 // outer_head: for (long outer_phi = init;;) {
 793 //   // outer_phi := Phi(outer_head, init, AddL(outer_phi, I2L(inner_phi)))
 794 //   ulong inner_iters_max = (ulong) MAX(0, ((extralong)limit + stride - outer_phi));
 795 //   long inner_iters_actual = MIN(inner_iters_limit, inner_iters_max);
 796 //   assert(inner_iters_actual == (int)inner_iters_actual);
 797 //   int inner_phi, inner_incr;
 798 //   x: for (inner_phi = 0;; inner_phi = inner_incr) {
 799 //     // inner_phi := Phi(x, intcon(0), inner_incr)
 800 //     // inner_incr := AddI(inner_phi, intcon(stride))
 801 //     inner_incr = inner_phi + stride;
 802 //     if (inner_incr < inner_iters_actual) {
 803 //       ... use phi=>(outer_phi+inner_phi) ...
 804 //       continue;
 805 //     }
 806 //     else break;
 807 //   }
 808 //   if ((outer_phi+inner_phi) < limit)  //OR (outer_phi+inner_incr) < limit
 809 //     continue;
 810 //   else break;
 811 // }
 812 //
 813 // The same logic is used to transform an int counted loop that contains long range checks into a loop nest of 2 int
 814 // loops with long range checks transformed to int range checks in the inner loop.
 815 bool PhaseIdealLoop::create_loop_nest(IdealLoopTree* loop, Node_List &old_new) {
 816   Node* x = loop->_head;
 817   // Only for inner loops
 818   if (loop->_child != nullptr || !x->is_BaseCountedLoop() || x->as_Loop()->is_loop_nest_outer_loop()) {
 819     return false;
 820   }
 821 
 822   if (x->is_CountedLoop() && !x->as_CountedLoop()->is_main_loop() && !x->as_CountedLoop()->is_normal_loop()) {
 823     return false;
 824   }
 825 
 826   BaseCountedLoopNode* head = x->as_BaseCountedLoop();
 827   BasicType bt = x->as_BaseCountedLoop()->bt();
 828 
 829   check_counted_loop_shape(loop, x, bt);
 830 
 831 #ifndef PRODUCT
 832   if (bt == T_LONG) {
 833     AtomicAccess::inc(&_long_loop_candidates);
 834   }
 835 #endif
 836 
 837   jlong stride_con_long = head->stride_con();
 838   assert(stride_con_long != 0, "missed some peephole opt");
 839   // We can't iterate for more than max int at a time.
 840   if (stride_con_long != (jint)stride_con_long || stride_con_long == min_jint) {
 841     assert(bt == T_LONG, "only for long loops");
 842     return false;
 843   }
 844   jint stride_con = checked_cast<jint>(stride_con_long);
 845   // The number of iterations for the integer count loop: guarantee no
 846   // overflow: max_jint - stride_con max. -1 so there's no need for a
 847   // loop limit check if the exit test is <= or >=.
 848   int iters_limit = max_jint - ABS(stride_con) - 1;
 849 #ifdef ASSERT
 850   if (bt == T_LONG && StressLongCountedLoop > 0) {
 851     iters_limit = iters_limit / StressLongCountedLoop;
 852   }
 853 #endif
 854   // At least 2 iterations so counted loop construction doesn't fail
 855   if (iters_limit/ABS(stride_con) < 2) {
 856     return false;
 857   }
 858 
 859   assert(iters_limit > 0, "can't be negative");
 860 
 861   PhiNode* phi = head->phi()->as_Phi();
 862 
 863   Node* back_control = head->in(LoopNode::LoopBackControl);
 864 
 865   // data nodes on back branch not supported
 866   if (back_control->outcnt() > 1) {
 867     return false;
 868   }
 869 
 870   Node* limit = head->limit();
 871   // We'll need to use the loop limit before the inner loop is entered
 872   if (!is_dominator(get_ctrl(limit), x)) {
 873     return false;
 874   }
 875 
 876   IfNode* exit_test = head->loopexit();
 877 
 878   assert(back_control->Opcode() == Op_IfTrue, "wrong projection for back edge");
 879 
 880   Node_List range_checks;
 881   iters_limit = extract_long_range_checks(loop, stride_con, iters_limit, phi, range_checks);
 882 
 883   if (bt == T_INT) {
 884     // The only purpose of creating a loop nest is to handle long range checks. If there are none, do not proceed further.
 885     if (range_checks.size() == 0) {
 886       return false;
 887     }
 888   }
 889 
 890   // Take what we know about the number of iterations of the long counted loop into account when computing the limit of
 891   // the inner loop.
 892   Node* init = head->init_trip();
 893   const TypeInteger* lo = _igvn.type(init)->is_integer(bt);
 894   const TypeInteger* hi = _igvn.type(limit)->is_integer(bt);
 895   if (stride_con < 0) {
 896     swap(lo, hi);
 897   }
 898   if (hi->hi_as_long() <= lo->lo_as_long()) {
 899     // not a loop after all
 900     return false;
 901   }
 902 
 903   if (range_checks.size() > 0) {
 904     // This transformation requires peeling one iteration. Also, if it has range checks and they are eliminated by Loop
 905     // Predication, then 2 Hoisted Check Predicates are added for one range check. Finally, transforming a long range
 906     // check requires extra logic to be executed before the loop is entered and for the outer loop. As a result, the
 907     // transformations can't pay off for a small number of iterations: roughly, if the loop runs for 3 iterations, it's
 908     // going to execute as many range checks once transformed with range checks eliminated (1 peeled iteration with
 909     // range checks + 2 predicates per range checks) as it would have not transformed. It also has to pay for the extra
 910     // logic on loop entry and for the outer loop.
 911     loop->compute_trip_count(this, bt);
 912     if (head->is_CountedLoop() && head->as_CountedLoop()->has_exact_trip_count()) {
 913       if (head->as_CountedLoop()->trip_count() <= 3) {
 914         return false;
 915       }
 916     } else {
 917       loop->compute_profile_trip_cnt(this);
 918       if (!head->is_profile_trip_failed() && head->profile_trip_cnt() <= 3) {
 919         return false;
 920       }
 921     }
 922   }
 923 
 924   if (try_make_short_running_loop(loop, stride_con, range_checks, iters_limit)) {
 925     C->set_major_progress();
 926     return true;
 927   }
 928 
 929   julong orig_iters = (julong)hi->hi_as_long() - lo->lo_as_long();
 930   iters_limit = checked_cast<int>(MIN2((julong)iters_limit, orig_iters));
 931 
 932   // We need a safepoint to insert Parse Predicates for the inner loop.
 933   SafePointNode* safepoint;
 934   if (bt == T_INT && head->as_CountedLoop()->is_strip_mined()) {
 935     // Loop is strip mined: use the safepoint of the outer strip mined loop
 936     OuterStripMinedLoopNode* outer_loop = head->as_CountedLoop()->outer_loop();
 937     assert(outer_loop != nullptr, "no outer loop");
 938     safepoint = outer_loop->outer_safepoint();
 939     outer_loop->transform_to_counted_loop(&_igvn, this);
 940     exit_test = head->loopexit();
 941   } else {
 942     safepoint = find_safepoint(back_control, x, loop);
 943   }
 944 
 945   Node* exit_branch = exit_test->proj_out(false);
 946   Node* entry_control = head->in(LoopNode::EntryControl);
 947 
 948   // Clone the control flow of the loop to build an outer loop
 949   Node* outer_back_branch = back_control->clone();
 950   Node* outer_exit_test = new IfNode(exit_test->in(0), exit_test->in(1), exit_test->_prob, exit_test->_fcnt);
 951   Node* inner_exit_branch = exit_branch->clone();
 952 
 953   LoopNode* outer_head = new LoopNode(entry_control, outer_back_branch);
 954   IdealLoopTree* outer_ilt = insert_outer_loop(loop, outer_head, outer_back_branch);
 955 
 956   const bool body_populated = true;
 957   register_control(outer_head, outer_ilt, entry_control, body_populated);
 958 
 959   _igvn.register_new_node_with_optimizer(inner_exit_branch);
 960   set_loop(inner_exit_branch, outer_ilt);
 961   set_idom(inner_exit_branch, exit_test, dom_depth(exit_branch));
 962 
 963   outer_exit_test->set_req(0, inner_exit_branch);
 964   register_control(outer_exit_test, outer_ilt, inner_exit_branch, body_populated);
 965 
 966   _igvn.replace_input_of(exit_branch, 0, outer_exit_test);
 967   set_idom(exit_branch, outer_exit_test, dom_depth(exit_branch));
 968 
 969   outer_back_branch->set_req(0, outer_exit_test);
 970   register_control(outer_back_branch, outer_ilt, outer_exit_test, body_populated);
 971 
 972   _igvn.replace_input_of(x, LoopNode::EntryControl, outer_head);
 973   set_idom(x, outer_head, dom_depth(x));
 974 
 975   // add an iv phi to the outer loop and use it to compute the inner
 976   // loop iteration limit
 977   Node* outer_phi = phi->clone();
 978   outer_phi->set_req(0, outer_head);
 979   register_new_node(outer_phi, outer_head);
 980 
 981   Node* inner_iters_max = nullptr;
 982   if (stride_con > 0) {
 983     inner_iters_max = MaxNode::max_diff_with_zero(limit, outer_phi, TypeInteger::bottom(bt), _igvn);
 984   } else {
 985     inner_iters_max = MaxNode::max_diff_with_zero(outer_phi, limit, TypeInteger::bottom(bt), _igvn);
 986   }
 987 
 988   Node* inner_iters_limit = _igvn.integercon(iters_limit, bt);
 989   // inner_iters_max may not fit in a signed integer (iterating from
 990   // Long.MIN_VALUE to Long.MAX_VALUE for instance). Use an unsigned
 991   // min.
 992   const TypeInteger* inner_iters_actual_range = TypeInteger::make(0, iters_limit, Type::WidenMin, bt);
 993   Node* inner_iters_actual = MaxNode::unsigned_min(inner_iters_max, inner_iters_limit, inner_iters_actual_range, _igvn);
 994 
 995   Node* inner_iters_actual_int;
 996   if (bt == T_LONG) {
 997     inner_iters_actual_int = new ConvL2INode(inner_iters_actual);
 998     _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
 999     // When the inner loop is transformed to a counted loop, a loop limit check is not expected to be needed because
1000     // the loop limit is less or equal to max_jint - stride - 1 (if stride is positive but a similar argument exists for
1001     // a negative stride). We add a CastII here to guarantee that, when the counted loop is created in a subsequent loop
1002     // opts pass, an accurate range of values for the limits is found.
1003     const TypeInt* inner_iters_actual_int_range = TypeInt::make(0, iters_limit, Type::WidenMin);
1004     inner_iters_actual_int = new CastIINode(outer_head, inner_iters_actual_int, inner_iters_actual_int_range, ConstraintCastNode::UnconditionalDependency);
1005     _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
1006   } else {
1007     inner_iters_actual_int = inner_iters_actual;
1008   }
1009 
1010   Node* int_zero = intcon(0);
1011   if (stride_con < 0) {
1012     inner_iters_actual_int = new SubINode(int_zero, inner_iters_actual_int);
1013     _igvn.register_new_node_with_optimizer(inner_iters_actual_int);
1014   }
1015 
1016   // Clone the iv data nodes as an integer iv
1017   Node* int_stride = intcon(stride_con);
1018   Node* inner_phi = new PhiNode(x->in(0), TypeInt::INT);
1019   Node* inner_incr = new AddINode(inner_phi, int_stride);
1020   Node* inner_cmp = nullptr;
1021   inner_cmp = new CmpINode(inner_incr, inner_iters_actual_int);
1022   Node* inner_bol = new BoolNode(inner_cmp, exit_test->in(1)->as_Bool()->_test._test);
1023   inner_phi->set_req(LoopNode::EntryControl, int_zero);
1024   inner_phi->set_req(LoopNode::LoopBackControl, inner_incr);
1025   register_new_node(inner_phi, x);
1026   register_new_node(inner_incr, x);
1027   register_new_node(inner_cmp, x);
1028   register_new_node(inner_bol, x);
1029 
1030   _igvn.replace_input_of(exit_test, 1, inner_bol);
1031 
1032   // Clone inner loop phis to outer loop
1033   for (uint i = 0; i < head->outcnt(); i++) {
1034     Node* u = head->raw_out(i);
1035     if (u->is_Phi() && u != inner_phi && u != phi) {
1036       assert(u->in(0) == head, "inconsistent");
1037       Node* clone = u->clone();
1038       clone->set_req(0, outer_head);
1039       register_new_node(clone, outer_head);
1040       _igvn.replace_input_of(u, LoopNode::EntryControl, clone);
1041     }
1042   }
1043 
1044   // Replace inner loop long iv phi as inner loop int iv phi + outer
1045   // loop iv phi
1046   Node* iv_add = loop_nest_replace_iv(phi, inner_phi, outer_phi, head, bt);
1047 
1048   set_subtree_ctrl(inner_iters_actual_int, body_populated);
1049 
1050   LoopNode* inner_head = create_inner_head(loop, head, exit_test);
1051 
1052   // Summary of steps from initial loop to loop nest:
1053   //
1054   // == old IR nodes =>
1055   //
1056   // entry_control: {...}
1057   // x:
1058   // for (long phi = init;;) {
1059   //   // phi := Phi(x, init, incr)
1060   //   // incr := AddL(phi, longcon(stride))
1061   //   exit_test:
1062   //   if (phi < limit)
1063   //     back_control: fallthrough;
1064   //   else
1065   //     exit_branch: break;
1066   //   long incr = phi + stride;
1067   //   ... use phi and incr ...
1068   //   phi = incr;
1069   // }
1070   //
1071   // == new IR nodes (just before final peel) =>
1072   //
1073   // entry_control: {...}
1074   // long adjusted_limit = limit + stride;  //because phi_incr != nullptr
1075   // assert(!limit_check_required || (extralong)limit + stride == adjusted_limit);  // else deopt
1076   // ulong inner_iters_limit = max_jint - ABS(stride) - 1;  //near 0x7FFFFFF0
1077   // outer_head:
1078   // for (long outer_phi = init;;) {
1079   //   // outer_phi := phi->clone(), in(0):=outer_head, => Phi(outer_head, init, incr)
1080   //   // REPLACE phi  => AddL(outer_phi, I2L(inner_phi))
1081   //   // REPLACE incr => AddL(outer_phi, I2L(inner_incr))
1082   //   // SO THAT outer_phi := Phi(outer_head, init, AddL(outer_phi, I2L(inner_incr)))
1083   //   ulong inner_iters_max = (ulong) MAX(0, ((extralong)adjusted_limit - outer_phi) * SGN(stride));
1084   //   int inner_iters_actual_int = (int) MIN(inner_iters_limit, inner_iters_max) * SGN(stride);
1085   //   inner_head: x: //in(1) := outer_head
1086   //   int inner_phi;
1087   //   for (inner_phi = 0;;) {
1088   //     // inner_phi := Phi(x, intcon(0), inner_phi + stride)
1089   //     int inner_incr = inner_phi + stride;
1090   //     bool inner_bol = (inner_incr < inner_iters_actual_int);
1091   //     exit_test: //exit_test->in(1) := inner_bol;
1092   //     if (inner_bol) // WAS (phi < limit)
1093   //       back_control: fallthrough;
1094   //     else
1095   //       inner_exit_branch: break;  //exit_branch->clone()
1096   //     ... use phi=>(outer_phi+inner_phi) ...
1097   //     inner_phi = inner_phi + stride;  // inner_incr
1098   //   }
1099   //   outer_exit_test:  //exit_test->clone(), in(0):=inner_exit_branch
1100   //   if ((outer_phi+inner_phi) < limit)  // WAS (phi < limit)
1101   //     outer_back_branch: fallthrough;  //back_control->clone(), in(0):=outer_exit_test
1102   //   else
1103   //     exit_branch: break;  //in(0) := outer_exit_test
1104   // }
1105 
1106   if (bt == T_INT) {
1107     outer_phi = new ConvI2LNode(outer_phi);
1108     register_new_node(outer_phi, outer_head);
1109   }
1110 
1111   transform_long_range_checks(stride_con, range_checks, outer_phi, inner_iters_actual_int,
1112                               inner_phi, iv_add, inner_head);
1113   // Peel one iteration of the loop and use the safepoint at the end
1114   // of the peeled iteration to insert Parse Predicates. If no well
1115   // positioned safepoint peel to guarantee a safepoint in the outer
1116   // loop.
1117   if (safepoint != nullptr || !loop->_has_call) {
1118     old_new.clear();
1119     do_peeling(loop, old_new);
1120   } else {
1121     C->set_major_progress();
1122   }
1123 
1124   if (safepoint != nullptr) {
1125     SafePointNode* cloned_sfpt = old_new[safepoint->_idx]->as_SafePoint();
1126 
1127     if (ShortRunningLongLoop) {
1128       add_parse_predicate(Deoptimization::Reason_short_running_long_loop, inner_head, outer_ilt, cloned_sfpt);
1129     }
1130     if (UseLoopPredicate) {
1131       add_parse_predicate(Deoptimization::Reason_predicate, inner_head, outer_ilt, cloned_sfpt);
1132       if (UseProfiledLoopPredicate) {
1133         add_parse_predicate(Deoptimization::Reason_profile_predicate, inner_head, outer_ilt, cloned_sfpt);
1134       }
1135     }
1136 
1137     if (UseAutoVectorizationPredicate) {
1138       // We only want to use the auto-vectorization check as a trap once per bci. And
1139       // PhaseIdealLoop::add_parse_predicate only checks trap limits per method, so
1140       // we do a custom check here.
1141       if (!C->too_many_traps(cloned_sfpt->jvms()->method(), cloned_sfpt->jvms()->bci(), Deoptimization::Reason_auto_vectorization_check)) {
1142         add_parse_predicate(Deoptimization::Reason_auto_vectorization_check, inner_head, outer_ilt, cloned_sfpt);
1143       }
1144     }
1145 
1146     add_parse_predicate(Deoptimization::Reason_loop_limit_check, inner_head, outer_ilt, cloned_sfpt);
1147   }
1148 
1149 #ifndef PRODUCT
1150   if (bt == T_LONG) {
1151     AtomicAccess::inc(&_long_loop_nests);
1152   }
1153 #endif
1154 
1155   inner_head->mark_loop_nest_inner_loop();
1156   outer_head->mark_loop_nest_outer_loop();
1157 
1158   return true;
1159 }
1160 
1161 // Make a copy of Parse/Template Assertion predicates below existing predicates at the loop passed as argument
1162 class CloneShortLoopPredicateVisitor : public PredicateVisitor {
1163   ClonePredicateToTargetLoop _clone_predicate_to_loop;
1164   PhaseIdealLoop* const _phase;
1165 
1166 public:
1167   CloneShortLoopPredicateVisitor(LoopNode* target_loop_head,
1168                                  const NodeInSingleLoopBody &node_in_loop_body,
1169                                  PhaseIdealLoop* phase)
1170     : _clone_predicate_to_loop(target_loop_head, node_in_loop_body, phase),
1171       _phase(phase) {
1172   }
1173   NONCOPYABLE(CloneShortLoopPredicateVisitor);
1174 
1175   using PredicateVisitor::visit;
1176 
1177   void visit(const ParsePredicate& parse_predicate) override {
1178     _clone_predicate_to_loop.clone_parse_predicate(parse_predicate, true);
1179     parse_predicate.kill(_phase->igvn());
1180   }
1181 
1182   void visit(const TemplateAssertionPredicate& template_assertion_predicate) override {
1183     _clone_predicate_to_loop.clone_template_assertion_predicate(template_assertion_predicate);
1184     template_assertion_predicate.kill(_phase->igvn());
1185   }
1186 };
1187 
1188 // If the loop is either statically known to run for a small enough number of iterations or if profile data indicates
1189 // that, we don't want an outer loop because the overhead of having an outer loop whose backedge is never taken, has a
1190 // measurable cost. Furthermore, creating the loop nest usually causes one iteration of the loop to be peeled so
1191 // predicates can be set up. If the loop is short running, then it's an extra iteration that's run with range checks
1192 // (compared to an int counted loop with int range checks).
1193 //
1194 // In the short running case, turn the loop into a regular loop again and transform the long range checks:
1195 // - LongCountedLoop: Create LoopNode but keep the loop limit type with a CastLL node to avoid that we later try to
1196 //                    create a Loop Limit Check when turning the LoopNode into a CountedLoopNode.
1197 // - CountedLoop: Can be reused.
1198 bool PhaseIdealLoop::try_make_short_running_loop(IdealLoopTree* loop, jint stride_con, const Node_List &range_checks,
1199                                                  const uint iters_limit) {
1200   if (!ShortRunningLongLoop) {
1201     return false;
1202   }
1203   BaseCountedLoopNode* head = loop->_head->as_BaseCountedLoop();
1204   BasicType bt = head->bt();
1205   Node* entry_control = head->skip_strip_mined()->in(LoopNode::EntryControl);
1206 
1207   loop->compute_trip_count(this, bt);
1208   // Loop must run for no more than iter_limits as it guarantees no overflow of scale * iv in long range checks (see
1209   // comment above PhaseIdealLoop::transform_long_range_checks()).
1210   // iters_limit / ABS(stride_con) is the largest trip count for which we know it's correct to not create a loop nest:
1211   // it's always beneficial to have a single loop rather than a loop nest, so we try to apply this transformation as
1212   // often as possible.
1213   bool known_short_running_loop = head->trip_count() <= iters_limit / ABS(stride_con);
1214   bool profile_short_running_loop = false;
1215   if (!known_short_running_loop) {
1216     loop->compute_profile_trip_cnt(this);
1217     if (StressShortRunningLongLoop) {
1218       profile_short_running_loop = true;
1219     } else {
1220       profile_short_running_loop = !head->is_profile_trip_failed() && head->profile_trip_cnt() <= iters_limit / ABS(stride_con);
1221     }
1222   }
1223 
1224   if (!known_short_running_loop && !profile_short_running_loop) {
1225     return false;
1226   }
1227 
1228   Node* limit = head->limit();
1229   Node* init = head->init_trip();
1230 
1231   Node* new_limit;
1232   if (stride_con > 0) {
1233     new_limit = SubNode::make(limit, init, bt);
1234   } else {
1235     new_limit = SubNode::make(init, limit, bt);
1236   }
1237   register_new_node(new_limit, entry_control);
1238 
1239   PhiNode* phi = head->phi()->as_Phi();
1240   if (profile_short_running_loop) {
1241     // Add a Short Running Long Loop Predicate. It's the first predicate in the predicate chain before entering a loop
1242     // because a cast that's control dependent on the Short Running Long Loop Predicate is added to narrow the limit and
1243     // future predicates may be dependent on the new limit (so have to be between the loop and Short Running Long Loop
1244     // Predicate). The current limit could, itself, be dependent on an existing predicate. Clone parse and template
1245     // assertion predicates below existing predicates to get proper ordering of predicates when walking from the loop
1246     // up: future predicates, Short Running Long Loop Predicate, existing predicates.
1247     //
1248     //        Existing Hoisted
1249     //        Check Predicates
1250     //               |
1251     //     New Short Running Long
1252     //         Loop Predicate
1253     //               |
1254     //   Cloned Parse Predicates and
1255     //  Template Assertion Predicates
1256     //  (future predicates added here)
1257     //               |
1258     //             Loop
1259     const Predicates predicates_before_cloning(entry_control);
1260     const PredicateBlock* short_running_long_loop_predicate_block = predicates_before_cloning.short_running_long_loop_predicate_block();
1261     if (!short_running_long_loop_predicate_block->has_parse_predicate()) { // already trapped
1262       return false;
1263     }
1264     PredicateIterator predicate_iterator(entry_control);
1265     NodeInSingleLoopBody node_in_short_loop_body(this, loop);
1266     CloneShortLoopPredicateVisitor clone_short_loop_predicates_visitor(head, node_in_short_loop_body, this);
1267     predicate_iterator.for_each(clone_short_loop_predicates_visitor);
1268 
1269     entry_control = head->skip_strip_mined()->in(LoopNode::EntryControl);
1270 
1271     const Predicates predicates_after_cloning(entry_control);
1272 
1273     ParsePredicateSuccessProj* short_running_loop_predicate_proj = predicates_after_cloning.
1274         short_running_long_loop_predicate_block()->
1275         parse_predicate_success_proj();
1276     assert(short_running_loop_predicate_proj->in(0)->is_ParsePredicate(), "must be parse predicate");
1277 
1278     const jlong iters_limit_long = iters_limit;
1279     Node* cmp_limit = CmpNode::make(new_limit, _igvn.integercon(iters_limit_long, bt), bt);
1280     Node* bol = new BoolNode(cmp_limit, BoolTest::le);
1281     Node* new_predicate_proj = create_new_if_for_predicate(short_running_loop_predicate_proj,
1282                                                            nullptr,
1283                                                            Deoptimization::Reason_short_running_long_loop,
1284                                                            Op_If);
1285     Node* iff = new_predicate_proj->in(0);
1286     _igvn.replace_input_of(iff, 1, bol);
1287     register_new_node(cmp_limit, iff->in(0));
1288     register_new_node(bol, iff->in(0));
1289     new_limit = ConstraintCastNode::make_cast_for_basic_type(new_predicate_proj, new_limit,
1290                                                              TypeInteger::make(1, iters_limit_long, Type::WidenMin, bt),
1291                                                              ConstraintCastNode::UnconditionalDependency, bt);
1292     register_new_node(new_limit, new_predicate_proj);
1293 
1294 #ifndef PRODUCT
1295     if (TraceLoopLimitCheck) {
1296       tty->print_cr("Short Long Loop Check Predicate generated:");
1297       DEBUG_ONLY(bol->dump(2);)
1298     }
1299 #endif
1300     entry_control = head->skip_strip_mined()->in(LoopNode::EntryControl);
1301   } else if (bt == T_LONG) {
1302     // We're turning a long counted loop into a regular loop that will be converted into an int counted loop. That loop
1303     // won't need loop limit check predicates (iters_limit guarantees that). Add a cast to make sure that, whatever
1304     // transformation happens by the time the counted loop is created (in a subsequent pass of loop opts), C2 knows
1305     // enough about the loop's limit that it doesn't try to add loop limit check predicates.
1306     const Predicates predicates(entry_control);
1307     const TypeLong* new_limit_t = new_limit->Value(&_igvn)->is_long();
1308     new_limit = ConstraintCastNode::make_cast_for_basic_type(predicates.entry(), new_limit,
1309                                                              TypeLong::make(0, new_limit_t->_hi, new_limit_t->_widen),
1310                                                              ConstraintCastNode::UnconditionalDependency, bt);
1311     register_new_node(new_limit, predicates.entry());
1312   } else {
1313     assert(bt == T_INT && known_short_running_loop, "only CountedLoop statically known to be short running");
1314   }
1315   IfNode* exit_test = head->loopexit();
1316 
1317   if (bt == T_LONG) {
1318     // The loop is short running so new_limit fits into an int: either we determined that statically or added a guard
1319     new_limit = new ConvL2INode(new_limit);
1320     register_new_node(new_limit, entry_control);
1321   }
1322 
1323   Node* int_zero = intcon(0);
1324   if (stride_con < 0) {
1325     new_limit = new SubINode(int_zero, new_limit);
1326     register_new_node(new_limit, entry_control);
1327   }
1328 
1329   // Clone the iv data nodes as an integer iv
1330   Node* int_stride = intcon(stride_con);
1331   Node* inner_phi = new PhiNode(head, TypeInt::INT);
1332   Node* inner_incr = new AddINode(inner_phi, int_stride);
1333   Node* inner_cmp = new CmpINode(inner_incr, new_limit);
1334   Node* inner_bol = new BoolNode(inner_cmp, exit_test->in(1)->as_Bool()->_test._test);
1335   inner_phi->set_req(LoopNode::EntryControl, int_zero);
1336   inner_phi->set_req(LoopNode::LoopBackControl, inner_incr);
1337   register_new_node(inner_phi, head);
1338   register_new_node(inner_incr, head);
1339   register_new_node(inner_cmp, head);
1340   register_new_node(inner_bol, head);
1341 
1342   _igvn.replace_input_of(exit_test, 1, inner_bol);
1343 
1344   // Replace inner loop long iv phi as inner loop int iv phi + outer
1345   // loop iv phi
1346   Node* iv_add = loop_nest_replace_iv(phi, inner_phi, init, head, bt);
1347 
1348   LoopNode* inner_head = head;
1349   if (bt == T_LONG) {
1350     // Turn the loop back to a counted loop
1351     inner_head = create_inner_head(loop, head, exit_test);
1352   } else {
1353     // Use existing counted loop
1354     revert_to_normal_loop(head);
1355   }
1356 
1357   if (bt == T_INT) {
1358     init = new ConvI2LNode(init);
1359     register_new_node(init, entry_control);
1360   }
1361 
1362   transform_long_range_checks(stride_con, range_checks, init, new_limit,
1363                               inner_phi, iv_add, inner_head);
1364 
1365   inner_head->mark_loop_nest_inner_loop();
1366 
1367   return true;
1368 }
1369 
1370 int PhaseIdealLoop::extract_long_range_checks(const IdealLoopTree* loop, jint stride_con, int iters_limit, PhiNode* phi,
1371                                               Node_List& range_checks) {
1372   const jlong min_iters = 2;
1373   jlong reduced_iters_limit = iters_limit;
1374   jlong original_iters_limit = iters_limit;
1375   for (uint i = 0; i < loop->_body.size(); i++) {
1376     Node* c = loop->_body.at(i);
1377     if (c->is_IfProj() && c->in(0)->is_RangeCheck()) {
1378       IfProjNode* if_proj = c->as_IfProj();
1379       CallStaticJavaNode* call = if_proj->is_uncommon_trap_if_pattern();
1380       if (call != nullptr) {
1381         Node* range = nullptr;
1382         Node* offset = nullptr;
1383         jlong scale = 0;
1384         if (loop->is_range_check_if(if_proj, this, T_LONG, phi, range, offset, scale) &&
1385             loop->is_invariant(range) && loop->is_invariant(offset) &&
1386             scale != min_jlong &&
1387             original_iters_limit / ABS(scale) >= min_iters * ABS(stride_con)) {
1388           assert(scale == (jint)scale, "scale should be an int");
1389           reduced_iters_limit = MIN2(reduced_iters_limit, original_iters_limit/ABS(scale));
1390           range_checks.push(c);
1391         }
1392       }
1393     }
1394   }
1395 
1396   return checked_cast<int>(reduced_iters_limit);
1397 }
1398 
1399 // One execution of the inner loop covers a sub-range of the entire iteration range of the loop: [A,Z), aka [A=init,
1400 // Z=limit). If the loop has at least one trip (which is the case here), the iteration variable i always takes A as its
1401 // first value, followed by A+S (S is the stride), next A+2S, etc. The limit is exclusive, so that the final value B of
1402 // i is never Z.  It will be B=Z-1 if S=1, or B=Z+1 if S=-1.
1403 
1404 // If |S|>1 the formula for the last value B would require a floor operation, specifically B=floor((Z-sgn(S)-A)/S)*S+A,
1405 // which is B=Z-sgn(S)U for some U in [1,|S|].  So when S>0, i ranges as i:[A,Z) or i:[A,B=Z-U], or else (in reverse)
1406 // as i:(Z,A] or i:[B=Z+U,A].  It will become important to reason about this inclusive range [A,B] or [B,A].
1407 
1408 // Within the loop there may be many range checks.  Each such range check (R.C.) is of the form 0 <= i*K+L < R, where K
1409 // is a scale factor applied to the loop iteration variable i, and L is some offset; K, L, and R are loop-invariant.
1410 // Because R is never negative (see below), this check can always be simplified to an unsigned check i*K+L <u R.
1411 
1412 // When a long loop over a 64-bit variable i (outer_iv) is decomposed into a series of shorter sub-loops over a 32-bit
1413 // variable j (inner_iv), j ranges over a shorter interval j:[0,B_2] or [0,Z_2) (assuming S > 0), where the limit is
1414 // chosen to prevent various cases of 32-bit overflow (including multiplications j*K below).  In the sub-loop the
1415 // logical value i is offset from j by a 64-bit constant C, so i ranges in i:C+[0,Z_2).
1416 
1417 // For S<0, j ranges (in reverse!) through j:[-|B_2|,0] or (-|Z_2|,0].  For either sign of S, we can say i=j+C and j
1418 // ranges through 32-bit ranges [A_2,B_2] or [B_2,A_2] (A_2=0 of course).
1419 
1420 // The disjoint union of all the C+[A_2,B_2] ranges from the sub-loops must be identical to the whole range [A,B].
1421 // Assuming S>0, the first C must be A itself, and the next C value is the previous C+B_2, plus S.  If |S|=1, the next
1422 // C value is also the previous C+Z_2.  In each sub-loop, j counts from j=A_2=0 and i counts from C+0 and exits at
1423 // j=B_2 (i=C+B_2), just before it gets to i=C+Z_2.  Both i and j count up (from C and 0) if S>0; otherwise they count
1424 // down (from C and 0 again).
1425 
1426 // Returning to range checks, we see that each i*K+L <u R expands to (C+j)*K+L <u R, or j*K+Q <u R, where Q=(C*K+L).
1427 // (Recall that K and L and R are loop-invariant scale, offset and range values for a particular R.C.)  This is still a
1428 // 64-bit comparison, so the range check elimination logic will not apply to it.  (The R.C.E. transforms operate only on
1429 // 32-bit indexes and comparisons, because they use 64-bit temporary values to avoid overflow; see
1430 // PhaseIdealLoop::add_constraint.)
1431 
1432 // We must transform this comparison so that it gets the same answer, but by means of a 32-bit R.C. (using j not i) of
1433 // the form j*K+L_2 <u32 R_2.  Note that L_2 and R_2 must be loop-invariant, but only with respect to the sub-loop.  Thus, the
1434 // problem reduces to computing values for L_2 and R_2 (for each R.C. in the loop) in the loop header for the sub-loop.
1435 // Then the standard R.C.E. transforms can take those as inputs and further compute the necessary minimum and maximum
1436 // values for the 32-bit counter j within which the range checks can be eliminated.
1437 
1438 // So, given j*K+Q <u R, we need to find some j*K+L_2 <u32 R_2, where L_2 and R_2 fit in 32 bits, and the 32-bit operations do
1439 // not overflow. We also need to cover the cases where i*K+L (= j*K+Q) overflows to a 64-bit negative, since that is
1440 // allowed as an input to the R.C., as long as the R.C. as a whole fails.
1441 
1442 // If 32-bit multiplication j*K might overflow, we adjust the sub-loop limit Z_2 closer to zero to reduce j's range.
1443 
1444 // For each R.C. j*K+Q <u32 R, the range of mathematical values of j*K+Q in the sub-loop is [Q_min, Q_max], where
1445 // Q_min=Q and Q_max=B_2*K+Q (if S>0 and K>0), Q_min=A_2*K+Q and Q_max=Q (if S<0 and K>0),
1446 // Q_min=B_2*K+Q and Q_max=Q if (S>0 and K<0), Q_min=Q and Q_max=A_2*K+Q (if S<0 and K<0)
1447 
1448 // Note that the first R.C. value is always Q=(S*K>0 ? Q_min : Q_max).  Also Q_{min,max} = Q + {min,max}(A_2*K,B_2*K).
