1 /*
   2  * Copyright (c) 2011, 2018, 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 "opto/loopnode.hpp"
  27 #include "opto/addnode.hpp"
  28 #include "opto/callnode.hpp"
  29 #include "opto/connode.hpp"
  30 #include "opto/convertnode.hpp"
  31 #include "opto/loopnode.hpp"
  32 #include "opto/matcher.hpp"
  33 #include "opto/mulnode.hpp"
  34 #include "opto/opaquenode.hpp"
  35 #include "opto/rootnode.hpp"
  36 #include "opto/subnode.hpp"
  37 #include <fenv.h>
  38 #include <math.h>
  39 
  40 /*
  41  * The general idea of Loop Predication is to insert a predicate on the entry
  42  * path to a loop, and raise a uncommon trap if the check of the condition fails.
  43  * The condition checks are promoted from inside the loop body, and thus
  44  * the checks inside the loop could be eliminated. Currently, loop predication
  45  * optimization has been applied to remove array range check and loop invariant
  46  * checks (such as null checks).
  47 */
  48 
  49 //-------------------------------register_control-------------------------
  50 void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred) {
  51   assert(n->is_CFG(), "must be control node");
  52   _igvn.register_new_node_with_optimizer(n);
  53   loop->_body.push(n);
  54   set_loop(n, loop);
  55   // When called from beautify_loops() idom is not constructed yet.
  56   if (_idom != NULL) {
  57     set_idom(n, pred, dom_depth(pred));
  58   }
  59 }
  60 
  61 //------------------------------create_new_if_for_predicate------------------------
  62 // create a new if above the uct_if_pattern for the predicate to be promoted.
  63 //
  64 //          before                                after
  65 //        ----------                           ----------
  66 //           ctrl                                 ctrl
  67 //            |                                     |
  68 //            |                                     |
  69 //            v                                     v
  70 //           iff                                 new_iff
  71 //          /    \                                /      \
  72 //         /      \                              /        \
  73 //        v        v                            v          v
  74 //  uncommon_proj cont_proj                   if_uct     if_cont
  75 // \      |        |                           |          |
  76 //  \     |        |                           |          |
  77 //   v    v        v                           |          v
  78 //     rgn       loop                          |         iff
  79 //      |                                      |        /     \
  80 //      |                                      |       /       \
  81 //      v                                      |      v         v
  82 // uncommon_trap                               | uncommon_proj cont_proj
  83 //                                           \  \    |           |
  84 //                                            \  \   |           |
  85 //                                             v  v  v           v
  86 //                                               rgn           loop
  87 //                                                |
  88 //                                                |
  89 //                                                v
  90 //                                           uncommon_trap
  91 //
  92 //
  93 // We will create a region to guard the uct call if there is no one there.
  94 // The true projection (if_cont) of the new_iff is returned.
  95 // This code is also used to clone predicates to cloned loops.
  96 ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
  97                                                       Deoptimization::DeoptReason reason,
  98                                                       int opcode) {
  99   assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
 100   IfNode* iff = cont_proj->in(0)->as_If();
 101 
 102   ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
 103   Node     *rgn   = uncommon_proj->unique_ctrl_out();
 104   assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
 105 
 106   uint proj_index = 1; // region's edge corresponding to uncommon_proj
 107   if (!rgn->is_Region()) { // create a region to guard the call
 108     assert(rgn->is_Call(), "must be call uct");
 109     CallNode* call = rgn->as_Call();
 110     IdealLoopTree* loop = get_loop(call);
 111     rgn = new RegionNode(1);
 112     rgn->add_req(uncommon_proj);
 113     register_control(rgn, loop, uncommon_proj);
 114     _igvn.replace_input_of(call, 0, rgn);
 115     // When called from beautify_loops() idom is not constructed yet.
 116     if (_idom != NULL) {
 117       set_idom(call, rgn, dom_depth(rgn));
 118     }
 119     for (DUIterator_Fast imax, i = uncommon_proj->fast_outs(imax); i < imax; i++) {
 120       Node* n = uncommon_proj->fast_out(i);
 121       if (n->is_Load() || n->is_Store()) {
 122         _igvn.replace_input_of(n, 0, rgn);
 123         --i; --imax;
 124       }
 125     }
 126   } else {
 127     // Find region's edge corresponding to uncommon_proj
 128     for (; proj_index < rgn->req(); proj_index++)
 129       if (rgn->in(proj_index) == uncommon_proj) break;
 130     assert(proj_index < rgn->req(), "sanity");
 131   }
 132 
 133   Node* entry = iff->in(0);
 134   if (new_entry != NULL) {
 135     // Clonning the predicate to new location.
 136     entry = new_entry;
 137   }
 138   // Create new_iff
 139   IdealLoopTree* lp = get_loop(entry);
 140   IfNode* new_iff = NULL;
 141   if (opcode == Op_If) {
 142     new_iff = new IfNode(entry, iff->in(1), iff->_prob, iff->_fcnt);
 143   } else {
 144     assert(opcode == Op_RangeCheck, "no other if variant here");
 145     new_iff = new RangeCheckNode(entry, iff->in(1), iff->_prob, iff->_fcnt);
 146   }
 147   register_control(new_iff, lp, entry);
 148   Node *if_cont = new IfTrueNode(new_iff);
 149   Node *if_uct  = new IfFalseNode(new_iff);
 150   if (cont_proj->is_IfFalse()) {
 151     // Swap
 152     Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
 153   }
 154   register_control(if_cont, lp, new_iff);
 155   register_control(if_uct, get_loop(rgn), new_iff);
 156 
 157   // if_uct to rgn
 158   _igvn.hash_delete(rgn);
 159   rgn->add_req(if_uct);
 160   // When called from beautify_loops() idom is not constructed yet.
 161   if (_idom != NULL) {
 162     Node* ridom = idom(rgn);
 163     Node* nrdom = dom_lca_internal(ridom, new_iff);
 164     set_idom(rgn, nrdom, dom_depth(rgn));
 165   }
 166 
 167   // If rgn has phis add new edges which has the same
 168   // value as on original uncommon_proj pass.
 169   assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
 170   bool has_phi = false;
 171   for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
 172     Node* use = rgn->fast_out(i);
 173     if (use->is_Phi() && use->outcnt() > 0) {
 174       assert(use->in(0) == rgn, "");
 175       _igvn.rehash_node_delayed(use);
 176       use->add_req(use->in(proj_index));
 177       has_phi = true;
 178     }
 179   }
 180   assert(!has_phi || rgn->req() > 3, "no phis when region is created");
 181 
 182   if (new_entry == NULL) {
 183     // Attach if_cont to iff
 184     _igvn.replace_input_of(iff, 0, if_cont);
 185     if (_idom != NULL) {
 186       set_idom(iff, if_cont, dom_depth(iff));
 187     }
 188   }
 189   return if_cont->as_Proj();
 190 }
 191 
 192 //------------------------------create_new_if_for_predicate------------------------
 193 // Create a new if below new_entry for the predicate to be cloned (IGVN optimization)
 194 ProjNode* PhaseIterGVN::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
 195                                                     Deoptimization::DeoptReason reason,
 196                                                     int opcode) {
 197   assert(new_entry != 0, "only used for clone predicate");
 198   assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
 199   IfNode* iff = cont_proj->in(0)->as_If();
 200 
 201   ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
 202   Node     *rgn   = uncommon_proj->unique_ctrl_out();
 203   assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
 204 
 205   uint proj_index = 1; // region's edge corresponding to uncommon_proj
 206   if (!rgn->is_Region()) { // create a region to guard the call
 207     assert(rgn->is_Call(), "must be call uct");
 208     CallNode* call = rgn->as_Call();
 209     rgn = new RegionNode(1);
 210     register_new_node_with_optimizer(rgn);
 211     rgn->add_req(uncommon_proj);
 212     replace_input_of(call, 0, rgn);
 213   } else {
 214     // Find region's edge corresponding to uncommon_proj
 215     for (; proj_index < rgn->req(); proj_index++)
 216       if (rgn->in(proj_index) == uncommon_proj) break;
 217     assert(proj_index < rgn->req(), "sanity");
 218   }
 219 
 220   // Create new_iff in new location.
