text: /*
   * Copyright (c) 2011, 2018, Oracle and/or its affiliates. All rights reserved.
   * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   *
   * This code is free software; you can redistribute it and/or modify it
   * under the terms of the GNU General Public License version 2 only, as
   * published by the Free Software Foundation.
   *
   * This code is distributed in the hope that it will be useful, but WITHOUT
   * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   * version 2 for more details (a copy is included in the LICENSE file that
   * accompanied this code).
   *
   * You should have received a copy of the GNU General Public License version
   * 2 along with this work; if not, write to the Free Software Foundation,
   * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   *
   * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   * or visit www.oracle.com if you need additional information or have any
   * questions.
   *
   */
  
  #include "precompiled.hpp"
  #include "opto/loopnode.hpp"
  #include "opto/addnode.hpp"
  #include "opto/callnode.hpp"
  #include "opto/connode.hpp"
  #include "opto/convertnode.hpp"
  #include "opto/loopnode.hpp"
  #include "opto/matcher.hpp"
  #include "opto/mulnode.hpp"
  #include "opto/opaquenode.hpp"
  #include "opto/rootnode.hpp"
  #include "opto/subnode.hpp"
  #include <fenv.h>
  #include <math.h>
  
  /*
   * The general idea of Loop Predication is to insert a predicate on the entry
   * path to a loop, and raise a uncommon trap if the check of the condition fails.
   * The condition checks are promoted from inside the loop body, and thus
   * the checks inside the loop could be eliminated. Currently, loop predication
   * optimization has been applied to remove array range check and loop invariant
   * checks (such as null checks).
  */
  
  //-------------------------------register_control-------------------------
  void PhaseIdealLoop::register_control(Node* n, IdealLoopTree *loop, Node* pred) {
    assert(n->is_CFG(), "must be control node");
    _igvn.register_new_node_with_optimizer(n);
    loop->_body.push(n);
    set_loop(n, loop);
    // When called from beautify_loops() idom is not constructed yet.
    if (_idom != NULL) {
      set_idom(n, pred, dom_depth(pred));
    }
  }
  
  //------------------------------create_new_if_for_predicate------------------------
  // create a new if above the uct_if_pattern for the predicate to be promoted.
  //
  //          before                                after
  //        ----------                           ----------
  //           ctrl                                 ctrl
  //            |                                     |
  //            |                                     |
  //            v                                     v
  //           iff                                 new_iff
  //          /    \                                /      \
  //         /      \                              /        \
  //        v        v                            v          v
  //  uncommon_proj cont_proj                   if_uct     if_cont
  // \      |        |                           |          |
  //  \     |        |                           |          |
  //   v    v        v                           |          v
  //     rgn       loop                          |         iff
  //      |                                      |        /     \
  //      |                                      |       /       \
  //      v                                      |      v         v
  // uncommon_trap                               | uncommon_proj cont_proj
  //                                           \  \    |           |
  //                                            \  \   |           |
  //                                             v  v  v           v
  //                                               rgn           loop
  //                                                |
  //                                                |
  //                                                v
  //                                           uncommon_trap
  //
  //
  // We will create a region to guard the uct call if there is no one there.
  // The true projection (if_cont) of the new_iff is returned.
  // This code is also used to clone predicates to cloned loops.
  ProjNode* PhaseIdealLoop::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
                                                        Deoptimization::DeoptReason reason,
                                                        int opcode) {
    assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
    IfNode* iff = cont_proj->in(0)->as_If();
  
    ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
    Node     *rgn   = uncommon_proj->unique_ctrl_out();
    assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
  
    uint proj_index = 1; // region's edge corresponding to uncommon_proj
    if (!rgn->is_Region()) { // create a region to guard the call
      assert(rgn->is_Call(), "must be call uct");
      CallNode* call = rgn->as_Call();
      IdealLoopTree* loop = get_loop(call);
      rgn = new RegionNode(1);
      rgn->add_req(uncommon_proj);
      register_control(rgn, loop, uncommon_proj);
      _igvn.replace_input_of(call, 0, rgn);
      // When called from beautify_loops() idom is not constructed yet.
      if (_idom != NULL) {
        set_idom(call, rgn, dom_depth(rgn));
      }
      for (DUIterator_Fast imax, i = uncommon_proj->fast_outs(imax); i < imax; i++) {
        Node* n = uncommon_proj->fast_out(i);
        if (n->is_Load() || n->is_Store()) {
          _igvn.replace_input_of(n, 0, rgn);
          --i; --imax;
        }
      }
    } else {
      // Find region's edge corresponding to uncommon_proj
      for (; proj_index < rgn->req(); proj_index++)
        if (rgn->in(proj_index) == uncommon_proj) break;
      assert(proj_index < rgn->req(), "sanity");
    }
  
    Node* entry = iff->in(0);
    if (new_entry != NULL) {
      // Clonning the predicate to new location.
      entry = new_entry;
    }
    // Create new_iff
    IdealLoopTree* lp = get_loop(entry);
    IfNode* new_iff = NULL;
    if (opcode == Op_If) {
      new_iff = new IfNode(entry, iff->in(1), iff->_prob, iff->_fcnt);
    } else {
      assert(opcode == Op_RangeCheck, "no other if variant here");
      new_iff = new RangeCheckNode(entry, iff->in(1), iff->_prob, iff->_fcnt);
    }
    register_control(new_iff, lp, entry);
    Node *if_cont = new IfTrueNode(new_iff);
    Node *if_uct  = new IfFalseNode(new_iff);
    if (cont_proj->is_IfFalse()) {
      // Swap
      Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
    }
    register_control(if_cont, lp, new_iff);
    register_control(if_uct, get_loop(rgn), new_iff);
  
    // if_uct to rgn
    _igvn.hash_delete(rgn);
    rgn->add_req(if_uct);
    // When called from beautify_loops() idom is not constructed yet.
    if (_idom != NULL) {
      Node* ridom = idom(rgn);
      Node* nrdom = dom_lca(ridom, new_iff);
      set_idom(rgn, nrdom, dom_depth(rgn));
    }
  
    // If rgn has phis add new edges which has the same
    // value as on original uncommon_proj pass.
    assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
    bool has_phi = false;
    for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
      Node* use = rgn->fast_out(i);
      if (use->is_Phi() && use->outcnt() > 0) {
        assert(use->in(0) == rgn, "");
        _igvn.rehash_node_delayed(use);
        use->add_req(use->in(proj_index));
        has_phi = true;
      }
    }
    assert(!has_phi || rgn->req() > 3, "no phis when region is created");
  
    if (new_entry == NULL) {
      // Attach if_cont to iff
      _igvn.replace_input_of(iff, 0, if_cont);
      if (_idom != NULL) {
        set_idom(iff, if_cont, dom_depth(iff));
      }
    }
    return if_cont->as_Proj();
  }
  
  //------------------------------create_new_if_for_predicate------------------------
  // Create a new if below new_entry for the predicate to be cloned (IGVN optimization)
  ProjNode* PhaseIterGVN::create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
                                                      Deoptimization::DeoptReason reason,
                                                      int opcode) {
    assert(new_entry != 0, "only used for clone predicate");
    assert(cont_proj->is_uncommon_trap_if_pattern(reason), "must be a uct if pattern!");
    IfNode* iff = cont_proj->in(0)->as_If();
  
