1 /*
   2  * Copyright (c) 1998, 2015, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciMethodData.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "libadt/vectset.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/callnode.hpp"
  32 #include "opto/connode.hpp"
  33 #include "opto/convertnode.hpp"
  34 #include "opto/divnode.hpp"
  35 #include "opto/idealGraphPrinter.hpp"
  36 #include "opto/loopnode.hpp"
  37 #include "opto/mulnode.hpp"
  38 #include "opto/rootnode.hpp"
  39 #include "opto/superword.hpp"
  40 
  41 //=============================================================================
  42 //------------------------------is_loop_iv-------------------------------------
  43 // Determine if a node is Counted loop induction variable.
  44 // The method is declared in node.hpp.
  45 const Node* Node::is_loop_iv() const {
  46   if (this->is_Phi() && !this->as_Phi()->is_copy() &&
  47       this->as_Phi()->region()->is_CountedLoop() &&
  48       this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
  49     return this;
  50   } else {
  51     return NULL;
  52   }
  53 }
  54 
  55 //=============================================================================
  56 //------------------------------dump_spec--------------------------------------
  57 // Dump special per-node info
  58 #ifndef PRODUCT
  59 void LoopNode::dump_spec(outputStream *st) const {
  60   if (is_inner_loop()) st->print( "inner " );
  61   if (is_partial_peel_loop()) st->print( "partial_peel " );
  62   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  63 }
  64 #endif
  65 
  66 //------------------------------is_valid_counted_loop-------------------------
  67 bool LoopNode::is_valid_counted_loop() const {
  68   if (is_CountedLoop()) {
  69     CountedLoopNode*    l  = as_CountedLoop();
  70     CountedLoopEndNode* le = l->loopexit();
  71     if (le != NULL &&
  72         le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  73       Node* phi  = l->phi();
  74       Node* exit = le->proj_out(0 /* false */);
  75       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  76           phi != NULL && phi->is_Phi() &&
  77           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  78           le->loopnode() == l && le->stride_is_con()) {
  79         return true;
  80       }
  81     }
  82   }
  83   return false;
  84 }
  85 
  86 //------------------------------get_early_ctrl---------------------------------
  87 // Compute earliest legal control
  88 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  89   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  90   uint i;
  91   Node *early;
  92   if (n->in(0) && !n->is_expensive()) {
  93     early = n->in(0);
  94     if (!early->is_CFG()) // Might be a non-CFG multi-def
  95       early = get_ctrl(early);        // So treat input as a straight data input
  96     i = 1;
  97   } else {
  98     early = get_ctrl(n->in(1));
  99     i = 2;
 100   }
 101   uint e_d = dom_depth(early);
 102   assert( early, "" );
 103   for (; i < n->req(); i++) {
 104     Node *cin = get_ctrl(n->in(i));
 105     assert( cin, "" );
 106     // Keep deepest dominator depth
 107     uint c_d = dom_depth(cin);
 108     if (c_d > e_d) {           // Deeper guy?
 109       early = cin;              // Keep deepest found so far
 110       e_d = c_d;
 111     } else if (c_d == e_d &&    // Same depth?
 112                early != cin) { // If not equal, must use slower algorithm
 113       // If same depth but not equal, one _must_ dominate the other
 114       // and we want the deeper (i.e., dominated) guy.
 115       Node *n1 = early;
 116       Node *n2 = cin;
 117       while (1) {
 118         n1 = idom(n1);          // Walk up until break cycle
 119         n2 = idom(n2);
 120         if (n1 == cin ||        // Walked early up to cin
 121             dom_depth(n2) < c_d)
 122           break;                // early is deeper; keep him
 123         if (n2 == early ||      // Walked cin up to early
 124             dom_depth(n1) < c_d) {
 125           early = cin;          // cin is deeper; keep him
 126           break;
 127         }
 128       }
 129       e_d = dom_depth(early);   // Reset depth register cache
 130     }
 131   }
 132 
 133   // Return earliest legal location
 134   assert(early == find_non_split_ctrl(early), "unexpected early control");
 135 
 136   if (n->is_expensive() && !_verify_only && !_verify_me) {
 137     assert(n->in(0), "should have control input");
 138     early = get_early_ctrl_for_expensive(n, early);
 139   }
 140 
 141   return early;
 142 }
 143 
 144 //------------------------------get_early_ctrl_for_expensive---------------------------------
 145 // Move node up the dominator tree as high as legal while still beneficial
 146 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 147   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 148   assert(OptimizeExpensiveOps, "optimization off?");
 149 
 150   Node* ctl = n->in(0);
 151   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 152   uint min_dom_depth = dom_depth(earliest);
 153 #ifdef ASSERT
 154   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 155     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 156     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 157   }
 158 #endif
 159   if (dom_depth(ctl) < min_dom_depth) {
 160     return earliest;
 161   }
 162 
 163   while (1) {
 164     Node *next = ctl;
 165     // Moving the node out of a loop on the projection of a If
 166     // confuses loop predication. So once we hit a Loop in a If branch
 167     // that doesn't branch to an UNC, we stop. The code that process
 168     // expensive nodes will notice the loop and skip over it to try to
 169     // move the node further up.
 170     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 171       if (!ctl->in(1)->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 172         break;
 173       }
 174       next = idom(ctl->in(1)->in(0));
 175     } else if (ctl->is_Proj()) {
 176       // We only move it up along a projection if the projection is
 177       // the single control projection for its parent: same code path,
 178       // if it's a If with UNC or fallthrough of a call.
 179       Node* parent_ctl = ctl->in(0);
 180       if (parent_ctl == NULL) {
 181         break;
 182       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 183         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 184       } else if (parent_ctl->is_If()) {
 185         if (!ctl->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none)) {
 186           break;
 187         }
 188         assert(idom(ctl) == parent_ctl, "strange");
 189         next = idom(parent_ctl);
 190       } else if (ctl->is_CatchProj()) {
 191         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 192           break;
 193         }
 194         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 195         next = parent_ctl->in(0)->in(0)->in(0);
 196       } else {
 197         // Check if parent control has a single projection (this
 198         // control is the only possible successor of the parent
 199         // control). If so, we can try to move the node above the
 200         // parent control.
 201         int nb_ctl_proj = 0;
 202         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 203           Node *p = parent_ctl->fast_out(i);
 204           if (p->is_Proj() && p->is_CFG()) {
 205             nb_ctl_proj++;
 206             if (nb_ctl_proj > 1) {
 207               break;
 208             }
 209           }
 210         }
 211 
 212         if (nb_ctl_proj > 1) {
 213           break;
 214         }
 215         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
 216         assert(idom(ctl) == parent_ctl, "strange");
 217         next = idom(parent_ctl);
 218       }
 219     } else {
 220       next = idom(ctl);
 221     }
 222     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 223       break;
 224     }
 225     ctl = next;
 226   }
 227 
 228   if (ctl != n->in(0)) {
 229     _igvn.replace_input_of(n, 0, ctl);
 230     _igvn.hash_insert(n);
 231   }
 232 
 233   return ctl;
 234 }
 235 
 236 
 237 //------------------------------set_early_ctrl---------------------------------
 238 // Set earliest legal control
 239 void PhaseIdealLoop::set_early_ctrl( Node *n ) {
 240   Node *early = get_early_ctrl(n);
 241 
 242   // Record earliest legal location
 243   set_ctrl(n, early);
 244 }
 245 
 246 //------------------------------set_subtree_ctrl-------------------------------
 247 // set missing _ctrl entries on new nodes
 248 void PhaseIdealLoop::set_subtree_ctrl( Node *n ) {
 249   // Already set?  Get out.
 250   if( _nodes[n->_idx] ) return;
 251   // Recursively set _nodes array to indicate where the Node goes
 252   uint i;
 253   for( i = 0; i < n->req(); ++i ) {
 254     Node *m = n->in(i);
 255     if( m && m != C->root() )
 256       set_subtree_ctrl( m );
 257   }
 258 
 259   // Fixup self
 260   set_early_ctrl( n );
 261 }
 262 
 263 //------------------------------is_counted_loop--------------------------------
 264 bool PhaseIdealLoop::is_counted_loop( Node *x, IdealLoopTree *loop ) {
 265   PhaseGVN *gvn = &_igvn;
 266 
 267   // Counted loop head must be a good RegionNode with only 3 not NULL
 268   // control input edges: Self, Entry, LoopBack.
 269   if (x->in(LoopNode::Self) == NULL || x->req() != 3 || loop->_irreducible) {
 270     return false;
 271   }
 272   Node *init_control = x->in(LoopNode::EntryControl);
 273   Node *back_control = x->in(LoopNode::LoopBackControl);
 274   if (init_control == NULL || back_control == NULL)    // Partially dead
 275     return false;
 276   // Must also check for TOP when looking for a dead loop
 277   if (init_control->is_top() || back_control->is_top())
 278     return false;
 279 
 280   // Allow funny placement of Safepoint
 281   if (back_control->Opcode() == Op_SafePoint)
 282     back_control = back_control->in(TypeFunc::Control);
 283 
 284   // Controlling test for loop
 285   Node *iftrue = back_control;
 286   uint iftrue_op = iftrue->Opcode();
 287   if (iftrue_op != Op_IfTrue &&
 288       iftrue_op != Op_IfFalse)
 289     // I have a weird back-control.  Probably the loop-exit test is in
 290     // the middle of the loop and I am looking at some trailing control-flow
 291     // merge point.  To fix this I would have to partially peel the loop.
 292     return false; // Obscure back-control
 293 
 294   // Get boolean guarding loop-back test
 295   Node *iff = iftrue->in(0);
 296   if (get_loop(iff) != loop || !iff->in(1)->is_Bool())
 297     return false;
 298   BoolNode *test = iff->in(1)->as_Bool();
 299   BoolTest::mask bt = test->_test._test;
 300   float cl_prob = iff->as_If()->_prob;
 301   if (iftrue_op == Op_IfFalse) {
 302     bt = BoolTest(bt).negate();
 303     cl_prob = 1.0 - cl_prob;
 304   }
 305   // Get backedge compare
 306   Node *cmp = test->in(1);
 307   int cmp_op = cmp->Opcode();
 308   if (cmp_op != Op_CmpI)
 309     return false;                // Avoid pointer & float compares
 310 
 311   // Find the trip-counter increment & limit.  Limit must be loop invariant.
 312   Node *incr  = cmp->in(1);
 313   Node *limit = cmp->in(2);
 314 
 315   // ---------
 316   // need 'loop()' test to tell if limit is loop invariant
 317   // ---------
 318 
 319   if (!is_member(loop, get_ctrl(incr))) { // Swapped trip counter and limit?
 320     Node *tmp = incr;            // Then reverse order into the CmpI
 321     incr = limit;
 322     limit = tmp;
 323     bt = BoolTest(bt).commute(); // And commute the exit test
 324   }
 325   if (is_member(loop, get_ctrl(limit))) // Limit must be loop-invariant
 326     return false;
 327   if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 328     return false;
 329 
 330   Node* phi_incr = NULL;
 331   // Trip-counter increment must be commutative & associative.
 332   if (incr->is_Phi()) {
 333     if (incr->as_Phi()->region() != x || incr->req() != 3)
 334       return false; // Not simple trip counter expression
 335     phi_incr = incr;
 336     incr = phi_incr->in(LoopNode::LoopBackControl); // Assume incr is on backedge of Phi
 337     if (!is_member(loop, get_ctrl(incr))) // Trip counter must be loop-variant
 338       return false;
 339   }
 340 
 341   Node* trunc1 = NULL;
 342   Node* trunc2 = NULL;
 343   const TypeInt* iv_trunc_t = NULL;
 344   if (!(incr = CountedLoopNode::match_incr_with_optional_truncation(incr, &trunc1, &trunc2, &iv_trunc_t))) {
 345     return false; // Funny increment opcode
 346   }
 347   assert(incr->Opcode() == Op_AddI, "wrong increment code");
 348 
 349   // Get merge point
 350   Node *xphi = incr->in(1);
 351   Node *stride = incr->in(2);
 352   if (!stride->is_Con()) {     // Oops, swap these
 353     if (!xphi->is_Con())       // Is the other guy a constant?
 354       return false;             // Nope, unknown stride, bail out
 355     Node *tmp = xphi;           // 'incr' is commutative, so ok to swap
 356     xphi = stride;
 357     stride = tmp;
 358   }
 359   // Stride must be constant
 360   int stride_con = stride->get_int();
 361   if (stride_con == 0)
 362     return false; // missed some peephole opt
 363 
 364   if (!xphi->is_Phi())
 365     return false; // Too much math on the trip counter
 366   if (phi_incr != NULL && phi_incr != xphi)
 367     return false;
 368   PhiNode *phi = xphi->as_Phi();
 369 
 370   // Phi must be of loop header; backedge must wrap to increment
 371   if (phi->region() != x)
 372     return false;
 373   if (trunc1 == NULL && phi->in(LoopNode::LoopBackControl) != incr ||
 374       trunc1 != NULL && phi->in(LoopNode::LoopBackControl) != trunc1) {
 375     return false;
 376   }
 377   Node *init_trip = phi->in(LoopNode::EntryControl);
 378 
 379   // If iv trunc type is smaller than int, check for possible wrap.
 380   if (!TypeInt::INT->higher_equal(iv_trunc_t)) {
 381     assert(trunc1 != NULL, "must have found some truncation");
 382 
 383     // Get a better type for the phi (filtered thru if's)
 384     const TypeInt* phi_ft = filtered_type(phi);
 385 
 386     // Can iv take on a value that will wrap?
 387     //
 388     // Ensure iv's limit is not within "stride" of the wrap value.
 389     //
 390     // Example for "short" type
 391     //    Truncation ensures value is in the range -32768..32767 (iv_trunc_t)
 392     //    If the stride is +10, then the last value of the induction
 393     //    variable before the increment (phi_ft->_hi) must be
 394     //    <= 32767 - 10 and (phi_ft->_lo) must be >= -32768 to
 395     //    ensure no truncation occurs after the increment.
 396 
 397     if (stride_con > 0) {
 398       if (iv_trunc_t->_hi - phi_ft->_hi < stride_con ||
 399           iv_trunc_t->_lo > phi_ft->_lo) {
 400         return false;  // truncation may occur
 401       }
 402     } else if (stride_con < 0) {
 403       if (iv_trunc_t->_lo - phi_ft->_lo > stride_con ||
 404           iv_trunc_t->_hi < phi_ft->_hi) {
 405         return false;  // truncation may occur
 406       }
 407     }
 408     // No possibility of wrap so truncation can be discarded
 409     // Promote iv type to Int
 410   } else {
 411     assert(trunc1 == NULL && trunc2 == NULL, "no truncation for int");
 412   }
 413 
 414   // If the condition is inverted and we will be rolling
 415   // through MININT to MAXINT, then bail out.
 416   if (bt == BoolTest::eq || // Bail out, but this loop trips at most twice!
 417       // Odd stride
 418       bt == BoolTest::ne && stride_con != 1 && stride_con != -1 ||
 419       // Count down loop rolls through MAXINT
 420       (bt == BoolTest::le || bt == BoolTest::lt) && stride_con < 0 ||
 421       // Count up loop rolls through MININT
 422       (bt == BoolTest::ge || bt == BoolTest::gt) && stride_con > 0) {
 423     return false; // Bail out
 424   }
 425 
 426   const TypeInt* init_t = gvn->type(init_trip)->is_int();
 427   const TypeInt* limit_t = gvn->type(limit)->is_int();
 428 
 429   if (stride_con > 0) {
 430     jlong init_p = (jlong)init_t->_lo + stride_con;
 431     if (init_p > (jlong)max_jint || init_p > (jlong)limit_t->_hi)
 432       return false; // cyclic loop or this loop trips only once
 433   } else {
 434     jlong init_p = (jlong)init_t->_hi + stride_con;
 435     if (init_p < (jlong)min_jint || init_p < (jlong)limit_t->_lo)
 436       return false; // cyclic loop or this loop trips only once
 437   }
 438 
 439   if (phi_incr != NULL) {
 440     // check if there is a possiblity of IV overflowing after the first increment
 441     if (stride_con > 0) {
 442       if (init_t->_hi > max_jint - stride_con) {
 443         return false;
 444       }
 445     } else {
 446       if (init_t->_lo < min_jint - stride_con) {
 447         return false;
 448       }
 449     }
 450   }
 451 
 452   // =================================================
 453   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 454   //
 455   assert(x->Opcode() == Op_Loop, "regular loops only");
 456   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 457 
 458   Node *hook = new Node(6);
 459 
 460   if (LoopLimitCheck) {
 461 
 462   // ===================================================
 463   // Generate loop limit check to avoid integer overflow
 464   // in cases like next (cyclic loops):
 465   //
 466   // for (i=0; i <= max_jint; i++) {}
 467   // for (i=0; i <  max_jint; i+=2) {}
 468   //
 469   //
 470   // Limit check predicate depends on the loop test:
 471   //
 472   // for(;i != limit; i++)       --> limit <= (max_jint)
 473   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 474   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 475   //
 476 
 477   // Check if limit is excluded to do more precise int overflow check.
 478   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 479   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 480 
 481   // If compare points directly to the phi we need to adjust
 482   // the compare so that it points to the incr. Limit have
 483   // to be adjusted to keep trip count the same and the
 484   // adjusted limit should be checked for int overflow.
 485   if (phi_incr != NULL) {
 486     stride_m  += stride_con;
 487   }
 488 
 489   if (limit->is_Con()) {
 490     int limit_con = limit->get_int();
 491     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 492         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 493       // Bailout: it could be integer overflow.
