1 /*
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   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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   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.
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  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).
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  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
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  24 
  25 #ifndef SHARE_CODE_NMETHOD_HPP
  26 #define SHARE_CODE_NMETHOD_HPP
  27 
  28 #include "code/compiledMethod.hpp"
  29 
  30 class DepChange;
  31 class DirectiveSet;
  32 class DebugInformationRecorder;
  33 
  34 // nmethods (native methods) are the compiled code versions of Java methods.
  35 //
  36 // An nmethod contains:
  37 //  - header                 (the nmethod structure)
  38 //  [Relocation]
  39 //  - relocation information
  40 //  - constant part          (doubles, longs and floats used in nmethod)
  41 //  - oop table
  42 //  [Code]
  43 //  - code body
  44 //  - exception handler
  45 //  - stub code
  46 //  [Debugging information]
  47 //  - oop array
  48 //  - data array
  49 //  - pcs
  50 //  [Exception handler table]
  51 //  - handler entry point array
  52 //  [Implicit Null Pointer exception table]
  53 //  - implicit null table array
  54 
  55 class nmethod : public CompiledMethod {
  56   friend class VMStructs;
  57   friend class JVMCIVMStructs;
  58   friend class NMethodSweeper;
  59   friend class CodeCache;  // scavengable oops
  60  private:
  61 
  62   // Shared fields for all nmethod's
  63   int       _entry_bci;        // != InvocationEntryBci if this nmethod is an on-stack replacement method
  64   jmethodID _jmethod_id;       // Cache of method()->jmethod_id()
  65 
  66 #if INCLUDE_JVMCI
  67   // A weak reference to an InstalledCode object associated with
  68   // this nmethod.
  69   jweak     _jvmci_installed_code;
  70 
  71   // A weak reference to a SpeculationLog object associated with
  72   // this nmethod.
  73   jweak     _speculation_log;
  74 
  75   // Determines whether this nmethod is unloaded when the
  76   // referent in _jvmci_installed_code is cleared. This
  77   // will be false if the referent is initialized to a
  78   // HotSpotNMethod object whose isDefault field is true.
  79   // That is, installed code other than a "default"
  80   // HotSpotNMethod causes nmethod unloading.
  81   // This field is ignored once _jvmci_installed_code is NULL.
  82   bool _jvmci_installed_code_triggers_invalidation;
  83 #endif
  84 
  85   // To support simple linked-list chaining of nmethods:
  86   nmethod*  _osr_link;         // from InstanceKlass::osr_nmethods_head
  87 
  88   static nmethod* volatile _oops_do_mark_nmethods;
  89   nmethod*        volatile _oops_do_mark_link;
  90 
  91   // offsets for entry points
  92   address _entry_point;                      // entry point with class check
  93   address _verified_entry_point;             // entry point without class check
  94   address _osr_entry_point;                  // entry point for on stack replacement
  95 
  96   // Offsets for different nmethod parts
  97   int  _exception_offset;
  98   // Offset of the unwind handler if it exists
  99   int _unwind_handler_offset;
 100 
 101   int _consts_offset;
 102   int _stub_offset;
 103   int _oops_offset;                       // offset to where embedded oop table begins (inside data)
 104   int _metadata_offset;                   // embedded meta data table
 105   int _scopes_data_offset;
 106   int _scopes_pcs_offset;
 107   int _dependencies_offset;
 108   int _handler_table_offset;
 109   int _nul_chk_table_offset;
 110   int _nmethod_end_offset;
 111 
 112   int code_offset() const { return (address) code_begin() - header_begin(); }
 113 
 114   // location in frame (offset for sp) that deopt can store the original
 115   // pc during a deopt.
 116   int _orig_pc_offset;
 117 
 118   int _compile_id;                           // which compilation made this nmethod
 119   int _comp_level;                           // compilation level
 120 
 121   // protected by CodeCache_lock
 122   bool _has_flushed_dependencies;            // Used for maintenance of dependencies (CodeCache_lock)
 123 
 124   // used by jvmti to track if an unload event has been posted for this nmethod.
