1 /*
   2  * Copyright (c) 1998, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciMethodData.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "gc/shared/barrierSet.hpp"
  29 #include "gc/shared/c2/barrierSetC2.hpp"
  30 #include "libadt/vectset.hpp"
  31 #include "memory/allocation.inline.hpp"
  32 #include "memory/resourceArea.hpp"
  33 #include "opto/addnode.hpp"
  34 #include "opto/callnode.hpp"
  35 #include "opto/connode.hpp"
  36 #include "opto/convertnode.hpp"
  37 #include "opto/divnode.hpp"
  38 #include "opto/idealGraphPrinter.hpp"
  39 #include "opto/loopnode.hpp"
  40 #include "opto/mulnode.hpp"
  41 #include "opto/rootnode.hpp"
  42 #include "opto/superword.hpp"
  43 
  44 //=============================================================================
  45 //--------------------------is_cloop_ind_var-----------------------------------
  46 // Determine if a node is a counted loop induction variable.
  47 // NOTE: The method is declared in "node.hpp".
  48 bool Node::is_cloop_ind_var() const {
  49   return (is_Phi() && !as_Phi()->is_copy() &&
  50           as_Phi()->region()->is_CountedLoop() &&
  51           as_Phi()->region()->as_CountedLoop()->phi() == this);
  52 }
  53 
  54 //=============================================================================
  55 //------------------------------dump_spec--------------------------------------
  56 // Dump special per-node info
  57 #ifndef PRODUCT
  58 void LoopNode::dump_spec(outputStream *st) const {
  59   if (is_inner_loop()) st->print( "inner " );
  60   if (is_partial_peel_loop()) st->print( "partial_peel " );
  61   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  62 }
  63 #endif
  64 
  65 //------------------------------is_valid_counted_loop-------------------------
  66 bool LoopNode::is_valid_counted_loop() const {
  67   if (is_CountedLoop()) {
  68     CountedLoopNode*    l  = as_CountedLoop();
  69     CountedLoopEndNode* le = l->loopexit_or_null();
  70     if (le != NULL &&
  71         le->proj_out_or_null(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  72       Node* phi  = l->phi();
  73       Node* exit = le->proj_out_or_null(0 /* false */);
  74       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  75           phi != NULL && phi->is_Phi() &&
  76           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  77           le->loopnode() == l && le->stride_is_con()) {
  78         return true;
  79       }
  80     }
  81   }
  82   return false;
  83 }
  84 
  85 //------------------------------get_early_ctrl---------------------------------
  86 // Compute earliest legal control
  87 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  88   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  89   uint i;
  90   Node *early;
  91   if (n->in(0) && !n->is_expensive()) {
  92     early = n->in(0);
  93     if (!early->is_CFG()) // Might be a non-CFG multi-def
  94       early = get_ctrl(early);        // So treat input as a straight data input
  95     i = 1;
  96   } else {
  97     early = get_ctrl(n->in(1));
  98     i = 2;
  99   }
 100   uint e_d = dom_depth(early);
 101   assert( early, "" );
 102   for (; i < n->req(); i++) {
 103     Node *cin = get_ctrl(n->in(i));
 104     assert( cin, "" );
 105     // Keep deepest dominator depth
 106     uint c_d = dom_depth(cin);
 107     if (c_d > e_d) {           // Deeper guy?
 108       early = cin;              // Keep deepest found so far
 109       e_d = c_d;
 110     } else if (c_d == e_d &&    // Same depth?
 111                early != cin) { // If not equal, must use slower algorithm
 112       // If same depth but not equal, one _must_ dominate the other
 113       // and we want the deeper (i.e., dominated) guy.
 114       Node *n1 = early;
 115       Node *n2 = cin;
 116       while (1) {
 117         n1 = idom(n1);          // Walk up until break cycle
 118         n2 = idom(n2);
 119         if (n1 == cin ||        // Walked early up to cin
 120             dom_depth(n2) < c_d)
 121           break;                // early is deeper; keep him
 122         if (n2 == early ||      // Walked cin up to early
 123             dom_depth(n1) < c_d) {
 124           early = cin;          // cin is deeper; keep him
 125           break;
 126         }
 127       }
 128       e_d = dom_depth(early);   // Reset depth register cache
 129     }
 130   }
 131 
 132   // Return earliest legal location
 133   assert(early == find_non_split_ctrl(early), "unexpected early control");
 134 
 135   if (n->is_expensive() && !_verify_only && !_verify_me) {
 136     assert(n->in(0), "should have control input");
 137     early = get_early_ctrl_for_expensive(n, early);
 138   }
 139 
 140   return early;
 141 }
 142 
 143 //------------------------------get_early_ctrl_for_expensive---------------------------------
 144 // Move node up the dominator tree as high as legal while still beneficial
 145 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 146   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 147   assert(OptimizeExpensiveOps, "optimization off?");
 148 
 149   Node* ctl = n->in(0);
 150   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 151   uint min_dom_depth = dom_depth(earliest);
 152 #ifdef ASSERT
 153   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 154     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 155     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 156   }
 157 #endif
 158   if (dom_depth(ctl) < min_dom_depth) {
 159     return earliest;
 160   }
 161 
 162   while (1) {
 163     Node *next = ctl;
 164     // Moving the node out of a loop on the projection of a If
 165     // confuses loop predication. So once we hit a Loop in a If branch
 166     // that doesn't branch to an UNC, we stop. The code that process
 167     // expensive nodes will notice the loop and skip over it to try to
 168     // move the node further up.
 169     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 170       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 171         break;
 172       }
 173       next = idom(ctl->in(1)->in(0));
 174     } else if (ctl->is_Proj()) {
 175       // We only move it up along a projection if the projection is
 176       // the single control projection for its parent: same code path,
 177       // if it's a If with UNC or fallthrough of a call.
 178       Node* parent_ctl = ctl->in(0);
 179       if (parent_ctl == NULL) {
 180         break;
 181       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 182         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 183       } else if (parent_ctl->is_If()) {
 184         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 185           break;
 186         }
 187         assert(idom(ctl) == parent_ctl, "strange");
 188         next = idom(parent_ctl);
 189       } else if (ctl->is_CatchProj()) {
 190         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 191           break;
 192         }
 193         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 194         next = parent_ctl->in(0)->in(0)->in(0);
 195       } else {
 196         // Check if parent control has a single projection (this
 197         // control is the only possible successor of the parent
 198         // control). If so, we can try to move the node above the
 199         // parent control.
 200         int nb_ctl_proj = 0;
 201         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 202           Node *p = parent_ctl->fast_out(i);
 203           if (p->is_Proj() && p->is_CFG()) {
 204             nb_ctl_proj++;
 205             if (nb_ctl_proj > 1) {
 206               break;
 207             }
 208           }
 209         }
 210 
 211         if (nb_ctl_proj > 1) {
 212           break;
 213         }
 214         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call() ||
 215                BarrierSet::barrier_set()->barrier_set_c2()->is_gc_barrier_node(parent_ctl), "unexpected node");
 216         assert(idom(ctl) == parent_ctl, "strange");
 217         next = idom(parent_ctl);
 218       }
 219     } else {
 220       next = idom(ctl);
 221     }
 222     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 223       break;
 224     }
 225     ctl = next;
 226   }
 227 
 228   if (ctl != n->in(0)) {
 229     _igvn.replace_input_of(n, 0, ctl);
 230     _igvn.hash_insert(n);
 231   }
 232 
 233   return ctl;
 234 }
 235 
 236 
 237 //------------------------------set_early_ctrl---------------------------------
 238 // Set earliest legal control
 239 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 240   Node *early = get_early_ctrl(n);
 241 
 242   // Record earliest legal location
 243   set_ctrl(n, early);
 244 }
 245 
 246 //------------------------------set_subtree_ctrl-------------------------------
 247 // set missing _ctrl entries on new nodes
 248 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 249   // Already set?  Get out.
 250   if( _nodes[n->_idx] ) return;
 251   // Recursively set _nodes array to indicate where the Node goes
 252   uint i;
 253   for( i = 0; i < n->req(); ++i ) {
 254     Node *m = n->in(i);
 255     if( m && m != C->root() )
 256       set_subtree_ctrl( m );
 257   }
 258 
 259   // Fixup self
 260   set_early_ctrl( n );
 261 }
 262 
 263 // Create a skeleton strip mined outer loop: a Loop head before the
 264 // inner strip mined loop, a safepoint and an exit condition guarded
 265 // by an opaque node after the inner strip mined loop with a backedge
 266 // to the loop head. The inner strip mined loop is left as it is. Only
 267 // once loop optimizations are over, do we adjust the inner loop exit
 268 // condition to limit its number of iterations, set the outer loop
 269 // exit condition and add Phis to the outer loop head. Some loop
 270 // optimizations that operate on the inner strip mined loop need to be
 271 // aware of the outer strip mined loop: loop unswitching needs to
 272 // clone the outer loop as well as the inner, unrolling needs to only
 273 // clone the inner loop etc. No optimizations need to change the outer
 274 // strip mined loop as it is only a skeleton.
 275 IdealLoopTree* PhaseIdealLoop::create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
 276                                                              IdealLoopTree* loop, float cl_prob, float le_fcnt,
 277                                                              Node*& entry_control, Node*& iffalse) {
 278   Node* outer_test = _igvn.intcon(0);
 279   set_ctrl(outer_test, C->root());
 280   Node *orig = iffalse;
 281   iffalse = iffalse->clone();
 282   _igvn.register_new_node_with_optimizer(iffalse);
 283   set_idom(iffalse, idom(orig), dom_depth(orig));
 284 
 285   IfNode *outer_le = new OuterStripMinedLoopEndNode(iffalse, outer_test, cl_prob, le_fcnt);
 286   Node *outer_ift = new IfTrueNode (outer_le);
 287   Node* outer_iff = orig;
 288   _igvn.replace_input_of(outer_iff, 0, outer_le);
 289 
 290   LoopNode *outer_l = new OuterStripMinedLoopNode(C, init_control, outer_ift);
 291   entry_control = outer_l;
 292 
 293   IdealLoopTree* outer_ilt = new IdealLoopTree(this, outer_l, outer_ift);
 294   IdealLoopTree* parent = loop->_parent;
 295   IdealLoopTree* sibling = parent->_child;
 296   if (sibling == loop) {
 297     parent->_child = outer_ilt;
 298   } else {
 299     while (sibling->_next != loop) {
 300       sibling = sibling->_next;
 301     }
 302     sibling->_next = outer_ilt;
 303   }
 304   outer_ilt->_next = loop->_next;
 305   outer_ilt->_parent = parent;
 306   outer_ilt->_child = loop;
 307   outer_ilt->_nest = loop->_nest;
 308   loop->_parent = outer_ilt;
 309   loop->_next = NULL;
 310   loop->_nest++;
 311 
 312   set_loop(iffalse, outer_ilt);
 313   register_control(outer_le, outer_ilt, iffalse);
 314   register_control(outer_ift, outer_ilt, outer_le);
 315   set_idom(outer_iff, outer_le, dom_depth(outer_le));
 316   _igvn.register_new_node_with_optimizer(outer_l);
 317   set_loop(outer_l, outer_ilt);
 318   set_idom(outer_l, init_control, dom_depth(init_control)+1);
 319 
 320   return outer_ilt;
 321 }
 322 
 323 void PhaseIdealLoop::insert_loop_limit_check(ProjNode* limit_check_proj, Node* cmp_limit, Node* bol) {
 324   Node* new_predicate_proj = create_new_if_for_predicate(limit_check_proj, NULL,
 325                                                          Deoptimization::Reason_loop_limit_check,
 326                                                          Op_If);
 327   Node* iff = new_predicate_proj->in(0);
 328   assert(iff->Opcode() == Op_If, "bad graph shape");
 329   Node* conv = iff->in(1);
 330   assert(conv->Opcode() == Op_Conv2B, "bad graph shape");
 331   Node* opaq = conv->in(1);
 332   assert(opaq->Opcode() == Op_Opaque1, "bad graph shape");
 333   cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 334   bol = _igvn.register_new_node_with_optimizer(bol);
 335   set_subtree_ctrl(bol);
 336   _igvn.replace_input_of(iff, 1, bol);
 337 
 338 #ifndef PRODUCT
 339   // report that the loop predication has been actually performed
 340   // for this loop
 341   if (TraceLoopLimitCheck) {
 342     tty->print_cr("Counted Loop Limit Check generated:");
 343     debug_only( bol->dump(2); )
 344   }
 345 #endif
 346 }
 347 
 348 //------------------------------is_counted_loop--------------------------------
 349 bool PhaseIdealLoop::is_counted_loop(Node* x, IdealLoopTree*& loop) {
 350   PhaseGVN *gvn = &_igvn;
 351 
 352   // Counted loop head must be a good RegionNode with only 3 not NULL
 353   // control input edges: Self, Entry, LoopBack.
 354   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 355     return false;
 356   }
 357   Node *init_control = x->in(LoopNode::EntryControl);
 358   Node *back_control = x->in(LoopNode::LoopBackControl);
 359   if (init_control == NULL || back_control == NULL)    // Partially dead
 360     return false;
 361   // Must also check for TOP when looking for a dead loop
 362   if (init_control->is_top() || back_control->is_top())
 363     return false;
 364 
 365   // Allow funny placement of Safepoint
 366   if (back_control->Opcode() == Op_SafePoint) {
 367     if (LoopStripMiningIter != 0) {
 368       // Leaving the safepoint on the backedge and creating a
 369       // CountedLoop will confuse optimizations. We can't move the
 370       // safepoint around because its jvm state wouldn't match a new
 371       // location. Give up on that loop.
 372       return false;
 373     }
 374     back_control = back_control->in(TypeFunc::Control);
 375   }
 376 
 377   // Controlling test for loop
 378   Node *iftrue = back_control;
 379   uint iftrue_op = iftrue->Opcode();
 380   if (iftrue_op != Op_IfTrue &&
 381       iftrue_op != Op_IfFalse)
 382     // I have a weird back-control.  Probably the loop-exit test is in
 383     // the middle of the loop and I am looking at some trailing control-flow
 384     // merge point.  To fix this I would have to partially peel the loop.
 385     return false; // Obscure back-control
 386 
 387   // Get boolean guarding loop-back test
 388   Node *iff = iftrue->in(0);
 389   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 390     return false;
 391   BoolNode *test = iff->in(1)->as_Bool();
 392   BoolTest::mask bt = test->_test._test;
 393   float cl_prob = iff->as_If()->_prob;
 394   if (iftrue_op == Op_IfFalse) {
 395     bt = BoolTest(bt).negate();
 396     cl_prob = 1.0 - cl_prob;
 397   }
 398   // Get backedge compare
 399   Node *cmp = test->in(1);
 400   int cmp_op = cmp->Opcode();
 401   if (cmp_op != Op_CmpI)
 402     return false;                // Avoid pointer & float compares
 403 
 404   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 405   Node *incr  = cmp->in(1);
 406   Node *limit = cmp->in(2);
 407 
 408   // ---------
 409   // need 'loop()' test to tell if limit is loop invariant
 410   // ---------
 411 
 412   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 413     Node *tmp = incr;            // Then reverse order into the CmpI
 414     incr = limit;
 415     limit = tmp;
 416     bt = BoolTest(bt).commute(); // And commute the exit test
 417   }
 418   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 419     return false;
 420   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 421     return false;
 422 
 423   Node* phi_incr = NULL;
 424   // Trip-counter increment must be commutative & associative.
 425   if (incr->Opcode() == Op_CastII) {
 426     incr = incr->in(1);
 427   }
 428   if (incr->is_Phi()) {
 429     if (incr->as_Phi()->region() != x || incr->req() != 3)
 430       return false; // Not simple trip counter expression
 431     phi_incr = incr;
 432     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 433     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 434       return false;
 435   }
 436 
 437   Node* trunc1 = NULL;
 438   Node* trunc2 = NULL;
 439   const TypeInt* iv_trunc_t = NULL;
 440   Node* orig_incr = incr;
 441   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 442     return false; // Funny increment opcode
 443   }
 444   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 445 
 446   const TypeInt* limit_t = gvn->type(limit)->is_int();
 447   if (trunc1 != NULL) {
 448     // When there is a truncation, we must be sure that after the truncation
 449     // the trip counter will end up higher than the limit, otherwise we are looking
 450     // at an endless loop. Can happen with range checks.
 451 
 452     // Example:
 453     // int i = 0;
 454     // while (true)
 455     //    sum + = array[i];
 456     //    i++;
 457     //    i = i && 0x7fff;
 458     //  }
 459     //
 460     // If the array is shorter than 0x8000 this exits through a AIOOB
 461     //  - Counted loop transformation is ok
 462     // If the array is longer then this is an endless loop
 463     //  - No transformation can be done.
 464 
 465     const TypeInt* incr_t = gvn->type(orig_incr)->is_int();
 466     if (limit_t->_hi > incr_t->_hi) {
 467       // if the limit can have a higher value than the increment (before the phi)
 468       return false;
 469     }
 470   }
 471 
 472   // Get merge point
 473   Node *xphi = incr->in(1);
 474   Node *stride = incr->in(2);
 475   if (!stride->is_Con()) {     // Oops, swap these
 476     if (!xphi->is_Con())       // Is the other guy a constant?
 477       return false;             // Nope, unknown stride, bail out
 478     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 479     xphi = stride;
 480     stride = tmp;
 481   }
 482   if (xphi->Opcode() == Op_CastII) {
 483     xphi = xphi->in(1);
 484   }
 485   // Stride must be constant
 486   int stride_con = stride->get_int();
 487   if (stride_con == 0)
 488     return false; // missed some peephole opt
 489 
 490   if (!xphi->is_Phi())
 491     return false; // Too much math on the trip counter
 492   if (phi_incr != NULL && phi_incr != xphi)
 493     return false;
 494   PhiNode *phi = xphi->as_Phi();
 495 
 496   // Phi must be of loop header; backedge must wrap to increment
 497   if (phi->region() != x)
 498     return false;
 499   if ((trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr) ||
 500       (trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1)) {
 501     return false;
 502   }
 503   Node *init_trip = phi->in(LoopNode::EntryControl);
 504 
 505   // If iv trunc type is smaller than int, check for possible wrap.
 506   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 507     assert(trunc1 != NULL, "must have found some truncation");
 508 
 509     // Get a better type for the phi (filtered thru if's)
 510     const TypeInt* phi_ft = filtered_type(phi);
 511 
 512     // Can iv take on a value that will wrap?
 513     //
 514     // Ensure iv's limit is not within "stride" of the wrap value.
 515     //
 516     // Example for "short" type
 517     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 518     //    If the stride is +10, then the last value of the induction
 519     //    variable before the increment (phi_ft->_hi) must be
 520     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 521     //    ensure no truncation occurs after the increment.
 522 
 523     if (stride_con > 0) {
 524       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 525           iv_trunc_t->_lo > phi_ft->_lo) {
 526         return false;  // truncation may occur
 527       }
 528     } else if (stride_con < 0) {
 529       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 530           iv_trunc_t->_hi < phi_ft->_hi) {
 531         return false;  // truncation may occur
 532       }
 533     }
 534     // No possibility of wrap so truncation can be discarded
 535     // Promote iv type to Int
 536   } else {
 537     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 538   }
 539 
 540   // If the condition is inverted and we will be rolling
 541   // through MININT to MAXINT, then bail out.
 542   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 543       // Odd stride
 544       (bt == BoolTest::ne && stride_con != 1 && stride_con != -1) ||
 545       // Count down loop rolls through MAXINT
 546       ((bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0) ||
 547       // Count up loop rolls through MININT
 548       ((bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0)) {
 549     return false; // Bail out
 550   }
 551 
 552   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 553 
 554   if (stride_con > 0) {
 555     jlong init_p = (jlong)init_t->_lo + stride_con;
 556     if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
 557       return false; // cyclic loop or this loop trips only once
 558   } else {
 559     jlong init_p = (jlong)init_t->_hi + stride_con;
 560     if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
 561       return false; // cyclic loop or this loop trips only once
 562   }
 563 
 564   if (phi_incr != NULL && bt != BoolTest::ne) {
 565     // check if there is a possiblity of IV overflowing after the first increment
 566     if (stride_con > 0) {
 567       if (init_t->_hi > max_jint - stride_con) {
 568         return false;
 569       }
 570     } else {
 571       if (init_t->_lo < min_jint - stride_con) {
 572         return false;
 573       }
 574     }
 575   }
 576 
 577   // =================================================
 578   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 579   //
 580   assert(x->Opcode() == Op_Loop, "regular loops only");
 581   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 582 
 583   Node *hook = new Node(6);
 584 
 585   // ===================================================
 586   // Generate loop limit check to avoid integer overflow
 587   // in cases like next (cyclic loops):
 588   //
 589   // for (i=0; i <= max_jint; i++) {}
 590   // for (i=0; i <  max_jint; i+=2) {}
 591   //
 592   //
 593   // Limit check predicate depends on the loop test:
 594   //
 595   // for(;i != limit; i++)       --> limit <= (max_jint)
 596   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 597   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 598   //
 599 
 600   // Check if limit is excluded to do more precise int overflow check.
 601   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 602   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 603 
 604   // If compare points directly to the phi we need to adjust
 605   // the compare so that it points to the incr. Limit have
 606   // to be adjusted to keep trip count the same and the
 607   // adjusted limit should be checked for int overflow.
 608   if (phi_incr != NULL) {
 609     stride_m  += stride_con;
 610   }
 611 
 612   if (limit->is_Con()) {
 613     int limit_con = limit->get_int();
 614     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 615         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 616       // Bailout: it could be integer overflow.
 617       return false;
 618     }
 619   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 620              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 621       // Limit's type may satisfy the condition, for example,
 622       // when it is an array length.
