1 /*
   2  * Copyright (c) 1998, 2015, 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/convertnode.hpp"
  34 #include "opto/divnode.hpp"
  35 #include "opto/idealGraphPrinter.hpp"
  36 #include "opto/loopnode.hpp"
  37 #include "opto/mulnode.hpp"
  38 #include "opto/rootnode.hpp"
  39 #include "opto/superword.hpp"
  40 
  41 //=============================================================================
  42 //------------------------------is_loop_iv-------------------------------------
  43 // Determine if a node is Counted loop induction variable.
  44 // The method is declared in node.hpp.
  45 const Node* Node::is_loop_iv() const {
  46   if (this->is_Phi() && !this->as_Phi()->is_copy() &&
  47       this->as_Phi()->region()->is_CountedLoop() &&
  48       this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
  49     return this;
  50   } else {
  51     return NULL;
  52   }
  53 }
  54 
  55 //=============================================================================
  56 //------------------------------dump_spec--------------------------------------
  57 // Dump special per-node info
  58 #ifndef PRODUCT
  59 void LoopNode::dump_spec(outputStream *st) const {
  60   if (is_inner_loop()) st->print( "inner " );
  61   if (is_partial_peel_loop()) st->print( "partial_peel " );
  62   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  63 }
  64 #endif
  65 
  66 //------------------------------is_valid_counted_loop-------------------------
  67 bool LoopNode::is_valid_counted_loop() const {
  68   if (is_CountedLoop()) {
  69     CountedLoopNode*    l  = as_CountedLoop();
  70     CountedLoopEndNode* le = l->loopexit();
  71     if (le != NULL &&
  72         le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  73       Node* phi  = l->phi();
  74       Node* exit = le->proj_out(0 /* false */);
  75       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  76           phi != NULL && phi->is_Phi() &&
  77           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  78           le->loopnode() == l && le->stride_is_con()) {
  79         return true;
  80       }
  81     }
  82   }
  83   return false;
  84 }
  85 
  86 //------------------------------get_early_ctrl---------------------------------
  87 // Compute earliest legal control
  88 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  89   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  90   uint i;
  91   Node *early;
  92   if (n->in(0) && !n->is_expensive()) {
  93     early = n->in(0);
  94     if (!early->is_CFG()) // Might be a non-CFG multi-def
  95       early = get_ctrl(early);        // So treat input as a straight data input
  96     i = 1;
  97   } else {
  98     early = get_ctrl(n->in(1));
  99     i = 2;
 100   }
 101   uint e_d = dom_depth(early);
 102   assert( early, "" );
 103   for (; i < n->req(); i++) {
 104     Node *cin = get_ctrl(n->in(i));
 105     assert( cin, "" );
 106     // Keep deepest dominator depth
 107     uint c_d = dom_depth(cin);
 108     if (c_d > e_d) {           // Deeper guy?
 109       early = cin;              // Keep deepest found so far
 110       e_d = c_d;
 111     } else if (c_d == e_d &&    // Same depth?
 112                early != cin) { // If not equal, must use slower algorithm
 113       // If same depth but not equal, one _must_ dominate the other
 114       // and we want the deeper (i.e., dominated) guy.
 115       Node *n1 = early;
 116       Node *n2 = cin;
 117       while (1) {
 118         n1 = idom(n1);          // Walk up until break cycle
 119         n2 = idom(n2);
 120         if (n1 == cin ||        // Walked early up to cin
 121             dom_depth(n2) < c_d)
 122           break;                // early is deeper; keep him
 123         if (n2 == early ||      // Walked cin up to early
 124             dom_depth(n1) < c_d) {
 125           early = cin;          // cin is deeper; keep him
 126           break;
 127         }
 128       }
 129       e_d = dom_depth(early);   // Reset depth register cache
 130     }
 131   }
 132 
 133   // Return earliest legal location
 134   assert(early == find_non_split_ctrl(early), "unexpected early control");
 135 
 136   if (n->is_expensive() && !_verify_only && !_verify_me) {
 137     assert(n->in(0), "should have control input");
 138     early = get_early_ctrl_for_expensive(n, early);
 139   }
 140 
 141   return early;
 142 }
 143 
 144 //------------------------------get_early_ctrl_for_expensive---------------------------------
 145 // Move node up the dominator tree as high as legal while still beneficial
 146 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 147   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 148   assert(OptimizeExpensiveOps, "optimization off?");
 149 
 150   Node* ctl = n->in(0);
 151   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 152   uint min_dom_depth = dom_depth(earliest);
 153 #ifdef ASSERT
 154   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 155     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 156     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 157   }
 158 #endif
 159   if (dom_depth(ctl) < min_dom_depth) {
 160     return earliest;
 161   }
 162 
 163   while (1) {
 164     Node *next = ctl;
 165     // Moving the node out of a loop on the projection of a If
 166     // confuses loop predication. So once we hit a Loop in a If branch
 167     // that doesn't branch to an UNC, we stop. The code that process
 168     // expensive nodes will notice the loop and skip over it to try to
 169     // move the node further up.
 170     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 171       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 172         break;
 173       }
 174       next = idom(ctl->in(1)->in(0));
 175     } else if (ctl->is_Proj()) {
 176       // We only move it up along a projection if the projection is
 177       // the single control projection for its parent: same code path,
 178       // if it's a If with UNC or fallthrough of a call.
 179       Node* parent_ctl = ctl->in(0);
 180       if (parent_ctl == NULL) {
 181         break;
 182       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 183         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 184       } else if (parent_ctl->is_If()) {
 185         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 186           break;
 187         }
 188         assert(idom(ctl) == parent_ctl, "strange");
 189         next = idom(parent_ctl);
 190       } else if (ctl->is_CatchProj()) {
 191         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 192           break;
 193         }
 194         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 195         next = parent_ctl->in(0)->in(0)->in(0);
 196       } else {
 197         // Check if parent control has a single projection (this
 198         // control is the only possible successor of the parent
 199         // control). If so, we can try to move the node above the
 200         // parent control.
 201         int nb_ctl_proj = 0;
 202         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 203           Node *p = parent_ctl->fast_out(i);
 204           if (p->is_Proj() && p->is_CFG()) {
 205             nb_ctl_proj++;
 206             if (nb_ctl_proj > 1) {
 207               break;
 208             }
 209           }
 210         }
 211 
 212         if (nb_ctl_proj > 1) {
 213           break;
 214         }
 215         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
 216         assert(idom(ctl) == parent_ctl, "strange");
 217         next = idom(parent_ctl);
 218       }
 219     } else {
 220       next = idom(ctl);
 221     }
 222     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 223       break;
 224     }
 225     ctl = next;
 226   }
 227 
 228   if (ctl != n->in(0)) {
 229     _igvn.replace_input_of(n, 0, ctl);
 230     _igvn.hash_insert(n);
 231   }
 232 
 233   return ctl;
 234 }
 235 
 236 
 237 //------------------------------set_early_ctrl---------------------------------
 238 // Set earliest legal control
 239 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 240   Node *early = get_early_ctrl(n);
 241 
 242   // Record earliest legal location
 243   set_ctrl(n, early);
 244 }
 245 
 246 //------------------------------set_subtree_ctrl-------------------------------
 247 // set missing _ctrl entries on new nodes
 248 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 249   // Already set?  Get out.
 250   if( _nodes[n->_idx] ) return;
 251   // Recursively set _nodes array to indicate where the Node goes
 252   uint i;
 253   for( i = 0; i < n->req(); ++i ) {
 254     Node *m = n->in(i);
 255     if( m && m != C->root() )
 256       set_subtree_ctrl( m );
 257   }
 258 
 259   // Fixup self
 260   set_early_ctrl( n );
 261 }
 262 
 263 //------------------------------is_counted_loop--------------------------------
 264 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
 265   PhaseGVN *gvn = &_igvn;
 266 
 267   // Counted loop head must be a good RegionNode with only 3 not NULL
 268   // control input edges: Self, Entry, LoopBack.
 269   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 270     return false;
 271   }
 272   Node *init_control = x->in(LoopNode::EntryControl);
 273   Node *back_control = x->in(LoopNode::LoopBackControl);
 274   if (init_control == NULL || back_control == NULL)    // Partially dead
 275     return false;
 276   // Must also check for TOP when looking for a dead loop
 277   if (init_control->is_top() || back_control->is_top())
 278     return false;
 279 
 280   // Allow funny placement of Safepoint
 281   if (back_control->Opcode() == Op_SafePoint)
 282     back_control = back_control->in(TypeFunc::Control);
 283 
 284   // Controlling test for loop
 285   Node *iftrue = back_control;
 286   uint iftrue_op = iftrue->Opcode();
 287   if (iftrue_op != Op_IfTrue &&
 288       iftrue_op != Op_IfFalse)
 289     // I have a weird back-control.  Probably the loop-exit test is in
 290     // the middle of the loop and I am looking at some trailing control-flow
 291     // merge point.  To fix this I would have to partially peel the loop.
 292     return false; // Obscure back-control
 293 
 294   // Get boolean guarding loop-back test
 295   Node *iff = iftrue->in(0);
 296   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 297     return false;
 298   BoolNode *test = iff->in(1)->as_Bool();
 299   BoolTest::mask bt = test->_test._test;
 300   float cl_prob = iff->as_If()->_prob;
 301   if (iftrue_op == Op_IfFalse) {
 302     bt = BoolTest(bt).negate();
 303     cl_prob = 1.0 - cl_prob;
 304   }
 305   // Get backedge compare
 306   Node *cmp = test->in(1);
 307   int cmp_op = cmp->Opcode();
 308   if (cmp_op != Op_CmpI)
 309     return false;                // Avoid pointer & float compares
 310 
 311   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 312   Node *incr  = cmp->in(1);
 313   Node *limit = cmp->in(2);
 314 
 315   // ---------
 316   // need 'loop()' test to tell if limit is loop invariant
 317   // ---------
 318 
 319   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 320     Node *tmp = incr;            // Then reverse order into the CmpI
 321     incr = limit;
 322     limit = tmp;
 323     bt = BoolTest(bt).commute(); // And commute the exit test
 324   }
 325   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 326     return false;
 327   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 328     return false;
 329 
 330   Node* phi_incr = NULL;
 331   // Trip-counter increment must be commutative & associative.
 332   if (incr->Opcode() == Op_CastII) {
 333     incr = incr->in(1);
 334   }
 335   if (incr->is_Phi()) {
 336     if (incr->as_Phi()->region() != x || incr->req() != 3)
 337       return false; // Not simple trip counter expression
 338     phi_incr = incr;
 339     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 340     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 341       return false;
 342   }
 343 
 344   Node* trunc1 = NULL;
 345   Node* trunc2 = NULL;
 346   const TypeInt* iv_trunc_t = NULL;
 347   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 348     return false; // Funny increment opcode
 349   }
 350   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 351 
 352   // Get merge point
 353   Node *xphi = incr->in(1);
 354   Node *stride = incr->in(2);
 355   if (!stride->is_Con()) {     // Oops, swap these
 356     if (!xphi->is_Con())       // Is the other guy a constant?
 357       return false;             // Nope, unknown stride, bail out
 358     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 359     xphi = stride;
 360     stride = tmp;
 361   }
 362   if (xphi->Opcode() == Op_CastII) {
 363     xphi = xphi->in(1);
 364   }
 365   // Stride must be constant
 366   int stride_con = stride->get_int();
 367   if (stride_con == 0)
 368     return false; // missed some peephole opt
 369 
 370   if (!xphi->is_Phi())
 371     return false; // Too much math on the trip counter
 372   if (phi_incr != NULL && phi_incr != xphi)
 373     return false;
 374   PhiNode *phi = xphi->as_Phi();
 375 
 376   // Phi must be of loop header; backedge must wrap to increment
 377   if (phi->region() != x)
 378     return false;
 379   if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
 380       trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) {
 381     return false;
 382   }
 383   Node *init_trip = phi->in(LoopNode::EntryControl);
 384 
 385   // If iv trunc type is smaller than int, check for possible wrap.
 386   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 387     assert(trunc1 != NULL, "must have found some truncation");
 388 
 389     // Get a better type for the phi (filtered thru if's)
 390     const TypeInt* phi_ft = filtered_type(phi);
 391 
 392     // Can iv take on a value that will wrap?
 393     //
 394     // Ensure iv's limit is not within "stride" of the wrap value.
 395     //
 396     // Example for "short" type
 397     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 398     //    If the stride is +10, then the last value of the induction
 399     //    variable before the increment (phi_ft->_hi) must be
 400     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 401     //    ensure no truncation occurs after the increment.
 402 
 403     if (stride_con > 0) {
 404       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 405           iv_trunc_t->_lo > phi_ft->_lo) {
 406         return false;  // truncation may occur
 407       }
 408     } else if (stride_con < 0) {
 409       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 410           iv_trunc_t->_hi < phi_ft->_hi) {
 411         return false;  // truncation may occur
 412       }
 413     }
 414     // No possibility of wrap so truncation can be discarded
 415     // Promote iv type to Int
 416   } else {
 417     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 418   }
 419 
 420   // If the condition is inverted and we will be rolling
 421   // through MININT to MAXINT, then bail out.
 422   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 423       // Odd stride
 424       bt == BoolTest::ne && stride_con != 1 && stride_con != -1 ||
 425       // Count down loop rolls through MAXINT
 426       (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 ||
 427       // Count up loop rolls through MININT
 428       (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) {
 429     return false; // Bail out
 430   }
 431 
 432   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 433   const TypeInt* limit_t = gvn->type(limit)->is_int();
 434 
 435   if (stride_con > 0) {
 436     jlong init_p = (jlong)init_t->_lo + stride_con;
 437     if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
 438       return false; // cyclic loop or this loop trips only once
 439   } else {
 440     jlong init_p = (jlong)init_t->_hi + stride_con;
 441     if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
 442       return false; // cyclic loop or this loop trips only once
 443   }
 444 
 445   if (phi_incr != NULL) {
 446     // check if there is a possiblity of IV overflowing after the first increment
 447     if (stride_con > 0) {
 448       if (init_t->_hi > max_jint - stride_con) {
 449         return false;
 450       }
 451     } else {
 452       if (init_t->_lo < min_jint - stride_con) {
 453         return false;
 454       }
 455     }
 456   }
 457 
 458   // =================================================
 459   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 460   //
 461   assert(x->Opcode() == Op_Loop, "regular loops only");
 462   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 463 
 464   Node *hook = new Node(6);
 465 
 466   if (LoopLimitCheck) {
 467 
 468   // ===================================================
 469   // Generate loop limit check to avoid integer overflow
 470   // in cases like next (cyclic loops):
 471   //
 472   // for (i=0; i <= max_jint; i++) {}
 473   // for (i=0; i <  max_jint; i+=2) {}
 474   //
 475   //
 476   // Limit check predicate depends on the loop test:
 477   //
 478   // for(;i != limit; i++)       --> limit <= (max_jint)
 479   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 480   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 481   //
 482 
 483   // Check if limit is excluded to do more precise int overflow check.
 484   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 485   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 486 
 487   // If compare points directly to the phi we need to adjust
 488   // the compare so that it points to the incr. Limit have
 489   // to be adjusted to keep trip count the same and the
 490   // adjusted limit should be checked for int overflow.
 491   if (phi_incr != NULL) {
 492     stride_m  += stride_con;
 493   }
 494 
 495   if (limit->is_Con()) {
 496     int limit_con = limit->get_int();
 497     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 498         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 499       // Bailout: it could be integer overflow.
 500       return false;
 501     }
 502   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 503              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 504       // Limit's type may satisfy the condition, for example,
 505       // when it is an array length.
 506   } else {
 507     // Generate loop's limit check.
 508     // Loop limit check predicate should be near the loop.
 509     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 510     if (!limit_check_proj) {
 511       // The limit check predicate is not generated if this method trapped here before.
 512 #ifdef ASSERT
 513       if (TraceLoopLimitCheck) {
 514         tty->print("missing loop limit check:");
 515         loop->dump_head();
 516         x->dump(1);
 517       }
 518 #endif
 519       return false;
 520     }
 521 
 522     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 523     Node* cmp_limit;
 524     Node* bol;
 525 
 526     if (stride_con > 0) {
 527       cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 528       bol = new BoolNode(cmp_limit, BoolTest::le);
 529     } else {
 530       cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 531       bol = new BoolNode(cmp_limit, BoolTest::ge);
 532     }
 533     cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 534     bol = _igvn.register_new_node_with_optimizer(bol);
 535     set_subtree_ctrl(bol);
 536 
 537     // Replace condition in original predicate but preserve Opaque node
 538     // so that previous predicates could be found.
 539     assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
 540            check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
 541     Node* opq = check_iff->in(1)->in(1);
 542     _igvn.replace_input_of(opq, 1, bol);
 543     // Update ctrl.
