rev 4773 : 8005849: JEP 167: Event-Based JVM Tracing
Reviewed-by: acorn, coleenp, sla
Contributed-by: Karen Kinnear <karen.kinnear@oracle.com>, Bengt Rutisson <bengt.rutisson@oracle.com>, Calvin Cheung <calvin.cheung@oracle.com>, Erik Gahlin <erik.gahlin@oracle.com>, Erik Helin <erik.helin@oracle.com>, Jesper Wilhelmsson <jesper.wilhelmsson@oracle.com>, Keith McGuigan <keith.mcguigan@oracle.com>, Mattias Tobiasson <mattias.tobiasson@oracle.com>, Markus Gronlund <markus.gronlund@oracle.com>, Mikael Auno <mikael.auno@oracle.com>, Nils Eliasson <nils.eliasson@oracle.com>, Nils Loodin <nils.loodin@oracle.com>, Rickard Backman <rickard.backman@oracle.com>, Staffan Larsen <staffan.larsen@oracle.com>, Stefan Karlsson <stefan.karlsson@oracle.com>, Yekaterina Kantserova <yekaterina.kantserova@oracle.com>

   1 /*
   2  * Copyright (c) 1998, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "ci/ciMethodData.hpp"
  27 #include "compiler/compileLog.hpp"
  28 #include "libadt/vectset.hpp"
  29 #include "memory/allocation.inline.hpp"
  30 #include "opto/addnode.hpp"
  31 #include "opto/callnode.hpp"
  32 #include "opto/connode.hpp"
  33 #include "opto/divnode.hpp"
  34 #include "opto/idealGraphPrinter.hpp"
  35 #include "opto/loopnode.hpp"
  36 #include "opto/mulnode.hpp"
  37 #include "opto/rootnode.hpp"
  38 #include "opto/superword.hpp"
  39 
  40 //=============================================================================
  41 //------------------------------is_loop_iv-------------------------------------
  42 // Determine if a node is Counted loop induction variable.
  43 // The method is declared in node.hpp.
  44 const Node* Node::is_loop_iv() const {
  45   if (this->is_Phi() && !this->as_Phi()->is_copy() &&
  46       this->as_Phi()->region()->is_CountedLoop() &&
  47       this->as_Phi()->region()->as_CountedLoop()->phi() == this) {
  48     return this;
  49   } else {
  50     return NULL;
  51   }
  52 }
  53 
  54 //=============================================================================
  55 //------------------------------dump_spec--------------------------------------
  56 // Dump special per-node info
  57 #ifndef PRODUCT
  58 void LoopNode::dump_spec(outputStream *st) const {
  59   if (is_inner_loop()) st->print( "inner " );
  60   if (is_partial_peel_loop()) st->print( "partial_peel " );
  61   if (partial_peel_has_failed()) st->print( "partial_peel_failed " );
  62 }
  63 #endif
  64 
  65 //------------------------------is_valid_counted_loop-------------------------
  66 bool LoopNode::is_valid_counted_loop() const {
  67   if (is_CountedLoop()) {
  68     CountedLoopNode*    l  = as_CountedLoop();
  69     CountedLoopEndNode* le = l->loopexit();
  70     if (le != NULL &&
  71         le->proj_out(1 /* true */) == l->in(LoopNode::LoopBackControl)) {
  72       Node* phi  = l->phi();
  73       Node* exit = le->proj_out(0 /* false */);
  74       if (exit != NULL && exit->Opcode() == Op_IfFalse &&
  75           phi != NULL && phi->is_Phi() &&
  76           phi->in(LoopNode::LoopBackControl) == l->incr() &&
  77           le->loopnode() == l && le->stride_is_con()) {
  78         return true;
  79       }
  80     }
  81   }
  82   return false;
  83 }
  84 
  85 //------------------------------get_early_ctrl---------------------------------
  86 // Compute earliest legal control
  87 Node *PhaseIdealLoop::get_early_ctrl( Node *n ) {
  88   assert( !n->is_Phi() && !n->is_CFG(), "this code only handles data nodes" );
  89   uint i;
  90   Node *early;
  91   if (n->in(0) && !n->is_expensive()) {
  92     early = n->in(0);
  93     if (!early->is_CFG()) // Might be a non-CFG multi-def
  94       early = get_ctrl(early);        // So treat input as a straight data input
  95     i = 1;
  96   } else {
  97     early = get_ctrl(n->in(1));
  98     i = 2;
  99   }
 100   uint e_d = dom_depth(early);
 101   assert( early, "" );
 102   for (; i < n->req(); i++) {
 103     Node *cin = get_ctrl(n->in(i));
 104     assert( cin, "" );
 105     // Keep deepest dominator depth
 106     uint c_d = dom_depth(cin);
 107     if (c_d > e_d) {           // Deeper guy?
 108       early = cin;              // Keep deepest found so far
 109       e_d = c_d;
 110     } else if (c_d == e_d &&    // Same depth?
 111                early != cin) { // If not equal, must use slower algorithm
 112       // If same depth but not equal, one _must_ dominate the other
 113       // and we want the deeper (i.e., dominated) guy.
 114       Node *n1 = early;
 115       Node *n2 = cin;
 116       while (1) {
 117         n1 = idom(n1);          // Walk up until break cycle
 118         n2 = idom(n2);
 119         if (n1 == cin ||        // Walked early up to cin
 120             dom_depth(n2) < c_d)
 121           break;                // early is deeper; keep him
 122         if (n2 == early ||      // Walked cin up to early
 123             dom_depth(n1) < c_d) {
 124           early = cin;          // cin is deeper; keep him
 125           break;
 126         }
 127       }
 128       e_d = dom_depth(early);   // Reset depth register cache
 129     }
 130   }
 131 
 132   // Return earliest legal location
 133   assert(early == find_non_split_ctrl(early), "unexpected early control");
 134 
 135   if (n->is_expensive()) {
 136     assert(n->in(0), "should have control input");
 137     early = get_early_ctrl_for_expensive(n, early);
 138   }
 139 
 140   return early;
 141 }
 142 
 143 //------------------------------get_early_ctrl_for_expensive---------------------------------
 144 // Move node up the dominator tree as high as legal while still beneficial
 145 Node *PhaseIdealLoop::get_early_ctrl_for_expensive(Node *n, Node* earliest) {
 146   assert(n->in(0) && n->is_expensive(), "expensive node with control input here");
 147   assert(OptimizeExpensiveOps, "optimization off?");
 148 
 149   Node* ctl = n->in(0);
 150   assert(ctl->is_CFG(), "expensive input 0 must be cfg");
 151   uint min_dom_depth = dom_depth(earliest);
 152 #ifdef ASSERT
 153   if (!is_dominator(ctl, earliest) && !is_dominator(earliest, ctl)) {
 154     dump_bad_graph("Bad graph detected in get_early_ctrl_for_expensive", n, earliest, ctl);
 155     assert(false, "Bad graph detected in get_early_ctrl_for_expensive");
 156   }
 157 #endif
 158   if (dom_depth(ctl) < min_dom_depth) {
 159     return earliest;
 160   }
 161 
 162   while (1) {
 163     Node *next = ctl;
 164     // Moving the node out of a loop on the projection of a If
 165     // confuses loop predication. So once we hit a Loop in a If branch
 166     // that doesn't branch to an UNC, we stop. The code that process
 167     // expensive nodes will notice the loop and skip over it to try to
 168     // move the node further up.
 169     if (ctl->is_CountedLoop() && ctl->in(1) != NULL && ctl->in(1)->in(0) != NULL && ctl->in(1)->in(0)->is_If()) {
 170       if (!is_uncommon_trap_if_pattern(ctl->in(1)->as_Proj(), Deoptimization::Reason_none)) {
 171         break;
 172       }
 173       next = idom(ctl->in(1)->in(0));
 174     } else if (ctl->is_Proj()) {
 175       // We only move it up along a projection if the projection is
 176       // the single control projection for its parent: same code path,
 177       // if it's a If with UNC or fallthrough of a call.
 178       Node* parent_ctl = ctl->in(0);
 179       if (parent_ctl == NULL) {
 180         break;
 181       } else if (parent_ctl->is_CountedLoopEnd() && parent_ctl->as_CountedLoopEnd()->loopnode() != NULL) {
 182         next = parent_ctl->as_CountedLoopEnd()->loopnode()->init_control();
 183       } else if (parent_ctl->is_If()) {
 184         if (!is_uncommon_trap_if_pattern(ctl->as_Proj(), Deoptimization::Reason_none)) {
 185           break;
 186         }
 187         assert(idom(ctl) == parent_ctl, "strange");
 188         next = idom(parent_ctl);
 189       } else if (ctl->is_CatchProj()) {
 190         if (ctl->as_Proj()->_con != CatchProjNode::fall_through_index) {
 191           break;
 192         }
 193         assert(parent_ctl->in(0)->in(0)->is_Call(), "strange graph");
 194         next = parent_ctl->in(0)->in(0)->in(0);
 195       } else {
 196         // Check if parent control has a single projection (this
 197         // control is the only possible successor of the parent
 198         // control). If so, we can try to move the node above the
 199         // parent control.
 200         int nb_ctl_proj = 0;
 201         for (DUIterator_Fast imax, i = parent_ctl->fast_outs(imax); i < imax; i++) {
 202           Node *p = parent_ctl->fast_out(i);
 203           if (p->is_Proj() && p->is_CFG()) {
 204             nb_ctl_proj++;
 205             if (nb_ctl_proj > 1) {
 206               break;
 207             }
 208           }
 209         }
 210 
 211         if (nb_ctl_proj > 1) {
 212           break;
 213         }
 214         assert(parent_ctl->is_Start() || parent_ctl->is_MemBar() || parent_ctl->is_Call(), "unexpected node");
 215         assert(idom(ctl) == parent_ctl, "strange");
 216         next = idom(parent_ctl);
 217       }
 218     } else {
 219       next = idom(ctl);
 220     }
 221     if (next->is_Root() || next->is_Start() || dom_depth(next) < min_dom_depth) {
 222       break;
 223     }
 224     ctl = next;
 225   }
 226 
 227   if (ctl != n->in(0)) {
 228     _igvn.hash_delete(n);
 229     n->set_req(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)
 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   // =================================================
 440   // ---- SUCCESS!   Found A Trip-Counted Loop!  -----
 441   //
 442   assert(x->Opcode() == Op_Loop, "regular loops only");
 443   C->print_method(PHASE_BEFORE_CLOOPS, 3);
 444 
 445   Node *hook = new (C) Node(6);
 446 
 447   if (LoopLimitCheck) {
 448 
 449   // ===================================================
 450   // Generate loop limit check to avoid integer overflow
 451   // in cases like next (cyclic loops):
 452   //
 453   // for (i=0; i <= max_jint; i++) {}
 454   // for (i=0; i <  max_jint; i+=2) {}
 455   //
 456   //
 457   // Limit check predicate depends on the loop test:
 458   //
 459   // for(;i != limit; i++)       --> limit <= (max_jint)
 460   // for(;i <  limit; i+=stride) --> limit <= (max_jint - stride + 1)
 461   // for(;i <= limit; i+=stride) --> limit <= (max_jint - stride    )
 462   //
 463 
 464   // Check if limit is excluded to do more precise int overflow check.
 465   bool incl_limit = (bt == BoolTest::le || bt == BoolTest::ge);
 466   int stride_m  = stride_con - (incl_limit ? 0 : (stride_con > 0 ? 1 : -1));
 467 
 468   // If compare points directly to the phi we need to adjust
 469   // the compare so that it points to the incr. Limit have
 470   // to be adjusted to keep trip count the same and the
 471   // adjusted limit should be checked for int overflow.
 472   if (phi_incr != NULL) {
 473     stride_m  += stride_con;
 474   }
 475 
 476   if (limit->is_Con()) {
 477     int limit_con = limit->get_int();
 478     if ((stride_con > 0 && limit_con > (max_jint - stride_m)) ||
 479         (stride_con < 0 && limit_con < (min_jint - stride_m))) {
 480       // Bailout: it could be integer overflow.
 481       return false;
 482     }
 483   } else if ((stride_con > 0 && limit_t->_hi <= (max_jint - stride_m)) ||
 484              (stride_con < 0 && limit_t->_lo >= (min_jint - stride_m))) {
 485       // Limit's type may satisfy the condition, for example,
 486       // when it is an array length.
 487   } else {
 488     // Generate loop's limit check.
 489     // Loop limit check predicate should be near the loop.
 490     ProjNode *limit_check_proj = find_predicate_insertion_point(init_control, Deoptimization::Reason_loop_limit_check);
 491     if (!limit_check_proj) {
 492       // The limit check predicate is not generated if this method trapped here before.
 493 #ifdef ASSERT
 494       if (TraceLoopLimitCheck) {
 495         tty->print("missing loop limit check:");
 496         loop->dump_head();
 497         x->dump(1);
 498       }
 499 #endif
 500       return false;
 501     }
 502 
 503     IfNode* check_iff = limit_check_proj->in(0)->as_If();
 504     Node* cmp_limit;
 505     Node* bol;
 506 
 507     if (stride_con > 0) {
 508       cmp_limit = new (C) CmpINode(limit, _igvn.intcon(max_jint - stride_m));
 509       bol = new (C) BoolNode(cmp_limit, BoolTest::le);
 510     } else {
 511       cmp_limit = new (C) CmpINode(limit, _igvn.intcon(min_jint - stride_m));
 512       bol = new (C) BoolNode(cmp_limit, BoolTest::ge);
 513     }
 514     cmp_limit = _igvn.register_new_node_with_optimizer(cmp_limit);
 515     bol = _igvn.register_new_node_with_optimizer(bol);
 516     set_subtree_ctrl(bol);
 517 
 518     // Replace condition in original predicate but preserve Opaque node
 519     // so that previous predicates could be found.
 520     assert(check_iff->in(1)->Opcode() == Op_Conv2B &&
 521            check_iff->in(1)->in(1)->Opcode() == Op_Opaque1, "");
 522     Node* opq = check_iff->in(1)->in(1);
 523     _igvn.hash_delete(opq);
 524     opq->set_req(1, bol);
 525     // Update ctrl.
 526     set_ctrl(opq, check_iff->in(0));
 527     set_ctrl(check_iff->in(1), check_iff->in(0));
 528 
 529 #ifndef PRODUCT
 530     // report that the loop predication has been actually performed
 531     // for this loop
 532     if (TraceLoopLimitCheck) {
 533       tty->print_cr("Counted Loop Limit Check generated:");
 534       debug_only( bol->dump(2); )
 535     }
 536 #endif
 537   }
 538 
 539   if (phi_incr != NULL) {
 540     // If compare points directly to the phi we need to adjust
 541     // the compare so that it points to the incr. Limit have
 542     // to be adjusted to keep trip count the same and we
 543     // should avoid int overflow.
 544     //
 545     //   i = init; do {} while(i++ < limit);
 546     // is converted to
 547     //   i = init; do {} while(++i < limit+1);
 548     //
 549     limit = gvn->transform(new (C) AddINode(limit, stride));
 550   }
 551 
 552   // Now we need to canonicalize loop condition.
 553   if (bt == BoolTest::ne) {
 554     assert(stride_con == 1 || stride_con == -1, "simple increment only");
 555     // 'ne' can be replaced with 'lt' only when init < limit.
 556     if (stride_con > 0 && init_t->_hi < limit_t->_lo)
 557       bt = BoolTest::lt;
 558     // 'ne' can be replaced with 'gt' only when init > limit.
 559     if (stride_con < 0 && init_t->_lo > limit_t->_hi)
 560       bt = BoolTest::gt;
 561   }
 562 
 563   if (incl_limit) {
 564     // The limit check guaranties that 'limit <= (max_jint - stride)' so
 565     // we can convert 'i <= limit' to 'i < limit+1' since stride != 0.
 566     //
 567     Node* one = (stride_con > 0) ? gvn->intcon( 1) : gvn->intcon(-1);
 568     limit = gvn->transform(new (C) AddINode(limit, one));
 569     if (bt == BoolTest::le)
 570       bt = BoolTest::lt;
 571     else if (bt == BoolTest::ge)
 572       bt = BoolTest::gt;
 573     else
 574       ShouldNotReachHere();
 575   }
 576   set_subtree_ctrl( limit );
 577 
 578   } else { // LoopLimitCheck
 579 
 580   // If compare points to incr, we are ok.  Otherwise the compare
 581   // can directly point to the phi; in this case adjust the compare so that
 582   // it points to the incr by adjusting the limit.
 583   if (cmp->in(1) == phi || cmp->in(2) == phi)
 584     limit = gvn->transform(new (C) AddINode(limit,stride));
 585 
 586   // trip-count for +-tive stride should be: (limit - init_trip + stride - 1)/stride.
 587   // Final value for iterator should be: trip_count * stride + init_trip.
 588   Node *one_p = gvn->intcon( 1);
 589   Node *one_m = gvn->intcon(-1);
 590 
 591   Node *trip_count = NULL;
 592   switch( bt ) {
 593   case BoolTest::eq:
 594     ShouldNotReachHere();
 595   case BoolTest::ne:            // Ahh, the case we desire
 596     if (stride_con == 1)
 597       trip_count = gvn->transform(new (C) SubINode(limit,init_trip));
 598     else if (stride_con == -1)
 599       trip_count = gvn->transform(new (C) SubINode(init_trip,limit));
 600     else
 601       ShouldNotReachHere();
 602     set_subtree_ctrl(trip_count);
 603     //_loop.map(trip_count->_idx,loop(limit));
 604     break;
 605   case BoolTest::le:            // Maybe convert to '<' case
 606     limit = gvn->transform(new (C) AddINode(limit,one_p));
 607     set_subtree_ctrl( limit );
 608     hook->init_req(4, limit);
 609 
 610     bt = BoolTest::lt;
 611     // Make the new limit be in the same loop nest as the old limit
 612     //_loop.map(limit->_idx,limit_loop);
 613     // Fall into next case
 614   case BoolTest::lt: {          // Maybe convert to '!=' case
 615     if (stride_con < 0) // Count down loop rolls through MAXINT
 616       ShouldNotReachHere();
 617     Node *range = gvn->transform(new (C) SubINode(limit,init_trip));
 618     set_subtree_ctrl( range );
 619     hook->init_req(0, range);
 620 
 621     Node *bias  = gvn->transform(new (C) AddINode(range,stride));
 622     set_subtree_ctrl( bias );
 623     hook->init_req(1, bias);
 624 
 625     Node *bias1 = gvn->transform(new (C) AddINode(bias,one_m));
 626     set_subtree_ctrl( bias1 );
 627     hook->init_req(2, bias1);
 628 
 629     trip_count  = gvn->transform(new (C) DivINode(0,bias1,stride));
 630     set_subtree_ctrl( trip_count );
 631     hook->init_req(3, trip_count);
 632     break;
 633   }
 634 
 635   case BoolTest::ge:            // Maybe convert to '>' case
 636     limit = gvn->transform(new (C) AddINode(limit,one_m));
 637     set_subtree_ctrl( limit );
 638     hook->init_req(4 ,limit);
 639 
 640     bt = BoolTest::gt;
 641     // Make the new limit be in the same loop nest as the old limit
 642     //_loop.map(limit->_idx,limit_loop);
 643     // Fall into next case
 644   case BoolTest::gt: {          // Maybe convert to '!=' case
 645     if (stride_con > 0) // count up loop rolls through MININT
 646       ShouldNotReachHere();
 647     Node *range = gvn->transform(new (C) SubINode(limit,init_trip));
 648     set_subtree_ctrl( range );
 649     hook->init_req(0, range);
 650 
 651     Node *bias  = gvn->transform(new (C) AddINode(range,stride));
 652     set_subtree_ctrl( bias );
 653     hook->init_req(1, bias);
 654 
 655     Node *bias1 = gvn->transform(new (C) AddINode(bias,one_p));
 656     set_subtree_ctrl( bias1 );
 657     hook->init_req(2, bias1);
 658 
 659     trip_count  = gvn->transform(new (C) DivINode(0,bias1,stride));
 660     set_subtree_ctrl( trip_count );
 661     hook->init_req(3, trip_count);
 662     break;
 663   }
 664   } // switch( bt )
 665 
 666   Node *span = gvn->transform(new (C) MulINode(trip_count,stride));
 667   set_subtree_ctrl( span );
 668   hook->init_req(5, span);
 669 
 670   limit = gvn->transform(new (C) AddINode(span,init_trip));
 671   set_subtree_ctrl( limit );
 672 
 673   } // LoopLimitCheck
 674 
 675   // Check for SafePoint on backedge and remove
 676   Node *sfpt = x->in(LoopNode::LoopBackControl);
 677   if (sfpt->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt)) {
 678     lazy_replace( sfpt, iftrue );
 679     if (loop->_safepts != NULL) {
 680       loop->_safepts->yank(sfpt);
 681     }
 682     loop->_tail = iftrue;
 683   }
 684 
 685   // Build a canonical trip test.
