1 /*
   2  * Copyright (c) 1998, 2019, 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 
  44 //=============================================================================
  45 //--------------------------is_cloop_ind_var-----------------------------------
  46 // Determine if a node is a counted loop induction variable.
  47 // NOTE: The method is declared in "node.hpp".
  48 bool Node::is_cloop_ind_var() const {
  49   return (is_Phi() && !as_Phi()->is_copy() &&
  50           as_Phi()->region()->is_CountedLoop() &&
  51           as_Phi()->region()->as_CountedLoop()->phi() == this);
  52 }
  53 
  54 //=============================================================================
  55 //------------------------------dump_spec--------------------------------------
  56 // Dump special per-node info
  57 #ifndef PRODUCT
  58 void LoopNode::dump_spec(outputStream *st) const {
  59   if (is_inner_loop()) st->print( "inner " );
  60   if (is_partial_peel_loop()) st->print( "partial_peel " );
  61   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  62 }
  63 #endif
  64 
  65 //------------------------------is_valid_counted_loop-------------------------
  66 bool LoopNode::is_valid_counted_loop() const {
  67   if (is_CountedLoop()) {
  68     CountedLoopNode*    l  = as_CountedLoop();
  69     CountedLoopEndNode* le = l->loopexit_or_null();
  70     if (le != NULL &&
  71         le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  72       Node* phi  = l->phi();
  73       Node* exit = le->proj_out_or_null(0 /* false */);
  74       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  75           phi != NULL && phi->is_Phi() &&
  76           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  77           le->loopnode() == l && le->stride_is_con()) {
  78         return true;
  79       }
  80     }
  81   }
  82   return false;
  83 }
  84 
  85 //------------------------------get_early_ctrl---------------------------------
  86 // Compute earliest legal control
  87 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  88   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  89   uint i;
  90   Node *early;
  91   if (n->in(0) && !n->is_expensive()) {
  92     early = n->in(0);
  93     if (!early->is_CFG()) // Might be a non-CFG multi-def
  94       early = get_ctrl(early);        // So treat input as a straight data input
  95     i = 1;
  96   } else {
  97     early = get_ctrl(n->in(1));
  98     i = 2;
  99   }
 100   uint e_d = dom_depth(early);
 101   assert( early, "" );
 102   for (; i < n->req(); i++) {
 103     Node *cin = get_ctrl(n->in(i));
 104     assert( cin, "" );
 105     // Keep deepest dominator depth
 106     uint c_d = dom_depth(cin);
 107     if (c_d > e_d) {           // Deeper guy?
 108       early = cin;              // Keep deepest found so far
 109       e_d = c_d;
 110     } else if (c_d == e_d &&    // Same depth?
 111                early != cin) { // If not equal, must use slower algorithm
 112       // If same depth but not equal, one _must_ dominate the other
 113       // and we want the deeper (i.e., dominated) guy.
 114       Node *n1 = early;
 115       Node *n2 = cin;
 116       while (1) {
 117         n1 = idom(n1);          // Walk up until break cycle
 118         n2 = idom(n2);
 119         if (n1 == cin ||        // Walked early up to cin
 120             dom_depth(n2) < c_d)
 121           break;                // early is deeper; keep him
 122         if (n2 == early ||      // Walked cin up to early
 123             dom_depth(n1) < c_d) {
 124           early = cin;          // cin is deeper; keep him
 125           break;
 126         }
 127       }
 128       e_d = dom_depth(early);   // Reset depth register cache
 129     }
 130   }
 131 
 132   // Return earliest legal location
 133   assert(early == find_non_split_ctrl(early), "unexpected early control");
 134 
 135   if (n->is_expensive() && !_verify_only && !_verify_me) {
 136     assert(n->in(0), "should have control input");
 137     early = get_early_ctrl_for_expensive(n, early);
 138   }
 139 
 140   return early;
 141 }
 142 
 143 //------------------------------get_early_ctrl_for_expensive---------------------------------
 144 // Move node up the dominator tree as high as legal while still beneficial
 145 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 146   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 147   assert(OptimizeExpensiveOps, "optimization off?");
 148 
 149   Node* ctl = n->in(0);
 150   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 151   uint min_dom_depth = dom_depth(earliest);
 152 #ifdef ASSERT
 153   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 154     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 155     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 156   }
 157 #endif
 158   if (dom_depth(ctl) < min_dom_depth) {
 159     return earliest;
 160   }
 161 
 162   while (1) {
 163     Node *next = ctl;
 164     // Moving the node out of a loop on the projection of a If
 165     // confuses loop predication. So once we hit a Loop in a If branch
 166     // that doesn't branch to an UNC, we stop. The code that process
 167     // expensive nodes will notice the loop and skip over it to try to
 168     // move the node further up.
 169     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 170       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 171         break;
 172       }
 173       next = idom(ctl->in(1)->in(0));
 174     } else if (ctl->is_Proj()) {
 175       // We only move it up along a projection if the projection is
 176       // the single control projection for its parent: same code path,
 177       // if it's a If with UNC or fallthrough of a call.
 178       Node* parent_ctl = ctl->in(0);
 179       if (parent_ctl == NULL) {
 180         break;
 181       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 182         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 183       } else if (parent_ctl->is_If()) {
 184         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 185           break;
 186         }
 187         assert(idom(ctl) == parent_ctl, "strange");
 188         next = idom(parent_ctl);
 189       } else if (ctl->is_CatchProj()) {
 190         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 191           break;
 192         }
 193         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 194         next = parent_ctl->in(0)->in(0)->in(0);
 195       } else {
 196         // Check if parent control has a single projection (this
 197         // control is the only possible successor of the parent
 198         // control). If so, we can try to move the node above the
 199         // parent control.
 200         int nb_ctl_proj = 0;
 201         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 202           Node *p = parent_ctl->fast_out(i);
 203           if (p->is_Proj() && p->is_CFG()) {
 204             nb_ctl_proj++;
 205             if (nb_ctl_proj > 1) {
 206               break;
 207             }
 208           }
 209         }
 210 
 211         if (nb_ctl_proj > 1) {
 212           break;
 213         }
 214         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
 215                BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
 216         assert(idom(ctl) == parent_ctl, "strange");
 217         next = idom(parent_ctl);
 218       }
 219     } else {
 220       next = idom(ctl);
 221     }
 222     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 223       break;
 224     }
 225     ctl = next;
 226   }
 227 
 228   if (ctl != n->in(0)) {
 229     _igvn.replace_input_of(n, 0, ctl);
 230     _igvn.hash_insert(n);
 231   }
 232 
 233   return ctl;
 234 }
 235 
 236 
 237 //------------------------------set_early_ctrl---------------------------------
 238 // Set earliest legal control
 239 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 240   Node *early = get_early_ctrl(n);
 241 
 242   // Record earliest legal location
 243   set_ctrl(n, early);
 244 }
 245 
 246 //------------------------------set_subtree_ctrl-------------------------------
 247 // set missing _ctrl entries on new nodes
 248 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 249   // Already set?  Get out.
 250   if( _nodes[n->_idx] ) return;
 251   // Recursively set _nodes array to indicate where the Node goes
 252   uint i;
 253   for( i = 0; i < n->req(); ++i ) {
 254     Node *m = n->in(i);
 255     if( m && m != C->root() )
 256       set_subtree_ctrl( m );
 257   }
 258 
 259   // Fixup self
 260   set_early_ctrl( n );
 261 }
 262 
 263 // Create a skeleton strip mined outer loop: a Loop head before the
 264 // inner strip mined loop, a safepoint and an exit condition guarded
 265 // by an opaque node after the inner strip mined loop with a backedge
 266 // to the loop head. The inner strip mined loop is left as it is. Only
 267 // once loop optimizations are over, do we adjust the inner loop exit
 268 // condition to limit its number of iterations, set the outer loop
 269 // exit condition and add Phis to the outer loop head. Some loop
 270 // optimizations that operate on the inner strip mined loop need to be
 271 // aware of the outer strip mined loop: loop unswitching needs to
 272 // clone the outer loop as well as the inner, unrolling needs to only
 273 // clone the inner loop etc. No optimizations need to change the outer
 274 // strip mined loop as it is only a skeleton.
 275 IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
 276                                                              IdealLoopTree* loop, float cl_prob, float le_fcnt,
 277                                                              Node*& entry_control, Node*& iffalse) {
 278   Node* outer_test = _igvn.intcon(0);
 279   set_ctrl(outer_test, C->root());
 280   Node *orig = iffalse;
 281   iffalse = iffalse->clone();
 282   _igvn.register_new_node_with_optimizer(iffalse);
 283   set_idom(iffalse, idom(orig), dom_depth(orig));
 284 
 285   IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
 286   Node *outer_ift = new IfTrueNode (outer_le);
 287   Node* outer_iff = orig;
 288   _igvn.replace_input_of(outer_iff, 0, outer_le);
 289 
 290   LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
 291   entry_control = outer_l;
 292 
 293   IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
 294   IdealLoopTree* parent = loop->_parent;
 295   IdealLoopTree* sibling = parent->_child;
 296   if (sibling == loop) {
 297     parent->_child = outer_ilt;
 298   } else {
 299     while (sibling->_next != loop) {
 300       sibling = sibling->_next;
 301     }
 302     sibling->_next = outer_ilt;
 303   }
 304   outer_ilt->_next = loop->_next;
 305   outer_ilt->_parent = parent;
 306   outer_ilt->_child = loop;
 307   outer_ilt->_nest = loop->_nest;
 308   loop->_parent = outer_ilt;
 309   loop->_next = NULL;
 310   loop->_nest++;
 311 
 312   set_loop(iffalse, outer_ilt);
 313   register_control(outer_le, outer_ilt, iffalse);
 314   register_control(outer_ift, outer_ilt, outer_le);
 315   set_idom(outer_iff, outer_le, dom_depth(outer_le));
 316   _igvn.register_new_node_with_optimizer(outer_l);
 317   set_loop(outer_l, outer_ilt);
 318   set_idom(outer_l, init_control, dom_depth(init_control)+1);
 319 
 320   return outer_ilt;
 321 }
 322 
 323 void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) {
 324   Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL,
 325                                                          Deoptimization::Reason_loop_limit_check,
 326                                                          Op_If);
 327   Node* iff = new_predicate_proj->in(0);
 328   assert(iff->Opcode() == Op_If, "bad graph shape");
 329   Node* conv = iff->in(1);
 330   assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
 331   Node* opaq = conv->in(1);
 332   assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
 333   cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 334   bol = _igvn.register_new_node_with_optimizer(bol);
 335   set_subtree_ctrl(bol);
 336   _igvn.replace_input_of(iff, 1, bol);
 337 
 338 #ifndef PRODUCT
 339   // report that the loop predication has been actually performed
 340   // for this loop
 341   if (TraceLoopLimitCheck) {
 342     tty->print_cr("Counted Loop Limit Check generated:");
 343     debug_only( bol->dump(2); )
 344   }
 345 #endif
 346 }
 347 
 348 //------------------------------is_counted_loop--------------------------------
 349 bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) {
 350   PhaseGVN *gvn = &_igvn;
 351 
 352   // Counted loop head must be a good RegionNode with only 3 not NULL
 353   // control input edges: Self, Entry, LoopBack.
 354   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 355     return false;
 356   }
 357   Node *init_control = x->in(LoopNode::EntryControl);
 358   Node *back_control = x->in(LoopNode::LoopBackControl);
 359   if (init_control == NULL || back_control == NULL)    // Partially dead
 360     return false;
 361   // Must also check for TOP when looking for a dead loop
 362   if (init_control->is_top() || back_control->is_top())
 363     return false;
 364 
 365   // Allow funny placement of Safepoint
 366   if (back_control->Opcode() == Op_SafePoint) {
 367     if (LoopStripMiningIter != 0) {
 368       // Leaving the safepoint on the backedge and creating a
 369       // CountedLoop will confuse optimizations. We can't move the
 370       // safepoint around because its jvm state wouldn't match a new
 371       // location. Give up on that loop.
 372       return false;
 373     }
 374     back_control = back_control->in(TypeFunc::Control);
 375   }
 376 
 377   // Controlling test for loop
 378   Node *iftrue = back_control;
 379   uint iftrue_op = iftrue->Opcode();
 380   if (iftrue_op != Op_IfTrue &&
 381       iftrue_op != Op_IfFalse)
 382     // I have a weird back-control.  Probably the loop-exit test is in
 383     // the middle of the loop and I am looking at some trailing control-flow
 384     // merge point.  To fix this I would have to partially peel the loop.
 385     return false; // Obscure back-control
 386 
 387   // Get boolean guarding loop-back test
 388   Node *iff = iftrue->in(0);
 389   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 390     return false;
 391   BoolNode *test = iff->in(1)->as_Bool();
 392   BoolTest::mask bt = test->_test._test;
 393   float cl_prob = iff->as_If()->_prob;
 394   if (iftrue_op == Op_IfFalse) {
 395     bt = BoolTest(bt).negate();
 396     cl_prob = 1.0 - cl_prob;
 397   }
 398   // Get backedge compare
 399   Node *cmp = test->in(1);
 400   int cmp_op = cmp->Opcode();
 401   if (cmp_op != Op_CmpI)
 402     return false;                // Avoid pointer & float compares
 403 
 404   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 405   Node *incr  = cmp->in(1);
 406   Node *limit = cmp->in(2);
 407 
 408   // ---------
 409   // need 'loop()' test to tell if limit is loop invariant
 410   // ---------
 411 
 412   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 413     Node *tmp = incr;            // Then reverse order into the CmpI
 414     incr = limit;
 415     limit = tmp;
 416     bt = BoolTest(bt).commute(); // And commute the exit test
 417   }
 418   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 419     return false;
 420   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 421     return false;
 422 
 423   Node* phi_incr = NULL;
 424   // Trip-counter increment must be commutative & associative.
 425   if (incr->Opcode() == Op_CastII) {
 426     incr = incr->in(1);
 427   }
 428   if (incr->is_Phi()) {
 429     if (incr->as_Phi()->region() != x || incr->req() != 3)
 430       return false; // Not simple trip counter expression
 431     phi_incr = incr;
 432     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 433     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 434       return false;
 435   }
 436 
 437   Node* trunc1 = NULL;
 438   Node* trunc2 = NULL;
 439   const TypeInt* iv_trunc_t = NULL;
 440   Node* orig_incr = incr;
 441   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 442     return false; // Funny increment opcode
 443   }
 444   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 445 
 446   const TypeInt* limit_t = gvn->type(limit)->is_int();
 447   if (trunc1 != NULL) {
 448     // When there is a truncation, we must be sure that after the truncation
 449     // the trip counter will end up higher than the limit, otherwise we are looking
 450     // at an endless loop. Can happen with range checks.
 451 
 452     // Example:
 453     // int i = 0;
 454     // while (true)
 455     //    sum + = array[i];
 456     //    i++;
 457     //    i = i && 0x7fff;
 458     //  }
 459     //
 460     // If the array is shorter than 0x8000 this exits through a AIOOB
 461     //  - Counted loop transformation is ok
 462     // If the array is longer then this is an endless loop
 463     //  - No transformation can be done.
 464 
 465     const TypeInt* incr_t = gvn->type(orig_incr)->is_int();
 466     if (limit_t->_hi > incr_t->_hi) {
 467       // if the limit can have a higher value than the increment (before the phi)
 468       return false;
 469     }
 470   }
 471 
 472   // Get merge point
 473   Node *xphi = incr->in(1);
 474   Node *stride = incr->in(2);
 475   if (!stride->is_Con()) {     // Oops, swap these
 476     if (!xphi->is_Con())       // Is the other guy a constant?
 477       return false;             // Nope, unknown stride, bail out
 478     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 479     xphi = stride;
 480     stride = tmp;
 481   }
 482   if (xphi->Opcode() == Op_CastII) {
 483     xphi = xphi->in(1);
 484   }
 485   // Stride must be constant
 486   int stride_con = stride->get_int();
 487   if (stride_con == 0)
 488     return false; // missed some peephole opt
 489 
 490   if (!xphi->is_Phi())
 491     return false; // Too much math on the trip counter
 492   if (phi_incr != NULL && phi_incr != xphi)
 493     return false;
 494   PhiNode *phi = xphi->as_Phi();
 495 
 496   // Phi must be of loop header; backedge must wrap to increment
 497   if (phi->region() != x)
 498     return false;
 499   if ((trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) ||
 500       (trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) {
 501     return false;
 502   }
 503   Node *init_trip = phi->in(LoopNode::EntryControl);
 504 
 505   // If iv trunc type is smaller than int, check for possible wrap.
 506   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 507     assert(trunc1 != NULL, "must have found some truncation");
 508 
 509     // Get a better type for the phi (filtered thru if's)
 510     const TypeInt* phi_ft = filtered_type(phi);
 511 
 512     // Can iv take on a value that will wrap?
 513     //
 514     // Ensure iv's limit is not within "stride" of the wrap value.
 515     //
 516     // Example for "short" type
 517     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 518     //    If the stride is +10, then the last value of the induction
 519     //    variable before the increment (phi_ft->_hi) must be
 520     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 521     //    ensure no truncation occurs after the increment.
 522 
 523     if (stride_con > 0) {
 524       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 525           iv_trunc_t->_lo > phi_ft->_lo) {
 526         return false;  // truncation may occur
 527       }
 528     } else if (stride_con < 0) {
 529       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 530           iv_trunc_t->_hi < phi_ft->_hi) {
 531         return false;  // truncation may occur
 532       }
 533     }
 534     // No possibility of wrap so truncation can be discarded
 535     // Promote iv type to Int
 536   } else {
 537     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 538   }
 539 
 540   // If the condition is inverted and we will be rolling
 541   // through MININT to MAXINT, then bail out.
 542   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 543       // Odd stride
 544       (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
 545       // Count down loop rolls through MAXINT
 546       ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
 547       // Count up loop rolls through MININT
 548       ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
 549     return false; // Bail out
 550   }
 551 
 552   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 553 
 554   if (stride_con > 0) {
 555     jlong init_p = (jlong)init_t->_lo + stride_con;
 556     if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
 557       return false; // cyclic loop or this loop trips only once
 558   } else {
 559     jlong init_p = (jlong)init_t->_hi + stride_con;
 560     if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
 561       return false; // cyclic loop or this loop trips only once
 562   }
 563 
 564   if (phi_incr != NULL && bt != BoolTest::ne) {
 565     // check if there is a possiblity of IV overflowing after the first increment
 566     if (stride_con > 0) {
 567       if (init_t->_hi > max_jint - stride_con) {
 568         return false;
 569       }
 570     } else {
 571       if (init_t->_lo < min_jint - stride_con) {
 572         return false;
 573       }
 574     }
 575   }
 576 
 577   // =================================================
 578   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 579   //
 580   assert(x->Opcode() == Op_Loop, "regular loops only");
 581   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 582 
 583   Node *hook = new Node(6);
 584 
 585   // ===================================================
 586   // Generate loop limit check to avoid integer overflow
 587   // in cases like next (cyclic loops):
 588   //
 589   // for (i=0; i <= max_jint; i++) {}
 590   // for (i=0; i <  max_jint; i+=2) {}
 591   //
 592   //
 593   // Limit check predicate depends on the loop test:
 594   //
 595   // for(;i != limit; i++)       --> limit <= (max_jint)
 596   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 597   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 598   //
 599 
 600   // Check if limit is excluded to do more precise int overflow check.
 601   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 602   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 603 
 604   // If compare points directly to the phi we need to adjust
 605   // the compare so that it points to the incr. Limit have
 606   // to be adjusted to keep trip count the same and the
 607   // adjusted limit should be checked for int overflow.
 608   if (phi_incr != NULL) {
 609     stride_m  += stride_con;
 610   }
 611 
 612   if (limit->is_Con()) {
 613     int limit_con = limit->get_int();
 614     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 615         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 616       // Bailout: it could be integer overflow.
 617       return false;
 618     }
 619   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 620              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 621       // Limit's type may satisfy the condition, for example,
 622       // when it is an array length.
 623   } else {
 624     // Generate loop's limit check.
 625     // Loop limit check predicate should be near the loop.
 626     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 627     if (!limit_check_proj) {
 628       // The limit check predicate is not generated if this method trapped here before.
