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 #ifdef ASSERT
 948 void LoopNode::verify_strip_mined(int expect_skeleton) const {
 949   if (!is_valid_counted_loop()) {
 950     return; // Skip malformed counted loop
 951   }
 952   const OuterStripMinedLoopNode* outer = NULL;
 953   const CountedLoopNode* inner = NULL;
 954   if (is_strip_mined()) {
 955     assert(is_CountedLoop(), "no Loop should be marked strip mined");
 956     inner = as_CountedLoop();
 957     outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
 958   } else if (is_OuterStripMinedLoop()) {
 959     outer = this->as_OuterStripMinedLoop();
 960     inner = outer->unique_ctrl_out()->as_CountedLoop();
 961     assert(inner->is_valid_counted_loop(), "OuterStripMinedLoop should have been removed");
 962     assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
 963   }
 964   if (inner != NULL || outer != NULL) {
 965     assert(inner != NULL && outer != NULL, "missing loop in strip mined nest");
 966     Node* outer_tail = outer->in(LoopNode::LoopBackControl);
 967     Node* outer_le = outer_tail->in(0);
 968     assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
 969     Node* sfpt = outer_le->in(0);
 970     assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
 971     Node* inner_out = sfpt->in(0);
 972     if (inner_out->outcnt() != 1) {
 973       ResourceMark rm;
 974       Unique_Node_List wq;
 975 
 976       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
 977         Node* u = inner_out->fast_out(i);
 978         if (u == sfpt) {
 979           continue;
 980         }
 981         wq.clear();
 982         wq.push(u);
 983         bool found_sfpt = false;
 984         for (uint next = 0; next < wq.size() && !found_sfpt; next++) {
 985           Node* n = wq.at(next);
 986           for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) {
 987             Node* u = n->fast_out(i);
 988             if (u == sfpt) {
 989               found_sfpt = true;
 990             }
 991             if (!u->is_CFG()) {
 992               wq.push(u);
 993             }
 994           }
 995         }
 996         assert(found_sfpt, "no node in loop that's not input to safepoint");
 997       }
 998     }
 999 
1000     CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
1001     assert(cle == inner->loopexit_or_null(), "mismatch");
1002     bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
1003     if (has_skeleton) {
1004       assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
1005       assert(outer->outcnt() == 2, "only phis");
1006     } else {
1007       assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
1008       uint phis = 0;
1009       for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
1010         Node* u = inner->fast_out(i);
1011         if (u->is_Phi()) {
1012           phis++;
1013         }
1014       }
1015       for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
1016         Node* u = outer->fast_out(i);
1017         assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
1018       }
1019       uint stores = 0;
1020       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
1021         Node* u = inner_out->fast_out(i);
1022         if (u->is_Store()) {
1023           stores++;
1024         }
1025       }
1026       assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
1027     }
1028     assert(sfpt->outcnt() == 1, "no data node");
1029     assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
1030   }
1031 }
1032 #endif
1033 
1034 //=============================================================================
1035 //------------------------------Ideal------------------------------------------
1036 // Return a node which is more "ideal" than the current node.
1037 // Attempt to convert into a counted-loop.
1038 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1039   return RegionNode::Ideal(phase, can_reshape);
1040 }
1041 
1042 //------------------------------dump_spec--------------------------------------
1043 // Dump special per-node info
1044 #ifndef PRODUCT
1045 void CountedLoopNode::dump_spec(outputStream *st) const {
1046   LoopNode::dump_spec(st);
1047   if (stride_is_con()) {
1048     st->print("stride: %d ",stride_con());
1049   }
1050   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
1051   if (is_main_loop()) st->print("main of N%d", _idx);
1052   if (is_post_loop()) st->print("post of N%d", _main_idx);
1053   if (is_strip_mined()) st->print(" strip mined");
1054 }
1055 #endif
1056 
1057 //=============================================================================
1058 int CountedLoopEndNode::stride_con() const {
1059   return stride()->bottom_type()->is_int()->get_con();
1060 }
1061 
1062 //=============================================================================
1063 //------------------------------Value-----------------------------------------
1064 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
1065   const Type* init_t   = phase->type(in(Init));
1066   const Type* limit_t  = phase->type(in(Limit));
1067   const Type* stride_t = phase->type(in(Stride));
1068   // Either input is TOP ==> the result is TOP
1069   if (init_t   == Type::TOP) return Type::TOP;
1070   if (limit_t  == Type::TOP) return Type::TOP;
1071   if (stride_t == Type::TOP) return Type::TOP;
1072 
1073   int stride_con = stride_t->is_int()->get_con();
1074   if (stride_con == 1)
1075     return NULL;  // Identity
1076 
1077   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
1078     // Use jlongs to avoid integer overflow.
1079     jlong init_con   =  init_t->is_int()->get_con();
1080     jlong limit_con  = limit_t->is_int()->get_con();
1081     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
1082     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
1083     jlong final_con  = init_con + stride_con*trip_count;
1084     int final_int = (int)final_con;
1085     // The final value should be in integer range since the loop
1086     // is counted and the limit was checked for overflow.
1087     assert(final_con == (jlong)final_int, "final value should be integer");
1088     return TypeInt::make(final_int);
1089   }
1090 
1091   return bottom_type(); // TypeInt::INT
1092 }
1093 
1094 //------------------------------Ideal------------------------------------------
1095 // Return a node which is more "ideal" than the current node.
1096 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1097   if (phase->type(in(Init))   == Type::TOP ||
1098       phase->type(in(Limit))  == Type::TOP ||
1099       phase->type(in(Stride)) == Type::TOP)
1100     return NULL;  // Dead
1101 
1102   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1103   if (stride_con == 1)
1104     return NULL;  // Identity
1105 
1106   if (in(Init)->is_Con() && in(Limit)->is_Con())
1107     return NULL;  // Value
1108 
1109   // Delay following optimizations until all loop optimizations
1110   // done to keep Ideal graph simple.
1111   if (!can_reshape || phase->C->major_progress())
1112     return NULL;
1113 
1114   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
1115   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
1116   int stride_p;
1117   jlong lim, ini;
1118   julong max;
1119   if (stride_con > 0) {
1120     stride_p = stride_con;
1121     lim = limit_t->_hi;
1122     ini = init_t->_lo;
1123     max = (julong)max_jint;
1124   } else {
1125     stride_p = -stride_con;
1126     lim = init_t->_hi;
1127     ini = limit_t->_lo;
1128     max = (julong)min_jint;
1129   }
1130   julong range = lim - ini + stride_p;
1131   if (range <= max) {
1132     // Convert to integer expression if it is not overflow.
1133     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
1134     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
1135     Node *bias  = phase->transform(new AddINode(range, stride_m));
1136     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
1137     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
1138     return new AddINode(span, in(Init)); // exact limit
1139   }
1140 
1141   if (is_power_of_2(stride_p) ||                // divisor is 2^n
1142       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
1143     // Convert to long expression to avoid integer overflow
1144     // and let igvn optimizer convert this division.
1145     //
1146     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
1147     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
1148     Node* stride   = phase->longcon(stride_con);
1149     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
1150 
1151     Node *range = phase->transform(new SubLNode(limit, init));
1152     Node *bias  = phase->transform(new AddLNode(range, stride_m));
1153     Node *span;
1154     if (stride_con > 0 && is_power_of_2(stride_p)) {
1155       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
1156       // and avoid generating rounding for division. Zero trip guard should
1157       // guarantee that init < limit but sometimes the guard is missing and
1158       // we can get situation when init > limit. Note, for the empty loop
1159       // optimization zero trip guard is generated explicitly which leaves
1160       // only RCE predicate where exact limit is used and the predicate
1161       // will simply fail forcing recompilation.
1162       Node* neg_stride   = phase->longcon(-stride_con);
1163       span = phase->transform(new AndLNode(bias, neg_stride));
1164     } else {
1165       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
1166       span = phase->transform(new MulLNode(trip, stride));
1167     }
1168     // Convert back to int
1169     Node *span_int = phase->transform(new ConvL2INode(span));
1170     return new AddINode(span_int, in(Init)); // exact limit
1171   }
1172 
1173   return NULL;    // No progress
1174 }
1175 
1176 //------------------------------Identity---------------------------------------
1177 // If stride == 1 return limit node.
1178 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1179   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1180   if (stride_con == 1 || stride_con == -1)
1181     return in(Limit);
1182   return this;
1183 }
1184 
1185 //=============================================================================
1186 //----------------------match_incr_with_optional_truncation--------------------
1187 // Match increment with optional truncation:
1188 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1189 // Return NULL for failure. Success returns the increment node.
1190 Node* CountedLoopNode::match_incr_with_optional_truncation(
1191                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1192   // Quick cutouts:
1193   if (expr == NULL || expr->req() != 3)  return NULL;
1194 
1195   Node *t1 = NULL;
1196   Node *t2 = NULL;
1197   const TypeInt* trunc_t = TypeInt::INT;
1198   Node* n1 = expr;
1199   int   n1op = n1->Opcode();
1200 
1201   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1202   if (n1op == Op_AndI &&
1203       n1->in(2)->is_Con() &&
1204       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1205     // %%% This check should match any mask of 2**K-1.
1206     t1 = n1;
1207     n1 = t1->in(1);
1208     n1op = n1->Opcode();
1209     trunc_t = TypeInt::CHAR;
1210   } else if (n1op == Op_RShiftI &&
1211              n1->in(1) != NULL &&
1212              n1->in(1)->Opcode() == Op_LShiftI &&
1213              n1->in(2) == n1->in(1)->in(2) &&
1214              n1->in(2)->is_Con()) {
1215     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1216     // %%% This check should match any shift in [1..31].
1217     if (shift == 16 || shift == 8) {
1218       t1 = n1;
1219       t2 = t1->in(1);
1220       n1 = t2->in(1);
1221       n1op = n1->Opcode();
1222       if (shift == 16) {
1223         trunc_t = TypeInt::SHORT;
1224       } else if (shift == 8) {
1225         trunc_t = TypeInt::BYTE;
1226       }
1227     }
1228   }
1229 
1230   // If (maybe after stripping) it is an AddI, we won:
1231   if (n1op == Op_AddI) {
1232     *trunc1 = t1;
1233     *trunc2 = t2;
1234     *trunc_type = trunc_t;
1235     return n1;
1236   }
1237 
1238   // failed
1239   return NULL;
1240 }
1241 
1242 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
1243   if (is_strip_mined()) {
1244     verify_strip_mined(expect_skeleton);
1245     return in(EntryControl)->as_Loop();
1246   }
1247   return this;
1248 }
1249 
1250 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
1251   assert(is_strip_mined(), "not a strip mined loop");
1252   Node* c = in(EntryControl);
1253   if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) {
1254     return NULL;
1255   }
1256   return c->as_OuterStripMinedLoop();
1257 }
1258 
1259 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
1260   Node* c = in(LoopBackControl);
1261   if (c == NULL || c->is_top()) {
1262     return NULL;
1263   }
1264   return c->as_IfTrue();
1265 }
1266 
1267 IfTrueNode* CountedLoopNode::outer_loop_tail() const {
1268   LoopNode* l = outer_loop();
1269   if (l == NULL) {
1270     return NULL;
1271   }
1272   return l->outer_loop_tail();
1273 }
1274 
1275 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
1276   IfTrueNode* proj = outer_loop_tail();
1277   if (proj == NULL) {
1278     return NULL;
1279   }
1280   Node* c = proj->in(0);
1281   if (c == NULL || c->is_top() || c->outcnt() != 2) {
1282     return NULL;
1283   }
1284   return c->as_OuterStripMinedLoopEnd();
1285 }
1286 
1287 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
1288   LoopNode* l = outer_loop();
1289   if (l == NULL) {
1290     return NULL;
1291   }
1292   return l->outer_loop_end();
1293 }
1294 
1295 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
1296   IfNode* le = outer_loop_end();
1297   if (le == NULL) {
1298     return NULL;
1299   }
1300   Node* c = le->proj_out_or_null(false);
1301   if (c == NULL) {
1302     return NULL;
1303   }
1304   return c->as_IfFalse();
1305 }
1306 
1307 IfFalseNode* CountedLoopNode::outer_loop_exit() const {
1308   LoopNode* l = outer_loop();
1309   if (l == NULL) {
1310     return NULL;
1311   }
1312   return l->outer_loop_exit();
1313 }
1314 
1315 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
1316   IfNode* le = outer_loop_end();
1317   if (le == NULL) {
1318     return NULL;
1319   }
1320   Node* c = le->in(0);
1321   if (c == NULL || c->is_top()) {
1322     return NULL;
1323   }
1324   assert(c->Opcode() == Op_SafePoint, "broken outer loop");
1325   return c->as_SafePoint();
1326 }
1327 
1328 SafePointNode* CountedLoopNode::outer_safepoint() const {
1329   LoopNode* l = outer_loop();
1330   if (l == NULL) {
1331     return NULL;
1332   }
1333   return l->outer_safepoint();
1334 }
1335 
1336 Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
1337     while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() &&
1338            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
1339            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) {
1340       ctrl = ctrl->in(0)->in(0);
1341     }
1342 
1343     return ctrl;
1344   }
1345 
1346 Node* CountedLoopNode::skip_predicates() {
1347   if (is_main_loop()) {
1348     Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
1349 
1350     return skip_predicates_from_entry(ctrl);
1351   }
1352   return in(LoopNode::EntryControl);
1353 }
1354 
1355 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
1356   // Look for the outer & inner strip mined loop, reduce number of
1357   // iterations of the inner loop, set exit condition of outer loop,
1358   // construct required phi nodes for outer loop.