 544     set_ctrl(opq, check_iff->in(0));
 545     set_ctrl(check_iff->in(1), check_iff->in(0));
 546 
 547 #ifndef PRODUCT
 548     // report that the loop predication has been actually performed
 549     // for this loop
 550     if (TraceLoopLimitCheck) {
 551       tty->print_cr("Counted Loop Limit Check generated:");
 552       debug_only( bol->dump(2); )
 553     }
 554 #endif
 555   }
 556 
 557   if (phi_incr != NULL) {
 558     // If compare points directly to the phi we need to adjust
 559     // the compare so that it points to the incr. Limit have
 560     // to be adjusted to keep trip count the same and we
 561     // should avoid int overflow.
 562     //
 563     //   i = init; do {} while(i++ < limit);
 564     // is converted to
 565     //   i = init; do {} while(++i < limit+1);
 566     //
 567     limit = gvn->transform(new AddINode(limit, stride));
 568   }
 569 
 570   // Now we need to canonicalize loop condition.
 571   if (bt == BoolTest::ne) {
 572     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 573     // 'ne' can be replaced with 'lt' only when init < limit.
 574     if (stride_con > 0 && init_t->_hi < limit_t->_lo)
 575       bt = BoolTest::lt;
 576     // 'ne' can be replaced with 'gt' only when init > limit.
 577     if (stride_con < 0 && init_t->_lo > limit_t->_hi)
 578       bt = BoolTest::gt;
 579   }
 580 
 581   if (incl_limit) {
 582     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 583     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 584     //
 585     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 586     limit = gvn->transform(new AddINode(limit, one));
 587     if (bt == BoolTest::le)
 588       bt = BoolTest::lt;
 589     else if (bt == BoolTest::ge)
 590       bt = BoolTest::gt;
 591     else
 592       ShouldNotReachHere();
 593   }
 594   set_subtree_ctrl( limit );
 595 
 596   } else { // LoopLimitCheck
 597 
 598   // If compare points to incr, we are ok.  Otherwise the compare
 599   // can directly point to the phi; in this case adjust the compare so that
 600   // it points to the incr by adjusting the limit.
 601   if (cmp->in(1) == phi || cmp->in(2) == phi)
 602     limit = gvn->transform(new AddINode(limit,stride));
 603 
 604   // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
 605   // Final value for iterator should be: trip_count * stride + init_trip.
 606   Node *one_p = gvn->intcon( 1);
 607   Node *one_m = gvn->intcon(-1);
 608 
 609   Node *trip_count = NULL;
 610   switch( bt ) {
 611   case BoolTest::eq:
 612     ShouldNotReachHere();
 613   case BoolTest::ne:            // Ahh, the case we desire
 614     if (stride_con == 1)
 615       trip_count = gvn->transform(new SubINode(limit,init_trip));
 616     else if (stride_con == -1)
 617       trip_count = gvn->transform(new SubINode(init_trip,limit));
 618     else
 619       ShouldNotReachHere();
 620     set_subtree_ctrl(trip_count);
 621     //_loop.map(trip_count->_idx,loop(limit));
 622     break;
 623   case BoolTest::le:            // Maybe convert to '<' case
 624     limit = gvn->transform(new AddINode(limit,one_p));
 625     set_subtree_ctrl( limit );
 626     hook->init_req(4, limit);
 627 
 628     bt = BoolTest::lt;
 629     // Make the new limit be in the same loop nest as the old limit
 630     //_loop.map(limit->_idx,limit_loop);
 631     // Fall into next case
 632   case BoolTest::lt: {          // Maybe convert to '!=' case
 633     if (stride_con < 0) // Count down loop rolls through MAXINT
 634       ShouldNotReachHere();
 635     Node *range = gvn->transform(new SubINode(limit,init_trip));
 636     set_subtree_ctrl( range );
 637     hook->init_req(0, range);
 638 
 639     Node *bias  = gvn->transform(new AddINode(range,stride));
 640     set_subtree_ctrl( bias );
 641     hook->init_req(1, bias);
 642 
 643     Node *bias1 = gvn->transform(new AddINode(bias,one_m));
 644     set_subtree_ctrl( bias1 );
 645     hook->init_req(2, bias1);
 646 
 647     trip_count  = gvn->transform(new DivINode(0,bias1,stride));
 648     set_subtree_ctrl( trip_count );
 649     hook->init_req(3, trip_count);
 650     break;
 651   }
 652 
 653   case BoolTest::ge:            // Maybe convert to '>' case
 654     limit = gvn->transform(new AddINode(limit,one_m));
 655     set_subtree_ctrl( limit );
 656     hook->init_req(4 ,limit);
 657 
 658     bt = BoolTest::gt;
 659     // Make the new limit be in the same loop nest as the old limit
 660     //_loop.map(limit->_idx,limit_loop);
 661     // Fall into next case
 662   case BoolTest::gt: {          // Maybe convert to '!=' case
 663     if (stride_con > 0) // count up loop rolls through MININT
 664       ShouldNotReachHere();
 665     Node *range = gvn->transform(new SubINode(limit,init_trip));
 666     set_subtree_ctrl( range );
 667     hook->init_req(0, range);
 668 
 669     Node *bias  = gvn->transform(new AddINode(range,stride));
 670     set_subtree_ctrl( bias );
 671     hook->init_req(1, bias);
 672 
 673     Node *bias1 = gvn->transform(new AddINode(bias,one_p));
 674     set_subtree_ctrl( bias1 );
 675     hook->init_req(2, bias1);
 676 
 677     trip_count  = gvn->transform(new DivINode(0,bias1,stride));
 678     set_subtree_ctrl( trip_count );
 679     hook->init_req(3, trip_count);
 680     break;
 681   }
 682   } // switch( bt )
 683 
 684   Node *span = gvn->transform(new MulINode(trip_count,stride));
 685   set_subtree_ctrl( span );
 686   hook->init_req(5, span);
 687 
 688   limit = gvn->transform(new AddINode(span,init_trip));
 689   set_subtree_ctrl( limit );
 690 
 691   } // LoopLimitCheck
 692 
 693   if (!UseCountedLoopSafepoints) {
 694     // Check for SafePoint on backedge and remove
 695     Node *sfpt = x->in(LoopNode::LoopBackControl);
 696     if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 697       lazy_replace( sfpt, iftrue );
 698       if (loop->_safepts != NULL) {
 699         loop->_safepts->yank(sfpt);
 700       }
 701       loop->_tail = iftrue;
 702     }
 703   }
 704 
 705   // Build a canonical trip test.
 706   // Clone code, as old values may be in use.
 707   incr = incr->clone();
 708   incr->set_req(1,phi);
 709   incr->set_req(2,stride);
 710   incr = _igvn.register_new_node_with_optimizer(incr);
 711   set_early_ctrl( incr );
 712   _igvn.rehash_node_delayed(phi);
 713   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 714 
 715   // If phi type is more restrictive than Int, raise to
 716   // Int to prevent (almost) infinite recursion in igvn
 717   // which can only handle integer types for constants or minint..maxint.
 718   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 719     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 720     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 721     nphi = _igvn.register_new_node_with_optimizer(nphi);
 722     set_ctrl(nphi, get_ctrl(phi));
 723     _igvn.replace_node(phi, nphi);
 724     phi = nphi->as_Phi();
 725   }
 726   cmp = cmp->clone();
 727   cmp->set_req(1,incr);
 728   cmp->set_req(2,limit);
 729   cmp = _igvn.register_new_node_with_optimizer(cmp);
 730   set_ctrl(cmp, iff->in(0));
 731 
 732   test = test->clone()->as_Bool();
 733   (*(BoolTest*)&test->_test)._test = bt;
 734   test->set_req(1,cmp);
 735   _igvn.register_new_node_with_optimizer(test);
 736   set_ctrl(test, iff->in(0));
 737 
 738   // Replace the old IfNode with a new LoopEndNode
 739   Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 740   IfNode *le = lex->as_If();
 741   uint dd = dom_depth(iff);
 742   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 743   set_loop(le, loop);
 744 
 745   // Get the loop-exit control
 746   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 747 
 748   // Need to swap loop-exit and loop-back control?
 749   if (iftrue_op == Op_IfFalse) {
 750     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
 751     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
 752 
 753     loop->_tail = back_control = ift2;
 754     set_loop(ift2, loop);
 755     set_loop(iff2, get_loop(iffalse));
 756 
 757     // Lazy update of 'get_ctrl' mechanism.
 758     lazy_replace_proj( iffalse, iff2 );
 759     lazy_replace_proj( iftrue,  ift2 );
 760 
 761     // Swap names
 762     iffalse = iff2;
 763     iftrue  = ift2;
 764   } else {
 765     _igvn.rehash_node_delayed(iffalse);
 766     _igvn.rehash_node_delayed(iftrue);
 767     iffalse->set_req_X( 0, le, &_igvn );
 768     iftrue ->set_req_X( 0, le, &_igvn );
 769   }
 770 
 771   set_idom(iftrue,  le, dd+1);
 772   set_idom(iffalse, le, dd+1);
 773   assert(iff->outcnt() == 0, "should be dead now");
 774   lazy_replace( iff, le ); // fix 'get_ctrl'
 775 
 776   // Now setup a new CountedLoopNode to replace the existing LoopNode
 777   CountedLoopNode *l = new CountedLoopNode(init_control, back_control);
 778   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 779   // The following assert is approximately true, and defines the intention
 780   // of can_be_counted_loop.  It fails, however, because phase->type
 781   // is not yet initialized for this loop and its parts.
 782   //assert(l->can_be_counted_loop(this), "sanity");
 783   _igvn.register_new_node_with_optimizer(l);
 784   set_loop(l, loop);
 785   loop->_head = l;
 786   // Fix all data nodes placed at the old loop head.
 787   // Uses the lazy-update mechanism of 'get_ctrl'.
 788   lazy_replace( x, l );
 789   set_idom(l, init_control, dom_depth(x));
 790 
 791   if (!UseCountedLoopSafepoints) {
 792     // Check for immediately preceding SafePoint and remove
 793     Node *sfpt2 = le->in(0);
 794     if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) {
 795       lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 796       if (loop->_safepts != NULL) {
 797         loop->_safepts->yank(sfpt2);
 798       }
 799     }
 800   }
 801 
 802   // Free up intermediate goo
 803   _igvn.remove_dead_node(hook);
 804 
 805 #ifdef ASSERT
 806   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 807   assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
 808 #endif
 809 #ifndef PRODUCT
 810   if (TraceLoopOpts) {
 811     tty->print("Counted      ");
 812     loop->dump_head();
 813   }
 814 #endif
 815 
 816   C->print_method(PHASE_AFTER_CLOOPS, 3);
 817 
 818   return true;
 819 }
 820 
 821 //----------------------exact_limit-------------------------------------------
 822 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 823   assert(loop->_head->is_CountedLoop(), "");
 824   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 825   assert(cl->is_valid_counted_loop(), "");
 826 
 827   if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
 828       cl->limit()->Opcode() == Op_LoopLimit) {
 829     // Old code has exact limit (it could be incorrect in case of int overflow).
 830     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 831     return cl->limit();
 832   }
 833   Node *limit = NULL;
 834 #ifdef ASSERT
 835   BoolTest::mask bt = cl->loopexit()->test_trip();
 836   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 837 #endif
 838   if (cl->has_exact_trip_count()) {
 839     // Simple case: loop has constant boundaries.
 840     // Use jlongs to avoid integer overflow.
 841     int stride_con = cl->stride_con();
 842     jlong  init_con = cl->init_trip()->get_int();
 843     jlong limit_con = cl->limit()->get_int();
 844     julong trip_cnt = cl->trip_count();
 845     jlong final_con = init_con + trip_cnt*stride_con;
 846     int final_int = (int)final_con;
 847     // The final value should be in integer range since the loop
 848     // is counted and the limit was checked for overflow.
 849     assert(final_con == (jlong)final_int, "final value should be integer");
 850     limit = _igvn.intcon(final_int);
 851   } else {
 852     // Create new LoopLimit node to get exact limit (final iv value).
 853     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 854     register_new_node(limit, cl->in(LoopNode::EntryControl));
 855   }
 856   assert(limit != NULL, "sanity");
 857   return limit;
 858 }
 859 
 860 //------------------------------Ideal------------------------------------------
 861 // Return a node which is more "ideal" than the current node.
 862 // Attempt to convert into a counted-loop.
 863 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 864   if (!can_be_counted_loop(phase)) {
 865     phase->C->set_major_progress();
 866   }
 867   return RegionNode::Ideal(phase, can_reshape);
 868 }
 869 
 870 
 871 //=============================================================================
 872 //------------------------------Ideal------------------------------------------
 873 // Return a node which is more "ideal" than the current node.
 874 // Attempt to convert into a counted-loop.
 875 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 876   return RegionNode::Ideal(phase, can_reshape);
 877 }
 878 
 879 //------------------------------dump_spec--------------------------------------
 880 // Dump special per-node info
 881 #ifndef PRODUCT
 882 void CountedLoopNode::dump_spec(outputStream *st) const {
 883   LoopNode::dump_spec(st);
 884   if (stride_is_con()) {
 885     st->print("stride: %d ",stride_con());
 886   }
 887   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
 888   if (is_main_loop()) st->print("main of N%d", _idx);
 889   if (is_post_loop()) st->print("post of N%d", _main_idx);
 890 }
 891 #endif
 892 
 893 //=============================================================================
 894 int CountedLoopEndNode::stride_con() const {
 895   return stride()->bottom_type()->is_int()->get_con();
 896 }
 897 
 898 //=============================================================================
 899 //------------------------------Value-----------------------------------------
 900 const Type* LoopLimitNode::Value(PhaseGVN* phase) const {
 901   const Type* init_t   = phase->type(in(Init));
 902   const Type* limit_t  = phase->type(in(Limit));
 903   const Type* stride_t = phase->type(in(Stride));
 904   // Either input is TOP ==> the result is TOP
 905   if (init_t   == Type::TOP) return Type::TOP;
 906   if (limit_t  == Type::TOP) return Type::TOP;
 907   if (stride_t == Type::TOP) return Type::TOP;
 908 
 909   int stride_con = stride_t->is_int()->get_con();
 910   if (stride_con == 1)
 911     return NULL;  // Identity
 912 
 913   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
 914     // Use jlongs to avoid integer overflow.
 915     jlong init_con   =  init_t->is_int()->get_con();
 916     jlong limit_con  = limit_t->is_int()->get_con();
 917     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
 918     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
 919     jlong final_con  = init_con + stride_con*trip_count;
 920     int final_int = (int)final_con;
 921     // The final value should be in integer range since the loop
 922     // is counted and the limit was checked for overflow.
 923     assert(final_con == (jlong)final_int, "final value should be integer");
 924     return TypeInt::make(final_int);
 925   }
 926 
 927   return bottom_type(); // TypeInt::INT
 928 }
 929 
 930 //------------------------------Ideal------------------------------------------
 931 // Return a node which is more "ideal" than the current node.
 932 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 933   if (phase->type(in(Init))   == Type::TOP ||
 934       phase->type(in(Limit))  == Type::TOP ||
 935       phase->type(in(Stride)) == Type::TOP)
 936     return NULL;  // Dead
 937 
 938   int stride_con = phase->type(in(Stride))->is_int()->get_con();
 939   if (stride_con == 1)
 940     return NULL;  // Identity
 941 
 942   if (in(Init)->is_Con() && in(Limit)->is_Con())
 943     return NULL;  // Value
 944 
 945   // Delay following optimizations until all loop optimizations
 946   // done to keep Ideal graph simple.
 947   if (!can_reshape || phase->C->major_progress())
 948     return NULL;
 949 
 950   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
 951   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
 952   int stride_p;
 953   jlong lim, ini;
 954   julong max;
 955   if (stride_con > 0) {
 956     stride_p = stride_con;
 957     lim = limit_t->_hi;
 958     ini = init_t->_lo;
 959     max = (julong)max_jint;
 960   } else {
 961     stride_p = -stride_con;
 962     lim = init_t->_hi;
 963     ini = limit_t->_lo;
 964     max = (julong)min_jint;
 965   }
 966   julong range = lim - ini + stride_p;
 967   if (range <= max) {
 968     // Convert to integer expression if it is not overflow.
 969     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
 970     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
 971     Node *bias  = phase->transform(new AddINode(range, stride_m));
 972     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
 973     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
 974     return new AddINode(span, in(Init)); // exact limit
 975   }
 976 
 977   if (is_power_of_2(stride_p) ||                // divisor is 2^n
 978       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
 979     // Convert to long expression to avoid integer overflow
 980     // and let igvn optimizer convert this division.
 981     //
 982     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
 983     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
 984     Node* stride   = phase->longcon(stride_con);
 985     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
 986 
 987     Node *range = phase->transform(new SubLNode(limit, init));
 988     Node *bias  = phase->transform(new AddLNode(range, stride_m));
 989     Node *span;
 990     if (stride_con > 0 && is_power_of_2(stride_p)) {
 991       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
 992       // and avoid generating rounding for division. Zero trip guard should
 993       // guarantee that init < limit but sometimes the guard is missing and
 994       // we can get situation when init > limit. Note, for the empty loop
 995       // optimization zero trip guard is generated explicitly which leaves
 996       // only RCE predicate where exact limit is used and the predicate
 997       // will simply fail forcing recompilation.