 494       return false;
 495     }
 496   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 497              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 498       // Limit's type may satisfy the condition, for example,
 499       // when it is an array length.
 500   } else {
 501     // Generate loop's limit check.
 502     // Loop limit check predicate should be near the loop.
 503     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 504     if (!limit_check_proj) {
 505       // The limit check predicate is not generated if this method trapped here before.
 506 #ifdef ASSERT
 507       if (TraceLoopLimitCheck) {
 508         tty->print("missing loop limit check:");
 509         loop->dump_head();
 510         x->dump(1);
 511       }
 512 #endif
 513       return false;
 514     }
 515 
 516     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 517     Node* cmp_limit;
 518     Node* bol;
 519 
 520     if (stride_con > 0) {
 521       cmp_limit = new CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 522       bol = new BoolNode(cmp_limit, BoolTest::le);
 523     } else {
 524       cmp_limit = new CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 525       bol = new BoolNode(cmp_limit, BoolTest::ge);
 526     }
 527     cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 528     bol = _igvn.register_new_node_with_optimizer(bol);
 529     set_subtree_ctrl(bol);
 530 
 531     // Replace condition in original predicate but preserve Opaque node
 532     // so that previous predicates could be found.
 533     assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
 534            check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
 535     Node* opq = check_iff->in(1)->in(1);
 536     _igvn.replace_input_of(opq, 1, bol);
 537     // Update ctrl.
 538     set_ctrl(opq, check_iff->in(0));
 539     set_ctrl(check_iff->in(1), check_iff->in(0));
 540 
 541 #ifndef PRODUCT
 542     // report that the loop predication has been actually performed
 543     // for this loop
 544     if (TraceLoopLimitCheck) {
 545       tty->print_cr("Counted Loop Limit Check generated:");
 546       debug_only( bol->dump(2); )
 547     }
 548 #endif
 549   }
 550 
 551   if (phi_incr != NULL) {
 552     // If compare points directly to the phi we need to adjust
 553     // the compare so that it points to the incr. Limit have
 554     // to be adjusted to keep trip count the same and we
 555     // should avoid int overflow.
 556     //
 557     //   i = init; do {} while(i++ < limit);
 558     // is converted to
 559     //   i = init; do {} while(++i < limit+1);
 560     //
 561     limit = gvn->transform(new AddINode(limit, stride));
 562   }
 563 
 564   // Now we need to canonicalize loop condition.
 565   if (bt == BoolTest::ne) {
 566     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 567     // 'ne' can be replaced with 'lt' only when init < limit.
 568     if (stride_con > 0 && init_t->_hi < limit_t->_lo)
 569       bt = BoolTest::lt;
 570     // 'ne' can be replaced with 'gt' only when init > limit.
 571     if (stride_con < 0 && init_t->_lo > limit_t->_hi)
 572       bt = BoolTest::gt;
 573   }
 574 
 575   if (incl_limit) {
 576     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 577     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 578     //
 579     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 580     limit = gvn->transform(new AddINode(limit, one));
 581     if (bt == BoolTest::le)
 582       bt = BoolTest::lt;
 583     else if (bt == BoolTest::ge)
 584       bt = BoolTest::gt;
 585     else
 586       ShouldNotReachHere();
 587   }
 588   set_subtree_ctrl( limit );
 589 
 590   } else { // LoopLimitCheck
 591 
 592   // If compare points to incr, we are ok.  Otherwise the compare
 593   // can directly point to the phi; in this case adjust the compare so that
 594   // it points to the incr by adjusting the limit.
 595   if (cmp->in(1) == phi || cmp->in(2) == phi)
 596     limit = gvn->transform(new AddINode(limit,stride));
 597 
 598   // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
 599   // Final value for iterator should be: trip_count * stride + init_trip.
 600   Node *one_p = gvn->intcon( 1);
 601   Node *one_m = gvn->intcon(-1);
 602 
 603   Node *trip_count = NULL;
 604   switch( bt ) {
 605   case BoolTest::eq:
 606     ShouldNotReachHere();
 607   case BoolTest::ne:            // Ahh, the case we desire
 608     if (stride_con == 1)
 609       trip_count = gvn->transform(new SubINode(limit,init_trip));
 610     else if (stride_con == -1)
 611       trip_count = gvn->transform(new SubINode(init_trip,limit));
 612     else
 613       ShouldNotReachHere();
 614     set_subtree_ctrl(trip_count);
 615     //_loop.map(trip_count->_idx,loop(limit));
 616     break;
 617   case BoolTest::le:            // Maybe convert to '<' case
 618     limit = gvn->transform(new AddINode(limit,one_p));
 619     set_subtree_ctrl( limit );
 620     hook->init_req(4, limit);
 621 
 622     bt = BoolTest::lt;
 623     // Make the new limit be in the same loop nest as the old limit
 624     //_loop.map(limit->_idx,limit_loop);
 625     // Fall into next case
 626   case BoolTest::lt: {          // Maybe convert to '!=' case
 627     if (stride_con < 0) // Count down loop rolls through MAXINT
 628       ShouldNotReachHere();
 629     Node *range = gvn->transform(new SubINode(limit,init_trip));
 630     set_subtree_ctrl( range );
 631     hook->init_req(0, range);
 632 
 633     Node *bias  = gvn->transform(new AddINode(range,stride));
 634     set_subtree_ctrl( bias );
 635     hook->init_req(1, bias);
 636 
 637     Node *bias1 = gvn->transform(new AddINode(bias,one_m));
 638     set_subtree_ctrl( bias1 );
 639     hook->init_req(2, bias1);
 640 
 641     trip_count  = gvn->transform(new DivINode(0,bias1,stride));
 642     set_subtree_ctrl( trip_count );
 643     hook->init_req(3, trip_count);
 644     break;
 645   }
 646 
 647   case BoolTest::ge:            // Maybe convert to '>' case
 648     limit = gvn->transform(new AddINode(limit,one_m));
 649     set_subtree_ctrl( limit );
 650     hook->init_req(4 ,limit);
 651 
 652     bt = BoolTest::gt;
 653     // Make the new limit be in the same loop nest as the old limit
 654     //_loop.map(limit->_idx,limit_loop);
 655     // Fall into next case
 656   case BoolTest::gt: {          // Maybe convert to '!=' case
 657     if (stride_con > 0) // count up loop rolls through MININT
 658       ShouldNotReachHere();
 659     Node *range = gvn->transform(new SubINode(limit,init_trip));
 660     set_subtree_ctrl( range );
 661     hook->init_req(0, range);
 662 
 663     Node *bias  = gvn->transform(new AddINode(range,stride));
 664     set_subtree_ctrl( bias );
 665     hook->init_req(1, bias);
 666 
 667     Node *bias1 = gvn->transform(new AddINode(bias,one_p));
 668     set_subtree_ctrl( bias1 );
 669     hook->init_req(2, bias1);
 670 
 671     trip_count  = gvn->transform(new DivINode(0,bias1,stride));
 672     set_subtree_ctrl( trip_count );
 673     hook->init_req(3, trip_count);
 674     break;
 675   }
 676   } // switch( bt )
 677 
 678   Node *span = gvn->transform(new MulINode(trip_count,stride));
 679   set_subtree_ctrl( span );
 680   hook->init_req(5, span);
 681 
 682   limit = gvn->transform(new AddINode(span,init_trip));
 683   set_subtree_ctrl( limit );
 684 
 685   } // LoopLimitCheck
 686 
 687   // Check for SafePoint on backedge and remove
 688   Node *sfpt = x->in(LoopNode::LoopBackControl);
 689   if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 690     lazy_replace( sfpt, iftrue );
 691     if (loop->_safepts != NULL) {
 692       loop->_safepts->yank(sfpt);
 693     }
 694     loop->_tail = iftrue;
 695   }
 696 
 697   // Build a canonical trip test.
 698   // Clone code, as old values may be in use.
 699   incr = incr->clone();
 700   incr->set_req(1,phi);
 701   incr->set_req(2,stride);
 702   incr = _igvn.register_new_node_with_optimizer(incr);
 703   set_early_ctrl( incr );
 704   _igvn.rehash_node_delayed(phi);
 705   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 706 
 707   // If phi type is more restrictive than Int, raise to
 708   // Int to prevent (almost) infinite recursion in igvn
 709   // which can only handle integer types for constants or minint..maxint.
 710   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 711     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 712     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 713     nphi = _igvn.register_new_node_with_optimizer(nphi);
 714     set_ctrl(nphi, get_ctrl(phi));
 715     _igvn.replace_node(phi, nphi);
 716     phi = nphi->as_Phi();
 717   }
 718   cmp = cmp->clone();
 719   cmp->set_req(1,incr);
 720   cmp->set_req(2,limit);
 721   cmp = _igvn.register_new_node_with_optimizer(cmp);
 722   set_ctrl(cmp, iff->in(0));
 723 
 724   test = test->clone()->as_Bool();
 725   (*(BoolTest*)&test->_test)._test = bt;
 726   test->set_req(1,cmp);
 727   _igvn.register_new_node_with_optimizer(test);
 728   set_ctrl(test, iff->in(0));
 729 
 730   // Replace the old IfNode with a new LoopEndNode
 731   Node *lex = _igvn.register_new_node_with_optimizer(new CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 732   IfNode *le = lex->as_If();
 733   uint dd = dom_depth(iff);
 734   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 735   set_loop(le, loop);
 736 
 737   // Get the loop-exit control
 738   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 739 
 740   // Need to swap loop-exit and loop-back control?
 741   if (iftrue_op == Op_IfFalse) {
 742     Node *ift2=_igvn.register_new_node_with_optimizer(new IfTrueNode (le));
 743     Node *iff2=_igvn.register_new_node_with_optimizer(new IfFalseNode(le));
 744 
 745     loop->_tail = back_control = ift2;
 746     set_loop(ift2, loop);
 747     set_loop(iff2, get_loop(iffalse));
 748 
 749     // Lazy update of 'get_ctrl' mechanism.
 750     lazy_replace_proj( iffalse, iff2 );
 751     lazy_replace_proj( iftrue,  ift2 );
 752 
 753     // Swap names
 754     iffalse = iff2;
 755     iftrue  = ift2;
 756   } else {
 757     _igvn.rehash_node_delayed(iffalse);
 758     _igvn.rehash_node_delayed(iftrue);
 759     iffalse->set_req_X( 0, le, &_igvn );
 760     iftrue ->set_req_X( 0, le, &_igvn );
 761   }
 762 
 763   set_idom(iftrue,  le, dd+1);
 764   set_idom(iffalse, le, dd+1);
 765   assert(iff->outcnt() == 0, "should be dead now");
 766   lazy_replace( iff, le ); // fix 'get_ctrl'
 767 
 768   // Now setup a new CountedLoopNode to replace the existing LoopNode
 769   CountedLoopNode *l = new CountedLoopNode(init_control, back_control);
 770   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 771   // The following assert is approximately true, and defines the intention
 772   // of can_be_counted_loop.  It fails, however, because phase->type
 773   // is not yet initialized for this loop and its parts.
 774   //assert(l->can_be_counted_loop(this), "sanity");
 775   _igvn.register_new_node_with_optimizer(l);
 776   set_loop(l, loop);
 777   loop->_head = l;
 778   // Fix all data nodes placed at the old loop head.
 779   // Uses the lazy-update mechanism of 'get_ctrl'.
 780   lazy_replace( x, l );
 781   set_idom(l, init_control, dom_depth(x));
 782 
 783   // Check for immediately preceding SafePoint and remove
 784   Node *sfpt2 = le->in(0);
 785   if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) {
 786     lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 787     if (loop->_safepts != NULL) {
 788       loop->_safepts->yank(sfpt2);
 789     }
 790   }
 791 
 792   // Free up intermediate goo
 793   _igvn.remove_dead_node(hook);
 794 
 795 #ifdef ASSERT
 796   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 797   assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
 798 #endif
 799 #ifndef PRODUCT
 800   if (TraceLoopOpts) {
 801     tty->print("Counted      ");
 802     loop->dump_head();
 803   }
 804 #endif
 805 
 806   C->print_method(PHASE_AFTER_CLOOPS, 3);
 807 
 808   return true;
 809 }
 810 
 811 //----------------------exact_limit-------------------------------------------
 812 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 813   assert(loop->_head->is_CountedLoop(), "");
 814   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 815   assert(cl->is_valid_counted_loop(), "");
 816 
 817   if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
 818       cl->limit()->Opcode() == Op_LoopLimit) {
 819     // Old code has exact limit (it could be incorrect in case of int overflow).
 820     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 821     return cl->limit();
 822   }
 823   Node *limit = NULL;
 824 #ifdef ASSERT
 825   BoolTest::mask bt = cl->loopexit()->test_trip();
 826   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 827 #endif
 828   if (cl->has_exact_trip_count()) {
 829     // Simple case: loop has constant boundaries.
 830     // Use jlongs to avoid integer overflow.
 831     int stride_con = cl->stride_con();
 832     jlong  init_con = cl->init_trip()->get_int();
 833     jlong limit_con = cl->limit()->get_int();
 834     julong trip_cnt = cl->trip_count();
 835     jlong final_con = init_con + trip_cnt*stride_con;
 836     int final_int = (int)final_con;
 837     // The final value should be in integer range since the loop
 838     // is counted and the limit was checked for overflow.
 839     assert(final_con == (jlong)final_int, "final value should be integer");
 840     limit = _igvn.intcon(final_int);
 841   } else {
 842     // Create new LoopLimit node to get exact limit (final iv value).
 843     limit = new LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 844     register_new_node(limit, cl->in(LoopNode::EntryControl));
 845   }
 846   assert(limit != NULL, "sanity");
 847   return limit;
 848 }
 849 
 850 //------------------------------Ideal------------------------------------------
 851 // Return a node which is more "ideal" than the current node.
 852 // Attempt to convert into a counted-loop.
 853 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 854   if (!can_be_counted_loop(phase)) {
 855     phase->C->set_major_progress();
 856   }
 857   return RegionNode::Ideal(phase, can_reshape);
 858 }
 859 
 860 
 861 //=============================================================================
 862 //------------------------------Ideal------------------------------------------
 863 // Return a node which is more "ideal" than the current node.
 864 // Attempt to convert into a counted-loop.
 865 Node *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 866   return RegionNode::Ideal(phase, can_reshape);
 867 }
 868 
 869 //------------------------------dump_spec--------------------------------------
 870 // Dump special per-node info
 871 #ifndef PRODUCT
 872 void CountedLoopNode::dump_spec(outputStream *st) const {
 873   LoopNode::dump_spec(st);
 874   if (stride_is_con()) {
 875     st->print("stride: %d ",stride_con());
 876   }
 877   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
 878   if (is_main_loop()) st->print("main of N%d", _idx);
 879   if (is_post_loop()) st->print("post of N%d", _main_idx);
 880 }
 881 #endif
 882 
 883 //=============================================================================
 884 int CountedLoopEndNode::stride_con() const {
 885   return stride()->bottom_type()->is_int()->get_con();
 886 }
 887 
 888 //=============================================================================
 889 //------------------------------Value-----------------------------------------
 890 const Type *LoopLimitNode::Value( PhaseTransform *phase ) const {
 891   const Type* init_t   = phase->type(in(Init));
 892   const Type* limit_t  = phase->type(in(Limit));
 893   const Type* stride_t = phase->type(in(Stride));
 894   // Either input is TOP ==> the result is TOP
 895   if (init_t   == Type::TOP) return Type::TOP;
 896   if (limit_t  == Type::TOP) return Type::TOP;
 897   if (stride_t == Type::TOP) return Type::TOP;
 898 
 899   int stride_con = stride_t->is_int()->get_con();
 900   if (stride_con == 1)
 901     return NULL;  // Identity
 902 
 903   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
 904     // Use jlongs to avoid integer overflow.
 905     jlong init_con   =  init_t->is_int()->get_con();
 906     jlong limit_con  = limit_t->is_int()->get_con();
 907     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
 908     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
 909     jlong final_con  = init_con + stride_con*trip_count;
 910     int final_int = (int)final_con;
 911     // The final value should be in integer range since the loop
 912     // is counted and the limit was checked for overflow.
 913     assert(final_con == (jlong)final_int, "final value should be integer");
 914     return TypeInt::make(final_int);
 915   }
 916 
 917   return bottom_type(); // TypeInt::INT
 918 }
 919 
 920 //------------------------------Ideal------------------------------------------
 921 // Return a node which is more "ideal" than the current node.
 922 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 923   if (phase->type(in(Init))   == Type::TOP ||
 924       phase->type(in(Limit))  == Type::TOP ||
 925       phase->type(in(Stride)) == Type::TOP)
 926     return NULL;  // Dead
 927 
 928   int stride_con = phase->type(in(Stride))->is_int()->get_con();
 929   if (stride_con == 1)
 930     return NULL;  // Identity
 931 
 932   if (in(Init)->is_Con() && in(Limit)->is_Con())
 933     return NULL;  // Value
 934 
 935   // Delay following optimizations until all loop optimizations
 936   // done to keep Ideal graph simple.
