jdk/src/hotspot/share/opto/loopnode.hpp

/*
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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
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#ifndef SHARE_OPTO_LOOPNODE_HPP
#define SHARE_OPTO_LOOPNODE_HPP

#include "opto/cfgnode.hpp"
#include "opto/multnode.hpp"
#include "opto/phaseX.hpp"
#include "opto/predicates.hpp"
#include "opto/subnode.hpp"
#include "opto/type.hpp"
#include "utilities/checkedCast.hpp"

class CmpNode;
class BaseCountedLoopEndNode;
class CountedLoopNode;
class IdealLoopTree;
class LoopNode;
class Node;
class OuterStripMinedLoopEndNode;
class PredicateBlock;
class PathFrequency;
class PhaseIdealLoop;
class UnswitchedLoopSelector;
class VectorSet;
class VSharedData;
class Invariance;
struct small_cache;

//
//                  I D E A L I Z E D   L O O P S
//
// Idealized loops are the set of loops I perform more interesting
// transformations on, beyond simple hoisting.

//------------------------------LoopNode---------------------------------------
// Simple loop header.  Fall in path on left, loop-back path on right.
class LoopNode : public RegionNode {
  // Size is bigger to hold the flags.  However, the flags do not change
  // the semantics so it does not appear in the hash & cmp functions.
  virtual uint size_of() const { return sizeof(*this); }
protected:
  uint _loop_flags;
  // Names for flag bitfields
  enum { Normal=0, Pre=1, Main=2, Post=3, PreMainPostFlagsMask=3,
         MainHasNoPreLoop      = 1<<2,
         HasExactTripCount     = 1<<3,
         InnerLoop             = 1<<4,
         PartialPeelLoop       = 1<<5,
         PartialPeelFailed     = 1<<6,
         WasSlpAnalyzed        = 1<<7,
         PassedSlpAnalysis     = 1<<8,
         DoUnrollOnly          = 1<<9,
         VectorizedLoop        = 1<<10,
         HasAtomicPostLoop     = 1<<11,
         StripMined            = 1<<12,
         SubwordLoop           = 1<<13,
         ProfileTripFailed     = 1<<14,
         LoopNestInnerLoop     = 1<<15,
         LoopNestLongOuterLoop = 1<<16 };
  char _unswitch_count;
  enum { _unswitch_max=3 };

  // Expected trip count from profile data
  float _profile_trip_cnt;

public:
  // Names for edge indices
  enum { Self=0, EntryControl, LoopBackControl };

  bool is_inner_loop() const { return _loop_flags & InnerLoop; }
  void set_inner_loop() { _loop_flags |= InnerLoop; }

  bool is_vectorized_loop() const { return _loop_flags & VectorizedLoop; }
  bool is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
  void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
  bool partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
  bool is_strip_mined() const { return _loop_flags & StripMined; }
  bool is_profile_trip_failed() const { return _loop_flags & ProfileTripFailed; }
  bool is_subword_loop() const { return _loop_flags & SubwordLoop; }
  bool is_loop_nest_inner_loop() const { return _loop_flags & LoopNestInnerLoop; }
  bool is_loop_nest_outer_loop() const { return _loop_flags & LoopNestLongOuterLoop; }

  void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
  void mark_was_slp() { _loop_flags |= WasSlpAnalyzed; }
  void mark_passed_slp() { _loop_flags |= PassedSlpAnalysis; }
  void mark_do_unroll_only() { _loop_flags |= DoUnrollOnly; }
  void mark_loop_vectorized() { _loop_flags |= VectorizedLoop; }
  void mark_has_atomic_post_loop() { _loop_flags |= HasAtomicPostLoop; }
  void mark_strip_mined() { _loop_flags |= StripMined; }
  void clear_strip_mined() { _loop_flags &= ~StripMined; }
  void mark_profile_trip_failed() { _loop_flags |= ProfileTripFailed; }
  void mark_subword_loop() { _loop_flags |= SubwordLoop; }
  void mark_loop_nest_inner_loop() { _loop_flags |= LoopNestInnerLoop; }
  void mark_loop_nest_outer_loop() { _loop_flags |= LoopNestLongOuterLoop; }

  int unswitch_max() { return _unswitch_max; }
  int unswitch_count() { return _unswitch_count; }

  void set_unswitch_count(int val) {
    assert (val <= unswitch_max(), "too many unswitches");
    _unswitch_count = val;
  }

  void set_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
  float profile_trip_cnt()             { return _profile_trip_cnt; }

  LoopNode(Node *entry, Node *backedge)
    : RegionNode(3), _loop_flags(0), _unswitch_count(0),
      _profile_trip_cnt(COUNT_UNKNOWN) {
    init_class_id(Class_Loop);
    init_req(EntryControl, entry);
    init_req(LoopBackControl, backedge);
  }

  virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
  virtual int Opcode() const;
  bool can_be_counted_loop(PhaseValues* phase) const {
    return req() == 3 && in(0) != nullptr &&
      in(1) != nullptr && phase->type(in(1)) != Type::TOP &&
      in(2) != nullptr && phase->type(in(2)) != Type::TOP;
  }
  bool is_valid_counted_loop(BasicType bt) const;
#ifndef PRODUCT
  virtual void dump_spec(outputStream *st) const;
#endif

  void verify_strip_mined(int expect_skeleton) const NOT_DEBUG_RETURN;
  virtual LoopNode* skip_strip_mined(int expect_skeleton = 1) { return this; }
  virtual IfTrueNode* outer_loop_tail() const { ShouldNotReachHere(); return nullptr; }
  virtual OuterStripMinedLoopEndNode* outer_loop_end() const { ShouldNotReachHere(); return nullptr; }
  virtual IfFalseNode* outer_loop_exit() const { ShouldNotReachHere(); return nullptr; }
  virtual SafePointNode* outer_safepoint() const { ShouldNotReachHere(); return nullptr; }
};

//------------------------------Counted Loops----------------------------------
// Counted loops are all trip-counted loops, with exactly 1 trip-counter exit
// path (and maybe some other exit paths).  The trip-counter exit is always
// last in the loop.  The trip-counter have to stride by a constant;
// the exit value is also loop invariant.

// CountedLoopNodes and CountedLoopEndNodes come in matched pairs.  The
// CountedLoopNode has the incoming loop control and the loop-back-control
// which is always the IfTrue before the matching CountedLoopEndNode.  The
// CountedLoopEndNode has an incoming control (possibly not the
// CountedLoopNode if there is control flow in the loop), the post-increment
// trip-counter value, and the limit.  The trip-counter value is always of
// the form (Op old-trip-counter stride).  The old-trip-counter is produced
// by a Phi connected to the CountedLoopNode.  The stride is constant.
// The Op is any commutable opcode, including Add, Mul, Xor.  The
// CountedLoopEndNode also takes in the loop-invariant limit value.

// From a CountedLoopNode I can reach the matching CountedLoopEndNode via the
// loop-back control.  From CountedLoopEndNodes I can reach CountedLoopNodes
// via the old-trip-counter from the Op node.

//------------------------------CountedLoopNode--------------------------------
// CountedLoopNodes head simple counted loops.  CountedLoopNodes have as
// inputs the incoming loop-start control and the loop-back control, so they
// act like RegionNodes.  They also take in the initial trip counter, the
// loop-invariant stride and the loop-invariant limit value.  CountedLoopNodes
// produce a loop-body control and the trip counter value.  Since
// CountedLoopNodes behave like RegionNodes I still have a standard CFG model.

class BaseCountedLoopNode : public LoopNode {
public:
  BaseCountedLoopNode(Node *entry, Node *backedge)
    : LoopNode(entry, backedge) {
  }

  Node *init_control() const { return in(EntryControl); }
  Node *back_control() const { return in(LoopBackControl); }

  Node* init_trip() const;
  Node* stride() const;
  bool stride_is_con() const;
  Node* limit() const;
  Node* incr() const;
  Node* phi() const;

  BaseCountedLoopEndNode* loopexit_or_null() const;
  BaseCountedLoopEndNode* loopexit() const;

  virtual BasicType bt() const = 0;

  jlong stride_con() const;

  static BaseCountedLoopNode* make(Node* entry, Node* backedge, BasicType bt);
};


class CountedLoopNode : public BaseCountedLoopNode {
  // Size is bigger to hold _main_idx.  However, _main_idx does not change
  // the semantics so it does not appear in the hash & cmp functions.
  virtual uint size_of() const { return sizeof(*this); }

  // For Pre- and Post-loops during debugging ONLY, this holds the index of
  // the Main CountedLoop.  Used to assert that we understand the graph shape.
  node_idx_t _main_idx;

  // Known trip count calculated by compute_exact_trip_count()
  uint  _trip_count;

  // Log2 of original loop bodies in unrolled loop
  int _unrolled_count_log2;

  // Node count prior to last unrolling - used to decide if
  // unroll,optimize,unroll,optimize,... is making progress
  int _node_count_before_unroll;

  // If slp analysis is performed we record the maximum
  // vector mapped unroll factor here
  int _slp_maximum_unroll_factor;

public:
  CountedLoopNode(Node *entry, Node *backedge)
    : BaseCountedLoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
      _unrolled_count_log2(0), _node_count_before_unroll(0),
      _slp_maximum_unroll_factor(0) {
    init_class_id(Class_CountedLoop);
    // Initialize _trip_count to the largest possible value.
    // Will be reset (lower) if the loop's trip count is known.
  }

  virtual int Opcode() const;
  virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

  CountedLoopEndNode* loopexit_or_null() const { return (CountedLoopEndNode*) BaseCountedLoopNode::loopexit_or_null(); }
  CountedLoopEndNode* loopexit() const { return (CountedLoopEndNode*) BaseCountedLoopNode::loopexit(); }
  int   stride_con() const;

  // Match increment with optional truncation
  static Node*
  match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInteger** trunc_type,
                                      BasicType bt);

  // A 'main' loop has a pre-loop and a post-loop.  The 'main' loop
  // can run short a few iterations and may start a few iterations in.
  // It will be RCE'd and unrolled and aligned.

  // A following 'post' loop will run any remaining iterations.  Used
  // during Range Check Elimination, the 'post' loop will do any final
  // iterations with full checks.  Also used by Loop Unrolling, where
  // the 'post' loop will do any epilog iterations needed.  Basically,
  // a 'post' loop can not profitably be further unrolled or RCE'd.

  // A preceding 'pre' loop will run at least 1 iteration (to do peeling),
  // it may do under-flow checks for RCE and may do alignment iterations
  // so the following main loop 'knows' that it is striding down cache
  // lines.