 686   // Clone code, as old values may be in use.
 687   incr = incr->clone();
 688   incr->set_req(1,phi);
 689   incr->set_req(2,stride);
 690   incr = _igvn.register_new_node_with_optimizer(incr);
 691   set_early_ctrl( incr );
 692   _igvn.hash_delete(phi);
 693   phi->set_req_X( LoopNode::LoopBackControl, incr, &_igvn );
 694 
 695   // If phi type is more restrictive than Int, raise to
 696   // Int to prevent (almost) infinite recursion in igvn
 697   // which can only handle integer types for constants or minint..maxint.
 698   if (!TypeInt::INT->higher_equal(phi->bottom_type())) {
 699     Node* nphi = PhiNode::make(phi->in(0), phi->in(LoopNode::EntryControl), TypeInt::INT);
 700     nphi->set_req(LoopNode::LoopBackControl, phi->in(LoopNode::LoopBackControl));
 701     nphi = _igvn.register_new_node_with_optimizer(nphi);
 702     set_ctrl(nphi, get_ctrl(phi));
 703     _igvn.replace_node(phi, nphi);
 704     phi = nphi->as_Phi();
 705   }
 706   cmp = cmp->clone();
 707   cmp->set_req(1,incr);
 708   cmp->set_req(2,limit);
 709   cmp = _igvn.register_new_node_with_optimizer(cmp);
 710   set_ctrl(cmp, iff->in(0));
 711 
 712   test = test->clone()->as_Bool();
 713   (*(BoolTest*)&test->_test)._test = bt;
 714   test->set_req(1,cmp);
 715   _igvn.register_new_node_with_optimizer(test);
 716   set_ctrl(test, iff->in(0));
 717 
 718   // Replace the old IfNode with a new LoopEndNode
 719   Node *lex = _igvn.register_new_node_with_optimizer(new (C) CountedLoopEndNode( iff->in(0), test, cl_prob, iff->as_If()->_fcnt ));
 720   IfNode *le = lex->as_If();
 721   uint dd = dom_depth(iff);
 722   set_idom(le, le->in(0), dd); // Update dominance for loop exit
 723   set_loop(le, loop);
 724 
 725   // Get the loop-exit control
 726   Node *iffalse = iff->as_If()->proj_out(!(iftrue_op == Op_IfTrue));
 727 
 728   // Need to swap loop-exit and loop-back control?
 729   if (iftrue_op == Op_IfFalse) {
 730     Node *ift2=_igvn.register_new_node_with_optimizer(new (C) IfTrueNode (le));
 731     Node *iff2=_igvn.register_new_node_with_optimizer(new (C) IfFalseNode(le));
 732 
 733     loop->_tail = back_control = ift2;
 734     set_loop(ift2, loop);
 735     set_loop(iff2, get_loop(iffalse));
 736 
 737     // Lazy update of 'get_ctrl' mechanism.
 738     lazy_replace_proj( iffalse, iff2 );
 739     lazy_replace_proj( iftrue,  ift2 );
 740 
 741     // Swap names
 742     iffalse = iff2;
 743     iftrue  = ift2;
 744   } else {
 745     _igvn.hash_delete(iffalse);
 746     _igvn.hash_delete(iftrue);
 747     iffalse->set_req_X( 0, le, &_igvn );
 748     iftrue ->set_req_X( 0, le, &_igvn );
 749   }
 750 
 751   set_idom(iftrue,  le, dd+1);
 752   set_idom(iffalse, le, dd+1);
 753   assert(iff->outcnt() == 0, "should be dead now");
 754   lazy_replace( iff, le ); // fix 'get_ctrl'
 755 
 756   // Now setup a new CountedLoopNode to replace the existing LoopNode
 757   CountedLoopNode *l = new (C) CountedLoopNode(init_control, back_control);
 758   l->set_unswitch_count(x->as_Loop()->unswitch_count()); // Preserve
 759   // The following assert is approximately true, and defines the intention
 760   // of can_be_counted_loop.  It fails, however, because phase->type
 761   // is not yet initialized for this loop and its parts.
 762   //assert(l->can_be_counted_loop(this), "sanity");
 763   _igvn.register_new_node_with_optimizer(l);
 764   set_loop(l, loop);
 765   loop->_head = l;
 766   // Fix all data nodes placed at the old loop head.
 767   // Uses the lazy-update mechanism of 'get_ctrl'.
 768   lazy_replace( x, l );
 769   set_idom(l, init_control, dom_depth(x));
 770 
 771   // Check for immediately preceding SafePoint and remove
 772   Node *sfpt2 = le->in(0);
 773   if (sfpt2->Opcode() == Op_SafePoint && is_deleteable_safept(sfpt2)) {
 774     lazy_replace( sfpt2, sfpt2->in(TypeFunc::Control));
 775     if (loop->_safepts != NULL) {
 776       loop->_safepts->yank(sfpt2);
 777     }
 778   }
 779 
 780   // Free up intermediate goo
 781   _igvn.remove_dead_node(hook);
 782 
 783 #ifdef ASSERT
 784   assert(l->is_valid_counted_loop(), "counted loop shape is messed up");
 785   assert(l == loop->_head && l->phi() == phi && l->loopexit() == lex, "" );
 786 #endif
 787 #ifndef PRODUCT
 788   if (TraceLoopOpts) {
 789     tty->print("Counted      ");
 790     loop->dump_head();
 791   }
 792 #endif
 793 
 794   C->print_method(PHASE_AFTER_CLOOPS, 3);
 795 
 796   return true;
 797 }
 798 
 799 //----------------------exact_limit-------------------------------------------
 800 Node* PhaseIdealLoop::exact_limit( IdealLoopTree *loop ) {
 801   assert(loop->_head->is_CountedLoop(), "");
 802   CountedLoopNode *cl = loop->_head->as_CountedLoop();
 803   assert(cl->is_valid_counted_loop(), "");
 804 
 805   if (!LoopLimitCheck || ABS(cl->stride_con()) == 1 ||
 806       cl->limit()->Opcode() == Op_LoopLimit) {
 807     // Old code has exact limit (it could be incorrect in case of int overflow).
 808     // Loop limit is exact with stride == 1. And loop may already have exact limit.
 809     return cl->limit();
 810   }
 811   Node *limit = NULL;
 812 #ifdef ASSERT
 813   BoolTest::mask bt = cl->loopexit()->test_trip();
 814   assert(bt == BoolTest::lt || bt == BoolTest::gt, "canonical test is expected");
 815 #endif
 816   if (cl->has_exact_trip_count()) {
 817     // Simple case: loop has constant boundaries.
 818     // Use jlongs to avoid integer overflow.
 819     int stride_con = cl->stride_con();
 820     jlong  init_con = cl->init_trip()->get_int();
 821     jlong limit_con = cl->limit()->get_int();
 822     julong trip_cnt = cl->trip_count();
 823     jlong final_con = init_con + trip_cnt*stride_con;
 824     int final_int = (int)final_con;
 825     // The final value should be in integer range since the loop
 826     // is counted and the limit was checked for overflow.
 827     assert(final_con == (jlong)final_int, "final value should be integer");
 828     limit = _igvn.intcon(final_int);
 829   } else {
 830     // Create new LoopLimit node to get exact limit (final iv value).
 831     limit = new (C) LoopLimitNode(C, cl->init_trip(), cl->limit(), cl->stride());
 832     register_new_node(limit, cl->in(LoopNode::EntryControl));
 833   }
 834   assert(limit != NULL, "sanity");
 835   return limit;
 836 }
 837 
 838 //------------------------------Ideal------------------------------------------
 839 // Return a node which is more "ideal" than the current node.
 840 // Attempt to convert into a counted-loop.
 841 Node *LoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 842   if (!can_be_counted_loop(phase)) {
 843     phase->C->set_major_progress();
 844   }
 845   return RegionNode::Ideal(phase, can_reshape);
 846 }
 847 
 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 *CountedLoopNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 854   return RegionNode::Ideal(phase, can_reshape);
 855 }
 856 
 857 //------------------------------dump_spec--------------------------------------
 858 // Dump special per-node info
 859 #ifndef PRODUCT
 860 void CountedLoopNode::dump_spec(outputStream *st) const {
 861   LoopNode::dump_spec(st);
 862   if (stride_is_con()) {
 863     st->print("stride: %d ",stride_con());
 864   }
 865   if (is_pre_loop ()) st->print("pre of N%d" , _main_idx);
 866   if (is_main_loop()) st->print("main of N%d", _idx);
 867   if (is_post_loop()) st->print("post of N%d", _main_idx);
 868 }
 869 #endif
 870 
 871 //=============================================================================
 872 int CountedLoopEndNode::stride_con() const {
 873   return stride()->bottom_type()->is_int()->get_con();
 874 }
 875 
 876 //=============================================================================
 877 //------------------------------Value-----------------------------------------
 878 const Type *LoopLimitNode::Value( PhaseTransform *phase ) const {
 879   const Type* init_t   = phase->type(in(Init));
 880   const Type* limit_t  = phase->type(in(Limit));
 881   const Type* stride_t = phase->type(in(Stride));
 882   // Either input is TOP ==> the result is TOP
 883   if (init_t   == Type::TOP) return Type::TOP;
 884   if (limit_t  == Type::TOP) return Type::TOP;
 885   if (stride_t == Type::TOP) return Type::TOP;
 886 
 887   int stride_con = stride_t->is_int()->get_con();
 888   if (stride_con == 1)
 889     return NULL;  // Identity
 890 
 891   if (init_t->is_int()->is_con() && limit_t->is_int()->is_con()) {
 892     // Use jlongs to avoid integer overflow.
 893     jlong init_con   =  init_t->is_int()->get_con();
 894     jlong limit_con  = limit_t->is_int()->get_con();
 895     int  stride_m   = stride_con - (stride_con > 0 ? 1 : -1);
 896     jlong trip_count = (limit_con - init_con + stride_m)/stride_con;
 897     jlong final_con  = init_con + stride_con*trip_count;
 898     int final_int = (int)final_con;
 899     // The final value should be in integer range since the loop
 900     // is counted and the limit was checked for overflow.
 901     assert(final_con == (jlong)final_int, "final value should be integer");
 902     return TypeInt::make(final_int);
 903   }
 904 
 905   return bottom_type(); // TypeInt::INT
 906 }
 907 
 908 //------------------------------Ideal------------------------------------------
 909 // Return a node which is more "ideal" than the current node.
 910 Node *LoopLimitNode::Ideal(PhaseGVN *phase, bool can_reshape) {
 911   if (phase->type(in(Init))   == Type::TOP ||
 912       phase->type(in(Limit))  == Type::TOP ||
 913       phase->type(in(Stride)) == Type::TOP)
 914     return NULL;  // Dead
 915 
 916   int stride_con = phase->type(in(Stride))->is_int()->get_con();
 917   if (stride_con == 1)
 918     return NULL;  // Identity
 919 
 920   if (in(Init)->is_Con() && in(Limit)->is_Con())
 921     return NULL;  // Value
 922 
 923   // Delay following optimizations until all loop optimizations
 924   // done to keep Ideal graph simple.
 925   if (!can_reshape || phase->C->major_progress())
 926     return NULL;
 927 
 928   const TypeInt* init_t  = phase->type(in(Init) )->is_int();
 929   const TypeInt* limit_t = phase->type(in(Limit))->is_int();
 930   int stride_p;
 931   jlong lim, ini;
 932   julong max;
 933   if (stride_con > 0) {
 934     stride_p = stride_con;
 935     lim = limit_t->_hi;
 936     ini = init_t->_lo;
 937     max = (julong)max_jint;
 938   } else {
 939     stride_p = -stride_con;
 940     lim = init_t->_hi;
 941     ini = limit_t->_lo;
 942     max = (julong)min_jint;
 943   }
 944   julong range = lim - ini + stride_p;
 945   if (range <= max) {
 946     // Convert to integer expression if it is not overflow.
 947     Node* stride_m = phase->intcon(stride_con - (stride_con > 0 ? 1 : -1));
 948     Node *range = phase->transform(new (phase->C) SubINode(in(Limit), in(Init)));
 949     Node *bias  = phase->transform(new (phase->C) AddINode(range, stride_m));
 950     Node *trip  = phase->transform(new (phase->C) DivINode(0, bias, in(Stride)));
 951     Node *span  = phase->transform(new (phase->C) MulINode(trip, in(Stride)));
 952     return new (phase->C) AddINode(span, in(Init)); // exact limit
 953   }
 954 
 955   if (is_power_of_2(stride_p) ||                // divisor is 2^n
 956       !Matcher::has_match_rule(Op_LoopLimit)) { // or no specialized Mach node?
 957     // Convert to long expression to avoid integer overflow
 958     // and let igvn optimizer convert this division.
 959     //
 960     Node*   init   = phase->transform( new (phase->C) ConvI2LNode(in(Init)));
 961     Node*  limit   = phase->transform( new (phase->C) ConvI2LNode(in(Limit)));
 962     Node* stride   = phase->longcon(stride_con);
 963     Node* stride_m = phase->longcon(stride_con - (stride_con > 0 ? 1 : -1));
 964 
 965     Node *range = phase->transform(new (phase->C) SubLNode(limit, init));
 966     Node *bias  = phase->transform(new (phase->C) AddLNode(range, stride_m));
 967     Node *span;
 968     if (stride_con > 0 && is_power_of_2(stride_p)) {
 969       // bias >= 0 if stride >0, so if stride is 2^n we can use &(-stride)
 970       // and avoid generating rounding for division. Zero trip guard should
 971       // guarantee that init < limit but sometimes the guard is missing and
 972       // we can get situation when init > limit. Note, for the empty loop
 973       // optimization zero trip guard is generated explicitly which leaves
 974       // only RCE predicate where exact limit is used and the predicate
 975       // will simply fail forcing recompilation.
 976       Node* neg_stride   = phase->longcon(-stride_con);
 977       span = phase->transform(new (phase->C) AndLNode(bias, neg_stride));
 978     } else {
 979       Node *trip  = phase->transform(new (phase->C) DivLNode(0, bias, stride));
 980       span = phase->transform(new (phase->C) MulLNode(trip, stride));
 981     }
 982     // Convert back to int
 983     Node *span_int = phase->transform(new (phase->C) ConvL2INode(span));
 984     return new (phase->C) AddINode(span_int, in(Init)); // exact limit
 985   }
 986 
 987   return NULL;    // No progress
 988 }
 989 
 990 //------------------------------Identity---------------------------------------
 991 // If stride == 1 return limit node.
 992 Node *LoopLimitNode::Identity( PhaseTransform *phase ) {
 993   int stride_con = phase->type(in(Stride))->is_int()->get_con();
 994   if (stride_con == 1 || stride_con == -1)
 995     return in(Limit);
 996   return this;
 997 }
 998 
 999 //=============================================================================
1000 //----------------------match_incr_with_optional_truncation--------------------
1001 // Match increment with optional truncation:
1002 // CHAR: (i+1)&0x7fff, BYTE: ((i+1)<<8)>>8, or SHORT: ((i+1)<<16)>>16
1003 // Return NULL for failure. Success returns the increment node.
1004 Node* CountedLoopNode::match_incr_with_optional_truncation(
1005                       Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type) {
1006   // Quick cutouts:
1007   if (expr == NULL || expr->req() != 3)  return NULL;
1008 
1009   Node *t1 = NULL;
1010   Node *t2 = NULL;
1011   const TypeInt* trunc_t = TypeInt::INT;
1012   Node* n1 = expr;
1013   int   n1op = n1->Opcode();
1014 
1015   // Try to strip (n1 & M) or (n1 << N >> N) from n1.
1016   if (n1op == Op_AndI &&
1017       n1->in(2)->is_Con() &&
1018       n1->in(2)->bottom_type()->is_int()->get_con() == 0x7fff) {
1019     // %%% This check should match any mask of 2**K-1.
1020     t1 = n1;
1021     n1 = t1->in(1);
1022     n1op = n1->Opcode();
1023     trunc_t = TypeInt::CHAR;
1024   } else if (n1op == Op_RShiftI &&
1025              n1->in(1) != NULL &&
1026              n1->in(1)->Opcode() == Op_LShiftI &&
1027              n1->in(2) == n1->in(1)->in(2) &&
1028              n1->in(2)->is_Con()) {
1029     jint shift = n1->in(2)->bottom_type()->is_int()->get_con();
1030     // %%% This check should match any shift in [1..31].
1031     if (shift == 16 || shift == 8) {
1032       t1 = n1;
1033       t2 = t1->in(1);
1034       n1 = t2->in(1);
1035       n1op = n1->Opcode();
1036       if (shift == 16) {
1037         trunc_t = TypeInt::SHORT;
1038       } else if (shift == 8) {
1039         trunc_t = TypeInt::BYTE;
1040       }
1041     }
1042   }
1043 
1044   // If (maybe after stripping) it is an AddI, we won:
1045   if (n1op == Op_AddI) {
1046     *trunc1 = t1;
1047     *trunc2 = t2;
1048     *trunc_type = trunc_t;
1049     return n1;
1050   }
1051 
1052   // failed
1053   return NULL;
1054 }
1055 
1056 
1057 //------------------------------filtered_type--------------------------------
1058 // Return a type based on condition control flow
1059 // A successful return will be a type that is restricted due
1060 // to a series of dominating if-tests, such as:
1061 //    if (i < 10) {
1062 //       if (i > 0) {
1063 //          here: "i" type is [1..10)
1064 //       }
1065 //    }
1066 // or a control flow merge
1067 //    if (i < 10) {
1068 //       do {
1069 //          phi( , ) -- at top of loop type is [min_int..10)
1070 //         i = ?
