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 /*

  * Copyright (c) 1997, 2014, 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

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  */

 #ifndef SHARE_VM_OOPS_KLASS_HPP

 #define SHARE_VM_OOPS_KLASS_HPP

 #include "memory/genOopClosures.hpp"

 #include "memory/iterator.hpp"

 #include "memory/memRegion.hpp"

 #include "memory/specialized_oop_closures.hpp"

 #include "oops/klassPS.hpp"

 #include "oops/metadata.hpp"

 #include "oops/oop.hpp"

 #ifdef MIPS64

 #include "runtime/orderAccess.hpp"

 #endif

 #include "trace/traceMacros.hpp"

 #include "utilities/accessFlags.hpp"

 #include "utilities/macros.hpp"

 #if INCLUDE_ALL_GCS

 #include "gc_implementation/concurrentMarkSweep/cmsOopClosures.hpp"

 #include "gc_implementation/g1/g1OopClosures.hpp"

 #include "gc_implementation/parNew/parOopClosures.hpp"

 #endif // INCLUDE_ALL_GCS

 //

 // A Klass provides:

 //  1: language level class object (method dictionary etc.)

 //  2: provide vm dispatch behavior for the object

 // Both functions are combined into one C++ class.

 // One reason for the oop/klass dichotomy in the implementation is

 // that we don't want a C++ vtbl pointer in every object.  Thus,

 // normal oops don't have any virtual functions.  Instead, they

 // forward all "virtual" functions to their klass, which does have

 // a vtbl and does the C++ dispatch depending on the object's

 // actual type.  (See oop.inline.hpp for some of the forwarding code.)

 // ALL FUNCTIONS IMPLEMENTING THIS DISPATCH ARE PREFIXED WITH "oop_"!

 //  Klass layout:

 //    [C++ vtbl ptr  ] (contained in Metadata)

 //    [layout_helper ]

 //    [super_check_offset   ] for fast subtype checks

 //    [name          ]

 //    [secondary_super_cache] for fast subtype checks

 //    [secondary_supers     ] array of 2ndary supertypes

 //    [primary_supers 0]

 //    [primary_supers 1]

 //    [primary_supers 2]

 //    ...

 //    [primary_supers 7]

 //    [java_mirror   ]

 //    [super         ]

 //    [subklass      ] first subclass

 //    [next_sibling  ] link to chain additional subklasses

 //    [next_link     ]

 //    [class_loader_data]

 //    [modifier_flags]

 //    [access_flags  ]

 //    [last_biased_lock_bulk_revocation_time] (64 bits)

 //    [prototype_header]

 //    [biased_lock_revocation_count]

 //    [_modified_oops]

 //    [_accumulated_modified_oops]

 //    [trace_id]

 // Forward declarations.

 template <class T> class Array;

 template <class T> class GrowableArray;

 class ClassLoaderData;

 class klassVtable;

 class ParCompactionManager;

 class KlassSizeStats;

 class fieldDescriptor;

 class Klass : public Metadata {

   friend class VMStructs;

  protected:

   // note: put frequently-used fields together at start of klass structure

   // for better cache behavior (may not make much of a difference but sure won't hurt)

   enum { _primary_super_limit = 8 };

   // The "layout helper" is a combined descriptor of object layout.

   // For klasses which are neither instance nor array, the value is zero.

   //

   // For instances, layout helper is a positive number, the instance size.

   // This size is already passed through align_object_size and scaled to bytes.

   // The low order bit is set if instances of this class cannot be

   // allocated using the fastpath.

   //

   // For arrays, layout helper is a negative number, containing four

   // distinct bytes, as follows:

   //    MSB:[tag, hsz, ebt, log2(esz)]:LSB

   // where:

   //    tag is 0x80 if the elements are oops, 0xC0 if non-oops

   //    hsz is array header size in bytes (i.e., offset of first element)

   //    ebt is the BasicType of the elements

   //    esz is the element size in bytes

   // This packed word is arranged so as to be quickly unpacked by the

   // various fast paths that use the various subfields.