 221   IfNode* new_iff = NULL;
 222   if (opcode == Op_If) {
 223     new_iff = new IfNode(new_entry, iff->in(1), iff->_prob, iff->_fcnt);
 224   } else {
 225     assert(opcode == Op_RangeCheck, "no other if variant here");
 226     new_iff = new RangeCheckNode(new_entry, iff->in(1), iff->_prob, iff->_fcnt);
 227   }
 228 
 229   register_new_node_with_optimizer(new_iff);
 230   Node *if_cont = new IfTrueNode(new_iff);
 231   Node *if_uct  = new IfFalseNode(new_iff);
 232   if (cont_proj->is_IfFalse()) {
 233     // Swap
 234     Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
 235   }
 236   register_new_node_with_optimizer(if_cont);
 237   register_new_node_with_optimizer(if_uct);
 238 
 239   // if_uct to rgn
 240   hash_delete(rgn);
 241   rgn->add_req(if_uct);
 242 
 243   // If rgn has phis add corresponding new edges which has the same
 244   // value as on original uncommon_proj pass.
 245   assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
 246   bool has_phi = false;
 247   for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
 248     Node* use = rgn->fast_out(i);
 249     if (use->is_Phi() && use->outcnt() > 0) {
 250       rehash_node_delayed(use);
 251       use->add_req(use->in(proj_index));
 252       has_phi = true;
 253     }
 254   }
 255   assert(!has_phi || rgn->req() > 3, "no phis when region is created");
 256 
 257   return if_cont->as_Proj();
 258 }
 259 
 260 //--------------------------clone_predicate-----------------------
 261 ProjNode* PhaseIdealLoop::clone_predicate(ProjNode* predicate_proj, Node* new_entry,
 262                                           Deoptimization::DeoptReason reason,
 263                                           PhaseIdealLoop* loop_phase,
 264                                           PhaseIterGVN* igvn) {
 265   ProjNode* new_predicate_proj;
 266   if (loop_phase != NULL) {
 267     new_predicate_proj = loop_phase->create_new_if_for_predicate(predicate_proj, new_entry, reason, Op_If);
 268   } else {
 269     new_predicate_proj =       igvn->create_new_if_for_predicate(predicate_proj, new_entry, reason, Op_If);
 270   }
 271   IfNode* iff = new_predicate_proj->in(0)->as_If();
 272   Node* ctrl  = iff->in(0);
 273 
 274   // Match original condition since predicate's projections could be swapped.
 275   assert(predicate_proj->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be");
 276   Node* opq = new Opaque1Node(igvn->C, predicate_proj->in(0)->in(1)->in(1)->in(1));
 277   igvn->C->add_predicate_opaq(opq);
 278 
 279   Node* bol = new Conv2BNode(opq);
 280   if (loop_phase != NULL) {
 281     loop_phase->register_new_node(opq, ctrl);
 282     loop_phase->register_new_node(bol, ctrl);
 283   } else {
 284     igvn->register_new_node_with_optimizer(opq);
 285     igvn->register_new_node_with_optimizer(bol);
 286   }
 287   igvn->hash_delete(iff);
 288   iff->set_req(1, bol);
 289   return new_predicate_proj;
 290 }
 291 
 292 
 293 //--------------------------clone_loop_predicates-----------------------
 294 // Interface from IGVN
 295 Node* PhaseIterGVN::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
 296   return PhaseIdealLoop::clone_loop_predicates(old_entry, new_entry, clone_limit_check, NULL, this);
 297 }
 298 
 299 // Interface from PhaseIdealLoop
 300 Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
 301   return clone_loop_predicates(old_entry, new_entry, clone_limit_check, this, &this->_igvn);
 302 }
 303 
 304 // Clone loop predicates to cloned loops (peeled, unswitched, split_if).
 305 Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry,
 306                                             bool clone_limit_check,
 307                                             PhaseIdealLoop* loop_phase,
 308                                             PhaseIterGVN* igvn) {
 309 #ifdef ASSERT
 310   if (new_entry == NULL || !(new_entry->is_Proj() || new_entry->is_Region() || new_entry->is_SafePoint())) {
 311     if (new_entry != NULL)
 312       new_entry->dump();
 313     assert(false, "not IfTrue, IfFalse, Region or SafePoint");
 314   }
 315 #endif
 316   // Search original predicates
 317   Node* entry = old_entry;
 318   ProjNode* limit_check_proj = NULL;
 319   limit_check_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
 320   if (limit_check_proj != NULL) {
 321     entry = skip_loop_predicates(entry);
 322   }
 323   ProjNode* profile_predicate_proj = NULL;
 324   ProjNode* predicate_proj = NULL;
 325   if (UseProfiledLoopPredicate) {
 326     profile_predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
 327     if (profile_predicate_proj != NULL) {
 328       entry = skip_loop_predicates(entry);
 329     }
 330   }
 331   if (UseLoopPredicate) {
 332     predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
 333   }
 334   if (predicate_proj != NULL) { // right pattern that can be used by loop predication
 335     // clone predicate
 336     new_entry = clone_predicate(predicate_proj, new_entry,
 337                                 Deoptimization::Reason_predicate,
 338                                 loop_phase, igvn);
 339     assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
 340     if (TraceLoopPredicate) {
 341       tty->print("Loop Predicate cloned: ");
 342       debug_only( new_entry->in(0)->dump(); );
 343     }
 344   }
 345   if (profile_predicate_proj != NULL) { // right pattern that can be used by loop predication
 346     // clone predicate
 347     new_entry = clone_predicate(profile_predicate_proj, new_entry,
 348                                 Deoptimization::Reason_profile_predicate,
 349                                 loop_phase, igvn);
 350     assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
 351     if (TraceLoopPredicate) {
 352       tty->print("Loop Predicate cloned: ");
 353       debug_only( new_entry->in(0)->dump(); );
 354     }
 355   }
 356   if (limit_check_proj != NULL && clone_limit_check) {
 357     // Clone loop limit check last to insert it before loop.
 358     // Don't clone a limit check which was already finalized
 359     // for this counted loop (only one limit check is needed).
 360     new_entry = clone_predicate(limit_check_proj, new_entry,
 361                                 Deoptimization::Reason_loop_limit_check,
 362                                 loop_phase, igvn);
 363     assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone limit check");
 364     if (TraceLoopLimitCheck) {
 365       tty->print("Loop Limit Check cloned: ");
 366       debug_only( new_entry->in(0)->dump(); )
 367     }
 368   }
 369   return new_entry;
 370 }
 371 
 372 //--------------------------skip_loop_predicates------------------------------
 373 // Skip related predicates.