 623   } else {
 624     // Generate loop's limit check.
 625     // Loop limit check predicate should be near the loop.
 626     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 627     if (!limit_check_proj) {
 628       // The limit check predicate is not generated if this method trapped here before.
 629 #ifdef ASSERT
 630       if (TraceLoopLimitCheck) {
 631         tty->print("missing loop limit check:");
 632         loop->dump_head();
 633         x->dump(1);
 634       }
 635 #endif
 636       return false;
 637     }
 638 
 639     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 640 
 641     if (!is_dominator(get_ctrl(limit), check_iff->in(0))) {
 642       return false;
 643     }
 644 
 645     Node* cmp_limit;
 646     Node* bol;
 647 
 648     if (stride_con > 0) {
 649       cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 650       bol = new BoolNode(cmp_limit, BoolTest::le);
 651     } else {
 652       cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 653       bol = new BoolNode(cmp_limit, BoolTest::ge);
 654     }
 655 
 656     insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 657   }
 658 
 659   // Now we need to canonicalize loop condition.
 660   if (bt == BoolTest::ne) {
 661     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 662     if (stride_con > 0 && init_t->_hi < limit_t->_lo) {
 663       // 'ne' can be replaced with 'lt' only when init < limit.
 664       bt = BoolTest::lt;
 665     } else if (stride_con < 0 && init_t->_lo > limit_t->_hi) {
 666       // 'ne' can be replaced with 'gt' only when init > limit.
 667       bt = BoolTest::gt;
 668     } else {
 669       ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 670       if (!limit_check_proj) {
 671         // The limit check predicate is not generated if this method trapped here before.
 672 #ifdef ASSERT
 673         if (TraceLoopLimitCheck) {
 674           tty->print("missing loop limit check:");
 675           loop->dump_head();
 676           x->dump(1);
 677         }
 678 #endif
 679         return false;
 680       }
 681       IfNode* check_iff = limit_check_proj->in(0)->as_If();
 682 
 683       if (!is_dominator(get_ctrl(limit), check_iff->in(0)) ||
 684           !is_dominator(get_ctrl(init_trip), check_iff->in(0))) {
 685         return false;
 686       }
 687 
 688       Node* cmp_limit;
 689       Node* bol;
 690 
 691       if (stride_con > 0) {
 692         cmp_limit = new CmpINode(init_trip, limit);
 693         bol = new BoolNode(cmp_limit, BoolTest::lt);
 694       } else {
 695         cmp_limit = new CmpINode(init_trip, limit);
 696         bol = new BoolNode(cmp_limit, BoolTest::gt);
 697       }
 698 
 699       insert_loop_limit_check(limit_check_proj, cmp_limit, bol);
 700 
 701       if (stride_con > 0) {
 702         // 'ne' can be replaced with 'lt' only when init < limit.
 703         bt = BoolTest::lt;
 704       } else if (stride_con < 0) {
 705         // 'ne' can be replaced with 'gt' only when init > limit.
 706         bt = BoolTest::gt;
 707       }
 708     }
 709   }
 710 
 711   if (phi_incr != NULL) {
 712     // If compare points directly to the phi we need to adjust
 713     // the compare so that it points to the incr. Limit have
 714     // to be adjusted to keep trip count the same and we
 715     // should avoid int overflow.
 716     //
 717     //   i = init; do {} while(i++ < limit);
 718     // is converted to
 719     //   i = init; do {} while(++i < limit+1);
 720     //
 721     limit = gvn->transform(new AddINode(limit, stride));
 722   }
 723 
 724   if (incl_limit) {
 725     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 726     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 727     //
 728     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 729     limit = gvn->transform(new AddINode(limit, one));
 730     if (bt == BoolTest::le)
 731       bt = BoolTest::lt;
 732     else if (bt == BoolTest::ge)
 733       bt = BoolTest::gt;
 734     else
 735       ShouldNotReachHere();
 736   }
 737   set_subtree_ctrl( limit );
 738 
 739   if (LoopStripMiningIter == 0) {
 740     // Check for SafePoint on backedge and remove
 741     Node *sfpt = x->in(LoopNode::LoopBackControl);
 742     if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 743       lazy_replace( sfpt, iftrue );
 744       if (loop->_safepts != NULL) {
 745         loop->_safepts->yank(sfpt);
 746       }
 747       loop->_tail = iftrue;
 748     }
 749   }
 750 
 751   // Build a canonical trip test.
 752   // Clone code, as old values may be in use.
 753   incr = incr->clone();
 754   incr->set_req(1,phi);
 755   incr->set_req(2,stride);
 756   incr = _igvn.register_new_node_with_optimizer(incr);
 757   set_early_ctrl( incr );
 758   _igvn.rehash_node_delayed(phi);
 759   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 760 
 761   // If phi type is more restrictive than Int, raise to
 762   // Int to prevent (almost) infinite recursion in igvn
 763   // which can only handle integer types for constants or minint..maxint.
 764   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 765     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 766     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 767     nphi = _igvn.register_new_node_with_optimizer(nphi);
 768     set_ctrl(nphi, get_ctrl(phi));
 769     _igvn.replace_node(phi, nphi);
 770     phi = nphi->as_Phi();
 771   }
 772   cmp = cmp->clone();
 773   cmp->set_req(1,incr);
 774   cmp->set_req(2,limit);
 775   cmp = _igvn.register_new_node_with_optimizer(cmp);
 776   set_ctrl(cmp, iff->in(0));
 777 
 778   test = test->clone()->as_Bool();
 779   (*(BoolTest*)&test->_test)._test = bt;
 780   test->set_req(1,cmp);
 781   _igvn.register_new_node_with_optimizer(test);
 782   set_ctrl(test, iff->in(0));
 783 
 784   // Replace the old IfNode with a new LoopEndNode
 785   Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 786   IfNode *le = lex->as_If();
 787   uint dd = dom_depth(iff);
 788   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 789   set_loop(le, loop);
 790 
 791   // Get the loop-exit control
 792   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 793 
 794   // Need to swap loop-exit and loop-back control?
 795   if (iftrue_op == Op_IfFalse) {
 796     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
 797     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
 798 
 799     loop->_tail = back_control = ift2;
 800     set_loop(ift2, loop);
 801     set_loop(iff2, get_loop(iffalse));
 802 
 803     // Lazy update of 'get_ctrl' mechanism.
 804     lazy_replace(iffalse, iff2);
 805     lazy_replace(iftrue,  ift2);
 806 
 807     // Swap names
 808     iffalse = iff2;
 809     iftrue  = ift2;
 810   } else {
 811     _igvn.rehash_node_delayed(iffalse);
 812     _igvn.rehash_node_delayed(iftrue);
 813     iffalse->set_req_X( 0, le, &_igvn );
 814     iftrue ->set_req_X( 0, le, &_igvn );
 815   }
 816 
 817   set_idom(iftrue,  le, dd+1);
 818   set_idom(iffalse, le, dd+1);
 819   assert(iff->outcnt() == 0, "should be dead now");
 820   lazy_replace( iff, le ); // fix 'get_ctrl'
 821 
 822   Node *sfpt2 = le->in(0);
 823 
 824   Node* entry_control = init_control;
 825   bool strip_mine_loop = LoopStripMiningIter > 1 && loop->_child == NULL &&
 826     sfpt2->Opcode() == Op_SafePoint && !loop->_has_call;
 827   IdealLoopTree* outer_ilt = NULL;
 828   if (strip_mine_loop) {
 829     outer_ilt = create_outer_strip_mined_loop(test, cmp, init_control, loop,
 830                                               cl_prob, le->_fcnt, entry_control,
 831                                               iffalse);
 832   }
 833 
 834   // Now setup a new CountedLoopNode to replace the existing LoopNode
 835   CountedLoopNode *l = new CountedLoopNode(entry_control, back_control);
 836   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 837   // The following assert is approximately true, and defines the intention
 838   // of can_be_counted_loop.  It fails, however, because phase->type
 839   // is not yet initialized for this loop and its parts.
 840   //assert(l->can_be_counted_loop(this), "sanity");
 841   _igvn.register_new_node_with_optimizer(l);
 842   set_loop(l, loop);
 843   loop->_head = l;
 844   // Fix all data nodes placed at the old loop head.
 845   // Uses the lazy-update mechanism of 'get_ctrl'.
 846   lazy_replace( x, l );
 847   set_idom(l, entry_control, dom_depth(entry_control) + 1);
 848 
 849   if (LoopStripMiningIter == 0 || strip_mine_loop) {
 850     // Check for immediately preceding SafePoint and remove
 851     if (sfpt2->Opcode() == Op_SafePoint && (LoopStripMiningIter != 0 || is_deleteable_safept(sfpt2))) {
 852       if (strip_mine_loop) {
 853         Node* outer_le = outer_ilt->_tail->in(0);
 854         Node* sfpt = sfpt2->clone();
 855         sfpt->set_req(0, iffalse);
 856         outer_le->set_req(0, sfpt);
 857         register_control(sfpt, outer_ilt, iffalse);
 858         set_idom(outer_le, sfpt, dom_depth(sfpt));
 859       }
 860       lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 861       if (loop->_safepts != NULL) {
 862         loop->_safepts->yank(sfpt2);
 863       }
 864     }
 865   }
 866 
 867   // Free up intermediate goo
 868   _igvn.remove_dead_node(hook);
 869 
 870 #ifdef ASSERT
 871   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 872   assert(l == loop->_head && l->phi() == phi && l->loopexit_or_null() == lex, "" );
 873 #endif
 874 #ifndef PRODUCT
 875   if (TraceLoopOpts) {
 876     tty->print("Counted      ");
 877     loop->dump_head();
 878   }
 879 #endif
 880 
 881   C->print_method(PHASE_AFTER_CLOOPS, 3);
 882 
 883   // Capture bounds of the loop in the induction variable Phi before
 884   // subsequent transformation (iteration splitting) obscures the
 885   // bounds
 886   l->phi()->as_Phi()->set_type(l->phi()->Value(&_igvn));
 887 
 888   if (strip_mine_loop) {
 889     l->mark_strip_mined();
 890     l->verify_strip_mined(1);
 891     outer_ilt->_head->as_Loop()->verify_strip_mined(1);
 892     loop = outer_ilt;
 893   }
 894 
 895   return true;
 896 }
 897 
 898 //----------------------exact_limit-------------------------------------------
 899 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 900   assert(loop->_head->is_CountedLoop(), "");
 901   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 902   assert(cl->is_valid_counted_loop(), "");
 903 
 904   if (ABS(cl->stride_con()) == 1 ||
 905       cl->limit()->Opcode() == Op_LoopLimit) {
 906     // Old code has exact limit (it could be incorrect in case of int overflow).
 907     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 908     return cl->limit();
 909   }
 910   Node *limit = NULL;
 911 #ifdef ASSERT
 912   BoolTest::mask bt = cl->loopexit()->test_trip();
 913   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 914 #endif
 915   if (cl->has_exact_trip_count()) {
 916     // Simple case: loop has constant boundaries.
 917     // Use jlongs to avoid integer overflow.
 918     int stride_con = cl->stride_con();
 919     jlong  init_con = cl->init_trip()->get_int();
 920     jlong limit_con = cl->limit()->get_int();
 921     julong trip_cnt = cl->trip_count();
 922     jlong final_con = init_con + trip_cnt*stride_con;
 923     int final_int = (int)final_con;
 924     // The final value should be in integer range since the loop
 925     // is counted and the limit was checked for overflow.
 926     assert(final_con == (jlong)final_int, "final value should be integer");
 927     limit = _igvn.intcon(final_int);
 928   } else {
 929     // Create new LoopLimit node to get exact limit (final iv value).
 930     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 931     register_new_node(limit, cl->in(LoopNode::EntryControl));
 932   }
 933   assert(limit != NULL, "sanity");
 934   return limit;
 935 }
 936 
 937 //------------------------------Ideal------------------------------------------
 938 // Return a node which is more "ideal" than the current node.
 939 // Attempt to convert into a counted-loop.
 940 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 941   if (!can_be_counted_loop(phase) && !is_OuterStripMinedLoop()) {
 942     phase->C->set_major_progress();
 943   }
 944   return RegionNode::Ideal(phase, can_reshape);
 945 }
 946 
 947 void LoopNode::verify_strip_mined(int expect_skeleton) const {
 948 #ifdef ASSERT
 949   const OuterStripMinedLoopNode* outer = NULL;
 950   const CountedLoopNode* inner = NULL;
 951   if (is_strip_mined()) {
 952     assert(is_CountedLoop(), "no Loop should be marked strip mined");
 953     inner = as_CountedLoop();
 954     outer = inner->in(LoopNode::EntryControl)->as_OuterStripMinedLoop();
 955   } else if (is_OuterStripMinedLoop()) {
 956     outer = this->as_OuterStripMinedLoop();
 957     inner = outer->unique_ctrl_out()->as_CountedLoop();
 958     assert(!is_strip_mined(), "outer loop shouldn't be marked strip mined");
 959   }
 960   if (inner != NULL || outer != NULL) {
 961     assert(inner != NULL && outer != NULL, "missing loop in strip mined nest");
 962     Node* outer_tail = outer->in(LoopNode::LoopBackControl);
 963     Node* outer_le = outer_tail->in(0);
 964     assert(outer_le->Opcode() == Op_OuterStripMinedLoopEnd, "tail of outer loop should be an If");
 965     Node* sfpt = outer_le->in(0);
 966     assert(sfpt->Opcode() == Op_SafePoint, "where's the safepoint?");
 967     Node* inner_out = sfpt->in(0);
 968     if (inner_out->outcnt() != 1) {
 969       ResourceMark rm;
 970       Unique_Node_List wq;
 971 
 972       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
 973         Node* u = inner_out->fast_out(i);
 974         if (u == sfpt) {
 975           continue;
 976         }
 977         wq.clear();
 978         wq.push(u);
 979         bool found_sfpt = false;
 980         for (uint next = 0; next < wq.size() && !found_sfpt; next++) {
 981           Node* n = wq.at(next);
 982           for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && !found_sfpt; i++) {
 983             Node* u = n->fast_out(i);
 984             if (u == sfpt) {
 985               found_sfpt = true;
 986             }
 987             if (!u->is_CFG()) {
 988               wq.push(u);
 989             }
 990           }
 991         }
 992         assert(found_sfpt, "no node in loop that's not input to safepoint");
 993       }
 994     }
 995 
 996     CountedLoopEndNode* cle = inner_out->in(0)->as_CountedLoopEnd();
 997     assert(cle == inner->loopexit_or_null(), "mismatch");
 998     bool has_skeleton = outer_le->in(1)->bottom_type()->singleton() && outer_le->in(1)->bottom_type()->is_int()->get_con() == 0;
 999     if (has_skeleton) {
1000       assert(expect_skeleton == 1 || expect_skeleton == -1, "unexpected skeleton node");
1001       assert(outer->outcnt() == 2, "only phis");
1002     } else {
1003       assert(expect_skeleton == 0 || expect_skeleton == -1, "no skeleton node?");
1004       uint phis = 0;
1005       for (DUIterator_Fast imax, i = inner->fast_outs(imax); i < imax; i++) {
1006         Node* u = inner->fast_out(i);
1007         if (u->is_Phi()) {
1008           phis++;
1009         }
1010       }
1011       for (DUIterator_Fast imax, i = outer->fast_outs(imax); i < imax; i++) {
1012         Node* u = outer->fast_out(i);
1013         assert(u == outer || u == inner || u->is_Phi(), "nothing between inner and outer loop");
1014       }
1015       uint stores = 0;
1016       for (DUIterator_Fast imax, i = inner_out->fast_outs(imax); i < imax; i++) {
1017         Node* u = inner_out->fast_out(i);
1018         if (u->is_Store()) {
1019           stores++;
1020         }
1021       }
1022       assert(outer->outcnt() >= phis + 2 && outer->outcnt() <= phis + 2 + stores + 1, "only phis");
1023     }
1024     assert(sfpt->outcnt() == 1, "no data node");
1025     assert(outer_tail->outcnt() == 1 || !has_skeleton, "no data node");
1026   }
1027 #endif
1028 }
1029 
1030 //=============================================================================
1031 //------------------------------Ideal------------------------------------------
1032 // Return a node which is more "ideal" than the current node.
1033 // Attempt to convert into a counted-loop.
1034 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1035   return RegionNode::Ideal(phase, can_reshape);
1036 }
1037 
1038 //------------------------------dump_spec--------------------------------------
1039 // Dump special per-node info
1040 #ifndef PRODUCT
1041 void CountedLoopNode::dump_spec(outputStream *st) const {
1042   LoopNode::dump_spec(st);
1043   if (stride_is_con()) {
1044     st->print("stride: %d ",stride_con());
1045   }
1046   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
1047   if (is_main_loop()) st->print("main of N%d", _idx);
1048   if (is_post_loop()) st->print("post of N%d", _main_idx);
1049   if (is_strip_mined()) st->print(" strip mined");
1050 }
1051 #endif
1052 
1053 //=============================================================================
1054 int CountedLoopEndNode::stride_con() const {
1055   return stride()->bottom_type()->is_int()->get_con();
1056 }
1057 
1058 //=============================================================================
1059 //------------------------------Value-----------------------------------------
1060 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
1061   const Type* init_t   = phase->type(in(Init));
1062   const Type* limit_t  = phase->type(in(Limit));
1063   const Type* stride_t = phase->type(in(Stride));
1064   // Either input is TOP ==> the result is TOP
1065   if (init_t   == Type::TOP) return Type::TOP;
1066   if (limit_t  == Type::TOP) return Type::TOP;
1067   if (stride_t == Type::TOP) return Type::TOP;
1068 
1069   int stride_con = stride_t->is_int()->get_con();
1070   if (stride_con == 1)
1071     return NULL;  // Identity
1072 
1073   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
1074     // Use jlongs to avoid integer overflow.
1075     jlong init_con   =  init_t->is_int()->get_con();
1076     jlong limit_con  = limit_t->is_int()->get_con();
1077     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
1078     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
1079     jlong final_con  = init_con + stride_con*trip_count;
1080     int final_int = (int)final_con;
1081     // The final value should be in integer range since the loop
1082     // is counted and the limit was checked for overflow.
1083     assert(final_con == (jlong)final_int, "final value should be integer");
1084     return TypeInt::make(final_int);
1085   }
1086 
1087   return bottom_type(); // TypeInt::INT
1088 }
1089 
1090 //------------------------------Ideal------------------------------------------
1091 // Return a node which is more "ideal" than the current node.
1092 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1093   if (phase->type(in(Init))   == Type::TOP ||
1094       phase->type(in(Limit))  == Type::TOP ||
1095       phase->type(in(Stride)) == Type::TOP)
1096     return NULL;  // Dead
1097 
1098   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1099   if (stride_con == 1)
1100     return NULL;  // Identity
1101 
1102   if (in(Init)->is_Con() && in(Limit)->is_Con())
1103     return NULL;  // Value
1104 
1105   // Delay following optimizations until all loop optimizations
1106   // done to keep Ideal graph simple.
1107   if (!can_reshape || phase->C->major_progress())
1108     return NULL;
1109 
1110   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
1111   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
1112   int stride_p;
1113   jlong lim, ini;
1114   julong max;
1115   if (stride_con > 0) {
1116     stride_p = stride_con;
1117     lim = limit_t->_hi;
1118     ini = init_t->_lo;
1119     max = (julong)max_jint;
1120   } else {
1121     stride_p = -stride_con;
1122     lim = init_t->_hi;
1123     ini = limit_t->_lo;
1124     max = (julong)min_jint;
1125   }
1126   julong range = lim - ini + stride_p;
1127   if (range <= max) {
1128     // Convert to integer expression if it is not overflow.
1129     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
1130     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
1131     Node *bias  = phase->transform(new AddINode(range, stride_m));
1132     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
1133     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
1134     return new AddINode(span, in(Init)); // exact limit
1135   }
1136 
1137   if (is_power_of_2(stride_p) ||                // divisor is 2^n
1138       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
1139     // Convert to long expression to avoid integer overflow
1140     // and let igvn optimizer convert this division.
1141     //
1142     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
1143     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
1144     Node* stride   = phase->longcon(stride_con);
1145     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
1146 
1147     Node *range = phase->transform(new SubLNode(limit, init));
1148     Node *bias  = phase->transform(new AddLNode(range, stride_m));
1149     Node *span;
1150     if (stride_con > 0 && is_power_of_2(stride_p)) {
1151       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
1152       // and avoid generating rounding for division. Zero trip guard should
1153       // guarantee that init < limit but sometimes the guard is missing and
1154       // we can get situation when init > limit. Note, for the empty loop
1155       // optimization zero trip guard is generated explicitly which leaves
1156       // only RCE predicate where exact limit is used and the predicate
1157       // will simply fail forcing recompilation.
1158       Node* neg_stride   = phase->longcon(-stride_con);
1159       span = phase->transform(new AndLNode(bias, neg_stride));
1160     } else {
1161       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
1162       span = phase->transform(new MulLNode(trip, stride));
1163     }
1164     // Convert back to int
1165     Node *span_int = phase->transform(new ConvL2INode(span));
1166     return new AddINode(span_int, in(Init)); // exact limit
1167   }
1168 
1169   return NULL;    // No progress
1170 }
1171 
1172 //------------------------------Identity---------------------------------------
1173 // If stride == 1 return limit node.
1174 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1175   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1176   if (stride_con == 1 || stride_con == -1)
1177     return in(Limit);
1178   return this;
1179 }
1180 
1181 //=============================================================================
1182 //----------------------match_incr_with_optional_truncation--------------------
1183 // Match increment with optional truncation:
1184 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1185 // Return NULL for failure. Success returns the increment node.
