1 /*
   2  * Copyright (c) 1998, 2011, 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 "libadt/vectset.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/callnode.hpp"
  32 #include "opto/connode.hpp"
  33 #include "opto/divnode.hpp"
  34 #include "opto/idealGraphPrinter.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/mulnode.hpp"
  37 #include "opto/rootnode.hpp"
  38 #include "opto/superword.hpp"
  39 
  40 //=============================================================================
  41 //------------------------------is_loop_iv-------------------------------------
  42 // Determine if a node is Counted loop induction variable.
  43 // The method is declared in node.hpp.
  44 const Node* Node::is_loop_iv() const {
  45   if (this->is_Phi() && !this->as_Phi()->is_copy() &&
  46       this->as_Phi()->region()->is_CountedLoop() &&
  47       this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
  48     return this;
  49   } else {
  50     return NULL;
  51   }
  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();
  70     if (le != NULL &&
  71         le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  72       Node* phi  = l->phi();
  73       Node* exit = le->proj_out(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) ) {
  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   return early;
 136 }
 137 
 138 //------------------------------set_early_ctrl---------------------------------
 139 // Set earliest legal control
 140 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 141   Node *early = get_early_ctrl(n);
 142 
 143   // Record earliest legal location
 144   set_ctrl(n, early);
 145 }
 146 
 147 //------------------------------set_subtree_ctrl-------------------------------
 148 // set missing _ctrl entries on new nodes
 149 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 150   // Already set?  Get out.
 151   if( _nodes[n->_idx] ) return;
 152   // Recursively set _nodes array to indicate where the Node goes
 153   uint i;
 154   for( i = 0; i < n->req(); ++i ) {
 155     Node *m = n->in(i);
 156     if( m && m != C->root() )
 157       set_subtree_ctrl( m );
 158   }
 159 
 160   // Fixup self
 161   set_early_ctrl( n );
 162 }
 163 
 164 //------------------------------is_counted_loop--------------------------------
 165 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
 166   PhaseGVN *gvn = &_igvn;
 167 
 168   // Counted loop head must be a good RegionNode with only 3 not NULL
 169   // control input edges: Self, Entry, LoopBack.
 170   if (x->in(LoopNode::Self) == NULL || x->req() != 3)
 171     return false;
 172 
 173   Node *init_control = x->in(LoopNode::EntryControl);
 174   Node *back_control = x->in(LoopNode::LoopBackControl);
 175   if (init_control == NULL || back_control == NULL)    // Partially dead
 176     return false;
 177   // Must also check for TOP when looking for a dead loop
 178   if (init_control->is_top() || back_control->is_top())
 179     return false;
 180 
 181   // Allow funny placement of Safepoint
 182   if (back_control->Opcode() == Op_SafePoint)
 183     back_control = back_control->in(TypeFunc::Control);
 184 
 185   // Controlling test for loop
 186   Node *iftrue = back_control;
 187   uint iftrue_op = iftrue->Opcode();
 188   if (iftrue_op != Op_IfTrue &&
 189       iftrue_op != Op_IfFalse)
 190     // I have a weird back-control.  Probably the loop-exit test is in
 191     // the middle of the loop and I am looking at some trailing control-flow
 192     // merge point.  To fix this I would have to partially peel the loop.
 193     return false; // Obscure back-control
 194 
 195   // Get boolean guarding loop-back test
 196   Node *iff = iftrue->in(0);
 197   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 198     return false;
 199   BoolNode *test = iff->in(1)->as_Bool();
 200   BoolTest::mask bt = test->_test._test;
 201   float cl_prob = iff->as_If()->_prob;
 202   if (iftrue_op == Op_IfFalse) {
 203     bt = BoolTest(bt).negate();
 204     cl_prob = 1.0 - cl_prob;
 205   }
 206   // Get backedge compare
 207   Node *cmp = test->in(1);
 208   int cmp_op = cmp->Opcode();
 209   if (cmp_op != Op_CmpI)
 210     return false;                // Avoid pointer & float compares
 211 
 212   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 213   Node *incr  = cmp->in(1);
 214   Node *limit = cmp->in(2);
 215 
 216   // ---------
 217   // need 'loop()' test to tell if limit is loop invariant
 218   // ---------
 219 
 220   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 221     Node *tmp = incr;            // Then reverse order into the CmpI
 222     incr = limit;
 223     limit = tmp;
 224     bt = BoolTest(bt).commute(); // And commute the exit test
 225   }
 226   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 227     return false;
 228   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 229     return false;
 230 
 231   Node* phi_incr = NULL;
 232   // Trip-counter increment must be commutative & associative.
 233   if (incr->is_Phi()) {
 234     if (incr->as_Phi()->region() != x || incr->req() != 3)
 235       return false; // Not simple trip counter expression
 236     phi_incr = incr;
 237     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 238     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 239       return false;
 240   }
 241 
 242   Node* trunc1 = NULL;
 243   Node* trunc2 = NULL;
 244   const TypeInt* iv_trunc_t = NULL;
 245   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 246     return false; // Funny increment opcode
 247   }
 248   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 249 
 250   // Get merge point
 251   Node *xphi = incr->in(1);
 252   Node *stride = incr->in(2);
 253   if (!stride->is_Con()) {     // Oops, swap these
 254     if (!xphi->is_Con())       // Is the other guy a constant?
 255       return false;             // Nope, unknown stride, bail out
 256     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 257     xphi = stride;
 258     stride = tmp;
 259   }
 260   // Stride must be constant
 261   int stride_con = stride->get_int();
 262   if (stride_con == 0)
 263     return false; // missed some peephole opt
 264 
 265   if (!xphi->is_Phi())
 266     return false; // Too much math on the trip counter
 267   if (phi_incr != NULL && phi_incr != xphi)
 268     return false;
 269   PhiNode *phi = xphi->as_Phi();
 270 
 271   // Phi must be of loop header; backedge must wrap to increment
 272   if (phi->region() != x)
 273     return false;
 274   if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
 275       trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) {
 276     return false;
 277   }
 278   Node *init_trip = phi->in(LoopNode::EntryControl);
 279 
 280   // If iv trunc type is smaller than int, check for possible wrap.
 281   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 282     assert(trunc1 != NULL, "must have found some truncation");
 283 
 284     // Get a better type for the phi (filtered thru if's)
 285     const TypeInt* phi_ft = filtered_type(phi);
 286 
 287     // Can iv take on a value that will wrap?
 288     //
 289     // Ensure iv's limit is not within "stride" of the wrap value.
 290     //
 291     // Example for "short" type
 292     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 293     //    If the stride is +10, then the last value of the induction
 294     //    variable before the increment (phi_ft->_hi) must be
 295     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 296     //    ensure no truncation occurs after the increment.
 297 
 298     if (stride_con > 0) {
 299       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 300           iv_trunc_t->_lo > phi_ft->_lo) {
 301         return false;  // truncation may occur
 302       }
 303     } else if (stride_con < 0) {
 304       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 305           iv_trunc_t->_hi < phi_ft->_hi) {
 306         return false;  // truncation may occur
 307       }
 308     }
 309     // No possibility of wrap so truncation can be discarded
 310     // Promote iv type to Int
 311   } else {
 312     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 313   }
 314 
 315   // If the condition is inverted and we will be rolling
 316   // through MININT to MAXINT, then bail out.
 317   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 318       // Odd stride
 319       bt == BoolTest::ne && stride_con != 1 && stride_con != -1 ||
 320       // Count down loop rolls through MAXINT
 321       (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 ||
 322       // Count up loop rolls through MININT
 323       (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) {
 324     return false; // Bail out
 325   }
 326 
 327   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 328   const TypeInt* limit_t = gvn->type(limit)->is_int();
 329 
 330   if (stride_con > 0) {
 331     long init_p = (long)init_t->_lo + stride_con;
 332     if (init_p > (long)max_jint || init_p > (long)limit_t->_hi)
 333       return false; // cyclic loop or this loop trips only once
 334   } else {
 335     long init_p = (long)init_t->_hi + stride_con;
 336     if (init_p < (long)min_jint || init_p < (long)limit_t->_lo)
 337       return false; // cyclic loop or this loop trips only once
 338   }
 339 
 340   // =================================================
 341   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 342   //
 343   assert(x->Opcode() == Op_Loop, "regular loops only");
 344   C->print_method("Before CountedLoop", 3);
 345 
 346   Node *hook = new (C, 6) Node(6);
 347 
 348   if (LoopLimitCheck) {
 349 
 350   // ===================================================
 351   // Generate loop limit check to avoid integer overflow
 352   // in cases like next (cyclic loops):
 353   //
 354   // for (i=0; i <= max_jint; i++) {}
 355   // for (i=0; i <  max_jint; i+=2) {}
 356   //
 357   //
 358   // Limit check predicate depends on the loop test:
 359   //
 360   // for(;i != limit; i++)       --> limit <= (max_jint)
 361   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 362   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 363   //
 364 
 365   // Check if limit is excluded to do more precise int overflow check.
 366   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 367   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 368 
 369   // If compare points directly to the phi we need to adjust
 370   // the compare so that it points to the incr. Limit have
 371   // to be adjusted to keep trip count the same and the
 372   // adjusted limit should be checked for int overflow.
 373   if (phi_incr != NULL) {
 374     stride_m  += stride_con;
 375   }
 376 
 377   if (limit->is_Con()) {
 378     int limit_con = limit->get_int();
 379     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 380         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 381       // Bailout: it could be integer overflow.
 382       return false;
 383     }
 384   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 385              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 386       // Limit's type may satisfy the condition, for example,
 387       // when it is an array length.
 388   } else {
 389     // Generate loop's limit check.
 390     // Loop limit check predicate should be near the loop.
 391     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 392     if (!limit_check_proj) {
 393       // The limit check predicate is not generated if this method trapped here before.
 394 #ifdef ASSERT
 395       if (TraceLoopLimitCheck) {
 396         tty->print("missing loop limit check:");
 397         loop->dump_head();
 398         x->dump(1);
 399       }
 400 #endif
 401       return false;
 402     }
 403 
 404     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 405     Node* cmp_limit;
 406     Node* bol;
 407 
 408     if (stride_con > 0) {
 409       cmp_limit = new (C, 3) CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 410       bol = new (C, 2) BoolNode(cmp_limit, BoolTest::le);
 411     } else {
 412       cmp_limit = new (C, 3) CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 413       bol = new (C, 2) BoolNode(cmp_limit, BoolTest::ge);
 414     }
 415     cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 416     bol = _igvn.register_new_node_with_optimizer(bol);
 417     set_subtree_ctrl(bol);
 418 
 419     // Replace condition in original predicate but preserve Opaque node
 420     // so that previous predicates could be found.
 421     assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
 422            check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
 423     Node* opq = check_iff->in(1)->in(1);
 424     _igvn.hash_delete(opq);
 425     opq->set_req(1, bol);
 426     // Update ctrl.
 427     set_ctrl(opq, check_iff->in(0));
 428     set_ctrl(check_iff->in(1), check_iff->in(0));
 429 
 430 #ifndef PRODUCT
 431     // report that the loop predication has been actually performed
 432     // for this loop
 433     if (TraceLoopLimitCheck) {
 434       tty->print_cr("Counted Loop Limit Check generated:");
 435       debug_only( bol->dump(2); )
 436     }
 437 #endif
 438   }
 439 
 440   if (phi_incr != NULL) {
 441     // If compare points directly to the phi we need to adjust
 442     // the compare so that it points to the incr. Limit have
 443     // to be adjusted to keep trip count the same and we
 444     // should avoid int overflow.
 445     //
 446     //   i = init; do {} while(i++ < limit);
 447     // is converted to
 448     //   i = init; do {} while(++i < limit+1);
 449     //
 450     limit = gvn->transform(new (C, 3) AddINode(limit, stride));
 451   }
 452 
 453   // Now we need to canonicalize loop condition.
 454   if (bt == BoolTest::ne) {
 455     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 456     // 'ne' can be replaced with 'lt' only when init < limit.
 457     if (stride_con > 0 && init_t->_hi < limit_t->_lo)
 458       bt = BoolTest::lt;
 459     // 'ne' can be replaced with 'gt' only when init > limit.
 460     if (stride_con < 0 && init_t->_lo > limit_t->_hi)
 461       bt = BoolTest::gt;
 462   }
 463 
 464   if (incl_limit) {
 465     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 466     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 467     //
 468     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 469     limit = gvn->transform(new (C, 3) AddINode(limit, one));
 470     if (bt == BoolTest::le)
 471       bt = BoolTest::lt;
 472     else if (bt == BoolTest::ge)
 473       bt = BoolTest::gt;
 474     else
 475       ShouldNotReachHere();
 476   }
 477   set_subtree_ctrl( limit );
 478 
 479   } else { // LoopLimitCheck
 480 
 481   // If compare points to incr, we are ok.  Otherwise the compare
 482   // can directly point to the phi; in this case adjust the compare so that
 483   // it points to the incr by adjusting the limit.
 484   if (cmp->in(1) == phi || cmp->in(2) == phi)
 485     limit = gvn->transform(new (C, 3) AddINode(limit,stride));
 486 
 487   // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
 488   // Final value for iterator should be: trip_count * stride + init_trip.
 489   Node *one_p = gvn->intcon( 1);
 490   Node *one_m = gvn->intcon(-1);
 491 
 492   Node *trip_count = NULL;
 493   switch( bt ) {
 494   case BoolTest::eq:
 495     ShouldNotReachHere();
 496   case BoolTest::ne:            // Ahh, the case we desire
 497     if (stride_con == 1)
 498       trip_count = gvn->transform(new (C, 3) SubINode(limit,init_trip));
 499     else if (stride_con == -1)
 500       trip_count = gvn->transform(new (C, 3) SubINode(init_trip,limit));
 501     else
 502       ShouldNotReachHere();
 503     set_subtree_ctrl(trip_count);
 504     //_loop.map(trip_count->_idx,loop(limit));
 505     break;
 506   case BoolTest::le:            // Maybe convert to '<' case
 507     limit = gvn->transform(new (C, 3) AddINode(limit,one_p));
 508     set_subtree_ctrl( limit );
 509     hook->init_req(4, limit);
 510 
 511     bt = BoolTest::lt;
 512     // Make the new limit be in the same loop nest as the old limit
 513     //_loop.map(limit->_idx,limit_loop);
 514     // Fall into next case
 515   case BoolTest::lt: {          // Maybe convert to '!=' case
 516     if (stride_con < 0) // Count down loop rolls through MAXINT
 517       ShouldNotReachHere();
 518     Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip));
 519     set_subtree_ctrl( range );
 520     hook->init_req(0, range);
 521 
 522     Node *bias  = gvn->transform(new (C, 3) AddINode(range,stride));
 523     set_subtree_ctrl( bias );
 524     hook->init_req(1, bias);
 525 
 526     Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_m));
 527     set_subtree_ctrl( bias1 );
 528     hook->init_req(2, bias1);
 529 
 530     trip_count  = gvn->transform(new (C, 3) DivINode(0,bias1,stride));
 531     set_subtree_ctrl( trip_count );
 532     hook->init_req(3, trip_count);
 533     break;
 534   }
 535 
 536   case BoolTest::ge:            // Maybe convert to '>' case
 537     limit = gvn->transform(new (C, 3) AddINode(limit,one_m));
 538     set_subtree_ctrl( limit );
 539     hook->init_req(4 ,limit);
 540 
 541     bt = BoolTest::gt;
 542     // Make the new limit be in the same loop nest as the old limit
 543     //_loop.map(limit->_idx,limit_loop);
 544     // Fall into next case
 545   case BoolTest::gt: {          // Maybe convert to '!=' case
 546     if (stride_con > 0) // count up loop rolls through MININT
 547       ShouldNotReachHere();
 548     Node *range = gvn->transform(new (C, 3) SubINode(limit,init_trip));
 549     set_subtree_ctrl( range );
 550     hook->init_req(0, range);
 551 
 552     Node *bias  = gvn->transform(new (C, 3) AddINode(range,stride));
 553     set_subtree_ctrl( bias );
 554     hook->init_req(1, bias);
 555 
 556     Node *bias1 = gvn->transform(new (C, 3) AddINode(bias,one_p));
 557     set_subtree_ctrl( bias1 );
 558     hook->init_req(2, bias1);
 559 
 560     trip_count  = gvn->transform(new (C, 3) DivINode(0,bias1,stride));
 561     set_subtree_ctrl( trip_count );
 562     hook->init_req(3, trip_count);
 563     break;
 564   }
 565   } // switch( bt )
 566 
 567   Node *span = gvn->transform(new (C, 3) MulINode(trip_count,stride));
 568   set_subtree_ctrl( span );
 569   hook->init_req(5, span);
 570 
 571   limit = gvn->transform(new (C, 3) AddINode(span,init_trip));
 572   set_subtree_ctrl( limit );
 573 
 574   } // LoopLimitCheck
 575 
 576   // Check for SafePoint on backedge and remove
 577   Node *sfpt = x->in(LoopNode::LoopBackControl);
 578   if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 579     lazy_replace( sfpt, iftrue );
 580     loop->_tail = iftrue;
 581   }
 582 
 583   // Build a canonical trip test.