  // A 'main' loop that is ONLY unrolled or peeled, never RCE'd or
  // Aligned, may be missing it's pre-loop.
  bool is_normal_loop   () const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
  bool is_pre_loop      () const { return (_loop_flags&PreMainPostFlagsMask) == Pre;    }
  bool is_main_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Main;   }
  bool is_post_loop     () const { return (_loop_flags&PreMainPostFlagsMask) == Post;   }
  bool was_slp_analyzed () const { return (_loop_flags&WasSlpAnalyzed) == WasSlpAnalyzed; }
  bool has_passed_slp   () const { return (_loop_flags&PassedSlpAnalysis) == PassedSlpAnalysis; }
  bool is_unroll_only   () const { return (_loop_flags&DoUnrollOnly) == DoUnrollOnly; }
  bool is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
  bool has_atomic_post_loop  () const { return (_loop_flags & HasAtomicPostLoop) == HasAtomicPostLoop; }
  void set_main_no_pre_loop() { _loop_flags |= MainHasNoPreLoop; }

  int main_idx() const { return _main_idx; }


  void set_pre_loop  (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Pre ; _main_idx = main->_idx; }
  void set_main_loop (                     ) { assert(is_normal_loop(),""); _loop_flags |= Main;                         }
  void set_post_loop (CountedLoopNode *main) { assert(is_normal_loop(),""); _loop_flags |= Post; _main_idx = main->_idx; }
  void set_normal_loop(                    ) { _loop_flags &= ~PreMainPostFlagsMask; }

  void set_trip_count(uint tc) { _trip_count = tc; }
  uint trip_count()            { return _trip_count; }

  bool has_exact_trip_count() const { return (_loop_flags & HasExactTripCount) != 0; }
  void set_exact_trip_count(uint tc) {
    _trip_count = tc;
    _loop_flags |= HasExactTripCount;
  }
  void set_nonexact_trip_count() {
    _loop_flags &= ~HasExactTripCount;
  }
  void set_notpassed_slp() {
    _loop_flags &= ~PassedSlpAnalysis;
  }

  void double_unrolled_count() { _unrolled_count_log2++; }
  int  unrolled_count()        { return 1 << MIN2(_unrolled_count_log2, BitsPerInt-3); }

  void set_node_count_before_unroll(int ct)  { _node_count_before_unroll = ct; }
  int  node_count_before_unroll()            { return _node_count_before_unroll; }
  void set_slp_max_unroll(int unroll_factor) { _slp_maximum_unroll_factor = unroll_factor; }
  int  slp_max_unroll() const                { return _slp_maximum_unroll_factor; }

  virtual LoopNode* skip_strip_mined(int expect_skeleton = 1);
  OuterStripMinedLoopNode* outer_loop() const;
  virtual IfTrueNode* outer_loop_tail() const;
  virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
  virtual IfFalseNode* outer_loop_exit() const;
  virtual SafePointNode* outer_safepoint() const;

  Node* skip_assertion_predicates_with_halt();

  virtual BasicType bt() const {
    return T_INT;
  }

  Node* is_canonical_loop_entry();
  CountedLoopEndNode* find_pre_loop_end();

#ifndef PRODUCT
  virtual void dump_spec(outputStream *st) const;
#endif
};

class LongCountedLoopNode : public BaseCountedLoopNode {
public:
  LongCountedLoopNode(Node *entry, Node *backedge)
    : BaseCountedLoopNode(entry, backedge) {
    init_class_id(Class_LongCountedLoop);
  }

  virtual int Opcode() const;

  virtual BasicType bt() const {
    return T_LONG;
  }

  LongCountedLoopEndNode* loopexit_or_null() const { return (LongCountedLoopEndNode*) BaseCountedLoopNode::loopexit_or_null(); }
  LongCountedLoopEndNode* loopexit() const { return (LongCountedLoopEndNode*) BaseCountedLoopNode::loopexit(); }
};


//------------------------------CountedLoopEndNode-----------------------------
// CountedLoopEndNodes end simple trip counted loops.  They act much like
// IfNodes.

class BaseCountedLoopEndNode : public IfNode {
public:
  enum { TestControl, TestValue };
  BaseCountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
    : IfNode(control, test, prob, cnt) {
    init_class_id(Class_BaseCountedLoopEnd);
  }

  Node *cmp_node() const            { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : nullptr; }
  Node* incr() const                { Node* tmp = cmp_node(); return (tmp && tmp->req() == 3) ? tmp->in(1) : nullptr; }
  Node* limit() const               { Node* tmp = cmp_node(); return (tmp && tmp->req() == 3) ? tmp->in(2) : nullptr; }
  Node* stride() const              { Node* tmp = incr(); return (tmp && tmp->req() == 3) ? tmp->in(2) : nullptr; }
  Node* init_trip() const           { Node* tmp = phi(); return (tmp && tmp->req() == 3) ? tmp->in(1) : nullptr; }
  bool stride_is_con() const        { Node *tmp = stride(); return (tmp != nullptr && tmp->is_Con()); }

  PhiNode* phi() const {
    Node* tmp = incr();
    if (tmp && tmp->req() == 3) {
      Node* phi = tmp->in(1);
      if (phi->is_Phi()) {
        return phi->as_Phi();
      }
    }
    return nullptr;
  }

  BaseCountedLoopNode* loopnode() const {
    // The CountedLoopNode that goes with this CountedLoopEndNode may
    // have been optimized out by the IGVN so be cautious with the
    // pattern matching on the graph
    PhiNode* iv_phi = phi();
    if (iv_phi == nullptr) {
      return nullptr;
    }
    Node* ln = iv_phi->in(0);
    if (!ln->is_BaseCountedLoop() || ln->as_BaseCountedLoop()->loopexit_or_null() != this) {
      return nullptr;
    }
    if (ln->as_BaseCountedLoop()->bt() != bt()) {
      return nullptr;
    }
    return ln->as_BaseCountedLoop();
  }

  BoolTest::mask test_trip() const  { return in(TestValue)->as_Bool()->_test._test; }

  jlong stride_con() const;
  virtual BasicType bt() const = 0;

  static BaseCountedLoopEndNode* make(Node* control, Node* test, float prob, float cnt, BasicType bt);
};

class CountedLoopEndNode : public BaseCountedLoopEndNode {
public:

  CountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
    : BaseCountedLoopEndNode(control, test, prob, cnt) {
    init_class_id(Class_CountedLoopEnd);
  }
  virtual int Opcode() const;

  CountedLoopNode* loopnode() const {
    return (CountedLoopNode*) BaseCountedLoopEndNode::loopnode();
  }

  virtual BasicType bt() const {
    return T_INT;
  }

#ifndef PRODUCT
  virtual void dump_spec(outputStream *st) const;
#endif
};

class LongCountedLoopEndNode : public BaseCountedLoopEndNode {
public:
  LongCountedLoopEndNode(Node *control, Node *test, float prob, float cnt)
    : BaseCountedLoopEndNode(control, test, prob, cnt) {
    init_class_id(Class_LongCountedLoopEnd);
  }

  LongCountedLoopNode* loopnode() const {
    return (LongCountedLoopNode*) BaseCountedLoopEndNode::loopnode();
  }

  virtual int Opcode() const;

  virtual BasicType bt() const {
    return T_LONG;
  }
};


inline BaseCountedLoopEndNode* BaseCountedLoopNode::loopexit_or_null() const {
  Node* bctrl = back_control();
  if (bctrl == nullptr) return nullptr;

  Node* lexit = bctrl->in(0);
  if (!lexit->is_BaseCountedLoopEnd()) {
    return nullptr;
  }
  BaseCountedLoopEndNode* result = lexit->as_BaseCountedLoopEnd();
  if (result->bt() != bt()) {
    return nullptr;
  }
  return result;
}

inline BaseCountedLoopEndNode* BaseCountedLoopNode::loopexit() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  assert(cle != nullptr, "loopexit is null");
  return cle;
}

inline Node* BaseCountedLoopNode::init_trip() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr ? cle->init_trip() : nullptr;
}
inline Node* BaseCountedLoopNode::stride() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr ? cle->stride() : nullptr;
}

inline bool BaseCountedLoopNode::stride_is_con() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr && cle->stride_is_con();
}
inline Node* BaseCountedLoopNode::limit() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr ? cle->limit() : nullptr;
}
inline Node* BaseCountedLoopNode::incr() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr ? cle->incr() : nullptr;
}
inline Node* BaseCountedLoopNode::phi() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr ? cle->phi() : nullptr;
}

inline jlong BaseCountedLoopNode::stride_con() const {
  BaseCountedLoopEndNode* cle = loopexit_or_null();
  return cle != nullptr ? cle->stride_con() : 0;
}


//------------------------------LoopLimitNode-----------------------------
// Counted Loop limit node which represents exact final iterator value:
// trip_count = (limit - init_trip + stride - 1)/stride
// final_value= trip_count * stride + init_trip.
// Use HW instructions to calculate it when it can overflow in integer.
// Note, final_value should fit into integer since counted loop has
// limit check: limit <= max_int-stride.
class LoopLimitNode : public Node {
  enum { Init=1, Limit=2, Stride=3 };
 public:
  LoopLimitNode( Compile* C, Node *init, Node *limit, Node *stride ) : Node(nullptr,init,limit,stride) {
    // Put it on the Macro nodes list to optimize during macro nodes expansion.
    init_flags(Flag_is_macro);
    C->add_macro_node(this);
  }
  virtual int Opcode() const;
  virtual const Type *bottom_type() const { return TypeInt::INT; }
  virtual uint ideal_reg() const { return Op_RegI; }
  virtual const Type* Value(PhaseGVN* phase) const;
  virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
  virtual Node* Identity(PhaseGVN* phase);
};

// Support for strip mining
class OuterStripMinedLoopNode : public LoopNode {
private:
  static void fix_sunk_stores(CountedLoopEndNode* inner_cle, LoopNode* inner_cl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop);

public:
  OuterStripMinedLoopNode(Compile* C, Node *entry, Node *backedge)
    : LoopNode(entry, backedge) {
    init_class_id(Class_OuterStripMinedLoop);
    init_flags(Flag_is_macro);
    C->add_macro_node(this);
  }

  virtual int Opcode() const;

  virtual IfTrueNode* outer_loop_tail() const;
  virtual OuterStripMinedLoopEndNode* outer_loop_end() const;
  virtual IfFalseNode* outer_loop_exit() const;
  virtual SafePointNode* outer_safepoint() const;
  void adjust_strip_mined_loop(PhaseIterGVN* igvn);

  void remove_outer_loop_and_safepoint(PhaseIterGVN* igvn) const;

  void transform_to_counted_loop(PhaseIterGVN* igvn, PhaseIdealLoop* iloop);

  static Node* register_new_node(Node* node, LoopNode* ctrl, PhaseIterGVN* igvn, PhaseIdealLoop* iloop);