   //

   // The esz bits can be used directly by a SLL instruction, without masking.

   //

   // Note that the array-kind tag looks like 0x00 for instance klasses,

   // since their length in bytes is always less than 24Mb.

   //

   // Final note:  This comes first, immediately after C++ vtable,

   // because it is frequently queried.

   jint        _layout_helper;

   // The fields _super_check_offset, _secondary_super_cache, _secondary_supers

   // and _primary_supers all help make fast subtype checks.  See big discussion

   // in doc/server_compiler/checktype.txt

   //

   // Where to look to observe a supertype (it is &_secondary_super_cache for

   // secondary supers, else is &_primary_supers[depth()].

   juint       _super_check_offset;

   // Class name.  Instance classes: java/lang/String, etc.  Array classes: [I,

   // [Ljava/lang/String;, etc.  Set to zero for all other kinds of classes.

   Symbol*     _name;

   // Cache of last observed secondary supertype

   Klass*      _secondary_super_cache;

   // Array of all secondary supertypes

   Array<Klass*>* _secondary_supers;

   // Ordered list of all primary supertypes

   Klass*      _primary_supers[_primary_super_limit];

   // java/lang/Class instance mirroring this class

   oop       _java_mirror;

   // Superclass

   Klass*      _super;

   // First subclass (NULL if none); _subklass->next_sibling() is next one

   Klass*      _subklass;

   // Sibling link (or NULL); links all subklasses of a klass

   Klass*      _next_sibling;

   // All klasses loaded by a class loader are chained through these links

   Klass*      _next_link;

   // The VM's representation of the ClassLoader used to load this class.

   // Provide access the corresponding instance java.lang.ClassLoader.

   ClassLoaderData* _class_loader_data;

   jint        _modifier_flags;  // Processed access flags, for use by Class.getModifiers.

   AccessFlags _access_flags;    // Access flags. The class/interface distinction is stored here.

   // Biased locking implementation and statistics

   // (the 64-bit chunk goes first, to avoid some fragmentation)

   jlong    _last_biased_lock_bulk_revocation_time;

   markOop  _prototype_header;   // Used when biased locking is both enabled and disabled for this type

   jint     _biased_lock_revocation_count;

   TRACE_DEFINE_KLASS_TRACE_ID;

   // Remembered sets support for the oops in the klasses.

   jbyte _modified_oops;             // Card Table Equivalent (YC/CMS support)

   jbyte _accumulated_modified_oops; // Mod Union Equivalent (CMS support)

 private:

   // This is an index into FileMapHeader::_classpath_entry_table[], to

   // associate this class with the JAR file where it's loaded from during

   // dump time. If a class is not loaded from the shared archive, this field is

   // -1.

   jshort _shared_class_path_index;

   friend class SharedClassUtil;

 protected:

   // Constructor

   Klass();

   void* operator new(size_t size, ClassLoaderData* loader_data, size_t word_size, TRAPS) throw();

  public:

   enum MethodLookupMode { normal, skip_overpass, skip_defaults };

   bool is_klass() const volatile { return true; }

   // super

   Klass* super() const               { return _super; }

   void set_super(Klass* k)           { _super = k; }

   // initializes _super link, _primary_supers & _secondary_supers arrays

   void initialize_supers(Klass* k, TRAPS);

   void initialize_supers_impl1(Klass* k);

   void initialize_supers_impl2(Klass* k);

   // klass-specific helper for initializing _secondary_supers

   virtual GrowableArray<Klass*>* compute_secondary_supers(int num_extra_slots);

   // java_super is the Java-level super type as specified by Class.getSuperClass.

   virtual Klass* java_super() const  { return NULL; }

   juint    super_check_offset() const  { return _super_check_offset; }

   void set_super_check_offset(juint o) { _super_check_offset = o; }

   Klass* secondary_super_cache() const     { return _secondary_super_cache; }

   void set_secondary_super_cache(Klass* k) { _secondary_super_cache = k; }

   Array<Klass*>* secondary_supers() const { return _secondary_supers; }

   void set_secondary_supers(Array<Klass*>* k) { _secondary_supers = k; }

   // Return the element of the _super chain of the given depth.