1071 //       } while ( i < 10)
1072 //
1073 const TypeInt* PhaseIdealLoop::filtered_type( Node *n, Node* n_ctrl) {
1074   assert(n && n->bottom_type()->is_int(), "must be int");
1075   const TypeInt* filtered_t = NULL;
1076   if (!n->is_Phi()) {
1077     assert(n_ctrl != NULL || n_ctrl == C->top(), "valid control");
1078     filtered_t = filtered_type_from_dominators(n, n_ctrl);
1079 
1080   } else {
1081     Node* phi    = n->as_Phi();
1082     Node* region = phi->in(0);
1083     assert(n_ctrl == NULL || n_ctrl == region, "ctrl parameter must be region");
1084     if (region && region != C->top()) {
1085       for (uint i = 1; i < phi->req(); i++) {
1086         Node* val   = phi->in(i);
1087         Node* use_c = region->in(i);
1088         const TypeInt* val_t = filtered_type_from_dominators(val, use_c);
1089         if (val_t != NULL) {
1090           if (filtered_t == NULL) {
1091             filtered_t = val_t;
1092           } else {
1093             filtered_t = filtered_t->meet(val_t)->is_int();
1094           }
1095         }
1096       }
1097     }
1098   }
1099   const TypeInt* n_t = _igvn.type(n)->is_int();
1100   if (filtered_t != NULL) {
1101     n_t = n_t->join(filtered_t)->is_int();
1102   }
1103   return n_t;
1104 }
1105 
1106 
1107 //------------------------------filtered_type_from_dominators--------------------------------
1108 // Return a possibly more restrictive type for val based on condition control flow of dominators
1109 const TypeInt* PhaseIdealLoop::filtered_type_from_dominators( Node* val, Node *use_ctrl) {
1110   if (val->is_Con()) {
1111      return val->bottom_type()->is_int();
1112   }
1113   uint if_limit = 10; // Max number of dominating if's visited
1114   const TypeInt* rtn_t = NULL;
1115 
1116   if (use_ctrl && use_ctrl != C->top()) {
1117     Node* val_ctrl = get_ctrl(val);
1118     uint val_dom_depth = dom_depth(val_ctrl);
1119     Node* pred = use_ctrl;
1120     uint if_cnt = 0;
1121     while (if_cnt < if_limit) {
1122       if ((pred->Opcode() == Op_IfTrue || pred->Opcode() == Op_IfFalse)) {
1123         if_cnt++;
1124         const TypeInt* if_t = IfNode::filtered_int_type(&_igvn, val, pred);
1125         if (if_t != NULL) {
1126           if (rtn_t == NULL) {
1127             rtn_t = if_t;
1128           } else {
1129             rtn_t = rtn_t->join(if_t)->is_int();
1130           }
1131         }
1132       }
1133       pred = idom(pred);
1134       if (pred == NULL || pred == C->top()) {
1135         break;
1136       }
1137       // Stop if going beyond definition block of val
1138       if (dom_depth(pred) < val_dom_depth) {
1139         break;
1140       }
1141     }
1142   }
1143   return rtn_t;
1144 }
1145 
1146 
1147 //------------------------------dump_spec--------------------------------------
1148 // Dump special per-node info
1149 #ifndef PRODUCT
1150 void CountedLoopEndNode::dump_spec(outputStream *st) const {
1151   if( in(TestValue)->is_Bool() ) {
1152     BoolTest bt( test_trip()); // Added this for g++.
1153 
1154     st->print("[");
1155     bt.dump_on(st);
1156     st->print("]");
1157   }
1158   st->print(" ");
1159   IfNode::dump_spec(st);
1160 }
1161 #endif
1162 
1163 //=============================================================================
1164 //------------------------------is_member--------------------------------------
1165 // Is 'l' a member of 'this'?
1166 int IdealLoopTree::is_member( const IdealLoopTree *l ) const {
1167   while( l->_nest > _nest ) l = l->_parent;
1168   return l == this;
1169 }
1170 
1171 //------------------------------set_nest---------------------------------------
1172 // Set loop tree nesting depth.  Accumulate _has_call bits.
1173 int IdealLoopTree::set_nest( uint depth ) {
1174   _nest = depth;
1175   int bits = _has_call;
1176   if( _child ) bits |= _child->set_nest(depth+1);
1177   if( bits ) _has_call = 1;
1178   if( _next  ) bits |= _next ->set_nest(depth  );
1179   return bits;
1180 }
1181 
1182 //------------------------------split_fall_in----------------------------------
1183 // Split out multiple fall-in edges from the loop header.  Move them to a
1184 // private RegionNode before the loop.  This becomes the loop landing pad.
1185 void IdealLoopTree::split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt ) {
1186   PhaseIterGVN &igvn = phase->_igvn;
1187   uint i;
1188 
1189   // Make a new RegionNode to be the landing pad.
1190   Node *landing_pad = new (phase->C) RegionNode( fall_in_cnt+1 );
1191   phase->set_loop(landing_pad,_parent);
1192   // Gather all the fall-in control paths into the landing pad
1193   uint icnt = fall_in_cnt;
1194   uint oreq = _head->req();
1195   for( i = oreq-1; i>0; i-- )
1196     if( !phase->is_member( this, _head->in(i) ) )
1197       landing_pad->set_req(icnt--,_head->in(i));
1198 
1199   // Peel off PhiNode edges as well
1200   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1201     Node *oj = _head->fast_out(j);
1202     if( oj->is_Phi() ) {
1203       PhiNode* old_phi = oj->as_Phi();
1204       assert( old_phi->region() == _head, "" );
1205       igvn.hash_delete(old_phi);   // Yank from hash before hacking edges
1206       Node *p = PhiNode::make_blank(landing_pad, old_phi);
1207       uint icnt = fall_in_cnt;
1208       for( i = oreq-1; i>0; i-- ) {
1209         if( !phase->is_member( this, _head->in(i) ) ) {
1210           p->init_req(icnt--, old_phi->in(i));
1211           // Go ahead and clean out old edges from old phi
1212           old_phi->del_req(i);
1213         }
1214       }
1215       // Search for CSE's here, because ZKM.jar does a lot of
1216       // loop hackery and we need to be a little incremental
1217       // with the CSE to avoid O(N^2) node blow-up.
1218       Node *p2 = igvn.hash_find_insert(p); // Look for a CSE
1219       if( p2 ) {                // Found CSE
1220         p->destruct();          // Recover useless new node
1221         p = p2;                 // Use old node
1222       } else {
1223         igvn.register_new_node_with_optimizer(p, old_phi);
1224       }
1225       // Make old Phi refer to new Phi.
1226       old_phi->add_req(p);
1227       // Check for the special case of making the old phi useless and
1228       // disappear it.  In JavaGrande I have a case where this useless
1229       // Phi is the loop limit and prevents recognizing a CountedLoop
1230       // which in turn prevents removing an empty loop.
1231       Node *id_old_phi = old_phi->Identity( &igvn );
1232       if( id_old_phi != old_phi ) { // Found a simple identity?
1233         // Note that I cannot call 'replace_node' here, because
1234         // that will yank the edge from old_phi to the Region and
1235         // I'm mid-iteration over the Region's uses.
1236         for (DUIterator_Last imin, i = old_phi->last_outs(imin); i >= imin; ) {
1237           Node* use = old_phi->last_out(i);
1238           igvn.rehash_node_delayed(use);
1239           uint uses_found = 0;
1240           for (uint j = 0; j < use->len(); j++) {
1241             if (use->in(j) == old_phi) {
1242               if (j < use->req()) use->set_req (j, id_old_phi);
1243               else                use->set_prec(j, id_old_phi);
1244               uses_found++;
1245             }
1246           }
1247           i -= uses_found;    // we deleted 1 or more copies of this edge
1248         }
1249       }
1250       igvn._worklist.push(old_phi);
1251     }
1252   }
1253   // Finally clean out the fall-in edges from the RegionNode
1254   for( i = oreq-1; i>0; i-- ) {
1255     if( !phase->is_member( this, _head->in(i) ) ) {
1256       _head->del_req(i);
1257     }
1258   }
1259   // Transform landing pad
1260   igvn.register_new_node_with_optimizer(landing_pad, _head);
1261   // Insert landing pad into the header
1262   _head->add_req(landing_pad);
1263 }
1264 
1265 //------------------------------split_outer_loop-------------------------------
1266 // Split out the outermost loop from this shared header.
1267 void IdealLoopTree::split_outer_loop( PhaseIdealLoop *phase ) {
1268   PhaseIterGVN &igvn = phase->_igvn;
1269 
1270   // Find index of outermost loop; it should also be my tail.
1271   uint outer_idx = 1;
1272   while( _head->in(outer_idx) != _tail ) outer_idx++;
1273 
1274   // Make a LoopNode for the outermost loop.
1275   Node *ctl = _head->in(LoopNode::EntryControl);
1276   Node *outer = new (phase->C) LoopNode( ctl, _head->in(outer_idx) );
1277   outer = igvn.register_new_node_with_optimizer(outer, _head);
1278   phase->set_created_loop_node();
1279 
1280   // Outermost loop falls into '_head' loop
1281   _head->set_req(LoopNode::EntryControl, outer);
1282   _head->del_req(outer_idx);
1283   // Split all the Phis up between '_head' loop and 'outer' loop.
1284   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1285     Node *out = _head->fast_out(j);
1286     if( out->is_Phi() ) {
1287       PhiNode *old_phi = out->as_Phi();
1288       assert( old_phi->region() == _head, "" );
1289       Node *phi = PhiNode::make_blank(outer, old_phi);
1290       phi->init_req(LoopNode::EntryControl,    old_phi->in(LoopNode::EntryControl));
1291       phi->init_req(LoopNode::LoopBackControl, old_phi->in(outer_idx));
1292       phi = igvn.register_new_node_with_optimizer(phi, old_phi);
1293       // Make old Phi point to new Phi on the fall-in path
1294       igvn.replace_input_of(old_phi, LoopNode::EntryControl, phi);
1295       old_phi->del_req(outer_idx);
1296     }
1297   }
1298 
1299   // Use the new loop head instead of the old shared one
1300   _head = outer;
1301   phase->set_loop(_head, this);
1302 }
1303 
1304 //------------------------------fix_parent-------------------------------------
1305 static void fix_parent( IdealLoopTree *loop, IdealLoopTree *parent ) {
1306   loop->_parent = parent;
1307   if( loop->_child ) fix_parent( loop->_child, loop   );
1308   if( loop->_next  ) fix_parent( loop->_next , parent );
1309 }
1310 
1311 //------------------------------estimate_path_freq-----------------------------
1312 static float estimate_path_freq( Node *n ) {
1313   // Try to extract some path frequency info
1314   IfNode *iff;
1315   for( int i = 0; i < 50; i++ ) { // Skip through a bunch of uncommon tests
1316     uint nop = n->Opcode();
1317     if( nop == Op_SafePoint ) {   // Skip any safepoint
1318       n = n->in(0);
1319       continue;
1320     }
1321     if( nop == Op_CatchProj ) {   // Get count from a prior call
1322       // Assume call does not always throw exceptions: means the call-site
1323       // count is also the frequency of the fall-through path.
1324       assert( n->is_CatchProj(), "" );
1325       if( ((CatchProjNode*)n)->_con != CatchProjNode::fall_through_index )
1326         return 0.0f;            // Assume call exception path is rare
1327       Node *call = n->in(0)->in(0)->in(0);
1328       assert( call->is_Call(), "expect a call here" );
1329       const JVMState *jvms = ((CallNode*)call)->jvms();
1330       ciMethodData* methodData = jvms->method()->method_data();
1331       if (!methodData->is_mature())  return 0.0f; // No call-site data
1332       ciProfileData* data = methodData->bci_to_data(jvms->bci());
1333       if ((data == NULL) || !data->is_CounterData()) {
1334         // no call profile available, try call's control input
1335         n = n->in(0);
1336         continue;
1337       }
1338       return data->as_CounterData()->count()/FreqCountInvocations;
1339     }
1340     // See if there's a gating IF test
1341     Node *n_c = n->in(0);
1342     if( !n_c->is_If() ) break;       // No estimate available
1343     iff = n_c->as_If();
1344     if( iff->_fcnt != COUNT_UNKNOWN )   // Have a valid count?
1345       // Compute how much count comes on this path
1346       return ((nop == Op_IfTrue) ? iff->_prob : 1.0f - iff->_prob) * iff->_fcnt;
1347     // Have no count info.  Skip dull uncommon-trap like branches.
1348     if( (nop == Op_IfTrue  && iff->_prob < PROB_LIKELY_MAG(5)) ||
1349         (nop == Op_IfFalse && iff->_prob > PROB_UNLIKELY_MAG(5)) )
1350       break;
1351     // Skip through never-taken branch; look for a real loop exit.
1352     n = iff->in(0);
1353   }
1354   return 0.0f;                  // No estimate available
1355 }
1356 
1357 //------------------------------merge_many_backedges---------------------------
1358 // Merge all the backedges from the shared header into a private Region.
1359 // Feed that region as the one backedge to this loop.
1360 void IdealLoopTree::merge_many_backedges( PhaseIdealLoop *phase ) {
1361   uint i;
1362 
1363   // Scan for the top 2 hottest backedges
1364   float hotcnt = 0.0f;
1365   float warmcnt = 0.0f;
1366   uint hot_idx = 0;
1367   // Loop starts at 2 because slot 1 is the fall-in path
1368   for( i = 2; i < _head->req(); i++ ) {
1369     float cnt = estimate_path_freq(_head->in(i));
1370     if( cnt > hotcnt ) {       // Grab hottest path
1371       warmcnt = hotcnt;
1372       hotcnt = cnt;
1373       hot_idx = i;
1374     } else if( cnt > warmcnt ) { // And 2nd hottest path
1375       warmcnt = cnt;
1376     }
1377   }
1378 
1379   // See if the hottest backedge is worthy of being an inner loop
1380   // by being much hotter than the next hottest backedge.
1381   if( hotcnt <= 0.0001 ||
1382       hotcnt < 2.0*warmcnt ) hot_idx = 0;// No hot backedge
1383 
1384   // Peel out the backedges into a private merge point; peel
1385   // them all except optionally hot_idx.
1386   PhaseIterGVN &igvn = phase->_igvn;
1387 
1388   Node *hot_tail = NULL;
1389   // Make a Region for the merge point
1390   Node *r = new (phase->C) RegionNode(1);
1391   for( i = 2; i < _head->req(); i++ ) {
1392     if( i != hot_idx )
1393       r->add_req( _head->in(i) );
1394     else hot_tail = _head->in(i);
1395   }
1396   igvn.register_new_node_with_optimizer(r, _head);
1397   // Plug region into end of loop _head, followed by hot_tail
1398   while( _head->req() > 3 ) _head->del_req( _head->req()-1 );
1399   _head->set_req(2, r);
1400   if( hot_idx ) _head->add_req(hot_tail);
1401 
1402   // Split all the Phis up between '_head' loop and the Region 'r'
1403   for (DUIterator_Fast jmax, j = _head->fast_outs(jmax); j < jmax; j++) {
1404     Node *out = _head->fast_out(j);
1405     if( out->is_Phi() ) {
1406       PhiNode* n = out->as_Phi();
1407       igvn.hash_delete(n);      // Delete from hash before hacking edges
1408       Node *hot_phi = NULL;
1409       Node *phi = new (phase->C) PhiNode(r, n->type(), n->adr_type());
1410       // Check all inputs for the ones to peel out
1411       uint j = 1;
1412       for( uint i = 2; i < n->req(); i++ ) {
1413         if( i != hot_idx )
1414           phi->set_req( j++, n->in(i) );
1415         else hot_phi = n->in(i);
1416       }
1417       // Register the phi but do not transform until whole place transforms
1418       igvn.register_new_node_with_optimizer(phi, n);
1419       // Add the merge phi to the old Phi
1420       while( n->req() > 3 ) n->del_req( n->req()-1 );
1421       n->set_req(2, phi);
1422       if( hot_idx ) n->add_req(hot_phi);
1423     }
1424   }
1425 
1426 
1427   // Insert a new IdealLoopTree inserted below me.  Turn it into a clone
1428   // of self loop tree.  Turn self into a loop headed by _head and with
1429   // tail being the new merge point.
1430   IdealLoopTree *ilt = new IdealLoopTree( phase, _head, _tail );
1431   phase->set_loop(_tail,ilt);   // Adjust tail
1432   _tail = r;                    // Self's tail is new merge point
1433   phase->set_loop(r,this);
1434   ilt->_child = _child;         // New guy has my children
1435   _child = ilt;                 // Self has new guy as only child
1436   ilt->_parent = this;          // new guy has self for parent
1437   ilt->_nest = _nest;           // Same nesting depth (for now)
1438 
1439   // Starting with 'ilt', look for child loop trees using the same shared
1440   // header.  Flatten these out; they will no longer be loops in the end.
1441   IdealLoopTree **pilt = &_child;
1442   while( ilt ) {
1443     if( ilt->_head == _head ) {
1444       uint i;
1445       for( i = 2; i < _head->req(); i++ )
1446         if( _head->in(i) == ilt->_tail )
1447           break;                // Still a loop
1448       if( i == _head->req() ) { // No longer a loop
1449         // Flatten ilt.  Hang ilt's "_next" list from the end of
1450         // ilt's '_child' list.  Move the ilt's _child up to replace ilt.
1451         IdealLoopTree **cp = &ilt->_child;
1452         while( *cp ) cp = &(*cp)->_next;   // Find end of child list
1453         *cp = ilt->_next;       // Hang next list at end of child list
1454         *pilt = ilt->_child;    // Move child up to replace ilt
1455         ilt->_head = NULL;      // Flag as a loop UNIONED into parent
1456         ilt = ilt->_child;      // Repeat using new ilt
1457         continue;               // do not advance over ilt->_child
1458       }
1459       assert( ilt->_tail == hot_tail, "expected to only find the hot inner loop here" );
1460       phase->set_loop(_head,ilt);
1461     }
1462     pilt = &ilt->_child;        // Advance to next
1463     ilt = *pilt;
1464   }
1465 
1466   if( _child ) fix_parent( _child, this );
1467 }
1468 
1469 //------------------------------beautify_loops---------------------------------
1470 // Split shared headers and insert loop landing pads.
1471 // Insert a LoopNode to replace the RegionNode.
1472 // Return TRUE if loop tree is structurally changed.
1473 bool IdealLoopTree::beautify_loops( PhaseIdealLoop *phase ) {
1474   bool result = false;
1475   // Cache parts in locals for easy
1476   PhaseIterGVN &igvn = phase->_igvn;
1477 
1478   igvn.hash_delete(_head);      // Yank from hash before hacking edges
1479 
1480   // Check for multiple fall-in paths.  Peel off a landing pad if need be.
1481   int fall_in_cnt = 0;
1482   for( uint i = 1; i < _head->req(); i++ )
1483     if( !phase->is_member( this, _head->in(i) ) )
1484       fall_in_cnt++;
1485   assert( fall_in_cnt, "at least 1 fall-in path" );
1486   if( fall_in_cnt > 1 )         // Need a loop landing pad to merge fall-ins
1487     split_fall_in( phase, fall_in_cnt );
1488 
1489   // Swap inputs to the _head and all Phis to move the fall-in edge to
1490   // the left.