  Node* register_control(Node* node, Node* loop, Node* idom, PhaseIterGVN* igvn,
                         PhaseIdealLoop* iloop);
};

class OuterStripMinedLoopEndNode : public IfNode {
public:
  OuterStripMinedLoopEndNode(Node *control, Node *test, float prob, float cnt)
    : IfNode(control, test, prob, cnt) {
    init_class_id(Class_OuterStripMinedLoopEnd);
  }

  virtual int Opcode() const;

  virtual const Type* Value(PhaseGVN* phase) const;
  virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);

  bool is_expanded(PhaseGVN *phase) const;
};

// -----------------------------IdealLoopTree----------------------------------
class IdealLoopTree : public ResourceObj {
public:
  IdealLoopTree *_parent;       // Parent in loop tree
  IdealLoopTree *_next;         // Next sibling in loop tree
  IdealLoopTree *_child;        // First child in loop tree

  // The head-tail backedge defines the loop.
  // If a loop has multiple backedges, this is addressed during cleanup where
  // we peel off the multiple backedges,  merging all edges at the bottom and
  // ensuring that one proper backedge flow into the loop.
  Node *_head;                  // Head of loop
  Node *_tail;                  // Tail of loop
  inline Node *tail();          // Handle lazy update of _tail field
  inline Node *head();          // Handle lazy update of _head field
  PhaseIdealLoop* _phase;
  int _local_loop_unroll_limit;
  int _local_loop_unroll_factor;

  Node_List _body;              // Loop body for inner loops

  uint16_t _nest;               // Nesting depth
  uint8_t _irreducible:1,       // True if irreducible
          _has_call:1,          // True if has call safepoint
          _has_sfpt:1,          // True if has non-call safepoint
          _rce_candidate:1,     // True if candidate for range check elimination
          _has_range_checks:1,
          _has_range_checks_computed:1;

  Node_List* _safepts;          // List of safepoints in this loop
  Node_List* _required_safept;  // A inner loop cannot delete these safepts;
  bool  _allow_optimizations;   // Allow loop optimizations

  IdealLoopTree( PhaseIdealLoop* phase, Node *head, Node *tail )
    : _parent(nullptr), _next(nullptr), _child(nullptr),
      _head(head), _tail(tail),
      _phase(phase),
      _local_loop_unroll_limit(0), _local_loop_unroll_factor(0),
      _body(Compile::current()->comp_arena()),
      _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0),
      _has_range_checks(0), _has_range_checks_computed(0),
      _safepts(nullptr),
      _required_safept(nullptr),
      _allow_optimizations(true)
  {
    precond(_head != nullptr);
    precond(_tail != nullptr);
  }

  // Is 'l' a member of 'this'?
  bool is_member(const IdealLoopTree *l) const; // Test for nested membership

  // Set loop nesting depth.  Accumulate has_call bits.
  int set_nest( uint depth );

  // Split out multiple fall-in edges from the loop header.  Move them to a
  // private RegionNode before the loop.  This becomes the loop landing pad.
  void split_fall_in( PhaseIdealLoop *phase, int fall_in_cnt );

  // Split out the outermost loop from this shared header.
  void split_outer_loop( PhaseIdealLoop *phase );

  // Merge all the backedges from the shared header into a private Region.
  // Feed that region as the one backedge to this loop.
  void merge_many_backedges( PhaseIdealLoop *phase );

  // Split shared headers and insert loop landing pads.
  // Insert a LoopNode to replace the RegionNode.
  // Returns TRUE if loop tree is structurally changed.
  bool beautify_loops( PhaseIdealLoop *phase );

  // Perform optimization to use the loop predicates for null checks and range checks.
  // Applies to any loop level (not just the innermost one)
  bool loop_predication( PhaseIdealLoop *phase);
  bool can_apply_loop_predication();

  // Perform iteration-splitting on inner loops.  Split iterations to
  // avoid range checks or one-shot null checks.  Returns false if the
  // current round of loop opts should stop.
  bool iteration_split( PhaseIdealLoop *phase, Node_List &old_new );

  // Driver for various flavors of iteration splitting.  Returns false
  // if the current round of loop opts should stop.
  bool iteration_split_impl( PhaseIdealLoop *phase, Node_List &old_new );

  // Given dominators, try to find loops with calls that must always be
  // executed (call dominates loop tail).  These loops do not need non-call
  // safepoints (ncsfpt).
  void check_safepts(VectorSet &visited, Node_List &stack);

  // Allpaths backwards scan from loop tail, terminating each path at first safepoint
  // encountered.
  void allpaths_check_safepts(VectorSet &visited, Node_List &stack);

  // Remove safepoints from loop. Optionally keeping one.
  void remove_safepoints(PhaseIdealLoop* phase, bool keep_one);

  // Convert to counted loops where possible
  void counted_loop( PhaseIdealLoop *phase );

  // Check for Node being a loop-breaking test
  Node *is_loop_exit(Node *iff) const;

  // Remove simplistic dead code from loop body
  void DCE_loop_body();

  // Look for loop-exit tests with my 50/50 guesses from the Parsing stage.
  // Replace with a 1-in-10 exit guess.
  void adjust_loop_exit_prob( PhaseIdealLoop *phase );

  // Return TRUE or FALSE if the loop should never be RCE'd or aligned.
  // Useful for unrolling loops with NO array accesses.
  bool policy_peel_only( PhaseIdealLoop *phase ) const;

  // Return TRUE or FALSE if the loop should be unswitched -- clone
  // loop with an invariant test
  bool policy_unswitching( PhaseIdealLoop *phase ) const;

  // Micro-benchmark spamming.  Remove empty loops.
  bool do_remove_empty_loop( PhaseIdealLoop *phase );

  // Convert one iteration loop into normal code.
  bool do_one_iteration_loop( PhaseIdealLoop *phase );

  // Return TRUE or FALSE if the loop should be peeled or not. Peel if we can
  // move some loop-invariant test (usually a null-check) before the loop.
  bool policy_peeling(PhaseIdealLoop *phase);

  uint estimate_peeling(PhaseIdealLoop *phase);

  // Return TRUE or FALSE if the loop should be maximally unrolled. Stash any
  // known trip count in the counted loop node.
  bool policy_maximally_unroll(PhaseIdealLoop *phase) const;

  // Return TRUE or FALSE if the loop should be unrolled or not. Apply unroll
  // if the loop is a counted loop and the loop body is small enough.
  bool policy_unroll(PhaseIdealLoop *phase);

  // Loop analyses to map to a maximal superword unrolling for vectorization.
  void policy_unroll_slp_analysis(CountedLoopNode *cl, PhaseIdealLoop *phase, int future_unroll_ct);

  // Return TRUE or FALSE if the loop should be range-check-eliminated.
  // Gather a list of IF tests that are dominated by iteration splitting;
  // also gather the end of the first split and the start of the 2nd split.
  bool policy_range_check(PhaseIdealLoop* phase, bool provisional, BasicType bt) const;

  // Return TRUE if "iff" is a range check.
  bool is_range_check_if(IfProjNode* if_success_proj, PhaseIdealLoop* phase, Invariance& invar DEBUG_ONLY(COMMA ProjNode* predicate_proj)) const;
  bool is_range_check_if(IfProjNode* if_success_proj, PhaseIdealLoop* phase, BasicType bt, Node* iv, Node*& range, Node*& offset,
                         jlong& scale) const;

  // Estimate the number of nodes required when cloning a loop (body).
  uint est_loop_clone_sz(uint factor) const;
  // Estimate the number of nodes required when unrolling a loop (body).
  uint est_loop_unroll_sz(uint factor) const;

  // Compute loop trip count if possible
  void compute_trip_count(PhaseIdealLoop* phase);

  // Compute loop trip count from profile data
  float compute_profile_trip_cnt_helper(Node* n);
  void compute_profile_trip_cnt( PhaseIdealLoop *phase );

  // Reassociate invariant expressions.
  void reassociate_invariants(PhaseIdealLoop *phase);
  // Reassociate invariant binary expressions.
  Node* reassociate(Node* n1, PhaseIdealLoop *phase);
  // Reassociate invariant add, subtract, and compare expressions.
  Node* reassociate_add_sub_cmp(Node* n1, int inv1_idx, int inv2_idx, PhaseIdealLoop* phase);
  // Return nonzero index of invariant operand if invariant and variant
  // are combined with an associative binary. Helper for reassociate_invariants.
  int find_invariant(Node* n, PhaseIdealLoop *phase);
  // Return TRUE if "n" is associative.
  bool is_associative(Node* n, Node* base=nullptr);
  // Return TRUE if "n" is an associative cmp node.
  bool is_associative_cmp(Node* n);

  // Return true if n is invariant
  bool is_invariant(Node* n) const;

  // Put loop body on igvn work list
  void record_for_igvn();

  bool is_root() { return _parent == nullptr; }
  // A proper/reducible loop w/o any (occasional) dead back-edge.
  bool is_loop() { return !_irreducible && !tail()->is_top(); }
  bool is_counted()   { return is_loop() && _head->is_CountedLoop(); }
  bool is_innermost() { return is_loop() && _child == nullptr; }

  void remove_main_post_loops(CountedLoopNode *cl, PhaseIdealLoop *phase);

  bool compute_has_range_checks() const;
  bool range_checks_present() {
    if (!_has_range_checks_computed) {
      if (compute_has_range_checks()) {
        _has_range_checks = 1;
      }
      _has_range_checks_computed = 1;
    }
    return _has_range_checks;
  }

  // Return the parent's IdealLoopTree for a strip mined loop which is the outer strip mined loop.
  // In all other cases, return this.
  IdealLoopTree* skip_strip_mined() {
    return _head->as_Loop()->is_strip_mined() ? _parent : this;
  }

#ifndef PRODUCT
  void dump_head();       // Dump loop head only
  void dump();            // Dump this loop recursively
#endif

#ifdef ASSERT
  GrowableArray<IdealLoopTree*> collect_sorted_children() const;
  bool verify_tree(IdealLoopTree* loop_verify) const;
#endif

 private:
  enum { EMPTY_LOOP_SIZE = 7 }; // Number of nodes in an empty loop.

