/*

 * Copyright (c) 2015, 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_DEPENDENCYCONTEXT_HPP

#define SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP

#include "memory/allocation.hpp"

#include "oops/oop.hpp"

#include "runtime/handles.hpp"

#include "runtime/perfData.hpp"

#include "runtime/safepoint.hpp"

class nmethod;

class DepChange;

//

// nmethodBucket is used to record dependent nmethods for

// deoptimization.  nmethod dependencies are actually <klass, method>

// pairs but we really only care about the klass part for purposes of

// finding nmethods which might need to be deoptimized.  Instead of

// recording the method, a count of how many times a particular nmethod

// was recorded is kept.  This ensures that any recording errors are

// noticed since an nmethod should be removed as many times are it's

// added.

//

class nmethodBucket: public CHeapObj<mtClass> {

  friend class VMStructs;

 private:

  nmethod*       _nmethod;

  int            _count;

  nmethodBucket* _next;

 public:

  nmethodBucket(nmethod* nmethod, nmethodBucket* next) :

   _nmethod(nmethod), _next(next), _count(1) {}

  int count()                             { return _count; }

  int increment()                         { _count += 1; return _count; }

  int decrement();

  nmethodBucket* next()                   { return _next; }

  void set_next(nmethodBucket* b)         { _next = b; }

  nmethod* get_nmethod()                  { return _nmethod; }

};

//

// Utility class to manipulate nmethod dependency context.

// The context consists of nmethodBucket* (a head of a linked list)

// and a boolean flag (does the list contains stale entries). The structure is

// encoded as an intptr_t: lower bit is used for the flag. It is possible since

// nmethodBucket* is aligned - the structure is malloc'ed in C heap.

// Dependency context can be attached either to an InstanceKlass (_dep_context field)

// or CallSiteContext oop for call_site_target dependencies (see javaClasses.hpp).

// DependencyContext class operates on some location which holds a intptr_t value.

//

class DependencyContext : public StackObj {

  friend class VMStructs;

  friend class TestDependencyContext;

 private:

  enum TagBits { _has_stale_entries_bit = 1, _has_stale_entries_mask = 1 };

  intptr_t* _dependency_context_addr;

  void set_dependencies(nmethodBucket* b) {

    assert((intptr_t(b) & _has_stale_entries_mask) == 0, "should be aligned");

    if (has_stale_entries()) {

      *_dependency_context_addr = intptr_t(b) | _has_stale_entries_mask;

    } else {

      *_dependency_context_addr = intptr_t(b);

    }

  }

  void set_has_stale_entries(bool x) {

    if (x) {

      *_dependency_context_addr |= _has_stale_entries_mask;

    } else {

      *_dependency_context_addr &= ~_has_stale_entries_mask;

    }

  }

  nmethodBucket* dependencies() {

    intptr_t value = *_dependency_context_addr;

    return (nmethodBucket*) (value & ~_has_stale_entries_mask);

  }

  bool has_stale_entries() const {

    intptr_t value = *_dependency_context_addr;

    return (value & _has_stale_entries_mask) != 0;

  }

  static PerfCounter* _perf_total_buckets_allocated_count;

  static PerfCounter* _perf_total_buckets_deallocated_count;

  static PerfCounter* _perf_total_buckets_stale_count;

  static PerfCounter* _perf_total_buckets_stale_acc_count;

 public:

#ifdef ASSERT

  // Safepoints are forbidden during DC lifetime. GC can invalidate

  // _dependency_context_addr if it relocates the holder

  // (e.g. CallSiteContext Java object).

  int _safepoint_counter;

  DependencyContext(intptr_t* addr) : _dependency_context_addr(addr),

    _safepoint_counter(SafepointSynchronize::_safepoint_counter) {}

  ~DependencyContext() {

    assert(_safepoint_counter == SafepointSynchronize::_safepoint_counter, "safepoint happened");

  }

#else

  DependencyContext(intptr_t* addr) : _dependency_context_addr(addr) {}

#endif // ASSERT

  static const intptr_t EMPTY = 0; // dependencies = NULL, has_stale_entries = false

  static void init();

  int  mark_dependent_nmethods(DepChange& changes);

  void add_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);

  void remove_dependent_nmethod(nmethod* nm, bool expunge_stale_entries = false);

  int  remove_all_dependents();

  void expunge_stale_entries();

  // Unsafe deallocation of nmethodBuckets. Used in IK::release_C_heap_structures

  // to clean up the context possibly containing live entries pointing to unloaded nmethods.

  void wipe();

#ifndef PRODUCT

  void print_dependent_nmethods(bool verbose);

  bool is_dependent_nmethod(nmethod* nm);

  bool find_stale_entries();

#endif //PRODUCT

};

#endif // SHARE_VM_CODE_DEPENDENCYCONTEXT_HPP