   // If there is no such element, return either NULL or this.

   Klass* primary_super_of_depth(juint i) const {

     assert(i < primary_super_limit(), "oob");

     Klass* super = _primary_supers[i];

     assert(super == NULL || super->super_depth() == i, "correct display");

     return super;

   }

   // Can this klass be a primary super?  False for interfaces and arrays of

   // interfaces.  False also for arrays or classes with long super chains.

   bool can_be_primary_super() const {

     const juint secondary_offset = in_bytes(secondary_super_cache_offset());

     return super_check_offset() != secondary_offset;

   }

   virtual bool can_be_primary_super_slow() const;

   // Returns number of primary supers; may be a number in the inclusive range [0, primary_super_limit].

   juint super_depth() const {

     if (!can_be_primary_super()) {

       return primary_super_limit();

     } else {

       juint d = (super_check_offset() - in_bytes(primary_supers_offset())) / sizeof(Klass*);

       assert(d < primary_super_limit(), "oob");

       assert(_primary_supers[d] == this, "proper init");

       return d;

     }

   }

   // store an oop into a field of a Klass

   void klass_oop_store(oop* p, oop v);

   void klass_oop_store(volatile oop* p, oop v);

   // java mirror

   oop java_mirror() const              { return _java_mirror; }

   void set_java_mirror(oop m) { klass_oop_store(&_java_mirror, m); }

   // modifier flags

   jint modifier_flags() const          { return _modifier_flags; }

   void set_modifier_flags(jint flags)  { _modifier_flags = flags; }

   // size helper

   int layout_helper() const            { return _layout_helper; }

   void set_layout_helper(int lh)       { _layout_helper = lh; }

   // Note: for instances layout_helper() may include padding.

   // Use InstanceKlass::contains_field_offset to classify field offsets.

   // sub/superklass links

   InstanceKlass* superklass() const;

   Klass* subklass() const;

   Klass* next_sibling() const;

   void append_to_sibling_list();           // add newly created receiver to superklass' subklass list

   void set_next_link(Klass* k) { _next_link = k; }

   Klass* next_link() const { return _next_link; }   // The next klass defined by the class loader.

   // class loader data

   ClassLoaderData* class_loader_data() const               { return _class_loader_data; }

   void set_class_loader_data(ClassLoaderData* loader_data) {  _class_loader_data = loader_data; }

   // The Klasses are not placed in the Heap, so the Card Table or

   // the Mod Union Table can't be used to mark when klasses have modified oops.

   // The CT and MUT bits saves this information for the individual Klasses.

   void record_modified_oops()            {

     _modified_oops = 1;

 #ifdef MIPS64

     if (UseSyncLevel >= 2000) OrderAccess::fence();

 #endif

   }

   void clear_modified_oops()             {

     _modified_oops = 0;

 #ifdef MIPS64

     if (UseSyncLevel >= 2000) OrderAccess::fence();

 #endif

   }

   bool has_modified_oops()               { return _modified_oops == 1; }

   void accumulate_modified_oops()        { if (has_modified_oops()) _accumulated_modified_oops = 1; }

   void clear_accumulated_modified_oops() { _accumulated_modified_oops = 0; }

   bool has_accumulated_modified_oops()   { return _accumulated_modified_oops == 1; }

   int shared_classpath_index() const   {

     return _shared_class_path_index;

   };

   void set_shared_classpath_index(int index) {

     _shared_class_path_index = index;