 584   // Clone code, as old values may be in use.
 585   Node* nphi = PhiNode::make(x, init_trip, TypeInt::INT);
 586   nphi = _igvn.register_new_node_with_optimizer(nphi);
 587   set_ctrl(nphi, get_ctrl(phi));
 588 
 589   incr = incr->clone();
 590   incr->set_req(1,nphi);
 591   incr->set_req(2,stride);
 592   incr = _igvn.register_new_node_with_optimizer(incr);
 593   set_early_ctrl( incr );
 594 
 595   nphi->set_req(LoopNode::LoopBackControl, incr);
 596   _igvn.replace_node(phi, nphi);
 597   phi = nphi->as_Phi();
 598 
 599   cmp = cmp->clone();
 600   cmp->set_req(1,incr);
 601   cmp->set_req(2,limit);
 602   cmp = _igvn.register_new_node_with_optimizer(cmp);
 603   set_ctrl(cmp, iff->in(0));
 604 
 605   test = test->clone()->as_Bool();
 606   (*(BoolTest*)&test->_test)._test = bt;
 607   test->set_req(1,cmp);
 608   _igvn.register_new_node_with_optimizer(test);
 609   set_ctrl(test, iff->in(0));
 610 
 611   // Replace the old IfNode with a new LoopEndNode
 612   Node *lex = _igvn.register_new_node_with_optimizer(new (C, 2) CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 613   IfNode *le = lex->as_If();
 614   uint dd = dom_depth(iff);
 615   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 616   set_loop(le, loop);
 617 
 618   // Get the loop-exit control
 619   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 620 
 621   // Need to swap loop-exit and loop-back control?
 622   if (iftrue_op == Op_IfFalse) {
 623     Node *ift2=_igvn.register_new_node_with_optimizer(new (C, 1) IfTrueNode (le));
 624     Node *iff2=_igvn.register_new_node_with_optimizer(new (C, 1) IfFalseNode(le));
 625 
 626     loop->_tail = back_control = ift2;
 627     set_loop(ift2, loop);
 628     set_loop(iff2, get_loop(iffalse));
 629 
 630     // Lazy update of 'get_ctrl' mechanism.
 631     lazy_replace_proj( iffalse, iff2 );
 632     lazy_replace_proj( iftrue,  ift2 );
 633 
 634     // Swap names
 635     iffalse = iff2;
 636     iftrue  = ift2;
 637   } else {
 638     _igvn.hash_delete(iffalse);
 639     _igvn.hash_delete(iftrue);
 640     iffalse->set_req_X( 0, le, &_igvn );
 641     iftrue ->set_req_X( 0, le, &_igvn );
 642   }
 643 
 644   set_idom(iftrue,  le, dd+1);
 645   set_idom(iffalse, le, dd+1);
 646   assert(iff->outcnt() == 0, "should be dead now");
 647   lazy_replace( iff, le ); // fix 'get_ctrl'
 648 
 649   // Now setup a new CountedLoopNode to replace the existing LoopNode
 650   CountedLoopNode *l = new (C, 3) CountedLoopNode(init_control, back_control);
 651   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 652   // The following assert is approximately true, and defines the intention
 653   // of can_be_counted_loop.  It fails, however, because phase->type
 654   // is not yet initialized for this loop and its parts.
 655   //assert(l->can_be_counted_loop(this), "sanity");
 656   _igvn.register_new_node_with_optimizer(l);
 657   set_loop(l, loop);
 658   loop->_head = l;
 659   // Fix all data nodes placed at the old loop head.
 660   // Uses the lazy-update mechanism of 'get_ctrl'.
 661   lazy_replace( x, l );
 662   set_idom(l, init_control, dom_depth(x));
 663 
 664   // Check for immediately preceding SafePoint and remove
 665   Node *sfpt2 = le->in(0);
 666   if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2))
 667     lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 668 
 669   // Free up intermediate goo
 670   _igvn.remove_dead_node(hook);
 671 
 672 #ifdef ASSERT
 673   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 674   assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
 675 #endif
 676 #ifndef PRODUCT
 677   if (TraceLoopOpts) {
 678     tty->print("Counted      ");
 679     loop->dump_head();
 680   }
 681 #endif
 682 
 683   C->print_method("After CountedLoop", 3);
 684 
 685   return true;
 686 }
 687 
 688 //----------------------exact_limit-------------------------------------------
 689 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 690   assert(loop->_head->is_CountedLoop(), "");
 691   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 692   assert(cl->is_valid_counted_loop(), "");
 693 
 694   if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
 695       cl->limit()->Opcode() == Op_LoopLimit) {
 696     // Old code has exact limit (it could be incorrect in case of int overflow).
 697     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 698     return cl->limit();
 699   }
 700   Node *limit = NULL;
 701 #ifdef ASSERT
 702   BoolTest::mask bt = cl->loopexit()->test_trip();
 703   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 704 #endif
 705   if (cl->has_exact_trip_count()) {
 706     // Simple case: loop has constant boundaries.
 707     // Use longs to avoid integer overflow.
 708     int stride_con = cl->stride_con();
 709     long  init_con = cl->init_trip()->get_int();
 710     long limit_con = cl->limit()->get_int();
 711     julong trip_cnt = cl->trip_count();
 712     long final_con = init_con + trip_cnt*stride_con;
 713     final_con -= stride_con;
 714     int final_int = (int)final_con;
 715     // The final value should be in integer range since the loop
 716     // is counted and the limit was checked for overflow.
 717     assert(final_con == (long)final_int, "final value should be integer");
 718     limit = _igvn.intcon(final_int);
 719   } else {
 720     // Create new LoopLimit node to get exact limit (final iv value).
 721     limit = new (C, 4) LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 722     register_new_node(limit, cl->in(LoopNode::EntryControl));
 723   }
 724   assert(limit != NULL, "sanity");
 725   return limit;
 726 }
 727 
 728 //------------------------------Ideal------------------------------------------
 729 // Return a node which is more "ideal" than the current node.
 730 // Attempt to convert into a counted-loop.
 731 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 732   if (!can_be_counted_loop(phase)) {
 733     phase->C->set_major_progress();
 734   }
 735   return RegionNode::Ideal(phase, can_reshape);
 736 }
 737 
 738 
 739 //=============================================================================
 740 //------------------------------Ideal------------------------------------------
 741 // Return a node which is more "ideal" than the current node.
 742 // Attempt to convert into a counted-loop.
 743 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 744   return RegionNode::Ideal(phase, can_reshape);
 745 }
 746 
 747 //------------------------------dump_spec--------------------------------------
 748 // Dump special per-node info
 749 #ifndef PRODUCT
 750 void CountedLoopNode::dump_spec(outputStream *st) const {
 751   LoopNode::dump_spec(st);
 752   if (stride_is_con()) {
 753     st->print("stride: %d ",stride_con());
 754   }
 755   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
 756   if (is_main_loop()) st->print("main of N%d", _idx);
 757   if (is_post_loop()) st->print("post of N%d", _main_idx);
 758 }
 759 #endif
 760 
 761 //=============================================================================
 762 int CountedLoopEndNode::stride_con() const {
 763   return stride()->bottom_type()->is_int()->get_con();
 764 }
 765 
 766 //=============================================================================
 767 //------------------------------Value-----------------------------------------
 768 const Type *LoopLimitNode::Value( PhaseTransform *phase ) const {
 769   const Type* init_t   = phase->type(in(Init));
 770   const Type* limit_t  = phase->type(in(Limit));
 771   const Type* stride_t = phase->type(in(Stride));
 772   // Either input is TOP ==> the result is TOP
 773   if (init_t   == Type::TOP) return Type::TOP;
 774   if (limit_t  == Type::TOP) return Type::TOP;
 775   if (stride_t == Type::TOP) return Type::TOP;
 776 
 777   int stride_con = stride_t->is_int()->get_con();
 778   if (stride_con == 1)
 779     return NULL;  // Identity
 780 
 781   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
 782     // Use longs to avoid integer overflow.
 783     long init_con   =  init_t->is_int()->get_con();
 784     long limit_con  = limit_t->is_int()->get_con();
 785     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
 786     long trip_count = (limit_con - init_con + stride_m)/stride_con;
 787     long final_con  = init_con + stride_con*trip_count;
 788     int final_int = (int)final_con;
 789     // The final value should be in integer range since the loop
 790     // is counted and the limit was checked for overflow.
 791     assert(final_con == (long)final_int, "final value should be integer");
 792     return TypeInt::make(final_int);
 793   }
 794 
 795   return bottom_type(); // TypeInt::INT
 796 }
 797 
 798 //------------------------------Ideal------------------------------------------
 799 // Return a node which is more "ideal" than the current node.
 800 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 801   if (phase->type(in(Init))   == Type::TOP ||
 802       phase->type(in(Limit))  == Type::TOP ||
 803       phase->type(in(Stride)) == Type::TOP)
 804     return NULL;  // Dead
 805 
 806   int stride_con = phase->type(in(Stride))->is_int()->get_con();
 807   if (stride_con == 1)
 808     return NULL;  // Identity
 809 
 810   if (in(Init)->is_Con() && in(Limit)->is_Con())
 811     return NULL;  // Value
 812 
 813   // Delay following optimizations until all loop optimizations
 814   // done to keep Ideal graph simple.
 815   if (!can_reshape || phase->C->major_progress())
 816     return NULL;
 817 
 818   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
 819   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
 820   int stride_p;
 821   long lim, ini;
 822   julong max;
 823   if (stride_con > 0) {
 824     stride_p = stride_con;
 825     lim = limit_t->_hi;
 826     ini = init_t->_lo;
 827     max = (julong)max_jint;
 828   } else {
 829     stride_p = -stride_con;
 830     lim = init_t->_hi;
 831     ini = limit_t->_lo;
 832     max = (julong)min_jint;
 833   }
 834   julong range = lim - ini + stride_p;
 835   if (range <= max) {
 836     // Convert to integer expression if it is not overflow.
 837     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
 838     Node *range = phase->transform(new (phase->C, 3) SubINode(in(Limit), in(Init)));
 839     Node *bias  = phase->transform(new (phase->C, 3) AddINode(range, stride_m));
 840     Node *trip  = phase->transform(new (phase->C, 3) DivINode(0, bias, in(Stride)));
 841     Node *span  = phase->transform(new (phase->C, 3) MulINode(trip, in(Stride)));
 842     return new (phase->C, 3) AddINode(span, in(Init)); // exact limit
 843   }
 844 
 845   if (is_power_of_2(stride_p) ||                // divisor is 2^n
 846       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
 847     // Convert to long expression to avoid integer overflow
 848     // and let igvn optimizer convert this division.
 849     //
 850     Node*   init   = phase->transform( new (phase->C, 2) ConvI2LNode(in(Init)));
 851     Node*  limit   = phase->transform( new (phase->C, 2) ConvI2LNode(in(Limit)));
 852     Node* stride   = phase->longcon(stride_con);
 853     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
 854 
 855     Node *range = phase->transform(new (phase->C, 3) SubLNode(limit, init));
 856     Node *bias  = phase->transform(new (phase->C, 3) AddLNode(range, stride_m));
 857     Node *span;
 858     if (stride_con > 0 && is_power_of_2(stride_p)) {
 859       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
 860       // and avoid generating rounding for division. Zero trip guard should
 861       // guarantee that init < limit but sometimes the guard is missing and
 862       // we can get situation when init > limit. Note, for the empty loop
 863       // optimization zero trip guard is generated explicitly which leaves
 864       // only RCE predicate where exact limit is used and the predicate
 865       // will simply fail forcing recompilation.
 866       Node* neg_stride   = phase->longcon(-stride_con);
 867       span = phase->transform(new (phase->C, 3) AndLNode(bias, neg_stride));
 868     } else {
 869       Node *trip  = phase->transform(new (phase->C, 3) DivLNode(0, bias, stride));
 870       span = phase->transform(new (phase->C, 3) MulLNode(trip, stride));
 871     }
 872     // Convert back to int
 873     Node *span_int = phase->transform(new (phase->C, 2) ConvL2INode(span));
 874     return new (phase->C, 3) AddINode(span_int, in(Init)); // exact limit
 875   }
 876 
 877   return NULL;    // No progress
 878 }
 879 
 880 //------------------------------Identity---------------------------------------
 881 // If stride == 1 return limit node.
 882 Node *LoopLimitNode::Identity( PhaseTransform *phase ) {
 883   int stride_con = phase->type(in(Stride))->is_int()->get_con();
 884   if (stride_con == 1 || stride_con == -1)
 885     return in(Limit);
 886   return this;
 887 }
 888 
 889 //=============================================================================
 890 //----------------------match_incr_with_optional_truncation--------------------
 891 // Match increment with optional truncation:
 892 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
 893 // Return NULL for failure. Success returns the increment node.
 894 Node* CountedLoopNode::match_incr_with_optional_truncation(
 895                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
 896   // Quick cutouts:
 897   if (expr == NULL || expr->req() != 3)  return false;
 898 
 899   Node *t1 = NULL;
 900   Node *t2 = NULL;
 901   const TypeInt* trunc_t = TypeInt::INT;
 902   Node* n1 = expr;
 903   int   n1op = n1->Opcode();
 904 
 905   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
 906   if (n1op == Op_AndI &&
 907       n1->in(2)->is_Con() &&
 908       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
 909     // %%% This check should match any mask of 2**K-1.
 910     t1 = n1;
 911     n1 = t1->in(1);
 912     n1op = n1->Opcode();
 913     trunc_t = TypeInt::CHAR;
 914   } else if (n1op == Op_RShiftI &&
 915              n1->in(1) != NULL &&
 916              n1->in(1)->Opcode() == Op_LShiftI &&
 917              n1->in(2) == n1->in(1)->in(2) &&
 918              n1->in(2)->is_Con()) {
 919     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
 920     // %%% This check should match any shift in [1..31].
