src/share/vm/oops/generateOopMap.hpp

Tue, 05 Apr 2011 14:12:31 -0700

author
trims
date
Tue, 05 Apr 2011 14:12:31 -0700
changeset 2708
1d1603768966
parent 2497
3582bf76420e
child 4037
da91efe96a93
permissions
-rw-r--r--

7010070: Update all 2010 Oracle-changed OpenJDK files to have the proper copyright dates - second pass
Summary: Update the copyright to be 2010 on all changed files in OpenJDK
Reviewed-by: ohair

     1 /*
     2  * Copyright (c) 1997, 2011, 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  */
    25 #ifndef SHARE_VM_OOPS_GENERATEOOPMAP_HPP
    26 #define SHARE_VM_OOPS_GENERATEOOPMAP_HPP
    28 #include "interpreter/bytecodeStream.hpp"
    29 #include "memory/allocation.inline.hpp"
    30 #include "memory/universe.inline.hpp"
    31 #include "oops/methodOop.hpp"
    32 #include "oops/oopsHierarchy.hpp"
    33 #include "runtime/signature.hpp"
    35 // Forward definition
    36 class MethodOopMap;
    37 class GenerateOopMap;
    38 class BasicBlock;
    39 class CellTypeState;
    40 class StackMap;
    42 // These two should be removed. But requires som code to be cleaned up
    43 #define MAXARGSIZE      256      // This should be enough
    44 #define MAX_LOCAL_VARS  65536    // 16-bit entry
    46 typedef void (*jmpFct_t)(GenerateOopMap *c, int bcpDelta, int* data);
    49 //  RetTable
    50 //
    51 // Contains maping between jsr targets and there return addresses. One-to-many mapping
    52 //
    53 class RetTableEntry : public ResourceObj {
    54  private:
    55   static int _init_nof_jsrs;                      // Default size of jsrs list
    56   int _target_bci;                                // Target PC address of jump (bytecode index)
    57   GrowableArray<intptr_t> * _jsrs;                     // List of return addresses  (bytecode index)
    58   RetTableEntry *_next;                           // Link to next entry
    59  public:
    60    RetTableEntry(int target, RetTableEntry *next)  { _target_bci=target; _jsrs = new GrowableArray<intptr_t>(_init_nof_jsrs); _next = next;  }
    62   // Query
    63   int target_bci() const                      { return _target_bci; }
    64   int nof_jsrs() const                        { return _jsrs->length(); }
    65   int jsrs(int i) const                       { assert(i>=0 && i<nof_jsrs(), "Index out of bounds"); return _jsrs->at(i); }
    67   // Update entry
    68   void add_jsr    (int return_bci)            { _jsrs->append(return_bci); }
    69   void add_delta  (int bci, int delta);
    70   RetTableEntry * next()  const               { return _next; }
    71 };
    74 class RetTable VALUE_OBJ_CLASS_SPEC {
    75  private:
    76   RetTableEntry *_first;
    77   static int _init_nof_entries;
    79   void add_jsr(int return_bci, int target_bci);   // Adds entry to list
    80  public:
    81   RetTable()                                                  { _first = NULL; }
    82   void compute_ret_table(methodHandle method);
    83   void update_ret_table(int bci, int delta);
    84   RetTableEntry* find_jsrs_for_target(int targBci);
    85 };
    87 //
    88 // CellTypeState
    89 //
    90 class CellTypeState VALUE_OBJ_CLASS_SPEC {
    91  private:
    92   unsigned int _state;
    94   // Masks for separating the BITS and INFO portions of a CellTypeState
    95   enum { info_mask            = right_n_bits(28),
    96          bits_mask            = (int)(~info_mask) };
    98   // These constant are used for manipulating the BITS portion of a
    99   // CellTypeState
   100   enum { uninit_bit           = (int)(nth_bit(31)),
   101          ref_bit              = nth_bit(30),
   102          val_bit              = nth_bit(29),
   103          addr_bit             = nth_bit(28),
   104          live_bits_mask       = (int)(bits_mask & ~uninit_bit) };
   106   // These constants are used for manipulating the INFO portion of a
   107   // CellTypeState
   108   enum { top_info_bit         = nth_bit(27),
   109          not_bottom_info_bit  = nth_bit(26),
   110          info_data_mask       = right_n_bits(26),
   111          info_conflict        = info_mask };
   113   // Within the INFO data, these values are used to distinguish different
   114   // kinds of references.
