Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 1997, 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_CODE_NMETHOD_HPP

 #define SHARE_VM_CODE_NMETHOD_HPP

 #include "code/codeBlob.hpp"

 #include "code/pcDesc.hpp"

 #include "oops/metadata.hpp"

 // This class is used internally by nmethods, to cache

 // exception/pc/handler information.

 class ExceptionCache : public CHeapObj<mtCode> {

   friend class VMStructs;

  private:

   enum { cache_size = 16 };

   Klass*   _exception_type;

   address  _pc[cache_size];

   address  _handler[cache_size];

   int      _count;

   ExceptionCache* _next;

   address pc_at(int index)                     { assert(index >= 0 && index < count(),""); return _pc[index]; }

   void    set_pc_at(int index, address a)      { assert(index >= 0 && index < cache_size,""); _pc[index] = a; }

   address handler_at(int index)                { assert(index >= 0 && index < count(),""); return _handler[index]; }

   void    set_handler_at(int index, address a) { assert(index >= 0 && index < cache_size,""); _handler[index] = a; }

   int     count()                              { return _count; }

   void    increment_count()                    { _count++; }

  public:

   ExceptionCache(Handle exception, address pc, address handler);

   Klass*    exception_type()                { return _exception_type; }

   ExceptionCache* next()                    { return _next; }

   void      set_next(ExceptionCache *ec)    { _next = ec; }

   address match(Handle exception, address pc);

   bool    match_exception_with_space(Handle exception) ;

   address test_address(address addr);

   bool    add_address_and_handler(address addr, address handler) ;

 };

 // cache pc descs found in earlier inquiries

 class PcDescCache VALUE_OBJ_CLASS_SPEC {

   friend class VMStructs;

  private:

   enum { cache_size = 4 };

   // The array elements MUST be volatile! Several threads may modify

   // and read from the cache concurrently. find_pc_desc_internal has

   // returned wrong results. C++ compiler (namely xlC12) may duplicate

   // C++ field accesses if the elements are not volatile.

   typedef PcDesc* PcDescPtr;

   volatile PcDescPtr _pc_descs[cache_size]; // last cache_size pc_descs found

  public:

   PcDescCache() { debug_only(_pc_descs[0] = NULL); }

   void    reset_to(PcDesc* initial_pc_desc);

   PcDesc* find_pc_desc(int pc_offset, bool approximate);

   void    add_pc_desc(PcDesc* pc_desc);

   PcDesc* last_pc_desc() { return _pc_descs[0]; }

 };

 // nmethods (native methods) are the compiled code versions of Java methods.

 //

 // An nmethod contains:

 //  - header                 (the nmethod structure)

 //  [Relocation]

 //  - relocation information

 //  - constant part          (doubles, longs and floats used in nmethod)

 //  - oop table

 //  [Code]

 //  - code body

 //  - exception handler

 //  - stub code

 //  [Debugging information]

 //  - oop array

 //  - data array

 //  - pcs

 //  [Exception handler table]

 //  - handler entry point array

 //  [Implicit Null Pointer exception table]

 //  - implicit null table array

 class Dependencies;

 class ExceptionHandlerTable;

 class ImplicitExceptionTable;

 class AbstractCompiler;

 class xmlStream;

 class nmethod : public CodeBlob {

   friend class VMStructs;

   friend class NMethodSweeper;

   friend class CodeCache;  // scavengable oops

  private:

   // Shared fields for all nmethod's

   Method*   _method;

   int       _entry_bci;        // != InvocationEntryBci if this nmethod is an on-stack replacement method

   jmethodID _jmethod_id;       // Cache of method()->jmethod_id()

   // To support simple linked-list chaining of nmethods:

   nmethod*  _osr_link;         // from InstanceKlass::osr_nmethods_head

   nmethod*  _scavenge_root_link; // from CodeCache::scavenge_root_nmethods

   static nmethod* volatile _oops_do_mark_nmethods;

   nmethod*        volatile _oops_do_mark_link;