 125   bool _unload_reported;
 126 
 127   // Protected by Patching_lock
 128   volatile signed char _state;               // {not_installed, in_use, not_entrant, zombie, unloaded}
 129 
 130 #ifdef ASSERT
 131   bool _oops_are_stale;  // indicates that it's no longer safe to access oops section
 132 #endif
 133 
 134 #if INCLUDE_RTM_OPT
 135   // RTM state at compile time. Used during deoptimization to decide
 136   // whether to restart collecting RTM locking abort statistic again.
 137   RTMState _rtm_state;
 138 #endif
 139 
 140   // Nmethod Flushing lock. If non-zero, then the nmethod is not removed
 141   // and is not made into a zombie. However, once the nmethod is made into
 142   // a zombie, it will be locked one final time if CompiledMethodUnload
 143   // event processing needs to be done.
 144   volatile jint _lock_count;
 145 
 146   // not_entrant method removal. Each mark_sweep pass will update
 147   // this mark to current sweep invocation count if it is seen on the
 148   // stack.  An not_entrant method can be removed when there are no
 149   // more activations, i.e., when the _stack_traversal_mark is less than
 150   // current sweep traversal index.
 151   volatile long _stack_traversal_mark;
 152 
 153   // The _hotness_counter indicates the hotness of a method. The higher
 154   // the value the hotter the method. The hotness counter of a nmethod is
 155   // set to [(ReservedCodeCacheSize / (1024 * 1024)) * 2] each time the method
 156   // is active while stack scanning (mark_active_nmethods()). The hotness
 157   // counter is decreased (by 1) while sweeping.
 158   int _hotness_counter;
 159 
 160   // Local state used to keep track of whether unloading is happening or not
 161   volatile uint8_t _is_unloading_state;
 162 
 163   // These are used for compiled synchronized native methods to
 164   // locate the owner and stack slot for the BasicLock so that we can
 165   // properly revoke the bias of the owner if necessary. They are
 166   // needed because there is no debug information for compiled native
 167   // wrappers and the oop maps are insufficient to allow
 168   // frame::retrieve_receiver() to work. Currently they are expected
 169   // to be byte offsets from the Java stack pointer for maximum code
 170   // sharing between platforms. Note that currently biased locking
 171   // will never cause Class instances to be biased but this code
 172   // handles the static synchronized case as well.
 173   // JVMTI's GetLocalInstance() also uses these offsets to find the receiver
 174   // for non-static native wrapper frames.
 175   ByteSize _native_receiver_sp_offset;
 176   ByteSize _native_basic_lock_sp_offset;
 177 
 178   friend class nmethodLocker;
 179 
 180   // For native wrappers
 181   nmethod(Method* method,
 182           CompilerType type,
 183           int nmethod_size,
 184           int compile_id,
 185           CodeOffsets* offsets,
 186           CodeBuffer *code_buffer,
 187           int frame_size,
 188           ByteSize basic_lock_owner_sp_offset, /* synchronized natives only */
 189           ByteSize basic_lock_sp_offset,       /* synchronized natives only */
 190           OopMapSet* oop_maps);
 191 
 192   // Creation support
 193   nmethod(Method* method,
 194           CompilerType type,
 195           int nmethod_size,
 196           int compile_id,
 197           int entry_bci,
 198           CodeOffsets* offsets,
 199           int orig_pc_offset,
 200           DebugInformationRecorder *recorder,
 201           Dependencies* dependencies,
 202           CodeBuffer *code_buffer,
 203           int frame_size,
 204           OopMapSet* oop_maps,
 205           ExceptionHandlerTable* handler_table,
 206           ImplicitExceptionTable* nul_chk_table,
 207           AbstractCompiler* compiler,
 208           int comp_level
 209 #if INCLUDE_JVMCI
 210           , jweak installed_code,
 211           jweak speculation_log
 212 #endif
 213           );
 214 
 215   // helper methods
 216   void* operator new(size_t size, int nmethod_size, int comp_level) throw();
 217 
 218   const char* reloc_string_for(u_char* begin, u_char* end);
 219   // Returns true if this thread changed the state of the nmethod or
 220   // false if another thread performed the transition.