1491   fall_in_cnt = 1;
1492   while( phase->is_member( this, _head->in(fall_in_cnt) ) )
1493     fall_in_cnt++;
1494   if( fall_in_cnt > 1 ) {
1495     // Since I am just swapping inputs I do not need to update def-use info
1496     Node *tmp = _head->in(1);
1497     _head->set_req( 1, _head->in(fall_in_cnt) );
1498     _head->set_req( fall_in_cnt, tmp );
1499     // Swap also all Phis
1500     for (DUIterator_Fast imax, i = _head->fast_outs(imax); i < imax; i++) {
1501       Node* phi = _head->fast_out(i);
1502       if( phi->is_Phi() ) {
1503         igvn.hash_delete(phi); // Yank from hash before hacking edges
1504         tmp = phi->in(1);
1505         phi->set_req( 1, phi->in(fall_in_cnt) );
1506         phi->set_req( fall_in_cnt, tmp );
1507       }
1508     }
1509   }
1510   assert( !phase->is_member( this, _head->in(1) ), "left edge is fall-in" );
1511   assert(  phase->is_member( this, _head->in(2) ), "right edge is loop" );
1512 
1513   // If I am a shared header (multiple backedges), peel off the many
1514   // backedges into a private merge point and use the merge point as
1515   // the one true backedge.
1516   if( _head->req() > 3 ) {
1517     // Merge the many backedges into a single backedge but leave
1518     // the hottest backedge as separate edge for the following peel.
1519     merge_many_backedges( phase );
1520     result = true;
1521   }
1522 
1523   // If I have one hot backedge, peel off myself loop.
1524   // I better be the outermost loop.
1525   if( _head->req() > 3 ) {
1526     split_outer_loop( phase );
1527     result = true;
1528 
1529   } else if( !_head->is_Loop() && !_irreducible ) {
1530     // Make a new LoopNode to replace the old loop head
1531     Node *l = new (phase->C) LoopNode( _head->in(1), _head->in(2) );
1532     l = igvn.register_new_node_with_optimizer(l, _head);
1533     phase->set_created_loop_node();
1534     // Go ahead and replace _head
1535     phase->_igvn.replace_node( _head, l );
1536     _head = l;
1537     phase->set_loop(_head, this);
1538   }
1539 
1540   // Now recursively beautify nested loops
1541   if( _child ) result |= _child->beautify_loops( phase );
1542   if( _next  ) result |= _next ->beautify_loops( phase );
1543   return result;
1544 }
1545 
1546 //------------------------------allpaths_check_safepts----------------------------
1547 // Allpaths backwards scan from loop tail, terminating each path at first safepoint
1548 // encountered.  Helper for check_safepts.
1549 void IdealLoopTree::allpaths_check_safepts(VectorSet &visited, Node_List &stack) {
1550   assert(stack.size() == 0, "empty stack");
1551   stack.push(_tail);
1552   visited.Clear();
1553   visited.set(_tail->_idx);
1554   while (stack.size() > 0) {
1555     Node* n = stack.pop();
1556     if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1557       // Terminate this path
1558     } else if (n->Opcode() == Op_SafePoint) {
1559       if (_phase->get_loop(n) != this) {
1560         if (_required_safept == NULL) _required_safept = new Node_List();
1561         _required_safept->push(n);  // save the one closest to the tail
1562       }
1563       // Terminate this path
1564     } else {
1565       uint start = n->is_Region() ? 1 : 0;
1566       uint end   = n->is_Region() && !n->is_Loop() ? n->req() : start + 1;
1567       for (uint i = start; i < end; i++) {
1568         Node* in = n->in(i);
1569         assert(in->is_CFG(), "must be");
1570         if (!visited.test_set(in->_idx) && is_member(_phase->get_loop(in))) {
1571           stack.push(in);
1572         }
1573       }
1574     }
1575   }
1576 }
1577 
1578 //------------------------------check_safepts----------------------------
1579 // Given dominators, try to find loops with calls that must always be
1580 // executed (call dominates loop tail).  These loops do not need non-call
1581 // safepoints (ncsfpt).
1582 //
1583 // A complication is that a safepoint in a inner loop may be needed
1584 // by an outer loop. In the following, the inner loop sees it has a
1585 // call (block 3) on every path from the head (block 2) to the
1586 // backedge (arc 3->2).  So it deletes the ncsfpt (non-call safepoint)
1587 // in block 2, _but_ this leaves the outer loop without a safepoint.
1588 //
1589 //          entry  0
1590 //                 |
1591 //                 v
1592 // outer 1,2    +->1
1593 //              |  |
1594 //              |  v
1595 //              |  2<---+  ncsfpt in 2
1596 //              |_/|\   |
1597 //                 | v  |
1598 // inner 2,3      /  3  |  call in 3
1599 //               /   |  |
1600 //              v    +--+
1601 //        exit  4
1602 //
1603 //
1604 // This method creates a list (_required_safept) of ncsfpt nodes that must
1605 // be protected is created for each loop. When a ncsfpt maybe deleted, it
1606 // is first looked for in the lists for the outer loops of the current loop.
1607 //
1608 // The insights into the problem:
1609 //  A) counted loops are okay
1610 //  B) innermost loops are okay (only an inner loop can delete
1611 //     a ncsfpt needed by an outer loop)
1612 //  C) a loop is immune from an inner loop deleting a safepoint
1613 //     if the loop has a call on the idom-path
1614 //  D) a loop is also immune if it has a ncsfpt (non-call safepoint) on the
1615 //     idom-path that is not in a nested loop
1616 //  E) otherwise, an ncsfpt on the idom-path that is nested in an inner
1617 //     loop needs to be prevented from deletion by an inner loop
1618 //
1619 // There are two analyses:
1620 //  1) The first, and cheaper one, scans the loop body from
1621 //     tail to head following the idom (immediate dominator)
1622 //     chain, looking for the cases (C,D,E) above.
1623 //     Since inner loops are scanned before outer loops, there is summary
1624 //     information about inner loops.  Inner loops can be skipped over
1625 //     when the tail of an inner loop is encountered.
1626 //
1627 //  2) The second, invoked if the first fails to find a call or ncsfpt on
1628 //     the idom path (which is rare), scans all predecessor control paths
1629 //     from the tail to the head, terminating a path when a call or sfpt
1630 //     is encountered, to find the ncsfpt's that are closest to the tail.
1631 //
1632 void IdealLoopTree::check_safepts(VectorSet &visited, Node_List &stack) {
1633   // Bottom up traversal
1634   IdealLoopTree* ch = _child;
1635   if (_child) _child->check_safepts(visited, stack);
1636   if (_next)  _next ->check_safepts(visited, stack);
1637 
1638   if (!_head->is_CountedLoop() && !_has_sfpt && _parent != NULL && !_irreducible) {
1639     bool  has_call         = false; // call on dom-path
1640     bool  has_local_ncsfpt = false; // ncsfpt on dom-path at this loop depth
1641     Node* nonlocal_ncsfpt  = NULL;  // ncsfpt on dom-path at a deeper depth
1642     // Scan the dom-path nodes from tail to head
1643     for (Node* n = tail(); n != _head; n = _phase->idom(n)) {
1644       if (n->is_Call() && n->as_Call()->guaranteed_safepoint()) {
1645         has_call = true;
1646         _has_sfpt = 1;          // Then no need for a safept!
1647         break;
1648       } else if (n->Opcode() == Op_SafePoint) {
1649         if (_phase->get_loop(n) == this) {
1650           has_local_ncsfpt = true;
1651           break;
1652         }
1653         if (nonlocal_ncsfpt == NULL) {
1654           nonlocal_ncsfpt = n; // save the one closest to the tail
1655         }
1656       } else {
1657         IdealLoopTree* nlpt = _phase->get_loop(n);
1658         if (this != nlpt) {
1659           // If at an inner loop tail, see if the inner loop has already
1660           // recorded seeing a call on the dom-path (and stop.)  If not,
1661           // jump to the head of the inner loop.
1662           assert(is_member(nlpt), "nested loop");
1663           Node* tail = nlpt->_tail;
1664           if (tail->in(0)->is_If()) tail = tail->in(0);
1665           if (n == tail) {
1666             // If inner loop has call on dom-path, so does outer loop
1667             if (nlpt->_has_sfpt) {
1668               has_call = true;
1669               _has_sfpt = 1;
1670               break;
1671             }
1672             // Skip to head of inner loop
1673             assert(_phase->is_dominator(_head, nlpt->_head), "inner head dominated by outer head");
1674             n = nlpt->_head;
1675           }
1676         }
1677       }
1678     }
1679     // Record safept's that this loop needs preserved when an
1680     // inner loop attempts to delete it's safepoints.
1681     if (_child != NULL && !has_call && !has_local_ncsfpt) {
1682       if (nonlocal_ncsfpt != NULL) {
1683         if (_required_safept == NULL) _required_safept = new Node_List();
1684         _required_safept->push(nonlocal_ncsfpt);
1685       } else {
1686         // Failed to find a suitable safept on the dom-path.  Now use
1687         // an all paths walk from tail to head, looking for safepoints to preserve.
1688         allpaths_check_safepts(visited, stack);
1689       }
1690     }
1691   }
1692 }
1693 
1694 //---------------------------is_deleteable_safept----------------------------
1695 // Is safept not required by an outer loop?
1696 bool PhaseIdealLoop::is_deleteable_safept(Node* sfpt) {
1697   assert(sfpt->Opcode() == Op_SafePoint, "");
1698   IdealLoopTree* lp = get_loop(sfpt)->_parent;
1699   while (lp != NULL) {
1700     Node_List* sfpts = lp->_required_safept;
1701     if (sfpts != NULL) {
1702       for (uint i = 0; i < sfpts->size(); i++) {
1703         if (sfpt == sfpts->at(i))
1704           return false;
1705       }
1706     }
1707     lp = lp->_parent;
1708   }
1709   return true;
1710 }
1711 
1712 //---------------------------replace_parallel_iv-------------------------------
1713 // Replace parallel induction variable (parallel to trip counter)
1714 void PhaseIdealLoop::replace_parallel_iv(IdealLoopTree *loop) {
1715   assert(loop->_head->is_CountedLoop(), "");
1716   CountedLoopNode *cl = loop->_head->as_CountedLoop();
1717   if (!cl->is_valid_counted_loop())
1718     return;         // skip malformed counted loop
1719   Node *incr = cl->incr();
1720   if (incr == NULL)
1721     return;         // Dead loop?
1722   Node *init = cl->init_trip();
1723   Node *phi  = cl->phi();
1724   int stride_con = cl->stride_con();
1725 
1726   // Visit all children, looking for Phis
1727   for (DUIterator i = cl->outs(); cl->has_out(i); i++) {
1728     Node *out = cl->out(i);
1729     // Look for other phis (secondary IVs). Skip dead ones
1730     if (!out->is_Phi() || out == phi || !has_node(out))
1731       continue;
1732     PhiNode* phi2 = out->as_Phi();
1733     Node *incr2 = phi2->in( LoopNode::LoopBackControl );
1734     // Look for induction variables of the form:  X += constant
1735     if (phi2->region() != loop->_head ||
1736         incr2->req() != 3 ||
1737         incr2->in(1) != phi2 ||
1738         incr2 == incr ||
1739         incr2->Opcode() != Op_AddI ||
1740         !incr2->in(2)->is_Con())
1741       continue;
1742 
1743     // Check for parallel induction variable (parallel to trip counter)
1744     // via an affine function.  In particular, count-down loops with
1745     // count-up array indices are common. We only RCE references off
1746     // the trip-counter, so we need to convert all these to trip-counter
1747     // expressions.
1748     Node *init2 = phi2->in( LoopNode::EntryControl );
1749     int stride_con2 = incr2->in(2)->get_int();
1750 
1751     // The general case here gets a little tricky.  We want to find the
1752     // GCD of all possible parallel IV's and make a new IV using this
1753     // GCD for the loop.  Then all possible IVs are simple multiples of
1754     // the GCD.  In practice, this will cover very few extra loops.
1755     // Instead we require 'stride_con2' to be a multiple of 'stride_con',
1756     // where +/-1 is the common case, but other integer multiples are
1757     // also easy to handle.
1758     int ratio_con = stride_con2/stride_con;
1759 
1760     if ((ratio_con * stride_con) == stride_con2) { // Check for exact
1761 #ifndef PRODUCT
1762       if (TraceLoopOpts) {
1763         tty->print("Parallel IV: %d ", phi2->_idx);
1764         loop->dump_head();
1765       }
1766 #endif
1767       // Convert to using the trip counter.  The parallel induction
1768       // variable differs from the trip counter by a loop-invariant
1769       // amount, the difference between their respective initial values.
1770       // It is scaled by the 'ratio_con'.
1771       Node* ratio = _igvn.intcon(ratio_con);
1772       set_ctrl(ratio, C->root());
1773       Node* ratio_init = new (C) MulINode(init, ratio);
1774       _igvn.register_new_node_with_optimizer(ratio_init, init);
1775       set_early_ctrl(ratio_init);
1776       Node* diff = new (C) SubINode(init2, ratio_init);
1777       _igvn.register_new_node_with_optimizer(diff, init2);
1778       set_early_ctrl(diff);
1779       Node* ratio_idx = new (C) MulINode(phi, ratio);
1780       _igvn.register_new_node_with_optimizer(ratio_idx, phi);
1781       set_ctrl(ratio_idx, cl);
1782       Node* add = new (C) AddINode(ratio_idx, diff);
1783       _igvn.register_new_node_with_optimizer(add);
1784       set_ctrl(add, cl);
1785       _igvn.replace_node( phi2, add );
1786       // Sometimes an induction variable is unused
1787       if (add->outcnt() == 0) {
1788         _igvn.remove_dead_node(add);
1789       }
1790       --i; // deleted this phi; rescan starting with next position
1791       continue;
1792     }
1793   }
1794 }
1795 
1796 //------------------------------counted_loop-----------------------------------
1797 // Convert to counted loops where possible
1798 void IdealLoopTree::counted_loop( PhaseIdealLoop *phase ) {
1799 
1800   // For grins, set the inner-loop flag here
1801   if (!_child) {
1802     if (_head->is_Loop()) _head->as_Loop()->set_inner_loop();
1803   }
1804 
1805   if (_head->is_CountedLoop() ||
1806       phase->is_counted_loop(_head, this)) {
1807     _has_sfpt = 1;              // Indicate we do not need a safepoint here
1808 
1809     // Look for safepoints to remove.
1810     Node_List* sfpts = _safepts;
1811     if (sfpts != NULL) {
1812       for (uint i = 0; i < sfpts->size(); i++) {
1813         Node* n = sfpts->at(i);
1814         assert(phase->get_loop(n) == this, "");
1815         if (phase->is_deleteable_safept(n)) {
1816           phase->lazy_replace(n, n->in(TypeFunc::Control));
1817         }
1818       }
1819     }
1820 
1821     // Look for induction variables
1822     phase->replace_parallel_iv(this);
1823 
1824   } else if (_parent != NULL && !_irreducible) {
1825     // Not a counted loop.
1826     // Look for a safepoint on the idom-path.
1827     Node* sfpt = tail();
1828     for (; sfpt != _head; sfpt = phase->idom(sfpt)) {
1829       if (sfpt->Opcode() == Op_SafePoint && phase->get_loop(sfpt) == this)
1830         break; // Found one
1831     }
1832     // Delete other safepoints in this loop.
1833     Node_List* sfpts = _safepts;
1834     if (sfpts != NULL && sfpt != _head && sfpt->Opcode() == Op_SafePoint) {
1835       for (uint i = 0; i < sfpts->size(); i++) {
1836         Node* n = sfpts->at(i);
1837         assert(phase->get_loop(n) == this, "");
1838         if (n != sfpt && phase->is_deleteable_safept(n)) {
1839           phase->lazy_replace(n, n->in(TypeFunc::Control));
1840         }
1841       }
1842     }
1843   }
1844 
1845   // Recursively
1846   if (_child) _child->counted_loop( phase );
1847   if (_next)  _next ->counted_loop( phase );
1848 }
1849 
1850 #ifndef PRODUCT
1851 //------------------------------dump_head--------------------------------------
1852 // Dump 1 liner for loop header info
1853 void IdealLoopTree::dump_head( ) const {
1854   for (uint i=0; i<_nest; i++)
1855     tty->print("  ");
1856   tty->print("Loop: N%d/N%d ",_head->_idx,_tail->_idx);
1857   if (_irreducible) tty->print(" IRREDUCIBLE");
1858   Node* entry = _head->in(LoopNode::EntryControl);
1859   if (LoopLimitCheck) {
1860     Node* predicate = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1861     if (predicate != NULL ) {
1862       tty->print(" limit_check");
1863       entry = entry->in(0)->in(0);
1864     }
1865   }
1866   if (UseLoopPredicate) {
1867     entry = PhaseIdealLoop::find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1868     if (entry != NULL) {
1869       tty->print(" predicated");
1870     }
1871   }
1872   if (_head->is_CountedLoop()) {
1873     CountedLoopNode *cl = _head->as_CountedLoop();
1874     tty->print(" counted");
1875 
1876     Node* init_n = cl->init_trip();
1877     if (init_n  != NULL &&  init_n->is_Con())
1878       tty->print(" [%d,", cl->init_trip()->get_int());
1879     else
1880       tty->print(" [int,");
1881     Node* limit_n = cl->limit();
1882     if (limit_n  != NULL &&  limit_n->is_Con())
1883       tty->print("%d),", cl->limit()->get_int());
1884     else
1885       tty->print("int),");
1886     int stride_con  = cl->stride_con();
1887     if (stride_con > 0) tty->print("+");
1888     tty->print("%d", stride_con);
1889 
1890     tty->print(" (%d iters) ", (int)cl->profile_trip_cnt());
1891 
1892     if (cl->is_pre_loop ()) tty->print(" pre" );
1893     if (cl->is_main_loop()) tty->print(" main");
1894     if (cl->is_post_loop()) tty->print(" post");
1895   }
1896   tty->cr();
1897 }
1898 
1899 //------------------------------dump-------------------------------------------
1900 // Dump loops by loop tree
1901 void IdealLoopTree::dump( ) const {
1902   dump_head();
1903   if (_child) _child->dump();
1904   if (_next)  _next ->dump();
1905 }
1906 
1907 #endif
1908 
1909 static void log_loop_tree(IdealLoopTree* root, IdealLoopTree* loop, CompileLog* log) {
1910   if (loop == root) {
1911     if (loop->_child != NULL) {
1912       log->begin_head("loop_tree");
1913       log->end_head();
1914       if( loop->_child ) log_loop_tree(root, loop->_child, log);
1915       log->tail("loop_tree");
1916       assert(loop->_next == NULL, "what?");
1917     }
1918   } else {
1919     Node* head = loop->_head;
1920     log->begin_head("loop");
1921     log->print(" idx='%d' ", head->_idx);
1922     if (loop->_irreducible) log->print("irreducible='1' ");
1923     if (head->is_Loop()) {
1924       if (head->as_Loop()->is_inner_loop()) log->print("inner_loop='1' ");
1925       if (head->as_Loop()->is_partial_peel_loop()) log->print("partial_peel_loop='1' ");
1926     }
1927     if (head->is_CountedLoop()) {
1928       CountedLoopNode* cl = head->as_CountedLoop();
1929       if (cl->is_pre_loop())  log->print("pre_loop='%d' ",  cl->main_idx());
1930       if (cl->is_main_loop()) log->print("main_loop='%d' ", cl->_idx);
1931       if (cl->is_post_loop()) log->print("post_loop='%d' ",  cl->main_idx());
1932     }
1933     log->end_head();
1934     if( loop->_child ) log_loop_tree(root, loop->_child, log);
1935     log->tail("loop");
1936     if( loop->_next  ) log_loop_tree(root, loop->_next, log);
1937   }
1938 }
1939 
1940 //---------------------collect_potentially_useful_predicates-----------------------
1941 // Helper function to collect potentially useful predicates to prevent them from
1942 // being eliminated by PhaseIdealLoop::eliminate_useless_predicates
1943 void PhaseIdealLoop::collect_potentially_useful_predicates(
1944                          IdealLoopTree * loop, Unique_Node_List &useful_predicates) {
1945   if (loop->_child) { // child
1946     collect_potentially_useful_predicates(loop->_child, useful_predicates);
1947   }
1948 
1949   // self (only loops that we can apply loop predication may use their predicates)
1950   if (loop->_head->is_Loop() &&
1951       !loop->_irreducible    &&
1952       !loop->tail()->is_top()) {
1953     LoopNode* lpn = loop->_head->as_Loop();
1954     Node* entry = lpn->in(LoopNode::EntryControl);
1955     Node* predicate_proj = find_predicate(entry); // loop_limit_check first
1956     if (predicate_proj != NULL ) { // right pattern that can be used by loop predication
1957       assert(entry->in(0)->in(1)->in(1)->Opcode() == Op_Opaque1, "must be");
1958       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
1959       entry = entry->in(0)->in(0);
1960     }
1961     predicate_proj = find_predicate(entry); // Predicate
1962     if (predicate_proj != NULL ) {
1963       useful_predicates.push(entry->in(0)->in(1)->in(1)); // good one
1964     }
1965   }
1966 
1967   if (loop->_next) { // sibling
1968     collect_potentially_useful_predicates(loop->_next, useful_predicates);
1969   }
1970 }
1971 
1972 //------------------------eliminate_useless_predicates-----------------------------
1973 // Eliminate all inserted predicates if they could not be used by loop predication.