 629 #ifdef ASSERT
 630       if (TraceLoopLimitCheck) {
 631         tty->print("missing loop limit check:");
 632         loop->dump_head();
 633         x->dump(1);
 634       }
 635 #endif
 636       return false;
 637     }
 638 
 639     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 640 
 641     if (!is_dominator(get_ctrl(limit), check_iff->in(0))) {
 642       return false;
 643     }
 644 
 645     Node* cmp_limit;
 646     Node* bol;
 647 
 648     if (stride_con > 0) {
 649       cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 650       bol = new BoolNode(cmp_limit, BoolTest::le);
 651     } else {
 652       cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 653       bol = new BoolNode(cmp_limit, BoolTest::ge);
 654     }
 655 
 656     insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 657   }
 658 
 659   // Now we need to canonicalize loop condition.
 660   if (bt == BoolTest::ne) {
 661     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 662     if (stride_con > 0 && init_t->_hi < limit_t->_lo) {
 663       // 'ne' can be replaced with 'lt' only when init < limit.
 664       bt = BoolTest::lt;
 665     } else if (stride_con < 0 && init_t->_lo > limit_t->_hi) {
 666       // 'ne' can be replaced with 'gt' only when init > limit.
 667       bt = BoolTest::gt;
 668     } else {
 669       ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 670       if (!limit_check_proj) {
 671         // The limit check predicate is not generated if this method trapped here before.
 672 #ifdef ASSERT
 673         if (TraceLoopLimitCheck) {
 674           tty->print("missing loop limit check:");
 675           loop->dump_head();
 676           x->dump(1);
 677         }
 678 #endif
 679         return false;
 680       }
 681       IfNode* check_iff = limit_check_proj->in(0)->as_If();
 682 
 683       if (!is_dominator(get_ctrl(limit), check_iff->in(0)) ||
 684           !is_dominator(get_ctrl(init_trip), check_iff->in(0))) {
 685         return false;
 686       }
 687 
 688       Node* cmp_limit;
 689       Node* bol;
 690 
 691       if (stride_con > 0) {
 692         cmp_limit = new CmpINode(init_trip, limit);
 693         bol = new BoolNode(cmp_limit, BoolTest::lt);
 694       } else {
 695         cmp_limit = new CmpINode(init_trip, limit);
 696         bol = new BoolNode(cmp_limit, BoolTest::gt);
 697       }
 698 
 699       insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 700 
 701       if (stride_con > 0) {
 702         // 'ne' can be replaced with 'lt' only when init < limit.
 703         bt = BoolTest::lt;
 704       } else if (stride_con < 0) {
 705         // 'ne' can be replaced with 'gt' only when init > limit.
 706         bt = BoolTest::gt;
 707       }
 708     }
 709   }
 710 
 711   if (phi_incr != NULL) {
 712     // If compare points directly to the phi we need to adjust
 713     // the compare so that it points to the incr. Limit have
 714     // to be adjusted to keep trip count the same and we
 715     // should avoid int overflow.
 716     //
 717     //   i = init; do {} while(i++ < limit);
 718     // is converted to
 719     //   i = init; do {} while(++i < limit+1);
 720     //
 721     limit = gvn->transform(new AddINode(limit, stride));
 722   }
 723 
 724   if (incl_limit) {
 725     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 726     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 727     //
 728     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 729     limit = gvn->transform(new AddINode(limit, one));
 730     if (bt == BoolTest::le)
 731       bt = BoolTest::lt;
 732     else if (bt == BoolTest::ge)
 733       bt = BoolTest::gt;
 734     else
 735       ShouldNotReachHere();
 736   }
 737   set_subtree_ctrl( limit );
 738 
 739   if (LoopStripMiningIter == 0) {
 740     // Check for SafePoint on backedge and remove
 741     Node *sfpt = x->in(LoopNode::LoopBackControl);
 742     if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 743       lazy_replace( sfpt, iftrue );
 744       if (loop->_safepts != NULL) {
 745         loop->_safepts->yank(sfpt);
 746       }
 747       loop->_tail = iftrue;
 748     }
 749   }
 750 
 751   // Build a canonical trip test.
 752   // Clone code, as old values may be in use.
 753   incr = incr->clone();
 754   incr->set_req(1,phi);
 755   incr->set_req(2,stride);
 756   incr = _igvn.register_new_node_with_optimizer(incr);
 757   set_early_ctrl( incr );
 758   _igvn.rehash_node_delayed(phi);
 759   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 760 
 761   // If phi type is more restrictive than Int, raise to
 762   // Int to prevent (almost) infinite recursion in igvn
 763   // which can only handle integer types for constants or minint..maxint.
 764   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 765     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 766     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 767     nphi = _igvn.register_new_node_with_optimizer(nphi);
 768     set_ctrl(nphi, get_ctrl(phi));
 769     _igvn.replace_node(phi, nphi);
 770     phi = nphi->as_Phi();
 771   }
 772   cmp = cmp->clone();
 773   cmp->set_req(1,incr);
 774   cmp->set_req(2,limit);
 775   cmp = _igvn.register_new_node_with_optimizer(cmp);
 776   set_ctrl(cmp, iff->in(0));
 777 
 778   test = test->clone()->as_Bool();
 779   (*(BoolTest*)&test->_test)._test = bt;
 780   test->set_req(1,cmp);
 781   _igvn.register_new_node_with_optimizer(test);
 782   set_ctrl(test, iff->in(0));
 783 
 784   // Replace the old IfNode with a new LoopEndNode
 785   Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 786   IfNode *le = lex->as_If();
 787   uint dd = dom_depth(iff);
 788   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 789   set_loop(le, loop);
 790 
 791   // Get the loop-exit control
 792   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 793 
 794   // Need to swap loop-exit and loop-back control?
 795   if (iftrue_op == Op_IfFalse) {
 796     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
 797     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
 798 
 799     loop->_tail = back_control = ift2;
 800     set_loop(ift2, loop);
 801     set_loop(iff2, get_loop(iffalse));
 802 
 803     // Lazy update of 'get_ctrl' mechanism.
 804     lazy_replace(iffalse, iff2);
 805     lazy_replace(iftrue,  ift2);
 806 
 807     // Swap names
 808     iffalse = iff2;
 809     iftrue  = ift2;
 810   } else {
 811     _igvn.rehash_node_delayed(iffalse);
 812     _igvn.rehash_node_delayed(iftrue);
 813     iffalse->set_req_X( 0, le, &_igvn );
 814     iftrue ->set_req_X( 0, le, &_igvn );
 815   }
 816 
 817   set_idom(iftrue,  le, dd+1);
 818   set_idom(iffalse, le, dd+1);
 819   assert(iff->outcnt() == 0, "should be dead now");
 820   lazy_replace( iff, le ); // fix 'get_ctrl'
 821 
 822   Node *sfpt2 = le->in(0);
 823 
 824   Node* entry_control = init_control;
 825   bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL &&
 826     sfpt2->Opcode() == Op_SafePoint && !loop->_has_call;
 827   IdealLoopTree* outer_ilt = NULL;
 828   if (strip_mine_loop) {
 829     outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
 830                                               cl_prob, le->_fcnt, entry_control,
 831                                               iffalse);
 832   }
 833 
 834   // Now setup a new CountedLoopNode to replace the existing LoopNode
 835   CountedLoopNode *l = new CountedLoopNode(entry_control, back_control);
 836   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 837   // The following assert is approximately true, and defines the intention
 838   // of can_be_counted_loop.  It fails, however, because phase->type
 839   // is not yet initialized for this loop and its parts.
 840   //assert(l->can_be_counted_loop(this), "sanity");
 841   _igvn.register_new_node_with_optimizer(l);
 842   set_loop(l, loop);
 843   loop->_head = l;
 844   // Fix all data nodes placed at the old loop head.
 845   // Uses the lazy-update mechanism of 'get_ctrl'.
 846   lazy_replace( x, l );
 847   set_idom(l, entry_control, dom_depth(entry_control) + 1);
 848 
 849   if (LoopStripMiningIter == 0 || strip_mine_loop) {
 850     // Check for immediately preceding SafePoint and remove
 851     if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) {
 852       if (strip_mine_loop) {
 853         Node* outer_le = outer_ilt->_tail->in(0);
 854         Node* sfpt = sfpt2->clone();
 855         sfpt->set_req(0, iffalse);
 856         outer_le->set_req(0, sfpt);
 857         register_control(sfpt, outer_ilt, iffalse);
 858         set_idom(outer_le, sfpt, dom_depth(sfpt));
 859       }
 860       lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 861       if (loop->_safepts != NULL) {
 862         loop->_safepts->yank(sfpt2);
 863       }
 864     }
 865   }
 866 
 867   // Free up intermediate goo
 868   _igvn.remove_dead_node(hook);
 869 
 870 #ifdef ASSERT
 871   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 872   assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
 873 #endif
 874 #ifndef PRODUCT
 875   if (TraceLoopOpts) {
 876     tty->print("Counted      ");
 877     loop->dump_head();
 878   }
 879 #endif
 880 
 881   C->print_method(PHASE_AFTER_CLOOPS, 3);
 882 
 883   // Capture bounds of the loop in the induction variable Phi before
 884   // subsequent transformation (iteration splitting) obscures the
 885   // bounds
 886   l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
 887 
 888   if (strip_mine_loop) {
 889     l->mark_strip_mined();
 890     l->verify_strip_mined(1);
 891     outer_ilt->_head->as_Loop()->verify_strip_mined(1);
 892     loop = outer_ilt;
 893   }
 894 
 895   return true;
 896 }
 897 
 898 //----------------------exact_limit-------------------------------------------
 899 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 900   assert(loop->_head->is_CountedLoop(), "");
 901   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 902   assert(cl->is_valid_counted_loop(), "");
 903 
 904   if (ABS(cl->stride_con()) == 1 ||
 905       cl->limit()->Opcode() == Op_LoopLimit) {
 906     // Old code has exact limit (it could be incorrect in case of int overflow).
 907     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 908     return cl->limit();
 909   }
 910   Node *limit = NULL;
 911 #ifdef ASSERT
 912   BoolTest::mask bt = cl->loopexit()->test_trip();
 913   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 914 #endif
 915   if (cl->has_exact_trip_count()) {
 916     // Simple case: loop has constant boundaries.
 917     // Use jlongs to avoid integer overflow.
 918     int stride_con = cl->stride_con();
 919     jlong  init_con = cl->init_trip()->get_int();
 920     jlong limit_con = cl->limit()->get_int();
 921     julong trip_cnt = cl->trip_count();
 922     jlong final_con = init_con + trip_cnt*stride_con;
 923     int final_int = (int)final_con;
 924     // The final value should be in integer range since the loop
 925     // is counted and the limit was checked for overflow.
 926     assert(final_con == (jlong)final_int, "final value should be integer");
 927     limit = _igvn.intcon(final_int);
 928   } else {
 929     // Create new LoopLimit node to get exact limit (final iv value).
 930     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 931     register_new_node(limit, cl->in(LoopNode::EntryControl));
 932   }
 933   assert(limit != NULL, "sanity");
 934   return limit;
 935 }
 936 
 937 //------------------------------Ideal------------------------------------------
 938 // Return a node which is more "ideal" than the current node.
 939 // Attempt to convert into a counted-loop.
 940 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 941   if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
 942     phase->C->set_major_progress();
 943   }
 944   return RegionNode::Ideal(phase, can_reshape);
 945 }
 946 
 947 void LoopNode::verify_strip_mined(int expect_skeleton) const {
 948 #ifdef ASSERT
 949   const OuterStripMinedLoopNode* outer = NULL;
 950   const CountedLoopNode* inner = NULL;
 951   if (is_strip_mined()) {
 952     assert(is_CountedLoop(), "no Loop should be marked strip mined");
 953     inner = as_CountedLoop();
 954     outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
 955   } else if (is_OuterStripMinedLoop()) {
 956     outer = this->as_OuterStripMinedLoop();
 957     inner = outer->unique_ctrl_out()->as_CountedLoop();
 958     assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
 959   }
 960   if (inner != NULL || outer != NULL) {
 961     assert(inner != NULL && outer != NULL, "missing loop in strip mined nest");
 962     Node* outer_tail = outer->in(LoopNode::LoopBackControl);
 963     Node* outer_le = outer_tail->in(0);
 964     assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
 965     Node* sfpt = outer_le->in(0);
 966     assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
 967     Node* inner_out = sfpt->in(0);
 968     if (inner_out->outcnt() != 1) {
 969       ResourceMark rm;
 970       Unique_Node_List wq;
 971 
 972       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
 973         Node* u = inner_out->fast_out(i);
 974         if (u == sfpt) {
 975           continue;
 976         }
 977         wq.clear();
 978         wq.push(u);
 979         bool found_sfpt = false;
 980         for (uint next = 0; next < wq.size() && !found_sfpt; next++) {
 981           Node* n = wq.at(next);
 982           for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) {
 983             Node* u = n->fast_out(i);
 984             if (u == sfpt) {
 985               found_sfpt = true;
 986             }
 987             if (!u->is_CFG()) {
 988               wq.push(u);
 989             }
 990           }
 991         }
 992         assert(found_sfpt, "no node in loop that's not input to safepoint");
 993       }
 994     }
 995 
 996     if (UseZGC && !inner_out->in(0)->is_CountedLoopEnd()) {
 997       // In some very special cases there can be a load that has no other uses than the
 998       // counted loop safepoint. Then its loadbarrier will be placed between the inner
 999       // loop exit and the safepoint. This is very rare
1000 
1001       Node* ifnode = inner_out->in(1)->in(0);
1002       // Region->IfTrue->If == Region->Iffalse->If
1003       if (ifnode == inner_out->in(2)->in(0)) {
1004         inner_out = ifnode->in(0);
1005       }
1006     }
1007 
1008     CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
1009     assert(cle == inner->loopexit_or_null(), "mismatch");
1010     bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
1011     if (has_skeleton) {
1012       assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
1013       assert(outer->outcnt() == 2, "only phis");
1014     } else {
1015       assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
1016       uint phis = 0;
1017       for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
1018         Node* u = inner->fast_out(i);
1019         if (u->is_Phi()) {
1020           phis++;
1021         }
1022       }
1023       for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
1024         Node* u = outer->fast_out(i);
1025         assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
1026       }
1027       uint stores = 0;
1028       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
1029         Node* u = inner_out->fast_out(i);
1030         if (u->is_Store()) {
1031           stores++;
1032         }
1033       }
1034       assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
1035     }
1036     assert(sfpt->outcnt() == 1, "no data node");
1037     assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
1038   }
1039 #endif
1040 }
1041 
1042 //=============================================================================
1043 //------------------------------Ideal------------------------------------------
1044 // Return a node which is more "ideal" than the current node.
1045 // Attempt to convert into a counted-loop.
1046 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1047   return RegionNode::Ideal(phase, can_reshape);
1048 }
1049 
1050 //------------------------------dump_spec--------------------------------------
1051 // Dump special per-node info
1052 #ifndef PRODUCT
1053 void CountedLoopNode::dump_spec(outputStream *st) const {
1054   LoopNode::dump_spec(st);
1055   if (stride_is_con()) {
1056     st->print("stride: %d ",stride_con());
1057   }
1058   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
1059   if (is_main_loop()) st->print("main of N%d", _idx);
1060   if (is_post_loop()) st->print("post of N%d", _main_idx);
1061   if (is_strip_mined()) st->print(" strip mined");
1062 }
1063 #endif
1064 
1065 //=============================================================================
1066 int CountedLoopEndNode::stride_con() const {
1067   return stride()->bottom_type()->is_int()->get_con();
1068 }
1069 
1070 //=============================================================================
1071 //------------------------------Value-----------------------------------------
1072 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
1073   const Type* init_t   = phase->type(in(Init));
1074   const Type* limit_t  = phase->type(in(Limit));
1075   const Type* stride_t = phase->type(in(Stride));
1076   // Either input is TOP ==> the result is TOP
1077   if (init_t   == Type::TOP) return Type::TOP;
1078   if (limit_t  == Type::TOP) return Type::TOP;
1079   if (stride_t == Type::TOP) return Type::TOP;
1080 
1081   int stride_con = stride_t->is_int()->get_con();
1082   if (stride_con == 1)
1083     return NULL;  // Identity
1084 
1085   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
1086     // Use jlongs to avoid integer overflow.
1087     jlong init_con   =  init_t->is_int()->get_con();
1088     jlong limit_con  = limit_t->is_int()->get_con();
1089     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
1090     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
1091     jlong final_con  = init_con + stride_con*trip_count;
1092     int final_int = (int)final_con;
1093     // The final value should be in integer range since the loop
1094     // is counted and the limit was checked for overflow.
1095     assert(final_con == (jlong)final_int, "final value should be integer");
1096     return TypeInt::make(final_int);
1097   }
1098 
1099   return bottom_type(); // TypeInt::INT
1100 }
1101 
1102 //------------------------------Ideal------------------------------------------
1103 // Return a node which is more "ideal" than the current node.
1104 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1105   if (phase->type(in(Init))   == Type::TOP ||
1106       phase->type(in(Limit))  == Type::TOP ||
1107       phase->type(in(Stride)) == Type::TOP)
1108     return NULL;  // Dead
1109 
1110   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1111   if (stride_con == 1)
1112     return NULL;  // Identity
1113 
1114   if (in(Init)->is_Con() && in(Limit)->is_Con())
1115     return NULL;  // Value
1116 
1117   // Delay following optimizations until all loop optimizations
1118   // done to keep Ideal graph simple.
1119   if (!can_reshape || phase->C->major_progress())
1120     return NULL;
1121 
1122   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
1123   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
1124   int stride_p;
1125   jlong lim, ini;
1126   julong max;
1127   if (stride_con > 0) {
1128     stride_p = stride_con;
1129     lim = limit_t->_hi;
1130     ini = init_t->_lo;
1131     max = (julong)max_jint;
1132   } else {
1133     stride_p = -stride_con;
1134     lim = init_t->_hi;
1135     ini = limit_t->_lo;
1136     max = (julong)min_jint;
1137   }
1138   julong range = lim - ini + stride_p;
1139   if (range <= max) {
1140     // Convert to integer expression if it is not overflow.
1141     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
1142     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
1143     Node *bias  = phase->transform(new AddINode(range, stride_m));
1144     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
1145     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
1146     return new AddINode(span, in(Init)); // exact limit
1147   }
1148 
1149   if (is_power_of_2(stride_p) ||                // divisor is 2^n
1150       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
1151     // Convert to long expression to avoid integer overflow
1152     // and let igvn optimizer convert this division.
1153     //
1154     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
1155     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
1156     Node* stride   = phase->longcon(stride_con);
1157     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
1158 
1159     Node *range = phase->transform(new SubLNode(limit, init));
1160     Node *bias  = phase->transform(new AddLNode(range, stride_m));
1161     Node *span;
1162     if (stride_con > 0 && is_power_of_2(stride_p)) {
1163       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
1164       // and avoid generating rounding for division. Zero trip guard should
1165       // guarantee that init < limit but sometimes the guard is missing and
1166       // we can get situation when init > limit. Note, for the empty loop
1167       // optimization zero trip guard is generated explicitly which leaves
1168       // only RCE predicate where exact limit is used and the predicate
1169       // will simply fail forcing recompilation.
1170       Node* neg_stride   = phase->longcon(-stride_con);
1171       span = phase->transform(new AndLNode(bias, neg_stride));
1172     } else {
1173       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
1174       span = phase->transform(new MulLNode(trip, stride));
1175     }
1176     // Convert back to int
1177     Node *span_int = phase->transform(new ConvL2INode(span));
1178     return new AddINode(span_int, in(Init)); // exact limit
1179   }
1180 
1181   return NULL;    // No progress
1182 }
1183 
1184 //------------------------------Identity---------------------------------------
1185 // If stride == 1 return limit node.
1186 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1187   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1188   if (stride_con == 1 || stride_con == -1)
1189     return in(Limit);
1190   return this;
1191 }
1192 
1193 //=============================================================================
1194 //----------------------match_incr_with_optional_truncation--------------------
1195 // Match increment with optional truncation:
1196 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1197 // Return NULL for failure. Success returns the increment node.
1198 Node* CountedLoopNode::match_incr_with_optional_truncation(
1199                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1200   // Quick cutouts:
1201   if (expr == NULL || expr->req() != 3)  return NULL;
1202 
1203   Node *t1 = NULL;
1204   Node *t2 = NULL;
1205   const TypeInt* trunc_t = TypeInt::INT;
1206   Node* n1 = expr;
1207   int   n1op = n1->Opcode();
1208 
1209   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1210   if (n1op == Op_AndI &&
1211       n1->in(2)->is_Con() &&
1212       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1213     // %%% This check should match any mask of 2**K-1.
