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 /*

  * Copyright (c) 2002, 2010, 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

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 #ifndef SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPROMOTIONLAB_HPP

 #define SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPROMOTIONLAB_HPP

 #include "gc_implementation/parallelScavenge/objectStartArray.hpp"

 #include "memory/allocation.hpp"

 //

 // PSPromotionLAB is a parallel scavenge promotion lab. This class acts very

 // much like a MutableSpace. We couldn't embed a MutableSpace, though, as

 // it has a considerable number of asserts and invariants that are violated.

 //

 class ObjectStartArray;

 class PSPromotionLAB : public CHeapObj {

  protected:

   static size_t filler_header_size;

   enum LabState {

     needs_flush,

     flushed,

     zero_size

   };

   HeapWord* _top;

   HeapWord* _bottom;

   HeapWord* _end;

   LabState _state;

   void set_top(HeapWord* value)    { _top = value; }

   void set_bottom(HeapWord* value) { _bottom = value; }

   void set_end(HeapWord* value)    { _end = value; }

   // The shared initialize code invokes this.

   debug_only(virtual bool lab_is_valid(MemRegion lab) { return false; });

   PSPromotionLAB() : _top(NULL), _bottom(NULL), _end(NULL) { }

  public:

   // Filling and flushing.

   void initialize(MemRegion lab);

   virtual void flush();

   // Accessors

   HeapWord* bottom() const           { return _bottom; }

   HeapWord* end() const              { return _end;    }

   HeapWord* top() const              { return _top;    }

   bool is_flushed()                  { return _state == flushed; }

   bool unallocate_object(HeapWord* obj, size_t obj_size);

   // Returns a subregion containing all objects in this space.

   MemRegion used_region()            { return MemRegion(bottom(), top()); }

   // Boolean querries.

   bool is_empty() const              { return used() == 0; }

   bool not_empty() const             { return used() > 0; }

   bool contains(const void* p) const { return _bottom <= p && p < _end; }

   // Size computations.  Sizes are in bytes.

   size_t capacity() const            { return byte_size(bottom(), end()); }

   size_t used() const                { return byte_size(bottom(), top()); }

   size_t free() const                { return byte_size(top(),    end()); }

 };

 class PSYoungPromotionLAB : public PSPromotionLAB {

  public:

   PSYoungPromotionLAB() { }

   // Not MT safe

   HeapWord* allocate(size_t size) {

     // Can't assert this, when young fills, we keep the LAB around, but flushed.

     // assert(_state != flushed, "Sanity");

     HeapWord* obj = top();

     HeapWord* new_top = obj + size;

     // The 'new_top>obj' check is needed to detect overflow of obj+size.

     if (new_top > obj && new_top <= end()) {

       set_top(new_top);

       assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),

              "checking alignment");

       return obj;

     }

     return NULL;

   }

   debug_only(virtual bool lab_is_valid(MemRegion lab));

 };

 class PSOldPromotionLAB : public PSPromotionLAB {

  private:

   ObjectStartArray* _start_array;

  public:

   PSOldPromotionLAB() : _start_array(NULL) { }

   PSOldPromotionLAB(ObjectStartArray* start_array) : _start_array(start_array) { }

   void set_start_array(ObjectStartArray* start_array) { _start_array = start_array; }

   void flush();

   // Not MT safe

   HeapWord* allocate(size_t size) {

     // Cannot test for this now that we're doing promotion failures

     // assert(_state != flushed, "Sanity");

     assert(_start_array != NULL, "Sanity");

     HeapWord* obj = top();

     HeapWord* new_top = obj + size;

     // The 'new_top>obj' check is needed to detect overflow of obj+size.

     if (new_top > obj && new_top <= end()) {

       set_top(new_top);

       assert(is_object_aligned((intptr_t)obj) && is_object_aligned((intptr_t)new_top),

              "checking alignment");

       _start_array->allocate_block(obj);

       return obj;

     }

     return NULL;

   }

   debug_only(virtual bool lab_is_valid(MemRegion lab));

 };

 #endif // SHARE_VM_GC_IMPLEMENTATION_PARALLELSCAVENGE_PSPROMOTIONLAB_HPP