1974 // Note: it will also eliminates loop limits check predicate since it also uses
1975 // Opaque1 node (see Parse::add_predicate()).
1976 void PhaseIdealLoop::eliminate_useless_predicates() {
1977   if (C->predicate_count() == 0)
1978     return; // no predicate left
1979 
1980   Unique_Node_List useful_predicates; // to store useful predicates
1981   if (C->has_loops()) {
1982     collect_potentially_useful_predicates(_ltree_root->_child, useful_predicates);
1983   }
1984 
1985   for (int i = C->predicate_count(); i > 0; i--) {
1986      Node * n = C->predicate_opaque1_node(i-1);
1987      assert(n->Opcode() == Op_Opaque1, "must be");
1988      if (!useful_predicates.member(n)) { // not in the useful list
1989        _igvn.replace_node(n, n->in(1));
1990      }
1991   }
1992 }
1993 
1994 //------------------------process_expensive_nodes-----------------------------
1995 // Expensive nodes have their control input set to prevent the GVN
1996 // from commoning them and as a result forcing the resulting node to
1997 // be in a more frequent path. Use CFG information here, to change the
1998 // control inputs so that some expensive nodes can be commoned while
1999 // not executed more frequently.
2000 bool PhaseIdealLoop::process_expensive_nodes() {
2001   assert(OptimizeExpensiveOps, "optimization off?");
2002 
2003   // Sort nodes to bring similar nodes together
2004   C->sort_expensive_nodes();
2005 
2006   bool progress = false;
2007 
2008   for (int i = 0; i < C->expensive_count(); ) {
2009     Node* n = C->expensive_node(i);
2010     int start = i;
2011     // Find nodes similar to n
2012     i++;
2013     for (; i < C->expensive_count() && Compile::cmp_expensive_nodes(n, C->expensive_node(i)) == 0; i++);
2014     int end = i;
2015     // And compare them two by two
2016     for (int j = start; j < end; j++) {
2017       Node* n1 = C->expensive_node(j);
2018       if (is_node_unreachable(n1)) {
2019         continue;
2020       }
2021       for (int k = j+1; k < end; k++) {
2022         Node* n2 = C->expensive_node(k);
2023         if (is_node_unreachable(n2)) {
2024           continue;
2025         }
2026 
2027         assert(n1 != n2, "should be pair of nodes");
2028 
2029         Node* c1 = n1->in(0);
2030         Node* c2 = n2->in(0);
2031 
2032         Node* parent_c1 = c1;
2033         Node* parent_c2 = c2;
2034 
2035         // The call to get_early_ctrl_for_expensive() moves the
2036         // expensive nodes up but stops at loops that are in a if
2037         // branch. See whether we can exit the loop and move above the
2038         // If.
2039         if (c1->is_Loop()) {
2040           parent_c1 = c1->in(1);
2041         }
2042         if (c2->is_Loop()) {
2043           parent_c2 = c2->in(1);
2044         }
2045 
2046         if (parent_c1 == parent_c2) {
2047           _igvn._worklist.push(n1);
2048           _igvn._worklist.push(n2);
2049           continue;
2050         }
2051 
2052         // Look for identical expensive node up the dominator chain.
2053         if (is_dominator(c1, c2)) {
2054           c2 = c1;
2055         } else if (is_dominator(c2, c1)) {
2056           c1 = c2;
2057         } else if (parent_c1->is_Proj() && parent_c1->in(0)->is_If() &&
2058                    parent_c2->is_Proj() && parent_c1->in(0) == parent_c2->in(0)) {
2059           // Both branches have the same expensive node so move it up
2060           // before the if.
2061           c1 = c2 = idom(parent_c1->in(0));
2062         }
2063         // Do the actual moves
2064         if (n1->in(0) != c1) {
2065           _igvn.hash_delete(n1);
2066           n1->set_req(0, c1);
2067           _igvn.hash_insert(n1);
2068           _igvn._worklist.push(n1);
2069           progress = true;
2070         }
2071         if (n2->in(0) != c2) {
2072           _igvn.hash_delete(n2);
2073           n2->set_req(0, c2);
2074           _igvn.hash_insert(n2);
2075           _igvn._worklist.push(n2);
2076           progress = true;
2077         }
2078       }
2079     }
2080   }
2081 
2082   return progress;
2083 }
2084 
2085 
2086 //=============================================================================
2087 //----------------------------build_and_optimize-------------------------------
2088 // Create a PhaseLoop.  Build the ideal Loop tree.  Map each Ideal Node to
2089 // its corresponding LoopNode.  If 'optimize' is true, do some loop cleanups.
2090 void PhaseIdealLoop::build_and_optimize(bool do_split_ifs, bool skip_loop_opts) {
2091   ResourceMark rm;
2092 
2093   int old_progress = C->major_progress();
2094   uint orig_worklist_size = _igvn._worklist.size();
2095 
2096   // Reset major-progress flag for the driver's heuristics
2097   C->clear_major_progress();
2098 
2099 #ifndef PRODUCT
2100   // Capture for later assert
2101   uint unique = C->unique();
2102   _loop_invokes++;
2103   _loop_work += unique;
2104 #endif
2105 
2106   // True if the method has at least 1 irreducible loop
2107   _has_irreducible_loops = false;
2108 
2109   _created_loop_node = false;
2110 
2111   Arena *a = Thread::current()->resource_area();
2112   VectorSet visited(a);
2113   // Pre-grow the mapping from Nodes to IdealLoopTrees.
2114   _nodes.map(C->unique(), NULL);
2115   memset(_nodes.adr(), 0, wordSize * C->unique());
2116 
2117   // Pre-build the top-level outermost loop tree entry
2118   _ltree_root = new IdealLoopTree( this, C->root(), C->root() );
2119   // Do not need a safepoint at the top level
2120   _ltree_root->_has_sfpt = 1;
2121 
2122   // Initialize Dominators.
2123   // Checked in clone_loop_predicate() during beautify_loops().
2124   _idom_size = 0;
2125   _idom      = NULL;
2126   _dom_depth = NULL;
2127   _dom_stk   = NULL;
2128 
2129   // Empty pre-order array
2130   allocate_preorders();
2131 
2132   // Build a loop tree on the fly.  Build a mapping from CFG nodes to
2133   // IdealLoopTree entries.  Data nodes are NOT walked.
2134   build_loop_tree();
2135   // Check for bailout, and return
2136   if (C->failing()) {
2137     return;
2138   }
2139 
2140   // No loops after all
2141   if( !_ltree_root->_child && !_verify_only ) C->set_has_loops(false);
2142 
2143   // There should always be an outer loop containing the Root and Return nodes.
2144   // If not, we have a degenerate empty program.  Bail out in this case.
2145   if (!has_node(C->root())) {
2146     if (!_verify_only) {
2147       C->clear_major_progress();
2148       C->record_method_not_compilable("empty program detected during loop optimization");
2149     }
2150     return;
2151   }
2152 
2153   // Nothing to do, so get out
2154   bool stop_early = !C->has_loops() && !skip_loop_opts && !do_split_ifs && !_verify_me && !_verify_only;
2155   bool do_expensive_nodes = C->should_optimize_expensive_nodes(_igvn);
2156   if (stop_early && !do_expensive_nodes) {
2157     _igvn.optimize();           // Cleanup NeverBranches
2158     return;
2159   }
2160 
2161   // Set loop nesting depth
2162   _ltree_root->set_nest( 0 );
2163 
2164   // Split shared headers and insert loop landing pads.
2165   // Do not bother doing this on the Root loop of course.
2166   if( !_verify_me && !_verify_only && _ltree_root->_child ) {
2167     C->print_method(PHASE_BEFORE_BEAUTIFY_LOOPS, 3);
2168     if( _ltree_root->_child->beautify_loops( this ) ) {
2169       // Re-build loop tree!
2170       _ltree_root->_child = NULL;
2171       _nodes.clear();
2172       reallocate_preorders();
2173       build_loop_tree();
2174       // Check for bailout, and return
2175       if (C->failing()) {
2176         return;
2177       }
2178       // Reset loop nesting depth
2179       _ltree_root->set_nest( 0 );
2180 
2181       C->print_method(PHASE_AFTER_BEAUTIFY_LOOPS, 3);
2182     }
2183   }
2184 
2185   // Build Dominators for elision of NULL checks & loop finding.
2186   // Since nodes do not have a slot for immediate dominator, make
2187   // a persistent side array for that info indexed on node->_idx.
2188   _idom_size = C->unique();
2189   _idom      = NEW_RESOURCE_ARRAY( Node*, _idom_size );
2190   _dom_depth = NEW_RESOURCE_ARRAY( uint,  _idom_size );
2191   _dom_stk   = NULL; // Allocated on demand in recompute_dom_depth
2192   memset( _dom_depth, 0, _idom_size * sizeof(uint) );
2193 
2194   Dominators();
2195 
2196   if (!_verify_only) {
2197     // As a side effect, Dominators removed any unreachable CFG paths
2198     // into RegionNodes.  It doesn't do this test against Root, so
2199     // we do it here.
2200     for( uint i = 1; i < C->root()->req(); i++ ) {
2201       if( !_nodes[C->root()->in(i)->_idx] ) {    // Dead path into Root?
2202         _igvn.delete_input_of(C->root(), i);
2203         i--;                      // Rerun same iteration on compressed edges
2204       }
2205     }
2206 
2207     // Given dominators, try to find inner loops with calls that must
2208     // always be executed (call dominates loop tail).  These loops do
2209     // not need a separate safepoint.
2210     Node_List cisstack(a);
2211     _ltree_root->check_safepts(visited, cisstack);
2212   }
2213 
2214   // Walk the DATA nodes and place into loops.  Find earliest control
2215   // node.  For CFG nodes, the _nodes array starts out and remains
2216   // holding the associated IdealLoopTree pointer.  For DATA nodes, the
2217   // _nodes array holds the earliest legal controlling CFG node.
2218 
2219   // Allocate stack with enough space to avoid frequent realloc
2220   int stack_size = (C->unique() >> 1) + 16; // (unique>>1)+16 from Java2D stats
2221   Node_Stack nstack( a, stack_size );
2222 
2223   visited.Clear();
2224   Node_List worklist(a);
2225   // Don't need C->root() on worklist since
2226   // it will be processed among C->top() inputs
2227   worklist.push( C->top() );
2228   visited.set( C->top()->_idx ); // Set C->top() as visited now
2229   build_loop_early( visited, worklist, nstack );
2230 
2231   // Given early legal placement, try finding counted loops.  This placement
2232   // is good enough to discover most loop invariants.
2233   if( !_verify_me && !_verify_only )
2234     _ltree_root->counted_loop( this );
2235 
2236   // Find latest loop placement.  Find ideal loop placement.
2237   visited.Clear();
2238   init_dom_lca_tags();
2239   // Need C->root() on worklist when processing outs
2240   worklist.push( C->root() );
2241   NOT_PRODUCT( C->verify_graph_edges(); )
2242   worklist.push( C->top() );
2243   build_loop_late( visited, worklist, nstack );
2244 
2245   if (_verify_only) {
2246     // restore major progress flag
2247     for (int i = 0; i < old_progress; i++)
2248       C->set_major_progress();
2249     assert(C->unique() == unique, "verification mode made Nodes? ? ?");
2250     assert(_igvn._worklist.size() == orig_worklist_size, "shouldn't push anything");
2251     return;
2252   }
2253 
2254   // clear out the dead code after build_loop_late
2255   while (_deadlist.size()) {
2256     _igvn.remove_globally_dead_node(_deadlist.pop());
2257   }
2258 
2259   if (stop_early) {
2260     assert(do_expensive_nodes, "why are we here?");
2261     if (process_expensive_nodes()) {
2262       // If we made some progress when processing expensive nodes then
2263       // the IGVN may modify the graph in a way that will allow us to
2264       // make some more progress: we need to try processing expensive
2265       // nodes again.
2266       C->set_major_progress();
2267     }
2268     _igvn.optimize();
2269     return;
2270   }
2271 
2272   // Some parser-inserted loop predicates could never be used by loop
2273   // predication or they were moved away from loop during some optimizations.
2274   // For example, peeling. Eliminate them before next loop optimizations.
2275   if (UseLoopPredicate || LoopLimitCheck) {
2276     eliminate_useless_predicates();
2277   }
2278 
2279 #ifndef PRODUCT
2280   C->verify_graph_edges();
2281   if (_verify_me) {             // Nested verify pass?
2282     // Check to see if the verify mode is broken
2283     assert(C->unique() == unique, "non-optimize mode made Nodes? ? ?");
2284     return;
2285   }
2286   if(VerifyLoopOptimizations) verify();
2287   if(TraceLoopOpts && C->has_loops()) {
2288     _ltree_root->dump();
2289   }
2290 #endif
2291 
2292   if (skip_loop_opts) {
2293     // Cleanup any modified bits
2294     _igvn.optimize();
2295 
2296     if (C->log() != NULL) {
2297       log_loop_tree(_ltree_root, _ltree_root, C->log());
2298     }
2299     return;
2300   }
2301 
2302   if (ReassociateInvariants) {
2303     // Reassociate invariants and prep for split_thru_phi
2304     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2305       IdealLoopTree* lpt = iter.current();
2306       if (!lpt->is_counted() || !lpt->is_inner()) continue;
2307 
2308       lpt->reassociate_invariants(this);
2309 
2310       // Because RCE opportunities can be masked by split_thru_phi,
2311       // look for RCE candidates and inhibit split_thru_phi
2312       // on just their loop-phi's for this pass of loop opts
2313       if (SplitIfBlocks && do_split_ifs) {
2314         if (lpt->policy_range_check(this)) {
2315           lpt->_rce_candidate = 1; // = true
2316         }
2317       }
2318     }
2319   }
2320 
2321   // Check for aggressive application of split-if and other transforms
2322   // that require basic-block info (like cloning through Phi's)
2323   if( SplitIfBlocks && do_split_ifs ) {
2324     visited.Clear();
2325     split_if_with_blocks( visited, nstack );
2326     NOT_PRODUCT( if( VerifyLoopOptimizations ) verify(); );
2327   }
2328 
2329   if (!C->major_progress() && do_expensive_nodes && process_expensive_nodes()) {
2330     C->set_major_progress();
2331   }
2332 
2333   // Perform loop predication before iteration splitting
2334   if (C->has_loops() && !C->major_progress() && (C->predicate_count() > 0)) {
2335     _ltree_root->_child->loop_predication(this);
2336   }
2337 
2338   if (OptimizeFill && UseLoopPredicate && C->has_loops() && !C->major_progress()) {
2339     if (do_intrinsify_fill()) {
2340       C->set_major_progress();
2341     }
2342   }
2343 
2344   // Perform iteration-splitting on inner loops.  Split iterations to avoid
2345   // range checks or one-shot null checks.
2346 
2347   // If split-if's didn't hack the graph too bad (no CFG changes)
2348   // then do loop opts.
2349   if (C->has_loops() && !C->major_progress()) {
2350     memset( worklist.adr(), 0, worklist.Size()*sizeof(Node*) );
2351     _ltree_root->_child->iteration_split( this, worklist );
2352     // No verify after peeling!  GCM has hoisted code out of the loop.
2353     // After peeling, the hoisted code could sink inside the peeled area.
2354     // The peeling code does not try to recompute the best location for
2355     // all the code before the peeled area, so the verify pass will always
2356     // complain about it.
2357   }
2358   // Do verify graph edges in any case
2359   NOT_PRODUCT( C->verify_graph_edges(); );
2360 
2361   if (!do_split_ifs) {
2362     // We saw major progress in Split-If to get here.  We forced a
2363     // pass with unrolling and not split-if, however more split-if's
2364     // might make progress.  If the unrolling didn't make progress
2365     // then the major-progress flag got cleared and we won't try
2366     // another round of Split-If.  In particular the ever-common
2367     // instance-of/check-cast pattern requires at least 2 rounds of
2368     // Split-If to clear out.
2369     C->set_major_progress();
2370   }
2371 
2372   // Repeat loop optimizations if new loops were seen
2373   if (created_loop_node()) {
2374     C->set_major_progress();
2375   }
2376 
2377   // Keep loop predicates and perform optimizations with them
2378   // until no more loop optimizations could be done.
2379   // After that switch predicates off and do more loop optimizations.
2380   if (!C->major_progress() && (C->predicate_count() > 0)) {
2381      C->cleanup_loop_predicates(_igvn);
2382 #ifndef PRODUCT
2383      if (TraceLoopOpts) {
2384        tty->print_cr("PredicatesOff");
2385      }
2386 #endif
2387      C->set_major_progress();
2388   }
2389 
2390   // Convert scalar to superword operations at the end of all loop opts.
2391   if (UseSuperWord && C->has_loops() && !C->major_progress()) {
2392     // SuperWord transform
2393     SuperWord sw(this);
2394     for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
2395       IdealLoopTree* lpt = iter.current();
2396       if (lpt->is_counted()) {
2397         sw.transform_loop(lpt);
2398       }
2399     }
2400   }
2401 
2402   // Cleanup any modified bits
2403   _igvn.optimize();
2404 
2405   // disable assert until issue with split_flow_path is resolved (6742111)
2406   // assert(!_has_irreducible_loops || C->parsed_irreducible_loop() || C->is_osr_compilation(),
2407   //        "shouldn't introduce irreducible loops");
2408 
2409   if (C->log() != NULL) {
2410     log_loop_tree(_ltree_root, _ltree_root, C->log());
2411   }
2412 }
2413 
2414 #ifndef PRODUCT
2415 //------------------------------print_statistics-------------------------------
2416 int PhaseIdealLoop::_loop_invokes=0;// Count of PhaseIdealLoop invokes
2417 int PhaseIdealLoop::_loop_work=0; // Sum of PhaseIdealLoop x unique
2418 void PhaseIdealLoop::print_statistics() {
2419   tty->print_cr("PhaseIdealLoop=%d, sum _unique=%d", _loop_invokes, _loop_work);
2420 }
2421 
2422 //------------------------------verify-----------------------------------------
2423 // Build a verify-only PhaseIdealLoop, and see that it agrees with me.