   115   enum { ref_not_lock_bit     = nth_bit(25),  // 0 if this reference is locked as a monitor
   116          ref_slot_bit         = nth_bit(24),  // 1 if this reference is a "slot" reference,
   117                                               // 0 if it is a "line" reference.
   118          ref_data_mask        = right_n_bits(24) };
   121   // These values are used to initialize commonly used CellTypeState
   122   // constants.
   123   enum { bottom_value         = 0,
   124          uninit_value         = (int)(uninit_bit | info_conflict),
   125          ref_value            = ref_bit,
   126          ref_conflict         = ref_bit | info_conflict,
   127          val_value            = val_bit | info_conflict,
   128          addr_value           = addr_bit,
   129          addr_conflict        = addr_bit | info_conflict };
   131  public:
   133   // Since some C++ constructors generate poor code for declarations of the
   134   // form...
   135   //
   136   //   CellTypeState vector[length];
   137   //
   138   // ...we avoid making a constructor for this class.  CellTypeState values
   139   // should be constructed using one of the make_* methods:
   141   static CellTypeState make_any(int state) {
   142     CellTypeState s;
   143     s._state = state;
   144     // Causes SS10 warning.
   145     // assert(s.is_valid_state(), "check to see if CellTypeState is valid");
   146     return s;
   147   }
   149   static CellTypeState make_bottom() {
   150     return make_any(0);
   151   }
   153   static CellTypeState make_top() {
   154     return make_any(AllBits);
   155   }
   157   static CellTypeState make_addr(int bci) {
   158     assert((bci >= 0) && (bci < info_data_mask), "check to see if ret addr is valid");
   159     return make_any(addr_bit | not_bottom_info_bit | (bci & info_data_mask));
   160   }
   162   static CellTypeState make_slot_ref(int slot_num) {
   163     assert(slot_num >= 0 && slot_num < ref_data_mask, "slot out of range");
   164     return make_any(ref_bit | not_bottom_info_bit | ref_not_lock_bit | ref_slot_bit |
   165                     (slot_num & ref_data_mask));
   166   }
   168   static CellTypeState make_line_ref(int bci) {
   169     assert(bci >= 0 && bci < ref_data_mask, "line out of range");
   170     return make_any(ref_bit | not_bottom_info_bit | ref_not_lock_bit |
   171                     (bci & ref_data_mask));
   172   }
   174   static CellTypeState make_lock_ref(int bci) {
   175     assert(bci >= 0 && bci < ref_data_mask, "line out of range");
   176     return make_any(ref_bit | not_bottom_info_bit | (bci & ref_data_mask));
   177   }
   179   // Query methods:
   180   bool is_bottom() const                { return _state == 0; }
   181   bool is_live() const                  { return ((_state & live_bits_mask) != 0); }
   182   bool is_valid_state() const {
   183     // Uninitialized and value cells must contain no data in their info field:
   184     if ((can_be_uninit() || can_be_value()) && !is_info_top()) {
   185       return false;
   186     }
   187     // The top bit is only set when all info bits are set:
   188     if (is_info_top() && ((_state & info_mask) != info_mask)) {
   189       return false;
   190     }
   191     // The not_bottom_bit must be set when any other info bit is set:
   192     if (is_info_bottom() && ((_state & info_mask) != 0)) {
   193       return false;
   194     }
   195     return true;
   196   }
   198   bool is_address() const               { return ((_state & bits_mask) == addr_bit); }
   199   bool is_reference() const             { return ((_state & bits_mask) == ref_bit); }
   200   bool is_value() const                 { return ((_state & bits_mask) == val_bit); }
   201   bool is_uninit() const                { return ((_state & bits_mask) == (uint)uninit_bit); }
   203   bool can_be_address() const           { return ((_state & addr_bit) != 0); }
   204   bool can_be_reference() const         { return ((_state & ref_bit) != 0); }
   205   bool can_be_value() const             { return ((_state & val_bit) != 0); }
   206   bool can_be_uninit() const            { return ((_state & uninit_bit) != 0); }
   208   bool is_info_bottom() const           { return ((_state & not_bottom_info_bit) == 0); }
   209   bool is_info_top() const              { return ((_state & top_info_bit) != 0); }
   210   int  get_info() const {
   211     assert((!is_info_top() && !is_info_bottom()),
   212            "check to make sure top/bottom info is not used");
   213     return (_state & info_data_mask);
   214   }
