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 * 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.

 *

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#ifndef SHARE_GC_G1_G1HEAPREGIONATTR_HPP

#define SHARE_GC_G1_G1HEAPREGIONATTR_HPP

#include "gc/g1/g1BiasedArray.hpp"

#include "gc/g1/heapRegion.hpp"

// Per-region attributes often used during garbage collection to avoid costly

// lookups for that information all over the place.

struct G1HeapRegionAttr {

public:

  // We use different types to represent the state value depending on platform as

  // some have issues loading parts of words.

#ifdef SPARC

  typedef int32_t region_type_t;

  typedef uint32_t needs_remset_update_t;

#else

  typedef int8_t region_type_t;

  typedef uint8_t needs_remset_update_t;

#endif

private:

  needs_remset_update_t _needs_remset_update;

  region_type_t _type;

public:

  // Selection of the values for the _type field were driven to micro-optimize the

  // encoding and frequency of the checks.

  // The most common check for a given reference is whether the region is in the

  // collection set or not, and which generation this region is in.

  // The selected encoding allows us to use a single check (> NotInCSet) for the

  // former.

  //

  // The other values are used for objects in regions requiring various special handling,

  // eager reclamation of humongous objects or optional regions.

  static const region_type_t Optional     =  -3;    // The region is optional not in the current collection set.

  static const region_type_t Humongous    =  -2;    // The region is a humongous candidate not in the current collection set.

  static const region_type_t NotInCSet    =  -1;    // The region is not in the collection set.

  static const region_type_t Young        =   0;    // The region is in the collection set and a young region.

  static const region_type_t Old          =   1;    // The region is in the collection set and an old region.

  static const region_type_t Num          =   2;

  G1HeapRegionAttr(region_type_t type = NotInCSet, bool needs_remset_update = false) :

    _needs_remset_update(needs_remset_update), _type(type) {

    assert(is_valid(), "Invalid type %d", _type);

  }

  region_type_t type() const           { return _type; }

  const char* get_type_str() const {

    switch (type()) {

      case Optional: return "Optional";

      case Humongous: return "Humongous";

      case NotInCSet: return "NotInCSet";

      case Young: return "Young";

      case Old: return "Old";

      default: ShouldNotReachHere(); return "";

    }

  }

  bool needs_remset_update() const     { return _needs_remset_update != 0; }

  void set_old()                       { _type = Old; }

  void clear_humongous()               {

    assert(is_humongous() || !is_in_cset(), "must be");

    _type = NotInCSet;

  }

  void set_has_remset(bool value)      { _needs_remset_update = value ? 1 : 0; }

  bool is_in_cset_or_humongous() const { return is_in_cset() || is_humongous(); }

  bool is_in_cset() const              { return type() >= Young; }

  bool is_humongous() const            { return type() == Humongous; }

  bool is_young() const                { return type() == Young; }

  bool is_old() const                  { return type() == Old; }

  bool is_optional() const             { return type() == Optional; }

#ifdef ASSERT

  bool is_default() const              { return type() == NotInCSet; }

  bool is_valid() const                { return (type() >= Optional && type() < Num); }

  bool is_valid_gen() const            { return (type() >= Young && type() <= Old); }

#endif

};

// Table for all regions in the heap for above.

//

// We use this to speed up reference processing during young collection and

// quickly reclaim humongous objects. For the latter, at the start of GC, by adding

// it as a humongous region we enable special handling for that region. During the

// reference iteration closures, when we see a humongous region, we then simply mark

// it as referenced, i.e. live, and remove it from this table to prevent further

// processing on it.

//

// This means that this does NOT completely correspond to the information stored

// in a HeapRegion, but only to what is interesting for the current young collection.

class G1HeapRegionAttrBiasedMappedArray : public G1BiasedMappedArray<G1HeapRegionAttr> {

 protected:

  G1HeapRegionAttr default_value() const { return G1HeapRegionAttr(G1HeapRegionAttr::NotInCSet); }

 public:

  void set_optional(uintptr_t index, bool needs_remset_update) {

    assert(get_by_index(index).is_default(),

           "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());

    set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Optional, needs_remset_update));

  }

  void set_humongous(uintptr_t index, bool needs_remset_update) {

    assert(get_by_index(index).is_default(),

           "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());

    set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Humongous, needs_remset_update));

  }

  void clear_humongous(uintptr_t index) {

    get_ref_by_index(index)->clear_humongous();

  }

  void set_has_remset(uintptr_t index, bool needs_remset_update) {

    get_ref_by_index(index)->set_has_remset(needs_remset_update);

  }

  void set_in_young(uintptr_t index) {

    assert(get_by_index(index).is_default(),

           "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());

    set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Young, true));

  }

  void set_in_old(uintptr_t index, bool needs_remset_update) {

    assert(get_by_index(index).is_default(),

           "Region attributes at index " INTPTR_FORMAT " should be default but is %s", index, get_by_index(index).get_type_str());

    set_by_index(index, G1HeapRegionAttr(G1HeapRegionAttr::Old, needs_remset_update));

  }

  bool is_in_cset_or_humongous(HeapWord* addr) const { return at(addr).is_in_cset_or_humongous(); }

  bool is_in_cset(HeapWord* addr) const { return at(addr).is_in_cset(); }

  bool is_in_cset(const HeapRegion* hr) const { return get_by_index(hr->hrm_index()).is_in_cset(); }

  G1HeapRegionAttr at(HeapWord* addr) const { return get_by_address(addr); }

  void clear() { G1BiasedMappedArray<G1HeapRegionAttr>::clear(); }

  void clear(const HeapRegion* hr) { return set_by_index(hr->hrm_index(), G1HeapRegionAttr(G1HeapRegionAttr::NotInCSet)); }

};

#endif // SHARE_GC_G1_G1HEAPREGIONATTR_HPP