    ProjNode *uncommon_proj = iff->proj_out(1 - cont_proj->_con);
    Node     *rgn   = uncommon_proj->unique_ctrl_out();
    assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
  
    uint proj_index = 1; // region's edge corresponding to uncommon_proj
    if (!rgn->is_Region()) { // create a region to guard the call
      assert(rgn->is_Call(), "must be call uct");
      CallNode* call = rgn->as_Call();
      rgn = new RegionNode(1);
      register_new_node_with_optimizer(rgn);
      rgn->add_req(uncommon_proj);
      replace_input_of(call, 0, rgn);
    } else {
      // Find region's edge corresponding to uncommon_proj
      for (; proj_index < rgn->req(); proj_index++)
        if (rgn->in(proj_index) == uncommon_proj) break;
      assert(proj_index < rgn->req(), "sanity");
    }
  
    // Create new_iff in new location.
    IfNode* new_iff = NULL;
    if (opcode == Op_If) {
      new_iff = new IfNode(new_entry, iff->in(1), iff->_prob, iff->_fcnt);
    } else {
      assert(opcode == Op_RangeCheck, "no other if variant here");
      new_iff = new RangeCheckNode(new_entry, iff->in(1), iff->_prob, iff->_fcnt);
    }
  
    register_new_node_with_optimizer(new_iff);
    Node *if_cont = new IfTrueNode(new_iff);
    Node *if_uct  = new IfFalseNode(new_iff);
    if (cont_proj->is_IfFalse()) {
      // Swap
      Node* tmp = if_uct; if_uct = if_cont; if_cont = tmp;
    }
    register_new_node_with_optimizer(if_cont);
    register_new_node_with_optimizer(if_uct);
  
    // if_uct to rgn
    hash_delete(rgn);
    rgn->add_req(if_uct);
  
    // If rgn has phis add corresponding new edges which has the same
    // value as on original uncommon_proj pass.
    assert(rgn->in(rgn->req() -1) == if_uct, "new edge should be last");
    bool has_phi = false;
    for (DUIterator_Fast imax, i = rgn->fast_outs(imax); i < imax; i++) {
      Node* use = rgn->fast_out(i);
      if (use->is_Phi() && use->outcnt() > 0) {
        rehash_node_delayed(use);
        use->add_req(use->in(proj_index));
        has_phi = true;
      }
    }
    assert(!has_phi || rgn->req() > 3, "no phis when region is created");
  
    return if_cont->as_Proj();
  }
  
  //--------------------------clone_predicate-----------------------
  ProjNode* PhaseIdealLoop::clone_predicate(ProjNode* predicate_proj, Node* new_entry,
                                            Deoptimization::DeoptReason reason,
                                            PhaseIdealLoop* loop_phase,
                                            PhaseIterGVN* igvn) {
    ProjNode* new_predicate_proj;
    if (loop_phase != NULL) {
      new_predicate_proj = loop_phase->create_new_if_for_predicate(predicate_proj, new_entry, reason, Op_If);
    } else {
      new_predicate_proj =       igvn->create_new_if_for_predicate(predicate_proj, new_entry, reason, Op_If);
    }
    IfNode* iff = new_predicate_proj->in(0)->as_If();
    Node* ctrl  = iff->in(0);
  
    // Match original condition since predicate's projections could be swapped.
    assert(predicate_proj->in(0)->in(1)->in(1)->Opcode()==Op_Opaque1, "must be");
    Node* opq = new Opaque1Node(igvn->C, predicate_proj->in(0)->in(1)->in(1)->in(1));
    igvn->C->add_predicate_opaq(opq);
  
    Node* bol = new Conv2BNode(opq);
    if (loop_phase != NULL) {
      loop_phase->register_new_node(opq, ctrl);
      loop_phase->register_new_node(bol, ctrl);
    } else {
      igvn->register_new_node_with_optimizer(opq);
      igvn->register_new_node_with_optimizer(bol);
    }
    igvn->hash_delete(iff);
    iff->set_req(1, bol);
    return new_predicate_proj;
  }
  
  
  //--------------------------clone_loop_predicates-----------------------
  // Interface from IGVN
  Node* PhaseIterGVN::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
    return PhaseIdealLoop::clone_loop_predicates(old_entry, new_entry, clone_limit_check, NULL, this);
  }
  
  // Interface from PhaseIdealLoop
  Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check) {
    return clone_loop_predicates(old_entry, new_entry, clone_limit_check, this, &this->_igvn);
  }
  
  // Clone loop predicates to cloned loops (peeled, unswitched, split_if).
  Node* PhaseIdealLoop::clone_loop_predicates(Node* old_entry, Node* new_entry,
                                                  bool clone_limit_check,
                                                  PhaseIdealLoop* loop_phase,
                                                  PhaseIterGVN* igvn) {
  #ifdef ASSERT
    if (new_entry == NULL || !(new_entry->is_Proj() || new_entry->is_Region() || new_entry->is_SafePoint())) {
      if (new_entry != NULL)
        new_entry->dump();
      assert(false, "not IfTrue, IfFalse, Region or SafePoint");
    }
  #endif
    // Search original predicates
    Node* entry = old_entry;
    ProjNode* limit_check_proj = NULL;
    limit_check_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
    if (limit_check_proj != NULL) {
      entry = entry->in(0)->in(0);
    }
    ProjNode* profile_predicate_proj = NULL;
    ProjNode* predicate_proj = NULL;
    if (UseProfiledLoopPredicate) {
      profile_predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
      if (profile_predicate_proj != NULL) {
        entry = skip_loop_predicates(entry);
      }
    }
    if (UseLoopPredicate) {
      predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
    }
    if (predicate_proj != NULL) { // right pattern that can be used by loop predication
      // clone predicate
      new_entry = clone_predicate(predicate_proj, new_entry,
                                  Deoptimization::Reason_predicate,
                                  loop_phase, igvn);
      assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
      if (TraceLoopPredicate) {
        tty->print("Loop Predicate cloned: ");
        debug_only( new_entry->in(0)->dump(); );
      }
    }
    if (profile_predicate_proj != NULL) { // right pattern that can be used by loop predication
      // clone predicate
      new_entry = clone_predicate(profile_predicate_proj, new_entry,
                                  Deoptimization::Reason_profile_predicate,
                                  loop_phase, igvn);
      assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone predicate");
      if (TraceLoopPredicate) {
        tty->print("Loop Predicate cloned: ");
        debug_only( new_entry->in(0)->dump(); );
      }
    }
    if (limit_check_proj != NULL && clone_limit_check) {
      // Clone loop limit check last to insert it before loop.
      // Don't clone a limit check which was already finalized
      // for this counted loop (only one limit check is needed).
      new_entry = clone_predicate(limit_check_proj, new_entry,
                                  Deoptimization::Reason_loop_limit_check,
                                  loop_phase, igvn);
      assert(new_entry != NULL && new_entry->is_Proj(), "IfTrue or IfFalse after clone limit check");
      if (TraceLoopLimitCheck) {
        tty->print("Loop Limit Check cloned: ");
        debug_only( new_entry->in(0)->dump(); )
      }
    }
    return new_entry;
  }
  