   };

  protected:                                // internal accessors

   Klass* subklass_oop() const            { return _subklass; }

   Klass* next_sibling_oop() const        { return _next_sibling; }

   void     set_subklass(Klass* s);

   void     set_next_sibling(Klass* s);

  public:

   // Compiler support

   static ByteSize super_offset()                 { return in_ByteSize(offset_of(Klass, _super)); }

   static ByteSize super_check_offset_offset()    { return in_ByteSize(offset_of(Klass, _super_check_offset)); }

   static ByteSize primary_supers_offset()        { return in_ByteSize(offset_of(Klass, _primary_supers)); }

   static ByteSize secondary_super_cache_offset() { return in_ByteSize(offset_of(Klass, _secondary_super_cache)); }

   static ByteSize secondary_supers_offset()      { return in_ByteSize(offset_of(Klass, _secondary_supers)); }

   static ByteSize java_mirror_offset()           { return in_ByteSize(offset_of(Klass, _java_mirror)); }

   static ByteSize modifier_flags_offset()        { return in_ByteSize(offset_of(Klass, _modifier_flags)); }

   static ByteSize layout_helper_offset()         { return in_ByteSize(offset_of(Klass, _layout_helper)); }

   static ByteSize access_flags_offset()          { return in_ByteSize(offset_of(Klass, _access_flags)); }

   // Unpacking layout_helper:

   enum {

     _lh_neutral_value           = 0,  // neutral non-array non-instance value

     _lh_instance_slow_path_bit  = 0x01,

     _lh_log2_element_size_shift = BitsPerByte*0,

     _lh_log2_element_size_mask  = BitsPerLong-1,

     _lh_element_type_shift      = BitsPerByte*1,

     _lh_element_type_mask       = right_n_bits(BitsPerByte),  // shifted mask

     _lh_header_size_shift       = BitsPerByte*2,

     _lh_header_size_mask        = right_n_bits(BitsPerByte),  // shifted mask

     _lh_array_tag_bits          = 2,

     _lh_array_tag_shift         = BitsPerInt - _lh_array_tag_bits,

     _lh_array_tag_type_value    = ~0x00,  // 0xC0000000 >> 30

     _lh_array_tag_obj_value     = ~0x01   // 0x80000000 >> 30

   };

   static int layout_helper_size_in_bytes(jint lh) {

     assert(lh > (jint)_lh_neutral_value, "must be instance");

     return (int) lh & ~_lh_instance_slow_path_bit;

   }

   static bool layout_helper_needs_slow_path(jint lh) {

     assert(lh > (jint)_lh_neutral_value, "must be instance");

     return (lh & _lh_instance_slow_path_bit) != 0;

   }

   static bool layout_helper_is_instance(jint lh) {

     return (jint)lh > (jint)_lh_neutral_value;

   }

   static bool layout_helper_is_array(jint lh) {

     return (jint)lh < (jint)_lh_neutral_value;

   }

   static bool layout_helper_is_typeArray(jint lh) {

     // _lh_array_tag_type_value == (lh >> _lh_array_tag_shift);

     return (juint)lh >= (juint)(_lh_array_tag_type_value << _lh_array_tag_shift);

   }

   static bool layout_helper_is_objArray(jint lh) {

     // _lh_array_tag_obj_value == (lh >> _lh_array_tag_shift);

     return (jint)lh < (jint)(_lh_array_tag_type_value << _lh_array_tag_shift);

   }

   static int layout_helper_header_size(jint lh) {

     assert(lh < (jint)_lh_neutral_value, "must be array");

     int hsize = (lh >> _lh_header_size_shift) & _lh_header_size_mask;

     assert(hsize > 0 && hsize < (int)sizeof(oopDesc)*3, "sanity");

     return hsize;

   }

   static BasicType layout_helper_element_type(jint lh) {

     assert(lh < (jint)_lh_neutral_value, "must be array");

     int btvalue = (lh >> _lh_element_type_shift) & _lh_element_type_mask;

     assert(btvalue >= T_BOOLEAN && btvalue <= T_OBJECT, "sanity");

     return (BasicType) btvalue;

