rev 10955 : undo
rev 11689 : 8161147: jvm crashes when -XX:+UseCountedLoopSafepoints is enabled
Summary: With UseCountedLoopSafepoints on do not convert loops to counted loop if they have a safepoint on the backedge
Reviewed-by:

   1 /*
   2  * Copyright (c) 1998, 2016, 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 "memory/resourceArea.hpp"
  31 #include "opto/addnode.hpp"
  32 #include "opto/callnode.hpp"
  33 #include "opto/connode.hpp"
  34 #include "opto/convertnode.hpp"
  35 #include "opto/divnode.hpp"
  36 #include "opto/idealGraphPrinter.hpp"
  37 #include "opto/loopnode.hpp"
  38 #include "opto/mulnode.hpp"
  39 #include "opto/rootnode.hpp"
  40 #include "opto/superword.hpp"
  41 
  42 //=============================================================================
  43 //------------------------------is_loop_iv-------------------------------------
  44 // Determine if a node is Counted loop induction variable.
  45 // The method is declared in node.hpp.
  46 const Node* Node::is_loop_iv() const {
  47   if (this->is_Phi() && !this->as_Phi()->is_copy() &&
  48       this->as_Phi()->region()->is_CountedLoop() &&
  49       this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
  50     return this;
  51   } else {
  52     return NULL;
  53   }
  54 }
  55 
  56 //=============================================================================
  57 //------------------------------dump_spec--------------------------------------
  58 // Dump special per-node info
  59 #ifndef PRODUCT
  60 void LoopNode::dump_spec(outputStream *st) const {
  61   if (is_inner_loop()) st->print( "inner " );
  62   if (is_partial_peel_loop()) st->print( "partial_peel " );
  63   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  64 }
  65 #endif
  66 
  67 //------------------------------is_valid_counted_loop-------------------------
  68 bool LoopNode::is_valid_counted_loop() const {
  69   if (is_CountedLoop()) {
  70     CountedLoopNode*    l  = as_CountedLoop();
  71     CountedLoopEndNode* le = l->loopexit();
  72     if (le != NULL &&
  73         le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  74       Node* phi  = l->phi();
  75       Node* exit = le->proj_out(0 /* false */);
  76       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  77           phi != NULL && phi->is_Phi() &&
  78           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  79           le->loopnode() == l && le->stride_is_con()) {
  80         return true;
  81       }
  82     }
  83   }
  84   return false;
  85 }
  86 
  87 //------------------------------get_early_ctrl---------------------------------
  88 // Compute earliest legal control
  89 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  90   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  91   uint i;
  92   Node *early;
  93   if (n->in(0) && !n->is_expensive()) {
  94     early = n->in(0);
  95     if (!early->is_CFG()) // Might be a non-CFG multi-def
  96       early = get_ctrl(early);        // So treat input as a straight data input
  97     i = 1;
  98   } else {
  99     early = get_ctrl(n->in(1));
 100     i = 2;
 101   }
 102   uint e_d = dom_depth(early);
 103   assert( early, "" );
 104   for (; i < n->req(); i++) {
 105     Node *cin = get_ctrl(n->in(i));
 106     assert( cin, "" );
 107     // Keep deepest dominator depth
 108     uint c_d = dom_depth(cin);
 109     if (c_d > e_d) {           // Deeper guy?
 110       early = cin;              // Keep deepest found so far
 111       e_d = c_d;
 112     } else if (c_d == e_d &&    // Same depth?
 113                early != cin) { // If not equal, must use slower algorithm
 114       // If same depth but not equal, one _must_ dominate the other
 115       // and we want the deeper (i.e., dominated) guy.
 116       Node *n1 = early;
 117       Node *n2 = cin;
 118       while (1) {
 119         n1 = idom(n1);          // Walk up until break cycle
 120         n2 = idom(n2);
 121         if (n1 == cin ||        // Walked early up to cin
 122             dom_depth(n2) < c_d)
 123           break;                // early is deeper; keep him
 124         if (n2 == early ||      // Walked cin up to early
 125             dom_depth(n1) < c_d) {
 126           early = cin;          // cin is deeper; keep him
 127           break;
 128         }
 129       }
 130       e_d = dom_depth(early);   // Reset depth register cache
 131     }
 132   }
 133 
 134   // Return earliest legal location
 135   assert(early == find_non_split_ctrl(early), "unexpected early control");
 136 
 137   if (n->is_expensive() && !_verify_only && !_verify_me) {
 138     assert(n->in(0), "should have control input");
 139     early = get_early_ctrl_for_expensive(n, early);
 140   }
 141 
 142   return early;
 143 }
 144 
 145 //------------------------------get_early_ctrl_for_expensive---------------------------------
 146 // Move node up the dominator tree as high as legal while still beneficial
 147 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 148   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 149   assert(OptimizeExpensiveOps, "optimization off?");