1449 // If S*K>0 then, as the loop iterations progress, each R.C. value i*K+L = j*K+Q goes up from Q=Q_min towards Q_max.
1450 // If S*K<0 then j*K+Q starts at Q=Q_max and goes down towards Q_min.
1451 
1452 // Case A: Some Negatives (but no overflow).
1453 // Number line:
1454 // |s64_min   .    .    .    0    .    .    .   s64_max|
1455 // |    .  Q_min..Q_max .    0    .    .    .     .    |  s64 negative
1456 // |    .     .    .    .    R=0  R<   R<   R<    R<   |  (against R values)
1457 // |    .     .    .  Q_min..0..Q_max  .    .     .    |  small mixed
1458 // |    .     .    .    .    R    R    R<   R<    R<   |  (against R values)
1459 //
1460 // R values which are out of range (>Q_max+1) are reduced to max(0,Q_max+1).  They are marked on the number line as R<.
1461 //
1462 // So, if Q_min <s64 0, then use this test:
1463 // j*K + s32_trunc(Q_min) <u32 clamp(R, 0, Q_max+1) if S*K>0 (R.C.E. steps upward)
1464 // j*K + s32_trunc(Q_max) <u32 clamp(R, 0, Q_max+1) if S*K<0 (R.C.E. steps downward)
1465 // Both formulas reduce to adding j*K to the 32-bit truncated value of the first R.C. expression value, Q:
1466 // j*K + s32_trunc(Q) <u32 clamp(R, 0, Q_max+1) for all S,K
1467 
1468 // If the 32-bit truncation loses information, no harm is done, since certainly the clamp also will return R_2=zero.
1469 
1470 // Case B: No Negatives.
1471 // Number line:
1472 // |s64_min   .    .    .    0    .    .    .   s64_max|
1473 // |    .     .    .    .    0 Q_min..Q_max .     .    |  small positive
1474 // |    .     .    .    .    R>   R    R    R<    R<   |  (against R values)
1475 // |    .     .    .    .    0    . Q_min..Q_max  .    |  s64 positive
1476 // |    .     .    .    .    R>   R>   R    R     R<   |  (against R values)
1477 //
1478 // R values which are out of range (<Q_min or >Q_max+1) are reduced as marked: R> up to Q_min, R< down to Q_max+1.
1479 // Then the whole comparison is shifted left by Q_min, so it can take place at zero, which is a nice 32-bit value.
1480 //
1481 // So, if both Q_min, Q_max+1 >=s64 0, then use this test:
1482 // j*K + 0         <u32 clamp(R, Q_min, Q_max+1) - Q_min if S*K>0
1483 // More generally:
1484 // j*K + Q - Q_min <u32 clamp(R, Q_min, Q_max+1) - Q_min for all S,K
1485 
1486 // Case C: Overflow in the 64-bit domain
1487 // Number line:
1488 // |..Q_max-2^64   .    .    0    .    .    .   Q_min..|  s64 overflow
1489 // |    .     .    .    .    R>   R>   R>   R>    R    |  (against R values)
1490 //
1491 // In this case, Q_min >s64 Q_max+1, even though the mathematical values of Q_min and Q_max+1 are correctly ordered.
1492 // The formulas from the previous case can be used, except that the bad upper bound Q_max is replaced by max_jlong.
1493 // (In fact, we could use any replacement bound from R to max_jlong inclusive, as the input to the clamp function.)
1494 //
1495 // So if Q_min >=s64 0 but Q_max+1 <s64 0, use this test:
1496 // j*K + 0         <u32 clamp(R, Q_min, max_jlong) - Q_min if S*K>0
1497 // More generally:
1498 // j*K + Q - Q_min <u32 clamp(R, Q_min, max_jlong) - Q_min for all S,K
1499 //
1500 // Dropping the bad bound means only Q_min is used to reduce the range of R:
1501 // j*K + Q - Q_min <u32 max(Q_min, R) - Q_min for all S,K
1502 //
1503 // Here the clamp function is a 64-bit min/max that reduces the dynamic range of its R operand to the required [L,H]:
1504 //     clamp(X, L, H) := max(L, min(X, H))
1505 // When degenerately L > H, it returns L not H.
1506 //
1507 // All of the formulas above can be merged into a single one:
1508 //     L_clamp = Q_min < 0 ? 0 : Q_min        --whether and how far to left-shift
1509 //     H_clamp = Q_max+1 < Q_min ? max_jlong : Q_max+1
1510 //             = Q_max+1 < 0 && Q_min >= 0 ? max_jlong : Q_max+1
1511 //     Q_first = Q = (S*K>0 ? Q_min : Q_max) = (C*K+L)
1512 //     R_clamp = clamp(R, L_clamp, H_clamp)   --reduced dynamic range
1513 //     replacement R.C.:
1514 //       j*K + Q_first - L_clamp <u32 R_clamp - L_clamp
1515 //     or equivalently:
1516 //       j*K + L_2 <u32 R_2
1517 //     where
1518 //       L_2 = Q_first - L_clamp
1519 //       R_2 = R_clamp - L_clamp
1520 //
1521 // Note on why R is never negative:
1522 //
1523 // Various details of this transformation would break badly if R could be negative, so this transformation only
1524 // operates after obtaining hard evidence that R<0 is impossible.  For example, if R comes from a LoadRange node, we
1525 // know R cannot be negative.  For explicit checks (of both int and long) a proof is constructed in
1526 // inline_preconditions_checkIndex, which triggers an uncommon trap if R<0, then wraps R in a ConstraintCastNode with a
1527 // non-negative type.  Later on, when IdealLoopTree::is_range_check_if looks for an optimizable R.C., it checks that
1528 // the type of that R node is non-negative.  Any "wild" R node that could be negative is not treated as an optimizable
1529 // R.C., but R values from a.length and inside checkIndex are good to go.
1530 //
1531 void PhaseIdealLoop::transform_long_range_checks(int stride_con, const Node_List &range_checks, Node* outer_phi,
1532                                                  Node* inner_iters_actual_int, Node* inner_phi,
1533                                                  Node* iv_add, LoopNode* inner_head) {
1534   Node* long_zero = longcon(0);
1535   Node* int_zero = intcon(0);
1536   Node* long_one = longcon(1);
1537   Node* int_stride = intcon(checked_cast<int>(stride_con));
1538 
1539   for (uint i = 0; i < range_checks.size(); i++) {
1540     ProjNode* proj = range_checks.at(i)->as_Proj();
1541     RangeCheckNode* rc = proj->in(0)->as_RangeCheck();
1542     jlong scale = 0;
1543     Node* offset = nullptr;
1544     Node* rc_bol = rc->in(1);
1545     Node* rc_cmp = rc_bol->in(1);
1546     if (rc_cmp->Opcode() == Op_CmpU) {
1547       // could be shared and have already been taken care of
1548       continue;
1549     }
1550     bool short_scale = false;
1551     bool ok = is_scaled_iv_plus_offset(rc_cmp->in(1), iv_add, T_LONG, &scale, &offset, &short_scale);
1552     assert(ok, "inconsistent: was tested before");
1553     Node* range = rc_cmp->in(2);
1554     Node* c = rc->in(0);
1555     Node* entry_control = inner_head->in(LoopNode::EntryControl);
1556 
1557     Node* R = range;
1558     Node* K = longcon(scale);
1559 
1560     Node* L = offset;
1561 
1562     if (short_scale) {
1563       // This converts:
1564       // (int)i*K + L <u64 R
1565       // with K an int into:
1566       // i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R)
1567       // to protect against an overflow of (int)i*K
1568       //
1569       // Because if (int)i*K overflows, there are K,L where:
1570       // (int)i*K + L <u64 R is false because (int)i*K+L overflows to a negative which becomes a huge u64 value.
1571       // But if i*(long)K + L is >u64 (long)max_jint and still is <u64 R, then
1572       // i*(long)K + L <u64 R is true.
1573       //
1574       // As a consequence simply converting i*K + L <u64 R to i*(long)K + L <u64 R could cause incorrect execution.
1575       //
1576       // It's always true that:
1577       // (int)i*K <u64 (long)max_jint + 1
1578       // which implies (int)i*K + L <u64 (long)max_jint + 1 + L
1579       // As a consequence:
1580       // i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R)
1581       // is always false in case of overflow of i*K
1582       //
1583       // Note, there are also K,L where i*K overflows and
1584       // i*K + L <u64 R is true, but
1585       // i*(long)K + L <u64 unsigned_min((long)max_jint + L + 1, R) is false
1586       // So this transformation could cause spurious deoptimizations and failed range check elimination
1587       // (but not incorrect execution) for unlikely corner cases with overflow.
1588       // If this causes problems in practice, we could maybe direct execution to a post-loop, instead of deoptimizing.
1589       Node* max_jint_plus_one_long = longcon((jlong)max_jint + 1);
1590       Node* max_range = new AddLNode(max_jint_plus_one_long, L);
1591       register_new_node(max_range, entry_control);
1592       R = MaxNode::unsigned_min(R, max_range, TypeLong::POS, _igvn);
1593       set_subtree_ctrl(R, true);
1594     }
1595 
1596     Node* C = outer_phi;
1597 
1598     // Start with 64-bit values:
1599     //   i*K + L <u64 R
1600     //   (C+j)*K + L <u64 R
1601     //   j*K + Q <u64 R    where Q = Q_first = C*K+L
1602     Node* Q_first = new MulLNode(C, K);
1603     register_new_node(Q_first, entry_control);
1604     Q_first = new AddLNode(Q_first, L);
1605     register_new_node(Q_first, entry_control);
1606 
1607     // Compute endpoints of the range of values j*K + Q.
1608     //  Q_min = (j=0)*K + Q;  Q_max = (j=B_2)*K + Q
1609     Node* Q_min = Q_first;
1610 
1611     // Compute the exact ending value B_2 (which is really A_2 if S < 0)
1612     Node* B_2 = new LoopLimitNode(this->C, int_zero, inner_iters_actual_int, int_stride);
1613     register_new_node(B_2, entry_control);
1614     B_2 = new SubINode(B_2, int_stride);
1615     register_new_node(B_2, entry_control);
1616     B_2 = new ConvI2LNode(B_2);
1617     register_new_node(B_2, entry_control);
1618 
1619     Node* Q_max = new MulLNode(B_2, K);
1620     register_new_node(Q_max, entry_control);
1621     Q_max = new AddLNode(Q_max, Q_first);
1622     register_new_node(Q_max, entry_control);
1623 
1624     if (scale * stride_con < 0) {
1625       swap(Q_min, Q_max);
1626     }
1627     // Now, mathematically, Q_max > Q_min, and they are close enough so that (Q_max-Q_min) fits in 32 bits.
1628 
1629     // L_clamp = Q_min < 0 ? 0 : Q_min
1630     Node* Q_min_cmp = new CmpLNode(Q_min, long_zero);
1631     register_new_node(Q_min_cmp, entry_control);
1632     Node* Q_min_bool = new BoolNode(Q_min_cmp, BoolTest::lt);
1633     register_new_node(Q_min_bool, entry_control);
1634     Node* L_clamp = new CMoveLNode(Q_min_bool, Q_min, long_zero, TypeLong::LONG);
1635     register_new_node(L_clamp, entry_control);
1636     // (This could also be coded bitwise as L_clamp = Q_min & ~(Q_min>>63).)
1637 
1638     Node* Q_max_plus_one = new AddLNode(Q_max, long_one);
1639     register_new_node(Q_max_plus_one, entry_control);
1640 
1641     // H_clamp = Q_max+1 < Q_min ? max_jlong : Q_max+1
1642     // (Because Q_min and Q_max are close, the overflow check could also be encoded as Q_max+1 < 0 & Q_min >= 0.)
1643     Node* max_jlong_long = longcon(max_jlong);
1644     Node* Q_max_cmp = new CmpLNode(Q_max_plus_one, Q_min);
1645     register_new_node(Q_max_cmp, entry_control);
1646     Node* Q_max_bool = new BoolNode(Q_max_cmp, BoolTest::lt);
1647     register_new_node(Q_max_bool, entry_control);
1648     Node* H_clamp = new CMoveLNode(Q_max_bool, Q_max_plus_one, max_jlong_long, TypeLong::LONG);
1649     register_new_node(H_clamp, entry_control);
1650     // (This could also be coded bitwise as H_clamp = ((Q_max+1)<<1 | M)>>>1 where M = (Q_max+1)>>63 & ~Q_min>>63.)
1651 
1652     // R_2 = clamp(R, L_clamp, H_clamp) - L_clamp
1653     // that is:  R_2 = clamp(R, L_clamp=0, H_clamp=Q_max)      if Q_min < 0
1654     // or else:  R_2 = clamp(R, L_clamp,   H_clamp) - Q_min    if Q_min >= 0
1655     // and also: R_2 = clamp(R, L_clamp,   Q_max+1) - L_clamp  if Q_min < Q_max+1 (no overflow)
1656     // or else:  R_2 = clamp(R, L_clamp, *no limit*)- L_clamp  if Q_max+1 < Q_min (overflow)
1657     Node* R_2 = clamp(R, L_clamp, H_clamp);
1658     R_2 = new SubLNode(R_2, L_clamp);
1659     register_new_node(R_2, entry_control);
1660     R_2 = new ConvL2INode(R_2, TypeInt::POS);
1661     register_new_node(R_2, entry_control);
1662 
1663     // L_2 = Q_first - L_clamp
1664     // We are subtracting L_clamp from both sides of the <u32 comparison.
1665     // If S*K>0, then Q_first == 0 and the R.C. expression at -L_clamp and steps upward to Q_max-L_clamp.
1666     // If S*K<0, then Q_first != 0 and the R.C. expression starts high and steps downward to Q_min-L_clamp.
1667     Node* L_2 = new SubLNode(Q_first, L_clamp);
1668     register_new_node(L_2, entry_control);
1669     L_2 = new ConvL2INode(L_2, TypeInt::INT);
1670     register_new_node(L_2, entry_control);
1671 
1672     // Transform the range check using the computed values L_2/R_2
1673     // from:   i*K + L   <u64 R
1674     // to:     j*K + L_2 <u32 R_2
1675     // that is:
1676     //   (j*K + Q_first) - L_clamp <u32 clamp(R, L_clamp, H_clamp) - L_clamp
1677     K = intcon(checked_cast<int>(scale));
1678     Node* scaled_iv = new MulINode(inner_phi, K);
1679     register_new_node(scaled_iv, c);
1680     Node* scaled_iv_plus_offset = new AddINode(scaled_iv, L_2);
1681     register_new_node(scaled_iv_plus_offset, c);
1682 
1683     Node* new_rc_cmp = new CmpUNode(scaled_iv_plus_offset, R_2);
1684     register_new_node(new_rc_cmp, c);
1685 
1686     _igvn.replace_input_of(rc_bol, 1, new_rc_cmp);
1687   }
1688 }
1689 
1690 Node* PhaseIdealLoop::clamp(Node* R, Node* L, Node* H) {
1691   Node* min = MaxNode::signed_min(R, H, TypeLong::LONG, _igvn);
1692   set_subtree_ctrl(min, true);
1693   Node* max = MaxNode::signed_max(L, min, TypeLong::LONG, _igvn);
1694   set_subtree_ctrl(max, true);
1695   return max;
1696 }
1697 
1698 LoopNode* PhaseIdealLoop::create_inner_head(IdealLoopTree* loop, BaseCountedLoopNode* head,
1699                                             IfNode* exit_test) {
1700   LoopNode* new_inner_head = new LoopNode(head->in(1), head->in(2));
1701   IfNode* new_inner_exit = new IfNode(exit_test->in(0), exit_test->in(1), exit_test->_prob, exit_test->_fcnt);
1702   _igvn.register_new_node_with_optimizer(new_inner_head);
1703   _igvn.register_new_node_with_optimizer(new_inner_exit);
1704   loop->_body.push(new_inner_head);
1705   loop->_body.push(new_inner_exit);
1706   loop->_body.yank(head);
1707   loop->_body.yank(exit_test);
1708   set_loop(new_inner_head, loop);
1709   set_loop(new_inner_exit, loop);
1710   set_idom(new_inner_head, idom(head), dom_depth(head));
1711   set_idom(new_inner_exit, idom(exit_test), dom_depth(exit_test));
1712   lazy_replace(head, new_inner_head);
1713   lazy_replace(exit_test, new_inner_exit);
1714   loop->_head = new_inner_head;
1715   return new_inner_head;
1716 }
1717 
1718 #ifdef ASSERT
1719 void PhaseIdealLoop::check_counted_loop_shape(IdealLoopTree* loop, Node* x, BasicType bt) {
1720   Node* back_control = loop_exit_control(x, loop);
1721   assert(back_control != nullptr, "no back control");
1722 
1723   BoolTest::mask mask = BoolTest::illegal;
1724   float cl_prob = 0;
1725   Node* incr = nullptr;
1726   Node* limit = nullptr;
1727 
1728   Node* cmp = loop_exit_test(back_control, loop, incr, limit, mask, cl_prob);
1729   assert(cmp != nullptr && cmp->Opcode() == Op_Cmp(bt), "no exit test");
1730 
1731   Node* phi_incr = nullptr;
1732   incr = loop_iv_incr(incr, x, loop, phi_incr);
1733   assert(incr != nullptr && incr->Opcode() == Op_Add(bt), "no incr");
1734 
1735   Node* xphi = nullptr;
1736   Node* stride = loop_iv_stride(incr, xphi);
1737 
1738   assert(stride != nullptr, "no stride");
1739 
1740   PhiNode* phi = loop_iv_phi(xphi, phi_incr, x);
1741 
1742   assert(phi != nullptr && phi->in(LoopNode::LoopBackControl) == incr, "No phi");
1743 
1744   jlong stride_con = stride->get_integer_as_long(bt);
1745 
1746   assert(condition_stride_ok(mask, stride_con), "illegal condition");
1747 
1748   assert(mask != BoolTest::ne, "unexpected condition");
1749   assert(phi_incr == nullptr, "bad loop shape");
1750   assert(cmp->in(1) == incr, "bad exit test shape");
1751 
1752   // Safepoint on backedge not supported
1753   assert(x->in(LoopNode::LoopBackControl)->Opcode() != Op_SafePoint, "no safepoint on backedge");
1754 }
1755 #endif
1756 
1757 #ifdef ASSERT
1758 // convert an int counted loop to a long counted to stress handling of
1759 // long counted loops
1760 bool PhaseIdealLoop::convert_to_long_loop(Node* cmp, Node* phi, IdealLoopTree* loop) {
1761   Unique_Node_List iv_nodes;
1762   Node_List old_new;
1763   iv_nodes.push(cmp);
1764   bool failed = false;
1765 
1766   for (uint i = 0; i < iv_nodes.size() && !failed; i++) {
1767     Node* n = iv_nodes.at(i);
1768     switch(n->Opcode()) {
1769       case Op_Phi: {
1770         Node* clone = new PhiNode(n->in(0), TypeLong::LONG);
1771         old_new.map(n->_idx, clone);
1772         break;
1773       }
1774       case Op_CmpI: {
1775         Node* clone = new CmpLNode(nullptr, nullptr);
1776         old_new.map(n->_idx, clone);
1777         break;
1778       }
1779       case Op_AddI: {
1780         Node* clone = new AddLNode(nullptr, nullptr);
1781         old_new.map(n->_idx, clone);
1782         break;
1783       }
1784       case Op_CastII: {
1785         failed = true;
1786         break;
1787       }
1788       default:
1789         DEBUG_ONLY(n->dump());
1790         fatal("unexpected");
1791     }
1792 
1793     for (uint i = 1; i < n->req(); i++) {
1794       Node* in = n->in(i);
1795       if (in == nullptr) {
1796         continue;
1797       }
1798       if (loop->is_member(get_loop(get_ctrl(in)))) {
1799         iv_nodes.push(in);
1800       }
1801     }
1802   }
1803 
1804   if (failed) {
1805     for (uint i = 0; i < iv_nodes.size(); i++) {
1806       Node* n = iv_nodes.at(i);
1807       Node* clone = old_new[n->_idx];
1808       if (clone != nullptr) {
1809         _igvn.remove_dead_node(clone);
1810       }
1811     }
1812     return false;
1813   }
1814 
1815   for (uint i = 0; i < iv_nodes.size(); i++) {
1816     Node* n = iv_nodes.at(i);
1817     Node* clone = old_new[n->_idx];
1818     for (uint i = 1; i < n->req(); i++) {
1819       Node* in = n->in(i);
1820       if (in == nullptr) {
1821         continue;
1822       }
1823       Node* in_clone = old_new[in->_idx];
1824       if (in_clone == nullptr) {
1825         assert(_igvn.type(in)->isa_int(), "");
1826         in_clone = new ConvI2LNode(in);
1827         _igvn.register_new_node_with_optimizer(in_clone);
1828         set_subtree_ctrl(in_clone, false);
1829       }
1830       if (in_clone->in(0) == nullptr) {
1831         in_clone->set_req(0, C->top());
1832         clone->set_req(i, in_clone);
1833         in_clone->set_req(0, nullptr);
1834       } else {
1835         clone->set_req(i, in_clone);
1836       }
1837     }
1838     _igvn.register_new_node_with_optimizer(clone);
1839   }
1840   set_ctrl(old_new[phi->_idx], phi->in(0));
1841 
1842   for (uint i = 0; i < iv_nodes.size(); i++) {
1843     Node* n = iv_nodes.at(i);
1844     Node* clone = old_new[n->_idx];
1845     set_subtree_ctrl(clone, false);
1846     Node* m = n->Opcode() == Op_CmpI ? clone : nullptr;
1847     for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1848       Node* u = n->fast_out(i);
1849       if (iv_nodes.member(u)) {
1850         continue;
1851       }
1852       if (m == nullptr) {
1853         m = new ConvL2INode(clone);
1854         _igvn.register_new_node_with_optimizer(m);
1855         set_subtree_ctrl(m, false);
1856       }
1857       _igvn.rehash_node_delayed(u);
1858       int nb = u->replace_edge(n, m, &_igvn);
1859       --i, imax -= nb;
1860     }
1861   }
1862   return true;
1863 }
1864 #endif
1865 
1866 //------------------------------is_counted_loop--------------------------------
1867 bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*&loop, BasicType iv_bt) {
1868   PhaseGVN *gvn = &_igvn;
1869 
1870   Node* back_control = loop_exit_control(x, loop);
1871   if (back_control == nullptr) {
1872     return false;
1873   }
1874 
1875   BoolTest::mask bt = BoolTest::illegal;
1876   float cl_prob = 0;
1877   Node* incr = nullptr;
1878   Node* limit = nullptr;
1879   Node* cmp = loop_exit_test(back_control, loop, incr, limit, bt, cl_prob);
1880   if (cmp == nullptr || cmp->Opcode() != Op_Cmp(iv_bt)) {
1881     return false; // Avoid pointer & float & 64-bit compares
1882   }
1883 
1884   // Trip-counter increment must be commutative & associative.
1885   if (incr->Opcode() == Op_Cast(iv_bt)) {
1886     incr = incr->in(1);
1887   }
1888 
1889   Node* phi_incr = nullptr;
1890   incr = loop_iv_incr(incr, x, loop, phi_incr);
1891   if (incr == nullptr) {
1892     return false;
1893   }
1894 
1895   Node* trunc1 = nullptr;
1896   Node* trunc2 = nullptr;
1897   const TypeInteger* iv_trunc_t = nullptr;
1898   Node* orig_incr = incr;
1899   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t, iv_bt))) {
1900     return false; // Funny increment opcode
1901   }
1902   assert(incr->Opcode() == Op_Add(iv_bt), "wrong increment code");
1903 
1904   Node* xphi = nullptr;
1905   Node* stride = loop_iv_stride(incr, xphi);
1906 
1907   if (stride == nullptr) {
1908     return false;
1909   }
1910 
1911   // Iteratively uncast the loop induction variable
1912   // until no more CastII/CastLL nodes are found.
1913   while (xphi->Opcode() == Op_Cast(iv_bt)) {
1914     xphi = xphi->in(1);
1915   }
1916 
1917   // Stride must be constant
1918   jlong stride_con = stride->get_integer_as_long(iv_bt);
1919   assert(stride_con != 0, "missed some peephole opt");
1920 
1921   PhiNode* phi = loop_iv_phi(xphi, phi_incr, x);
1922 
1923   if (phi == nullptr ||
1924       (trunc1 == nullptr && phi->in(LoopNode::LoopBackControl) != incr) ||
1925       (trunc1 != nullptr && phi->in(LoopNode::LoopBackControl) != trunc1)) {
1926     return false;
1927   }
1928 
1929   Node* iftrue = back_control;
1930   uint iftrue_op = iftrue->Opcode();
1931   Node* iff = iftrue->in(0);
1932   BoolNode* test = iff->in(1)->as_Bool();
1933 
1934   const TypeInteger* limit_t = gvn->type(limit)->is_integer(iv_bt);
1935   if (trunc1 != nullptr) {
1936     // When there is a truncation, we must be sure that after the truncation
1937     // the trip counter will end up higher than the limit, otherwise we are looking
1938     // at an endless loop. Can happen with range checks.
1939 
1940     // Example:
1941     // int i = 0;
1942     // while (true)
1943     //    sum + = array[i];
1944     //    i++;
1945     //    i = i && 0x7fff;
1946     //  }
1947     //
1948     // If the array is shorter than 0x8000 this exits through a AIOOB
1949     //  - Counted loop transformation is ok
1950     // If the array is longer then this is an endless loop
1951     //  - No transformation can be done.
1952 
1953     const TypeInteger* incr_t = gvn->type(orig_incr)->is_integer(iv_bt);
1954     if (limit_t->hi_as_long() > incr_t->hi_as_long()) {
1955       // if the limit can have a higher value than the increment (before the phi)
1956       return false;
1957     }
1958   }
1959 
1960   Node *init_trip = phi->in(LoopNode::EntryControl);
1961 
1962   // If iv trunc type is smaller than int, check for possible wrap.
1963   if (!TypeInteger::bottom(iv_bt)->higher_equal(iv_trunc_t)) {
1964     assert(trunc1 != nullptr, "must have found some truncation");
1965 
1966     // Get a better type for the phi (filtered thru if's)
1967     const TypeInteger* phi_ft = filtered_type(phi);
1968 
1969     // Can iv take on a value that will wrap?
1970     //
1971     // Ensure iv's limit is not within "stride" of the wrap value.
1972     //
1973     // Example for "short" type
1974     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
1975     //    If the stride is +10, then the last value of the induction
1976     //    variable before the increment (phi_ft->_hi) must be
1977     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
1978     //    ensure no truncation occurs after the increment.
1979 
1980     if (stride_con > 0) {
1981       if (iv_trunc_t->hi_as_long() - phi_ft->hi_as_long() < stride_con ||
1982           iv_trunc_t->lo_as_long() > phi_ft->lo_as_long()) {
1983         return false;  // truncation may occur
1984       }
1985     } else if (stride_con < 0) {
1986       if (iv_trunc_t->lo_as_long() - phi_ft->lo_as_long() > stride_con ||
1987           iv_trunc_t->hi_as_long() < phi_ft->hi_as_long()) {
1988         return false;  // truncation may occur
1989       }
1990     }
1991     // No possibility of wrap so truncation can be discarded
1992     // Promote iv type to Int
1993   } else {
1994     assert(trunc1 == nullptr && trunc2 == nullptr, "no truncation for int");
1995   }
1996 
1997   if (!condition_stride_ok(bt, stride_con)) {
1998     return false;
1999   }
2000 
2001   const TypeInteger* init_t = gvn->type(init_trip)->is_integer(iv_bt);
2002 
2003   if (stride_con > 0) {
2004     if (init_t->lo_as_long() > max_signed_integer(iv_bt) - stride_con) {
2005       return false; // cyclic loop
2006     }
2007   } else {
2008     if (init_t->hi_as_long() < min_signed_integer(iv_bt) - stride_con) {
2009       return false; // cyclic loop
2010     }
2011   }
2012 
2013   if (phi_incr != nullptr && bt != BoolTest::ne) {
2014     // check if there is a possibility of IV overflowing after the first increment
2015     if (stride_con > 0) {
2016       if (init_t->hi_as_long() > max_signed_integer(iv_bt) - stride_con) {
2017         return false;
2018       }
2019     } else {
2020       if (init_t->lo_as_long() < min_signed_integer(iv_bt) - stride_con) {
2021         return false;
2022       }
2023     }
2024   }
2025 
2026   // =================================================
2027   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
2028   //
2029 
2030   if (x->Opcode() == Op_Region) {
2031     // x has not yet been transformed to Loop or LongCountedLoop.
2032     // This should only happen if we are inside an infinite loop.
2033     // It happens like this:
2034     //   build_loop_tree -> do not attach infinite loop and nested loops
2035     //   beautify_loops  -> does not transform the infinite and nested loops to LoopNode, because not attached yet
2036     //   build_loop_tree -> find and attach infinite and nested loops
2037     //   counted_loop    -> nested Regions are not yet transformed to LoopNodes, we land here
2038     assert(x->as_Region()->is_in_infinite_subgraph(),
2039            "x can only be a Region and not Loop if inside infinite loop");
2040     // Come back later when Region is transformed to LoopNode
2041     return false;
2042   }
2043 
2044   assert(x->Opcode() == Op_Loop || x->Opcode() == Op_LongCountedLoop, "regular loops only");
2045   C->print_method(PHASE_BEFORE_CLOOPS, 3, x);
2046 
2047   // ===================================================
2048   // We can only convert this loop to a counted loop if we can guarantee that the iv phi will never overflow at runtime.
2049   // This is an implicit assumption taken by some loop optimizations. We therefore must ensure this property at all cost.
2050   // At this point, we've already excluded some trivial cases where an overflow could have been proven statically.
2051   // But even though we cannot prove that an overflow will *not* happen, we still want to speculatively convert this loop
2052   // to a counted loop. This can be achieved by adding additional iv phi overflow checks before the loop. If they fail,
2053   // we trap and resume execution before the loop without having executed any iteration of the loop, yet.
2054   //
2055   // These additional iv phi overflow checks can be inserted as Loop Limit Check Predicates above the Loop Limit Check
2056   // Parse Predicate which captures a JVM state just before the entry of the loop. If there is no such Parse Predicate,
2057   // we cannot generate a Loop Limit Check Predicate and thus cannot speculatively convert the loop to a counted loop.
2058   //
2059   // In the following, we only focus on int loops with stride > 0 to keep things simple. The argumentation and proof
2060   // for stride < 0 is analogously. For long loops, we would replace max_int with max_long.
2061   //
2062   //
2063   // The loop to be converted does not always need to have the often used shape:
2064   //
2065   //                                                 i = init
2066   //     i = init                                loop:
2067   //     do {                                        ...
2068   //         // ...               equivalent         i+=stride
2069   //         i+=stride               <==>            if (i < limit)
2070   //     } while (i < limit);                          goto loop
2071   //                                             exit:
2072   //                                                 ...
2073   //
2074   // where the loop exit check uses the post-incremented iv phi and a '<'-operator.
2075   //
2076   // We could also have '<='-operator (or '>='-operator for negative strides) or use the pre-incremented iv phi value
2077   // in the loop exit check:
2078   //
2079   //         i = init
2080   //     loop:
2081   //         ...
2082   //         if (i <= limit)
2083   //             i+=stride
2084   //             goto loop
2085   //     exit:
2086   //         ...
2087   //
2088   // Let's define the following terms:
2089   // - iv_pre_i: The pre-incremented iv phi before the i-th iteration.
2090   // - iv_post_i: The post-incremented iv phi after the i-th iteration.
2091   //
2092   // The iv_pre_i and iv_post_i have the following relation:
2093   //      iv_pre_i + stride = iv_post_i
2094   //
2095   // When converting a loop to a counted loop, we want to have a canonicalized loop exit check of the form:
2096   //     iv_post_i < adjusted_limit
2097   //
2098   // If that is not the case, we need to canonicalize the loop exit check by using different values for adjusted_limit:
2099   // (LE1) iv_post_i < limit: Already canonicalized. We can directly use limit as adjusted_limit.
2100   //           -> adjusted_limit = limit.
2101   // (LE2) iv_post_i <= limit:
2102   //           iv_post_i < limit + 1
2103   //           -> adjusted limit = limit + 1
2104   // (LE3) iv_pre_i < limit:
2105   //           iv_pre_i + stride < limit + stride
2106   //           iv_post_i < limit + stride
2107   //           -> adjusted_limit = limit + stride
2108   // (LE4) iv_pre_i <= limit:
2109   //           iv_pre_i < limit + 1
2110   //           iv_pre_i + stride < limit + stride + 1
2111   //           iv_post_i < limit + stride + 1
2112   //           -> adjusted_limit = limit + stride + 1
2113   //
2114   // Note that:
2115   //     (AL) limit <= adjusted_limit.
2116   //
2117   // The following loop invariant has to hold for counted loops with n iterations (i.e. loop exit check true after n-th
2118   // loop iteration) and a canonicalized loop exit check to guarantee that no iv_post_i over- or underflows:
2119   // (INV) For i = 1..n, min_int <= iv_post_i <= max_int
2120   //
2121   // To prove (INV), we require the following two conditions/assumptions:
2122   // (i): adjusted_limit - 1 + stride <= max_int
2123   // (ii): init < limit
2124   //
2125   // If we can prove (INV), we know that there can be no over- or underflow of any iv phi value. We prove (INV) by
2126   // induction by assuming (i) and (ii).
2127   //
2128   // Proof by Induction
2129   // ------------------
2130   // > Base case (i = 1): We show that (INV) holds after the first iteration:
2131   //     min_int <= iv_post_1 = init + stride <= max_int
2132   // Proof:
2133   //     First, we note that (ii) implies
2134   //         (iii) init <= limit - 1
2135   //     max_int >= adjusted_limit - 1 + stride   [using (i)]
2136   //             >= limit - 1 + stride            [using (AL)]
2137   //             >= init + stride                 [using (iii)]
2138   //             >= min_int                       [using stride > 0, no underflow]
2139   // Thus, no overflow happens after the first iteration and (INV) holds for i = 1.
2140   //
2141   // Note that to prove the base case we need (i) and (ii).
2142   //
2143   // > Induction Hypothesis (i = j, j > 1): Assume that (INV) holds after the j-th iteration:
2144   //     min_int <= iv_post_j <= max_int
2145   // > Step case (i = j + 1): We show that (INV) also holds after the j+1-th iteration:
2146   //     min_int <= iv_post_{j+1} = iv_post_j + stride <= max_int
2147   // Proof:
2148   // If iv_post_j >= adjusted_limit:
2149   //     We exit the loop after the j-th iteration, and we don't execute the j+1-th iteration anymore. Thus, there is
2150   //     also no iv_{j+1}. Since (INV) holds for iv_j, there is nothing left to prove.