   }

   static int layout_helper_log2_element_size(jint lh) {

     assert(lh < (jint)_lh_neutral_value, "must be array");

     int l2esz = (lh >> _lh_log2_element_size_shift) & _lh_log2_element_size_mask;

     assert(l2esz <= LogBitsPerLong,

         err_msg("sanity. l2esz: 0x%x for lh: 0x%x", (uint)l2esz, (uint)lh));

     return l2esz;

   }

   static jint array_layout_helper(jint tag, int hsize, BasicType etype, int log2_esize) {

     return (tag        << _lh_array_tag_shift)

       |    (hsize      << _lh_header_size_shift)

       |    ((int)etype << _lh_element_type_shift)

       |    (log2_esize << _lh_log2_element_size_shift);

   }

   static jint instance_layout_helper(jint size, bool slow_path_flag) {

     return (size << LogHeapWordSize)

       |    (slow_path_flag ? _lh_instance_slow_path_bit : 0);

   }

   static int layout_helper_to_size_helper(jint lh) {

     assert(lh > (jint)_lh_neutral_value, "must be instance");

     // Note that the following expression discards _lh_instance_slow_path_bit.

     return lh >> LogHeapWordSize;

   }

   // Out-of-line version computes everything based on the etype:

   static jint array_layout_helper(BasicType etype);

   // What is the maximum number of primary superclasses any klass can have?

 #ifdef PRODUCT

   static juint primary_super_limit()         { return _primary_super_limit; }

 #else

   static juint primary_super_limit() {

     assert(FastSuperclassLimit <= _primary_super_limit, "parameter oob");

     return FastSuperclassLimit;

   }

 #endif

   // vtables

   virtual klassVtable* vtable() const        { return NULL; }

   virtual int vtable_length() const          { return 0; }

   // subclass check

   bool is_subclass_of(const Klass* k) const;

   // subtype check: true if is_subclass_of, or if k is interface and receiver implements it

   bool is_subtype_of(Klass* k) const {

     juint    off = k->super_check_offset();

     Klass* sup = *(Klass**)( (address)this + off );

     const juint secondary_offset = in_bytes(secondary_super_cache_offset());

     if (sup == k) {

       return true;

     } else if (off != secondary_offset) {

       return false;

     } else {

       return search_secondary_supers(k);

     }

   }

   bool search_secondary_supers(Klass* k) const;

   // Find LCA in class hierarchy

   Klass *LCA( Klass *k );

   // Check whether reflection/jni/jvm code is allowed to instantiate this class;

   // if not, throw either an Error or an Exception.

   virtual void check_valid_for_instantiation(bool throwError, TRAPS);

   // array copying

   virtual void  copy_array(arrayOop s, int src_pos, arrayOop d, int dst_pos, int length, TRAPS);

   // tells if the class should be initialized

   virtual bool should_be_initialized() const    { return false; }

   // initializes the klass

   virtual void initialize(TRAPS);

   // lookup operation for MethodLookupCache

   friend class MethodLookupCache;

   virtual Klass* find_field(Symbol* name, Symbol* signature, fieldDescriptor* fd) const;

   virtual Method* uncached_lookup_method(Symbol* name, Symbol* signature, MethodLookupMode mode) const;

  public:

   Method* lookup_method(Symbol* name, Symbol* signature) const {

     return uncached_lookup_method(name, signature, normal);

   }

   // array class with specific rank

   Klass* array_klass(int rank, TRAPS)         {  return array_klass_impl(false, rank, THREAD); }

   // array class with this klass as element type

   Klass* array_klass(TRAPS)                   {  return array_klass_impl(false, THREAD); }

   // These will return NULL instead of allocating on the heap:

   // NB: these can block for a mutex, like other functions with TRAPS arg.