1186 Node* CountedLoopNode::match_incr_with_optional_truncation(
1187                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1188   // Quick cutouts:
1189   if (expr == NULL || expr->req() != 3)  return NULL;
1190 
1191   Node *t1 = NULL;
1192   Node *t2 = NULL;
1193   const TypeInt* trunc_t = TypeInt::INT;
1194   Node* n1 = expr;
1195   int   n1op = n1->Opcode();
1196 
1197   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1198   if (n1op == Op_AndI &&
1199       n1->in(2)->is_Con() &&
1200       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1201     // %%% This check should match any mask of 2**K-1.
1202     t1 = n1;
1203     n1 = t1->in(1);
1204     n1op = n1->Opcode();
1205     trunc_t = TypeInt::CHAR;
1206   } else if (n1op == Op_RShiftI &&
1207              n1->in(1) != NULL &&
1208              n1->in(1)->Opcode() == Op_LShiftI &&
1209              n1->in(2) == n1->in(1)->in(2) &&
1210              n1->in(2)->is_Con()) {
1211     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1212     // %%% This check should match any shift in [1..31].
1213     if (shift == 16 || shift == 8) {
1214       t1 = n1;
1215       t2 = t1->in(1);
1216       n1 = t2->in(1);
1217       n1op = n1->Opcode();
1218       if (shift == 16) {
1219         trunc_t = TypeInt::SHORT;
1220       } else if (shift == 8) {
1221         trunc_t = TypeInt::BYTE;
1222       }
1223     }
1224   }
1225 
1226   // If (maybe after stripping) it is an AddI, we won:
1227   if (n1op == Op_AddI) {
1228     *trunc1 = t1;
1229     *trunc2 = t2;
1230     *trunc_type = trunc_t;
1231     return n1;
1232   }
1233 
1234   // failed
1235   return NULL;
1236 }
1237 
1238 LoopNode* CountedLoopNode::skip_strip_mined(int expect_skeleton) {
1239   if (is_strip_mined()) {
1240     verify_strip_mined(expect_skeleton);
1241     return in(EntryControl)->as_Loop();
1242   }
1243   return this;
1244 }
1245 
1246 OuterStripMinedLoopNode* CountedLoopNode::outer_loop() const {
1247   assert(is_strip_mined(), "not a strip mined loop");
1248   Node* c = in(EntryControl);
1249   if (c == NULL || c->is_top() || !c->is_OuterStripMinedLoop()) {
1250     return NULL;
1251   }
1252   return c->as_OuterStripMinedLoop();
1253 }
1254 
1255 IfTrueNode* OuterStripMinedLoopNode::outer_loop_tail() const {
1256   Node* c = in(LoopBackControl);
1257   if (c == NULL || c->is_top()) {
1258     return NULL;
1259   }
1260   return c->as_IfTrue();
1261 }
1262 
1263 IfTrueNode* CountedLoopNode::outer_loop_tail() const {
1264   LoopNode* l = outer_loop();
1265   if (l == NULL) {
1266     return NULL;
1267   }
1268   return l->outer_loop_tail();
1269 }
1270 
1271 OuterStripMinedLoopEndNode* OuterStripMinedLoopNode::outer_loop_end() const {
1272   IfTrueNode* proj = outer_loop_tail();
1273   if (proj == NULL) {
1274     return NULL;
1275   }
1276   Node* c = proj->in(0);
1277   if (c == NULL || c->is_top() || c->outcnt() != 2) {
1278     return NULL;
1279   }
1280   return c->as_OuterStripMinedLoopEnd();
1281 }
1282 
1283 OuterStripMinedLoopEndNode* CountedLoopNode::outer_loop_end() const {
1284   LoopNode* l = outer_loop();
1285   if (l == NULL) {
1286     return NULL;
1287   }
1288   return l->outer_loop_end();
1289 }
1290 
1291 IfFalseNode* OuterStripMinedLoopNode::outer_loop_exit() const {
1292   IfNode* le = outer_loop_end();
1293   if (le == NULL) {
1294     return NULL;
1295   }
1296   Node* c = le->proj_out_or_null(false);
1297   if (c == NULL) {
1298     return NULL;
1299   }
1300   return c->as_IfFalse();
1301 }
1302 
1303 IfFalseNode* CountedLoopNode::outer_loop_exit() const {
1304   LoopNode* l = outer_loop();
1305   if (l == NULL) {
1306     return NULL;
1307   }
1308   return l->outer_loop_exit();
1309 }
1310 
1311 SafePointNode* OuterStripMinedLoopNode::outer_safepoint() const {
1312   IfNode* le = outer_loop_end();
1313   if (le == NULL) {
1314     return NULL;
1315   }
1316   Node* c = le->in(0);
1317   if (c == NULL || c->is_top()) {
1318     return NULL;
1319   }
1320   assert(c->Opcode() == Op_SafePoint, "broken outer loop");
1321   return c->as_SafePoint();
1322 }
1323 
1324 SafePointNode* CountedLoopNode::outer_safepoint() const {
1325   LoopNode* l = outer_loop();
1326   if (l == NULL) {
1327     return NULL;
1328   }
1329   return l->outer_safepoint();
1330 }
1331 
1332 Node* CountedLoopNode::skip_predicates_from_entry(Node* ctrl) {
1333     while (ctrl != NULL && ctrl->is_Proj() && ctrl->in(0)->is_If() &&
1334            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->outcnt() == 1 &&
1335            ctrl->in(0)->as_If()->proj_out(1-ctrl->as_Proj()->_con)->unique_out()->Opcode() == Op_Halt) {
1336       ctrl = ctrl->in(0)->in(0);
1337     }
1338 
1339     return ctrl;
1340   }
1341 
1342 Node* CountedLoopNode::skip_predicates() {
1343   if (is_main_loop()) {
1344     Node* ctrl = skip_strip_mined()->in(LoopNode::EntryControl);
1345 
1346     return skip_predicates_from_entry(ctrl);
1347   }
1348   return in(LoopNode::EntryControl);
1349 }
1350 
1351 void OuterStripMinedLoopNode::adjust_strip_mined_loop(PhaseIterGVN* igvn) {
1352   // Look for the outer & inner strip mined loop, reduce number of
1353   // iterations of the inner loop, set exit condition of outer loop,
1354   // construct required phi nodes for outer loop.
1355   CountedLoopNode* inner_cl = unique_ctrl_out()->as_CountedLoop();
1356   assert(inner_cl->is_strip_mined(), "inner loop should be strip mined");
1357   Node* inner_iv_phi = inner_cl->phi();
1358   if (inner_iv_phi == NULL) {
1359     IfNode* outer_le = outer_loop_end();
1360     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1361     igvn->replace_node(outer_le, iff);
1362     inner_cl->clear_strip_mined();
1363     return;
1364   }
1365   CountedLoopEndNode* inner_cle = inner_cl->loopexit();
1366 
1367   int stride = inner_cl->stride_con();
1368   jlong scaled_iters_long = ((jlong)LoopStripMiningIter) * ABS(stride);
1369   int scaled_iters = (int)scaled_iters_long;
1370   int short_scaled_iters = LoopStripMiningIterShortLoop* ABS(stride);
1371   const TypeInt* inner_iv_t = igvn->type(inner_iv_phi)->is_int();
1372   jlong iter_estimate = (jlong)inner_iv_t->_hi - (jlong)inner_iv_t->_lo;
1373   assert(iter_estimate > 0, "broken");
1374   if ((jlong)scaled_iters != scaled_iters_long || iter_estimate <= short_scaled_iters) {
1375     // Remove outer loop and safepoint (too few iterations)
1376     Node* outer_sfpt = outer_safepoint();
1377     Node* outer_out = outer_loop_exit();
1378     igvn->replace_node(outer_out, outer_sfpt->in(0));
1379     igvn->replace_input_of(outer_sfpt, 0, igvn->C->top());
1380     inner_cl->clear_strip_mined();
1381     return;
1382   }
1383   if (iter_estimate <= scaled_iters_long) {
1384     // We would only go through one iteration of
1385     // the outer loop: drop the outer loop but
1386     // keep the safepoint so we don't run for
1387     // too long without a safepoint
1388     IfNode* outer_le = outer_loop_end();
1389     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1390     igvn->replace_node(outer_le, iff);
1391     inner_cl->clear_strip_mined();
1392     return;
1393   }
1394 
1395   Node* cle_tail = inner_cle->proj_out(true);
1396   ResourceMark rm;
1397   Node_List old_new;
1398   if (cle_tail->outcnt() > 1) {
1399     // Look for nodes on backedge of inner loop and clone them
1400     Unique_Node_List backedge_nodes;
1401     for (DUIterator_Fast imax, i = cle_tail->fast_outs(imax); i < imax; i++) {
1402       Node* u = cle_tail->fast_out(i);
1403       if (u != inner_cl) {
1404         assert(!u->is_CFG(), "control flow on the backedge?");
1405         backedge_nodes.push(u);
1406       }
1407     }
1408     uint last = igvn->C->unique();
1409     for (uint next = 0; next < backedge_nodes.size(); next++) {
1410       Node* n = backedge_nodes.at(next);
1411       old_new.map(n->_idx, n->clone());
1412       for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
1413         Node* u = n->fast_out(i);
1414         assert(!u->is_CFG(), "broken");
1415         if (u->_idx >= last) {
1416           continue;
1417         }
1418         if (!u->is_Phi()) {
1419           backedge_nodes.push(u);
1420         } else {
1421           assert(u->in(0) == inner_cl, "strange phi on the backedge");
1422         }
1423       }
1424     }
1425     // Put the clones on the outer loop backedge
1426     Node* le_tail = outer_loop_tail();
1427     for (uint next = 0; next < backedge_nodes.size(); next++) {
1428       Node *n = old_new[backedge_nodes.at(next)->_idx];
1429       for (uint i = 1; i < n->req(); i++) {
1430         if (n->in(i) != NULL && old_new[n->in(i)->_idx] != NULL) {
1431           n->set_req(i, old_new[n->in(i)->_idx]);
1432         }
1433       }
1434       if (n->in(0) != NULL && n->in(0) == cle_tail) {
1435         n->set_req(0, le_tail);
1436       }
1437       igvn->register_new_node_with_optimizer(n);
1438     }
1439   }
1440 
1441   Node* iv_phi = NULL;
1442   // Make a clone of each phi in the inner loop
1443   // for the outer loop
1444   for (uint i = 0; i < inner_cl->outcnt(); i++) {
1445     Node* u = inner_cl->raw_out(i);
1446     if (u->is_Phi()) {
1447       assert(u->in(0) == inner_cl, "inconsistent");
1448       Node* phi = u->clone();
1449       phi->set_req(0, this);
1450       Node* be = old_new[phi->in(LoopNode::LoopBackControl)->_idx];
1451       if (be != NULL) {
1452         phi->set_req(LoopNode::LoopBackControl, be);
1453       }
1454       phi = igvn->transform(phi);
1455       igvn->replace_input_of(u, LoopNode::EntryControl, phi);
1456       if (u == inner_iv_phi) {
1457         iv_phi = phi;
1458       }
1459     }
1460   }
1461   Node* cle_out = inner_cle->proj_out(false);
1462   if (cle_out->outcnt() > 1) {
1463     // Look for chains of stores that were sunk
1464     // out of the inner loop and are in the outer loop
1465     for (DUIterator_Fast imax, i = cle_out->fast_outs(imax); i < imax; i++) {
1466       Node* u = cle_out->fast_out(i);
1467       if (u->is_Store()) {
1468         Node* first = u;
1469         for(;;) {
1470           Node* next = first->in(MemNode::Memory);
1471           if (!next->is_Store() || next->in(0) != cle_out) {
1472             break;
1473           }
1474           first = next;
1475         }
1476         Node* last = u;
1477         for(;;) {
1478           Node* next = NULL;
1479           for (DUIterator_Fast jmax, j = last->fast_outs(jmax); j < jmax; j++) {
1480             Node* uu = last->fast_out(j);
1481             if (uu->is_Store() && uu->in(0) == cle_out) {
1482               assert(next == NULL, "only one in the outer loop");
1483               next = uu;
1484             }
1485           }
1486           if (next == NULL) {
1487             break;
1488           }
1489           last = next;
1490         }
1491         Node* phi = NULL;
1492         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1493           Node* uu = fast_out(j);
1494           if (uu->is_Phi()) {
1495             Node* be = uu->in(LoopNode::LoopBackControl);
1496             if (be->is_Store() && old_new[be->_idx] != NULL) {
1497               assert(false, "store on the backedge + sunk stores: unsupported");
1498               // drop outer loop
1499               IfNode* outer_le = outer_loop_end();
1500               Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1501               igvn->replace_node(outer_le, iff);
1502               inner_cl->clear_strip_mined();
1503               return;
1504             }
1505             if (be == last || be == first->in(MemNode::Memory)) {
1506               assert(phi == NULL, "only one phi");
1507               phi = uu;
1508             }
1509           }
1510         }
1511 #ifdef ASSERT
1512         for (DUIterator_Fast jmax, j = fast_outs(jmax); j < jmax; j++) {
1513           Node* uu = fast_out(j);
1514           if (uu->is_Phi() && uu->bottom_type() == Type::MEMORY) {
1515             if (uu->adr_type() == igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type()))) {
1516               assert(phi == uu, "what's that phi?");
1517             } else if (uu->adr_type() == TypePtr::BOTTOM) {
1518               Node* n = uu->in(LoopNode::LoopBackControl);
1519               uint limit = igvn->C->live_nodes();
1520               uint i = 0;
1521               while (n != uu) {
1522                 i++;
1523                 assert(i < limit, "infinite loop");
1524                 if (n->is_Proj()) {
1525                   n = n->in(0);
1526                 } else if (n->is_SafePoint() || n->is_MemBar()) {
1527                   n = n->in(TypeFunc::Memory);
1528                 } else if (n->is_Phi()) {
1529                   n = n->in(1);
1530                 } else if (n->is_MergeMem()) {
1531                   n = n->as_MergeMem()->memory_at(igvn->C->get_alias_index(u->adr_type()));
1532                 } else if (n->is_Store() || n->is_LoadStore() || n->is_ClearArray()) {
1533                   n = n->in(MemNode::Memory);
1534                 } else {
1535                   n->dump();
1536                   ShouldNotReachHere();
1537                 }
1538               }
1539             }
1540           }
1541         }
1542 #endif
1543         if (phi == NULL) {
1544           // If the an entire chains was sunk, the
1545           // inner loop has no phi for that memory
1546           // slice, create one for the outer loop
1547           phi = PhiNode::make(this, first->in(MemNode::Memory), Type::MEMORY,
1548                               igvn->C->get_adr_type(igvn->C->get_alias_index(u->adr_type())));
1549           phi->set_req(LoopNode::LoopBackControl, last);
1550           phi = igvn->transform(phi);
1551           igvn->replace_input_of(first, MemNode::Memory, phi);
1552         } else {
1553           // Or fix the outer loop fix to include
1554           // that chain of stores.
1555           Node* be = phi->in(LoopNode::LoopBackControl);
1556           assert(!(be->is_Store() && old_new[be->_idx] != NULL), "store on the backedge + sunk stores: unsupported");
1557           if (be == first->in(MemNode::Memory)) {
1558             if (be == phi->in(LoopNode::LoopBackControl)) {
1559               igvn->replace_input_of(phi, LoopNode::LoopBackControl, last);
1560             } else {
1561               igvn->replace_input_of(be, MemNode::Memory, last);
1562             }
1563           } else {
1564 #ifdef ASSERT
1565             if (be == phi->in(LoopNode::LoopBackControl)) {
1566               assert(phi->in(LoopNode::LoopBackControl) == last, "");
1567             } else {
1568               assert(be->in(MemNode::Memory) == last, "");
1569             }
1570 #endif
1571           }
1572         }
1573       }
1574     }
1575   }
1576 
1577   if (iv_phi != NULL) {
1578     // Now adjust the inner loop's exit condition
1579     Node* limit = inner_cl->limit();
1580     Node* sub = NULL;
1581     if (stride > 0) {
1582       sub = igvn->transform(new SubINode(limit, iv_phi));
1583     } else {
1584       sub = igvn->transform(new SubINode(iv_phi, limit));
1585     }
1586     Node* min = igvn->transform(new MinINode(sub, igvn->intcon(scaled_iters)));
1587     Node* new_limit = NULL;
1588     if (stride > 0) {
1589       new_limit = igvn->transform(new AddINode(min, iv_phi));
1590     } else {
1591       new_limit = igvn->transform(new SubINode(iv_phi, min));
1592     }
1593     Node* inner_cmp = inner_cle->cmp_node();
1594     Node* inner_bol = inner_cle->in(CountedLoopEndNode::TestValue);
1595     Node* outer_bol = inner_bol;
1596     // cmp node for inner loop may be shared
1597     inner_cmp = inner_cmp->clone();
1598     inner_cmp->set_req(2, new_limit);
1599     inner_bol = inner_bol->clone();
1600     inner_bol->set_req(1, igvn->transform(inner_cmp));
1601     igvn->replace_input_of(inner_cle, CountedLoopEndNode::TestValue, igvn->transform(inner_bol));
1602     // Set the outer loop's exit condition too
1603     igvn->replace_input_of(outer_loop_end(), 1, outer_bol);
1604   } else {
1605     assert(false, "should be able to adjust outer loop");
1606     IfNode* outer_le = outer_loop_end();
1607     Node* iff = igvn->transform(new IfNode(outer_le->in(0), outer_le->in(1), outer_le->_prob, outer_le->_fcnt));
1608     igvn->replace_node(outer_le, iff);
1609     inner_cl->clear_strip_mined();
1610   }
1611 }
1612 
1613 const Type* OuterStripMinedLoopEndNode::Value(PhaseGVN* phase) const {
1614   if (!in(0)) return Type::TOP;
1615   if (phase->type(in(0)) == Type::TOP)
1616     return Type::TOP;
1617 
1618   return TypeTuple::IFBOTH;
1619 }
1620 
1621 Node *OuterStripMinedLoopEndNode::Ideal(PhaseGVN *phase, bool can_reshape) {
1622   if (remove_dead_region(phase, can_reshape))  return this;
1623 
1624   return NULL;
1625 }
1626 
1627 //------------------------------filtered_type--------------------------------
1628 // Return a type based on condition control flow
1629 // A successful return will be a type that is restricted due
1630 // to a series of dominating if-tests, such as:
1631 //    if (i < 10) {
1632 //       if (i > 0) {
1633 //          here: "i" type is [1..10)
1634 //       }
1635 //    }
1636 // or a control flow merge
1637 //    if (i < 10) {
1638 //       do {
1639 //          phi( , ) -- at top of loop type is [min_int..10)
1640 //         i = ?
1641 //       } while ( i < 10)
1642 //
1643 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1644   assert(n && n->bottom_type()->is_int(), "must be int");
1645   const TypeInt* filtered_t = NULL;
1646   if (!n->is_Phi()) {
1647     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1648     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1649 
1650   } else {
1651     Node* phi    = n->as_Phi();
1652     Node* region = phi->in(0);
1653     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1654     if (region && region != C->top()) {
1655       for (uint i = 1; i < phi->req(); i++) {
1656         Node* val   = phi->in(i);
1657         Node* use_c = region->in(i);
1658         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1659         if (val_t != NULL) {
1660           if (filtered_t == NULL) {
1661             filtered_t = val_t;
1662           } else {
1663             filtered_t = filtered_t->meet(val_t)->is_int();
1664           }
1665         }
1666       }
1667     }
1668   }
1669   const TypeInt* n_t = _igvn.type(n)->is_int();
1670   if (filtered_t != NULL) {
1671     n_t = n_t->join(filtered_t)->is_int();
1672   }
1673   return n_t;
1674 }
1675 
1676 
1677 //------------------------------filtered_type_from_dominators--------------------------------
1678 // Return a possibly more restrictive type for val based on condition control flow of dominators
1679 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1680   if (val->is_Con()) {
1681      return val->bottom_type()->is_int();
1682   }
1683   uint if_limit = 10; // Max number of dominating if's visited
1684   const TypeInt* rtn_t = NULL;
1685 
1686   if (use_ctrl && use_ctrl != C->top()) {
1687     Node* val_ctrl = get_ctrl(val);
1688     uint val_dom_depth = dom_depth(val_ctrl);
1689     Node* pred = use_ctrl;
1690     uint if_cnt = 0;
1691     while (if_cnt < if_limit) {
1692       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1693         if_cnt++;
1694         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1695         if (if_t != NULL) {
1696           if (rtn_t == NULL) {
1697             rtn_t = if_t;
1698           } else {
1699             rtn_t = rtn_t->join(if_t)->is_int();
1700           }
1701         }
1702       }
1703       pred = idom(pred);
1704       if (pred == NULL || pred == C->top()) {
1705         break;
1706       }
1707       // Stop if going beyond definition block of val
1708       if (dom_depth(pred) < val_dom_depth) {
1709         break;
1710       }
1711     }
1712   }
1713   return rtn_t;
1714 }
1715 
1716 
1717 //------------------------------dump_spec--------------------------------------
1718 // Dump special per-node info
1719 #ifndef PRODUCT
1720 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1721   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1722     BoolTest bt( test_trip()); // Added this for g++.
1723 
1724     st->print("[");
1725     bt.dump_on(st);
1726     st->print("]");
1727   }
1728   st->print(" ");
1729   IfNode::dump_spec(st);
1730 }
1731 #endif
1732 
1733 //=============================================================================
1734 //------------------------------is_member--------------------------------------
1735 // Is 'l' a member of 'this'?
1736 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1737   while( l->_nest > _nest ) l = l->_parent;
1738   return l == this;
1739 }
1740 
1741 //------------------------------set_nest---------------------------------------
1742 // Set loop tree nesting depth.  Accumulate _has_call bits.