 150 
 151   Node* ctl = n->in(0);
 152   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 153   uint min_dom_depth = dom_depth(earliest);
 154 #ifdef ASSERT
 155   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 156     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 157     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 158   }
 159 #endif
 160   if (dom_depth(ctl) < min_dom_depth) {
 161     return earliest;
 162   }
 163 
 164   while (1) {
 165     Node *next = ctl;
 166     // Moving the node out of a loop on the projection of a If
 167     // confuses loop predication. So once we hit a Loop in a If branch
 168     // that doesn't branch to an UNC, we stop. The code that process
 169     // expensive nodes will notice the loop and skip over it to try to
 170     // move the node further up.
 171     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 172       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 173         break;
 174       }
 175       next = idom(ctl->in(1)->in(0));
 176     } else if (ctl->is_Proj()) {
 177       // We only move it up along a projection if the projection is
 178       // the single control projection for its parent: same code path,
 179       // if it's a If with UNC or fallthrough of a call.
 180       Node* parent_ctl = ctl->in(0);
 181       if (parent_ctl == NULL) {
 182         break;
 183       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 184         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 185       } else if (parent_ctl->is_If()) {
 186         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 187           break;
 188         }
 189         assert(idom(ctl) == parent_ctl, "strange");
 190         next = idom(parent_ctl);
 191       } else if (ctl->is_CatchProj()) {
 192         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 193           break;
 194         }
 195         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 196         next = parent_ctl->in(0)->in(0)->in(0);
 197       } else {
 198         // Check if parent control has a single projection (this
 199         // control is the only possible successor of the parent
 200         // control). If so, we can try to move the node above the
 201         // parent control.
 202         int nb_ctl_proj = 0;
 203         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 204           Node *p = parent_ctl->fast_out(i);
 205           if (p->is_Proj() && p->is_CFG()) {
 206             nb_ctl_proj++;
 207             if (nb_ctl_proj > 1) {
 208               break;
 209             }
 210           }
 211         }
 212 
 213         if (nb_ctl_proj > 1) {
 214           break;
 215         }
 216         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
 217         assert(idom(ctl) == parent_ctl, "strange");
 218         next = idom(parent_ctl);
 219       }
 220     } else {
 221       next = idom(ctl);
 222     }
 223     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 224       break;
 225     }
 226     ctl = next;
 227   }
 228 
 229   if (ctl != n->in(0)) {
 230     _igvn.replace_input_of(n, 0, ctl);
 231     _igvn.hash_insert(n);
 232   }
 233 
 234   return ctl;
 235 }
 236 
 237 
 238 //------------------------------set_early_ctrl---------------------------------
 239 // Set earliest legal control
 240 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 241   Node *early = get_early_ctrl(n);
 242 
 243   // Record earliest legal location
 244   set_ctrl(n, early);
 245 }
 246 
 247 //------------------------------set_subtree_ctrl-------------------------------
 248 // set missing _ctrl entries on new nodes
 249 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 250   // Already set?  Get out.
 251   if( _nodes[n->_idx] ) return;
 252   // Recursively set _nodes array to indicate where the Node goes
 253   uint i;
 254   for( i = 0; i < n->req(); ++i ) {
 255     Node *m = n->in(i);
 256     if( m && m != C->root() )
 257       set_subtree_ctrl( m );
 258   }
 259 
 260   // Fixup self
 261   set_early_ctrl( n );
 262 }
 263 
 264 //------------------------------is_counted_loop--------------------------------
 265 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
 266   PhaseGVN *gvn = &_igvn;
 267 
 268   // Counted loop head must be a good RegionNode with only 3 not NULL
 269   // control input edges: Self, Entry, LoopBack.
 270   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 271     return false;
 272   }
 273   Node *init_control = x->in(LoopNode::EntryControl);
 274   Node *back_control = x->in(LoopNode::LoopBackControl);
 275   if (init_control == NULL || back_control == NULL)    // Partially dead
 276     return false;
 277   // Must also check for TOP when looking for a dead loop
 278   if (init_control->is_top() || back_control->is_top())
 279     return false;
 280 
 281   // Allow funny placement of Safepoint
 282   if (back_control->Opcode() == Op_SafePoint)







 283     back_control = back_control->in(TypeFunc::Control);

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