2151   // If iv_post_j < adjusted_limit:
2152   //     First, we note that:
2153   //         (iv) iv_post_j <= adjusted_limit - 1
2154   //     max_int >= adjusted_limit - 1 + stride    [using (i)]
2155   //             >= iv_post_j + stride             [using (iv)]
2156   //             >= min_int                        [using stride > 0, no underflow]
2157   //
2158   // Note that to prove the step case we only need (i).
2159   //
2160   // Thus, by assuming (i) and (ii), we proved (INV).
2161   //
2162   //
2163   // It is therefore enough to add the following two Loop Limit Check Predicates to check assumptions (i) and (ii):
2164   //
2165   // (1) Loop Limit Check Predicate for (i):
2166   //     Using (i): adjusted_limit - 1 + stride <= max_int
2167   //
2168   //     This condition is now restated to use limit instead of adjusted_limit:
2169   //
2170   //     To prevent an overflow of adjusted_limit -1 + stride itself, we rewrite this check to
2171   //         max_int - stride + 1 >= adjusted_limit
2172   //     We can merge the two constants into
2173   //         canonicalized_correction = stride - 1
2174   //     which gives us
2175   //        max_int - canonicalized_correction >= adjusted_limit
2176   //
2177   //     To directly use limit instead of adjusted_limit in the predicate condition, we split adjusted_limit into:
2178   //         adjusted_limit = limit + limit_correction
2179   //     Since stride > 0 and limit_correction <= stride + 1, we can restate this with no over- or underflow into:
2180   //         max_int - canonicalized_correction - limit_correction >= limit
2181   //     Since canonicalized_correction and limit_correction are both constants, we can replace them with a new constant:
2182   //         (v) final_correction = canonicalized_correction + limit_correction
2183   //
2184   //     which gives us:
2185   //
2186   //     Final predicate condition:
2187   //         max_int - final_correction >= limit
2188   //
2189   //     However, we need to be careful that (v) does not over- or underflow.
2190   //     We know that:
2191   //         canonicalized_correction = stride - 1
2192   //     and
2193   //         limit_correction <= stride + 1
2194   //     and thus
2195   //         canonicalized_correction + limit_correction <= 2 * stride
2196   //     To prevent an over- or underflow of (v), we must ensure that
2197   //         2 * stride <= max_int
2198   //     which can safely be checked without over- or underflow with
2199   //         (vi) stride != min_int AND abs(stride) <= max_int / 2
2200   //
2201   //     We could try to further optimize the cases where (vi) does not hold but given that such large strides are
2202   //     very uncommon and the loop would only run for a very few iterations anyway, we simply bail out if (vi) fails.
2203   //
2204   // (2) Loop Limit Check Predicate for (ii):
2205   //     Using (ii): init < limit
2206   //
2207   //     This Loop Limit Check Predicate is not required if we can prove at compile time that either:
2208   //        (2.1) type(init) < type(limit)
2209   //             In this case, we know:
2210   //                 all possible values of init < all possible values of limit
2211   //             and we can skip the predicate.
2212   //
2213   //        (2.2) init < limit is already checked before (i.e. found as a dominating check)
2214   //            In this case, we do not need to re-check the condition and can skip the predicate.
2215   //            This is often found for while- and for-loops which have the following shape:
2216   //
2217   //                if (init < limit) { // Dominating test. Do not need the Loop Limit Check Predicate below.
2218   //                    i = init;
2219   //                    if (init >= limit) { trap(); } // Here we would insert the Loop Limit Check Predicate
2220   //                    do {
2221   //                        i += stride;
2222   //                    } while (i < limit);
2223   //                }
2224   //
2225   //        (2.3) init + stride <= max_int
2226   //            In this case, there is no overflow of the iv phi after the first loop iteration.
2227   //            In the proof of the base case above we showed that init + stride <= max_int by using assumption (ii):
2228   //                init < limit
2229   //            In the proof of the step case above, we did not need (ii) anymore. Therefore, if we already know at
2230   //            compile time that init + stride <= max_int then we have trivially proven the base case and that
2231   //            there is no overflow of the iv phi after the first iteration. In this case, we don't need to check (ii)
2232   //            again and can skip the predicate.
2233 
2234   // Check (vi) and bail out if the stride is too big.
2235   if (stride_con == min_signed_integer(iv_bt) || (ABS(stride_con) > max_signed_integer(iv_bt) / 2)) {
2236     return false;
2237   }
2238 
2239   // Accounting for (LE3) and (LE4) where we use pre-incremented phis in the loop exit check.
2240   const jlong limit_correction_for_pre_iv_exit_check = (phi_incr != nullptr) ? stride_con : 0;
2241 
2242   // Accounting for (LE2) and (LE4) where we use <= or >= in the loop exit check.
2243   const bool includes_limit = (bt == BoolTest::le || bt == BoolTest::ge);
2244   const jlong limit_correction_for_le_ge_exit_check = (includes_limit ? (stride_con > 0 ? 1 : -1) : 0);
2245 
2246   const jlong limit_correction = limit_correction_for_pre_iv_exit_check + limit_correction_for_le_ge_exit_check;
2247   const jlong canonicalized_correction = stride_con + (stride_con > 0 ? -1 : 1);
2248   const jlong final_correction = canonicalized_correction + limit_correction;
2249 
2250   int sov = check_stride_overflow(final_correction, limit_t, iv_bt);
2251   Node* init_control = x->in(LoopNode::EntryControl);
2252 
2253   // If sov==0, limit's type always satisfies the condition, for
2254   // example, when it is an array length.
2255   if (sov != 0) {
2256     if (sov < 0) {
2257       return false;  // Bailout: integer overflow is certain.
2258     }
2259     // (1) Loop Limit Check Predicate is required because we could not statically prove that
2260     //     limit + final_correction = adjusted_limit - 1 + stride <= max_int
2261     assert(!x->as_Loop()->is_loop_nest_inner_loop(), "loop was transformed");
2262     const Predicates predicates(init_control);
2263     const PredicateBlock* loop_limit_check_predicate_block = predicates.loop_limit_check_predicate_block();
2264     if (!loop_limit_check_predicate_block->has_parse_predicate()) {
2265       // The Loop Limit Check Parse Predicate is not generated if this method trapped here before.
2266 #ifdef ASSERT
2267       if (TraceLoopLimitCheck) {
2268         tty->print("Missing Loop Limit Check Parse Predicate:");
2269         loop->dump_head();
2270         x->dump(1);
2271       }
2272 #endif
2273       return false;
2274     }
2275 
2276     ParsePredicateNode* loop_limit_check_parse_predicate = loop_limit_check_predicate_block->parse_predicate();
2277     if (!is_dominator(get_ctrl(limit), loop_limit_check_parse_predicate->in(0))) {
2278       return false;
2279     }
2280 
2281     Node* cmp_limit;
2282     Node* bol;
2283 
2284     if (stride_con > 0) {
2285       cmp_limit = CmpNode::make(limit, _igvn.integercon(max_signed_integer(iv_bt) - final_correction, iv_bt), iv_bt);
2286       bol = new BoolNode(cmp_limit, BoolTest::le);
2287     } else {
2288       cmp_limit = CmpNode::make(limit, _igvn.integercon(min_signed_integer(iv_bt) - final_correction, iv_bt), iv_bt);
2289       bol = new BoolNode(cmp_limit, BoolTest::ge);
2290     }
2291 
2292     insert_loop_limit_check_predicate(init_control->as_IfTrue(), cmp_limit, bol);
2293   }
2294 
2295   // (2.3)
2296   const bool init_plus_stride_could_overflow =
2297           (stride_con > 0 && init_t->hi_as_long() > max_signed_integer(iv_bt) - stride_con) ||
2298           (stride_con < 0 && init_t->lo_as_long() < min_signed_integer(iv_bt) - stride_con);
2299   // (2.1)
2300   const bool init_gte_limit = (stride_con > 0 && init_t->hi_as_long() >= limit_t->lo_as_long()) ||
2301                               (stride_con < 0 && init_t->lo_as_long() <= limit_t->hi_as_long());
2302 
2303   if (init_gte_limit && // (2.1)
2304      ((bt == BoolTest::ne || init_plus_stride_could_overflow) && // (2.3)
2305       !has_dominating_loop_limit_check(init_trip, limit, stride_con, iv_bt, init_control))) { // (2.2)
2306     // (2) Iteration Loop Limit Check Predicate is required because neither (2.1), (2.2), nor (2.3) holds.
2307     // We use the following condition:
2308     // - stride > 0: init < limit
2309     // - stride < 0: init > limit
2310     //
2311     // This predicate is always required if we have a non-equal-operator in the loop exit check (where stride = 1 is
2312     // a requirement). We transform the loop exit check by using a less-than-operator. By doing so, we must always
2313     // check that init < limit. Otherwise, we could have a different number of iterations at runtime.
2314 
2315     const Predicates predicates(init_control);
2316     const PredicateBlock* loop_limit_check_predicate_block = predicates.loop_limit_check_predicate_block();
2317     if (!loop_limit_check_predicate_block->has_parse_predicate()) {
2318       // The Loop Limit Check Parse Predicate is not generated if this method trapped here before.
2319 #ifdef ASSERT
2320       if (TraceLoopLimitCheck) {
2321         tty->print("Missing Loop Limit Check Parse Predicate:");
2322         loop->dump_head();
2323         x->dump(1);
2324       }
2325 #endif
2326       return false;
2327     }
2328 
2329     ParsePredicateNode* loop_limit_check_parse_predicate = loop_limit_check_predicate_block->parse_predicate();
2330     Node* parse_predicate_entry = loop_limit_check_parse_predicate->in(0);
2331     if (!is_dominator(get_ctrl(limit), parse_predicate_entry) ||
2332         !is_dominator(get_ctrl(init_trip), parse_predicate_entry)) {
2333       return false;
2334     }
2335 
2336     Node* cmp_limit;
2337     Node* bol;
2338 
2339     if (stride_con > 0) {
2340       cmp_limit = CmpNode::make(init_trip, limit, iv_bt);
2341       bol = new BoolNode(cmp_limit, BoolTest::lt);
2342     } else {
2343       cmp_limit = CmpNode::make(init_trip, limit, iv_bt);
2344       bol = new BoolNode(cmp_limit, BoolTest::gt);
2345     }
2346 
2347     insert_loop_limit_check_predicate(init_control->as_IfTrue(), cmp_limit, bol);
2348   }
2349 
2350   if (bt == BoolTest::ne) {
2351     // Now we need to canonicalize the loop condition if it is 'ne'.
2352     assert(stride_con == 1 || stride_con == -1, "simple increment only - checked before");
2353     if (stride_con > 0) {
2354       // 'ne' can be replaced with 'lt' only when init < limit. This is ensured by the inserted predicate above.
2355       bt = BoolTest::lt;
2356     } else {
2357       assert(stride_con < 0, "must be");
2358       // 'ne' can be replaced with 'gt' only when init > limit. This is ensured by the inserted predicate above.
2359       bt = BoolTest::gt;
2360     }
2361   }
2362 
2363   Node* sfpt = nullptr;
2364   if (loop->_child == nullptr) {
2365     sfpt = find_safepoint(back_control, x, loop);
2366   } else {
2367     sfpt = iff->in(0);
2368     if (sfpt->Opcode() != Op_SafePoint) {
2369       sfpt = nullptr;
2370     }
2371   }
2372 
2373   if (x->in(LoopNode::LoopBackControl)->Opcode() == Op_SafePoint) {
2374     Node* backedge_sfpt = x->in(LoopNode::LoopBackControl);
2375     if (((iv_bt == T_INT && LoopStripMiningIter != 0) ||
2376          iv_bt == T_LONG) &&
2377         sfpt == nullptr) {
2378       // Leaving the safepoint on the backedge and creating a
2379       // CountedLoop will confuse optimizations. We can't move the
2380       // safepoint around because its jvm state wouldn't match a new
2381       // location. Give up on that loop.
2382       return false;
2383     }
2384     if (is_deleteable_safept(backedge_sfpt)) {
2385       lazy_replace(backedge_sfpt, iftrue);
2386       if (loop->_safepts != nullptr) {
2387         loop->_safepts->yank(backedge_sfpt);
2388       }
2389       loop->_tail = iftrue;
2390     }
2391   }
2392 
2393 
2394 #ifdef ASSERT
2395   if (iv_bt == T_INT &&
2396       !x->as_Loop()->is_loop_nest_inner_loop() &&
2397       StressLongCountedLoop > 0 &&
2398       trunc1 == nullptr &&
2399       convert_to_long_loop(cmp, phi, loop)) {
2400     return false;
2401   }
2402 #endif
2403 
2404   Node* adjusted_limit = limit;
2405   if (phi_incr != nullptr) {
2406     // If compare points directly to the phi we need to adjust
2407     // the compare so that it points to the incr. Limit have
2408     // to be adjusted to keep trip count the same and we
2409     // should avoid int overflow.
2410     //
2411     //   i = init; do {} while(i++ < limit);
2412     // is converted to
2413     //   i = init; do {} while(++i < limit+1);
2414     //
2415     adjusted_limit = gvn->transform(AddNode::make(limit, stride, iv_bt));
2416   }
2417 
2418   if (includes_limit) {
2419     // The limit check guaranties that 'limit <= (max_jint - stride)' so
2420     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
2421     //
2422     Node* one = (stride_con > 0) ? gvn->integercon( 1, iv_bt) : gvn->integercon(-1, iv_bt);
2423     adjusted_limit = gvn->transform(AddNode::make(adjusted_limit, one, iv_bt));
2424     if (bt == BoolTest::le)
2425       bt = BoolTest::lt;
2426     else if (bt == BoolTest::ge)
2427       bt = BoolTest::gt;
2428     else
2429       ShouldNotReachHere();
2430   }
2431   set_subtree_ctrl(adjusted_limit, false);
2432 
2433   // Build a canonical trip test.
2434   // Clone code, as old values may be in use.
2435   incr = incr->clone();
2436   incr->set_req(1,phi);
2437   incr->set_req(2,stride);
2438   incr = _igvn.register_new_node_with_optimizer(incr);
2439   set_early_ctrl(incr, false);
2440   _igvn.rehash_node_delayed(phi);
2441   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
2442 
2443   // If phi type is more restrictive than Int, raise to
2444   // Int to prevent (almost) infinite recursion in igvn
2445   // which can only handle integer types for constants or minint..maxint.
2446   if (!TypeInteger::bottom(iv_bt)->higher_equal(phi->bottom_type())) {
2447     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInteger::bottom(iv_bt));
2448     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
2449     nphi = _igvn.register_new_node_with_optimizer(nphi);
2450     set_ctrl(nphi, get_ctrl(phi));
2451     _igvn.replace_node(phi, nphi);
2452     phi = nphi->as_Phi();
2453   }
2454   cmp = cmp->clone();
2455   cmp->set_req(1,incr);
2456   cmp->set_req(2, adjusted_limit);
2457   cmp = _igvn.register_new_node_with_optimizer(cmp);
2458   set_ctrl(cmp, iff->in(0));
2459 
2460   test = test->clone()->as_Bool();
2461   (*(BoolTest*)&test->_test)._test = bt;
2462   test->set_req(1,cmp);
2463   _igvn.register_new_node_with_optimizer(test);
2464   set_ctrl(test, iff->in(0));
2465 
2466   // Replace the old IfNode with a new LoopEndNode
2467   Node *lex = _igvn.register_new_node_with_optimizer(BaseCountedLoopEndNode::make(iff->in(0), test, cl_prob, iff->as_If()->_fcnt, iv_bt));
2468   IfNode *le = lex->as_If();
2469   uint dd = dom_depth(iff);
2470   set_idom(le, le->in(0), dd); // Update dominance for loop exit
2471   set_loop(le, loop);
2472 
2473   // Get the loop-exit control
2474   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
2475 
2476   // Need to swap loop-exit and loop-back control?
2477   if (iftrue_op == Op_IfFalse) {
2478     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
2479     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
2480 
2481     loop->_tail = back_control = ift2;
2482     set_loop(ift2, loop);
2483     set_loop(iff2, get_loop(iffalse));
2484 
2485     // Lazy update of 'get_ctrl' mechanism.
2486     lazy_replace(iffalse, iff2);
2487     lazy_replace(iftrue,  ift2);
2488 
2489     // Swap names
2490     iffalse = iff2;
2491     iftrue  = ift2;
2492   } else {
2493     _igvn.rehash_node_delayed(iffalse);
2494     _igvn.rehash_node_delayed(iftrue);
2495     iffalse->set_req_X( 0, le, &_igvn );
2496     iftrue ->set_req_X( 0, le, &_igvn );
2497   }
2498 
2499   set_idom(iftrue,  le, dd+1);
2500   set_idom(iffalse, le, dd+1);
2501   assert(iff->outcnt() == 0, "should be dead now");
2502   lazy_replace( iff, le ); // fix 'get_ctrl'
2503 
2504   Node* entry_control = init_control;
2505   bool strip_mine_loop = iv_bt == T_INT &&
2506                          loop->_child == nullptr &&
2507                          sfpt != nullptr &&
2508                          !loop->_has_call &&
2509                          is_deleteable_safept(sfpt);
2510   IdealLoopTree* outer_ilt = nullptr;
2511   if (strip_mine_loop) {
2512     outer_ilt = create_outer_strip_mined_loop(init_control, loop, cl_prob, le->_fcnt,
2513                                               entry_control, iffalse);
2514   }
2515 
2516   // Now setup a new CountedLoopNode to replace the existing LoopNode
2517   BaseCountedLoopNode *l = BaseCountedLoopNode::make(entry_control, back_control, iv_bt);
2518   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
2519   // The following assert is approximately true, and defines the intention
2520   // of can_be_counted_loop.  It fails, however, because phase->type
2521   // is not yet initialized for this loop and its parts.
2522   //assert(l->can_be_counted_loop(this), "sanity");
2523   _igvn.register_new_node_with_optimizer(l);
2524   set_loop(l, loop);
2525   loop->_head = l;
2526   // Fix all data nodes placed at the old loop head.
2527   // Uses the lazy-update mechanism of 'get_ctrl'.
2528   lazy_replace( x, l );
2529   set_idom(l, entry_control, dom_depth(entry_control) + 1);
2530 
2531   if (iv_bt == T_INT && (LoopStripMiningIter == 0 || strip_mine_loop)) {
2532     // Check for immediately preceding SafePoint and remove
2533     if (sfpt != nullptr && (strip_mine_loop || is_deleteable_safept(sfpt))) {
2534       if (strip_mine_loop) {
2535         Node* outer_le = outer_ilt->_tail->in(0);
2536         Node* sfpt_clone = sfpt->clone();
2537         sfpt_clone->set_req(0, iffalse);
2538         outer_le->set_req(0, sfpt_clone);
2539 
2540         Node* polladdr = sfpt_clone->in(TypeFunc::Parms);
2541         if (polladdr != nullptr && polladdr->is_Load()) {
2542           // Polling load should be pinned outside inner loop.
2543           Node* new_polladdr = polladdr->clone();
2544           new_polladdr->set_req(0, iffalse);
2545           _igvn.register_new_node_with_optimizer(new_polladdr, polladdr);
2546           set_ctrl(new_polladdr, iffalse);
2547           sfpt_clone->set_req(TypeFunc::Parms, new_polladdr);
2548         }
2549         // When this code runs, loop bodies have not yet been populated.
2550         const bool body_populated = false;
2551         register_control(sfpt_clone, outer_ilt, iffalse, body_populated);
2552         set_idom(outer_le, sfpt_clone, dom_depth(sfpt_clone));
2553       }
2554       lazy_replace(sfpt, sfpt->in(TypeFunc::Control));
2555       if (loop->_safepts != nullptr) {
2556         loop->_safepts->yank(sfpt);
2557       }
2558     }
2559   }
2560 
2561 #ifdef ASSERT
2562   assert(l->is_valid_counted_loop(iv_bt), "counted loop shape is messed up");
2563   assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
2564 #endif
2565 #ifndef PRODUCT
2566   if (TraceLoopOpts) {
2567     tty->print("Counted      ");
2568     loop->dump_head();
2569   }
2570 #endif
2571 
2572   C->print_method(PHASE_AFTER_CLOOPS, 3, l);
2573 
2574   // Capture bounds of the loop in the induction variable Phi before
2575   // subsequent transformation (iteration splitting) obscures the
2576   // bounds
2577   l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
2578 
2579   if (strip_mine_loop) {
2580     l->mark_strip_mined();
2581     l->verify_strip_mined(1);
2582     outer_ilt->_head->as_Loop()->verify_strip_mined(1);
2583     loop = outer_ilt;
2584   }
2585 
2586 #ifndef PRODUCT
2587   if (x->as_Loop()->is_loop_nest_inner_loop() && iv_bt == T_LONG) {
2588     AtomicAccess::inc(&_long_loop_counted_loops);
2589   }
2590 #endif
2591   if (iv_bt == T_LONG && x->as_Loop()->is_loop_nest_outer_loop()) {
2592     l->mark_loop_nest_outer_loop();
2593   }
2594 
2595   return true;
2596 }
2597 
2598 // Check if there is a dominating loop limit check of the form 'init < limit' starting at the loop entry.
2599 // If there is one, then we do not need to create an additional Loop Limit Check Predicate.
2600 bool PhaseIdealLoop::has_dominating_loop_limit_check(Node* init_trip, Node* limit, const jlong stride_con,
2601                                                      const BasicType iv_bt, Node* loop_entry) {
2602   // Eagerly call transform() on the Cmp and Bool node to common them up if possible. This is required in order to
2603   // successfully find a dominated test with the If node below.
2604   Node* cmp_limit;
2605   Node* bol;
2606   if (stride_con > 0) {
2607     cmp_limit = _igvn.transform(CmpNode::make(init_trip, limit, iv_bt));
2608     bol = _igvn.transform(new BoolNode(cmp_limit, BoolTest::lt));
2609   } else {
2610     cmp_limit = _igvn.transform(CmpNode::make(init_trip, limit, iv_bt));
2611     bol = _igvn.transform(new BoolNode(cmp_limit, BoolTest::gt));
2612   }
2613 
2614   // Check if there is already a dominating init < limit check. If so, we do not need a Loop Limit Check Predicate.
2615   IfNode* iff = new IfNode(loop_entry, bol, PROB_MIN, COUNT_UNKNOWN);
2616   // Also add fake IfProj nodes in order to call transform() on the newly created IfNode.
2617   IfFalseNode* if_false = new IfFalseNode(iff);
2618   IfTrueNode* if_true = new IfTrueNode(iff);
2619   Node* dominated_iff = _igvn.transform(iff);
2620   // ConI node? Found dominating test (IfNode::dominated_by() returns a ConI node).
2621   const bool found_dominating_test = dominated_iff != nullptr && dominated_iff->is_ConI();
2622 
2623   // Kill the If with its projections again in the next IGVN round by cutting it off from the graph.
2624   _igvn.replace_input_of(iff, 0, C->top());
2625   _igvn.replace_input_of(iff, 1, C->top());
2626   return found_dominating_test;
2627 }
2628 
2629 //----------------------exact_limit-------------------------------------------
2630 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
2631   assert(loop->_head->is_CountedLoop(), "");
2632   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2633   assert(cl->is_valid_counted_loop(T_INT), "");
2634 
2635   if (cl->stride_con() == 1 ||
2636       cl->stride_con() == -1 ||
2637       cl->limit()->Opcode() == Op_LoopLimit) {
2638     // Old code has exact limit (it could be incorrect in case of int overflow).
2639     // Loop limit is exact with stride == 1. And loop may already have exact limit.
2640     return cl->limit();
2641   }
2642   Node *limit = nullptr;
2643 #ifdef ASSERT
2644   BoolTest::mask bt = cl->loopexit()->test_trip();
2645   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
2646 #endif
2647   if (cl->has_exact_trip_count()) {
2648     // Simple case: loop has constant boundaries.
2649     // Use jlongs to avoid integer overflow.
2650     int stride_con = cl->stride_con();
2651     jlong  init_con = cl->init_trip()->get_int();
2652     jlong limit_con = cl->limit()->get_int();
2653     julong trip_cnt = cl->trip_count();
2654     jlong final_con = init_con + trip_cnt*stride_con;
2655     int final_int = (int)final_con;
2656     // The final value should be in integer range since the loop
2657     // is counted and the limit was checked for overflow.
2658     assert(final_con == (jlong)final_int, "final value should be integer");
2659     limit = _igvn.intcon(final_int);
2660   } else {
2661     // Create new LoopLimit node to get exact limit (final iv value).
2662     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
2663     register_new_node(limit, cl->in(LoopNode::EntryControl));
2664   }
2665   assert(limit != nullptr, "sanity");
2666   return limit;
2667 }
2668 
2669 //------------------------------Ideal------------------------------------------
2670 // Return a node which is more "ideal" than the current node.
2671 // Attempt to convert into a counted-loop.
2672 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2673   if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
2674     phase->C->set_major_progress();
2675   }
2676   return RegionNode::Ideal(phase, can_reshape);
2677 }
2678 
2679 #ifdef ASSERT
2680 void LoopNode::verify_strip_mined(int expect_skeleton) const {
2681   const OuterStripMinedLoopNode* outer = nullptr;
2682   const CountedLoopNode* inner = nullptr;
2683   if (is_strip_mined()) {
2684     if (!is_valid_counted_loop(T_INT)) {
2685       return; // Skip malformed counted loop
2686     }
2687     assert(is_CountedLoop(), "no Loop should be marked strip mined");
2688     inner = as_CountedLoop();
2689     outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
2690   } else if (is_OuterStripMinedLoop()) {
2691     outer = this->as_OuterStripMinedLoop();
2692     inner = outer->unique_ctrl_out()->as_CountedLoop();
2693     assert(inner->is_valid_counted_loop(T_INT) && inner->is_strip_mined(), "OuterStripMinedLoop should have been removed");
2694     assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
2695   }
2696   if (inner != nullptr || outer != nullptr) {
2697     assert(inner != nullptr && outer != nullptr, "missing loop in strip mined nest");
2698     Node* outer_tail = outer->in(LoopNode::LoopBackControl);
2699     Node* outer_le = outer_tail->in(0);
2700     assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
2701     Node* sfpt = outer_le->in(0);
2702     assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
2703     Node* inner_out = sfpt->in(0);
2704     CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
2705     assert(cle == inner->loopexit_or_null(), "mismatch");
2706     bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
2707     if (has_skeleton) {
2708       assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
2709       assert(outer->outcnt() == 2, "only control nodes");
2710     } else {
2711       assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
2712       uint phis = 0;
2713       uint be_loads = 0;
2714       Node* be = inner->in(LoopNode::LoopBackControl);
2715       for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
2716         Node* u = inner->fast_out(i);
2717         if (u->is_Phi()) {
2718           phis++;
2719           for (DUIterator_Fast jmax, j = be->fast_outs(jmax); j < jmax; j++) {
2720             Node* n = be->fast_out(j);
2721             if (n->is_Load()) {
2722               assert(n->in(0) == be || n->find_prec_edge(be) > 0, "should be on the backedge");
2723               do {
2724                 n = n->raw_out(0);
2725               } while (!n->is_Phi());
2726               if (n == u) {
2727                 be_loads++;
2728                 break;
2729               }
2730             }
2731           }
2732         }
2733       }
2734       assert(be_loads <= phis, "wrong number phis that depends on a pinned load");
2735       for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
2736         Node* u = outer->fast_out(i);
2737         assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
2738       }
2739       uint stores = 0;
2740       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
2741         Node* u = inner_out->fast_out(i);
2742         if (u->is_Store()) {
2743           stores++;
2744         }
2745       }
2746       // Late optimization of loads on backedge can cause Phi of outer loop to be eliminated but Phi of inner loop is
2747       // not guaranteed to be optimized out.
2748       assert(outer->outcnt() >= phis + 2 - be_loads && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
2749     }
2750     assert(sfpt->outcnt() == 1, "no data node");
2751     assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
2752   }
2753 }
2754 #endif
2755 
2756 //=============================================================================
2757 //------------------------------Ideal------------------------------------------
2758 // Return a node which is more "ideal" than the current node.
2759 // Attempt to convert into a counted-loop.
2760 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2761   return RegionNode::Ideal(phase, can_reshape);
2762 }
2763 
2764 //------------------------------dump_spec--------------------------------------
2765 // Dump special per-node info
2766 #ifndef PRODUCT
2767 void CountedLoopNode::dump_spec(outputStream *st) const {
2768   LoopNode::dump_spec(st);
2769   if (stride_is_con()) {
2770     st->print("stride: %d ",stride_con());
2771   }
2772   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
2773   if (is_main_loop()) st->print("main of N%d", _idx);
2774   if (is_post_loop()) st->print("post of N%d", _main_idx);
2775   if (is_strip_mined()) st->print(" strip mined");
2776   if (is_multiversion_fast_loop())         { st->print(" multiversion_fast"); }
2777   if (is_multiversion_slow_loop())         { st->print(" multiversion_slow"); }
2778   if (is_multiversion_delayed_slow_loop()) { st->print(" multiversion_delayed_slow"); }
2779 }
2780 #endif
2781 
2782 //=============================================================================
2783 jlong BaseCountedLoopEndNode::stride_con() const {
2784   return stride()->bottom_type()->is_integer(bt())->get_con_as_long(bt());
2785 }
2786 
2787 
2788 BaseCountedLoopEndNode* BaseCountedLoopEndNode::make(Node* control, Node* test, float prob, float cnt, BasicType bt) {
2789   if (bt == T_INT) {
2790     return new CountedLoopEndNode(control, test, prob, cnt);
2791   }
2792   assert(bt == T_LONG, "unsupported");
2793   return new LongCountedLoopEndNode(control, test, prob, cnt);
2794 }
2795 
2796 //=============================================================================
2797 //------------------------------Value-----------------------------------------
2798 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
2799   const Type* init_t   = phase->type(in(Init));
2800   const Type* limit_t  = phase->type(in(Limit));
2801   const Type* stride_t = phase->type(in(Stride));
2802   // Either input is TOP ==> the result is TOP
2803   if (init_t   == Type::TOP) return Type::TOP;
2804   if (limit_t  == Type::TOP) return Type::TOP;
2805   if (stride_t == Type::TOP) return Type::TOP;
2806 
2807   int stride_con = stride_t->is_int()->get_con();
2808   if (stride_con == 1)
2809     return bottom_type();  // Identity
2810 
2811   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
2812     // Use jlongs to avoid integer overflow.
2813     jlong init_con   =  init_t->is_int()->get_con();
2814     jlong limit_con  = limit_t->is_int()->get_con();
2815     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
2816     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
2817     jlong final_con  = init_con + stride_con*trip_count;
2818     int final_int = (int)final_con;
2819     // The final value should be in integer range in almost all cases,
2820     // since the loop is counted and the limit was checked for overflow.
2821     // There some exceptions, for example:
2822     // - During CCP, there might be a temporary overflow from PhiNodes, see JDK-8309266.
2823     // - During PhaseIdealLoop::split_thru_phi, the LoopLimitNode floats possibly far above
2824     //   the loop and its predicates, and we might get constants on one side of the phi that
2825     //   would lead to overflows. Such a code path would never lead us to enter the loop
2826     //   because of the loop limit overflow check that happens after the LoopLimitNode
2827     //   computation with overflow, but before we enter the loop, see JDK-8335747.
2828     if (final_con == (jlong)final_int) {
2829       return TypeInt::make(final_int);
2830     } else {
2831       return bottom_type();
2832     }
2833   }
2834 
2835   return bottom_type(); // TypeInt::INT
2836 }
2837 
2838 //------------------------------Ideal------------------------------------------
2839 // Return a node which is more "ideal" than the current node.
2840 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
2841   if (phase->type(in(Init))   == Type::TOP ||
2842       phase->type(in(Limit))  == Type::TOP ||
2843       phase->type(in(Stride)) == Type::TOP)
2844     return nullptr;  // Dead
2845 
2846   int stride_con = phase->type(in(Stride))->is_int()->get_con();
2847   if (stride_con == 1)
2848     return nullptr;  // Identity
2849 
2850   // Delay following optimizations until all loop optimizations
2851   // done to keep Ideal graph simple.
2852   if (!can_reshape || !phase->C->post_loop_opts_phase()) {
2853     phase->C->record_for_post_loop_opts_igvn(this);
2854     return nullptr;
2855   }
2856 
2857   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
2858   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
2859   jlong stride_p;
2860   jlong lim, ini;
2861   julong max;
2862   if (stride_con > 0) {
2863     stride_p = stride_con;
2864     lim = limit_t->_hi;
2865     ini = init_t->_lo;
2866     max = (julong)max_jint;
2867   } else {
2868     stride_p = -(jlong)stride_con;
2869     lim = init_t->_hi;
2870     ini = limit_t->_lo;
2871     max = (julong)(juint)min_jint; // double cast to get 0x0000000080000000, not 0xffffffff80000000
2872   }
2873   julong range = lim - ini + stride_p;
2874   if (range <= max) {
2875     // Convert to integer expression if it is not overflow.
2876     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
2877     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
2878     Node *bias  = phase->transform(new AddINode(range, stride_m));
2879     Node *trip  = phase->transform(new DivINode(nullptr, bias, in(Stride)));
2880     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
2881     return new AddINode(span, in(Init)); // exact limit
2882   }
2883 
2884   if (is_power_of_2(stride_p) ||                // divisor is 2^n
2885       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
2886     // Convert to long expression to avoid integer overflow
2887     // and let igvn optimizer convert this division.
2888     //
2889     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
2890     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
2891     Node* stride   = phase->longcon(stride_con);
2892     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
2893 
2894     Node *range = phase->transform(new SubLNode(limit, init));
2895     Node *bias  = phase->transform(new AddLNode(range, stride_m));
2896     Node *span;
2897     if (stride_con > 0 && is_power_of_2(stride_p)) {
2898       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
2899       // and avoid generating rounding for division. Zero trip guard should
2900       // guarantee that init < limit but sometimes the guard is missing and
2901       // we can get situation when init > limit. Note, for the empty loop
2902       // optimization zero trip guard is generated explicitly which leaves
2903       // only RCE predicate where exact limit is used and the predicate
2904       // will simply fail forcing recompilation.
2905       Node* neg_stride   = phase->longcon(-stride_con);
2906       span = phase->transform(new AndLNode(bias, neg_stride));
2907     } else {
2908       Node *trip  = phase->transform(new DivLNode(nullptr, bias, stride));
2909       span = phase->transform(new MulLNode(trip, stride));
2910     }
2911     // Convert back to int
2912     Node *span_int = phase->transform(new ConvL2INode(span));
2913     return new AddINode(span_int, in(Init)); // exact limit
2914   }
2915 
2916   return nullptr;    // No progress
2917 }
2918 
2919 //------------------------------Identity---------------------------------------
2920 // If stride == 1 return limit node.
2921 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
2922   int stride_con = phase->type(in(Stride))->is_int()->get_con();
2923   if (stride_con == 1 || stride_con == -1)
2924     return in(Limit);
2925   return this;
2926 }
2927 
2928 //=============================================================================
2929 //----------------------match_incr_with_optional_truncation--------------------
2930 // Match increment with optional truncation:
2931 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
2932 // Return null for failure. Success returns the increment node.