1743 int IdealLoopTree::set_nest( uint depth ) {
1744   _nest = depth;
1745   int bits = _has_call;
1746   if( _child ) bits |= _child->set_nest(depth+1);
1747   if( bits ) _has_call = 1;
1748   if( _next  ) bits |= _next ->set_nest(depth  );
1749   return bits;
1750 }
1751 
1752 //------------------------------split_fall_in----------------------------------
1753 // Split out multiple fall-in edges from the loop header.  Move them to a
1754 // private RegionNode before the loop.  This becomes the loop landing pad.
1755 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1756   PhaseIterGVN &igvn = phase->_igvn;
1757   uint i;
1758 
1759   // Make a new RegionNode to be the landing pad.
1760   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1761   phase->set_loop(landing_pad,_parent);
1762   // Gather all the fall-in control paths into the landing pad
1763   uint icnt = fall_in_cnt;
1764   uint oreq = _head->req();
1765   for( i = oreq-1; i>0; i-- )
1766     if( !phase->is_member( this, _head->in(i) ) )
1767       landing_pad->set_req(icnt--,_head->in(i));
1768 
1769   // Peel off PhiNode edges as well
1770   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1771     Node *oj = _head->fast_out(j);
1772     if( oj->is_Phi() ) {
1773       PhiNode* old_phi = oj->as_Phi();
1774       assert( old_phi->region() == _head, "" );
1775       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1776       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1777       uint icnt = fall_in_cnt;
1778       for( i = oreq-1; i>0; i-- ) {
1779         if( !phase->is_member( this, _head->in(i) ) ) {
1780           p->init_req(icnt--, old_phi->in(i));
1781           // Go ahead and clean out old edges from old phi
1782           old_phi->del_req(i);
1783         }
1784       }
1785       // Search for CSE's here, because ZKM.jar does a lot of
1786       // loop hackery and we need to be a little incremental
1787       // with the CSE to avoid O(N^2) node blow-up.
1788       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1789       if( p2 ) {                // Found CSE
1790         p->destruct();          // Recover useless new node
1791         p = p2;                 // Use old node
1792       } else {
1793         igvn.register_new_node_with_optimizer(p, old_phi);
1794       }
1795       // Make old Phi refer to new Phi.
1796       old_phi->add_req(p);
1797       // Check for the special case of making the old phi useless and
1798       // disappear it.  In JavaGrande I have a case where this useless
1799       // Phi is the loop limit and prevents recognizing a CountedLoop
1800       // which in turn prevents removing an empty loop.
1801       Node *id_old_phi = igvn.apply_identity(old_phi);
1802       if( id_old_phi != old_phi ) { // Found a simple identity?
1803         // Note that I cannot call 'replace_node' here, because
1804         // that will yank the edge from old_phi to the Region and
1805         // I'm mid-iteration over the Region's uses.
1806         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1807           Node* use = old_phi->last_out(i);
1808           igvn.rehash_node_delayed(use);
1809           uint uses_found = 0;
1810           for (uint j = 0; j < use->len(); j++) {
1811             if (use->in(j) == old_phi) {
1812               if (j < use->req()) use->set_req (j, id_old_phi);
1813               else                use->set_prec(j, id_old_phi);
1814               uses_found++;
1815             }
1816           }
1817           i -= uses_found;    // we deleted 1 or more copies of this edge
1818         }
1819       }
1820       igvn._worklist.push(old_phi);
1821     }
1822   }
1823   // Finally clean out the fall-in edges from the RegionNode
1824   for( i = oreq-1; i>0; i-- ) {
1825     if( !phase->is_member( this, _head->in(i) ) ) {
1826       _head->del_req(i);
1827     }
1828   }
1829   igvn.rehash_node_delayed(_head);
1830   // Transform landing pad
1831   igvn.register_new_node_with_optimizer(landing_pad, _head);
1832   // Insert landing pad into the header
1833   _head->add_req(landing_pad);
1834 }
1835 
1836 //------------------------------split_outer_loop-------------------------------
1837 // Split out the outermost loop from this shared header.
1838 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1839   PhaseIterGVN &igvn = phase->_igvn;
1840 
1841   // Find index of outermost loop; it should also be my tail.
1842   uint outer_idx = 1;
1843   while( _head->in(outer_idx) != _tail ) outer_idx++;
1844 
1845   // Make a LoopNode for the outermost loop.
1846   Node *ctl = _head->in(LoopNode::EntryControl);
1847   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1848   outer = igvn.register_new_node_with_optimizer(outer, _head);
1849   phase->set_created_loop_node();
1850 
1851   // Outermost loop falls into '_head' loop
1852   _head->set_req(LoopNode::EntryControl, outer);
1853   _head->del_req(outer_idx);
1854   // Split all the Phis up between '_head' loop and 'outer' loop.
1855   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1856     Node *out = _head->fast_out(j);
1857     if( out->is_Phi() ) {
1858       PhiNode *old_phi = out->as_Phi();
1859       assert( old_phi->region() == _head, "" );
1860       Node *phi = PhiNode::make_blank(outer, old_phi);
1861       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1862       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1863       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1864       // Make old Phi point to new Phi on the fall-in path
1865       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1866       old_phi->del_req(outer_idx);
1867     }
1868   }
1869 
1870   // Use the new loop head instead of the old shared one
1871   _head = outer;
1872   phase->set_loop(_head, this);
1873 }
1874 
1875 //------------------------------fix_parent-------------------------------------
1876 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1877   loop->_parent = parent;
1878   if( loop->_child ) fix_parent( loop->_child, loop   );
1879   if( loop->_next  ) fix_parent( loop->_next , parent );
1880 }
1881 
1882 //------------------------------estimate_path_freq-----------------------------
1883 static float estimate_path_freq( Node *n ) {
1884   // Try to extract some path frequency info
1885   IfNode *iff;
1886   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1887     uint nop = n->Opcode();
1888     if( nop == Op_SafePoint ) {   // Skip any safepoint
1889       n = n->in(0);
1890       continue;
1891     }
1892     if( nop == Op_CatchProj ) {   // Get count from a prior call
1893       // Assume call does not always throw exceptions: means the call-site
1894       // count is also the frequency of the fall-through path.
1895       assert( n->is_CatchProj(), "" );
1896       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1897         return 0.0f;            // Assume call exception path is rare
1898       Node *call = n->in(0)->in(0)->in(0);
1899       assert( call->is_Call(), "expect a call here" );
1900       const JVMState *jvms = ((CallNode*)call)->jvms();
1901       ciMethodData* methodData = jvms->method()->method_data();
1902       if (!methodData->is_mature())  return 0.0f; // No call-site data
1903       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1904       if ((data == NULL) || !data->is_CounterData()) {
1905         // no call profile available, try call's control input
1906         n = n->in(0);
1907         continue;
1908       }
1909       return data->as_CounterData()->count()/FreqCountInvocations;
1910     }
1911     // See if there's a gating IF test
1912     Node *n_c = n->in(0);
1913     if( !n_c->is_If() ) break;       // No estimate available
1914     iff = n_c->as_If();
1915     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1916       // Compute how much count comes on this path
1917       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1918     // Have no count info.  Skip dull uncommon-trap like branches.
1919     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1920         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1921       break;
1922     // Skip through never-taken branch; look for a real loop exit.
1923     n = iff->in(0);
1924   }
1925   return 0.0f;                  // No estimate available
1926 }
1927 
1928 //------------------------------merge_many_backedges---------------------------
1929 // Merge all the backedges from the shared header into a private Region.
1930 // Feed that region as the one backedge to this loop.
1931 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1932   uint i;
1933 
1934   // Scan for the top 2 hottest backedges
1935   float hotcnt = 0.0f;
1936   float warmcnt = 0.0f;
1937   uint hot_idx = 0;
1938   // Loop starts at 2 because slot 1 is the fall-in path
1939   for( i = 2; i < _head->req(); i++ ) {
1940     float cnt = estimate_path_freq(_head->in(i));
1941     if( cnt > hotcnt ) {       // Grab hottest path
1942       warmcnt = hotcnt;
1943       hotcnt = cnt;
1944       hot_idx = i;
1945     } else if( cnt > warmcnt ) { // And 2nd hottest path
1946       warmcnt = cnt;
1947     }
1948   }
1949 
1950   // See if the hottest backedge is worthy of being an inner loop
1951   // by being much hotter than the next hottest backedge.
1952   if( hotcnt <= 0.0001 ||
1953       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1954 
1955   // Peel out the backedges into a private merge point; peel
1956   // them all except optionally hot_idx.
1957   PhaseIterGVN &igvn = phase->_igvn;
1958 
1959   Node *hot_tail = NULL;
1960   // Make a Region for the merge point
1961   Node *r = new RegionNode(1);
1962   for( i = 2; i < _head->req(); i++ ) {
1963     if( i != hot_idx )
1964       r->add_req( _head->in(i) );
1965     else hot_tail = _head->in(i);
1966   }
1967   igvn.register_new_node_with_optimizer(r, _head);
1968   // Plug region into end of loop _head, followed by hot_tail
1969   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1970   igvn.replace_input_of(_head, 2, r);
1971   if( hot_idx ) _head->add_req(hot_tail);
1972 
1973   // Split all the Phis up between '_head' loop and the Region 'r'
1974   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1975     Node *out = _head->fast_out(j);
1976     if( out->is_Phi() ) {
1977       PhiNode* n = out->as_Phi();
1978       igvn.hash_delete(n);      // Delete from hash before hacking edges
1979       Node *hot_phi = NULL;
1980       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1981       // Check all inputs for the ones to peel out
1982       uint j = 1;
1983       for( uint i = 2; i < n->req(); i++ ) {
1984         if( i != hot_idx )
1985           phi->set_req( j++, n->in(i) );
1986         else hot_phi = n->in(i);
1987       }
1988       // Register the phi but do not transform until whole place transforms
1989       igvn.register_new_node_with_optimizer(phi, n);
1990       // Add the merge phi to the old Phi
1991       while( n->req() > 3 ) n->del_req( n->req()-1 );
1992       igvn.replace_input_of(n, 2, phi);
1993       if( hot_idx ) n->add_req(hot_phi);
1994     }
1995   }
1996 
1997 
1998   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
1999   // of self loop tree.  Turn self into a loop headed by _head and with
2000   // tail being the new merge point.
2001   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
2002   phase->set_loop(_tail,ilt);   // Adjust tail
2003   _tail = r;                    // Self's tail is new merge point
2004   phase->set_loop(r,this);
2005   ilt->_child = _child;         // New guy has my children
2006   _child = ilt;                 // Self has new guy as only child
2007   ilt->_parent = this;          // new guy has self for parent
2008   ilt->_nest = _nest;           // Same nesting depth (for now)
2009 
2010   // Starting with 'ilt', look for child loop trees using the same shared
2011   // header.  Flatten these out; they will no longer be loops in the end.
2012   IdealLoopTree **pilt = &_child;
2013   while( ilt ) {
2014     if( ilt->_head == _head ) {
2015       uint i;
2016       for( i = 2; i < _head->req(); i++ )
2017         if( _head->in(i) == ilt->_tail )
2018           break;                // Still a loop
2019       if( i == _head->req() ) { // No longer a loop
2020         // Flatten ilt.  Hang ilt's "_next" list from the end of
2021         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
2022         IdealLoopTree **cp = &ilt->_child;
2023         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
2024         *cp = ilt->_next;       // Hang next list at end of child list
2025         *pilt = ilt->_child;    // Move child up to replace ilt
2026         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
2027         ilt = ilt->_child;      // Repeat using new ilt
2028         continue;               // do not advance over ilt->_child
2029       }
2030       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
2031       phase->set_loop(_head,ilt);
2032     }
2033     pilt = &ilt->_child;        // Advance to next
2034     ilt = *pilt;
2035   }
2036 
2037   if( _child ) fix_parent( _child, this );
2038 }
2039 
2040 //------------------------------beautify_loops---------------------------------
2041 // Split shared headers and insert loop landing pads.
2042 // Insert a LoopNode to replace the RegionNode.
2043 // Return TRUE if loop tree is structurally changed.
2044 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
2045   bool result = false;
2046   // Cache parts in locals for easy
2047   PhaseIterGVN &igvn = phase->_igvn;
2048 
2049   igvn.hash_delete(_head);      // Yank from hash before hacking edges
2050 
2051   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
2052   int fall_in_cnt = 0;
2053   for( uint i = 1; i < _head->req(); i++ )
2054     if( !phase->is_member( this, _head->in(i) ) )
2055       fall_in_cnt++;
2056   assert( fall_in_cnt, "at least 1 fall-in path" );
2057   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
2058     split_fall_in( phase, fall_in_cnt );
2059 
2060   // Swap inputs to the _head and all Phis to move the fall-in edge to
2061   // the left.
2062   fall_in_cnt = 1;
2063   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
2064     fall_in_cnt++;
2065   if( fall_in_cnt > 1 ) {
2066     // Since I am just swapping inputs I do not need to update def-use info
2067     Node *tmp = _head->in(1);
2068     igvn.rehash_node_delayed(_head);
2069     _head->set_req( 1, _head->in(fall_in_cnt) );
2070     _head->set_req( fall_in_cnt, tmp );
2071     // Swap also all Phis
2072     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
2073       Node* phi = _head->fast_out(i);
2074       if( phi->is_Phi() ) {
2075         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
2076         tmp = phi->in(1);
2077         phi->set_req( 1, phi->in(fall_in_cnt) );
2078         phi->set_req( fall_in_cnt, tmp );
2079       }
2080     }
2081   }
2082   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
2083   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
2084 
2085   // If I am a shared header (multiple backedges), peel off the many
2086   // backedges into a private merge point and use the merge point as
2087   // the one true backedge.
2088   if( _head->req() > 3 ) {
2089     // Merge the many backedges into a single backedge but leave
2090     // the hottest backedge as separate edge for the following peel.
2091     merge_many_backedges( phase );
2092     result = true;
2093   }
2094 
2095   // If I have one hot backedge, peel off myself loop.
2096   // I better be the outermost loop.
2097   if (_head->req() > 3 && !_irreducible) {
2098     split_outer_loop( phase );
2099     result = true;
2100 
2101   } else if (!_head->is_Loop() && !_irreducible) {
2102     // Make a new LoopNode to replace the old loop head
2103     Node *l = new LoopNode( _head->in(1), _head->in(2) );
2104     l = igvn.register_new_node_with_optimizer(l, _head);
2105     phase->set_created_loop_node();
2106     // Go ahead and replace _head
2107     phase->_igvn.replace_node( _head, l );
2108     _head = l;
2109     phase->set_loop(_head, this);
2110   }
2111 
2112   // Now recursively beautify nested loops
2113   if( _child ) result |= _child->beautify_loops( phase );
2114   if( _next  ) result |= _next ->beautify_loops( phase );
2115   return result;
2116 }
2117 
2118 //------------------------------allpaths_check_safepts----------------------------
2119 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
2120 // encountered.  Helper for check_safepts.
2121 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
2122   assert(stack.size() == 0, "empty stack");
2123   stack.push(_tail);
2124   visited.clear();
2125   visited.set(_tail->_idx);
2126   while (stack.size() > 0) {
2127     Node* n = stack.pop();
2128     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2129       // Terminate this path
2130     } else if (n->Opcode() == Op_SafePoint) {
2131       if (_phase->get_loop(n) != this) {
2132         if (_required_safept == NULL) _required_safept = new Node_List();
2133         _required_safept->push(n);  // save the one closest to the tail
2134       }
2135       // Terminate this path
2136     } else {
2137       uint start = n->is_Region() ? 1 : 0;
2138       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
2139       for (uint i = start; i < end; i++) {
2140         Node* in = n->in(i);
2141         assert(in->is_CFG(), "must be");
2142         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
2143           stack.push(in);
2144         }
2145       }
2146     }
2147   }
2148 }
2149 
2150 //------------------------------check_safepts----------------------------
2151 // Given dominators, try to find loops with calls that must always be
2152 // executed (call dominates loop tail).  These loops do not need non-call
2153 // safepoints (ncsfpt).
2154 //
2155 // A complication is that a safepoint in a inner loop may be needed
2156 // by an outer loop. In the following, the inner loop sees it has a
2157 // call (block 3) on every path from the head (block 2) to the
2158 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
2159 // in block 2, _but_ this leaves the outer loop without a safepoint.
2160 //
2161 //          entry  0
2162 //                 |
2163 //                 v
2164 // outer 1,2    +->1
2165 //              |  |
2166 //              |  v
2167 //              |  2<---+  ncsfpt in 2
2168 //              |_/|\   |
2169 //                 | v  |
2170 // inner 2,3      /  3  |  call in 3
2171 //               /   |  |
2172 //              v    +--+
2173 //        exit  4
2174 //
2175 //
2176 // This method creates a list (_required_safept) of ncsfpt nodes that must
2177 // be protected is created for each loop. When a ncsfpt maybe deleted, it
2178 // is first looked for in the lists for the outer loops of the current loop.
2179 //
2180 // The insights into the problem:
2181 //  A) counted loops are okay
2182 //  B) innermost loops are okay (only an inner loop can delete
2183 //     a ncsfpt needed by an outer loop)
2184 //  C) a loop is immune from an inner loop deleting a safepoint
2185 //     if the loop has a call on the idom-path
2186 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
2187 //     idom-path that is not in a nested loop
2188 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
2189 //     loop needs to be prevented from deletion by an inner loop
2190 //
2191 // There are two analyses:
2192 //  1) The first, and cheaper one, scans the loop body from
2193 //     tail to head following the idom (immediate dominator)
2194 //     chain, looking for the cases (C,D,E) above.
2195 //     Since inner loops are scanned before outer loops, there is summary
2196 //     information about inner loops.  Inner loops can be skipped over
2197 //     when the tail of an inner loop is encountered.
2198 //
2199 //  2) The second, invoked if the first fails to find a call or ncsfpt on
2200 //     the idom path (which is rare), scans all predecessor control paths
2201 //     from the tail to the head, terminating a path when a call or sfpt
2202 //     is encountered, to find the ncsfpt's that are closest to the tail.
2203 //
2204 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
2205   // Bottom up traversal
2206   IdealLoopTree* ch = _child;
2207   if (_child) _child->check_safepts(visited, stack);
2208   if (_next)  _next ->check_safepts(visited, stack);
2209 
2210   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
2211     bool  has_call         = false; // call on dom-path
2212     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
2213     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
2214     // Scan the dom-path nodes from tail to head
2215     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
2216       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
2217         has_call = true;
2218         _has_sfpt = 1;          // Then no need for a safept!
2219         break;
2220       } else if (n->Opcode() == Op_SafePoint) {
2221         if (_phase->get_loop(n) == this) {
2222           has_local_ncsfpt = true;
2223           break;
2224         }
2225         if (nonlocal_ncsfpt == NULL) {
2226           nonlocal_ncsfpt = n; // save the one closest to the tail
2227         }
2228       } else {
2229         IdealLoopTree* nlpt = _phase->get_loop(n);
2230         if (this != nlpt) {
2231           // If at an inner loop tail, see if the inner loop has already
2232           // recorded seeing a call on the dom-path (and stop.)  If not,
2233           // jump to the head of the inner loop.
2234           assert(is_member(nlpt), "nested loop");
2235           Node* tail = nlpt->_tail;
2236           if (tail->in(0)->is_If()) tail = tail->in(0);
2237           if (n == tail) {
2238             // If inner loop has call on dom-path, so does outer loop
2239             if (nlpt->_has_sfpt) {
2240               has_call = true;
2241               _has_sfpt = 1;
2242               break;
2243             }
2244             // Skip to head of inner loop
2245             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
2246             n = nlpt->_head;
2247           }
2248         }
2249       }
2250     }
2251     // Record safept's that this loop needs preserved when an
2252     // inner loop attempts to delete it's safepoints.
2253     if (_child != NULL && !has_call && !has_local_ncsfpt) {
2254       if (nonlocal_ncsfpt != NULL) {
2255         if (_required_safept == NULL) _required_safept = new Node_List();
2256         _required_safept->push(nonlocal_ncsfpt);
2257       } else {
2258         // Failed to find a suitable safept on the dom-path.  Now use
2259         // an all paths walk from tail to head, looking for safepoints to preserve.
2260         allpaths_check_safepts(visited, stack);
2261       }
2262     }
2263   }
2264 }
2265 
2266 //---------------------------is_deleteable_safept----------------------------
2267 // Is safept not required by an outer loop?
2268 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
2269   assert(sfpt->Opcode() == Op_SafePoint, "");
2270   IdealLoopTree* lp = get_loop(sfpt)->_parent;
2271   while (lp != NULL) {
2272     Node_List* sfpts = lp->_required_safept;
2273     if (sfpts != NULL) {
2274       for (uint i = 0; i < sfpts->size(); i++) {
2275         if (sfpt == sfpts->at(i))
2276           return false;
2277       }
2278     }
2279     lp = lp->_parent;
2280   }
2281   return true;
2282 }
2283 
2284 //---------------------------replace_parallel_iv-------------------------------
2285 // Replace parallel induction variable (parallel to trip counter)
2286 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
2287   assert(loop->_head->is_CountedLoop(), "");
2288   CountedLoopNode *cl = loop->_head->as_CountedLoop();
2289   if (!cl->is_valid_counted_loop())
2290     return;         // skip malformed counted loop
2291   Node *incr = cl->incr();
2292   if (incr == NULL)
2293     return;         // Dead loop?