1214     t1 = n1;
1215     n1 = t1->in(1);
1216     n1op = n1->Opcode();
1217     trunc_t = TypeInt::CHAR;
1218   } else if (n1op == Op_RShiftI &&
1219              n1->in(1) != NULL &&
1220              n1->in(1)->Opcode() == Op_LShiftI &&
1221              n1->in(2) == n1->in(1)->in(2) &&
1222              n1->in(2)->is_Con()) {
1223     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1224     // %%% This check should match any shift in [1..31].
1225     if (shift == 16 || shift == 8) {
1226       t1 = n1;
1227       t2 = t1->in(1);
1228       n1 = t2->in(1);
1229       n1op = n1->Opcode();
1230       if (shift == 16) {
1231         trunc_t = TypeInt::SHORT;
1232       } else if (shift == 8) {
1233         trunc_t = TypeInt::BYTE;
1234       }
1235     }
1236   }
1237 
1238   // If (maybe after stripping) it is an AddI, we won:
1239   if (n1op == Op_AddI) {
1240     *trunc1 = t1;
1241     *trunc2 = t2;
1242     *trunc_type = trunc_t;
1243     return n1;
1244   }
1245 
1246   // failed
1247   return NULL;
1248 }
1249 
1250 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
1251   if (is_strip_mined()) {
1252     verify_strip_mined(expect_skeleton);
1253     return in(EntryControl)->as_Loop();
1254   }
1255   return this;
1256 }
1257 
1258 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
1259   assert(is_strip_mined(), "not a strip mined loop");
1260   Node* c = in(EntryControl);
1261   if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) {
1262     return NULL;
1263   }
1264   return c->as_OuterStripMinedLoop();
1265 }
1266 
1267 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
1268   Node* c = in(LoopBackControl);
1269   if (c == NULL || c->is_top()) {
1270     return NULL;
1271   }
1272   return c->as_IfTrue();
1273 }
1274 
1275 IfTrueNode* CountedLoopNode::outer_loop_tail() const {
1276   LoopNode* l = outer_loop();
1277   if (l == NULL) {
1278     return NULL;
1279   }
1280   return l->outer_loop_tail();
1281 }
1282 
1283 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
1284   IfTrueNode* proj = outer_loop_tail();
1285   if (proj == NULL) {
1286     return NULL;
1287   }
1288   Node* c = proj->in(0);
1289   if (c == NULL || c->is_top() || c->outcnt() != 2) {
1290     return NULL;
1291   }
1292   return c->as_OuterStripMinedLoopEnd();
1293 }
1294 
1295 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
1296   LoopNode* l = outer_loop();
1297   if (l == NULL) {
1298     return NULL;
1299   }
1300   return l->outer_loop_end();
1301 }
1302 
1303 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
1304   IfNode* le = outer_loop_end();
1305   if (le == NULL) {
1306     return NULL;
1307   }
1308   Node* c = le->proj_out_or_null(false);
1309   if (c == NULL) {
1310     return NULL;
1311   }
1312   return c->as_IfFalse();
1313 }
1314 
1315 IfFalseNode* CountedLoopNode::outer_loop_exit() const {
1316   LoopNode* l = outer_loop();
1317   if (l == NULL) {
1318     return NULL;
1319   }
1320   return l->outer_loop_exit();
1321 }
1322 
1323 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
1324   IfNode* le = outer_loop_end();
1325   if (le == NULL) {
1326     return NULL;
1327   }
1328   Node* c = le->in(0);
1329   if (c == NULL || c->is_top()) {
1330     return NULL;
1331   }
1332   assert(c->Opcode() == Op_SafePoint, "broken outer loop");
1333   return c->as_SafePoint();
1334 }
1335 
1336 SafePointNode* CountedLoopNode::outer_safepoint() const {
1337   LoopNode* l = outer_loop();
1338   if (l == NULL) {
1339     return NULL;
1340   }
1341   return l->outer_safepoint();
1342 }
1343 
1344 Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
1345     while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() &&
1346            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
1347            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) {
1348       ctrl = ctrl->in(0)->in(0);
1349     }
1350 
1351     return ctrl;
1352   }
1353 
1354 Node* CountedLoopNode::skip_predicates() {
1355   if (is_main_loop()) {
1356     Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
1357 
1358     return skip_predicates_from_entry(ctrl);
1359   }
1360   return in(LoopNode::EntryControl);
1361 }
1362 
1363 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
1364   // Look for the outer & inner strip mined loop, reduce number of
1365   // iterations of the inner loop, set exit condition of outer loop,
1366   // construct required phi nodes for outer loop.
1367   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
1368   assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
1369   Node* inner_iv_phi = inner_cl->phi();
1370   if (inner_iv_phi == NULL) {
1371     IfNode* outer_le = outer_loop_end();
1372     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1373     igvn->replace_node(outer_le, iff);
1374     inner_cl->clear_strip_mined();
1375     return;
1376   }
1377   CountedLoopEndNode* inner_cle = inner_cl->loopexit();
1378 
1379   int stride = inner_cl->stride_con();
1380   jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
1381   int scaled_iters = (int)scaled_iters_long;
1382   int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
1383   const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
1384   jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
1385   assert(iter_estimate > 0, "broken");
1386   if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
1387     // Remove outer loop and safepoint (too few iterations)
1388     Node* outer_sfpt = outer_safepoint();
1389     Node* outer_out = outer_loop_exit();
1390     igvn->replace_node(outer_out, outer_sfpt->in(0));
1391     igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
1392     inner_cl->clear_strip_mined();
1393     return;
1394   }
1395   if (iter_estimate <= scaled_iters_long) {
1396     // We would only go through one iteration of
1397     // the outer loop: drop the outer loop but
1398     // keep the safepoint so we don't run for
1399     // too long without a safepoint
1400     IfNode* outer_le = outer_loop_end();
1401     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1402     igvn->replace_node(outer_le, iff);
1403     inner_cl->clear_strip_mined();
1404     return;
1405   }
1406 
1407   Node* cle_tail = inner_cle->proj_out(true);
1408   ResourceMark rm;
1409   Node_List old_new;
1410   if (cle_tail->outcnt() > 1) {
1411     // Look for nodes on backedge of inner loop and clone them
1412     Unique_Node_List backedge_nodes;
1413     for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
1414       Node* u = cle_tail->fast_out(i);
1415       if (u != inner_cl) {
1416         assert(!u->is_CFG(), "control flow on the backedge?");
1417         backedge_nodes.push(u);
1418       }
1419     }
1420     uint last = igvn->C->unique();
1421     for (uint next = 0; next < backedge_nodes.size(); next++) {
1422       Node* n = backedge_nodes.at(next);
1423       old_new.map(n->_idx, n->clone());
1424       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1425         Node* u = n->fast_out(i);
1426         assert(!u->is_CFG(), "broken");
1427         if (u->_idx >= last) {
1428           continue;
1429         }
1430         if (!u->is_Phi()) {
1431           backedge_nodes.push(u);
1432         } else {
1433           assert(u->in(0) == inner_cl, "strange phi on the backedge");
1434         }
1435       }
1436     }
1437     // Put the clones on the outer loop backedge
1438     Node* le_tail = outer_loop_tail();
1439     for (uint next = 0; next < backedge_nodes.size(); next++) {
1440       Node *n = old_new[backedge_nodes.at(next)->_idx];
1441       for (uint i = 1; i < n->req(); i++) {
1442         if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) {
1443           n->set_req(i, old_new[n->in(i)->_idx]);
1444         }
1445       }
1446       if (n->in(0) != NULL && n->in(0) == cle_tail) {
1447         n->set_req(0, le_tail);
1448       }
1449       igvn->register_new_node_with_optimizer(n);
1450     }
1451   }
1452 
1453   Node* iv_phi = NULL;
1454   // Make a clone of each phi in the inner loop
1455   // for the outer loop
1456   for (uint i = 0; i < inner_cl->outcnt(); i++) {
1457     Node* u = inner_cl->raw_out(i);
1458     if (u->is_Phi()) {
1459       assert(u->in(0) == inner_cl, "inconsistent");
1460       Node* phi = u->clone();
1461       phi->set_req(0, this);
1462       Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
1463       if (be != NULL) {
1464         phi->set_req(LoopNode::LoopBackControl, be);
1465       }
1466       phi = igvn->transform(phi);
1467       igvn->replace_input_of(u, LoopNode::EntryControl, phi);
1468       if (u == inner_iv_phi) {
1469         iv_phi = phi;
1470       }
1471     }
1472   }
1473   Node* cle_out = inner_cle->proj_out(false);
1474   if (cle_out->outcnt() > 1) {
1475     // Look for chains of stores that were sunk
1476     // out of the inner loop and are in the outer loop
1477     for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
1478       Node* u = cle_out->fast_out(i);
1479       if (u->is_Store()) {
1480         Node* first = u;
1481         for(;;) {
1482           Node* next = first->in(MemNode::Memory);
1483           if (!next->is_Store() || next->in(0) != cle_out) {
1484             break;
1485           }
1486           first = next;
1487         }
1488         Node* last = u;
1489         for(;;) {
1490           Node* next = NULL;
1491           for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
1492             Node* uu = last->fast_out(j);
1493             if (uu->is_Store() && uu->in(0) == cle_out) {
1494               assert(next == NULL, "only one in the outer loop");
1495               next = uu;
1496             }
1497           }
1498           if (next == NULL) {
1499             break;
1500           }
1501           last = next;
1502         }
1503         Node* phi = NULL;
1504         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1505           Node* uu = fast_out(j);
1506           if (uu->is_Phi()) {
1507             Node* be = uu->in(LoopNode::LoopBackControl);
1508             if (be->is_Store() && old_new[be->_idx] != NULL) {
1509               assert(false, "store on the backedge + sunk stores: unsupported");
1510               // drop outer loop
1511               IfNode* outer_le = outer_loop_end();
1512               Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1513               igvn->replace_node(outer_le, iff);
1514               inner_cl->clear_strip_mined();
1515               return;
1516             }
1517             if (be == last || be == first->in(MemNode::Memory)) {
1518               assert(phi == NULL, "only one phi");
1519               phi = uu;
1520             }
1521           }
1522         }
1523 #ifdef ASSERT
1524         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1525           Node* uu = fast_out(j);
1526           if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
1527             if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
1528               assert(phi == uu, "what's that phi?");
1529             } else if (uu->adr_type() == TypePtr::BOTTOM) {
1530               Node* n = uu->in(LoopNode::LoopBackControl);
1531               uint limit = igvn->C->live_nodes();
1532               uint i = 0;
1533               while (n != uu) {
1534                 i++;
1535                 assert(i < limit, "infinite loop");
1536                 if (n->is_Proj()) {
1537                   n = n->in(0);
1538                 } else if (n->is_SafePoint() || n->is_MemBar()) {
1539                   n = n->in(TypeFunc::Memory);
1540                 } else if (n->is_Phi()) {
1541                   n = n->in(1);
1542                 } else if (n->is_MergeMem()) {
1543                   n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
1544                 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
1545                   n = n->in(MemNode::Memory);
1546                 } else {
1547                   n->dump();
1548                   ShouldNotReachHere();
1549                 }
1550               }
1551             }
1552           }
1553         }
1554 #endif
1555         if (phi == NULL) {
1556           // If the an entire chains was sunk, the
1557           // inner loop has no phi for that memory
1558           // slice, create one for the outer loop
1559           phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY,
1560                               igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
1561           phi->set_req(LoopNode::LoopBackControl, last);
1562           phi = igvn->transform(phi);
1563           igvn->replace_input_of(first, MemNode::Memory, phi);
1564         } else {
1565           // Or fix the outer loop fix to include
1566           // that chain of stores.
1567           Node* be = phi->in(LoopNode::LoopBackControl);
1568           assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported");
1569           if (be == first->in(MemNode::Memory)) {
1570             if (be == phi->in(LoopNode::LoopBackControl)) {
1571               igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
1572             } else {
1573               igvn->replace_input_of(be, MemNode::Memory, last);
1574             }
1575           } else {
1576 #ifdef ASSERT
1577             if (be == phi->in(LoopNode::LoopBackControl)) {
1578               assert(phi->in(LoopNode::LoopBackControl) == last, "");
1579             } else {
1580               assert(be->in(MemNode::Memory) == last, "");
1581             }
1582 #endif
1583           }
1584         }
1585       }
1586     }
1587   }
1588 
1589   if (iv_phi != NULL) {
1590     // Now adjust the inner loop's exit condition
1591     Node* limit = inner_cl->limit();
1592     Node* sub = NULL;
1593     if (stride > 0) {
1594       sub = igvn->transform(new SubINode(limit, iv_phi));
1595     } else {
1596       sub = igvn->transform(new SubINode(iv_phi, limit));
1597     }
1598     Node* min = igvn->transform(new MinINode(sub, igvn->intcon(scaled_iters)));
1599     Node* new_limit = NULL;
1600     if (stride > 0) {
1601       new_limit = igvn->transform(new AddINode(min, iv_phi));
1602     } else {
1603       new_limit = igvn->transform(new SubINode(iv_phi, min));
1604     }
1605     Node* inner_cmp = inner_cle->cmp_node();
1606     Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
1607     Node* outer_bol = inner_bol;
1608     // cmp node for inner loop may be shared
1609     inner_cmp = inner_cmp->clone();
1610     inner_cmp->set_req(2, new_limit);
1611     inner_bol = inner_bol->clone();
1612     inner_bol->set_req(1, igvn->transform(inner_cmp));
1613     igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
1614     // Set the outer loop's exit condition too
1615     igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
1616   } else {
1617     assert(false, "should be able to adjust outer loop");
1618     IfNode* outer_le = outer_loop_end();
1619     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1620     igvn->replace_node(outer_le, iff);
1621     inner_cl->clear_strip_mined();
1622   }
1623 }
1624 
1625 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
1626   if (!in(0)) return Type::TOP;
1627   if (phase->type(in(0)) == Type::TOP)
1628     return Type::TOP;
1629 
1630   return TypeTuple::IFBOTH;
1631 }
1632 
1633 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1634   if (remove_dead_region(phase, can_reshape))  return this;
1635 
1636   return NULL;
1637 }
1638 
1639 //------------------------------filtered_type--------------------------------
1640 // Return a type based on condition control flow
1641 // A successful return will be a type that is restricted due
1642 // to a series of dominating if-tests, such as:
1643 //    if (i < 10) {
1644 //       if (i > 0) {
1645 //          here: "i" type is [1..10)
1646 //       }
1647 //    }
1648 // or a control flow merge
1649 //    if (i < 10) {
1650 //       do {
1651 //          phi( , ) -- at top of loop type is [min_int..10)
1652 //         i = ?
1653 //       } while ( i < 10)
1654 //
1655 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1656   assert(n && n->bottom_type()->is_int(), "must be int");
1657   const TypeInt* filtered_t = NULL;
1658   if (!n->is_Phi()) {
1659     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1660     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1661 
1662   } else {
1663     Node* phi    = n->as_Phi();
1664     Node* region = phi->in(0);
1665     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1666     if (region && region != C->top()) {
1667       for (uint i = 1; i < phi->req(); i++) {
1668         Node* val   = phi->in(i);
1669         Node* use_c = region->in(i);
1670         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1671         if (val_t != NULL) {
1672           if (filtered_t == NULL) {
1673             filtered_t = val_t;
1674           } else {
1675             filtered_t = filtered_t->meet(val_t)->is_int();
1676           }
1677         }
1678       }
1679     }
1680   }
1681   const TypeInt* n_t = _igvn.type(n)->is_int();
1682   if (filtered_t != NULL) {
1683     n_t = n_t->join(filtered_t)->is_int();
1684   }
1685   return n_t;
1686 }
1687 
1688 
1689 //------------------------------filtered_type_from_dominators--------------------------------
1690 // Return a possibly more restrictive type for val based on condition control flow of dominators
1691 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1692   if (val->is_Con()) {
1693      return val->bottom_type()->is_int();
1694   }
1695   uint if_limit = 10; // Max number of dominating if's visited
1696   const TypeInt* rtn_t = NULL;
1697 
1698   if (use_ctrl && use_ctrl != C->top()) {
1699     Node* val_ctrl = get_ctrl(val);
1700     uint val_dom_depth = dom_depth(val_ctrl);
1701     Node* pred = use_ctrl;
1702     uint if_cnt = 0;
1703     while (if_cnt < if_limit) {
1704       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1705         if_cnt++;
1706         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1707         if (if_t != NULL) {
1708           if (rtn_t == NULL) {
1709             rtn_t = if_t;
1710           } else {
1711             rtn_t = rtn_t->join(if_t)->is_int();
1712           }
1713         }
1714       }
1715       pred = idom(pred);
1716       if (pred == NULL || pred == C->top()) {
1717         break;
1718       }
1719       // Stop if going beyond definition block of val
1720       if (dom_depth(pred) < val_dom_depth) {
1721         break;
1722       }
1723     }
1724   }
1725   return rtn_t;
1726 }
1727 
1728 
1729 //------------------------------dump_spec--------------------------------------
1730 // Dump special per-node info
1731 #ifndef PRODUCT
1732 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1733   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1734     BoolTest bt( test_trip()); // Added this for g++.
1735 
1736     st->print("[");
1737     bt.dump_on(st);
1738     st->print("]");
1739   }
1740   st->print(" ");
1741   IfNode::dump_spec(st);
1742 }
1743 #endif
1744 
1745 //=============================================================================
1746 //------------------------------is_member--------------------------------------
1747 // Is 'l' a member of 'this'?
1748 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1749   while( l->_nest > _nest ) l = l->_parent;
1750   return l == this;
1751 }
1752 
1753 //------------------------------set_nest---------------------------------------
1754 // Set loop tree nesting depth.  Accumulate _has_call bits.
1755 int IdealLoopTree::set_nest( uint depth ) {
1756   _nest = depth;
1757   int bits = _has_call;
1758   if( _child ) bits |= _child->set_nest(depth+1);
1759   if( bits ) _has_call = 1;
1760   if( _next  ) bits |= _next ->set_nest(depth  );
1761   return bits;
1762 }
1763 
1764 //------------------------------split_fall_in----------------------------------
1765 // Split out multiple fall-in edges from the loop header.  Move them to a
1766 // private RegionNode before the loop.  This becomes the loop landing pad.
1767 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1768   PhaseIterGVN &igvn = phase->_igvn;
1769   uint i;
1770 
1771   // Make a new RegionNode to be the landing pad.
1772   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1773   phase->set_loop(landing_pad,_parent);
1774   // Gather all the fall-in control paths into the landing pad
1775   uint icnt = fall_in_cnt;
1776   uint oreq = _head->req();
1777   for( i = oreq-1; i>0; i-- )
1778     if( !phase->is_member( this, _head->in(i) ) )
1779       landing_pad->set_req(icnt--,_head->in(i));
1780 
1781   // Peel off PhiNode edges as well
1782   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1783     Node *oj = _head->fast_out(j);
1784     if( oj->is_Phi() ) {
1785       PhiNode* old_phi = oj->as_Phi();
1786       assert( old_phi->region() == _head, "" );
1787       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1788       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1789       uint icnt = fall_in_cnt;
1790       for( i = oreq-1; i>0; i-- ) {
1791         if( !phase->is_member( this, _head->in(i) ) ) {
1792           p->init_req(icnt--, old_phi->in(i));
1793           // Go ahead and clean out old edges from old phi
1794           old_phi->del_req(i);
1795         }
1796       }
1797       // Search for CSE's here, because ZKM.jar does a lot of
1798       // loop hackery and we need to be a little incremental
1799       // with the CSE to avoid O(N^2) node blow-up.
1800       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1801       if( p2 ) {                // Found CSE
1802         p->destruct();          // Recover useless new node
1803         p = p2;                 // Use old node
1804       } else {
1805         igvn.register_new_node_with_optimizer(p, old_phi);
1806       }
1807       // Make old Phi refer to new Phi.
1808       old_phi->add_req(p);
1809       // Check for the special case of making the old phi useless and
1810       // disappear it.  In JavaGrande I have a case where this useless
1811       // Phi is the loop limit and prevents recognizing a CountedLoop
1812       // which in turn prevents removing an empty loop.
