1 /*
   2  * Copyright (c) 1998, 2018, 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 "precompiled.hpp"
  26 #include "ci/ciMethodData.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "libadt/vectset.hpp"
  31 #include "memory/allocation.inline.hpp"
  32 #include "memory/resourceArea.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/callnode.hpp"
  35 #include "opto/connode.hpp"
  36 #include "opto/convertnode.hpp"
  37 #include "opto/divnode.hpp"
  38 #include "opto/idealGraphPrinter.hpp"
  39 #include "opto/loopnode.hpp"
  40 #include "opto/mulnode.hpp"
  41 #include "opto/rootnode.hpp"
  42 #include "opto/superword.hpp"
  43 #include "utilities/macros.hpp"
  44 #if INCLUDE_SHENANDOAHGC
  45 #include "gc/shenandoah/c2/shenandoahBarrierSetC2.hpp"
  46 #endif
  47 
  48 //=============================================================================
  49 //------------------------------is_loop_iv-------------------------------------
  50 // Determine if a node is Counted loop induction variable.
  51 // The method is declared in node.hpp.
  52 const Node* Node::is_loop_iv() const {
  53   if (this->is_Phi() && !this->as_Phi()->is_copy() &&
  54       this->as_Phi()->region()->is_CountedLoop() &&
  55       this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
  56     return this;
  57   } else {
  58     return NULL;
  59   }
  60 }
  61 
  62 //=============================================================================
  63 //------------------------------dump_spec--------------------------------------
  64 // Dump special per-node info
  65 #ifndef PRODUCT
  66 void LoopNode::dump_spec(outputStream *st) const {
  67   if (is_inner_loop()) st->print( "inner " );
  68   if (is_partial_peel_loop()) st->print( "partial_peel " );
  69   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  70 }
  71 #endif
  72 
  73 //------------------------------is_valid_counted_loop-------------------------
  74 bool LoopNode::is_valid_counted_loop() const {
  75   if (is_CountedLoop()) {
  76     CountedLoopNode*    l  = as_CountedLoop();
  77     CountedLoopEndNode* le = l->loopexit_or_null();
  78     if (le != NULL &&
  79         le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  80       Node* phi  = l->phi();
  81       Node* exit = le->proj_out_or_null(0 /* false */);
  82       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  83           phi != NULL && phi->is_Phi() &&
  84           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  85           le->loopnode() == l && le->stride_is_con()) {
  86         return true;
  87       }
  88     }
  89   }
  90   return false;
  91 }
  92 
  93 //------------------------------get_early_ctrl---------------------------------
  94 // Compute earliest legal control
  95 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  96   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  97   uint i;
  98   Node *early;
  99   if (n->in(0) && !n->is_expensive()) {
 100     early = n->in(0);
 101     if (!early->is_CFG()) // Might be a non-CFG multi-def
 102       early = get_ctrl(early);        // So treat input as a straight data input
 103     i = 1;
 104   } else {
 105     early = get_ctrl(n->in(1));
 106     i = 2;
 107   }
 108   uint e_d = dom_depth(early);
 109   assert( early, "" );
 110   for (; i < n->req(); i++) {
 111     Node *cin = get_ctrl(n->in(i));
 112     assert( cin, "" );
 113     // Keep deepest dominator depth
 114     uint c_d = dom_depth(cin);
 115     if (c_d > e_d) {           // Deeper guy?
 116       early = cin;              // Keep deepest found so far
 117       e_d = c_d;
 118     } else if (c_d == e_d &&    // Same depth?
 119                early != cin) { // If not equal, must use slower algorithm
 120       // If same depth but not equal, one _must_ dominate the other
 121       // and we want the deeper (i.e., dominated) guy.
 122       Node *n1 = early;
 123       Node *n2 = cin;
 124       while (1) {
 125         n1 = idom(n1);          // Walk up until break cycle
 126         n2 = idom(n2);
 127         if (n1 == cin ||        // Walked early up to cin
 128             dom_depth(n2) < c_d)
 129           break;                // early is deeper; keep him
 130         if (n2 == early ||      // Walked cin up to early
 131             dom_depth(n1) < c_d) {
 132           early = cin;          // cin is deeper; keep him
 133           break;
 134         }
 135       }
 136       e_d = dom_depth(early);   // Reset depth register cache
 137     }
 138   }
 139 
 140   // Return earliest legal location
 141   assert(early == find_non_split_ctrl(early), "unexpected early control");
 142 
 143   if (n->is_expensive() && !_verify_only && !_verify_me) {
 144     assert(n->in(0), "should have control input");
 145     early = get_early_ctrl_for_expensive(n, early);
 146   }
 147 
 148   return early;
 149 }
 150 
 151 //------------------------------get_early_ctrl_for_expensive---------------------------------
 152 // Move node up the dominator tree as high as legal while still beneficial
 153 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 154   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 155   assert(OptimizeExpensiveOps, "optimization off?");
 156 
 157   Node* ctl = n->in(0);
 158   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 159   uint min_dom_depth = dom_depth(earliest);
 160 #ifdef ASSERT
 161   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 162     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 163     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 164   }
 165 #endif
 166   if (dom_depth(ctl) < min_dom_depth) {
 167     return earliest;
 168   }
 169 
 170   while (1) {
 171     Node *next = ctl;
 172     // Moving the node out of a loop on the projection of a If
 173     // confuses loop predication. So once we hit a Loop in a If branch
 174     // that doesn't branch to an UNC, we stop. The code that process
 175     // expensive nodes will notice the loop and skip over it to try to
 176     // move the node further up.
 177     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 178       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 179         break;
 180       }
 181       next = idom(ctl->in(1)->in(0));
 182     } else if (ctl->is_Proj()) {
 183       // We only move it up along a projection if the projection is
 184       // the single control projection for its parent: same code path,
 185       // if it's a If with UNC or fallthrough of a call.
 186       Node* parent_ctl = ctl->in(0);
 187       if (parent_ctl == NULL) {
 188         break;
 189       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 190         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 191       } else if (parent_ctl->is_If()) {
 192         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 193           break;
 194         }
 195         assert(idom(ctl) == parent_ctl, "strange");
 196         next = idom(parent_ctl);
 197       } else if (ctl->is_CatchProj()) {
 198         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 199           break;
 200         }
 201         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 202         next = parent_ctl->in(0)->in(0)->in(0);
 203       } else {
 204         // Check if parent control has a single projection (this
 205         // control is the only possible successor of the parent
 206         // control). If so, we can try to move the node above the
 207         // parent control.
 208         int nb_ctl_proj = 0;
 209         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 210           Node *p = parent_ctl->fast_out(i);
 211           if (p->is_Proj() && p->is_CFG()) {
 212             nb_ctl_proj++;
 213             if (nb_ctl_proj > 1) {
 214               break;
 215             }
 216           }
 217         }
 218 
 219         if (nb_ctl_proj > 1) {
 220           break;
 221         }
 222         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
 223                BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
 224         assert(idom(ctl) == parent_ctl, "strange");
 225         next = idom(parent_ctl);
 226       }
 227     } else {
 228       next = idom(ctl);
 229     }
 230     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 231       break;
 232     }
 233     ctl = next;
 234   }
 235 
 236   if (ctl != n->in(0)) {
 237     _igvn.replace_input_of(n, 0, ctl);
 238     _igvn.hash_insert(n);
 239   }
 240 
 241   return ctl;
 242 }
 243 
 244 
 245 //------------------------------set_early_ctrl---------------------------------
 246 // Set earliest legal control
 247 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 248   Node *early = get_early_ctrl(n);
 249 
 250   // Record earliest legal location
 251   set_ctrl(n, early);
 252 }
 253 
 254 //------------------------------set_subtree_ctrl-------------------------------
 255 // set missing _ctrl entries on new nodes
 256 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 257   // Already set?  Get out.
 258   if( _nodes[n->_idx] ) return;
 259   // Recursively set _nodes array to indicate where the Node goes
 260   uint i;
 261   for( i = 0; i < n->req(); ++i ) {
 262     Node *m = n->in(i);
 263     if( m && m != C->root() )
 264       set_subtree_ctrl( m );
 265   }
 266 
 267   // Fixup self
 268   set_early_ctrl( n );
 269 }
 270 
 271 // Create a skeleton strip mined outer loop: a Loop head before the
 272 // inner strip mined loop, a safepoint and an exit condition guarded
 273 // by an opaque node after the inner strip mined loop with a backedge
 274 // to the loop head. The inner strip mined loop is left as it is. Only
 275 // once loop optimizations are over, do we adjust the inner loop exit
 276 // condition to limit its number of iterations, set the outer loop
 277 // exit condition and add Phis to the outer loop head. Some loop
 278 // optimizations that operate on the inner strip mined loop need to be
 279 // aware of the outer strip mined loop: loop unswitching needs to
 280 // clone the outer loop as well as the inner, unrolling needs to only
 281 // clone the inner loop etc. No optimizations need to change the outer
 282 // strip mined loop as it is only a skeleton.
 283 IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
 284                                                              IdealLoopTree* loop, float cl_prob, float le_fcnt,
 285                                                              Node*& entry_control, Node*& iffalse) {
 286   Node* outer_test = _igvn.intcon(0);
 287   set_ctrl(outer_test, C->root());
 288   Node *orig = iffalse;
 289   iffalse = iffalse->clone();
 290   _igvn.register_new_node_with_optimizer(iffalse);
 291   set_idom(iffalse, idom(orig), dom_depth(orig));
 292 
 293   IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
 294   Node *outer_ift = new IfTrueNode (outer_le);
 295   Node* outer_iff = orig;
 296   _igvn.replace_input_of(outer_iff, 0, outer_le);
 297 
 298   LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
 299   entry_control = outer_l;
 300 
 301   IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
 302   IdealLoopTree* parent = loop->_parent;
 303   IdealLoopTree* sibling = parent->_child;
 304   if (sibling == loop) {
 305     parent->_child = outer_ilt;
 306   } else {
 307     while (sibling->_next != loop) {
 308       sibling = sibling->_next;
 309     }
 310     sibling->_next = outer_ilt;
 311   }
 312   outer_ilt->_next = loop->_next;
 313   outer_ilt->_parent = parent;
 314   outer_ilt->_child = loop;
 315   outer_ilt->_nest = loop->_nest;
 316   loop->_parent = outer_ilt;
 317   loop->_next = NULL;
 318   loop->_nest++;
 319 
 320   set_loop(iffalse, outer_ilt);
 321   register_control(outer_le, outer_ilt, iffalse);
 322   register_control(outer_ift, outer_ilt, outer_le);
 323   set_idom(outer_iff, outer_le, dom_depth(outer_le));
 324   _igvn.register_new_node_with_optimizer(outer_l);
 325   set_loop(outer_l, outer_ilt);
 326   set_idom(outer_l, init_control, dom_depth(init_control)+1);
 327 
 328   return outer_ilt;
 329 }
 330 
 331 void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) {
 332   Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL,
 333                                                          Deoptimization::Reason_loop_limit_check,
 334                                                          Op_If);
 335   Node* iff = new_predicate_proj->in(0);
 336   assert(iff->Opcode() == Op_If, "bad graph shape");
 337   Node* conv = iff->in(1);
 338   assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
 339   Node* opaq = conv->in(1);
 340   assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
 341   cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 342   bol = _igvn.register_new_node_with_optimizer(bol);
 343   set_subtree_ctrl(bol);
 344   _igvn.replace_input_of(iff, 1, bol);
 345 
 346 #ifndef PRODUCT
 347   // report that the loop predication has been actually performed
 348   // for this loop
 349   if (TraceLoopLimitCheck) {
 350     tty->print_cr("Counted Loop Limit Check generated:");
 351     debug_only( bol->dump(2); )
 352   }
 353 #endif
 354 }
 355 
 356 //------------------------------is_counted_loop--------------------------------
 357 bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) {
 358   PhaseGVN *gvn = &_igvn;
 359 
 360   // Counted loop head must be a good RegionNode with only 3 not NULL
 361   // control input edges: Self, Entry, LoopBack.
 362   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 363     return false;
 364   }
 365   Node *init_control = x->in(LoopNode::EntryControl);
 366   Node *back_control = x->in(LoopNode::LoopBackControl);
 367   if (init_control == NULL || back_control == NULL)    // Partially dead
 368     return false;
 369   // Must also check for TOP when looking for a dead loop
 370   if (init_control->is_top() || back_control->is_top())
 371     return false;
 372 
 373   // Allow funny placement of Safepoint
 374   if (back_control->Opcode() == Op_SafePoint) {
 375     if (LoopStripMiningIter != 0) {
 376       // Leaving the safepoint on the backedge and creating a
 377       // CountedLoop will confuse optimizations. We can't move the
 378       // safepoint around because its jvm state wouldn't match a new
 379       // location. Give up on that loop.
 380       return false;
 381     }
 382     back_control = back_control->in(TypeFunc::Control);
 383   }
 384 
 385   // Controlling test for loop
 386   Node *iftrue = back_control;
 387   uint iftrue_op = iftrue->Opcode();
 388   if (iftrue_op != Op_IfTrue &&
 389       iftrue_op != Op_IfFalse)
 390     // I have a weird back-control.  Probably the loop-exit test is in
 391     // the middle of the loop and I am looking at some trailing control-flow
 392     // merge point.  To fix this I would have to partially peel the loop.
 393     return false; // Obscure back-control
 394 
 395   // Get boolean guarding loop-back test
 396   Node *iff = iftrue->in(0);
 397   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 398     return false;
 399   BoolNode *test = iff->in(1)->as_Bool();
 400   BoolTest::mask bt = test->_test._test;
 401   float cl_prob = iff->as_If()->_prob;
 402   if (iftrue_op == Op_IfFalse) {
 403     bt = BoolTest(bt).negate();
 404     cl_prob = 1.0 - cl_prob;
 405   }
 406   // Get backedge compare
 407   Node *cmp = test->in(1);
 408   int cmp_op = cmp->Opcode();
 409   if (cmp_op != Op_CmpI)
 410     return false;                // Avoid pointer & float compares
 411 
 412   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 413   Node *incr  = cmp->in(1);
 414   Node *limit = cmp->in(2);
 415 
 416   // ---------
 417   // need 'loop()' test to tell if limit is loop invariant
 418   // ---------
 419 
 420   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 421     Node *tmp = incr;            // Then reverse order into the CmpI
 422     incr = limit;
 423     limit = tmp;
 424     bt = BoolTest(bt).commute(); // And commute the exit test
 425   }
 426   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 427     return false;
 428   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 429     return false;
 430 
 431   Node* phi_incr = NULL;
 432   // Trip-counter increment must be commutative & associative.
 433   if (incr->Opcode() == Op_CastII) {
 434     incr = incr->in(1);
 435   }
 436   if (incr->is_Phi()) {
 437     if (incr->as_Phi()->region() != x || incr->req() != 3)
 438       return false; // Not simple trip counter expression
 439     phi_incr = incr;
 440     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 441     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 442       return false;
 443   }
 444 
 445   Node* trunc1 = NULL;
 446   Node* trunc2 = NULL;
 447   const TypeInt* iv_trunc_t = NULL;
 448   Node* orig_incr = incr;
 449   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 450     return false; // Funny increment opcode
 451   }
 452   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 453 
 454   const TypeInt* limit_t = gvn->type(limit)->is_int();
 455   if (trunc1 != NULL) {
 456     // When there is a truncation, we must be sure that after the truncation
 457     // the trip counter will end up higher than the limit, otherwise we are looking
 458     // at an endless loop. Can happen with range checks.
 459 
 460     // Example:
 461     // int i = 0;
 462     // while (true)
 463     //    sum + = array[i];
 464     //    i++;
 465     //    i = i && 0x7fff;
 466     //  }
 467     //
 468     // If the array is shorter than 0x8000 this exits through a AIOOB
 469     //  - Counted loop transformation is ok
 470     // If the array is longer then this is an endless loop
 471     //  - No transformation can be done.
 472 
 473     const TypeInt* incr_t = gvn->type(orig_incr)->is_int();
 474     if (limit_t->_hi > incr_t->_hi) {
 475       // if the limit can have a higher value than the increment (before the phi)
 476       return false;
 477     }
 478   }
 479 
 480   // Get merge point
 481   Node *xphi = incr->in(1);
 482   Node *stride = incr->in(2);
 483   if (!stride->is_Con()) {     // Oops, swap these
 484     if (!xphi->is_Con())       // Is the other guy a constant?
 485       return false;             // Nope, unknown stride, bail out
 486     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 487     xphi = stride;
 488     stride = tmp;
 489   }
 490   if (xphi->Opcode() == Op_CastII) {
 491     xphi = xphi->in(1);
 492   }
 493   // Stride must be constant
 494   int stride_con = stride->get_int();
 495   if (stride_con == 0)
 496     return false; // missed some peephole opt
 497 
 498   if (!xphi->is_Phi())
 499     return false; // Too much math on the trip counter
 500   if (phi_incr != NULL && phi_incr != xphi)
 501     return false;
 502   PhiNode *phi = xphi->as_Phi();
 503 
 504   // Phi must be of loop header; backedge must wrap to increment
 505   if (phi->region() != x)
 506     return false;
 507   if ((trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) ||
 508       (trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) {
 509     return false;
 510   }
 511   Node *init_trip = phi->in(LoopNode::EntryControl);
 512 
 513   // If iv trunc type is smaller than int, check for possible wrap.
 514   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 515     assert(trunc1 != NULL, "must have found some truncation");
 516 
 517     // Get a better type for the phi (filtered thru if's)
 518     const TypeInt* phi_ft = filtered_type(phi);
 519 
 520     // Can iv take on a value that will wrap?
 521     //
 522     // Ensure iv's limit is not within "stride" of the wrap value.
 523     //
 524     // Example for "short" type
 525     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 526     //    If the stride is +10, then the last value of the induction
 527     //    variable before the increment (phi_ft->_hi) must be
 528     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 529     //    ensure no truncation occurs after the increment.
 530 
 531     if (stride_con > 0) {
 532       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 533           iv_trunc_t->_lo > phi_ft->_lo) {
 534         return false;  // truncation may occur
 535       }
 536     } else if (stride_con < 0) {
 537       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 538           iv_trunc_t->_hi < phi_ft->_hi) {
 539         return false;  // truncation may occur
 540       }
 541     }
 542     // No possibility of wrap so truncation can be discarded
 543     // Promote iv type to Int
 544   } else {
 545     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 546   }
 547 
 548   // If the condition is inverted and we will be rolling
 549   // through MININT to MAXINT, then bail out.
 550   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 551       // Odd stride
 552       (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
 553       // Count down loop rolls through MAXINT
 554       ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
 555       // Count up loop rolls through MININT
 556       ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
 557     return false; // Bail out
 558   }
 559 
 560   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 561 
 562   if (stride_con > 0) {
 563     jlong init_p = (jlong)init_t->_lo + stride_con;
 564     if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
 565       return false; // cyclic loop or this loop trips only once
 566   } else {
 567     jlong init_p = (jlong)init_t->_hi + stride_con;
 568     if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
 569       return false; // cyclic loop or this loop trips only once
 570   }
 571 
 572   if (phi_incr != NULL && bt != BoolTest::ne) {
 573     // check if there is a possiblity of IV overflowing after the first increment
 574     if (stride_con > 0) {
 575       if (init_t->_hi > max_jint - stride_con) {
 576         return false;
 577       }
 578     } else {
 579       if (init_t->_lo < min_jint - stride_con) {
 580         return false;
 581       }
 582     }
 583   }
 584 
 585   // =================================================
 586   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 587   //
 588   assert(x->Opcode() == Op_Loop, "regular loops only");
 589   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 590 
 591   Node *hook = new Node(6);
 592 
 593   // ===================================================
 594   // Generate loop limit check to avoid integer overflow
 595   // in cases like next (cyclic loops):
 596   //
 597   // for (i=0; i <= max_jint; i++) {}
 598   // for (i=0; i <  max_jint; i+=2) {}
 599   //
 600   //
 601   // Limit check predicate depends on the loop test:
 602   //
 603   // for(;i != limit; i++)       --> limit <= (max_jint)
 604   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 605   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 606   //
 607 
 608   // Check if limit is excluded to do more precise int overflow check.