 921     if (shift == 16 || shift == 8) {
 922       t1 = n1;
 923       t2 = t1->in(1);
 924       n1 = t2->in(1);
 925       n1op = n1->Opcode();
 926       if (shift == 16) {
 927         trunc_t = TypeInt::SHORT;
 928       } else if (shift == 8) {
 929         trunc_t = TypeInt::BYTE;
 930       }
 931     }
 932   }
 933 
 934   // If (maybe after stripping) it is an AddI, we won:
 935   if (n1op == Op_AddI) {
 936     *trunc1 = t1;
 937     *trunc2 = t2;
 938     *trunc_type = trunc_t;
 939     return n1;
 940   }
 941 
 942   // failed
 943   return NULL;
 944 }
 945 
 946 
 947 //------------------------------filtered_type--------------------------------
 948 // Return a type based on condition control flow
 949 // A successful return will be a type that is restricted due
 950 // to a series of dominating if-tests, such as:
 951 //    if (i < 10) {
 952 //       if (i > 0) {
 953 //          here: "i" type is [1..10)
 954 //       }
 955 //    }
 956 // or a control flow merge
 957 //    if (i < 10) {
 958 //       do {
 959 //          phi( , ) -- at top of loop type is [min_int..10)
 960 //         i = ?
 961 //       } while ( i < 10)
 962 //
 963 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
 964   assert(n && n->bottom_type()->is_int(), "must be int");
 965   const TypeInt* filtered_t = NULL;
 966   if (!n->is_Phi()) {
 967     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
 968     filtered_t = filtered_type_from_dominators(n, n_ctrl);
 969 
 970   } else {
 971     Node* phi    = n->as_Phi();
 972     Node* region = phi->in(0);
 973     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
 974     if (region && region != C->top()) {
 975       for (uint i = 1; i < phi->req(); i++) {
 976         Node* val   = phi->in(i);
 977         Node* use_c = region->in(i);
 978         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
 979         if (val_t != NULL) {
 980           if (filtered_t == NULL) {
 981             filtered_t = val_t;
 982           } else {
 983             filtered_t = filtered_t->meet(val_t)->is_int();
 984           }
 985         }
 986       }
 987     }
 988   }
 989   const TypeInt* n_t = _igvn.type(n)->is_int();
 990   if (filtered_t != NULL) {
 991     n_t = n_t->join(filtered_t)->is_int();
 992   }
 993   return n_t;
 994 }
 995 
 996 
 997 //------------------------------filtered_type_from_dominators--------------------------------
 998 // Return a possibly more restrictive type for val based on condition control flow of dominators
 999 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1000   if (val->is_Con()) {
1001      return val->bottom_type()->is_int();
1002   }
1003   uint if_limit = 10; // Max number of dominating if's visited
1004   const TypeInt* rtn_t = NULL;
1005 
1006   if (use_ctrl && use_ctrl != C->top()) {
1007     Node* val_ctrl = get_ctrl(val);
1008     uint val_dom_depth = dom_depth(val_ctrl);
1009     Node* pred = use_ctrl;
1010     uint if_cnt = 0;
1011     while (if_cnt < if_limit) {
1012       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1013         if_cnt++;
1014         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1015         if (if_t != NULL) {
1016           if (rtn_t == NULL) {
1017             rtn_t = if_t;
1018           } else {
1019             rtn_t = rtn_t->join(if_t)->is_int();
1020           }
1021         }
1022       }
1023       pred = idom(pred);
1024       if (pred == NULL || pred == C->top()) {
1025         break;
1026       }
1027       // Stop if going beyond definition block of val
1028       if (dom_depth(pred) < val_dom_depth) {
1029         break;
1030       }
1031     }
1032   }
1033   return rtn_t;
1034 }
1035 
1036 
1037 //------------------------------dump_spec--------------------------------------
1038 // Dump special per-node info
1039 #ifndef PRODUCT
1040 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1041   if( in(TestValue)->is_Bool() ) {
1042     BoolTest bt( test_trip()); // Added this for g++.
1043 
1044     st->print("[");
1045     bt.dump_on(st);
1046     st->print("]");
1047   }
1048   st->print(" ");
1049   IfNode::dump_spec(st);
1050 }
1051 #endif
1052 
1053 //=============================================================================
1054 //------------------------------is_member--------------------------------------
1055 // Is 'l' a member of 'this'?
1056 int IdealLoopTree::is_member( const IdealLoopTree *l ) const {
1057   while( l->_nest > _nest ) l = l->_parent;
1058   return l == this;
1059 }
1060 
1061 //------------------------------set_nest---------------------------------------
1062 // Set loop tree nesting depth.  Accumulate _has_call bits.
1063 int IdealLoopTree::set_nest( uint depth ) {
1064   _nest = depth;
1065   int bits = _has_call;
1066   if( _child ) bits |= _child->set_nest(depth+1);
1067   if( bits ) _has_call = 1;
1068   if( _next  ) bits |= _next ->set_nest(depth  );
1069   return bits;
1070 }
1071 
1072 //------------------------------split_fall_in----------------------------------
1073 // Split out multiple fall-in edges from the loop header.  Move them to a
1074 // private RegionNode before the loop.  This becomes the loop landing pad.
1075 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1076   PhaseIterGVN &igvn = phase->_igvn;
1077   uint i;
1078 
1079   // Make a new RegionNode to be the landing pad.
1080   Node *landing_pad = new (phase->C, fall_in_cnt+1) RegionNode( fall_in_cnt+1 );
1081   phase->set_loop(landing_pad,_parent);
1082   // Gather all the fall-in control paths into the landing pad
1083   uint icnt = fall_in_cnt;
1084   uint oreq = _head->req();
1085   for( i = oreq-1; i>0; i-- )
1086     if( !phase->is_member( this, _head->in(i) ) )
1087       landing_pad->set_req(icnt--,_head->in(i));
1088 
1089   // Peel off PhiNode edges as well
1090   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1091     Node *oj = _head->fast_out(j);
1092     if( oj->is_Phi() ) {
1093       PhiNode* old_phi = oj->as_Phi();
1094       assert( old_phi->region() == _head, "" );
1095       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1096       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1097       uint icnt = fall_in_cnt;
1098       for( i = oreq-1; i>0; i-- ) {
1099         if( !phase->is_member( this, _head->in(i) ) ) {
1100           p->init_req(icnt--, old_phi->in(i));
1101           // Go ahead and clean out old edges from old phi
1102           old_phi->del_req(i);
1103         }
1104       }
1105       // Search for CSE's here, because ZKM.jar does a lot of
1106       // loop hackery and we need to be a little incremental
1107       // with the CSE to avoid O(N^2) node blow-up.
1108       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1109       if( p2 ) {                // Found CSE
1110         p->destruct();          // Recover useless new node
1111         p = p2;                 // Use old node
1112       } else {
1113         igvn.register_new_node_with_optimizer(p, old_phi);
1114       }
1115       // Make old Phi refer to new Phi.
1116       old_phi->add_req(p);
1117       // Check for the special case of making the old phi useless and
1118       // disappear it.  In JavaGrande I have a case where this useless
1119       // Phi is the loop limit and prevents recognizing a CountedLoop
1120       // which in turn prevents removing an empty loop.
1121       Node *id_old_phi = old_phi->Identity( &igvn );
1122       if( id_old_phi != old_phi ) { // Found a simple identity?
1123         // Note that I cannot call 'replace_node' here, because
1124         // that will yank the edge from old_phi to the Region and
1125         // I'm mid-iteration over the Region's uses.
1126         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1127           Node* use = old_phi->last_out(i);
1128           igvn.hash_delete(use);
1129           igvn._worklist.push(use);
1130           uint uses_found = 0;
1131           for (uint j = 0; j < use->len(); j++) {
1132             if (use->in(j) == old_phi) {
1133               if (j < use->req()) use->set_req (j, id_old_phi);
1134               else                use->set_prec(j, id_old_phi);
1135               uses_found++;
1136             }
1137           }
1138           i -= uses_found;    // we deleted 1 or more copies of this edge
1139         }
1140       }
1141       igvn._worklist.push(old_phi);
1142     }
1143   }
1144   // Finally clean out the fall-in edges from the RegionNode
1145   for( i = oreq-1; i>0; i-- ) {
1146     if( !phase->is_member( this, _head->in(i) ) ) {
1147       _head->del_req(i);
1148     }
1149   }
1150   // Transform landing pad
1151   igvn.register_new_node_with_optimizer(landing_pad, _head);
1152   // Insert landing pad into the header
1153   _head->add_req(landing_pad);
1154 }
1155 
1156 //------------------------------split_outer_loop-------------------------------
1157 // Split out the outermost loop from this shared header.
1158 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1159   PhaseIterGVN &igvn = phase->_igvn;
1160 
1161   // Find index of outermost loop; it should also be my tail.
1162   uint outer_idx = 1;
1163   while( _head->in(outer_idx) != _tail ) outer_idx++;
1164 
1165   // Make a LoopNode for the outermost loop.
1166   Node *ctl = _head->in(LoopNode::EntryControl);
1167   Node *outer = new (phase->C, 3) LoopNode( ctl, _head->in(outer_idx) );
1168   outer = igvn.register_new_node_with_optimizer(outer, _head);
1169   phase->set_created_loop_node();
1170 
1171   // Outermost loop falls into '_head' loop
1172   _head->set_req(LoopNode::EntryControl, outer);
1173   _head->del_req(outer_idx);
1174   // Split all the Phis up between '_head' loop and 'outer' loop.
1175   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1176     Node *out = _head->fast_out(j);
1177     if( out->is_Phi() ) {
1178       PhiNode *old_phi = out->as_Phi();
1179       assert( old_phi->region() == _head, "" );
1180       Node *phi = PhiNode::make_blank(outer, old_phi);
1181       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1182       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1183       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1184       // Make old Phi point to new Phi on the fall-in path
1185       igvn.hash_delete(old_phi);
1186       old_phi->set_req(LoopNode::EntryControl, phi);
1187       old_phi->del_req(outer_idx);
1188       igvn._worklist.push(old_phi);
1189     }
1190   }
1191 
1192   // Use the new loop head instead of the old shared one
1193   _head = outer;
1194   phase->set_loop(_head, this);
1195 }
1196 
1197 //------------------------------fix_parent-------------------------------------
1198 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1199   loop->_parent = parent;
1200   if( loop->_child ) fix_parent( loop->_child, loop   );
1201   if( loop->_next  ) fix_parent( loop->_next , parent );
1202 }
1203 
1204 //------------------------------estimate_path_freq-----------------------------
1205 static float estimate_path_freq( Node *n ) {
1206   // Try to extract some path frequency info
1207   IfNode *iff;
1208   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1209     uint nop = n->Opcode();
1210     if( nop == Op_SafePoint ) {   // Skip any safepoint
1211       n = n->in(0);
1212       continue;
1213     }
1214     if( nop == Op_CatchProj ) {   // Get count from a prior call
1215       // Assume call does not always throw exceptions: means the call-site
1216       // count is also the frequency of the fall-through path.
1217       assert( n->is_CatchProj(), "" );
1218       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1219         return 0.0f;            // Assume call exception path is rare
1220       Node *call = n->in(0)->in(0)->in(0);
1221       assert( call->is_Call(), "expect a call here" );
1222       const JVMState *jvms = ((CallNode*)call)->jvms();
1223       ciMethodData* methodData = jvms->method()->method_data();
1224       if (!methodData->is_mature())  return 0.0f; // No call-site data
1225       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1226       if ((data == NULL) || !data->is_CounterData()) {
1227         // no call profile available, try call's control input
1228         n = n->in(0);
1229         continue;
1230       }
1231       return data->as_CounterData()->count()/FreqCountInvocations;
1232     }
1233     // See if there's a gating IF test
1234     Node *n_c = n->in(0);
1235     if( !n_c->is_If() ) break;       // No estimate available
1236     iff = n_c->as_If();
1237     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1238       // Compute how much count comes on this path
1239       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1240     // Have no count info.  Skip dull uncommon-trap like branches.
1241     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1242         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1243       break;
1244     // Skip through never-taken branch; look for a real loop exit.
1245     n = iff->in(0);
1246   }
1247   return 0.0f;                  // No estimate available
1248 }
1249 
1250 //------------------------------merge_many_backedges---------------------------
1251 // Merge all the backedges from the shared header into a private Region.
1252 // Feed that region as the one backedge to this loop.
1253 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1254   uint i;
1255 
1256   // Scan for the top 2 hottest backedges
1257   float hotcnt = 0.0f;
1258   float warmcnt = 0.0f;
1259   uint hot_idx = 0;
1260   // Loop starts at 2 because slot 1 is the fall-in path
1261   for( i = 2; i < _head->req(); i++ ) {
1262     float cnt = estimate_path_freq(_head->in(i));
1263     if( cnt > hotcnt ) {       // Grab hottest path
1264       warmcnt = hotcnt;
1265       hotcnt = cnt;
1266       hot_idx = i;
1267     } else if( cnt > warmcnt ) { // And 2nd hottest path
1268       warmcnt = cnt;
1269     }
1270   }
1271 
1272   // See if the hottest backedge is worthy of being an inner loop
1273   // by being much hotter than the next hottest backedge.
1274   if( hotcnt <= 0.0001 ||
1275       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1276 
1277   // Peel out the backedges into a private merge point; peel
1278   // them all except optionally hot_idx.
1279   PhaseIterGVN &igvn = phase->_igvn;
1280 
1281   Node *hot_tail = NULL;
1282   // Make a Region for the merge point
1283   Node *r = new (phase->C, 1) RegionNode(1);
1284   for( i = 2; i < _head->req(); i++ ) {
1285     if( i != hot_idx )
1286       r->add_req( _head->in(i) );
1287     else hot_tail = _head->in(i);
1288   }
1289   igvn.register_new_node_with_optimizer(r, _head);
1290   // Plug region into end of loop _head, followed by hot_tail
1291   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1292   _head->set_req(2, r);
1293   if( hot_idx ) _head->add_req(hot_tail);
1294 
1295   // Split all the Phis up between '_head' loop and the Region 'r'
1296   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1297     Node *out = _head->fast_out(j);
1298     if( out->is_Phi() ) {
1299       PhiNode* n = out->as_Phi();
1300       igvn.hash_delete(n);      // Delete from hash before hacking edges
1301       Node *hot_phi = NULL;
1302       Node *phi = new (phase->C, r->req()) PhiNode(r, n->type(), n->adr_type());
1303       // Check all inputs for the ones to peel out
1304       uint j = 1;
1305       for( uint i = 2; i < n->req(); i++ ) {
1306         if( i != hot_idx )
1307           phi->set_req( j++, n->in(i) );
1308         else hot_phi = n->in(i);
1309       }
1310       // Register the phi but do not transform until whole place transforms
1311       igvn.register_new_node_with_optimizer(phi, n);
1312       // Add the merge phi to the old Phi
1313       while( n->req() > 3 ) n->del_req( n->req()-1 );
1314       n->set_req(2, phi);
1315       if( hot_idx ) n->add_req(hot_phi);
1316     }
1317   }
1318 
1319 
1320   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
1321   // of self loop tree.  Turn self into a loop headed by _head and with
1322   // tail being the new merge point.
1323   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
1324   phase->set_loop(_tail,ilt);   // Adjust tail
1325   _tail = r;                    // Self's tail is new merge point
1326   phase->set_loop(r,this);
1327   ilt->_child = _child;         // New guy has my children
1328   _child = ilt;                 // Self has new guy as only child
1329   ilt->_parent = this;          // new guy has self for parent
1330   ilt->_nest = _nest;           // Same nesting depth (for now)
1331 
1332   // Starting with 'ilt', look for child loop trees using the same shared
1333   // header.  Flatten these out; they will no longer be loops in the end.