2294   Node *init = cl->init_trip();
2295   Node *phi  = cl->phi();
2296   int stride_con = cl->stride_con();
2297 
2298   // Visit all children, looking for Phis
2299   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
2300     Node *out = cl->out(i);
2301     // Look for other phis (secondary IVs). Skip dead ones
2302     if (!out->is_Phi() || out == phi || !has_node(out))
2303       continue;
2304     PhiNode* phi2 = out->as_Phi();
2305     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
2306     // Look for induction variables of the form:  X += constant
2307     if (phi2->region() != loop->_head ||
2308         incr2->req() != 3 ||
2309         incr2->in(1) != phi2 ||
2310         incr2 == incr ||
2311         incr2->Opcode() != Op_AddI ||
2312         !incr2->in(2)->is_Con())
2313       continue;
2314 
2315     // Check for parallel induction variable (parallel to trip counter)
2316     // via an affine function.  In particular, count-down loops with
2317     // count-up array indices are common. We only RCE references off
2318     // the trip-counter, so we need to convert all these to trip-counter
2319     // expressions.
2320     Node *init2 = phi2->in( LoopNode::EntryControl );
2321     int stride_con2 = incr2->in(2)->get_int();
2322 
2323     // The ratio of the two strides cannot be represented as an int
2324     // if stride_con2 is min_int and stride_con is -1.
2325     if (stride_con2 == min_jint && stride_con == -1) {
2326       continue;
2327     }
2328 
2329     // The general case here gets a little tricky.  We want to find the
2330     // GCD of all possible parallel IV's and make a new IV using this
2331     // GCD for the loop.  Then all possible IVs are simple multiples of
2332     // the GCD.  In practice, this will cover very few extra loops.
2333     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
2334     // where +/-1 is the common case, but other integer multiples are
2335     // also easy to handle.
2336     int ratio_con = stride_con2/stride_con;
2337 
2338     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
2339 #ifndef PRODUCT
2340       if (TraceLoopOpts) {
2341         tty->print("Parallel IV: %d ", phi2->_idx);
2342         loop->dump_head();
2343       }
2344 #endif
2345       // Convert to using the trip counter.  The parallel induction
2346       // variable differs from the trip counter by a loop-invariant
2347       // amount, the difference between their respective initial values.
2348       // It is scaled by the 'ratio_con'.
2349       Node* ratio = _igvn.intcon(ratio_con);
2350       set_ctrl(ratio, C->root());
2351       Node* ratio_init = new MulINode(init, ratio);
2352       _igvn.register_new_node_with_optimizer(ratio_init, init);
2353       set_early_ctrl(ratio_init);
2354       Node* diff = new SubINode(init2, ratio_init);
2355       _igvn.register_new_node_with_optimizer(diff, init2);
2356       set_early_ctrl(diff);
2357       Node* ratio_idx = new MulINode(phi, ratio);
2358       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
2359       set_ctrl(ratio_idx, cl);
2360       Node* add = new AddINode(ratio_idx, diff);
2361       _igvn.register_new_node_with_optimizer(add);
2362       set_ctrl(add, cl);
2363       _igvn.replace_node( phi2, add );
2364       // Sometimes an induction variable is unused
2365       if (add->outcnt() == 0) {
2366         _igvn.remove_dead_node(add);
2367       }
2368       --i; // deleted this phi; rescan starting with next position
2369       continue;
2370     }
2371   }
2372 }
2373 
2374 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
2375   Node* keep = NULL;
2376   if (keep_one) {
2377     // Look for a safepoint on the idom-path.
2378     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
2379       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
2380         keep = i;
2381         break; // Found one
2382       }
2383     }
2384   }
2385 
2386   // Don't remove any safepoints if it is requested to keep a single safepoint and
2387   // no safepoint was found on idom-path. It is not safe to remove any safepoint
2388   // in this case since there's no safepoint dominating all paths in the loop body.
2389   bool prune = !keep_one || keep != NULL;
2390 
2391   // Delete other safepoints in this loop.
2392   Node_List* sfpts = _safepts;
2393   if (prune && sfpts != NULL) {
2394     assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
2395     for (uint i = 0; i < sfpts->size(); i++) {
2396       Node* n = sfpts->at(i);
2397       assert(phase->get_loop(n) == this, "");
2398       if (n != keep && phase->is_deleteable_safept(n)) {
2399         phase->lazy_replace(n, n->in(TypeFunc::Control));
2400       }
2401     }
2402   }
2403 }
2404 
2405 //------------------------------counted_loop-----------------------------------
2406 // Convert to counted loops where possible
2407 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
2408 
2409   // For grins, set the inner-loop flag here
2410   if (!_child) {
2411     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
2412   }
2413 
2414   IdealLoopTree* loop = this;
2415   if (_head->is_CountedLoop() ||
2416       phase->is_counted_loop(_head, loop)) {
2417 
2418     if (LoopStripMiningIter == 0 || (LoopStripMiningIter > 1 && _child == NULL)) {
2419       // Indicate we do not need a safepoint here
2420       _has_sfpt = 1;
2421     }
2422 
2423     // Remove safepoints
2424     bool keep_one_sfpt = !(_has_call || _has_sfpt);
2425     remove_safepoints(phase, keep_one_sfpt);
2426 
2427     // Look for induction variables
2428     phase->replace_parallel_iv(this);
2429 
2430   } else if (_parent != NULL && !_irreducible) {
2431     // Not a counted loop. Keep one safepoint.
2432     bool keep_one_sfpt = true;
2433     remove_safepoints(phase, keep_one_sfpt);
2434   }
2435 
2436   // Recursively
2437   assert(loop->_child != this || (loop->_head->as_Loop()->is_OuterStripMinedLoop() && _head->as_CountedLoop()->is_strip_mined()), "what kind of loop was added?");
2438   assert(loop->_child != this || (loop->_child->_child == NULL && loop->_child->_next == NULL), "would miss some loops");
2439   if (loop->_child && loop->_child != this) loop->_child->counted_loop(phase);
2440   if (loop->_next)  loop->_next ->counted_loop(phase);
2441 }
2442 
2443 
2444 // The Estimated Loop Clone Size:
2445 //   CloneFactor * (~112% * BodySize + BC) + CC + FanOutTerm,
2446 // where  BC and  CC are  totally ad-hoc/magic  "body" and "clone" constants,
2447 // respectively, used to ensure that the node usage estimates made are on the
2448 // safe side, for the most part. The FanOutTerm is an attempt to estimate the
2449 // possible additional/excessive nodes generated due to data and control flow
2450 // merging, for edges reaching outside the loop.
2451 uint IdealLoopTree::est_loop_clone_sz(uint factor) const {
2452 
2453   precond(0 < factor && factor < 16);
2454 
2455   uint const bc = 13;
2456   uint const cc = 17;
2457   uint const sz = _body.size() + (_body.size() + 7) / 8;
2458   uint estimate = factor * (sz + bc) + cc;
2459 
2460   assert((estimate - cc) / factor == sz + bc, "overflow");
2461 
2462   return estimate + est_loop_flow_merge_sz();
2463 }
2464 
2465 // The Estimated Loop (full-) Unroll Size:
2466 //   UnrollFactor * (~106% * BodySize) + CC + FanOutTerm,
2467 // where CC is a (totally) ad-hoc/magic "clone" constant, used to ensure that
2468 // node usage estimates made are on the safe side, for the most part. This is
2469 // a "light" version of the loop clone size calculation (above), based on the
2470 // assumption that most of the loop-construct overhead will be unraveled when
2471 // (fully) unrolled. Defined for unroll factors larger or equal to one (>=1),
2472 // including an overflow check and returning UINT_MAX in case of an overflow.
2473 uint IdealLoopTree::est_loop_unroll_sz(uint factor) const {
2474 
2475   precond(factor > 0);
2476 
2477   // Take into account that after unroll conjoined heads and tails will fold.
2478   uint const b0 = _body.size() - EMPTY_LOOP_SIZE;
2479   uint const cc = 7;
2480   uint const sz = b0 + (b0 + 15) / 16;
2481   uint estimate = factor * sz + cc;
2482 
2483   if ((estimate - cc) / factor != sz) {
2484     return UINT_MAX;
2485   }
2486 
2487   return estimate + est_loop_flow_merge_sz();
2488 }
2489 
2490 // Estimate the growth effect (in nodes) of merging control and data flow when
2491 // cloning a loop body, based on the amount of  control and data flow reaching
2492 // outside of the (current) loop body.
2493 uint IdealLoopTree::est_loop_flow_merge_sz() const {
2494 
2495   uint ctrl_edge_out_cnt = 0;
2496   uint data_edge_out_cnt = 0;
2497 
2498   for (uint i = 0; i < _body.size(); i++) {
2499     Node* node = _body.at(i);
2500     uint outcnt = node->outcnt();
2501 
2502     for (uint k = 0; k < outcnt; k++) {
2503       Node* out = node->raw_out(k);
2504 
2505       if (out->is_CFG()) {
2506         if (!is_member(_phase->get_loop(out))) {
2507           ctrl_edge_out_cnt++;
2508         }
2509       } else {
2510         Node* ctrl = _phase->get_ctrl(out);
2511         assert(ctrl->is_CFG(), "must be");
2512         if (!is_member(_phase->get_loop(ctrl))) {
2513           data_edge_out_cnt++;
2514         }
2515       }
2516     }
2517   }
2518   // Use data and control count (x2.0) in estimate iff both are > 0. This is
2519   // a rather pessimistic estimate for the most part, in particular for some
2520   // complex loops, but still not enough to capture all loops.
2521   if (ctrl_edge_out_cnt > 0 && data_edge_out_cnt > 0) {
2522     return 2 * (ctrl_edge_out_cnt + data_edge_out_cnt);
2523   }
2524   return 0;
2525 }
2526 
2527 #ifndef PRODUCT
2528 //------------------------------dump_head--------------------------------------
2529 // Dump 1 liner for loop header info
2530 void IdealLoopTree::dump_head() const {
2531   tty->sp(2 * _nest);
2532   tty->print("Loop: N%d/N%d ", _head->_idx, _tail->_idx);
2533   if (_irreducible) tty->print(" IRREDUCIBLE");
2534   Node* entry = _head->is_Loop() ? _head->as_Loop()->skip_strip_mined(-1)->in(LoopNode::EntryControl) : _head->in(LoopNode::EntryControl);
2535   Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
2536   if (predicate != NULL ) {
2537     tty->print(" limit_check");
2538     entry = PhaseIdealLoop::skip_loop_predicates(entry);
2539   }
2540   if (UseLoopPredicate) {
2541     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
2542     if (entry != NULL) {
2543       tty->print(" predicated");
2544       entry = PhaseIdealLoop::skip_loop_predicates(entry);
2545     }
2546   }
2547   if (UseProfiledLoopPredicate) {
2548     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
2549     if (entry != NULL) {
2550       tty->print(" profile_predicated");
2551     }
2552   }
2553   if (_head->is_CountedLoop()) {
2554     CountedLoopNode *cl = _head->as_CountedLoop();
2555     tty->print(" counted");
2556 
2557     Node* init_n = cl->init_trip();
2558     if (init_n  != NULL &&  init_n->is_Con())
2559       tty->print(" [%d,", cl->init_trip()->get_int());
2560     else
2561       tty->print(" [int,");
2562     Node* limit_n = cl->limit();
2563     if (limit_n  != NULL &&  limit_n->is_Con())
2564       tty->print("%d),", cl->limit()->get_int());
2565     else
2566       tty->print("int),");
2567     int stride_con  = cl->stride_con();
2568     if (stride_con > 0) tty->print("+");
2569     tty->print("%d", stride_con);
2570 
2571     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
2572 
2573     if (cl->is_pre_loop ()) tty->print(" pre" );
2574     if (cl->is_main_loop()) tty->print(" main");
2575     if (cl->is_post_loop()) tty->print(" post");
2576     if (cl->is_vectorized_loop()) tty->print(" vector");
2577     if (cl->range_checks_present()) tty->print(" rc ");
2578     if (cl->is_multiversioned()) tty->print(" multi ");
2579   }
2580   if (_has_call) tty->print(" has_call");
2581   if (_has_sfpt) tty->print(" has_sfpt");
2582   if (_rce_candidate) tty->print(" rce");
2583   if (_safepts != NULL && _safepts->size() > 0) {
2584     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
2585   }
2586   if (_required_safept != NULL && _required_safept->size() > 0) {
2587     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
2588   }
2589   if (Verbose) {
2590     tty->print(" body={"); _body.dump_simple(); tty->print(" }");
2591   }
2592   if (_head->is_Loop() && _head->as_Loop()->is_strip_mined()) {
2593     tty->print(" strip_mined");
2594   }
2595   tty->cr();
2596 }
2597 
2598 //------------------------------dump-------------------------------------------
2599 // Dump loops by loop tree
2600 void IdealLoopTree::dump() const {
2601   dump_head();
2602   if (_child) _child->dump();
2603   if (_next)  _next ->dump();
2604 }
2605 
2606 #endif
2607 
2608 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
2609   if (loop == root) {
2610     if (loop->_child != NULL) {
2611       log->begin_head("loop_tree");
2612       log->end_head();
2613       if( loop->_child ) log_loop_tree(root, loop->_child, log);
2614       log->tail("loop_tree");
2615       assert(loop->_next == NULL, "what?");
2616     }
2617   } else {
2618     Node* head = loop->_head;
2619     log->begin_head("loop");
2620     log->print(" idx='%d' ", head->_idx);
2621     if (loop->_irreducible) log->print("irreducible='1' ");
2622     if (head->is_Loop()) {
2623       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
2624       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
2625     }
2626     if (head->is_CountedLoop()) {
2627       CountedLoopNode* cl = head->as_CountedLoop();
2628       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
2629       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
2630       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
2631     }
2632     log->end_head();
2633     if( loop->_child ) log_loop_tree(root, loop->_child, log);
2634     log->tail("loop");
2635     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
2636   }
2637 }
2638 
2639 //---------------------collect_potentially_useful_predicates-----------------------
2640 // Helper function to collect potentially useful predicates to prevent them from
2641 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
2642 void PhaseIdealLoop::collect_potentially_useful_predicates(
2643                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
2644   if (loop->_child) { // child
2645     collect_potentially_useful_predicates(loop->_child, useful_predicates);
2646   }
2647 
2648   // self (only loops that we can apply loop predication may use their predicates)
2649   if (loop->_head->is_Loop() &&
2650       !loop->_irreducible    &&
2651       !loop->tail()->is_top()) {
2652     LoopNode* lpn = loop->_head->as_Loop();
2653     Node* entry = lpn->in(LoopNode::EntryControl);
2654     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2655     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2656       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2657       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2658       entry = skip_loop_predicates(entry);
2659     }
2660     predicate_proj = find_predicate(entry); // Predicate
2661     if (predicate_proj != NULL ) {
2662       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2663       entry = skip_loop_predicates(entry);
2664     }
2665     if (UseProfiledLoopPredicate) {
2666       predicate_proj = find_predicate(entry); // Predicate
2667       if (predicate_proj != NULL ) {
2668         useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2669       }
2670     }
2671   }
2672 
2673   if (loop->_next) { // sibling
2674     collect_potentially_useful_predicates(loop->_next, useful_predicates);
2675   }
2676 }
2677 
2678 //------------------------eliminate_useless_predicates-----------------------------
2679 // Eliminate all inserted predicates if they could not be used by loop predication.
2680 // Note: it will also eliminates loop limits check predicate since it also uses
2681 // Opaque1 node (see Parse::add_predicate()).
2682 void PhaseIdealLoop::eliminate_useless_predicates() {
2683   if (C->predicate_count() == 0)
2684     return; // no predicate left
2685 
2686   Unique_Node_List useful_predicates; // to store useful predicates
2687   if (C->has_loops()) {
2688     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2689   }
2690 
2691   for (int i = C->predicate_count(); i > 0; i--) {
2692      Node * n = C->predicate_opaque1_node(i-1);
2693      assert(n->Opcode() == Op_Opaque1, "must be");
2694      if (!useful_predicates.member(n)) { // not in the useful list
2695        _igvn.replace_node(n, n->in(1));
2696      }
2697   }
2698 }
2699 
2700 //------------------------process_expensive_nodes-----------------------------
2701 // Expensive nodes have their control input set to prevent the GVN
2702 // from commoning them and as a result forcing the resulting node to
2703 // be in a more frequent path. Use CFG information here, to change the
2704 // control inputs so that some expensive nodes can be commoned while
2705 // not executed more frequently.
2706 bool PhaseIdealLoop::process_expensive_nodes() {
2707   assert(OptimizeExpensiveOps, "optimization off?");
2708 
2709   // Sort nodes to bring similar nodes together
2710   C->sort_expensive_nodes();
2711 
2712   bool progress = false;
2713 
2714   for (int i = 0; i < C->expensive_count(); ) {
2715     Node* n = C->expensive_node(i);
2716     int start = i;
2717     // Find nodes similar to n
2718     i++;
2719     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2720     int end = i;
2721     // And compare them two by two
2722     for (int j = start; j < end; j++) {
2723       Node* n1 = C->expensive_node(j);
2724       if (is_node_unreachable(n1)) {
2725         continue;
2726       }
2727       for (int k = j+1; k < end; k++) {
2728         Node* n2 = C->expensive_node(k);
2729         if (is_node_unreachable(n2)) {
2730           continue;
2731         }
2732 
2733         assert(n1 != n2, "should be pair of nodes");
2734 
2735         Node* c1 = n1->in(0);
2736         Node* c2 = n2->in(0);
2737 
2738         Node* parent_c1 = c1;
2739         Node* parent_c2 = c2;
2740 
2741         // The call to get_early_ctrl_for_expensive() moves the
2742         // expensive nodes up but stops at loops that are in a if
2743         // branch. See whether we can exit the loop and move above the
2744         // If.
2745         if (c1->is_Loop()) {
2746           parent_c1 = c1->in(1);
2747         }
2748         if (c2->is_Loop()) {
2749           parent_c2 = c2->in(1);
2750         }
2751 
2752         if (parent_c1 == parent_c2) {
2753           _igvn._worklist.push(n1);
2754           _igvn._worklist.push(n2);
2755           continue;
2756         }
2757 
2758         // Look for identical expensive node up the dominator chain.
2759         if (is_dominator(c1, c2)) {
2760           c2 = c1;
2761         } else if (is_dominator(c2, c1)) {
2762           c1 = c2;
2763         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2764                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2765           // Both branches have the same expensive node so move it up
2766           // before the if.
2767           c1 = c2 = idom(parent_c1->in(0));
2768         }
2769         // Do the actual moves
2770         if (n1->in(0) != c1) {
2771           _igvn.hash_delete(n1);
2772           n1->set_req(0, c1);
2773           _igvn.hash_insert(n1);
2774           _igvn._worklist.push(n1);
2775           progress = true;
2776         }
2777         if (n2->in(0) != c2) {
2778           _igvn.hash_delete(n2);
2779           n2->set_req(0, c2);
2780           _igvn.hash_insert(n2);
2781           _igvn._worklist.push(n2);
2782           progress = true;
2783         }
2784       }
2785     }
2786   }
2787 
2788   return progress;
2789 }
2790 
2791 
2792 //=============================================================================
2793 //----------------------------build_and_optimize-------------------------------
2794 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2795 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2796 void PhaseIdealLoop::build_and_optimize(LoopOptsMode mode) {
2797   bool do_split_ifs = (mode == LoopOptsDefault);
2798   bool skip_loop_opts = (mode == LoopOptsNone);
2799 
2800   int old_progress = C->major_progress();
2801   uint orig_worklist_size = _igvn._worklist.size();
2802 
2803   // Reset major-progress flag for the driver's heuristics
2804   C->clear_major_progress();
2805 
2806 #ifndef PRODUCT
2807   // Capture for later assert
2808   uint unique = C->unique();
2809   _loop_invokes++;
2810   _loop_work += unique;
2811 #endif
2812 
2813   // True if the method has at least 1 irreducible loop
2814   _has_irreducible_loops = false;
2815 
2816   _created_loop_node = false;
2817 
2818   Arena *a = Thread::current()->resource_area();
2819   VectorSet visited(a);
2820   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2821   _nodes.map(C->unique(), NULL);
2822   memset(_nodes.adr(), 0, wordSize * C->unique());
2823 
2824   // Pre-build the top-level outermost loop tree entry
2825   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2826   // Do not need a safepoint at the top level
2827   _ltree_root->_has_sfpt = 1;
2828 
2829   // Initialize Dominators.
2830   // Checked in clone_loop_predicate() during beautify_loops().
2831   _idom_size = 0;
2832   _idom      = NULL;
2833   _dom_depth = NULL;
2834   _dom_stk   = NULL;
2835 
2836   // Empty pre-order array
2837   allocate_preorders();
2838 
2839   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2840   // IdealLoopTree entries.  Data nodes are NOT walked.
2841   build_loop_tree();
2842   // Check for bailout, and return
2843   if (C->failing()) {
2844     return;
2845   }
2846 
2847   // No loops after all
2848   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2849 
2850   // There should always be an outer loop containing the Root and Return nodes.
2851   // If not, we have a degenerate empty program.  Bail out in this case.
2852   if (!has_node(C->root())) {
2853     if (!_verify_only) {
2854       C->clear_major_progress();
2855       C->record_method_not_compilable("empty program detected during loop optimization");
2856     }
2857     return;
2858   }
2859 
2860   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
2861   // Nothing to do, so get out
2862   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only &&
2863     !bs->is_gc_specific_loop_opts_pass(mode);
2864   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2865   bool strip_mined_loops_expanded = bs->strip_mined_loops_expanded(mode);
2866   if (stop_early && !do_expensive_nodes) {
2867     _igvn.optimize();           // Cleanup NeverBranches
2868     return;
2869   }
2870 
2871   // Set loop nesting depth
2872   _ltree_root->set_nest( 0 );
2873 
2874   // Split shared headers and insert loop landing pads.
