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 * 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.

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 * 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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 */

// 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;

};