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hotspot/src/share/vm/memory/barrierSet.hpp

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+/*
+ * Copyright 2000-2002 Sun Microsystems, Inc.  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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
+ * CA 95054 USA or visit www.sun.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,
+    Other,
+    Uninit
+  };
+
+protected:
+  int _max_covered_regions;
+  Name _kind;
+
+public:
+
+  // To get around prohibition on RTTI.
+  virtual 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_prim_barrier() = 0;
+
+  // These functions indicate whether a particular access of the given
+  // kinds requires a barrier.
+  virtual bool read_ref_needs_barrier(oop* field) = 0;
+  virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
+  virtual bool write_ref_needs_barrier(oop* 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(oop* 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.)
+  inline void write_ref_field(oop* field, oop new_val);
+protected:
+  virtual void write_ref_field_work(oop* 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_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;
+
+  inline void write_ref_array(MemRegion mr);
+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:
+
+  // The remaining sets of operations are called by compilers or other code
+  // generators to insert barriers into generated code.  There may be
+  // several such code generators; the signatures of these
+  // barrier-generating functions may differ from generator to generator.
+  // There will be a set of four function signatures for each code
+  // generator, which accomplish the generation of barriers of the four
+  // kinds listed above.
+
+#ifdef TBD
+  // Generates code to invoke the barrier, if any, necessary when reading
+  // the ref field at "offset" in "obj".
+  virtual void gen_read_ref_field() = 0;
+
+  // Generates code to invoke the barrier, if any, necessary when reading
+  // the primitive field of "bytes" bytes at offset" in "obj".
+  virtual void gen_read_prim_field() = 0;
+
+  // Generates code to invoke the barrier, if any, necessary when writing
+  // "new_val" into the ref field at "offset" in "obj".
+  virtual void gen_write_ref_field() = 0;
+
+  // Generates code to invoke the barrier, if any, necessary when writing
+  // the "bytes"-byte value "new_val" into the primitive field at "offset"
+  // in "obj".
+  virtual void gen_write_prim_field() = 0;
+#endif
+
+  // 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;
+
+};