 937   if (!can_reshape || phase->C->major_progress())
 938     return NULL;
 939 
 940   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
 941   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
 942   int stride_p;
 943   jlong lim, ini;
 944   julong max;
 945   if (stride_con > 0) {
 946     stride_p = stride_con;
 947     lim = limit_t->_hi;
 948     ini = init_t->_lo;
 949     max = (julong)max_jint;
 950   } else {
 951     stride_p = -stride_con;
 952     lim = init_t->_hi;
 953     ini = limit_t->_lo;
 954     max = (julong)min_jint;
 955   }
 956   julong range = lim - ini + stride_p;
 957   if (range <= max) {
 958     // Convert to integer expression if it is not overflow.
 959     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
 960     Node *range = phase->transform(new SubINode(in(Limit), in(Init)));
 961     Node *bias  = phase->transform(new AddINode(range, stride_m));
 962     Node *trip  = phase->transform(new DivINode(0, bias, in(Stride)));
 963     Node *span  = phase->transform(new MulINode(trip, in(Stride)));
 964     return new AddINode(span, in(Init)); // exact limit
 965   }
 966 
 967   if (is_power_of_2(stride_p) ||                // divisor is 2^n
 968       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
 969     // Convert to long expression to avoid integer overflow
 970     // and let igvn optimizer convert this division.
 971     //
 972     Node*   init   = phase->transform( new ConvI2LNode(in(Init)));
 973     Node*  limit   = phase->transform( new ConvI2LNode(in(Limit)));
 974     Node* stride   = phase->longcon(stride_con);
 975     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
 976 
 977     Node *range = phase->transform(new SubLNode(limit, init));
 978     Node *bias  = phase->transform(new AddLNode(range, stride_m));
 979     Node *span;
 980     if (stride_con > 0 && is_power_of_2(stride_p)) {
 981       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
 982       // and avoid generating rounding for division. Zero trip guard should
 983       // guarantee that init < limit but sometimes the guard is missing and
 984       // we can get situation when init > limit. Note, for the empty loop
 985       // optimization zero trip guard is generated explicitly which leaves
 986       // only RCE predicate where exact limit is used and the predicate
 987       // will simply fail forcing recompilation.
 988       Node* neg_stride   = phase->longcon(-stride_con);
 989       span = phase->transform(new AndLNode(bias, neg_stride));
 990     } else {
 991       Node *trip  = phase->transform(new DivLNode(0, bias, stride));
 992       span = phase->transform(new MulLNode(trip, stride));
 993     }
 994     // Convert back to int
 995     Node *span_int = phase->transform(new ConvL2INode(span));
 996     return new AddINode(span_int, in(Init)); // exact limit
 997   }
 998 
 999   return NULL;    // No progress
1000 }
1001 
1002 //------------------------------Identity---------------------------------------
1003 // If stride == 1 return limit node.
1004 Node *LoopLimitNode::Identity( PhaseTransform *phase ) {
1005   int stride_con = phase->type(in(Stride))->is_int()->get_con();
1006   if (stride_con == 1 || stride_con == -1)
1007     return in(Limit);
1008   return this;
1009 }
1010 
1011 //=============================================================================
1012 //----------------------match_incr_with_optional_truncation--------------------
1013 // Match increment with optional truncation:
1014 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1015 // Return NULL for failure. Success returns the increment node.
1016 Node* CountedLoopNode::match_incr_with_optional_truncation(
1017                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1018   // Quick cutouts:
1019   if (expr == NULL || expr->req() != 3)  return NULL;
1020 
1021   Node *t1 = NULL;
1022   Node *t2 = NULL;
1023   const TypeInt* trunc_t = TypeInt::INT;
1024   Node* n1 = expr;
1025   int   n1op = n1->Opcode();
1026 
1027   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1028   if (n1op == Op_AndI &&
1029       n1->in(2)->is_Con() &&
1030       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1031     // %%% This check should match any mask of 2**K-1.
1032     t1 = n1;
1033     n1 = t1->in(1);
1034     n1op = n1->Opcode();
1035     trunc_t = TypeInt::CHAR;
1036   } else if (n1op == Op_RShiftI &&
1037              n1->in(1) != NULL &&
1038              n1->in(1)->Opcode() == Op_LShiftI &&
1039              n1->in(2) == n1->in(1)->in(2) &&
1040              n1->in(2)->is_Con()) {
1041     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1042     // %%% This check should match any shift in [1..31].
1043     if (shift == 16 || shift == 8) {
1044       t1 = n1;
1045       t2 = t1->in(1);
1046       n1 = t2->in(1);
1047       n1op = n1->Opcode();
1048       if (shift == 16) {
1049         trunc_t = TypeInt::SHORT;
1050       } else if (shift == 8) {
1051         trunc_t = TypeInt::BYTE;
1052       }
1053     }
1054   }
1055 
1056   // If (maybe after stripping) it is an AddI, we won:
1057   if (n1op == Op_AddI) {
1058     *trunc1 = t1;
1059     *trunc2 = t2;
1060     *trunc_type = trunc_t;
1061     return n1;
1062   }
1063 
1064   // failed
1065   return NULL;
1066 }
1067 
1068 
1069 //------------------------------filtered_type--------------------------------
1070 // Return a type based on condition control flow
1071 // A successful return will be a type that is restricted due
1072 // to a series of dominating if-tests, such as:
1073 //    if (i < 10) {
1074 //       if (i > 0) {
1075 //          here: "i" type is [1..10)
1076 //       }
1077 //    }
1078 // or a control flow merge
1079 //    if (i < 10) {
1080 //       do {
1081 //          phi( , ) -- at top of loop type is [min_int..10)
1082 //         i = ?
1083 //       } while ( i < 10)
1084 //
1085 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1086   assert(n && n->bottom_type()->is_int(), "must be int");
1087   const TypeInt* filtered_t = NULL;
1088   if (!n->is_Phi()) {
1089     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1090     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1091 
1092   } else {
1093     Node* phi    = n->as_Phi();
1094     Node* region = phi->in(0);
1095     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1096     if (region && region != C->top()) {
1097       for (uint i = 1; i < phi->req(); i++) {
1098         Node* val   = phi->in(i);
1099         Node* use_c = region->in(i);
1100         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1101         if (val_t != NULL) {
1102           if (filtered_t == NULL) {
1103             filtered_t = val_t;
1104           } else {
1105             filtered_t = filtered_t->meet(val_t)->is_int();
1106           }
1107         }
1108       }
1109     }
1110   }
1111   const TypeInt* n_t = _igvn.type(n)->is_int();
1112   if (filtered_t != NULL) {
1113     n_t = n_t->join(filtered_t)->is_int();
1114   }
1115   return n_t;
1116 }
1117 
1118 
1119 //------------------------------filtered_type_from_dominators--------------------------------
1120 // Return a possibly more restrictive type for val based on condition control flow of dominators
1121 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1122   if (val->is_Con()) {
1123      return val->bottom_type()->is_int();
1124   }
1125   uint if_limit = 10; // Max number of dominating if's visited
1126   const TypeInt* rtn_t = NULL;
1127 
1128   if (use_ctrl && use_ctrl != C->top()) {
1129     Node* val_ctrl = get_ctrl(val);
1130     uint val_dom_depth = dom_depth(val_ctrl);
1131     Node* pred = use_ctrl;
1132     uint if_cnt = 0;
1133     while (if_cnt < if_limit) {
1134       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1135         if_cnt++;
1136         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1137         if (if_t != NULL) {
1138           if (rtn_t == NULL) {
1139             rtn_t = if_t;
1140           } else {
1141             rtn_t = rtn_t->join(if_t)->is_int();
1142           }
1143         }
1144       }
1145       pred = idom(pred);
1146       if (pred == NULL || pred == C->top()) {
1147         break;
1148       }
1149       // Stop if going beyond definition block of val
1150       if (dom_depth(pred) < val_dom_depth) {
1151         break;
1152       }
1153     }
1154   }
1155   return rtn_t;
1156 }
1157 
1158 
1159 //------------------------------dump_spec--------------------------------------
1160 // Dump special per-node info
1161 #ifndef PRODUCT
1162 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1163   if( in(TestValue) != NULL && in(TestValue)->is_Bool() ) {
1164     BoolTest bt( test_trip()); // Added this for g++.
1165 
1166     st->print("[");
1167     bt.dump_on(st);
1168     st->print("]");
1169   }
1170   st->print(" ");
1171   IfNode::dump_spec(st);
1172 }
1173 #endif
1174 
1175 //=============================================================================
1176 //------------------------------is_member--------------------------------------
1177 // Is 'l' a member of 'this'?
1178 bool IdealLoopTree::is_member(const IdealLoopTree *l) const {
1179   while( l->_nest > _nest ) l = l->_parent;
1180   return l == this;
1181 }
1182 
1183 //------------------------------set_nest---------------------------------------
1184 // Set loop tree nesting depth.  Accumulate _has_call bits.
1185 int IdealLoopTree::set_nest( uint depth ) {
1186   _nest = depth;
1187   int bits = _has_call;
1188   if( _child ) bits |= _child->set_nest(depth+1);
1189   if( bits ) _has_call = 1;
1190   if( _next  ) bits |= _next ->set_nest(depth  );
1191   return bits;
1192 }
1193 
1194 //------------------------------split_fall_in----------------------------------
1195 // Split out multiple fall-in edges from the loop header.  Move them to a
1196 // private RegionNode before the loop.  This becomes the loop landing pad.
1197 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1198   PhaseIterGVN &igvn = phase->_igvn;
1199   uint i;
1200 
1201   // Make a new RegionNode to be the landing pad.
1202   Node *landing_pad = new RegionNode( fall_in_cnt+1 );
1203   phase->set_loop(landing_pad,_parent);
1204   // Gather all the fall-in control paths into the landing pad
1205   uint icnt = fall_in_cnt;
1206   uint oreq = _head->req();
1207   for( i = oreq-1; i>0; i-- )
1208     if( !phase->is_member( this, _head->in(i) ) )
1209       landing_pad->set_req(icnt--,_head->in(i));
1210 
1211   // Peel off PhiNode edges as well
1212   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1213     Node *oj = _head->fast_out(j);
1214     if( oj->is_Phi() ) {
1215       PhiNode* old_phi = oj->as_Phi();
1216       assert( old_phi->region() == _head, "" );
1217       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1218       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1219       uint icnt = fall_in_cnt;
1220       for( i = oreq-1; i>0; i-- ) {
1221         if( !phase->is_member( this, _head->in(i) ) ) {
1222           p->init_req(icnt--, old_phi->in(i));
1223           // Go ahead and clean out old edges from old phi
1224           old_phi->del_req(i);
1225         }
1226       }
1227       // Search for CSE's here, because ZKM.jar does a lot of
1228       // loop hackery and we need to be a little incremental
1229       // with the CSE to avoid O(N^2) node blow-up.
1230       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1231       if( p2 ) {                // Found CSE
1232         p->destruct();          // Recover useless new node
1233         p = p2;                 // Use old node
1234       } else {
1235         igvn.register_new_node_with_optimizer(p, old_phi);
1236       }
1237       // Make old Phi refer to new Phi.
1238       old_phi->add_req(p);
1239       // Check for the special case of making the old phi useless and
1240       // disappear it.  In JavaGrande I have a case where this useless
1241       // Phi is the loop limit and prevents recognizing a CountedLoop
1242       // which in turn prevents removing an empty loop.
1243       Node *id_old_phi = old_phi->Identity( &igvn );
1244       if( id_old_phi != old_phi ) { // Found a simple identity?
1245         // Note that I cannot call 'replace_node' here, because
1246         // that will yank the edge from old_phi to the Region and
1247         // I'm mid-iteration over the Region's uses.
1248         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1249           Node* use = old_phi->last_out(i);
1250           igvn.rehash_node_delayed(use);
1251           uint uses_found = 0;
1252           for (uint j = 0; j < use->len(); j++) {
1253             if (use->in(j) == old_phi) {
1254               if (j < use->req()) use->set_req (j, id_old_phi);
1255               else                use->set_prec(j, id_old_phi);
1256               uses_found++;
1257             }
1258           }
1259           i -= uses_found;    // we deleted 1 or more copies of this edge
1260         }
1261       }
1262       igvn._worklist.push(old_phi);
1263     }
1264   }
1265   // Finally clean out the fall-in edges from the RegionNode
1266   for( i = oreq-1; i>0; i-- ) {
1267     if( !phase->is_member( this, _head->in(i) ) ) {
1268       _head->del_req(i);
1269     }
1270   }
1271   igvn.rehash_node_delayed(_head);
1272   // Transform landing pad
1273   igvn.register_new_node_with_optimizer(landing_pad, _head);
1274   // Insert landing pad into the header
1275   _head->add_req(landing_pad);
1276 }
1277 
1278 //------------------------------split_outer_loop-------------------------------
1279 // Split out the outermost loop from this shared header.
1280 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1281   PhaseIterGVN &igvn = phase->_igvn;
1282 
1283   // Find index of outermost loop; it should also be my tail.
1284   uint outer_idx = 1;
1285   while( _head->in(outer_idx) != _tail ) outer_idx++;
1286 
1287   // Make a LoopNode for the outermost loop.
1288   Node *ctl = _head->in(LoopNode::EntryControl);
1289   Node *outer = new LoopNode( ctl, _head->in(outer_idx) );
1290   outer = igvn.register_new_node_with_optimizer(outer, _head);
1291   phase->set_created_loop_node();
1292 
1293   // Outermost loop falls into '_head' loop
1294   _head->set_req(LoopNode::EntryControl, outer);
1295   _head->del_req(outer_idx);
1296   // Split all the Phis up between '_head' loop and 'outer' loop.
1297   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1298     Node *out = _head->fast_out(j);
1299     if( out->is_Phi() ) {
1300       PhiNode *old_phi = out->as_Phi();
1301       assert( old_phi->region() == _head, "" );
1302       Node *phi = PhiNode::make_blank(outer, old_phi);
1303       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1304       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1305       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1306       // Make old Phi point to new Phi on the fall-in path
1307       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1308       old_phi->del_req(outer_idx);
1309     }
1310   }
1311 
1312   // Use the new loop head instead of the old shared one
1313   _head = outer;
1314   phase->set_loop(_head, this);
1315 }
1316 
1317 //------------------------------fix_parent-------------------------------------
1318 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1319   loop->_parent = parent;
1320   if( loop->_child ) fix_parent( loop->_child, loop   );
1321   if( loop->_next  ) fix_parent( loop->_next , parent );
1322 }
1323 
1324 //------------------------------estimate_path_freq-----------------------------
1325 static float estimate_path_freq( Node *n ) {
1326   // Try to extract some path frequency info
1327   IfNode *iff;
1328   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1329     uint nop = n->Opcode();
1330     if( nop == Op_SafePoint ) {   // Skip any safepoint
1331       n = n->in(0);
1332       continue;
1333     }
1334     if( nop == Op_CatchProj ) {   // Get count from a prior call
1335       // Assume call does not always throw exceptions: means the call-site
1336       // count is also the frequency of the fall-through path.
1337       assert( n->is_CatchProj(), "" );
1338       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1339         return 0.0f;            // Assume call exception path is rare
1340       Node *call = n->in(0)->in(0)->in(0);
1341       assert( call->is_Call(), "expect a call here" );
1342       const JVMState *jvms = ((CallNode*)call)->jvms();
1343       ciMethodData* methodData = jvms->method()->method_data();
1344       if (!methodData->is_mature())  return 0.0f; // No call-site data
1345       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1346       if ((data == NULL) || !data->is_CounterData()) {
1347         // no call profile available, try call's control input
1348         n = n->in(0);
1349         continue;
1350       }
1351       return data->as_CounterData()->count()/FreqCountInvocations;
1352     }
1353     // See if there's a gating IF test
1354     Node *n_c = n->in(0);
1355     if( !n_c->is_If() ) break;       // No estimate available
1356     iff = n_c->as_If();
1357     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1358       // Compute how much count comes on this path
1359       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1360     // Have no count info.  Skip dull uncommon-trap like branches.
1361     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1362         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1363       break;
1364     // Skip through never-taken branch; look for a real loop exit.
1365     n = iff->in(0);
1366   }
1367   return 0.0f;                  // No estimate available
1368 }
1369 
1370 //------------------------------merge_many_backedges---------------------------
1371 // Merge all the backedges from the shared header into a private Region.
1372 // Feed that region as the one backedge to this loop.
1373 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1374   uint i;
1375 
1376   // Scan for the top 2 hottest backedges
1377   float hotcnt = 0.0f;
1378   float warmcnt = 0.0f;
1379   uint hot_idx = 0;
1380   // Loop starts at 2 because slot 1 is the fall-in path
1381   for( i = 2; i < _head->req(); i++ ) {
1382     float cnt = estimate_path_freq(_head->in(i));
1383     if( cnt > hotcnt ) {       // Grab hottest path
1384       warmcnt = hotcnt;
1385       hotcnt = cnt;
1386       hot_idx = i;
1387     } else if( cnt > warmcnt ) { // And 2nd hottest path
1388       warmcnt = cnt;
1389     }
1390   }
1391 
1392   // See if the hottest backedge is worthy of being an inner loop
1393   // by being much hotter than the next hottest backedge.
1394   if( hotcnt <= 0.0001 ||
1395       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1396 
1397   // Peel out the backedges into a private merge point; peel
1398   // them all except optionally hot_idx.
