/*

 * 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

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 */

#include "memory/universe.hpp"

#include "runtime/handles.hpp"

#include "utilities/growableArray.hpp"

// Recording and retrieval of either oop relocations or metadata in compiled code.

class CodeBlob;

template <class T> class ValueRecorder : public StackObj {

 public:

  // A two-way mapping from positive indexes to oop handles.

  // The zero index is reserved for a constant (sharable) null.

  // Indexes may not be negative.

  // Use the given arena to manage storage, if not NULL.

  // By default, uses the current ResourceArea.

  ValueRecorder(Arena* arena = NULL);

  // Generate a new index on which nmethod::oop_addr_at will work.

  // allocate_index and find_index never return the same index,

  // and allocate_index never returns the same index twice.

  // In fact, two successive calls to allocate_index return successive ints.

  int allocate_index(T h) {

    return add_handle(h, false);

  }

  // For a given jobject or Metadata*, this will return the same index

  // repeatedly. The index can later be given to nmethod::oop_at or

  // metadata_at to retrieve the oop.

  // However, the oop must not be changed via nmethod::oop_addr_at.

  int find_index(T h) {

    int index = maybe_find_index(h);

    if (index < 0) {  // previously unallocated

      index = add_handle(h, true);

    }

    return index;

  }

  // returns the size of the generated oop/metadata table, for sizing the

  // CodeBlob. Must be called after all oops are allocated!

  int size();

  // Retrieve the value at a given index.

  T at(int index);

  int count() {

    if (_handles == NULL) return 0;

    // there is always a NULL virtually present as first object

    return _handles->length() + first_index;

  }

  // Helper function; returns false for NULL or Universe::non_oop_word().

  bool is_real(T h) {

    return h != NULL && h != (T)Universe::non_oop_word();

  }

  // copy the generated table to nmethod

  void copy_values_to(nmethod* nm);

  bool is_unused() { return _handles == NULL && !_complete; }

#ifdef ASSERT

  bool is_complete() { return _complete; }

#endif

 private:

  // variant of find_index which does not allocate if not found (yields -1)

  int maybe_find_index(T h);

  // leaky hash table of handle => index, to help detect duplicate insertion

  template <class X> class IndexCache : public ResourceObj {

    // This class is only used by the ValueRecorder class.

    friend class ValueRecorder;

    enum {

      _log_cache_size = 9,

      _cache_size = (1<<_log_cache_size),

      // Index entries are ints.  The LSBit is a collision indicator.

      _collision_bit_shift = 0,

      _collision_bit = 1,

      _index_shift = _collision_bit_shift+1

    };

    int _cache[_cache_size];

    static juint cache_index(X handle) {

      juint ci = (int) (intptr_t) handle;

      ci ^= ci >> (BitsPerByte*2);

      ci += ci >> (BitsPerByte*1);

      return ci & (_cache_size-1);

    }

    int* cache_location(X handle) {

      return &_cache[ cache_index(handle) ];

    }

    static bool cache_location_collision(int* cloc) {

      return ((*cloc) & _collision_bit) != 0;

    }

    static int cache_location_index(int* cloc) {

      return (*cloc) >> _index_shift;

    }

    static void set_cache_location_index(int* cloc, int index) {

      int cval0 = (*cloc);

      int cval1 = (index << _index_shift);

      if (cval0 != 0 && cval1 != cval0)  cval1 += _collision_bit;

      (*cloc) = cval1;

    }

    IndexCache();

  };

  void maybe_initialize();

  int add_handle(T h, bool make_findable);

  enum { null_index = 0, first_index = 1, index_cache_threshold = 20 };

  GrowableArray<T>*        _handles;  // ordered list (first is always NULL)

  GrowableArray<int>*       _no_finds; // all unfindable indexes; usually empty

  IndexCache<T>*           _indexes;  // map: handle -> its probable index

  Arena*                    _arena;

  bool                      _complete;

#ifdef ASSERT

  static int _find_index_calls, _hit_indexes, _missed_indexes;

#endif

};

class OopRecorder;

class ObjectLookup : public ResourceObj {

 private:

  class ObjectEntry {

   private:

    jobject _value;

    int     _index;

   public:

    ObjectEntry(jobject value, int index) : _value(value), _index(index) {}

    ObjectEntry() : _value(NULL), _index(0) {}

    oop oop_value() const;

    int index() { return _index; }

  };

  GrowableArray<ObjectEntry> _values;

  unsigned int _gc_count;

  // Utility sort functions

  static int sort_by_address(oop a, oop b);

  static int sort_by_address(ObjectEntry* a, ObjectEntry* b);

  static int sort_oop_by_address(oop const& a, ObjectEntry const& b);

 public:

  ObjectLookup();

  // Resort list if a GC has occurred since the last sort

  void maybe_resort();

  int find_index(jobject object, OopRecorder* oop_recorder);

};

class OopRecorder : public ResourceObj {

 private:

  ValueRecorder<jobject>      _oops;

  ValueRecorder<Metadata*>    _metadata;

  ObjectLookup*               _object_lookup;

 public:

  OopRecorder(Arena* arena = NULL, bool deduplicate = false): _oops(arena), _metadata(arena) {

    if (deduplicate) {

      _object_lookup = new ObjectLookup();

    } else {

      _object_lookup = NULL;

    }

  }

  int allocate_oop_index(jobject h) {

    return _oops.allocate_index(h);

  }

  virtual int find_index(jobject h) {

    return _object_lookup != NULL ? _object_lookup->find_index(h, this) : _oops.find_index(h);

  }

  jobject oop_at(int index) {

    return _oops.at(index);

  }

  int oop_size() {

    return _oops.size();

  }

  int oop_count() {

    return _oops.count();

  }

  bool is_real(jobject h) {

    return _oops.is_real(h);

  }

  int allocate_metadata_index(Metadata* oop) {

    return _metadata.allocate_index(oop);

  }

  virtual int find_index(Metadata* h) {

    return _metadata.find_index(h);

  }

  Metadata* metadata_at(int index) {

    return _metadata.at(index);

  }

  int metadata_size() {

    return _metadata.size();

  }

  int metadata_count() {

    return _metadata.count();

  }

  bool is_real(Metadata* h) {

    return _metadata.is_real(h);

  }

  bool is_unused() {

    return _oops.is_unused() && _metadata.is_unused();

  }

  void freeze() {

    _oops.size();

    _metadata.size();

  }

  void copy_values_to(nmethod* nm) {

    if (!_oops.is_unused()) {

      _oops.copy_values_to(nm);

    }

    if (!_metadata.is_unused()) {

      _metadata.copy_values_to(nm);

    }

  }

#ifdef ASSERT

  bool is_complete() {

    assert(_oops.is_complete() == _metadata.is_complete(), "must agree");

    return _oops.is_complete();

  }

#endif

};