  //--------------------------skip_loop_predicates------------------------------
  // Skip related predicates.
  Node* PhaseIdealLoop::skip_loop_predicates(Node* entry) {
    IfNode* iff = entry->in(0)->as_If();
    ProjNode* uncommon_proj = iff->proj_out(1 - entry->as_Proj()->_con);
    Node* rgn = uncommon_proj->unique_ctrl_out();
    assert(rgn->is_Region() || rgn->is_Call(), "must be a region or call uct");
    entry = entry->in(0)->in(0);
    while (entry != NULL && entry->is_Proj() && entry->in(0)->is_If()) {
      uncommon_proj = entry->in(0)->as_If()->proj_out(1 - entry->as_Proj()->_con);
      if (uncommon_proj->unique_ctrl_out() != rgn)
        break;
      entry = entry->in(0)->in(0);
    }
    return entry;
  }
  
  Node* PhaseIdealLoop::skip_all_loop_predicates(Node* entry) {
    Node* predicate = NULL;
    predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
    if (predicate != NULL) {
      entry = entry->in(0)->in(0);
    }
    if (UseProfiledLoopPredicate) {
      predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
      if (predicate != NULL) { // right pattern that can be used by loop predication
        entry = skip_loop_predicates(entry);
      }
    }
    if (UseLoopPredicate) {
      predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
      if (predicate != NULL) { // right pattern that can be used by loop predication
        entry = skip_loop_predicates(entry);
      }
    }
    return entry;
  }
  
  //--------------------------find_predicate_insertion_point-------------------
  // Find a good location to insert a predicate
  ProjNode* PhaseIdealLoop::find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason) {
    if (start_c == NULL || !start_c->is_Proj())
      return NULL;
    if (start_c->as_Proj()->is_uncommon_trap_if_pattern(reason)) {
      return start_c->as_Proj();
    }
    return NULL;
  }
  
  //--------------------------find_predicate------------------------------------
  // Find a predicate
  Node* PhaseIdealLoop::find_predicate(Node* entry) {
    Node* predicate = NULL;
    predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
    if (predicate != NULL) { // right pattern that can be used by loop predication
      return entry;
    }
    if (UseLoopPredicate) {
      predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
      if (predicate != NULL) { // right pattern that can be used by loop predication
        return entry;
      }
    }
    if (UseProfiledLoopPredicate) {
      predicate = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
      if (predicate != NULL) { // right pattern that can be used by loop predication
        return entry;
      }
    }
    return NULL;
  }
  
  //------------------------------Invariance-----------------------------------
  // Helper class for loop_predication_impl to compute invariance on the fly and
  // clone invariants.
  class Invariance : public StackObj {
    VectorSet _visited, _invariant;
    Node_Stack _stack;
    VectorSet _clone_visited;
    Node_List _old_new; // map of old to new (clone)
    IdealLoopTree* _lpt;
    PhaseIdealLoop* _phase;
  
    // Helper function to set up the invariance for invariance computation
    // If n is a known invariant, set up directly. Otherwise, look up the
    // the possibility to push n onto the stack for further processing.
    void visit(Node* use, Node* n) {
      if (_lpt->is_invariant(n)) { // known invariant
        _invariant.set(n->_idx);
      } else if (!n->is_CFG()) {
        Node *n_ctrl = _phase->ctrl_or_self(n);
        Node *u_ctrl = _phase->ctrl_or_self(use); // self if use is a CFG
        if (_phase->is_dominator(n_ctrl, u_ctrl)) {
          _stack.push(n, n->in(0) == NULL ? 1 : 0);
        }
      }
    }
  
    // Compute invariance for "the_node" and (possibly) all its inputs recursively
    // on the fly
    void compute_invariance(Node* n) {
      assert(_visited.test(n->_idx), "must be");
      visit(n, n);
      while (_stack.is_nonempty()) {
        Node*  n = _stack.node();
        uint idx = _stack.index();
        if (idx == n->req()) { // all inputs are processed
          _stack.pop();
          // n is invariant if it's inputs are all invariant
          bool all_inputs_invariant = true;
          for (uint i = 0; i < n->req(); i++) {
            Node* in = n->in(i);
            if (in == NULL) continue;
            assert(_visited.test(in->_idx), "must have visited input");
            if (!_invariant.test(in->_idx)) { // bad guy
              all_inputs_invariant = false;
              break;
            }
          }
          if (all_inputs_invariant) {
            // If n's control is a predicate that was moved out of the
            // loop, it was marked invariant but n is only invariant if
            // it depends only on that test. Otherwise, unless that test
            // is out of the loop, it's not invariant.
            if (n->is_CFG() || n->depends_only_on_test() || n->in(0) == NULL || !_phase->is_member(_lpt, n->in(0))) {
              _invariant.set(n->_idx); // I am a invariant too
            }
          }
        } else { // process next input
          _stack.set_index(idx + 1);
          Node* m = n->in(idx);
          if (m != NULL && !_visited.test_set(m->_idx)) {
            visit(n, m);
          }
        }
      }
    }
  
    // Helper function to set up _old_new map for clone_nodes.
    // If n is a known invariant, set up directly ("clone" of n == n).
    // Otherwise, push n onto the stack for real cloning.
    void clone_visit(Node* n) {
      assert(_invariant.test(n->_idx), "must be invariant");
      if (_lpt->is_invariant(n)) { // known invariant
        _old_new.map(n->_idx, n);
      } else { // to be cloned
        assert(!n->is_CFG(), "should not see CFG here");
        _stack.push(n, n->in(0) == NULL ? 1 : 0);
      }
    }
  
    // Clone "n" and (possibly) all its inputs recursively
    void clone_nodes(Node* n, Node* ctrl) {
      clone_visit(n);
      while (_stack.is_nonempty()) {
        Node*  n = _stack.node();
        uint idx = _stack.index();
        if (idx == n->req()) { // all inputs processed, clone n!
          _stack.pop();
          // clone invariant node
          Node* n_cl = n->clone();
          _old_new.map(n->_idx, n_cl);
          _phase->register_new_node(n_cl, ctrl);
          for (uint i = 0; i < n->req(); i++) {
            Node* in = n_cl->in(i);
            if (in == NULL) continue;
            n_cl->set_req(i, _old_new[in->_idx]);
          }
        } else { // process next input
          _stack.set_index(idx + 1);
          Node* m = n->in(idx);
          if (m != NULL && !_clone_visited.test_set(m->_idx)) {
            clone_visit(m); // visit the input
          }
        }
      }
    }
  
   public:
    Invariance(Arena* area, IdealLoopTree* lpt) :
      _lpt(lpt), _phase(lpt->_phase),
      _visited(area), _invariant(area), _stack(area, 10 /* guess */),
      _clone_visited(area), _old_new(area)
    {
      LoopNode* head = _lpt->_head->as_Loop();
      Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
      if (entry->outcnt() != 1) {
        // If a node is pinned between the predicates and the loop
        // entry, we won't be able to move any node in the loop that
        // depends on it above it in a predicate. Mark all those nodes
        // as non loop invariatnt.
        Unique_Node_List wq;
        wq.push(entry);
        for (uint next = 0; next < wq.size(); ++next) {
          Node *n = wq.at(next);
          for (DUIterator_Fast imax, i = n->fast_outs(imax); i < imax; i++) {
            Node* u = n->fast_out(i);
            if (!u->is_CFG()) {
              Node* c = _phase->get_ctrl(u);
              if (_lpt->is_member(_phase->get_loop(c)) || _phase->is_dominator(c, head)) {
                _visited.set(u->_idx);
                wq.push(u);
              }
            }
          }
        }
      }
    }
  