1399   PhaseIterGVN &igvn = phase->_igvn;
1400 
1401   Node *hot_tail = NULL;
1402   // Make a Region for the merge point
1403   Node *r = new RegionNode(1);
1404   for( i = 2; i < _head->req(); i++ ) {
1405     if( i != hot_idx )
1406       r->add_req( _head->in(i) );
1407     else hot_tail = _head->in(i);
1408   }
1409   igvn.register_new_node_with_optimizer(r, _head);
1410   // Plug region into end of loop _head, followed by hot_tail
1411   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1412   igvn.replace_input_of(_head, 2, r);
1413   if( hot_idx ) _head->add_req(hot_tail);
1414 
1415   // Split all the Phis up between '_head' loop and the Region 'r'
1416   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1417     Node *out = _head->fast_out(j);
1418     if( out->is_Phi() ) {
1419       PhiNode* n = out->as_Phi();
1420       igvn.hash_delete(n);      // Delete from hash before hacking edges
1421       Node *hot_phi = NULL;
1422       Node *phi = new PhiNode(r, n->type(), n->adr_type());
1423       // Check all inputs for the ones to peel out
1424       uint j = 1;
1425       for( uint i = 2; i < n->req(); i++ ) {
1426         if( i != hot_idx )
1427           phi->set_req( j++, n->in(i) );
1428         else hot_phi = n->in(i);
1429       }
1430       // Register the phi but do not transform until whole place transforms
1431       igvn.register_new_node_with_optimizer(phi, n);
1432       // Add the merge phi to the old Phi
1433       while( n->req() > 3 ) n->del_req( n->req()-1 );
1434       igvn.replace_input_of(n, 2, phi);
1435       if( hot_idx ) n->add_req(hot_phi);
1436     }
1437   }
1438 
1439 
1440   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
1441   // of self loop tree.  Turn self into a loop headed by _head and with
1442   // tail being the new merge point.
1443   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
1444   phase->set_loop(_tail,ilt);   // Adjust tail
1445   _tail = r;                    // Self's tail is new merge point
1446   phase->set_loop(r,this);
1447   ilt->_child = _child;         // New guy has my children
1448   _child = ilt;                 // Self has new guy as only child
1449   ilt->_parent = this;          // new guy has self for parent
1450   ilt->_nest = _nest;           // Same nesting depth (for now)
1451 
1452   // Starting with 'ilt', look for child loop trees using the same shared
1453   // header.  Flatten these out; they will no longer be loops in the end.
1454   IdealLoopTree **pilt = &_child;
1455   while( ilt ) {
1456     if( ilt->_head == _head ) {
1457       uint i;
1458       for( i = 2; i < _head->req(); i++ )
1459         if( _head->in(i) == ilt->_tail )
1460           break;                // Still a loop
1461       if( i == _head->req() ) { // No longer a loop
1462         // Flatten ilt.  Hang ilt's "_next" list from the end of
1463         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
1464         IdealLoopTree **cp = &ilt->_child;
1465         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
1466         *cp = ilt->_next;       // Hang next list at end of child list
1467         *pilt = ilt->_child;    // Move child up to replace ilt
1468         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
1469         ilt = ilt->_child;      // Repeat using new ilt
1470         continue;               // do not advance over ilt->_child
1471       }
1472       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
1473       phase->set_loop(_head,ilt);
1474     }
1475     pilt = &ilt->_child;        // Advance to next
1476     ilt = *pilt;
1477   }
1478 
1479   if( _child ) fix_parent( _child, this );
1480 }
1481 
1482 //------------------------------beautify_loops---------------------------------
1483 // Split shared headers and insert loop landing pads.
1484 // Insert a LoopNode to replace the RegionNode.
1485 // Return TRUE if loop tree is structurally changed.
1486 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
1487   bool result = false;
1488   // Cache parts in locals for easy
1489   PhaseIterGVN &igvn = phase->_igvn;
1490 
1491   igvn.hash_delete(_head);      // Yank from hash before hacking edges
1492 
1493   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
1494   int fall_in_cnt = 0;
1495   for( uint i = 1; i < _head->req(); i++ )
1496     if( !phase->is_member( this, _head->in(i) ) )
1497       fall_in_cnt++;
1498   assert( fall_in_cnt, "at least 1 fall-in path" );
1499   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
1500     split_fall_in( phase, fall_in_cnt );
1501 
1502   // Swap inputs to the _head and all Phis to move the fall-in edge to
1503   // the left.
1504   fall_in_cnt = 1;
1505   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
1506     fall_in_cnt++;
1507   if( fall_in_cnt > 1 ) {
1508     // Since I am just swapping inputs I do not need to update def-use info
1509     Node *tmp = _head->in(1);
1510     igvn.rehash_node_delayed(_head);
1511     _head->set_req( 1, _head->in(fall_in_cnt) );
1512     _head->set_req( fall_in_cnt, tmp );
1513     // Swap also all Phis
1514     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
1515       Node* phi = _head->fast_out(i);
1516       if( phi->is_Phi() ) {
1517         igvn.rehash_node_delayed(phi); // Yank from hash before hacking edges
1518         tmp = phi->in(1);
1519         phi->set_req( 1, phi->in(fall_in_cnt) );
1520         phi->set_req( fall_in_cnt, tmp );
1521       }
1522     }
1523   }
1524   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
1525   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
1526 
1527   // If I am a shared header (multiple backedges), peel off the many
1528   // backedges into a private merge point and use the merge point as
1529   // the one true backedge.
1530   if( _head->req() > 3 ) {
1531     // Merge the many backedges into a single backedge but leave
1532     // the hottest backedge as separate edge for the following peel.
1533     merge_many_backedges( phase );
1534     result = true;
1535   }
1536 
1537   // If I have one hot backedge, peel off myself loop.
1538   // I better be the outermost loop.
1539   if (_head->req() > 3 && !_irreducible) {
1540     split_outer_loop( phase );
1541     result = true;
1542 
1543   } else if (!_head->is_Loop() && !_irreducible) {
1544     // Make a new LoopNode to replace the old loop head
1545     Node *l = new LoopNode( _head->in(1), _head->in(2) );
1546     l = igvn.register_new_node_with_optimizer(l, _head);
1547     phase->set_created_loop_node();
1548     // Go ahead and replace _head
1549     phase->_igvn.replace_node( _head, l );
1550     _head = l;
1551     phase->set_loop(_head, this);
1552   }
1553 
1554   // Now recursively beautify nested loops
1555   if( _child ) result |= _child->beautify_loops( phase );
1556   if( _next  ) result |= _next ->beautify_loops( phase );
1557   return result;
1558 }
1559 
1560 //------------------------------allpaths_check_safepts----------------------------
1561 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
1562 // encountered.  Helper for check_safepts.
1563 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
1564   assert(stack.size() == 0, "empty stack");
1565   stack.push(_tail);
1566   visited.Clear();
1567   visited.set(_tail->_idx);
1568   while (stack.size() > 0) {
1569     Node* n = stack.pop();
1570     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1571       // Terminate this path
1572     } else if (n->Opcode() == Op_SafePoint) {
1573       if (_phase->get_loop(n) != this) {
1574         if (_required_safept == NULL) _required_safept = new Node_List();
1575         _required_safept->push(n);  // save the one closest to the tail
1576       }
1577       // Terminate this path
1578     } else {
1579       uint start = n->is_Region() ? 1 : 0;
1580       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
1581       for (uint i = start; i < end; i++) {
1582         Node* in = n->in(i);
1583         assert(in->is_CFG(), "must be");
1584         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
1585           stack.push(in);
1586         }
1587       }
1588     }
1589   }
1590 }
1591 
1592 //------------------------------check_safepts----------------------------
1593 // Given dominators, try to find loops with calls that must always be
1594 // executed (call dominates loop tail).  These loops do not need non-call
1595 // safepoints (ncsfpt).
1596 //
1597 // A complication is that a safepoint in a inner loop may be needed
1598 // by an outer loop. In the following, the inner loop sees it has a
1599 // call (block 3) on every path from the head (block 2) to the
1600 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
1601 // in block 2, _but_ this leaves the outer loop without a safepoint.
1602 //
1603 //          entry  0
1604 //                 |
1605 //                 v
1606 // outer 1,2    +->1
1607 //              |  |
1608 //              |  v
1609 //              |  2<---+  ncsfpt in 2
1610 //              |_/|\   |
1611 //                 | v  |
1612 // inner 2,3      /  3  |  call in 3
1613 //               /   |  |
1614 //              v    +--+
1615 //        exit  4
1616 //
1617 //
1618 // This method creates a list (_required_safept) of ncsfpt nodes that must
1619 // be protected is created for each loop. When a ncsfpt maybe deleted, it
1620 // is first looked for in the lists for the outer loops of the current loop.
1621 //
1622 // The insights into the problem:
1623 //  A) counted loops are okay
1624 //  B) innermost loops are okay (only an inner loop can delete
1625 //     a ncsfpt needed by an outer loop)
1626 //  C) a loop is immune from an inner loop deleting a safepoint
1627 //     if the loop has a call on the idom-path
1628 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
1629 //     idom-path that is not in a nested loop
1630 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
1631 //     loop needs to be prevented from deletion by an inner loop
1632 //
1633 // There are two analyses:
1634 //  1) The first, and cheaper one, scans the loop body from
1635 //     tail to head following the idom (immediate dominator)
1636 //     chain, looking for the cases (C,D,E) above.
1637 //     Since inner loops are scanned before outer loops, there is summary
1638 //     information about inner loops.  Inner loops can be skipped over
1639 //     when the tail of an inner loop is encountered.
1640 //
1641 //  2) The second, invoked if the first fails to find a call or ncsfpt on
1642 //     the idom path (which is rare), scans all predecessor control paths
1643 //     from the tail to the head, terminating a path when a call or sfpt
1644 //     is encountered, to find the ncsfpt's that are closest to the tail.
1645 //
1646 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
1647   // Bottom up traversal
1648   IdealLoopTree* ch = _child;
1649   if (_child) _child->check_safepts(visited, stack);
1650   if (_next)  _next ->check_safepts(visited, stack);
1651 
1652   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
1653     bool  has_call         = false; // call on dom-path
1654     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
1655     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
1656     // Scan the dom-path nodes from tail to head
1657     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
1658       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1659         has_call = true;
1660         _has_sfpt = 1;          // Then no need for a safept!
1661         break;
1662       } else if (n->Opcode() == Op_SafePoint) {
1663         if (_phase->get_loop(n) == this) {
1664           has_local_ncsfpt = true;
1665           break;
1666         }
1667         if (nonlocal_ncsfpt == NULL) {
1668           nonlocal_ncsfpt = n; // save the one closest to the tail
1669         }
1670       } else {
1671         IdealLoopTree* nlpt = _phase->get_loop(n);
1672         if (this != nlpt) {
1673           // If at an inner loop tail, see if the inner loop has already
1674           // recorded seeing a call on the dom-path (and stop.)  If not,
1675           // jump to the head of the inner loop.
1676           assert(is_member(nlpt), "nested loop");
1677           Node* tail = nlpt->_tail;
1678           if (tail->in(0)->is_If()) tail = tail->in(0);
1679           if (n == tail) {
1680             // If inner loop has call on dom-path, so does outer loop
1681             if (nlpt->_has_sfpt) {
1682               has_call = true;
1683               _has_sfpt = 1;
1684               break;
1685             }
1686             // Skip to head of inner loop
1687             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
1688             n = nlpt->_head;
1689           }
1690         }
1691       }
1692     }
1693     // Record safept's that this loop needs preserved when an
1694     // inner loop attempts to delete it's safepoints.
1695     if (_child != NULL && !has_call && !has_local_ncsfpt) {
1696       if (nonlocal_ncsfpt != NULL) {
1697         if (_required_safept == NULL) _required_safept = new Node_List();
1698         _required_safept->push(nonlocal_ncsfpt);
1699       } else {
1700         // Failed to find a suitable safept on the dom-path.  Now use
1701         // an all paths walk from tail to head, looking for safepoints to preserve.
1702         allpaths_check_safepts(visited, stack);
1703       }
1704     }
1705   }
1706 }
1707 
1708 //---------------------------is_deleteable_safept----------------------------
1709 // Is safept not required by an outer loop?
1710 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
1711   assert(sfpt->Opcode() == Op_SafePoint, "");
1712   IdealLoopTree* lp = get_loop(sfpt)->_parent;
1713   while (lp != NULL) {
1714     Node_List* sfpts = lp->_required_safept;
1715     if (sfpts != NULL) {
1716       for (uint i = 0; i < sfpts->size(); i++) {
1717         if (sfpt == sfpts->at(i))
1718           return false;
1719       }
1720     }
1721     lp = lp->_parent;
1722   }
1723   return true;
1724 }
1725 
1726 //---------------------------replace_parallel_iv-------------------------------
1727 // Replace parallel induction variable (parallel to trip counter)
1728 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
1729   assert(loop->_head->is_CountedLoop(), "");
1730   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1731   if (!cl->is_valid_counted_loop())
1732     return;         // skip malformed counted loop
1733   Node *incr = cl->incr();
1734   if (incr == NULL)
1735     return;         // Dead loop?
1736   Node *init = cl->init_trip();
1737   Node *phi  = cl->phi();
1738   int stride_con = cl->stride_con();
1739 
1740   // Visit all children, looking for Phis
1741   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
1742     Node *out = cl->out(i);
1743     // Look for other phis (secondary IVs). Skip dead ones
1744     if (!out->is_Phi() || out == phi || !has_node(out))
1745       continue;
1746     PhiNode* phi2 = out->as_Phi();
1747     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
1748     // Look for induction variables of the form:  X += constant
1749     if (phi2->region() != loop->_head ||
1750         incr2->req() != 3 ||
1751         incr2->in(1) != phi2 ||
1752         incr2 == incr ||
1753         incr2->Opcode() != Op_AddI ||
1754         !incr2->in(2)->is_Con())
1755       continue;
1756 
1757     // Check for parallel induction variable (parallel to trip counter)
1758     // via an affine function.  In particular, count-down loops with
1759     // count-up array indices are common. We only RCE references off
1760     // the trip-counter, so we need to convert all these to trip-counter
1761     // expressions.
1762     Node *init2 = phi2->in( LoopNode::EntryControl );
1763     int stride_con2 = incr2->in(2)->get_int();
1764 
1765     // The general case here gets a little tricky.  We want to find the
1766     // GCD of all possible parallel IV's and make a new IV using this
1767     // GCD for the loop.  Then all possible IVs are simple multiples of
1768     // the GCD.  In practice, this will cover very few extra loops.
1769     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
1770     // where +/-1 is the common case, but other integer multiples are
1771     // also easy to handle.
1772     int ratio_con = stride_con2/stride_con;
1773 
1774     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
1775 #ifndef PRODUCT
1776       if (TraceLoopOpts) {
1777         tty->print("Parallel IV: %d ", phi2->_idx);
1778         loop->dump_head();
1779       }
1780 #endif
1781       // Convert to using the trip counter.  The parallel induction
1782       // variable differs from the trip counter by a loop-invariant
1783       // amount, the difference between their respective initial values.
1784       // It is scaled by the 'ratio_con'.
1785       Node* ratio = _igvn.intcon(ratio_con);
1786       set_ctrl(ratio, C->root());
1787       Node* ratio_init = new MulINode(init, ratio);
1788       _igvn.register_new_node_with_optimizer(ratio_init, init);
1789       set_early_ctrl(ratio_init);
1790       Node* diff = new SubINode(init2, ratio_init);
1791       _igvn.register_new_node_with_optimizer(diff, init2);
1792       set_early_ctrl(diff);
1793       Node* ratio_idx = new MulINode(phi, ratio);
1794       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
1795       set_ctrl(ratio_idx, cl);
1796       Node* add = new AddINode(ratio_idx, diff);
1797       _igvn.register_new_node_with_optimizer(add);
1798       set_ctrl(add, cl);
1799       _igvn.replace_node( phi2, add );
1800       // Sometimes an induction variable is unused
1801       if (add->outcnt() == 0) {
1802         _igvn.remove_dead_node(add);
1803       }
1804       --i; // deleted this phi; rescan starting with next position
1805       continue;
1806     }
1807   }
1808 }
1809 
1810 //------------------------------counted_loop-----------------------------------
1811 // Convert to counted loops where possible
1812 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
1813 
1814   // For grins, set the inner-loop flag here
1815   if (!_child) {
1816     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
1817   }
1818 
1819   if (_head->is_CountedLoop() ||
1820       phase->is_counted_loop(_head, this)) {
1821     _has_sfpt = 1;              // Indicate we do not need a safepoint here
1822 
1823     // Look for safepoints to remove.
1824     Node_List* sfpts = _safepts;
1825     if (sfpts != NULL) {
1826       for (uint i = 0; i < sfpts->size(); i++) {
1827         Node* n = sfpts->at(i);
1828         assert(phase->get_loop(n) == this, "");
1829         if (phase->is_deleteable_safept(n)) {
1830           phase->lazy_replace(n, n->in(TypeFunc::Control));
1831         }
1832       }
1833     }
1834 
1835     // Look for induction variables
1836     phase->replace_parallel_iv(this);
1837 
1838   } else if (_parent != NULL && !_irreducible) {
1839     // Not a counted loop.
1840     // Look for a safepoint on the idom-path.
1841     Node* sfpt = tail();
1842     for (; sfpt != _head; sfpt = phase->idom(sfpt)) {
1843       if (sfpt->Opcode() == Op_SafePoint && phase->get_loop(sfpt) == this)
1844         break; // Found one
1845     }
1846     // Delete other safepoints in this loop.