 374 Node* PhaseIdealLoop::skip_loop_predicates(Node* entry) {
 375   IfNode* iff = entry->in(0)->as_If();
 376   ProjNode* uncommon_proj = iff->proj_out(1 - entry->as_Proj()->_con);
 377   Node* rgn = uncommon_proj->unique_ctrl_out();
 378   assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
 379   entry = entry->in(0)->in(0);
 380   while (entry != NULL && entry->is_Proj() && entry->in(0)->is_If()) {
 381     uncommon_proj = entry->in(0)->as_If()->proj_out(1 - entry->as_Proj()->_con);
 382     if (uncommon_proj->unique_ctrl_out() != rgn)
 383       break;
 384     entry = entry->in(0)->in(0);
 385   }
 386   return entry;
 387 }
 388 
 389 Node* PhaseIdealLoop::skip_all_loop_predicates(Node* entry) {
 390   Node* predicate = NULL;
 391   predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
 392   if (predicate != NULL) {
 393     entry = skip_loop_predicates(entry);
 394   }
 395   if (UseProfiledLoopPredicate) {
 396     predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
 397     if (predicate != NULL) { // right pattern that can be used by loop predication
 398       entry = skip_loop_predicates(entry);
 399     }
 400   }
 401   if (UseLoopPredicate) {
 402     predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
 403     if (predicate != NULL) { // right pattern that can be used by loop predication
 404       entry = skip_loop_predicates(entry);
 405     }
 406   }
 407   return entry;
 408 }
 409 
 410 //--------------------------find_predicate_insertion_point-------------------
 411 // Find a good location to insert a predicate
 412 ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason) {
 413   if (start_c == NULL || !start_c->is_Proj())
 414     return NULL;
 415   if (start_c->as_Proj()->is_uncommon_trap_if_pattern(reason)) {
 416     return start_c->as_Proj();
 417   }
 418   return NULL;
 419 }
 420 
 421 //--------------------------find_predicate------------------------------------
 422 // Find a predicate
 423 Node* PhaseIdealLoop::find_predicate(Node* entry) {
 424   Node* predicate = NULL;
 425   predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
 426   if (predicate != NULL) { // right pattern that can be used by loop predication
 427     return entry;
 428   }
 429   if (UseLoopPredicate) {
 430     predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
 431     if (predicate != NULL) { // right pattern that can be used by loop predication
 432       return entry;
 433     }
 434   }
 435   if (UseProfiledLoopPredicate) {
 436     predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
 437     if (predicate != NULL) { // right pattern that can be used by loop predication
 438       return entry;
 439     }
 440   }
 441   return NULL;
 442 }
 443 
 444 //------------------------------Invariance-----------------------------------
 445 // Helper class for loop_predication_impl to compute invariance on the fly and
 446 // clone invariants.
 447 class Invariance : public StackObj {
 448   VectorSet _visited, _invariant;
 449   Node_Stack _stack;
 450   VectorSet _clone_visited;
 451   Node_List _old_new; // map of old to new (clone)
 452   IdealLoopTree* _lpt;
 453   PhaseIdealLoop* _phase;
 454 
 455   // Helper function to set up the invariance for invariance computation
 456   // If n is a known invariant, set up directly. Otherwise, look up the
 457   // the possibility to push n onto the stack for further processing.
 458   void visit(Node* use, Node* n) {
 459     if (_lpt->is_invariant(n)) { // known invariant
 460       _invariant.set(n->_idx);
 461     } else if (!n->is_CFG()) {
 462       Node *n_ctrl = _phase->ctrl_or_self(n);
 463       Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
 464       if (_phase->is_dominator(n_ctrl, u_ctrl)) {
 465         _stack.push(n, n->in(0) == NULL ? 1 : 0);
 466       }
 467     }
 468   }
 469 
 470   // Compute invariance for "the_node" and (possibly) all its inputs recursively
 471   // on the fly
 472   void compute_invariance(Node* n) {
 473     assert(_visited.test(n->_idx), "must be");
 474     visit(n, n);
 475     while (_stack.is_nonempty()) {
 476       Node*  n = _stack.node();
 477       uint idx = _stack.index();
 478       if (idx == n->req()) { // all inputs are processed
 479         _stack.pop();
 480         // n is invariant if it's inputs are all invariant
 481         bool all_inputs_invariant = true;
 482         for (uint i = 0; i < n->req(); i++) {
 483           Node* in = n->in(i);
 484           if (in == NULL) continue;
 485           assert(_visited.test(in->_idx), "must have visited input");
 486           if (!_invariant.test(in->_idx)) { // bad guy
 487             all_inputs_invariant = false;
 488             break;
 489           }
 490         }
 491         if (all_inputs_invariant) {
 492           // If n's control is a predicate that was moved out of the
 493           // loop, it was marked invariant but n is only invariant if
 494           // it depends only on that test. Otherwise, unless that test
 495           // is out of the loop, it's not invariant.
 496           if (n->is_CFG() || n->depends_only_on_test() || n->in(0) == NULL || !_phase->is_member(_lpt, n->in(0))) {
 497             _invariant.set(n->_idx); // I am a invariant too
 498           }
 499         }
 500       } else { // process next input
 501         _stack.set_index(idx + 1);
 502         Node* m = n->in(idx);
 503         if (m != NULL && !_visited.test_set(m->_idx)) {
 504           visit(n, m);
 505         }
 506       }
 507     }
 508   }
 509 
 510   // Helper function to set up _old_new map for clone_nodes.
 511   // If n is a known invariant, set up directly ("clone" of n == n).
 512   // Otherwise, push n onto the stack for real cloning.
 513   void clone_visit(Node* n) {
 514     assert(_invariant.test(n->_idx), "must be invariant");
 515     if (_lpt->is_invariant(n)) { // known invariant
 516       _old_new.map(n->_idx, n);
 517     } else { // to be cloned
 518       assert(!n->is_CFG(), "should not see CFG here");
 519       _stack.push(n, n->in(0) == NULL ? 1 : 0);
 520     }
 521   }
 522 
 523   // Clone "n" and (possibly) all its inputs recursively
 524   void clone_nodes(Node* n, Node* ctrl) {
 525     clone_visit(n);
 526     while (_stack.is_nonempty()) {
 527       Node*  n = _stack.node();
 528       uint idx = _stack.index();
 529       if (idx == n->req()) { // all inputs processed, clone n!
 530         _stack.pop();
 531         // clone invariant node
 532         Node* n_cl = n->clone();
 533         _old_new.map(n->_idx, n_cl);
 534         _phase->register_new_node(n_cl, ctrl);
 535         for (uint i = 0; i < n->req(); i++) {
 536           Node* in = n_cl->in(i);
 537           if (in == NULL) continue;
 538           n_cl->set_req(i, _old_new[in->_idx]);
 539         }
 540       } else { // process next input
 541         _stack.set_index(idx + 1);
 542         Node* m = n->in(idx);
 543         if (m != NULL && !_clone_visited.test_set(m->_idx)) {
 544           clone_visit(m); // visit the input
 545         }
 546       }
 547     }
 548   }
 549 
 550  public:
 551   Invariance(Arena* area, IdealLoopTree* lpt) :
 552     _lpt(lpt), _phase(lpt->_phase),
 553     _visited(area), _invariant(area), _stack(area, 10 /* guess */),
 554     _clone_visited(area), _old_new(area)
 555   {
 556     LoopNode* head = _lpt->_head->as_Loop();
 557     Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
 558     if (entry->outcnt() != 1) {
 559       // If a node is pinned between the predicates and the loop
 560       // entry, we won't be able to move any node in the loop that
 561       // depends on it above it in a predicate. Mark all those nodes
 562       // as non loop invariatnt.