2875   // Do not bother doing this on the Root loop of course.
2876   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2877     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2878     if( _ltree_root->_child->beautify_loops( this ) ) {
2879       // Re-build loop tree!
2880       _ltree_root->_child = NULL;
2881       _nodes.clear();
2882       reallocate_preorders();
2883       build_loop_tree();
2884       // Check for bailout, and return
2885       if (C->failing()) {
2886         return;
2887       }
2888       // Reset loop nesting depth
2889       _ltree_root->set_nest( 0 );
2890 
2891       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2892     }
2893   }
2894 
2895   // Build Dominators for elision of NULL checks & loop finding.
2896   // Since nodes do not have a slot for immediate dominator, make
2897   // a persistent side array for that info indexed on node->_idx.
2898   _idom_size = C->unique();
2899   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2900   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2901   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2902   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2903 
2904   Dominators();
2905 
2906   if (!_verify_only) {
2907     // As a side effect, Dominators removed any unreachable CFG paths
2908     // into RegionNodes.  It doesn't do this test against Root, so
2909     // we do it here.
2910     for( uint i = 1; i < C->root()->req(); i++ ) {
2911       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2912         _igvn.delete_input_of(C->root(), i);
2913         i--;                      // Rerun same iteration on compressed edges
2914       }
2915     }
2916 
2917     // Given dominators, try to find inner loops with calls that must
2918     // always be executed (call dominates loop tail).  These loops do
2919     // not need a separate safepoint.
2920     Node_List cisstack(a);
2921     _ltree_root->check_safepts(visited, cisstack);
2922   }
2923 
2924   // Walk the DATA nodes and place into loops.  Find earliest control
2925   // node.  For CFG nodes, the _nodes array starts out and remains
2926   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2927   // _nodes array holds the earliest legal controlling CFG node.
2928 
2929   // Allocate stack with enough space to avoid frequent realloc
2930   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2931   Node_Stack nstack( a, stack_size );
2932 
2933   visited.clear();
2934   Node_List worklist(a);
2935   // Don't need C->root() on worklist since
2936   // it will be processed among C->top() inputs
2937   worklist.push(C->top());
2938   visited.set(C->top()->_idx); // Set C->top() as visited now
2939   build_loop_early( visited, worklist, nstack );
2940 
2941   // Given early legal placement, try finding counted loops.  This placement
2942   // is good enough to discover most loop invariants.
2943   if (!_verify_me && !_verify_only && !strip_mined_loops_expanded) {
2944     _ltree_root->counted_loop( this );
2945   }
2946 
2947   // Find latest loop placement.  Find ideal loop placement.
2948   visited.clear();
2949   init_dom_lca_tags();
2950   // Need C->root() on worklist when processing outs
2951   worklist.push(C->root());
2952   NOT_PRODUCT( C->verify_graph_edges(); )
2953   worklist.push(C->top());
2954   build_loop_late( visited, worklist, nstack );
2955 
2956   if (_verify_only) {
2957     C->restore_major_progress(old_progress);
2958     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2959     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2960     return;
2961   }
2962 
2963   // clear out the dead code after build_loop_late
2964   while (_deadlist.size()) {
2965     _igvn.remove_globally_dead_node(_deadlist.pop());
2966   }
2967 
2968   if (stop_early) {
2969     assert(do_expensive_nodes, "why are we here?");
2970     if (process_expensive_nodes()) {
2971       // If we made some progress when processing expensive nodes then
2972       // the IGVN may modify the graph in a way that will allow us to
2973       // make some more progress: we need to try processing expensive
2974       // nodes again.
2975       C->set_major_progress();
2976     }
2977     _igvn.optimize();
2978     return;
2979   }
2980 
2981   // Some parser-inserted loop predicates could never be used by loop
2982   // predication or they were moved away from loop during some optimizations.
2983   // For example, peeling. Eliminate them before next loop optimizations.
2984   eliminate_useless_predicates();
2985 
2986 #ifndef PRODUCT
2987   C->verify_graph_edges();
2988   if (_verify_me) {             // Nested verify pass?
2989     // Check to see if the verify mode is broken
2990     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2991     return;
2992   }
2993   if (VerifyLoopOptimizations) verify();
2994   if (TraceLoopOpts && C->has_loops()) {
2995     _ltree_root->dump();
2996   }
2997 #endif
2998 
2999   if (skip_loop_opts) {
3000     // restore major progress flag
3001     C->restore_major_progress(old_progress);
3002 
3003     // Cleanup any modified bits
3004     _igvn.optimize();
3005 
3006     if (C->log() != NULL) {
3007       log_loop_tree(_ltree_root, _ltree_root, C->log());
3008     }
3009     return;
3010   }
3011 
3012   if (bs->optimize_loops(this, mode, visited, nstack, worklist)) {
3013     _igvn.optimize();
3014     if (C->log() != NULL) {
3015       log_loop_tree(_ltree_root, _ltree_root, C->log());
3016     }
3017     return;
3018   }
3019 
3020   if (ReassociateInvariants) {
3021     // Reassociate invariants and prep for split_thru_phi
3022     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3023       IdealLoopTree* lpt = iter.current();
3024       bool is_counted = lpt->is_counted();
3025       if (!is_counted || !lpt->is_innermost()) continue;
3026 
3027       // check for vectorized loops, any reassociation of invariants was already done
3028       if (is_counted && lpt->_head->as_CountedLoop()->is_unroll_only()) {
3029         continue;
3030       } else {
3031         AutoNodeBudget node_budget(this);
3032         lpt->reassociate_invariants(this);
3033       }
3034       // Because RCE opportunities can be masked by split_thru_phi,
3035       // look for RCE candidates and inhibit split_thru_phi
3036       // on just their loop-phi's for this pass of loop opts
3037       if (SplitIfBlocks && do_split_ifs) {
3038         AutoNodeBudget node_budget(this, AutoNodeBudget::NO_BUDGET_CHECK);
3039         if (lpt->policy_range_check(this)) {
3040           lpt->_rce_candidate = 1; // = true
3041         }
3042       }
3043     }
3044   }
3045 
3046   // Check for aggressive application of split-if and other transforms
3047   // that require basic-block info (like cloning through Phi's)
3048   if( SplitIfBlocks && do_split_ifs ) {
3049     visited.clear();
3050     split_if_with_blocks( visited, nstack);
3051     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
3052   }
3053 
3054   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
3055     C->set_major_progress();
3056   }
3057 
3058   // Perform loop predication before iteration splitting
3059   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
3060     _ltree_root->_child->loop_predication(this);
3061   }
3062 
3063   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
3064     if (do_intrinsify_fill()) {
3065       C->set_major_progress();
3066     }
3067   }
3068 
3069   // Perform iteration-splitting on inner loops.  Split iterations to avoid
3070   // range checks or one-shot null checks.
3071 
3072   // If split-if's didn't hack the graph too bad (no CFG changes)
3073   // then do loop opts.
3074   if (C->has_loops() && !C->major_progress()) {
3075     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
3076     _ltree_root->_child->iteration_split( this, worklist );
3077     // No verify after peeling!  GCM has hoisted code out of the loop.
3078     // After peeling, the hoisted code could sink inside the peeled area.
3079     // The peeling code does not try to recompute the best location for
3080     // all the code before the peeled area, so the verify pass will always
3081     // complain about it.
3082   }
3083   // Do verify graph edges in any case
3084   NOT_PRODUCT( C->verify_graph_edges(); );
3085 
3086   if (!do_split_ifs) {
3087     // We saw major progress in Split-If to get here.  We forced a
3088     // pass with unrolling and not split-if, however more split-if's
3089     // might make progress.  If the unrolling didn't make progress
3090     // then the major-progress flag got cleared and we won't try
3091     // another round of Split-If.  In particular the ever-common
3092     // instance-of/check-cast pattern requires at least 2 rounds of
3093     // Split-If to clear out.
3094     C->set_major_progress();
3095   }
3096 
3097   // Repeat loop optimizations if new loops were seen
3098   if (created_loop_node()) {
3099     C->set_major_progress();
3100   }
3101 
3102   // Keep loop predicates and perform optimizations with them
3103   // until no more loop optimizations could be done.
3104   // After that switch predicates off and do more loop optimizations.
3105   if (!C->major_progress() && (C->predicate_count() > 0)) {
3106      C->cleanup_loop_predicates(_igvn);
3107      if (TraceLoopOpts) {
3108        tty->print_cr("PredicatesOff");
3109      }
3110      C->set_major_progress();
3111   }
3112 
3113   // Convert scalar to superword operations at the end of all loop opts.
3114   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
3115     // SuperWord transform
3116     SuperWord sw(this);
3117     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
3118       IdealLoopTree* lpt = iter.current();
3119       if (lpt->is_counted()) {
3120         CountedLoopNode *cl = lpt->_head->as_CountedLoop();
3121 
3122         if (PostLoopMultiversioning && cl->is_rce_post_loop() && !cl->is_vectorized_loop()) {
3123           // Check that the rce'd post loop is encountered first, multiversion after all
3124           // major main loop optimization are concluded
3125           if (!C->major_progress()) {
3126             IdealLoopTree *lpt_next = lpt->_next;
3127             if (lpt_next && lpt_next->is_counted()) {
3128               CountedLoopNode *cl = lpt_next->_head->as_CountedLoop();
3129               has_range_checks(lpt_next);
3130               if (cl->is_post_loop() && cl->range_checks_present()) {
3131                 if (!cl->is_multiversioned()) {
3132                   if (multi_version_post_loops(lpt, lpt_next) == false) {
3133                     // Cause the rce loop to be optimized away if we fail
3134                     cl->mark_is_multiversioned();
3135                     cl->set_slp_max_unroll(0);
3136                     poison_rce_post_loop(lpt);
3137                   }
3138                 }
3139               }
3140             }
3141             sw.transform_loop(lpt, true);
3142           }
3143         } else if (cl->is_main_loop()) {
3144           sw.transform_loop(lpt, true);
3145         }
3146       }
3147     }
3148   }
3149 
3150   // Cleanup any modified bits
3151   _igvn.optimize();
3152 
3153   // disable assert until issue with split_flow_path is resolved (6742111)
3154   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
3155   //        "shouldn't introduce irreducible loops");
3156 
3157   if (C->log() != NULL) {
3158     log_loop_tree(_ltree_root, _ltree_root, C->log());
3159   }
3160 }
3161 
3162 #ifndef PRODUCT
3163 //------------------------------print_statistics-------------------------------
3164 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
3165 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
3166 void PhaseIdealLoop::print_statistics() {
3167   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
3168 }
3169 
3170 //------------------------------verify-----------------------------------------
3171 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
3172 static int fail;                // debug only, so its multi-thread dont care
3173 void PhaseIdealLoop::verify() const {
3174   int old_progress = C->major_progress();
3175   ResourceMark rm;
3176   PhaseIdealLoop loop_verify( _igvn, this );
3177   VectorSet visited(Thread::current()->resource_area());
3178 
3179   fail = 0;
3180   verify_compare( C->root(), &loop_verify, visited );
3181   assert( fail == 0, "verify loops failed" );
3182   // Verify loop structure is the same
3183   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
3184   // Reset major-progress.  It was cleared by creating a verify version of
3185   // PhaseIdealLoop.
3186   C->restore_major_progress(old_progress);
3187 }
3188 
3189 //------------------------------verify_compare---------------------------------
3190 // Make sure me and the given PhaseIdealLoop agree on key data structures
3191 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
3192   if( !n ) return;
3193   if( visited.test_set( n->_idx ) ) return;
3194   if( !_nodes[n->_idx] ) {      // Unreachable
3195     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
3196     return;
3197   }
3198 
3199   uint i;
3200   for( i = 0; i < n->req(); i++ )
3201     verify_compare( n->in(i), loop_verify, visited );
3202 
3203   // Check the '_nodes' block/loop structure
3204   i = n->_idx;
3205   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
3206     if( _nodes[i] != loop_verify->_nodes[i] &&
3207         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
3208       tty->print("Mismatched control setting for: ");
3209       n->dump();
3210       if( fail++ > 10 ) return;
3211       Node *c = get_ctrl_no_update(n);
3212       tty->print("We have it as: ");
3213       if( c->in(0) ) c->dump();
3214         else tty->print_cr("N%d",c->_idx);
3215       tty->print("Verify thinks: ");
3216       if( loop_verify->has_ctrl(n) )
3217         loop_verify->get_ctrl_no_update(n)->dump();
3218       else
3219         loop_verify->get_loop_idx(n)->dump();
3220       tty->cr();
3221     }
3222   } else {                    // We have a loop
3223     IdealLoopTree *us = get_loop_idx(n);
3224     if( loop_verify->has_ctrl(n) ) {
3225       tty->print("Mismatched loop setting for: ");
3226       n->dump();
3227       if( fail++ > 10 ) return;
3228       tty->print("We have it as: ");
3229       us->dump();
3230       tty->print("Verify thinks: ");
3231       loop_verify->get_ctrl_no_update(n)->dump();
3232       tty->cr();
3233     } else if (!C->major_progress()) {
3234       // Loop selection can be messed up if we did a major progress
3235       // operation, like split-if.  Do not verify in that case.
3236       IdealLoopTree *them = loop_verify->get_loop_idx(n);
3237       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
3238         tty->print("Unequals loops for: ");
3239         n->dump();
3240         if( fail++ > 10 ) return;
3241         tty->print("We have it as: ");
3242         us->dump();
3243         tty->print("Verify thinks: ");
3244         them->dump();
3245         tty->cr();
3246       }
3247     }
3248   }
3249 
3250   // Check for immediate dominators being equal
3251   if( i >= _idom_size ) {
3252     if( !n->is_CFG() ) return;
3253     tty->print("CFG Node with no idom: ");
3254     n->dump();
3255     return;
3256   }
3257   if( !n->is_CFG() ) return;
3258   if( n == C->root() ) return; // No IDOM here
3259 
3260   assert(n->_idx == i, "sanity");
3261   Node *id = idom_no_update(n);
3262   if( id != loop_verify->idom_no_update(n) ) {
3263     tty->print("Unequals idoms for: ");
3264     n->dump();
3265     if( fail++ > 10 ) return;
3266     tty->print("We have it as: ");
3267     id->dump();
3268     tty->print("Verify thinks: ");
3269     loop_verify->idom_no_update(n)->dump();
3270     tty->cr();
3271   }
3272 
3273 }
3274 
3275 //------------------------------verify_tree------------------------------------
3276 // Verify that tree structures match.  Because the CFG can change, siblings
3277 // within the loop tree can be reordered.  We attempt to deal with that by
3278 // reordering the verify's loop tree if possible.
3279 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
3280   assert( _parent == parent, "Badly formed loop tree" );
3281 
3282   // Siblings not in same order?  Attempt to re-order.
3283   if( _head != loop->_head ) {
3284     // Find _next pointer to update
3285     IdealLoopTree **pp = &loop->_parent->_child;
3286     while( *pp != loop )
3287       pp = &((*pp)->_next);
3288     // Find proper sibling to be next
3289     IdealLoopTree **nn = &loop->_next;
3290     while( (*nn) && (*nn)->_head != _head )
3291       nn = &((*nn)->_next);
3292 
3293     // Check for no match.
3294     if( !(*nn) ) {
3295       // Annoyingly, irreducible loops can pick different headers
3296       // after a major_progress operation, so the rest of the loop
3297       // tree cannot be matched.
3298       if (_irreducible && Compile::current()->major_progress())  return;
3299       assert( 0, "failed to match loop tree" );
3300     }
3301 
3302     // Move (*nn) to (*pp)
3303     IdealLoopTree *hit = *nn;
3304     *nn = hit->_next;
3305     hit->_next = loop;
3306     *pp = loop;
3307     loop = hit;
3308     // Now try again to verify
3309   }
3310 
3311   assert( _head  == loop->_head , "mismatched loop head" );
3312   Node *tail = _tail;           // Inline a non-updating version of
3313   while( !tail->in(0) )         // the 'tail()' call.
3314     tail = tail->in(1);
3315   assert( tail == loop->_tail, "mismatched loop tail" );
3316 
3317   // Counted loops that are guarded should be able to find their guards
3318   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
3319     CountedLoopNode *cl = _head->as_CountedLoop();
3320     Node *init = cl->init_trip();
3321     Node *ctrl = cl->in(LoopNode::EntryControl);
3322     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
3323     Node *iff  = ctrl->in(0);
3324     assert( iff->Opcode() == Op_If, "" );
3325     Node *bol  = iff->in(1);
3326     assert( bol->Opcode() == Op_Bool, "" );
3327     Node *cmp  = bol->in(1);
3328     assert( cmp->Opcode() == Op_CmpI, "" );
3329     Node *add  = cmp->in(1);
3330     Node *opaq;
3331     if( add->Opcode() == Op_Opaque1 ) {
3332       opaq = add;
3333     } else {
3334       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
3335       assert( add == init, "" );
3336       opaq = cmp->in(2);
3337     }
3338     assert( opaq->Opcode() == Op_Opaque1, "" );
3339 
3340   }
3341 
3342   if (_child != NULL)  _child->verify_tree(loop->_child, this);
3343   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
3344   // Innermost loops need to verify loop bodies,
3345   // but only if no 'major_progress'
3346   int fail = 0;
3347   if (!Compile::current()->major_progress() && _child == NULL) {
3348     for( uint i = 0; i < _body.size(); i++ ) {
3349       Node *n = _body.at(i);
3350       if (n->outcnt() == 0)  continue; // Ignore dead
3351       uint j;
3352       for( j = 0; j < loop->_body.size(); j++ )
3353         if( loop->_body.at(j) == n )
3354           break;
3355       if( j == loop->_body.size() ) { // Not found in loop body
3356         // Last ditch effort to avoid assertion: Its possible that we
3357         // have some users (so outcnt not zero) but are still dead.
3358         // Try to find from root.
3359         if (Compile::current()->root()->find(n->_idx)) {
3360           fail++;
3361           tty->print("We have that verify does not: ");
3362           n->dump();
3363         }
3364       }
3365     }
3366     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
3367       Node *n = loop->_body.at(i2);
3368       if (n->outcnt() == 0)  continue; // Ignore dead
3369       uint j;
3370       for( j = 0; j < _body.size(); j++ )
3371         if( _body.at(j) == n )
3372           break;
3373       if( j == _body.size() ) { // Not found in loop body
3374         // Last ditch effort to avoid assertion: Its possible that we
3375         // have some users (so outcnt not zero) but are still dead.
3376         // Try to find from root.
3377         if (Compile::current()->root()->find(n->_idx)) {
3378           fail++;
3379           tty->print("Verify has that we do not: ");
3380           n->dump();
3381         }
3382       }
3383     }
3384     assert( !fail, "loop body mismatch" );
3385   }
3386 }
3387 
3388 #endif
3389 
3390 //------------------------------set_idom---------------------------------------
3391 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
3392   uint idx = d->_idx;
3393   if (idx >= _idom_size) {
3394     uint newsize = next_power_of_2(idx);
3395     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
3396     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
3397     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
3398     _idom_size = newsize;
3399   }
3400   _idom[idx] = n;
3401   _dom_depth[idx] = dom_depth;
3402 }
3403 
3404 //------------------------------recompute_dom_depth---------------------------------------
3405 // The dominator tree is constructed with only parent pointers.
3406 // This recomputes the depth in the tree by first tagging all
3407 // nodes as "no depth yet" marker.  The next pass then runs up
3408 // the dom tree from each node marked "no depth yet", and computes
3409 // the depth on the way back down.
3410 void PhaseIdealLoop::recompute_dom_depth() {
3411   uint no_depth_marker = C->unique();
3412   uint i;
3413   // Initialize depth to "no depth yet" and realize all lazy updates
3414   for (i = 0; i < _idom_size; i++) {
3415     // Only indices with a _dom_depth has a Node* or NULL (otherwise uninitalized).
3416     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
3417       _dom_depth[i] = no_depth_marker;
3418 
3419       // heal _idom if it has a fwd mapping in _nodes
3420       if (_idom[i]->in(0) == NULL) {
3421         idom(i);
3422       }
3423     }
3424   }
3425   if (_dom_stk == NULL) {
3426     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
3427     if (init_size < 10) init_size = 10;
3428     _dom_stk = new GrowableArray<uint>(init_size);
3429   }
3430   // Compute new depth for each node.
3431   for (i = 0; i < _idom_size; i++) {
3432     uint j = i;
3433     // Run up the dom tree to find a node with a depth
3434     while (_dom_depth[j] == no_depth_marker) {
3435       _dom_stk->push(j);
3436       j = _idom[j]->_idx;
3437     }
3438     // Compute the depth on the way back down this tree branch
3439     uint dd = _dom_depth[j] + 1;
3440     while (_dom_stk->length() > 0) {
3441       uint j = _dom_stk->pop();
3442       _dom_depth[j] = dd;
3443       dd++;
3444     }
3445   }
3446 }
3447 
3448 //------------------------------sort-------------------------------------------
3449 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
3450 // loop tree, not the root.
3451 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
3452   if( !innermost ) return loop; // New innermost loop
3453 
3454   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
3455   assert( loop_preorder, "not yet post-walked loop" );
3456   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
3457   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
3458 
3459   // Insert at start of list
3460   while( l ) {                  // Insertion sort based on pre-order
3461     if( l == loop ) return innermost; // Already on list!
3462     int l_preorder = get_preorder(l->_head); // Cache pre-order number
3463     assert( l_preorder, "not yet post-walked l" );
3464     // Check header pre-order number to figure proper nesting
3465     if( loop_preorder > l_preorder )
3466       break;                    // End of insertion
3467     // If headers tie (e.g., shared headers) check tail pre-order numbers.