1813       Node *id_old_phi = igvn.apply_identity(old_phi);
1814       if( id_old_phi != old_phi ) { // Found a simple identity?
1815         // Note that I cannot call 'replace_node' here, because
1816         // that will yank the edge from old_phi to the Region and
1817         // I'm mid-iteration over the Region's uses.
1818         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1819           Node* use = old_phi->last_out(i);
1820           igvn.rehash_node_delayed(use);
1821           uint uses_found = 0;
1822           for (uint j = 0; j < use->len(); j++) {
1823             if (use->in(j) == old_phi) {
1824               if (j < use->req()) use->set_req (j, id_old_phi);
1825               else                use->set_prec(j, id_old_phi);
1826               uses_found++;
1827             }
1828           }
1829           i -= uses_found;    // we deleted 1 or more copies of this edge
1830         }
1831       }
1832       igvn._worklist.push(old_phi);
1833     }
1834   }
1835   // Finally clean out the fall-in edges from the RegionNode
1836   for( i = oreq-1; i>0; i-- ) {
1837     if( !phase->is_member( this, _head->in(i) ) ) {
1838       _head->del_req(i);
1839     }
1840   }
1841   igvn.rehash_node_delayed(_head);
1842   // Transform landing pad
1843   igvn.register_new_node_with_optimizer(landing_pad, _head);
1844   // Insert landing pad into the header
1845   _head->add_req(landing_pad);
1846 }
1847 
1848 //------------------------------split_outer_loop-------------------------------
1849 // Split out the outermost loop from this shared header.
1850 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1851   PhaseIterGVN &igvn = phase->_igvn;
1852 
1853   // Find index of outermost loop; it should also be my tail.
1854   uint outer_idx = 1;
1855   while( _head->in(outer_idx) != _tail ) outer_idx++;
1856 
1857   // Make a LoopNode for the outermost loop.
1858   Node *ctl = _head->in(LoopNode::EntryControl);
1859   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1860   outer = igvn.register_new_node_with_optimizer(outer, _head);
1861   phase->set_created_loop_node();
1862 
1863   // Outermost loop falls into '_head' loop
1864   _head->set_req(LoopNode::EntryControl, outer);
1865   _head->del_req(outer_idx);
1866   // Split all the Phis up between '_head' loop and 'outer' loop.
1867   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1868     Node *out = _head->fast_out(j);
1869     if( out->is_Phi() ) {
1870       PhiNode *old_phi = out->as_Phi();
1871       assert( old_phi->region() == _head, "" );
1872       Node *phi = PhiNode::make_blank(outer, old_phi);
1873       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1874       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1875       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1876       // Make old Phi point to new Phi on the fall-in path
1877       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1878       old_phi->del_req(outer_idx);
1879     }
1880   }
1881 
1882   // Use the new loop head instead of the old shared one
1883   _head = outer;
1884   phase->set_loop(_head, this);
1885 }
1886 
1887 //------------------------------fix_parent-------------------------------------
1888 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1889   loop->_parent = parent;
1890   if( loop->_child ) fix_parent( loop->_child, loop   );
1891   if( loop->_next  ) fix_parent( loop->_next , parent );
1892 }
1893 
1894 //------------------------------estimate_path_freq-----------------------------
1895 static float estimate_path_freq( Node *n ) {
1896   // Try to extract some path frequency info
1897   IfNode *iff;
1898   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1899     uint nop = n->Opcode();
1900     if( nop == Op_SafePoint ) {   // Skip any safepoint
1901       n = n->in(0);
1902       continue;
1903     }
1904     if( nop == Op_CatchProj ) {   // Get count from a prior call
1905       // Assume call does not always throw exceptions: means the call-site
1906       // count is also the frequency of the fall-through path.
1907       assert( n->is_CatchProj(), "" );
1908       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1909         return 0.0f;            // Assume call exception path is rare
1910       Node *call = n->in(0)->in(0)->in(0);
1911       assert( call->is_Call(), "expect a call here" );
1912       const JVMState *jvms = ((CallNode*)call)->jvms();
1913       ciMethodData* methodData = jvms->method()->method_data();
1914       if (!methodData->is_mature())  return 0.0f; // No call-site data
1915       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1916       if ((data == NULL) || !data->is_CounterData()) {
1917         // no call profile available, try call's control input
1918         n = n->in(0);
1919         continue;
1920       }
1921       return data->as_CounterData()->count()/FreqCountInvocations;
1922     }
1923     // See if there's a gating IF test
1924     Node *n_c = n->in(0);
1925     if( !n_c->is_If() ) break;       // No estimate available
1926     iff = n_c->as_If();
1927     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1928       // Compute how much count comes on this path
1929       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1930     // Have no count info.  Skip dull uncommon-trap like branches.
1931     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1932         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1933       break;
1934     // Skip through never-taken branch; look for a real loop exit.
1935     n = iff->in(0);
1936   }
1937   return 0.0f;                  // No estimate available
1938 }
1939 
1940 //------------------------------merge_many_backedges---------------------------
1941 // Merge all the backedges from the shared header into a private Region.
1942 // Feed that region as the one backedge to this loop.
1943 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1944   uint i;
1945 
1946   // Scan for the top 2 hottest backedges
1947   float hotcnt = 0.0f;
1948   float warmcnt = 0.0f;
1949   uint hot_idx = 0;
1950   // Loop starts at 2 because slot 1 is the fall-in path
1951   for( i = 2; i < _head->req(); i++ ) {
1952     float cnt = estimate_path_freq(_head->in(i));
1953     if( cnt > hotcnt ) {       // Grab hottest path
1954       warmcnt = hotcnt;
1955       hotcnt = cnt;
1956       hot_idx = i;
1957     } else if( cnt > warmcnt ) { // And 2nd hottest path
1958       warmcnt = cnt;
1959     }
1960   }
1961 
1962   // See if the hottest backedge is worthy of being an inner loop
1963   // by being much hotter than the next hottest backedge.
1964   if( hotcnt <= 0.0001 ||
1965       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1966 
1967   // Peel out the backedges into a private merge point; peel
1968   // them all except optionally hot_idx.
1969   PhaseIterGVN &igvn = phase->_igvn;
1970 
1971   Node *hot_tail = NULL;
1972   // Make a Region for the merge point
1973   Node *r = new RegionNode(1);
1974   for( i = 2; i < _head->req(); i++ ) {
1975     if( i != hot_idx )
1976       r->add_req( _head->in(i) );
1977     else hot_tail = _head->in(i);
1978   }
1979   igvn.register_new_node_with_optimizer(r, _head);
1980   // Plug region into end of loop _head, followed by hot_tail
1981   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1982   igvn.replace_input_of(_head, 2, r);
1983   if( hot_idx ) _head->add_req(hot_tail);
1984 
1985   // Split all the Phis up between '_head' loop and the Region 'r'
1986   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1987     Node *out = _head->fast_out(j);
1988     if( out->is_Phi() ) {
1989       PhiNode* n = out->as_Phi();
1990       igvn.hash_delete(n);      // Delete from hash before hacking edges
1991       Node *hot_phi = NULL;
1992       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1993       // Check all inputs for the ones to peel out
1994       uint j = 1;
1995       for( uint i = 2; i < n->req(); i++ ) {
1996         if( i != hot_idx )
1997           phi->set_req( j++, n->in(i) );
1998         else hot_phi = n->in(i);
1999       }
2000       // Register the phi but do not transform until whole place transforms
2001       igvn.register_new_node_with_optimizer(phi, n);
2002       // Add the merge phi to the old Phi
2003       while( n->req() > 3 ) n->del_req( n->req()-1 );
2004       igvn.replace_input_of(n, 2, phi);
2005       if( hot_idx ) n->add_req(hot_phi);
2006     }
2007   }
2008 
2009 
2010   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
2011   // of self loop tree.  Turn self into a loop headed by _head and with
2012   // tail being the new merge point.
2013   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
2014   phase->set_loop(_tail,ilt);   // Adjust tail
2015   _tail = r;                    // Self's tail is new merge point
2016   phase->set_loop(r,this);
2017   ilt->_child = _child;         // New guy has my children
2018   _child = ilt;                 // Self has new guy as only child
2019   ilt->_parent = this;          // new guy has self for parent
2020   ilt->_nest = _nest;           // Same nesting depth (for now)
2021 
2022   // Starting with 'ilt', look for child loop trees using the same shared
2023   // header.  Flatten these out; they will no longer be loops in the end.
2024   IdealLoopTree **pilt = &_child;
2025   while( ilt ) {
2026     if( ilt->_head == _head ) {
2027       uint i;
2028       for( i = 2; i < _head->req(); i++ )
2029         if( _head->in(i) == ilt->_tail )
2030           break;                // Still a loop
2031       if( i == _head->req() ) { // No longer a loop
2032         // Flatten ilt.  Hang ilt's "_next" list from the end of
2033         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
2034         IdealLoopTree **cp = &ilt->_child;
2035         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
2036         *cp = ilt->_next;       // Hang next list at end of child list
2037         *pilt = ilt->_child;    // Move child up to replace ilt
2038         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
2039         ilt = ilt->_child;      // Repeat using new ilt
2040         continue;               // do not advance over ilt->_child
2041       }
2042       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
2043       phase->set_loop(_head,ilt);
2044     }
2045     pilt = &ilt->_child;        // Advance to next
2046     ilt = *pilt;
2047   }
2048 
2049   if( _child ) fix_parent( _child, this );
2050 }
2051 
2052 //------------------------------beautify_loops---------------------------------
2053 // Split shared headers and insert loop landing pads.
2054 // Insert a LoopNode to replace the RegionNode.
2055 // Return TRUE if loop tree is structurally changed.
2056 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
2057   bool result = false;
2058   // Cache parts in locals for easy
2059   PhaseIterGVN &igvn = phase->_igvn;
2060 
2061   igvn.hash_delete(_head);      // Yank from hash before hacking edges
2062 
2063   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
2064   int fall_in_cnt = 0;
2065   for( uint i = 1; i < _head->req(); i++ )
2066     if( !phase->is_member( this, _head->in(i) ) )
2067       fall_in_cnt++;
2068   assert( fall_in_cnt, "at least 1 fall-in path" );
2069   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
2070     split_fall_in( phase, fall_in_cnt );
2071 
2072   // Swap inputs to the _head and all Phis to move the fall-in edge to
2073   // the left.
2074   fall_in_cnt = 1;
2075   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
2076     fall_in_cnt++;
2077   if( fall_in_cnt > 1 ) {
2078     // Since I am just swapping inputs I do not need to update def-use info
2079     Node *tmp = _head->in(1);
2080     igvn.rehash_node_delayed(_head);
2081     _head->set_req( 1, _head->in(fall_in_cnt) );
2082     _head->set_req( fall_in_cnt, tmp );
2083     // Swap also all Phis
2084     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
2085       Node* phi = _head->fast_out(i);
2086       if( phi->is_Phi() ) {
2087         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
2088         tmp = phi->in(1);
2089         phi->set_req( 1, phi->in(fall_in_cnt) );
2090         phi->set_req( fall_in_cnt, tmp );
2091       }
2092     }
2093   }
2094   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
2095   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
2096 
2097   // If I am a shared header (multiple backedges), peel off the many
2098   // backedges into a private merge point and use the merge point as
2099   // the one true backedge.
2100   if( _head->req() > 3 ) {
2101     // Merge the many backedges into a single backedge but leave
2102     // the hottest backedge as separate edge for the following peel.
2103     merge_many_backedges( phase );
2104     result = true;
2105   }
2106 
2107   // If I have one hot backedge, peel off myself loop.
2108   // I better be the outermost loop.
2109   if (_head->req() > 3 && !_irreducible) {
2110     split_outer_loop( phase );
2111     result = true;
2112 
2113   } else if (!_head->is_Loop() && !_irreducible) {
2114     // Make a new LoopNode to replace the old loop head
2115     Node *l = new LoopNode( _head->in(1), _head->in(2) );
2116     l = igvn.register_new_node_with_optimizer(l, _head);
2117     phase->set_created_loop_node();
2118     // Go ahead and replace _head
2119     phase->_igvn.replace_node( _head, l );
2120     _head = l;
2121     phase->set_loop(_head, this);
2122   }
2123 
2124   // Now recursively beautify nested loops
2125   if( _child ) result |= _child->beautify_loops( phase );
2126   if( _next  ) result |= _next ->beautify_loops( phase );
2127   return result;
2128 }
2129 
2130 //------------------------------allpaths_check_safepts----------------------------
2131 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
2132 // encountered.  Helper for check_safepts.
2133 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
2134   assert(stack.size() == 0, "empty stack");
2135   stack.push(_tail);
2136   visited.Clear();
2137   visited.set(_tail->_idx);
2138   while (stack.size() > 0) {
2139     Node* n = stack.pop();
2140     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2141       // Terminate this path
2142     } else if (n->Opcode() == Op_SafePoint) {
2143       if (_phase->get_loop(n) != this) {
2144         if (_required_safept == NULL) _required_safept = new Node_List();
2145         _required_safept->push(n);  // save the one closest to the tail
2146       }
2147       // Terminate this path
2148     } else {
2149       uint start = n->is_Region() ? 1 : 0;
2150       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
2151       for (uint i = start; i < end; i++) {
2152         Node* in = n->in(i);
2153         assert(in->is_CFG(), "must be");
2154         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
2155           stack.push(in);
2156         }
2157       }
2158     }
2159   }
2160 }
2161 
2162 //------------------------------check_safepts----------------------------
2163 // Given dominators, try to find loops with calls that must always be
2164 // executed (call dominates loop tail).  These loops do not need non-call
2165 // safepoints (ncsfpt).
2166 //
2167 // A complication is that a safepoint in a inner loop may be needed
2168 // by an outer loop. In the following, the inner loop sees it has a
2169 // call (block 3) on every path from the head (block 2) to the
2170 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
2171 // in block 2, _but_ this leaves the outer loop without a safepoint.
2172 //
2173 //          entry  0
2174 //                 |
2175 //                 v
2176 // outer 1,2    +->1
2177 //              |  |
2178 //              |  v
2179 //              |  2<---+  ncsfpt in 2
2180 //              |_/|\   |
2181 //                 | v  |
2182 // inner 2,3      /  3  |  call in 3
2183 //               /   |  |
2184 //              v    +--+
2185 //        exit  4
2186 //
2187 //
2188 // This method creates a list (_required_safept) of ncsfpt nodes that must
2189 // be protected is created for each loop. When a ncsfpt maybe deleted, it
2190 // is first looked for in the lists for the outer loops of the current loop.
2191 //
2192 // The insights into the problem:
2193 //  A) counted loops are okay
2194 //  B) innermost loops are okay (only an inner loop can delete
2195 //     a ncsfpt needed by an outer loop)
2196 //  C) a loop is immune from an inner loop deleting a safepoint
2197 //     if the loop has a call on the idom-path
2198 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
2199 //     idom-path that is not in a nested loop
2200 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
2201 //     loop needs to be prevented from deletion by an inner loop
2202 //
2203 // There are two analyses:
2204 //  1) The first, and cheaper one, scans the loop body from
2205 //     tail to head following the idom (immediate dominator)
2206 //     chain, looking for the cases (C,D,E) above.
2207 //     Since inner loops are scanned before outer loops, there is summary
2208 //     information about inner loops.  Inner loops can be skipped over
2209 //     when the tail of an inner loop is encountered.
2210 //
2211 //  2) The second, invoked if the first fails to find a call or ncsfpt on
2212 //     the idom path (which is rare), scans all predecessor control paths
2213 //     from the tail to the head, terminating a path when a call or sfpt
2214 //     is encountered, to find the ncsfpt's that are closest to the tail.
2215 //
2216 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
2217   // Bottom up traversal
2218   IdealLoopTree* ch = _child;
2219   if (_child) _child->check_safepts(visited, stack);
2220   if (_next)  _next ->check_safepts(visited, stack);
2221 
2222   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
2223     bool  has_call         = false; // call on dom-path
2224     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
2225     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
2226     // Scan the dom-path nodes from tail to head
2227     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
2228       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2229         has_call = true;
2230         _has_sfpt = 1;          // Then no need for a safept!
2231         break;
2232       } else if (n->Opcode() == Op_SafePoint) {
2233         if (_phase->get_loop(n) == this) {
2234           has_local_ncsfpt = true;
2235           break;
2236         }
2237         if (nonlocal_ncsfpt == NULL) {
2238           nonlocal_ncsfpt = n; // save the one closest to the tail
2239         }
2240       } else {
2241         IdealLoopTree* nlpt = _phase->get_loop(n);
2242         if (this != nlpt) {
2243           // If at an inner loop tail, see if the inner loop has already
2244           // recorded seeing a call on the dom-path (and stop.)  If not,
2245           // jump to the head of the inner loop.
2246           assert(is_member(nlpt), "nested loop");
2247           Node* tail = nlpt->_tail;
2248           if (tail->in(0)->is_If()) tail = tail->in(0);
2249           if (n == tail) {
2250             // If inner loop has call on dom-path, so does outer loop
2251             if (nlpt->_has_sfpt) {
2252               has_call = true;
2253               _has_sfpt = 1;
2254               break;
2255             }
2256             // Skip to head of inner loop
2257             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
2258             n = nlpt->_head;
2259           }
2260         }
2261       }
2262     }
2263     // Record safept's that this loop needs preserved when an
2264     // inner loop attempts to delete it's safepoints.
2265     if (_child != NULL && !has_call && !has_local_ncsfpt) {
2266       if (nonlocal_ncsfpt != NULL) {
2267         if (_required_safept == NULL) _required_safept = new Node_List();
2268         _required_safept->push(nonlocal_ncsfpt);
2269       } else {
2270         // Failed to find a suitable safept on the dom-path.  Now use
2271         // an all paths walk from tail to head, looking for safepoints to preserve.
2272         allpaths_check_safepts(visited, stack);
2273       }
2274     }
2275   }
2276 }
2277 
2278 //---------------------------is_deleteable_safept----------------------------
2279 // Is safept not required by an outer loop?
2280 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
2281   assert(sfpt->Opcode() == Op_SafePoint, "");
2282   IdealLoopTree* lp = get_loop(sfpt)->_parent;
2283   while (lp != NULL) {
2284     Node_List* sfpts = lp->_required_safept;
2285     if (sfpts != NULL) {
2286       for (uint i = 0; i < sfpts->size(); i++) {
2287         if (sfpt == sfpts->at(i))
2288           return false;
2289       }
2290     }
2291     lp = lp->_parent;
2292   }
2293   return true;
2294 }
2295 
2296 //---------------------------replace_parallel_iv-------------------------------
2297 // Replace parallel induction variable (parallel to trip counter)
2298 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
2299   assert(loop->_head->is_CountedLoop(), "");
2300   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2301   if (!cl->is_valid_counted_loop())
2302     return;         // skip malformed counted loop
2303   Node *incr = cl->incr();
2304   if (incr == NULL)
2305     return;         // Dead loop?
2306   Node *init = cl->init_trip();
2307   Node *phi  = cl->phi();
2308   int stride_con = cl->stride_con();
2309 
2310   // Visit all children, looking for Phis
2311   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
2312     Node *out = cl->out(i);
2313     // Look for other phis (secondary IVs). Skip dead ones
2314     if (!out->is_Phi() || out == phi || !has_node(out))
2315       continue;
2316     PhiNode* phi2 = out->as_Phi();
2317     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
2318     // Look for induction variables of the form:  X += constant
2319     if (phi2->region() != loop->_head ||
2320         incr2->req() != 3 ||
2321         incr2->in(1) != phi2 ||
2322         incr2 == incr ||
2323         incr2->Opcode() != Op_AddI ||
2324         !incr2->in(2)->is_Con())
2325       continue;
2326 
2327     // Check for parallel induction variable (parallel to trip counter)
2328     // via an affine function.  In particular, count-down loops with
2329     // count-up array indices are common. We only RCE references off
2330     // the trip-counter, so we need to convert all these to trip-counter
2331     // expressions.
2332     Node *init2 = phi2->in( LoopNode::EntryControl );
2333     int stride_con2 = incr2->in(2)->get_int();
2334 
2335     // The ratio of the two strides cannot be represented as an int
2336     // if stride_con2 is min_int and stride_con is -1.