  // Estimate the number of nodes resulting from control and data flow merge.
  uint est_loop_flow_merge_sz() const;

  // Check if the number of residual iterations is large with unroll_cnt.
  // Return true if the residual iterations are more than 10% of the trip count.
  bool is_residual_iters_large(int unroll_cnt, CountedLoopNode *cl) const {
    return (unroll_cnt - 1) * (100.0 / LoopPercentProfileLimit) > cl->profile_trip_cnt();
  }

  void collect_loop_core_nodes(PhaseIdealLoop* phase, Unique_Node_List& wq) const;

  bool empty_loop_with_data_nodes(PhaseIdealLoop* phase) const;

  void enqueue_data_nodes(PhaseIdealLoop* phase, Unique_Node_List& empty_loop_nodes, Unique_Node_List& wq) const;

  bool process_safepoint(PhaseIdealLoop* phase, Unique_Node_List& empty_loop_nodes, Unique_Node_List& wq,
                         Node* sfpt) const;

  bool empty_loop_candidate(PhaseIdealLoop* phase) const;

  bool empty_loop_with_extra_nodes_candidate(PhaseIdealLoop* phase) const;
};

// -----------------------------PhaseIdealLoop---------------------------------
// Computes the mapping from Nodes to IdealLoopTrees. Organizes IdealLoopTrees
// into a loop tree. Drives the loop-based transformations on the ideal graph.
class PhaseIdealLoop : public PhaseTransform {
  friend class IdealLoopTree;
  friend class SuperWord;
  friend class ShenandoahBarrierC2Support;
  friend class AutoNodeBudget;

  // Map loop membership for CFG nodes, and ctrl for non-CFG nodes.
  Node_List _loop_or_ctrl;

  // Pre-computed def-use info
  PhaseIterGVN &_igvn;

  // Head of loop tree
  IdealLoopTree* _ltree_root;

  // Array of pre-order numbers, plus post-visited bit.
  // ZERO for not pre-visited.  EVEN for pre-visited but not post-visited.
  // ODD for post-visited.  Other bits are the pre-order number.
  uint *_preorders;
  uint _max_preorder;

  ReallocMark _nesting; // Safety checks for arena reallocation

  const PhaseIdealLoop* _verify_me;
  bool _verify_only;

  // Allocate _preorders[] array
  void allocate_preorders() {
    _max_preorder = C->unique()+8;
    _preorders = NEW_RESOURCE_ARRAY(uint, _max_preorder);
    memset(_preorders, 0, sizeof(uint) * _max_preorder);
  }

  // Allocate _preorders[] array
  void reallocate_preorders() {
    _nesting.check(); // Check if a potential re-allocation in the resource arena is safe
    if ( _max_preorder < C->unique() ) {
      _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, C->unique());
      _max_preorder = C->unique();
    }
    memset(_preorders, 0, sizeof(uint) * _max_preorder);
  }

  // Check to grow _preorders[] array for the case when build_loop_tree_impl()
  // adds new nodes.
  void check_grow_preorders( ) {
    _nesting.check(); // Check if a potential re-allocation in the resource arena is safe
    if ( _max_preorder < C->unique() ) {
      uint newsize = _max_preorder<<1;  // double size of array
      _preorders = REALLOC_RESOURCE_ARRAY(uint, _preorders, _max_preorder, newsize);
      memset(&_preorders[_max_preorder],0,sizeof(uint)*(newsize-_max_preorder));
      _max_preorder = newsize;
    }
  }
  // Check for pre-visited.  Zero for NOT visited; non-zero for visited.
  int is_visited( Node *n ) const { return _preorders[n->_idx]; }
  // Pre-order numbers are written to the Nodes array as low-bit-set values.
  void set_preorder_visited( Node *n, int pre_order ) {
    assert( !is_visited( n ), "already set" );
    _preorders[n->_idx] = (pre_order<<1);
  };
  // Return pre-order number.
  int get_preorder( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]>>1; }

  // Check for being post-visited.
  // Should be previsited already (checked with assert(is_visited(n))).
  int is_postvisited( Node *n ) const { assert( is_visited(n), "" ); return _preorders[n->_idx]&1; }

  // Mark as post visited
  void set_postvisited( Node *n ) { assert( !is_postvisited( n ), "" ); _preorders[n->_idx] |= 1; }

public:
  // Set/get control node out.  Set lower bit to distinguish from IdealLoopTree
  // Returns true if "n" is a data node, false if it's a control node.
  bool has_ctrl(const Node* n) const { return ((intptr_t)_loop_or_ctrl[n->_idx]) & 1; }

private:
  // clear out dead code after build_loop_late
  Node_List _deadlist;
  Node_List _zero_trip_guard_opaque_nodes;

  // Support for faster execution of get_late_ctrl()/dom_lca()
  // when a node has many uses and dominator depth is deep.
  GrowableArray<jlong> _dom_lca_tags;
  uint _dom_lca_tags_round;
  void   init_dom_lca_tags();

  // Helper for debugging bad dominance relationships
  bool verify_dominance(Node* n, Node* use, Node* LCA, Node* early);

  Node* compute_lca_of_uses(Node* n, Node* early, bool verify = false);

  // Inline wrapper for frequent cases:
  // 1) only one use
  // 2) a use is the same as the current LCA passed as 'n1'
  Node *dom_lca_for_get_late_ctrl( Node *lca, Node *n, Node *tag ) {
    assert( n->is_CFG(), "" );
    // Fast-path null lca
    if( lca != nullptr && lca != n ) {
      assert( lca->is_CFG(), "" );
      // find LCA of all uses
      n = dom_lca_for_get_late_ctrl_internal( lca, n, tag );
    }
    return find_non_split_ctrl(n);
  }
  Node *dom_lca_for_get_late_ctrl_internal( Node *lca, Node *n, Node *tag );

  // Helper function for directing control inputs away from CFG split points.
  Node *find_non_split_ctrl( Node *ctrl ) const {
    if (ctrl != nullptr) {
      if (ctrl->is_MultiBranch()) {
        ctrl = ctrl->in(0);
      }
      assert(ctrl->is_CFG(), "CFG");
    }
    return ctrl;
  }

#ifdef ASSERT
  static void ensure_zero_trip_guard_proj(Node* node, bool is_main_loop);
#endif
 private:
  static void get_template_assertion_predicates(ParsePredicateSuccessProj* parse_predicate_proj, Unique_Node_List& list, bool get_opaque = false);
  void update_main_loop_assertion_predicates(CountedLoopNode* main_loop_head);
  void initialize_assertion_predicates_for_peeled_loop(CountedLoopNode* peeled_loop_head,
                                                       CountedLoopNode* remaining_loop_head,
                                                       uint first_node_index_in_cloned_loop_body,
                                                       const Node_List& old_new);
  void initialize_assertion_predicates_for_main_loop(CountedLoopNode* pre_loop_head,
                                                     CountedLoopNode* main_loop_head,
                                                     uint first_node_index_in_cloned_loop_body,
                                                     const Node_List& old_new);
  void initialize_assertion_predicates_for_post_loop(CountedLoopNode* main_loop_head, CountedLoopNode* post_loop_head,
                                                     uint first_node_index_in_cloned_loop_body);
  void create_assertion_predicates_at_loop(CountedLoopNode* source_loop_head, CountedLoopNode* target_loop_head,
                                           const NodeInLoopBody& _node_in_loop_body, bool clone_template);
  void insert_loop_limit_check_predicate(ParsePredicateSuccessProj* loop_limit_check_parse_proj, Node* cmp_limit,
                                         Node* bol);
  void log_loop_tree();

public:

  PhaseIterGVN &igvn() const { return _igvn; }

  bool has_node(const Node* n) const {
    guarantee(n != nullptr, "No Node.");
    return _loop_or_ctrl[n->_idx] != nullptr;
  }
  // check if transform created new nodes that need _ctrl recorded
  Node *get_late_ctrl( Node *n, Node *early );
  Node *get_early_ctrl( Node *n );
  Node *get_early_ctrl_for_expensive(Node *n, Node* earliest);
  void set_early_ctrl(Node* n, bool update_body);
  void set_subtree_ctrl(Node* n, bool update_body);
  void set_ctrl( Node *n, Node *ctrl ) {
    assert( !has_node(n) || has_ctrl(n), "" );
    assert( ctrl->in(0), "cannot set dead control node" );
    assert( ctrl == find_non_split_ctrl(ctrl), "must set legal crtl" );
    _loop_or_ctrl.map(n->_idx, (Node*)((intptr_t)ctrl + 1));
  }
  // Set control and update loop membership
  void set_ctrl_and_loop(Node* n, Node* ctrl) {
    IdealLoopTree* old_loop = get_loop(get_ctrl(n));
    IdealLoopTree* new_loop = get_loop(ctrl);
    if (old_loop != new_loop) {
      if (old_loop->_child == nullptr) old_loop->_body.yank(n);
      if (new_loop->_child == nullptr) new_loop->_body.push(n);
    }
    set_ctrl(n, ctrl);
  }
  // Control nodes can be replaced or subsumed.  During this pass they
  // get their replacement Node in slot 1.  Instead of updating the block
  // location of all Nodes in the subsumed block, we lazily do it.  As we
  // pull such a subsumed block out of the array, we write back the final
  // correct block.
  Node* get_ctrl(const Node* i) {
    assert(has_node(i), "");
    Node *n = get_ctrl_no_update(i);
    _loop_or_ctrl.map(i->_idx, (Node*)((intptr_t)n + 1));
    assert(has_node(i) && has_ctrl(i), "");
    assert(n == find_non_split_ctrl(n), "must return legal ctrl" );
    return n;
  }

  bool is_dominator(Node* dominator, Node* n);
  bool is_strict_dominator(Node* dominator, Node* n);

  // return get_ctrl for a data node and self(n) for a CFG node
  Node* ctrl_or_self(Node* n) {
    if (has_ctrl(n))
      return get_ctrl(n);
    else {
      assert (n->is_CFG(), "must be a CFG node");
      return n;
    }
  }

  Node* get_ctrl_no_update_helper(const Node* i) const {
    assert(has_ctrl(i), "should be control, not loop");
    return (Node*)(((intptr_t)_loop_or_ctrl[i->_idx]) & ~1);
  }

  Node* get_ctrl_no_update(const Node* i) const {
    assert( has_ctrl(i), "" );
    Node *n = get_ctrl_no_update_helper(i);
    if (!n->in(0)) {
      // Skip dead CFG nodes
      do {
        n = get_ctrl_no_update_helper(n);
      } while (!n->in(0));
      n = find_non_split_ctrl(n);
    }
    return n;
  }

  // Check for loop being set
  // "n" must be a control node. Returns true if "n" is known to be in a loop.
  bool has_loop( Node *n ) const {
    assert(!has_node(n) || !has_ctrl(n), "");
    return has_node(n);
  }
  // Set loop
  void set_loop( Node *n, IdealLoopTree *loop ) {
    _loop_or_ctrl.map(n->_idx, (Node*)loop);
  }
  // Lazy-dazy update of 'get_ctrl' and 'idom_at' mechanisms.  Replace
  // the 'old_node' with 'new_node'.  Kill old-node.  Add a reference
  // from old_node to new_node to support the lazy update.  Reference
  // replaces loop reference, since that is not needed for dead node.
  void lazy_update(Node *old_node, Node *new_node) {
    assert(old_node != new_node, "no cycles please");
    // Re-use the side array slot for this node to provide the
    // forwarding pointer.
    _loop_or_ctrl.map(old_node->_idx, (Node*)((intptr_t)new_node + 1));
  }
  void lazy_replace(Node *old_node, Node *new_node) {
    _igvn.replace_node(old_node, new_node);
    lazy_update(old_node, new_node);
  }

private:

