jdk8-mips64-public/hotspot: src/share/vm/opto/loopnode.hpp@7ae4e26cb1e0 (annotated)

src/share/vm/opto/loopnode.hpp@7ae4e26cb1e0 (annotated)

src/share/vm/opto/loopnode.hpp

Thu, 12 Oct 2017 21:27:07 +0800

author: aoqi
date: Thu, 12 Oct 2017 21:27:07 +0800
changeset 7535: 7ae4e26cb1e0
parent 7394: 5b8e0f84f00f
parent 6876: 710a3c8b516e
child 8604: 04d83ba48607
permissions: -rw-r--r--

merge

 /*
  * Copyright (c) 1998, 2013, 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.
  *
  */
 #ifndef SHARE_VM_OPTO_LOOPNODE_HPP
 #define SHARE_VM_OPTO_LOOPNODE_HPP
 #include "opto/cfgnode.hpp"
 #include "opto/multnode.hpp"
 #include "opto/phaseX.hpp"
 #include "opto/subnode.hpp"
 #include "opto/type.hpp"
 class CmpNode;
 class CountedLoopEndNode;
 class CountedLoopNode;
 class IdealLoopTree;
 class LoopNode;
 class Node;
 class PhaseIdealLoop;
 class VectorSet;
 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:
   short _loop_flags;
   // Names for flag bitfields
   enum { Normal=0, Pre=1, Main=2, Post=3, PreMainPostFlagsMask=3,
          MainHasNoPreLoop=4,
          HasExactTripCount=8,
          InnerLoop=16,
          PartialPeelLoop=32,
          PartialPeelFailed=64 };
   char _unswitch_count;
   enum { _unswitch_max=3 };
 public:
   // Names for edge indices
   enum { Self=0, EntryControl, LoopBackControl };
   int is_inner_loop() const { return _loop_flags & InnerLoop; }
   void set_inner_loop() { _loop_flags |= InnerLoop; }
   int is_partial_peel_loop() const { return _loop_flags & PartialPeelLoop; }
   void set_partial_peel_loop() { _loop_flags |= PartialPeelLoop; }
   int partial_peel_has_failed() const { return _loop_flags & PartialPeelFailed; }
   void mark_partial_peel_failed() { _loop_flags |= PartialPeelFailed; }
   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;
   }
   LoopNode( Node *entry, Node *backedge ) : RegionNode(3), _loop_flags(0), _unswitch_count(0) {
     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(PhaseTransform* phase) const {
     return req() == 3 && in(0) != NULL &&
       in(1) != NULL && phase->type(in(1)) != Type::TOP &&
       in(2) != NULL && phase->type(in(2)) != Type::TOP;
   }
   bool is_valid_counted_loop() const;
 #ifndef PRODUCT
   virtual void dump_spec(outputStream *st) const;
 #endif
 };
 //------------------------------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 CountedLoopNode : public LoopNode {
   // 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;
   // Expected trip count from profile data
   float _profile_trip_cnt;
   // 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;
 public:
   CountedLoopNode( Node *entry, Node *backedge )
     : LoopNode(entry, backedge), _main_idx(0), _trip_count(max_juint),
       _profile_trip_cnt(COUNT_UNKNOWN), _unrolled_count_log2(0),
       _node_count_before_unroll(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);
   Node *init_control() const { return in(EntryControl); }
   Node *back_control() const { return in(LoopBackControl); }
   CountedLoopEndNode *loopexit() const;
   Node *init_trip() const;
   Node *stride() const;
   int   stride_con() const;
   bool  stride_is_con() const;
   Node *limit() const;
   Node *incr() const;
   Node *phi() const;
   // Match increment with optional truncation
   static Node* match_incr_with_optional_truncation(Node* expr, Node** trunc1, Node** trunc2, const TypeInt** trunc_type);
   // 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.
   int is_normal_loop() const { return (_loop_flags&PreMainPostFlagsMask) == Normal; }
   int is_pre_loop   () const { return (_loop_flags&PreMainPostFlagsMask) == Pre;    }
   int is_main_loop  () const { return (_loop_flags&PreMainPostFlagsMask) == Main;   }
   int is_post_loop  () const { return (_loop_flags&PreMainPostFlagsMask) == Post;   }
   int is_main_no_pre_loop() const { return _loop_flags & MainHasNoPreLoop; }
   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_profile_trip_cnt(float ptc) { _profile_trip_cnt = ptc; }
   float profile_trip_cnt()             { return _profile_trip_cnt; }
   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; }
 #ifndef PRODUCT
   virtual void dump_spec(outputStream *st) const;
 #endif
 };
 //------------------------------CountedLoopEndNode-----------------------------
 // CountedLoopEndNodes end simple trip counted loops.  They act much like
 // IfNodes.
 class CountedLoopEndNode : public IfNode {