 609   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 610   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 611 
 612   // If compare points directly to the phi we need to adjust
 613   // the compare so that it points to the incr. Limit have
 614   // to be adjusted to keep trip count the same and the
 615   // adjusted limit should be checked for int overflow.
 616   if (phi_incr != NULL) {
 617     stride_m  += stride_con;
 618   }
 619 
 620   if (limit->is_Con()) {
 621     int limit_con = limit->get_int();
 622     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 623         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 624       // Bailout: it could be integer overflow.
 625       return false;
 626     }
 627   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 628              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 629       // Limit's type may satisfy the condition, for example,
 630       // when it is an array length.
 631   } else {
 632     // Generate loop's limit check.
 633     // Loop limit check predicate should be near the loop.
 634     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 635     if (!limit_check_proj) {
 636       // The limit check predicate is not generated if this method trapped here before.
 637 #ifdef ASSERT
 638       if (TraceLoopLimitCheck) {
 639         tty->print("missing loop limit check:");
 640         loop->dump_head();
 641         x->dump(1);
 642       }
 643 #endif
 644       return false;
 645     }
 646 
 647     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 648 
 649     if (!is_dominator(get_ctrl(limit), check_iff->in(0))) {
 650       return false;
 651     }
 652 
 653     Node* cmp_limit;
 654     Node* bol;
 655 
 656     if (stride_con > 0) {
 657       cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 658       bol = new BoolNode(cmp_limit, BoolTest::le);
 659     } else {
 660       cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 661       bol = new BoolNode(cmp_limit, BoolTest::ge);
 662     }
 663 
 664     insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 665   }
 666 
 667   // Now we need to canonicalize loop condition.
 668   if (bt == BoolTest::ne) {
 669     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 670     if (stride_con > 0 && init_t->_hi < limit_t->_lo) {
 671       // 'ne' can be replaced with 'lt' only when init < limit.
 672       bt = BoolTest::lt;
 673     } else if (stride_con < 0 && init_t->_lo > limit_t->_hi) {
 674       // 'ne' can be replaced with 'gt' only when init > limit.
 675       bt = BoolTest::gt;
 676     } else {
 677       ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 678       if (!limit_check_proj) {
 679         // The limit check predicate is not generated if this method trapped here before.
 680 #ifdef ASSERT
 681         if (TraceLoopLimitCheck) {
 682           tty->print("missing loop limit check:");
 683           loop->dump_head();
 684           x->dump(1);
 685         }
 686 #endif
 687         return false;
 688       }
 689       IfNode* check_iff = limit_check_proj->in(0)->as_If();
 690 
 691       if (!is_dominator(get_ctrl(limit), check_iff->in(0)) ||
 692           !is_dominator(get_ctrl(init_trip), check_iff->in(0))) {
 693         return false;
 694       }
 695 
 696       Node* cmp_limit;
 697       Node* bol;
 698 
 699       if (stride_con > 0) {
 700         cmp_limit = new CmpINode(init_trip, limit);
 701         bol = new BoolNode(cmp_limit, BoolTest::lt);
 702       } else {
 703         cmp_limit = new CmpINode(init_trip, limit);
 704         bol = new BoolNode(cmp_limit, BoolTest::gt);
 705       }
 706 
 707       insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 708 
 709       if (stride_con > 0) {
 710         // 'ne' can be replaced with 'lt' only when init < limit.
 711         bt = BoolTest::lt;
 712       } else if (stride_con < 0) {
 713         // 'ne' can be replaced with 'gt' only when init > limit.
 714         bt = BoolTest::gt;
 715       }
 716     }
 717   }
 718 
 719   if (phi_incr != NULL) {
 720     // If compare points directly to the phi we need to adjust
 721     // the compare so that it points to the incr. Limit have
 722     // to be adjusted to keep trip count the same and we
 723     // should avoid int overflow.
 724     //
 725     //   i = init; do {} while(i++ < limit);
 726     // is converted to
 727     //   i = init; do {} while(++i < limit+1);
 728     //
 729     limit = gvn->transform(new AddINode(limit, stride));
 730   }
 731 
 732   if (incl_limit) {
 733     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 734     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 735     //
 736     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 737     limit = gvn->transform(new AddINode(limit, one));
 738     if (bt == BoolTest::le)
 739       bt = BoolTest::lt;
 740     else if (bt == BoolTest::ge)
 741       bt = BoolTest::gt;
 742     else
 743       ShouldNotReachHere();
 744   }
 745   set_subtree_ctrl( limit );
 746 
 747   if (LoopStripMiningIter == 0) {
 748     // Check for SafePoint on backedge and remove
 749     Node *sfpt = x->in(LoopNode::LoopBackControl);
 750     if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 751       lazy_replace( sfpt, iftrue );
 752       if (loop->_safepts != NULL) {
 753         loop->_safepts->yank(sfpt);
 754       }
 755       loop->_tail = iftrue;
 756     }
 757   }
 758 
 759   // Build a canonical trip test.
 760   // Clone code, as old values may be in use.
 761   incr = incr->clone();
 762   incr->set_req(1,phi);
 763   incr->set_req(2,stride);
 764   incr = _igvn.register_new_node_with_optimizer(incr);
 765   set_early_ctrl( incr );
 766   _igvn.rehash_node_delayed(phi);
 767   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 768 
 769   // If phi type is more restrictive than Int, raise to
 770   // Int to prevent (almost) infinite recursion in igvn
 771   // which can only handle integer types for constants or minint..maxint.
 772   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 773     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 774     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 775     nphi = _igvn.register_new_node_with_optimizer(nphi);
 776     set_ctrl(nphi, get_ctrl(phi));
 777     _igvn.replace_node(phi, nphi);
 778     phi = nphi->as_Phi();
 779   }
 780   cmp = cmp->clone();
 781   cmp->set_req(1,incr);
 782   cmp->set_req(2,limit);
 783   cmp = _igvn.register_new_node_with_optimizer(cmp);
 784   set_ctrl(cmp, iff->in(0));
 785 
 786   test = test->clone()->as_Bool();
 787   (*(BoolTest*)&test->_test)._test = bt;
 788   test->set_req(1,cmp);
 789   _igvn.register_new_node_with_optimizer(test);
 790   set_ctrl(test, iff->in(0));
 791 
 792   // Replace the old IfNode with a new LoopEndNode
 793   Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 794   IfNode *le = lex->as_If();
 795   uint dd = dom_depth(iff);
 796   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 797   set_loop(le, loop);
 798 
 799   // Get the loop-exit control
 800   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 801 
 802   // Need to swap loop-exit and loop-back control?
 803   if (iftrue_op == Op_IfFalse) {
 804     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
 805     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
 806 
 807     loop->_tail = back_control = ift2;
 808     set_loop(ift2, loop);
 809     set_loop(iff2, get_loop(iffalse));
 810 
 811     // Lazy update of 'get_ctrl' mechanism.
 812     lazy_replace(iffalse, iff2);
 813     lazy_replace(iftrue,  ift2);
 814 
 815     // Swap names
 816     iffalse = iff2;
 817     iftrue  = ift2;
 818   } else {
 819     _igvn.rehash_node_delayed(iffalse);
 820     _igvn.rehash_node_delayed(iftrue);
 821     iffalse->set_req_X( 0, le, &_igvn );
 822     iftrue ->set_req_X( 0, le, &_igvn );
 823   }
 824 
 825   set_idom(iftrue,  le, dd+1);
 826   set_idom(iffalse, le, dd+1);
 827   assert(iff->outcnt() == 0, "should be dead now");
 828   lazy_replace( iff, le ); // fix 'get_ctrl'
 829 
 830   Node *sfpt2 = le->in(0);
 831 
 832   Node* entry_control = init_control;
 833   bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL &&
 834     sfpt2->Opcode() == Op_SafePoint && !loop->_has_call;
 835   IdealLoopTree* outer_ilt = NULL;
 836   if (strip_mine_loop) {
 837     outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
 838                                               cl_prob, le->_fcnt, entry_control,
 839                                               iffalse);
 840   }
 841 
 842   // Now setup a new CountedLoopNode to replace the existing LoopNode
 843   CountedLoopNode *l = new CountedLoopNode(entry_control, back_control);
 844   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 845   // The following assert is approximately true, and defines the intention
 846   // of can_be_counted_loop.  It fails, however, because phase->type
 847   // is not yet initialized for this loop and its parts.
 848   //assert(l->can_be_counted_loop(this), "sanity");
 849   _igvn.register_new_node_with_optimizer(l);
 850   set_loop(l, loop);
 851   loop->_head = l;
 852   // Fix all data nodes placed at the old loop head.
 853   // Uses the lazy-update mechanism of 'get_ctrl'.
 854   lazy_replace( x, l );
 855   set_idom(l, entry_control, dom_depth(entry_control) + 1);
 856 
 857   if (LoopStripMiningIter == 0 || strip_mine_loop) {
 858     // Check for immediately preceding SafePoint and remove
 859     if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) {
 860       if (strip_mine_loop) {
 861         Node* outer_le = outer_ilt->_tail->in(0);
 862         Node* sfpt = sfpt2->clone();
 863         sfpt->set_req(0, iffalse);
 864         outer_le->set_req(0, sfpt);
 865         register_control(sfpt, outer_ilt, iffalse);
 866         set_idom(outer_le, sfpt, dom_depth(sfpt));
 867       }
 868       lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 869       if (loop->_safepts != NULL) {
 870         loop->_safepts->yank(sfpt2);
 871       }
 872     }
 873   }
 874 
 875   // Free up intermediate goo
 876   _igvn.remove_dead_node(hook);
 877 
 878 #ifdef ASSERT
 879   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 880   assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
 881 #endif
 882 #ifndef PRODUCT
 883   if (TraceLoopOpts) {
 884     tty->print("Counted      ");
 885     loop->dump_head();
 886   }
 887 #endif
 888 
 889   C->print_method(PHASE_AFTER_CLOOPS, 3);
 890 
 891   // Capture bounds of the loop in the induction variable Phi before
 892   // subsequent transformation (iteration splitting) obscures the
 893   // bounds
 894   l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
 895 
 896   if (strip_mine_loop) {
 897     l->mark_strip_mined();
 898     l->verify_strip_mined(1);
 899     outer_ilt->_head->as_Loop()->verify_strip_mined(1);
 900     loop = outer_ilt;
 901   }
 902 
 903   return true;
 904 }
 905 
 906 //----------------------exact_limit-------------------------------------------
 907 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 908   assert(loop->_head->is_CountedLoop(), "");
 909   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 910   assert(cl->is_valid_counted_loop(), "");
 911 
 912   if (ABS(cl->stride_con()) == 1 ||
 913       cl->limit()->Opcode() == Op_LoopLimit) {
 914     // Old code has exact limit (it could be incorrect in case of int overflow).
 915     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 916     return cl->limit();
 917   }
 918   Node *limit = NULL;
 919 #ifdef ASSERT
 920   BoolTest::mask bt = cl->loopexit()->test_trip();
 921   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 922 #endif
 923   if (cl->has_exact_trip_count()) {
 924     // Simple case: loop has constant boundaries.
 925     // Use jlongs to avoid integer overflow.
 926     int stride_con = cl->stride_con();
 927     jlong  init_con = cl->init_trip()->get_int();
 928     jlong limit_con = cl->limit()->get_int();
 929     julong trip_cnt = cl->trip_count();
 930     jlong final_con = init_con + trip_cnt*stride_con;
 931     int final_int = (int)final_con;
 932     // The final value should be in integer range since the loop
 933     // is counted and the limit was checked for overflow.
 934     assert(final_con == (jlong)final_int, "final value should be integer");
 935     limit = _igvn.intcon(final_int);
 936   } else {
 937     // Create new LoopLimit node to get exact limit (final iv value).
 938     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 939     register_new_node(limit, cl->in(LoopNode::EntryControl));
 940   }
 941   assert(limit != NULL, "sanity");
 942   return limit;
 943 }
 944 
 945 //------------------------------Ideal------------------------------------------
 946 // Return a node which is more "ideal" than the current node.
 947 // Attempt to convert into a counted-loop.
 948 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 949   if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
 950     phase->C->set_major_progress();
 951   }
 952   return RegionNode::Ideal(phase, can_reshape);
 953 }
 954 
 955 void LoopNode::verify_strip_mined(int expect_skeleton) const {
 956 #ifdef ASSERT
 957   const OuterStripMinedLoopNode* outer = NULL;
 958   const CountedLoopNode* inner = NULL;
 959   if (is_strip_mined()) {
 960     assert(is_CountedLoop(), "no Loop should be marked strip mined");
 961     inner = as_CountedLoop();
 962     outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
 963   } else if (is_OuterStripMinedLoop()) {
 964     outer = this->as_OuterStripMinedLoop();
 965     inner = outer->unique_ctrl_out()->as_CountedLoop();
 966     assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
 967   }
 968   if (inner != NULL || outer != NULL) {
 969     assert(inner != NULL && outer != NULL, "missing loop in strip mined nest");
 970     Node* outer_tail = outer->in(LoopNode::LoopBackControl);
 971     Node* outer_le = outer_tail->in(0);
 972     assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
 973     Node* sfpt = outer_le->in(0);
 974     assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
 975     Node* inner_out = sfpt->in(0);
 976     if (inner_out->outcnt() != 1) {
 977       ResourceMark rm;
 978       Unique_Node_List wq;
 979 
 980       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
 981         Node* u = inner_out->fast_out(i);
 982         if (u == sfpt) {
 983           continue;
 984         }
 985         wq.clear();
 986         wq.push(u);
 987         bool found_sfpt = false;
 988         for (uint next = 0; next < wq.size() && !found_sfpt; next++) {
 989           Node *n = wq.at(next);
 990           for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) {
 991             Node* u = n->fast_out(i);
 992             if (u == sfpt) {
 993               found_sfpt = true;
 994             }
 995             if (!u->is_CFG()) {
 996               wq.push(u);
 997             }
 998           }
 999         }
1000         assert(found_sfpt, "no node in loop that's not input to safepoint");
1001       }
1002     }
1003     bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
1004     if (has_skeleton) {
1005       CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
1006       assert(cle == inner->loopexit_or_null(), "mismatch");
1007       assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
1008       assert(outer->outcnt() == 2, "only phis");
1009     } else {
1010       assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
1011       uint phis = 0;
1012       for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
1013         Node* u = inner->fast_out(i);
1014         if (u->is_Phi()) {
1015           phis++;
1016         }
1017       }
1018       for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
1019         Node* u = outer->fast_out(i);
1020         assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
1021       }
1022       uint stores = 0;
1023       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
1024         Node* u = inner_out->fast_out(i);
1025         if (u->is_Store()) {
1026           stores++;
1027         }
1028       }
1029       assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
1030     }
1031     assert(sfpt->outcnt() == 1, "no data node");
1032     assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
1033   }
1034 #endif
1035 }
1036 
1037 //=============================================================================
1038 //------------------------------Ideal------------------------------------------
1039 // Return a node which is more "ideal" than the current node.
1040 // Attempt to convert into a counted-loop.
1041 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1042   return RegionNode::Ideal(phase, can_reshape);
1043 }
1044 
1045 //------------------------------dump_spec--------------------------------------
1046 // Dump special per-node info
1047 #ifndef PRODUCT
1048 void CountedLoopNode::dump_spec(outputStream *st) const {
1049   LoopNode::dump_spec(st);
1050   if (stride_is_con()) {
1051     st->print("stride: %d ",stride_con());
1052   }
1053   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
1054   if (is_main_loop()) st->print("main of N%d", _idx);
1055   if (is_post_loop()) st->print("post of N%d", _main_idx);
1056   if (is_strip_mined()) st->print(" strip mined");
1057 }
1058 #endif
1059 
1060 //=============================================================================
1061 int CountedLoopEndNode::stride_con() const {
1062   return stride()->bottom_type()->is_int()->get_con();
1063 }
1064 
1065 //=============================================================================
1066 //------------------------------Value-----------------------------------------
1067 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
1068   const Type* init_t   = phase->type(in(Init));
1069   const Type* limit_t  = phase->type(in(Limit));
1070   const Type* stride_t = phase->type(in(Stride));
1071   // Either input is TOP ==> the result is TOP
1072   if (init_t   == Type::TOP) return Type::TOP;
1073   if (limit_t  == Type::TOP) return Type::TOP;
1074   if (stride_t == Type::TOP) return Type::TOP;
1075 
1076   int stride_con = stride_t->is_int()->get_con();
1077   if (stride_con == 1)
1078     return NULL;  // Identity
1079 
1080   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
1081     // Use jlongs to avoid integer overflow.
1082     jlong init_con   =  init_t->is_int()->get_con();
1083     jlong limit_con  = limit_t->is_int()->get_con();
1084     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
1085     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
1086     jlong final_con  = init_con + stride_con*trip_count;
1087     int final_int = (int)final_con;
1088     // The final value should be in integer range since the loop
1089     // is counted and the limit was checked for overflow.
1090     assert(final_con == (jlong)final_int, "final value should be integer");
1091     return TypeInt::make(final_int);
1092   }
1093 
1094   return bottom_type(); // TypeInt::INT
1095 }
1096 
1097 //------------------------------Ideal------------------------------------------
1098 // Return a node which is more "ideal" than the current node.
1099 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1100   if (phase->type(in(Init))   == Type::TOP ||
1101       phase->type(in(Limit))  == Type::TOP ||
1102       phase->type(in(Stride)) == Type::TOP)
1103     return NULL;  // Dead
1104 
1105   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1106   if (stride_con == 1)
1107     return NULL;  // Identity
1108 
1109   if (in(Init)->is_Con() && in(Limit)->is_Con())
1110     return NULL;  // Value
1111 
1112   // Delay following optimizations until all loop optimizations
1113   // done to keep Ideal graph simple.
1114   if (!can_reshape || phase->C->major_progress())
1115     return NULL;
1116 
1117   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
1118   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
1119   int stride_p;
1120   jlong lim, ini;
1121   julong max;
1122   if (stride_con > 0) {
1123     stride_p = stride_con;
1124     lim = limit_t->_hi;
1125     ini = init_t->_lo;
1126     max = (julong)max_jint;
1127   } else {
1128     stride_p = -stride_con;
1129     lim = init_t->_hi;
1130     ini = limit_t->_lo;
1131     max = (julong)min_jint;
1132   }
1133   julong range = lim - ini + stride_p;
1134   if (range <= max) {
1135     // Convert to integer expression if it is not overflow.
1136     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
1137     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
1138     Node *bias  = phase->transform(new AddINode(range, stride_m));
1139     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
1140     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
1141     return new AddINode(span, in(Init)); // exact limit
1142   }
1143 
1144   if (is_power_of_2(stride_p) ||                // divisor is 2^n
1145       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
1146     // Convert to long expression to avoid integer overflow
1147     // and let igvn optimizer convert this division.
1148     //
1149     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
1150     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
1151     Node* stride   = phase->longcon(stride_con);
1152     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
1153 
1154     Node *range = phase->transform(new SubLNode(limit, init));
1155     Node *bias  = phase->transform(new AddLNode(range, stride_m));
1156     Node *span;
1157     if (stride_con > 0 && is_power_of_2(stride_p)) {
1158       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
1159       // and avoid generating rounding for division. Zero trip guard should
1160       // guarantee that init < limit but sometimes the guard is missing and
1161       // we can get situation when init > limit. Note, for the empty loop
1162       // optimization zero trip guard is generated explicitly which leaves
1163       // only RCE predicate where exact limit is used and the predicate
1164       // will simply fail forcing recompilation.
1165       Node* neg_stride   = phase->longcon(-stride_con);
1166       span = phase->transform(new AndLNode(bias, neg_stride));
1167     } else {
1168       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
1169       span = phase->transform(new MulLNode(trip, stride));
1170     }
1171     // Convert back to int
1172     Node *span_int = phase->transform(new ConvL2INode(span));
1173     return new AddINode(span_int, in(Init)); // exact limit
1174   }
1175 
1176   return NULL;    // No progress
1177 }
1178 
1179 //------------------------------Identity---------------------------------------
1180 // If stride == 1 return limit node.
1181 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1182   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1183   if (stride_con == 1 || stride_con == -1)
1184     return in(Limit);
1185   return this;
1186 }
1187 
1188 //=============================================================================
1189 //----------------------match_incr_with_optional_truncation--------------------
1190 // Match increment with optional truncation:
1191 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1192 // Return NULL for failure. Success returns the increment node.
