1 /*
   2  * Copyright (c) 1997, 2010, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_OPTO_CHAITIN_HPP
  26 #define SHARE_VM_OPTO_CHAITIN_HPP
  27 
  28 #include "code/vmreg.hpp"
  29 #include "libadt/port.hpp"
  30 #include "memory/resourceArea.hpp"
  31 #include "opto/connode.hpp"
  32 #include "opto/live.hpp"
  33 #include "opto/matcher.hpp"
  34 #include "opto/phase.hpp"
  35 #include "opto/regalloc.hpp"
  36 #include "opto/regmask.hpp"
  37 
  38 class LoopTree;
  39 class MachCallNode;
  40 class MachSafePointNode;
  41 class Matcher;
  42 class PhaseCFG;
  43 class PhaseLive;
  44 class PhaseRegAlloc;
  45 class   PhaseChaitin;
  46 
  47 #define OPTO_DEBUG_SPLIT_FREQ  BLOCK_FREQUENCY(0.001)
  48 #define OPTO_LRG_HIGH_FREQ     BLOCK_FREQUENCY(0.25)
  49 
  50 //------------------------------LRG--------------------------------------------
  51 // Live-RanGe structure.
  52 class LRG : public ResourceObj {
  53 public:
  54   enum { SPILL_REG=29999 };     // Register number of a spilled LRG
  55 
  56   double _cost;                 // 2 for loads/1 for stores times block freq
  57   double _area;                 // Sum of all simultaneously live values
  58   double score() const;         // Compute score from cost and area
  59   double _maxfreq;              // Maximum frequency of any def or use
  60 
  61   Node *_def;                   // Check for multi-def live ranges
  62 #ifndef PRODUCT
  63   GrowableArray<Node*>* _defs;
  64 #endif
  65 
  66   uint _risk_bias;              // Index of LRG which we want to avoid color
  67   uint _copy_bias;              // Index of LRG which we want to share color
  68 
  69   uint _next;                   // Index of next LRG in linked list
  70   uint _prev;                   // Index of prev LRG in linked list
  71 private:
  72   uint _reg;                    // Chosen register; undefined if mask is plural
  73 public:
  74   // Return chosen register for this LRG.  Error if the LRG is not bound to
  75   // a single register.
  76   OptoReg::Name reg() const { return OptoReg::Name(_reg); }
  77   void set_reg( OptoReg::Name r ) { _reg = r; }
  78 
  79 private:
  80   uint _eff_degree;             // Effective degree: Sum of neighbors _num_regs
  81 public:
  82   int degree() const { assert( _degree_valid, "" ); return _eff_degree; }
  83   // Degree starts not valid and any change to the IFG neighbor
  84   // set makes it not valid.
  85   void set_degree( uint degree ) { _eff_degree = degree; debug_only(_degree_valid = 1;) }
  86   // Made a change that hammered degree
  87   void invalid_degree() { debug_only(_degree_valid=0;) }
  88   // Incrementally modify degree.  If it was correct, it should remain correct
  89   void inc_degree( uint mod ) { _eff_degree += mod; }
  90   // Compute the degree between 2 live ranges
  91   int compute_degree( LRG &l ) const;
  92 
  93 private:
  94   RegMask _mask;                // Allowed registers for this LRG
  95   uint _mask_size;              // cache of _mask.Size();
  96 public:
  97   int compute_mask_size() const { return _mask.is_AllStack() ? 65535 : _mask.Size(); }
  98   void set_mask_size( int size ) {
  99     assert((size == 65535) || (size == (int)_mask.Size()), "");
 100     _mask_size = size;
 101     debug_only(_msize_valid=1;)
 102     debug_only( if( _num_regs == 2 && !_fat_proj ) _mask.VerifyPairs(); )
 103   }
 104   void compute_set_mask_size() { set_mask_size(compute_mask_size()); }
 105   int mask_size() const { assert( _msize_valid, "mask size not valid" );
 106                           return _mask_size; }
 107   // Get the last mask size computed, even if it does not match the
 108   // count of bits in the current mask.