   216   bool is_good_address() const          { return is_address() && !is_info_top(); }
   217   bool is_lock_reference() const {
   218     return ((_state & (bits_mask | top_info_bit | ref_not_lock_bit)) == ref_bit);
   219   }
   220   bool is_nonlock_reference() const {
   221     return ((_state & (bits_mask | top_info_bit | ref_not_lock_bit)) == (ref_bit | ref_not_lock_bit));
   222   }
   224   bool equal(CellTypeState a) const     { return _state == a._state; }
   225   bool equal_kind(CellTypeState a) const {
   226     return (_state & bits_mask) == (a._state & bits_mask);
   227   }
   229   char to_char() const;
   231   // Merge
   232   CellTypeState merge (CellTypeState cts, int slot) const;
   234   // Debugging output
   235   void print(outputStream *os);
   237   // Default values of common values
   238   static CellTypeState bottom;
   239   static CellTypeState uninit;
   240   static CellTypeState ref;
   241   static CellTypeState value;
   242   static CellTypeState refUninit;
   243   static CellTypeState varUninit;
   244   static CellTypeState top;
   245   static CellTypeState addr;
   246 };
   249 //
   250 // BasicBlockStruct
   251 //
   252 class BasicBlock: ResourceObj {
   253  private:
   254   bool            _changed;                 // Reached a fixpoint or not
   255  public:
   256   enum Constants {
   257     _dead_basic_block = -2,
   258     _unreached        = -1                  // Alive but not yet reached by analysis
   259     // >=0                                  // Alive and has a merged state
   260   };
   262   int             _bci;                     // Start of basic block
   263   int             _end_bci;                 // Bci of last instruction in basicblock
   264   int             _max_locals;              // Determines split between vars and stack
   265   int             _max_stack;               // Determines split between stack and monitors
   266   CellTypeState*  _state;                   // State (vars, stack) at entry.
   267   int             _stack_top;               // -1 indicates bottom stack value.
   268   int             _monitor_top;             // -1 indicates bottom monitor stack value.
   270   CellTypeState* vars()                     { return _state; }
   271   CellTypeState* stack()                    { return _state + _max_locals; }
   273   bool changed()                            { return _changed; }
   274   void set_changed(bool s)                  { _changed = s; }
   276   bool is_reachable() const                 { return _stack_top >= 0; }  // Analysis has reached this basicblock
   278   // All basicblocks that are unreachable are going to have a _stack_top == _dead_basic_block.
   279   // This info. is setup in a pre-parse before the real abstract interpretation starts.
   280   bool is_dead() const                      { return _stack_top == _dead_basic_block; }
   281   bool is_alive() const                     { return _stack_top != _dead_basic_block; }
   282   void mark_as_alive()                      { assert(is_dead(), "must be dead"); _stack_top = _unreached; }
   283 };
   286 //
   287 //  GenerateOopMap
   288 //
   289 // Main class used to compute the pointer-maps in a MethodOop
   290 //
   291 class GenerateOopMap VALUE_OBJ_CLASS_SPEC {
   292  protected:
   294   // _monitor_top is set to this constant to indicate that a monitor matching
   295   // problem was encountered prior to this point in control flow.
   296   enum { bad_monitors = -1 };
   298   // Main variables
   299   methodHandle _method;                     // The method we are examine
   300   RetTable     _rt;                         // Contains the return address mappings
   301   int          _max_locals;                 // Cached value of no. of locals
   302   int          _max_stack;                  // Cached value of max. stack depth
   303   int          _max_monitors;               // Cached value of max. monitor stack depth
   304   int          _has_exceptions;             // True, if exceptions exist for method
   305   bool         _got_error;                  // True, if an error occurred during interpretation.
   306   Handle       _exception;                  // Exception if got_error is true.
   307   bool         _did_rewriting;              // was bytecodes rewritten
   308   bool         _did_relocation;             // was relocation neccessary
   309   bool         _monitor_safe;               // The monitors in this method have been determined
   310                                             // to be safe.