2933 Node* CountedLoopNode::match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2,
2934                                                            const TypeInteger** trunc_type,
2935                                                            BasicType bt) {
2936   // Quick cutouts:
2937   if (expr == nullptr || expr->req() != 3)  return nullptr;
2938 
2939   Node *t1 = nullptr;
2940   Node *t2 = nullptr;
2941   Node* n1 = expr;
2942   int   n1op = n1->Opcode();
2943   const TypeInteger* trunc_t = TypeInteger::bottom(bt);
2944 
2945   if (bt == T_INT) {
2946     // Try to strip (n1 & M) or (n1 << N >> N) from n1.
2947     if (n1op == Op_AndI &&
2948         n1->in(2)->is_Con() &&
2949         n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
2950       // %%% This check should match any mask of 2**K-1.
2951       t1 = n1;
2952       n1 = t1->in(1);
2953       n1op = n1->Opcode();
2954       trunc_t = TypeInt::CHAR;
2955     } else if (n1op == Op_RShiftI &&
2956                n1->in(1) != nullptr &&
2957                n1->in(1)->Opcode() == Op_LShiftI &&
2958                n1->in(2) == n1->in(1)->in(2) &&
2959                n1->in(2)->is_Con()) {
2960       jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
2961       // %%% This check should match any shift in [1..31].
2962       if (shift == 16 || shift == 8) {
2963         t1 = n1;
2964         t2 = t1->in(1);
2965         n1 = t2->in(1);
2966         n1op = n1->Opcode();
2967         if (shift == 16) {
2968           trunc_t = TypeInt::SHORT;
2969         } else if (shift == 8) {
2970           trunc_t = TypeInt::BYTE;
2971         }
2972       }
2973     }
2974   }
2975 
2976   // If (maybe after stripping) it is an AddI, we won:
2977   if (n1op == Op_Add(bt)) {
2978     *trunc1 = t1;
2979     *trunc2 = t2;
2980     *trunc_type = trunc_t;
2981     return n1;
2982   }
2983 
2984   // failed
2985   return nullptr;
2986 }
2987 
2988 IfNode* CountedLoopNode::find_multiversion_if_from_multiversion_fast_main_loop() {
2989   assert(is_main_loop() && is_multiversion_fast_loop(), "must be multiversion fast main loop");
2990   CountedLoopEndNode* pre_end = find_pre_loop_end();
2991   if (pre_end == nullptr) { return nullptr; }
2992   Node* pre_entry = pre_end->loopnode()->in(LoopNode::EntryControl);
2993   const Predicates predicates(pre_entry);
2994   IfTrueNode* before_predicates = predicates.entry()->isa_IfTrue();
2995   if (before_predicates != nullptr &&
2996       before_predicates->in(0)->in(1)->is_OpaqueMultiversioning()) {
2997     return before_predicates->in(0)->as_If();
2998   }
2999   return nullptr;
3000 }
3001 
3002 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
3003   if (is_strip_mined() && in(EntryControl) != nullptr && in(EntryControl)->is_OuterStripMinedLoop()) {
3004     verify_strip_mined(expect_skeleton);
3005     return in(EntryControl)->as_Loop();
3006   }
3007   return this;
3008 }
3009 
3010 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
3011   assert(is_strip_mined(), "not a strip mined loop");
3012   Node* c = in(EntryControl);
3013   if (c == nullptr || c->is_top() || !c->is_OuterStripMinedLoop()) {
3014     return nullptr;
3015   }
3016   return c->as_OuterStripMinedLoop();
3017 }
3018 
3019 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
3020   Node* c = in(LoopBackControl);
3021   if (c == nullptr || c->is_top()) {
3022     return nullptr;
3023   }
3024   return c->as_IfTrue();
3025 }
3026 
3027 IfTrueNode* CountedLoopNode::outer_loop_tail() const {
3028   LoopNode* l = outer_loop();
3029   if (l == nullptr) {
3030     return nullptr;
3031   }
3032   return l->outer_loop_tail();
3033 }
3034 
3035 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
3036   IfTrueNode* proj = outer_loop_tail();
3037   if (proj == nullptr) {
3038     return nullptr;
3039   }
3040   Node* c = proj->in(0);
3041   if (c == nullptr || c->is_top() || c->outcnt() != 2) {
3042     return nullptr;
3043   }
3044   return c->as_OuterStripMinedLoopEnd();
3045 }
3046 
3047 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
3048   LoopNode* l = outer_loop();
3049   if (l == nullptr) {
3050     return nullptr;
3051   }
3052   return l->outer_loop_end();
3053 }
3054 
3055 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
3056   IfNode* le = outer_loop_end();
3057   if (le == nullptr) {
3058     return nullptr;
3059   }
3060   Node* c = le->proj_out_or_null(false);
3061   if (c == nullptr) {
3062     return nullptr;
3063   }
3064   return c->as_IfFalse();
3065 }
3066 
3067 IfFalseNode* CountedLoopNode::outer_loop_exit() const {
3068   LoopNode* l = outer_loop();
3069   if (l == nullptr) {
3070     return nullptr;
3071   }
3072   return l->outer_loop_exit();
3073 }
3074 
3075 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
3076   IfNode* le = outer_loop_end();
3077   if (le == nullptr) {
3078     return nullptr;
3079   }
3080   Node* c = le->in(0);
3081   if (c == nullptr || c->is_top()) {
3082     return nullptr;
3083   }
3084   assert(c->Opcode() == Op_SafePoint, "broken outer loop");
3085   return c->as_SafePoint();
3086 }
3087 
3088 SafePointNode* CountedLoopNode::outer_safepoint() const {
3089   LoopNode* l = outer_loop();
3090   if (l == nullptr) {
3091     return nullptr;
3092   }
3093   return l->outer_safepoint();
3094 }
3095 
3096 Node* CountedLoopNode::skip_assertion_predicates_with_halt() {
3097   Node* ctrl = in(LoopNode::EntryControl);
3098   if (ctrl == nullptr) {
3099     // Dying loop.
3100     return nullptr;
3101   }
3102   if (is_main_loop()) {
3103     ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
3104   }
3105   if (is_main_loop() || is_post_loop()) {
3106     AssertionPredicates assertion_predicates(ctrl);
3107     return assertion_predicates.entry();
3108   }
3109   return ctrl;
3110 }
3111 
3112 
3113 int CountedLoopNode::stride_con() const {
3114   CountedLoopEndNode* cle = loopexit_or_null();
3115   return cle != nullptr ? cle->stride_con() : 0;
3116 }
3117 
3118 BaseCountedLoopNode* BaseCountedLoopNode::make(Node* entry, Node* backedge, BasicType bt) {
3119   if (bt == T_INT) {
3120     return new CountedLoopNode(entry, backedge);
3121   }
3122   assert(bt == T_LONG, "unsupported");
3123   return new LongCountedLoopNode(entry, backedge);
3124 }
3125 
3126 void OuterStripMinedLoopNode::fix_sunk_stores_when_back_to_counted_loop(PhaseIterGVN* igvn,
3127                                                                         PhaseIdealLoop* iloop) const {
3128   CountedLoopNode* inner_cl = inner_counted_loop();
3129   IfFalseNode* cle_out = inner_loop_exit();
3130 
3131   if (cle_out->outcnt() > 1) {
3132     // Look for chains of stores that were sunk
3133     // out of the inner loop and are in the outer loop
3134     for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
3135       Node* u = cle_out->fast_out(i);
3136       if (u->is_Store()) {
3137         int alias_idx = igvn->C->get_alias_index(u->adr_type());
3138         Node* first = u;
3139         for (;;) {
3140           Node* next = first->in(MemNode::Memory);
3141           if (!next->is_Store() || next->in(0) != cle_out) {
3142             break;
3143           }
3144           assert(igvn->C->get_alias_index(next->adr_type()) == alias_idx, "");
3145           first = next;
3146         }
3147         Node* last = u;
3148         for (;;) {
3149           Node* next = nullptr;
3150           for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
3151             Node* uu = last->fast_out(j);
3152             if (uu->is_Store() && uu->in(0) == cle_out) {
3153               assert(next == nullptr, "only one in the outer loop");
3154               next = uu;
3155               assert(igvn->C->get_alias_index(next->adr_type()) == alias_idx, "");
3156             }
3157           }
3158           if (next == nullptr) {
3159             break;
3160           }
3161           last = next;
3162         }
3163         Node* phi = nullptr;
3164         for (DUIterator_Fast jmax, j = inner_cl->fast_outs(jmax); j < jmax; j++) {
3165           Node* uu = inner_cl->fast_out(j);
3166           if (uu->is_Phi()) {
3167             Node* be = uu->in(LoopNode::LoopBackControl);
3168             if (be->is_Store() && be->in(0) == inner_cl->in(LoopNode::LoopBackControl)) {
3169               assert(igvn->C->get_alias_index(uu->adr_type()) != alias_idx && igvn->C->get_alias_index(uu->adr_type()) != Compile::AliasIdxBot, "unexpected store");
3170             }
3171             if (be == last || be == first->in(MemNode::Memory)) {
3172               assert(igvn->C->get_alias_index(uu->adr_type()) == alias_idx || igvn->C->get_alias_index(uu->adr_type()) == Compile::AliasIdxBot, "unexpected alias");
3173               assert(phi == nullptr, "only one phi");
3174               phi = uu;
3175             }
3176           }
3177         }
3178 #ifdef ASSERT
3179         for (DUIterator_Fast jmax, j = inner_cl->fast_outs(jmax); j < jmax; j++) {
3180           Node* uu = inner_cl->fast_out(j);
3181           if (uu->is_memory_phi()) {
3182             if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
3183               assert(phi == uu, "what's that phi?");
3184             } else if (uu->adr_type() == TypePtr::BOTTOM) {
3185               Node* n = uu->in(LoopNode::LoopBackControl);
3186               uint limit = igvn->C->live_nodes();
3187               uint i = 0;
3188               while (n != uu) {
3189                 i++;
3190                 assert(i < limit, "infinite loop");
3191                 if (n->is_Proj()) {
3192                   n = n->in(0);
3193                 } else if (n->is_SafePoint() || n->is_MemBar()) {
3194                   n = n->in(TypeFunc::Memory);
3195                 } else if (n->is_Phi()) {
3196                   n = n->in(1);
3197                 } else if (n->is_MergeMem()) {
3198                   n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
3199                 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
3200                   n = n->in(MemNode::Memory);
3201                 } else {
3202                   n->dump();
3203                   ShouldNotReachHere();
3204                 }
3205               }
3206             }
3207           }
3208         }
3209 #endif
3210         if (phi == nullptr) {
3211           // If an entire chains was sunk, the
3212           // inner loop has no phi for that memory
3213           // slice, create one for the outer loop
3214           phi = PhiNode::make(inner_cl, first->in(MemNode::Memory), Type::MEMORY,
3215                               igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
3216           phi->set_req(LoopNode::LoopBackControl, last);
3217           phi = register_new_node(phi, inner_cl, igvn, iloop);
3218           igvn->replace_input_of(first, MemNode::Memory, phi);
3219         } else {
3220           // Or fix the outer loop fix to include
3221           // that chain of stores.
3222           Node* be = phi->in(LoopNode::LoopBackControl);
3223           assert(!(be->is_Store() && be->in(0) == inner_cl->in(LoopNode::LoopBackControl)), "store on the backedge + sunk stores: unsupported");
3224           if (be == first->in(MemNode::Memory)) {
3225             if (be == phi->in(LoopNode::LoopBackControl)) {
3226               igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
3227             } else {
3228               igvn->replace_input_of(be, MemNode::Memory, last);
3229             }
3230           } else {
3231 #ifdef ASSERT
3232             if (be == phi->in(LoopNode::LoopBackControl)) {
3233               assert(phi->in(LoopNode::LoopBackControl) == last, "");
3234             } else {
3235               assert(be->in(MemNode::Memory) == last, "");
3236             }
3237 #endif
3238           }
3239         }
3240       }
3241     }
3242   }
3243 }
3244 
3245 // The outer strip mined loop is initially only partially constructed. In particular Phis are omitted.
3246 // See comment above: PhaseIdealLoop::create_outer_strip_mined_loop()
3247 // We're now in the process of finishing the construction of the outer loop. For each Phi in the inner loop, a Phi in
3248 // the outer loop was just now created. However, Sunk Stores cause an extra challenge:
3249 // 1) If all Stores in the inner loop were sunk for a particular memory slice, there's no Phi left for that memory slice
3250 //    in the inner loop anymore, and hence we did not yet add a Phi for the outer loop. So an extra Phi must now be
3251 //    added for each chain of sunk Stores for a particular memory slice.
3252 // 2) If some Stores were sunk and some left in the inner loop, a Phi was already created in the outer loop but
3253 //    its backedge input wasn't wired correctly to the last Store of the chain: the backedge input was set to the
3254 //    backedge of the inner loop Phi instead, but it needs to be the last Store of the chain in the outer loop. We now
3255 //    have to fix that too.
3256 void OuterStripMinedLoopNode::handle_sunk_stores_when_finishing_construction(PhaseIterGVN* igvn) {
3257   IfFalseNode* cle_exit_proj = inner_loop_exit();
3258 
3259   // Find Sunk stores: Sunk stores are pinned on the loop exit projection of the inner loop. Indeed, because Sunk Stores
3260   // modify the memory state captured by the SafePoint in the outer strip mined loop, they must be above it. The
3261   // SafePoint's control input is the loop exit projection. It's also the only control out of the inner loop above the
3262   // SafePoint.
3263 #ifdef ASSERT
3264   int stores_in_outer_loop_cnt = 0;
3265   for (DUIterator_Fast imax, i = cle_exit_proj->fast_outs(imax); i < imax; i++) {
3266     Node* u = cle_exit_proj->fast_out(i);
3267     if (u->is_Store()) {
3268       stores_in_outer_loop_cnt++;
3269     }
3270   }
3271 #endif
3272 
3273   // Sunk stores are reachable from the memory state of the outer loop safepoint
3274   SafePointNode* safepoint = outer_safepoint();
3275   MergeMemNode* mm = safepoint->in(TypeFunc::Memory)->isa_MergeMem();
3276   if (mm == nullptr) {
3277     // There is no MergeMem, which should only happen if there was no memory node
3278     // sunk out of the loop.
3279     assert(stores_in_outer_loop_cnt == 0, "inconsistent");
3280     return;
3281   }
3282   DEBUG_ONLY(int stores_in_outer_loop_cnt2 = 0);
3283   for (MergeMemStream mms(mm); mms.next_non_empty();) {
3284     Node* mem = mms.memory();
3285     // Traverse up the chain of stores to find the first store pinned
3286     // at the loop exit projection.
3287     Node* last = mem;
3288     Node* first = nullptr;
3289     while (mem->is_Store() && mem->in(0) == cle_exit_proj) {
3290       DEBUG_ONLY(stores_in_outer_loop_cnt2++);
3291       first = mem;
3292       mem = mem->in(MemNode::Memory);
3293     }
3294     if (first != nullptr) {
3295       // Found a chain of Stores that were sunk
3296       // Do we already have a memory Phi for that slice on the outer loop? If that is the case, that Phi was created
3297       // by cloning an inner loop Phi. The inner loop Phi should have mem, the memory state of the first Store out of
3298       // the inner loop, as input on the backedge. So does the outer loop Phi given it's a clone.
3299       Node* phi = nullptr;
3300       for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3301         Node* u = mem->fast_out(i);
3302         if (u->is_Phi() && u->in(0) == this && u->in(LoopBackControl) == mem) {
3303           assert(phi == nullptr, "there should be only one");
3304           phi = u;
3305           PRODUCT_ONLY(break);
3306         }
3307       }
3308       if (phi == nullptr) {
3309         // No outer loop Phi? create one
3310         phi = PhiNode::make(this, last);
3311         phi->set_req(EntryControl, mem);
3312         phi = igvn->transform(phi);
3313         igvn->replace_input_of(first, MemNode::Memory, phi);
3314       } else {
3315         // Fix memory state along the backedge: it should be the last sunk Store of the chain
3316         igvn->replace_input_of(phi, LoopBackControl, last);
3317       }
3318     }
3319   }
3320   assert(stores_in_outer_loop_cnt == stores_in_outer_loop_cnt2, "inconsistent");
3321 }
3322 
3323 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
3324   verify_strip_mined(1);
3325   // Look for the outer & inner strip mined loop, reduce number of
3326   // iterations of the inner loop, set exit condition of outer loop,
3327   // construct required phi nodes for outer loop.
3328   CountedLoopNode* inner_cl = inner_counted_loop();
3329   assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
3330   if (LoopStripMiningIter == 0) {
3331     remove_outer_loop_and_safepoint(igvn);
3332     return;
3333   }
3334   if (LoopStripMiningIter == 1) {
3335     transform_to_counted_loop(igvn, nullptr);
3336     return;
3337   }
3338   Node* inner_iv_phi = inner_cl->phi();
3339   if (inner_iv_phi == nullptr) {
3340     IfNode* outer_le = outer_loop_end();
3341     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
3342     igvn->replace_node(outer_le, iff);
3343     inner_cl->clear_strip_mined();
3344     return;
3345   }
3346   CountedLoopEndNode* inner_cle = inner_counted_loop_end();
3347 
3348   int stride = inner_cl->stride_con();
3349   // For a min int stride, LoopStripMiningIter * stride overflows the int range for all values of LoopStripMiningIter
3350   // except 0 or 1. Those values are handled early on in this method and causes the method to return. So for a min int
3351   // stride, the method is guaranteed to return at the next check below.
3352   jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS((jlong)stride);
3353   int scaled_iters = (int)scaled_iters_long;
3354   if ((jlong)scaled_iters != scaled_iters_long) {
3355     // Remove outer loop and safepoint (too few iterations)
3356     remove_outer_loop_and_safepoint(igvn);
3357     return;
3358   }
3359   jlong short_scaled_iters = LoopStripMiningIterShortLoop * ABS(stride);
3360   const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
3361   jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
3362   assert(iter_estimate > 0, "broken");
3363   if (iter_estimate <= short_scaled_iters) {
3364     // Remove outer loop and safepoint: loop executes less than LoopStripMiningIterShortLoop
3365     remove_outer_loop_and_safepoint(igvn);
3366     return;
3367   }
3368   if (iter_estimate <= scaled_iters_long) {
3369     // We would only go through one iteration of
3370     // the outer loop: drop the outer loop but
3371     // keep the safepoint so we don't run for
3372     // too long without a safepoint
3373     IfNode* outer_le = outer_loop_end();
3374     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
3375     igvn->replace_node(outer_le, iff);
3376     inner_cl->clear_strip_mined();
3377     return;
3378   }
3379 
3380   Node* cle_tail = inner_cle->proj_out(true);
3381   ResourceMark rm;
3382   Node_List old_new;
3383   if (cle_tail->outcnt() > 1) {
3384     // Look for nodes on backedge of inner loop and clone them
3385     Unique_Node_List backedge_nodes;
3386     for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
3387       Node* u = cle_tail->fast_out(i);
3388       if (u != inner_cl) {
3389         assert(!u->is_CFG(), "control flow on the backedge?");
3390         backedge_nodes.push(u);
3391       }
3392     }
3393     uint last = igvn->C->unique();
3394     for (uint next = 0; next < backedge_nodes.size(); next++) {
3395       Node* n = backedge_nodes.at(next);
3396       old_new.map(n->_idx, n->clone());
3397       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3398         Node* u = n->fast_out(i);
3399         assert(!u->is_CFG(), "broken");
3400         if (u->_idx >= last) {
3401           continue;
3402         }
3403         if (!u->is_Phi()) {
3404           backedge_nodes.push(u);
3405         } else {
3406           assert(u->in(0) == inner_cl, "strange phi on the backedge");
3407         }
3408       }
3409     }
3410     // Put the clones on the outer loop backedge
3411     Node* le_tail = outer_loop_tail();
3412     for (uint next = 0; next < backedge_nodes.size(); next++) {
3413       Node *n = old_new[backedge_nodes.at(next)->_idx];
3414       for (uint i = 1; i < n->req(); i++) {
3415         if (n->in(i) != nullptr && old_new[n->in(i)->_idx] != nullptr) {
3416           n->set_req(i, old_new[n->in(i)->_idx]);
3417         }
3418       }
3419       if (n->in(0) != nullptr && n->in(0) == cle_tail) {
3420         n->set_req(0, le_tail);
3421       }
3422       igvn->register_new_node_with_optimizer(n);
3423     }
3424   }
3425 
3426   Node* iv_phi = nullptr;
3427   // Make a clone of each phi in the inner loop for the outer loop
3428   // When Stores were Sunk, after this step, a Phi may still be missing or its backedge incorrectly wired. See
3429   // handle_sunk_stores_when_finishing_construction()
3430   for (uint i = 0; i < inner_cl->outcnt(); i++) {
3431     Node* u = inner_cl->raw_out(i);
3432     if (u->is_Phi()) {
3433       assert(u->in(0) == inner_cl, "inconsistent");
3434       Node* phi = u->clone();
3435       phi->set_req(0, this);
3436       Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
3437       if (be != nullptr) {
3438         phi->set_req(LoopNode::LoopBackControl, be);
3439       }
3440       phi = igvn->transform(phi);
3441       igvn->replace_input_of(u, LoopNode::EntryControl, phi);
3442       if (u == inner_iv_phi) {
3443         iv_phi = phi;
3444       }
3445     }
3446   }
3447 
3448   handle_sunk_stores_when_finishing_construction(igvn);
3449 
3450   if (iv_phi != nullptr) {
3451     // Now adjust the inner loop's exit condition
3452     Node* limit = inner_cl->limit();
3453     // If limit < init for stride > 0 (or limit > init for stride < 0),
3454     // the loop body is run only once. Given limit - init (init - limit resp.)
3455     // would be negative, the unsigned comparison below would cause
3456     // the loop body to be run for LoopStripMiningIter.
3457     Node* max = nullptr;
3458     if (stride > 0) {
3459       max = MaxNode::max_diff_with_zero(limit, iv_phi, TypeInt::INT, *igvn);
3460     } else {
3461       max = MaxNode::max_diff_with_zero(iv_phi, limit, TypeInt::INT, *igvn);
3462     }
3463     // sub is positive and can be larger than the max signed int
3464     // value. Use an unsigned min.
3465     Node* const_iters = igvn->intcon(scaled_iters);
3466     Node* min = MaxNode::unsigned_min(max, const_iters, TypeInt::make(0, scaled_iters, Type::WidenMin), *igvn);
3467     // min is the number of iterations for the next inner loop execution:
3468     // unsigned_min(max(limit - iv_phi, 0), scaled_iters) if stride > 0
3469     // unsigned_min(max(iv_phi - limit, 0), scaled_iters) if stride < 0
3470 
3471     Node* new_limit = nullptr;
3472     if (stride > 0) {
3473       new_limit = igvn->transform(new AddINode(min, iv_phi));
3474     } else {
3475       new_limit = igvn->transform(new SubINode(iv_phi, min));
3476     }
3477     Node* inner_cmp = inner_cle->cmp_node();
3478     Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
3479     Node* outer_bol = inner_bol;
3480     // cmp node for inner loop may be shared
3481     inner_cmp = inner_cmp->clone();
3482     inner_cmp->set_req(2, new_limit);
3483     inner_bol = inner_bol->clone();
3484     inner_bol->set_req(1, igvn->transform(inner_cmp));
3485     igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
3486     // Set the outer loop's exit condition too
3487     igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
3488   } else {
3489     assert(false, "should be able to adjust outer loop");
3490     IfNode* outer_le = outer_loop_end();
3491     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
3492     igvn->replace_node(outer_le, iff);
3493     inner_cl->clear_strip_mined();
3494   }
3495 }
3496 
3497 void OuterStripMinedLoopNode::transform_to_counted_loop(PhaseIterGVN* igvn, PhaseIdealLoop* iloop) {
3498   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
3499   CountedLoopEndNode* cle = inner_cl->loopexit();
3500   Node* inner_test = cle->in(1);
3501   IfNode* outer_le = outer_loop_end();
3502   CountedLoopEndNode* inner_cle = inner_cl->loopexit();
3503   Node* safepoint = outer_safepoint();
3504 
3505   fix_sunk_stores_when_back_to_counted_loop(igvn, iloop);
3506 
3507   // make counted loop exit test always fail
3508   ConINode* zero = igvn->intcon(0);
3509   if (iloop != nullptr) {
3510     iloop->set_root_as_ctrl(zero);
3511   }
3512   igvn->replace_input_of(cle, 1, zero);
3513   // replace outer loop end with CountedLoopEndNode with formers' CLE's exit test
3514   Node* new_end = new CountedLoopEndNode(outer_le->in(0), inner_test, cle->_prob, cle->_fcnt);
3515   register_control(new_end, inner_cl, outer_le->in(0), igvn, iloop);
3516   if (iloop == nullptr) {
3517     igvn->replace_node(outer_le, new_end);
3518   } else {
3519     iloop->lazy_replace(outer_le, new_end);
3520   }
3521   // the backedge of the inner loop must be rewired to the new loop end
3522   Node* backedge = cle->proj_out(true);
3523   igvn->replace_input_of(backedge, 0, new_end);
3524   if (iloop != nullptr) {
3525     iloop->set_idom(backedge, new_end, iloop->dom_depth(new_end) + 1);
3526   }
3527   // make the outer loop go away
3528   igvn->replace_input_of(in(LoopBackControl), 0, igvn->C->top());
3529   igvn->replace_input_of(this, LoopBackControl, igvn->C->top());
3530   inner_cl->clear_strip_mined();
3531   if (iloop != nullptr) {
3532     Unique_Node_List wq;
3533     wq.push(safepoint);
3534 
3535     IdealLoopTree* outer_loop_ilt = iloop->get_loop(this);
3536     IdealLoopTree* loop = iloop->get_loop(inner_cl);
3537 
3538     for (uint i = 0; i < wq.size(); i++) {
3539       Node* n = wq.at(i);
3540       for (uint j = 0; j < n->req(); ++j) {
3541         Node* in = n->in(j);
3542         if (in == nullptr || in->is_CFG()) {
3543           continue;
3544         }
3545         if (iloop->get_loop(iloop->get_ctrl(in)) != outer_loop_ilt) {
3546           continue;
3547         }
3548         wq.push(in);
3549       }
3550       assert(!loop->_body.contains(n), "Shouldn't append node to body twice");
3551       loop->_body.push(n);
3552     }
3553     iloop->set_loop(safepoint, loop);
3554     loop->_body.push(safepoint);
3555     iloop->set_loop(safepoint->in(0), loop);
3556     loop->_body.push(safepoint->in(0));
3557     outer_loop_ilt->_tail = igvn->C->top();
3558   }
3559 }
3560 
3561 void OuterStripMinedLoopNode::remove_outer_loop_and_safepoint(PhaseIterGVN* igvn) const {
3562   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
3563   Node* outer_sfpt = outer_safepoint();
3564   Node* outer_out = outer_loop_exit();
3565   igvn->replace_node(outer_out, outer_sfpt->in(0));
3566   igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
3567   inner_cl->clear_strip_mined();
3568 }
3569 
3570 Node* OuterStripMinedLoopNode::register_new_node(Node* node, LoopNode* ctrl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop) {
3571   if (iloop == nullptr) {
3572     return igvn->transform(node);
3573   }
3574   iloop->register_new_node(node, ctrl);
3575   return node;
3576 }
3577 
3578 Node* OuterStripMinedLoopNode::register_control(Node* node, Node* loop, Node* idom, PhaseIterGVN* igvn,
3579                                                 PhaseIdealLoop* iloop) {
3580   if (iloop == nullptr) {
3581     return igvn->transform(node);
3582   }
3583   iloop->register_control(node, iloop->get_loop(loop), idom);
3584   return node;
3585 }
3586 
3587 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
3588   if (!in(0)) return Type::TOP;
3589   if (phase->type(in(0)) == Type::TOP)
3590     return Type::TOP;
3591 
3592   // Until expansion, the loop end condition is not set so this should not constant fold.
3593   if (is_expanded(phase)) {
3594     return IfNode::Value(phase);
3595   }
3596 
3597   return TypeTuple::IFBOTH;
3598 }
3599 
3600 bool OuterStripMinedLoopEndNode::is_expanded(PhaseGVN *phase) const {
3601   // The outer strip mined loop head only has Phi uses after expansion
3602   if (phase->is_IterGVN()) {
3603     Node* backedge = proj_out_or_null(true);
3604     if (backedge != nullptr) {
3605       Node* head = backedge->unique_ctrl_out_or_null();
3606       if (head != nullptr && head->is_OuterStripMinedLoop()) {
3607         if (head->find_out_with(Op_Phi) != nullptr) {
3608           return true;
3609         }
3610       }
3611     }
3612   }
3613   return false;
3614 }
3615 
3616 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
3617   if (remove_dead_region(phase, can_reshape))  return this;
3618 
3619   return nullptr;
3620 }
3621 
3622 //------------------------------filtered_type--------------------------------
3623 // Return a type based on condition control flow
3624 // A successful return will be a type that is restricted due
3625 // to a series of dominating if-tests, such as:
3626 //    if (i < 10) {
3627 //       if (i > 0) {
3628 //          here: "i" type is [1..10)
3629 //       }
3630 //    }
3631 // or a control flow merge
3632 //    if (i < 10) {
3633 //       do {
3634 //          phi( , ) -- at top of loop type is [min_int..10)
3635 //         i = ?
3636 //       } while ( i < 10)
3637 //
3638 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
3639   assert(n && n->bottom_type()->is_int(), "must be int");
3640   const TypeInt* filtered_t = nullptr;
3641   if (!n->is_Phi()) {
3642     assert(n_ctrl != nullptr || n_ctrl == C->top(), "valid control");
3643     filtered_t = filtered_type_from_dominators(n, n_ctrl);
3644 
3645   } else {
3646     Node* phi    = n->as_Phi();
3647     Node* region = phi->in(0);
3648     assert(n_ctrl == nullptr || n_ctrl == region, "ctrl parameter must be region");
3649     if (region && region != C->top()) {
3650       for (uint i = 1; i < phi->req(); i++) {
3651         Node* val   = phi->in(i);
3652         Node* use_c = region->in(i);
3653         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
3654         if (val_t != nullptr) {
3655           if (filtered_t == nullptr) {
3656             filtered_t = val_t;
3657           } else {
3658             filtered_t = filtered_t->meet(val_t)->is_int();
3659           }
3660         }
3661       }
3662     }
3663   }
3664   const TypeInt* n_t = _igvn.type(n)->is_int();
3665   if (filtered_t != nullptr) {
3666     n_t = n_t->join(filtered_t)->is_int();
3667   }
3668   return n_t;
3669 }
3670 
3671 
3672 //------------------------------filtered_type_from_dominators--------------------------------
3673 // Return a possibly more restrictive type for val based on condition control flow of dominators
3674 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
3675   if (val->is_Con()) {
3676      return val->bottom_type()->is_int();
3677   }
3678   uint if_limit = 10; // Max number of dominating if's visited
3679   const TypeInt* rtn_t = nullptr;
3680 
3681   if (use_ctrl && use_ctrl != C->top()) {
3682     Node* val_ctrl = get_ctrl(val);
3683     uint val_dom_depth = dom_depth(val_ctrl);
3684     Node* pred = use_ctrl;
3685     uint if_cnt = 0;
3686     while (if_cnt < if_limit) {
3687       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
3688         if_cnt++;
3689         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
3690         if (if_t != nullptr) {
3691           if (rtn_t == nullptr) {
3692             rtn_t = if_t;
3693           } else {
3694             rtn_t = rtn_t->join(if_t)->is_int();
3695           }
3696         }
3697       }
3698       pred = idom(pred);
3699       if (pred == nullptr || pred == C->top()) {
3700         break;
3701       }
3702       // Stop if going beyond definition block of val
3703       if (dom_depth(pred) < val_dom_depth) {
3704         break;
3705       }
3706     }
3707   }
3708   return rtn_t;
3709 }
3710 
3711 
3712 //------------------------------dump_spec--------------------------------------
3713 // Dump special per-node info
3714 #ifndef PRODUCT
3715 void CountedLoopEndNode::dump_spec(outputStream *st) const {
3716   if( in(TestValue) != nullptr && in(TestValue)->is_Bool() ) {
3717     BoolTest bt( test_trip()); // Added this for g++.
3718 
3719     st->print("[");
3720     bt.dump_on(st);
3721     st->print("]");
3722   }
3723   st->print(" ");
3724   IfNode::dump_spec(st);
3725 }
3726 #endif
3727 
3728 //=============================================================================
3729 //------------------------------is_member--------------------------------------
3730 // Is 'l' a member of 'this'?
3731 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
3732   while( l->_nest > _nest ) l = l->_parent;
3733   return l == this;
3734 }
3735 
3736 //------------------------------set_nest---------------------------------------
3737 // Set loop tree nesting depth.  Accumulate _has_call bits.
3738 int IdealLoopTree::set_nest( uint depth ) {
3739   assert(depth <= SHRT_MAX, "sanity");
3740   _nest = depth;
3741   int bits = _has_call;
3742   if( _child ) bits |= _child->set_nest(depth+1);
3743   if( bits ) _has_call = 1;
3744   if( _next  ) bits |= _next ->set_nest(depth  );
3745   return bits;
3746 }
3747 
3748 //------------------------------split_fall_in----------------------------------
3749 // Split out multiple fall-in edges from the loop header.  Move them to a
3750 // private RegionNode before the loop.  This becomes the loop landing pad.
3751 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
3752   PhaseIterGVN &igvn = phase->_igvn;
3753   uint i;
3754 
3755   // Make a new RegionNode to be the landing pad.
3756   RegionNode* landing_pad = new RegionNode(fall_in_cnt + 1);
3757   phase->set_loop(landing_pad,_parent);
3758   // If _head was irreducible loop entry, landing_pad may now be too
3759   landing_pad->set_loop_status(_head->as_Region()->loop_status());
3760   // Gather all the fall-in control paths into the landing pad
3761   uint icnt = fall_in_cnt;
3762   uint oreq = _head->req();
3763   for( i = oreq-1; i>0; i-- )
3764     if( !phase->is_member( this, _head->in(i) ) )
3765       landing_pad->set_req(icnt--,_head->in(i));
3766 
3767   // Peel off PhiNode edges as well
3768   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
3769     Node *oj = _head->fast_out(j);
3770     if( oj->is_Phi() ) {
3771       PhiNode* old_phi = oj->as_Phi();
3772       assert( old_phi->region() == _head, "" );
3773       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
3774       Node *p = PhiNode::make_blank(landing_pad, old_phi);
3775       uint icnt = fall_in_cnt;
3776       for( i = oreq-1; i>0; i-- ) {
3777         if( !phase->is_member( this, _head->in(i) ) ) {
3778           p->init_req(icnt--, old_phi->in(i));
3779           // Go ahead and clean out old edges from old phi
3780           old_phi->del_req(i);
3781         }
3782       }
3783       // Search for CSE's here, because ZKM.jar does a lot of
3784       // loop hackery and we need to be a little incremental
3785       // with the CSE to avoid O(N^2) node blow-up.