1847     Node_List* sfpts = _safepts;
1848     if (sfpts != NULL && sfpt != _head && sfpt->Opcode() == Op_SafePoint) {
1849       for (uint i = 0; i < sfpts->size(); i++) {
1850         Node* n = sfpts->at(i);
1851         assert(phase->get_loop(n) == this, "");
1852         if (n != sfpt && phase->is_deleteable_safept(n)) {
1853           phase->lazy_replace(n, n->in(TypeFunc::Control));
1854         }
1855       }
1856     }
1857   }
1858 
1859   // Recursively
1860   if (_child) _child->counted_loop( phase );
1861   if (_next)  _next ->counted_loop( phase );
1862 }
1863 
1864 #ifndef PRODUCT
1865 //------------------------------dump_head--------------------------------------
1866 // Dump 1 liner for loop header info
1867 void IdealLoopTree::dump_head( ) const {
1868   for (uint i=0; i<_nest; i++)
1869     tty->print("  ");
1870   tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
1871   if (_irreducible) tty->print(" IRREDUCIBLE");
1872   Node* entry = _head->in(LoopNode::EntryControl);
1873   if (LoopLimitCheck) {
1874     Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1875     if (predicate != NULL ) {
1876       tty->print(" limit_check");
1877       entry = entry->in(0)->in(0);
1878     }
1879   }
1880   if (UseLoopPredicate) {
1881     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1882     if (entry != NULL) {
1883       tty->print(" predicated");
1884     }
1885   }
1886   if (_head->is_CountedLoop()) {
1887     CountedLoopNode *cl = _head->as_CountedLoop();
1888     tty->print(" counted");
1889 
1890     Node* init_n = cl->init_trip();
1891     if (init_n  != NULL &&  init_n->is_Con())
1892       tty->print(" [%d,", cl->init_trip()->get_int());
1893     else
1894       tty->print(" [int,");
1895     Node* limit_n = cl->limit();
1896     if (limit_n  != NULL &&  limit_n->is_Con())
1897       tty->print("%d),", cl->limit()->get_int());
1898     else
1899       tty->print("int),");
1900     int stride_con  = cl->stride_con();
1901     if (stride_con > 0) tty->print("+");
1902     tty->print("%d", stride_con);
1903 
1904     tty->print(" (%0.f iters) ", cl->profile_trip_cnt());
1905 
1906     if (cl->is_pre_loop ()) tty->print(" pre" );
1907     if (cl->is_main_loop()) tty->print(" main");
1908     if (cl->is_post_loop()) tty->print(" post");
1909   }
1910   tty->cr();
1911 }
1912 
1913 //------------------------------dump-------------------------------------------
1914 // Dump loops by loop tree
1915 void IdealLoopTree::dump( ) const {
1916   dump_head();
1917   if (_child) _child->dump();
1918   if (_next)  _next ->dump();
1919 }
1920 
1921 #endif
1922 
1923 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
1924   if (loop == root) {
1925     if (loop->_child != NULL) {
1926       log->begin_head("loop_tree");
1927       log->end_head();
1928       if( loop->_child ) log_loop_tree(root, loop->_child, log);
1929       log->tail("loop_tree");
1930       assert(loop->_next == NULL, "what?");
1931     }
1932   } else {
1933     Node* head = loop->_head;
1934     log->begin_head("loop");
1935     log->print(" idx='%d' ", head->_idx);
1936     if (loop->_irreducible) log->print("irreducible='1' ");
1937     if (head->is_Loop()) {
1938       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
1939       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
1940     }
1941     if (head->is_CountedLoop()) {
1942       CountedLoopNode* cl = head->as_CountedLoop();
1943       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
1944       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
1945       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
1946     }
1947     log->end_head();
1948     if( loop->_child ) log_loop_tree(root, loop->_child, log);
1949     log->tail("loop");
1950     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
1951   }
1952 }
1953 
1954 //---------------------collect_potentially_useful_predicates-----------------------
1955 // Helper function to collect potentially useful predicates to prevent them from
1956 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
1957 void PhaseIdealLoop::collect_potentially_useful_predicates(
1958                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
1959   if (loop->_child) { // child
1960     collect_potentially_useful_predicates(loop->_child, useful_predicates);
1961   }
1962 
1963   // self (only loops that we can apply loop predication may use their predicates)
1964   if (loop->_head->is_Loop() &&
1965       !loop->_irreducible    &&
1966       !loop->tail()->is_top()) {
1967     LoopNode* lpn = loop->_head->as_Loop();
1968     Node* entry = lpn->in(LoopNode::EntryControl);
1969     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
1970     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
1971       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
1972       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
1973       entry = entry->in(0)->in(0);
1974     }
1975     predicate_proj = find_predicate(entry); // Predicate
1976     if (predicate_proj != NULL ) {
1977       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
1978     }
1979   }
1980 
1981   if (loop->_next) { // sibling
1982     collect_potentially_useful_predicates(loop->_next, useful_predicates);
1983   }
1984 }
1985 
1986 //------------------------eliminate_useless_predicates-----------------------------
1987 // Eliminate all inserted predicates if they could not be used by loop predication.
1988 // Note: it will also eliminates loop limits check predicate since it also uses
1989 // Opaque1 node (see Parse::add_predicate()).
1990 void PhaseIdealLoop::eliminate_useless_predicates() {
1991   if (C->predicate_count() == 0)
1992     return; // no predicate left
1993 
1994   Unique_Node_List useful_predicates; // to store useful predicates
1995   if (C->has_loops()) {
1996     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
1997   }
1998 
1999   for (int i = C->predicate_count(); i > 0; i--) {
2000      Node * n = C->predicate_opaque1_node(i-1);
2001      assert(n->Opcode() == Op_Opaque1, "must be");
2002      if (!useful_predicates.member(n)) { // not in the useful list
2003        _igvn.replace_node(n, n->in(1));
2004      }
2005   }
2006 }
2007 
2008 //------------------------process_expensive_nodes-----------------------------
2009 // Expensive nodes have their control input set to prevent the GVN
2010 // from commoning them and as a result forcing the resulting node to
2011 // be in a more frequent path. Use CFG information here, to change the
2012 // control inputs so that some expensive nodes can be commoned while
2013 // not executed more frequently.
2014 bool PhaseIdealLoop::process_expensive_nodes() {
2015   assert(OptimizeExpensiveOps, "optimization off?");
2016 
2017   // Sort nodes to bring similar nodes together
2018   C->sort_expensive_nodes();
2019 
2020   bool progress = false;
2021 
2022   for (int i = 0; i < C->expensive_count(); ) {
2023     Node* n = C->expensive_node(i);
2024     int start = i;
2025     // Find nodes similar to n
2026     i++;
2027     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2028     int end = i;
2029     // And compare them two by two
2030     for (int j = start; j < end; j++) {
2031       Node* n1 = C->expensive_node(j);
2032       if (is_node_unreachable(n1)) {
2033         continue;
2034       }
2035       for (int k = j+1; k < end; k++) {
2036         Node* n2 = C->expensive_node(k);
2037         if (is_node_unreachable(n2)) {
2038           continue;
2039         }
2040 
2041         assert(n1 != n2, "should be pair of nodes");
2042 
2043         Node* c1 = n1->in(0);
2044         Node* c2 = n2->in(0);
2045 
2046         Node* parent_c1 = c1;
2047         Node* parent_c2 = c2;
2048 
2049         // The call to get_early_ctrl_for_expensive() moves the
2050         // expensive nodes up but stops at loops that are in a if
2051         // branch. See whether we can exit the loop and move above the
2052         // If.
2053         if (c1->is_Loop()) {
2054           parent_c1 = c1->in(1);
2055         }
2056         if (c2->is_Loop()) {
2057           parent_c2 = c2->in(1);
2058         }
2059 
2060         if (parent_c1 == parent_c2) {
2061           _igvn._worklist.push(n1);
2062           _igvn._worklist.push(n2);
2063           continue;
2064         }
2065 
2066         // Look for identical expensive node up the dominator chain.
2067         if (is_dominator(c1, c2)) {
2068           c2 = c1;
2069         } else if (is_dominator(c2, c1)) {
2070           c1 = c2;
2071         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2072                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2073           // Both branches have the same expensive node so move it up
2074           // before the if.
2075           c1 = c2 = idom(parent_c1->in(0));
2076         }
2077         // Do the actual moves
2078         if (n1->in(0) != c1) {
2079           _igvn.hash_delete(n1);
2080           n1->set_req(0, c1);
2081           _igvn.hash_insert(n1);
2082           _igvn._worklist.push(n1);
2083           progress = true;
2084         }
2085         if (n2->in(0) != c2) {
2086           _igvn.hash_delete(n2);
2087           n2->set_req(0, c2);
2088           _igvn.hash_insert(n2);
2089           _igvn._worklist.push(n2);
2090           progress = true;
2091         }
2092       }
2093     }
2094   }
2095 
2096   return progress;
2097 }
2098 
2099 
2100 //=============================================================================
2101 //----------------------------build_and_optimize-------------------------------
2102 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2103 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2104 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool skip_loop_opts) {
2105   ResourceMark rm;
2106 
2107   int old_progress = C->major_progress();
2108   uint orig_worklist_size = _igvn._worklist.size();
2109 
2110   // Reset major-progress flag for the driver's heuristics
2111   C->clear_major_progress();
2112 
2113 #ifndef PRODUCT
2114   // Capture for later assert
2115   uint unique = C->unique();
2116   _loop_invokes++;
2117   _loop_work += unique;
2118 #endif
2119 
2120   // True if the method has at least 1 irreducible loop
2121   _has_irreducible_loops = false;
2122 
2123   _created_loop_node = false;
2124 
2125   Arena *a = Thread::current()->resource_area();
2126   VectorSet visited(a);
2127   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2128   _nodes.map(C->unique(), NULL);
2129   memset(_nodes.adr(), 0, wordSize * C->unique());
2130 
2131   // Pre-build the top-level outermost loop tree entry
2132   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2133   // Do not need a safepoint at the top level
2134   _ltree_root->_has_sfpt = 1;
2135 
2136   // Initialize Dominators.
2137   // Checked in clone_loop_predicate() during beautify_loops().
2138   _idom_size = 0;
2139   _idom      = NULL;
2140   _dom_depth = NULL;
2141   _dom_stk   = NULL;
2142 
2143   // Empty pre-order array
2144   allocate_preorders();
2145 
2146   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2147   // IdealLoopTree entries.  Data nodes are NOT walked.
2148   build_loop_tree();
2149   // Check for bailout, and return
2150   if (C->failing()) {
2151     return;
2152   }
2153 
2154   // No loops after all
2155   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2156 
2157   // There should always be an outer loop containing the Root and Return nodes.
2158   // If not, we have a degenerate empty program.  Bail out in this case.
2159   if (!has_node(C->root())) {
2160     if (!_verify_only) {
2161       C->clear_major_progress();
2162       C->record_method_not_compilable("empty program detected during loop optimization");
2163     }
2164     return;
2165   }
2166 
2167   // Nothing to do, so get out
2168   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only;
2169   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2170   if (stop_early && !do_expensive_nodes) {
2171     _igvn.optimize();           // Cleanup NeverBranches
2172     return;
2173   }
2174 
2175   // Set loop nesting depth
2176   _ltree_root->set_nest( 0 );
2177 
2178   // Split shared headers and insert loop landing pads.
2179   // Do not bother doing this on the Root loop of course.
2180   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2181     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2182     if( _ltree_root->_child->beautify_loops( this ) ) {
2183       // Re-build loop tree!
2184       _ltree_root->_child = NULL;
2185       _nodes.clear();
2186       reallocate_preorders();
2187       build_loop_tree();
2188       // Check for bailout, and return
2189       if (C->failing()) {
2190         return;
2191       }
2192       // Reset loop nesting depth
2193       _ltree_root->set_nest( 0 );
2194 
2195       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2196     }
2197   }
2198 
2199   // Build Dominators for elision of NULL checks & loop finding.
2200   // Since nodes do not have a slot for immediate dominator, make
2201   // a persistent side array for that info indexed on node->_idx.
2202   _idom_size = C->unique();
2203   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2204   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2205   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2206   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2207 
2208   Dominators();
2209 
2210   if (!_verify_only) {
2211     // As a side effect, Dominators removed any unreachable CFG paths
2212     // into RegionNodes.  It doesn't do this test against Root, so
2213     // we do it here.
2214     for( uint i = 1; i < C->root()->req(); i++ ) {
2215       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2216         _igvn.delete_input_of(C->root(), i);
2217         i--;                      // Rerun same iteration on compressed edges
2218       }
2219     }
2220 
2221     // Given dominators, try to find inner loops with calls that must
2222     // always be executed (call dominates loop tail).  These loops do
2223     // not need a separate safepoint.
2224     Node_List cisstack(a);
2225     _ltree_root->check_safepts(visited, cisstack);
2226   }
2227 
2228   // Walk the DATA nodes and place into loops.  Find earliest control
2229   // node.  For CFG nodes, the _nodes array starts out and remains
2230   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2231   // _nodes array holds the earliest legal controlling CFG node.
2232 
2233   // Allocate stack with enough space to avoid frequent realloc
2234   int stack_size = (C->live_nodes() >> 1) + 16; // (live_nodes>>1)+16 from Java2D stats
2235   Node_Stack nstack( a, stack_size );
2236 
2237   visited.Clear();
2238   Node_List worklist(a);
2239   // Don't need C->root() on worklist since
2240   // it will be processed among C->top() inputs
2241   worklist.push( C->top() );
2242   visited.set( C->top()->_idx ); // Set C->top() as visited now
2243   build_loop_early( visited, worklist, nstack );
2244 
2245   // Given early legal placement, try finding counted loops.  This placement
2246   // is good enough to discover most loop invariants.
2247   if( !_verify_me && !_verify_only )
2248     _ltree_root->counted_loop( this );
2249 
2250   // Find latest loop placement.  Find ideal loop placement.
2251   visited.Clear();
2252   init_dom_lca_tags();
2253   // Need C->root() on worklist when processing outs
2254   worklist.push( C->root() );
2255   NOT_PRODUCT( C->verify_graph_edges(); )
2256   worklist.push( C->top() );
2257   build_loop_late( visited, worklist, nstack );
2258 
2259   if (_verify_only) {
2260     // restore major progress flag
2261     for (int i = 0; i < old_progress; i++)
2262       C->set_major_progress();
2263     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2264     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2265     return;
2266   }
2267 
2268   // clear out the dead code after build_loop_late
2269   while (_deadlist.size()) {
2270     _igvn.remove_globally_dead_node(_deadlist.pop());
2271   }
2272 
2273   if (stop_early) {
2274     assert(do_expensive_nodes, "why are we here?");
2275     if (process_expensive_nodes()) {
2276       // If we made some progress when processing expensive nodes then
2277       // the IGVN may modify the graph in a way that will allow us to
2278       // make some more progress: we need to try processing expensive
2279       // nodes again.
2280       C->set_major_progress();
2281     }
2282     _igvn.optimize();
2283     return;
2284   }
2285 
2286   // Some parser-inserted loop predicates could never be used by loop
2287   // predication or they were moved away from loop during some optimizations.
2288   // For example, peeling. Eliminate them before next loop optimizations.
2289   if (UseLoopPredicate || LoopLimitCheck) {
2290     eliminate_useless_predicates();
2291   }
2292 
2293 #ifndef PRODUCT
2294   C->verify_graph_edges();
2295   if (_verify_me) {             // Nested verify pass?
2296     // Check to see if the verify mode is broken
2297     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2298     return;
2299   }
2300   if(VerifyLoopOptimizations) verify();
2301   if(TraceLoopOpts && C->has_loops()) {
2302     _ltree_root->dump();
2303   }
2304 #endif
2305 
2306   if (skip_loop_opts) {
2307     // Cleanup any modified bits
2308     _igvn.optimize();
2309 
2310     if (C->log() != NULL) {
2311       log_loop_tree(_ltree_root, _ltree_root, C->log());
2312     }
2313     return;
2314   }
2315 
2316   if (ReassociateInvariants) {
2317     // Reassociate invariants and prep for split_thru_phi
2318     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2319       IdealLoopTree* lpt = iter.current();
2320       bool is_counted = lpt->is_counted();
2321       if (!is_counted || !lpt->is_inner()) continue;
2322 
2323       // check for vectorized loops, any reassociation of invariants was already done
2324       if (is_counted && lpt->_head->as_CountedLoop()->do_unroll_only()) continue;
2325 
2326       lpt->reassociate_invariants(this);
2327 
2328       // Because RCE opportunities can be masked by split_thru_phi,
2329       // look for RCE candidates and inhibit split_thru_phi
2330       // on just their loop-phi's for this pass of loop opts
2331       if (SplitIfBlocks && do_split_ifs) {
2332         if (lpt->policy_range_check(this)) {
2333           lpt->_rce_candidate = 1; // = true
2334         }
2335       }
2336     }
2337   }
2338 
2339   // Check for aggressive application of split-if and other transforms
2340   // that require basic-block info (like cloning through Phi's)
2341   if( SplitIfBlocks && do_split_ifs ) {
2342     visited.Clear();
2343     split_if_with_blocks( visited, nstack );
2344     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2345   }
2346 
2347   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
2348     C->set_major_progress();
2349   }
2350 
2351   // Perform loop predication before iteration splitting
2352   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2353     _ltree_root->_child->loop_predication(this);
2354   }
2355 
2356   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2357     if (do_intrinsify_fill()) {
2358       C->set_major_progress();
2359     }
2360   }
2361 
2362   // Perform iteration-splitting on inner loops.  Split iterations to avoid
2363   // range checks or one-shot null checks.
2364 
2365   // If split-if's didn't hack the graph too bad (no CFG changes)
2366   // then do loop opts.