2424 static int fail;                // debug only, so its multi-thread dont care
2425 void PhaseIdealLoop::verify() const {
2426   int old_progress = C->major_progress();
2427   ResourceMark rm;
2428   PhaseIdealLoop loop_verify( _igvn, this );
2429   VectorSet visited(Thread::current()->resource_area());
2430 
2431   fail = 0;
2432   verify_compare( C->root(), &loop_verify, visited );
2433   assert( fail == 0, "verify loops failed" );
2434   // Verify loop structure is the same
2435   _ltree_root->verify_tree(loop_verify._ltree_root, NULL);
2436   // Reset major-progress.  It was cleared by creating a verify version of
2437   // PhaseIdealLoop.
2438   for( int i=0; i<old_progress; i++ )
2439     C->set_major_progress();
2440 }
2441 
2442 //------------------------------verify_compare---------------------------------
2443 // Make sure me and the given PhaseIdealLoop agree on key data structures
2444 void PhaseIdealLoop::verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const {
2445   if( !n ) return;
2446   if( visited.test_set( n->_idx ) ) return;
2447   if( !_nodes[n->_idx] ) {      // Unreachable
2448     assert( !loop_verify->_nodes[n->_idx], "both should be unreachable" );
2449     return;
2450   }
2451 
2452   uint i;
2453   for( i = 0; i < n->req(); i++ )
2454     verify_compare( n->in(i), loop_verify, visited );
2455 
2456   // Check the '_nodes' block/loop structure
2457   i = n->_idx;
2458   if( has_ctrl(n) ) {           // We have control; verify has loop or ctrl
2459     if( _nodes[i] != loop_verify->_nodes[i] &&
2460         get_ctrl_no_update(n) != loop_verify->get_ctrl_no_update(n) ) {
2461       tty->print("Mismatched control setting for: ");
2462       n->dump();
2463       if( fail++ > 10 ) return;
2464       Node *c = get_ctrl_no_update(n);
2465       tty->print("We have it as: ");
2466       if( c->in(0) ) c->dump();
2467         else tty->print_cr("N%d",c->_idx);
2468       tty->print("Verify thinks: ");
2469       if( loop_verify->has_ctrl(n) )
2470         loop_verify->get_ctrl_no_update(n)->dump();
2471       else
2472         loop_verify->get_loop_idx(n)->dump();
2473       tty->cr();
2474     }
2475   } else {                    // We have a loop
2476     IdealLoopTree *us = get_loop_idx(n);
2477     if( loop_verify->has_ctrl(n) ) {
2478       tty->print("Mismatched loop setting for: ");
2479       n->dump();
2480       if( fail++ > 10 ) return;
2481       tty->print("We have it as: ");
2482       us->dump();
2483       tty->print("Verify thinks: ");
2484       loop_verify->get_ctrl_no_update(n)->dump();
2485       tty->cr();
2486     } else if (!C->major_progress()) {
2487       // Loop selection can be messed up if we did a major progress
2488       // operation, like split-if.  Do not verify in that case.
2489       IdealLoopTree *them = loop_verify->get_loop_idx(n);
2490       if( us->_head != them->_head ||  us->_tail != them->_tail ) {
2491         tty->print("Unequals loops for: ");
2492         n->dump();
2493         if( fail++ > 10 ) return;
2494         tty->print("We have it as: ");
2495         us->dump();
2496         tty->print("Verify thinks: ");
2497         them->dump();
2498         tty->cr();
2499       }
2500     }
2501   }
2502 
2503   // Check for immediate dominators being equal
2504   if( i >= _idom_size ) {
2505     if( !n->is_CFG() ) return;
2506     tty->print("CFG Node with no idom: ");
2507     n->dump();
2508     return;
2509   }
2510   if( !n->is_CFG() ) return;
2511   if( n == C->root() ) return; // No IDOM here
2512 
2513   assert(n->_idx == i, "sanity");
2514   Node *id = idom_no_update(n);
2515   if( id != loop_verify->idom_no_update(n) ) {
2516     tty->print("Unequals idoms for: ");
2517     n->dump();
2518     if( fail++ > 10 ) return;
2519     tty->print("We have it as: ");
2520     id->dump();
2521     tty->print("Verify thinks: ");
2522     loop_verify->idom_no_update(n)->dump();
2523     tty->cr();
2524   }
2525 
2526 }
2527 
2528 //------------------------------verify_tree------------------------------------
2529 // Verify that tree structures match.  Because the CFG can change, siblings
2530 // within the loop tree can be reordered.  We attempt to deal with that by
2531 // reordering the verify's loop tree if possible.
2532 void IdealLoopTree::verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const {
2533   assert( _parent == parent, "Badly formed loop tree" );
2534 
2535   // Siblings not in same order?  Attempt to re-order.
2536   if( _head != loop->_head ) {
2537     // Find _next pointer to update
2538     IdealLoopTree **pp = &loop->_parent->_child;
2539     while( *pp != loop )
2540       pp = &((*pp)->_next);
2541     // Find proper sibling to be next
2542     IdealLoopTree **nn = &loop->_next;
2543     while( (*nn) && (*nn)->_head != _head )
2544       nn = &((*nn)->_next);
2545 
2546     // Check for no match.
2547     if( !(*nn) ) {
2548       // Annoyingly, irreducible loops can pick different headers
2549       // after a major_progress operation, so the rest of the loop
2550       // tree cannot be matched.
2551       if (_irreducible && Compile::current()->major_progress())  return;
2552       assert( 0, "failed to match loop tree" );
2553     }
2554 
2555     // Move (*nn) to (*pp)
2556     IdealLoopTree *hit = *nn;
2557     *nn = hit->_next;
2558     hit->_next = loop;
2559     *pp = loop;
2560     loop = hit;
2561     // Now try again to verify
2562   }
2563 
2564   assert( _head  == loop->_head , "mismatched loop head" );
2565   Node *tail = _tail;           // Inline a non-updating version of
2566   while( !tail->in(0) )         // the 'tail()' call.
2567     tail = tail->in(1);
2568   assert( tail == loop->_tail, "mismatched loop tail" );
2569 
2570   // Counted loops that are guarded should be able to find their guards
2571   if( _head->is_CountedLoop() && _head->as_CountedLoop()->is_main_loop() ) {
2572     CountedLoopNode *cl = _head->as_CountedLoop();
2573     Node *init = cl->init_trip();
2574     Node *ctrl = cl->in(LoopNode::EntryControl);
2575     assert( ctrl->Opcode() == Op_IfTrue || ctrl->Opcode() == Op_IfFalse, "" );
2576     Node *iff  = ctrl->in(0);
2577     assert( iff->Opcode() == Op_If, "" );
2578     Node *bol  = iff->in(1);
2579     assert( bol->Opcode() == Op_Bool, "" );
2580     Node *cmp  = bol->in(1);
2581     assert( cmp->Opcode() == Op_CmpI, "" );
2582     Node *add  = cmp->in(1);
2583     Node *opaq;
2584     if( add->Opcode() == Op_Opaque1 ) {
2585       opaq = add;
2586     } else {
2587       assert( add->Opcode() == Op_AddI || add->Opcode() == Op_ConI , "" );
2588       assert( add == init, "" );
2589       opaq = cmp->in(2);
2590     }
2591     assert( opaq->Opcode() == Op_Opaque1, "" );
2592 
2593   }
2594 
2595   if (_child != NULL)  _child->verify_tree(loop->_child, this);
2596   if (_next  != NULL)  _next ->verify_tree(loop->_next,  parent);
2597   // Innermost loops need to verify loop bodies,
2598   // but only if no 'major_progress'
2599   int fail = 0;
2600   if (!Compile::current()->major_progress() && _child == NULL) {
2601     for( uint i = 0; i < _body.size(); i++ ) {
2602       Node *n = _body.at(i);
2603       if (n->outcnt() == 0)  continue; // Ignore dead
2604       uint j;
2605       for( j = 0; j < loop->_body.size(); j++ )
2606         if( loop->_body.at(j) == n )
2607           break;
2608       if( j == loop->_body.size() ) { // Not found in loop body
2609         // Last ditch effort to avoid assertion: Its possible that we
2610         // have some users (so outcnt not zero) but are still dead.
2611         // Try to find from root.
2612         if (Compile::current()->root()->find(n->_idx)) {
2613           fail++;
2614           tty->print("We have that verify does not: ");
2615           n->dump();
2616         }
2617       }
2618     }
2619     for( uint i2 = 0; i2 < loop->_body.size(); i2++ ) {
2620       Node *n = loop->_body.at(i2);
2621       if (n->outcnt() == 0)  continue; // Ignore dead
2622       uint j;
2623       for( j = 0; j < _body.size(); j++ )
2624         if( _body.at(j) == n )
2625           break;
2626       if( j == _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("Verify has that we do not: ");
2633           n->dump();
2634         }
2635       }
2636     }
2637     assert( !fail, "loop body mismatch" );
2638   }
2639 }
2640 
2641 #endif
2642 
2643 //------------------------------set_idom---------------------------------------
2644 void PhaseIdealLoop::set_idom(Node* d, Node* n, uint dom_depth) {
2645   uint idx = d->_idx;
2646   if (idx >= _idom_size) {
2647     uint newsize = _idom_size<<1;
2648     while( idx >= newsize ) {
2649       newsize <<= 1;
2650     }
2651     _idom      = REALLOC_RESOURCE_ARRAY( Node*,     _idom,_idom_size,newsize);
2652     _dom_depth = REALLOC_RESOURCE_ARRAY( uint, _dom_depth,_idom_size,newsize);
2653     memset( _dom_depth + _idom_size, 0, (newsize - _idom_size) * sizeof(uint) );
2654     _idom_size = newsize;
2655   }
2656   _idom[idx] = n;
2657   _dom_depth[idx] = dom_depth;
2658 }
2659 
2660 //------------------------------recompute_dom_depth---------------------------------------
2661 // The dominator tree is constructed with only parent pointers.
2662 // This recomputes the depth in the tree by first tagging all
2663 // nodes as "no depth yet" marker.  The next pass then runs up
2664 // the dom tree from each node marked "no depth yet", and computes
2665 // the depth on the way back down.
2666 void PhaseIdealLoop::recompute_dom_depth() {
2667   uint no_depth_marker = C->unique();
2668   uint i;
2669   // Initialize depth to "no depth yet"
2670   for (i = 0; i < _idom_size; i++) {
2671     if (_dom_depth[i] > 0 && _idom[i] != NULL) {
2672      _dom_depth[i] = no_depth_marker;
2673     }
2674   }
2675   if (_dom_stk == NULL) {
2676     uint init_size = C->unique() / 100; // Guess that 1/100 is a reasonable initial size.
2677     if (init_size < 10) init_size = 10;
2678     _dom_stk = new GrowableArray<uint>(init_size);
2679   }
2680   // Compute new depth for each node.
2681   for (i = 0; i < _idom_size; i++) {
2682     uint j = i;
2683     // Run up the dom tree to find a node with a depth
2684     while (_dom_depth[j] == no_depth_marker) {
2685       _dom_stk->push(j);
2686       j = _idom[j]->_idx;
2687     }
2688     // Compute the depth on the way back down this tree branch
2689     uint dd = _dom_depth[j] + 1;
2690     while (_dom_stk->length() > 0) {
2691       uint j = _dom_stk->pop();
2692       _dom_depth[j] = dd;
2693       dd++;
2694     }
2695   }
2696 }
2697 
2698 //------------------------------sort-------------------------------------------
2699 // Insert 'loop' into the existing loop tree.  'innermost' is a leaf of the
2700 // loop tree, not the root.
2701 IdealLoopTree *PhaseIdealLoop::sort( IdealLoopTree *loop, IdealLoopTree *innermost ) {
2702   if( !innermost ) return loop; // New innermost loop
2703 
2704   int loop_preorder = get_preorder(loop->_head); // Cache pre-order number
2705   assert( loop_preorder, "not yet post-walked loop" );
2706   IdealLoopTree **pp = &innermost;      // Pointer to previous next-pointer
2707   IdealLoopTree *l = *pp;               // Do I go before or after 'l'?
2708 
2709   // Insert at start of list
2710   while( l ) {                  // Insertion sort based on pre-order
2711     if( l == loop ) return innermost; // Already on list!
2712     int l_preorder = get_preorder(l->_head); // Cache pre-order number
2713     assert( l_preorder, "not yet post-walked l" );
2714     // Check header pre-order number to figure proper nesting
2715     if( loop_preorder > l_preorder )
2716       break;                    // End of insertion
2717     // If headers tie (e.g., shared headers) check tail pre-order numbers.
2718     // Since I split shared headers, you'd think this could not happen.
2719     // BUT: I must first do the preorder numbering before I can discover I
2720     // have shared headers, so the split headers all get the same preorder
2721     // number as the RegionNode they split from.
2722     if( loop_preorder == l_preorder &&
2723         get_preorder(loop->_tail) < get_preorder(l->_tail) )
2724       break;                    // Also check for shared headers (same pre#)
2725     pp = &l->_parent;           // Chain up list
2726     l = *pp;
2727   }
2728   // Link into list
2729   // Point predecessor to me
2730   *pp = loop;
2731   // Point me to successor
2732   IdealLoopTree *p = loop->_parent;
2733   loop->_parent = l;            // Point me to successor
2734   if( p ) sort( p, innermost ); // Insert my parents into list as well
2735   return innermost;
2736 }
2737 
2738 //------------------------------build_loop_tree--------------------------------
2739 // I use a modified Vick/Tarjan algorithm.  I need pre- and a post- visit
2740 // bits.  The _nodes[] array is mapped by Node index and holds a NULL for
2741 // not-yet-pre-walked, pre-order # for pre-but-not-post-walked and holds the
2742 // tightest enclosing IdealLoopTree for post-walked.
2743 //
2744 // During my forward walk I do a short 1-layer lookahead to see if I can find
2745 // a loop backedge with that doesn't have any work on the backedge.  This
2746 // helps me construct nested loops with shared headers better.
2747 //
2748 // Once I've done the forward recursion, I do the post-work.  For each child
2749 // I check to see if there is a backedge.  Backedges define a loop!  I
2750 // insert an IdealLoopTree at the target of the backedge.
2751 //
2752 // During the post-work I also check to see if I have several children
2753 // belonging to different loops.  If so, then this Node is a decision point
2754 // where control flow can choose to change loop nests.  It is at this
2755 // decision point where I can figure out how loops are nested.  At this
2756 // time I can properly order the different loop nests from my children.
2757 // Note that there may not be any backedges at the decision point!
2758 //
2759 // Since the decision point can be far removed from the backedges, I can't
2760 // order my loops at the time I discover them.  Thus at the decision point
2761 // I need to inspect loop header pre-order numbers to properly nest my
2762 // loops.  This means I need to sort my childrens' loops by pre-order.
2763 // The sort is of size number-of-control-children, which generally limits
2764 // it to size 2 (i.e., I just choose between my 2 target loops).
2765 void PhaseIdealLoop::build_loop_tree() {
2766   // Allocate stack of size C->unique()/2 to avoid frequent realloc
2767   GrowableArray <Node *> bltstack(C->unique() >> 1);
2768   Node *n = C->root();
2769   bltstack.push(n);
2770   int pre_order = 1;
2771   int stack_size;
2772 
2773   while ( ( stack_size = bltstack.length() ) != 0 ) {
2774     n = bltstack.top(); // Leave node on stack
2775     if ( !is_visited(n) ) {
2776       // ---- Pre-pass Work ----
2777       // Pre-walked but not post-walked nodes need a pre_order number.
2778 
2779       set_preorder_visited( n, pre_order ); // set as visited
2780 
2781       // ---- Scan over children ----
2782       // Scan first over control projections that lead to loop headers.
2783       // This helps us find inner-to-outer loops with shared headers better.
2784 
2785       // Scan children's children for loop headers.
2786       for ( int i = n->outcnt() - 1; i >= 0; --i ) {
2787         Node* m = n->raw_out(i);       // Child
2788         if( m->is_CFG() && !is_visited(m) ) { // Only for CFG children
2789           // Scan over children's children to find loop
2790           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2791             Node* l = m->fast_out(j);
2792             if( is_visited(l) &&       // Been visited?
2793                 !is_postvisited(l) &&  // But not post-visited
2794                 get_preorder(l) < pre_order ) { // And smaller pre-order
2795               // Found!  Scan the DFS down this path before doing other paths
2796               bltstack.push(m);
2797               break;
2798             }
2799           }
2800         }
2801       }
2802       pre_order++;
2803     }
2804     else if ( !is_postvisited(n) ) {
2805       // Note: build_loop_tree_impl() adds out edges on rare occasions,
2806       // such as com.sun.rsasign.am::a.
2807       // For non-recursive version, first, process current children.
2808       // On next iteration, check if additional children were added.
2809       for ( int k = n->outcnt() - 1; k >= 0; --k ) {
2810         Node* u = n->raw_out(k);
2811         if ( u->is_CFG() && !is_visited(u) ) {
2812           bltstack.push(u);
2813         }
2814       }
2815       if ( bltstack.length() == stack_size ) {
2816         // There were no additional children, post visit node now
2817         (void)bltstack.pop(); // Remove node from stack
2818         pre_order = build_loop_tree_impl( n, pre_order );
2819         // Check for bailout
2820         if (C->failing()) {
2821           return;
2822         }
2823         // Check to grow _preorders[] array for the case when
2824         // build_loop_tree_impl() adds new nodes.
2825         check_grow_preorders();
2826       }
2827     }
2828     else {
2829       (void)bltstack.pop(); // Remove post-visited node from stack
2830     }
2831   }
2832 }
2833 
2834 //------------------------------build_loop_tree_impl---------------------------
2835 int PhaseIdealLoop::build_loop_tree_impl( Node *n, int pre_order ) {
2836   // ---- Post-pass Work ----
2837   // Pre-walked but not post-walked nodes need a pre_order number.
2838 
2839   // Tightest enclosing loop for this Node
2840   IdealLoopTree *innermost = NULL;
2841 
2842   // For all children, see if any edge is a backedge.  If so, make a loop
2843   // for it.  Then find the tightest enclosing loop for the self Node.
2844   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
2845     Node* m = n->fast_out(i);   // Child
2846     if( n == m ) continue;      // Ignore control self-cycles
2847     if( !m->is_CFG() ) continue;// Ignore non-CFG edges
2848 
2849     IdealLoopTree *l;           // Child's loop
2850     if( !is_postvisited(m) ) {  // Child visited but not post-visited?
2851       // Found a backedge
2852       assert( get_preorder(m) < pre_order, "should be backedge" );
2853       // Check for the RootNode, which is already a LoopNode and is allowed
2854       // to have multiple "backedges".
2855       if( m == C->root()) {     // Found the root?
2856         l = _ltree_root;        // Root is the outermost LoopNode
2857       } else {                  // Else found a nested loop
2858         // Insert a LoopNode to mark this loop.