   AbstractCompiler* _compiler; // The compiler which compiled this nmethod

   // offsets for entry points

   address _entry_point;                      // entry point with class check

   address _verified_entry_point;             // entry point without class check

   address _osr_entry_point;                  // entry point for on stack replacement

   // Offsets for different nmethod parts

   int _exception_offset;

   // All deoptee's will resume execution at this location described by

   // this offset.

   int _deoptimize_offset;

   // All deoptee's at a MethodHandle call site will resume execution

   // at this location described by this offset.

   int _deoptimize_mh_offset;

   // Offset of the unwind handler if it exists

   int _unwind_handler_offset;

 #ifdef HAVE_DTRACE_H

   int _trap_offset;

 #endif // def HAVE_DTRACE_H

   int _consts_offset;

   int _stub_offset;

   int _oops_offset;                       // offset to where embedded oop table begins (inside data)

   int _metadata_offset;                   // embedded meta data table

   int _scopes_data_offset;

   int _scopes_pcs_offset;

   int _dependencies_offset;

   int _handler_table_offset;

   int _nul_chk_table_offset;

   int _nmethod_end_offset;

   // location in frame (offset for sp) that deopt can store the original

   // pc during a deopt.

   int _orig_pc_offset;

   int _compile_id;                           // which compilation made this nmethod

   int _comp_level;                           // compilation level

   // protected by CodeCache_lock

   bool _has_flushed_dependencies;            // Used for maintenance of dependencies (CodeCache_lock)

   bool _marked_for_reclamation;              // Used by NMethodSweeper (set only by sweeper)

   bool _marked_for_deoptimization;           // Used for stack deoptimization

   // used by jvmti to track if an unload event has been posted for this nmethod.

   bool _unload_reported;

   // set during construction

   unsigned int _has_unsafe_access:1;         // May fault due to unsafe access.

   unsigned int _has_method_handle_invokes:1; // Has this method MethodHandle invokes?

   unsigned int _lazy_critical_native:1;      // Lazy JNI critical native

   unsigned int _has_wide_vectors:1;          // Preserve wide vectors at safepoints

   // Protected by Patching_lock

   volatile unsigned char _state;             // {alive, not_entrant, zombie, unloaded}

 #ifdef ASSERT

   bool _oops_are_stale;  // indicates that it's no longer safe to access oops section

 #endif

   enum { in_use       = 0,   // executable nmethod

          not_entrant  = 1,   // marked for deoptimization but activations may still exist,

                              // will be transformed to zombie when all activations are gone

          zombie       = 2,   // no activations exist, nmethod is ready for purge

          unloaded     = 3 }; // there should be no activations, should not be called,

                              // will be transformed to zombie immediately

   jbyte _scavenge_root_state;

 #if INCLUDE_RTM_OPT

   // RTM state at compile time. Used during deoptimization to decide

   // whether to restart collecting RTM locking abort statistic again.

   RTMState _rtm_state;

 #endif

   // Nmethod Flushing lock. If non-zero, then the nmethod is not removed

   // and is not made into a zombie. However, once the nmethod is made into

   // a zombie, it will be locked one final time if CompiledMethodUnload

   // event processing needs to be done.

   jint  _lock_count;

   // not_entrant method removal. Each mark_sweep pass will update

   // this mark to current sweep invocation count if it is seen on the

   // stack.  An not_entrant method can be removed when there are no

   // more activations, i.e., when the _stack_traversal_mark is less than

   // current sweep traversal index.

   long _stack_traversal_mark;

   // The _hotness_counter indicates the hotness of a method. The higher

   // the value the hotter the method. The hotness counter of a nmethod is

   // set to [(ReservedCodeCacheSize / (1024 * 1024)) * 2] each time the method

   // is active while stack scanning (mark_active_nmethods()). The hotness

   // counter is decreased (by 1) while sweeping.

   int _hotness_counter;

   ExceptionCache *_exception_cache;

   PcDescCache     _pc_desc_cache;

   // These are used for compiled synchronized native methods to

   // locate the owner and stack slot for the BasicLock so that we can

   // properly revoke the bias of the owner if necessary. They are

   // needed because there is no debug information for compiled native

   // wrappers and the oop maps are insufficient to allow

   // frame::retrieve_receiver() to work. Currently they are expected

   // to be byte offsets from the Java stack pointer for maximum code

   // sharing between platforms. Note that currently biased locking

   // will never cause Class instances to be biased but this code

   // handles the static synchronized case as well.

