Quelle oopMapCache.hpp Sprache: C

/*
* Copyright (c) 1997, 2022, 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_INTERPRETER_OOPMAPCACHE_HPP
#define SHARE_INTERPRETER_OOPMAPCACHE_HPP

#include "oops/generateOopMap.hpp"
#include "runtime/mutex.hpp"

// A Cache for storing (method, bci) -> oopMap.
// The memory management system uses the cache when locating object
// references in an interpreted frame.
//
// OopMapCache's are allocated lazily per InstanceKlass.

// The oopMap (InterpreterOopMap) is stored as a bit mask. If the
// bit_mask can fit into two words it is stored in
// the _bit_mask array, otherwise it is allocated on the heap.
// For OopMapCacheEntry the bit_mask is allocated in the C heap
// because these entries persist between garbage collections.
// For InterpreterOopMap the bit_mask is allocated in
// a resource area for better performance.  InterpreterOopMap
// should only be created and deleted during same garbage collection.
//
// If ENABBLE_ZAP_DEAD_LOCALS is defined, two bits are used
// per entry instead of one. In all cases,
// the first bit is set to indicate oops as opposed to other
// values. If the second bit is available,
// it is set for dead values. We get the following encoding:
//
// 00 live value
// 01 live oop
// 10 dead value
// 11 <unused>                                   (we cannot distinguish between dead oops or values with the current oop map generator)

class OffsetClosure  {
public:
  virtual void offset_do(int offset) = 0;
};

class OopMapCacheEntry;

class InterpreterOopMap: ResourceObj {
  friend class OopMapCache;

public:
  enum {
    N                = 4,                // the number of words reserved
                                         // for inlined mask storage
    small_mask_limit = N * BitsPerWord,  // the maximum number of bits
                                         // available for small masks,
                                         // small_mask_limit can be set to 0
                                         // for testing bit_mask allocation

    bits_per_entry   = 2,
    dead_bit_number  = 1,
    oop_bit_number   = 0
  };

private:
  Method*        _method;         // the method for which the mask is valid
  unsigned short _bci;            // the bci    for which the mask is valid
  int            _mask_size;      // the mask size in bits
  int            _expression_stack_size; // the size of the expression stack in slots

protected:
  intptr_t       _bit_mask[N];    // the bit mask if
                                  // mask_size <= small_mask_limit,
                                  // ptr to bit mask otherwise
                                  // "protected" so that sub classes can
                                  // access it without using trickery in
                                  // method bit_mask().
  int            _num_oops;
#ifdef ASSERT
  bool _resource_allocate_bit_mask;
#endif

  // access methods
  Method*        method() const                  { return _method; }
  void           set_method(Method* v)           { _method = v; }
  int            bci() const                     { return _bci; }
  void           set_bci(int v)                  { _bci = v; }
  int            mask_size() const               { return _mask_size; }
  void           set_mask_size(int v)            { _mask_size = v; }
  // Test bit mask size and return either the in-line bit mask or allocated
  // bit mask.
  uintptr_t*  bit_mask() const                   { return (uintptr_t*)(mask_size() <= small_mask_limit ? (intptr_t)_bit_mask : _bit_mask[0]); }

  // return the word size of_bit_mask.  mask_size() <= 4 * MAX_USHORT
  size_t mask_word_size() const {
    return (mask_size() + BitsPerWord - 1) / BitsPerWord;
  }

  uintptr_t entry_at(int offset) const           { int i = offset * bits_per_entry; return bit_mask()[i / BitsPerWord] >> (i % BitsPerWord); }

  void set_expression_stack_size(int sz)         { _expression_stack_size = sz; }

  // Lookup
  bool match(const methodHandle& method, int bci) const { return _method == method() && _bci == bci; }
  bool is_empty() const;

  // Initialization
  void initialize();

public:
  InterpreterOopMap();
  ~InterpreterOopMap();

  // Copy the OopMapCacheEntry in parameter "from" into this
  // InterpreterOopMap.  If the _bit_mask[0] in "from" points to
  // allocated space (i.e., the bit mask was to large to hold
  // in-line), allocate the space from a Resource area.
  void resource_copy(OopMapCacheEntry* from);

  void iterate_oop(OffsetClosure* oop_closure) const;
  void print() const;

  int number_of_entries() const                  { return mask_size() / bits_per_entry; }
  bool is_dead(int offset) const                 { return (entry_at(offset) & (1 << dead_bit_number)) != 0; }
  bool is_oop (int offset) const                 { return (entry_at(offset) & (1 << oop_bit_number )) != 0; }
  int  num_oops() const                          { return _num_oops; }

  int expression_stack_size() const              { return _expression_stack_size; }

};

class OopMapCache : public CHeapObj<mtClass> {
static OopMapCacheEntry* volatile _old_entries;
private:
  enum { _size        = 32,     // Use fixed size for now
         _probe_depth = 3       // probe depth in case of collisions
  };

  OopMapCacheEntry* volatile * _array;

  unsigned int hash_value_for(const methodHandle& method, int bci) const;
  OopMapCacheEntry* entry_at(int i) const;
  bool put_at(int i, OopMapCacheEntry* entry, OopMapCacheEntry* old);

  static void enqueue_for_cleanup(OopMapCacheEntry* entry);

  void flush();

public:
  OopMapCache();
  ~OopMapCache();                                // free up memory

  // flush cache entry is occupied by an obsolete method
  void flush_obsolete_entries();

  // Returns the oopMap for (method, bci) in parameter "entry".
  // Returns false if an oop map was not found.
  void lookup(const methodHandle& method, int bci, InterpreterOopMap* entry);

  // Compute an oop map without updating the cache or grabbing any locks (for debugging)
  static void compute_one_oop_map(const methodHandle& method, int bci, InterpreterOopMap* entry);
  static void cleanup_old_entries();
};

#endif // SHARE_INTERPRETER_OOPMAPCACHE_HPP

quality100%

¤ Dauer der Verarbeitung: 0.14 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.