1334   IdealLoopTree **pilt = &_child;
1335   while( ilt ) {
1336     if( ilt->_head == _head ) {
1337       uint i;
1338       for( i = 2; i < _head->req(); i++ )
1339         if( _head->in(i) == ilt->_tail )
1340           break;                // Still a loop
1341       if( i == _head->req() ) { // No longer a loop
1342         // Flatten ilt.  Hang ilt's "_next" list from the end of
1343         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
1344         IdealLoopTree **cp = &ilt->_child;
1345         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
1346         *cp = ilt->_next;       // Hang next list at end of child list
1347         *pilt = ilt->_child;    // Move child up to replace ilt
1348         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
1349         ilt = ilt->_child;      // Repeat using new ilt
1350         continue;               // do not advance over ilt->_child
1351       }
1352       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
1353       phase->set_loop(_head,ilt);
1354     }
1355     pilt = &ilt->_child;        // Advance to next
1356     ilt = *pilt;
1357   }
1358 
1359   if( _child ) fix_parent( _child, this );
1360 }
1361 
1362 //------------------------------beautify_loops---------------------------------
1363 // Split shared headers and insert loop landing pads.
1364 // Insert a LoopNode to replace the RegionNode.
1365 // Return TRUE if loop tree is structurally changed.
1366 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
1367   bool result = false;
1368   // Cache parts in locals for easy
1369   PhaseIterGVN &igvn = phase->_igvn;
1370 
1371   igvn.hash_delete(_head);      // Yank from hash before hacking edges
1372 
1373   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
1374   int fall_in_cnt = 0;
1375   for( uint i = 1; i < _head->req(); i++ )
1376     if( !phase->is_member( this, _head->in(i) ) )
1377       fall_in_cnt++;
1378   assert( fall_in_cnt, "at least 1 fall-in path" );
1379   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
1380     split_fall_in( phase, fall_in_cnt );
1381 
1382   // Swap inputs to the _head and all Phis to move the fall-in edge to
1383   // the left.
1384   fall_in_cnt = 1;
1385   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
1386     fall_in_cnt++;
1387   if( fall_in_cnt > 1 ) {
1388     // Since I am just swapping inputs I do not need to update def-use info
1389     Node *tmp = _head->in(1);
1390     _head->set_req( 1, _head->in(fall_in_cnt) );
1391     _head->set_req( fall_in_cnt, tmp );
1392     // Swap also all Phis
1393     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
1394       Node* phi = _head->fast_out(i);
1395       if( phi->is_Phi() ) {
1396         igvn.hash_delete(phi); // Yank from hash before hacking edges
1397         tmp = phi->in(1);
1398         phi->set_req( 1, phi->in(fall_in_cnt) );
1399         phi->set_req( fall_in_cnt, tmp );
1400       }
1401     }
1402   }
1403   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
1404   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
1405 
1406   // If I am a shared header (multiple backedges), peel off the many
1407   // backedges into a private merge point and use the merge point as
1408   // the one true backedge.
1409   if( _head->req() > 3 ) {
1410     // Merge the many backedges into a single backedge but leave
1411     // the hottest backedge as separate edge for the following peel.
1412     merge_many_backedges( phase );
1413     result = true;
1414   }
1415 
1416   // If I have one hot backedge, peel off myself loop.
1417   // I better be the outermost loop.
1418   if( _head->req() > 3 ) {
1419     split_outer_loop( phase );
1420     result = true;
1421 
1422   } else if( !_head->is_Loop() && !_irreducible ) {
1423     // Make a new LoopNode to replace the old loop head
1424     Node *l = new (phase->C, 3) LoopNode( _head->in(1), _head->in(2) );
1425     l = igvn.register_new_node_with_optimizer(l, _head);
1426     phase->set_created_loop_node();
1427     // Go ahead and replace _head
1428     phase->_igvn.replace_node( _head, l );
1429     _head = l;
1430     phase->set_loop(_head, this);
1431   }
1432 
1433   // Now recursively beautify nested loops
1434   if( _child ) result |= _child->beautify_loops( phase );
1435   if( _next  ) result |= _next ->beautify_loops( phase );
1436   return result;
1437 }
1438 
1439 //------------------------------allpaths_check_safepts----------------------------
1440 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
1441 // encountered.  Helper for check_safepts.
1442 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
1443   assert(stack.size() == 0, "empty stack");
1444   stack.push(_tail);
1445   visited.Clear();
1446   visited.set(_tail->_idx);
1447   while (stack.size() > 0) {
1448     Node* n = stack.pop();
1449     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1450       // Terminate this path
1451     } else if (n->Opcode() == Op_SafePoint) {
1452       if (_phase->get_loop(n) != this) {
1453         if (_required_safept == NULL) _required_safept = new Node_List();
1454         _required_safept->push(n);  // save the one closest to the tail
1455       }
1456       // Terminate this path
1457     } else {
1458       uint start = n->is_Region() ? 1 : 0;
1459       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
1460       for (uint i = start; i < end; i++) {
1461         Node* in = n->in(i);
1462         assert(in->is_CFG(), "must be");
1463         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
1464           stack.push(in);
1465         }
1466       }
1467     }
1468   }
1469 }
1470 
1471 //------------------------------check_safepts----------------------------
1472 // Given dominators, try to find loops with calls that must always be
1473 // executed (call dominates loop tail).  These loops do not need non-call
1474 // safepoints (ncsfpt).
1475 //
1476 // A complication is that a safepoint in a inner loop may be needed
1477 // by an outer loop. In the following, the inner loop sees it has a
1478 // call (block 3) on every path from the head (block 2) to the
1479 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
1480 // in block 2, _but_ this leaves the outer loop without a safepoint.
1481 //
1482 //          entry  0
1483 //                 |
1484 //                 v
1485 // outer 1,2    +->1
1486 //              |  |
1487 //              |  v
1488 //              |  2<---+  ncsfpt in 2
1489 //              |_/|\   |
1490 //                 | v  |
1491 // inner 2,3      /  3  |  call in 3
1492 //               /   |  |
1493 //              v    +--+
1494 //        exit  4
1495 //
1496 //
1497 // This method creates a list (_required_safept) of ncsfpt nodes that must
1498 // be protected is created for each loop. When a ncsfpt maybe deleted, it
1499 // is first looked for in the lists for the outer loops of the current loop.
1500 //
1501 // The insights into the problem:
1502 //  A) counted loops are okay
1503 //  B) innermost loops are okay (only an inner loop can delete
1504 //     a ncsfpt needed by an outer loop)
1505 //  C) a loop is immune from an inner loop deleting a safepoint
1506 //     if the loop has a call on the idom-path
1507 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
1508 //     idom-path that is not in a nested loop
1509 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
1510 //     loop needs to be prevented from deletion by an inner loop
1511 //
1512 // There are two analyses:
1513 //  1) The first, and cheaper one, scans the loop body from
1514 //     tail to head following the idom (immediate dominator)
1515 //     chain, looking for the cases (C,D,E) above.
1516 //     Since inner loops are scanned before outer loops, there is summary
1517 //     information about inner loops.  Inner loops can be skipped over
1518 //     when the tail of an inner loop is encountered.
1519 //
1520 //  2) The second, invoked if the first fails to find a call or ncsfpt on
1521 //     the idom path (which is rare), scans all predecessor control paths
1522 //     from the tail to the head, terminating a path when a call or sfpt
1523 //     is encountered, to find the ncsfpt's that are closest to the tail.
1524 //
1525 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
1526   // Bottom up traversal
1527   IdealLoopTree* ch = _child;
1528   while (ch != NULL) {
1529     ch->check_safepts(visited, stack);
1530     ch = ch->_next;
1531   }
1532 
1533   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
1534     bool  has_call         = false; // call on dom-path
1535     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
1536     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
1537     // Scan the dom-path nodes from tail to head
1538     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
1539       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1540         has_call = true;
1541         _has_sfpt = 1;          // Then no need for a safept!
1542         break;
1543       } else if (n->Opcode() == Op_SafePoint) {
1544         if (_phase->get_loop(n) == this) {
1545           has_local_ncsfpt = true;
1546           break;
1547         }
1548         if (nonlocal_ncsfpt == NULL) {
1549           nonlocal_ncsfpt = n; // save the one closest to the tail
1550         }
1551       } else {
1552         IdealLoopTree* nlpt = _phase->get_loop(n);
1553         if (this != nlpt) {
1554           // If at an inner loop tail, see if the inner loop has already
1555           // recorded seeing a call on the dom-path (and stop.)  If not,
1556           // jump to the head of the inner loop.
1557           assert(is_member(nlpt), "nested loop");
1558           Node* tail = nlpt->_tail;
1559           if (tail->in(0)->is_If()) tail = tail->in(0);
1560           if (n == tail) {
1561             // If inner loop has call on dom-path, so does outer loop
1562             if (nlpt->_has_sfpt) {
1563               has_call = true;
1564               _has_sfpt = 1;
1565               break;
1566             }
1567             // Skip to head of inner loop
1568             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
1569             n = nlpt->_head;
1570           }
1571         }
1572       }
1573     }
1574     // Record safept's that this loop needs preserved when an
1575     // inner loop attempts to delete it's safepoints.
1576     if (_child != NULL && !has_call && !has_local_ncsfpt) {
1577       if (nonlocal_ncsfpt != NULL) {
1578         if (_required_safept == NULL) _required_safept = new Node_List();
1579         _required_safept->push(nonlocal_ncsfpt);
1580       } else {
1581         // Failed to find a suitable safept on the dom-path.  Now use
1582         // an all paths walk from tail to head, looking for safepoints to preserve.
1583         allpaths_check_safepts(visited, stack);
1584       }
1585     }
1586   }
1587 }
1588 
1589 //---------------------------is_deleteable_safept----------------------------
1590 // Is safept not required by an outer loop?
1591 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
1592   assert(sfpt->Opcode() == Op_SafePoint, "");
1593   IdealLoopTree* lp = get_loop(sfpt)->_parent;
1594   while (lp != NULL) {
1595     Node_List* sfpts = lp->_required_safept;
1596     if (sfpts != NULL) {
1597       for (uint i = 0; i < sfpts->size(); i++) {
1598         if (sfpt == sfpts->at(i))
1599           return false;
1600       }
1601     }
1602     lp = lp->_parent;
1603   }
1604   return true;
1605 }
1606 
1607 //---------------------------replace_parallel_iv-------------------------------
1608 // Replace parallel induction variable (parallel to trip counter)
1609 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
1610   assert(loop->_head->is_CountedLoop(), "");
1611   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1612   if (!cl->is_valid_counted_loop())
1613     return;         // skip malformed counted loop
1614   Node *incr = cl->incr();
1615   if (incr == NULL)
1616     return;         // Dead loop?
1617   Node *init = cl->init_trip();
1618   Node *phi  = cl->phi();



1619   int stride_con = cl->stride_con();
1620 
1621   PhaseGVN *gvn = &_igvn;
1622 
1623   // Visit all children, looking for Phis
1624   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
1625     Node *out = cl->out(i);
1626     // Look for other phis (secondary IVs). Skip dead ones
1627     if (!out->is_Phi() || out == phi || !has_node(out))
1628       continue;
1629     PhiNode* phi2 = out->as_Phi();
1630     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
1631     // Look for induction variables of the form:  X += constant
1632     if (phi2->region() != loop->_head ||
1633         incr2->req() != 3 ||
1634         incr2->in(1) != phi2 ||
1635         incr2 == incr ||
1636         incr2->Opcode() != Op_AddI ||
1637         !incr2->in(2)->is_Con())
1638       continue;
1639 
1640     // Check for parallel induction variable (parallel to trip counter)
1641     // via an affine function.  In particular, count-down loops with
1642     // count-up array indices are common. We only RCE references off
1643     // the trip-counter, so we need to convert all these to trip-counter
1644     // expressions.
1645     Node *init2 = phi2->in( LoopNode::EntryControl );
1646     int stride_con2 = incr2->in(2)->get_int();
1647 
1648     // The general case here gets a little tricky.  We want to find the
1649     // GCD of all possible parallel IV's and make a new IV using this
1650     // GCD for the loop.  Then all possible IVs are simple multiples of
1651     // the GCD.  In practice, this will cover very few extra loops.
1652     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
1653     // where +/-1 is the common case, but other integer multiples are
1654     // also easy to handle.
1655     int ratio_con = stride_con2/stride_con;
1656 
1657     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
1658       // Convert to using the trip counter.  The parallel induction
1659       // variable differs from the trip counter by a loop-invariant
1660       // amount, the difference between their respective initial values.
1661       // It is scaled by the 'ratio_con'.
1662       // Perform local Ideal transformation since in most cases ratio == 1.
1663       Node* ratio = _igvn.intcon(ratio_con);
1664       set_ctrl(ratio, C->root());
1665       Node* hook = new (C, 3) Node(3);
1666       Node* ratio_init = gvn->transform(new (C, 3) MulINode(init, ratio));
1667       hook->init_req(0, ratio_init);
1668       Node* diff = gvn->transform(new (C, 3) SubINode(init2, ratio_init));
1669       hook->init_req(1, diff);
1670       Node* ratio_idx = gvn->transform(new (C, 3) MulINode(phi, ratio));
1671       hook->init_req(2, ratio_idx);
1672       Node* add  = gvn->transform(new (C, 3) AddINode(ratio_idx, diff));
1673       set_subtree_ctrl(add);
1674       _igvn.replace_node( phi2, add );
1675       // Free up intermediate goo
1676       _igvn.remove_dead_node(hook);
1677       // Sometimes an induction variable is unused
1678       if (add->outcnt() == 0) {
1679         _igvn.remove_dead_node(add);
1680       }
1681       --i; // deleted this phi; rescan starting with next position
1682       continue;
1683     }
1684   }
1685 }
1686 
1687 //------------------------------counted_loop-----------------------------------
1688 // Convert to counted loops where possible
1689 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
1690 
1691   // For grins, set the inner-loop flag here
1692   if (!_child) {
1693     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
1694   }
1695 
1696   if (_head->is_CountedLoop() ||
1697       phase->is_counted_loop(_head, this)) {
1698     _has_sfpt = 1;              // Indicate we do not need a safepoint here
1699 
1700     // Look for a safepoint to remove
1701     for (Node* n = tail(); n != _head; n = phase->idom(n))
1702       if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this &&
1703           phase->is_deleteable_safept(n))
1704         phase->lazy_replace(n,n->in(TypeFunc::Control));
1705 
1706     // Look for induction variables
1707     phase->replace_parallel_iv(this);
1708 
1709   } else if (_parent != NULL && !_irreducible) {
1710     // Not a counted loop.