3468     // Since I split shared headers, you'd think this could not happen.
3469     // BUT: I must first do the preorder numbering before I can discover I
3470     // have shared headers, so the split headers all get the same preorder
3471     // number as the RegionNode they split from.
3472     if( loop_preorder == l_preorder &&
3473         get_preorder(loop->_tail) < get_preorder(l->_tail) )
3474       break;                    // Also check for shared headers (same pre#)
3475     pp = &l->_parent;           // Chain up list
3476     l = *pp;
3477   }
3478   // Link into list
3479   // Point predecessor to me
3480   *pp = loop;
3481   // Point me to successor
3482   IdealLoopTree *p = loop->_parent;
3483   loop->_parent = l;            // Point me to successor
3484   if( p ) sort( p, innermost ); // Insert my parents into list as well
3485   return innermost;
3486 }
3487 
3488 //------------------------------build_loop_tree--------------------------------
3489 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
3490 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
3491 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
3492 // tightest enclosing IdealLoopTree for post-walked.
3493 //
3494 // During my forward walk I do a short 1-layer lookahead to see if I can find
3495 // a loop backedge with that doesn't have any work on the backedge.  This
3496 // helps me construct nested loops with shared headers better.
3497 //
3498 // Once I've done the forward recursion, I do the post-work.  For each child
3499 // I check to see if there is a backedge.  Backedges define a loop!  I
3500 // insert an IdealLoopTree at the target of the backedge.
3501 //
3502 // During the post-work I also check to see if I have several children
3503 // belonging to different loops.  If so, then this Node is a decision point
3504 // where control flow can choose to change loop nests.  It is at this
3505 // decision point where I can figure out how loops are nested.  At this
3506 // time I can properly order the different loop nests from my children.
3507 // Note that there may not be any backedges at the decision point!
3508 //
3509 // Since the decision point can be far removed from the backedges, I can't
3510 // order my loops at the time I discover them.  Thus at the decision point
3511 // I need to inspect loop header pre-order numbers to properly nest my
3512 // loops.  This means I need to sort my childrens' loops by pre-order.
3513 // The sort is of size number-of-control-children, which generally limits
3514 // it to size 2 (i.e., I just choose between my 2 target loops).
3515 void PhaseIdealLoop::build_loop_tree() {
3516   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
3517   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
3518   Node *n = C->root();
3519   bltstack.push(n);
3520   int pre_order = 1;
3521   int stack_size;
3522 
3523   while ( ( stack_size = bltstack.length() ) != 0 ) {
3524     n = bltstack.top(); // Leave node on stack
3525     if ( !is_visited(n) ) {
3526       // ---- Pre-pass Work ----
3527       // Pre-walked but not post-walked nodes need a pre_order number.
3528 
3529       set_preorder_visited( n, pre_order ); // set as visited
3530 
3531       // ---- Scan over children ----
3532       // Scan first over control projections that lead to loop headers.
3533       // This helps us find inner-to-outer loops with shared headers better.
3534 
3535       // Scan children's children for loop headers.
3536       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
3537         Node* m = n->raw_out(i);       // Child
3538         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
3539           // Scan over children's children to find loop
3540           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3541             Node* l = m->fast_out(j);
3542             if( is_visited(l) &&       // Been visited?
3543                 !is_postvisited(l) &&  // But not post-visited
3544                 get_preorder(l) < pre_order ) { // And smaller pre-order
3545               // Found!  Scan the DFS down this path before doing other paths
3546               bltstack.push(m);
3547               break;
3548             }
3549           }
3550         }
3551       }
3552       pre_order++;
3553     }
3554     else if ( !is_postvisited(n) ) {
3555       // Note: build_loop_tree_impl() adds out edges on rare occasions,
3556       // such as com.sun.rsasign.am::a.
3557       // For non-recursive version, first, process current children.
3558       // On next iteration, check if additional children were added.
3559       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
3560         Node* u = n->raw_out(k);
3561         if ( u->is_CFG() && !is_visited(u) ) {
3562           bltstack.push(u);
3563         }
3564       }
3565       if ( bltstack.length() == stack_size ) {
3566         // There were no additional children, post visit node now
3567         (void)bltstack.pop(); // Remove node from stack
3568         pre_order = build_loop_tree_impl( n, pre_order );
3569         // Check for bailout
3570         if (C->failing()) {
3571           return;
3572         }
3573         // Check to grow _preorders[] array for the case when
3574         // build_loop_tree_impl() adds new nodes.
3575         check_grow_preorders();
3576       }
3577     }
3578     else {
3579       (void)bltstack.pop(); // Remove post-visited node from stack
3580     }
3581   }
3582 }
3583 
3584 //------------------------------build_loop_tree_impl---------------------------
3585 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
3586   // ---- Post-pass Work ----
3587   // Pre-walked but not post-walked nodes need a pre_order number.
3588 
3589   // Tightest enclosing loop for this Node
3590   IdealLoopTree *innermost = NULL;
3591 
3592   // For all children, see if any edge is a backedge.  If so, make a loop
3593   // for it.  Then find the tightest enclosing loop for the self Node.
3594   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
3595     Node* m = n->fast_out(i);   // Child
3596     if( n == m ) continue;      // Ignore control self-cycles
3597     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
3598 
3599     IdealLoopTree *l;           // Child's loop
3600     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
3601       // Found a backedge
3602       assert( get_preorder(m) < pre_order, "should be backedge" );
3603       // Check for the RootNode, which is already a LoopNode and is allowed
3604       // to have multiple "backedges".
3605       if( m == C->root()) {     // Found the root?
3606         l = _ltree_root;        // Root is the outermost LoopNode
3607       } else {                  // Else found a nested loop
3608         // Insert a LoopNode to mark this loop.
3609         l = new IdealLoopTree(this, m, n);
3610       } // End of Else found a nested loop
3611       if( !has_loop(m) )        // If 'm' does not already have a loop set
3612         set_loop(m, l);         // Set loop header to loop now
3613 
3614     } else {                    // Else not a nested loop
3615       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
3616       l = get_loop(m);          // Get previously determined loop
3617       // If successor is header of a loop (nest), move up-loop till it
3618       // is a member of some outer enclosing loop.  Since there are no
3619       // shared headers (I've split them already) I only need to go up
3620       // at most 1 level.
3621       while( l && l->_head == m ) // Successor heads loop?
3622         l = l->_parent;         // Move up 1 for me
3623       // If this loop is not properly parented, then this loop
3624       // has no exit path out, i.e. its an infinite loop.
3625       if( !l ) {
3626         // Make loop "reachable" from root so the CFG is reachable.  Basically
3627         // insert a bogus loop exit that is never taken.  'm', the loop head,
3628         // points to 'n', one (of possibly many) fall-in paths.  There may be
3629         // many backedges as well.
3630 
3631         // Here I set the loop to be the root loop.  I could have, after
3632         // inserting a bogus loop exit, restarted the recursion and found my
3633         // new loop exit.  This would make the infinite loop a first-class
3634         // loop and it would then get properly optimized.  What's the use of
3635         // optimizing an infinite loop?
3636         l = _ltree_root;        // Oops, found infinite loop
3637 
3638         if (!_verify_only) {
3639           // Insert the NeverBranch between 'm' and it's control user.
3640           NeverBranchNode *iff = new NeverBranchNode( m );
3641           _igvn.register_new_node_with_optimizer(iff);
3642           set_loop(iff, l);
3643           Node *if_t = new CProjNode( iff, 0 );
3644           _igvn.register_new_node_with_optimizer(if_t);
3645           set_loop(if_t, l);
3646 
3647           Node* cfg = NULL;       // Find the One True Control User of m
3648           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
3649             Node* x = m->fast_out(j);
3650             if (x->is_CFG() && x != m && x != iff)
3651               { cfg = x; break; }
3652           }
3653           assert(cfg != NULL, "must find the control user of m");
3654           uint k = 0;             // Probably cfg->in(0)
3655           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
3656           cfg->set_req( k, if_t ); // Now point to NeverBranch
3657           _igvn._worklist.push(cfg);
3658 
3659           // Now create the never-taken loop exit
3660           Node *if_f = new CProjNode( iff, 1 );
3661           _igvn.register_new_node_with_optimizer(if_f);
3662           set_loop(if_f, l);
3663           // Find frame ptr for Halt.  Relies on the optimizer
3664           // V-N'ing.  Easier and quicker than searching through
3665           // the program structure.
3666           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
3667           _igvn.register_new_node_with_optimizer(frame);
3668           // Halt & Catch Fire
3669           Node* halt = new HaltNode(if_f, frame, "never-taken loop exit reached");
3670           _igvn.register_new_node_with_optimizer(halt);
3671           set_loop(halt, l);
3672           C->root()->add_req(halt);
3673         }
3674         set_loop(C->root(), _ltree_root);
3675       }
3676     }
3677     // Weeny check for irreducible.  This child was already visited (this
3678     // IS the post-work phase).  Is this child's loop header post-visited
3679     // as well?  If so, then I found another entry into the loop.
3680     if (!_verify_only) {
3681       while( is_postvisited(l->_head) ) {
3682         // found irreducible
3683         l->_irreducible = 1; // = true
3684         l = l->_parent;
3685         _has_irreducible_loops = true;
3686         // Check for bad CFG here to prevent crash, and bailout of compile
3687         if (l == NULL) {
3688           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
3689           return pre_order;
3690         }
3691       }
3692       C->set_has_irreducible_loop(_has_irreducible_loops);
3693     }
3694 
3695     // This Node might be a decision point for loops.  It is only if
3696     // it's children belong to several different loops.  The sort call
3697     // does a trivial amount of work if there is only 1 child or all
3698     // children belong to the same loop.  If however, the children
3699     // belong to different loops, the sort call will properly set the
3700     // _parent pointers to show how the loops nest.
3701     //
3702     // In any case, it returns the tightest enclosing loop.
3703     innermost = sort( l, innermost );
3704   }
3705 
3706   // Def-use info will have some dead stuff; dead stuff will have no
3707   // loop decided on.
3708 
3709   // Am I a loop header?  If so fix up my parent's child and next ptrs.
3710   if( innermost && innermost->_head == n ) {
3711     assert( get_loop(n) == innermost, "" );
3712     IdealLoopTree *p = innermost->_parent;
3713     IdealLoopTree *l = innermost;
3714     while( p && l->_head == n ) {
3715       l->_next = p->_child;     // Put self on parents 'next child'
3716       p->_child = l;            // Make self as first child of parent
3717       l = p;                    // Now walk up the parent chain
3718       p = l->_parent;
3719     }
3720   } else {
3721     // Note that it is possible for a LoopNode to reach here, if the
3722     // backedge has been made unreachable (hence the LoopNode no longer
3723     // denotes a Loop, and will eventually be removed).
3724 
3725     // Record tightest enclosing loop for self.  Mark as post-visited.
3726     set_loop(n, innermost);
3727     // Also record has_call flag early on
3728     if( innermost ) {
3729       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3730         // Do not count uncommon calls
3731         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3732           Node *iff = n->in(0)->in(0);
3733           // No any calls for vectorized loops.
3734           if( UseSuperWord || !iff->is_If() ||
3735               (n->in(0)->Opcode() == Op_IfFalse &&
3736                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3737               (iff->as_If()->_prob >= 0.01) )
3738             innermost->_has_call = 1;
3739         }
3740       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3741         // Disable loop optimizations if the loop has a scalar replaceable
3742         // allocation. This disabling may cause a potential performance lost
3743         // if the allocation is not eliminated for some reason.
3744         innermost->_allow_optimizations = false;
3745         innermost->_has_call = 1; // = true
3746       } else if (n->Opcode() == Op_SafePoint) {
3747         // Record all safepoints in this loop.
3748         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3749         innermost->_safepts->push(n);
3750       }
3751     }
3752   }
3753 
3754   // Flag as post-visited now
3755   set_postvisited(n);
3756   return pre_order;
3757 }
3758 
3759 
3760 //------------------------------build_loop_early-------------------------------
3761 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3762 // First pass computes the earliest controlling node possible.  This is the
3763 // controlling input with the deepest dominating depth.
3764 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3765   while (worklist.size() != 0) {
3766     // Use local variables nstack_top_n & nstack_top_i to cache values
3767     // on nstack's top.
3768     Node *nstack_top_n = worklist.pop();
3769     uint  nstack_top_i = 0;
3770 //while_nstack_nonempty:
3771     while (true) {
3772       // Get parent node and next input's index from stack's top.
3773       Node  *n = nstack_top_n;
3774       uint   i = nstack_top_i;
3775       uint cnt = n->req(); // Count of inputs
3776       if (i == 0) {        // Pre-process the node.
3777         if( has_node(n) &&            // Have either loop or control already?
3778             !has_ctrl(n) ) {          // Have loop picked out already?
3779           // During "merge_many_backedges" we fold up several nested loops
3780           // into a single loop.  This makes the members of the original
3781           // loop bodies pointing to dead loops; they need to move up
3782           // to the new UNION'd larger loop.  I set the _head field of these
3783           // dead loops to NULL and the _parent field points to the owning
3784           // loop.  Shades of UNION-FIND algorithm.
3785           IdealLoopTree *ilt;
3786           while( !(ilt = get_loop(n))->_head ) {
3787             // Normally I would use a set_loop here.  But in this one special
3788             // case, it is legal (and expected) to change what loop a Node
3789             // belongs to.
3790             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3791           }
3792           // Remove safepoints ONLY if I've already seen I don't need one.
3793           // (the old code here would yank a 2nd safepoint after seeing a
3794           // first one, even though the 1st did not dominate in the loop body
3795           // and thus could be avoided indefinitely)
3796           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3797               is_deleteable_safept(n)) {
3798             Node *in = n->in(TypeFunc::Control);
3799             lazy_replace(n,in);       // Pull safepoint now
3800             if (ilt->_safepts != NULL) {
3801               ilt->_safepts->yank(n);
3802             }
3803             // Carry on with the recursion "as if" we are walking
3804             // only the control input
3805             if( !visited.test_set( in->_idx ) ) {
3806               worklist.push(in);      // Visit this guy later, using worklist
3807             }
3808             // Get next node from nstack:
3809             // - skip n's inputs processing by setting i > cnt;
3810             // - we also will not call set_early_ctrl(n) since
3811             //   has_node(n) == true (see the condition above).
3812             i = cnt + 1;
3813           }
3814         }
3815       } // if (i == 0)
3816 
3817       // Visit all inputs
3818       bool done = true;       // Assume all n's inputs will be processed
3819       while (i < cnt) {
3820         Node *in = n->in(i);
3821         ++i;
3822         if (in == NULL) continue;
3823         if (in->pinned() && !in->is_CFG())
3824           set_ctrl(in, in->in(0));
3825         int is_visited = visited.test_set( in->_idx );
3826         if (!has_node(in)) {  // No controlling input yet?
3827           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3828           assert( !is_visited, "visit only once" );
3829           nstack.push(n, i);  // Save parent node and next input's index.
3830           nstack_top_n = in;  // Process current input now.
3831           nstack_top_i = 0;
3832           done = false;       // Not all n's inputs processed.
3833           break; // continue while_nstack_nonempty;
3834         } else if (!is_visited) {
3835           // This guy has a location picked out for him, but has not yet
3836           // been visited.  Happens to all CFG nodes, for instance.
3837           // Visit him using the worklist instead of recursion, to break
3838           // cycles.  Since he has a location already we do not need to
3839           // find his location before proceeding with the current Node.
3840           worklist.push(in);  // Visit this guy later, using worklist
3841         }
3842       }
3843       if (done) {
3844         // All of n's inputs have been processed, complete post-processing.
3845 
3846         // Compute earliest point this Node can go.
3847         // CFG, Phi, pinned nodes already know their controlling input.
3848         if (!has_node(n)) {
3849           // Record earliest legal location
3850           set_early_ctrl( n );
3851         }
3852         if (nstack.is_empty()) {
3853           // Finished all nodes on stack.
3854           // Process next node on the worklist.
3855           break;
3856         }
3857         // Get saved parent node and next input's index.
3858         nstack_top_n = nstack.node();
3859         nstack_top_i = nstack.index();
3860         nstack.pop();
3861       }
3862     } // while (true)
3863   }
3864 }
3865 
3866 //------------------------------dom_lca_internal--------------------------------
3867 // Pair-wise LCA
3868 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3869   if( !n1 ) return n2;          // Handle NULL original LCA
3870   assert( n1->is_CFG(), "" );
3871   assert( n2->is_CFG(), "" );
3872   // find LCA of all uses
3873   uint d1 = dom_depth(n1);
3874   uint d2 = dom_depth(n2);
3875   while (n1 != n2) {
3876     if (d1 > d2) {
3877       n1 =      idom(n1);
3878       d1 = dom_depth(n1);
3879     } else if (d1 < d2) {
3880       n2 =      idom(n2);
3881       d2 = dom_depth(n2);
3882     } else {
3883       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3884       // of the tree might have the same depth.  These sections have
3885       // to be searched more carefully.
3886 
3887       // Scan up all the n1's with equal depth, looking for n2.
3888       Node *t1 = idom(n1);
3889       while (dom_depth(t1) == d1) {
3890         if (t1 == n2)  return n2;
3891         t1 = idom(t1);
3892       }
3893       // Scan up all the n2's with equal depth, looking for n1.
3894       Node *t2 = idom(n2);
3895       while (dom_depth(t2) == d2) {
3896         if (t2 == n1)  return n1;
3897         t2 = idom(t2);
3898       }
3899       // Move up to a new dominator-depth value as well as up the dom-tree.
3900       n1 = t1;
3901       n2 = t2;
3902       d1 = dom_depth(n1);
3903       d2 = dom_depth(n2);
3904     }
3905   }
3906   return n1;
3907 }
3908 
3909 //------------------------------compute_idom-----------------------------------
3910 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3911 // IDOMs are correct.
3912 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3913   assert( region->is_Region(), "" );
3914   Node *LCA = NULL;
3915   for( uint i = 1; i < region->req(); i++ ) {
3916     if( region->in(i) != C->top() )
3917       LCA = dom_lca( LCA, region->in(i) );
3918   }
3919   return LCA;
3920 }
3921 
3922 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3923   bool had_error = false;
3924 #ifdef ASSERT
3925   if (early != C->root()) {
3926     // Make sure that there's a dominance path from LCA to early
3927     Node* d = LCA;
3928     while (d != early) {
3929       if (d == C->root()) {
3930         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3931         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3932         had_error = true;
3933         break;
3934       }
3935       d = idom(d);
3936     }
3937   }
3938 #endif
3939   return had_error;
3940 }
3941 
3942 
3943 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3944   // Compute LCA over list of uses
3945   bool had_error = false;
3946   Node *LCA = NULL;
3947   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3948     Node* c = n->fast_out(i);
3949     if (_nodes[c->_idx] == NULL)
3950       continue;                 // Skip the occasional dead node
3951     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3952       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3953         if( c->in(j) == n ) {   // Found matching input?
3954           Node *use = c->in(0)->in(j);
3955           if (_verify_only && use->is_top()) continue;
3956           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3957           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3958         }
3959       }
3960     } else {
3961       // For CFG data-users, use is in the block just prior
3962       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3963       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3964       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3965     }
3966   }
3967   assert(!had_error, "bad dominance");
3968   return LCA;
3969 }
3970 
3971 // Check the shape of the graph at the loop entry. In some cases,
3972 // the shape of the graph does not match the shape outlined below.
3973 // That is caused by the Opaque1 node "protecting" the shape of
3974 // the graph being removed by, for example, the IGVN performed
3975 // in PhaseIdealLoop::build_and_optimize().
3976 //
3977 // After the Opaque1 node has been removed, optimizations (e.g., split-if,
3978 // loop unswitching, and IGVN, or a combination of them) can freely change
3979 // the graph's shape. As a result, the graph shape outlined below cannot
3980 // be guaranteed anymore.
3981 bool PhaseIdealLoop::is_canonical_loop_entry(CountedLoopNode* cl) {
3982   if (!cl->is_main_loop() && !cl->is_post_loop()) {
3983     return false;
3984   }
3985   Node* ctrl = cl->skip_predicates();
3986 
3987   if (ctrl == NULL || (!ctrl->is_IfTrue() && !ctrl->is_IfFalse())) {
3988     return false;
3989   }
3990   Node* iffm = ctrl->in(0);
3991   if (iffm == NULL || !iffm->is_If()) {
3992     return false;
3993   }
3994   Node* bolzm = iffm->in(1);
3995   if (bolzm == NULL || !bolzm->is_Bool()) {
3996     return false;
3997   }
3998   Node* cmpzm = bolzm->in(1);
3999   if (cmpzm == NULL || !cmpzm->is_Cmp()) {
4000     return false;
4001   }
4002   // compares can get conditionally flipped
4003   bool found_opaque = false;
4004   for (uint i = 1; i < cmpzm->req(); i++) {
4005     Node* opnd = cmpzm->in(i);
4006     if (opnd && opnd->Opcode() == Op_Opaque1) {
4007       found_opaque = true;
4008       break;
4009     }
4010   }
4011   if (!found_opaque) {
4012     return false;
4013   }
4014   return true;
4015 }
4016 
4017 //------------------------------get_late_ctrl----------------------------------
4018 // Compute latest legal control.
4019 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
4020   assert(early != NULL, "early control should not be NULL");
4021 
4022   Node* LCA = compute_lca_of_uses(n, early);
4023 #ifdef ASSERT
4024   if (LCA == C->root() && LCA != early) {
4025     // def doesn't dominate uses so print some useful debugging output
4026     compute_lca_of_uses(n, early, true);
4027   }
4028 #endif
4029 
4030   // if this is a load, check for anti-dependent stores
4031   // We use a conservative algorithm to identify potential interfering
4032   // instructions and for rescheduling the load.  The users of the memory
4033   // input of this load are examined.  Any use which is not a load and is
4034   // dominated by early is considered a potentially interfering store.