   Klass* array_klass_or_null(int rank);

   Klass* array_klass_or_null();

   virtual oop protection_domain() const = 0;

   oop class_loader() const;

   virtual oop klass_holder() const      { return class_loader(); }

  protected:

   virtual Klass* array_klass_impl(bool or_null, int rank, TRAPS);

   virtual Klass* array_klass_impl(bool or_null, TRAPS);

  public:

   // CDS support - remove and restore oops from metadata. Oops are not shared.

   virtual void remove_unshareable_info();

   virtual void restore_unshareable_info(ClassLoaderData* loader_data, Handle protection_domain, TRAPS);

  protected:

   // computes the subtype relationship

   virtual bool compute_is_subtype_of(Klass* k);

  public:

   // subclass accessor (here for convenience; undefined for non-klass objects)

   virtual bool is_leaf_class() const { fatal("not a class"); return false; }

  public:

   // ALL FUNCTIONS BELOW THIS POINT ARE DISPATCHED FROM AN OOP

   // These functions describe behavior for the oop not the KLASS.

   // actual oop size of obj in memory

   virtual int oop_size(oop obj) const = 0;

   // Size of klass in word size.

   virtual int size() const = 0;

 #if INCLUDE_SERVICES

   virtual void collect_statistics(KlassSizeStats *sz) const;

 #endif

   // Returns the Java name for a class (Resource allocated)

   // For arrays, this returns the name of the element with a leading '['.

   // For classes, this returns the name with the package separators

   //     turned into '.'s.

   const char* external_name() const;

   // Returns the name for a class (Resource allocated) as the class

   // would appear in a signature.

   // For arrays, this returns the name of the element with a leading '['.

   // For classes, this returns the name with a leading 'L' and a trailing ';'

   //     and the package separators as '/'.

   virtual const char* signature_name() const;

   // garbage collection support

   virtual void oop_follow_contents(oop obj) = 0;

   virtual int  oop_adjust_pointers(oop obj) = 0;

   // Parallel Scavenge and Parallel Old

   PARALLEL_GC_DECLS_PV

   // type testing operations

  protected:

   virtual bool oop_is_instance_slow()       const { return false; }

   virtual bool oop_is_array_slow()          const { return false; }

   virtual bool oop_is_objArray_slow()       const { return false; }

   virtual bool oop_is_typeArray_slow()      const { return false; }

  public:

   virtual bool oop_is_instanceClassLoader() const { return false; }

   virtual bool oop_is_instanceMirror()      const { return false; }

   virtual bool oop_is_instanceRef()         const { return false; }

   // Fast non-virtual versions

   #ifndef ASSERT

   #define assert_same_query(xval, xcheck) xval

   #else

  private:

   static bool assert_same_query(bool xval, bool xslow) {

     assert(xval == xslow, "slow and fast queries agree");

     return xval;

   }

  public:

   #endif

   inline  bool oop_is_instance()            const { return assert_same_query(

                                                     layout_helper_is_instance(layout_helper()),

                                                     oop_is_instance_slow()); }

   inline  bool oop_is_array()               const { return assert_same_query(

                                                     layout_helper_is_array(layout_helper()),

                                                     oop_is_array_slow()); }

   inline  bool oop_is_objArray()            const { return assert_same_query(

                                                     layout_helper_is_objArray(layout_helper()),

                                                     oop_is_objArray_slow()); }

   inline  bool oop_is_typeArray()           const { return assert_same_query(

                                                     layout_helper_is_typeArray(layout_helper()),

                                                     oop_is_typeArray_slow()); }

   #undef assert_same_query

   // Access flags

   AccessFlags access_flags() const         { return _access_flags;  }

   void set_access_flags(AccessFlags flags) { _access_flags = flags; }

   bool is_public() const                { return _access_flags.is_public(); }

   bool is_final() const                 { return _access_flags.is_final(); }

   bool is_interface() const             { return _access_flags.is_interface(); }

   bool is_abstract() const              { return _access_flags.is_abstract(); }

   bool is_super() const                 { return _access_flags.is_super(); }

   bool is_synthetic() const             { return _access_flags.is_synthetic(); }

   void set_is_synthetic()               { _access_flags.set_is_synthetic(); }

   bool has_finalizer() const            { return _access_flags.has_finalizer(); }

   bool has_final_method() const         { return _access_flags.has_final_method(); }