   // JVMTI's GetLocalInstance() also uses these offsets to find the receiver

   // for non-static native wrapper frames.

   ByteSize _native_receiver_sp_offset;

   ByteSize _native_basic_lock_sp_offset;

   friend class nmethodLocker;

   // For native wrappers

   nmethod(Method* method,

           int nmethod_size,

           int compile_id,

           CodeOffsets* offsets,

           CodeBuffer *code_buffer,

           int frame_size,

           ByteSize basic_lock_owner_sp_offset, /* synchronized natives only */

           ByteSize basic_lock_sp_offset,       /* synchronized natives only */

           OopMapSet* oop_maps);

 #ifdef HAVE_DTRACE_H

   // For native wrappers

   nmethod(Method* method,

           int nmethod_size,

           CodeOffsets* offsets,

           CodeBuffer *code_buffer,

           int frame_size);

 #endif // def HAVE_DTRACE_H

   // Creation support

   nmethod(Method* method,

           int nmethod_size,

           int compile_id,

           int entry_bci,

           CodeOffsets* offsets,

           int orig_pc_offset,

           DebugInformationRecorder *recorder,

           Dependencies* dependencies,

           CodeBuffer *code_buffer,

           int frame_size,

           OopMapSet* oop_maps,

           ExceptionHandlerTable* handler_table,

           ImplicitExceptionTable* nul_chk_table,

           AbstractCompiler* compiler,

           int comp_level);

   // helper methods

   void* operator new(size_t size, int nmethod_size) throw();

   const char* reloc_string_for(u_char* begin, u_char* end);

   // Returns true if this thread changed the state of the nmethod or

   // false if another thread performed the transition.

   bool make_not_entrant_or_zombie(unsigned int state);

   void inc_decompile_count();

   // Used to manipulate the exception cache

   void add_exception_cache_entry(ExceptionCache* new_entry);

   ExceptionCache* exception_cache_entry_for_exception(Handle exception);

   // Inform external interfaces that a compiled method has been unloaded

   void post_compiled_method_unload();

   // Initailize fields to their default values

   void init_defaults();

  public:

   // create nmethod with entry_bci

   static nmethod* new_nmethod(methodHandle method,

                               int compile_id,

                               int entry_bci,

                               CodeOffsets* offsets,

                               int orig_pc_offset,

                               DebugInformationRecorder* recorder,

                               Dependencies* dependencies,

                               CodeBuffer *code_buffer,

                               int frame_size,

                               OopMapSet* oop_maps,

                               ExceptionHandlerTable* handler_table,

                               ImplicitExceptionTable* nul_chk_table,

                               AbstractCompiler* compiler,

                               int comp_level);

   static nmethod* new_native_nmethod(methodHandle method,

                                      int compile_id,

                                      CodeBuffer *code_buffer,

                                      int vep_offset,

                                      int frame_complete,

                                      int frame_size,

                                      ByteSize receiver_sp_offset,

                                      ByteSize basic_lock_sp_offset,

                                      OopMapSet* oop_maps);

 #ifdef HAVE_DTRACE_H

   // The method we generate for a dtrace probe has to look

   // like an nmethod as far as the rest of the system is concerned

   // which is somewhat unfortunate.

   static nmethod* new_dtrace_nmethod(methodHandle method,

                                      CodeBuffer *code_buffer,

                                      int vep_offset,

                                      int trap_offset,

                                      int frame_complete,

                                      int frame_size);

   int trap_offset() const      { return _trap_offset; }

   address trap_address() const { return insts_begin() + _trap_offset; }

 #endif // def HAVE_DTRACE_H

   // accessors

   Method* method() const                          { return _method; }

   AbstractCompiler* compiler() const              { return _compiler; }

   // type info

   bool is_nmethod() const                         { return true; }

   bool is_java_method() const                     { return !method()->is_native(); }

   bool is_native_method() const                   { return method()->is_native(); }

   bool is_osr_method() const                      { return _entry_bci != InvocationEntryBci; }

   bool is_compiled_by_c1() const;

   bool is_compiled_by_c2() const;

   bool is_compiled_by_shark() const;

