/*

 * Copyright (c) 2017, 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.

 */

#include "precompiled.hpp"

#include "gc/z/zAddressRangeMap.inline.hpp"

#include "gc/z/zBarrier.inline.hpp"

#include "gc/z/zGlobals.hpp"

#include "gc/z/zHeapIterator.hpp"

#include "gc/z/zOop.inline.hpp"

#include "gc/z/zRootsIterator.hpp"

#include "oops/oop.inline.hpp"

#include "utilities/bitMap.inline.hpp"

#include "utilities/stack.inline.hpp"

class ZHeapIteratorBitMap : public CHeapObj<mtGC> {

private:

  CHeapBitMap _map;

public:

  ZHeapIteratorBitMap(size_t size_in_bits) :

      _map(size_in_bits) {}

  bool try_set_bit(size_t index) {

    if (_map.at(index)) {

      return false;

    }

    _map.set_bit(index);

    return true;

  }

};

class ZHeapIteratorRootOopClosure : public OopClosure {

private:

  ZHeapIterator* const _iter;

  ObjectClosure* const _cl;

public:

  ZHeapIteratorRootOopClosure(ZHeapIterator* iter, ObjectClosure* cl) :

      _iter(iter),

      _cl(cl) {}

  virtual void do_oop(oop* p) {

    // Load barrier needed here for the same reason we

    // need fixup_partial_loads() in ZHeap::mark_end()

    const oop obj = RootAccess<>::oop_load(p);

    _iter->push(obj);

    _iter->drain(_cl);

  }

  virtual void do_oop(narrowOop* p) {

    ShouldNotReachHere();

  }

};

class ZHeapIteratorPushOopClosure : public ExtendedOopClosure {

private:

  ZHeapIterator* const _iter;

  const oop            _base;

public:

  ZHeapIteratorPushOopClosure(ZHeapIterator* iter, oop base) :

      _iter(iter),

      _base(base) {}

  void do_oop_nv(oop* p) {

    const oop obj = HeapAccess<ON_UNKNOWN_OOP_REF>::oop_load_at(_base, _base->field_offset(p));

    _iter->push(obj);

  }

  void do_oop_nv(narrowOop* p) {

    ShouldNotReachHere();

  }

  virtual void do_oop(oop* p) {

    do_oop_nv(p);

  }

  virtual void do_oop(narrowOop* p) {

    do_oop_nv(p);

  }

#ifdef ASSERT

  virtual bool should_verify_oops() {

    return false;

  }

#endif

};

ZHeapIterator::ZHeapIterator() :

    _visit_stack(),

    _visit_map() {}

ZHeapIterator::~ZHeapIterator() {

  ZVisitMapIterator iter(&_visit_map);

  for (ZHeapIteratorBitMap* map; iter.next(&map);) {

    delete map;

  }

}

size_t ZHeapIterator::object_index_max() const {

  return ZPageSizeMin >> ZObjectAlignmentSmallShift;

}

size_t ZHeapIterator::object_index(oop obj) const {

  const uintptr_t addr = ZOop::to_address(obj);

  const uintptr_t offset = ZAddress::offset(addr);

  const uintptr_t mask = (1 << ZPageSizeMinShift) - 1;

  return (offset & mask) >> ZObjectAlignmentSmallShift;

}

ZHeapIteratorBitMap* ZHeapIterator::object_map(oop obj) {

  const uintptr_t addr = ZOop::to_address(obj);

  ZHeapIteratorBitMap* map = _visit_map.get(addr);

  if (map == NULL) {

    map = new ZHeapIteratorBitMap(object_index_max());

    _visit_map.put(addr, map);

  }

  return map;

}

void ZHeapIterator::push(oop obj) {

  if (obj == NULL) {

    // Ignore

    return;

  }

  ZHeapIteratorBitMap* const map = object_map(obj);

  const size_t index = object_index(obj);

  if (!map->try_set_bit(index)) {

    // Already pushed

    return;

  }

  // Push

  _visit_stack.push(obj);

}

void ZHeapIterator::drain(ObjectClosure* cl) {

  while (!_visit_stack.is_empty()) {

    const oop obj = _visit_stack.pop();

    // Visit

    cl->do_object(obj);

    // Push members to visit

    ZHeapIteratorPushOopClosure push_cl(this, obj);

    obj->oop_iterate(&push_cl);

  }

}

void ZHeapIterator::objects_do(ObjectClosure* cl) {

  ZHeapIteratorRootOopClosure root_cl(this, cl);

  ZRootsIterator roots;

  // Follow roots. Note that we also visit the JVMTI weak tag map

  // as if they where strong roots to make sure we visit all tagged

  // objects, even those that might now have become unreachable.

  // If we didn't do this the user would have expected to see

  // ObjectFree events for unreachable objects in the tag map.

  roots.oops_do(&root_cl, true /* visit_jvmti_weak_export */);

}