1193 Node* CountedLoopNode::match_incr_with_optional_truncation(
1194                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1195   // Quick cutouts:
1196   if (expr == NULL || expr->req() != 3)  return NULL;
1197 
1198   Node *t1 = NULL;
1199   Node *t2 = NULL;
1200   const TypeInt* trunc_t = TypeInt::INT;
1201   Node* n1 = expr;
1202   int   n1op = n1->Opcode();
1203 
1204   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1205   if (n1op == Op_AndI &&
1206       n1->in(2)->is_Con() &&
1207       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1208     // %%% This check should match any mask of 2**K-1.
1209     t1 = n1;
1210     n1 = t1->in(1);
1211     n1op = n1->Opcode();
1212     trunc_t = TypeInt::CHAR;
1213   } else if (n1op == Op_RShiftI &&
1214              n1->in(1) != NULL &&
1215              n1->in(1)->Opcode() == Op_LShiftI &&
1216              n1->in(2) == n1->in(1)->in(2) &&
1217              n1->in(2)->is_Con()) {
1218     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1219     // %%% This check should match any shift in [1..31].
1220     if (shift == 16 || shift == 8) {
1221       t1 = n1;
1222       t2 = t1->in(1);
1223       n1 = t2->in(1);
1224       n1op = n1->Opcode();
1225       if (shift == 16) {
1226         trunc_t = TypeInt::SHORT;
1227       } else if (shift == 8) {
1228         trunc_t = TypeInt::BYTE;
1229       }
1230     }
1231   }
1232 
1233   // If (maybe after stripping) it is an AddI, we won:
1234   if (n1op == Op_AddI) {
1235     *trunc1 = t1;
1236     *trunc2 = t2;
1237     *trunc_type = trunc_t;
1238     return n1;
1239   }
1240 
1241   // failed
1242   return NULL;
1243 }
1244 
1245 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
1246   if (is_strip_mined()) {
1247     verify_strip_mined(expect_skeleton);
1248     return in(EntryControl)->as_Loop();
1249   }
1250   return this;
1251 }
1252 
1253 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
1254   assert(is_strip_mined(), "not a strip mined loop");
1255   Node* c = in(EntryControl);
1256   if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) {
1257     return NULL;
1258   }
1259   return c->as_OuterStripMinedLoop();
1260 }
1261 
1262 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
1263   Node* c = in(LoopBackControl);
1264   if (c == NULL || c->is_top()) {
1265     return NULL;
1266   }
1267   return c->as_IfTrue();
1268 }
1269 
1270 IfTrueNode* CountedLoopNode::outer_loop_tail() const {
1271   LoopNode* l = outer_loop();
1272   if (l == NULL) {
1273     return NULL;
1274   }
1275   return l->outer_loop_tail();
1276 }
1277 
1278 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
1279   IfTrueNode* proj = outer_loop_tail();
1280   if (proj == NULL) {
1281     return NULL;
1282   }
1283   Node* c = proj->in(0);
1284   if (c == NULL || c->is_top() || c->outcnt() != 2) {
1285     return NULL;
1286   }
1287   return c->as_OuterStripMinedLoopEnd();
1288 }
1289 
1290 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
1291   LoopNode* l = outer_loop();
1292   if (l == NULL) {
1293     return NULL;
1294   }
1295   return l->outer_loop_end();
1296 }
1297 
1298 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
1299   IfNode* le = outer_loop_end();
1300   if (le == NULL) {
1301     return NULL;
1302   }
1303   Node* c = le->proj_out_or_null(false);
1304   if (c == NULL) {
1305     return NULL;
1306   }
1307   return c->as_IfFalse();
1308 }
1309 
1310 IfFalseNode* CountedLoopNode::outer_loop_exit() const {
1311   LoopNode* l = outer_loop();
1312   if (l == NULL) {
1313     return NULL;
1314   }
1315   return l->outer_loop_exit();
1316 }
1317 
1318 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
1319   IfNode* le = outer_loop_end();
1320   if (le == NULL) {
1321     return NULL;
1322   }
1323   Node* c = le->in(0);
1324   if (c == NULL || c->is_top()) {
1325     return NULL;
1326   }
1327   assert(c->Opcode() == Op_SafePoint, "broken outer loop");
1328   return c->as_SafePoint();
1329 }
1330 
1331 SafePointNode* CountedLoopNode::outer_safepoint() const {
1332   LoopNode* l = outer_loop();
1333   if (l == NULL) {
1334     return NULL;
1335   }
1336   return l->outer_safepoint();
1337 }
1338 
1339 Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
1340     while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() &&
1341            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
1342            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) {
1343       ctrl = ctrl->in(0)->in(0);
1344     }
1345 
1346     return ctrl;
1347   }
1348 
1349 Node* CountedLoopNode::skip_predicates() {
1350   if (is_main_loop()) {
1351     Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
1352 
1353     return skip_predicates_from_entry(ctrl);
1354   }
1355   return in(LoopNode::EntryControl);
1356 }
1357 
1358 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
1359   // Look for the outer & inner strip mined loop, reduce number of
1360   // iterations of the inner loop, set exit condition of outer loop,
1361   // construct required phi nodes for outer loop.
1362   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
1363   assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
1364   Node* inner_iv_phi = inner_cl->phi();
1365   if (inner_iv_phi == NULL) {
1366     IfNode* outer_le = outer_loop_end();
1367     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1368     igvn->replace_node(outer_le, iff);
1369     inner_cl->clear_strip_mined();
1370     return;
1371   }
1372   CountedLoopEndNode* inner_cle = inner_cl->loopexit();
1373 
1374   int stride = inner_cl->stride_con();
1375   jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
1376   int scaled_iters = (int)scaled_iters_long;
1377   int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
1378   const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
1379   jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
1380   assert(iter_estimate > 0, "broken");
1381   if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
1382     // Remove outer loop and safepoint (too few iterations)
1383     Node* outer_sfpt = outer_safepoint();
1384     Node* outer_out = outer_loop_exit();
1385     igvn->replace_node(outer_out, outer_sfpt->in(0));
1386     igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
1387     inner_cl->clear_strip_mined();
1388     return;
1389   }
1390   if (iter_estimate <= scaled_iters_long) {
1391     // We would only go through one iteration of
1392     // the outer loop: drop the outer loop but
1393     // keep the safepoint so we don't run for
1394     // too long without a safepoint
1395     IfNode* outer_le = outer_loop_end();
1396     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1397     igvn->replace_node(outer_le, iff);
1398     inner_cl->clear_strip_mined();
1399     return;
1400   }
1401 
1402   Node* cle_tail = inner_cle->proj_out(true);
1403   ResourceMark rm;
1404   Node_List old_new;
1405   if (cle_tail->outcnt() > 1) {
1406     // Look for nodes on backedge of inner loop and clone them
1407     Unique_Node_List backedge_nodes;
1408     for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
1409       Node* u = cle_tail->fast_out(i);
1410       if (u != inner_cl) {
1411         assert(!u->is_CFG(), "control flow on the backedge?");
1412         backedge_nodes.push(u);
1413       }
1414     }
1415     uint last = igvn->C->unique();
1416     for (uint next = 0; next < backedge_nodes.size(); next++) {
1417       Node* n = backedge_nodes.at(next);
1418       old_new.map(n->_idx, n->clone());
1419       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1420         Node* u = n->fast_out(i);
1421         assert(!u->is_CFG(), "broken");
1422         if (u->_idx >= last) {
1423           continue;
1424         }
1425         if (!u->is_Phi()) {
1426           backedge_nodes.push(u);
1427         } else {
1428           assert(u->in(0) == inner_cl, "strange phi on the backedge");
1429         }
1430       }
1431     }
1432     // Put the clones on the outer loop backedge
1433     Node* le_tail = outer_loop_tail();
1434     for (uint next = 0; next < backedge_nodes.size(); next++) {
1435       Node *n = old_new[backedge_nodes.at(next)->_idx];
1436       for (uint i = 1; i < n->req(); i++) {
1437         if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) {
1438           n->set_req(i, old_new[n->in(i)->_idx]);
1439         }
1440       }
1441       if (n->in(0) != NULL && n->in(0) == cle_tail) {
1442         n->set_req(0, le_tail);
1443       }
1444       igvn->register_new_node_with_optimizer(n);
1445     }
1446   }
1447 
1448   Node* iv_phi = NULL;
1449   // Make a clone of each phi in the inner loop
1450   // for the outer loop
1451   for (uint i = 0; i < inner_cl->outcnt(); i++) {
1452     Node* u = inner_cl->raw_out(i);
1453     if (u->is_Phi()) {
1454       assert(u->in(0) == inner_cl, "inconsistent");
1455       Node* phi = u->clone();
1456       phi->set_req(0, this);
1457       Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
1458       if (be != NULL) {
1459         phi->set_req(LoopNode::LoopBackControl, be);
1460       }
1461       phi = igvn->transform(phi);
1462       igvn->replace_input_of(u, LoopNode::EntryControl, phi);
1463       if (u == inner_iv_phi) {
1464         iv_phi = phi;
1465       }
1466     }
1467   }
1468   Node* cle_out = inner_cle->proj_out(false);
1469   if (cle_out->outcnt() > 1) {
1470     // Look for chains of stores that were sunk
1471     // out of the inner loop and are in the outer loop
1472     for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
1473       Node* u = cle_out->fast_out(i);
1474       if (u->is_Store()) {
1475         Node* first = u;
1476         for(;;) {
1477           Node* next = first->in(MemNode::Memory);
1478           if (!next->is_Store() || next->in(0) != cle_out) {
1479             break;
1480           }
1481           first = next;
1482         }
1483         Node* last = u;
1484         for(;;) {
1485           Node* next = NULL;
1486           for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
1487             Node* uu = last->fast_out(j);
1488             if (uu->is_Store() && uu->in(0) == cle_out) {
1489               assert(next == NULL, "only one in the outer loop");
1490               next = uu;
1491             }
1492           }
1493           if (next == NULL) {
1494             break;
1495           }
1496           last = next;
1497         }
1498         Node* phi = NULL;
1499         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1500           Node* uu = fast_out(j);
1501           if (uu->is_Phi()) {
1502             Node* be = uu->in(LoopNode::LoopBackControl);
1503             if (be->is_Store() && old_new[be->_idx] != NULL) {
1504               assert(false, "store on the backedge + sunk stores: unsupported");
1505               // drop outer loop
1506               IfNode* outer_le = outer_loop_end();
1507               Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1508               igvn->replace_node(outer_le, iff);
1509               inner_cl->clear_strip_mined();
1510               return;
1511             }
1512             if (be == last || be == first->in(MemNode::Memory)) {
1513               assert(phi == NULL, "only one phi");
1514               phi = uu;
1515             }
1516           }
1517         }
1518 #ifdef ASSERT
1519         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1520           Node* uu = fast_out(j);
1521           if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
1522             if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
1523               assert(phi == uu, "what's that phi?");
1524             } else if (uu->adr_type() == TypePtr::BOTTOM) {
1525               Node* n = uu->in(LoopNode::LoopBackControl);
1526               uint limit = igvn->C->live_nodes();
1527               uint i = 0;
1528               while (n != uu) {
1529                 i++;
1530                 assert(i < limit, "infinite loop");
1531                 if (n->is_Proj()) {
1532                   n = n->in(0);
1533                 } else if (n->is_SafePoint() || n->is_MemBar()) {
1534                   n = n->in(TypeFunc::Memory);
1535                 } else if (n->is_Phi()) {
1536                   n = n->in(1);
1537                 } else if (n->is_MergeMem()) {
1538                   n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
1539                 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
1540                   n = n->in(MemNode::Memory);
1541                 } else {
1542                   n->dump();
1543                   ShouldNotReachHere();
1544                 }
1545               }
1546             }
1547           }
1548         }
1549 #endif
1550         if (phi == NULL) {
1551           // If the an entire chains was sunk, the
1552           // inner loop has no phi for that memory
1553           // slice, create one for the outer loop
1554           phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY,
1555                               igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
1556           phi->set_req(LoopNode::LoopBackControl, last);
1557           phi = igvn->transform(phi);
1558           igvn->replace_input_of(first, MemNode::Memory, phi);
1559         } else {
1560           // Or fix the outer loop fix to include
1561           // that chain of stores.
1562           Node* be = phi->in(LoopNode::LoopBackControl);
1563           assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported");
1564           if (be == first->in(MemNode::Memory)) {
1565             if (be == phi->in(LoopNode::LoopBackControl)) {
1566               igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
1567             } else {
1568               igvn->replace_input_of(be, MemNode::Memory, last);
1569             }
1570           } else {
1571 #ifdef ASSERT
1572             if (be == phi->in(LoopNode::LoopBackControl)) {
1573               assert(phi->in(LoopNode::LoopBackControl) == last, "");
1574             } else {
1575               assert(be->in(MemNode::Memory) == last, "");
1576             }
1577 #endif
1578           }
1579         }
1580       }
1581     }
1582   }
1583 
1584   if (iv_phi != NULL) {
1585     // Now adjust the inner loop's exit condition
1586     Node* limit = inner_cl->limit();
1587     Node* sub = NULL;
1588     if (stride > 0) {
1589       sub = igvn->transform(new SubINode(limit, iv_phi));
1590     } else {
1591       sub = igvn->transform(new SubINode(iv_phi, limit));
1592     }
1593     Node* min = igvn->transform(new MinINode(sub, igvn->intcon(scaled_iters)));
1594     Node* new_limit = NULL;
1595     if (stride > 0) {
1596       new_limit = igvn->transform(new AddINode(min, iv_phi));
1597     } else {
1598       new_limit = igvn->transform(new SubINode(iv_phi, min));
1599     }
1600     Node* inner_cmp = inner_cle->cmp_node();
1601     Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
1602     Node* outer_bol = inner_bol;
1603     // cmp node for inner loop may be shared
1604     inner_cmp = inner_cmp->clone();
1605     inner_cmp->set_req(2, new_limit);
1606     inner_bol = inner_bol->clone();
1607     inner_bol->set_req(1, igvn->transform(inner_cmp));
1608     igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
1609     // Set the outer loop's exit condition too
1610     igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
1611   } else {
1612     assert(false, "should be able to adjust outer loop");
1613     IfNode* outer_le = outer_loop_end();
1614     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1615     igvn->replace_node(outer_le, iff);
1616     inner_cl->clear_strip_mined();
1617   }
1618 }
1619 
1620 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
1621   if (!in(0)) return Type::TOP;
1622   if (phase->type(in(0)) == Type::TOP)
1623     return Type::TOP;
1624 
1625   return TypeTuple::IFBOTH;
1626 }
1627 
1628 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1629   if (remove_dead_region(phase, can_reshape))  return this;
1630 
1631   return NULL;
1632 }
1633 
1634 //------------------------------filtered_type--------------------------------
1635 // Return a type based on condition control flow
1636 // A successful return will be a type that is restricted due
1637 // to a series of dominating if-tests, such as:
1638 //    if (i < 10) {
1639 //       if (i > 0) {
1640 //          here: "i" type is [1..10)
1641 //       }
1642 //    }
1643 // or a control flow merge
1644 //    if (i < 10) {
1645 //       do {
1646 //          phi( , ) -- at top of loop type is [min_int..10)
1647 //         i = ?
1648 //       } while ( i < 10)
1649 //
1650 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1651   assert(n && n->bottom_type()->is_int(), "must be int");
1652   const TypeInt* filtered_t = NULL;
1653   if (!n->is_Phi()) {
1654     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1655     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1656 
1657   } else {
1658     Node* phi    = n->as_Phi();
1659     Node* region = phi->in(0);
1660     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1661     if (region && region != C->top()) {
1662       for (uint i = 1; i < phi->req(); i++) {
1663         Node* val   = phi->in(i);
1664         Node* use_c = region->in(i);
1665         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1666         if (val_t != NULL) {
1667           if (filtered_t == NULL) {
1668             filtered_t = val_t;
1669           } else {
1670             filtered_t = filtered_t->meet(val_t)->is_int();
1671           }
1672         }
1673       }
1674     }
1675   }
1676   const TypeInt* n_t = _igvn.type(n)->is_int();
1677   if (filtered_t != NULL) {
1678     n_t = n_t->join(filtered_t)->is_int();
1679   }
1680   return n_t;
1681 }
1682 
1683 
1684 //------------------------------filtered_type_from_dominators--------------------------------
1685 // Return a possibly more restrictive type for val based on condition control flow of dominators
1686 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1687   if (val->is_Con()) {
1688      return val->bottom_type()->is_int();
1689   }
1690   uint if_limit = 10; // Max number of dominating if's visited
1691   const TypeInt* rtn_t = NULL;
1692 
1693   if (use_ctrl && use_ctrl != C->top()) {
1694     Node* val_ctrl = get_ctrl(val);
1695     uint val_dom_depth = dom_depth(val_ctrl);
1696     Node* pred = use_ctrl;
1697     uint if_cnt = 0;
1698     while (if_cnt < if_limit) {
1699       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1700         if_cnt++;
1701         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1702         if (if_t != NULL) {
1703           if (rtn_t == NULL) {
1704             rtn_t = if_t;
1705           } else {
1706             rtn_t = rtn_t->join(if_t)->is_int();
1707           }
1708         }
1709       }
1710       pred = idom(pred);
1711       if (pred == NULL || pred == C->top()) {
1712         break;
1713       }
1714       // Stop if going beyond definition block of val
1715       if (dom_depth(pred) < val_dom_depth) {
1716         break;
1717       }
1718     }
1719   }
1720   return rtn_t;
1721 }
1722 
1723 
1724 //------------------------------dump_spec--------------------------------------
1725 // Dump special per-node info
1726 #ifndef PRODUCT
1727 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1728   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1729     BoolTest bt( test_trip()); // Added this for g++.
1730 
1731     st->print("[");
1732     bt.dump_on(st);
1733     st->print("]");
1734   }
1735   st->print(" ");
1736   IfNode::dump_spec(st);
1737 }
1738 #endif
1739 
1740 //=============================================================================
1741 //------------------------------is_member--------------------------------------
1742 // Is 'l' a member of 'this'?
1743 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1744   while( l->_nest > _nest ) l = l->_parent;
1745   return l == this;
1746 }
1747 
1748 //------------------------------set_nest---------------------------------------
1749 // Set loop tree nesting depth.  Accumulate _has_call bits.
1750 int IdealLoopTree::set_nest( uint depth ) {
1751   _nest = depth;
1752   int bits = _has_call;
1753   if( _child ) bits |= _child->set_nest(depth+1);
1754   if( bits ) _has_call = 1;
1755   if( _next  ) bits |= _next ->set_nest(depth  );
1756   return bits;
1757 }
1758 
1759 //------------------------------split_fall_in----------------------------------
1760 // Split out multiple fall-in edges from the loop header.  Move them to a
1761 // private RegionNode before the loop.  This becomes the loop landing pad.
1762 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1763   PhaseIterGVN &igvn = phase->_igvn;
1764   uint i;
1765 
1766   // Make a new RegionNode to be the landing pad.
1767   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1768   phase->set_loop(landing_pad,_parent);
1769   // Gather all the fall-in control paths into the landing pad
1770   uint icnt = fall_in_cnt;
1771   uint oreq = _head->req();
1772   for( i = oreq-1; i>0; i-- )
1773     if( !phase->is_member( this, _head->in(i) ) )
1774       landing_pad->set_req(icnt--,_head->in(i));
1775 
1776   // Peel off PhiNode edges as well
1777   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1778     Node *oj = _head->fast_out(j);
1779     if( oj->is_Phi() ) {
1780       PhiNode* old_phi = oj->as_Phi();
1781       assert( old_phi->region() == _head, "" );
1782       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1783       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1784       uint icnt = fall_in_cnt;
1785       for( i = oreq-1; i>0; i-- ) {
1786         if( !phase->is_member( this, _head->in(i) ) ) {
1787           p->init_req(icnt--, old_phi->in(i));
1788           // Go ahead and clean out old edges from old phi
1789           old_phi->del_req(i);
1790         }
1791       }
1792       // Search for CSE's here, because ZKM.jar does a lot of
1793       // loop hackery and we need to be a little incremental
1794       // with the CSE to avoid O(N^2) node blow-up.