 221   bool make_not_entrant_or_zombie(int state);
 222   bool make_entrant() { Unimplemented(); return false; }
 223   void inc_decompile_count();
 224 
 225   // Inform external interfaces that a compiled method has been unloaded
 226   void post_compiled_method_unload();
 227 
 228   // Initailize fields to their default values
 229   void init_defaults();
 230 
 231   // Offsets
 232   int content_offset() const                  { return content_begin() - header_begin(); }
 233   int data_offset() const                     { return _data_offset; }
 234 
 235   address header_end() const                  { return (address)    header_begin() + header_size(); }
 236 
 237  public:
 238   // create nmethod with entry_bci
 239   static nmethod* new_nmethod(const methodHandle& method,
 240                               int compile_id,
 241                               int entry_bci,
 242                               CodeOffsets* offsets,
 243                               int orig_pc_offset,
 244                               DebugInformationRecorder* recorder,
 245                               Dependencies* dependencies,
 246                               CodeBuffer *code_buffer,
 247                               int frame_size,
 248                               OopMapSet* oop_maps,
 249                               ExceptionHandlerTable* handler_table,
 250                               ImplicitExceptionTable* nul_chk_table,
 251                               AbstractCompiler* compiler,
 252                               int comp_level
 253 #if INCLUDE_JVMCI
 254                               , jweak installed_code = NULL,
 255                               jweak speculation_log = NULL
 256 #endif
 257   );
 258 
 259   // Only used for unit tests.
 260   nmethod()
 261     : CompiledMethod(),
 262       _is_unloading_state(0),
 263       _native_receiver_sp_offset(in_ByteSize(-1)),
 264       _native_basic_lock_sp_offset(in_ByteSize(-1)) {}
 265 
 266 
 267   static nmethod* new_native_nmethod(const methodHandle& method,
 268                                      int compile_id,
 269                                      CodeBuffer *code_buffer,
 270                                      int vep_offset,
 271                                      int frame_complete,
 272                                      int frame_size,
 273                                      ByteSize receiver_sp_offset,
 274                                      ByteSize basic_lock_sp_offset,
 275                                      OopMapSet* oop_maps);
 276 
 277   // type info
 278   bool is_nmethod() const                         { return true; }
 279   bool is_osr_method() const                      { return _entry_bci != InvocationEntryBci; }
 280 
 281   // boundaries for different parts
 282   address consts_begin          () const          { return           header_begin() + _consts_offset        ; }
 283   address consts_end            () const          { return           code_begin()                           ; }
 284   address stub_begin            () const          { return           header_begin() + _stub_offset          ; }
 285   address stub_end              () const          { return           header_begin() + _oops_offset          ; }
 286   address exception_begin       () const          { return           header_begin() + _exception_offset     ; }
 287   address unwind_handler_begin  () const          { return _unwind_handler_offset != -1 ? (header_begin() + _unwind_handler_offset) : NULL; }
 288   oop*    oops_begin            () const          { return (oop*)   (header_begin() + _oops_offset)         ; }
 289   oop*    oops_end              () const          { return (oop*)   (header_begin() + _metadata_offset)     ; }
 290 
 291   Metadata** metadata_begin   () const            { return (Metadata**)  (header_begin() + _metadata_offset)     ; }
 292   Metadata** metadata_end     () const            { return (Metadata**)  _scopes_data_begin; }
 293 
 294   address scopes_data_end       () const          { return           header_begin() + _scopes_pcs_offset    ; }
 295   PcDesc* scopes_pcs_begin      () const          { return (PcDesc*)(header_begin() + _scopes_pcs_offset   ); }
 296   PcDesc* scopes_pcs_end        () const          { return (PcDesc*)(header_begin() + _dependencies_offset) ; }
 297   address dependencies_begin    () const          { return           header_begin() + _dependencies_offset  ; }
 298   address dependencies_end      () const          { return           header_begin() + _handler_table_offset ; }
 299   address handler_table_begin   () const          { return           header_begin() + _handler_table_offset ; }