 public:
   enum { TestControl, TestValue };
   CountedLoopEndNode( Node *control, Node *test, float prob, float cnt )
     : IfNode( control, test, prob, cnt) {
     init_class_id(Class_CountedLoopEnd);
   }
   virtual int Opcode() const;
   Node *cmp_node() const            { return (in(TestValue)->req() >=2) ? in(TestValue)->in(1) : NULL; }
   Node *incr() const                { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
   Node *limit() const               { Node *tmp = cmp_node(); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
   Node *stride() const              { Node *tmp = incr    (); return (tmp && tmp->req()==3) ? tmp->in(2) : NULL; }
   Node *phi() const                 { Node *tmp = incr    (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
   Node *init_trip() const           { Node *tmp = phi     (); return (tmp && tmp->req()==3) ? tmp->in(1) : NULL; }
   int stride_con() const;
   bool stride_is_con() const        { Node *tmp = stride  (); return (tmp != NULL && tmp->is_Con()); }
   BoolTest::mask test_trip() const  { return in(TestValue)->as_Bool()->_test._test; }
   CountedLoopNode *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
     if (phi() == NULL) {
       return NULL;
     }
     Node *ln = phi()->in(0);
     if (ln->is_CountedLoop() && ln->as_CountedLoop()->loopexit() == this) {
       return (CountedLoopNode*)ln;
     }
     return NULL;
   }
 #ifndef PRODUCT
   virtual void dump_spec(outputStream *st) const;
 #endif
 };
 inline CountedLoopEndNode *CountedLoopNode::loopexit() const {
   Node *bc = back_control();
   if( bc == NULL ) return NULL;
   Node *le = bc->in(0);
   if( le->Opcode() != Op_CountedLoopEnd )
     return NULL;
   return (CountedLoopEndNode*)le;
 }
 inline Node *CountedLoopNode::init_trip() const { return loopexit() ? loopexit()->init_trip() : NULL; }
 inline Node *CountedLoopNode::stride() const { return loopexit() ? loopexit()->stride() : NULL; }
 inline int CountedLoopNode::stride_con() const { return loopexit() ? loopexit()->stride_con() : 0; }
 inline bool CountedLoopNode::stride_is_con() const { return loopexit() && loopexit()->stride_is_con(); }
 inline Node *CountedLoopNode::limit() const { return loopexit() ? loopexit()->limit() : NULL; }
 inline Node *CountedLoopNode::incr() const { return loopexit() ? loopexit()->incr() : NULL; }
 inline Node *CountedLoopNode::phi() const { return loopexit() ? loopexit()->phi() : NULL; }
 //------------------------------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(0,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( PhaseTransform *phase ) const;
   virtual Node *Ideal(PhaseGVN *phase, bool can_reshape);
   virtual Node *Identity( PhaseTransform *phase );
 };
 // -----------------------------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 tail is NULL then this loop has multiple backedges as part of the
   // same loop.  During cleanup I'll peel off the multiple backedges; merge
   // them at the loop bottom and flow 1 real backedge into the loop.
   Node *_head;                  // Head of loop
   Node *_tail;                  // Tail of loop
   inline Node *tail();          // Handle lazy update of _tail field
   PhaseIdealLoop* _phase;
   Node_List _body;              // Loop body for inner loops
   uint8 _nest;                  // Nesting depth
   uint8 _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
   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(0), _next(0), _child(0),
       _head(head), _tail(tail),
       _phase(phase),
       _safepts(NULL),
       _required_safept(NULL),
       _allow_optimizations(true),
       _nest(0), _irreducible(0), _has_call(0), _has_sfpt(0), _rce_candidate(0)
   { }
   // Is 'l' a member of 'this'?
   int 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);
   // 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);
   // 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;
   // Returns true if ctrl is executed on every complete iteration
   bool dominates_backedge(Node* ctrl);
   // 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 policy_do_remove_empty_loop( PhaseIdealLoop *phase );
   // Convert one iteration loop into normal code.
   bool policy_do_one_iteration_loop( PhaseIdealLoop *phase );
   // Return TRUE or FALSE if the loop should be peeled or not.  Peel if we can
   // make some loop-invariant test (usually a null-check) happen before the