1359   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
1360   assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
1361   Node* inner_iv_phi = inner_cl->phi();
1362   if (inner_iv_phi == NULL) {
1363     IfNode* outer_le = outer_loop_end();
1364     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1365     igvn->replace_node(outer_le, iff);
1366     inner_cl->clear_strip_mined();
1367     return;
1368   }
1369   CountedLoopEndNode* inner_cle = inner_cl->loopexit();
1370 
1371   int stride = inner_cl->stride_con();
1372   jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
1373   int scaled_iters = (int)scaled_iters_long;
1374   int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
1375   const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
1376   jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
1377   assert(iter_estimate > 0, "broken");
1378   if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
1379     // Remove outer loop and safepoint (too few iterations)
1380     Node* outer_sfpt = outer_safepoint();
1381     Node* outer_out = outer_loop_exit();
1382     igvn->replace_node(outer_out, outer_sfpt->in(0));
1383     igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
1384     inner_cl->clear_strip_mined();
1385     return;
1386   }
1387   if (iter_estimate <= scaled_iters_long) {
1388     // We would only go through one iteration of
1389     // the outer loop: drop the outer loop but
1390     // keep the safepoint so we don't run for
1391     // too long without a safepoint
1392     IfNode* outer_le = outer_loop_end();
1393     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1394     igvn->replace_node(outer_le, iff);
1395     inner_cl->clear_strip_mined();
1396     return;
1397   }
1398 
1399   Node* cle_tail = inner_cle->proj_out(true);
1400   ResourceMark rm;
1401   Node_List old_new;
1402   if (cle_tail->outcnt() > 1) {
1403     // Look for nodes on backedge of inner loop and clone them
1404     Unique_Node_List backedge_nodes;
1405     for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
1406       Node* u = cle_tail->fast_out(i);
1407       if (u != inner_cl) {
1408         assert(!u->is_CFG(), "control flow on the backedge?");
1409         backedge_nodes.push(u);
1410       }
1411     }
1412     uint last = igvn->C->unique();
1413     for (uint next = 0; next < backedge_nodes.size(); next++) {
1414       Node* n = backedge_nodes.at(next);
1415       old_new.map(n->_idx, n->clone());
1416       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1417         Node* u = n->fast_out(i);
1418         assert(!u->is_CFG(), "broken");
1419         if (u->_idx >= last) {
1420           continue;
1421         }
1422         if (!u->is_Phi()) {
1423           backedge_nodes.push(u);
1424         } else {
1425           assert(u->in(0) == inner_cl, "strange phi on the backedge");
1426         }
1427       }
1428     }
1429     // Put the clones on the outer loop backedge
1430     Node* le_tail = outer_loop_tail();
1431     for (uint next = 0; next < backedge_nodes.size(); next++) {
1432       Node *n = old_new[backedge_nodes.at(next)->_idx];
1433       for (uint i = 1; i < n->req(); i++) {
1434         if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) {
1435           n->set_req(i, old_new[n->in(i)->_idx]);
1436         }
1437       }
1438       if (n->in(0) != NULL && n->in(0) == cle_tail) {
1439         n->set_req(0, le_tail);
1440       }
1441       igvn->register_new_node_with_optimizer(n);
1442     }
1443   }
1444 
1445   Node* iv_phi = NULL;
1446   // Make a clone of each phi in the inner loop
1447   // for the outer loop
1448   for (uint i = 0; i < inner_cl->outcnt(); i++) {
1449     Node* u = inner_cl->raw_out(i);
1450     if (u->is_Phi()) {
1451       assert(u->in(0) == inner_cl, "inconsistent");
1452       Node* phi = u->clone();
1453       phi->set_req(0, this);
1454       Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
1455       if (be != NULL) {
1456         phi->set_req(LoopNode::LoopBackControl, be);
1457       }
1458       phi = igvn->transform(phi);
1459       igvn->replace_input_of(u, LoopNode::EntryControl, phi);
1460       if (u == inner_iv_phi) {
1461         iv_phi = phi;
1462       }
1463     }
1464   }
1465   Node* cle_out = inner_cle->proj_out(false);
1466   if (cle_out->outcnt() > 1) {
1467     // Look for chains of stores that were sunk
1468     // out of the inner loop and are in the outer loop
1469     for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
1470       Node* u = cle_out->fast_out(i);
1471       if (u->is_Store()) {
1472         Node* first = u;
1473         for(;;) {
1474           Node* next = first->in(MemNode::Memory);
1475           if (!next->is_Store() || next->in(0) != cle_out) {
1476             break;
1477           }
1478           first = next;
1479         }
1480         Node* last = u;
1481         for(;;) {
1482           Node* next = NULL;
1483           for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
1484             Node* uu = last->fast_out(j);
1485             if (uu->is_Store() && uu->in(0) == cle_out) {
1486               assert(next == NULL, "only one in the outer loop");
1487               next = uu;
1488             }
1489           }
1490           if (next == NULL) {
1491             break;
1492           }
1493           last = next;
1494         }
1495         Node* phi = NULL;
1496         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1497           Node* uu = fast_out(j);
1498           if (uu->is_Phi()) {
1499             Node* be = uu->in(LoopNode::LoopBackControl);
1500             if (be->is_Store() && old_new[be->_idx] != NULL) {
1501               assert(false, "store on the backedge + sunk stores: unsupported");
1502               // drop outer loop
1503               IfNode* outer_le = outer_loop_end();
1504               Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1505               igvn->replace_node(outer_le, iff);
1506               inner_cl->clear_strip_mined();
1507               return;
1508             }
1509             if (be == last || be == first->in(MemNode::Memory)) {
1510               assert(phi == NULL, "only one phi");
1511               phi = uu;
1512             }
1513           }
1514         }
1515 #ifdef ASSERT
1516         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1517           Node* uu = fast_out(j);
1518           if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
1519             if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
1520               assert(phi == uu, "what's that phi?");
1521             } else if (uu->adr_type() == TypePtr::BOTTOM) {
1522               Node* n = uu->in(LoopNode::LoopBackControl);
1523               uint limit = igvn->C->live_nodes();
1524               uint i = 0;
1525               while (n != uu) {
1526                 i++;
1527                 assert(i < limit, "infinite loop");
1528                 if (n->is_Proj()) {
1529                   n = n->in(0);
1530                 } else if (n->is_SafePoint() || n->is_MemBar()) {
1531                   n = n->in(TypeFunc::Memory);
1532                 } else if (n->is_Phi()) {
1533                   n = n->in(1);
1534                 } else if (n->is_MergeMem()) {
1535                   n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
1536                 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
1537                   n = n->in(MemNode::Memory);
1538                 } else {
1539                   n->dump();
1540                   ShouldNotReachHere();
1541                 }
1542               }
1543             }
1544           }
1545         }
1546 #endif
1547         if (phi == NULL) {
1548           // If the an entire chains was sunk, the
1549           // inner loop has no phi for that memory
1550           // slice, create one for the outer loop
1551           phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY,
1552                               igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
1553           phi->set_req(LoopNode::LoopBackControl, last);
1554           phi = igvn->transform(phi);
1555           igvn->replace_input_of(first, MemNode::Memory, phi);
1556         } else {
1557           // Or fix the outer loop fix to include
1558           // that chain of stores.
1559           Node* be = phi->in(LoopNode::LoopBackControl);
1560           assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported");
1561           if (be == first->in(MemNode::Memory)) {
1562             if (be == phi->in(LoopNode::LoopBackControl)) {
1563               igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
1564             } else {
1565               igvn->replace_input_of(be, MemNode::Memory, last);
1566             }
1567           } else {
1568 #ifdef ASSERT
1569             if (be == phi->in(LoopNode::LoopBackControl)) {
1570               assert(phi->in(LoopNode::LoopBackControl) == last, "");
1571             } else {
1572               assert(be->in(MemNode::Memory) == last, "");
1573             }
1574 #endif
1575           }
1576         }
1577       }
1578     }
1579   }
1580 
1581   if (iv_phi != NULL) {
1582     // Now adjust the inner loop's exit condition
1583     Node* limit = inner_cl->limit();
1584     Node* sub = NULL;
1585     if (stride > 0) {
1586       sub = igvn->transform(new SubINode(limit, iv_phi));
1587     } else {
1588       sub = igvn->transform(new SubINode(iv_phi, limit));
1589     }
1590     Node* min = igvn->transform(new MinINode(sub, igvn->intcon(scaled_iters)));
1591     Node* new_limit = NULL;
1592     if (stride > 0) {
1593       new_limit = igvn->transform(new AddINode(min, iv_phi));
1594     } else {
1595       new_limit = igvn->transform(new SubINode(iv_phi, min));
1596     }
1597     Node* inner_cmp = inner_cle->cmp_node();
1598     Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
1599     Node* outer_bol = inner_bol;
1600     // cmp node for inner loop may be shared
1601     inner_cmp = inner_cmp->clone();
1602     inner_cmp->set_req(2, new_limit);
1603     inner_bol = inner_bol->clone();
1604     inner_bol->set_req(1, igvn->transform(inner_cmp));
1605     igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
1606     // Set the outer loop's exit condition too
1607     igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
1608   } else {
1609     assert(false, "should be able to adjust outer loop");
1610     IfNode* outer_le = outer_loop_end();
1611     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1612     igvn->replace_node(outer_le, iff);
1613     inner_cl->clear_strip_mined();
1614   }
1615 }
1616 
1617 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
1618   if (!in(0)) return Type::TOP;
1619   if (phase->type(in(0)) == Type::TOP)
1620     return Type::TOP;
1621 
1622   return TypeTuple::IFBOTH;
1623 }
1624 
1625 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1626   if (remove_dead_region(phase, can_reshape))  return this;
1627 
1628   return NULL;
1629 }
1630 
1631 //------------------------------filtered_type--------------------------------
1632 // Return a type based on condition control flow
1633 // A successful return will be a type that is restricted due
1634 // to a series of dominating if-tests, such as:
1635 //    if (i < 10) {
1636 //       if (i > 0) {
1637 //          here: "i" type is [1..10)
1638 //       }
1639 //    }
1640 // or a control flow merge
1641 //    if (i < 10) {
1642 //       do {
1643 //          phi( , ) -- at top of loop type is [min_int..10)
1644 //         i = ?
1645 //       } while ( i < 10)
1646 //
1647 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1648   assert(n && n->bottom_type()->is_int(), "must be int");
1649   const TypeInt* filtered_t = NULL;
1650   if (!n->is_Phi()) {
1651     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1652     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1653 
1654   } else {
1655     Node* phi    = n->as_Phi();
1656     Node* region = phi->in(0);
1657     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1658     if (region && region != C->top()) {
1659       for (uint i = 1; i < phi->req(); i++) {
1660         Node* val   = phi->in(i);
1661         Node* use_c = region->in(i);
1662         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1663         if (val_t != NULL) {
1664           if (filtered_t == NULL) {
1665             filtered_t = val_t;
1666           } else {
1667             filtered_t = filtered_t->meet(val_t)->is_int();
1668           }
1669         }
1670       }
1671     }
1672   }
1673   const TypeInt* n_t = _igvn.type(n)->is_int();
1674   if (filtered_t != NULL) {
1675     n_t = n_t->join(filtered_t)->is_int();
1676   }
1677   return n_t;
1678 }
1679 
1680 
1681 //------------------------------filtered_type_from_dominators--------------------------------
1682 // Return a possibly more restrictive type for val based on condition control flow of dominators
1683 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1684   if (val->is_Con()) {
1685      return val->bottom_type()->is_int();
1686   }
1687   uint if_limit = 10; // Max number of dominating if's visited
1688   const TypeInt* rtn_t = NULL;
1689 
1690   if (use_ctrl && use_ctrl != C->top()) {
1691     Node* val_ctrl = get_ctrl(val);
1692     uint val_dom_depth = dom_depth(val_ctrl);
1693     Node* pred = use_ctrl;
1694     uint if_cnt = 0;
1695     while (if_cnt < if_limit) {
1696       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1697         if_cnt++;
1698         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1699         if (if_t != NULL) {
1700           if (rtn_t == NULL) {
1701             rtn_t = if_t;
1702           } else {
1703             rtn_t = rtn_t->join(if_t)->is_int();
1704           }
1705         }
1706       }
1707       pred = idom(pred);
1708       if (pred == NULL || pred == C->top()) {
1709         break;
1710       }
1711       // Stop if going beyond definition block of val
1712       if (dom_depth(pred) < val_dom_depth) {
1713         break;
1714       }
1715     }
1716   }
1717   return rtn_t;
1718 }
1719 
1720 
1721 //------------------------------dump_spec--------------------------------------
1722 // Dump special per-node info
1723 #ifndef PRODUCT
1724 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1725   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1726     BoolTest bt( test_trip()); // Added this for g++.
1727 
1728     st->print("[");
1729     bt.dump_on(st);
1730     st->print("]");
1731   }
1732   st->print(" ");
1733   IfNode::dump_spec(st);
1734 }
1735 #endif
1736 
1737 //=============================================================================
1738 //------------------------------is_member--------------------------------------
1739 // Is 'l' a member of 'this'?
1740 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1741   while( l->_nest > _nest ) l = l->_parent;
1742   return l == this;
1743 }
1744 
1745 //------------------------------set_nest---------------------------------------
1746 // Set loop tree nesting depth.  Accumulate _has_call bits.
1747 int IdealLoopTree::set_nest( uint depth ) {
1748   _nest = depth;
1749   int bits = _has_call;
1750   if( _child ) bits |= _child->set_nest(depth+1);
1751   if( bits ) _has_call = 1;
1752   if( _next  ) bits |= _next ->set_nest(depth  );
1753   return bits;
1754 }
1755 
1756 //------------------------------split_fall_in----------------------------------
1757 // Split out multiple fall-in edges from the loop header.  Move them to a
1758 // private RegionNode before the loop.  This becomes the loop landing pad.
1759 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1760   PhaseIterGVN &igvn = phase->_igvn;
1761   uint i;
1762 
1763   // Make a new RegionNode to be the landing pad.
1764   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1765   phase->set_loop(landing_pad,_parent);
1766   // Gather all the fall-in control paths into the landing pad
1767   uint icnt = fall_in_cnt;
1768   uint oreq = _head->req();
1769   for( i = oreq-1; i>0; i-- )
1770     if( !phase->is_member( this, _head->in(i) ) )
1771       landing_pad->set_req(icnt--,_head->in(i));
1772 
1773   // Peel off PhiNode edges as well
1774   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1775     Node *oj = _head->fast_out(j);
1776     if( oj->is_Phi() ) {
1777       PhiNode* old_phi = oj->as_Phi();
1778       assert( old_phi->region() == _head, "" );
1779       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1780       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1781       uint icnt = fall_in_cnt;
1782       for( i = oreq-1; i>0; i-- ) {
1783         if( !phase->is_member( this, _head->in(i) ) ) {
1784           p->init_req(icnt--, old_phi->in(i));
1785           // Go ahead and clean out old edges from old phi
1786           old_phi->del_req(i);
1787         }
1788       }
1789       // Search for CSE's here, because ZKM.jar does a lot of
1790       // loop hackery and we need to be a little incremental
1791       // with the CSE to avoid O(N^2) node blow-up.
1792       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1793       if( p2 ) {                // Found CSE
1794         p->destruct();          // Recover useless new node
1795         p = p2;                 // Use old node
1796       } else {
1797         igvn.register_new_node_with_optimizer(p, old_phi);
1798       }
1799       // Make old Phi refer to new Phi.
1800       old_phi->add_req(p);
1801       // Check for the special case of making the old phi useless and
1802       // disappear it.  In JavaGrande I have a case where this useless
1803       // Phi is the loop limit and prevents recognizing a CountedLoop
1804       // which in turn prevents removing an empty loop.
1805       Node *id_old_phi = igvn.apply_identity(old_phi);
1806       if( id_old_phi != old_phi ) { // Found a simple identity?
1807         // Note that I cannot call 'replace_node' here, because
1808         // that will yank the edge from old_phi to the Region and
1809         // I'm mid-iteration over the Region's uses.
1810         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1811           Node* use = old_phi->last_out(i);
1812           igvn.rehash_node_delayed(use);
1813           uint uses_found = 0;
1814           for (uint j = 0; j < use->len(); j++) {
1815             if (use->in(j) == old_phi) {
1816               if (j < use->req()) use->set_req (j, id_old_phi);
1817               else                use->set_prec(j, id_old_phi);
1818               uses_found++;
1819             }
1820           }
1821           i -= uses_found;    // we deleted 1 or more copies of this edge
1822         }
1823       }
1824       igvn._worklist.push(old_phi);
1825     }
1826   }
1827   // Finally clean out the fall-in edges from the RegionNode
1828   for( i = oreq-1; i>0; i-- ) {
1829     if( !phase->is_member( this, _head->in(i) ) ) {
1830       _head->del_req(i);
1831     }
1832   }
1833   igvn.rehash_node_delayed(_head);
1834   // Transform landing pad
1835   igvn.register_new_node_with_optimizer(landing_pad, _head);
1836   // Insert landing pad into the header
1837   _head->add_req(landing_pad);
1838 }
1839 
1840 //------------------------------split_outer_loop-------------------------------
1841 // Split out the outermost loop from this shared header.
1842 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1843   PhaseIterGVN &igvn = phase->_igvn;
1844 
1845   // Find index of outermost loop; it should also be my tail.
1846   uint outer_idx = 1;
1847   while( _head->in(outer_idx) != _tail ) outer_idx++;
1848 
1849   // Make a LoopNode for the outermost loop.
1850   Node *ctl = _head->in(LoopNode::EntryControl);
1851   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1852   outer = igvn.register_new_node_with_optimizer(outer, _head);
1853   phase->set_created_loop_node();
1854 
1855   // Outermost loop falls into '_head' loop
1856   _head->set_req(LoopNode::EntryControl, outer);
1857   _head->del_req(outer_idx);
1858   // Split all the Phis up between '_head' loop and 'outer' loop.
1859   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1860     Node *out = _head->fast_out(j);
1861     if( out->is_Phi() ) {
1862       PhiNode *old_phi = out->as_Phi();
1863       assert( old_phi->region() == _head, "" );
1864       Node *phi = PhiNode::make_blank(outer, old_phi);
1865       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1866       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1867       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1868       // Make old Phi point to new Phi on the fall-in path
1869       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1870       old_phi->del_req(outer_idx);
1871     }
1872   }
1873 
1874   // Use the new loop head instead of the old shared one
1875   _head = outer;
1876   phase->set_loop(_head, this);
1877 }
1878 
1879 //------------------------------fix_parent-------------------------------------
1880 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1881   loop->_parent = parent;
1882   if( loop->_child ) fix_parent( loop->_child, loop   );
1883   if( loop->_next  ) fix_parent( loop->_next , parent );
1884 }
1885 
1886 //------------------------------estimate_path_freq-----------------------------
1887 static float estimate_path_freq( Node *n ) {
1888   // Try to extract some path frequency info
1889   IfNode *iff;
1890   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1891     uint nop = n->Opcode();
1892     if( nop == Op_SafePoint ) {   // Skip any safepoint
1893       n = n->in(0);
1894       continue;
1895     }
1896     if( nop == Op_CatchProj ) {   // Get count from a prior call
1897       // Assume call does not always throw exceptions: means the call-site
1898       // count is also the frequency of the fall-through path.