 300   address handler_table_end     () const          { return           header_begin() + _nul_chk_table_offset ; }
 301   address nul_chk_table_begin   () const          { return           header_begin() + _nul_chk_table_offset ; }
 302   address nul_chk_table_end     () const          { return           header_begin() + _nmethod_end_offset   ; }
 303 
 304   // Sizes
 305   int oops_size         () const                  { return (address)  oops_end         () - (address)  oops_begin         (); }
 306   int metadata_size     () const                  { return (address)  metadata_end     () - (address)  metadata_begin     (); }
 307   int dependencies_size () const                  { return            dependencies_end () -            dependencies_begin (); }
 308 
 309   int     oops_count() const { assert(oops_size() % oopSize == 0, "");  return (oops_size() / oopSize) + 1; }
 310   int metadata_count() const { assert(metadata_size() % wordSize == 0, ""); return (metadata_size() / wordSize) + 1; }
 311 
 312   int total_size        () const;
 313 
 314   void dec_hotness_counter()        { _hotness_counter--; }
 315   void set_hotness_counter(int val) { _hotness_counter = val; }
 316   int  hotness_counter() const      { return _hotness_counter; }
 317 
 318   // Containment
 319   bool oops_contains         (oop*    addr) const { return oops_begin         () <= addr && addr < oops_end         (); }
 320   bool metadata_contains     (Metadata** addr) const   { return metadata_begin     () <= addr && addr < metadata_end     (); }
 321   bool scopes_data_contains  (address addr) const { return scopes_data_begin  () <= addr && addr < scopes_data_end  (); }
 322   bool scopes_pcs_contains   (PcDesc* addr) const { return scopes_pcs_begin   () <= addr && addr < scopes_pcs_end   (); }
 323 
 324   // entry points
 325   address entry_point() const                     { return _entry_point;             } // normal entry point
 326   address verified_entry_point() const            { return _verified_entry_point;    } // if klass is correct
 327 
 328   // flag accessing and manipulation
 329   bool  is_not_installed() const                  { return _state == not_installed; }
 330   bool  is_in_use() const                         { return _state <= in_use; }
 331   bool  is_alive() const                          { return _state < zombie; }
 332   bool  is_not_entrant() const                    { return _state == not_entrant; }
 333   bool  is_zombie() const                         { return _state == zombie; }
 334   bool  is_unloaded() const                       { return _state == unloaded; }
 335 
 336   void clear_unloading_state();
 337   virtual bool is_unloading();
 338   virtual void do_unloading(bool unloading_occurred);
 339 
 340 #if INCLUDE_RTM_OPT
 341   // rtm state accessing and manipulating
 342   RTMState  rtm_state() const                     { return _rtm_state; }
 343   void set_rtm_state(RTMState state)              { _rtm_state = state; }
 344 #endif
 345 
 346   void make_in_use()                              { _state = in_use; }
 347   // Make the nmethod non entrant. The nmethod will continue to be
 348   // alive.  It is used when an uncommon trap happens.  Returns true
 349   // if this thread changed the state of the nmethod or false if
 350   // another thread performed the transition.
 351   bool  make_not_entrant() {
 352     assert(!method()->is_method_handle_intrinsic(), "Cannot make MH intrinsic not entrant");
 353     return make_not_entrant_or_zombie(not_entrant);
 354   }
 355   bool  make_not_used()    { return make_not_entrant(); }
 356   bool  make_zombie()      { return make_not_entrant_or_zombie(zombie); }
 357 
 358   // used by jvmti to track if the unload event has been reported
 359   bool  unload_reported()                         { return _unload_reported; }
 360   void  set_unload_reported()                     { _unload_reported = true; }
 361 
 362   int get_state() const {
 363     return _state;
 364   }
 365 
 366   void  make_unloaded();
 367 
 368   bool has_dependencies()                         { return dependencies_size() != 0; }
 369   void flush_dependencies(bool delete_immediately);
 370   bool has_flushed_dependencies()                 { return _has_flushed_dependencies; }
 371   void set_has_flushed_dependencies()             {
 372     assert(!has_flushed_dependencies(), "should only happen once");
 373     _has_flushed_dependencies = 1;
 374   }
 375 
 376   int   comp_level() const                        { return _comp_level; }
 377 
 378   void unlink_from_method();
 379 
 380   // Support for oops in scopes and relocs:
 381   // Note: index 0 is reserved for null.