3786       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
3787       if( p2 ) {                // Found CSE
3788         p->destruct(&igvn);     // Recover useless new node
3789         p = p2;                 // Use old node
3790       } else {
3791         igvn.register_new_node_with_optimizer(p, old_phi);
3792       }
3793       // Make old Phi refer to new Phi.
3794       old_phi->add_req(p);
3795       // Check for the special case of making the old phi useless and
3796       // disappear it.  In JavaGrande I have a case where this useless
3797       // Phi is the loop limit and prevents recognizing a CountedLoop
3798       // which in turn prevents removing an empty loop.
3799       Node *id_old_phi = old_phi->Identity(&igvn);
3800       if( id_old_phi != old_phi ) { // Found a simple identity?
3801         // Note that I cannot call 'replace_node' here, because
3802         // that will yank the edge from old_phi to the Region and
3803         // I'm mid-iteration over the Region's uses.
3804         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
3805           Node* use = old_phi->last_out(i);
3806           igvn.rehash_node_delayed(use);
3807           uint uses_found = 0;
3808           for (uint j = 0; j < use->len(); j++) {
3809             if (use->in(j) == old_phi) {
3810               if (j < use->req()) use->set_req (j, id_old_phi);
3811               else                use->set_prec(j, id_old_phi);
3812               uses_found++;
3813             }
3814           }
3815           i -= uses_found;    // we deleted 1 or more copies of this edge
3816         }
3817       }
3818       igvn._worklist.push(old_phi);
3819     }
3820   }
3821   // Finally clean out the fall-in edges from the RegionNode
3822   for( i = oreq-1; i>0; i-- ) {
3823     if( !phase->is_member( this, _head->in(i) ) ) {
3824       _head->del_req(i);
3825     }
3826   }
3827   igvn.rehash_node_delayed(_head);
3828   // Transform landing pad
3829   igvn.register_new_node_with_optimizer(landing_pad, _head);
3830   // Insert landing pad into the header
3831   _head->add_req(landing_pad);
3832 }
3833 
3834 //------------------------------split_outer_loop-------------------------------
3835 // Split out the outermost loop from this shared header.
3836 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
3837   PhaseIterGVN &igvn = phase->_igvn;
3838 
3839   // Find index of outermost loop; it should also be my tail.
3840   uint outer_idx = 1;
3841   while( _head->in(outer_idx) != _tail ) outer_idx++;
3842 
3843   // Make a LoopNode for the outermost loop.
3844   Node *ctl = _head->in(LoopNode::EntryControl);
3845   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
3846   outer = igvn.register_new_node_with_optimizer(outer, _head);
3847   phase->set_created_loop_node();
3848 
3849   // Outermost loop falls into '_head' loop
3850   _head->set_req(LoopNode::EntryControl, outer);
3851   _head->del_req(outer_idx);
3852   // Split all the Phis up between '_head' loop and 'outer' loop.
3853   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
3854     Node *out = _head->fast_out(j);
3855     if( out->is_Phi() ) {
3856       PhiNode *old_phi = out->as_Phi();
3857       assert( old_phi->region() == _head, "" );
3858       Node *phi = PhiNode::make_blank(outer, old_phi);
3859       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
3860       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
3861       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
3862       // Make old Phi point to new Phi on the fall-in path
3863       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
3864       old_phi->del_req(outer_idx);
3865     }
3866   }
3867 
3868   // Use the new loop head instead of the old shared one
3869   _head = outer;
3870   phase->set_loop(_head, this);
3871 }
3872 
3873 //------------------------------fix_parent-------------------------------------
3874 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
3875   loop->_parent = parent;
3876   if( loop->_child ) fix_parent( loop->_child, loop   );
3877   if( loop->_next  ) fix_parent( loop->_next , parent );
3878 }
3879 
3880 //------------------------------estimate_path_freq-----------------------------
3881 static float estimate_path_freq( Node *n ) {
3882   // Try to extract some path frequency info
3883   IfNode *iff;
3884   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
3885     uint nop = n->Opcode();
3886     if( nop == Op_SafePoint ) {   // Skip any safepoint
3887       n = n->in(0);
3888       continue;
3889     }
3890     if( nop == Op_CatchProj ) {   // Get count from a prior call
3891       // Assume call does not always throw exceptions: means the call-site
3892       // count is also the frequency of the fall-through path.
3893       assert( n->is_CatchProj(), "" );
3894       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
3895         return 0.0f;            // Assume call exception path is rare
3896       Node *call = n->in(0)->in(0)->in(0);
3897       assert( call->is_Call(), "expect a call here" );
3898       const JVMState *jvms = ((CallNode*)call)->jvms();
3899       ciMethodData* methodData = jvms->method()->method_data();
3900       if (!methodData->is_mature())  return 0.0f; // No call-site data
3901       ciProfileData* data = methodData->bci_to_data(jvms->bci());
3902       if ((data == nullptr) || !data->is_CounterData()) {
3903         // no call profile available, try call's control input
3904         n = n->in(0);
3905         continue;
3906       }
3907       return data->as_CounterData()->count()/FreqCountInvocations;
3908     }
3909     // See if there's a gating IF test
3910     Node *n_c = n->in(0);
3911     if( !n_c->is_If() ) break;       // No estimate available
3912     iff = n_c->as_If();
3913     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
3914       // Compute how much count comes on this path
3915       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
3916     // Have no count info.  Skip dull uncommon-trap like branches.
3917     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
3918         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
3919       break;
3920     // Skip through never-taken branch; look for a real loop exit.
3921     n = iff->in(0);
3922   }
3923   return 0.0f;                  // No estimate available
3924 }
3925 
3926 //------------------------------merge_many_backedges---------------------------
3927 // Merge all the backedges from the shared header into a private Region.
3928 // Feed that region as the one backedge to this loop.
3929 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
3930   uint i;
3931 
3932   // Scan for the top 2 hottest backedges
3933   float hotcnt = 0.0f;
3934   float warmcnt = 0.0f;
3935   uint hot_idx = 0;
3936   // Loop starts at 2 because slot 1 is the fall-in path
3937   for( i = 2; i < _head->req(); i++ ) {
3938     float cnt = estimate_path_freq(_head->in(i));
3939     if( cnt > hotcnt ) {       // Grab hottest path
3940       warmcnt = hotcnt;
3941       hotcnt = cnt;
3942       hot_idx = i;
3943     } else if( cnt > warmcnt ) { // And 2nd hottest path
3944       warmcnt = cnt;
3945     }
3946   }
3947 
3948   // See if the hottest backedge is worthy of being an inner loop
3949   // by being much hotter than the next hottest backedge.
3950   if( hotcnt <= 0.0001 ||
3951       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
3952 
3953   // Peel out the backedges into a private merge point; peel
3954   // them all except optionally hot_idx.
3955   PhaseIterGVN &igvn = phase->_igvn;
3956 
3957   Node *hot_tail = nullptr;
3958   // Make a Region for the merge point
3959   Node *r = new RegionNode(1);
3960   for( i = 2; i < _head->req(); i++ ) {
3961     if( i != hot_idx )
3962       r->add_req( _head->in(i) );
3963     else hot_tail = _head->in(i);
3964   }
3965   igvn.register_new_node_with_optimizer(r, _head);
3966   // Plug region into end of loop _head, followed by hot_tail
3967   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
3968   igvn.replace_input_of(_head, 2, r);
3969   if( hot_idx ) _head->add_req(hot_tail);
3970 
3971   // Split all the Phis up between '_head' loop and the Region 'r'
3972   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
3973     Node *out = _head->fast_out(j);
3974     if( out->is_Phi() ) {
3975       PhiNode* n = out->as_Phi();
3976       igvn.hash_delete(n);      // Delete from hash before hacking edges
3977       Node *hot_phi = nullptr;
3978       Node *phi = new PhiNode(r, n->type(), n->adr_type());
3979       // Check all inputs for the ones to peel out
3980       uint j = 1;
3981       for( uint i = 2; i < n->req(); i++ ) {
3982         if( i != hot_idx )
3983           phi->set_req( j++, n->in(i) );
3984         else hot_phi = n->in(i);
3985       }
3986       // Register the phi but do not transform until whole place transforms
3987       igvn.register_new_node_with_optimizer(phi, n);
3988       // Add the merge phi to the old Phi
3989       while( n->req() > 3 ) n->del_req( n->req()-1 );
3990       igvn.replace_input_of(n, 2, phi);
3991       if( hot_idx ) n->add_req(hot_phi);
3992     }
3993   }
3994 
3995 
3996   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
3997   // of self loop tree.  Turn self into a loop headed by _head and with
3998   // tail being the new merge point.
3999   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
4000   phase->set_loop(_tail,ilt);   // Adjust tail
4001   _tail = r;                    // Self's tail is new merge point
4002   phase->set_loop(r,this);
4003   ilt->_child = _child;         // New guy has my children
4004   _child = ilt;                 // Self has new guy as only child
4005   ilt->_parent = this;          // new guy has self for parent
4006   ilt->_nest = _nest;           // Same nesting depth (for now)
4007 
4008   // Starting with 'ilt', look for child loop trees using the same shared
4009   // header.  Flatten these out; they will no longer be loops in the end.
4010   IdealLoopTree **pilt = &_child;
4011   while( ilt ) {
4012     if( ilt->_head == _head ) {
4013       uint i;
4014       for( i = 2; i < _head->req(); i++ )
4015         if( _head->in(i) == ilt->_tail )
4016           break;                // Still a loop
4017       if( i == _head->req() ) { // No longer a loop
4018         // Flatten ilt.  Hang ilt's "_next" list from the end of
4019         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
4020         IdealLoopTree **cp = &ilt->_child;
4021         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
4022         *cp = ilt->_next;       // Hang next list at end of child list
4023         *pilt = ilt->_child;    // Move child up to replace ilt
4024         ilt->_head = nullptr;   // Flag as a loop UNIONED into parent
4025         ilt = ilt->_child;      // Repeat using new ilt
4026         continue;               // do not advance over ilt->_child
4027       }
4028       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
4029       phase->set_loop(_head,ilt);
4030     }
4031     pilt = &ilt->_child;        // Advance to next
4032     ilt = *pilt;
4033   }
4034 
4035   if( _child ) fix_parent( _child, this );
4036 }
4037 
4038 //------------------------------beautify_loops---------------------------------
4039 // Split shared headers and insert loop landing pads.
4040 // Insert a LoopNode to replace the RegionNode.
4041 // Return TRUE if loop tree is structurally changed.
4042 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
4043   bool result = false;
4044   // Cache parts in locals for easy
4045   PhaseIterGVN &igvn = phase->_igvn;
4046 
4047   igvn.hash_delete(_head);      // Yank from hash before hacking edges
4048 
4049   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
4050   int fall_in_cnt = 0;
4051   for( uint i = 1; i < _head->req(); i++ )
4052     if( !phase->is_member( this, _head->in(i) ) )
4053       fall_in_cnt++;
4054   assert( fall_in_cnt, "at least 1 fall-in path" );
4055   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
4056     split_fall_in( phase, fall_in_cnt );
4057 
4058   // Swap inputs to the _head and all Phis to move the fall-in edge to
4059   // the left.
4060   fall_in_cnt = 1;
4061   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
4062     fall_in_cnt++;
4063   if( fall_in_cnt > 1 ) {
4064     // Since I am just swapping inputs I do not need to update def-use info
4065     Node *tmp = _head->in(1);
4066     igvn.rehash_node_delayed(_head);
4067     _head->set_req( 1, _head->in(fall_in_cnt) );
4068     _head->set_req( fall_in_cnt, tmp );
4069     // Swap also all Phis
4070     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
4071       Node* phi = _head->fast_out(i);
4072       if( phi->is_Phi() ) {
4073         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
4074         tmp = phi->in(1);
4075         phi->set_req( 1, phi->in(fall_in_cnt) );
4076         phi->set_req( fall_in_cnt, tmp );
4077       }
4078     }
4079   }
4080   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
4081   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
4082 
4083   // If I am a shared header (multiple backedges), peel off the many
4084   // backedges into a private merge point and use the merge point as
4085   // the one true backedge.
4086   if (_head->req() > 3) {
4087     // Merge the many backedges into a single backedge but leave
4088     // the hottest backedge as separate edge for the following peel.
4089     if (!_irreducible) {
4090       merge_many_backedges( phase );
4091     }
4092 
4093     // When recursively beautify my children, split_fall_in can change
4094     // loop tree structure when I am an irreducible loop. Then the head
4095     // of my children has a req() not bigger than 3. Here we need to set
4096     // result to true to catch that case in order to tell the caller to
4097     // rebuild loop tree. See issue JDK-8244407 for details.
4098     result = true;
4099   }
4100 
4101   // If I have one hot backedge, peel off myself loop.
4102   // I better be the outermost loop.
4103   if (_head->req() > 3 && !_irreducible) {
4104     split_outer_loop( phase );
4105     result = true;
4106 
4107   } else if (!_head->is_Loop() && !_irreducible) {
4108     // Make a new LoopNode to replace the old loop head
4109     Node *l = new LoopNode( _head->in(1), _head->in(2) );
4110     l = igvn.register_new_node_with_optimizer(l, _head);
4111     phase->set_created_loop_node();
4112     // Go ahead and replace _head
4113     phase->_igvn.replace_node( _head, l );
4114     _head = l;
4115     phase->set_loop(_head, this);
4116   }
4117 
4118   // Now recursively beautify nested loops
4119   if( _child ) result |= _child->beautify_loops( phase );
4120   if( _next  ) result |= _next ->beautify_loops( phase );
4121   return result;
4122 }
4123 
4124 //------------------------------allpaths_check_safepts----------------------------
4125 // Allpaths backwards scan. Starting at the head, traversing all backedges, and the body. Terminating each path at first
4126 // safepoint encountered.  Helper for check_safepts.
4127 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
4128   assert(stack.size() == 0, "empty stack");
4129   stack.push(_head);
4130   visited.clear();
4131   visited.set(_head->_idx);
4132   while (stack.size() > 0) {
4133     Node* n = stack.pop();
4134     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
4135       // Terminate this path
4136     } else if (n->Opcode() == Op_SafePoint) {
4137       if (_phase->get_loop(n) != this) {
4138         if (_required_safept == nullptr) _required_safept = new Node_List();
4139         // save the first we run into on that path: closest to the tail if the head has a single backedge
4140         _required_safept->push(n);
4141       }
4142       // Terminate this path
4143     } else {
4144       uint start = n->is_Region() ? 1 : 0;
4145       uint end   = n->is_Region() && (!n->is_Loop() || n == _head) ? n->req() : start + 1;
4146       for (uint i = start; i < end; i++) {
4147         Node* in = n->in(i);
4148         assert(in->is_CFG(), "must be");
4149         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
4150           stack.push(in);
4151         }
4152       }
4153     }
4154   }
4155 }
4156 
4157 //------------------------------check_safepts----------------------------
4158 // Given dominators, try to find loops with calls that must always be
4159 // executed (call dominates loop tail).  These loops do not need non-call
4160 // safepoints (ncsfpt).
4161 //
4162 // A complication is that a safepoint in a inner loop may be needed
4163 // by an outer loop. In the following, the inner loop sees it has a
4164 // call (block 3) on every path from the head (block 2) to the
4165 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
4166 // in block 2, _but_ this leaves the outer loop without a safepoint.
4167 //
4168 //          entry  0
4169 //                 |
4170 //                 v
4171 // outer 1,2    +->1
4172 //              |  |
4173 //              |  v
4174 //              |  2<---+  ncsfpt in 2
4175 //              |_/|\   |
4176 //                 | v  |
4177 // inner 2,3      /  3  |  call in 3
4178 //               /   |  |
4179 //              v    +--+
4180 //        exit  4
4181 //
4182 //
4183 // This method creates a list (_required_safept) of ncsfpt nodes that must
4184 // be protected is created for each loop. When a ncsfpt maybe deleted, it
4185 // is first looked for in the lists for the outer loops of the current loop.
4186 //
4187 // The insights into the problem:
4188 //  A) counted loops are okay
4189 //  B) innermost loops are okay (only an inner loop can delete
4190 //     a ncsfpt needed by an outer loop)
4191 //  C) a loop is immune from an inner loop deleting a safepoint
4192 //     if the loop has a call on the idom-path
4193 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
4194 //     idom-path that is not in a nested loop
4195 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
4196 //     loop needs to be prevented from deletion by an inner loop
4197 //
4198 // There are two analyses:
4199 //  1) The first, and cheaper one, scans the loop body from
4200 //     tail to head following the idom (immediate dominator)
4201 //     chain, looking for the cases (C,D,E) above.
4202 //     Since inner loops are scanned before outer loops, there is summary
4203 //     information about inner loops.  Inner loops can be skipped over
4204 //     when the tail of an inner loop is encountered.
4205 //
4206 //  2) The second, invoked if the first fails to find a call or ncsfpt on
4207 //     the idom path (which is rare), scans all predecessor control paths
4208 //     from the tail to the head, terminating a path when a call or sfpt
4209 //     is encountered, to find the ncsfpt's that are closest to the tail.
4210 //
4211 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
4212   // Bottom up traversal
4213   IdealLoopTree* ch = _child;
4214   if (_child) _child->check_safepts(visited, stack);
4215   if (_next)  _next ->check_safepts(visited, stack);
4216 
4217   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != nullptr) {
4218     bool  has_call         = false;    // call on dom-path
4219     bool  has_local_ncsfpt = false;    // ncsfpt on dom-path at this loop depth
4220     Node* nonlocal_ncsfpt  = nullptr;  // ncsfpt on dom-path at a deeper depth
4221     if (!_irreducible) {
4222       // Scan the dom-path nodes from tail to head
4223       for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
4224         if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
4225           has_call = true;
4226           _has_sfpt = 1;          // Then no need for a safept!
4227           break;
4228         } else if (n->Opcode() == Op_SafePoint) {
4229           if (_phase->get_loop(n) == this) {
4230             has_local_ncsfpt = true;
4231             break;
4232           }
4233           if (nonlocal_ncsfpt == nullptr) {
4234             nonlocal_ncsfpt = n; // save the one closest to the tail
4235           }
4236         } else {
4237           IdealLoopTree* nlpt = _phase->get_loop(n);
4238           if (this != nlpt) {
4239             // If at an inner loop tail, see if the inner loop has already
4240             // recorded seeing a call on the dom-path (and stop.)  If not,
4241             // jump to the head of the inner loop.
4242             assert(is_member(nlpt), "nested loop");
4243             Node* tail = nlpt->_tail;
4244             if (tail->in(0)->is_If()) tail = tail->in(0);
4245             if (n == tail) {
4246               // If inner loop has call on dom-path, so does outer loop
4247               if (nlpt->_has_sfpt) {
4248                 has_call = true;
4249                 _has_sfpt = 1;
4250                 break;
4251               }
4252               // Skip to head of inner loop
4253               assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
4254               n = nlpt->_head;
4255               if (_head == n) {
4256                 // this and nlpt (inner loop) have the same loop head. This should not happen because
4257                 // during beautify_loops we call merge_many_backedges. However, infinite loops may not
4258                 // have been attached to the loop-tree during build_loop_tree before beautify_loops,
4259                 // but then attached in the build_loop_tree afterwards, and so still have unmerged
4260                 // backedges. Check if we are indeed in an infinite subgraph, and terminate the scan,
4261                 // since we have reached the loop head of this.
4262                 assert(_head->as_Region()->is_in_infinite_subgraph(),
4263                        "only expect unmerged backedges in infinite loops");
4264                 break;
4265               }
4266             }
4267           }
4268         }
4269       }
4270     }
4271     // Record safept's that this loop needs preserved when an
4272     // inner loop attempts to delete it's safepoints.
4273     if (_child != nullptr && !has_call && !has_local_ncsfpt) {
4274       if (nonlocal_ncsfpt != nullptr) {
4275         if (_required_safept == nullptr) _required_safept = new Node_List();
4276         _required_safept->push(nonlocal_ncsfpt);
4277       } else {
4278         // Failed to find a suitable safept on the dom-path.  Now use
4279         // an all paths walk from tail to head, looking for safepoints to preserve.
4280         allpaths_check_safepts(visited, stack);
4281       }
4282     }
4283   }
4284 }
4285 
4286 //---------------------------is_deleteable_safept----------------------------
4287 // Is safept not required by an outer loop?
4288 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
4289   assert(sfpt->Opcode() == Op_SafePoint, "");
4290   IdealLoopTree* lp = get_loop(sfpt)->_parent;
4291   while (lp != nullptr) {
4292     Node_List* sfpts = lp->_required_safept;
4293     if (sfpts != nullptr) {
4294       for (uint i = 0; i < sfpts->size(); i++) {
4295         if (sfpt == sfpts->at(i))
4296           return false;
4297       }
4298     }
4299     lp = lp->_parent;
4300   }
4301   return true;
4302 }
4303 
4304 //---------------------------replace_parallel_iv-------------------------------
4305 // Replace parallel induction variable (parallel to trip counter)
4306 // This optimization looks for patterns similar to:
4307 //
4308 //    int a = init2;
4309 //    for (int iv = init; iv < limit; iv += stride_con) {
4310 //      a += stride_con2;
4311 //    }
4312 //
4313 // and transforms it to:
4314 //
4315 //    int iv2 = init2
4316 //    int iv = init
4317 //    loop:
4318 //      if (iv >= limit) goto exit
4319 //      iv += stride_con
4320 //      iv2 = init2 + (iv - init) * (stride_con2 / stride_con)
4321 //      goto loop
4322 //    exit:
4323 //    ...
4324 //
4325 // Such transformation introduces more optimization opportunities. In this
4326 // particular example, the loop can be eliminated entirely given that
4327 // `stride_con2 / stride_con` is exact  (i.e., no remainder). Checks are in
4328 // place to only perform this optimization if such a division is exact. This
4329 // example will be transformed into its semantic equivalence:
4330 //
4331 //     int iv2 = (iv * stride_con2 / stride_con) + (init2 - (init * stride_con2 / stride_con))
4332 //
4333 // which corresponds to the structure of transformed subgraph.
4334 //
4335 // However, if there is a mismatch between types of the loop and the parallel
4336 // induction variable (e.g., a long-typed IV in an int-typed loop), type
4337 // conversions are required:
4338 //
4339 //     long iv2 = ((long) iv * stride_con2 / stride_con) + (init2 - ((long) init * stride_con2 / stride_con))
4340 //
4341 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
4342   assert(loop->_head->is_CountedLoop(), "");
4343   CountedLoopNode *cl = loop->_head->as_CountedLoop();
4344   if (!cl->is_valid_counted_loop(T_INT)) {
4345     return;         // skip malformed counted loop
4346   }
4347   Node *incr = cl->incr();
4348   if (incr == nullptr) {
4349     return;         // Dead loop?
4350   }
4351   Node *init = cl->init_trip();
4352   Node *phi  = cl->phi();
4353   jlong stride_con = cl->stride_con();
4354 
4355   // Visit all children, looking for Phis
4356   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
4357     Node *out = cl->out(i);
4358     // Look for other phis (secondary IVs). Skip dead ones
4359     if (!out->is_Phi() || out == phi || !has_node(out)) {
4360       continue;
4361     }
4362 
4363     PhiNode* phi2 = out->as_Phi();
4364     Node* incr2 = phi2->in(LoopNode::LoopBackControl);
4365     // Look for induction variables of the form:  X += constant
4366     if (phi2->region() != loop->_head ||
4367         incr2->req() != 3 ||
4368         incr2->in(1)->uncast() != phi2 ||
4369         incr2 == incr ||
4370         (incr2->Opcode() != Op_AddI && incr2->Opcode() != Op_AddL) ||
4371         !incr2->in(2)->is_Con()) {
4372       continue;
4373     }
4374 
4375     if (incr2->in(1)->is_ConstraintCast() &&
4376         !(incr2->in(1)->in(0)->is_IfProj() && incr2->in(1)->in(0)->in(0)->is_RangeCheck())) {
4377       // Skip AddI->CastII->Phi case if CastII is not controlled by local RangeCheck
4378       continue;
4379     }
4380     // Check for parallel induction variable (parallel to trip counter)
4381     // via an affine function.  In particular, count-down loops with
4382     // count-up array indices are common. We only RCE references off
4383     // the trip-counter, so we need to convert all these to trip-counter
4384     // expressions.
4385     Node* init2 = phi2->in(LoopNode::EntryControl);
4386 
4387     // Determine the basic type of the stride constant (and the iv being incremented).
4388     BasicType stride_con2_bt = incr2->Opcode() == Op_AddI ? T_INT : T_LONG;
4389     jlong stride_con2 = incr2->in(2)->get_integer_as_long(stride_con2_bt);
4390 
4391     // The ratio of the two strides cannot be represented as an int
4392     // if stride_con2 is min_jint (or min_jlong, respectively) and
4393     // stride_con is -1.
4394     if (stride_con2 == min_signed_integer(stride_con2_bt) && stride_con == -1) {
4395       continue;
4396     }
4397 
4398     // The general case here gets a little tricky.  We want to find the
4399     // GCD of all possible parallel IV's and make a new IV using this
4400     // GCD for the loop.  Then all possible IVs are simple multiples of
4401     // the GCD.  In practice, this will cover very few extra loops.
4402     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
4403     // where +/-1 is the common case, but other integer multiples are
4404     // also easy to handle.
4405     jlong ratio_con = stride_con2 / stride_con;
4406 
4407     if ((ratio_con * stride_con) != stride_con2) { // Check for exact (no remainder)
4408         continue;
4409     }
4410 
4411 #ifndef PRODUCT
4412     if (TraceLoopOpts) {
4413       tty->print("Parallel IV: %d ", phi2->_idx);
4414       loop->dump_head();
4415     }
4416 #endif
4417 
4418     // Convert to using the trip counter.  The parallel induction
4419     // variable differs from the trip counter by a loop-invariant
4420     // amount, the difference between their respective initial values.
4421     // It is scaled by the 'ratio_con'.
4422     Node* ratio = integercon(ratio_con, stride_con2_bt);
4423 
4424     Node* init_converted = insert_convert_node_if_needed(stride_con2_bt, init);
4425     Node* phi_converted = insert_convert_node_if_needed(stride_con2_bt, phi);
4426 
4427     Node* ratio_init = MulNode::make(init_converted, ratio, stride_con2_bt);
4428     _igvn.register_new_node_with_optimizer(ratio_init, init_converted);
4429     set_early_ctrl(ratio_init, false);
4430 
4431     Node* diff = SubNode::make(init2, ratio_init, stride_con2_bt);
4432     _igvn.register_new_node_with_optimizer(diff, init2);
4433     set_early_ctrl(diff, false);
4434 
4435     Node* ratio_idx = MulNode::make(phi_converted, ratio, stride_con2_bt);
4436     _igvn.register_new_node_with_optimizer(ratio_idx, phi_converted);
4437     set_ctrl(ratio_idx, cl);
4438 
4439     Node* add = AddNode::make(ratio_idx, diff, stride_con2_bt);
4440     _igvn.register_new_node_with_optimizer(add);
4441     set_ctrl(add, cl);
4442 
4443     _igvn.replace_node( phi2, add );
4444     // Sometimes an induction variable is unused
4445     if (add->outcnt() == 0) {
4446       _igvn.remove_dead_node(add);
4447     }
4448     --i; // deleted this phi; rescan starting with next position
4449   }
4450 }
4451 
4452 Node* PhaseIdealLoop::insert_convert_node_if_needed(BasicType target, Node* input) {
4453   BasicType source = _igvn.type(input)->basic_type();
4454   if (source == target) {
4455     return input;
4456   }
4457 
4458   Node* converted = ConvertNode::create_convert(source, target, input);
4459   _igvn.register_new_node_with_optimizer(converted, input);
4460   set_early_ctrl(converted, false);
4461 
4462   return converted;
4463 }
4464 
4465 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
4466   Node* keep = nullptr;
4467   if (keep_one) {
4468     // Look for a safepoint on the idom-path.
4469     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
4470       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
4471         keep = i;
4472         break; // Found one
4473       }
4474     }
4475   }
4476 
4477   // Don't remove any safepoints if it is requested to keep a single safepoint and
4478   // no safepoint was found on idom-path. It is not safe to remove any safepoint
4479   // in this case since there's no safepoint dominating all paths in the loop body.
4480   bool prune = !keep_one || keep != nullptr;
4481 
4482   // Delete other safepoints in this loop.
4483   Node_List* sfpts = _safepts;
4484   if (prune && sfpts != nullptr) {
4485     assert(keep == nullptr || keep->Opcode() == Op_SafePoint, "not safepoint");
4486     for (uint i = 0; i < sfpts->size(); i++) {
4487       Node* n = sfpts->at(i);
4488       assert(phase->get_loop(n) == this, "");
4489       if (n != keep && phase->is_deleteable_safept(n)) {
4490         phase->lazy_replace(n, n->in(TypeFunc::Control));
4491       }
4492     }
4493   }
4494 }
4495 
4496 //------------------------------counted_loop-----------------------------------
4497 // Convert to counted loops where possible
4498 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
4499 
4500   // For grins, set the inner-loop flag here
4501   if (!_child) {
4502     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
4503   }
4504 
4505   IdealLoopTree* loop = this;
4506   if (_head->is_CountedLoop() ||
4507       phase->is_counted_loop(_head, loop, T_INT)) {
4508 
4509     if (LoopStripMiningIter == 0 || _head->as_CountedLoop()->is_strip_mined()) {
4510       // Indicate we do not need a safepoint here
4511       _has_sfpt = 1;
4512     }
4513 
4514     // Remove safepoints
4515     bool keep_one_sfpt = !(_has_call || _has_sfpt);
4516     remove_safepoints(phase, keep_one_sfpt);
4517 
4518     // Look for induction variables
4519     phase->replace_parallel_iv(this);
4520   } else if (_head->is_LongCountedLoop() ||
4521              phase->is_counted_loop(_head, loop, T_LONG)) {
4522     remove_safepoints(phase, true);
4523   } else {
4524     assert(!_head->is_Loop() || !_head->as_Loop()->is_loop_nest_inner_loop(), "transformation to counted loop should not fail");
4525     if (_parent != nullptr && !_irreducible) {
4526       // Not a counted loop. Keep one safepoint.
4527       bool keep_one_sfpt = true;
4528       remove_safepoints(phase, keep_one_sfpt);
4529     }
4530   }
4531 
4532   // Recursively
4533   assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
4534   assert(loop->_child != this || (loop->_child->_child == nullptr && loop->_child->_next == nullptr), "would miss some loops");
4535   if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
4536   if (loop->_next)  loop->_next ->counted_loop(phase);
4537 }
4538 
4539 
4540 // The Estimated Loop Clone Size:
4541 //   CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
4542 // where  BC and  CC are  totally ad-hoc/magic  "body" and "clone" constants,
4543 // respectively, used to ensure that the node usage estimates made are on the
4544 // safe side, for the most part. The FanOutTerm is an attempt to estimate the
4545 // possible additional/excessive nodes generated due to data and control flow
4546 // merging, for edges reaching outside the loop.
4547 uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
4548 
4549   precond(0 < factor && factor < 16);
4550 
4551   uint const bc = 13;
4552   uint const cc = 17;
4553   uint const sz = _body.size() + (_body.size() + 7) / 2;
4554   uint estimate = factor * (sz + bc) + cc;
4555 
4556   assert((estimate - cc) / factor == sz + bc, "overflow");
4557 
4558   return estimate + est_loop_flow_merge_sz();
4559 }
4560 
4561 // The Estimated Loop (full-) Unroll Size:
4562 //   UnrollFactor * (~106% * BodySize) + CC + FanOutTerm,
4563 // where CC is a (totally) ad-hoc/magic "clone" constant, used to ensure that
4564 // node usage estimates made are on the safe side, for the most part. This is
4565 // a "light" version of the loop clone size calculation (above), based on the
4566 // assumption that most of the loop-construct overhead will be unraveled when
4567 // (fully) unrolled. Defined for unroll factors larger or equal to one (>=1),
4568 // including an overflow check and returning UINT_MAX in case of an overflow.
4569 uint IdealLoopTree::est_loop_unroll_sz(uint factor) const {
4570 
4571   precond(factor > 0);
4572 
4573   // Take into account that after unroll conjoined heads and tails will fold.
4574   uint const b0 = _body.size() - EMPTY_LOOP_SIZE;
4575   uint const cc = 7;
4576   uint const sz = b0 + (b0 + 15) / 16;
4577   uint estimate = factor * sz + cc;
4578 
4579   if ((estimate - cc) / factor != sz) {
4580     return UINT_MAX;
4581   }
4582 
4583   return estimate + est_loop_flow_merge_sz();
4584 }
4585 
4586 // Estimate the growth effect (in nodes) of merging control and data flow when
4587 // cloning a loop body, based on the amount of  control and data flow reaching
4588 // outside of the (current) loop body.
4589 uint IdealLoopTree::est_loop_flow_merge_sz() const {
4590 
4591   uint ctrl_edge_out_cnt = 0;
4592   uint data_edge_out_cnt = 0;
4593 
4594   for (uint i = 0; i < _body.size(); i++) {
4595     Node* node = _body.at(i);
4596     uint outcnt = node->outcnt();
4597 
4598     for (uint k = 0; k < outcnt; k++) {
4599       Node* out = node->raw_out(k);
4600       if (out == nullptr) continue;
4601       if (out->is_CFG()) {
4602         if (!is_member(_phase->get_loop(out))) {
4603           ctrl_edge_out_cnt++;
4604         }
4605       } else if (_phase->has_ctrl(out)) {
4606         Node* ctrl = _phase->get_ctrl(out);
4607         assert(ctrl != nullptr, "must be");
4608         assert(ctrl->is_CFG(), "must be");
4609         if (!is_member(_phase->get_loop(ctrl))) {
4610           data_edge_out_cnt++;
4611         }
4612       }
4613     }
4614   }
4615   // Use data and control count (x2.0) in estimate iff both are > 0. This is
4616   // a rather pessimistic estimate for the most part, in particular for some
4617   // complex loops, but still not enough to capture all loops.