    // Map old to n for invariance computation and clone
    void map_ctrl(Node* old, Node* n) {
      assert(old->is_CFG() && n->is_CFG(), "must be");
      _old_new.map(old->_idx, n); // "clone" of old is n
      _invariant.set(old->_idx);  // old is invariant
      _clone_visited.set(old->_idx);
    }
  
    // Driver function to compute invariance
    bool is_invariant(Node* n) {
      if (!_visited.test_set(n->_idx))
        compute_invariance(n);
      return (_invariant.test(n->_idx) != 0);
    }
  
    // Driver function to clone invariant
    Node* clone(Node* n, Node* ctrl) {
      assert(ctrl->is_CFG(), "must be");
      assert(_invariant.test(n->_idx), "must be an invariant");
      if (!_clone_visited.test(n->_idx))
        clone_nodes(n, ctrl);
      return _old_new[n->_idx];
    }
  };
  
  //------------------------------is_range_check_if -----------------------------------
  // Returns true if the predicate of iff is in "scale*iv + offset u< load_range(ptr)" format
  // Note: this function is particularly designed for loop predication. We require load_range
  //       and offset to be loop invariant computed on the fly by "invar"
  bool IdealLoopTree::is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const {
    if (!is_loop_exit(iff)) {
      return false;
    }
    if (!iff->in(1)->is_Bool()) {
      return false;
    }
    const BoolNode *bol = iff->in(1)->as_Bool();
    if (bol->_test._test != BoolTest::lt) {
      return false;
    }
    if (!bol->in(1)->is_Cmp()) {
      return false;
    }
    const CmpNode *cmp = bol->in(1)->as_Cmp();
    if (cmp->Opcode() != Op_CmpU) {
      return false;
    }
    Node* range = cmp->in(2);
    if (range->Opcode() != Op_LoadRange && !iff->is_RangeCheck()) {
      const TypeInt* tint = phase->_igvn.type(range)->isa_int();
      if (tint == NULL || tint->empty() || tint->_lo < 0) {
        // Allow predication on positive values that aren't LoadRanges.
        // This allows optimization of loops where the length of the
        // array is a known value and doesn't need to be loaded back
        // from the array.
        return false;
      }
    }
    if (!invar.is_invariant(range)) {
      return false;
    }
    Node *iv     = _head->as_CountedLoop()->phi();
    int   scale  = 0;
    Node *offset = NULL;
    if (!phase->is_scaled_iv_plus_offset(cmp->in(1), iv, &scale, &offset)) {
      return false;
    }
    if (offset && !invar.is_invariant(offset)) { // offset must be invariant
      return false;
    }
    return true;
  }
  
  //------------------------------rc_predicate-----------------------------------
  // Create a range check predicate
  //
  // for (i = init; i < limit; i += stride) {
  //    a[scale*i+offset]
  // }
  //
  // Compute max(scale*i + offset) for init <= i < limit and build the predicate
  // as "max(scale*i + offset) u< a.length".
  //
  // There are two cases for max(scale*i + offset):
  // (1) stride*scale > 0
  //   max(scale*i + offset) = scale*(limit-stride) + offset
  // (2) stride*scale < 0
  //   max(scale*i + offset) = scale*init + offset
  BoolNode* PhaseIdealLoop::rc_predicate(IdealLoopTree *loop, Node* ctrl,
                                         int scale, Node* offset,
                                         Node* init, Node* limit, jint stride,
                                         Node* range, bool upper, bool &overflow) {
    jint con_limit  = (limit != NULL && limit->is_Con())  ? limit->get_int()  : 0;
    jint con_init   = init->is_Con()   ? init->get_int()   : 0;
    jint con_offset = offset->is_Con() ? offset->get_int() : 0;
  
    stringStream* predString = NULL;
    if (TraceLoopPredicate) {
      predString = new stringStream();
      predString->print("rc_predicate ");
    }
  
    overflow = false;
    Node* max_idx_expr = NULL;
    const TypeInt* idx_type = TypeInt::INT;
    if ((stride > 0) == (scale > 0) == upper) {
      guarantee(limit != NULL, "sanity");
      if (TraceLoopPredicate) {
        if (limit->is_Con()) {
          predString->print("(%d ", con_limit);
        } else {
          predString->print("(limit ");
        }
        predString->print("- %d) ", stride);
      }
      // Check if (limit - stride) may overflow
      const TypeInt* limit_type = _igvn.type(limit)->isa_int();
      jint limit_lo = limit_type->_lo;
      jint limit_hi = limit_type->_hi;
      if ((stride > 0 && (java_subtract(limit_lo, stride) < limit_lo)) ||
          (stride < 0 && (java_subtract(limit_hi, stride) > limit_hi))) {
        // No overflow possible
        ConINode* con_stride = _igvn.intcon(stride);
        set_ctrl(con_stride, C->root());
        max_idx_expr = new SubINode(limit, con_stride);
        idx_type = TypeInt::make(limit_lo - stride, limit_hi - stride, limit_type->_widen);
      } else {
        // May overflow
        overflow = true;
        limit = new ConvI2LNode(limit);
        register_new_node(limit, ctrl);
        ConLNode* con_stride = _igvn.longcon(stride);
        set_ctrl(con_stride, C->root());
        max_idx_expr = new SubLNode(limit, con_stride);
      }
      register_new_node(max_idx_expr, ctrl);
    } else {
      if (TraceLoopPredicate) {
        if (init->is_Con()) {
          predString->print("%d ", con_init);
        } else {
          predString->print("init ");
        }
      }
      idx_type = _igvn.type(init)->isa_int();
      max_idx_expr = init;
    }
  
    if (scale != 1) {
      ConNode* con_scale = _igvn.intcon(scale);
      set_ctrl(con_scale, C->root());
      if (TraceLoopPredicate) {
        predString->print("* %d ", scale);
      }
      // Check if (scale * max_idx_expr) may overflow
      const TypeInt* scale_type = TypeInt::make(scale);
      MulINode* mul = new MulINode(max_idx_expr, con_scale);
      idx_type = (TypeInt*)mul->mul_ring(idx_type, scale_type);
      if (overflow || TypeInt::INT->higher_equal(idx_type)) {
        // May overflow
        mul->destruct();
        if (!overflow) {
          max_idx_expr = new ConvI2LNode(max_idx_expr);
          register_new_node(max_idx_expr, ctrl);
        }
        overflow = true;
        con_scale = _igvn.longcon(scale);
        set_ctrl(con_scale, C->root());
        max_idx_expr = new MulLNode(max_idx_expr, con_scale);
      } else {
        // No overflow possible
        max_idx_expr = mul;
      }
      register_new_node(max_idx_expr, ctrl);
    }
  