1899       assert( n->is_CatchProj(), "" );
1900       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1901         return 0.0f;            // Assume call exception path is rare
1902       Node *call = n->in(0)->in(0)->in(0);
1903       assert( call->is_Call(), "expect a call here" );
1904       const JVMState *jvms = ((CallNode*)call)->jvms();
1905       ciMethodData* methodData = jvms->method()->method_data();
1906       if (!methodData->is_mature())  return 0.0f; // No call-site data
1907       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1908       if ((data == NULL) || !data->is_CounterData()) {
1909         // no call profile available, try call's control input
1910         n = n->in(0);
1911         continue;
1912       }
1913       return data->as_CounterData()->count()/FreqCountInvocations;
1914     }
1915     // See if there's a gating IF test
1916     Node *n_c = n->in(0);
1917     if( !n_c->is_If() ) break;       // No estimate available
1918     iff = n_c->as_If();
1919     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1920       // Compute how much count comes on this path
1921       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1922     // Have no count info.  Skip dull uncommon-trap like branches.
1923     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1924         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1925       break;
1926     // Skip through never-taken branch; look for a real loop exit.
1927     n = iff->in(0);
1928   }
1929   return 0.0f;                  // No estimate available
1930 }
1931 
1932 //------------------------------merge_many_backedges---------------------------
1933 // Merge all the backedges from the shared header into a private Region.
1934 // Feed that region as the one backedge to this loop.
1935 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1936   uint i;
1937 
1938   // Scan for the top 2 hottest backedges
1939   float hotcnt = 0.0f;
1940   float warmcnt = 0.0f;
1941   uint hot_idx = 0;
1942   // Loop starts at 2 because slot 1 is the fall-in path
1943   for( i = 2; i < _head->req(); i++ ) {
1944     float cnt = estimate_path_freq(_head->in(i));
1945     if( cnt > hotcnt ) {       // Grab hottest path
1946       warmcnt = hotcnt;
1947       hotcnt = cnt;
1948       hot_idx = i;
1949     } else if( cnt > warmcnt ) { // And 2nd hottest path
1950       warmcnt = cnt;
1951     }
1952   }
1953 
1954   // See if the hottest backedge is worthy of being an inner loop
1955   // by being much hotter than the next hottest backedge.
1956   if( hotcnt <= 0.0001 ||
1957       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1958 
1959   // Peel out the backedges into a private merge point; peel
1960   // them all except optionally hot_idx.
1961   PhaseIterGVN &igvn = phase->_igvn;
1962 
1963   Node *hot_tail = NULL;
1964   // Make a Region for the merge point
1965   Node *r = new RegionNode(1);
1966   for( i = 2; i < _head->req(); i++ ) {
1967     if( i != hot_idx )
1968       r->add_req( _head->in(i) );
1969     else hot_tail = _head->in(i);
1970   }
1971   igvn.register_new_node_with_optimizer(r, _head);
1972   // Plug region into end of loop _head, followed by hot_tail
1973   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1974   igvn.replace_input_of(_head, 2, r);
1975   if( hot_idx ) _head->add_req(hot_tail);
1976 
1977   // Split all the Phis up between '_head' loop and the Region 'r'
1978   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1979     Node *out = _head->fast_out(j);
1980     if( out->is_Phi() ) {
1981       PhiNode* n = out->as_Phi();
1982       igvn.hash_delete(n);      // Delete from hash before hacking edges
1983       Node *hot_phi = NULL;
1984       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1985       // Check all inputs for the ones to peel out
1986       uint j = 1;
1987       for( uint i = 2; i < n->req(); i++ ) {
1988         if( i != hot_idx )
1989           phi->set_req( j++, n->in(i) );
1990         else hot_phi = n->in(i);
1991       }
1992       // Register the phi but do not transform until whole place transforms
1993       igvn.register_new_node_with_optimizer(phi, n);
1994       // Add the merge phi to the old Phi
1995       while( n->req() > 3 ) n->del_req( n->req()-1 );
1996       igvn.replace_input_of(n, 2, phi);
1997       if( hot_idx ) n->add_req(hot_phi);
1998     }
1999   }
2000 
2001 
2002   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
2003   // of self loop tree.  Turn self into a loop headed by _head and with
2004   // tail being the new merge point.
2005   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
2006   phase->set_loop(_tail,ilt);   // Adjust tail
2007   _tail = r;                    // Self's tail is new merge point
2008   phase->set_loop(r,this);
2009   ilt->_child = _child;         // New guy has my children
2010   _child = ilt;                 // Self has new guy as only child
2011   ilt->_parent = this;          // new guy has self for parent
2012   ilt->_nest = _nest;           // Same nesting depth (for now)
2013 
2014   // Starting with 'ilt', look for child loop trees using the same shared
2015   // header.  Flatten these out; they will no longer be loops in the end.
2016   IdealLoopTree **pilt = &_child;
2017   while( ilt ) {
2018     if( ilt->_head == _head ) {
2019       uint i;
2020       for( i = 2; i < _head->req(); i++ )
2021         if( _head->in(i) == ilt->_tail )
2022           break;                // Still a loop
2023       if( i == _head->req() ) { // No longer a loop
2024         // Flatten ilt.  Hang ilt's "_next" list from the end of
2025         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
2026         IdealLoopTree **cp = &ilt->_child;
2027         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
2028         *cp = ilt->_next;       // Hang next list at end of child list
2029         *pilt = ilt->_child;    // Move child up to replace ilt
2030         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
2031         ilt = ilt->_child;      // Repeat using new ilt
2032         continue;               // do not advance over ilt->_child
2033       }
2034       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
2035       phase->set_loop(_head,ilt);
2036     }
2037     pilt = &ilt->_child;        // Advance to next
2038     ilt = *pilt;
2039   }
2040 
2041   if( _child ) fix_parent( _child, this );
2042 }
2043 
2044 //------------------------------beautify_loops---------------------------------
2045 // Split shared headers and insert loop landing pads.
2046 // Insert a LoopNode to replace the RegionNode.
2047 // Return TRUE if loop tree is structurally changed.
2048 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
2049   bool result = false;
2050   // Cache parts in locals for easy
2051   PhaseIterGVN &igvn = phase->_igvn;
2052 
2053   igvn.hash_delete(_head);      // Yank from hash before hacking edges
2054 
2055   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
2056   int fall_in_cnt = 0;
2057   for( uint i = 1; i < _head->req(); i++ )
2058     if( !phase->is_member( this, _head->in(i) ) )
2059       fall_in_cnt++;
2060   assert( fall_in_cnt, "at least 1 fall-in path" );
2061   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
2062     split_fall_in( phase, fall_in_cnt );
2063 
2064   // Swap inputs to the _head and all Phis to move the fall-in edge to
2065   // the left.
2066   fall_in_cnt = 1;
2067   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
2068     fall_in_cnt++;
2069   if( fall_in_cnt > 1 ) {
2070     // Since I am just swapping inputs I do not need to update def-use info
2071     Node *tmp = _head->in(1);
2072     igvn.rehash_node_delayed(_head);
2073     _head->set_req( 1, _head->in(fall_in_cnt) );
2074     _head->set_req( fall_in_cnt, tmp );
2075     // Swap also all Phis
2076     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
2077       Node* phi = _head->fast_out(i);
2078       if( phi->is_Phi() ) {
2079         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
2080         tmp = phi->in(1);
2081         phi->set_req( 1, phi->in(fall_in_cnt) );
2082         phi->set_req( fall_in_cnt, tmp );
2083       }
2084     }
2085   }
2086   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
2087   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
2088 
2089   // If I am a shared header (multiple backedges), peel off the many
2090   // backedges into a private merge point and use the merge point as
2091   // the one true backedge.
2092   if( _head->req() > 3 ) {
2093     // Merge the many backedges into a single backedge but leave
2094     // the hottest backedge as separate edge for the following peel.
2095     merge_many_backedges( phase );
2096     result = true;
2097   }
2098 
2099   // If I have one hot backedge, peel off myself loop.
2100   // I better be the outermost loop.
2101   if (_head->req() > 3 && !_irreducible) {
2102     split_outer_loop( phase );
2103     result = true;
2104 
2105   } else if (!_head->is_Loop() && !_irreducible) {
2106     // Make a new LoopNode to replace the old loop head
2107     Node *l = new LoopNode( _head->in(1), _head->in(2) );
2108     l = igvn.register_new_node_with_optimizer(l, _head);
2109     phase->set_created_loop_node();
2110     // Go ahead and replace _head
2111     phase->_igvn.replace_node( _head, l );
2112     _head = l;
2113     phase->set_loop(_head, this);
2114   }
2115 
2116   // Now recursively beautify nested loops
2117   if( _child ) result |= _child->beautify_loops( phase );
2118   if( _next  ) result |= _next ->beautify_loops( phase );
2119   return result;
2120 }
2121 
2122 //------------------------------allpaths_check_safepts----------------------------
2123 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
2124 // encountered.  Helper for check_safepts.
2125 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
2126   assert(stack.size() == 0, "empty stack");
2127   stack.push(_tail);
2128   visited.clear();
2129   visited.set(_tail->_idx);
2130   while (stack.size() > 0) {
2131     Node* n = stack.pop();
2132     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2133       // Terminate this path
2134     } else if (n->Opcode() == Op_SafePoint) {
2135       if (_phase->get_loop(n) != this) {
2136         if (_required_safept == NULL) _required_safept = new Node_List();
2137         _required_safept->push(n);  // save the one closest to the tail
2138       }
2139       // Terminate this path
2140     } else {
2141       uint start = n->is_Region() ? 1 : 0;
2142       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
2143       for (uint i = start; i < end; i++) {
2144         Node* in = n->in(i);
2145         assert(in->is_CFG(), "must be");
2146         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
2147           stack.push(in);
2148         }
2149       }
2150     }
2151   }
2152 }
2153 
2154 //------------------------------check_safepts----------------------------
2155 // Given dominators, try to find loops with calls that must always be
2156 // executed (call dominates loop tail).  These loops do not need non-call
2157 // safepoints (ncsfpt).
2158 //
2159 // A complication is that a safepoint in a inner loop may be needed
2160 // by an outer loop. In the following, the inner loop sees it has a
2161 // call (block 3) on every path from the head (block 2) to the
2162 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
2163 // in block 2, _but_ this leaves the outer loop without a safepoint.
2164 //
2165 //          entry  0
2166 //                 |
2167 //                 v
2168 // outer 1,2    +->1
2169 //              |  |
2170 //              |  v
2171 //              |  2<---+  ncsfpt in 2
2172 //              |_/|\   |
2173 //                 | v  |
2174 // inner 2,3      /  3  |  call in 3
2175 //               /   |  |
2176 //              v    +--+
2177 //        exit  4
2178 //
2179 //
2180 // This method creates a list (_required_safept) of ncsfpt nodes that must
2181 // be protected is created for each loop. When a ncsfpt maybe deleted, it
2182 // is first looked for in the lists for the outer loops of the current loop.
2183 //
2184 // The insights into the problem:
2185 //  A) counted loops are okay
2186 //  B) innermost loops are okay (only an inner loop can delete
2187 //     a ncsfpt needed by an outer loop)
2188 //  C) a loop is immune from an inner loop deleting a safepoint
2189 //     if the loop has a call on the idom-path
2190 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
2191 //     idom-path that is not in a nested loop
2192 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
2193 //     loop needs to be prevented from deletion by an inner loop
2194 //
2195 // There are two analyses:
2196 //  1) The first, and cheaper one, scans the loop body from
2197 //     tail to head following the idom (immediate dominator)
2198 //     chain, looking for the cases (C,D,E) above.
2199 //     Since inner loops are scanned before outer loops, there is summary
2200 //     information about inner loops.  Inner loops can be skipped over
2201 //     when the tail of an inner loop is encountered.
2202 //
2203 //  2) The second, invoked if the first fails to find a call or ncsfpt on
2204 //     the idom path (which is rare), scans all predecessor control paths
2205 //     from the tail to the head, terminating a path when a call or sfpt
2206 //     is encountered, to find the ncsfpt's that are closest to the tail.
2207 //
2208 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
2209   // Bottom up traversal
2210   IdealLoopTree* ch = _child;
2211   if (_child) _child->check_safepts(visited, stack);
2212   if (_next)  _next ->check_safepts(visited, stack);
2213 
2214   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
2215     bool  has_call         = false; // call on dom-path
2216     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
2217     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
2218     // Scan the dom-path nodes from tail to head
2219     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
2220       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2221         has_call = true;
2222         _has_sfpt = 1;          // Then no need for a safept!
2223         break;
2224       } else if (n->Opcode() == Op_SafePoint) {
2225         if (_phase->get_loop(n) == this) {
2226           has_local_ncsfpt = true;
2227           break;
2228         }
2229         if (nonlocal_ncsfpt == NULL) {
2230           nonlocal_ncsfpt = n; // save the one closest to the tail
2231         }
2232       } else {
2233         IdealLoopTree* nlpt = _phase->get_loop(n);
2234         if (this != nlpt) {
2235           // If at an inner loop tail, see if the inner loop has already
2236           // recorded seeing a call on the dom-path (and stop.)  If not,
2237           // jump to the head of the inner loop.
2238           assert(is_member(nlpt), "nested loop");
2239           Node* tail = nlpt->_tail;
2240           if (tail->in(0)->is_If()) tail = tail->in(0);
2241           if (n == tail) {
2242             // If inner loop has call on dom-path, so does outer loop
2243             if (nlpt->_has_sfpt) {
2244               has_call = true;
2245               _has_sfpt = 1;
2246               break;
2247             }
2248             // Skip to head of inner loop
2249             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
2250             n = nlpt->_head;
2251           }
2252         }
2253       }
2254     }
2255     // Record safept's that this loop needs preserved when an
2256     // inner loop attempts to delete it's safepoints.
2257     if (_child != NULL && !has_call && !has_local_ncsfpt) {
2258       if (nonlocal_ncsfpt != NULL) {
2259         if (_required_safept == NULL) _required_safept = new Node_List();
2260         _required_safept->push(nonlocal_ncsfpt);
2261       } else {
2262         // Failed to find a suitable safept on the dom-path.  Now use
2263         // an all paths walk from tail to head, looking for safepoints to preserve.
2264         allpaths_check_safepts(visited, stack);
2265       }
2266     }
2267   }
2268 }
2269 
2270 //---------------------------is_deleteable_safept----------------------------
2271 // Is safept not required by an outer loop?
2272 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
2273   assert(sfpt->Opcode() == Op_SafePoint, "");
2274   IdealLoopTree* lp = get_loop(sfpt)->_parent;
2275   while (lp != NULL) {
2276     Node_List* sfpts = lp->_required_safept;
2277     if (sfpts != NULL) {
2278       for (uint i = 0; i < sfpts->size(); i++) {
2279         if (sfpt == sfpts->at(i))
2280           return false;
2281       }
2282     }
2283     lp = lp->_parent;
2284   }
2285   return true;
2286 }
2287 
2288 //---------------------------replace_parallel_iv-------------------------------
2289 // Replace parallel induction variable (parallel to trip counter)
2290 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
2291   assert(loop->_head->is_CountedLoop(), "");
2292   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2293   if (!cl->is_valid_counted_loop())
2294     return;         // skip malformed counted loop
2295   Node *incr = cl->incr();
2296   if (incr == NULL)
2297     return;         // Dead loop?
2298   Node *init = cl->init_trip();
2299   Node *phi  = cl->phi();
2300   int stride_con = cl->stride_con();
2301 
2302   // Visit all children, looking for Phis
2303   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
2304     Node *out = cl->out(i);
2305     // Look for other phis (secondary IVs). Skip dead ones
2306     if (!out->is_Phi() || out == phi || !has_node(out))
2307       continue;
2308     PhiNode* phi2 = out->as_Phi();
2309     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
2310     // Look for induction variables of the form:  X += constant
2311     if (phi2->region() != loop->_head ||
2312         incr2->req() != 3 ||
2313         incr2->in(1) != phi2 ||
2314         incr2 == incr ||
2315         incr2->Opcode() != Op_AddI ||
2316         !incr2->in(2)->is_Con())
2317       continue;
2318 
2319     // Check for parallel induction variable (parallel to trip counter)
2320     // via an affine function.  In particular, count-down loops with
2321     // count-up array indices are common. We only RCE references off
2322     // the trip-counter, so we need to convert all these to trip-counter
2323     // expressions.
2324     Node *init2 = phi2->in( LoopNode::EntryControl );
2325     int stride_con2 = incr2->in(2)->get_int();
2326 
2327     // The ratio of the two strides cannot be represented as an int
2328     // if stride_con2 is min_int and stride_con is -1.
2329     if (stride_con2 == min_jint && stride_con == -1) {
2330       continue;
2331     }
2332 
2333     // The general case here gets a little tricky.  We want to find the
2334     // GCD of all possible parallel IV's and make a new IV using this
2335     // GCD for the loop.  Then all possible IVs are simple multiples of
2336     // the GCD.  In practice, this will cover very few extra loops.