 109   int get_invalid_mask_size() const { return _mask_size; }
 110   const RegMask &mask() const { return _mask; }
 111   void set_mask( const RegMask &rm ) { _mask = rm; debug_only(_msize_valid=0;)}
 112   void AND( const RegMask &rm ) { _mask.AND(rm); debug_only(_msize_valid=0;)}
 113   void SUBTRACT( const RegMask &rm ) { _mask.SUBTRACT(rm); debug_only(_msize_valid=0;)}
 114   void Clear()   { _mask.Clear()  ; debug_only(_msize_valid=1); _mask_size = 0; }
 115   void Set_All() { _mask.Set_All(); debug_only(_msize_valid=1); _mask_size = RegMask::CHUNK_SIZE; }
 116   void Insert( OptoReg::Name reg ) { _mask.Insert(reg);  debug_only(_msize_valid=0;) }
 117   void Remove( OptoReg::Name reg ) { _mask.Remove(reg);  debug_only(_msize_valid=0;) }
 118   void ClearToPairs() { _mask.ClearToPairs(); debug_only(_msize_valid=0;) }
 119 
 120   // Number of registers this live range uses when it colors
 121 private:
 122   uint8 _num_regs;              // 2 for Longs and Doubles, 1 for all else
 123                                 // except _num_regs is kill count for fat_proj
 124 public:
 125   int num_regs() const { return _num_regs; }
 126   void set_num_regs( int reg ) { assert( _num_regs == reg || !_num_regs, "" ); _num_regs = reg; }
 127 
 128 private:
 129   // Number of physical registers this live range uses when it colors
 130   // Architecture and register-set dependent
 131   uint8 _reg_pressure;
 132 public:
 133   void set_reg_pressure(int i)  { _reg_pressure = i; }
 134   int      reg_pressure() const { return _reg_pressure; }
 135 
 136   // How much 'wiggle room' does this live range have?
 137   // How many color choices can it make (scaled by _num_regs)?
 138   int degrees_of_freedom() const { return mask_size() - _num_regs; }
 139   // Bound LRGs have ZERO degrees of freedom.  We also count
 140   // must_spill as bound.
 141   bool is_bound  () const { return _is_bound; }
 142   // Negative degrees-of-freedom; even with no neighbors this
 143   // live range must spill.
 144   bool not_free() const { return degrees_of_freedom() <  0; }
 145   // Is this live range of "low-degree"?  Trivially colorable?
 146   bool lo_degree () const { return degree() <= degrees_of_freedom(); }
 147   // Is this live range just barely "low-degree"?  Trivially colorable?
 148   bool just_lo_degree () const { return degree() == degrees_of_freedom(); }
 149 
 150   uint   _is_oop:1,             // Live-range holds an oop
 151          _is_float:1,           // True if in float registers
 152          _was_spilled1:1,       // True if prior spilling on def
 153          _was_spilled2:1,       // True if twice prior spilling on def
 154          _is_bound:1,           // live range starts life with no
 155                                 // degrees of freedom.
 156          _direct_conflict:1,    // True if def and use registers in conflict
 157          _must_spill:1,         // live range has lost all degrees of freedom
 158     // If _fat_proj is set, live range does NOT require aligned, adjacent
 159     // registers and has NO interferences.
 160     // If _fat_proj is clear, live range requires num_regs() to be a power of
 161     // 2, and it requires registers to form an aligned, adjacent set.
 162          _fat_proj:1,           //
 163          _was_lo:1,             // Was lo-degree prior to coalesce
 164          _msize_valid:1,        // _mask_size cache valid
 165          _degree_valid:1,       // _degree cache valid
 166          _has_copy:1,           // Adjacent to some copy instruction
 167          _at_risk:1;            // Simplify says this guy is at risk to spill
 168 
 169 
 170   // Alive if non-zero, dead if zero
 171   bool alive() const { return _def != NULL; }
 172   bool is_multidef() const { return _def == NodeSentinel; }
 173   bool is_singledef() const { return _def != NodeSentinel; }
 174 
 175 #ifndef PRODUCT
 176   void dump( ) const;
 177 #endif
 178 };
 179 
 180 //------------------------------LRG_List---------------------------------------
 181 // Map Node indices to Live RanGe indices.