2337     if (stride_con2 == min_jint && stride_con == -1) {
2338       continue;
2339     }
2340 
2341     // The general case here gets a little tricky.  We want to find the
2342     // GCD of all possible parallel IV's and make a new IV using this
2343     // GCD for the loop.  Then all possible IVs are simple multiples of
2344     // the GCD.  In practice, this will cover very few extra loops.
2345     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
2346     // where +/-1 is the common case, but other integer multiples are
2347     // also easy to handle.
2348     int ratio_con = stride_con2/stride_con;
2349 
2350     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
2351 #ifndef PRODUCT
2352       if (TraceLoopOpts) {
2353         tty->print("Parallel IV: %d ", phi2->_idx);
2354         loop->dump_head();
2355       }
2356 #endif
2357       // Convert to using the trip counter.  The parallel induction
2358       // variable differs from the trip counter by a loop-invariant
2359       // amount, the difference between their respective initial values.
2360       // It is scaled by the 'ratio_con'.
2361       Node* ratio = _igvn.intcon(ratio_con);
2362       set_ctrl(ratio, C->root());
2363       Node* ratio_init = new MulINode(init, ratio);
2364       _igvn.register_new_node_with_optimizer(ratio_init, init);
2365       set_early_ctrl(ratio_init);
2366       Node* diff = new SubINode(init2, ratio_init);
2367       _igvn.register_new_node_with_optimizer(diff, init2);
2368       set_early_ctrl(diff);
2369       Node* ratio_idx = new MulINode(phi, ratio);
2370       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
2371       set_ctrl(ratio_idx, cl);
2372       Node* add = new AddINode(ratio_idx, diff);
2373       _igvn.register_new_node_with_optimizer(add);
2374       set_ctrl(add, cl);
2375       _igvn.replace_node( phi2, add );
2376       // Sometimes an induction variable is unused
2377       if (add->outcnt() == 0) {
2378         _igvn.remove_dead_node(add);
2379       }
2380       --i; // deleted this phi; rescan starting with next position
2381       continue;
2382     }
2383   }
2384 }
2385 
2386 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
2387   Node* keep = NULL;
2388   if (keep_one) {
2389     // Look for a safepoint on the idom-path.
2390     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
2391       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
2392         keep = i;
2393         break; // Found one
2394       }
2395     }
2396   }
2397 
2398   // Don't remove any safepoints if it is requested to keep a single safepoint and
2399   // no safepoint was found on idom-path. It is not safe to remove any safepoint
2400   // in this case since there's no safepoint dominating all paths in the loop body.
2401   bool prune = !keep_one || keep != NULL;
2402 
2403   // Delete other safepoints in this loop.
2404   Node_List* sfpts = _safepts;
2405   if (prune && sfpts != NULL) {
2406     assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
2407     for (uint i = 0; i < sfpts->size(); i++) {
2408       Node* n = sfpts->at(i);
2409       assert(phase->get_loop(n) == this, "");
2410       if (n != keep && phase->is_deleteable_safept(n)) {
2411         phase->lazy_replace(n, n->in(TypeFunc::Control));
2412       }
2413     }
2414   }
2415 }
2416 
2417 //------------------------------counted_loop-----------------------------------
2418 // Convert to counted loops where possible
2419 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
2420 
2421   // For grins, set the inner-loop flag here
2422   if (!_child) {
2423     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
2424   }
2425 
2426   IdealLoopTree* loop = this;
2427   if (_head->is_CountedLoop() ||
2428       phase->is_counted_loop(_head, loop)) {
2429 
2430     if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) {
2431       // Indicate we do not need a safepoint here
2432       _has_sfpt = 1;
2433     }
2434 
2435     // Remove safepoints
2436     bool keep_one_sfpt = !(_has_call || _has_sfpt);
2437     remove_safepoints(phase, keep_one_sfpt);
2438 
2439     // Look for induction variables
2440     phase->replace_parallel_iv(this);
2441 
2442   } else if (_parent != NULL && !_irreducible) {
2443     // Not a counted loop. Keep one safepoint.
2444     bool keep_one_sfpt = true;
2445     remove_safepoints(phase, keep_one_sfpt);
2446   }
2447 
2448   // Recursively
2449   assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
2450   assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops");
2451   if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
2452   if (loop->_next)  loop->_next ->counted_loop(phase);
2453 }
2454 
2455 
2456 // The Estimated Loop Clone Size:
2457 //   CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
2458 // where  BC and  CC are  totally ad-hoc/magic  "body" and "clone" constants,
2459 // respectively, used to ensure that the node usage estimates made are on the
2460 // safe side, for the most part. The FanOutTerm is an attempt to estimate the
2461 // possible additional/excessive nodes generated due to data and control flow
2462 // merging, for edges reaching outside the loop.
2463 uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
2464 
2465   precond(0 < factor && factor < 16);
2466 
2467   uint const bc = 13;
2468   uint const cc = 17;
2469   uint const sz = _body.size() + (_body.size() + 7) / 8;
2470   uint estimate = factor * (sz + bc) + cc;
2471 
2472   assert((estimate - cc) / factor == sz + bc, "overflow");
2473 
2474   uint ctrl_edge_out_cnt = 0;
2475   uint data_edge_out_cnt = 0;
2476 
2477   for (uint i = 0; i < _body.size(); i++) {
2478     Node* node = _body.at(i);
2479     uint outcnt = node->outcnt();
2480 
2481     for (uint k = 0; k < outcnt; k++) {
2482       Node* out = node->raw_out(k);
2483 
2484       if (out->is_CFG()) {
2485         if (!is_member(_phase->get_loop(out))) {
2486           ctrl_edge_out_cnt++;
2487         }
2488       } else {
2489         Node* ctrl = _phase->get_ctrl(out);
2490         assert(ctrl->is_CFG(), "must be");
2491         if (!is_member(_phase->get_loop(ctrl))) {
2492           data_edge_out_cnt++;
2493         }
2494       }
2495     }
2496   }
2497   // Add data (x1.5) and control (x1.0) count to estimate iff both are > 0.
2498   if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
2499     estimate += ctrl_edge_out_cnt + data_edge_out_cnt + data_edge_out_cnt / 2;
2500   }
2501 
2502   return estimate;
2503 }
2504 
2505 #ifndef PRODUCT
2506 //------------------------------dump_head--------------------------------------
2507 // Dump 1 liner for loop header info
2508 void IdealLoopTree::dump_head() const {
2509   for (uint i = 0; i < _nest; i++) {
2510     tty->print("  ");
2511   }
2512   tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
2513   if (_irreducible) tty->print(" IRREDUCIBLE");
2514   Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl);
2515   Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
2516   if (predicate != NULL ) {
2517     tty->print(" limit_check");
2518     entry = PhaseIdealLoop::skip_loop_predicates(entry);
2519   }
2520   if (UseLoopPredicate) {
2521     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2522     if (entry != NULL) {
2523       tty->print(" predicated");
2524       entry = PhaseIdealLoop::skip_loop_predicates(entry);
2525     }
2526   }
2527   if (UseProfiledLoopPredicate) {
2528     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
2529     if (entry != NULL) {
2530       tty->print(" profile_predicated");
2531     }
2532   }
2533   if (_head->is_CountedLoop()) {
2534     CountedLoopNode *cl = _head->as_CountedLoop();
2535     tty->print(" counted");
2536 
2537     Node* init_n = cl->init_trip();
2538     if (init_n  != NULL &&  init_n->is_Con())
2539       tty->print(" [%d,", cl->init_trip()->get_int());
2540     else
2541       tty->print(" [int,");
2542     Node* limit_n = cl->limit();
2543     if (limit_n  != NULL &&  limit_n->is_Con())
2544       tty->print("%d),", cl->limit()->get_int());
2545     else
2546       tty->print("int),");
2547     int stride_con  = cl->stride_con();
2548     if (stride_con > 0) tty->print("+");
2549     tty->print("%d", stride_con);
2550 
2551     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
2552 
2553     if (cl->is_pre_loop ()) tty->print(" pre" );
2554     if (cl->is_main_loop()) tty->print(" main");
2555     if (cl->is_post_loop()) tty->print(" post");
2556     if (cl->is_vectorized_loop()) tty->print(" vector");
2557     if (cl->range_checks_present()) tty->print(" rc ");
2558     if (cl->is_multiversioned()) tty->print(" multi ");
2559   }
2560   if (_has_call) tty->print(" has_call");
2561   if (_has_sfpt) tty->print(" has_sfpt");
2562   if (_rce_candidate) tty->print(" rce");
2563   if (_safepts != NULL && _safepts->size() > 0) {
2564     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
2565   }
2566   if (_required_safept != NULL && _required_safept->size() > 0) {
2567     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
2568   }
2569   if (Verbose) {
2570     tty->print(" body={"); _body.dump_simple(); tty->print(" }");
2571   }
2572   if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
2573     tty->print(" strip_mined");
2574   }
2575   tty->cr();
2576 }
2577 
2578 //------------------------------dump-------------------------------------------
2579 // Dump loops by loop tree
2580 void IdealLoopTree::dump() const {
2581   dump_head();
2582   if (_child) _child->dump();
2583   if (_next)  _next ->dump();
2584 }
2585 
2586 #endif
2587 
2588 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
2589   if (loop == root) {
2590     if (loop->_child != NULL) {
2591       log->begin_head("loop_tree");
2592       log->end_head();
2593       if( loop->_child ) log_loop_tree(root, loop->_child, log);
2594       log->tail("loop_tree");
2595       assert(loop->_next == NULL, "what?");
2596     }
2597   } else {
2598     Node* head = loop->_head;
2599     log->begin_head("loop");
2600     log->print(" idx='%d' ", head->_idx);
2601     if (loop->_irreducible) log->print("irreducible='1' ");
2602     if (head->is_Loop()) {
2603       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
2604       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
2605     }
2606     if (head->is_CountedLoop()) {
2607       CountedLoopNode* cl = head->as_CountedLoop();
2608       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
2609       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
2610       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
2611     }
2612     log->end_head();
2613     if( loop->_child ) log_loop_tree(root, loop->_child, log);
2614     log->tail("loop");
2615     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
2616   }
2617 }
2618 
2619 //---------------------collect_potentially_useful_predicates-----------------------
2620 // Helper function to collect potentially useful predicates to prevent them from
2621 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
2622 void PhaseIdealLoop::collect_potentially_useful_predicates(
2623                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
2624   if (loop->_child) { // child
2625     collect_potentially_useful_predicates(loop->_child, useful_predicates);
2626   }
2627 
2628   // self (only loops that we can apply loop predication may use their predicates)
2629   if (loop->_head->is_Loop() &&
2630       !loop->_irreducible    &&
2631       !loop->tail()->is_top()) {
2632     LoopNode* lpn = loop->_head->as_Loop();
2633     Node* entry = lpn->in(LoopNode::EntryControl);
2634     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2635     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2636       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2637       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2638       entry = skip_loop_predicates(entry);
2639     }
2640     predicate_proj = find_predicate(entry); // Predicate
2641     if (predicate_proj != NULL ) {
2642       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2643       entry = skip_loop_predicates(entry);
2644     }
2645     if (UseProfiledLoopPredicate) {
2646       predicate_proj = find_predicate(entry); // Predicate
2647       if (predicate_proj != NULL ) {
2648         useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2649       }
2650     }
2651   }
2652 
2653   if (loop->_next) { // sibling
2654     collect_potentially_useful_predicates(loop->_next, useful_predicates);
2655   }
2656 }
2657 
2658 //------------------------eliminate_useless_predicates-----------------------------
2659 // Eliminate all inserted predicates if they could not be used by loop predication.
2660 // Note: it will also eliminates loop limits check predicate since it also uses
2661 // Opaque1 node (see Parse::add_predicate()).
2662 void PhaseIdealLoop::eliminate_useless_predicates() {
2663   if (C->predicate_count() == 0)
2664     return; // no predicate left
2665 
2666   Unique_Node_List useful_predicates; // to store useful predicates
2667   if (C->has_loops()) {
2668     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2669   }
2670 
2671   for (int i = C->predicate_count(); i > 0; i--) {
2672      Node * n = C->predicate_opaque1_node(i-1);
2673      assert(n->Opcode() == Op_Opaque1, "must be");
2674      if (!useful_predicates.member(n)) { // not in the useful list
2675        _igvn.replace_node(n, n->in(1));
2676      }
2677   }
2678 }
2679 
2680 //------------------------process_expensive_nodes-----------------------------
2681 // Expensive nodes have their control input set to prevent the GVN
2682 // from commoning them and as a result forcing the resulting node to
2683 // be in a more frequent path. Use CFG information here, to change the
2684 // control inputs so that some expensive nodes can be commoned while
2685 // not executed more frequently.
2686 bool PhaseIdealLoop::process_expensive_nodes() {
2687   assert(OptimizeExpensiveOps, "optimization off?");
2688 
2689   // Sort nodes to bring similar nodes together
2690   C->sort_expensive_nodes();
2691 
2692   bool progress = false;
2693 
2694   for (int i = 0; i < C->expensive_count(); ) {
2695     Node* n = C->expensive_node(i);
2696     int start = i;
2697     // Find nodes similar to n
2698     i++;
2699     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2700     int end = i;
2701     // And compare them two by two
2702     for (int j = start; j < end; j++) {
2703       Node* n1 = C->expensive_node(j);
2704       if (is_node_unreachable(n1)) {
2705         continue;
2706       }
2707       for (int k = j+1; k < end; k++) {
2708         Node* n2 = C->expensive_node(k);
2709         if (is_node_unreachable(n2)) {
2710           continue;
2711         }
2712 
2713         assert(n1 != n2, "should be pair of nodes");
2714 
2715         Node* c1 = n1->in(0);
2716         Node* c2 = n2->in(0);
2717 
2718         Node* parent_c1 = c1;
2719         Node* parent_c2 = c2;
2720 
2721         // The call to get_early_ctrl_for_expensive() moves the
2722         // expensive nodes up but stops at loops that are in a if
2723         // branch. See whether we can exit the loop and move above the
2724         // If.
2725         if (c1->is_Loop()) {
2726           parent_c1 = c1->in(1);
2727         }
2728         if (c2->is_Loop()) {
2729           parent_c2 = c2->in(1);
2730         }
2731 
2732         if (parent_c1 == parent_c2) {
2733           _igvn._worklist.push(n1);
2734           _igvn._worklist.push(n2);
2735           continue;
2736         }
2737 
2738         // Look for identical expensive node up the dominator chain.
2739         if (is_dominator(c1, c2)) {
2740           c2 = c1;
2741         } else if (is_dominator(c2, c1)) {
2742           c1 = c2;
2743         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2744                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2745           // Both branches have the same expensive node so move it up
2746           // before the if.
2747           c1 = c2 = idom(parent_c1->in(0));
2748         }
2749         // Do the actual moves
2750         if (n1->in(0) != c1) {
2751           _igvn.hash_delete(n1);
2752           n1->set_req(0, c1);
2753           _igvn.hash_insert(n1);
2754           _igvn._worklist.push(n1);
2755           progress = true;
2756         }
2757         if (n2->in(0) != c2) {
2758           _igvn.hash_delete(n2);
2759           n2->set_req(0, c2);
2760           _igvn.hash_insert(n2);
2761           _igvn._worklist.push(n2);
2762           progress = true;
2763         }
2764       }
2765     }
2766   }
2767 
2768   return progress;
2769 }
2770 
2771 
2772 //=============================================================================
2773 //----------------------------build_and_optimize-------------------------------
2774 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2775 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2776 void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) {
2777   bool do_split_ifs = (mode == LoopOptsDefault);
2778   bool skip_loop_opts = (mode == LoopOptsNone);
2779 
2780   int old_progress = C->major_progress();
2781   uint orig_worklist_size = _igvn._worklist.size();
2782 
2783   // Reset major-progress flag for the driver's heuristics
2784   C->clear_major_progress();
2785 
2786 #ifndef PRODUCT
2787   // Capture for later assert
2788   uint unique = C->unique();
2789   _loop_invokes++;
2790   _loop_work += unique;
2791 #endif
2792 
2793   // True if the method has at least 1 irreducible loop
2794   _has_irreducible_loops = false;
2795 
2796   _created_loop_node = false;
2797 
2798   Arena *a = Thread::current()->resource_area();
2799   VectorSet visited(a);
2800   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2801   _nodes.map(C->unique(), NULL);
2802   memset(_nodes.adr(), 0, wordSize * C->unique());
2803 
2804   // Pre-build the top-level outermost loop tree entry
2805   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2806   // Do not need a safepoint at the top level
2807   _ltree_root->_has_sfpt = 1;
2808 
2809   // Initialize Dominators.
2810   // Checked in clone_loop_predicate() during beautify_loops().
2811   _idom_size = 0;
2812   _idom      = NULL;
2813   _dom_depth = NULL;
2814   _dom_stk   = NULL;
2815 
2816   // Empty pre-order array
2817   allocate_preorders();
2818 
2819   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2820   // IdealLoopTree entries.  Data nodes are NOT walked.
2821   build_loop_tree();
2822   // Check for bailout, and return
2823   if (C->failing()) {
2824     return;
2825   }
2826 
2827   // No loops after all
2828   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2829 
2830   // There should always be an outer loop containing the Root and Return nodes.
2831   // If not, we have a degenerate empty program.  Bail out in this case.
2832   if (!has_node(C->root())) {
2833     if (!_verify_only) {
2834       C->clear_major_progress();
2835       C->record_method_not_compilable("empty program detected during loop optimization");
2836     }
2837     return;
2838   }
2839 
2840   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2841   // Nothing to do, so get out
2842   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only &&
2843     !bs->is_gc_specific_loop_opts_pass(mode);
2844   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2845   bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(mode);
2846   if (stop_early && !do_expensive_nodes) {
2847     _igvn.optimize();           // Cleanup NeverBranches
2848     return;
2849   }
2850 
2851   // Set loop nesting depth
2852   _ltree_root->set_nest( 0 );
2853 
2854   // Split shared headers and insert loop landing pads.
2855   // Do not bother doing this on the Root loop of course.
2856   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2857     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2858     if( _ltree_root->_child->beautify_loops( this ) ) {
2859       // Re-build loop tree!
2860       _ltree_root->_child = NULL;
2861       _nodes.clear();
2862       reallocate_preorders();
2863       build_loop_tree();
2864       // Check for bailout, and return
2865       if (C->failing()) {
2866         return;
2867       }
2868       // Reset loop nesting depth
2869       _ltree_root->set_nest( 0 );
2870 
2871       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2872     }
2873   }
2874 
2875   // Build Dominators for elision of NULL checks & loop finding.
2876   // Since nodes do not have a slot for immediate dominator, make
2877   // a persistent side array for that info indexed on node->_idx.
2878   _idom_size = C->unique();
2879   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2880   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2881   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2882   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2883 
2884   Dominators();
2885 
2886   if (!_verify_only) {
2887     // As a side effect, Dominators removed any unreachable CFG paths
2888     // into RegionNodes.  It doesn't do this test against Root, so
2889     // we do it here.
2890     for( uint i = 1; i < C->root()->req(); i++ ) {
2891       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2892         _igvn.delete_input_of(C->root(), i);
2893         i--;                      // Rerun same iteration on compressed edges
2894       }
2895     }
2896 
2897     // Given dominators, try to find inner loops with calls that must
2898     // always be executed (call dominates loop tail).  These loops do
2899     // not need a separate safepoint.
2900     Node_List cisstack(a);
2901     _ltree_root->check_safepts(visited, cisstack);
2902   }
2903 
2904   // Walk the DATA nodes and place into loops.  Find earliest control
2905   // node.  For CFG nodes, the _nodes array starts out and remains
2906   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2907   // _nodes array holds the earliest legal controlling CFG node.
2908 
2909   // Allocate stack with enough space to avoid frequent realloc
2910   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2911   Node_Stack nstack( a, stack_size );
2912 
2913   visited.Clear();
2914   Node_List worklist(a);
2915   // Don't need C->root() on worklist since
2916   // it will be processed among C->top() inputs
2917   worklist.push( C->top() );
2918   visited.set( C->top()->_idx ); // Set C->top() as visited now
2919   build_loop_early( visited, worklist, nstack );
2920 
2921   // Given early legal placement, try finding counted loops.  This placement
2922   // is good enough to discover most loop invariants.
2923   if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
2924     _ltree_root->counted_loop( this );
2925   }
2926 
2927   // Find latest loop placement.  Find ideal loop placement.