 998       Node* neg_stride   = phase->longcon(-stride_con);
 999       span = phase->transform(new AndLNode(bias, neg_stride));
1000     } else {
1001       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
1002       span = phase->transform(new MulLNode(trip, stride));
1003     }
1004     // Convert back to int
1005     Node *span_int = phase->transform(new ConvL2INode(span));
1006     return new AddINode(span_int, in(Init)); // exact limit
1007   }
1008 
1009   return NULL;    // No progress
1010 }
1011 
1012 //------------------------------Identity---------------------------------------
1013 // If stride == 1 return limit node.
1014 Node* LoopLimitNode::Identity(PhaseGVN* phase) {
1015   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1016   if (stride_con == 1 || stride_con == -1)
1017     return in(Limit);
1018   return this;
1019 }
1020 
1021 //=============================================================================
1022 //----------------------match_incr_with_optional_truncation--------------------
1023 // Match increment with optional truncation:
1024 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1025 // Return NULL for failure. Success returns the increment node.
1026 Node* CountedLoopNode::match_incr_with_optional_truncation(
1027                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1028   // Quick cutouts:
1029   if (expr == NULL || expr->req() != 3)  return NULL;
1030 
1031   Node *t1 = NULL;
1032   Node *t2 = NULL;
1033   const TypeInt* trunc_t = TypeInt::INT;
1034   Node* n1 = expr;
1035   int   n1op = n1->Opcode();
1036 
1037   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1038   if (n1op == Op_AndI &&
1039       n1->in(2)->is_Con() &&
1040       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1041     // %%% This check should match any mask of 2**K-1.
1042     t1 = n1;
1043     n1 = t1->in(1);
1044     n1op = n1->Opcode();
1045     trunc_t = TypeInt::CHAR;
1046   } else if (n1op == Op_RShiftI &&
1047              n1->in(1) != NULL &&
1048              n1->in(1)->Opcode() == Op_LShiftI &&
1049              n1->in(2) == n1->in(1)->in(2) &&
1050              n1->in(2)->is_Con()) {
1051     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1052     // %%% This check should match any shift in [1..31].
1053     if (shift == 16 || shift == 8) {
1054       t1 = n1;
1055       t2 = t1->in(1);
1056       n1 = t2->in(1);
1057       n1op = n1->Opcode();
1058       if (shift == 16) {
1059         trunc_t = TypeInt::SHORT;
1060       } else if (shift == 8) {
1061         trunc_t = TypeInt::BYTE;
1062       }
1063     }
1064   }
1065 
1066   // If (maybe after stripping) it is an AddI, we won:
1067   if (n1op == Op_AddI) {
1068     *trunc1 = t1;
1069     *trunc2 = t2;
1070     *trunc_type = trunc_t;
1071     return n1;
1072   }
1073 
1074   // failed
1075   return NULL;
1076 }
1077 
1078 
1079 //------------------------------filtered_type--------------------------------
1080 // Return a type based on condition control flow
1081 // A successful return will be a type that is restricted due
1082 // to a series of dominating if-tests, such as:
1083 //    if (i < 10) {
1084 //       if (i > 0) {
1085 //          here: "i" type is [1..10)
1086 //       }
1087 //    }
1088 // or a control flow merge
1089 //    if (i < 10) {
1090 //       do {
1091 //          phi( , ) -- at top of loop type is [min_int..10)
1092 //         i = ?
1093 //       } while ( i < 10)
1094 //
1095 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1096   assert(n && n->bottom_type()->is_int(), "must be int");
1097   const TypeInt* filtered_t = NULL;
1098   if (!n->is_Phi()) {
1099     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1100     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1101 
1102   } else {
1103     Node* phi    = n->as_Phi();
1104     Node* region = phi->in(0);
1105     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1106     if (region && region != C->top()) {
1107       for (uint i = 1; i < phi->req(); i++) {
1108         Node* val   = phi->in(i);
1109         Node* use_c = region->in(i);
1110         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1111         if (val_t != NULL) {
1112           if (filtered_t == NULL) {
1113             filtered_t = val_t;
1114           } else {
1115             filtered_t = filtered_t->meet(val_t)->is_int();
1116           }
1117         }
1118       }
1119     }
1120   }
1121   const TypeInt* n_t = _igvn.type(n)->is_int();
1122   if (filtered_t != NULL) {
1123     n_t = n_t->join(filtered_t)->is_int();
1124   }
1125   return n_t;
1126 }
1127 
1128 
1129 //------------------------------filtered_type_from_dominators--------------------------------
1130 // Return a possibly more restrictive type for val based on condition control flow of dominators
1131 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1132   if (val->is_Con()) {
1133      return val->bottom_type()->is_int();
1134   }
1135   uint if_limit = 10; // Max number of dominating if's visited
1136   const TypeInt* rtn_t = NULL;
1137 
1138   if (use_ctrl && use_ctrl != C->top()) {
1139     Node* val_ctrl = get_ctrl(val);
1140     uint val_dom_depth = dom_depth(val_ctrl);
1141     Node* pred = use_ctrl;
1142     uint if_cnt = 0;
1143     while (if_cnt < if_limit) {
1144       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1145         if_cnt++;
1146         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1147         if (if_t != NULL) {
1148           if (rtn_t == NULL) {
1149             rtn_t = if_t;
1150           } else {
1151             rtn_t = rtn_t->join(if_t)->is_int();
1152           }
1153         }
1154       }
1155       pred = idom(pred);
1156       if (pred == NULL || pred == C->top()) {
1157         break;
1158       }
1159       // Stop if going beyond definition block of val
1160       if (dom_depth(pred) < val_dom_depth) {
1161         break;
1162       }
1163     }
1164   }
1165   return rtn_t;
1166 }
1167 
1168 
1169 //------------------------------dump_spec--------------------------------------
1170 // Dump special per-node info
1171 #ifndef PRODUCT
1172 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1173   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1174     BoolTest bt( test_trip()); // Added this for g++.
1175 
1176     st->print("[");
1177     bt.dump_on(st);
1178     st->print("]");
1179   }
1180   st->print(" ");
1181   IfNode::dump_spec(st);
1182 }
1183 #endif
1184 
1185 //=============================================================================
1186 //------------------------------is_member--------------------------------------
1187 // Is 'l' a member of 'this'?
1188 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1189   while( l->_nest > _nest ) l = l->_parent;
1190   return l == this;
1191 }
1192 
1193 //------------------------------set_nest---------------------------------------
1194 // Set loop tree nesting depth.  Accumulate _has_call bits.
1195 int IdealLoopTree::set_nest( uint depth ) {
1196   _nest = depth;
1197   int bits = _has_call;
1198   if( _child ) bits |= _child->set_nest(depth+1);
1199   if( bits ) _has_call = 1;
1200   if( _next  ) bits |= _next ->set_nest(depth  );
1201   return bits;
1202 }
1203 
1204 //------------------------------split_fall_in----------------------------------
1205 // Split out multiple fall-in edges from the loop header.  Move them to a
1206 // private RegionNode before the loop.  This becomes the loop landing pad.
1207 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1208   PhaseIterGVN &igvn = phase->_igvn;
1209   uint i;
1210 
1211   // Make a new RegionNode to be the landing pad.
1212   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1213   phase->set_loop(landing_pad,_parent);
1214   // Gather all the fall-in control paths into the landing pad
1215   uint icnt = fall_in_cnt;
1216   uint oreq = _head->req();
1217   for( i = oreq-1; i>0; i-- )
1218     if( !phase->is_member( this, _head->in(i) ) )
1219       landing_pad->set_req(icnt--,_head->in(i));
1220 
1221   // Peel off PhiNode edges as well
1222   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1223     Node *oj = _head->fast_out(j);
1224     if( oj->is_Phi() ) {
1225       PhiNode* old_phi = oj->as_Phi();
1226       assert( old_phi->region() == _head, "" );
1227       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1228       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1229       uint icnt = fall_in_cnt;
1230       for( i = oreq-1; i>0; i-- ) {
1231         if( !phase->is_member( this, _head->in(i) ) ) {
1232           p->init_req(icnt--, old_phi->in(i));
1233           // Go ahead and clean out old edges from old phi
1234           old_phi->del_req(i);
1235         }
1236       }
1237       // Search for CSE's here, because ZKM.jar does a lot of
1238       // loop hackery and we need to be a little incremental
1239       // with the CSE to avoid O(N^2) node blow-up.
1240       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1241       if( p2 ) {                // Found CSE
1242         p->destruct();          // Recover useless new node
1243         p = p2;                 // Use old node
1244       } else {
1245         igvn.register_new_node_with_optimizer(p, old_phi);
1246       }
1247       // Make old Phi refer to new Phi.
1248       old_phi->add_req(p);
1249       // Check for the special case of making the old phi useless and
1250       // disappear it.  In JavaGrande I have a case where this useless
1251       // Phi is the loop limit and prevents recognizing a CountedLoop
1252       // which in turn prevents removing an empty loop.
1253       Node *id_old_phi = old_phi->Identity( &igvn );
1254       if( id_old_phi != old_phi ) { // Found a simple identity?
1255         // Note that I cannot call 'replace_node' here, because
1256         // that will yank the edge from old_phi to the Region and
1257         // I'm mid-iteration over the Region's uses.
1258         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1259           Node* use = old_phi->last_out(i);
1260           igvn.rehash_node_delayed(use);
1261           uint uses_found = 0;
1262           for (uint j = 0; j < use->len(); j++) {
1263             if (use->in(j) == old_phi) {
1264               if (j < use->req()) use->set_req (j, id_old_phi);
1265               else                use->set_prec(j, id_old_phi);
1266               uses_found++;
1267             }
1268           }
1269           i -= uses_found;    // we deleted 1 or more copies of this edge
1270         }
1271       }
1272       igvn._worklist.push(old_phi);
1273     }
1274   }
1275   // Finally clean out the fall-in edges from the RegionNode
1276   for( i = oreq-1; i>0; i-- ) {
1277     if( !phase->is_member( this, _head->in(i) ) ) {
1278       _head->del_req(i);
1279     }
1280   }
1281   igvn.rehash_node_delayed(_head);
1282   // Transform landing pad
1283   igvn.register_new_node_with_optimizer(landing_pad, _head);
1284   // Insert landing pad into the header
1285   _head->add_req(landing_pad);
1286 }
1287 
1288 //------------------------------split_outer_loop-------------------------------
1289 // Split out the outermost loop from this shared header.
1290 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1291   PhaseIterGVN &igvn = phase->_igvn;
1292 
1293   // Find index of outermost loop; it should also be my tail.
1294   uint outer_idx = 1;
1295   while( _head->in(outer_idx) != _tail ) outer_idx++;
1296 
1297   // Make a LoopNode for the outermost loop.
1298   Node *ctl = _head->in(LoopNode::EntryControl);
1299   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1300   outer = igvn.register_new_node_with_optimizer(outer, _head);
1301   phase->set_created_loop_node();
1302 
1303   // Outermost loop falls into '_head' loop
1304   _head->set_req(LoopNode::EntryControl, outer);
1305   _head->del_req(outer_idx);
1306   // Split all the Phis up between '_head' loop and 'outer' loop.
1307   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1308     Node *out = _head->fast_out(j);
1309     if( out->is_Phi() ) {
1310       PhiNode *old_phi = out->as_Phi();
1311       assert( old_phi->region() == _head, "" );
1312       Node *phi = PhiNode::make_blank(outer, old_phi);
1313       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1314       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1315       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1316       // Make old Phi point to new Phi on the fall-in path
1317       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1318       old_phi->del_req(outer_idx);
1319     }
1320   }
1321 
1322   // Use the new loop head instead of the old shared one
1323   _head = outer;
1324   phase->set_loop(_head, this);
1325 }
1326 
1327 //------------------------------fix_parent-------------------------------------
1328 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1329   loop->_parent = parent;
1330   if( loop->_child ) fix_parent( loop->_child, loop   );
1331   if( loop->_next  ) fix_parent( loop->_next , parent );
1332 }
1333 
1334 //------------------------------estimate_path_freq-----------------------------
1335 static float estimate_path_freq( Node *n ) {
1336   // Try to extract some path frequency info
1337   IfNode *iff;
1338   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1339     uint nop = n->Opcode();
1340     if( nop == Op_SafePoint ) {   // Skip any safepoint
1341       n = n->in(0);
1342       continue;
1343     }
1344     if( nop == Op_CatchProj ) {   // Get count from a prior call
1345       // Assume call does not always throw exceptions: means the call-site
1346       // count is also the frequency of the fall-through path.
1347       assert( n->is_CatchProj(), "" );
1348       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1349         return 0.0f;            // Assume call exception path is rare
1350       Node *call = n->in(0)->in(0)->in(0);
1351       assert( call->is_Call(), "expect a call here" );
1352       const JVMState *jvms = ((CallNode*)call)->jvms();
1353       ciMethodData* methodData = jvms->method()->method_data();
1354       if (!methodData->is_mature())  return 0.0f; // No call-site data
1355       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1356       if ((data == NULL) || !data->is_CounterData()) {
1357         // no call profile available, try call's control input
1358         n = n->in(0);
1359         continue;
1360       }
1361       return data->as_CounterData()->count()/FreqCountInvocations;
1362     }
1363     // See if there's a gating IF test
1364     Node *n_c = n->in(0);
1365     if( !n_c->is_If() ) break;       // No estimate available
1366     iff = n_c->as_If();
1367     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1368       // Compute how much count comes on this path
1369       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1370     // Have no count info.  Skip dull uncommon-trap like branches.
1371     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1372         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1373       break;
1374     // Skip through never-taken branch; look for a real loop exit.
1375     n = iff->in(0);
1376   }
1377   return 0.0f;                  // No estimate available
1378 }
1379 
1380 //------------------------------merge_many_backedges---------------------------
1381 // Merge all the backedges from the shared header into a private Region.
1382 // Feed that region as the one backedge to this loop.
1383 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1384   uint i;
1385 
1386   // Scan for the top 2 hottest backedges
1387   float hotcnt = 0.0f;
1388   float warmcnt = 0.0f;
1389   uint hot_idx = 0;
1390   // Loop starts at 2 because slot 1 is the fall-in path
1391   for( i = 2; i < _head->req(); i++ ) {
1392     float cnt = estimate_path_freq(_head->in(i));
1393     if( cnt > hotcnt ) {       // Grab hottest path
1394       warmcnt = hotcnt;
1395       hotcnt = cnt;
1396       hot_idx = i;
1397     } else if( cnt > warmcnt ) { // And 2nd hottest path
1398       warmcnt = cnt;
1399     }
1400   }
1401 
1402   // See if the hottest backedge is worthy of being an inner loop
1403   // by being much hotter than the next hottest backedge.
1404   if( hotcnt <= 0.0001 ||
1405       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1406 
1407   // Peel out the backedges into a private merge point; peel
1408   // them all except optionally hot_idx.
1409   PhaseIterGVN &igvn = phase->_igvn;
1410 
1411   Node *hot_tail = NULL;
1412   // Make a Region for the merge point
1413   Node *r = new RegionNode(1);
1414   for( i = 2; i < _head->req(); i++ ) {
1415     if( i != hot_idx )
1416       r->add_req( _head->in(i) );
1417     else hot_tail = _head->in(i);
1418   }
1419   igvn.register_new_node_with_optimizer(r, _head);
1420   // Plug region into end of loop _head, followed by hot_tail
1421   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1422   igvn.replace_input_of(_head, 2, r);
1423   if( hot_idx ) _head->add_req(hot_tail);
1424 
1425   // Split all the Phis up between '_head' loop and the Region 'r'
1426   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1427     Node *out = _head->fast_out(j);
1428     if( out->is_Phi() ) {
1429       PhiNode* n = out->as_Phi();
1430       igvn.hash_delete(n);      // Delete from hash before hacking edges
1431       Node *hot_phi = NULL;
1432       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1433       // Check all inputs for the ones to peel out
1434       uint j = 1;
1435       for( uint i = 2; i < n->req(); i++ ) {
1436         if( i != hot_idx )
1437           phi->set_req( j++, n->in(i) );
1438         else hot_phi = n->in(i);
1439       }
1440       // Register the phi but do not transform until whole place transforms
1441       igvn.register_new_node_with_optimizer(phi, n);
1442       // Add the merge phi to the old Phi
1443       while( n->req() > 3 ) n->del_req( n->req()-1 );
1444       igvn.replace_input_of(n, 2, phi);
1445       if( hot_idx ) n->add_req(hot_phi);
1446     }
1447   }
1448 
1449 
1450   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
1451   // of self loop tree.  Turn self into a loop headed by _head and with
1452   // tail being the new merge point.
1453   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
1454   phase->set_loop(_tail,ilt);   // Adjust tail
1455   _tail = r;                    // Self's tail is new merge point
1456   phase->set_loop(r,this);
1457   ilt->_child = _child;         // New guy has my children
1458   _child = ilt;                 // Self has new guy as only child
1459   ilt->_parent = this;          // new guy has self for parent
1460   ilt->_nest = _nest;           // Same nesting depth (for now)
1461 
1462   // Starting with 'ilt', look for child loop trees using the same shared
1463   // header.  Flatten these out; they will no longer be loops in the end.