 563       Unique_Node_List wq;
 564       wq.push(entry);
 565       for (uint next = 0; next < wq.size(); ++next) {
 566         Node *n = wq.at(next);
 567         for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
 568           Node* u = n->fast_out(i);
 569           if (!u->is_CFG()) {
 570             Node* c = _phase->get_ctrl(u);
 571             if (_lpt->is_member(_phase->get_loop(c)) || _phase->is_dominator(c, head)) {
 572               _visited.set(u->_idx);
 573               wq.push(u);
 574             }
 575           }
 576         }
 577       }
 578     }
 579   }
 580 
 581   // Map old to n for invariance computation and clone
 582   void map_ctrl(Node* old, Node* n) {
 583     assert(old->is_CFG() && n->is_CFG(), "must be");
 584     _old_new.map(old->_idx, n); // "clone" of old is n
 585     _invariant.set(old->_idx);  // old is invariant
 586     _clone_visited.set(old->_idx);
 587   }
 588 
 589   // Driver function to compute invariance
 590   bool is_invariant(Node* n) {
 591     if (!_visited.test_set(n->_idx))
 592       compute_invariance(n);
 593     return (_invariant.test(n->_idx) != 0);
 594   }
 595 
 596   // Driver function to clone invariant
 597   Node* clone(Node* n, Node* ctrl) {
 598     assert(ctrl->is_CFG(), "must be");
 599     assert(_invariant.test(n->_idx), "must be an invariant");
 600     if (!_clone_visited.test(n->_idx))
 601       clone_nodes(n, ctrl);
 602     return _old_new[n->_idx];
 603   }
 604 };
 605 
 606 //------------------------------is_range_check_if -----------------------------------
 607 // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
 608 // Note: this function is particularly designed for loop predication. We require load_range
 609 //       and offset to be loop invariant computed on the fly by "invar"
 610 bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
 611   if (!is_loop_exit(iff)) {
 612     return false;
 613   }
 614   if (!iff->in(1)->is_Bool()) {
 615     return false;
 616   }
 617   const BoolNode *bol = iff->in(1)->as_Bool();
 618   if (bol->_test._test != BoolTest::lt) {
 619     return false;
 620   }
 621   if (!bol->in(1)->is_Cmp()) {
 622     return false;
 623   }
 624   const CmpNode *cmp = bol->in(1)->as_Cmp();
 625   if (cmp->Opcode() != Op_CmpU) {
 626     return false;
 627   }
 628   Node* range = cmp->in(2);
 629   if (range->Opcode() != Op_LoadRange && !iff->is_RangeCheck()) {
 630     const TypeInt* tint = phase->_igvn.type(range)->isa_int();
 631     if (tint == NULL || tint->empty() || tint->_lo < 0) {
 632       // Allow predication on positive values that aren't LoadRanges.
 633       // This allows optimization of loops where the length of the
 634       // array is a known value and doesn't need to be loaded back
 635       // from the array.
 636       return false;
 637     }
 638   }
 639   if (!invar.is_invariant(range)) {
 640     return false;
 641   }
 642   Node *iv     = _head->as_CountedLoop()->phi();
 643   int   scale  = 0;
 644   Node *offset = NULL;
 645   if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
 646     return false;
 647   }
 648   if (offset && !invar.is_invariant(offset)) { // offset must be invariant
 649     return false;
 650   }
 651   return true;
 652 }
 653 
 654 //------------------------------rc_predicate-----------------------------------
 655 // Create a range check predicate
 656 //
 657 // for (i = init; i < limit; i += stride) {
 658 //    a[scale*i+offset]
 659 // }
 660 //
 661 // Compute max(scale*i + offset) for init <= i < limit and build the predicate
 662 // as "max(scale*i + offset) u< a.length".
 663 //
 664 // There are two cases for max(scale*i + offset):
 665 // (1) stride*scale > 0
 666 //   max(scale*i + offset) = scale*(limit-stride) + offset
 667 // (2) stride*scale < 0
 668 //   max(scale*i + offset) = scale*init + offset
 669 BoolNode* PhaseIdealLoop::rc_predicate(IdealLoopTree *loop, Node* ctrl,
 670                                        int scale, Node* offset,
 671                                        Node* init, Node* limit, jint stride,
 672                                        Node* range, bool upper, bool &overflow) {
 673   jint con_limit  = (limit != NULL && limit->is_Con())  ? limit->get_int()  : 0;
 674   jint con_init   = init->is_Con()   ? init->get_int()   : 0;
 675   jint con_offset = offset->is_Con() ? offset->get_int() : 0;
 676 
 677   stringStream* predString = NULL;
 678   if (TraceLoopPredicate) {
 679     predString = new stringStream();
 680     predString->print("rc_predicate ");
 681   }
 682 
 683   overflow = false;
 684   Node* max_idx_expr = NULL;
 685   const TypeInt* idx_type = TypeInt::INT;
 686   if ((stride > 0) == (scale > 0) == upper) {
 687     guarantee(limit != NULL, "sanity");
 688     if (TraceLoopPredicate) {
 689       if (limit->is_Con()) {
 690         predString->print("(%d ", con_limit);
 691       } else {
 692         predString->print("(limit ");
 693       }
 694       predString->print("- %d) ", stride);
 695     }
 696     // Check if (limit - stride) may overflow
 697     const TypeInt* limit_type = _igvn.type(limit)->isa_int();
 698     jint limit_lo = limit_type->_lo;
 699     jint limit_hi = limit_type->_hi;
 700     if ((stride > 0 && (java_subtract(limit_lo, stride) < limit_lo)) ||
 701         (stride < 0 && (java_subtract(limit_hi, stride) > limit_hi))) {
 702       // No overflow possible
 703       ConINode* con_stride = _igvn.intcon(stride);
 704       set_ctrl(con_stride, C->root());
 705       max_idx_expr = new SubINode(limit, con_stride);
 706       idx_type = TypeInt::make(limit_lo - stride, limit_hi - stride, limit_type->_widen);
 707     } else {
 708       // May overflow
 709       overflow = true;
 710       limit = new ConvI2LNode(limit);
 711       register_new_node(limit, ctrl);
 712       ConLNode* con_stride = _igvn.longcon(stride);
 713       set_ctrl(con_stride, C->root());
 714       max_idx_expr = new SubLNode(limit, con_stride);
 715     }
 716     register_new_node(max_idx_expr, ctrl);
 717   } else {
 718     if (TraceLoopPredicate) {
 719       if (init->is_Con()) {
 720         predString->print("%d ", con_init);
 721       } else {
 722         predString->print("init ");
 723       }
 724     }
 725     idx_type = _igvn.type(init)->isa_int();
 726     max_idx_expr = init;
 727   }
 728 
 729   if (scale != 1) {
 730     ConNode* con_scale = _igvn.intcon(scale);
 731     set_ctrl(con_scale, C->root());
 732     if (TraceLoopPredicate) {
 733       predString->print("* %d ", scale);
 734     }
 735     // Check if (scale * max_idx_expr) may overflow
 736     const TypeInt* scale_type = TypeInt::make(scale);
 737     MulINode* mul = new MulINode(max_idx_expr, con_scale);
 738     idx_type = (TypeInt*)mul->mul_ring(idx_type, scale_type);
 739     if (overflow || TypeInt::INT->higher_equal(idx_type)) {
 740       // May overflow
 741       mul->destruct();
 742       if (!overflow) {
 743         max_idx_expr = new ConvI2LNode(max_idx_expr);
 744         register_new_node(max_idx_expr, ctrl);
 745       }
 746       overflow = true;
