/*

 * Copyright (c) 2017, 2019, 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/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 "memory/iterator.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 ZRootsIteratorClosure {

private:

  ZHeapIterator* const _iter;

public:

  ZHeapIteratorRootOopClosure(ZHeapIterator* iter) :

      _iter(iter) {}

  virtual void do_oop(oop* p) {

    // Load barrier needed here, even on non-concurrent strong roots,

    // for the same reason we need fixup_partial_loads() in ZHeap::mark_end().

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

    _iter->push(obj);

  }

  virtual void do_oop(narrowOop* p) {

    ShouldNotReachHere();

  }

};

class ZHeapIteratorOopClosure : public BasicOopIterateClosure {

private:

  ZHeapIterator* const _iter;

  const oop            _base;

  const bool           _visit_referents;

  oop load_oop(oop* p) const {

    if (_visit_referents) {

      return HeapAccess<ON_UNKNOWN_OOP_REF | AS_NO_KEEPALIVE>::oop_load_at(_base, _base->field_offset(p));

    } else {

      return HeapAccess<AS_NO_KEEPALIVE>::oop_load(p);

    }

  }

public:

  ZHeapIteratorOopClosure(ZHeapIterator* iter, oop base, bool visit_referents) :

      _iter(iter),

      _base(base),

      _visit_referents(visit_referents) {}

  virtual ReferenceIterationMode reference_iteration_mode() {

    return _visit_referents ? DO_FIELDS : DO_FIELDS_EXCEPT_REFERENT;

  }

  virtual void do_oop(oop* p) {

    const oop obj = load_oop(p);

    _iter->push(obj);

  }

  virtual void do_oop(narrowOop* p) {

    ShouldNotReachHere();

  }

#ifdef ASSERT

  virtual bool should_verify_oops() {

    return false;

  }

#endif

};

ZHeapIterator::ZHeapIterator(bool visit_referents) :

    _visit_stack(),

    _visit_map(),

    _visit_referents(visit_referents) {}

ZHeapIterator::~ZHeapIterator() {

  ZVisitMapIterator iter(&_visit_map);

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

    delete map;

  }

}

static size_t object_index_max() {

  return ZGranuleSize >> ZObjectAlignmentSmallShift;

}

static size_t object_index(oop obj) {

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

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

  const uintptr_t mask = ZGranuleSize - 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::objects_do(ObjectClosure* cl) {

  // Note that the heap iterator visits all reachable objects, including

  // objects that might be unreachable from the application, such as a

  // not yet cleared JNIWeakGloablRef. However, also note that visiting

  // the JVMTI tag map is a requirement to make sure we visit all tagged

  // objects, even those that might now have become phantom reachable.

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

  // ObjectFree events for phantom reachable objects in the tag map.

  ZHeapIteratorRootOopClosure root_cl(this);

  // Push strong roots onto stack

  {

    ZRootsIterator roots;

    roots.oops_do(&root_cl);

  }

  {

    ZConcurrentRootsIterator roots;

    roots.oops_do(&root_cl);

  }

  // Push weak roots onto stack

  {

    ZWeakRootsIterator roots;

    roots.oops_do(&root_cl);

  }

  {

    ZConcurrentWeakRootsIterator roots;

    roots.oops_do(&root_cl);

  }

  // Drain stack

  while (!_visit_stack.is_empty()) {

    const oop obj = _visit_stack.pop();

    // Visit

    cl->do_object(obj);

    // Push members to visit

    ZHeapIteratorOopClosure push_cl(this, obj, _visit_referents);

    obj->oop_iterate(&push_cl);

  }

}