 182 // Array lookup in the optimized case.
 183 class LRG_List : public ResourceObj {
 184   uint _cnt, _max;
 185   uint* _lidxs;
 186   ReallocMark _nesting;         // assertion check for reallocations
 187 public:
 188   LRG_List( uint max );
 189 
 190   uint lookup( uint nidx ) const {
 191     return _lidxs[nidx];
 192   }
 193   uint operator[] (uint nidx) const { return lookup(nidx); }
 194 
 195   void map( uint nidx, uint lidx ) {
 196     assert( nidx < _cnt, "oob" );
 197     _lidxs[nidx] = lidx;
 198   }
 199   void extend( uint nidx, uint lidx );
 200 
 201   uint Size() const { return _cnt; }
 202 };
 203 
 204 //------------------------------IFG--------------------------------------------
 205 //                         InterFerence Graph
 206 // An undirected graph implementation.  Created with a fixed number of
 207 // vertices.  Edges can be added & tested.  Vertices can be removed, then
 208 // added back later with all edges intact.  Can add edges between one vertex
 209 // and a list of other vertices.  Can union vertices (and their edges)
 210 // together.  The IFG needs to be really really fast, and also fairly
 211 // abstract!  It needs abstraction so I can fiddle with the implementation to
 212 // get even more speed.
 213 class PhaseIFG : public Phase {
 214   // Current implementation: a triangular adjacency list.
 215 
 216   // Array of adjacency-lists, indexed by live-range number
 217   IndexSet *_adjs;
 218 
 219   // Assertion bit for proper use of Squaring
 220   bool _is_square;
 221 
 222   // Live range structure goes here
 223   LRG *_lrgs;                   // Array of LRG structures
 224 
 225 public:
 226   // Largest live-range number
 227   uint _maxlrg;
 228 
 229   Arena *_arena;
 230 
 231   // Keep track of inserted and deleted Nodes
 232   VectorSet *_yanked;
 233 
 234   PhaseIFG( Arena *arena );
 235   void init( uint maxlrg );
 236 
 237   // Add edge between a and b.  Returns true if actually addded.
 238   int add_edge( uint a, uint b );
 239 
 240   // Add edge between a and everything in the vector
 241   void add_vector( uint a, IndexSet *vec );
 242 
 243   // Test for edge existance
 244   int test_edge( uint a, uint b ) const;
 245 
 246   // Square-up matrix for faster Union
 247   void SquareUp();
 248 
 249   // Return number of LRG neighbors
 250   uint neighbor_cnt( uint a ) const { return _adjs[a].count(); }
 251   // Union edges of b into a on Squared-up matrix
 252   void Union( uint a, uint b );
 253   // Test for edge in Squared-up matrix
 254   int test_edge_sq( uint a, uint b ) const;
 255   // Yank a Node and all connected edges from the IFG.  Be prepared to
 256   // re-insert the yanked Node in reverse order of yanking.  Return a
 257   // list of neighbors (edges) yanked.
 258   IndexSet *remove_node( uint a );
 259   // Reinsert a yanked Node
 260   void re_insert( uint a );
 261   // Return set of neighbors
 262   IndexSet *neighbors( uint a ) const { return &_adjs[a]; }
 263 
 264 #ifndef PRODUCT
 265   // Dump the IFG
 266   void dump() const;
 267   void stats() const;
 268   void verify( const PhaseChaitin * ) const;
 269 #endif
 270 
 271   //--------------- Live Range Accessors
 272   LRG &lrgs(uint idx) const { assert(idx < _maxlrg, "oob"); return _lrgs[idx]; }
 273 
 274   // Compute and set effective degree.  Might be folded into SquareUp().
 275   void Compute_Effective_Degree();
 276 
 277   // Compute effective degree as the sum of neighbors' _sizes.