   // boundaries for different parts

   address consts_begin          () const          { return           header_begin() + _consts_offset        ; }

   address consts_end            () const          { return           header_begin() +  code_offset()        ; }

   address insts_begin           () const          { return           header_begin() +  code_offset()        ; }

   address insts_end             () const          { return           header_begin() + _stub_offset          ; }

   address stub_begin            () const          { return           header_begin() + _stub_offset          ; }

   address stub_end              () const          { return           header_begin() + _oops_offset          ; }

   address exception_begin       () const          { return           header_begin() + _exception_offset     ; }

   address deopt_handler_begin   () const          { return           header_begin() + _deoptimize_offset    ; }

   address deopt_mh_handler_begin() const          { return           header_begin() + _deoptimize_mh_offset ; }

   address unwind_handler_begin  () const          { return _unwind_handler_offset != -1 ? (header_begin() + _unwind_handler_offset) : NULL; }

   oop*    oops_begin            () const          { return (oop*)   (header_begin() + _oops_offset)         ; }

   oop*    oops_end              () const          { return (oop*)   (header_begin() + _metadata_offset)     ; }

   Metadata** metadata_begin   () const            { return (Metadata**)  (header_begin() + _metadata_offset)     ; }

   Metadata** metadata_end     () const            { return (Metadata**)  (header_begin() + _scopes_data_offset)  ; }

   address scopes_data_begin     () const          { return           header_begin() + _scopes_data_offset   ; }

   address scopes_data_end       () const          { return           header_begin() + _scopes_pcs_offset    ; }

   PcDesc* scopes_pcs_begin      () const          { return (PcDesc*)(header_begin() + _scopes_pcs_offset   ); }

   PcDesc* scopes_pcs_end        () const          { return (PcDesc*)(header_begin() + _dependencies_offset) ; }

   address dependencies_begin    () const          { return           header_begin() + _dependencies_offset  ; }

   address dependencies_end      () const          { return           header_begin() + _handler_table_offset ; }

   address handler_table_begin   () const          { return           header_begin() + _handler_table_offset ; }

   address handler_table_end     () const          { return           header_begin() + _nul_chk_table_offset ; }

   address nul_chk_table_begin   () const          { return           header_begin() + _nul_chk_table_offset ; }

   address nul_chk_table_end     () const          { return           header_begin() + _nmethod_end_offset   ; }

   // Sizes

   int consts_size       () const                  { return            consts_end       () -            consts_begin       (); }

   int insts_size        () const                  { return            insts_end        () -            insts_begin        (); }

   int stub_size         () const                  { return            stub_end         () -            stub_begin         (); }

   int oops_size         () const                  { return (address)  oops_end         () - (address)  oops_begin         (); }

   int metadata_size     () const                  { return (address)  metadata_end     () - (address)  metadata_begin     (); }

   int scopes_data_size  () const                  { return            scopes_data_end  () -            scopes_data_begin  (); }

   int scopes_pcs_size   () const                  { return (intptr_t) scopes_pcs_end   () - (intptr_t) scopes_pcs_begin   (); }

   int dependencies_size () const                  { return            dependencies_end () -            dependencies_begin (); }

   int handler_table_size() const                  { return            handler_table_end() -            handler_table_begin(); }

   int nul_chk_table_size() const                  { return            nul_chk_table_end() -            nul_chk_table_begin(); }

   int total_size        () const;

   void dec_hotness_counter()        { _hotness_counter--; }

   void set_hotness_counter(int val) { _hotness_counter = val; }

   int  hotness_counter() const      { return _hotness_counter; }

   // Containment

   bool consts_contains       (address addr) const { return consts_begin       () <= addr && addr < consts_end       (); }

   bool insts_contains        (address addr) const { return insts_begin        () <= addr && addr < insts_end        (); }