 382   oop   oop_at(int index) const;
 383   oop*  oop_addr_at(int index) const {  // for GC
 384     // relocation indexes are biased by 1 (because 0 is reserved)
 385     assert(index > 0 && index <= oops_count(), "must be a valid non-zero index");
 386     assert(!_oops_are_stale, "oops are stale");
 387     return &oops_begin()[index - 1];
 388   }
 389 
 390   // Support for meta data in scopes and relocs:
 391   // Note: index 0 is reserved for null.
 392   Metadata*     metadata_at(int index) const      { return index == 0 ? NULL: *metadata_addr_at(index); }
 393   Metadata**  metadata_addr_at(int index) const {  // for GC
 394     // relocation indexes are biased by 1 (because 0 is reserved)
 395     assert(index > 0 && index <= metadata_count(), "must be a valid non-zero index");
 396     return &metadata_begin()[index - 1];
 397   }
 398 
 399   void copy_values(GrowableArray<jobject>* oops);
 400   void copy_values(GrowableArray<Metadata*>* metadata);
 401 
 402   // Relocation support
 403 private:
 404   void fix_oop_relocations(address begin, address end, bool initialize_immediates);
 405   inline void initialize_immediate_oop(oop* dest, jobject handle);
 406 
 407 public:
 408   void fix_oop_relocations(address begin, address end) { fix_oop_relocations(begin, end, false); }
 409   void fix_oop_relocations()                           { fix_oop_relocations(NULL, NULL, false); }
 410 
 411   // Sweeper support
 412   long  stack_traversal_mark()                    { return _stack_traversal_mark; }
 413   void  set_stack_traversal_mark(long l)          { _stack_traversal_mark = l; }
 414 
 415   // implicit exceptions support
 416   address continuation_for_implicit_exception(address pc);
 417 
 418   // On-stack replacement support
 419   int   osr_entry_bci() const                     { assert(is_osr_method(), "wrong kind of nmethod"); return _entry_bci; }
 420   address  osr_entry() const                      { assert(is_osr_method(), "wrong kind of nmethod"); return _osr_entry_point; }
 421   void  invalidate_osr_method();
 422   nmethod* osr_link() const                       { return _osr_link; }
 423   void     set_osr_link(nmethod *n)               { _osr_link = n; }
 424 
 425   // Verify calls to dead methods have been cleaned.
 426   void verify_clean_inline_caches();
 427 
 428   // unlink and deallocate this nmethod
 429   // Only NMethodSweeper class is expected to use this. NMethodSweeper is not
 430   // expected to use any other private methods/data in this class.
 431 
 432  protected:
 433   void flush();
 434 
 435  public:
 436   // When true is returned, it is unsafe to remove this nmethod even if
 437   // it is a zombie, since the VM or the ServiceThread might still be
 438   // using it.
 439   bool is_locked_by_vm() const                    { return _lock_count >0; }
 440 
 441   // See comment at definition of _last_seen_on_stack
 442   void mark_as_seen_on_stack();
 443   bool can_convert_to_zombie();
 444 
 445   // Evolution support. We make old (discarded) compiled methods point to new Method*s.
 446   void set_method(Method* method) { _method = method; }
 447 
 448 #if INCLUDE_JVMCI
 449   // Gets the InstalledCode object associated with this nmethod
 450   // which may be NULL if this nmethod was not compiled by JVMCI
 451   // or the weak reference has been cleared.
 452   oop jvmci_installed_code();
 453 
 454   // Copies the value of the name field in the InstalledCode
 455   // object (if any) associated with this nmethod into buf.
 456   // Returns the value of buf if it was updated otherwise NULL.
 457   char* jvmci_installed_code_name(char* buf, size_t buflen) const;
 458 
 459   // Updates the state of the InstalledCode (if any) associated with
 460   // this nmethod based on the current value of _state.