1711     // Look for a safepoint on the idom-path to remove, preserving the first one
1712     bool found = false;
1713     Node* n = tail();
1714     for (; n != _head && !found; n = phase->idom(n)) {
1715       if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this)
1716         found = true; // Found one
1717     }
1718     // Skip past it and delete the others
1719     for (; n != _head; n = phase->idom(n)) {
1720       if (n->Opcode() == Op_SafePoint && phase->get_loop(n) == this &&
1721           phase->is_deleteable_safept(n))
1722         phase->lazy_replace(n,n->in(TypeFunc::Control));
1723     }
1724   }
1725 
1726   // Recursively
1727   if (_child) _child->counted_loop( phase );
1728   if (_next)  _next ->counted_loop( phase );
1729 }
1730 
1731 #ifndef PRODUCT
1732 //------------------------------dump_head--------------------------------------
1733 // Dump 1 liner for loop header info
1734 void IdealLoopTree::dump_head( ) const {
1735   for (uint i=0; i<_nest; i++)
1736     tty->print("  ");
1737   tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
1738   if (_irreducible) tty->print(" IRREDUCIBLE");
1739   Node* entry = _head->in(LoopNode::EntryControl);
1740   if (LoopLimitCheck) {
1741     Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1742     if (predicate != NULL ) {
1743       tty->print(" limit_check");
1744       entry = entry->in(0)->in(0);
1745     }
1746   }
1747   if (UseLoopPredicate) {
1748     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1749     if (entry != NULL) {
1750       tty->print(" predicated");
1751     }
1752   }
1753   if (_head->is_CountedLoop()) {
1754     CountedLoopNode *cl = _head->as_CountedLoop();
1755     tty->print(" counted");
1756 
1757     Node* init_n = cl->init_trip();
1758     if (init_n  != NULL &&  init_n->is_Con())
1759       tty->print(" [%d,", cl->init_trip()->get_int());
1760     else
1761       tty->print(" [int,");
1762     Node* limit_n = cl->limit();
1763     if (limit_n  != NULL &&  limit_n->is_Con())
1764       tty->print("%d),", cl->limit()->get_int());
1765     else
1766       tty->print("int),");
1767     int stride_con  = cl->stride_con();
1768     if (stride_con > 0) tty->print("+");
1769     tty->print("%d", stride_con);
1770 
1771     if (cl->is_pre_loop ()) tty->print(" pre" );
1772     if (cl->is_main_loop()) tty->print(" main");
1773     if (cl->is_post_loop()) tty->print(" post");
1774   }
1775   tty->cr();
1776 }
1777 
1778 //------------------------------dump-------------------------------------------
1779 // Dump loops by loop tree
1780 void IdealLoopTree::dump( ) const {
1781   dump_head();
1782   if (_child) _child->dump();
1783   if (_next)  _next ->dump();
1784 }
1785 
1786 #endif
1787 
1788 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
1789   if (loop == root) {
1790     if (loop->_child != NULL) {
1791       log->begin_head("loop_tree");
1792       log->end_head();
1793       if( loop->_child ) log_loop_tree(root, loop->_child, log);
1794       log->tail("loop_tree");
1795       assert(loop->_next == NULL, "what?");
1796     }
1797   } else {
1798     Node* head = loop->_head;
1799     log->begin_head("loop");
1800     log->print(" idx='%d' ", head->_idx);
1801     if (loop->_irreducible) log->print("irreducible='1' ");
1802     if (head->is_Loop()) {
1803       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
1804       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
1805     }
1806     if (head->is_CountedLoop()) {
1807       CountedLoopNode* cl = head->as_CountedLoop();
1808       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
1809       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
1810       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
1811     }
1812     log->end_head();
1813     if( loop->_child ) log_loop_tree(root, loop->_child, log);
1814     log->tail("loop");
1815     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
1816   }
1817 }
1818 
1819 //---------------------collect_potentially_useful_predicates-----------------------
1820 // Helper function to collect potentially useful predicates to prevent them from
1821 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
1822 void PhaseIdealLoop::collect_potentially_useful_predicates(
1823                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
1824   if (loop->_child) { // child
1825     collect_potentially_useful_predicates(loop->_child, useful_predicates);
1826   }
1827 
1828   // self (only loops that we can apply loop predication may use their predicates)
1829   if (loop->_head->is_Loop() &&
1830       !loop->_irreducible    &&
1831       !loop->tail()->is_top()) {
1832     LoopNode* lpn = loop->_head->as_Loop();
1833     Node* entry = lpn->in(LoopNode::EntryControl);
1834     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
1835     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
1836       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
1837       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
1838       entry = entry->in(0)->in(0);
1839     }
1840     predicate_proj = find_predicate(entry); // Predicate
1841     if (predicate_proj != NULL ) {
1842       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
1843     }
1844   }
1845 
1846   if (loop->_next) { // sibling
1847     collect_potentially_useful_predicates(loop->_next, useful_predicates);
1848   }
1849 }
1850 
1851 //------------------------eliminate_useless_predicates-----------------------------
1852 // Eliminate all inserted predicates if they could not be used by loop predication.
1853 // Note: it will also eliminates loop limits check predicate since it also uses
1854 // Opaque1 node (see Parse::add_predicate()).
1855 void PhaseIdealLoop::eliminate_useless_predicates() {
1856   if (C->predicate_count() == 0)
1857     return; // no predicate left
1858 
1859   Unique_Node_List useful_predicates; // to store useful predicates
1860   if (C->has_loops()) {
1861     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
1862   }
1863 
1864   for (int i = C->predicate_count(); i > 0; i--) {
1865      Node * n = C->predicate_opaque1_node(i-1);
1866      assert(n->Opcode() == Op_Opaque1, "must be");
1867      if (!useful_predicates.member(n)) { // not in the useful list
1868        _igvn.replace_node(n, n->in(1));
1869      }
1870   }
1871 }
1872 
1873 //=============================================================================
1874 //----------------------------build_and_optimize-------------------------------
1875 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
1876 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
1877 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs) {
1878   ResourceMark rm;
1879 
1880   int old_progress = C->major_progress();
1881   uint orig_worklist_size = _igvn._worklist.size();
1882 
1883   // Reset major-progress flag for the driver's heuristics
1884   C->clear_major_progress();
1885 
1886 #ifndef PRODUCT
1887   // Capture for later assert
1888   uint unique = C->unique();
1889   _loop_invokes++;
1890   _loop_work += unique;
1891 #endif
1892 
1893   // True if the method has at least 1 irreducible loop
1894   _has_irreducible_loops = false;
1895 
1896   _created_loop_node = false;
1897 
1898   Arena *a = Thread::current()->resource_area();
1899   VectorSet visited(a);
1900   // Pre-grow the mapping from Nodes to IdealLoopTrees.
1901   _nodes.map(C->unique(), NULL);
1902   memset(_nodes.adr(), 0, wordSize * C->unique());
1903 
1904   // Pre-build the top-level outermost loop tree entry
1905   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
1906   // Do not need a safepoint at the top level
1907   _ltree_root->_has_sfpt = 1;
1908 
1909   // Initialize Dominators.
1910   // Checked in clone_loop_predicate() during beautify_loops().
1911   _idom_size = 0;
1912   _idom      = NULL;
1913   _dom_depth = NULL;
1914   _dom_stk   = NULL;
1915 
1916   // Empty pre-order array
1917   allocate_preorders();
1918 
1919   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
1920   // IdealLoopTree entries.  Data nodes are NOT walked.
1921   build_loop_tree();
1922   // Check for bailout, and return
1923   if (C->failing()) {
1924     return;
1925   }
1926 
1927   // No loops after all
1928   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
1929 
1930   // There should always be an outer loop containing the Root and Return nodes.
1931   // If not, we have a degenerate empty program.  Bail out in this case.
1932   if (!has_node(C->root())) {
1933     if (!_verify_only) {
1934       C->clear_major_progress();
1935       C->record_method_not_compilable("empty program detected during loop optimization");
1936     }
1937     return;
1938   }
1939 
1940   // Nothing to do, so get out
1941   if( !C->has_loops() && !do_split_ifs && !_verify_me && !_verify_only ) {
1942     _igvn.optimize();           // Cleanup NeverBranches
1943     return;
1944   }
1945 
1946   // Set loop nesting depth
1947   _ltree_root->set_nest( 0 );
1948 
1949   // Split shared headers and insert loop landing pads.
1950   // Do not bother doing this on the Root loop of course.
1951   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
1952     C->print_method("Before beautify loops", 3);
1953     if( _ltree_root->_child->beautify_loops( this ) ) {
1954       // Re-build loop tree!
1955       _ltree_root->_child = NULL;
1956       _nodes.clear();
1957       reallocate_preorders();
1958       build_loop_tree();
1959       // Check for bailout, and return
1960       if (C->failing()) {
1961         return;
1962       }
1963       // Reset loop nesting depth
1964       _ltree_root->set_nest( 0 );
1965 
1966       C->print_method("After beautify loops", 3);
1967     }
1968   }
1969 
1970   // Build Dominators for elision of NULL checks & loop finding.
1971   // Since nodes do not have a slot for immediate dominator, make
1972   // a persistent side array for that info indexed on node->_idx.
1973   _idom_size = C->unique();
1974   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
1975   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
1976   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
1977   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
1978 
1979   Dominators();
1980 
1981   if (!_verify_only) {
1982     // As a side effect, Dominators removed any unreachable CFG paths
1983     // into RegionNodes.  It doesn't do this test against Root, so
1984     // we do it here.
1985     for( uint i = 1; i < C->root()->req(); i++ ) {
1986       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
1987         _igvn.hash_delete(C->root());
1988         C->root()->del_req(i);
1989         _igvn._worklist.push(C->root());
1990         i--;                      // Rerun same iteration on compressed edges
1991       }
1992     }
1993 
1994     // Given dominators, try to find inner loops with calls that must
1995     // always be executed (call dominates loop tail).  These loops do
1996     // not need a separate safepoint.
1997     Node_List cisstack(a);
1998     _ltree_root->check_safepts(visited, cisstack);
1999   }
2000 
2001   // Walk the DATA nodes and place into loops.  Find earliest control
2002   // node.  For CFG nodes, the _nodes array starts out and remains
2003   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2004   // _nodes array holds the earliest legal controlling CFG node.
2005 
2006   // Allocate stack with enough space to avoid frequent realloc
2007   int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats
2008   Node_Stack nstack( a, stack_size );
2009 
2010   visited.Clear();
2011   Node_List worklist(a);
2012   // Don't need C->root() on worklist since
2013   // it will be processed among C->top() inputs
2014   worklist.push( C->top() );
2015   visited.set( C->top()->_idx ); // Set C->top() as visited now
2016   build_loop_early( visited, worklist, nstack );
2017 
2018   // Given early legal placement, try finding counted loops.  This placement
2019   // is good enough to discover most loop invariants.
2020   if( !_verify_me && !_verify_only )
2021     _ltree_root->counted_loop( this );
2022 
2023   // Find latest loop placement.  Find ideal loop placement.
2024   visited.Clear();
2025   init_dom_lca_tags();
2026   // Need C->root() on worklist when processing outs
2027   worklist.push( C->root() );
2028   NOT_PRODUCT( C->verify_graph_edges(); )
2029   worklist.push( C->top() );
2030   build_loop_late( visited, worklist, nstack );
2031 
2032   if (_verify_only) {
2033     // restore major progress flag
2034     for (int i = 0; i < old_progress; i++)
2035       C->set_major_progress();
2036     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2037     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2038     return;
2039   }
2040 
2041   // Some parser-inserted loop predicates could never be used by loop
2042   // predication or they were moved away from loop during some optimizations.
2043   // For example, peeling. Eliminate them before next loop optimizations.
2044   if (UseLoopPredicate || LoopLimitCheck) {
2045     eliminate_useless_predicates();
2046   }
2047 
2048   // clear out the dead code
2049   while(_deadlist.size()) {
2050     _igvn.remove_globally_dead_node(_deadlist.pop());
2051   }
2052 
2053 #ifndef PRODUCT
2054   C->verify_graph_edges();
2055   if (_verify_me) {             // Nested verify pass?
2056     // Check to see if the verify mode is broken
2057     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2058     return;
2059   }
2060   if(VerifyLoopOptimizations) verify();
2061   if(TraceLoopOpts && C->has_loops()) {
2062     _ltree_root->dump();
2063   }
2064 #endif
2065 
2066   if (ReassociateInvariants) {
2067     // Reassociate invariants and prep for split_thru_phi
2068     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2069       IdealLoopTree* lpt = iter.current();
2070       if (!lpt->is_counted() || !lpt->is_inner()) continue;
2071 
2072       lpt->reassociate_invariants(this);
2073 
2074       // Because RCE opportunities can be masked by split_thru_phi,
2075       // look for RCE candidates and inhibit split_thru_phi
2076       // on just their loop-phi's for this pass of loop opts
2077       if (SplitIfBlocks && do_split_ifs) {
2078         if (lpt->policy_range_check(this)) {
2079           lpt->_rce_candidate = 1; // = true
2080         }
2081       }
2082     }
2083   }
2084 
2085   // Check for aggressive application of split-if and other transforms
2086   // that require basic-block info (like cloning through Phi's)
2087   if( SplitIfBlocks && do_split_ifs ) {
2088     visited.Clear();
2089     split_if_with_blocks( visited, nstack );
2090     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2091   }
2092 
2093   // Perform loop predication before iteration splitting
2094   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2095     _ltree_root->_child->loop_predication(this);
2096   }
2097 
2098   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2099     if (do_intrinsify_fill()) {
2100       C->set_major_progress();
2101     }
2102   }
2103 
2104   // Perform iteration-splitting on inner loops.  Split iterations to avoid
2105   // range checks or one-shot null checks.
2106 
2107   // If split-if's didn't hack the graph too bad (no CFG changes)
2108   // then do loop opts.
2109   if (C->has_loops() && !C->major_progress()) {
2110     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
2111     _ltree_root->_child->iteration_split( this, worklist );
2112     // No verify after peeling!  GCM has hoisted code out of the loop.
2113     // After peeling, the hoisted code could sink inside the peeled area.
2114     // The peeling code does not try to recompute the best location for
2115     // all the code before the peeled area, so the verify pass will always
2116     // complain about it.
2117   }
2118   // Do verify graph edges in any case
2119   NOT_PRODUCT( C->verify_graph_edges(); );
2120 
2121   if (!do_split_ifs) {
2122     // We saw major progress in Split-If to get here.  We forced a
2123     // pass with unrolling and not split-if, however more split-if's
2124     // might make progress.  If the unrolling didn't make progress
2125     // then the major-progress flag got cleared and we won't try
2126     // another round of Split-If.  In particular the ever-common
2127     // instance-of/check-cast pattern requires at least 2 rounds of
2128     // Split-If to clear out.
2129     C->set_major_progress();
2130   }
2131 
2132   // Repeat loop optimizations if new loops were seen
2133   if (created_loop_node()) {
2134     C->set_major_progress();
2135   }
2136 
2137   // Keep loop predicates and perform optimizations with them
2138   // until no more loop optimizations could be done.
2139   // After that switch predicates off and do more loop optimizations.
2140   if (!C->major_progress() && (C->predicate_count() > 0)) {
2141      C->cleanup_loop_predicates(_igvn);
2142 #ifndef PRODUCT
2143      if (TraceLoopOpts) {
2144        tty->print_cr("PredicatesOff");
2145      }
2146 #endif
2147      C->set_major_progress();
2148   }
2149 
2150   // Convert scalar to superword operations at the end of all loop opts.
2151   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
2152     // SuperWord transform
2153     SuperWord sw(this);
2154     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2155       IdealLoopTree* lpt = iter.current();
2156       if (lpt->is_counted()) {
2157         sw.transform_loop(lpt);
2158       }
2159     }
2160   }
2161 
2162   // Cleanup any modified bits
2163   _igvn.optimize();
2164 
2165   // disable assert until issue with split_flow_path is resolved (6742111)
2166   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
2167   //        "shouldn't introduce irreducible loops");
2168 
2169   if (C->log() != NULL) {
2170     log_loop_tree(_ltree_root, _ltree_root, C->log());
2171   }
2172 }
2173 
2174 #ifndef PRODUCT
2175 //------------------------------print_statistics-------------------------------
2176 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
2177 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
2178 void PhaseIdealLoop::print_statistics() {
2179   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
2180 }
2181 
2182 //------------------------------verify-----------------------------------------
2183 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
2184 static int fail;                // debug only, so its multi-thread dont care
2185 void PhaseIdealLoop::verify() const {
2186   int old_progress = C->major_progress();
2187   ResourceMark rm;
2188   PhaseIdealLoop loop_verify( _igvn, this );
2189   VectorSet visited(Thread::current()->resource_area());
2190 
2191   fail = 0;
2192   verify_compare( C->root(), &loop_verify, visited );
2193   assert( fail == 0, "verify loops failed" );
2194   // Verify loop structure is the same
2195   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
2196   // Reset major-progress.  It was cleared by creating a verify version of
2197   // PhaseIdealLoop.