2337     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
2338     // where +/-1 is the common case, but other integer multiples are
2339     // also easy to handle.
2340     int ratio_con = stride_con2/stride_con;
2341 
2342     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
2343 #ifndef PRODUCT
2344       if (TraceLoopOpts) {
2345         tty->print("Parallel IV: %d ", phi2->_idx);
2346         loop->dump_head();
2347       }
2348 #endif
2349       // Convert to using the trip counter.  The parallel induction
2350       // variable differs from the trip counter by a loop-invariant
2351       // amount, the difference between their respective initial values.
2352       // It is scaled by the 'ratio_con'.
2353       Node* ratio = _igvn.intcon(ratio_con);
2354       set_ctrl(ratio, C->root());
2355       Node* ratio_init = new MulINode(init, ratio);
2356       _igvn.register_new_node_with_optimizer(ratio_init, init);
2357       set_early_ctrl(ratio_init);
2358       Node* diff = new SubINode(init2, ratio_init);
2359       _igvn.register_new_node_with_optimizer(diff, init2);
2360       set_early_ctrl(diff);
2361       Node* ratio_idx = new MulINode(phi, ratio);
2362       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
2363       set_ctrl(ratio_idx, cl);
2364       Node* add = new AddINode(ratio_idx, diff);
2365       _igvn.register_new_node_with_optimizer(add);
2366       set_ctrl(add, cl);
2367       _igvn.replace_node( phi2, add );
2368       // Sometimes an induction variable is unused
2369       if (add->outcnt() == 0) {
2370         _igvn.remove_dead_node(add);
2371       }
2372       --i; // deleted this phi; rescan starting with next position
2373       continue;
2374     }
2375   }
2376 }
2377 
2378 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
2379   Node* keep = NULL;
2380   if (keep_one) {
2381     // Look for a safepoint on the idom-path.
2382     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
2383       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
2384         keep = i;
2385         break; // Found one
2386       }
2387     }
2388   }
2389 
2390   // Don't remove any safepoints if it is requested to keep a single safepoint and
2391   // no safepoint was found on idom-path. It is not safe to remove any safepoint
2392   // in this case since there's no safepoint dominating all paths in the loop body.
2393   bool prune = !keep_one || keep != NULL;
2394 
2395   // Delete other safepoints in this loop.
2396   Node_List* sfpts = _safepts;
2397   if (prune && sfpts != NULL) {
2398     assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
2399     for (uint i = 0; i < sfpts->size(); i++) {
2400       Node* n = sfpts->at(i);
2401       assert(phase->get_loop(n) == this, "");
2402       if (n != keep && phase->is_deleteable_safept(n)) {
2403         phase->lazy_replace(n, n->in(TypeFunc::Control));
2404       }
2405     }
2406   }
2407 }
2408 
2409 //------------------------------counted_loop-----------------------------------
2410 // Convert to counted loops where possible
2411 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
2412 
2413   // For grins, set the inner-loop flag here
2414   if (!_child) {
2415     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
2416   }
2417 
2418   IdealLoopTree* loop = this;
2419   if (_head->is_CountedLoop() ||
2420       phase->is_counted_loop(_head, loop)) {
2421 
2422     if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) {
2423       // Indicate we do not need a safepoint here
2424       _has_sfpt = 1;
2425     }
2426 
2427     // Remove safepoints
2428     bool keep_one_sfpt = !(_has_call || _has_sfpt);
2429     remove_safepoints(phase, keep_one_sfpt);
2430 
2431     // Look for induction variables
2432     phase->replace_parallel_iv(this);
2433 
2434   } else if (_parent != NULL && !_irreducible) {
2435     // Not a counted loop. Keep one safepoint.
2436     bool keep_one_sfpt = true;
2437     remove_safepoints(phase, keep_one_sfpt);
2438   }
2439 
2440   // Recursively
2441   assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
2442   assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops");
2443   if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
2444   if (loop->_next)  loop->_next ->counted_loop(phase);
2445 }
2446 
2447 
2448 // The Estimated Loop Clone Size:
2449 //   CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
2450 // where  BC and  CC are  totally ad-hoc/magic  "body" and "clone" constants,
2451 // respectively, used to ensure that the node usage estimates made are on the
2452 // safe side, for the most part. The FanOutTerm is an attempt to estimate the
2453 // possible additional/excessive nodes generated due to data and control flow
2454 // merging, for edges reaching outside the loop.
2455 uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
2456 
2457   precond(0 < factor && factor < 16);
2458 
2459   uint const bc = 13;
2460   uint const cc = 17;
2461   uint const sz = _body.size() + (_body.size() + 7) / 8;
2462   uint estimate = factor * (sz + bc) + cc;
2463 
2464   assert((estimate - cc) / factor == sz + bc, "overflow");
2465 
2466   return estimate + est_loop_flow_merge_sz();
2467 }
2468 
2469 // The Estimated Loop (full-) Unroll Size:
2470 //   UnrollFactor * (~106% * BodySize) + CC + FanOutTerm,
2471 // where CC is a (totally) ad-hoc/magic "clone" constant, used to ensure that
2472 // node usage estimates made are on the safe side, for the most part. This is
2473 // a "light" version of the loop clone size calculation (above), based on the
2474 // assumption that most of the loop-construct overhead will be unraveled when
2475 // (fully) unrolled. Defined for unroll factors larger or equal to one (>=1),
2476 // including an overflow check and returning UINT_MAX in case of an overflow.
2477 uint IdealLoopTree::est_loop_unroll_sz(uint factor) const {
2478 
2479   precond(factor > 0);
2480 
2481   // Take into account that after unroll conjoined heads and tails will fold.
2482   uint const b0 = _body.size() - EMPTY_LOOP_SIZE;
2483   uint const cc = 7;
2484   uint const sz = b0 + (b0 + 15) / 16;
2485   uint estimate = factor * sz + cc;
2486 
2487   if ((estimate - cc) / factor != sz) {
2488     return UINT_MAX;
2489   }
2490 
2491   return estimate + est_loop_flow_merge_sz();
2492 }
2493 
2494 // Estimate the growth effect (in nodes) of merging control and data flow when
2495 // cloning a loop body, based on the amount of  control and data flow reaching
2496 // outside of the (current) loop body.
2497 uint IdealLoopTree::est_loop_flow_merge_sz() const {
2498 
2499   uint ctrl_edge_out_cnt = 0;
2500   uint data_edge_out_cnt = 0;
2501 
2502   for (uint i = 0; i < _body.size(); i++) {
2503     Node* node = _body.at(i);
2504     uint outcnt = node->outcnt();
2505 
2506     for (uint k = 0; k < outcnt; k++) {
2507       Node* out = node->raw_out(k);
2508 
2509       if (out->is_CFG()) {
2510         if (!is_member(_phase->get_loop(out))) {
2511           ctrl_edge_out_cnt++;
2512         }
2513       } else {
2514         Node* ctrl = _phase->get_ctrl(out);
2515         assert(ctrl->is_CFG(), "must be");
2516         if (!is_member(_phase->get_loop(ctrl))) {
2517           data_edge_out_cnt++;
2518         }
2519       }
2520     }
2521   }
2522   // Use data and control count (x2.0) in estimate iff both are > 0. This is
2523   // a rather pessimistic estimate for the most part, in particular for some
2524   // complex loops, but still not enough to capture all loops.
2525   if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
2526     return 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
2527   }
2528   return 0;
2529 }
2530 
2531 #ifndef PRODUCT
2532 //------------------------------dump_head--------------------------------------
2533 // Dump 1 liner for loop header info
2534 void IdealLoopTree::dump_head() const {
2535   tty->sp(2 * _nest);
2536   tty->print("Loop: N%d/N%d ", _head->_idx, _tail->_idx);
2537   if (_irreducible) tty->print(" IRREDUCIBLE");
2538   Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl);
2539   Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
2540   if (predicate != NULL ) {
2541     tty->print(" limit_check");
2542     entry = PhaseIdealLoop::skip_loop_predicates(entry);
2543   }
2544   if (UseLoopPredicate) {
2545     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2546     if (entry != NULL) {
2547       tty->print(" predicated");
2548       entry = PhaseIdealLoop::skip_loop_predicates(entry);
2549     }
2550   }
2551   if (UseProfiledLoopPredicate) {
2552     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
2553     if (entry != NULL) {
2554       tty->print(" profile_predicated");
2555     }
2556   }
2557   if (_head->is_CountedLoop()) {
2558     CountedLoopNode *cl = _head->as_CountedLoop();
2559     tty->print(" counted");
2560 
2561     Node* init_n = cl->init_trip();
2562     if (init_n  != NULL &&  init_n->is_Con())
2563       tty->print(" [%d,", cl->init_trip()->get_int());
2564     else
2565       tty->print(" [int,");
2566     Node* limit_n = cl->limit();
2567     if (limit_n  != NULL &&  limit_n->is_Con())
2568       tty->print("%d),", cl->limit()->get_int());
2569     else
2570       tty->print("int),");
2571     int stride_con  = cl->stride_con();
2572     if (stride_con > 0) tty->print("+");
2573     tty->print("%d", stride_con);
2574 
2575     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
2576 
2577     if (cl->is_pre_loop ()) tty->print(" pre" );
2578     if (cl->is_main_loop()) tty->print(" main");
2579     if (cl->is_post_loop()) tty->print(" post");
2580     if (cl->is_vectorized_loop()) tty->print(" vector");
2581     if (cl->range_checks_present()) tty->print(" rc ");
2582     if (cl->is_multiversioned()) tty->print(" multi ");
2583   }
2584   if (_has_call) tty->print(" has_call");
2585   if (_has_sfpt) tty->print(" has_sfpt");
2586   if (_rce_candidate) tty->print(" rce");
2587   if (_safepts != NULL && _safepts->size() > 0) {
2588     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
2589   }
2590   if (_required_safept != NULL && _required_safept->size() > 0) {
2591     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
2592   }
2593   if (Verbose) {
2594     tty->print(" body={"); _body.dump_simple(); tty->print(" }");
2595   }
2596   if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
2597     tty->print(" strip_mined");
2598   }
2599   tty->cr();
2600 }
2601 
2602 //------------------------------dump-------------------------------------------
2603 // Dump loops by loop tree
2604 void IdealLoopTree::dump() const {
2605   dump_head();
2606   if (_child) _child->dump();
2607   if (_next)  _next ->dump();
2608 }
2609 
2610 #endif
2611 
2612 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
2613   if (loop == root) {
2614     if (loop->_child != NULL) {
2615       log->begin_head("loop_tree");
2616       log->end_head();
2617       if( loop->_child ) log_loop_tree(root, loop->_child, log);
2618       log->tail("loop_tree");
2619       assert(loop->_next == NULL, "what?");
2620     }
2621   } else {
2622     Node* head = loop->_head;
2623     log->begin_head("loop");
2624     log->print(" idx='%d' ", head->_idx);
2625     if (loop->_irreducible) log->print("irreducible='1' ");
2626     if (head->is_Loop()) {
2627       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
2628       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
2629     }
2630     if (head->is_CountedLoop()) {
2631       CountedLoopNode* cl = head->as_CountedLoop();
2632       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
2633       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
2634       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
2635     }
2636     log->end_head();
2637     if( loop->_child ) log_loop_tree(root, loop->_child, log);
2638     log->tail("loop");
2639     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
2640   }
2641 }
2642 
2643 //---------------------collect_potentially_useful_predicates-----------------------
2644 // Helper function to collect potentially useful predicates to prevent them from
2645 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
2646 void PhaseIdealLoop::collect_potentially_useful_predicates(
2647                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
2648   if (loop->_child) { // child
2649     collect_potentially_useful_predicates(loop->_child, useful_predicates);
2650   }
2651 
2652   // self (only loops that we can apply loop predication may use their predicates)
2653   if (loop->_head->is_Loop() &&
2654       !loop->_irreducible    &&
2655       !loop->tail()->is_top()) {
2656     LoopNode* lpn = loop->_head->as_Loop();
2657     Node* entry = lpn->in(LoopNode::EntryControl);
2658     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2659     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2660       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2661       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2662       entry = skip_loop_predicates(entry);
2663     }
2664     predicate_proj = find_predicate(entry); // Predicate
2665     if (predicate_proj != NULL ) {
2666       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2667       entry = skip_loop_predicates(entry);
2668     }
2669     if (UseProfiledLoopPredicate) {
2670       predicate_proj = find_predicate(entry); // Predicate
2671       if (predicate_proj != NULL ) {
2672         useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2673       }
2674     }
2675   }
2676 
2677   if (loop->_next) { // sibling
2678     collect_potentially_useful_predicates(loop->_next, useful_predicates);
2679   }
2680 }
2681 
2682 //------------------------eliminate_useless_predicates-----------------------------
2683 // Eliminate all inserted predicates if they could not be used by loop predication.
2684 // Note: it will also eliminates loop limits check predicate since it also uses
2685 // Opaque1 node (see Parse::add_predicate()).
2686 void PhaseIdealLoop::eliminate_useless_predicates() {
2687   if (C->predicate_count() == 0)
2688     return; // no predicate left
2689 
2690   Unique_Node_List useful_predicates; // to store useful predicates
2691   if (C->has_loops()) {
2692     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2693   }
2694 
2695   for (int i = C->predicate_count(); i > 0; i--) {
2696      Node * n = C->predicate_opaque1_node(i-1);
2697      assert(n->Opcode() == Op_Opaque1, "must be");
2698      if (!useful_predicates.member(n)) { // not in the useful list
2699        _igvn.replace_node(n, n->in(1));
2700      }
2701   }
2702 }
2703 
2704 //------------------------process_expensive_nodes-----------------------------
2705 // Expensive nodes have their control input set to prevent the GVN
2706 // from commoning them and as a result forcing the resulting node to
2707 // be in a more frequent path. Use CFG information here, to change the
2708 // control inputs so that some expensive nodes can be commoned while
2709 // not executed more frequently.
2710 bool PhaseIdealLoop::process_expensive_nodes() {
2711   assert(OptimizeExpensiveOps, "optimization off?");
2712 
2713   // Sort nodes to bring similar nodes together
2714   C->sort_expensive_nodes();
2715 
2716   bool progress = false;
2717 
2718   for (int i = 0; i < C->expensive_count(); ) {
2719     Node* n = C->expensive_node(i);
2720     int start = i;
2721     // Find nodes similar to n
2722     i++;
2723     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2724     int end = i;
2725     // And compare them two by two
2726     for (int j = start; j < end; j++) {
2727       Node* n1 = C->expensive_node(j);
2728       if (is_node_unreachable(n1)) {
2729         continue;
2730       }
2731       for (int k = j+1; k < end; k++) {
2732         Node* n2 = C->expensive_node(k);
2733         if (is_node_unreachable(n2)) {
2734           continue;
2735         }
2736 
2737         assert(n1 != n2, "should be pair of nodes");
2738 
2739         Node* c1 = n1->in(0);
2740         Node* c2 = n2->in(0);
2741 
2742         Node* parent_c1 = c1;
2743         Node* parent_c2 = c2;
2744 
2745         // The call to get_early_ctrl_for_expensive() moves the
2746         // expensive nodes up but stops at loops that are in a if
2747         // branch. See whether we can exit the loop and move above the
2748         // If.
2749         if (c1->is_Loop()) {
2750           parent_c1 = c1->in(1);
2751         }
2752         if (c2->is_Loop()) {
2753           parent_c2 = c2->in(1);
2754         }
2755 
2756         if (parent_c1 == parent_c2) {
2757           _igvn._worklist.push(n1);
2758           _igvn._worklist.push(n2);
2759           continue;
2760         }
2761 
2762         // Look for identical expensive node up the dominator chain.
2763         if (is_dominator(c1, c2)) {
2764           c2 = c1;
2765         } else if (is_dominator(c2, c1)) {
2766           c1 = c2;
2767         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2768                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2769           // Both branches have the same expensive node so move it up
2770           // before the if.