 278   int effective_degree( uint lidx ) const;
 279 };
 280 
 281 // TEMPORARILY REPLACED WITH COMMAND LINE FLAG
 282 
 283 //// !!!!! Magic Constants need to move into ad file
 284 #ifdef SPARC
 285 //#define FLOAT_PRESSURE 30  /*     SFLT_REG_mask.Size() - 1 */
 286 //#define INT_PRESSURE   23  /* NOTEMP_I_REG_mask.Size() - 1 */
 287 #define FLOAT_INCREMENT(regs) regs
 288 #else
 289 //#define FLOAT_PRESSURE 6
 290 //#define INT_PRESSURE   6
 291 #define FLOAT_INCREMENT(regs) 1
 292 #endif
 293 
 294 //------------------------------Chaitin----------------------------------------
 295 // Briggs-Chaitin style allocation, mostly.
 296 class PhaseChaitin : public PhaseRegAlloc {
 297 
 298   int _trip_cnt;
 299   int _alternate;
 300 
 301   uint _maxlrg;                 // Max live range number
 302   LRG &lrgs(uint idx) const { return _ifg->lrgs(idx); }
 303   PhaseLive *_live;             // Liveness, used in the interference graph
 304   PhaseIFG *_ifg;               // Interference graph (for original chunk)
 305   Node_List **_lrg_nodes;       // Array of node; lists for lrgs which spill
 306   VectorSet _spilled_once;      // Nodes that have been spilled
 307   VectorSet _spilled_twice;     // Nodes that have been spilled twice
 308 
 309   LRG_List _names;              // Map from Nodes to Live RanGes
 310 
 311   // Union-find map.  Declared as a short for speed.
 312   // Indexed by live-range number, it returns the compacted live-range number
 313   LRG_List _uf_map;
 314   // Reset the Union-Find map to identity
 315   void reset_uf_map( uint maxlrg );
 316   // Remove the need for the Union-Find mapping
 317   void compress_uf_map_for_nodes( );
 318 
 319   // Combine the Live Range Indices for these 2 Nodes into a single live
 320   // range.  Future requests for any Node in either live range will
 321   // return the live range index for the combined live range.
 322   void Union( const Node *src, const Node *dst );
 323 
 324   void new_lrg( const Node *x, uint lrg );
 325 
 326   // Compact live ranges, removing unused ones.  Return new maxlrg.
 327   void compact();
 328 
 329   uint _lo_degree;              // Head of lo-degree LRGs list
 330   uint _lo_stk_degree;          // Head of lo-stk-degree LRGs list
 331   uint _hi_degree;              // Head of hi-degree LRGs list
 332   uint _simplified;             // Linked list head of simplified LRGs
 333 
 334   // Helper functions for Split()
 335   uint split_DEF( Node *def, Block *b, int loc, uint max, Node **Reachblock, Node **debug_defs, GrowableArray<uint> splits, int slidx );
 336   uint split_USE( Node *def, Block *b, Node *use, uint useidx, uint max, bool def_down, bool cisc_sp, GrowableArray<uint> splits, int slidx );
 337   int clone_projs( Block *b, uint idx, Node *con, Node *copy, uint &maxlrg );
 338   Node *split_Rematerialize(Node *def, Block *b, uint insidx, uint &maxlrg, GrowableArray<uint> splits,
 339                             int slidx, uint *lrg2reach, Node **Reachblock, bool walkThru);
 340   // True if lidx is used before any real register is def'd in the block
 341   bool prompt_use( Block *b, uint lidx );
 342   Node *get_spillcopy_wide( Node *def, Node *use, uint uidx );
 343   // Insert the spill at chosen location.  Skip over any intervening Proj's or
 344   // Phis.  Skip over a CatchNode and projs, inserting in the fall-through block
 345   // instead.  Update high-pressure indices.  Create a new live range.
