1 /*
   2  * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #ifndef SHARE_VM_MEMORY_BARRIERSET_HPP
  26 #define SHARE_VM_MEMORY_BARRIERSET_HPP
  27 
  28 #include "memory/memRegion.hpp"
  29 #include "oops/oopsHierarchy.hpp"
  30 
  31 // This class provides the interface between a barrier implementation and
  32 // the rest of the system.
  33 
  34 class BarrierSet: public CHeapObj<mtGC> {
  35   friend class VMStructs;
  36 public:
  37   enum Name {
  38     ModRef,
  39     CardTableModRef,
  40     CardTableExtension,
  41     G1SATBCT,
  42     G1SATBCTLogging,
  43     ShenandoahBarrierSet,
  44     Other,
  45     Uninit
  46   };
  47 
  48   enum Flags {
  49     None                = 0,
  50     TargetUninitialized = 1
  51   };
  52 protected:
  53   int _max_covered_regions;
  54   Name _kind;
  55 
  56 public:
  57 
  58   BarrierSet() { _kind = Uninit; }
  59   // To get around prohibition on RTTI.
  60   BarrierSet::Name kind() { return _kind; }
  61   virtual bool is_a(BarrierSet::Name bsn) = 0;
  62 
  63   // These operations indicate what kind of barriers the BarrierSet has.
  64   virtual bool has_read_ref_barrier() = 0;
  65   virtual bool has_read_prim_barrier() = 0;
  66   virtual bool has_write_ref_barrier() = 0;
  67   virtual bool has_write_ref_pre_barrier() = 0;
  68   virtual bool has_write_prim_barrier() = 0;
  69 
  70   // These functions indicate whether a particular access of the given
  71   // kinds requires a barrier.
  72   virtual bool read_ref_needs_barrier(void* field) = 0;
  73   virtual bool read_prim_needs_barrier(HeapWord* field, size_t bytes) = 0;
  74   virtual bool write_prim_needs_barrier(HeapWord* field, size_t bytes,
  75                                         juint val1, juint val2) = 0;
  76 
  77   // The first four operations provide a direct implementation of the
  78   // barrier set.  An interpreter loop, for example, could call these
  79   // directly, as appropriate.
  80 
  81   // Invoke the barrier, if any, necessary when reading the given ref field.
  82   virtual void read_ref_field(void* field) = 0;
  83 
  84   // Invoke the barrier, if any, necessary when reading the given primitive
  85   // "field" of "bytes" bytes in "obj".
  86   virtual void read_prim_field(HeapWord* field, size_t bytes) = 0;
  87 
  88   // Invoke the barrier, if any, necessary when writing "new_val" into the
  89   // ref field at "offset" in "obj".
  90   // (For efficiency reasons, this operation is specialized for certain
  91   // barrier types.  Semantically, it should be thought of as a call to the
  92   // virtual "_work" function below, which must implement the barrier.)
  93   // First the pre-write versions...
  94   template <class T> inline void write_ref_field_pre(T* field, oop new_val);
  95 private:
  96   // Keep this private so as to catch violations at build time.
  97   virtual void write_ref_field_pre_work(     void* field, oop new_val) { guarantee(false, "Not needed"); };
  98 protected:
  99   virtual void write_ref_field_pre_work(      oop* field, oop new_val) {};
 100   virtual void write_ref_field_pre_work(narrowOop* field, oop new_val) {};
 101 public:
 102 
 103   // ...then the post-write version.
 104   inline void write_ref_field(void* field, oop new_val, bool release = false);
 105 protected:
 106   virtual void write_ref_field_work(void* field, oop new_val, bool release = false) = 0;
 107 public:
 108 
 109   // Invoke the barrier, if any, necessary when writing the "bytes"-byte
 110   // value(s) "val1" (and "val2") into the primitive "field".
 111   virtual void write_prim_field(HeapWord* field, size_t bytes,
 112                                 juint val1, juint val2) = 0;
 113 
 114   // Operations on arrays, or general regions (e.g., for "clone") may be
 115   // optimized by some barriers.
 116 
 117   // The first six operations tell whether such an optimization exists for
 118   // the particular barrier.
 119   virtual bool has_read_ref_array_opt() = 0;
 120   virtual bool has_read_prim_array_opt() = 0;
 121   virtual bool has_write_ref_array_pre_opt() { return true; }
 122   virtual bool has_write_ref_array_opt() = 0;
 123   virtual bool has_write_prim_array_opt() = 0;
 124 
 125   virtual bool has_read_region_opt() = 0;
 126   virtual bool has_write_region_opt() = 0;
 127 
 128   // These operations should assert false unless the correponding operation
 129   // above returns true.  Otherwise, they should perform an appropriate
 130   // barrier for an array whose elements are all in the given memory region.
 131   virtual void read_ref_array(MemRegion mr) = 0;
 132   virtual void read_prim_array(MemRegion mr) = 0;
 133 
 134   // Below length is the # array elements being written
 135   virtual void write_ref_array_pre(oop* dst, int length,
 136                                    bool dest_uninitialized = false) {}
 137   virtual void write_ref_array_pre(narrowOop* dst, int length,
 138                                    bool dest_uninitialized = false) {}
 139   // Below count is the # array elements being written, starting
 140   // at the address "start", which may not necessarily be HeapWord-aligned
 141   virtual void write_ref_array(HeapWord* start, size_t count);
 142 
 143   // Static versions, suitable for calling from generated code;
 144   // count is # array elements being written, starting with "start",
 145   // which may not necessarily be HeapWord-aligned.
 146   static void static_write_ref_array_pre(HeapWord* start, size_t count);
 147   static void static_write_ref_array_post(HeapWord* start, size_t count);
 148 
 149 protected:
 150   virtual void write_ref_array_work(MemRegion mr) = 0;
 151 public:
 152   virtual void write_prim_array(MemRegion mr) = 0;
 153 
 154   virtual void read_region(MemRegion mr) = 0;
 155 
 156   // (For efficiency reasons, this operation is specialized for certain
 157   // barrier types.  Semantically, it should be thought of as a call to the
 158   // virtual "_work" function below, which must implement the barrier.)
 159   inline void write_region(MemRegion mr);
 160 protected:
 161   virtual void write_region_work(MemRegion mr) = 0;
 162 public:
 163 
 164   // Some barrier sets create tables whose elements correspond to parts of
 165   // the heap; the CardTableModRefBS is an example.  Such barrier sets will
 166   // normally reserve space for such tables, and commit parts of the table
 167   // "covering" parts of the heap that are committed.  The constructor is
 168   // passed the maximum number of independently committable subregions to
 169   // be covered, and the "resize_covoered_region" function allows the
 170   // sub-parts of the heap to inform the barrier set of changes of their
 171   // sizes.
 172   BarrierSet(int max_covered_regions) :
 173     _max_covered_regions(max_covered_regions) {}
 174 
 175   // Inform the BarrierSet that the the covered heap region that starts
 176   // with "base" has been changed to have the given size (possibly from 0,
 177   // for initialization.)
 178   virtual void resize_covered_region(MemRegion new_region) = 0;
 179 
 180   // If the barrier set imposes any alignment restrictions on boundaries
 181   // within the heap, this function tells whether they are met.
 182   virtual bool is_aligned(HeapWord* addr) = 0;
 183 
 184   // Print a description of the memory for the barrier set
 185   virtual void print_on(outputStream* st) const = 0;
 186 };
 187 
 188 #endif // SHARE_VM_MEMORY_BARRIERSET_HPP
--- EOF ---