2771           c1 = c2 = idom(parent_c1->in(0));
2772         }
2773         // Do the actual moves
2774         if (n1->in(0) != c1) {
2775           _igvn.hash_delete(n1);
2776           n1->set_req(0, c1);
2777           _igvn.hash_insert(n1);
2778           _igvn._worklist.push(n1);
2779           progress = true;
2780         }
2781         if (n2->in(0) != c2) {
2782           _igvn.hash_delete(n2);
2783           n2->set_req(0, c2);
2784           _igvn.hash_insert(n2);
2785           _igvn._worklist.push(n2);
2786           progress = true;
2787         }
2788       }
2789     }
2790   }
2791 
2792   return progress;
2793 }
2794 
2795 
2796 //=============================================================================
2797 //----------------------------build_and_optimize-------------------------------
2798 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2799 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2800 void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) {
2801   bool do_split_ifs = (mode == LoopOptsDefault);
2802   bool skip_loop_opts = (mode == LoopOptsNone);
2803 
2804   int old_progress = C->major_progress();
2805   uint orig_worklist_size = _igvn._worklist.size();
2806 
2807   // Reset major-progress flag for the driver's heuristics
2808   C->clear_major_progress();
2809 
2810 #ifndef PRODUCT
2811   // Capture for later assert
2812   uint unique = C->unique();
2813   _loop_invokes++;
2814   _loop_work += unique;
2815 #endif
2816 
2817   // True if the method has at least 1 irreducible loop
2818   _has_irreducible_loops = false;
2819 
2820   _created_loop_node = false;
2821 
2822   Arena *a = Thread::current()->resource_area();
2823   VectorSet visited(a);
2824   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2825   _nodes.map(C->unique(), NULL);
2826   memset(_nodes.adr(), 0, wordSize * C->unique());
2827 
2828   // Pre-build the top-level outermost loop tree entry
2829   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2830   // Do not need a safepoint at the top level
2831   _ltree_root->_has_sfpt = 1;
2832 
2833   // Initialize Dominators.
2834   // Checked in clone_loop_predicate() during beautify_loops().
2835   _idom_size = 0;
2836   _idom      = NULL;
2837   _dom_depth = NULL;
2838   _dom_stk   = NULL;
2839 
2840   // Empty pre-order array
2841   allocate_preorders();
2842 
2843   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2844   // IdealLoopTree entries.  Data nodes are NOT walked.
2845   build_loop_tree();
2846   // Check for bailout, and return
2847   if (C->failing()) {
2848     return;
2849   }
2850 
2851   // No loops after all
2852   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2853 
2854   // There should always be an outer loop containing the Root and Return nodes.
2855   // If not, we have a degenerate empty program.  Bail out in this case.
2856   if (!has_node(C->root())) {
2857     if (!_verify_only) {
2858       C->clear_major_progress();
2859       C->record_method_not_compilable("empty program detected during loop optimization");
2860     }
2861     return;
2862   }
2863 
2864   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2865   // Nothing to do, so get out
2866   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only &&
2867     !bs->is_gc_specific_loop_opts_pass(mode);
2868   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2869   bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(mode);
2870   if (stop_early && !do_expensive_nodes) {
2871     _igvn.optimize();           // Cleanup NeverBranches
2872     return;
2873   }
2874 
2875   // Set loop nesting depth
2876   _ltree_root->set_nest( 0 );
2877 
2878   // Split shared headers and insert loop landing pads.
2879   // Do not bother doing this on the Root loop of course.
2880   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2881     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2882     if( _ltree_root->_child->beautify_loops( this ) ) {
2883       // Re-build loop tree!
2884       _ltree_root->_child = NULL;
2885       _nodes.clear();
2886       reallocate_preorders();
2887       build_loop_tree();
2888       // Check for bailout, and return
2889       if (C->failing()) {
2890         return;
2891       }
2892       // Reset loop nesting depth
2893       _ltree_root->set_nest( 0 );
2894 
2895       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2896     }
2897   }
2898 
2899   // Build Dominators for elision of NULL checks & loop finding.
2900   // Since nodes do not have a slot for immediate dominator, make
2901   // a persistent side array for that info indexed on node->_idx.
2902   _idom_size = C->unique();
2903   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2904   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2905   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2906   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2907 
2908   Dominators();
2909 
2910   if (!_verify_only) {
2911     // As a side effect, Dominators removed any unreachable CFG paths
2912     // into RegionNodes.  It doesn't do this test against Root, so
2913     // we do it here.
2914     for( uint i = 1; i < C->root()->req(); i++ ) {
2915       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2916         _igvn.delete_input_of(C->root(), i);
2917         i--;                      // Rerun same iteration on compressed edges
2918       }
2919     }
2920 
2921     // Given dominators, try to find inner loops with calls that must
2922     // always be executed (call dominates loop tail).  These loops do
2923     // not need a separate safepoint.
2924     Node_List cisstack(a);
2925     _ltree_root->check_safepts(visited, cisstack);
2926   }
2927 
2928   // Walk the DATA nodes and place into loops.  Find earliest control
2929   // node.  For CFG nodes, the _nodes array starts out and remains
2930   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2931   // _nodes array holds the earliest legal controlling CFG node.
2932 
2933   // Allocate stack with enough space to avoid frequent realloc
2934   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2935   Node_Stack nstack( a, stack_size );
2936 
2937   visited.clear();
2938   Node_List worklist(a);
2939   // Don't need C->root() on worklist since
2940   // it will be processed among C->top() inputs
2941   worklist.push(C->top());
2942   visited.set(C->top()->_idx); // Set C->top() as visited now
2943   build_loop_early( visited, worklist, nstack );
2944 
2945   // Given early legal placement, try finding counted loops.  This placement
2946   // is good enough to discover most loop invariants.
2947   if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
2948     _ltree_root->counted_loop( this );
2949   }
2950 
2951   // Find latest loop placement.  Find ideal loop placement.
2952   visited.clear();
2953   init_dom_lca_tags();
2954   // Need C->root() on worklist when processing outs
2955   worklist.push(C->root());
2956   NOT_PRODUCT( C->verify_graph_edges(); )
2957   worklist.push(C->top());
2958   build_loop_late( visited, worklist, nstack );
2959 
2960   if (_verify_only) {
2961     C->restore_major_progress(old_progress);
2962     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2963     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2964     return;
2965   }
2966 
2967   // clear out the dead code after build_loop_late
2968   while (_deadlist.size()) {
2969     _igvn.remove_globally_dead_node(_deadlist.pop());
2970   }
2971 
2972   if (stop_early) {
2973     assert(do_expensive_nodes, "why are we here?");
2974     if (process_expensive_nodes()) {
2975       // If we made some progress when processing expensive nodes then
2976       // the IGVN may modify the graph in a way that will allow us to
2977       // make some more progress: we need to try processing expensive
2978       // nodes again.
2979       C->set_major_progress();
2980     }
2981     _igvn.optimize();
2982     return;
2983   }
2984 
2985   // Some parser-inserted loop predicates could never be used by loop
2986   // predication or they were moved away from loop during some optimizations.
2987   // For example, peeling. Eliminate them before next loop optimizations.
2988   eliminate_useless_predicates();
2989 
2990 #ifndef PRODUCT
2991   C->verify_graph_edges();
2992   if (_verify_me) {             // Nested verify pass?
2993     // Check to see if the verify mode is broken
2994     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2995     return;
2996   }
2997   if (VerifyLoopOptimizations) verify();
2998   if (TraceLoopOpts && C->has_loops()) {
2999     _ltree_root->dump();
3000   }
3001 #endif
3002 
3003   if (skip_loop_opts) {
3004     // restore major progress flag
3005     C->restore_major_progress(old_progress);
3006 
3007     // Cleanup any modified bits
3008     _igvn.optimize();
3009 
3010     if (C->log() != NULL) {
3011       log_loop_tree(_ltree_root, _ltree_root, C->log());
3012     }
3013     return;
3014   }
3015 
3016   if (bs->optimize_loops(this, mode, visited, nstack, worklist)) {
3017     _igvn.optimize();
3018     if (C->log() != NULL) {
3019       log_loop_tree(_ltree_root, _ltree_root, C->log());
3020     }
3021     return;
3022   }
3023 
3024   if (ReassociateInvariants) {
3025     // Reassociate invariants and prep for split_thru_phi
3026     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3027       IdealLoopTree* lpt = iter.current();
3028       bool is_counted = lpt->is_counted();
3029       if (!is_counted || !lpt->is_innermost()) continue;
3030 
3031       // check for vectorized loops, any reassociation of invariants was already done
3032       if (is_counted && lpt->_head->as_CountedLoop()->is_unroll_only()) {
3033         continue;
3034       } else {
3035         AutoNodeBudget node_budget(this);
3036         lpt->reassociate_invariants(this);
3037       }
3038       // Because RCE opportunities can be masked by split_thru_phi,
3039       // look for RCE candidates and inhibit split_thru_phi
3040       // on just their loop-phi's for this pass of loop opts
3041       if (SplitIfBlocks && do_split_ifs) {
3042         AutoNodeBudget node_budget(this, AutoNodeBudget::NO_BUDGET_CHECK);
3043         if (lpt->policy_range_check(this)) {
3044           lpt->_rce_candidate = 1; // = true
3045         }
3046       }
3047     }
3048   }
3049 
3050   // Check for aggressive application of split-if and other transforms
3051   // that require basic-block info (like cloning through Phi's)
3052   if( SplitIfBlocks && do_split_ifs ) {
3053     visited.clear();
3054     split_if_with_blocks( visited, nstack);
3055     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
3056   }
3057 
3058   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
3059     C->set_major_progress();
3060   }
3061 
3062   // Perform loop predication before iteration splitting
3063   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
3064     _ltree_root->_child->loop_predication(this);
3065   }
3066 
3067   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
3068     if (do_intrinsify_fill()) {
3069       C->set_major_progress();
3070     }
3071   }
3072 
3073   // Perform iteration-splitting on inner loops.  Split iterations to avoid
3074   // range checks or one-shot null checks.
3075 
3076   // If split-if's didn't hack the graph too bad (no CFG changes)
3077   // then do loop opts.
3078   if (C->has_loops() && !C->major_progress()) {
3079     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3080     _ltree_root->_child->iteration_split( this, worklist );
3081     // No verify after peeling!  GCM has hoisted code out of the loop.
3082     // After peeling, the hoisted code could sink inside the peeled area.
3083     // The peeling code does not try to recompute the best location for
3084     // all the code before the peeled area, so the verify pass will always
3085     // complain about it.
3086   }
3087   // Do verify graph edges in any case
3088   NOT_PRODUCT( C->verify_graph_edges(); );
3089 
3090   if (!do_split_ifs) {
3091     // We saw major progress in Split-If to get here.  We forced a
3092     // pass with unrolling and not split-if, however more split-if's
3093     // might make progress.  If the unrolling didn't make progress
3094     // then the major-progress flag got cleared and we won't try
3095     // another round of Split-If.  In particular the ever-common
3096     // instance-of/check-cast pattern requires at least 2 rounds of
3097     // Split-If to clear out.
3098     C->set_major_progress();
3099   }
3100 
3101   // Repeat loop optimizations if new loops were seen
3102   if (created_loop_node()) {
3103     C->set_major_progress();
3104   }
3105 
3106   // Keep loop predicates and perform optimizations with them
3107   // until no more loop optimizations could be done.
3108   // After that switch predicates off and do more loop optimizations.
3109   if (!C->major_progress() && (C->predicate_count() > 0)) {
3110      C->cleanup_loop_predicates(_igvn);
3111      if (TraceLoopOpts) {
3112        tty->print_cr("PredicatesOff");
3113      }
3114      C->set_major_progress();
3115   }
3116 
3117   // Convert scalar to superword operations at the end of all loop opts.
3118   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
3119     // SuperWord transform
3120     SuperWord sw(this);
3121     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3122       IdealLoopTree* lpt = iter.current();
3123       if (lpt->is_counted()) {
3124         CountedLoopNode *cl = lpt->_head->as_CountedLoop();
3125 
3126         if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
3127           // Check that the rce'd post loop is encountered first, multiversion after all
3128           // major main loop optimization are concluded
3129           if (!C->major_progress()) {
3130             IdealLoopTree *lpt_next = lpt->_next;
3131             if (lpt_next && lpt_next->is_counted()) {
3132               CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
3133               has_range_checks(lpt_next);
3134               if (cl->is_post_loop() && cl->range_checks_present()) {
3135                 if (!cl->is_multiversioned()) {
3136                   if (multi_version_post_loops(lpt, lpt_next) == false) {
3137                     // Cause the rce loop to be optimized away if we fail
3138                     cl->mark_is_multiversioned();
3139                     cl->set_slp_max_unroll(0);
3140                     poison_rce_post_loop(lpt);
3141                   }
3142                 }
3143               }
3144             }
3145             sw.transform_loop(lpt, true);
3146           }
3147         } else if (cl->is_main_loop()) {
3148           sw.transform_loop(lpt, true);
3149         }
3150       }
3151     }
3152   }
3153 
3154   // Cleanup any modified bits
3155   _igvn.optimize();
3156 
3157   // disable assert until issue with split_flow_path is resolved (6742111)
3158   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
3159   //        "shouldn't introduce irreducible loops");
3160 
3161   if (C->log() != NULL) {
3162     log_loop_tree(_ltree_root, _ltree_root, C->log());
3163   }
3164 }
3165 
3166 #ifndef PRODUCT
3167 //------------------------------print_statistics-------------------------------
3168 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
3169 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
3170 void PhaseIdealLoop::print_statistics() {
3171   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
3172 }
3173 
3174 //------------------------------verify-----------------------------------------
3175 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
3176 static int fail;                // debug only, so its multi-thread dont care
3177 void PhaseIdealLoop::verify() const {
3178   int old_progress = C->major_progress();
3179   ResourceMark rm;
3180   PhaseIdealLoop loop_verify( _igvn, this );
3181   VectorSet visited(Thread::current()->resource_area());
3182 
3183   fail = 0;
3184   verify_compare( C->root(), &loop_verify, visited );
3185   assert( fail == 0, "verify loops failed" );
3186   // Verify loop structure is the same
3187   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
3188   // Reset major-progress.  It was cleared by creating a verify version of
3189   // PhaseIdealLoop.
3190   C->restore_major_progress(old_progress);
3191 }
3192 
3193 //------------------------------verify_compare---------------------------------
3194 // Make sure me and the given PhaseIdealLoop agree on key data structures
3195 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
3196   if( !n ) return;
3197   if( visited.test_set( n->_idx ) ) return;
3198   if( !_nodes[n->_idx] ) {      // Unreachable
3199     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
3200     return;
3201   }
3202 
3203   uint i;
3204   for( i = 0; i < n->req(); i++ )
3205     verify_compare( n->in(i), loop_verify, visited );
3206 
3207   // Check the '_nodes' block/loop structure
3208   i = n->_idx;
3209   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
3210     if( _nodes[i] != loop_verify->_nodes[i] &&
3211         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
3212       tty->print("Mismatched control setting for: ");
3213       n->dump();
3214       if( fail++ > 10 ) return;
3215       Node *c = get_ctrl_no_update(n);
3216       tty->print("We have it as: ");
3217       if( c->in(0) ) c->dump();
3218         else tty->print_cr("N%d",c->_idx);
3219       tty->print("Verify thinks: ");
3220       if( loop_verify->has_ctrl(n) )
3221         loop_verify->get_ctrl_no_update(n)->dump();
3222       else
3223         loop_verify->get_loop_idx(n)->dump();
3224       tty->cr();
3225     }
3226   } else {                    // We have a loop
3227     IdealLoopTree *us = get_loop_idx(n);
3228     if( loop_verify->has_ctrl(n) ) {
3229       tty->print("Mismatched loop setting for: ");
3230       n->dump();
3231       if( fail++ > 10 ) return;
3232       tty->print("We have it as: ");
3233       us->dump();
3234       tty->print("Verify thinks: ");
3235       loop_verify->get_ctrl_no_update(n)->dump();
3236       tty->cr();
3237     } else if (!C->major_progress()) {
3238       // Loop selection can be messed up if we did a major progress
3239       // operation, like split-if.  Do not verify in that case.
3240       IdealLoopTree *them = loop_verify->get_loop_idx(n);
3241       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
3242         tty->print("Unequals loops for: ");
3243         n->dump();
3244         if( fail++ > 10 ) return;
3245         tty->print("We have it as: ");
3246         us->dump();
3247         tty->print("Verify thinks: ");
3248         them->dump();
3249         tty->cr();
3250       }
3251     }
3252   }
3253 
3254   // Check for immediate dominators being equal
3255   if( i >= _idom_size ) {
3256     if( !n->is_CFG() ) return;
3257     tty->print("CFG Node with no idom: ");
3258     n->dump();
3259     return;
3260   }
3261   if( !n->is_CFG() ) return;
3262   if( n == C->root() ) return; // No IDOM here
3263 
3264   assert(n->_idx == i, "sanity");
3265   Node *id = idom_no_update(n);
3266   if( id != loop_verify->idom_no_update(n) ) {
3267     tty->print("Unequals idoms for: ");
3268     n->dump();
3269     if( fail++ > 10 ) return;
3270     tty->print("We have it as: ");
3271     id->dump();
3272     tty->print("Verify thinks: ");
3273     loop_verify->idom_no_update(n)->dump();
3274     tty->cr();
3275   }
3276 
3277 }
3278 
3279 //------------------------------verify_tree------------------------------------
3280 // Verify that tree structures match.  Because the CFG can change, siblings
3281 // within the loop tree can be reordered.  We attempt to deal with that by
3282 // reordering the verify's loop tree if possible.