4618   if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
4619     return 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
4620   }
4621   return 0;
4622 }
4623 
4624 #ifndef PRODUCT
4625 //------------------------------dump_head--------------------------------------
4626 // Dump 1 liner for loop header info
4627 void IdealLoopTree::dump_head() {
4628   tty->sp(2 * _nest);
4629   tty->print("Loop: N%d/N%d ", _head->_idx, _tail->_idx);
4630   if (_irreducible) tty->print(" IRREDUCIBLE");
4631   Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl)
4632                                  : _head->in(LoopNode::EntryControl);
4633   const Predicates predicates(entry);
4634   if (predicates.loop_limit_check_predicate_block()->is_non_empty()) {
4635     tty->print(" limit_check");
4636   }
4637   if (predicates.short_running_long_loop_predicate_block()->is_non_empty()) {
4638     tty->print(" short_running");
4639   }
4640   if (UseLoopPredicate) {
4641     if (UseProfiledLoopPredicate && predicates.profiled_loop_predicate_block()->is_non_empty()) {
4642       tty->print(" profile_predicated");
4643     }
4644     if (predicates.loop_predicate_block()->is_non_empty()) {
4645       tty->print(" predicated");
4646     }
4647   }
4648   if (UseAutoVectorizationPredicate && predicates.auto_vectorization_check_block()->is_non_empty()) {
4649     tty->print(" auto_vectorization_check_predicate");
4650   }
4651   if (_head->is_CountedLoop()) {
4652     CountedLoopNode *cl = _head->as_CountedLoop();
4653     tty->print(" counted");
4654 
4655     Node* init_n = cl->init_trip();
4656     if (init_n  != nullptr &&  init_n->is_Con())
4657       tty->print(" [%d,", cl->init_trip()->get_int());
4658     else
4659       tty->print(" [int,");
4660     Node* limit_n = cl->limit();
4661     if (limit_n  != nullptr &&  limit_n->is_Con())
4662       tty->print("%d),", cl->limit()->get_int());
4663     else
4664       tty->print("int),");
4665     int stride_con  = cl->stride_con();
4666     if (stride_con > 0) tty->print("+");
4667     tty->print("%d", stride_con);
4668 
4669     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
4670 
4671     if (cl->is_pre_loop ()) tty->print(" pre" );
4672     if (cl->is_main_loop()) tty->print(" main");
4673     if (cl->is_post_loop()) tty->print(" post");
4674     if (cl->is_vectorized_loop()) tty->print(" vector");
4675     if (range_checks_present()) tty->print(" rc ");
4676     if (cl->is_multiversion_fast_loop())         { tty->print(" multiversion_fast"); }
4677     if (cl->is_multiversion_slow_loop())         { tty->print(" multiversion_slow"); }
4678     if (cl->is_multiversion_delayed_slow_loop()) { tty->print(" multiversion_delayed_slow"); }
4679   }
4680   if (_has_call) tty->print(" has_call");
4681   if (_has_sfpt) tty->print(" has_sfpt");
4682   if (_rce_candidate) tty->print(" rce");
4683   if (_safepts != nullptr && _safepts->size() > 0) {
4684     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
4685   }
4686   if (_required_safept != nullptr && _required_safept->size() > 0) {
4687     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
4688   }
4689   if (Verbose) {
4690     tty->print(" body={"); _body.dump_simple(); tty->print(" }");
4691   }
4692   if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
4693     tty->print(" strip_mined");
4694   }
4695   tty->cr();
4696 }
4697 
4698 //------------------------------dump-------------------------------------------
4699 // Dump loops by loop tree
4700 void IdealLoopTree::dump() {
4701   dump_head();
4702   if (_child) _child->dump();
4703   if (_next)  _next ->dump();
4704 }
4705 
4706 #endif
4707 
4708 static void log_loop_tree_helper(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
4709   if (loop == root) {
4710     if (loop->_child != nullptr) {
4711       log->begin_head("loop_tree");
4712       log->end_head();
4713       log_loop_tree_helper(root, loop->_child, log);
4714       log->tail("loop_tree");
4715       assert(loop->_next == nullptr, "what?");
4716     }
4717   } else if (loop != nullptr) {
4718     Node* head = loop->_head;
4719     log->begin_head("loop");
4720     log->print(" idx='%d' ", head->_idx);
4721     if (loop->_irreducible) log->print("irreducible='1' ");
4722     if (head->is_Loop()) {
4723       if (head->as_Loop()->is_inner_loop())        log->print("inner_loop='1' ");
4724       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
4725     } else if (head->is_CountedLoop()) {
4726       CountedLoopNode* cl = head->as_CountedLoop();
4727       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
4728       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
4729       if (cl->is_post_loop()) log->print("post_loop='%d' ", cl->main_idx());
4730     }
4731     log->end_head();
4732     log_loop_tree_helper(root, loop->_child, log);
4733     log->tail("loop");
4734     log_loop_tree_helper(root, loop->_next, log);
4735   }
4736 }
4737 
4738 void PhaseIdealLoop::log_loop_tree() {
4739   if (C->log() != nullptr) {
4740     log_loop_tree_helper(_ltree_root, _ltree_root, C->log());
4741   }
4742 }
4743 
4744 // Eliminate all Parse and Template Assertion Predicates that are not associated with a loop anymore. The eliminated
4745 // predicates will be removed during the next round of IGVN.
4746 void PhaseIdealLoop::eliminate_useless_predicates() const {
4747   if (C->parse_predicate_count() == 0 && C->template_assertion_predicate_count() == 0) {
4748     return; // No predicates left.
4749   }
4750 
4751   EliminateUselessPredicates eliminate_useless_predicates(_igvn, _ltree_root);
4752   eliminate_useless_predicates.eliminate();
4753 }
4754 
4755 // If a post or main loop is removed due to an assert predicate, the opaque that guards the loop is not needed anymore
4756 void PhaseIdealLoop::eliminate_useless_zero_trip_guard() {
4757   if (_zero_trip_guard_opaque_nodes.size() == 0) {
4758     return;
4759   }
4760   Unique_Node_List useful_zero_trip_guard_opaques_nodes;
4761   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4762     IdealLoopTree* lpt = iter.current();
4763     if (lpt->_child == nullptr && lpt->is_counted()) {
4764       CountedLoopNode* head = lpt->_head->as_CountedLoop();
4765       Node* opaque = head->is_canonical_loop_entry();
4766       if (opaque != nullptr) {
4767         useful_zero_trip_guard_opaques_nodes.push(opaque);
4768       }
4769     }
4770   }
4771   for (uint i = 0; i < _zero_trip_guard_opaque_nodes.size(); ++i) {
4772     OpaqueZeroTripGuardNode* opaque = ((OpaqueZeroTripGuardNode*)_zero_trip_guard_opaque_nodes.at(i));
4773     DEBUG_ONLY(CountedLoopNode* guarded_loop = opaque->guarded_loop());
4774     if (!useful_zero_trip_guard_opaques_nodes.member(opaque)) {
4775       IfNode* iff = opaque->if_node();
4776       IdealLoopTree* loop = get_loop(iff);
4777       while (loop != _ltree_root && loop != nullptr) {
4778         loop = loop->_parent;
4779       }
4780       if (loop == nullptr) {
4781         // unreachable from _ltree_root: zero trip guard is in a newly discovered infinite loop.
4782         // We can't tell if the opaque node is useful or not
4783         assert(guarded_loop == nullptr || guarded_loop->is_in_infinite_subgraph(), "");
4784       } else {
4785         assert(guarded_loop == nullptr, "");
4786         this->_igvn.replace_node(opaque, opaque->in(1));
4787       }
4788     } else {
4789       assert(guarded_loop != nullptr, "");
4790     }
4791   }
4792 }
4793 
4794 void PhaseIdealLoop::eliminate_useless_multiversion_if() {
4795   if (_multiversion_opaque_nodes.size() == 0) {
4796     return;
4797   }
4798 
4799   ResourceMark rm;
4800   Unique_Node_List useful_multiversioning_opaque_nodes;
4801 
4802   // The OpaqueMultiversioning is only used from the fast main loop in AutoVectorization, to add
4803   // speculative runtime-checks to the multiversion_if. Thus, a OpaqueMultiversioning is only
4804   // useful if it can be found from a fast main loop. If it can not be found from a fast main loop,
4805   // then we cannot ever use that multiversion_if to add more speculative runtime-checks, and hence
4806   // it is useless. If it is still in delayed mode, i.e. has not yet had any runtime-checks added,
4807   // then we can let it constant fold towards the fast loop.
4808   for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
4809     IdealLoopTree* lpt = iter.current();
4810     if (lpt->_child == nullptr && lpt->is_counted()) {
4811       CountedLoopNode* head = lpt->_head->as_CountedLoop();
4812       if (head->is_main_loop() && head->is_multiversion_fast_loop()) {
4813         // There are fast_loop pre/main/post loops, but the finding traversal starts at the main
4814         // loop, and traverses via the fast pre loop to the multiversion_if.
4815         IfNode* multiversion_if = head->find_multiversion_if_from_multiversion_fast_main_loop();
4816         if (multiversion_if != nullptr) {
4817             useful_multiversioning_opaque_nodes.push(multiversion_if->in(1)->as_OpaqueMultiversioning());
4818         } else {
4819           // We could not find the multiversion_if, and would never find it again. Remove the
4820           // multiversion marking for consistency.
4821           head->set_no_multiversion();
4822         }
4823       }
4824     }
4825   }
4826 
4827   for (uint i = 0; i < _multiversion_opaque_nodes.size(); i++) {
4828     OpaqueMultiversioningNode* opaque = _multiversion_opaque_nodes.at(i)->as_OpaqueMultiversioning();
4829     if (!useful_multiversioning_opaque_nodes.member(opaque)) {
4830       if (opaque->is_delayed_slow_loop()) {
4831         // We cannot hack the node directly, otherwise the slow_loop will complain that it cannot
4832         // find the multiversioning opaque node. Instead, we mark the opaque node as useless, and
4833         // it can be constant folded during IGVN.
4834         opaque->mark_useless(_igvn);
4835       }
4836     }
4837   }
4838 }
4839 
4840 //------------------------process_expensive_nodes-----------------------------
4841 // Expensive nodes have their control input set to prevent the GVN
4842 // from commoning them and as a result forcing the resulting node to
4843 // be in a more frequent path. Use CFG information here, to change the
4844 // control inputs so that some expensive nodes can be commoned while
4845 // not executed more frequently.
4846 bool PhaseIdealLoop::process_expensive_nodes() {
4847   assert(OptimizeExpensiveOps, "optimization off?");
4848 
4849   // Sort nodes to bring similar nodes together
4850   C->sort_expensive_nodes();
4851 
4852   bool progress = false;
4853 
4854   for (int i = 0; i < C->expensive_count(); ) {
4855     Node* n = C->expensive_node(i);
4856     int start = i;
4857     // Find nodes similar to n
4858     i++;
4859     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
4860     int end = i;
4861     // And compare them two by two
4862     for (int j = start; j < end; j++) {
4863       Node* n1 = C->expensive_node(j);
4864       if (is_node_unreachable(n1)) {
4865         continue;
4866       }
4867       for (int k = j+1; k < end; k++) {
4868         Node* n2 = C->expensive_node(k);
4869         if (is_node_unreachable(n2)) {
4870           continue;
4871         }
4872 
4873         assert(n1 != n2, "should be pair of nodes");
4874 
4875         Node* c1 = n1->in(0);
4876         Node* c2 = n2->in(0);
4877 
4878         Node* parent_c1 = c1;
4879         Node* parent_c2 = c2;
4880 
4881         // The call to get_early_ctrl_for_expensive() moves the
4882         // expensive nodes up but stops at loops that are in a if
4883         // branch. See whether we can exit the loop and move above the
4884         // If.
4885         if (c1->is_Loop()) {
4886           parent_c1 = c1->in(1);
4887         }
4888         if (c2->is_Loop()) {
4889           parent_c2 = c2->in(1);
4890         }
4891 
4892         if (parent_c1 == parent_c2) {
4893           _igvn._worklist.push(n1);
4894           _igvn._worklist.push(n2);
4895           continue;
4896         }
4897 
4898         // Look for identical expensive node up the dominator chain.
4899         if (is_dominator(c1, c2)) {
4900           c2 = c1;
4901         } else if (is_dominator(c2, c1)) {
4902           c1 = c2;
4903         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
4904                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
4905           // Both branches have the same expensive node so move it up
4906           // before the if.
4907           c1 = c2 = idom(parent_c1->in(0));
4908         }
4909         // Do the actual moves
4910         if (n1->in(0) != c1) {
4911           _igvn.replace_input_of(n1, 0, c1);
4912           progress = true;
4913         }
4914         if (n2->in(0) != c2) {
4915           _igvn.replace_input_of(n2, 0, c2);
4916           progress = true;
4917         }
4918       }
4919     }
4920   }
4921 
4922   return progress;
4923 }
4924 
4925 //=============================================================================
4926 //----------------------------build_and_optimize-------------------------------
4927 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
4928 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
4929 void PhaseIdealLoop::build_and_optimize() {
4930   assert(!C->post_loop_opts_phase(), "no loop opts allowed");
4931 
4932   bool do_split_ifs = (_mode == LoopOptsDefault);
4933   bool skip_loop_opts = (_mode == LoopOptsNone);
4934   bool do_max_unroll = (_mode == LoopOptsMaxUnroll);
4935 
4936 
4937   int old_progress = C->major_progress();
4938   uint orig_worklist_size = _igvn._worklist.size();
4939 
4940   // Reset major-progress flag for the driver's heuristics
4941   C->clear_major_progress();
4942 
4943 #ifndef PRODUCT
4944   // Capture for later assert
4945   uint unique = C->unique();
4946   _loop_invokes++;
4947   _loop_work += unique;
4948 #endif
4949 
4950   // True if the method has at least 1 irreducible loop
4951   _has_irreducible_loops = false;
4952 
4953   _created_loop_node = false;
4954 
4955   VectorSet visited;
4956   // Pre-grow the mapping from Nodes to IdealLoopTrees.
4957   _loop_or_ctrl.map(C->unique(), nullptr);
4958   memset(_loop_or_ctrl.adr(), 0, wordSize * C->unique());
4959 
4960   // Pre-build the top-level outermost loop tree entry
4961   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
4962   // Do not need a safepoint at the top level
4963   _ltree_root->_has_sfpt = 1;
4964 
4965   // Initialize Dominators.
4966   // Checked in clone_loop_predicate() during beautify_loops().
4967   _idom_size = 0;
4968   _idom      = nullptr;
4969   _dom_depth = nullptr;
4970   _dom_stk   = nullptr;
4971 
4972   // Empty pre-order array
4973   allocate_preorders();
4974 
4975   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
4976   // IdealLoopTree entries.  Data nodes are NOT walked.
4977   build_loop_tree();
4978   // Check for bailout, and return
4979   if (C->failing()) {
4980     return;
4981   }
4982 
4983   // Verify that the has_loops() flag set at parse time is consistent with the just built loop tree. When the back edge
4984   // is an exception edge, parsing doesn't set has_loops().
4985   assert(_ltree_root->_child == nullptr || C->has_loops() || C->has_exception_backedge(), "parsing found no loops but there are some");
4986   // No loops after all
4987   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
4988 
4989   // There should always be an outer loop containing the Root and Return nodes.
4990   // If not, we have a degenerate empty program.  Bail out in this case.
4991   if (!has_node(C->root())) {
4992     if (!_verify_only) {
4993       C->clear_major_progress();
4994       assert(false, "empty program detected during loop optimization");
4995       C->record_method_not_compilable("empty program detected during loop optimization");
4996     }
4997     return;
4998   }
4999 
5000   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
5001   // Nothing to do, so get out
5002   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !do_max_unroll && !_verify_me &&
5003           !_verify_only && !bs->is_gc_specific_loop_opts_pass(_mode);
5004   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
5005   bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(_mode);
5006   if (stop_early && !do_expensive_nodes) {
5007     return;
5008   }
5009 
5010   // Set loop nesting depth
5011   _ltree_root->set_nest( 0 );
5012 
5013   // Split shared headers and insert loop landing pads.
5014   // Do not bother doing this on the Root loop of course.
5015   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
5016     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
5017     if( _ltree_root->_child->beautify_loops( this ) ) {
5018       // Re-build loop tree!
5019       _ltree_root->_child = nullptr;
5020       _loop_or_ctrl.clear();
5021       reallocate_preorders();
5022       build_loop_tree();
5023       // Check for bailout, and return
5024       if (C->failing()) {
5025         return;
5026       }
5027       // Reset loop nesting depth
5028       _ltree_root->set_nest( 0 );
5029 
5030       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
5031     }
5032   }
5033 
5034   // Build Dominators for elision of null checks & loop finding.
5035   // Since nodes do not have a slot for immediate dominator, make
5036   // a persistent side array for that info indexed on node->_idx.
5037   _idom_size = C->unique();
5038   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
5039   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
5040   _dom_stk   = nullptr; // Allocated on demand in recompute_dom_depth
5041   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
5042 
5043   Dominators();
5044 
5045   if (!_verify_only) {
5046     // As a side effect, Dominators removed any unreachable CFG paths
5047     // into RegionNodes.  It doesn't do this test against Root, so
5048     // we do it here.
5049     for( uint i = 1; i < C->root()->req(); i++ ) {
5050       if (!_loop_or_ctrl[C->root()->in(i)->_idx]) { // Dead path into Root?
5051         _igvn.delete_input_of(C->root(), i);
5052         i--;                      // Rerun same iteration on compressed edges
5053       }
5054     }
5055 
5056     // Given dominators, try to find inner loops with calls that must
5057     // always be executed (call dominates loop tail).  These loops do
5058     // not need a separate safepoint.
5059     Node_List cisstack;
5060     _ltree_root->check_safepts(visited, cisstack);
5061   }
5062 
5063   // Walk the DATA nodes and place into loops.  Find earliest control
5064   // node.  For CFG nodes, the _loop_or_ctrl array starts out and remains
5065   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
5066   // _loop_or_ctrl array holds the earliest legal controlling CFG node.
5067 
5068   // Allocate stack with enough space to avoid frequent realloc
5069   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
5070   Node_Stack nstack(stack_size);
5071 
5072   visited.clear();
5073   Node_List worklist;
5074   // Don't need C->root() on worklist since
5075   // it will be processed among C->top() inputs
5076   worklist.push(C->top());
5077   visited.set(C->top()->_idx); // Set C->top() as visited now
5078   build_loop_early( visited, worklist, nstack );
5079 
5080   // Given early legal placement, try finding counted loops.  This placement
5081   // is good enough to discover most loop invariants.
5082   if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
5083     _ltree_root->counted_loop( this );
5084   }
5085 
5086   // Find latest loop placement.  Find ideal loop placement.
5087   visited.clear();
5088   init_dom_lca_tags();
5089   // Need C->root() on worklist when processing outs
5090   worklist.push(C->root());
5091   NOT_PRODUCT( C->verify_graph_edges(); )
5092   worklist.push(C->top());
5093   build_loop_late( visited, worklist, nstack );
5094   if (C->failing()) { return; }
5095 
5096   if (_verify_only) {
5097     C->restore_major_progress(old_progress);
5098     assert(C->unique() == unique, "verification _mode made Nodes? ? ?");
5099     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
5100     return;
5101   }
5102 
5103   // clear out the dead code after build_loop_late
5104   while (_deadlist.size()) {
5105     _igvn.remove_globally_dead_node(_deadlist.pop());
5106   }
5107 
5108   eliminate_useless_zero_trip_guard();
5109   eliminate_useless_multiversion_if();
5110 
5111   if (stop_early) {
5112     assert(do_expensive_nodes, "why are we here?");
5113     if (process_expensive_nodes()) {
5114       // If we made some progress when processing expensive nodes then
5115       // the IGVN may modify the graph in a way that will allow us to
5116       // make some more progress: we need to try processing expensive
5117       // nodes again.
5118       C->set_major_progress();
5119     }
5120     return;
5121   }
5122 
5123   // Some parser-inserted loop predicates could never be used by loop
5124   // predication or they were moved away from loop during some optimizations.
5125   // For example, peeling. Eliminate them before next loop optimizations.
5126   eliminate_useless_predicates();
5127 
5128 #ifndef PRODUCT
5129   C->verify_graph_edges();
5130   if (_verify_me) {             // Nested verify pass?
5131     // Check to see if the verify _mode is broken
5132     assert(C->unique() == unique, "non-optimize _mode made Nodes? ? ?");
5133     return;
5134   }
5135   DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
5136   if (TraceLoopOpts && C->has_loops()) {
5137     _ltree_root->dump();
5138   }
5139 #endif
5140 
5141   if (skip_loop_opts) {
5142     C->restore_major_progress(old_progress);
5143     return;
5144   }
5145 
5146   if (do_max_unroll) {
5147     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
5148       IdealLoopTree* lpt = iter.current();
5149       if (lpt->is_innermost() && lpt->_allow_optimizations && !lpt->_has_call && lpt->is_counted()) {
5150         lpt->compute_trip_count(this, T_INT);
5151         if (!lpt->do_one_iteration_loop(this) &&
5152             !lpt->do_remove_empty_loop(this)) {
5153           AutoNodeBudget node_budget(this);
5154           if (lpt->_head->as_CountedLoop()->is_normal_loop() &&
5155               lpt->policy_maximally_unroll(this)) {
5156             memset( worklist.adr(), 0, worklist.max()*sizeof(Node*) );
5157             do_maximally_unroll(lpt, worklist);
5158           }
5159         }
5160       }
5161     }
5162 
5163     C->restore_major_progress(old_progress);
5164     return;
5165   }
5166 
5167   if (bs->optimize_loops(this, _mode, visited, nstack, worklist)) {
5168     return;
5169   }
5170 
5171   if (ReassociateInvariants && !C->major_progress()) {
5172     // Reassociate invariants and prep for split_thru_phi
5173     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
5174       IdealLoopTree* lpt = iter.current();
5175       if (!lpt->is_loop()) {
5176         continue;
5177       }
5178       Node* head = lpt->_head;
5179       if (!head->is_BaseCountedLoop() || !lpt->is_innermost()) continue;
5180 
5181       // check for vectorized loops, any reassociation of invariants was already done
5182       if (head->is_CountedLoop()) {
5183         if (head->as_CountedLoop()->is_unroll_only()) {
5184           continue;
5185         } else {
5186           AutoNodeBudget node_budget(this);
5187           lpt->reassociate_invariants(this);
5188         }
5189       }
5190       // Because RCE opportunities can be masked by split_thru_phi,
5191       // look for RCE candidates and inhibit split_thru_phi
5192       // on just their loop-phi's for this pass of loop opts
5193       if (SplitIfBlocks && do_split_ifs &&
5194           head->as_BaseCountedLoop()->is_valid_counted_loop(head->as_BaseCountedLoop()->bt()) &&
5195           (lpt->policy_range_check(this, true, T_LONG) ||
5196            (head->is_CountedLoop() && lpt->policy_range_check(this, true, T_INT)))) {
5197         lpt->_rce_candidate = 1; // = true
5198       }
5199     }
5200   }
5201 
5202   // Check for aggressive application of split-if and other transforms
5203   // that require basic-block info (like cloning through Phi's)
5204   if (!C->major_progress() && SplitIfBlocks && do_split_ifs) {
5205     visited.clear();
5206     split_if_with_blocks(visited, nstack);
5207     if (C->failing()) {
5208       return;
5209     }
5210     DEBUG_ONLY( if (VerifyLoopOptimizations) { verify(); } );
5211   }
5212 
5213   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
5214     C->set_major_progress();
5215   }
5216 
5217   // Perform loop predication before iteration splitting
5218   if (UseLoopPredicate && C->has_loops() && !C->major_progress() && (C->parse_predicate_count() > 0)) {
5219     _ltree_root->_child->loop_predication(this);
5220   }
5221 
5222   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
5223     if (do_intrinsify_fill()) {
5224       C->set_major_progress();
5225     }
5226   }
5227 
5228   // Perform iteration-splitting on inner loops.  Split iterations to avoid
5229   // range checks or one-shot null checks.
5230 
5231   // If split-if's didn't hack the graph too bad (no CFG changes)
5232   // then do loop opts.
5233   if (C->has_loops() && !C->major_progress()) {
5234     memset( worklist.adr(), 0, worklist.max()*sizeof(Node*) );
5235     _ltree_root->_child->iteration_split( this, worklist );
5236     // No verify after peeling!  GCM has hoisted code out of the loop.
5237     // After peeling, the hoisted code could sink inside the peeled area.
5238     // The peeling code does not try to recompute the best location for
5239     // all the code before the peeled area, so the verify pass will always
5240     // complain about it.
5241   }
5242 
5243   // Check for bailout, and return
5244   if (C->failing()) {
5245     return;
5246   }
5247 
5248   // Do verify graph edges in any case
5249   NOT_PRODUCT( C->verify_graph_edges(); );
5250 
5251   if (!do_split_ifs) {
5252     // We saw major progress in Split-If to get here.  We forced a
5253     // pass with unrolling and not split-if, however more split-if's
5254     // might make progress.  If the unrolling didn't make progress
5255     // then the major-progress flag got cleared and we won't try
5256     // another round of Split-If.  In particular the ever-common
5257     // instance-of/check-cast pattern requires at least 2 rounds of
5258     // Split-If to clear out.
5259     C->set_major_progress();
5260   }
5261 
5262   // Repeat loop optimizations if new loops were seen
5263   if (created_loop_node()) {
5264     C->set_major_progress();
5265   }
5266 
5267   // Auto-vectorize main-loop
5268   if (C->do_superword() && C->has_loops() && !C->major_progress()) {
5269     Compile::TracePhase tp(_t_autoVectorize);
5270 
5271     // Shared data structures for all AutoVectorizations, to reduce allocations
5272     // of large arrays.
5273     VSharedData vshared;
5274     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
5275       IdealLoopTree* lpt = iter.current();
5276       AutoVectorizeStatus status = auto_vectorize(lpt, vshared);
5277 
5278       if (status == AutoVectorizeStatus::TriedAndFailed) {
5279         // We tried vectorization, but failed. From now on only unroll the loop.
5280         CountedLoopNode* cl = lpt->_head->as_CountedLoop();
5281         if (cl->has_passed_slp()) {
5282           C->set_major_progress();
5283           cl->set_notpassed_slp();
5284           cl->mark_do_unroll_only();
5285         }
5286       }
5287     }
5288   }
5289 
5290   // Keep loop predicates and perform optimizations with them
5291   // until no more loop optimizations could be done.
5292   // After that switch predicates off and do more loop optimizations.
5293   if (!C->major_progress() && (C->parse_predicate_count() > 0)) {
5294     C->mark_parse_predicate_nodes_useless(_igvn);
5295     assert(C->parse_predicate_count() == 0, "should be zero now");
5296     if (TraceLoopOpts) {
5297       tty->print_cr("PredicatesOff");
5298     }
5299     C->set_major_progress();
5300   }
5301 }
5302 
5303 #ifndef PRODUCT
5304 //------------------------------print_statistics-------------------------------
5305 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
5306 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
5307 volatile int PhaseIdealLoop::_long_loop_candidates=0; // Number of long loops seen
5308 volatile int PhaseIdealLoop::_long_loop_nests=0; // Number of long loops successfully transformed to a nest
5309 volatile int PhaseIdealLoop::_long_loop_counted_loops=0; // Number of long loops successfully transformed to a counted loop
5310 void PhaseIdealLoop::print_statistics() {
5311   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d, long loops=%d/%d/%d", _loop_invokes, _loop_work, _long_loop_counted_loops, _long_loop_nests, _long_loop_candidates);
5312 }
5313 #endif
5314 
5315 #ifdef ASSERT
5316 // Build a verify-only PhaseIdealLoop, and see that it agrees with "this".
5317 void PhaseIdealLoop::verify() const {
5318   ResourceMark rm;
5319   int old_progress = C->major_progress();
5320   bool success = true;
5321 
5322   PhaseIdealLoop phase_verify(_igvn, this);
5323   if (C->failing_internal()) {
5324     return;
5325   }
5326 
5327   // Verify ctrl and idom of every node.
5328   success &= verify_idom_and_nodes(C->root(), &phase_verify);
5329 
5330   // Verify loop-tree.
5331   success &= _ltree_root->verify_tree(phase_verify._ltree_root);
5332 
5333   assert(success, "VerifyLoopOptimizations failed");
5334 
5335   // Major progress was cleared by creating a verify version of PhaseIdealLoop.
5336   C->restore_major_progress(old_progress);
5337 }
5338 
5339 // Perform a BFS starting at n, through all inputs.
5340 // Call verify_idom and verify_node on all nodes of BFS traversal.
5341 bool PhaseIdealLoop::verify_idom_and_nodes(Node* root, const PhaseIdealLoop* phase_verify) const {
5342   Unique_Node_List worklist;
5343   worklist.push(root);
5344   bool success = true;
5345   for (uint i = 0; i < worklist.size(); i++) {
5346     Node* n = worklist.at(i);
5347     // process node
5348     success &= verify_idom(n, phase_verify);
5349     success &= verify_loop_ctrl(n, phase_verify);
5350     // visit inputs
5351     for (uint j = 0; j < n->req(); j++) {
5352       if (n->in(j) != nullptr) {
5353         worklist.push(n->in(j));
5354       }
5355     }
5356   }
5357   return success;
5358 }
5359 
5360 // Verify dominator structure (IDOM).
5361 bool PhaseIdealLoop::verify_idom(Node* n, const PhaseIdealLoop* phase_verify) const {
5362   // Verify IDOM for all CFG nodes (except root).
5363   if (!n->is_CFG() || n->is_Root()) {
5364     return true; // pass
5365   }
5366 
5367   if (n->_idx >= _idom_size) {
5368     tty->print("CFG Node with no idom: ");
5369     n->dump();
5370     return false; // fail
5371   }
5372 
5373   Node* id = idom_no_update(n);
5374   Node* id_verify = phase_verify->idom_no_update(n);
5375   if (id != id_verify) {
5376     tty->print("Mismatching idom for node: ");
5377     n->dump();
5378     tty->print("  We have idom: ");
5379     id->dump();
5380     tty->print("  Verify has idom: ");
5381     id_verify->dump();
5382     tty->cr();
5383     return false; // fail
5384   }
5385   return true; // pass
5386 }
5387 
5388 // Verify "_loop_or_ctrl": control and loop membership.
5389 //  (0) _loop_or_ctrl[i] == nullptr -> node not reachable.
5390 //  (1) has_ctrl -> check lowest bit. 1 -> data node. 0 -> ctrl node.
5391 //  (2) has_ctrl true: get_ctrl_no_update returns ctrl of data node.
5392 //  (3) has_ctrl false: get_loop_idx returns IdealLoopTree for ctrl node.
5393 bool PhaseIdealLoop::verify_loop_ctrl(Node* n, const PhaseIdealLoop* phase_verify) const {
5394   const uint i = n->_idx;
5395   // The loop-tree was built from def to use (top-down).
5396   // The verification happens from use to def (bottom-up).
5397   // We may thus find nodes during verification that are not in the loop-tree.
5398   if (_loop_or_ctrl[i] == nullptr || phase_verify->_loop_or_ctrl[i] == nullptr) {
5399     if (_loop_or_ctrl[i] != nullptr || phase_verify->_loop_or_ctrl[i] != nullptr) {
5400       tty->print_cr("Was reachable in only one. this %d, verify %d.",
5401                  _loop_or_ctrl[i] != nullptr, phase_verify->_loop_or_ctrl[i] != nullptr);
5402       n->dump();
5403       return false; // fail
5404     }
5405     // Not reachable for both.
5406     return true; // pass
5407   }
5408 
5409   if (n->is_CFG() == has_ctrl(n)) {
5410     tty->print_cr("Exactly one should be true: %d for is_CFG, %d for has_ctrl.", n->is_CFG(), has_ctrl(n));
5411     n->dump();
5412     return false; // fail
5413   }
5414 
5415   if (has_ctrl(n) != phase_verify->has_ctrl(n)) {
5416     tty->print_cr("Mismatch has_ctrl: %d for this, %d for verify.", has_ctrl(n), phase_verify->has_ctrl(n));
5417     n->dump();
5418     return false; // fail
5419   } else if (has_ctrl(n)) {
5420     assert(phase_verify->has_ctrl(n), "sanity");
5421     // n is a data node.
5422     // Verify that its ctrl is the same.
5423 
5424     // Broken part of VerifyLoopOptimizations (A)
5425     // Reason:
5426     //   BUG, wrong control set for example in
5427     //   PhaseIdealLoop::split_if_with_blocks
5428     //   at "set_ctrl(x, new_ctrl);"
5429     /*
5430     if( _loop_or_ctrl[i] != loop_verify->_loop_or_ctrl[i] &&
5431         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
5432       tty->print("Mismatched control setting for: ");
5433       n->dump();
5434       if( fail++ > 10 ) return;
5435       Node *c = get_ctrl_no_update(n);
5436       tty->print("We have it as: ");
5437       if( c->in(0) ) c->dump();
5438         else tty->print_cr("N%d",c->_idx);
5439       tty->print("Verify thinks: ");
5440       if( loop_verify->has_ctrl(n) )
5441         loop_verify->get_ctrl_no_update(n)->dump();
5442       else
5443         loop_verify->get_loop_idx(n)->dump();
5444       tty->cr();
5445     }
5446     */
5447     return true; // pass
5448   } else {
5449     assert(!phase_verify->has_ctrl(n), "sanity");
5450     // n is a ctrl node.
5451     // Verify that not has_ctrl, and that get_loop_idx is the same.
5452 
5453     // Broken part of VerifyLoopOptimizations (B)
5454     // Reason:
5455     //   NeverBranch node for example is added to loop outside its scope.
5456     //   Once we run build_loop_tree again, it is added to the correct loop.
5457     /*
5458     if (!C->major_progress()) {
5459       // Loop selection can be messed up if we did a major progress
5460       // operation, like split-if.  Do not verify in that case.
5461       IdealLoopTree *us = get_loop_idx(n);
5462       IdealLoopTree *them = loop_verify->get_loop_idx(n);
5463       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
5464         tty->print("Unequals loops for: ");
5465         n->dump();
5466         if( fail++ > 10 ) return;
5467         tty->print("We have it as: ");
5468         us->dump();
5469         tty->print("Verify thinks: ");
5470         them->dump();
5471         tty->cr();
5472       }
5473     }
5474     */
5475     return true; // pass
5476   }
5477 }
5478 
5479 static int compare_tree(IdealLoopTree* const& a, IdealLoopTree* const& b) {
5480   assert(a != nullptr && b != nullptr, "must be");
5481   return a->_head->_idx - b->_head->_idx;
5482 }
5483 
5484 GrowableArray<IdealLoopTree*> IdealLoopTree::collect_sorted_children() const {
5485   GrowableArray<IdealLoopTree*> children;
5486   IdealLoopTree* child = _child;
5487   while (child != nullptr) {
5488     assert(child->_parent == this, "all must be children of this");
5489     children.insert_sorted<compare_tree>(child);
5490     child = child->_next;
5491   }
5492   return children;
5493 }
5494 
5495 // Verify that tree structures match. Because the CFG can change, siblings
5496 // within the loop tree can be reordered. We attempt to deal with that by
5497 // reordering the verify's loop tree if possible.
5498 bool IdealLoopTree::verify_tree(IdealLoopTree* loop_verify) const {
5499   assert(_head == loop_verify->_head, "mismatched loop head");
5500   assert(this->_parent != nullptr || this->_next == nullptr, "is_root_loop implies has_no_sibling");
5501 
5502   // Collect the children
5503   GrowableArray<IdealLoopTree*> children = collect_sorted_children();
5504   GrowableArray<IdealLoopTree*> children_verify = loop_verify->collect_sorted_children();
5505 
5506   bool success = true;
5507 
5508   // Compare the two children lists
5509   for (int i = 0, j = 0; i < children.length() || j < children_verify.length(); ) {
5510     IdealLoopTree* child        = nullptr;
5511     IdealLoopTree* child_verify = nullptr;
5512     // Read from both lists, if possible.