   312   // Working Cell type state
   313   int            _state_len;                // Size of states
   314   CellTypeState *_state;                    // list of states
   315   char          *_state_vec_buf;            // Buffer used to print a readable version of a state
   316   int            _stack_top;
   317   int            _monitor_top;
   319   // Timing and statistics
   320   static elapsedTimer _total_oopmap_time;   // Holds cumulative oopmap generation time
   321   static long         _total_byte_count;    // Holds cumulative number of bytes inspected
   323   // Cell type methods
   324   void            init_state();
   325   void            make_context_uninitialized ();
   326   int             methodsig_to_effect        (Symbol* signature, bool isStatic, CellTypeState* effect);
   327   bool            merge_local_state_vectors  (CellTypeState* cts, CellTypeState* bbts);
   328   bool            merge_monitor_state_vectors(CellTypeState* cts, CellTypeState* bbts);
   329   void            copy_state                 (CellTypeState *dst, CellTypeState *src);
   330   void            merge_state_into_bb        (BasicBlock *bb);
   331   static void     merge_state                (GenerateOopMap *gom, int bcidelta, int* data);
   332   void            set_var                    (int localNo, CellTypeState cts);
   333   CellTypeState   get_var                    (int localNo);
   334   CellTypeState   pop                        ();
   335   void            push                       (CellTypeState cts);
   336   CellTypeState   monitor_pop                ();
   337   void            monitor_push               (CellTypeState cts);
   338   CellTypeState * vars                       ()                                             { return _state; }
   339   CellTypeState * stack                      ()                                             { return _state+_max_locals; }
   340   CellTypeState * monitors                   ()                                             { return _state+_max_locals+_max_stack; }
   342   void            replace_all_CTS_matches    (CellTypeState match,
   343                                               CellTypeState replace);
   344   void            print_states               (outputStream *os, CellTypeState *vector, int num);
   345   void            print_current_state        (outputStream   *os,
   346                                               BytecodeStream *itr,
   347                                               bool            detailed);
   348   void            report_monitor_mismatch    (const char *msg);
   350   // Basicblock info
   351   BasicBlock *    _basic_blocks;             // Array of basicblock info
   352   int             _gc_points;
   353   int             _bb_count;
   354   BitMap          _bb_hdr_bits;
   356   // Basicblocks methods
   357   void          initialize_bb               ();
   358   void          mark_bbheaders_and_count_gc_points();
   359   bool          is_bb_header                (int bci) const   {
   360     return _bb_hdr_bits.at(bci);
   361   }
   362   int           gc_points                   () const                          { return _gc_points; }
   363   int           bb_count                    () const                          { return _bb_count; }
   364   void          set_bbmark_bit              (int bci) {
   365     _bb_hdr_bits.at_put(bci, true);
   366   }
   367   void          clear_bbmark_bit            (int bci) {
   368     _bb_hdr_bits.at_put(bci, false);
   369   }
   370   BasicBlock *  get_basic_block_at          (int bci) const;
   371   BasicBlock *  get_basic_block_containing  (int bci) const;
   372   void          interp_bb                   (BasicBlock *bb);
   373   void          restore_state               (BasicBlock *bb);
   374   int           next_bb_start_pc            (BasicBlock *bb);
   375   void          update_basic_blocks         (int bci, int delta, int new_method_size);
   376   static void   bb_mark_fct                 (GenerateOopMap *c, int deltaBci, int *data);
   378   // Dead code detection
   379   void          mark_reachable_code();
   380   static void   reachable_basicblock        (GenerateOopMap *c, int deltaBci, int *data);
   382   // Interpretation methods (primary)
   383   void  do_interpretation                   ();
   384   void  init_basic_blocks                   ();
   385   void  setup_method_entry_state            ();
   386   void  interp_all                          ();
   388   // Interpretation methods (secondary)
   389   void  interp1                             (BytecodeStream *itr);
   390   void  do_exception_edge                   (BytecodeStream *itr);
   391   void  check_type                          (CellTypeState expected, CellTypeState actual);
   392   void  ppstore                             (CellTypeState *in,  int loc_no);
   393   void  ppload                              (CellTypeState *out, int loc_no);
   394   void  ppush1                              (CellTypeState in);
   395   void  ppush                               (CellTypeState *in);
   396   void  ppop1                               (CellTypeState out);
   397   void  ppop                                (CellTypeState *out);
   398   void  ppop_any                            (int poplen);
   399   void  pp                                  (CellTypeState *in, CellTypeState *out);