   bool stub_contains         (address addr) const { return stub_begin         () <= addr && addr < stub_end         (); }

   bool oops_contains         (oop*    addr) const { return oops_begin         () <= addr && addr < oops_end         (); }

   bool metadata_contains     (Metadata** addr) const   { return metadata_begin     () <= addr && addr < metadata_end     (); }

   bool scopes_data_contains  (address addr) const { return scopes_data_begin  () <= addr && addr < scopes_data_end  (); }

   bool scopes_pcs_contains   (PcDesc* addr) const { return scopes_pcs_begin   () <= addr && addr < scopes_pcs_end   (); }

   bool handler_table_contains(address addr) const { return handler_table_begin() <= addr && addr < handler_table_end(); }

   bool nul_chk_table_contains(address addr) const { return nul_chk_table_begin() <= addr && addr < nul_chk_table_end(); }

   // entry points

   address entry_point() const                     { return _entry_point;             } // normal entry point

   address verified_entry_point() const            { return _verified_entry_point;    } // if klass is correct

   // flag accessing and manipulation

   bool  is_in_use() const                         { return _state == in_use; }

   bool  is_alive() const                          { return _state == in_use || _state == not_entrant; }

   bool  is_not_entrant() const                    { return _state == not_entrant; }

   bool  is_zombie() const                         { return _state == zombie; }

   bool  is_unloaded() const                       { return _state == unloaded;   }

 #if INCLUDE_RTM_OPT

   // rtm state accessing and manipulating

   RTMState  rtm_state() const                     { return _rtm_state; }

   void set_rtm_state(RTMState state)              { _rtm_state = state; }

 #endif

   // Make the nmethod non entrant. The nmethod will continue to be

   // alive.  It is used when an uncommon trap happens.  Returns true

   // if this thread changed the state of the nmethod or false if

   // another thread performed the transition.

   bool  make_not_entrant() { return make_not_entrant_or_zombie(not_entrant); }

   bool  make_zombie()      { return make_not_entrant_or_zombie(zombie); }

   // used by jvmti to track if the unload event has been reported

   bool  unload_reported()                         { return _unload_reported; }

   void  set_unload_reported()                     { _unload_reported = true; }

   bool  is_marked_for_deoptimization() const      { return _marked_for_deoptimization; }

   void  mark_for_deoptimization()                 { _marked_for_deoptimization = true; }

   void  make_unloaded(BoolObjectClosure* is_alive, oop cause);

   bool has_dependencies()                         { return dependencies_size() != 0; }

   void flush_dependencies(BoolObjectClosure* is_alive);

   bool has_flushed_dependencies()                 { return _has_flushed_dependencies; }

   void set_has_flushed_dependencies()             {

     assert(!has_flushed_dependencies(), "should only happen once");

     _has_flushed_dependencies = 1;

   }

   bool  is_marked_for_reclamation() const         { return _marked_for_reclamation; }

   void  mark_for_reclamation()                    { _marked_for_reclamation = 1; }

   bool  has_unsafe_access() const                 { return _has_unsafe_access; }

   void  set_has_unsafe_access(bool z)             { _has_unsafe_access = z; }

   bool  has_method_handle_invokes() const         { return _has_method_handle_invokes; }

   void  set_has_method_handle_invokes(bool z)     { _has_method_handle_invokes = z; }

   bool  is_lazy_critical_native() const           { return _lazy_critical_native; }

   void  set_lazy_critical_native(bool z)          { _lazy_critical_native = z; }

   bool  has_wide_vectors() const                  { return _has_wide_vectors; }

   void  set_has_wide_vectors(bool z)              { _has_wide_vectors = z; }

   int   comp_level() const                        { return _comp_level; }

   // Support for oops in scopes and relocs:

   // Note: index 0 is reserved for null.

   oop   oop_at(int index) const                   { return index == 0 ? (oop) NULL: *oop_addr_at(index); }

   oop*  oop_addr_at(int index) const {  // for GC

     // relocation indexes are biased by 1 (because 0 is reserved)

     assert(index > 0 && index <= oops_size(), "must be a valid non-zero index");

     assert(!_oops_are_stale, "oops are stale");

     return &oops_begin()[index - 1];

   }

   // Support for meta data in scopes and relocs:

   // Note: index 0 is reserved for null.