   void set_has_finalizer()              { _access_flags.set_has_finalizer(); }

   void set_has_final_method()           { _access_flags.set_has_final_method(); }

   bool is_cloneable() const             { return _access_flags.is_cloneable(); }

   void set_is_cloneable()               { _access_flags.set_is_cloneable(); }

   bool has_vanilla_constructor() const  { return _access_flags.has_vanilla_constructor(); }

   void set_has_vanilla_constructor()    { _access_flags.set_has_vanilla_constructor(); }

   bool has_miranda_methods () const     { return access_flags().has_miranda_methods(); }

   void set_has_miranda_methods()        { _access_flags.set_has_miranda_methods(); }

   // Biased locking support

   // Note: the prototype header is always set up to be at least the

   // prototype markOop. If biased locking is enabled it may further be

   // biasable and have an epoch.

   markOop prototype_header() const      { return _prototype_header; }

   // NOTE: once instances of this klass are floating around in the

   // system, this header must only be updated at a safepoint.

   // NOTE 2: currently we only ever set the prototype header to the

   // biasable prototype for instanceKlasses. There is no technical

   // reason why it could not be done for arrayKlasses aside from

   // wanting to reduce the initial scope of this optimization. There

   // are potential problems in setting the bias pattern for

   // JVM-internal oops.

   inline void set_prototype_header(markOop header);

   static ByteSize prototype_header_offset() { return in_ByteSize(offset_of(Klass, _prototype_header)); }

   int  biased_lock_revocation_count() const { return (int) _biased_lock_revocation_count; }

   // Atomically increments biased_lock_revocation_count and returns updated value

   int atomic_incr_biased_lock_revocation_count();

   void set_biased_lock_revocation_count(int val) { _biased_lock_revocation_count = (jint) val; }

   jlong last_biased_lock_bulk_revocation_time() { return _last_biased_lock_bulk_revocation_time; }

   void  set_last_biased_lock_bulk_revocation_time(jlong cur_time) { _last_biased_lock_bulk_revocation_time = cur_time; }

   TRACE_DEFINE_KLASS_METHODS;

   // garbage collection support

   virtual void oops_do(OopClosure* cl);

   // Iff the class loader (or mirror for anonymous classes) is alive the

   // Klass is considered alive.

   // The is_alive closure passed in depends on the Garbage Collector used.

   bool is_loader_alive(BoolObjectClosure* is_alive);

   static void clean_weak_klass_links(BoolObjectClosure* is_alive, bool clean_alive_klasses = true);

   static void clean_subklass_tree(BoolObjectClosure* is_alive) {

     clean_weak_klass_links(is_alive, false /* clean_alive_klasses */);

   }

   // iterators

   virtual int oop_oop_iterate(oop obj, ExtendedOopClosure* blk) = 0;

   virtual int oop_oop_iterate_v(oop obj, ExtendedOopClosure* blk) {

     return oop_oop_iterate(obj, blk);

   }

 #if INCLUDE_ALL_GCS

   // In case we don't have a specialized backward scanner use forward

   // iteration.

   virtual int oop_oop_iterate_backwards_v(oop obj, ExtendedOopClosure* blk) {

     return oop_oop_iterate_v(obj, blk);

   }

 #endif // INCLUDE_ALL_GCS

   // Iterates "blk" over all the oops in "obj" (of type "this") within "mr".