 346   void insert_proj( Block *b, uint i, Node *spill, uint maxlrg );
 347 
 348   bool is_high_pressure( Block *b, LRG *lrg, uint insidx );
 349 
 350   uint _oldphi;                 // Node index which separates pre-allocation nodes
 351 
 352   Block **_blks;                // Array of blocks sorted by frequency for coalescing
 353 
 354   float _high_frequency_lrg;    // Frequency at which LRG will be spilled for debug info
 355 
 356 #ifndef PRODUCT
 357   bool _trace_spilling;
 358 #endif
 359 
 360 public:
 361   PhaseChaitin( uint unique, PhaseCFG &cfg, Matcher &matcher );
 362   ~PhaseChaitin() {}
 363 
 364   // Convert a Node into a Live Range Index - a lidx
 365   uint Find( const Node *n ) {
 366     uint lidx = n2lidx(n);
 367     uint uf_lidx = _uf_map[lidx];
 368     return (uf_lidx == lidx) ? uf_lidx : Find_compress(n);
 369   }
 370   uint Find_const( uint lrg ) const;
 371   uint Find_const( const Node *n ) const;
 372 
 373   // Do all the real work of allocate
 374   void Register_Allocate();
 375 
 376   uint n2lidx( const Node *n ) const { return _names[n->_idx]; }
 377 
 378   float high_frequency_lrg() const { return _high_frequency_lrg; }
 379 
 380 #ifndef PRODUCT
 381   bool trace_spilling() const { return _trace_spilling; }
 382 #endif
 383 
 384 private:
 385   // De-SSA the world.  Assign registers to Nodes.  Use the same register for
 386   // all inputs to a PhiNode, effectively coalescing live ranges.  Insert
 387   // copies as needed.
 388   void de_ssa();
 389   uint Find_compress( const Node *n );
 390   uint Find( uint lidx ) {
 391     uint uf_lidx = _uf_map[lidx];
 392     return (uf_lidx == lidx) ? uf_lidx : Find_compress(lidx);
 393   }
 394   uint Find_compress( uint lidx );
 395 
 396   uint Find_id( const Node *n ) {
 397     uint retval = n2lidx(n);
 398     assert(retval == Find(n),"Invalid node to lidx mapping");
 399     return retval;
 400   }
 401 
 402   // Add edge between reg and everything in the vector.
 403   // Same as _ifg->add_vector(reg,live) EXCEPT use the RegMask
 404   // information to trim the set of interferences.  Return the
 405   // count of edges added.
 406   void interfere_with_live( uint reg, IndexSet *live );
 407   // Count register pressure for asserts
 408   uint count_int_pressure( IndexSet *liveout );
 409   uint count_float_pressure( IndexSet *liveout );
 410 
 411   // Build the interference graph using virtual registers only.
 412   // Used for aggressive coalescing.
 413   void build_ifg_virtual( );
 414 
 415   // Build the interference graph using physical registers when available.
 416   // That is, if 2 live ranges are simultaneously alive but in their
 417   // acceptable register sets do not overlap, then they do not interfere.
 418   uint build_ifg_physical( ResourceArea *a );
 419 
 420   // Gather LiveRanGe information, including register masks and base pointer/
 421   // derived pointer relationships.
 422   void gather_lrg_masks( bool mod_cisc_masks );
 423 
 424   // Force the bases of derived pointers to be alive at GC points.
 425   bool stretch_base_pointer_live_ranges( ResourceArea *a );
 426   // Helper to stretch above; recursively discover the base Node for
 427   // a given derived Node.  Easy for AddP-related machine nodes, but
 428   // needs to be recursive for derived Phis.
 429   Node *find_base_for_derived( Node **derived_base_map, Node *derived, uint &maxlrg );
 430 
 431   // Set the was-lo-degree bit.  Conservative coalescing should not change the
 432   // colorability of the graph.  If any live range was of low-degree before
 433   // coalescing, it should Simplify.  This call sets the was-lo-degree bit.
 434   void set_was_low();
 435 
 436   // Split live-ranges that must spill due to register conflicts (as opposed
 437   // to capacity spills).  Typically these are things def'd in a register
 438   // and used on the stack or vice-versa.
 439   void pre_spill();
 440 
 441   // Init LRG caching of degree, numregs.  Init lo_degree list.
 442   void cache_lrg_info( );
 443 
 444   // Simplify the IFG by removing LRGs of low degree with no copies
 445   void Pre_Simplify();
 446 
 447   // Simplify the IFG by removing LRGs of low degree
 448   void Simplify();
 449 
 450   // Select colors by re-inserting edges into the IFG.
 451   // Return TRUE if any spills occurred.