4035   // This can produce false positives.
4036   if (n->is_Load() && LCA != early) {
4037     int load_alias_idx = C->get_alias_index(n->adr_type());
4038     if (C->alias_type(load_alias_idx)->is_rewritable()) {
4039 
4040       Node_List worklist;
4041 
4042       Node *mem = n->in(MemNode::Memory);
4043       for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
4044         Node* s = mem->fast_out(i);
4045         worklist.push(s);
4046       }
4047       while(worklist.size() != 0 && LCA != early) {
4048         Node* s = worklist.pop();
4049         if (s->is_Load() || s->Opcode() == Op_SafePoint ||
4050             (s->is_CallStaticJava() && s->as_CallStaticJava()->uncommon_trap_request() != 0)) {
4051           continue;
4052         } else if (s->is_MergeMem()) {
4053           for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
4054             Node* s1 = s->fast_out(i);
4055             worklist.push(s1);
4056           }
4057         } else {
4058           Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
4059           assert(sctrl != NULL || s->outcnt() == 0, "must have control");
4060           if (sctrl != NULL && !sctrl->is_top() && C->can_alias(s->adr_type(), load_alias_idx) && is_dominator(early, sctrl)) {
4061             LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
4062           }
4063         }
4064       }
4065     }
4066   }
4067 
4068   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
4069   return LCA;
4070 }
4071 
4072 // true if CFG node d dominates CFG node n
4073 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
4074   if (d == n)
4075     return true;
4076   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
4077   uint dd = dom_depth(d);
4078   while (dom_depth(n) >= dd) {
4079     if (n == d)
4080       return true;
4081     n = idom(n);
4082   }
4083   return false;
4084 }
4085 
4086 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
4087 // Pair-wise LCA with tags.
4088 // Tag each index with the node 'tag' currently being processed
4089 // before advancing up the dominator chain using idom().
4090 // Later calls that find a match to 'tag' know that this path has already
4091 // been considered in the current LCA (which is input 'n1' by convention).
4092 // Since get_late_ctrl() is only called once for each node, the tag array
4093 // does not need to be cleared between calls to get_late_ctrl().
4094 // Algorithm trades a larger constant factor for better asymptotic behavior
4095 //
4096 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
4097   uint d1 = dom_depth(n1);
4098   uint d2 = dom_depth(n2);
4099 
4100   do {
4101     if (d1 > d2) {
4102       // current lca is deeper than n2
4103       _dom_lca_tags.map(n1->_idx, tag);
4104       n1 =      idom(n1);
4105       d1 = dom_depth(n1);
4106     } else if (d1 < d2) {
4107       // n2 is deeper than current lca
4108       Node *memo = _dom_lca_tags[n2->_idx];
4109       if( memo == tag ) {
4110         return n1;    // Return the current LCA
4111       }
4112       _dom_lca_tags.map(n2->_idx, tag);
4113       n2 =      idom(n2);
4114       d2 = dom_depth(n2);
4115     } else {
4116       // Here d1 == d2.  Due to edits of the dominator-tree, sections
4117       // of the tree might have the same depth.  These sections have
4118       // to be searched more carefully.
4119 
4120       // Scan up all the n1's with equal depth, looking for n2.
4121       _dom_lca_tags.map(n1->_idx, tag);
4122       Node *t1 = idom(n1);
4123       while (dom_depth(t1) == d1) {
4124         if (t1 == n2)  return n2;
4125         _dom_lca_tags.map(t1->_idx, tag);
4126         t1 = idom(t1);
4127       }
4128       // Scan up all the n2's with equal depth, looking for n1.
4129       _dom_lca_tags.map(n2->_idx, tag);
4130       Node *t2 = idom(n2);
4131       while (dom_depth(t2) == d2) {
4132         if (t2 == n1)  return n1;
4133         _dom_lca_tags.map(t2->_idx, tag);
4134         t2 = idom(t2);
4135       }
4136       // Move up to a new dominator-depth value as well as up the dom-tree.
4137       n1 = t1;
4138       n2 = t2;
4139       d1 = dom_depth(n1);
4140       d2 = dom_depth(n2);
4141     }
4142   } while (n1 != n2);
4143   return n1;
4144 }
4145 
4146 //------------------------------init_dom_lca_tags------------------------------
4147 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4148 // Intended use does not involve any growth for the array, so it could
4149 // be of fixed size.
4150 void PhaseIdealLoop::init_dom_lca_tags() {
4151   uint limit = C->unique() + 1;
4152   _dom_lca_tags.map( limit, NULL );
4153 #ifdef ASSERT
4154   for( uint i = 0; i < limit; ++i ) {
4155     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4156   }
4157 #endif // ASSERT
4158 }
4159 
4160 //------------------------------clear_dom_lca_tags------------------------------
4161 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
4162 // Intended use does not involve any growth for the array, so it could
4163 // be of fixed size.
4164 void PhaseIdealLoop::clear_dom_lca_tags() {
4165   uint limit = C->unique() + 1;
4166   _dom_lca_tags.map( limit, NULL );
4167   _dom_lca_tags.clear();
4168 #ifdef ASSERT
4169   for( uint i = 0; i < limit; ++i ) {
4170     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
4171   }
4172 #endif // ASSERT
4173 }
4174 
4175 //------------------------------build_loop_late--------------------------------
4176 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4177 // Second pass finds latest legal placement, and ideal loop placement.
4178 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
4179   while (worklist.size() != 0) {
4180     Node *n = worklist.pop();
4181     // Only visit once
4182     if (visited.test_set(n->_idx)) continue;
4183     uint cnt = n->outcnt();
4184     uint   i = 0;
4185     while (true) {
4186       assert( _nodes[n->_idx], "no dead nodes" );
4187       // Visit all children
4188       if (i < cnt) {
4189         Node* use = n->raw_out(i);
4190         ++i;
4191         // Check for dead uses.  Aggressively prune such junk.  It might be
4192         // dead in the global sense, but still have local uses so I cannot
4193         // easily call 'remove_dead_node'.
4194         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
4195           // Due to cycles, we might not hit the same fixed point in the verify
4196           // pass as we do in the regular pass.  Instead, visit such phis as
4197           // simple uses of the loop head.
4198           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
4199             if( !visited.test(use->_idx) )
4200               worklist.push(use);
4201           } else if( !visited.test_set(use->_idx) ) {
4202             nstack.push(n, i); // Save parent and next use's index.
4203             n   = use;         // Process all children of current use.
4204             cnt = use->outcnt();
4205             i   = 0;
4206           }
4207         } else {
4208           // Do not visit around the backedge of loops via data edges.
4209           // push dead code onto a worklist
4210           _deadlist.push(use);
4211         }
4212       } else {
4213         // All of n's children have been processed, complete post-processing.
4214         build_loop_late_post(n);
4215         if (nstack.is_empty()) {
4216           // Finished all nodes on stack.
4217           // Process next node on the worklist.
4218           break;
4219         }
4220         // Get saved parent node and next use's index. Visit the rest of uses.
4221         n   = nstack.node();
4222         cnt = n->outcnt();
4223         i   = nstack.index();
4224         nstack.pop();
4225       }
4226     }
4227   }
4228 }
4229 
4230 // Verify that no data node is scheduled in the outer loop of a strip
4231 // mined loop.
4232 void PhaseIdealLoop::verify_strip_mined_scheduling(Node *n, Node* least) {
4233 #ifdef ASSERT
4234   if (get_loop(least)->_nest == 0) {
4235     return;
4236   }
4237   IdealLoopTree* loop = get_loop(least);
4238   Node* head = loop->_head;
4239   if (head->is_OuterStripMinedLoop() &&
4240       // Verification can't be applied to fully built strip mined loops
4241       head->as_Loop()->outer_loop_end()->in(1)->find_int_con(-1) == 0) {
4242     Node* sfpt = head->as_Loop()->outer_safepoint();
4243     ResourceMark rm;
4244     Unique_Node_List wq;
4245     wq.push(sfpt);
4246     for (uint i = 0; i < wq.size(); i++) {
4247       Node *m = wq.at(i);
4248       for (uint i = 1; i < m->req(); i++) {
4249         Node* nn = m->in(i);
4250         if (nn == n) {
4251           return;
4252         }
4253         if (nn != NULL && has_ctrl(nn) && get_loop(get_ctrl(nn)) == loop) {
4254           wq.push(nn);
4255         }
4256       }
4257     }
4258     ShouldNotReachHere();
4259   }
4260 #endif
4261 }
4262 
4263 
4264 //------------------------------build_loop_late_post---------------------------
4265 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
4266 // Second pass finds latest legal placement, and ideal loop placement.
4267 void PhaseIdealLoop::build_loop_late_post(Node *n) {
4268   BarrierSetC2* bs = BarrierSet::barrier_set()->barrier_set_c2();
4269 
4270   if (bs->build_loop_late_post(this, n)) {
4271     return;
4272   }
4273 
4274   build_loop_late_post_work(n, true);
4275 }
4276 
4277 void PhaseIdealLoop::build_loop_late_post_work(Node *n, bool pinned) {
4278 
4279   if (n->req() == 2 && (n->Opcode() == Op_ConvI2L || n->Opcode() == Op_CastII) && !C->major_progress() && !_verify_only) {
4280     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
4281   }
4282 
4283 #ifdef ASSERT
4284   if (_verify_only && !n->is_CFG()) {
4285     // Check def-use domination.
4286     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
4287   }
4288 #endif
4289 
4290   // CFG and pinned nodes already handled
4291   if( n->in(0) ) {
4292     if( n->in(0)->is_top() ) return; // Dead?
4293 
4294     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
4295     // _must_ be pinned (they have to observe their control edge of course).
4296     // Unlike Stores (which modify an unallocable resource, the memory
4297     // state), Mods/Loads can float around.  So free them up.
4298     switch( n->Opcode() ) {
4299     case Op_DivI:
4300     case Op_DivF:
4301     case Op_DivD:
4302     case Op_ModI:
4303     case Op_ModF:
4304     case Op_ModD:
4305     case Op_LoadB:              // Same with Loads; they can sink
4306     case Op_LoadUB:             // during loop optimizations.
4307     case Op_LoadUS:
4308     case Op_LoadD:
4309     case Op_LoadF:
4310     case Op_LoadI:
4311     case Op_LoadKlass:
4312     case Op_LoadNKlass:
4313     case Op_LoadL:
4314     case Op_LoadS:
4315     case Op_LoadP:
4316     case Op_LoadN:
4317     case Op_LoadRange:
4318     case Op_LoadD_unaligned:
4319     case Op_LoadL_unaligned:
4320     case Op_StrComp:            // Does a bunch of load-like effects
4321     case Op_StrEquals:
4322     case Op_StrIndexOf:
4323     case Op_StrIndexOfChar:
4324     case Op_AryEq:
4325     case Op_HasNegatives:
4326       pinned = false;
4327     }
4328     if( pinned ) {
4329       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
4330       if( !chosen_loop->_child )       // Inner loop?
4331         chosen_loop->_body.push(n); // Collect inner loops
4332       return;
4333     }
4334   } else {                      // No slot zero
4335     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
4336       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
4337       return;
4338     }
4339     assert(!n->is_CFG() || n->outcnt() == 0, "");
4340   }
4341 
4342   // Do I have a "safe range" I can select over?
4343   Node *early = get_ctrl(n);// Early location already computed
4344 
4345   // Compute latest point this Node can go
4346   Node *LCA = get_late_ctrl( n, early );
4347   // LCA is NULL due to uses being dead
4348   if( LCA == NULL ) {
4349 #ifdef ASSERT
4350     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
4351       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
4352     }
4353 #endif
4354     _nodes.map(n->_idx, 0);     // This node is useless
4355     _deadlist.push(n);
4356     return;
4357   }
4358   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
4359 
4360   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
4361   Node *least = legal;          // Best legal position so far
4362   while( early != legal ) {     // While not at earliest legal
4363 #ifdef ASSERT
4364     if (legal->is_Start() && !early->is_Root()) {
4365       // Bad graph. Print idom path and fail.
4366       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
4367       assert(false, "Bad graph detected in build_loop_late");
4368     }
4369 #endif
4370     // Find least loop nesting depth
4371     legal = idom(legal);        // Bump up the IDOM tree
4372     // Check for lower nesting depth
4373     if( get_loop(legal)->_nest < get_loop(least)->_nest )
4374       least = legal;
4375   }
4376   assert(early == legal || legal != C->root(), "bad dominance of inputs");
4377 
4378   // Try not to place code on a loop entry projection
4379   // which can inhibit range check elimination.
4380   if (least != early) {
4381     Node* ctrl_out = least->unique_ctrl_out();
4382     if (ctrl_out && ctrl_out->is_Loop() &&
4383         least == ctrl_out->in(LoopNode::EntryControl)) {
4384       // Move the node above predicates as far up as possible so a
4385       // following pass of loop predication doesn't hoist a predicate
4386       // that depends on it above that node.
4387       Node* new_ctrl = least;
4388       for (;;) {
4389         if (!new_ctrl->is_Proj()) {
4390           break;
4391         }
4392         CallStaticJavaNode* call = new_ctrl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
4393         if (call == NULL) {
4394           break;
4395         }
4396         int req = call->uncommon_trap_request();
4397         Deoptimization::DeoptReason trap_reason = Deoptimization::trap_request_reason(req);
4398         if (trap_reason != Deoptimization::Reason_loop_limit_check &&
4399             trap_reason != Deoptimization::Reason_predicate &&
4400             trap_reason != Deoptimization::Reason_profile_predicate) {
4401           break;
4402         }
4403         Node* c = new_ctrl->in(0)->in(0);
4404         if (is_dominator(c, early) && c != early) {
4405           break;
4406         }
4407         new_ctrl = c;
4408       }
4409       least = new_ctrl;
4410     }
4411   }
4412 
4413 #ifdef ASSERT
4414   // If verifying, verify that 'verify_me' has a legal location
4415   // and choose it as our location.
4416   if( _verify_me ) {
4417     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
4418     Node *legal = LCA;
4419     while( early != legal ) {   // While not at earliest legal
4420       if( legal == v_ctrl ) break;  // Check for prior good location
4421       legal = idom(legal)      ;// Bump up the IDOM tree
4422     }
4423     // Check for prior good location
4424     if( legal == v_ctrl ) least = legal; // Keep prior if found
4425   }
4426 #endif
4427 
4428   // Assign discovered "here or above" point
4429   least = find_non_split_ctrl(least);
4430   verify_strip_mined_scheduling(n, least);
4431   set_ctrl(n, least);
4432 
4433   // Collect inner loop bodies
4434   IdealLoopTree *chosen_loop = get_loop(least);
4435   if( !chosen_loop->_child )   // Inner loop?
4436     chosen_loop->_body.push(n);// Collect inner loops
4437 }
4438 
4439 #ifdef ASSERT
4440 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
4441   tty->print_cr("%s", msg);
4442   tty->print("n: "); n->dump();
4443   tty->print("early(n): "); early->dump();
4444   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
4445       n->in(0) != early && !n->in(0)->is_Root()) {
4446     tty->print("n->in(0): "); n->in(0)->dump();
4447   }
4448   for (uint i = 1; i < n->req(); i++) {
4449     Node* in1 = n->in(i);
4450     if (in1 != NULL && in1 != n && !in1->is_top()) {
4451       tty->print("n->in(%d): ", i); in1->dump();
4452       Node* in1_early = get_ctrl(in1);
4453       tty->print("early(n->in(%d)): ", i); in1_early->dump();
4454       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
4455           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
4456         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
4457       }
4458       for (uint j = 1; j < in1->req(); j++) {
4459         Node* in2 = in1->in(j);
4460         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
4461           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
4462           Node* in2_early = get_ctrl(in2);
4463           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
4464           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
4465               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
4466             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
4467           }
4468         }
4469       }
4470     }
4471   }
4472   tty->cr();
4473   tty->print("LCA(n): "); LCA->dump();
4474   for (uint i = 0; i < n->outcnt(); i++) {
4475     Node* u1 = n->raw_out(i);
4476     if (u1 == n)
4477       continue;
4478     tty->print("n->out(%d): ", i); u1->dump();
4479     if (u1->is_CFG()) {
4480       for (uint j = 0; j < u1->outcnt(); j++) {
4481         Node* u2 = u1->raw_out(j);
4482         if (u2 != u1 && u2 != n && u2->is_CFG()) {
4483           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4484         }
4485       }
4486     } else {
4487       Node* u1_later = get_ctrl(u1);
4488       tty->print("later(n->out(%d)): ", i); u1_later->dump();
4489       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
4490           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
4491         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
4492       }
4493       for (uint j = 0; j < u1->outcnt(); j++) {
4494         Node* u2 = u1->raw_out(j);
4495         if (u2 == n || u2 == u1)
4496           continue;
4497         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
4498         if (!u2->is_CFG()) {
4499           Node* u2_later = get_ctrl(u2);
4500           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
4501           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
4502               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
4503             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
4504           }
4505         }
4506       }
4507     }
4508   }
4509   tty->cr();
4510   int ct = 0;
4511   Node *dbg_legal = LCA;
4512   while(!dbg_legal->is_Start() && ct < 100) {
4513     tty->print("idom[%d] ",ct); dbg_legal->dump();
4514     ct++;
4515     dbg_legal = idom(dbg_legal);
4516   }
4517   tty->cr();
4518 }
4519 #endif
4520 
4521 #ifndef PRODUCT
4522 //------------------------------dump-------------------------------------------
4523 void PhaseIdealLoop::dump() const {
4524   ResourceMark rm;
4525   Arena* arena = Thread::current()->resource_area();
4526   Node_Stack stack(arena, C->live_nodes() >> 2);
4527   Node_List rpo_list;
4528   VectorSet visited(arena);
4529   visited.set(C->top()->_idx);
4530   rpo(C->root(), stack, visited, rpo_list);
4531   // Dump root loop indexed by last element in PO order
4532   dump(_ltree_root, rpo_list.size(), rpo_list);
4533 }
4534 
4535 void PhaseIdealLoop::dump(IdealLoopTree* loop, uint idx, Node_List &rpo_list) const {
4536   loop->dump_head();
4537 
4538   // Now scan for CFG nodes in the same loop
4539   for (uint j = idx; j > 0; j--) {
4540     Node* n = rpo_list[j-1];
4541     if (!_nodes[n->_idx])      // Skip dead nodes
4542       continue;
4543 
4544     if (get_loop(n) != loop) { // Wrong loop nest
4545       if (get_loop(n)->_head == n &&    // Found nested loop?
4546           get_loop(n)->_parent == loop)
4547         dump(get_loop(n), rpo_list.size(), rpo_list);     // Print it nested-ly
4548       continue;
4549     }
4550 
4551     // Dump controlling node
4552     tty->sp(2 * loop->_nest);
4553     tty->print("C");
4554     if (n == C->root()) {
4555       n->dump();
4556     } else {
4557       Node* cached_idom   = idom_no_update(n);
4558       Node* computed_idom = n->in(0);
4559       if (n->is_Region()) {
4560         computed_idom = compute_idom(n);
4561         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
4562         // any MultiBranch ctrl node), so apply a similar transform to
4563         // the cached idom returned from idom_no_update.
4564         cached_idom = find_non_split_ctrl(cached_idom);
4565       }
4566       tty->print(" ID:%d", computed_idom->_idx);
4567       n->dump();
4568       if (cached_idom != computed_idom) {
4569         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
4570                       computed_idom->_idx, cached_idom->_idx);
4571       }
4572     }
4573     // Dump nodes it controls
4574     for (uint k = 0; k < _nodes.Size(); k++) {
4575       // (k < C->unique() && get_ctrl(find(k)) == n)
4576       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
4577         Node* m = C->root()->find(k);
4578         if (m && m->outcnt() > 0) {
4579           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
4580             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
4581                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
4582           }
4583           tty->sp(2 * loop->_nest + 1);
4584           m->dump();
4585         }
4586       }
4587     }
4588   }
4589 }
4590 #endif
4591 
4592 // Collect a R-P-O for the whole CFG.
4593 // Result list is in post-order (scan backwards for RPO)
4594 void PhaseIdealLoop::rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const {
4595   stk.push(start, 0);
4596   visited.set(start->_idx);
4597 
4598   while (stk.is_nonempty()) {
4599     Node* m   = stk.node();
4600     uint  idx = stk.index();
4601     if (idx < m->outcnt()) {
4602       stk.set_index(idx + 1);
4603       Node* n = m->raw_out(idx);
4604       if (n->is_CFG() && !visited.test_set(n->_idx)) {
4605         stk.push(n, 0);
4606       }
4607     } else {
4608       rpo_list.push(m);
4609       stk.pop();
4610     }
4611   }
4612 }
4613 
4614 
4615 //=============================================================================
4616 //------------------------------LoopTreeIterator-------------------------------
4617 
4618 // Advance to next loop tree using a preorder, left-to-right traversal.
4619 void LoopTreeIterator::next() {
4620   assert(!done(), "must not be done.");
4621   if (_curnt->_child != NULL) {
4622     _curnt = _curnt->_child;
4623   } else if (_curnt->_next != NULL) {
4624     _curnt = _curnt->_next;
4625   } else {
4626     while (_curnt != _root && _curnt->_next == NULL) {
4627       _curnt = _curnt->_parent;
4628     }
4629     if (_curnt == _root) {
4630       _curnt = NULL;
4631       assert(done(), "must be done.");
4632     } else {
4633       assert(_curnt->_next != NULL, "must be more to do");
4634       _curnt = _curnt->_next;
4635     }
4636   }
4637 }