2367   if (C->has_loops() && !C->major_progress()) {
2368     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
2369     _ltree_root->_child->iteration_split( this, worklist );
2370     // No verify after peeling!  GCM has hoisted code out of the loop.
2371     // After peeling, the hoisted code could sink inside the peeled area.
2372     // The peeling code does not try to recompute the best location for
2373     // all the code before the peeled area, so the verify pass will always
2374     // complain about it.
2375   }
2376   // Do verify graph edges in any case
2377   NOT_PRODUCT( C->verify_graph_edges(); );
2378 
2379   if (!do_split_ifs) {
2380     // We saw major progress in Split-If to get here.  We forced a
2381     // pass with unrolling and not split-if, however more split-if's
2382     // might make progress.  If the unrolling didn't make progress
2383     // then the major-progress flag got cleared and we won't try
2384     // another round of Split-If.  In particular the ever-common
2385     // instance-of/check-cast pattern requires at least 2 rounds of
2386     // Split-If to clear out.
2387     C->set_major_progress();
2388   }
2389 
2390   // Repeat loop optimizations if new loops were seen
2391   if (created_loop_node()) {
2392     C->set_major_progress();
2393   }
2394 
2395   // Keep loop predicates and perform optimizations with them
2396   // until no more loop optimizations could be done.
2397   // After that switch predicates off and do more loop optimizations.
2398   if (!C->major_progress() && (C->predicate_count() > 0)) {
2399      C->cleanup_loop_predicates(_igvn);
2400 #ifndef PRODUCT
2401      if (TraceLoopOpts) {
2402        tty->print_cr("PredicatesOff");
2403      }
2404 #endif
2405      C->set_major_progress();
2406   }
2407 
2408   // Convert scalar to superword operations at the end of all loop opts.
2409   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
2410     // SuperWord transform
2411     SuperWord sw(this);
2412     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2413       IdealLoopTree* lpt = iter.current();
2414       if (lpt->is_counted()) {
2415         sw.transform_loop(lpt, true);
2416       }
2417     }
2418   }
2419 
2420   // Cleanup any modified bits
2421   _igvn.optimize();
2422 
2423   // disable assert until issue with split_flow_path is resolved (6742111)
2424   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
2425   //        "shouldn't introduce irreducible loops");
2426 
2427   if (C->log() != NULL) {
2428     log_loop_tree(_ltree_root, _ltree_root, C->log());
2429   }
2430 }
2431 
2432 #ifndef PRODUCT
2433 //------------------------------print_statistics-------------------------------
2434 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
2435 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
2436 void PhaseIdealLoop::print_statistics() {
2437   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
2438 }
2439 
2440 //------------------------------verify-----------------------------------------
2441 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
2442 static int fail;                // debug only, so its multi-thread dont care
2443 void PhaseIdealLoop::verify() const {
2444   int old_progress = C->major_progress();
2445   ResourceMark rm;
2446   PhaseIdealLoop loop_verify( _igvn, this );
2447   VectorSet visited(Thread::current()->resource_area());
2448 
2449   fail = 0;
2450   verify_compare( C->root(), &loop_verify, visited );
2451   assert( fail == 0, "verify loops failed" );
2452   // Verify loop structure is the same
2453   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
2454   // Reset major-progress.  It was cleared by creating a verify version of
2455   // PhaseIdealLoop.
2456   for( int i=0; i<old_progress; i++ )
2457     C->set_major_progress();
2458 }
2459 
2460 //------------------------------verify_compare---------------------------------
2461 // Make sure me and the given PhaseIdealLoop agree on key data structures
2462 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
2463   if( !n ) return;
2464   if( visited.test_set( n->_idx ) ) return;
2465   if( !_nodes[n->_idx] ) {      // Unreachable
2466     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
2467     return;
2468   }
2469 
2470   uint i;
2471   for( i = 0; i < n->req(); i++ )
2472     verify_compare( n->in(i), loop_verify, visited );
2473 
2474   // Check the '_nodes' block/loop structure
2475   i = n->_idx;
2476   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
2477     if( _nodes[i] != loop_verify->_nodes[i] &&
2478         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
2479       tty->print("Mismatched control setting for: ");
2480       n->dump();
2481       if( fail++ > 10 ) return;
2482       Node *c = get_ctrl_no_update(n);
2483       tty->print("We have it as: ");
2484       if( c->in(0) ) c->dump();
2485         else tty->print_cr("N%d",c->_idx);
2486       tty->print("Verify thinks: ");
2487       if( loop_verify->has_ctrl(n) )
2488         loop_verify->get_ctrl_no_update(n)->dump();
2489       else
2490         loop_verify->get_loop_idx(n)->dump();
2491       tty->cr();
2492     }
2493   } else {                    // We have a loop
2494     IdealLoopTree *us = get_loop_idx(n);
2495     if( loop_verify->has_ctrl(n) ) {
2496       tty->print("Mismatched loop setting for: ");
2497       n->dump();
2498       if( fail++ > 10 ) return;
2499       tty->print("We have it as: ");
2500       us->dump();
2501       tty->print("Verify thinks: ");
2502       loop_verify->get_ctrl_no_update(n)->dump();
2503       tty->cr();
2504     } else if (!C->major_progress()) {
2505       // Loop selection can be messed up if we did a major progress
2506       // operation, like split-if.  Do not verify in that case.
2507       IdealLoopTree *them = loop_verify->get_loop_idx(n);
2508       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
2509         tty->print("Unequals loops for: ");
2510         n->dump();
2511         if( fail++ > 10 ) return;
2512         tty->print("We have it as: ");
2513         us->dump();
2514         tty->print("Verify thinks: ");
2515         them->dump();
2516         tty->cr();
2517       }
2518     }
2519   }
2520 
2521   // Check for immediate dominators being equal
2522   if( i >= _idom_size ) {
2523     if( !n->is_CFG() ) return;
2524     tty->print("CFG Node with no idom: ");
2525     n->dump();
2526     return;
2527   }
2528   if( !n->is_CFG() ) return;
2529   if( n == C->root() ) return; // No IDOM here
2530 
2531   assert(n->_idx == i, "sanity");
2532   Node *id = idom_no_update(n);
2533   if( id != loop_verify->idom_no_update(n) ) {
2534     tty->print("Unequals idoms for: ");
2535     n->dump();
2536     if( fail++ > 10 ) return;
2537     tty->print("We have it as: ");
2538     id->dump();
2539     tty->print("Verify thinks: ");
2540     loop_verify->idom_no_update(n)->dump();
2541     tty->cr();
2542   }
2543 
2544 }
2545 
2546 //------------------------------verify_tree------------------------------------
2547 // Verify that tree structures match.  Because the CFG can change, siblings
2548 // within the loop tree can be reordered.  We attempt to deal with that by
2549 // reordering the verify's loop tree if possible.
2550 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
2551   assert( _parent == parent, "Badly formed loop tree" );
2552 
2553   // Siblings not in same order?  Attempt to re-order.
2554   if( _head != loop->_head ) {
2555     // Find _next pointer to update
2556     IdealLoopTree **pp = &loop->_parent->_child;
2557     while( *pp != loop )
2558       pp = &((*pp)->_next);
2559     // Find proper sibling to be next
2560     IdealLoopTree **nn = &loop->_next;
2561     while( (*nn) && (*nn)->_head != _head )
2562       nn = &((*nn)->_next);
2563 
2564     // Check for no match.
2565     if( !(*nn) ) {
2566       // Annoyingly, irreducible loops can pick different headers
2567       // after a major_progress operation, so the rest of the loop
2568       // tree cannot be matched.
2569       if (_irreducible && Compile::current()->major_progress())  return;
2570       assert( 0, "failed to match loop tree" );
2571     }
2572 
2573     // Move (*nn) to (*pp)
2574     IdealLoopTree *hit = *nn;
2575     *nn = hit->_next;
2576     hit->_next = loop;
2577     *pp = loop;
2578     loop = hit;
2579     // Now try again to verify
2580   }
2581 
2582   assert( _head  == loop->_head , "mismatched loop head" );
2583   Node *tail = _tail;           // Inline a non-updating version of
2584   while( !tail->in(0) )         // the 'tail()' call.
2585     tail = tail->in(1);
2586   assert( tail == loop->_tail, "mismatched loop tail" );
2587 
2588   // Counted loops that are guarded should be able to find their guards
2589   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
2590     CountedLoopNode *cl = _head->as_CountedLoop();
2591     Node *init = cl->init_trip();
2592     Node *ctrl = cl->in(LoopNode::EntryControl);
2593     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
2594     Node *iff  = ctrl->in(0);
2595     assert( iff->Opcode() == Op_If, "" );
2596     Node *bol  = iff->in(1);
2597     assert( bol->Opcode() == Op_Bool, "" );
2598     Node *cmp  = bol->in(1);
2599     assert( cmp->Opcode() == Op_CmpI, "" );
2600     Node *add  = cmp->in(1);
2601     Node *opaq;
2602     if( add->Opcode() == Op_Opaque1 ) {
2603       opaq = add;
2604     } else {
2605       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
2606       assert( add == init, "" );
2607       opaq = cmp->in(2);
2608     }
2609     assert( opaq->Opcode() == Op_Opaque1, "" );
2610 
2611   }
2612 
2613   if (_child != NULL)  _child->verify_tree(loop->_child, this);
2614   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
2615   // Innermost loops need to verify loop bodies,
2616   // but only if no 'major_progress'
2617   int fail = 0;
2618   if (!Compile::current()->major_progress() && _child == NULL) {
2619     for( uint i = 0; i < _body.size(); i++ ) {
2620       Node *n = _body.at(i);
2621       if (n->outcnt() == 0)  continue; // Ignore dead
2622       uint j;
2623       for( j = 0; j < loop->_body.size(); j++ )
2624         if( loop->_body.at(j) == n )
2625           break;
2626       if( j == loop->_body.size() ) { // Not found in loop body
2627         // Last ditch effort to avoid assertion: Its possible that we
2628         // have some users (so outcnt not zero) but are still dead.
2629         // Try to find from root.
2630         if (Compile::current()->root()->find(n->_idx)) {
2631           fail++;
2632           tty->print("We have that verify does not: ");
2633           n->dump();
2634         }
2635       }
2636     }
2637     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
2638       Node *n = loop->_body.at(i2);
2639       if (n->outcnt() == 0)  continue; // Ignore dead
2640       uint j;
2641       for( j = 0; j < _body.size(); j++ )
2642         if( _body.at(j) == n )
2643           break;
2644       if( j == _body.size() ) { // Not found in loop body
2645         // Last ditch effort to avoid assertion: Its possible that we
2646         // have some users (so outcnt not zero) but are still dead.
2647         // Try to find from root.
2648         if (Compile::current()->root()->find(n->_idx)) {
2649           fail++;
2650           tty->print("Verify has that we do not: ");
2651           n->dump();
2652         }
2653       }
2654     }
2655     assert( !fail, "loop body mismatch" );
2656   }
2657 }
2658 
2659 #endif
2660 
2661 //------------------------------set_idom---------------------------------------
2662 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
2663   uint idx = d->_idx;
2664   if (idx >= _idom_size) {
2665     uint newsize = _idom_size<<1;
2666     while( idx >= newsize ) {
2667       newsize <<= 1;
2668     }
2669     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
2670     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
2671     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
2672     _idom_size = newsize;
2673   }
2674   _idom[idx] = n;
2675   _dom_depth[idx] = dom_depth;
2676 }
2677 
2678 //------------------------------recompute_dom_depth---------------------------------------
2679 // The dominator tree is constructed with only parent pointers.
2680 // This recomputes the depth in the tree by first tagging all
2681 // nodes as "no depth yet" marker.  The next pass then runs up
2682 // the dom tree from each node marked "no depth yet", and computes
2683 // the depth on the way back down.
2684 void PhaseIdealLoop::recompute_dom_depth() {
2685   uint no_depth_marker = C->unique();
2686   uint i;
2687   // Initialize depth to "no depth yet"
2688   for (i = 0; i < _idom_size; i++) {
2689     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
2690      _dom_depth[i] = no_depth_marker;
2691     }
2692   }
2693   if (_dom_stk == NULL) {
2694     uint init_size = C->live_nodes() / 100; // Guess that 1/100 is a reasonable initial size.
2695     if (init_size < 10) init_size = 10;
2696     _dom_stk = new GrowableArray<uint>(init_size);
2697   }
2698   // Compute new depth for each node.
2699   for (i = 0; i < _idom_size; i++) {
2700     uint j = i;
2701     // Run up the dom tree to find a node with a depth
2702     while (_dom_depth[j] == no_depth_marker) {
2703       _dom_stk->push(j);
2704       j = _idom[j]->_idx;
2705     }
2706     // Compute the depth on the way back down this tree branch
2707     uint dd = _dom_depth[j] + 1;
2708     while (_dom_stk->length() > 0) {
2709       uint j = _dom_stk->pop();
2710       _dom_depth[j] = dd;
2711       dd++;
2712     }
2713   }
2714 }
2715 
2716 //------------------------------sort-------------------------------------------
2717 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
2718 // loop tree, not the root.
2719 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
2720   if( !innermost ) return loop; // New innermost loop
2721 
2722   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
2723   assert( loop_preorder, "not yet post-walked loop" );
2724   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
2725   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
2726 
2727   // Insert at start of list
2728   while( l ) {                  // Insertion sort based on pre-order
2729     if( l == loop ) return innermost; // Already on list!
2730     int l_preorder = get_preorder(l->_head); // Cache pre-order number
2731     assert( l_preorder, "not yet post-walked l" );
2732     // Check header pre-order number to figure proper nesting
2733     if( loop_preorder > l_preorder )
2734       break;                    // End of insertion
2735     // If headers tie (e.g., shared headers) check tail pre-order numbers.
2736     // Since I split shared headers, you'd think this could not happen.
2737     // BUT: I must first do the preorder numbering before I can discover I
2738     // have shared headers, so the split headers all get the same preorder
2739     // number as the RegionNode they split from.
2740     if( loop_preorder == l_preorder &&
2741         get_preorder(loop->_tail) < get_preorder(l->_tail) )
2742       break;                    // Also check for shared headers (same pre#)
2743     pp = &l->_parent;           // Chain up list
2744     l = *pp;
2745   }
2746   // Link into list
2747   // Point predecessor to me
2748   *pp = loop;
2749   // Point me to successor
2750   IdealLoopTree *p = loop->_parent;
2751   loop->_parent = l;            // Point me to successor
2752   if( p ) sort( p, innermost ); // Insert my parents into list as well
2753   return innermost;
2754 }
2755 
2756 //------------------------------build_loop_tree--------------------------------
2757 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
2758 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
2759 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
2760 // tightest enclosing IdealLoopTree for post-walked.
2761 //
2762 // During my forward walk I do a short 1-layer lookahead to see if I can find
2763 // a loop backedge with that doesn't have any work on the backedge.  This
2764 // helps me construct nested loops with shared headers better.
2765 //
2766 // Once I've done the forward recursion, I do the post-work.  For each child
2767 // I check to see if there is a backedge.  Backedges define a loop!  I
2768 // insert an IdealLoopTree at the target of the backedge.
2769 //
2770 // During the post-work I also check to see if I have several children
2771 // belonging to different loops.  If so, then this Node is a decision point
2772 // where control flow can choose to change loop nests.  It is at this
2773 // decision point where I can figure out how loops are nested.  At this
2774 // time I can properly order the different loop nests from my children.
2775 // Note that there may not be any backedges at the decision point!
2776 //
2777 // Since the decision point can be far removed from the backedges, I can't
2778 // order my loops at the time I discover them.  Thus at the decision point
2779 // I need to inspect loop header pre-order numbers to properly nest my
2780 // loops.  This means I need to sort my childrens' loops by pre-order.
2781 // The sort is of size number-of-control-children, which generally limits
2782 // it to size 2 (i.e., I just choose between my 2 target loops).
2783 void PhaseIdealLoop::build_loop_tree() {
2784   // Allocate stack of size C->live_nodes()/2 to avoid frequent realloc
2785   GrowableArray <Node *> bltstack(C->live_nodes() >> 1);
2786   Node *n = C->root();
2787   bltstack.push(n);
2788   int pre_order = 1;
2789   int stack_size;
2790 
2791   while ( ( stack_size = bltstack.length() ) != 0 ) {
2792     n = bltstack.top(); // Leave node on stack
2793     if ( !is_visited(n) ) {
2794       // ---- Pre-pass Work ----
2795       // Pre-walked but not post-walked nodes need a pre_order number.
2796 
2797       set_preorder_visited( n, pre_order ); // set as visited
2798 
2799       // ---- Scan over children ----
2800       // Scan first over control projections that lead to loop headers.
2801       // This helps us find inner-to-outer loops with shared headers better.
2802 
2803       // Scan children's children for loop headers.
2804       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
2805         Node* m = n->raw_out(i);       // Child
2806         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
2807           // Scan over children's children to find loop
2808           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2809             Node* l = m->fast_out(j);
2810             if( is_visited(l) &&       // Been visited?
2811                 !is_postvisited(l) &&  // But not post-visited
2812                 get_preorder(l) < pre_order ) { // And smaller pre-order
2813               // Found!  Scan the DFS down this path before doing other paths
2814               bltstack.push(m);
2815               break;
2816             }
2817           }
2818         }
2819       }
2820       pre_order++;
2821     }
2822     else if ( !is_postvisited(n) ) {
2823       // Note: build_loop_tree_impl() adds out edges on rare occasions,
2824       // such as com.sun.rsasign.am::a.