2198   for( int i=0; i<old_progress; i++ )
2199     C->set_major_progress();
2200 }
2201 
2202 //------------------------------verify_compare---------------------------------
2203 // Make sure me and the given PhaseIdealLoop agree on key data structures
2204 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
2205   if( !n ) return;
2206   if( visited.test_set( n->_idx ) ) return;
2207   if( !_nodes[n->_idx] ) {      // Unreachable
2208     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
2209     return;
2210   }
2211 
2212   uint i;
2213   for( i = 0; i < n->req(); i++ )
2214     verify_compare( n->in(i), loop_verify, visited );
2215 
2216   // Check the '_nodes' block/loop structure
2217   i = n->_idx;
2218   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
2219     if( _nodes[i] != loop_verify->_nodes[i] &&
2220         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
2221       tty->print("Mismatched control setting for: ");
2222       n->dump();
2223       if( fail++ > 10 ) return;
2224       Node *c = get_ctrl_no_update(n);
2225       tty->print("We have it as: ");
2226       if( c->in(0) ) c->dump();
2227         else tty->print_cr("N%d",c->_idx);
2228       tty->print("Verify thinks: ");
2229       if( loop_verify->has_ctrl(n) )
2230         loop_verify->get_ctrl_no_update(n)->dump();
2231       else
2232         loop_verify->get_loop_idx(n)->dump();
2233       tty->cr();
2234     }
2235   } else {                    // We have a loop
2236     IdealLoopTree *us = get_loop_idx(n);
2237     if( loop_verify->has_ctrl(n) ) {
2238       tty->print("Mismatched loop setting for: ");
2239       n->dump();
2240       if( fail++ > 10 ) return;
2241       tty->print("We have it as: ");
2242       us->dump();
2243       tty->print("Verify thinks: ");
2244       loop_verify->get_ctrl_no_update(n)->dump();
2245       tty->cr();
2246     } else if (!C->major_progress()) {
2247       // Loop selection can be messed up if we did a major progress
2248       // operation, like split-if.  Do not verify in that case.
2249       IdealLoopTree *them = loop_verify->get_loop_idx(n);
2250       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
2251         tty->print("Unequals loops for: ");
2252         n->dump();
2253         if( fail++ > 10 ) return;
2254         tty->print("We have it as: ");
2255         us->dump();
2256         tty->print("Verify thinks: ");
2257         them->dump();
2258         tty->cr();
2259       }
2260     }
2261   }
2262 
2263   // Check for immediate dominators being equal
2264   if( i >= _idom_size ) {
2265     if( !n->is_CFG() ) return;
2266     tty->print("CFG Node with no idom: ");
2267     n->dump();
2268     return;
2269   }
2270   if( !n->is_CFG() ) return;
2271   if( n == C->root() ) return; // No IDOM here
2272 
2273   assert(n->_idx == i, "sanity");
2274   Node *id = idom_no_update(n);
2275   if( id != loop_verify->idom_no_update(n) ) {
2276     tty->print("Unequals idoms for: ");
2277     n->dump();
2278     if( fail++ > 10 ) return;
2279     tty->print("We have it as: ");
2280     id->dump();
2281     tty->print("Verify thinks: ");
2282     loop_verify->idom_no_update(n)->dump();
2283     tty->cr();
2284   }
2285 
2286 }
2287 
2288 //------------------------------verify_tree------------------------------------
2289 // Verify that tree structures match.  Because the CFG can change, siblings
2290 // within the loop tree can be reordered.  We attempt to deal with that by
2291 // reordering the verify's loop tree if possible.
2292 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
2293   assert( _parent == parent, "Badly formed loop tree" );
2294 
2295   // Siblings not in same order?  Attempt to re-order.
2296   if( _head != loop->_head ) {
2297     // Find _next pointer to update
2298     IdealLoopTree **pp = &loop->_parent->_child;
2299     while( *pp != loop )
2300       pp = &((*pp)->_next);
2301     // Find proper sibling to be next
2302     IdealLoopTree **nn = &loop->_next;
2303     while( (*nn) && (*nn)->_head != _head )
2304       nn = &((*nn)->_next);
2305 
2306     // Check for no match.
2307     if( !(*nn) ) {
2308       // Annoyingly, irreducible loops can pick different headers
2309       // after a major_progress operation, so the rest of the loop
2310       // tree cannot be matched.
2311       if (_irreducible && Compile::current()->major_progress())  return;
2312       assert( 0, "failed to match loop tree" );
2313     }
2314 
2315     // Move (*nn) to (*pp)
2316     IdealLoopTree *hit = *nn;
2317     *nn = hit->_next;
2318     hit->_next = loop;
2319     *pp = loop;
2320     loop = hit;
2321     // Now try again to verify
2322   }
2323 
2324   assert( _head  == loop->_head , "mismatched loop head" );
2325   Node *tail = _tail;           // Inline a non-updating version of
2326   while( !tail->in(0) )         // the 'tail()' call.
2327     tail = tail->in(1);
2328   assert( tail == loop->_tail, "mismatched loop tail" );
2329 
2330   // Counted loops that are guarded should be able to find their guards
2331   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
2332     CountedLoopNode *cl = _head->as_CountedLoop();
2333     Node *init = cl->init_trip();
2334     Node *ctrl = cl->in(LoopNode::EntryControl);
2335     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
2336     Node *iff  = ctrl->in(0);
2337     assert( iff->Opcode() == Op_If, "" );
2338     Node *bol  = iff->in(1);
2339     assert( bol->Opcode() == Op_Bool, "" );
2340     Node *cmp  = bol->in(1);
2341     assert( cmp->Opcode() == Op_CmpI, "" );
2342     Node *add  = cmp->in(1);
2343     Node *opaq;
2344     if( add->Opcode() == Op_Opaque1 ) {
2345       opaq = add;
2346     } else {
2347       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
2348       assert( add == init, "" );
2349       opaq = cmp->in(2);
2350     }
2351     assert( opaq->Opcode() == Op_Opaque1, "" );
2352 
2353   }
2354 
2355   if (_child != NULL)  _child->verify_tree(loop->_child, this);
2356   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
2357   // Innermost loops need to verify loop bodies,
2358   // but only if no 'major_progress'
2359   int fail = 0;
2360   if (!Compile::current()->major_progress() && _child == NULL) {
2361     for( uint i = 0; i < _body.size(); i++ ) {
2362       Node *n = _body.at(i);
2363       if (n->outcnt() == 0)  continue; // Ignore dead
2364       uint j;
2365       for( j = 0; j < loop->_body.size(); j++ )
2366         if( loop->_body.at(j) == n )
2367           break;
2368       if( j == loop->_body.size() ) { // Not found in loop body
2369         // Last ditch effort to avoid assertion: Its possible that we
2370         // have some users (so outcnt not zero) but are still dead.
2371         // Try to find from root.
2372         if (Compile::current()->root()->find(n->_idx)) {
2373           fail++;
2374           tty->print("We have that verify does not: ");
2375           n->dump();
2376         }
2377       }
2378     }
2379     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
2380       Node *n = loop->_body.at(i2);
2381       if (n->outcnt() == 0)  continue; // Ignore dead
2382       uint j;
2383       for( j = 0; j < _body.size(); j++ )
2384         if( _body.at(j) == n )
2385           break;
2386       if( j == _body.size() ) { // Not found in loop body
2387         // Last ditch effort to avoid assertion: Its possible that we
2388         // have some users (so outcnt not zero) but are still dead.
2389         // Try to find from root.
2390         if (Compile::current()->root()->find(n->_idx)) {
2391           fail++;
2392           tty->print("Verify has that we do not: ");
2393           n->dump();
2394         }
2395       }
2396     }
2397     assert( !fail, "loop body mismatch" );
2398   }
2399 }
2400 
2401 #endif
2402 
2403 //------------------------------set_idom---------------------------------------
2404 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
2405   uint idx = d->_idx;
2406   if (idx >= _idom_size) {
2407     uint newsize = _idom_size<<1;
2408     while( idx >= newsize ) {
2409       newsize <<= 1;
2410     }
2411     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
2412     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
2413     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
2414     _idom_size = newsize;
2415   }
2416   _idom[idx] = n;
2417   _dom_depth[idx] = dom_depth;
2418 }
2419 
2420 //------------------------------recompute_dom_depth---------------------------------------
2421 // The dominator tree is constructed with only parent pointers.
2422 // This recomputes the depth in the tree by first tagging all
2423 // nodes as "no depth yet" marker.  The next pass then runs up
2424 // the dom tree from each node marked "no depth yet", and computes
2425 // the depth on the way back down.
2426 void PhaseIdealLoop::recompute_dom_depth() {
2427   uint no_depth_marker = C->unique();
2428   uint i;
2429   // Initialize depth to "no depth yet"
2430   for (i = 0; i < _idom_size; i++) {
2431     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
2432      _dom_depth[i] = no_depth_marker;
2433     }
2434   }
2435   if (_dom_stk == NULL) {
2436     uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size.
2437     if (init_size < 10) init_size = 10;
2438     _dom_stk = new GrowableArray<uint>(init_size);
2439   }
2440   // Compute new depth for each node.
2441   for (i = 0; i < _idom_size; i++) {
2442     uint j = i;
2443     // Run up the dom tree to find a node with a depth
2444     while (_dom_depth[j] == no_depth_marker) {
2445       _dom_stk->push(j);
2446       j = _idom[j]->_idx;
2447     }
2448     // Compute the depth on the way back down this tree branch
2449     uint dd = _dom_depth[j] + 1;
2450     while (_dom_stk->length() > 0) {
2451       uint j = _dom_stk->pop();
2452       _dom_depth[j] = dd;
2453       dd++;
2454     }
2455   }
2456 }
2457 
2458 //------------------------------sort-------------------------------------------
2459 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
2460 // loop tree, not the root.
2461 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
2462   if( !innermost ) return loop; // New innermost loop
2463 
2464   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
2465   assert( loop_preorder, "not yet post-walked loop" );
2466   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
2467   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
2468 
2469   // Insert at start of list
2470   while( l ) {                  // Insertion sort based on pre-order
2471     if( l == loop ) return innermost; // Already on list!
2472     int l_preorder = get_preorder(l->_head); // Cache pre-order number
2473     assert( l_preorder, "not yet post-walked l" );
2474     // Check header pre-order number to figure proper nesting
2475     if( loop_preorder > l_preorder )
2476       break;                    // End of insertion
2477     // If headers tie (e.g., shared headers) check tail pre-order numbers.
2478     // Since I split shared headers, you'd think this could not happen.
2479     // BUT: I must first do the preorder numbering before I can discover I
2480     // have shared headers, so the split headers all get the same preorder
2481     // number as the RegionNode they split from.
2482     if( loop_preorder == l_preorder &&
2483         get_preorder(loop->_tail) < get_preorder(l->_tail) )
2484       break;                    // Also check for shared headers (same pre#)
2485     pp = &l->_parent;           // Chain up list
2486     l = *pp;
2487   }
2488   // Link into list
2489   // Point predecessor to me
2490   *pp = loop;
2491   // Point me to successor
2492   IdealLoopTree *p = loop->_parent;
2493   loop->_parent = l;            // Point me to successor
2494   if( p ) sort( p, innermost ); // Insert my parents into list as well
2495   return innermost;
2496 }
2497 
2498 //------------------------------build_loop_tree--------------------------------
2499 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
2500 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
2501 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
2502 // tightest enclosing IdealLoopTree for post-walked.
2503 //
2504 // During my forward walk I do a short 1-layer lookahead to see if I can find
2505 // a loop backedge with that doesn't have any work on the backedge.  This
2506 // helps me construct nested loops with shared headers better.
2507 //
2508 // Once I've done the forward recursion, I do the post-work.  For each child
2509 // I check to see if there is a backedge.  Backedges define a loop!  I
2510 // insert an IdealLoopTree at the target of the backedge.
2511 //
2512 // During the post-work I also check to see if I have several children
2513 // belonging to different loops.  If so, then this Node is a decision point
2514 // where control flow can choose to change loop nests.  It is at this
2515 // decision point where I can figure out how loops are nested.  At this
2516 // time I can properly order the different loop nests from my children.
2517 // Note that there may not be any backedges at the decision point!
2518 //
2519 // Since the decision point can be far removed from the backedges, I can't
2520 // order my loops at the time I discover them.  Thus at the decision point
2521 // I need to inspect loop header pre-order numbers to properly nest my
2522 // loops.  This means I need to sort my childrens' loops by pre-order.
2523 // The sort is of size number-of-control-children, which generally limits
2524 // it to size 2 (i.e., I just choose between my 2 target loops).
2525 void PhaseIdealLoop::build_loop_tree() {
2526   // Allocate stack of size C->unique()/2 to avoid frequent realloc
2527   GrowableArray <Node *> bltstack(C->unique() >> 1);
2528   Node *n = C->root();
2529   bltstack.push(n);
2530   int pre_order = 1;
2531   int stack_size;
2532 
2533   while ( ( stack_size = bltstack.length() ) != 0 ) {
2534     n = bltstack.top(); // Leave node on stack
2535     if ( !is_visited(n) ) {
2536       // ---- Pre-pass Work ----
2537       // Pre-walked but not post-walked nodes need a pre_order number.
2538 
2539       set_preorder_visited( n, pre_order ); // set as visited
2540 
2541       // ---- Scan over children ----
2542       // Scan first over control projections that lead to loop headers.
2543       // This helps us find inner-to-outer loops with shared headers better.
2544 
2545       // Scan children's children for loop headers.
2546       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
2547         Node* m = n->raw_out(i);       // Child
2548         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
2549           // Scan over children's children to find loop
2550           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2551             Node* l = m->fast_out(j);
2552             if( is_visited(l) &&       // Been visited?
2553                 !is_postvisited(l) &&  // But not post-visited
2554                 get_preorder(l) < pre_order ) { // And smaller pre-order
2555               // Found!  Scan the DFS down this path before doing other paths
2556               bltstack.push(m);
2557               break;
2558             }
2559           }
2560         }
2561       }
2562       pre_order++;
2563     }
2564     else if ( !is_postvisited(n) ) {
2565       // Note: build_loop_tree_impl() adds out edges on rare occasions,
2566       // such as com.sun.rsasign.am::a.
2567       // For non-recursive version, first, process current children.
2568       // On next iteration, check if additional children were added.
2569       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
2570         Node* u = n->raw_out(k);
2571         if ( u->is_CFG() && !is_visited(u) ) {
2572           bltstack.push(u);
2573         }
2574       }
2575       if ( bltstack.length() == stack_size ) {
2576         // There were no additional children, post visit node now
2577         (void)bltstack.pop(); // Remove node from stack
2578         pre_order = build_loop_tree_impl( n, pre_order );
2579         // Check for bailout
2580         if (C->failing()) {
2581           return;
2582         }
2583         // Check to grow _preorders[] array for the case when
2584         // build_loop_tree_impl() adds new nodes.
2585         check_grow_preorders();
2586       }
2587     }
2588     else {
2589       (void)bltstack.pop(); // Remove post-visited node from stack
2590     }
2591   }
2592 }
2593 
2594 //------------------------------build_loop_tree_impl---------------------------
2595 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
2596   // ---- Post-pass Work ----
2597   // Pre-walked but not post-walked nodes need a pre_order number.