5513     if (i < children.length()) {
5514       child = children.at(i);
5515     }
5516     if (j < children_verify.length()) {
5517       child_verify = children_verify.at(j);
5518     }
5519     assert(child != nullptr || child_verify != nullptr, "must find at least one");
5520     if (child != nullptr && child_verify != nullptr && child->_head != child_verify->_head) {
5521       // We found two non-equal children. Select the smaller one.
5522       if (child->_head->_idx < child_verify->_head->_idx) {
5523         child_verify = nullptr;
5524       } else {
5525         child = nullptr;
5526       }
5527     }
5528     // Process the two children, or potentially log the failure if we only found one.
5529     if (child_verify == nullptr) {
5530       if (child->_irreducible && Compile::current()->major_progress()) {
5531         // Irreducible loops can pick a different header (one of its entries).
5532       } else {
5533         tty->print_cr("We have a loop that verify does not have");
5534         child->dump();
5535         success = false;
5536       }
5537       i++; // step for this
5538     } else if (child == nullptr) {
5539       if (child_verify->_irreducible && Compile::current()->major_progress()) {
5540         // Irreducible loops can pick a different header (one of its entries).
5541       } else if (child_verify->_head->as_Region()->is_in_infinite_subgraph()) {
5542         // Infinite loops do not get attached to the loop-tree on their first visit.
5543         // "this" runs before "loop_verify". It is thus possible that we find the
5544         // infinite loop only for "child_verify". Only finding it with "child" would
5545         // mean that we lost it, which is not ok.
5546       } else {
5547         tty->print_cr("Verify has a loop that we do not have");
5548         child_verify->dump();
5549         success = false;
5550       }
5551       j++; // step for verify
5552     } else {
5553       assert(child->_head == child_verify->_head, "We have both and they are equal");
5554       success &= child->verify_tree(child_verify); // Recursion
5555       i++; // step for this
5556       j++; // step for verify
5557     }
5558   }
5559 
5560   // Broken part of VerifyLoopOptimizations (D)
5561   // Reason:
5562   //   split_if has to update the _tail, if it is modified. But that is done by
5563   //   checking to what loop the iff belongs to. That info can be wrong, and then
5564   //   we do not update the _tail correctly.
5565   /*
5566   Node *tail = _tail;           // Inline a non-updating version of
5567   while( !tail->in(0) )         // the 'tail()' call.
5568     tail = tail->in(1);
5569   assert( tail == loop->_tail, "mismatched loop tail" );
5570   */
5571 
5572   if (_head->is_CountedLoop()) {
5573     CountedLoopNode *cl = _head->as_CountedLoop();
5574 
5575     Node* ctrl     = cl->init_control();
5576     Node* back     = cl->back_control();
5577     assert(ctrl != nullptr && ctrl->is_CFG(), "sane loop in-ctrl");
5578     assert(back != nullptr && back->is_CFG(), "sane loop backedge");
5579     cl->loopexit(); // assert implied
5580   }
5581 
5582   // Broken part of VerifyLoopOptimizations (E)
5583   // Reason:
5584   //   PhaseIdealLoop::split_thru_region creates new nodes for loop that are not added
5585   //   to the loop body. Or maybe they are not added to the correct loop.
5586   //   at "Node* x = n->clone();"
5587   /*
5588   // Innermost loops need to verify loop bodies,
5589   // but only if no 'major_progress'
5590   int fail = 0;
5591   if (!Compile::current()->major_progress() && _child == nullptr) {
5592     for( uint i = 0; i < _body.size(); i++ ) {
5593       Node *n = _body.at(i);
5594       if (n->outcnt() == 0)  continue; // Ignore dead
5595       uint j;
5596       for( j = 0; j < loop->_body.size(); j++ )
5597         if( loop->_body.at(j) == n )
5598           break;
5599       if( j == loop->_body.size() ) { // Not found in loop body
5600         // Last ditch effort to avoid assertion: Its possible that we
5601         // have some users (so outcnt not zero) but are still dead.
5602         // Try to find from root.
5603         if (Compile::current()->root()->find(n->_idx)) {
5604           fail++;
5605           tty->print("We have that verify does not: ");
5606           n->dump();
5607         }
5608       }
5609     }
5610     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
5611       Node *n = loop->_body.at(i2);
5612       if (n->outcnt() == 0)  continue; // Ignore dead
5613       uint j;
5614       for( j = 0; j < _body.size(); j++ )
5615         if( _body.at(j) == n )
5616           break;
5617       if( j == _body.size() ) { // Not found in loop body
5618         // Last ditch effort to avoid assertion: Its possible that we
5619         // have some users (so outcnt not zero) but are still dead.
5620         // Try to find from root.
5621         if (Compile::current()->root()->find(n->_idx)) {
5622           fail++;
5623           tty->print("Verify has that we do not: ");
5624           n->dump();
5625         }
5626       }
5627     }
5628     assert( !fail, "loop body mismatch" );
5629   }
5630   */
5631   return success;
5632 }
5633 #endif
5634 
5635 //------------------------------set_idom---------------------------------------
5636 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
5637   _nesting.check(); // Check if a potential reallocation in the resource arena is safe
5638   uint idx = d->_idx;
5639   if (idx >= _idom_size) {
5640     uint newsize = next_power_of_2(idx);
5641     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
5642     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
5643     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
5644     _idom_size = newsize;
5645   }
5646   _idom[idx] = n;
5647   _dom_depth[idx] = dom_depth;
5648 }
5649 
5650 //------------------------------recompute_dom_depth---------------------------------------
5651 // The dominator tree is constructed with only parent pointers.
5652 // This recomputes the depth in the tree by first tagging all
5653 // nodes as "no depth yet" marker.  The next pass then runs up
5654 // the dom tree from each node marked "no depth yet", and computes
5655 // the depth on the way back down.
5656 void PhaseIdealLoop::recompute_dom_depth() {
5657   uint no_depth_marker = C->unique();
5658   uint i;
5659   // Initialize depth to "no depth yet" and realize all lazy updates
5660   for (i = 0; i < _idom_size; i++) {
5661     // Only indices with a _dom_depth has a Node* or null (otherwise uninitialized).
5662     if (_dom_depth[i] > 0 && _idom[i] != nullptr) {
5663       _dom_depth[i] = no_depth_marker;
5664 
5665       // heal _idom if it has a fwd mapping in _loop_or_ctrl
5666       if (_idom[i]->in(0) == nullptr) {
5667         idom(i);
5668       }
5669     }
5670   }
5671   if (_dom_stk == nullptr) {
5672     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
5673     if (init_size < 10) init_size = 10;
5674     _dom_stk = new GrowableArray<uint>(init_size);
5675   }
5676   // Compute new depth for each node.
5677   for (i = 0; i < _idom_size; i++) {
5678     uint j = i;
5679     // Run up the dom tree to find a node with a depth
5680     while (_dom_depth[j] == no_depth_marker) {
5681       _dom_stk->push(j);
5682       j = _idom[j]->_idx;
5683     }
5684     // Compute the depth on the way back down this tree branch
5685     uint dd = _dom_depth[j] + 1;
5686     while (_dom_stk->length() > 0) {
5687       uint j = _dom_stk->pop();
5688       _dom_depth[j] = dd;
5689       dd++;
5690     }
5691   }
5692 }
5693 
5694 //------------------------------sort-------------------------------------------
5695 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
5696 // loop tree, not the root.
5697 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
5698   if( !innermost ) return loop; // New innermost loop
5699 
5700   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
5701   assert( loop_preorder, "not yet post-walked loop" );
5702   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
5703   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
5704 
5705   // Insert at start of list
5706   while( l ) {                  // Insertion sort based on pre-order
5707     if( l == loop ) return innermost; // Already on list!
5708     int l_preorder = get_preorder(l->_head); // Cache pre-order number
5709     assert( l_preorder, "not yet post-walked l" );
5710     // Check header pre-order number to figure proper nesting
5711     if( loop_preorder > l_preorder )
5712       break;                    // End of insertion
5713     // If headers tie (e.g., shared headers) check tail pre-order numbers.
5714     // Since I split shared headers, you'd think this could not happen.
5715     // BUT: I must first do the preorder numbering before I can discover I
5716     // have shared headers, so the split headers all get the same preorder
5717     // number as the RegionNode they split from.
5718     if( loop_preorder == l_preorder &&
5719         get_preorder(loop->_tail) < get_preorder(l->_tail) )
5720       break;                    // Also check for shared headers (same pre#)
5721     pp = &l->_parent;           // Chain up list
5722     l = *pp;
5723   }
5724   // Link into list
5725   // Point predecessor to me
5726   *pp = loop;
5727   // Point me to successor
5728   IdealLoopTree *p = loop->_parent;
5729   loop->_parent = l;            // Point me to successor
5730   if( p ) sort( p, innermost ); // Insert my parents into list as well
5731   return innermost;
5732 }
5733 
5734 //------------------------------build_loop_tree--------------------------------
5735 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
5736 // bits.  The _loop_or_ctrl[] array is mapped by Node index and holds a null for
5737 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
5738 // tightest enclosing IdealLoopTree for post-walked.
5739 //
5740 // During my forward walk I do a short 1-layer lookahead to see if I can find
5741 // a loop backedge with that doesn't have any work on the backedge.  This
5742 // helps me construct nested loops with shared headers better.
5743 //
5744 // Once I've done the forward recursion, I do the post-work.  For each child
5745 // I check to see if there is a backedge.  Backedges define a loop!  I
5746 // insert an IdealLoopTree at the target of the backedge.
5747 //
5748 // During the post-work I also check to see if I have several children
5749 // belonging to different loops.  If so, then this Node is a decision point
5750 // where control flow can choose to change loop nests.  It is at this
5751 // decision point where I can figure out how loops are nested.  At this
5752 // time I can properly order the different loop nests from my children.
5753 // Note that there may not be any backedges at the decision point!
5754 //
5755 // Since the decision point can be far removed from the backedges, I can't
5756 // order my loops at the time I discover them.  Thus at the decision point
5757 // I need to inspect loop header pre-order numbers to properly nest my
5758 // loops.  This means I need to sort my childrens' loops by pre-order.
5759 // The sort is of size number-of-control-children, which generally limits
5760 // it to size 2 (i.e., I just choose between my 2 target loops).
5761 void PhaseIdealLoop::build_loop_tree() {
5762   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
5763   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
5764   Node *n = C->root();
5765   bltstack.push(n);
5766   int pre_order = 1;
5767   int stack_size;
5768 
5769   while ( ( stack_size = bltstack.length() ) != 0 ) {
5770     n = bltstack.top(); // Leave node on stack
5771     if ( !is_visited(n) ) {
5772       // ---- Pre-pass Work ----
5773       // Pre-walked but not post-walked nodes need a pre_order number.
5774 
5775       set_preorder_visited( n, pre_order ); // set as visited
5776 
5777       // ---- Scan over children ----
5778       // Scan first over control projections that lead to loop headers.
5779       // This helps us find inner-to-outer loops with shared headers better.
5780 
5781       // Scan children's children for loop headers.
5782       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
5783         Node* m = n->raw_out(i);       // Child
5784         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
5785           // Scan over children's children to find loop
5786           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
5787             Node* l = m->fast_out(j);
5788             if( is_visited(l) &&       // Been visited?
5789                 !is_postvisited(l) &&  // But not post-visited
5790                 get_preorder(l) < pre_order ) { // And smaller pre-order
5791               // Found!  Scan the DFS down this path before doing other paths
5792               bltstack.push(m);
5793               break;
5794             }
5795           }
5796         }
5797       }
5798       pre_order++;
5799     }
5800     else if ( !is_postvisited(n) ) {
5801       // Note: build_loop_tree_impl() adds out edges on rare occasions,
5802       // such as com.sun.rsasign.am::a.
5803       // For non-recursive version, first, process current children.
5804       // On next iteration, check if additional children were added.
5805       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
5806         Node* u = n->raw_out(k);
5807         if ( u->is_CFG() && !is_visited(u) ) {
5808           bltstack.push(u);
5809         }
5810       }
5811       if ( bltstack.length() == stack_size ) {
5812         // There were no additional children, post visit node now
5813         (void)bltstack.pop(); // Remove node from stack
5814         pre_order = build_loop_tree_impl(n, pre_order);
5815         // Check for bailout
5816         if (C->failing()) {
5817           return;
5818         }
5819         // Check to grow _preorders[] array for the case when
5820         // build_loop_tree_impl() adds new nodes.
5821         check_grow_preorders();
5822       }
5823     }
5824     else {
5825       (void)bltstack.pop(); // Remove post-visited node from stack
5826     }
5827   }
5828   DEBUG_ONLY(verify_regions_in_irreducible_loops();)
5829 }
5830 
5831 //------------------------------build_loop_tree_impl---------------------------
5832 int PhaseIdealLoop::build_loop_tree_impl(Node* n, int pre_order) {
5833   // ---- Post-pass Work ----
5834   // Pre-walked but not post-walked nodes need a pre_order number.
5835 
5836   // Tightest enclosing loop for this Node
5837   IdealLoopTree *innermost = nullptr;
5838 
5839   // For all children, see if any edge is a backedge.  If so, make a loop
5840   // for it.  Then find the tightest enclosing loop for the self Node.
5841   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
5842     Node* m = n->fast_out(i);   // Child
5843     if (n == m) continue;      // Ignore control self-cycles
5844     if (!m->is_CFG()) continue;// Ignore non-CFG edges
5845 
5846     IdealLoopTree *l;           // Child's loop
5847     if (!is_postvisited(m)) {  // Child visited but not post-visited?
5848       // Found a backedge
5849       assert(get_preorder(m) < pre_order, "should be backedge");
5850       // Check for the RootNode, which is already a LoopNode and is allowed
5851       // to have multiple "backedges".
5852       if (m == C->root()) {     // Found the root?
5853         l = _ltree_root;        // Root is the outermost LoopNode
5854       } else {                  // Else found a nested loop
5855         // Insert a LoopNode to mark this loop.
5856         l = new IdealLoopTree(this, m, n);
5857       } // End of Else found a nested loop
5858       if (!has_loop(m)) {        // If 'm' does not already have a loop set
5859         set_loop(m, l);         // Set loop header to loop now
5860       }
5861     } else {                    // Else not a nested loop
5862       if (!_loop_or_ctrl[m->_idx]) continue; // Dead code has no loop
5863       IdealLoopTree* m_loop = get_loop(m);
5864       l = m_loop;          // Get previously determined loop
5865       // If successor is header of a loop (nest), move up-loop till it
5866       // is a member of some outer enclosing loop.  Since there are no
5867       // shared headers (I've split them already) I only need to go up
5868       // at most 1 level.
5869       while (l && l->_head == m) { // Successor heads loop?
5870         l = l->_parent;         // Move up 1 for me
5871       }
5872       // If this loop is not properly parented, then this loop
5873       // has no exit path out, i.e. its an infinite loop.
5874       if (!l) {
5875         // Make loop "reachable" from root so the CFG is reachable.  Basically
5876         // insert a bogus loop exit that is never taken.  'm', the loop head,
5877         // points to 'n', one (of possibly many) fall-in paths.  There may be
5878         // many backedges as well.
5879 
5880         if (!_verify_only) {
5881           // Insert the NeverBranch between 'm' and it's control user.
5882           NeverBranchNode *iff = new NeverBranchNode( m );
5883           _igvn.register_new_node_with_optimizer(iff);
5884           set_loop(iff, m_loop);
5885           Node *if_t = new CProjNode( iff, 0 );
5886           _igvn.register_new_node_with_optimizer(if_t);
5887           set_loop(if_t, m_loop);
5888 
5889           Node* cfg = nullptr;       // Find the One True Control User of m
5890           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
5891             Node* x = m->fast_out(j);
5892             if (x->is_CFG() && x != m && x != iff)
5893               { cfg = x; break; }
5894           }
5895           assert(cfg != nullptr, "must find the control user of m");
5896           uint k = 0;             // Probably cfg->in(0)
5897           while( cfg->in(k) != m ) k++; // But check in case cfg is a Region
5898           _igvn.replace_input_of(cfg, k, if_t); // Now point to NeverBranch
5899 
5900           // Now create the never-taken loop exit
5901           Node *if_f = new CProjNode( iff, 1 );
5902           _igvn.register_new_node_with_optimizer(if_f);
5903           set_loop(if_f, _ltree_root);
5904           // Find frame ptr for Halt.  Relies on the optimizer
5905           // V-N'ing.  Easier and quicker than searching through
5906           // the program structure.
5907           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
5908           _igvn.register_new_node_with_optimizer(frame);
5909           // Halt & Catch Fire
5910           Node* halt = new HaltNode(if_f, frame, "never-taken loop exit reached");
5911           _igvn.register_new_node_with_optimizer(halt);
5912           set_loop(halt, _ltree_root);
5913           _igvn.add_input_to(C->root(), halt);
5914         }
5915         set_loop(C->root(), _ltree_root);
5916         // move to outer most loop with same header
5917         l = m_loop;
5918         while (true) {
5919           IdealLoopTree* next = l->_parent;
5920           if (next == nullptr || next->_head != m) {
5921             break;
5922           }
5923           l = next;
5924         }
5925         // properly insert infinite loop in loop tree
5926         sort(_ltree_root, l);
5927         // fix child link from parent
5928         IdealLoopTree* p = l->_parent;
5929         l->_next = p->_child;
5930         p->_child = l;
5931         // code below needs enclosing loop
5932         l = l->_parent;
5933       }
5934     }
5935     if (is_postvisited(l->_head)) {
5936       // We are currently visiting l, but its head has already been post-visited.
5937       // l is irreducible: we just found a second entry m.
5938       _has_irreducible_loops = true;
5939       RegionNode* secondary_entry = m->as_Region();
5940 
5941       if (!secondary_entry->can_be_irreducible_entry()) {
5942         assert(!VerifyNoNewIrreducibleLoops, "A new irreducible loop was created after parsing.");
5943         C->record_method_not_compilable("A new irreducible loop was created after parsing.");
5944         return pre_order;
5945       }
5946 
5947       // Walk up the loop-tree, mark all loops that are already post-visited as irreducible
5948       // Since m is a secondary entry to them all.
5949       while( is_postvisited(l->_head) ) {
5950         l->_irreducible = 1; // = true
5951         RegionNode* head = l->_head->as_Region();
5952         if (!head->can_be_irreducible_entry()) {
5953           assert(!VerifyNoNewIrreducibleLoops, "A new irreducible loop was created after parsing.");
5954           C->record_method_not_compilable("A new irreducible loop was created after parsing.");
5955           return pre_order;
5956         }
5957         l = l->_parent;
5958         // Check for bad CFG here to prevent crash, and bailout of compile
5959         if (l == nullptr) {
5960 #ifndef PRODUCT
5961           if (TraceLoopOpts) {
5962             tty->print_cr("bailout: unhandled CFG: infinite irreducible loop");
5963             m->dump();
5964           }
5965 #endif
5966           // This is a rare case that we do not want to handle in C2.
5967           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
5968           return pre_order;
5969         }
5970       }
5971     }
5972     if (!_verify_only) {
5973       C->set_has_irreducible_loop(_has_irreducible_loops);
5974     }
5975 
5976     // This Node might be a decision point for loops.  It is only if
5977     // it's children belong to several different loops.  The sort call
5978     // does a trivial amount of work if there is only 1 child or all
5979     // children belong to the same loop.  If however, the children
5980     // belong to different loops, the sort call will properly set the
5981     // _parent pointers to show how the loops nest.
5982     //
5983     // In any case, it returns the tightest enclosing loop.
5984     innermost = sort( l, innermost );
5985   }
5986 
5987   // Def-use info will have some dead stuff; dead stuff will have no
5988   // loop decided on.
5989 
5990   // Am I a loop header?  If so fix up my parent's child and next ptrs.
5991   if( innermost && innermost->_head == n ) {
5992     assert( get_loop(n) == innermost, "" );
5993     IdealLoopTree *p = innermost->_parent;
5994     IdealLoopTree *l = innermost;
5995     while (p && l->_head == n) {
5996       l->_next = p->_child;     // Put self on parents 'next child'
5997       p->_child = l;            // Make self as first child of parent
5998       l = p;                    // Now walk up the parent chain
5999       p = l->_parent;
6000     }
6001   } else {
6002     // Note that it is possible for a LoopNode to reach here, if the
6003     // backedge has been made unreachable (hence the LoopNode no longer
6004     // denotes a Loop, and will eventually be removed).
6005 
6006     // Record tightest enclosing loop for self.  Mark as post-visited.
6007     set_loop(n, innermost);
6008     // Also record has_call flag early on
6009     if (innermost) {
6010       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
6011         // Do not count uncommon calls
6012         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
6013           Node *iff = n->in(0)->in(0);
6014           // No any calls for vectorized loops.
6015           if (C->do_superword() ||
6016               !iff->is_If() ||
6017               (n->in(0)->Opcode() == Op_IfFalse && (1.0 - iff->as_If()->_prob) >= 0.01) ||
6018               iff->as_If()->_prob >= 0.01) {
6019             innermost->_has_call = 1;
6020           }
6021         }
6022       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
6023         // Disable loop optimizations if the loop has a scalar replaceable
6024         // allocation. This disabling may cause a potential performance lost
6025         // if the allocation is not eliminated for some reason.
6026         innermost->_allow_optimizations = false;
6027         innermost->_has_call = 1; // = true
6028       } else if (n->Opcode() == Op_SafePoint) {
6029         // Record all safepoints in this loop.
6030         if (innermost->_safepts == nullptr) innermost->_safepts = new Node_List();
6031         innermost->_safepts->push(n);
6032       }
6033     }
6034   }
6035 
6036   // Flag as post-visited now
6037   set_postvisited(n);
6038   return pre_order;
6039 }
6040 
6041 #ifdef ASSERT
6042 //--------------------------verify_regions_in_irreducible_loops----------------
6043 // Iterate down from Root through CFG, verify for every region:
6044 // if it is in an irreducible loop it must be marked as such
6045 void PhaseIdealLoop::verify_regions_in_irreducible_loops() {
6046   ResourceMark rm;
6047   if (!_has_irreducible_loops) {
6048     // last build_loop_tree has not found any irreducible loops
6049     // hence no region has to be marked is_in_irreduible_loop
6050     return;
6051   }
6052 
6053   RootNode* root = C->root();
6054   Unique_Node_List worklist; // visit all nodes once
6055   worklist.push(root);
6056   bool failure = false;
6057   for (uint i = 0; i < worklist.size(); i++) {
6058     Node* n = worklist.at(i);
6059     if (n->is_Region()) {
6060       RegionNode* region = n->as_Region();
6061       if (is_in_irreducible_loop(region) &&
6062           region->loop_status() == RegionNode::LoopStatus::Reducible) {
6063         failure = true;
6064         tty->print("irreducible! ");
6065         region->dump();
6066       }
6067     }
6068     for (DUIterator_Fast jmax, j = n->fast_outs(jmax); j < jmax; j++) {
6069       Node* use = n->fast_out(j);
6070       if (use->is_CFG()) {
6071         worklist.push(use); // push if was not pushed before
6072       }
6073     }
6074   }
6075   assert(!failure, "region in irreducible loop was marked as reducible");
6076 }
6077 
6078 //---------------------------is_in_irreducible_loop-------------------------
6079 // Analogous to ciTypeFlow::Block::is_in_irreducible_loop
6080 bool PhaseIdealLoop::is_in_irreducible_loop(RegionNode* region) {
6081   if (!_has_irreducible_loops) {
6082     return false; // no irreducible loop in graph
6083   }
6084   IdealLoopTree* l = get_loop(region); // l: innermost loop that contains region
6085   do {
6086     if (l->_irreducible) {
6087       return true; // found it
6088     }
6089     if (l == _ltree_root) {
6090       return false; // reached root, terimnate
6091     }
6092     l = l->_parent;
6093   } while (l != nullptr);
6094   assert(region->is_in_infinite_subgraph(), "must be in infinite subgraph");
6095   // We have "l->_parent == nullptr", which happens only for infinite loops,
6096   // where no parent is attached to the loop. We did not find any irreducible
6097   // loop from this block out to lp. Thus lp only has one entry, and no exit
6098   // (it is infinite and reducible). We can always rewrite an infinite loop
6099   // that is nested inside other loops:
6100   // while(condition) { infinite_loop; }
6101   // with an equivalent program where the infinite loop is an outermost loop
6102   // that is not nested in any loop:
6103   // while(condition) { break; } infinite_loop;
6104   // Thus, we can understand lp as an outermost loop, and can terminate and
6105   // conclude: this block is in no irreducible loop.
6106   return false;
6107 }
6108 #endif
6109 
6110 //------------------------------build_loop_early-------------------------------
6111 // Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
6112 // First pass computes the earliest controlling node possible.  This is the
6113 // controlling input with the deepest dominating depth.
6114 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
6115   while (worklist.size() != 0) {
6116     // Use local variables nstack_top_n & nstack_top_i to cache values
6117     // on nstack's top.
6118     Node *nstack_top_n = worklist.pop();
6119     uint  nstack_top_i = 0;
6120 //while_nstack_nonempty:
6121     while (true) {
6122       // Get parent node and next input's index from stack's top.
6123       Node  *n = nstack_top_n;
6124       uint   i = nstack_top_i;
6125       uint cnt = n->req(); // Count of inputs
6126       if (i == 0) {        // Pre-process the node.
6127         if( has_node(n) &&            // Have either loop or control already?
6128             !has_ctrl(n) ) {          // Have loop picked out already?
6129           // During "merge_many_backedges" we fold up several nested loops
6130           // into a single loop.  This makes the members of the original
6131           // loop bodies pointing to dead loops; they need to move up
6132           // to the new UNION'd larger loop.  I set the _head field of these
6133           // dead loops to null and the _parent field points to the owning
6134           // loop.  Shades of UNION-FIND algorithm.
6135           IdealLoopTree *ilt;
6136           while( !(ilt = get_loop(n))->_head ) {
6137             // Normally I would use a set_loop here.  But in this one special
6138             // case, it is legal (and expected) to change what loop a Node
6139             // belongs to.
6140             _loop_or_ctrl.map(n->_idx, (Node*)(ilt->_parent));
6141           }
6142           // Remove safepoints ONLY if I've already seen I don't need one.
6143           // (the old code here would yank a 2nd safepoint after seeing a
6144           // first one, even though the 1st did not dominate in the loop body
6145           // and thus could be avoided indefinitely)
6146           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
6147               is_deleteable_safept(n)) {
6148             Node *in = n->in(TypeFunc::Control);
6149             lazy_replace(n,in);       // Pull safepoint now
6150             if (ilt->_safepts != nullptr) {
6151               ilt->_safepts->yank(n);
6152             }
6153             // Carry on with the recursion "as if" we are walking
6154             // only the control input
6155             if( !visited.test_set( in->_idx ) ) {
6156               worklist.push(in);      // Visit this guy later, using worklist
6157             }
6158             // Get next node from nstack:
6159             // - skip n's inputs processing by setting i > cnt;
6160             // - we also will not call set_early_ctrl(n) since
6161             //   has_node(n) == true (see the condition above).
6162             i = cnt + 1;
6163           }
6164         }
6165       } // if (i == 0)
6166 
6167       // Visit all inputs
6168       bool done = true;       // Assume all n's inputs will be processed
6169       while (i < cnt) {
6170         Node *in = n->in(i);
6171         ++i;
6172         if (in == nullptr) continue;
6173         if (in->pinned() && !in->is_CFG())
6174           set_ctrl(in, in->in(0));
6175         int is_visited = visited.test_set( in->_idx );
6176         if (!has_node(in)) {  // No controlling input yet?
6177           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
6178           assert( !is_visited, "visit only once" );
6179           nstack.push(n, i);  // Save parent node and next input's index.
6180           nstack_top_n = in;  // Process current input now.
6181           nstack_top_i = 0;
6182           done = false;       // Not all n's inputs processed.
6183           break; // continue while_nstack_nonempty;
6184         } else if (!is_visited) {
6185           // This guy has a location picked out for him, but has not yet
6186           // been visited.  Happens to all CFG nodes, for instance.
6187           // Visit him using the worklist instead of recursion, to break
6188           // cycles.  Since he has a location already we do not need to
6189           // find his location before proceeding with the current Node.
6190           worklist.push(in);  // Visit this guy later, using worklist
6191         }
6192       }
6193       if (done) {
6194         // All of n's inputs have been processed, complete post-processing.
6195 
6196         // Compute earliest point this Node can go.
6197         // CFG, Phi, pinned nodes already know their controlling input.
6198         if (!has_node(n)) {
6199           // Record earliest legal location
6200           set_early_ctrl(n, false);
6201         }
6202         if (nstack.is_empty()) {
6203           // Finished all nodes on stack.
6204           // Process next node on the worklist.
6205           break;
6206         }
6207         // Get saved parent node and next input's index.
6208         nstack_top_n = nstack.node();
6209         nstack_top_i = nstack.index();
6210         nstack.pop();
6211       }
6212     } // while (true)
6213   }
6214 }
6215 
6216 //------------------------------dom_lca_internal--------------------------------
6217 // Pair-wise LCA
6218 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
6219   if( !n1 ) return n2;          // Handle null original LCA
6220   assert( n1->is_CFG(), "" );
6221   assert( n2->is_CFG(), "" );
6222   // find LCA of all uses
6223   uint d1 = dom_depth(n1);
6224   uint d2 = dom_depth(n2);
6225   while (n1 != n2) {
6226     if (d1 > d2) {
6227       n1 =      idom(n1);
6228       d1 = dom_depth(n1);
6229     } else if (d1 < d2) {
6230       n2 =      idom(n2);
6231       d2 = dom_depth(n2);
6232     } else {
6233       // Here d1 == d2.  Due to edits of the dominator-tree, sections
6234       // of the tree might have the same depth.  These sections have
6235       // to be searched more carefully.
6236 
6237       // Scan up all the n1's with equal depth, looking for n2.
6238       Node *t1 = idom(n1);
6239       while (dom_depth(t1) == d1) {
6240         if (t1 == n2)  return n2;
6241         t1 = idom(t1);
6242       }
6243       // Scan up all the n2's with equal depth, looking for n1.
6244       Node *t2 = idom(n2);
6245       while (dom_depth(t2) == d2) {
6246         if (t2 == n1)  return n1;
6247         t2 = idom(t2);
6248       }
6249       // Move up to a new dominator-depth value as well as up the dom-tree.
6250       n1 = t1;
6251       n2 = t2;
6252       d1 = dom_depth(n1);
6253       d2 = dom_depth(n2);
6254     }
6255   }
6256   return n1;
6257 }
6258 
6259 //------------------------------compute_idom-----------------------------------
6260 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
6261 // IDOMs are correct.
6262 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
6263   assert( region->is_Region(), "" );
6264   Node *LCA = nullptr;
6265   for( uint i = 1; i < region->req(); i++ ) {
6266     if( region->in(i) != C->top() )
6267       LCA = dom_lca( LCA, region->in(i) );
6268   }
6269   return LCA;
6270 }
6271 
6272 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
6273   bool had_error = false;
6274 #ifdef ASSERT
6275   if (early != C->root()) {
6276     // Make sure that there's a dominance path from LCA to early
6277     Node* d = LCA;
6278     while (d != early) {
6279       if (d == C->root()) {
6280         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
6281         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
6282         had_error = true;
6283         break;
6284       }
6285       d = idom(d);
6286     }
6287   }
6288 #endif
6289   return had_error;
6290 }
6291 
6292 
6293 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
6294   // Compute LCA over list of uses
6295   bool had_error = false;
6296   Node *LCA = nullptr;
6297   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
6298     Node* c = n->fast_out(i);
6299     if (_loop_or_ctrl[c->_idx] == nullptr)
6300       continue;                 // Skip the occasional dead node
6301     if( c->is_Phi() ) {         // For Phis, we must land above on the path
6302       for( uint j=1; j<c->req(); j++ ) {// For all inputs
6303         if( c->in(j) == n ) {   // Found matching input?
6304           Node *use = c->in(0)->in(j);
6305           if (_verify_only && use->is_top()) continue;
6306           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
6307           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
6308         }
6309       }
6310     } else {
6311       // For CFG data-users, use is in the block just prior
6312       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
6313       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
6314       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
6315     }
6316   }
6317   assert(!had_error, "bad dominance");
6318   return LCA;
6319 }
6320 
6321 // Check the shape of the graph at the loop entry. In some cases,
6322 // the shape of the graph does not match the shape outlined below.
6323 // That is caused by the Opaque1 node "protecting" the shape of
6324 // the graph being removed by, for example, the IGVN performed
6325 // in PhaseIdealLoop::build_and_optimize().
6326 //
6327 // After the Opaque1 node has been removed, optimizations (e.g., split-if,
6328 // loop unswitching, and IGVN, or a combination of them) can freely change
6329 // the graph's shape. As a result, the graph shape outlined below cannot
6330 // be guaranteed anymore.
6331 Node* CountedLoopNode::is_canonical_loop_entry() {
6332   if (!is_main_loop() && !is_post_loop()) {
6333     return nullptr;
6334   }
6335   Node* ctrl = skip_assertion_predicates_with_halt();
6336 
6337   if (ctrl == nullptr || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
6338     return nullptr;
6339   }
6340   Node* iffm = ctrl->in(0);
6341   if (iffm == nullptr || iffm->Opcode() != Op_If) {
6342     return nullptr;
6343   }
6344   Node* bolzm = iffm->in(1);
6345   if (bolzm == nullptr || !bolzm->is_Bool()) {
6346     return nullptr;
6347   }
6348   Node* cmpzm = bolzm->in(1);
6349   if (cmpzm == nullptr || !cmpzm->is_Cmp()) {
6350     return nullptr;
6351   }
6352 
6353   uint input = is_main_loop() ? 2 : 1;
6354   if (input >= cmpzm->req() || cmpzm->in(input) == nullptr) {
6355     return nullptr;
6356   }
6357   bool res = cmpzm->in(input)->Opcode() == Op_OpaqueZeroTripGuard;
6358 #ifdef ASSERT
6359   bool found_opaque = false;
6360   for (uint i = 1; i < cmpzm->req(); i++) {
6361     Node* opnd = cmpzm->in(i);
6362     if (opnd && opnd->is_Opaque1()) {
6363       found_opaque = true;
6364       break;
6365     }
6366   }
6367   assert(found_opaque == res, "wrong pattern");
6368 #endif
6369   return res ? cmpzm->in(input) : nullptr;
6370 }
6371 
6372 // Find pre loop end from main loop. Returns nullptr if none.
6373 CountedLoopEndNode* CountedLoopNode::find_pre_loop_end() {
6374   assert(is_main_loop(), "Can only find pre-loop from main-loop");
6375   // The loop cannot be optimized if the graph shape at the loop entry is
6376   // inappropriate.