1464   IdealLoopTree **pilt = &_child;
1465   while( ilt ) {
1466     if( ilt->_head == _head ) {
1467       uint i;
1468       for( i = 2; i < _head->req(); i++ )
1469         if( _head->in(i) == ilt->_tail )
1470           break;                // Still a loop
1471       if( i == _head->req() ) { // No longer a loop
1472         // Flatten ilt.  Hang ilt's "_next" list from the end of
1473         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
1474         IdealLoopTree **cp = &ilt->_child;
1475         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
1476         *cp = ilt->_next;       // Hang next list at end of child list
1477         *pilt = ilt->_child;    // Move child up to replace ilt
1478         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
1479         ilt = ilt->_child;      // Repeat using new ilt
1480         continue;               // do not advance over ilt->_child
1481       }
1482       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
1483       phase->set_loop(_head,ilt);
1484     }
1485     pilt = &ilt->_child;        // Advance to next
1486     ilt = *pilt;
1487   }
1488 
1489   if( _child ) fix_parent( _child, this );
1490 }
1491 
1492 //------------------------------beautify_loops---------------------------------
1493 // Split shared headers and insert loop landing pads.
1494 // Insert a LoopNode to replace the RegionNode.
1495 // Return TRUE if loop tree is structurally changed.
1496 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
1497   bool result = false;
1498   // Cache parts in locals for easy
1499   PhaseIterGVN &igvn = phase->_igvn;
1500 
1501   igvn.hash_delete(_head);      // Yank from hash before hacking edges
1502 
1503   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
1504   int fall_in_cnt = 0;
1505   for( uint i = 1; i < _head->req(); i++ )
1506     if( !phase->is_member( this, _head->in(i) ) )
1507       fall_in_cnt++;
1508   assert( fall_in_cnt, "at least 1 fall-in path" );
1509   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
1510     split_fall_in( phase, fall_in_cnt );
1511 
1512   // Swap inputs to the _head and all Phis to move the fall-in edge to
1513   // the left.
1514   fall_in_cnt = 1;
1515   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
1516     fall_in_cnt++;
1517   if( fall_in_cnt > 1 ) {
1518     // Since I am just swapping inputs I do not need to update def-use info
1519     Node *tmp = _head->in(1);
1520     igvn.rehash_node_delayed(_head);
1521     _head->set_req( 1, _head->in(fall_in_cnt) );
1522     _head->set_req( fall_in_cnt, tmp );
1523     // Swap also all Phis
1524     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
1525       Node* phi = _head->fast_out(i);
1526       if( phi->is_Phi() ) {
1527         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
1528         tmp = phi->in(1);
1529         phi->set_req( 1, phi->in(fall_in_cnt) );
1530         phi->set_req( fall_in_cnt, tmp );
1531       }
1532     }
1533   }
1534   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
1535   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
1536 
1537   // If I am a shared header (multiple backedges), peel off the many
1538   // backedges into a private merge point and use the merge point as
1539   // the one true backedge.
1540   if( _head->req() > 3 ) {
1541     // Merge the many backedges into a single backedge but leave
1542     // the hottest backedge as separate edge for the following peel.
1543     merge_many_backedges( phase );
1544     result = true;
1545   }
1546 
1547   // If I have one hot backedge, peel off myself loop.
1548   // I better be the outermost loop.
1549   if (_head->req() > 3 && !_irreducible) {
1550     split_outer_loop( phase );
1551     result = true;
1552 
1553   } else if (!_head->is_Loop() && !_irreducible) {
1554     // Make a new LoopNode to replace the old loop head
1555     Node *l = new LoopNode( _head->in(1), _head->in(2) );
1556     l = igvn.register_new_node_with_optimizer(l, _head);
1557     phase->set_created_loop_node();
1558     // Go ahead and replace _head
1559     phase->_igvn.replace_node( _head, l );
1560     _head = l;
1561     phase->set_loop(_head, this);
1562   }
1563 
1564   // Now recursively beautify nested loops
1565   if( _child ) result |= _child->beautify_loops( phase );
1566   if( _next  ) result |= _next ->beautify_loops( phase );
1567   return result;
1568 }
1569 
1570 //------------------------------allpaths_check_safepts----------------------------
1571 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
1572 // encountered.  Helper for check_safepts.
1573 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
1574   assert(stack.size() == 0, "empty stack");
1575   stack.push(_tail);
1576   visited.Clear();
1577   visited.set(_tail->_idx);
1578   while (stack.size() > 0) {
1579     Node* n = stack.pop();
1580     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1581       // Terminate this path
1582     } else if (n->Opcode() == Op_SafePoint) {
1583       if (_phase->get_loop(n) != this) {
1584         if (_required_safept == NULL) _required_safept = new Node_List();
1585         _required_safept->push(n);  // save the one closest to the tail
1586       }
1587       // Terminate this path
1588     } else {
1589       uint start = n->is_Region() ? 1 : 0;
1590       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
1591       for (uint i = start; i < end; i++) {
1592         Node* in = n->in(i);
1593         assert(in->is_CFG(), "must be");
1594         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
1595           stack.push(in);
1596         }
1597       }
1598     }
1599   }
1600 }
1601 
1602 //------------------------------check_safepts----------------------------
1603 // Given dominators, try to find loops with calls that must always be
1604 // executed (call dominates loop tail).  These loops do not need non-call
1605 // safepoints (ncsfpt).
1606 //
1607 // A complication is that a safepoint in a inner loop may be needed
1608 // by an outer loop. In the following, the inner loop sees it has a
1609 // call (block 3) on every path from the head (block 2) to the
1610 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
1611 // in block 2, _but_ this leaves the outer loop without a safepoint.
1612 //
1613 //          entry  0
1614 //                 |
1615 //                 v
1616 // outer 1,2    +->1
1617 //              |  |
1618 //              |  v
1619 //              |  2<---+  ncsfpt in 2
1620 //              |_/|\   |
1621 //                 | v  |
1622 // inner 2,3      /  3  |  call in 3
1623 //               /   |  |
1624 //              v    +--+
1625 //        exit  4
1626 //
1627 //
1628 // This method creates a list (_required_safept) of ncsfpt nodes that must
1629 // be protected is created for each loop. When a ncsfpt maybe deleted, it
1630 // is first looked for in the lists for the outer loops of the current loop.
1631 //
1632 // The insights into the problem:
1633 //  A) counted loops are okay
1634 //  B) innermost loops are okay (only an inner loop can delete
1635 //     a ncsfpt needed by an outer loop)
1636 //  C) a loop is immune from an inner loop deleting a safepoint
1637 //     if the loop has a call on the idom-path
1638 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
1639 //     idom-path that is not in a nested loop
1640 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
1641 //     loop needs to be prevented from deletion by an inner loop
1642 //
1643 // There are two analyses:
1644 //  1) The first, and cheaper one, scans the loop body from
1645 //     tail to head following the idom (immediate dominator)
1646 //     chain, looking for the cases (C,D,E) above.
1647 //     Since inner loops are scanned before outer loops, there is summary
1648 //     information about inner loops.  Inner loops can be skipped over
1649 //     when the tail of an inner loop is encountered.
1650 //
1651 //  2) The second, invoked if the first fails to find a call or ncsfpt on
1652 //     the idom path (which is rare), scans all predecessor control paths
1653 //     from the tail to the head, terminating a path when a call or sfpt
1654 //     is encountered, to find the ncsfpt's that are closest to the tail.
1655 //
1656 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
1657   // Bottom up traversal
1658   IdealLoopTree* ch = _child;
1659   if (_child) _child->check_safepts(visited, stack);
1660   if (_next)  _next ->check_safepts(visited, stack);
1661 
1662   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
1663     bool  has_call         = false; // call on dom-path
1664     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
1665     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
1666     // Scan the dom-path nodes from tail to head
1667     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
1668       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1669         has_call = true;
1670         _has_sfpt = 1;          // Then no need for a safept!
1671         break;
1672       } else if (n->Opcode() == Op_SafePoint) {
1673         if (_phase->get_loop(n) == this) {
1674           has_local_ncsfpt = true;
1675           break;
1676         }
1677         if (nonlocal_ncsfpt == NULL) {
1678           nonlocal_ncsfpt = n; // save the one closest to the tail
1679         }
1680       } else {
1681         IdealLoopTree* nlpt = _phase->get_loop(n);
1682         if (this != nlpt) {
1683           // If at an inner loop tail, see if the inner loop has already
1684           // recorded seeing a call on the dom-path (and stop.)  If not,
1685           // jump to the head of the inner loop.
1686           assert(is_member(nlpt), "nested loop");
1687           Node* tail = nlpt->_tail;
1688           if (tail->in(0)->is_If()) tail = tail->in(0);
1689           if (n == tail) {
1690             // If inner loop has call on dom-path, so does outer loop
1691             if (nlpt->_has_sfpt) {
1692               has_call = true;
1693               _has_sfpt = 1;
1694               break;
1695             }
1696             // Skip to head of inner loop
1697             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
1698             n = nlpt->_head;
1699           }
1700         }
1701       }
1702     }
1703     // Record safept's that this loop needs preserved when an
1704     // inner loop attempts to delete it's safepoints.
1705     if (_child != NULL && !has_call && !has_local_ncsfpt) {
1706       if (nonlocal_ncsfpt != NULL) {
1707         if (_required_safept == NULL) _required_safept = new Node_List();
1708         _required_safept->push(nonlocal_ncsfpt);
1709       } else {
1710         // Failed to find a suitable safept on the dom-path.  Now use
1711         // an all paths walk from tail to head, looking for safepoints to preserve.
1712         allpaths_check_safepts(visited, stack);
1713       }
1714     }
1715   }
1716 }
1717 
1718 //---------------------------is_deleteable_safept----------------------------
1719 // Is safept not required by an outer loop?
1720 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
1721   assert(sfpt->Opcode() == Op_SafePoint, "");
1722   IdealLoopTree* lp = get_loop(sfpt)->_parent;
1723   while (lp != NULL) {
1724     Node_List* sfpts = lp->_required_safept;
1725     if (sfpts != NULL) {
1726       for (uint i = 0; i < sfpts->size(); i++) {
1727         if (sfpt == sfpts->at(i))
1728           return false;
1729       }
1730     }
1731     lp = lp->_parent;
1732   }
1733   return true;
1734 }
1735 
1736 //---------------------------replace_parallel_iv-------------------------------
1737 // Replace parallel induction variable (parallel to trip counter)
1738 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
1739   assert(loop->_head->is_CountedLoop(), "");
1740   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1741   if (!cl->is_valid_counted_loop())
1742     return;         // skip malformed counted loop
1743   Node *incr = cl->incr();
1744   if (incr == NULL)
1745     return;         // Dead loop?
1746   Node *init = cl->init_trip();
1747   Node *phi  = cl->phi();
1748   int stride_con = cl->stride_con();
1749 
1750   // Visit all children, looking for Phis
1751   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
1752     Node *out = cl->out(i);
1753     // Look for other phis (secondary IVs). Skip dead ones
1754     if (!out->is_Phi() || out == phi || !has_node(out))
1755       continue;
1756     PhiNode* phi2 = out->as_Phi();
1757     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
1758     // Look for induction variables of the form:  X += constant
1759     if (phi2->region() != loop->_head ||
1760         incr2->req() != 3 ||
1761         incr2->in(1) != phi2 ||
1762         incr2 == incr ||
1763         incr2->Opcode() != Op_AddI ||
1764         !incr2->in(2)->is_Con())
1765       continue;
1766 
1767     // Check for parallel induction variable (parallel to trip counter)
1768     // via an affine function.  In particular, count-down loops with
1769     // count-up array indices are common. We only RCE references off
1770     // the trip-counter, so we need to convert all these to trip-counter
1771     // expressions.
1772     Node *init2 = phi2->in( LoopNode::EntryControl );
1773     int stride_con2 = incr2->in(2)->get_int();
1774 
1775     // The general case here gets a little tricky.  We want to find the
1776     // GCD of all possible parallel IV's and make a new IV using this
1777     // GCD for the loop.  Then all possible IVs are simple multiples of
1778     // the GCD.  In practice, this will cover very few extra loops.
1779     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
1780     // where +/-1 is the common case, but other integer multiples are
1781     // also easy to handle.
1782     int ratio_con = stride_con2/stride_con;
1783 
1784     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
1785 #ifndef PRODUCT
1786       if (TraceLoopOpts) {
1787         tty->print("Parallel IV: %d ", phi2->_idx);
1788         loop->dump_head();
1789       }
1790 #endif
1791       // Convert to using the trip counter.  The parallel induction
1792       // variable differs from the trip counter by a loop-invariant
1793       // amount, the difference between their respective initial values.
1794       // It is scaled by the 'ratio_con'.
1795       Node* ratio = _igvn.intcon(ratio_con);
1796       set_ctrl(ratio, C->root());
1797       Node* ratio_init = new MulINode(init, ratio);
1798       _igvn.register_new_node_with_optimizer(ratio_init, init);
1799       set_early_ctrl(ratio_init);
1800       Node* diff = new SubINode(init2, ratio_init);
1801       _igvn.register_new_node_with_optimizer(diff, init2);
1802       set_early_ctrl(diff);
1803       Node* ratio_idx = new MulINode(phi, ratio);
1804       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
1805       set_ctrl(ratio_idx, cl);
1806       Node* add = new AddINode(ratio_idx, diff);
1807       _igvn.register_new_node_with_optimizer(add);
1808       set_ctrl(add, cl);
1809       _igvn.replace_node( phi2, add );
1810       // Sometimes an induction variable is unused
1811       if (add->outcnt() == 0) {
1812         _igvn.remove_dead_node(add);
1813       }
1814       --i; // deleted this phi; rescan starting with next position
1815       continue;
1816     }
1817   }
1818 }
1819 
1820 void IdealLoopTree::remove_safepoints(PhaseIdealLoop* phase, bool keep_one) {
1821   Node* keep = NULL;
1822   if (keep_one) {
1823     // Look for a safepoint on the idom-path.
1824     for (Node* i = tail(); i != _head; i = phase->idom(i)) {
1825       if (i->Opcode() == Op_SafePoint && phase->get_loop(i) == this) {
1826         keep = i;
1827         break; // Found one
1828       }
1829     }
1830   }
1831 
1832   // Don't remove any safepoints if it is requested to keep a single safepoint and
1833   // no safepoint was found on idom-path. It is not safe to remove any safepoint
1834   // in this case since there's no safepoint dominating all paths in the loop body.
1835   bool prune = !keep_one || keep != NULL;
1836 
1837   // Delete other safepoints in this loop.
1838   Node_List* sfpts = _safepts;
1839   if (prune && sfpts != NULL) {
1840     assert(keep == NULL || keep->Opcode() == Op_SafePoint, "not safepoint");
1841     for (uint i = 0; i < sfpts->size(); i++) {
1842       Node* n = sfpts->at(i);
1843       assert(phase->get_loop(n) == this, "");
1844       if (n != keep && phase->is_deleteable_safept(n)) {
1845         phase->lazy_replace(n, n->in(TypeFunc::Control));
1846       }
1847     }
1848   }
1849 }
1850 
1851 //------------------------------counted_loop-----------------------------------
1852 // Convert to counted loops where possible
1853 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
1854 
1855   // For grins, set the inner-loop flag here
1856   if (!_child) {
1857     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
1858   }
1859 
1860   if (_head->is_CountedLoop() ||
1861       phase->is_counted_loop(_head, this)) {
1862 
1863     if (!UseCountedLoopSafepoints) {
1864       // Indicate we do not need a safepoint here
1865       _has_sfpt = 1;
1866     }
1867 
1868     // Remove safepoints
1869     bool keep_one_sfpt = !(_has_call || _has_sfpt);
1870     remove_safepoints(phase, keep_one_sfpt);
1871 
1872     // Look for induction variables
1873     phase->replace_parallel_iv(this);
1874 
1875   } else if (_parent != NULL && !_irreducible) {
1876     // Not a counted loop. Keep one safepoint.