  // Place 'n' in some loop nest, where 'n' is a CFG node
  void build_loop_tree();
  int build_loop_tree_impl(Node* n, int pre_order);
  // Insert loop into the existing loop tree.  'innermost' is a leaf of the
  // loop tree, not the root.
  IdealLoopTree *sort( IdealLoopTree *loop, IdealLoopTree *innermost );

#ifdef ASSERT
  // verify that regions in irreducible loops are marked is_in_irreducible_loop
  void verify_regions_in_irreducible_loops();
  bool is_in_irreducible_loop(RegionNode* region);
#endif

  // Place Data nodes in some loop nest
  void build_loop_early( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
  void build_loop_late ( VectorSet &visited, Node_List &worklist, Node_Stack &nstack );
  void build_loop_late_post_work(Node* n, bool pinned);
  void build_loop_late_post(Node* n);
  void verify_strip_mined_scheduling(Node *n, Node* least);

  // Array of immediate dominance info for each CFG node indexed by node idx
private:
  uint _idom_size;
  Node **_idom;                  // Array of immediate dominators
  uint *_dom_depth;              // Used for fast LCA test
  GrowableArray<uint>* _dom_stk; // For recomputation of dom depth
  LoopOptsMode _mode;

  // build the loop tree and perform any requested optimizations
  void build_and_optimize();

  // Dominators for the sea of nodes
  void Dominators();

  // Compute the Ideal Node to Loop mapping
  PhaseIdealLoop(PhaseIterGVN& igvn, LoopOptsMode mode) :
    PhaseTransform(Ideal_Loop),
    _loop_or_ctrl(igvn.C->comp_arena()),
    _igvn(igvn),
    _verify_me(nullptr),
    _verify_only(false),
    _mode(mode),
    _nodes_required(UINT_MAX) {
    assert(mode != LoopOptsVerify, "wrong constructor to verify IdealLoop");
    build_and_optimize();
  }

#ifndef PRODUCT
  // Verify that verify_me made the same decisions as a fresh run
  // or only verify that the graph is valid if verify_me is null.
  PhaseIdealLoop(PhaseIterGVN& igvn, const PhaseIdealLoop* verify_me = nullptr) :
    PhaseTransform(Ideal_Loop),
    _loop_or_ctrl(igvn.C->comp_arena()),
    _igvn(igvn),
    _verify_me(verify_me),
    _verify_only(verify_me == nullptr),
    _mode(LoopOptsVerify),
    _nodes_required(UINT_MAX) {
    DEBUG_ONLY(C->set_phase_verify_ideal_loop();)
    build_and_optimize();
    DEBUG_ONLY(C->reset_phase_verify_ideal_loop();)
  }
#endif

  Node* insert_convert_node_if_needed(BasicType target, Node* input);

public:
  Node* idom_no_update(Node* d) const {
    return idom_no_update(d->_idx);
  }

  Node* idom_no_update(uint didx) const {
    assert(didx < _idom_size, "oob");
    Node* n = _idom[didx];
    assert(n != nullptr,"Bad immediate dominator info.");
    while (n->in(0) == nullptr) { // Skip dead CFG nodes
      n = (Node*)(((intptr_t)_loop_or_ctrl[n->_idx]) & ~1);
      assert(n != nullptr,"Bad immediate dominator info.");
    }
    return n;
  }

  Node *idom(Node* d) const {
    return idom(d->_idx);
  }

  Node *idom(uint didx) const {
    Node *n = idom_no_update(didx);
    _idom[didx] = n; // Lazily remove dead CFG nodes from table.
    return n;
  }

  uint dom_depth(Node* d) const {
    guarantee(d != nullptr, "Null dominator info.");
    guarantee(d->_idx < _idom_size, "");
    return _dom_depth[d->_idx];
  }
  void set_idom(Node* d, Node* n, uint dom_depth);
  // Locally compute IDOM using dom_lca call
  Node *compute_idom( Node *region ) const;
  // Recompute dom_depth
  void recompute_dom_depth();

  // Is safept not required by an outer loop?
  bool is_deleteable_safept(Node* sfpt);

  // Replace parallel induction variable (parallel to trip counter)
  void replace_parallel_iv(IdealLoopTree *loop);

  Node *dom_lca( Node *n1, Node *n2 ) const {
    return find_non_split_ctrl(dom_lca_internal(n1, n2));
  }
  Node *dom_lca_internal( Node *n1, Node *n2 ) const;

  Node* dominated_node(Node* c1, Node* c2) {
    assert(is_dominator(c1, c2) || is_dominator(c2, c1), "nodes must be related");
    return is_dominator(c1, c2) ? c2 : c1;
  }

  // Return control node that's dominated by the 2 others
  Node* dominated_node(Node* c1, Node* c2, Node* c3) {
    return dominated_node(c1, dominated_node(c2, c3));
  }

  // Build and verify the loop tree without modifying the graph.  This
  // is useful to verify that all inputs properly dominate their uses.
  static void verify(PhaseIterGVN& igvn) {
#ifdef ASSERT
    ResourceMark rm;
    Compile::TracePhase tp(_t_idealLoopVerify);
    PhaseIdealLoop v(igvn);
#endif
  }

  // Recommended way to use PhaseIdealLoop.
  // Run PhaseIdealLoop in some mode and allocates a local scope for memory allocations.
  static void optimize(PhaseIterGVN &igvn, LoopOptsMode mode) {
    ResourceMark rm;
    PhaseIdealLoop v(igvn, mode);

    Compile* C = Compile::current();
    if (!C->failing()) {
      // Cleanup any modified bits
      igvn.optimize();
      if (C->failing()) { return; }
      v.log_loop_tree();
    }
  }

  // True if the method has at least 1 irreducible loop
  bool _has_irreducible_loops;

  // Per-Node transform
  virtual Node* transform(Node* n) { return nullptr; }

  Node* loop_exit_control(Node* x, IdealLoopTree* loop);
  Node* loop_exit_test(Node* back_control, IdealLoopTree* loop, Node*& incr, Node*& limit, BoolTest::mask& bt, float& cl_prob);
  Node* loop_iv_incr(Node* incr, Node* x, IdealLoopTree* loop, Node*& phi_incr);
  Node* loop_iv_stride(Node* incr, IdealLoopTree* loop, Node*& xphi);
  PhiNode* loop_iv_phi(Node* xphi, Node* phi_incr, Node* x, IdealLoopTree* loop);

  bool is_counted_loop(Node* x, IdealLoopTree*&loop, BasicType iv_bt);

  Node* loop_nest_replace_iv(Node* iv_to_replace, Node* inner_iv, Node* outer_phi, Node* inner_head, BasicType bt);
  bool create_loop_nest(IdealLoopTree* loop, Node_List &old_new);
#ifdef ASSERT
  bool convert_to_long_loop(Node* cmp, Node* phi, IdealLoopTree* loop);
#endif
  void add_parse_predicate(Deoptimization::DeoptReason reason, Node* inner_head, IdealLoopTree* loop, SafePointNode* sfpt);
  SafePointNode* find_safepoint(Node* back_control, Node* x, IdealLoopTree* loop);
  IdealLoopTree* insert_outer_loop(IdealLoopTree* loop, LoopNode* outer_l, Node* outer_ift);
  IdealLoopTree* create_outer_strip_mined_loop(BoolNode *test, Node *cmp, Node *init_control,
                                               IdealLoopTree* loop, float cl_prob, float le_fcnt,
                                               Node*& entry_control, Node*& iffalse);

  Node* exact_limit( IdealLoopTree *loop );

  // Return a post-walked LoopNode
  IdealLoopTree *get_loop( Node *n ) const {
    // Dead nodes have no loop, so return the top level loop instead
    if (!has_node(n))  return _ltree_root;
    assert(!has_ctrl(n), "");
    return (IdealLoopTree*)_loop_or_ctrl[n->_idx];
  }

  IdealLoopTree* ltree_root() const { return _ltree_root; }

  // Is 'n' a (nested) member of 'loop'?
  int is_member( const IdealLoopTree *loop, Node *n ) const {
    return loop->is_member(get_loop(n)); }

  // This is the basic building block of the loop optimizations.  It clones an
  // entire loop body.  It makes an old_new loop body mapping; with this
  // mapping you can find the new-loop equivalent to an old-loop node.  All
  // new-loop nodes are exactly equal to their old-loop counterparts, all
  // edges are the same.  All exits from the old-loop now have a RegionNode
  // that merges the equivalent new-loop path.  This is true even for the
  // normal "loop-exit" condition.  All uses of loop-invariant old-loop values
  // now come from (one or more) Phis that merge their new-loop equivalents.
  // Parameter side_by_side_idom:
  //   When side_by_size_idom is null, the dominator tree is constructed for
  //      the clone loop to dominate the original.  Used in construction of
  //      pre-main-post loop sequence.
  //   When nonnull, the clone and original are side-by-side, both are
  //      dominated by the passed in side_by_side_idom node.  Used in
  //      construction of unswitched loops.
  enum CloneLoopMode {
    IgnoreStripMined = 0,        // Only clone inner strip mined loop
    CloneIncludesStripMined = 1, // clone both inner and outer strip mined loops
    ControlAroundStripMined = 2  // Only clone inner strip mined loop,
                                 // result control flow branches
                                 // either to inner clone or outer
                                 // strip mined loop.
  };
  void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
                  CloneLoopMode mode, Node* side_by_side_idom = nullptr);
  void clone_loop_handle_data_uses(Node* old, Node_List &old_new,
                                   IdealLoopTree* loop, IdealLoopTree* companion_loop,
                                   Node_List*& split_if_set, Node_List*& split_bool_set,
                                   Node_List*& split_cex_set, Node_List& worklist,
                                   uint new_counter, CloneLoopMode mode);
  void clone_outer_loop(LoopNode* head, CloneLoopMode mode, IdealLoopTree *loop,
                        IdealLoopTree* outer_loop, int dd, Node_List &old_new,
                        Node_List& extra_data_nodes);

  // If we got the effect of peeling, either by actually peeling or by
  // making a pre-loop which must execute at least once, we can remove
  // all loop-invariant dominated tests in the main body.
  void peeled_dom_test_elim( IdealLoopTree *loop, Node_List &old_new );