    if (offset && (!offset->is_Con() || con_offset != 0)){
      if (TraceLoopPredicate) {
        if (offset->is_Con()) {
          predString->print("+ %d ", con_offset);
        } else {
          predString->print("+ offset");
        }
      }
      // Check if (max_idx_expr + offset) may overflow
      const TypeInt* offset_type = _igvn.type(offset)->isa_int();
      jint lo = java_add(idx_type->_lo, offset_type->_lo);
      jint hi = java_add(idx_type->_hi, offset_type->_hi);
      if (overflow || (lo > hi) ||
          ((idx_type->_lo & offset_type->_lo) < 0 && lo >= 0) ||
          ((~(idx_type->_hi | offset_type->_hi)) < 0 && hi < 0)) {
        // May overflow
        if (!overflow) {
          max_idx_expr = new ConvI2LNode(max_idx_expr);
          register_new_node(max_idx_expr, ctrl);
        }
        overflow = true;
        offset = new ConvI2LNode(offset);
        register_new_node(offset, ctrl);
        max_idx_expr = new AddLNode(max_idx_expr, offset);
      } else {
        // No overflow possible
        max_idx_expr = new AddINode(max_idx_expr, offset);
      }
      register_new_node(max_idx_expr, ctrl);
    }
  
    CmpNode* cmp = NULL;
    if (overflow) {
      // Integer expressions may overflow, do long comparison
      range = new ConvI2LNode(range);
      register_new_node(range, ctrl);
      cmp = new CmpULNode(max_idx_expr, range);
    } else {
      cmp = new CmpUNode(max_idx_expr, range);
    }
    register_new_node(cmp, ctrl);
    BoolNode* bol = new BoolNode(cmp, BoolTest::lt);
    register_new_node(bol, ctrl);
  
    if (TraceLoopPredicate) {
      predString->print_cr("<u range");
      tty->print("%s", predString->as_string());
    }
    return bol;
  }
  
  // Should loop predication look not only in the path from tail to head
  // but also in branches of the loop body?
  bool PhaseIdealLoop::loop_predication_should_follow_branches(IdealLoopTree *loop, ProjNode *predicate_proj, float& loop_trip_cnt) {
    if (!UseProfiledLoopPredicate) {
      return false;
    }
  
    if (predicate_proj == NULL) {
      return false;
    }
  
    LoopNode* head = loop->_head->as_Loop();
    bool follow_branches = true;
    IdealLoopTree* l = loop->_child;
    // For leaf loops and loops with a single inner loop
    while (l != NULL && follow_branches) {
      IdealLoopTree* child = l;
      if (child->_child != NULL &&
          child->_head->is_OuterStripMinedLoop()) {
        assert(child->_child->_next == NULL, "only one inner loop for strip mined loop");
        assert(child->_child->_head->is_CountedLoop() && child->_child->_head->as_CountedLoop()->is_strip_mined(), "inner loop should be strip mined");
        child = child->_child;
      }
      if (child->_child != NULL || child->_irreducible) {
        follow_branches = false;
      }
      l = l->_next;
    }
    if (follow_branches) {
      loop->compute_profile_trip_cnt(this);
      if (head->is_profile_trip_failed()) {
        follow_branches = false;
      } else {
        loop_trip_cnt = head->profile_trip_cnt();
        if (head->is_CountedLoop()) {
          CountedLoopNode* cl = head->as_CountedLoop();
          if (cl->phi() != NULL) {
            const TypeInt* t = _igvn.type(cl->phi())->is_int();
            float worst_case_trip_cnt = ((float)t->_hi - t->_lo) / ABS(cl->stride_con());
            if (worst_case_trip_cnt < loop_trip_cnt) {
              loop_trip_cnt = worst_case_trip_cnt;
            }
          }
        }
      }
    }
    return follow_branches;
  }
  
  // Compute probability of reaching some CFG node from a fixed
  // dominating CFG node
  class PathFrequency {
  private:
    Node* _dom; // frequencies are computed relative to this node
    Node_Stack _stack;
    GrowableArray<float> _freqs_stack; // keep track of intermediate result at regions
    GrowableArray<float> _freqs; // cache frequencies
    PhaseIdealLoop* _phase;
  
  public:
    PathFrequency(Node* dom, PhaseIdealLoop* phase)
      : _dom(dom), _stack(0), _phase(phase) {
    }
  