1877     bool keep_one_sfpt = true;
1878     remove_safepoints(phase, keep_one_sfpt);
1879   }
1880 
1881   // Recursively
1882   if (_child) _child->counted_loop( phase );
1883   if (_next)  _next ->counted_loop( phase );
1884 }
1885 
1886 #ifndef PRODUCT
1887 //------------------------------dump_head--------------------------------------
1888 // Dump 1 liner for loop header info
1889 void IdealLoopTree::dump_head( ) const {
1890   for (uint i=0; i<_nest; i++)
1891     tty->print("  ");
1892   tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
1893   if (_irreducible) tty->print(" IRREDUCIBLE");
1894   Node* entry = _head->in(LoopNode::EntryControl);
1895   if (LoopLimitCheck) {
1896     Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1897     if (predicate != NULL ) {
1898       tty->print(" limit_check");
1899       entry = entry->in(0)->in(0);
1900     }
1901   }
1902   if (UseLoopPredicate) {
1903     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1904     if (entry != NULL) {
1905       tty->print(" predicated");
1906     }
1907   }
1908   if (_head->is_CountedLoop()) {
1909     CountedLoopNode *cl = _head->as_CountedLoop();
1910     tty->print(" counted");
1911 
1912     Node* init_n = cl->init_trip();
1913     if (init_n  != NULL &&  init_n->is_Con())
1914       tty->print(" [%d,", cl->init_trip()->get_int());
1915     else
1916       tty->print(" [int,");
1917     Node* limit_n = cl->limit();
1918     if (limit_n  != NULL &&  limit_n->is_Con())
1919       tty->print("%d),", cl->limit()->get_int());
1920     else
1921       tty->print("int),");
1922     int stride_con  = cl->stride_con();
1923     if (stride_con > 0) tty->print("+");
1924     tty->print("%d", stride_con);
1925 
1926     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
1927 
1928     if (cl->is_pre_loop ()) tty->print(" pre" );
1929     if (cl->is_main_loop()) tty->print(" main");
1930     if (cl->is_post_loop()) tty->print(" post");
1931   }
1932   if (_has_call) tty->print(" has_call");
1933   if (_has_sfpt) tty->print(" has_sfpt");
1934   if (_rce_candidate) tty->print(" rce");
1935   if (_safepts != NULL && _safepts->size() > 0) {
1936     tty->print(" sfpts={"); _safepts->dump_simple(); tty->print(" }");
1937   }
1938   if (_required_safept != NULL && _required_safept->size() > 0) {
1939     tty->print(" req={"); _required_safept->dump_simple(); tty->print(" }");
1940   }
1941   tty->cr();
1942 }
1943 
1944 //------------------------------dump-------------------------------------------
1945 // Dump loops by loop tree
1946 void IdealLoopTree::dump( ) const {
1947   dump_head();
1948   if (_child) _child->dump();
1949   if (_next)  _next ->dump();
1950 }
1951 
1952 #endif
1953 
1954 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
1955   if (loop == root) {
1956     if (loop->_child != NULL) {
1957       log->begin_head("loop_tree");
1958       log->end_head();
1959       if( loop->_child ) log_loop_tree(root, loop->_child, log);
1960       log->tail("loop_tree");
1961       assert(loop->_next == NULL, "what?");
1962     }
1963   } else {
1964     Node* head = loop->_head;
1965     log->begin_head("loop");
1966     log->print(" idx='%d' ", head->_idx);
1967     if (loop->_irreducible) log->print("irreducible='1' ");
1968     if (head->is_Loop()) {
1969       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
1970       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
1971     }
1972     if (head->is_CountedLoop()) {
1973       CountedLoopNode* cl = head->as_CountedLoop();
1974       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
1975       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
1976       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
1977     }
1978     log->end_head();
1979     if( loop->_child ) log_loop_tree(root, loop->_child, log);
1980     log->tail("loop");
1981     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
1982   }
1983 }
1984 
1985 //---------------------collect_potentially_useful_predicates-----------------------
1986 // Helper function to collect potentially useful predicates to prevent them from
1987 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
1988 void PhaseIdealLoop::collect_potentially_useful_predicates(
1989                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
1990   if (loop->_child) { // child
1991     collect_potentially_useful_predicates(loop->_child, useful_predicates);
1992   }
1993 
1994   // self (only loops that we can apply loop predication may use their predicates)
1995   if (loop->_head->is_Loop() &&
1996       !loop->_irreducible    &&
1997       !loop->tail()->is_top()) {
1998     LoopNode* lpn = loop->_head->as_Loop();
1999     Node* entry = lpn->in(LoopNode::EntryControl);
2000     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
2001     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
2002       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
2003       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2004       entry = entry->in(0)->in(0);
2005     }
2006     predicate_proj = find_predicate(entry); // Predicate
2007     if (predicate_proj != NULL ) {
2008       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
2009     }
2010   }
2011 
2012   if (loop->_next) { // sibling
2013     collect_potentially_useful_predicates(loop->_next, useful_predicates);
2014   }
2015 }
2016 
2017 //------------------------eliminate_useless_predicates-----------------------------
2018 // Eliminate all inserted predicates if they could not be used by loop predication.
2019 // Note: it will also eliminates loop limits check predicate since it also uses
2020 // Opaque1 node (see Parse::add_predicate()).
2021 void PhaseIdealLoop::eliminate_useless_predicates() {
2022   if (C->predicate_count() == 0)
2023     return; // no predicate left
2024 
2025   Unique_Node_List useful_predicates; // to store useful predicates
2026   if (C->has_loops()) {
2027     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
2028   }
2029 
2030   for (int i = C->predicate_count(); i > 0; i--) {
2031      Node * n = C->predicate_opaque1_node(i-1);
2032      assert(n->Opcode() == Op_Opaque1, "must be");
2033      if (!useful_predicates.member(n)) { // not in the useful list
2034        _igvn.replace_node(n, n->in(1));
2035      }
2036   }
2037 }
2038 
2039 //------------------------process_expensive_nodes-----------------------------
2040 // Expensive nodes have their control input set to prevent the GVN
2041 // from commoning them and as a result forcing the resulting node to
2042 // be in a more frequent path. Use CFG information here, to change the
2043 // control inputs so that some expensive nodes can be commoned while
2044 // not executed more frequently.
2045 bool PhaseIdealLoop::process_expensive_nodes() {
2046   assert(OptimizeExpensiveOps, "optimization off?");
2047 
2048   // Sort nodes to bring similar nodes together
2049   C->sort_expensive_nodes();
2050 
2051   bool progress = false;
2052 
2053   for (int i = 0; i < C->expensive_count(); ) {
2054     Node* n = C->expensive_node(i);
2055     int start = i;
2056     // Find nodes similar to n
2057     i++;
2058     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2059     int end = i;
2060     // And compare them two by two
2061     for (int j = start; j < end; j++) {
2062       Node* n1 = C->expensive_node(j);
2063       if (is_node_unreachable(n1)) {
2064         continue;
2065       }
2066       for (int k = j+1; k < end; k++) {
2067         Node* n2 = C->expensive_node(k);
2068         if (is_node_unreachable(n2)) {
2069           continue;
2070         }
2071 
2072         assert(n1 != n2, "should be pair of nodes");
2073 
2074         Node* c1 = n1->in(0);
2075         Node* c2 = n2->in(0);
2076 
2077         Node* parent_c1 = c1;
2078         Node* parent_c2 = c2;
2079 
2080         // The call to get_early_ctrl_for_expensive() moves the
2081         // expensive nodes up but stops at loops that are in a if
2082         // branch. See whether we can exit the loop and move above the
2083         // If.
2084         if (c1->is_Loop()) {
2085           parent_c1 = c1->in(1);
2086         }
2087         if (c2->is_Loop()) {
2088           parent_c2 = c2->in(1);
2089         }
2090 
2091         if (parent_c1 == parent_c2) {
2092           _igvn._worklist.push(n1);
2093           _igvn._worklist.push(n2);
2094           continue;
2095         }
2096 
2097         // Look for identical expensive node up the dominator chain.
2098         if (is_dominator(c1, c2)) {
2099           c2 = c1;
2100         } else if (is_dominator(c2, c1)) {
2101           c1 = c2;
2102         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2103                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2104           // Both branches have the same expensive node so move it up
2105           // before the if.
2106           c1 = c2 = idom(parent_c1->in(0));
2107         }
2108         // Do the actual moves
2109         if (n1->in(0) != c1) {
2110           _igvn.hash_delete(n1);
2111           n1->set_req(0, c1);
2112           _igvn.hash_insert(n1);
2113           _igvn._worklist.push(n1);
2114           progress = true;
2115         }
2116         if (n2->in(0) != c2) {
2117           _igvn.hash_delete(n2);
2118           n2->set_req(0, c2);
2119           _igvn.hash_insert(n2);
2120           _igvn._worklist.push(n2);
2121           progress = true;
2122         }
2123       }
2124     }
2125   }
2126 
2127   return progress;
2128 }
2129 
2130 
2131 //=============================================================================
2132 //----------------------------build_and_optimize-------------------------------
2133 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2134 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2135 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool skip_loop_opts) {
2136   ResourceMark rm;
2137 
2138   int old_progress = C->major_progress();
2139   uint orig_worklist_size = _igvn._worklist.size();
2140 
2141   // Reset major-progress flag for the driver's heuristics
2142   C->clear_major_progress();
2143 
2144 #ifndef PRODUCT
2145   // Capture for later assert
2146   uint unique = C->unique();
2147   _loop_invokes++;
2148   _loop_work += unique;
2149 #endif
2150 
2151   // True if the method has at least 1 irreducible loop
2152   _has_irreducible_loops = false;
2153 
2154   _created_loop_node = false;
2155 
2156   Arena *a = Thread::current()->resource_area();
2157   VectorSet visited(a);
2158   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2159   _nodes.map(C->unique(), NULL);
2160   memset(_nodes.adr(), 0, wordSize * C->unique());
2161 
2162   // Pre-build the top-level outermost loop tree entry
2163   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2164   // Do not need a safepoint at the top level
2165   _ltree_root->_has_sfpt = 1;
2166 
2167   // Initialize Dominators.
2168   // Checked in clone_loop_predicate() during beautify_loops().
2169   _idom_size = 0;
2170   _idom      = NULL;
2171   _dom_depth = NULL;
2172   _dom_stk   = NULL;
2173 
2174   // Empty pre-order array
2175   allocate_preorders();
2176 
2177   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2178   // IdealLoopTree entries.  Data nodes are NOT walked.
2179   build_loop_tree();
2180   // Check for bailout, and return
2181   if (C->failing()) {
2182     return;
2183   }
2184 
2185   // No loops after all
2186   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2187 
2188   // There should always be an outer loop containing the Root and Return nodes.
2189   // If not, we have a degenerate empty program.  Bail out in this case.
2190   if (!has_node(C->root())) {
2191     if (!_verify_only) {
2192       C->clear_major_progress();
2193       C->record_method_not_compilable("empty program detected during loop optimization");
2194     }
2195     return;
2196   }
2197 
2198   // Nothing to do, so get out
2199   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only;
2200   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2201   if (stop_early && !do_expensive_nodes) {
2202     _igvn.optimize();           // Cleanup NeverBranches
2203     return;
2204   }
2205 
2206   // Set loop nesting depth
2207   _ltree_root->set_nest( 0 );
2208 
2209   // Split shared headers and insert loop landing pads.
2210   // Do not bother doing this on the Root loop of course.
2211   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2212     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2213     if( _ltree_root->_child->beautify_loops( this ) ) {
2214       // Re-build loop tree!
2215       _ltree_root->_child = NULL;
2216       _nodes.clear();
2217       reallocate_preorders();
2218       build_loop_tree();
2219       // Check for bailout, and return
2220       if (C->failing()) {
2221         return;
2222       }
2223       // Reset loop nesting depth
2224       _ltree_root->set_nest( 0 );
2225 
2226       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2227     }
2228   }
2229 
2230   // Build Dominators for elision of NULL checks & loop finding.
2231   // Since nodes do not have a slot for immediate dominator, make
2232   // a persistent side array for that info indexed on node->_idx.
2233   _idom_size = C->unique();
2234   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2235   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2236   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2237   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2238 
2239   Dominators();
2240 
2241   if (!_verify_only) {
2242     // As a side effect, Dominators removed any unreachable CFG paths
2243     // into RegionNodes.  It doesn't do this test against Root, so
2244     // we do it here.
2245     for( uint i = 1; i < C->root()->req(); i++ ) {
2246       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2247         _igvn.delete_input_of(C->root(), i);
2248         i--;                      // Rerun same iteration on compressed edges
2249       }
2250     }
2251 
2252     // Given dominators, try to find inner loops with calls that must
2253     // always be executed (call dominates loop tail).  These loops do
2254     // not need a separate safepoint.
2255     Node_List cisstack(a);
2256     _ltree_root->check_safepts(visited, cisstack);
2257   }
2258 
2259   // Walk the DATA nodes and place into loops.  Find earliest control
2260   // node.  For CFG nodes, the _nodes array starts out and remains
2261   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2262   // _nodes array holds the earliest legal controlling CFG node.
2263 
2264   // Allocate stack with enough space to avoid frequent realloc
2265   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2266   Node_Stack nstack( a, stack_size );
2267 
2268   visited.Clear();
2269   Node_List worklist(a);
2270   // Don't need C->root() on worklist since
2271   // it will be processed among C->top() inputs
2272   worklist.push( C->top() );
2273   visited.set( C->top()->_idx ); // Set C->top() as visited now
2274   build_loop_early( visited, worklist, nstack );
2275 
2276   // Given early legal placement, try finding counted loops.  This placement
2277   // is good enough to discover most loop invariants.
2278   if( !_verify_me && !_verify_only )
2279     _ltree_root->counted_loop( this );
2280 
2281   // Find latest loop placement.  Find ideal loop placement.
2282   visited.Clear();
2283   init_dom_lca_tags();
2284   // Need C->root() on worklist when processing outs
2285   worklist.push( C->root() );
2286   NOT_PRODUCT( C->verify_graph_edges(); )
2287   worklist.push( C->top() );
2288   build_loop_late( visited, worklist, nstack );
2289 
2290   if (_verify_only) {
2291     // restore major progress flag
2292     for (int i = 0; i < old_progress; i++)
2293       C->set_major_progress();
2294     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2295     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2296     return;
2297   }
2298 
2299   // clear out the dead code after build_loop_late
2300   while (_deadlist.size()) {
2301     _igvn.remove_globally_dead_node(_deadlist.pop());
2302   }
2303 
2304   if (stop_early) {
2305     assert(do_expensive_nodes, "why are we here?");
2306     if (process_expensive_nodes()) {
2307       // If we made some progress when processing expensive nodes then
2308       // the IGVN may modify the graph in a way that will allow us to
2309       // make some more progress: we need to try processing expensive
2310       // nodes again.
2311       C->set_major_progress();
2312     }
2313     _igvn.optimize();
2314     return;
2315   }
2316 
2317   // Some parser-inserted loop predicates could never be used by loop
2318   // predication or they were moved away from loop during some optimizations.
2319   // For example, peeling. Eliminate them before next loop optimizations.
2320   if (UseLoopPredicate || LoopLimitCheck) {
2321     eliminate_useless_predicates();
2322   }
2323 
2324 #ifndef PRODUCT
2325   C->verify_graph_edges();
2326   if (_verify_me) {             // Nested verify pass?
2327     // Check to see if the verify mode is broken
2328     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2329     return;
2330   }
2331   if(VerifyLoopOptimizations) verify();
2332   if(TraceLoopOpts && C->has_loops()) {
2333     _ltree_root->dump();
2334   }
2335 #endif
2336 
2337   if (skip_loop_opts) {
2338     // restore major progress flag
2339     for (int i = 0; i < old_progress; i++) {
2340       C->set_major_progress();
2341     }
2342 
2343     // Cleanup any modified bits
2344     _igvn.optimize();
2345 
2346     if (C->log() != NULL) {
2347       log_loop_tree(_ltree_root, _ltree_root, C->log());
2348     }
2349     return;
2350   }
2351 
2352   if (ReassociateInvariants) {
2353     // Reassociate invariants and prep for split_thru_phi
2354     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2355       IdealLoopTree* lpt = iter.current();
2356       bool is_counted = lpt->is_counted();
2357       if (!is_counted || !lpt->is_inner()) continue;
2358 
2359       // check for vectorized loops, any reassociation of invariants was already done
2360       if (is_counted && lpt->_head->as_CountedLoop()->do_unroll_only()) continue;
2361 
2362       lpt->reassociate_invariants(this);
2363 
2364       // Because RCE opportunities can be masked by split_thru_phi,
2365       // look for RCE candidates and inhibit split_thru_phi
2366       // on just their loop-phi's for this pass of loop opts
2367       if (SplitIfBlocks && do_split_ifs) {
2368         if (lpt->policy_range_check(this)) {
2369           lpt->_rce_candidate = 1; // = true
2370         }
2371       }
2372     }
2373   }
2374 
2375   // Check for aggressive application of split-if and other transforms
2376   // that require basic-block info (like cloning through Phi's)
2377   if( SplitIfBlocks && do_split_ifs ) {
2378     visited.Clear();
2379     split_if_with_blocks( visited, nstack );
2380     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2381   }
2382 
2383   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
2384     C->set_major_progress();
2385   }
2386 
2387   // Perform loop predication before iteration splitting
2388   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2389     _ltree_root->_child->loop_predication(this);
2390   }
2391 
2392   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2393     if (do_intrinsify_fill()) {
2394       C->set_major_progress();
2395     }
2396   }
2397 
2398   // Perform iteration-splitting on inner loops.  Split iterations to avoid
2399   // range checks or one-shot null checks.
2400 
2401   // If split-if's didn't hack the graph too bad (no CFG changes)
2402   // then do loop opts.
2403   if (C->has_loops() && !C->major_progress()) {
2404     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
2405     _ltree_root->_child->iteration_split( this, worklist );
2406     // No verify after peeling!  GCM has hoisted code out of the loop.
2407     // After peeling, the hoisted code could sink inside the peeled area.
2408     // The peeling code does not try to recompute the best location for
2409     // all the code before the peeled area, so the verify pass will always
2410     // complain about it.