1795       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1796       if( p2 ) {                // Found CSE
1797         p->destruct();          // Recover useless new node
1798         p = p2;                 // Use old node
1799       } else {
1800         igvn.register_new_node_with_optimizer(p, old_phi);
1801       }
1802       // Make old Phi refer to new Phi.
1803       old_phi->add_req(p);
1804       // Check for the special case of making the old phi useless and
1805       // disappear it.  In JavaGrande I have a case where this useless
1806       // Phi is the loop limit and prevents recognizing a CountedLoop
1807       // which in turn prevents removing an empty loop.
1808       Node *id_old_phi = igvn.apply_identity(old_phi);
1809       if( id_old_phi != old_phi ) { // Found a simple identity?
1810         // Note that I cannot call 'replace_node' here, because
1811         // that will yank the edge from old_phi to the Region and
1812         // I'm mid-iteration over the Region's uses.
1813         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1814           Node* use = old_phi->last_out(i);
1815           igvn.rehash_node_delayed(use);
1816           uint uses_found = 0;
1817           for (uint j = 0; j < use->len(); j++) {
1818             if (use->in(j) == old_phi) {
1819               if (j < use->req()) use->set_req (j, id_old_phi);
1820               else                use->set_prec(j, id_old_phi);
1821               uses_found++;
1822             }
1823           }
1824           i -= uses_found;    // we deleted 1 or more copies of this edge
1825         }
1826       }
1827       igvn._worklist.push(old_phi);
1828     }
1829   }
1830   // Finally clean out the fall-in edges from the RegionNode
1831   for( i = oreq-1; i>0; i-- ) {
1832     if( !phase->is_member( this, _head->in(i) ) ) {
1833       _head->del_req(i);
1834     }
1835   }
1836   igvn.rehash_node_delayed(_head);
1837   // Transform landing pad
1838   igvn.register_new_node_with_optimizer(landing_pad, _head);
1839   // Insert landing pad into the header
1840   _head->add_req(landing_pad);
1841 }
1842 
1843 //------------------------------split_outer_loop-------------------------------
1844 // Split out the outermost loop from this shared header.
1845 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1846   PhaseIterGVN &igvn = phase->_igvn;
1847 
1848   // Find index of outermost loop; it should also be my tail.
1849   uint outer_idx = 1;
1850   while( _head->in(outer_idx) != _tail ) outer_idx++;
1851 
1852   // Make a LoopNode for the outermost loop.
1853   Node *ctl = _head->in(LoopNode::EntryControl);
1854   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1855   outer = igvn.register_new_node_with_optimizer(outer, _head);
1856   phase->set_created_loop_node();
1857 
1858   // Outermost loop falls into '_head' loop
1859   _head->set_req(LoopNode::EntryControl, outer);
1860   _head->del_req(outer_idx);
1861   // Split all the Phis up between '_head' loop and 'outer' loop.
1862   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1863     Node *out = _head->fast_out(j);
1864     if( out->is_Phi() ) {
1865       PhiNode *old_phi = out->as_Phi();
1866       assert( old_phi->region() == _head, "" );
1867       Node *phi = PhiNode::make_blank(outer, old_phi);
1868       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1869       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1870       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1871       // Make old Phi point to new Phi on the fall-in path
1872       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1873       old_phi->del_req(outer_idx);
1874     }
1875   }
1876 
1877   // Use the new loop head instead of the old shared one
1878   _head = outer;
1879   phase->set_loop(_head, this);
1880 }
1881 
1882 //------------------------------fix_parent-------------------------------------
1883 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1884   loop->_parent = parent;
1885   if( loop->_child ) fix_parent( loop->_child, loop   );
1886   if( loop->_next  ) fix_parent( loop->_next , parent );
1887 }
1888 
1889 //------------------------------estimate_path_freq-----------------------------
1890 static float estimate_path_freq( Node *n ) {
1891   // Try to extract some path frequency info
1892   IfNode *iff;
1893   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1894     uint nop = n->Opcode();
1895     if( nop == Op_SafePoint ) {   // Skip any safepoint
1896       n = n->in(0);
1897       continue;
1898     }
1899     if( nop == Op_CatchProj ) {   // Get count from a prior call
1900       // Assume call does not always throw exceptions: means the call-site
1901       // count is also the frequency of the fall-through path.
1902       assert( n->is_CatchProj(), "" );
1903       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1904         return 0.0f;            // Assume call exception path is rare
1905       Node *call = n->in(0)->in(0)->in(0);
1906       assert( call->is_Call(), "expect a call here" );
1907       const JVMState *jvms = ((CallNode*)call)->jvms();
1908       ciMethodData* methodData = jvms->method()->method_data();
1909       if (!methodData->is_mature())  return 0.0f; // No call-site data
1910       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1911       if ((data == NULL) || !data->is_CounterData()) {
1912         // no call profile available, try call's control input
1913         n = n->in(0);
1914         continue;
1915       }
1916       return data->as_CounterData()->count()/FreqCountInvocations;
1917     }
1918     // See if there's a gating IF test
1919     Node *n_c = n->in(0);
1920     if( !n_c->is_If() ) break;       // No estimate available
1921     iff = n_c->as_If();
1922     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1923       // Compute how much count comes on this path
1924       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1925     // Have no count info.  Skip dull uncommon-trap like branches.
1926     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1927         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1928       break;
1929     // Skip through never-taken branch; look for a real loop exit.
1930     n = iff->in(0);
1931   }
1932   return 0.0f;                  // No estimate available
1933 }
1934 
1935 //------------------------------merge_many_backedges---------------------------
1936 // Merge all the backedges from the shared header into a private Region.
1937 // Feed that region as the one backedge to this loop.
1938 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1939   uint i;
1940 
1941   // Scan for the top 2 hottest backedges
1942   float hotcnt = 0.0f;
1943   float warmcnt = 0.0f;
1944   uint hot_idx = 0;
1945   // Loop starts at 2 because slot 1 is the fall-in path
1946   for( i = 2; i < _head->req(); i++ ) {
1947     float cnt = estimate_path_freq(_head->in(i));
1948     if( cnt > hotcnt ) {       // Grab hottest path
1949       warmcnt = hotcnt;
1950       hotcnt = cnt;
1951       hot_idx = i;
1952     } else if( cnt > warmcnt ) { // And 2nd hottest path
1953       warmcnt = cnt;
1954     }
1955   }
1956 
1957   // See if the hottest backedge is worthy of being an inner loop
1958   // by being much hotter than the next hottest backedge.
1959   if( hotcnt <= 0.0001 ||
1960       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1961 
1962   // Peel out the backedges into a private merge point; peel
1963   // them all except optionally hot_idx.
1964   PhaseIterGVN &igvn = phase->_igvn;
1965 
1966   Node *hot_tail = NULL;
1967   // Make a Region for the merge point
1968   Node *r = new RegionNode(1);
1969   for( i = 2; i < _head->req(); i++ ) {
1970     if( i != hot_idx )
1971       r->add_req( _head->in(i) );
1972     else hot_tail = _head->in(i);
1973   }
1974   igvn.register_new_node_with_optimizer(r, _head);
1975   // Plug region into end of loop _head, followed by hot_tail
1976   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1977   igvn.replace_input_of(_head, 2, r);
1978   if( hot_idx ) _head->add_req(hot_tail);
1979 
1980   // Split all the Phis up between '_head' loop and the Region 'r'
1981   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1982     Node *out = _head->fast_out(j);
1983     if( out->is_Phi() ) {
1984       PhiNode* n = out->as_Phi();
1985       igvn.hash_delete(n);      // Delete from hash before hacking edges
1986       Node *hot_phi = NULL;
1987       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1988       // Check all inputs for the ones to peel out
1989       uint j = 1;
1990       for( uint i = 2; i < n->req(); i++ ) {
1991         if( i != hot_idx )
1992           phi->set_req( j++, n->in(i) );
1993         else hot_phi = n->in(i);
1994       }
1995       // Register the phi but do not transform until whole place transforms
1996       igvn.register_new_node_with_optimizer(phi, n);
1997       // Add the merge phi to the old Phi
1998       while( n->req() > 3 ) n->del_req( n->req()-1 );
1999       igvn.replace_input_of(n, 2, phi);
2000       if( hot_idx ) n->add_req(hot_phi);
2001     }
2002   }
2003 
2004 
2005   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
2006   // of self loop tree.  Turn self into a loop headed by _head and with
2007   // tail being the new merge point.
2008   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
2009   phase->set_loop(_tail,ilt);   // Adjust tail
2010   _tail = r;                    // Self's tail is new merge point
2011   phase->set_loop(r,this);
2012   ilt->_child = _child;         // New guy has my children
2013   _child = ilt;                 // Self has new guy as only child
2014   ilt->_parent = this;          // new guy has self for parent
2015   ilt->_nest = _nest;           // Same nesting depth (for now)
2016 
2017   // Starting with 'ilt', look for child loop trees using the same shared
2018   // header.  Flatten these out; they will no longer be loops in the end.
2019   IdealLoopTree **pilt = &_child;
2020   while( ilt ) {
2021     if( ilt->_head == _head ) {
2022       uint i;
2023       for( i = 2; i < _head->req(); i++ )
2024         if( _head->in(i) == ilt->_tail )
2025           break;                // Still a loop
2026       if( i == _head->req() ) { // No longer a loop
2027         // Flatten ilt.  Hang ilt's "_next" list from the end of
2028         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
2029         IdealLoopTree **cp = &ilt->_child;
2030         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
2031         *cp = ilt->_next;       // Hang next list at end of child list
2032         *pilt = ilt->_child;    // Move child up to replace ilt
2033         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
2034         ilt = ilt->_child;      // Repeat using new ilt
2035         continue;               // do not advance over ilt->_child
2036       }
2037       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
2038       phase->set_loop(_head,ilt);
2039     }
2040     pilt = &ilt->_child;        // Advance to next
2041     ilt = *pilt;
2042   }
2043 
2044   if( _child ) fix_parent( _child, this );
2045 }
2046 
2047 //------------------------------beautify_loops---------------------------------
2048 // Split shared headers and insert loop landing pads.
2049 // Insert a LoopNode to replace the RegionNode.
2050 // Return TRUE if loop tree is structurally changed.
2051 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
2052   bool result = false;
2053   // Cache parts in locals for easy
2054   PhaseIterGVN &igvn = phase->_igvn;
2055 
2056   igvn.hash_delete(_head);      // Yank from hash before hacking edges
2057 
2058   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
2059   int fall_in_cnt = 0;
2060   for( uint i = 1; i < _head->req(); i++ )
2061     if( !phase->is_member( this, _head->in(i) ) )
2062       fall_in_cnt++;
2063   assert( fall_in_cnt, "at least 1 fall-in path" );
2064   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
2065     split_fall_in( phase, fall_in_cnt );
2066 
2067   // Swap inputs to the _head and all Phis to move the fall-in edge to
2068   // the left.
2069   fall_in_cnt = 1;
2070   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
2071     fall_in_cnt++;
2072   if( fall_in_cnt > 1 ) {
2073     // Since I am just swapping inputs I do not need to update def-use info
2074     Node *tmp = _head->in(1);
2075     igvn.rehash_node_delayed(_head);
2076     _head->set_req( 1, _head->in(fall_in_cnt) );
2077     _head->set_req( fall_in_cnt, tmp );
2078     // Swap also all Phis
2079     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
2080       Node* phi = _head->fast_out(i);
2081       if( phi->is_Phi() ) {
2082         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
2083         tmp = phi->in(1);
2084         phi->set_req( 1, phi->in(fall_in_cnt) );
2085         phi->set_req( fall_in_cnt, tmp );
2086       }
2087     }
2088   }
2089   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
2090   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
2091 
2092   // If I am a shared header (multiple backedges), peel off the many
2093   // backedges into a private merge point and use the merge point as
2094   // the one true backedge.
2095   if( _head->req() > 3 ) {
2096     // Merge the many backedges into a single backedge but leave
2097     // the hottest backedge as separate edge for the following peel.
2098     merge_many_backedges( phase );
2099     result = true;
2100   }
2101 
2102   // If I have one hot backedge, peel off myself loop.
2103   // I better be the outermost loop.
2104   if (_head->req() > 3 && !_irreducible) {
2105     split_outer_loop( phase );
2106     result = true;
2107 
2108   } else if (!_head->is_Loop() && !_irreducible) {
2109     // Make a new LoopNode to replace the old loop head
2110     Node *l = new LoopNode( _head->in(1), _head->in(2) );
2111     l = igvn.register_new_node_with_optimizer(l, _head);
2112     phase->set_created_loop_node();
2113     // Go ahead and replace _head
2114     phase->_igvn.replace_node( _head, l );
2115     _head = l;
2116     phase->set_loop(_head, this);
2117   }
2118 
2119   // Now recursively beautify nested loops
2120   if( _child ) result |= _child->beautify_loops( phase );
2121   if( _next  ) result |= _next ->beautify_loops( phase );
2122   return result;
2123 }
2124 
2125 //------------------------------allpaths_check_safepts----------------------------
2126 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
2127 // encountered.  Helper for check_safepts.
2128 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
2129   assert(stack.size() == 0, "empty stack");
2130   stack.push(_tail);
2131   visited.Clear();
2132   visited.set(_tail->_idx);
2133   while (stack.size() > 0) {
2134     Node* n = stack.pop();
2135     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2136       // Terminate this path
2137     } else if (n->Opcode() == Op_SafePoint) {
2138       if (_phase->get_loop(n) != this) {
2139         if (_required_safept == NULL) _required_safept = new Node_List();
2140         _required_safept->push(n);  // save the one closest to the tail
2141       }
2142       // Terminate this path
2143     } else {
2144       uint start = n->is_Region() ? 1 : 0;
2145       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
2146       for (uint i = start; i < end; i++) {
2147         Node* in = n->in(i);
2148         assert(in->is_CFG(), "must be");
2149         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
2150           stack.push(in);
2151         }
2152       }
2153     }
2154   }
2155 }
2156 
2157 //------------------------------check_safepts----------------------------
2158 // Given dominators, try to find loops with calls that must always be
2159 // executed (call dominates loop tail).  These loops do not need non-call
2160 // safepoints (ncsfpt).
2161 //
2162 // A complication is that a safepoint in a inner loop may be needed
2163 // by an outer loop. In the following, the inner loop sees it has a
2164 // call (block 3) on every path from the head (block 2) to the
2165 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
2166 // in block 2, _but_ this leaves the outer loop without a safepoint.
2167 //
2168 //          entry  0
2169 //                 |
2170 //                 v
2171 // outer 1,2    +->1
2172 //              |  |
2173 //              |  v
2174 //              |  2<---+  ncsfpt in 2
2175 //              |_/|\   |
2176 //                 | v  |
2177 // inner 2,3      /  3  |  call in 3
2178 //               /   |  |
2179 //              v    +--+
2180 //        exit  4
2181 //
2182 //
2183 // This method creates a list (_required_safept) of ncsfpt nodes that must
2184 // be protected is created for each loop. When a ncsfpt maybe deleted, it
2185 // is first looked for in the lists for the outer loops of the current loop.
2186 //
2187 // The insights into the problem:
2188 //  A) counted loops are okay
2189 //  B) innermost loops are okay (only an inner loop can delete
2190 //     a ncsfpt needed by an outer loop)
2191 //  C) a loop is immune from an inner loop deleting a safepoint
2192 //     if the loop has a call on the idom-path
2193 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
2194 //     idom-path that is not in a nested loop
2195 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
2196 //     loop needs to be prevented from deletion by an inner loop
2197 //
2198 // There are two analyses:
2199 //  1) The first, and cheaper one, scans the loop body from
2200 //     tail to head following the idom (immediate dominator)
2201 //     chain, looking for the cases (C,D,E) above.
2202 //     Since inner loops are scanned before outer loops, there is summary
2203 //     information about inner loops.  Inner loops can be skipped over
2204 //     when the tail of an inner loop is encountered.
2205 //
2206 //  2) The second, invoked if the first fails to find a call or ncsfpt on
2207 //     the idom path (which is rare), scans all predecessor control paths
2208 //     from the tail to the head, terminating a path when a call or sfpt
2209 //     is encountered, to find the ncsfpt's that are closest to the tail.
2210 //
2211 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
2212   // Bottom up traversal
2213   IdealLoopTree* ch = _child;
2214   if (_child) _child->check_safepts(visited, stack);
2215   if (_next)  _next ->check_safepts(visited, stack);
2216 
2217   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
2218     bool  has_call         = false; // call on dom-path
2219     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
2220     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
2221     // Scan the dom-path nodes from tail to head
2222     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
2223       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2224         has_call = true;
2225         _has_sfpt = 1;          // Then no need for a safept!
2226         break;
2227       } else if (n->Opcode() == Op_SafePoint) {
2228         if (_phase->get_loop(n) == this) {
2229           has_local_ncsfpt = true;
2230           break;
2231         }
2232         if (nonlocal_ncsfpt == NULL) {
2233           nonlocal_ncsfpt = n; // save the one closest to the tail
2234         }
2235       } else {
2236         IdealLoopTree* nlpt = _phase->get_loop(n);
2237         if (this != nlpt) {
2238           // If at an inner loop tail, see if the inner loop has already
2239           // recorded seeing a call on the dom-path (and stop.)  If not,
2240           // jump to the head of the inner loop.
2241           assert(is_member(nlpt), "nested loop");
2242           Node* tail = nlpt->_tail;
2243           if (tail->in(0)->is_If()) tail = tail->in(0);
2244           if (n == tail) {
2245             // If inner loop has call on dom-path, so does outer loop
2246             if (nlpt->_has_sfpt) {
2247               has_call = true;
2248               _has_sfpt = 1;
2249               break;
2250             }
2251             // Skip to head of inner loop
2252             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
2253             n = nlpt->_head;
2254           }
2255         }
2256       }
2257     }
2258     // Record safept's that this loop needs preserved when an
2259     // inner loop attempts to delete it's safepoints.
2260     if (_child != NULL && !has_call && !has_local_ncsfpt) {
2261       if (nonlocal_ncsfpt != NULL) {
2262         if (_required_safept == NULL) _required_safept = new Node_List();
2263         _required_safept->push(nonlocal_ncsfpt);
2264       } else {
2265         // Failed to find a suitable safept on the dom-path.  Now use
2266         // an all paths walk from tail to head, looking for safepoints to preserve.
2267         allpaths_check_safepts(visited, stack);
2268       }
2269     }
2270   }
2271 }
2272 
2273 //---------------------------is_deleteable_safept----------------------------
2274 // Is safept not required by an outer loop?
2275 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
2276   assert(sfpt->Opcode() == Op_SafePoint, "");
2277   IdealLoopTree* lp = get_loop(sfpt)->_parent;
2278   while (lp != NULL) {
2279     Node_List* sfpts = lp->_required_safept;
2280     if (sfpts != NULL) {
2281       for (uint i = 0; i < sfpts->size(); i++) {
2282         if (sfpt == sfpts->at(i))
2283           return false;
2284       }
2285     }
2286     lp = lp->_parent;
2287   }
2288   return true;
2289 }
2290 
2291 //---------------------------replace_parallel_iv-------------------------------
2292 // Replace parallel induction variable (parallel to trip counter)
2293 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
2294   assert(loop->_head->is_CountedLoop(), "");
2295   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2296   if (!cl->is_valid_counted_loop())
2297     return;         // skip malformed counted loop
2298   Node *incr = cl->incr();
2299   if (incr == NULL)
2300     return;         // Dead loop?
2301   Node *init = cl->init_trip();
2302   Node *phi  = cl->phi();
2303   int stride_con = cl->stride_con();
2304 
2305   // Visit all children, looking for Phis
2306   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
2307     Node *out = cl->out(i);
2308     // Look for other phis (secondary IVs). Skip dead ones
2309     if (!out->is_Phi() || out == phi || !has_node(out))
2310       continue;
2311     PhiNode* phi2 = out->as_Phi();
2312     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
2313     // Look for induction variables of the form:  X += constant
2314     if (phi2->region() != loop->_head ||
2315         incr2->req() != 3 ||
2316         incr2->in(1) != phi2 ||
2317         incr2 == incr ||
2318         incr2->Opcode() != Op_AddI ||
2319         !incr2->in(2)->is_Con())
2320       continue;
2321 
2322     // Check for parallel induction variable (parallel to trip counter)
2323     // via an affine function.  In particular, count-down loops with
2324     // count-up array indices are common. We only RCE references off
2325     // the trip-counter, so we need to convert all these to trip-counter
2326     // expressions.