2859         l = new IdealLoopTree(this, m, n);
2860       } // End of Else found a nested loop
2861       if( !has_loop(m) )        // If 'm' does not already have a loop set
2862         set_loop(m, l);         // Set loop header to loop now
2863 
2864     } else {                    // Else not a nested loop
2865       if( !_nodes[m->_idx] ) continue; // Dead code has no loop
2866       l = get_loop(m);          // Get previously determined loop
2867       // If successor is header of a loop (nest), move up-loop till it
2868       // is a member of some outer enclosing loop.  Since there are no
2869       // shared headers (I've split them already) I only need to go up
2870       // at most 1 level.
2871       while( l && l->_head == m ) // Successor heads loop?
2872         l = l->_parent;         // Move up 1 for me
2873       // If this loop is not properly parented, then this loop
2874       // has no exit path out, i.e. its an infinite loop.
2875       if( !l ) {
2876         // Make loop "reachable" from root so the CFG is reachable.  Basically
2877         // insert a bogus loop exit that is never taken.  'm', the loop head,
2878         // points to 'n', one (of possibly many) fall-in paths.  There may be
2879         // many backedges as well.
2880 
2881         // Here I set the loop to be the root loop.  I could have, after
2882         // inserting a bogus loop exit, restarted the recursion and found my
2883         // new loop exit.  This would make the infinite loop a first-class
2884         // loop and it would then get properly optimized.  What's the use of
2885         // optimizing an infinite loop?
2886         l = _ltree_root;        // Oops, found infinite loop
2887 
2888         if (!_verify_only) {
2889           // Insert the NeverBranch between 'm' and it's control user.
2890           NeverBranchNode *iff = new (C) NeverBranchNode( m );
2891           _igvn.register_new_node_with_optimizer(iff);
2892           set_loop(iff, l);
2893           Node *if_t = new (C) CProjNode( iff, 0 );
2894           _igvn.register_new_node_with_optimizer(if_t);
2895           set_loop(if_t, l);
2896 
2897           Node* cfg = NULL;       // Find the One True Control User of m
2898           for (DUIterator_Fast jmax, j = m->fast_outs(jmax); j < jmax; j++) {
2899             Node* x = m->fast_out(j);
2900             if (x->is_CFG() && x != m && x != iff)
2901               { cfg = x; break; }
2902           }
2903           assert(cfg != NULL, "must find the control user of m");
2904           uint k = 0;             // Probably cfg->in(0)
2905           while( cfg->in(k) != m ) k++; // But check incase cfg is a Region
2906           cfg->set_req( k, if_t ); // Now point to NeverBranch
2907 
2908           // Now create the never-taken loop exit
2909           Node *if_f = new (C) CProjNode( iff, 1 );
2910           _igvn.register_new_node_with_optimizer(if_f);
2911           set_loop(if_f, l);
2912           // Find frame ptr for Halt.  Relies on the optimizer
2913           // V-N'ing.  Easier and quicker than searching through
2914           // the program structure.
2915           Node *frame = new (C) ParmNode( C->start(), TypeFunc::FramePtr );
2916           _igvn.register_new_node_with_optimizer(frame);
2917           // Halt & Catch Fire
2918           Node *halt = new (C) HaltNode( if_f, frame );
2919           _igvn.register_new_node_with_optimizer(halt);
2920           set_loop(halt, l);
2921           C->root()->add_req(halt);
2922         }
2923         set_loop(C->root(), _ltree_root);
2924       }
2925     }
2926     // Weeny check for irreducible.  This child was already visited (this
2927     // IS the post-work phase).  Is this child's loop header post-visited
2928     // as well?  If so, then I found another entry into the loop.
2929     if (!_verify_only) {
2930       while( is_postvisited(l->_head) ) {
2931         // found irreducible
2932         l->_irreducible = 1; // = true
2933         l = l->_parent;
2934         _has_irreducible_loops = true;
2935         // Check for bad CFG here to prevent crash, and bailout of compile
2936         if (l == NULL) {
2937           C->record_method_not_compilable("unhandled CFG detected during loop optimization");
2938           return pre_order;
2939         }
2940       }
2941     }
2942 
2943     // This Node might be a decision point for loops.  It is only if
2944     // it's children belong to several different loops.  The sort call
2945     // does a trivial amount of work if there is only 1 child or all
2946     // children belong to the same loop.  If however, the children
2947     // belong to different loops, the sort call will properly set the
2948     // _parent pointers to show how the loops nest.
2949     //
2950     // In any case, it returns the tightest enclosing loop.
2951     innermost = sort( l, innermost );
2952   }
2953 
2954   // Def-use info will have some dead stuff; dead stuff will have no
2955   // loop decided on.
2956 
2957   // Am I a loop header?  If so fix up my parent's child and next ptrs.
2958   if( innermost && innermost->_head == n ) {
2959     assert( get_loop(n) == innermost, "" );
2960     IdealLoopTree *p = innermost->_parent;
2961     IdealLoopTree *l = innermost;
2962     while( p && l->_head == n ) {
2963       l->_next = p->_child;     // Put self on parents 'next child'
2964       p->_child = l;            // Make self as first child of parent
2965       l = p;                    // Now walk up the parent chain
2966       p = l->_parent;
2967     }
2968   } else {
2969     // Note that it is possible for a LoopNode to reach here, if the
2970     // backedge has been made unreachable (hence the LoopNode no longer
2971     // denotes a Loop, and will eventually be removed).
2972 
2973     // Record tightest enclosing loop for self.  Mark as post-visited.
2974     set_loop(n, innermost);
2975     // Also record has_call flag early on
2976     if( innermost ) {
2977       if( n->is_Call() && !n->is_CallLeaf() && !n->is_macro() ) {
2978         // Do not count uncommon calls
2979         if( !n->is_CallStaticJava() || !n->as_CallStaticJava()->_name ) {
2980           Node *iff = n->in(0)->in(0);
2981           // No any calls for vectorized loops.
2982           if( UseSuperWord || !iff->is_If() ||
2983               (n->in(0)->Opcode() == Op_IfFalse &&
2984                (1.0 - iff->as_If()->_prob) >= 0.01) ||
2985               (iff->as_If()->_prob >= 0.01) )
2986             innermost->_has_call = 1;
2987         }
2988       } else if( n->is_Allocate() && n->as_Allocate()->_is_scalar_replaceable ) {
2989         // Disable loop optimizations if the loop has a scalar replaceable
2990         // allocation. This disabling may cause a potential performance lost
2991         // if the allocation is not eliminated for some reason.
2992         innermost->_allow_optimizations = false;
2993         innermost->_has_call = 1; // = true
2994       } else if (n->Opcode() == Op_SafePoint) {
2995         // Record all safepoints in this loop.
2996         if (innermost->_safepts == NULL) innermost->_safepts = new Node_List();
2997         innermost->_safepts->push(n);
2998       }
2999     }
3000   }
3001 
3002   // Flag as post-visited now
3003   set_postvisited(n);
3004   return pre_order;
3005 }
3006 
3007 
3008 //------------------------------build_loop_early-------------------------------
3009 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3010 // First pass computes the earliest controlling node possible.  This is the
3011 // controlling input with the deepest dominating depth.
3012 void PhaseIdealLoop::build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3013   while (worklist.size() != 0) {
3014     // Use local variables nstack_top_n & nstack_top_i to cache values
3015     // on nstack's top.
3016     Node *nstack_top_n = worklist.pop();
3017     uint  nstack_top_i = 0;
3018 //while_nstack_nonempty:
3019     while (true) {
3020       // Get parent node and next input's index from stack's top.
3021       Node  *n = nstack_top_n;
3022       uint   i = nstack_top_i;
3023       uint cnt = n->req(); // Count of inputs
3024       if (i == 0) {        // Pre-process the node.
3025         if( has_node(n) &&            // Have either loop or control already?
3026             !has_ctrl(n) ) {          // Have loop picked out already?
3027           // During "merge_many_backedges" we fold up several nested loops
3028           // into a single loop.  This makes the members of the original
3029           // loop bodies pointing to dead loops; they need to move up
3030           // to the new UNION'd larger loop.  I set the _head field of these
3031           // dead loops to NULL and the _parent field points to the owning
3032           // loop.  Shades of UNION-FIND algorithm.
3033           IdealLoopTree *ilt;
3034           while( !(ilt = get_loop(n))->_head ) {
3035             // Normally I would use a set_loop here.  But in this one special
3036             // case, it is legal (and expected) to change what loop a Node
3037             // belongs to.
3038             _nodes.map(n->_idx, (Node*)(ilt->_parent) );
3039           }
3040           // Remove safepoints ONLY if I've already seen I don't need one.
3041           // (the old code here would yank a 2nd safepoint after seeing a
3042           // first one, even though the 1st did not dominate in the loop body
3043           // and thus could be avoided indefinitely)
3044           if( !_verify_only && !_verify_me && ilt->_has_sfpt && n->Opcode() == Op_SafePoint &&
3045               is_deleteable_safept(n)) {
3046             Node *in = n->in(TypeFunc::Control);
3047             lazy_replace(n,in);       // Pull safepoint now
3048             if (ilt->_safepts != NULL) {
3049               ilt->_safepts->yank(n);
3050             }
3051             // Carry on with the recursion "as if" we are walking
3052             // only the control input
3053             if( !visited.test_set( in->_idx ) ) {
3054               worklist.push(in);      // Visit this guy later, using worklist
3055             }
3056             // Get next node from nstack:
3057             // - skip n's inputs processing by setting i > cnt;
3058             // - we also will not call set_early_ctrl(n) since
3059             //   has_node(n) == true (see the condition above).
3060             i = cnt + 1;
3061           }
3062         }
3063       } // if (i == 0)
3064 
3065       // Visit all inputs
3066       bool done = true;       // Assume all n's inputs will be processed
3067       while (i < cnt) {
3068         Node *in = n->in(i);
3069         ++i;
3070         if (in == NULL) continue;
3071         if (in->pinned() && !in->is_CFG())
3072           set_ctrl(in, in->in(0));
3073         int is_visited = visited.test_set( in->_idx );
3074         if (!has_node(in)) {  // No controlling input yet?
3075           assert( !in->is_CFG(), "CFG Node with no controlling input?" );
3076           assert( !is_visited, "visit only once" );
3077           nstack.push(n, i);  // Save parent node and next input's index.
3078           nstack_top_n = in;  // Process current input now.
3079           nstack_top_i = 0;
3080           done = false;       // Not all n's inputs processed.
3081           break; // continue while_nstack_nonempty;
3082         } else if (!is_visited) {
3083           // This guy has a location picked out for him, but has not yet
3084           // been visited.  Happens to all CFG nodes, for instance.
3085           // Visit him using the worklist instead of recursion, to break
3086           // cycles.  Since he has a location already we do not need to
3087           // find his location before proceeding with the current Node.
3088           worklist.push(in);  // Visit this guy later, using worklist
3089         }
3090       }
3091       if (done) {
3092         // All of n's inputs have been processed, complete post-processing.
3093 
3094         // Compute earliest point this Node can go.
3095         // CFG, Phi, pinned nodes already know their controlling input.
3096         if (!has_node(n)) {
3097           // Record earliest legal location
3098           set_early_ctrl( n );
3099         }
3100         if (nstack.is_empty()) {
3101           // Finished all nodes on stack.
3102           // Process next node on the worklist.
3103           break;
3104         }
3105         // Get saved parent node and next input's index.
3106         nstack_top_n = nstack.node();
3107         nstack_top_i = nstack.index();
3108         nstack.pop();
3109       }
3110     } // while (true)
3111   }
3112 }
3113 
3114 //------------------------------dom_lca_internal--------------------------------
3115 // Pair-wise LCA
3116 Node *PhaseIdealLoop::dom_lca_internal( Node *n1, Node *n2 ) const {
3117   if( !n1 ) return n2;          // Handle NULL original LCA
3118   assert( n1->is_CFG(), "" );
3119   assert( n2->is_CFG(), "" );
3120   // find LCA of all uses
3121   uint d1 = dom_depth(n1);
3122   uint d2 = dom_depth(n2);
3123   while (n1 != n2) {
3124     if (d1 > d2) {
3125       n1 =      idom(n1);
3126       d1 = dom_depth(n1);
3127     } else if (d1 < d2) {
3128       n2 =      idom(n2);
3129       d2 = dom_depth(n2);
3130     } else {
3131       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3132       // of the tree might have the same depth.  These sections have
3133       // to be searched more carefully.
3134 
3135       // Scan up all the n1's with equal depth, looking for n2.
3136       Node *t1 = idom(n1);
3137       while (dom_depth(t1) == d1) {
3138         if (t1 == n2)  return n2;
3139         t1 = idom(t1);
3140       }
3141       // Scan up all the n2's with equal depth, looking for n1.
3142       Node *t2 = idom(n2);
3143       while (dom_depth(t2) == d2) {
3144         if (t2 == n1)  return n1;
3145         t2 = idom(t2);
3146       }
3147       // Move up to a new dominator-depth value as well as up the dom-tree.
3148       n1 = t1;
3149       n2 = t2;
3150       d1 = dom_depth(n1);
3151       d2 = dom_depth(n2);
3152     }
3153   }
3154   return n1;
3155 }
3156 
3157 //------------------------------compute_idom-----------------------------------
3158 // Locally compute IDOM using dom_lca call.  Correct only if the incoming
3159 // IDOMs are correct.
3160 Node *PhaseIdealLoop::compute_idom( Node *region ) const {
3161   assert( region->is_Region(), "" );
3162   Node *LCA = NULL;
3163   for( uint i = 1; i < region->req(); i++ ) {
3164     if( region->in(i) != C->top() )
3165       LCA = dom_lca( LCA, region->in(i) );
3166   }
3167   return LCA;
3168 }
3169 
3170 bool PhaseIdealLoop::verify_dominance(Node* n, Node* use, Node* LCA, Node* early) {
3171   bool had_error = false;
3172 #ifdef ASSERT
3173   if (early != C->root()) {
3174     // Make sure that there's a dominance path from use to LCA
3175     Node* d = use;
3176     while (d != LCA) {
3177       d = idom(d);
3178       if (d == C->root()) {
3179         tty->print_cr("*** Use %d isn't dominated by def %s", use->_idx, n->_idx);
3180         n->dump();
3181         use->dump();
3182         had_error = true;
3183         break;
3184       }
3185     }
3186   }
3187 #endif
3188   return had_error;
3189 }
3190 
3191 
3192 Node* PhaseIdealLoop::compute_lca_of_uses(Node* n, Node* early, bool verify) {
3193   // Compute LCA over list of uses
3194   bool had_error = false;
3195   Node *LCA = NULL;
3196   for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax && LCA != early; i++) {
3197     Node* c = n->fast_out(i);
3198     if (_nodes[c->_idx] == NULL)
3199       continue;                 // Skip the occasional dead node
3200     if( c->is_Phi() ) {         // For Phis, we must land above on the path
3201       for( uint j=1; j<c->req(); j++ ) {// For all inputs
3202         if( c->in(j) == n ) {   // Found matching input?
3203           Node *use = c->in(0)->in(j);
3204           if (_verify_only && use->is_top()) continue;
3205           LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3206           if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3207         }
3208       }
3209     } else {
3210       // For CFG data-users, use is in the block just prior
3211       Node *use = has_ctrl(c) ? get_ctrl(c) : c->in(0);
3212       LCA = dom_lca_for_get_late_ctrl( LCA, use, n );
3213       if (verify) had_error = verify_dominance(n, use, LCA, early) || had_error;
3214     }
3215   }
3216   assert(!had_error, "bad dominance");
3217   return LCA;
3218 }
3219 
3220 //------------------------------get_late_ctrl----------------------------------
3221 // Compute latest legal control.
3222 Node *PhaseIdealLoop::get_late_ctrl( Node *n, Node *early ) {
3223   assert(early != NULL, "early control should not be NULL");
3224 
3225   Node* LCA = compute_lca_of_uses(n, early);
3226 #ifdef ASSERT
3227   if (LCA == C->root() && LCA != early) {
3228     // def doesn't dominate uses so print some useful debugging output
3229     compute_lca_of_uses(n, early, true);
3230   }
3231 #endif
3232 
3233   // if this is a load, check for anti-dependent stores
3234   // We use a conservative algorithm to identify potential interfering
3235   // instructions and for rescheduling the load.  The users of the memory
3236   // input of this load are examined.  Any use which is not a load and is
3237   // dominated by early is considered a potentially interfering store.
3238   // This can produce false positives.
3239   if (n->is_Load() && LCA != early) {
3240     Node_List worklist;
3241 
3242     Node *mem = n->in(MemNode::Memory);
3243     for (DUIterator_Fast imax, i = mem->fast_outs(imax); i < imax; i++) {
3244       Node* s = mem->fast_out(i);
3245       worklist.push(s);
3246     }
3247     while(worklist.size() != 0 && LCA != early) {
3248       Node* s = worklist.pop();
3249       if (s->is_Load()) {
3250         continue;
3251       } else if (s->is_MergeMem()) {
3252         for (DUIterator_Fast imax, i = s->fast_outs(imax); i < imax; i++) {
3253           Node* s1 = s->fast_out(i);
3254           worklist.push(s1);
3255         }
3256       } else {
3257         Node *sctrl = has_ctrl(s) ? get_ctrl(s) : s->in(0);
3258         assert(sctrl != NULL || s->outcnt() == 0, "must have control");
3259         if (sctrl != NULL && !sctrl->is_top() && is_dominator(early, sctrl)) {
3260           LCA = dom_lca_for_get_late_ctrl(LCA, sctrl, n);
3261         }
3262       }
3263     }
3264   }
3265 
3266   assert(LCA == find_non_split_ctrl(LCA), "unexpected late control");
3267   return LCA;
3268 }
3269 
3270 // true if CFG node d dominates CFG node n
3271 bool PhaseIdealLoop::is_dominator(Node *d, Node *n) {
3272   if (d == n)
3273     return true;
3274   assert(d->is_CFG() && n->is_CFG(), "must have CFG nodes");
3275   uint dd = dom_depth(d);
3276   while (dom_depth(n) >= dd) {
3277     if (n == d)
3278       return true;
3279     n = idom(n);
3280   }
3281   return false;
3282 }
3283 
3284 //------------------------------dom_lca_for_get_late_ctrl_internal-------------
3285 // Pair-wise LCA with tags.
3286 // Tag each index with the node 'tag' currently being processed
3287 // before advancing up the dominator chain using idom().
3288 // Later calls that find a match to 'tag' know that this path has already
3289 // been considered in the current LCA (which is input 'n1' by convention).
3290 // Since get_late_ctrl() is only called once for each node, the tag array
3291 // does not need to be cleared between calls to get_late_ctrl().
3292 // Algorithm trades a larger constant factor for better asymptotic behavior
3293 //
3294 Node *PhaseIdealLoop::dom_lca_for_get_late_ctrl_internal( Node *n1, Node *n2, Node *tag ) {
3295   uint d1 = dom_depth(n1);
3296   uint d2 = dom_depth(n2);
3297 
3298   do {
3299     if (d1 > d2) {
3300       // current lca is deeper than n2
3301       _dom_lca_tags.map(n1->_idx, tag);
3302       n1 =      idom(n1);
3303       d1 = dom_depth(n1);
3304     } else if (d1 < d2) {
3305       // n2 is deeper than current lca
3306       Node *memo = _dom_lca_tags[n2->_idx];
3307       if( memo == tag ) {
3308         return n1;    // Return the current LCA
3309       }
3310       _dom_lca_tags.map(n2->_idx, tag);
3311       n2 =      idom(n2);
3312       d2 = dom_depth(n2);
3313     } else {
3314       // Here d1 == d2.  Due to edits of the dominator-tree, sections
3315       // of the tree might have the same depth.  These sections have
3316       // to be searched more carefully.