2928   visited.Clear();
2929   init_dom_lca_tags();
2930   // Need C->root() on worklist when processing outs
2931   worklist.push( C->root() );
2932   NOT_PRODUCT( C->verify_graph_edges(); )
2933   worklist.push( C->top() );
2934   build_loop_late( visited, worklist, nstack );
2935 
2936   if (_verify_only) {
2937     C->restore_major_progress(old_progress);
2938     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2939     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2940     return;
2941   }
2942 
2943   // clear out the dead code after build_loop_late
2944   while (_deadlist.size()) {
2945     _igvn.remove_globally_dead_node(_deadlist.pop());
2946   }
2947 
2948   if (stop_early) {
2949     assert(do_expensive_nodes, "why are we here?");
2950     if (process_expensive_nodes()) {
2951       // If we made some progress when processing expensive nodes then
2952       // the IGVN may modify the graph in a way that will allow us to
2953       // make some more progress: we need to try processing expensive
2954       // nodes again.
2955       C->set_major_progress();
2956     }
2957     _igvn.optimize();
2958     return;
2959   }
2960 
2961   // Some parser-inserted loop predicates could never be used by loop
2962   // predication or they were moved away from loop during some optimizations.
2963   // For example, peeling. Eliminate them before next loop optimizations.
2964   eliminate_useless_predicates();
2965 
2966 #ifndef PRODUCT
2967   C->verify_graph_edges();
2968   if (_verify_me) {             // Nested verify pass?
2969     // Check to see if the verify mode is broken
2970     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2971     return;
2972   }
2973   if (VerifyLoopOptimizations) verify();
2974   if (TraceLoopOpts && C->has_loops()) {
2975     _ltree_root->dump();
2976   }
2977 #endif
2978 
2979   if (skip_loop_opts) {
2980     // restore major progress flag
2981     C->restore_major_progress(old_progress);
2982 
2983     // Cleanup any modified bits
2984     _igvn.optimize();
2985 
2986     if (C->log() != NULL) {
2987       log_loop_tree(_ltree_root, _ltree_root, C->log());
2988     }
2989     return;
2990   }
2991 
2992   if (bs->optimize_loops(this, mode, visited, nstack, worklist)) {
2993     _igvn.optimize();
2994     if (C->log() != NULL) {
2995       log_loop_tree(_ltree_root, _ltree_root, C->log());
2996     }
2997     return;
2998   }
2999 
3000   if (ReassociateInvariants) {
3001     // Reassociate invariants and prep for split_thru_phi
3002     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3003       IdealLoopTree* lpt = iter.current();
3004       bool is_counted = lpt->is_counted();
3005       if (!is_counted || !lpt->is_innermost()) continue;
3006 
3007       // check for vectorized loops, any reassociation of invariants was already done
3008       if (is_counted && lpt->_head->as_CountedLoop()->is_unroll_only()) {
3009         continue;
3010       } else {
3011         AutoNodeBudget node_budget(this);
3012         lpt->reassociate_invariants(this);
3013       }
3014       // Because RCE opportunities can be masked by split_thru_phi,
3015       // look for RCE candidates and inhibit split_thru_phi
3016       // on just their loop-phi's for this pass of loop opts
3017       if (SplitIfBlocks && do_split_ifs) {
3018         AutoNodeBudget node_budget(this, AutoNodeBudget::NO_BUDGET_CHECK);
3019         if (lpt->policy_range_check(this)) {
3020           lpt->_rce_candidate = 1; // = true
3021         }
3022       }
3023     }
3024   }
3025 
3026   // Check for aggressive application of split-if and other transforms
3027   // that require basic-block info (like cloning through Phi's)
3028   if( SplitIfBlocks && do_split_ifs ) {
3029     visited.Clear();
3030     split_if_with_blocks( visited, nstack);
3031     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
3032   }
3033 
3034   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
3035     C->set_major_progress();
3036   }
3037 
3038   // Perform loop predication before iteration splitting
3039   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
3040     _ltree_root->_child->loop_predication(this);
3041   }
3042 
3043   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
3044     if (do_intrinsify_fill()) {
3045       C->set_major_progress();
3046     }
3047   }
3048 
3049   // Perform iteration-splitting on inner loops.  Split iterations to avoid
3050   // range checks or one-shot null checks.
3051 
3052   // If split-if's didn't hack the graph too bad (no CFG changes)
3053   // then do loop opts.
3054   if (C->has_loops() && !C->major_progress()) {
3055     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3056     _ltree_root->_child->iteration_split( this, worklist );
3057     // No verify after peeling!  GCM has hoisted code out of the loop.
3058     // After peeling, the hoisted code could sink inside the peeled area.
3059     // The peeling code does not try to recompute the best location for
3060     // all the code before the peeled area, so the verify pass will always
3061     // complain about it.
3062   }
3063   // Do verify graph edges in any case
3064   NOT_PRODUCT( C->verify_graph_edges(); );
3065 
3066   if (!do_split_ifs) {
3067     // We saw major progress in Split-If to get here.  We forced a
3068     // pass with unrolling and not split-if, however more split-if's
3069     // might make progress.  If the unrolling didn't make progress
3070     // then the major-progress flag got cleared and we won't try
3071     // another round of Split-If.  In particular the ever-common
3072     // instance-of/check-cast pattern requires at least 2 rounds of
3073     // Split-If to clear out.
3074     C->set_major_progress();
3075   }
3076 
3077   // Repeat loop optimizations if new loops were seen
3078   if (created_loop_node()) {
3079     C->set_major_progress();
3080   }
3081 
3082   // Keep loop predicates and perform optimizations with them
3083   // until no more loop optimizations could be done.
3084   // After that switch predicates off and do more loop optimizations.
3085   if (!C->major_progress() && (C->predicate_count() > 0)) {
3086      C->cleanup_loop_predicates(_igvn);
3087      if (TraceLoopOpts) {
3088        tty->print_cr("PredicatesOff");
3089      }
3090      C->set_major_progress();
3091   }
3092 
3093   // Convert scalar to superword operations at the end of all loop opts.
3094   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
3095     // SuperWord transform
3096     SuperWord sw(this);
3097     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3098       IdealLoopTree* lpt = iter.current();
3099       if (lpt->is_counted()) {
3100         CountedLoopNode *cl = lpt->_head->as_CountedLoop();
3101 
3102         if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
3103           // Check that the rce'd post loop is encountered first, multiversion after all
3104           // major main loop optimization are concluded
3105           if (!C->major_progress()) {
3106             IdealLoopTree *lpt_next = lpt->_next;
3107             if (lpt_next && lpt_next->is_counted()) {
3108               CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
3109               has_range_checks(lpt_next);
3110               if (cl->is_post_loop() && cl->range_checks_present()) {
3111                 if (!cl->is_multiversioned()) {
3112                   if (multi_version_post_loops(lpt, lpt_next) == false) {
3113                     // Cause the rce loop to be optimized away if we fail
3114                     cl->mark_is_multiversioned();
3115                     cl->set_slp_max_unroll(0);
3116                     poison_rce_post_loop(lpt);
3117                   }
3118                 }
3119               }
3120             }
3121             sw.transform_loop(lpt, true);
3122           }
3123         } else if (cl->is_main_loop()) {
3124           sw.transform_loop(lpt, true);
3125         }
3126       }
3127     }
3128   }
3129 
3130   // Cleanup any modified bits
3131   _igvn.optimize();
3132 
3133   // disable assert until issue with split_flow_path is resolved (6742111)
3134   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
3135   //        "shouldn't introduce irreducible loops");
3136 
3137   if (C->log() != NULL) {
3138     log_loop_tree(_ltree_root, _ltree_root, C->log());
3139   }
3140 }
3141 
3142 #ifndef PRODUCT
3143 //------------------------------print_statistics-------------------------------
3144 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
3145 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
3146 void PhaseIdealLoop::print_statistics() {
3147   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
3148 }
3149 
3150 //------------------------------verify-----------------------------------------
3151 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
3152 static int fail;                // debug only, so its multi-thread dont care
3153 void PhaseIdealLoop::verify() const {
3154   int old_progress = C->major_progress();
3155   ResourceMark rm;
3156   PhaseIdealLoop loop_verify( _igvn, this );
3157   VectorSet visited(Thread::current()->resource_area());
3158 
3159   fail = 0;
3160   verify_compare( C->root(), &loop_verify, visited );
3161   assert( fail == 0, "verify loops failed" );
3162   // Verify loop structure is the same
3163   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
3164   // Reset major-progress.  It was cleared by creating a verify version of
3165   // PhaseIdealLoop.
3166   C->restore_major_progress(old_progress);
3167 }
3168 
3169 //------------------------------verify_compare---------------------------------
3170 // Make sure me and the given PhaseIdealLoop agree on key data structures
3171 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
3172   if( !n ) return;
3173   if( visited.test_set( n->_idx ) ) return;
3174   if( !_nodes[n->_idx] ) {      // Unreachable
3175     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
3176     return;
3177   }
3178 
3179   uint i;
3180   for( i = 0; i < n->req(); i++ )
3181     verify_compare( n->in(i), loop_verify, visited );
3182 
3183   // Check the '_nodes' block/loop structure
3184   i = n->_idx;
3185   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
3186     if( _nodes[i] != loop_verify->_nodes[i] &&
3187         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
3188       tty->print("Mismatched control setting for: ");
3189       n->dump();
3190       if( fail++ > 10 ) return;
3191       Node *c = get_ctrl_no_update(n);
3192       tty->print("We have it as: ");
3193       if( c->in(0) ) c->dump();
3194         else tty->print_cr("N%d",c->_idx);
3195       tty->print("Verify thinks: ");
3196       if( loop_verify->has_ctrl(n) )
3197         loop_verify->get_ctrl_no_update(n)->dump();
3198       else
3199         loop_verify->get_loop_idx(n)->dump();
3200       tty->cr();
3201     }
3202   } else {                    // We have a loop
3203     IdealLoopTree *us = get_loop_idx(n);
3204     if( loop_verify->has_ctrl(n) ) {
3205       tty->print("Mismatched loop setting for: ");
3206       n->dump();
3207       if( fail++ > 10 ) return;
3208       tty->print("We have it as: ");
3209       us->dump();
3210       tty->print("Verify thinks: ");
3211       loop_verify->get_ctrl_no_update(n)->dump();
3212       tty->cr();
3213     } else if (!C->major_progress()) {
3214       // Loop selection can be messed up if we did a major progress
3215       // operation, like split-if.  Do not verify in that case.
3216       IdealLoopTree *them = loop_verify->get_loop_idx(n);
3217       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
3218         tty->print("Unequals loops for: ");
3219         n->dump();
3220         if( fail++ > 10 ) return;
3221         tty->print("We have it as: ");
3222         us->dump();
3223         tty->print("Verify thinks: ");
3224         them->dump();
3225         tty->cr();
3226       }
3227     }
3228   }
3229 
3230   // Check for immediate dominators being equal
3231   if( i >= _idom_size ) {
3232     if( !n->is_CFG() ) return;
3233     tty->print("CFG Node with no idom: ");
3234     n->dump();
3235     return;
3236   }
3237   if( !n->is_CFG() ) return;
3238   if( n == C->root() ) return; // No IDOM here
3239 
3240   assert(n->_idx == i, "sanity");
3241   Node *id = idom_no_update(n);
3242   if( id != loop_verify->idom_no_update(n) ) {
3243     tty->print("Unequals idoms for: ");
3244     n->dump();
3245     if( fail++ > 10 ) return;
3246     tty->print("We have it as: ");
3247     id->dump();
3248     tty->print("Verify thinks: ");
3249     loop_verify->idom_no_update(n)->dump();
3250     tty->cr();
3251   }
3252 
3253 }
3254 
3255 //------------------------------verify_tree------------------------------------
3256 // Verify that tree structures match.  Because the CFG can change, siblings
3257 // within the loop tree can be reordered.  We attempt to deal with that by
3258 // reordering the verify's loop tree if possible.
3259 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
3260   assert( _parent == parent, "Badly formed loop tree" );
3261 
3262   // Siblings not in same order?  Attempt to re-order.
3263   if( _head != loop->_head ) {
3264     // Find _next pointer to update
3265     IdealLoopTree **pp = &loop->_parent->_child;
3266     while( *pp != loop )
3267       pp = &((*pp)->_next);
3268     // Find proper sibling to be next
3269     IdealLoopTree **nn = &loop->_next;
3270     while( (*nn) && (*nn)->_head != _head )
3271       nn = &((*nn)->_next);
3272 
3273     // Check for no match.
3274     if( !(*nn) ) {
3275       // Annoyingly, irreducible loops can pick different headers
3276       // after a major_progress operation, so the rest of the loop
3277       // tree cannot be matched.
3278       if (_irreducible && Compile::current()->major_progress())  return;
3279       assert( 0, "failed to match loop tree" );
3280     }
3281 
3282     // Move (*nn) to (*pp)
3283     IdealLoopTree *hit = *nn;
3284     *nn = hit->_next;
3285     hit->_next = loop;
3286     *pp = loop;
3287     loop = hit;
3288     // Now try again to verify
3289   }
3290 
3291   assert( _head  == loop->_head , "mismatched loop head" );
3292   Node *tail = _tail;           // Inline a non-updating version of
3293   while( !tail->in(0) )         // the 'tail()' call.
3294     tail = tail->in(1);
3295   assert( tail == loop->_tail, "mismatched loop tail" );
3296 
3297   // Counted loops that are guarded should be able to find their guards
3298   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
3299     CountedLoopNode *cl = _head->as_CountedLoop();
3300     Node *init = cl->init_trip();
3301     Node *ctrl = cl->in(LoopNode::EntryControl);
3302     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
3303     Node *iff  = ctrl->in(0);
3304     assert( iff->Opcode() == Op_If, "" );
3305     Node *bol  = iff->in(1);
3306     assert( bol->Opcode() == Op_Bool, "" );
3307     Node *cmp  = bol->in(1);
3308     assert( cmp->Opcode() == Op_CmpI, "" );
3309     Node *add  = cmp->in(1);
3310     Node *opaq;
3311     if( add->Opcode() == Op_Opaque1 ) {
3312       opaq = add;
3313     } else {
3314       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
3315       assert( add == init, "" );
3316       opaq = cmp->in(2);
3317     }
3318     assert( opaq->Opcode() == Op_Opaque1, "" );
3319 
3320   }
3321 
3322   if (_child != NULL)  _child->verify_tree(loop->_child, this);
3323   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
3324   // Innermost loops need to verify loop bodies,
3325   // but only if no 'major_progress'
3326   int fail = 0;
3327   if (!Compile::current()->major_progress() && _child == NULL) {
3328     for( uint i = 0; i < _body.size(); i++ ) {
3329       Node *n = _body.at(i);
3330       if (n->outcnt() == 0)  continue; // Ignore dead
3331       uint j;
3332       for( j = 0; j < loop->_body.size(); j++ )
3333         if( loop->_body.at(j) == n )
3334           break;
3335       if( j == loop->_body.size() ) { // Not found in loop body
3336         // Last ditch effort to avoid assertion: Its possible that we
3337         // have some users (so outcnt not zero) but are still dead.
3338         // Try to find from root.
3339         if (Compile::current()->root()->find(n->_idx)) {
3340           fail++;
3341           tty->print("We have that verify does not: ");
3342           n->dump();
3343         }
3344       }
3345     }
3346     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
3347       Node *n = loop->_body.at(i2);
3348       if (n->outcnt() == 0)  continue; // Ignore dead
3349       uint j;
3350       for( j = 0; j < _body.size(); j++ )
3351         if( _body.at(j) == n )
3352           break;
3353       if( j == _body.size() ) { // Not found in loop body
3354         // Last ditch effort to avoid assertion: Its possible that we
3355         // have some users (so outcnt not zero) but are still dead.
3356         // Try to find from root.
3357         if (Compile::current()->root()->find(n->_idx)) {
3358           fail++;
3359           tty->print("Verify has that we do not: ");
3360           n->dump();
3361         }
3362       }
3363     }
3364     assert( !fail, "loop body mismatch" );
3365   }
3366 }
3367 
3368 #endif
3369 
3370 //------------------------------set_idom---------------------------------------
3371 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
3372   uint idx = d->_idx;
3373   if (idx >= _idom_size) {
3374     uint newsize = _idom_size<<1;
3375     while( idx >= newsize ) {
3376       newsize <<= 1;
3377     }
3378     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
3379     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
3380     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
3381     _idom_size = newsize;
3382   }
3383   _idom[idx] = n;
3384   _dom_depth[idx] = dom_depth;
3385 }
3386 
3387 //------------------------------recompute_dom_depth---------------------------------------
3388 // The dominator tree is constructed with only parent pointers.
3389 // This recomputes the depth in the tree by first tagging all
3390 // nodes as "no depth yet" marker.  The next pass then runs up
3391 // the dom tree from each node marked "no depth yet", and computes
3392 // the depth on the way back down.
3393 void PhaseIdealLoop::recompute_dom_depth() {
3394   uint no_depth_marker = C->unique();
3395   uint i;
3396   // Initialize depth to "no depth yet" and realize all lazy updates
3397   for (i = 0; i < _idom_size; i++) {
3398     // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized).
3399     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
3400       _dom_depth[i] = no_depth_marker;
3401 
3402       // heal _idom if it has a fwd mapping in _nodes
3403       if (_idom[i]->in(0) == NULL) {
3404         idom(i);
3405       }
3406     }
3407   }
3408   if (_dom_stk == NULL) {
3409     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
3410     if (init_size < 10) init_size = 10;
3411     _dom_stk = new GrowableArray<uint>(init_size);
3412   }
3413   // Compute new depth for each node.
3414   for (i = 0; i < _idom_size; i++) {
3415     uint j = i;
3416     // Run up the dom tree to find a node with a depth
3417     while (_dom_depth[j] == no_depth_marker) {
3418       _dom_stk->push(j);
3419       j = _idom[j]->_idx;
3420     }
3421     // Compute the depth on the way back down this tree branch
3422     uint dd = _dom_depth[j] + 1;
3423     while (_dom_stk->length() > 0) {
3424       uint j = _dom_stk->pop();
3425       _dom_depth[j] = dd;
3426       dd++;
3427     }
3428   }
3429 }
3430 
3431 //------------------------------sort-------------------------------------------
3432 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
3433 // loop tree, not the root.
3434 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
3435   if( !innermost ) return loop; // New innermost loop
3436 
3437   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
3438   assert( loop_preorder, "not yet post-walked loop" );
3439   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
3440   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
3441 
3442   // Insert at start of list
3443   while( l ) {                  // Insertion sort based on pre-order
3444     if( l == loop ) return innermost; // Already on list!
3445     int l_preorder = get_preorder(l->_head); // Cache pre-order number
3446     assert( l_preorder, "not yet post-walked l" );
3447     // Check header pre-order number to figure proper nesting
3448     if( loop_preorder > l_preorder )
3449       break;                    // End of insertion
3450     // If headers tie (e.g., shared headers) check tail pre-order numbers.
3451     // Since I split shared headers, you'd think this could not happen.
3452     // BUT: I must first do the preorder numbering before I can discover I
3453     // have shared headers, so the split headers all get the same preorder
3454     // number as the RegionNode they split from.
3455     if( loop_preorder == l_preorder &&
3456         get_preorder(loop->_tail) < get_preorder(l->_tail) )
3457       break;                    // Also check for shared headers (same pre#)
3458     pp = &l->_parent;           // Chain up list
3459     l = *pp;
3460   }
3461   // Link into list
3462   // Point predecessor to me
3463   *pp = loop;
3464   // Point me to successor
3465   IdealLoopTree *p = loop->_parent;
3466   loop->_parent = l;            // Point me to successor
3467   if( p ) sort( p, innermost ); // Insert my parents into list as well
3468   return innermost;
3469 }
3470 
3471 //------------------------------build_loop_tree--------------------------------
3472 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
3473 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
3474 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
3475 // tightest enclosing IdealLoopTree for post-walked.
3476 //
3477 // During my forward walk I do a short 1-layer lookahead to see if I can find
3478 // a loop backedge with that doesn't have any work on the backedge.  This
3479 // helps me construct nested loops with shared headers better.
3480 //
3481 // Once I've done the forward recursion, I do the post-work.  For each child
3482 // I check to see if there is a backedge.  Backedges define a loop!  I
3483 // insert an IdealLoopTree at the target of the backedge.