   // loop.
   bool policy_peeling( PhaseIdealLoop *phase ) const;
   // 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.  Unroll if
   // the loop is a CountedLoop and the body is small enough.
   bool policy_unroll( PhaseIdealLoop *phase ) const;
   // 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 ) const;
   // Return TRUE or FALSE if the loop should be cache-line aligned.
   // Gather the expression that does the alignment.  Note that only
   // one array base can be aligned in a loop (unless the VM guarantees
   // mutual alignment).  Note that if we vectorize short memory ops
   // into longer memory ops, we may want to increase alignment.
   bool policy_align( PhaseIdealLoop *phase ) const;
   // Return TRUE if "iff" is a range check.
   bool is_range_check_if(IfNode *iff, PhaseIdealLoop *phase, Invariance& invar) const;
   // Compute loop exact trip count if possible
   void compute_exact_trip_count( PhaseIdealLoop *phase );
   // Compute loop trip count from profile data
   void compute_profile_trip_cnt( PhaseIdealLoop *phase );
   // Reassociate invariant expressions.
   void reassociate_invariants(PhaseIdealLoop *phase);
   // Reassociate invariant add and subtract expressions.
   Node* reassociate_add_sub(Node* n1, PhaseIdealLoop *phase);
   // Return nonzero index of invariant operand if invariant and variant
   // are combined with an Add or Sub. Helper for reassociate_invariants.
   int is_invariant_addition(Node* n, PhaseIdealLoop *phase);
   // 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_loop()    { return !_irreducible && _tail && !_tail->is_top(); }
   bool is_inner()   { return is_loop() && _child == NULL; }
   bool is_counted() { return is_loop() && _head != NULL && _head->is_CountedLoop(); }
 #ifndef PRODUCT
   void dump_head( ) const;      // Dump loop head only
   void dump() const;            // Dump this loop recursively
   void verify_tree(IdealLoopTree *loop, const IdealLoopTree *parent) const;
 #endif
 };
 // -----------------------------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;
   // 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;
   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() {
     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( ) {
     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; }
   // 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( Node *n ) const { return ((intptr_t)_nodes[n->_idx]) & 1; }
   // clear out dead code after build_loop_late
   Node_List _deadlist;
   // Support for faster execution of get_late_ctrl()/dom_lca()
   // when a node has many uses and dominator depth is deep.
   Node_Array _dom_lca_tags;
   void   init_dom_lca_tags();
   void   clear_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 != NULL && 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 != NULL) {
       if (ctrl->is_MultiBranch()) {
         ctrl = ctrl->in(0);
       }
       assert(ctrl->is_CFG(), "CFG");
     }
     return ctrl;
   }
   bool cast_incr_before_loop(Node* incr, Node* ctrl, Node* loop);
 public:
   bool has_node( Node* n ) const {
     guarantee(n != NULL, "No Node.");
     return _nodes[n->_idx] != NULL;
   }
   // 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 );
   void set_subtree_ctrl( Node *root );
   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" );
     _nodes.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 == NULL) old_loop->_body.yank(n);
       if (new_loop->_child == NULL) 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( Node *i ) {
     assert(has_node(i), "");
     Node *n = get_ctrl_no_update(i);
     _nodes.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;
   }
   // true if CFG node d dominates CFG node n
   bool is_dominator(Node *d, 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;
     }
   }
 private:
   Node *get_ctrl_no_update( Node *i ) const {
     assert( has_ctrl(i), "" );
     Node *n = (Node*)(((intptr_t)_nodes[i->_idx]) & ~1);
     if (!n->in(0)) {
       // Skip dead CFG nodes
       do {
         n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
       } 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 ) {
     _nodes.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.
 public:
   void lazy_update( Node *old_node, Node *new_node ) {
     assert( old_node != new_node, "no cycles please" );
     //old_node->set_req( 1, new_node /*NO DU INFO*/ );