2411   }
2412   // Do verify graph edges in any case
2413   NOT_PRODUCT( C->verify_graph_edges(); );
2414 
2415   if (!do_split_ifs) {
2416     // We saw major progress in Split-If to get here.  We forced a
2417     // pass with unrolling and not split-if, however more split-if's
2418     // might make progress.  If the unrolling didn't make progress
2419     // then the major-progress flag got cleared and we won't try
2420     // another round of Split-If.  In particular the ever-common
2421     // instance-of/check-cast pattern requires at least 2 rounds of
2422     // Split-If to clear out.
2423     C->set_major_progress();
2424   }
2425 
2426   // Repeat loop optimizations if new loops were seen
2427   if (created_loop_node()) {
2428     C->set_major_progress();
2429   }
2430 
2431   // Keep loop predicates and perform optimizations with them
2432   // until no more loop optimizations could be done.
2433   // After that switch predicates off and do more loop optimizations.
2434   if (!C->major_progress() && (C->predicate_count() > 0)) {
2435      C->cleanup_loop_predicates(_igvn);
2436      if (TraceLoopOpts) {
2437        tty->print_cr("PredicatesOff");
2438      }
2439      C->set_major_progress();
2440   }
2441 
2442   // Convert scalar to superword operations at the end of all loop opts.
2443   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
2444     // SuperWord transform
2445     SuperWord sw(this);
2446     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2447       IdealLoopTree* lpt = iter.current();
2448       if (lpt->is_counted()) {
2449         sw.transform_loop(lpt, true);
2450       }
2451     }
2452   }
2453 
2454   // Cleanup any modified bits
2455   _igvn.optimize();
2456 
2457   // disable assert until issue with split_flow_path is resolved (6742111)
2458   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
2459   //        "shouldn't introduce irreducible loops");
2460 
2461   if (C->log() != NULL) {
2462     log_loop_tree(_ltree_root, _ltree_root, C->log());
2463   }
2464 }
2465 
2466 #ifndef PRODUCT
2467 //------------------------------print_statistics-------------------------------
2468 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
2469 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
2470 void PhaseIdealLoop::print_statistics() {
2471   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
2472 }
2473 
2474 //------------------------------verify-----------------------------------------
2475 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
2476 static int fail;                // debug only, so its multi-thread dont care
2477 void PhaseIdealLoop::verify() const {
2478   int old_progress = C->major_progress();
2479   ResourceMark rm;
2480   PhaseIdealLoop loop_verify( _igvn, this );
2481   VectorSet visited(Thread::current()->resource_area());
2482 
2483   fail = 0;
2484   verify_compare( C->root(), &loop_verify, visited );
2485   assert( fail == 0, "verify loops failed" );
2486   // Verify loop structure is the same
2487   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
2488   // Reset major-progress.  It was cleared by creating a verify version of
2489   // PhaseIdealLoop.
2490   for( int i=0; i<old_progress; i++ )
2491     C->set_major_progress();
2492 }
2493 
2494 //------------------------------verify_compare---------------------------------
2495 // Make sure me and the given PhaseIdealLoop agree on key data structures
2496 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
2497   if( !n ) return;
2498   if( visited.test_set( n->_idx ) ) return;
2499   if( !_nodes[n->_idx] ) {      // Unreachable
2500     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
2501     return;
2502   }
2503 
2504   uint i;
2505   for( i = 0; i < n->req(); i++ )
2506     verify_compare( n->in(i), loop_verify, visited );
2507 
2508   // Check the '_nodes' block/loop structure
2509   i = n->_idx;
2510   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
2511     if( _nodes[i] != loop_verify->_nodes[i] &&
2512         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
2513       tty->print("Mismatched control setting for: ");
2514       n->dump();
2515       if( fail++ > 10 ) return;
2516       Node *c = get_ctrl_no_update(n);
2517       tty->print("We have it as: ");
2518       if( c->in(0) ) c->dump();
2519         else tty->print_cr("N%d",c->_idx);
2520       tty->print("Verify thinks: ");
2521       if( loop_verify->has_ctrl(n) )
2522         loop_verify->get_ctrl_no_update(n)->dump();
2523       else
2524         loop_verify->get_loop_idx(n)->dump();
2525       tty->cr();
2526     }
2527   } else {                    // We have a loop
2528     IdealLoopTree *us = get_loop_idx(n);
2529     if( loop_verify->has_ctrl(n) ) {
2530       tty->print("Mismatched loop setting for: ");
2531       n->dump();
2532       if( fail++ > 10 ) return;
2533       tty->print("We have it as: ");
2534       us->dump();
2535       tty->print("Verify thinks: ");
2536       loop_verify->get_ctrl_no_update(n)->dump();
2537       tty->cr();
2538     } else if (!C->major_progress()) {
2539       // Loop selection can be messed up if we did a major progress
2540       // operation, like split-if.  Do not verify in that case.
2541       IdealLoopTree *them = loop_verify->get_loop_idx(n);
2542       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
2543         tty->print("Unequals loops for: ");
2544         n->dump();
2545         if( fail++ > 10 ) return;
2546         tty->print("We have it as: ");
2547         us->dump();
2548         tty->print("Verify thinks: ");
2549         them->dump();
2550         tty->cr();
2551       }
2552     }
2553   }
2554 
2555   // Check for immediate dominators being equal
2556   if( i >= _idom_size ) {
2557     if( !n->is_CFG() ) return;
2558     tty->print("CFG Node with no idom: ");
2559     n->dump();
2560     return;
2561   }
2562   if( !n->is_CFG() ) return;
2563   if( n == C->root() ) return; // No IDOM here
2564 
2565   assert(n->_idx == i, "sanity");
2566   Node *id = idom_no_update(n);
2567   if( id != loop_verify->idom_no_update(n) ) {
2568     tty->print("Unequals idoms for: ");
2569     n->dump();
2570     if( fail++ > 10 ) return;
2571     tty->print("We have it as: ");
2572     id->dump();
2573     tty->print("Verify thinks: ");
2574     loop_verify->idom_no_update(n)->dump();
2575     tty->cr();
2576   }
2577 
2578 }
2579 
2580 //------------------------------verify_tree------------------------------------
2581 // Verify that tree structures match.  Because the CFG can change, siblings
2582 // within the loop tree can be reordered.  We attempt to deal with that by
2583 // reordering the verify's loop tree if possible.
2584 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
2585   assert( _parent == parent, "Badly formed loop tree" );
2586 
2587   // Siblings not in same order?  Attempt to re-order.
2588   if( _head != loop->_head ) {
2589     // Find _next pointer to update
2590     IdealLoopTree **pp = &loop->_parent->_child;
2591     while( *pp != loop )
2592       pp = &((*pp)->_next);
2593     // Find proper sibling to be next
2594     IdealLoopTree **nn = &loop->_next;
2595     while( (*nn) && (*nn)->_head != _head )
2596       nn = &((*nn)->_next);
2597 
2598     // Check for no match.
2599     if( !(*nn) ) {
2600       // Annoyingly, irreducible loops can pick different headers
2601       // after a major_progress operation, so the rest of the loop
2602       // tree cannot be matched.
2603       if (_irreducible && Compile::current()->major_progress())  return;
2604       assert( 0, "failed to match loop tree" );
2605     }
2606 
2607     // Move (*nn) to (*pp)
2608     IdealLoopTree *hit = *nn;
2609     *nn = hit->_next;
2610     hit->_next = loop;
2611     *pp = loop;
2612     loop = hit;
2613     // Now try again to verify
2614   }
2615 
2616   assert( _head  == loop->_head , "mismatched loop head" );
2617   Node *tail = _tail;           // Inline a non-updating version of
2618   while( !tail->in(0) )         // the 'tail()' call.
2619     tail = tail->in(1);
2620   assert( tail == loop->_tail, "mismatched loop tail" );
2621 
2622   // Counted loops that are guarded should be able to find their guards
2623   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
2624     CountedLoopNode *cl = _head->as_CountedLoop();
2625     Node *init = cl->init_trip();
2626     Node *ctrl = cl->in(LoopNode::EntryControl);
2627     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
2628     Node *iff  = ctrl->in(0);
2629     assert( iff->Opcode() == Op_If, "" );
2630     Node *bol  = iff->in(1);
2631     assert( bol->Opcode() == Op_Bool, "" );
2632     Node *cmp  = bol->in(1);
2633     assert( cmp->Opcode() == Op_CmpI, "" );
2634     Node *add  = cmp->in(1);
2635     Node *opaq;
2636     if( add->Opcode() == Op_Opaque1 ) {
2637       opaq = add;
2638     } else {
2639       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
2640       assert( add == init, "" );
2641       opaq = cmp->in(2);
2642     }
2643     assert( opaq->Opcode() == Op_Opaque1, "" );
2644 
2645   }
2646 
2647   if (_child != NULL)  _child->verify_tree(loop->_child, this);
2648   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
2649   // Innermost loops need to verify loop bodies,
2650   // but only if no 'major_progress'
2651   int fail = 0;
2652   if (!Compile::current()->major_progress() && _child == NULL) {
2653     for( uint i = 0; i < _body.size(); i++ ) {
2654       Node *n = _body.at(i);
2655       if (n->outcnt() == 0)  continue; // Ignore dead
2656       uint j;
2657       for( j = 0; j < loop->_body.size(); j++ )
2658         if( loop->_body.at(j) == n )
2659           break;
2660       if( j == loop->_body.size() ) { // Not found in loop body
2661         // Last ditch effort to avoid assertion: Its possible that we
2662         // have some users (so outcnt not zero) but are still dead.
2663         // Try to find from root.
2664         if (Compile::current()->root()->find(n->_idx)) {
2665           fail++;
2666           tty->print("We have that verify does not: ");
2667           n->dump();
2668         }
2669       }
2670     }
2671     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
2672       Node *n = loop->_body.at(i2);
2673       if (n->outcnt() == 0)  continue; // Ignore dead
2674       uint j;
2675       for( j = 0; j < _body.size(); j++ )
2676         if( _body.at(j) == n )
2677           break;
2678       if( j == _body.size() ) { // Not found in loop body
2679         // Last ditch effort to avoid assertion: Its possible that we
2680         // have some users (so outcnt not zero) but are still dead.
2681         // Try to find from root.
2682         if (Compile::current()->root()->find(n->_idx)) {
2683           fail++;
2684           tty->print("Verify has that we do not: ");
2685           n->dump();
2686         }
2687       }
2688     }
2689     assert( !fail, "loop body mismatch" );
2690   }
2691 }
2692 
2693 #endif
2694 
2695 //------------------------------set_idom---------------------------------------
2696 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
2697   uint idx = d->_idx;
2698   if (idx >= _idom_size) {
2699     uint newsize = _idom_size<<1;
2700     while( idx >= newsize ) {
2701       newsize <<= 1;
2702     }
2703     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
2704     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
2705     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
2706     _idom_size = newsize;
2707   }
2708   _idom[idx] = n;
2709   _dom_depth[idx] = dom_depth;
2710 }
2711 
2712 //------------------------------recompute_dom_depth---------------------------------------
2713 // The dominator tree is constructed with only parent pointers.
2714 // This recomputes the depth in the tree by first tagging all
2715 // nodes as "no depth yet" marker.  The next pass then runs up
2716 // the dom tree from each node marked "no depth yet", and computes
2717 // the depth on the way back down.
2718 void PhaseIdealLoop::recompute_dom_depth() {
2719   uint no_depth_marker = C->unique();
2720   uint i;
2721   // Initialize depth to "no depth yet"
2722   for (i = 0; i < _idom_size; i++) {
2723     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
2724      _dom_depth[i] = no_depth_marker;
2725     }
2726   }
2727   if (_dom_stk == NULL) {
2728     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
2729     if (init_size < 10) init_size = 10;
2730     _dom_stk = new GrowableArray<uint>(init_size);
2731   }
2732   // Compute new depth for each node.
2733   for (i = 0; i < _idom_size; i++) {
2734     uint j = i;
2735     // Run up the dom tree to find a node with a depth
2736     while (_dom_depth[j] == no_depth_marker) {
2737       _dom_stk->push(j);
2738       j = _idom[j]->_idx;
2739     }
2740     // Compute the depth on the way back down this tree branch
2741     uint dd = _dom_depth[j] + 1;
2742     while (_dom_stk->length() > 0) {
2743       uint j = _dom_stk->pop();
2744       _dom_depth[j] = dd;
2745       dd++;
2746     }
2747   }
2748 }
2749 
2750 //------------------------------sort-------------------------------------------
2751 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
2752 // loop tree, not the root.
2753 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
2754   if( !innermost ) return loop; // New innermost loop
2755 
2756   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
2757   assert( loop_preorder, "not yet post-walked loop" );
2758   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
2759   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
2760 
2761   // Insert at start of list
2762   while( l ) {                  // Insertion sort based on pre-order
2763     if( l == loop ) return innermost; // Already on list!
2764     int l_preorder = get_preorder(l->_head); // Cache pre-order number
2765     assert( l_preorder, "not yet post-walked l" );
2766     // Check header pre-order number to figure proper nesting
2767     if( loop_preorder > l_preorder )
2768       break;                    // End of insertion
2769     // If headers tie (e.g., shared headers) check tail pre-order numbers.
2770     // Since I split shared headers, you'd think this could not happen.
2771     // BUT: I must first do the preorder numbering before I can discover I
2772     // have shared headers, so the split headers all get the same preorder
2773     // number as the RegionNode they split from.
2774     if( loop_preorder == l_preorder &&
2775         get_preorder(loop->_tail) < get_preorder(l->_tail) )
2776       break;                    // Also check for shared headers (same pre#)
2777     pp = &l->_parent;           // Chain up list
2778     l = *pp;
2779   }
2780   // Link into list
2781   // Point predecessor to me
2782   *pp = loop;
2783   // Point me to successor
2784   IdealLoopTree *p = loop->_parent;
2785   loop->_parent = l;            // Point me to successor
2786   if( p ) sort( p, innermost ); // Insert my parents into list as well
2787   return innermost;
2788 }
2789 
2790 //------------------------------build_loop_tree--------------------------------
2791 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
2792 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
2793 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
2794 // tightest enclosing IdealLoopTree for post-walked.
2795 //
2796 // During my forward walk I do a short 1-layer lookahead to see if I can find
2797 // a loop backedge with that doesn't have any work on the backedge.  This
2798 // helps me construct nested loops with shared headers better.
2799 //
2800 // Once I've done the forward recursion, I do the post-work.  For each child
2801 // I check to see if there is a backedge.  Backedges define a loop!  I
2802 // insert an IdealLoopTree at the target of the backedge.
2803 //
2804 // During the post-work I also check to see if I have several children
2805 // belonging to different loops.  If so, then this Node is a decision point
2806 // where control flow can choose to change loop nests.  It is at this
2807 // decision point where I can figure out how loops are nested.  At this
2808 // time I can properly order the different loop nests from my children.
2809 // Note that there may not be any backedges at the decision point!
2810 //
2811 // Since the decision point can be far removed from the backedges, I can't
2812 // order my loops at the time I discover them.  Thus at the decision point
2813 // I need to inspect loop header pre-order numbers to properly nest my
2814 // loops.  This means I need to sort my childrens' loops by pre-order.
2815 // The sort is of size number-of-control-children, which generally limits
2816 // it to size 2 (i.e., I just choose between my 2 target loops).
2817 void PhaseIdealLoop::build_loop_tree() {
2818   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
2819   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
2820   Node *n = C->root();
2821   bltstack.push(n);
2822   int pre_order = 1;
2823   int stack_size;
2824 
2825   while ( ( stack_size = bltstack.length() ) != 0 ) {
2826     n = bltstack.top(); // Leave node on stack
2827     if ( !is_visited(n) ) {
2828       // ---- Pre-pass Work ----
2829       // Pre-walked but not post-walked nodes need a pre_order number.
2830 
2831       set_preorder_visited( n, pre_order ); // set as visited
2832 
2833       // ---- Scan over children ----
2834       // Scan first over control projections that lead to loop headers.
2835       // This helps us find inner-to-outer loops with shared headers better.
2836 
2837       // Scan children's children for loop headers.
2838       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
2839         Node* m = n->raw_out(i);       // Child
2840         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
2841           // Scan over children's children to find loop
2842           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2843             Node* l = m->fast_out(j);
2844             if( is_visited(l) &&       // Been visited?
2845                 !is_postvisited(l) &&  // But not post-visited
2846                 get_preorder(l) < pre_order ) { // And smaller pre-order
2847               // Found!  Scan the DFS down this path before doing other paths
2848               bltstack.push(m);
2849               break;
2850             }
2851           }
2852         }
2853       }
2854       pre_order++;
2855     }
2856     else if ( !is_postvisited(n) ) {
2857       // Note: build_loop_tree_impl() adds out edges on rare occasions,
2858       // such as com.sun.rsasign.am::a.
2859       // For non-recursive version, first, process current children.
2860       // On next iteration, check if additional children were added.