3484 //
3485 // During the post-work I also check to see if I have several children
3486 // belonging to different loops.  If so, then this Node is a decision point
3487 // where control flow can choose to change loop nests.  It is at this
3488 // decision point where I can figure out how loops are nested.  At this
3489 // time I can properly order the different loop nests from my children.
3490 // Note that there may not be any backedges at the decision point!
3491 //
3492 // Since the decision point can be far removed from the backedges, I can't
3493 // order my loops at the time I discover them.  Thus at the decision point
3494 // I need to inspect loop header pre-order numbers to properly nest my
3495 // loops.  This means I need to sort my childrens' loops by pre-order.
3496 // The sort is of size number-of-control-children, which generally limits
3497 // it to size 2 (i.e., I just choose between my 2 target loops).
3498 void PhaseIdealLoop::build_loop_tree() {
3499   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
3500   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
3501   Node *n = C->root();
3502   bltstack.push(n);
3503   int pre_order = 1;
3504   int stack_size;
3505 
3506   while ( ( stack_size = bltstack.length() ) != 0 ) {
3507     n = bltstack.top(); // Leave node on stack
3508     if ( !is_visited(n) ) {
3509       // ---- Pre-pass Work ----
3510       // Pre-walked but not post-walked nodes need a pre_order number.
3511 
3512       set_preorder_visited( n, pre_order ); // set as visited
3513 
3514       // ---- Scan over children ----
3515       // Scan first over control projections that lead to loop headers.
3516       // This helps us find inner-to-outer loops with shared headers better.
3517 
3518       // Scan children's children for loop headers.
3519       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
3520         Node* m = n->raw_out(i);       // Child
3521         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
3522           // Scan over children's children to find loop
3523           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3524             Node* l = m->fast_out(j);
3525             if( is_visited(l) &&       // Been visited?
3526                 !is_postvisited(l) &&  // But not post-visited
3527                 get_preorder(l) < pre_order ) { // And smaller pre-order
3528               // Found!  Scan the DFS down this path before doing other paths
3529               bltstack.push(m);
3530               break;
3531             }
3532           }
3533         }
3534       }
3535       pre_order++;
3536     }
3537     else if ( !is_postvisited(n) ) {
3538       // Note: build_loop_tree_impl() adds out edges on rare occasions,
3539       // such as com.sun.rsasign.am::a.
3540       // For non-recursive version, first, process current children.
3541       // On next iteration, check if additional children were added.
3542       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
3543         Node* u = n->raw_out(k);
3544         if ( u->is_CFG() && !is_visited(u) ) {
3545           bltstack.push(u);
3546         }
3547       }
3548       if ( bltstack.length() == stack_size ) {
3549         // There were no additional children, post visit node now
3550         (void)bltstack.pop(); // Remove node from stack
3551         pre_order = build_loop_tree_impl( n, pre_order );
3552         // Check for bailout
3553         if (C->failing()) {
3554           return;
3555         }
3556         // Check to grow _preorders[] array for the case when
3557         // build_loop_tree_impl() adds new nodes.
3558         check_grow_preorders();
3559       }
3560     }
3561     else {
3562       (void)bltstack.pop(); // Remove post-visited node from stack
3563     }
3564   }
3565 }
3566 
3567 //------------------------------build_loop_tree_impl---------------------------
3568 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
3569   // ---- Post-pass Work ----
3570   // Pre-walked but not post-walked nodes need a pre_order number.
3571 
3572   // Tightest enclosing loop for this Node
3573   IdealLoopTree *innermost = NULL;
3574 
3575   // For all children, see if any edge is a backedge.  If so, make a loop
3576   // for it.  Then find the tightest enclosing loop for the self Node.
3577   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3578     Node* m = n->fast_out(i);   // Child
3579     if( n == m ) continue;      // Ignore control self-cycles
3580     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
3581 
3582     IdealLoopTree *l;           // Child's loop
3583     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
3584       // Found a backedge
3585       assert( get_preorder(m) < pre_order, "should be backedge" );
3586       // Check for the RootNode, which is already a LoopNode and is allowed
3587       // to have multiple "backedges".
3588       if( m == C->root()) {     // Found the root?
3589         l = _ltree_root;        // Root is the outermost LoopNode
3590       } else {                  // Else found a nested loop
3591         // Insert a LoopNode to mark this loop.
3592         l = new IdealLoopTree(this, m, n);
3593       } // End of Else found a nested loop
3594       if( !has_loop(m) )        // If 'm' does not already have a loop set
3595         set_loop(m, l);         // Set loop header to loop now
3596 
3597     } else {                    // Else not a nested loop
3598       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
3599       l = get_loop(m);          // Get previously determined loop
3600       // If successor is header of a loop (nest), move up-loop till it
3601       // is a member of some outer enclosing loop.  Since there are no
3602       // shared headers (I've split them already) I only need to go up
3603       // at most 1 level.
3604       while( l && l->_head == m ) // Successor heads loop?
3605         l = l->_parent;         // Move up 1 for me
3606       // If this loop is not properly parented, then this loop
3607       // has no exit path out, i.e. its an infinite loop.
3608       if( !l ) {
3609         // Make loop "reachable" from root so the CFG is reachable.  Basically
3610         // insert a bogus loop exit that is never taken.  'm', the loop head,
3611         // points to 'n', one (of possibly many) fall-in paths.  There may be
3612         // many backedges as well.
3613 
3614         // Here I set the loop to be the root loop.  I could have, after
3615         // inserting a bogus loop exit, restarted the recursion and found my
3616         // new loop exit.  This would make the infinite loop a first-class
3617         // loop and it would then get properly optimized.  What's the use of
3618         // optimizing an infinite loop?
3619         l = _ltree_root;        // Oops, found infinite loop
3620 
3621         if (!_verify_only) {
3622           // Insert the NeverBranch between 'm' and it's control user.
3623           NeverBranchNode *iff = new NeverBranchNode( m );
3624           _igvn.register_new_node_with_optimizer(iff);
3625           set_loop(iff, l);
3626           Node *if_t = new CProjNode( iff, 0 );
3627           _igvn.register_new_node_with_optimizer(if_t);
3628           set_loop(if_t, l);
3629 
3630           Node* cfg = NULL;       // Find the One True Control User of m
3631           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3632             Node* x = m->fast_out(j);
3633             if (x->is_CFG() && x != m && x != iff)
3634               { cfg = x; break; }
3635           }
3636           assert(cfg != NULL, "must find the control user of m");
3637           uint k = 0;             // Probably cfg->in(0)
3638           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
3639           cfg->set_req( k, if_t ); // Now point to NeverBranch
3640           _igvn._worklist.push(cfg);
3641 
3642           // Now create the never-taken loop exit
3643           Node *if_f = new CProjNode( iff, 1 );
3644           _igvn.register_new_node_with_optimizer(if_f);
3645           set_loop(if_f, l);
3646           // Find frame ptr for Halt.  Relies on the optimizer
3647           // V-N'ing.  Easier and quicker than searching through
3648           // the program structure.
3649           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
3650           _igvn.register_new_node_with_optimizer(frame);
3651           // Halt & Catch Fire
3652           Node *halt = new HaltNode( if_f, frame );
3653           _igvn.register_new_node_with_optimizer(halt);
3654           set_loop(halt, l);
3655           C->root()->add_req(halt);
3656         }
3657         set_loop(C->root(), _ltree_root);
3658       }
3659     }
3660     // Weeny check for irreducible.  This child was already visited (this
3661     // IS the post-work phase).  Is this child's loop header post-visited
3662     // as well?  If so, then I found another entry into the loop.
3663     if (!_verify_only) {
3664       while( is_postvisited(l->_head) ) {
3665         // found irreducible
3666         l->_irreducible = 1; // = true
3667         l = l->_parent;
3668         _has_irreducible_loops = true;
3669         // Check for bad CFG here to prevent crash, and bailout of compile
3670         if (l == NULL) {
3671           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
3672           return pre_order;
3673         }
3674       }
3675       C->set_has_irreducible_loop(_has_irreducible_loops);
3676     }
3677 
3678     // This Node might be a decision point for loops.  It is only if
3679     // it's children belong to several different loops.  The sort call
3680     // does a trivial amount of work if there is only 1 child or all
3681     // children belong to the same loop.  If however, the children
3682     // belong to different loops, the sort call will properly set the
3683     // _parent pointers to show how the loops nest.
3684     //
3685     // In any case, it returns the tightest enclosing loop.
3686     innermost = sort( l, innermost );
3687   }
3688 
3689   // Def-use info will have some dead stuff; dead stuff will have no
3690   // loop decided on.
3691 
3692   // Am I a loop header?  If so fix up my parent's child and next ptrs.
3693   if( innermost && innermost->_head == n ) {
3694     assert( get_loop(n) == innermost, "" );
3695     IdealLoopTree *p = innermost->_parent;
3696     IdealLoopTree *l = innermost;
3697     while( p && l->_head == n ) {
3698       l->_next = p->_child;     // Put self on parents 'next child'
3699       p->_child = l;            // Make self as first child of parent
3700       l = p;                    // Now walk up the parent chain
3701       p = l->_parent;
3702     }
3703   } else {
3704     // Note that it is possible for a LoopNode to reach here, if the
3705     // backedge has been made unreachable (hence the LoopNode no longer
3706     // denotes a Loop, and will eventually be removed).
3707 
3708     // Record tightest enclosing loop for self.  Mark as post-visited.
3709     set_loop(n, innermost);
3710     // Also record has_call flag early on
3711     if( innermost ) {
3712       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3713         // Do not count uncommon calls
3714         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3715           Node *iff = n->in(0)->in(0);
3716           // No any calls for vectorized loops.
3717           if( UseSuperWord || !iff->is_If() ||
3718               (n->in(0)->Opcode() == Op_IfFalse &&
3719                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3720               (iff->as_If()->_prob >= 0.01) )
3721             innermost->_has_call = 1;
3722         }
3723       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3724         // Disable loop optimizations if the loop has a scalar replaceable
3725         // allocation. This disabling may cause a potential performance lost
3726         // if the allocation is not eliminated for some reason.
3727         innermost->_allow_optimizations = false;
3728         innermost->_has_call = 1; // = true
3729       } else if (n->Opcode() == Op_SafePoint) {
3730         // Record all safepoints in this loop.
3731         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3732         innermost->_safepts->push(n);
3733       }
3734     }
3735   }
3736 
3737   // Flag as post-visited now
3738   set_postvisited(n);
3739   return pre_order;
3740 }
3741 
3742 
3743 //------------------------------build_loop_early-------------------------------
3744 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3745 // First pass computes the earliest controlling node possible.  This is the
3746 // controlling input with the deepest dominating depth.
3747 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3748   while (worklist.size() != 0) {
3749     // Use local variables nstack_top_n & nstack_top_i to cache values
3750     // on nstack's top.
3751     Node *nstack_top_n = worklist.pop();
3752     uint  nstack_top_i = 0;
3753 //while_nstack_nonempty:
3754     while (true) {
3755       // Get parent node and next input's index from stack's top.
3756       Node  *n = nstack_top_n;
3757       uint   i = nstack_top_i;
3758       uint cnt = n->req(); // Count of inputs
3759       if (i == 0) {        // Pre-process the node.
3760         if( has_node(n) &&            // Have either loop or control already?
3761             !has_ctrl(n) ) {          // Have loop picked out already?
3762           // During "merge_many_backedges" we fold up several nested loops
3763           // into a single loop.  This makes the members of the original
3764           // loop bodies pointing to dead loops; they need to move up
3765           // to the new UNION'd larger loop.  I set the _head field of these
3766           // dead loops to NULL and the _parent field points to the owning
3767           // loop.  Shades of UNION-FIND algorithm.
3768           IdealLoopTree *ilt;
3769           while( !(ilt = get_loop(n))->_head ) {
3770             // Normally I would use a set_loop here.  But in this one special
3771             // case, it is legal (and expected) to change what loop a Node
3772             // belongs to.
3773             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3774           }
3775           // Remove safepoints ONLY if I've already seen I don't need one.
3776           // (the old code here would yank a 2nd safepoint after seeing a
3777           // first one, even though the 1st did not dominate in the loop body
3778           // and thus could be avoided indefinitely)
3779           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3780               is_deleteable_safept(n)) {
3781             Node *in = n->in(TypeFunc::Control);
3782             lazy_replace(n,in);       // Pull safepoint now
3783             if (ilt->_safepts != NULL) {
3784               ilt->_safepts->yank(n);
3785             }
3786             // Carry on with the recursion "as if" we are walking
3787             // only the control input
3788             if( !visited.test_set( in->_idx ) ) {
3789               worklist.push(in);      // Visit this guy later, using worklist
3790             }
3791             // Get next node from nstack:
3792             // - skip n's inputs processing by setting i > cnt;
3793             // - we also will not call set_early_ctrl(n) since
3794             //   has_node(n) == true (see the condition above).
3795             i = cnt + 1;
3796           }
3797         }
3798       } // if (i == 0)
3799 
3800       // Visit all inputs
3801       bool done = true;       // Assume all n's inputs will be processed
3802       while (i < cnt) {
3803         Node *in = n->in(i);
3804         ++i;
3805         if (in == NULL) continue;
3806         if (in->pinned() && !in->is_CFG())
3807           set_ctrl(in, in->in(0));
3808         int is_visited = visited.test_set( in->_idx );
3809         if (!has_node(in)) {  // No controlling input yet?
3810           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3811           assert( !is_visited, "visit only once" );
3812           nstack.push(n, i);  // Save parent node and next input's index.
3813           nstack_top_n = in;  // Process current input now.
3814           nstack_top_i = 0;
3815           done = false;       // Not all n's inputs processed.
3816           break; // continue while_nstack_nonempty;
3817         } else if (!is_visited) {
3818           // This guy has a location picked out for him, but has not yet
3819           // been visited.  Happens to all CFG nodes, for instance.
3820           // Visit him using the worklist instead of recursion, to break
3821           // cycles.  Since he has a location already we do not need to
3822           // find his location before proceeding with the current Node.
3823           worklist.push(in);  // Visit this guy later, using worklist
3824         }
3825       }
3826       if (done) {
3827         // All of n's inputs have been processed, complete post-processing.
3828 
3829         // Compute earliest point this Node can go.
3830         // CFG, Phi, pinned nodes already know their controlling input.
3831         if (!has_node(n)) {
3832           // Record earliest legal location
3833           set_early_ctrl( n );
3834         }
3835         if (nstack.is_empty()) {
3836           // Finished all nodes on stack.
3837           // Process next node on the worklist.
3838           break;
3839         }
3840         // Get saved parent node and next input's index.
3841         nstack_top_n = nstack.node();
3842         nstack_top_i = nstack.index();
3843         nstack.pop();
3844       }
3845     } // while (true)
3846   }
3847 }
3848 
3849 //------------------------------dom_lca_internal--------------------------------
3850 // Pair-wise LCA
3851 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3852   if( !n1 ) return n2;          // Handle NULL original LCA
3853   assert( n1->is_CFG(), "" );
3854   assert( n2->is_CFG(), "" );
3855   // find LCA of all uses
3856   uint d1 = dom_depth(n1);
3857   uint d2 = dom_depth(n2);
3858   while (n1 != n2) {
3859     if (d1 > d2) {
3860       n1 =      idom(n1);
3861       d1 = dom_depth(n1);
3862     } else if (d1 < d2) {
3863       n2 =      idom(n2);
3864       d2 = dom_depth(n2);
3865     } else {
3866       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3867       // of the tree might have the same depth.  These sections have
3868       // to be searched more carefully.
3869 
3870       // Scan up all the n1's with equal depth, looking for n2.
3871       Node *t1 = idom(n1);
3872       while (dom_depth(t1) == d1) {
3873         if (t1 == n2)  return n2;
3874         t1 = idom(t1);
3875       }
3876       // Scan up all the n2's with equal depth, looking for n1.
3877       Node *t2 = idom(n2);
3878       while (dom_depth(t2) == d2) {
3879         if (t2 == n1)  return n1;
3880         t2 = idom(t2);
3881       }
3882       // Move up to a new dominator-depth value as well as up the dom-tree.
3883       n1 = t1;
3884       n2 = t2;
3885       d1 = dom_depth(n1);
3886       d2 = dom_depth(n2);
3887     }
3888   }
3889   return n1;
3890 }
3891 
3892 //------------------------------compute_idom-----------------------------------
3893 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3894 // IDOMs are correct.
3895 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3896   assert( region->is_Region(), "" );
3897   Node *LCA = NULL;
3898   for( uint i = 1; i < region->req(); i++ ) {
3899     if( region->in(i) != C->top() )
3900       LCA = dom_lca( LCA, region->in(i) );
3901   }
3902   return LCA;
3903 }
3904 
3905 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3906   bool had_error = false;
3907 #ifdef ASSERT
3908   if (early != C->root()) {
3909     // Make sure that there's a dominance path from LCA to early
3910     Node* d = LCA;
3911     while (d != early) {
3912       if (d == C->root()) {
3913         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3914         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3915         had_error = true;
3916         break;
3917       }
3918       d = idom(d);
3919     }
3920   }
3921 #endif
3922   return had_error;
3923 }
3924 
3925 
3926 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3927   // Compute LCA over list of uses
3928   bool had_error = false;
3929   Node *LCA = NULL;
3930   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3931     Node* c = n->fast_out(i);
3932     if (_nodes[c->_idx] == NULL)
3933       continue;                 // Skip the occasional dead node
3934     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3935       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3936         if( c->in(j) == n ) {   // Found matching input?
3937           Node *use = c->in(0)->in(j);
3938           if (_verify_only && use->is_top()) continue;
3939           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3940           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3941         }
3942       }
3943     } else {
3944       // For CFG data-users, use is in the block just prior
3945       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3946       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3947       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3948     }
3949   }
3950   assert(!had_error, "bad dominance");
3951   return LCA;
3952 }
3953 
3954 // Check the shape of the graph at the loop entry. In some cases,
3955 // the shape of the graph does not match the shape outlined below.
3956 // That is caused by the Opaque1 node "protecting" the shape of
3957 // the graph being removed by, for example, the IGVN performed
3958 // in PhaseIdealLoop::build_and_optimize().
3959 //
3960 // After the Opaque1 node has been removed, optimizations (e.g., split-if,
3961 // loop unswitching, and IGVN, or a combination of them) can freely change
3962 // the graph's shape. As a result, the graph shape outlined below cannot
3963 // be guaranteed anymore.
3964 bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) {
3965   if (!cl->is_main_loop() && !cl->is_post_loop()) {
3966     return false;
3967   }
3968   Node* ctrl = cl->skip_predicates();
3969 
3970   if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
3971     return false;
3972   }
3973   Node* iffm = ctrl->in(0);
3974   if (iffm == NULL || !iffm->is_If()) {
3975     return false;
3976   }
3977   Node* bolzm = iffm->in(1);
3978   if (bolzm == NULL || !bolzm->is_Bool()) {
3979     return false;
3980   }
3981   Node* cmpzm = bolzm->in(1);
3982   if (cmpzm == NULL || !cmpzm->is_Cmp()) {
3983     return false;
3984   }
3985   // compares can get conditionally flipped
3986   bool found_opaque = false;
3987   for (uint i = 1; i < cmpzm->req(); i++) {
3988     Node* opnd = cmpzm->in(i);
3989     if (opnd && opnd->Opcode() == Op_Opaque1) {
3990       found_opaque = true;
3991       break;
3992     }
3993   }
3994   if (!found_opaque) {
3995     return false;
3996   }
3997   return true;
3998 }
3999 
4000 //------------------------------get_late_ctrl----------------------------------
4001 // Compute latest legal control.
4002 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
4003   assert(early != NULL, "early control should not be NULL");
4004 
4005   Node* LCA = compute_lca_of_uses(n, early);
4006 #ifdef ASSERT
4007   if (LCA == C->root() && LCA != early) {
4008     // def doesn't dominate uses so print some useful debugging output
4009     compute_lca_of_uses(n, early, true);
4010   }
4011 #endif
4012 
4013   // if this is a load, check for anti-dependent stores
4014   // We use a conservative algorithm to identify potential interfering
4015   // instructions and for rescheduling the load.  The users of the memory
4016   // input of this load are examined.  Any use which is not a load and is
4017   // dominated by early is considered a potentially interfering store.