    float to(Node* n) {
      // post order walk on the CFG graph from n to _dom
      fesetround(FE_TOWARDZERO); // make sure rounding doesn't push frequency above 1
      IdealLoopTree* loop = _phase->get_loop(_dom);
      Node* c = n;
      for (;;) {
        assert(_phase->get_loop(c) == loop, "have to be in the same loop");
        if (c == _dom || _freqs.at_grow(c->_idx, -1) >= 0) {
          float f = c == _dom ? 1 : _freqs.at(c->_idx);
          Node* prev = c;
          while (_stack.size() > 0 && prev == c) {
            Node* n = _stack.node();
            if (!n->is_Region()) {
              if (_phase->get_loop(n) != _phase->get_loop(n->in(0))) {
                // Found an inner loop: compute frequency of reaching this
                // exit from the loop head by looking at the number of
                // times each loop exit was taken
                IdealLoopTree* inner_loop = _phase->get_loop(n->in(0));
                LoopNode* inner_head = inner_loop->_head->as_Loop();
                assert(_phase->get_loop(n) == loop, "only 1 inner loop");
                if (inner_head->is_OuterStripMinedLoop()) {
                  inner_head->verify_strip_mined(1);
                  if (n->in(0) == inner_head->in(LoopNode::LoopBackControl)->in(0)) {
                    n = n->in(0)->in(0)->in(0);
                  }
                  inner_loop = inner_loop->_child;
                  inner_head = inner_loop->_head->as_Loop();
                  inner_head->verify_strip_mined(1);
                }
                fesetround(FE_UPWARD);  // make sure rounding doesn't push frequency above 1
                float loop_exit_cnt = 0.0f;
                for (uint i = 0; i < inner_loop->_body.size(); i++) {
                  Node *n = inner_loop->_body[i];
                  float c = inner_loop->compute_profile_trip_cnt_helper(n);
                  loop_exit_cnt += c;
                }
                fesetround(FE_TOWARDZERO);
                float cnt = -1;
                if (n->in(0)->is_If()) {
                  IfNode* iff = n->in(0)->as_If();
                  float p = n->in(0)->as_If()->_prob;
                  if (n->Opcode() == Op_IfFalse) {
                    p = 1 - p;
                  }
                  if (p > PROB_MIN) {
                    cnt = p * iff->_fcnt;
                  } else {
                    cnt = 0;
                  }
                } else {
                  assert(n->in(0)->is_Jump(), "unsupported node kind");
                  JumpNode* jmp = n->in(0)->as_Jump();
                  float p = n->in(0)->as_Jump()->_probs[n->as_JumpProj()->_con];
                  cnt = p * jmp->_fcnt;
                }
                float this_exit_f = cnt > 0 ? cnt / loop_exit_cnt : 0;
                assert(this_exit_f <= 1 && this_exit_f >= 0, "Incorrect frequency");
                f = f * this_exit_f;
                assert(f <= 1 && f >= 0, "Incorrect frequency");
              } else {
                float p = -1;
                if (n->in(0)->is_If()) {
                  p = n->in(0)->as_If()->_prob;
                  if (n->Opcode() == Op_IfFalse) {
                    p = 1 - p;
                  }
                } else {
                  assert(n->in(0)->is_Jump(), "unsupported node kind");
                  p = n->in(0)->as_Jump()->_probs[n->as_JumpProj()->_con];
                }
                f = f * p;
                assert(f <= 1 && f >= 0, "Incorrect frequency");
              }
              _freqs.at_put_grow(n->_idx, (float)f, -1);
              _stack.pop();
            } else {
              float prev_f = _freqs_stack.pop();
              float new_f = f;
              f = new_f + prev_f;
              assert(f <= 1 && f >= 0, "Incorrect frequency");
              uint i = _stack.index();
              if (i < n->req()) {
                c = n->in(i);
                _stack.set_index(i+1);
                _freqs_stack.push(f);
              } else {
                _freqs.at_put_grow(n->_idx, f, -1);
                _stack.pop();
              }
            }
          }
          if (_stack.size() == 0) {
            fesetround(FE_TONEAREST);
            assert(f >= 0 && f <= 1, "should have been computed");
            return f;
          }
        } else if (c->is_Loop()) {
          ShouldNotReachHere();
          c = c->in(LoopNode::EntryControl);
        } else if (c->is_Region()) {
          _freqs_stack.push(0);
          _stack.push(c, 2);
          c = c->in(1);
        } else {
          if (c->is_IfProj()) {
            IfNode* iff = c->in(0)->as_If();
            if (iff->_prob == PROB_UNKNOWN) {
              // assume never taken
              _freqs.at_put_grow(c->_idx, 0, -1);
            } else if (_phase->get_loop(c) != _phase->get_loop(iff)) {
              if (iff->_fcnt == COUNT_UNKNOWN) {
                // assume never taken
                _freqs.at_put_grow(c->_idx, 0, -1);
              } else {
                // skip over loop
                _stack.push(c, 1);
                c = _phase->get_loop(c->in(0))->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl);
              }
            } else {
              _stack.push(c, 1);
              c = iff;
            }
          } else if (c->is_JumpProj()) {
            JumpNode* jmp = c->in(0)->as_Jump();
            if (_phase->get_loop(c) != _phase->get_loop(jmp)) {
              if (jmp->_fcnt == COUNT_UNKNOWN) {
                // assume never taken
                _freqs.at_put_grow(c->_idx, 0, -1);
              } else {
                // skip over loop
                _stack.push(c, 1);
                c = _phase->get_loop(c->in(0))->_head->as_Loop()->skip_strip_mined()->in(LoopNode::EntryControl);
              }
            } else {
              _stack.push(c, 1);
              c = jmp;
            }
          } else if (c->Opcode() == Op_CatchProj &&
                     c->in(0)->Opcode() == Op_Catch &&
                     c->in(0)->in(0)->is_Proj() &&
                     c->in(0)->in(0)->in(0)->is_Call()) {
            // assume exceptions are never thrown
            uint con = c->as_Proj()->_con;
            if (con == CatchProjNode::fall_through_index) {
              Node* call = c->in(0)->in(0)->in(0)->in(0);
              if (_phase->get_loop(call) != _phase->get_loop(c)) {
                _freqs.at_put_grow(c->_idx, 0, -1);
              } else {
                c = call;
              }
            } else {
              assert(con >= CatchProjNode::catch_all_index, "what else?");
              _freqs.at_put_grow(c->_idx, 0, -1);
            }
          } else if (c->unique_ctrl_out() == NULL && !c->is_If() && !c->is_Jump()) {
            ShouldNotReachHere();
          } else {
            c = c->in(0);
          }
        }
      }
      ShouldNotReachHere();
      return -1;
    }
  };
  
  void PhaseIdealLoop::loop_predication_follow_branches(Node *n, IdealLoopTree *loop, float loop_trip_cnt,
                                                        PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
                                                        Node_List& if_proj_list) {
    assert(n->is_Region(), "start from a region");
    Node* tail = loop->tail();
    stack.push(n, 1);
    do {
      Node* c = stack.node();
      assert(c->is_Region() || c->is_IfProj(), "only region here");
      uint i = stack.index();
  
      if (i < c->req()) {
        stack.set_index(i+1);
        Node* in = c->in(i);
        while (!is_dominator(in, tail) && !seen.test_set(in->_idx)) {
          IdealLoopTree* in_loop = get_loop(in);
          if (in_loop != loop) {
            in = in_loop->_head->in(LoopNode::EntryControl);
          } else if (in->is_Region()) {
            stack.push(in, 1);
            break;
          } else if (in->is_IfProj() &&
                     in->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
                     (in->in(0)->Opcode() == Op_If ||
                      in->in(0)->Opcode() == Op_RangeCheck)) {
            if (pf.to(in) * loop_trip_cnt >= 1) {
              stack.push(in, 1);
            }
            in = in->in(0);
          } else {
            in = in->in(0);
          }
        }
      } else {
        if (c->is_IfProj()) {
          if_proj_list.push(c);
        }
        stack.pop();
      }
  
    } while (stack.size() > 0);
  }
  
  
  bool PhaseIdealLoop::loop_predication_impl_helper(IdealLoopTree *loop, ProjNode* proj, ProjNode *predicate_proj,
                                                    CountedLoopNode *cl, ConNode* zero, Invariance& invar,
                                                    Deoptimization::DeoptReason reason) {
    // Following are changed to nonnull when a predicate can be hoisted
    ProjNode* new_predicate_proj = NULL;
    IfNode*   iff  = proj->in(0)->as_If();
    Node*     test = iff->in(1);
    if (!test->is_Bool()){ //Conv2B, ...
      return false;
    }
    BoolNode* bol = test->as_Bool();
    if (invar.is_invariant(bol)) {
      // Invariant test
      new_predicate_proj = create_new_if_for_predicate(predicate_proj, NULL,
                                                       reason,
                                                       iff->Opcode());
      Node* ctrl = new_predicate_proj->in(0)->as_If()->in(0);
      BoolNode* new_predicate_bol = invar.clone(bol, ctrl)->as_Bool();
  