2825       // For non-recursive version, first, process current children.
2826       // On next iteration, check if additional children were added.
2827       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
2828         Node* u = n->raw_out(k);
2829         if ( u->is_CFG() && !is_visited(u) ) {
2830           bltstack.push(u);
2831         }
2832       }
2833       if ( bltstack.length() == stack_size ) {
2834         // There were no additional children, post visit node now
2835         (void)bltstack.pop(); // Remove node from stack
2836         pre_order = build_loop_tree_impl( n, pre_order );
2837         // Check for bailout
2838         if (C->failing()) {
2839           return;
2840         }
2841         // Check to grow _preorders[] array for the case when
2842         // build_loop_tree_impl() adds new nodes.
2843         check_grow_preorders();
2844       }
2845     }
2846     else {
2847       (void)bltstack.pop(); // Remove post-visited node from stack
2848     }
2849   }
2850 }
2851 
2852 //------------------------------build_loop_tree_impl---------------------------
2853 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
2854   // ---- Post-pass Work ----
2855   // Pre-walked but not post-walked nodes need a pre_order number.
2856 
2857   // Tightest enclosing loop for this Node
2858   IdealLoopTree *innermost = NULL;
2859 
2860   // For all children, see if any edge is a backedge.  If so, make a loop
2861   // for it.  Then find the tightest enclosing loop for the self Node.
2862   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2863     Node* m = n->fast_out(i);   // Child
2864     if( n == m ) continue;      // Ignore control self-cycles
2865     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
2866 
2867     IdealLoopTree *l;           // Child's loop
2868     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
2869       // Found a backedge
2870       assert( get_preorder(m) < pre_order, "should be backedge" );
2871       // Check for the RootNode, which is already a LoopNode and is allowed
2872       // to have multiple "backedges".
2873       if( m == C->root()) {     // Found the root?
2874         l = _ltree_root;        // Root is the outermost LoopNode
2875       } else {                  // Else found a nested loop
2876         // Insert a LoopNode to mark this loop.
2877         l = new IdealLoopTree(this, m, n);
2878       } // End of Else found a nested loop
2879       if( !has_loop(m) )        // If 'm' does not already have a loop set
2880         set_loop(m, l);         // Set loop header to loop now
2881 
2882     } else {                    // Else not a nested loop
2883       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
2884       l = get_loop(m);          // Get previously determined loop
2885       // If successor is header of a loop (nest), move up-loop till it
2886       // is a member of some outer enclosing loop.  Since there are no
2887       // shared headers (I've split them already) I only need to go up
2888       // at most 1 level.
2889       while( l && l->_head == m ) // Successor heads loop?
2890         l = l->_parent;         // Move up 1 for me
2891       // If this loop is not properly parented, then this loop
2892       // has no exit path out, i.e. its an infinite loop.
2893       if( !l ) {
2894         // Make loop "reachable" from root so the CFG is reachable.  Basically
2895         // insert a bogus loop exit that is never taken.  'm', the loop head,
2896         // points to 'n', one (of possibly many) fall-in paths.  There may be
2897         // many backedges as well.
2898 
2899         // Here I set the loop to be the root loop.  I could have, after
2900         // inserting a bogus loop exit, restarted the recursion and found my
2901         // new loop exit.  This would make the infinite loop a first-class
2902         // loop and it would then get properly optimized.  What's the use of
2903         // optimizing an infinite loop?
2904         l = _ltree_root;        // Oops, found infinite loop
2905 
2906         if (!_verify_only) {
2907           // Insert the NeverBranch between 'm' and it's control user.
2908           NeverBranchNode *iff = new NeverBranchNode( m );
2909           _igvn.register_new_node_with_optimizer(iff);
2910           set_loop(iff, l);
2911           Node *if_t = new CProjNode( iff, 0 );
2912           _igvn.register_new_node_with_optimizer(if_t);
2913           set_loop(if_t, l);
2914 
2915           Node* cfg = NULL;       // Find the One True Control User of m
2916           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2917             Node* x = m->fast_out(j);
2918             if (x->is_CFG() && x != m && x != iff)
2919               { cfg = x; break; }
2920           }
2921           assert(cfg != NULL, "must find the control user of m");
2922           uint k = 0;             // Probably cfg->in(0)
2923           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
2924           cfg->set_req( k, if_t ); // Now point to NeverBranch
2925           _igvn._worklist.push(cfg);
2926 
2927           // Now create the never-taken loop exit
2928           Node *if_f = new CProjNode( iff, 1 );
2929           _igvn.register_new_node_with_optimizer(if_f);
2930           set_loop(if_f, l);
2931           // Find frame ptr for Halt.  Relies on the optimizer
2932           // V-N'ing.  Easier and quicker than searching through
2933           // the program structure.
2934           Node *frame = new ParmNode( C->start(), TypeFunc::FramePtr );
2935           _igvn.register_new_node_with_optimizer(frame);
2936           // Halt & Catch Fire
2937           Node *halt = new HaltNode( if_f, frame );
2938           _igvn.register_new_node_with_optimizer(halt);
2939           set_loop(halt, l);
2940           C->root()->add_req(halt);
2941         }
2942         set_loop(C->root(), _ltree_root);
2943       }
2944     }
2945     // Weeny check for irreducible.  This child was already visited (this
2946     // IS the post-work phase).  Is this child's loop header post-visited
2947     // as well?  If so, then I found another entry into the loop.
2948     if (!_verify_only) {
2949       while( is_postvisited(l->_head) ) {
2950         // found irreducible
2951         l->_irreducible = 1; // = true
2952         l = l->_parent;
2953         _has_irreducible_loops = true;
2954         // Check for bad CFG here to prevent crash, and bailout of compile
2955         if (l == NULL) {
2956           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
2957           return pre_order;
2958         }
2959       }
2960       C->set_has_irreducible_loop(_has_irreducible_loops);
2961     }
2962 
2963     // This Node might be a decision point for loops.  It is only if
2964     // it's children belong to several different loops.  The sort call
2965     // does a trivial amount of work if there is only 1 child or all
2966     // children belong to the same loop.  If however, the children
2967     // belong to different loops, the sort call will properly set the
2968     // _parent pointers to show how the loops nest.
2969     //
2970     // In any case, it returns the tightest enclosing loop.
2971     innermost = sort( l, innermost );
2972   }
2973 
2974   // Def-use info will have some dead stuff; dead stuff will have no
2975   // loop decided on.
2976 
2977   // Am I a loop header?  If so fix up my parent's child and next ptrs.
2978   if( innermost && innermost->_head == n ) {
2979     assert( get_loop(n) == innermost, "" );
2980     IdealLoopTree *p = innermost->_parent;
2981     IdealLoopTree *l = innermost;
2982     while( p && l->_head == n ) {
2983       l->_next = p->_child;     // Put self on parents 'next child'
2984       p->_child = l;            // Make self as first child of parent
2985       l = p;                    // Now walk up the parent chain
2986       p = l->_parent;
2987     }
2988   } else {
2989     // Note that it is possible for a LoopNode to reach here, if the
2990     // backedge has been made unreachable (hence the LoopNode no longer
2991     // denotes a Loop, and will eventually be removed).
2992 
2993     // Record tightest enclosing loop for self.  Mark as post-visited.
2994     set_loop(n, innermost);
2995     // Also record has_call flag early on
2996     if( innermost ) {
2997       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
2998         // Do not count uncommon calls
2999         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
3000           Node *iff = n->in(0)->in(0);
3001           // No any calls for vectorized loops.
3002           if( UseSuperWord || !iff->is_If() ||
3003               (n->in(0)->Opcode() == Op_IfFalse &&
3004                (1.0 - iff->as_If()->_prob) >= 0.01) ||
3005               (iff->as_If()->_prob >= 0.01) )
3006             innermost->_has_call = 1;
3007         }
3008       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
3009         // Disable loop optimizations if the loop has a scalar replaceable
3010         // allocation. This disabling may cause a potential performance lost
3011         // if the allocation is not eliminated for some reason.
3012         innermost->_allow_optimizations = false;
3013         innermost->_has_call = 1; // = true
3014       } else if (n->Opcode() == Op_SafePoint) {
3015         // Record all safepoints in this loop.
3016         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
3017         innermost->_safepts->push(n);
3018       }
3019     }
3020   }
3021 
3022   // Flag as post-visited now
3023   set_postvisited(n);
3024   return pre_order;
3025 }
3026 
3027 
3028 //------------------------------build_loop_early-------------------------------
3029 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3030 // First pass computes the earliest controlling node possible.  This is the
3031 // controlling input with the deepest dominating depth.
3032 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3033   while (worklist.size() != 0) {
3034     // Use local variables nstack_top_n & nstack_top_i to cache values
3035     // on nstack's top.
3036     Node *nstack_top_n = worklist.pop();
3037     uint  nstack_top_i = 0;
3038 //while_nstack_nonempty:
3039     while (true) {
3040       // Get parent node and next input's index from stack's top.
3041       Node  *n = nstack_top_n;
3042       uint   i = nstack_top_i;
3043       uint cnt = n->req(); // Count of inputs
3044       if (i == 0) {        // Pre-process the node.
3045         if( has_node(n) &&            // Have either loop or control already?
3046             !has_ctrl(n) ) {          // Have loop picked out already?
3047           // During "merge_many_backedges" we fold up several nested loops
3048           // into a single loop.  This makes the members of the original
3049           // loop bodies pointing to dead loops; they need to move up
3050           // to the new UNION'd larger loop.  I set the _head field of these
3051           // dead loops to NULL and the _parent field points to the owning
3052           // loop.  Shades of UNION-FIND algorithm.
3053           IdealLoopTree *ilt;
3054           while( !(ilt = get_loop(n))->_head ) {
3055             // Normally I would use a set_loop here.  But in this one special
3056             // case, it is legal (and expected) to change what loop a Node
3057             // belongs to.
3058             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3059           }
3060           // Remove safepoints ONLY if I've already seen I don't need one.
3061           // (the old code here would yank a 2nd safepoint after seeing a
3062           // first one, even though the 1st did not dominate in the loop body
3063           // and thus could be avoided indefinitely)
3064           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3065               is_deleteable_safept(n)) {
3066             Node *in = n->in(TypeFunc::Control);
3067             lazy_replace(n,in);       // Pull safepoint now
3068             if (ilt->_safepts != NULL) {
3069               ilt->_safepts->yank(n);
3070             }
3071             // Carry on with the recursion "as if" we are walking
3072             // only the control input
3073             if( !visited.test_set( in->_idx ) ) {
3074               worklist.push(in);      // Visit this guy later, using worklist
3075             }
3076             // Get next node from nstack:
3077             // - skip n's inputs processing by setting i > cnt;
3078             // - we also will not call set_early_ctrl(n) since
3079             //   has_node(n) == true (see the condition above).
3080             i = cnt + 1;
3081           }
3082         }
3083       } // if (i == 0)
3084 
3085       // Visit all inputs
3086       bool done = true;       // Assume all n's inputs will be processed
3087       while (i < cnt) {
3088         Node *in = n->in(i);
3089         ++i;
3090         if (in == NULL) continue;
3091         if (in->pinned() && !in->is_CFG())
3092           set_ctrl(in, in->in(0));
3093         int is_visited = visited.test_set( in->_idx );
3094         if (!has_node(in)) {  // No controlling input yet?
3095           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3096           assert( !is_visited, "visit only once" );
3097           nstack.push(n, i);  // Save parent node and next input's index.
3098           nstack_top_n = in;  // Process current input now.
3099           nstack_top_i = 0;
3100           done = false;       // Not all n's inputs processed.
3101           break; // continue while_nstack_nonempty;
3102         } else if (!is_visited) {
3103           // This guy has a location picked out for him, but has not yet
3104           // been visited.  Happens to all CFG nodes, for instance.
3105           // Visit him using the worklist instead of recursion, to break
3106           // cycles.  Since he has a location already we do not need to
3107           // find his location before proceeding with the current Node.
3108           worklist.push(in);  // Visit this guy later, using worklist
3109         }
3110       }
3111       if (done) {
3112         // All of n's inputs have been processed, complete post-processing.
3113 
3114         // Compute earliest point this Node can go.
3115         // CFG, Phi, pinned nodes already know their controlling input.
3116         if (!has_node(n)) {
3117           // Record earliest legal location
3118           set_early_ctrl( n );
3119         }
3120         if (nstack.is_empty()) {
3121           // Finished all nodes on stack.
3122           // Process next node on the worklist.
3123           break;
3124         }
3125         // Get saved parent node and next input's index.
3126         nstack_top_n = nstack.node();
3127         nstack_top_i = nstack.index();
3128         nstack.pop();
3129       }
3130     } // while (true)
3131   }
3132 }
3133 
3134 //------------------------------dom_lca_internal--------------------------------
3135 // Pair-wise LCA
3136 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3137   if( !n1 ) return n2;          // Handle NULL original LCA
3138   assert( n1->is_CFG(), "" );
3139   assert( n2->is_CFG(), "" );
3140   // find LCA of all uses
3141   uint d1 = dom_depth(n1);
3142   uint d2 = dom_depth(n2);
3143   while (n1 != n2) {
3144     if (d1 > d2) {
3145       n1 =      idom(n1);
3146       d1 = dom_depth(n1);
3147     } else if (d1 < d2) {
3148       n2 =      idom(n2);
3149       d2 = dom_depth(n2);
3150     } else {
3151       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3152       // of the tree might have the same depth.  These sections have
3153       // to be searched more carefully.
3154 
3155       // Scan up all the n1's with equal depth, looking for n2.
3156       Node *t1 = idom(n1);
3157       while (dom_depth(t1) == d1) {
3158         if (t1 == n2)  return n2;
3159         t1 = idom(t1);
3160       }
3161       // Scan up all the n2's with equal depth, looking for n1.
3162       Node *t2 = idom(n2);
3163       while (dom_depth(t2) == d2) {
3164         if (t2 == n1)  return n1;
3165         t2 = idom(t2);
3166       }
3167       // Move up to a new dominator-depth value as well as up the dom-tree.
3168       n1 = t1;
3169       n2 = t2;
3170       d1 = dom_depth(n1);
3171       d2 = dom_depth(n2);
3172     }
3173   }
3174   return n1;
3175 }
3176 
3177 //------------------------------compute_idom-----------------------------------
3178 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3179 // IDOMs are correct.
3180 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3181   assert( region->is_Region(), "" );
3182   Node *LCA = NULL;
3183   for( uint i = 1; i < region->req(); i++ ) {
3184     if( region->in(i) != C->top() )
3185       LCA = dom_lca( LCA, region->in(i) );
3186   }
3187   return LCA;
3188 }
3189 
3190 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3191   bool had_error = false;
3192 #ifdef ASSERT
3193   if (early != C->root()) {
3194     // Make sure that there's a dominance path from LCA to early
3195     Node* d = LCA;
3196     while (d != early) {
3197       if (d == C->root()) {
3198         dump_bad_graph("Bad graph detected in compute_lca_of_uses", n, early, LCA);
3199         tty->print_cr("*** Use %d isn't dominated by def %d ***", use->_idx, n->_idx);
3200         had_error = true;
3201         break;
3202       }
3203       d = idom(d);
3204     }
3205   }
3206 #endif
3207   return had_error;
3208 }
3209 
3210 
3211 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3212   // Compute LCA over list of uses
3213   bool had_error = false;
3214   Node *LCA = NULL;
3215   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3216     Node* c = n->fast_out(i);
3217     if (_nodes[c->_idx] == NULL)
3218       continue;                 // Skip the occasional dead node
3219     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3220       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3221         if( c->in(j) == n ) {   // Found matching input?
3222           Node *use = c->in(0)->in(j);
3223           if (_verify_only && use->is_top()) continue;
3224           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3225           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3226         }
3227       }
3228     } else {
3229       // For CFG data-users, use is in the block just prior
3230       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3231       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3232       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3233     }
3234   }
3235   assert(!had_error, "bad dominance");
3236   return LCA;
3237 }
3238 
3239 //------------------------------get_late_ctrl----------------------------------
3240 // Compute latest legal control.
3241 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
3242   assert(early != NULL, "early control should not be NULL");
3243 
3244   Node* LCA = compute_lca_of_uses(n, early);
3245 #ifdef ASSERT
3246   if (LCA == C->root() && LCA != early) {
3247     // def doesn't dominate uses so print some useful debugging output
3248     compute_lca_of_uses(n, early, true);
3249   }
3250 #endif
3251 
3252   // if this is a load, check for anti-dependent stores
3253   // We use a conservative algorithm to identify potential interfering
3254   // instructions and for rescheduling the load.  The users of the memory
3255   // input of this load are examined.  Any use which is not a load and is
3256   // dominated by early is considered a potentially interfering store.
3257   // This can produce false positives.
3258   if (n->is_Load() && LCA != early) {
3259     Node_List worklist;
3260 
3261     Node *mem = n->in(MemNode::Memory);
3262     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3263       Node* s = mem->fast_out(i);
3264       worklist.push(s);
3265     }
3266     while(worklist.size() != 0 && LCA != early) {
3267       Node* s = worklist.pop();
3268       if (s->is_Load()) {
3269         continue;
3270       } else if (s->is_MergeMem()) {
3271         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3272           Node* s1 = s->fast_out(i);
3273           worklist.push(s1);
3274         }
3275       } else {
3276         Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3277         assert(sctrl != NULL || s->outcnt() == 0, "must have control");
3278         if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3279           LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3280         }
3281       }
3282     }
3283   }
3284 
3285   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
3286   return LCA;
3287 }
3288 
3289 // true if CFG node d dominates CFG node n
3290 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
3291   if (d == n)
3292     return true;
3293   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
3294   uint dd = dom_depth(d);
3295   while (dom_depth(n) >= dd) {
3296     if (n == d)
3297       return true;
3298     n = idom(n);
3299   }
3300   return false;
3301 }
3302 
3303 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
3304 // Pair-wise LCA with tags.