 747       con_scale = _igvn.longcon(scale);
 748       set_ctrl(con_scale, C->root());
 749       max_idx_expr = new MulLNode(max_idx_expr, con_scale);
 750     } else {
 751       // No overflow possible
 752       max_idx_expr = mul;
 753     }
 754     register_new_node(max_idx_expr, ctrl);
 755   }
 756 
 757   if (offset && (!offset->is_Con() || con_offset != 0)){
 758     if (TraceLoopPredicate) {
 759       if (offset->is_Con()) {
 760         predString->print("+ %d ", con_offset);
 761       } else {
 762         predString->print("+ offset");
 763       }
 764     }
 765     // Check if (max_idx_expr + offset) may overflow
 766     const TypeInt* offset_type = _igvn.type(offset)->isa_int();
 767     jint lo = java_add(idx_type->_lo, offset_type->_lo);
 768     jint hi = java_add(idx_type->_hi, offset_type->_hi);
 769     if (overflow || (lo > hi) ||
 770         ((idx_type->_lo & offset_type->_lo) < 0 && lo >= 0) ||
 771         ((~(idx_type->_hi | offset_type->_hi)) < 0 && hi < 0)) {
 772       // May overflow
 773       if (!overflow) {
 774         max_idx_expr = new ConvI2LNode(max_idx_expr);
 775         register_new_node(max_idx_expr, ctrl);
 776       }
 777       overflow = true;
 778       offset = new ConvI2LNode(offset);
 779       register_new_node(offset, ctrl);
 780       max_idx_expr = new AddLNode(max_idx_expr, offset);
 781     } else {
 782       // No overflow possible
 783       max_idx_expr = new AddINode(max_idx_expr, offset);
 784     }
 785     register_new_node(max_idx_expr, ctrl);
 786   }
 787 
 788   CmpNode* cmp = NULL;
 789   if (overflow) {
 790     // Integer expressions may overflow, do long comparison
 791     range = new ConvI2LNode(range);
 792     register_new_node(range, ctrl);
 793     cmp = new CmpULNode(max_idx_expr, range);
 794   } else {
 795     cmp = new CmpUNode(max_idx_expr, range);
 796   }
 797   register_new_node(cmp, ctrl);
 798   BoolNode* bol = new BoolNode(cmp, BoolTest::lt);
 799   register_new_node(bol, ctrl);
 800 
 801   if (TraceLoopPredicate) {
 802     predString->print_cr("<u range");
 803     tty->print("%s", predString->as_string());
 804   }
 805   return bol;
 806 }
 807 
 808 // Should loop predication look not only in the path from tail to head
 809 // but also in branches of the loop body?
 810 bool PhaseIdealLoop::loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt) {
 811   if (!UseProfiledLoopPredicate) {
 812     return false;
 813   }
 814 
 815   if (predicate_proj == NULL) {
 816     return false;
 817   }
 818 
 819   LoopNode* head = loop->_head->as_Loop();
 820   bool follow_branches = true;
 821   IdealLoopTree* l = loop->_child;
 822   // For leaf loops and loops with a single inner loop
 823   while (l != NULL && follow_branches) {
 824     IdealLoopTree* child = l;
 825     if (child->_child != NULL &&
 826         child->_head->is_OuterStripMinedLoop()) {
 827       assert(child->_child->_next == NULL, "only one inner loop for strip mined loop");
 828       assert(child->_child->_head->is_CountedLoop() && child->_child->_head->as_CountedLoop()->is_strip_mined(), "inner loop should be strip mined");
 829       child = child->_child;
 830     }
 831     if (child->_child != NULL || child->_irreducible) {
 832       follow_branches = false;
 833     }
 834     l = l->_next;
 835   }
 836   if (follow_branches) {
 837     loop->compute_profile_trip_cnt(this);
 838     if (head->is_profile_trip_failed()) {
 839       follow_branches = false;
 840     } else {
 841       loop_trip_cnt = head->profile_trip_cnt();
 842       if (head->is_CountedLoop()) {
 843         CountedLoopNode* cl = head->as_CountedLoop();
 844         if (cl->phi() != NULL) {
 845           const TypeInt* t = _igvn.type(cl->phi())->is_int();
 846           float worst_case_trip_cnt = ((float)t->_hi - t->_lo) / ABS(cl->stride_con());
 847           if (worst_case_trip_cnt < loop_trip_cnt) {
 848             loop_trip_cnt = worst_case_trip_cnt;
 849           }
 850         }
 851       }
 852     }
 853   }
 854   return follow_branches;
 855 }
 856 
 857 // Compute probability of reaching some CFG node from a fixed
 858 // dominating CFG node
 859 class PathFrequency {
 860 private:
 861   Node* _dom; // frequencies are computed relative to this node
 862   Node_Stack _stack;
 863   GrowableArray<float> _freqs_stack; // keep track of intermediate result at regions
 864   GrowableArray<float> _freqs; // cache frequencies
 865   PhaseIdealLoop* _phase;
 866 
 867   void set_rounding(int mode) {
 868     // fesetround is broken on windows
 869     NOT_WINDOWS(fesetround(mode);)
 870   }
 871 
 872   void check_frequency(float f) {
 873     NOT_WINDOWS(assert(f <= 1 && f >= 0, "Incorrect frequency");)
 874   }
 875 
 876 public:
 877   PathFrequency(Node* dom, PhaseIdealLoop* phase)
 878     : _dom(dom), _stack(0), _phase(phase) {
 879   }
 880 
 881   float to(Node* n) {
 882     // post order walk on the CFG graph from n to _dom
 883     set_rounding(FE_TOWARDZERO); // make sure rounding doesn't push frequency above 1
 884     IdealLoopTree* loop = _phase->get_loop(_dom);
 885     Node* c = n;
 886     for (;;) {
 887       assert(_phase->get_loop(c) == loop, "have to be in the same loop");
 888       if (c == _dom || _freqs.at_grow(c->_idx, -1) >= 0) {
 889         float f = c == _dom ? 1 : _freqs.at(c->_idx);
 890         Node* prev = c;
 891         while (_stack.size() > 0 && prev == c) {
 892           Node* n = _stack.node();
 893           if (!n->is_Region()) {
 894             if (_phase->get_loop(n) != _phase->get_loop(n->in(0))) {
 895               // Found an inner loop: compute frequency of reaching this
 896               // exit from the loop head by looking at the number of
 897               // times each loop exit was taken
 898               IdealLoopTree* inner_loop = _phase->get_loop(n->in(0));
 899               LoopNode* inner_head = inner_loop->_head->as_Loop();
 900               assert(_phase->get_loop(n) == loop, "only 1 inner loop");
 901               if (inner_head->is_OuterStripMinedLoop()) {
 902                 inner_head->verify_strip_mined(1);
 903                 if (n->in(0) == inner_head->in(LoopNode::LoopBackControl)->in(0)) {
 904                   n = n->in(0)->in(0)->in(0);
 905                 }
 906                 inner_loop = inner_loop->_child;
 907                 inner_head = inner_loop->_head->as_Loop();
 908                 inner_head->verify_strip_mined(1);
 909               }
 910               set_rounding(FE_UPWARD);  // make sure rounding doesn't push frequency above 1
 911               float loop_exit_cnt = 0.0f;
 912               for (uint i = 0; i < inner_loop->_body.size(); i++) {
 913                 Node *n = inner_loop->_body[i];
 914                 float c = inner_loop->compute_profile_trip_cnt_helper(n);
 915                 loop_exit_cnt += c;
 916               }
 917               set_rounding(FE_TOWARDZERO);
 918               float cnt = -1;
 919               if (n->in(0)->is_If()) {
 920                 IfNode* iff = n->in(0)->as_If();
 921                 float p = n->in(0)->as_If()->_prob;