 452   uint Select( );
 453   // Helper function for select which allows biased coloring
 454   OptoReg::Name choose_color( LRG &lrg, int chunk );
 455   // Helper function which implements biasing heuristic
 456   OptoReg::Name bias_color( LRG &lrg, int chunk );
 457 
 458   // Split uncolorable live ranges
 459   // Return new number of live ranges
 460   uint Split( uint maxlrg );
 461 
 462   // Copy 'was_spilled'-edness from one Node to another.
 463   void copy_was_spilled( Node *src, Node *dst );
 464   // Set the 'spilled_once' or 'spilled_twice' flag on a node.
 465   void set_was_spilled( Node *n );
 466 
 467   // Convert ideal spill-nodes into machine loads & stores
 468   // Set C->failing when fixup spills could not complete, node limit exceeded.
 469   void fixup_spills();
 470 
 471   // Post-Allocation peephole copy removal
 472   void post_allocate_copy_removal();
 473   Node *skip_copies( Node *c );
 474   // Replace the old node with the current live version of that value
 475   // and yank the old value if it's dead.
 476   int replace_and_yank_if_dead( Node *old, OptoReg::Name nreg,
 477                                 Block *current_block, Node_List& value, Node_List& regnd ) {
 478     Node* v = regnd[nreg];
 479     assert(v->outcnt() != 0, "no dead values");
 480     old->replace_by(v);
 481     return yank_if_dead(old, current_block, &value, &regnd);
 482   }
 483 
 484   int yank_if_dead( Node *old, Block *current_block, Node_List *value, Node_List *regnd );
 485   int elide_copy( Node *n, int k, Block *current_block, Node_List &value, Node_List &regnd, bool can_change_regs );
 486   int use_prior_register( Node *copy, uint idx, Node *def, Block *current_block, Node_List &value, Node_List &regnd );
 487   bool may_be_copy_of_callee( Node *def ) const;
 488 
 489   // If nreg already contains the same constant as val then eliminate it
 490   bool eliminate_copy_of_constant(Node* val, Node* n,
 491                                   Block *current_block, Node_List& value, Node_List &regnd,
 492                                   OptoReg::Name nreg, OptoReg::Name nreg2);
 493   // Extend the node to LRG mapping
 494   void add_reference( const Node *node, const Node *old_node);
 495 
 496 private:
 497 
 498   static int _final_loads, _final_stores, _final_copies, _final_memoves;
 499   static double _final_load_cost, _final_store_cost, _final_copy_cost, _final_memove_cost;
 500   static int _conserv_coalesce, _conserv_coalesce_pair;
 501   static int _conserv_coalesce_trie, _conserv_coalesce_quad;
 502   static int _post_alloc;
 503   static int _lost_opp_pp_coalesce, _lost_opp_cflow_coalesce;
 504   static int _used_cisc_instructions, _unused_cisc_instructions;
 505   static int _allocator_attempts, _allocator_successes;
 506 
 507 #ifndef PRODUCT
 508   static uint _high_pressure, _low_pressure;
 509 
 510   void dump() const;
 511   void dump( const Node *n ) const;
 512   void dump( const Block * b ) const;
 513   void dump_degree_lists() const;
 514   void dump_simplified() const;
 515   void dump_lrg( uint lidx, bool defs_only) const;
 516   void dump_lrg( uint lidx) const {
 517     // dump defs and uses by default
 518     dump_lrg(lidx, false);
 519   }
 520   void dump_bb( uint pre_order ) const;
 521 
 522   // Verify that base pointers and derived pointers are still sane
 523   void verify_base_ptrs( ResourceArea *a ) const;
 524 
 525   void verify( ResourceArea *a, bool verify_ifg = false ) const;
 526 
 527   void dump_for_spill_split_recycle() const;
 528 
 529 public:
 530   void dump_frame() const;
 531   char *dump_register( const Node *n, char *buf  ) const;
 532 private:
 533   static void print_chaitin_statistics();
 534 #endif
 535   friend class PhaseCoalesce;
 536   friend class PhaseAggressiveCoalesce;
 537   friend class PhaseConservativeCoalesce;
 538 };
 539 
 540 #endif // SHARE_VM_OPTO_CHAITIN_HPP