     // Nodes always have DU info now, so re-use the side array slot
     // for this node to provide the forwarding pointer.
     _nodes.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 );
   }
   void lazy_replace_proj( Node *old_node, Node *new_node ) {
     assert( old_node->req() == 1, "use this for Projs" );
     _igvn.hash_delete(old_node); // Must hash-delete before hacking edges
     old_node->add_req( NULL );
     lazy_replace( 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 );
   // 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 ( Node* n );
   // 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
   Node* idom_no_update(Node* d) const {
     assert(d->_idx < _idom_size, "oob");
     Node* n = _idom[d->_idx];
     assert(n != NULL,"Bad immediate dominator info.");
     while (n->in(0) == NULL) {  // Skip dead CFG nodes
       //n = n->in(1);
       n = (Node*)(((intptr_t)_nodes[n->_idx]) & ~1);
       assert(n != NULL,"Bad immediate dominator info.");
     }
     return n;
   }
   Node *idom(Node* d) const {
     uint didx = d->_idx;
     Node *n = idom_no_update(d);
     _idom[didx] = n;            // Lazily remove dead CFG nodes from table.
     return n;
   }
   uint dom_depth(Node* d) const {
     guarantee(d != NULL, "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);
   // Perform verification that the graph is valid.
   PhaseIdealLoop( PhaseIterGVN &igvn) :
     PhaseTransform(Ideal_Loop),
     _igvn(igvn),
     _dom_lca_tags(arena()), // Thread::resource_area
     _verify_me(NULL),
     _verify_only(true) {
     build_and_optimize(false, false);
   }
   // build the loop tree and perform any requested optimizations
   void build_and_optimize(bool do_split_if, bool skip_loop_opts);
 public:
   // Dominators for the sea of nodes
   void Dominators();
   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;
   // Compute the Ideal Node to Loop mapping
   PhaseIdealLoop( PhaseIterGVN &igvn, bool do_split_ifs, bool skip_loop_opts = false) :
     PhaseTransform(Ideal_Loop),
     _igvn(igvn),
     _dom_lca_tags(arena()), // Thread::resource_area
     _verify_me(NULL),
     _verify_only(false) {
     build_and_optimize(do_split_ifs, skip_loop_opts);
   }
   // Verify that verify_me made the same decisions as a fresh run.
   PhaseIdealLoop( PhaseIterGVN &igvn, const PhaseIdealLoop *verify_me) :
     PhaseTransform(Ideal_Loop),
     _igvn(igvn),
     _dom_lca_tags(arena()), // Thread::resource_area
     _verify_me(verify_me),
     _verify_only(false) {
     build_and_optimize(false, false);
   }
   // 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
     PhaseIdealLoop v(igvn);
 #endif
   }
   // True if the method has at least 1 irreducible loop
   bool _has_irreducible_loops;
   // Per-Node transform
   virtual Node *transform( Node *a_node ) { return 0; }
   bool is_counted_loop( Node *x, IdealLoopTree *loop );
   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*)_nodes[n->_idx];
   }
   // 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.
   void clone_loop( IdealLoopTree *loop, Node_List &old_new, int dom_depth,
                    Node* side_by_side_idom = NULL);
   // 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 );
   // 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, int* p_scale);
   // Return true if exp is a scaled induction var plus (or minus) constant
   bool is_scaled_iv_plus_offset(Node* exp, Node* iv, int* p_scale, Node** p_offset, int depth = 0);
   // Create a new if above the uncommon_trap_if_pattern for the predicate to be promoted
   ProjNode* create_new_if_for_predicate(ProjNode* cont_proj, Node* new_entry,
                                         Deoptimization::DeoptReason reason);
   void register_control(Node* n, IdealLoopTree *loop, Node* pred);
   // Clone loop predicates to cloned loops (peeled, unswitched)
   static ProjNode* clone_predicate(ProjNode* predicate_proj, Node* new_entry,
                                    Deoptimization::DeoptReason reason,
                                    PhaseIdealLoop* loop_phase,
                                    PhaseIterGVN* igvn);
   static Node* clone_loop_predicates(Node* old_entry, Node* new_entry,
                                          bool clone_limit_check,
                                          PhaseIdealLoop* loop_phase,
                                          PhaseIterGVN* igvn);