 922                 if (n->Opcode() == Op_IfFalse) {
 923                   p = 1 - p;
 924                 }
 925                 if (p > PROB_MIN) {
 926                   cnt = p * iff->_fcnt;
 927                 } else {
 928                   cnt = 0;
 929                 }
 930               } else {
 931                 assert(n->in(0)->is_Jump(), "unsupported node kind");
 932                 JumpNode* jmp = n->in(0)->as_Jump();
 933                 float p = n->in(0)->as_Jump()->_probs[n->as_JumpProj()->_con];
 934                 cnt = p * jmp->_fcnt;
 935               }
 936               float this_exit_f = cnt > 0 ? cnt / loop_exit_cnt : 0;
 937               check_frequency(this_exit_f);
 938               f = f * this_exit_f;
 939               check_frequency(f);
 940             } else {
 941               float p = -1;
 942               if (n->in(0)->is_If()) {
 943                 p = n->in(0)->as_If()->_prob;
 944                 if (n->Opcode() == Op_IfFalse) {
 945                   p = 1 - p;
 946                 }
 947               } else {
 948                 assert(n->in(0)->is_Jump(), "unsupported node kind");
 949                 p = n->in(0)->as_Jump()->_probs[n->as_JumpProj()->_con];
 950               }
 951               f = f * p;
 952               check_frequency(f);
 953             }
 954             _freqs.at_put_grow(n->_idx, (float)f, -1);
 955             _stack.pop();
 956           } else {
 957             float prev_f = _freqs_stack.pop();
 958             float new_f = f;
 959             f = new_f + prev_f;
 960             check_frequency(f);
 961             uint i = _stack.index();
 962             if (i < n->req()) {
 963               c = n->in(i);
 964               _stack.set_index(i+1);
 965               _freqs_stack.push(f);
 966             } else {
 967               _freqs.at_put_grow(n->_idx, f, -1);
 968               _stack.pop();
 969             }
 970           }
 971         }
 972         if (_stack.size() == 0) {
 973           set_rounding(FE_TONEAREST);
 974           check_frequency(f);
 975           return f;
 976         }
 977       } else if (c->is_Loop()) {
 978         ShouldNotReachHere();
 979         c = c->in(LoopNode::EntryControl);
 980       } else if (c->is_Region()) {
 981         _freqs_stack.push(0);
 982         _stack.push(c, 2);
 983         c = c->in(1);
 984       } else {
 985         if (c->is_IfProj()) {
 986           IfNode* iff = c->in(0)->as_If();
 987           if (iff->_prob == PROB_UNKNOWN) {
 988             // assume never taken
 989             _freqs.at_put_grow(c->_idx, 0, -1);
 990           } else if (_phase->get_loop(c) != _phase->get_loop(iff)) {
 991             if (iff->_fcnt == COUNT_UNKNOWN) {
 992               // assume never taken
 993               _freqs.at_put_grow(c->_idx, 0, -1);
 994             } else {
 995               // skip over loop
 996               _stack.push(c, 1);
 997               c = _phase->get_loop(c->in(0))->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl);
 998             }
 999           } else {
1000             _stack.push(c, 1);
1001             c = iff;
1002           }
1003         } else if (c->is_JumpProj()) {
1004           JumpNode* jmp = c->in(0)->as_Jump();
1005           if (_phase->get_loop(c) != _phase->get_loop(jmp)) {
1006             if (jmp->_fcnt == COUNT_UNKNOWN) {
1007               // assume never taken
1008               _freqs.at_put_grow(c->_idx, 0, -1);
1009             } else {
1010               // skip over loop
1011               _stack.push(c, 1);
1012               c = _phase->get_loop(c->in(0))->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl);
1013             }
1014           } else {
1015             _stack.push(c, 1);
1016             c = jmp;
1017           }
1018         } else if (c->Opcode() == Op_CatchProj &&
1019                    c->in(0)->Opcode() == Op_Catch &&
1020                    c->in(0)->in(0)->is_Proj() &&
1021                    c->in(0)->in(0)->in(0)->is_Call()) {
1022           // assume exceptions are never thrown
1023           uint con = c->as_Proj()->_con;
1024           if (con == CatchProjNode::fall_through_index) {
1025             Node* call = c->in(0)->in(0)->in(0)->in(0);
1026             if (_phase->get_loop(call) != _phase->get_loop(c)) {
1027               _freqs.at_put_grow(c->_idx, 0, -1);
1028             } else {
1029               c = call;
1030             }
1031           } else {
1032             assert(con >= CatchProjNode::catch_all_index, "what else?");
1033             _freqs.at_put_grow(c->_idx, 0, -1);
1034           }
1035         } else if (c->unique_ctrl_out() == NULL && !c->is_If() && !c->is_Jump()) {
1036           ShouldNotReachHere();
1037         } else {
1038           c = c->in(0);
1039         }
1040       }
1041     }
1042     ShouldNotReachHere();
1043     return -1;
1044   }
1045 };
1046 
1047 void PhaseIdealLoop::loop_predication_follow_branches(Node *n, IdealLoopTree *loop, float loop_trip_cnt,
1048                                                       PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
1049                                                       Node_List& if_proj_list) {
1050   assert(n->is_Region(), "start from a region");
1051   Node* tail = loop->tail();
1052   stack.push(n, 1);
1053   do {
1054     Node* c = stack.node();
1055     assert(c->is_Region() || c->is_IfProj(), "only region here");
1056     uint i = stack.index();
1057 
1058     if (i < c->req()) {
1059       stack.set_index(i+1);
1060       Node* in = c->in(i);
1061       while (!is_dominator(in, tail) && !seen.test_set(in->_idx)) {
1062         IdealLoopTree* in_loop = get_loop(in);
1063         if (in_loop != loop) {
1064           in = in_loop->_head->in(LoopNode::EntryControl);
1065         } else if (in->is_Region()) {
1066           stack.push(in, 1);
1067           break;
1068         } else if (in->is_IfProj() &&
1069                    in->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1070                    (in->in(0)->Opcode() == Op_If ||
1071                     in->in(0)->Opcode() == Op_RangeCheck)) {
1072           if (pf.to(in) * loop_trip_cnt >= 1) {
1073             stack.push(in, 1);
1074           }
1075           in = in->in(0);
1076         } else {
1077           in = in->in(0);
1078         }
1079       }
1080     } else {
1081       if (c->is_IfProj()) {
1082         if_proj_list.push(c);
1083       }
1084       stack.pop();
1085     }
1086 
1087   } while (stack.size() > 0);
1088 }
1089 
1090 
1091 bool PhaseIdealLoop::loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
1092                                                   CountedLoopNode *cl, ConNode* zero, Invariance& invar,
1093                                                   Deoptimization::DeoptReason reason) {
1094   // Following are changed to nonnull when a predicate can be hoisted
1095   ProjNode* new_predicate_proj = NULL;
1096   IfNode*   iff  = proj->in(0)->as_If();
1097   Node*     test = iff->in(1);
1098   if (!test->is_Bool()){ //Conv2B, ...