3283 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
3284   assert( _parent == parent, "Badly formed loop tree" );
3285 
3286   // Siblings not in same order?  Attempt to re-order.
3287   if( _head != loop->_head ) {
3288     // Find _next pointer to update
3289     IdealLoopTree **pp = &loop->_parent->_child;
3290     while( *pp != loop )
3291       pp = &((*pp)->_next);
3292     // Find proper sibling to be next
3293     IdealLoopTree **nn = &loop->_next;
3294     while( (*nn) && (*nn)->_head != _head )
3295       nn = &((*nn)->_next);
3296 
3297     // Check for no match.
3298     if( !(*nn) ) {
3299       // Annoyingly, irreducible loops can pick different headers
3300       // after a major_progress operation, so the rest of the loop
3301       // tree cannot be matched.
3302       if (_irreducible && Compile::current()->major_progress())  return;
3303       assert( 0, "failed to match loop tree" );
3304     }
3305 
3306     // Move (*nn) to (*pp)
3307     IdealLoopTree *hit = *nn;
3308     *nn = hit->_next;
3309     hit->_next = loop;
3310     *pp = loop;
3311     loop = hit;
3312     // Now try again to verify
3313   }
3314 
3315   assert( _head  == loop->_head , "mismatched loop head" );
3316   Node *tail = _tail;           // Inline a non-updating version of
3317   while( !tail->in(0) )         // the 'tail()' call.
3318     tail = tail->in(1);
3319   assert( tail == loop->_tail, "mismatched loop tail" );
3320 
3321   // Counted loops that are guarded should be able to find their guards
3322   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
3323     CountedLoopNode *cl = _head->as_CountedLoop();
3324     Node *init = cl->init_trip();
3325     Node *ctrl = cl->in(LoopNode::EntryControl);
3326     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
3327     Node *iff  = ctrl->in(0);
3328     assert( iff->Opcode() == Op_If, "" );
3329     Node *bol  = iff->in(1);
3330     assert( bol->Opcode() == Op_Bool, "" );
3331     Node *cmp  = bol->in(1);
3332     assert( cmp->Opcode() == Op_CmpI, "" );
3333     Node *add  = cmp->in(1);
3334     Node *opaq;
3335     if( add->Opcode() == Op_Opaque1 ) {
3336       opaq = add;
3337     } else {
3338       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
3339       assert( add == init, "" );
3340       opaq = cmp->in(2);
3341     }
3342     assert( opaq->Opcode() == Op_Opaque1, "" );
3343 
3344   }
3345 
3346   if (_child != NULL)  _child->verify_tree(loop->_child, this);
3347   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
3348   // Innermost loops need to verify loop bodies,
3349   // but only if no 'major_progress'
3350   int fail = 0;
3351   if (!Compile::current()->major_progress() && _child == NULL) {
3352     for( uint i = 0; i < _body.size(); i++ ) {
3353       Node *n = _body.at(i);
3354       if (n->outcnt() == 0)  continue; // Ignore dead
3355       uint j;
3356       for( j = 0; j < loop->_body.size(); j++ )
3357         if( loop->_body.at(j) == n )
3358           break;
3359       if( j == loop->_body.size() ) { // Not found in loop body
3360         // Last ditch effort to avoid assertion: Its possible that we
3361         // have some users (so outcnt not zero) but are still dead.
3362         // Try to find from root.
3363         if (Compile::current()->root()->find(n->_idx)) {
3364           fail++;
3365           tty->print("We have that verify does not: ");
3366           n->dump();
3367         }
3368       }
3369     }
3370     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
3371       Node *n = loop->_body.at(i2);
3372       if (n->outcnt() == 0)  continue; // Ignore dead
3373       uint j;
3374       for( j = 0; j < _body.size(); j++ )
3375         if( _body.at(j) == n )
3376           break;
3377       if( j == _body.size() ) { // Not found in loop body
3378         // Last ditch effort to avoid assertion: Its possible that we
3379         // have some users (so outcnt not zero) but are still dead.
3380         // Try to find from root.
3381         if (Compile::current()->root()->find(n->_idx)) {
3382           fail++;
3383           tty->print("Verify has that we do not: ");
3384           n->dump();
3385         }
3386       }
3387     }
3388     assert( !fail, "loop body mismatch" );
3389   }
3390 }
3391 
3392 #endif
3393 
3394 //------------------------------set_idom---------------------------------------
3395 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
3396   uint idx = d->_idx;
3397   if (idx >= _idom_size) {
3398     uint newsize = next_power_of_2(idx);
3399     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
3400     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
3401     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
3402     _idom_size = newsize;
3403   }
3404   _idom[idx] = n;
3405   _dom_depth[idx] = dom_depth;
3406 }
3407 
3408 //------------------------------recompute_dom_depth---------------------------------------
3409 // The dominator tree is constructed with only parent pointers.
3410 // This recomputes the depth in the tree by first tagging all
3411 // nodes as "no depth yet" marker.  The next pass then runs up
3412 // the dom tree from each node marked "no depth yet", and computes
3413 // the depth on the way back down.
3414 void PhaseIdealLoop::recompute_dom_depth() {
3415   uint no_depth_marker = C->unique();
3416   uint i;
3417   // Initialize depth to "no depth yet" and realize all lazy updates
3418   for (i = 0; i < _idom_size; i++) {
3419     // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized).
3420     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
3421       _dom_depth[i] = no_depth_marker;
3422 
3423       // heal _idom if it has a fwd mapping in _nodes
3424       if (_idom[i]->in(0) == NULL) {
3425         idom(i);
3426       }
3427     }
3428   }
3429   if (_dom_stk == NULL) {
3430     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
3431     if (init_size < 10) init_size = 10;
3432     _dom_stk = new GrowableArray<uint>(init_size);
3433   }
3434   // Compute new depth for each node.
3435   for (i = 0; i < _idom_size; i++) {
3436     uint j = i;
3437     // Run up the dom tree to find a node with a depth
3438     while (_dom_depth[j] == no_depth_marker) {
3439       _dom_stk->push(j);
3440       j = _idom[j]->_idx;
3441     }
3442     // Compute the depth on the way back down this tree branch
3443     uint dd = _dom_depth[j] + 1;
3444     while (_dom_stk->length() > 0) {
3445       uint j = _dom_stk->pop();
3446       _dom_depth[j] = dd;
3447       dd++;
3448     }
3449   }
3450 }
3451 
3452 //------------------------------sort-------------------------------------------
3453 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
3454 // loop tree, not the root.
3455 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
3456   if( !innermost ) return loop; // New innermost loop
3457 
3458   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
3459   assert( loop_preorder, "not yet post-walked loop" );
3460   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
3461   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
3462 
3463   // Insert at start of list
3464   while( l ) {                  // Insertion sort based on pre-order
3465     if( l == loop ) return innermost; // Already on list!
3466     int l_preorder = get_preorder(l->_head); // Cache pre-order number
3467     assert( l_preorder, "not yet post-walked l" );
3468     // Check header pre-order number to figure proper nesting
3469     if( loop_preorder > l_preorder )
3470       break;                    // End of insertion
3471     // If headers tie (e.g., shared headers) check tail pre-order numbers.
3472     // Since I split shared headers, you'd think this could not happen.
3473     // BUT: I must first do the preorder numbering before I can discover I
3474     // have shared headers, so the split headers all get the same preorder
3475     // number as the RegionNode they split from.
3476     if( loop_preorder == l_preorder &&
3477         get_preorder(loop->_tail) < get_preorder(l->_tail) )
3478       break;                    // Also check for shared headers (same pre#)
3479     pp = &l->_parent;           // Chain up list
3480     l = *pp;
3481   }
3482   // Link into list
3483   // Point predecessor to me
3484   *pp = loop;
3485   // Point me to successor
3486   IdealLoopTree *p = loop->_parent;
3487   loop->_parent = l;            // Point me to successor
3488   if( p ) sort( p, innermost ); // Insert my parents into list as well
3489   return innermost;
3490 }
3491 
3492 //------------------------------build_loop_tree--------------------------------
3493 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
3494 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
3495 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
3496 // tightest enclosing IdealLoopTree for post-walked.
3497 //
3498 // During my forward walk I do a short 1-layer lookahead to see if I can find
3499 // a loop backedge with that doesn't have any work on the backedge.  This
3500 // helps me construct nested loops with shared headers better.
3501 //
3502 // Once I've done the forward recursion, I do the post-work.  For each child
3503 // I check to see if there is a backedge.  Backedges define a loop!  I
3504 // insert an IdealLoopTree at the target of the backedge.
3505 //
3506 // During the post-work I also check to see if I have several children
3507 // belonging to different loops.  If so, then this Node is a decision point
3508 // where control flow can choose to change loop nests.  It is at this
3509 // decision point where I can figure out how loops are nested.  At this
3510 // time I can properly order the different loop nests from my children.
3511 // Note that there may not be any backedges at the decision point!
3512 //
3513 // Since the decision point can be far removed from the backedges, I can't
3514 // order my loops at the time I discover them.  Thus at the decision point
3515 // I need to inspect loop header pre-order numbers to properly nest my
3516 // loops.  This means I need to sort my childrens' loops by pre-order.
3517 // The sort is of size number-of-control-children, which generally limits
3518 // it to size 2 (i.e., I just choose between my 2 target loops).
3519 void PhaseIdealLoop::build_loop_tree() {
3520   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
3521   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
3522   Node *n = C->root();
3523   bltstack.push(n);
3524   int pre_order = 1;
3525   int stack_size;
3526 
3527   while ( ( stack_size = bltstack.length() ) != 0 ) {
3528     n = bltstack.top(); // Leave node on stack
3529     if ( !is_visited(n) ) {
3530       // ---- Pre-pass Work ----
3531       // Pre-walked but not post-walked nodes need a pre_order number.
3532 
3533       set_preorder_visited( n, pre_order ); // set as visited
3534 
3535       // ---- Scan over children ----
3536       // Scan first over control projections that lead to loop headers.
3537       // This helps us find inner-to-outer loops with shared headers better.
3538 
3539       // Scan children's children for loop headers.
3540       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
3541         Node* m = n->raw_out(i);       // Child
3542         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
3543           // Scan over children's children to find loop
3544           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3545             Node* l = m->fast_out(j);
3546             if( is_visited(l) &&       // Been visited?
3547                 !is_postvisited(l) &&  // But not post-visited
3548                 get_preorder(l) < pre_order ) { // And smaller pre-order
3549               // Found!  Scan the DFS down this path before doing other paths
3550               bltstack.push(m);
3551               break;
3552             }
3553           }
3554         }
3555       }
3556       pre_order++;
3557     }
3558     else if ( !is_postvisited(n) ) {
3559       // Note: build_loop_tree_impl() adds out edges on rare occasions,
3560       // such as com.sun.rsasign.am::a.
3561       // For non-recursive version, first, process current children.
3562       // On next iteration, check if additional children were added.
3563       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
3564         Node* u = n->raw_out(k);
3565         if ( u->is_CFG() && !is_visited(u) ) {
3566           bltstack.push(u);
3567         }
3568       }
3569       if ( bltstack.length() == stack_size ) {
3570         // There were no additional children, post visit node now
3571         (void)bltstack.pop(); // Remove node from stack
3572         pre_order = build_loop_tree_impl( n, pre_order );
3573         // Check for bailout
3574         if (C->failing()) {
3575           return;
3576         }
3577         // Check to grow _preorders[] array for the case when
3578         // build_loop_tree_impl() adds new nodes.
3579         check_grow_preorders();
3580       }
3581     }
3582     else {
3583       (void)bltstack.pop(); // Remove post-visited node from stack
3584     }
3585   }
3586 }
3587 
3588 //------------------------------build_loop_tree_impl---------------------------
3589 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
3590   // ---- Post-pass Work ----
3591   // Pre-walked but not post-walked nodes need a pre_order number.
3592 
3593   // Tightest enclosing loop for this Node
3594   IdealLoopTree *innermost = NULL;
3595 
3596   // For all children, see if any edge is a backedge.  If so, make a loop
3597   // for it.  Then find the tightest enclosing loop for the self Node.
3598   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3599     Node* m = n->fast_out(i);   // Child
3600     if( n == m ) continue;      // Ignore control self-cycles
3601     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
3602 
3603     IdealLoopTree *l;           // Child's loop
3604     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
3605       // Found a backedge
3606       assert( get_preorder(m) < pre_order, "should be backedge" );
3607       // Check for the RootNode, which is already a LoopNode and is allowed
3608       // to have multiple "backedges".
3609       if( m == C->root()) {     // Found the root?
3610         l = _ltree_root;        // Root is the outermost LoopNode
3611       } else {                  // Else found a nested loop
3612         // Insert a LoopNode to mark this loop.
3613         l = new IdealLoopTree(this, m, n);
3614       } // End of Else found a nested loop
3615       if( !has_loop(m) )        // If 'm' does not already have a loop set
3616         set_loop(m, l);         // Set loop header to loop now
3617 
3618     } else {                    // Else not a nested loop
3619       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
3620       l = get_loop(m);          // Get previously determined loop
3621       // If successor is header of a loop (nest), move up-loop till it
3622       // is a member of some outer enclosing loop.  Since there are no
3623       // shared headers (I've split them already) I only need to go up
3624       // at most 1 level.
3625       while( l && l->_head == m ) // Successor heads loop?
3626         l = l->_parent;         // Move up 1 for me
3627       // If this loop is not properly parented, then this loop
3628       // has no exit path out, i.e. its an infinite loop.
3629       if( !l ) {
3630         // Make loop "reachable" from root so the CFG is reachable.  Basically
3631         // insert a bogus loop exit that is never taken.  'm', the loop head,
3632         // points to 'n', one (of possibly many) fall-in paths.  There may be
3633         // many backedges as well.
3634 
3635         // Here I set the loop to be the root loop.  I could have, after
3636         // inserting a bogus loop exit, restarted the recursion and found my
3637         // new loop exit.  This would make the infinite loop a first-class
3638         // loop and it would then get properly optimized.  What's the use of
3639         // optimizing an infinite loop?
3640         l = _ltree_root;        // Oops, found infinite loop
3641 
3642         if (!_verify_only) {
3643           // Insert the NeverBranch between 'm' and it's control user.
3644           NeverBranchNode *iff = new NeverBranchNode( m );
3645           _igvn.register_new_node_with_optimizer(iff);
3646           set_loop(iff, l);
3647           Node *if_t = new CProjNode( iff, 0 );
3648           _igvn.register_new_node_with_optimizer(if_t);
3649           set_loop(if_t, l);
3650 
3651           Node* cfg = NULL;       // Find the One True Control User of m
3652           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3653             Node* x = m->fast_out(j);
3654             if (x->is_CFG() && x != m && x != iff)
3655               { cfg = x; break; }
3656           }
3657           assert(cfg != NULL, "must find the control user of m");
3658           uint k = 0;             // Probably cfg->in(0)
3659           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
3660           cfg->set_req( k, if_t ); // Now point to NeverBranch
3661           _igvn._worklist.push(cfg);
3662 
3663           // Now create the never-taken loop exit
3664           Node *if_f = new CProjNode( iff, 1 );
3665           _igvn.register_new_node_with_optimizer(if_f);
3666           set_loop(if_f, l);
3667           // Find frame ptr for Halt.  Relies on the optimizer
3668           // V-N'ing.  Easier and quicker than searching through
3669           // the program structure.
3670           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
3671           _igvn.register_new_node_with_optimizer(frame);
3672           // Halt & Catch Fire
3673           Node* halt = new HaltNode(if_f, frame, "never-taken loop exit reached");
3674           _igvn.register_new_node_with_optimizer(halt);
3675           set_loop(halt, l);
3676           C->root()->add_req(halt);
3677         }
3678         set_loop(C->root(), _ltree_root);
3679       }
3680     }
3681     // Weeny check for irreducible.  This child was already visited (this
3682     // IS the post-work phase).  Is this child's loop header post-visited
3683     // as well?  If so, then I found another entry into the loop.