   400   void  pp_new_ref                          (CellTypeState *in, int bci);
   401   void  ppdupswap                           (int poplen, const char *out);
   402   void  do_ldc                              (int bci);
   403   void  do_astore                           (int idx);
   404   void  do_jsr                              (int delta);
   405   void  do_field                            (int is_get, int is_static, int idx, int bci);
   406   void  do_method                           (int is_static, int is_interface, int idx, int bci);
   407   void  do_multianewarray                   (int dims, int bci);
   408   void  do_monitorenter                     (int bci);
   409   void  do_monitorexit                      (int bci);
   410   void  do_return_monitor_check             ();
   411   void  do_checkcast                        ();
   412   CellTypeState *sigchar_to_effect          (char sigch, int bci, CellTypeState *out);
   413   int copy_cts                              (CellTypeState *dst, CellTypeState *src);
   415   // Error handling
   416   void  error_work                          (const char *format, va_list ap);
   417   void  report_error                        (const char *format, ...);
   418   void  verify_error                        (const char *format, ...);
   419   bool  got_error()                         { return _got_error; }
   421   // Create result set
   422   bool  _report_result;
   423   bool  _report_result_for_send;            // Unfortunatly, stackmaps for sends are special, so we need some extra
   424   BytecodeStream *_itr_send;                // variables to handle them properly.
   426   void  report_result                       ();
   428   // Initvars
   429   GrowableArray<intptr_t> * _init_vars;
   431   void  initialize_vars                     ();
   432   void  add_to_ref_init_set                 (int localNo);
   434   // Conflicts rewrite logic
   435   bool      _conflict;                      // True, if a conflict occurred during interpretation
   436   int       _nof_refval_conflicts;          // No. of conflicts that require rewrites
   437   int *     _new_var_map;
   439   void record_refval_conflict               (int varNo);
   440   void rewrite_refval_conflicts             ();
   441   void rewrite_refval_conflict              (int from, int to);
   442   bool rewrite_refval_conflict_inst         (BytecodeStream *i, int from, int to);
   443   bool rewrite_load_or_store                (BytecodeStream *i, Bytecodes::Code bc, Bytecodes::Code bc0, unsigned int varNo);
   445   void expand_current_instr                 (int bci, int ilen, int newIlen, u_char inst_buffer[]);
   446   bool is_astore                            (BytecodeStream *itr, int *index);
   447   bool is_aload                             (BytecodeStream *itr, int *index);
   449   // List of bci's where a return address is on top of the stack
   450   GrowableArray<intptr_t> *_ret_adr_tos;
   452   bool stack_top_holds_ret_addr             (int bci);
   453   void compute_ret_adr_at_TOS               ();
   454   void update_ret_adr_at_TOS                (int bci, int delta);
   456   int  binsToHold                           (int no)                      { return  ((no+(BitsPerWord-1))/BitsPerWord); }
   457   char *state_vec_to_string                 (CellTypeState* vec, int len);
   459   // Helper method. Can be used in subclasses to fx. calculate gc_points. If the current instuction
   460   // is a control transfer, then calls the jmpFct all possible destinations.
   461   void  ret_jump_targets_do                 (BytecodeStream *bcs, jmpFct_t jmpFct, int varNo,int *data);
   462   bool  jump_targets_do                     (BytecodeStream *bcs, jmpFct_t jmpFct, int *data);
   464   friend class RelocCallback;
   465  public:
   466   GenerateOopMap(methodHandle method);
   468   // Compute the map.
   469   void compute_map(TRAPS);
   470   void result_for_basicblock(int bci);    // Do a callback on fill_stackmap_for_opcodes for basicblock containing bci
   472   // Query
   473   int max_locals() const                           { return _max_locals; }
   474   methodOop method() const                         { return _method(); }
   475   methodHandle method_as_handle() const            { return _method; }
   477   bool did_rewriting()                             { return _did_rewriting; }
   478   bool did_relocation()                            { return _did_relocation; }
   480   static void print_time();
   482   // Monitor query
   483   bool monitor_safe()                              { return _monitor_safe; }
   485   // Specialization methods. Intended use:
   486   // - possible_gc_point must return true for every bci for which the stackmaps must be returned
   487   // - fill_stackmap_prolog is called just before the result is reported. The arguments tells the estimated
   488   //   number of gc points
   489   // - fill_stackmap_for_opcodes is called once for each bytecode index in order (0...code_length-1)
   490   // - fill_stackmap_epilog is called after all results has been reported. Note: Since the algorithm does not report
   491   //   stackmaps for deadcode, fewer gc_points might have been encounted than assumed during the epilog. It is the
   492   //   responsibility of the subclass to count the correct number.