1099     return false;
1100   }
1101   BoolNode* bol = test->as_Bool();
1102   if (invar.is_invariant(bol)) {
1103     // Invariant test
1104     new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
1105                                                      reason,
1106                                                      iff->Opcode());
1107     Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
1108     BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
1109 
1110     // Negate test if necessary
1111     bool negated = false;
1112     if (proj->_con != predicate_proj->_con) {
1113       new_predicate_bol = new BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
1114       register_new_node(new_predicate_bol, ctrl);
1115       negated = true;
1116     }
1117     IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
1118     _igvn.hash_delete(new_predicate_iff);
1119     new_predicate_iff->set_req(1, new_predicate_bol);
1120 #ifndef PRODUCT
1121     if (TraceLoopPredicate) {
1122       tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
1123       loop->dump_head();
1124     } else if (TraceLoopOpts) {
1125       tty->print("Predicate IC ");
1126       loop->dump_head();
1127     }
1128 #endif
1129   } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
1130     // Range check for counted loops
1131     const Node*    cmp    = bol->in(1)->as_Cmp();
1132     Node*          idx    = cmp->in(1);
1133     assert(!invar.is_invariant(idx), "index is variant");
1134     Node* rng = cmp->in(2);
1135     assert(rng->Opcode() == Op_LoadRange || iff->is_RangeCheck() || _igvn.type(rng)->is_int()->_lo >= 0, "must be");
1136     assert(invar.is_invariant(rng), "range must be invariant");
1137     int scale    = 1;
1138     Node* offset = zero;
1139     bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
1140     assert(ok, "must be index expression");
1141 
1142     Node* init    = cl->init_trip();
1143     // Limit is not exact.
1144     // Calculate exact limit here.
1145     // Note, counted loop's test is '<' or '>'.
1146     Node* limit   = exact_limit(loop);
1147     int  stride   = cl->stride()->get_int();
1148 
1149     // Build if's for the upper and lower bound tests.  The
1150     // lower_bound test will dominate the upper bound test and all
1151     // cloned or created nodes will use the lower bound test as
1152     // their declared control.
1153 
1154     // Perform cloning to keep Invariance state correct since the
1155     // late schedule will place invariant things in the loop.
1156     Node *ctrl = predicate_proj->in(0)->as_If()->in(0);
1157     rng = invar.clone(rng, ctrl);
1158     if (offset && offset != zero) {
1159       assert(invar.is_invariant(offset), "offset must be loop invariant");
1160       offset = invar.clone(offset, ctrl);
1161     }
1162     // If predicate expressions may overflow in the integer range, longs are used.
1163     bool overflow = false;
1164 
1165     // Test the lower bound
1166     BoolNode* lower_bound_bol = rc_predicate(loop, ctrl, scale, offset, init, limit, stride, rng, false, overflow);
1167     // Negate test if necessary
1168     bool negated = false;
1169     if (proj->_con != predicate_proj->_con) {
1170       lower_bound_bol = new BoolNode(lower_bound_bol->in(1), lower_bound_bol->_test.negate());
1171       register_new_node(lower_bound_bol, ctrl);
1172       negated = true;
1173     }
1174     ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, reason, overflow ? Op_If : iff->Opcode());
1175     IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
1176     _igvn.hash_delete(lower_bound_iff);
1177     lower_bound_iff->set_req(1, lower_bound_bol);
1178     if (TraceLoopPredicate) tty->print_cr("lower bound check if: %s %d ", negated ? " negated" : "", lower_bound_iff->_idx);
1179 
1180     // Test the upper bound
1181     BoolNode* upper_bound_bol = rc_predicate(loop, lower_bound_proj, scale, offset, init, limit, stride, rng, true, overflow);
1182     negated = false;
1183     if (proj->_con != predicate_proj->_con) {
1184       upper_bound_bol = new BoolNode(upper_bound_bol->in(1), upper_bound_bol->_test.negate());
1185       register_new_node(upper_bound_bol, ctrl);
1186       negated = true;
1187     }
1188     ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, reason, overflow ? Op_If : iff->Opcode());
1189     assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
1190     IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
1191     _igvn.hash_delete(upper_bound_iff);
1192     upper_bound_iff->set_req(1, upper_bound_bol);
1193     if (TraceLoopPredicate) tty->print_cr("upper bound check if: %s %d ", negated ? " negated" : "", lower_bound_iff->_idx);
1194 
1195     // Fall through into rest of the clean up code which will move
1196     // any dependent nodes onto the upper bound test.
1197     new_predicate_proj = upper_bound_proj;
1198 
1199     if (iff->is_RangeCheck()) {
1200       new_predicate_proj = insert_skeleton_predicate(iff, loop, proj, predicate_proj, upper_bound_proj, scale, offset, init, limit, stride, rng, overflow, reason);
1201     }
1202 
1203 #ifndef PRODUCT
1204     if (TraceLoopOpts && !TraceLoopPredicate) {
1205       tty->print("Predicate RC ");
1206       loop->dump_head();
1207     }
1208 #endif
1209   } else {
1210     // Loop variant check (for example, range check in non-counted loop)
1211     // with uncommon trap.
1212     return false;
1213   }
1214   assert(new_predicate_proj != NULL, "sanity");
1215   // Success - attach condition (new_predicate_bol) to predicate if
1216   invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
1217 
1218   // Eliminate the old If in the loop body
1219   dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
1220 
1221   C->set_major_progress();
1222   return true;
1223 }
1224 
1225 
1226 // After pre/main/post loops are created, we'll put a copy of some
1227 // range checks between the pre and main loop to validate the value
1228 // of the main loop induction variable. Make a copy of the predicates
1229 // here with an opaque node as a place holder for the value (will be
1230 // updated by PhaseIdealLoop::update_skeleton_predicate()).
1231 ProjNode* PhaseIdealLoop::insert_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
1232                                                     ProjNode* proj, ProjNode *predicate_proj,
1233                                                     ProjNode* upper_bound_proj,
1234                                                     int scale, Node* offset,
1235                                                     Node* init, Node* limit, jint stride,
1236                                                     Node* rng, bool &overflow,
1237                                                     Deoptimization::DeoptReason reason) {
1238   assert(proj->_con && predicate_proj->_con, "not a range check?");
1239   Node* opaque_init = new Opaque1Node(C, init);
1240   register_new_node(opaque_init, upper_bound_proj);
1241   BoolNode* bol = rc_predicate(loop, upper_bound_proj, scale, offset, opaque_init, limit, stride, rng, (stride > 0) != (scale > 0), overflow);
1242   Node* opaque_bol = new Opaque4Node(C, bol, _igvn.intcon(1)); // This will go away once loop opts are over
1243   register_new_node(opaque_bol, upper_bound_proj);
1244   ProjNode* new_proj = create_new_if_for_predicate(predicate_proj, NULL, reason, overflow ? Op_If : iff->Opcode());
1245   _igvn.replace_input_of(new_proj->in(0), 1, opaque_bol);
1246   assert(opaque_init->outcnt() > 0, "should be used");
1247   return new_proj;
1248 }
1249 
1250 //------------------------------ loop_predication_impl--------------------------
1251 // Insert loop predicates for null checks and range checks
1252 bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
1253   if (!UseLoopPredicate) return false;
1254 
1255   if (!loop->_head->is_Loop()) {
1256     // Could be a simple region when irreducible loops are present.