   // (I don't see why the _m should be required, but without it the Solaris

   // C++ gives warning messages about overridings of the "oop_oop_iterate"

   // defined above "hiding" this virtual function.  (DLD, 6/20/00)) */

   virtual int oop_oop_iterate_m(oop obj, ExtendedOopClosure* blk, MemRegion mr) = 0;

   virtual int oop_oop_iterate_v_m(oop obj, ExtendedOopClosure* blk, MemRegion mr) {

     return oop_oop_iterate_m(obj, blk, mr);

   }

   // Versions of the above iterators specialized to particular subtypes

   // of OopClosure, to avoid closure virtual calls.

 #define Klass_OOP_OOP_ITERATE_DECL(OopClosureType, nv_suffix)                \

   virtual int oop_oop_iterate##nv_suffix(oop obj, OopClosureType* blk) {     \

     /* Default implementation reverts to general version. */                 \

     return oop_oop_iterate(obj, blk);                                        \

   }                                                                          \

                                                                              \

   /* Iterates "blk" over all the oops in "obj" (of type "this") within "mr". \

      (I don't see why the _m should be required, but without it the Solaris  \

      C++ gives warning messages about overridings of the "oop_oop_iterate"   \

      defined above "hiding" this virtual function.  (DLD, 6/20/00)) */       \

   virtual int oop_oop_iterate##nv_suffix##_m(oop obj,                        \

                                              OopClosureType* blk,            \

                                              MemRegion mr) {                 \

     return oop_oop_iterate_m(obj, blk, mr);                                  \

   }

   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_1(Klass_OOP_OOP_ITERATE_DECL)

   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_2(Klass_OOP_OOP_ITERATE_DECL)

 #if INCLUDE_ALL_GCS

 #define Klass_OOP_OOP_ITERATE_BACKWARDS_DECL(OopClosureType, nv_suffix)      \

   virtual int oop_oop_iterate_backwards##nv_suffix(oop obj,                  \

                                                    OopClosureType* blk) {    \

     /* Default implementation reverts to general version. */                 \

     return oop_oop_iterate_backwards_v(obj, blk);                            \

   }

   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_1(Klass_OOP_OOP_ITERATE_BACKWARDS_DECL)

   SPECIALIZED_OOP_OOP_ITERATE_CLOSURES_2(Klass_OOP_OOP_ITERATE_BACKWARDS_DECL)

 #endif // INCLUDE_ALL_GCS

   virtual void array_klasses_do(void f(Klass* k)) {}

   // Return self, except for abstract classes with exactly 1

   // implementor.  Then return the 1 concrete implementation.

   Klass *up_cast_abstract();

   // klass name

   Symbol* name() const                   { return _name; }

   void set_name(Symbol* n);

  public:

   // jvm support

   virtual jint compute_modifier_flags(TRAPS) const;

   // JVMTI support

   virtual jint jvmti_class_status() const;

   // Printing

   virtual void print_on(outputStream* st) const;

   virtual void oop_print_value_on(oop obj, outputStream* st);

   virtual void oop_print_on      (oop obj, outputStream* st);

   virtual const char* internal_name() const = 0;

   // Verification

   virtual void verify_on(outputStream* st);

   void verify() { verify_on(tty); }

 #ifndef PRODUCT

   bool verify_vtable_index(int index);

   bool verify_itable_index(int index);

 #endif

   virtual void oop_verify_on(oop obj, outputStream* st);

   static bool is_null(narrowKlass obj);

   static bool is_null(Klass* obj);

   // klass encoding for klass pointer in objects.

   static narrowKlass encode_klass_not_null(Klass* v);

   static narrowKlass encode_klass(Klass* v);

   static Klass* decode_klass_not_null(narrowKlass v);

   static Klass* decode_klass(narrowKlass v);

  private:

   // barriers used by klass_oop_store

   void klass_update_barrier_set(oop v);

   void klass_update_barrier_set_pre(oop* p, oop v);

 };

 #endif // SHARE_VM_OOPS_KLASS_HPP