3317 
3318       // Scan up all the n1's with equal depth, looking for n2.
3319       _dom_lca_tags.map(n1->_idx, tag);
3320       Node *t1 = idom(n1);
3321       while (dom_depth(t1) == d1) {
3322         if (t1 == n2)  return n2;
3323         _dom_lca_tags.map(t1->_idx, tag);
3324         t1 = idom(t1);
3325       }
3326       // Scan up all the n2's with equal depth, looking for n1.
3327       _dom_lca_tags.map(n2->_idx, tag);
3328       Node *t2 = idom(n2);
3329       while (dom_depth(t2) == d2) {
3330         if (t2 == n1)  return n1;
3331         _dom_lca_tags.map(t2->_idx, tag);
3332         t2 = idom(t2);
3333       }
3334       // Move up to a new dominator-depth value as well as up the dom-tree.
3335       n1 = t1;
3336       n2 = t2;
3337       d1 = dom_depth(n1);
3338       d2 = dom_depth(n2);
3339     }
3340   } while (n1 != n2);
3341   return n1;
3342 }
3343 
3344 //------------------------------init_dom_lca_tags------------------------------
3345 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3346 // Intended use does not involve any growth for the array, so it could
3347 // be of fixed size.
3348 void PhaseIdealLoop::init_dom_lca_tags() {
3349   uint limit = C->unique() + 1;
3350   _dom_lca_tags.map( limit, NULL );
3351 #ifdef ASSERT
3352   for( uint i = 0; i < limit; ++i ) {
3353     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3354   }
3355 #endif // ASSERT
3356 }
3357 
3358 //------------------------------clear_dom_lca_tags------------------------------
3359 // Tag could be a node's integer index, 32bits instead of 64bits in some cases
3360 // Intended use does not involve any growth for the array, so it could
3361 // be of fixed size.
3362 void PhaseIdealLoop::clear_dom_lca_tags() {
3363   uint limit = C->unique() + 1;
3364   _dom_lca_tags.map( limit, NULL );
3365   _dom_lca_tags.clear();
3366 #ifdef ASSERT
3367   for( uint i = 0; i < limit; ++i ) {
3368     assert(_dom_lca_tags[i] == NULL, "Must be distinct from each node pointer");
3369   }
3370 #endif // ASSERT
3371 }
3372 
3373 //------------------------------build_loop_late--------------------------------
3374 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3375 // Second pass finds latest legal placement, and ideal loop placement.
3376 void PhaseIdealLoop::build_loop_late( VectorSet &visited, Node_List &worklist, Node_Stack &nstack ) {
3377   while (worklist.size() != 0) {
3378     Node *n = worklist.pop();
3379     // Only visit once
3380     if (visited.test_set(n->_idx)) continue;
3381     uint cnt = n->outcnt();
3382     uint   i = 0;
3383     while (true) {
3384       assert( _nodes[n->_idx], "no dead nodes" );
3385       // Visit all children
3386       if (i < cnt) {
3387         Node* use = n->raw_out(i);
3388         ++i;
3389         // Check for dead uses.  Aggressively prune such junk.  It might be
3390         // dead in the global sense, but still have local uses so I cannot
3391         // easily call 'remove_dead_node'.
3392         if( _nodes[use->_idx] != NULL || use->is_top() ) { // Not dead?
3393           // Due to cycles, we might not hit the same fixed point in the verify
3394           // pass as we do in the regular pass.  Instead, visit such phis as
3395           // simple uses of the loop head.
3396           if( use->in(0) && (use->is_CFG() || use->is_Phi()) ) {
3397             if( !visited.test(use->_idx) )
3398               worklist.push(use);
3399           } else if( !visited.test_set(use->_idx) ) {
3400             nstack.push(n, i); // Save parent and next use's index.
3401             n   = use;         // Process all children of current use.
3402             cnt = use->outcnt();
3403             i   = 0;
3404           }
3405         } else {
3406           // Do not visit around the backedge of loops via data edges.
3407           // push dead code onto a worklist
3408           _deadlist.push(use);
3409         }
3410       } else {
3411         // All of n's children have been processed, complete post-processing.
3412         build_loop_late_post(n);
3413         if (nstack.is_empty()) {
3414           // Finished all nodes on stack.
3415           // Process next node on the worklist.
3416           break;
3417         }
3418         // Get saved parent node and next use's index. Visit the rest of uses.
3419         n   = nstack.node();
3420         cnt = n->outcnt();
3421         i   = nstack.index();
3422         nstack.pop();
3423       }
3424     }
3425   }
3426 }
3427 
3428 //------------------------------build_loop_late_post---------------------------
3429 // Put Data nodes into some loop nest, by setting the _nodes[]->loop mapping.
3430 // Second pass finds latest legal placement, and ideal loop placement.
3431 void PhaseIdealLoop::build_loop_late_post( Node *n ) {
3432 
3433   if (n->req() == 2 && n->Opcode() == Op_ConvI2L && !C->major_progress() && !_verify_only) {
3434     _igvn._worklist.push(n);  // Maybe we'll normalize it, if no more loops.
3435   }
3436 
3437   // CFG and pinned nodes already handled
3438   if( n->in(0) ) {
3439     if( n->in(0)->is_top() ) return; // Dead?
3440 
3441     // We'd like +VerifyLoopOptimizations to not believe that Mod's/Loads
3442     // _must_ be pinned (they have to observe their control edge of course).
3443     // Unlike Stores (which modify an unallocable resource, the memory
3444     // state), Mods/Loads can float around.  So free them up.
3445     bool pinned = true;
3446     switch( n->Opcode() ) {
3447     case Op_DivI:
3448     case Op_DivF:
3449     case Op_DivD:
3450     case Op_ModI:
3451     case Op_ModF:
3452     case Op_ModD:
3453     case Op_LoadB:              // Same with Loads; they can sink
3454     case Op_LoadUB:             // during loop optimizations.
3455     case Op_LoadUS:
3456     case Op_LoadD:
3457     case Op_LoadF:
3458     case Op_LoadI:
3459     case Op_LoadKlass:
3460     case Op_LoadNKlass:
3461     case Op_LoadL:
3462     case Op_LoadS:
3463     case Op_LoadP:
3464     case Op_LoadN:
3465     case Op_LoadRange:
3466     case Op_LoadD_unaligned:
3467     case Op_LoadL_unaligned:
3468     case Op_StrComp:            // Does a bunch of load-like effects
3469     case Op_StrEquals:
3470     case Op_StrIndexOf:
3471     case Op_AryEq:
3472       pinned = false;
3473     }
3474     if( pinned ) {
3475       IdealLoopTree *chosen_loop = get_loop(n->is_CFG() ? n : get_ctrl(n));
3476       if( !chosen_loop->_child )       // Inner loop?
3477         chosen_loop->_body.push(n); // Collect inner loops
3478       return;
3479     }
3480   } else {                      // No slot zero
3481     if( n->is_CFG() ) {         // CFG with no slot 0 is dead
3482       _nodes.map(n->_idx,0);    // No block setting, it's globally dead
3483       return;
3484     }
3485     assert(!n->is_CFG() || n->outcnt() == 0, "");
3486   }
3487 
3488   // Do I have a "safe range" I can select over?
3489   Node *early = get_ctrl(n);// Early location already computed
3490 
3491   // Compute latest point this Node can go
3492   Node *LCA = get_late_ctrl( n, early );
3493   // LCA is NULL due to uses being dead
3494   if( LCA == NULL ) {
3495 #ifdef ASSERT
3496     for (DUIterator i1 = n->outs(); n->has_out(i1); i1++) {
3497       assert( _nodes[n->out(i1)->_idx] == NULL, "all uses must also be dead");
3498     }
3499 #endif
3500     _nodes.map(n->_idx, 0);     // This node is useless
3501     _deadlist.push(n);
3502     return;
3503   }
3504   assert(LCA != NULL && !LCA->is_top(), "no dead nodes");
3505 
3506   Node *legal = LCA;            // Walk 'legal' up the IDOM chain
3507   Node *least = legal;          // Best legal position so far
3508   while( early != legal ) {     // While not at earliest legal
3509 #ifdef ASSERT
3510     if (legal->is_Start() && !early->is_Root()) {
3511       // Bad graph. Print idom path and fail.
3512       dump_bad_graph("Bad graph detected in build_loop_late", n, early, LCA);
3513       assert(false, "Bad graph detected in build_loop_late");
3514     }
3515 #endif
3516     // Find least loop nesting depth
3517     legal = idom(legal);        // Bump up the IDOM tree
3518     // Check for lower nesting depth
3519     if( get_loop(legal)->_nest < get_loop(least)->_nest )
3520       least = legal;
3521   }
3522   assert(early == legal || legal != C->root(), "bad dominance of inputs");
3523 
3524   // Try not to place code on a loop entry projection
3525   // which can inhibit range check elimination.
3526   if (least != early) {
3527     Node* ctrl_out = least->unique_ctrl_out();
3528     if (ctrl_out && ctrl_out->is_CountedLoop() &&
3529         least == ctrl_out->in(LoopNode::EntryControl)) {
3530       Node* least_dom = idom(least);
3531       if (get_loop(least_dom)->is_member(get_loop(least))) {
3532         least = least_dom;
3533       }
3534     }
3535   }
3536 
3537 #ifdef ASSERT
3538   // If verifying, verify that 'verify_me' has a legal location
3539   // and choose it as our location.
3540   if( _verify_me ) {
3541     Node *v_ctrl = _verify_me->get_ctrl_no_update(n);
3542     Node *legal = LCA;
3543     while( early != legal ) {   // While not at earliest legal
3544       if( legal == v_ctrl ) break;  // Check for prior good location
3545       legal = idom(legal)      ;// Bump up the IDOM tree
3546     }
3547     // Check for prior good location
3548     if( legal == v_ctrl ) least = legal; // Keep prior if found
3549   }
3550 #endif
3551 
3552   // Assign discovered "here or above" point
3553   least = find_non_split_ctrl(least);
3554   set_ctrl(n, least);
3555 
3556   // Collect inner loop bodies
3557   IdealLoopTree *chosen_loop = get_loop(least);
3558   if( !chosen_loop->_child )   // Inner loop?
3559     chosen_loop->_body.push(n);// Collect inner loops
3560 }
3561 
3562 #ifdef ASSERT
3563 void PhaseIdealLoop::dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA) {
3564   tty->print_cr(msg);
3565   tty->print("n: "); n->dump();
3566   tty->print("early(n): "); early->dump();
3567   if (n->in(0) != NULL  && !n->in(0)->is_top() &&
3568       n->in(0) != early && !n->in(0)->is_Root()) {
3569     tty->print("n->in(0): "); n->in(0)->dump();
3570   }
3571   for (uint i = 1; i < n->req(); i++) {
3572     Node* in1 = n->in(i);
3573     if (in1 != NULL && in1 != n && !in1->is_top()) {
3574       tty->print("n->in(%d): ", i); in1->dump();
3575       Node* in1_early = get_ctrl(in1);
3576       tty->print("early(n->in(%d)): ", i); in1_early->dump();
3577       if (in1->in(0) != NULL     && !in1->in(0)->is_top() &&
3578           in1->in(0) != in1_early && !in1->in(0)->is_Root()) {
3579         tty->print("n->in(%d)->in(0): ", i); in1->in(0)->dump();
3580       }
3581       for (uint j = 1; j < in1->req(); j++) {
3582         Node* in2 = in1->in(j);
3583         if (in2 != NULL && in2 != n && in2 != in1 && !in2->is_top()) {
3584           tty->print("n->in(%d)->in(%d): ", i, j); in2->dump();
3585           Node* in2_early = get_ctrl(in2);
3586           tty->print("early(n->in(%d)->in(%d)): ", i, j); in2_early->dump();
3587           if (in2->in(0) != NULL     && !in2->in(0)->is_top() &&
3588               in2->in(0) != in2_early && !in2->in(0)->is_Root()) {
3589             tty->print("n->in(%d)->in(%d)->in(0): ", i, j); in2->in(0)->dump();
3590           }
3591         }
3592       }
3593     }
3594   }
3595   tty->cr();
3596   tty->print("LCA(n): "); LCA->dump();
3597   for (uint i = 0; i < n->outcnt(); i++) {
3598     Node* u1 = n->raw_out(i);
3599     if (u1 == n)
3600       continue;
3601     tty->print("n->out(%d): ", i); u1->dump();
3602     if (u1->is_CFG()) {
3603       for (uint j = 0; j < u1->outcnt(); j++) {
3604         Node* u2 = u1->raw_out(j);
3605         if (u2 != u1 && u2 != n && u2->is_CFG()) {
3606           tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3607         }
3608       }
3609     } else {
3610       Node* u1_later = get_ctrl(u1);
3611       tty->print("later(n->out(%d)): ", i); u1_later->dump();
3612       if (u1->in(0) != NULL     && !u1->in(0)->is_top() &&
3613           u1->in(0) != u1_later && !u1->in(0)->is_Root()) {
3614         tty->print("n->out(%d)->in(0): ", i); u1->in(0)->dump();
3615       }
3616       for (uint j = 0; j < u1->outcnt(); j++) {
3617         Node* u2 = u1->raw_out(j);
3618         if (u2 == n || u2 == u1)
3619           continue;
3620         tty->print("n->out(%d)->out(%d): ", i, j); u2->dump();
3621         if (!u2->is_CFG()) {
3622           Node* u2_later = get_ctrl(u2);
3623           tty->print("later(n->out(%d)->out(%d)): ", i, j); u2_later->dump();
3624           if (u2->in(0) != NULL     && !u2->in(0)->is_top() &&
3625               u2->in(0) != u2_later && !u2->in(0)->is_Root()) {
3626             tty->print("n->out(%d)->in(0): ", i); u2->in(0)->dump();
3627           }
3628         }
3629       }
3630     }
3631   }
3632   tty->cr();
3633   int ct = 0;
3634   Node *dbg_legal = LCA;
3635   while(!dbg_legal->is_Start() && ct < 100) {
3636     tty->print("idom[%d] ",ct); dbg_legal->dump();
3637     ct++;
3638     dbg_legal = idom(dbg_legal);
3639   }
3640   tty->cr();
3641 }
3642 #endif
3643 
3644 #ifndef PRODUCT
3645 //------------------------------dump-------------------------------------------
3646 void PhaseIdealLoop::dump( ) const {
3647   ResourceMark rm;
3648   Arena* arena = Thread::current()->resource_area();
3649   Node_Stack stack(arena, C->unique() >> 2);
3650   Node_List rpo_list;
3651   VectorSet visited(arena);
3652   visited.set(C->top()->_idx);
3653   rpo( C->root(), stack, visited, rpo_list );
3654   // Dump root loop indexed by last element in PO order
3655   dump( _ltree_root, rpo_list.size(), rpo_list );
3656 }
3657 
3658 void PhaseIdealLoop::dump( IdealLoopTree *loop, uint idx, Node_List &rpo_list ) const {
3659   loop->dump_head();
3660 
3661   // Now scan for CFG nodes in the same loop
3662   for( uint j=idx; j > 0;  j-- ) {
3663     Node *n = rpo_list[j-1];
3664     if( !_nodes[n->_idx] )      // Skip dead nodes
3665       continue;
3666     if( get_loop(n) != loop ) { // Wrong loop nest
3667       if( get_loop(n)->_head == n &&    // Found nested loop?
3668           get_loop(n)->_parent == loop )
3669         dump(get_loop(n),rpo_list.size(),rpo_list);     // Print it nested-ly
3670       continue;
3671     }
3672 
3673     // Dump controlling node
3674     for( uint x = 0; x < loop->_nest; x++ )
3675       tty->print("  ");
3676     tty->print("C");
3677     if( n == C->root() ) {
3678       n->dump();
3679     } else {
3680       Node* cached_idom   = idom_no_update(n);
3681       Node *computed_idom = n->in(0);
3682       if( n->is_Region() ) {
3683         computed_idom = compute_idom(n);
3684         // computed_idom() will return n->in(0) when idom(n) is an IfNode (or
3685         // any MultiBranch ctrl node), so apply a similar transform to
3686         // the cached idom returned from idom_no_update.
3687         cached_idom = find_non_split_ctrl(cached_idom);
3688       }
3689       tty->print(" ID:%d",computed_idom->_idx);
3690       n->dump();
3691       if( cached_idom != computed_idom ) {
3692         tty->print_cr("*** BROKEN IDOM!  Computed as: %d, cached as: %d",
3693                       computed_idom->_idx, cached_idom->_idx);
3694       }
3695     }
3696     // Dump nodes it controls
3697     for( uint k = 0; k < _nodes.Size(); k++ ) {
3698       // (k < C->unique() && get_ctrl(find(k)) == n)
3699       if (k < C->unique() && _nodes[k] == (Node*)((intptr_t)n + 1)) {
3700         Node *m = C->root()->find(k);
3701         if( m && m->outcnt() > 0 ) {
3702           if (!(has_ctrl(m) && get_ctrl_no_update(m) == n)) {
3703             tty->print_cr("*** BROKEN CTRL ACCESSOR!  _nodes[k] is %p, ctrl is %p",
3704                           _nodes[k], has_ctrl(m) ? get_ctrl_no_update(m) : NULL);
3705           }
3706           for( uint j = 0; j < loop->_nest; j++ )
3707             tty->print("  ");
3708           tty->print(" ");
3709           m->dump();
3710         }
3711       }
3712     }
3713   }
3714 }
3715 
3716 // Collect a R-P-O for the whole CFG.
3717 // Result list is in post-order (scan backwards for RPO)
3718 void PhaseIdealLoop::rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const {
3719   stk.push(start, 0);
3720   visited.set(start->_idx);
3721 
3722   while (stk.is_nonempty()) {
3723     Node* m   = stk.node();
3724     uint  idx = stk.index();
3725     if (idx < m->outcnt()) {
3726       stk.set_index(idx + 1);
3727       Node* n = m->raw_out(idx);
3728       if (n->is_CFG() && !visited.test_set(n->_idx)) {
3729         stk.push(n, 0);
3730       }
3731     } else {
3732       rpo_list.push(m);
3733       stk.pop();
3734     }
3735   }
3736 }
3737 #endif
3738 
3739 
3740 //=============================================================================
3741 //------------------------------LoopTreeIterator-----------------------------------
3742 
3743 // Advance to next loop tree using a preorder, left-to-right traversal.
3744 void LoopTreeIterator::next() {
3745   assert(!done(), "must not be done.");
3746   if (_curnt->_child != NULL) {
3747     _curnt = _curnt->_child;
3748   } else if (_curnt->_next != NULL) {
3749     _curnt = _curnt->_next;
3750   } else {
3751     while (_curnt != _root && _curnt->_next == NULL) {
3752       _curnt = _curnt->_parent;
3753     }
3754     if (_curnt == _root) {
3755       _curnt = NULL;
3756       assert(done(), "must be done.");
3757     } else {
3758       assert(_curnt->_next != NULL, "must be more to do");
3759       _curnt = _curnt->_next;
3760     }
3761   }
3762 }
--- EOF ---