2861       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
2862         Node* u = n->raw_out(k);
2863         if ( u->is_CFG() && !is_visited(u) ) {
2864           bltstack.push(u);
2865         }
2866       }
2867       if ( bltstack.length() == stack_size ) {
2868         // There were no additional children, post visit node now
2869         (void)bltstack.pop(); // Remove node from stack
2870         pre_order = build_loop_tree_impl( n, pre_order );
2871         // Check for bailout
2872         if (C->failing()) {
2873           return;
2874         }
2875         // Check to grow _preorders[] array for the case when
2876         // build_loop_tree_impl() adds new nodes.
2877         check_grow_preorders();
2878       }
2879     }
2880     else {
2881       (void)bltstack.pop(); // Remove post-visited node from stack
2882     }
2883   }
2884 }
2885 
2886 //------------------------------build_loop_tree_impl---------------------------
2887 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
2888   // ---- Post-pass Work ----
2889   // Pre-walked but not post-walked nodes need a pre_order number.
2890 
2891   // Tightest enclosing loop for this Node
2892   IdealLoopTree *innermost = NULL;
2893 
2894   // For all children, see if any edge is a backedge.  If so, make a loop
2895   // for it.  Then find the tightest enclosing loop for the self Node.
2896   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2897     Node* m = n->fast_out(i);   // Child
2898     if( n == m ) continue;      // Ignore control self-cycles
2899     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
2900 
2901     IdealLoopTree *l;           // Child's loop
2902     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
2903       // Found a backedge
2904       assert( get_preorder(m) < pre_order, "should be backedge" );
2905       // Check for the RootNode, which is already a LoopNode and is allowed
2906       // to have multiple "backedges".
2907       if( m == C->root()) {     // Found the root?
2908         l = _ltree_root;        // Root is the outermost LoopNode
2909       } else {                  // Else found a nested loop
2910         // Insert a LoopNode to mark this loop.
2911         l = new IdealLoopTree(this, m, n);
2912       } // End of Else found a nested loop
2913       if( !has_loop(m) )        // If 'm' does not already have a loop set
2914         set_loop(m, l);         // Set loop header to loop now
2915 
2916     } else {                    // Else not a nested loop
2917       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
2918       l = get_loop(m);          // Get previously determined loop
2919       // If successor is header of a loop (nest), move up-loop till it
2920       // is a member of some outer enclosing loop.  Since there are no
2921       // shared headers (I've split them already) I only need to go up
2922       // at most 1 level.
2923       while( l && l->_head == m ) // Successor heads loop?
2924         l = l->_parent;         // Move up 1 for me
2925       // If this loop is not properly parented, then this loop
2926       // has no exit path out, i.e. its an infinite loop.
2927       if( !l ) {
2928         // Make loop "reachable" from root so the CFG is reachable.  Basically
2929         // insert a bogus loop exit that is never taken.  'm', the loop head,
2930         // points to 'n', one (of possibly many) fall-in paths.  There may be
2931         // many backedges as well.
2932 
2933         // Here I set the loop to be the root loop.  I could have, after
2934         // inserting a bogus loop exit, restarted the recursion and found my
2935         // new loop exit.  This would make the infinite loop a first-class
2936         // loop and it would then get properly optimized.  What's the use of
2937         // optimizing an infinite loop?
2938         l = _ltree_root;        // Oops, found infinite loop
2939 
2940         if (!_verify_only) {
2941           // Insert the NeverBranch between 'm' and it's control user.
2942           NeverBranchNode *iff = new NeverBranchNode( m );
2943           _igvn.register_new_node_with_optimizer(iff);
2944           set_loop(iff, l);
2945           Node *if_t = new CProjNode( iff, 0 );
2946           _igvn.register_new_node_with_optimizer(if_t);
2947           set_loop(if_t, l);
2948 
2949           Node* cfg = NULL;       // Find the One True Control User of m
2950           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2951             Node* x = m->fast_out(j);
2952             if (x->is_CFG() && x != m && x != iff)
2953               { cfg = x; break; }
2954           }
2955           assert(cfg != NULL, "must find the control user of m");
2956           uint k = 0;             // Probably cfg->in(0)
2957           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
2958           cfg->set_req( k, if_t ); // Now point to NeverBranch
2959           _igvn._worklist.push(cfg);
2960 
2961           // Now create the never-taken loop exit
2962           Node *if_f = new CProjNode( iff, 1 );
2963           _igvn.register_new_node_with_optimizer(if_f);
2964           set_loop(if_f, l);
2965           // Find frame ptr for Halt.  Relies on the optimizer
2966           // V-N'ing.  Easier and quicker than searching through
2967           // the program structure.
2968           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
2969           _igvn.register_new_node_with_optimizer(frame);
2970           // Halt & Catch Fire
2971           Node *halt = new HaltNode( if_f, frame );
2972           _igvn.register_new_node_with_optimizer(halt);
2973           set_loop(halt, l);
2974           C->root()->add_req(halt);
2975         }
2976         set_loop(C->root(), _ltree_root);
2977       }
2978     }
2979     // Weeny check for irreducible.  This child was already visited (this
2980     // IS the post-work phase).  Is this child's loop header post-visited
2981     // as well?  If so, then I found another entry into the loop.
2982     if (!_verify_only) {
2983       while( is_postvisited(l->_head) ) {
2984         // found irreducible
2985         l->_irreducible = 1; // = true
2986         l = l->_parent;
2987         _has_irreducible_loops = true;
2988         // Check for bad CFG here to prevent crash, and bailout of compile
2989         if (l == NULL) {
2990           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
2991           return pre_order;
2992         }
2993       }
2994       C->set_has_irreducible_loop(_has_irreducible_loops);
2995     }
2996 
2997     // This Node might be a decision point for loops.  It is only if
2998     // it's children belong to several different loops.  The sort call
2999     // does a trivial amount of work if there is only 1 child or all
3000     // children belong to the same loop.  If however, the children
3001     // belong to different loops, the sort call will properly set the
3002     // _parent pointers to show how the loops nest.
3003     //
3004     // In any case, it returns the tightest enclosing loop.
3005     innermost = sort( l, innermost );
3006   }
3007 
3008   // Def-use info will have some dead stuff; dead stuff will have no
3009   // loop decided on.
3010 
3011   // Am I a loop header?  If so fix up my parent's child and next ptrs.
3012   if( innermost && innermost->_head == n ) {
3013     assert( get_loop(n) == innermost, "" );
3014     IdealLoopTree *p = innermost->_parent;
3015     IdealLoopTree *l = innermost;
3016     while( p && l->_head == n ) {
3017       l->_next = p->_child;     // Put self on parents 'next child'
3018       p->_child = l;            // Make self as first child of parent
3019       l = p;                    // Now walk up the parent chain
3020       p = l->_parent;
3021     }
3022   } else {
3023     // Note that it is possible for a LoopNode to reach here, if the
3024     // backedge has been made unreachable (hence the LoopNode no longer
3025     // denotes a Loop, and will eventually be removed).
3026 
3027     // Record tightest enclosing loop for self.  Mark as post-visited.
3028     set_loop(n, innermost);
3029     // Also record has_call flag early on
3030     if( innermost ) {
3031       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
3032         // Do not count uncommon calls
3033         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3034           Node *iff = n->in(0)->in(0);
3035           // No any calls for vectorized loops.
3036           if( UseSuperWord || !iff->is_If() ||
3037               (n->in(0)->Opcode() == Op_IfFalse &&
3038                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3039               (iff->as_If()->_prob >= 0.01) )
3040             innermost->_has_call = 1;
3041         }
3042       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3043         // Disable loop optimizations if the loop has a scalar replaceable
3044         // allocation. This disabling may cause a potential performance lost
3045         // if the allocation is not eliminated for some reason.
3046         innermost->_allow_optimizations = false;
3047         innermost->_has_call = 1; // = true
3048       } else if (n->Opcode() == Op_SafePoint) {
3049         // Record all safepoints in this loop.
3050         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3051         innermost->_safepts->push(n);
3052       }
3053     }
3054   }
3055 
3056   // Flag as post-visited now
3057   set_postvisited(n);
3058   return pre_order;
3059 }
3060 
3061 
3062 //------------------------------build_loop_early-------------------------------
3063 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3064 // First pass computes the earliest controlling node possible.  This is the
3065 // controlling input with the deepest dominating depth.
3066 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3067   while (worklist.size() != 0) {
3068     // Use local variables nstack_top_n & nstack_top_i to cache values
3069     // on nstack's top.
3070     Node *nstack_top_n = worklist.pop();
3071     uint  nstack_top_i = 0;
3072 //while_nstack_nonempty:
3073     while (true) {
3074       // Get parent node and next input's index from stack's top.
3075       Node  *n = nstack_top_n;
3076       uint   i = nstack_top_i;
3077       uint cnt = n->req(); // Count of inputs
3078       if (i == 0) {        // Pre-process the node.
3079         if( has_node(n) &&            // Have either loop or control already?
3080             !has_ctrl(n) ) {          // Have loop picked out already?
3081           // During "merge_many_backedges" we fold up several nested loops
3082           // into a single loop.  This makes the members of the original
3083           // loop bodies pointing to dead loops; they need to move up
3084           // to the new UNION'd larger loop.  I set the _head field of these
3085           // dead loops to NULL and the _parent field points to the owning
3086           // loop.  Shades of UNION-FIND algorithm.
3087           IdealLoopTree *ilt;
3088           while( !(ilt = get_loop(n))->_head ) {
3089             // Normally I would use a set_loop here.  But in this one special
3090             // case, it is legal (and expected) to change what loop a Node
3091             // belongs to.
3092             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3093           }
3094           // Remove safepoints ONLY if I've already seen I don't need one.
3095           // (the old code here would yank a 2nd safepoint after seeing a
3096           // first one, even though the 1st did not dominate in the loop body
3097           // and thus could be avoided indefinitely)
3098           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3099               is_deleteable_safept(n)) {
3100             Node *in = n->in(TypeFunc::Control);
3101             lazy_replace(n,in);       // Pull safepoint now
3102             if (ilt->_safepts != NULL) {
3103               ilt->_safepts->yank(n);
3104             }
3105             // Carry on with the recursion "as if" we are walking
3106             // only the control input
3107             if( !visited.test_set( in->_idx ) ) {
3108               worklist.push(in);      // Visit this guy later, using worklist
3109             }
3110             // Get next node from nstack:
3111             // - skip n's inputs processing by setting i > cnt;
3112             // - we also will not call set_early_ctrl(n) since
3113             //   has_node(n) == true (see the condition above).
3114             i = cnt + 1;
3115           }
3116         }
3117       } // if (i == 0)
3118 
3119       // Visit all inputs
3120       bool done = true;       // Assume all n's inputs will be processed
3121       while (i < cnt) {
3122         Node *in = n->in(i);
3123         ++i;
3124         if (in == NULL) continue;
3125         if (in->pinned() && !in->is_CFG())
3126           set_ctrl(in, in->in(0));
3127         int is_visited = visited.test_set( in->_idx );
3128         if (!has_node(in)) {  // No controlling input yet?
3129           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3130           assert( !is_visited, "visit only once" );
3131           nstack.push(n, i);  // Save parent node and next input's index.
3132           nstack_top_n = in;  // Process current input now.
3133           nstack_top_i = 0;
3134           done = false;       // Not all n's inputs processed.
3135           break; // continue while_nstack_nonempty;
3136         } else if (!is_visited) {
3137           // This guy has a location picked out for him, but has not yet
3138           // been visited.  Happens to all CFG nodes, for instance.
3139           // Visit him using the worklist instead of recursion, to break
3140           // cycles.  Since he has a location already we do not need to
3141           // find his location before proceeding with the current Node.
3142           worklist.push(in);  // Visit this guy later, using worklist
3143         }
3144       }
3145       if (done) {
3146         // All of n's inputs have been processed, complete post-processing.
3147 
3148         // Compute earliest point this Node can go.
3149         // CFG, Phi, pinned nodes already know their controlling input.
3150         if (!has_node(n)) {
3151           // Record earliest legal location
3152           set_early_ctrl( n );
3153         }
3154         if (nstack.is_empty()) {
3155           // Finished all nodes on stack.
3156           // Process next node on the worklist.
3157           break;
3158         }
3159         // Get saved parent node and next input's index.
3160         nstack_top_n = nstack.node();
3161         nstack_top_i = nstack.index();
3162         nstack.pop();
3163       }
3164     } // while (true)
3165   }
3166 }
3167 
3168 //------------------------------dom_lca_internal--------------------------------
3169 // Pair-wise LCA
3170 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3171   if( !n1 ) return n2;          // Handle NULL original LCA
3172   assert( n1->is_CFG(), "" );
3173   assert( n2->is_CFG(), "" );
3174   // find LCA of all uses
3175   uint d1 = dom_depth(n1);
3176   uint d2 = dom_depth(n2);
3177   while (n1 != n2) {
3178     if (d1 > d2) {
3179       n1 =      idom(n1);
3180       d1 = dom_depth(n1);
3181     } else if (d1 < d2) {
3182       n2 =      idom(n2);
3183       d2 = dom_depth(n2);
3184     } else {
3185       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3186       // of the tree might have the same depth.  These sections have
3187       // to be searched more carefully.
3188 
3189       // Scan up all the n1's with equal depth, looking for n2.
3190       Node *t1 = idom(n1);
3191       while (dom_depth(t1) == d1) {
3192         if (t1 == n2)  return n2;
3193         t1 = idom(t1);
3194       }
3195       // Scan up all the n2's with equal depth, looking for n1.
3196       Node *t2 = idom(n2);
3197       while (dom_depth(t2) == d2) {
3198         if (t2 == n1)  return n1;
3199         t2 = idom(t2);
3200       }
3201       // Move up to a new dominator-depth value as well as up the dom-tree.
3202       n1 = t1;
3203       n2 = t2;
3204       d1 = dom_depth(n1);
3205       d2 = dom_depth(n2);
3206     }
3207   }
3208   return n1;
3209 }
3210 
3211 //------------------------------compute_idom-----------------------------------
3212 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3213 // IDOMs are correct.
3214 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3215   assert( region->is_Region(), "" );
3216   Node *LCA = NULL;
3217   for( uint i = 1; i < region->req(); i++ ) {
3218     if( region->in(i) != C->top() )
3219       LCA = dom_lca( LCA, region->in(i) );
3220   }
3221   return LCA;
3222 }
3223 
3224 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3225   bool had_error = false;
3226 #ifdef ASSERT
3227   if (early != C->root()) {
3228     // Make sure that there's a dominance path from LCA to early
3229     Node* d = LCA;
3230     while (d != early) {
3231       if (d == C->root()) {
3232         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3233         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3234         had_error = true;
3235         break;
3236       }
3237       d = idom(d);
3238     }
3239   }
3240 #endif
3241   return had_error;
3242 }
3243 
3244 
3245 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3246   // Compute LCA over list of uses
3247   bool had_error = false;
3248   Node *LCA = NULL;
3249   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3250     Node* c = n->fast_out(i);
3251     if (_nodes[c->_idx] == NULL)
3252       continue;                 // Skip the occasional dead node
3253     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3254       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3255         if( c->in(j) == n ) {   // Found matching input?
3256           Node *use = c->in(0)->in(j);
3257           if (_verify_only && use->is_top()) continue;
3258           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3259           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3260         }
3261       }
3262     } else {
3263       // For CFG data-users, use is in the block just prior
3264       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3265       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3266       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3267     }
3268   }
3269   assert(!had_error, "bad dominance");
3270   return LCA;
3271 }
3272 
3273 //------------------------------get_late_ctrl----------------------------------
3274 // Compute latest legal control.
3275 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
3276   assert(early != NULL, "early control should not be NULL");
3277 
3278   Node* LCA = compute_lca_of_uses(n, early);
3279 #ifdef ASSERT
3280   if (LCA == C->root() && LCA != early) {
3281     // def doesn't dominate uses so print some useful debugging output
3282     compute_lca_of_uses(n, early, true);
3283   }
3284 #endif
3285 
3286   // if this is a load, check for anti-dependent stores
3287   // We use a conservative algorithm to identify potential interfering
3288   // instructions and for rescheduling the load.  The users of the memory
3289   // input of this load are examined.  Any use which is not a load and is
3290   // dominated by early is considered a potentially interfering store.
3291   // This can produce false positives.
3292   if (n->is_Load() && LCA != early) {
3293     Node_List worklist;
3294 
3295     Node *mem = n->in(MemNode::Memory);
3296     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3297       Node* s = mem->fast_out(i);
3298       worklist.push(s);
3299     }
3300     while(worklist.size() != 0 && LCA != early) {
3301       Node* s = worklist.pop();
3302       if (s->is_Load()) {
3303         continue;
3304       } else if (s->is_MergeMem()) {
3305         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3306           Node* s1 = s->fast_out(i);
3307           worklist.push(s1);
3308         }
3309       } else {
3310         Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3311         assert(sctrl != NULL || s->outcnt() == 0, "must have control");
3312         if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3313           LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3314         }
3315       }
3316     }
3317   }
3318 
3319   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
3320   return LCA;
3321 }
3322 
3323 // true if CFG node d dominates CFG node n
3324 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
3325   if (d == n)
3326     return true;
3327   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
3328   uint dd = dom_depth(d);
3329   while (dom_depth(n) >= dd) {
3330     if (n == d)
3331       return true;
3332     n = idom(n);
3333   }
3334   return false;
3335 }
3336 
3337 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
3338 // Pair-wise LCA with tags.