 461   void maybe_invalidate_installed_code();
 462 
 463   // Deoptimizes the nmethod (if any) in the address field of a given
 464   // InstalledCode object. The address field is zeroed upon return.
 465   static void invalidate_installed_code(Handle installed_code, TRAPS);
 466 
 467   // Gets the SpeculationLog object associated with this nmethod
 468   // which may be NULL if this nmethod was not compiled by JVMCI
 469   // or the weak reference has been cleared.
 470   oop speculation_log();
 471 
 472  private:
 473   // Deletes the weak reference (if any) to the InstalledCode object
 474   // associated with this nmethod.
 475   void clear_jvmci_installed_code();
 476 
 477   // Deletes the weak reference (if any) to the SpeculationLog object
 478   // associated with this nmethod.
 479   void clear_speculation_log();
 480 
 481  public:
 482 #endif
 483 
 484  public:
 485   void oops_do(OopClosure* f) { oops_do(f, false); }
 486   void oops_do(OopClosure* f, bool allow_zombie);
 487 
 488   bool test_set_oops_do_mark();
 489   static void oops_do_marking_prologue();
 490   static void oops_do_marking_epilogue();
 491   static bool oops_do_marking_is_active() { return _oops_do_mark_nmethods != NULL; }
 492   bool test_oops_do_mark() { return _oops_do_mark_link != NULL; }
 493 
 494  private:
 495   ScopeDesc* scope_desc_in(address begin, address end);
 496 
 497   address* orig_pc_addr(const frame* fr);
 498 
 499  public:
 500   // copying of debugging information
 501   void copy_scopes_pcs(PcDesc* pcs, int count);
 502   void copy_scopes_data(address buffer, int size);
 503 
 504   // Accessor/mutator for the original pc of a frame before a frame was deopted.
 505   address get_original_pc(const frame* fr) { return *orig_pc_addr(fr); }
 506   void    set_original_pc(const frame* fr, address pc) { *orig_pc_addr(fr) = pc; }
 507 
 508   // jvmti support:
 509   void post_compiled_method_load_event();
 510   jmethodID get_and_cache_jmethod_id();
 511 
 512   // verify operations
 513   void verify();
 514   void verify_scopes();
 515   void verify_interrupt_point(address interrupt_point);
 516 
 517   // printing support
 518   void print()                          const;
 519   void print_relocations()                        PRODUCT_RETURN;
 520   void print_pcs()                                PRODUCT_RETURN;
 521   void print_scopes()                             PRODUCT_RETURN;
 522   void print_dependencies()                       PRODUCT_RETURN;
 523   void print_value_on(outputStream* st) const     PRODUCT_RETURN;
 524   void print_calls(outputStream* st)              PRODUCT_RETURN;
 525   void print_handler_table()                      PRODUCT_RETURN;
 526   void print_nul_chk_table()                      PRODUCT_RETURN;
 527   void print_recorded_oops()                      PRODUCT_RETURN;
 528   void print_recorded_metadata()                  PRODUCT_RETURN;
 529 
 530   void maybe_print_nmethod(DirectiveSet* directive);
 531   void print_nmethod(bool print_code);
 532 
 533   // need to re-define this from CodeBlob else the overload hides it
 534   virtual void print_on(outputStream* st) const { CodeBlob::print_on(st); }
 535   void print_on(outputStream* st, const char* msg) const;
 536 
 537   // Logging
 538   void log_identity(xmlStream* log) const;
 539   void log_new_nmethod() const;
 540   void log_state_change() const;
 541 
 542   // Prints block-level comments, including nmethod specific block labels:
 543   virtual void print_block_comment(outputStream* stream, address block_begin) const {
 544     print_nmethod_labels(stream, block_begin);
 545     CodeBlob::print_block_comment(stream, block_begin);
 546   }
 547   void print_nmethod_labels(outputStream* stream, address block_begin) const;
 548 
 549   // Prints a comment for one native instruction (reloc info, pc desc)
 550   void print_code_comment_on(outputStream* st, int column, address begin, address end);
 551   static void print_statistics() PRODUCT_RETURN;
 552 
 553   // Compiler task identification.  Note that all OSR methods
 554   // are numbered in an independent sequence if CICountOSR is true,
 555   // and native method wrappers are also numbered independently if
 556   // CICountNative is true.