2598 
2599   // Tightest enclosing loop for this Node
2600   IdealLoopTree *innermost = NULL;
2601 
2602   // For all children, see if any edge is a backedge.  If so, make a loop
2603   // for it.  Then find the tightest enclosing loop for the self Node.
2604   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2605     Node* m = n->fast_out(i);   // Child
2606     if( n == m ) continue;      // Ignore control self-cycles
2607     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
2608 
2609     IdealLoopTree *l;           // Child's loop
2610     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
2611       // Found a backedge
2612       assert( get_preorder(m) < pre_order, "should be backedge" );
2613       // Check for the RootNode, which is already a LoopNode and is allowed
2614       // to have multiple "backedges".
2615       if( m == C->root()) {     // Found the root?
2616         l = _ltree_root;        // Root is the outermost LoopNode
2617       } else {                  // Else found a nested loop
2618         // Insert a LoopNode to mark this loop.
2619         l = new IdealLoopTree(this, m, n);
2620       } // End of Else found a nested loop
2621       if( !has_loop(m) )        // If 'm' does not already have a loop set
2622         set_loop(m, l);         // Set loop header to loop now
2623 
2624     } else {                    // Else not a nested loop
2625       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
2626       l = get_loop(m);          // Get previously determined loop
2627       // If successor is header of a loop (nest), move up-loop till it
2628       // is a member of some outer enclosing loop.  Since there are no
2629       // shared headers (I've split them already) I only need to go up
2630       // at most 1 level.
2631       while( l && l->_head == m ) // Successor heads loop?
2632         l = l->_parent;         // Move up 1 for me
2633       // If this loop is not properly parented, then this loop
2634       // has no exit path out, i.e. its an infinite loop.
2635       if( !l ) {
2636         // Make loop "reachable" from root so the CFG is reachable.  Basically
2637         // insert a bogus loop exit that is never taken.  'm', the loop head,
2638         // points to 'n', one (of possibly many) fall-in paths.  There may be
2639         // many backedges as well.
2640 
2641         // Here I set the loop to be the root loop.  I could have, after
2642         // inserting a bogus loop exit, restarted the recursion and found my
2643         // new loop exit.  This would make the infinite loop a first-class
2644         // loop and it would then get properly optimized.  What's the use of
2645         // optimizing an infinite loop?
2646         l = _ltree_root;        // Oops, found infinite loop
2647 
2648         if (!_verify_only) {
2649           // Insert the NeverBranch between 'm' and it's control user.
2650           NeverBranchNode *iff = new (C, 1) NeverBranchNode( m );
2651           _igvn.register_new_node_with_optimizer(iff);
2652           set_loop(iff, l);
2653           Node *if_t = new (C, 1) CProjNode( iff, 0 );
2654           _igvn.register_new_node_with_optimizer(if_t);
2655           set_loop(if_t, l);
2656 
2657           Node* cfg = NULL;       // Find the One True Control User of m
2658           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2659             Node* x = m->fast_out(j);
2660             if (x->is_CFG() && x != m && x != iff)
2661               { cfg = x; break; }
2662           }
2663           assert(cfg != NULL, "must find the control user of m");
2664           uint k = 0;             // Probably cfg->in(0)
2665           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
2666           cfg->set_req( k, if_t ); // Now point to NeverBranch
2667 
2668           // Now create the never-taken loop exit
2669           Node *if_f = new (C, 1) CProjNode( iff, 1 );
2670           _igvn.register_new_node_with_optimizer(if_f);
2671           set_loop(if_f, l);
2672           // Find frame ptr for Halt.  Relies on the optimizer
2673           // V-N'ing.  Easier and quicker than searching through
2674           // the program structure.
2675           Node *frame = new (C, 1) ParmNode( C->start(), TypeFunc::FramePtr );
2676           _igvn.register_new_node_with_optimizer(frame);
2677           // Halt & Catch Fire
2678           Node *halt = new (C, TypeFunc::Parms) HaltNode( if_f, frame );
2679           _igvn.register_new_node_with_optimizer(halt);
2680           set_loop(halt, l);
2681           C->root()->add_req(halt);
2682         }
2683         set_loop(C->root(), _ltree_root);
2684       }
2685     }
2686     // Weeny check for irreducible.  This child was already visited (this
2687     // IS the post-work phase).  Is this child's loop header post-visited
2688     // as well?  If so, then I found another entry into the loop.
2689     if (!_verify_only) {
2690       while( is_postvisited(l->_head) ) {
2691         // found irreducible
2692         l->_irreducible = 1; // = true
2693         l = l->_parent;
2694         _has_irreducible_loops = true;
2695         // Check for bad CFG here to prevent crash, and bailout of compile
2696         if (l == NULL) {
2697           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
2698           return pre_order;
2699         }
2700       }
2701     }
2702 
2703     // This Node might be a decision point for loops.  It is only if
2704     // it's children belong to several different loops.  The sort call
2705     // does a trivial amount of work if there is only 1 child or all
2706     // children belong to the same loop.  If however, the children
2707     // belong to different loops, the sort call will properly set the
2708     // _parent pointers to show how the loops nest.
2709     //
2710     // In any case, it returns the tightest enclosing loop.
2711     innermost = sort( l, innermost );
2712   }
2713 
2714   // Def-use info will have some dead stuff; dead stuff will have no
2715   // loop decided on.
2716 
2717   // Am I a loop header?  If so fix up my parent's child and next ptrs.
2718   if( innermost && innermost->_head == n ) {
2719     assert( get_loop(n) == innermost, "" );
2720     IdealLoopTree *p = innermost->_parent;
2721     IdealLoopTree *l = innermost;
2722     while( p && l->_head == n ) {
2723       l->_next = p->_child;     // Put self on parents 'next child'
2724       p->_child = l;            // Make self as first child of parent
2725       l = p;                    // Now walk up the parent chain
2726       p = l->_parent;
2727     }
2728   } else {
2729     // Note that it is possible for a LoopNode to reach here, if the
2730     // backedge has been made unreachable (hence the LoopNode no longer
2731     // denotes a Loop, and will eventually be removed).
2732 
2733     // Record tightest enclosing loop for self.  Mark as post-visited.
2734     set_loop(n, innermost);
2735     // Also record has_call flag early on
2736     if( innermost ) {
2737       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
2738         // Do not count uncommon calls
2739         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
2740           Node *iff = n->in(0)->in(0);
2741           if( !iff->is_If() ||
2742               (n->in(0)->Opcode() == Op_IfFalse &&
2743                (1.0 - iff->as_If()->_prob) >= 0.01) ||
2744               (iff->as_If()->_prob >= 0.01) )
2745             innermost->_has_call = 1;
2746         }
2747       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
2748         // Disable loop optimizations if the loop has a scalar replaceable
2749         // allocation. This disabling may cause a potential performance lost
2750         // if the allocation is not eliminated for some reason.
2751         innermost->_allow_optimizations = false;
2752         innermost->_has_call = 1; // = true
2753       }
2754     }
2755   }
2756 
2757   // Flag as post-visited now
2758   set_postvisited(n);
2759   return pre_order;
2760 }
2761 
2762 
2763 //------------------------------build_loop_early-------------------------------
2764 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
2765 // First pass computes the earliest controlling node possible.  This is the
2766 // controlling input with the deepest dominating depth.
2767 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
2768   while (worklist.size() != 0) {
2769     // Use local variables nstack_top_n & nstack_top_i to cache values
2770     // on nstack's top.
2771     Node *nstack_top_n = worklist.pop();
2772     uint  nstack_top_i = 0;
2773 //while_nstack_nonempty:
2774     while (true) {
2775       // Get parent node and next input's index from stack's top.
2776       Node  *n = nstack_top_n;
2777       uint   i = nstack_top_i;
2778       uint cnt = n->req(); // Count of inputs
2779       if (i == 0) {        // Pre-process the node.
2780         if( has_node(n) &&            // Have either loop or control already?
2781             !has_ctrl(n) ) {          // Have loop picked out already?
2782           // During "merge_many_backedges" we fold up several nested loops
2783           // into a single loop.  This makes the members of the original
2784           // loop bodies pointing to dead loops; they need to move up
2785           // to the new UNION'd larger loop.  I set the _head field of these
2786           // dead loops to NULL and the _parent field points to the owning
2787           // loop.  Shades of UNION-FIND algorithm.
2788           IdealLoopTree *ilt;
2789           while( !(ilt = get_loop(n))->_head ) {
2790             // Normally I would use a set_loop here.  But in this one special
2791             // case, it is legal (and expected) to change what loop a Node
2792             // belongs to.
2793             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
2794           }
2795           // Remove safepoints ONLY if I've already seen I don't need one.
2796           // (the old code here would yank a 2nd safepoint after seeing a
2797           // first one, even though the 1st did not dominate in the loop body
2798           // and thus could be avoided indefinitely)
2799           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
2800               is_deleteable_safept(n)) {
2801             Node *in = n->in(TypeFunc::Control);
2802             lazy_replace(n,in);       // Pull safepoint now
2803             // Carry on with the recursion "as if" we are walking
2804             // only the control input
2805             if( !visited.test_set( in->_idx ) ) {
2806               worklist.push(in);      // Visit this guy later, using worklist
2807             }
2808             // Get next node from nstack:
2809             // - skip n's inputs processing by setting i > cnt;
2810             // - we also will not call set_early_ctrl(n) since
2811             //   has_node(n) == true (see the condition above).
2812             i = cnt + 1;
2813           }
2814         }
2815       } // if (i == 0)
2816 
2817       // Visit all inputs
2818       bool done = true;       // Assume all n's inputs will be processed
2819       while (i < cnt) {
2820         Node *in = n->in(i);
2821         ++i;
2822         if (in == NULL) continue;
2823         if (in->pinned() && !in->is_CFG())
2824           set_ctrl(in, in->in(0));
2825         int is_visited = visited.test_set( in->_idx );
2826         if (!has_node(in)) {  // No controlling input yet?
2827           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
2828           assert( !is_visited, "visit only once" );
2829           nstack.push(n, i);  // Save parent node and next input's index.
2830           nstack_top_n = in;  // Process current input now.
2831           nstack_top_i = 0;
2832           done = false;       // Not all n's inputs processed.
2833           break; // continue while_nstack_nonempty;
2834         } else if (!is_visited) {
2835           // This guy has a location picked out for him, but has not yet
2836           // been visited.  Happens to all CFG nodes, for instance.
2837           // Visit him using the worklist instead of recursion, to break
2838           // cycles.  Since he has a location already we do not need to
2839           // find his location before proceeding with the current Node.
2840           worklist.push(in);  // Visit this guy later, using worklist
2841         }
2842       }
2843       if (done) {
2844         // All of n's inputs have been processed, complete post-processing.
2845 
2846         // Compute earliest point this Node can go.
2847         // CFG, Phi, pinned nodes already know their controlling input.
2848         if (!has_node(n)) {
2849           // Record earliest legal location
2850           set_early_ctrl( n );
2851         }
2852         if (nstack.is_empty()) {
2853           // Finished all nodes on stack.
2854           // Process next node on the worklist.
2855           break;
2856         }
2857         // Get saved parent node and next input's index.
2858         nstack_top_n = nstack.node();
2859         nstack_top_i = nstack.index();
2860         nstack.pop();
2861       }
2862     } // while (true)
2863   }
2864 }
2865 
2866 //------------------------------dom_lca_internal--------------------------------
2867 // Pair-wise LCA
2868 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
2869   if( !n1 ) return n2;          // Handle NULL original LCA
2870   assert( n1->is_CFG(), "" );
2871   assert( n2->is_CFG(), "" );
2872   // find LCA of all uses
2873   uint d1 = dom_depth(n1);
2874   uint d2 = dom_depth(n2);
2875   while (n1 != n2) {
2876     if (d1 > d2) {
2877       n1 =      idom(n1);
2878       d1 = dom_depth(n1);
2879     } else if (d1 < d2) {
2880       n2 =      idom(n2);
2881       d2 = dom_depth(n2);
2882     } else {
2883       // Here d1 == d2.  Due to edits of the dominator-tree, sections
2884       // of the tree might have the same depth.  These sections have
2885       // to be searched more carefully.
2886 
2887       // Scan up all the n1's with equal depth, looking for n2.
2888       Node *t1 = idom(n1);
2889       while (dom_depth(t1) == d1) {
2890         if (t1 == n2)  return n2;
2891         t1 = idom(t1);
2892       }
2893       // Scan up all the n2's with equal depth, looking for n1.
2894       Node *t2 = idom(n2);
2895       while (dom_depth(t2) == d2) {
2896         if (t2 == n1)  return n1;
2897         t2 = idom(t2);
2898       }
2899       // Move up to a new dominator-depth value as well as up the dom-tree.
2900       n1 = t1;
2901       n2 = t2;
2902       d1 = dom_depth(n1);
2903       d2 = dom_depth(n2);
2904     }
2905   }
2906   return n1;
2907 }
2908 
2909 //------------------------------compute_idom-----------------------------------
2910 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
2911 // IDOMs are correct.
2912 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
2913   assert( region->is_Region(), "" );
2914   Node *LCA = NULL;
2915   for( uint i = 1; i < region->req(); i++ ) {
2916     if( region->in(i) != C->top() )
2917       LCA = dom_lca( LCA, region->in(i) );
2918   }
2919   return LCA;
2920 }
2921 
2922 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
2923   bool had_error = false;
2924 #ifdef ASSERT
2925   if (early != C->root()) {
2926     // Make sure that there's a dominance path from use to LCA
2927     Node* d = use;
2928     while (d != LCA) {
2929       d = idom(d);
2930       if (d == C->root()) {
2931         tty->print_cr("*** Use %d isn't dominated by def %s", use->_idx, n->_idx);
2932         n->dump();
2933         use->dump();
2934         had_error = true;
2935         break;
2936       }
2937     }
2938   }
2939 #endif
2940   return had_error;
2941 }
2942 
2943 
2944 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
2945   // Compute LCA over list of uses
2946   bool had_error = false;
2947   Node *LCA = NULL;
2948   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
2949     Node* c = n->fast_out(i);
2950     if (_nodes[c->_idx] == NULL)
2951       continue;                 // Skip the occasional dead node
2952     if( c->is_Phi() ) {         // For Phis, we must land above on the path
2953       for( uint j=1; j<c->req(); j++ ) {// For all inputs
2954         if( c->in(j) == n ) {   // Found matching input?
2955           Node *use = c->in(0)->in(j);
2956           if (_verify_only && use->is_top()) continue;
2957           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
2958           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
2959         }
2960       }
2961     } else {
2962       // For CFG data-users, use is in the block just prior
2963       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
2964       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
2965       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
2966     }
2967   }
2968   assert(!had_error, "bad dominance");
2969   return LCA;
2970 }
2971 
2972 //------------------------------get_late_ctrl----------------------------------
2973 // Compute latest legal control.
2974 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
2975   assert(early != NULL, "early control should not be NULL");
2976 
2977   Node* LCA = compute_lca_of_uses(n, early);
2978 #ifdef ASSERT
2979   if (LCA == C->root() && LCA != early) {
2980     // def doesn't dominate uses so print some useful debugging output
2981     compute_lca_of_uses(n, early, true);
2982   }
2983 #endif
2984 
2985   // if this is a load, check for anti-dependent stores
2986   // We use a conservative algorithm to identify potential interfering
2987   // instructions and for rescheduling the load.  The users of the memory
2988   // input of this load are examined.  Any use which is not a load and is
2989   // dominated by early is considered a potentially interfering store.
2990   // This can produce false positives.