3339 // Tag each index with the node 'tag' currently being processed
3340 // before advancing up the dominator chain using idom().
3341 // Later calls that find a match to 'tag' know that this path has already
3342 // been considered in the current LCA (which is input 'n1' by convention).
3343 // Since get_late_ctrl() is only called once for each node, the tag array
3344 // does not need to be cleared between calls to get_late_ctrl().
3345 // Algorithm trades a larger constant factor for better asymptotic behavior
3346 //
3347 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
3348   uint d1 = dom_depth(n1);
3349   uint d2 = dom_depth(n2);
3350 
3351   do {
3352     if (d1 > d2) {
3353       // current lca is deeper than n2
3354       _dom_lca_tags.map(n1->_idx, tag);
3355       n1 =      idom(n1);
3356       d1 = dom_depth(n1);
3357     } else if (d1 < d2) {
3358       // n2 is deeper than current lca
3359       Node *memo = _dom_lca_tags[n2->_idx];
3360       if( memo == tag ) {
3361         return n1;    // Return the current LCA
3362       }
3363       _dom_lca_tags.map(n2->_idx, tag);
3364       n2 =      idom(n2);
3365       d2 = dom_depth(n2);
3366     } else {
3367       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3368       // of the tree might have the same depth.  These sections have
3369       // to be searched more carefully.
3370 
3371       // Scan up all the n1's with equal depth, looking for n2.
3372       _dom_lca_tags.map(n1->_idx, tag);
3373       Node *t1 = idom(n1);
3374       while (dom_depth(t1) == d1) {
3375         if (t1 == n2)  return n2;
3376         _dom_lca_tags.map(t1->_idx, tag);
3377         t1 = idom(t1);
3378       }
3379       // Scan up all the n2's with equal depth, looking for n1.
3380       _dom_lca_tags.map(n2->_idx, tag);
3381       Node *t2 = idom(n2);
3382       while (dom_depth(t2) == d2) {
3383         if (t2 == n1)  return n1;
3384         _dom_lca_tags.map(t2->_idx, tag);
3385         t2 = idom(t2);
3386       }
3387       // Move up to a new dominator-depth value as well as up the dom-tree.
3388       n1 = t1;
3389       n2 = t2;
3390       d1 = dom_depth(n1);
3391       d2 = dom_depth(n2);
3392     }
3393   } while (n1 != n2);
3394   return n1;
3395 }
3396 
3397 //------------------------------init_dom_lca_tags------------------------------
3398 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3399 // Intended use does not involve any growth for the array, so it could
3400 // be of fixed size.
3401 void PhaseIdealLoop::init_dom_lca_tags() {
3402   uint limit = C->unique() + 1;
3403   _dom_lca_tags.map( limit, NULL );
3404 #ifdef ASSERT
3405   for( uint i = 0; i < limit; ++i ) {
3406     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3407   }
3408 #endif // ASSERT
3409 }
3410 
3411 //------------------------------clear_dom_lca_tags------------------------------
3412 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3413 // Intended use does not involve any growth for the array, so it could
3414 // be of fixed size.
3415 void PhaseIdealLoop::clear_dom_lca_tags() {
3416   uint limit = C->unique() + 1;
3417   _dom_lca_tags.map( limit, NULL );
3418   _dom_lca_tags.clear();
3419 #ifdef ASSERT
3420   for( uint i = 0; i < limit; ++i ) {
3421     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3422   }
3423 #endif // ASSERT
3424 }
3425 
3426 //------------------------------build_loop_late--------------------------------
3427 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3428 // Second pass finds latest legal placement, and ideal loop placement.
3429 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3430   while (worklist.size() != 0) {
3431     Node *n = worklist.pop();
3432     // Only visit once
3433     if (visited.test_set(n->_idx)) continue;
3434     uint cnt = n->outcnt();
3435     uint   i = 0;
3436     while (true) {
3437       assert( _nodes[n->_idx], "no dead nodes" );
3438       // Visit all children
3439       if (i < cnt) {
3440         Node* use = n->raw_out(i);
3441         ++i;
3442         // Check for dead uses.  Aggressively prune such junk.  It might be
3443         // dead in the global sense, but still have local uses so I cannot
3444         // easily call 'remove_dead_node'.
3445         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
3446           // Due to cycles, we might not hit the same fixed point in the verify
3447           // pass as we do in the regular pass.  Instead, visit such phis as
3448           // simple uses of the loop head.
3449           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
3450             if( !visited.test(use->_idx) )
3451               worklist.push(use);
3452           } else if( !visited.test_set(use->_idx) ) {
3453             nstack.push(n, i); // Save parent and next use's index.
3454             n   = use;         // Process all children of current use.
3455             cnt = use->outcnt();
3456             i   = 0;
3457           }
3458         } else {
3459           // Do not visit around the backedge of loops via data edges.
3460           // push dead code onto a worklist
3461           _deadlist.push(use);
3462         }
3463       } else {
3464         // All of n's children have been processed, complete post-processing.
3465         build_loop_late_post(n);
3466         if (nstack.is_empty()) {
3467           // Finished all nodes on stack.
3468           // Process next node on the worklist.
3469           break;
3470         }
3471         // Get saved parent node and next use's index. Visit the rest of uses.
3472         n   = nstack.node();
3473         cnt = n->outcnt();
3474         i   = nstack.index();
3475         nstack.pop();
3476       }
3477     }
3478   }
3479 }
3480 
3481 //------------------------------build_loop_late_post---------------------------
3482 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3483 // Second pass finds latest legal placement, and ideal loop placement.
3484 void PhaseIdealLoop::build_loop_late_post( Node *n ) {
3485 
3486   if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
3487     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
3488   }
3489 
3490 #ifdef ASSERT
3491   if (_verify_only && !n->is_CFG()) {
3492     // Check def-use domination.
3493     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
3494   }
3495 #endif
3496 
3497   // CFG and pinned nodes already handled
3498   if( n->in(0) ) {
3499     if( n->in(0)->is_top() ) return; // Dead?
3500 
3501     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
3502     // _must_ be pinned (they have to observe their control edge of course).
3503     // Unlike Stores (which modify an unallocable resource, the memory
3504     // state), Mods/Loads can float around.  So free them up.
3505     bool pinned = true;
3506     switch( n->Opcode() ) {
3507     case Op_DivI:
3508     case Op_DivF:
3509     case Op_DivD:
3510     case Op_ModI:
3511     case Op_ModF:
3512     case Op_ModD:
3513     case Op_LoadB:              // Same with Loads; they can sink
3514     case Op_LoadUB:             // during loop optimizations.
3515     case Op_LoadUS:
3516     case Op_LoadD:
3517     case Op_LoadF:
3518     case Op_LoadI:
3519     case Op_LoadKlass:
3520     case Op_LoadNKlass:
3521     case Op_LoadL:
3522     case Op_LoadS:
3523     case Op_LoadP:
3524     case Op_LoadN:
3525     case Op_LoadRange:
3526     case Op_LoadD_unaligned:
3527     case Op_LoadL_unaligned:
3528     case Op_StrComp:            // Does a bunch of load-like effects
3529     case Op_StrEquals:
3530     case Op_StrIndexOf:
3531     case Op_StrIndexOfChar:
3532     case Op_AryEq:
3533     case Op_HasNegatives:
3534       pinned = false;
3535     }
3536     if( pinned ) {
3537       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
3538       if( !chosen_loop->_child )       // Inner loop?
3539         chosen_loop->_body.push(n); // Collect inner loops
3540       return;
3541     }
3542   } else {                      // No slot zero
3543     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
3544       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
3545       return;
3546     }
3547     assert(!n->is_CFG() || n->outcnt() == 0, "");
3548   }
3549 
3550   // Do I have a "safe range" I can select over?
3551   Node *early = get_ctrl(n);// Early location already computed
3552 
3553   // Compute latest point this Node can go
3554   Node *LCA = get_late_ctrl( n, early );
3555   // LCA is NULL due to uses being dead
3556   if( LCA == NULL ) {
3557 #ifdef ASSERT
3558     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
3559       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
3560     }
3561 #endif
3562     _nodes.map(n->_idx, 0);     // This node is useless
3563     _deadlist.push(n);
3564     return;
3565   }
3566   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
3567 
3568   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
3569   Node *least = legal;          // Best legal position so far
3570   while( early != legal ) {     // While not at earliest legal
3571 #ifdef ASSERT
3572     if (legal->is_Start() && !early->is_Root()) {
3573       // Bad graph. Print idom path and fail.
3574       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
3575       assert(false, "Bad graph detected in build_loop_late");
3576     }
3577 #endif
3578     // Find least loop nesting depth
3579     legal = idom(legal);        // Bump up the IDOM tree
3580     // Check for lower nesting depth
3581     if( get_loop(legal)->_nest < get_loop(least)->_nest )
3582       least = legal;
3583   }
3584   assert(early == legal || legal != C->root(), "bad dominance of inputs");
3585 
3586   // Try not to place code on a loop entry projection
3587   // which can inhibit range check elimination.
3588   if (least != early) {
3589     Node* ctrl_out = least->unique_ctrl_out();
3590     if (ctrl_out && ctrl_out->is_CountedLoop() &&
3591         least == ctrl_out->in(LoopNode::EntryControl)) {
3592       Node* least_dom = idom(least);
3593       if (get_loop(least_dom)->is_member(get_loop(least))) {
3594         least = least_dom;
3595       }
3596     }
3597   }
3598 
3599 #ifdef ASSERT
3600   // If verifying, verify that 'verify_me' has a legal location
3601   // and choose it as our location.
3602   if( _verify_me ) {
3603     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
3604     Node *legal = LCA;
3605     while( early != legal ) {   // While not at earliest legal
3606       if( legal == v_ctrl ) break;  // Check for prior good location
3607       legal = idom(legal)      ;// Bump up the IDOM tree
3608     }
3609     // Check for prior good location
3610     if( legal == v_ctrl ) least = legal; // Keep prior if found
3611   }
3612 #endif
3613 
3614   // Assign discovered "here or above" point
3615   least = find_non_split_ctrl(least);
3616   set_ctrl(n, least);
3617 
3618   // Collect inner loop bodies
3619   IdealLoopTree *chosen_loop = get_loop(least);
3620   if( !chosen_loop->_child )   // Inner loop?
3621     chosen_loop->_body.push(n);// Collect inner loops
3622 }
3623 
3624 #ifdef ASSERT
3625 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
3626   tty->print_cr("%s", msg);
3627   tty->print("n: "); n->dump();
3628   tty->print("early(n): "); early->dump();
3629   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
3630       n->in(0) != early && !n->in(0)->is_Root()) {
3631     tty->print("n->in(0): "); n->in(0)->dump();
3632   }
3633   for (uint i = 1; i < n->req(); i++) {
3634     Node* in1 = n->in(i);
3635     if (in1 != NULL && in1 != n && !in1->is_top()) {
3636       tty->print("n->in(%d): ", i); in1->dump();
3637       Node* in1_early = get_ctrl(in1);
3638       tty->print("early(n->in(%d)): ", i); in1_early->dump();
3639       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
3640           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
3641         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
3642       }
3643       for (uint j = 1; j < in1->req(); j++) {
3644         Node* in2 = in1->in(j);
3645         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
3646           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
3647           Node* in2_early = get_ctrl(in2);
3648           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
3649           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
3650               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
3651             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
3652           }
3653         }
3654       }
3655     }
3656   }
3657   tty->cr();
3658   tty->print("LCA(n): "); LCA->dump();
3659   for (uint i = 0; i < n->outcnt(); i++) {
3660     Node* u1 = n->raw_out(i);
3661     if (u1 == n)
3662       continue;
3663     tty->print("n->out(%d): ", i); u1->dump();
3664     if (u1->is_CFG()) {
3665       for (uint j = 0; j < u1->outcnt(); j++) {
3666         Node* u2 = u1->raw_out(j);
3667         if (u2 != u1 && u2 != n && u2->is_CFG()) {
3668           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3669         }
3670       }
3671     } else {
3672       Node* u1_later = get_ctrl(u1);
3673       tty->print("later(n->out(%d)): ", i); u1_later->dump();
3674       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
3675           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
3676         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
3677       }
3678       for (uint j = 0; j < u1->outcnt(); j++) {
3679         Node* u2 = u1->raw_out(j);
3680         if (u2 == n || u2 == u1)
3681           continue;
3682         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3683         if (!u2->is_CFG()) {
3684           Node* u2_later = get_ctrl(u2);
3685           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
3686           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
3687               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
3688             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
3689           }
3690         }
3691       }
3692     }
3693   }
3694   tty->cr();
3695   int ct = 0;
3696   Node *dbg_legal = LCA;
3697   while(!dbg_legal->is_Start() && ct < 100) {
3698     tty->print("idom[%d] ",ct); dbg_legal->dump();
3699     ct++;
3700     dbg_legal = idom(dbg_legal);
3701   }
3702   tty->cr();
3703 }
3704 #endif
3705 
3706 #ifndef PRODUCT
3707 //------------------------------dump-------------------------------------------
3708 void PhaseIdealLoop::dump( ) const {
3709   ResourceMark rm;
3710   Arena* arena = Thread::current()->resource_area();
3711   Node_Stack stack(arena, C->live_nodes() >> 2);
3712   Node_List rpo_list;
3713   VectorSet visited(arena);
3714   visited.set(C->top()->_idx);
3715   rpo( C->root(), stack, visited, rpo_list );
3716   // Dump root loop indexed by last element in PO order
3717   dump( _ltree_root, rpo_list.size(), rpo_list );
3718 }
3719 
3720 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
3721   loop->dump_head();
3722 
3723   // Now scan for CFG nodes in the same loop
3724   for( uint j=idx; j > 0;  j-- ) {
3725     Node *n = rpo_list[j-1];
3726     if( !_nodes[n->_idx] )      // Skip dead nodes
3727       continue;
3728     if( get_loop(n) != loop ) { // Wrong loop nest
3729       if( get_loop(n)->_head == n &&    // Found nested loop?
3730           get_loop(n)->_parent == loop )
3731         dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
3732       continue;
3733     }
3734 
3735     // Dump controlling node
3736     for( uint x = 0; x < loop->_nest; x++ )
3737       tty->print("  ");
3738     tty->print("C");
3739     if( n == C->root() ) {
3740       n->dump();
3741     } else {
3742       Node* cached_idom   = idom_no_update(n);
3743       Node *computed_idom = n->in(0);
3744       if( n->is_Region() ) {
3745         computed_idom = compute_idom(n);
3746         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
3747         // any MultiBranch ctrl node), so apply a similar transform to
3748         // the cached idom returned from idom_no_update.
3749         cached_idom = find_non_split_ctrl(cached_idom);
3750       }
3751       tty->print(" ID:%d",computed_idom->_idx);
3752       n->dump();
3753       if( cached_idom != computed_idom ) {
3754         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
3755                       computed_idom->_idx, cached_idom->_idx);
3756       }
3757     }
3758     // Dump nodes it controls
3759     for( uint k = 0; k < _nodes.Size(); k++ ) {
3760       // (k < C->unique() && get_ctrl(find(k)) == n)
3761       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
3762         Node *m = C->root()->find(k);
3763         if( m && m->outcnt() > 0 ) {
3764           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
3765             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
3766                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
3767           }
3768           for( uint j = 0; j < loop->_nest; j++ )
3769             tty->print("  ");
3770           tty->print(" ");
3771           m->dump();
3772         }
3773       }
3774     }
3775   }
3776 }
3777 
3778 // Collect a R-P-O for the whole CFG.
3779 // Result list is in post-order (scan backwards for RPO)
3780 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
3781   stk.push(start, 0);
3782   visited.set(start->_idx);
3783 
3784   while (stk.is_nonempty()) {
3785     Node* m   = stk.node();
3786     uint  idx = stk.index();
3787     if (idx < m->outcnt()) {
3788       stk.set_index(idx + 1);
3789       Node* n = m->raw_out(idx);
3790       if (n->is_CFG() && !visited.test_set(n->_idx)) {
3791         stk.push(n, 0);
3792       }
3793     } else {
3794       rpo_list.push(m);
3795       stk.pop();
3796     }
3797   }
3798 }
3799 #endif
3800 
3801 
3802 //=============================================================================
3803 //------------------------------LoopTreeIterator-----------------------------------
3804 
3805 // Advance to next loop tree using a preorder, left-to-right traversal.
3806 void LoopTreeIterator::next() {
3807   assert(!done(), "must not be done.");
3808   if (_curnt->_child != NULL) {
3809     _curnt = _curnt->_child;
3810   } else if (_curnt->_next != NULL) {
3811     _curnt = _curnt->_next;
3812   } else {
3813     while (_curnt != _root && _curnt->_next == NULL) {
3814       _curnt = _curnt->_parent;
3815     }
3816     if (_curnt == _root) {
3817       _curnt = NULL;
3818       assert(done(), "must be done.");
3819     } else {
3820       assert(_curnt->_next != NULL, "must be more to do");
3821       _curnt = _curnt->_next;
3822     }
3823   }
3824 }