  // Generate code to do a loop peel for the given loop (and body).
  // old_new is a temp array.
  void do_peeling( IdealLoopTree *loop, Node_List &old_new );

  // Add pre and post loops around the given loop.  These loops are used
  // during RCE, unrolling and aligning loops.
  void insert_pre_post_loops( IdealLoopTree *loop, Node_List &old_new, bool peel_only );

  // Add post loop after the given loop.
  Node *insert_post_loop(IdealLoopTree* loop, Node_List& old_new,
                         CountedLoopNode* main_head, CountedLoopEndNode* main_end,
                         Node*& incr, Node* limit, CountedLoopNode*& post_head);

  // Add a vector post loop between a vector main loop and the current post loop
  void insert_vector_post_loop(IdealLoopTree *loop, Node_List &old_new);
  // If Node n lives in the back_ctrl block, we clone a private version of n
  // in preheader_ctrl block and return that, otherwise return n.
  Node *clone_up_backedge_goo( Node *back_ctrl, Node *preheader_ctrl, Node *n, VectorSet &visited, Node_Stack &clones );

  // Take steps to maximally unroll the loop.  Peel any odd iterations, then
  // unroll to do double iterations.  The next round of major loop transforms
  // will repeat till the doubled loop body does all remaining iterations in 1
  // pass.
  void do_maximally_unroll( IdealLoopTree *loop, Node_List &old_new );

  // Unroll the loop body one step - make each trip do 2 iterations.
  void do_unroll( IdealLoopTree *loop, Node_List &old_new, bool adjust_min_trip );

  // Return true if exp is a constant times an induction var
  bool is_scaled_iv(Node* exp, Node* iv, BasicType bt, jlong* p_scale, bool* p_short_scale, int depth = 0);

  bool is_iv(Node* exp, Node* iv, BasicType bt);

  // Return true if exp is a scaled induction var plus (or minus) constant
  bool is_scaled_iv_plus_offset(Node* exp, Node* iv, BasicType bt, jlong* p_scale, Node** p_offset, bool* p_short_scale = nullptr, int depth = 0);
  bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset) {
    jlong long_scale;
    if (is_scaled_iv_plus_offset(exp, iv, T_INT, &long_scale, p_offset)) {
      int int_scale = checked_cast<int>(long_scale);
      if (p_scale != nullptr) {
        *p_scale = int_scale;
      }
      return true;
    }
    return false;
  }
  // Helper for finding more complex matches to is_scaled_iv_plus_offset.
  bool is_scaled_iv_plus_extra_offset(Node* exp1, Node* offset2, Node* iv,
                                      BasicType bt,
                                      jlong* p_scale, Node** p_offset,
                                      bool* p_short_scale, int depth);

  // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
  IfTrueNode* create_new_if_for_predicate(
      ParsePredicateSuccessProj* parse_predicate_proj, Node* new_entry, Deoptimization::DeoptReason reason, int opcode,
      bool rewire_uncommon_proj_phi_inputs = false,
      AssertionPredicateType assertion_predicate_type = AssertionPredicateType::None);

 private:
  // Helper functions for create_new_if_for_predicate()
  void set_ctrl_of_nodes_with_same_ctrl(Node* start_node, ProjNode* old_uncommon_proj, Node* new_uncommon_proj);
  Unique_Node_List find_nodes_with_same_ctrl(Node* node, const ProjNode* ctrl);
  Node* clone_nodes_with_same_ctrl(Node* start_node, ProjNode* old_uncommon_proj, Node* new_uncommon_proj);
  void fix_cloned_data_node_controls(const ProjNode* orig, Node* new_uncommon_proj,
                                     const OrigToNewHashtable& orig_to_clone);
  bool has_dominating_loop_limit_check(Node* init_trip, Node* limit, jlong stride_con, BasicType iv_bt,
                                       Node* loop_entry);

 public:
  void register_control(Node* n, IdealLoopTree *loop, Node* pred, bool update_body = true);

  void replace_loop_entry(LoopNode* loop_head, Node* new_entry) {
    _igvn.replace_input_of(loop_head, LoopNode::EntryControl, new_entry);
    set_idom(loop_head, new_entry, dom_depth(new_entry));
  }

  // Construct a range check for a predicate if
  BoolNode* rc_predicate(Node* ctrl, int scale, Node* offset, Node* init, Node* limit,
                         jint stride, Node* range, bool upper, bool& overflow);

  // Implementation of the loop predication to promote checks outside the loop
  bool loop_predication_impl(IdealLoopTree *loop);

 private:
  bool loop_predication_impl_helper(IdealLoopTree* loop, IfProjNode* if_success_proj,
                                    ParsePredicateSuccessProj* parse_predicate_proj, CountedLoopNode* cl, ConNode* zero,
                                    Invariance& invar, Deoptimization::DeoptReason deopt_reason);
  bool can_create_loop_predicates(const PredicateBlock* profiled_loop_predicate_block) const;
  bool loop_predication_should_follow_branches(IdealLoopTree* loop, float& loop_trip_cnt);
  void loop_predication_follow_branches(Node *c, IdealLoopTree *loop, float loop_trip_cnt,
                                        PathFrequency& pf, Node_Stack& stack, VectorSet& seen,
                                        Node_List& if_proj_list);
  IfTrueNode* create_template_assertion_predicate(CountedLoopNode* loop_head, ParsePredicateNode* parse_predicate,
                                                  IfProjNode* new_control, int scale, Node* offset, Node* range);
  void eliminate_hoisted_range_check(IfTrueNode* hoisted_check_proj, IfTrueNode* template_assertion_predicate_proj);

  // Helper function to collect predicate for eliminating the useless ones
  void eliminate_useless_predicates();

  void eliminate_useless_parse_predicates();
  void mark_all_parse_predicates_useless() const;
  void mark_loop_associated_parse_predicates_useful();
  static void mark_useful_parse_predicates_for_loop(IdealLoopTree* loop);
  void add_useless_parse_predicates_to_igvn_worklist();

  void eliminate_useless_template_assertion_predicates();
  void collect_useful_template_assertion_predicates(Unique_Node_List& useful_predicates);
  static void collect_useful_template_assertion_predicates_for_loop(IdealLoopTree* loop, Unique_Node_List& useful_predicates);
  void eliminate_useless_template_assertion_predicates(Unique_Node_List& useful_predicates);

  void eliminate_useless_zero_trip_guard();

 public:
  // Change the control input of expensive nodes to allow commoning by
  // IGVN when it is guaranteed to not result in a more frequent
  // execution of the expensive node. Return true if progress.
  bool process_expensive_nodes();

  // Check whether node has become unreachable
  bool is_node_unreachable(Node *n) const {
    return !has_node(n) || n->is_unreachable(_igvn);
  }

  // Eliminate range-checks and other trip-counter vs loop-invariant tests.
  void do_range_check(IdealLoopTree *loop, Node_List &old_new);

  // Clone loop with an invariant test (that does not exit) and
  // insert a clone of the test that selects which version to
  // execute.
  void do_unswitching(IdealLoopTree* loop, Node_List& old_new);

  IfNode* find_unswitch_candidate(const IdealLoopTree* loop) const;

 private:
  static bool has_control_dependencies_from_predicates(LoopNode* head);
  static void revert_to_normal_loop(const LoopNode* loop_head);

  void hoist_invariant_check_casts(const IdealLoopTree* loop, const Node_List& old_new,
                                   const UnswitchedLoopSelector& unswitched_loop_selector);
  void add_unswitched_loop_version_bodies_to_igvn(IdealLoopTree* loop, const Node_List& old_new);
  static void increment_unswitch_counts(LoopNode* original_head, LoopNode* new_head);
  void remove_unswitch_candidate_from_loops(const Node_List& old_new, const UnswitchedLoopSelector& unswitched_loop_selector);
#ifndef PRODUCT
  static void trace_loop_unswitching_count(IdealLoopTree* loop, LoopNode* original_head);
  static void trace_loop_unswitching_impossible(const LoopNode* original_head);
  static void trace_loop_unswitching_result(const UnswitchedLoopSelector& unswitched_loop_selector,
                                            const LoopNode* original_head, const LoopNode* new_head);
#endif

 public:

  // Range Check Elimination uses this function!
  // Constrain the main loop iterations so the affine function:
  //    low_limit <= scale_con * I + offset  <  upper_limit
  // always holds true.  That is, either increase the number of iterations in
  // the pre-loop or the post-loop until the condition holds true in the main
  // loop.  Scale_con, offset and limit are all loop invariant.
  void add_constraint(jlong stride_con, jlong scale_con, Node* offset, Node* low_limit, Node* upper_limit, Node* pre_ctrl, Node** pre_limit, Node** main_limit);
  // Helper function for add_constraint().
  Node* adjust_limit(bool reduce, Node* scale, Node* offset, Node* rc_limit, Node* old_limit, Node* pre_ctrl, bool round);

  // Partially peel loop up through last_peel node.
  bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
  bool duplicate_loop_backedge(IdealLoopTree *loop, Node_List &old_new);

  // AutoVectorize the loop: replace scalar ops with vector ops.
  enum AutoVectorizeStatus {
    Impossible,      // This loop has the wrong shape to even try vectorization.
    Success,         // We just successfully vectorized the loop.
    TriedAndFailed,  // We tried to vectorize, but failed.
  };
  AutoVectorizeStatus auto_vectorize(IdealLoopTree* lpt, VSharedData &vshared);

  // Move an unordered Reduction out of loop if possible
  void move_unordered_reduction_out_of_loop(IdealLoopTree* loop);

  // Create a scheduled list of nodes control dependent on ctrl set.
  void scheduled_nodelist( IdealLoopTree *loop, VectorSet& ctrl, Node_List &sched );
  // Has a use in the vector set
  bool has_use_in_set( Node* n, VectorSet& vset );
  // Has use internal to the vector set (ie. not in a phi at the loop head)
  bool has_use_internal_to_set( Node* n, VectorSet& vset, IdealLoopTree *loop );
  // clone "n" for uses that are outside of loop
  int  clone_for_use_outside_loop( IdealLoopTree *loop, Node* n, Node_List& worklist );
  // clone "n" for special uses that are in the not_peeled region
  void clone_for_special_use_inside_loop( IdealLoopTree *loop, Node* n,
                                          VectorSet& not_peel, Node_List& sink_list, Node_List& worklist );
  // Insert phi(lp_entry_val, back_edge_val) at use->in(idx) for loop lp if phi does not already exist
  void insert_phi_for_loop( Node* use, uint idx, Node* lp_entry_val, Node* back_edge_val, LoopNode* lp );
#ifdef ASSERT
  // Validate the loop partition sets: peel and not_peel
  bool is_valid_loop_partition( IdealLoopTree *loop, VectorSet& peel, Node_List& peel_list, VectorSet& not_peel );
  // Ensure that uses outside of loop are of the right form
  bool is_valid_clone_loop_form( IdealLoopTree *loop, Node_List& peel_list,
                                 uint orig_exit_idx, uint clone_exit_idx);
  bool is_valid_clone_loop_exit_use( IdealLoopTree *loop, Node* use, uint exit_idx);
#endif