3684     if (!_verify_only) {
3685       while( is_postvisited(l->_head) ) {
3686         // found irreducible
3687         l->_irreducible = 1; // = true
3688         l = l->_parent;
3689         _has_irreducible_loops = true;
3690         // Check for bad CFG here to prevent crash, and bailout of compile
3691         if (l == NULL) {
3692           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
3693           return pre_order;
3694         }
3695       }
3696       C->set_has_irreducible_loop(_has_irreducible_loops);
3697     }
3698 
3699     // This Node might be a decision point for loops.  It is only if
3700     // it's children belong to several different loops.  The sort call
3701     // does a trivial amount of work if there is only 1 child or all
3702     // children belong to the same loop.  If however, the children
3703     // belong to different loops, the sort call will properly set the
3704     // _parent pointers to show how the loops nest.
3705     //
3706     // In any case, it returns the tightest enclosing loop.
3707     innermost = sort( l, innermost );
3708   }
3709 
3710   // Def-use info will have some dead stuff; dead stuff will have no
3711   // loop decided on.
3712 
3713   // Am I a loop header?  If so fix up my parent's child and next ptrs.
3714   if( innermost && innermost->_head == n ) {
3715     assert( get_loop(n) == innermost, "" );
3716     IdealLoopTree *p = innermost->_parent;
3717     IdealLoopTree *l = innermost;
3718     while( p && l->_head == n ) {
3719       l->_next = p->_child;     // Put self on parents 'next child'
3720       p->_child = l;            // Make self as first child of parent
3721       l = p;                    // Now walk up the parent chain
3722       p = l->_parent;
3723     }
3724   } else {
3725     // Note that it is possible for a LoopNode to reach here, if the
3726     // backedge has been made unreachable (hence the LoopNode no longer
3727     // denotes a Loop, and will eventually be removed).
3728 
3729     // Record tightest enclosing loop for self.  Mark as post-visited.
3730     set_loop(n, innermost);
3731     // Also record has_call flag early on
3732     if( innermost ) {
3733       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3734         // Do not count uncommon calls
3735         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3736           Node *iff = n->in(0)->in(0);
3737           // No any calls for vectorized loops.
3738           if( UseSuperWord || !iff->is_If() ||
3739               (n->in(0)->Opcode() == Op_IfFalse &&
3740                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3741               (iff->as_If()->_prob >= 0.01) )
3742             innermost->_has_call = 1;
3743         }
3744       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3745         // Disable loop optimizations if the loop has a scalar replaceable
3746         // allocation. This disabling may cause a potential performance lost
3747         // if the allocation is not eliminated for some reason.
3748         innermost->_allow_optimizations = false;
3749         innermost->_has_call = 1; // = true
3750       } else if (n->Opcode() == Op_SafePoint) {
3751         // Record all safepoints in this loop.
3752         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3753         innermost->_safepts->push(n);
3754       }
3755     }
3756   }
3757 
3758   // Flag as post-visited now
3759   set_postvisited(n);
3760   return pre_order;
3761 }
3762 
3763 
3764 //------------------------------build_loop_early-------------------------------
3765 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3766 // First pass computes the earliest controlling node possible.  This is the
3767 // controlling input with the deepest dominating depth.
3768 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3769   while (worklist.size() != 0) {
3770     // Use local variables nstack_top_n & nstack_top_i to cache values
3771     // on nstack's top.
3772     Node *nstack_top_n = worklist.pop();
3773     uint  nstack_top_i = 0;
3774 //while_nstack_nonempty:
3775     while (true) {
3776       // Get parent node and next input's index from stack's top.
3777       Node  *n = nstack_top_n;
3778       uint   i = nstack_top_i;
3779       uint cnt = n->req(); // Count of inputs
3780       if (i == 0) {        // Pre-process the node.
3781         if( has_node(n) &&            // Have either loop or control already?
3782             !has_ctrl(n) ) {          // Have loop picked out already?
3783           // During "merge_many_backedges" we fold up several nested loops
3784           // into a single loop.  This makes the members of the original
3785           // loop bodies pointing to dead loops; they need to move up
3786           // to the new UNION'd larger loop.  I set the _head field of these
3787           // dead loops to NULL and the _parent field points to the owning
3788           // loop.  Shades of UNION-FIND algorithm.
3789           IdealLoopTree *ilt;
3790           while( !(ilt = get_loop(n))->_head ) {
3791             // Normally I would use a set_loop here.  But in this one special
3792             // case, it is legal (and expected) to change what loop a Node
3793             // belongs to.
3794             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3795           }
3796           // Remove safepoints ONLY if I've already seen I don't need one.
3797           // (the old code here would yank a 2nd safepoint after seeing a
3798           // first one, even though the 1st did not dominate in the loop body
3799           // and thus could be avoided indefinitely)
3800           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3801               is_deleteable_safept(n)) {
3802             Node *in = n->in(TypeFunc::Control);
3803             lazy_replace(n,in);       // Pull safepoint now
3804             if (ilt->_safepts != NULL) {
3805               ilt->_safepts->yank(n);
3806             }
3807             // Carry on with the recursion "as if" we are walking
3808             // only the control input
3809             if( !visited.test_set( in->_idx ) ) {
3810               worklist.push(in);      // Visit this guy later, using worklist
3811             }
3812             // Get next node from nstack:
3813             // - skip n's inputs processing by setting i > cnt;
3814             // - we also will not call set_early_ctrl(n) since
3815             //   has_node(n) == true (see the condition above).
3816             i = cnt + 1;
3817           }
3818         }
3819       } // if (i == 0)
3820 
3821       // Visit all inputs
3822       bool done = true;       // Assume all n's inputs will be processed
3823       while (i < cnt) {
3824         Node *in = n->in(i);
3825         ++i;
3826         if (in == NULL) continue;
3827         if (in->pinned() && !in->is_CFG())
3828           set_ctrl(in, in->in(0));
3829         int is_visited = visited.test_set( in->_idx );
3830         if (!has_node(in)) {  // No controlling input yet?
3831           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3832           assert( !is_visited, "visit only once" );
3833           nstack.push(n, i);  // Save parent node and next input's index.
3834           nstack_top_n = in;  // Process current input now.
3835           nstack_top_i = 0;
3836           done = false;       // Not all n's inputs processed.
3837           break; // continue while_nstack_nonempty;
3838         } else if (!is_visited) {
3839           // This guy has a location picked out for him, but has not yet
3840           // been visited.  Happens to all CFG nodes, for instance.
3841           // Visit him using the worklist instead of recursion, to break
3842           // cycles.  Since he has a location already we do not need to
3843           // find his location before proceeding with the current Node.
3844           worklist.push(in);  // Visit this guy later, using worklist
3845         }
3846       }
3847       if (done) {
3848         // All of n's inputs have been processed, complete post-processing.
3849 
3850         // Compute earliest point this Node can go.
3851         // CFG, Phi, pinned nodes already know their controlling input.
3852         if (!has_node(n)) {
3853           // Record earliest legal location
3854           set_early_ctrl( n );
3855         }
3856         if (nstack.is_empty()) {
3857           // Finished all nodes on stack.
3858           // Process next node on the worklist.
3859           break;
3860         }
3861         // Get saved parent node and next input's index.
3862         nstack_top_n = nstack.node();
3863         nstack_top_i = nstack.index();
3864         nstack.pop();
3865       }
3866     } // while (true)
3867   }
3868 }
3869 
3870 //------------------------------dom_lca_internal--------------------------------
3871 // Pair-wise LCA
3872 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3873   if( !n1 ) return n2;          // Handle NULL original LCA
3874   assert( n1->is_CFG(), "" );
3875   assert( n2->is_CFG(), "" );
3876   // find LCA of all uses
3877   uint d1 = dom_depth(n1);
3878   uint d2 = dom_depth(n2);
3879   while (n1 != n2) {
3880     if (d1 > d2) {
3881       n1 =      idom(n1);
3882       d1 = dom_depth(n1);
3883     } else if (d1 < d2) {
3884       n2 =      idom(n2);
3885       d2 = dom_depth(n2);
3886     } else {
3887       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3888       // of the tree might have the same depth.  These sections have
3889       // to be searched more carefully.
3890 
3891       // Scan up all the n1's with equal depth, looking for n2.
3892       Node *t1 = idom(n1);
3893       while (dom_depth(t1) == d1) {
3894         if (t1 == n2)  return n2;
3895         t1 = idom(t1);
3896       }
3897       // Scan up all the n2's with equal depth, looking for n1.
3898       Node *t2 = idom(n2);
3899       while (dom_depth(t2) == d2) {
3900         if (t2 == n1)  return n1;
3901         t2 = idom(t2);
3902       }
3903       // Move up to a new dominator-depth value as well as up the dom-tree.
3904       n1 = t1;
3905       n2 = t2;
3906       d1 = dom_depth(n1);
3907       d2 = dom_depth(n2);
3908     }
3909   }
3910   return n1;
3911 }
3912 
3913 //------------------------------compute_idom-----------------------------------
3914 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3915 // IDOMs are correct.
3916 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3917   assert( region->is_Region(), "" );
3918   Node *LCA = NULL;
3919   for( uint i = 1; i < region->req(); i++ ) {
3920     if( region->in(i) != C->top() )
3921       LCA = dom_lca( LCA, region->in(i) );
3922   }
3923   return LCA;
3924 }
3925 
3926 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3927   bool had_error = false;
3928 #ifdef ASSERT
3929   if (early != C->root()) {
3930     // Make sure that there's a dominance path from LCA to early
3931     Node* d = LCA;
3932     while (d != early) {
3933       if (d == C->root()) {
3934         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3935         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3936         had_error = true;
3937         break;
3938       }
3939       d = idom(d);
3940     }
3941   }
3942 #endif
3943   return had_error;
3944 }
3945 
3946 
3947 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3948   // Compute LCA over list of uses
3949   bool had_error = false;
3950   Node *LCA = NULL;
3951   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3952     Node* c = n->fast_out(i);
3953     if (_nodes[c->_idx] == NULL)
3954       continue;                 // Skip the occasional dead node
3955     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3956       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3957         if( c->in(j) == n ) {   // Found matching input?
3958           Node *use = c->in(0)->in(j);
3959           if (_verify_only && use->is_top()) continue;
3960           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3961           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3962         }
3963       }
3964     } else {
3965       // For CFG data-users, use is in the block just prior
3966       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3967       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3968       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3969     }
3970   }
3971   assert(!had_error, "bad dominance");
3972   return LCA;
3973 }
3974 
3975 // Check the shape of the graph at the loop entry. In some cases,
3976 // the shape of the graph does not match the shape outlined below.
3977 // That is caused by the Opaque1 node "protecting" the shape of
3978 // the graph being removed by, for example, the IGVN performed
3979 // in PhaseIdealLoop::build_and_optimize().
3980 //
3981 // After the Opaque1 node has been removed, optimizations (e.g., split-if,
3982 // loop unswitching, and IGVN, or a combination of them) can freely change
3983 // the graph's shape. As a result, the graph shape outlined below cannot
3984 // be guaranteed anymore.
3985 bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) {
3986   if (!cl->is_main_loop() && !cl->is_post_loop()) {
3987     return false;
3988   }
3989   Node* ctrl = cl->skip_predicates();
3990 
3991   if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
3992     return false;
3993   }
3994   Node* iffm = ctrl->in(0);
3995   if (iffm == NULL || !iffm->is_If()) {
3996     return false;
3997   }
3998   Node* bolzm = iffm->in(1);
3999   if (bolzm == NULL || !bolzm->is_Bool()) {
4000     return false;
4001   }
4002   Node* cmpzm = bolzm->in(1);
4003   if (cmpzm == NULL || !cmpzm->is_Cmp()) {
4004     return false;
4005   }
4006   // compares can get conditionally flipped
4007   bool found_opaque = false;
4008   for (uint i = 1; i < cmpzm->req(); i++) {
4009     Node* opnd = cmpzm->in(i);
4010     if (opnd && opnd->Opcode() == Op_Opaque1) {
4011       found_opaque = true;
4012       break;
4013     }
4014   }
4015   if (!found_opaque) {
4016     return false;
4017   }
4018   return true;
4019 }
4020 
4021 //------------------------------get_late_ctrl----------------------------------
4022 // Compute latest legal control.
4023 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
4024   assert(early != NULL, "early control should not be NULL");
4025 
4026   Node* LCA = compute_lca_of_uses(n, early);
4027 #ifdef ASSERT
4028   if (LCA == C->root() && LCA != early) {
4029     // def doesn't dominate uses so print some useful debugging output
4030     compute_lca_of_uses(n, early, true);
4031   }
4032 #endif
4033 
4034   // if this is a load, check for anti-dependent stores
4035   // We use a conservative algorithm to identify potential interfering
4036   // instructions and for rescheduling the load.  The users of the memory
4037   // input of this load are examined.  Any use which is not a load and is
4038   // dominated by early is considered a potentially interfering store.
4039   // This can produce false positives.
4040   if (n->is_Load() && LCA != early) {
4041     int load_alias_idx = C->get_alias_index(n->adr_type());
4042     if (C->alias_type(load_alias_idx)->is_rewritable()) {
4043 
4044       Node_List worklist;
4045 
4046       Node *mem = n->in(MemNode::Memory);
4047       for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
4048         Node* s = mem->fast_out(i);
4049         worklist.push(s);
4050       }
4051       while(worklist.size() != 0 && LCA != early) {
4052         Node* s = worklist.pop();
4053         if (s->is_Load() || s->Opcode() == Op_SafePoint ||
4054             (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
4055           continue;
4056         } else if (s->is_MergeMem()) {
4057           for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
4058             Node* s1 = s->fast_out(i);
4059             worklist.push(s1);
4060           }
4061         } else {
4062           Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
4063           assert(sctrl != NULL || s->outcnt() == 0, "must have control");
4064           if (sctrl != NULL && !sctrl->is_top() && C->can_alias(s->adr_type(), load_alias_idx) && is_dominator(early, sctrl)) {
4065             LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
4066           }
4067         }
4068       }
4069     }
4070   }
4071 
4072   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
4073   return LCA;
4074 }
4075 
4076 // true if CFG node d dominates CFG node n
4077 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
4078   if (d == n)
4079     return true;
4080   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
4081   uint dd = dom_depth(d);
4082   while (dom_depth(n) >= dd) {
4083     if (n == d)
4084       return true;
4085     n = idom(n);
4086   }
4087   return false;
4088 }
4089 
4090 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
4091 // Pair-wise LCA with tags.
4092 // Tag each index with the node 'tag' currently being processed
4093 // before advancing up the dominator chain using idom().
4094 // Later calls that find a match to 'tag' know that this path has already
4095 // been considered in the current LCA (which is input 'n1' by convention).
4096 // Since get_late_ctrl() is only called once for each node, the tag array
4097 // does not need to be cleared between calls to get_late_ctrl().
4098 // Algorithm trades a larger constant factor for better asymptotic behavior
4099 //
4100 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
4101   uint d1 = dom_depth(n1);
4102   uint d2 = dom_depth(n2);
4103 
4104   do {
4105     if (d1 > d2) {
4106       // current lca is deeper than n2
4107       _dom_lca_tags.map(n1->_idx, tag);
4108       n1 =      idom(n1);
4109       d1 = dom_depth(n1);
4110     } else if (d1 < d2) {
4111       // n2 is deeper than current lca
4112       Node *memo = _dom_lca_tags[n2->_idx];
4113       if( memo == tag ) {
4114         return n1;    // Return the current LCA
4115       }
4116       _dom_lca_tags.map(n2->_idx, tag);
4117       n2 =      idom(n2);
4118       d2 = dom_depth(n2);
4119     } else {
4120       // Here d1 == d2.  Due to edits of the dominator-tree, sections
4121       // of the tree might have the same depth.  These sections have
4122       // to be searched more carefully.
4123 
4124       // Scan up all the n1's with equal depth, looking for n2.
4125       _dom_lca_tags.map(n1->_idx, tag);
4126       Node *t1 = idom(n1);
4127       while (dom_depth(t1) == d1) {
4128         if (t1 == n2)  return n2;
4129         _dom_lca_tags.map(t1->_idx, tag);
4130         t1 = idom(t1);
4131       }
4132       // Scan up all the n2's with equal depth, looking for n1.
4133       _dom_lca_tags.map(n2->_idx, tag);
4134       Node *t2 = idom(n2);
4135       while (dom_depth(t2) == d2) {
4136         if (t2 == n1)  return n1;
4137         _dom_lca_tags.map(t2->_idx, tag);
4138         t2 = idom(t2);
4139       }
4140       // Move up to a new dominator-depth value as well as up the dom-tree.
4141       n1 = t1;
4142       n2 = t2;
4143       d1 = dom_depth(n1);
4144       d2 = dom_depth(n2);
4145     }
4146   } while (n1 != n2);
4147   return n1;
4148 }
4149 
4150 //------------------------------init_dom_lca_tags------------------------------
4151 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4152 // Intended use does not involve any growth for the array, so it could
4153 // be of fixed size.