4018   // This can produce false positives.
4019   if (n->is_Load() && LCA != early) {
4020     Node_List worklist;
4021 
4022     Node *mem = n->in(MemNode::Memory);
4023     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
4024       Node* s = mem->fast_out(i);
4025       worklist.push(s);
4026     }
4027     while(worklist.size() != 0 && LCA != early) {
4028       Node* s = worklist.pop();
4029       if (s->is_Load() || s->Opcode() == Op_SafePoint ||
4030           (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
4031         continue;
4032       } else if (s->is_MergeMem()) {
4033         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
4034           Node* s1 = s->fast_out(i);
4035           worklist.push(s1);
4036         }
4037       } else {
4038         Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
4039         assert(sctrl != NULL || s->outcnt() == 0, "must have control");
4040         if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
4041           LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
4042         }
4043       }
4044     }
4045   }
4046 
4047   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
4048   return LCA;
4049 }
4050 
4051 // true if CFG node d dominates CFG node n
4052 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
4053   if (d == n)
4054     return true;
4055   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
4056   uint dd = dom_depth(d);
4057   while (dom_depth(n) >= dd) {
4058     if (n == d)
4059       return true;
4060     n = idom(n);
4061   }
4062   return false;
4063 }
4064 
4065 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
4066 // Pair-wise LCA with tags.
4067 // Tag each index with the node 'tag' currently being processed
4068 // before advancing up the dominator chain using idom().
4069 // Later calls that find a match to 'tag' know that this path has already
4070 // been considered in the current LCA (which is input 'n1' by convention).
4071 // Since get_late_ctrl() is only called once for each node, the tag array
4072 // does not need to be cleared between calls to get_late_ctrl().
4073 // Algorithm trades a larger constant factor for better asymptotic behavior
4074 //
4075 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
4076   uint d1 = dom_depth(n1);
4077   uint d2 = dom_depth(n2);
4078 
4079   do {
4080     if (d1 > d2) {
4081       // current lca is deeper than n2
4082       _dom_lca_tags.map(n1->_idx, tag);
4083       n1 =      idom(n1);
4084       d1 = dom_depth(n1);
4085     } else if (d1 < d2) {
4086       // n2 is deeper than current lca
4087       Node *memo = _dom_lca_tags[n2->_idx];
4088       if( memo == tag ) {
4089         return n1;    // Return the current LCA
4090       }
4091       _dom_lca_tags.map(n2->_idx, tag);
4092       n2 =      idom(n2);
4093       d2 = dom_depth(n2);
4094     } else {
4095       // Here d1 == d2.  Due to edits of the dominator-tree, sections
4096       // of the tree might have the same depth.  These sections have
4097       // to be searched more carefully.
4098 
4099       // Scan up all the n1's with equal depth, looking for n2.
4100       _dom_lca_tags.map(n1->_idx, tag);
4101       Node *t1 = idom(n1);
4102       while (dom_depth(t1) == d1) {
4103         if (t1 == n2)  return n2;
4104         _dom_lca_tags.map(t1->_idx, tag);
4105         t1 = idom(t1);
4106       }
4107       // Scan up all the n2's with equal depth, looking for n1.
4108       _dom_lca_tags.map(n2->_idx, tag);
4109       Node *t2 = idom(n2);
4110       while (dom_depth(t2) == d2) {
4111         if (t2 == n1)  return n1;
4112         _dom_lca_tags.map(t2->_idx, tag);
4113         t2 = idom(t2);
4114       }
4115       // Move up to a new dominator-depth value as well as up the dom-tree.
4116       n1 = t1;
4117       n2 = t2;
4118       d1 = dom_depth(n1);
4119       d2 = dom_depth(n2);
4120     }
4121   } while (n1 != n2);
4122   return n1;
4123 }
4124 
4125 //------------------------------init_dom_lca_tags------------------------------
4126 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4127 // Intended use does not involve any growth for the array, so it could
4128 // be of fixed size.
4129 void PhaseIdealLoop::init_dom_lca_tags() {
4130   uint limit = C->unique() + 1;
4131   _dom_lca_tags.map( limit, NULL );
4132 #ifdef ASSERT
4133   for( uint i = 0; i < limit; ++i ) {
4134     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4135   }
4136 #endif // ASSERT
4137 }
4138 
4139 //------------------------------clear_dom_lca_tags------------------------------
4140 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4141 // Intended use does not involve any growth for the array, so it could
4142 // be of fixed size.
4143 void PhaseIdealLoop::clear_dom_lca_tags() {
4144   uint limit = C->unique() + 1;
4145   _dom_lca_tags.map( limit, NULL );
4146   _dom_lca_tags.clear();
4147 #ifdef ASSERT
4148   for( uint i = 0; i < limit; ++i ) {
4149     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4150   }
4151 #endif // ASSERT
4152 }
4153 
4154 //------------------------------build_loop_late--------------------------------
4155 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4156 // Second pass finds latest legal placement, and ideal loop placement.
4157 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
4158   while (worklist.size() != 0) {
4159     Node *n = worklist.pop();
4160     // Only visit once
4161     if (visited.test_set(n->_idx)) continue;
4162     uint cnt = n->outcnt();
4163     uint   i = 0;
4164     while (true) {
4165       assert( _nodes[n->_idx], "no dead nodes" );
4166       // Visit all children
4167       if (i < cnt) {
4168         Node* use = n->raw_out(i);
4169         ++i;
4170         // Check for dead uses.  Aggressively prune such junk.  It might be
4171         // dead in the global sense, but still have local uses so I cannot
4172         // easily call 'remove_dead_node'.
4173         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
4174           // Due to cycles, we might not hit the same fixed point in the verify
4175           // pass as we do in the regular pass.  Instead, visit such phis as
4176           // simple uses of the loop head.
4177           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
4178             if( !visited.test(use->_idx) )
4179               worklist.push(use);
4180           } else if( !visited.test_set(use->_idx) ) {
4181             nstack.push(n, i); // Save parent and next use's index.
4182             n   = use;         // Process all children of current use.
4183             cnt = use->outcnt();
4184             i   = 0;
4185           }
4186         } else {
4187           // Do not visit around the backedge of loops via data edges.
4188           // push dead code onto a worklist
4189           _deadlist.push(use);
4190         }
4191       } else {
4192         // All of n's children have been processed, complete post-processing.
4193         build_loop_late_post(n);
4194         if (nstack.is_empty()) {
4195           // Finished all nodes on stack.
4196           // Process next node on the worklist.
4197           break;
4198         }
4199         // Get saved parent node and next use's index. Visit the rest of uses.
4200         n   = nstack.node();
4201         cnt = n->outcnt();
4202         i   = nstack.index();
4203         nstack.pop();
4204       }
4205     }
4206   }
4207 }
4208 
4209 // Verify that no data node is scheduled in the outer loop of a strip
4210 // mined loop.
4211 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
4212 #ifdef ASSERT
4213   if (get_loop(least)->_nest == 0) {
4214     return;
4215   }
4216   IdealLoopTree* loop = get_loop(least);
4217   Node* head = loop->_head;
4218   if (head->is_OuterStripMinedLoop() &&
4219       // Verification can't be applied to fully built strip mined loops
4220       head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
4221     Node* sfpt = head->as_Loop()->outer_safepoint();
4222     ResourceMark rm;
4223     Unique_Node_List wq;
4224     wq.push(sfpt);
4225     for (uint i = 0; i < wq.size(); i++) {
4226       Node *m = wq.at(i);
4227       for (uint i = 1; i < m->req(); i++) {
4228         Node* nn = m->in(i);
4229         if (nn == n) {
4230           return;
4231         }
4232         if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
4233           wq.push(nn);
4234         }
4235       }
4236     }
4237     ShouldNotReachHere();
4238   }
4239 #endif
4240 }
4241 
4242 
4243 //------------------------------build_loop_late_post---------------------------
4244 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4245 // Second pass finds latest legal placement, and ideal loop placement.
4246 void PhaseIdealLoop::build_loop_late_post(Node *n) {
4247   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4248 
4249   if (bs->build_loop_late_post(this, n)) {
4250     return;
4251   }
4252 
4253   build_loop_late_post_work(n, true);
4254 }
4255 
4256 void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
4257 
4258   if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
4259     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
4260   }
4261 
4262 #ifdef ASSERT
4263   if (_verify_only && !n->is_CFG()) {
4264     // Check def-use domination.
4265     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
4266   }
4267 #endif
4268 
4269   // CFG and pinned nodes already handled
4270   if( n->in(0) ) {
4271     if( n->in(0)->is_top() ) return; // Dead?
4272 
4273     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
4274     // _must_ be pinned (they have to observe their control edge of course).
4275     // Unlike Stores (which modify an unallocable resource, the memory
4276     // state), Mods/Loads can float around.  So free them up.
4277     switch( n->Opcode() ) {
4278     case Op_DivI:
4279     case Op_DivF:
4280     case Op_DivD:
4281     case Op_ModI:
4282     case Op_ModF:
4283     case Op_ModD:
4284     case Op_LoadB:              // Same with Loads; they can sink
4285     case Op_LoadUB:             // during loop optimizations.
4286     case Op_LoadUS:
4287     case Op_LoadD:
4288     case Op_LoadF:
4289     case Op_LoadI:
4290     case Op_LoadKlass:
4291     case Op_LoadNKlass:
4292     case Op_LoadL:
4293     case Op_LoadS:
4294     case Op_LoadP:
4295     case Op_LoadBarrierSlowReg:
4296     case Op_LoadN:
4297     case Op_LoadRange:
4298     case Op_LoadD_unaligned:
4299     case Op_LoadL_unaligned:
4300     case Op_StrComp:            // Does a bunch of load-like effects
4301     case Op_StrEquals:
4302     case Op_StrIndexOf:
4303     case Op_StrIndexOfChar:
4304     case Op_AryEq:
4305     case Op_HasNegatives:
4306       pinned = false;
4307     }
4308     if( pinned ) {
4309       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
4310       if( !chosen_loop->_child )       // Inner loop?
4311         chosen_loop->_body.push(n); // Collect inner loops
4312       return;
4313     }
4314   } else {                      // No slot zero
4315     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
4316       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
4317       return;
4318     }
4319     assert(!n->is_CFG() || n->outcnt() == 0, "");
4320   }
4321 
4322   // Do I have a "safe range" I can select over?
4323   Node *early = get_ctrl(n);// Early location already computed
4324 
4325   // Compute latest point this Node can go
4326   Node *LCA = get_late_ctrl( n, early );
4327   // LCA is NULL due to uses being dead
4328   if( LCA == NULL ) {
4329 #ifdef ASSERT
4330     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
4331       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
4332     }
4333 #endif
4334     _nodes.map(n->_idx, 0);     // This node is useless
4335     _deadlist.push(n);
4336     return;
4337   }
4338   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
4339 
4340   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
4341   Node *least = legal;          // Best legal position so far
4342   while( early != legal ) {     // While not at earliest legal
4343 #ifdef ASSERT
4344     if (legal->is_Start() && !early->is_Root()) {
4345       // Bad graph. Print idom path and fail.
4346       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
4347       assert(false, "Bad graph detected in build_loop_late");
4348     }
4349 #endif
4350     // Find least loop nesting depth
4351     legal = idom(legal);        // Bump up the IDOM tree
4352     // Check for lower nesting depth
4353     if( get_loop(legal)->_nest < get_loop(least)->_nest )
4354       least = legal;
4355   }
4356   assert(early == legal || legal != C->root(), "bad dominance of inputs");
4357 
4358   // Try not to place code on a loop entry projection
4359   // which can inhibit range check elimination.
4360   if (least != early) {
4361     Node* ctrl_out = least->unique_ctrl_out();
4362     if (ctrl_out && ctrl_out->is_Loop() &&
4363         least == ctrl_out->in(LoopNode::EntryControl)) {
4364       // Move the node above predicates as far up as possible so a
4365       // following pass of loop predication doesn't hoist a predicate
4366       // that depends on it above that node.
4367       Node* new_ctrl = least;
4368       for (;;) {
4369         if (!new_ctrl->is_Proj()) {
4370           break;
4371         }
4372         CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
4373         if (call == NULL) {
4374           break;
4375         }
4376         int req = call->uncommon_trap_request();
4377         Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
4378         if (trap_reason != Deoptimization::Reason_loop_limit_check &&
4379             trap_reason != Deoptimization::Reason_predicate &&
4380             trap_reason != Deoptimization::Reason_profile_predicate) {
4381           break;
4382         }
4383         Node* c = new_ctrl->in(0)->in(0);
4384         if (is_dominator(c, early) && c != early) {
4385           break;
4386         }
4387         new_ctrl = c;
4388       }
4389       least = new_ctrl;
4390     }
4391   }
4392 
4393 #ifdef ASSERT
4394   // If verifying, verify that 'verify_me' has a legal location
4395   // and choose it as our location.
4396   if( _verify_me ) {
4397     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
4398     Node *legal = LCA;
4399     while( early != legal ) {   // While not at earliest legal
4400       if( legal == v_ctrl ) break;  // Check for prior good location
4401       legal = idom(legal)      ;// Bump up the IDOM tree
4402     }
4403     // Check for prior good location
4404     if( legal == v_ctrl ) least = legal; // Keep prior if found
4405   }
4406 #endif
4407 
4408   // Assign discovered "here or above" point
4409   least = find_non_split_ctrl(least);
4410   verify_strip_mined_scheduling(n, least);
4411   set_ctrl(n, least);
4412 
4413   // Collect inner loop bodies
4414   IdealLoopTree *chosen_loop = get_loop(least);
4415   if( !chosen_loop->_child )   // Inner loop?
4416     chosen_loop->_body.push(n);// Collect inner loops
4417 }
4418 
4419 #ifdef ASSERT
4420 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
4421   tty->print_cr("%s", msg);
4422   tty->print("n: "); n->dump();
4423   tty->print("early(n): "); early->dump();
4424   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
4425       n->in(0) != early && !n->in(0)->is_Root()) {
4426     tty->print("n->in(0): "); n->in(0)->dump();
4427   }
4428   for (uint i = 1; i < n->req(); i++) {
4429     Node* in1 = n->in(i);
4430     if (in1 != NULL && in1 != n && !in1->is_top()) {
4431       tty->print("n->in(%d): ", i); in1->dump();
4432       Node* in1_early = get_ctrl(in1);
4433       tty->print("early(n->in(%d)): ", i); in1_early->dump();
4434       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
4435           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
4436         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
4437       }
4438       for (uint j = 1; j < in1->req(); j++) {
4439         Node* in2 = in1->in(j);
4440         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
4441           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
4442           Node* in2_early = get_ctrl(in2);
4443           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
4444           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
4445               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
4446             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
4447           }
4448         }
4449       }
4450     }
4451   }
4452   tty->cr();
4453   tty->print("LCA(n): "); LCA->dump();
4454   for (uint i = 0; i < n->outcnt(); i++) {
4455     Node* u1 = n->raw_out(i);
4456     if (u1 == n)
4457       continue;
4458     tty->print("n->out(%d): ", i); u1->dump();
4459     if (u1->is_CFG()) {
4460       for (uint j = 0; j < u1->outcnt(); j++) {
4461         Node* u2 = u1->raw_out(j);
4462         if (u2 != u1 && u2 != n && u2->is_CFG()) {
4463           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4464         }
4465       }
4466     } else {
4467       Node* u1_later = get_ctrl(u1);
4468       tty->print("later(n->out(%d)): ", i); u1_later->dump();
4469       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
4470           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
4471         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
4472       }
4473       for (uint j = 0; j < u1->outcnt(); j++) {
4474         Node* u2 = u1->raw_out(j);
4475         if (u2 == n || u2 == u1)
4476           continue;
4477         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4478         if (!u2->is_CFG()) {
4479           Node* u2_later = get_ctrl(u2);
4480           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
4481           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
4482               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
4483             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
4484           }
4485         }
4486       }
4487     }
4488   }
4489   tty->cr();
4490   int ct = 0;
4491   Node *dbg_legal = LCA;
4492   while(!dbg_legal->is_Start() && ct < 100) {
4493     tty->print("idom[%d] ",ct); dbg_legal->dump();
4494     ct++;
4495     dbg_legal = idom(dbg_legal);
4496   }
4497   tty->cr();
4498 }
4499 #endif
4500 
4501 #ifndef PRODUCT
4502 //------------------------------dump-------------------------------------------
4503 void PhaseIdealLoop::dump( ) const {
4504   ResourceMark rm;
4505   Arena* arena = Thread::current()->resource_area();
4506   Node_Stack stack(arena, C->live_nodes() >> 2);
4507   Node_List rpo_list;
4508   VectorSet visited(arena);
4509   visited.set(C->top()->_idx);
4510   rpo( C->root(), stack, visited, rpo_list );
4511   // Dump root loop indexed by last element in PO order
4512   dump( _ltree_root, rpo_list.size(), rpo_list );
4513 }
4514 
4515 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
4516   loop->dump_head();
4517 
4518   // Now scan for CFG nodes in the same loop
4519   for( uint j=idx; j > 0;  j-- ) {
4520     Node *n = rpo_list[j-1];
4521     if( !_nodes[n->_idx] )      // Skip dead nodes
4522       continue;
4523     if( get_loop(n) != loop ) { // Wrong loop nest
4524       if( get_loop(n)->_head == n &&    // Found nested loop?
4525           get_loop(n)->_parent == loop )
4526         dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
4527       continue;
4528     }
4529 
4530     // Dump controlling node
4531     for( uint x = 0; x < loop->_nest; x++ )
4532       tty->print("  ");
4533     tty->print("C");
4534     if( n == C->root() ) {
4535       n->dump();
4536     } else {
4537       Node* cached_idom   = idom_no_update(n);
4538       Node *computed_idom = n->in(0);
4539       if( n->is_Region() ) {
4540         computed_idom = compute_idom(n);
4541         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
4542         // any MultiBranch ctrl node), so apply a similar transform to
4543         // the cached idom returned from idom_no_update.
4544         cached_idom = find_non_split_ctrl(cached_idom);
4545       }
4546       tty->print(" ID:%d",computed_idom->_idx);
4547       n->dump();
4548       if( cached_idom != computed_idom ) {
4549         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
4550                       computed_idom->_idx, cached_idom->_idx);
4551       }
4552     }
4553     // Dump nodes it controls
4554     for( uint k = 0; k < _nodes.Size(); k++ ) {
4555       // (k < C->unique() && get_ctrl(find(k)) == n)
4556       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
4557         Node *m = C->root()->find(k);
4558         if( m && m->outcnt() > 0 ) {
4559           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
4560             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
4561                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
4562           }
4563           for( uint j = 0; j < loop->_nest; j++ )
4564             tty->print("  ");
4565           tty->print(" ");
4566           m->dump();
4567         }
4568       }
4569     }
4570   }
4571 }
4572 #endif
4573 
4574 // Collect a R-P-O for the whole CFG.
4575 // Result list is in post-order (scan backwards for RPO)
4576 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
4577   stk.push(start, 0);
4578   visited.set(start->_idx);
4579 
4580   while (stk.is_nonempty()) {
4581     Node* m   = stk.node();
4582     uint  idx = stk.index();
4583     if (idx < m->outcnt()) {
4584       stk.set_index(idx + 1);
4585       Node* n = m->raw_out(idx);
4586       if (n->is_CFG() && !visited.test_set(n->_idx)) {
4587         stk.push(n, 0);
4588       }
4589     } else {
4590       rpo_list.push(m);
4591       stk.pop();
4592     }
4593   }
4594 }
4595 
4596 
4597 //=============================================================================
4598 //------------------------------LoopTreeIterator-----------------------------------
4599 
4600 // Advance to next loop tree using a preorder, left-to-right traversal.
4601 void LoopTreeIterator::next() {
4602   assert(!done(), "must not be done.");
4603   if (_curnt->_child != NULL) {
4604     _curnt = _curnt->_child;
4605   } else if (_curnt->_next != NULL) {
4606     _curnt = _curnt->_next;
4607   } else {
4608     while (_curnt != _root && _curnt->_next == NULL) {
4609       _curnt = _curnt->_parent;
4610     }
4611     if (_curnt == _root) {
4612       _curnt = NULL;
4613       assert(done(), "must be done.");
4614     } else {
4615       assert(_curnt->_next != NULL, "must be more to do");
4616       _curnt = _curnt->_next;
4617     }
4618   }
4619 }