3305 // Tag each index with the node 'tag' currently being processed
3306 // before advancing up the dominator chain using idom().
3307 // Later calls that find a match to 'tag' know that this path has already
3308 // been considered in the current LCA (which is input 'n1' by convention).
3309 // Since get_late_ctrl() is only called once for each node, the tag array
3310 // does not need to be cleared between calls to get_late_ctrl().
3311 // Algorithm trades a larger constant factor for better asymptotic behavior
3312 //
3313 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
3314   uint d1 = dom_depth(n1);
3315   uint d2 = dom_depth(n2);
3316 
3317   do {
3318     if (d1 > d2) {
3319       // current lca is deeper than n2
3320       _dom_lca_tags.map(n1->_idx, tag);
3321       n1 =      idom(n1);
3322       d1 = dom_depth(n1);
3323     } else if (d1 < d2) {
3324       // n2 is deeper than current lca
3325       Node *memo = _dom_lca_tags[n2->_idx];
3326       if( memo == tag ) {
3327         return n1;    // Return the current LCA
3328       }
3329       _dom_lca_tags.map(n2->_idx, tag);
3330       n2 =      idom(n2);
3331       d2 = dom_depth(n2);
3332     } else {
3333       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3334       // of the tree might have the same depth.  These sections have
3335       // to be searched more carefully.
3336 
3337       // Scan up all the n1's with equal depth, looking for n2.
3338       _dom_lca_tags.map(n1->_idx, tag);
3339       Node *t1 = idom(n1);
3340       while (dom_depth(t1) == d1) {
3341         if (t1 == n2)  return n2;
3342         _dom_lca_tags.map(t1->_idx, tag);
3343         t1 = idom(t1);
3344       }
3345       // Scan up all the n2's with equal depth, looking for n1.
3346       _dom_lca_tags.map(n2->_idx, tag);
3347       Node *t2 = idom(n2);
3348       while (dom_depth(t2) == d2) {
3349         if (t2 == n1)  return n1;
3350         _dom_lca_tags.map(t2->_idx, tag);
3351         t2 = idom(t2);
3352       }
3353       // Move up to a new dominator-depth value as well as up the dom-tree.
3354       n1 = t1;
3355       n2 = t2;
3356       d1 = dom_depth(n1);
3357       d2 = dom_depth(n2);
3358     }
3359   } while (n1 != n2);
3360   return n1;
3361 }
3362 
3363 //------------------------------init_dom_lca_tags------------------------------
3364 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3365 // Intended use does not involve any growth for the array, so it could
3366 // be of fixed size.
3367 void PhaseIdealLoop::init_dom_lca_tags() {
3368   uint limit = C->unique() + 1;
3369   _dom_lca_tags.map( limit, NULL );
3370 #ifdef ASSERT
3371   for( uint i = 0; i < limit; ++i ) {
3372     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3373   }
3374 #endif // ASSERT
3375 }
3376 
3377 //------------------------------clear_dom_lca_tags------------------------------
3378 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3379 // Intended use does not involve any growth for the array, so it could
3380 // be of fixed size.
3381 void PhaseIdealLoop::clear_dom_lca_tags() {
3382   uint limit = C->unique() + 1;
3383   _dom_lca_tags.map( limit, NULL );
3384   _dom_lca_tags.clear();
3385 #ifdef ASSERT
3386   for( uint i = 0; i < limit; ++i ) {
3387     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3388   }
3389 #endif // ASSERT
3390 }
3391 
3392 //------------------------------build_loop_late--------------------------------
3393 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3394 // Second pass finds latest legal placement, and ideal loop placement.
3395 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3396   while (worklist.size() != 0) {
3397     Node *n = worklist.pop();
3398     // Only visit once
3399     if (visited.test_set(n->_idx)) continue;
3400     uint cnt = n->outcnt();
3401     uint   i = 0;
3402     while (true) {
3403       assert( _nodes[n->_idx], "no dead nodes" );
3404       // Visit all children
3405       if (i < cnt) {
3406         Node* use = n->raw_out(i);
3407         ++i;
3408         // Check for dead uses.  Aggressively prune such junk.  It might be
3409         // dead in the global sense, but still have local uses so I cannot
3410         // easily call 'remove_dead_node'.
3411         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
3412           // Due to cycles, we might not hit the same fixed point in the verify
3413           // pass as we do in the regular pass.  Instead, visit such phis as
3414           // simple uses of the loop head.
3415           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
3416             if( !visited.test(use->_idx) )
3417               worklist.push(use);
3418           } else if( !visited.test_set(use->_idx) ) {
3419             nstack.push(n, i); // Save parent and next use's index.
3420             n   = use;         // Process all children of current use.
3421             cnt = use->outcnt();
3422             i   = 0;
3423           }
3424         } else {
3425           // Do not visit around the backedge of loops via data edges.
3426           // push dead code onto a worklist
3427           _deadlist.push(use);
3428         }
3429       } else {
3430         // All of n's children have been processed, complete post-processing.
3431         build_loop_late_post(n);
3432         if (nstack.is_empty()) {
3433           // Finished all nodes on stack.
3434           // Process next node on the worklist.
3435           break;
3436         }
3437         // Get saved parent node and next use's index. Visit the rest of uses.
3438         n   = nstack.node();
3439         cnt = n->outcnt();
3440         i   = nstack.index();
3441         nstack.pop();
3442       }
3443     }
3444   }
3445 }
3446 
3447 //------------------------------build_loop_late_post---------------------------
3448 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3449 // Second pass finds latest legal placement, and ideal loop placement.
3450 void PhaseIdealLoop::build_loop_late_post( Node *n ) {
3451 
3452   if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
3453     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
3454   }
3455 
3456 #ifdef ASSERT
3457   if (_verify_only && !n->is_CFG()) {
3458     // Check def-use domination.
3459     compute_lca_of_uses(n, get_ctrl(n), true /* verify */);
3460   }
3461 #endif
3462 
3463   // CFG and pinned nodes already handled
3464   if( n->in(0) ) {
3465     if( n->in(0)->is_top() ) return; // Dead?
3466 
3467     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
3468     // _must_ be pinned (they have to observe their control edge of course).
3469     // Unlike Stores (which modify an unallocable resource, the memory
3470     // state), Mods/Loads can float around.  So free them up.
3471     bool pinned = true;
3472     switch( n->Opcode() ) {
3473     case Op_DivI:
3474     case Op_DivF:
3475     case Op_DivD:
3476     case Op_ModI:
3477     case Op_ModF:
3478     case Op_ModD:
3479     case Op_LoadB:              // Same with Loads; they can sink
3480     case Op_LoadUB:             // during loop optimizations.
3481     case Op_LoadUS:
3482     case Op_LoadD:
3483     case Op_LoadF:
3484     case Op_LoadI:
3485     case Op_LoadKlass:
3486     case Op_LoadNKlass:
3487     case Op_LoadL:
3488     case Op_LoadS:
3489     case Op_LoadP:
3490     case Op_LoadN:
3491     case Op_LoadRange:
3492     case Op_LoadD_unaligned:
3493     case Op_LoadL_unaligned:
3494     case Op_StrComp:            // Does a bunch of load-like effects
3495     case Op_StrEquals:
3496     case Op_StrIndexOf:

3497     case Op_AryEq:

3498       pinned = false;
3499     }
3500     if( pinned ) {
3501       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
3502       if( !chosen_loop->_child )       // Inner loop?
3503         chosen_loop->_body.push(n); // Collect inner loops
3504       return;
3505     }
3506   } else {                      // No slot zero
3507     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
3508       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
3509       return;
3510     }
3511     assert(!n->is_CFG() || n->outcnt() == 0, "");
3512   }
3513 
3514   // Do I have a "safe range" I can select over?
3515   Node *early = get_ctrl(n);// Early location already computed
3516 
3517   // Compute latest point this Node can go
3518   Node *LCA = get_late_ctrl( n, early );
3519   // LCA is NULL due to uses being dead
3520   if( LCA == NULL ) {
3521 #ifdef ASSERT
3522     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
3523       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
3524     }
3525 #endif
3526     _nodes.map(n->_idx, 0);     // This node is useless
3527     _deadlist.push(n);
3528     return;
3529   }
3530   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
3531 
3532   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
3533   Node *least = legal;          // Best legal position so far
3534   while( early != legal ) {     // While not at earliest legal
3535 #ifdef ASSERT
3536     if (legal->is_Start() && !early->is_Root()) {
3537       // Bad graph. Print idom path and fail.
3538       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
3539       assert(false, "Bad graph detected in build_loop_late");
3540     }
3541 #endif
3542     // Find least loop nesting depth
3543     legal = idom(legal);        // Bump up the IDOM tree
3544     // Check for lower nesting depth
3545     if( get_loop(legal)->_nest < get_loop(least)->_nest )
3546       least = legal;
3547   }
3548   assert(early == legal || legal != C->root(), "bad dominance of inputs");
3549 
3550   // Try not to place code on a loop entry projection
3551   // which can inhibit range check elimination.
3552   if (least != early) {
3553     Node* ctrl_out = least->unique_ctrl_out();
3554     if (ctrl_out && ctrl_out->is_CountedLoop() &&
3555         least == ctrl_out->in(LoopNode::EntryControl)) {
3556       Node* least_dom = idom(least);
3557       if (get_loop(least_dom)->is_member(get_loop(least))) {
3558         least = least_dom;
3559       }
3560     }
3561   }
3562 
3563 #ifdef ASSERT
3564   // If verifying, verify that 'verify_me' has a legal location
3565   // and choose it as our location.
3566   if( _verify_me ) {
3567     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
3568     Node *legal = LCA;
3569     while( early != legal ) {   // While not at earliest legal
3570       if( legal == v_ctrl ) break;  // Check for prior good location
3571       legal = idom(legal)      ;// Bump up the IDOM tree
3572     }
3573     // Check for prior good location
3574     if( legal == v_ctrl ) least = legal; // Keep prior if found
3575   }
3576 #endif
3577 
3578   // Assign discovered "here or above" point
3579   least = find_non_split_ctrl(least);
3580   set_ctrl(n, least);
3581 
3582   // Collect inner loop bodies
3583   IdealLoopTree *chosen_loop = get_loop(least);
3584   if( !chosen_loop->_child )   // Inner loop?
3585     chosen_loop->_body.push(n);// Collect inner loops
3586 }
3587 
3588 #ifdef ASSERT
3589 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
3590   tty->print_cr("%s", msg);
3591   tty->print("n: "); n->dump();
3592   tty->print("early(n): "); early->dump();
3593   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
3594       n->in(0) != early && !n->in(0)->is_Root()) {
3595     tty->print("n->in(0): "); n->in(0)->dump();
3596   }
3597   for (uint i = 1; i < n->req(); i++) {
3598     Node* in1 = n->in(i);
3599     if (in1 != NULL && in1 != n && !in1->is_top()) {
3600       tty->print("n->in(%d): ", i); in1->dump();
3601       Node* in1_early = get_ctrl(in1);
3602       tty->print("early(n->in(%d)): ", i); in1_early->dump();
3603       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
3604           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
3605         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
3606       }
3607       for (uint j = 1; j < in1->req(); j++) {
3608         Node* in2 = in1->in(j);
3609         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
3610           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
3611           Node* in2_early = get_ctrl(in2);
3612           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
3613           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
3614               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
3615             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
3616           }
3617         }
3618       }
3619     }
3620   }
3621   tty->cr();
3622   tty->print("LCA(n): "); LCA->dump();
3623   for (uint i = 0; i < n->outcnt(); i++) {
3624     Node* u1 = n->raw_out(i);
3625     if (u1 == n)
3626       continue;
3627     tty->print("n->out(%d): ", i); u1->dump();
3628     if (u1->is_CFG()) {
3629       for (uint j = 0; j < u1->outcnt(); j++) {
3630         Node* u2 = u1->raw_out(j);
3631         if (u2 != u1 && u2 != n && u2->is_CFG()) {
3632           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3633         }
3634       }
3635     } else {
3636       Node* u1_later = get_ctrl(u1);
3637       tty->print("later(n->out(%d)): ", i); u1_later->dump();
3638       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
3639           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
3640         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
3641       }
3642       for (uint j = 0; j < u1->outcnt(); j++) {
3643         Node* u2 = u1->raw_out(j);
3644         if (u2 == n || u2 == u1)
3645           continue;
3646         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3647         if (!u2->is_CFG()) {
3648           Node* u2_later = get_ctrl(u2);
3649           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
3650           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
3651               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
3652             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
3653           }
3654         }
3655       }
3656     }
3657   }
3658   tty->cr();
3659   int ct = 0;
3660   Node *dbg_legal = LCA;
3661   while(!dbg_legal->is_Start() && ct < 100) {
3662     tty->print("idom[%d] ",ct); dbg_legal->dump();
3663     ct++;
3664     dbg_legal = idom(dbg_legal);
3665   }
3666   tty->cr();
3667 }
3668 #endif
3669 
3670 #ifndef PRODUCT
3671 //------------------------------dump-------------------------------------------
3672 void PhaseIdealLoop::dump( ) const {
3673   ResourceMark rm;
3674   Arena* arena = Thread::current()->resource_area();
3675   Node_Stack stack(arena, C->live_nodes() >> 2);
3676   Node_List rpo_list;
3677   VectorSet visited(arena);
3678   visited.set(C->top()->_idx);
3679   rpo( C->root(), stack, visited, rpo_list );
3680   // Dump root loop indexed by last element in PO order
3681   dump( _ltree_root, rpo_list.size(), rpo_list );
3682 }
3683 
3684 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
3685   loop->dump_head();
3686 
3687   // Now scan for CFG nodes in the same loop
3688   for( uint j=idx; j > 0;  j-- ) {
3689     Node *n = rpo_list[j-1];
3690     if( !_nodes[n->_idx] )      // Skip dead nodes
3691       continue;
3692     if( get_loop(n) != loop ) { // Wrong loop nest
3693       if( get_loop(n)->_head == n &&    // Found nested loop?
3694           get_loop(n)->_parent == loop )
3695         dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
3696       continue;
3697     }
3698 
3699     // Dump controlling node
3700     for( uint x = 0; x < loop->_nest; x++ )
3701       tty->print("  ");
3702     tty->print("C");
3703     if( n == C->root() ) {
3704       n->dump();
3705     } else {
3706       Node* cached_idom   = idom_no_update(n);
3707       Node *computed_idom = n->in(0);
3708       if( n->is_Region() ) {
3709         computed_idom = compute_idom(n);
3710         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
3711         // any MultiBranch ctrl node), so apply a similar transform to
3712         // the cached idom returned from idom_no_update.
3713         cached_idom = find_non_split_ctrl(cached_idom);
3714       }
3715       tty->print(" ID:%d",computed_idom->_idx);
3716       n->dump();
3717       if( cached_idom != computed_idom ) {
3718         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
3719                       computed_idom->_idx, cached_idom->_idx);
3720       }
3721     }
3722     // Dump nodes it controls
3723     for( uint k = 0; k < _nodes.Size(); k++ ) {
3724       // (k < C->unique() && get_ctrl(find(k)) == n)
3725       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
3726         Node *m = C->root()->find(k);
3727         if( m && m->outcnt() > 0 ) {
3728           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
3729             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
3730                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
3731           }
3732           for( uint j = 0; j < loop->_nest; j++ )
3733             tty->print("  ");
3734           tty->print(" ");
3735           m->dump();
3736         }
3737       }
3738     }
3739   }
3740 }
3741 
3742 // Collect a R-P-O for the whole CFG.
3743 // Result list is in post-order (scan backwards for RPO)
3744 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
3745   stk.push(start, 0);
3746   visited.set(start->_idx);
3747 
3748   while (stk.is_nonempty()) {
3749     Node* m   = stk.node();
3750     uint  idx = stk.index();
3751     if (idx < m->outcnt()) {
3752       stk.set_index(idx + 1);
3753       Node* n = m->raw_out(idx);
3754       if (n->is_CFG() && !visited.test_set(n->_idx)) {
3755         stk.push(n, 0);
3756       }
3757     } else {
3758       rpo_list.push(m);
3759       stk.pop();
3760     }
3761   }
3762 }
3763 #endif
3764 
3765 
3766 //=============================================================================
3767 //------------------------------LoopTreeIterator-----------------------------------
3768 
3769 // Advance to next loop tree using a preorder, left-to-right traversal.
3770 void LoopTreeIterator::next() {
3771   assert(!done(), "must not be done.");
3772   if (_curnt->_child != NULL) {
3773     _curnt = _curnt->_child;
3774   } else if (_curnt->_next != NULL) {
3775     _curnt = _curnt->_next;
3776   } else {
3777     while (_curnt != _root && _curnt->_next == NULL) {
3778       _curnt = _curnt->_parent;
3779     }
3780     if (_curnt == _root) {
3781       _curnt = NULL;
3782       assert(done(), "must be done.");
3783     } else {
3784       assert(_curnt->_next != NULL, "must be more to do");
3785       _curnt = _curnt->_next;
3786     }
3787   }
3788 }
--- EOF ---