4154 void PhaseIdealLoop::init_dom_lca_tags() {
4155   uint limit = C->unique() + 1;
4156   _dom_lca_tags.map( limit, NULL );
4157 #ifdef ASSERT
4158   for( uint i = 0; i < limit; ++i ) {
4159     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4160   }
4161 #endif // ASSERT
4162 }
4163 
4164 //------------------------------clear_dom_lca_tags------------------------------
4165 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4166 // Intended use does not involve any growth for the array, so it could
4167 // be of fixed size.
4168 void PhaseIdealLoop::clear_dom_lca_tags() {
4169   uint limit = C->unique() + 1;
4170   _dom_lca_tags.map( limit, NULL );
4171   _dom_lca_tags.clear();
4172 #ifdef ASSERT
4173   for( uint i = 0; i < limit; ++i ) {
4174     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4175   }
4176 #endif // ASSERT
4177 }
4178 
4179 //------------------------------build_loop_late--------------------------------
4180 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4181 // Second pass finds latest legal placement, and ideal loop placement.
4182 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
4183   while (worklist.size() != 0) {
4184     Node *n = worklist.pop();
4185     // Only visit once
4186     if (visited.test_set(n->_idx)) continue;
4187     uint cnt = n->outcnt();
4188     uint   i = 0;
4189     while (true) {
4190       assert( _nodes[n->_idx], "no dead nodes" );
4191       // Visit all children
4192       if (i < cnt) {
4193         Node* use = n->raw_out(i);
4194         ++i;
4195         // Check for dead uses.  Aggressively prune such junk.  It might be
4196         // dead in the global sense, but still have local uses so I cannot
4197         // easily call 'remove_dead_node'.
4198         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
4199           // Due to cycles, we might not hit the same fixed point in the verify
4200           // pass as we do in the regular pass.  Instead, visit such phis as
4201           // simple uses of the loop head.
4202           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
4203             if( !visited.test(use->_idx) )
4204               worklist.push(use);
4205           } else if( !visited.test_set(use->_idx) ) {
4206             nstack.push(n, i); // Save parent and next use's index.
4207             n   = use;         // Process all children of current use.
4208             cnt = use->outcnt();
4209             i   = 0;
4210           }
4211         } else {
4212           // Do not visit around the backedge of loops via data edges.
4213           // push dead code onto a worklist
4214           _deadlist.push(use);
4215         }
4216       } else {
4217         // All of n's children have been processed, complete post-processing.
4218         build_loop_late_post(n);
4219         if (nstack.is_empty()) {
4220           // Finished all nodes on stack.
4221           // Process next node on the worklist.
4222           break;
4223         }
4224         // Get saved parent node and next use's index. Visit the rest of uses.
4225         n   = nstack.node();
4226         cnt = n->outcnt();
4227         i   = nstack.index();
4228         nstack.pop();
4229       }
4230     }
4231   }
4232 }
4233 
4234 // Verify that no data node is scheduled in the outer loop of a strip
4235 // mined loop.
4236 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
4237 #ifdef ASSERT
4238   if (get_loop(least)->_nest == 0) {
4239     return;
4240   }
4241   IdealLoopTree* loop = get_loop(least);
4242   Node* head = loop->_head;
4243   if (head->is_OuterStripMinedLoop() &&
4244       // Verification can't be applied to fully built strip mined loops
4245       head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
4246     Node* sfpt = head->as_Loop()->outer_safepoint();
4247     ResourceMark rm;
4248     Unique_Node_List wq;
4249     wq.push(sfpt);
4250     for (uint i = 0; i < wq.size(); i++) {
4251       Node *m = wq.at(i);
4252       for (uint i = 1; i < m->req(); i++) {
4253         Node* nn = m->in(i);
4254         if (nn == n) {
4255           return;
4256         }
4257         if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
4258           wq.push(nn);
4259         }
4260       }
4261     }
4262     ShouldNotReachHere();
4263   }
4264 #endif
4265 }
4266 
4267 
4268 //------------------------------build_loop_late_post---------------------------
4269 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4270 // Second pass finds latest legal placement, and ideal loop placement.
4271 void PhaseIdealLoop::build_loop_late_post(Node *n) {
4272   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4273 
4274   if (bs->build_loop_late_post(this, n)) {
4275     return;
4276   }
4277 
4278   build_loop_late_post_work(n, true);
4279 }
4280 
4281 void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
4282 
4283   if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
4284     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
4285   }
4286 
4287 #ifdef ASSERT
4288   if (_verify_only && !n->is_CFG()) {
4289     // Check def-use domination.
4290     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
4291   }
4292 #endif
4293 
4294   // CFG and pinned nodes already handled
4295   if( n->in(0) ) {
4296     if( n->in(0)->is_top() ) return; // Dead?
4297 
4298     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
4299     // _must_ be pinned (they have to observe their control edge of course).
4300     // Unlike Stores (which modify an unallocable resource, the memory
4301     // state), Mods/Loads can float around.  So free them up.
4302     switch( n->Opcode() ) {
4303     case Op_DivI:
4304     case Op_DivF:
4305     case Op_DivD:
4306     case Op_ModI:
4307     case Op_ModF:
4308     case Op_ModD:
4309     case Op_LoadB:              // Same with Loads; they can sink
4310     case Op_LoadUB:             // during loop optimizations.
4311     case Op_LoadUS:
4312     case Op_LoadD:
4313     case Op_LoadF:
4314     case Op_LoadI:
4315     case Op_LoadKlass:
4316     case Op_LoadNKlass:
4317     case Op_LoadL:
4318     case Op_LoadS:
4319     case Op_LoadP:
4320     case Op_LoadN:
4321     case Op_LoadRange:
4322     case Op_LoadD_unaligned:
4323     case Op_LoadL_unaligned:
4324     case Op_StrComp:            // Does a bunch of load-like effects
4325     case Op_StrEquals:
4326     case Op_StrIndexOf:
4327     case Op_StrIndexOfChar:
4328     case Op_AryEq:
4329     case Op_HasNegatives:
4330       pinned = false;
4331     }
4332     if( pinned ) {
4333       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
4334       if( !chosen_loop->_child )       // Inner loop?
4335         chosen_loop->_body.push(n); // Collect inner loops
4336       return;
4337     }
4338   } else {                      // No slot zero
4339     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
4340       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
4341       return;
4342     }
4343     assert(!n->is_CFG() || n->outcnt() == 0, "");
4344   }
4345 
4346   // Do I have a "safe range" I can select over?
4347   Node *early = get_ctrl(n);// Early location already computed
4348 
4349   // Compute latest point this Node can go
4350   Node *LCA = get_late_ctrl( n, early );
4351   // LCA is NULL due to uses being dead
4352   if( LCA == NULL ) {
4353 #ifdef ASSERT
4354     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
4355       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
4356     }
4357 #endif
4358     _nodes.map(n->_idx, 0);     // This node is useless
4359     _deadlist.push(n);
4360     return;
4361   }
4362   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
4363 
4364   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
4365   Node *least = legal;          // Best legal position so far
4366   while( early != legal ) {     // While not at earliest legal
4367 #ifdef ASSERT
4368     if (legal->is_Start() && !early->is_Root()) {
4369       // Bad graph. Print idom path and fail.
4370       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
4371       assert(false, "Bad graph detected in build_loop_late");
4372     }
4373 #endif
4374     // Find least loop nesting depth
4375     legal = idom(legal);        // Bump up the IDOM tree
4376     // Check for lower nesting depth
4377     if( get_loop(legal)->_nest < get_loop(least)->_nest )
4378       least = legal;
4379   }
4380   assert(early == legal || legal != C->root(), "bad dominance of inputs");
4381 
4382   // Try not to place code on a loop entry projection
4383   // which can inhibit range check elimination.
4384   if (least != early) {
4385     Node* ctrl_out = least->unique_ctrl_out();
4386     if (ctrl_out && ctrl_out->is_Loop() &&
4387         least == ctrl_out->in(LoopNode::EntryControl)) {
4388       // Move the node above predicates as far up as possible so a
4389       // following pass of loop predication doesn't hoist a predicate
4390       // that depends on it above that node.
4391       Node* new_ctrl = least;
4392       for (;;) {
4393         if (!new_ctrl->is_Proj()) {
4394           break;
4395         }
4396         CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
4397         if (call == NULL) {
4398           break;
4399         }
4400         int req = call->uncommon_trap_request();
4401         Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
4402         if (trap_reason != Deoptimization::Reason_loop_limit_check &&
4403             trap_reason != Deoptimization::Reason_predicate &&
4404             trap_reason != Deoptimization::Reason_profile_predicate) {
4405           break;
4406         }
4407         Node* c = new_ctrl->in(0)->in(0);
4408         if (is_dominator(c, early) && c != early) {
4409           break;
4410         }
4411         new_ctrl = c;
4412       }
4413       least = new_ctrl;
4414     }
4415   }
4416 
4417 #ifdef ASSERT
4418   // If verifying, verify that 'verify_me' has a legal location
4419   // and choose it as our location.
4420   if( _verify_me ) {
4421     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
4422     Node *legal = LCA;
4423     while( early != legal ) {   // While not at earliest legal
4424       if( legal == v_ctrl ) break;  // Check for prior good location
4425       legal = idom(legal)      ;// Bump up the IDOM tree
4426     }
4427     // Check for prior good location
4428     if( legal == v_ctrl ) least = legal; // Keep prior if found
4429   }
4430 #endif
4431 
4432   // Assign discovered "here or above" point
4433   least = find_non_split_ctrl(least);
4434   verify_strip_mined_scheduling(n, least);
4435   set_ctrl(n, least);
4436 
4437   // Collect inner loop bodies
4438   IdealLoopTree *chosen_loop = get_loop(least);
4439   if( !chosen_loop->_child )   // Inner loop?
4440     chosen_loop->_body.push(n);// Collect inner loops
4441 }
4442 
4443 #ifdef ASSERT
4444 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
4445   tty->print_cr("%s", msg);
4446   tty->print("n: "); n->dump();
4447   tty->print("early(n): "); early->dump();
4448   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
4449       n->in(0) != early && !n->in(0)->is_Root()) {
4450     tty->print("n->in(0): "); n->in(0)->dump();
4451   }
4452   for (uint i = 1; i < n->req(); i++) {
4453     Node* in1 = n->in(i);
4454     if (in1 != NULL && in1 != n && !in1->is_top()) {
4455       tty->print("n->in(%d): ", i); in1->dump();
4456       Node* in1_early = get_ctrl(in1);
4457       tty->print("early(n->in(%d)): ", i); in1_early->dump();
4458       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
4459           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
4460         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
4461       }
4462       for (uint j = 1; j < in1->req(); j++) {
4463         Node* in2 = in1->in(j);
4464         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
4465           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
4466           Node* in2_early = get_ctrl(in2);
4467           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
4468           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
4469               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
4470             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
4471           }
4472         }
4473       }
4474     }
4475   }
4476   tty->cr();
4477   tty->print("LCA(n): "); LCA->dump();
4478   for (uint i = 0; i < n->outcnt(); i++) {
4479     Node* u1 = n->raw_out(i);
4480     if (u1 == n)
4481       continue;
4482     tty->print("n->out(%d): ", i); u1->dump();
4483     if (u1->is_CFG()) {
4484       for (uint j = 0; j < u1->outcnt(); j++) {
4485         Node* u2 = u1->raw_out(j);
4486         if (u2 != u1 && u2 != n && u2->is_CFG()) {
4487           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4488         }
4489       }
4490     } else {
4491       Node* u1_later = get_ctrl(u1);
4492       tty->print("later(n->out(%d)): ", i); u1_later->dump();
4493       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
4494           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
4495         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
4496       }
4497       for (uint j = 0; j < u1->outcnt(); j++) {
4498         Node* u2 = u1->raw_out(j);
4499         if (u2 == n || u2 == u1)
4500           continue;
4501         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4502         if (!u2->is_CFG()) {
4503           Node* u2_later = get_ctrl(u2);
4504           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
4505           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
4506               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
4507             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
4508           }
4509         }
4510       }
4511     }
4512   }
4513   tty->cr();
4514   int ct = 0;
4515   Node *dbg_legal = LCA;
4516   while(!dbg_legal->is_Start() && ct < 100) {
4517     tty->print("idom[%d] ",ct); dbg_legal->dump();
4518     ct++;
4519     dbg_legal = idom(dbg_legal);
4520   }
4521   tty->cr();
4522 }
4523 #endif
4524 
4525 #ifndef PRODUCT
4526 //------------------------------dump-------------------------------------------
4527 void PhaseIdealLoop::dump() const {
4528   ResourceMark rm;
4529   Arena* arena = Thread::current()->resource_area();
4530   Node_Stack stack(arena, C->live_nodes() >> 2);
4531   Node_List rpo_list;
4532   VectorSet visited(arena);
4533   visited.set(C->top()->_idx);
4534   rpo(C->root(), stack, visited, rpo_list);
4535   // Dump root loop indexed by last element in PO order
4536   dump(_ltree_root, rpo_list.size(), rpo_list);
4537 }
4538 
4539 void PhaseIdealLoop::dump(IdealLoopTree* loop, uint idx, Node_List &rpo_list) const {
4540   loop->dump_head();
4541 
4542   // Now scan for CFG nodes in the same loop
4543   for (uint j = idx; j > 0; j--) {
4544     Node* n = rpo_list[j-1];
4545     if (!_nodes[n->_idx])      // Skip dead nodes
4546       continue;
4547 
4548     if (get_loop(n) != loop) { // Wrong loop nest
4549       if (get_loop(n)->_head == n &&    // Found nested loop?
4550           get_loop(n)->_parent == loop)
4551         dump(get_loop(n), rpo_list.size(), rpo_list);     // Print it nested-ly
4552       continue;
4553     }
4554 
4555     // Dump controlling node
4556     tty->sp(2 * loop->_nest);
4557     tty->print("C");
4558     if (n == C->root()) {
4559       n->dump();
4560     } else {
4561       Node* cached_idom   = idom_no_update(n);
4562       Node* computed_idom = n->in(0);
4563       if (n->is_Region()) {
4564         computed_idom = compute_idom(n);
4565         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
4566         // any MultiBranch ctrl node), so apply a similar transform to
4567         // the cached idom returned from idom_no_update.
4568         cached_idom = find_non_split_ctrl(cached_idom);
4569       }
4570       tty->print(" ID:%d", computed_idom->_idx);
4571       n->dump();
4572       if (cached_idom != computed_idom) {
4573         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
4574                       computed_idom->_idx, cached_idom->_idx);
4575       }
4576     }
4577     // Dump nodes it controls
4578     for (uint k = 0; k < _nodes.Size(); k++) {
4579       // (k < C->unique() && get_ctrl(find(k)) == n)
4580       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
4581         Node* m = C->root()->find(k);
4582         if (m && m->outcnt() > 0) {
4583           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
4584             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
4585                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
4586           }
4587           tty->sp(2 * loop->_nest + 1);
4588           m->dump();
4589         }
4590       }
4591     }
4592   }
4593 }
4594 #endif
4595 
4596 // Collect a R-P-O for the whole CFG.
4597 // Result list is in post-order (scan backwards for RPO)
4598 void PhaseIdealLoop::rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const {
4599   stk.push(start, 0);
4600   visited.set(start->_idx);
4601 
4602   while (stk.is_nonempty()) {
4603     Node* m   = stk.node();
4604     uint  idx = stk.index();
4605     if (idx < m->outcnt()) {
4606       stk.set_index(idx + 1);
4607       Node* n = m->raw_out(idx);
4608       if (n->is_CFG() && !visited.test_set(n->_idx)) {
4609         stk.push(n, 0);
4610       }
4611     } else {
4612       rpo_list.push(m);
4613       stk.pop();
4614     }
4615   }
4616 }
4617 
4618 
4619 //=============================================================================
4620 //------------------------------LoopTreeIterator-------------------------------
4621 
4622 // Advance to next loop tree using a preorder, left-to-right traversal.
4623 void LoopTreeIterator::next() {
4624   assert(!done(), "must not be done.");
4625   if (_curnt->_child != NULL) {
4626     _curnt = _curnt->_child;
4627   } else if (_curnt->_next != NULL) {
4628     _curnt = _curnt->_next;
4629   } else {
4630     while (_curnt != _root && _curnt->_next == NULL) {
4631       _curnt = _curnt->_parent;
4632     }
4633     if (_curnt == _root) {
4634       _curnt = NULL;
4635       assert(done(), "must be done.");
4636     } else {
4637       assert(_curnt->_next != NULL, "must be more to do");
4638       _curnt = _curnt->_next;
4639     }
4640   }
4641 }