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 /*

  * Copyright (c) 2000, 2008, 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.

  *

  */

 // This class provides the interface between a barrier implementation and

 // the rest of the system.

 class BarrierSet: public CHeapObj {

   friend class VMStructs;

 public:

   enum Name {

     ModRef,

     CardTableModRef,

     CardTableExtension,

     G1SATBCT,

     G1SATBCTLogging,

     Other,

     Uninit

   };

 protected:

   int _max_covered_regions;

   Name _kind;

 public:

   BarrierSet() { _kind = Uninit; }

   // To get around prohibition on RTTI.

   BarrierSet::Name kind() { return _kind; }

   virtual bool is_a(BarrierSet::Name bsn) = 0;

   // These operations indicate what kind of barriers the BarrierSet has.

   virtual bool has_read_ref_barrier() = 0;

   virtual bool has_read_prim_barrier() = 0;

   virtual bool has_write_ref_barrier() = 0;

   virtual bool has_write_ref_pre_barrier() = 0;

   virtual bool has_write_prim_barrier() = 0;

   // These functions indicate whether a particular access of the given

   // kinds requires a barrier.

   virtual bool read_ref_needs_barrier(void* field) = 0;

   virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;

   virtual bool write_ref_needs_barrier(void* field, oop new_val) = 0;

   virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,

                                         juint val1, juint val2) = 0;

   // The first four operations provide a direct implementation of the

   // barrier set.  An interpreter loop, for example, could call these

   // directly, as appropriate.

   // Invoke the barrier, if any, necessary when reading the given ref field.

   virtual void read_ref_field(void* field) = 0;

   // Invoke the barrier, if any, necessary when reading the given primitive

   // "field" of "bytes" bytes in "obj".

   virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;

   // Invoke the barrier, if any, necessary when writing "new_val" into the

   // ref field at "offset" in "obj".

   // (For efficiency reasons, this operation is specialized for certain

   // barrier types.  Semantically, it should be thought of as a call to the

   // virtual "_work" function below, which must implement the barrier.)

   // First the pre-write versions...

   template <class T> inline void write_ref_field_pre(T* field, oop new_val);

 private:

   // Keep this private so as to catch violations at build time.

   virtual void write_ref_field_pre_work(     void* field, oop new_val) { guarantee(false, "Not needed"); };

 protected:

   virtual void write_ref_field_pre_work(      oop* field, oop new_val) {};

   virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};

 public:

   // ...then the post-write version.

   inline void write_ref_field(void* field, oop new_val);

 protected:

   virtual void write_ref_field_work(void* field, oop new_val) = 0;

 public:

   // Invoke the barrier, if any, necessary when writing the "bytes"-byte

   // value(s) "val1" (and "val2") into the primitive "field".

   virtual void write_prim_field(HeapWord* field, size_t bytes,

                                 juint val1, juint val2) = 0;

   // Operations on arrays, or general regions (e.g., for "clone") may be

   // optimized by some barriers.

   // The first six operations tell whether such an optimization exists for

   // the particular barrier.

   virtual bool has_read_ref_array_opt() = 0;

   virtual bool has_read_prim_array_opt() = 0;

   virtual bool has_write_ref_array_pre_opt() { return true; }

   virtual bool has_write_ref_array_opt() = 0;

   virtual bool has_write_prim_array_opt() = 0;

   virtual bool has_read_region_opt() = 0;

   virtual bool has_write_region_opt() = 0;

   // These operations should assert false unless the correponding operation

   // above returns true.  Otherwise, they should perform an appropriate

   // barrier for an array whose elements are all in the given memory region.

   virtual void read_ref_array(MemRegion mr) = 0;

   virtual void read_prim_array(MemRegion mr) = 0;

   // Below length is the # array elements being written

   virtual void write_ref_array_pre(      oop* dst, int length) {}

   virtual void write_ref_array_pre(narrowOop* dst, int length) {}

   // Below count is the # array elements being written, starting

   // at the address "start", which may not necessarily be HeapWord-aligned

   inline void write_ref_array(HeapWord* start, size_t count);

   // Static versions, suitable for calling from generated code;

   // count is # array elements being written, starting with "start",

   // which may not necessarily be HeapWord-aligned.

   static void static_write_ref_array_pre(HeapWord* start, size_t count);

   static void static_write_ref_array_post(HeapWord* start, size_t count);

 protected:

   virtual void write_ref_array_work(MemRegion mr) = 0;

 public:

   virtual void write_prim_array(MemRegion mr) = 0;

   virtual void read_region(MemRegion mr) = 0;

   // (For efficiency reasons, this operation is specialized for certain

   // barrier types.  Semantically, it should be thought of as a call to the

   // virtual "_work" function below, which must implement the barrier.)

   inline void write_region(MemRegion mr);

 protected:

   virtual void write_region_work(MemRegion mr) = 0;

 public:

   // Some barrier sets create tables whose elements correspond to parts of

   // the heap; the CardTableModRefBS is an example.  Such barrier sets will

   // normally reserve space for such tables, and commit parts of the table

   // "covering" parts of the heap that are committed.  The constructor is

   // passed the maximum number of independently committable subregions to

   // be covered, and the "resize_covoered_region" function allows the

   // sub-parts of the heap to inform the barrier set of changes of their

   // sizes.

   BarrierSet(int max_covered_regions) :

     _max_covered_regions(max_covered_regions) {}

   // Inform the BarrierSet that the the covered heap region that starts

   // with "base" has been changed to have the given size (possibly from 0,

   // for initialization.)

   virtual void resize_covered_region(MemRegion new_region) = 0;

   // If the barrier set imposes any alignment restrictions on boundaries

   // within the heap, this function tells whether they are met.

   virtual bool is_aligned(HeapWord* addr) = 0;

 };