2327     Node *init2 = phi2->in( LoopNode::EntryControl );
2328     int stride_con2 = incr2->in(2)->get_int();
2329 
2330     // The ratio of the two strides cannot be represented as an int
2331     // if stride_con2 is min_int and stride_con is -1.
2332     if (stride_con2 == min_jint && stride_con == -1) {
2333       continue;
2334     }
2335 
2336     // The general case here gets a little tricky.  We want to find the
2337     // GCD of all possible parallel IV's and make a new IV using this
2338     // GCD for the loop.  Then all possible IVs are simple multiples of
2339     // the GCD.  In practice, this will cover very few extra loops.
2340     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
2341     // where +/-1 is the common case, but other integer multiples are
2342     // also easy to handle.
2343     int ratio_con = stride_con2/stride_con;
2344 
2345     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
2346 #ifndef PRODUCT
2347       if (TraceLoopOpts) {
2348         tty->print("Parallel IV: %d ", phi2->_idx);
2349         loop->dump_head();
2350       }
2351 #endif
2352       // Convert to using the trip counter.  The parallel induction
2353       // variable differs from the trip counter by a loop-invariant
2354       // amount, the difference between their respective initial values.
2355       // It is scaled by the 'ratio_con'.
2356       Node* ratio = _igvn.intcon(ratio_con);
2357       set_ctrl(ratio, C->root());
2358       Node* ratio_init = new MulINode(init, ratio);
2359       _igvn.register_new_node_with_optimizer(ratio_init, init);
2360       set_early_ctrl(ratio_init);
2361       Node* diff = new SubINode(init2, ratio_init);
2362       _igvn.register_new_node_with_optimizer(diff, init2);
2363       set_early_ctrl(diff);
2364       Node* ratio_idx = new MulINode(phi, ratio);
2365       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
2366       set_ctrl(ratio_idx, cl);
2367       Node* add = new AddINode(ratio_idx, diff);
2368       _igvn.register_new_node_with_optimizer(add);
2369       set_ctrl(add, cl);
2370       _igvn.replace_node( phi2, add );
2371       // Sometimes an induction variable is unused
2372       if (add->outcnt() == 0) {
2373         _igvn.remove_dead_node(add);
2374       }
2375       --i; // deleted this phi; rescan starting with next position
2376       continue;
2377     }
2378   }
2379 }
2380 
2381 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
2382   Node* keep = NULL;
2383   if (keep_one) {
2384     // Look for a safepoint on the idom-path.
2385     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
2386       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
2387         keep = i;
2388         break; // Found one
2389       }
2390     }
2391   }
2392 
2393   // Don't remove any safepoints if it is requested to keep a single safepoint and
2394   // no safepoint was found on idom-path. It is not safe to remove any safepoint
2395   // in this case since there's no safepoint dominating all paths in the loop body.
2396   bool prune = !keep_one || keep != NULL;
2397 
2398   // Delete other safepoints in this loop.
2399   Node_List* sfpts = _safepts;
2400   if (prune && sfpts != NULL) {
2401     assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
2402     for (uint i = 0; i < sfpts->size(); i++) {
2403       Node* n = sfpts->at(i);
2404       assert(phase->get_loop(n) == this, "");
2405       if (n != keep && phase->is_deleteable_safept(n)) {
2406         phase->lazy_replace(n, n->in(TypeFunc::Control));
2407       }
2408     }
2409   }
2410 }
2411 
2412 //------------------------------counted_loop-----------------------------------
2413 // Convert to counted loops where possible
2414 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
2415 
2416   // For grins, set the inner-loop flag here
2417   if (!_child) {
2418     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
2419   }
2420 
2421   IdealLoopTree* loop = this;
2422   if (_head->is_CountedLoop() ||
2423       phase->is_counted_loop(_head, loop)) {
2424 
2425     if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) {
2426       // Indicate we do not need a safepoint here
2427       _has_sfpt = 1;
2428     }
2429 
2430     // Remove safepoints
2431     bool keep_one_sfpt = !(_has_call || _has_sfpt);
2432     remove_safepoints(phase, keep_one_sfpt);
2433 
2434     // Look for induction variables
2435     phase->replace_parallel_iv(this);
2436 
2437   } else if (_parent != NULL && !_irreducible) {
2438     // Not a counted loop. Keep one safepoint.
2439     bool keep_one_sfpt = true;
2440     remove_safepoints(phase, keep_one_sfpt);
2441   }
2442 
2443   // Recursively
2444   assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
2445   assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops");
2446   if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
2447   if (loop->_next)  loop->_next ->counted_loop(phase);
2448 }
2449 
2450 #ifndef PRODUCT
2451 //------------------------------dump_head--------------------------------------
2452 // Dump 1 liner for loop header info
2453 void IdealLoopTree::dump_head( ) const {
2454   for (uint i=0; i<_nest; i++)
2455     tty->print("  ");
2456   tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
2457   if (_irreducible) tty->print(" IRREDUCIBLE");
2458   Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl);
2459   Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
2460   if (predicate != NULL ) {
2461     tty->print(" limit_check");
2462     entry = PhaseIdealLoop::skip_loop_predicates(entry);
2463   }
2464   if (UseLoopPredicate) {
2465     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2466     if (entry != NULL) {
2467       tty->print(" predicated");
2468       entry = PhaseIdealLoop::skip_loop_predicates(entry);
2469     }
2470   }
2471   if (UseProfiledLoopPredicate) {
2472     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
2473     if (entry != NULL) {
2474       tty->print(" profile_predicated");
2475     }
2476   }
2477   if (_head->is_CountedLoop()) {
2478     CountedLoopNode *cl = _head->as_CountedLoop();
2479     tty->print(" counted");
2480 
2481     Node* init_n = cl->init_trip();
2482     if (init_n  != NULL &&  init_n->is_Con())
2483       tty->print(" [%d,", cl->init_trip()->get_int());
2484     else
2485       tty->print(" [int,");
2486     Node* limit_n = cl->limit();
2487     if (limit_n  != NULL &&  limit_n->is_Con())
2488       tty->print("%d),", cl->limit()->get_int());
2489     else
2490       tty->print("int),");
2491     int stride_con  = cl->stride_con();
2492     if (stride_con > 0) tty->print("+");
2493     tty->print("%d", stride_con);
2494 
2495     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
2496 
2497     if (cl->is_pre_loop ()) tty->print(" pre" );
2498     if (cl->is_main_loop()) tty->print(" main");
2499     if (cl->is_post_loop()) tty->print(" post");
2500     if (cl->is_vectorized_loop()) tty->print(" vector");
2501     if (cl->range_checks_present()) tty->print(" rc ");
2502     if (cl->is_multiversioned()) tty->print(" multi ");
2503   }
2504   if (_has_call) tty->print(" has_call");
2505   if (_has_sfpt) tty->print(" has_sfpt");
2506   if (_rce_candidate) tty->print(" rce");
2507   if (_safepts != NULL && _safepts->size() > 0) {
2508     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
2509   }
2510   if (_required_safept != NULL && _required_safept->size() > 0) {
2511     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
2512   }
2513   if (Verbose) {
2514     tty->print(" body={"); _body.dump_simple(); tty->print(" }");
2515   }
2516   if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
2517     tty->print(" strip_mined");
2518   }
2519   tty->cr();
2520 }
2521 
2522 //------------------------------dump-------------------------------------------
2523 // Dump loops by loop tree
2524 void IdealLoopTree::dump( ) const {
2525   dump_head();
2526   if (_child) _child->dump();
2527   if (_next)  _next ->dump();
2528 }
2529 
2530 #endif
2531 
2532 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
2533   if (loop == root) {
2534     if (loop->_child != NULL) {
2535       log->begin_head("loop_tree");
2536       log->end_head();
2537       if( loop->_child ) log_loop_tree(root, loop->_child, log);
2538       log->tail("loop_tree");
2539       assert(loop->_next == NULL, "what?");
2540     }
2541   } else {
2542     Node* head = loop->_head;
2543     log->begin_head("loop");
2544     log->print(" idx='%d' ", head->_idx);
2545     if (loop->_irreducible) log->print("irreducible='1' ");
2546     if (head->is_Loop()) {
2547       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
2548       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
2549     }
2550     if (head->is_CountedLoop()) {
2551       CountedLoopNode* cl = head->as_CountedLoop();
2552       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
2553       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
2554       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
2555     }
2556     log->end_head();
2557     if( loop->_child ) log_loop_tree(root, loop->_child, log);
2558     log->tail("loop");
2559     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
2560   }
2561 }
2562 
2563 //---------------------collect_potentially_useful_predicates-----------------------
2564 // Helper function to collect potentially useful predicates to prevent them from
2565 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
2566 void PhaseIdealLoop::collect_potentially_useful_predicates(
2567                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
2568   if (loop->_child) { // child
2569     collect_potentially_useful_predicates(loop->_child, useful_predicates);
2570   }
2571 
2572   // self (only loops that we can apply loop predication may use their predicates)
2573   if (loop->_head->is_Loop() &&
2574       !loop->_irreducible    &&
2575       !loop->tail()->is_top()) {
2576     LoopNode* lpn = loop->_head->as_Loop();
2577     Node* entry = lpn->in(LoopNode::EntryControl);
2578     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2579     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2580       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2581       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2582       entry = skip_loop_predicates(entry);
2583     }
2584     predicate_proj = find_predicate(entry); // Predicate
2585     if (predicate_proj != NULL ) {
2586       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2587       entry = skip_loop_predicates(entry);
2588     }
2589     if (UseProfiledLoopPredicate) {
2590       predicate_proj = find_predicate(entry); // Predicate
2591       if (predicate_proj != NULL ) {
2592         useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2593       }
2594     }
2595   }
2596 
2597   if (loop->_next) { // sibling
2598     collect_potentially_useful_predicates(loop->_next, useful_predicates);
2599   }
2600 }
2601 
2602 //------------------------eliminate_useless_predicates-----------------------------
2603 // Eliminate all inserted predicates if they could not be used by loop predication.
2604 // Note: it will also eliminates loop limits check predicate since it also uses
2605 // Opaque1 node (see Parse::add_predicate()).
2606 void PhaseIdealLoop::eliminate_useless_predicates() {
2607   if (C->predicate_count() == 0)
2608     return; // no predicate left
2609 
2610   Unique_Node_List useful_predicates; // to store useful predicates
2611   if (C->has_loops()) {
2612     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2613   }
2614 
2615   for (int i = C->predicate_count(); i > 0; i--) {
2616      Node * n = C->predicate_opaque1_node(i-1);
2617      assert(n->Opcode() == Op_Opaque1, "must be");
2618      if (!useful_predicates.member(n)) { // not in the useful list
2619        _igvn.replace_node(n, n->in(1));
2620      }
2621   }
2622 }
2623 
2624 //------------------------process_expensive_nodes-----------------------------
2625 // Expensive nodes have their control input set to prevent the GVN
2626 // from commoning them and as a result forcing the resulting node to
2627 // be in a more frequent path. Use CFG information here, to change the
2628 // control inputs so that some expensive nodes can be commoned while
2629 // not executed more frequently.
2630 bool PhaseIdealLoop::process_expensive_nodes() {
2631   assert(OptimizeExpensiveOps, "optimization off?");
2632 
2633   // Sort nodes to bring similar nodes together
2634   C->sort_expensive_nodes();
2635 
2636   bool progress = false;
2637 
2638   for (int i = 0; i < C->expensive_count(); ) {
2639     Node* n = C->expensive_node(i);
2640     int start = i;
2641     // Find nodes similar to n
2642     i++;
2643     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2644     int end = i;
2645     // And compare them two by two
2646     for (int j = start; j < end; j++) {
2647       Node* n1 = C->expensive_node(j);
2648       if (is_node_unreachable(n1)) {
2649         continue;
2650       }
2651       for (int k = j+1; k < end; k++) {
2652         Node* n2 = C->expensive_node(k);
2653         if (is_node_unreachable(n2)) {
2654           continue;
2655         }
2656 
2657         assert(n1 != n2, "should be pair of nodes");
2658 
2659         Node* c1 = n1->in(0);
2660         Node* c2 = n2->in(0);
2661 
2662         Node* parent_c1 = c1;
2663         Node* parent_c2 = c2;
2664 
2665         // The call to get_early_ctrl_for_expensive() moves the
2666         // expensive nodes up but stops at loops that are in a if
2667         // branch. See whether we can exit the loop and move above the
2668         // If.
2669         if (c1->is_Loop()) {
2670           parent_c1 = c1->in(1);
2671         }
2672         if (c2->is_Loop()) {
2673           parent_c2 = c2->in(1);
2674         }
2675 
2676         if (parent_c1 == parent_c2) {
2677           _igvn._worklist.push(n1);
2678           _igvn._worklist.push(n2);
2679           continue;
2680         }
2681 
2682         // Look for identical expensive node up the dominator chain.
2683         if (is_dominator(c1, c2)) {
2684           c2 = c1;
2685         } else if (is_dominator(c2, c1)) {
2686           c1 = c2;
2687         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2688                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2689           // Both branches have the same expensive node so move it up
2690           // before the if.
2691           c1 = c2 = idom(parent_c1->in(0));
2692         }
2693         // Do the actual moves
2694         if (n1->in(0) != c1) {
2695           _igvn.hash_delete(n1);
2696           n1->set_req(0, c1);
2697           _igvn.hash_insert(n1);
2698           _igvn._worklist.push(n1);
2699           progress = true;
2700         }
2701         if (n2->in(0) != c2) {
2702           _igvn.hash_delete(n2);
2703           n2->set_req(0, c2);
2704           _igvn.hash_insert(n2);
2705           _igvn._worklist.push(n2);
2706           progress = true;
2707         }
2708       }
2709     }
2710   }
2711 
2712   return progress;
2713 }
2714 
2715 
2716 //=============================================================================
2717 //----------------------------build_and_optimize-------------------------------
2718 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2719 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2720 void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) {
2721   bool do_split_ifs = (mode == LoopOptsDefault || mode == LoopOptsZgcLastRound);
2722   bool skip_loop_opts = (mode == LoopOptsNone) ;
2723   bool shenandoah_opts = (mode == LoopOptsShenandoahExpand ||
2724                           mode == LoopOptsShenandoahPostExpand);
2725 
2726   ResourceMark rm;
2727 
2728   int old_progress = C->major_progress();
2729   uint orig_worklist_size = _igvn._worklist.size();
2730 
2731   // Reset major-progress flag for the driver's heuristics
2732   C->clear_major_progress();
2733 
2734 #ifndef PRODUCT
2735   // Capture for later assert
2736   uint unique = C->unique();
2737   _loop_invokes++;
2738   _loop_work += unique;
2739 #endif
2740 
2741   // True if the method has at least 1 irreducible loop
2742   _has_irreducible_loops = false;
2743 
2744   _created_loop_node = false;
2745 
2746   Arena *a = Thread::current()->resource_area();
2747   VectorSet visited(a);
2748   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2749   _nodes.map(C->unique(), NULL);
2750   memset(_nodes.adr(), 0, wordSize * C->unique());
2751 
2752   // Pre-build the top-level outermost loop tree entry
2753   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2754   // Do not need a safepoint at the top level
2755   _ltree_root->_has_sfpt = 1;
2756 
2757   // Initialize Dominators.
2758   // Checked in clone_loop_predicate() during beautify_loops().
2759   _idom_size = 0;
2760   _idom      = NULL;
2761   _dom_depth = NULL;
2762   _dom_stk   = NULL;
2763 
2764   // Empty pre-order array
2765   allocate_preorders();
2766 
2767   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2768   // IdealLoopTree entries.  Data nodes are NOT walked.
2769   build_loop_tree();
2770   // Check for bailout, and return
2771   if (C->failing()) {
2772     return;
2773   }
2774 
2775   // No loops after all
2776   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2777 
2778   // There should always be an outer loop containing the Root and Return nodes.
2779   // If not, we have a degenerate empty program.  Bail out in this case.
2780   if (!has_node(C->root())) {
2781     if (!_verify_only) {
2782       C->clear_major_progress();
2783       C->record_method_not_compilable("empty program detected during loop optimization");
2784     }
2785     return;
2786   }
2787 
2788   // Nothing to do, so get out
2789   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only && !shenandoah_opts;
2790   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2791   if (stop_early && !do_expensive_nodes) {
2792     _igvn.optimize();           // Cleanup NeverBranches
2793     return;
2794   }
2795 
2796   // Set loop nesting depth
2797   _ltree_root->set_nest( 0 );
2798 
2799   // Split shared headers and insert loop landing pads.
2800   // Do not bother doing this on the Root loop of course.
2801   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2802     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2803     if( _ltree_root->_child->beautify_loops( this ) ) {
2804       // Re-build loop tree!
2805       _ltree_root->_child = NULL;
2806       _nodes.clear();
2807       reallocate_preorders();
2808       build_loop_tree();
2809       // Check for bailout, and return
2810       if (C->failing()) {
2811         return;
2812       }
2813       // Reset loop nesting depth
2814       _ltree_root->set_nest( 0 );
2815 
2816       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2817     }
2818   }
2819 
2820   // Build Dominators for elision of NULL checks & loop finding.
2821   // Since nodes do not have a slot for immediate dominator, make
2822   // a persistent side array for that info indexed on node->_idx.
2823   _idom_size = C->unique();
2824   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2825   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2826   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2827   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2828 
2829   Dominators();
2830 
2831   if (!_verify_only) {
2832     // As a side effect, Dominators removed any unreachable CFG paths
2833     // into RegionNodes.  It doesn't do this test against Root, so
2834     // we do it here.
2835     for( uint i = 1; i < C->root()->req(); i++ ) {
2836       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2837         _igvn.delete_input_of(C->root(), i);
2838         i--;                      // Rerun same iteration on compressed edges
2839       }
2840     }
2841 
2842     // Given dominators, try to find inner loops with calls that must
2843     // always be executed (call dominates loop tail).  These loops do
2844     // not need a separate safepoint.
2845     Node_List cisstack(a);
2846     _ltree_root->check_safepts(visited, cisstack);
2847   }
2848 
2849   // Walk the DATA nodes and place into loops.  Find earliest control
2850   // node.  For CFG nodes, the _nodes array starts out and remains
2851   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2852   // _nodes array holds the earliest legal controlling CFG node.
2853 
2854   // Allocate stack with enough space to avoid frequent realloc
2855   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2856   Node_Stack nstack( a, stack_size );
2857 
2858   visited.Clear();
2859   Node_List worklist(a);
2860   // Don't need C->root() on worklist since
2861   // it will be processed among C->top() inputs
2862   worklist.push( C->top() );
2863   visited.set( C->top()->_idx ); // Set C->top() as visited now
2864   build_loop_early( visited, worklist, nstack );
2865 
2866   // Given early legal placement, try finding counted loops.  This placement
2867   // is good enough to discover most loop invariants.
2868   if (!_verify_me && !_verify_only && !shenandoah_opts) {
2869     _ltree_root->counted_loop(this);
2870   }
2871 
2872   // Find latest loop placement.  Find ideal loop placement.
2873   visited.Clear();
2874   init_dom_lca_tags();
2875   // Need C->root() on worklist when processing outs
2876   worklist.push( C->root() );
2877   NOT_PRODUCT( C->verify_graph_edges(); )
2878   worklist.push( C->top() );
2879   build_loop_late(visited, worklist, nstack, !shenandoah_opts);
2880 
2881   if (_verify_only) {
2882     // restore major progress flag
2883     for (int i = 0; i < old_progress; i++)
2884       C->set_major_progress();
2885     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2886     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2887     return;
2888   }
2889 
2890   // clear out the dead code after build_loop_late
2891   while (_deadlist.size()) {
2892     _igvn.remove_globally_dead_node(_deadlist.pop());
2893   }
2894 
2895   if (stop_early) {
2896     assert(do_expensive_nodes, "why are we here?");
2897     if (process_expensive_nodes()) {
2898       // If we made some progress when processing expensive nodes then
2899       // the IGVN may modify the graph in a way that will allow us to
2900       // make some more progress: we need to try processing expensive
2901       // nodes again.