   Metadata*     metadata_at(int index) const      { return index == 0 ? NULL: *metadata_addr_at(index); }

   Metadata**  metadata_addr_at(int index) const {  // for GC

     // relocation indexes are biased by 1 (because 0 is reserved)

     assert(index > 0 && index <= metadata_size(), "must be a valid non-zero index");

     return &metadata_begin()[index - 1];

   }

   void copy_values(GrowableArray<jobject>* oops);

   void copy_values(GrowableArray<Metadata*>* metadata);

   // Relocation support

 private:

   void fix_oop_relocations(address begin, address end, bool initialize_immediates);

   inline void initialize_immediate_oop(oop* dest, jobject handle);

 public:

   void fix_oop_relocations(address begin, address end) { fix_oop_relocations(begin, end, false); }

   void fix_oop_relocations()                           { fix_oop_relocations(NULL, NULL, false); }

   void verify_oop_relocations();

   bool is_at_poll_return(address pc);

   bool is_at_poll_or_poll_return(address pc);

   // Scavengable oop support

   bool  on_scavenge_root_list() const                  { return (_scavenge_root_state & 1) != 0; }

  protected:

   enum { sl_on_list = 0x01, sl_marked = 0x10 };

   void  set_on_scavenge_root_list()                    { _scavenge_root_state = sl_on_list; }

   void  clear_on_scavenge_root_list()                  { _scavenge_root_state = 0; }

   // assertion-checking and pruning logic uses the bits of _scavenge_root_state

 #ifndef PRODUCT

   void  set_scavenge_root_marked()                     { _scavenge_root_state |= sl_marked; }

   void  clear_scavenge_root_marked()                   { _scavenge_root_state &= ~sl_marked; }

   bool  scavenge_root_not_marked()                     { return (_scavenge_root_state &~ sl_on_list) == 0; }

   // N.B. there is no positive marked query, and we only use the not_marked query for asserts.

 #endif //PRODUCT

   nmethod* scavenge_root_link() const                  { return _scavenge_root_link; }

   void     set_scavenge_root_link(nmethod *n)          { _scavenge_root_link = n; }

  public:

   // Sweeper support

   long  stack_traversal_mark()                    { return _stack_traversal_mark; }

   void  set_stack_traversal_mark(long l)          { _stack_traversal_mark = l; }

   // Exception cache support

   ExceptionCache* exception_cache() const         { return _exception_cache; }

   void set_exception_cache(ExceptionCache *ec)    { _exception_cache = ec; }

   address handler_for_exception_and_pc(Handle exception, address pc);

   void add_handler_for_exception_and_pc(Handle exception, address pc, address handler);

   void remove_from_exception_cache(ExceptionCache* ec);

   // implicit exceptions support

   address continuation_for_implicit_exception(address pc);

   // On-stack replacement support

   int   osr_entry_bci() const                     { assert(is_osr_method(), "wrong kind of nmethod"); return _entry_bci; }

   address  osr_entry() const                      { assert(is_osr_method(), "wrong kind of nmethod"); return _osr_entry_point; }

   void  invalidate_osr_method();

   nmethod* osr_link() const                       { return _osr_link; }

   void     set_osr_link(nmethod *n)               { _osr_link = n; }

   // tells whether frames described by this nmethod can be deoptimized

   // note: native wrappers cannot be deoptimized.

   bool can_be_deoptimized() const { return is_java_method(); }

   // Inline cache support

   void clear_inline_caches();

   void cleanup_inline_caches();

   bool inlinecache_check_contains(address addr) const {

     return (addr >= code_begin() && addr < verified_entry_point());

   }

   // Check that all metadata is still alive

   void verify_metadata_loaders(address low_boundary, BoolObjectClosure* is_alive);

   // unlink and deallocate this nmethod

   // Only NMethodSweeper class is expected to use this. NMethodSweeper is not

   // expected to use any other private methods/data in this class.

  protected:

   void flush();

  public:

   // When true is returned, it is unsafe to remove this nmethod even if

   // it is a zombie, since the VM or the ServiceThread might still be

   // using it.

   bool is_locked_by_vm() const                    { return _lock_count >0; }

   // See comment at definition of _last_seen_on_stack

   void mark_as_seen_on_stack();

   bool can_not_entrant_be_converted();

   // Evolution support. We make old (discarded) compiled methods point to new Method*s.

   void set_method(Method* method) { _method = method; }

   // GC support

   void do_unloading(BoolObjectClosure* is_alive, bool unloading_occurred);

   bool can_unload(BoolObjectClosure* is_alive, oop* root, bool unloading_occurred);

   void preserve_callee_argument_oops(frame fr, const RegisterMap *reg_map,

                                      OopClosure* f);

   void oops_do(OopClosure* f) { oops_do(f, false); }

   void oops_do(OopClosure* f, bool allow_zombie);

   bool detect_scavenge_root_oops();

   void verify_scavenge_root_oops() PRODUCT_RETURN;

   bool test_set_oops_do_mark();

   static void oops_do_marking_prologue();

   static void oops_do_marking_epilogue();

   static bool oops_do_marking_is_active() { return _oops_do_mark_nmethods != NULL; }

   bool test_oops_do_mark() { return _oops_do_mark_link != NULL; }

   // ScopeDesc for an instruction

   ScopeDesc* scope_desc_at(address pc);

  private:

   ScopeDesc* scope_desc_in(address begin, address end);

   address* orig_pc_addr(const frame* fr) { return (address*) ((address)fr->unextended_sp() + _orig_pc_offset); }

   PcDesc* find_pc_desc_internal(address pc, bool approximate);

   PcDesc* find_pc_desc(address pc, bool approximate) {

     PcDesc* desc = _pc_desc_cache.last_pc_desc();

     if (desc != NULL && desc->pc_offset() == pc - code_begin()) {

       return desc;

     }

     return find_pc_desc_internal(pc, approximate);

   }

  public:

   // ScopeDesc retrieval operation

   PcDesc* pc_desc_at(address pc)   { return find_pc_desc(pc, false); }

   // pc_desc_near returns the first PcDesc at or after the givne pc.

   PcDesc* pc_desc_near(address pc) { return find_pc_desc(pc, true); }

  public:

   // copying of debugging information

   void copy_scopes_pcs(PcDesc* pcs, int count);

   void copy_scopes_data(address buffer, int size);

   // Deopt

   // Return true is the PC is one would expect if the frame is being deopted.

   bool is_deopt_pc      (address pc) { return is_deopt_entry(pc) || is_deopt_mh_entry(pc); }

   bool is_deopt_entry   (address pc) { return pc == deopt_handler_begin(); }

   bool is_deopt_mh_entry(address pc) { return pc == deopt_mh_handler_begin(); }

   // Accessor/mutator for the original pc of a frame before a frame was deopted.

   address get_original_pc(const frame* fr) { return *orig_pc_addr(fr); }

   void    set_original_pc(const frame* fr, address pc) { *orig_pc_addr(fr) = pc; }

   static address get_deopt_original_pc(const frame* fr);

   // MethodHandle

   bool is_method_handle_return(address return_pc);

   // jvmti support:

   void post_compiled_method_load_event();

   jmethodID get_and_cache_jmethod_id();

   // verify operations

   void verify();

   void verify_scopes();

   void verify_interrupt_point(address interrupt_point);

   // printing support

   void print()                          const;

   void print_code();

   void print_relocations()                        PRODUCT_RETURN;

   void print_pcs()                                PRODUCT_RETURN;

   void print_scopes()                             PRODUCT_RETURN;

   void print_dependencies()                       PRODUCT_RETURN;

   void print_value_on(outputStream* st) const     PRODUCT_RETURN;

   void print_calls(outputStream* st)              PRODUCT_RETURN;

   void print_handler_table()                      PRODUCT_RETURN;

   void print_nul_chk_table()                      PRODUCT_RETURN;

   void print_nmethod(bool print_code);