1257     return false;
1258   }
1259   LoopNode* head = loop->_head->as_Loop();
1260 
1261   if (head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
1262     // do nothing for infinite loops
1263     return false;
1264   }
1265 
1266   if (head->is_OuterStripMinedLoop()) {
1267     return false;
1268   }
1269 
1270   CountedLoopNode *cl = NULL;
1271   if (head->is_valid_counted_loop()) {
1272     cl = head->as_CountedLoop();
1273     // do nothing for iteration-splitted loops
1274     if (!cl->is_normal_loop()) return false;
1275     // Avoid RCE if Counted loop's test is '!='.
1276     BoolTest::mask bt = cl->loopexit()->test_trip();
1277     if (bt != BoolTest::lt && bt != BoolTest::gt)
1278       cl = NULL;
1279   }
1280 
1281   Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
1282   ProjNode *loop_limit_proj = NULL;
1283   ProjNode *predicate_proj = NULL;
1284   ProjNode *profile_predicate_proj = NULL;
1285   // Loop limit check predicate should be near the loop.
1286   loop_limit_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
1287   if (loop_limit_proj != NULL) {
1288     entry = skip_loop_predicates(loop_limit_proj);
1289   }
1290   bool has_profile_predicates = false;
1291   profile_predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
1292   if (profile_predicate_proj != NULL) {
1293     Node* n = skip_loop_predicates(entry);
1294     // Check if predicates were already added to the profile predicate
1295     // block
1296     if (n != entry->in(0)->in(0) || n->outcnt() != 1) {
1297       has_profile_predicates = true;
1298     }
1299     entry = n;
1300   }
1301   predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
1302 
1303   float loop_trip_cnt = -1;
1304   bool follow_branches = loop_predication_should_follow_branches(loop, profile_predicate_proj, loop_trip_cnt);
1305   assert(!follow_branches || loop_trip_cnt >= 0, "negative trip count?");
1306 
1307   if (predicate_proj == NULL && !follow_branches) {
1308 #ifndef PRODUCT
1309     if (TraceLoopPredicate) {
1310       tty->print("missing predicate:");
1311       loop->dump_head();
1312       head->dump(1);
1313     }
1314 #endif
1315     return false;
1316   }
1317   ConNode* zero = _igvn.intcon(0);
1318   set_ctrl(zero, C->root());
1319 
1320   ResourceArea *area = Thread::current()->resource_area();
1321   Invariance invar(area, loop);
1322 
1323   // Create list of if-projs such that a newer proj dominates all older
1324   // projs in the list, and they all dominate loop->tail()
1325   Node_List if_proj_list(area);
1326   Node_List regions(area);
1327   Node *current_proj = loop->tail(); //start from tail
1328 
1329 
1330   Node_List controls(area);
1331   while (current_proj != head) {
1332     if (loop == get_loop(current_proj) && // still in the loop ?
1333         current_proj->is_Proj()        && // is a projection  ?
1334         (current_proj->in(0)->Opcode() == Op_If ||
1335          current_proj->in(0)->Opcode() == Op_RangeCheck)) { // is a if projection ?
1336       if_proj_list.push(current_proj);
1337     }
1338     if (follow_branches &&
1339         current_proj->Opcode() == Op_Region &&
1340         loop == get_loop(current_proj)) {
1341       regions.push(current_proj);
1342     }
1343     current_proj = idom(current_proj);
1344   }
1345 
1346   bool hoisted = false; // true if at least one proj is promoted
1347 
1348   if (!has_profile_predicates) {
1349     while (if_proj_list.size() > 0) {
1350       Node* n = if_proj_list.pop();
1351 
1352       ProjNode* proj = n->as_Proj();
1353       IfNode*   iff  = proj->in(0)->as_If();
1354 
1355       CallStaticJavaNode* call = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
1356       if (call == NULL) {
1357         if (loop->is_loop_exit(iff)) {
1358           // stop processing the remaining projs in the list because the execution of them
1359           // depends on the condition of "iff" (iff->in(1)).
1360           break;
1361         } else {
1362           // Both arms are inside the loop. There are two cases:
1363           // (1) there is one backward branch. In this case, any remaining proj
1364           //     in the if_proj list post-dominates "iff". So, the condition of "iff"
1365           //     does not determine the execution the remining projs directly, and we
1366           //     can safely continue.
1367           // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
1368           //     does not dominate loop->tail(), so it can not be in the if_proj list.
1369           continue;
1370         }
1371       }
1372       Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(call->uncommon_trap_request());
1373       if (reason == Deoptimization::Reason_predicate) {
1374         break;
1375       }
1376 
1377       if (predicate_proj != NULL) {
1378         hoisted = loop_predication_impl_helper(loop, proj, predicate_proj, cl, zero, invar, Deoptimization::Reason_predicate) | hoisted;
1379       }
1380     } // end while
1381   }
1382 
1383   Node_List if_proj_list_freq(area);
1384   if (follow_branches) {
1385     PathFrequency pf(loop->_head, this);
1386 
1387     // Some projections were skipped by regular predicates because of
1388     // an early loop exit. Try them with profile data.
1389     while (if_proj_list.size() > 0) {
1390       Node* proj = if_proj_list.pop();
1391       float f = pf.to(proj);
1392       if (proj->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
1393           f * loop_trip_cnt >= 1) {
1394         hoisted = loop_predication_impl_helper(loop, proj->as_Proj(), profile_predicate_proj, cl, zero, invar, Deoptimization::Reason_profile_predicate) | hoisted;
1395       }
1396     }
1397 
1398     // And look into all branches
1399     Node_Stack stack(0);
1400     VectorSet seen(Thread::current()->resource_area());
1401     while (regions.size() > 0) {
1402       Node* c = regions.pop();
1403       loop_predication_follow_branches(c, loop, loop_trip_cnt, pf, stack, seen, if_proj_list_freq);
1404     }
1405 
1406     for (uint i = 0; i < if_proj_list_freq.size(); i++) {
1407       ProjNode* proj = if_proj_list_freq.at(i)->as_Proj();
1408       hoisted = loop_predication_impl_helper(loop, proj, profile_predicate_proj, cl, zero, invar, Deoptimization::Reason_profile_predicate) | hoisted;
1409     }
1410   }
1411 
1412 #ifndef PRODUCT
1413   // report that the loop predication has been actually performed
1414   // for this loop
1415   if (TraceLoopPredicate && hoisted) {
1416     tty->print("Loop Predication Performed:");
1417     loop->dump_head();
1418   }
1419 #endif
1420 
1421   head->verify_strip_mined(1);
1422 
1423   return hoisted;
1424 }
1425 
1426 //------------------------------loop_predication--------------------------------
1427 // driver routine for loop predication optimization
1428 bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
1429   bool hoisted = false;
1430   // Recursively promote predicates
1431   if (_child) {
1432     hoisted = _child->loop_predication( phase);
1433   }
1434 
1435   // self
1436   if (!_irreducible && !tail()->is_top()) {
1437     hoisted |= phase->loop_predication_impl(this);
1438   }
1439 
1440   if (_next) { //sibling
1441     hoisted |= _next->loop_predication( phase);
1442   }
1443 
1444   return hoisted;
1445 }