  // Returns nonzero constant stride if-node is a possible iv test (otherwise returns zero.)
  int stride_of_possible_iv( Node* iff );
  bool is_possible_iv_test( Node* iff ) { return stride_of_possible_iv(iff) != 0; }
  // Return the (unique) control output node that's in the loop (if it exists.)
  Node* stay_in_loop( Node* n, IdealLoopTree *loop);
  // Insert a signed compare loop exit cloned from an unsigned compare.
  IfNode* insert_cmpi_loop_exit(IfNode* if_cmpu, IdealLoopTree *loop);
  void remove_cmpi_loop_exit(IfNode* if_cmp, IdealLoopTree *loop);
  // Utility to register node "n" with PhaseIdealLoop
  void register_node(Node* n, IdealLoopTree* loop, Node* pred, uint ddepth);
  // Utility to create an if-projection
  ProjNode* proj_clone(ProjNode* p, IfNode* iff);
  // Force the iff control output to be the live_proj
  Node* short_circuit_if(IfNode* iff, ProjNode* live_proj);
  // Insert a region before an if projection
  RegionNode* insert_region_before_proj(ProjNode* proj);
  // Insert a new if before an if projection
  ProjNode* insert_if_before_proj(Node* left, bool Signed, BoolTest::mask relop, Node* right, ProjNode* proj);

  // Passed in a Phi merging (recursively) some nearly equivalent Bool/Cmps.
  // "Nearly" because all Nodes have been cloned from the original in the loop,
  // but the fall-in edges to the Cmp are different.  Clone bool/Cmp pairs
  // through the Phi recursively, and return a Bool.
  Node* clone_iff(PhiNode* phi);
  CmpNode* clone_bool(PhiNode* phi);


  // Rework addressing expressions to get the most loop-invariant stuff
  // moved out.  We'd like to do all associative operators, but it's especially
  // important (common) to do address expressions.
  Node* remix_address_expressions(Node* n);
  Node* remix_address_expressions_add_left_shift(Node* n, IdealLoopTree* n_loop, Node* n_ctrl, BasicType bt);

  // Convert add to muladd to generate MuladdS2I under certain criteria
  Node * convert_add_to_muladd(Node * n);

  // Attempt to use a conditional move instead of a phi/branch
  Node *conditional_move( Node *n );

  bool split_thru_phi_could_prevent_vectorization(Node* n, Node* n_blk);

  // Check for aggressive application of 'split-if' optimization,
  // using basic block level info.
  void  split_if_with_blocks     ( VectorSet &visited, Node_Stack &nstack);
  Node *split_if_with_blocks_pre ( Node *n );
  void  split_if_with_blocks_post( Node *n );
  Node *has_local_phi_input( Node *n );
  // Mark an IfNode as being dominated by a prior test,
  // without actually altering the CFG (and hence IDOM info).
  void dominated_by(IfProjNode* prevdom, IfNode* iff, bool flip = false, bool pin_array_access_nodes = false);
  void rewire_safe_outputs_to_dominator(Node* source, Node* dominator, bool pin_array_access_nodes);

  // Split Node 'n' through merge point
  RegionNode* split_thru_region(Node* n, RegionNode* region);
  // Split Node 'n' through merge point if there is enough win.
  Node *split_thru_phi( Node *n, Node *region, int policy );
  // Found an If getting its condition-code input from a Phi in the
  // same block.  Split thru the Region.
  void do_split_if(Node *iff, RegionNode** new_false_region = nullptr, RegionNode** new_true_region = nullptr);

  // Conversion of fill/copy patterns into intrinsic versions
  bool do_intrinsify_fill();
  bool intrinsify_fill(IdealLoopTree* lpt);
  bool match_fill_loop(IdealLoopTree* lpt, Node*& store, Node*& store_value,
                       Node*& shift, Node*& offset);

private:
  // Return a type based on condition control flow
  const TypeInt* filtered_type( Node *n, Node* n_ctrl);
  const TypeInt* filtered_type( Node *n ) { return filtered_type(n, nullptr); }
 // Helpers for filtered type
  const TypeInt* filtered_type_from_dominators( Node* val, Node *val_ctrl);

  // Helper functions
  Node *spinup( Node *iff, Node *new_false, Node *new_true, Node *region, Node *phi, small_cache *cache );
  Node *find_use_block( Node *use, Node *def, Node *old_false, Node *new_false, Node *old_true, Node *new_true );
  void handle_use( Node *use, Node *def, small_cache *cache, Node *region_dom, Node *new_false, Node *new_true, Node *old_false, Node *old_true );
  bool split_up( Node *n, Node *blk1, Node *blk2 );

  Node* place_outside_loop(Node* useblock, IdealLoopTree* loop) const;
  Node* try_move_store_before_loop(Node* n, Node *n_ctrl);
  void try_move_store_after_loop(Node* n);
  bool identical_backtoback_ifs(Node *n);
  bool can_split_if(Node *n_ctrl);
  bool cannot_split_division(const Node* n, const Node* region) const;
  static bool is_divisor_loop_phi(const Node* divisor, const Node* loop);
  bool loop_phi_backedge_type_contains_zero(const Node* phi_divisor, const Type* zero) const;

  // Determine if a method is too big for a/another round of split-if, based on
  // a magic (approximate) ratio derived from the equally magic constant 35000,
  // previously used for this purpose (but without relating to the node limit).
  bool must_throttle_split_if() {
    uint threshold = C->max_node_limit() * 2 / 5;
    return C->live_nodes() > threshold;
  }

  // A simplistic node request tracking mechanism, where
  //   = UINT_MAX   Request not valid or made final.
  //   < UINT_MAX   Nodes currently requested (estimate).
  uint _nodes_required;

  enum { REQUIRE_MIN = 70 };

  uint nodes_required() const { return _nodes_required; }

  // Given the _currently_  available number of nodes, check  whether there is
  // "room" for an additional request or not, considering the already required
  // number of  nodes.  Return TRUE if  the new request is  exceeding the node
  // budget limit, otherwise return FALSE.  Note that this interpretation will
  // act pessimistic on  additional requests when new nodes  have already been
  // generated since the 'begin'.  This behaviour fits with the intention that
  // node estimates/requests should be made upfront.
  bool exceeding_node_budget(uint required = 0) {
    assert(C->live_nodes() < C->max_node_limit(), "sanity");
    uint available = C->max_node_limit() - C->live_nodes();
    return available < required + _nodes_required + REQUIRE_MIN;
  }

  uint require_nodes(uint require, uint minreq = REQUIRE_MIN) {
    precond(require > 0);
    _nodes_required += MAX2(require, minreq);
    return _nodes_required;
  }

  bool may_require_nodes(uint require, uint minreq = REQUIRE_MIN) {
    return !exceeding_node_budget(require) && require_nodes(require, minreq) > 0;
  }

  uint require_nodes_begin() {
    assert(_nodes_required == UINT_MAX, "Bad state (begin).");
    _nodes_required = 0;
    return C->live_nodes();
  }

  // When a node request is final,  optionally check that the requested number
  // of nodes was  reasonably correct with respect to the  number of new nodes
  // introduced since the last 'begin'. Always check that we have not exceeded
  // the maximum node limit.
  void require_nodes_final(uint live_at_begin, bool check_estimate) {
    assert(_nodes_required < UINT_MAX, "Bad state (final).");

#ifdef ASSERT
    if (check_estimate) {
      // Check that the node budget request was not off by too much (x2).
      // Should this be the case we _surely_ need to improve the estimates
      // used in our budget calculations.
      if (C->live_nodes() - live_at_begin > 2 * _nodes_required) {
        log_info(compilation)("Bad node estimate: actual = %d >> request = %d",
                              C->live_nodes() - live_at_begin, _nodes_required);
      }
    }
#endif
    // Assert that we have stayed within the node budget limit.
    assert(C->live_nodes() < C->max_node_limit(),
           "Exceeding node budget limit: %d + %d > %d (request = %d)",
           C->live_nodes() - live_at_begin, live_at_begin,
           C->max_node_limit(), _nodes_required);

    _nodes_required = UINT_MAX;
  }

 public:
  // Clone Parse Predicates to slow and fast loop when unswitching a loop
  void clone_parse_and_assertion_predicates_to_unswitched_loop(IdealLoopTree* loop, Node_List& old_new,
                                                               IfProjNode*& true_path_loop_entry,
                                                               IfProjNode*& false_path_loop_entry);
 private:
  void clone_loop_predication_predicates_to_unswitched_loop(IdealLoopTree* loop, const Node_List& old_new,
                                                            const PredicateBlock* predicate_block,
                                                            Deoptimization::DeoptReason reason,
                                                            IfProjNode*& true_path_loop_entry,
                                                            IfProjNode*& false_path_loop_entry);
  void clone_parse_predicate_to_unswitched_loops(const PredicateBlock* predicate_block, Deoptimization::DeoptReason reason,
                                                 IfProjNode*& iffast_pred, IfProjNode*& ifslow_pred);
  IfProjNode* clone_parse_predicate_to_unswitched_loop(ParsePredicateSuccessProj* parse_predicate_proj, Node* new_entry,
                                                       Deoptimization::DeoptReason reason, bool slow_loop);
  void clone_assertion_predicates_to_unswitched_loop(IdealLoopTree* loop, const Node_List& old_new,
                                                     ParsePredicateSuccessProj* old_parse_predicate_proj,
                                                     ParsePredicateNode* true_path_loop_parse_predicate,
                                                     ParsePredicateNode* false_path_loop_parse_predicate);
  IfTrueNode* clone_assertion_predicate_for_unswitched_loops(IfTrueNode* template_assertion_predicate_success_proj,
                                                             ParsePredicateNode* unswitched_loop_parse_predicate);
  static void check_cloned_parse_predicate_for_unswitching(const Node* new_entry, bool is_fast_loop) PRODUCT_RETURN;

  bool _created_loop_node;
  DEBUG_ONLY(void dump_idoms(Node* early, Node* wrong_lca);)
  NOT_PRODUCT(void dump_idoms_in_reverse(const Node* n, const Node_List& idom_list) const;)

public:
  void set_created_loop_node() { _created_loop_node = true; }
  bool created_loop_node()     { return _created_loop_node; }
  void register_new_node(Node* n, Node* blk);
  void register_new_node_with_ctrl_of(Node* new_node, Node* ctrl_of) {
    register_new_node(new_node, get_ctrl(ctrl_of));
  }