2902       C->set_major_progress();
2903     }
2904     _igvn.optimize();
2905     return;
2906   }
2907 
2908   // Some parser-inserted loop predicates could never be used by loop
2909   // predication or they were moved away from loop during some optimizations.
2910   // For example, peeling. Eliminate them before next loop optimizations.
2911   eliminate_useless_predicates();
2912 
2913 #ifndef PRODUCT
2914   C->verify_graph_edges();
2915   if (_verify_me) {             // Nested verify pass?
2916     // Check to see if the verify mode is broken
2917     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2918     return;
2919   }
2920   if(VerifyLoopOptimizations) verify();
2921   if(TraceLoopOpts && C->has_loops()) {
2922     _ltree_root->dump();
2923   }
2924 #endif
2925 
2926   if (skip_loop_opts) {
2927     // restore major progress flag
2928     for (int i = 0; i < old_progress; i++) {
2929       C->set_major_progress();
2930     }
2931 
2932     // Cleanup any modified bits
2933     _igvn.optimize();
2934 
2935     if (C->log() != NULL) {
2936       log_loop_tree(_ltree_root, _ltree_root, C->log());
2937     }
2938     return;
2939   }
2940 
2941 #if INCLUDE_SHENANDOAHGC
2942   if (UseShenandoahGC && ((ShenandoahBarrierSetC2*) BarrierSet::barrier_set()->barrier_set_c2())->optimize_loops(this, mode, visited, nstack, worklist)) {
2943     _igvn.optimize();
2944     if (C->log() != NULL) {
2945       log_loop_tree(_ltree_root, _ltree_root, C->log());
2946     }
2947     return;
2948   }
2949 #endif
2950 
2951   if (ReassociateInvariants) {
2952     // Reassociate invariants and prep for split_thru_phi
2953     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2954       IdealLoopTree* lpt = iter.current();
2955       bool is_counted = lpt->is_counted();
2956       if (!is_counted || !lpt->is_inner()) continue;
2957 
2958       // check for vectorized loops, any reassociation of invariants was already done
2959       if (is_counted && lpt->_head->as_CountedLoop()->do_unroll_only()) continue;
2960 
2961       lpt->reassociate_invariants(this);
2962 
2963       // Because RCE opportunities can be masked by split_thru_phi,
2964       // look for RCE candidates and inhibit split_thru_phi
2965       // on just their loop-phi's for this pass of loop opts
2966       if (SplitIfBlocks && do_split_ifs) {
2967         if (lpt->policy_range_check(this)) {
2968           lpt->_rce_candidate = 1; // = true
2969         }
2970       }
2971     }
2972   }
2973 
2974   // Check for aggressive application of split-if and other transforms
2975   // that require basic-block info (like cloning through Phi's)
2976   if( SplitIfBlocks && do_split_ifs ) {
2977     visited.Clear();
2978     split_if_with_blocks( visited, nstack, mode == LoopOptsZgcLastRound );
2979     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2980     if (mode == LoopOptsZgcLastRound) {
2981       C->set_major_progress();
2982     }
2983   }
2984 
2985   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
2986     C->set_major_progress();
2987   }
2988 
2989   // Perform loop predication before iteration splitting
2990   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2991     _ltree_root->_child->loop_predication(this);
2992   }
2993 
2994   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2995     if (do_intrinsify_fill()) {
2996       C->set_major_progress();
2997     }
2998   }
2999 
3000   // Perform iteration-splitting on inner loops.  Split iterations to avoid
3001   // range checks or one-shot null checks.
3002 
3003   // If split-if's didn't hack the graph too bad (no CFG changes)
3004   // then do loop opts.
3005   if (C->has_loops() && !C->major_progress()) {
3006     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3007     _ltree_root->_child->iteration_split( this, worklist );
3008     // No verify after peeling!  GCM has hoisted code out of the loop.
3009     // After peeling, the hoisted code could sink inside the peeled area.
3010     // The peeling code does not try to recompute the best location for
3011     // all the code before the peeled area, so the verify pass will always
3012     // complain about it.
3013   }
3014   // Do verify graph edges in any case
3015   NOT_PRODUCT( C->verify_graph_edges(); );
3016 
3017   if (!do_split_ifs) {
3018     // We saw major progress in Split-If to get here.  We forced a
3019     // pass with unrolling and not split-if, however more split-if's
3020     // might make progress.  If the unrolling didn't make progress
3021     // then the major-progress flag got cleared and we won't try
3022     // another round of Split-If.  In particular the ever-common
3023     // instance-of/check-cast pattern requires at least 2 rounds of
3024     // Split-If to clear out.
3025     C->set_major_progress();
3026   }
3027 
3028   // Repeat loop optimizations if new loops were seen
3029   if (created_loop_node()) {
3030     C->set_major_progress();
3031   }
3032 
3033   // Keep loop predicates and perform optimizations with them
3034   // until no more loop optimizations could be done.
3035   // After that switch predicates off and do more loop optimizations.
3036   if (!C->major_progress() && (C->predicate_count() > 0)) {
3037      C->cleanup_loop_predicates(_igvn);
3038      if (TraceLoopOpts) {
3039        tty->print_cr("PredicatesOff");
3040      }
3041      C->set_major_progress();
3042   }
3043 
3044   // Convert scalar to superword operations at the end of all loop opts.
3045   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
3046     // SuperWord transform
3047     SuperWord sw(this);
3048     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3049       IdealLoopTree* lpt = iter.current();
3050       if (lpt->is_counted()) {
3051         CountedLoopNode *cl = lpt->_head->as_CountedLoop();
3052 
3053         if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
3054           // Check that the rce'd post loop is encountered first, multiversion after all
3055           // major main loop optimization are concluded
3056           if (!C->major_progress()) {
3057             IdealLoopTree *lpt_next = lpt->_next;
3058             if (lpt_next && lpt_next->is_counted()) {
3059               CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
3060               has_range_checks(lpt_next);
3061               if (cl->is_post_loop() && cl->range_checks_present()) {
3062                 if (!cl->is_multiversioned()) {
3063                   if (multi_version_post_loops(lpt, lpt_next) == false) {
3064                     // Cause the rce loop to be optimized away if we fail
3065                     cl->mark_is_multiversioned();
3066                     cl->set_slp_max_unroll(0);
3067                     poison_rce_post_loop(lpt);
3068                   }
3069                 }
3070               }
3071             }
3072             sw.transform_loop(lpt, true);
3073           }
3074         } else if (cl->is_main_loop()) {
3075           sw.transform_loop(lpt, true);
3076         }
3077       }
3078     }
3079   }
3080 
3081   // Cleanup any modified bits
3082   _igvn.optimize();
3083 
3084   // disable assert until issue with split_flow_path is resolved (6742111)
3085   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
3086   //        "shouldn't introduce irreducible loops");
3087 
3088   if (C->log() != NULL) {
3089     log_loop_tree(_ltree_root, _ltree_root, C->log());
3090   }
3091 }
3092 
3093 #ifndef PRODUCT
3094 //------------------------------print_statistics-------------------------------
3095 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
3096 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
3097 void PhaseIdealLoop::print_statistics() {
3098   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
3099 }
3100 
3101 //------------------------------verify-----------------------------------------
3102 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
3103 static int fail;                // debug only, so its multi-thread dont care
3104 void PhaseIdealLoop::verify() const {
3105   int old_progress = C->major_progress();
3106   ResourceMark rm;
3107   PhaseIdealLoop loop_verify( _igvn, this );
3108   VectorSet visited(Thread::current()->resource_area());
3109 
3110   fail = 0;
3111   verify_compare( C->root(), &loop_verify, visited );
3112   assert( fail == 0, "verify loops failed" );
3113   // Verify loop structure is the same
3114   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
3115   // Reset major-progress.  It was cleared by creating a verify version of
3116   // PhaseIdealLoop.
3117   for( int i=0; i<old_progress; i++ )
3118     C->set_major_progress();
3119 }
3120 
3121 //------------------------------verify_compare---------------------------------
3122 // Make sure me and the given PhaseIdealLoop agree on key data structures
3123 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
3124   if( !n ) return;
3125   if( visited.test_set( n->_idx ) ) return;
3126   if( !_nodes[n->_idx] ) {      // Unreachable
3127     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
3128     return;
3129   }
3130 
3131   uint i;
3132   for( i = 0; i < n->req(); i++ )
3133     verify_compare( n->in(i), loop_verify, visited );
3134 
3135   // Check the '_nodes' block/loop structure
3136   i = n->_idx;
3137   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
3138     if( _nodes[i] != loop_verify->_nodes[i] &&
3139         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
3140       tty->print("Mismatched control setting for: ");
3141       n->dump();
3142       if( fail++ > 10 ) return;
3143       Node *c = get_ctrl_no_update(n);
3144       tty->print("We have it as: ");
3145       if( c->in(0) ) c->dump();
3146         else tty->print_cr("N%d",c->_idx);
3147       tty->print("Verify thinks: ");
3148       if( loop_verify->has_ctrl(n) )
3149         loop_verify->get_ctrl_no_update(n)->dump();
3150       else
3151         loop_verify->get_loop_idx(n)->dump();
3152       tty->cr();
3153     }
3154   } else {                    // We have a loop
3155     IdealLoopTree *us = get_loop_idx(n);
3156     if( loop_verify->has_ctrl(n) ) {
3157       tty->print("Mismatched loop setting for: ");
3158       n->dump();
3159       if( fail++ > 10 ) return;
3160       tty->print("We have it as: ");
3161       us->dump();
3162       tty->print("Verify thinks: ");
3163       loop_verify->get_ctrl_no_update(n)->dump();
3164       tty->cr();
3165     } else if (!C->major_progress()) {
3166       // Loop selection can be messed up if we did a major progress
3167       // operation, like split-if.  Do not verify in that case.
3168       IdealLoopTree *them = loop_verify->get_loop_idx(n);
3169       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
3170         tty->print("Unequals loops for: ");
3171         n->dump();
3172         if( fail++ > 10 ) return;
3173         tty->print("We have it as: ");
3174         us->dump();
3175         tty->print("Verify thinks: ");
3176         them->dump();
3177         tty->cr();
3178       }
3179     }
3180   }
3181 
3182   // Check for immediate dominators being equal
3183   if( i >= _idom_size ) {
3184     if( !n->is_CFG() ) return;
3185     tty->print("CFG Node with no idom: ");
3186     n->dump();
3187     return;
3188   }
3189   if( !n->is_CFG() ) return;
3190   if( n == C->root() ) return; // No IDOM here
3191 
3192   assert(n->_idx == i, "sanity");
3193   Node *id = idom_no_update(n);
3194   if( id != loop_verify->idom_no_update(n) ) {
3195     tty->print("Unequals idoms for: ");
3196     n->dump();
3197     if( fail++ > 10 ) return;
3198     tty->print("We have it as: ");
3199     id->dump();
3200     tty->print("Verify thinks: ");
3201     loop_verify->idom_no_update(n)->dump();
3202     tty->cr();
3203   }
3204 
3205 }
3206 
3207 //------------------------------verify_tree------------------------------------
3208 // Verify that tree structures match.  Because the CFG can change, siblings
3209 // within the loop tree can be reordered.  We attempt to deal with that by
3210 // reordering the verify's loop tree if possible.
3211 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
3212   assert( _parent == parent, "Badly formed loop tree" );
3213 
3214   // Siblings not in same order?  Attempt to re-order.
3215   if( _head != loop->_head ) {
3216     // Find _next pointer to update
3217     IdealLoopTree **pp = &loop->_parent->_child;
3218     while( *pp != loop )
3219       pp = &((*pp)->_next);
3220     // Find proper sibling to be next
3221     IdealLoopTree **nn = &loop->_next;
3222     while( (*nn) && (*nn)->_head != _head )
3223       nn = &((*nn)->_next);
3224 
3225     // Check for no match.
3226     if( !(*nn) ) {
3227       // Annoyingly, irreducible loops can pick different headers
3228       // after a major_progress operation, so the rest of the loop
3229       // tree cannot be matched.
3230       if (_irreducible && Compile::current()->major_progress())  return;
3231       assert( 0, "failed to match loop tree" );
3232     }
3233 
3234     // Move (*nn) to (*pp)
3235     IdealLoopTree *hit = *nn;
3236     *nn = hit->_next;
3237     hit->_next = loop;
3238     *pp = loop;
3239     loop = hit;
3240     // Now try again to verify
3241   }
3242 
3243   assert( _head  == loop->_head , "mismatched loop head" );
3244   Node *tail = _tail;           // Inline a non-updating version of
3245   while( !tail->in(0) )         // the 'tail()' call.
3246     tail = tail->in(1);
3247   assert( tail == loop->_tail, "mismatched loop tail" );
3248 
3249   // Counted loops that are guarded should be able to find their guards
3250   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
3251     CountedLoopNode *cl = _head->as_CountedLoop();
3252     Node *init = cl->init_trip();
3253     Node *ctrl = cl->in(LoopNode::EntryControl);
3254     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
3255     Node *iff  = ctrl->in(0);
3256     assert( iff->Opcode() == Op_If, "" );
3257     Node *bol  = iff->in(1);
3258     assert( bol->Opcode() == Op_Bool, "" );
3259     Node *cmp  = bol->in(1);
3260     assert( cmp->Opcode() == Op_CmpI, "" );
3261     Node *add  = cmp->in(1);
3262     Node *opaq;
3263     if( add->Opcode() == Op_Opaque1 ) {
3264       opaq = add;
3265     } else {
3266       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
3267       assert( add == init, "" );
3268       opaq = cmp->in(2);
3269     }
3270     assert( opaq->Opcode() == Op_Opaque1, "" );
3271 
3272   }
3273 
3274   if (_child != NULL)  _child->verify_tree(loop->_child, this);
3275   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
3276   // Innermost loops need to verify loop bodies,
3277   // but only if no 'major_progress'
3278   int fail = 0;
3279   if (!Compile::current()->major_progress() && _child == NULL) {
3280     for( uint i = 0; i < _body.size(); i++ ) {
3281       Node *n = _body.at(i);
3282       if (n->outcnt() == 0)  continue; // Ignore dead
3283       uint j;
3284       for( j = 0; j < loop->_body.size(); j++ )
3285         if( loop->_body.at(j) == n )
3286           break;
3287       if( j == loop->_body.size() ) { // Not found in loop body
3288         // Last ditch effort to avoid assertion: Its possible that we
3289         // have some users (so outcnt not zero) but are still dead.
3290         // Try to find from root.
3291         if (Compile::current()->root()->find(n->_idx)) {
3292           fail++;
3293           tty->print("We have that verify does not: ");
3294           n->dump();
3295         }
3296       }
3297     }
3298     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
3299       Node *n = loop->_body.at(i2);
3300       if (n->outcnt() == 0)  continue; // Ignore dead
3301       uint j;
3302       for( j = 0; j < _body.size(); j++ )
3303         if( _body.at(j) == n )
3304           break;
3305       if( j == _body.size() ) { // Not found in loop body
3306         // Last ditch effort to avoid assertion: Its possible that we
3307         // have some users (so outcnt not zero) but are still dead.
3308         // Try to find from root.
3309         if (Compile::current()->root()->find(n->_idx)) {
3310           fail++;
3311           tty->print("Verify has that we do not: ");
3312           n->dump();
3313         }
3314       }
3315     }
3316     assert( !fail, "loop body mismatch" );
3317   }
3318 }
3319 
3320 #endif
3321 
3322 //------------------------------set_idom---------------------------------------
3323 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
3324   uint idx = d->_idx;
3325   if (idx >= _idom_size) {
3326     uint newsize = _idom_size<<1;
3327     while( idx >= newsize ) {
3328       newsize <<= 1;
3329     }
3330     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
3331     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
3332     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
3333     _idom_size = newsize;
3334   }
3335   _idom[idx] = n;
3336   _dom_depth[idx] = dom_depth;
3337 }
3338 
3339 //------------------------------recompute_dom_depth---------------------------------------
3340 // The dominator tree is constructed with only parent pointers.
3341 // This recomputes the depth in the tree by first tagging all
3342 // nodes as "no depth yet" marker.  The next pass then runs up
3343 // the dom tree from each node marked "no depth yet", and computes
3344 // the depth on the way back down.
3345 void PhaseIdealLoop::recompute_dom_depth() {
3346   uint no_depth_marker = C->unique();
3347   uint i;
3348   // Initialize depth to "no depth yet" and realize all lazy updates
3349   for (i = 0; i < _idom_size; i++) {
3350     // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized).
3351     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
3352       _dom_depth[i] = no_depth_marker;
3353 
3354       // heal _idom if it has a fwd mapping in _nodes
3355       if (_idom[i]->in(0) == NULL) {
3356         idom(i);
3357       }
3358     }
3359   }
3360   if (_dom_stk == NULL) {
3361     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
3362     if (init_size < 10) init_size = 10;
3363     _dom_stk = new GrowableArray<uint>(init_size);
3364   }
3365   // Compute new depth for each node.
3366   for (i = 0; i < _idom_size; i++) {
3367     uint j = i;
3368     // Run up the dom tree to find a node with a depth
3369     while (_dom_depth[j] == no_depth_marker) {
3370       _dom_stk->push(j);
3371       j = _idom[j]->_idx;
3372     }
3373     // Compute the depth on the way back down this tree branch
3374     uint dd = _dom_depth[j] + 1;
3375     while (_dom_stk->length() > 0) {
3376       uint j = _dom_stk->pop();
3377       _dom_depth[j] = dd;
3378       dd++;
3379     }
3380   }
3381 }
3382 
3383 //------------------------------sort-------------------------------------------
3384 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
3385 // loop tree, not the root.
3386 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
3387   if( !innermost ) return loop; // New innermost loop
3388 
3389   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
3390   assert( loop_preorder, "not yet post-walked loop" );
3391   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
3392   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
3393 
3394   // Insert at start of list
3395   while( l ) {                  // Insertion sort based on pre-order
3396     if( l == loop ) return innermost; // Already on list!
3397     int l_preorder = get_preorder(l->_head); // Cache pre-order number
3398     assert( l_preorder, "not yet post-walked l" );
3399     // Check header pre-order number to figure proper nesting
3400     if( loop_preorder > l_preorder )
3401       break;                    // End of insertion
3402     // If headers tie (e.g., shared headers) check tail pre-order numbers.
3403     // Since I split shared headers, you'd think this could not happen.
3404     // BUT: I must first do the preorder numbering before I can discover I
3405     // have shared headers, so the split headers all get the same preorder
3406     // number as the RegionNode they split from.
3407     if( loop_preorder == l_preorder &&
3408         get_preorder(loop->_tail) < get_preorder(l->_tail) )
3409       break;                    // Also check for shared headers (same pre#)
3410     pp = &l->_parent;           // Chain up list
3411     l = *pp;
3412   }
3413   // Link into list
3414   // Point predecessor to me
3415   *pp = loop;
3416   // Point me to successor
3417   IdealLoopTree *p = loop->_parent;
3418   loop->_parent = l;            // Point me to successor
3419   if( p ) sort( p, innermost ); // Insert my parents into list as well
3420   return innermost;
3421 }
3422 
3423 //------------------------------build_loop_tree--------------------------------
3424 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
3425 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
3426 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
3427 // tightest enclosing IdealLoopTree for post-walked.
3428 //
3429 // During my forward walk I do a short 1-layer lookahead to see if I can find
3430 // a loop backedge with that doesn't have any work on the backedge.  This
3431 // helps me construct nested loops with shared headers better.
3432 //
3433 // Once I've done the forward recursion, I do the post-work.  For each child
3434 // I check to see if there is a backedge.  Backedges define a loop!  I
3435 // insert an IdealLoopTree at the target of the backedge.
3436 //
3437 // During the post-work I also check to see if I have several children
3438 // belonging to different loops.  If so, then this Node is a decision point
3439 // where control flow can choose to change loop nests.  It is at this
3440 // decision point where I can figure out how loops are nested.  At this
3441 // time I can properly order the different loop nests from my children.