6377   if (is_canonical_loop_entry() == nullptr) {
6378     return nullptr;
6379   }
6380 
6381   Node* p_f = skip_assertion_predicates_with_halt()->in(0)->in(0);
6382   if (!p_f->is_IfFalse() || !p_f->in(0)->is_CountedLoopEnd()) {
6383     return nullptr;
6384   }
6385   CountedLoopEndNode* pre_end = p_f->in(0)->as_CountedLoopEnd();
6386   CountedLoopNode* loop_node = pre_end->loopnode();
6387   if (loop_node == nullptr || !loop_node->is_pre_loop()) {
6388     return nullptr;
6389   }
6390   return pre_end;
6391 }
6392 
6393 Node* CountedLoopNode::uncasted_init_trip(bool uncast) {
6394   Node* init = init_trip();
6395   if (uncast && init->is_CastII()) {
6396     // skip over the cast added by PhaseIdealLoop::cast_incr_before_loop() when pre/post/main loops are created because
6397     // it can get in the way of type propagation. For instance, the index tested by an Assertion Predicate, if the cast
6398     // is not skipped over, could be (1):
6399     // (AddI (CastII (AddI pre_loop_iv -2) int) 1)
6400     // while without the cast, it is (2):
6401     // (AddI (AddI pre_loop_iv -2) 1)
6402     // which is be transformed to (3):
6403     // (AddI pre_loop_iv -1)
6404     // The compiler may be able to constant fold the Assertion Predicate condition for (3) but not (1)
6405     assert(init->as_CastII()->carry_dependency() && skip_assertion_predicates_with_halt() == init->in(0), "casted iv phi from pre loop expected");
6406     init = init->in(1);
6407   }
6408   return init;
6409 }
6410 
6411 //------------------------------get_late_ctrl----------------------------------
6412 // Compute latest legal control.
6413 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
6414   assert(early != nullptr, "early control should not be null");
6415 
6416   Node* LCA = compute_lca_of_uses(n, early);
6417 #ifdef ASSERT
6418   if (LCA == C->root() && LCA != early) {
6419     // def doesn't dominate uses so print some useful debugging output
6420     compute_lca_of_uses(n, early, true);
6421   }
6422 #endif
6423 
6424   if (n->is_Load() && LCA != early) {
6425     LCA = get_late_ctrl_with_anti_dep(n->as_Load(), early, LCA);
6426   }
6427 
6428   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
6429   return LCA;
6430 }
6431 
6432 // if this is a load, check for anti-dependent stores
6433 // We use a conservative algorithm to identify potential interfering
6434 // instructions and for rescheduling the load.  The users of the memory
6435 // input of this load are examined.  Any use which is not a load and is
6436 // dominated by early is considered a potentially interfering store.
6437 // This can produce false positives.
6438 Node* PhaseIdealLoop::get_late_ctrl_with_anti_dep(LoadNode* n, Node* early, Node* LCA) {
6439   int load_alias_idx = C->get_alias_index(n->adr_type());
6440   if (C->alias_type(load_alias_idx)->is_rewritable()) {
6441     Unique_Node_List worklist;
6442 
6443     Node* mem = n->in(MemNode::Memory);
6444     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
6445       Node* s = mem->fast_out(i);
6446       worklist.push(s);
6447     }
6448     for (uint i = 0; i < worklist.size() && LCA != early; i++) {
6449       Node* s = worklist.at(i);
6450       if (s->is_Load() || s->Opcode() == Op_SafePoint ||
6451           (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0) ||
6452           s->is_Phi()) {
6453         continue;
6454       } else if (s->is_MergeMem()) {
6455         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
6456           Node* s1 = s->fast_out(i);
6457           worklist.push(s1);
6458         }
6459       } else {
6460         Node* sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
6461         assert(sctrl != nullptr || !s->is_reachable_from_root(), "must have control");
6462         if (sctrl != nullptr && !sctrl->is_top() && is_dominator(early, sctrl)) {
6463           const TypePtr* adr_type = s->adr_type();
6464           if (s->is_ArrayCopy()) {
6465             // Copy to known instance needs destination type to test for aliasing
6466             const TypePtr* dest_type = s->as_ArrayCopy()->_dest_type;
6467             if (dest_type != TypeOopPtr::BOTTOM) {
6468               adr_type = dest_type;
6469             }
6470           }
6471           if (C->can_alias(adr_type, load_alias_idx)) {
6472             LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
6473           } else if (s->is_CFG() && s->is_Multi()) {
6474             // Look for the memory use of s (that is the use of its memory projection)
6475             for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
6476               Node* s1 = s->fast_out(i);
6477               assert(s1->is_Proj(), "projection expected");
6478               if (_igvn.type(s1) == Type::MEMORY) {
6479                 for (DUIterator_Fast jmax, j = s1->fast_outs(jmax); j < jmax; j++) {
6480                   Node* s2 = s1->fast_out(j);
6481                   worklist.push(s2);
6482                 }
6483               }
6484             }
6485           }
6486         }
6487       }
6488     }
6489     // For Phis only consider Region's inputs that were reached by following the memory edges
6490     if (LCA != early) {
6491       for (uint i = 0; i < worklist.size(); i++) {
6492         Node* s = worklist.at(i);
6493         if (s->is_Phi() && C->can_alias(s->adr_type(), load_alias_idx)) {
6494           Node* r = s->in(0);
6495           for (uint j = 1; j < s->req(); j++) {
6496             Node* in = s->in(j);
6497             Node* r_in = r->in(j);
6498             // We can't reach any node from a Phi because we don't enqueue Phi's uses above
6499             if (((worklist.member(in) && !in->is_Phi()) || in == mem) && is_dominator(early, r_in)) {
6500               LCA = dom_lca_for_get_late_ctrl(LCA, r_in, n);
6501             }
6502           }
6503         }
6504       }
6505     }
6506   }
6507   return LCA;
6508 }
6509 
6510 // Is CFG node 'dominator' dominating node 'n'?
6511 bool PhaseIdealLoop::is_dominator(Node* dominator, Node* n) {
6512   if (dominator == n) {
6513     return true;
6514   }
6515   assert(dominator->is_CFG() && n->is_CFG(), "must have CFG nodes");
6516   uint dd = dom_depth(dominator);
6517   while (dom_depth(n) >= dd) {
6518     if (n == dominator) {
6519       return true;
6520     }
6521     n = idom(n);
6522   }
6523   return false;
6524 }
6525 
6526 // Is CFG node 'dominator' strictly dominating node 'n'?
6527 bool PhaseIdealLoop::is_strict_dominator(Node* dominator, Node* n) {
6528   return dominator != n && is_dominator(dominator, n);
6529 }
6530 
6531 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
6532 // Pair-wise LCA with tags.
6533 // Tag each index with the node 'tag' currently being processed
6534 // before advancing up the dominator chain using idom().
6535 // Later calls that find a match to 'tag' know that this path has already
6536 // been considered in the current LCA (which is input 'n1' by convention).
6537 // Since get_late_ctrl() is only called once for each node, the tag array
6538 // does not need to be cleared between calls to get_late_ctrl().
6539 // Algorithm trades a larger constant factor for better asymptotic behavior
6540 //
6541 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal(Node *n1, Node *n2, Node *tag_node) {
6542   uint d1 = dom_depth(n1);
6543   uint d2 = dom_depth(n2);
6544   jlong tag = tag_node->_idx | (((jlong)_dom_lca_tags_round) << 32);
6545 
6546   do {
6547     if (d1 > d2) {
6548       // current lca is deeper than n2
6549       _dom_lca_tags.at_put_grow(n1->_idx, tag);
6550       n1 =      idom(n1);
6551       d1 = dom_depth(n1);
6552     } else if (d1 < d2) {
6553       // n2 is deeper than current lca
6554       jlong memo = _dom_lca_tags.at_grow(n2->_idx, 0);
6555       if (memo == tag) {
6556         return n1;    // Return the current LCA
6557       }
6558       _dom_lca_tags.at_put_grow(n2->_idx, tag);
6559       n2 =      idom(n2);
6560       d2 = dom_depth(n2);
6561     } else {
6562       // Here d1 == d2.  Due to edits of the dominator-tree, sections
6563       // of the tree might have the same depth.  These sections have
6564       // to be searched more carefully.
6565 
6566       // Scan up all the n1's with equal depth, looking for n2.
6567       _dom_lca_tags.at_put_grow(n1->_idx, tag);
6568       Node *t1 = idom(n1);
6569       while (dom_depth(t1) == d1) {
6570         if (t1 == n2)  return n2;
6571         _dom_lca_tags.at_put_grow(t1->_idx, tag);
6572         t1 = idom(t1);
6573       }
6574       // Scan up all the n2's with equal depth, looking for n1.
6575       _dom_lca_tags.at_put_grow(n2->_idx, tag);
6576       Node *t2 = idom(n2);
6577       while (dom_depth(t2) == d2) {
6578         if (t2 == n1)  return n1;
6579         _dom_lca_tags.at_put_grow(t2->_idx, tag);
6580         t2 = idom(t2);
6581       }
6582       // Move up to a new dominator-depth value as well as up the dom-tree.
6583       n1 = t1;
6584       n2 = t2;
6585       d1 = dom_depth(n1);
6586       d2 = dom_depth(n2);
6587     }
6588   } while (n1 != n2);
6589   return n1;
6590 }
6591 
6592 //------------------------------init_dom_lca_tags------------------------------
6593 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
6594 // Intended use does not involve any growth for the array, so it could
6595 // be of fixed size.
6596 void PhaseIdealLoop::init_dom_lca_tags() {
6597   uint limit = C->unique() + 1;
6598   _dom_lca_tags.at_grow(limit, 0);
6599   _dom_lca_tags_round = 0;
6600 #ifdef ASSERT
6601   for (uint i = 0; i < limit; ++i) {
6602     assert(_dom_lca_tags.at(i) == 0, "Must be distinct from each node pointer");
6603   }
6604 #endif // ASSERT
6605 }
6606 
6607 //------------------------------build_loop_late--------------------------------
6608 // Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
6609 // Second pass finds latest legal placement, and ideal loop placement.
6610 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
6611   while (worklist.size() != 0) {
6612     Node *n = worklist.pop();
6613     // Only visit once
6614     if (visited.test_set(n->_idx)) continue;
6615     uint cnt = n->outcnt();
6616     uint   i = 0;
6617     while (true) {
6618       assert(_loop_or_ctrl[n->_idx], "no dead nodes");
6619       // Visit all children
6620       if (i < cnt) {
6621         Node* use = n->raw_out(i);
6622         ++i;
6623         // Check for dead uses.  Aggressively prune such junk.  It might be
6624         // dead in the global sense, but still have local uses so I cannot
6625         // easily call 'remove_dead_node'.
6626         if (_loop_or_ctrl[use->_idx] != nullptr || use->is_top()) { // Not dead?
6627           // Due to cycles, we might not hit the same fixed point in the verify
6628           // pass as we do in the regular pass.  Instead, visit such phis as
6629           // simple uses of the loop head.
6630           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
6631             if( !visited.test(use->_idx) )
6632               worklist.push(use);
6633           } else if( !visited.test_set(use->_idx) ) {
6634             nstack.push(n, i); // Save parent and next use's index.
6635             n   = use;         // Process all children of current use.
6636             cnt = use->outcnt();
6637             i   = 0;
6638           }
6639         } else {
6640           // Do not visit around the backedge of loops via data edges.
6641           // push dead code onto a worklist
6642           _deadlist.push(use);
6643         }
6644       } else {
6645         // All of n's children have been processed, complete post-processing.
6646         build_loop_late_post(n);
6647         if (C->failing()) { return; }
6648         if (nstack.is_empty()) {
6649           // Finished all nodes on stack.
6650           // Process next node on the worklist.
6651           break;
6652         }
6653         // Get saved parent node and next use's index. Visit the rest of uses.
6654         n   = nstack.node();
6655         cnt = n->outcnt();
6656         i   = nstack.index();
6657         nstack.pop();
6658       }
6659     }
6660   }
6661 }
6662 
6663 // Verify that no data node is scheduled in the outer loop of a strip
6664 // mined loop.
6665 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
6666 #ifdef ASSERT
6667   if (get_loop(least)->_nest == 0) {
6668     return;
6669   }
6670   IdealLoopTree* loop = get_loop(least);
6671   Node* head = loop->_head;
6672   if (head->is_OuterStripMinedLoop() &&
6673       // Verification can't be applied to fully built strip mined loops
6674       head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
6675     Node* sfpt = head->as_Loop()->outer_safepoint();
6676     ResourceMark rm;
6677     Unique_Node_List wq;
6678     wq.push(sfpt);
6679     for (uint i = 0; i < wq.size(); i++) {
6680       Node *m = wq.at(i);
6681       for (uint i = 1; i < m->req(); i++) {
6682         Node* nn = m->in(i);
6683         if (nn == n) {
6684           return;
6685         }
6686         if (nn != nullptr && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
6687           wq.push(nn);
6688         }
6689       }
6690     }
6691     ShouldNotReachHere();
6692   }
6693 #endif
6694 }
6695 
6696 
6697 //------------------------------build_loop_late_post---------------------------
6698 // Put Data nodes into some loop nest, by setting the _loop_or_ctrl[]->loop mapping.
6699 // Second pass finds latest legal placement, and ideal loop placement.
6700 void PhaseIdealLoop::build_loop_late_post(Node *n) {
6701   build_loop_late_post_work(n, true);
6702 }
6703 
6704 // Class to visit all predicates in a predicate chain to find out which are dominated by a given node. Keeps track of
6705 // the entry to the earliest predicate that is still dominated by the given dominator. This class is used when trying to
6706 // legally skip all predicates when figuring out the latest placement such that a node does not interfere with Loop
6707 // Predication or creating a Loop Limit Check Predicate later.
6708 class DominatedPredicates : public UnifiedPredicateVisitor {
6709   Node* const _dominator;
6710   Node* _earliest_dominated_predicate_entry;
6711   bool _should_continue;
6712   PhaseIdealLoop* const _phase;
6713 
6714  public:
6715   DominatedPredicates(Node* dominator, Node* start_node, PhaseIdealLoop* phase)
6716       : _dominator(dominator),
6717         _earliest_dominated_predicate_entry(start_node),
6718         _should_continue(true),
6719         _phase(phase) {}
6720   NONCOPYABLE(DominatedPredicates);
6721 
6722   bool should_continue() const override {
6723     return _should_continue;
6724   }
6725 
6726   // Returns the entry to the earliest predicate that is still dominated by the given dominator (all could be dominated).
6727   Node* earliest_dominated_predicate_entry() const {
6728     return _earliest_dominated_predicate_entry;
6729   }
6730 
6731   void visit_predicate(const Predicate& predicate) override {
6732     Node* entry = predicate.entry();
6733     if (_phase->is_strict_dominator(entry, _dominator)) {
6734       _should_continue = false;
6735     } else {
6736       _earliest_dominated_predicate_entry = entry;
6737     }
6738   }
6739 };
6740 
6741 void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
6742 
6743   if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
6744     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
6745   }
6746 
6747 #ifdef ASSERT
6748   if (_verify_only && !n->is_CFG()) {
6749     // Check def-use domination.
6750     // We would like to expose this check in product but it appears to be expensive.
6751     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
6752   }
6753 #endif
6754 
6755   // CFG and pinned nodes already handled
6756   if( n->in(0) ) {
6757     if( n->in(0)->is_top() ) return; // Dead?
6758 
6759     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
6760     // _must_ be pinned (they have to observe their control edge of course).
6761     // Unlike Stores (which modify an unallocable resource, the memory
6762     // state), Mods/Loads can float around.  So free them up.
6763     switch( n->Opcode() ) {
6764     case Op_DivI:
6765     case Op_DivF:
6766     case Op_DivD:
6767     case Op_ModI:
6768     case Op_LoadB:              // Same with Loads; they can sink
6769     case Op_LoadUB:             // during loop optimizations.
6770     case Op_LoadUS:
6771     case Op_LoadD:
6772     case Op_LoadF:
6773     case Op_LoadI:
6774     case Op_LoadKlass:
6775     case Op_LoadNKlass:
6776     case Op_LoadL:
6777     case Op_LoadS:
6778     case Op_LoadP:
6779     case Op_LoadN:
6780     case Op_LoadRange:
6781     case Op_LoadD_unaligned:
6782     case Op_LoadL_unaligned:
6783     case Op_StrComp:            // Does a bunch of load-like effects
6784     case Op_StrEquals:
6785     case Op_StrIndexOf:
6786     case Op_StrIndexOfChar:
6787     case Op_AryEq:
6788     case Op_VectorizedHashCode:
6789     case Op_CountPositives:
6790       pinned = false;
6791     }
6792     if (n->is_CMove() || n->is_ConstraintCast()) {
6793       pinned = false;
6794     }
6795     if( pinned ) {
6796       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
6797       if( !chosen_loop->_child )       // Inner loop?
6798         chosen_loop->_body.push(n); // Collect inner loops
6799       return;
6800     }
6801   } else {                      // No slot zero
6802     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
6803       _loop_or_ctrl.map(n->_idx,nullptr); // No block setting, it's globally dead
6804       return;
6805     }
6806     assert(!n->is_CFG() || n->outcnt() == 0, "");
6807   }
6808 
6809   // Do I have a "safe range" I can select over?
6810   Node *early = get_ctrl(n);// Early location already computed
6811 
6812   // Compute latest point this Node can go
6813   Node *LCA = get_late_ctrl( n, early );
6814   // LCA is null due to uses being dead
6815   if( LCA == nullptr ) {
6816 #ifdef ASSERT
6817     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
6818       assert(_loop_or_ctrl[n->out(i1)->_idx] == nullptr, "all uses must also be dead");
6819     }
6820 #endif
6821     _loop_or_ctrl.map(n->_idx, nullptr); // This node is useless
6822     _deadlist.push(n);
6823     return;
6824   }
6825   assert(LCA != nullptr && !LCA->is_top(), "no dead nodes");
6826 
6827   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
6828   Node *least = legal;          // Best legal position so far
6829   while( early != legal ) {     // While not at earliest legal
6830     if (legal->is_Start() && !early->is_Root()) {
6831 #ifdef ASSERT
6832       // Bad graph. Print idom path and fail.
6833       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
6834       assert(false, "Bad graph detected in build_loop_late");
6835 #endif
6836       C->record_method_not_compilable("Bad graph detected in build_loop_late");
6837       return;
6838     }
6839     // Find least loop nesting depth
6840     legal = idom(legal);        // Bump up the IDOM tree
6841     // Check for lower nesting depth
6842     if( get_loop(legal)->_nest < get_loop(least)->_nest )
6843       least = legal;
6844   }
6845   assert(early == legal || legal != C->root(), "bad dominance of inputs");
6846 
6847   if (least != early) {
6848     // Move the node above predicates as far up as possible so a
6849     // following pass of Loop Predication doesn't hoist a predicate
6850     // that depends on it above that node.
6851     const PredicateIterator predicate_iterator(least);
6852     DominatedPredicates dominated_predicates(early, least, this);
6853     predicate_iterator.for_each(dominated_predicates);
6854     least = dominated_predicates.earliest_dominated_predicate_entry();
6855   }
6856   // Try not to place code on a loop entry projection
6857   // which can inhibit range check elimination.
6858   if (least != early && !BarrierSet::barrier_set()->barrier_set_c2()->is_gc_specific_loop_opts_pass(_mode)) {
6859     Node* ctrl_out = least->unique_ctrl_out_or_null();
6860     if (ctrl_out != nullptr && ctrl_out->is_Loop() &&
6861         least == ctrl_out->in(LoopNode::EntryControl) &&
6862         (ctrl_out->is_CountedLoop() || ctrl_out->is_OuterStripMinedLoop())) {
6863       Node* least_dom = idom(least);
6864       if (get_loop(least_dom)->is_member(get_loop(least))) {
6865         least = least_dom;
6866       }
6867     }
6868   }
6869   // Don't extend live ranges of raw oops
6870   if (least != early && n->is_ConstraintCast() && n->in(1)->bottom_type()->isa_rawptr() &&
6871       !n->bottom_type()->isa_rawptr()) {
6872     least = early;
6873   }
6874 
6875 #ifdef ASSERT
6876   // Broken part of VerifyLoopOptimizations (F)
6877   // Reason:
6878   //   _verify_me->get_ctrl_no_update(n) seems to return wrong result
6879   /*
6880   // If verifying, verify that 'verify_me' has a legal location
6881   // and choose it as our location.
6882   if( _verify_me ) {
6883     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
6884     Node *legal = LCA;
6885     while( early != legal ) {   // While not at earliest legal
6886       if( legal == v_ctrl ) break;  // Check for prior good location
6887       legal = idom(legal)      ;// Bump up the IDOM tree
6888     }
6889     // Check for prior good location
6890     if( legal == v_ctrl ) least = legal; // Keep prior if found
6891   }
6892   */
6893 #endif
6894 
6895   // Assign discovered "here or above" point
6896   least = find_non_split_ctrl(least);
6897   verify_strip_mined_scheduling(n, least);
6898   set_ctrl(n, least);
6899 
6900   // Collect inner loop bodies
6901   IdealLoopTree *chosen_loop = get_loop(least);
6902   if( !chosen_loop->_child )   // Inner loop?
6903     chosen_loop->_body.push(n);// Collect inner loops
6904 
6905   if (!_verify_only && n->Opcode() == Op_OpaqueZeroTripGuard) {
6906     _zero_trip_guard_opaque_nodes.push(n);
6907   }
6908 
6909   if (!_verify_only && n->Opcode() == Op_OpaqueMultiversioning) {
6910     _multiversion_opaque_nodes.push(n);
6911   }
6912 }
6913 
6914 #ifdef ASSERT
6915 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
6916   tty->print_cr("%s", msg);
6917   tty->print("n: "); n->dump();
6918   tty->print("early(n): "); early->dump();
6919   if (n->in(0) != nullptr  && !n->in(0)->is_top() &&
6920       n->in(0) != early && !n->in(0)->is_Root()) {
6921     tty->print("n->in(0): "); n->in(0)->dump();
6922   }
6923   for (uint i = 1; i < n->req(); i++) {
6924     Node* in1 = n->in(i);
6925     if (in1 != nullptr && in1 != n && !in1->is_top()) {
6926       tty->print("n->in(%d): ", i); in1->dump();
6927       Node* in1_early = get_ctrl(in1);
6928       tty->print("early(n->in(%d)): ", i); in1_early->dump();
6929       if (in1->in(0) != nullptr     && !in1->in(0)->is_top() &&
6930           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
6931         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
6932       }
6933       for (uint j = 1; j < in1->req(); j++) {
6934         Node* in2 = in1->in(j);
6935         if (in2 != nullptr && in2 != n && in2 != in1 && !in2->is_top()) {
6936           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
6937           Node* in2_early = get_ctrl(in2);
6938           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
6939           if (in2->in(0) != nullptr     && !in2->in(0)->is_top() &&
6940               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
6941             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
6942           }
6943         }
6944       }
6945     }
6946   }
6947   tty->cr();
6948   tty->print("LCA(n): "); LCA->dump();
6949   for (uint i = 0; i < n->outcnt(); i++) {
6950     Node* u1 = n->raw_out(i);
6951     if (u1 == n)
6952       continue;
6953     tty->print("n->out(%d): ", i); u1->dump();
6954     if (u1->is_CFG()) {
6955       for (uint j = 0; j < u1->outcnt(); j++) {
6956         Node* u2 = u1->raw_out(j);
6957         if (u2 != u1 && u2 != n && u2->is_CFG()) {
6958           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
6959         }
6960       }
6961     } else {
6962       Node* u1_later = get_ctrl(u1);
6963       tty->print("later(n->out(%d)): ", i); u1_later->dump();
6964       if (u1->in(0) != nullptr     && !u1->in(0)->is_top() &&
6965           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
6966         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
6967       }
6968       for (uint j = 0; j < u1->outcnt(); j++) {
6969         Node* u2 = u1->raw_out(j);
6970         if (u2 == n || u2 == u1)
6971           continue;
6972         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
6973         if (!u2->is_CFG()) {
6974           Node* u2_later = get_ctrl(u2);
6975           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
6976           if (u2->in(0) != nullptr     && !u2->in(0)->is_top() &&
6977               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
6978             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
6979           }
6980         }
6981       }
6982     }
6983   }
6984   dump_idoms(early, LCA);
6985   tty->cr();
6986 }
6987 
6988 // Class to compute the real LCA given an early node and a wrong LCA in a bad graph.
6989 class RealLCA {
6990   const PhaseIdealLoop* _phase;
6991   Node* _early;
6992   Node* _wrong_lca;
6993   uint _early_index;
6994   int _wrong_lca_index;
6995 
6996   // Given idom chains of early and wrong LCA: Walk through idoms starting at StartNode and find the first node which
6997   // is different: Return the previously visited node which must be the real LCA.
6998   // The node lists also contain _early and _wrong_lca, respectively.
6999   Node* find_real_lca(Unique_Node_List& early_with_idoms, Unique_Node_List& wrong_lca_with_idoms) {
7000     int early_index = early_with_idoms.size() - 1;
7001     int wrong_lca_index = wrong_lca_with_idoms.size() - 1;
7002     bool found_difference = false;
7003     do {
7004       if (early_with_idoms[early_index] != wrong_lca_with_idoms[wrong_lca_index]) {
7005         // First time early and wrong LCA idoms differ. Real LCA must be at the previous index.
7006         found_difference = true;
7007         break;
7008       }
7009       early_index--;
7010       wrong_lca_index--;
7011     } while (wrong_lca_index >= 0);
7012 
7013     assert(early_index >= 0, "must always find an LCA - cannot be early");
7014     _early_index = early_index;
7015     _wrong_lca_index = wrong_lca_index;
7016     Node* real_lca = early_with_idoms[_early_index + 1]; // Plus one to skip _early.
7017     assert(found_difference || real_lca == _wrong_lca, "wrong LCA dominates early and is therefore the real LCA");
7018     return real_lca;
7019   }
7020 
7021   void dump(Node* real_lca) {
7022     tty->cr();
7023     tty->print_cr("idoms of early \"%d %s\":", _early->_idx, _early->Name());
7024     _phase->dump_idom(_early, _early_index + 1);
7025 
7026     tty->cr();
7027     tty->print_cr("idoms of (wrong) LCA \"%d %s\":", _wrong_lca->_idx, _wrong_lca->Name());
7028     _phase->dump_idom(_wrong_lca, _wrong_lca_index + 1);
7029 
7030     tty->cr();
7031     tty->print("Real LCA of early \"%d %s\" (idom[%d]) and wrong LCA \"%d %s\"",
7032                _early->_idx, _early->Name(), _early_index, _wrong_lca->_idx, _wrong_lca->Name());
7033     if (_wrong_lca_index >= 0) {
7034       tty->print(" (idom[%d])", _wrong_lca_index);
7035     }
7036     tty->print_cr(":");
7037     real_lca->dump();
7038   }
7039 
7040  public:
7041   RealLCA(const PhaseIdealLoop* phase, Node* early, Node* wrong_lca)
7042       : _phase(phase), _early(early), _wrong_lca(wrong_lca), _early_index(0), _wrong_lca_index(0) {
7043     assert(!wrong_lca->is_Start(), "StartNode is always a common dominator");
7044   }
7045 
7046   void compute_and_dump() {
7047     ResourceMark rm;
7048     Unique_Node_List early_with_idoms;
7049     Unique_Node_List wrong_lca_with_idoms;
7050     early_with_idoms.push(_early);
7051     wrong_lca_with_idoms.push(_wrong_lca);
7052     _phase->get_idoms(_early, 10000, early_with_idoms);
7053     _phase->get_idoms(_wrong_lca, 10000, wrong_lca_with_idoms);
7054     Node* real_lca = find_real_lca(early_with_idoms, wrong_lca_with_idoms);
7055     dump(real_lca);
7056   }
7057 };
7058 
7059 // Dump the idom chain of early, of the wrong LCA and dump the real LCA of early and wrong LCA.
7060 void PhaseIdealLoop::dump_idoms(Node* early, Node* wrong_lca) {
7061   assert(!is_dominator(early, wrong_lca), "sanity check that early does not dominate wrong lca");
7062   assert(!has_ctrl(early) && !has_ctrl(wrong_lca), "sanity check, no data nodes");
7063 
7064   RealLCA real_lca(this, early, wrong_lca);
7065   real_lca.compute_and_dump();
7066 }
7067 #endif // ASSERT
7068 
7069 #ifndef PRODUCT
7070 //------------------------------dump-------------------------------------------
7071 void PhaseIdealLoop::dump() const {
7072   ResourceMark rm;
7073   Node_Stack stack(C->live_nodes() >> 2);
7074   Node_List rpo_list;
7075   VectorSet visited;
7076   visited.set(C->top()->_idx);
7077   rpo(C->root(), stack, visited, rpo_list);
7078   // Dump root loop indexed by last element in PO order
7079   dump(_ltree_root, rpo_list.size(), rpo_list);
7080 }
7081 
7082 void PhaseIdealLoop::dump(IdealLoopTree* loop, uint idx, Node_List &rpo_list) const {
7083   loop->dump_head();
7084 
7085   // Now scan for CFG nodes in the same loop
7086   for (uint j = idx; j > 0; j--) {
7087     Node* n = rpo_list[j-1];
7088     if (!_loop_or_ctrl[n->_idx])      // Skip dead nodes
7089       continue;
7090 
7091     if (get_loop(n) != loop) { // Wrong loop nest
7092       if (get_loop(n)->_head == n &&    // Found nested loop?
7093           get_loop(n)->_parent == loop)
7094         dump(get_loop(n), rpo_list.size(), rpo_list);     // Print it nested-ly
7095       continue;
7096     }
7097 
7098     // Dump controlling node
7099     tty->sp(2 * loop->_nest);
7100     tty->print("C");
7101     if (n == C->root()) {
7102       n->dump();
7103     } else {
7104       Node* cached_idom   = idom_no_update(n);
7105       Node* computed_idom = n->in(0);
7106       if (n->is_Region()) {
7107         computed_idom = compute_idom(n);
7108         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
7109         // any MultiBranch ctrl node), so apply a similar transform to
7110         // the cached idom returned from idom_no_update.
7111         cached_idom = find_non_split_ctrl(cached_idom);
7112       }
7113       tty->print(" ID:%d", computed_idom->_idx);
7114       n->dump();
7115       if (cached_idom != computed_idom) {
7116         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
7117                       computed_idom->_idx, cached_idom->_idx);
7118       }
7119     }
7120     // Dump nodes it controls
7121     for (uint k = 0; k < _loop_or_ctrl.max(); k++) {
7122       // (k < C->unique() && get_ctrl(find(k)) == n)
7123       if (k < C->unique() && _loop_or_ctrl[k] == (Node*)((intptr_t)n + 1)) {
7124         Node* m = C->root()->find(k);
7125         if (m && m->outcnt() > 0) {
7126           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
7127             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _loop_or_ctrl[k] is %p, ctrl is %p",
7128                           _loop_or_ctrl[k], has_ctrl(m) ? get_ctrl_no_update(m) : nullptr);
7129           }
7130           tty->sp(2 * loop->_nest + 1);
7131           m->dump();
7132         }
7133       }
7134     }
7135   }
7136 }
7137 
7138 void PhaseIdealLoop::dump_idom(Node* n, const uint count) const {
7139   if (has_ctrl(n)) {
7140     tty->print_cr("No idom for data nodes");
7141   } else {
7142     ResourceMark rm;
7143     Unique_Node_List idoms;
7144     get_idoms(n, count, idoms);
7145     dump_idoms_in_reverse(n, idoms);
7146   }
7147 }
7148 
7149 void PhaseIdealLoop::get_idoms(Node* n, const uint count, Unique_Node_List& idoms) const {
7150   Node* next = n;
7151   for (uint i = 0; !next->is_Start() && i < count; i++) {
7152     next = idom(next);
7153     assert(!idoms.member(next), "duplicated idom is not possible");
7154     idoms.push(next);
7155   }
7156 }
7157 
7158 void PhaseIdealLoop::dump_idoms_in_reverse(const Node* n, const Node_List& idom_list) const {
7159   Node* next;
7160   uint padding = 3;
7161   uint node_index_padding_width = (C->unique() == 0 ? 0 : static_cast<int>(log10(static_cast<double>(C->unique())))) + 1;
7162   for (int i = idom_list.size() - 1; i >= 0; i--) {
7163     if (i == 9 || i == 99) {
7164       padding++;
7165     }
7166     next = idom_list[i];
7167     tty->print_cr("idom[%d]:%*c%*d  %s", i, padding, ' ', node_index_padding_width, next->_idx, next->Name());
7168   }
7169   tty->print_cr("n:      %*c%*d  %s", padding, ' ', node_index_padding_width, n->_idx, n->Name());
7170 }
7171 #endif // NOT PRODUCT
7172 
7173 // Collect a R-P-O for the whole CFG.
7174 // Result list is in post-order (scan backwards for RPO)
7175 void PhaseIdealLoop::rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const {
7176   stk.push(start, 0);
7177   visited.set(start->_idx);
7178 
7179   while (stk.is_nonempty()) {
7180     Node* m   = stk.node();
7181     uint  idx = stk.index();
7182     if (idx < m->outcnt()) {
7183       stk.set_index(idx + 1);
7184       Node* n = m->raw_out(idx);
7185       if (n->is_CFG() && !visited.test_set(n->_idx)) {
7186         stk.push(n, 0);
7187       }
7188     } else {
7189       rpo_list.push(m);
7190       stk.pop();
7191     }
7192   }
7193 }
7194 
7195 ConINode* PhaseIdealLoop::intcon(jint i) {
7196   ConINode* node = _igvn.intcon(i);
7197   set_root_as_ctrl(node);
7198   return node;
7199 }
7200 
7201 ConLNode* PhaseIdealLoop::longcon(jlong i) {
7202   ConLNode* node = _igvn.longcon(i);
7203   set_root_as_ctrl(node);
7204   return node;
7205 }
7206 
7207 ConNode* PhaseIdealLoop::makecon(const Type* t) {
7208   ConNode* node = _igvn.makecon(t);
7209   set_root_as_ctrl(node);
7210   return node;
7211 }
7212 
7213 ConNode* PhaseIdealLoop::integercon(jlong l, BasicType bt) {
7214   ConNode* node = _igvn.integercon(l, bt);
7215   set_root_as_ctrl(node);
7216   return node;
7217 }
7218 
7219 ConNode* PhaseIdealLoop::zerocon(BasicType bt) {
7220   ConNode* node = _igvn.zerocon(bt);
7221   set_root_as_ctrl(node);
7222   return node;
7223 }
7224 
7225 
7226 //=============================================================================
7227 //------------------------------LoopTreeIterator-------------------------------
7228 
7229 // Advance to next loop tree using a preorder, left-to-right traversal.
7230 void LoopTreeIterator::next() {
7231   assert(!done(), "must not be done.");
7232   if (_curnt->_child != nullptr) {
7233     _curnt = _curnt->_child;
7234   } else if (_curnt->_next != nullptr) {
7235     _curnt = _curnt->_next;
7236   } else {
7237     while (_curnt != _root && _curnt->_next == nullptr) {
7238       _curnt = _curnt->_parent;
7239     }
7240     if (_curnt == _root) {
7241       _curnt = nullptr;
7242       assert(done(), "must be done.");
7243     } else {
7244       assert(_curnt->_next != nullptr, "must be more to do");
7245       _curnt = _curnt->_next;
7246     }
7247   }
7248 }