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 /*

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  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.

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  * This code is free software; you can redistribute it and/or modify it

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  * 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_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP

 #include "gc_implementation/g1/g1BiasedArray.hpp"

 #include "memory/allocation.hpp"

 // Per-region state during garbage collection.

 struct InCSetState {

  public:

   // We use different types to represent the state value. Particularly SPARC puts

   // values in structs from "left to right", i.e. MSB to LSB. This results in many

   // unnecessary shift operations when loading and storing values of this type.

   // This degrades performance significantly (>10%) on that platform.

   // Other tested ABIs do not seem to have this problem, and actually tend to

   // favor smaller types, so we use the smallest usable type there.

 #ifdef SPARC

   #define CSETSTATE_FORMAT INTPTR_FORMAT

   typedef intptr_t in_cset_state_t;

 #else

   #define CSETSTATE_FORMAT "%d"

   typedef int8_t in_cset_state_t;

 #endif

  private:

   in_cset_state_t _value;

  public:

   enum {

     // Selection of the values were driven to micro-optimize the encoding and

     // frequency of the checks.

     // The most common check is whether the region is in the collection set or not.

     // This encoding allows us to use an != 0 check which in some architectures

     // (x86*) can be encoded slightly more efficently than a normal comparison

     // against zero.

     // The same situation occurs when checking whether the region is humongous

     // or not, which is encoded by values < 0.

     // The other values are simply encoded in increasing generation order, which

     // makes getting the next generation fast by a simple increment.

     Humongous    = -1,    // The region is humongous - note that actually any value < 0 would be possible here.

     NotInCSet    =  0,    // The region is not in the collection set.

     Young        =  1,    // The region is in the collection set and a young region.

     Old          =  2,    // The region is in the collection set and an old region.

     Num

   };

   InCSetState(in_cset_state_t value = NotInCSet) : _value(value) {

     assert(is_valid(), err_msg("Invalid state %d", _value));

   }

   in_cset_state_t value() const        { return _value; }

   void set_old()                       { _value = Old; }

   bool is_in_cset_or_humongous() const { return _value != NotInCSet; }

   bool is_in_cset() const              { return _value > NotInCSet; }

   bool is_humongous() const            { return _value < NotInCSet; }

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

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

 #ifdef ASSERT

   bool is_default() const              { return !is_in_cset_or_humongous(); }

   bool is_valid() const                { return (_value >= Humongous) && (_value < Num); }

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

 #endif

 };

 // Instances of this class are used for quick tests on whether a reference points

 // into the collection set and into which generation or is a humongous object

 //

 // Each of the array's elements indicates whether the corresponding region is in

 // the collection set and if so in which generation, or a humongous region.

 //

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

 // quickly reclaim humongous objects. For the latter, by making a humongous region

 // succeed this test, we sort-of add it to the collection set. During the reference

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

 // referenced, i.e. live.

 class G1InCSetStateFastTestBiasedMappedArray : public G1BiasedMappedArray<InCSetState> {

  protected:

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

  public:

   void set_humongous(uintptr_t index) {

     assert(get_by_index(index).is_default(),

            err_msg("State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()));

     set_by_index(index, InCSetState::Humongous);

   }

   void clear_humongous(uintptr_t index) {

     set_by_index(index, InCSetState::NotInCSet);

   }

   void set_in_young(uintptr_t index) {

     assert(get_by_index(index).is_default(),

            err_msg("State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()));

     set_by_index(index, InCSetState::Young);

   }

   void set_in_old(uintptr_t index) {

     assert(get_by_index(index).is_default(),

            err_msg("State at index " INTPTR_FORMAT " should be default but is " CSETSTATE_FORMAT, index, get_by_index(index).value()));

     set_by_index(index, InCSetState::Old);

   }

   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(); }

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

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

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_G1_G1INCSETSTATE_HPP