   493   // - fill_init_vars are called once with the result of the init_vars computation
   494   //
   495   // All these methods are used during a call to: compute_map. Note: Non of the return results are valid
   496   // after compute_map returns, since all values are allocated as resource objects.
   497   //
   498   // All virtual method must be implemented in subclasses
   499   virtual bool allow_rewrites             () const                        { return false; }
   500   virtual bool report_results             () const                        { return true;  }
   501   virtual bool report_init_vars           () const                        { return true;  }
   502   virtual bool possible_gc_point          (BytecodeStream *bcs)           { ShouldNotReachHere(); return false; }
   503   virtual void fill_stackmap_prolog       (int nof_gc_points)             { ShouldNotReachHere(); }
   504   virtual void fill_stackmap_epilog       ()                              { ShouldNotReachHere(); }
   505   virtual void fill_stackmap_for_opcodes  (BytecodeStream *bcs,
   506                                            CellTypeState* vars,
   507                                            CellTypeState* stack,
   508                                            int stackTop)                  { ShouldNotReachHere(); }
   509   virtual void fill_init_vars             (GrowableArray<intptr_t> *init_vars) { ShouldNotReachHere();; }
   510 };
   512 //
   513 // Subclass of the GenerateOopMap Class that just do rewrites of the method, if needed.
   514 // It does not store any oopmaps.
   515 //
   516 class ResolveOopMapConflicts: public GenerateOopMap {
   517  private:
   519   bool _must_clear_locals;
   521   virtual bool report_results() const     { return false; }
   522   virtual bool report_init_vars() const   { return true;  }
   523   virtual bool allow_rewrites() const     { return true;  }
   524   virtual bool possible_gc_point          (BytecodeStream *bcs)           { return false; }
   525   virtual void fill_stackmap_prolog       (int nof_gc_points)             {}
   526   virtual void fill_stackmap_epilog       ()                              {}
   527   virtual void fill_stackmap_for_opcodes  (BytecodeStream *bcs,
   528                                            CellTypeState* vars,
   529                                            CellTypeState* stack,
   530                                            int stack_top)                 {}
   531   virtual void fill_init_vars             (GrowableArray<intptr_t> *init_vars) { _must_clear_locals = init_vars->length() > 0; }
   533 #ifndef PRODUCT
   534   // Statistics
   535   static int _nof_invocations;
   536   static int _nof_rewrites;
   537   static int _nof_relocations;
   538 #endif
   540  public:
   541   ResolveOopMapConflicts(methodHandle method) : GenerateOopMap(method) { _must_clear_locals = false; };
   543   methodHandle do_potential_rewrite(TRAPS);
   544   bool must_clear_locals() const { return _must_clear_locals; }
   545 };
   548 //
   549 // Subclass used by the compiler to generate pairing infomation
   550 //
   551 class GeneratePairingInfo: public GenerateOopMap {
   552  private:
   554   virtual bool report_results() const     { return false; }
   555   virtual bool report_init_vars() const   { return false; }
   556   virtual bool allow_rewrites() const     { return false;  }
   557   virtual bool possible_gc_point          (BytecodeStream *bcs)           { return false; }
   558   virtual void fill_stackmap_prolog       (int nof_gc_points)             {}
   559   virtual void fill_stackmap_epilog       ()                              {}
   560   virtual void fill_stackmap_for_opcodes  (BytecodeStream *bcs,
   561                                            CellTypeState* vars,
   562                                            CellTypeState* stack,
   563                                            int stack_top)                 {}
   564   virtual void fill_init_vars             (GrowableArray<intptr_t> *init_vars) {}
   565  public:
   566   GeneratePairingInfo(methodHandle method) : GenerateOopMap(method)       {};
   568   // Call compute_map(CHECK) to generate info.
   569 };
   571 #endif // SHARE_VM_OOPS_GENERATEOOPMAP_HPP

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