3442 // Note that there may not be any backedges at the decision point!
3443 //
3444 // Since the decision point can be far removed from the backedges, I can't
3445 // order my loops at the time I discover them.  Thus at the decision point
3446 // I need to inspect loop header pre-order numbers to properly nest my
3447 // loops.  This means I need to sort my childrens' loops by pre-order.
3448 // The sort is of size number-of-control-children, which generally limits
3449 // it to size 2 (i.e., I just choose between my 2 target loops).
3450 void PhaseIdealLoop::build_loop_tree() {
3451   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
3452   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
3453   Node *n = C->root();
3454   bltstack.push(n);
3455   int pre_order = 1;
3456   int stack_size;
3457 
3458   while ( ( stack_size = bltstack.length() ) != 0 ) {
3459     n = bltstack.top(); // Leave node on stack
3460     if ( !is_visited(n) ) {
3461       // ---- Pre-pass Work ----
3462       // Pre-walked but not post-walked nodes need a pre_order number.
3463 
3464       set_preorder_visited( n, pre_order ); // set as visited
3465 
3466       // ---- Scan over children ----
3467       // Scan first over control projections that lead to loop headers.
3468       // This helps us find inner-to-outer loops with shared headers better.
3469 
3470       // Scan children's children for loop headers.
3471       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
3472         Node* m = n->raw_out(i);       // Child
3473         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
3474           // Scan over children's children to find loop
3475           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3476             Node* l = m->fast_out(j);
3477             if( is_visited(l) &&       // Been visited?
3478                 !is_postvisited(l) &&  // But not post-visited
3479                 get_preorder(l) < pre_order ) { // And smaller pre-order
3480               // Found!  Scan the DFS down this path before doing other paths
3481               bltstack.push(m);
3482               break;
3483             }
3484           }
3485         }
3486       }
3487       pre_order++;
3488     }
3489     else if ( !is_postvisited(n) ) {
3490       // Note: build_loop_tree_impl() adds out edges on rare occasions,
3491       // such as com.sun.rsasign.am::a.
3492       // For non-recursive version, first, process current children.
3493       // On next iteration, check if additional children were added.
3494       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
3495         Node* u = n->raw_out(k);
3496         if ( u->is_CFG() && !is_visited(u) ) {
3497           bltstack.push(u);
3498         }
3499       }
3500       if ( bltstack.length() == stack_size ) {
3501         // There were no additional children, post visit node now
3502         (void)bltstack.pop(); // Remove node from stack
3503         pre_order = build_loop_tree_impl( n, pre_order );
3504         // Check for bailout
3505         if (C->failing()) {
3506           return;
3507         }
3508         // Check to grow _preorders[] array for the case when
3509         // build_loop_tree_impl() adds new nodes.
3510         check_grow_preorders();
3511       }
3512     }
3513     else {
3514       (void)bltstack.pop(); // Remove post-visited node from stack
3515     }
3516   }
3517 }
3518 
3519 //------------------------------build_loop_tree_impl---------------------------
3520 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
3521   // ---- Post-pass Work ----
3522   // Pre-walked but not post-walked nodes need a pre_order number.
3523 
3524   // Tightest enclosing loop for this Node
3525   IdealLoopTree *innermost = NULL;
3526 
3527   // For all children, see if any edge is a backedge.  If so, make a loop
3528   // for it.  Then find the tightest enclosing loop for the self Node.
3529   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3530     Node* m = n->fast_out(i);   // Child
3531     if( n == m ) continue;      // Ignore control self-cycles
3532     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
3533 
3534     IdealLoopTree *l;           // Child's loop
3535     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
3536       // Found a backedge
3537       assert( get_preorder(m) < pre_order, "should be backedge" );
3538       // Check for the RootNode, which is already a LoopNode and is allowed
3539       // to have multiple "backedges".
3540       if( m == C->root()) {     // Found the root?
3541         l = _ltree_root;        // Root is the outermost LoopNode
3542       } else {                  // Else found a nested loop
3543         // Insert a LoopNode to mark this loop.
3544         l = new IdealLoopTree(this, m, n);
3545       } // End of Else found a nested loop
3546       if( !has_loop(m) )        // If 'm' does not already have a loop set
3547         set_loop(m, l);         // Set loop header to loop now
3548 
3549     } else {                    // Else not a nested loop
3550       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
3551       l = get_loop(m);          // Get previously determined loop
3552       // If successor is header of a loop (nest), move up-loop till it
3553       // is a member of some outer enclosing loop.  Since there are no
3554       // shared headers (I've split them already) I only need to go up
3555       // at most 1 level.
3556       while( l && l->_head == m ) // Successor heads loop?
3557         l = l->_parent;         // Move up 1 for me
3558       // If this loop is not properly parented, then this loop
3559       // has no exit path out, i.e. its an infinite loop.
3560       if( !l ) {
3561         // Make loop "reachable" from root so the CFG is reachable.  Basically
3562         // insert a bogus loop exit that is never taken.  'm', the loop head,
3563         // points to 'n', one (of possibly many) fall-in paths.  There may be
3564         // many backedges as well.
3565 
3566         // Here I set the loop to be the root loop.  I could have, after
3567         // inserting a bogus loop exit, restarted the recursion and found my
3568         // new loop exit.  This would make the infinite loop a first-class
3569         // loop and it would then get properly optimized.  What's the use of
3570         // optimizing an infinite loop?
3571         l = _ltree_root;        // Oops, found infinite loop
3572 
3573         if (!_verify_only) {
3574           // Insert the NeverBranch between 'm' and it's control user.
3575           NeverBranchNode *iff = new NeverBranchNode( m );
3576           _igvn.register_new_node_with_optimizer(iff);
3577           set_loop(iff, l);
3578           Node *if_t = new CProjNode( iff, 0 );
3579           _igvn.register_new_node_with_optimizer(if_t);
3580           set_loop(if_t, l);
3581 
3582           Node* cfg = NULL;       // Find the One True Control User of m
3583           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3584             Node* x = m->fast_out(j);
3585             if (x->is_CFG() && x != m && x != iff)
3586               { cfg = x; break; }
3587           }
3588           assert(cfg != NULL, "must find the control user of m");
3589           uint k = 0;             // Probably cfg->in(0)
3590           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
3591           cfg->set_req( k, if_t ); // Now point to NeverBranch
3592           _igvn._worklist.push(cfg);
3593 
3594           // Now create the never-taken loop exit
3595           Node *if_f = new CProjNode( iff, 1 );
3596           _igvn.register_new_node_with_optimizer(if_f);
3597           set_loop(if_f, l);
3598           // Find frame ptr for Halt.  Relies on the optimizer
3599           // V-N'ing.  Easier and quicker than searching through
3600           // the program structure.
3601           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
3602           _igvn.register_new_node_with_optimizer(frame);
3603           // Halt & Catch Fire
3604           Node *halt = new HaltNode( if_f, frame );
3605           _igvn.register_new_node_with_optimizer(halt);
3606           set_loop(halt, l);
3607           C->root()->add_req(halt);
3608         }
3609         set_loop(C->root(), _ltree_root);
3610       }
3611     }
3612     // Weeny check for irreducible.  This child was already visited (this
3613     // IS the post-work phase).  Is this child's loop header post-visited
3614     // as well?  If so, then I found another entry into the loop.
3615     if (!_verify_only) {
3616       while( is_postvisited(l->_head) ) {
3617         // found irreducible
3618         l->_irreducible = 1; // = true
3619         l = l->_parent;
3620         _has_irreducible_loops = true;
3621         // Check for bad CFG here to prevent crash, and bailout of compile
3622         if (l == NULL) {
3623           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
3624           return pre_order;
3625         }
3626       }
3627       C->set_has_irreducible_loop(_has_irreducible_loops);
3628     }
3629 
3630     // This Node might be a decision point for loops.  It is only if
3631     // it's children belong to several different loops.  The sort call
3632     // does a trivial amount of work if there is only 1 child or all
3633     // children belong to the same loop.  If however, the children
3634     // belong to different loops, the sort call will properly set the
3635     // _parent pointers to show how the loops nest.
3636     //
3637     // In any case, it returns the tightest enclosing loop.
3638     innermost = sort( l, innermost );
3639   }
3640 
3641   // Def-use info will have some dead stuff; dead stuff will have no
3642   // loop decided on.
3643 
3644   // Am I a loop header?  If so fix up my parent's child and next ptrs.
3645   if( innermost && innermost->_head == n ) {
3646     assert( get_loop(n) == innermost, "" );
3647     IdealLoopTree *p = innermost->_parent;
3648     IdealLoopTree *l = innermost;
3649     while( p && l->_head == n ) {
3650       l->_next = p->_child;     // Put self on parents 'next child'
3651       p->_child = l;            // Make self as first child of parent
3652       l = p;                    // Now walk up the parent chain
3653       p = l->_parent;
3654     }
3655   } else {
3656     // Note that it is possible for a LoopNode to reach here, if the
3657     // backedge has been made unreachable (hence the LoopNode no longer
3658     // denotes a Loop, and will eventually be removed).
3659 
3660     // Record tightest enclosing loop for self.  Mark as post-visited.
3661     set_loop(n, innermost);
3662     // Also record has_call flag early on
3663     if( innermost ) {
3664       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3665         // Do not count uncommon calls
3666         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3667           Node *iff = n->in(0)->in(0);
3668           // No any calls for vectorized loops.
3669           if( UseSuperWord || !iff->is_If() ||
3670               (n->in(0)->Opcode() == Op_IfFalse &&
3671                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3672               (iff->as_If()->_prob >= 0.01) )
3673             innermost->_has_call = 1;
3674         }
3675       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3676         // Disable loop optimizations if the loop has a scalar replaceable
3677         // allocation. This disabling may cause a potential performance lost
3678         // if the allocation is not eliminated for some reason.
3679         innermost->_allow_optimizations = false;
3680         innermost->_has_call = 1; // = true
3681       } else if (n->Opcode() == Op_SafePoint) {
3682         // Record all safepoints in this loop.
3683         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3684         innermost->_safepts->push(n);
3685       }
3686     }
3687   }
3688 
3689   // Flag as post-visited now
3690   set_postvisited(n);
3691   return pre_order;
3692 }
3693 
3694 
3695 //------------------------------build_loop_early-------------------------------
3696 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3697 // First pass computes the earliest controlling node possible.  This is the
3698 // controlling input with the deepest dominating depth.
3699 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3700   while (worklist.size() != 0) {
3701     // Use local variables nstack_top_n & nstack_top_i to cache values
3702     // on nstack's top.
3703     Node *nstack_top_n = worklist.pop();
3704     uint  nstack_top_i = 0;
3705 //while_nstack_nonempty:
3706     while (true) {
3707       // Get parent node and next input's index from stack's top.
3708       Node  *n = nstack_top_n;
3709       uint   i = nstack_top_i;
3710       uint cnt = n->req(); // Count of inputs
3711       if (i == 0) {        // Pre-process the node.
3712         if( has_node(n) &&            // Have either loop or control already?
3713             !has_ctrl(n) ) {          // Have loop picked out already?
3714           // During "merge_many_backedges" we fold up several nested loops
3715           // into a single loop.  This makes the members of the original
3716           // loop bodies pointing to dead loops; they need to move up
3717           // to the new UNION'd larger loop.  I set the _head field of these
3718           // dead loops to NULL and the _parent field points to the owning
3719           // loop.  Shades of UNION-FIND algorithm.
3720           IdealLoopTree *ilt;
3721           while( !(ilt = get_loop(n))->_head ) {
3722             // Normally I would use a set_loop here.  But in this one special
3723             // case, it is legal (and expected) to change what loop a Node
3724             // belongs to.
3725             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3726           }
3727           // Remove safepoints ONLY if I've already seen I don't need one.
3728           // (the old code here would yank a 2nd safepoint after seeing a
3729           // first one, even though the 1st did not dominate in the loop body
3730           // and thus could be avoided indefinitely)
3731           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3732               is_deleteable_safept(n)) {
3733             Node *in = n->in(TypeFunc::Control);
3734             lazy_replace(n,in);       // Pull safepoint now
3735             if (ilt->_safepts != NULL) {
3736               ilt->_safepts->yank(n);
3737             }
3738             // Carry on with the recursion "as if" we are walking
3739             // only the control input
3740             if( !visited.test_set( in->_idx ) ) {
3741               worklist.push(in);      // Visit this guy later, using worklist
3742             }
3743             // Get next node from nstack:
3744             // - skip n's inputs processing by setting i > cnt;
3745             // - we also will not call set_early_ctrl(n) since
3746             //   has_node(n) == true (see the condition above).
3747             i = cnt + 1;
3748           }
3749         }
3750       } // if (i == 0)
3751 
3752       // Visit all inputs
3753       bool done = true;       // Assume all n's inputs will be processed
3754       while (i < cnt) {
3755         Node *in = n->in(i);
3756         ++i;
3757         if (in == NULL) continue;
3758         if (in->pinned() && !in->is_CFG())
3759           set_ctrl(in, in->in(0));
3760         int is_visited = visited.test_set( in->_idx );
3761         if (!has_node(in)) {  // No controlling input yet?
3762           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3763           assert( !is_visited, "visit only once" );
3764           nstack.push(n, i);  // Save parent node and next input's index.
3765           nstack_top_n = in;  // Process current input now.
3766           nstack_top_i = 0;
3767           done = false;       // Not all n's inputs processed.
3768           break; // continue while_nstack_nonempty;
3769         } else if (!is_visited) {
3770           // This guy has a location picked out for him, but has not yet
3771           // been visited.  Happens to all CFG nodes, for instance.
3772           // Visit him using the worklist instead of recursion, to break
3773           // cycles.  Since he has a location already we do not need to
3774           // find his location before proceeding with the current Node.
3775           worklist.push(in);  // Visit this guy later, using worklist
3776         }
3777       }
3778       if (done) {
3779         // All of n's inputs have been processed, complete post-processing.
3780 
3781         // Compute earliest point this Node can go.
3782         // CFG, Phi, pinned nodes already know their controlling input.
3783         if (!has_node(n)) {
3784           // Record earliest legal location
3785           set_early_ctrl( n );
3786         }
3787         if (nstack.is_empty()) {
3788           // Finished all nodes on stack.
3789           // Process next node on the worklist.
3790           break;
3791         }
3792         // Get saved parent node and next input's index.
3793         nstack_top_n = nstack.node();
3794         nstack_top_i = nstack.index();
3795         nstack.pop();
3796       }
3797     } // while (true)
3798   }
3799 }
3800 
3801 //------------------------------dom_lca_internal--------------------------------
3802 // Pair-wise LCA
3803 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3804   if( !n1 ) return n2;          // Handle NULL original LCA
3805   assert( n1->is_CFG(), "" );
3806   assert( n2->is_CFG(), "" );
3807   // find LCA of all uses
3808   uint d1 = dom_depth(n1);
3809   uint d2 = dom_depth(n2);
3810   while (n1 != n2) {
3811     if (d1 > d2) {
3812       n1 =      idom(n1);
3813       d1 = dom_depth(n1);
3814     } else if (d1 < d2) {
3815       n2 =      idom(n2);
3816       d2 = dom_depth(n2);
3817     } else {
3818       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3819       // of the tree might have the same depth.  These sections have
3820       // to be searched more carefully.
3821 
3822       // Scan up all the n1's with equal depth, looking for n2.
3823       Node *t1 = idom(n1);
3824       while (dom_depth(t1) == d1) {
3825         if (t1 == n2)  return n2;
3826         t1 = idom(t1);
3827       }
3828       // Scan up all the n2's with equal depth, looking for n1.
3829       Node *t2 = idom(n2);
3830       while (dom_depth(t2) == d2) {
3831         if (t2 == n1)  return n1;
3832         t2 = idom(t2);
3833       }
3834       // Move up to a new dominator-depth value as well as up the dom-tree.
3835       n1 = t1;
3836       n2 = t2;
3837       d1 = dom_depth(n1);
3838       d2 = dom_depth(n2);
3839     }
3840   }
3841   return n1;
3842 }
3843 
3844 //------------------------------compute_idom-----------------------------------
3845 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3846 // IDOMs are correct.
3847 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3848   assert( region->is_Region(), "" );
3849   Node *LCA = NULL;
3850   for( uint i = 1; i < region->req(); i++ ) {
3851     if( region->in(i) != C->top() )
3852       LCA = dom_lca( LCA, region->in(i) );
3853   }
3854   return LCA;
3855 }
3856 
3857 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3858   bool had_error = false;
3859 #ifdef ASSERT
3860   if (early != C->root()) {
3861     // Make sure that there's a dominance path from LCA to early
3862     Node* d = LCA;
3863     while (d != early) {
3864       if (d == C->root()) {
3865         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3866         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3867         had_error = true;
3868         break;
3869       }
3870       d = idom(d);
3871     }
3872   }
3873 #endif
3874   return had_error;
3875 }
3876 
3877 
3878 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3879   // Compute LCA over list of uses
3880   bool had_error = false;
3881   Node *LCA = NULL;
3882   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3883     Node* c = n->fast_out(i);
3884     if (_nodes[c->_idx] == NULL)
3885       continue;                 // Skip the occasional dead node
3886     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3887       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3888         if( c->in(j) == n ) {   // Found matching input?
3889           Node *use = c->in(0)->in(j);
3890           if (_verify_only && use->is_top()) continue;
3891           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3892           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3893         }
3894       }
3895     } else {
3896       // For CFG data-users, use is in the block just prior
3897       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3898       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3899       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3900     }
3901   }
3902   assert(!had_error, "bad dominance");
3903   return LCA;
3904 }
3905 
3906 // Check the shape of the graph at the loop entry. In some cases,
3907 // the shape of the graph does not match the shape outlined below.
3908 // That is caused by the Opaque1 node "protecting" the shape of
3909 // the graph being removed by, for example, the IGVN performed
3910 // in PhaseIdealLoop::build_and_optimize().
3911 //
3912 // After the Opaque1 node has been removed, optimizations (e.g., split-if,
3913 // loop unswitching, and IGVN, or a combination of them) can freely change
3914 // the graph's shape. As a result, the graph shape outlined below cannot
3915 // be guaranteed anymore.
3916 bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) {
3917   if (!cl->is_main_loop() && !cl->is_post_loop()) {
3918     return false;
3919   }
3920   Node* ctrl = cl->skip_predicates();
3921 
3922   if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
3923     return false;
3924   }
3925   Node* iffm = ctrl->in(0);
3926   if (iffm == NULL || !iffm->is_If()) {
3927     return false;
3928   }
3929   Node* bolzm = iffm->in(1);
3930   if (bolzm == NULL || !bolzm->is_Bool()) {
3931     return false;
3932   }
3933   Node* cmpzm = bolzm->in(1);
3934   if (cmpzm == NULL || !cmpzm->is_Cmp()) {
3935     return false;
3936   }
3937   // compares can get conditionally flipped
3938   bool found_opaque = false;
3939   for (uint i = 1; i < cmpzm->req(); i++) {
3940     Node* opnd = cmpzm->in(i);
3941     if (opnd && opnd->Opcode() == Op_Opaque1) {
3942       found_opaque = true;
3943       break;
3944     }
3945   }
3946   if (!found_opaque) {
3947     return false;
3948   }
3949   return true;
3950 }
3951 
3952 //------------------------------get_late_ctrl----------------------------------
3953 // Compute latest legal control.
3954 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
3955   assert(early != NULL, "early control should not be NULL");
3956 
3957   Node* LCA = compute_lca_of_uses(n, early);
3958 #ifdef ASSERT
3959   if (LCA == C->root() && LCA != early) {
3960     // def doesn't dominate uses so print some useful debugging output
3961     compute_lca_of_uses(n, early, true);
3962   }
3963 #endif
3964 
3965   // if this is a load, check for anti-dependent stores
3966   // We use a conservative algorithm to identify potential interfering
3967   // instructions and for rescheduling the load.  The users of the memory
3968   // input of this load are examined.  Any use which is not a load and is
3969   // dominated by early is considered a potentially interfering store.
3970   // This can produce false positives.