   Node* clone_loop_predicates(Node* old_entry, Node* new_entry, bool clone_limit_check);
   static Node* skip_loop_predicates(Node* entry);
   // Find a good location to insert a predicate
   static ProjNode* find_predicate_insertion_point(Node* start_c, Deoptimization::DeoptReason reason);
   // Find a predicate
   static Node* find_predicate(Node* entry);
   // Construct a range check for a predicate if
   BoolNode* rc_predicate(IdealLoopTree *loop, Node* ctrl,
                          int scale, Node* offset,
                          Node* init, Node* limit, Node* stride,
                          Node* range, bool upper);
   // Implementation of the loop predication to promote checks outside the loop
   bool loop_predication_impl(IdealLoopTree *loop);
   // Helper function to collect predicate for eliminating the useless ones
   void collect_potentially_useful_predicates(IdealLoopTree *loop, Unique_Node_List &predicate_opaque1);
   void eliminate_useless_predicates();
   // 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 );
   // Create a slow version of the loop by cloning the loop
   // and inserting an if to select fast-slow versions.
   ProjNode* create_slow_version_of_loop(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);
   // Find candidate "if" for unswitching
   IfNode* find_unswitching_candidate(const IdealLoopTree *loop) const;
   // 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( int stride_con, int 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( int stride_con, Node * scale, Node *offset, Node *rc_limit, Node *loop_limit, Node *pre_ctrl );
   // Partially peel loop up through last_peel node.
   bool partial_peel( IdealLoopTree *loop, Node_List &old_new );
   // 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, int 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.
   BoolNode *clone_iff( PhiNode *phi, IdealLoopTree *loop );
   CmpNode *clone_bool( PhiNode *phi, IdealLoopTree *loop );
   // 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 );
   // Attempt to use a conditional move instead of a phi/branch
   Node *conditional_move( Node *n );
   // Reorganize offset computations to lower register pressure.
   // Mostly prevent loop-fallout uses of the pre-incremented trip counter
   // (which are then alive with the post-incremented trip counter
   // forcing an extra register move)
   void reorg_offsets( IdealLoopTree *loop );
   // 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( Node *prevdom, Node *iff, bool flip = false, bool exclude_loop_predicate = false );
   // Split Node 'n' through merge point
   Node *split_thru_region( Node *n, Node *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 );
   // Conversion of fill/copy patterns into intrisic 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, NULL); }
  // 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 );
   void sink_use( Node *use, Node *post_loop );
   Node *place_near_use( Node *useblock ) const;
   bool _created_loop_node;
 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 );
 #ifdef ASSERT
   void dump_bad_graph(const char* msg, Node* n, Node* early, Node* LCA);
 #endif
 #ifndef PRODUCT
   void dump( ) const;
   void dump( IdealLoopTree *loop, uint rpo_idx, Node_List &rpo_list ) const;
   void rpo( Node *start, Node_Stack &stk, VectorSet &visited, Node_List &rpo_list ) const;
   void verify() const;          // Major slow  :-)
   void verify_compare( Node *n, const PhaseIdealLoop *loop_verify, VectorSet &visited ) const;
   IdealLoopTree *get_loop_idx(Node* n) const {
     // Dead nodes have no loop, so return the top level loop instead
     return _nodes[n->_idx] ? (IdealLoopTree*)_nodes[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
 #endif
 };
 inline Node* IdealLoopTree::tail() {
 // Handle lazy update of _tail field
   Node *n = _tail;
   //while( !n->in(0) )  // Skip dead CFG nodes
     //n = n->in(1);
   if (n->in(0) == NULL)
     n = _phase->get_ctrl(n);
   _tail = n;
   return n;
 }
 // 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 == NULL; }       // Finished iterating?
   void next();                                 // Advance to next loop tree
   IdealLoopTree* current() { return _curnt; }  // Return current value of iterator.
 };
 #endif // SHARE_VM_OPTO_LOOPNODE_HPP

Mercurial > jdk8-mips64-public > hotspot / annotate

src/share/vm/opto/loopnode.hpp@7ae4e26cb1e0 (annotated)

src/share/vm/opto/loopnode.hpp