2991   if (n->is_Load() && LCA != early) {
2992     Node_List worklist;
2993 
2994     Node *mem = n->in(MemNode::Memory);
2995     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
2996       Node* s = mem->fast_out(i);
2997       worklist.push(s);
2998     }
2999     while(worklist.size() != 0 && LCA != early) {
3000       Node* s = worklist.pop();
3001       if (s->is_Load()) {
3002         continue;
3003       } else if (s->is_MergeMem()) {
3004         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3005           Node* s1 = s->fast_out(i);
3006           worklist.push(s1);
3007         }
3008       } else {
3009         Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3010         assert(sctrl != NULL || s->outcnt() == 0, "must have control");
3011         if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3012           LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3013         }
3014       }
3015     }
3016   }
3017 
3018   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
3019   return LCA;
3020 }
3021 
3022 // true if CFG node d dominates CFG node n
3023 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
3024   if (d == n)
3025     return true;
3026   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
3027   uint dd = dom_depth(d);
3028   while (dom_depth(n) >= dd) {
3029     if (n == d)
3030       return true;
3031     n = idom(n);
3032   }
3033   return false;
3034 }
3035 
3036 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
3037 // Pair-wise LCA with tags.
3038 // Tag each index with the node 'tag' currently being processed
3039 // before advancing up the dominator chain using idom().
3040 // Later calls that find a match to 'tag' know that this path has already
3041 // been considered in the current LCA (which is input 'n1' by convention).
3042 // Since get_late_ctrl() is only called once for each node, the tag array
3043 // does not need to be cleared between calls to get_late_ctrl().
3044 // Algorithm trades a larger constant factor for better asymptotic behavior
3045 //
3046 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
3047   uint d1 = dom_depth(n1);
3048   uint d2 = dom_depth(n2);
3049 
3050   do {
3051     if (d1 > d2) {
3052       // current lca is deeper than n2
3053       _dom_lca_tags.map(n1->_idx, tag);
3054       n1 =      idom(n1);
3055       d1 = dom_depth(n1);
3056     } else if (d1 < d2) {
3057       // n2 is deeper than current lca
3058       Node *memo = _dom_lca_tags[n2->_idx];
3059       if( memo == tag ) {
3060         return n1;    // Return the current LCA
3061       }
3062       _dom_lca_tags.map(n2->_idx, tag);
3063       n2 =      idom(n2);
3064       d2 = dom_depth(n2);
3065     } else {
3066       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3067       // of the tree might have the same depth.  These sections have
3068       // to be searched more carefully.
3069 
3070       // Scan up all the n1's with equal depth, looking for n2.
3071       _dom_lca_tags.map(n1->_idx, tag);
3072       Node *t1 = idom(n1);
3073       while (dom_depth(t1) == d1) {
3074         if (t1 == n2)  return n2;
3075         _dom_lca_tags.map(t1->_idx, tag);
3076         t1 = idom(t1);
3077       }
3078       // Scan up all the n2's with equal depth, looking for n1.
3079       _dom_lca_tags.map(n2->_idx, tag);
3080       Node *t2 = idom(n2);
3081       while (dom_depth(t2) == d2) {
3082         if (t2 == n1)  return n1;
3083         _dom_lca_tags.map(t2->_idx, tag);
3084         t2 = idom(t2);
3085       }
3086       // Move up to a new dominator-depth value as well as up the dom-tree.
3087       n1 = t1;
3088       n2 = t2;
3089       d1 = dom_depth(n1);
3090       d2 = dom_depth(n2);
3091     }
3092   } while (n1 != n2);
3093   return n1;
3094 }
3095 
3096 //------------------------------init_dom_lca_tags------------------------------
3097 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3098 // Intended use does not involve any growth for the array, so it could
3099 // be of fixed size.
3100 void PhaseIdealLoop::init_dom_lca_tags() {
3101   uint limit = C->unique() + 1;
3102   _dom_lca_tags.map( limit, NULL );
3103 #ifdef ASSERT
3104   for( uint i = 0; i < limit; ++i ) {
3105     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3106   }
3107 #endif // ASSERT
3108 }
3109 
3110 //------------------------------clear_dom_lca_tags------------------------------
3111 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3112 // Intended use does not involve any growth for the array, so it could
3113 // be of fixed size.
3114 void PhaseIdealLoop::clear_dom_lca_tags() {
3115   uint limit = C->unique() + 1;
3116   _dom_lca_tags.map( limit, NULL );
3117   _dom_lca_tags.clear();
3118 #ifdef ASSERT
3119   for( uint i = 0; i < limit; ++i ) {
3120     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3121   }
3122 #endif // ASSERT
3123 }
3124 
3125 //------------------------------build_loop_late--------------------------------
3126 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3127 // Second pass finds latest legal placement, and ideal loop placement.
3128 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3129   while (worklist.size() != 0) {
3130     Node *n = worklist.pop();
3131     // Only visit once
3132     if (visited.test_set(n->_idx)) continue;
3133     uint cnt = n->outcnt();
3134     uint   i = 0;
3135     while (true) {
3136       assert( _nodes[n->_idx], "no dead nodes" );
3137       // Visit all children
3138       if (i < cnt) {
3139         Node* use = n->raw_out(i);
3140         ++i;
3141         // Check for dead uses.  Aggressively prune such junk.  It might be
3142         // dead in the global sense, but still have local uses so I cannot
3143         // easily call 'remove_dead_node'.
3144         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
3145           // Due to cycles, we might not hit the same fixed point in the verify
3146           // pass as we do in the regular pass.  Instead, visit such phis as
3147           // simple uses of the loop head.
3148           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
3149             if( !visited.test(use->_idx) )
3150               worklist.push(use);
3151           } else if( !visited.test_set(use->_idx) ) {
3152             nstack.push(n, i); // Save parent and next use's index.
3153             n   = use;         // Process all children of current use.
3154             cnt = use->outcnt();
3155             i   = 0;
3156           }
3157         } else {
3158           // Do not visit around the backedge of loops via data edges.
3159           // push dead code onto a worklist
3160           _deadlist.push(use);
3161         }
3162       } else {
3163         // All of n's children have been processed, complete post-processing.
3164         build_loop_late_post(n);
3165         if (nstack.is_empty()) {
3166           // Finished all nodes on stack.
3167           // Process next node on the worklist.
3168           break;
3169         }
3170         // Get saved parent node and next use's index. Visit the rest of uses.
3171         n   = nstack.node();
3172         cnt = n->outcnt();
3173         i   = nstack.index();
3174         nstack.pop();
3175       }
3176     }
3177   }
3178 }
3179 
3180 //------------------------------build_loop_late_post---------------------------
3181 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3182 // Second pass finds latest legal placement, and ideal loop placement.
3183 void PhaseIdealLoop::build_loop_late_post( Node *n ) {
3184 
3185   if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
3186     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
3187   }
3188 
3189   // CFG and pinned nodes already handled
3190   if( n->in(0) ) {
3191     if( n->in(0)->is_top() ) return; // Dead?
3192 
3193     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
3194     // _must_ be pinned (they have to observe their control edge of course).
3195     // Unlike Stores (which modify an unallocable resource, the memory
3196     // state), Mods/Loads can float around.  So free them up.
3197     bool pinned = true;
3198     switch( n->Opcode() ) {
3199     case Op_DivI:
3200     case Op_DivF:
3201     case Op_DivD:
3202     case Op_ModI:
3203     case Op_ModF:
3204     case Op_ModD:
3205     case Op_LoadB:              // Same with Loads; they can sink
3206     case Op_LoadUS:             // during loop optimizations.
3207     case Op_LoadD:
3208     case Op_LoadF:
3209     case Op_LoadI:
3210     case Op_LoadKlass:
3211     case Op_LoadNKlass:
3212     case Op_LoadL:
3213     case Op_LoadS:
3214     case Op_LoadP:
3215     case Op_LoadN:
3216     case Op_LoadRange:
3217     case Op_LoadD_unaligned:
3218     case Op_LoadL_unaligned:
3219     case Op_StrComp:            // Does a bunch of load-like effects
3220     case Op_StrEquals:
3221     case Op_StrIndexOf:
3222     case Op_AryEq:
3223       pinned = false;
3224     }
3225     if( pinned ) {
3226       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
3227       if( !chosen_loop->_child )       // Inner loop?
3228         chosen_loop->_body.push(n); // Collect inner loops
3229       return;
3230     }
3231   } else {                      // No slot zero
3232     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
3233       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
3234       return;
3235     }
3236     assert(!n->is_CFG() || n->outcnt() == 0, "");
3237   }
3238 
3239   // Do I have a "safe range" I can select over?
3240   Node *early = get_ctrl(n);// Early location already computed
3241 
3242   // Compute latest point this Node can go
3243   Node *LCA = get_late_ctrl( n, early );
3244   // LCA is NULL due to uses being dead
3245   if( LCA == NULL ) {
3246 #ifdef ASSERT
3247     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
3248       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
3249     }
3250 #endif
3251     _nodes.map(n->_idx, 0);     // This node is useless
3252     _deadlist.push(n);
3253     return;
3254   }
3255   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
3256 
3257   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
3258   Node *least = legal;          // Best legal position so far
3259   while( early != legal ) {     // While not at earliest legal
3260 #ifdef ASSERT
3261     if (legal->is_Start() && !early->is_Root()) {
3262       // Bad graph. Print idom path and fail.
3263       tty->print_cr( "Bad graph detected in build_loop_late");
3264       tty->print("n: ");n->dump(); tty->cr();
3265       tty->print("early: ");early->dump(); tty->cr();
3266       int ct = 0;
3267       Node *dbg_legal = LCA;
3268       while(!dbg_legal->is_Start() && ct < 100) {
3269         tty->print("idom[%d] ",ct); dbg_legal->dump(); tty->cr();
3270         ct++;
3271         dbg_legal = idom(dbg_legal);
3272       }
3273       assert(false, "Bad graph detected in build_loop_late");
3274     }
3275 #endif
3276     // Find least loop nesting depth
3277     legal = idom(legal);        // Bump up the IDOM tree
3278     // Check for lower nesting depth
3279     if( get_loop(legal)->_nest < get_loop(least)->_nest )
3280       least = legal;
3281   }
3282   assert(early == legal || legal != C->root(), "bad dominance of inputs");
3283 
3284   // Try not to place code on a loop entry projection
3285   // which can inhibit range check elimination.
3286   if (least != early) {
3287     Node* ctrl_out = least->unique_ctrl_out();
3288     if (ctrl_out && ctrl_out->is_CountedLoop() &&
3289         least == ctrl_out->in(LoopNode::EntryControl)) {
3290       Node* least_dom = idom(least);
3291       if (get_loop(least_dom)->is_member(get_loop(least))) {
3292         least = least_dom;
3293       }
3294     }
3295   }
3296 
3297 #ifdef ASSERT
3298   // If verifying, verify that 'verify_me' has a legal location
3299   // and choose it as our location.
3300   if( _verify_me ) {
3301     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
3302     Node *legal = LCA;
3303     while( early != legal ) {   // While not at earliest legal
3304       if( legal == v_ctrl ) break;  // Check for prior good location
3305       legal = idom(legal)      ;// Bump up the IDOM tree
3306     }
3307     // Check for prior good location
3308     if( legal == v_ctrl ) least = legal; // Keep prior if found
3309   }
3310 #endif
3311 
3312   // Assign discovered "here or above" point
3313   least = find_non_split_ctrl(least);
3314   set_ctrl(n, least);
3315 
3316   // Collect inner loop bodies
3317   IdealLoopTree *chosen_loop = get_loop(least);
3318   if( !chosen_loop->_child )   // Inner loop?
3319     chosen_loop->_body.push(n);// Collect inner loops
3320 }
3321 
3322 #ifndef PRODUCT
3323 //------------------------------dump-------------------------------------------
3324 void PhaseIdealLoop::dump( ) const {
3325   ResourceMark rm;
3326   Arena* arena = Thread::current()->resource_area();
3327   Node_Stack stack(arena, C->unique() >> 2);
3328   Node_List rpo_list;
3329   VectorSet visited(arena);
3330   visited.set(C->top()->_idx);
3331   rpo( C->root(), stack, visited, rpo_list );
3332   // Dump root loop indexed by last element in PO order
3333   dump( _ltree_root, rpo_list.size(), rpo_list );
3334 }
3335 
3336 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
3337   loop->dump_head();
3338 
3339   // Now scan for CFG nodes in the same loop
3340   for( uint j=idx; j > 0;  j-- ) {
3341     Node *n = rpo_list[j-1];
3342     if( !_nodes[n->_idx] )      // Skip dead nodes
3343       continue;
3344     if( get_loop(n) != loop ) { // Wrong loop nest
3345       if( get_loop(n)->_head == n &&    // Found nested loop?
3346           get_loop(n)->_parent == loop )
3347         dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
3348       continue;
3349     }
3350 
3351     // Dump controlling node
3352     for( uint x = 0; x < loop->_nest; x++ )
3353       tty->print("  ");
3354     tty->print("C");
3355     if( n == C->root() ) {
3356       n->dump();
3357     } else {
3358       Node* cached_idom   = idom_no_update(n);
3359       Node *computed_idom = n->in(0);
3360       if( n->is_Region() ) {
3361         computed_idom = compute_idom(n);
3362         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
3363         // any MultiBranch ctrl node), so apply a similar transform to
3364         // the cached idom returned from idom_no_update.
3365         cached_idom = find_non_split_ctrl(cached_idom);
3366       }
3367       tty->print(" ID:%d",computed_idom->_idx);
3368       n->dump();
3369       if( cached_idom != computed_idom ) {
3370         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
3371                       computed_idom->_idx, cached_idom->_idx);
3372       }
3373     }
3374     // Dump nodes it controls
3375     for( uint k = 0; k < _nodes.Size(); k++ ) {
3376       // (k < C->unique() && get_ctrl(find(k)) == n)
3377       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
3378         Node *m = C->root()->find(k);
3379         if( m && m->outcnt() > 0 ) {
3380           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
3381             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
3382                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
3383           }
3384           for( uint j = 0; j < loop->_nest; j++ )
3385             tty->print("  ");
3386           tty->print(" ");
3387           m->dump();
3388         }
3389       }
3390     }
3391   }
3392 }
3393 
3394 // Collect a R-P-O for the whole CFG.
3395 // Result list is in post-order (scan backwards for RPO)
3396 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
3397   stk.push(start, 0);
3398   visited.set(start->_idx);
3399 
3400   while (stk.is_nonempty()) {
3401     Node* m   = stk.node();
3402     uint  idx = stk.index();
3403     if (idx < m->outcnt()) {
3404       stk.set_index(idx + 1);
3405       Node* n = m->raw_out(idx);
3406       if (n->is_CFG() && !visited.test_set(n->_idx)) {
3407         stk.push(n, 0);
3408       }
3409     } else {
3410       rpo_list.push(m);
3411       stk.pop();
3412     }
3413   }
3414 }
3415 #endif
3416 
3417 
3418 //=============================================================================
3419 //------------------------------LoopTreeIterator-----------------------------------
3420 
3421 // Advance to next loop tree using a preorder, left-to-right traversal.
3422 void LoopTreeIterator::next() {
3423   assert(!done(), "must not be done.");
3424   if (_curnt->_child != NULL) {
3425     _curnt = _curnt->_child;
3426   } else if (_curnt->_next != NULL) {
3427     _curnt = _curnt->_next;
3428   } else {
3429     while (_curnt != _root && _curnt->_next == NULL) {
3430       _curnt = _curnt->_parent;
3431     }
3432     if (_curnt == _root) {
3433       _curnt = NULL;
3434       assert(done(), "must be done.");
3435     } else {
3436       assert(_curnt->_next != NULL, "must be more to do");
3437       _curnt = _curnt->_next;
3438     }
3439   }
3440 }
--- EOF ---