  Node* clone_and_register(Node* n, Node* ctrl) {
    n = n->clone();
    register_new_node(n, ctrl);
    return n;
  }

#ifdef ASSERT
  void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
#endif

#ifndef PRODUCT
  void dump() const;
  void dump_idom(Node* n) const { dump_idom(n, 1000); } // For debugging
  void dump_idom(Node* n, uint count) const;
  void get_idoms(Node* n, uint count, Unique_Node_List& idoms) const;
  void dump(IdealLoopTree* loop, uint rpo_idx, Node_List &rpo_list) const;
  IdealLoopTree* get_loop_idx(Node* n) const {
    // Dead nodes have no loop, so return the top level loop instead
    return _loop_or_ctrl[n->_idx] ? (IdealLoopTree*)_loop_or_ctrl[n->_idx] : _ltree_root;
  }
  // Print some stats
  static void print_statistics();
  static int _loop_invokes;     // Count of PhaseIdealLoop invokes
  static int _loop_work;        // Sum of PhaseIdealLoop x _unique
  static volatile int _long_loop_candidates;
  static volatile int _long_loop_nests;
  static volatile int _long_loop_counted_loops;
#endif

#ifdef ASSERT
  void verify() const;
  bool verify_idom_and_nodes(Node* root, const PhaseIdealLoop* phase_verify) const;
  bool verify_idom(Node* n, const PhaseIdealLoop* phase_verify) const;
  bool verify_loop_ctrl(Node* n, const PhaseIdealLoop* phase_verify) const;
#endif

  void rpo(Node* start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list) const;

  void check_counted_loop_shape(IdealLoopTree* loop, Node* x, BasicType bt) NOT_DEBUG_RETURN;

  LoopNode* create_inner_head(IdealLoopTree* loop, BaseCountedLoopNode* head, IfNode* exit_test);


  int extract_long_range_checks(const IdealLoopTree* loop, jint stride_con, int iters_limit, PhiNode* phi,
                                Node_List &range_checks);

  void transform_long_range_checks(int stride_con, const Node_List &range_checks, Node* outer_phi,
                                   Node* inner_iters_actual_int, Node* inner_phi,
                                   Node* iv_add, LoopNode* inner_head);

  Node* get_late_ctrl_with_anti_dep(LoadNode* n, Node* early, Node* LCA);

  bool ctrl_of_use_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop, Node* ctrl);

  bool ctrl_of_all_uses_out_of_loop(const Node* n, Node* n_ctrl, IdealLoopTree* n_loop);

  Node* compute_early_ctrl(Node* n, Node* n_ctrl);

  void try_sink_out_of_loop(Node* n);

  Node* clamp(Node* R, Node* L, Node* H);

  bool safe_for_if_replacement(const Node* dom) const;

  void push_pinned_nodes_thru_region(IfNode* dom_if, Node* region);

  bool try_merge_identical_ifs(Node* n);

  void clone_loop_body(const Node_List& body, Node_List &old_new, CloneMap* cm);

  void fix_body_edges(const Node_List &body, IdealLoopTree* loop, const Node_List &old_new, int dd,
                      IdealLoopTree* parent, bool partial);

  void fix_ctrl_uses(const Node_List& body, const IdealLoopTree* loop, Node_List &old_new, CloneLoopMode mode,
                Node* side_by_side_idom, CloneMap* cm, Node_List &worklist);

  void fix_data_uses(Node_List& body, IdealLoopTree* loop, CloneLoopMode mode, IdealLoopTree* outer_loop,
                     uint new_counter, Node_List& old_new, Node_List& worklist, Node_List*& split_if_set,
                     Node_List*& split_bool_set, Node_List*& split_cex_set);

  void finish_clone_loop(Node_List* split_if_set, Node_List* split_bool_set, Node_List* split_cex_set);

  bool at_relevant_ctrl(Node* n, const Node* blk1, const Node* blk2);

  bool clone_cmp_loadklass_down(Node* n, const Node* blk1, const Node* blk2);
  void clone_loadklass_nodes_at_cmp_index(const Node* n, Node* cmp, int i);
  bool clone_cmp_down(Node* n, const Node* blk1, const Node* blk2);
  void clone_template_assertion_expression_down(Node* node);

  Node* similar_subtype_check(const Node* x, Node* r_in);

  void update_addp_chain_base(Node* x, Node* old_base, Node* new_base);

  bool can_move_to_inner_loop(Node* n, LoopNode* n_loop, Node* x);

  void pin_array_access_nodes_dependent_on(Node* ctrl);

  Node* ensure_node_and_inputs_are_above_pre_end(CountedLoopEndNode* pre_end, Node* node);
};


class AutoNodeBudget : public StackObj
{
public:
  enum budget_check_t { BUDGET_CHECK, NO_BUDGET_CHECK };

  AutoNodeBudget(PhaseIdealLoop* phase, budget_check_t chk = BUDGET_CHECK)
    : _phase(phase),
      _check_at_final(chk == BUDGET_CHECK),
      _nodes_at_begin(0)
  {
    precond(_phase != nullptr);

    _nodes_at_begin = _phase->require_nodes_begin();
  }

  ~AutoNodeBudget() {
#ifndef PRODUCT
    if (TraceLoopOpts) {
      uint request = _phase->nodes_required();
      uint delta   = _phase->C->live_nodes() - _nodes_at_begin;

      if (request < delta) {
        tty->print_cr("Exceeding node budget: %d < %d", request, delta);
      } else {
        uint const REQUIRE_MIN = PhaseIdealLoop::REQUIRE_MIN;
        // Identify the worst estimates as "poor" ones.
        if (request > REQUIRE_MIN && delta > 0) {
          if ((delta >  REQUIRE_MIN && request >  3 * delta) ||
              (delta <= REQUIRE_MIN && request > 10 * delta)) {
            tty->print_cr("Poor node estimate: %d >> %d", request, delta);
          }
        }
      }
    }
#endif // PRODUCT
    _phase->require_nodes_final(_nodes_at_begin, _check_at_final);
  }

private:
  PhaseIdealLoop* _phase;
  bool _check_at_final;
  uint _nodes_at_begin;
};

inline Node* IdealLoopTree::tail() {
  // Handle lazy update of _tail field.
  if (_tail->in(0) == nullptr) {
    _tail = _phase->get_ctrl(_tail);
  }
  return _tail;
}

inline Node* IdealLoopTree::head() {
  // Handle lazy update of _head field.
  if (_head->in(0) == nullptr) {
    _head = _phase->get_ctrl(_head);
  }
  return _head;
}

// Iterate over the loop tree using a preorder, left-to-right traversal.
//
// Example that visits all counted loops from within PhaseIdealLoop
//
//  for (LoopTreeIterator iter(_ltree_root); !iter.done(); iter.next()) {
//   IdealLoopTree* lpt = iter.current();
//   if (!lpt->is_counted()) continue;
//   ...
class LoopTreeIterator : public StackObj {
private:
  IdealLoopTree* _root;
  IdealLoopTree* _curnt;

public:
  LoopTreeIterator(IdealLoopTree* root) : _root(root), _curnt(root) {}

  bool done() { return _curnt == nullptr; }       // Finished iterating?

  void next();                                 // Advance to next loop tree

  IdealLoopTree* current() { return _curnt; }  // Return current value of iterator.
};

// 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;

  float check_and_truncate_frequency(float f) {
    assert(f >= 0, "Incorrect frequency");
    // We do not perform an exact (f <= 1) check
    // this would be error prone with rounding of floats.
    // Performing a check like (f <= 1+eps) would be of benefit,
    // however, it is not evident how to determine such an eps,
    // given that an arbitrary number of add/mul operations
    // are performed on these frequencies.
    return (f > 1) ? 1 : f;
  }

public:
  PathFrequency(Node* dom, PhaseIdealLoop* phase)
    : _dom(dom), _stack(0), _phase(phase) {
  }

  float to(Node* n);
};

// Class to clone a data node graph by taking a list of data nodes. This is done in 2 steps:
//   1. Clone the data nodes
//   2. Fix the cloned data inputs pointing to the old nodes to the cloned inputs by using an old->new mapping.
class DataNodeGraph : public StackObj {
  PhaseIdealLoop* const _phase;
  const Unique_Node_List& _data_nodes;
  OrigToNewHashtable _orig_to_new;

 public:
  DataNodeGraph(const Unique_Node_List& data_nodes, PhaseIdealLoop* phase)
      : _phase(phase),
        _data_nodes(data_nodes),
        // Use 107 as best guess which is the first resize value in ResizeableResourceHashtable::large_table_sizes.
        _orig_to_new(107, MaxNodeLimit)
  {
#ifdef ASSERT
    for (uint i = 0; i < data_nodes.size(); i++) {
      assert(!data_nodes[i]->is_CFG(), "only data nodes");
    }
#endif
  }
  NONCOPYABLE(DataNodeGraph);

 private:
  void clone(Node* node, Node* new_ctrl);
  void clone_data_nodes(Node* new_ctrl);
  void clone_data_nodes_and_transform_opaque_loop_nodes(const TransformStrategyForOpaqueLoopNodes& transform_strategy,
                                                        Node* new_ctrl);
  void rewire_clones_to_cloned_inputs();
  void transform_opaque_node(const TransformStrategyForOpaqueLoopNodes& transform_strategy, Node* node);

 public:
  // Clone the provided data node collection and rewire the clones in such a way to create an identical graph copy.
  // Set 'new_ctrl' as ctrl for the cloned nodes.
  const OrigToNewHashtable& clone(Node* new_ctrl) {
    assert(_orig_to_new.number_of_entries() == 0, "should not call this method twice in a row");
    clone_data_nodes(new_ctrl);
    rewire_clones_to_cloned_inputs();
    return _orig_to_new;
  }

  // Create a copy of the data nodes provided to the constructor by doing the following:
  // Clone all non-OpaqueLoop* nodes and rewire them to create an identical subgraph copy. For the OpaqueLoop* nodes,
  // apply the provided transformation strategy and include the transformed node into the subgraph copy to get a complete
  // "cloned-and-transformed" graph copy. For all newly cloned nodes (which could also be new OpaqueLoop* nodes), set
  // `new_ctrl` as ctrl.
  const OrigToNewHashtable& clone_with_opaque_loop_transform_strategy(
      const TransformStrategyForOpaqueLoopNodes& transform_strategy,
      Node* new_ctrl) {
    clone_data_nodes_and_transform_opaque_loop_nodes(transform_strategy, new_ctrl);
    rewire_clones_to_cloned_inputs();
    return _orig_to_new;
  }
};
#endif // SHARE_OPTO_LOOPNODE_HPP