 557   virtual int compile_id() const { return _compile_id; }
 558   const char* compile_kind() const;
 559 
 560   // tells if any of this method's dependencies have been invalidated
 561   // (this is expensive!)
 562   static void check_all_dependencies(DepChange& changes);
 563 
 564   // tells if this compiled method is dependent on the given changes,
 565   // and the changes have invalidated it
 566   bool check_dependency_on(DepChange& changes);
 567 
 568   // Fast breakpoint support. Tells if this compiled method is
 569   // dependent on the given method. Returns true if this nmethod
 570   // corresponds to the given method as well.
 571   virtual bool is_dependent_on_method(Method* dependee);
 572 
 573   // is it ok to patch at address?
 574   bool is_patchable_at(address instr_address);
 575 
 576   // UseBiasedLocking support
 577   ByteSize native_receiver_sp_offset() {
 578     return _native_receiver_sp_offset;
 579   }
 580   ByteSize native_basic_lock_sp_offset() {
 581     return _native_basic_lock_sp_offset;
 582   }
 583 
 584   // support for code generation
 585   static int verified_entry_point_offset()        { return offset_of(nmethod, _verified_entry_point); }
 586   static int osr_entry_point_offset()             { return offset_of(nmethod, _osr_entry_point); }
 587   static int state_offset()                       { return offset_of(nmethod, _state); }
 588 
 589   virtual void metadata_do(MetadataClosure* f);
 590 
 591   NativeCallWrapper* call_wrapper_at(address call) const;
 592   NativeCallWrapper* call_wrapper_before(address return_pc) const;
 593   address call_instruction_address(address pc) const;
 594 
 595   virtual CompiledStaticCall* compiledStaticCall_at(Relocation* call_site) const;
 596   virtual CompiledStaticCall* compiledStaticCall_at(address addr) const;
 597   virtual CompiledStaticCall* compiledStaticCall_before(address addr) const;
 598 };
 599 
 600 // Locks an nmethod so its code will not get removed and it will not
 601 // be made into a zombie, even if it is a not_entrant method. After the
 602 // nmethod becomes a zombie, if CompiledMethodUnload event processing
 603 // needs to be done, then lock_nmethod() is used directly to keep the
 604 // generated code from being reused too early.
 605 class nmethodLocker : public StackObj {
 606   CompiledMethod* _nm;
 607 
 608  public:
 609 
 610   // note: nm can be NULL
 611   // Only JvmtiDeferredEvent::compiled_method_unload_event()
 612   // should pass zombie_ok == true.
 613   static void lock_nmethod(CompiledMethod* nm, bool zombie_ok = false);
 614   static void unlock_nmethod(CompiledMethod* nm); // (ditto)
 615 
 616   nmethodLocker(address pc); // derive nm from pc
 617   nmethodLocker(nmethod *nm) { _nm = nm; lock_nmethod(_nm); }
 618   nmethodLocker(CompiledMethod *nm) {
 619     _nm = nm;
 620     lock(_nm);
 621   }
 622 
 623   static void lock(CompiledMethod* method) {
 624     if (method == NULL) return;
 625     lock_nmethod(method);
 626   }
 627 
 628   static void unlock(CompiledMethod* method) {
 629     if (method == NULL) return;
 630     unlock_nmethod(method);
 631   }
 632 
 633   nmethodLocker() { _nm = NULL; }
 634   ~nmethodLocker() {
 635     unlock(_nm);
 636   }
 637 
 638   CompiledMethod* code() { return _nm; }
 639   void set_code(CompiledMethod* new_nm) {
 640     unlock(_nm);   // note:  This works even if _nm==new_nm.
 641     _nm = new_nm;
 642     lock(_nm);
 643   }
 644 };
 645 
 646 #endif // SHARE_CODE_NMETHOD_HPP