      // Negate test if necessary
      bool negated = false;
      if (proj->_con != predicate_proj->_con) {
        new_predicate_bol = new BoolNode(new_predicate_bol->in(1), new_predicate_bol->_test.negate());
        register_new_node(new_predicate_bol, ctrl);
        negated = true;
      }
      IfNode* new_predicate_iff = new_predicate_proj->in(0)->as_If();
      _igvn.hash_delete(new_predicate_iff);
      new_predicate_iff->set_req(1, new_predicate_bol);
  #ifndef PRODUCT
      if (TraceLoopPredicate) {
        tty->print("Predicate invariant if%s: %d ", negated ? " negated" : "", new_predicate_iff->_idx);
        loop->dump_head();
      } else if (TraceLoopOpts) {
        tty->print("Predicate IC ");
        loop->dump_head();
      }
  #endif
    } else if (cl != NULL && loop->is_range_check_if(iff, this, invar)) {
      // Range check for counted loops
      const Node*    cmp    = bol->in(1)->as_Cmp();
      Node*          idx    = cmp->in(1);
      assert(!invar.is_invariant(idx), "index is variant");
      Node* rng = cmp->in(2);
      assert(rng->Opcode() == Op_LoadRange || iff->is_RangeCheck() || _igvn.type(rng)->is_int()->_lo >= 0, "must be");
      assert(invar.is_invariant(rng), "range must be invariant");
      int scale    = 1;
      Node* offset = zero;
      bool ok = is_scaled_iv_plus_offset(idx, cl->phi(), &scale, &offset);
      assert(ok, "must be index expression");
  
      Node* init    = cl->init_trip();
      // Limit is not exact.
      // Calculate exact limit here.
      // Note, counted loop's test is '<' or '>'.
      Node* limit   = exact_limit(loop);
      int  stride   = cl->stride()->get_int();
  
      // Build if's for the upper and lower bound tests.  The
      // lower_bound test will dominate the upper bound test and all
      // cloned or created nodes will use the lower bound test as
      // their declared control.
  
      // Perform cloning to keep Invariance state correct since the
      // late schedule will place invariant things in the loop.
      Node *ctrl = predicate_proj->in(0)->as_If()->in(0);
      rng = invar.clone(rng, ctrl);
      if (offset && offset != zero) {
        assert(invar.is_invariant(offset), "offset must be loop invariant");
        offset = invar.clone(offset, ctrl);
      }
      // If predicate expressions may overflow in the integer range, longs are used.
      bool overflow = false;
  
      // Test the lower bound
      BoolNode* lower_bound_bol = rc_predicate(loop, ctrl, scale, offset, init, limit, stride, rng, false, overflow);
      // Negate test if necessary
      bool negated = false;
      if (proj->_con != predicate_proj->_con) {
        lower_bound_bol = new BoolNode(lower_bound_bol->in(1), lower_bound_bol->_test.negate());
        register_new_node(lower_bound_bol, ctrl);
        negated = true;
      }
      ProjNode* lower_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, reason, overflow ? Op_If : iff->Opcode());
      IfNode* lower_bound_iff = lower_bound_proj->in(0)->as_If();
      _igvn.hash_delete(lower_bound_iff);
      lower_bound_iff->set_req(1, lower_bound_bol);
      if (TraceLoopPredicate) tty->print_cr("lower bound check if: %s %d ", negated ? " negated" : "", lower_bound_iff->_idx);
  
      // Test the upper bound
      BoolNode* upper_bound_bol = rc_predicate(loop, lower_bound_proj, scale, offset, init, limit, stride, rng, true, overflow);
      negated = false;
      if (proj->_con != predicate_proj->_con) {
        upper_bound_bol = new BoolNode(upper_bound_bol->in(1), upper_bound_bol->_test.negate());
        register_new_node(upper_bound_bol, ctrl);
        negated = true;
      }
      ProjNode* upper_bound_proj = create_new_if_for_predicate(predicate_proj, NULL, reason, overflow ? Op_If : iff->Opcode());
      assert(upper_bound_proj->in(0)->as_If()->in(0) == lower_bound_proj, "should dominate");
      IfNode* upper_bound_iff = upper_bound_proj->in(0)->as_If();
      _igvn.hash_delete(upper_bound_iff);
      upper_bound_iff->set_req(1, upper_bound_bol);
      if (TraceLoopPredicate) tty->print_cr("upper bound check if: %s %d ", negated ? " negated" : "", lower_bound_iff->_idx);
  
      // Fall through into rest of the clean up code which will move
      // any dependent nodes onto the upper bound test.
      new_predicate_proj = upper_bound_proj;
  
      if (iff->is_RangeCheck()) {
        new_predicate_proj = insert_skeleton_predicate(iff, loop, proj, predicate_proj, upper_bound_proj, scale, offset, init, limit, stride, rng, overflow, reason);
      }
  
  #ifndef PRODUCT
      if (TraceLoopOpts && !TraceLoopPredicate) {
        tty->print("Predicate RC ");
        loop->dump_head();
      }
  #endif
    } else {
      // Loop variant check (for example, range check in non-counted loop)
      // with uncommon trap.
      return false;
    }
    assert(new_predicate_proj != NULL, "sanity");
    // Success - attach condition (new_predicate_bol) to predicate if
    invar.map_ctrl(proj, new_predicate_proj); // so that invariance test can be appropriate
  
    // Eliminate the old If in the loop body
    dominated_by( new_predicate_proj, iff, proj->_con != new_predicate_proj->_con );
  
    C->set_major_progress();
    return true;
  }
  
  
  // After pre/main/post loops are created, we'll put a copy of some
  // range checks between the pre and main loop to validate the value
  // of the main loop induction variable. Make a copy of the predicates
  // here with an opaque node as a place holder for the value (will be
  // updated by PhaseIdealLoop::update_skeleton_predicate()).
  ProjNode* PhaseIdealLoop::insert_skeleton_predicate(IfNode* iff, IdealLoopTree *loop,
                                                      ProjNode* proj, ProjNode *predicate_proj,
                                                      ProjNode* upper_bound_proj,
                                                      int scale, Node* offset,
                                                      Node* init, Node* limit, jint stride,
                                                      Node* rng, bool &overflow,
                                                      Deoptimization::DeoptReason reason) {
    assert(proj->_con && predicate_proj->_con, "not a range check?");
    Node* opaque_init = new Opaque1Node(C, init);
    register_new_node(opaque_init, upper_bound_proj);
    BoolNode* bol = rc_predicate(loop, upper_bound_proj, scale, offset, opaque_init, limit, stride, rng, (stride > 0) != (scale > 0), overflow);
    Node* opaque_bol = new Opaque4Node(C, bol, _igvn.intcon(1)); // This will go away once loop opts are over
    register_new_node(opaque_bol, upper_bound_proj);
    ProjNode* new_proj = create_new_if_for_predicate(predicate_proj, NULL, reason, overflow ? Op_If : iff->Opcode());
    _igvn.replace_input_of(new_proj->in(0), 1, opaque_bol);
    assert(opaque_init->outcnt() > 0, "should be used");
    return new_proj;
  }
  