3971   if (n->is_Load() && LCA != early) {
3972     Node_List worklist;
3973 
3974     Node *mem = n->in(MemNode::Memory);
3975     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3976       Node* s = mem->fast_out(i);
3977       worklist.push(s);
3978     }
3979     while(worklist.size() != 0 && LCA != early) {
3980       Node* s = worklist.pop();
3981       if (s->is_Load() || s->is_ShenandoahBarrier() || s->Opcode() == Op_SafePoint ||
3982           (UseShenandoahGC && s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
3983         continue;
3984       } else if (s->is_MergeMem()) {
3985         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3986           Node* s1 = s->fast_out(i);
3987           worklist.push(s1);
3988         }
3989       } else {
3990         Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3991         assert(sctrl != NULL || s->outcnt() == 0, "must have control");
3992         if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3993           LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3994         }
3995       }
3996     }
3997   }
3998 
3999   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
4000   return LCA;
4001 }
4002 
4003 // true if CFG node d dominates CFG node n
4004 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
4005   if (d == n)
4006     return true;
4007   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
4008   uint dd = dom_depth(d);
4009   while (dom_depth(n) >= dd) {
4010     if (n == d)
4011       return true;
4012     n = idom(n);
4013   }
4014   return false;
4015 }
4016 
4017 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
4018 // Pair-wise LCA with tags.
4019 // Tag each index with the node 'tag' currently being processed
4020 // before advancing up the dominator chain using idom().
4021 // Later calls that find a match to 'tag' know that this path has already
4022 // been considered in the current LCA (which is input 'n1' by convention).
4023 // Since get_late_ctrl() is only called once for each node, the tag array
4024 // does not need to be cleared between calls to get_late_ctrl().
4025 // Algorithm trades a larger constant factor for better asymptotic behavior
4026 //
4027 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
4028   uint d1 = dom_depth(n1);
4029   uint d2 = dom_depth(n2);
4030 
4031   do {
4032     if (d1 > d2) {
4033       // current lca is deeper than n2
4034       _dom_lca_tags.map(n1->_idx, tag);
4035       n1 =      idom(n1);
4036       d1 = dom_depth(n1);
4037     } else if (d1 < d2) {
4038       // n2 is deeper than current lca
4039       Node *memo = _dom_lca_tags[n2->_idx];
4040       if( memo == tag ) {
4041         return n1;    // Return the current LCA
4042       }
4043       _dom_lca_tags.map(n2->_idx, tag);
4044       n2 =      idom(n2);
4045       d2 = dom_depth(n2);
4046     } else {
4047       // Here d1 == d2.  Due to edits of the dominator-tree, sections
4048       // of the tree might have the same depth.  These sections have
4049       // to be searched more carefully.
4050 
4051       // Scan up all the n1's with equal depth, looking for n2.
4052       _dom_lca_tags.map(n1->_idx, tag);
4053       Node *t1 = idom(n1);
4054       while (dom_depth(t1) == d1) {
4055         if (t1 == n2)  return n2;
4056         _dom_lca_tags.map(t1->_idx, tag);
4057         t1 = idom(t1);
4058       }
4059       // Scan up all the n2's with equal depth, looking for n1.
4060       _dom_lca_tags.map(n2->_idx, tag);
4061       Node *t2 = idom(n2);
4062       while (dom_depth(t2) == d2) {
4063         if (t2 == n1)  return n1;
4064         _dom_lca_tags.map(t2->_idx, tag);
4065         t2 = idom(t2);
4066       }
4067       // Move up to a new dominator-depth value as well as up the dom-tree.
4068       n1 = t1;
4069       n2 = t2;
4070       d1 = dom_depth(n1);
4071       d2 = dom_depth(n2);
4072     }
4073   } while (n1 != n2);
4074   return n1;
4075 }
4076 
4077 //------------------------------init_dom_lca_tags------------------------------
4078 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4079 // Intended use does not involve any growth for the array, so it could
4080 // be of fixed size.
4081 void PhaseIdealLoop::init_dom_lca_tags() {
4082   uint limit = C->unique() + 1;
4083   _dom_lca_tags.map( limit, NULL );
4084 #ifdef ASSERT
4085   for( uint i = 0; i < limit; ++i ) {
4086     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4087   }
4088 #endif // ASSERT
4089 }
4090 
4091 //------------------------------clear_dom_lca_tags------------------------------
4092 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4093 // Intended use does not involve any growth for the array, so it could
4094 // be of fixed size.
4095 void PhaseIdealLoop::clear_dom_lca_tags() {
4096   uint limit = C->unique() + 1;
4097   _dom_lca_tags.map( limit, NULL );
4098   _dom_lca_tags.clear();
4099 #ifdef ASSERT
4100   for( uint i = 0; i < limit; ++i ) {
4101     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4102   }
4103 #endif // ASSERT
4104 }
4105 
4106 //------------------------------build_loop_late--------------------------------
4107 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4108 // Second pass finds latest legal placement, and ideal loop placement.
4109 void PhaseIdealLoop::build_loop_late(VectorSet &visited, Node_List &worklist, Node_Stack &nstack, bool verify_strip_mined) {
4110   while (worklist.size() != 0) {
4111     Node *n = worklist.pop();
4112     // Only visit once
4113     if (visited.test_set(n->_idx)) continue;
4114     uint cnt = n->outcnt();
4115     uint   i = 0;
4116     while (true) {
4117       assert( _nodes[n->_idx], "no dead nodes" );
4118       // Visit all children
4119       if (i < cnt) {
4120         Node* use = n->raw_out(i);
4121         ++i;
4122         // Check for dead uses.  Aggressively prune such junk.  It might be
4123         // dead in the global sense, but still have local uses so I cannot
4124         // easily call 'remove_dead_node'.
4125         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
4126           // Due to cycles, we might not hit the same fixed point in the verify
4127           // pass as we do in the regular pass.  Instead, visit such phis as
4128           // simple uses of the loop head.
4129           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
4130             if( !visited.test(use->_idx) )
4131               worklist.push(use);
4132           } else if( !visited.test_set(use->_idx) ) {
4133             nstack.push(n, i); // Save parent and next use's index.
4134             n   = use;         // Process all children of current use.
4135             cnt = use->outcnt();
4136             i   = 0;
4137           }
4138         } else {
4139           // Do not visit around the backedge of loops via data edges.
4140           // push dead code onto a worklist
4141           _deadlist.push(use);
4142         }
4143       } else {
4144         // All of n's children have been processed, complete post-processing.
4145         build_loop_late_post(n, verify_strip_mined);
4146         if (nstack.is_empty()) {
4147           // Finished all nodes on stack.
4148           // Process next node on the worklist.
4149           break;
4150         }
4151         // Get saved parent node and next use's index. Visit the rest of uses.
4152         n   = nstack.node();
4153         cnt = n->outcnt();
4154         i   = nstack.index();
4155         nstack.pop();
4156       }
4157     }
4158   }
4159 }
4160 
4161 // Verify that no data node is schedules in the outer loop of a strip
4162 // mined loop.
4163 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
4164 #ifdef ASSERT
4165   if (get_loop(least)->_nest == 0) {
4166     return;
4167   }
4168   IdealLoopTree* loop = get_loop(least);
4169   Node* head = loop->_head;
4170   if (head->is_OuterStripMinedLoop()) {
4171     Node* sfpt = head->as_Loop()->outer_safepoint();
4172     ResourceMark rm;
4173     Unique_Node_List wq;
4174     wq.push(sfpt);
4175     for (uint i = 0; i < wq.size(); i++) {
4176       Node *m = wq.at(i);
4177       for (uint i = 1; i < m->req(); i++) {
4178         Node* nn = m->in(i);
4179         if (nn == n) {
4180           return;
4181         }
4182         if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
4183           wq.push(nn);
4184         }
4185       }
4186     }
4187     ShouldNotReachHere();
4188   }
4189 #endif
4190 }
4191 
4192 
4193 //------------------------------build_loop_late_post---------------------------
4194 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4195 // Second pass finds latest legal placement, and ideal loop placement.
4196 void PhaseIdealLoop::build_loop_late_post(Node *n, bool verify_strip_mined) {
4197 
4198   if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
4199     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
4200   }
4201 
4202 #ifdef ASSERT
4203   if (_verify_only && !n->is_CFG()) {
4204     // Check def-use domination.
4205     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
4206   }
4207 #endif
4208 
4209   // CFG and pinned nodes already handled
4210   if( n->in(0) ) {
4211     if( n->in(0)->is_top() ) return; // Dead?
4212 
4213     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
4214     // _must_ be pinned (they have to observe their control edge of course).
4215     // Unlike Stores (which modify an unallocable resource, the memory
4216     // state), Mods/Loads can float around.  So free them up.
4217     bool pinned = true;
4218     switch( n->Opcode() ) {
4219     case Op_DivI:
4220     case Op_DivF:
4221     case Op_DivD:
4222     case Op_ModI:
4223     case Op_ModF:
4224     case Op_ModD:
4225     case Op_LoadB:              // Same with Loads; they can sink
4226     case Op_LoadUB:             // during loop optimizations.
4227     case Op_LoadUS:
4228     case Op_LoadD:
4229     case Op_LoadF:
4230     case Op_LoadI:
4231     case Op_LoadKlass:
4232     case Op_LoadNKlass:
4233     case Op_LoadL:
4234     case Op_LoadS:
4235     case Op_LoadP:
4236     case Op_LoadBarrierSlowReg:
4237     case Op_LoadBarrierWeakSlowReg:
4238     case Op_LoadN:
4239     case Op_LoadRange:
4240     case Op_LoadD_unaligned:
4241     case Op_LoadL_unaligned:
4242     case Op_StrComp:            // Does a bunch of load-like effects
4243     case Op_StrEquals:
4244     case Op_StrIndexOf:
4245     case Op_StrIndexOfChar:
4246     case Op_AryEq:
4247     case Op_HasNegatives:
4248       pinned = false;
4249     }
4250     if( pinned ) {
4251       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
4252       if( !chosen_loop->_child )       // Inner loop?
4253         chosen_loop->_body.push(n); // Collect inner loops
4254       return;
4255     }
4256   } else {                      // No slot zero
4257     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
4258       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
4259       return;
4260     }
4261     assert(!n->is_CFG() || n->outcnt() == 0, "");
4262   }
4263 
4264   // Do I have a "safe range" I can select over?
4265   Node *early = get_ctrl(n);// Early location already computed
4266 
4267   // Compute latest point this Node can go
4268   Node *LCA = get_late_ctrl( n, early );
4269   // LCA is NULL due to uses being dead
4270   if( LCA == NULL ) {
4271 #ifdef ASSERT
4272     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
4273       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
4274     }
4275 #endif
4276     _nodes.map(n->_idx, 0);     // This node is useless
4277     _deadlist.push(n);
4278     return;
4279   }
4280   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
4281 
4282   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
4283   Node *least = legal;          // Best legal position so far
4284   while( early != legal ) {     // While not at earliest legal
4285 #ifdef ASSERT
4286     if (legal->is_Start() && !early->is_Root()) {
4287       // Bad graph. Print idom path and fail.
4288       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
4289       assert(false, "Bad graph detected in build_loop_late");
4290     }
4291 #endif
4292     // Find least loop nesting depth
4293     legal = idom(legal);        // Bump up the IDOM tree
4294     // Check for lower nesting depth
4295     if( get_loop(legal)->_nest < get_loop(least)->_nest )
4296       least = legal;
4297   }
4298   assert(early == legal || legal != C->root(), "bad dominance of inputs");
4299 
4300   // Try not to place code on a loop entry projection
4301   // which can inhibit range check elimination.
4302   if (least != early) {
4303     Node* ctrl_out = least->unique_ctrl_out();
4304     if (ctrl_out && ctrl_out->is_Loop() &&
4305         least == ctrl_out->in(LoopNode::EntryControl)) {
4306       // Move the node above predicates as far up as possible so a
4307       // following pass of loop predication doesn't hoist a predicate
4308       // that depends on it above that node.
4309       Node* new_ctrl = least;
4310       for (;;) {
4311         if (!new_ctrl->is_Proj()) {
4312           break;
4313         }
4314         CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
4315         if (call == NULL) {
4316           break;
4317         }
4318         int req = call->uncommon_trap_request();
4319         Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
4320         if (trap_reason != Deoptimization::Reason_loop_limit_check &&
4321             trap_reason != Deoptimization::Reason_predicate &&
4322             trap_reason != Deoptimization::Reason_profile_predicate) {
4323           break;
4324         }
4325         Node* c = new_ctrl->in(0)->in(0);
4326         if (is_dominator(c, early) && c != early) {
4327           break;
4328         }
4329         new_ctrl = c;
4330       }
4331       least = new_ctrl;
4332     }
4333   }
4334 
4335 #ifdef ASSERT
4336   // If verifying, verify that 'verify_me' has a legal location
4337   // and choose it as our location.
4338   if( _verify_me ) {
4339     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
4340     Node *legal = LCA;
4341     while( early != legal ) {   // While not at earliest legal
4342       if( legal == v_ctrl ) break;  // Check for prior good location
4343       legal = idom(legal)      ;// Bump up the IDOM tree
4344     }
4345     // Check for prior good location
4346     if( legal == v_ctrl ) least = legal; // Keep prior if found
4347   }
4348 #endif
4349 
4350   // Assign discovered "here or above" point
4351   least = find_non_split_ctrl(least);
4352   if (verify_strip_mined && !_verify_only) {
4353     verify_strip_mined_scheduling(n, least);
4354   }
4355   set_ctrl(n, least);
4356 
4357   // Collect inner loop bodies
4358   IdealLoopTree *chosen_loop = get_loop(least);
4359   if( !chosen_loop->_child )   // Inner loop?
4360     chosen_loop->_body.push(n);// Collect inner loops
4361 }
4362 
4363 #ifdef ASSERT
4364 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
4365   tty->print_cr("%s", msg);
4366   tty->print("n: "); n->dump();
4367   tty->print("early(n): "); early->dump();
4368   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
4369       n->in(0) != early && !n->in(0)->is_Root()) {
4370     tty->print("n->in(0): "); n->in(0)->dump();
4371   }
4372   for (uint i = 1; i < n->req(); i++) {
4373     Node* in1 = n->in(i);
4374     if (in1 != NULL && in1 != n && !in1->is_top()) {
4375       tty->print("n->in(%d): ", i); in1->dump();
4376       Node* in1_early = get_ctrl(in1);
4377       tty->print("early(n->in(%d)): ", i); in1_early->dump();
4378       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
4379           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
4380         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
4381       }
4382       for (uint j = 1; j < in1->req(); j++) {
4383         Node* in2 = in1->in(j);
4384         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
4385           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
4386           Node* in2_early = get_ctrl(in2);
4387           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
4388           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
4389               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
4390             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
4391           }
4392         }
4393       }
4394     }
4395   }
4396   tty->cr();
4397   tty->print("LCA(n): "); LCA->dump();
4398   for (uint i = 0; i < n->outcnt(); i++) {
4399     Node* u1 = n->raw_out(i);
4400     if (u1 == n)
4401       continue;
4402     tty->print("n->out(%d): ", i); u1->dump();
4403     if (u1->is_CFG()) {
4404       for (uint j = 0; j < u1->outcnt(); j++) {
4405         Node* u2 = u1->raw_out(j);
4406         if (u2 != u1 && u2 != n && u2->is_CFG()) {
4407           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4408         }
4409       }
4410     } else {
4411       Node* u1_later = get_ctrl(u1);
4412       tty->print("later(n->out(%d)): ", i); u1_later->dump();
4413       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
4414           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
4415         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
4416       }
4417       for (uint j = 0; j < u1->outcnt(); j++) {
4418         Node* u2 = u1->raw_out(j);
4419         if (u2 == n || u2 == u1)
4420           continue;
4421         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4422         if (!u2->is_CFG()) {
4423           Node* u2_later = get_ctrl(u2);
4424           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
4425           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
4426               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
4427             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
4428           }
4429         }
4430       }
4431     }
4432   }
4433   tty->cr();
4434   int ct = 0;
4435   Node *dbg_legal = LCA;
4436   while(!dbg_legal->is_Start() && ct < 100) {
4437     tty->print("idom[%d] ",ct); dbg_legal->dump();
4438     ct++;
4439     dbg_legal = idom(dbg_legal);
4440   }
4441   tty->cr();
4442 }
4443 #endif
4444 
4445 #ifndef PRODUCT
4446 //------------------------------dump-------------------------------------------
4447 void PhaseIdealLoop::dump( ) const {
4448   ResourceMark rm;
4449   Arena* arena = Thread::current()->resource_area();
4450   Node_Stack stack(arena, C->live_nodes() >> 2);
4451   Node_List rpo_list;
4452   VectorSet visited(arena);
4453   visited.set(C->top()->_idx);
4454   rpo( C->root(), stack, visited, rpo_list );
4455   // Dump root loop indexed by last element in PO order
4456   dump( _ltree_root, rpo_list.size(), rpo_list );
4457 }
4458 
4459 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
4460   loop->dump_head();
4461 
4462   // Now scan for CFG nodes in the same loop
4463   for( uint j=idx; j > 0;  j-- ) {
4464     Node *n = rpo_list[j-1];
4465     if( !_nodes[n->_idx] )      // Skip dead nodes
4466       continue;
4467     if( get_loop(n) != loop ) { // Wrong loop nest
4468       if( get_loop(n)->_head == n &&    // Found nested loop?
4469           get_loop(n)->_parent == loop )
4470         dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
4471       continue;
4472     }
4473 
4474     // Dump controlling node
4475     for( uint x = 0; x < loop->_nest; x++ )
4476       tty->print("  ");
4477     tty->print("C");
4478     if( n == C->root() ) {
4479       n->dump();
4480     } else {
4481       Node* cached_idom   = idom_no_update(n);
4482       Node *computed_idom = n->in(0);
4483       if( n->is_Region() ) {
4484         computed_idom = compute_idom(n);
4485         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
4486         // any MultiBranch ctrl node), so apply a similar transform to
4487         // the cached idom returned from idom_no_update.
4488         cached_idom = find_non_split_ctrl(cached_idom);
4489       }
4490       tty->print(" ID:%d",computed_idom->_idx);
4491       n->dump();
4492       if( cached_idom != computed_idom ) {
4493         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
4494                       computed_idom->_idx, cached_idom->_idx);
4495       }
4496     }
4497     // Dump nodes it controls
4498     for( uint k = 0; k < _nodes.Size(); k++ ) {
4499       // (k < C->unique() && get_ctrl(find(k)) == n)
4500       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
4501         Node *m = C->root()->find(k);
4502         if( m && m->outcnt() > 0 ) {
4503           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
4504             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
4505                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
4506           }
4507           for( uint j = 0; j < loop->_nest; j++ )
4508             tty->print("  ");
4509           tty->print(" ");
4510           m->dump();
4511         }
4512       }
4513     }
4514   }
4515 }
4516 #endif
4517 
4518 // Collect a R-P-O for the whole CFG.
4519 // Result list is in post-order (scan backwards for RPO)
4520 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
4521   stk.push(start, 0);
4522   visited.set(start->_idx);
4523 
4524   while (stk.is_nonempty()) {
4525     Node* m   = stk.node();
4526     uint  idx = stk.index();
4527     if (idx < m->outcnt()) {
4528       stk.set_index(idx + 1);
4529       Node* n = m->raw_out(idx);
4530       if (n->is_CFG() && !visited.test_set(n->_idx)) {
4531         stk.push(n, 0);
4532       }
4533     } else {
4534       rpo_list.push(m);
4535       stk.pop();
4536     }
4537   }
4538 }
4539 
4540 
4541 //=============================================================================
4542 //------------------------------LoopTreeIterator-----------------------------------
4543 
4544 // Advance to next loop tree using a preorder, left-to-right traversal.
4545 void LoopTreeIterator::next() {
4546   assert(!done(), "must not be done.");
4547   if (_curnt->_child != NULL) {
4548     _curnt = _curnt->_child;
4549   } else if (_curnt->_next != NULL) {
4550     _curnt = _curnt->_next;
4551   } else {
4552     while (_curnt != _root && _curnt->_next == NULL) {
4553       _curnt = _curnt->_parent;
4554     }
4555     if (_curnt == _root) {
4556       _curnt = NULL;
4557       assert(done(), "must be done.");
4558     } else {
4559       assert(_curnt->_next != NULL, "must be more to do");
4560       _curnt = _curnt->_next;
4561     }
4562   }
4563 }