   // need to re-define this from CodeBlob else the overload hides it

   virtual void print_on(outputStream* st) const { CodeBlob::print_on(st); }

   void print_on(outputStream* st, const char* msg) const;

   // Logging

   void log_identity(xmlStream* log) const;

   void log_new_nmethod() const;

   void log_state_change() const;

   // Prints block-level comments, including nmethod specific block labels:

   virtual void print_block_comment(outputStream* stream, address block_begin) const {

     print_nmethod_labels(stream, block_begin);

     CodeBlob::print_block_comment(stream, block_begin);

   }

   void print_nmethod_labels(outputStream* stream, address block_begin) const;

   // Prints a comment for one native instruction (reloc info, pc desc)

   void print_code_comment_on(outputStream* st, int column, address begin, address end);

   static void print_statistics()                  PRODUCT_RETURN;

   // Compiler task identification.  Note that all OSR methods

   // are numbered in an independent sequence if CICountOSR is true,

   // and native method wrappers are also numbered independently if

   // CICountNative is true.

   int  compile_id() const                         { return _compile_id; }

   const char* compile_kind() const;

   // For debugging

   // CompiledIC*    IC_at(char* p) const;

   // PrimitiveIC*   primitiveIC_at(char* p) const;

   oop embeddedOop_at(address p);

   // tells if any of this method's dependencies have been invalidated

   // (this is expensive!)

   bool check_all_dependencies();

   // tells if this compiled method is dependent on the given changes,

   // and the changes have invalidated it

   bool check_dependency_on(DepChange& changes);

   // Evolution support. Tells if this compiled method is dependent on any of

   // methods m() of class dependee, such that if m() in dependee is replaced,

   // this compiled method will have to be deoptimized.

   bool is_evol_dependent_on(Klass* dependee);

   // Fast breakpoint support. Tells if this compiled method is

   // dependent on the given method. Returns true if this nmethod

   // corresponds to the given method as well.

   bool is_dependent_on_method(Method* dependee);

   // is it ok to patch at address?

   bool is_patchable_at(address instr_address);

   // UseBiasedLocking support

   ByteSize native_receiver_sp_offset() {

     return _native_receiver_sp_offset;

   }

   ByteSize native_basic_lock_sp_offset() {

     return _native_basic_lock_sp_offset;

   }

   // support for code generation

   static int verified_entry_point_offset()        { return offset_of(nmethod, _verified_entry_point); }

   static int osr_entry_point_offset()             { return offset_of(nmethod, _osr_entry_point); }

   static int entry_bci_offset()                   { return offset_of(nmethod, _entry_bci); }

   // RedefineClasses support.   Mark metadata in nmethods as on_stack so that

   // redefine classes doesn't purge it.

   static void mark_on_stack(nmethod* nm) {

     nm->metadata_do(Metadata::mark_on_stack);

   }

   void metadata_do(void f(Metadata*));

 };

 // Locks an nmethod so its code will not get removed and it will not

 // be made into a zombie, even if it is a not_entrant method. After the

 // nmethod becomes a zombie, if CompiledMethodUnload event processing

 // needs to be done, then lock_nmethod() is used directly to keep the

 // generated code from being reused too early.

 class nmethodLocker : public StackObj {

   nmethod* _nm;

  public:

   // note: nm can be NULL

   // Only JvmtiDeferredEvent::compiled_method_unload_event()

   // should pass zombie_ok == true.

   static void lock_nmethod(nmethod* nm, bool zombie_ok = false);

   static void unlock_nmethod(nmethod* nm); // (ditto)

   nmethodLocker(address pc); // derive nm from pc

   nmethodLocker(nmethod *nm) { _nm = nm; lock_nmethod(_nm); }

   nmethodLocker() { _nm = NULL; }

   ~nmethodLocker() { unlock_nmethod(_nm); }

   nmethod* code() { return _nm; }

   void set_code(nmethod* new_nm) {

     unlock_nmethod(_nm);   // note:  This works even if _nm==new_nm.

     _nm = new_nm;

     lock_nmethod(_nm);

   }

 };

 #endif // SHARE_VM_CODE_NMETHOD_HPP