  //------------------------------ loop_predication_impl--------------------------
  // Insert loop predicates for null checks and range checks
  bool PhaseIdealLoop::loop_predication_impl(IdealLoopTree *loop) {
    if (!UseLoopPredicate) return false;
  
    if (!loop->_head->is_Loop()) {
      // Could be a simple region when irreducible loops are present.
      return false;
    }
    LoopNode* head = loop->_head->as_Loop();
  
    if (head->unique_ctrl_out()->Opcode() == Op_NeverBranch) {
      // do nothing for infinite loops
      return false;
    }
  
    if (head->is_OuterStripMinedLoop()) {
      return false;
    }
  
    CountedLoopNode *cl = NULL;
    if (head->is_valid_counted_loop()) {
      cl = head->as_CountedLoop();
      // do nothing for iteration-splitted loops
      if (!cl->is_normal_loop()) return false;
      // Avoid RCE if Counted loop's test is '!='.
      BoolTest::mask bt = cl->loopexit()->test_trip();
      if (bt != BoolTest::lt && bt != BoolTest::gt)
        cl = NULL;
    }
  
    Node* entry = head->skip_strip_mined()->in(LoopNode::EntryControl);
    ProjNode *loop_limit_proj = NULL;
    ProjNode *predicate_proj = NULL;
    ProjNode *profile_predicate_proj = NULL;
    // Loop limit check predicate should be near the loop.
    loop_limit_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_loop_limit_check);
    if (loop_limit_proj != NULL) {
      entry = loop_limit_proj->in(0)->in(0);
    }
    bool has_profile_predicates = false;
    profile_predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_profile_predicate);
    if (profile_predicate_proj != NULL) {
      Node* n = skip_loop_predicates(entry);
      // Check if predicates were already added to the profile predicate
      // block
      if (n != entry->in(0)->in(0) || n->outcnt() != 1) {
        has_profile_predicates = true;
      }
      entry = n;
    }
    predicate_proj = find_predicate_insertion_point(entry, Deoptimization::Reason_predicate);
  
    float loop_trip_cnt = -1;
    bool follow_branches = loop_predication_should_follow_branches(loop, profile_predicate_proj, loop_trip_cnt);
    assert(!follow_branches || loop_trip_cnt >= 0, "negative trip count?");
  
    if (predicate_proj == NULL && !follow_branches) {
  #ifndef PRODUCT
      if (TraceLoopPredicate) {
        tty->print("missing predicate:");
        loop->dump_head();
        head->dump(1);
      }
  #endif
      return false;
    }
    ConNode* zero = _igvn.intcon(0);
    set_ctrl(zero, C->root());
  
    ResourceArea *area = Thread::current()->resource_area();
    Invariance invar(area, loop);
  
    // Create list of if-projs such that a newer proj dominates all older
    // projs in the list, and they all dominate loop->tail()
    Node_List if_proj_list(area);
    Node_List regions(area);
    Node *current_proj = loop->tail(); //start from tail
  
  
    Node_List controls(area);
    while (current_proj != head) {
      if (loop == get_loop(current_proj) && // still in the loop ?
          current_proj->is_Proj()        && // is a projection  ?
          (current_proj->in(0)->Opcode() == Op_If ||
           current_proj->in(0)->Opcode() == Op_RangeCheck)) { // is a if projection ?
        if_proj_list.push(current_proj);
      }
      if (follow_branches &&
          current_proj->Opcode() == Op_Region &&
          loop == get_loop(current_proj)) {
        regions.push(current_proj);
      }
      current_proj = idom(current_proj);
    }
  
    bool hoisted = false; // true if at least one proj is promoted
  
    if (!has_profile_predicates) {
      while (if_proj_list.size() > 0) {
        Node* n = if_proj_list.pop();
  
        ProjNode* proj = n->as_Proj();
        IfNode*   iff  = proj->in(0)->as_If();
  
        CallStaticJavaNode* call = proj->is_uncommon_trap_if_pattern(Deoptimization::Reason_none);
        if (call == NULL) {
          if (loop->is_loop_exit(iff)) {
            // stop processing the remaining projs in the list because the execution of them
            // depends on the condition of "iff" (iff->in(1)).
            break;
          } else {
            // Both arms are inside the loop. There are two cases:
            // (1) there is one backward branch. In this case, any remaining proj
            //     in the if_proj list post-dominates "iff". So, the condition of "iff"
            //     does not determine the execution the remining projs directly, and we
            //     can safely continue.
            // (2) both arms are forwarded, i.e. a diamond shape. In this case, "proj"
            //     does not dominate loop->tail(), so it can not be in the if_proj list.
            continue;
          }
        }
        Deoptimization::DeoptReason reason = Deoptimization::trap_request_reason(call->uncommon_trap_request());
        if (reason == Deoptimization::Reason_predicate) {
          break;
        }
  
        if (predicate_proj != NULL) {
          hoisted = loop_predication_impl_helper(loop, proj, predicate_proj, cl, zero, invar, Deoptimization::Reason_predicate) | hoisted;
        }
      } // end while
    }
  
    Node_List if_proj_list_freq(area);
    if (follow_branches) {
      PathFrequency pf(loop->_head, this);
  
      // Some projections were skipped by regular predicates because of
      // an early loop exit. Try them with profile data.
      while (if_proj_list.size() > 0) {
        Node* proj = if_proj_list.pop();
        float f = pf.to(proj);
        if (proj->as_Proj()->is_uncommon_trap_if_pattern(Deoptimization::Reason_none) &&
            f * loop_trip_cnt >= 1) {
          hoisted = loop_predication_impl_helper(loop, proj->as_Proj(), profile_predicate_proj, cl, zero, invar, Deoptimization::Reason_profile_predicate) | hoisted;
        }
      }
  
      // And look into all branches
      Node_Stack stack(0);
      VectorSet seen(Thread::current()->resource_area());
      while (regions.size() > 0) {
        Node* c = regions.pop();
        loop_predication_follow_branches(c, loop, loop_trip_cnt, pf, stack, seen, if_proj_list_freq);
      }
  
      for (uint i = 0; i < if_proj_list_freq.size(); i++) {
        ProjNode* proj = if_proj_list_freq.at(i)->as_Proj();
        hoisted = loop_predication_impl_helper(loop, proj, profile_predicate_proj, cl, zero, invar, Deoptimization::Reason_profile_predicate) | hoisted;
      }
    }
  
  #ifndef PRODUCT
    // report that the loop predication has been actually performed
    // for this loop
    if (TraceLoopPredicate && hoisted) {
      tty->print("Loop Predication Performed:");
      loop->dump_head();
    }
  #endif
  
    head->verify_strip_mined(1);
  
    return hoisted;
  }
  
  //------------------------------loop_predication--------------------------------
  // driver routine for loop predication optimization
  bool IdealLoopTree::loop_predication( PhaseIdealLoop *phase) {
    bool hoisted = false;
    // Recursively promote predicates
    if (_child) {
      hoisted = _child->loop_predication( phase);
    }
  
    // self
    if (!_irreducible && !tail()->is_top()) {
      hoisted |= phase->loop_predication_impl(this);
    }
  
    if (_next) { //sibling
      hoisted |= _next->loop_predication( phase);
    }
  
    return hoisted;
  }
  